Spatiotemporal mapping and statistical analysis of the raw water quality exploited from tube wells in a karst region in southern Brazil

Monitoring the drinking water quality in alternative water supply systems is extremely important, as untreated water can contain many contaminants. This study used secondary data, from 2016 to 2021 of nine tube wells in an urban area over the karst region of Ponta Grossa, a city in southern Brazil. The statistical analysis of the raw water quality parameters evaluated, such as total coliforms (TC), Escherichia coli, turbidity, and fluoride indicated that 35 % of the samples were non-potable. A variable spatial distribution was identified between the years, mainly because of the higher contamination rates of the raw water samples related to the microbiological parameters. The analysis evidenced a correlation between rainfall and the parameters of TC (p = 0.002) and Escherichia coli (p = 0 .037). S ome w ells were identified as vulnerable, particularly after rainfall, increasing the risk of underground water contamination and becoming a critical factor in.../...