How do reservoirs affect ice conditions on the Volga River?

The construction of dams and reservoirs along the Volga River has significantly altered its temperature regime, directly impacting ice conditions along the waterway.1

By accumulating large masses of water, these reservoir complexes have changed the duration of ice cover in two distinct ways:
* Headwaters: The duration of ice has increased on the headwaters of the reservoirs.1
* Downstream: The duration of ice has decreased on the river stretches located below the dams.1

This occurs because water held in reservoirs is often warmer than the freezing point. When released in sufficient quantities, this water can create extended areas of open water downstream, as the heat stored in the reservoir water must be lost to the cold air before the river can freeze.2