Western Mega Drought Threatens Arizona Water Supplies

Back in April, scientists sounded the alarm bell: The American West May Be Entering a ‘Megadrought’ Worse Than Any in Historical Record:

Drought has scorched western North America for the better part of two decades, withering crops, draining rivers and fueling fires. Scientists now warn that this trend could be just the beginning of an extended megadrought that ranks among the very worst of the past 1,200 years and would be unlike anything known in recorded history.

“No matter which way you slice it, the clear indication is that the current drought ranks right up there with the worst in more than a thousand years, and there’s a human influence on this of at least 30 percent and possibly as much as 50 percent in terms of its severity,” says Jason Smerdon, a paleoclimatologist at Columbia University’s Lamont Doherty Earth Observatory who co-authored the new research published today in Science. “It would have been a bad drought without anthropogenic warming, but not a contender to rival these really heavyweight droughts that occurred during the Medieval Era.”

Megadroughts, by definition, are occasional events of unusual severity lasting for at least 20 years. During the past 1,200 years, four major megadroughts occurred in the American West: during the 800s, the mid-1100s, the 1200s, and the late 1500s.

Some evidence suggests these events upended life in the West. For example, no one is certain what circumstances led the Anasazi people to abandon their cliff dwellings at Chaco Canyon during the 12th century and Mesa Verde during the late 13th century, but researchers have long theorized that megadroughts corresponding to those periods drove their inhabitants to seek reliable sources of water. The worst known drought of the entire 1,200-year period, in the 16th century, may have helped to amplify the devastating epidemics of cocoliztli in Mexico, which killed perhaps half of the indigenous population. Theories suggest drought weakened a malnourished population, or that conditions became ideal for the disease to spread widely among rodent hosts.

“There’s always been the prospect that by chance we could have one of these droughts in the West, but we haven’t had one since the late 1500s,” Smerdon says.

The evidence was already alarming. A 2016 study by some of the same researchers tried to model the probabilities that a megadrought of 35 years or longer would occur by 2100 if global climate change continued unabated, and put that probability at 90 percent.

Now the new research reveals that the period of drought between 2000 and 2018 was the second driest of all 19-year periods in the past 1,200 years. “Suddenly, looking at the data since 2000, they’re definitely suggesting that we are currently on a megadrought trajectory,” Smerdon says. And while 20 years is a long time to live with drought, the megadroughts recorded in the paleorecord lasted far longer, like 50 or even 90 years.

Earlier this week, the Washington Post reported, California facing drought crisis as water shortages mount and fire danger escalates:

California’s deepening drought has worsened into a crisis, as a second dry year in a row has diminished the state’s water supply and another difficult fire season looks inevitable. Nearly three-quarters of the state is in extreme to exceptional drought. With the wet season all but over and a hot, dry summer probably ahead, water shortages and fire danger are poised to intensify.

The past several weeks have shown dramatic change in drought status: Extreme drought has expanded through the northern Sierra’s crucial water region and in the agricultural San Joaquin Valley.

Exceptional drought, the worst category in the federal government’s U.S. Drought Monitor, has descended upon the Bay Area and the nearly snow-free southern Sierra. Moderate drought conditions or worse cover all of California.

Cindy Matthews, senior hydrologist with the National Weather Service’s Sacramento office, said the recent drought progression is a result of the dry winter, which has been followed by a very warm and dry spring. Most of the state has received less than a half-inch of rain since April 1.

California Gov. Gavin Newsom (D) has declared a drought emergency in 41 counties, a move that will help to conserve water in reservoirs, although many sectors will vie for that limited supply downstream, including households, farmers and freshwater ecosystems.

“There is not enough water available, so reservoir operators have reduced their allocations to those who have rights to that water,” Matthews said in an interview. There are reports of farmers allowing fields to go fallow this spring because there probably will not be enough water to sustain some crops through the season. Freshwater fish species such as salmon are also threatened by low stream levels.

The drought is hitting especially hard in the wetter northern half of the state, where major reservoirs are fed by mountain snowmelt. The two largest of those, Lake Shasta and Lake Oroville, are at 46 percent and 40 percent, respectively, of their total capacity this week and are lower than they were at this date during the 2012-2016 drought. Because of climate change, the prolonged dry spells of the past 10 years are much warmer and therefore more severe than those that occurred decades ago.

