O IMPACTO DO USO DA TERRA SOBRE O BALANÇO HÍDRICO NA BACIA HIDROGRÁFICA DO RIO SANTA MARIA – OESTE DO RIO GRANDE DO SUL – BRASIL

Abstract

Land use is undergoing rapid transformation in Rio Grande do Sul. The major transformations in the forms of land use have significantly contributed to the change in the water balance, and consequently in the flow of rivers. The present work aims to analyze the effect that land occupation has on the water balance in the Santa Maria whatershed. This whatershed has an area of 14,913 km² and is located in the southwestern portion of the state of Rio Grande do Sul, southern Brazil, on the border with the country of Uruguay, making up a significant area of the Pampa Biome. The methodology is based on the SWAT hydrological model (Soil & Water Assessment Tool), which is based on the calculation of the water balance in relation to climate, soil, slope, vegetation cover associated with hydrological response units, and on equations of transfer of flow in the aquifer and in the hydrological network. The results show that the contribution is quite different between the cultures and pastures present in the basin, since in addition to the specific contributions of the characteristics of the soils and slope of the basin, the way of handling the cultures allows great differences in the characteristics of the elements of the water balance. Changes in use, with the shift from native grassland areas to soybean or rice plantations, or even forestry, tend to have a significant impact on the water balance of the basin.