Аннотация
The relevance of research into the state of aquatic ecosystems in nuclear test areas is determined by the long-term persistence of the effects of radioactive contamination in natural environments. In areas exposed to nuclear explosions, the problem of radioactive contamination of surface and groundwater remains one of the key environmental challenges. One such site is the Shagan River, located on the territory of the Semipalatinsk test site. Particular attention is paid to sections of the riverbed where contaminated groundwater and fissure water discharge into surface watercourses, contributing to the further spread of radionuclides in the water system. A comprehensive study of the temperature regime and water flow of the Shagan River within the zone of influence of the Balapan test site of the Semipalatinsk test site was conducted. The main focus was on sections where groundwater containing tritium (3H) discharges and on analyzing their spatial and temporal variability. Unlike previous radioecological studies of the Shagan River, which focused primarily on assessing contamination, this study emphasizes the interaction between groundwater and surface water and its role in shaping the hydrological regime and transporting radioactive components. Thermometric measurements taken at 50 m intervals along the riverbed over a distance of 5.4 km revealed zones of abnormally low temperatures (8,5...10 0C) corresponding to areas of discharge of contaminated groundwater. Hydrometric measurements showed that the water flow varies from 0,01 to 0,21 m3 /s, with significant losses due to filtration. The maximum specific activity of 3H is recorded at the bottom of the watercourse near sections 2650...2800 m and 4950...5350 m downstream from Lake «Atomnoe», confirming the link between temperature anomalies and groundwater inflow.