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Title: Water Erosion Distribution in the Itutinga/Camargos Hydroelectric Plant Watershed (Minas Gerais, Brazil) using Distributed Modeling

item Norton, Lloyd

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2009
Publication Date: 8/5/2009
Citation: Beskow, S., Mello, C.R., Norton, L.D., Curi, N., Viola, M.R., Avanzi, J.C. 2009. Water Erosion Distribution in the Itutinga/Camargos Hydroelectric Plant Watershed (Minas Gerais, Brazil) using Distributed Modeling. Catena. 79(1):49-59.

Interpretive Summary: Energy production in an environmentally friendly way is a priority over the entire world. One of the most environmentally friendly methods is to utilize hydroelectric generating power where it is feasible. In Brazil, there has been large scale development of hydroelectric schemes that has been a driving force for economic development. Due to land use changes and increased soil erosion since construction, the longevity of these facilities is being threatened. The purpose of this research was to develop a simple tool that can be used to predict the most critical areas within a catchment above such a hydroelectric facility to identify where soil and water conservation will have the greatest impact. We used a simple Geographical Information System (GIS) to develop predictions of Universal Soil Loss Equation based erosion estimates thoughout the catchment above a hydroelectric reservoir. We utilized available data on climate, soils, land use and topography to predict critically eroding areas and calculate a sediment delivery ratio to the reservoir. The effort showed that over one third of the land in the watershed had erosion losses greater than the tolerable level, meaning that the present land use in these areas is not sufficient control erosion and should be changed. These areas were easily mapped in the GIS and can be easily prepared for decision makers and conservationists. The implication of this research is that the methodology developed for this watershed can be used for other reserviors in Brazil and other parts of the world to help better manage areas above hydroelectric facilities for a more sustainable environment.

Technical Abstract: Mapping and assessment of erosion risk is an important tool for planning of natural resources management, allowing researchers to modify land-use properly and implement management strategies more sustainable in the long-term. The Grande River Basin (GRB), located in Minas Gerais State, is one of the Planning Units for Management of Water Resources (UPGRH) and is divided into seven smaller units of UPGRH. GD1 is one of them that is essential for the future development of Minas Gerais State due to its high water yield capacity and potential for electric energy production. The objective of this work was to program the Universal Soil Loss Equation (USLE) using the PCRaster GIS programming language, in order to simulate erosion and map critical areas in the GRB (GD1) so that the most critical areas susceptible to water erosion can be identified. For the USLE model, the following factors were used: rainfall erosivity (R), erodibility (K), topographic (LS), cover-management (C) and support practice (P). The Fournier Index was applied to estimate R for the basin using six pluviometric stations. Maps of the K, C, LS and P factors were derived from the digital elevation model (DEM), soil and land-use maps, taking into account information available in the literature. In order to validate the simulation process, Sediment Delivery Ratio (SDR) was estimated, which is based on transported sediment (TS) to basin outlet and mean soil loss in the basin (MSL). The SDR calculation included data (total solids in the water and respective discharge) between 1996 and 2003 which was measured at a gauging station located on the Grande River and a daily flow data set was obtained from Brazilian National Water Agency (ANA). It was possible to validate the erosion process based on the USLE and SDR application for the basin conditions, since absolute errors of estimate were low. The major area of the basin (about 63%) had an average annual soil loss of less than 5 t ha-1 yr-1. With the results obtained we were able to conclude that 37.5% of overall basin presently has soil loss greater than the tolerable rate, thus indicating that there are zones where the erosive process is critical, meaning that both management and land-use have not been used appropriately in these areas of the basin. The methodology applied showed acceptable precision and allowed identification of the most susceptible areas to water erosion, constituting an important predictive tool for soil and environmental management in this region, which is highly relevant for prediction of varying development scenarios for Minas Gerais State due to its hydroelectric energy potential. This approach can be applied to other areas for simple, reliable identification of critical areas of soil erosion in watersheds.