The Nova Kakhovka Dam on the Dnipro River has been breached. Russian milbloggers are blaming Ukraine, but Russian military occupiers are believed to have mined the dam six months or so ago.
The dam holds back an enormous reservoir that supplies drinking and agricultural water, along with coolant water for the six reactors at the Zaporizhzhia Nuclear Power Plant and the Crimean Canal. Russia was reported to be filling Crimean reservoirs over the winter. I will make a wild-assed guess that it will take several days to drain the reservoir to a point where the level will cause problems for the ZNPP, but the clock is ticking. I expect we’ll hear from the IAEA by morning.
There will also be damage to the cities downstream.