Upper Gotvand Dam and Hydro Power Plant Dealing With Salinity in ...

INTERNATIONAL SYMPOSIUM ON

Bali, Indonesia, June 1ST

– 6TH

, 2014

Upper Gotvand Dam and Hydro Power Plant

Dealing With Salinity in Reservoir

hhdTTjjhkljdjjsgshjhfsdkjhskslsl;s;s;;s;;s;;sjsjkjffffrtttttttfggjfgjgkfkjkjf fffffjfjjfkkfjjj Challenges, Remedies and Evaluations

2(14pt)

D. Mahjoob Farshchi & A. Sadatifard Iran Water and Power Resources Development, Tehran, Iran

[email protected] & [email protected]

H. Hassani & A. Zia MahabGhodss Consulting Engineering Company, Tehran, Iran

ABSTRACT:

Due to a karstic formation with halite layers which were coming into direct contact with the

reservoir after impounding, salinity has been a crucial challenge in Upper Gotvand Hydro

Power Plant and Dam Project. Using a versatile numerical tool as an important part of comprehensive studies carried out in this regard, quality conditions were predicted for the

reservoir and also for downstream water before starting the impounding. According to the

numerical results, effective volume of the formation and also dissolution rate were diagnosed

as the predominant parameters. The model also showed that distinct stratification of salinity

was formed in the reservoir depending on density and temperature. Based on these results,

rehabilitative solutions plan was designed and carried out proportional to conditions of each

stage of impounding. It was showed that during the first stage which the reservoir volume was

small, direct contact between the halite layers and reservoir should be prevented somehow to

reduce the dissolution rate. To this purpose, efficiency of different proposed solutions was

examined in a physical hydraulic mode. Accordingly the clay blanket was selected as the final

rehabilitative method of this stage. Furthermore, as the interim part of the rehabilitative plan

three additional intakes were added in the different levels to avoid collecting saline water in

the reservoir keeping the downstream water quality in the allowable limits. Finally as the

lifetime solution, a pipeline which is under construction was proposed to transfer the high

density water of the reservoir bottom to a convenient place. It was showed that the pipeline

can improve the water qualitative conditions starkly. Efficiency of the rehabilitative plan

which was carried out and monitored during the initial years after impounding, is discussed in

this paper in more details.

Keywords: Karst, Halite, Salinity, Impounding.

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mailto:[email protected]


1. INTRODUCTION

Gotvand dam is the most downstream one of a cascade of 11 large dams on Karoun River.

Karoun is the largest river by discharge in Iran and just after the Gotvand dam traverses the

Khuzestan plain, the main agricultural area in the south of Iran, before discharges into the

Persian Gulf.

Gotvand Dam is a rockfill dam with a height of 182 meters mainly built to

generate hydroelectric power and provide flood control.

The average annual runoff volume at the dam section is about 13.3 billion m3 and the

reservoir capacity with a length of 90 kilometers is about 5.1 billion m3 at the maximum

normal operation elevation (234 masl).

There is a geological formation consisting of alternate layers of halite, anhydrite and marl,

located in 4 kilometers upstream of the dam axis. This formation with a height of 120 meters

(80.0 to 300.0 masl) is extended 3 kilometer along the left bank of the river. The total volume

of the formation is about 600 million m3 and the area of the halite outcrops is about 150000 m

2

(see Fig. 1).

Figure 1. Gachsaran Formation

Since the halite areas were coming into direct contact with the reservoir after impounding and

due to high dissolution rate of the halite, reservoir water quality has been the most technical

challenging concern in Gotvand Project.

This paper tries to explain the issue and its solutions.

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http://en.wikipedia.org/wiki/Gotvand_Dam

http://en.wikipedia.org/wiki/Hydroelectric_power

http://en.wikipedia.org/wiki/Flood_control

2. APPROACH

In order to study the effects of the formation on water quality of the reservoir and the dam

discharge, the measures were focused to find answers of the following questions:

How many percent of the formation would be involved with impoundment?

How much is the dissolution rate?

How will distribute salinity in the reservoir?

A comprehensive study consisting of in-situ and office investigations was carried out in this

regard. The results showed that the area is extremely karstified with different size of sinkholes.

Geotechnical investigations showed that 4% of its whole volume has been formed by the

cavities without specified connections between them. Furthermore it was turned out that the

formation has been constituted by non continuous alternate layers of halite, anhydrite and marl

and therefore merely a part of halite could be dissolved after the impounding. The total

volume of halite was estimated about 60 mcm.

In order to measure the dissolution rate, extensive physical tests with different laboratorial

scales were implemented. The results showed the dissolution rate of anhydrite is really slow

while that of halite is quite high having remarkable effects on the water quality. These tests

also proved that the salt dissolution is an intricate phenomenon depending on different

parameters such as water temperature, pressure, flow rates, turbidity and pureness. Meanwhile

due to obtaining a wide range of values for the dissolution rate (from 5 to 75 cm of thickness

of sample per day), it was determined to estimate this in a large scale model considering the

real conditions as much as possible.

Afterwards using the estimated requisite parameters such as the involved volume of the salt

and its dissolution rate and a numerical versatile model, the salinity conditions of the reservoir

was predicted and accordingly details of the impounding scenario were defined.

3. NUMERICAL AND PHYSICAL MODELS

3.1 Numerical Model

Water quality in the reservoir and the dam outlet was predicted using two individual numerical

tools ” MIKE and CEQUAL” before impounding. Effective volume of halite, dissolution rate,

entrance mechanism of saline flow into the reservoir and daily temperature (using the 40 year

statistics) were introduced into the model as the most important parameters. The numerical

models will be discussed in details in a paper which is under preparation by the authors.

The results of short and long term analyses showed that both thermal and salinity

stratifications would be formed in the reservoir. Therefore vertical salinity profile would be

made up in the reservoir with high density water layers in the bottom. It was seen that the level

of high density layers would be limited to that of the dam openings dependent on their

discharge capacity. The temperature would be constant during the year in the lower part of the

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reservoir height. It was also foreseen the thermal stratification would be disappeared in the

winter. This would be occurred in the surface layers because the temperature of the upper

layers would not be lower than 12 Celsius degrees due to the climate conditions of the dam.

Furthermore it was seen that the dissolution rate was the most important parameter influencing

the salinity condition. Considering these results a comprehensive remedial plan was design

and carried out to control the salinity issue in the reservoir. This will be discussed in the

following Section 4.

3.2 Physical Model, Needs for Understanding and Prediction

The most reliable information about a physical process such as dissolving and salinity

distribution among the reservoir may be given by experimental measurement. To reach this

achievement, a number of partial physical models with different scales were built. These

models have been shown in Fig. 2. The most notable measurements and features of processes

which expected to be explored during study by the models are as follows:

Evaluating the dissolution rate,

Estimating dissolution rate under currents,

Understanding effect of cover on the halite dissolution

To see stratification in the reservoir more precisely

Testing rate of impounding on behavior of the outcrops of halite and the stratifications

Alternate of the halite and marl layers and also outlets at different levels were foreseen in the

model. Impounding rate was fully under control and stopped at some already determined

levels to see probable instability. At the same time, water quality parameters were measured

along and in the whole depth of model to see stratification. Each test took 3 to 7 days. At the

end of the tests, dissolved mass was determined by weighting the rest of undissolved halite

mass. These were carried out repeatedly for various impounding rates. They were also

implemented to evaluate the efficiency of different alternatives for covering the outcrops

proposed to decrease the dissolution rate.

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Figure 2. Different physical models to measure the dissolution rate

4. REMEDIAL PLAN

According to the results discussed in the previous section, strong stratification of salinity was

predicted to form in the reservoir after impounding. Furthermore the dissolution rate was

diagnosed as a crucial factor in this regard. Therefore in order to deal with the salinity

problem, a comprehensive remedial plan consisting of the following items was carried out:

minimize the dissolution rate and salinity stratification management, filling the sinkholes, the

additional intakes in the different levels, preliminary impounding, monitoring reservoir,

proportional operation scenarios and complementary solution.

4.1 Minimize the dissolution rate and salinity stratification management

In order to reduce the dissolution rate (specially during the first stage of impounding which the

reservoir volume is small) and conducting the high density waters to the bottom preventing

them to be mixed with upper fresh water of the reservoir, it was determined to prevent the

direct contact between the outcrops and water by covering the slopes. To find out the most

efficient coating material, the geological conditions of the area consisting of the alternate

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layers of halite, anhydrate and marl were constructed and coated by the different alternatives

in the physical model and efficiency of each one was evaluated under impounding via separate

experiments:

4.1.1 Geo-Membrane

Although Geo-Membrane has been diagnosed as a successful alternative during the

laboratorial investigations, it was not selected as the justifiable final one due to being

vulnerable against probable large point load perpendicular to its surface and also to large

settlement of its foundation caused by dissolution and in other hand due to its high expenses.

4.1.2 Nano, polyurethane and asphaltic materials

Application of new synthetic materials such as Nano, polyurethane and asphaltic ones were

also investigated in the model. The test results showed that the coating adhesion was

disappeared because the area had been formed by the different materials due to its geological

conditions. Moreover impacts of this alternative are unknown.

4.1.3 Concrete blocks

This alternative was rejected because of lack of enough flexibility against large settlement of

the foundation and also its high expenses.

4.1.4 Clay blanket

In order to examine the efficiency of this alternative, the slopes were stabilized firstly and then

covered by a layer of clay blanket along with a layer of protective riprap. The results showed

that due to high flexibility against large settlement, its tailor-ability, available borrow areas

and justifiable performance expenses, this can be considered as the most efficient solution.

This was confirmed after impounding based on the reservoir monitoring results which will be

discussed in the next section of this paper.

4.2 Filling the sinkholes

To reduce the area permeability, most of sinkholes were filled by slurry.

4.3 The additional intakes in the different levels

Since the numerical and physical results showed that salinity stratification would be formed in

the reservoir, it was determined to add some new intakes to the ones such as bottom outlet,

power plant and spillway intakes which had been constructed in the levels of 123, 160 to185

and 218 (masl) respectively based on the project main objectives. To do this, three intakes

were added in the levels of 90, 110 and 158 (masl), it should be noted that the level of river

bottom is 70 (masl) in the dam axis location. Therefore the project team could apply different

operation scenarios preventing salinity accumulation in the reservoir simultaneous with

providing the adequate water for the downstream people. Validity of these will be discussed in

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the next section based on monitoring results of the reservoir which were observed after

impounding.

4.4 Preliminary impounding

In order to verify the efficiency of the above mentioned plan, a preliminary phase was defined

for the impounding. Based on this, the level of water surface was kept constant for 3 months at

the level of 140 to monitor the reservoir conditions and quality of the water releasing to the

downstream. A relevant plan was also defined for any urgent need to instant depletion. As it

will be discussed in Section 5, it was seen that the predicted solutions were really successful.

4.5 Monitoring the reservoir and proportional operation scenarios

Since beginning of the impounding so far, seven important parameters consisting of soluble

oxygen, electrical conductivity, pressure, density, TDS, temperature and density are measured

online using a hi-tech instrument which was designed and installed in the reservoir. This

system sends out the data to the operation center as vertical profile which shows the water

conditions from the bottom to the surface. Based on these results, it was seen that the

stratification has been formed in the reservoir as it has been predicted before impounding. In

addition, these results are used to calibrate the numerical model and to define proportional

operation scenarios. This model was applied as a tool to predict long term behavior of the

reservoir.

4.6 Complementary solution

Based on the numerical results, a pipeline system as a complementary solution has been

designed to be constructed to transfer the high density water collected in the reservoir bottom

to industrial oil centers in order to use as crude material if needed.

5. RESERVOIR CONDITIONS

As mentioned in Section 4.4, the reservoir conditions have been daily monitored using a high-

tech measuring system. As predicted by the numerical modeling, the monitoring results show

that the thermal and salinity stratifications have been formed in the reservoir after impounding

(see Fig. 3). Furthermore according to these it was turned out that the thermal stratification

will be disappeared at the beginning of the winter. This occurred in a depth limited to the

surface layers (see Fig. 4).

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Figure 3. Salinity distribution in the reservoir

Least but not last the monitoring results indicate that the quality of the reservoir and of the

released water to the downstream have been satisfactory during the three years after

impounding.

Figure 4. Thermal stratification

It should be noted that the monitoring results have been used to precisely estimation of the

halite dissolution rate and calibration of the numerical model which is used by the operation

team to predict the long term conditions of the reservoir as a versatile tool.

6. SUMMARY AND CONCLUSIONS

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Inside Gotvand reservoir there is a huge massive formation with the volume of 600

million m3 which contains 60 million m3 of halite. This event could make a crucial

threat for downstream water quality.

Extensive study and vast range of investigations including physical and numerical

modeling proved that a key point to choose a method for dealing with the problem is to

reduce the dissolution rate of halite.

Another key finding is to provide conditions to form strong stratification and prevent

mixing the layers inside the reservoir. Strong stratification means considerable

difference in the salinity and hence in the density of each layer.

In order to reduce the dissolution rate and restrict the direct contact between the water

and halite outcrops, the slopes were covered with the clay blanket and a protective

riprap layer. With regarding to formation of strong salinity stratification in the

reservoir, three additional intakes were added in the different levels. This allowed the

project team to define and apply proportional operation scenarios to prevent

accumulation of saline water in the reservoir in addition to providing adequate water

for downstream people.

To have a practical evaluation on the efficiency of the above mentioned solutions, a

preliminary stage was defined in the impounding plan.

Based on the numerical results, a pipeline system as a complementary solution has

been designed to be constructed to transfer the high density water collected in the

reservoir bottom to industrial oil centers in order to use as crude material if needed.

To verify the numerical results and definition of proportional operation scenarios, a

high-tech monitoring system has been installed in the dam lake. The monitoring results

show that the reservoir quality conditions have been satisfactory from the impounding

time so far.

ACKNOWLEDGEMENT Special thanks to Mr. Naderan from Iran Water and Power Resources Development Company and Mr.

Zafari from Mahab Ghods Company for their supports.

REFERENCES

Mahab Ghodss Consulting Engineering Company (2011): Upper Gotvand reservoir water

quality modeling report, Iran





Mahab Ghodss Consulting Engineering Company (2008): Upper Gotvand reservoir geology

investigation report, Iran

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Mahab Ghodss Consulting Engineering Company (2012): Upper Gotvand reservoir geology

investigation report, Iran

Mahab Ghodss Consulting Engineering Company (2012): Upper Gotvand reservoir

monitoring Data and Analysis report

Mahab Ghodss Consulting Engineering Company (2013): Upper Gotvand reservoir

monitoring Data and Analysis report

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Bali, Indonesia, June 1ST – 6TH , 2014

Integrated Approach for Environmental Management in Tenryu River

Yuichi KITAMURA, Dr.

Technical Director, Chigasaki Research Institute, Electric Power Development Co.,Ltd.(J-POWER), Japan [email protected]

Tetuo MURAKAMI, Dr. B Professor, Faculity of Domestic Science, Nagoya Womens’s University, Japan

ABSTRACT: The environmental impacts on rivers are unavoidable by dam construction. The sedimentations in upstream of dams, discharges of turbidity water to downstream and changes in water temperature are typical environmental issues for dam impoundment. These impacts restricted not only near the impoundment but also on upstream and downstream. Therefore the more integrated environmental management approach has been required for the whole river system including from catchment area to sea. The "Tenryu River Natural Resources Reproduction Committee" has been established on 2012 through three years preparation. The purpose of the committee is the preservation, and conservation for the environmental condition of the Tenryu River, especially for inland water fisheries. The committee is composed of the fishermen's cooperative association, researchers of ecology and limnology, and the dam administrators. Information about the environment of the Tenryu and the technical development for fisheries are discussed in the committee over each standing point. The committee now gives prominence on three important issue for fishery product; "attached algae productivity of river with dams", the "spawning bed creation for “ayu fish” (sweet fish; Plecoglossus altivelis) and "information dissemination of these research to local communities. In this report, we present the outline of new approach of the committee for river environment conservation and reconstruction of inland fisheries in the Tenryu River. Keywords: Impacts on environmental condition; Multivariate and quantification analysis; Investigation and evaluation technique; Attached algae; Productivity of river. 1. INTRODUCTION The environmental impacts of dam impoundment on rivers are subjects which have started since dam construction. Sedimentation in impoundment discharge of cool and turbid water to downstream, and changes in nutrient concentrations caused by planktonic algal production are severe problems in the Japanese rivers which have been constructed dams. Moreover, these environmental impacts may also effect on lives and distribution of the aquatic organisms of rivers, and as results may lead to depression of fisheries and changes in human lives in local communities along the river. The influences does not restrict only near impoundment, but also wide area which includes lower and upper streams far from

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reservoir. There are also many stakeholders in connection with a river, and therefore the more synthetic environmental management over the whole river from headstream to sea is needed. In this report, we present outline of newly started actions by fishermen, researchers and dam administrators for conservation of fluvial environment in the Tenryu River, Central Japan. 2. REPRODUCTION OF THE TENRYU RIVER 2.1. Outline of Tenryu River The Tenryu River is originated from Lake Suwa in Nagano Prefecture, and it flows through the mountain area of Okumikawa and the Hokuen, and into the Pacific Ocean (Fig. 1). It has 213 km long, and has 5,094 km2 catchment area. In the Tenryu River, many dams were built until now for the purpose of flood control, irrigation, and power generation. Sakuma Dam, the largest one in the river system, is the concrete gravity dam, and has 294 m length and 156 m height built in the middle of the Tenryu River and the electric power generated provides 1/3 of the potential water power. There are also two small dams for power generation and irrigation, Akiba and Funagira Dams downstream of the Sakuma Dam.

Figure 1. Tenryu River system and target area 2.2. The Tenryu River Natural Resources Reproduction Committee The Tenryu River flows through the erodible area near the Median Tectonic Line in Japan Islands, and therefore continuously carries a lot of sediment during flood periods. The accumulative sediment in Sakuma Dam measured in 2013has reached to 37% of reservoir capacity (327 million m3). Moreover, since the scale of the reservoir is large, discharge of the turbid water containing clay, silt and fine sand has been severe problems. The turbid water effects directly and indirectly to the main fishery resources of the sweet fish (referred later as “ayu fish”; Plecoglossus altivelis). There is also the tendency for the recreational fishing person to keep away to use as a fishery field because of turbid water. In recent years, it is a reason for causing the depression of inland water fisheries.

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Moreover, there are also many stakeholders, and it needs a long period of time for the understanding the problems, the adjustment, and the implementation of further plan for the fluvial environment. In many rivers, the fishermen’s union is the only association that has legal rights for economic activity. Under the present situation where environmental rights without economic interests are not common, unions have a strong voice against artificial interference with their fishing grounds. Therefore the more integrated environmental management by fishermen has been required for the whole river system, including not only the dam impoundment, but also up- and downstream. The "Tenryu River Natural Resources Reproduction Committee" has been established on 2012. The purpose of the committee is the conservation of fluvial environment and recreation for of inland fisheries especially ayu fish. The committee is composed of the fishermen's cooperative association, researchers for limnology and ecology, and the dam administrators. The information about the environment of Tenryu River, and the technical problems for further development are discussed cross-boundary of the members (Fig. 2).

Figure 2. The Tenryu River Natural Resources Reproduction Committee 3. ENVIRONMENTAL CAPABILITY OF TENRYU RIVER 3.1. Environmental capability containing river ecology The grasp of the environmental characteristics of the target river is important in the preservation and the reproduction of in fluvial environment. Instream Flow Incremental Methodology (IFIM), and Index of Index of Biological Integrity (IBI), etc. are recently proposed as the methods of evaluating the environmental characteristics including the river ecology (Nakamura 1999, and Koshimizu1997). But these evaluation methods need the detailed investigation in the rivers, even if the effective methods which is applicable. On the other hand, ayu fish is the main fish stocks in the river from which it is distributed all over rivers in Japan. The ayu fish is the fish representing river ecology environment. Moreover, the main target of inland water fisheries is the ayu fish in Japan. The ayu fish has the special feeding habits which use a primary production (attached algae) as food is (Kitamura 2002). Production of the minute attached algae to grasp is greatly influenced by water temperature and turbid water compared with another living thing with large-scale and high mobility.

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For this reason, in many rivers, investigation about the prolonged ayu fish productivity and various related environment is conducted, and it has been accumulated as official announcement data. Then, the fluvial environment of Tenryu River was positioned based on the results of an investigation about main rivers all over the country. 3.2. Relevance of ayu fish productivity and environmental capability The 22 main rivers all over Japan are compared with Tenryu River about the environment condition. The information about ayu fish productivity, ayu fish planting, habitation range of ayu fish, land use of catchment areas, etc., were used about the ecology environment of a river. The catchment area, the river length, the river bed slope, the reservoir area of structures (dams, and weir, etc.), and the discharge flow were used about the physical environment. Furthermore, suspended solid concentration (SS), water temperature, dissolved oxygen (DO), biological need for oxygen (BOD), etc. were used about the water quality environment. The multivariate and quantification analysis was conducted about the relation of the environmental capability of 22 rivers and the ayu fish productivity with above environment parameters (Hayashi 1993). Fig. 3 shows the mean value of ayu fish productivity (ratio of ayu fish productivity with catchment area) in Japan was evaluated to 71kg/km2 for from 1988 to 1998. And the result of the single correlation analysis shows the relation into the centering on ayu fish productivity between the factors was investigated in Fig. 4.

Figure 3. Comparison of ayu fish productivity of 22 rivers in Japan Through the principal component analysis, the water temperature, the maximum discharge flow/average discharge flow, and DO have the positive correlation with the ayu fish productivity. And the river bed slope, SS, and the ratio of reservoir area and the catchment area have the negative correlation with the productivity in the factors. 22 rivers were plotted based on these main ingredients in Fig. 5. The group of high productivity (o) has been arranged on the 1st quadrant. These results show that the ayu fish productivity of Tenryu River is located near the boundary of the group of high productivity and the low productivity.

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Figure 4. Single correlation of ayu fish productivity with environmental factors

Figure 5. Position of 22 rivers with ayu fish productivity by principal component 3.3. Ayu fish productivity of Tenryu River The ayu fish productivity, ayu fish planting, the physical environment, and the water quality environment about Tenryu River were analyzed by the regression analysis and the principal component analysis for the data. The environmental factors were analyzed about the influence for the change of the ayu fish productivity through 26 years data from 1979 to 2005. Through regression analysis, Fig. 6 shows that the annual change of ayu fish productivity has high correlation with the ayu fish planting, and is strongly influenced to the artificial influence. On the other hand, the water temperature, DO, the minimum discharge flow, and the mean discharge flow have the positive correlation with the ayu fish productivity. Moreover, the relation between the change of ayu fish productivity and the environmental factors were examined through the principal component analysis by using the same parameter above mentioned regression analysis (Hayashi 1988). Fig. 7 shows the result of

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the analysis that the 1st ingredient has the positive correlation with SS and the mean discharge flow, and the negative correlation with the water temperature. And it shows that the 2nd ingredient has the positive correlation with the fish productivity/catchment area, DO, BOD, and the ayu fish planting. It shows that the change of fish productivity in Tenryu River becomes higher with BOD and DO which have high correlation with the main ingredients 2, and the fish planting is higher years. On the other hand, the change of fish productivity in Tenryu River has no relation with SS and the mean discharge flow. In addition, the water temperature (from January to May, and from October to December of the previous year) has small relation of the ayu fish productivity and the environment factor of river because of small loading to the main ingredients 1 and the 2nd ingredients.

Figure 6. Estimation of ayu fish productivity by regression analysis (Tenryu River)

Figure 7. Relation about ayu fish productivity and other factors (Tenryu River)

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4. MEASURES AND EXAMINATION METHOD 4.1. Structure of ecosystem, and improvement in fishes productivity The recovery of ayu fish productivity in Tenryu River is related to SS, the water temperature, DO, BOD, and the discharge flow through the statistical analysis about environmental factors. It is convinced through the structure of a river ecosystem shown in Fig. 8. The quantity of attached algae on the surface of the river bed materials is influenced because of the change of the water quality, discharge flow, and the organic matter in the river, and, the fish productivity and DO change with the influences of them as the result. Moreover, the physical states in the river such as the movement of the bed material and the particle diameter changes, then the attached algae on the bed material which is the food of fishes changes, and the fish productivity also changes. For this reason, the field investigation about the attached algae and DO gives the important key for the change of the ecology environment of the river, or the fish productivity.

Figure 8. Structure of ecosystem in river system 4.2. Ayu fish productivity of Tenryu River Adult ayu fish feeds on attached algae (periphytic algae) developing on gravels in the river. Algal biomass as dry weight, chlorophyll a, and species composition of attached algae were measured. The species composition of the attached organism and the biomass are not uniform, and a number of samples for statistical analyses are needed (Otani 2009). For this reason, the convenient measurement of the attached algae is required in the field. Fig. 9 shows that the results of investigation by the fluorometric method to roughly estimate biomass and species composition of the attached algae in present research (Beutler 2002). Biomass of blue-green algae and diatoms in just downstream of the Funagira Dam are shown in Fig. 10. Dominant species was diatoms. Gravels surface was covered by clay and silt. The fed part by ayu fish on the gravel (Samples No.41 and 43) was lager biomass than other part of gravel (Sample No.42). Therefore this suggests the growth of algae will be influenced by turbid water.

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Figure 9. Measurement of attached algae on gravel by fluorometric method

Figure 10. Algae on gravels at Shiomid bridge downstream of Funagira Dam (left: results of measurement, right: gravel after fed by ayu fish)

4.3. Production rate investigation The quality of the ayu fish of primary production foods is influenced to the species composition of periphytic algal community and the biomass of attached algae. And the algal productivity is also important factor. The productivity of attached algae is influenced by the current. It is difficult to estimate the production in the laboratory. Therefore it is more suitable to observe directly in the open system by which the flow is maintained. We measure daily fluctuations in the DO, which is changed by algal production and respiration. Fig. 11, 12, and 13 show the diurnal fluctuations in DO concentration. Fig. 11 shows that the daily changes in DO in just downstream of Funagira Dam (red line) and lower riffle far from the dam (blue line). It shows low productivity just downstream of the dam. On the other hands, Fig. 12 shows productivity just downstream of the dam (red line) was higher than the Keta River, a tributary without dam (blue line). Fig. 13 shows the long period investigation of DO at the downstream left bank of Funagira Dam. Algal production and respiration increased by development of algal community. Thick algal community indicated by such high productivity was not suitable food environment for ayu fish. Thick algal community was washed out after heavy precipitation and began succession of algal community again. Dam impoundment can decrease in frequency such flood event. Moreover, from the results of the investigation shown in Fig. 13, the production rate (P) of attached algae of Funagira Dam in the downstream, changes greatly with the renewal time

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and the sunshine conditions, and is estimated roughly 0-20 mgO2/m3/day through the DO

with taking account the water temperature. The respiration rate (R) under the fine weather is same range in general, and the ratio of P/R is almost 1.0. However, the daylight hours are short, the breathing may exceed production.

Figure 11. Change range of DO at downstream Figure 12. Daily change of DO at and lower riffle of Funagira Dam Funagira Dam and Keta River

Figure 13. Long period change of DO, water temperature and rain at downstream of Funagira Dam

5. CONCLUSION It is introduced about the outline of new approach of the committee for fluvial environment conservation and reconstruction of inland fisheries in the Tenryu River. The purpose of the committee is the preservation, and conservation for the environmental condition of the Tenryu River. In order to make reproduction of Tenryu River successful, it is important to get to know well about the environmental capability about Tenryu River. Same valuable conclusions can be drawn as followers: (1) Through the statistical analysis about 22 rivers in Japan with the official announcement

data, the fluvial environment of Tenryu River was evaluated at the boundary of the

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group of high productivity and the low productivity in Japan, and has the positive correlation with water temperature, discharge, and DO.

(2) In Tenryu River, the annual change of ayu fish productivity is strongly influenced to

the artificial influence of fish planting. Through the principal component analysis it is suggested the recovery of ayu fish productivity and the environment improve in Tenryu River have been necessary to SS, the water temperature, DO, BOD, and the discharge.

(3) The fluorometric method to estimate biomass and species composition of the attached

algae in the field, and the growth of algae on the surface of gravel will be influenced by turbid water from the results of investigation.

(4) The productivity of attached algae was investigated through the measure of daily

fluctuations in the DO concentration in the river, and changed because frequency of flood events. The production rate is estimated roughly 0-20 mgO2/m

3/day The committee gives the importance of information dissemination, therefore the environmental preservation of Tenryu River, technology, and other information are always disseminated to the various local communities and stakeholders by the homepage (URL: www.tenryugawa.jp). Furthermore, in the committee, the DNA microarray of the ayu fish has been created for the first time in the world as the new method of an environmental impact assessment. Gene expression analysis by the river water of Tenryu River was conducted, and it investigated about the influence in the gene level. We want to report at the next opportunity. REFERENCES

Nakamura S. (1999) : Introduction of IFIM (United States Department of the Interior), Foundation for Riverfront Improvement and Restoration, Japan (in Japanese).

Koshimizu N. and Matuismiya Y. (1997) : Habitat Environment Assessment of River Fish Fauna by Index of Biotic Integrity, Japanese Soc. of Fisheries Oceanography: Vol.61, pp.144-156, Japan (in Japanese).

Kitamura Y., Matsumoto M., and Katsuyama I. (2002) : Development of the Prediction and Evaluation method for River Ecosystem by the Catches of Ayu fish, Proceedings o Rivers Engineering and Technology JSCE, Japan (in Japanese).

Hayashi C. (1993): Quantification method, Theory and Method (Statistical Library), Asakura-Shupan, Japan (in Japanese).

Hayashi C. (1988) : Fundamental Method of Data Analysis, Open University of Japan, Japan (in Japanese).

Otani H., Kitamura Y., and Shinjo T. (2009) : Study for Evaluation of Attached algae on Riverbed by Wavelengths Absorbance Method, Journal of Electric Power Civil Engineering, Japan (in Japanese).

Beutler M., Wiltshire K. H., Meyer B., Moldaenke C., Luring C., Meyerhofer M., Hansen U. P., and Dau H. (2002) : A Fluorometric Method for the Differentiation of Algal Populations in Vivo and Situ, Photosynthesis Research 72, the Netherlands.

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LIDAR – ALS Application for Construction of the Digital Model of the Dam Reservoir Bowl

A. Kosik

Institute of Meteorology and Water Management, Warsaw, Poland [email protected]

K. Mańk

Institute of Meteorology and Water Management, Warsaw, Poland

E. Sieinski Institute of Meteorology and Water Management, Dams Monitoring Center, Warsaw, Poland

J. Winter

Institute of Meteorology and Water Management, Warsaw, Poland

A. Wita Institute of Meteorology and Water Management, Warsaw, Poland

ABSTRACT:

Accumulation takes place all along during the dam reservoir exploitation. The reservoir capacity loss and limitation of its usefulness are the consequences. Since one of the reasons for building dam reservoirs is flood protection, a decrease of the flood capacity limits their effectiveness. The understanding of the relationships between the water level in the reservoir and the volume of the water in the reservoir (reservoir capacity curve) is essential for their correct exploitation. Digital hydroaccoustic probes combined with GPS receivers mounted on measurement boats are currently used for bathymetric measurements of dam reservoirs. digital models of the dam reservoir bowl, a bathymetric map of the reservoir as well as reservoir capacity curve are drawn upon processed data. The measurements should be carried out during the maximum water level so that the digital model of the dam reservoir bowl would cover the whole range of the water level. Unfortunately it is not always possible and additional geodesy measurements have to be done to the uncovered parts of the reservoir bowl which may be difficult to reach for the measurement teams because of the slushy conditions. Additional difficulties may be faced during the measurements of the backwater area due to shallow water level and limited access to this area by the measurement boat. In the article a solution to the problem was presented using LIDAR on the uncovered parts of the reservoir bowl. The Digital Terrain Models of the bathymetric measurements and LiDAR- ASL were combined. The integrated model of the reservoir area allows for the dimensional analysis with GIS software as well as other tools including tables, capacity curves and surface flood area essential for correct exploitation of the reservoir especially during floods. The results for one of the reservoirs in Poland were presented in the article.

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Keyword : sedimentation, bathymetric measurements, losing reservoir capacity, LiDAR-ALS

1. INTRODUCTION

In hydrological studies of reservoirs, it is very important to define the morphometry. First of all, the characteristics of the size and the characteristics of the capacity, depth and the bottom of the reservoir. Stating of those values is possible on the basis of the bathymetric plan of the reservoir drawn upon a Digital Terrain Model (DTM) of the bottom of the reservoir. In order to describe the bottom of the reservoir, in the form of a bathymetric plan or a Digital Terrain Model, a set of points with known parameters, specifying their position in space, evenly spaced on the surface of the bottom is necessary. This task can be performed in different ways, depending on the technical possibilities and the desired accuracy of the plan. The best way to do bathymetric measurement is to use a probe with GPS navigation receiver. Hydrographic work carried out in this way requires integrated measurement techniques including differential measurements, DGNSS or RTK as well as probing. During the measurements the horizontal position of the vessel as well as the depth are recorded. To develop the Digital Terrain Model of the bottom of the reservoir it is necessary to precisely link both data in order to avoid errors arising from transferring the measurements over time. 2. BATHYMETRIC MEASUREMENTS As far as the bathymetric measurements of water reservoirs are concerned, depth measurements are usually limited by the shoreline of the reservoir. So beforehand, a file with the reservoir shoreline, as well as intersection lines for the depth measurements are essential. Orthophotomaps are best source of information about the shoreline. However due to the problems which may result form the misinterpretation of some of its fragments, such as forested parts of the shore, it is necessary to verify or complete some parts through direct geodetic measurements on location. Another possibility is the determination of the shoreline on the basis of topographic maps. GPS Satellite Positioning System marks the position of the vessel in real time with accuracy to a few inches, allowing for the precise navigation boat along previously designed profiles .

The data from a GPS receiver combined with probes allow developing the numerical model of the reservoir bowl. The position of each point is determined by the coordinates (x, y, z) where x, y, are geodetic coordinates and z is depth. A collection of all the coordinates describing the bathymetry of the reservoir should be downloaded into GIS software and interpolated. Consequently, a set of data processed into grid nodes with the grid size depending on the required resolution. The Digital Terrain Model of the bottom of the reservoir allows for automatic generation of contours, cross-sections and calculation of the ground mass volume.

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ArcGIS by ESRI extensions-3D Analyst and Spatial Analyst can be applied for the creation of the numerical models of the bottom of water reservoirs. They allow for the development of a digital model of the bottom and to plot izobats, in case of the development of the bathymetric plan of the reservoir (fig. 1).

Figure 1. Digital Terrain Model the bottom of the reservoir, with the generated isobaths As it was proved, the collection and processing of the bathymetric data is complicated. It begins with the preparation of measurements by identifying the shoreline and establishing the basic measurements cross sections. The preparation of the cross section lines aims to cover systematically the whole area of the probed reservoir in such a way so as to obtain the best scan possible of the changes in shape of the bottom of the reservoir. Reservoir capacity research is performed by digital hydroaccoustic probes combined with GPS receivers. However, during the hydrographic work, there are frequent complications during the measurements of the backwater area of the reservoir. It is due to shallow water level and limited access to this area by the measurement boat. These difficulties can be overcome with the application of the LiDAR-ASL technology for inaccessible areas, or those difficult to reach. 3. LiDAR - ASL LiDAR technology (Light Detection and Ranging) involves measuring distances from flying aircraft or helicopter to plot points. The time difference between sending and receiving a single laser pulse is determined. The system includes the emitter, which is a device producing the laser beam and a receiver, which is the device collecting recurring data beam after reflection. For uncovered areas the beam, after reflection from the surface goes back to the emitting unit and is recorded. In the case of land covered by vegetation (e.g., forests), returning beam is scattered, and is registered as rays reflecting from the surface of the land, and the tree branches. A cloud of points obtained this way needs to be

IV - 23

filtered depending on the needs. LiDAR data filtration processes are used to build up the DTM and involve the elimination of the points that have been reflected from the land cover elements, buildings or vegetation. The most important advantages of LiDAR-ASL which make it different from mother measurements technologies include: • independence from weather conditions (clouds base higher than the cruising altitude,

only heavy rains and fog have a negative impact), • independence of lighting conditions (scanning at night), • penetration of the vegetation layer, • high density of spatial points • sufficient accuracy of the determination of X-and Y-coordinates, and high accuracy of

determination of Z coordinates, • quick result in the form of finished product, • relatively low costs (especially for large areas). Unfortunately, LiDAR technology also has disadvantages and among them the following: • penetration of the laser pulse under the water surface, • difficulties in determining skeletal lines and lines of discontinuities in the area, • a large amount of data to be processed during postprocessing. The bathymetric measurements should be done during high water levels in the reservoir, while LiDAR should be performed during low water levels. Therefore a Digital Terrain Model of the reservoir bowl is obtained with an interim zone for which the altitude data will be repeated. The next stage is the combination of these two models. 4. BATHYMETRIC MEASUREMENTS ON THE EXAMPLE OF TRESNA RESERVOIR In conducted tests, Digital Terrain Model and Digital Model of the reservoir bowl has a raster structure of the pixel size of 0.5 m.

Figure 2. Digital Terrain Model of Tresna reservoirs with the use of LiDAR

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Figure 3. Integrated Digital Model of the reservoir bottom with the DTM made with the use of LiDAR.

In water management the integrated Digital Terrain Model can be used for a variety of purposes which can be presented in the example of the analyzed reservoir. Here are the main of them. 4.1. Measurement cross - sections Generated cross sections based on integrated, DTM may be applied during the assessment of the reservoir abrasion. For example, DTMs from different measurement dates, can be compared according to the vertical cross-sections done along the same line. It allows observing the changes that arise as a result of the erosion.

Figure 4. Automatic generation of the cross-section in a given place.

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4.2. Volume calculation Integrated DTM allows for better calculation of the volume limited by the terrain surface and planes freely situated in relation to the surface. Therefore, the Digital Terrain Model prepared in such a way enables the processing of the surface and reservoir capacity curves for any elevation. A sample spatial analysis based on the integrated DTM allowing for the calculation of the size and capacity of the reservoir at maximum water level (MaxWL), was shown in Fig. 5.

Figure. 5. Sample spatial analysis based on an integrated DTM. Capacity curve as well as the surface curve allows to determine the volume and surface size for any water level and any layer of the reservoir and additionally to determine on what altitudes large increase in flooded areas take place. Capacity curve is a mass diagram curve of the water volume (V) between particular levels. Table 1 shows the results of the calculations of the reservoir volume and size for different elevations. Information about the size and volume of the reservoir were collected as a result of the spatial analyses carried out on the basis of the integrated DTM. Table 1.

Elevation [m a.s.l.] Area [km2] Capacity [million m 3]

MaxWL 344.86 9.89 93.99

344.5 9.83 90.47

344 9.71 85.63

343.5 9.58 80.84

343 9.43 76.13

342.5 9.25 71.49

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342 9.04 66.95

NWL 1 341.5 8.78 62.53

341 8.44 58.25

NWL 2 340.5 8.12 54.14

340 7.74 50.18

339.5 7.27 46.46

339 6.93 42.92

338.5 6.55 39.56

338 6.21 36.38

337.5 5.89 33.37

337 5.59 30.51

336.5 5.33 27.78

336 5.05 25.20

335.5 4.80 22.75

335 4.56 20.41

334.5 4.26 18.21

334 4.01 16.15

333.5 3.76 14.21

333 3.47 12.41

332.5 3.17 10.75

332 2.84 9.25

331.5 2.56 7.90

331 2.28 6.69

330.5 1.97 5.63

330 1.67 4.73

329.5 1.36 3.98

329 1.16 3.36

328.5 1.01 2.82

MinWL 328.36 0.98 2.68 NWL1-Normal Water Level (1.X.-31.V.), NWL2-Normal Water Level (15.VI.-15.IX.), MinWL-Minimal Water Level, MaxWL – Maximal Water Level On the basis of such a table, it is possible to draw a surface curve and a capacity curve of the reservoir (Fig. 6.)

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Figure 6. The surface curve of the Tresna reservoir.

Figure 7. The capacity curve of the Tresna reservoir. 5. VIZUALIZATION USE GIS software allows for the representation of the terrain surrounding the reservoir at any scale with the dynamic change of the viewing position (fig. 8). For better presentation of the topography you can also apply profiles generated from the NTM (fig. 9 and 10).

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Figure 8. DTM of the area surrounding Tresna reservoir.

Figure 9.The DTM of the area surrounding Tresna reservoir with contour lines.

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Figure 10. DTM of the area surrounding Tresna reservoir with isobaths of the reservoir bowl.

5. CONCLUSIONS The article presented an attempt of the construction of the Digital Terrain Model of the uncovered parts of the reservoir bowl. Digital models have been derived from the bathymetric measurements and LiDAR measurements of the reservoir bowl combined. The integrated model of the reservoir bowl obtained in such a way allows for spatial analysis with the use of GIS software and other tools, including the processing, of the tables, curves and surface of the reservoir that are essential for the correct exploitation of the reservoir, particularly in terms of floods. The article presents the results obtained for one of the reservoirs in Poland - Tresna reservoir. REFERENCES Kosik A., New measurement techniques in the assessment of the dam reservoir abrasion (in polish). Ogólnokrajowe Sympozjum Hydrotechnika XV’2013. Ustroń, 2013. Kosik A., Kloze J., Wita A.: Study of Sedimentation of Reservoirs in Poland. Proceedings of International Symposium on DAMS FOR A CHANGING WORLD - Need for Knowledge Transfer across the Generations & the World. Kyoto, Japan, 2012. Kosik A., Leszczyński W., Mroziński J., Wita A.: Bed and Banks Changes evaluation of Water Reservoirs. Proceedings of International Conference Prehradny Dny. Seč, Czech Republic, 2012 LIDAR for Tresna reservoir (in polish). MGGP Aero, 2010. RESERVOIRS in Poland. KZGW, Warsaw, 2011. LiDAR application for the observation of the shore abrasion (in polish). Technology and systems in evaluation of the water quality and dam structures. Task 2 in research theme DS-B2. IMGW-PIB, Warszawa, 2013. Tresna water reservoir. Evaluation of the shore abrasion. IMGW-PIB, Warszawa 2010.

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INTERNATIONAL SYMPOSIUM ON Bali, Indonesia, June 1ST – 6TH , 2014

Comparative Study On Settling Rate Evaluation

For Soil Particles In Reservoirs

H. Umino & N. Hakoishi

Public works Research Institute, Tsukuba, Japan [email protected]

ABSTRACT: This study aims to present an appropriate method on settling rate evaluation for soil particles in reservoirs. For the execution of numerical simulation on sediment in reservoirs, it is indispensable to decide the settling rate of soil particles. Laser diffraction method has been commonly used for grain size analysis and grain size is converted into settling rate by Stokes’ Formula, nevertheless, it has been indicated that the settling rate calculated by this method differs from the actual one. We obtained turbid water from a river while flooding, investigated and compared settling rate distribution by settling cylinder method, centrifugal sedimentation method and laser diffraction method. Settling cylinder method could give reliable results, but it needs a plenty of turbid water and took long time to get results. Centrifugal sedimentation method could shorten time for analysis, but the equipment for this method is not disseminated. The laser diffraction method has been regarded as the standard method. We estimated that actual settling rate was slower than calculation of the Stokes’ Formula because several particles formed flocks and each flocks was porous. Through this study three points were concluded. (1) Settling cylinder method was the most reliable for evaluating the settling rate of fine particles. (2) Centrifugal sedimentation method could alternate the settling cylinder method. (3) In case of using laser diffraction method, similar settling rate distribution to settling cylinder method could be obtained by ultrasonic distribution treatment. Keywords: Reservoir, Soil Particles, Settling Rate, Settling Cylinder, Laser Diffraction Method. 1. INTRODUCTION Sediment accumulation is one of management problems for reservoirs in Japan (Fig. 1.). Some bypass channels for releasing turbid water from upstream of a reservoir have been adopted and the effects have been highly evaluated. In case of designing specifications and practical use of sediment releasing facilities, numerical simulations for sediment accumulation in reservoirs have been conducted. For accurate simulations, the evaluation of settling rate is important matter. This paper aims to present an appropriate method for determining settling rate of soil particles. Firstly, we collected turbid water from a site of mountainous river while heavy rainfalls and observed settling rate of particles in settling cylinder. Secondly, we analyzed grain size distribution of turbid water by using laser diffraction method and centrifugal sedimentation method. These two methods were relatively easy to get grain size

IV - 31

distribution and then applied Stokes’ Formula to the conversion from grain size into settling rate distribution. Finally, we present an appropriate method for determining settling rate distribution by comparing the results of three methods, i.e., settling cylinder method, centrifugal sedimentation method and laser diffraction method.

Figure 1. Accumulated Sediment in Nibutani Dam 2. PROCEDURE OF INVESTGATION In the former paper, presented in ICOLD Kyoto 2012, we had reported the results of investigation by analyzing the two samples of turbid water flowing into reservoirs after heavy storm in September 2007. When we presented that paper, we got a comment that we should compare and discuss the differences of settling rate distribution of soil particles instead of grain size distribution. In this paper, we report the settling rate distributions of four samples collected in Yamaguchi River, Tonegawa River System, Ibaraki Prefecture in Japan while in heavy rainfalls in September, 2010 (Fig. 2.). The procedure of investigation will be described below.

IV - 32

CA: Catchment Area

Presented by Geospatial Information

Authority of Japan

Figure 2. Location of Sampling Site 2.1. Measuring Method of Settling Rate Distribution In case of conducting numerical simulation of sediment accumulation in reservoirs, it is necessary to determine settling rate distribution of soil particles. Laser diffraction method has been commonly used for grain size analysis of fine soil particles and settling rate is converted by Stokes’ Formula because these methods do not need much effort to get result. On the other hand, an accurate data of settling rate can be given by conducting settling cylinder method, however, the size of cylinder and measurement specifications have not been standardized. In this report, we conducted three types’ settling rate analysis, i.e., settling cylinder method, centrifugal sedimentation method and laser diffraction method and compared the results. The shape of settling cylinder used in this study is shown in Fig. 3. The specification of measuring method is shown in Table 1.

Yamaguchi R. St.

Sofugamine St.

CA=3.12km2

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200

2200

200

2000

Figure 3. Shape of Settling Cylinder

Table 1. Measuring Method of Settling Rate Distribution Measuring

method Settling cylinder method Centrifugal

sedimentation methodLaser diffraction

method

Measuring instruments

Settling cylinder

φ200mm× L2.2m

SKC-2000

Seishin Co.,Ltd.

SALD-3000S

Shimadzu Co.,Ltd.

Measuring conditions

Constant temperature (20℃)

Range: 0.3μm～50 μm Range: 0.05μm～

3000μm

Measuring items

Water level, Suspended solids (SS),

Water temperature

Grain size distribution Grain size distribution

Measuring procedure

Pouring turbid water until 2m depth. Collecting sample water at 0.5m above bottom.

Analysing SS of water.

Putting 100mL of turbid water into

instrument, and then operating.

Putting 50 to 100mL of turbid water into

instrument, and then operating.

Measuring intervals

13 times. (0hr, 15m, 30m,1hr, 3hr, 6hr, 12hr, 24hr, 3days,

7days, 14days, 21days, 42days)

1 time

1 time

Others Unfixed measuring method Not disseminated Ordinarily adopted

Drain

Unit: mm

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The calculation method of settling rate distribution and the conversion method from grain size into settling rate are as follows: If a particle in water is regarded to settle distance l from water surface to intake within time t , average settling rate )(tw is presented as Eq.1.

( )tltw = (1)

Among time t , the share of already settled suspended solids )(1 tF is equal to the difference of suspended solids between the start of experiment ( 0=t ) and t , so that )(1 tF is presented as Eq.2.

( ) ( )0

01

=

= −=

t

t

SStSSSStF (2)

In Eq.2, SS means suspended solids [mg/L]. In Eq.2, )(1 tF increases gradually with time and one variation of Eq.2 is presented as Eq.3. In this equation, )(2 tF gradually decreases with time and increases with settling rate. Eq.3 is corresponding with setting rate accumulation curve.

( ) ( )0

2=

=tSStSStF (3)

In condition of single globular particle’s settlement, moreover, the Reynolds Number of particle ( ν/se wdR ⋅= , ν is coefficient of kinematic viscosity of water.) is less than 1, both diameter of particle and settling rate can be converted each other.

( )μ

ρρ18

2ws

sgdw −

= (4)

In this equation, settling rate of particle is ws, diameter of particle is d, gravity acceleration is g, density of particle is ρs, density of water is ρw, and viscosity coefficient of water is μ. The diameter d is called Stokes’ Diameter because it is calculated from settling rate by applied Stokes’ Formula. In settling cylinder method, turbid water was poured up to the depth of 2m, then water depth variation and suspended solids were measured at predetermined intervals. As mentioned above, in case of executing numerical simulation on sediment accumulation in reservoirs, laser diffraction method has been commonly used for grain size analysis and settling rate is converted by Stokes’ Formula for fine soil particles. On the other hand, it has been indicated that the settling rate calculated by this method differs from the actual one (KASHIWAI 2006). In settling cylinder method, the settling rate distribution is directly measured by observing the variation of suspended solids with time and this method is regarded to give accurate settling rate.

IV - 35

2.2. Grain Size Calibration Soil colloidal particles contained in turbid water tend to move at random affected by the interaction of surroundings. Because of this movement, soil colloidal particles happen to collide with one another and if strong attraction is acted among these particles a flock could be formed. In case of grain size analysis, a larger distribution could be obtained if flocculated particles are directly measured, so that the settling rate distribution tends to be largely evaluated. A distribution treatment was considered for the purpose of avoiding excess evaluation of settling rate. In this study, distribution treatments were introduced in some cases of both laser diffraction method and centrifugal sedimentation method. An ultrasonic distributor FU-10C manufactured by TGK Co., Ltd. was used for the distribution treatment. The procedure of treatment was to add ultrasonic distribution by ultrasonic distributor of 60W in power and 28 kHz in frequency. The 10 minutes of ultrasonic distribution was given to 1L of turbid water to obtain enough dispersion of particles. The method of distribution is shown in Table 2.

Table 2. Distribution of Soil particles in Turbid Water Distribution methods Measuring method

Non-distribution With distribution

Centrifugal sedimentation method

Stirring by hands 10 minutes of ultrasonic distribution (60W)

Laser diffraction method Stirring by hands 10 minutes of ultrasonic distribution (60W)

2.3. Procedure of Experiment Firstly, we collected turbid water from mountainous river during heavy rainfalls in September, 2010. The sample site was Yamaguchi River, Ibaraki Prefecture in Japan. Sampling was executed once at the time of peak discharge and three times after the peak. Sampling time and analyzed turbidities were shown in Table 3, precipitation data was in Fig. 4., and discharge was in Fig. 5. As mentioned above, settling rates were analyzed by three methods and in some cases the ultrasonic distribution treatments were added. And then, the differences between settling rate distributions were considered.

