Anthropogenic impacts on water quality in southern Brazil: a multidimensional analysis of tributaries and the Chavantes reservoir

Freshwater is a vital resource, and its quality is critical for both human and environmental health. This study evaluated physicochemical and microbiological parameters of water from the Chavantes Reservoir, upstream tributaries to the reservoir, and downstream sites in the Paranapanema River and in its downstream tributaries, as well as the antimicrobial susceptibility of Escherichia coli. The results showed that variables such as temperature, turbidity, and total dissolved solids remained within the limits established by Brazil’s Environment Council (CONAMA) Resolution 357/2005 and Minister’s Office/ Ministry of Health (GM/MS) Ordinance 888/2021. In contrast, thermotolerant coliforms and E. coli exceeded the permitted values in several tributaries upstream. A strong correlation was observed between turbidity and coliforms, indicating fecal pollution sources related to the lack of sanitation and inadequate waste management. Antimicrobial resistance analysis revealed the presence of tetracycline- and gentamicin-resistant genes in E. coli strains, highlighting the impacts of agricultural activities and the indiscriminate use of antibiotics. Principal component analysis indicated greater dispersion among the upstream tributaries, reflecting high variability, while reservoir samples exhibited lower microbiological contamination, suggesting a dilution effect. These findings reinforce the need for continuous monitoring, riparian zone restoration, and the implementation of integrated sanitation and environmental management strategies. This study contributes to understanding anthropogenic impacts on water resources and supports public policies aimed at conserving water quality in the Chavantes Reservoir region.