1. Irrigation and Benefits of Irrigation
The process of supplying water to crops by artificial means such as canals, tube wells, tanks etc.
is known as irrigation. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall. In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed or dryland farming.
Mankind is getting benefits of irrigation system since ancient time. Archaeological investigation has identified evidence of irrigation where the natural rainfall was insufficient to support crops. For example, Perennial irrigation was practiced in Mesopotamian plains, Terrace irrigation in Syria, Basin irrigation in Egypt etc. With the advent of diesel and electric motors in 20th century, humans increased the area under irrigation by pumping more and more ground water and extending the canals etc.
In greater part of India, agriculture is rain-fed. In the incidence of failure of monsoon, the crop fails. The behavior of Indian monsoon is highly erratic. Excess rainfall may cause floods, but scanty rainfall may reduce the crop yield substantially, and in acute cases the crop may be a complete failure.
India has very large population and it is estimated that India needs more than 450 million tonnes of grain to meet the demand of growing population. Climate change will result into more instances of erratic climatic conditions and thus, crops are more prone to high variability in rain. The present productivity of irrigated land is about 2.5 tonnes/hectare and less than 0.5 tonnes/hectare for rainfed lands. In this context, there is an urgent need to implement and plan irrigation strategies.
India possesses 4% of the total average annual run off in the rivers of the world. The per capita water availability of natural run off is at least 1100 cubic meters/yr. The amount of water that can
actually be to put to beneficial use is much less due to severe limitations imposed by
physiographic, topographic, interstate issues and the present technology to harness water
resources economically.