Table 3. Sampling Time and Analyzed Turbidities Sample No. Sampling Date Sampling time Turbidity Suspended Solids

[NTU] [mg/L]

1 16 SEP 2010 10:55 787 944

2 16 SEP 2010 11:25 432 466

3 16 SEP 2010 12:35 143 189

4 16 SEP 2010 13:50 59 93

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0

2

4

6

8

10

12

14

16

18

20

0.5 6.5 12.5

Time　[h]

Pre

cip

itat

ion[m

m/h]

Precipitation（Sofugamine St.)

0 6 12

Figure 4. Precipitation on Sampling Day

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 6 12 18

Dis

char

ge[m

3/s]

Time ［ｈ］

Discharge

(Yamaguchi River)

↑

↑

↑

↑

↑：Sampling time

Figure 5. Discharge on Sampling Day 3. RESULTS The results of experiments and analysis were shown in Fig. 6. to Fig. 9. Firstly, we consider the results of turbidity (Table 3). The Sample 1 was extracted at the time of peak discharge and it showed the highest turbidity among the four. The analyzed turbidity became lower with decreasing discharge. In this study, we could not extract samples at the

IV - 37

phase of increasing discharge; however, preparatory standby at the sampling site should be taken for investigating turbidity change through all phases. Secondly, we compare the results of settling cylinder method (Fig. 6. to Fig. 9.). These figure show that the particles in the residual ratio have higher rate than the certain settling rate. When we focus on the settling rate of 0.1 cm/s, 57% sediments were faster in Sample 1, 45 % in Sample 2, 33 % in Sample 3 and 22 % in Sample 4. According to the results of settling cylinder method, the settling rate became slower with time at the phase of decreasing discharge. It is regarded that the inflow discharge after the peak does less contribution to the accumulation of sediment in a reservoir; on the other hand, it may cause long-term persistence of turbid water in a reservoir after floods. Thirdly, we take Sample 1 as an example and compare the settling rate among different analysis methods (Fig. 6.). It showed similar curve between settling cylinder method and centrifugal sedimentation method (non distribution), especially in the range of less than 0.01cm/s. On the other hand, the results of laser diffraction method (non distribution) showed relatively faster settling rate distribution compared with settling cylinder method or centrifugal sedimentation method (non distribution). Fourthly, we consider the effects of ultrasonic distribution treatments. The purpose of distribution treatment is to avoid excess evaluation of settling rate. From the results of the Sample 1(Fig. 6.) and Sample 2 (Fig. 7.), the slower settling rates were given in both the centrifugal sedimentation method and the laser diffraction method by adding ultrasonic distribution treatment. From these results, some particles in flooding water form flocks and may cause rapid settlement in a reservoir. In Sample 2, the laser diffraction method with 10 minutes’ ultrasonic distribution treatment shows relatively similar to the results of settling cylinder method.

0

10

20

30

40

50

60

70

80

90

100

1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01

Settling rate ［cm/s］

Pas

sage

rat

io ［

％］

Cylinder

Centrifugal(10min. dist.)

Centrifugal(Non-dist)

Laser (10min. dist.)

Laser (Non-dist.)

Note: dist. means distribution

Figure 6. Settling Rate Distribution (Sample 1)

IV - 38

0

10

20

30

40

50

60

70

80

90

100

1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01


Pas

sage

rat

io ［

％］

Cylinder




Laser (Non-dist.)



0

10

20

30

40

50

60

70

80

90

100

1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01


Pas

sage

rat

io ［

％］ Cylinder




Laser (Non-dist.)



IV - 39

0

10

20

30

40

50

60

70

80

90

100

1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01


Pas

sage

rat

io ［

％］

Cylinder




Laser (Non-dist.)



According to the results of above mentioned examinations, it was found out that similar settling rate distribution to settling cylinder method could be obtained by conducting centrifugal sedimentation method without distribution treatment, however, the results of laser diffraction method gave relatively faster settling rate distribution especially in the slow settling rate range and differed from the results of settling cylinder method. It suggests that if we use laser diffraction method for giving settling rate distribution, it may cause the results of larger accumulation of sediment in a reservoir compared to the actual one. 4. CONCLUSION Through this study three points were concluded. (1) Settling cylinder method was the most reliable for evaluating the settling rate of fine particles. (2) Centrifugal sedimentation method could alternate the settling cylinder method because it gave similar settling rate to the settling cylinder method. (3) In case of using laser diffraction method, grain size distribution similar to settling cylinder method could be obtained by adding ultrasonic distribution treatment. REFERENCES H. Umino, and N. Hakoishi (2012): A Comparative Study on Grain Size Analysis for

Sediments Flowing into Reservoirs, Proceedings of The International Symposium on Dams for a Changing World, ICOLD 2012 Kyoto, CD, 2_184, Kyoto, Japan

J. Kashiwai (2006): Coagulation Effects against Turbidity with Natural Coagulant, Dam Engineering No.236, pp20-pp28 (in Japanese), Japan Dam Engineering Center, Tokyo, JAPAN

IV - 40

Multi-objective Reservoir Optimization upon Pareto Front Considering

Reservoir Sedimentation with Application to the Three Gorges

ProjecthhdTTjjhkljdjjsgshjhfsdkjhskslsl;s;s;;s;;s;;sjsjkjffffrtttttttfggjfgjgkfkjkj

f fffffjfjjfkkfjjj

Reservoir Sedimentation with Application to the Three Gorges Project

F.F. Li, J. Qiu & J.H. Wei Tsinghua University, Beijing,China

[email protected]

ABSTRACT: Among multiple objectives of reservoir operation, increasing power generation and reducing

sediment deposition in reservoir is a pair of great importance, but significantly conflicting

operational goals. To improve the power generation efficiency, a high water level should be

maintained in the reservoir,and thus slow down the flow velocity, therefore, more sedimentation

will be deposited in the reservoir. Due to the contradiction and incommensurability between the

targets, traditional multi-objective optimization methodwhich simply incorporates the targets into a

single objective cannot be usedin multi-objective reservoir operations. Researches onmulti-

objective optimization algorithms found that evolutionary algorithmsare very suitable for solving

this type of problems. Evolutionary algorithms (EA) regard every feasible solution as an individual,

and provide those individuals with better fitness more opportunity to survive by genetic operators,

such as selection, crossover and mutation. This study firstly establishes a formula to calculate the

suspended sediment transport rate for reservoirs according to the diffusion theory and the extended

vertical distribution of suspended sediment. Based on the formula, a multi-objective model

considering simultaneously the sediment transporting efficiency and power generation efficiency is

built, and the Non-dominated Sorting Genetic Algorithm (NSGA) upon ParetoOptimality is used to

find the Pareto Front of the reservoir operation. In this study, the proposed model and method are

applied to the Three Gorges Project in China. A group of measured data of suspended sediment

concentration-relative depth, and flow velocity- relative depth, as well as the actual position and

scale of the spillway are used to calibrate the parameters in the formula calculating the suspended

sediment transport rate. The research results prove the validity of the established multi-objective

reservoir optimization model, and the Pareto Front from the model can provide references for the

practical reservoir operations.

Keywords: Reservoir sedimentation; Multi-objective optimization; Pareto front; The Three

Gorges Project.

1. INSTRUCTIONS

After the completion of the reservoir, the deposition occurs resulting from the raised water

level, and the decreased sediment transport capacity. Reservoir siltation has been one of

the most controversial problems for Three Gorges Reservoir (TGR) from the beginning of

the project. In order to benefit flood control, power generation, navigation, as well as other

designed function, sufficient capacity has to be maintained within the design years for the

TGR. Due to large amount of the sediment load of the Yangtze River, it is necessary to

IV - 41

properly flush the sediment of the river, and take advantage of the abundant runoff of the

Yangtze River to optimize the reservoir operation.

Essentially, the operation of reservoir is a multi-objective optimization problem with

complex constraints, considering power generation, flood control, water supply, irrigation

and other features. However, because of the contradiction and incommensurability between

the power generation and the desilting, the existing studies mainly focus on the theories of

dynamics of river sediment movement, but fail to run in conjunction with other reservoir

targets.

In this study, the power generation benefits and sediment problems are considered

simultaneously, and a multi-objective optimization model is established. A suitable

optimization algorithm for this multi-objective optimization model of cascade reservoirs is

determined.Pareto optimal solutions between improving economic performance and

prolonging service life of reservoirs are found through the change of reservoir operations.

The model presented in this study is applied to the Three Gorges Reservoir (TGR). The

quantitative relationship between enhancing the sediment desiling efficiency and the

responding cost of power generation is analyzed to provide reference for the actual

operation of the reservoir.

2. METHODOLOGY

2.1. Calculation of the suspended load delivery

Gravitational sedimentation causes the vertical concentration distribution of the two phase

flows. From the surface to the bottom, the flow changes from supernatant to turbid flow.

According to the diffusion theory, when the stable sediment concentration distribution of

the suspended sediment occurs along the vertical line, the two-dimensional diffusion

equation for sediment can be expressed as shown in Eq. 1.

+

=0 (1)

Suppose the diffusion coefficient of sediment equals to the momentum exchange

coefficient . From the linear distribution of the shear force in open channel steady

flowsalong the verticalline

, as well as the logarithmic distribution of the

longitudinal velocity along the vertical line

, Eq.2 can be derived:

(2)

where k=0.4, is the Karman constant.

Plugging Eq.2 into Eq. 1and integrating the function, Eq. 3 can be derived.

(

)

(3)

Makingy=a as the reference point, where the sediment concentration is denoted by , Eq.

4 is finally obtained.

IV - 42

(4)

where the exponent Z is expressed as shown in Eq. 5.

(5)

Z is also called suspending indicators. The value of Z in Eq.4 determines the uniformity

degree of the sediment distribution along vertical line. The smaller the Z is, the more

homogeneous the suspended load distributes.

(6)

Eq. 6 is the logarithmic formula of the velocity distribution of turbulent flow. Although it

is derived under the condition near the wall, the experimental research proves that Eq. 6 is

suitable for the entire flowing section except the viscous sublayer.

Using the measured data of runoff and sediment, the parameters in Eq. 4 and Eq. 6 are

calibrated, and thus the vertical distribution of suspended sediment concentration Sv and

velocity U are obtained. According to those distributions, the sediment fluxes at elevation

y per unit time on the flow sectionUSv can be calculated. Integrating USv vertically, the

suspended load discharge per unit can be derived.

The incoming flow into the TGR is larger in flood season, when the water level in front of

the Three Gorges Dam is lower. The reservoir performs characteristics of river channel.

The sediment concentrationand the flow velocity increase significantly, while the

distributions of flow velocity and sediment concentration are not consistent. The surface

flow velocity of the mainstream in front of the dam is greater than other layers. There

appears stratification vertically for the surface, the middle, and the bottom layer. The

sediment concentration at bottom or near the bottom is greater. The main period for

sediment flushing is the main flood season, and the desilting mainlygoes through the

spillway. Calculatingthe average sediment concentration of the spillway with all the

spillway of the Three Gorges Dam open, Eq.7 is derived.

∫

⁄

(7)

2.2 Multi-objective optimization model

Increasing power generation and reducing sediment deposition in reservoir is a pair of

greatly important, but significantly conflicting operational goals. To improve the power

generating efficiency, a high water level should be maintained in the reservoir, and less

water should be discharged, which leads to an increment of water storage and also a

deceleration of the flow, as a result, more sediment is deposited in the reservoir. On the

contrary, if more water is discharged for sediment sluice, the water level will be lowered

and the power generating efficiency is reduced. In order to coordinate the contradiction

between sedimentation and power generation in the reservoir operation, this study takes

maximizing the desilting efficiency and the power generation as the objectives to build a

multi-objective optimization model. The comprehensive benefits of the reservoir are

enhanced by adjust the reservoir operation.

IV - 43

2.2.1 Objective function

(1) Objective 1: Maximizing the power generation of the system

Taking maximizing the power generation as one of the operational objective is to utilize

the water head to increase the generation while reducing the abandoned water. The

objective function can be written as:

∑ ∑ ∑

(8)

where is the total annual power generation; is the average output of each hydro-power

unit; is the time step; is the serial number of the hydropower unit, is the length of the

time.

(2) Objective 2: Maximizing the sediment desilting

Taking maximizing the sediment desilting of reservoir as another objective of reservoir

operation, the sediment should be flushed away by releasing flood waters through spillway

in flood season. The incoming sediment of the TGR mainly comes from flood season, thus

increasing the sediment desilting in flood season according to the calculation equation in

Eq.7, the objective function can be written as:

∑

(9)

where is the suspended sediment discharge from the TGR, with unit ; is the flood

discharge, is the average sediment concentration in the spillway, calculted by Eq.7, with

unit kg/m3.

2.2.2 Decision variables

According to Eq.8 and Eq.9, discharge not only influences power output of the TGR, but

also determines the suspended load of sediment desilting. Hence the discharge from the

TGR is selected as the decision variables. At the same time, the turbine discharge being

used for power generation is distinguished from the flood discharge through the spillway.

In non-flood season, the turbine discharge is regarded as the decision variables; while in

flood season, both the turbine discharge and the flood discharge are considered as the

decision variables. Since the flood season for the TGR lasts for 4 months from June to

September, taking month as the time step, the decision variables can be expressed as:

(10)

When applying Genetic Algorithms (GA), there are 16 genes on each chromosome.

2.2.3 Constraints

The constraints of the operation of the TGR can be classified into:

(1) Constraint on water level

In order to ensure the security and protect the district downstream, the TGR has to reserve

some flood control storage to lower the water level below the flood control level. The

regulation rule also needs to be followed in non-flood season. The safe operation of the

TGR is realized by the control of the water level:

(11)

IV - 44

where and

are the allowable lowest and highest level during time ,

respectively.

(2) Constraints on the water discharge of the reservoir

The lower limit of the water discharge from the TGR is to satisfy the needs of navigation

and ecology, while the upper limit of the discharge is the maximum allowable discharge of

the reservoir. Hence, the optimization needs to search the optimum in a large range, and

thus brings about a large number of infeasible solutions. These infeasible solutions lead to

extreme results such as emptying the reservoir or overtopping the dam. The population is

inundated with invalid individuals.

In order to improve the efficiency of the GA, the limits of the discharge of the TGR are set

according to the incoming inflow and the actual operation process, as shown in Eq. 12.

(12)

where and

are the minimum and maximum of the inflow in current month,

respectively; and

are the minimum and maximum of the actual

discharge in current month, respectively.

(3) Constraints on daily amplitude of variation

As the largest river in China, the Yangtze River undertakes important navigation tasks.

Thus not only the water level of the channel needs to achieve a certain height, but also the

variation of the water level cannot be too violent.

All the constraints are realized by two means: either being satisfied automatically when the

initial and new populations are generated, or being checked after the calculation. The

infeasible solutions are eliminated without taking part in evolution.

2.2.4 State equations

State equations refer to the hydraulic and electric conditions during the calculation,

classified into:

(1) Water balance equation

(13)

where is the storage; is the incoming inflow; is the total discharge of the

TGR, including turbine discharge and the flood discharge .

(2) Water level- storage curve

The relationship between water level and the reservoir storage is presented by piecewise

linear interpolations function :

(14)

where is the water level of the reservoir.

IV - 45

(3) Tailwater level- discharge curve

The relationship between tailwater level and the discharge is also presented by piecewise

linear interpolations function :

(15)

where is the tailwater level.

(4) The characteristic curve of unit output

When the water head is settled, the power output of hydropower unit can be expressed

as the function of the turbine discharge :

(16)

(5) The vertical distribution curve of the velocity

The logarithmic velocity distribution formula in Eq. 6 is adopted to fit the vertical

distribution curve of the velocity in front of the dam, using measured data. The flow

velocity can be presented as a function of the relative depth :

ℎ (17)

(6) The vertical distribution curve of the suspended load concentration

The vertical distribution curve of the suspended load concentration is calculated by the

formula in Eq. 4, using the measured velocity data. The suspended load concentration is

the function of the relative depth :

(18)

2.3 Multi-objective optimization algorithms

Multi-Objective Genetic Algorithm (MOGA) is based on genetic algorithms, the research

of which in recent years mainly tends to optimization method upon Pareto optimum. The

basic idea of MOGA is to construct the Pareto non-dominated set of the population, and

make the set approach the optimal boundary closer and closer by evolutionary. Before the

convergence of the algorithms, such a non-dominated set is the local optimum. A new non-

dominated set is constructed for each iteration of the algorithm, i.e. each generation of the

evolutionary.

For a tentative exploration, the MOGA used in this study is relatively simple, mainly

including the following steps:

(1) coding of the chromosome;

(2) calculating the objective function;

(3) genetic operation: selecting m individuals with better objectives from n chromosomes

to proceed crossover and mutation, and generating new population.

After a certain number of generations, the iteration is stopped, and a Pareto Front is

obtained.

3. RESULT

IV - 46

The parameters in this study are set as follows: initial population size: 100; iterations: 100;

the sediment concentration at the spillway in flood season: 0.066738 kg/m3; crossover

probability: 0.75; mutation probability: 0.02; and the variation amplitude of the daily

discharge is 500 m3/s.

Figure 1 shows the evolutionary process of the Pareto Front. The green scatters signify the

objective values of the initial population; the blue data points indicate the objective values

of the non-dominated individuals after iteration once, i.e. the Pareto Front. The red points

are the Pareto Front after 5 iterations. Similarly, the pink points and the cyan points are the

Pareto Front after 10 iterations and 25 iterations respectively, both of which almost overlap

on the black points indicating the Pareto Front after 100 iterations. Thus, the algorithm

converges quickly to the optimum right after 10 iterations.

Figure 1. Evolutionary process of the Pareto Front. Extracte the Pareto Front information of the 100

th iteration in Figure 1 to analyze. The

maximum annual power output of the Pareto optimum in the 100th generation and

corresponding sediment discharge are shown in Table 1, as well as the maximum annual

sediment discharge and corresponding power output.

Table 1 Analysis on Optimums of Pareto Front

Max Power

Output

(x107kw)

Corresponding Sediment

Discharge

(x108t)

Max Sediment

Discharge

(x108t)

Corresponding Power

Output

(x107kw)

8.1151

(+5.29%)

0.1003

(+0.10%)

0.1033

(+3.09%)

7.8733

(+2.15%)

Comprehensive analysis on Figure 1 and Table 1 implies:

IV - 47

(1) The number of the non-dominated solutions decreases with the iteration going on.

Such property indicates the convergence of the algorithm. GA has been proved being

convergent, i.e., it will finally converges to a certain Pareto Front if the iteration is infinite.

(2) Both the power generation and the sediment desilting have room for optimization.

From Table 1, it can be told that there are optimizing rooms for both the power generation

and the sediment desilting. The maximum annual power output can be enhanced by 5.29%

with the cost of increasing 0.10% sedimentation; while the maximum annual sediment

desilting can be improved by 3.09%, with the annual power output only increasing 2.15%.

It should be illustrated that this study takes the historical hydrologic series as the input

without taking the uncertainty of the inflow into account. Thus the result here only

provides a theoretical optimal operation given the known inflow.

ACKNOWLEDGEMENT

This work was conducted in collaboration with the China Three Gorges Corporation, supported by

“Key Projects in the National Science & Technology Pillar Program during the Twelfth Five-year

Plan Period (Grant No. 2013BAB05B05 & No. 2013BAB05B03)”, and “China Postdoctoral

Sustentation Fund(Grant No. 2012M521488 & No. 2013T60104)”.

REFERENCES

Srinivas, N., Deb, K. (1994): Multi-Objective function optimization using non-dominated

sorting in genetic algorithms, Evolutionary computation, 2: 3, 221-248.

Alexandre, M.B., Darrell, G.F. (2008): Use of Multi objective Particle Swam Optimization

in Water Resources Management [J], Journal of water resources planning and

management, 134: 3, 257-265.

Chen L., McPhee, J., Yeh, W.W.G. (2007): A diversified multi-objective GA for optimizing

reservoir rule curves [J], Advances in water resources, 30:1082-1093.

Janga, R.M., Nagesh, K.D. (2007): Multi-objective differential evolution with application

to reservoir system optimization [J], Journal of computing in civil engineering, 21: 2,

136-146.

Li, F.F., Shoemaker, C.A., Wei, J.W., Fu, X.D. (2012): Estimating maximal annual energy

given heterogeneous hydropower generating units with application to the Three

Gorges system, Journal of water resources planning &management, 139: 3, 265-276.

Li, F.F., Wei, J.W., Fu, X.D., Wan, X.Y. (2012): An effective approach to long-term

optimal operation of large-scale reservoir systems: case study of the three gorges

system [J], Water resources management, 26: 14, 4073-4090.

IV - 48


Bali, Indonesia, June 1

ST – 6

TH , 2014

How water column stability affects the surface chlorophyll a in a deep

hhdTTjjhkljdjjsgshjhfsdkjhskslsl;s;s;;s;;s;;sjsjkjffffrtttttttfggjfgjgkfkjkjf fffffjfjjfkkfjjj subtropical reservoir and the time lags under different nutrient backgrounds?

2(14pt)

M. Zhang & Z.Y. Sun

M. Zhang & Q.H. Cai Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China

ABSTRACT Cyanobacterial blooms are threatening the sustainable uses of the water resources in large

reservoirs, therefore a better understanding of how to control the cyanobacterial blooms is

urgently needed. Hydrodynamic conditions are considered to be very important to the control of

algal blooms. However, many traditional studies used weekly or daily measurements, which may

miss important event of physical process of the water-body, and cause inaccurate evaluations. In

this study, high frequency (15-min interval) measurements of the water column stability using

thermistor chains was used to analyze the effect to the surface chlorophyll a (Chl a), and the time

lags under different nutrients backgrounds in the Xiangxi Bay, Three Gorges Reservoir, China.

Cross-correlation analysis between the relative water column stability (RWCS) and Chl a was

performed in different stages divided by TN/TP ratio = 29. The results showed that water column

stability above the euphotic depth influenced surface Chl a most significantly. Lower RWCS (< 20)

could limit the increase of the Chl a concentration; higher RWCS caused significant increase of the

Chl a only when the nutrients were not limited (TN/TP < 29). In the water-body with very low Chl

a concentration (almost 0), about 2 days were needed to cause the significant increase of Chl a.

During the bloom period, decline of RWCS could decrease the Chl a significantly in a very short

time (about half an hour). Therefore, we could reduce the water column stability to control the

cyanobacterial bloom through regulating the water level of the reservoir.

Keywords: hydrodynamic; time lag; high-frequency monitoring; Three Gorges reservoir

1. INTRODUCTION

The growth of phytoplankton is regulated by a variety of environmental factors, e.g.

nutrients, light, water temperature, predator, hydrodynamic conditions, etc. (Paerl and

Huisman 2008, Bouman et al. 2011). All of the factors impact directly or indirectly the

general phytoplankton composition, through their synergistic effects. High concentrations

of nutrients are indispensable to the algal blooming, but not the determined factor. In some

areas, the algal blooms always break out accompanying with the increased water

temperature, and the presence of the stratification (Bleiker and Schanz 1997, Carrias et al.

2001). Some studies found that the blooms did not break out in the littoral zones with high

China Three Gorges Corporation, Beijing, P. R. China

[email protected]

IV - 49


levels of nutrients content, but in the pelagic zone with weak water disturbance

(Buranapratheprat et al. 2008).

In light of the important role of hydrodynamics to the breakout of the algal blooms, many

researchers focused on the study of the hydrodynamics conditions’ effect in recent years,

especially the influence of the water mixing regime, water retention time and water column

stability relevant with stratification. Becker et al (2010) found that, in a deep

Mediterranean reservoir, increases in water-column stability during spring stratification led

to phytoplankton biomass increases due to the dominance of small flagellate functional

groups. Jones and Elliott (2007) found that the shortage of the water retention time under a

fixed nutrient load resulted in a reduced chlorophyll concentration; longer water retention

time caused the spring bloom to start earlier and the autumn bloom to persist longer.

Despite the hydrodynamic conditions are of great importance, most previous studies

always used discrete weekly or daily data to assess the hydrodynamic conditions and

evaluate the effect to phytoplankton (Coloso et al. 2008). In reservoirs, however,

hydrodynamic conditions change frequently due to water level fluctuations and the diel

variations of the water temperature. Weekly or daily measurement may miss the important

event of the physical processes, e.g. deepening of the stratification, and lead to the

imprecise estimation about the effect of the hydrodynamic parameters. Additionally,

organisms cannot immediately track the environmental changes. There are specific time

lags between physical disturbance and their influence to the phytoplankton (Millet and

Cecchi 1992). Therefore, high-frequency and continuous monitoring becomes more

important. In recent years, auto-monitoring devices have been used widely (Staehr et al.

2010, Coloso et al. 2011). In this study, we measured the water temperature profile and

chlorophyll a using a automated device at high-frequency, in order to analyze more

accurate quantitive relationships between hydrodynamic parameters and chlorophyll a.

In view of previous studies revealed that light, temperature and nutrients are essential to

the algae growth, we hypothesized that the water column stability plays an important role

in algal blooms dynamics when the resources (light, temperature and nutrients) are

available. To test our hypothesis, we divided the study period into several stages according

to the availability of the resources, analyzed the correlations between the water column

stability and surface chlorophyll a content in different stages, and discussed the time lags

between them. Although it may be very important to the phytoplankton community

composition, we did not consider the zooplankton grazing in this study, because it is also

influenced by the water column stability (Coyle et al. 2008).

2. MATERIALS AND METHODS

2.1 Study Site

The sampling site is located in the middle region of the Xiangxi Bay, Three Gorges

Reservoir (TGR) of China (Fig.1). TGR is the largest man-made reservoir in China, with

flood control as the most important task. Xiangxi river, is the largest tributary of the TGR

near the dam. Since the impoundment of the TGR in June 2003, the lower reach of the

river evolved as the Xiangxi Bay. As the slowing down of the water velocity and the

prolonging of the water retention time, the risk of the eutrophication increased. The algal

blooms broke out more frequently and seriously, especially in the middle region of the bay

IV - 50

(Ye et al. 2007, Xu et al. 2009). This region belongs to the lacustrine zone according to the

zonation theory of Straskraba and Tundisi (Straskraba and Tundisi 1999). The stable

environment of this zone contributed a lot to the outbreak of the algal blooms.

Figure 1. Location of the study site

2.2 Field Sampling and Data Analysis

The survey was carried out during the flood season of 2008 in the Xiangxi Bay.

Cyanobacterial blooms broke out from 1 June to 23 July. The monitoring site is located at

the Xiangxi Ecosystem monitoring station of Chinese Academy of Sciences/China Three

Gorges Corporation (Fig. 1). During the study period, water level of the TGR fluctuated

between144.66 and 146.84 m (Fig.2). The depth of the study site ranged from 12.3 ~ 14.5

m, and less than 13.0 m in most time. Therefore, we consider 12 m as the depth of the

whole water column.

Figure 2. Water level fluctuations (m above sea level, m a.s.l.) of the Three Gorges Reservoir from

1 June to 23 July of 2008

Water samples were collected (0.5m underneath the surface) every day, except 5 to 18 June

when weekly samples were collected, for water chemistry analysis (total nitrogen (TN),

IV - 51

total phosphorus (TP)). The samples were stored in a plastic bottle pre-cleaned and

acidified to pH < 2 with sulfuric acid. The water chemistry was measured with a

segmented flow analyzer (Skalar San++, Netherlands). Simultaneously with the water

sampling, transparency (Sd) was measured using 20 cm diameter Secchi disk.

Photosynthetically available radiation (PAR) was monitored using a quantum sensor (Li-

cor 192SA, the Unite State of America (USA)) at 5-min intervals from 6:00 to 19:00

during the daytime. The depth of the euphotic zone was calculated as 2.7 times the

transparency (Cole 1994). The water level data of the TGR was provided by China Three

Gorges Corporation. The surface chlorophyll a (Chl a) was measured with a multi-

parameter water quality sonde (YSI, EDS 6600V2, USA). The measurements of water

temperature profile were carried out using a thermistor chains. Both the measurements

were 15 min intervals. The thermistor was placed at 1 m intervals from 1 m to 12 m. The

YSI and thermistor chains were combined by a data logger device (EcoTech Umwelt-

Meßsysteme, GmbH, Germany), in order that they could make the synchronous

measurements.

Relative water column stability (RWCS) was used to describe the hydrodynamics

conditions (Padisák et al. 2003), as Eq. 1:

(1)

in which: Db: density of the bottom water; Ds: density of the surface water (1m); D4, D5:

the water density at 4℃ and 5℃ respectively.

High values of stability indicate water column stratification, while low stability signifies

mixing. In order to identify the depth which could cause significant effect to the surface

Chl a, we calculated the RWCS of each depth from 2 m to 12 m at 1 m intervals. For

example, the relative stability of the column above 3m, we call it 3m-RWCS (Db is the

water density of 3m), and the relative stability of the column above 12m, we call it 12m-

RWCS (Db is the water density of 12m).

Cross-Correlation analysis was used to display the correlationships between the time series

over a selected range of time differential (lags), using SPSS 16.0 software. The 15-min-

interval data was used, therefore, 1 lag represents 15 minutes. In the analysis, we set the

maximum lag number as 400, and compared the cross-correlation coefficients (CCF) under

different lags between RWCS and Chl a.

3. RESULTS

3.1 Physical and Chemical Conditions

The daily PAR showed the highest value in 26 June and 8 July (Fig. 3), 1161 and 1172

μmol·s-1

m-2

, respectively. But the instantaneous maximum appeared in 11:00 ~ 12:00 on

23 June, with PAR higher than 2420 μmol·s-1

m-2

. The fluctuation of PAR was not

remarkable, except in7 ~ 9 June, 20 ~ 22 June and 22 July, with PAR less than 300 μmol·s-

1 m

-2. The euphotic zone was very deep in the beginning of the study period, and became

shallower after 11 June, (Fig. 3) with the average euphotic depth 3.83 m (range: 0.54 ~

10.26 m). It ranged from 2 m to 5 m in most time. Surface water temperature in the

IV - 52

Xiangxi Bay fluctuated between 23.06 and 30.75 ℃, and exceeded 25℃ in most time.

There were evident stratifications, especially when water temperature increased (Fig. 4).

Figure 3. Variations of the daily photosynthetically available radiation and the euphotic depth in

the Xiangxi Bay from 1 June to 23 July of 2008.

Figure 4. Isolines of daily average water temperature (WT) profile, and daily average relative

water column stability (RWCS) of different water column (2m water column to 12m water column,

1m interval) in Xiangxi Bay from 1 June to 23 July of 2008. The white area is bottom of the bay.

Corresponding to the water stratification, the RWCS increased as the stratification became

more evident (Fig. 4). RWCS of the upper water column was much lower comparing to

that of the whole water column (12 m), and it showed marked fluctuations, implying the

water exchange in the upper water column was very frequent. RWCS was much lower

before 9 June, especially that of the upper water column. From 10 June, it gradually

increased and reached the peak on 14 June, however, the increasing magnitude of 2m-

RWCS was very small. Then, it experienced several times obvious fluctuations.

TN content ranged from 1.14 to 2.30 mg/L, and TP ranged from 0.022 to 0.125 mg/L (Fig.

5). TP showed a temporal pattern of “high-low-high-low”, with evident decrease in the end

of June and July, which caused the fluctuations of TN/TP ratio.

3.2 Surface Chlorophyll a

Two phases could be obtained based on the fluctuations of Chl a: 1 ~ 29 June, and 30 June

~ 23 July. The maximum of Chl a concentration in the first phase was 75.30 μg/L (14

June), and 46.70 μg/L in the second phase (16 July) (Fig. 6).

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53-14

-12

-10

-8

-6

-4

-2

0

20

21

22

23

24

25

26

27

28

29

WT (℃ )

Depth

(m

)

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 1 3 5 7 9 11 13 15 17 19 21 23

June July

IV - 53

Figure 5. Daily variations of the nutrients in surface water in the Xiangxi Bay from 1 June to 23

July of 2008. The dot line in the figure of TN/TP ratio represents TN/TP = 29.

Figure 6. Variations of the Chl a in the Xiangxi Bay from 1 June to 23 July of 2008

3.3 Cross-Correlation Analysis between Water Column Stability and Chlorophyll a

In order to confirm the hypothesis we proposed, we need to divide the whole study period

into several stages according to the availability of these resources. Light is the essential

condition for the phytoplankton growth, but it could not be the limiting factor for algal

blooms, especially, cyanobacteria dominance is related to the low light intensity (Mur

1983). Therefore, we consider the PAR of the Xiangxi Bay during the study period cannot

limit the phytoplankton growth. Cyanobacteria generally grow better at higher temperature

(often above 25 ℃) than do other phytoplankton species such as diatoms and green algae

(Jöhnk et al. 2008, Paerl and Huisman 2008). However, it is not necessarily inevitable that

cyanobacteria will grow to “bloom” proportions in aquatic ecosystems (Brookes and Carey

2011). Thereby, we considered the water temperature in the study period also could not be

the limiting factor for cyanobacteria growth.

The research of Smith (1983) indicated that, cyanobacteria tended to be dominant in low

TN/TP ratio waters. When TN/TP ratios are greater than 29, it would limit the

cyanobacteria dominance. Therefore, in this study, the whole survey period was divided

into 4 stages according to TN/TP ratio = 29: S1 (1 ~ 17 June); S2 (18 June ~ 1 July); S3 (2

~ 14 July); S4 (15 ~ 23 July). Among the 4 stages, weekly monitoring of water chemistry

IV - 54

was performed from 6 to 17 June of S1, we considered those days as one stage according

to the overall changing trend of TN/TP ratio.

Cross-correlation analysis was carried out between RWCS above different depth and Chl a

of different stages (S1 ~ S4 and the whole period). We extracted the highest CCF and the

relative lag number (Table 1).

Table 1. The Cross-Correlation Coefficient and the lag number between the RWCS of each layer

and the surface chlorophyll a (p < 0.05). A: all data during the study period. (1 lag represents 15

minutes)

RWCS

2m 3m 4m 5m 6m 7m 8m 9m 10m 11m 12m

A CCF 0.28 0.32 0.34 0.32 0.28 0.25 0.21 0.18 0.17 0.14 0.13

lag 195 101 103 104 97 97 97 98 97 97 97

S1 CCF 0.49 0.61 0.69 0.70 0.69 0.66 0.64 0.60 0.54 0.47 0.44

lag 202 202 202 200 200 200 199 199 200 200 200

S2 CCF -0.32 -0.40 -0.47 -0.49 -0.46 -0.41 -0.38 -0.37 -0.37 -0.37 -0.37

lag -109 -112 -112 -112 -112 -111 -125 -207 -207 -207 -312

S3 CCF 0.43 0.54 0.62 0.64 0.63 0.58 0.51 0.46 0.40 0.34 0.28

lag 0 0 3 2 2 2 2 2 2 2 2

S4 CCF 0.42 0.60 0.51 0.39 0.30 0.34 0.32 0.27 0.19 0.11 0.04

lag 0 2 3 2 2 2 2 2 2 3 3

The whole period: When the data of the whole study period entered the analysis, the

relationship between RWCS and Chl a was significant, but the CCF was very low.

S1: About 200 lag number (50 hours) was found for the response of Chl a to changes of

RWCS. The highest CCF appeared between 5 m-RWCS and Chl a, indicating the stability

of the water column above 5 m caused most significantly effect to surface Chl a. S2: All of

the lag numbers were minus, indicating no significant effect was caused by RWCS to Chl a.

S3: The lag number between 2m-RWCS and Chl a, and 3m-RWCS and Chl a were both 0,

implying that Chl a responsed quickly following thedisturbance of the water column above

2m and 3m. The response time of Chl a to the RWCS of other water columns was 30 min

(2 lags). The CCF between 5m-RWCS and Chl a showed the highest value. This indicated

that, the disturbance of the upper 3m water column caused simultaneous influence to the

surface Chl a, but the effect of RWCS above 5m was most prominent. S4: Similar with S3,

the changes of 2m-RWCS affected significantly Chl a immediately, but the influence of

3m-RWCS was most remarkable, with the lag delay 30 min (2 lags).

4. DISCUSSION

Light is inevitable for the phytoplankton growth, and very important to the accumulation of

the phytoplankton biomass (Mitchell et al. 1991). Euphotic zone is the maximum depth of

the light zone suitable for phytoplankton photosynthesis. It could influence the vertical

distribution of the phytoplankton biomass (Becker et al. 2008, Znachor et al. 2008). After

11 June, the euphotic depth in the Xiangxi Bay ranged from 2m to 5m. At the same period,

the average residence depth of the cyanobacteria also fluctuated between 2m and 5m

(Wang et al. 2011). In S1 and S3, what influenced the surface Chl a most significantly was

the stability of the upper part of the water column, especially the water column above 5m.

IV - 55

Therefore, we concluded that, during the bloom period, cyanobacteria mainly concentrated

in the euphotic zone, and the stability of the water column above the euphotic depth caused

most remarkable effect to the surface Chl a concentration.

Water column stability is one of the most important factors influencing the prevalence of

cyanobacteria (Bouman et al. 2011, Brookes and Carey 2011). Cyanobacteria can benefit

from their vertical migration in the stratified water, by regulating their buoyancy which

give them the advantage in competing with other species (e.g. diatoms, green algae) for

nutrients and light (Dokulil and Teubner 2000, Jöhnk et al. 2008). But in those regions

with high river flow or short residence time, the intensive water disturbance could limit the

phytoplankton biomass (Alpine and Cloern 1992). During our study period, there was a

similar fluctuation trend between RWCS and Chl a. In the beginning of S1, RWCS was

usually lower than 20, especially in the water column above 5 m. Therefore, the Chl a

concentration was very low although the nutrients contents and the TN/TP ratio were all

suitable. We concluded that lower RWCS (< 20) of the water column restrained the growth

of the phytoplankton and limited the cyanobacteria bloom.

As the increase of the RWCS, together with enough nutrients, Chl a concentration

increased in S1. However, it decreased in S2 although RWCS was similar with that in S1.

Higher TN/TP ratio usually limited the cyanobacteria dominance (Smith 1983), and

therefore the higher TN/TP ratio in S2 caused the decrease of the Chl a. This confirmed

our hypothesis that high RWCS could trigger the cyanobacterial bloom only when the

nutrients, water temperature and light could not be the limiting factors.

Time lags, or delays, are common in many systems. For example, the effect of toxic

phytoplankton bloom to zooplankton mortality occurs after some time lapse (Sarkar et al.

2007); bacterial biomass was positively correlated with Chl a with a time lag of 4 days

(Weisse et al. 1990). Some researcher also studied the time lags between Chl a and the

environmental factors, e.g. the study of Nezline and Li (2003) in the Santa Monica Bay

indicated that chlorophyll biomass correlated significantly with air temperature with a time

lag of 5 days. These studies usually considered only one environment factor, and neglected

the synergistic effect caused by other factors. In this article, if we did not consider the

effect of nutrients and used all data of the study period to perform the analysis, a

significant correlationship and the relative lag time could also be obtained, but with lower

CCF and inaccurate lag time. The analysis based on the data of different stages, however,

indicated the lag time was different under different backgrounds. The correlationship was

positive both in S1 and S3, while the response time of Chl a to RWCS was different, 50 h

and 30 min, respectively. S1 and S3 were the two phases of this cyanobacterial bloom.

Usually, the phytoplankton biomass of the first algal bloom decreases due to the nutrients

exhaustion. Then with recharged of the nutrients and the favorable water environment, the

second phytoplankton bloom would break out rapidly (Weisse et al. 1990). This could be

one of the main reason why the response time in S3 was much shorter than that in S1.

Additionally, the average 5m-RWCS during the Chl a increase period of S1 (1 ~ 15 June)

was 32.52 (range: 0 ~ 112.15), while that in S3 was 69.49 (range: 5.74~ 189.42), impling

that higher RWCS could be another main factor causing the increase of the surface Chl a in

a short time.

It is clear that short-term dynamic of the water column stability, especially the stability of

the upper part water column could impact the surface Chl a significantly. When nutrients,

water temperature and light are sufficient, stable water environment could cause the

IV - 56

prominent increase of Chl a within about 2 days, and lower stability (less than 20) could

limit the cyanobacteria growth. Water column stability is usually depends on water

temperature, water disturbance and residence time. Temperature could not be controlled

artificially, but the other two factors are related to the water level fluctuations of the

reservoir. As a highly regulated man-made system, the water level fluctuations of

reservoirs mainly depend on the inflow discharge from upstream and the water demand of

the downstream. Therefore, in the prevalence period of cyanobacterial blooms, we could

reduce the water column stability to limit the algae growth by regulating the water level

fluctuations of the reservoir, in order to control the cyanobacterial blooms.

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http://www.sciencedirect.com/science/journal/07692609

http://www.sciencedirect.com/science/journal/07692609

Study and practice of reducing sedimentation in the tail area of the Three Gorges Reservoir

Zhou Man

China Three Gorges Corporation, Yichang,, China [email protected]

Hu Xinge

China Three Gorges Corporation, Yichang,, China

Xu tao China Yangtze Power Co., Ltd., Yichang, China

ABSTRACT: After the impoundment of the Three Gorges Reservoir, major erosion period in the tail area changes from September and October under natural condition to fluctuating period from April to June. In order to increase the erosion in fluctuating period and reduce the sedimentation in local reaches which may block navigation. Regulations to reduce sedimentation in the tail area of the reservoir are presented based on one-dimensional unsteady flow-sediment model. The results show that the optimal operation schemes with high erosion are as follows: the water level in front of the dam is in the range of 160~162m; the discharge at Cuntan hydrometric station is above 7000m3/s; and the rate of declining water level is between 0.4m/d to 0.6m/d. According to the results above, experiments were successfully carried out in the fluctuating period of 2012 and 2013. The total measured erosion quantity in the tail area are 2.411 million m3 and 4.413 million m3 respectively, which imply good effects on reducing sedimentation. Besides, the measured data in 2012 are used to validate the mathematical model. Comparison between the measured data and the calculated results show that the model is essentially effective on qualitative calculation and basically reasonable for quantification in most of the reaches. Keywords: sediment; reducing sedimentation; practice; the Three Gorges Reservoir 1. GENERAL INTRODUCTIONS Sedimentation of the Three Gorges Reservoir involves a series of important problems, such as lifespan of the reservoir, flood level raised in the terminal of backwater zone, the influence to navigation in the tail reaches (from Dadukou section to Fuling section in Chongqing, including the Jialingjiang river), as well as the sediment erosion downstream the dam[1]. Among all the problems, sediment erosion and deposition in the tail reaches has a critical priority. The main conclusion of this problem in the preliminary design is that the navigation condition and wharf operation can benefit from the initial normal operation of the reservoir under the conditions of “hydrologic series in the 1960s regardless of the reservoirs upstream”. In the middle and later periods of the reservoir operation, the wharf operation will be affected by deposition and navigation-obstructing gradually. However, sediment problem in the tail reaches can be solved by optimizing reservoir operation and improving channel[1].

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Since impoundment in 2003, the inbound sediment of the Three Gorges Reservoir has largely decreased compared to the preliminary design, which creates opportunities to optimize operation. Measured data show that the sediment deposition is better than expectation in the preliminary design. Yet, major period of erosion in the tail reaches changes from September and October under natural condition to fluctuating period from April to June because of impounding water in advance. In addition, after experimental impoundment of 175m water level, as the water level rising in the flood season, sediment deposition is gradually increasing upstream[4]. Erosion occupies the main position in the tail reaches, but a cumulative deposition appears in local area, which may have adverse effect on navigation. In this paper, in order to increase the erosion and avoid adverse effect on navigation, one-dimensional unsteady flow-sediment model is adopted to study the regulations of reducing sedimentation in the tail reaches, attempting to benefit the navigation by optimizing operation of the Three Gorges Reservoir. 2. RESERVOIR OPERATION AND CHANGES OF SEDIMENT EROSION AND DEPOSITION 2.1. Reservoir operation The arrangement of the Three Gorges Reservoir impoundment in preliminary design is as follows: storage level is raised to 135m in 2003, entering cofferdam power generation period; storage level is raised to 156m in 2007, entering the stage of initial operation. How to raise the storage level up from 156m to the normal storage level 175m depends on the resettlement situation, and the observed sediment deposition in Chongqing port, the tentative schedule of which lasts for 6 years [1]. When the reservoir reaches the normal water level of 175m, in the flood season from June to September the water level must be maintained below the flood control level of 145m. When the inbound flow of the Three Gorges Reservoir is more than 55000m3/s, the reservoir is put into the operation of flood control. After the flood, the level drops to the flood limit level. The reservoir begins impoundment again in October after flood season[1]. Compared with the preliminary design, since impounding of the Three Gorges Reservoir, the work of complex construction, relocation and resettlement, geological disaster prevention have been ahead of the initial design and sedimentation situation is better than anticipated. Phased impounding is achieved ahead of schedule. Storage level reached 156m in October 2006, a year in advance compared to the preliminary design. On September 28th, 2008, the Three Gorges Reservoir started to experimentally impound water to the normal level of 175m, 5 years ahead of the preliminary design[3]. Simultaneously, compared with the preliminary design, the operational conditions have changed greatly since the impoundment of the Three Gorges Reservoir, such as the constructions of the reservoirs upstream, the reduction of the inbound flow and sediment, and the increase of the water utilization. Under the new conditions, from 2008 to 2012, regulations were optimized, including impounding water in advance, raising limit water level, regulating small and medium floods, illustrated specifically as follows : (1) water storage time is changed from October 1st in the initial design to September 28th, September 15th, and September 10th step by step; (2) the highest level can be raised to 146.5m without increasing the burden of the flood control downstream; (3) based on real-time rainfall forecasting, small and medium floods are utilized. Then comprehensive benefits such as flood control, power generation and navigation are improved through the optimized regulations.

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2.2. Changes of sediment erosion and deposition 2.1.1. The sediment erosion and deposition on the whole From 2003 to 2012, due to the sediment blocking of the upstream reservoirs, conservation of water and soil, as well as climate change, the annual inbound sediment is 190 million tons, which is 62.7% less than the initial design (509 million tons). And the annual inbound sediment will continue reducing with the reservoirs upstream gradually put into operation. In 2013, due to the impoundment of the Xiangjiaba and Xiluodu power station, the annual inbound sediment is only 130 million tons. As the inbound sediment reduces greatly, the average annual sediment deposition (144 million tons) is only 42% of the preliminary design. After the optimized operations are carried out in the Three Gorges Reservoir, the average annual deposition is only 45% of the initial design. As to the distribution of sedimentation, the deposition area is gradually moving upstream with the impoundment. However, 99% of the deposition is below 145m, the dead water level of the Three Gorges Reservoir. Only 1% is in the fluctuating backwater zone. 2.1.2. Features of sediment erosion and deposition in the tail reach Table 1. Erosion and deposition in the main urban area of Chongqing (from September 5th, 2008 to

October 15th, 2012) The depth of erosion and deposition

(m) reaches The quantity of erosion and

deposition (million m3) average maximum

The whole reach -2.284 -0.07 8.7 The upper reaches of Chaotianmen

-2.216 -0.14 2.7

The lower reaches of Chaotianmen

0.057 0.01 8.7

The Jialingjiang river

-0.125 -0.01 3.2

+: deposition; -: erosion Major period of erosion in the tail reaches is from the middle of September to the middle of October under natural condition (the discharge at Cuntan hydrometric station is between 12000 to 25000m3/s). Second period is from the middle of October to the end of December (the range of the discharge at Cuntan hydrometric station is 5000～12000m3/s). Sediment stops moving when the discharge at Cuntan hydrometric station is less than 5000m3/s. After the experimental impoundment to the water level of 175m, deposition is gradually replaced by erosion from the middle of September to the end of December under natural condition. Major period of erosion in the tail reaches changes to fluctuating period. From September 5th, 2008 to October 15th, 2012, features of sediment erosion and deposition in the tail reach are different from year to year. In the flood season, deposition occurs in most of the years except for the year of 2010. The inbound flow and sediment are relatively high in the year of 2012 with the deposition of 2.756 million m3. In the impoundment period, deposition exists in 2008, 2010 and 2011, yet little erosion exists in 2009. In fluctuating period, erosion is dominant in most of years except 2010. The erosion quantity is larger in fluctuating period with large deposition in flood season and impoundment period[4]. As to the distribution of deposition, the erosion quantity are 2.216 million m3 and 125 thousand m3 in the Jinglingjiang river and the upper reaches of Chaotianmen respectively, and the

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deposition quantity in lower reaches of Chaotianmen is 57 thousand m3, as demonstrated in Table 1, which has no impact on navigation. 3. PROPOSAL FOR THE REGULATION OF REDUCING SEDIMENTATION Regulation of reducing sedimentation in fluctuating period in the tail reach of the Three Gorges Reservoir aims at increasing erosion, and carrying sediment to the dead storage of the Three Gorges Reservoir. The target region is the tail reach of the Three Gorges Reservoir, which is located in the main urban area of Chongqing. Key parameters such as the optimal time of regulation, daily reduction of the water level, initial water level in front of the dam and the discharge at Cuntan hydrometric station should be proposed in this study. 3.1. The preferred time for regulation Due to the experimental impoundment to the water level of 175m, an important period of erosion in the tail reaches turns into early April to late May. With water flow and sediment concentration increasing, deposition occurs in the reach gradually after middle June. Since the inbound flow and sediment of the Three Gorges Reservoir in late April too low to erode the sediment, the effect of reducing sedimentation is poor. Also, fluctuation too early is not beneficial for navigation. But as time goes on, with the conditions for daily reduction less than 0.6 m/d, high water level in early stage goes against fluctuating to the flood limit level. So the preferred time for regulation is early May. 3.2. The initial water level in front of the dam and discharge at Cuntan hydrometric station In order to fix the initial water level in front of the dam and the discharge at Cuntan hydrometric station, one-dimensional unsteady flow-sediment model is developed to calculate the erosion and deposition in the tail reaches with different combination of the water level in front of the dam and discharge at Cuntan hydrometric station [5-6]. The computation district covers the mainstream from Zhutuo section to the dam of the Three Gorges Reservoir with a length of 760km and 14 tributaries including the Jinglingjiang and the Wujiang river. The combination of the water level in front of the dam and discharge at Cuntan hydrometric station is listed below: (1) the discharge at Cuntan hydrometric station of 7000, 9000, 12000 and 15000m3/s respectively; (2) the water level in front of the dam of 155, 157, 160, 162 and 165m; (3) duration of 1, 2 and 3 days. For comparison, regulation is divided into two parts: (a) basic regulation: the water level in front of the dam remains invariable; (b) regulation of reducing sedimentation: the water level in front of the dam reduces by increasing the outbound flow with 5000m3/s based on the basic regulation, and the following conditions for daily reduction less than 0.6 m/d (requirement of slope stability of the Three Gorges Reservoir) should be met simultaneously.

