The water tower in my town is several hundred feet tall (many units) and has a big bulb tank at the top. When you pump a gallon of water up into the tank, it is raised hundreds of feet and contributes a fraction of an inch to the total height of the water stored.
It's an actual implementation of energy storage, the water is pumped up there and then gravity distributes it, so there is a buffer if the pumps can't run for some reason.
