A novel approach for mapping and prioritizing optimal stormwater harvesting sites in urban and peri-urban environments

Rapid urbanization and climate variability often intensify water scarcity and urban flooding in developing cities, necessitating sustainable alternatives to conventional water supply systems. Stormwater harvesting (SWH) offers a promising solution by utilizing locally available runoff for non-potable demands while mitigating flood risks. This study proposes a novel, GIS-integrated hydrological modeling and Analytic Hierarchy Process (AHP)–based framework to identify and prioritize suitable Stormwater Drainage Outlets (SDOs) for urban stormwater harvesting. The methodology takes into account runoff–demand ratio, weighted average distance (WAD), slope, land use-land cover (LULC), and groundwater recharge potential (GRP) to evaluate hotspot suitability across two spatial scales defined by radius of influence (ROI) of 1 km and 0.5 km. The framework was applied to Bhopal, India, a rapidly growing city facing increasing water stress. Results reveal significant spatial variability in hydrological conditions and accessibility, with runoff–demand ratio emerging as the most influential criterion. Hotspot rankings demonstrate scale dependency, where larger ROIs favor hydrological availability, while smaller ROIs emphasize accessibility and localized conditions. The proposed approach enables systematic screening and ranking of SDOs and provides a scalable decision-support tool for decentralized stormwater reuse, contributing to sustainable urban water management and enhanced resilience to water scarcity.