WATERSHED ATLAS OF INDIA

In this Atlas, the entire river systems of the country have been divided into 6 Water Resources Region, which has been further, divided into 35 basins and 112 catchments.  These catchments have been further divided into 500 sub-catchments and 3237 watersheds. 

Category of Hydrologic Units in India

S. No.	Category of Hydrologic Units	Size Range (ha)	No. of Units
1.	Water Resource Region	270,00,000-1130,00,000	6
2.	Basins	30,00,000-300,00,000	35
3.	Catchments	10,00,000-50,00,000	112
4.	Sub-catchments	200,000-10,00,000	500
5.	Watersheds	20,000-300,000	3237
6.	Sub-watersheds	5,000-9,000	12000
7.	Micro-watersheds	500-1,500	400000

(Source: Watershed Atlas of India http://cgwb.gov.in/watershed)

Water Resource Regions in India:

1. Indus

2. Rivers draining into Arabian Sea

3. Rivers draining into Bay of Bengal

4. Brahmaputra Drainage

5. Minor River Draining into other Basin/Country
6. Island Drainage