Avaliação da qualidade da água de mananciais nos municípios de Camaquã, Cristal, Capão do Leão e Rio Grande, no estado do Rio Grande do Sul

Abstract

Economic development and population growth require increasing volumes of water to serve different uses, the public supply being one of the most noble of these. However, the quality of surface and underground water can change according to geology, surface runoff, soil management and local occupation, and it is essential to know and monitor the characteristics of the sources to identify whether they face loss of water quality. The proposed study aims to assess the quality of raw water from different sources that supply the municipalities of: Camaquã (dam), Cristal (water tables), Capão do Leão (brook) and Rio Grande (channel). The development took place through descriptive research of secondary data provided by Companhia de Saneamento Estadual using reports of analytical tests obtained in 6 years, referring to the period from 2013 to 2018. From these results were extracted from several variables in order to understand the variations and relations of certain physical-chemical parameters of the studied sources, using statistical analysis, which were also analyzed according to what CONAMA Resolutions 357/2005 and 396/2008 recommend. The Trophic State Index (EIT) using the parameter total phosphorus (PT) to assess the degree of trophy of the study sites was also performed, as well as the Water Quality Index (IQA) developed by the Canadian Council of Ministers of the Environment (CCME) for surface and underground water sources. Correlation was found in the underground water source between metals and organic matter and in the surface water sources, the correlation of PT with color, turbidity and metals predominated. When comparing the results of surface water sources with the limits established by CONAMA Resolution 357/2005, parameters were found to be in disagreement with the limits of class 3. The same occurred for the underground water source, belonging to class 3 during the analyzed period. The application of the EIT demonstrated a greater impairment of the degree of trophy for the reservoir-type source that supplies Camaquã. The calculation of the IQA-CCME resulted in a worse value for the underground source that supplies the Cristal, in view of the amplitude of nonconformities with the reference standard. It is possible to conclude that the data generated in the monitoring of the water sources by the concessionaire add important information for the monitoring of the framing goals and the attendance to the classes required for the use destined for public supply, being necessary actions for the preservation of these water resources.