This is what will happen. We'll use solar, or maybe someday fusion, to desalinate sea water. Then we'll need to pipe it where it's needed. We're not going to run out of water long term, it will just be more expensive. Short term, yeah, there will be issues, and they could get bad.

We need to rein in capitalism and replace money with compassion as the driving motivation. I know it seems impossible, but it will happen one way or another. Either for billions of us, or for whoever is left after the apocalypse.