The quality of water resources in urban areas has undergone degradation due to the discharge of domestic and industrial wastewaters and urbanization among other factors. Despite the legal instruments that aim to preserve water bodies, other mechanisms should be implemented, such as monitoring networks and reporting results. Another challenge is the interpretation of the results that may support decision making on the actions that must be taken to preserve the water quality. In this study, we examined the results of physicochemical and microbiological analyses in a monitoring network that comprised 12 sampling stations. Results were compared with water quality standards established in legislation and calculation of two water quality indexes, the Canadian Council of Ministers of the Environment water quality index (CCME WQI) and the National Sanitation Foundation–Environmental Sanitation Technology Company of the State of São Paulo (Cetesb) WQI. Conclusion is that the comparison with quality threshold limits as defned in the legislation, although complete, prevents the reporting on the overall quality of the water body. Application of the quality index allowed communication and interpretation of the results. Another conclusion is that the Cetesb WQI can indicate the degree of contamination of waters impacted by domestic sewage, while the CCME WQI is an effective tool to assess water resources considering different sources of contamination and current legal aspects.
water quality index, water quality monitoring, water resources
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