On the depth thing, I really only meant to mean you need lots and lots of water. You could have a shallow basis, and take over a huge area of land, or or smaller amount of land if you have deeper water. Deeper also allows for less evaporation, less land area.

Perhaps your and my definitions of favourable geography are different. You need a water source, due to evaporation, you need a big resovoir at elevation, and another lower. If you don't want to build it all yourself you need valleys that you can close off at one end. You need ground that is not permeable, so the water you have stays where you want it.

Perhaps I am misreading you, but you seem a bit agitated with your in fact writing style. We're all friends here. I am not anti pumped storage. Far from it. If you can make it work economically, it's a great solution. It will definitely be part of the mix. But there's reasons it's not being rolled out everywhere, and a lot of this is due to cost and unfavorable geography.