The
Kosi or
Koshi is a transboundary river which flows through China, Nepal and India. It drains the northern slopes of the Himalayas in Tibet and the southern slopes in Nepal. From a major confluence of tributaries north of the Chatra Gorge onwards, the Kosi River is also known as the
Saptakoshi for its seven upper tributaries. These include the Tamur River originating from the Kanchenjunga area in the east and Arun River and the Sun Kosi from Tibet. The Sun Koshi's tributaries from east to west are the Dudh Koshi, Likhu Khola, Tamakoshi River, Bhote Koshi and Indravati. The Saptakoshi crosses into northern Bihar, India where it branches into distributaries before joining the Ganges near Kursela in Katihar district. The Kosi is the third-largest tributary of the Ganges by water discharge after the Ghaghara and the Yamuna.