Nepal is often called the “water tower of Asia” — and for good reason. Its Himalayan glaciers and monsoon rains feed rivers that flow south into the Ganges, providing water for hundreds of millions of people in Nepal and India.
Nepal’s rivers are grouped into three major systems: the Koshi (east), the Gandaki (center), and the Karnali (west). Together, they drain nearly all of Nepal’s territory.
Why Nepal’s Rivers Matter
- Freshwater supply: They provide drinking water, irrigation, and hydroelectric power
- Agriculture: Terai farmers depend on river water for rice, wheat, and sugarcane
- Biodiversity: River valleys support forests, wildlife, and fish species
- Culture: Rivers are sacred in Hindu and Buddhist traditions
1. The Koshi River System
The Koshi is the largest river system in Nepal in terms of drainage area and discharge.
Key facts:
- Catchment area: 60,400 km² (46% within Nepal)
- Annual discharge: ~45 billion m³
- Main tributaries: Sunkoshi, Arun, Tamur, Dudh Koshi, Tama Koshi, Likhu, Indrawati
Seven major rivers join to form the Sapta Koshi (“Seven Koshi”) in southeastern Nepal. The name “Koshi” comes from the sage Kaushik, who is said to have meditated on its banks.
The Koshi basin contains about 40% of Nepal’s glacial lakes, making it important for hydropower but also vulnerable to glacial lake outburst floods (GLOFs).
Key districts: Solukhumbu, Sankhuwasabha, Taplejung, Terhathum, Bhojpur, Dhankuta, Morang, Sunsari, Udayapur
2. The Gandaki River System
The Gandaki flows through central Nepal and is also known as the Narayani after it reaches the plains.
Key facts:
- Catchment area: 34,960 km² (90% within Nepal)
- Annual discharge: ~50 billion m³
- Main tributaries: Trishuli, Budhi Gandaki, Marsyangdi, Seti, Kali Gandaki
The Kali Gandaki is famous for creating the Kali Gandaki Gorge — considered one of the deepest gorges in the world, lying between the Dhaulagiri and Annapurna massifs.
The Gandaki basin has fewer glacial lakes than the Koshi or Karnali, but carries the highest sediment yield of the three systems.
Key districts: Mustang, Manang, Myagdi, Kaski, Tanahun, Gorkha, Chitwan, Nawalpur
3. The Karnali River System
The Karnali is the longest river in Nepal and flows through the remote western region.
Key facts:
- Catchment area: 43,960 km² (94% within Nepal)
- Annual discharge: ~44 billion m³
- Main tributaries: Bheri, Tila, Mugu Karnali, Humla Karnali, West Seti, Kawari
The Karnali basin has the most glacial lakes of any basin in Nepal — about 50% of the national total. However, fewer of these are considered “potentially dangerous” compared to the Koshi basin.
The Karnali is known for its white-water rafting, considered some of the best in the world. It also supports the Karnali River dolphin, an endangered freshwater species.
Key districts: Humla, Mugu, Dolpa, Jumla, Kalikot, Jajarkot, Dailekh, Surkhet, Bardiya, Kailali
Comparison Table
| River System | Catchment (km²) | In Nepal | Annual Discharge (billion m³) | Main Tributaries | Key Districts |
|---|---|---|---|---|---|
| Koshi | 60,400 | 46% | 45 | Sunkoshi, Arun, Tamur | Solukhumbu, Morang |
| Gandaki | 34,960 | 90% | 50 | Trishuli, Kali Gandaki | Kaski, Mustang, Chitwan |
| Karnali | 43,960 | 94% | 44 | Bheri, Mugu Karnali | Humla, Surkhet, Bardiya |
Frequently Asked Questions
Q: What is the longest river in Nepal? The Karnali is the longest river system entirely within Nepal’s borders.
Q: Which river system is the largest in Nepal? The Koshi has the largest drainage area (60,400 km² total).
Q: Where do Nepal’s rivers originate? Most originate in the Himalayas from glacial melt and monsoon rain. Some, like the Arun and Humla Karnali, originate in Tibet.
Q: Why are Nepal’s rivers important? They provide water for drinking, irrigation, and hydropower; support biodiversity; and are culturally significant. They also sustain agriculture in the Terai — Nepal’s “granary.”
Q: Which river flows through the Kali Gandaki Gorge? The Kali Gandaki, a tributary of the Gandaki system, flows through the famous gorge between Dhaulagiri and Annapurna.