Rivers of Eastern Nepal:
Saptakoshi, Arun, Tamor
and Their Tributaries
From the glaciers of Kanchenjunga and the Tibetan plateau, seven great rivers converge in the hills of eastern Nepal before crossing into India and joining the Ganges. This is the story of each one.
Introduction
One River System, Dozens of Lives Sustained
Eastern Nepal is river country. From the moment the Himalayan glaciers begin to melt, water finds its way downward through gorges, across plains, and eventually into India — carrying snowmelt, sediment, and the freshwater that sustains tens of millions of people across the subcontinent. At the center of this system is the Saptakoshi: a single great river formed by the convergence of seven tributaries, each with its own origin, character, and ecological story.
The name Saptakoshi means literally "seven Koshis" — a reference to those seven upper rivers: the Tamor, Arun, Sun Koshi, Dudh Koshi, Bhote Koshi, Tamakoshi, and Indravati. Understanding them separately is the key to understanding the landscape of eastern Nepal, because each river shapes its own valley, supports its own communities, and carves its own route through the mountains before they all eventually become one.
This guide covers each major river individually — its origin, its tributaries, its ecological significance, and where relevant, the adventure opportunities it provides for rafters, kayakers, and trekkers.
- River system
- Saptakoshi (Koshi)
- Tributaries
- Seven upper rivers
- Major confluence
- Tribenighat (Tamor + Arun + Sun Koshi)
- Final destination
- Ganges near Kursela, Katihar, India
- Glacial sources
- Kanchenjunga, Everest, Tibet
- Adventure rivers
- Tamor, Arun, Bhote Koshi
- Highest river
- Dudh Koshi (by elevation)
- Trans-boundary
- Arun, Bhote Koshi (Tibet origin)
The Rivers
Each River, Explained
Seven distinct rivers. Seven different origins, landscapes, and stories — all converging into one of South Asia's great river systems.
Saptakoshi (Sapta Koshi)
The collective river — formed at Tribenighat
The Saptakoshi is Nepal's largest river system by drainage area, and one of the most significant rivers in the entire Indian subcontinent. It does not begin as a single stream — it is born at the confluence where the Tamor, Arun, and Sun Koshi rivers meet at a point called Tribenighat, forming the combined flow that takes the Saptakoshi name.
From Tribenighat, the Saptakoshi crosses the Terai lowlands of eastern Nepal and enters the Indian state of Bihar, where it fans out into distributaries across the Gangetic plain before joining the Ganges near Kursela in Katihar district. This final stretch through Bihar makes it one of the major rivers of the Ganges basin — and also one of Bihar's most significant flood risks during the monsoon.
In Hindu religious tradition, the Saptakoshi is considered sacred. Its waters carry snow from the world's highest mountains, and its confluence points — particularly where the Koka river meets the Koshi near Baraha Kshetra — are pilgrimage sites of considerable importance.
- Formed at
- Tribenighat confluence
- Enters India via
- Eastern Nepal Terai
- Joins Ganges near
- Kursela, Katihar, Bihar
- Religious status
- Sacred in Hindu tradition
Tamor River (Tamor Nadi)
Eastern Koshi tributary — born at Kanchenjunga
The Tamor River — also called Tamor Nadi — is the easternmost major tributary of the Saptakoshi. It originates in the Kanchenjunga area of Taplejung district, drawing its water from the glaciers and snowfields that surround the world's third-highest peak. From those glacial headwaters, the Tamor carves a long course southwestward through some of eastern Nepal's most dramatic gorge country.
At Tribenighat, the Tamor meets the Arun and the Sun Koshi to form the Saptakoshi — the endpoint of a journey that begins in permanent snow above 8,000 metres and ends in the Terai. Along the way, the Tamor has become one of Nepal's most sought-after rivers for white-water adventure. Its rapids, which range from moderate to genuinely challenging depending on the section and season, draw rafters and kayakers from across the country and internationally.
