ESTIMATE OF THE CURRENT EROSION OF THE PARACATU RIVER BASIN, BRAZIL

Abstract

The universal soil loss equation (USLE) is widely used all over the world in the prediction of soil loss and in the definition of best management practices of single slopes. However, despite its potential of application, a few factors of the equation are difficult to obtain, such as the slope length factor (L factor), particularly in watersheds. The purpose of the present study was to apply the USLE, which was originally developed for individual slopes, to large watersheds. In order to achieve that, a methodology for automatic calculation of the L factor, was developed by Desmet and Govers (1996), using a geographic information system (GIS). This methodology was used to estimate the actual erosion. Existing thematic maps, in association with ancillary information about soil, land use, relief and climate, were used in order to obtain GIS coverages. These coverages were overlaid on the GIS and maps of actual erosion were generated. This study concludes that 67.2% of the total area of the Rio Paracatu basin is within the soil loss tolerance limit (less to 10 t.ha^-1/year). In addition, the slope length factor, as developed by Desmet and Govers (1996), which accounts for accumulated flow, showed satisfactory results in a large watershed. The proposed methodology was validated with sedimentometric data in two sections of the watershed, and measured and calculated silting yield data agreed.

KEY-WORDS: Erosion; USLE; L factor; GIS.