4. Our Water Resources
4.(i) Oceans: Our country has a 6000 Km long coastline. We do not use ocean water as primary resource.
4.(ii) Ground Water: In our country, ground water is a primary source of freshwater in several towns and rural areas. The existing utilization of ground water in India is currently estimated to 4500 million m3. It is widely used as a source of water for irrigation and for other farm uses. The contribution of ground water to total irrigation is about 40% in India.
4.(iii) Lakes and Reservoirs: Constructing dams make the reservoirs across the rivers. They serve for the variety of purposes like domestic water supplies, industrial processes, irrigation, navigation, fish and water fowl, flood protection, recreation and generation of hydroelectricity. In the rural areas or small communities, ponds may become important source of water for cloth-washing, bathing and for cattle.
In India, there are several large existing multipurpose reservoirs beside several large natural lakes and innumerable small tanks and ponds.
4.(iv) Rivers: India has a very rich river system having 14 major rivers contributing 85% of the total water flow, and more than 50 medium and minor rivers with remaining 15% of water flow. The 14 major river basins in India are- Indus, Ganga, Brahmaputra, Sabarmati, Mahi, Narmada, Tapi, Subarnarekha, Brahmani, Mahanadi, Godavari, Krishna, Pennar and Cauvery. The total annual flow in all the rivers is estimated to be 188100 million m3, according to the Central Water and Power Commission (Kayastha, 1989). The rivers are exploited for almost every use. They are also commonly used for wastewater disposal, due to which the rivers have become highly polluted in many areas