Enhancing SWAT model performance for climate change impact studies in watersheds with missing flow data

Hydrological models play a crucial role in assessing the impacts of climate change on water resources. This study evaluates the performance of single- and multi-site calibration approaches for the SWAT model in the Mudurnu River Basin, located in the Black Sea Region of Türkiye. The results indicate that both single- and multi-site calibration approaches yielded high model accuracy without significant differences in performance, providing 0.87, 0.87 R2, 0.87, 0.87 NSE, –3.6, 3.7 PBIAS, and 0.36, 0.36 RSR for validation, respectively. These findings suggest that single-site calibration at the basin outlet may be a practical alternative to multi-site calibration in small basins.