Changes to water releases from Lake Mendocino helping

A change in releases at Lake Mendocino is helping water suppliers hold back precious reserves as the region’s dry spell wears on and threatens to cut historically low reservoir stores to critical levels.

The new protocol could prevent as much as 5,000 acre feet of water - one-sixth of Lake Mendocino’s current supply - from slipping down the Russian River before the end of November, an official with the Mendocino County Russian River Flood Control and Water Conservation Improvement District said.

“Five thousand acre feet is going to be about what we used for the entire year this year, so it’s a meaningful amount for us,” the district’s general manager, Sean White, said. “It’s our whole annual budget.”

Savings projections supplied by the Sonoma County Water Agency were closer to 3,600 acre feet, with the potential for salmon migrating upstream triggering additional releases after Nov. 1.

But White said the effort - preserving about 100 acre feet a day - “is definitely going to make a difference.”

“I would have liked more, earlier, but I’ll take what I can get,” he said.

Not everyone will notice reduced river volumes, especially along the lower Russian River south of Healdsburg and the river’s confluence with Dry Creek, where water from Lake Sonoma flows in.

But north from there, it’s pretty clear the water level is lower and the river narrowing because of it, said Larry Laba, owner of SOAR Inflatables and Russian River Adventures in Healdsburg.

“We’ve been watching it go down,” Laba said, “both online as well as onshore. ”

State water regulators approved the reduction in Lake Mendocino releases in late August. The action came in response to requests from White’s district, which holds rights to 8,000 acre feet of water in Lake Mendocino, and the Sonoma County Water Agency, which supplies about 600,000 customers in Sonoma County and parts of northern Marin County.

The two agencies operate under permits from the state Water Resources Control Board, governed largely by a 1986 regime dictating how much water needs to be in the river at different times of year.

The two districts sought the change this fall after projections made clear that, without reduced releases or additional rain, water levels in Lake Mendocino would drop to about 20,000 acre feet by Nov. 1, depleting carryover reserves that might be needed in the event of another dry winter and creating “serious impacts to human health and welfare,” as well as aquatic wildlife, and permanent crop loss.

The decision to grant the request was made by officials with the state water board, which regulates river flows in a manner designed to meet consumer demand and ensure optimal habitats for fish, particularly coho and chinook salmon and steelhead trout. All three species are listed as threatened or endangered under the federal Endangered Species Act.

Managing flows is a delicate dance, dependent in part on weather forecasts, projected demand on the part of downstream consumers, calculations of how long it takes release changes to register downstream, and how water from Lake Sonoma via Dry Creek might offset shifts in outflow from Lake Mendocino.

Lake Sonoma, a much larger reservoir than Lake Mendocino, has a more plentiful water supply, for instance. But releases are limited because of concerns about ensuring flow rates in Dry Creek are kept low, which is optimal for juvenile salmon.

But the state board approved petitions filed by the two water agencies in mid-August seeking permission to release less water from Lake Mendocino even if it meant reduced flows in the Russian River. Permission was granted Aug. 25, effective immediately.

A spokeswoman for the Sonoma County Water Agency, Ann DuBay, credited the shift in dam releases, in part, with Lake Mendocino’s current storage of just more than 30,000 acre feet, though conservation efforts and weather also played roles. That’s about a quarter of its water supply capacity.

The agency’s staff had projected storage of 26,545 acre feet by last week, without the change in protocols. The agency predicts 3,600 acre feet will be conserved by Nov. 1, DuBay said.

Lake Sonoma currently holds about 151,000 acre feet of water, or about 61 percent of its supply capacity.

An acre foot - enough to cover a football field about a foot deep in water - used to be said to be enough to supply a family of four for a year, though of course that would depend on if the family had lawns to irrigate or was conserving water because of drought, as most Californians are being asked.

The approval authorizes upper river flows, between Ukiah and Healdsburg, to be cut by a third - from an average 75 cubic feet per second to 50 cubic feet per second. In the lower Russian River, between Dry Creek and Jenner, the approval permitted the average flow rate to drop from 85 to 60 cfs.

White said he would have preferred to see the state board authorize a cut in upper river flows to 25 cubic feet, though he did not believe the Sonoma County Water Agency or the state would have supported that drastic a drop.

“This year is critically dry by any measure,” White said.

“It’s grim,” said Judy Hatch, a trustee with the Mendocino County water district, who took a drive to the lake on Friday to see how it looks. “Today, when we went out there, it made my stomach hurt.”

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