What is River Basin and Watersheds?


A river basin is an area drained by a river and its tributaries. It simply means that the area through which the river and its tributaries collect water and flow through its course of the journey from origin to the destination is known as River Basin.

The area from which water flows into the main river (or river drains the water) is called ‘Catchment Area’.

The Catchments of large rivers are known as “River Basins”

(River Basin is a type of Catchment)

For Example. the Ganga Basin is the area that is covered (drained) by the river Ganga and all its tributaries like Yamuna, Gomti, Ghaghara, Kosi, etc.

Watershed is defined as the boundary line separating one river or drainage basin from the other.

In simple terms, the Catchment Area of small rivers (rivulets and rills) is known as Watershed.

So, the difference between a River Basin and a Watershed is that River Basin cover large areas whereas Watershed cover small areas.

Classification of Indian Drainage System

Basis of ClassificationClassification
Discharge of Water1. Arabian Sea Drainage
2. Bay of Bengal Drainage
Size of Watershed1. Major river basins with more than 20,000 sq. km of Catchment area.
2.Medium river basins with Catchment area between 2,000 – 20,000 sq. km
3.Minor River basins with less than 2,000 sq. km of Catchment area.
Mode of Origin, nature
and Characteristics
1. Himalayan Drainage
2. Peninsular Drainage