The Sunkoshi, also spelled Sunkosi, is a river that is part of the Koshi or Saptkoshi River system in

Nepal Nepal, officially the Federal Democratic Republic of Nepal, is a landlocked country in South Asia. It is mainly situated in the Himalayas, but also includes parts of the Indo-Gangetic Plain. It borders the Tibet Autonomous Region of China Ch ...

. Sunkoshi has two source streams, one that arises within Nepal in Choukati, and the other more significant stream that flows in from

Nyalam County Nyalam County ( zh, s=聂拉木县; ) is a county in Shigatse, Tibet Tibet (; ''Böd''; ), or Greater Tibet, is a region in the western part of East Asia, covering much of the Tibetan Plateau and spanning about . It is the homeland of the ...

in the

Tibet Tibet (; ''Böd''; ), or Greater Tibet, is a region in the western part of East Asia, covering much of the Tibetan Plateau and spanning about . It is the homeland of the Tibetan people. Also resident on the plateau are other ethnic groups s ...

region of China. (See especially Figure 1). The latter is called

Bhote Koshi Bhote Koshi in Nepal and Poiqu in Tibet (both names roughly mean "Tibetan river") is the name given to the upper course (main tributary) of the Sun Kosi river. It is part of the Koshi River system in Nepal.Shrestha, A. B., Eriksson, M., Mool, ...

in Nepal and Matsang Tsangpo in Tibet. Due to the significant flows from Bhote Koshi, the Sun Koshi river basin is often regarded as a trans-border river basin.

River course

The Sunkoshi's headwaters are located in the Zhangzangbo

Glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

in Tibet.Mool, P. K.; Joshi, S. P.; Bajracharya, S. R. (2001). Glacial Lake Outburst Floods and Damage in the Country. Pages 121–136 in: Inventory of Glaciers, Glacial Lakes and Glacial Lake Outburst Floods: Monitoring and Early Warning Systems in the Hindu Kush-Himalayan Region, Nepal. International Centre for Integrated Mountain Development, Kathmandu. Both Sunkoshi and Bhote Koshi river courses together form one basin that covers an area of about . The Indravati meets the Sunkoshi at Dolaghat, where it is followed by the Arniko Rajmarg. From there, the Sunkoshi flows eastwards through the valley formed between the Mahabharat Range and the

Himalayas The Himalayas, or Himalaya ( ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than list of h ...

. The Tamakosi, Likhu, Dudhkosi, Arun and Tamor are its left tributaries and Indravati is the right tributary. The average annual flow is 2.2 x 10¹⁰ m³. The average

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

load is 5.4 x 10⁷ m³. The Tamur and the Arun rivers join the Sunkoshi at Tribenighat to form the Saptkoshi, which flows through the

Chatra Gorge The Chatra Gorge is a canyon cut by the Kosi River across the Mahabharat Range in Nepal. Kosi river system The Kosi, or Sapt Kosi, drains eastern Nepal. It is known as Sapt Koshi because of the seven rivers which join together in east-central N ...

across the Mahabharat Range onto the

Gangetic plain The Indo-Gangetic Plain, also known as the Northern Plain or North Indian River Plain, is a fertile plain spanning across the northern and north-eastern part of the Indian subcontinent. It encompasses northern and eastern India, eastern Pakist ...

.Sharma, U. P. (1996). Ecology of the Koshi river in Nepal-India (north Bihar): a typical river ecosystem. In: Jha, P. K., Ghimire, G. P. S., Karmacharya, S. B., Baral, S. R., Lacoul, P. (eds.) Environment and biodiversity in the context of South Asia. Proceedings of the Regional Conference on Environment and Biodiversity, 7–9 March 1994, Kathmandu. Ecological Society, Kathmandu. Pp 92–99. There are also a few smaller tributaries of the Sunkoshi, such as Rosi Khola, Junga Khola, and Sapsu Khola.

Names and etymology

Nepali language Nepali (; , ), or ''Gorkhali'' is an Indo-Aryan languages, Indo-Aryan language native to the Himalayas region of South Asia. It is the official and most widely spoken Languages of Nepal, language of Nepal, where it also serves as a ''lingua fr ...

, the word "sun" means

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

and golden; and the word "kosi" means river.

Koshi River system

The Koshi River drains eastern Nepal. It is also known as Saptkoshi River because of the seven rivers joining in east-central Nepal to form this river. The main rivers forming the Koshi River system are Sunkoshi, Indravati, Tamba Koshi,

Dudh Kosi Dudh Koshi (दुधकोशी नदी, ''Milk-Koshi River'') is a river in eastern Nepal. It is the highest river in terms of elevation. Dudh Koshi originates from the glacier lakes at the height of 5,100 meters above sea level and meets Sapt ...

