A new report warns that Arizona could suffer the most pain if Lake Mead’s shrinkage triggers a shortage declaration. The state has done a lot to prepare, but more drastic steps may be necessary.

In Arizona, water scarcity is like the background hum of conversation in a popular restaurant: unrelenting. But even in this desert state, the ever-present strain on water supplies could soon be felt more acutely.

As soon as 2019, the water level in Lake Mead on the Colorado River could drop below an elevation of 1,075 feet. That will trigger mandatory cutbacks in water diversions from the reservoir under an agreement negotiated between the federal government and three lower-basin states that rely on the river: Arizona, California and Nevada.

A drought in the watershed now stretching 17 years long is to blame, along with overallocation of the river’s water supplies. Every year, the lower basin states have rights to extract 1.2 million acre-feet more water than the river actually produces. This is known as a “structural deficit” in the river’s water supplies. It is this combination of factors that enlarges the ugly “bathtub ring” around Lake Mead as water levels shrink year after year.

Arizona water officials have been preparing for long-term shortage for decades. But for the state’s 6.7 million residents, the threat has largely been an academic issue, if they’ve thought about it at all. They could be in for a rude wakeup call when shortage conditions begin.

“This sustained drought we’ve had, and chronic overuse of the river, have revealed pretty important shortcomings,” said Drew Beckwith, water policy manager at Western Resource Advocates, a conservation group based in Boulder, Colorado.

Beckwith’s group has released a report, “Arizona’s Water Future,” that explains the potential for cutbacks in the state’s Colorado River supply and suggests measures to adapt.

Arizona will feel cutbacks the worst, because it has relatively low-priority water rights. It also relies on the river more heavily than the other states. It would lose 320,000 acre-feet of water under shortage conditions in 2019, or about 12 percent of its Colorado River supply.

Beckwith’s report notes this could end farming in some parts of Central Arizona, halt new housing subdivisions and increase water rates for many Arizonans.

More cuts will come if Lake Mead shrinks below the additional trigger points of 1,050 and 1,025 feet.

“We are prepared for shortages, but we are not prepared for a worst-case scenario,” said Kathryn Sorensen, director of water services for the city of Phoenix. “There are some real challenges ahead of us.”

Arizona’s leaders long ago embraced the realities of life in the desert and adopted a wide range of water conservation measures. Its 1980 state groundwater management law, for instance, ties housing development to water availability and is recognized as a national model.

So reducing water consumption isn’t as simple as, say, mandating low-flow toilets. That kind of work has been done. Total water consumption in the state has declined since 1990, even though the population nearly doubled.

Beckwith’s report proposes other measures:

Fix water distribution leakage averaging 10 percent across the state (a rate not uncommon in many other states).

Apply advanced data gathering to customer accounts to track water consumption and leakage more closely, and to tailor conservation programs for unique uses.

Develop water markets and sharing networks so water is easier to transfer between users and to support the environment.

Improve infrastructure (pumps, pipes and power lines) to extract and deliver banked groundwater where it’s most needed.

Phoenix and other entities in Arizona have already begun voluntary measures to reduce their reliance on Colorado River diversions. This allowed water levels in Lake Mead to nearly stabilize last year.

“I believe we are close to leaving something like 375,000 acre-feet in the last two years in Mead,” said Sarah Porter, director of the Kyl Center for Water Policy at Arizona State University. “There are scenarios where a shortage would be painful for Arizona. But we can withstand the first cut.”

The three lower-basin states are also negotiating a “drought contingency plan” to prevent Lake Mead from shrinking far enough to trigger shortages. It’s essentially a treaty that commits each state to leave even more water in Lake Mead, which would require them to tap other water supplies and adopt more conservation measures. Negotiations are dragging, and it remains to be seen if a deal can be reached before a shortage actually occurs.

Arizona’s population center, stretching between Phoenix and Tucson, has banked about 9 million acre-feet of water in underground aquifers, Porter said. This happened as a result of diligent conservation, creating a water surplus that could be saved.

