Water quality modulations under influence of rainfall and land cover in a mountain basin in southeast Brazil

Abstract

In the context of climate change, there are projections of an increase in storm occurrence and larger periods of drought that threaten water resources for human supply and ecosystems in South America. Based on this problem, this study aimed to understand how rainfall affects different water quality parameters and its relationship with changes in land cover. To this end, rainfall data were cross-referenced with water quality monitoring, and it was compared at two sampling points on the Rio Preto: upstream and downstream from a human settlement (Maromba District). The parameter thermotolerant coliforms was the parameter that showed the most divergence between the two sampling points, which often exceeded Brazilian legislation limits for supply and recreational use, and their variability over time was not related to rainfall. Dissolved oxygen and nitrates were the most correlated parameters with rainfall. Turbidity increases correlated to rainfall only downstream, being the parameter with the greatest difference between points in response to rain. However, the parameters that correlated in some way with rainfall remained within satisfactory values in the Maromba District. We believe that the virtual absence of agriculture in the basin is the key factor for maintaining satisfactory values of eutrophic parameters downstream, but it is noteworthy that human activity linked to tourism threatens water quality due to coliform contamination.