Nepal's River System

Nepal measures about 800 kilometers (497 mi) along its Himalayan axis by 150 to 250 kilometers (93 to 155 mi) across. With 147,181 square kilometers (56,827 sq mi) it slightly outranks Bangladesh or the state of Arkansas. Nepal is landlocked by India on three sides and China's Xizang Autonomous Region (Tibet) to the north. West Bengal's narrow Siliguri Corridor or Chicken's Neck separate Nepal and Bangladesh. To the east are India—and Bhutan. Nepalese rivers can be grouped into three categories on the basis of their origin.

  • Antecedent to Himalaya
  • After the Mahabharat
  • After the Churia range


Antecedent rivers
Belong to the period prior to the rise of the Himalaya. These rivers added their tributaries during or after the Himalayan origin along with the development of monsoon climate. After the formation of Mahabharata hills, the antecedent rivers changed their courses as Mahabharata stood as a barrier. As a result, most of the rivers changed their courses either to the east or west. Most of these rivers were responsible to deposit the sediments in the Churia basin.

The major river systems namely the Koshi, the Karnali and the Gandaki belong to the Antecedent group. Rivers originating from the Mahabharat range and cutting through Churia hills come under the second group these include Kankai, Bagmati, Kamala etc. The third group of rivers originates from the southern face of the Churia hills.

As mentioned above and divided into different system, Nepal has three categories of rivers. The largest systems -— from east to west Koshi, Gandaki/Narayani, Karnali/Goghra and Mahakali -- originate in multiple tributaries rising in or beyond the high Himalaya that maintain substantial flows from snowmelt through the hot, droughty spring before the summer monsoon. These tributaries cross the highest mountains in deep gorges, flow south through the Middle Hills, then join in candelabra -like configuration before crossing the Mahabharat Range and emerging onto the plains where they have deposited megafans exceeding 10,000 km2 (3,861 sq mi) area.

The Koshi is also called Sapta Koshi for its seven Himalayan tributaries in eastern Nepal: Indrawati, Sun Koshi, Tama Koshi, Dudh Koshi, Liku, Arun, and Tamur. The Arun rises in Tibet some 150 km. beyond Nepal's northern border. A tributary of the Sun Koshi, Bhote Koshi also rises in Tibet and is followed by the Arniko Highway connecting Kathmandu and Lhasa.

The Gandaki/Narayani has seven Himalayan tributaries in the center of the country: Daraudi, Seti Gandaki, Madi, Kali, Marsyandi, Budhi, and Trisuli also called Sapta Gandaki. The Kali Gandaki rises on the edge of the Tibetan Plateau and flows through the semi-independent Kingdom of Mustang, then between the 8,000-meter (26,247 ft) Dhaulagiri and Annapurna ranges in the world's deepest valley. The Trisuli rises north of the international border inside Tibet. After the seven upper tributaries join, the river becomes the Narayani inside Nepal and is joined by the (East) Rapti from Chitwan Valley.  Once crossed into India, its name changes to Gandak.

The Karnali drains western Nepal, with the Bheri and Seti as major tributaries. The upper Bheri drains Dolpo, a remote valley beyond the Dhaulagiri Himalaya with traditional Tibetan cultural affinities. The upper Karnali rises inside Tibet near sacred Lake Manasarovar and Mount Kailash. The area around these features is the hydrographic nexus of South Asia since it holds the sources of the Indus and its major tributary the Sutlej, the Karnali -- a Ganges tributary -- and the Yarlung Zangbo/Brahmaputra. It is the center of the universe according to traditional cosmography. The Mahakali or Kali along the Nepal-India border on the west joins the Karnali in India, where the river is known as Goghra or Ghaghara.

Second category rivers rise in the Middle Hills and Mahabharat Range, from east to west the Mechi, Kankai and Kamala south of the Kosi; the Bagmati that drains Kathmandu Valley between the Kosi and Gandaki systems, then the West Rapti and the Babai between the Gandaki and Karnali systems. Without glacial sources, annual flow regimes in these rivers are more variable although limited flow persists through the dry sea

For the purpose of commercial rafting, the following rivers systems are in use in Nepal:

  • The Trishuli (Trishuli Narayanghat)
  • The Kaligandaki (Kusma- Tiger Tops)
  • The Bheri (Birendranagar- Chisapani)
  • The Seti (Damauli- Tiger Tops)
  • The Sunkoshi (Baseri- Chatara)
  • The Karnali (Bhankhet- Chisapani)
  • The Tama Kohsi (Basti- Chatara)
  • The Arun (Tumlingtar- Chatara)

Glance of Jungle Safari