Topic : Hydrology, Run-off Measurement Instruments & Site Analysis.

GROUP MEMBERS :1. SHANKAR SHEGADE2. DINESH PATIL3. RAVEEN RAMANAN4. MAHESH YENNAM5. ASHISH SINGH

Contents

Introduction-Hydrology. Hydrological Cycle. Literature Review Runoff (Definition, Needs & Factors). Runoff Measurement Methods. Runoff measuring instruments. Factors considered for Site Analysis of Hydro-Electric

power plants. Case Study.

Introduction• The science of hydrology deals with the occurrence and distribution

of water over and above the earth’s surface.• Hydrology is that branch of physical science, which deals with the

origin, distribution, and properties of water of the earth. • It deals with the transportation of water through the air, over the

ground surface and through the earth strata. • The knowledge of hydrology is of basic importance in all walks of life

that involve the use and supply of water for any purpose what so ever.

• Therefore the knowledge of hydrology is not only useful in the field of engineering, but also in agriculture, forestry and other branches of natural sciences.

HYDROLOGICAL CYCLE

A hydrological cycle involves the following processes :-

1) Precipitation (Rainfall, Snowfall, Dew & Mist). It Varies by :-a. Amountb. Intensityc. Form by Seasond. Geographic Location.

2) Interception (precipitation that does not reach the soil, but is instead intercepted by the leaves and branches of plants and the forest floor).

3) Infiltration (It is the process by which water on the ground surface enters the soil).Depends on :-

I. soil characteristicsII. Rainfall intensity.

4) Transpiration (process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers).

5) Evaporation 6) Condensation7) Surface Run-off (flows over the land surface).8) Sub-Surface Run-off (water that infiltrates in soil).

Literature Review SR. NO

Authors & Year Title Conclusion

1. R. D. Stewart1, Z. Liu2, D. E. Rupp3, C. W. Higgins2, and J. S. Selker2. (2015)

Instrument to measure plot-scale runoff.

The instrument is accurate low cost simple reliable and proper choice measuring runoff.

2. Bhoumika Sahu1, Sanjiv Kumar2 , Dhananjay Kumar Sahu3 ,Brijesh patel4,Kalpit P. Kaurase5. (2015)

Performance of Gangrel Hydroelectric PowerPlant.

Should increase the use of renewable energy sources and reduce the use of non-renewable resources.

3. Imran Ahmed, Siraj Y. Abed. (2014)

A SIMULATION MODEL FOR STAGE –IV KOYNA HYDROPOWER PLANT

The model helped to identify the optimal values of different input parameters namely head, flow rate & turbine efficiency which are key elements to maximize power generation.

4. Meenakshi Lohani. (2014) Impact of Landuse Change on Hydrology:A Case Study of Gurgaon City.

Groundwater harvesting is essential for the region. Rain water Harvesting should be made mandatory for new constructions.

5. T.S.Mehra1), N.I.Alvi1) , A.Rajasekhar1). (2007)

Tawa Hydroelectric power plant.

The encouraging performance shown by the Tawa project itself set an example for inviting private investment in the small Hydro Power Project sector.

Runoff• The water available after hydrological process in the form of stream flows,

rivers, lakes, etc is known as Runoff. Mathematical form,

Runoff(R) = Precipitation(P) – Losses(L)

Runoff(R) = Surface runoff + Subsurface runoff

Need of Runoff

Design of drains, canals & other channels. Prediction of water levels in streams & rivers. Storage for irrigation, power generation, river transport.

Rainfall Pattern. Character of catchment area. Hill slope. Vegetation. Weather condition. Geology of area.

Factors affecting the runoff

Run-Off Measurement Methods

It can be measured by the following methods-1. From rainfall records

2. Empirical formulaea) Khosla’s formula

R-Annual run-off in mm.P-Annual rainfall in mm.T-mean temperature in ˚C.

b) Inglis formula for areas of MaharashtraFor ghat region,

For plain region,

R = 0.88 P – 304.8

R = (P-177.8) x P / 2540

R = P - 4.811 T

Run-off over the catchment = rainfall x coefficient

c) Lacey’s formula

R = monsoon run-off in mm.S = catchment area factor.F = monsoon duration factor.P = monsoon rainfall in mm.

Type of catchment

Value of S

Flat, cultivated & black cotton soils

0.25

Flat, partly cultivated, various soils

0.6

Average catchment

1.0

Hills & place with little cultivation

1.70

Very hilly & steep, with hardly any cultivation

3.45

Class of monsoon

Value of F

Very short 0.50

Standard length 1.00

Very long 1.50

R = P / (1 + 3084 F / PS)

3. Run-off curves

a. Hydrograph(Discharge v/s Time(months) Graph) It indicates the power

available from the stream at different times of day, week, month or year

b. Flow duration curve(Discharge v/s Time(%) Graph) Flow duration curves are

most useful for preliminary studies and for comparison between streams.

Mass CurveCumulative discharge v/s Time Graph.

