This set of Engineering Hydrology Multiple Choice Questions & Answers (MCQs) focuses on “Groundwater – Recharge – Set 2”.
1. The rainfall infiltration factor for a 2 km2 plain area is 0.22. If the normal rainfall in this region during the monsoon season is 300 mm, what will be the recharge during monsoon season?
a) 13200 m3
b) 13.2 ha-m
c) 0.00132 km3
d) 0.132 ha-m
View Answer
Explanation: Given f = 0.22, A = 2 km2 = 2 x 106 m2, P = 300 mm = 0.3 m.
As per rainfall infiltration method,
R=f*A*P=0.22*2*106*0.3=132000 m3=1.32*10-4 km3=13.2 ha.m
2. The rainfall during the third quarter of 2020 in an area was found to be 27 cm. The recharge due to the rainfall in that area during that time was estimated to be 150 million litres. If the rainfall infiltration for the region is 8%, find the area over which the recharge takes place?
a) 0.694 km2
b) 6.94 km2
c) 6.94 ha
d) 69.44 ha
View Answer
Explanation: Given f = 0.08, P = 27 cm = 0.27 m, R = 150 x 106 L = 150000 m3.
From rainfall infiltration method
R=f*A*P ⇒A=\(\frac{R}{f*P}=\frac{150000}{0.08*0.27}\)=6944444.44 m2=6.94 km2=694.44 ha
3. Which of the following is true for recharge values due to seepage from canals?
a) Unlined canals in sandy soils have higher seepage than unlined canals in normal soils
b) Unlined canals have same seepage irrespective of the soil they are present in
c) Seepage in lined canals is approximately 50% of that in unlined canals
d) Seepage in lined canals is approximately 1/5th of that in unlined canals
View Answer
Explanation: Recharge values due to seepage from canals suggested as per GREC are – for unlined canals in sandy soils 15 to 20 ha-m/day/km2; for unlined canals in normal soils 25 to 30 ha-m/day/km2; for lined canals it is 20% of values for unlined canals.
4. The value of recharge for an unlined and lined canal present in sandy soil is given as X and Y, respectively. What will be the value of recharge from an unlined canal present in hard rock?
a) 0.2X
b) 0.2Y
c) 0.5X
d) 0.5Y
View Answer
Explanation: Since the given canal is present in hard rock, the seepage from it will be taken as 20% of the seepage from the unlined canal. Hence it is 0.2X.
5. As per the GREC, which of the following criteria is not considered for estimating the recharge from irrigation?
a) Source of irrigation
b) Type of crop
c) Duration of irrigation
d) Depth of water table below ground level
View Answer
Explanation: The recharge due to irrigation is obtained based on three criteria – source of irrigation (surface or groundwater), type of crop (paddy or non-paddy) and depth of water table below ground level.
6. Which of the following combinations will give the highest recharge due to irrigation?
a) Paddy crop, surface irrigation, water table 10 m below ground level
b) Paddy crop, surface irrigation, water table 30 m below ground level
c) Paddy crop, groundwater irrigation, water table 20 m below ground level
d) Non-paddy crop, groundwater irrigation, water table 20 m below ground level
View Answer
Explanation: Surface irrigation provides a higher percentage of recharge compared to groundwater irrigation. Paddy contributes more towards recharge than non-paddy crops. Further, as the depth of water table below the ground increases, the percentage of recharge decreases.
7. What percentage of the gross storage of check dams is taken as recharge due to the structure?
a) 0%
b) 15%
c) 25%
d) 50%
View Answer
Explanation: Recharge due to percolation tanks, check dams and nala bunds is taken as 50% of its gross storage. 50% of this recharge volume is assumed to take place during the monsoon season.
8. A combination of non-paddy crop irrigated by groundwater irrigation with the water table less than 10 m below the ground level will give the least amount of recharge due to irrigation.
a) True
b) False
View Answer
Explanation: A combination of non-paddy crop irrigated by groundwater irrigation with the water table more than 25 m below the ground level will give the least amount of recharge due to irrigation.
Sanfoundry Global Education & Learning Series – Engineering Hydrology.
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