Analysis of the Influence of Water Quality Parameters in the Final WQI Result Through Statistical Correlation Methods: Mirim Lagoon, RS, Brazil, Case Study

In a scenario of increased degradation of the quality of water resources, the Water Quality Index appears in the USA, developed by the National Sanitation Foundation, one of the most used methods currently for monitoring water quality, using variables that reflect the changes that have occurred in the hydrographic basin region. This method was adapted for use in Brazil by the Environmental Company of the state of São Paulo (CETESB) and the variables used to calculate the WQI in this adaptation, as well as their relative weights, are the same regardless of the location where the water resource is inserted. Thus, this study aims to show that the relative weights of these variables do not reflect the reality of all locations, and for the case study in Mirim Lagoon, variables with less theoretical relative weight can influence the final result of the WQI in greater quantities, as observed by the correlation between phosphorus-WQI at points ML4 and ML5 of Mirim Lagoon, a correlation that overcomes in intensity parameter-WQI correlations of variables with higher theoretical weights. The use of statistical correlation methods makes it possible to make well-supported inferences about the monitoring data used, showing that variables with less expression within the calculation of the WQI may, indeed, represent great importance in the final result of this index, depending on the factors that influence quality of each water resource.