Optimal site selection for rainwater harvesting through a combined approach of GIS and MCDM

Water scarcity is a critical issue in the northwestern part of Bangladesh, particularly across the Rangpur and the Rajshahi divisions. Rainwater harvesting (RWH) presents a low-cost and sustainable solution to address this challenge by increasing local water availability. This study determines potential sites for RWH implementation using Geographic Information System (GIS) integrated with the Analytic Hierarchy Process (AHP), a widely used Multi-Criteria Decision Making (MCDM) approach. Fourteen criteria, including nine bio-physical criteria and five socio-economic criteria, were chosen to evaluate RWH sites. The correlation of bio-physical and socio-economic criteria was analyzed through a single pairwise comparison matrix. This globally applicable methodology was executed in the northwestern part of Bangladesh, including Rangpur and Rajshahi divisions. A sensitivity analysis was conducted under four different weighting scenarios to demonstrate diversity in decision-making judgements. To select the optimal scenario, validation was performed through an accuracy assessment method, where kappa accuracy was calculated 60% for scenario 1, 63% for scenario 2, 70% for scenario 3, and 100% for scenario 4. Based on kappa accuracy, scenario 4 is the optimal scenario for future RWH initiatives in the study area, which shows 39%, 55%, and 6% of the total area as poor, moderate, and good RWH potential zones. The final output showed that Thakurgaon, Panchagarh, Kurigram, Lalmonirhat, Nilphamari districts, along with some parts of Pabna district, were the most suitable for harvesting rainwater.