This research aimed to understand the fast water degradation process in overpopulated áreas as a result of inadequate land use and land cover practices. Therefore, the objetive of this study is to assess the relationship between the trophic state of the Barra Bonita Reservoir(SP) and the pollution potential of its drainage basin in space and time. The trophic state determination was based in water samples collected at 32 stations evenly distributed in the lake in two dates: 1990 and 2002. These samples were used to determine the key parameters for the computation of the Trophic State Index (TSI), which was then spatialised with aid of the ESRI ArcView 3.2 sofware. The pollution potential was based on several data: land use and land cover maps derived from the Landsat /Thematic Mapper images acquired in 1990 and 2002; population growth and nitrogen and phosphor load. The results showed the increase in the water trophic level from 1990 to 2002, but this increase was not homogenous. The water quality degradation, as expressed by the TSI was highest in Tietê river compartment due to response to the higher pollution potential of São Paulo city. The space and time integrated analyses of the terrestrial and aquatic system allowed to conclude that the water quality degradation is closely connected to both land use and land cover changes in the drainage basin and to the population growth. Other important finding was that the pollution potential is not homogenous throughout the drainage basin, and that therefore, the pollution control police must be focused in more critical areas, where the degradation is more intense.
Barra Bonita; water quality; land use; point and nonpoint pollution
