Spatial and Temporal Variability of Groundwater Quality Parameters in the Bauru Aquifer System (São Paulo State, Brazil)

Abstract

Chemical substances can be harmful to humans when present in water at concentrations above the limits permitted by legislation. The present study analyzes the spatial-temporal variability of barium, chromium, nitrate and vanadium concentrations in groundwaters of the Bauru Aquifer System (BAS). For this purpose, triennial water-quality monitoring data (2016-2018) were acquired from CETESB (São Paulo Environmental Company). Descriptive statistical methods and geostatistical techniques (kriging) were applied. Results attest the spatial dependence of the water-quality parameters along time. Variograms indicate spatial determination coefficients (R²) between 0.435 and 0.961. The municipality of Presidente Prudente has the worst scenario, with estimates chromium and vanadium above the Maximum Allowed Values (MAV). The fact that most of licensed wells exploit water for urban supply makes the results worrying and shows up that public agencies must take some actions to decrease these concentrations.