Do I need to look up for you how much pumped-hydro storage is already online? Or list a dozen other technologies also under large-scale construction? You could look that up yourself, if you cared.
Hydro storage is a completely different animal than native hydro generation.
A reservoir for the latter requires a river collecting water from a large area watershed, and a dam lower down backing water up the river course.
Hydro storage requires only an elevated basin, and a pipe (penstock) leading up to it from a ready source of water -- even groundwater -- no watershed needed. Such basins are legion, and filling them typically discomfits no one.
