Look at the countries that produce all or nearly all their electricity from renewables. It's dominated by hydroelectricity: https://en.wikipedia.org/wiki/List_of_countries_by_renewable...
And since it's a well understood problem we can just build it everywhere, in arbitrary quantities.
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.