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-70

-60

-50

-40

-30

-20

-10155 157 160 162 165

water level in front of the dam(m)qu

antit

y

(ten

thou

sand

m3 )7000a

7000b

9000a

9000b

12000a

12000b

15000a

15000b

Figure 1. Erosion and deposition of different regulations in major urban area of Chongqing(3 days)

-7

-6

-5

-4

-3

-2

-1

0155 157 160 162 165

water level in front of the dam(m)

quan

tity

(ten

thou

sand

m3 )

7000

9000

12000

15000

Figure 2. Reducing sedimentation of different regulations in major urban area of Chongqing(3 days)

Figure 1 and 2 show the erosion and deposition of different regulations in major urban area of Chongqing for 3 days. The calculated results for basic regulation demonstrate that with low water level in front of the dam, high discharge at Cuntan hydrometric station and long duration of regulation, good effect is achieved. Comparatively, the calculated results for regulation of reducing sedimentation indicate that great effect is high water level in front of the dam and long duration of regulation. In order to achieve good effect of reducing sedimentation, the discharges at Cuntan hydrometric station of 12000, 9000 and 7000m3/s are suitable as the water level in front of the dam are 165, 155 and 162m respectively; and when the water level in front of the dam are 160 and 157m, lower discharge at Cuntan hydrometric station leads to good effect. Approximately, the terminal of backwater zone with different water levels in front of the dam are as below: 145m-Fuling section, 157m-Tongluoxia section, 160m-Chaotianmen section, 162m-Jiulongpo section, and 165m-Dadukou section. Measured data indicate that

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the main urban area of Chongqing is still in natural state as the water level in front of the dam is below 157m. Then, sediment transport is less affected by the water level of the Three Gorges Reservoir. As the water level in front of the dam increases to the range of 160～162m, the terminal of backwater zone covers most of the main urban area of Chongqing including Chaotianmen section and Jiulongpo section. Then, the water level of the Three Gorges Reservoir plays a great role in sediment transport. Take all factor in to consideration, when the water level in front of the dam is in the range of 160～162m and the discharge at Cuntan hydrometric station is 7000m3/s, it is suitable for implementing the regulation of reducing sedimentation. 3.3. Proposal for regulation of reducing sedimentation 10 years from 1991 to 2000 are adopted as typical years for the calculation of sediment erosion and deposition. The results show that as the water level in front of the dam is above 160m, it is disadvantageous for sediment transport when the daily reduction of the water level is less than 0.1m; on the contrary, the daily reduction of the water level more than 0.2m is better. In order to attain good effect, the range of daily reduction for 0.4～0.6m is suitable in consideration of the probability of the inbound flow and sediment. Analysis suggests that the water level in front of the dam has greatest influence on the erosion in the tail reach. And it is efficient to reduce the water level when the inbound flow and sediment increase. So regulation of reducing sedimentation can be proposed as operating the water level in front of the dam reducing 0.5m/d for 10 days when the water level in front of the dam is in the range of 160～162m and the discharge at Cuntan hydrometric station is above 7000m3/s. The deficiency is that the water level in front of the dam and the discharge at Cuntan hydrometric station are not simultaneously satisfied. Fortunately, this difficulty can be resolved when the operation of reservoirs in upper reaches including Xiangjiaba and Xiluodu hydropower station are carried out in coordination with the Three Gorges Reservoir. 4. REGULATIONS PRACTICE OF REDUCING SEDIMENTATION Based on the research above, in the fluctuating period of 2012 and 2013, when the water level of the dam and the discharge at Cuntan hydrometric station basically satisfy the condition of reducing sedimentation in the tail reach, regulation practice of reducing sedimentation are carried out. 4.1. Regulation practice in 2012 May 7th ~ 18th, 2012, the first regulation practice of reducing sedimentation in the Three Gorges Reservoir was implemented, lasting for 12 days. During the first regulation period, average discharge of Cuntan hydrometric station was 6850m3/s. The water level of the dam fell 5.21m accumulatively (from 161.97m to 156.76m) and average daily reduction of the water level was 0.43m/d. Measured data showed that the tail reach broadly eroded and the total erosion quantity were 2.411 million m3 from Dadukou section to Fuling section in Chongqing (include the Jinglingjiang river, totally length of reach is 169km). Thereinto, the erosion quantity is 1.011 million m3 in the main urban area of Chongqing and 1.4 million m3 from Tongluoxia section to Fuling section. As to the distribution of sedimentation, the erosion quantity is 0.843 million m3 in the main stream of main urban area in Chongqing(from Dadukou section to Tongluoxia section, the length of reach is

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35.5km), 0.168 million m3 in the Jinglingjiang river (from Jingkou section to Chaotianmen section, the length of reach is 20km) and from Tongluoxia section to Fuling section, there is erosion in the upper reaches of Qingyanzi section in Linshi town and deposition in lower reaches. The erosion quantity is 2.939 million m3 from Tongluoxia section to Linshi town (length of reach is 86.2km), yet quantity of 1.538 million m3 sediment deposites from Linshi town to Fuling section. 4.2. Regulation practice in 2013 May 13th~20th, 2013, the second regulation practice was implemented, lasting for 7.5 days. During the test, average discharge of Cuntan hydrometric station was 6209m3/s. The water level of the dam fell to 4.43m accumulatively (from 160.17m to 155.74m) with the average rate of 0.59m/d. Measured data showed that the total erosion quantity is 4.413 million m3 in the tail reach. And the erosion quantity of 0.333 million m3 was in the main urban area of Chongqing and 4.08million m3 from Tongluoxia section to Fuling section. Compared with the year of 2012, the second regulation practice sedimentation is more effective in 2013, especially from Tongluoxia section to Fuling section: On the one hand, the total erosion quantity in 2013 is 4.08 million m3 from Tongluoxia section to Fuling section, which is approximately 1.9 times of that in 2012. On the other hand, erosion and deposition appear simultaneously in 2012 from Tongluoxia section to Fuling section. And there is erosion in the upper reaches of Qingyanzi section in Linshi town and deposition in lower reaches. The erosion quantity is 2.939 million m3 from Tongluoxia section to Linshi town, yet quantity of 1.538 million m3 deposite from Linshi town to Fuling section. In 2013, erosion occurrs all along the reaches. It is noted that Luoqi and Qingyanzi sections as the significant deposition areas in the past change to erosion, the erosion quantity are 0.182 and 1.245 million m3 respectively. Contrastively in the period of reducing sedimentation in 2012, the erosion quantity is 1.614 million m3 in Louqi section and Qingyanzi section presents deposition with quantity of 0.362 million m3( mainly in Niusiqi reach with quantity of 0.583 million m3). 5. REGULATION OF REDUCING SEDIMENTATION MODEL VADIDATION

Table 1. Erosion and deposition in the major urban area of Chongqing

Reaches Mesured data(ten

thousand m3)

Calculated data(ten

thousand m3)

Absolute error(%)

Relative error(%)

Dadukou-Chaotianmen -52.7 -80 -27.3 51.8 Chaotianmen -Tongluoxia -31.6 -10 21.6 -68.4 Jingkou-Chaotiamen in the

Jingling rive -16.8 0 16.8 -100

Dadukou-Tongluoxia -84.3 -90 -5.7 6.8 the main urban area of

Chongqing -101.1 -90 11.1 -11.0

Tongluoxia-Linshi -293.9 -310 -16.1 5.5 Linshi-Fuling 153.8 340 186.2 121.1

Dadukou-Fulin (inculding the Jinglingjiang river) -241.1 -60 181.1 -75.1

+: deposition; -: erosion

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In this paper, the observed data of sediment in 2012 is used to validate the mathematical model. The calculation results are summarized in Table 2. Most reaches are found to erode except Linshi town to Fuling section due to the observed data. Overall, the calculated data is qualitatively consistent with the observed data and basically reasonable in quantitative. Sediment with large quantities deposited in Niusiqi reach is the reason for highest error of Linshi town to Fuling section. Analysis indicates that sediment deposited because of the morphology characters along with section area suddenly increasing and the flow velocity suddenly reducing accordingly. Most of one-dimensional models are mainly applied to solve the computation problem for long period of time and long reaches. Yet since the statistical time and length is not long enough in this study, quantitative error is unavoidable. Also Linshi town to Fuling section is in the critical reach between erosion and deposition and has a major impact by local morphology, which leads to low accuracy. So the computation results can generally provide support for the regulation of reducing sedimentation in fluctuating period of the Three Gorges Reservoir. As the observed date accumulated and deep understanding for the rule of erosion and deposition in the tail area of the Three Gorges Reservoir, the present model should be improved for high precision. 6. CONCLUSION After experimental impoundment of 175m water level, erosion occupies the main position in the tail reaches, but a cumulative deposition appears in local area. And the rule of sediment movement changes greatly. Major period of erosion in the tail reaches changes from September and October under natural condition to fluctuating period from April to June. A one-dimensional unsteady flow-sediment mathematical model is developed to propose the regulation of reducing sedimentation in fluctuating period of the Three Gorges Reservoir, which is applied in fluctuating period of 2012 and 2013 with good results. The deficiency is that the water level in the front of the dam and the discharge at Cuntan hydrometric station are not simultaneously satisfied. Fortunately, this difficulty can be resolved after the operation of reservoirs in upper reaches carried out in coordination with the Three Gorges Reservoir. Measured data in the regulation of reducing sedimentation in fluctuating period in 2012 is used to verify the accuracy of the model. It demonstrates that the calculated data is qualitatively consistent with the measured data and basically reasonable in quantitative. In order to increase the accuracy of the present model, deepened understanding of the rule of sediment movement in the tail reach of the Three Gorges Reservoir and improving the present model are necessary. ACKNOWLEDGEMENT The work reported in this manuscript is a part of the research program funded by China 12th five-year national science and technology support plan “sediment regulation and control and multi-objective optimizing operation of the Three Gorges Reservoir”(Grant No. , 2012BAB04B05). REFERENCES

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Yangtze river water resource commission. (1992). Preliminary design report of the Three Gorges Project. Yangtze river water resource commission. Wuhan, China.

XIE, J.H. (1987): Simple explanation of sediment problem in the Three Gorges Project, Yangtze River, (2):1-11,Wuhan, China.

ZHANG, S.G. and ZHOU, M. (2011): Operation and regulation of the Three Gorges Reservoir, Engineering Sciences, 13:7, pp. 61-65. Beijing, China.

Yangtze river water resources commission, Bureau of Hydrology. (2013): Hydrology and sediment observation report in 2008～2012 of the Three Gorges Reservoir. Yangtze river water resource commission, Bureau of Hydrology. Wuhan, China.

HUANG, R.Y. and HUANG, Y. (2009): Preliminary study on 1-D numerical simulation of unsteady flow and sediment transport in mainstream and tributaries of the Three Gorges Reservoir area, Journal of Yangtze River Scientific Research Institute, 26:2, pp. 9-13. Wuhan, China.

HUANG, R.Y., LI, F. and ZHANG, X.B. (2012): Numerical simulation of flow and sediment transport in the early stage of Three Gorges Reservoir operation, Journal of Yangtze River Scientific Research Institute, 29:1, pp. 7-12. Wuhan, China.

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BIODIVERSITY MANAGEMENT PLAN

IN THE PROJECT AREAS OF THE UCPS HEPP DEVELOPMENT [Blank line 11 pt]

A. Heryana, T. Indora & A. Nugroho PT PLN (Persero)UIP VI , Bandung, Indonesia

[email protected] [Blank line 10 pt] [Blank line 10 pt] [Blank line 10 pt] [Blank line 10 pt]

ABSTRACT: PT PLN (Persero) is currently planning the development of Upper Cisokan Pumped Storage hydroelectric power plant (UCPS HEPP) which has a capacity of 1040 MW (4 x 260 MW) located in the province of West Java. The land area that must be acquired is covering 720 Ha, consisting of citizen lands and forest lands. As a project that will occupy forest lands and requires relatively large areas, one of environmental issues arises is the biodiversity issues. In 2012, PLN has conducted biodiversity study aimed to analyze the vulnerability of flora and fauna that live in the project areas, and also to complement the previous studies data. At least 376 species of plants and 159 species of fauna from different classes have been identified in the project areas, including 9 species of mammals and 18 species of birds are reserved. The studies also mentioned that with or without the presence of UCPS HEPP project, the sustainability of some species in the project areas will not be able to last a long time considering the forest as a habitat for fauna obtain a high pressure, either due to illegal hunting or because of land clearing by local residents. In order to protect the biodiversity levels at the project site, PLN has compiled a biodiversity management plan as a reference for the construction and operational activities of UCPS HEPP. Biodiversity management plan will use an adaptive management approach to make in situ conservation as a priority. Some of the management actions that will be performed including the improvement of habitat quality around the project areas, the development of a corridor for wildlife movement, community involvement to protect areas from the activities of illegal hunting and collaboration with relevant stakeholders, especially stakeholders in the management of forest conservation areas. [Blank line 10 pt] Keywords: HEPP, Upper Cisokan Pumped Storage, biodiversity, conservation [Blank line 10 pt] [Blank line 10 pt] 1. INTRODUCTION [Blank line 10 pt] In an effort to increase the power supply capacity in the electric power shortage regions and to diversify energy resources for the sake of conventional fuel saving, the Government of Indonesia is actively promoting development of alternative energy for coal, oil and natural gas. Particularly, the development of hydroelectric power plants is strongly encouraged because there are abundant hydroelectric power resources in the country. Under the circumstances, PT PLN (Persero) has planned to develop a new hydroelectric power plant at the West Java Province where the energy demand has been increasing 8.97% a year on average. PLN intends to proceed with the development of Upper Cisokan Pumped Storage Hydroelectric Power Plant Project. The total installed capacity of the

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UCPS HEPP Project will be 1040 MW. Four pump turbines are to be installed, each turbine unit having a nominal capacity of 260 MW (for generating). The UCPS HEPP Project will be the first pumped storage project in Indonesia. It will be located about 150 km southeast of Jakarta in the upstream region of the Cisokan River Basin, the main tributary of the Citarum River, in West Java Province, Republic of Indonesia. The Citarum River, the largest river in West Java with its catchment area of about 6,000 km2, runs northward into the Java Sea. The UCPS HEPP Project has two reservoirs, the upper reservoir and lower reservoir, each having an active volume of 10 million m3. At peak hours, the water will flow from the upper reservoir to the lower reservoir to generate electricity. At base load, the water collected in the lower reservoir will be pumped back to the upper reservoir, using electrical energy supplied from power plants that bear the base load. Operation of UCPS HEPP provides a cheaper method for PLN to meet the daily peak load and the additional load demand. Upper reservoir water surface area at the maximum height of the water level is 80 Ha and while the lower reservoir is 260 Ha. The total area of land required for the whole project is 720 Ha, which covers an area of 382 Ha of forest lands and citizen lands area of 338 Ha. Based on the land utilization map issued by the Government of West Bandung Regency and Cianjur Regency, general land usage patterns in the project area consists of forest, mixed farms, fields, cultivated and settlements. Most of the land requirements is forested which is a production forest managed by Perum Perhutani. Types of plants grown in production forests are pine and teak. Most of the forest is a secondary forest patches from fragmented forest production. Secondary forests are generally found in locations that are difficult to reach by people such as cliffs, river banks and other location including water fall. The forest is generally predominantly dominated by forest trees, including Baros (Magnolia glauca), Manglid (Magnolia blumei), Teureup (Artocarpus elasticus), Kiara (Ficus spp), and several species that are commonly found in destructed forest, such as Mara (Macaranga spp). 2. BIODIVERSITY CONDITIONS IN THE LOCATION OF THE PROJECT As a project that will occupy forest area and requires large lands, one environmental issue that arises is the issue of biodiversity. EIA documents prepared in 2007 stated that the level of biodiversity in the UCPS HEPP Project area is quite high. In the area surrounding the project plan and recorded fauna species particularly of the class Mammalia, herpetofauna, Pisces, and Aves. Total species recorded was 85 species, consisting mostly of class Aves (birds) i.e. 53 species, then as many as 11 species of Mammalia, Reptiles as many as 6 species, Pisces (fish) as many as 3 species, and Amphibian as many as 3 species. In 2012, PLN conducted a survey of flora and fauna in the project area again. This survey aimed to complement biodiversity information from previous reports and analyze the level of vulnerability of the flora and fauna that are in the project area. Studies conducted over 1 year in two different seasons (rainy season and dry season). The study found that at least 376 plant species: 268 genera and 160 families inhabited the UCPS HEPP Project area. Based on the field study, the forest area in the watershed Cisokan has been seriously disturbed as indicated by the opened area which covers up to 90% of the study area. Based on satellite imagery sighting photo which used as the basis of a field study, at least there

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are seven types of land use, i.e. a) secondary forest with some remaining primary forest trees, b) pine forest, c) mixed-garden, d) garden for planting dried paddy and annual crops, e) paddy field along the river bank at the level area, f) residential areas distributed in several locations near watershed area, g) river. While for the fauna, there were 30 mammal species, 81 bird species, 15 fish species and 33 amphibian and reptiles existed in HEPP-UCPS (Quarry, Access road, Upper dam, Lower dam and Transmission area). Nine of 30 mammals species were treated as protected species under Indonesian law, CITES, and IUCN. In addition, among 81 bird species, 18 species were also protected species. None protected species of either fish or herpetofauna found in this study area. In addition to direct observation, observation was also made by installing a 10 camera traps in the vicinity of the lower reservoir for 3 months and managed to record the presence of wildlife including several endangered animals as follows: a. Panthera pardus melas (Leopard) Two of the 10 camera traps shot the leopard in the secondary forest near the next new lower dam, which is in Gowek Forest and Pasir Nangka. The existence of leopards in this region is also supported by direct observation in the field such as feces, traces and scratches on trees that were found in the area of the Cisokan River. The analysis of the camera trap indicates that only a single leopard was documented to inhabit this lower dam area. Considering the population size and the habitat condition which were not able to support their survival, it can be ascertained that under present conditions this leopard will not be able to survive in this area. b. Prionailurus bengalensis javanensis (Leopard Cat) By using 10 camera traps, a leopard cat was documented to exist in the lower dam. After establishing camera traps during 3 months, two camera traps successfully recorded a leopard cat at two different locations, which is in Palisiran and Pasir Nangka. Based on the analysis of camera traps’ record, it is possible that the two camera sets recorded the same individual since those two camera traps were set up within a short distance (< 1 km), it can be concluded that at least there is a leopard cat inhabited the lower dam area. As an illustration, Palisirian and Pasir Nangka area where the leopard cat was recorded by camera traps were bushes and mixed-garden areas which were always used for gardening by local residents. Based on the analysis of the population size and their habitat, whether there is UCPS project or not, the leopard cat is going to be extinct in the lower dam. c. Hylobates moloch (Gibbon) Based on the field observation in the area study, there were at least seven Java Gibbons inhabit the Curug walet, Powerhouse, Cimanggu and the secondary forest Gowek near to the next new Lower Dam. Their existence in this area was under serious threats, especially the habitat conversion. Land clearing and illegal logging of their habitat have been conducted for a long time. d. Presbytis comate (Grizzled Leaf Monkey) The existence of Grizzled Leaf Monkey in the Upper Dam, based on the interview data as well as direct observation in the field. At least, four individuals of Grizzled Leaf Monkey were observed during the 1st survey in the mixed-garden of Cibuluh area. The existence of the Grizzled Leaf Monkey in the Lower Dam were identified by hearing of the voice and documentation in the field results. During this study four sub populations of Grizzled Leaf Monkey were successfully documented in the following areas: the secondary forest Gowek

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(near to the next new Lower Dam); surrounding Cilengkong river; Cadas Gantung area, and upstream of Cisokan River (Bojong Salam village). e. Trachypithecus auratus (Javan Langur) In this survey in the lower dam, about 21 individuals were recorded. Total population is still relatively high in this region due to the ability of adaptation to their food which not only depends on one kind of food available all the year. Their population found in the powerhouse area (Cimanggu, Cilengkong River, and Curug wallet) and secondary forest Gowek (near the next new lower dam). f. Tragulus javanicus (Lesser Mouse-Deer) Lesser Mouse-Deers were found in Palisiran, Cimanggu, Batu Bedil dan Gowek Forest. Based on the analisys of camera traps, there was a possibility that the detected individuals were different individuals. Therefore, it is concluded that there were minimally four mouse deer in this lower dam area. Their natural habitat is primary forest, but these animals can adapt to the secondary forest as a result of the habitat degradation. The main threats of these animals are the habitat degradation and the animal hunting to consume the meat. Whether there is UCPS HEPP Project or not, the existence of mouse deer is threatened to be extinct resulted by the fast habitat damage in this area. g. Hystrix javanica (Javan Porcupine) The camera traps set in Palisiran could document the existence of Hystrix javanica, whereas an observation in the Upper Dam area found one. Therefore, it is concluded that there was minimally one Hystrix javanica in the lower dam area and one in the upper dam area. Hystrix javanica is an animal which is active in the night time. The habitats are various, ranging from secondary to primary forests. Hystrix javanica is one of animals hunted by local community. The high economic value of the meat and the high medical specialty of the parts of body triggered the lower population almost in all Java areas. For this reason, whether there is a UCPS HEPP Project or not, the existence of this animal is threated by the illegal hunting in this area. h. Manis javanica (Pangolin) The existence of Manis javanica was gained only from observations, i.e. the foot marks and the active lair. The difficulty to find Manis javanica in this area describes the population which was very low resulted from the vast illegal hunting since this animal has high economic value. Manis javanica was one of animals which is highly hunted by local community. For this reason, whether there is a UCPS project or not, the existence of this animal is threatened by illegal huntings. i. Birds The total bird species found in all survey location of the entire project area was 81 species from 37 families. Of the total, 11 species were birds endemic in Java, 1 species was in the category of Near threatened IUCN, 7 species were in Appendix II CITES and 18 species were the protected by Indonesian government regulation. The richness of the highest species was found in the lower dam area and the lowest species in the quarry. The group of birds which will be affected by the project construction is the bird group which is very tolerant to any disturbance and is a group of deforestation survivor going on hundreds of years, local extinction will probably not happen.

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j. Fish The study in Cisokan watershed found 15 species of fish from 10 families, 11 types of which were indigeneous fish, 4 of which were the introduced fish. This was caused by the community activities that took the fish using insecticide (Potassium, Thiodan and Takodan) especially in the dry season so that many fish species were missing in this water system. This phenomenon shows that the construction of UCPS in Cisokan watershed will not affect seriously the fish species diversity in this area. k. Herpetofauna The study in the UCPS HEPP Project found 33 species, i.e. 17 amphibies and 16 reptiles. All species of herpetofauna in this area are not included either in the list of fish protected by Indonesian government regulation or in the category of Appendix CITES and other conventions. The result of the study shows that some species of herpetofauna found in all UCPS project areas were common species found either around occupant residences, paddy fields, gardens, mixed-plantations (talun), or rivers. The common species living in various types of habitats can easily find new habitats and they easily can ajust the new place when there is an environmental change. The construction of UCPS project will not disturb the conservation of these common species because they can still find a new similar habitat in the surrounding area. 3. THE THREAT TO THE BIODIVERSITY IN PROJECT AREAS The condition of the forest in the upper reservoir areas were seriously threatened by logging and clearing the forests for farming purposes, especially on the hills. Some areas still existed, undisturbed, especially at the valleys with very steep edges (angle > 65%). In this area, a lot of large decayed logs were resulted from logging. They used only the good timber for building constructions. Based on the study conducted also known that there was a serious threat to the habitat of mammals in this lower dam. The main threat was the change of land use of the secondary forest turned into rice fields or agricultural areas by local residents. This activity will certainly lead to the rise of open land in both the valley and the location of areas with steep slope, so that the area was originally a secondary forest turned into agricultural land. This condition leads to forest fragmentation into small spots of secondary forests and the loss of forest corridors that connect between a forest spot with other spot forest. This process continuously occurred parallel with the resident population increase, and their needs for residential and farming area. It threatens the survival of the mammals, especially for the big mammals which are difficult to adapt to the open area. They need a specific habitat such as more heterogeneous forests. Forest habitat area which is getting smaller and the pressure of increasing population activity created conditions which do not favor the development of animal population. As an example, there is only a single leopard inhabited this lower dam. This leopard will not be able to survive in this area. Even if there were a couple of them, they would not survive since their habitat in the lower dam was seriously threatened by illegal logging and land clearing. Naturally, they will possibly survive only up to first generation since there is no sub population that is necessary to exchange their genetic resources. Breeding with their parents will lead to survive possibly up to second generation due to their genetic degradation. As an illustration, the condition of the secondary forest Gowek where the

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leopard was successfully recorded by the camera traps started to degrade and the size was less than 10 ha. Illegal logging occured continuously eventhough the accessibility of this forest was limited due to the steep hill. 4. BIODIVERSITY MANAGEMENT PLAN IN THE PROJECT AREAS

Environmental is one of the essential requirements in the implementation of construction activities and operation of UCPS HEPP. In order to protect biodiversity at the project site, PLN has prepared biodiversity management plan. The purpose of biodiversity management plan is to prepare mitigation required to: Protect, and whenever possible improve the quality of habitat at the project site. Protect and restore the greenbelt area in the reservoir as an additional habitat for local

wildlife. Protect, and whenever possible improve the survival of endangered species in the

project area. The planned mitigation would include at least the following three components: a. Remnant secondary forest

- No reduction in the population of endangered species - Maintenance and protection of the secondary forest remnants.

b. Recovery of Greenbelt - Recovery using local forest species. - Protection from the construction, agriculture, land clearing, settlement, hunting or

harvesting. c. River Environment

- No reduction in the population of food species for the surrounding community. - No reduction in the population of local fish species

Some of the management actions that will be performed include: 1. Limiting the use of the access road just for the benefit of the project. This is done to

prevent land clearing/forest for agriculture and wildlife poaching by local and non-local residents whose access is getting easier with the access road.

2. Improving understanding of wildlife protection and a ban on hunting/catching wild animals to the public and construction workers.

3. Building a wildlife corridor for the movement of the column that has been defined as the movement of an alternative pathway. This corridor is expected to be a path that connects the movement of wildlife between forest spot to spot one another forest.

4. Signaling in plants/vegetation (trees/shrubs) found a place/habitat nest, feed and animal movement places in order not to be disturbed land clearing and construction activities, at least until these animals to be relocated by in-situ.

5. Compiling standard procedures for the implementation of construction activities in the region which borders the wildlife habitat, including the handling and rescue procedures when the animals entering the project areas.

6. Conducting handling and rescue against animals were found nesting with a long incubation period.

7. Collaborating with relevant stakeholders, the main stakeholders in the management of forest conservation areas.

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Biodiversity management plan will use an adaptive management approach to make in situ conservation as a priority. Adaptive management process includes the development of typical policies or repetition programs which begins from the initial investigation and identification of the problem, find the option for mitigation of impacts, develop and implement prevention efforts, and to monitor and review the results of the program before the loop starts again. Implementation of this effort will involve PLN, construction supervision consultants, contractors, communities, NGOs working in the field of conservation, Perum Perhutani as forest stakeholders, and other government agencies such as Natural Resources Conservation Agency and Ministry of Forestry. 5. CONCLUSION

Based on the above, there are several conclusions as follows: a. UCPS HEPP Project area is an area that has a high level of biodiversity. There are 9

species of mammals and 18 species of birds are protected. The area around the Lower Dam are regions with the highest level of biodiversity.

b. There are a few activities around the project that pose a threat to the survival of wildlife. The main threats caused by illegal hunting and shifting function of secondary forests into paddy fields or agricultural use by local residents.

c. Sustainability of protected species in the project area remains threatened, either with or without the presence of UCPS HEPP Project.

d. With the goal of protecting biodiversity levels at the project site, PLN has developed a biodiversity management plan with an adaptive management approach to guide the management of biodiversity in the implementation of construction activities and operation of UCPS HEPP

e. Implementation of biodiversity management plan will involve various stakeholders, including PLN, contractors, communities, NGOs, Perum Perhutani as forest stakeholders and other government agencies.

REFERENCES

PPSDAL Unpad. 2013: Laporan Isu dan Opsi, Bandung, Indonesia. PT PLN (Persero). 2007: Analisis Dampak Lingkungan PLTA Cisokan Hulu Pumped

Storage, Bandung, Indonesia. Pusat Penelitian Biologi LIPI (Sutrisno H., et. Al). 2012: Studi Flora dan Fauna pada Lokasi

Proyek PLTA Upper Cisokan Pumped Storage, Bogor, Indonesia. Rahmat A. 2009: Survei Keragaman Hayati UCPS, Additional Environmental Studies,

Bandung, Indonesia.

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Reservoir sedimentation and the dredging solution

S.C. OoijensIHC Merwede, Kinderdijk, The Netherlands

[email protected]

I.W. WielingIHC Merwede, Kinderdijk, The Netherlands

G. BusserIHC Merwede, Singapore, Singapore

ABSTRACT:Sedimentation is a large problem for many reservoirs and hydro power plants. It leads to clogging(too) close to the turbines, a disruption of the sediment balance in rivers, loss of capacity andeventually to the reservoir falling into abeyance. Quite some sediment management strategies aremore or less suitable; yield reduction by means of afforestation, slope protection, bypassing,sluicing, venting or flushing. Though implementation of these strategies might be unwantedbecause of practicality or timing (too late). Raising the dam or building a new one is often not apreferred option.

An alternative option is to actively remove the sediment out of the reservoir by usingexisting and/ or innovative dredging techniques. This can be done by clearing the turbine entrance,restoring the sediment balance in a river or just by removing sediments.

Dredging solutions for these reservoirs demand specific systems and techniques. In manycases the dredgers have to be transported and mobilized in mountainous regions which requiresthe dredger to be dismountable and easy transportable. Another challenge is the supply restrictionof energy in these remote areas. The equipment has to be operated in environmentally vulnerableareas and therefore requiring a well-designed product taking into account these specificconditions. Many reservoirs are up to 200 meters deep and demand unconventional dredgingmethods. Needless to say that the options for getting rid of the sediment are challenging.

In this paper the authors will highlight several state-of-the-art techniques for removingsediment by means of dredging equipment.

KEYWORDS: SEDIMENTATION, DREDGING, MAINTENANCE, DAMS, HYDROPOWER

1. INTRODUCTION

This paper can be considered as an effort to bridge the worlds of the large dams and thedredging technologist. A knowledge transfer will help both parties to better asses dredgingscenarios for dams. Written by dredging specialists, this paper focusses on introducingreservoir dredging from a technological point of view. Addressing researchers, designers,engineers and owners working with sedimentation challenges.

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Every reservoir has unique characteristics and therefore each of them will need a specialsedimentation strategy. Figure 1 states a classification of different strategies.

Figure 1. Sedimentation strategies, adapted from [1]

There are dredging solutions available that often remain underexposed; manysedimentation handbooks and sediment management studies discuss only basic dredgingsolutions and wrongly conclude that dredging is an unprofitable option. New-build damsalso benefit from an early assessment of the dredging scenario including a sedimentationstrategy.

There is no such thing as a one size fits all strategy for reservoir dredging and dredging isnot always the best option when it comes to solving sedimentation problems. Studying thefeasibility of the dredging scenario it is common practice to compare the costs of theoperation with the cost of the capacity of a new-build dam. The value of the dredgingsolution can also be assessed using indirect aspects:

- Impossibility to expand the reservoir or no locations for new-build- Value of the uptime of the turbines- Value of the produced electricity- Value of water- Environmental benefit of extending the life of the reservoir

Yield reduction

Afforestation and vegetation

Settling and storage basins

Slope and bank protection

Sediment check dams

Routing

Sediment bypassing

Sediment sluicing

Turbidity current venting

Flushing

Mechanical

Hydraulical

Removal

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- Ecological benefit of bringing sediments back into the river, nutrients, spawningareas

- (Environmental) costs of alternative strategies; flushing- Costs of decommissioning the dam.

Considering dredging as a method to mitigate sedimentation in a reservoir requires insightin the sedimentation process in the reservoir but also in the available dredging methods.Choosing the right (most effective) equipment then improves the economics of the damand the reservoir.

This paper is an overview of state-of-the-art solutions for dredging of reservoirs. Specificdifferences and conditions considering reservoirs will be addressed and the correspondingdredging solution. Solutions for sediment removal (mechanically and hydraulically) andalso a solution for supporting flushing, sluicing and venting will be discussed.

2. DIFFERENTIATION OF THE SEDIMENTATION PROBLEM

Every reservoir is defined by its own local circumstances and constraints. Theseconstraints can be technical, economic, social and political. The circumstances andconstraints together determine the need for sedimentation mitigation, and thus the solutionhas to be tailor made in order to be effective.

Sedimentation problems can be divided into three main categories. These differentproblems will influence the selection of the specific dredging solution.

Plugging the turbineThis is a very local sedimentation problem. Even deep reservoirs, where capacity loss isnot an urgent problem, sedimentation can raise problems. If flushing of sediments is notpossible or allowed dredging can bring relief.

Loss of capacityThe severity of capacity loss of a reservoir due to sedimentation problems depends on thesedimentation yield. Storage losses of 1% per year are an estimated average [2]. problemswill eventually occur but however will be recognized after years of operation. In someareas the annual loss is much higher with a negative effect on the life time . In these casesthe problem is more urgent and for a sustainable operation relatively high volumes ofsediment have to be taken away.

Sediment balance in the riverA dam causes an unnatural disturbance in a river. This means that not only the normal flowin a river is changed (leading to an environmental impact), but also the sediment flux.Sedimentation in a reservoir can lead to erosion downstream and a loss of nutrients. Awell-known example of this is the Ashwan Dam in the river Nile. Sedimentation does notdirectly lead to a capacity loss of the dam, but causes problems further up in the course ofthe river: first of all the riverbanks are in shortage of nutrients and second an increasederosion of the river and coastline are caused by the disturbance in the sediment flux.

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3. TECHNICAL DIFFERENTIATION FOR DREDGING

There are a lot of aspects to consider when assessing dredging scenarios. These can bedifferentiated by:

- The function of the reservoir- Location of the dam- Sediment type- Sediment location- Dimensions

Figure 2. Relevant technical aspects for dredging scenario

Most important parameters are type of sediment and depth of the reservoir.

3.1. Sediment type

One of the main parameters for deciding on which dredging operation is suitable, is thecombination of characteristics of the sediment. These affect the sedimentation itself butalso influence the chosen mitigation solution.

Since hydro reservoirs are a large sedimentation basin, all soil types that are transported bythe river leave their traces in the reservoirs. In general, non-cohesive materials with alarger gain size diameter are found at the entrance of the reservoir as they quickly settle.Closer to the dam smaller particles tend to settle. Over time these smaller particles ‘form alayer of cohesive clays. In order to effectively dredge these cohesive soils a solutionincorporating the use of a mechanical excavation tool (such as a grab or a cutter) needs tobe put in place.

Functionreservoir

Water conservation

Flood prevention Hydro-energy

Locationdam

Seasonal variation

Legislation & regulation

Accessibility

Environment

Sediment type

Waste and wood Organic sludge

Rock / gravel / sand / clay

Dimensionsreservoir

Quantity

Transport distance

Depth

Sedimentlocation

Dump zone

Delta

Landslide

Turbine inlet

Bed

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An additional complicating factor is the debris on the bottom (mainly trees that have falleninto the river).

3.2. Depth

An important parameter for dredging is the dredging depth. On average with dredgingoperations such as waterways maintenance dredging, depths run up to approximately 25meters. However for hydropower dams this can be significantly deeper. This challengesdredge equipment designers to keep productions, positioning and costs in balance.

4. THE DREDGING SOLUTION: DREDGING METHODS AND RESERVOIRDREDGERS

The aspects described in chapter 2 and 3 will determine the selection of the specificdredging method and of course also the dredging equipment.

The development of dredging equipment for reservoirs requires additional considerations:

Transport equipment - modular, lightweightSince most reservoirs are located in mountainous regions it is required to use transportableequipment which can be deployed on location.

Clean environment - no emission, low ecological damage and low noise levelsSince many reservoirs are located in environmentally sensitive areas environment friendlymeasures in the design of equipment is required.

Maintenance dredging - all year long dredging vs. a short dredging phaseIn many situations the problems are only then recognized when sedimentation leads tourgent problems. In other words, when turbines get plugged or get high wear rates, when aloss of capacity has led to significant downtime or when downstream erosion has led toenvironmental problems, people start to search for a solution. As for the dredging systemthis also influences the choice. Although it took years for the sedimentation to settle,suddenly an urgent solution is required. The needed capacities put a strain on the technicalstandards of the equipment (leading to a high CAPEX) and make it more difficult to find away to deposit these high volumes of sediment. Alternatively all year long maintenancedredging requires smaller dredging equipment (low CAPEX) and results in prevention ofurgent dredging campaigns.

Electric driveDue to environmental regulation, and taking into account the difficult fuel logistics ofbringing fuel into the mountains, often an electric power supply and drive is preferred.

As stated reservoir dredging can benefit from a dedicated solution in excavation, transportand processing of the sediment. However in general the solutions can be categorized in 4classical types of equipment, which can be reengineered to the above given requirements.

4.1. Cutter Suction Dredgers

Cutter Suction Dredgers (CSD) are estimated to cover about 80% of all large-scaledredging operations in reservoirs. Due to the slurrification process and the hydraulic

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transport relatively high production rates can be achieved. Since these dredgers use anexcavation tool they can handle most of the soil types. Even for cohesive materials such asclay the dredgers can be equipped with specific excavation tools such as a dredging wheel.It can dredge up to a significant depth (approximately 85 meters).

Figure 3. Dredging wheel

The CSD is a relatively large dredging solution. To work in mountainous regions it has tobe made dismountable for transport.

Figure 4. Typical transport of a CSD

4.2. TT-pumps

A cost effective method for dredging is a submersible pump suspended from a land-basedcrane or from a pontoon. Typical pipe diameters range from 100 [mm] up to 500 [mm].Combined with a cutter or jet-water system the pump can be used to dredge compactednon-cohesive material. No forces can be applied to the pump so it is mainly used for spotdredging in front of the turbine inlet. Since the pump is suspended on a wire high dredgingdepths can be reached (up to at least 200 meters). The system can be transported inside astandard container.

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Figure 5. Pontoon with TT-pump

4.3. Mechanical dredgers

Land-based grabs, draglines and excavators can be made floating and placed on pontoons.Optimized equipment for work on water can be more effective. Since mechanical dredgersonly dig and bring the material up, the material will be dumped in a barge or rehandlingplant. Their ability to handle debris such as trees and boulders makes them effective toolsfor certain hydro-power lakes. Since a grab is hoisted with a wire a large dredging depthcan be reached. However at larger depths the cycle time will be higher and production willbe lower.

4.4. Crawlers

The crawler is a remotely operated dredger with a vertical transport system and asupporting pontoon. The system can be compared with ROV’s. For example de Beers inNamibia is using a crawler at depths up to 140 meter for mining diamonds. These toolsenable dredging at a large depth of relativity cohesive soils which cannot be dredgedeffectively with mechanical dredgers or TT-pumps. Until now the investment costs arerelatively high, but the technology is maturing at a high pace.

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a.b.

c. d.

Figure 6. a) CSD, b) submersible TT-pump, c) grab, d) crawler

4.5. Dredging to support sediment flow

Dredgers can be used to create artificial density currents. Agitation dredging or jet watertechnology is used to suspend the sediments. The sediment must be able to form a stablesuspension (i.e. fine sand) and a minor slope is requirements for good operation. Bottomoutlets or a diversion channel must be present, so the sediments can be sluiced out of thereservoir.

Water injection dredgers are basically high flow pumps on a vessel with a jet bar forinjecting the water in the sediment. Typical flow per meter jet bar is 1000 [m3/h/m] andtypical pressures range from 1,5 [bar] to 5,0 [bar]. The effectiveness of this method is acombination of a dredger and a dredging strategy. Modelling of the reservoir, the dredgerand induced currents is recommended.

In preparing a flushing operation, using an agitation dredger can be effective. It is possibleto prepare the reservoir bed for more effective flushing and to increase the sediment flowduring flushing.

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Figure 7. Water Injection Dredger

4.6. Selecting a dredger

With different local situations and different total morphological solutions the selection of adredger will be part of the total scheme. As can be seen dredgers can be selected for arange of situations.

Table 1. Indicative table to the use of dredging equipment as per constraintSoil Depth CapacityGravel Sand Clay Silt Debris

CSD + + + + < 85 m HighTT-pump + + + < 200 m ModerateMechanical/ grab + < 200 m LowROV/ crawler + + + + < 200 m ModerateAgitation/ WID + < 20 m High+ possible solution

Taking into account the type of sedimentation problem in practice the cutter dredger isselected for a large number of reservoirs. However the selection of a dredger should beconsidered separately for each reservoir.

Table 2: Indicative table to the use of dredging equipment as per problemInlet Capacity Sediment

balanceCSD + ++ ++TT-pump + +Mechanical/ grab + + +ROV/ crawler +Agitation/ WID ++ possible solution ++ highly possible solution

When assessing dredging solutions not only the excavation should be considered, but also:

Bottom outlet

Turbidity current

Bottom set bed

Water Injection Dredger

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ProcessingThe processing can vary from bringing the sediment back in to the river downstream,dumping in a dumping location within the lake or on land (landfill), reuses of sand forconcrete, etc.

TransportThe transport of sediment can be by pipelines but also by using barges and if needed bytrucks or a conveyor.

For these process steps a wide range of solutions is available, which again will have theirinfluence on the costs. The selection of a dredger system is a complex issue. The finalselection will depend not only on the chosen technical solution but also on manycircumstances including dumping location, local requirements, local facilities, etc.

6. CONCLUSIONS

With many reservoirs aging, sedimentation will become more and more a challenge.Solutions to mitigate sediments get more attention when the life time of a reservoir can beextended or operational costs can be lowered. Not only the costs of the measures but alsothe natural sediment balance and local environment are nowadays taken into account.

Every reservoir has its own characteristics. Taking into account the local situations a totalsediment solution can be drafted by specialized engineering firms. Depending on the localsituation dredging can be a part of the solution and provide an active intervention to bringback a natural balance.

There is a wide range of equipment available. When assessing dredging scenarios it isrecommended to evaluate using the right equipment in mind. Dredging systems can be anintegrated part of an effective and sustainable sediment management system.

REFERENCES

[1] Kantoush, S.A. Sumi, T. (2010): River Morphology and Sediment ManagementStrategies for Sustainable Reservoir in Japan and European Alps, Annuals of Disas. Prev.Res. Inst, No. 53 B, Kyoto Univ., Japan.[2] Morris, G.L., Fan, J. (1998): Reservoir Sedimentation Handbook, McGraw-Hill BookCo., New York.

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Aerating Turbines at the new Dam Toe Hydroelectric Power Plants

at the existing Belesar & Peares Reservoirs (Spain)

V. Mendiola & G. Rodríguez Gas Natural Fenosa engineering

[email protected]

ABSTRACT: Gas Natural Fenosa has designed and built two new dam toe power plants on the existing Belesar and Los Peares reservoirs, both located in the Miño River (Galicia, North-western Spain). The new Belesar II and Los Peares II hydroelectric power plants will be equipped with two Francis vertical axis turbines each. Each turbine at Belesar II will be 10.4 MW with a flow rate of 10 m3/s, and each turbine at Peares II will be 9.1 Mw with a flow rate of 11.5 m3/s. These dam toe power plants have been designed and built in an effort to add a greater presence of self-supply and renewable energy to the Spanish energy system as well as to recover the aquatic habitat of the dam toe river stretches which originally featured an insufficient flow rate upstream the discharge of the existing power plants. The decision was made to create a by-pass in the dam bottom outlets for the intake to the new power plants. However, given the significant depth at which these outlets are located and the natural reservoir stratification processes, this will mean water will be used with low dissolved oxygen content during some months of the year. Releasing water with low dissolved oxygen levels into the river would cause critical harm to the river habitat. In order to solve this problem and include the environmental variable into the new projects, Gas Natural Fenosa is adding Andritz Hydro turbine air injection systems to the design of the new power units that will make it possible to reach the ideal dissolved oxygen values at the discharge of the new power plants for the aquatic life in the Miño river stretches downstream from the Belesar and Los Peares dams. Keywords: water quality, oxygen, hydroelectric, dam toe power plant 1. INTRODUCTION After the second half of the 20th century, Spain saw the greatest development of hydroelectric projects, going from an installed power of nearly 1,900 MW in 1950 to nearly 11,000 MW in 1970 (Espejo & García, 2010). During this period, the economic

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liberalisation and government stimulation programmes allowed private companies to build most of the major hydraulic regulation and power generation infrastructures. At the time, the hydroelectric potential in north-western Spain stood out due to its abundant water resources and land morphology. It was in fact in Galicia, in the northwest of Spain, where “Fuerzas Eléctricas de Noroeste S.A. (FENOSA)” built the Belesar (1963) and Los Peares (1955), dams and their power plants associated on the Miño River.

Figure 1: Location of the Belesar and Peares dams

1.1 Hydraulic Power Plants at Belesar and Los Peares During its construction, Belesar dam was considered an engineering benchmark in Europe. It’s an arch dam with two gravity abutments. The dam height is 127 m above the riverbed. The height above the foundation is 132 m and the crest length is 500 m, including the abutments. The dam features two ski jump spillways, one in each abutment with a maximum evacuation flow of 4,000 m3/s. The dam also features four bottom outlets comprised of 1.50 diameter pipes. The flow capacity of each one of the outlets is 40 m3/s for a total capacity of 160 m3/s. The main data for the reservoir and the power plant are as follows:

Table 1. Belesar Power Plant and reservoir main data Belesar Reservoir

Reservoir capacity 654 Hm3

Area 2,000 ha Annual average inflow 100 m3/s

Belesar Power Plant Number of power units 3 Unit flow rate per power unit 67 m3/s

Installed capacity 225 MW

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Los Peares dam and reservoir are located immediately downstream from Belesar reservoir on the same Miño River. Peares is a gravity dam with a circular layout, a crest length of 261 m and a height of 92 m above the riverbed. The spillway is located in the middle of the dam and it features four spans (15 m each) which house the Stoney floodgates. The spilling capacity at Normal Operation Level is 3,568 m3/s. The dam features two bottom outlets on the left bank and the horizontal pipes have 2 m diameter. The water evacuated by the bottom outlets is conducted via a parallel canal to the stilling basin, discharging downstream from this basin through a lateral spillway. The theoretical flow capacity of each bottom outlets is 50 m3/s. The main data for Los Peares reservoir and the power plant associated are as follows:

Table 2. Los Peares Power Plant and reservoir main data Los Peares Reservoir

Reservoir capacity (MNL) 182 Hm3 Surface area 535 ha Annual average inflow 100 m3/s

Los Peares Power Plant Number of power units 3 Unit flow rate per power unit 67 m3/s Installed capacity 160 MW

Figure 2: Belesar Dam Figure 3: Los Peares Dam

1.2. Belesar II and Los Peares II Power Plants In the 21st century, it was needed to optimise the facilities built years before, as well as reinforce the sustainability of the existing infrastructures. These issues led to the new dam toe power plant projects at Belesar and Los Peares, which would maintain a base flow in the Miño River affected by the dams to get the environmental recovery of the river courses located between the dams and the discharge of the respective power plants.

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Figure 4: Plan view sketch of the Belesar infrastructures

Belesar II HPP would allow water flows from the foot of the dam, providing the environmental recovery of the river bed. Furthermore, in order to minimize the environmental impact of the new construction it will use part of the existing Belesar HPP facilities, taking the flow from the middle-bottom outlets of the dam and using an existing cavern as location for the new powerhouse.

Table 3. Belesar II Power Plant main data Belesar II Power Plant

Number of power units 2 Francis Flow rate per power unit 10 m3/s

Maximum net head 113 m

Unit capacity 9.7 MW

Figure 5: Three-dimensional model of the new Belesar II Hydroelectric Power Plant

Just like Belesar II, Peares II HPP will take the flow from the bottom outlets of the dam. The tailwater race of the new power plant will be at the foot of the existing Peares dam, so the water will flow again all along the river bed.

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Table 4. Peares II Power Plant main data Los Peares II Power Plant

Number of power units 2 Francis Flow rate per power unit 11.5 m3/s

Maximum net head 83 m

Unit capacity 9.1 MW

Figure 6: Three-dimensional model of the new Peares II Hydroelectric Power Plant

2. ISSUE Although the new Belesar II and Peares II HPP projects were already designed in order to optimise the use of pre-existing facilities and to recover the riverbed, there was discussion on the possibility that if the water was taken from the dam bottom outlets it may be poor in dissolved oxygen during the period of thermal stratification of the reservoirs. Most aquatic organisms need dissolved oxygen (DO) to survive and grow. Plus, DO is important for: photosynthesis, oxidation-reduction, mineral solubility and the decomposition of organic matter. Besides causing the death of species due to anoxia or hypoxia, discharging water with insufficient dissolved oxygen could cause undesirable environmental effects on the fish and macro invertebrates such as (EPRI, 2002):

Effects on their growth Effects on their reproduction Effects on their behaviour and swimming abilities Poorly formed eggs and larvae Reduced fish diversity Greater susceptibility to disease Changes in the trophic chain Changes in the composition and abundance of macro invertebrates.

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On the other hand, the release of water with anoxia or hypoxia caused by a hydroelectric facility has risks and effects for the developer such as:

Fines and sanctions due to the breach of the law. Restrictions on the operation of the power plant by competent authorities Damages to a company’s corporate image.

In an effort to avoid all of the undesired effects outlined above, Gas Natural Fenosa conducted a preliminary analysis of the limnology of the Belesar and Los Peares reservoirs to identify possible baseline problems related to oxygen insufficiency at the bottom of the two reservoirs, which is where the water would be taken for the new power plants.

Figure 8: Profiles of Belesar reservoir during the 2012 stratification months

Figure 9: Profiles of Peares reservoir during the 2012 stratification months

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The data found (figures 8 and 9) showed that the two reservoirs featured thermal stratification, which takes some time to form in the summer but last throughout the autumn. This is perhaps because they are large reservoirs. Likewise, hypoxia and even anoxia levels were found in the hipolimnion which corroborates the problem of the lack of oxygen at the bottom of the reservoirs. 3. ANALYSIS OF ALTERNATIVES AND CHOSEN SOLUTION After verifying the existence of the problem, the different technological solutions available to mitigate the risk detected were studied. The scientific literature was consulted with different options for action found basically as EPRI texts (2002, 2009).

