Gandaki Basin
- Page status
- Registry record
- Updated
- 2026-05-11
Summary
The Gandaki (Narayani) basin is Nepal's central major river system, draining ~32,148 km² within Nepal. Its tributaries include Kali Gandaki, Marsyangdi, Budhi Gandaki, Trishuli, Seti, Madi, and East Rapti. The Kali Gandaki gorge between Annapurna and Dhaulagiri drops >5,500 vertical meters — by some measures the world's deepest.
This is Nepal's most developed hydropower corridor.
Key Facts
| Fact | Value |
|---|---|
| Area in Nepal | 32,148 km² |
| Average discharge (border) | 1,952 m³/s (~61.6 BCM/yr) |
| Monsoon share | 74–80% |
| Peak-to-dry ratio | 22–30:1 |
| Gross hydropower potential | 19,803 MW (27.3% of national total) |
Hydropower Significance
The most mature "buildable" basin. Hosts Nepal's early landmark projects — Kali Gandaki A (144 MW), Middle Marsyangdi (70 MW), and the Kulekhani Cascade (on a tributary). The corridor benefited from road access (Prithvi and Siddhartha highways) and historical institutional familiarity.
The proposed Budhigandaki Hydroelectric Project (1,200 MW) would be the basin's first major storage project and a system-shaping intervention for Nepal Energy Profile.
Constraints
- Sediment as Design Constraint — the Kali Gandaki A plant is the definitive case study for turbine erosion. Suspended sediment spikes from 20 ppm (dry) to 50,000 ppm (monsoon). 65 million tonnes/year pass the dam site.
- More developed does not mean fully tapped. Significant untapped tributary potential remains.
Downstream Significance
The Gandak system irrigates ~1.5–2 million ha in Bihar and eastern Uttar Pradesh. The Gandak Treaty (1959) gave Nepal only 15 MW from a major barrage — one of the most cited examples of treaty asymmetry. See Hydro-Geopolitics.
Limitations & Controversies
Sediment as design constraint. The Kali Gandaki A plant is the definitive case study for turbine erosion. Suspended sediment spikes from 20 ppm (dry) to 50,000 ppm (monsoon), with 65 million tonnes/year passing the dam site. Abrasive silt is a first-order design constraint across the basin, not just an implementation detail after head and flow are set.
Treaty asymmetry. The Gandak Treaty (1959) gave Nepal only 15 MW from a major barrage — one of the most cited examples of treaty inequity in South Asian water governance. Future projects in this basin carry the memory of that history.
Most developed does not mean fully tapped. Road access and institutional familiarity have concentrated development on the main stem and larger tributaries. Significant untapped potential remains on smaller tributaries, but the financing and grid-access gaps that blocked them historically persist.