Groundwater contamination risks and land use changes in a typical Agreste/Caatinga transition zone in northeastern Brazil

Effective management of limited and fragile groundwater resources is essential to ensure a sustainable, safe, and high-quality water supply. However, intensive anthropogenic activities are placing increasing pressure on groundwater systems worldwide. Groundwater contamination and changes in land use and land cover in water-scarce cities represent serious environmental challenges, particularly in the Agreste/Caatinga transition zone of northeastern Brazil. This study therefore assesses groundwater contamination risks and land use changes in the city of Campina Grande, located in northeastern Brazil. The following procedures were employed: (a) identification of wells through data collection from public agencies; (b) evaluation of the natural vulnerability to groundwater contamination using the Groundwater Overall Depth (GOD) method; (c) spatiotemporal analysis of land use and land cover changes using the Google Earth Engine platform; (d) identification of point sources of contamination and assessment of potential contamination risk using the Pollutant Origin and its Surcharge Hydraulically (POSH) method; and (e) mapping of groundwater vulnerability and contamination risk. The study area was classified into three distinct levels of natural vulnerability-low, medium, and high. The results indicate an increase in groundwater extraction beginning in the 1990s, particularly between 1995 and 2000, strongly correlated with drought periods. The findings also reveal rapid urban expansion and an increase in the number of pollution sources. Approximately 33% of the study area exhibits high vulnerability on the aquifer's natural vulnerability map, as determined using the GOD index. It is concluded that land use changes and the associated risks of groundwater contamination in Campina Grande represent serious threats to environmental quality and water availability for the city.