Indicadores ambientais para diagnóstico dos processos de eutrofização na unidade de gerenciamento de recursos hídricos 6 - Alto Tietê - São Paulo/ SP – Brasil.

Abstract

The availability and quality of water became a topic discussed worldwide, considering its different uses as: recreation, fishing, irrigation, public supply and power generation. In this sense, one of the great challenges to guarantee the quality of water resources refers to the problems inherent to the undue release of nutrients in rivers and reservoirs, which favors the emergence of the eutrophication phenomenon. Eutrophication can be observed in the aquatic system by increasing the flowering of algae, such as cyanobacteria, which are toxic. This study presents the analysis of the environmental indicators and diagnosis of eutrophication processes, obtained from the reports on the Surface Water Quality Monitoring Network [RMQAS], for the Water Resources Management Unit 6 [UGRH-6] - Basin of the Alto Tietê, which comprises the Metropolitan Region of São Paulo, made available by the Environmental Company of the State of São Paulo [CETESB]. In order to investigate the degree of eutrophication of water bodies, quantitative data were considered between 1996 and 2016 for Chlorophyll - a [Cl-a] and Total Phosphorus [PT], which are the main parameters used in the determination of trophic degrees by contamination, originating from domestic effluents. The study was based on the premise that untreated sewage in spring areas should be the preponderant factor for the occurrence of eutrophication, since it has been observed a rapid urban growth in Water Resources Protection and Recovery Areas [APRM], which has contributed significantly for environmental deterioration, as presented in the maps elaborated with Trophic State Indices [EIT]. In the maps, it was verified the spreading of the population density, in the regions that comprise the areas of the springs and their influence for the deterioration of their waters, due to the reception of the domestic effluents without treatment. Also, it was observed in the main reservoirs that supply the RMSP (Billings and Guarapiranga) the evolution of the EIT values over the years, the values of EIT showed the classification of waters in eutrophic, supereutrophic and hypereutrophic. It was concluded that the urbanization process is continuous and that, even with public policies aimed at preserving the quality of the water supply, technical actions are necessary, which prevent the enrichment of nutrients, such as phosphorus, in water bodies. It is also pointed out the importance of the elaboration of a study that identifies the fragilities in the integration and effectiveness of social and educational policies, so that in fact it is possible to minimize the impacts caused by the disposal of untreated effluents in sewage networks; common practice in aquatic environments, which impairs the quality of the sources, as in the case of the Alto Tietê Basin and affects the public supply of the RMSP.