Figure 10: Analysis of alternatives studied

The key was finding the most favourable cost/benefit solution to increase the dissolved oxygen levels from 0 mg/l in the intake to 6mg/l in the riverbed, as established by current law. Diagnosing the problem during the design phase of the two new power plants was decisive. Finally, and in accordance with the literature previously consulted (Fisher et al, 2009) (Hopping, March & Wolff, 1999), with references to the fact that systems integrated in the design of the electromechanical equipment, are the ones that offer the best cost-benefit system with the lowest efficiency losses and the best guarantee for results, the decision was made to include the oxygen gain technology and guarantee criteria for the aerating turbines in the tender documents.

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3.1. Aerating turbines The company Andritz Hydro was finally awarded with the contract for the aerating turbines for the two power plants, as they offered oxygen gain guarantees with an aerating system in the draft tubes of each generator. The system consists of: (1) a blower that supplies compressed air, (2) a natural entrance of air for natural suction of the turbine and (3) an air duct that connects the two previous suppliers to a profiled manifold attached to the draft tube outer wall along the periphery (4), connected to the inside by a serial of holes, and (5) protected from the stream through internal deflectors located upstream the holes.

Figure 11: Aerating system installed and developed by Andritz Hydro

The compressor is equipped with a 75 kW engine and a frequency variator that allows it to operate from 33 Hz to 60 Hz. By varying the quantity of air introduced and the initial proportion of dissolved oxygen in the water, the proportion of oxygen finally absorbed by the turbined water will vary. This is achieved by varying the frequency, with the possibility of introducing air flows from 1500 Nm3/h (33 Hz) to 3000 Nm3/h (60 Hz). The system includes a pressure gauge with an indication of the pressure, and a PT100 probe to ensure the parameters of the introduced air are correct. The goal of this system is to feed the draft tube with air by natural suction and/or with compressed air in order to get an acceptable level of DO downstream the draft tube, to facilitate and allow fish life and also minimizing the effect on the efficiency. The cost of the aerating systems was less than 7% of the total cost of the electromechanical equipment for the two power plants.

(1)

(2)(4)

(3)

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4. RESULTS In 2013, the aerating devices were tested in the two power units at Los Peares II Hydroelectric Power Plant, due to the fact that construction and assembly ended prior to the thermal stratification break in Los Peares reservoir. The testson the devices in both Los Peares II units were successful, even in the worst case scenario, with the water starting with 0 mg/l of DO in the dam bottom outlets where the intake for the new power plant is located. All expectations were met as far as the dissolved oxygen gain (from 0 to 4 mg/l) at the tailrace is concerned, and with barely any efficiency losses (0.5%) with the aerators operating at full load. Moreover, although the water at Los Peares II tailrace channel had 4 mg/l of DO, the turbulence created barely a few metres downstream by existing rapids, increased the DO to at least the 6 mg/l required by the administration.

Figure 12: Peares II HPP tailrace Figure 13: Downstream rapids that raise the DO

The graphs in figure 14 show the results obtained in the tests of the Los Peares II generators, always starting at 0 mg/l of DO in the intake. Three different situations were observed through the results:

With low loads (up to 40%) and starting with 0 mg/l of DO in the intake, the natural ventilation connected to the aspiration pipe is enough to reach values of up to 7.5 mg/l of DO in the discharge.

With a 50% load, oxygen is added via the natural ventilation but it does not exceed 3 mg/l, meaning aerators must be used even though not used at full power.

From 60% to 100% load for each generator, the natural ventilation hardly contributes any oxygen to the unit discharge meaning the level of DO must be raised to 4 mg/l using the aerators.

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Figure 14. Results of the aerator tests at the Peares II Power Plant

5. CONCLUSIONS AND RECOMMENDATIONS It is important to take into account the environmental variables in project design phases given that this is the phase when the greatest cost-benefit results can be achieved to mitigate environmental and social problems. Likewise, and specifically for hydroelectric projects, it is essential to have representative and quality baseline data on the social and environmental scope of the project, given that it is only with solid data that solid decisions can be made and possible problems or opportunities for the project can be detected. For this article, it was essential to have limnological data on the two reservoirs during the project design phase. This made it possible to detect the anoxia problem at future power plants and prevent later problems, both for the environment and the company. If a similar problem is detected in a design phase of a hydroelectric project, the option of integrating aeration in the electromechanical equipment seems ideal, given that it reduces maintenance costs and efficiency losses are normally low. These losses even disappear when the aerating devices are not activated during most part of the year, when due to seasonal variances the water at the bottom of the reservoir has sufficient dissolved oxygen. REFERENCES Espejo,C. ,García, R. (2010): Agua y energía: producción hidroeléctrica en España, Investigaciones Geográficas, 51: pp. 107-129. Universidad de Alicante, Spain. Maintaining and Monitoring Dissolved Oxygen at Hydroelectric Projects: Status Report, EPRI, Palo Alto, CA: 2002 1005194. Hydropower Technology Roundup Report: Technology Update on Aerating Turbines. EPRI, Palo Alto, CA: 2008. 1017966. Foust, J.M. , Fisher, R.K. , Thompson, P.M. , Ratliff, M.M. , March, P.A. (2009): Integrating Turbine Rehabilitation and Environmental Technologies: Aerating Runners for Water Quality Enhancement at Osage Plant, Waterpower XVI, Penn Well Corporation. Hopping, P. N., P. A. March, and P. J. Wolff. 1999. Justifying, Specifying, and Verifying Performance of Aerating Turbines. Proceedings of Waterpower 99. New York, New York: American Society of Civil Engineers.

0

1

2

3

4

5

6

7

8

9

40 50 60 70 80 90 100

DO (m

g/l)

LOAD (%)

Unit I. Air OFF

Unit II. Air OFF

Unit I. Air ON

Unit II. Air ON

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– 6TH

, 2014

“EFFECTIVE SEDIMENT CONTROL IN A RESERVOIR”

Pranoto.SA, Suripin,Suharyanto Diponegoto University

[email protected]

Djoko Legono Gajah Mada University

Isdiana River Research Center,Surakarta

ABSTRACT

Sedimentation in a reservoir cannot be avoided. The average rate of sedimentation on the storage

volume reduction of a reservoir in the world is about 1 % per year (Yoon,1992), meanwhile, the

storage volume reduction in several reservoir in Indonesia reaches 1,64% to 2,83% per year

(Atmojo,2012). These sediment’s accumulations in the reservoir will continually reduce the storage

volume, thus the intended functions of reservoirs for flood control (Atmojo, 2013), irrigation and water

supply, electric generation, etc. will also reduced and not optimal.

Some of sediment control measures have been practiced in reducing sediment accumulation in

reservoirs around the world. In principle, there are two approaches i.e., reduce the sediment input to a

reservoir by land conservation, construction of check dam, sand pocket, diversion channel, etc. and

reduce the sedimentation in the reservoir by sluicing, turbidity current, dredging, and flushing (Morris

and Fan, 1998; Emamgholizadeh et al., 2006).

This paper presents the performance of sediment’s reduction from a reservoir by flushing, sluicing,

and disturbing flushing based on some laboratories results (Atmojo,2012). It is expected that this

paper can contribute to elicits some finding on the selection of which suitable method for sediment

reduction from a reservoir.

Keywords: control on reservoir sedimentation, flushing, sluicing, disturbing flushing.

INTRODUCTION

Sedimentation in a reservoir cannot be avoided. The average rate of sedimentation on the

storage volume reduction of a reservoir in the world is about 1 % per year (Yoon,1992),

meanwhile, the storage volume reduction in several reservoir in Indonesia reaches 1,64% to

2,83% per year (Atmojo,2012). These sediment’s accumulations in the reservoir will

continually reduce the storage volume, thus the intended functions of reservoirs for flood

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control (Atmojo, 2013), irrigation and water supply, electric generation, etc. will also reduced

and not optimal.

Some of techniques for reservoir sedimentation control are available. Principally they are:

1. To prevent sediment material from entering the reservoir,

2. To prevent settlement of the sediment material in the reservoir, and

3. To remove sediment material which are already settled in reservoir.

The measures to prevent sediment material to enter into a reservoir is by reducing erosion

upstream i.e., by constructing check dam, sand pocket, and/or by diversion channel. The

measures to prevent the sediment material from settled down is by opening flushing gate

during river flood or by opening under sluice gate such that higher consentrated sediment to

flush out and not settling in (venting) (Morris and Fan, 1998; Emamgholizadeh et al., 2006).

Meanwhile, the sediment already settled in a reservoir can be removed by flushing, disturbing

flushing, and dredging (Jugovic et al., 2009; Tallebbeydokti and Naghshineh, 2004; Shen,

1999).

This paper discusses the performance of reservoir sedimentation control by sluicing, flushing,

and disturbing flushing based on physical model.

METHOD AND MATERIAL

This paper presents the sediment control with the physical hydraulic model, to model sediment

removal by means of sluicing, flushing, and flushing with disturbed (disturbing flushing). The

model is performed at River Research Center Surakarta, based on prototype of design flushing

gate at Gajah Mungkur Dam (JICA, 2007), and the sediment material is represented by coal

ash. Basically, the data used is from research on the sluicing and disturbing flushing

performed by River Research Center Surakarta, in addition to the flushing model by

Pranoto.SA.

Modelling Procedures:

The physical model made is using length scale 1:66.67.

Slucing Modeling: The sediment material poured at upstream 350 cm from gate at the rate of

60 liter/hour. The discharge and gate openings are 5.5 l/s with opening 2.50 cm; and 11.02 l/s

with opening 5.30 cm. The water level at upstream of the gate is constant 13.95 cm. After each

model running is finish, the sediment material leaved behind will be measured. Therefore the

“flushed” sediment can be calculated, and efficiency is known by comparing with the poured

sediment number before running.

Flushing Modeling: it is aimed to analyse the scouring of sediment already settled in by

opening flushing gate. It’s modeled with 3.00 cm sediment thickness and maintained upstream

water level at 13.95 cm. the gate is then opened for one hour for each discharge variation. It

uses discharge variation similar to those used for sluicing model. The sediment material is first

made wet by 14% of water to prevent it from floating. It is then slightly compacted with 3.00

cm thicks. After each modeling is finish, the remaining sediment material can be measured.

Therefore the “flushed” sediment can be also analysed.

Disturbing Flushing: is aimed to model the amount of flushed away of sediment when the

sediment has already settled in by flushing with disturb (disturbing flushing). In reality, the

disturbed may caused by excavator action. The sediment thickness is similar to flushing

model, i.e. 3.00 cm. However, during the flushing it is also combined with disturbing the

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sediment. After finishing each model run, the remaining sediment material as well as the

flushed away sediment can be calculated. The modeling used the similar discharge and

opening with sluice model.

Material:

The water used is circulating water pump from ground reservoir and the used water flow back

into the ground storage. The model situation and the gate position is shown at Figue 1, 2, and

3. The flushing gate has dimension of 2x11.25 cm. The length of storage 495.00 cm, the width

of storage 250.00 cm. The velocity measurements at upstream is conducted by Laboratory

current meter SV. 108 with blade seri-A, at downstream it used V-Nocth B=0.945 m, D=0.331

m which has been calibarated. The sediment material used is coal ash with unit weight 1.558

kg/l. The sediment used before and after model running is measured at the same water content.

Figure.1 Model Situation

Stilling Bazin

Stilling Bazin

Pump

Water Supplay Canal

Baffle

Structure

Dra

in C

an

al

Flushing Gates

IV - 97

Figure.2 Long Section of Flushing Gate

Figure.3 3D of The Flushing Gate and Photo

Location of Water level

measurement

Step plate

Elevation of Sediment

IV - 98

MODELLING AND RESULT

The modeling result of sluicing, flushing and disturbing flushing are shown at Table 1, 2, and

3 respectively.

Sluicing Model:

The result of the sluicing model run is shown at Tabel.1. It shows that the percentage of

sediment removal is 30% (from discharge 5.51 l/s) and 35.83% (for discharge 11.02 l/s). It

shows common trend that higher discharge is higher sediment removal

Table 1 Percentage of Sediment Release Result From Sluicing Method

Discharge

(l/s)

Vol Sediment

Before Running

(liter)

Gate

Opening

(cm)

u/s

Water level

(cm)

Vol Sediment

After Running

(liter)

Sediment

Removal (%)

5.51

11.02

60

60

2.50

5.30

13.95

13.95

42.00

38.50

30.00

35.83

Flushing Model:

The result of flushing model is shown at Tabel.2. It shows that the percentage of sediment

removed using this flushing method is 4.21% and 6.18% which are much smaller than that

used by sluicing.

Table 2 Percentage of Sediment Release Result From Flushing Method

Discharge

(l/s)

Vol Sediment

Before Running

(liter)

Gate

Opening

(cm)

u/s

Water level

(m)

Vol Sediment

After Running

(liter)

Sediment

Removal (%)

5.51

11.02

272.00

275.00

2.50

5.30

13.95

13.95

260.55

258.00

4.21

6.18

Disturbing Flushing:

The results from using disturbing flushing is shown at Tabel.3. It a glance, the percentage of

sediment removal is 22.48% and 23.52% for discharge 5.51 l/s and 11.02 l/s respectively.

In general that we see only the sediment remove, we will conclude that the most effective

measure is sluicing, then disturbing flushing, and the lastly by flushing only.

Table 3 Percentage of Sediment Release Result From Disturbing Flushing Method

Discharge

(l/s)

Vol Sediment

Before Running

Gate

Opening

u/s

Water level

Vol Sediment

After Running

Sediment

Removal (%)

IV - 99

(liter) (cm) (m) (liter)

5.51

11.02

231.76

231.76

2.50

5.30

13.95

13.95

179.65

177.25

22.48

23.52

DISCUSSION

In order to justify the efficiency of sediment removal, it need to also consider the sediment

removal per unit of water discharge. The sluicing method is more effective due to mainly to

the stage of sediment material which are not yet settled in. Therefore, in this case, there does

not requires energy to overcome initial tractive force to move the sediment material.

Meanwhile, the purely flushing will require energy to overcome the initial tractive force in

order to move the sediment material, which therefore reducing the sediment to be removed.

Similary, in disturbing flushing, although additional energy has been given to “strirred” the

settled in sediment, still not all settled in sediment can be strirred up. The removal of sediment

result from that method is higher than purely flushing, but still lower then that result from

sluicing. In fact, for disturbing flushing will also depend on the duration and speed of

disturbing.

Figure.4 Sediment’s Removal Efficiency

Table 4 Average Removal of Sediment Result From Sluicing

Discharge

Q (l/s)

Gate

Opening Cm

Sediment

Remove (%)

Sed Remove per

liter Disch (%)

Average Removal

of Sediment %

(1) (2) (3) (4)=(3)/(1) (5)

5.51

11.02

2.5

5.3

30

35.83

5.44

3.25

4.35

3035.83

4.21 6.18

22.48 23.52

0

10

20

30

40

50

60

2.5 5.3

Slucing Flushing Distr Flushing

Gate Opening-cm

Effi

cin

cy-%

IV - 100

Table 5 Average Removal of Sediment Result From Flushing

Discharge

Q (l/s)

Gate

Opening Cm

Sediment

Remove (%)

Sed Remove per

liter Disch (%)

Average Removal

of Sediment %

(1) (2) (3) (4)=(3)/(1) (5)

5.51

11.02

2.5

5.3

4.21

6.18

0.76

0.56

0.66

Table 6 Average Removal of Sediment Result From Disturbing Flushing

Discharge

Q (l/s)

Gate

Opening Cm

Sediment

Remove (%)

Sed Remove per

liter Disch (%)

Average Removal

of Sediment %

(1) (2) (3) (4)=(3)/(1) (5)

5.51

11.02

2.5

5.3

22.48

23.52

4.08

2.13

3.11

CONCLUSION AND RECOMMENDATION

Conclusion:

1. The sluicing method is more efficient compare to the flushing and disturbing flushing

2. The efficiency of sluicing 1.4 times higher than disturbing flushing, and 6.6 times higher

than flushing.

3. Sediment flushing by maintaining upstream water level constant is more efficient for

frequent small discharges than bigger discharges.

Recommendation:

In order to the sharper modeling result, advanced modeling needs to include:

-More discharge variation

-Large running time

-More upstream water level variation.

ACKNOWLEDGEMENT

I sincerely thanks to the River Research Center Surakarta, who has allowed me to conduct this research

at laboratory. Specially thanks to all colleges who has helped this research well.

REFERENCES

Atmojo P.S,2012. The Effect of Water Level on The Effectiveness of Sediment Flushing,

International Journal of Waste Resources, Vol 2, N0 2 (2012), p 20-31.

IV - 101

Atmojo PS, 2013. Sedimentation Effect in Reservoir Toward The Declining Fuction of Flood

Control, International Seminar on Water Related Disaster Solutions, Jogyakarta,

Indonesia.

Emamgholizadeh, S., Bina M., Fathimoghadam, M., and Ghomeyshi, M., 2006. Investigation

and Evaluation of the Pressure Flow Flushing Through Storage Reservoir, ARPN

Journal of Engineering and Applied Science Vol. 1, No.4, December 2006.

JICA, 2007, Final Repot, Volume III Supporting Report I : The Study on Countermeasure For

Sedimentation in The Wonogiri Multipurpose Dam Reservoir in The Republic of

Indonesia, Directorate General Of Water Resources Ministry of Public Works The

Republic of Indonesia

Jugovic, J.C., Stefan, S., Schuster, G., Nachtnebel, HP, 2009. Hydraulic Flushing of Alpine

Reservoir, International Symposium on Water Management and Hydraulic Engineering,

,1-5 September 2009 , Ohrid/Mecadonia

Morris G.L, Fan J, 1998, Reservoir Sedimentation Handbook Design and Management of

Dam,Reservoir, and Watersheds for Sustainable Use, McGrow-Hill Companies,Inc.,

New York.

Shen, H.W, 1999. Flushing Sediment Through Reservoir, Journal of Hydraulic

Reasearch,Vol.37, 1996, No.6

Talebbeydokhti, N. and Nagheshineh, A., 2004. Flushing Sediment Through Reservoir,

Iranian Journal of Schience and Technology, Transaction B, Vol.28, No.B1, 2004.

Yang Chih Ted, 1996. Sediment Transport Theory and Practice, McGraw-Hill,Singapore.

Yoon,Y.N,1992, The State and The Prospective of Direct Sediment Removal Method From

Reservoir. International Journal of Sediment Research, 7, No 2, 99-116

IV - 102



Ways to Improve Water Quality in Diponegoro Reservoir at Krengseng Watershed, Semarang

2(14pt [Blank line 11 pt]

Grace Lucy Secioputri & Rahmat Kurniawan Civil Engineering, Diponegoro University, Semarang, Indonesia

[email protected] [Blank Line 10 pt]

Suseno Darsono Civil Engineering, Diponegoro University, Semarang, Indonesia

[Blank Line 10 pt] Sudarno

Environmental Engineering, Diponegoro University, Semarang, Indonesia [Blank line 10 pt] [Blank line 10 pt] [Blank line 10 pt] [Blank line 10 pt]

ABSTRACT This paper explains how to maintain and improve water quality of the Diponegoro Reservoir. Krengseng watershed is located in Banyumanik sub-district and Tembalang sub-district, which is part of Diponegoro University campus area. The influent water to the reservoir mostly comes from urbanize areas, therefore the quality of the reservoir inflow will fit with domestic wastewater quality standards. In order to improve the reservoir water quality, domestic wastewater sewerage systems and treatment plants are necessary for the Krengseng watershed area. Water samples were taken from the Krengseng River at 17 locations during the end of the dry season. Parameter such as COD, DO, pH, temperature, nitrogen, and phosphate was determined. From the results of samples, concentrations of COD, nitrogen and phosphate exceeded the water discharge criteria. Therefore, a wastewater treatment plant should be designed. Septic tanks as primary treatment and anaerobic filters as secondary treatment were chosen for the treatment plant. EPA SWMM 5.0 was utilized to analyze and design the sewer system. A small bore sewer was used as the main idea for the sewer system. Specifications of the piping system must meet the following criteria; such as minimum pipe slope more than 0.006, flow rate between 0.6-3 m/s, and water flow quantity in the pipe between 0.2-0.8 of the pipe diameter. Total cost for this design was Rp 133.819.636.500. [Blank line 10 pt] Keywords: Water Quality, Wastewater, Sewerage System. [Blank line 10 pt] [Blank line 10 pt] 1. INTRODUCTION [Blank line 10 pt] Diponegoro dam is located in Krengseng River and the dam is still under construction. The main purpose of the reservoir is for education. The reservoir also can be used to reduce the peak of Krengseng River flood and as a source of water for local domestic water treatment plant. The catchment area of the reservoir is part of Tembalang and Banyumanik sub-district, which is used as residential area, business and industrial areas. During the dry season, most of the reservoir inflow comes from domestic wastewater. It is important to improve and to maintain the quality of water influent using domestic wastewater treatment systems. According to The Agency for Regional Development and Central Bureau of Statistics City of Semarang, the population growth rate of Semarang is quite high. Based

IV - 103

on the City of Semarang population data in 2012, Tembalang sub-district population growth rate is around 3.69% and Banyumanik sub-district population growth rate is around 1.09%. Moreover, all faculties of Diponegoro University had moved to new campus at Tembalang sub-District. This will cause the number of houses and business area in Tembalang sub-District and Banyumanik sub-District increasing. As the increasing population, the quantity of domestic wastewater will also increase. [Blank line 10 pt] Nowadays, the drainage system in Tembalang and Banyumanik sub-districts are still a combined system and all of the water flows into Krengseng River. It makes the quality of influent water-to-water body not compliant with the wastewater standards of the Environmental State Minister Regulation No.112 Year 2003. Therefore, a domestic wastewater treatment system should be planned in order to obtain wastewater quality that suitable with wastewater standard. [Blank line 10 pt] [Blank line 10 pt] 2. METHOD OF STUDY [Blank line 10 pt] Investigating the existing water quality of Krengseng River and designing wastewater networks are two activities in this study for improving the future water quality reservoir. According to topographical conditions and flow directions, the Krengseng river watershed consists of 17 sub-catchments (see figure 1). These seventeen outlets of sub-catchment were determined as sampling location for the river water. [Blank line 10 pt] Sampling of river water was conducted during dry season. The river discharge, flow velocity, pH, and DO were measured. In addition, parameters such as COD, Ammonium, Nitrate, Nitrite and Phospate were measured from water samples in laboratorium (Sudarno et al, 2013). [Blank line 10 pt]

[Blank line 10 pt]

Figure 1. Krengseng River Sub-Watershed Reference: Sudarno et al, 2013.

[Blank line 10 pt] On site physical condition and topographical maps, population, infrastructure facilities, and socioeconomic condition of catchment area are required for designing the wastewater system. These data will be used for analyzing the most suitable domestic wastewater system such as pipe diameter, pipe slope, flow rate in pipe, and dimension of the wastewater treatment plant. According to the topographical condition of the catchment area and in order to minimizing operational costs, the wastewater system was implemented using a gravitational system. EPA SWMM 5.0 hydraulic software was utilized for

IV - 104

analyzing the hydraulic dynamics of the open channel pipe networks such as; flow rate, pipe slope and flow quantity in pipe network. [Blank line 10 pt] [Blank line 10 pt] 3. RESULTS AND DISCUSSION [Blank line 10 pt] 3.1. Water Quality [Blank line 10 pt] Water quality of sampling point is summarized in Table 1. Parameters, expecially COD, NH3, NO2

- and Phosphate exceed the recomendation value, that might cause a loss in exosystem fuctnion and increase risk of downstream eutrophication. A control over COD and nutrient loads into river which are asociated mainly with human activity, should be taken. [Blank line 10 pt]

Table 1 Water Characteristic Sampling Location

TSS (mg/l)

COD (mg/l)

NH3 (mg/l)

NO2- - N

(mg/l) NO3

- - N (mg/l)

Phosphate (mg/l)

T1 30 45* 4,23* 0,01 0,02 0,27* T2 68 45* 3,65* 1,61* 4,05 0,19 T3 26 33* 4,99* 0,01 0,16 0,16 T4 70 70* 7,29* 0,01 0,28 0,17 T5 26 30* 3,39* 1,75* 0,26 0,16 T6 300 47* 3,86* 0,90* 0,10 0,19 T7 114 30* 3,16* 0,61* 0,06 0,27* T8 62 285* 2,98* 1,12* 0,12 0,25* T9 60 113* 1,40* 0,45* 0,41 0,51* T10 90 77* 53,08* 0,54* 0,52 0,27* T11 20 113* 3,78* 0,44* 0,22 0,30* T12 180 30* 4,43* 0,61* 0,33 0,31* T13 112 65* 4,59* 0,50* 0,30 0,25* T14 180 53* 4,20* 0,64* 0,15 0,31* T15 62 40* 4,50* 1,20* 4,40 0,29* T16 62 28* 4,49* 0,38* 0,01 0,25* T17 120 23 4,25* 10,11* 0,25 0,30*

* exceeds the river water quality standard according to Government Regulation No. 82 Year 2001 Reference : Sudarno et al, 2013.

[Blank line 10 pt] [Blank line 10 pt] 3.2. Service Area [Blank line 10 pt] In order to plan wastewater treatment system, service area should be determined. The wastewater treatment was located at a lower elevation than local residence, so that the system could avoid the utilization of pumps. Also, the wastewater location must be close to the river so that the wastewater influent can easily flow into river. Here are the steps: The service area for the wastewater treatment system in the Krengseng River

catchment area was divided into several zones or sub-service areas. According to topographical condition of the Krengseng River catchment area was divided into 24 zones or sub-service areas, the sub-service area cannot be determined according to administrative areas. The locations of each sub-service area are shown in figure 2.

IV - 105

[Blank line 10 pt]

[Blank line 10 pt] Figure 2. Service Area

Reference: Grace and Rahmat, 2013. [Blank line 10 pt] The pipes of the sewerage system should be placed along the roadside and equipped

with a manhole for every pipe junction. A manhole should also be placed every 50 m for the purpose of sewerage maintenance of a straight-line pipe.

[Blank line 10 pt] [Blank line 10 pt] 3.3. Wastewater Sewerage and Treatment Plant Design [Blank line 10 pt] Banyumanik and Tembalang sub-districts are still served with combined drainage system that will cause degradation in the water quality of the Krengseng River. For that reason, the wastewater network system must be separated with a drainage system. Based on recent study of domestic wastewater management in Banyumanik and Tembalang sub-districts, 99% of houses have been equipped with septic tank (Rahman, 2012). Therefore, a small-bore sewer system was chosen as a domestic wastewater sewerage system which is most of the influent water into the domestic wastewater sewerage system only contains minimum sediment (Grace and Rahmat, 2013). [Blank line 10 pt] A domestic wastewater system with gravitation flow was planned for this domestic wastewater system. Septic tank was selected as the primary treatment of the system and an anaerobic filter as the secondary treatment. An anaerobic filter system was chosen for maximizing the quality of outflow water, because it will decrease BOD until 70-90%. Also this system is compatible for treating domestic and industrial wastewater with low TSS (Grace and Rahmat, 2013). [Blank line 10 pt] [Blank line 10 pt] 3.4. Pipe Design [Blank line 10 pt] An open channel flow assumption was used to calculated the pipe dimensions, with flow discharge in pipe between 0.2 m3/s<D<0.8 m3/s, flow velocity between 0.6-3 m/s, and minimum pipe slope was 0.006 or 0.6%. PVC for wastewater or PVC class D was used for

Diponegoro Education

Dam

IV - 106

the domestic wastewater network with pipe diameters from 48 mm until 267 mm and the total length was 69.905,26 m [Blank line 10 pt] 3.3.1. Wastewater Treatment Plant Design [Blank line 10 pt] In this design, septic tank was used as primary treatment and anaerobic filter as secondary treatment with a wastewater influent BOD values of 250 mg/l. This value was based on assumption from literature which stated that normally BOD5 values for domestic wastewater are from 100-250 mg/l and COD values are from 200-600 mg/l. The wastewater treatment plant dimensions design was calculated from the domestic wastewater discharge which used the average domestic wastewater discharge. Here are the steps for analyzing dimensions of the wastewater treatment plant: a. Septic Tank Calculation of COD effluent from septic tank. COD removal is estimated based on the effect of sediment settlement and settling time or HRT. In this case HRT was assumed to equal to 2 hours. Figure 3 is a graph that shows the relationship between domestic wastewater settling time and COD removal rate. [Blank line 10 pt]

[Blank line 10 pt] Figure 3. Domestic Wastewater Settling Time with COD Removal Graphic

Reference: Development of Settlement Environmental Health Directorate, 2013. [Blank line 10 pt] Equation (1) and Equation (2) are equations for estimating COD removal rate from septic tank. [Blank line 10 pt]

COD removal= SS Ratio /COD0.6

× multiplier factor (1) [Blank line 10 pt] The multiplier factor can be determined from figure 3. [Blank line 10 pt]

CODef luent(%) = % % (2) [Blank line 10 pt] Calculation of BOD removal Correlation between BOD removal and COD removal is not linear. Therefore for the domestic wastewater correlation between the percentage of COD removal and BOD removal used multiplier factor shown in figure 4. [Blank line 10 pt]

Mul

tiplie

r Fa

ctor

for

CO

D R

emov

al R

ate

Settling Time (hour)

IV - 107

[Blank line 10 pt] Figure 4. Correlation between COD Removal Percentage and Multiplier Factor for BOD

Removal Reference: Development of Settlement Environmental Health Directorate, 2013.

[Blank line 10 pt] In order to calculate BOD removal rate from septic tank, Equation (3) and Equation (4) is needed. [Blank line 10 pt]

BODremoval = multiplierfactor × CODremoval (3) [Blank line 10 pt] The multiplier factor can be determined from figure 4 and COD removal can be determined from equation (1). [Blank line 10 pt]

BODef luent = (100%− %BODremoval) × BOD (4) [Blank line 10 pt] Calculation of septic tank volume Each gram of BOD removal will produce 0.005 liter of sludge. Figure 5 shows the relationship between the sludge shrinkage and storage time. [Blank line 10 pt]

[Blank line 10 pt]

Figure 5. Correlation between Sludge Shrinkage and Storage Time Reference: Development of Settlement Environmental Health Directorate, 2013.

[Blank line 10 pt] Equation (5) is an equation for estimating the required volume for septic tank. [Blank line 10 pt]

Required Volume = (Sludge Volume + V) + 10% (Sludge Volume + V) (5) [Blank line 10 pt] Where : Sludge Volume = time of storage (month) x 30 x average domestic wastewater discharge x

lt/gr BOD removal x (BOD influent – BOD effluent)/1000 x volume every one gram

V = HRT x flow rate/hour [Blank line 10 pt] b. Anaerobic Filter Calculation of COD removal

Mul

tiplie

r fa

ctor

Months

IV - 108

Temperature is an important factor and it will affect the pollutant decomposition in anaerobic system. Normally, Indonesian average temperature is above 25oC. The correlation between temperature and temperature factor for COD removal is illustrated in figure 6. [Blank line 10 pt]

[Blank line 10 pt] Figure 6. Correlation Between Temperature Factor in COD Removal and Temperature

Reference: Development of Settlement Environmental Health Directorate, 2013. [Blank line 10 pt] Anaerobic decomposition process is affected by the initial COD content (wastewater strength) which shown in figure 7. [Blank line 10 pt]

[Blank line 10 pt] Figure 7. Correlation Between COD Removal Strength Factor and COD Value Reference: Development of Settlement Environmental Health Directorate, 2013.

[Blank line 10 pt] Media filter area also affected the capability of anaerobic filter to decompose pollutants. The correlation between COD removal factor and media filter area (specific surface area) is shown in figure 8. [Blank line 10 pt]

[Blank line 10 pt]

Figure 8. Correlation between COD Removal Factor and Media Filter Area Reference: Development of Settlement Environmental Health Directorate, 2013.

[Blank line 10 pt] As well as septic tank, the HRT also effects the COD removal. Figure 9 demonstrate the correlation between HRT and COD removal.

Tem

pera

ture

Fac

tor

Temperature OC

Stre

ngth

Fa

ctor

SS

A fa

ctor

SSA in m2/m3

IV - 109

[Blank line 10 pt]

[Blank line 10 pt] Figure 9. Correlation between COD Removal Factor and HRT

Reference: Development of Settlement Environmental Health Directorate, 2013. [Blank line 10 pt] The more chambers used in anaerobic filters it will produce 4% more efficient per chamber, although the effective volume in chambers were unchanged. To calculate COD removal, Equation (6) is needed. [Blank line 10 pt]

CODremoval = f.temperature x f.strength x f.SSA x f.HRT x (1+(total chamber x efficiency per chamber)) (6)

[Blank line 10 pt] Where f. temperature is a COD removal factor due to the temperature which is shown in figure 6, f. strength is a COD removal factor because of the initial COD content shown in figure 7, f.SSA is a COD removal factor due to the specific surface area of the media filter which is shown in figure 8 and f. HRT is a COD removal factor due to the settling time in chamber which is shown in figure 9. [Blank line 10 pt] If the result > 0.9, 0.9 will be used as an upper ceiling for the BOD removal in anaerobic filter system. If the result < 0.9, then that resulted number will be used. Final COD effluent can be calculated with Equation (7) and Equation (8) [Blank line 10 pt]

Final COD effluent after being processed = (100% - %COD removal) x COD influent (7) [Blank line 10 pt]

퐶푂퐷 = (퐼푛푖푡푖푎푙퐶푂퐷– 퐹푖푛푎푙퐶푂퐷)/퐼푛푖푡푖푎푙퐶푂퐷 (8) [Blank line 10 pt] Calculation of BOD removal It has the same calculation concept with BOD removal in septic tank. Calculation of anaerobic filter volume as secondary treatment Anaerobic filter dimension is determined based on the required volume of the anaerobic filter was calculated by Equation (9) [Blank line 10 pt]

Volume = HRT in anaerobic filter x average wastewater discharge/ 24 hours (9) [Blank line 10 pt] Table 2 illustrates the final wastewater treatment plant dimension design per zone or sub-service area and the wastewater treatment plant design shown in figure 10. Polypropylene and gravel was used as a media filter. [Blank line 10 pt]

Table 2. Wastewater Treatment Plant Dimension

Zone Unit Dimension (m) Length Width Height

A ST 8.5 5.5 3 AF 2.5 7 3

B ST 7 4.5 3 AF 2.5 5 3


C ST 6 5 3 AF 2.5 6 3

D ST 7 5 3 AF 2.5 6 3

CO

D R

emov

al F

acto

r

HRT (hour)

IV - 110


E ST 11 7 3 AF 2.5 9 3

F ST 13.5 7 3.5 AF 3 9 3.5

G(1) ST 8.5 5 3 AF 2.5 7 3

G(2) ST 9.5 6.5 3 AF 2.5 7 3

G(3) ST 4 3 3 AF 2.5 4 3

H ST 7.5 4 3 AF 2.5 4 3 I ST 8.5 5.5 3 AF 2.5 6 3 J ST 8 3.5 3 AF 2.5 4 3

K ST 5.5 4 3 AF 2.5 7 3

L ST 10.5 5 3 AF 2.5 7 3


M ST 10 5.5 3 AF 2.5 6 3

N(1) ST 9 4 3 AF 2.5 5 3

N(2) ST 4.5 4 3 AF 2.5 5 3

O ST 10 5.5 3 AF 2.5 6 3

P ST 7.5 4.5 3 AF 2.5 6 3

Q ST 4 4 3 AF 2.5 5 3

R ST 6 4 3 AF 2.5 5 3

S ST 13 7 3 AF 2.5 8 3

T ST 5 4.5 3 AF 2.5 6 3

U ST 12.5 8 3 AF 2.5 9 3

Explanation: ST = Septic Tank AF = Anaerobic Filter

Reference: Grace and Rahmat, 2013. [Blank line 10 pt]

[Blank line 10 pt] Figure 10. Typical of Wastewater Treatment Plant

Reference: Grace and Rahmat, 2013. [Blank line 10 pt] [Blank line 10 pt] 3.5. Cost Estimation [Blank line 10 pt] The estimate total cost of the project including tax for the construction of domestic wastewater treatment system was Rp 133.819.636.500,-. The total cost comes from the following components; Preparatory work, Rp 906.284.978,- Pipe work, Rp 37.347.365.704,- Manhole work, Rp 8.130.608.577,- Wastewater treatment plant work, Rp 66.252.177.514,- Other such as road reinstallation work, Rp 9.017.778.024,- [Blank line 10 pt] [Blank line 10 pt]

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CONCLUSION [Blank line 10 pt] The river water quality investigation showed that the water temperature, pH and Nitrate from the Krengseng river water can fulfill water quality level II. However, TSS, Phosphate, Nitrite, COD and DO from the Krengseng river are over allowable water quality level II. Therefore, eutrophication is a possible problem which may occur at the Diponegoro education reservoir (Sudarno et al, 2013). [Blank line 10 pt] Therefore, domestic waste water systems for the Krengseng river was needed to solve the eutrophication problem and maintain reservoir water quality at the Diponegoro education reservoir. The total pipes length of domestic wastewater sewerage system was 69.905,26 m. The wastewater sewerage system utilized the small-bore concept, septic tank and anaerobic filter with Cascade Filterpak YTH1140–Polypropylene and gravel as filter media in anaerobic filter system. The total cost of the domestic waste water system was Rp 133.819.636.500,- . [Blank line 10 pt] A mathematical model should be developed for improving and monitoring of the reservoir water quality, since the main purpose of the reservoir is for education. However, it is necessary to conduct further research in order to find an accurate BOD value and BOD removal rate. This will result in a domestic wastewater treatment plant which is more efficient and project cost will be reduced. Moreover, a further population survey for more details regarding the on-site population is necessary. This will make the average wastewater discharge value closer with the real on-site conditions. [Blank line 10 pt] It should be introduced and socialized to the inhabitants or residence of the Krengseng watershed area because of the public participation is an important key for operating and maintaining the domestic sewerage system. [Blank line 9 pt] [Blank line 9 pt] REFERENCES [Blank line 9 pt] Agency for Regional Development with Semarang City and Central Bureau of Statistics,

Semarang City. (2012): Semarang City population profile, pp.55. Semarang, Indonesia.

Development of Settlement Environmental Health Directorate. (2013): Wastewater Lesson 1. Dissemination and Socialization Sector of Settlement Environmental Health. The Ministry Of Public Works Directorate General Of Cipta Karya, Indonesia.

Elshemy1, M. Le, T.T. H.,Meon, G. and Heikal, G. (2010): First IAHR European Congress Available from: http://web.sbe.hw.ac.uk/staffprofiles/bdgsa/IAHR_2010_European_Congress/Papers%20by%20session%20final/Eco-Hydraulics%20II/EHIIe.pdf [Accessed 24th February 2014].

Environmental State Minister Regulation No.112 Year 2003. (2003). Indonesia. Rahman, Nova Henri. (2012): Study Research of Domestic Wastewater Management in

Tembalang, Candisari, Banyumanik, and Pedurungan Sub-District, Final Paper on Environmental Engineering. Diponegoro University, Semarang, Indonesia.

Secioputri, Grace Lucy and Kurniawan, Rahmat. (2013): Design of Domestic Wastewater Sewerage System for Krengseng Watershed, Semarang, Final Paper on Civil Engineering. Diponegoro University, Semarang, Indonesia.

Sudarno, Nugroho H., Samudro G, Manjo D. A. M., Wiratama F. A. (2013): Study of Eutrophication Risk in Diponegoro Education Dam, Semarang, Indonesia.

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– 6TH

, 2014

The Relationship Between Polycentropodidae Larva (Trichoptera) Abundance

anda hhdTTjjhkljdjjsgshjhfsdkjhskslsl;s;s;;s;;s;;sjsjkjffffrtttttttfggjfgjgkfkjkjf fffffjfjjfkkfjjj

and Characteristic Sediment in Sempor Reservoir,

2(14pt) Kebumen, Central Java

Kisworo Rahayu, Bondhan Wiriawan & Rr. Vicky Ariyanti BBWS Serayu Opak, Yogyakarta, Indonesia

[email protected]

ABSTRACT

The purpose of this research is to know the relationship between the abundance of

Polycentropodidae larva in Sempor Reservoir with the sediment’s characteristic and other

environmental factors that influence the abundance of Polycentropodidae larva. This larva is used

as aquatic indicator that states how rich organic material is in sediment. Sediment characteristics,

i.e. sandy or clay or silt has influence on larva’s live cycle. Larva benefited nutrients from clay

more than from sand. Therefore, the higher the rate of larva, the more clay sediment the reservoir

has. This also shows potency of additional bed load.

Samples of sediment was taken by using Petersen Dredge, measured 25 x 30 cm2, while samples of

water on sediment’s surface was taken by using water sampler, in four different stations, namely;

station I (Pakuwuhan), station II (Pengantalan), station III (Kumambang), and station IV

(Kedungwringin). To obtain Polycentropodidae larva sample, the sediment was filtered by sing

mesh net size 20-60 m, and the sample were identified and calculated. Data analysis for this study

uses Anava test and DMRT test. Correlation test was used to know the relation of abundance with

environment factors.

The result showed that the highest of abundance Polycentropodidae larva is 53,3 ind/m2 in station

IV (Kedungwringin), and the lowest 4 ind/m2 in station II (Pengantalan). Physical and chemical

characteristic of sediment are influencing the abundance Polycentropodidae larva. While other

environment factors that contributed much influence in the abundance of Polycentropodidae larva

are Ca, N, detritus and depth. This study concludes that the use of larva as indicator of sediment

characteristics can help to determine type of sedimentation condition in a reservoir.

Keywords: Polycentropodidae larva, sediment characteristic

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2

I. BACKGROUND

Reservoir is an artifical lake where water collected and stored by means of building a

dam. Current usage for a dam is not just a reservoir for irrigation and flood control

alone, but for a variety of purposes such as hydroelectric power generation, propulsion

machinery urban needs, irrigating canals and fisheries.

Sempor Reservoir is an artificial lake located in the village of Sempor, District

Sempor, Kebumen Central Java Province. This reservoir’s catchment is located on the

south side of South Mountain Serayu. In this catchment flows Pletuk river, Bleduk

river and Penusupan river are accommodated to fill the reservoir. Sempor Reservoir

catchment is located at altitude 7 30' 00'' to 7 35' 00'' and langitude between 109 25' 57''

to 109 33’ 27”.

Sempor Reservoir catchment area consist of 3 sub-catchments, namely:

1. Sub-catchment Pletuk with an area of 23.5 km2;

2. Sub-catchment Bleduk with an area of 15.4 km2;

3. Sub-catchment Penusupan with an area of 4.1 km2.

Sempor reservoirs began operating early in 1978, located in the catchment area of

approximately 43 km2 for the reservoir with a complex physical condition. This area

has a slope that varies from 25 – 50 degrees. The soil type is mostly regosol podzolic,

with land use of forest and non-forest. Area of non-forest area has reached 42% of the

reservoir catchment area consist of paddy fields, dry fields and villages (Mardjohan,

1980). If this condition continues to progressed there will be degradation of the forest

functions, which is green belt as rainwater catchment and the carrying capacity of the

reservoir waters Sempor. Haryanto (1999), reported that there had been forest logging

around the reservoir Sempor primarily located in Pengantalan river basin about 36 m2

each year. Logging is a major problem because it can lead to erosion and resulting

sedimentation of reservoirs. Increased sediment and eutrophication will accelerate the

silting of reservoirs and affect the ecological condition of the reservoir waters. Harsono

in Anonymous (2002) states that by the end of September 2012, reservoir’s silting

sedimentation Sempor reach 12 million m3. In addition to this, inevitable influx of

river flows into the reservoir which cause sediment transport and in the end created

silting process of reservoirs sediment. Improved materials that goes in a particular

reservoir waters will make changes to the reservoir environment. An example of this

condition can be seen in a marine sedimentation that describe the process of erosion in

the catchment area, but it can also reflect the productivity of lakes or reservoirs.

II. PROBLEM

Land in the catchment of Sempor Reservoir is earmarked for green belt, but many of

which are used for agriculture and settlements that can be a source of pollutants and

sediment into the reservoir. Activities of residents around the reservoir and as well as

its catchment area produces waste that goes into the reservoir, which can cause

decrease in reservoir’s water quality. This condition will cause the sedimentation

process to go faster and eutrification process may occur that ultimately will affect the

lives of aquatic organisms.

III. OBJECTIVES

1. Assessing the abundance of larvae Polycentropodidae in Sempor Reservoir.

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2. Assessing the relationship between the abundance of larvae Polycentropodidae with

Sempor Reservoir sediment characteristics.

IV. BENEFIT OF RESEARCH

Results are expected to complete the information of Sempor Reservoir’s Limnological

and provide information to the repertoire of science, society, and as consideration

materials for Sempor Reservoir’s manager and related agencies.

V. REVIEW OF LITERATURE

a. The Position of The Taxonomy and General Characteristics

Polycentropodidae ( Caddisfly Larvae )

Classification Polycentropodidae :

Phylum : Arthopoda

Class : insects

Division: Endopterygota

Order : Trichoptera

Family : Polycentropodidae ( Stehr , 1987)

Polycentro larvae live in a wide variety of aquatic habitats ranging from swamps,

reservoirs and rivers. Its small and soft body shape (delicate) Larvae

Polycentropodidae is included in division of Endopterygota (holometabola) then it

metamorphosed perfectly, from gelatinous eggs laid in surface water or moist soil.

These eggs will hatch after 3-4 days and become larvae that live in the sediment at the

bottom of a river or lake

The advantages of the presence of larvae Polycentropodidae on nutrient-rich lake

community is assumed not only as members of the ecology, but also as agents of

nutrient cycling. Larvae in aquatic habitats are mostly plant eating aquatic detritivor

(Stehr, 1987). Larvae adapt to live in the waters and sediments of the stream to avoid

bottom waters by constructing a building from grain of sand and detritus (caddis)

(Ward, 1992).

Although larvae Polycentropodidae is not considered for its great economic benefits,

but it is an important component of biological organisms indicator to determine the

quality of water (Mackay & Wiggins, 1978). Polycentropodidae larvae usually

function as food for fish and other aquatic vertebrates. Polypodidae larvae have a wide

range of variation in sensitivity to pollution of the dam's and it is able to live at high

temperatures and low levels of oxygen (Rosenberg & Resh , 1993).

b . Abundance

An abundance of organism is marked by number of individuals in a population that is

found in all specific areas. The above statement illustrates the magnitude of population

abundance in an area. Abundance of a population is influenced by competitors or

predators in the physical condition of environment and level of available resources

(Odum , 1971).

c . Sediments and sedimentation

Sediment is one very important part in the aquatic ecosystem. This is due to its

function as habitat for organisms. Sediment is transported materials in the form of

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suspension or precipitated minerals (bed load) by water or wind (Linsely , 1949).

Sources of sediment derived from a material in which there is not only a mechanical

activity alone but also a form of biological activity of vegetation biomass or animal

biomass (Goenadi , 2003). The water from river flows into reservoir, while carrying

sediment. In these reservoirs, the material may undergo deposition due to various

influence factors. The force of gravity, weight materials, reduced water velocity and

turbulence of the river is all factors that led to deposition. Therefore, material

deposition took place in the reservoir, then the process is commonly known as

reservoir sedimentation (Gupta , 1979) .

The materials can be deposited as elementary charge (bed load) and suspension load.

What is meant by elementary charge sediment are particles moving in a way gliding on

the river bottom layer, while the suspension is charge particles moving above the

elementary charge and mixed with the flow (Hsien Wen Sien , 1971). In addition to the

above charges are dissolved load, which is the chemical composition of the water,

which is produced from a variety of gas and can also be produced from materials

dissolved during its journey through rock or a solution derived from chemical reactions

and caused by human activities (John, 1971). This can lead to the accumulation of

sediment into nutrient and materials that are toxic and cause environmental degradation

in basic freshwater ecosystem.

VI. RESEARCH METHODOLOGY

Sampling in this research is using a Petersen Dredge sediments method and surface

water sampling using a Van Dorn Water Sampler. Another tool is a plastic bag to place

sediments, water jerry cans to place water samples, benthic filter -rise size 20, 40 and

60 mesh to filter sediment samples, a thermometer to measure temperature, pH meter

to measure the degree of acidity, DO kit to measure the oxygen content dissolved

The study includes three phases of the research:

1. Preparation, in the form of field surveys, preparation tools and materials used for

research

2. Implementation in the field

a. Sediment sampling was conducted at four locations: Station I

(Pakuwuhan) , Station II (Pengantalan) , Station III (Kumambang) and IV

Station (Kedungwringin) , each of 20 stations were taken at random

replications. Sampling using a Petersen Dredge 25 x 30 cm2.

b. Measurement of physical - chemical parameters, including: measurement

of temperature, light transparency, DO, CO2-free, alkalinity, pH, firmness

3. Laboratory observations such as measurements of available N, available P, organic

C and soil texture as well as the identification of benthos.

Data analysis

Data from benthic samples obtained by Petersen dredge 25 x 30 cm2 area expressed in

units. Benthos abundance calculated using the following formula:

000.10.

xSA

ON

Description:

N = abundance

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A = area of the mouth dredge

S = Number of decision to dredge

O = Number of individuals counted (WELCH, 1952)

Correlation analysis will examine the relationship between the variables change. The

results of the study analyzed the correlation between larval Polycentropodidae includes

correlation with environmental parameters sediment and detritus types.

VII . RESULTS AND DISCUSSION

The results showed the presence of larval abundance Polycentropodidae are likely to

differ in four observation stations are Station I (Pakuwuhan), Station II (Pengantalan) ,

Station III (Kumambang) and IV Station (Kedungwringin) .

Results abundance in the study area is described in Table 1 below.

