Sun Kosi

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Sun Koshi (Matsang Tsangpo)
Origin Tibet, China
Mouth Confluence with Arun and Tamur to form Sapta Koshi at Trivenighat, Nepal 26°54′47″N 87°09′25″E / 26.913°N 87.157°E / 26.913; 87.157.
Basin countries China, Nepal
River system Kosi River
Left tributaries Bhote Koshi, Dudh Koshi
Right tributaries Indravati

The Sun Kosi (Nepali: सुनकोशी; Chinese: 桑科西; pinyin: Sāng Kēxī) or Matsang Tsangpo (Tibetan: མ་གཙང་གཙང་པོ།Wylie: ma gtsang gtsang po, Chinese: 麻章藏布; pinyin: Mázhāng Zàngbù) is a trans-boundary river and is part of the Koshi or Sapta Koshi river system in Nepal. It originates in Tibet Autonomous Region of China.


Sun Koshi or Sona Koshi means river of gold. In the local languages sun means gold and koshi means river. It could have been so named because of the gold sometimes picked up with the gravels, or because of the colour of the water loaded with alluvium during the monsoons.[1] The Sun Koshi is known as Matsang Tsangpo in Tibet.[2] The suffix Tsangpo denotes a river flowing from or through Tsang, i.e. Tibet west of Lhasa.

Koshi river system[edit]

The Koshi or Sapt Koshi drains eastern Nepal. It is known as Sapt Koshi because of the seven rivers which join together in east-central Nepal to form this river. The main rivers forming the Koshi system are – the Sun Koshi River, the Indravati River, the Bhote Koshi, the Dudh Koshi, the Arun River, Barun River, and Tamur River. The combined river flows through the Chatra Gorge in a southerly direction to emerge from the hills.[3][4]

The Sun Koshi contributes 44 per cent of the total water in the Sapta Koshi, the Arun 37 per cent and the Tamur 19 per cent.[5]


The Sino-Nepal Friendship Bridge over the Sun Kosi at Kodari

The westernmost part of Tsang province is traditionally known as Lato, the highland region of Tibet. North Lato comprises the upper reaches of the Yarlung Tsangpo and Raga Tsangpo. South Lato comprises the upper reaches of Matsang Tsangpo, Bum-chu, and Kyirong Tsangpo.[6]

The Sun Koshi or Matsang Tsangpo rises as a number of snow fed streams beyond Gosainthan massif in Tibet.[3] South of the town of Pengyeling, in Nyalam County of Tibet, Matsang Tsangpo gorge cuts through the Himalayas.

In Nepal, the Arniko Rajmarg follows the Sun Koshi up to Dolaghat.[7] It is joined by the Bhote Koshi just downstream from Barabise, in Nepal.[8] The Indravati meets the Sun Kosi at Dolaghat.[9] The Sun Kosi then flows eastwards through the valley between the Mahabharat Range and the Himalayas. The area has no roads or towns, just the occasional picturesque village.[10] There are few more tributaries of Sun Kosi as Rosi Khola, Junga Khola, Tamakosi (copper river), Dudh Kosi (milk river), and Rasuwa Khola.[11] The Tamur, the Arun join the Sun Kosi at Tribenighat to form the giant Saptakoshi which flows through the Chatra Gorge across the Mahabharat Range on to the Gangetic plain.[12]

The Sun Kosi basin covers an area of 18,800 square kilometres (7,300 sq mi). Average annual flow is 22 x 109 m3. Average sediment load is 54 x 106 m3.[13]

Water sports[edit]

The Sun Kosi is used for both rafting and intermediate kayaking. It has grade III-IV rapids.[14] The most common put in point of a Sun Kosi river trip is Dolalghat,[15] at a height of 620 metres (2,030 ft) and it ends at the Chatra Gorge at 115 metres (377 ft), a distance of around 272 kilometres (169 mi).[16]

Sun Kosi-Kamala multipurpose project[edit]

The Sun Kosi has a 90 per cent reliable flow of 126 cubic metres per second (4,400 cu ft/s). It has been proposed that water be diverted from a small weir across the river near Kurule through a 16.6 kilometres (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.[17][18]


  1. ^ Kapoor, Subodh. "Encyclopaedia of ancient Indian geography". p. 429. Google books. Retrieved 2010-05-15. 
  2. ^ "Dingri County". Tibet Retrieved 2010-05-15. 
  3. ^ a b Negi, Sharad Singh. "Himalayan rivers, lakes and glaciers". Kosi River System, p. 89. Google books. Retrieved 2010-05-14. 
  4. ^ Bahadur, Jagdish. "Himalayan snow and glaciers: associated environmental problems, progress". Koshi, p. 90. Google books. Retrieved 2010-05-14. 
  5. ^ K.L.Rao. "India’s Water Wealth". p. 70. Google books. Retrieved 2010-05-25. 
  6. ^ Dorje, Gyurme. "Footprint Tibet handbook: with Bhutan". Dingri County, p. 296. Google books. Retrieved 2010-05-18. 
  7. ^ Dorje, Gyurme. "Footprint Tibet Handbook: with Bhutan". Nyalam County, pp. 304-305. Google books. Retrieved 2010-05-14. 
  8. ^ "Sun Kosi River". . Retrieved 2010-05-14. 
  9. ^ Dorje, Gyurme. "Footprint Tibet handbook: with Bhutan". p. 821. Google books. Retrieved 2010-05-15. 
  10. ^ "Sun Kosi River". . Retrieved 2010-05-14. 
  11. ^ "Rafting in Nepal – Sun Koshi Rafting". Himalman’s weblog. Retrieved 2010-05-14. 
  12. ^ "a complete guide to Nepal’s rivers". Sun Koshi river trip. . Retrieved 2010-05-14. 
  13. ^ Kattelmann, Richard. "Hydrology for the Water Management of Large River Bas". Hydrlogic regime of the Saft Kosi basin, Nepal. Vienna Symposium, August 1991. Retrieved 2010-05-14. 
  14. ^ "Sun Kosi river Expedition". rafting Retrieved 2010-05-14. 
  15. ^ "a complete guide to Nepal’s rivers". Sun Koshi river trip. . Retrieved 2010-05-14. 
  16. ^ Tom Woodhatch, "Nepal Handbook", p. 167, Footprint, ISBN 0658000160
  17. ^ Dwarika N. Dhungel, Santa B. Pun. "The Nepal-India Water Relationship: Challenges". p. 91. Google Books. Retrieved 2010-05-17. 
  18. ^ "High dam proposed for Nepal’s Sapta Koshi river". Environment News Service . Retrieved 2010-05-14.