Genesis of the Rivers Maximum Water Content and Water Regime Variability in Contemporary Climatic Period.

Abstract

The article deals with the water regime of the Upper Don`s rivers in the current climatic period, comparing characteristics of 1939-1970, 1971-2000, 2001-2014. The features of the formation of flood peaks were identified. The spring flood caused by melting snow increased to about 10 days. The shortest period of spring flood on the Don River near the town of Liski lasted 41 days in 1961, and the longest – 78 days in 2001.The timing of the beginning of the spring flood has shifted toward earlier dates of its occurrence and the ending -to the side of later dates. With increasing total duration of spring flood on 15-20 days, the late onset of the highs was observed. Due to milder winters and reduction of depths of soil freezing on the pick of the spring flood, water on the slopes of the river filtered to a greater extent in the soil, than goes on the formation of slope runoff. And only during a more intense snowmelt and water flow in the riverbed is formed the maximum flow of floods. Temporal and spatial heterogeneity of the formation of maxima in the river system of Don and of Khoper were marked. In the upper reaches they represent two independent, isolated from each other zone of runoff formation. In the basin of the Khoper highs are formed later than in the Don`s basin. The emergence of the thaw in February is almost natural now. In February of 2016, with abnormal weather conditions, the boundary between the winter and spring seasons due to numerous thaws were conditional. The frequency of occurrence the bimodal spring floods in the basin of the Khoper has frequented. In 2010, the spring flood hydrograph had atypical ridged shape. Reduction of runoff of spring flood and its share in annual volume in this century up to 38-45 % in the rivers of the Central Russian upland on the right bank of the Don leads to a change in the priority of sources of supply. The dominant source of power for the rivers of the basin of the hopper remains the snow supply.