Bulletin WKU

The article presents the results of a study on the sanitary and ecological condition of the Karatomar and Verkhnetobolskoye reservoirs, located in the Kostanay region of the Republic of Kazakhstan. Special attention is given to the analysis of the oxygen regime as one of the key indicators of water quality, which affects the vital activity of aquatic organisms and self-purification processes. The study covers data from 2017 to 2024 on water temperature, hydrogen index (pH), dissolved oxygen content, and biochemical oxygen demand (BOD). Sampling and laboratory analysis were carried out in accordance with current regulatory methodologies. The results showed that the water in both reservoirs corresponds to quality classes I–III according to the Unified System of Water Quality Classification. The greatest variability was observed in the biochemical oxygen demand indicator. The study revealed seasonal and annual fluctuations in parameters and confirmed the relevance of continuous monitoring to ensure the stable functioning of the region's aquatic ecosystems.