No one is saying you should waste water, but in Phoenix it's hard to come up with a reason not to

But it's a slow process. It has to be done mechanically, methodically. There is no way to capture the extra water from a violent rainstorm. Some might seep into the aquifers on its own, but the rest ends up down in Gila Bend, where farmers have first rights, or as far away as Mexico. (In fact, agriculture currently uses about 70 percent of the state's total water.)

And it takes a while to fill these aquifers, especially because we've been drawing from them for years. Arizona is in its 10th year of water banking and has saved 3 million acre-feet through the process, enough to supply CAP's system with water for just under two years.

All the future plans to augment Arizona's water supply come with caveats — they're controversial, they're slow, and, most of all, they're expensive.

Because no state is going to give up a portion of its allotment without a fight, and taking away Mexico's supply would require an international treaty, some high-tech augmentation methods have been proposed.

Water reuse has been the most popular solution so far. For one thing, we have the resources to do it. For another, using treated wastewater on landscaping and non-edible agriculture leaves more good water for people.

Still, at $1,700 an acre-foot, it isn't exactly a bargain.

Water here is cheap right now. If we want to keep it that way, we'd better conserve, says Herb Guenther, director of the Arizona Department of Water Resources.

"The cheapest way to save water is to conserve," he says. "That's why conservation is important. It keeps water rates low."

If we don't conserve what we have, the only option in the future could be throwing millions of dollars into artificial augmentation.

That might be the best water-conservation sell.

No one really wants to turn off the water while lathering up in the shower, or play golf on a Xeriscaped course, so water lags a bit behind the rest of the green movement.

Melanie Ford, who works for the AZDWR as a drought planner, spending her time trying to persuade people to conserve water, has definitely noticed what a tough pitch it is.

"It's hard to get people to change their lifestyle. People don't want to take a shorter shower," she says. "It's easy to drive a Prius, but tearing out your grass that you love is a bigger change than just buying a new car. There's no immediate reward."

Correction (posted April 24, 2008): It should have been reported the Central Arizona Project gets 1.5 million acre-feet a year, and that one acre-foot can support two households for a year. Also, the article should have reported the number of gallons in an acre-foot as 325,851.