Reservoir eutrophication in the Brazilian semiarid: modeling of sediment removal and control of external loads as remediation measures.

Abstract

Eutrophication, driven by nutrient enrichment, poses a global challenge, impacting the ecosystem, water supply systems, and ultimately, human health. In this research, water unavailability due to phosphorus pollution was assessed in Brazilian semiarid reservoirs with data measured over a decade. Management strategies to control eutrophication were simulated using physical-mathematical modeling of the phosphorus budget in the water and sediment layers. The model parameters were calibrated from 1976 to 2021, and the results were validated by comparing measured and modeled duration curves of phosphorus concentration. Water unavailability due to phosphorus pollution occurred approximately 61% of the time, indicating the need for effective control strategies. Simulation of sediment removal when the reservoirs dry up showed potential to contribute to water quality in reservoirs with high emptying frequency, while external phosphorus load reduction proved to be more widely efficient. The variation in the effectiveness of the techniques among the studied reservoirs emphasizes the need for approaches adapted to the specific conditions. This work contributes to improve the understanding of phosphorus dynamics in reservoirs with high water level fluctuations and appropriate management measures to control eutrophication in dry environments.