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North Coast breathing easier after recent rains, but reservoirs still historically low

The recent storm provided a respite, but reservoir levels remain historically low.|

Last week’s surprisingly generous storm and several smaller rain systems expected this week are allowing water managers, ranchers and farmers around the region to breathe a sigh of relief.

Abundant rainfall has raised creeks and rivers, filled some storage ponds and provided flexibility to shift to greater reliance on surface water for a spell, reducing the pressure to lean so heavily on groundwater wells in some places.

It also filled smaller storage ponds and has started a new greening of the landscape in pastures that had been grazed down to cracked earth long ago.

“We’re all just in awe,” said Healdsburg dairyman John Bucher. “It’s almost like you can watch it grow. It’s just crazy.”

It also means domestic consumers are using substantially less water for outdoor irrigation, reducing demand on the system, said Don Seymour, principal engineer with the Sonoma County Water Agency.

But while recent wet weather has allowed most folks to take a bit of a breather, it’s likely just that, however: a breather, a respite.

Long-term reserves, especially in Lake Mendocino, are still at abysmally low levels. A significant amount of rain is still needed to raise water levels enough to face next spring and summer with any confidence that there will be sufficient supplies to get through to the winter afterward.

“There’s a big hole to fill,” Seymour said.

Recent rains have added about 5,000 acre feet of storage to Lake Mendocino, arriving just a week or so before the lake would otherwise have matched its lowest level ever: 12,081 acre feet.

Instead, it rose from about 12,864 acre feet on Oct. 22 to 17,676 acre feet a week later.

The gain was about half the 10,000 acre feet that flowed into the reservoir in all of last winter. (An acre foot is equal to 325,851 gallons, or about the amount of water needed to flood most of a football field one foot deep. It would supply almost 3½ water-efficient California households for a year, according to the Water Education Foundation.)

But that remains the second-lowest level since the reservoir was completed in 1959, and it is still almost 100,000 acre feet below the spillway, meaning the amount of water in the lake could be multiplied 6½ times before the reservoir reaches capacity.

Last weekend's storm enriched local reservoirs with additional water supply, but storage levels remain substantially below an average water year and even those of the last drought. (Sonoma Water)
Last weekend's storm enriched local reservoirs with additional water supply, but storage levels remain substantially below an average water year and even those of the last drought. (Sonoma Water)

Lake Sonoma, a far larger reservoir, gained about 14,500 acre feet in additional reserves after the big storm, bringing total storage to about 120,000 acre feet by Thursday. But that was still less than half the lake’s 245,000-acre-foot capacity.

Seymour said that both reservoirs receive water from catchment areas close to the same size — 105 square miles in the case of Lake Mendocino and 130 square miles in the case of Lake Sonoma.

However, Lake Mendocino will be more challenged to make up ground after two years of critically low rainfall because it’s located in a watershed that simply isn’t blessed with the same amount of rainfall as Lake Sonoma.

Adding to Lake Mendocino’s woes is the shutdown of the Pacific Gas & Elecric hydroelectric plant in Potter Valley. Water from the Eel River is usually transferred through the plant to the Russian River and Lake Mendocino, but water diversions there are now about one-sixth what they normally would be.

“This great gift of rain like we got last weekend is not enough to dig us out of drought,” Nick Malasavage, chief of operations and readiness for the U.S. Army Corps of Engineers, San Francisco District, which operates the two reservoirs, said Friday. “We are still at historically low pools for this time of year.”

Any success the future might hold in augmenting existing storage remains, as always, in question, but particularly so this year. An intensifying La Niña season along the West Coast that means the Pacific Northwest likely will see more rain than usual this winter and the southwest, less, but uncertain prospects for the transition zone in and around the North Coast.

As for the immediate future, it’s likely to include more moisture than usual, however, with some rain on Monday and again on Wednesday, though likely a fraction of an inch in most inland areas.

The ground already is wet, so less will soak in before running into creeks and rivers, however, and more might be captured in reservoirs, water managers said.

These rains also demonstrate “a very active weather system” that bodes well for the immediate future, said David King, a meteorologist with the National Weather Service in Monterey.

“I tend to be little pessimistic about all this stuff,” said Eureka forecaster Jeff Tonkin. “But I’m really optimistic, so there you go.

“The great news in all this,” he added, “is we’re not seeing any huge ridging, sustained ridging off the coast that would push storms to our north or to our south. That would be a real deal breaker.”

Whether it’s possible to get the 25 inches that Seymour roughly calculated might be needed by the end of the calendar year to get back on track remains in question.

Normal seasonal rainfall in Santa Rosa, for instance, is just over 30 inches a year.

In the meantime, there is water in the pond at Neil McIsaac & Son Dairy in the Two Rock area of south Sonoma County for the first time in two years, said Neil McIsaac Jr.

That means his son, Neil III, who has spent the midnight hour and the early morning hours of each day trucking water from Petaluma to the ranch for over a year, could take a week off knowing the cows could be watered even if he got a little extra rest.

“I’ve noticed driving around the area that some of the smaller ponds are full,” said McIsaac Jr. “Hopefully it will continue on.”

In Fort Bragg, the Noyo River has flowed so well ever since late-September’s river showers that water trucking from Ukiah for sale on the Mendocino Coast has been suspended, given supplies in the Fort Bragg reservoir accumulated from earlier deliveries and diversions from the river, Public Works Director John Smith said.

The State Water Resources Control Board has suspended curtailments on diversions from the Russian River for hundreds of water rights holders through what could be Nov. 30. It also has loosened restrictions on Sonoma Water, potentially allowing for greater use of surface water and a pull back from well withdrawals, Seymour said.

But in general, water suppliers and managers say there’s no room to let up on conservation, as long as long-term supplies remain so limited.

“It’s not over until we see significant improvement at the reservoir,” Seymour said. “This was great, but we’ve got a way to go.”

You can reach Staff Writer Mary Callahan at 707-521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.

Mary Callahan

Environment and Climate Change, The Press Democrat

I am in awe of the breathtaking nature here in Sonoma County and am so grateful to live in this spectacular region we call home. I am amazed, too, by the expertise in our community and by the commitment to protecting the land, its waterways, its wildlife and its residents. My goal is to improve understanding of the issues, to find hope and to help all of us navigate the future of our environment. 

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