Sun Kosi

Sun Kosi (Poiqu)

The Sino-Nepal Friendship Bridge over the Sun Kosi at Kodari
Origin Tibet
Mouth Confluence with Arun and Tamur to form Saptkoshi at Trivenighat, Nepal 26°54′47″N 87°09′25″E / 26.913°N 87.157°E
Basin countries Tibet, Nepal
Source elevation 8,012 m (26,286 ft)
Mouth elevation 640 m (2,100 ft)[1]
River system Koshi River
Left tributaries Tamba Koshi, Likhu Khola, Dudh Koshi
Right tributaries Indravati River

The Sun Kosi, also called Sun Koshi, is a trans-boundary river that originates in the Tibet and it is part of the Koshi or Saptkoshi River system in Nepal.[1]

River course

The Sun Kosi's headwaters are located in the Zhangzangbo Glacier in Tibet.[2] Its upper course, the Bhote Koshi, is known as Poiqu in Tibet.[3] Both river courses together form one basin that covers an area of about 3,394 km2 (1,310 sq mi).[1]

The Indravati meets the Sun Kosi at Dolaghat, up to where it is followed by the Arniko Rajmarg.[4] From there, the Sun Kosi flows eastwards through the valley formed between the Mahabharat Range and the Himalayas.[1]

The average annual flow is 22 x 109 m3. The average sediment load is 54 x 106 m3.[5]

The Tamur and the Arun rivers join the Sun Kosi at Tribenighat to form the Saptkoshi, which flows through the Chatra Gorge across the Mahabharat Range on to the Gangetic plain.[6]

There are few more smaller tributaries of the Sun Kosi such as Rosi Khola, Junga Khola, Tamakosi, Dudh Kosi, and Rasuwa Khola.

Names and etymology

Nepali: सुनकोशी

In Nepali language, the word "sun" means gold and golden;[7] and the word "kosi" means river.[8]

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 Sun Koshi, 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.[6][9]

The Sun Koshi contributes about 44% of the total water of the Saptakoshi, the Arun 37% and the Tamur 19%.[10]

Sun Kosi–Kamala multipurpose project

The Sun Kosi has a 90% 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.[11][12]

Hazards

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.[2]

On 2 August 2014, a landslide blocked the river downstream from Barabise and created a large lake that submerged a hydropower station. The collapsed river bed buried several houses, more than 30 people died. The area has been declared a flood crisis zone, and local communities are evacuated. Power supply is interrupted, and the Arniko Highway blocked.[13] See also 2014 Sunkoshi blockage

Water sports

The Sun Kosi is used for both rafting and intermediate kayaking. It has grade III-IV rapids. The most common put in point of a Sun Kosi river trip is Dolalghat, at a height 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).[14]

References

  1. ↑ 1.0 1.1 1.2 1.3 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.
  2. ↑ 2.0 2.1 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.
  3. ↑ Yamada, T., Sharma, C. K. (1993). Glacier lakes and outburst floods in the Nepal Himalaya. IAHS Publications-Publications of the International Association of Hydrological Sciences, 218: 319–330.
  4. ↑ Dorje, G. (1999). Tibet Handbook: with Bhutan. Bath: Footprint Handbooks.
  5. ↑ Kattelmann, R. (1991). "Hydrologic regime of the Sapt Kosi basin, Nepal". Hydrology for Water Management of Large River Basins (Proceedings of the Vienna Symposium). 201: 139–148.
  6. ↑ 6.0 6.1 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, March 7–9, 1994, Kathmandu. Ecological Society, Kathmandu. Pp 92–99.
  7. ↑ Turner, R. L. (1931). "sun". A Comparative and Etymological Dictionary of the Nepali Language. K. Paul, Trench, Trubner, London.
  8. ↑ Turner, R. L. (1931). "kosi". A Comparative and Etymological Dictionary of the Nepali Language. K. Paul, Trench, Trubner, London.
  9. ↑ Negi, S. S. (1991). "Kosi River System". Himalayan Rivers, Lakes, and Glaciers. New Delhi: Indus Publishing Company. pp. 89–90.
  10. ↑ Rao, K. L. (1995). India’s Water Wealth. Hyderabad: Orient Longman Ltd. p. 70.
  11. ↑ Bhattarai, D. (2009). "Multi-purpose Projects". In Dhungel, D. N., Pun, S. B. (eds.). The Nepal-India Water Relationship: Challenges. Springer Science & Business Media. pp. 69–98.
  12. ↑ Gajurel, D. (2004). "High Dam Planned for Nepal's Sapta Koshi River". Environment News Service. Retrieved 2010-05-14.
  13. ↑ Shrestha, A. B., Khanal, N. R., Shrestha, M., Nibanupudi, H. K. and Molden, D. (2014). Eye on the Sun Koshi Landslide: Monitoring and Infrastructure Planning Key to Minimizing Scale of Disasters. International Centre for Integrated Mountain Development, Kathmandu.
  14. ↑ Woodhatch, T. (1999). Nepal Handbook. p. 167, Footprint Handbooks, Augusta ISBN 0658000160