Spatiotemporal analysis of water quality indicators in a watershed in Brazilian Cerrado

Tools for monitoring and evaluating water quality are necessary for the measurement of environmental impacts arising from diverse activities in hydrographic basins. Here, the water quality of the Verdinho River, an important hydrographic basin of Brazilian Cerrado, was evaluated using 16 physical–chemical parameters. The indicators with major interference with water quality were identified by principal component analysis (PCA), in order to suggest less laborious and less expensive assessments. The water quality index (WQI) was applied considering seasonal changes and the analysis of eutrophication potential was determined using the trophic state index (TSI). The concentrations of chemical water quality indicators (e.g., nitrate, total phosphorus, total nitrogen) increased mainly in the rainy season. The PCA explained 73.69% of the variance among the data. Total solids, temperature, turbidity, alkalinity, biochemical oxygen demand, hardness, total phosphorus, nitrite, nitrate and ammonia showed strong correlations. The water quality was classified in the ‘good’ category in most of the evaluations. The TSI presented conditions between mesotrophic and eutrophic. The indicators that are analyzed seasonally and spatially are associated with natural and anthropic factors. The future implementation of a water catchment project water depends on environmental planning strategies to reduce the impacts on the water quality of this hydrographic basin. HIGHLIGHTS Changes in water quality in a watershed with a water catchment project for public supply.; Water quality indicators are associated with soils, rainfall intensity and land use watershed.; Use of PCA, WQI and TSI applied to a water quality diagnostic scenario.; The highest concentrations of chemical water quality indicators were in the middle and lower parts of the hydrographic basin.