Unless you count the Colorado River itself as a water system. :)

I would guess that almost none of the water that California gets from the Colorado falls in California. Coloradans sure feel that the down river states don't have the natural right to water that falls on their land.

I think most people are largely unaware of the geography of the Colorado. There is a general lack of understanding of the fundamentals of the water crisis out west. Most don't have a clear picture even of how different states draw from the Colorado for instance. And how those different methods impact watersheds and downstream infrastructure.

The lack of information actually exacerbates the entire problem out west, as people give undue concern to, say, Los Angeles. While, say, Scottsdale sits oblivious to the precarious nature of it's situation vis-a-vis water.