Lake Mendocino allowed to top its water limit again

The U.S. Army Corps of Engineers is allowing Lake Mendocino’s water level to rise almost 6,000 acre-feet above its normal winter limit, an increase aimed at maintaining enough water for both people and fish later in the year.

It may not seem like a huge amount, but “it’s not unsubstantial,” said Don Seymour, the Sonoma County Water Agency’s principal engineer.

He said the change could make a difference in the amount and quality of water available for releases into the Russian River later in the year when fish are migrating.

But the Corps will stop holding extra water behind the lake’s dam if it threatens to exacerbate flooding on the Russian River or the dam somehow becomes damaged, officials said, noting the dam’s foremost function is flood control.

Only after flood threats disappear can the releases be managed for water supply by the Sonoma County Water Agency.

The lake on Monday afternoon held 71,895 acre-feet of water, 3,495 more than is usually allowed in the reservoir this time of year, when flood protection is the top priority.

An acre-foot of water is equal to 325,851 gallons and is generally described as enough water to sustain a family of four for a year.

The Corps will allow up to 5,820 acre-feet more of water to be held in the dam than usual, said Mike Dillabough, chief of the operations and readiness division for the federal agency’s San Francisco district.

The “minor deviation” to the lake’s water-management regulations is an extension of a variance granted to local water agencies last year to help conserve water, he said.

It will expire in mid-March, but by then, the amount the lake is allowed to hold will already be increased under standard operating procedures.

The lake’s management goals call for increased water conservation beginning the first week of March, and the amount of water stored begins to gradually rise. From May to the end of September, the maximum holding capacity increases to 111,000 acre-feet.

Water officials are hoping that rain will continue to arrive in fairly steady but not overwhelming amounts so that the reservoir’s level continues to rise, providing much-needed drought relief on the North Coast.

“The jury’s still out” on whether the drought’s end is in sight, Dillabough said. “A lot depends on what happens between now and the end of April.”

You can reach Staff Writer Glenda Anderson at 462-6473 or glenda.anderson@pressdemocrat.com. On Twitter @MendoReporter