ICIMOD Threats to the Koshi River Basin
ICIMOD's basin-level account of Koshi sediment loads, erosion and environmental threats.
- Page status
- Verified core
- Updated
- 2026-05-12
- Last reviewed
- 2026-07-19
- Review due
- 2027-07-19
Summary
ICIMOD's 2018 outreach publication Understanding Sediment Management, focused on sediment dynamics, erosion, and environmental threats in the Koshi Basin. Provides the evidence base for treating sediment as a central engineering and planning constraint.
Key Data Points
- Although the Koshi basin represents only 9% of the Ganges river system, ICIMOD reports that it contributes nearly 25% of the Ganges sediment load: 100-135 million tonnes per year.
- Estimated soil-loss rates in the source include 22 tonnes/ha/year from barren land, 5.3 tonnes/ha/year from agricultural areas, 5 tonnes/ha/year from grassland, and 0.5 tonnes/ha/year from forested areas.
- Suspended-sediment budgeting reports 101 million tonnes/year at Chatara, 81 million tonnes/year at Birpur, and 43 million tonnes/year at Baltara, implying substantial deposition between those stations.
- Sediment, flood, and erosion risks are interconnected.
- Climate change is intensifying GLOF, landslide, and sediment-pulse risks.
Limitations
- Date: Published 2020; climate-sediment dynamics and GLOF hazard profiles may have shifted since publication.
- Basin scope: Covers the Koshi basin only; does not assess sediment regimes in Karnali, Gandaki, or Mahakali basins.
- Outreach-publication scope: The assessment provides several useful quantitative anchors, but it is not a full technical sediment design manual for hydropower projects.
- Source type: ICIMOD is a regional knowledge centre; data should be cross-referenced with WECS river-basin plans and project-level feasibility studies where possible.