Water Quality Index Applied to an Urban Stream Located in Porto Alegre, Rio Grande Do Sul, Brazil

Water quality monitoring is an important tool to preserve water resources In this study, the water quality index (WQI) adapted by Environmental Company of the state of São Paulo (CETESB) was calculated and used to classify the water quality of an urban stream in the period between 2002 and 2012. It was used raw data on the concentrations of each WQI parameter. The parameters are: water temperature; total solids; turbidity; dissolved oxygen; biochemical oxygen demand; pH; total nitrogen; total phosphorus and Escherichia Coli. The results showed that the water quality was classified as "Low" or "Very low" in all samples, according to National Agency of Water (ANA) classification. Statistical analyses were performed for each parameter with the purpose of identifying variations over time and between different locations along the stream. The results showed that these variations were identified in those parameters generally related to domestic sewage, i.e.: DO; BOD5 and Escherichia Coli.