Karnali Basin
- Page status
- Registry record
- Updated
- 2026-05-11
Summary
The Karnali basin is Nepal's western major river system and the largest by area at ~43,153 km² within Nepal. Its tributaries include Bheri, West Seti, Humla Karnali, Mugu Karnali, and Tila. The Karnali feeds the Ghaghara, which contributes ~40% of the Ganges' baseflow at Varanasi.
This is Nepal's most dramatically underused basin — essentially zero large-scale hydropower despite having the best sites.
Key Facts
| Fact | Value |
|---|---|
| Area in Nepal | 43,153 km² |
| Average discharge (border) | 1,256 m³/s (~39.6 BCM/yr) |
| Monsoon share | 65–72% |
| Peak-to-dry ratio | 15–20:1 (best stability) |
| Gross hydropower potential | 20,385 MW (28.1% of national total) |
Why It Matters Most
The Karnali has the best dry-season flow stability of any major Nepali system (lowest peak-to-dry ratio at 15–20:1 vs 25–50:1 for Koshi). WECS calls it the basin with the highest hydropower potential. It is the most obvious strategic priority for future development.
Why It Remains Undeveloped
- Remoteness — western Nepal has historically had fewer roads, less political attention, and less financing reach
- Transmission gap — the grid west of Butwal relies on legacy 132 kV lines incapable of handling large generation
- Political neglect — eastern-centric development patterns systematically disadvantaged the west
- The proposed Karnali Chisapani Project (10,800 MW) alone would transform Nepal's energy posture, but it remains conceptual
Climate Projections
CMIP6 modeling projects the Karnali will experience 3–23% decrease in winter/spring discharge by end of century, alongside 18–51% increase in monsoon/post-monsoon discharge. Temporal concentration of water will become even more extreme. See Peak Water.
A useful basin-specific warning from ICIMOD: over 1981–2012, average precipitation in the Karnali study basin trended downward by 4.91 mm/year, yet discharge stayed broadly constant over the observed record. That is exactly the kind of rainfall-flow decoupling that makes annual averages misleading for energy planning.
Limitations & Controversies
Remoteness and infrastructure gap. Western Nepal has historically had fewer roads, less political attention, and less financing reach than the central and eastern corridors. The grid west of Butwal relies on legacy 132 kV lines incapable of handling large generation, creating a chicken-and-egg problem: no transmission, no projects; no projects, no transmission justification.
Political neglect. Eastern-centric development patterns have systematically disadvantaged the west. Every national hydropower master plan since the 1960s has identified Karnali as a priority; none has funded the pre-feasibility or transmission backbone to make it actionable.
Climate uncertainty. CMIP6 projects a 3–23% decrease in winter/spring discharge by end of century, alongside 18–51% increase in monsoon/post-monsoon discharge. The basin's current advantage — the best dry-season stability in Nepal — may erode, making long-lead-time investments riskier.
Karnali Chisapani remains conceptual. At 10,800 MW, the basin's signature project has no DPR, no timeline, and no institutional champion. Four decades of appearing in master plans without advancing is a credibility tax on the entire basin.
Downstream Significance
The Karnali/Ghaghara system serves ~2–3 million ha in UP and connects to Bangladesh's Ganges flow. See Nepal's Contribution to the Ganges.