We had a nuclear power plant here in Michigan that in off peak hours would pump water out of Lake Michigan up to a nearby holding reservoir - usually at night. Then, during peak usage hours they would release that water back through hydro generators.
I seem to recall that nuclear plants take about 24 hours to ramp and down.
So the water storage idea worked great.
Then the State - at the urging of the greenie weenies - sued the power company because there were too many fish being killed at the intake screens on Lake Michigan.
Forced the power company to give up lots of land along rivers above dams they had built long ago as part of the settlement.
“I seem to recall that nuclear plants take about 24 hours to ramp and down.”
Early plants were provided with load-follow analysis but proved to be great base-load plants running 100% 24/7.
Nuclear plants can ramp up and down pretty quick.