Ganga basin is the largest river basin in India interms of catchment area, constituting 26% of the country's land mass (8,61,404 Sq. km) and supporting about 43% of its population (448.3 million as per 2001 census). The basin lies between East longitudes 73?30and 89? 0 and North latitudes of 22?30 and 31?30, covering an area of 1,086,000 sq km, extending over India, Nepal and Bangladesh. About 79% area of Ganga basin is in India. The basin covers 11 states viz., Uttarakhand, U.P., M.P., Rajasthan, Haryana, Himachal Pradesh, Chhattisgarh, Jharkhand, Bihar, West Bengal and Delhi. The drainage area in each state is given in Table ..

States Drainage area(km)
Uttarakhand and Uttar Pradesh 294,364
Madhya Pradesh and Chhattisgarh 198,962
Bihar and Jharkhand 143,961
Rajasthan 112,490
West Bengal 71,485
Haryana 34,341
Himachal Pradesh 4,317
Delhi 1,484
Total 861,404