Watershed Prioritization in GIS: A Comparison of Multiple Approaches

Abstract

Various Soil and Water Conservation (SWC) measures are widely implemented to reduce the surface runoff in the degraded and drought-prone watersheds. However, their implementation requires thorough assessment of morphometric and hydrological parameters prevailing in the watershed. This research was conducted to characterize the sub-watersheds for SWC in a drought-prone watershed of Ahmednagar district, Maharashtra using morpho-metric analysis in GIS domain. Their prioritization has been carried out using two different Multi-Criteria Decision Analysis (MCDA) approaches viz. Analytical Hierarchy Process (AHP) and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) for a comparative assessment. The findings were further supplemented based on the severity of surface processes, quantitative estimation of soil erosion and surface runoff derived using Soil and Water Assessment Tool (SWAT). The priority value obtained using the AHP and TOPSIS ranged from 1.452–2.658 to 0.215–0.586, respectively. The comparison based on normalized values from the two approaches, shows similar results for the 73% of sub-watersheds and slight variation in the remaining. However, surface runoff and soil erosion-based prioritization carried out using SWAT have been found to have slightly better semblance with the TOPSIS model as compared to that of AHP. The study concludes that though the morphometric analysis and MCDA is and continue to remain the most widely used tool for watershed characterization, supplementing them with the hydrological inputs derived from SWAT provides a more effective approach for planning SWC measures at a local level.