Also completely ignoring the fact that every joule provided by solar is one less joule that hydro needs to provide, which in turn extends their stored energy life.
Pumped-storage hydro is pumping water behind a dam.
You can TRY to hollow out the top of a mountain and put the water there (yeah, that's also suuuuuuper environmentally friendly), but it's incredibly difficult to do it at reasonable scale, and when it fails it wipes out towns.
You'll find the only reasonable way to store enough water to make a difference it is to put it in a valley, where the terrain helps you.
And in the end, you've just rube-goldberged your way to hydro power; to actually get scale, it has very comparable environmental impact to hydropower because it ends up being almost the same thing.
Define "battery". Pumped-storage hydro is literally hydro as a "battery".
https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
Also completely ignoring the fact that every joule provided by solar is one less joule that hydro needs to provide, which in turn extends their stored energy life.