Water levels on the Danube have fallen to historic lows, with the river dropping to around 10 centimetres in Budapest—well below the previous record of 33 centimetres set in 2018—and flow in Romania collapsing to 1,500 cubic metres per second, less than a third of the July average. The immediate effect has been a sharp curtailment of nuclear generation: Hungary’s sole nuclear plant, Paks, was operating at just over 10% of its 2-gigawatt capacity on Monday, producing only 240 megawatts, while Romania’s Cernavoda station has already shut one of its two reactors and is struggling to keep the second online.

The plants rely on Danube water for reactor cooling, and the combination of prolonged drought and successive heatwaves—with temperatures forecast to reach 42°C in Hungary and 41°C in Romania—has left the river too shallow and too warm to sustain normal operations. Hungarian Prime Minister Péter Magyar said engineers had managed to keep Paks’s last turbine running temporarily, delaying a full shutdown that had been expected over the weekend, but warned that a complete halt could come within days. In Romania, the defence ministry used 180 kilogrammes of explosives to blast a rock formation in a Danube tributary, aiming to redirect more water toward Cernavoda; authorities also plan to sink barges to create a makeshift dam.

Governments have responded with emergency conservation orders. Hungary appealed for voluntary reductions in electricity use, which cut demand by 700 megawatts on Sunday, and restricted electric freight trains during peak hours. Romania declared a national energy alert, and carmakers Dacia and Ford agreed to halt production until 19 August, saving an estimated 200 megawatts. Both countries are increasing electricity imports to cover the shortfall, even as the heatwave drives up demand for cooling. Serbia, too, has seen hydropower output at its largest plant fall to 20% of capacity and has called on citizens to conserve power.

The immediate outlook depends on water levels, which are not expected to recover soon in the absence of significant rainfall. Hungarian authorities anticipate some improvement by the weekend if rains arrive in Austria, while Romanian engineers aim to complete river-diversion works by Wednesday. For now, the region’s energy systems are operating on a knife-edge, with the next milestone being whether Paks can avoid its first total shutdown in 44 years.