Water is fundamental for the survival of every specie on planet Earth and is a crucial element of the environment. Water bodies, however, have degraded over time due to various natural and mainly human-polluting activities. As a result, water quality control is required to monitor and reduce polluting agents while maintaining river health. The adoption of a Water Quality Index is one of the most extensively utilized ways of water quality control (WQI). The WQI developed by the National Sanitation Foundation determines the water quality of a river in a single value ranging from 0 to 100 by analyzing many physical, chemical, and biological parameters and employing mathematical methods. The water quality of the Fervença River in Bragança, Portugal, was assessed to use the WQI by monthly collections between January 2022 and June 2022. Samples were taken at five distinct locations along the river within the city so that the results could be compared over time and at different locations. In general, points 1 to 4 showed good water quality indexes and similar results. Point 5 on the other hand, had the lowest water quality indexes of all campaigns, which could be attributed to the neighboring city wastewater treatment plant. The winter (the region's wettest period) was characterized by a severe drought, hence no effect of rain on the analytical data could be found, as was predicted primarily for the months of January to March. From the comparison of the results obtained, it is possible to conclude that as the Fervença River flows through the city of Bragança, the quality indexes decrease in most of the campaigns, especially after point 5, demonstrating the city's negative influence on the river water quality.