Perda e aporte de sedimentos estimados pelos modelos RUSLE e SEDD em bacia hidrográfica de clima subtropical

Abstract

The soil erosion process occurs naturally, helping to shape the Earth's surface. However, water erosion can negatively affect the environment, especially when there are intensive human activities. Inappropriate soil use management can have an impact on the structure, fertility and availability of water in the soil. In addition, off-situ impacts can contribute to the increase of sedimentation and eutrophication of water resources. Soil erosion prediction models have been used to estimate such impacts, contributing to establish mitigation plans for this process in a distributed and effective way. The Candiota region, Rio Grande do Sul, Brazil, has intense anthropic activity related to mining activities. In that way, monitoring in the watershed that comprise the region is of high socio-environmental importance, assisting in the planning, management and conservation of soil and water. Therefore, the objective of this work was to estimate the total annual soil loss and to spatialize the sediment delivery, through the Revised Universal Soil Loss Equation and Sediment Delivery Distributed, respectively, in Candiota sub watershed, located in the city of Candiota, Southern Brazil. In addition, an erosion risk classification for the watershed has been proposed. Information on altitude, slope, use and soil classes was used, in addition to measured data on solid suspended discharge. To perform the analysis and spatialization of the data, geospatial platforms were used. The estimated average annual losses were 42 to 102 Mg·ha-1 ·year-1 , according to the variation in the images used to classify the land use (january, may and september, respectively). The extreme values of the soil loss index are predominantly related to exposed soil use. Thus, 47 to 68% of the total area in watershed has erosion risk, depending on the month used for classification of land use. The spatial distribution of sediment delivery through hydrosedimentological modeling indicated that flat slopes, as well as regions close to watercourses, are more prone to sediment accumulation. The results obtained shows the need for changes in conservation and use practices present in the watershed, considering the capacity of land use and soil support. In addition, these actions can assist in decision-making regarding the implement strategies related to the control of water erosion, as well as the sediment delivery, in the watershed.