- Origin
- Kanchenjunga area, Taplejung
- Joins at
- Tribenighat (forms Saptakoshi)
- Adventure
- Rafting and kayaking
- Direction
- Flows southwest to confluence
The Arun River cutting through the remote gorges of eastern Nepal — it originates in Tibet as the Phung Chu and flows through Makalu-Barun National Park before joining the Saptakoshi at Tribenighat
Arun River
Trans-boundary river from Tibet — through Makalu-Barun
The Arun is one of Nepal's most geologically remarkable rivers. It originates in the Tibet Autonomous Region of China, where it is known as the Phung Chu or Bum-chu, and crosses into Nepal through terrain that is among the most rugged in the country. In the process, it cuts one of the deepest gorges in the Himalayas — dropping from high Tibetan plateau elevations to the sub-tropical valleys of eastern Nepal in a remarkably short horizontal distance.
Its route through Nepal passes directly through the Makalu-Barun National Park, which surrounds both the Barun Valley and the approaches to Mount Makalu (8,485 m). The national park was partly established to protect the Arun's watershed, and the river's remote character has kept its immediate valley one of the least-disturbed in Nepal.
The combination of steep gradient, high water volume, and remote location makes the Arun one of Nepal's premier white-water rafting and kayaking rivers for experienced paddlers — though it demands a significantly higher skill level than more accessible rivers like the Trishuli or upper Kali Gandaki.
- Origin
- Tibet (as Phung Chu / Bum-chu)
- Passes through
- Makalu-Barun National Park
- Joins at
- Tribenighat (Saptakoshi)
- Character
- Deep gorges, high volume, steep gradient
Sun Koshi River
The central Koshi — from Zhangzangbo Glacier, Tibet
The Sun Koshi — "River of Gold" — is the central artery of the Koshi system. Its headwaters originate in the Zhangzangbo Glacier in Tibet, and its upper course is known as the Bhote Koshi — or Poiqu in Tibetan. Together, the Bhote Koshi and Sun Koshi cover a combined basin area of approximately 3,394 km², making it a major catchment even before its own tributaries join.
The Sun Koshi receives water from some of the world's most dramatic glacial environments through its eastern tributaries: the Dudh Koshi (which drains the Everest slopes), the Bhote Koshi (from the Tibet border northeast of Kathmandu), the Tamakoshi, the Likhu Khola, and the Indravati. All of these rivers flow into the Sun Koshi before it meets the Tamor and Arun at Tribenighat.
- Origin
- Zhangzangbo Glacier, Tibet
- Upper name
- Bhote Koshi (Poiqu in Tibet)
- Basin area
- ~3,394 km2
- Key tributaries
- Dudh Koshi, Bhote Koshi, Tamakoshi, Likhu, Indravati
Sun Koshi tributaries (east to west)
| River | Origin | Notable for |
|---|---|---|
| Dudh Koshi | Khumbu / Everest glaciers | Highest river by elevation; Everest drainage |
| Bhote Koshi | Tibet border (NE of Kathmandu) | Upper Sun Koshi; white-water rafting |
| Tamakoshi | Tibetan plateau | Hydropower development |
| Likhu Khola | Eastern hills, Ramechhap | 23 MW hydropower; 75 km length |
| Indravati | Western hills near Kathmandu | Hydropower; water supply |
The Sun Koshi and Dudh Koshi — the Dudh Koshi (Milk River) is the world's highest-elevation river and drains the slopes of Everest before joining the broader Koshi system
Dudh Koshi
The Milk River — drains the slopes of Everest
The Dudh Koshi — meaning "Milk River," named for the colour of its glacially turbid water — is the highest-elevation major river in Nepal and one of the highest in the world. Its water comes directly from the Khumbu Glacier above Everest Base Camp, draining the most famous mountain terrain on the planet.
