Water Quality Assessment of the Black Sea Rivers Within the Odesa Region According to Hydrochemical Indicators

Problem Statement and Purpose. In today’s environment, the problems associated with the ecological state of rivers and the formation of water quality in them are becoming particularly relevant. This is especially true for small rivers with low water flows, where the impact of natural and anthropogenic factors is more pronounced. The intensive use of both rivers and watersheds in the national economy disrupts their natural hydrochemical and hydrobiological regime, and water quality deteriorates. Data & Methods. The research uses hydrochemical indicators to monitor data collected between 2013 and 2021 of several rivers in the Black Sea region within the Odesa region—namely, Saratа, Khadzhyder, Kaplan, Alkaliya, and Kogylnyk. Two key methodologies were employed to assess the water quality: the modified Water Pollution Index (WPI) and the Pollution Coefficient (PC). These approaches allowed for a comprehensive understanding of the studied rivers’ chemical composition and pollution levels. The study also provides a comparative evaluation of the methodologies used. The modified WPI effectively categorized water quality by integrating key hydrochemical parameters, while the PC offered a broader scope by including additional indicators such as nitrogen compounds and heavy metals. Results. Based on the results of the studies conducted from 2013 to 2021, it can be stated that the quality status of surface waters in the studied areas is negatively affected by both natural factors — such as insufficient precipitation, extremely high summer temperatures causing significant evaporation, and high concentrations of sulfate and chloride salts in soils and rock formations — as well as human activities in the region and in the neighboring republic, from which pollutants are also introduced. When comparing the two methods used, it was decided to recommend primarily using the Pollution Coefficient method for assessing such water bodies, as it allows for the evaluation of a greater number of indicators and thus provides a more thorough assessment of surface water quality. For more detailed analysis, it is recommended, where possible, to also apply the surface water quality assessment methodology according to relevant categories. Currently, the condition of the studied rivers can be characterized as critical according to both methods, as evidenced by poor water quality results, which require urgent resolution. This is because the extensive exploitation of small rivers’ biological resources, their regulation, significant water abstraction for irrigation and domestic use, as well as the transformation of rivers into wastewater collectors, will lead to a significant deterioration of their condition and potentially to their complete disappearance.