Why did the Volga River have major spring floods before reservoirs were built?

Before the construction of dams and reservoirs regulated its flow, the Volga River experienced significant annual spring floods, known as polovodye. These floods were primarily driven by the river's reliance on snowmelt, which accounted for approximately 60 percent of its annual discharge.1

Because the river's natural, untamed regime was heavily dependent on this seasonal influx of water from melting snow, the river level fluctuated dramatically throughout the year. Before regulation, these annual variations in water level reached as high as 36 feet on the upper Volga, 46 feet on the middle Volga, and up to 49 feet on the lower Volga. The remaining portions of the river's discharge were supplied by underground water (30 percent) and rainwater (10 percent).1