Abstract
<jats:p>A comprehensive assessment of the water resources of the Berezina and Sved Rivers at the planned intake sites was conducted to justify the reconstruction of the Svetlogorskoye reservoir. Based on long-term hydrological observations and regional calculation methods, the main statistical characteristics of the flow, its intra-annual distribution, and environmentally permissible withdrawal volumes were determined. Using the probability transfer method, updated environmental flow values were obtained for the Berezina and Sved Rivers. A water management balance for the reservoir was developed for two estimated probability levels (75 % and 90 %). The criterion for permissible withdrawal was the difference between the estimated probability flow and the environmental flow determined by the probability transfer method. The total withdrawal volume from the Berezina River amounted to 37,720 thousand m³, and from the Sved River is 3,673,700 m³, which is corresponding to a decrease in annual flow of 1.0% and 8.3 %, respectively. Long-term climate and runoff changes in the Berezina River basin from 1961 to 2018 were analyzed, revealing statistically significant trends: an increase in winter runoff (11...21 %) and a decrease in spring flood runoff (30...40 %). Based on IPCC (RCP) scenarios, a runoff change forecast was generated to 2035, showing a possible reduction in spring and summer-autumn runoff. Suggestions for improving monitoring and adaptive management of the reservoir's water resources were provided.</jats:p>