Resumo:
In just over 5 years, two technological disasters, related to iron mining dams, occurred in Brazil, both in the State of Minas Gerais. The collapse of the Fundão dam, located in the municipality of Mariana, in 2015 led to a dispersion of tailings along 3 rivers in the Rio Doce basin and two states (Minas Gerais and Espírito Santo). In turn, in 2019, the rupture of dam B1, located in the municipality of Brumadinho, also caused similar impacts along the Feijão and Paraopeba streams, located in the São Francisco River basin. The Velhas River hydrographic basin, the work's study area, is one of the basins most susceptible to this type of disaster, as it is where most of the mines by upstream elevation are located, similar to the ones that ruptured. With the purpose of contributing to the minimization of social impacts on populations that depend on water from the Velhas River, were evaluated studies by the Minas Gerais Water Management Institute (IGAM), carried out soon after the disasters, and investigated the parameters that changed after the disruptions of mining dams, proposing the use of a group of parameters in which the Canadian Water Quality Index (CCME WQI) was applied, both in the impacted rivers before and after the disasters and in the Velhas River, to be used as a tool for performance proactively by responsible agents. Dissolved aluminum, dissolved iron, total manganese, TSS, turbidity and zinc were selected. With the application of CCME WQI, it was observed that there was a worsening of the post-disaster index in almost all evaluated stations. The result of the CCME WQI in Rio das Velhas showed that the water quality in that river, even with the absence of dam failures, is worrying, with rates worse than those observed after the failure in the other evaluated rivers.
