Water levels in the Danube have hit a record low, forcing the shutdown of Hungary’s only nuclear power plant; a nuclear reactor in Romania has also been shut down.

Hungarian Prime Minister Péter Magyar stated that due to record-low water levels in the Danube River, the country’s only nuclear power plant, Paks, will be forced to shut down completely for the first time. The Paks Nuclear Power Plant uses water from the Danube for cooling, but the water level is currently too low for the intake nozzles to reach the river. Magyar warned that the shutdown of the Paks nuclear power plant, combined with the ongoing heat wave, could cause Hungary’s energy supply to become “critical” starting Monday. In addition, one of the two 706-megawatt reactors at the Cernavoda nuclear power plant in Romania—which supplies about 20 percent of the country’s electricity—has also been shut down. Water levels in the Danube have fallen to their lowest in 30 years in several countries, including Serbia and Romania.