Water flow to be cut for dam tests
Warm Springs reduction begins Sept. 22, will allow for study of Dry Creek fish
Published: Thursday, September 11, 2008 at 5:23 a.m.
Last Modified: Thursday, September 11, 2008 at 12:13 p.m.
The amount of water flowing out of Lake Sonoma will be drastically reduced later this month so the Army Corps of Engineers can inspect Warm Springs Dam.
Facts
WHAT DOES IT MEAN?
Facts about the plan to cut the flow of water from Warm Springs Dam:
* The amount of water released from the dam will be cut from an average of 105 to 125 cubic feet per second to between 40 and 50 cfs.
* The Russian River below Dry Creek will drop as much as 5 inches.
* Recreational boating might be impacted.
* No service disruptions are expected.
“The five-year inspection is a huge deal for us,” said Mike Dillabough, the corps’ division chief of operations. “We take it very seriously.
We bring in a lot of folks and a lot of experts to make sure everything is working well.”
The lower flows will also drop the level of Dry Creek, allowing Sonoma County Water Agency biologists to study Chinook and coho salmon and steelhead to assess how they are doing.
“We don’t really know what makes the fish population in Dry Creek tick,” said Dave Manning, a fisheries biologist with the Water Agency.
“We will try to see the abundance and distribution of these fish.”
The dam is subject to an annual inspection, with a detailed inspection conducted every five years.
The Water Agency will reduce the amount of water released from the dam from an average of 105 to 125 cubic feet a second to 40 to 50 cfs for four days beginning Sept. 22.
The water from the lake is released into Dry Creek, which then joins the Russian River just south of Healdsburg.
The Russian River below Dry Creek will be lower by as much as 5 inches, which could impact recreational boating, even as that season is winding down, said Pam Jeane, the Water Agency’s deputy director of operations.
“It will look similar to last year,” Jeane said.
“The difference between that and what people see today is 3 to 5 inches.”
Jeane said there will be enough water in the agency’s percolation ponds near Forestville to serve the 600,000 residents in the cities and districts from Windsor to San Rafael during the four-day period.
Warm Springs Dam was completed 25 years ago at a cost of $330 million, creating Lake Sonoma as a source of water and recreation and as a flood-control project, taking 5 to 8 feet off floodwaters downstream at Guerneville.
The compacted earthen dam is 3,000 feet wide and 319 feet tall and made of 30 million yards of dirt and rock scraped off the surrounding hills.
Water from the lake flows through a 2,400-foot-long tunnel into Dry Creek, controlled by gates inside a 300-foot tower dug into the dam.
During the inspection, the corps will look at the dam face for erosion, movement and even rodents digging into the dirt.
There are also instruments under the dam that measure seismicity and earth movement.
The 14½-foot-diameter outlet tunnel is measured for any deformities to within a thousandth of an inch by workers on a special $60,000 vehicle built by the corps to drive inside.
“It has held up fantastic so far,” Dillabough said of the dam. “Any structure this size, there are always minor things, but to date the dam has done very well.”
You can reach Staff Writer Bob Norberg at 521-5206 or bob.norberg@pressdemocrat.com.
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