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]
River course
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]
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
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
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
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
^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").
^
abMool, 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.
^
abSharma, 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.