The upper Dudh Koshi is fed by the Imja Khola, which begins where the Khumbu Glacier melts into the Lobuche River and flows southward past the confluence at Tengboche monastery. The Imja Khola collects water from the Imja Glacier through the Dingboche Valley before joining the Dudh Koshi proper. Further south, the Hongu River — which flows through Sankhuwasabha district — joins via the Hinku River, adding another glacial source to the Dudh Koshi's volume before it eventually reaches the Sun Koshi.
The Dudh Koshi valley is one of the most trekked routes in the world — the Everest Base Camp trail follows its course — meaning this river is familiar to hundreds of thousands of visitors every year even if they don't know its name.
- Meaning
- Dudh = Milk (glacial turbidity)
- Upper source
- Khumbu Glacier, Everest
- Key tributary
- Imja Khola (via Lobuche River)
- Joins
- Sun Koshi system
Bhote Koshi
Upper Sun Koshi — from Tibet border, northeast of Kathmandu
The Bhote Koshi is technically the upper course of the Sun Koshi — the same river before it enters the Kathmandu valley region. In Tibet, it is called Poiqu. Flowing from the Tibet border northeast of Kathmandu, the Bhote Koshi drops rapidly as it descends from the Tibetan plateau through the Himalayan foothills, making it one of Nepal's steepest major rivers.
That steep gradient is what gives the Bhote Koshi its reputation as one of Nepal's top white-water rafting rivers. Its rapids — powerful, technical, and set against dramatic gorge scenery — are among the most challenging on the commercial rafting circuit. The river is also a significant source of hydropower; multiple projects tap its flow to contribute to Nepal's electricity supply.
- Origin
- Tibet (as Poiqu)
- Location
- NE of Kathmandu, Sindhupalchok
- Identity
- Upper course of Sun Koshi
- Uses
- Rafting; major hydropower source
Likhu Khola
Ramechhap district tributary — 75 km, 23 MW hydro
The Likhu Khola is a lesser-known but ecologically and economically important tributary of the Sun Koshi. With a length of approximately 75 km, it flows through Ramechhap district in a catchment bordered to the west by the Tamakoshi river system and to the east by the Dudh Koshi. The Likhu Hydropower Project, with a generation capacity of 23 MW, operates on the Likhu Khola — one of several hydropower developments in Nepal's eastern hills tapping the reliable flow of Himalayan rivers.
The river is also notable for its fish diversity. Snow trout — a cold-water species well adapted to the clear, fast-flowing streams of the upper Himalayas — are found in the upper reaches of the Likhu Khola, making it of interest to both ecologists and local fishing communities.
- District
- Ramechhap
- Length
- ~75 km
- Hydro capacity
- 23 MW (Likhu Hydropower Project)
- Wildlife
- Snow trout in upper reaches
Dudh Koshi deep-dive: The Dudh Koshi has its own dedicated guide on East Nepal covering the Imja Khola glacier connections, the Khumbu Valley drainage, and the river's ecology in more detail. Read the Dudh Koshi (दुधकोशी नदी) full article here.
Adventure note: The Tamor, Arun, and Bhote Koshi are all classified as expert-to-intermediate white-water rivers. Reputable operators with proper safety certification should always be used. River conditions change significantly with the monsoon (June-September) and the water volume and rapid grades vary considerably by season.
The Big Picture
How the Seven Rivers Become One
The convergence that creates the Saptakoshi happens at Tribenighat — a name that means "three-river confluence" — where the Tamor (from Kanchenjunga's glaciers in the east), the Arun (from the Tibetan plateau in the north), and the Sun Koshi (with all its own tributaries from the west) meet. From that single point, the Saptakoshi carries the combined water of the entire eastern Himalayan arc southward.
From Nepal to the Ganges
Crossing the Terai, the Saptakoshi enters Bihar and becomes one of the defining geographical features of the northern Indian state. Its annual floods — fed by monsoon precipitation across the entire Koshi catchment — are among the most significant in South Asia, and the river has shifted course repeatedly over the past centuries, earning it the name "Bihar's Sorrow" in some accounts.
