Mendocino County officials asked the state Wednesday to drastically reduce the amount of water required in the Russian River in an effort to keep Lake Mendocino from running dry this summer.

"Lake Mendocino is the whole show, we don't have another reservoir," said Sean White, general manager of the Mendocino County Flood Control and Conservation District.

Lake Mendocino, which is 60 percent full, and wells are the only sources of water for 150,000 residents and growers from Ukiah to Healdsburg.

Quirks in state water regulations, however, are resulting in this being classified as a normal water supply year, requiring flows in the Russian River near Healdsburg of 185 cubic feet per second.

Those flows, set in 1985 to accommodate growers, recreation and residents, use water flowing into Lake Pillsbury as the guideline, even though Lake Pillsbury is no longer a major source of water for Lake Mendocino.

The Sonoma County Water Agency on Wednesday increased the amount of water being released from Lake Mendocino to meet those flow requirements, said Water Agency spokesman Brad Sherwood.

At the current flow, however, Lake Mendocino will drop 10,000 acre-feet a month and be dry by late summer or early fall, White said.

The Mendocino County district filed an urgency petition with the state Water Resources Control Board on Wednesday asking that flow requirements be reduced May 1 to half the current flow and beginning June 1 to a sixth of what they are now.

Even so, those in the stretch of river from Ukiah to Healdsburg will have to conserve by 50 percent, White said.

"We could conserve until we are purple in the head, but if we don't conserve and get a temporary order, the lake will be empty," White said. "Even with the change petition and very high levels of mandatory conservation, it doesn't leave much more than a puddle by winter."

The Sonoma County Water Agency, which controls the flows from Coyote Dam at Lake Mendocino, is negotiating with state and federal agencies and within the next one to two weeks will be filing a similar petition, said Don Seymour, the Water Agency's principal engineer.

Because there are chinook and coho salmon and steelhead in the river, which are on the federal government's threatened and endangered list, state Fish and Game and the National Marine Fisheries Service will have a voice in the decision.

"Once we are able to submit it, it will move along quickly . . . we are trying to make sure everybody is going to be supportive of the petition," Seymour said.

The Water Agency serves 600,000 residents and businesses from Windsor to San Rafael, who face possible conservation measures of 20 percent to 30 percent this year. The agency's major water source is Lake Sonoma, which drains into the Russian River south of Healdsburg.

You can reach Staff Writer Bob Norberg at 521-5206 or bob.norberg@pressdemocrat.com