The Danube has dropped to minus 133 centimetres. One more centimetre down and Hungary's Paks nuclear power plant will, for the first time in its 44 years of operation, stop producing electricity entirely. Not because of a fault, not because of sanctions, not because of war - but because the river it draws its cooling water from has simply disappeared.

Hungarian Prime Minister Péter Magyar has already announced what would have sounded like science fiction two years ago: the country is entering a regime in which the state can disconnect large industrial consumers from the grid if they do not cut consumption themselves. The decree took effect at 7 pm. Three levels - crisis threat I, crisis threat II, and actual crisis. Somebody in Budapest sat down and wrote out, in advance, the ladder the country will descend.

When a river is part of the energy system

Paks announced that because of the continuing drop in water level, the turbogenerator of the first block is being shut down, while specialists work round the clock to keep the plant operating safely. Magyar announced a complete shutdown of the plant by the middle of next week. This is a plant that covers most of Hungary's electricity production - and it depends on the height of one river.

Romania did not wait for decrees. There, today, crews blasted a rock formation in the bed of the Danube to redirect the river's flow and secure water for the Cernavodă nuclear plant. That is it. When the system is under pressure, you blow up part of the riverbed and force the water to go where it needs to. That is the measure of a state that has calculated it has no time for a more elegant solution.

Five critical days

"The most critical five days are ahead of us. Tomorrow Paks will no longer produce electricity, and the hottest days are coming, with temperatures of 40 degrees," Magyar said, calling on citizens to cut consumption, especially between 5 pm and 10 pm, and above all between 6 and 9. He asked shopping centres to turn down their cooling, and local and religious institutions to temporarily switch off decorative lighting.

Several hundred Hungarian settlements have already introduced consumption limits and irrigation bans. Drinking water supply, with a few exceptions, has not been cut off so far - but the prime minister urged people to respect the saving measures, with the message that "every drop of water matters".

Along its entire course, the river is retreating and leaving behind a landscape not seen in decades - a cracked bed, new sandbanks, water squeezed into a thin ribbon in the middle of what used to be a shipping lane.

What does this teach us?

Hungary is not a distant country with an exotic problem. It is an EU member with a modern grid, a nuclear plant, a fully functioning state - and within five days it will reach the point where the prime minister personally asks shopping centres to turn down the air conditioning. If a system with those resources buckles under 40 degrees and one drought, how thin is everybody else's margin?

This is not a story about the weather. It is a story about infrastructure designed for a climate that no longer exists. The Paks nuclear plant was built at a time when nobody calculated that the Danube could fall below minus 133. Romania has to blast rock to supply Cernavodă with water. Both states are now improvising around facilities that were meant to be the most stable part of the system.

The rains will come, the water level will return, Paks will restart and this week will be forgotten. The question is whether anyone will sit down and work out what to do next time - or whether we wait for it to fall to minus 134 again before the blasting starts.