ИСТИНА

Modern changes in the water regime of rivers now are evident. The main tendency, for the most rivers of the European territory of Russia, is smoothing of the annual runoff hydrograph. This leads to a reduction in the flow of spring months associated with the interception of part of melt water by thawing floods. Simultaneously with this process, there is an increase in runoff during the low-flow periods of the year - the summer-autumn and winter. Reducing the depth of freezing of the soil, due to warmer winters, leads to an increase nourishment of the groundwater. Simultaneously, the loss of runoff to surface retention and evaporation during the winter and especially in the spring period is increasing. Almost all seasons, especially in the western part of the Russian Plain, there is an increase in the number of flood peaks. They are superimposed on a wave of main, seasonal melt flood, making it drawing up as separate phase of the water regime in some years practically impossible. A similar situation can be traced for the winter low-flow period, especially for the rivers of the western part of the Russian Plain. Low flow period, which is usually understood as the long period of steadily low discharge, when the rivers are transferred completely to groundwater nourishment, not forming in the last two decades. Throughout the winter, river runoff is increased; the hydrograph has a “piolo-like” shape, associated with precipitation in the mixed or liquid phase. Increasingly, the phenomenon of winter ice drift is observed on the rivers, due also to increased run-off and frequent thaws. These trends are to a lesser extent observed in the north and northeast of the Russian Plain. Significant transformation of the water regime is expressed in the Don and Oka basins