The river basins under this Organisation are Upper reaches of Ganga Basin (excluding Yamuna Basin) up to Shahzadpur in Uttar Pradesh and lies in the states of Uttarakhand and Uttar Pradesh including the main Ganga river and its tributaries Ramganga, Sharda, Gomti, Rapti, Ghaghra, etc.
The Ganga basin is one of the largest river basins. It lies in China, Nepal, India and Bangladesh and drains an area of about 10,00,000 sq. kms. In India, its catchment lies in the states of Uttar Pradesh, Uttarakhand, Madhya Pradesh, Chhattisgarh, Bihar, Jharkhand Rajasthan, West Bengal, Haryana, Himachal Pradesh and Delhi. It lies between latitude 22.450 N and 31.470 N and longitude 73.370 E and 89.310 E.
The Ganga originates as Bhagirathi from the Gangotri Glaciers in the Himalayas at an elevation of about 7,000 m above mean sea level, in the Uttarkashi district of Uttarakhand. The Bhagirathi is joined by the Alaknanda at Deoprayag and the combined stream under the name Ganga flowing through the mountain region debouches into the plains at Rishikesh. It is joined by a large number of tributaries on both the banks in the course of its total run of about 2,500 km before its outfall into the Bay of Bengal.
The important tributaries are the Yamuna, the Ramaganga, the Gomti, the Ghagra, the Son, the Gandak, the Burhi Gandak, the Kosi and the Mahananda. At Farakka in West Bengal, the river divides into two arms namely the Padma which flows to Bangladesh and the Bhagirathi which flows through West Bengal.
Major Tributaries of the River Ganga under Upper Ganga Basin Organization are as follows: