I. INTRODUCTION
1.1 General
Water is an inexhaustible commodity. As population and its economic activities go on
increasing so is the demand for water. To ensure a reliable water supply at the time of
needs, the proper and judicious use and management of water resources is required.
Hydropower generation and agriculture is major user of water resources in this
world .Hydropower plants, by their nature, require low operating cost and at the same
time provide great flexibility (especially reservoir based hydropower) in the use relative
to other sources of energy identified so far.
Benefits of water resources depends upon mainly on the three factors such as the physical
dimension of the system, the scale of development and the operating policies adopted for
the system.
Hydrological, geo-topographical factors have great influence on the physical dimension
of a reservoir. But with the advent of simulation techniques, not only optimal design is
achieved but also adverse effects are minimized and maximum benefits are accrued.
1.2 Problem Identification
Development of a country can be gauged by the amount of energy it consumes. Energy is
very important medium for the overall development of a nation .Hydropower is one of the
main sources of energy in Nepal. It accounts for nearly 90% of installed capacity and
95% of total generation of energy. Except for the firewood and Hydropower, Nepal has to
import all other types of energy paying scarce hard currencies while being extremely rich
in water resources. So, the proper utilization of its water resources is required for the
development.
In spite of potential resources of hydropower, Nepal has faced power crisis for several years
because most of the hydropower projects are based on the river run-off schemes except
Kulekhani-I (60 MW). To meet the power crises, storage scheme will be quite essential for the
country.
The predominant nature of hydroelectric source particularly, run of river type supply in
Integrated Power System(INPS) has exhibited that seasonal deficits of hydro energy is
bound to occur frequently along with seasonal surpluses. This has been the situation of
1
INPS even after the commissioning of Projects like Khimti, Mid Maryshandi
The estimated hydropower potential of Nepal is 83, 000 MW of which 114 projects
having 45,610 MW have been identified economically feasible However, to date, Nepal
has developed less than 1 percent of its vast hydropower potential. The total installed
capacity is about 680MW, of which 635 MW (93%) is generated by hydropower in the
integrated system. Peaking capacity as well as energy output of the power system drops in
the dry season of December to May due to the shortage of available runoff.
The peak power and energy demand is growing by about 11% annually, creating the
electricity shortage in Nepal. Demand has been exceeding supply every year. To meet the
significant difference between demand and supply, NEA had increased power cuts in the
country up to 18 hours a day in January 2009. Greater challenges of the NEA are bridging
the gap between supply and demand of electricity.
All the existing and future (scheduled to be commissioned by next five years)
hydropower plants are run-of-river types except Kulekhani power plant, Proposed Upper
Seti Hydropower Project and some of them are with daily regulating capacity. Therefore,
load shedding hours in the dry season depends on the availability of water in the
Kulekhani reservoir.
Figure 1.1: Contribution of energy in Nepal
1.3 Need of research
Due to limited power supply, optimum operation of water resources is
unavoidable. Latest estimates show, the demand for power in Nepal will be 1500 MW in
2015. Supply of this demand is only possible if more storage type hydropower projects are
constructed. [NEA, 2001]
2
Therefore, it is required that most of research be undertaken toward saving, storage,
management and water demand of water resources in this country. Ingredients include
analyzing various parameters such as population, economy, water use efficiency and etc.
[Siminovic, S.P, 2002].
Upper Seti Hydroelectric project with installed capacity of 127 MW has storage capacity of
374 million cubic meters [NEA, 2001]. In this study, simulation model was used for
system evaluation. Simulation model is a best way of using physical rules and a series
of operational rules try to simulate genuine phenomena and approach and accurate
scheme to predict the behavior of the system under a specific policy [Yeh W.W-G, 1985].
Input data of simulation model could be classified in three parts: fixed data, design data
and time series data. Fixed data are properties of system such as physical and economic
properties and relationship between them. Design data, in fact, are decision variables
which are determined in modeling process are reservoir capacity and plant generating
power capacity. Inflow to system is in the form of artificial data or time series data.
Simulation models can present efficiency and system performance in different
combination of reservoir, plant powers, reservoir storage, output etc. and in this
manner, they have good flexibility.
In the present study HEC-ResSim simulation model was used to evaluate performance of
Upper Seti storage dam operation and ability of the model to simulate of reservoir system
was studied.
1.4 Objectives of study:
The objective of reservoir simulation is to compute the plant capacity and the
corresponding maximum plant discharge, the reservoir drawdown pattern, the dry season
and the wet season energy and the total annual energy. The available inflow and the
reservoir live storage have to be fully utilized. The output data obtained from the
simulation are to evaluate the energy generations for two scenarios.
In view of the above factors the major objectives of the present study are as follows:
To compute plant capacity and the maximum plant discharge
To compute the dry and wet season energy
To compute the total energy generation
3
To develop a guide curve for computing the reservoir drawdown pattern
and operation of reservoir.
To compare the results obtained from HEC-Res Sim with the results obtained from
other models.
1.5 Scope of study:
This study is mainly focused on the development of reservoir operation model for
USHEP using HEC Res Sim. The study covers the following scope of works.
Literature reviews on Hydropower reservoir and its various aspects.
Review on present energy scenario of Nepal.
Study and collection of all relevant hydrological and topographical data of the
Upper Seti Basin.
Literature review on sediment studies on Upper Seti Basin.
Literature review on history of reservoir simulation.
Literature review on the operation of reservoir in Nepal and aborad.
Literature review on the operation of reservoir using HEC Res Sim models.
Recommend the model to be used for other reservoir operation under various
conditions.
1.6 Limitations:
Following limitations are set for the study:
Due to time and study limitations, sediment analysis for the reservoir has not been
performed.
Due to unavailability of required data seepage loss and hydraulic loss has been
neglected.
Input data used are collected from past study reports of NEA and JICA so that
comparisons of output could be effective and reliable.
If sediment analysis, seepage data and hydraulic loss data are used, the accuracy and
reliability of the results obtained would be increased.
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1.7 Organization of the Study
This thesis consists of seven chapters. Chapter 1 includes the introduction to the topic
with the need, objective, scope and limitations of the study. Chapter 2 reviews current
power production scenarios. Chapter 3 contains literature reviews .Chapter 4 contains
description of the site area and project. Chapter 5 contains the detailed model description,
research methodology and processes adopted to achieve the objective of the study.
Chapter 6 presents the results, its discussions and validation with tables and figures.
Finally, Chapter 7 presents the final conclusion of this study and recommendations for
further study.
The references and Annexes are incorporated at the end of this thesis while the
acknowledgements and abstract are given in the preface portion.
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II. HYDROPOWER AND ENERGY SITUATION IN NEPAL
2.1 Hydropower Potential
Nepal's water resource is considered to be abundant. The average annual precipitation is
about 1700mm (80% of which occurs during monsoon season from June to September).
The total annual average run-off from Nepal's 6000 rivers is over 200 billion m 3. [NEA,
2001]
Surface resources are distributed in the river system consisting of four major rivers (viz.
the Mahakali, the Karnali, the Gandaki and the Koshi), seven medium rivers and a large
number of small rivers.
Harnessing the water flowing from the Himalayas is Nepal’s development agenda for
increasing its national wealth. Water storage potential in Nepal is 88 billion m3. Nepal’s
theoretical hydropower potential is estimated at 83, 000 MW. At present altogether 114
projects having 45,610 MW capacity have been identified economically feasible The
country hopes to bring about development through three strategic consideration which
include building large-scale storage projects envisaged primarily for exporting energy,
medium scale projects for meeting national needs and small scale projects for serving
local communities. As such, four major storage projects are proposed as Indo-Nepal co-
operative initiatives. These are the Chisapani Karnali (10,800 MW), the Pancheswor
(7,200 MW), Budhi Gandaki (600 MW) and the Sapta Koshi high dam (3,600 MW)
which in total, would provide 22,200 MW installed capacity. Recent policy promotes
external and domestic private sector initiatives for hydropower development. Some of the
large projects with feasibility study completed are presented in table 2.1.
Table 2.1: Large Hydropower Projects with Feasibility Study
Project Name Capacity (MW)
Cost million USD
Year of Study Type
Karnali (Chisapani)
10,800 7 666 Updated in 2001
Storage
Pancheswor 6,480 2 980 1995 Storage
West Seti 750 1 098 1997 Storage
Arun-III 402 859 1991 Storage
Upper Tamakoshi 309 464 May 2005 PROR
Dudhkoshi 300 690 1998 Storage
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2.2 Energy Situation
Figure 2.1 shows the location map of power generation and transmission facilities in
Nepal. The power generating facilities in Nepal consists of hydro, diesel and solar power
plants but it is basically a hydropower-oriented system. The total installed capacity is
about 680 MW, which with 635 MW (93%) is generated by hydropower in the integrated
system.
Figure 2.1: Existing Power Stations and Distribution System
2.2.2 Available Energy and Peak Load Demand
NEA published total energy available and peak load demand in NEA annual report
2007/08 from 1999 to 2008. Figure 2.2 and Table 2.4 shows that the peak load demand
before 2001 was only 391 MW which is less than the total capacity of 398 MW including
IPP. Kaligandaki A Power plant was commissioned in 2001 and total capacity after it was
541 MW after the Kaligandaki A there was not any major power plant implemented in
7
Nepal except small power plants developed by IPPs. Significant load shedding started
from year 2005 but energy have always been spilled during wet season
Figure 2.2: Available energy and total peak load demand
Table 2.2:Available energy and total peak load demand
Figure2.3:Monthly energy generation from Kulekhani I
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Figure2.4:Monthly energy generation from Marsyangdi
Figures 2.3 to 2.5 (Kulekhani I, Marsyangdi and Kaligandaki A) present the energy
generation from major power plants of Nepal. These figures show that Run of river plants
(Marsyangdi and Kaligandaki A) generated with lower capacity (up to 50% of the total
capacity) during the wet season but at the same time reservoir power plants (Kulekhani
A) also generated up to 50% of its total capacity.( Shrestha, 2007)
Figure 2.5: Monthly energy generation from Kaligandaki A
Figure 2.6 shows the system load curve of the peak load demand of the year in 2007
(December 31, 2007) and Figure 2.7 shows a typical system load curve in wet days. Both
figures show that the peak load demand is from 6 PM to 9 PM. Load demand at day time
is only about 60% of the peak demand.
9
Figure 2.6:System load curve on 31 December 2007
Figure 2. 7:Typical system load curve in wet season.
Nepalese are already facing acute shortage of electricity whole year, if proper initiative is
not taken to develop more hydropower projects, it seems that the situation will be more
severe and power cut-off will be increased for more hours per week during dry period as
well as in wet season. Power and energy demand grew by 11.31% and 10.76%
respectively in the year 2008. The system demand of 721.73 MW recorded on December
31 2007 happened to the peak power demand observed in FY 2007/08. Likewise energy
demand over the year 2008 totalled 3490.12 GWh. As this amount of energy was not
available with the system the deficit amounting to 309.46 GWh had to be shedded to keep
the electricity service running. (Shrestha, 2007)
10
Figure 2.8:Energy and peak load demand forecast charts (NEA, 2000)
NEA made the power demand forecast for the further 18 years from 2009 to 2025 as
shown in figure 2.2 and Table 2.4. According to the forecast, the peak load is estimated to
be 1271.7 MW in 2013/14. The average annual growth rate for peak demand is estimated
to be about 10% for next 5 years. The further energy demand is also forecasted to be
5859.9 GWH in 2013.
Table 2.3: Energy and peak load demand forecast.
Source: NEA annual report, 2007/8
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Electricity generation should be increased by more than 10% per year to meet demand,
which is far high additional demand compare to additional generation rate at present.
