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. The Sun Kosi's headwaters are located in the Zhangzangbo Glacier in Tibet. Its upper course, the Bhote Koshi, is known as Poiqu in Tibet. Both river courses together form one basin that covers an area of about 3,394 km2 (1,310 sq mi). The Indravati meets the Sun Kosi at Dolaghat, up to where it is followed by the Arniko Rajmarg. From there, the Sun Kosi flows eastwards through the valley formed between the Mahabharat Range and the Himalayas. The average annual flow is 22 x 109 m3. The average sediment load is 54 x 106 m3. 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. There are few more smaller tributaries of the Sun Kosi such as Rosi Khola, Junga Khola, Tamakosi, Dudh Kosi, and Rasuwa Khola. 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. The Sun Koshi contributes about 44% of the total water of the Saptakoshi, the Arun 37% and the Tamur. 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)
Day 01: After three hours driving from Kathmandu we will reach Damauli. Lunch, set up the rafts, safety briefing, load the gears and set off the river. Grade 2 rapids, Hindu temple and camp on Butterfly Beach.
Day 02: Breakfast, rafting , passing day with two big class rapids "No exit" (Grade 3) and "Meatgrinder" (Grade -4) and other small ones. On the way Tamba Kosi joins the river increasing the volume just before we reach our camp. Cliff jumps, bat caves and track for tiger footprints etc. are the major attraction while on the trek.
Day 03: The river starts to build up in Likhu Khola and you will be facing rapids, pre, post and "High Anxiety". Overnight at camp.
Day 04: This day you will be dealing with hard rafts "Hakapur" the biggest rapid. After up and down we will camp at the confluence of the Sun Kosi and Dudh Kodi.
Day 05-08: In this days you will pass "Jaws" I, II & III’, "Rhino Rock" and “Jungle Corridor”. The "Big Dipper" and "Black Hole" are the last big rapids on the river and a fitting finale to the Sun Kosi. On the journey we will stop by the Arun and Tamur rivers to holy Hindu temple to view the sights. We will end our journey at Chatra, unload the gear one final time and jump in our bus/plane back to Kathmandu.
Day 09: Flight will take you Kathmandu by 8th day but the bus needs 15 hours back to Kathmandu.