Resumo:
Mathematical modeling of water quality is essential for evaluating the impact of pollutant discharges on water bodies. It enables the assessment of intervention scenarios, the implementation of control measures, the verification and quantification of self-purification processes in water bodies, and the simulation of current and future water quality scenarios in rivers. The main objective of this research was to conduct water quality modeling of the Santa Bárbara River to support water resources management. For the mathematical modeling, the parameters dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrogen variations (organic, ammoniacal, nitrite, and nitrate), and phosphorus were modeled using the QUAL-UFMG model. Additionally, future scenarios were examined that accounted for population growth in the watershed, with projections for 2033. In Scenario 1, the urban centers of the municipalities of Barão de Cocais and Santa Bárbara were considered to have implemented sewage treatment for 90% of their populations, while in Scenario 2, all urban centers within the study area of the basin were considered to have implemented sewage treatment for 90% of their populations. In the current scenario, with the exception of phosphorus, all studied parameters remained within the limits established for Class 2 waters according to CONAMA Resolution 357/2005 for 100% of the studied section, with only 7.6% compliance for phosphorus. For Scenarios 1 and 2 in 2033, the analyzed parameters would remain within the established limits for Class 2 waters according to CONAMA Resolution 357/2005 along the entire study section for all parameters, except for phosphorus, which remained non-compliant in 92.4% of the studied water body. Thus, it was concluded that for improved water resources management in the Santa Bárbara River watershed, it is necessary not only to intensify effluent treatment and control pollution sources, considering sewage treatment efficiency and population size of the main cities within the watershed, but also to address diffuse pollution sources arising from land use and occupation (such as agricultural residues, soil erosion, and sediments) originating from its tributaries.
