Simulação da qualidade da água do rio Poti no município de Crateús ­- CE utilizando o modelo QUAL- UFMG

Abstract

Water is an essential resource for life and sustainable development, yet it faces increasing scarcity and degradation due to inappropriate use, especially in semi-arid regions such as the Brazilian Northeast. In this context, the present monograph aimed to model the water quality of the Poti River, in the section located in the municipality of Crateús (Ceará), using the QUAL-UFMG software. The choice of the study area is justified by the environmental fragility of the region, low water availability, and lack of adequate infrastructure for the treatment and disposal of effluents. The methodology included a literature review, basin characterization, data collection, parameter input into the QUAL-UFMG model spreadsheet, and comparative analysis of the results with the standards established by CONAMA Resolution No. 357/2005 and data from SEMACE. The parameters evaluated included dissolved oxygen (DO), biochemical oxygen demand (BOD₅), total nitrogen, total phosphorus, un-ionized ammonia, thermotolerant coliforms, and streamflow. The results indicated high concentrations of nutrients and organic matter, suggesting risks of eutrophication, fecal contamination, and impairment of aquatic life, although the DO concentration remained above the legal minimum threshold. The observed low flow further reinforces the river’s vulnerability to pollution, especially during dry periods. Considering the simulated values and the region's environmental context, the Water Quality Index (WQI) for the analyzed stretch is estimated to fall within the “good” category, although it still demands attention. It is concluded that water quality modeling using QUAL-UFMG constitutes a strategic tool to support water resources management, enabling impact forecasting, identification of non-compliances, and the development of public policies aimed at the conservation of water resources in critical regions.