Major tributaries – The major rivers that join the Ganges from the north are – Ghaghra, Gandak, Bagmati, Kamala Balan, Budhi Gandak and Mahananda. Whereas the major rivers that meet from the south side are - Karmanasha, Son, Punpun, Ghaghar, Falgu, Kiul river.
Bagmati River
Total length – 597 km.
Length in Bihar – 394 km.
The catchment area in Bihar – 6,500 sq.km.
Origin – Mahabharata Range (Nepal)
Confluence – Lalbakeya River (Devapur)
Tributaries – Vishnumati River, Lakhandei River, Lal Bakeya River, Chaknaha River, Jamune River, Sipridhar River, Choti Bagmati and Kola River.
Kosi River
Total Length – 720 km.
Length in Bihar – 260 km.
The catchment area in Bihar – 11,410 sq. km.
Place of Origin – Gosai Place (Saptakushiki, Nepal)
Sangam – River Ganges (near Kursela)
Ghaghra (Saryu River)
Total length – 1180 km.
Length in Bihar – 83 km.
The catchment area in Bihar – 2,995 sq. km.
Origin – Nan Pha (Nepal) near Gurla Mandhata Peak
Sangam – River Ganges (near Chhapra)
Tributaries – Rapti
Gandak River
Total length – 630 kms.
Length in Bihar – 260 km
The catchment area in Bihar – 4,188 sq.km.
Origin – Between Manangmot and Kutang of Annapurna range
Confluence – River Ganga (Hajipur)
old gandak river
Total length – 320 km.
Length in Bihar – 320 km.
The catchment area in Bihar – 9,601 sq. km.
Place of Origin – Chautarwa Chaur near Vishambharpur of Someshwar Range