4. Discharge observation method To find out the sub-surface run-off it is essential to separate the subsurface flow

from the total flow. The separation can be on an approximate basis but with correct analysis.

Runoff Measuring Instruments• In field most commonly used devices

for measuring water runoff are-

1. Weirs2. Pre shall flumes3. Orifices4. Meter gates.

1. Weirs: Weirs are used to measure the flow of runoff; an irrigation channel or discharged

of a well or channel outlet at the source.Discharge can be Summarised as:

where Q = flow rate of fluid C = constant for structure L = width of the crest H = height of head of water over the crest n = varies with structure.

Types of weirs :- 1. Sharp Crested: A. Rectangular weir (comparatively large discharge).

Q = CLHn

2. Broad crested.Broad crested weirs are robust structures that are generally constructed from

reinforced concrete and which usually span the full width of the channel.

B. Cipolletti weir (medium discharge).

C. V-notch weir (small discharge).

2. Pre shall flumes

3. Orifices

Factors considered for Site Analysis of Hydro-Electric power plants

1. Availability of water– All other designs are based on it.– Estimate should be made about the average quantity of water available throughout the year and

also about maximum and minimum quantity of water available during the year.– These details are necessary to decide the capacity of the hydropower plant, and– It also provide adequate spillways or gate relief during flood period.

2. Water storage– Since there a is wide variation in rainfall during the year, therefore it is necessary to store the water

for continuous generation of power. The storage capacity can be calculated with the help of mass curve.

– The two types of storages in use are1. The storage is so constructed that it can make water available for power generation for one

year only.2. Water is available in sufficient quantity even during the worst dry periods.

3. Water head– In order to generate a requisite quantity of power it is necessary that a large quantity of water at

sufficient head should be available.– An increase in effective head for a given output, reduces the quantity of water required to be

supplied to the turbines.

4. Accessibility of site– The site where hydro-electric plant is to be constructed should be easy accessible. This is important

if the electric power generated is to be utilized at or near the plant site.– The site selected should have transportation facilities of rail and road.

5. Distance from the load centre– Power plant should be set up near the load centre, this will reduce the cost of maintenance of

transmission line.

6. Type of the land of the site– The land to be selected for the site should be cheap and rocky.– The ideal site will be one where the dam will have largest catchment area to store water at high

head and will be economical in construction.– Necessary requirement of the foundation rocks for masonry dam are-

• The rock should be strong enough to withstand the stresses transmitted from the dam structure as well as the thrust of the water when the reservoir is full.

• The rock in the foundation of the dam should be reasonably impervious.• The rock should remain stable under all conditions.

Case StudyA new instrument to measure the plot scale runoff

R.D.Stewart1, Z.Liu2,D.E.Rupp3,C.W.Higgins2,and J.S.Selker2 Upwelling Bernoulli Tube (UBeTube).

Limitation of previous methods1) Not useful in long term monitoring studies.2) Expensive installation like tipping bucket, flume/weir systems.3) Not accurate.4) Cannot measure high flow and errors are large.

UBeTube Instrument1) It is a pipe with slots machined in its side that is installed vertically at the base of the runoff.2) Flow is measured by deducing the water height within the pipe.3) Measurements both depends on the geometry of slot and accuracy of water level

measurements.4) It is similar in function to V notch weir, instrument is self empting, no moving parts.

UBeTube Diagram

Construction and working1) Consists of vertical 10cm diameter pipe, with slot machine at one end.2) Material Used :- schedule 40 aluminum pipe (relatively low cost and

rigidity ,strength , resistance to corrosion.3) The tube is attached to the bottom of the runoff plot.4) Runoff system piping can be buried below grade which secures the system.5) Instrument can have variation in slots.6) By finding the water height , inside pipe , flow rate is measured.

Measuring water height 1) Use here vented pressure transducer system.2) 10 cm tube has range 0.3 to 300 L/min.3) With correction factor the error are reduced less than 14.

Conclusion :- The instrument is accurate low cost simple reliable and proper choice measuring runoff.

References• Blair, A., Sanger, D., White, D., Holland, A. F., Vandiver, L.,Bowker, C., and

White, S. Quantifying and simulating storm water runoff in watersheds, Hydro. Process., 28, 559–569, 2014.

• Blume, T., Zehe, E., Reusser, D. E., Iroumé, A., and Bronstert, A.:Investigation of runoff generation in a pristine, poorly gauged catchment in the Chilean Andes I: A multi-method experimental study, Hydro. Process., 22, 3661–3675, 2008.

• Biswas, A.K.,History of Hydrology,Amer.Elsevier, New York,348 pp.,1970.• Nehls, T., Nam Rim, Y., and Wessolek, G.: Technical note on measuring run-

off dynamics from pavements using a new device: the weighable tipping bucket, Hydro. Earth Syst. Sci., 15, 1379–1386, doi:10.5194/hess-15-1379-2011, 2011.

• Power System Engineering By R.K. Rajput

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