ИСТИНА

Long phases (more than 10-15 years) of decreased and increased river water flow, heat flux, suspended sediment load and major ions flux of the Ob’, Yenisei, Lena and Northern Dvina Rivers at their outlets during the period of observation from 1930-1940 till 2000 have been revealed by statistical criteria as well as with normalized cumulative deviation curves. The contrasting phases of naturalized (i.e., excluding anthropogenic changes, mainly due to the river flow regulation by reservoirs) geo-flux components have been evaluated. The identified phases display statistically significant differences in average values for the considered geo-runoff components. Their long-term changes are mainly characterized by two major long phases with a border between the 1970-1990s on all rivers under consideration with the exception of the Ob’ River, where such contrasting long-term phases for suspended sediment load were not identified. The difference between the average values of geo-flux components for contrasting phases varies from 10 to 20 % reaching its 40 % maximum in the Yenisei River winter water flow and 50% in the Lena River suspended sediment load. Anthropogenic factors (mainly river flow regulation by reservoirs) have significantly decreased the differences between average values of geo-flux components for contrasting phases.