My city is on the Mississippi river but we get our water from a massive 2000 year old aquifer. But you’re correct as most cities were built close to easy accessible rivers & lakes where many are now polluted and/or losing their capacity to retain normal levels. The west is now on fire and it’s become obvious many will have to relocate to survive.

What’s the old saying: “Water water everywhere but not a drop to drink”? The minds of the world better get busy to find a cheap desalination process for the oceans or many will perish quickly.