The destruction of the Nova Kakhovka dam on the Dnipro River that separates Russian and Ukrainian forces in southern Ukraine has sent a torrent of water gushing through the breached facility, creating a new humanitarian disaster at the heart of the war zone and stoking fears of a nuclear escalation.
Ukrainian and Russian officials on Tuesday accused each other of destroying the Russian-held Nova Kakhovka dam in Kherson province, long earmarked as a potential target owing to its strategic importance and destructive potential.
The fallout could have far-reaching consequences, flooding residential areas along the Dnipro, depleting water levels around the Russian-held Zaporizhzhia nuclear plant, and draining supplies of fresh water in Russian-annexed Crimea.
It could also hold back Ukrainian forces as they seek to retake territory occupied by Russian forces east of the Dnipro.
A strategic location
The Kakhovka Hydroelectric Power Plant is located in the city of Nova Kakhovka, on the left bank of the mighty Dnipro River, in a part of Ukraine's Kherson region that remains under Russian occupation.
It was captured by Russian forces in the early stages of the invasion, along with the nearby Zaporizhzhia plant, Europe's largest nuclear facility.
Built in the Soviet era, it is one of six dams along the Dnipro, which runs from its northern border with Belarus down to the Black Sea and is crucial for the entire country's drinking water and power supply.
The Kakhovka dam - the one furthest downstream - is the only one under Russian control.
The dam is 30 metres tall and hundreds of metres wide, holding back a huge reservoir of water, roughly equivalent to the Great Salt Lake in Utah.
Ukraine and Russia have previously accused each other of targeting the dam, and last October Ukraine's President Volodymyr Zelensky predicted that Russia would destroy it in order to cause a flood and halt Ukraine's counteroffensive in Kherson province.
On Tuesday, footage from what appeared to be a monitoring camera that was circulating on social media purported to show a flash, explosion and breakage of the dam.
Ukraine accused Russia of blowing up the dam from the inside in a deliberate war crime, with Zelensky claiming in a Telegram message that Russian forces "carried out an internal detonation of the structures" of the dam.
Ukraine's state hydroelectric power generating company, Ukrhydroenergo, said Russia had blown up the station from inside the engine room, writing in a statement: "The station cannot be restored."
Russian-installed officials gave conflicting accounts, some blaming Ukrainian shelling, others saying the dam had burst on its own due to earlier damage.
The Russian-installed mayor of Nova Kakhovka, Vladimir Leontyev, spoke of numerous strikes targeting the Kakhovka hydroelectric plant and destroying its valves.
Neither side offered immediate evidence proving who was to blame, though both sides agreed that the damage to the station was beyond repair.
A humanitarian and ecological disaster
Mykhailo Podolyak, a senior advisor to Zelensky, said "a global ecological disaster is playing out now, online, and thousands of animals and ecosystems will be destroyed in the next few hours", while Ukraine's Foreign Minister Dmytro Kuleba described the dam's destruction as "probably Europe's largest technological disaster in decades" and a "heinous war crime".
Videos posted online began testifying to the spillover: one showed floodwaters inundating a long roadway, another showed a beaver scurrying for high ground from rising waters.
According to the Ukraine War Environmental Consequences Working Group, which documents the war's environmental effects, a total collapse in the dam would wash away much of the left bank, which remains under Russian control.
Downstream from the dam, residents will be seriously affected, said FRANCE 24's Ukraine correspondent, Gulliver Cragg.
"People on the Ukrainian side are being evacuated. The Russian-held side of the Dnipro River, the left bank, is likely to be worse affected. We don't have much information at the moment about evacuations on that side," said Cragg.
The World Data Center for Geoinformatics and Sustainable Development, a Ukrainian nongovernmental organisation, estimated that nearly 100 villages and towns would be flooded. It also reckoned that the water level would start dropping only after 5-7 days.
Russian emergency services, meanwhile, said around 600 houses had been flooded in the town of Nova Kakhovka, where evacuations are under way. However, Moscow-installed officials played down threats to major population centres, stopping short of evacuating city residents.
"The increase of the water level downstream from the hydroelectric power station is between two and four metres which is no threat to major population centres," said Andrei Alexeyenko, head of the local government in the Russian-occupied part of Kherson region.
What consequences for Europe's largest nuclear plant?
Kyiv says the dam's collapse has heightened the risk of a nuclear disaster at the Russian-controlled Zaporizhzhia power plant, located around 150 kilometres upstream, though Russian officials have denied any major risk.
"The world once again finds itself on the brink of a nuclear disaster, because the Zaporizhzhia nuclear power plant lost its source of cooling. And this danger is now growing rapidly," said Podolyak, the Ukrainian presidential advisor.
Russia's state nuclear energy corporation Rosatom said the dam's breach did not pose a threat to the Zaporizhzhia plant for now, adding that the situation was being monitored.
Yury Chernichuk, director of the Russian-controlled power station, said in a statement on the Telegram messaging app that water cooling the facility's spent nuclear fuel storage pools was on a closed circuit and had no direct contact with water coming from the Kakhovka Reservoir.
Ukraine's state atomic energy agency Energoatom also said the situation at the plant was under control, but stressed that the rapidly lowering level of the reservoir posed an "additional threat" to the plant because some of its systems relied on the reservoir's water to operate.
A spokesman for Energoatom told FRANCE 24's Cragg that right now, since all the reactors at Zaporizhzhia are not operational, "it does not need nearly as much cooling waters as it would if it was actually generating electricity".
The Energoatom spokesman said that for the moment, the amount of water they have in their reserve reservoirs will be enough to "avoid any kind of meltdown at the Zaporizhzhia plant", Cragg explained.
The UN's International Atomic Energy Agency wrote on Twitter that its experts were closely monitoring the situation at the plant, and there was "no immediate nuclear safety risk" at the facility.
The plant should have enough water to cool its reactors for "some months", IAEA chief Rafael Grossi said in a statement, urging all sides to ensure nothing is done "to potentially undermine its integrity".
Crimea's water supplies under threat
Tuesday's blast "also has very major implications for Crimea because the reservoir behind the Kakhovka dam supplied the Dnipro Crimea Canal, which provides the peninsula with fresh water", said Cragg.
The Crimean peninsula, which Russia annexed in 2014, is heavily dependent on the canal, which carries fresh water from the Dnipro River.
The Russian-backed governor of Crimea said there is a risk that water levels in the canal could fall following the breach. The level of risk would become clear in the coming days, Sergei Aksyonov wrote in a statement on Telegram, adding that the peninsula had sufficient water reserves for the moment.
The canal was blocked by Ukraine after Russia annexed Crimea in 2014. The blockade led to acute water shortages on the peninsula that ended only after Russian forces seized the canal in March 2022.