The reservoirs of Russia are an important source of fresh water and therefore there is no way to overestimate their significance for population and economy. Inflow to the reservoirs is one of the sufficient components of sustainable functioning of hydropower plants, flood control, navigation, water supply. That’s why the problem of inflow change at global warming is very urgent in the 21st century. Since the late 19th century the mean annual air temperature has increased by about 1.29ºС for the Russian territory that surpasses the global annual air temperature increase. Recent years the tendency towards warming has grown significantly. The year 2010 was warm in Russia. Anomalies of air temperatures were positive for all seasons, except for winter, with the summer air temperature anomaly being the highest. The last winter in Russia was one in a ten coldest winters. Analysis of time series shows that the most common regularity for all large reservoirs of Russia is the sufficient duration (10-15 years) of period