An analysis of 17 physicochemical parameters of water of the Bug River in the period 2010–2019 was carried out at ten stations and throughout four seasons. A spatio-temporal analysis was performed on this database. Based on the cluster analysis, four clusters of stations were distin- guished. There were statistically significant differences between the clusters and between the seasons (Kruskal–Wallis test). Average concentrations of parameters meet the standards of good ecological status. The spatial variability between the station was related to the content of nitro- gen and phosphorus compounds and the amount of oxygen. The analysis of seasonal variability showed that the concentration of chlorides, sulfates and nitrates was the highest in winter. Hot spot analysis made it possible to detect the highest pollution in the head of the river and decreased along the flow path of the river. The periodic increase in water pollution is related to urbaniza- tion, wetland drainage and cropland management. Decreasing water quality reduces biodiver- sity and limits the possibilities of water use by people. The research results indicate that most of the physicochemical parameters of the Bug River waters require discernible consideration due to intense land-use changes and municipal wastewater discharges.