Efeitos da sazonalidade climática na qualidade da água de rios em um bacia hidrográfica

Abstract

Water quality issues are a matter of worldwide interest due to the importance that this natural resource exerts on terrestrial life and the complexity of its relations or interactions with the environment. Thus, the quantity and quality of available waters suffer variations influenced by natural and anthropic processes, such as climatic seasonality and dynamics of land use and land cover (LULC). Evapotranspiration, together with precipitation, plays a key role in water balance as a variable responsible for drainage system flows. In this study, the objective was outlined from the need to know the weaknesses present in the system of a watershed, in order to subsidize actions of environmental pollution control and management of water resources of the Limoeiro stream watershed. We present the influence of climatological water balance on surface water quality and its impacts when interacting with LULC. We analyzed the water quality of this region through the parameters, dissolved oxygen, pH, biochemical oxygen demand, temperature, total nitrogen, total phosphorus, turbidity, total residues, Escherichia Coli and Chlorophyll a. From these parameters, we estimate the indices of water quality and trophic state. Water quality monitoring was performed in the 4 seasons (spring, summer, fall and winter) from 11 monitoring points. We verified that in the field campaign corresponding to the summer season, 73% of the points were classified with a useful water quality index, while in the autumn only 18% had this classification. During winter, 55% were classified as valuable and in the spring, 82% of the points had good or excellent ratings. Trophic state indices varied from hypereutrophic to ultraoligotrophic, with the worst indices obtained for the season with the highest water deficit (winter). We conclude that water deficiency impairs the quality of surface water. Moreover, in the seasonal station with water surplus, the monitoring points received more interference due to diffuse pollution caused by the interaction between the hydrological cycle and LULC