Ground-water is tapped by digging shallow and large diameter percolation wells or drilling deep tube-wells and lifting it to the surface. Shallow wells derive their water-supply from the surrounding area through seepage, percolation, high-water table, etc. the deep wells depend for their water on aquifers, which may have their source at some distance. River valleys, canal-irrigated areas, low-lying places, natural vegetation and trees growing luxuriantly are indications of the presence of ground-water resources. The rate at which the water can be pumped out from a well depends upon recharging rate which, in turn, depends upon the permeability of the surrounding area in the case of shallow wells and on the thickness and the magnitude of aquifers.

Utilization of water resources. The scientific utilization of water resources for crop production involves the consideration of the suitability of land and water for irrigation and then planning of crops and water-management practices commensurate with them. Water-management practices include irrigation and drainage. Irrigation comprises three fundamentals: how much to drain, how best to drain and how rapidly to drain under a given situation of soil, water, and crops. These problems are discussed in this chapter.