The Koshi or Kosi River 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 Koshi 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 Koshi 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 where it branches into distributaries before joining the Ganges near Kursela in Katihar district.
The Kosi River is a trans-boundary river, running across important cities in Bihar and Nepal such as Biratnagar, Purnia, and Katihar. The Koshi River System includes some rivers that have their sources in the self-governing territory of Tibet in China. These rivers include the Sun Kosi, the Arun, and the Bhote Kosi.
The Kosi River is famous for being one of the biggest tributaries of the Ganga (or the Ganges).
Beneath the furthest bases of the Shivalik Mountain Range, the Kosi River has formed a megafan. The megafan is 15,000 km2 in area, forcing an entry to over 12 separate canals with changing itineraries because of inundation. The main tributaries of the Koshi River are the Kamlā, Budhi Gandak, and Bāghmati (also known as Kareh). In addition, the river also has some small tributaries such as Bhutahi Balān. Throughout an extensive period spanning 250 years, the river has changed its itinerary on 120 km (75 miles) from the east to the west. The unsteady characteristics of the river has been ascribed to the high level of siltation transported by the river during the monsoon periods. Deluging in the Indian subcontinent has severe outcomes and the nation ranks second all over the world next to Bangladesh in terms of casualties because of inundation, representing 20% of casualties from deluge in the world. The Kosi River has another name, the Sorrow of Bihar. It drains the terrains of northern Bihar with one of its main tributaries like the Gandak River. North Bihar is marked as the most inundation-prone region in India.
The Kosi is a perennial river similar to the Ramganga and the drainage basin is situated in part in Corbett National Park. From Mohan across Dhikuli upto Ramnagar, the Kosi creates the eastern frontier of Jim Corbett National Park.
Length 729 km (453 mi)
Mouth Ganges
Source Sun Koshi, Arun and Tamor form Saptakoshi
Countries Tibet (China), Nepal, India
Floods
The Koshi River is known as the "Sorrow of Bihar" as the annual floods affect about 21,000 km2 (8,100 sq mi) of fertile agricultural lands thereby disturbing the rural economy.[3][17] The Koshi has an average water flow (discharge) of 2,166 cubic metres per second (76,500 cu ft/s). During floods, it increases to as much as 18 times the average. The greatest recorded flood was 24,200 m3/s (850,000 cu ft/s) on 24 August 1954. The Koshi Barrage has been designed for a peak flood of 27,014 m3/s (954,000 cu ft/s).
Extensive soil erosion and landslides in its upper catchment have produced a silt yield of about 19 m3/ha/year (10 cu yd/acre/yr), one of the highest in the world. Of major tributaries, the Arun brings the greatest amount of coarse silt in proportion to its total sediment load. The river transports sediment down the steep gradients and narrow gorges in the mountains and foothills where the gradient is at least ten metres per km. On the plains beyond Chatra, the gradient falls below one metre per km to as little as 6 cm per km as the river approaches the Ganges. Current slows and the sediment load settles out of the water and is deposited on an immense alluvial fan that has grown to an area of about 15 000 km2. This fan extends some 180 km from its apex where it leaves the foothills, across the international border into Bihar state and on to the Ganges. The river has numerous interlacing channels that shift laterally over the fan from time to time. Without channelisation, floods spread out very widely. The record flow of 24 200 m3/s is equivalent to water a metre deep and more than 24 km wide, flowing at one metre per second. The Koshi's alluvial fan has fertile soil and abundant groundwater in a part of the world where agricultural land is in great demand. Subsistence farmers balance the threat of starvation with that of floods. As a result, the flood-prone area is densely populated and subject to heavy loss of life. India has more flood deaths than any country except Bangladesh.
Koshi barrage and irrigation
Koshi Barrage 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 Koshi 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 Koshi 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 Koshi 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.
Koshi Tappu Wildlife Reserve
The Koshi Tappu Wildlife Reserve is situated in the flood plains of the Saptkoshi River in the eastern Terai. It covers an area of 175 km2 (68 sq mi) comprising grasslands and khair–sissoo riverine forests. It was established in 1976 and was declared a Ramsar site in 1987. The reserve provides habitat for hog deer, spotted deer, wild boar, blue bull, gaur, smooth-coated otter, jackal, 485 bird species including 114 water bird species, 200 fish species, 24 reptile and 11 amphibian species. The last surviving population of wild water buffalo in Nepal is found in the reserve, as well as gharial, Gangetic dolphin, swamp francolin and rufous-vented prinia. A small population of the critically endangered Bengal florican is present along the Koshi River. There are also records of white-throated bush chat and Finn's weaver. The bristled grassbird breeds in the reserve.The reserve together with the Koshi Barrage was identified as one of 27 Important Bird Areas of Nepal.
