This article appeared in the March-April 2004 issue of Science & Spirit.

At the tail end of the summer monsoon, a storm deluged the far-east side of Tucson. A driving rain pelted the bare, desert soil for more than an hour, accompanied by marble-sized hail that hit the ground and bounced. I walked through the house, opening windows with enough overhang to keep out the wet, delighting in the feel of the moist air and the sound of pattering rain. A rainstorm feels more of a miracle in the desert than it does near the southern tip of Lake Michigan, where I grew up.

With hard-packed sand substituting for lawns here, there is nothing to soak up a long, drenching rain. As the rain tapered off, I heard rushing water: The storm had transformed the normally dry wash winding through our neighborhood into a fierce torrent. The fast-running water, no higher than my ankles, became dirty-beige wavelets as it sped through our backyard.

Hundreds of washes gouge this region, hardtack-dry most of the time. But during a heavy rain, many of them roil with unstoppable water: Even when it’s only a foot deep, fast-moving water can float a vehicle and carry it away. Thus, many streets throughout this sprawling city display yellow signs warning, “Do Not Enter When Flooded.” It’s surprising how many people ignore them; local fire departments rescue the swept-away during nearly every significant downpour. This is such a common occurrence that Arizona has a “Stupid Motorist Law,” stating that people who drive around barricades into a flooded roadway can be liable for the cost of their rescue, up to $2,000.

Within an hour of the storm’s end, the empty, damp bed of my backyard wash was the only trace of its brief life as a small river. But the surprise of the earlier flow started me thinking about the inherent paradox: Sometimes, there can be too much water in the desert.

Flash floods occur every monsoon season and every winter, occasionally drowning people caught unaware. At lower elevations, floods can explode under blue skies, rain having let loose over the mountains surrounding the city. This past August, the National Weather Service reported 1.8 inches of rainfall in twenty-five minutes in the nearby Oracle area one afternoon. A man died when a flood from that storm swept down Bonito Canyon and through his home, possibly hurtling him through the downstream corner, then nearly a mile further. The floodwaters also rammed his Toyota 4Runner into the next house, 100 feet away.

Although Arizona is experiencing one of its worst droughts on record, floodwaters in the Cañada del Oro Wash recently ran at 7,000 cubic feet per second, or four times the level of the last big flood, in 1993. In the last two years, horrendous fires have devastated almost 200 square miles in the Catalina Mountains, from which Bonito Canyon and Cañada del Oro descend. The vegetation that normally slows the rainwater in its descent from the mountains has been burned away. Floods will threaten many homes in this area for years to come.

Normal flash floods are dangerous enough, but after fires of this magnitude, they also carry tons of topsoil, ash, and charred wood, giving the water the appearance of an oil slick. Devoid of oxygen, this sludgy water can suffocate aquatic species. When post-fire floods this past summer threatened the endangered Gila chub, a fish native to Sabino Creek, the chub were moved to holding facilities until the danger passed. But the floods also played a positive role in the creek, which flows from high atop fire-ravaged Mt. Lemmon. They killed many non-native green sunfish, which prey upon the Gila chub, and the ashy deposits they left behind are providing rich nutrients for riparian plants.

But far more often in the desert, there is too little water. And sometimes that leads to tragedy. More than 300 illegal immigrants, funneled into the desert by tighter Border Patrol measures in the larger border cities, have perished in this region during the last two years. Humanitarian groups stock scattered water stations, but people trudging for hours and days in arid temperatures reaching 110 degrees or more don’t last long without gallons of water.

In Tucson’s pioneer days, a daily bath was considered a waste of good water. Today, we’re more than wasteful. In a region that receives only twelve inches of water annually in nondrought years, we slurp up this precious resource like there’s no tomorrow. At one time, the region’s top user was agriculture (cotton, wheat, barley, alfalfa, vegetables, and nuts), but with a Pima County population approaching one million and showing no sign of slowing down, home use has taken over that distinction. Industry, including mining, uses a large amount. We also lavish nearly four billion gallons annually on lawns and several dozen golf courses--only some of which use reclaimed water.

Already, formerly vital rivers have dried up, fertile riparian habitats supporting wildlife and lush vegetation have disappeared, and parts of Tucson have begun to subside as the soil compacts over a falling water table.

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