Cernavodă stays on by centimetres

On 3 August, Romanian military divers blew up a rock formation in the Danube. The result, near Cernavodă, was a rise in the water level of about two centimetres (Euronews România, Financial Intelligence).

In most places, two centimetres would barely register. At Cernavodă, Romania's only nuclear plant and its largest source of steady electricity, it can mean another day of cooling water. The Danube had been falling by 2-3 cm a day, leaving the plant roughly four to five days from losing the flow it needed to keep operating (AGERPRES).

Hungary has already shown what happens when that margin disappears. Paks, which normally supplies roughly half the country's electricity (World Nuclear Association), began shutting down in stages from 27 July after the Danube fell too low for the pumps drawing cooling water from the river. By 2 August, only one of eight turbogenerators was still running (MVM). In both countries, factories were asked to cut consumption so households could keep the lights on.

Engineering the river

The Pârjoaia rock sat near the point where the Danube divides. One route, the Old Danube, feeds Cernavodă's cooling intake. The other, the Bala Branch, had been taking too much of the remaining flow.

The blast was only the most dramatic part of the job. Crews also dredged the silted intake channel and sank four barges loaded with stone, creating a temporary underwater wall to push more water towards the plant (Curs de Guvernare, Libertatea). The Romanian government set aside about 7 million lei for the work. For emergency river engineering, that is not a large bill. It is certainly cheaper than replacing Cernavodă's output with imported power.

Energy Minister Radu Miruță said the gain reached about +4 cm once the water moved downstream (Digi24). The full package is meant to deliver 10-12 cm (HotNews).

But the Danube is still falling. Hydrologists expect the flow at Baziaș to drop to 1,350 m³/s by 10 August, below the 1,400 m³/s historic minimum recorded in 1985 (AGERPRES). The blast bought time. It did not change the weather.

Hungary's missing megawatts became everyone's price problem

During one peak hour on 4 August, Hungary imported 3,195 MW while producing 3,049 MW at home. More than half the country's electricity was coming from abroad (Portfolio).

That kind of sudden demand does not stay neatly inside national borders. Central and south-eastern European grids are tied together through cross-border auctions. When one country needs more electricity than it can generate, it bids for imports. The price then rises across the connected zones.

By 29 July, day-ahead prices, meaning the auction price set the day before electricity is delivered, averaged €132/MWh in the Hungarian-Serbian corridor. Hourly spikes reached €268/MWh (Serbia Energy). Forward contracts for the following week climbed into the €250-263/MWh range (Argus).

The mechanism is straightforward enough. Take 2 GW of nuclear capacity off the system during a heatwave, when air conditioning is pushing up demand across the region, and the replacement power has to be bought wherever it can be found. The forward prices show traders expected the squeeze to last.

Not every plant is equally exposed

Bulgaria's Kozloduy nuclear plant is better placed. It draws cooling water through a pumping station in a deep bay, which leaves it less exposed than Cernavodă's open channel. Bulgaria's energy ministry said it expected no significant reduction for at least three weeks (BTA).

Austria shows the other side of the same drought. VERBUND, the country's biggest hydropower operator, reported first-half 2026 generation 9.8% below the previous year (VERBUND). Yet Austria still exported electricity in June (APG). It had enough other generation and grid flexibility to absorb the blow.

Romania can buy days with barges, dredging and explosives. What it cannot do, if hotter and lower summers keep returning, is keep treating cooling water as a last-minute engineering problem.