Modelagem da qualidade da água na região hidrográfica do Rio Paraguai utilizando o HEC-RAS

The Upper Cuiabá River Basin, located in the Planning and Management Unit P4 (UPG-P4) on the plateau of the Paraguay River Basin, is an area of significant interest for water quality control. This region, which is home to approximately one million people, is experiencing rapid agricultural expansion. Being upstream of the Pantanal, one of the largest wetlands in the world, it becomes a region of great importance for environmental management. The primary water quality issues in the Paraguay River Basin are caused by the transport of sediments and diffuse pollutants from the plateau to the Pantanal. In this context, this study evaluated the impact of phosphorus control measures in UPG-P4 on the water quality of the Cuiabá River, using the HEC-RAS software for steady-state one-dimensional modelling. Four scenarios were simulated in the study, showing that the phosphorus limits of Class 2 of CONAMA Resolution 357/2005 were met only in Scenario 1 (an 80% reduction of phosphorus in pasture and agricultural areas), and only in the section between the Manso River and the beginning of the urban area of Cuiabá. The study found that pasture areas have a more significant impact than agricultural areas, and the model proved useful for planning water quality control and can be adapted for other regions of the Paraguay River Basin.