Still, if Lake Mead drops below 1,075 feet, it will trigger a series of events that could literally change the face of Arizona, said Beckwith.

The initial “Tier 1” water diversion cuts would halt 320,000 acre-feet of annual deliveries via the Central Arizona Project, a network of canals and pumps built by the federal government to divert Colorado River water to the state’s interior.

Two groundwater recharge agencies are expected to be the first to get hit with cuts, followed by several agricultural irrigation districts in Central Arizona.

These irrigation districts serve a lot of low-value, thirsty crops like cotton and alfalfa. They have low-priority water rights designed to be cut first, ensuring water remains available for others with higher-priority rights, including urban areas and Indian tribes. But it means thousands of productive farm acres could be fallowed indefinitely.

Maricopa-Stanfield Irrigation and Drainage District receives one of the largest shares of this water. The district serves 59,000 acres of farmland in Pinal County, south of Phoenix. Its general manager, Brian Betcher, did not respond to a request for comment.

Arizona’s celebrated 1980 groundwater law, among other things, requires developers of new housing subdivisions to demonstrate they have enough water to serve those new homes for 100 years. But there’s a loophole in the law that means, ironically, some of these homes may also be among the first to see cuts in water supply, said John Fleck, author of “Water is for Fighting Over,” a book published last year about the Colorado River conflict.

Some developers were allowed to meet the 100-year requirement by paying into a fund maintained by the Central Arizona Groundwater Replenishment District. The district, to serve those water users, spends the money to acquire additional water as it becomes available.

But not all the necessary water has been acquired yet, said Fleck, director of the University of New Mexico Water Resources Program. In some cases, that additional water is intended to offset groundwater pumping now serving some homes – a finite supply.

“If there is a shortage on the Colorado River, the amount of water available to offset that pumping is potentially a phantom, and that’s the risk,” Fleck said. “If the communities are willing to conserve more, there’s enough water. But they’re going to have to do more.”

That could require measures such as more aggressive lawn “buy-back” programs to eliminate thirsty ornamental turf, and steeper water rates to penalize heavy users.

There also isn’t enough infrastructure to deliver banked groundwater where it’s needed during a shortage in Colorado River supplies.

For many years, the state diverted its full Colorado River entitlement even when it wasn’t needed. One reason was to ensure the water didn’t get taken by California if it was left in the river, Sorensen said. Arizona banked any excess diversions in groundwater aquifers. But there wasn’t much thought given to the logistics of actually pumping it back out some day.

“This is an area where we really do need to focus,” Sorensen said. “There are some obstacles to recovering that water.”

Phoenix is beginning to drill new wells for that purpose. It may also need new pipelines to distribute the water, and maybe even new power lines to run the pumps.

“We do have plans to drill additional wells over the next five years,” Sorensen said. “It’s too early at this point to know if there’s going to be a large impact on water rates.”

The obstacles are not just physical. In some cases, agreements are needed to move water between water agencies, to share plumbing facilities and to trade and sell water. One important deal was reached this month when the U.S. Bureau of Reclamation agreed to allow Central Arizona Project facilities to be used by other agencies to transport water.

Another example is a water-sharing agreement reached in 2016 between Phoenix and Tucson. It allows Phoenix to store surplus Colorado River water in Tucson aquifers, helping to sustain groundwater levels there. During a shortage, Tucson gets to use that stored water as its own, while Phoenix would receive an equivalent amount of Colorado River water that belongs to Tucson.

More such water-sharing deals are needed, Beckwith said, especially to sustain wildlife habitat, which is often left to suffer during shortages.

On the bright side, the Colorado River watershed ended the winter with an above-average snowpack. This reduces odds of a shortage condition within the next few years. But it won’t prevent inevitable shortages driven by overallocation of the river.

“One good snow year does not erase the math problem that is the structural deficit,” Beckwith said. “Hopefully, we can apply some pressure to get some of these things going that are really necessary for Arizona to live in a future with less water.”

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