[NEA,2001]
In February 2008 Government of Nepal formed a Committee for Solving the Load
Shedding Problem. The committee had prepared a report and recommended 25 points for
solving the load shedding problem. Some of them are development of Storage power
project like Upper Seti, speed up the construction of Upper Tama Koshi, Upper Trishuli
A, Upper Trishuli B, Kulekhani III and encourage IPPs for hydropower development.
They have also studied the energy production from existing and forthcoming hydropower
projects up to 2013/14. They have also developed energy and capacity balance per day of
the month from 2009/10 to 2013/14. Figure 2.9 and Table 2.6 presents the energy and
capacity balance per day of the month for year 2013/14. The figures show that capacity
will be surplused in wet season and deficit during the dry season. But the energy surplus
will be in every month.
Figure 2.9:Estimated Capacity and Energy balance in 2013/14
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Table 2.4:Estimated Capacity and Energy balance in 2013/14
Description Shrawan Bhadra Asoj Kartik Mangsir Paush
Jul/Aug Aug/Sep Sep/Oct Oct/Nov Nov/Dec December
Energy
Demand(MWh)16,264 16,093 15,715 13,974 15,806 16,136
Energy
Available(MWh)
28,129 28,129 28,129 28,129 21,199 19,983
Energy
Surplus(MWh)11,865 12,036 12,414 14,154 5,392 3,847
Peak demand(MWh) 1,073 1,065 1,090 1,090 1,161 1,208
Peak capacity(MW) 1,167 1,167 1,167 1,167 929 823
Av. Power
Deficit(MW)
(94) (102) (77) (77) 232 385
Description Magh Falgun Chaitra Baishakh Jesth Asar
Jan/Feb Feb/Mar Mar/Apr Apr/May May/Jun Jun/Jul
Energy
Demand(MWh)
16,466 16,136 15,806 15,477 16,384 17,231
Energy
Available(MWh)
17,830 17,474 16,085 16,735 21,880 26,729
Energy
Surplus(MWh)
1,364 1,338 279 1,258 5,496 9,498
Peak demand(MW) 1,197 1,162 1,124 1,107 1,134 1,157
Peak capacity(MW) 880 864 802 858 946 1,161
Av. Power
Deficit(MW)
317 298 321 249 188 (4)
III. LITERATURE REVIEW
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3.1 General
Determination of the optimum mode of operation for a reservoir has always been an
important task for water resources engineers for many years and yet no completely
satisfactory solution has been obtained in general and the problems have to be simplified
to fit each individual purpose as the problems are site specific and time specific.
Numerous methodologies such as Linear programming, Dynamic programming and
Simulation method are proposed as tools to optimize the reservoir operation. The
application of these techniques is reviewed below.
3.2 Reservoir operation problems
Reddy (1962) noted that it was customary for a long time to operate reservoir on the basis
of personal judgment by storing all inflows in the reservoir till it is required to release the
water to fulfill the target demand of different users. Such a method ignores the fact that
optimality is obtained only when the system operation takes into account that storage and
release can be apportioned among various system elements, purposes and operation time.
Optimum operation policy is sequential decision problem and consequently, systematic
approaches which model this sequential decision making are the appropriate ones to be
applied to solve the system operational problem.
Harboe et al.(1970) noted that in short operation the physical objective is to find
optimum hourly releases from a reservoir and in long term operation, the physical
objective is to find out monthly releases from the reservoir over an extended period such
as a critical period or the economic life of the project. Since the hydro plants are
connected with thermal, diesel or gas power station, the economic objective is the
minimization of the operational cost of the total power generation system while the
specific demand for energy is satisfied.
Harboe (1986) proposed a three stepped approach for establishing reservoir operational
rules. The three steps were optimization, simulation and multi objective analysis. The
method was applied to the real world system for low augmentation. First each reservoir
was sequentially optimized by dynamic programming. Then the results were taken as the
targets for standard operating rule on which simulation model was based .then several
simulation runs were performed with different targets when reservoir level was below a
certain critical level was also introduced. The alternative operating rules thus derived
were analyzed using multi objective analysis to select the acceptable solution to all.
14
Lian (1976) summarized that vital in the reservoir operation policies is the existence of
the rule curves which provide an effective guide in the operation of the systems. It
explains the range of storage level in its period to enable maintain smooth transition
control of operation between periods. This envelope of defined corridor secures a basis
for system releases and storage regulation.
With the development of computer technology and system analysis, attempts have been
made to select the optimal reservoir operation with the requirement of providing the best
return from the system.
3.3 Review of simulation technique
Simulation is one of the earliest and perhaps the most widely used method for evaluating
alternative water resource system. A simulation model may be deterministic or stochastic
depending upon whether random components are involved or not. The reason for its
popularity lies in its mathematical simplicity and versatility.
Hall and Dracup (1970) defined simulation as reproducing the essence of a system
without reproducing the system itself. Simulation model is a creation of a model which is
a mathematical representation of the system under consideration. it enables the rational
assessment of the system behavior under various inputs and sets of system parameters.
However, the simulation does not ensure a systematic search over the decision space of
the controllable input data.
Simulation technique is an effective method for evaluating alternative configurations of
plant capacity, water use allocations, operating policies etc, they are not very effective
means for choosing the best configuration of capacity, target and policy. For this
optimization tools have been proven to be more effective. However, Loucks (1976)
pointed out that mathematical, computational, and data limitations restrict the use of
optimization models, while simulation models are far less restricted .hence they are better
suited for evaluating more precisely the alternatives defined by optimization models.
Thus, though simulation by definition doesn't ensure optimality and a local optimum may
be determined while the global optimum is bypassed in essentially what might be called a
trial and error approach, its importance in operational studies is unquestioned .In
particular, simulation being less stringent than an optimization model can be better
adopted to reflect peculiarities of the real system.
3.4 Reservoir Simulation
15
3.4.1 Initial developments
In the 1930’s, interest grew in estimating more accurately the quantity of water passing
through a water power station. Until that time, calculations had been based on the
nominal head capacity combined with the technical efficiency of the turbines and
generators [Laurent J., 1936]. However, the efficiency of a turbine varies to a high degree
with the load, so that this approach needed to be improved by a more accurate
measurement of the flow passing through the turbines [Hartzell H., 1936]. These accurate
measurements were critical in order to maintain the stocked water in the reservoir at secure
levels and prevent flood events, since the natural flow had been replaced with a regulated
water discharge.
A few decades later in the early 70’s, many detailed studies were conducted in an
attempt to improve water resources systems, because of the enormous investments involved
in their design and operation. Programming techniques, such as linear and dynamic
programming, started to be used for optimum design and operation of water resource
systems. However, these techniques were based on steady inflow and water demands and
presented definite limitations when dealing with a natural stream flow with
stochastic properties [Charalampos Shaolikaris,2008].
The optimization of the operation of a reservoir based on the coupling of reservoir
simulation with hydrology was initiated in 1975. With this scheme, the first module is
a system model which simulates and evaluates the operation of a reservoir system on a
monthly basis for water supply, low flow regulation, power generation and recreation,
with storage and release constraints for flood control. The second module is a catchments
model which is usually meant for the simulation of short-time flow series meant to
reproduce flood periods [Beard L.R., 1975]. This coupled approach was initially
tested on the operational optimization of the dam’s complex in the Velika Morava
basin in the former Yugoslavia[Djordjevic B et.al] .It is nowadays the most common
program structure adopted in dam simulation software.
3.5 About the model
3.5.1 Introducing HEC Res Sim
16
The U.S. Army Corp of Engineers - Hydrologic Engineering Center developed in 1973
the HEC-5 program for the simulation of flood control and conservation systems. It
was initially written for flood control operation of single flood events. The program was
later expanded to multi-events floods and included basic water supply and hydropower
analysis capabilities. Pumped-storage hydropower analysis capability was finally added in
1977.All versions were developed in FORTRAN and interfaced with the HEC-DSS
data storage system. [USACE-HEC, 2007]
HEC-5 recently evolved into the HEC-ResSim software with the addition of a graphical
user interface (GUI). Its hydropower simulation capabilities include analysis of run-of-
river generation, peak power generation, pumped storage and system power operation. To
simulate hydropower operation, the reservoir releases are determined to meet power
production goals which may vary on a monthly, daily, or hourly basis.
Additionally, the hydropower component takes into account the penstock capacity
and losses, as well as leakage parameters. [USACE-HEC, 2007]
The model allows the user to define alternatives and run simulations simultaneously to
compare results. Schematic elements in HEC-ResSim allow the representation of
watershed, reservoir network and simulation data visually in a geo-referenced context
that interacts with associated data. Additionally, HEC-ResSim is compatible with ArcGIS
shape files and AutoCAD drawing files, which can be used as a background layer and
facilitate the better representation of the physical system. Watershed boundaries,
reservoirs, channel networks, diversions, etc. can be superimposed over the shape file.
[USACE-HEC, 2007]
The HEC-ResSim program is divided into three modules(Fig.1) which are
respectively, the watershed setup, the reservoir network definition and the
simulation scenario management. [USACE-HEC, 2007]
17
Figure 3.1 - Graphical illustration of the HEC-ResSim modules
• Watershed setup
The purpose of this module is to provide a common framework for watershed creation and
definition. A watershed is associated with a geographic region for which multiple
models and layers of information can be configured. A watershed may include all of the
streams, projects, e.g., reservoirs, levees, gage locations, impact areas, time-series locations,
and hydrologic and hydraulic data for a specific area. All of these details together, once
configured, form a watershed framework. [USACE-HEC, 2007]
• Reservoir network definition
The purpose of the Reservoir Network module is to isolate the development of the
reservoir model from the output analysis. This module facilitates the creation of the
network schematic, the description of the physical and operational elements of the
reservoir model, and the definition the management alternatives to be analyzed.
Reservoirs are further divided into multiple technical elements such the pool, the dam,
and one or more outlets. The criteria for reservoir release decisions are drawn from a set
of discrete pool heights, power production levels and release rules. Reservoirs are
connected to the river network as well diversions or junctions. After finalizing the
connection network schematic, physical and operational data for each network element
are defined. Management alternatives are created to compare results using different model
schematics, i.e. physical properties, operation sets, inflows, and/or initial conditions.
[USACE-HEC, 2007]
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• Simulation scenario management
The purpose of the Simulation module is to isolate the output analysis from the model
development process. Once the reservoir model is complete and the alternatives have
been defined, the Simulation module enables the model to test various river flow
hypotheses.
3.6 Review on past studies:
Feasibility Study of Upper Seti Storage Hydroelectric Project: NEA, 2001
NEA conducted detailed feasibility study on USHEP in 2001 which also includes the
reservoir simulation. It was envisaged to make a detail study of the power generation
possibility with respect to the available water resources and find the most suitable option
in terms of energy benefit. A tool was developed in –house for this purpose by NEA by
the Project Optimization Group in the form of a computer software named "Reservoir
Simulation Version 1.0" using C++ language.
The reservoir simulation has been carries out for the USHEP using the updated version
1.1 of the above mentioned software. Simulation was carried out for the three sets of
options depending on tail water level and the development concept. Two sets of
simulation are run for the Option A, one for the shaft powerhouse option (Alternate A1.1
and A1.2) and another for the Underground powerhouse option (Alternate A2.1 and
A2.2). One simulation was run for the Option B, toe development.
Design alternative of reservoir
During inception and feasibility study stage various alternatives for the project layout was
done by NEA. The study showed two options based on the findings of preliminary study
and site investigation.
