The Arizona Republic's Shaun McKinnon did a fine job of using the breach in the CAP canal to provide a primer on the system and some of its challenges (here, here and here). This blog has written extensively on water and Arizona, but while a few people are paying attention, let me make a few essential points:
• The Colorado River is over-subscribed. There are, as the water geeks say, too many straws sucking from the river. When the Colorado River Compact was first sealed in 1922 (with Arizona disputing the allotments, chiefly because it believed it was due more because the Gila and its in-state tributaries flow into the Colorado), the Southwest was largely unpopulated and even Los Angeles' population in the most recent Census was less than 600,000. The river was to be "tamed" for reclamation. Nobody ever imagined Las Vegas, a tiny stop on the Union Pacific Railroad, would become a major metropolis. Critically, the river levels used to make the allotments were around 500-year highs. Now there's simply not enough water to go around. The Upper Basin states, especially the state of Colorado, always felt defrauded by the deal and the subsequent settlement of Arizona v. California. They will be much more jealous of their water resources now. Mexico was shortchanged, as well, with catastrophic destruction of the Colorado delta resulting.
• Climate change will transform all assumptions about water in the Southwest, especially its effect on snowmelt, both in the Rockies feeding the Colorado River, and the Arizona mountains whose snow charges the lakes of the Salt River Project. There will be less water and higher temperatures. We have no historical roadmap for what this will mean, especially because, as Ed Abbey would say, one has established a city where no city should be.