Himalayan River

Kosi

Koshi / Sorrow of Bihar
🏔️ Nepal Himalayas (five tributaries converge in Nepal) → Ganga, near Katihar, Bihar
720 kmTotal Length
74,500Basin km²
PerennialFlow Type
1States
Gangetic DolphinFlagship Species

About the Kosi

The Kosi is known as the "Sorrow of Bihar" — a river that has changed course 120 kilometres eastward over the past 200 years, repeatedly devastating the agricultural plains of Bihar with catastrophic floods. The river drains the eastern Himalayan front of Nepal, collecting five major tributaries before emerging onto the plains where it fans out into a constantly shifting braided channel across one of India's poorest agricultural regions. Yet the same floods that bring devastation also deposit extraordinarily fertile silt that has sustained the dense agricultural population of the Mithila region for millennia.

The Kosi's upper reaches in Nepal flow through some of the world's highest terrain — the Dudh Kosi tributary passes through the Khumbu valley beneath Mount Everest. In the lower plains, the river is an important habitat for Gangetic dolphins and provides critical nesting habitat for turtles on its sandy banks. The Kosi Tappu Wildlife Reserve in Nepal, on the river's banks, is one of South Asia's most important bird observatories, particularly for wintering ducks and wading birds.

States along this river
Bihar (India), Nepal (upper reaches)
Length (vs Ganga, 2525 km)
720 km — 28% of India's longest river
Key tributaries

Arun · Sun Kosi · Tamur · Dudh Kosi · Tamakoshi

Wildlife along this river
Gangetic Dolphin 🐬Gharial 🐊Bengal Tiger 🐯Asian Elephant 🐘Gharial 🐊
Best time to explore
JanFebMarAprMayJunJulAugSepOctNovDec
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