Hydro is still vulnerable to downturns, though they need to be more prolonged to equal what's happening with the wind in this report. (California's 2021 drought is a good example of how hydro power can fall short.)

I mentally think of power generation reliability as: Uncontrollably variable from hour-to-hour: wind, solar, tidal motion Uncontrollably variable on month-to-year spans: hydro Pretty controllable: nuclear (and fossil fuels)