The region around the lake Mead (Arizona, Nevada, California) will become really funky in term of war for water.
It already is funky. The states have been fighting over water rights allocations for years. I seem to recall some positive movement once the federal government threatened to step in and solve it for them. But I know until that point they were using insane numbers for the Colorado river watershed – essentially all their calculations were based on a volume that the Colorado river had never even come close to having.