Serbia is discovering the most uncomfortable thing about energy independence: it depends on how much water is in one river. And the river has dried up.

Đerdap, Serbia's largest hydropower plant, is running at just a quarter of its capacity. According to the minister of mining and energy, water inflow at Đerdap fell on Monday to „historically low levels of only 1,450 cubic metres per second”. Not a breakdown, not maintenance, not a sanction. The Danube simply does not have enough water.

The consequence shows up immediately in the price. Electricity on the exchange passed 500 euros per megawatt-hour - a level not seen since the energy crisis of 2022. The government admits that whatever is missing has to be bought on market terms, which translates as: at a price somebody else sets.

Thermal plants instead of water

The gap is being covered by the coal plants at Kostolac and „Nikola Tesla” in Obrenovac. The Perućac pumped-storage plant on the Drina holds reserves of 140 gigawatts, officially „enough to respond to unforeseen circumstances”.

The phrasing is accurate and slightly disingenuous at the same time. When a state explains how well prepared it is for unforeseen circumstances, it usually means the circumstance has already arrived.

Heat that will not let up

On top of all this came the heatwave. Serbia issued a red warning for temperatures between 37 and 39 degrees, with up to 48 expected in direct sunlight. Forecasts bring no relief before the end of the week - which means electricity consumption for cooling will rise on exactly the days when production is weakest.

Then there is the broader question, which concerns the whole region: for decades hydropower was sold as a stable, clean and domestic source. That was true while the climate behaved predictably. When a river cuts its flow to a quarter of what was expected, „domestic source” survives only on paper, and the bill is settled on the European exchange.

Has anyone here run the same scenarios for our own hydropower plants, or are we also waiting for the river to recede first and do the maths afterwards?