Transferability of Basin Hydrological Parameters for Assessing Hydrological Processes in Sri Lankan Wet Zone River Basins

In the context of urbanization and population growth, sustainable water management is crucial. This study examines hydrological parameter transferability within Sri Lankan wet zone river basins, using the Hydrologic Engineering Center’s Hydrologic Modelling System (HEC-HMS) modelling to overcome data limitations for accurate streamflow estimation. The HEC-HMS model was applied to three subbasins: Ellagawa, Ratnapura, and Baddegama in the Kalu River and Gin River basins. Spatial and temporal transferability approaches were assessed using Nash-Sutcliffe Efficiency (NSE) and Mean Ratio Absolute Error (MRAE) as objective functions. Model performance for the calibrated sub-basins yielded satisfactory NSE values (0.62-0.78) and MRAE (0.35-0.74). Within-basin transferability showed moderate success (NSE 0.60-0.63, MRAE 0.51-0.84), while across-basin transferability initially resulted in low accuracy. However, adjusting sensitive parameters improved performance to an overall accuracy of 8587% in both sub-basins. The temporal transferability approach achieved better results, suggesting its potential for transferring parameters from main to sub-basins. These findings demonstrate the applicability of the HEC-HMS model with transferable parameters for sustainable water resource management in Sri Lanka.