page_title: Kosi River
section_title: Koshi barrage and irrigation
hierarchical_section_title: Kosi River / Development scenario / Koshi barrage and irrigation
caption_attribution_description: English: Barrage
context_page_description: The Kosi or Koshi is a trans-boundary river which flows through Tibet, 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 Saptakoshi for its seven upper tributaries. These include the Tamor River originating from the Kanchenjunga area in the east and Arun River and Sun Kosi from Tibet. The Sun Koshi's tributaries from east to west are Dudh Koshi, Bhote Koshi, Tamakoshi River, Likhu Khola 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 River is 720 km long and drains an area of about 74,500 km² in Tibet, Nepal and Bihar. In the past, several authors proposed that the river has shifted its course for more than 133 km from east to west during the last 200 years. But a review of 28 historical maps dating 1760 to 1960 revealed a slight eastward shift for a long duration, and that the shifting was random and oscillating in nature.
context_section_description: Koshi Barrage, also called Bhimnagar Barrage, was built between 1959 and 1963 and straddles the Indo-Nepal border. It is an irrigation, flood control and hydropower generation project on the Kosi River built under a bilateral agreement between Nepal and India: the entire cost of the project was borne by India. The catchment area of the river is 61,788 km² (23,856 sq mi) in Nepal at the barrage site. The highest peaks lie in its catchment. About 10% is snow-fed. The Eastern Canal and the Western Canal taking off from the barrage, were designed for a discharge capacity of 455 cubic metres per second (16,100 cu ft/s) to irrigate 6,125 square kilometres (1,514,000 acres) and 210 cubic metres per second (7,400 cu ft/s) to irrigate 3,566.1 square kilometres (881,200 acres), respectively. A hydropower plant has been built on the Eastern Canal, at a canal drop (3.6 km (2.2 mi) from the Kosi Barrage), to generate 20 MW. The Western Koshi Canal provides irrigation to 250 square kilometres (62,000 acres) in Nepal. A valuable bridge over the barrage opened up the East-West highway in the eastern sector of Nepal.
  An inundation canal taking off at Chatra, where the Kosi River debouches into the plains, has been built to irrigate a gross area of 860 km² in Nepal. The project was renovated with IDA assistance after Nepal took over the project in 1976.
caption: Koshi Barrage
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