Bacia do rio Pomba (MG): uso e ocupação do solo e impactos ambientais nos recursos hídricos

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Universidade Federal de Goiás
The impacts of anthropogenic activities change the water quality of a river basin. In the Pomba river basin (MG/RJ), encompassing an area of 8.544 km², pastures are the predominant ground cover and, among the 618,418 inhabitants, 86.3% live in cities or towns. The present study aimed to assess and characterize the possible negative environmental impacts on the Pomba river basin as well as to select environmental variables that describe and are important for the determination of these impacts. Therefore, this thesis was divided into three chapters. In the first chapter, the dynamics of the aquatic ecosystem of the river basin was presented, based on limnological, sanitary, and biotic data, as well as on the relationship with the main anthropogenic activities in the basin, using spatial distribution in the dry season and temporal distribution in the sampling points in the rainy season. For the purposes of this study, the Pomba river basin was divided into four sub-basins, and 46 water samples were collected in the dry season and 21 in the rainy season. It was evidenced that the water quality was more critical in the dry season. Environmental (n = 3) and limnological (n = 24) variables considered important for water quality were selected based on PCA. As a result, the variables dissolved oxygen, total phosphorus, electrical conductivity, dissolved organic carbon, and BOD were significant to evaluate the water quality of the basin. Also, chlorophyll a and pheophytin a were significant in the dry season and turbidity in the rainy season. In the secund chapter, the goal was to verify how the land use interferes with the quality of water. The types of land use (n = 10) and limnological variables (n = 18) analyzed in the dry and rainy seasons, in the 21 sampling points, were ordered using the principal component analysis (PCA). The classification of land use was carried out using the satellite LandSat 8 images. Higher water quality deterioration was registered in more urbanized areas and in areas with pastures. In the third chapter, the importance of the effluents from dairy industries was simulated and it was verified how this economic activity affects the water quality. To achieve this goal, the physical, chemical, and microbiological variables of the effluents from five dairy industries were analyzed, and the dynamics of a water body in which the effluent was disposed was simulated. It was evidenced that a part of the effluents from the dairy industries was disposed on water bodies without any treatment, whereas the other part was not efficiently treated prior to disposal. Regarding the simulation, it was concluded that, in order not to alter the conditions for water use downstream, the efficiency of biochemical oxygen demand (BOD) reduction of the effluents should be of at least 60%. At the end of this study, it was concluded that the situation along the Pomba river basin, due to the impacts on both the scenario and the water, is critical in the regions of the Xopotó river sub-basin, das Posses stream, and Feijão Cru stream. The quality of the water in low discharge rivers and downstream of municipalities is more affected. Although some tributaries of the Pomba river also presented critical characteristics, their self purification is still taking place when they flow into the main river bed. The different types of land use were the main causes of impact on the quality of river water, especially the domestic sewage from urban areas in the dry season, as well as the lack of soil conservation and inappropriate management in the rainy season.
SILVA, Roselir Ribeiro. Bacia do rio Pomba (MG): uso e ocupação do solo e impactos ambientais nos recursos hídricos. 2014. 135 f. Tese (Doutorado em Ciências Ambientais) - Universidade Federal de Goiás, Goiânia, 2014.