That is an interesting theory NicoleC, and I've heard the California secession idea too. But I can't help but wonder where California and the Southwest thinks it would get it's water from--they'd have to invade their neighbors to keep diverting it!

"California" is not synonymous which what people outside CA usually consider to be true, which is that CA = LA. Smetimes SF is included in that image, but SF isn't particularly "north" in CA, even though we call it Northern California.

So Cal is relatively deprived of water, but No Cal has plenty extra, most of which is sent down the aqueduct to So Cal. OR and WA also have plenty of potable water. The other major source of water for So Cal is the Colorado River, which serves much of CA below LA. 35% of the fresh water in So Cal comes from aquifiers or groundwater.

As for the rest of the southwest, Arizona, Nevada, and New Mexico get their water from the Colorado River. Lake Mead has a 2 year supply behind the Hoover Dam.

I think it's fallicious to assume that war would be necessary to procure water anyway, since water rights are a tradeable commodity. Water is an important political subject in the SW and So Cal; one that the west coast is very well practiced at negotiating.