Classificação de estado trófico de reservatórios : estudo de caso : reservatório de Rio Bonito (ES)

Abstract

The small hydroelectric reservoir of Rio Bonito, located in the basin of the Santa Maria da Vitória river, Espírito Santo State, Brazil. This river is one of the main water supply sources for Vitória metropolitan region and receives nutrients from sewage, agricultural crops, farms and piggeries. In this study, conditions of the water body were analyzed, considering results from bimonthly water quality monitoring developed during October 2008 to September 2009 hydrological year. Surveys were carried out at 3 (three) points located inside the reservoir and 2 (two) points located upstream and downstream, respectively. The trophic state was classified by using different mathematical models and trophic state index (TSI), including Salas and Martino (1991) and OECD models, and Carlson, Lamparelli and Florida TSI. Morphoedaphic Index (MEI) was used to estimate the total phosphorus "natural" concentration in the reservoir of Rio Bonito. It was concluded that the application different models can result in different trophic levels classifications. It was also concluded that the downstream point presented better water quality condition than the upstream point, considering several parameters monitored, indicating that the reservoir is working as a waste stabilization pond.