As noted in the linked article, people in urban areas are paying many times the price for water that farmers are. If farmers had to pay municipal water prices, it's much less clear whether their farming would be profitable.
> Urban metropolises shouldn't be built where profitable farming can make better use of the water.
You have it exactly backwards: planting crops that are only profitable (and MUCH less profitable than comparable urban uses would be), and which make a horrible use of water, due to outdated legal ownership theories of water.
That's because the actual problem is intractable. Urban metropolises shouldn't be built where profitable farming can make better use of the water.
But good luck evacuating the greater Los Angeles area. Or getting people to move to areas better suited for living, in general.