As California’s 2022 water year ended this week, the parched state is bracing for another dry year — its fourth in a row.
So far in California’s recorded history, six previous droughts have lasted four or more years, including two in the past 35 years.
Despite some rain in September, weather watchers expect a warm, dry fall and warn that this winter could bring warm temperatures and below-average rainfall.
According to Daniel Swain, a climatologist at UCLA and The Nature Conservancy, the conditions are shaping up to be a “recipe for drought”: a La Niña climate pattern plus warm temperatures in the western tropical Pacific that could mean rains and storms of snow reviews are lacking in California. .
Swain said California’s fate will depend on exactly how the storm’s track moves, and seasonal forecasts are inherently uncertain. Even so, “I would still put my money dry, even in the northern third of the state,” he said. “It’s not a guarantee. But if you were to see 50 winters like this, most of them would be dry.
Until August, no other three-year period in California’s history was so dry, even during the last historic drought from 2012 to 2016.
“Where did the last drought end? What is the bigger question,” said John Abatzoglou, professor of climatology at UC Merced. “We basically have droughts that are interrupted by wet periods.”
California has experienced long droughts before, including two seven-year droughts that began in the late 1920s and 1940s. A more recent one lasted six years, from 1987 to 1992.
“To get those kinds of years, we have to go back to the late 1920s and the 1930s, which were the Dust Bowl years,” said California state climatologist Michael Anderson. It has had far more dry than wet years since the turn of the millennium. “If you look at the 21st century, we really only have a handful of wet years to work with.”
It’s not just the lack of rain and snow. Warmer temperatures are also worsening California droughts. January through August is California’s fifth hottest year yet, following the hottest 2021 summer on record.
“One thing that unfortunately becomes easier to anticipate is warmer than average conditions due to climate change,” Swain said.
The heat helps to make the atmosphere, plants, and soils thirstier, which increases demand and reduces runoff that flows into reservoirs. “It takes what was once a really rotten rainfall drought, the worst in the instrumental record, and makes it an even worse drought,” Abatzoglou said.
Will it rain this winter?
What the coming year of water, which begins on October 1, will bring is still relevant. But La Niña conditions are very likely to continue at least through the fall, with an 80% chance of persisting through January, for a third consecutive year.
A “three-round” La Niña is rare: it has only happened twice since records began. La Niña occurs when ocean temperatures in the eastern tropical Pacific are below normal, which can alter the path of storms on which California depends.
“Seeing things we’ve never seen before is very much on the table,” said John Yarbrough, deputy deputy director of the State Water Project, which delivers water from Northern California to 27 million people and 750,000 acres of farmland.
Often, La Niña means drier conditions in Southern California, but effects on Northern California’s watersheds, critical to the state’s water supply, can be harder to predict, Julie says. Kalansky, deputy director of the Center for Western Weather and Water Extremes at the Scripps Institution of Oceanography.
“Each year is such a unique story for water, which makes California exciting, but it’s also hard to predict and tell what’s next,” Kalansky said.
What will ultimately shape the next hydrological year is the number of storms called atmospheric rivers that make landfall and the amount of precipitation they release. Timing will also be important, Anderson said: When rain and snow fall can affect how much of California’s precious snow rushes into reservoirs or soaks into the ground.
“From a water management perspective, we are aware that it could very well be dry,” Yarbrough said. “At the same time, we have to be aware that it could be very wet and you could have flooding. Both are still possible.
Dry spells punctuated by wet years are part of “California’s history,” Abazoglou said. “But obviously the last decade has shifted the balance towards more droughts.”
What about snow in winter?
Snow is also difficult to predict for the coming year.
“It’s definitely more of a guessing game. You’re just crossing your fingers and hoping,” said Michael Reitzell, president of Ski California, a trade association representing Nevada and California resorts.
It’s been a strange year for the ski industry, he said – marked first by wildfires that damaged the Sierra-at-Tahoe resort, then by extreme snowstorms in late December. which forced some stations to close.
