What you're describing sounds a lot like open-loop pumped storage [1]. You don't hear about it much because it's already quite common and has been for decades.

What you're describing sounds a lot like open-loop pumped storage [1]. You don't hear about it much because it's already quite common and has been for decades. There's something like 22GW of capacity in the US alone. [1] https://www.energy.gov/sites/prod/files/2016/10/f33/Hydropower-Vision-Chapter-2-10212016.pdf#page=118 https://www.energy.gov/sites/prod/files/2016/10/f33/Hydropow... (p. 183-195)