After water levels at a California dam fell to historic lows this summer, the main hydropower plant it feeds was shut down. At the Hoover Dam in Nevada—one of the country's biggest hydropower generators—production is down by 25%. If extreme drought persists, federal officials say a dam in Arizona could stop producing electricity in coming years.
source https://techxplore.com/news/2021-10-hydropower-decline-strain-power-grids.html