Groundwater potential zoning in the Grande River Basin: A semi-arid region of Northeast Brazil

Seasonal water scarcity in western Bahia, Brazil, has led to increased dependence on groundwater resources; however, basin-scale hydrogeological measurements remain insufficient for preliminary assessments. This study presents a geographic information system-based groundwater potential map for the Grande River Hydrographic Basin (GRHB), where groundwater potential is defined as a relative index reflecting conditions favorable for recharge and subsurface storage, rather than a direct measure of aquifer productivity. Ten hydrogeological and terrain proxy layers, derived from existing datasets and remote sensing, were standardized and integrated using an analytic hierarchy process weighting scheme and a weighted linear combination. The resulting index was classified into five groundwater potential categories. The very high- and high-potential classes account for 48.08 and 25.41% of the basin, respectively, while the moderate class accounts for 19.90%, and the low- and very low-potential classes together comprise 6.59%. Spatial association with available well locations was evaluated using receiver operating characteristic analysis and the area under the curve, which yielded a value of 0.821, indicating that wells are more frequently located in areas with higher index values. Additionally, a groundwater abstraction-pressure proxy, derived from wells with reported daily abstraction volumes, was used to identify potential stress areas where high favorability coincides with concentrated abstraction activities. These outputs serve as a first-order screening tool to guide field verification, monitoring, and targeted data acquisition across the basin.