Romanian military engineers have carried out a powerful underwater explosion on the Danube in an extraordinary attempt to redirect water towards the Cernavodă Nuclear Power Plant.

The operation was resumed on Monday morning after two controlled explosions on Sunday failed to remove the Pârjoaia rock formation from the Bala branch of the river. Military divers placed a much larger explosive charge underwater, with several Romanian media outlets reporting that approximately 100 kilograms of explosives were used.

The detonation partially destroyed the rock formation and cleared the way for the next stage of an emergency engineering operation intended to increase the amount of water flowing through the Old Danube channel towards Cernavodă.

More than 100 military personnel and 16 pieces of specialised equipment were reportedly involved in Sunday’s operation. The first test explosion used only two kilograms of explosives, while a second underwater charge of around 30 kilograms failed to dislodge the main obstacle. The military subsequently returned with a significantly larger charge.

Four barges to be sunk in the river

Removing the Pârjoaia rock is only the first phase of the operation. Romanian authorities are also preparing to sink four stone-filled barges across the Bala branch.

Each vessel is approximately 70 metres long and three metres high. Positioned side by side, they will form a temporary underwater barrier designed to restrict the flow into the Bala branch and redirect more water towards the Old Danube and the Cernavodă plant.

At present, the Bala branch is drawing away a substantial part of the Danube’s flow before the river reaches Cernavodă. The unusual combination of explosives, dredging and deliberately sunken vessels is intended to change this distribution.

The operation is technically difficult and highly dependent on local water conditions. Romania’s National Administration “Apele Române” has warned that the exceptionally low level of the river could prevent the temporary structures from producing the required hydraulic effect. The works may also cause a short-term increase in water turbidity.

Only ten centimetres from the shutdown threshold

The intervention has become a race against time. The water level at the Cernavodă plant’s intake system was recently reported at approximately 2.05 metres—only ten centimetres above the 1.95-metre level at which the remaining reactor would have to begin a safety shutdown.

Cernavodă has two operating CANDU reactors. Unit 1 was disconnected from Romania’s national electricity grid on 28 July because of what the operator described as the Danube’s “very low, unprecedented water level” caused by severe drought. Nuclearelectrica confirmed that the shutdown was controlled and carried out in accordance with the plant’s safety procedures.

The current river engineering operation is therefore focused on preserving the water supply required to keep Unit 2 in operation. Nuclear reactors require a stable source of water to cool their systems and safely produce electricity.

Danube approaches historic low

Hydrologists expect the flow of the Danube at Romania’s western border to fall towards 1,400 cubic metres per second—close to the historic minimum recorded in 1985. The normal multi-year average for August is approximately 3,900 cubic metres per second.

The crisis is the result of prolonged drought and extreme heat across much of the Danube basin. Water levels have also fallen sharply in Hungary and Serbia, disrupting shipping, agriculture, drinking-water supplies and power production.

Hungary has already been forced to shut down the Paks Nuclear Power Plant, which normally supplies nearly half of the country’s electricity. The plant had gradually reduced its output as the Danube receded before preparing for its first complete shutdown in more than four decades. Reuters reported that Hungary could face serious pressure on its electricity system if the drought continues.

Romanian water authorities say the country’s 40 main reservoirs remain approximately 70% full, providing a strategic reserve for the population. Nevertheless, citizens and businesses have been urged to reduce their consumption of water and electricity.

The explosion on the Danube illustrates the severity of the regional crisis. Romanian authorities are now attempting to physically alter the river’s flow to keep one of the country’s most important power plants operating—but whether the intervention will provide enough additional water remains uncertain.