The Koshi or Kosi River 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 Koshi 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 Koshi 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 where it branches into distributaries before joining the Ganges near Kursela in Katihar district.
The Kosi River is a trans-boundary river, running across important cities in Bihar and Nepal such as Biratnagar, Purnia, and Katihar. The Koshi River System includes some rivers that have their sources in the self-governing territory of Tibet in China. These rivers include the Sun Kosi, the Arun, and the Bhote Kosi.
The Kosi River is famous for being one of the biggest tributaries of the Ganga (or the Ganges).
Beneath the furthest bases of the Shivalik Mountain Range, the Kosi River has formed a megafan. The megafan is 15,000 km2 in area, forcing an entry to over 12 separate canals with changing itineraries because of inundation. The main tributaries of the Koshi River are the Kamlā, Budhi Gandak, and Bāghmati (also known as Kareh). In addition, the river also has some small tributaries such as Bhutahi Balān. Throughout an extensive period spanning 250 years, the river has changed its itinerary on 120 km (75 miles) from the east to the west. The unsteady characteristics of the river has been ascribed to the high level of siltation transported by the river during the monsoon periods. Deluging in the Indian subcontinent has severe outcomes and the nation ranks second all over the world next to Bangladesh in terms of casualties because of inundation, representing 20% of casualties from deluge in the world. The Kosi River has another name, the Sorrow of Bihar. It drains the terrains of northern Bihar with one of its main tributaries like the Gandak River. North Bihar is marked as the most inundation-prone region in India.
The Kosi is a perennial river similar to the Ramganga and the drainage basin is situated in part in Corbett National Park. From Mohan across Dhikuli upto Ramnagar, the Kosi creates the eastern frontier of Jim Corbett National Park.
Length 729 km (453 mi)
Mouth Ganges
Source Sun Koshi, Arun and Tamor form Saptakoshi
Countries Tibet (China), Nepal, India
Floods
The Koshi River is known as the "Sorrow of Bihar" as the annual floods affect about 21,000 km2 (8,100 sq mi) of fertile agricultural lands thereby disturbing the rural economy.[3][17] The Koshi has an average water flow (discharge) of 2,166 cubic metres per second (76,500 cu ft/s). During floods, it increases to as much as 18 times the average. The greatest recorded flood was 24,200 m3/s (850,000 cu ft/s) on 24 August 1954. The Koshi Barrage has been designed for a peak flood of 27,014 m3/s (954,000 cu ft/s).
Extensive soil erosion and landslides in its upper catchment have produced a silt yield of about 19 m3/ha/year (10 cu yd/acre/yr), one of the highest in the world. Of major tributaries, the Arun brings the greatest amount of coarse silt in proportion to its total sediment load. The river transports sediment down the steep gradients and narrow gorges in the mountains and foothills where the gradient is at least ten metres per km. On the plains beyond Chatra, the gradient falls below one metre per km to as little as 6 cm per km as the river approaches the Ganges. Current slows and the sediment load settles out of the water and is deposited on an immense alluvial fan that has grown to an area of about 15 000 km2. This fan extends some 180 km from its apex where it leaves the foothills, across the international border into Bihar state and on to the Ganges. The river has numerous interlacing channels that shift laterally over the fan from time to time. Without channelisation, floods spread out very widely. The record flow of 24 200 m3/s is equivalent to water a metre deep and more than 24 km wide, flowing at one metre per second. The Koshi's alluvial fan has fertile soil and abundant groundwater in a part of the world where agricultural land is in great demand. Subsistence farmers balance the threat of starvation with that of floods. As a result, the flood-prone area is densely populated and subject to heavy loss of life. India has more flood deaths than any country except Bangladesh.
Koshi barrage and irrigation
Koshi Barrage 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 Koshi 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 Koshi 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 Koshi 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.
Koshi Tappu Wildlife Reserve
The Koshi Tappu Wildlife Reserve is situated in the flood plains of the Saptkoshi River in the eastern Terai. It covers an area of 175 km2 (68 sq mi) comprising grasslands and khair–sissoo riverine forests. It was established in 1976 and was declared a Ramsar site in 1987. The reserve provides habitat for hog deer, spotted deer, wild boar, blue bull, gaur, smooth-coated otter, jackal, 485 bird species including 114 water bird species, 200 fish species, 24 reptile and 11 amphibian species. The last surviving population of wild water buffalo in Nepal is found in the reserve, as well as gharial, Gangetic dolphin, swamp francolin and rufous-vented prinia. A small population of the critically endangered Bengal florican is present along the Koshi River. There are also records of white-throated bush chat and Finn's weaver. The bristled grassbird breeds in the reserve.The reserve together with the Koshi Barrage was identified as one of 27 Important Bird Areas of Nepal.
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