GIS application to map watershed physical features contributing to reservoir water quality

The eutrophication process in aquatic systems may be caused by point and non-point pollution sources. The latter is hard to be quantified and determined. In this framework, new methods using the advances in geotechnologies can represent a powerful tool to improve the estimates of non-point sources. This paper proposes the integration of watershed physical variables using the GIS technology as a tool to improve non-point load estimates in aquatic ecosystems. Barra Bonita reservoir watershed was selected as test site. The georeferenced database includes the following layers: drainage density, sub basin limits, distance from sub basins to the reservoir and rainfall distribution. Based upon those variables the potential non-point pollution for each basin is computed using a multi-criteria decision technique. In the next step of the research, these data will be integrated to a model that estimates the potential pollutant export rates taking into account the various degrees of human interference in the reservoir drainage basin.