Table 1 . Larval Polycentropodidae abundance in the reservoir Sempor

Station Abundance (individuals/m2)

Augustus November February

I 3.3 0 4

II 0 4 0

III 20 8 7.3

IV 33.3 6 14

Differences Polycentropodidae larval abundance in the four stations during the month

of August, November and February habitat conditions thought to be caused either

physically or chemically conditions. Differences habitat conditions can affect the

abundance of larvae Polycentropodidae. Polypocentropodidae larvae are abundant in

station IV (Kedungwringin), which has caused physical and chemical environmental

conditions that are suitable or appropriate to the life of the larvae include a shallow

container, adequate oxygen content and abundant detritus. Environmental conditions

are also associated with the current weather situation of research timing. Increased

rainfall will cause the water level rise will lead to increased volume of the reservoir

and extending inundation area. Inundation area around the dam were mostly consists of

pine trees, teak trees and shrubs will soon decay into organic waste. This flooding

could be expected to result in the number of minerals in water that is supplied from the

mainland that are now flooded. Thus, flooding will enrich waters’ nutrients. Increased

mineral and material suspended in water can be derived from the surrounding soil

erosion by rainwater and into the waters of lakes or reservoirs. In fertile waters, it

would make organisms population stability, including the population of

Polycentropodidae larvae.

a. Reservoir water environment parameters of Sempor

Aquatic environmental parameters such as measurement of physical factors, namely

water chemistry measurements of temperature, transparency, pH, alkalinity, dissolved

oxygen, dissolved carbon dioxide, firmness, detritus dry weight, levels of C - organic,

available N, available P and sediment texture are used.

b . Reservoir sedimentary characteristics of Sempor

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Physical characteristics of Sempor Reservoir sediments are generally arranged by the

clay fraction (0 < 63 micrometer), except at the edges with a depth of 0-5 m at Station

III composed mainly by sand. Low organic matter characterizes chemical

characteristics of sediments, generally below 10 % (>100 mg.g - 1 sediment), the

proportion of organic carbon < 4 % and C: N ratio is relatively high.

Table 2. Characteristics of Reservoir Sediment Sempor

Location

Strata (m)

Sediment

Texture

C-

Organic

(%)

Ratio

C:N

Organic

Materials

(%)

Silt/Clay

(%)

Sand

(%)

Dust

(%)

Station I

0 - 5 Clay 1,225 120,46 1,68 69,72 4,2 26,09

5 - 10 Clay loam

10 - 15 Silty clay

15 - 20 Clay

20 - 25 Clay

Station II 1,09 76,52 1,81 53,71 7,3 38,95

0 - 5 Silty clay

5 - 10 Clay

10 - 15 Silty clay loam

15 - 20 Clay

20 - 25 Clay

Station III 0,82 48,27 2,03 28,85 9,31 61,83

0-5 Sand

5 - 10 Clay


15 - 20 Clay

20 - 25 Clay

Station IV 0,81 78,35 1,58 30,98 18,98 50,04

0 - 5 Silty clay

5 - 10 Clay


Clay fraction and dust are the dominant reservoir sediment Sempor, even by further

study, it is indicated that the location of the station, especially the first (Pakuwuhan),

which is fine fraction of clay showed a fairly high proportion is 69.72 %. Natural state

and size of the catchment area of the lake or reservoir is the determinant of the input

material buildup. The area around the reservoir Sempor is largely a forest, which is

57.67 % of the total area of the reservoir area catchment Sempor. This contributes to

low erosion components and supports the high proportion of clay.

c. Relationship with the larvae Polycentropodidae reservoir sediment

characteristics Sempor

Larvae Polycentropodidae is one of the aquatic insects of the order Trichoptera that

lived aquatic sediments. Therefore, sediment characteristics are the factors that

determine the distribution and abundance of aquatic insect larvae especially

Polycentropodidae. From the results analysis on the sediment from four stations, it is

known that there are 3 types of Sempor sediment texture, namely clay, clay loam and

silty clay. There is a difference between the sediment composition of clay, sand and

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dust. The results showed that the sediment at the four stations have a relatively lower

content of sand than clay and found the relative abundance of different

Polycentropodidae larvae. The big difference in the composition of the sediment in the

Sempor reservoir is a result of suspected effect on Polycentropodidae larval

abundance.

Results of correlation analysis between sediment textures with Polycentropodidae

larval abundance indicate that the sand content in the sediment gives negative affect

larval abundance. Substrate of sand and gravel content the least amount of food for the

larvae. While the clay content of the sediments showed a positive and significant

impact on Polycentropodidae larval abundance. The higher the clay contents the higher

the Polycentropodidae larvae abundance.

VII. CONCLUSION

1. Highest larval abundance Polycentropodidae 53.3 individuals/m2 at Station IV

(Kedungwringin) and the lowest is 4 individuals/m2 at Station II (Pengantalan).

2. Physical and chemical characteristics of the sediment reservoir effect on larval

abundance Polycentropodidae.

3. Environmental parameters that give influence on larval abundance levels

Polycentropodidae are Ca, N, detritus and container.

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8

REFERENCE

Goenadi, S. 2003. Sedimen Transport, dalam makalah Seminar Nasional Optimalisasi

Fungsi Danau Sebagai Mikrokosmos.

Gupta, B.L. 1979. Water Resources Engineering and Hydrology. New Chand Jain. New

Delhi.

Haryono, E. 1999. Distribusi dan Kemelimpahan Larva Chironomus sp (Diptera

Chironomidae) di Waduk Sempor. Skripsi. Universitas Gadjah Mada.

Linsely, R.K. Kohler, M.A&Paulhus, IKH. 1949. Applied Hydrology. McGraw-Hill.New

York.

Mackay, R.J&G.B. Wiggins. 1978. Ecological Diversity in the Trichoptera. Annual

Review of Entimology. http://www.Tolweb.org/tree?group=Trichoptera&contgroup=

Endopterygota (dk 2 Maret 2013).

Mardjohan. 1980. Studi Volume Penimbunan Sedimen di Waduk Sempor Kabupaten

Kebumen Jawa Tengah. Skripsi. Fakultas Geografi. UGM. Yogyakarta.

Rosenberg, D.M.&V.H. Resh (editor). 1993. Freshwater Biomonitoring and Benthic

Macroinvertebrates. Chapman and Hall. New York http://www.tolweb.org/tree?

group=Trichoptera&contgroup= Endopterygota (dk 2 Maret 2013).

Stehr, F.W. 1987. Immature Insect. Volume 2. Kendall/Hunt Publishing Company. Iowa.

Ward, J.V.1992. Aquatic Insect Ecology. Biology and Habitat. John Willey and Sons Inc.

New York.

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http://www.tolweb.org/tree?group=Trichoptera&contgroup

http://www.tolweb.org/tree



Simulating the effects of reduction in dam height on water quality of reservoir (Case study of Baghan Dam)

Seied morteza Rad Office of Technical Planning, Bushehr Bureau of Water, Bushehr, Iran

[email protected]

Bahman Yargholi Asist. Prof., Agricultural Engineering Research Institute (AERI), Karaj, Iran

Fereidoon karampour

Office of Technical Planning, Bushehr Bureau of Water, Bushehr, Iran

ABSTRACT Water harvesting and dam building have been orthodox approaches to address water shortages in IRAN. A prime goal of dams is providing reliable resources for drinking and agricultural uses, where both quantity and quality have outmost importance. The water quality in dams is a function of the geometry of reservoir, long term planning for dams, water residence time in the reservoir, climatology of the region, and temperature and quality stratifications. In order to ensure appropriate water quality in reservoirs, simulation of water quality, by including temperature and quality gradients as a function of depth of reservoirs, before construction of dams is a vital prerequisite. In this contribution, temperature and quality stratifications of water in the Baghan dam– in Busher province in south of IRAN, are simulated at depths 48 and 60 meters using the CE-QUAL-W2 software. The input parameters for simulation include temperature, phosphorous, biological oxygen deficit, soluble oxygen, total dissolved solids, and algae growth which were sampled and monitored monthly in a time span of one year. Results indicate that for a twelve percent reduction in dam’s height the concentration of phosphorous and algae exhibit 50 and 43 percent reduction, respectively, where TDS increases by eight percent and ammonium and nitrate do not show significant differences. In conclusion, reduction in the height of dams not only decreases the construction costs but also improves water quality of reservoirs and environmental health. Keywords: Dam reservoir • quality simulation, • CE-QUAL-W2, • temperature stratifications, • quality stratifications

1. INTRODUCTION

Iran is located in an arid/semi-arid area. In such regions, dam construction is of vital importance in controlling water steams for future uses such as drinking, agricultural irrigation, industrial uses and hydropower. To meet such demands, dam construction and surface water controlling establishment were always of special focus in economic development planning. Considering several restrictions on water quality and quantity, the demand for a decision tool becomes important. Several factors affect water quality in a dam reservoir. This could be to an extent where the water quality at the outlet is

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significantly different from that of inlet. Climate, reservoir shape, inlet stream quantity and quality are the most affecting features triggering such factors.

Temperature stratification and subsequent qualitative stratification are the most important processes occurring in dam reservoirs. Such phenomena are directly affected by surface water temperature, which cause temperature and density gradient from water surface to the depth. Stability of this phenomenon is basically related to stratification power and mixing factor forces. Mixing forces include wind and dynamic forces from inlet and outlet streams. required work to be done is also dependent to stratification power, size and shape of the reservoir. Stratification power is a function of temperature difference between upper layer (Epiliminion) and lower layer (Hypoliminion). As a result, since dam construction is an expensive and effortful item, to ensure water quality features for different uses and also reservoir water quality management, identifying relationship, rules and factors affecting water quality is essentials (Bani saeid et al. 2003, Wells, S. 2002). For exact assessment of dam construction effects on water quality in ordinary situations long waiting time until the end of construction and putting into operation and then sampling different depths (for at least 1 year) is required. This involved time-taking, costly efforts which are only practical during exploitation period. Today, water quality simulation has extended its application in water resources planning and policy making to reduce costs and save time. These models are prepared by using mathematical methods, such as, finite elements to solve physical, chemical and biological processes’ equations and depict reservoir and outlet stream water quality overview (Yargholi et al, 2008)

Baghan dam which was constructed to meet drinking demands, irrigation uses and industrial needs is located over a branch of Mand river, 6 km southeast of Baghan village, 170 km southeast of Bushehr in 52° and 56’ East and 28° and 8’ North, as shown in Figure 1. Baghan dam is 55 m height with the dam reservoir volume of 30.5 MCM and a lake area of about 2.05 km2. Average precipitation is estimated about 376 mm and average annual temperatures of the basin and construction site are 21.7 and 24.8 ° centigrads accordingly. Based on hydrologic studies, average annual yield of the river in construction site is 31.1 MCM with minimum, maximum and average electric conductivity of 785, 11620 and 2383 µS/cm (Afrazpimayesh Consulting Engineers , 2007). Based on previous researches (Yargholi et al, 2008), many of the dams in Iran, has been affected by several environmental problems like high salinity and eutrophication due to different factors such as weakness of accurate studies and water quality monitoring in all stages, from designing to operation and even after operation-time (Yargholi et al, 2008).

map. 1: Baghan dam position

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Numerous models have been composed in order to simulate and evaluate water quality systems; HEC-5Q, WASP7T DYRESSM, CE-QUAL-W, WQRRS are among these models (Yargholi et al, 2008, Rezaei benis, 2007). In this study, based on previous researches and comparisons on models abilities to simulate water quality, CE-QUAL-W has been chosen to simulate outlet water quality for different uses.

In a research by Arhami et al, 2003, Temperature changes, Dissolved Oxygen and Total Dissolved Solids in Latian dam reservoir was modeled using HEC-5Q. Results of the study show acceptable reliability of the model in simulating parameter changing trends and stratification (Arhami, M et al, 2003). Also, Bani saeid ,2003, studied water quality changes and stratification in Cheragh Weiss dam using HEC-5Q (Bani saeid, et al, 2003) They estimated minimum environmental water demand, released from dam outlet, using maximum allowable Nitrogen and Phosphorus concentration in release water. Sarang compared in-situ observations in Boukan dam reservoir with that result from HEC-5Q in simulating water quality and stratification (Sarang, et al, 2003). Tafarroj (Tafarroj, et al, 2007) simulated TDS and temperature in Kandak dam reservoir using HEC-5Q. Results show that selective release during non-irrigation months in order to save flood streams leads to reservoir water quality improvement. Results from eutrophication and temperature stratification simulation in Shahr-e-Bijar dam reservoir using CE-QUAL-W2 model showed that the reservoir water is classified as fresh and outlet water has high BOD and low dissolved oxygen concentration (Yargholi et al, 2008). Markofsky and Harleman (Markofsky and Harleman, 1973) have developed a mathematical water quality model based on DO concentration, which is then put together with temperature stratification simulation model. Kuo and Yan (Kuo and Yan, 2000) simulated water quality of the Fitsui dam reservoir using WASP5 and CE-QUAL-W2 model. Results from the study showed that the reservoir is rich in nitrogen, but algae expansion is limited due to lack of phosphor.

2. MATERIALS AND METHODS

In this study, the results from stratification and quality simulations of Baghan dam reservoir in before and after height reduction are presented (Tabel 1). Taking into account salinity limitations of water resources in Bushehr province and Baghan river, the main goal in this study is to assure water salinity condition in dam reservoir and its outlet stream and also comparing it with irrigation standards.

Tabel.1: Dam characteristics before and after height reduction Height of 54 meters Height of 62 meters Factor

Water supply for agriculture, industry and drinking

Water supply for agriculture, industry and drinking

purpose of dam

246 m 260 Normal level

32 MCM 63 MCM Reservoir volume at

normal level 54 m 62 m Height

18.5 mcm 18 Adjustable water

( annually)

CE-QUAL-W2 model is used for the reason. This model was developed by Environmental Engineering center of the US Army with cooperation of civil and environmental

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engineering department of the Portland state university, in order to simulate the river-reservoir system. From a hydrodynamic point of view, CE-QUAL-W2 model can forecast changes in water level, velocity and temperature. Since temperature changes leads to subsequent changes in water density, calculations related to temperature is implanted in hydrodynamic system and it should not be eliminated from calculation processes. In water quality investigations every combination of water quality parameters in simulation could practically be taken into account or be eliminated from the process. The algorithm to study water quality in this model is completely componential and other water quality parameters could be easily added via additional sub-plans.

Input model data is reservoir’s shape and geometry, initial and boundary conditions, hydraulic parameters, daily inlet and outlet discharges, daily water temperature, water quality concentrations and meteorological parameters. Input data which is presented as bth.npt files is extracted from topographic maps by taking elements within the reservoir length. Volume-area and height relationships are important in assessing geometrical shape presentation accuracy. In this section each element’s width, length and angle within the reservoir length is presented to the model. Meteorological data that are presented to the model in met.npt format involves: air temperature, dew point, cloudiness, wind velocity and wind direction in daily time scales. Inlet and outlet stream daily data are presented in qin.npt and qot.npt file formats. Water quality data includes studied factors in weekly format by cin.npt are presented to the model. Water temperature is also presented separately in daily time scales under tin.npt file formats. Using long time data history in the construction site, the time period between 1997 and 1998 was chosen due to existence of rainy, dry and average precipitation seasons and the model was simulated in daily time scale.

3. RESULTS AND DISCUTION

Figure1 shows simulated water temperature in Baghan dam reservoir within a 5 year period. As is shown in the figure, reservoir includes a stratification cycle which lasts for at least 10 months of a year. This stratification starts in mid February and reaches its peak during summer months. The stratification is weakened during the cold season due to decline in input energy to the reservoir and gradually disappears. Results show that the complete mixing occurs during late January and early February and temperature changes from surface to depth is not meaningful. New cycle commences again from mid-February. Based on simulations, maximum difference between upper and lower levels of the reservoir is about 24° centigrade which occurs during June. Within June and July the depth of upper layer is about 2 to 4 meters and the mid-layer is 10-15 meters. However, by decreasing input solar energy, the depth of upper layer gradually increases. This depth reaches 6-10 meters during early fall. At the same time, depth of the mid-layer reduces to 10 meters. The procedure goes on until the two layers mix and overturn occurs.

Figure 2 shows temperature profile in Baghan dam reservoir depth during selected days of the year. As shown in figures, trends in water temperature changes within the depth and also changes in layer depths are detectable. In addition to this, as could be noticed in figure 3, changes in the temperature of inlet water to the reservoir and outlet water from it during the 5 year simulated period is shown. It is clear from the diagram that the temperature of the outlet stream from the reservoir during the cold seasons is less or merely equal to that of inlet stream, and is lower than the inlet water otherwise. This difference is maximized

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during the summer. Analyzing results from the simulations of the outlet stream shows that strong fluctuations in upstream entering water temperature to the reservoir is balanced in outlet streams.

Fig. 1: Water temperature profile in Baghan dam

reservoir’s depth in monthly time-scale Fig. 2: Water temperature simulation results in

depth during the 5 year period

As discussed before, analyzing existing and performed water quality records suggests that water salinity (Electric conductivity) is known as the most critical restricting water quality parameters. Water EC fluctuates between 785 µS/cm during flood season to 11620 µS/cm within the dry period with an average electric conductivity of about 2383 µS/cm. Comparing these results to those presented by FAO (700-3000 µS/cm: low to moderate restriction, more than 3000 µS/cm: high restriction for irrigation), Baghan river water quality is of low to moderate restriction in average situation and high restriction in extreme events. (FAO 1985). Figure 3 shows Electric Conductivity simulation in Baghan dam reservoir dam during a 5 year period. As it is clear from the figure, changes in the reservoir water EC are simultaneous with those of temperature stratification. Temperature stratification also changes depending on fluctuations of the inlet stream to the reservoir. These fluctuations are particularly a function of river hydrologic features. For example, the electric conductivity of the water increases during the dry season. Based on these results, during the dry season, which is also simultaneous with the end of chosen period, EC increases. This could be mainly because of decreased entering flood streams to the Baghan dam reservoir, which works during normal time periods as an adjustment to the reservoir’s water quality.

Figure 4 shows the EC profile in Baghan dam reservoir depth during different months of the year. As it could be noticed in the figure, a detectable trend in EC of different depths and changing layer depths is recognizable. During January, while no stratification could be detected, EC is merely constant in all depths. In other months, such as; February, March, April and May, Electric conductivity of upper layers is less than that of lower levels, while in other unnamed months the phenomenon is inverse. The important point here is the inter-dependency of temperature stratification and EC layering. As for figure 2, EC alteration within the upper 15-17 meters is not significant, while a dramatic variation could be detected within 17-25 meters, and again from these depths to the river bed, changes are not considerable.

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Figure 5 shows changes in water quality of different dam height within a 5 year period. Results show that the

- At 48m normal level, outlet phosphate concentration decreased considerably. At first normal level, 248m, outlet TDS on moist years decreased compared to 260m but at dry years, reservoir with 260m normal level has less outlet TDS.

- For ammonium and nitrate, reservoir with 260m normal level, has little difference from better condition compared to 248m.

- Totally, decrease in reservoir eight compared to previous one, apart from reducing running costs, has been accepted for reservoir water quality as well as environmental issues, and in spite of little increase in water EC, resulted in considerable decrease in reservoir phosphorous concentration and also maintaining the reservoir freshness and inhibited from eutrophication which is the problem of many

of dams in Iran, especially in tropical and southern provinces.

Alinity of in-stream and out-streams differ significantly and that the difference is of bigger domain during raining seasons, compared to dry season. The diagram shows that, although the salinity of out-stream water is lower than that of in-stream; fluctuations in outlet streams’ EC are also of very smaller amplitudes. This could be explained by longer retention times of reservoir water (almost a year) and also water quality balancing because of high volume, less saline inlet streams during floods. As it is observed in the results of simulation, the electric conductivity of the released water is always below 3000 µS/cm, which could be even lower during wet periods. An interesting point is the increasing trend of the outlet stream EC during the simulation of the dry period along with a decrease in the difference between inlet and outlet stream ECs. Analyzing electric conductivity of outlet streams from sluices with different levels, as shown in table 1, shows the variations in water quality of different levels, as well as stratification in all months. Based on model results, the best water quality could be reached in upper levels between February and April, mid-levels during May and June and lower levels for months July to December. In January water quality is homogenous within all layers due to complete mixing.

Fig. 3: Baghan dam reservoir EC-depth profile in different months

Fig. 4: Results of the 5 year EC simulation in different depth

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Table 1: Average EC of different levels and proposed optimum level for withdrawal

Month Electric conductivity in different levels of Baghan dam (µS/cm) Preferred

withdrawal level Upper levels (180-175) Mid levels (170-165) Lower level (155-150)

January 2577 2572 2575 All February 2150 2518 2568 Upper March 2257 2540 2565 Upper April 2350 2586 2564 Upper May 2710 2520 2558 Mid - lower June 2717 2525 2560 Mid – lower July 2945 2430 2570 Mid

August 3185 2450 2565 Mid September 3220 2455 2562 Mid October 3005 2510 2565 Mid

November 2880 2752 2565 Lower December 2830 2780 3571 Lower

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Fig. 5: Comparing outlet TDS , Algae,NO3 and Po4, results at different Scenarios

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CONCLUSION:

The temperature stratification in Baghan dam reservoir is actually very strong and stable. This phenomenon is more severe during hot seasons, particularly July and August. During these months, the temperature difference between upper and lower layers reaches 20° centigrads. Temperature variation gradient is very high between 20-25 and 35-40 meters, while little or no variation is detected in upper and lower layers. In dam reservoirs, outlet stream water quality shows less variation, compared to that of inlet water due to temperature stratification, longer retention time and water quality layering. During summer, outlet stream temperature is about 5-10 ° centigrade cooler than inlet water. The latter is very important from an ecological point of view, since dissolved oxygen concentration increases and maintains aquatic life. Inversely, inlet and outlet stream temperature converges during cold season. In addition to longer retention time in dams reservoirs, stratification due to EC has caused alterations between inlet and outlet water streams. The difference between the two ECs ranges from 0 to 500 µS/cm during different months and years. Figure 6 shows that released water salinity was significantly higher than inlet water during flood events. However, during following months after the flood season, salinity of the outlet stream decreases, causing considerable difference between in and out water qualities; this difference ranges from 500 µS/cm, within the first and second months after the flood season, to lower difference. Analysis show that the difference between in and out water salinity was higher during upper-normal water year (1997-1998), and lower differences within lower-normal months (last months of the simulation period) because of lower precipitations and diminution of flood streams. Electric conductivity, which assumes to be the major restricting parameter in Baghan river for drinking and irrigation uses, is balanced in the reservoir during the year, meaning less limitations for water withdrawals. Simulation results suggests an average outlet water salinity of about 2600 µS/cm which ranges from 2400 to 3000 µS/cm, while time averages salinity of inlet water streams is about 3000 µS/cm. Table 1 shows that the release water quality from different sluices differ within months and that water quality simulation results could be utilized as a reliable tool to manage water withdrawals for different uses and required qualities. According to Table 2, mean gravimetric concentration of qualitative parameters and also their mean annual weight in reservoir outlet are as following Table.

Table. 2: mean gravimetric concentration of quality parameters in reservoir (mg/l)

outlet in normal level 260 m

outlet in normal level 246 m

inlet qualitative parameters 4.25 4.89 6.9 NO3

0.006 0.0013 - PO4 0.01 0.01 0.03 NH4 0.01 0.003 0.04 TP 4.29 4.93 - TN 0.02 0.01 3.54 BOD 817 883 921 TDS

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According to above results, all simulated parameters concentration in reservoir are permissible level for domestic and agricultural uses. Considering to the appropriate quality condition of reservoir water, outlet quality from different reservoir levels are in standard level but pool level from 220 to 230 creates best condition for water quality of reservoir outlet.

Decreasing reservoir level in comparison with previous one, apart from decreasing running costs, most accepted with the regard of reservoir water quality as well as environmental issues and has better condition and in spite of slight increase in water EC, resulted in considerable decrease in reservoir phosphorous content and maintenance of reservoir freshness and inhibition of reservoir eutrophication which is the threat for most of dams in Iran, especially in tropical and southern provinces.

REFERENCES: Afrazpimayesh Consulting Engineers , 2007. final report of Bagan dam environmental

assessment report. Arhami, M., Tajrishi, M., Abrishamchi, A. 2003. Modeling the latian dam water quality. J.

water and waste water. 44, 2-14. Bani saeid, N., Rezaei benis, N., Jafarzadeh, N. 2003. prediction of water quality change

and stratified Cheraghvise dam water quality with HEC-5Q. 7th international River Engineering seminar. Shahide chamran university . ahvaz, 202-215.

Kuo, J. T., Yang, M. D. (2000).”Water quality modeling in reservoirs,” proceedings of the Fourteenth Engineering Mechanics Symposium (EM2000) of the American Society of civil Engineers,

Markofsky, M., Harleman, D.R.F (1973).”prediction of water quality stratified reservoir” Hydraulic division, ASCE, 99(5), pp. 703-729

Maleki, R., vali samani, M., Mohammadi, K. 2007. Investigation the drainages effects on pesyan river water quality with WASP6. National Irrigation and drainage seminar. Shahide Chamran university . ahvaz, 54-68.

Rezaei benis, N. 1997. A systematic approach on the patterns of opration of the dams in Irarn and their quality and quantity management. Title MSC hesis, Amirkabir University and Technology.

Study and Modeling the Kondak dam water quality with HEC-5Q . Proceeding of the 7th international River Engineering seminar. Shahide chamran university . ahvaz, 120-133.

Sarang, A., Tajrishi, M., Abrishamchi, A. 2003. Modeling the Bokan dam water quality. J. water and waste water. 37, 2-15.

Tafarroj, N., Rezaei benis, N., Izadjo, F. 2007. Study and Modeling the Kondak dam water quality with HEC-5Q . Proceeding of the 7th international River Engineering seminar. Shahide chamran university . ahvaz, 120-133.

Wells, S. (2002) “Basis of the CE-QUAL-W2 Version 3 River Basin Hydrodynamic and Water Quality Model,” Proceedings, 2nd Federal InterAgency Hydrologic Modeling Conference, Las Vegas, July 28-Aug 1, 2002.

Yargholi, B., shiati, K., dehzad, B. 2008. Simulation of The Shahre bijar dam Water quality and eutrofication. Proceedings of soil and water pollution Seminar. Aborihan university. waramin, 38-53.

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Thermal and salinity Stratification Modeling of Dalaki Reservoir with the aim of agricultural use study

Bahman Yargholi Asist. Prof., Agricultural Engineering Research Institute (AERI), Karaj, Iran

[email protected]

Jahan Kadkhodapour Office of Technical Planning, Bushehr Bureau of Water, Bushehr, Iran

Fereidoon karampour

Office of Technical Planning, Bushehr Bureau of Water, Bushehr, Iran

ABSTRACT For water sector decision makers, dam construction is typically regarded as a common measure of water crisis prevention by taming surface waters. Under the impact of dimensions, reservoir retention time, climate, thermal stratification and eutrophication, water quality of reservoirs is degraded and consequently, outflow quality becomes different from the inflow. Situated in an arid area, Dalaki River Basin in the South of Iran is faced with several water quality-quantity shortages, particularly from the aspect of salinity. This limitation is an issue of much importance for agricultural activities as the largest water user of the Region.To ensure the appropriate quality of water for different users, water quality monitoring and modeling is essential before dam construction to prepare an applicable tool for water quality management of reservoir and to propose the best elevation of intake gates. In this study, results of water quality modeling of Dalaki Reservoir, which is under construction in Dalaki Basin, are presented. Regarding the fact that main restriction of Dalaki river is recognized as salinity, water quality is thoroughly simulated in order to analyze this parameter. For this purpose, based on water quality data obtained from one-year water quality monitoring program with a monthly frequency, thermal and salinity stratification of the reservoir are simulated using CE-QUAL-W2. Results depict that thermal stratification will be occurred during March to November, in which from June to July temperature differences will reach up to 18 centigrade. Salinity stratification modeling also depicts that TDS in various elevations will fluctuate up to 800 mg/lit. The results provide an appropriate tool of water quality management to take water from different elevations during the year.

Keywords: Dalaki Reservoir • Water Quality Modeling • Salinity • Thermal stratification• CE-Qual-W2 1. INTRODUCTION Iran is located in an arid/semi-arid area. In such regions, dam construction is of vital importance in controlling water steams for future uses such as drinking, agricultural irrigation, industrial uses and hydropower. To meet such demands, dam construction and surface water controlling establishment were always of special focus in economic development planning. Considering several restrictions on water quality and quantity, the demand for a decision tool becomes important. Several factors affect water quality in a

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dam reservoir. This could be to an extent where the water quality at the outlet is significantly different from that of inlet. Climate, reservoir shape, inlet stream quantity and quality are the most affecting features triggering such factors. Temperature stratification and subsequent qualitative stratification are the most important processes occurring in dam reservoirs. Such phenomena are directly affected by surface water temperature, which cause temperature and density gradient from water surface to the depth. Stability of this phenomenon is basically related to stratification power and mixing factor forces. Mixing forces include wind and dynamic forces from inlet and outlet streams. required work to be done is also dependent to stratification power, size and shape of the reservoir. Stratification power is a function of temperature difference between upper layer (Epiliminion) and lower layer (Hypoliminion). As a result, since dam construction is an expensive and effortful item, to ensure water quality features for different uses and also reservoir water quality management, identifying relationship, rules and factors affecting water quality is essentials (Bani saeid et al. 2003, Wells, S. 2002). For exact assessment of dam construction effects on water quality in ordinary situations long waiting time until the end of construction and putting into operation and then sampling different depths (for at least 1 year) is required. This involved time-taking, costly efforts which are only practical during exploitation period. Today, water quality simulation has extended its application in water resources planning and policy making to reduce costs and save time. These models are prepared by using mathematical methods, such as, finite elements to solve physical, chemical and biological processes’ equations and depict reservoir and outlet stream water quality overview (Yargholi et al, 2008) Dalaky dam which was constructed to meet irrigation uses and industrial needs is located over a branch of Dalaky river, 25 km Northeast of Dalaky city, 100 km Northwest of Bushehr. As shown in Figure1. Dalaky dam is 105 m height with the dam reservoir volume of 260 MCM and a lake area of about 9.1 km2. Average precipitation is estimated about 330 mm and average annual temperatures of the basin and construction site are 15.2 and 18.1° centigrade accordingly. Based on hydrologic studies, average annual yield of the river in construction site is 580 MCM with minimum, maximum and average TDS of 1660, 7604 and 4614 µS/cm (Yekom Consulting Engineers, 2012) Based on previous researches (Yargholi et al, 2008), many of the dams in Iran, has been affected by several environmental problems like high salinity and eutrophication due to different factors such as weakness of accurate studies and water quality monitoring in all stages, from designing to operation and even after operation-time (Yargholi et al, 2008).

Map. 1: Dalaky dam position

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Numerous models have been composed in order to simulate and evaluate water quality systems; HEC-5Q, WASP7T DYRESSM, CE-QUAL-W, WQRRS are among these models (Yargholi et al, 2008, Rezaei benis, 2007). In this study, based on previous researches and comparisons on models abilities to simulate water quality, CE-QUAL-W has been chosen to simulate outlet water quality for different uses. In a research by Arhami et al, 2003, Temperature changes, Dissolved Oxygen and Total Dissolved Solids in Latian dam reservoir was modeled using HEC-5Q. Results of the study show acceptable reliability of the model in simulating parameter changing trends and stratification (Arhami, et al, 2003). Also, Bani saeid ,2003, studied water quality changes and stratification in Cheragh Weiss dam using HEC-5Q (Bani saeid, et al, 2003) They estimated minimum environmental water demand, released from dam outlet, using maximum allowable Nitrogen and Phosphorus concentration in release water. Sarang compared in-situ observations in Boukan dam reservoir with that result from HEC-5Q in simulating water quality and stratification (Sarang, et al, 2003). Maleki, suggested that drainages are among the most affecting sources of pollution in Pasikhan river, Guilan (Maleki, et al, 2007). In this study, Ammonium, Nitrate, Nitrogen and Phosphate concentrations were measured and compared to simulation results from WASP6. Results show that WASP6 model could simulate river water quality with great accuracy. Tafarroj (Tafarroj, et al, 2007) simulated TDS and temperature in Kandak dam reservoir using HEC-5Q. Results show that selective release during non-irrigation months in order to save flood streams leads to reservoir water quality improvement. Results from eutrophication and temperature stratification simulation in Shahr-e-Bijar dam reservoir using CE-QUAL-W2 model showed that the reservoir water is classified as fresh and outlet water has high BOD and low dissolved oxygen concentration (Yargholi et al, 2008). Markofsky and Harleman (Markofsky and Harleman, 1973) have developed a mathematical water quality model based on DO concentration, which is then put together with temperature stratification simulation model. Kuo and Yan (Kuo and Yan, 2000) simulated water quality of the Fitsui dam reservoir using WASP5 and CE-QUAL-W2 model. Results from the study showed that the reservoir is rich in nitrogen, but algae expansion is limited due to lack of phosphor. Since Dalaky river water salinity is the main limiting water quality factor, in this study it is desired to study water quality changes of the Dalaky dam reservoir from temperature stratification and TDS point of view, using CE-QUAL-W2. The main goal is to investigate temperature stratification situation and reservoir salinity and determining salinity in different depths in order to manage withdrawals with reliable quality for different uses from determined water levels. For this mean, changes in upstream inlet water quality (temporal TDS changes along with changes in different levels) were simulated using gathered base data, exact dam components identification, choosing indicator period, that were themselves extracted from long-time water quality data and monthly quality monitoring during a one year period. To do so, in addition to simulation of dam reservoir water quality, the quality of releasing water is also simulated. 2. MATERIALS AND METHODS In this study, the results from stratification and salinity simulations of Dalaky dam reservoir are presented. Taking into account salinity limitations of water resources in Bushehr province and Dalaky river, the main goal in this study is to assure water salinity condition in dam reservoir and its outlet stream and also comparing it with irrigation standards. CE-QUAL-W2 model is used for the reason. This model was developed by

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Environmental Engineering center of the US Army with cooperation of civil and environmental engineering department of the Portland state university, in order to simulate the river-reservoir system. From a hydrodynamic point of view, CE-QUAL-W2 model can forecast changes in water level, velocity and temperature. Since temperature changes leads to subsequent changes in water density, calculations related to temperature is implanted in hydrodynamic system and it should not be eliminated from calculation processes. In water quality investigations every combination of water quality parameters in simulation could practically be taken into account or be eliminated from the process. The algorithm to study water quality in this model is completely componential and other water quality parameters could be easily added via additional sub-plans. Input model data is reservoir’s shape and geometry, initial and boundary conditions, hydraulic parameters, daily inlet and outlet discharges, daily water temperature, water quality concentrations and meteorological parameters. Input data which is presented as bth.npt files is extracted from topographic maps by taking elements within the reservoir length. Volume-area and height relationships are important in assessing geometrical shape presentation accuracy. In this section each element’s width, length and angle within the reservoir length is presented to the model. Meteorological data that are presented to the model in met.npt format involves: air temperature, dew point, cloudiness, wind velocity and wind direction in daily time scales. Inlet and outlet stream daily data are presented in qin.npt and qot.npt file formats. Water quality data includes studied factors in weekly format by cin.npt are presented to the model. Water temperature is also presented separately in daily time scales under tin.npt file formats. Using long time data history in the construction site, the time period between 1973 and 1977 was chosen due to existence of rainy, dry and average precipitation seasons and the model was simulated in daily time scale. 3. RESULTS AND DISCUTION Figure 1 and 2 shows simulated water temperature in Dalaky dam reservoir within a 5 year period and different months. As is shown in the figure, reservoir includes a stratification cycle which lasts for at least 9 months of a year. This stratification starts in mid February and reaches its peak during summer months. The stratification is weakened during the cold season due to decline in input energy to the reservoir and gradually disappears. Results show that the complete mixing occurs during late January and early February and temperature changes from surface to depth is not meaningful. New cycle commences again from mid-February. Based on simulations, maximum difference between upper and lower levels of the reservoir is about 20° centigrade which occurs during July. Within June and July the depth of upper layer is about 6 to 10 meters and the mid-layer is 10-15 meters. However, by decreasing input solar energy, the depth of upper layer gradually increases. This depth reaches 15meters during early fall. At the same time, depth of the mid-layer reaches to 25 meters. The procedure goes on until the two layers mix and overturn occurs. Figure 2 shows temperature profile in Dalaky dam reservoir depth during selected days of 5 year. As shown in figures, trends in water temperature changes within the depth and also changes in layer depths are detectable. In addition to this, as could be noticed in figure 3, changes in the temperature of inlet water to the reservoir and outlet water from it during the 5 year simulated period is shown. It is clear from the diagram that the temperature of the outlet stream from the reservoir during the cold seasons is less or merely equal to that of inlet stream, and is lower than the inlet water otherwise. This difference is maximized

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during the summer. Analyzing results from the simulations of the outlet stream shows that strong fluctuations in upstream entering water temperature to the reservoir is balanced in outlet streams.

Fig. 2: Dalaky dam reservoir Temperature-depth profile in different months

Fig. 2: Water temperature simulation results in depth during the 5 year period

As discussed before, analyzing existing and performed water quality records suggests that water salinity (TDS) is known as the most critical restricting water quality parameters. Water EC fluctuates between 1660 µS/cm during flood season to 7600 µS/cm within the dry period with an average TDS of about 4614 µS/cm. Comparing these results to those

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presented by FAO (700-3000 µS/cm: low to moderate restriction, more than 3000 µS/cm: high restriction for irrigation), Dalaky river water quality is of low to moderate restriction in average situation and high restriction in extreme events. (FAO 1985) Figure 3 shows the EC profile in Dalaky dam reservoir depth during different months of the year. As it could be noticed in the figure, a detectable trend in EC of different depths and changing layer depths is recognizable. During January, February and December TDS of lover layers is less than that of upeper levels. In other months, such as; March, April, May and… TDS of upper layers is less than that of lower levels, while in other unnamed months the phenomenon is inverse. The important point here is the inter-dependency of temperature stratification and EC layering. Figure 4 shows TDS simulation in Dalaky dam reservoir during a 5 year period. As it is clear from the figure, changes in the reservoir water EC are simultaneous with those of temperature stratification. Temperature stratification also changes depending on fluctuations of the inlet stream to the reservoir. These fluctuations are particularly a function of river hydrologic features. For example, the TDS of the water increases during the dry season. Based on these results, during the dry season, which is also simultaneous with the end of chosen period, EC increases (the ending part of figure 1). This could be mainly because of decreased entering flood streams to the Dalaky dam reservoir, which works during normal time periods as an adjustment to the reservoir’s water quality. Figure 5 shows changes in TDS of inlet and outlet streams within a 5 year period. Results show that the salinity of in-stream and out-streams differ significantly and that the difference is of bigger domain during raining seasons, compared to dry season. The diagram shows that, although the salinity of out-stream water is lower than that of in-stream; fluctuations in outlet streams’ EC are also of very smaller amplitudes. This could be explained by longer retention times of reservoir water (almost a year) and also water quality balancing because of high volume, less saline inlet streams during floods. As it is observed in the results of simulation, the TDS of the released water is always below 3000 µS/cm, which could be even lower during wet periods. An interesting point is the increasing trend of the outlet stream EC during the simulation of the dry period along with a decrease in the difference between inlet and outlet stream ECs. Analyzing TDS in reservoir in different month, as shown in Figure 3, shows the variations in water quality of different levels, as well as stratification in all months. Based on model results, the best water quality could be reached in upper levels between December, January and February; mid-levels during June, july and August; lower levels for September, October and November. In march and april water quality is homogenous within all layers.

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Fig. 3: Dalaky dam reservoir TDS-depth profile in different months

Fig 4: Results of the 5 year TDS simulation in different depth

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Fig. 5: Changes in TDS of inlet and outlet streams during simulation Dalaky dam reservoir

In order to evaluation the effect of reservoir thermal stratification on reservoir water and outlet different scenarios as followings were evaluated:

- Scenario 1 (main status): use of upper pool for reservoir water deployment without application of the effect of reservoir's structure dissolving.

- Scenario 2: the effect of 15% salinity on structures dissolution over two years from first exploiting year and use of upper pool for reservoir water deployment.

- Scenario 3: use of upper pool and lower deployment at 250 m level spontaneously, without application of the effect of reservoir's structure dissolving.

- Scenario 4: use of lower deployment at 250 m level spontaneously, without application of the effect of reservoir's structure dissolving.

- Scenario 5: use of lower deployment at 250 m level and water overflow at this level in order to reservoir cleaning, without application of the effect of reservoir's structure dissolving.

Table 1 show the reservoir outlet TDS at different Scenarios and compares them with scenario 1 (main status). In order to study the effect of different pool levels on outlet quality, 220 and 230 m levels separately introduced to model. After model running for 5-year simulation period with same conditions, reservoir outlet quality amounts compared with each other.

Table 1: mean weight outlet TDS at different Scenarios

Scenarios 1 2 3 4 5 Outlet TDS (mg/l) 3033 3171 3053 3059 3043 4. CONCLUSION The temperature stratification in Dalaky dam reservoir is actually very strong and stable. This phenomenon is more severe during hot seasons, particularly June, July and August. During these months, the temperature difference between upper and lower layers reaches 20°. In addition to longer retention time in dams reservoirs, stratification due to TDS has caused alterations between inlet and outlet water streams. The difference between the two TDSs ranges from 0 to 800 mg/l during different months and years. Figure 6 shows that released water salinity was significantly lower than inlet water.

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Reservoir has summer stratification. Stratification initiated on late March until December month for 9 months. Water temperature difference between upper and lower layers in July, August and June months reaches to 20 °C. On dey, summer stratification became weak and became complete mixture for two months. By increasing temperature in March, summer stratification forms again. Having regard to high TDS levels in inlet, TDS concentration in reservoir reaches 4000 mg/l which decreased by flooding inlets in winter months and early spring. TDS concentration profile changes in depths based on stratification intensity, so that in winter after layers disturbance, TDS concentration in lower layer is much more. This trend continues in spring. By increasing stratification intensity and warming up of surface layers, TDS amounts of upper layers increased too. In this situation, mid layers has the least TDS. In fall, most TDS concentration is related to upper layers and the least amounts is related to lower ones. The effect of reservoir internal structures dissolving on outlet quality could be considerable. In order to study the effect of these structures dissolving on reservoir water quality, it is necessary to determine of exact dissolution and applied in reservoir simulation. The effect of using pools by considering the simulation results and available data in long term period on outlet TDS concentration is not considerable, but by water harvesting from layers with appropriate quality at growing season and water deployment from saline layer at flooding period or non-cultivation season, we could manage reservoir water quality. In order to model calibration, it is suggested that measuring the water quality parameters especially in dam place continued and measurements regularly and monthly should be conducted even after dam water filing. REFERENCES Yekom Consulting Engineers , 2012. final report of dalaky dam environmental

assessment report. Yekom Consulting Engineers , 2011. final report of dalaky dam hydrology assessment

report. Arhami, M., Tajrishi, M., Abrishamchi, A. 2003. Modeling the latian dam water quality. J.

water and waste water. 44, 2-14. Bani saeid, N., Rezaei benis, N., Jafarzadeh, N. 2003. prediction of water quality change

and stratified Cheraghvise dam water quality with HEC-5Q. 7th international River Engineering seminar. Shahide chamran university . ahvaz, 202-215.

Kuo, J. T., Yang, M. D. (2000).”Water quality modeling in reservoirs,” proceedings of the Fourteenth Engineering Mechanics Symposium (EM2000) of the American Society of civil Engineers,

Markofsky, M., Harleman, D.R.F (1973).”prediction of water quality stratified reservoir” Hydraulic division, ASCE, 99(5), pp. 703-729

Maleki, R., vali samani, M., Mohammadi, K. 2007. Investigation the drainages effects on pesyan river water quality with WASP6. National Irrigation and drainage seminar. Shahide Chamran university . ahvaz, 54-68.

Rezaei benis, N. 1997. A systematic approach on the patterns of opration of the dams in Irarn and their quality and quantity management. Title MSC hesis, Amirkabir University and Technology.

Study and Modeling the Kondak dam water quality with HEC-5Q . Proceeding of the 7th international River Engineering seminar. Shahide chamran university . ahvaz, 120-133.

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Sarang, A., Tajrishi, M., Abrishamchi, A. 2003. Modeling the Bokan dam water quality. J. water and waste water. 37, 2-15.

Tafarroj, N., Rezaei benis, N., Izadjo, F. 2007. Study and Modeling the Kondak dam water quality with HEC-5Q . Proceeding of the 7th international River Engineering seminar. Shahide chamran university . ahvaz, 120-133.

Wells, S. (2002) “Basis of the CE-QUAL-W2 Version 3 River Basin Hydrodynamic and Water Quality Model,” Proceedings, 2nd Federal InterAgency Hydrologic Modeling Conference, Las Vegas, July 28-Aug 1, 2002.

Yargholi, B., shiati, K., dehzad, B. 2008. Simulation of The Shahre bijar dam Water quality and eutrofication. Proceedings of soil and water pollution Seminar. Aborihan university. waramin, 38-53.

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– 6TH

, 2014

Underground Dam in karst Region, case study

Bribin Seropan, Yogyakarta, Indonesia

Nugroho, Bani. [1

] & Pranantya Pulung A. [2]

[1]

Doctoral Candidtate,

Geological Department, Padjajaran University,

Bandung Indonesia

[email protected] [2]

Researcher, Research Center for Water Resources,

Research and Development Agency,

Ministry of Public Works, Indonesia

ABSTRACT

Karst topography is a geological formation shaped by the dissolution of a layer or layers of soluble

bedrock, usually carbonate rock such as limestone or dolomite, and also in gypsum. Karst is an

unique area that consist of several distinctive surface features, with cenotes and sinkholes (also

called dolines) being the most common. biggest challenges in karst areas are the provision of water

to meet the requirement of drinking water and irrigation. Although it appears arid on the surface,

karst region has an abundant water resources in the subsurface, whics is lays in underground river

or intrafracture current. In order to produce the subsurface water, several attemps has been

made,some of them has been sucseed. Most of the method applied are very expensive so it can only

be applied to meet the needs for households. Another new technology and method has been

developed as a prototipe is combining undergrounds dam with hydropower. One prototipe has been

made to answer the requirements for cheap and sustained water. Trough this technology,

expectations for the provision of cheap water can be achieved. Another expectation is this

technology can be developed in other karst areas that require cheap prices water.

Keywords: underground dam, karst, hydropower, irrigation

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INTRODUCTION

Gunung Kidul, is a unique area because it has a typology of karst topography , namely the

formation of a typical landscape in carbonate rocks ( limestone ) as a result of tectonic

processes followed by the dissolution and the presence of a crack formed where water

flows ( Sir McDonald , 1982) .

Availability of water in arid areas is a necessity that can not be avoided. Despite the

surface water, but water is available that have poor quality and requires intensive

processing to be used as a source of raw water. In addition, in karst areas , surface water

often can not be available all year round and its presence is often far from areas that need

it. As a result, the use of groundwater as a source of raw water to meet the needs of a

mainstay of domestic , industrial and irrigation .

Water sources are underground karst areas , such as caves or underground rivers is a

challenge that must be faced in the provision of water , such as in the area Pawonsari

(Pacitan, Wonogiri and Wonosari), West Nusa Tenggara, East Nusa Tenggara and other.

Required for the utilization of technology to raise the water from the water source to

effectively and efficiently so that the user community is able to perform operations and

maintenance (sustainable).

One of the main problems is the cost to remove the water in the underground river to the

surface. The amount of the fee due to the method of water removal is commonly done

using electricity or diesel. As the solution is hydropower technology , which although it

has some limitations but is very cheap to operate (Wibawa, 2005) .

In implementing this technology research is needed to address the various issues that arise

in its application . The prototype installation has been built and are in the area Sindon,

Dadapayu, Semanu, Gunung Kidul, the underground river in Bribin for water . In today's

discussion , will be presented on the development of hydropower in an underground river

in the cave Bribin take the example of an underground river in Bribin and installations in

Sindon (BBWS Serayu - Opak , 2010)

Hydropower

Hydro-power or water power is power derived from the energy of falling water and

running water, which may be harnessed for useful purposes. Since ancient times, hydro-

power has been used for irrigation and the operation of various mechanical devices, such

as watermills, sawmills, textile mills, dock cranes, domestic lifts, power houses and paint

making.

Water's power is manifested in hydrology, by the forces of water on the riverbed and banks

of a river. When a river is in flood, it is at its most powerful, and moves the greatest

amount of sediment. This higher force results in the removal of sediment and other

material from the riverbed and banks of the river, locally causing erosion, transport and,

with lower flow, sedimentation downstream.

In smaller scale, hydropower ussually called as microhydro, which is implemented in one

of Gunung Sewu caves at Gunung Kidul, Yogyakarta. Micro-hydro is a technology that

can be applied to small-scale water resources to change the existing hydropower potential

into electrical power and other equipment or players include water pumps, rice milling

machine, etc., which will indirectly useful to support social and economic activities of

society in the countryside e.g see fig 1 and 2.

IV - 142

Benefits of hydropowers, because these technologies utilize renewable resources, the

operating costs and lower maintenance compared to diesel engines that use fossil energy

(fuel). Its application is relatively easy and environmentally friendly, does not cause

pollutions. If this technology is used to rotate the water pump, because the pump is not

driven safely with electric motors as other benefit that besides better efficiency. If the

installation of the turbine system in such a way that irrigation water turbines can be fed

back to the channel, the efficiency becomes greater, because then the irrigation water

increased power use.

Figure 1. Schematic system of Hydropower turbine (Wibawa, 2005)

Figure 2. Example of instalation for crossflow type turbine, located in Leles-Garut, Indonesia

Geology

Gunung Sewu Karst limestone composed of Middle Miocene to Upper Pliosin called

Wonosari Formation and Oyo Formation ( Bote , 1929) . Limestone is composed of

massive coral limestone in the southern part and the northern part of the layered limestone

( Rahadjo et al . , 1995) . Total thickness of limestone more than 650 m . Coral limestone

lithology varies , but is dominated limestones are rudstones , packstones , and framestones

. Formation bedrock of Wonosari and Oyo in the form of volcanic rock formations and

volcanic clastic Oligocene - Miocene age (Semilir, Nglanggran, Sambipitu, Oyo,

Wonosari, Kepek Formation).

This formation is found at several locations to base of Gunung Sewu karst . Wonosari

Formation and Oyo Formation raptured Quaternary Period began starters, forming steep

cliffs high (25-100 m) along the southern edge (Balazs 1968; van Bemmelen 1970; Surono

IV - 143

et al . 1992; NLI 1994). North-south pressure due to the meeting of tectonic plates that

produce intense deformation and fracture produces stocky northeast-southwest, northwest-

southeast, north-south and east-west (Balazs 1968; van Bemmelen 1970; Surono et al.

1992; NLI, 1994, Haryono, et al., 2005) .

In physiographic Gunung Sewu Karst Mountains are part of the South Island of Java (van

Bemmelen, 1970). South Mountains resulting from the appointment process which started

since the beginning of the Late Tertiary or Quaternary. The northern part of the Southern

Mountains zone of depression is separated from the island of Java by faulting. Gunung

Sewu itself is characterized by karst hills.

On the north side, Gunung Sewu Karst experiencing the bending and shaping faults at

Wonosari Basin and Basin Baturetno. In the second depression, limited karstification

process and its surface is covered by silty soil with a thickness up to 10 m (Waltham et al.,

1983, Samodra, 1983). Karst morphology growing in Gunung Sewu Karst is a type of cone

karst or karst Kegel . This form was first introduced by Lehman (1936) and named Type

Gunung Sewu e.g. see table 1.

