GIS- and Remote Sensing-Based Multi-Criteria Analysis for Rainwater Harvesting Site Selection: A Case Study of Wadi Sarkhar Watershed, Wasit, Iraq

In response to escalating water demand and the depletion of natural freshwater resources, the strategic identification of suitable sites for rainwater harvesting (RWH) has emerged as a sustainable approach to mitigate water scarcity and flood risks in arid and semi-arid regions.In this study, a geospatially integrated multi-criteria decision analysis (MCDA) was conducted to delineate optimal RWH zones within the Wadi Sarkhar watershed, located in Wasit, Iraq.A total of eleven critical factors-encompassing hydrological, topographical, climatic, land use, and infrastructural parameters-were selected based on their relevance to runoff generation and storage potential.This included rainfall, runoff, evaporation, slope, land cover, soil type, proximity to roads and settlements, and stream orders (fifth to seventh).Weights were assigned to each criterion using the analytic hierarchy process (AHP), and the pairwise comparison matrix yielded a consistency ratio (CR) of 0.012, which is significantly below the accepted threshold of 0.1, indicating strong internal consistency.Spatial analysis and overlay operations were performed using ArcGIS 10.8, with the Raster Calculator employed to synthesize a final suitability map categorized into five classes: very high, high, moderate, low, and very low suitability.Results indicated that approximately 34.33% of the watershed area (435.14 km ) was classified as having high to very high suitability for RWH interventions, while the remaining 65.67% (834.41 km ) was deemed less favourable.A sensitivity analysis was also carried out to assess the robustness of the model by adjusting the weights of dominant criteria, confirming the model's resilience and reliability.The findings offer a robust spatial planning framework to inform policymakers, environmental engineers, and water resource managers in the development of region-specific RWH strategies that enhance water availability, reduce flood risk, and contribute to long-term ecological resilience.