, Arun and Tamur Rivers. The Saptkoshi River flows through the

in a southerly direction into northern

Bihar Bihar ( ) is a states and union territories of India, state in Eastern India. It is the list of states and union territories of India by population, second largest state by population, the List of states and union territories of India by are ...

and joins the

Ganges The Ganges ( ; in India: Ganga, ; in Bangladesh: Padma, ). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international which goes through India, Bangladesh, Nepal and China." is a trans-boundary rive ...

. The Sunkoshi contributes about 44% of the total water of the Saptakoshi, the Arun 37% and the Tamur 19%.

Infrastructures

*Sunkosi–Kamala multipurpose project: The Sunkoshi has a 90% reliable flow of . It was proposed to divert the water from a small

weir A weir or low-head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the water level. Weirs are also used to control the flow of water for outlets of l ...

across the river near Kurule through a tunnel and a 61.4 MW associated powerhouse to the

Kamala River The Kamala River (Hindi and ; romanized: Kamalā nadī) originates in Nepal and flows through the Indian state of Bihar. Course The Kamala originates from the Churia Range near Maithan which is near Sindhuli Gadhi in Sindhuli District of Nepal ...

, flowing through central Nepal. Some of water would be transferred to the Kamala River for the irrigation and further generation of power.

Hazards

In July 1981, a sudden ice

avalanche An avalanche is a rapid flow of snow down a Grade (slope), slope, such as a hill or mountain. Avalanches can be triggered spontaneously, by factors such as increased precipitation or snowpack weakening, or by external means such as humans, othe ...

caused a

Glacial Lake Outburst Flood A glacial lake outburst flood (GLOF) is a type of outburst flood caused by the failure of a dam containing a glacial lake. An event similar to a GLOF, where a body of water contained by a glacier melts or overflows the glacier, is called a j� ...

in the

moraine A moraine is any accumulation of unconsolidated debris (regolith and Rock (geology), rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a gla ...

-dammed Zhangzangbu-Cho Lake in the headwaters of the Poiqu in Tibet. The ensuing

debris Debris (, ) is rubble, wreckage, ruins, litter and discarded waste, garbage/refuse/trash, scattered remains of something destroyed, or, as in geology, large rock fragments left by a melting glacier, etc. Depending on context, ''debris'' can ref ...

flow destroyed bridges, and sections of both the Arniko and the Nepal–China highways. On 2 August 2014, a

landslide Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...

at Jure blocked the river downstream from Barabise and created a large lake that submerged a

hydropower Hydropower (from Ancient Greek -, "water"), also known as water power or water energy, is the use of falling or fast-running water to Electricity generation, produce electricity or to power machines. This is achieved by energy transformation, ...

station. This huge rockslide of approximately blocked the Sunkoshi River upstream of Jure village. This landslide killed approximately 155 people and destroyed approximately 120 houses completely and 37 partially. The area was declared a

flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

crisis zone, and local communities were evacuated. The power supply was interrupted, and the Arniko Highway was blocked.

Water sports

The Sunkoshi is used for both

rafting Rafting and whitewater rafting are recreational outdoor activities which use an inflatable raft to navigate a river or other body of water. This is often done on whitewater or different degrees of rough water. Dealing with risk is often a ...

and intermediate

kayaking Kayaking is the use of a kayak for moving over water. It is distinguished from canoeing by the sitting position of the paddler and the number of blades on the paddle. A kayak is a low-to-the-water, canoe-like boat in which the paddler sits fac ...

. It has grade III-IV rapids. The most common put-in point of a Sunkoshi river trip is Dolaghat, at an elevation of and it ends at the Chatra Gorge at , a distance of around . The first successful descent of the Sunkoshi was made in late September 1970 by Daniel C. Taylor, Terry Bech, Cheri Bremer-Kamp, and Carl Schiffler. They entered the river at Dolaghat and exited at the Nepal-India border. Their expedition took four days. Before this successful trip, there were four known unsuccessful attempts to descend the river, and one unsuccessful attempt to ascend the river in a jet boat under the leadership of Edmund Hillary.Taylor, D. C. "Yeti: An Ecology of a Mystery." New Delhi: Oxford University Press, pp. 119-130.

Notes

References

External links

Sun Kosi River
OpenStreetMap, retrieved 19 December 2021.
Bhote Kosi River
(Upper Sun Kosi), OpenStreetMap, retrieved 19 December 2021.
Arun River
OpenStreetMap, retrieved 19 December 2021.
Sapta Kosi River
OpenStreetMap, retrieved 19 December 2021. {{Kosi basin Rivers of Koshi Province Rivers of Tibet International rivers of Asia