There are more than 400 rivers in the Indian subcontinent. [1] As per the classification of Food and Agriculture Organization, the Indian rivers are combined into 20 river units, which includes 14 major river systems and 99 smaller river basins grouped into six river units. They are grouped into four groups: Himalayan, Deccan, Coastal, and Inland drainage, based on their origin and drainage. [2] [3]
Most of the rivers in India originate from the four major watersheds in India. The Himalayan watershed is the source of the majority of the major river systems in India, including the three longest rivers: the Ganges, the Brahmaputra and the Indus. [3] [4] These three river systems are fed by more than 5000 glaciers. [5]
The Aravalli range running along the north-western part of India is the origin of a few of the smaller rivers. In Central India, rivers including the Narmada and Tapti rivers originate from the Vindhya and Satpura. [4] In the peninsular India, the majority of the rivers originate from the Western Ghats in the west and flow towards the Bay of Bengal in the east, while a few rivers flow from east to west from the Eastern Ghats to the Arabian Sea. This is because of the difference in elevation of the Deccan plateau, which slopes gently from the west to the east. [6] The major peninsular rivers include the Godavari, the Krishna, the Mahanadi and the Kaveri. [3] [4]