Engineering Hydrology

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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 
2TSw
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
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