Long-Term Changes in Moisture Circulation Processes by Data of Water Balance Stations in the Central Don Basin

Abstract

The materials of long-term observations at water balance stations in the Don basin confirm the existence of climate changes, which have led to changes in water runoff formation and other water balance elements. It is shown that the major changes in the hydrological regime of water bodies have been induced by the weakening of the effect of cryogenic regulation of water exchange in the basin. This can be seen in two processes: an increase in the infiltration of atmospheric precipitation into aeration zone and groundwater and better drainage of groundwater by the hydrographic network. The first process dominates in the initial period, leading to an increase in the share of surface runoff, a rise in groundwater table, i.e., an increase in groundwater inflow into rivers. Later, the contribution of the second process increases, resulting in a decrease in groundwater reserves in the basin and a drop of groundwater table and river runoff in the dry season. The budget of the processes of replenishment and drawdown of groundwater recovers after the cessation of the formation of cryogenic phenomena in the river basin caused by phase transitions in water–ice (snow)–water system. It is very likely that the transformation of these processes is now coming to an end.