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Sunkoshi River

The Sunkoshi, also spelt Sunkosi, is a river that is part of the Koshi or Saptkoshi River system in Nepal. Sunkoshi has two source streams, one that arises within Nepal in Choukati, and the other more significant stream that flows in from Nyalam County in the Tibet region of China.[1] The latter is called Bhote Koshi in Nepal and Matsang Tsangpo in Tibet.[2][a] Due to the significant flows from Bhote Koshi, the Sun Koshi river basin is often regarded as a trans-border river basin.[1][5]

Sunkoshi
The Sino-Nepal Friendship Bridge over Bhote Koshi at Kodari
Map
Location
CountryTibet, Nepal
Physical characteristics
Source 
 • locationChoukati, Nepal
 • coordinates27°45′23″N 86°00′11″E / 27.7563°N 86.0031°E / 27.7563; 86.0031
 • elevation2,400 m (7,900 ft)
2nd source 
 • locationNyalam County, Tibet
 • coordinates28°27′09″N 86°18′24″E / 28.4525°N 86.3067°E / 28.4525; 86.3067
 • elevation5,300 m (17,400 ft)
Mouth 
 • location
Confluence with Arun and Tamur to form Saptkoshi at Trivenighat, Nepal
 • coordinates
26°54′37″N 87°09′41″E / 26.9102°N 87.1613°E / 26.9102; 87.1613
 • elevation
640 m (2,100 ft)[1]
Basin features
River systemKoshi River
Tributaries 
 • leftTamba Koshi, Likhu Khola, Dudh Koshi
 • rightBhote Koshi, Indravati River

River course

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Map showing the course of Sun Koshi (AMS, 1955)

The Sunkoshi's headwaters are located in the Zhangzangbo Glacier in Tibet.[6] Both Sunkoshi and Bhote Koshi river courses together form one basin that covers an area of about 3,394 km2 (1,310 sq mi).[1]

The Indravati meets the Sunkoshi at Dolaghat, up to where it is followed by the Arniko Rajmarg.[7] From there, the Sunkoshi flows eastwards through the valley formed between the Mahabharat Range and the Himalayas.[1] 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 load is 5.4 x 107 m3.[8]

 
Sunkoshi river in December 2023

The Tamur and the Arun rivers join the Sunkoshi at Tribenighat to form the Saptkoshi, which flows through the Chatra Gorge across the Mahabharat Range on to the Gangetic plain.[9] There are also a few smaller tributaries of the Sunkoshi, such as Rosi Khola, Junga Khola, and Sapsu Khola.[citation needed]

Names and etymology

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Nepali: सुनकोशी

In Nepali language, the word "sun" means gold and golden;[10] and the word "kosi" means river.[11]

Koshi River system

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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, Bhote Koshi, Dudh Kosi, Arun and Tamur Rivers. The Saptkoshi River flows through the Chatra Gorge in a southerly direction into northern Bihar and joins the Ganges.[9][12]

The Sunkoshi contributes about 44% of the total water of the Saptakoshi, the Arun 37% and the Tamur 19%.[13]

Infrastructures

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  • Sunkosi–Kamala multipurpose project: The Sunkoshi has a 90% reliable flow of 126 cubic metres per second (4,400 cu ft/s). It was proposed to divert the water from a small weir across the river near Kurule through a 16.6 km (10.3 mi) tunnel and a 61.4 MW associated power house to the Kamala River, flowing through central Nepal. Some 72 cubic metres per second (2,500 cu ft/s) of water would be transferred to the Kamala River for the purposes of irrigation and further generation of power.[14][15]

Hazards

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In July 1981, a sudden ice avalanche caused a Glacial Lake Outburst Flood in the moraine-dammed Zhangzangbu-Cho Lake in the headwaters of the Poiqu in Tibet. The ensuing debris flow destroyed bridges, and sections of both the Arniko and the Nepal–China highways.[6]

On 2 August 2014, a landslide at Jure blocked the river downstream from Barabise and created a large lake that submerged a hydropower station. This huge rockslide of approximately 5,000,000 m3 (180,000,000 cu ft) blocked the Sunkoshi River upstream of Jure village. This landslide killed approximately 155 people, destroyed approximately 120 houses completely and 37 partially.[16] The area was declared a flood crisis zone, and local communities were evacuated. Power supply was interrupted, and the Arniko Highway blocked.[17]

Water sports

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The Sunkoshi is used for both rafting and intermediate kayaking. It has grade III-IV rapids. The most common put in point of a Sunkoshi river trip is Dolaghat, at an elevation of 620 m (2,030 ft) and it ends at the Chatra Gorge at 115 m (377 ft), a distance of around 272 km (169 mi).[18]

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.[19] Prior to this successful trip, there are 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.[20]

Notes

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  1. ^ An alternative Tibetan name Bö Chu (Tibetan: བོད་ཆུ, Wylie: bod chu), also spelt Po Chu or Poi Chu, is also used in sources.[3][4] It would appear to be a literal translation of Bhote Kosi ("Tibetan river").

