New York environmental regulators this week released a plan to protect aquatic life in the state’s rivers that could cost power generators billions to upgrade their facilities.

The plan, which still needs final approval, would affect most of the state’s six nuclear power plants and several facilities powered by fossil fuels that use water for cooling. The state Department of Environmental Conservation (DEC) wants the facilities to recycle and reuse the water in a closed-cycle cooling system rather than discharging the heated water into rivers.