BUCHAREST—Last week, the Romanian navy used 180 kilograms of explosives to detonate a submerged rock in the Danube east of Bucharest. The limestone shelf was not a threat to navigation, but it had diverted a portion of the river away from the cooling-water intake at Cernavodă, Romania’s nuclear power plant.
The successful detonation raised the water level at the intake basin by two centimeters, buying the plant roughly two additional days of operation. Four barges loaded with stone were sunk across a side channel to push more flow toward the reactor.
These exceptional steps highlight a larger trend across Central and Eastern Europe, as countries work to secure their energy supply amid persistent drought, low rainfall, and dangerous heatwaves.
As the water level falls
A drought that began in May across southern Germany, Austria, Slovakia, Czechia, and Hungary has pushed the Danube to some of the lowest levels on record along much of its length. At Pfelling in Bavaria, the gauge fell to 216 centimeters, below the previous low of 221 set in August 2022. In Budapest, the river dropped to roughly 10 centimeters last week, against a prior record of 33 centimeters from 2018.
The flow numbers matter just as much as the river depth, and here, too, the numbers are concerning. The Danube enters Romania at around 1,500 cubic meters per second. The multiannual July average is 4,700; for August, 3,900. Romanian hydrologists expect the flow this year to fall below 1,400 cubic meters per second, which would be lower than the current minimum set in 1985.
Rivers do not generate most of the region’s electricity, but they cool the plants that do, and they carry the fuel that supplies the rest.
Hungary has come closest to the edge. The Paks nuclear plant, composed of four Soviet-built reactors that normally deliver 2,000 megawatts and close to half the country’s electricity, has cut output in stages since late July. Last week, the plant was producing just 240 megawatts, and Hungarian Prime Minister Péter Magyar said that the plant was within “a few millimeters” of river depth from a complete shutdown, which would be the first in its forty-four years of operation. MAVIR, Hungary’s transmission operator, has activated its protocol for a major system disturbance. To conserve energy, Budapest has switched off decorative lighting on more than three hundred municipal buildings; several major companies have cut their evening electricity consumption voluntarily.
Romania shut down Cernavodă unit 1 on July 28, and it announced the possible shutdown of unit 2 the following day, before overnight measurements showed operating parameters still within limits. Unit 2 is still running, producing about 680 megawatts, but plant management has given it days rather than weeks absent a hydrological turn. On July 31, the government declared a national state of alert in the energy sector for the month of August and released 7 million lei from the budget reserve for the emergency works in the river. To conserve power, Prime Minister Ilie Bolojan asked households and large industrial users to shift consumption later in the evening. At present, Romania is importing roughly 1,700 megawatts of electricity during the evening hours; losing unit 2 would push that figure above 2,500 megawatts.
That window has since narrowed. On August 12, Cernavodă management announced that unit 2 will begin a controlled shutdown on August 13, as the Danube’s level and forecasted decline no longer allow normal operation.
Serbia offers the hydropower version of the same story. Đerdap 1, the country’s single most important plant, is delivering a little over 5,000 megawatt-hours a day, about a third of its normal output. Cooling constraints have also cut output at the Kostolac thermal plants, while the drop in river depth has also made it more difficult for Serbia to import fuel by river.
Austria is the upstream warning sign. Verbund, which operates eleven power plants on the Danube, reports water flow down by a third and generation down by roughly a quarter. If trends continue, 2026 could be the driest year in the company’s seventy-year history, and the second consecutive year below average in a country that depends on hydropower for around 60 percent of its electricity.
That is the pattern: not one plant, country, or technology, but a shared river system collapsing several power systems at once.
Why it matters
The falling water level has revealed three urgent issues:
First, the region’s energy import needs are rising at the same time. Every energy-security plan in Central and Eastern Europe assumes that a national power deficit could be covered by neighbors. But a drought in the Danube basin removes nuclear capacity in Hungary, nuclear capacity in Romania, and hydropower in Serbia and Austria simultaneously, while a heatwave drives all their demand to winter levels at the same time.
Electrical interconnection is necessary, but it is not enough. The region also needs more capacity uncorrelated with river flow. Above all, it needs electricity storage capacity, including through investments in battery energy storage systems. Serbia’s reversible plant at Bajina Bašta and the 400 megawatts of solar, wind, and battery capacity Romania is now fast-tracking through emergency permitting are a useful response. Projects such as Nova Power & Gas’s 200 MW/400 MWh system in Cluj and the 250 MW/500 MWh Gura Ialomiței project demonstrate the scale of storage now becoming possible in Romania, but substantially greater capacity will be needed to ensure long-term energy-system resilience.
The problem is that these projects are being pushed forward only in an emergency, rather than after the last major drought three years ago.
Second, Ukraine has become a net exporter to NATO and EU members. Romania has begun buying Ukrainian electricity through an arrangement between Nuclearelectrica and the Moldovan supplier Energocom under a 2023 memorandum. Ukraine’s electricity imports fell roughly 40 percent in July, and it turned into a net exporter for the first time in ten months. A country whose grid Russia has bombed for four consecutive winters is currently helping keep the lights on in the European Union. This should reframe how Brussels and Washington think about Ukrainian grid integration: not as postwar reconstruction, but as an immediate matter of regional generation adequacy. The benefits run both ways: Ukraine’s surplus is a daytime, summer surplus, and Kyiv will need those interconnectors running the other way come January.
Third, water is now a siting criterion, not a footnote. The region intends to build a great deal of new nuclear capacity: Cernavodă units 3 and 4, Paks II, Kozloduy 7 and 8, small modular reactors at Doicești. Every one of those projects is water-cooled and, except for Kozloduy, sits on a river that has twice in four years approached its recorded minimum. Kozloduy’s intake design offers the cheapest lesson available. Retrofitting cooling intakes, dredging and stabilizing approach channels, and stress-testing new projects against 1985-and-worse flow scenarios cost a fraction of the plants themselves.
Where to go from here
Regional leaders should respond in four ways:
- Treat demand response as a market. On July 29, the Romanian prime minister asked citizens to help conserve power by using less electricity each evening; Electrica has offered industrial users free midday consumption to move their load from the high-demand close of day, as well. These are the right instincts, albeit reached through improvisation. Standing, priced interruptible contracts with large consumers, coordinated regionally, would deliver the same megawatts more predictably.
- Write a Danube low-water protocol. States along the Danube are currently managing a shared river through unilateral emergency works. The Danube Commission and the European Commission should provide agreed thresholds, notification duties, and coordinated dredging and flow-management priorities before the next dry summer. September and October are statistically the lowest-flow months, and this one is not over.
- Fund water resilience alongside generation. European Union financing instruments for nuclear and hydro in the region should carry explicit cooling-water and channel-maintenance requirements. Romania’s Bala–Old Danube rebalancing project, stalled since April, is the case study.
- Accelerate Ukrainian and Moldovan interconnection capacity on the assumption that it will be used in both directions in different seasons.