Watershed delineation and morphometric analysis of Dhansiri River using SRTM DEM and ArcSWAT

Ecological conservation of various watershed is under pressure due to shrinking natural boundaries and disappearing tributary systems. Thus, delineating watersheds is an essential step which supports research across multiple water resource management. This study provides the first DEM-based morphometric analysis and watershed delineation for the entire Dhansiri River watershed area. Soil and Water Assessment Tool (ArcSWAT) within ArcGIS system is applied for delineating Dhansiri River watershed using Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM). Accuracy and validations for the delineated watershed is checked against area data from Central Pollution Control Board (CPCB). Delineation results reveal a watershed area of 10,183.68 km2, which corresponds to approximately 80.9% of the CPCB-reported area, highlighting a –19% difference. Such differences are generally expected from DEM-based watershed delineation due to limited (~ 30 m) spatial resolution and built-in uncertainties of SRTM DEM. Despite such limitations, delineation was able to effectively capture the overall watershed extent and essential hydrological features. Based on the outlet points, four sub-watersheds were divided into three “5th order” streams (SW1, SW2, and SW4) and one “4th order” stream (SW3), making it suitable for practical applications such as flood management, watershed planning on a regional basis, and sustainable land-use values involving decision-making.