Table 1. list of geoogical formation in Wonosari and its surroundings

Karst, The term is derived from Slovenian Kras - means barren rocky land. Nowadays the

term is used to describe a region or landscape that has undergone a process of dissolving in

space and geological time. Ford and Williams (1989) defines as a karst terrain with

distinctive hydrology as a result of rock-soluble and has a well-developed secondary

porosity.

Some karst region identifier ( Ford & Williams, 1989) are as follows:

1. The presence of closed basins or valleys and dry in a variety of sizes and shapes

2. Scarcity or absence of surface drainage or river

3. The presence of the cave of the underground drainage system.

Limestone is a rock that has a composition karbonatan dominant, therefore the karst region

can grow well in an area with limestone lithologies. A region can be regarded as karst

areas where it has been undergoing a process of karstification. Kartisifikasi is a series of

processes ranging from the lifting of the limestone surface of the earth due to the earth

IV - 144

(endogenous) and a process of the dissolution of the limestone, in space and geological

time scales to finally produce a distinctive karst landscape. If a region has a composition of

limestone karstification process but have not experienced it can not be said to be a karst

area (Koesoemadinata, 1987).

The system is very different hydrogeological characteristics of karst regions with non-karst

areas. Porosity limestones are dominated by secondary porosity where the water escapes

through cracks (Fracture), rock layering (bedding plane) and faults (fault) on the limestone

formations. While the space between the grains of porosity values (primary) and the

permeability of the limestone reefs (nonklastik) is very low (Fetter, 1994). Primary

porosity and permeability will be high if the clastic limestone because it has a space

between the grains .

The flow of water in the aquifer flows simultaneously dissolving limestone bedding plane ,

fractures and faults. Most stream of water flowing through fractures and bedding plane has

a large hydraulic conductivity. The nature of the limestone aquifer is not continuous

laterally and not uniform due to the flow of water on limestone aquifer flowing through

cracks and bedding plane. The flow of incoming water will flow immediately passes to the

baseflow. The accumulated flow pattern forming subsurface flow like a river as on the

surface. In the same time enlarge the dissolution process cracks and bedding plane aisle

cave system formed. The halls of the cave serves as a corridor leading to the underground

river system (Koesoemadinata, 1987).

Base flow in the river is generally underground water table and aquifer limestones tend to

be flat (flat water table). Water supply underground river and stream surfaces can come in

through the mouth of the cave is horizontal (shallow holes) or vertical cave (Sink Hole)

and infiltration and surface soil layers above that go through small cracks below the soil

layer. The flow of the underground river water may reappear on the surface as springs

(Kars Spring) or out of the outlet of the cave stream (Sir McDonald, 1982).

The existence of an underground river (underground river) flowing in the cave can be said

to be certain bare existence and its potential if it had been done a search and mapping of

the cave. Another method to determine the initial certainty where the water in the cave is

located and where the flow of water, the water needs to be traced using chemical or

radioisotope.

Tracking ground water (water table) in an underground river in the karst region is

complicated and not simple, this is due to the terrain of the cave is an extreme

environment, the search techniques are needed as well as mapping the hallway cave system

(caving) safely. Search for tracking cave underground river system is one of the

applications of science Speleology (Yulianto, 2010).

Hydropower in karst area

Usefulness of Micro Hydro Power Water Pump or hydropower is to to raise the water from

the lower to the higher energy by utilizing the flow of water that has a high water elevation

(Head) and certain large flow rate. Microhydro generally used for raw water to meet the

needs of rural settlements and small-scale irrigation is available on the condition of high

water fall at least 2 m and has a water discharge that is sufficient to enable the turbine

(Wibawa, 2005).

Microhydro working principle is to make the process of change of potential energy into

kinetic energy. There are several advantages to applying the principles Microhydro,

IV - 145

including the operation does not require any special skills. Another advantage is that it can

work automatically continuously for 24 hours, relatively very little noise when operated.

High efficiency is also an advantage because the water pump turbine wheel is rotated by a

belt transmission and does not require electricity, so it is very efficient. Operational and

maintenance costs because it does not require a small electric or diesel fuel in the

operation, and only requires periodic replacement of the transmission Oil. Besides these

advantages, there are some drawbacks, including the pumping discharge is relatively small

compared with the discharge required for the proper functioning of the turbine and capital

costs are still relatively high, especially for The turbine because production is still

dependent on the order, not mass-produced (Wibawa, 2005).

The method used in the study in Bribin - Sindon, Wonosari, using secondary data obtained

from the results of geological, geotechnical, so the creation of an underground river weir

and the complementary data, consists of several fields, including the field of Speleology. In

hydrological investigations, the tool "Automatic Water Level Recorder" and the calculation

of discharge in open channels. Used in the field of hydraulics and hydrology Speleology

measurement data as a baseline by using numerical calculations. Overall the secondary

data is used for the results of the investigation and development for the feasibility of

hydropower installations. In its application, the result is to get economic calculation cost to

get the water to the surface.

DISCUSSION

Bribin is an underground river that is located in Semanu , Gunung Kidul and this place

made a prototype experiment in conducting underground river damming for the

hydropower manufacture. Based on measurements of the Acyntyacunyata Speleological

Club (ASC), as the initial overview.

Bribin is one area in Gunung Kidul-Yogyakarta which has a quite large potential

underground river. Implementation work underground river water utilization in the Region

Bribin conducted by the Central River Region Serayu-Opak (BBWS), General Directorate

of Water Resources, Ministry of Public Works, Government of Yogyakarta Special

Province, the Batan, In collaboration with the Institute for Water Resources Management,

Hydraulic and Rural Engineering (IWK), University of Karlsruhe, the German Federal

Government.

Feasibility studies have been carried out by the Center for Serayu-Opak since 1998 with

the results of the comparison between the amount of water demand by the avaiability

value. Utilization of water using a pump with diesel power does not result in the growth of

water users (supply for connected households, industry and agriculture). Therefore, water

management systems that support the development of new measures set evenly on the

entire region, the need of the hour terutarna operation. Within the scope of the feasibility

study (2000-2002), conducted on behalf of the Ministry of Research and Education of the

German Federal Government (BMBF), the Institute for Water Resources Management,

Hydraulic and Rural Engineering (IWK).

Bribin Caves chosen because it is the right location to implement this idea. It features

water inside the cave can accommodate approximately 400,000 m3. Underground river

flow in the dry season 1000 It/s is sufficient , after damming the water level as high as 15

meters. With the installation of micro-hydro power plants underground number four (4)

units will be able to drain the water 70 It/s is continuous to the ground. And this will be

IV - 146

sufficient for drinking water to a population of 75,000 inhabitants consume 80

It/person/day. While the dry season will be able to meet the needs of the population with

the same number, but with the consumption of 10 It/person/day.

Management of underground river systems in the Bribin area done with stem and cover the

whole underground cavern hole so the water level can increase. With the rising water level,

will also raise the height difference of water pressure (head) to be eligible to drive the

water pump micro water pump to the surface, e.g see fig.3, even up to 130 meters height of

Kaligoro of the local ground level. Height difference (head) to be achieved by the micro

water pump is approximately 240 meters .

Figure 3. Schematic representation of the underground river damming up Sindon Bribin (without

scale, source: IWK)

Bribin cave is located about 45 miles Southeast of Yogyakarta city. Their path is

Yogyakarta - Wonosari-through road leading towards Bedoyo. Located 100 meters from

the road Wonosari - Bedoyo. Seropan located in Gunung Kidul - Yogyakarta. Bribin an

underground river with river sufficient capacity both slope and flow rate.

Hydraulics installation in Sindon, has been completed and the evaluation phase. Based on

the evaluation results, while the analysis is done is to review the performance of micro

hydro has a design 20 liters / sec at each station with a tap 13 meters high. Based on

information from the management field, micro pump it works well, but is still constrained

geological problems. Installed micro-hydro installation consists of five pieces of micro

water pump, e.g see fig. 4. University of Karlsruhe develop micro hydro water pump with

9 step (nine step pump).

IV - 147

Figure 4. Situation of pump and turbine isntallation at Bribin

(Source: Puslitbang SDA)

Figure 5. Pump and turbine sceme of Bribin Installation

(no scale, Source: Puslitbang SDA)

The results of the calculation or estimation of the cost of the construction of this

installation is a very significant savings. The savings are calculated based on a comparison

of conventional pumps use electricity to pump hydro. The comparison result can be seen in

the table below, see table 2.

Table 2. The results of the comparison of conventional electric pump with hydro pump.

Condition /

Asumption

Price / cost

Pump Discharege/

month

(Rainy season: 5

modules in

operation)

124.400 m³ / month

Pump discharge /

month

(Dry sason: 3 modul

in operation)

74.600 m³ / month

IV - 148

Pump discharge /

year

(5 months rainy

season, 6 month dry

season)

1,07 million. m³ /

year

Average price / m³

water

3.000 IDR / m³

Konventional pump

cost / year

3,21 billion

IDR

hydropower cost /

year

0,43 billion

IDR

Benefits of

hydropower / year

2,78 billion

IDR

With a total of 1,005,919,803 m3 of water requirements in Wonosari, the water supply in

the area Wonosari would be very expensive. Simple illustration shown below.

1.005.919.803 m3 x 3000 IDR/m3

= 3.017.759.408.370 IDR per year

Maintenance costs to be incurred for the installation of hydropower, in Sindon amounted to

430 million IDR/year for discharge pumping of 100,000,000 m3. In a simple calculation of

operating costs amounted to 4.3 IDR/m3 pump . Then the operating costs to be incurred by

hydropower amounted to 4,325,455,152 IDR. With this comparison, the energy cost

savings reached 3,013,433,953,218 IDR.

Besides the many advantages of the installation hydropower, in karst areas, there are other

things that should be of concern is a lot of leaks in the ceiling installation due to high water

on the upstream side of the column. water led to hydraulic pressure rock crevice and

seepage occurs at the ceiling until intalasi . Already done in the form of grouting treatment

step upstream to prevent seepage .

Over time , it has been done several times on the channel discharge measurements , the

discharge was recorded only at 9 liters/sec/pump, and the pump capacity that can be

switched in parallel is 2 pieces. This is due to the increase in intensity seepage happened

on the ceiling of the cave. with higher intensity of seepage, worried would affect the

stability of the walls and ceiling of the cave, so it should be a decrease in the water column

height in the upstream. By decreasing the water column is high, then the pumping

discharge were also significantly reduced.

CONCLUTION

The application of a hydropower station in Wonosari prototype experiment shows

that it can be used as a reference for the manufacture of multiplication.

The method of implementation is doing contructing dam for the entire wall of the

cave, so there are some problems that arise from it.

Containment methods that need to be done differently with more attention to

ecological problems and the stability of the cave.

IV - 149

Underground dam with hydropower instalation is the most efficient achievable

technology today to fullfill the water requirements for karst arid area.

TABLE OF REFERENCE

Ford, D. and Williams, P. (1989) Karst Geomorphology and Hydrology, Unwin Hyman Ltd., London.Fetter, 1994.

Karlsruhe Institute of Technology (KIT), 2010, Pre-Design of the Hydropower Plat with Wood Stave Pipeline in Gua Seropan, Joint Project Integrated Water Rescources Management (IWRM) in Gunung Kidul, Indonesia, Yogyakarta.

Koesoemadinata, 1987. Reff Carbonate Exploration, Institut Teknologi Bandung, Bandung. Mori, K., M. Asano, and T. Shirakawa. 1996. Lithology and Permeability of Lyukyu Limestone in

Sunagawa Subsurface Dam in Miyakojima (in Japanese). The Japan Geology Association. Pusat Litbang Sumber Daya Air, 2009, Pengembangan Teknologi Reservoir Bawah Tanah, Laporan

Akhir, Bandung. Pusat Litbang Sumber Daya Air, 2010, Pengembangan Teknologi Reservoir Bawah Tanah, Laporan

Akhir, Bandung. Pusat Litbang Sumber Daya Air, 2011, Pengembangan Teknologi Reservoir Bawah Tanah, Laporan

Akhir, Bandung. Pusat Litbang Sumber Daya Air, “Pengkajian Penerapan Mikro Hidro Standar untuk Masyarakat

Pedesaan”, Laporan Akhir, Desember 2001. Pusat Litbang Sumber Daya Air, “Pengkajian Dan Penerapan Pompa-Hidro Untuk Penyediaan Air

Baku Dan Tenaga Listrik Di Daerah Pegunungan”, Laporan Akhir, Desember 2004. Sir McDonald, 1982, Laporan Penyelidikan Gunung Pegunungan Sewu, vol. III, di Kabupaten

Gunung Kidul, Wonosari-Daerah Istimewa Yogyakarta. Suharyadi, 1984, Geohidrologi, Jurusan Teknik Geologi fakultas Teknik Universitas Gajah Mada,

Yogyakarta. Wibawa, Yanto, 2005, Studi potensi penerapan mikrohidro untuk penyediaan air baku dan tenaga

listrik di saluran irigasi Tumiyang, Grumbul, Jurangmangu, Desa Tumiyang Kecamatan Pekuncen, Kabupaten Banyumas, Propinsi Jawa Tengah, Puslitbang SDA, Bandung.

Yulianto, Bagus,2010, Goa Seropan – Bahan Referensi IWRM, Yayasan Acintyacunyata,

Yogyakarta.

IV - 150



Water Quality Management by Free-selective Air-lock Intake

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Hideaki Kawasaki Japan Dam Engineering Center, Tokyo, Japan

[email protected]

Hiroki Yamamoto Yachiyo Engineering Co., Ltd., Tokyo, Japan

Kazuhiro Kuwahara Marsima Aqua System Corp., Ohsaka, Japan

ABSTRACT: Selecting the intake depth of the reservoir is beneficial for quality management of the reservoir and

water supply. This paper presents a selective intake system based on the air-lock method which can

be operated and maintained easier than conventional systems.

The free-selective air-lock intake systems (another name: Continuous Siphon) are rapidly extended

for these ten years. Nowadays, they are in operation at 5 dams, and under construction at 2 dams

in Japan. Firstly, this paper describes these situations.

Secondly, this paper describes the basic study to validate the shape of intake tube which decided by

hydrologic accounting. The loss coefficient affecting the shape of intake tube was validated to be

2.5 in this study using hydraulic model experiment and numerical model simulation. The results of

model studies are also evaluated by comparing with the measurement results of one of the system

in operation.

Thirdly, this paper presents the design and construction case of this intake system in Yubari-

Shuparo dam located in the north Japan, which is the latest and one of the biggest systems

completed. Its maximum amount intake water is 83m3/s and its range of intake depth is 45m.

Additionally, this intake system in Yubari-Shuparo dam enabled to intake water from one or more

tubes simultaneously, using inverse V-shaped tubes which are placed at different elevations, while

the other intake tubes are stopped by air-locking. Further, this intake system realized the high

economic performance by no use of multistage metal gates which include parts to be frequently

maintained such as rubber sealants and wire ropes, no use of heavy steel structures and hoist

equipment, and no tower structure on the dam crest.

Keywords: free-selective air-lock intake system, compressed air, air-lock, safe design

1. INTRODUCTION

1.1 Background

Selecting the depth of water intake is beneficial in managing the quality of water supplied

from a dam. Water intake should ideally be positioned low in order to take water at all

times from fluctuating reservoir water level. On the other hand, water at bottom of a

reservoir may have negative impact on downstream environment for reasons such as

excessively cold temperature or low level of dissolved oxygen.

IV - 151

In order to solve this problem, selective water intake system has been developed as a

facility that freely changes the depth of water intake and predominantly takes surface water

from fluctuating water level at reservoir.

However, conventional selective water intake system mainly uses steel multistage gate and

hoist. This has resulted in extremely high construction cost for dams with large water

intake volume and intake depth. Moreover, high cost is required for maintenance related to

watertight rubber used at watertight area between each gate.

1.2 Free-selective Air-lock Intake System

The free-selective air-lock intake system is a new intake system with air-lock multistage

continuous structure that has compressed air locked into reverse V-shaped pipe. It is an

ingenious gateless water intake system in that it does not use any gates. The technology

was initially developed in the 1990s as multistage air-lock selective intake system applied

at Haji Dam. Since then, it has evolved into current shape as Continuous Siphon by

placing intake pipes continuously and separating them with a partition.

As of February 2014, this intake system is already in use at five dams, i.e. Shitsumi Dam

(Shimane), Obara Dam (Shimane), Tono Dam (Shimane), Kurokui Joryu Dam

(Yamaguchi), Yunishigawa Dam (Tochigi). Construction work for this intake system is

also under way at two dams, i.e. Yubari Shuparo Dam (Hokkaido) and Kirimegawa Dam

(Wakayama). Both are scheduled to go into service in 2014.

Figure 1. Conceptual diagram of the operation of free-selective air-lock intake system

2. FREE-SELECTIVE AIR-LOCK INTAKE SYSTEM

2.1 Basic Principle

The free-selective air-lock intake system uses steel reverse V-shaped intake pipe and air

control unit. It makes intake possible from any water level as a result of air-locked

condition created by passing water through intake pipe at any water level and filling other

intake pipes with compressed air. Pneumatic control system consists of compressor,

receiver tank, feed valve and exhaust valve. Opening the feed valve sends compressed air

into intake pipe to perform air lock. Opening the exhaust valve releases the air inside

intake pipe into atmosphere to pass the water.

Supplying compressed air to the tube

Releasing air from the tube Receiver tank

Air compressor

Air-locked

Unlocked

Reservoir

Reservoir

Reservoir

Dam body

Dam body

Dam body

Valve Valve Valve

IV - 152

Figure 2. Conceptual diagram of free-selective air-lock intake system

3. BASIC RESEARCH RELATED TO THE SHAPE OF INTAKE PIPE

3.1 Difference in Water Level during Water Intake and Loss Coefficient

Water level difference d, which corresponds to head loss at intake pipe with flowing water,

occurs inside and outside the intake tower of the free-selective air-lock intake system

during water intake. This water level difference d coincides with difference in water level

between upstream and downstream sections inside the air-locked intake pipe.

Consideration is required when examining the shape of intake pipe so that upstream water

level will not overflow from the highest point of intake pipe due to this difference in water

level during normal operation.

Here, water level difference d can be expressed by formula (1) using loss coefficient f of

intake pipe. Loss coefficient f is a coefficient determined by the pipe shape and roughness

of pipe interior. Although it can be obtained by calculation based on hydrologic empirical

formula, multifaceted verification through hydrologic experiments was required as it is a

value that affects the basis of facility's function.

Power plant

Conveyance pipe

Intake tubes

Screen

Intake tubes

Emergency gate

Normal water level

Free flow spillway on the dam crest

Flood control capacity

Compressor

Receiver tank

Operation room

Discharge control

facility

Air supply/release pipe

Energy dissipater

Free-selective air-lock intake

Air locked tubes

Unlocked tube

IV - 153

g2

vfd

2

··················· (1)

Whereas

d: Difference in water level during water

intake

v: Flow velocity inside intake pipe

g: Gravitational acceleration

f: Loss coefficient at intake pipe

Figure 3. Conceptual diagram of water level

difference during water intake

3.2 Verification of Loss Coefficient

3.2.1 Design Value of Loss Coefficient

Head loss from inflow and friction obtained from hydrologic accounting came to 2.2.

However, loss coefficient was set at 2.5 to allow some leeway in the track of a similar

precedent.

3.2.2 Hydrologic Model Experiment

One-tenth scale hydrologic model based on the free-selective air-lock intake system at

Obara Dam was used for the experiment in order to verify the loss coefficient. Loss

coefficient based on the results of hydrologic model experiment shown in Table 1 was 3.04.

Table 1. Loss coefficient at hydrologic model experiment

1/1 0 model Measured and converted values

Flow rate 0.025 m3/s 8.0 m3/s

Number of plates used 1 1

Intake pipe width 0.4m 4.0m

Intake pipe height 0.2m 2.0m

Flow speed 0.63 m/s 2.0 m/s

Difference in water level at water intake 0.062 m 0.62 m

Loss coefficient - 3.04

Figure 4. Hydraulic model

Figure 5. Photo of hydraulic model

Reservoir

Intake tower

Wa

ter-

lev

el

dif

fere

nce

d

d

v

IV - 154

3.2.3 Numerical Model Simulation

Numerical model simulation was conducted based on selective water intake facility at

Shitsumi Dam in order to verify the loss coefficient. Difference in water level during

water intake was calculated by simulation and was used to inversely calculate the loss

coefficient.

The purpose of conducting this numerical model simulation lies in grasping the deviation

of loss coefficient in numerical model simulation by comparing with the results of

experiment at the facility that is actually built in preparation for improving the shape of

intake pipe in the future.

The results of numerical model simulation are shown in Table 2. Loss coefficient was 1.92.

Table 2. Loss coefficient at numerical model

1/1 numerical model

Water density 997.0 kg/m3

Water kinematic

viscosity coefficient

8.572 E-7 m/s2

Air molecular weight 29.0 kg/kmol

Air viscosity 1.772 E-5 Pa-s

Analysis program CFD-ACE+

Figure 6. Mesh pattern of numerical model

Table 3. Loss coefficient at numerical model

Flow rate 8.0 m3/s

Number of plates used 1

Intake pipe width 3.0m

Intake pipe height 0.70m

Flow speed 1.905 m/s

Difference in water level at water intake 0.354 m

Loss coefficient 1.92

Figure 7. Simulation of numerical model

3.3 Comparative Verification with Actual System Test

A test was conducted while water was running through the actual system. Loss coefficient

calculated from difference in water level inside and outside the tower during the test

conducted with running water came to 2.33.

Table 4. Loss coefficient at on-site test

Flow rate 7.1 m3/s




Flow speed 1.690 m/s

Difference in water

level at water intake 0.34 m



IV - 155

http://ejje.weblio.jp/content/kinematic+viscosity+coefficient

http://ejje.weblio.jp/content/kinematic+viscosity+coefficient

http://ejje.weblio.jp/content/molecular+weight

http://ejje.weblio.jp/content/analysis+program

3.4 Summary of Loss Coefficient

The results of loss coefficient calculation from hydrologic accounting, hydrologic model

experiment and numerical model analysis are summarized in Table 5. Loss coefficient

obtained from hydrologic accounting was below the design value of 2.5 which is adequate.

Loss coefficient from hydrologic accounting was smaller than that on the actual system test

while loss coefficient from numerical model analysis was greater than that on the actual

system test.

The deviation between the actual system and hydrologic model obtained here will be used

for verification of the functions of large facilities in Chapter 4.s

Table 5. Summary of loss coefficient

Loss coefficient Difference with actual system test

Hydrologic accounting 2.17 +7.3%

Hydrologic model 3.04 +29.9%

Numerical model 1.90 -17.6%

Actual system test 2.34 -

4. APPLICATION IN LARGE INTAKE FACILITIES

4.1 Yubari Shuparo Dam

Yubari Shuparo Dam is a multipurpose dam under construction on Yubari River which is

part of Ishikari River Water System in Hokkaido.

Table 6. Yubari Shuparo Dam Specifications


Yubari Shuparo Dam Specifications

Type Gravity concrete dam

Location Southern region of

Yubari City, Hokkaido

Dam height 110.8 m

Crest length 390.0 m

Dam volume Approx. 941,000 m3

Water surface area 15.1 km2

Total reservoir capacity 433,000,000 m3

Maximum water utilization

discharge

83 m3/s

4.2 Adoption of Free-Selective Air-Lock Intake System

As Yubari Shuparo Dam has large maximum water utilization discharge of 83 m3/s,

selective water intake facility that covers this singlehandedly will be the largest of its kind

in the country.

The free-selective air-lock intake system has been adopted as a system superior in terms of

economy and maintenance. Compared to other systems, however, it had inferior water

intake performance from reservoir surface due to the depth of water intake required for

securing the distance from intake pipe to water surface.

Yubari-Shuparo Dam

IV - 156

4.3 Improvement of Surface Water Intake Performance

The shape of intake pipe was improved to take water from locations closer to reservoir

surface than conventional intake pipes. The shape of rim was moved upward to improve

intake performance from the surface without changing the condition of water level

difference. The results from verification of loss coefficient for the improved intake pipe

are described below.

Figure 10. Conceptual diagram of improved intake pipe

4.4 Verification of Loss Coefficient Using Numerical Model

Loss coefficient of 2.5 was also selected in the design phase for Yubari Shuparo Dam as well.

In this study, loss coefficient for the improved intake pipe shape was verified by using a

numerical model. As shown in Table 7, loss coefficient obtained from numerical model

comes to 2.49 in view of the 17.6% deviation included in the numerical model formed in

this study. Consequently, validity of design value 2.5 was verified. Conditions of analysis

are same as those in Table 2.

Table 7. Loss coefficient of improved intake pipe

Water level difference at water intake

according to numerical model 83m3/s




Velocity inside pipe 2.767m/s


Deviation of numerical model 17.6%

Loss coefficient considering deviation 2.49

Figure 11. Simulation of numerical model

5. CONSTRUCTION IN YUBARI SHUPARO DAM

Lastly, the case of Yubari Shuparo Dam will be introduced to exemplify the construction

of the free-selective air-lock intake system.

5.1 Fabrication

Intake pipe must have an integrated structure using welding connection and installed in

order according to the placement process of dam body concrete. For this reason, intake

pipe was not divided in the direction of span. Instead, it was divided into three parts in

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depth direction on each layer so that it will conform with shipping restrictions. In addition,

welding and air-tightness test were performed repeatedly on each intake pipe parts to meet

high air-tightness requirements, and pre-assembly identical to actual installation was

performed to simplify replication on the site.

Air control unit was comprised of commercially available compressor, air-driven ball valve,

vacuum pump and receiver tank among others. Air-driven ball valve and manual ball

valve were combined and mounted on a frame to serve as an air control unit, and was

transported to the site after a performance test and leakage inspection..

Figure 12. Intake Pipe

Welding


Airtightness Test


Assembly

Figure 15. Intake Pipe Temporary

Assembly

Figure 16. Bottom Intake Pipe

Temporary Assembly

Figure 17. Air Control Unit

Figure 18. Air Control Unit

Interior

5.2 Construction

As RCD method is used for placement of concrete for the dam body, each placement is

performed over a period of approximately 7 days. For this reason, intake pipes were

installed by setting up a temporary assembly base on the upstream area of the left bank in

order to avoid impact on concrete placement. Intake pipes that were transported in segments

were assembled and were lifted by 300t crawler crane to the top of the dam body for

installation. Stages for temporary storage of materials were built successively around and

above intake pipes that were lifted to the dam body. These stages were equipped with

sliding scaffold, power generator, welding machine and compressor in order to perform the

IV - 158

http://ejje.weblio.jp/content/commercially+available

construction without placing the materials on the dam body concrete placement surface. As

a result, it was possible to install intake pipes completely separate from concrete placement

for dam body and the installation was ultimately completed prior to concrete placement.


Installation


In-situ Assembly


Lowering In

Figure 22. Intake Lowering In

Figure 26. Outline Drawing of Yubari Shuparo Dam

Intake Facilities

Figure 23. Air Pipe Installation

Figure 24. Receiver Tank Installation

Figure 25. Yubari Shuparo Dam

Intake Facilities

Intake tower

Emergency gate

Screen

Reverse V-shaped tube

Reverse

V-shaped tube

Operation room

Receiver tank

Conveyance pipe (83m3/s)

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6. CONCLUSION

Fundamental study was conducted on the free-selective air-lock intake system with regard

to loss coefficient f on intake pipe which is a design parameter unique to this intake system.

In addition, knowledge obtained from this study was used to verify the design adequacy of

a larger system. Main conclusions are as follows.

1) This intake system, which is a new format of selective intake system, enables intake of

water from any layer by filling and releasing air in reverse V-shaped intake pipe. For

this reason, obtaining water level difference generated inside air-locked intake pipe

through calculation is important in determining the shape of intake pipe.

2) As water level difference generated inside air-locked intake pipe will be equal to head

loss of water passing through at intake pipe with flowing water, setting the correct loss

coefficient f for intake pipe will be very important in designing this intake system.

Confirming the adequacy of intake pipe loss coefficient f leads to establishment of

intake pipe shape design method for various intake volume requirements.

3) Intake pipe loss coefficient f was obtained from water level difference measured

between inside and outside the intake tower in hydrologic model, numerical model

and actual system, and was compared with the results of hydrologic accounting.

Deviation between the results of numerical model simulation and actual system was

grasped as a result.

4) Comparative results of intake pipe loss coefficient f was used to compensate the

results from numerical model simulation in order to verify the design adequacy of the

free-selective air-lock intake system at Yubari Shuparo Dam.

5) This intake system has many materials that are buried into the dam body. At Yubari

Shuparo Dam, however, assembly was performed prior to placement of concrete for

the dam body by using sliding scaffold to carry out the construction without affecting

the concrete placement.

REFERENCES

Kawasaki,H. Nakagawa,T. Katsuyama B. (2011), Development and Operation of Free-

Selective Air-Lock Intake in Shitsumi Dam, Proceedings of the International

Commission On Large Dams 79th Annual Meeting, Luzern.

Kawasaki,H. Kina,T. Hashimura,K. Tsukayama,S. (2001), Study on a New-Type Selective

Intake Facility, Dam Engineering,Vol.11,No.4, pp.275-288, in Japanese.

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The New Practical Method For Screening Musty-odor / Non-odor Species In Oscillatoriales (Cyanophyta)

F.KIMURA

Senior Researcher of Water Quality Research Division , Japan Water Resources Environment Center [email protected]

T.HOMMA

A water quality management section chief, Civil Engineering and Eco-technology consultants Co., Ltd.

K.USHIJIMA Project assistant professor, Laboratory on engineering for sustainable sanitation,

faculty of engineering, Hokkaido University

E.FURUSATO Assistant Professor, Graduate School of Sci. and Eng. Saitama University

Y.TANAKA

Senior Engineering Adviser, Water Resources Department, Japan Water Agency

ABSTRACT: A musty-odor problem, caused by cyanobacteria belonged to Oscillatoriales, is not understood enough in reservoirs. One of causes, Oscillatoriales has morphological similar species including musty-odor / non-odor species. Musty-odor species cannot be identified by present morphological identification technique or a separation method of green / brown strains using a fluorescence microscope. Recently, Komárek and Anagnostidis have proposed a new classification system of Oscillatoriales. It is revealed that the detailed classification research based on this classification system can determine a separation of musty-odor / non-odor species. As a result, cases of successful separation of musty-odor / non-odor species in Oscillatoriales have increased. However, classification and identification of Oscillatoriales based on a new classification system is too hard to be directly applied in a regular phytoplankton monitoring, since it is performed by focusing on motility of trichome and detailed morphological characteristics at high magnification with microscope. In order to implement the daily water quality management, an elucidation and measures of musty-odor phenomenon in dam reservoirs, it is necessary to develop simple method for identification of musty-odor species, which is based to a new classification systems proposed by Komárek, et al. This paper introduces the consideration on a development of new morphological identification method to discriminate musty odor-species from Oscillatoriales. This method will be possible for reservoirs to predict risk of a musty-odor outbreak. This identification has been characterized by having adopted four new standards in a conventional standard. We assumed four conditions as classification standards. Keywords: Oscillatoriales (Cyanophyta), morphological identification, 2-Methylisoborneol 1. INTRODUCTION

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To Japanese tap water, we expect to be hygienic and good taste water. Under such circumstances, 2-Methylisoborneol (hereinafter 2-MIB) and geosmin, which are responsible for musty odor, were established as quality demand standards of a tap water based on the Water Supply Act of March 2003. Generally, a musty-odor producing materials are produced from some Cyanophyta and Actinomycetes. The abnormal bloom of Cyanophyta associated with the eutrophication of lakes, swamps, dams and reservoirs is often the cause of the production of such materials. Water suppliers and dam managers have implemented various measures to preserve water quality as a measure to solve musty odor problems. Although such measures have produced definite effects, they have not provided fundamental solutions. One of the reasons that musty odor problems have not been eliminated is the problems concerning the morphological identification of algae, including, Phormidium tenue, belonging in Oscillatoriales, Order Nestocales and Class Cyanophyceae (hereinafter Phormidium tenue), which is considered to be the algae that cause abnormal odor and taste. In many cases, the problems of 2-MIB induced abnormal odor and taste in dams and reservoirs are thought to be originated in Phormidium tenue. Yet, some have pointed out that some organisms in this species produce 2-MIB, while some do not. Studies have verified that they belong in genetically different groups. As a method to distinguish them at fields, methods such as focusing on the differences in antenna pigment have been suggested, but exceptions have also been reported. Therefore, it has been concluded that accurate screening of these two is difficult. Thus, as in many cases, a clear relationship between variations in the cell density of Phormidium tenue and the 2-MIB concentration is not recognized. As a result, studies have neither fully revealed the mechanisms of the onset of abnormal odor nor the taste and the effects of reducing them. This situation is forcing people at fields where Phormidium tenue has been found, but no 2-MIB has been detected, to conduct management while being anxious about the onset of problems which could occur at any time. In 2005, Komárek and Anagnostidis suggested a new classification system for Cyanophyceae based on unique viewpoints which differ from conventional perspectives. Studies in Japan are also starting to report cases suggesting the possibility of screening musty-odor / non-producing species based on detailed algae classification research conducted using the method of Komárek and Anagnostidis. Yet, it is difficult to use this morphological identification of Cyanophyceae directly based on the new classification system at actual fields because it is conducted by focusing on detailed morphological characteristics of algae and the mobility of trichome. Therefore, it is necessary to develop simplified identification methods so that people at actual fields can identify musty-odor producing species with their identification techniques and in their identification environment using the classification method suggested by Komárek et al. in order to use the method for daily water quality management and finding causes of the musty odor phenomenon. This paper is introducing the simple identification manual for Phormidium tenue (hereinafter manual) that the authors have been working to develop since 2011 and reporting the results of verifications conducted using the data obtained from 2011 to 2012. 2. IDENTIFICATION MANUAL 2.1. Overview of the simple identification manual The authors prepared the simple identification manual which is intended to separate Phormidium tenue into musty-odor and non-producing species based on comparisons between conventional morphological identification methods and morphological

IV - 162

identification based on “Komárek and Anagnostidis, 2005”, research of published literature on musty-odor causing algae, and results of morphological identification at Kasumigaura. This manual adopted the following four conditions as classification standards which were prepared by organizing the findings of past research in addition to conventional morphological identification standards for Phormidium tenue which is based on “cell diameter: 5 μm or less and the L/W ratio of a cell (the ratio between the length (L) and the width (W) of a cell): 6 or less.” This enables the selection of four types of musty-odor producing species from 14 species of Phormidium tenue, which used to be identified as one species without conducting detailed morphological identification, and distinguishing ten remaining species as non-producing species. (See Fig 1 and Table 1.)

(i) Cell diameter: 0.5 to 2.5μm (ii) L/W ratio of a cell: 2 to 5 (iii) Deformation at the tip of a cell: None (iv) Cleavage on cell wall: Available

Based on the above, 2-MIB producing algae can be distinguished among Phormidium tenue only by simple observation under a microscope without depending on the detailed identification of species by Cyanophyceae classification experts who are very limited in number.

Cell diameter(W)：5μm or less

L/W ratio of a cell：6 or less

Cell diameter(W)：0.5 to 2.5μm

L/W ratio of a cell：2 to 5

Cleavage on cell wall : Available

Deformation at the tip of a cell : None

Cleavage on cell wall : None

Deformation at the tip of a cell : Available

Figure 1. Point of interest on the simple identification manual 2.2. Expected effects of using the simple identification manual This simple identification manual cannot reveal names of existing algae species. Its feature is to enable the screening of species which produce musty odor and ones which do not produce the odor. There are mainly two effects expected from using this manual. One is that it enables the identification and forecast of the risks of musty odor generating in higher accuracy than conventional methods in regular water quality monitoring. This means that incorporating this manual into daily water quality monitoring (e.g. periodical water quality investigation) in dams and reservoirs where Phormidium tenue is found but no musty odor is detected, enables identification of whether the detected Phormidium tenue belongs in the group of musty-odor producing species.

IV - 163

Table 1. Correspondence between the species name and point of interest on the manual

Cell diameter L/W ratio Cell diameter L/W ratio0.5～2.5μm 2～5 0.5～2.5μm 2～5

Komvophoron cf. minutum × × Pseudanabaena catenata 〇〇

Komvophoron schmidlei × × Pseudanabaena limnetica 〇〇

Leptolyngbya tenuis ○ ○ Pseudanabaena galeata 〇〇

Geitlerinema sp. ○ ○ Pseudanabaena biceps 〇〇

Planktolyngbya limnetica △ △

Leptolyngbya sp. △ △

Geitlerinema nematodes ○ △ Geitlerinema amphibium ○ ○

Geitlerinema splendidum ○ ○ Limnothrix redekei 〇 △

Limnothrix planktonica ○ ○

Jaaginema gracile × ×

The species name ： The species name that is based on the identification by experts.　　　　　　　　　　　　　　 (Gray Hatching is 2-MIB producing algae)Thick line box ： Grope of 2-MIB producing algae that is based on the simple identification manual〇：In range、△：Both、×：Out of range

Deformation at the tip of a cellAvailable None

Cle

avag

e on

cel

l wal

l

Ava

ilabl

eN

one

The species name The species name

In addition, this manual enables the forecasting the increasing risks of the onset of musty odor if a group of musty-odor producing species starts to be detected although no such species were found in the same dams and reservoirs before. Such forecasts can be used for the implementation of detailed investigations and the provision of smooth communication and warnings to relevant organizations. This is an extremely beneficial in water quality management. The other point is the possibility of progress in revealing mechanisms at the onset of musty odor which used to have many unknown aspects. As mentioned earlier, in many cases, no clear relationship is recognized between variations in the cell density of Phormidium tenue and the concentration of 2-MIB which are identified using the currently available morphological identification methods. Yet, if the onset of odor can be identified by specifically extracting the group of musty-odor producing species, analyzing its responses to environmental factors of the same time enables one to specify the preferred environment for the bloom of musty-odor producing species, which can then be used for effective measures to prevent the bloom. A case in which morphological identification was actually conducted and examined based on this manual is introduced below. Phormidium tenue is being detected almost throughout the year in dam K in Japan. Yet, the onset of its bloom is not necessarily synchronized with the bloom of 2-MIB. Similarly, no clear relationship is found between the peak value of the cell density of Phormidium tenue and the peak value of the 2-MIB concentration. Therefore, the mechanism of the onset of the musty odor had not been revealed. Therefore, Phormidium tenue at the surface was identified and counted at the center of the lake (see Fig 2) based on this manual. As a result, 2-MIB was found in two timeframes, from early April to early July (period (i)) and from mid-August to late September (period (ii)). A clear difference found here was that in the period (i), a group of musty-odor producing species was found, whereas no musty-odor producing species were found in the period (ii). This suggests that the bloom of the group of musty-odor producing species in the reservoir water became the cause of the production of 2-MIB in the period (i), while 2-MIB was detected in the water of the reservoir although the group of musty-odor producing species was not present in the water in the period (ii). Also, algae investigation found no musty-odor producing algae besides Phormidium tenue.

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This indicates that the musty odor in period (ii) occurred because there was a source of odor outside of the water of the reservoir, and 2-MIB was supplied to the water in the reservoir in a dissolved state from the source. Given this finding, people at dam K are now looking for sources of the odor outside of the reservoir and investigating and examining the mechanisms of the supply of musty odor from the source to the lake water. As discussed above, the development of the simple identification manual is necessary for improving the level of water quality management in dams and reservoirs (early detection of problems and the establishment of better methods to counteract problems).

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

Cel

l den

sity

(cel

ls/m

L)

Total 2-MIB producing algae 2-MIB nonproducing algae

0

3

6

9

12

15

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2-M

IB C

once

ntra

tion

(ng/

L)

T-2-MIB D-2-MIB P-2-MIB

Figure 2. Correspondence relationship between identification and count that is based on the

simple identification manual and 2-MIB concentration T-2-MIB：It means total 2-MIB. We extract the 2-MIB algal cells by sonication method, to

analyze the 2-MIB of all of the water. D-2-MIB：It means dissolved 2-MIB. The obtained value by analyzing the 2-MIB, which are

dissolved in water P-2-MIB：It means particulate 2-MIB. The difference between the D-2MIB and T-2-MIB.

3. VERIFICATION OF THE SIMPLE IDENTIFICATION MANUAL 3.1. Method of verification Verifications are conducted based on the method below to check whether musty-odor producing species can be accurately identified by people at fields based on this manual. “People at fields” as used here means engineers in private companies that are identifying, counting, and analyzing algae as a part of periodical water quality examinations in reservoirs. They are expected to be capable of identifying and counting algae using classification books and pictorial references which are commonly used today.

Eighteen samples, including the Phormidium tenue collected from August to October, 2011 and from July to August, 2012 in dam K in Japan (ten samples from 2011 and eight samples from 2012) were sent to the people at fields, who examined them under microscopes based on this manual.

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In the microscope examination, they identified Phormidium tenue and then examined (i) cell diameter, (ii) the L/W ratio of cells, (iii) deformation at the tip of the cell, and (iv) the presence of cleavage on cell walls; and took photographs of targeted algae.

Results obtained in the microscope examination were plotted in the recording format shown in Fig 3.

Photographs taken by the people at fields were examined, and Phormidium tenue in the sample was identified based on “Komárek and Anagnostidis, 2005.”

The result of the identification by “Komárek and Anagnostidis, 2005” was compared with the results of the microscope examination conducted by people at fields to check their ability to accurately identify algae.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 5 10 15

L/W

ratio

Width(μm)

Criteria of a conventional

Criteria of the manual

Figure 3. The recording format for verification

3.2. Result of verification The result of the verification of the samples is described below. Fig 4 shows entries of the results in a recording format, and Fig 5 shows species that were identified in this verification.

A hundred and twenty five filamentous algae were found within a size category which would be classified as Phormidium tenue in conventional classification systems.

The morphological identification of these 125 filamentous algae by the authors based on the photographs taken by the people at fields found nine species shown in Table 2. Among them, Pseudanabaena catenata was the only 2-MIB producing species.

Sixteen filamentous algae were recognized as 2-MIB producing species, and 109 filamentous algae were recognized as non-2-MIB producing species based on the manual.

The result of the comparison between the 16 filamentous algae recognized as 2-MIB producing species and the result of additional morphological identification conducted

Deformation《Explanatory notes》

Available None

Ava

ilabl

eC

leav

age

Non

e

◇ ○

□ △

IV - 166

by the authors is as follows: Nine filamentous algae belonged in the genus Pseudanabaena (Pseudanabaena catenata: 2-MIB producing species), and remaining six filamentous algae belonged in the genus Geitlerinema (Geitlerinema nematodes: non-2-MIB producing species), the genus Jaaginema (Jaaginema gracile: non-2-MIB producing species), and the genus Leptlyngbya (Leptlyngbya sp.: non-2-MIB producing species).

Among the non 2-MIB producing species listed above, Geitlerinema nematodes is supposed to be classified as “Deformation at the tip of a cell: Available, Cleavage on a cell wall: None,” and Jaaginema gracile as “Deformation at the tip of a cell: None, Cleavage on a cell wall: None.” However, the people at fields identified both of them as “Deformation at the tip of a cell: None, Cleavage on a cell wall: Available.”

The comparison of the 109 filamentous algae identified by the people at fields identified as non-2-MIB producing species with the result of the morphological identification by the authors found that all of them were non-2-MIB producing species.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 5 10 15

L/W

ratio

Width(μm)

●：Samples that have been determined to be musty odor producing species by checking the expert

Figure 4. The result of the entry into the recording format

《Explanatory notes》

Cle

avag

e

Available NoneDeformation

◇ 〇,●

□ △A

vaila

ble

Non

e

IV - 167

Pseudanabaena catenata Leptolyngbya sp.

Limnothrix redekei Komvophoron sp.

Figure 5. The main appearance species has been confirmed this research

Table 2. The verification of classification results between expert and people at fields

Cell diameter L/W ratio Cell diameter L/W ratio0.5～2.5μm 2～5 0.5～2.5μm 2～5

Geitlerinema sp. ○ ○ Pseudanabaena catenata 〇〇

Komvophoron sp. × × Leptlyngbya sp. △ △

Geitlerinema nematodes ○ △ Geitlerinema amphibium ○ ○

Geitlerinema splendidum ○ ○ Limnothrix redekei 〇 △

Jaaginema gracile × ×

Cle

avag

e on

cel

l wal

lA

vaila

ble

Non

e

Deformation at the tip of a cellAvailable None

The species name The species name

3.3. Adequacy of the simple identification manual In this verification, the people at fields could not specifically isolate 2-MIB producing species using the manual. Yet, they were able to eliminate 109 out of 125 filamentous algae (six species) as non-2-MIB producing species and narrowed down the candidate of odor-causing algae into 16 filamentous algae (three species). The same person at fields identified two species belonging in the genus of Geitlerinema and Jaaginema based on this manual during the verification conducted over two years. The identification by the person in 2011 did not match with the identification based on this manual, but this mistake was accurately corrected in the verification in the following year. These two species have microscopic granular structures which scatter light in low-magnitude observation (x100 to 200), and make a cell appear as if it has a cleavage on the cell wall. Therefore, the magnitude of a microscope needs to be x500 to x1,000 in some cases to accurately identify whether a cell really has a cleavage on the cell wall. Providing proper descriptions and

IV - 168

explanations for classification in the manual is necessary for species which require special attention like this. At the same time, people at fields need to have some experience with these classifications. In addition, Planktolyngbya limnetica, which belongs in the same category as musty-odor causing algae (the genus Pseudanabaena) constantly form clearly visible mucilaginous sheaths; thus, it can be easily distinguished from species in the genus Pseudanabaena, which do not form mucilaginous sheaths. Other species in the genus Leptolyngbya (Leptlyngbya sp.) do not necessarily form mucilaginous sheath, and it is difficult to clearly distinguish them from musty-odor causing algae. These points are the issues which need to be improved in this manual. The verification above indicated a possibility that people at fields can screen musty-odor / non-producing species among Phormidium tenue using this manual. There is great value in improving the accuracy of screening 2-MIB producing species at fields in terms of water quality management at dams and reservoirs. 4. FUTURE STUDIES AND PERSPECTIVES This paper discussed the development of a new morphological identification manual which allows people at fields to identify Phormidium tenue that used to be identifiable only when musty-odor and non-producing species are present in the same water, and examined its accuracy and workability at fields. As a result, the screening of musty-odor / non-producing species using this manual is found to be possible to a level that can be effectively used in actual operations, although there is a necessity to add descriptions for species which require special attention in identification and some experiences of people at fields. This verification indicated the adequacy of this manual. There are still issues to be solved, however, concerning the adequacy of this manual, certainty of implementing this process by people at fields, and usability at fields because the result obtained this time is based on the verification targeting samples from one dam, and that verification only examined one person working at the fields. Therefore, the manual needs to be properly improved by continuing to accumulate and examine more data and adding descriptions with sketches and examples with photographs. The authors are now collecting samples from multiple reservoirs and conducting examinations targeting multiple people at fields. While this manual was only targeted to Phormidium tenue, there are reports from actual fields on musty odors caused by the genus Oscillatoria and by geosmin. Also, both musty-odor and non-producing species are present in large quantities in algae which used to be considered as a part of the genus Oscillatoria.Based on the above, these algae need to be organized in similar fashion and added in manuals in the future. In addition, if the use of this manual improves confusion at fields caused by the mixed presence of musty-odor / non-producing species which originate in problems in classifications, the analysis of morphological characteristics of these taxonomical groups is expected to progress, which results in the implementation of more appropriate measures to protect water quality. ACKNOWLEDGEMENT This paper provides a report on some of the outcomes of “The Third Study Session Concerning Morphological Identification Methods for Oscillatoriales (Cyanophyta)”. In the process of writing this report, the author et al. received much advice from Mr. Kaoru Niwa, chief of engineering at Token C.E.E. Consultants, and Mr. Makoto Kuno, senior engineer at Japan Water Agency, who participated in the study session as observers. We appreciate their support.

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REFERENCES Akiba, M. (2003): Examinations of odor in tap water, Water supply and wastewater, Vol.

45:11, Japan. (In Japanese) Yamamura, S. (1993): Background on revising the Water Supply Act, Public Health

Research, Vol. 42:4, Japan. (In Japanese) Japan Water Works Association (1999): Guidelines on preventing abnormal odor and taste

in water which are caused by biological factors.pp.6, Japan. (In Japanese) Oikawa, E. and Ishibashi, Y (2004): Species specificity of musty-odor producing

Phormidium tenue in Lake Kamafusa, Water Science and Technology, Vol. 49:pp. 41-46, IWA, UK.

Nakamura, T. (1987): Taxonomical and morphological examination of Phormidium tenue, Japanese Society of Water Treatment Biology, Attachment 7:pp. 69, Japan. (In Japanese)

Kudo, K., Kawakami, T. and Yamada, T. (2004): Phormidium and musty odor in dams and reservoirs, Journal of Japan Society of Hydrology and Water Resources, Vol. 17:pp. 331-342, Japan. (In Japanese)

Matsukawa, M., Inagaki, N. and Otomo, T. (2008): Lake management at the Kamafusa Dam “Current condition of aeration measures and new efforts”, The 2008 presentation of engineering researches of Tohoku Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism, Japan. (In Japanese)

Sato, H. and Amano, M. (2007): Effect of shallow reservoir and lowered water level on 2-MIB “The Watarase Reservoir as an example”, Ecology and Civil Engineering Society, Vol. 10:pp. 141-154, Japan. (In Japanese)

Komárek, J. and Anagnostidis, K. (2005): Cyanobacteria 2. Teil/2nd Part: Oscillatoriales. In: B. Büdel, L.Krienitz, G. Gärtner and M. Schagerl (Ed.) Süsswasserflora from central 19/2, Elsevier/Spectrum, Heidelberg, Germany.