Option A
In this alternative, different options for locations for the main intake and the powerhouse
are recognized. The four alternatives are based on two different powerhouse types
associated with two different location of the main intake and the resulting four different
alignments of the headrace tunnel. Intake No.1 and Intake No. 2 is 130 m and 300 m
upstream from the dam axis respectively. These are grouped as
Alternative A1.1 : Intake No.1 with Shaft Type Powerhouse
19
Alternative A1.2 : Intake No.2 with Shaft Type Powerhouse
Alternative A2.1 : Intake No.1 with Underground Powerhouse
Alternative A2.2 : Intake No.2 with Underground Powerhouse
Option B
This option consists of only one alternative i.e toe development underground powerhouse.
This option is adopted during the feasibility study by NEA.
Alternative: B1 : Toe development
Option A and B both have 142 m high Roller Compacted Concrete dam with integrated
spillway and the river diversion structures. The dam is founded on bedrock of dolomite.
The head race tunnel is located at uphill side of the Seti River, which passes through the
dolomite and slate.
The economic and financial analysis conducted by NEA has shown that Option B is the
best alternative.
Simulated results obtained for Option B is shown in table 3.1.
Table 3.1: Simulated results obtained by NEA
Full Supply Level(FSL) (m) 425.00 m
Sediment Deposit Level (m) 399.56
Minimum Operating Level (MOL) (m) 410.96
Storage Volume at FSL (Mm^3) 333.71
Storage Volume at MOL (Mm^3) 237.00
Sediment Deposit Volume (Mm^3) 172.96
Weighted Average Head (m) 111.04
Discharge Utility Factor 0.68
Maximum Plant Discharge (m^3/s) 141.14
Minimum Plant Discharge (m^3/s) 124.21
Optimum Plant Capacity MW) 122.20
Plant Factor 0.555
Dry Season Energy (GWh) 171.93
Wet Season Energy (GWh) 422.43
Total Annual Energy(GWh) 594.36
20
Upgrading Feasibility Study on the USHEP in Nepal
-JICA, Electric Power Development Co. Ltd, Nippon Koei Co. Ltd, 2007
JICA conducted the study in 2007 using the same input data as used by NEA in its
feasibility study. The study focused on sediment deposition pattern as well. The
simulation was carried out with the program named EPDC/KCC FLOW 500 MODEL.
The Reservoir is estimated to be filled with sediment in several decades, so the measures
against sedimentation shall be taken. A degree of importance for sediment management is
classified with the following two indices as shown.
Life of reservoir = Reservoir Capacity (CAP) /Average annual sediment inflow (MAS)
=331.7 MCM /(11.55 MCM/Year)
= 28.72 years
Turnover rate of reservoir = Reservoir Capacity (CAP) /Average annual inflow (MAR)
=331.7 MCM / 3,381 MCM
= 0.098
Average sediment deposit of the reservoir
=specific sediment yield X catchment area X trap efficiency
=6,244 X 1,502 X 0.85
=7.97 MCM / Year
Necessary number of years the reservoir will be filled with sediment is calculated as
270.3 MCM / 7.97 MCM / year
=34 years (in terms of effective capacity)
331.7 MCM / 7.97 MCM / year
=42 years (in terms of gross capacity)
21
Numerical values of the above indices show that the reservoir will be filled with sediment
in a short period of year without sediment management and has relatively large turnover
rate.
A decrease in effective storage capacity of the Reservoir is as shown in Table 3.2:
Table 3.2: Storage capacity of reservoir
Years of Completion Effective Storage Capacity(MCM)
0 270.30
25 197.40
50 134.81
Sediment volume for different sill elevation is given in Table 3.3
Table 3.3: Sediment volume
Sediment flushing gate Sediment volume in Reservoir
sill elevation
After 108 yearsMaximum sediment volume
Volume
Years of completion(1,000 m^3)(1,000 m^3)
320.00 126,434 138,635 89330.00 162,952 169,943 89
The simulation results showed that sediment advances year by year without the yearly
sediment flushing operation. The cumulative and maximum sediment volumes after 108
years from completion, as well as the year in which the sediment volume peaks, are
shown in Table 3.4
Table 3.4: Sediment Volume in Reservoir
Frequency of sediment Sediment volume in Reservoir
flushing operation
After 108 yearsMaximum sediment volume
Volume
Years of completion(1,000 m^3)(1,000 m^3)
Every year 126,434 138,635 89Every 2 year 246,733 261,389 89Every 3 year 283,314 288,390 107
Table 3.5 shows other simulated results
Table3.5: Simulated results (JICA)
22
Full Supply Level(FSL) (m) 425.00 m
Sill Level of Flushing gates(m) 320
Minimum Operating Level (MOL) (m) 370
Weighted Average Head (m) 116.2
Optimum Plant Capacity MW) 126
Plant Factor 0.52
Dry Season Energy (GWh) 230.1
Wet Season Energy (GWh) 344
Total Annual Energy(GWh) 574.1
Conclusion drawn by JICA:
The project has a lot of sediment inflow to the Reservoir, and the sediment flushing
facilities are indispensable to maintenance of the effective Reservoir capacity.
It is recommended that the facilities be installed at EL.320.00 m considering the
topography of the Dam site.
Sediment flushing operation shall be carried out every year.
Assessment of Energy production from major Hydropower projects in Nepal-
(Shrestha, 2007)
The objective of this study was to assess the energy production from the major existing
hydropower plants and planned hydropower projects in next five years using nMAG
model. USHEP was also a part of the study and the study results are shown in Table 3.6.
Table3.6: Summary of the results (nMAG)
Total Energy Generated(GWh) 673.3
Maximum Discharge(m^3/s) 127.4
Maximum Power (MW) 132.698
Utility Factor 58.2
3.6.4 Some practical applications
23
In 2004, [Babazadeh et al, 2007]. for evaluation and reservoir management of Tigris and
Euphrates rivers system in Iraq HEC-ResSim 2.0 was used. First, multi-reservoir system of
these rivers where setup on HEC-ResSim. Model contains six main reservoirs, three off-
stream reservoirs and seven small reservoirs and many diversion dams for diverting
water from Tigris and Euphrates rivers. Priority in these multipurpose reservoir system
are water supply for agriculture demand then flood control, while, hydroelectric power
was also generated. HEC-ResSim 2.0 was used for simulation history events special flood
and drought periods.
USACE experts used HEC-ResSim for water resources simulation in Afghanistan.
Engineers of US Army Corps of Engineers and Afghani engineers created a team for
simulation of Kajakai reservoir and project development downstream plains. This
model simulates system operation for power generation, flood control, irrigation and
changes in power generation capacity, live storage and release structures [ Babazadeh et al,
2007].
Jhiroft dam simulation
Halil River is one of biggest river of Jazmourian basin and Kerman province, Iran. The
area of Halil river basin is 31462 km2. The starting point of this permanent river is
snow covered mountain near city of Baft and Rabor in Kerman province. Annual
volume of water carried by Halil River as measured by monitoring station in 42 years
time series is 515 MCM. Jiroft storage dam is the largest dam in this river basin that
started operation in 1992. Average annual inflow of dam reservoir over 42 years is 422
MCM and from initial operation up to 1995 is 536 MCM. First of all, operation
reservoir volume is 415 MCM at elevation 1184 meter from sea level and inactive
level is 1126 meters from sea level. This is an arched dam and average evaporation
from water surface is 2076 mm. Length of dam crest is 250 m and its height from river
bed is 125 m and crest width is 5 m. This dam has two Francis turbines with power
generation 32 MW. Main purpose of this dam construction is supply of downstream
agriculture water demand, flood control of Halil River and secondary is hydropower
generation. Due to drought in recent years, power station was not operated. [Babazadeh et
al, 2007].
72 months operation from 1999 to 2005, data of Jiroft Storage Dam (such as: inflow,
outflow, reservoir level, storage and power generation as daily data) have been
24
recorded by Jiroft Dam Operation Company. These data were used for validation and
estimation of model accuracy. [Babazadeh et al, 2007].
Study and evaluation of Jiroft storage dam in present conditions,
sedimentation condition and developing condition was performed using HEC-ResSim
Results of model validation showed that model was capable of simulation
with suitable accurate. For study of accuracy and validation of model, observed data
from April 1999 to March 2005 was used. Therefore, input data, output data and reservoir
and dam properties were supplied to the model and changes in computed volume of
reservoir were compared with observed data. Observed data input to model as history data
and reservoir storage were compared with observed data in observation periods. The value
of absolute error was 11% and root of mean square error was estimated 23 million cubic
meters. Therefore, model ability and efficiency are acceptable. [Babazadeh et al, 2007].
25
IV. DESCRIPTION OF SITE AREA AND THE PROJECT
4.1 Location
The Upper Seti (Damauli) Storage Hydroelectric Project has a capacity of 127 MW[NEA,
2001], the storage type scheme, and includes 1000 m long horse shoe headrace tunnel,
140 m high concrete gravity dam, two diversion tunnels of lengths 712 m and 881 m and an
underground powerhouse. [NEA, 2001]
The site is located in the upper part of the Seti River, a tributary of the Trishuli River
flowing in the central part of Nepal. The Seti River originates at the Annapurna (at an
elevation of 7,555 m above sea level) of the Himalayas and joins the Madi river 2 km
downstream from the proposed Dam site after flowing roughly from north to south. The
length of the Seti River from the origin to the Dam Site is about 120 km, and the
catchments area at the Dam site is 1,502 sq km. [NEA, 2001]
The Seti River basin belongs to a high mountain and a humid subtropical climate zone.
The NEA's report states that the average annual precipitation in the project basin is 2,973
mm, of which about 80% falls between June and September due to the influence of the
southwest monsoon. Records of temperature exceeding 36 Degree Celcius from April
through June as against a lower value of approximately 5 Degree Celcius from January
through February on average. [NEA, 2001]
4.2 Main Features of Upper Seti Storage Hydroelectric Project
River Name of River Seti River
Catchments Area 1502 km2
Annual Inflow 3,380 x 10^6 m^3
Reservoir Full Supply Level 425.0 m
Minimum Operating Level 370 m
Available Depth 55 m
Effective Storage Capacity 270.30 MCM
Dam Type Concrete Gravity Dam
Height x Crest Length 140.0 m, 170.0 m
Power House Type Underground
Size Wide 22mx High 42m length 90 m
26
Discharge Maximum 127.4 cumecs
Installed Capacity 127 MW
Turbine Type Vertical Shaft, Francis Turbine
Turbine Output x Number 65,100 KW x 2
Figure: 4.1: Location of the site
4.3 River System
The total length of the Seti River from the dam site to the source is about 120 km. Seti
river meets many medium and small tributaries upstream of the dam site. These are
described below.
Starting at dam site, the Seti River meets Jyamdi and Kyangdi River at 28 km upstream at
Khairenitar. The river gradient from dam site to this confluence is 1:280.The river
gradient is flatter and flows almost west to east. From Jyamdi and Seti River confluence
the river flows south to north and meets Saraudi River. The river has gradient 1:120 and
the length of the river reach is 7 km.
27
From Saraudi River and Seti River confluence, the Seti River meets Khudi River at Kotre.
The river reach is 3 km and gradient 1:120.Further Upstream Seti River meets Bijaypure
River. The river length is 12 km gradient 1:100.
At short distance, the Set River meets Phusre River. The river length is 2 km and gradient
1:90.From Phusre and Seti River confluence, the Seti River meets Yandi River at about
18 km upstream. The river flows almost north to south and has a gradient 1:70.
The river upstream of Yandi and Seti confluence, the river flows through Phokhara
valley.The Seti River flows through the Mahendra Pul. The highest gorge, that is, river
undercutting are seen at the Pokhara valley due to the Seti River. Upsream of Pokhara
valley, the river meets mardi River at Lahachowk. The river reach length is 7 km and
average gradient 1:53.