The Sacramento Bee reports, “California’s water supply got cut again Wednesday, with the federal government reducing allocations to cities and farms as the drought intensified.” Federal government slashes water deliveries to farms, cities as California drought worsens:

The U.S. Bureau of Reclamation announced that municipal water agencies that rely on the Central Valley Project will have this year’s allocations slashed from 55% down to 25% — a level not seen since the drought of 2015.

[R]eclamation also announced that most farm-irrigation districts that belong to the Central Valley Project will get no water at all this year, the first time that’s happened since 2015. Previously, the agency announced a 5% allocation, but said it was suspended for the time being.

Farm groups have been predicting major cutbacks in plantings this year, and Wednesday’s announcement reinforced their gloom.

“Reclamation’s inability to make water available for irrigation and ability to make only a small amount of water available for domestic use in the second year of drought is one more reminder that the state’s water supply infrastructure is inadequate,” said Tom Birmingham, manager of the vast Westlands Water District in Fresno and Kings counties. “The Central Valley Project was originally designed and constructed to supply water through even extended droughts.”

Although Westlands mainly serves farm irrigators, the district announced it was forbidding all outdoor landscape watering for now.

Unlike the previous drought, when former Gov. Jerry Brown ordered a 25% cut in urban water consumption, Newsom hasn’t issued any comparable mandates. But his water policy advisors say the governor could crack down on urban usage if the state endures a third consecutive dry winter. State officials say conditions have gotten at least as bad as they were in 2015, if not worse.

While California runs dry from a mega drought and faces another horrific fire season, Arizona’s legislature is wasting its time on voter suppression measures and a GQP sham “fraudit” of the 2020 election instead of addressing a coming water emergency.

Arizona is also in a mega drought (see the map above), and Arizona is first on the list for having our share of Colorado River water reduced in a water emergency. CNN reports, First-ever Colorado River water shortage is now almost certain, new projections show:

Thousands of people will celebrate Memorial Day this weekend on the water of Lake Mead, just 24 miles east of Las Vegas on the border of Arizona and Nevada.

What they may not realize is that the oasis they’re enjoying in the desert is entering uncharted territory, with significant ramifications for millions across the Southwest in the years to come.

On Tuesday, the water level in Lake Mead — the largest US reservoir, and fed by the Colorado River — fell below the elevation of 1,075 feet. It has hit that mark only a handful of times since the Hoover Dam was finished in the 1930s, but it always recovered shortly after. It may not this time, at least not any time soon.

The US Bureau of Reclamation (USBR) forecasts the lake’s levels to continue to decline, without any sign of recovery through at least the end of 2022. If the next major study in August from the USBR projects water levels in the lake will be below 1,075 feet on January 1, it would trigger the first-ever shortage declaration on the Colorado River, meaning some communities would begin to see their water deliveries cut significantly next year.

Lake Mead and nearby Lake Powell — the two largest reservoirs on the Colorado River — have drained at an alarming rate. Lake Mead has fallen more than 139 feet since January of 2000.

Lake Mead is currently 16 feet below where it was this time last year and the reservoir is only 37% full, while Lake Powell is down 35 feet from last year and sits at just 34% of the lake’s total capacity.

The Colorado River, which supplies water to more than 40 million people and irrigates millions of acres of farmland, has seen its supply sapped by drought and climate change.

The significance of the dwindling supplies in both reservoirs cannot be overstated. Water flowing down the Colorado River fills the two reservoirs, which are part of a river system that supplies over 40 million people living across seven Western states and Mexico.

A drought that has persisted for two decades has left the much of the Western US parched.

In addition to dwindling snowpack, which provides most of the river’s water supply, experts say dry, thirsty soils across the basin are soaking up meltwater, meaning that less makes it into the river system.

“It’s a pretty awful year,” said Ted Cooke, the general manager of the Central Arizona Project, a massive, 336-mile canal and pipeline system that carries Colorado River water to Phoenix, Tucson and farms and towns in between. “Last year wasn’t so bad as far as the snowpack went, but with the higher temperatures and drier soils that we’re still experiencing this year, we’re seeing even less runoff that actually makes it into the waterways and in the reservoirs.”

