Assessing the Impact of Digital Elevation Model Selection on Hydrological Predictions

Digital elevation models (DEMs) play a fundamental role in hydrological modeling by controlling watershed delineation, stream networks and runoff generation processes. This study assess the impact of global DEM product provided by Shuttle Radar Topography Mission SRTM and the Indian national CartoDEM developed by ISRO-Bhuvan (Indian Space Research Organisation-Bhuvan) on streamflow simulation using the Soil and Water Assessment Tool (SWAT) in the Ong River watershed (4650 sq. km), India. The study area is characterized by forest and cropland. Both DEMs, resampled to 30m resolution, were used as inputs to SWAT, along with meteorological data (IMD), land use/land cover data (Sentinel-2), and soil data (FAO). Streamflow data was sourced from Global Flood Awareness System discharge data (GloFAS). Model calibration (2011-2017) and validation (2018-2020) were performed using SWAT-CUP with the SUFI2 algorithm. Model performance was evaluated using Willmott's index of agreement, Nash-Sutcliffe Efficiency (NSE), R², PBIAS, and RSR. Results showed that both DEMs performed satisfactorily, with CartoDEM exhibiting slightly better performance (higher NSE and R², lower PBIAS and RSR) during both calibration and validation periods. Sensitivity analysis revealed that the runoff curve number was the most sensitive parameter, highlighting the impact of DEM selection on surface runoff simulation. The study concluded that CartoDEM is a preferable choice for hydrological modeling in similar catchments, though further research on stream accuracy and catchment delineation in diverse topographies can be explored.