Climate Emergency: A Western Megadrought And CAP Mandatory Water Cutbacks

Above: Current water levels on Lake Meade for the 2021 accumulation projections can be seen well from the Mike O’Callaghan-Pat Tillman Memorial Bridge above the Hoover Dam on January 29, 2021, in Las Vegas. (L.E. Baskow/Las Vegas Review-Journal).

CBS News reports,  a Megadrought emerging in western U.S. could be the worst in 1,200 years, study finds:

Catastrophic wildfires, decreasing snowpack and dwindling water resources have become a normal part of life for residents in the western U.S. And, as a result of climate change, this may be just the beginning. A new study from Columbia University says the region has now entered into a climate-driven megadrought — possibly the worst in modern history.

Since 2000, the West has experienced one of its driest 20-year periods in history due to a combination of a dry natural cycle and the changing climate. While there have been some wet years like in 2019, overall water resources have been under unprecedented stress in the modern era.

Going back over a thousand years, there’s evidence that naturally driven megadroughts have devastated the region several times in history. These droughts led to upheavals among indigenous civilizations in the Southwest.

Scientists have long suspected that the current situation has been evolving into one of these megadroughts. This new research, published in the journal Science, not only confirms that suspicion, but also concludes this megadrought is as bad or worse than anything known before.

To reach this conclusion, the team conducted what they call the “most up-to-date and comprehensive long-term analysis” covering an area stretching across nine U.S. states from Oregon and Montana down through California, New Mexico and part of northern Mexico.

Their analysis utilized 1,200 years of tree ring data, modern weather observations and dozens of climate models. While reliable modern observations only date back to about 1900, yearly growth of tree-rings allows scientists to gauge annual changes in soil moisture centuries in the past.

“We now have enough observations of current drought and tree-ring records of past drought to say that we’re on the same trajectory as the worst prehistoric droughts,” says lead author Park Williams, a research professor in the Lamont-Doherty Earth Observatory at Columbia University.

Using the tree-ring data, Williams and his team detected dozens of droughts across the region, starting in 800 AD. Four of those stand out as megadroughts — with extreme dryness which lasted for decades — in the late 800s, mid-1100s, the 1200s and the late 1500s.

The team then compared the ancient megadroughts to soil moisture records from the years 2000 to 2018. As illustrated in the image below, they found that this 19-year period was the second-driest, already outdoing the three earliest ones and on par with the fourth period which spanned from 1575 to 1603. The other megadroughts lasted longer, which is why their red shading is wider, but they all began on a similar path to this modern drought.

What separates this drought from past megadroughts is that the natural dry cycle is magnified by a warming climate. This has caused the modern megadrought to impact an even wider area than any of the past ones. 

Climate change has boosted temperatures in this part of the West upward by 2.2 degrees Fahrenheit in the past 20 years. Since warmer air holds more moisture, extra moisture is increasingly being drawn from the ground, intensifying drying soils.

The researchers say rising temperatures due to human-caused climate change are responsible for about half the pace and severity of the current drought. Since regional temperatures in the West are projected to keep rising, this trend is likely to continue.

“Because the background is getting warmer, the dice are increasingly loaded toward longer and more severe droughts,” said Williams.

Another interesting finding in the research: The 20th century was the wettest century in the entire 1,200-year record. So the conditions we may think of as “normal” were actually a historical fluke.

“The 20th century gave us an overly optimistic view of how much water is potentially available,” said co-author Benjamin Cook.  [And this is what CAP water allotments were based on.]

This is problematic for water resource managers, especially with an exploding population. Because the past century was not representative of typical water availability, and climate change is stripping away water at an ever increasing rate, policy makers and managers have been forced to grapple with the new climate reality.

[T]his urgency is motivated by a strain on once abundant water resources. The mighty reservoirs of Lake Mead and Lake Powell along the Colorado River, which supply water to agriculture around the region, have shrunk dramatically. In addition, insect outbreaks are ravaging dried-out forests, making them more vulnerable and generating fuel for wildfires.