References

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  1. ^ a b c d e Shrestha, A. B., Eriksson, M., Mool, P., Ghimire, P., Mishra, B. & Khanal, N. R. (2010). "Glacial lake outburst flood risk assessment of Sun Koshi basin, Nepal". Geomatics, Natural Hazards and Risk. 1 (2): 157–169. doi:10.1080/19475701003668968. S2CID 129446680.{{cite journal}}: CS1 maint: multiple names: authors list (link) (See especially Figure 1).
  2. ^ Dorje, Gyurme (2004), Footprint Tibet Handbook with Bhutan (3rd ed.), Bath: Footprint Handbooks, p. 321, ISBN 1-903471-30-3 – via archive.org
  3. ^ Yamada, T; Sharma, C.K. (1993). "Glacier lakes and outburst floods in the Nepal Himalaya" (PDF). International Association of Hydrological Sciences. pp. 319–330. Archived from the original (PDF) on 20 March 2020.
  4. ^ Su, Pengcheng; Liu, Jingjing; Li, Yong; Liu, Wei; Wang, Yang; Ma, Chun; Li, Qimin (11 November 2021). "Changes in glacial lakes in the Poiqu River basin in the central Himalayas". Hydrology and Earth System Sciences. 25 (11): 5879–5903. doi:10.5194/hess-25-5879-2021. eISSN 1607-7938. the Poiqu River (Bhote Koshi River), a tributary of the Sun Koshi River ... The Poiqu River (known as the Bhotekoshi River in Nepal) is the boundary river between China and Nepal
  5. ^ Bhattarai, Keshav; Conway, Dennis (23 November 2020). Contemporary Environmental Problems in Nepal: Geographic Perspectives. Springer Nature. p. 495. ISBN 978-3-03-050168-6.
  6. ^ a b 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.
  7. ^ Dorje, G. (1999). Tibet Handbook: with Bhutan. Bath: Footprint Handbooks. ISBN 9781900949330.
  8. ^ Kattelmann, R. (1991). "Hydrologic regime of the Sapt Kosi basin, Nepal" (PDF). Hydrology for Water Management of Large River Basins (Proceedings of the Vienna Symposium). 201: 139–148.
  9. ^ a b 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.
  10. ^ Turner, R. L. (1931). "sun". A Comparative and Etymological Dictionary of the Nepali Language. K. Paul, Trench, Trubner, London.
  11. ^ Turner, R. L. (1931). "kosi". A Comparative and Etymological Dictionary of the Nepali Language. K. Paul, Trench, Trubner, London.
  12. ^ Negi, S. S. (1991). "Kosi River System". Himalayan Rivers, Lakes, and Glaciers. New Delhi: Indus Publishing Company. pp. 89–90. ISBN 9788185182612.
  13. ^ Rao, K. L. (1995). India's Water Wealth. Hyderabad: Orient Longman Ltd. p. 70. ISBN 9788125007043.
  14. ^ Bhattarai, D. (2009). "Sunkosi–Kamala Multi–purpose Project". In Dhungel, D. N.; Pun, S. B. (eds.). The Nepal–India Water Relationship: Challenges. Springer Science & Business Media. pp. 92–93. ISBN 9781402084034.
  15. ^ Gajurel, D. (2004). "High Dam Planned for Nepal's Sapta Koshi River". Environment News Service. Retrieved 14 May 2010.
  16. ^ Jaboyedoff, M.; Leibundgut, G.; Penna, I.; Dahal, R. K.; Sevkota, S.; Sudmeier, K. (2015). Characterization of the Jure (Sindhupalchok, Nepal) Landslide by TLS and field investigations. European Geosciences Union General Assembly 12–17 April 2015. Vienna, Austria: European Geosciences Union. p. 11858. Bibcode:2015EGUGA..1711858J.
  17. ^ Shrestha, A. B.; Khanal, N. R.; Shrestha, M.; Nibanupudi, H. K.; Molden, D. (2014). Eye on the Sun Koshi Landslide: Monitoring and Infrastructure Planning Key to Minimizing Scale of Disasters (PDF) (Report). Kathmandu: International Centre for Integrated Mountain Development.
  18. ^ Woodhatch, T. (1999). Nepal Handbook. p. 167, Footprint Handbooks, Augusta ISBN 0658000160
  19. ^ Taylor-Ide, D. (1995). "Something Hidden Behind the Ranges." San Francisco: Mercury House
  20. ^ Taylor, D. C. "Yeti: An Ecology of a Mystery." New Delhi: Oxford University Press, pp. 119-130.
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