Assessment of water quality in the lower reaches of the Inhulets River

Abstract

The level of water availability in Ukraine remains low, while the spatial distribution of water resources is uneven and does not correspond to the location of the most water-intensive economic sectors. The share of the agricultural sector in total water consumption reaches approximately 40 %, whereas the average daily water use per capita is about 270 liters. At the same time, nearly 50% of abstracted water is returned to water bodies in the form of wastewater or drainage water [1]. The regions that most deficient in water resources are those with a high concentration of industrial enterprises, particularly Donbas, the southern regions of the country, the Kryvyi Rih basin, and the territory of the Autonomous Republic of Crimea. The economic complex of the Kryvyi Rih region is represented by industries characterized by significant consumption of natural resources, energy, and water. The main water body in the region is the Inhulets River, which serves as a receiver of highly mineralized tailings wastewater and insufficiently treated industrial effluents. The volume of polluted wastewater discharges into the Inhulets and Saksahan rivers (a left tributary of the Inhulets) reaches approximately 12 million m3 per year, resulting in significant deterioration of water quality within the area from Kirovohrad region (Iskrivka village) to Mykolaiv region (Snihurivka city) and Kherson region (Dariivka village). A substantial increase in concentrations of total dissolved solids (from 800 to 4200 mg/dm3), chlorides (from 90 to 2084 mg/dm³), sulfates (from 240 to 998 mg/dm3), biochemical oxygen demand (BOD5) (from 1.2 to 5.8 mg/dm3), as well as elevated iron content from 0.1 to 0.3 mg/dm3 has been recorded (data for 2019-2020). Comparative results of water quality assessment based on hydrochemical indicators [7], obtained using different methodologies, indicate significant discrepancies in conclusions, highlighting the limitations of relying on a single approach for a comprehensive evaluation of the ecological status of the Inhulets River. In this regard, conducting a comparative analysis of existing methodological approaches and identifying the most appropriate system for integrated water quality assessment in the lower reaches of the Inhulets as a habitat for aquatic organisms is of particular relevance.