The Seti River upstream of Maridi and Seti confluence, the river gradient is steep ,more
than 1:27 upto Sadhu River confluence. The confluence height is about 2000 m above
mean sea level .the river length is 75 km. Above this the Seti River is very steep, the
gradient is more than 1:10,the remaining river length is 20 km up to the glacier tongue.
[NEA, 2001]
4.4 Meteorological and Hydrological Stations
Meteorological stations and gauging stations are arranged in the Seti River and
surrounding basin. The Department of Hydrology and Meteorology (DHM), a subordinate
organization of the Ministry of Environment, Science and Technology, carries out
meteorological observation and river discharge measurements and provides NEA with
those data. A few meteorological stations are also equipped with a thermometer. a
hygrometer, an anemometer and an evaporation pan, while the other stations are provided
with only a rain gauge.
Table 4.1: Rain Gauge Stations Near and at the Seti River Basin
Index.No. Station name Lat.-Long. ElevationYears of Records
Deg/Min m
613 Karki Neta 28 d 11'-84 d 45' 1720 1977-94
706 Damkauli 27d 41'-84d 13' 154 1971-95
726 Garakot 27d 52'-83d 48' 500 1980-96
802 Khudi Bazar 28d 27'-84d 22' 823 1957-97
803 Pokhara Hospital 28d 14'-84d 00' 866 1956-75
28
804 Pokhara Airport 28d 13'-84d 00' 827 1968-94
805 Shyangja 28d 06'-83d 53' 868 1973-94
806 Larke Samdo 28d 40'-84d 47' 3650 1978-94
807 Kuncha 28d 08'-84d 21' 855 1956-94
808 Bandipur 27d 56'-84d 32' 965 1956-95
810 Chapkot 27d 53'-83d 49' 460 1957-94
811 Male Patan 28d 13'-83d 57' 856 1966-94
813 Bhadaure Deurali 28d 16'-83d 49' 1600 1985-94
814 Lumle 28d 18'-83d 48' 1740 1969-94
815 Khairini Tar 28d 02'-84d 06' 500 1971-94
816 Chame 28d 33'-84d 14' 2680 1974-94
817 Damauli 27d 58'-84d 17' 358 1974-94
818 Lamachaur 28d 16'-83d 58' 1070 1972-94
820 Manag Bhot 28d 40'-84d 01' 3420 1975-94
821 Ghandruk 28d 23'-83d 48' 1960 1976-94
822 Khuldi 28d 26'-83d 5u0' 2440 1973-86
823 Gharedhanga 28d 12'-84d 37' 1120 1976-94
824 Slklesh 28d 22'-84d 06' 1820 1977-94
Source: NEA, 2001
4.5 Climate study
The total number of climate gauge stations is around 157 according to NEA.A few
climate gauging stations are equipped with precipitation gauge , temperature data,
humidity data, wind data and evaporation data.
The catchment lies in the High Himalayas and the Lesser Himalayas and the
physiographic characteristics of the Seti River influences the climate change with
variation of altitude. Therefore, the catchment area experiences severe cold, subtropical to
temperate climate. As in other parts of Nepal, the Seti River catchment also experiences
the effects of the southwest monsoon, which on an average lasts from June to the end of
September. The region receives rainfall approximately 80% of the annual rainfall during
this period. Rainfall intensifies vary throughout the basin with maximum intensity
occurring on the south facing slopes. During the monsoon period, relative humidity
reaches at their maximum, temperature are lower compared to the pre-monsoon period.
29
4.6 Stream Flow Data
The earliest data recorded for major rivers in Nepal is from 1962.The gauging stations in
the major rivers are equipped with discharge measurement, automatic water surface
record chart and the staff gauge. DHM provides records of the monthly flows for study
purpose. The locations of the gauging stations are shown below:
Table 4.2: Stream Flow data around the catchment area
Stream
GaugeRiver Name Location
Year of
Records
Latitude. /
Longitude
Drainage
Area(km^2)
406.5 Modi River Nayapool 1988-94 28d 13'-83d 42' 647
428 Mardi River Lahachowk 1974-90 28d 13'-83d 55' 160
430 Seti River Phoolbari 1964-84 28d 14'-84d 00' 582
N.A Seti River Damauli(Patan) Recent 500 m d/s of dam site 1505
438 Madi River Shisaghat 1978-90 28d 06'-84d 14' 858
439.3 Khudi River Khudi Bazar 1983-93 28d 17'-84d 21' 147
439.7 Marsyandi River Bimal Nagar 1987-93 27d 57'-84d 25' N.A
439.8 Marsyandi River Gopling Ghat 1973-86 27d 55'-84d 29' 3850
Source: NEA, 2001
4.7 Topographic Characteristic of the Basin
Seti River is one of the main tributaries of Sapta Gandaki River System. Annapurna
Himalayas is the main source of Seti River. The major source of the basin consists of
several peaks such as "Annapurna III(EL.7555 m), Annapurna Peak V(EL.7525 m)and
Machapuchre (EL.6999 m).The total area of Seti River basin up to site intake is 1502
km^2,in which 50 km^2 is covered with snow.
Table 4.3: Catchment Characteristic
Area(km^2) Upper Seti Intake
Total Area 1502
Area below 5000 m 1452
Area above 5000 m 1276
Source: NEA, 2001
30
Table 4.4: Major Lakes in the Seti River Basin
Lakes Lake Area(km^2) Catchment Area(km^2)
Phewa Lake 4.35 126.8
Begnas Lake 3.3 18.5
Rupa Lake 1.14 26.3
DipangLake 0.075 -
Maidi Lake 0.0125 -
Khasti Lake 0.100 -
Nyurehi Lake 0.0375 -
Total 9.185 171.6
Source: NEA, 2001
4.8 Evaporation
The evaporation data are available from the year 1977 to 1984 and shown in table 4.5.
The figure indicates that the evaporation occurs at the maximum rate during the dry
period of the pre-mansoon season.
Table 4.5: Monthly Evaporation Data
year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1977 N.A N.A N.A 3.5 5.8 7.1 5.7 6.2 4.7 3.5 2.6 1.3
1978 1.6 2.1 4.8 3.7 6.2 5 5.9 4.7 3.9 3.2 2.3 1.6
1979 1.7 2.8 4.7 5.6 6 6.6 3.9 4.5 3.9 3.4 2.4 1.6
1980 1.4 2.7 4.4 5.9 5.3 5.1 4.8 4.6 4.4 3.4 2.3 1.9
1981 2.2 2.5 4.5 5.2 6.1 5.6 4.9 4.4 4.7 3.4 2.4 1.8
1982 2.3 2.5 3.8 6.9 5.6 6 5.3 5.1 3.9 2.9 2.1 1.7
1983 1.9 2.5 4.2 4.1 5.6 6.8 6.2 5.3 5.9 3.5 2.4 1.5
1984 1.6 2.8 5.3 5.8 4.8 5 5.5 5.7 4.6 3 2 1.3
Days
Average
31
1.81
28
2.56
31
4.53
30
5.09
31
5.68
30
5.90
31
5.2
8
31
5.06
30
4.50
31
3.2
9
30
2.31
31
1.59
Evaporation
Mm/month
56 72 140 153 176 177 164 157 135 102 69 49
Reservoir
Evaporation(mm/mth)
39 50 98 107 123 124 114 110 95 71 49 34
Source: NEA, 2001
31
4.9 Probable Maximum Precipitation
Probable maximum precipitation (PMP) over the basin is used to determine the Probable
maximum flood. It is shown in table 4.6.
Table 4.6: Probable Maximum Precipitation
S.No Index No. Station PMP
1 706 Damkauli 1107
2 726 Garakot 1142
3 802 Khudi Bazar 844
4 803 Pokhara Hospital 867
5 804 Pokhara Airport 742
6 805 Shyangja 982
7 806 Larke Samdo 652
8 807 Kuncha 724
9 808 Bandipur 821
10 809 Chapkot 516
11 810 Male Patan 950
12 811 Bhadaure Deurali 920
13 813 Lumle 1005
14 814 Khairini Tar 856
15 815 Chame 668
16 816 Damauli 512
17 817 Lamachaur 1245
18 818 Manag Bhot 1063
19 820 Ghandruk 571
20 821 Khuldi 731
21 823 Gharedhanga 808
22 824 Siklesh 768
Source: NEA, 2001
32
4.10 Probable Maximum Flood (PMF)
The hourly flood hydrograph is given in the Table 4.7.
Table 4.7: Probable Maximum Flood
Time inHours
PMF Hydrographm^3/s
Dry season FloodHydrograph
123456789
1011121314151617181920212223242526272829303132333435363738394041424344
100.0100.0100.0100.0100.0100.0100.0111.2193.3330.9538.1812.6
1,148.11,538.51,977.52,457.82,970.43,506.44,057.54,615.45,170.05,707.06,215.26,681.47,099.57,463.67,768.28,008.58,180.68,281.08,306.78,255.48,126.57,931.27,692.77,429.37,152.26,869.96,589.76,317.26,055.25,804.05,563.35,332.5
10.010.010.010.010.010.010.010.010.010.010.215.521.829.337.646.856.566.777.287.898.3
108.6118.2127.1135.0142.0147.8152.3155.6157.5158.0157.0154.6150.9146.3141.3136.1130.7125.4120.2115.2110.4105.8101.4
33
45464748495051525354555657585960616263646566676869707172
5,111.44,899.44,696.24,501.44,314.74,135.73,964.23,799.83,642.23,491.13,346.33,207.53,074.52,947.02,848.82,707.62,595.32,487.72,384.52,285.62,190.82,099.92,012.81,929.41,849.31,772.61,699.11,628.6
97.293.289.385.682.178.775.472.369.366.463.761.058.556.153.751.549.447.345.443.541.739.938.336.735.233.732.331.0
Source: NEA, 2001
4.11 Temperature
The annual maximum air temperature occurs generally I month of May and ranges from
36 degree Celsius to 41 degree Celsius and slightly decrease in June. The Minimum
temperature occurs in December and January ranging from 1.5 degree Celsius to 7 degree
Celsius.
4.12 Humidity
The maximum and minimum monthly humidity are 100 % and 40%respectively.The
atmosphere is humid with average monthly relative humidity ranging from 77% to 100 %
in Janaury.April is the driest month with relative humidity at 40 %.
4.13 Wind Speed
The average monthly maximum wind speed at the dam site is 3.8 km/hr.
34
V. RESEARCH METHODOLOGY
5.1 Application of the model
HEC-ResSim uses an original rule-based approach to mimic the actual decision-making
process that reservoir operators must use to meet operating requirements for flood
control, power generation, water supply, and environmental quality. Parameters that may
influence flow requirements at a reservoir include time of year, hydrologic conditions,
water temperature, and simultaneous operations by other reservoirs in a system. The
reservoirs designated to meet the flow requirements may have multiple and/or conflicted
constraints on their operation. ResSim describes these flow requirements and constraints
for the operating zones of a reservoir using a separate set of prioritized rules for each
zone. Basic reservoir operating goals are defined by flexible at-site and downstream
control functions. As HEC-ResSim has evolved, advanced features such as multi-
reservoir system constraints, outlet prioritization, scripted state variables, and conditional
rule logic have made it possible to model more complex systems and operational
requirements. The graphical user interface makes HEC-ResSim easy to use and the
customizable plotting and reporting tools facilitate output analysis. [Charalampos
Shaulikaris, 2008]
HEC Res Sim model was used in reservoir simulation for water release for power
production and flood control with different operation policy. This model has three
main modules: Watershed Setup, Reservoir Network and Simulation. In this model we
can make different management in reservoir system by defining scenarios in a time
series data. Model input data are: reservoir properties (Volume-Area and Elevation
Curve, Operation levels, Operation rules and etc) control and operation points and time
series input file. The highest capability of this model was
defining of different operation rules in power plant generation flood control
conditions, creating scenarios for conditional operation, downstream control point,
reservoir system balance to imitate the hydrological condition and
installing of different structures in dam body, comparison of output with observed
data, defining of different operational level, different computational steps (15 min to a
day) and adjustment of output results . [Charalampos Shaulikaris, 2008]
5.2 ResSim Modules
ResSim offers three separate sets of functions called Modules that provide access to specific
35
types of data within a watershed. These modules are Watershed Setup, Reservoir Network,
and Simulation. Each module has a unique purpose and an associated set of functions
accessible through menus, toolbars, and schematic elements.
