With snowpack levels in the Sierra Nevada registering at 90% of normal Thursday and state reservoirs at record historic levels, the urban water supply picture for 2020 could hardly be any rosier.

Southern California water managers are trying to restrain their joy, not because of a picture-postcard mountain top, but for the bounty that will come in spring when the snow melts, sending pristine water into state reservoirs and more importantly, southward via the State Water Project aqueduct, a source that supplies 30% of Southern California’s drinking water.

Once that happens, local ground water managers will take a portion to restore overpumped basins still low from the five-year drought that ended in 2016, water managers say. And Metropolitan Water District of Southern California, the largest wholesaler of water in the nation, says it will be there to facilitate that water transfer as long as its member agencies can pay for the purchases.

“We are going into this year with 3.1 million acre-feet of storage — water in the bank. That is the highest storage level we’ve ever had,” said Demetri Polyzos, MWD resource planning team manager on Thursday, Jan. 2. (One acre foot equals 326,000 gallons, about as much as a Southern California family uses in a year).

MWD cannot take any more water at its Diamond Valley Lake Reservoir in Hemet, which sit 98% full as of Jan. 2. Instead, it wants to supply basins in Los Angeles, San Bernardino, Orange and Riverside counties with extra storage.

“We are here to provide supplemental water to the region. We certainly have the supplies,” Polyzos said.

Other MWD reservoirs are also filling up: Lake Mathews in Riverside County is 84% full; Lake Skinner in western Riverside County, 87%; Castaic Lake in northern Los Angeles County, 79%.

Major state reservoirs are doing even better: Shasta Lake, the state’s largest reservoir, near Redding, is currently 73% full, or 117% of normal. Lake Oroville, in Butte County, is currently 59% full, or 96% of normal. New Melones Lake, in the Sierra Foothills of Calaveras and Tuolumne counties, is 83% full, or 143% of its historic average. And San Luis Reservoir, near Los Banos, is 63% full, or 96% of its historical average.

As of Thursday, the statewide Sierra Nevada snowpack stood at 90% of its historical average — the highest total in early January in four years, when it came in at 101% on Jan. 2, 2016.

“It’s a good start,” said Chris Orrock, a spokesman for the state Department of Water Resources. “It’s better than it was last year. But it’s still early. We’re cautiously optimistic.”

Last year on Jan. 2, the statewide snowpack was just 69% of normal.

Officials from the state Department of Water Resources conducted their first Sierra Nevada snowpack survey of the season, with the media in tow, at Phillips Station along Highway 50 near Sierra-at-Tahoe ski resort in El Dorado County.

At that location, the snow was 33 inches deep. Its water content was 97% of the historical average for early January. Readings at that site date back to 1941.

How much snow falls every winter is critical to California’s water picture because this vast, “frozen reservoir” over a 400-mile long Sierra mountain range is the source of one-third of the state’s supply for cities and farms as it slowly melts in the spring and summer months. The melt sends billions of gallons of clean, fresh water flowing down dozens of rivers and streams into reservoirs.

It also is key to the state’s ski industry, which suffered significantly during the 2012-16 drought. That drought was broken by the drenching winter of 2016-17. But ever since then, water officials have nervously monitored weather patterns, hopeful that drought conditions don’t re-emerge any time soon.

State water officials said their reservoir levels registered in the teens during the drought. But the last two years of snow and rain radically changed the picture. “Our reservoir levels are good right now; the majority are at or above historic averages,” Orrock said.

The precipitation of last year helped the Chino Basin add water to a thirsty basin from September through December of 2019, said Peter Kavounas, general manager. “And when you have more snowpack up north, we’ll have more water to import. It helps us better manage our ground-water basin,” he said Thursday.

Water allocations from the state aqueduct reached 75% in 2019. That has been reset to 10% on Thursday by a conservative Department of Water Resources. However, both Kavounas and Polyzos said they expect allocations to increase very soon. But local managers may wait for more local rain and snow before buying more expensive water from northern California, Polyzos said.

Metropolitan estimates a need of 1.5 million acre feet of water in 2020 for its 19 million customers in Southern California, a number that has gone down due to conservation practices in Southern California, he said. The agency will import about 1 million acre-feet from the Colorado River, needing only 500,000 acre-feet from the SWP, an amount expected with only a 35% allocation rate. “That is very achievable,” he said.

However, state water officials warn that climate change is expected to shrink the Sierra snowpack in the coming decades as temperatures continue to warm. With massive wildfires and heat waves crippling Australia this week, the issue has gained new visibility.

Orrock says the long-term forecast is for drier conditions in the state in the coming weeks, due to a high-pressure zone off west coast that could stick around for several weeks.

“We still need to see how the rest of the rainy season plays out. We may not get a significant storm the rest of this year,” he said.

Can the wet weather continue into January and February? That is something that worries state water managers.

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Ambitious restoration project returns Bee Flat Canyon to its natural beauty “This is the first of our big three months — December, January and February — when we expect half of our annual precipitation,” said Michael Anderson, California’s state climatologist. “The first one has done well. Two to go.”

Meanwhile, rainfall totals in parts of the state are mediocre. In the Bay Area, for example, San Francisco has received 6.3 inches of rain, or 71% of its historic average for this date. San Jose is at 62% and Oakland is at 54%. Southern California is faring better, with rainfall in Los Angeles at 168% of normal for early January and San Diego at 212%.

California’s historic drought of 2012-16 may be over. But it’s legacy lives on. Because of a law that former Gov. Jerry Brown signed, local water officials in the areas with the most heavily over-pumped groundwater basins are required to submit plans to the state by the end of this month spelling out how they will replenish them.

“Be prepared for anything,” Anderson said. “A single atmospheric river storm can bring a fantastic amount of water in a very short time and change conditions in a hurry.”

Bay Area News Group reporter Paul Rogers contributed to this story