Influências da composição e estrutura da paisagem sobre a qualidade da água em múltiplas extensões espaciais na unidade hidrológica do Rio Doce em Minas Gerais

Abstract

The degradation of aquatic environments promotes water contamination, implying a worsening in the quality of ecosystems. The Doce River basin has a history of environmental degradation, mainly because industrial expansion and intensive farming. Furthermore, in 2015, the Fundão tailings dam (Samarco, BHP Billiton and Vale) broke up launching ore tailings over the basin's water courses, abruptly changing its socio-environmental context and becoming one of the biggest environmental disasters in brazilian history. The objective of this study was to analyze the relationship between landscape characteristics and water quality in the Doce River basin (MG) using multiple spatial extensions. For this, statistical models were analyzed and they showed the relationship between water quality parameters and land use/land cover and landscape metrics for 2008, 2013 and 2018. Three spatial extensions were used: sub-basin, which corresponds to the entire drainage area upstream of the monitoring point; riparian, corresponding to a 200 m buffer of the watercourse upstream of the monitoring point; and local corresponding to a 200 m buffer of the watercourse upstream of the monitoring point within a 2 km radius. The parameters used correspond to the monitoring of the wet and dry seasons in 64 stations, namely: total barium, nitrate, total solids and turbidity. The relationship between the variables was verified using multiple linear regression which allowed to build and select models with the best fit and the identification of the variables that had the highest weights on the models. The models that showed the best explanatory capacity were the sub-basin (R²aj = 0.20-0.57; median: R²aj = 0.35) and riparian (R²aj = 0.23-0.48; median: R²aj = 0.39). Human activities such as agriculture, urbanization, eucalyptus forests and mining were associated with the worsening of water quality in all analyzed areas. On the other hand, the presence of patches of natural vegetation has been shown to function as water quality controllers. The study reinforces the urgent need to contain deforestation and degradation in areas close to water courses and the entire hydrographic basin. Ancestral knowledge of Quilombolas and Native Peoples is the center for how we should relate to rivers, forests and everything on earth due to their trajectory of bionteraction – relations of mutual respect with the ecosystem. In addition, the protection of riparian forest needs to consider more comprehensive preservation areas than is demanded by Brazilian legislation. The methodological approach has limitations, however, reinforces the need for more studies that contrast the developmental speech of public and private institutions that degrade the Doce River basin and its territories.