Limnologia da paisagem com uso de regressão geograficamente ponderada: estudo da qualidade da água na represa de Chapéu D’Uvas, MG

Abstract

The Chapeu D'Uvas dam is an important source of public water supply for the municipality of Juiz de Fora, MG, with the expectation of guaranteeing water for the coming decades in quantity and quality. Over the years the watershed of the dam has undergone a process of anthropic occupation, being worrying the possibility of impacts on the source. The research presented here aimed to identify the spatial relationships between land use and land cover in the watershed of the Chapeu D'Uvas dam and the water quality of the reservoir. The methodology underwent a study with remote sensing and geoprocessing to know the conditions of use and land cover, and the maintenance of permanent preservation areas. Historical data on water quality at the catchment point provided by the Companhia de Saneamento Municipal de Juiz de Fora, Cesama, were analyzed for the years 2005 to 2017. Campaigns were also conducted for sampling at the reservoir and at the main tributaries, in the years 2016 and 2017. Data on land use and land cover and water quality were analyzed from the principles of landscape limnology and the application of geographically weighted regression. The results showed that the variables density of cyanobacteria, E. coil, electrical conductivity, oxygen consumed, orthophosphate, nitrate and chemical oxygen demand were influenced mainly by the percentage of forest, silviculture, pasture, and urbanized areas. The longitudinal profile of the sub basins also influenced the results. The geographic weighting differentiated the influences of the sub basins according to their position closest to or farther from the dam. Thus, through the analysis of the correlations between the variables, it was possible to identify the effects of the occupation of the basin of contribution on water quality, and, thus, to relate the main issues that deserve attention of the managers of the source.