A recent barrage of winter storms has helped rescue much of California from years of drought, but the state is bracing for possible floods and continued groundwater shortages in the months ahead.
At this time last year, the entire Golden State was coping with drought. Now nearly 64 percent of it is drought-free, after a series of “atmospheric rivers” inundated much of the region with rainfall and heaped piles of snow across the Sierra Nevada mountain range this season.
The improvements have been so drastic that the Metropolitan Water District of Southern California even moved this week to rescind all water use restrictions.
“The abnormally wet winter will further improve drought across much of the western U.S. as the snowpack melts in the coming months,” the National Oceanic and Atmospheric Administration (NOAA) declared in its Spring Outlook this week.
These circumstances have “wiped out exceptional and extreme drought in California for the first time since 2020,” with further progress anticipated this spring, the agency added.
But with such an influx of water also come many challenges — including the risk of dangerous floods, as well as a need to improve methods for filling up depleted groundwater reservoirs.
“Coming out of a drought and having this much snowpack in the mountains and a threat of floods, clearly there is a big interest in squirreling away as much of this water as we can,” Thomas Harter, a professor of water resources at University of California, Davis, told The Hill.
Snowmelt this spring could lead to “welcomed water supply benefits” in much of California and the Great Basin, while helping boost key Colorado River reservoirs, according to NOAA.
Yet floods have already begun to bombard the U.S. West — conditions that will likely worsen this spring, as Sierra Nevada snowpack melts on already saturated soil, according to NOAA.
“California’s historic snowpack, coupled with spring rain, is heightening the potential for spring floods,” Ed Clark, director of NOAA’s National Water Center, said in a statement.
And it’s not just California that could be facing floods. Clark said that “approximately 44 percent of the U.S. is at risk for flooding this spring.”
Most of the eastern half of the continental U.S. will experience some flood risk in the coming months, with moderate to major flooding along the Mississippi River, according to NOAA.
In California, there are two specific regions currently experiencing significant floods: the Salinas Valley and the southern Sierra Nevadas, according to University of California, Los Angeles climate scientist Daniel Swain.
The Salinas Valley, where rainfall recently ruptured a levee on the Pajaro River, is among the most productive agricultural areas in the state.
“This has been really disruptive in these communities and will have significant impacts on agriculture coming out of the Salinas Valley probably for a while,” Swain said during virtual office hours on Friday.
Meanwhile, a prolonged period of lower-elevation snowmelt in the southern Sierra Nevadas has filled the area’s small reservoirs to capacity, meaning that “they’re spilling water essentially as fast as it comes in,” according to Swain.
He warned that this water is spilling into the foothills, especially into the San Joaquin Valley, another important agricultural region that neighbors the Salinas Valley.
“This is not going to be over the next few days. This is likely going to persist and potentially get worse in the weeks to come,” Swain said.
During that time, this winter’s massive amount of precipitation will also be challenging the state to optimize its storage capabilities — particularly as groundwater stockpiles remain low.
Harter, from UC Davis, described “a spatial disconnect” between the mountain locations where most of the precipitation occurs and the valley floors where most water users are located.
“Most of the water falls in the winter and we really need most of it in the summer, and so we have a time disconnect,” he said.
Effective storage and conveyance mechanisms are therefore critical to bridge these gaps, according to Harter.
He described three types of natural storage that can refill in one season: snowpack, surface water reservoirs and soil moisture.
But the fourth type of storage, groundwater reservoirs, requires much more time to fill, the professor explained.
“We need at least one average or wet year to make up for what we’re pulling out of groundwater extra in a dry year,” Harter said.
Over the past 25 years, he continued, there have been nine average or wet years and 16 dry years — creating a budgetary imbalance.
Stressing that it is possible, however, to accelerate the groundwater recharge process, Harter credited California’s government for recently pushing forward a variety of related policies.
Earlier this month, for example, the California State Water Board approved a petition from the federal Bureau of Reclamation to divert more than 600,000 acre-feet of San Joaquin River floodwaters for storage, recharge and wildlife refuges.
“We need to increase the amount of charge,” Harter said. “It’s like a bank account. You either increase the amount of earnings, or you decrease the amount of outlays from your account.”
California may need to prepare itself to inject even more into that account, as a three-year La Niña streak concludes and El Niño conditions begin to take shape this summer, according to the NOAA Spring Outlook.
El Niño typically brings hotter and drier conditions to the northern U.S. and Canada and increased flooding in the Gulf Coast, the Southeast and parts of California, according to NOAA’s National Ocean Service.
In line with these patterns, the NOAA Spring Outlook predicted ongoing extreme to exceptional drought across portions of the southern High Plains, the Northwest U.S. and the northern Rocky Mountains, as well as in parts of New Mexico and Washington state.
“There is right now a pretty strong prediction that we are headed for an El Niño territory,” said Swain, describing a “sudden shift” from cold to “very warm” temperatures in the eastern Pacific.
“From late 2023 into 2024, I would expect global average temperatures to be really on the highest end of what we’ve seen historically, if not above that,” he added.
Stressing that it is still early to speculate as to what this means for California, Swain said that a strong El Niño event could come with another “very active wet winter next year.”
While years of record-breaking drought are currently providing “a bit of a buffer from a flood risk perspective,” there would be no such barrier during next year, he explained.
“We are going to have the legacy of this year’s very wet conditions and especially the very heavy snowpack, probably all the way through the summer,” Swain said.
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