River Watch Header Image

Lake Mendocino’s Water Level to be Raised

By Glenda Anderson
THE PRESS DEMOCRAT
March 5, 2008

Lake Mendocino

The Army Corps of Engineers has agreed to raise Lake Mendocino’s maximum level in an attempt to blunt the impacts of dry weather that last year forced cuts in water use and reduced the lake to mud flats.

“Hallelujah. This is good news,” said Don Butow, chairman of the Redwood Valley water district, which was forced to curtail water use 50 percent last year when the lake dropped to near record lows.

The change, requested by the Sonoma County Water Agency, potentially could increase the lake’s summertime depth by almost 14 feet, adding about 25,000 acre-feet to the reservoir, said Mike Dillabough, the Army Corps’ chief of operations and readiness for the San Francisco district.

The reservoir, which serves both flood control and water storage functions, dropped to such a low level last year that the state mandated water conservation in the North Bay.

Diversions from the Russian River were cut 15 percent between July and October to maintain water levels in the lake for the fall salmon run.

A combination of conservation measures and increased pumping of ground water allowed the Sonoma County Water Agency to cut diversions from the river 21.6 percent compared with 2004, officials said.

If Lake Mendocino actually rises to the maximum level, it will affect access to the boat ramps and to some of the lake’s almost 300 camp sites, Dillabough said. He said the potential impacts of higher water levels are still being evaluated.

Because the increase is dependant on more rainfall and, therefore, unreliable, it will not create the opportunity for additional water rights to lake water, said Barbara Spazek, executive director of the Russian River Flood Control and Water Conservation Improvement District, which holds Mendocino County’s 8,000 acre-foot right to the lake’s water.

Sonoma County owns the bulk of the lake’s water rights.

It also manages water flows outside of the rainy season and is responsible for releasing sufficient amounts of water for spawning and migrating fish downstream of the dam.

In addition to drier springs, lake water levels have been affected by mandated downstream flow increases to benefit fish and a 33 percent cutback in the Eel River diversion into the Russian River, which feeds Lake Mendocino.

The management change does two things: It alters the maximum amount of water allowed to be stored in the lake once the rainy season subsides, and it changes the estimated date of the rainy season from the end of March to March 1, Dillabough said.

Normally, the summertime lake level maximum is 748 feet, measured from sea level. Maximum will now be 761.8 feet, Dillabough said.

The lake level was at 745.5 feet on Tuesday. The lake bottom near the dam is at about 637 feet above sea level.

The Corps’ operational change moves by one month the date at which the Corps begins holding more water in the lake in preparation for switching from flood control management to water conservation.

The Sonoma County Water Agency requested the date be changed because it appears there is less rainfall in the spring than there once was, said Pam Jeane, the agency’s deputy chief engineer.

During most of the winter, when storms are expected, the Corps holds the level at 737.5 feet, although heavy rains may temporarily raise the water much higher. It would gradually begin increasing the amount of water in the lake at the end of March, Dillabough said.

While the water level boost promises to combat drought-like conditions, whether it materializes depends on Mother Nature, Dillabough said.

The lake will likely reach the higher level only if there is mild but steady rainfall during the next two months, he said.

“If we get anywhere close to that (new maximum), I’ll be surprised,” Dillabough said.

An increase also could be hampered by a heavy storm, which would force the Corps to again release water from the dam when levels reach 737.5 feet to prevent potential flooding, its primary charge.