Natalia LEMESHKO, Tataiana GRONSKAYA
State Hydrological Institute 2-nd Liniya 23, 199053 St.Petersburg, Russia Tel. 7(812) 3233343 Fax: 7(812) 3231028 e-mail: natlem@mail.ru
Inflow to the reservoirs is one of the sufficient components of sustainable functioning of hydropower plants, flood control, navigation, water and power supply, reservoirs biota and etc. Thatís why the problem of inflow change at global warming is very urgent in the 21st century. The air temperature empirical data show growth in different latitude zones, which is the most pronounced for high and temperate latitudes. This phenomenon is characteristic for the territory of Russia as well.
The common tendency of the mean annual temperature for Russia is evaluated by positive linear trend 2,6ºС/100years. The most considerable positive trends have been received for mean monthly temperature in February-April and monthly precipitation in January-March especially during last two decades.
The long-term variation of the inflow to the largest reservoirs of Russia in 20th century is analysed on the background of climate change. The period of analyses varies from 120-80 years for the reservoirs on the River Don and the Volga River to 28 years for the Khantayskoe Reservoir located at the northern tributary of the Yenisei River.
Analysis of time series shows that the most common regularity for all reservoirs of Russia is the sufficient duration (10-15 years) of periods with low and high inflow. Last two decades of the 20-th century are characterised by normal or high inflow to almost all reservoirs, excluding reservoirs on the Don and Ob rivers. The most high runoff is characteristic for rivers inflowing the Volga in its upper and middle parts. The most pronounced changes in inflow monthly distribution are observed for the reservoirs of the Volga-Kama catchment: decrease of the part of spring flood. The monthly distribution of inflow to the reservoirs of the Siberia and the Far East is above normal.
The historical analogue approach is used to examine the respond of inflow to the study reservoirs of Russia to the recorded extremes in the weather. The inflow of the extreme years when the mean year temperature is 20C higher than normal for each reservoir catchments is employed for these purposes. The future global warming by 20C should influence dramatically on inflow to the reservoirs of Russia, especially on its monthly distribution.