Spatial analysis of the potential impact of contaminated areas on wells and aquifers in the Upper Tietê Basin, São Paulo, Brazil

Upper Tietê stands out as the basin with the highest concentration of contaminated areas in São Paulo, Brazil, thereby exerting a pronounced impact on the quality of groundwater and directly affecting the resident population. Recognizing the importance of developing indicators for effective aquifer management, this study proposed to identify and assess the degree of risk, vulnerability, and contamination of aquifers and wells in the Upper Tietê Basin. Were applied the Aquifer Vulnerability Index method to evaluate the aquifer vulnerability in the region; the delimitation of safety perimeters and identification of wells at risk; and the integrated risk index, unifying information on social and aquifer vulnerabilities, hazards and exposure. The results reveal that the aquifers have a high vulnerability, mainly due to the thickness of their unsaturated layer. Furthermore, there were 7,958 wells at risk around the basin (77.15%), and the most vulnerable municipalities are on the outskirts of the basin. This study provides important insights, mainly due to the holistic approach, serving as a basis for identifying the regions with the highest risks, which can be prevented and mitigated with appropriate actions.