5.2.1. Watershed Setup Module
The purpose of the Watershed Setup module is to provide a common framework for
watershed creation and definition among different modeling applications. This module is
currently common to HECResSim, HEC-FIA, and the CWMS CAVI.
A watershed is associated with a geographic region for which multiple models and area
coverages can be configured. A watershed may include all of the streams, projects (e.g.,
reservoirs, levees), gauge locations, impact areas, time-series locations, and hydrologic and
hydraulic data for a specific area. All of these details together, once configured, form a
watershed framework.
When a new watershed is created, Res Sim generates a directory structure for all files
associated with the watershed.
In the Watershed Setup module, items are assembled, that describe a watershed’s physical
arrangement. Once a new watershed is created, it is possible to import maps from external
sources, specify the units of measure for viewing the watershed, add layers containing
additional information about the watershed, create a common stream alignment, and configure
elements. Projects can be added and time-series icons can be created within the Watershed
Setup module.
5.2.2. Reservoir Network Module
The purpose of the Reservoir Network module is to isolate the development of the reservoir
model from the output analysis. In the Reservoir Network module, river schematic is built,
physical and operational elements of reservoir model are described, and alternatives are
developed for analyzing. Using configurations that are created in the watershed Setup module
as a template, basis of a reservoir network is created. Routing reaches are and possibly other
network elements to complete the connectivity of your network schematic. Once the schematic
is complete, physical and operational data for each network element are defined. Also,
alternatives are created that specify the reservoir network, operation set(s), initial conditions,
and assignment of DSS pathnames (time-series mapping).
36
5.2.3. Simulation Module
The purpose of the Simulation module is to isolate output analysis from the model
development process. Once the reservoir model is complete and the alternatives have been
defined, the Simulation module is used to configure the simulation. The computations are
performed and results are viewed within the Simulation module. When you create a
simulation you must specify a simulation time window, a computation interval, and the
alternatives to be analyzed. Then, ResSim creates a directory structure within the rss folder of
the watershed that represents the “simulation”. Within this “simulation” tree will be a copy of
the watershed, including only those files needed by the selected alternatives. Also created in
the simulation is a DSS file called simulation. dss, which will ultimately contain all the DSS
records that represent the input and output for the selected alternatives. Additionally, elements
can be edited and saved for subsequent simulations.
Figure: 5.1: Procedural Flow Chart
37
5.3 Model development
The centerline (stream alignment) of the watershed model includes the river
system and the reservoir created by the construction of 140 m high concrete dam.
The current study is performed considering the one and only priority of the
project is the power production and no obligation for downstream release.
However, 10% of stream flow has been targeted as minimum downstream
release. Future development of the model can feature one or more reservoirs and
other water management issues.
5.3.1. Input Data for HEC Res Sim
The reservoir is the key component in the most hydropower projects. It is the reservoir
that makes it possible to store water in periods with a large inflow and less demand, and
release it in periods with less inflow and larger demand. In other words, the reservoir
works as a "buffer" to reduce the problems that show up when inflow and demand do not
occur at the same time.
Following data is provided for each reservoir module to run HEC Resevoir Simulation:
1. Topographic map of the study area.
An AUTOCAD drawing containing physical features of the study area such as stream
alignments, location of reservoir, area of the reservoir, contour, impact area etc was
imported as background map. Then required model was drawn on the basis of the
background map. River alignment, reservoir area, impact area, river junctions,
computational points are the required physical data.
2. Hydrological Data.
Major computational points are included as the inlet and outlet of the reservoir. The
input for the inlet is the average daily stream flow calculated from the data recorded from
1964 to 1999. Mean monthly flow at the dam site is shown in Table 12 at Annex -
III .Similarly Input of Daily Stream Flow is shown in Table 4.4.
The area volume curve of the reservoir has been adopted from the study
conducted by JICA in 2007.Other required data as evaporation data, climate
data have been extracted from the feasibility study report by NEA in 2001.
38
Table 5.1: Monthly Average Flow (MAF) -Evaporation Rate (ER)
Source: NEA, 2001
Table 5.2: Reservoir Volume and Elevation
S.N Month MAF(m3/s)ER (mm/month)
1 Jan 27.03 69.09
2 Feb 23.72 91.97
3 Mar 24.01 152
4 April 27.43 176
5 May 41.07 184.5
6 June 113.84 200.7
7 July 287.22 191
8 August 322.61 189.4
9 Sept 225.77 166
10 Oct 112.43 129.4
11 Nov 52.01 80.3
12 Dec 34.36 64.76
39
S.NHeight
(m) Area(km^2) Volume(MCM)
1 310 0.02 0
2 315 0.15 0.42
3 320 0.32 1.59
4 325 0.46 3.54
5 330 0.56 6.1
6 335 0.71 9.29
7 340 1.10 13.82
8 345 1.29 19.81
9 350 1.48 26.74
10 355 1.73 34.77
11 360 2.11 44.38
12 365 2.38 55.6
13 370 2.88 68.74
14 375 3.37 84.35
15 380 3.85 102.4
16 385 4.36 122.93
17 390 4.79 145.78
18 395 5.20 170.74
19 400 5.73 198.06
20 405 6.23 227.95
21 410 6.70 260.25
22 415 7.26 295.14
23 420 7.92 333.08
24 425 8.67 374.57
25 430 9.82 420.79
26 435 11.24 473.45
Source: NEA, 2001
3. Time-Step
40
A daily time-step HEC-ResSim model was developed for the study to simulate the
1964-1999 period-of-records. The monthly average generated daily records have
been taken .This average stream flow data accounts for nearly 45 % probability
of exceedence. (Annex-III, Table 11)
4. Guide curve
A guide curve suggests the level of water at the reservoir at any time of the year.
Rule curves are simply elevations at each reservoir that help guide the operation (i.e.
drafting or filling)
Rule curves specify the highest and the lowest elevation that a reservoir should be
operated to in order to stay within the planning objective.
Intermediate rule curves help determine which projects release water first when
energy is needed.
Flood Control
– defines the drawdown required to assure adequate space to store the
anticipated runoff without causing downstream flooding (Maximum Elevation).
Critical Rule Curve
– defines how deep a reservoir can be drafted in order to meet the firm energy requirements during the poorest water conditions on record (Minimum Elevation).
5.4 Modeling the dams complex
The modeling of the Upper Seti Hydro Electric Project dam using HEC-ResSim is carried
out in a three phase process: the Watershed network setup, the parameterization of the dam's
components and the simulation of the different operational scenarios.
5.4.1 The watershed network setup
The initial phase of the modeling concerns the tracing of the connected flow elements
of the river watercourse between Dhulegauda and the dam site. Apart from the main
course, the modeling includes the placement of stream junctions at the
segments gathering the water drained from the various watersheds nourishing the Seti
River. An inlet computational point (CP3) has been artificially placed at the upstream end of
41
the reservoir in order to simulate the total inflow to the reservoir. Similarly an outlet
computational point (CP4) is placed at the dam outlet to simulate the release. The stream
junction points of the watershed are as follows:
Jyagdi Khola junction
Pirun Khola junction
Wantan Khola junction
Bange Khola junction
Kumle Khola junction
Guhe(Kumle Khola tributary) junction
Kyangdi Khola junction
Figure 5.2: Representation of the watershed in HEC-ResSim
5.4.2. The parameterization of the study dam
42
Following the geographic placement of the HEC-ResSim elements including main stream
segments, inflow point, dams with their connections to the main river stream as well as
outflow point , the next step of the HEC-ResSim set-up is the definition of the technical
parameters defining for dam: the geometric properties of the pool, the capability of the
hydropower plant and the definition of the various management constraints regarding
the electric power production, the regime of released flow and the operation in
conditions of flooding.
5.4.3. Operational Parameters
River flow catchment (Km2) 1502
Maximum discharge (m3/sec) 127
Full Supply level (F.S.L) (m) 425
Minimum operation level (M.O.L) (m) 370
Volume in (F.S.L) 106 m^3 374.57
Volume in (M.O.L) 106 m^3 68.74
Reservoir surface in F.S.L (Km2) 8.67
Tailrace water level (m) 289
Upper spillway level 385.82
Elevation of crest dam (m) 430
Height of dam (m) 140
Number of Turbine units 2
Total installed power (MW) 127
As an illustration of how HEC-ResSim dam parameters have been set, the detailed
process followed for the Upper Seti Dam is presented as follows:
5.4.4 Definition of the pool parameters
For the reservoir characteristics, the minimum operating level is 370 m and upper crest
of the gate is maintained at 320 m. This defines the lowest elevation from which it is
possible to release water. Below this level the storage capacity of the reservoir is considered
to be equal to zero since the stored water cannot be used. When the upper operation level is
reached at 425 m the volume of the stored water is 374.57 million m3 and the area
covered with water is 8.67 km2. HEC-ResSim provides various models of relation
43
between pool area and water height.
