It Rained! Is the Drought Over?

On a recent mid-September afternoon, a wonderful thunderstorm, the kind of storm monsoon-lovers dream of, dumped about 3” of much needed rain in Carefree. Leaves glistened, the aroma of wet creosote bushes permeated the air, washes flowed, temperatures dropped, albeit temporarily, and, after months of dormancy, windshield wipers came to life. It was a very special day!

For communities in the grips of a 25+ year drought and facing significant Colorado River water delivery cuts, the storm felt like a much needed, overdue reprieve. Unfortunately, one major storm is not a drought breaker. The reason why lies in the complexity of our water supply.

While the water portfolio for every municipality or water company varies, many, like Carefree, derive their water from the Colorado River through the Central Arizona Project and groundwater delivered via wells drawing from aquifers. In Carefree, about 70% of our delivered water originates from the Colorado River and about 30% of our water comes from wells pulling water from an aquifer under our town.

The Colorado River relies on Rocky Mountain snowpack for its health and to fill Lake Powell and Lake Mead reservoirs. Local rain does not impact snowpack in the headwaters of the Colorado River drainage system.

But certainly, significant rainfall must replenish our aquifers! If it was only that simple. Most Sonoran Desert rain never reaches an aquifer. Only about 2 to 3% of desert precipitation becomes groundwater. Most desert rain is lost to evaporation, flows away as runoff, or is used by plants. The time needed for rain to find its way to an aquifer can be measured in decades, not days or weeks. Water must percolate slowly through dry, often fine grained sediments. The time it takes for rainwater to travel from the surface to an aquifer depends on the local geology and the depth of the aquifer. Desert aquifers are typically hundreds of feet below ground.

While local rainstorms, no matter how big, do not make a significant impact on our water supply, those storms decrease wildfire risk, bring the desert to life, reduce dust, and recharge soil moisture. Plus, they set the stage for water conservation. Outdoor water use – irrigation, swimming pools, fountains – account for about 70% of residential water use. For a few days after a heavy rain, irrigation systems can be suspended and pools can coast on additional inches of rainwater.

While a good thunderstorm is always welcome, it does not change the reality of a decades long drought. Our responsibility to manage scarce water resources remains and will continue for years to come.