Water Quality Assessment of the Uvac River (Serbia) Using the Water Pollution Index (WPI): Relevance for Protected Area Sustainability and Tourism

Although water resources are very significant natural assets of protected areas, the increasingly intensive tourism development in national parks and nature reserves brings them under constant anthropogenic pressure. Therefore, the analysis of water quality and pollution in them is of great importance. This study evaluates the water quality of the Uvac River (Serbia) at the Priboj hydrological station using the Water Pollution Index (WPI), based on physicochemical data for the period 2021–2023. As part of the WPI methodology, Ci/Si ratios between mean annual parameter concentrations and reference values for Class I (excellent water quality status) were analyzed. For seasonal analysis, Ci/Si between seasonal parameter concentrations and reference values for Class I were calculated. Relationships between WPI and selected water-quality parameters were also analyzed. Annual WPI values ranged from 0.89 to 0.99, indicating stable Class II water quality throughout the study period. Seasonal analysis showed occasional shifts to Class III during autumn and winter, associated with increased organic matter and nutrient inputs. Correlation analysis revealed strong relationships between WPI and TOC, BOD5, and CODMn, while moderate correlations with ammonium, suspended solids, and phosphorus compounds suggest the influence of nutrient inputs and hydrological conditions.