Jeff Lukas, with the Western Water Assessment at University of Colorado, says although water availability has been an issue, so far urban water supplies have been pretty resilient and managers have done a good job at reducing per-capita water use. “The biggest impact to everyday people from the changing climate and inevitable future megadroughts is not — perhaps surprisingly — towns and cities running out of water,” explains Lukas.

Instead, he is more concerned about out-of-control blazes.

“I think the biggest impact is the West-wide increase in very large and intense wildfires, which will get even worse in a warmer future and perhaps unimaginable during a future megadrought.”

Lilli Pike adds at Vox, What the megadrought in the West means for wildfire season.

The CAP water supply is entirely dependent on snowpack in the Colorado River Basin. Becky Bolinger, assistant state climatologist for Colorado and a research scientist at Colorado State University, reports at the Washington Post,  Colorado River Basin’s snowpack season earns low grades: Bad news for water in the West:

The snowpack season is ending in the Colorado River Basin as the spring melt is underway. If we take stock of the water supply over this vast basin, a critical resource for millions of people in the West, the news is not good.

The snowpack season, so important for the storage of water that can be tapped during the dry summer months, fell well short of expectations. The consequences of the shortfall for the basin, encompassing Arizona and parts of six other states, from Wyoming to California, are major.

1. There is an increased risk for large wildfires that can devastate state and national forests, reduce summer recreation activities, compromise air quality for large areas of the country and put populations near the urban-forest intersections in danger.

2. The reduced water supply affects municipal and agricultural water users not only within the basin’s 246,000 square miles, but also outside it, including Denver, Salt Lake City and Los Angeles.

3. Prolonged drought could ultimately affect food supply, causing reductions in crop yields and livestock herds.

To put this season in perspective, I’ve made a report card of the various indicators of snowpack to illustrate why the low grades are so serious.

The snowpack itself: C

The snowpack picture seemed promising at times in recent months, especially in February when several storms unloaded hefty snows. Even now, some late season snow in the northern part of the basin is working in some extra credit. But it’s not enough.

At the headwaters of the Colorado River, the snowpack peaked on April 2, about 10 days ahead of average. Since then, more than two inches of water have melted. In fact, since the beginning of April, the majority of stations in the upper Colorado River basin have seen melt rates between 2 and 6 inches. When the snowpack peaks and melts early it often portends a lower water supply during the dry season.

Indeed, throughout the entire Colorado River Basin, snowpack values peaked at levels well below average. From the Upper Green Basin in Wyoming and south through Utah and Colorado, many locations peaked in the bottom 25th percentile.

Soils: F

Soils have been the problem child since the very beginning of the water season, when the summer-fall monsoon was essentially a no-show.

If the monsoon had provided the needed moisture in June-September to the lower part of the basin and the southern portion of the upper basin, healthy soils would have been locked in during the cold season. But without the monsoon moisture [the “Nonsoon”], the basin went into the snowy part of the season with dry soil, essentially saddling the water supply with a debt that is far from being repaid.

Streams: D

Stream flow data doesn’t look too bad at the moment. According to the U.S. Geological Survey, the percent of the upper part of the basin observing near normal flow conditions has actually increased from 21 percent to 42 percent. But don’t let that deceive you.

Late in the water season, streams often appear to be doing better than they actually are. So, what’s happening?

Check out the hydrograph (above) from the Colorado River at the Colorado-Utah state line. The black line shows the average flow in recent months, compared with historical values (indicated by the colored shading).

Back at the beginning of March, flows were in the brown shading, ranking in the bottom 10th percentile. More recently, you can see that flows have bumped up to the yellow category, slightly improved from the brown. But this bump is mainly due to an early rise toward the peak. That early rise has been kicked off by early melting of the snow. The “improvement” is only an artifact of the early snow melt and will not be sustained.

