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First mandatory cutback of CAP water now likely in 2022
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First mandatory cutback of CAP water now likely in 2022

The Central Arizona Project seems almost certain to suffer its first significant shortage in water deliveries next year.

Reservoirs are expected to fall so low by the end of 2021 to warrant cutting nearly two-thirds of the CAP water that Pinal County farmers now get. At that point, CAP deliveries used by the state to store water in the ground for future use by cities and tribes would also be cut. So would CAP water supplies sold to the Central Arizona Groundwater Replenishment District, an agency that recharges water into aquifers across the state's urban centers to compensate for groundwater pumped elsewhere for new development.

The loss for farms has been expected for years. But possible cuts for other water customers now loom sooner than anticipated, as the Colorado River’s situation worsens.

For the first time, a federal agency’s river forecast predicts that at the end of 2022, the Lake Mead reservoir will be at or very near a point where CAP must cut deliveries to other categories of water users.

Those cuts would fall upon Phoenix-area cities and on Arizona tribes, including possibly the Tohono O’Odham whose reservation is south and west of Tucson.

If they happen, the cuts would also start slicing deliveries of relatively small amounts of CAP water to Rosemont Copper and Freeport McMoran Copper in the Tucson area and to Resolution Copper in the Superior area.

Tucson depends on CAP for drinking water, but its supplies wouldn’t yet be affected.

The cuts to farmers will be required if Lake Mead falls below 1,075 feet at the end of this year. The Bureau of Reclamation’s new forecast — announced Thursday for the river — puts the expected level at 1,067 feet by then. The bureau will likely decide in August whether to declare a shortage for 2022.

The additional cuts to tribes and to Phoenix-area cities would be required in 2023, if Lake Mead falls below 1,050 feet. The new forecast is for the lake to be at 1,050.31 feet by December 2022.

Tucson’s CAP supply wouldn’t be cut unless the lake fell below 1,025 feet.

Conditions changing rapidly

The first shortage would come nearly 37 years after the CAP went online and well over a half-century after Congress authorized its $4 billion network of pipelines and canals to bring Colorado River water to the state’s arid midsection.

Scientists and environmentalists have warned for decades that shortages were inevitable because the river is over-allocated among its many holders of water rights, and because of climate change and the worsening drought, which has now lasted since 2000.

This year’s drought conditions continue after last year’s hot, dry weather caused snowpack to evaporate earlier and baked soils in the river’s Upper Basin. The soils carried very little moisture, meaning that melted snows often soaked directly into the ground rather than run off into the river and its many tributaries.

Then, early this month, record or near-record temperatures caused snowpack to melt early. It’s cooled off in that area since then.

However, on Friday, April 16, a federal climate forecaster trimmed its prediction for April to July runoff flows into Lake Powell, to 38% of normal, from a 45%-of-normal forecast made just two weeks earlier.

Lake Powell, at the Arizona-Utah border, controls Colorado River water flows into Lake Mead, which stores drinking and irrigation water for CAP supplies that are served to Tucson, Phoenix and Pinal County.

Arizona officials say they’re prepared

Arizona’s top water officials reacted calmly in the last week to news of the expected cuts, saying they were not surprised due to the ongoing dry weather.

They said the state is prepared for the cuts because the groundwork was laid in early 2019, when the Legislature and Gov. Doug Ducey approved a drought contingency plan. It set priorities for whose deliveries would be cut at particular time periods and when the water in Lake Mead hits particular elevations.

The state’s preparedness is due “in large part to Arizona’s unique collaborative efforts among water leaders including tribes, cities, agriculture, industry and environmental organizations that developed innovative conservation and mitigation programs” for the drought plan, said the Arizona Department of Water Resources and the Central Arizona Project in a joint statement.

With the drought plan, the state forestalled or delayed the need for much steeper cuts that could have threatened urban water supplies, the agencies’ statement said.

“It’s a grave situation”

But Arizona State University researchers are much more concerned about the impending cuts.

One reason is that reservoir levels are now expected to fall rapidly, with no end in sight. By the end of 2022, Lake Mead’s water level is expected to stand 30 feet from where it was last December, and 40 feet from where it stood at the end of 2019.

“That’s the scary thing. It’s not what happens this August, it’s what happens thereafter if this lake keeps declining,” said Kathryn Sorensen, research director at ASU’s Kyl Center for Water Policy. August is when the bureau decides whether the CAP will have to cut back.

She pointed to an observation in a blog post Friday by University of New Mexico water researcher John Fleck. He warned that Mead could keep falling further into 2023 if drought conditions continue on their current path.

Fleck noted that the Bureau of Reclamation is now on track to deliver only 7.48 million acre-feet from Lake Powell to Lake Mead in each of the next two years.

