Water Levels in Lake Mills Reservoir to be Lowered Six Feet to Encourage Erosion along New Pilot Channel

Date: April 22, 2011
Contact: Barb Maynes, 360-565-3005
Contact: Dave Reynolds, 360-565-2985

As preparations for removal of the two Elwha River dams continue, Bureau of Reclamation dam managers will again lower the water level in the Lake Mills reservoir to help accelerate erosion along a pilot channel created last fall.

The drawdown will begin within the next several days; managers estimate that the water level will drop approximately one-and-a-half feet each day until the reservoir is six feet lower than normal. This is expected to occur by the end of April. The Lake Mills boat launch will be inaccessible and unusable for the duration of the drawdown. Following the drawdown, the reservoir will be allowed to refill and will reach full pool no later than June 1.

Last fall, contractors completed an erosion-enhancement project at the Lake Mills delta. Over a five-week period in September and October, workers removed trees, created a pilot channel through the middle of the delta and repositioned a logjam to direct the river into the new channel.

Prior to last autumn's erosion-enhancement project, alder trees had overgrown over much of the delta, and large logs had been deposited by the river, stabilizing the sediments that make up the delta.  Removing the trees and establishing the pilot channel gave the river a "head start" at eroding the delta. Lowering the reservoir will help maximize that ongoing erosion.

"During the dam removal process, the river will carry large amounts of sediment downstream where it will restore fish habitat, shellfish beds and beaches along the Strait of Juan de Fuca," said Karen Gustin, Olympic National Park Superintendent. "Lowering the reservoir level now will continue to give the river the head start it needs to erode the sediment."

As reservoir levels drop during and after dam removal, the river will naturally erode and carry downstream the sediments that have accumulated in the reservoirs, replenishing downstream spawning beds and the estuary and beaches at the river's mouth.