Table 5.3: Gate Settings
Elevation Max capacity (cms)for gate settings(m)
(m) 1 5 9 12.5
310 0 0 0 0
315 910.26 678.47 678.47 678.47
320 1322.58 1175.15 1006.33 1006.33
325 1633.97 1517.11 1390.45 1269.3
330 1894.87 1795.07 1689.38 1591.16
335 2123.95 2035.41 1942.84 1858.07
340 2330.62 2250.23 2166.86 2091.19
345 2520.41 2446.26 2369.8 2300.81
350 2696.87 2627.71 2556.67 2492.86
355 2862.47 2797.41 2730.79 2671.14
360 3019 2957.39 2894.46 2838.25
365 3167.81 3109.14 3049.35 2996.05
370 3309.94 3253.83 3196.74 3145.94
375 3446.2 3392.35 3337.64 3289.01
380 3577.29 3525.44 3472.82 3426.11
385 3703.73 3653.68 3602.93 3557.93
390 3826 3777.57 3728.5 3685.04
395 3944.48 3897.52 3849.99 3807.91
400 4059.5 4013.89 3967.75 3926.93
405 4171.35 4126.98 4082.12 4042.46
410 4280.29 4237.05 4193.37 4154.77
415 4386.51 4344.33 4301.74 4264.12
420 4490.23 4449.03 4407.45 4370.74
425 4591.6 4551.32 4510.68 4474.82
430 4690.78 4651.36 4611.61 4576.54
435 4787.91 4749.3 4710.37 4676.04
44
Capacity (cms)
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Ele
v (m
)
300
320
340
360
380
400
420
440
1.00-Elevation 5.00-Elevation
9.00-Elevation 12.50-Elevation
Figure 5.3: Gate settings curve
Table 5.4: Reservoir pool parameter
Elevation(m) Storage Area(m) (m^3) (ha)310 0.00 2.00315 420,000.00 15.00320 1,590,000.00 32.00325 3,540,000.00 46.00330 6,100,000.00 56.00335 9,290,000.00 71.00340 13,820,000.00 110.00345 19,810,000.00 129.00350 26,740,000.00 148.00355 34,770,000.00 173.00360 44,380,000.00 211.00365 55,600,000.00 238.00370 68,740,000.00 288.00375 84,350,000.00 337.00380 102,400,000.00 385.00385 122,930,000.00 436.00390 145,780,000.00 479.00395 170,740,000.00 520.00400 198,060,000.00 573.00405 227,950,000.00 623.00410 260,250,000.00 670.00415 295,140,000.00 726.00420 333,080,000.00 792.00425 374,570,000.00 867.00430 420,790,000.00 982.00435 473,450,000.00 1124.00
45
Stor (m3)
0 1.0E8 2.0E8 3.0E8 4.0E8 5.0E8
Ele
v (m
)
300
320
340
360
380
400
420
440
Area (ha)
0 200 400 600 800 1000 1200E
lev
(m)
300
320
340
360
380
400
420
440
Storage Capacity
Area
Figure 5.3: Area Storage Graph
Table 5.5: Input (Daily Stream flow)
Month/Day Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1 29.74 25.02 23.60 25.48 32.49 48.63 242.01 354.45 290.23 151.22 66.02 40.46
2 29.51 24.33 23.27 25.00 31.26 49.59 228.53 349.36 276.70 148.65 64.62 40.04
3 29.36 24.05 23.14 25.09 33.15 55.71 239.71 469.73 278.41 168.18 61.53 39.42
4 28.99 24.25 23.64 24.08 32.92 55.69 230.83 344.67 266.15 173.72 62.94 38.84
5 28.75 24.04 23.65 24.61 34.11 55.01 239.03 353.71 266.06 171.04 63.12 38.57
6 28.48 24.23 23.82 23.97 34.01 61.43 240.45 332.13 275.48 153.64 57.97 37.68
7 28.33 23.74 23.74 23.86 34.01 59.98 253.02 335.08 251.19 144.33 56.41 37.32
8 29.07 24.20 23.36 24.23 33.06 57.87 251.37 336.09 254.49 140.02 56.20 37.18
9 28.44 23.89 23.49 25.43 36.11 79.97 252.45 306.33 250.73 137.18 54.54 36.77
10 27.91 23.78 23.27 25.44 36.90 75.18 270.84 327.93 255.33 132.28 52.69 37.28
11 27.44 24.08 23.08 25.72 35.55 72.85 285.14 350.20 248.72 130.82 53.85 36.25
12 27.24 23.54 24.70 25.83 36.00 82.58 274.15 354.08 251.56 125.12 53.44 36.06
13 27.06 23.52 24.88 26.29 35.89 97.10 260.62 338.63 248.38 143.43 52.39 35.77
14 26.94 23.63 23.79 27.55 38.12 94.37 295.79 331.14 312.37 118.70 51.64 35.75
15 27.80 24.05 23.65 26.89 42.91 99.99 288.25 304.23 225.28 109.87 50.85 34.48
16 27.45 23.60 23.62 27.39 48.99 104.59 296.06 300.60 216.40 105.08 50.38 34.04
17 27.16 23.54 23.86 27.92 46.66 120.75 305.69 303.37 217.19 98.42 49.29 33.48
18 26.72 23.78 23.99 27.44 45.44 141.52 323.13 341.21 205.19 97.42 48.97 32.96
19 26.27 23.07 24.25 27.66 42.02 131.92 304.02 307.04 208.29 93.86 47.70 32.50
20 26.16 23.24 23.87 28.38 40.89 132.76 303.64 302.26 202.61 91.77 47.20 32.01
21 26.01 23.24 24.29 27.47 43.23 143.05 286.68 316.80 199.25 87.57 46.97 31.59
22 25.87 23.26 24.25 29.89 42.29 136.77 294.92 304.57 187.99 84.94 45.88 31.10
23 25.69 23.24 24.89 31.84 45.48 146.27 304.51 315.09 187.63 82.76 45.23 30.72
24 25.46 23.06 24.42 30.06 44.46 160.01 309.96 304.96 183.99 81.09 44.29 30.88
25 25.40 23.18 23.78 31.58 43.31 165.48 331.63 309.68 181.31 78.36 43.72 30.67
26 25.39 23.17 23.98 29.11 48.87 169.25 309.76 324.81 178.68 76.60 43.51 31.51
46
27 25.47 23.07 24.08 29.50 53.47 174.18 325.26 293.94 172.15 74.36 42.83 30.80
28 25.03 23.07 23.85 30.93 49.95 189.05 324.28 280.15 167.49 72.93 41.98 30.08
29 25.02 24.17 31.50 48.69 214.30 349.24 290.17 175.50 71.94 41.41 29.47
30 24.82 25.20 31.81 48.07 223.36 333.02 273.54 160.84 71.07 39.78 29.16
31 24.53 24.48 46.99 335.69 264.13 67.79 28.27
Avg 27.02 23.67 23.94 27.40 40.82 113.31 286.76 323.23 226.52 112.39 51.24 34.23
Source: NEA, 2001
5.4.5 The power plant parameters
In HEC-ResSim, the power plant module is used in order to define the electric power
generated by the turbines. The total installed capacity of the Upper Seti Plant is 127 MW
at the maximum discharge of 127.4 cumecs. The tail water elevation is set at 289.00 m.
The efficiency of the power plant is taken as 90%.The simulation performed in this study
is set to a daily time interval
5.4.6 Definition of Operational parameters
In HEC-ResSim, the dam operation is defined by three typical operation modes, also
called “zones”, which are respectively called: Flood control, Conservation and Inactive.
These “zones” of operation are based on specific reservoir elevations and contain a set of
rules that describe the goals and constraints that should be followed when the reservoir's pool
elevation is within a particular zone.
Operation zones are provided for each month. For each mode of operation (zone), the rules
are ordered by priority. The HEC- ResSim ad-Hoc algorithm attempts to fulfill the
requirements of the highest priority rule, if these are successfully reached, the program
switches to the next rule and will proceed in the same fashion.
5.4.7 The flow requirements for environmental constraints
As my study is primarily aimed at studying the possible benefits of the
Upper Seti project in terms of maximum power production, particular focus has been put
on the flow requirements necessary to meet this goal the environmental obligation as well.
Regarding the state of the environment, it has been assumed that 10 % of original river
flow will be set as minimum downstream release.
5.4.8 Operational Strategy
Identifying the optimum operating strategy is one of the major tasks of water resource
planning. The approach is always based on how to manage or run the reservoir during
47
each time-step. The reservoir must be operated in accordance with a predefined strategy.
The strategy alternatives are:
• Automatic reservoir balancing
• Reservoir release specification
• Reservoir guide curve
One of these strategies must be used for reservoir defined.
Development of Reservoir guide curve is one of the objectives to be provided for the
operation of reservoir. The reservoir guide curve tells us how the reservoir should be
operated most economically.
VI. RESULTS AND DISCUSSION
The study was conducted for the optimum operation of the reservoir of USHEP
using HEC Reservoir Simulation model. Since the only priority of the project is the
power production, simulation was carried out for maximum of power generation.
As an environmental mandatory release minimum of monthly inflow was allocated
as downstream release. For this purpose, two different scenarios were analyzed.
6.1 Scenario 1: When reservoir sediment flushing operation is carried out.
Sedimentation in reservoir is a serious problem wherein the live storage capacity is
decreased effecting the operation of the reservoir. In this case, the sediment
flushing facilities were proposed at the lowest possible elevation, thus the sill level
of the facilities was decided at Elevation 320 .00m as recommended by JICA study
in 2007.
The reservoir water level is lowered less than MOL during the sediment flushing
operation which is carried out during rainy season, so power generation is at
minimum during this operation. It is estimated that suspension of power generation
of the Project in the rainy season does not affect electricity supply in national grid
48
because other ROR type plants can supply sufficient electricity during this period.
The sediment flushing operation is carried out in former half of the rainy season
because flood forecast network is not prepared in Nepal, the sediment flushing
operation may not be completed within the rainy season if the operation is planned
in the period of season in which inflow of river water decreases.
According the daily river discharge record, the average monthly discharge gets to
the maximum in August ,so it is not desirable that the sediment flushing operation
is carried out in August so that river flows through sediment flushing facilities. It is
desirable that the sediment flushing operation is carried out in June so that
secondary electricity generation decreases due to flushing operation as little as
possible.
The results obtained shows that maximum power can be generated during August
and September and gradually decreases as the inflow is decreased with the
reservoir level is maintained at FSL. During January, the power produced increases
as the drawdown begins. Simulated results are shown in Table 5.1.
Table 6.1: Scenario 1 Results
Simulated Jan Feb Mar Apr May JunParameters Inflow (cm) 27.02 23.67 23.94 27.40 40.82 113.31Reservoir Storage(Mcm) 340.70 270.04 204.56 155.36 92.74 16.20Reservoir Elevation(m) 420.85 411.35 401.34 391.53 376.81 335.79Power generated(MW) 62.10 51.97 43.22 38.94 51.62 4.88Total Energy(GWh) 46.20 34.92 32.16 28.04 38.41 3.39Plant Factor 0.49 0.41 0.34 0.31 0.41 0.04Release for Power(m^3) 53.31 48.54 43.65 42.75 65.35 12.69Target Elevation (m) 419.50 408.50 397.50 386.50 375.50 345.00
Table 6.1: Scenario 1 Results (contd...)
Simulated Jul Aug Sep Oct Nov DecParameters Inflow (cm) 286.76 323.23 226.52 112.39 51.24 34.23Reservoir Storage(Mcm) 24.58 209.08 374.59 374.55 374.57 374.42Reservoir Elevation(m) 344.66 399.69 425.00 425.00 425.00 424.98
49
Power generated(MW) 56.81 127.00 127.00 107.48 54.61 36.72Total Energy(GWh) 42.27 94.49 94.49 79.97 39.32 27.32Plant Factor 0.44 1.00 1.00 0.85 0.43 0.30Release for Power(m^3) 111.69 134.30 107.08 90.63 46.04 30.96Target Elevation (m) 346.25 398.75 425.00 425.00 425.00 425.00
The guide curve developed suggested that the following ideal criteria for operational
purpose:
1. The reservoir is operated for 6 hours daily during dry period.
2. The power station is operated 24 hours in wet period.
3. The drawdown in the reservoir, if required, starts on January 1.
4. The reservoir is at MOL on June1, if possible.
5. The reservoir flushing operation starts on June 1 and is expected to
take 20 days to lower the reservoir level to sill level of the sediment flushing gates.
6. The reservoir sediment flushing gates are closed on July 31.
7. Filling of the reservoir starts on August 1, if not earlier.
8. The reservoir is full on September 1, if not earlier.
9. Inflow of the river and plant discharge is equal for the month of October and the
reservoir is full, if possible.
10. Minimum downstream discharge (10%) shall be spilled during
October to June, if possible.
11. If more water is available in the month of July, August and September than utilized by
the optimum plant capacity, it will be spilled.
12. Dry season energy is the available from the month of November to
May.
13. Wet season energy is available energy for the months June to
October.
The reservoir operation curve developed is as shown in figure below.
50
Figure 6.1: Rule curve for scenario 1
51
6.2 Scenario 2: When no sediment flushing operation carried out and inflow is
reduced by 20 %.
