The Imperial Valley in California gets 20% of all water from the Colorado River. During this time of extreme drought, sooner or later this will have to change. There’s no way Arizona will ship the water through to California while they have mandatory cutbacks or worse. The same is true for Nevada and Lake Mead. Vegas will not go thirsty so California agriculture gets water. The laws and rules that govern Colorado River water are antiquated, counter-productive, and need to be replaced.
If the Western drought continues, Arizona would have to bear almost the entire brunt of water shortages before California gives up a drop of its appropriation from the river. Few observers of Western water affairs believe that’s politically practical, but few have offered practical alternatives.
A few years back, Nevada tried to grab Utah water. The governor of Utah basically told Nevada to go screw themselves and Utahns said they’d be at the lakes with rifles if Nevada tried. (It didn’t.)