This set of Irrigation Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Ground Water through Wells and Tubewells – Infiltration”.
1. The field measurement of infiltration is done by ____________________
Explanation: Infiltrometer is used for field measurement of infiltration. There are two types of infiltrometer – Single ring infiltrometer and Double ring infiltrometer. Single ring infiltrometer always overestimate because of the lateral movement of water and to overcome this double-ring infiltrometer is used.
2. Which of the following is used for laboratory measurement of infiltration?
b) Rainfall Simulator
Explanation: Rainfall simulators are used for laboratory measurement of infiltration and Infiltrometer is used for field measurement of infiltration. Lysimeter is used to measure evapotranspiration and tensiometer is used to measure capillary potential.
3. As the temperature increases, the rate of infiltration also increases.
Explanation: The rate of infiltration is directly proportional to the temperature. As temperature increases, viscosity decreases and resistance to flow decreases and infiltration increases.
4. Sandy soil has more infiltration capacity as compared to clayey soil.
Explanation: Soils having small pore size such as clay have low infiltration capacity than the soils having large pore size such as sandy soil. One exception is when the clay is present in dry conditions; the soil can develop large cracks which lead to higher infiltration capacity.
5. Rate of infiltration determined by infiltrometer is less than the one determined by rainfall simulator.
Explanation: The rate of infiltration measured by infiltrometer is more than the infiltration rate determined by the rainfall simulator. The rate of infiltration is directly proportional to the depth of surface retention. As the depth of retention is more in infiltrometer hence the rate of infiltration is more in infiltrometer.
6. Deep vertical movement of water in the ground is called as ____________________
Explanation: Infiltration is the process by which the water seeps into the surface strata of the earth to meet soil moisture deficiencies. Percolation is the deep vertical movement of water in the ground.
7. Vegetation cover or grass-cover _____________
a) increases the field capacity
b) decreases the field capacity
c) may increase or decrease the field capacity
d) have no effect on field capacity
Explanation: Grass cover or vegetation cover increases the field capacity by trapping water and reducing the effect of raindrop compaction. Vegetation and grass cover also reduces the surface compaction of the soil which again allows for increased infiltration.
8. What is the correct expression of Horton’s equation?
a) ft = fC + (fC – fO) e-K.t
b) ft = fC + (fC – fO) eK.t
c) ft = fC + (fO – fC) eK.t
d) ft = fC + (fO – fC) e-K.t
Explanation: Horton’s equation assumes an infinite water supply at the surface i.e. it assumes the saturation conditions at the soil surface. The infiltration rate at any time‘t’ is given by –
ft = fC + (fO – fC) e-K.t
Where fC = final constant rate of infiltration at saturation, fO = initial rate of infiltration capacity, k is the decay constant depending upon soil and vegetation and t = time from the beginning of the storm.
Sanfoundry Global Education & Learning Series – Irrigation Engineering.
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