Identificação e análise de tendências das variáveis hidrológicas e mudanças no uso e ocupação das terras no alto curso da bacia hidrográfica do Rio Uberaba, em Minas Gerais

Abstract

Studies about hydrological data time series are important to know the river basins’ realities, as the water availability over the time, as the entering water in the water system through the rainfall, and how much water is lost through evapotranspiration, etc. Also, knowing the dynamics of the use and occupation of land in the hidrografic basins becomes important to understand whether the externalities infer impacts on hydrological systems, as has been widely studied by the scientific community. This study aimed to identify the occurrence of trends in hydrologic variables time series(stream flow and precipitation), and how use and occupation of land in the upper course of the Uberaba river basin has been evolved over the past three decades and these factors relate to each other. Were used flow measurements performed by the National Agency of Water – ANA and meteorological measurements performed by the National Institute of Meterology – INMET aiming to observe the behavior of atmospheric variables between the years 1978 and 2014 (precipitation). Each time series were subjected to linear regression test and the Mann-Kendall trend test, Mann-Kendall Seasonal, Sen’s slope and Pettitt, in order to identify changes in hydro-climatic data. To understand the changes in use and occupation of land in the upper course of the Uberaba river basin, literature surveys were performed and maps were done using images from Landsat 5 and 8 satellites. The results shows a reduction in flow rates of 7, 15, 20, 30 and 45 dry days and the monthly minimum flows and increased maximum monthly flows. The total annual precipitation and precipitation in the dry season (April to September) also showed a downward trend. The precipitations on the late months of the wet season (october to march) showed upward trends. It is possible that the increased water uptake rate for public supply in the city of Uberaba is the most impacting agent of drought flows. Regarding the use and occupation of land, it was found an increase of 0.36% to 13.48% of the areas occupied by agriculture between mid-1980 and the year 2014, and an increase of 4.55% to 7.07% of the urban area of the same period. The most significant land use in the upper course of Uberaba river basin is pasture whose area currently reaches just over 50%. Evidences was found that the increase in the urban area, characterized by the paving of roads and construction of buildings, is increasing the maximum flow rates.