We can't substitute water for anything, though. Hundreds of millions of people will lose their water, won't adapt to that, and will move to the northern hemisph

We can't substitute water for anything, though. Hundreds of millions of people will lose their water, won't adapt to that, and will move to the northern hemisphere which holds the vast majority of the world's surface level fresh water, or they'll die trying. If people think the current refugee crisis is bad, boy are they in for a shocker.