Applying environmental fragility in studies evaluating watershed can guide policy decisions on monitoring and management regarding soil use planning, improving water quality for public supply. The objective of this study is to characterize the environmental fragility as well as to relate it to water quality factors of catchment rivers for public supply in western Paraná, Brazil, in order to evaluate the influence of anthropic actions on catchment sources. Water quality data such as temperature (Temp; C), electrical conductivity (Ec; mS/cm−1), dissolved oxygen (DO; mg L−1), turbidity (Turb; NTU) and pH were measured on site by the multi-parameter probe HORIBA brand, model U-5000. Slope data were obtained from the site of the National Institute of Space Research (INPE). Soil use and occupation was performed in the QGis software, with image obtained from the Sentinel 2A Satelite. Köppen-Geiger classification was used for the climate type. For the environmental fragility maps, the variables slope, climate, soil use and occupation were analyzed using the QGis raster software calculator. The intermediate fragility class predominates in the nine municipalities studied, making it necessary to manage them aimed at restoration and conservation, and the municipalities that are the largest areas of high fragility class are: Guaraniaçu, Catanduvas and Cascavel, demanding greater attention. The variation in fragility mainly responded to the pH, E. coli and DQO temperature values, which can be strongly associated with the difference in soil use and slope of the areas evaluated.