Honma, T. (2007): The flora of Oscillatoriales (Cyanophyta) in Kasumigaura, The Annual Report of Ibaraki Kasumigaura Environmental Science Center, Vol. 3:pp. 24-128, Japan. (In Japanese)

Kimura, F., Honma, T., Maeda, M. and Matsukawa, M. (2013): Effects of musty-odor producing materials and musty-odor causing algae supplied from upstream areas on musty odor in dams and reservoirs, Dam Engineering, Vol.23:1:pp. 39-49, Japan. (In Japanese)

Kimura, F., Honma, T., Ushijima, K., Furusato, E. and Tanaka, Y. (2013): Efforts to develop morphological identification method for Oscillatoriales (Cyanophyta) with focus on odor-producing/non-producing properties. Dam Engineering, Vol.23:4, Japan. (In Japanese)

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– 6TH

, 2014

Assessment of Capacity and Water Level Profile hhdTTjjhkljdjjsgshjhfsdkjhskslsl;s;s;;s;;s;;sjsjkjffffrtttttttfggjfgjgkfkjkjf fffffjfjjfkkfjjj at the Cidanau Head Work

2(14pt) Sustaining Cidanau Headwork

Satyanto K. Saptomo, Budi I. Setiawan, Z. Akbar Murdiono, Rizqah Pangestu Department of Civil and Environmental Engineering, Bogor Agricultural University (IPB), Indonesia

[email protected]

M. Budi Saputra, Saritomo PT. Krakatau Tirta Industri (KTI), Cilegon, Indonesia

ABSTRACT

This study aims to evaluate the hydraulics of Cidanau Headwork at the downstream of Cidanau

River to assess the urgency of Headwork Redesign and river dredging after decades of

establishment. This paper is the first part that present the evaluation of Cidanau River capacity and

the profile of water level at Cidanau Weir. The first was done by Nakayasu Method and HEC-MHS

model to estimate the dependent flow. The 100 year dependent flow and PMF were estimated at

49.83452 x106m3 and 11.021586 x106m

3 which are still sufficient as the abiotic and biotic

ecosystem in the surrounding could be preserved. The second analysis was conducted by estimating

the sedimentation which caused the increase of water level over the weir during the last 10 years

by analyzing river base profile. During the past 10 years there had been the decreasing in the river

water quality due to sedimentation. The sedimentation was estimated between 451.232 to 822.528

m3/year and had increased the water level 0.05 m above the weir. The results had shown that there

are changes in Cidanau Weir due to sedimentation, but either the capacity or water level profile

are still acceptable.

Keywords : river hydrology, sedimentation, Cidanau Watershed, industrial water

1. INTRODUCTION

Cidanau watershed lays at 105° 57’ 00” - 106° 22’ 00” East and 5° 21’ 00” - 6° 21’ 00”

south, has an area of 22620 ha is the most important watershed in the industrial and

regional development of Banten Province, especially western part of Serang and Cilegon

city. It is divided into flat plain cosists of Rawa Danau Natural Reserves and paddy fields

with total area of 8821ha; and surrounding hilly sub-catchments which stream are flowing

to the plain. In the last twenty years, Cidanau experienced environmental degradation

which endangers its sustainability.

Cidanau rivers water is diverted by the establishment of Cidanau Headwork at the

downstream, which is operated by Krakatau Industrial Water Company (KTI) for industrial

as well as domestic use clean water supply of the surrounding areas The headwork is

located 600 m from the estuary and has length of 30m. Intake discharge is regulated by

sluice gate which then transmited to the sandtrap and sump pump and finally sent to water

treatment plant, which is operated from Pump Station.

IV - 171

Decreasing of Cindanau river capacity will have impact to decreasing of its water quality,

which should be prevented through better river management. The effort can be initiated

with determination of quantity and quality of potential contaminant that get itu the stream

such as solids from erosion. Determination of sedimentation which also related to water

level and the capacity of river will be the basis for decision making of effort to manage and

normalization of the river.

This paper is the first part of the subject of weir evaluation by using hydrological,

headwork structures hydraulic and design, and river topographic data. The objective of this

study presented in this paper is to evaluate the current Cidanau river capacity and water

level profile which information are required in the maintenance planning of the weir.

2. METHODOLOGY

The assessment of river capacity and water level based on hydrology and biophisical data

which includes: climatology data (Ciomas st., Serang st. and Padarincang st.) from 1996-

2012, land use, discharge and water level. Discharge analysis was done by using HEC-

HMS which then to be compare with discharge from Nakayasu (Fig.1). The result is to be

compared with rating curve of Cidanau River which uses water level data recorded by

AWLR (Automatic Water Level Recorder) owned by Krakatau Industrial Water (KTI).

Data input for HEC-HMS area land use, rainfall and discharge.

Figure 1. Flow chart of River Capacity Assesment

HEC-HMS modeling utilizes six components which are meteorology, loss, baseflow, direct

run-off, routing and reservoir. Steps on HEC-HMS modelling is presented in Fig.2.

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Figure 2 HEC-HMS Modeling Steps

Data processing was started with determination of missing rainfall data, followed by

propable rainfall frequency analysis and finally probable rainfall calculation. By using

synthetic unit hydrograph, flood discharge was analysis. There are 4 synthetic unit

hydrograph which were done, the most proper method to be used in this case is Nakayasu

Method (Fig…) which is also known to be suitable for tropical region such as Cidanau

Watershed in Indonesia.

Flood Routing calculation is the fundamental for maksimum water level calculation and

maximum outflow discharge. In principle, Flood Routing calculation used continuity

equation as follow :

Qinflow – Qoutflow = ds/dt (1)

where:

Q inflow : Inflow (m3/s)

Q outflow : Outflow (m3/s)

S : Water storage in dam (m3)

Loss Component

Direct Runoff component

Baseflow

component

Routing

Component

Component of

Reservoir

Meteorological Component

Rainfall

Losses Direct Runoff

Baseflow

Reservoir Operator

Pervioussurface

Catchment outlet

River and canal

Aquifer

Impervious surface

IV - 173

t : Time according to flood hydrograph(k)

Outflow is the run off over spillway which affected by inflow. Taking into account inflow

and spillway dimension, the outflow hydrograph can be obtained. Keluaran dari outflow

Spillway adalah hidrograf outflow. For the dam safety purpose, flood routing was

calculated based on 100 year and PMF discharge.

Spillway Capacity was calculated following the next equation:

Q = C.B. H3/2

(2)

where:

Q = discharge over spillway (m3/det)

B = spillway width (m)

H = Head over spillway (m)

C = Coefficient of discharge over spillway

In this case width and elevation of spillway are 25 meter and 87.5 meter.

Water surface elevation measurement was carried out by using Automatic Water Level

Recorder (AWLR) and Sofware HEC-RAS, on the completion of the above data

processing. As for the sedimentation, contour/topography of the river in different years

were compared to and so the sedimentation can be estimated.

Figure 3. HSS Nakayasu (Kamiana, 2011)

3. RESULTS AND DISCUSSION

3.1. Rainfall analysis

There are missing rainfall data, namely of Ciomas Station from 2007 to 2010. In order to

substitute the missing data, Normal Ratio Method was used by utilizing data from the

nearest two stations : Serang and Padarincang. Examples of the estimation is as follows:

- Rainfall at Padarincang Januari 2007 (RA) = 242 mm

- Averaged annual rainfall of Padarincang = 2334 mm

- Rainfall at Serang Januari 2007 (RB) = 207 mm

IV - 174

- Averaged annual rainfall Serang = 1528 mm

- Averaged annual rainfall Ciomas = 2336 mm

The following Table 1 shows the substitutes of missing data of Ciomas in year 2007-2010:

Tabel 1. Subtituting rainfall data for Ciomas.

Tahun Jan Feb Mar Apr Mei Jun Jul Agt Sep Okt Nop Des

2007 438 460 677 267 317 157 147 71 12 243 134 565

2008 667 807 411 268 180 107 0 170 85 306 615 348

2009 722 665 301 228 232 140 35 3 67 138 706 152

2010 782 422 392 146 295 329 475 284 686 516 378 439

Consistency of the new data was analyzed by using double mass curve. Comparison of

rainfalls of Ciomas to Serang and Padarincang which are completed is showed in

following Fig. 4.

Figure 4. Double Mass Curve of Ciomas Station to Serang and Padarincang

The relationship between averaged data from Serang and Padarincang to Ciomas is

represented with the value of α = 1.082 and β = 0.756. Correction factor was obtained 0.7.

Correction to Ciomas data from year 1996 to 1999 was also done by dividing data with

correction factor and the data was plotted to chart shown in Fig. 5.

Figure 5. Double Mass Curve of corrected Ciomas Station data to Serang and Padarincang

Corrected Double Mass curve shows no significant slope changes to the uncorrected one.

This suggests that new data to Ciomas Station Data is consistent.

IV - 175

Thiesen method was used with using the 3 stations data. Thiesen polygon was made GIS

software, afterwhich stations points and each area of influence to Cidanau watershed was

determined. Fig 6 shows the area of influence by Thiesen Polygon, where upper part is

influenced by Cilegon station, left part is by Serang station and lower part is by

Padarincang station. Table 2 shows the extents of each polygon. Recapitulation of rainfall

of the region is as shown in Fig. 7.

Figure 6. Cidanau Watershed division with Polygon Thiessen

Table 2. Influence extension of rainfall station to Cidanau Watershed

No

Station

Area (km

2)

Weighing

factor

1 Serang 76.984 0.346

2 Ciomas 62.010 0.279

3 Padarincang 83.291 0.375

Total area 222.286 1.000

Figure 7. Recapitulation of maximum rainfall

3.2. Probable Rainfall Frequency Analysis

Frequency analysis was done statistically using parameters of mean ( X ), standard

deviation (dS), variance coefficient (Cv), skewness coefficient (Cs) and kurtosis

coefficient (Ck). The parameters were calculated based on the recorded maximum

averaged daily rainfall within the last 20 years.

IV - 176

Table 3. Statistical Parameters

Parameters Variables Calculation results

Number of data n 17.000

Standard Deviation SD 22.906

Variety Coefficient Cv 0.745

Skewness Coefficient Cs 1.564

Kurtosis Coefficient Ck 2.937

Median (Sx) 19.399

Table 4 Statistical parameters of each distribution type

No Distribution Requirements Calculations

1 Normal (𝑥 ± 𝑠) = 68.27%

(𝑥 ± 2𝑠) = 95.44%

𝐶𝑠 ≈ 0

𝐶𝑘 ≈ 3

Cs = 1.564

Ck = 2.937

2 Log Normal 𝐶𝑠 = 𝐶𝑣3 + 3𝐶𝑣

𝐶𝑘 = 𝐶𝑣8 + 6𝐶𝑣6 + 15𝐶𝑣4 +16𝐶𝑣2 + 3 Cs = 0.9

Ck = 1.8

Cs = 0.9

Ck = 1.8

3 Gumbel 𝐶𝑠 = 1.14

𝐶𝑘 = 5.4

Cs = 1.56

Ck = 2.937

4 Log Pearson III Other than above values Cs = 0.9

Ck = 1.8

Values obtained from distributions were tested for compatibility. After calculation result

was compared with the requirement, Log Pearson III was choosen as the distribution for

this case with Cs = 0.9 and Cv = 0.195.

3.3. Nakayasu Flood Analysis

Probable flood was calculated using Nakayasu synthetic unit hydrograph Fig. 8. Probable

flood discharge was calculated based on rainfall of 100 years dan PMF (Probability

Maximum Flood) based on probable rainfall and the catchment characteristic. Area that

was taken into accounts are before the Curug Betung Waterfall (upper Cidanau

Watershed):

1. Catchment area before waterfall (A1) = 192.56 km2

2. Length of main river before waterfall (L1) = 18.31 km

3. Catchment slope before waterfall ( I1 ) = 0.11358

4. Catchment area below Waterfall (down stream) (A1) = 21.37 km2

5. Length of main river below Waterfall (L1) = 8.0595 km

IV - 177

Figure 8. Recapitulation of Hydrographs for each return periods.

Inflow and outflow flood discharge for return periods 2 to 1000 year (PMF) are shown in

Table 5. Summary of flood routing for return periods of 100 years and PMF are shown in

Table 6.

Table 5. Inflow and Outflow Discharge

Flood Discharge (m3/det)

2

years

5

years

10

years

25

years

50

years

100

years

200

years

1000

Years

Imax (m3/s) 107.71 192.10 275.24 422.71 571.87 763.96 1010.96 2225.27

Omax (m3/s) 7.82 11.67 14.95 20.08 25.39 31.85 39.63 57.95

Table 6. Flood routing recapitulation using Nakayasu Method

No. Description Inflow

(m3/s)

Outflow

(m3/s)

Water

elevation (m) Storage

(1000 m3)

1 100 763.96 39.23 + 93.88 49834.52

2 PMF 1892.82 70.625 + 95.14 110215.86

3.4. HEC-HMS

Three hydrographs in HEC-HMS was calculated: Snyder, SCS and Clark. In order to

obtain the hydrographs, the following data were used: 1. Rainfall; 2. Sub Catchment Area;

3. Weight of each sub catchment in regards of the previously made Thiesen Polygons; 4.

All HEC-HMS basin model parameters; 5. Control specification in HEC-HMS simulation;

6. Precipitation analysis with gage weights methods. Based on this calculation, flood

routing was carried out and the result is shown in Table 7

Table 7 Flood routing recapitulation using HEC-HMS

No. Description Inflow

(m3/s)

Outflow

(m3/s)

Water elevation

Air (m) Storage

(1000 m3)

1 100 253.86 210.63 + 92.11 9638.92

2 PMF 736.72 310.93 + 93.48 37672.70

-500

0

500

1000

1500

2000

2500

0 20 40 60 80 100 120

Dis

char

ge (

m3/s

)

Hour

Tr 2 Tahun

Tr 5 Tahun

Tr 10 Tahun

Tr 25 Tahun

Tr 50 Tahun

Tr 100 Tahun

Tr 200 Tahun

RPMF

IV - 178

3.5 HEC-RAS

Water level profile was estimated using HEC-RAS assuming discharge from 1 m3/s to 60

m3/s occured. The outflows of every return period from previous flood routing (Table 5)

which are 7.82 m3/s, 11.67 m

3/s, 14.95 m

3/s, 20.08 m

3/s, 25.39 m

3/s, 31.85 m

3/s, 39.63

m3/s, and 57.95 m

3/s were input into HEC-RAS to obtain water level profile (Fig. 9) to

obtain respective water level. These elevation data for year 2001 and 2012 were then

compared. Based on the program’s results (Table 8), rating curves were made to show

relation between water level and discharge over the weir (Fig. 10).

Figure 9. Plotting Discharge Data in HEC-RAS

Figure 10. Rating curves for 2001 and 2012.

IV - 179

Table 8 Water level increase at Cidanau Weir

Periode

Ulang

Debit

Sungai

(m3/s)

Water Surface (m) Tinggi Di atas Mercu

2001 2012 2001 2012 Kenaikan

Tr=2 7.82 3.66 3.69 0.21 0.24 0.03

Tr=5 11.67 3.73 3.76 0.28 0.31 0.03

Tr=10 14.95 3.78 3.82 0.33 0.37 0.04

Tr=25 20.08 3.85 3.90 0.40 0.45 0.05

Tr=50 25.39 3.92 3.98 0.47 0.53 0.06

Tr=100 31.85 4.00 4.06 0.55 0.61 0.06

Tr=200 39.63 4.08 4.15 0.63 0.70 0.07

RPMF 57.95 4.25 4.35 0.80 0.90 0.10

In year 2001 mean level of river water was 0.46 m over the weir crest, while in 2012 for

every return period was increased to 0.51 m. This is caused by sedimentation, which

estimated happened between 451.232m3/year to 822.528m

3/year. Sedimentation that

happens within 10 years had increased water level 0.05 meter.

4. CONCLUSION

The 100 year dependent flow and PMF were estimated at 49.83452 x106m

3 and 11.021586

x106m

3, which are still sufficient as the abiotic and biotic ecosystem in the surrounding

could be preserved. The second analysis was conducted by estimating the sedimentation

which caused the increase of water level over the weir during the last 10 years by

analyzing river base profile. During the past 10 years there had been the decreasing in the

river water quality due to sedimentation. The sedimentation was estimated between

451.232 m3/year to 822.528m

3/year and had increased the water level 0.05 m above the

weir. The results had shown that there are changes in Cidanau Weir due to sedimentation,

but both the capacity and water level profile is still acceptable for present condition.

ACKNOWLEDGEMENT

This study is an outcome of the joint research and activity between Bogor Agricultural University

(IPB) and Krakatau Industrial Water Company (KTI). The authors express their gratitude to IPB

and KTI for the support.

REFERENCES

Kamiama. 2011. Analisis Hidrologi. Jogjakarta

Budianto, Muh.Bagus.2007.Kalibrasi Parameter Hidrolika Sungai Pos AWLRJangkok Bug

Bug.Lombok

Hindarko, Ir. S.2002.Drainase Kawasan Daerah.Jakarta : Esha.

Istiarto.2012. Simulasi Aliran 1-Dimensi Dengan Bantuan Paket Program Hidrodinamika

HEC-RAS.Yogyakarta. (http://istiarto.staff.ugm.ac.id/.)

Kamiama, I Made.2011.Teknik Perhitungan Debit Rencana Bangunan Air. Yogyakarta:

Graha Ilmu.

Suripin, Dr, Ir, M.Eng. Diktat Kuliah Hidrolika dan Mekanika Fluida. UNDIP.

Triatmodjo, Bambang.2008. Hidrologi Terapan.Yogyakarta: Beta Offse,t Yogyakarta.

IV - 180



– 6TH

, 2014

Evaluating the Hydraulic of Cidanau Weirs Intake

2(14pt)

(Sustaining Cidanau Headwork Part 2)

Satyanto K. Saptomo, Budi I. Setiawan, Asep Suryadi Department of Civil and Environmental Engineering, Bogor Agricultural University (IPB), Indonesia

[email protected]

M. Budi Saputra, Muhammad Nasir PT. Krakatau Tirta Industri, Cilegon, Indonesia

ABSTRACT

This study aims to evaluate the hydraulics of Cidanau Headwork at the downstream of Cidanau River

to assess the urgency of Headwork Redesign and river dredging after decades of establishment. This

paper is the secondpart that focuses on the re-calculation of hydraulics of Cidanau Weir intake to the

sandtrap due to sedimentation of the river. The result shows that during 11 years of sedimentation in

Cidanau River, instead of decreasing, the intake flow increased about 10 to 40 l/s. Therefore, the

dredging of Cidanau River’s base is not necessary for the time being. Although there is no river

maintenance required, the intake is recommended to be opened 25% to 26% of the gate’s height,

which are equal to 40 to 41.6 cm. This consideration has also taken into account the seasonal

changing of the river discharge.

Keywords : weir hydraulics, sedimentation, Cidanau Watershed, industrial water

1.INTRODUCTION

Headwork can be defined as complex of structures that is designed along a river or stream

with purpose to divert water to canal network to be utilized for irrigation or other uses. It can

lower sedimentation and can be used for measuring the quantity of water flow through it.

Headwork consists of weir with energy dissipator, one or two intakes, flushing duck, stilling

basin, etc. Intake has function to control quantity of water taken into canal and prevent solids

and coarse material from entering the canal.

When a weir is constructed, its efficiency and life-span can be determined based on the

prediction of generation of sediment. The longer the operation of a weir, sediment

accumulation at the weir structure will increase. Thus, the river will become shallower and its

capacity decreases. When this occurs, with the same discharge of water, the velocity of the

flow will increase and causes more erosion of the river walls which worsen the sedimentation.

Sediment in water is a problem to companies who use river water as their raw water. Water

treatment will be required to lower sediment concentration in the water. Moreover river

environment should be well managed to minimize sedimentation. The increasing of water

flow rate means more sediment get into the intake and consequently the cost of water

treatment will increase.

IV - 181

The objective of this study is to analysis and to evaluate the hydraulics of Cidanau Weir to the

sandtrap that is affected by sediment transported by river water from the upstream. In this

case the proper intake’s gate opening height is to be determined to assume ideal water inflow.

2. MATERIAL AND METHODS

The study was carried out as a joint work with Raw Water Office (Dinas Air Baku) Krakatau

Industrial Water Company which operated Cidanau weir. Intake work evaluation of Cidanau

weir was done following two stages which are data collection and then the data analysis.

Required data that was collected includes the information that will be used for analysis which

are river bed topography year 2001 and 2012 and the Cidanau river hydraulics.

Evaluation of the intake’s hydraulics was carried out by using HEC RAS (USACE, 2010)

software. The program simulates the flows form of Cidanau water entering the intake. HEC

RAS can be used for calculation of permanent flow water level profile, non permanent flow

profile, sediment transport calculation and water quality calculation. At first, Cidanau River

flow’s profile was simulated, starting with reproduction of the river’s geometry, followed by

reproduction the river hydraulics and data extraction from the simulation results.

Figure. 1. Simulation of Cidanau River with HEC RAS

After computer simulation was completed, sandtrap planning was carried out. Information of

technical drawing of the river and its surrounding, as well as weir design, flushing duct

design, discharge data, sediment load and transport capacity. Sandtrap had been planned and

designed based on Guidemce of Construction and Building (Pedoman Konstruksi dan

Bangunan (Pd T-15-2004-A)). The sandtrap includes the design of sedimentation rate,

sedimentation bed, sandtrap dimension, perencanaan dimensi sandtrap, matching of calculated

dimension and actual dimension; and designed flow rate in the sandtrap.

The Last step of the evaluation is to calculate the intake’s hydraulics, where the discharge and

velocity of water that flows through the intake’s gate in a unit time is to be determined.

Generally, the evaluation of intake’s hydraulics is shown in the following flowchart (Fig. 2)

IV - 182

Figure 2. Hydraulics evaluation flowchart of Cidanau Weir’s intake

3. RESULTS AND DISCUSSION

3.1 Current condition of Cidanau Headwork and the Complimentary Building

Cidanau Weir, located at about 30 km from the city of Cilegon directing to Labuhan city, is

a headwork structure at Cidanau to increase the water level as so water can be flown to water

treatment plant (WTP) and/or Krenceng Dam in Cilegon, which is managed by Division of

Operation PT Krakatau Tirta Industri (PT. KTI).

Figure 3. Cidanau Weir and the complimentary structures.

Cidanau headwork was established on 1976, having total width of 30 meter and height of 5

meter, which is complimented by intake, flushing duct and sandtrap built at the right side of

the weir. The intake is situated at 600 m from the estuary and has maximum discharge load

3.5 m3/s. Water flow through the intake is managed by using gate which is operated from

pump station office. Sandtrap has function as sedimentation pond, located between the inlet

and bypass canal to sump pump. It divided into 2 chambers which only one of them are used

each time.

IV - 183

3.2. HEC RAS and Rating Curve

Hydrological data was analyzed using HEC-RAS application. Data input of the river

geometry and hydraulics are required. Geometry of the river was reproduced for the

condition in year 2001 and 2012 with objective to estimate the sediment addition to the

riverbed during the period. Geometric reproduction was only carried out for 200m length

with the centrizoid is Cidanau Weir so as the reproduction has 100m of upstream part and the

same length for doswnstream part. Fig. 4 shows this reproduction which also includes intake

and sandtrap.

(a) (b)

Figure 4. Geometric reproduction of Cidanau River (a) year 2001, (b) year 2012

As also presented in the first part of this study, river hydraulics is reproduced starting with

inputing river discharge data. Data input was repeated 60 times due to uncertainty of actual

discharge, started with 1 m3/s up to 60 m

3/s. As for river boundary condition reproduce, water

level at downstream of the river was assumed 2 m and at intake downstream was 1.5 m.

Table 1. Calculation result of water level and water flow with HEC RAS

Discharge

(m3/s)

Water Level (m) Water flow (m/s) Water

level

increase

(m) Year 2001 Year 2012 Year 2001 Year 2012

1 3.49 3.50 0.04 0.05 0.01

2 3.53 3.54 0.08 0.09 0.01

4 3.58 3.60 0.13 0.15 0.02

6 3.62 3.64 0.17 0.19 0.02

8 3.66 3.69 0.21 0.24 0.03

10 3.70 3.73 0.25 0.28 0.03

20 3.85 3.90 0.40 0.45 0.05

30 3.98 4.03 0.53 0.58 0.05

40 4.08 4.15 0.63 0.70 0.07

50 4.18 4.26 0.73 0.81 0.08

60 4.29 4.37 0.84 0.92 0.08

IV - 184

Figure 5. Rating curve of Cidanau River by using HEC RAS

Table 1 shows that the increase of water level between 1 to 8 cm had been occurred caused by

topographic changes during 11 years. As maximum observed discharge was 30 m3, according

to Table 1. After period of 11 years, there had been increase of water level up to 5 cm.

3.3. Sandtrap Design Analysis

Analysis was done following the national standard guidance of hydrological and hydraulic

planning for river structures (SNI 03-1724-1989), guidance of general planning for dam (SNI

03-2401-1991), and standards of irrigation (KP 02). Design analysis aims to determine the

eligibility and suitability of the structures to the standard

First step of analysis is to find the value of settling velocity (ws) in the sandtrap, which is

affected by size of the sediment’s granules (D), shape of the granules, fluid temperature and

the existence of other particles within the flow which are observed as sediment concentration

(c). As coarse sand or higher density fraction (sand’s density (ρs) = 2.650 kg/m3) are not to be

transported to WTP network, the analysis the value of D = 0,074 mm was choosen. Water

temperature was assumed at T = 30o C as the site is situated in tropical country. Following

Stokes law, the settling velocity of sediment’s particle is 5.55 x 10-3

m/s.

The sediment is not composed by only one type of particles which will affect the rate of

sedimentation of sand. If the concentration of non-sand particles concentration (c) was

assumed as 0.2 %, actual settling velocity of sand was calculated 4.98 x 10-3

m/s. Using this

value the effective settling basin area was analized. According to operation and maintenance

guide book for Cidanau Headwork, Qdesign of the intake is 3.5 m3/s and thus the effective

area of settling basin is 701.47 m2 . Regarding the criteria of

L

B≥ 8, L was determined 74.91 m

and B is 9.3 m. Comparing this result to real dimension it can be concluded that there is no

misdesign of Cidanau weir’s the sandtrap.

Table 2. Comparison of sandtrap dimension

Calculated Measured

Length 74.91 meter 77 meter

Width 9.3 meter 6.5 meter

Sedimentation process will be effective if the waterflow is not greater than permitted value.

Calculation shows the flow shall not be greater than 0,2071 m/s.

3.45

3.65

3.85

4.05

4.25

4.45

0 10 20 30 40 50 60

Ele

vati

on

(m

)

Discharge (m3/s)

2001

2012

IV - 185

3.4. Hydraulic Evaluation of Intake dan Sandtrap

Hydraulic evaluation of intake dan sandtrap was differed into three stages which are

determination of intake charge, water level and water flow. Intake charge was determined

using data from HEC RAS calculation. This was done for year 2001 and 2012’s river

topography. The following Table 3 shows the calculation results assuming the intake’s gate

was opened 30%.

Table 3. Intake charge calculated with year 2001 data (intake’s gate opened 30%)

River Discharge

(m3/s)

Water

Surface (m) Flow (m/s) αV1

2/2g Qintake (m

3/s)

1 3.49 0.04 0.00009 2.47

4 3.58 0.13 0.00099 2.53

8 3.66 0.21 0.00258 2.59

12 3.73 0.28 0.00460 2.64

16 3.79 0.34 0.00678 2.68

20 3.85 0.40 0.00938 2.72

24 3.90 0.45 0.01187 2.75

25 3.91 0.46 0.01240 2.76

Table 4. Intake charge calculated with year 2012 data (intake’s gate opened 30%)

River

Discharge

(m3/s)

Water

Surface (m) Flow (m/s) αV1

2/2g Qintake (m

3/s)

1 3.50 0.05 0.00015 2.48

4 3.60 0.15 0.00132 2.55

8 3.69 0.24 0.00338 2.61

12 3.76 0.31 0.00563 2.66

16 3.83 0.38 0.00846 2.70

20 3.90 0.45 0.01187 2.75

24 3.95 0.50 0.01465 2.78

25 3.97 0.52 0.01585 2.80

According to data in Table 3 dan Table 4, decrease in Cidanau river capacity did not radically

affect the water discharge to intake. Sedimentation caused increase of discharge between 0.01

– 0.04 m3 or 10 - 40 l after 11 years period.

Water level determination was based of Manning equation, starting with plotting a chart on

the relation between Manning’s AR2/3

and y, followed by finding the curve’s equation for

intake and sandtrap’s cross-sectional width 2.65 m and 6.5 m. Both were input into the

curve’s equation to obtain water level yn.

IV - 186

Table 5. Calculation result of water level and flowrate in intake and sandtrap

Qintake

(m3/s)

Width = 2,65 m Width = 6,5 m

nQ/(s0.5

) h1 (m) A1 (m2)

V1

(m/s) nQ/(s

0.5) h2 (m) A2 (m

2)

V2

(m/s)

1.50 1.48492 0.86204 2.28442 0.65662 7.93725 1.26190 8.20235 0.18287

1.75 1.73241 0.97157 2.57466 0.67970 9.26013 1.38040 8.97261 0.19504

2.00 1.97990 1.07639 2.85244 0.70115 10.58301 1.57663 10.24813 0.19516

2.25 2.22739 1.17651 3.11776 0.72167 11.90588 1.72403 11.20617 0.20078

2.50 2.47487 1.27193 3.37060 0.74171 13.22876 1.86582 12.12782 0.20614

2.55 2.52437 1.29044 3.41968 0.74568 13.49333 1.89351 12.30778 0.20719

(a)

(b)

Fig. 6. Comparison curves of y and AR2/3

(a) width = 2,65 m (b) width = 6,5 m

Table 5 suggests intake’s discharge should not exceed 2.5 m3/s in order to have an effective

settling of sediment as the permitted flowrate in sandtrap is 0.2071 m/s. Minimum discharge

required by the company is 2.0 m3/s and regarding above result, maximum discharge allowed

is 2.5 m3/s, and thus readjustment of intake’s gate opening should be done. Assuming 30% of

intake gate is opened the previous condition will only fulfilled with river discharge of 1-2

m3/s as shown in Table 4. In this case new appropriate opening should be considered. New

intake opening calculation effort is shown in Table 6.

Table 6. Hasil pencarian bukaan pintu intake yang baru

Debit

Sungai

(m3/s)

Water

Surface

(m)

Kecepatan

(m/s) αV1

2/2g

Qintake (m3/s) at opening

0.1 0.25 0.26 0.27

1 3.50 0.05 0.00015 0.83 2.06 2.15 2.23

5 3.62 0.17 0.00169 0.85 2.13 2.22 2.30

10 3.73 0.28 0.00460 0.88 2.20 2.28 2.37

15 3.82 0.37 0.00802 0.90 2.25 2.34 2.43

20 3.90 0.45 0.01187 0.92 2.29 2.38 2.48

25 3.97 0.52 0.01585 0.93 2.33 2.42 2.52

Here, intake gate opening is suggested between 25-26% or equal 40.0 – 41.6 cm.

y = -0.038x2 + 0.566x + 0.106

0.00

0.50

1.00

1.50

2.00

y

AR2/3

y = -0.001x2 + 0.147x + 0.195

0.000

0.700

1.400

2.100

2.800

3.500

y

AR2/3

IV - 187

4. CONCLUSIONS

Hydraulics of Cidanau Headworks intake was evaluated using HEC-RAS based on

hydrological, design and river topographyc information. The result suggests the sedimentation

during 11 years period was not significantly affect discharge to the intake. It was found that

intake discharge approximately had increased 10 - 40 liter/s. However, the opening of intake’s

gate should be adjusted with recommended value is 25% or 26% which are equal to 40 cm

dan 41.6 cm. The method of hydraulics analysis that has been demonstrated in this study can

be an alternative solution for evaluating water infrastructures especially weir, barrage or dam

before physical action is to be carried out.

ACKNOWLEDGEMENT

This study is an outcome of the joint research and activity between Bogor Agricultural University

(IPB) and Krakatau Industrial Water Company (KTI). The authors express their gratitude to IPB and

KTI for the support.

REFERENCES

Chow, Ven Te. 1959. Open Channel Hydraulics. USA: McGraw-Hill Book Company Inc.

Departemen Pekerjaan Umum Direktorat Jenderal Pengairan. 1986. Standar Perencanaan

Irigasi Kriteria Perencanaan Bagian Bangunan Utama KP-02. Jakarta: PU.

Departemen Permukiman dan Prasarana Wilayah. 2004. Perencanaan hidraulik, operasi dan

pemeliharaan bangunan penangkap pasir tipe PUSAIR. Jakarta: PU.

PT. Krakatau Tirta Industri. 2012. Pedoman Operasi dan Pemeliharaan Bendung Cidanau.

POPBC. 1(1). 1-9.

USACE. 2010. HEC-RAS River Analysis System Hydraulic Reference Manual. Washington:

Institute For Water Resources.

IV - 188



– 6TH

, 2014

Study on Water Quality Assessment and Eutrophication

Countermeasures of the Panjiakou-Daheiting Reservoir

HU Zuoliang

Haihe RiverWater Conservancy Commission of Ministry of Water Resources, Tianjin 300170, China

[email protected]

ABSTRACT:

Panjiakou-Daheiting reservoir is a large water supply system for inter-basin water transfer. The

water quality and eutrophication of reservoirs were studed in this paper. The results showed that

water quality of Panjiakou reservoir and Daheiting reservoir were class Ⅲ. Both reservoirs were

in the state of eutrophication and were mild and moderate in flood and non-flood season

respectively. The high concentration of TN was one of the major factors of eutrophication. The

dominant algae species was Pseudanabaena belonging to blue-green algae. The dominant algae

has changed from diatom to blue-green algae in the past 20 years. Microcystin-LR concentration

was very low(<0.02 ppb). In order to control eutrophication state of the reservoirs, water resource

protection area should be delineated, cage culture should be banned in the reservoirs and soil

erosion and non-point pollution should be controled.

Key words: Panjiakou reservior; Daheiting reservoir; Water quality assessment; Eutrophication;

Countermeasures

1. INTRODUCTION

Water quality refers to the chemical (inorganics and organics), physical (such as color,

turbidity, odor, etc.) and biological (bacteria, microbes, plankton, and benthos)

characteristics of water. Water quality is evaluated according to the biotic species or human

needs, and often assessed by the reference of a certain set of standard. The most common

standards used to assess water quality relate to health of ecosystems, safety of human

contact and drinking water. In order to evaluate water quality conditions, China has also

developed a series of water quality parameters and quality standards [1-3]

. Water quality

evaluation is not only to enable people to know the water quality, to make people

understand main pollution factors, but also provides scientific basis support for the

efficient use of water resources.

Eutrophication is the enrichment of an ecosystem with chemical nutrients, typical

IV - 189


compounds contain nitrogen, phosphorus and other nutrient salts accumulated gradually.

Eutrophication can be a natural process in lakes developing gradually as they age through

geological time, and human activities can accelerate the process of it. Eutrophication

usually causes algae and other plankton multiplying rapidly; it leads to aquatic biological

diversity and stability reduction, transparency decline, dissolved oxygen decrease and

water quality degradation [4]

. Eutrophication not only affects the water supply and water

landscape, but also causes "water blooms" which usually releases toxins and odor

substances that threaten human health and damage the ecological balance.

With the rapid socioeconomic development, large amounts of urban sewage and industrial

and agricultural waste water produced, water eutrophication has become a major water

pollution problem all over the world nowadays. More than 75% of the world's closed water

bodies exists eutrophication problems [5]. Panjiakou-Daheiting Reservoir, the major

drinking water source for the city of Tianjin and Tangshan, also face the threat of

eutrophication[6]. The water quality and eutrophication status of Panjiakou-Daheiting

Reservoir were analyzed in this paper based on water monitoring data. The result provides

important reference for the sustainable utilization of water resources and harmonious

development of natural eco-environment and social economy in Tianjin and Tangshan

2. STUDY AREA

Panjiakou-Daheiting Reservoir is located in northern Hebei Province within the Luanhe

River basin, which is one of the several major watersheds under the administration of the

Haihe River Water Conservancy Commission under the Ministry of Water Resources.

Construction of the Panjiakou Reservoir began in 1975 and it started to store water from

1979. Hydroelectric power generation began in 1984. The length of the Panjiakou dam is

1039m and with a maximum height of 107.5 m. The total storage capacity of Panjiakou

Reservoir is 2.93 ×109m

3. The total surface area of the reservoir, if full, would be 70 km

2,

but usually is 40 km2. Construction of Daheiting Reservoir began in 1973 and it started to

store water from 1979. The Daheiting reservoir has a total storage capacity of 0.337

×109m

3 of water. The total surface area of the Daheiting Reservoir is 25 km

2. The

Daheiting Reservoir receives most of its water from the Panjiakou Reservoir, but a few

tributaries, such as the Sa He River, also contribute water. The Luanhe River is the major

source of water for the Panjiakou Reservoir. Other important tributaries contributing flow

include the Liu He River, and the Bao He River. The reservoirs are located in mountain

canyon of mixed lithology that includes carbonate and metamorphic rocks. The upstream

watershed has a mix of land uses including agriculture, forest, and one large urban center.

The reservoirs have a primary use for storage of drinking water and partially supply

Tianjin City with its annual needs by inter-basin water transfer-Yinluan project. Secondary

uses include flood control, agricultural irrigation, aqua culture (fish cages). By the end of

2012, Panjiakou-Daheiting Reservoir has supplied 35.7×109m

3 of water for Tianjin,

Tangshan. The reservoirs have made significant contribution for economic construction,

social stability and sustainable development of the region.

Since the mid-1980s, urban industrial and domestic waste water has discharged into

Luanhe River increasingly with the socioeconomic development year by year according to

IV - 190

the Panjiakou Reservoir upstream pollution monitoring data analysis. The amount of

sewage discharged into the river Luan River Basin in 2003 was trebled than in 1985.

Agriculture might have a significant impact on the water quality of reservoir because of the

large amounts of fertilizers used in the region. Soil erosion in the upstream and around

reservoir is also a serious pollution for the reservoir. Since 1990s, with the increasing of

aquaculture intensity and scale, more and more fish cages have been installed, and large

amount of fish feed increased the load of nitrogen, phosphorus and other nutrients in the

reservoir. The reservoir currently being assessed for its eutrophication status and may be in

a trend of exacerbation [7-8]

. According to a research of benthos community of Luan River

Basin, the density of Oligochaeta (pollution tolerant species) has increased significantly,

and this represent trend of pollution increasing [9-10]

.

3. METHODS

Surface water samples were collected from 20 cm depth monthly from two stations of dam

for one year since January 2013 to December 2013. Surface water temperature, pH,

electrical conductivity (EC), dissolved oxygen (DO) and Chlorophyll-a(Chl-a) were

measured in situ by using YSI (6610) portable. Transparency was measured by Behcet's

plate. Total phosphorus(TP), Total nitrogen(TN), Permanganate index(IMn),

ammonia(NH3-N), Volatile phenol(VP), Arsenic(AS), Chromium(Cr), Cuprum(Cu),

Plumbum(Pb), Zinc(Zn), Cadmium(Cd), Hydrargyrum(Hg), Cyanide(CN), fecal

coliform(FC), Chlorides(Cl) and Fluorides(F) were measured by ‘Water and Wastewater

Monitoring and Analysis Methods[11]

.

The water quality of the reservoir was classified by the standard surface water quality of

China-"Surface Water Quality Standards" [3]

. Water quality is divided into 5 categories in

the standard, and water only above third category is suitable for household consumption

after being properly treated. All the analysis was finished by the water quality laboratory of

Haihe river basin Water Quality Monitoring Center. The evaluation parameters were

consists of water temperature (WT), pH, dissolved oxygen(DO), permanganate index,

ammonia, volatile phenol, arsenic, chromium, cuprum, Plumbum, zinc, cadmium, mercury,

cyanide, fecal coliform, chloride and fluoride (Table 1). Total phosphorus and Total

nitrogen were usually not referred in the assessment because of high concentration.

Table1 Water quality evaluation standard

Unit: mg/L

Water quality category

parameter Ⅰ Ⅱ Ⅲ Ⅳ Ⅴ

WT(℃)

Environmental temperature change caused by human

temperature (℃) should be limited to: weekly average

maximum temperature rise≤1, the maximum weekly average

temperature drop≤2

pH dimensionle 6-9

IV - 191

ss

DO ≥ 7.5 6 5 3 2

IMn ≤ 2 4 6 10 15

NH3-N ≤ 0.05 0.5 1.0 1.5 2

VP ≤ 0.002 0.002 0.005 0.01 0.1

As ≤ 0.05 0.05 0.05 0.1 0.1

Pb ≤ 0.00005 0.00005 0.0001 0.0001 0.0001

Cd ≤ 0.001 0.0005 0.0005 0.0005 0.01

Cu ≤ 0.01 1.0 1.0 1.0 1.0

Zn ≤ 0.01 1.0 1.0 2.0 2.0

CN ≤ 0.005 0.05 0.2 0.2 0.2

Cr(VI) ≤ 0.01 0.05 0.05 0.05 0.1

Pb ≤ 0.01 0.01 0.05 0.05 0.1

FC ≤ 200 2000 10000 20000 40000

F ≤ 1.0 1.0 1.0 1.5 1.5

Cl ≤ 250

Eutrophication was evaluated basing on the standard of "Technical Regulations of Surface

Water Quality Evaluation"[1]

. Parameters used for the evaluation include chlorophyll-a,

total phosphorus, total nitrogen, permanganate index and transparency. Method for

evaluating eutrophication status of lake and reservoir is shown in Table 2. Eutrophication

status index (EI) was calculated by interpolation method. Calculation formula

was NEEIN

n

n /1

, EI: Eutrophication score, En: evaluated scores of the parameters

assigned scores; N: evaluate the number of parameters.

Table 2 Lakes, reservoirs nutritional status evaluation standard and classification method

Unit: mg/ L

Parameter

item score

（En）

TP TN chloroph

ylla

Permang

anate

index

Transpar

ency

Oligotrophic

0≤EI≤20

10 0.001 0.020 0.0005 0.15 10

20 0.004 0.050 0.0010 0.40 5.0

Mesotrophy

20<EI≤50

30 0.010 0.10 0.0020 1.0 3.0

40 0.025 0.30 0.0040 2.0 1.5

IV - 192

50 0.050 0.50 0.010 4.0 1.0

eutro

phicat

ion

Mild

eutrophic

ation

50<EI≤60

60 0.10 1.0 0.026 8.0 0.5

Moderate

eutrophic

ation

60<EI≤80

70 0.20 2.0 0.064 10 0.4

80 0.60 6.0 0.16 25 0.3

Severe

eutrophic

ation

80<EI≤10

0

90 0.90 9.0 0.40 40 0.2

100 1.3 16.0 1.0 60 0.12

4. RESULTS

4.1 Water Quality Assessment

Flood season is from June to September in Haihe River basin, and other months are

non-flood season. Water quality data of flood season and non-flood season of 2013 were

analyzed (shown in Table 3).

Table 3 Water quality data of Panjiakou-Daheiting Reservoir

Unit：mg/L

Panjiakou Reservoir Daheiting Reservoir

flood season non-flood season flood season non-flood season

WT(℃) 21.45 6.08 21.65 8.36

pH 8.3 7.94 8.03 7.99

DO 7.3 8.8 9.1 11.2

IMn 4.63 3.68 5.2 3.9

NH3-N 3.1 -- 2.15 --

VP 0.4 0.42 0.44 0.4

As <DL <DL <DL <DL

Pb 0.0006 0.0004 0.0006 0.0005

Cd <DL <DL <DL <DL

Cu 0.0168 0.0093 0.0168 0.013

Zn <DL <DL <DL <DL

CN <DL <DL <DL <DL

Cr(VI) 0.55 0.54 0.47 0.39

Pb <DL <DL <DL <DL

FC <DL <DL <DL <DL

F 172 20 -- --

IV - 193

Cl 0.55 0.54 0.47 0.39

Temperature varied within the range of 0-25.7℃ in the two reservoirs. The maximum

occurred in July and August, which contribute to the growth of algae and other aquatic

ecosystem components. The mean water temperature of flood season was higher than that

in non-flood season. The pH value varied within the range of 6.2-9.4 and it showed the

value in flood season was higher than that in non-flood season. Because algae consumes

large amount of CO2 in water in the summer, which leads to a rise of pH value, The pH

and the chlorophyll-a showed a significant positive linear correlation, so pH values was

slightly higher in algae growth season [12]

. Dissolved oxygen value in non-flood season was

higher than that in flood season in the two Reservoirs. Dissolved oxygen value was related

with water disturbance process, algae oxygen releasing, organic degradation, and aquatic

organisms respiration etc. Low dissolved oxygen in flood season may be due to cage

aquaculture, the fish feed of which consumes too much oxygen. Water quality of Panjiakou

Reservoir was class Ⅱ while Daheiting Reservoir was class Ⅰ when evaluated by

dissolved oxygen.

Permanganate index value in flood season was higher than non-flood season in the two

reservoirs. The growth of algae in flood season increased the biomass in water, which may

cause a higher Permanganate index value. Both of two Reservoirs water quality evaluation

was class III when evaluated by Permanganate index. Transparency values varied within

the range of 1.1-8.5 m. The highest value of transparency appeared in June when the

dominant algal species changed from diatoms and dinoflagellates to blue-green algae and

green algae.

Ammonia concentration varied within the range of 0.20-0.79 mg/L and the water quality

measured up to class Ⅱ. Volatile phenols concentration was under detected level(<DL)

and the water quality measured up to class Ⅰ. Arsenic concentration varied within the

range of 0.0001-0.001 mg/Lin the two reservoirs and Water quality measured up to class

Ⅲ. Hydrargyrum, Plumbum, Plumbum, Cuprum, Zinc and Cyanide were not detected in

the two reservoirs (<DL), and Water quality measured up to class Ⅰ . Hexavalent

Chromium concentration varied within the range of 0-0.023 mg/L and water quality

measured up to class Ⅰ. Fecal coliforms concentration varied within the range of 0-540

cfu/L and Water quality measured up to class Ⅰ. Fluoride concentration varied within the

range of 0.26-0.7 mg/L and water quality measured up to class Ⅰ. Chloride concentration

varied within the range of 0.26-0.59 mg/L and did not exceed the standard limit (below

250 mg/L).

The general water quality of Panjiakou Reservoir and Daheiting Reservoir were class Ⅲ.

There were seven months (including flood season) with water quality class Ⅲ, and two

months with water quality class Ⅱ in Panjiakou Reservoir and Daheiting Reservoir in

2013.

4.2 Eutrophication Evaluation

The water trophic state index (EI) of flood and non-flood season of Panjiakou-Daheiting

reservoir in 2013 was shown in Table 4. Trophic state index (EI) of flood and non-flood

IV - 194

season of Panjiakou reservoir was 52.11 and 62.09 respectively. And it was showed that

eutrophication state was mild and moderate in flood and non-flood season in Panjiakou

reservoir. Trophic state index (EI) of flood and non-flood season of Daheiting reservoir

was 54.85 and 64.71 respectively. And it was showed that eutrophication state was also

mild and moderate in flood and non-flood season in Daheiting reservoir.

Table 4 Panjiakou - Daheiting water quality eutrophication value

IMn TP TN Transpa

rency

chlorop

hylla Means

Nutritio

nal

status(E

n)

Panjiak

ou

Reserv

oir

Floo

d

seaso

n

51.56 46.6 76.55 29.63 56.19 52.11

Mild

eutrophi

cation

Non-

flood

seaso

n

48.375 59.75 78.16 -- -- 62.09

Moderat

e

eutrophi

cation

Daheiti

ng

Reserv

oir

Floo

d

seaso

n

53 52.5 78.75 35.67 54.33 54.85

Mild

eutrophi

cation

Non-

flood

seaso

n

49.5 66.65 78.00 -- -- 64.71

Moderat

e

eutrophi

cation

Both of two reservoirs were in the state of eutrophication. The eutrophication state was

very serious and we should pay attention to it. The eutrophication state in flood season was

slightly better than in non flood season. The high concentration of total phosphorus, total

nitrogen and permanganate index which resulted in higher scores of trophic state index

(EI). In particular, the concentration of total nitrogen was higher than 4 mg/L and it greatly

increased the trophic state index (EI).

The trophic state index (EI) of the reservoir changed from oligotrophic in the early period

after was built to light or moderate eutropher now [13]

. Total nitrogen concentration has

exceeded the severe eutrophication state, and total phosphorus concentration was between

mild eutrophication to moderate eutrophication state. Comparison of the normalized

phosphorus loading and chlorophyll-a response of this system to other reservoirs

throughout the world indicate a level of eutrophication that will require up to an

approximate 5-10-fold decrease in annual phosphorus load to bring the system to a more

acceptable level of algal productivity [14].

4.3Algae Analysis

IV - 195

Through the algae investigation in Panjiakou-Daheiting reservoir in recent years, there

were 62 genera belonging to 34 families in 8 phyla of algae. In summer and autumn, the

algal density value was high and dominate species was blue-green algae and green algae [15]

. Panjiakou-Daheiting reservoir was mesotrophy to moderate eutrophication by

evaluation of biological indicators of lake algae and the community structure was

"cyanobacteria, green algae, diatoms, Cosmarium" type[16]

. Algae cell density reached to

3×107 cells/L in the peak of the algae growth. Pseudanabaena was dominant genus in

summer and autumn.

Dominate algae species for the past 20 years in the reservoirs were shown in Table 5.

Cyclotella was dominant specie in May and September in late 1980s and the community

structure was diatom type [17]. Ceratium and Nitzschia were dominant specie in

September of 2001 and Dinobryon, Asterionella and Navicula in May of 2002. Synedra,

Cyclotella and Pseudanabaena were dominate specie in May and were Pseudanabaena,

Scenedesmus and Chlamydomonas in September of 2009. The algae community structure

has changed from diatoms type to blue-green algae and green algae type. The algae density

increased by nearly 20 times.

Table5 Dominant genera change in recent years

year Dominant species in May Dominant species in

september

1987-1989 Cyclotella Cyclotella

2001-2002 Dinobryon、Asterionella、Navicula Nitzschia、Ceratium

2009 Synedra、Cyclotella、

Pseudanabaena

Pseudanabaena、Scenedesmus

Microcystin-LR was detected in the water of Panjiakou Daheiting reservoirs in 2010[19]

.

But the concentration was very low (<0.02 ppb) and did not exceed allowable limits (1 ppb)

of "standards for drinking water quality".

5.COUNTERMEASURES

5.1 Delineation of Water Source Protection Area

Ministry of Water Resources and Haihe River Water Conservancy Commission have

designated Panjiakou-Daheiting as water source protection areas. Water resource was used

by the people of Tianjin, but the Reservoirs are located in Hebei province. Although water

users hoped that the water resources should be effectively protected, the local government

and people only cared about the economic development and thought little about the water

resource protection. The reservoirs have not been effectively protected in its surrounding

areas and upstream.

Due to the exacerbated industrial and urban pollution in the upstream, amount of

Ammonia-N and chemical oxygen demand (COD) increased year by year in the rivers. The

discharge amount of COD and ammonia-N of the upstream of main Luanhe River were

140,000 t and 4 000 t respectively in 2005. The concentration of nitrogen, phosphorus of

IV - 196

Reservoirs continued to rise, resulting in higher nutrition loads of the reservoirs [20]

.

