[Manuel_D]

Reservoir towers don't hold nearly enough water to be viable energy stores. You need a big alpine lake like this: https://en.m.wikipedia.org/wiki/Turlough_Hill

And you need a reservoir down below to receive the water as it passes through turbines otherwise you're waiting for rainfall to fill that upper reservoir up naturally.

The geographic conditions to make pumped hydro are far more constrained than you seem to think. Most water reservoirs for municipal water supplies don't have the elevation drop to be used for generation and they don't have the lower reservoir to capture and feed water back into the upper reservoir.

[Schroedingersat]

By some bizarre coincidence they hold exactly enough energy to move the water down the hill to its destination at the pressure specified whenthe tower was built. So weird how that happens. Almost as if heating and transporting water have been trivially dispatchable loads for centuries before electricity was used to do them at all.