BUDAPEST — The national water authority in Budapest measured the Danube's water level at 23 centimeters (9 inches) on Wednesday morning. This measurement marks a new record low for the river, surpassing the previous all-time low of 33 centimeters (13 inches) set in 2018.

Hungary’s Paks nuclear plant began powering down a reactor on Wednesday due to restricted cooling-water supplies. The facility supplies nearly half of Hungary’s electricity and had undergone two successive reductions in power output in two reactors over the two days prior to Wednesday.

Prime Minister Péter Magyar stated that Hungary's only nuclear power plant will be forced to shut down entirely for the first time due to record low water levels of the River Danube. He warned that Hungary's energy supply could become critical from Monday due to the Paks shutdown and the ongoing heatwave.

Magyar asked Hungarians to limit activities that required significant energy consumption between 17:00 and 22:00, including charging electric cars and using air conditioning equipment. He stated that a rotational shutdown regime was possible if other efforts were not enough to maintain the balance of the national grid.

Temperatures across the region are expected to rise to over 38 degrees Celsius (100 degrees Fahrenheit) with no significant rain in the forecast. The Hungarian Meteorological Service reported that 90-day precipitation totals are between 80-130 millimeters (3.1-5.1 inches) lower across nearly the entire country compared to multi-year averages.

Hungary’s Ministry of Transport and Investment stated that low water levels have forced popular cruise ships to dock far upriver and cargo ships have stopped operating nearly entirely. The Ministry of Transport is the type of ministry responsible for transport infrastructure and operations.

Authorities in Romania shut down a reactor unit at the Cernavoda power plant on Tuesday for safety reasons due to low Danube water flow. Romanian authorities announced that a second reactor unit at the Cernavoda power plant would be shut down soon, though state-owned company Nuclearelectrica was trying to avoid closing down the second reactor on Thursday.

The Cernavoda power plant provides about 20% of Romania's power. Romania's National Institute of Hydrology stated that the average river flow where the Danube enters the country is 4,700 cubic metres per second in July. The institute reported that the Danube flow was down to less than a third of the July average, at 1,600 cubic meters per second, on Wednesday.

Romania's National Institute of Hydrology forecast that the Danube flow would continue to fall to 1,500 cubic meters per second by Tuesday. Danube water flow in Romania had fallen to 1,630 cubic meters per second, around a third of a typical July average.

Photographer Gábor Kertész documented exposed rocks and dry sand bars at the base of Budapest’s Margaret Bridge on Tuesday. "The bare rocks, the dry sand bars around the bridge pillars.. it’s all shocking to see how things were before and how they are now," Kertész said.

"Where will this lead, what will happen? We don’t know that yet, but this must be the result of climate change," Kertész said. Authorities in Budapest closed the Margaret Bridge last week after a World War II bomb was exposed at its base by receding water levels.

Treasure hunter Zsolt Horváth used a powerful magnet to fish metal objects from the exposed bank on Tuesday. "Having so little water in the Danube is a blessing for this kind of activity, otherwise, it’s a curse," Horváth said.

The remains of a sunken Hungarian cargo ship resurfaced in Croatia due to low water levels. The hulks of a German river flotilla were seen in Serbia due to low water levels. A resident of Ruse, Bulgaria, found mammoth remains, including a lower jaw, two tusks, and possibly a rib, on the Danube river bed.

Ivan Zhekov, head of river supervision at Bulgaria's maritime administration agency, stated that there has not been a similar situation of low water levels since 1990. The Danube runs 2,857km (1,775 miles) through 19 countries, an increase from earlier counts of 10 countries.

The record low water levels in the Danube have triggered immediate operational failures in critical energy infrastructure across multiple nations. The shutdown of reactor units at both the Paks and Cernavoda nuclear plants removes significant capacity from the national grids of Hungary and Romania during a period of extreme heat. According to the Copernicus climate service, Europe is heating up twice as fast as the global average, providing context for the intensifying frequency of such hydrological extremes.

A study titled Developments in water quality monitoring and management in large river catchments using the Danube River as an example was published in 2016 in Environmental Science & Policy, showing long-standing concerns about the river's management. The current crisis exposes the vulnerability of river-dependent energy and transport systems to climate-driven droughts. The exposure of historical artifacts, from World War II ordnance to prehistoric mammoth remains, illustrates the physical scale of the water withdrawal, which has receded some 15 to 20 meters (50 to 65 feet) from shores in some areas.