Demand of Water for Irrigation

In agriculture, water is used primarily for irrigation. The reason irrigation becomes necessary is the spatio-temporal variability of rainfall across India. Rainfall is not uniform in space or time — some regions get plenty, others very little, and the timing is concentrated in the monsoon months.

Large parts of the country are rainfall-deficient and drought-prone. Two major areas that face this problem are north-western India and the Deccan plateau. In most of the country, both winter and summer seasons are more or less dry. Without assured irrigation, practising agriculture in such conditions is extremely difficult.

The total utilisable water resource in India is estimated at 1,869 cubic km. However, due to topographical, hydrological, and other constraints, only about 690 cubic km — that is, 32 per cent of the available surface water — can actually be used.

The amount of water flowing in a river depends on two factors:

• The size of its catchment area (or river basin)
• The amount of rainfall within that catchment area …