Reservoirs: D

The water stored in reservoirs is akin to the output of a group project, contingent on the performance of its contributors. Since snow quantities, soil moisture and streams underachieved, reservoirs also end up with a low grade.

According to the April 1 water supply forecast, published by the Colorado Basin River Forecast Center, all of the Colorado River Basin will experience below-average water supply.

Across the Lower Colorado River, water supply accumulations began in January and most of the snow has completely melted. For the Lower Basin and southern half of the Upper Basin, water supplies are expected to be below 50 percent of average. Lake Powell inflows are forecast at 38 percent of average, a deficit of almost 4 million acre-feet! For perspective, current levels are already 6 million acre-feet below what they should be right now.

Lake Powell, which represents the majority of the Upper Colorado River Basin’s water supply, has still not recovered from the drought in the early 2000s. It takes more hits from each new drought. The system had a nice recovery from the 2018 drought, but still hasn’t made up lost ground from another drought in 2012-2013. Unfortunately, we’ll put 2021 down as another year to further deplete this system.

Lake Meade has remained below full capacity since 1983, due to drought and increased water demand.

The Associated Press reports, US West prepares for possible 1st water shortage declaration:

The man-made lakes that store water supplying millions of people in the U.S. West and Mexico are projected to shrink to historic lows in the coming months, dropping to levels that could trigger the federal government’s first-ever official shortage declaration and prompt cuts in Arizona and Nevada.

The U.S. Bureau of Reclamation released 24-month projections this week forecasting that less Colorado River water will cascade down from the Rocky Mountains through Lake Powell and Lake Mead and into the arid deserts of the U.S. Southwest and the Gulf of California. Water levels in the two lakes are expected to plummet low enough for the agency to declare an official shortage for the first time, threatening the supply of Colorado River water that growing cities and farms rely on.

[T]he agency’s models project Lake Mead will fall below 1,075 feet (328 meters) for the first time in June 2021. That’s the level that prompts a shortage declaration under agreements negotiated by seven states that rely on Colorado River water: Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming.

Arizona, Nevada and Mexico have voluntarily given up water under a drought contingency plan for the river signed in 2019. A shortage declaration would subject the two U.S. states to their first mandatory reductions. Both rely on the Colorado River more than any other water source, and Arizona stands to lose roughly one-third of its supply.

Tony Davis reports at the Arizona Daily Star, 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.

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.

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.

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.

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.

[U]nder 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.

Hydroelectric Power Supply At Risk

The AP continues:

The Bureau of Reclamation also projected that Lake Mead will drop to the point they worried in the past could threaten electricity generation at Hoover Dam. The hydropower serves millions of customers in Arizona, California and Nevada.

To prepare for a future with less water, the bureau has spent 10 years replacing parts of five of the dam’s 17 turbines that rotate to generate power. Len Schilling, a dam manager with the bureau, said the addition of wide-head turbines allow the dam to operate more efficiently at lower water levels. He said the turbines will be able to generate power almost to a point called “deadpool,” when there won’t be enough water for the dam to function.

But Schilling noted that less water moving through Hoover Dam means less hydropower to go around.

“As the elevation declines at the lake, then our ability to produce power declines as well because we have less water pushing on the turbines,” he said.

The hydropower costs substantially less than the energy sold on the wholesale electricity market because the government charges customers only for the cost of producing it and maintaining the dam.

Lincoln County Power District General Manager Dave Luttrell said infrastructure updates, less hydropower from Hoover Dam and supplemental power from other sources like natural gas raised costs and alarmed customers in his rural Nevada district.

“Rural economies in Arizona and Nevada live and die by the hydropower that is produced at Hoover Dam. It might not be a big deal to NV Energy,” he said of Nevada’s largest utility. “It might be a decimal point to Los Angeles Department of Water and Power. But for Lincoln County, it adds huge impact.”