In average to good years on the river, the bureau typically sends 8.23 million to 9 million acre-feet from Powell to Mead.

The last time that Mead only got 7.48 million acre-feet, in 2014, the reservoir dropped 25 feet in a single year, noted Fleck, director of UNM’s Water Resources Research Center.

“It’s a grave situation,” said Kyl Center Director Sarah Porter, even though the cuts now being discussed were contemplated by the 2019 drought contingency plan, known as DCP.

“I think the Arizona DCP was designed to sort of, as far as possible, avoid shortage impacts to cities, but we’re getting really close,” Porter said.

“New normal” of much less water available

“This just underscores again that we are moving into a new normal of much less Colorado River water available than we’ve had the luxury of in the past,” Porter said.

“DCP could be seen as easing our way into this new normal, which has all kinds of pain for all kinds of users,” she added.

Assuming the water release levels projected in the bureau’s latest monthly report, the “most likely” scenario is for Mead to fall to about 1,035 feet by the end of September 2023, blogger Fleck wrote.

That’s only 10 feet above 1,025 feet, the level at which the federal government could conceivably take over management of river water allocations. That’s also when Tucson, Phoenix and other cities and tribes would have to start taking cuts in water supplies, including supplies that are considered highest priority, or the last to face cuts during a shortage.

“Remember that I’m talking about the midpoint in a range of possible outcomes,” Fleck wrote of his “most likely” scenario. “A run of wet weather could make things substantially better. But a run of dry weather could make them worse.”

Overall, the cuts expected next year will reduce CAP deliveries by about 520,000 acre-feet from a normal annual total of about 1.4 million to 1.5 million acre-feet. An acre-foot is enough to cover a football field a foot deep in water.

Farms face tough decisions

The vast majority of these cuts, about 250,000 acre-feet, will fall upon Pinal County farmers, who grow cotton, alfalfa, other grains and some vegetables and fruits.

The CAP will deliver the farmers about 105,000 acre-feet a year in alternate surface water supplies for the first year of those cuts. But those “mitigation” supplies will disappear once Lake Mead falls low enough to put the project into its next round of shortages.

The farmers are also supposed to get enough state and federal money to drill wells to pump another 70,000 acre- feet of groundwater, although most of the federal money needed still hasn’t come in.

But even with the mitigation supplies and the new wells, Pinal farmers may have to leave about 20% to 30% of their land fallow, if they want to keep growing crops with the same amount of water as before, said Paul Orme, a Phoenix attorney and agricultural lobbyist.

“Farmers have to decide: ‘I can irrigate all my land with less water, or irrigate some of the land completely using the same water as before,’ “ Orme said.

If a second round of cuts is needed in 2023, CAP would lose 590,000 acre-feet of water. If the lake drops below 1,045 feet, unlikely until 2024 at the earliest, CAP would then lose 640,000 acre-feet.

Impact on other water users

These later rounds of cuts would fall on tribes, cities and industries who get what CAP officials call non-Indian agriculture water. Those supplies once were delivered and sold to farmers, but were eventually reallocated to other parties after farmers decided they couldn’t afford to buy them at higher costs than for taking pumped groundwater.

Phoenix, the Gila River Indian Community, the Tohono O’Odham Nation, Scottsdale, Chandler and several other Phoenix-area cities have had subcontracts enabling them to take some of this water for many years.

In the Tucson area, by far the biggest holder of this water is the Tohono tribe, which has about 28,200 acre-feet.

In a January 2021 decision, the federal government also reallocated another 45,000 acre-feet of non-Indian agriculture water to a number of tribes, cities and companies.

Among them, Freeport McMoran got about 5,800 acre-feet for its Sierrita Mine west of Green Valley. Rosemont Copper got 1,000 acre-feet, presumably to store each year in recharge basins in the Sahuarita area to compensate for the pumping of groundwater needed for its proposed Rosemont Mine.

The single biggest share of this water, about 18,000 acre-feet, went to the three-county Central Arizona Groundwater Replenishment District, which recharges renewable supplies such as CAP to compensate for pumping done to serve developments elsewhere in Pima, Pinal and Maricopa counties.

Under the drought plan, holders of these water rights would lose only 25% of their water at first. But if Lake Mead keeps falling, their shares of that water will slowly get pared down to nothing, once Mead falls below 1,025 feet.

Contact Tony Davis at 520-349-0350 or tdavis@tucson.com. Follow Davis on Twitter@tonydavis987.


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  • Updated

Federal officials say it's likely Lake Mead at the Nevada border will be low enough at the end of 2021 to trigger the first major cutback in CAP deliveries to the Arizona's parched midsection.

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