In the early hours of 4 August 2026, Hungary's Paks nuclear power plant came within millimetres of a complete shutdown as record-low Danube water levels threatened to strip the facility of its cooling capacity. Nuclear reactors like the ones at Paks rely on river water to absorb and carry away the immense heat they produce — without enough water flowing through the cooling system, the reactor cannot operate safely. Hungarian prime minister Péter Magyar said that around 1:30 a.m. the water level stopped falling and by morning had risen 1.5 cm, allowing the last operating turbine to continue running. The plant is currently operating at just over 10% of capacity, a drastic cut forced by the Danube's descent to record lows that made proper reactor cooling impossible. The Guardian

The crisis at Paks has been building since late July, when nuclear plants along the Danube in both Hungary and Romania were forced to cut output amid falling river levels. On 31 July, Magyar warned that low Danube levels could keep Paks shut for weeks. By 2 August, he flagged "critical" days ahead, confirming the plant would not be generating power the following day as temperatures approached 40°C. In a Facebook video posted on 3 August, Magyar said the hardest five days were coming for Paks and that experts had previously warned the Danube's falling level created a critical need for a new, modern safety system. Reuters

The cooling-water dependency is concrete, not theoretical. In a Facebook post on 1 August, Magyar noted that the Danube measured 97 cm in 2018 and stands at 121 cm now, in the context of the cooling-water requirements for Paks II's two new reactors. He also reported Danube readings of 390 cm at Passau and 218 cm at Bratislava in a 30 July post, and questioned whether the Austrian and Slovak prime ministers should be asked not to shut off the Danube's water, pointing to the transboundary dimension of river-flow management during drought. The upstream readings at Passau and Bratislava, substantially higher than downstream levels, show how the river's flow is progressively consumed or lost as it moves through multiple countries before reaching Paks.

Hungarian energy minister István Kapitány said on 4 August that energy-saving measures succeeded in lowering consumption enough to keep the grid secure. The measures went well beyond the power sector. The grocery chain Lidl in Hungary changed its baking shifts and turned off its drink fridges during peak hours, and electric car chargers in its car parks could only be used until 5 p.m., despite temperatures expected to approach 40°C. The Guardian

Romania faces a parallel crisis at its Cernavodă nuclear plant and has taken more aggressive engineering measures. The Romanian government declared a state of emergency as record-low Danube water levels cut power output and threatened nuclear operations in both countries. On 3 August, Reuters reported that Romania carried out a controlled explosion of a rock outcrop on the Danube to redirect vital cooling water to its nuclear plants. The government subsequently celebrated a two-centimetre rise in Danube water levels following the blast. The manager of the Cernavodă plant said the water-level rise should keep the facility running over the next few days, with more interventions planned, including sinking old barges to further divert the river's flow. Reuters

The broader context here is the collision of two structural dependencies: nuclear generation's reliance on river-water cooling, and the Danube's role as a shared resource flowing through ten countries before reaching Hungary and Romania. When water levels drop below the intake thresholds that cooling systems require, the physics is unforgiving. Reactors must throttle down or shut down entirely. There is no workaround once the river itself becomes the constraint. Romania's controlled detonation of a rock outcrop and its plan to scuttle barges as flow diverters are improvised engineering responses to a hydrological crisis, not long-term infrastructure solutions.

For Paks specifically, the margin was measured in millimetres. The plant supplies roughly half of Hungary's electricity, and its curtailment to 10% capacity during a heatwave — when cooling demand peaks across the grid — places simultaneous stress on generation and distribution. The energy-saving measures, from Lidl's modified shifts to EV charger curfews, reflect the depth of the demand-side response required to keep the system intact.

Magyar's references to Paks II, the planned expansion with two additional reactors, add a forward-looking dimension. If the current cooling infrastructure at Paks cannot sustain existing reactors during drought conditions measured in centimetres of river depth, the calculus for adding two more reactors with their own cooling-water requirements invites scrutiny that Hungarian officials will need to address. The comparison Magyar drew between the 97 cm level in 2018 and the current 121 cm, framed around Paks II's needs, suggests this question is already part of the political conversation in Budapest.

Romania's declaration of a state of emergency, its controlled explosion, and the planned barge-sinking operations indicate that Bucharest is treating the Danube's low water as an active crisis requiring physical intervention in the riverbed. The Cernavodă plant manager's assessment that the two-centimetre rise buys only a few days suggests the engineering measures are temporary fixes, not a durable resolution. Further interventions are expected.

Both governments are managing a hydrological emergency that has no single national solution. The Danube's flow at Paks and Cernavodă depends on upstream conditions in Germany, Austria, and Slovakia. Magyar's public questioning of whether Vienna and Bratislava should be asked not to shut off the Danube's water, however diplomatically unusual the framing, identifies the core tension: each country along the river draws from the same diminishing resource, and each has its own energy and water security priorities. The coming days will test whether the reprieve at Paks holds and whether Romania's interventions at Cernavodă buy enough time for river levels to recover, or whether further curtailments become necessary.