Rivers in India may be classified as 1) Himalayan, 2) Peninsular, 3) Coastal and 4) those of the inland drainage basin.The Himalayan rivers are perennial as they are generally snow-fed and have reasonable flow throughout the year. During the monsoon the Himalayas receive very heavy rain and the river carry the maximum quantity of water causing floods.

The peninsular rivers are generally rain-fed and, therefore, fluctuate in volume. A large number of the streams is non-perennial. The coastal streams, especially on the west coast, are short in length and have limited catchment area. The streams of the inland drainage basin of western Rajasthan are few and far between. They drain towards the individual basins or salt lakes like the Sambhar or are lost in the sands having no outlet to the sea. The Luni is the only river of this category that drains into the Runn of Kutch.

The Ganga sub-basin which is part of the larger Ganga- Brahamputra - Meghana basin is the largest in India receiving waters from an area which comprises one-quarter of the total area of the country (7500 Sq, km). The Ganga flows through Uttar Pradesh, Bihar, West Bengal and then enters Bangladesh. The Ganga is joined by a number of the Himalayan rivers including the Yamuna, the Ghagra, the Gomati, the Gandak and the Kosi. Among the important rivers flowing north from central India into the Yamuna are Chamba, Betwa and Sone.

The Brahmaputra and the Barak flowing from east to west in north-eastern regions have immense water resources. The Ganga and the Brahmputra carry 61 % of the total water of the country's rivers.

The Godavari in the southern Peninsula has the second largest river basin covering 10% of the area of India. Next is the Krishna basin while the Mahanadi has the third largest basin. The basin of the Narmada in the uplands of the Deccan flowing to the Arabian Sea and the Kaveri in the south falling into the Bay of Bengal are about the same size.

The two other river systems, small but agriculturally important, are the Tapti in the north and the Pennar in the south. These west coast river of great importance as they contain as much as 11 % of the country's water resources irrigating about 10% of the land area. There are 14 major river basins, each with drainage area of above 20,000 Sq. Km., 44 medium basins. The total water in all river systems of India has been estimated roughly at 16,45,000 million cubic meters.