ELABORAÇÃO E APLICAÇÃO DE UM ÍNDICE DE QUALIDADE DA ÁGUA EM CONSONÂNCIA COM A LEGISLAÇÃO BRASILEIRA

Abstract

The water quality index (WQI) is an important tool for assessing the status of water quality; synthesizing the information provided by physical, chemical and biological parameters. This work had as general objective the elaboration and application of a water quality index in accordance with the Brazilian legislation. For the development of a new index, denominated IQAc, the information of the parameters that compose it and the practicality of calculation was linked to the legislation in force in Brazil. For this purpose, 30 water monitoring stations were selected, in the domains of the hydrographic unit of Alto Iguaçu- Parana, Brazil. To these data, three methodologies for calculating WQIs were applied: the NSF method (NSFWQI), Bascarán (WQIb) and the method proposed in this research denominated Bascarán-CONAMA (IQAc). The indices were compared in different pluviometric periods and seasons. Subsequently, the IQAc was applied to the Hydrographic Basins of the Tibagi River and the Cinzas River, located in the State of Parana, where 24 water monitoring points were monitored from July 2014 to June 2016.Ponderations were made from a viewpoint of more and less rainy annual periods, as well as a seasonal perspective. Georeferenced maps were elaborated using the Weighted Distance Inverse (IDW) interpolation method, in order to obtain the spatial distribution of the estimated values. Statistical analyzes were performed at a significance level of 1%. From the results obtained in this research, it was concluded that the new water quality index developed was adequate for water quality assessment. It was observed that the development of WQI as a function of regionality is an important aspect for assessing water quality in water bodies. It was found that the water quality in the evaluated area of the Tibagi and Cinzas rivers complies with the minimum water quality requirements in Brazilian legislation for Class 2 rivers. It was concluded that the seasonal factor hasn’t had a significant influence on water quality, since in the comparison between rainfall periods and seasons, no statistically significant differences were observed in the monitoring points.