Climate change is also taking a toll on the river’s water supply. A study by US Geological Survey scientists published in 2020 found that the Colorado River’s flow has declined by about 20% over the last century, and over half of that decline can be attributed to warming temperatures across the basin.

Who would the shortage affect?

With the level of Lake Mead dipping below 1,075 feet on Tuesday and forecast to drop further, it is nearly certain that the Bureau of Reclamation will declare a Tier 1 shortage later this summer.

If a Tier 1 shortage is declared, Colorado River water deliveries would be reduced for Arizona and Nevada as soon as next year, based on the terms of the 2019 drought contingency plan signed by the lower Colorado River basin states.

The looming water cuts will have the greatest impact in Arizona.

As part of the lower basin’s drought contingency plan, the Central Arizona Project would see its water supply slashed by about one third in 2022 due to its junior rights to the river’s water.

While Arizona’s main population centers will be spared, the effects of those water cuts will be felt most acutely on farms in central Arizona, due to their lower priority status in a complex tier system used to determine who loses water first in the event of a shortage.

California’s water deliveries would not be impacted in a Tier 1 shortage, according to the drought contingency plan.

Water officials in Arizona say that while the falling water levels and future projections are concerning, the state is prepared to absorb the cuts.

“We’re concerned … but we’ve allowed for something like this to happen, and as a matter of fact, keep on happening,” Cooke said. “Hopefully it doesn’t but if it does, we’re prepared.”

Sorry … hope and prayer is not a contingency plan, Mr. Cooke. You better have more than that in your toolbox.

What happens if Lake Mead sinks further?

In the event of a Tier 2 shortage — which the USBR projects could happen as soon as late 2022 — the cuts would impact some cities and tribes in Arizona that receive water from the Central Arizona Project canal.

“I’m definitely concerned that the raw projections continue to go downward and that we are heading towards potentially a Tier 2 [shortage] in 2023,” said Tom Buschatzke, director of the Arizona Department of Water Resources.

Joanna Allhands at the Arizona Republic adds, Lake Mead could be in a Tier 2 shortage by 2023. What’s that mean for Arizona?

If the forecast holds, it’s now likely that we will fall into a more severe Tier 2 shortage by 2023, spreading painful cuts to even more water users in Arizona.

That nugget of bad news comes from the U.S. Bureau of Reclamation’s 24-month study, which is updated each month to predict reservoir conditions for the next two years. In April, the projection was that Lake Mead – the reservoir that provides nearly 40% of Arizona’s water – would most certainly be in a Tier 1 shortage in 2022 but would miss the Tier 2 cutoff for 2023 by three-tenths of a foot.

Now, in May, the most likely projection is that Lake Mead will end 2022 at 1,048.83 feet of elevation – more than a foot past the trigger to put us in Tier 2.

[I]t’s worth noting that if we didn’t have the Drought Contingency Plan (DCP) in place to conserve water, we would already be in this shape. That agreement didn’t solve our problems, but it has bought us time and certainty as deeper cuts play out – which is exactly what it was intended to do.

That said, we’re still hot and dry, with more than half of the Colorado River basin now in extreme drought, the most severe category. Unless that trajectory changes, the forecast is probably not going to get much better.

And, even worse, we’re getting down into the V-shaped part of Lake Mead, meaning it takes a loss of less water to drop lake levels than it once did. Losing smaller volumes of water can have bigger impacts.

Which is why there’s also a 1 in 4 chance that we could fall into a Tier 3 shortage by 2025 – the worst-case scenario spelled out under DCP and one that would much more heavily impact metro Phoenix cities.

[W]e’re also less than 20 feet from triggering what might be called the doomsday provision within DCP.

If the lake is projected to fall below 1,030 feet any time within two years, Arizona, California and Nevada must reconvene to decide what additional steps they will take to keep Mead from falling below 1,020 feet – an elevation that many consider the crash point. The next milestone below that is “dead pool,” where no water leaves the lake.

And that provision is triggered by any part of the forecast – not just the maximum or most probable scenario, but the minimum probable scenario, too.

It’s anyone’s guess what will happen then.

Mark Twain said, “Whiskey is for drinking—water is for fighting.”