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POKHARA UNIVERSITY Level: Bachelor Semester – Fall Programme: BE Course: Engineering Hydrology Year : 2009 Full Marks : 100 Time : 3hrs. Candidates are required to give their answers in their own words as far as practicable. The figures in the margin indicate full marks. Attempt all the questions. 1. a. Discuss the application of engineering hydrology in water resources projects like a hydropower project, an irrigation project and a water supply project. b. Precipitation station X was inoperative for part of a month during which a storm occurred. The respective storm at three surrounding stations A, B and C were 107,89 and 122mm. the normal annual precipitation amounts of stations X, A, B and C are respectively 978,1120,935 and 1200mm. estimate the storm precipitation of station X. Take 10%. The annual rainfall data being reported from a station A for 16 years are 2. available since 1970. In order to check the consistency of this data, six neighbouring stations have been chosen and the annual rainfall values of these stations have been averaged for all the years on record since 1970 in tabular form given below. Find out inconsistency in precipitation (ppt) record of station A and adjust the recorded data at station A and determine its mean annual precipitation. Year 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 Yearly ppt.at station A in cm 144 178 162 194 168 196 144 160 196 141 158 145 132 95 1 6 station avg. yearly ppt in cm 132 146 247 161 155 152 117 128 193 156 164 155 143 115 8 7 15 1984 1985 148 142 135 163 3. a. Describe the factors affecting the flood hydrograph of a catchment. b. Discuss the methods of reducing evaporation from a water body. 4. a. During a high flow, water surface elevations of a small stream were noted at two stations A and B 10 km apart. These elevations and other salient hydraulic properties are given below. Estimate the discharge in the stream, assuming Manning's coefficient n as 0.020 Station A B Water surface elevation (m) 104.771 104.50 Area cross section (m2) 73.293 93.375 8 7 10 Hydraulic radius (m) 2.733 3.089 The value of eddy-loss coefficient Ke for gradual expansion and gradual contraction are 0.3 and 0.1 respectively. b. Why a river rating curve needs to be updated periodically? 5. a. Using the 3 hr unit hydrograph of a gauge station given below, find the ordinates of DRH resulting from two successive 3 hr periods of rainfall production 0.35 and 0.87 cm of runoff respectively from a basin. Time in hours Flow m3/s 7. 8 0 1 2 3 4 5 6 7 8 9 10 11 12 0 16 58 173 337 400 285 215 165 90 60 16 0 b. A spillway has a design life of 25 years. Estimate the required return period of a flood if the acceptable risk of failure spillway is 10% i In any year ii Over its design life. 6. 5 a. Derive the equation Q 2TSw for confined flow into a well. ln( R / rw) b. Describe the different methods of ground water recharge. Write short notes on (Any Two): a. Gumbel's method of flood frequency studies b. Sources of ground water contamination c. Safe yield 2 7 7 8 5×2 3