Comparing with the investigation of 1980s, the concentration of total phosphorus and total

nitrogen has increased by 1.41 times and 3.63 times respectively [15]. Eutrophication of

Panjiakou-Daheiting Reservoir has becoming more aggravated. Eutrophication status of

the Reservoir decreased from oligotrophic to the current mild eutrophication and water

category dropped significantly [21]

.

It is suggested that the local government of Hebei Province should issue the policy for

water protection of Luan River and delineate drinking water source protection areas in

Panjiakou-Daheiting Reservoir as soon as possible, so as to against harmful water activities

and behaviors in the region. It should also accelerate the progress of construction of

centralized sewage treatment plant of upstream and around the reservoirs.

5.2 Cage Culture Control

Cage culture water pollution is mainly from the delivery of feed, fertilizers,

pharmaceuticals and fish excrement, sediment release and other aspects [7, 22-24]. Studies

show that the impact of cage culture on the water environment is great and becomes one of

the main reasons of eutrophication [25-26].

Cage culture began in the late 1980s. Due to huge economic benefits, the reservoir area of

fish cage culture expanded year by year. According to recent statistics, there are more than

50,000 cages in the reservoirs now [20-21]. Cage culture area accounts for more than

17.0 ‰ surface area of Panjiakou Reservoir. In Daheiting reservoir, cage culture leads to

nitrogen and phosphorus load, about 30% of the total pollution load.

Cage culture should be banned in the two reservoirs, and then the pollution sources can be

reduced. It needs strong measures from national and local governments and establishes

compensation mechanism.

5.3 Soil Erosion and Non-point Pollution Control

Soil erosion of the upstream of the Panjiakou reservoir was very serious. According to the

survey, the existing soil erosion area of Chengde City in the Panjiakou reservoir upstream

was 20,000 km2 [22]. Soil erosion caused 90.3% of the total nitrogen loads of Panjiakou

reservoir non-point pollution and 95.7% of total phosphorus. So the soil erosion is one of

the main causes of non-point pollution to the reservoir [21, 23].

Small watershed management project should be launched to control plane pollution source.

Fertilizer use in farmland should be reduced gradually. And sloping fields up than 25

degrees should be returned to forest and grassland [6].

ACKNOWLEDGEMENT

The Research was supported by international science & technology cooperation program

of China (Grant No. 2013DFA71340).

REFERENCES

[1]Ministry of Water Resources of China. (2007), Technical Specification for Surface

Water Quality Assessment, China Water Power Press, Beijing, China.

IV - 197

[2]The ministry of health of the People's Republic of China and Standardization

Administration of China. (2006), Standards for drinking water quality, China

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[3] Ministry of Environmental Protection and General Adminstration of Quality

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[4] Freedman, B. (2002), Environmental Ecology, Academic Press, San diego.

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Sedimentation Effect on Daily Inflow Calculation in Run of River Dam Type PLTA Bakaru

Wahyu Jatmika Hadi, ST.

Assistant Engineer System Owner PT PLN (Persero) Sektor Pembangkitan Bakaru [email protected]

ABSTRACT: Based on measurement held by LPPM Unhas in 2010, sedimentation rate in PLTA Bakaru’s dam has reached 700,000 m3/year from its basic design calculation as 133,000 m3/year. It straightly affects daily dam’s volume change. The annually measurement from 1991 – 2010 results a wide range of fluctuation in dam volume at 615,50 m above sea level from 6,919,900 m3 in 1991 to 564,579 m3 in 2004. On the other side, sedimentation reductions emanate from mechanical dredging and flushing out or sluicing when flood come. Since PLTA Bakaru dam type is run of river which its daily operation highly depends on inflow, it fazes directly to the choosing of the right volume table data for operational dam gate guidance which is clarified by Gate Operating Number (GON). Unsuitable dam volume table will heighten the risk when significant inflow alteration in relatively short time happened. The best alternative parameter which can be used to monitor inflow is water level measured in telemetering station Silei located 6 km away before dam. Based on data recorded, inflow can be predicted more than 45 m3/sec when it reaches more than 100 cm. But it has to be recalculated since the sedimentation which attains river near Silei will heighten the measured water level. Direct inflow determination using non contact sensor for water flow rate and reconstructing the bridge across the river for better water quantity calculation in this location as CSR can be best alternative solution. Keywords: sedimentation, volume, inflow, measurement, Bakaru. 1. INTRODUCTION PLTA Bakaru began its commercial operation in 13 May 1991 with maximum output power 126 MW. This run of river type dam was designed to receive 6,919,900 m3 of water with 133,000 m3/years sedimentation rate. During the last 10 years, the head area of Mamasa river i.e. Kabupaten Mamasa started to be a new county. Transformation from forest into living place and roads brings some materials away along the river. Since there is no check dam or other water catchment from Mamasa to Bakaru, the materials stop in Bakaru’s dam and switch into sediment. The more alteration from forest into land, the more sediment caught in the dam. The last measurement held by LPPM Unhas in 2010 results the sedimentation rate is rapidly increased to be 700,000 m3/years or more than 526% from its basic design.

IV - 200

Since calculation of inflow is based on dam volume, PLTA Bakaru builds correlation table between dam capacity and dam water elevation regularly to get the exact volume. By the change of sediment quantity, the volume table has been revised several times. 2. FLUCTUATION OF DAM VOLUME A change of dam volume is affected by two factors, i.e. abating dam volume by sediment arriving into dam and adding it by mechanical dredging and flushing out or sluicing when flood come 2.1. Sedimentation Determining quantity of sediment is carried out by measuring dam base profile lying across the dam. The water depth is counted every 10 meters in some location across the main stream according to pond’s peg (GN) lighted in dam side. The result of measurement is presented in Table 1.

Table 1. Measurement of Sediment

No Measurement Date

Dam Volume

at 615.50 m

Sediment Volume

at 615.50

Sediment Volume above 615.50

Total Sediment Volume

1. NEWJEC inundating 30 Sep 1990 6,919,900 2. PLN Sektor Bakaru Feb 1994 4,469,697 2,450,203 3. PLN Pusat Oct 1995 3,250,000 3,669,900 4. PLN Sektor Bakaru Sep 1996 2,310,498 4,609,402 5. PSL Unhas Oct 1997 2,165,506 4,754,394 6. PSL Unhas Apr 1999 902,265 6,017,635 7. PLN Sektor Bakaru Mar 2000 1,335,563 5,584,300 8. PSL Unhas Nov 2000 1,245,210 5,674,690 9. LPPM Unhas Apr 2001 923,249 5,996,651

10. PLN Sektor Bakaru Dec 2001 846,908 6,072,992 11. PLN Sektor Bakaru Dec 2002 983,469 5,936,431 965,424 6,901,855 12. LPPM Unhas May 2004 564,579 6,355,321 1,741,070 8,096,391 13. PLN Sektor Bakaru Jun 2005 588,500 6,331,400 1,926,700 8,528,100 14. LPPM Unhas Jun 2010 1,355,604 5,564,296 1,363,600 6,927,896

2.2. Mechanical dredging and flushing Continuous program from PLN to increase dam volume is mechanical dredging by excavating sediment. The main target is redesign the main river stream so the sediment won’t be achieved to intake. The sediment dissolved in water entering turbine causes turbine and its auxiliary abrasion and cooling pipes clogged up. Quantity of sediment successfully fetched by mechanical dredging is shown in Table 2.

Table 2. Sediment Fetched by Mechanical Dredging

No. Company Name Dredging Date Sediment Volume (m3)

1. PT. Brantas Abipraya 15 Nov 2005 – 22 Apr 2006 80,000 2. PT. Buminata Aji Perkasa 29 Dec 2006 – 5 Sep 2007 696,220 3. PT. Aneka Jasa Sorowako 28 Dec 2007 – 22 Nov 2008 700,000

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Table 2. Sediment Fetched by Mechanical Dredging (continued)

No. Company Name Dredging Date Sediment Volume (m3)

4. PT. Aneka Jasa Sorowako 31 Dec 2008 – 24 Apr 2010 1,400,000 5. PT. Delima Mas Gasindo 29 Dec 2011 – 27 Dec 2012 725,000

When the flood comes or inflow reaches more than 300 m3/sec, operator controls the gate opening to optimize the stream scrapes off sediment settled as much as possible. The longer duration and higher inflow, the more sediment swept away. As shown in Fig. 1 below, the biggest number of sediment vanished by flushing is 1,269,640 m3 done in two times during 2007.

Figure 1. Sediment disposed estimation by flushing 3. INFLOW CALCULATION Dam inflow calculation based on its volume is shown in Eq. 1 below.

𝑉𝑉𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑛𝑛𝑜𝑜𝑛𝑛 = 𝑉𝑉𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑏𝑏𝑜𝑜𝑏𝑏𝑜𝑜𝑏𝑏𝑜𝑜 + (𝐼𝐼𝑛𝑛𝑏𝑏𝑜𝑜𝑜𝑜𝑛𝑛 − 𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷ℎ𝑎𝑎𝑏𝑏𝑎𝑎𝑜𝑜 − 𝑂𝑂𝑜𝑜𝑂𝑂𝑏𝑏𝑜𝑜𝑜𝑜𝑛𝑛) × 1 ℎ (1)

According to this formula, inflow calculation is straightly influenced by dam volume estimation while discharge can be directly read by digital instrument and outflow can be measured separately using GON table. PLN Sektor Bakaru has released six different table contains correlation between dam water elevation and its equivalent volume. The variation of those tables can be seen in Fig.2 below. Operator decided the right table by selecting nearest dam volume at the last measurement and observing how the volume table impacts to inflow calculation. The selected table used by now is 2006 table.

893,500.00

444,562.00 543,429.00

162,000.00

1,269,640.00

863,284.41

205,970.40 102,045.65

266,984.81

-

200,000.00

400,000.00

600,000.00

800,000.00

1,000,000.00

1,200,000.00

1,400,000.00

2000 2001 2002 2005 2007 2008 2009 2012 2013

Sedi

men

t Vol

ume

(m3)

Sediment Disposed by Flushing

IV - 202

Figure 2. The variation of dam volume tables The effect of choosing different table in a single time can be shown in Fig.3 and 4. For example, the chosen data record in 30 December 2013 all day long is used and the dam volume estimation is simulated using 2006 and 2010 table. It is clearly shown that inflow calculation result is dissimilar.

Figure 3. Dam volume calculation using 2006 and 2010 table

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000

615.

60

615.

50

615.

40

615.

30

615.

20

615.

10

615.

00

614.

90

614.

80

614.

70

614.

60

614.

50

614.

40

614.

30

614.

20

614.

10

614.

00

613.

90

613.

80

613.

70

613.

60

613.

50

613.

40

613.

30

613.

20

613.

10

613.

00

612.

90

612.

80

612.

70

612.

60

612.

50

612.

40

612.

30

612.

20

612.

10

612.

00

Dam

Vol

ume

(m3)

Elevation (m)

Dam Volume Table

2000 2002 2005 2006 2009 2010

614.50

615.00

615.50

616.00

616.50

617.00

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Dam

Ele

vatio

n (m

)

Dam

Vol

ume

(m3)

Hour

Dam Volume Calculation Comparison (30 Dec 2013)

2006 2010 Elevation (m)

IV - 203

Figure 4. Different inflow calculation result Although the fluctuation trend is similar the number of inflow is different. The 2010 table gives higher inflow fluctuation than 2006 table. The consequence to daily dam operation can be seen in Fig. 5 shown discharge correlated to inflow prediction. The maximum output power uses approximately 42 m3/s turbine discharge.

Figure 5. Inflow versus turbine discharge

The decision of increasing or decreasing output power is based on inflow calculation. The different decision in the first five hour can be happened as illustrated below. Using 2006

614.5

614.7

614.9

615.1

615.3

615.5

30.00

35.00

40.00

45.00

50.00

55.00

60.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Elev

atio

n (m

)

Inflo

w (m

3/s)

Hour

Inflow Calculation Comparison (30 Dec 2013)

2006 2010 Elevation (m)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Disc

harg

e (m

3/s)

Inflo

w C

alcu

late

d (m

3/s)

Hour

Inflow vs Discharge (30 Dec 2013)

2006 2010 Discharge

IV - 204

table, operators evaluate the inflow raise is quietly small so they decide to decrease output power and maintain it while rising dam elevation for morning peak load preparation. While using 2010 table, operators probably retain the load at maximum until morning since inflow is monitored rising more than 45 m3/s. It means power plant take the chance of producing full power output all day long.

4. DIRECT INFLOW MEASUREMENT FOR ALTERNATIVE Perceiving distinction of inflow results by different volume table, the alternative choice is direct inflow measurement. Since the precise direct measurement needs supporting infrastructure such as tunnel with exact dimension, stream velocity measurement, and water level gauge, it means a sizing station near the tunnel in dam upstream is required. Telemetry station in Silei shown in Fig. 6 is selected for this purpose. The advantages are:

a. It is located around 6 km from dam and no more tributary river between the station and dam.

b. It is a water level and rainfall gauge station. c. It has a hanging bridge near the water level gauging location which can be modeled

as tunnel as shown in Fig.7. The tunnel modeling means foundation reinforcement in both sides of bridge which can be considered as CSR program.

Figure 6. Hanging bridge and water level gauging in Silei

Figure 7. Hanging bridge modeled as tunnel with exact dimension

width

IV - 205

The direct inflow measurement needs a non contact current meter addition and modeled hanging bridge to fulfill the debit equation Eq. 2 where Q is debit, w is tunnel’s width, h is water level, and v is stream velocity.

𝑄𝑄 = 𝑛𝑛 × ℎ × 𝑣𝑣 (2) Since Silei is remote station powered by solar cell, maintain power usage is a must. To make the data sending more efficient, microcontroller collects all data and store it into its internal memory every 5 minutes. After an hour, radio transmits the gathered data to master station in Dam Control Center (DCC). By this scenario, the biggest power needed for transmitting data via radio is done hourly. The detail scheme is shown in Fig. 8.

Figure 8. Collecting and sending data from Silei to DCC 5. CONCLUSION Considering the fluctuation of dam volume affected by sediment arriving, mechanical dredging, and flushing influences the decision making of operational planning by inflow determined, direct inflow measuring combines bridge foundation reinforcing as CSR program will be the best solution. ACKNOWLEDGEMENT The author is thankful to Suprianto, Bambang Dwi Purnomo Putro, Afip Nurul Hudah from Sektor Bakaru for sharing and providing necessary facilities for preparation of this paper. REFERENCES (12PT BOLD AND ALL CAPS) LPPM Unhas. (2010): Laporan Pengukuran Pendangkalan/Sedimentasi dan Kualitas Air

Waduk PLTA Bakaru, LPPM Unhas, Makassar, Indonesia. LPPM Unhas. (2010): Analisa Hubungan Elevasi Air dengan Volume Waduk, pp. 1-12,

LPPM Unhas, Makassar, Indonesia. PLTA Bakaru. (2013): Laporan Pengoperasian Pusat Pengendali Bendungan Bulan

Desember 2013, PLTA Bakaru, Bakaru, Indonesia.

PLC INFLOW FORMULA

FLOATING TYPE WATER LEVEL

SENSOR

ULTRASONIC WATER FLOW

SENSOR

TIME WATER LEVEL WATER FLOW INFLOW

TIMER 5 MINUTES

REAL TIME WATCH

SEND EVERY 1 HOUR

RAINFALL

IV - 206



– 6TH

, 2014

Peer Study between Sediment Distribution Pattern in Reservoir Using

Empirical Method and Estimation of Reservoir Real Life Time Empirical Method and Estimation of Reservoir Real Life Time

Lily Montarcih Limantara, Aniek Masrevaniah, and Mohammad Bisri Department of Water Resources, Faculty of Engineering, University of Brawijaya, Malang, East Java of Indonesia

[email protected]; [email protected]; [email protected]

ABSTRACT Generally, the assumption on reservoir design is that the form of sedimentation is relative plain

and fulfilling the reservoir bed under the certain elevation. However, the real sedimentation in

reservoir is not like that. Sediment will distribute on the whole of reservoir bed and part of them is

on the reservoir upstream of effective storage. This paper intended to implement the peer study

between sediment distribution pattern and estimation of real life time of reservoir. The study was

conducted in Karangkates Reservoir and the analysis used empirical method. Result showed that

sediment measurement in Karangkates Reservoir indicated thatimennt 70% of sediment total

loaded in the upstream of reservoir such as in effective storage. Sedimentation in the upstream of

reservoir will give advantage by increasing reservoir life time but there is the storage capacity

decreasing of sediment volume. In addition, the process of sediment consolidation is paralel with

the duration of sedimentation. Therefore, sediment will reduce and it will increase the resrvoir life

time.

Keywords: sediment distribution, life time, reservoir

INTRODUCTION

The main problem on development of a dam is the more sediment that is occurred in

reservoir (Bisri, 2011a and 2011b). This case is indicated by the frequent appearance of pro

and contra in building dam which is related with the quantity of sediment that is settled in

reservoir. The quantity of sediment will determined the economic value of reservoir

development (Bisri, 2011b). Generally, the used assumption on design of a reservoir is that

design sediment will directly fills the dead storage of reservoir. However, the sediment

deposit that is happened is not like that (Priyantoro and Masrevaniah, 2012).

Process of sediment deposit in reservoir is generally competed by the process of

erosion (Andawayanti, 2010) in the watershed and the river itself. Then, the erosion

material is transported into the river together with the run-off. For the next, sediment in

river upstream will be transported to the downstream by river flow and by the end it is

deposited in reservoir bed. This process is continuously happened and it will be developed

by the sediment distribution pattern (Andawayanti, 2010) due to the characteristic of

sediment material and reservoir that will more influence the deposition process.

However, the sediment formerly settles in reservoir upstream and part of it will

gradually flow towards the reservoir downstream or on the dead storage of reservoir. This

condition is indicated by Karangkates reservoir on the measuring of sediment on 1982.

After 10 years of operation, the reservoir bed in front of intake was still far under the

IV - 207




intake such as on the elevation of +210. However, on the assumption of basic design, the

reservoir has reached the elevation of +230. Result of the measuring indicated that 70% of

sediment deposited in reservoir upstream. This study intended to apply the empirical

method in reservoir and to compare the results with the result of sediment measuring

directly in Karangkates Reservoir.

Hasil pengukuran menunjukkan bahwa 70% jumlah sedimen mengendap di hulu

waduk. Kajian ini bertujuan untuk menerapkan metode empiris sedimen di waduk dan

membandingkan hasil tsb dengan hasil pengukuran sedimen secara langsung di waduk

Karangkates.

MATERIALS AND METHODS

This study is conducted in Karangkates Reservoir. Location of study and reservoir

was as in Figure 1 and 2. Technical data of Karangkates Reservoir are as follow: number

area of watershed is 2,050 km2, Flood Water Level (FWL) is +275.5 m, Normal Water

Level (NWL) is +272.5 m, Low Water Level (LWL) is +246.0 m, deposit area number on

NWL is 15.0 km2, capacity of bruto storage is 343x10

6 m

3, and capacity of effective

storage is 253 x 106 m

3..

Figure 1 Lokasi Waduk Karangkates

IV - 208

Figure 2 Karangkates Reservoir

Method of Moody’s Modification – Area Reduction (Brabben, 1979; Daril, 1976;

Robert and Ernest, 1982)

This method was developed by Borland and Miller that consisted of the area

reduction and as the mathematical approch which was based on the observation of

sediment distribution on some reservoirs in USA. Based on the observation that has been

carried out, reservoir was classified into 4 (four) types as described in Table 1. The base of

classification was the relation between depth and capacity of reservoir storage.

Table 1 Standard classification of reservoir type

Depth Type of reservoir Standard classificaiont

1.0 - 1.5 George IV

1.5 – 2.5 Bill III

2.5 – 3.5 Flood – plain – foot - hill II

3.5 -4.5 Lake 1

The sediment distribution has a trend to follow the four types of reservoir as above.

The general steps of using the area reduction method for estimating the sediment

distribution is as follow:

Classification of reservoir is determined into one of the available standard type.

Area number is determined by trial and error until it is obtained the volume of

analysis result (Vs’) which is the same with observation result (Vs).

Based on the four types of reservoir standard as above, it is built the design curve of

sediment area number which is as the relation between relative sediment area number and

relative storage depth. Moody (1962) has developed the method by missing the trial and

error for making effort to obtain the new storage elevation with the base equation as follow

(Daril, 1976):

yo h

S = ʃ A dy + ʃ k.ap dy ………………………………………… (1)

0 yo

Note:

S = total quantity of sediment in reservoir

IV - 209

0 = the initial bed elevation of reservoir

yo = the new reservoir bed elevation after sedimentation

A = area number of reservoir on the new bed elevation

H = elevation of normal water level

K = constant of relative and real area number

ap = relative area number

dy = addition of depth

By integrating the base equation as aboe, it is obtained as follow (Daril, 1976):

(1 - vo)/ao = (S – vo)/(H . A0) ………………………………….. (2)

Note:

vo = relative volume of reservoir on the new reservoir base elevation

ao = relative area number of reservoir on the new reservoir bed elevation

Ao = initial area number of reservoir on the new reservoir bed elevation

H = total of reservoir depth

RESULTS AND DISCUSSION Empirical result of Area Reduction - Moody’s Modification

The classification of reservoir standard type is carried out by plotting the depth

reservoir (feet) as the ordinate and the storage capacity (acre-feet) as the absis in

logarithmis paper. Based on the curve which the breaking line on the elevation of +225.00

will be obtained 2 types of line slope such as 5.03 and 4.10. Sediment deposit in reservoir

indicated that 70% of sediment was deposited on the area over the elevation of +225.00.

Therefore, the reservoir was classified as the standard type of I.

Analysis of the new reservoir bed elevation was presented as in Table 2. Then, by

plotting the analysis result on the semi logarithmis paper with P as the absis and h’(p) as

the ordinate, it was obtained the meeting point with the curve of type I, and it was obtained

the absis value (relative depth): Po = 0.205. Therefore:

Depth of the new reservoir bed = 86.5 x 0.205 = 17.733 m

Elevation of new reservoir bed = +186.00 + 17.733 m = 203.73 ~ 204

Table 2 Analysis on elevation of the new reservoir bed

Elevation

(m)

Relative

Depth (%)

Reservoir

Area

A (pH)

(m2)

Reservoir

Storage

V (pH)

(m3)

S – V (pH)

H. A (pH)

m3

h’(p)

186 0 0 0 28,190,000 0 -

190 4.624 8,200 10,000 28,180,000 709,300 39.7293

195 10.405 11,220 60,000 28,130,000 970,530 28.9840

200 16.185 35,243 180,000 28,010,000 3,048,519 9.1881

205 21.965 103,000 500,000 27,740,000 8,872,305 3.1135

210 27.746 229,000 1,285,000 26,905,000 19,771,391 1.3585

215 33.526 800,000 4.500,000 23,690,000 69,200,000 0.3423

220 39.306 1,180,000 9.600,000 18,590,000 102,070,000 0.1821

225 45.087 1,700,000 18,500,000 9,690,000 147,050,000 0.0669

IV - 210

Table 3 presented the analysis result of area number and new reservoir due to the method

of Area Reduction Moody’s Modification

Table 3 Analysis result of sediment distribution due to the Area Reduction Moody’s Modification

Elevation

(m)

Area number of

old reservoir

(m2)

Old storage

reservoir

m3

Area number of

new reservoir

(m2)

New storage

reservoir

(m3)

186.0 0 0 0 0

190.0 6,200 10,000 0 0

195.0 11,220 60,000 0 0

200.0 35,243 180,000 0 0

204.0 90,000 399,000 0 0

205.0 103,000 500,000 16,630 13,600

210.0 229,000 1,285,000 89,914 235,649

215.0 800,000 4,500,000 609,448 2,625,306

220.0 1,180,000 9,600,000 391,198 6,626,048

225.0 1,700,000 18,500,000 1,390,647 14,132,683

230.0 2,300,000 28,500,000 1,928,486 22,432,944

235.0 3,250,000 42,300,000 2,816,611 34,223,520

240.0 4,400,000 61,0000,000 3,907,309 49,611,541

245.0 5,500,000 85,000,000 4,953,485 72,017,099

250.0 6,700,000 114,000,000 6,109,006 98,177,190

252.5 7,200,000 150,000,000 6,591,918 112,682,321

255.0 7,800,000 159,000,000 7,179,511 131,150,664

257.5 8,600,000 168,000,000 7,973,057 149,150,664

260.0 9,400,000 198,000,000 8,774,345 176,033,016

262.5 10,200,000 221,000,000 9,586,035 197,488,305

265.0 11,400,000 247,000,000 10,812,506 222,990,322

267.5 12,500,000 275,000,000 11,962,186 248,587,203

270.0 13,700,000 308,000,000 13,256,867 280,363,916

272.5 15,000.000 343,000,000 15,000,000 314,810,000

The base of comparing on applying the empirical method of sediment distribution

pattern in this study was the measuring result of sediment in Karangkates reservoir in

1982. This result has been represented into sediment distribution with the small relatively

of elevation interval. Table 4 presented the analysis of error square on the method of Area

Reduction Moody’s Modification

Table 4 Analysis of error square on the method of Area Reduction Moody’s Modification

Elevation

(m)

Volume of sediment (103 m

3) (VOB – VOS)

(103 m

3)

(VOB-VOS)2/VOB

(103 m

3 Survey 1982

(VOB)

Distribution

pattern

(VOS)

186 0 0 0 0

190.0 10 10 0 0

195.0 60 60 0 0

200.0 180 180 0 0

205.0 500 486.62 13.38 0.36

210.0 1,285 1,049.35 235.65 43.21

215.0 3,580 1,874.69 1,705.31 812.31

220.0 5,420 2,973.95 2,446.05 1,103.90

IV - 211

225.0 8,180 4,367.32 3,812.68 1,777.08

230.0 8,800 6,067.06 2,732.94 848.75

235.0 9.310 8,076.48 1,233.52 163.43

240.0 9,910 10,388.46 -478.46 23.10

245.0 10,340 12,982.90 -2,642.90 675.52

250.0 10,910 15,882.81 -4,912.81 2,212.26

252.5 12,000 17,317.68 -5,317.68 2,2356.48

255.0 13,920 18,849.34 -4,929.34 1,745.57

257.5 18,550 20,404.53 -1,854.53 185.41

260.0 22,530 21,966.18 563.82 14.11

262.5 23,450 23,511.70 -61.70 0.16

265.0 25,440 25,099.68 340.32 4.55

267.5 25,960 26,412.80 -452.80 7.90

270.0 27,660 27,636.08 23.92 0.01

272.5 28,190 28,190.00 0 0

Analysis of reservoir real life time

The end of reservoir life time was indicated by if the dead storage has been fully

filled by the sediment (Linsley et.al, 1985 and Priyantoro, 1987). The decreasing velocity

of reservoir life time is due to: 1) the quantity of sediment that is entered; 2) efficiency of

storage catchment; and 3) spesific gravity of deposited sediment.

The life time ending of Karangkates Reservoir was determined by the condition

which the sediment surface has reached the intake of hydropower such as on the elevation

of +233.2 m. Total of sediment deposit was calculated by using Moody’;s Modification so

it was obtained the sediment surface on the elevation of +233 m. However, the pattern of

sediment distribution was analyzed by using the method of Area Reduction. From the

result of trial and error, it was produced total of sediment volume was 190,000,000 m3.

Analysis of sediment volume total and the distribution pattern was presented as in Table 5.

Table 5 Analysis of bed elevation on the end of Karangkates Reservoir life time

Elevation

(m)

Relative

depth

(%)

Area

number of

reservoir

A (pH), m2

Reservoir

storage

V (pH), m3

S – V (pH)

(106 m3)

H. A (pH)

(106 m3)

H’(p)

215.0 33,526 800,000 4,500,000 185.500 69.200 2.6810

220.0 39.306 1,180,000 9,600,000 180.400 102.070 1.7674

225.0 45.088 1,700,000 18,500,000 171.500 147.050 1.1663

230.0 50.867 2,300,000 28,500,000 161.500 198.950 0.8118

235.0 56.647 3,250,000 42,300,000 147.700 281.125 0.5254

240.0 62.428 4,400,000 61,0000,000 129.000 380.600 0.3389

245.0 68.208 5,500,000 85,000,000 105.000 475.750 0.2207

250.0 73.988 6,700,000 114,000,000 76.000 579.550 0.1311

The depositing rate in estimating reservoir life time is carried out in every depositing of 5

million m3. Analysis of Karangkates Reservoir life time was presented as in Table 6.

Table 6 Analysis of Karangkates Reservoir life time

Reservoir

storage

(106 m

3)

Annual

input

(106 m

3)

Annual sediment

volume

(m3)

Sediment

deposit in T

year

(m3)

Time of

T year

(year)

Commulative

time

(year)

IV - 212

158 2.211 3,432,462.02 5,000,000 1.7727 1.7727

163 2.211 3,207,798.64 5,000,000 1.8865 3.6592

168 2.211 3,088,712.37 5,000,000 1.9486 5.6078

173 2.211 3,009,233.28 5,000,000 1.9902 7,5980

178 2.211 2,950,303.80 5,000,000 2.0201 9,6181

183 2.211 2,903,845.87 5,000,000 2.0430 11.6611

188 2.211 2,865,707.84 5,000,000 2.0615 13.7226

193 2.211 2,833,497.83 5,000,000 2.0763 15.7989

198 2.211 2,805,707.73 5,000,000 2.0886 17.8875

203 2.211 2,781,327.56 5,000,000 2.0993 19.9868

208 2.211 2,799,657.74 5,000,000 2.1082 22.0950

213 2.211 2,740,185.22 5,000,000 2.1162 24.2112

218 2.211 2,722,539.93 5,000,000 2.1219 26.3331

223 2.211 2,706,413.14 5,000,000 2.1288 28.4619

228 2.211 2,691,582.73 5,000,000 2.1344 30.5963

233 2.211 2,677,869.52 5,000,000 2.1391 32.7354

238 2.211 2,665,124.99 5,000,000 2.1436 34.8790

243 2.211 2,653,230.12 5,000,000 2.1475 37.0265

248 2.211 2,642,085.47 5,000,000 2.1510 39.1775

253 2.211 2,631,606.04 5,000,000 2.1545 41.3320

258 2.211 2,621,722.49 5,000,000 2.1575 43.4895

263 2.211 2,612,374,07 5,000,000 2.1604 45.6499

268 2.211 2,603,509.52 5,000,000 2.1630 47.8129

273 2.211 2,595,084.19 5,000,000 2.1654 49.9783

278 2.211 2,587,058.20 5,000,000 2.1679 52.1462

283 2.211 2,579,398.44 5,000,000 2.1700 54.3162

288 2.211 2,572,074.79 5,000,000 2.1720 56.4882

293 2.211 2,565,060.34 5,000,000 2.1740 58.6622

298 2.211 2,558,331.52 5,000,000 2.1759 60.8381

303 2.211 2,551,667.03 5,000,000 2.1778 63.0159

308 2.211 2,545,648.67 5,000,000 2.1794 65.1953

313 2.211 2,539,659.29 5,000,000 2.1810 67.3763

318 2.211 2,533,883.28 5,000,000 2.1826 69.5589

323 2.211 2,528,307.02 5,000,000 2.1841 71.7430

328 2.211 2,522,917.78 5,000,000 2.1856 73.9286

333 2.211 2,517,704.21 5,000,000 2.1870 76.1156

338 2.211 2,512,655.99 5,000,000 2.1885 78.3039

343 2.211 2,507,763.22 5,000,000 2.1897 80.4936

80.4936

CONCLUSION

Based on the analysis as above, it was concluded as follow:

1. Based on the sediment measuring in reservoir, it indicated that estimation of

sediment deposit form and fulfil the bed under the certain elevation was not too

accurate. Sediment deposit has distributed in all of reservoir bed elevation and most

of them was happened in the upstream of reservoir such as in the bed of reservoir

on storage area of reservoir life time.

2. Based on the deposit pattern of design assumption, it was concluded as follow:

- Total of sediment deposit which could be stored until the intake of hydropower

(Elevation of +233 m) was 35,500,000 m3.

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- Life time of Karangkates Reservoir which was analyzed based on the design

depositing (0.25 mm/year) was 69 years. However, based on the depositing rate

of measuring result on 1982 was 12.6 years.

3. Based on the analysis of sediment distribution pattern, it was concluded as follow:

- Total of sediment deposit which could be stored until the intake of hydropower

(Elevation of +233 m) was 190,000,000 m3.

- Life time of Karangkates Reservoir which was analyzed based on the

depositing rate of measuring result on 1982 and due to the consolidation factor

reached 80.5 years.

AKNOWLEDGEMENT

The authors were very thankful to Nurhadi Alhuri as the undergraduate student of

Water Resources Department, Faculty of Engineering, University of Brawijaya, Malang,

Indonesia which has been supported the data of this study.

REFERENCES

Andawayanti, Ussy. (2010): Sediment Transport in Estuary. International Journal of

Academic Research, 2(5): 224-226

Bisri, Mohammad. (2011a): Estimation of Remaining Usage Age at Sutami Reservoir

Using Sediment Analysis, International Journal of Academic Research, 3(3): 497-500

Bisri, Mohammad. (2011b). Conservation Based on Erosion Sedimentation Spatially,

Journal of applied Sciences Research, 7(6): 732-736

Brabben, TE. (1979): Reservoir Sedimentation Study, Karangkates, Hydraulics Research

Station, Holling Ford, England.

Daril, B. Simon. (1976): Sediment Transport Technology, Water Resources Publication

Lithocrafters, Ann Arbor, Michigan, USA.

Juwono, Pitojo Tri. (2011): Evaluation of Water Price Due to Sediment Dredging, 1(7):

764-769

Linsley, Ray K.; Max A., Kohler; and Joseph, L.H. Paulus. (1985): Hydrology for

Engineers, translated by Yandi Hermawan, Erlangga, Jakarta.

Priyantoro, Dwi. (1987): Technique of Sediment Transport. Department of Water

Resources, Faculty of Engineering, University of Brawijaya, malang, Indonesia.

Priyantoro, Dwi and Masrevaniah, Aniek. (2012): Sedimentation Evaluation at Water

Intake Gate of Grati PLTGU Jetty Blockade, 2(12): 34-48

Robert, I.S and Ernest, I.P. (1982). Reservoir Sedimentation, Division of Planning

Technical Services Engineering and Research Center, Denver, Colorado.

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– 6TH

, 2014

Emergency Response against Water Quality Accident hhdTTjjhkljdjjsgshjhfsdkjhskslsl;s;s;;s;;s;;sjsjkjffffrtttttttfggjfgjgkfkjkjf fffffjfjjfkkfjjj to Secure Safe Water Supply for Capital Area

2(14pt)

S. Ojima & Y. Murakami Japan Water Agency, Saitama, Japan

[email protected])

ABSTRACT: Japan is one of the countries where people drink tap water directly. Therefore, careful water

resources management is required especially in supplying drinking water. On May 17, 2012,

formaldehyde (HCHO in chemical formula), one of harmful substance, was detected as exceeding

the limit for drinking water regulation near capital area of Japan, and, eventually, water supply for

around 360 thousand houses was stopped in Chiba Prefecture, next to Tokyo metropolis.

Japan Water Agency (JWA) is in charge of operation of water resources management facilities in

major river basins in Japan such as dams, weirs and canals, etc. Therefore, JWA worked together

with river administrator against the water quality accident through emergency operation which

aimed at reducing consistency of causative substance of formaldehyde and to prevent expansion of

troubles. Emergency discharge from upstream dams, stopping water delivery through canals which

connects 2 river basins, etc. were implemented as emergency operation. Finally, most of water

supply service area didn’t suffer from water quality accident. Through the experience of the water

quality accident and emergency operation, JWA learned importance of 1) appropriate information

sharing and 2) grasping the potential risk in the basin in advance. In addition, JWA reminded that

enhancing the capacity of risk management is essential to achieve the mission of “to deliver safe

water stably” since water quality accident are directly link to citizens’ daily lives and one trouble

can give negative impact into wide area through the network of rivers, canals and water supply

facilities.

Keywords: water quality accident, basin-wide response, emergency discharge, risk management,

1. ROLE OF JAPAN WATER AGENCY IN CAPITAL AREA ON WATER

RESOURCES MANAGEMENT

1.1. Water Resources Development in Tone and Ara River Basins

Tone River, one of Japan’s major large rivers, originates in Mt. Ohminakami on the north

boarder of Kanto Region. The river encompasses most of the Kanto Plain, collecting the

waters of numerous tributaries and empties into the Pacific Ocean with part of the flow

diverted at Sekiyado by the Edo River that enters Tokyo Bay (see Figure 1). The area of

Tone River basin is 16,840km2, the largest in Japan, and covers most of the prefectures of

Kanto Region, including some part of metropolis of Tokyo. The large river has long been

providing abundant water resources and enriching the soils, but has also been causing

floods and other great disasters. Between 1961 and 1964, serious drought generally

IV - 215

referred to as the “Tokyo Olympics drought” occurred, which had great influence on

subsequent water resources development policies in Japan.

Figure 1. Tone and Ara River basins

Ara River with headwaters in Mt. Kobushigatake locates western side of Kanto Plain runs

through a group of major cities in Saitama and Tokyo in the south of the Kanto Plain, and

reaches Tokyo Bay (see Figure 1). The basin occupies 2,940km2, next to Tone River basin.

Tone River basin and Ara River basin is connected by Musashi Canal, which is constructed

near Tone Barrage, to deliver water which is developed in Tone River basin to Ara River

basin (see Figure 1). The combined river basin of the Tone and Ara River Systems covers

an area of 19,780km2, which represents 66% of five prefectures and a metropolis. The

basin of both river systems is at the center of Japan’s political, economic and cultural

activities. Water use and flood control in the basin is therefore of great significance.

1.2. Role of Japan Water Agency

Japan Water Agency (JWA), based on the Basic Plan for Water Resources Development

Plan for Major seven river systems (Tone, Ara, Kiso, Yodo, Yoshino and Chikugo River

Systems) designated for water resources development, is working on construction,

operation, management and re-construction of water resources management facilities such

as dams, estuary barrages, facilities for lake and marsh development, and canals (see

Figure 2).

IV - 216

The seven river systems designated for water resources development where the plan above

mentioned is applied cover major areas in Japan. Although the area of these river basins is

only 16% of national land, the population and industrial shipments in value in the covered

area account for 51% and 47% of national totals, respectively. Most of major cities in

Japan are located in these cities. (e.g. Tokyo in Tone and Ara River basin, Kyoto and

Osaka in Yodo River basin, Nagoya in Kiso River basin)

Figure 2. Cover area of Japan Water Agency

JWA has constructed 4 dams in upstream of Tone River System and 2 dams in Ara River

System, and also a canal which connects Tone River and Ara River to deliver water

collected in Tone River basin, larger river basin, to Ara River which goes through

population concentrated area to meet water demand there. In addition, JWA worked on the

development of lakes, construction of barrages and canals in Kanto Plain. JWA has

completed and managing 18 projects in both river systems and, at present, implementing

construction of 6 facilities.

JWA manages 72% of water resources developed in both river basins which is worth for

drinking water for 14,000,000 people, provides agricultural water for 94,000ha, and

contributing industrial production of approximately 36 billion USD per year.

2. DETECTION OF HARMFUL SUBSTANCE IN PURIFIED WATER

On May 17, 2012, “formaldehyde”, one of harmful substance, was detected as exceeding

the limit for drinking water at a water purification plant in Saitama Prefecture, locating

next to Tokyo.

“Formaldehyde” is an organic compound with the formula CH2O or HCHO. It is the

simplest aldehyde, so that it exists everywhere in the world. However, it has toxicity and

IV - 217

volatility, exposure to formaldehyde is a significant consideration for human health. It is

known as a cancer-causing material in highest category of International Agency for

Research on Cancer under WHO. On the other hand, formaldehyde is commonly used as

industrial materials, construction materials, etc. because of its low price.

In Japan, ordinance by Ministry of Health, Labour and Welfare on drinking water defines

formaldehyde as one of the 50 regulated items and if consistency of the items in water

exceeds their limits, water suppliers are not allowed to provide the water as drinking water.

Therefore, the fact that the consistency of formaldehyde in the treated water, which is to be

supplied for drinking use, exceeded the regulated value means quite serious situation

because water supplier cannot provide drinking water for its service area. Eventually, water

supply service for around 360,000 houses stopped because of excessive formaldehyde.

3. EMERGENCY OPERATION

3.1. Outline of Emergency Operation

The purification plant where formaldehyde was detected takes raw water from Tone River

through the intake gate placed at Tone Barrage. Detection of formaldehyde made relevant

organizations start emergency operation. The detection of formaldehyde at a plant which

takes raw water from Tone River raised following concerns.

a) The plant where formaldehyde was detected cannot provide drinking water, which

brings problems in water supply service in cover area.

b) Same problem can happen in other plants which take water from Tone River

In case formaldehyde is detected in other plants in capital area, it cause serious problem in

water supply service in the area which bring large negative impact for the lives of the

citizens there. Therefore, following actions should be implemented urgently.

a) Identifying causative substance and preventing contamination

b) Decision of “stop or not to stop” on water intake from Tone River at other

purification plants

c) Prevention of trouble expansion

For identification of causative substance and prevention of contamination were conducted

by Ministry of Health, Labour and Welfare and local governments, and some days later, it

was announced that the hexamethylenetetramine (HMT) which was contained in the

effluent from waste disposer which is located in upper stream area was the causative

chemical substance of formaldehyde.

As for the decision of water intake from Tone River, Ministry of Land, Infrastructure,

Transport and Tourism (MLIT), as river administrator, implemented urgent water quality

tests along the Tone River and Edo River which diverted from Tone River repeatedly and

provided the result to relevant organizations. As a result, many purification plants stopped,

temporary, water intake from Tone River on May 19. One of them stopped water intake for

3 days

JWA contributed on prevention of trouble expansion. JWA implemented emergency

operation of facilities under the coordination with MLIT, river administrator.

IV - 218

3.2. Outline of Emergency Operation by JWA

JWA and MLIT implemented emergency operation of water resources management

facilities in Tone River System to prevent expansion of troubles, assuming the causative

substance is coming through Tone River.

3.2.1. Announcement of emergency response mode and stopping water delivery through

Musashi Canal

Receiving first report of detection of formaldehyde from Saitama Prefecture at 17:30, May

18, JWA Headquarters (JWA-HQ) and related branch offices announced emergency

response mode and implemented emergency operation under coordination with MLIT.

Assuming that the causative substance reached the purification plant through Tone River,

one of the significant emergency operations was “stopping water delivery through Musashi

Canal”.

Musashi Canal is the canal which connects Tone River and Ara River (see Figure 3). One

of the objectives of the canal is to deliver water developed in Tone River Basin which has

large area to Ara River which run through a group of major cities in Saitama and Tokyo for

effective water supply. The canal was constructed in 1967, and has been delivering 40% of

drinking water of Tokyo and 80% of Saitama through the canal of 14.5km.

Figure 3. Location of Musashi Canal and other major facilities in 2 river basins

If the causative substance reaches to Ara River from Tone River through the canal, water

supply in Tokyo and Saitama may be affected by significant impact. Since Musashi Canal

takes water from Tone Barrage, same place of troubled purification plant, stopping water

delivery through the canal was essential operation to prevent capital area from expansion

of serious troubles.

IV - 219

After the coordination with relevant organizations, JWA stopped Musashi Canal at 23:10

on May 18. The JWA-HQ’s emergency operation mode is changed to higher level at the

same time.

The operation was announced to public in the midnight, 24:00 with MLIT.

3.2.2. Emergency water discharge from dams

The other important emergency operations were “to reduce the consistency of causative

substance in river flow” and “to wash causative substance into sea”.

Through the consultation, JWA and MLIT decided to release water in reservoirs in

upstream area as emergency operation to achieve these missions.

At 1:30 on May 19, JWA started emergency water discharge at Shimokubo Dam, located

in upstream of Tone River, with the amount of 200m3/s in maximum.

Photo 1. Shimokubo Dam

200m3/s of water never releases from the dam except the case of flood. Such large amount

of water released from the dam as emergency operation. Normally, water users want to

save water in reservoir to prepare against drought. However, to avoid the situation of

closing intake gates of purification plants in downstream area, it is unavoidable option to

improve the situation. Also dams of MLIT started emergency water discharge as well.

The emergency water discharge has not only problem of preparation against drought, but

also technical problem. Rapid decrease of water level of reservoir may cause land slide

around reservoir if geological condition doesn’t fit.

Therefore, emergency water discharge was implemented under careful observation of the

condition around the reservoirs as well as checking water quality test result of downstream

IV - 220

area to seek improvement of downstream condition and to avoid unnecessary trouble in

reservoir management.

Emergency water discharged from dams of MLIT and JWA in upstream area of Tone

River recorded 543m3/s, maximum in the emergency operation duration, at 5:00 on May

19.

On the other hand, many water purification plants along the Tone River and Edo River

stopped water intake from the rivers to check water quality test result, and after confirming

the safety of the water intake, they resumed taking water to their plants. Most of them

started with the interval less than half day. But one of the plants stopped for 3 days. During

the duration stopping water intake water from the river, the purification plants could

deliver water for some time utilizing stored water, however, water supply service to around

360,000 houses, around 870,000 people in population, stopped for half – one day

eventually. On May 23, the last plant which kept stopping water intake for 3 days restarted

their operation.

3.2.3. Alternative operation against stopping water delivery through Musashi Canal

The emergency operation, stopping water delivery through Musashi Canal, to prevent

capital area from expansion of troubles raised another problem. Water volume in Ara River

which normally receives water through the canal reduces when canal stopped water

delivery. It may cause water shortage in Tokyo and Saitama Area.

Photo 2. Musashi Canal

Therefore, JWA carefully observed water discharge volume of the control points along Ara

River whether it fits water demand of the area, considering the condition of storaged water

volume of 2 dams in upstream of Ara River and the possibility of additional discharge as

alternative option of stopping water delivery of Musashi Canal to avoid unexpected water

shortage in capital area.

3.2.4. Finishing emergency operation

IV - 221

Considering water quality monitoring data, discharge volume of emergency operation from

dams was reduced gradually. Since no additional troubles in the purification plants

occurred, and consistency of formaldehyde was kept low than regulation value even after

the reduction of emergency water discharge volume, MLIT as river administrator decided

to stop emergency discharge of all the dams, and to restart water supply through Musashi

Canal. Emergency operation for 7 days finished at 15:00 on May 24. Series of major

emergency operation by JWA are shown in the table below.

Table 1. Emergency operation by JWA

Date Time Operation by JWA Remarks

May 18 17:30 Received first report of detection

of formaldehyde from Saitama

Prefecture

18:00 Announced emergency response

mode by JWA-HQ

23:10 Closed Musashi Canal which

normally delivers water from

Tone River to Ara River for water

use of major cities in Tokyo and

Saitama area

24:00 Press release on emergency

operation of Musashi Canal

May 19 01:30 Started emergency water

discharge from Shimokubo Dam

which is located in upstream of

Tone River

Emergency discharge was

continuously conducted from

reservoirs in upstream area

under coordination with

MLIT.

05:00 Emergency discharge from

reservoirs recorded 543m3/s in

total.

<maximum volume during the

emergency operation>

08:30 Stopped emergency water

discharge from Shimokubo Dam

based on the coordination with

MLIT

JWA kept standing by

additional emergency

discharge from dams in

upstream area.

22:30 Started emergency water

discharge from Yagisawa Dam

which is located in upstream of

Tone River

May 20 05:30 Stopped emergency water

discharge from Yagisawa Dam

May 21-24 Conducted several times of

emergency water discharge from

Yagisawa Dam

May 24 15:00 Restarted water delivery through

Musashi Canal

JWA continued careful

monitoring of water quality of

rivers and purification plants

until finishing emergency

response mode on June 8.

June 8 09:00 Finished emergency response

mode

IV - 222

After stopping emergency operation, JWA-HQ continued emergency response mode until

June 8 and conducted checking water quality of the rivers and plants to secure safety water

supply for water user organizations.

Causative substance was also identified by central and local government and announced to

public about the cause and process of the water quality accident.

3.2.5. Information Release

Since the water quality accident is directly linked to peoples’ daily life, prompt information

release is required to related organizations. Therefore, during the emergency operation,

JWA released information to public through website 6 times, and held press conference

together with MLIT 4 times, in addition to frequent information sharing with relevant

organizations on water resources management.

4. CONCLUSION

In general, troubles in water supply service are directly link to citizens’ daily lives and one

trouble may give impact into wide area in river basin because of installed water supply

network and rivers/canals.

In the case of emergency operation in May 2012, flexible facility operation of dams, canals,

etc. contributed a lot to avoid expansion of water quality trouble in capital area. However,

implementation of flexible facility operation was not so easy because it required proper

decision making which meets sudden changes in circumstances and which is to be

accepted by stakeholders.

Through the experience of water quality accident and emergency operation, JWA learned

importance of 1) appropriate information sharing and 2) grasping the potential risk in the

basin.

“Appropriate information sharing” means information sharing which is timely, including

necessary information for receivers, and contributing well to share the recognition of each

other, etc. and it is applied for information sharing between JWA and water user

organizations, as well as between JWA and MLIT, and among JWA-HQ and branch

offices in the Basin.

The characteristic of the trouble in this case was 1) trouble which directly link to citizens’

lives, and 2) emergency operation was needed in large area of wide 2 river basins.

Therefore, information sharing and coordination among various stakeholders such as river

administrator, facility management authorities, water users, related ministries, etc. were

essential and significant. The important information for proper decision making for

emergency response in each organization should be delivered appropriately and

sufficiently beyond the “wall” of organizations in any case. It is a key for success in risk

management and information scheme and measures should be always reviewed and

improved.

In addition, JWA leaned importance of “grasping potential risk in the river basin”, such as

information of the companies who treat dangerous material, for the preparation of

IV - 223

emergency response simulation against quality accident in advance. It helps a lot prevent

identifying source of accident and expansion of troubles.

Lastly, through the water quality accident, JWA reminded the importance of upgrading the

capacity of risk management as one of the organizations which is working in the field of

water supply service and water resources management under the mission of “deliver safe

water to water users stably”.

REFERENCES

Ministry of Land, Infrastructure, Transport and Tourism of Japan (2012): Press release

documents from May 18 to 24, 2012, (in Japanese), Tokyo, Japan

Ministry of Health, Labour and Welfare of Japan (2012): Press release documents on June

7, 2012, (in Japanese), Tokyo, Japan

Wikipedia “Formaldehyde”: http://en.wikipedia.org/wiki/Formaldehyde

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