Despite that difficult reputation, the Saptakoshi-Ganges system also represents one of the world's great water highways — moving Himalayan snowmelt across the entire width of the subcontinent, recharging the aquifers of the Indo-Gangetic plain, and eventually reaching the Bay of Bengal. The rivers of eastern Nepal are, in that sense, not local features: they are part of a continental-scale hydrological system that sustains agriculture across four countries.
Cultural and Religious Significance
For Nepali and Indian Hindu communities, these rivers carry meaning beyond hydrology. The Saptakoshi is considered sacred. Its confluence points — particularly at Tribenighat and at Baraha Kshetra, where the Koka meets the Koshi — are active pilgrimage sites. Ritual bathing at these junctions is believed to carry spiritual benefit, and the semi-Kumbha Mela at Baraha Kshetra draws hundreds of thousands of pilgrims specifically to the river's edge.
Quick Answers
Frequently Asked Questions
Written for Google PAA, voice search, Gemini, Perplexity and Bing Copilot.
What are the seven rivers of the Saptakoshi?
The Saptakoshi (meaning "seven Koshis") is formed by seven upper tributaries: the Tamor, Arun, Sun Koshi, Dudh Koshi, Bhote Koshi, Tamakoshi, and Indravati. The Tamor, Arun, and Sun Koshi meet at Tribenighat to form the main Saptakoshi channel, which then crosses into Bihar, India before joining the Ganges.
Where does the Tamor River originate?
The Tamor River (also called Tamor Nadi) originates in the Kanchenjunga area of Taplejung district in eastern Nepal. It flows southwest through deep gorge country before joining the Arun River and Sun Koshi at Tribenighat to form the Saptakoshi.
Where does the Arun River come from?
The Arun River originates in the Tibet Autonomous Region of China, where it is known as the Phung Chu or Bum-chu. It is a trans-boundary river that crosses into Nepal and flows through the Makalu-Barun National Park, cutting some of the deepest gorges in the Himalayas before joining the Saptakoshi at Tribenighat.
What is the highest river in Nepal?
The Dudh Koshi is considered Nepal's highest river in terms of elevation. It drains the slopes of Mount Everest — the Khumbu Glacier melts into the Lobuche River, which flows as the Imja Khola before joining the Dudh Koshi near Tengboche monastery. The Dudh Koshi then joins the Sun Koshi system on its way to the Saptakoshi.
What is the Bhote Koshi river?
The Bhote Koshi is a trans-boundary river originating in Tibet (where it is called Poiqu) that flows into Nepal northeast of Kathmandu. It is technically the upper course of the Sun Koshi and is known for its steep gradient, turbulent rapids, and popularity as a white-water rafting destination. It is also a significant source of hydropower for Nepal.
Where does the Saptakoshi join the Ganges?
After crossing through Nepal's eastern Terai and northern Bihar in India, the Saptakoshi joins the Ganges River near Kursela in Katihar district, Bihar. Along the way it branches into distributaries across the Gangetic plain.
Which rivers in eastern Nepal are good for rafting?
The Tamor, Arun, and Bhote Koshi are the primary white-water rivers of eastern Nepal. The Tamor offers a multi-day rafting expedition through remote gorge country from the Kanchenjunga area. The Arun is expert-level due to its remote location and high water volume. The Bhote Koshi is the most accessible and has some of Nepal's most technical commercial rapids.
What is the Likhu Khola known for?
The Likhu Khola is a 75-kilometre tributary of the Sun Koshi in Ramechhap district, known for the 23 MW Likhu Hydropower Project on its banks and for hosting snow trout in its upper reaches. Its catchment lies between the Tamakoshi to the west and the Dudh Koshi to the east.
Explore More of Eastern Nepal
The rivers are just the beginning. Discover the valleys, peaks, temples and cultures of Koshi Province.
Browse East Nepal Guides
Hi! Please, Do not Spam in Comments