Effects of Digital Elevation Model Resolution on Watershed-Based Hydrologic Simulation

This paper investigated effects of Digital Elevation Model (DEM) resolution on flow simulation by applying the HSPF watershed model to three U.S. watersheds with different topographic conditions. Each watershed was delineated automatically and manually with four DEMs of the resolution ranging from 3.5 to 100 m. Results indicated that the simulated flow decreased with lowering DEM resolutions due to the reduction in the delineated drainage area particularly in low gradient watersheds. The DEM resolution impact was minimal when the manual method for watershed delineation was applied. The parameter uncertainty was found to be substantially greater than the resolution uncertainty in two out of three tested watersheds, indicating that the calibration of water balance parameters can alleviate the adverse effects of coarse DEM resolution for watersheds with high to moderate gradients. The findings are important to reducing the uncertainty, caused by DEM resolutions, in watershed modelling results, serving as guidelines for watershed modelling-based water resources management.