The Kosi River (ko-SEE), ca.200 mi/322 km long, is the northern tributary of the Ganga River, in eastern Nepal and northeastern India (Bihar state). It is formed by the confluence of three headstreams (Sun Kosi, Arun Kosi, and Tamur Kosi Rivers) 13 mi/21 km west southwest of Dhankuta, Nepal. As the Sapta Kosi River, it flows southward across the Indian border, where name changes to Kosi River, through Saharsa Plain in the north part of Bihar state — here it divides into two main arms and many shifting channels, joining again east of Khagaria, Bihar — and eastward to the Ganga River 25 mi/40 km south southwest of Purnea, Bihar.
A dam (770 ft/235 m high) was constructed at Barakahshetra, below confluence of headstreams, just south of the Kosi Thapu Wildlife Sanctuary, and barrage at Chatara. With two canals extending from both banks, the Kosi River irrigates approximately 4,688 sq mi/12,142 sq km–6,250 sq mi/16,188 sq km. The dam provides power, navigation, control of destructive floods in Indian State of Bihar, drainage, malarial control, land reclamation, fish hatcheries, and recreational facilities.
Nepal encompasses an area of 147,181 sq. km (56,136 sq. mi.), about the size of the U.S. state of Tennessee. Its capital, Kathmandu, has an estimated population of 2.2 million people. Nepal's terrain consists of a flat river plain of the Ganges in south, a central hill region, and the rugged Himalayas in north. It shares its borders with China to the north and India to the south.
India is located in Southern Asia, bordering the Arabian Sea and the Bay of Bengal, surrounded by Burma, China and Pakistan. Although India occupies only 2.4% of the world's land area, it supports over 15% of the world's population. Only China has a larger population. Almost 40% of Indians are younger than 15 years of age. About 70% of the people live in more than 550,000 villages, and the remainder in more than 200 towns and cities.
The Columbia Gazeteer; CIA World Factbook; U.S. State Department Background Notes, 2005; 03/2000; 03/2008; 11/2007