Two types of water is found on earth-saline and fresh. Man uses freshwater for different purposes. Its sources are :
1. Rainfall: Rainfall is the major source of water on the earth. Some water is evaporated, some water flows down to the oceans and some water goes underground through percolation. India has average annual rainfall of 118 cm.
Rain water or running water flowing on the surface of land is called surface water. It includes water in oceans, seas, lakes, rivers, etc. India’s total surface water resources are 1869 billion cubic metres.
2. Ground Water: Rain water that goes beneath the surface of the earth by percolation is called ground water. India has a total ground water resources of 40 million hectare metres. This water can be obtained by digging wells. Sometimes it comes out through springs also.
3. Rivers and Canals: From early periods, rivers and canals have been very important. Many civilisations developed along river banks. Man built dams on rivers to use water for irrigation through canals.
4. Tanks: Tanks are found in areas deficit in rainfall. The water level is very deep so it is difficult to use it. Rain water is collected in depressions called tanks. Tanks are mostly found in southern India.
