New petition filed to conserve Lake Mendocino water

The Sonoma County Water Agency is again seeking reductions in mandated Russian River water flows to try to conserve declining supplies in Lake Mendocino and better manage the precious resource during the persistent drought.

The agency on Tuesday filed a temporary change petition with the state Water Resources Control Board that would reduce the minimum flow between Lake Mendocino and Dry Creek, near Healdsburg, from 185 cubic feet per second to 75 cfs, agency officials said Wednesday. It also would reduce mandated flows between Dry Creek and the ocean from 125 cfs to 85 cfs. The change would go into effect May 1 and last 180 days.

Mendocino County water officials welcomed the request, which is expected to preserve about 6,500 acre-feet of water in Lake Mendocino, or about one-tenth of its current water supply. An acre-foot is roughly enough to fill a football field with one foot of water or supply one household with 893 gallons of water a day for a year.

The reservoir provides water to residents and farmers between the Redwood Valley and the Alexander Valley in Sonoma County.

“We support the change petition entirely,” said Sean White, director of the Russian River Flood Control and Water Conservation Improvement District, which holds Mendocino County’s right to 8,000 acres of the lake’s water. But he and other water and county officials agree the solution lies with permanent, long-term changes in how water releases from the lake are regulated.

Existing requirements do not accurately reflect conditions in the Russian River watershed, according to the Sonoma County Water Agency, which is charged with regulating Russian River flows. The agency also is seeking permanent changes to better reflect real conditions.

Its officials expect to have a draft environmental impact study on the proposed revisions completed later this year, said Pam Jeane, the agency’s assistant general manager.

Currently, water releases from Lake Mendocino are based on calculations tied to flows into Lake Pillsbury. Those calculations have resulted in a flow regime that assumes the lake is weathering a normal rain year, rather than the existing drought, Mendocino County supervisors noted in a letter they plan to send to the state Water Resources Control Board.

The connection between the two reservoirs was once strong, but since 2006, reductions of a diversion of water from the Eel River - fed by Lake Pillsbury - to Lake Mendocino greatly reduced the tie, said officials from Sonoma and Mendocino counties.

Altering the existing flow regimes to reflect the change likely will take at least two years, barring litigation, Jeane said.

Meanwhile, the variances are necessary to manage the area’s water both for people and fish, she said.

Preparing and implementing each of the variances costs about $200,000, Jeane said. But the agency does not consider the cost when deciding whether to pursue a variance, she said.

“We’re going to file a petition because it’s the right thing to do,” Jeane said.

The temporary variance currently being sought primarily would save water in Lake Mendocino in May. The flows are expected to decline in June under the regular schedule.

Currently, 176 cfs are being released from the lake to maintain the higher instream river flows, draining the lake of about 180 acre-feet a day. According to the U.S. Army Corps of Engineers, the lake at noon Thursday held 59,826 acre-feet, about 61 percent of its capacity. Lake Sonoma is at about 87 percent of capacity.

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