THE LEVEL REGIME OF THE THREE LARGEST LAKES IN EUROPE: THE PAST AND THE PRESENT

Abstract

The largest lakes in Europe, as well as all water objects in the region, are under the influence of climate change.The most pronounced changes in the water regime of lakes are noted in the intra-annual distribution of the water level. The increasein the average annual air temperature (by 1.3℃ on average) and annual precipitation layers (from 35 to 77 mm/year on average) inthe second climatic period practically did not affect the average annual water levels of lakes Ladoga and Peipus, whereas the averageannual water level of Lake Onega in the second climatic period (1991 – 2020) increased by 10% compared to the first period (1961 –1990). At the same time, the inflow to Lake Onega has not changed and is about 16.7 km3/year. For more than 140 years, there havebeen pronounced trends toward a decrease in the average annual water level of Peipus and Ladoga and toward an increase in theaverage annual water level of Onega. For the significance level =0.1, the trends of changes in the levels of the studied lakes aresignificant. The increase in the level of Onega is explained by the fact that this lake is under the influence of the Verkhne-SvirskayaHPP and is characterized by a retaining regime. The influence of the retaining regime also determined the heterogeneity of the average annual water levels of Lake Onega. In addition, the relative proximity of this reservoir to the White Sea results in a morepronounced influence of the Arctic air mass transfer on the conditions for the formation of runoff in the Onega catchment.