Supporting agencies: The study was supported by the Russian Science Foundation Project No. 17-77- 10035. We express our gratitude to Eugene Osipchuk (Ph.D., Melentiev Energy Systems Institute, Siberian Branch, Russian Academy of Sciences) who prepared data on catchment areas of Lake Baikal and Selenga River. We thank The Global Precipitation Climatology Centre (Public Datasets: https://apps. ecmwf.int/datasets/), especially Dr. Andreas Becker (Head Precipitation Monitoring Unit (KU42) and Global Precipitation Climatology Centre (GPCC)) and European Centre for Medium-Range Weather Forecasts Public Datasets: https:// apps.ecmwf.int/datasets/). We are also grateful to Irkutsk Hydrometeorological Administration for the possibility to work with synoptic maps.