QUALIDADE DE ÁGUA EM RESERVATÓRIO DE BREJO DE ALTITUDE SOB SECA EXTREMA

Abstract

The increasing human population and its activities have generated an increase impacts on the aquatic ecosystems, thus compromising the multiple uses of water in lakes and reservoirs in Brazil and worldwide. One of the main processes that compromise water quality is eutrophication, a phenomenon that involves the increasing of fertility of the aquatic environments due to the excessive increase of nutrients, mainly phosphorus and nitrogen. In the perennial and intermittent reservoirs of Northeastern Brazil, this scenario is even more alarming, associated with multiple anthropogenic pressures, extreme climatic conditions, irregular spatio-temporal distribution of precipitation, soils with reduced water storage capacity, prolonged high evaporation rates and extreme droughts. The objective of this work was to evaluate the fluctuation of the water quality and trophic status of the Vaca Brava reservoir, located in the city of Areia, in the state of Paraíba. In situ parameters such as pH, electrical conductivity, temperature, total dissolved solids and transparency were analyzed. The total phosphorus and orthophosphate contents in the water were determined in the laboratory. For the calculation of the EIT, were used the Carlson index, modified for tropical environments by Toledo Jr. et al. It was observed the influence of seasonality in the majority of analyzed parameters, with emphasis on the electrical conductivity and total dissolved solids. The reservoir presented in half of the months as oligotrophic, having an increase in its EIT in the later months, result of the concentration of nutrients in the dry period. The Principal Component Analysis (PCA) recorded 84.1% of the explanation in the first two axes and showed the strong relation of accumulated volume and precipitation under the analyzed variables.