The world doesn’t have a shortage of water; it’s just that the water is in the wrong places for some people. If water in arid regions gets scarce and/or expensive enough, sooner or later it will be cost feasible to build huge pipelines from Canada — not from oil fields, but from polar ice which is melting due to global warming — or, so we are told, and told, and told again.
Yep — the Romans did it. And LA would still be be a desert without the water from Mammoth Lakes.