Assessment of Rainfall-Runoff Dynamics using ARC SWAT Modeling: A Comparative Analysis of Varying Sub-Basin Configurations

Optimal management of natural water resources is a crucial strategy for mitigating the negative effects of climate extremes by ensuring sufficient water availability. A thorough assessment of hydrological system components is essential in watershed studies. In this context, the SWAT (Soil and Water Assessment Tool) model, integrated with ArcGIS, was applied to evaluate the overall hydrological conditions, with a focus on surface runoff in the ‘KatePurna’ catchment, a tributary of the ‘Purna’ River in the ‘Tapi’ Basin, India. KatePurna catchment has an area of 1130 square kilometers with a length of 108 km to meeting Point of Purna River. The data set for SWAT model running were Digital Elevation Model (DEM), slope map, soil map, LandUse LandCover (LULC) map, and climatic data in the form of precipitation, minimum/ maximum air temperature. The ArcSWAT model simulation performed for estimation of Rainfall-runoff in 2 scenarios, 1. by considering the sub-basins derived from default threshold value and 2. by increasing threshold value so as to decrease number of sub-basins. Scenario-1 derived 23 sub-basins and model simulation results obtained a runoff depth of 266.63 mm. The scenario-2 derived 11 sub-basins and resulted runoff depth was 268.43 mm. The variation of runoff depth between two scenarios less than 1%. The SWAT model simulation results, when examined, reveal an interesting pattern like catchments with fewer sub-basins exhibited a higher runoff depth of 268.43 mm, whereas those with a greater number of sub-basins displayed a lower runoff depth of 266.63 mm. The model could not be calibrated due to a lack of sufficient data required for the calibration process. Despite this, the SWAT model's results related to the water balance elements in the watershed demonstrate its effectiveness as a tool for hydrological assessments, particularly in situations where data is limited or unavailable for various reasons.