Context
A provincial irrigation department needed a basin-wide understanding of streamflow variability to support both irrigation allocation planning and upstream flood mitigation siting.
Approach
A SWAT model was constructed across the full 2,400 km² basin using SRTM DEM data, satellite-derived land cover (Sentinel-2), and soil data from the regional soil survey. The model was calibrated and validated against 12 years of gauge records at two monitoring stations using SWAT-CUP.
Outcome
The calibrated model achieved NSE > 0.75 at both validation stations and now underpins the department's annual irrigation allocation planning process.
Methodology
SRTM 30m DEM watershed delineation into 14 sub-basins; Sentinel-2 derived land cover classification; SWAT model construction with regional soil survey inputs; calibration and validation against 12 years of gauge records at 2 stations using SWAT-CUP (SUFI-2 algorithm); sensitivity analysis on curve number and baseflow recession parameters.
Results & Outcomes
- Achieved NSE > 0.75 at both calibration/validation gauge stations
- Delineated 2,400 km² watershed into 14 actionable sub-basins
- Now used as the basis for annual irrigation allocation planning
- Identified 3 sub-basins as priority sites for upstream flood-mitigation structures
Challenges
Sparse rainfall gauge coverage across the basin's upper reaches required blending ground observations with CHIRPS satellite-derived precipitation, with a bias-correction step validated against the two available long-record gauges before basin-wide application.
“Their SWAT calibration held up under donor technical review with zero revisions requested — that doesn't happen often.”
Thomas Berg, Water Resources Lead
An International NGO