Would it not be simple to have in place regulations that state that "the natural resources of an area can accommodate a certain number of dwellings, once reached, contractors would have to go build elsewhere on land that has available resources"? It is obvious that certain areas in the southwest have reached that point, and we need to shift populations to areas where nature can still provide. Sounds Orwellian, but realistic.
It's an interesting concept, and it's consistent with what J.W. Powell's perspective was when he came back from his ventures in the West. He saw there wasn't enough water the way they developed things in the East. Of course, part of his conceptual solution was to "reclaim" land through irrigation, which also assumed there'd never be a very large population in the West, and that the water would be applied mostly for agricultural pursuits. I think he'd be surprised to see how many people live in the West today.
But your idea of using resource limitations to limit growth potential is at the heart of environmental planning as a profession, and has been tried to different degrees of success by a lot of cities in the west, particularly in California... But that approach inevitably runs into one problem or another, including the fact that you can't push population growth toward someone else's property, or tell another city or state what it can do. But the most basic problem is that the overall population of the 11 western states (not including Alaska and Hawaii) is about 80 million, and 110 million if you throw in Texas. In 1890, the same area had only 3 million people (5 million if you include Texas). But it's the same amount of water today as in 1890, actually less, since the aquifers in the West have been on average dropping over time, and climate change is reducing rainfall potential in the long run. Reservoirs are useful, but only as a means of temporary impoundment and as a distribution center for water. Over time, if it doesn't rain, there is no water, and reservoirs are empty.
Of course, you can try to incentivize people to move around and settle elsewhere where there are more resources, but there also have to be jobs there, and top-down approaches related to population settlement have never really worked (except in the mid-1800s, when there was an "unlimited" amount of "unsettled" land in the West, two false assumptions that had big long-term consequences). Besides, population movement tends to happen naturally through rising land or resource costs in the most attractive places compared to income potential.
Ultimately, even those who love the idea of "command economies" realize they don't really work because there's too many variables you can't control. You can put in policies at the state level that try to redirect growth, but at the end of the day land use decisions are best done locally, where the key issues are best understood. But local politicians are always driven by short-term economic growth, which leads to greater revenue and public services, which results in re-election. And they'd rather have that growth happen in their city than the neighboring one, because then the money flows to them, not their neighbor. It's the rare successful politician that is driven by a long-term vision, mainly because their constituents are mostly concerned about short-term things, like cheap groceries, safe streets, a roof over their head, and clean water coming out of the tap.
But resources, as you allude to, are finite, and they are not evenly distributed. But to many, that's a problem for the next generation.
And then there's this. Even if it were possible to move people around, and direct growth, you run into the biggest puzzle of all, and that's that in the big picture, unchecked population growth on a global scale is at the heart of most problems we have. It's one planet, finite resources, too many people.