Addis Ababa University
Africa Centre of Excellence for Water Management
Assignment – Hydrology (WM 6017)
Chapter 1. Introduction
1.
2.
3.
4.
5.
Define hydrology and hydrologic cycle.
Why is a good understanding the hydrologic processes important in hydrologic studies?
Describe the water resources potential of your country.
List and describe the major factors that determine a catchment’s response to a given rainfall.
Given that Ethiopian Population is 110 million, and the surface water and ground water potential of
2.6BM, respectively, what is the rate of water availability in the country terms of stress index? What
is your suggestion to improve the situation?
6. Clear lake has a surface area of 708,000m2. In the month of March 2022, this lake had an inflow of
1.5m3/s and an outflow of 1.25m3/s with a storage change of +708,000m3. If the total depth of rainfall
recorded at the local rainguage was 225mm for the month, estimate the evaporation loss from the
lake. Assume seepage loss is negligible.
7. During the water year 2020/21, a catchment area of 2500km2 received 1300mm of precipitation. The
average discharge at the catchment outlet was 30m3/s.
a. Estimate the amount of water lost due to the combined effects of evaporation, transpiration
and percolation to groundwater.
b. Compute the volumetric runoff coefficient for the catchment in the water year.
Chapter 2. Precipitation
1.
2.
3.
4.
What is the difference between precipitation and rainfall?
Describe the different forms of precipitation.
Briefly state about the cyclonic, convective and orographic precipitation.
There are four raingauge stations existing in the catchment. The average annual rainfall values at
these stations are 800, 620, 400 and 540mm, respectively.
a. Determine the optimum number of rain gauges in the catchment if it is desired to limit the
error in the mean value of rainfall to 10%.
b. How many more gauges will then be required to be installed.
5. Based on the following annual precipitation recorded at a raingauge station, estimate the value of
precipitation which has a recurrence interval of 5years.
Year
Annual Precipitation (cm)
Year
Annual Precipitation (cm)
2010
36.5
2016
71.2
2011
29.0
2017
48.3
2012
56.2
2018
31.4
2013
82.0
2019
18.1
2014
27.8
2020
29.0
Chapter 3. Evaporation and Evapotranspiration
1. What are the major factors affecting the rate of evaporation from a free water body?
2. What is the difference between actual and potential evapotranspiration?
3. Describe the Hargreaves Equation which is used to find ETo.
1
2015
23.4
2021
65.6
4. How do you find the parameters such as Rn,  , , es, and ea in the Penman-Monteith
equation?
5. Calculate by the energy method the daily evaporation rate from an open water surface, if the
net radiation is 200 W/m2 and the air temperature is 25oC assuming no sensible heat or
ground heat flux.
6. If the amounts of water added to bring the level to the fixed point are as follows,
a. Compute the daily evaporation from a Class A-pan.
b. What is the evaporation loss of water in this week from a lake (surface area=640ha)
in the vicinity, assuming a pan coefficient of 0.75?
Day
Rainfall (mm)
Water added(mm)
1
14
-5
(removed)
2
6
3
3
12
0
4
8
0
5
0
7
6
5
4
7
6
3
Chapter 4. Runoff and Stream flow
1. What are the similarity and difference between direct runoff and base flow?
2. Briefly discuss on the importance of estimating yield of a river basin in water resource development
study.
3. Why is information about the river discharge important?
4. Write the principle of operation of parshall and cut-throat flumes to measure discharge.
5. What are the components of a flood hydrograph?
6. Write the major factors affecting a flood hydrograph.
7. What are the important assumptions in the rational method of estimating peak flow rate?
8. What is the advantage of the probability distribution functions over the plotting position in the
prediction of flood peak?
9. Annual rainfall and runoff values (in cm) of a catchment panning a period of 21 years are given
below.
a. estimate the 75% and 50% dependable annual yield of the catchment,
b. Plot the best fit line for rainfall-runoff correlation and show the regression equation.
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10. Based on the following data of gauge and discharge collected at a particular section of a river,
develop a stage-discharge relationship (rating equation) of the form:
Q  Cr (G  a)
in which Q is stream discharge, G is gauge height (stage), a is a constant which represent the gauge
reading corresponding to zero discharge, and Cr and  are rating curve constants. Use a value of a =
7.50m for the gauge reading corresponding to zero discharge. Also, plot the rating curve.
11. The record of annual peak discharges at a stream gauging station is as follows:
Year
2011
2012
2013
2014
2015
2016
2017
2018
2019
Discharge (m3/s)
45.3
27.5
16.9
41.1
31.2
19.9
22.7
59.0
35.4
Determine using the lognormal distribution:
a. The probability that an annual flood peak of 42.5m3/s will not be exceeded.
b. The return period of a discharge of 42.5m3/s
c. The magnitude of a 20year flood.
12. Calculate the 5 and 50 year return period annual maximum discharge of the Guadalupe River near
Victoria, Texas, using the Log-Normal and Log-Pearson Type III Distributions. The discharge data
from 1935 to 1978 gives the following logarithmic statistics.
y  4.2743
S y  4.2743
Cs  0.0696
13. The mean annual flood of a river is 600m3/s and the standard deviation of the annual flood time series
is 150m3/s. What is the probability of a flood of magnitude 1000m3/s. Use Gumbel’s method and
assume the sample size to be very large.
https://studylib.net/doc/15006183/frequency-analysis#
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