SIG E SENSORIAMENTO REMOTO APLICADOS À AVALIAÇÃO DA CONTRIBUIÇÃO DE SUB-BACIAS PARA A POLUIÇÃO DIFUSA DO RESERVATÓRIO DE BARRA BONITA - SP

This paper presents a methodology to assess catchment basin diffuse contribution to the pollution of Barra Bonita reservoir, located in the Sao Paulo state, Brazil. Geographic Information System (GIS) and remote sensing techniques were applied. First, the Tietê drainage basin limits were defined and divided into smaller basins by digitizing its limits onto a 1:250 000 topographic map directly in the screen. The drainage network was then digitized at the same scale and the drainage density calculated for each catchment basin. The distance from each catchment basin to the reservoir was measured and this information will be integrated to a land use map derived from 2002 ETM+/Landsat7 images and ground checking. Finally, the AHP3 multi-criterion decision technique will be used to reach a more objective jugdgement of the role of each selected variable: drainage density, distance and land use classes. Map algebra will be applied to superpose the different features to determine the contribution of each catchment basin to the degradation of the Barra Bonita reservoir water quality. It is hypothesized that catchment basins presenting high drainage density, intensive land use and nearer to the reservoir will be the largest non-point sources of pollution.