As forecasts tease California with rainstorms this week, the state鈥檚 reservoirs are already flush with water.
It鈥檚 a big departure from a year ago: The state鈥檚 major reservoirs 鈥� which store water collected mostly from rivers in the northern portion of the state 鈥� are in good shape, with levels at . In late 2022, lined lakes that had collectively dipped to about two-thirds of average 鈥� until heavy winter storms in January filled many of them almost to the brim.
Yet healthy water levels don鈥檛 mean California鈥檚 reservoirs are full. Most of California鈥檚 large reservoirs are operated for flood control as well as water storage, with space kept empty to rein in winter storm runoff.
The wet season has arrived in California, with El Ni帽o conditions . But for the Golden State, with its unpredictable swings from dry to wet and back again, El Ni帽o doesn鈥檛 guarantee heavy rainfall.
And as California鈥檚 water managers plan for the water year ahead, they鈥檙e faced, as always, with their dueling responsibilities: forestalling floods while preparing for possible scarcity in a state where water supplies are often stretched thin and long droughts are common.
When state climatologist Michael Anderson looks into California鈥檚 water year ahead, he says the crystal ball is cloudy.
A murky forecast, both near and far
Threats of a major storm dissolved into showers in parts of California this week, with . Rainfall is only expected to reach 1 to 2 inches statewide through Saturday morning, with light snowfall predicted in the Sierra Nevada mountains at higher elevations.
鈥淥verall this is looking to be a beneficial rainfall event for Southern California, which is definitely welcome during the typical peak of our fire season,鈥� the National Weather Service office for San Diego reported earlier this week.
Some headlines heralded it as the first storm of many as El Ni帽o continues to strengthen and intensify. Characterized , El Ni帽o is .
But in California, the connection is more tenuous. Of seven El Ni帽o events over the past 23 years, Anderson said, two have been dry, three have been roughly average and two have been wet. One recent study reported that El Ni帽o accounts for only about 25% of the .
鈥淲hat that tells me is anything goes,鈥� Anderson said. 鈥淓l Ni帽o by itself doesn鈥檛 define our water year.鈥�
In fact, the year is actually off to a drier start: Statewide, California has since this water year began Oct. 1.
鈥淲hat that tells me is anything goes. El Ni帽o by itself doesn鈥檛 define our water year.鈥�MICHAEL ANDERSON, STATE CLIMATOLOGIST
Marty Ralph, director of the Center for Western Weather and Water Extremes at UC San Diego, suspects that it鈥檚 that will determine whether El Ni帽o will bring a firehose or a trickle to California.
It鈥檚 like you鈥檙e playing poker, and you鈥檝e got a good hand 鈥� that鈥檚 El Ni帽o for us. But we haven鈥檛 finished the round of the game, and we still have to draw a couple cards,鈥� Ralph said. 鈥淏ut we might not draw the good cards.鈥�
Waste not, want not?
With seasonal outlooks unable to whether a winter will be wet or dry, water managers must plan for both.
Fortunately there鈥檚 some wiggle room this year, according to Jeanine Jones, the Department of Water Resources鈥� interstate resources manager. Last year鈥檚 filled the state鈥檚 reservoirs enough that even if this rainy season leans dry, she said, 鈥淲e鈥檙e going into next year with a cushion, which is always good.鈥�
That doesn鈥檛 mean the reservoirs are full, though. Lake Oroville 鈥� the , which sends water south to farms and cities 鈥� and Lake Shasta 鈥� critical to growers and other water users reliant on the 鈥� are .
That鈥檚 because with reservoirs that serve the , water managers must to wrangle possible floods during the wet season, Jones said.
The water that flows into rivers and streams and out to the ocean . But waste is in the eye of the beholder, said Jay Lund, vice-director of the Center for Watershed Sciences at UC Davis.
鈥淲ater that鈥檚 鈥榳asted鈥� is always water used by somebody else,鈥� Lund said.
The list of benefits for fishing, conservation, Delta farmers, water quality and healthy shorelines . Water allowed to flow out into the San Francisco Bay, for instance, washes away salts and pollutants, transports sediment and sand necessary to maintain marshes and restore eroding beaches, assists salmon in migrations and helps maintain healthy ecosystems.
Still, the Public Policy Institute of California reports that California water last year, had there been better ways to ferry water from full rivers to groundwater recharge sites, and better coordination among landowners, local agencies, and others.
鈥淚 tend to think that there is room for capturing more surface water 鈥� if you could afford the cost of capturing it,鈥� agreed Lund. 鈥淭hat, to me, is the biggest problem.鈥�
The , for instance, is projected to cost more than $4.4 billion. The reservoir, planned in the western Sacramento Valley, would store as much as 1.5 million acre-feet of , alarming environmental groups that say drawing more water from the river will imperil its already-struggling fish.
鈥淚 tend to think that there is room for capturing more surface water 鈥� if you could afford the cost of capturing it. That, to me, is the biggest problem.鈥�JAY LUND, CENTER FOR WATERSHED SCIENCES AT UC DAVIS
, Gov. Gavin Newsom cleared the project to be fast-tracked 鈥渢o the extent feasible鈥� through any litigation challenging it under the landmark California Environmental Quality Act. That move was . Even so, the project is not expected to be .
In the meantime, researchers like UC San Diego鈥檚 Ralph, along with local, state and federal agencies, hope to operate the state鈥檚 reservoirs more nimbly by incorporating new weather forecasting tools into decades-old rulebooks governing when to hold onto water and when to release it.
The program allowed the Russian River watershed to hold onto about 7,000 to 8,000 acre-feet more water in Lake Mendocino this past year, and an additional 19,000 acre-feet more in Lake Sonoma, according to Donald Seymour, deputy director of engineering with Sonoma Water. The Department of Water Resources announced that it is expanding , as well.
Many are looking down rather than up for opportunities to store more water. The Department of Water Resources estimates that was captured through groundwater recharge by last summer.
The Southern California water import giant, the Metropolitan Water District, also recently announced a $211 million groundwater bank in the Antelope Valley. The bank can store , enough to fill Castaic Lake, . Though construction to allow withdrawals hasn鈥檛 been completed yet, the bank stands ready to accept deposits.
The bank is aimed at providing a little more net for the tightrope walk that California鈥檚 water managers start anew every water year.
鈥淲e always plan for it to be potentially very dry, or very wet,鈥� said Brad Coffey, Metropolitan鈥檚 water resources manager. 鈥淣o matter what kind of year we had this year.鈥�
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