California's water outlook for 2025 starts off positive.
The statewide snowpack within the Sierra Nevada – which provides nearly a 3rd of California's water supply – was 108% of its historic Jan. 2 average on Thursday, following a series of atmospheric river storms within the northern a part of the state in late November and mid-year. December, which increased the quantity of snow and provided nice conditions for skiers.
California's reservoirs are also in higher condition than normal after heavy rain and snow last 12 months and in 2023. As of Thursday, the state's major reservoirs were at 121% of their historic average capability from early January.
California's winter snow and rain season, which usually ends in early April, continues for about three months. Droughts could bring rainfall to a halt, experts noted Thursday.
“We're feeling good today, but we have more storms to come,” said Andy Reising, chief of the snow surveys and water supply forecast division for the state Department of Water Resources.
Reising noted that January snow levels don't at all times indicate how winter will end. Last 12 months, the statewide snowpack within the Sierra was at 28% of normal on January 2nd, but by April 1st it had increased to 111%. Conversely, in 2022, the snowpack was 150% of average on January 2nd, but after that precipitation virtually stopped, in order that on April 1st the snowpack was only 37%.
But this 12 months's reservoir levels combined with a healthy snowpack make water shortages this summer seem unlikely in most cities across the state.
Shasta, the state's largest reservoir, near Redding, was 77% full Thursday, while the second largest – Oroville in Butte County – was 68% full and San Luis Reservoir east of Gilroy was 69% full. To the south, Diamond Valley, a big downstream reservoir in Riverside County that’s critical to water supplies in Los Angeles and surrounding cities, was 97% full.
Of particular note this 12 months is the dramatic difference in precipitation between Northern California and Southern California.
The Northern Sierra snowpack was 161% of its historical average on Thursday. The Central Sierra snowpack was 94%. But the Southern Sierra was only 75% of average.
“Above the I-80 corridor we got a lot of snow with these atmospheric rivers, but it's getting less and less as we move south,” Reising said.
The rainfall amounts are much more dramatic.
Since October 1, San Francisco has received 10.2 inches of rain, or 121% of normal. But Los Angeles received virtually none in any respect throughout the same period — just 0.16 inches — or 4% of the historical average. Sunny, hot conditions kept fire danger high across Southern California over Christmas and New Year's, although Northern California's fire season almost ended around Thanksgiving when heavy rains drenched the bottom and vegetation.
Historically, Northern California gets more rain than Southern California, which is why nearly the entire state's largest reservoirs were in-built the north, said Jay Lund, associate director of the Center for Watershed Sciences at UC Davis. Much of this water is transported south to towns and farms by the large canal and pump systems of the State Water Project and the Central Valley Project.
“So far this year has been very unusual,” Lund said. “The north is unusually wet and the south is very unusually dry.”
From a statewide water perspective, Lund said if one a part of the state must be dry, it's higher if it's the south.
Aside from moderate rain and snow on Friday, mostly dry conditions are forecast across the state for the subsequent two weeks.
“Extreme swings between dry and wet conditions continue to occur this winter,” said Karla Nemeth, director of the state Department of Water Resources. “If the last few years are any indication, anything could happen by April and we need to be prepared.”
California has faced three severe droughts within the last generation: from 2007 to 2009, then from 2012 to 2016 and most recently from 2020 to 2022. Scientists say that climate warming is making droughts worse, temperatures are rising and the danger of fires is increasing. However, when large atmospheric river storms blow in from the Pacific Ocean, warmer temperatures may cause them to evaporate more water, often resulting in large snowstorms and flooding risks, triggering “weather whiplash” for California and other western states.
Many experts say that given this shift, the state must do more to conserve water during wet years to cut back the severity of water shortages during droughts. Gov. Gavin Newsom is pushing for construction of Sites Reservoir, a $4.5 billion off-stream reservoir in rural Colusa County north of Davis that will be in-built distant ranching areas and draw some water from the Sacramento River in wet years derives to store it in a dry place for years.
The project, backed by President Biden and each California senators, has secured most of its funding and survived two lawsuits from environmental groups that say it could harm fish within the Sacramento-San Joaquin River Delta. Before construction can begin, there may be one final hurdle that have to be cleared – obtaining water rights from the State Water Resources Control Board this 12 months.
Originally published:
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