It has been the wettest November on record for Southland cities like Van Nuys and San Luis Obispo. Santa Barbara has received a whopping 10 inches of rain since Oct. 1, marking the city’s wettest start to the water year on record.
According to the Department of Water Resources, the state is totaling 186% of average rainfall so far this water year.
But experts say that despite the promising start, it’s still too early to say what the rest of California’s traditional rainy season will look like.
“The total impact on our water supply is yet to be determined [to be determined] is the best way to put it,” said Jeff Mount, senior fellow at the Public Policy Institute of California’s Water Policy Center. “We haven’t even really entered the wet season yet.”
California receives most of its rain and snow between December and March, trapping runoff in reservoirs and storing it during the hot, dry seasons that follow.
(Robert Gauthier/Los Angeles Times)
Those large reservoirs are now filled to 100% to 145% of the average for this date. That’s not just because of the recent storms — early-season rain tends to soak into parched soil — but also because California is building on three previous wet winters, said state climatologist Michael Anderson.
A record-breaking wet winter of 2022-2023 ended the state’s driest three-year spell on record. That was followed by two years that were wetter than average for Northern California, but drier than average for the southern half, amounting to about average precipitation across the state.
According to the latest U.S. Drought Monitor report, issued last week before the last of the recent storms had completely soaked the state, more than 70% of California was drought-free, up from 49% a week earlier. Nearly 47% of Los Angeles County has experienced moderate drought, while other parts improved to abnormally dry, the map shows. Abnormally dry conditions also ended in Ventura, Santa Barbara and San Luis Obispo counties and much of Kern County, along with parts of Central California, according to the map. Conditions improved in the far south and southeast of the state, but still ranged from abnormally dry to moderate drought, the map shows.
The early season storms will play an important role in preparing watersheds for the rest of the winter, experts say. By watering the soil, they make it easier for future rains to enter reservoirs and for snow to accumulate in the Sierra Nevada.
“By building snowpack on hydrated watersheds, we can avoid losing potential spring runoff to dry lands later in the season,” Anderson wrote in an email.
Snowpack is critical to sustaining California during the hot, dry seasons because it enters waterways as it melts, replenishing reservoirs and providing at least 30% of the state’s water supply, said Andrew Schwartz, director of UC Berkeley’s Central Sierra Snow Lab.
The research station at Donner Pass has recorded 2 feet of snow. While that’s about 89% of normal for this date, warmer temperatures mean much of it has already melted, Schwartz said. The snow water equivalent, which measures how much water the snow would produce if it were to melt, now stands at 50%, he said.
“That’s really something that tells the story of this season so far,” he said. “We’ve had a lot of rain in the Sierra, but not as much snowfall as we would normally hope for so far.”
This dynamic has become increasingly common with climate change, Schwartz said. The snow often forms later in the season and melts earlier, and more precipitation falls in the form of rain, he said. Because reservoirs must leave some room in the winter to limit flooding, they aren’t always able to accommodate all this poorly timed runoff, he said.
And the sooner the snow melts, the more time plants and soils have to dry out in the summer heat, preparing the landscape for major wildfires, Schwartz said. Although Northern California has been spared from massive fires in recent seasons, Schwartz fears that luck could run out if the region doesn’t get at least an average amount of snow this year.
For now, long-range forecasts call for equal chances of wet and dry conditions this winter, Mount said. What happens in the coming months will be crucial. California depends on just a few strong atmospheric river storms to provide moisture; Just five to seven could ultimately be responsible for more than half the year’s water supply, he said.
“We live on the edge all the time,” he says. “A handful of storms makes the difference whether we have a dry year or a wet year.”
Although the state’s drought picture has currently improved, scientists warn that conditions in the West are becoming increasingly hotter and drier due to the burning of fossil fuels and resulting climate change. In addition to importing water from Northern California via the Sacramento-San Joaquin River Delta, Southern California depends on water from the Colorado River. There is still a shortage of this waterway and the largest reservoir is only about one-third full.
Additionally, research has shown that as the planet has warmed, the atmosphere has become thirstier, sucking more moisture from plants and soils and ensuring dry years are drier. At the same time, there is healthy debate about whether the same phenomenon also makes wet periods wetter, because warmer air can hold more moisture, potentially leading to storms.
As a result, swings between wet and dry appear to be widening from year to year — and even within a year — in California and elsewhere, Mount said. That increase in uncertainty has made water supply management more difficult overall, he said.
Still, California has a lot of experience dealing with such extremes because of its climate, says Jay Lund, professor emeritus of civil and environmental engineering at UC Davis.
“We must always prepare for floods and prepare for drought, no matter how wet or dry it is.”
Times staff writer Ian James contributed to this report.
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