Irrigation Efficiencies - Free MCQ Practice Test with solutions, GATE Civil

It is the ratio of water delivered into the fields to the water entering into the channel. This efficiency accounts for the conveyance or transit losses.

The water application efficiency is the ratio of water stored in the root zone to the water actually delivered to the field. It takes into consideration the water lost in the farm hence, it is also known as on-farm efficiency.

Leaching is the supply of additional water to wash away the salts in a saline prone area. The presence of excess salts in water requires high water storage efficiency in order to keep the salts washed out of the soil.

The formula for distribution efficiency is:
N_d = (1- d/D) x 100; where d = mean deviation and D = mean depth of water
Given, d=0.1 cm and D = 1.5 cm
Hence, N_d = 93%.

By definition, Conveyance efficiency N_c = (output/input) x 100
Given, Output = 1.6 cumec and Input = 2 cumec
So, N_c = 80%.

It is the ratio of normal consumptive use of water to the net amount of water depleted from the root zone. It accounts for the loss of water by deep percolation and evaporation following irrigation.

Water distribution efficiency is also known as the uniformity coefficient. It is the measure of how uniformly water is applied to the area being irrigated. The effectiveness of irrigation is measured by its uniformity coefficient.

The formula for distribution efficiency is:
N_d = (1- d/D) x 100; where d = mean deviation and D = mean depth of water
Given, d=0.1 cm and D = 1.5 cm
Hence, N_d = 93%.

The correct representation of the formula is N_d = 1-d/D.
Where N_d = water distribution efficiency, d = deviation from the mean depth and D = mean depth.

It represents the extent to which the water has penetrated to a uniform depth throughout the area. If the water penetrates uniformly throughout the field, the deviation from the mean depth is zero and hence, water distribution efficiency is 1.0.