CHANGE OF THE TROPIC STATE IN PROLONGED DRYING PERIOD OF RESERVOIRS OF THE SEMIARID REGION
Water quality. Prolonged drought event. Eutrophication. Supply sources.
Eutrophication is a global problem and a major cause of deterioration of aquatic ecosystems. In the semi-arid region, the climatic and hydrological factors, with peculiar behavior characterized by concentrated rains and a prolonged dry period, govern the limnological characteristics the reservoirs. Global climate change models are predicting a greater occurrence of extreme events as more frequency of drought events in semi-arid region, generating impacts on the water quality. The aim of this work is to evaluate extreme hydrological events, such as prolonged drought, and their impacts on the trophic state of reservoirs in the semi-arid region. The hypothesis of this work is that there is a trophic state change in the reservoirs due to extreme drought events, increasing eutrophication due to the increase of the autochthonous supply of the system. The studied reservoirs will be Boqueirão and Passagem das Traíras reservoirs, located in the tropical semi-arid region. The work will be carried out in three different periods, according to the water volume of the reservoirs. The periods were marked by precipitation below the annual historical average and were thus inserted in a prolonged drought period. The variables water transparency, turbidity, electrical conductivity, pH, total phosphorus, dissolved reactive phosphorus, nitrate and chlorophyll-a will be analyzed. A principal component analysis (PCA) will be performed to verify the patterns of the variables in reaction to the sample units. It is expected that the results of this work point to a degradation of the water quality of the reservoirs, due to the decrease in the water volume of the springs resulting from the extreme event of prolonged drought. With this, we expect to observe a change in the trophic state of these water systems, evidenced by the prolonged drought event.