In this case, the inflow is reduced by 20 % of the input provided in scenario 1.Other
physical parameters of the reservoir are similar to those of the scenario 1.Daily
Simulation is carried out for every month .Results show that the power production
decreases uniformly as the inflow decreases. The water level drops to MOL (370.00 m)
during the month of June wherein the storage drops to an average of 83.54 MCM. The
power generated is to maximum capacity during July, August and September. (127
MW).Due to increased inflow the water level increases and attains FSL (425.00 m)
during September. The water level is maintained at FSL up to the month of December
before the drawdown starts from the month of January.
Table 6.2: Scenario 2 Results
Simulated Jan Feb Mar Apr May JunParameters Inflow (cm) 21.62 18.94 19.15 21.92 32.66 90.65Reservoir Storage(Mcm) 339.66 269.42 210.04 159.45 117.34 83.54Reservoir Elevation(m) 420.55 411.35 402.18 392.67 383.48 374.28Power generated(MW) 52.80 45.01 36.85 33.69 35.93 75.70Total Energy(GWh) 42.57 29.13 31.14 22.86 26.01 53.47Plant Factor 0.45 0.34 0.33 0.24 0.28 0.57Release for Power(m^3) 56.76 40.88 43.19 35.06 35.93 102.45Target Elevation (m) 419.50 408.50 397.50 386.50 375.50 370.00
Table 6.2: Scenario 2 Results (contd...)
Simulated Jul Aug Sep Oct Nov DecParameters Inflow (cm) 229.41 258.58 181.22 89.91 40.99 27.38Reservoir Storage(Mcm) 95.48 303.17 374.57 374.57 374.57 374.57Reservoir Elevation(m) 377.52 415.34 425.00 425.00 425.00 424.98Power generated(MW) 127.00 127.00 127.00 99.31 47.03 30.96Total Energy(GWh) 3048.00 3048.00 2961.20 1228.10 805.80 0.00Plant Factor 1.00 1.00 0.97 0.40 0.26 0.00Release for Power(m^3) 120.01 107.05 103.44 42.48 27.89 0.00Target Elevation (m) 383.75 411.25 425.00 425.00 425.00 425.00
The guide curve developed suggested that the following ideal criteria for operational
52
purpose:
1. The reservoir is operated for 6 hours daily during dry period.
2. The power station is operated 24 hours in wet period.
3. The drawdown in the reservoir, if required, starts on January 1.
4. The reservoir is at MOL on June1, if possible.
5. The reservoir water level is maintained at MOL up to July 1 to make room for
expected flood.
6. Filling of the reservoir starts on August 1, if not earlier.
7. The reservoir is full on September 1, if not earlier.
8. Minimum downstream discharge (1 cumecs) shall be spilled during October to
June, if possible.
9. If more water is available in the month of July, August and September than
utilized by the optimum plant capacity, it will be spilled.
10. Dry season energy is the available from the month of November to May.
11. Wet season energy is available energy for the months June to October.
Summary of the results obtained from scenario 2 are tabulated below.
The reservoir operation curve developed is as shown in fig 5.8:
53
54
Figure 6.2: Rule curve for scenario 2
55
6.3 Scenario 3: When no sediment flushing operation carried out.
In this case, the inflow provided is similar as in scenario 1.Other physical parameters of
the reservoir are similar as well. Daily Simulation is carried out for every month .Results
show that the power production decreases uniformly as the inflow decreases. The water
level drops to MOL (370.00 m) during the month of June wherein the storage drops to an
average of 82.24 MCM. The power generated is to maximum capacity during July,
August and September. (127 MW).Due to increased inflow the water level increases and
attains FSL (425.00 m) during September. The water level is maintained at FSL up to the
month of December before the drawdown starts from the month of January. The guide
curve developed is similar to that of scenario 2.
Table 6.3: Scenario 3 Results
Simulated Jan Feb Mar Apr May JunParameters Inflow (cm) 27.02 23.67 23.94 27.40 40.82 113.31Reservoir Storage(Mcm) 333.56 270.21 211.11 161.64 100.93 82.24Reservoir Elevation(m) 419.95 411.39 402.14 393.13 379.18 374.20Power generated(MW) 63.08 49.87 43.21 39.61 46.67 87.72Total Energy(GWh) 46.93 33.66 32.15 29.47 34.72 63.16Plant Factor 0.50 0.39 0.34 0.31 0.37 0.69Release for Power(m^3) 54.50 47.11 43.68 43.53 59.21 118.92Target Elevation (m) 419.50 408.50 397.50 386.50 375.50 370.00
Table 6.3: Scenario 3 Results (contd...)
Simulated Jul Aug Sep Oct Nov DecParameters Inflow (cm) 0.00 0.00 0.00 0.00 0.00 0.00Reservoir Storage(Mcm) 218.36 374.57 374.57 374.57 374.57 0.00Reservoir Elevation(m) 403.40 425.00 425.00 425.00 425.00 425.00Power generated(MW) 127.00 127.00 127.00 60.47 49.82 0.00Total Energy(GWh) 3048.00 3048.00 3048.00 1451.20 1195.70 0.00Plant Factor 1.00 1.00 1.00 0.48 0.39 0.00Release for Power(m^3) 122.88 107.07 106.84 50.96 42.18 0.00Target Elevation (m) 383.75 411.25 425.00 425.00 425.00 425.00
Figures 6.3 to 6.9 shows the comparative graphs of all the scenarios mentioned above.
56
0.00
50.00
100.00
150.00
200.00
250.00
300.00
350.00
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00
Months
Infl
ow
(Cu
mec
s)Scenario 1 and 3
Scenario 2
Figures 6.3: Inflow Curve
0.00
50.00
100.00
150.00
200.00
250.00
300.00
350.00
400.00
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00
Months
Res
ervo
ir S
tora
ge(
MC
M) Scenario 1
Scenario 2
Scenario 3
Figures 6.4: Reservoir Storage Curve
57
0.00
50.00
100.00
150.00
200.00
250.00
300.00
350.00
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00
Months
Infl
ow
an
d R
ele
as
e(C
um
ec
s)
Inflow 1 and 3
Q-Power 1
Inflow 2
Q-Power 2
Q-Power 3
Figures 6.5: Inflow and Release Curve
300.00
320.00
340.00
360.00
380.00
400.00
420.00
440.00
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00
Months
Re
se
rvo
ir E
lev
ati
on
(m)
Scenario 1Scenario 2Scenario 3Target 1Target 2 and 3
Figures 6.6: Reservoir Elevation Curve
58
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00
Months
Po
wer
(M
W)
Scenario 1
Scenario 2
Scenario 3
Figures 6.7: Power Production Curve
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00
Months
To
tal
En
erg
y(G
Wh
)
Scenario 1
Scenario 2
Scenario 3
Figures 6.8: Annual Energy Generation Curve
59
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00
Months
Pla
nt
Fac
tor
Scenario 1
Scenario 2
Scenario 3
Figures 6.9: Plant Factor Curve
6.4 Validation of results
In order to gain confidence that the HEC-ResSim model developed for the Upper
Seti Hydroelectric Project is acceptable for modeling and simulating the operating
plants, comparison is done with other study results conducted by NEA and
JICA. The models used by NEA and JICA were "Reservoir Simulation
Version 1.0" and EPDC/KCC FLOW 500 MODEL respectively. The
comparision charts are shown below:
Table 6.4: Comparision chart-1 (With Sediment Flushing)
S.NAverage Head
Optimum Plant
Plant Capacity Wet season Dry season
Annual Energy
(m) Capacity(MW) Energy(GWh) Energy(GWh) (GWh)
JICA 116.2 126 0.52 344 230.1 574.1
Current Study 109.5 127 0.505 314.6 246.35 560.95
Table 6.5: Comparision chart-2 (Without Sediment Flushing)
60
S.NAverage Head
Optimum Plant
Plant Capacity Wet season Dry season
Annual Energy
(m) Capacity(MW) Energy(GWh) Energy(GWh) (GWh)
NEA 111.04 122.2 0.555 422.43 171.93 594.36
Current Study 114 127 0607 425.11 253.43 678.54
These validation results show that the HEC-ResSim model developed for the
current study shows good reflection with the results obtained from the NEA and
JICA model simulations and can be used to assess the relative impacts of the
various operating plans on the Reservoir system of Upper Seti Project. It can be
concluded that the HEC Reservoir Simulation model has proved to be flexible
enough to adequately simulate the operating plans for reservoir.
VII. CONCLUSIONS AND RECOMMENDATIONS
61
7.1. Conclusion
The conclusions that can be drawn from this study are as follows:
1. The application of simulation models is one of the most efficient ways of analyzing
water resources systems, which is based on physical relations accompanied by a series
of operational rules attempting to simulate a phenomena as close as possible to reality
and the system behavior under a specified policy. HEC-ResSim is one of the
simulation models that possess of multi reservoir simulators and can simulate water
resources systems. In this research, performance of Upper Seti storage dam and its
water supply was evaluated. Model verification results of Upper Seti reservoir indicate
that, this model is able to simulate the behavior of the system very well.
2. The results obtained from the simulation suggest that it is in close agreement with the
results of the feasibility study prepared by JICA in 2007.The rule curve suggested by
the present study shows the reservoir is filled by September 1.The study suggests that
reservoir be filled maximum in the first day of September instead of December. Water
level should be allowed to go below the FSL before the start of dry season so that
peak demand can be fulfilled.
3. Results obtained from scenario 1 suggest that sediment flushing operation can be
carried out before the start of rainy season. Inflow considered was 45 % probability
of exceedence and this inflow is enough to recover the water level to FSL before the
end of wet season.
4. Results obtained from scenario 2 suggest that production of energy is not affected
even by decreasing the inflow by 20 % .Inflow considered was 70 % probability of
exceedence and this inflow is also enough to recover the water level to FSL before
the end of wet season.
5. Results obtained from scenario 3 suggest that higher plant factor is achieved than
previous scenarios and annual energy generation is increased by 17.32% and 8.68%
than scenario 1 and scenario 2 respectively.
6. Total annual generation of energy with and without sediment flushing facilities is
560.95 GWh and 678. GWh respectively, whereas, 619.63 GWh energy is generated
when sediment flushing facilities are not carried out and inflow decreased by 20% of
previous scenarios. This shows that higher plant factor is obtained if sediment
flushing is not carried out but it would decrease the live storage of the reservoir in
62
future.
7.2. Recommendations
Based on the present study, following recommendations are made for further work:
1. The present study is done with generated daily stream flow data. Simulation is
done for a typical year taking average of the generated data. It is recommended that
simulation to be done for every year i.e from 1964 to present.
2. Due to time and study limitations, the study focused on the power generation only. It
is recommended that other aspects of the simulation like downstream routing,
provision of multiple reservoirs could be taken into account.
3. The present study has performed with simple operation rules. HEC Res Sim is
equipped with advanced operating system which also includes scripted operation
rules. This allows the project to be studied with more elaborate operation rules.
4. It is recommended to perform the simulation taking in consideration of reservoir
sedimentation.
5. Reliability, resiliency and vulnerability indices were not used for system evaluation.
These model verification results indicate would further help in establishing it as a
powerful tool in reservoir simulation.
REFERENCES
63
1. Beard L.R., 1975. Models for optimizing the multipurpose operation of
a reservoir system. Proceedings of Application of Mathematical Models in
Hydrology and Water Resources Systems, Bratislava 1975, pp. 13-21.
