I suppose I'm struggling to come to terms with how The Authorities (city planners, engineers, etc.) can just stand by while this happens.

A fair question. The Salon article points to the answer:

"The Authorities" think they have a water SUPPLY problem, rather than a water DEMAND problem.

It's like this: ecosystems are fragile and do not respond well to overload. Any city is an overload for the ecosystem, it just depends on how much of an overload. You can fix that overload one of two ways: you can decrease the demand on it or you can increase the raw inputs. And, as our understanding of "ecosystems" isn't yet half a century old, our attempts at the latter are quixotic at best.

Yeah, you can "conserve water." The problem is that in order to seriously affect change, we're talking "Stillsuits on Arakkis" water conservation, not "only water your lawn on odd-numbered dates" water conservation. Consider Brazil - they're mostly rainforest but they're running out of water. They're taking baby steps that, let's be honest, would go over like a fart in church in Arizona. After all, we're busy fighting low-flow toilets and fluorescent bulbs in the name of "liberty."

Don't get me wrong: Change can be made. It has to be wanted and fought for by everyone, though. Bill Mollison famously restored some australian town or other from total collapse through permaculture. He can't visit it, though, because they want to string him up for planting hawthornes, which are spikey and mean enough that their thorns can puncture tires (they also don't take a lot of water and are great "guild" starters). So - their town was saved from oblivion through greening the desert, but they want to kill the guy who did it because his methods were rough on their tires.

This is Arizona we're talking about. They don't like black people, don't like Mexicans, don't like Daylight Savings and, by the way, are experiencing their greatest population growth from aging Boomers retiring away from the snow. This is a population that you can barely get to recycle their aluminum cans. You think they're going to put up with effective (but radical) water conservation? A lot of them don't even "believe" in "anthropocentric global warming."

The United States didn't even sign the Kyoto Protocol. Which doesn't matter any more, because it expired Dec 31 2012. Ask any climatologist and they'll say that it's too late to do anything but strap in. We're well past the tipping point and the only question left to ask is "how bad is it going to be."

I would argue that if you're in Phoenix, it's going to be excessively fucking bad. Same with Albuquerque. Same with Los Angeles. Same with Salt Lake City. Same with Vegas. Same with Kansas City. Same with Tulsa. It's going to look like Nogales halfway through Nebraska by the time we're all dead but it will have happened so slowly that nobody will have bothered to do anything. Kind of like all the dry, dead farms up in the San Joaquin - all the water that grows crops can't because it's too busy watering lawns in Pasadena.