Drainage System in India
Important Concepts
Tributary: A river or stream which contributes its water to a main river. For example, the Yamuna is the tributary of the Ganga.
Distributary: A branch or outlet which leaves a main river and does not rejoin it, carrying its water to the sea or a lake.
Delta: A triangular shaped alluvial tract, formed at the mouth of a river. For instance the delta of the Ganges is the largest delta in the world.
Doab: The alluvial tract of land between two adjacent rivers, e.g. the plain between the Ganges and the Yamuna.
Catchment Basin (Drainage Area): The region which drains all the river water that falls on it into a river or stream.
Breakwater: A barrier built into the sea in order to break the force of the waves and thus to serve as a protection against them.
Estuary: The mouth of a river where tidal effects are felt and where fresh water and sea water mix.
Drainage Patterns: River and its tributaries drain an area, which is called a ‘river basin’. Its boundary formed by the crest line of the surrounding highland is the watershed of the basin A river system usually develops a pattern which is related to the general structure of the basin.
A dendritic pattern develops in a region made of rocks which offer some resistance to erosion and which has a uniform structure. A trellis drainage pattern develops in a region made up of alternate belts of hard and soft rocks all of which dip in the same direction and which lie at right angles to the general slope, down which the river flows. A radial pattern develops on a dome or volcanic cone.
Classification of Drainage System: Over 90% of India’s land surface drains into the Bay of Bengal and almost all the remaining area drains into the Arabian Sea. Only a very small area in Rajasthan has an inland drainage.
Our river system can be classified into:
- The Himalayan River System
- The Peninsular River System
The Himalayan rivers fall into four broad groups:
- Pre-Himalayan Rivers: Arun, Indus, Satluj and
- Great-Himalayan Rivers: Ganga, Kali, Ghaghra, Gandak, Tista
- Lesser -Himalayan Rivers: Beas, Ravi, Chenab, Jhelum etc.
- Siwalik Rivers: Hindan, Sonali
The peninsular rivers fall into two categories, viz., the coastal rivers and the inland rivers. The former are comparatively small streams. The west-coast rivers are of great importance. Although only 3 percent of the areal extent of the basins of India is drained by these rivers, as much as 14 percent of the country’s water resources are contained by them.
- Rivers rising from the Western Ghats: the Godavari, the Krishna, the Cauvery, the Pennar, the Palar, the Vaigai
- Rivers flowing into the Arabian Sea: The Narmada, the Tapi, the Sharavati
Rivers originating in the Vindhyas and Satpura but flowing north-east towards Ganga: The Chambal, the Betwa, the Damodar, the Son, the Ken etc. The Narmada and the Tapi flow in the fault created by them during the Himalayan uplift.
