Groundwater is a strategic resource, which is experiencing a growing threat of contamination worldwide. This study aimed to assess the vulnerability of the groundwaters in the basins of the rivers Gala, Tenguel, and Siete in the Ponce Enriquez mining area, considering as a hypothesis that anthropogenic activities (mainly mining and agricultural) conducted in the area generate a high risk of contamination. Vulnerability to contamination was quantified using the DRASTIC and GOD methods. In addition, the risk of contamination (Rc) was calculated considering the vulnerability index (I_V) and the danger index (I_P). Geographic information system (GIS) environment was used for the spatial analysis and the generation of vulnerability maps. The DRASTIC method showed that the negligible-to-low vulnerability category was predominant (50.7% of the area), followed by moderate vulnerability (25.6%), and high-to-extreme vulnerability (23.7%). Regarding the GOD method, the low and medium vulnerability categories were predominant in 41.4% and 27.5% of the area, respectively. Both methods agree that the center area, where the mining activities are located, has a vulnerability ranging from negligible to moderate. The I_P was low in the eastern zone (58.7 km²) and ranged from moderate (426.2 km²) to high in the central and western zones (371.1 km²), where mining activities predominate. The R_C revealed that 20% of the study area corresponded to a high contamination index; from which, 87% comes from agricultural activities, 9% from mining activities, and 4% due to shrimp farms and urban areas. This is the first study that evaluates the vulnerability to the contamination of groundwater in a mining area of Ecuador. The results of this research can serve as a baseline for future research, since the methodology used provides information on the priority areas for the protection of aquifers, considering the current land use in the study area.

Groundwater is a vital resource that supplies nearly half of the world’s population and sustains ecosystem integrity. In the Santa Rosa River basin (SW Ecuador), groundwater plays an essential role due to the variable quality of surface water resources. This study assessed groundwater contamination risk based on the premise that floodplain sectors with shallow water tables and high permeability are more susceptible to contamination, with the aim of supporting environmental management priorities. Cartographic and secondary data were integrated with field investigations. Intrinsic vulnerability was assessed using the GOD and DRASTIC methods, whereas contamination hazards were evaluated using the POSH approach, supported by in-situ measurements of water-table levels and physicochemical parameters. The GOD method classified the basin into negligible (371.18 km²; 49.31%), low (263.39 km²; 34.99%), and moderate (118.13 km²; 15.70%) vulnerability classes. DRASTIC identified low vulnerability as the dominant class (58.18%), mainly across the central, southern, and eastern sectors of the basin, whereas high vulnerability represented the second-largest class (21.75%) and was concentrated primarily in the western–northwestern sector, with localized patches along the northern margin. This spatial pattern is related to shallow groundwater conditions, permeable alluvial deposits, and low-relief terrain. The main pollution sources included agrochemicals, urban discharges, livestock excreta, artisanal mining, and solid waste. The integrated risk map identified moderate to high contamination risk across 56.0% of the basin, particularly in the western-northwestern sector and along major river and road corridors. These findings provide a regional-scale basis for prioritizing groundwater monitoring and contamination management in vulnerable sectors of the basin, supporting groundwater-quality protection and safer water-resource planning in the priority areas identified in this study.