Is the Current Drought Our Only Water Supply Problem? | Desert Botanical Garden

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This article ran in the Winter 2019 Sonoran Quarterly issue

 

Paul Hirt
Senior Sustainability Scholer, Arizona State University

 

If you were in Arizona this past summer, you may have experienced what some now call our “nonsoon” season—no monsoon. In 2019, most of northern Arizona was far drier than normal. Phoenix had its third driest monsoon in 73 years of record keeping; Prescott had its ninth driest mon-soon; Flagstaff won the dubious prize of having the driest monsoon ever recorded. Southern Arizona counties did better but only because of an anomalous incursion of late September rainfall from several tropical depressions.

This is not an isolated bad year for precipitation. The entire Southwest has been in a two-decade long dry spell that ranks as one of the longest droughts in the region’s history. In only three of the past 20 years did Arizona experience “normal” precipitation. Ominously, both our summer rains and our winter rains have declined. 

Is the current drought in Arizona simply one of our naturally recurring dry spells or a more persistent consequence of climate change—a new normal? Time will tell, but clima-tologists are warning us to prepare for a much warmer and drier future.  

Drought directly reduces the annual flow of our rivers and streams, which are Arizona’s only renewable water supply. To enhance resilience, the federal government built dozens of dams on Southwestern rivers during the 20th century, storing tens of millions of acre-feet of water in reservoirs as a buffer during times of drought. Over the last century, a normal drought would last only three to five years, allowing our reservoirs to easily make up for the deficit during those dry spells. But the persistent drought since 2000 has been  a game-changer. 

In 1999 the Southwest’s two largest storage reservoirs—Lakes Mead and Powell on the Colorado River—were 98% full. They have never been even close to full since then and may never be full again in our lifetimes. The drop in reservoir levels after 2000 was so rapid and unexpected that Arizona, California and Nevada had to quickly hammer out a contin-gency plan they called the “Colorado River Interim Guide-lines for Lower Basin Shortages,” signed into law in 2007. Even that document proved inadequate as the drought persisted and the reservoirs continued to decline.

By 2015, it was clear that even more drastic action was required to keep Lake Mead from falling to dead pool. After years of wrangling, the seven basin states that share the Colorado River agreed to a new, stricter Drought Contingency Plan (DCP) confirmed by an Act of Congress in early 2019.

Many water managers and policy makers praise this agree-ment as historic, but it is only a partial temporary fix that simply determines who loses how much water when Lake Mead’s reservoir drops below specific elevations. 

Arizona has already lost 192,000 acre-feet of its Colorado River allocation, because Lake Mead is below 1,090-foot elevation. If the lake drops below 1,075 foot elevation, Arizona will lose a little over half a million acre-feet of Colorado River water—virtually all of it coming out of the CAP Canal that serves metro Phoenix and Tucson. When running at full capacity, the CAP Canal carries 1.6 million acre-feet of water annually to central and southern Arizona. So a third of our renewable water supply is currently at risk.

The elevation of Lake Mead has been hovering near 1,075 since 2015 and has remained above that triggering elevation only because the feds, states, tribes and Mexico have all voluntarily left some water in the reservoir to keep it above 1,075. Even with these conservation measures, most hydrol-ogists expect Lake Mead to drop below 1,075 in 2022. Nearly everyone expected Mead to drop to 1,075 this year. But we had an exceptionally good year of snowpack in the Colorado Rockies, which sent a lot of runoff into Lake Powell this spring and summer, postponing the reckoning for a couple years.

Our water supply in Arizona is a combination of surface water and groundwater. Some communities have access to the former—some to the latter, some to both. The vast majority of our groundwater aquifer is not renewable in any mean-ingful sense. It’s like a savings account. When it’s pumped out it’s gone. Arizonans have been extracting groundwater for nearly a century with only a small fraction being replen-ished. In some groundwater basins, water levels have dropped by 300 to 400 feet, making water pumping ever more difficult and expensive and increasing our long-term sustainability challenges. 

Concerned about groundwater overdraft, the Arizona legis-lature passed the Groundwater Management Act (GMA) in 1980, mandating conservation planning to try to get to “Safe Yield” of groundwater by 2025. The GMA also required new housing developments to show that they had a 100-Year Assured Water Supply. These laudable goals unfortunately have often been ignored or circumvented. After 40 years of implementation, we are still unable to meet the fundamental goals of the GMA.

Both groundwater and surface water supplies in Arizona are limited and declining, requiring our full attention and care. Both are deeply interconnected, too. Pumping water from the aquifer in a river valley can reduce the flow of the river, even dry it up completely. Conversely, the only location where groundwater recharge naturally occurs is in the alluvium along river valleys. Without groundwater there are no flowing rivers; without rivers there is no groundwater replenishment.

One of the main strategies of water managers in the state during times of drought is to increase groundwater pumping to compensate for the decline of surface water supplies.  

This is what SRP does for its customers in Maricopa County, but that’s only sustainable if droughts are temporary and river flows return to expected levels.

Similarly, Arizona’s 2019 Drought Contingency Plan allocated tens of millions of Arizona taxpayer dollars to drill new high- capacity wells to pump groundwater for Pinal County farmers who are losing their access to CAP water from the Colorado River. While that may be a short-term solution for Pinal farmers, it exacerbates our long-term sustainability challenge.

What’s the long-term solution? Demand management—for more than 100 years Arizona leaders have adopted creative, expensive and often environmentally destructive “supply side” solutions. We’ve built dams, reservoirs, canals, pumps and pipelines to bring water from one place to another. When we faced scarcity, we sought to increase the supply.

But that’s only one side of the coin. Managing our water  demand is the other side. There is no longer any unclaimed, unused water available for acquisition and transfer. Besides, we get the most bang for the buck with conservation and efficiency programs. It is time to manage ourselves as ex-pertly and assertively as we have managed water supplies.

To reach sustainable water use, we need to reduce the amount of water we pump from aquifers by at least two- thirds and we need to get used to having about 20% less water flowing in our rivers. That will take a lot of effort and will affect our lives, landscapes and businesses in significant ways. But it is certainly doable. We have to change our water culture to focus not on “development” but  on sustainability and justice—ensuring that everyone has access to a minimum amount of clean water and that future generations will have as much opportunity as the present. 

One important caveat, however: in our effort to squeeze ever greater efficiencies from our water supply/demand system, we must remember that we are not the only species on the planet that relies on fresh, clean water. We cannot capture and consume every drop for ourselves. Our health, our quality of life and our moral compass requires that we take into account the entire biotic world when we make de-cisions about managing natural resources. Once again, this underscores the importance of managing our own demands.

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