Avaliação Espaço-Temporal da Qualidade da água e do Estado Trófico no Reservatório Chasqueiro e na Bacia Hidrográfica Lagoa Mirim

Abstract

The Lagoa Mirim Watershed stands out as one of the main transboundary regions in South America, playing a strategic role in potable water supply, livestock production, industrial activity, and agricultural irrigation, with an emphasis on rice cultivation. In this context, the objectives of the study are to evaluate the water quality of the Chasqueiro Reservoir through in situ collections and validation of the AlgaeMap application, aiming to analyze chlorophyll-a behavior and understand the seasonal variations associated with agricultural activity, as well as provide a spatiotemporal analysis of the water quality of several water bodies in the basin, in order to map trophic indices and identify the influences of intensive water use for irrigation. Furthermore, an analysis of the trophic state dynamics of 30 water bodies in the Lagoa Mirim Watershed was conducted. The results show that the water quality parameters of the Chasqueiro Reservoir are, in part, within the limits established by CONAMA Resolution 357/2005, while also showing significant variations, and reveal correlations indicating the influence of the irrigation regime in the reservoir. Meanwhile, the spatiotemporal analysis of the Lagoa Mirim Watershed reveals that water bodies, both on the Brazilian and Uruguayan sides, predominantly exhibit eutrophic characteristics, with no clear seasonal pattern, suggesting that local factors, including land use, agricultural practices, and hydrodynamic characteristics, play a decisive role in each reservoir. This emphasizes the need for continuous and detailed monitoring to identify the main degradation agents and guide the development of more effective management and conservation strategies.