The river system of an area is called drainage. The area drained by a single river system is called a drainage basin. On the basis of origin, nature and characteristics, rivers of India are classified as the Himalayan rivers and the Peninsular rivers. Most of the Himalayan rivers like the Indus, the Ganga and the Brahmaputra are perennial. Most fresh water lakes are in the Himalayan region. These lakes are of glacial origin. These are formed when glaciers dug out a basin, which was later filled with snowmelt.
Most of the major rivers of the Peninsula such as the Mahanadi, the Godavari, the Krishna and the Kaveri flow eastwards and drain into the Bay of Bengal. The Narmada and the Tapi are the only long rivers, which flow west and make estuaries.
Water from the rivers is a basic natural resource, essential for various human activities. The rivers of India are of great use for us because they comprise of a great source of fresh water. Large quantity of water is supplied to the cities and villages for domestic consumption.
River, which is such an important resource, is getting polluted these days. The pollution is generally because of the growing demand in domestic sector, municipal sector, industrial sector, agricultural sector, etc.
Due to the increasing river pollution, the government is taking several steps to conserve river. One of the important measures taken by the Government is the Ganga Action Plan. Ganga Action Plan Phase one was initiated in 1985, and closed on 31st March, 2000. The Ganga Action Plan envisaged intercepting, diverting and treating 882 million litres water per day, out of 1340 million litres water per day of wastewater.