Definition of potential sites to implement urban rainwater harvesting systems in water-stressed cities by integrating GIS and AHP tools

This study proposes a novel methodology to identify optimal locations for Urban Rainwater Harvesting Systems (URWHS) in water-stressed cities by integrating Geographic Information Systems (GIS) with the Analytic Hierarchy Process (AHP). The research focuses on the La Silla River sub-basin in the Monterrey Metropolitan Area, addressing critical challenges such as climate change, rapid urbanization, and inadequate stormwater management. A multi-criteria decision analysis (MCDA) was applied to spatial data layers, evaluating variables including annual precipitation, catchment area, extreme rain events, slope, and urban water consumption. Expert surveys were conducted to assign weights to these parameters, identifying the annual precipitation and catchment area as the most influential criteria. Using a grid-based spatial approach, the study pinpointed high-priority zones, especially in the middle basin where the implementation of URWHS could achieve significant water savings. The potential reduction in water demand is estimated at 13,783 m³/year, nearly ten times the annual water demand required in the area. The results underscore the effectiveness of combining GIS and AHP for sustainable urban water management, offering a replicable model to mitigate water scarcity and enhance urban resilience.