How can warm-water discharges from power plants affect lake and river ice?

Warm-water discharges from power plants, including both fossil-fueled and nuclear facilities, can act as a source of thermal energy to melt ice in rivers and lakes. While these discharges are sometimes suggested as a method for clearing ice, their effectiveness is generally limited to localized areas.1

The power requirements necessary to melt ice over extended distances are immense, making such discharges insufficient for large-scale ice removal. In contrast, water released from reservoirs can have a more significant impact, as these large volumes of water—often warmer than the freezing point—can maintain open water for longer distances downstream until the heat is lost to the cold atmosphere.1

In natural settings, ice decay is also influenced by other warm-water inflows, such as streams, which cause ice to melt faster near their mouths than in the center of a lake. This process is part of the broader ice decay cycle, where heat from solar radiation, bottom sediments, and inflowing water contributes to the thinning and eventual clearing of ice cover.2