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65
Annex A: Monthly Operation curves
A1: Operation for January
66
A2: Operation for February
Fig A3: Operation for March
A4: Operation for April
67
A5: Operation for May
A6: Operation for June
Fig A7: Operation for July
68
Fig A8: Operation for August
Fig A9: Operation for September
Fig A10: Operation for October
69
Fig A11: Operation for November
Fig A12: Operation for December
70
Annex B: Monthly Power Production curves
71
B1: Power for January
B2: Power for February
B3: Power for March
72
B4: Power for April
B5: Power for May
B6: Power for June
73
B7: Power for July
B8: Power for August
B9: Power for September
74
B10: Power for October
B11: Power for November
B12: Power for December
75
Annex C: Tables
76
C1 - Table:Probability of Exceedance of flow at Dam Site
SN ExceedenceDischarge Equalled or Exceeded(Cumecs)
Janaury Feb March April May June July Aug Sep Oct Nov Dec
1 0% 39.85 36.60 36.11 40.78 68.91 255.88 445.10 460.52 319.36 326.56 85.89 53.81
2 5% 37.09 33.68 33.54 39.22 63.95 188.31 425.60 448.37 313.19 175.77 75.75 48.96
3 10% 35.44 32.78 31.74 36.78 59.12 169.23 390.80 429.28 292.85 144.43 68.69 44.32
4 15% 33.72 30.70 30.14 34.07 54.47 152.67 380.67 410.96 273.87 137.29 60.31 41.07
5 20% 33.02 29.58 29.80 32.62 51.25 150.99 343.35 389.00 264.03 129.86 57.50 39.24
6 25% 31.90 28.33 29.72 31.19 48.70 147.29 334.08 374.10 252.78 125.15 56.09 39.00
7 30% 30.64 27.63 27.87 30.34 46.58 129.74 320.26 365.49 250.88 119.80 55.87 37.73
8 35% 29.90 26.33 27.17 29.80 40.75 114.94 309.58 347.78 247.12 113.54 54.62 36.32
9 40% 28.12 24.00 26.47 29.13 40.07 111.73 291.21 328.44 242.69 111.56 54.23 35.63
10 45% 27.35 23.17 25.46 28.86 39.05 107.04 288.18 320.68 238.99 107.83 53.24 34.18
11 50% 25.49 21.90 24.70 28.61 38.46 102.18 280.50 320.09 219.37 106.64 51.86 33.80
12 55% 25.06 21.16 21.59 26.38 37.43 96.65 270.09 313.90 215.54 105.17 50.01 33.43
13 60% 24.71 20.61 21.10 25.27 36.80 92.91 264.43 300.57 212.78 102.64 49.27 33.31
14 65% 24.32 20.44 20.78 24.87 35.66 91.84 258.44 287.91 203.97 96.29 45.59 31.92
15 70% 23.62 20.38 19.70 24.33 34.94 88.07 247.84 279.18 199.78 87.81 44.12 30.98
16 75% 23.08 19.94 18.83 23.46 34.42 83.81 230.90 267.82 193.15 85.04 43.59 30.47
17 80% 22.32 18.66 18.00 22.82 31.00 77.94 228.35 259.65 185.77 79.47 43.27 27.33
18 85% 20.78 17.82 16.76 20.34 28.84 73.35 220.57 243.71 177.83 69.85 40.72 26.13
19 90% 20.09 17.41 15.93 19.00 26.02 70.70 198.38 235.62 166.98 65.14 37.11 25.77
20 95% 18.32 14.78 14.99 14.90 23.50 62.04 171.68 209.30 152.36 62.39 32.06 21.68
21 100% 10.52 9.93 11.28 11.93 16.63 34.36 127.99 193.91 141.59 37.74 17.67 12.93
0
50
100
150
200
250
300
350
400
450
500
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Probability of Exceedance (%)
Dis
char
ge
(m3/
s)
Jan
Feb
Mar
Apr
May
Jun
July
Aug
Sep
Oct
Nov
Dec
77
C - 2: Mean monthly flows at the dam site
Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1964 31.80 30.40 30.10 31.90 68.90 78.00 134.30 460.50 313.10 112.40 82.00 53.80
1965 34.00 29.50 29.70 32.70 36.30 151.00 293.50 368.50 190.30 62.60 46.90 31.30
1966 24.60 22.20 21.00 19.40 22.20 63.50 228.40 259.60 159.80 66.00 48.60 25.50
1967 20.60 20.70 20.10 22.80 24.50 57.80 231.30 213.20 185.80 77.20 43.50 33.80
1968 24.90 20.50 24.70 25.30 34.90 141.90 336.10 287.00 222.70 326.60 42.10 23.70
1969 18.30 14.60 15.20 15.00 16.60 34.40 128.00 315.00 264.00 79.50 40.30 26.10
1970 20.20 17.30 16.30 24.60 35.30 91.20 380.80 412.00 202.10 106.10 56.80 33.40
1971 23.70 18.70 18.80 29.10 39.60 187.70 291.20 300.60 212.80 145.70 67.70 40.00
1972 25.70 20.30 19.40 20.50 52.90 106.60 325.60 362.50 251.60 108.60 51.40 33.40
1973 25.10 17.60 18.00 25.80 39.20 176.30 244.00 389.00 265.30 259.40 74.40 39.20
1974 36.80 33.70 32.60 40.80 39.00 91.70 343.30 411.60 254.40 131.70 43.80 34.10
1975 33.00 32.10 30.20 22.80 24.00 84.90 427.00 328.40 305.50 139.20 54.10 30.40
1976 22.30 23.10 19.80 24.90 40.90 190.20 380.30 342.30 216.00 88.40 43.60 33.80
1977 22.70 20.40 20.70 30.20 46.80 92.40 288.50 409.00 428.30 111.80 74.80 43.30
1978 32.30 29.60 27.20 29.40 68.70 162.10 381.00 349.60 215.60 106.00 64.30 47.70
1979 37.70 33.70 29.80 37.70 51.90 84.70 315.00 447.00 239.40 107.20 57.50 34.60
1980 25.20 22.90 25.30 26.60 37.10 107.90 425.10 446.50 313.70 82.50 43.80 26.20
1981 18.20 14.90 15.60 28.70 40.10 95.50 400.60 376.50 242.70 97.00 50.20 36.90
1982 33.30 30.80 36.10 40.10 48.90 96.90 257.70 271.30 155.50 85.90 54.50 45.30
1983 39.80 36.60 35.30 34.50 46.70 72.80 210.40 270.50 276.70 143.20 54.70 35.60
1984 28.00 21.20 21.70 24.00 62.80 151.90 445.10 287.30 243.50 96.10 58.60 41.30
1985 36.90 33.50 33.00 39.10 61.10 114.90 333.40 197.50 202.90 126.20 56.50 36.00
1986 24.70 19.80 21.40 28.50 27.90 117.60 260.70 259.80 280.20 147.90 59.20 30.70
1987 23.50 20.40 21.40 23.60 31.20 72.20 280.00 279.50 183.60 87.30 54.20 39.20
1988 30.20 26.80 27.00 28.80 40.70 111.70 264.40 320.50 238.90 102.60 52.90 38.60
1989 33.90 27.80 27.80 30.50 59.40 146.60 251.70 310.70 240.20 113.90 53.80 36.40
1990 28.10 24.80 26.00 35.90 55.20 152.90 271.90 237.30 194.10 102.80 44.50 27.30
1991 20.00 17.60 16.80 20.30 33.40 114.90 281.00 320.40 250.20 117.20 56.30 39.00
1992 31.10 27.90 26.50 25.20 35.70 82.00 188.90 289.80 197.40 124.80 50.30 30.50
1993 23.20 20.60 14.50 14.70 30.00 97.80 218.40 321.30 215.40 122.40 56.80 33.30
1994 29.30 27.50 29.80 30.10 37.00 106.80 184.20 233.90 142.80 37.70 17.70 12.90
1995 10.50 9.90 11.30 11.90 28.30 255.90 314.90 193.90 175.90 129.90 85.90 52.70
1996 30.10 21.60 30.90 31.00 37.60 69.20 227.00 319.80 252.20 107.60 45.80 31.50
1997 27.20 24.00 28.40 32.60 38.40 74.90 229.60 258.90 141.60 61.80 35.00 33.10
1998 24.20 21.50 24.90 29.10 48.70 149.30 288.10 452.60 207.30 64.20 35.60 26.00
1999 21.30 17.90 17.00 18.80 34.80 93.10 264.80 238.70 174.20 67.40 23.10 15.30
max 39.80 36.60 36.10 40.80 68.90 255.90 445.10 460.50 428.30 326.60 85.90 53.80
mean 27.01 23.68 24.01 27.41 41.02 113.31 286.84 320.63 229.33 112.41 52.26 34.22
min 10.50 9.90 11.30 11.90 16.60 34.40 128.00 193.90 141.60 37.70 17.70 12.90
972.40 852.40 864.30 986.90 1476.70 4079.20 10326.20 11542.50 8255.70 4046.80 1881.20 1231.90
78
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mean Montly Flow
Flo
w (
m3
/s)
C – 3: Probability of Exceedance of flow at Dam SiteSN Exceedence Discharge Equalled or
79
Exceeded (cumecs)1 0% 460.502 5% 338.893 10% 288.024 15% 254.935 20% 215.566 25% 165.137 30% 120.968 35% 96.229 40% 72.56
10 45% 56.5211 50% 46.7512 55% 39.2013 60% 35.7814 65% 33.3915 70% 30.5016 75% 28.4817 80% 25.7218 85% 23.6719 90% 20.7020 95% 17.9621 100% 9.90
0
50
100
150
200
250
300
350
400
450
500
0% 20% 40% 60% 80% 100%Probability of Exceedance (%)
Dis
char
ge
(m3/
s)
C – 4: Probability of Exceedance of flow at Dam Site
SN ExceedenceDischarge Equalled or
Exceeded (cumecs)
80
1 0% 460.502 1% 439.893 2% 411.754 3% 381.565 4% 367.066 5% 338.897 6% 325.748 7% 318.989 8% 313.41
9.1 9% 294.9910 10% 288.0211 11% 280.1212 12% 271.4713 13% 264.3914 14% 259.5315 15% 254.9316 16% 250.2617 17% 239.9818 18% 235.3319 19% 227.1520 20% 215.5621 21% 208.8222 22% 197.4223 23% 190.0324 24% 183.9425 25% 165.1326 26% 151.8527 27% 146.2728 28% 141.7029 29% 129.9230 30% 120.9631 31% 114.2932 32% 108.8533 33% 106.7534 34% 102.6935 35% 96.2236 36% 91.6237 37% 85.9038 38% 82.1139 39% 76.9940 40% 72.5641 41% 67.9942 42% 64.1943 43% 61.5744 44% 58.0945 45% 56.5246 46% 54.4247 47% 53.2948 48% 51.4649 49% 48.6850 50% 46.75
81
51 51% 43.9352 52% 43.1653 53% 40.7654 54% 40.0355 55% 39.2056 56% 38.8657 57% 37.7058 58% 36.9059 59% 36.3760 60% 35.7861 61% 35.3062 62% 34.5863 63% 33.9564 64% 33.7065 65% 33.3966 66% 33.0067 67% 32.3768 68% 31.4869 69% 30.9670 70% 30.5071 71% 30.2072 72% 30.0773 73% 29.6474 74% 29.1175 75% 28.4876 76% 27.9477 77% 27.5478 78% 26.9679 79% 26.1580 80% 25.7281 81% 25.2082 82% 24.9083 83% 24.6384 84% 24.0085 85% 23.6786 86% 23.1087 87% 22.7088 88% 21.6789 89% 21.3490 90% 20.7091 91% 20.4892 92% 20.2593 93% 19.8094 94% 18.7995 95% 17.9696 96% 17.3797 97% 16.2598 98% 14.9699 99% 13.40
100 100% 9.90
82
Flow Duration Curve
0
50
100
150
200
250
300
350
400
450
500
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Probability of Exceedence (%)
Dis
char
ge
(m3/
s)
83