JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year WATER RESOURCES ENGINEERING Previous Question Paper (February - 2022 - R16)
Answer any five questions
All questions carry equal marks
Main
Explain the method of determination of optimum number of rain gauges in a catchment.
Answer
The optimum number of rain gauges in a catchment is determined based on the allowable percentage error in the estimation of the mean rainfall. Since rainfall is a random variable, the number of gauges required depends on the variability of the rainfall data collected from existing stations.
The procedure follows these steps:
- Calculate the mean precipitation (P) of the existing 'n' rain gauge stations: P = (ΣPi) / n
- Calculate the standard deviation (σ) of the rainfall data: σ = sqrt(Σ(Pi - P)^2 / (n - 1))
- Calculate the coefficient of variation (Cv) of the rainfall: Cv = (σ / P) * 100
- Determine the allowable percentage error (ε) in the estimation of the mean rainfall.
- Calculate the optimum number of rain gauges (N) using the formula: N = (Cv / ε)^2
- If the calculated N is greater than the existing number of stations 'n', additional gauges required are (N - n). If N is less than or equal to 'n', the existing network is considered sufficient.
This statistical approach ensures that the mean rainfall over the entire catchment is estimated within a specified level of precision, balancing the cost of installing and maintaining gauges with the accuracy of the hydrological data required for water resources planning.
In a catchment area, the annual rainfall recorded by rain gauges A, B, C, D, E and F are 52, 63, 35, 56, 40 and 59 cm respectively. For a 10% error in estimation of mean rainfall, calculate the optimum number of rain gauges in the area.
Answer
To calculate the optimum number of rain gauges, we first determine the mean rainfall and the standard deviation of the recorded data. The given rainfall values are: 52, 63, 35, 56, 40, and 59 cm.
The mean rainfall (Pavg) is calculated as:
The standard deviation (σ) is calculated using the formula:
Calculating the deviations (Pi - Pavg)2:
- (52 - 50.83)2 = 1.369
- (63 - 50.83)2 = 148.119
- (35 - 50.83)2 = 250.589
- (56 - 50.83)2 = 26.729
- (40 - 50.83)2 = 117.289
- (59 - 50.83)2 = 66.749
Sum of squares = 610.844. With n = 6, the standard deviation is:
The coefficient of variation (Cv) is:
For a permissible error (ε) of 10%, the optimum number of rain gauges (N) is calculated as:
Rounding to the nearest whole number, the optimum number of rain gauges required is 5.
Given below are the ordinates of 4 hr UH of a basin. Derive 2 hr UH of the basin using S-curve method.
Answer
Sign in to view the complete answer paper.
With neat sketches discuss any two methods of base flow separation.
Answer
Sign in to view the complete answer paper.
A gravity well has a diameter of 65 cm. The depth of water in the well is 45 m before pumping has started. When pumping is done at the rate of 40 litres/s, the drawdown in a well 12 m away is 4.5 m and in another well, 24 m away, the drawdown is 3m. Determine:
Radius of zero drawdown
Answer
Sign in to view the complete answer paper.
Coefficient of permeability
Answer
Sign in to view the complete answer paper.
Drawdown in the well
Answer
Sign in to view the complete answer paper.
Maximum rate at which water can be discharged from the well.
Answer
Sign in to view the complete answer paper.
Derive an expression to find the discharge through an unconfined aquifer.
Answer
Sign in to view the complete answer paper.
Differentiate between perennial and inundation irrigation.
Answer
Sign in to view the complete answer paper.
List out the standards of quality for irrigation water.
Answer
Sign in to view the complete answer paper.
A crop grown in an area of 5000 ha is fed by a canal system. Find daily consumptive use and discharge in m3/s required in the area if,
Optimum moisture = 10%
Permanent wilting point = 8%
Effective depth of root zone = 70 cm
Relative density of soil = 1.3
Answer
Sign in to view the complete answer paper.