Controle da eutrofização em reservatórios no semiárido brasileiro: modelagem dos efeitos da operação, do manejo de sedimentos e da redução de cargas externas

Abstract

Eutrophication, resulting from nutrient enrichment, especially phosphorus, poses a global challenge to aquatic ecosystems, with direct impacts on human health. To address this issue, this study aimed to evaluate the impact of phosphorus management in small reservoirs. Management strategies to control eutrophication were assessed through physical-mathematical modeling of phosphorus balance in water and sediment layers, using climatic, hydrological, and water quality data from official databases. In this study, six reservoirs located in the state of Ceará, Brazil, with capacities ranging from 0.06 to 8.0 hm³, were analyzed. The model parameters were calibrated from 1976 to 2021, and the results were validated by comparing measured and modeled phosphorus concentration duration curves. The first scenario examined the impact of sediment removal when the reservoir was empty. The simulation indicates that this action would result in a temporary improvement in water quality. The second scenario proposed intensifying water extraction from the reservoirs, but the simulation suggests that this would not result in improved water quality. The third scenario combined the first two. The simulation suggests that, in this case, there would be improvements in reservoirs with frequent drying. The fourth and final scenario proposed reducing the inflow of phosphorus (external load) to the reservoir, which would lead to more pronounced impacts on water quality. The results highlight the complexity in phosphorus management and the need for efficient control of pollution sources, as well as efficient management of internal load. Sediment removal has been shown to be a promising technique but requires simultaneous efficient control of external loads.