“During the holiday period, some stations lost full days that would have been huge days of huge revenue,” Reitzell said. “It certainly puts a punch in things.”
This year’s snowfall measured 38 percent of the state average, at a time when it should have been deepest on April 1. It was the worst snowfall in seven years and the sixth-lowest April measurement in state history. The 2015 snowpack was the lowest on record.
The measure followed a record dry spell from January to March, with warm temperatures causing an early season melt. It’s hard to recover from this kind of early melt, said Andrew Schwartz, a senior scientist and station manager at the University of California, Berkeley’s Central Sierra Snow Lab..
“Our soils dry out and absorb any additional rain or snow that comes in, so it doesn’t get into our reservoirs. And then we get these mass forest kills and the resulting wildfires,” Schwartz said.
He agreed that it’s hard to say what La Niña will mean for the Sierra Nevada this winter. He said “absolutely massive snow years” occurred during La Niña years.
“But we also had some of the worst years on record here. So La Niña doesn’t seem to play too big of a role here, because traditionally it doesn’t,” he said. “That being said, I expect drier and warmer than average conditions.”
A deep water deficit
California enters next year with water deficit unlikely to recover with average rainfall year.
Groundwater levels in nearly two-thirds of the assessed wells fell below average, and by the end of August reservoir storage had reached 69% of normal for the date. This is an improvement on last year, when reservoir levels were down to just 60% of average by that date.
But the reservoirs are still not where they should be. “We’re still way below average, still way below where we’d like to be,” Yarbrough said.
Lake Oroville, at 1.24 million acre-feet, remains below the 1.6 million acre-feet threshold that managers would like to see by the end of the year before considering exports . Last year, deliveries from the State Water Project dipped to 5% of supplies requested in March.
Initial water allocations are expected to be announced Dec. 1, and Yarbrough wouldn’t say what they were likely to be. Still, he said, “Expect him to be at the bottom of the scale.”
The U.S. Bureau of Reclamation, which manages the Central Valley project, also wouldn’t say how much water its beneficiaries, including Central Valley growers, can expect next year. That announcement will come in February, spokeswoman Mary Lee Knecht said.
But Ryan Jacobsen, CEO of the Fresno County Farm Bureau, doesn’t expect the news to be good.
“We find ourselves this year with such a significant decline over the previous three years that even an average year is very likely going to mean poor allocations to farmers here in the Valley,” he said.
Jacobsen said local growers have already reduced plantings for fall and winter crops. He expects more fields to go fallow as farmers decide not to plant annual crops like tomatoes, melons and maize in order to preserve their scarce water reserves for permanent crops like walnuts. and grapes.
One source of California’s water supply is in even worse condition than in previous droughts: the Colorado River, which remained a reliable source of water supply even during the 2012-2016 California drought. This time, the river’s huge reservoirs have reached historic lows.
“The Colorado River system is in deep crisis,” said Alex Hall, professor of atmospheric and oceanic sciences at UCLA. “That means Southern California is in a tougher position than in the past.”
Southern California’s water-importing giant, the Metropolitan Water District, last spring imposed unprecedented outdoor watering restrictions for the 6 million people in its vast service area who rely on state supplies. Water Project dried up. In the past three years, the Water District has received its lowest total deliveries from reservoirs in Northern California.
Now the water importer is weighing how potential future reductions on the Colorado River could affect the rest of its customers as California, Arizona and Nevada reach a deal to conserve river water, Demetri said. Polyzos, Metropolitan Resource Planning Manager.
“People say, ‘Hey, we’ve been through this before. California is used to droughts,'” Polyzos said. But we see these things getting worse and worse and harder and harder to deal with. »
What is becoming increasingly clear is that the nature of drought in the West shifts from plural to singular as it lasts for long periods punctuated by brief periods of wet years.
“The idea of drought as something temporary and transient is changing,” Swain said. “We should think more about long-term aridification.”
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