Groundwater Potential Zonation in a Tropical Hard-Rock Basin, South India: An Evidence-Based Approach

Groundwater potential zonation is a crucial tool for identifying regions with varying groundwater availability, integrating geological, hydrological, and environmental factors. This study evaluates the groundwater potential of the Kadalundi River Basin (KRB) in northern Kerala, India, using the Analytic Hierarchy Process (AHP) and Geographic Information System (GIS) techniques, and validates the results with subsurface geophysical signatures and well-yield data. Key geo-environmental variables, including geology, geomorphology, groundwater level fluctuations (GWLF), lineament density, land use/land cover (LU/LC), slope, soil texture, rainfall, topographic wetness index (TWI), terrain curvature, and topographic position index (TPI), were analyzed for their influence on groundwater occurrence. Based on the study, the groundwater potential zones in KRB were classified as very poor, poor, moderate, high, and very high, covering approximately 20.0%, 19.7%, 19.8%, 20.3%, and 20.2% of the basin, respectively, with high and very high zones concentrated mainly in the southeastern and western sectors. Lithology emerged as the most influential controlling factor (weight 0.246), followed by geomorphology (0.180). The reliability of the zonation was assessed using a two-fold validation based on VES (Vertical Electrical Sounding) and observed well yield data. The predicted index showed strong agreement with well yield (R 2 = 0.877). The spatial variability of groundwater potential across KRB provides valuable insights for sustainable groundwater management. The study provides a reliable background for groundwater potential assessment in similar hydrogeological settings and supports informed decision-making for water resource planning in the region.