How did reservoirs change the natural water-level changes of the Volga River?

The natural, untamed regime of the Volga River was historically defined by significant annual fluctuations in water level, characterized by high spring floods known as polovodye. Before regulation, these fluctuations ranged from 23 to 36 feet on the upper Volga, 39 to 46 feet on the middle reaches, and 10 to 49 feet on the lower river.1

The construction of a series of dams and reservoirs has fundamentally altered this natural cycle by converting the river into a chain of man-made lakes. These reservoirs serve to regulate the flow of the river, effectively smoothing out the extreme seasonal variations that once occurred. While this development has provided hydroelectric power and improved navigation, it has also resulted in water loss through impoundment, evaporation, and diversion for irrigation, which has diminished the total discharge at the river's mouth. Additionally, the accumulation of large masses of water in these reservoirs has modified the river's temperature regime, impacting the duration of ice cover on different sections of the waterway.2345