ИСТИНА

New intelligence on the mechanism of seasonal and occasional flood formation has been achieved. Based on data for the period 1946-2015 yy., changes in the coefficient of natural runoff regulation were identified. It is shown that the transformation of spring flood type is closely related to the other phases of the water regime. Mostly it connected with the changes in the characteristics of occasional floods in different seasons (spatially winter thaws). Statistical analysis shown, that these changes are various in different geographical regions. The role of peak flow increase in the central and in the southern sub regions, while on the north it decreases. Through the author's original program, based on the genetic daily hydrograph separation, according to the methodology of B.I. Kudelin, the calculations of seasonal flood characteristics were done. After that the parameterization scheme of these changes was created. The main selected parameters include maximum to the 5-day minimum ratio, seasonal peak in compared to flash flood maximum, the minimum flow during summer and winter for the annual. It is shown that, the most of the rivers is characterized by reduction in these rates exponentially. Series of the inequalities describing the state and variability of water resources have been developed.