Three fine rivers flow through the district - the Ganges, Kusi and Ghagri.
The Kusi rises in the Himalayas and falls into the Ganges near Colgong within Bhagalpur.
Farther to the east it receives the Kusi, and then, skirting the Rajmahal hills, turns sharply to the southward, passing near the site of the ruined city of Gaur.
Behar abounds in great rivers, such as the Ganges, with its tributaries, the Ghagra, Gandak, Kusi, Mahananda and Sone.
The other principal rivers in Bengal are the Sone, Gogra, Gandak, Kusi, Tista; the Hugh, formed by the junction of the Bhagirathi and Jalangi, and farther to the west, the Damodar and Rupnarayan; and in the south-west, the Mahanadi or great river of Orissa.