Drainage Systems of India
Drainage means the river system of a region. India has two major systems: the Himalayan rivers and the Peninsular rivers; nearly all rivers drain to the Bay of Bengal (about 77 per cent of the drainage), the Arabian Sea (about 23 per cent), or into inland basins.
Basic terms
| Term | Meaning |
|---|---|
| Drainage basin | Area drained by a river and its tributaries |
| Watershed (water divide) | Upland separating two basins |
| Catchment | Area from which a river collects water |
| Tributary | Smaller river joining a larger one |
| Distributary | Channel branching off from the main river (delta) |
| Confluence | Meeting point of two rivers |
Major watersheds
- Himalaya-Western Ghats separate rivers draining to the Bay of Bengal from those draining to the Arabian Sea. Nearly all big peninsular rivers begin in the Western Ghats and flow east.
- Indus-Ganga divide lies near the Ambala high ground (Siwaliks).
- Vindhyas and Aravalli divide the Ganga and Narmada-Tapi basins.
Drainage patterns
| Pattern | Description | Example |
|---|---|---|
| Dendritic | Tree-like, on uniform rock | Northern plains |
| Trellis | Parallel main streams, short side streams at right angles | Singbhum, Himalaya foothills |
| Rectangular | Right-angled bends along joints | Vindhyan, Kaimur |
| Radial | Flow outward from a central high ground | Amarkantak, Chotanagpur, Girnar |
| Parallel | Rivers parallel on steep slope | Western Ghats (west coast rivers) |
| Centripetal | Flow into a central depression | Lakes (Loktak) |
| Deranged | Irregular | Glaciated areas |
Classification by size (CWC)
- Major rivers (catchment above 20,000 sq km): 14, including the Indus, Ganga, Brahmaputra, Sabarmati, Mahi, Narmada, Tapi, Subarnarekha, Brahmani, Mahanadi, Godavari, Krishna, Pennar, Cauvery.
- Medium (2,000-20,000 sq km): about 44; minor below 2,000 sq km.
Keep practising
Notes are only half the work. Test yourself with questions and discuss doubts with other aspirants.
Prepared for exam revision from NCERT, standard geography textbooks, the Census of India 2011, the India State of Forest Report, IMD, Ministry of Agriculture and other official sources. Maps are schematic teaching maps, not Survey of India maps, and zone boundaries are approximate. Figures such as production, capacity, counts of parks and ports, and census status change, so check the latest official source before relying on them. Found a mistake? Tell us.