OLYMPIC NATIONAL PARK — The water level in Lake Mills will begin to be drawn down beginning as early as Monday, lowering it by 6 feet by the end of April and making the boat launch inaccessible.
U.S. Bureau of Reclamation dam managers will lower the water level in the Lake Mills reservoir to help accelerate erosion along a pilot channel created last fall in preparation for the removal of two Elwha River dams, said Barb Maynes, Olympic National Park spokeswoman, on Friday.
The drawdown will begin within the next several days; the earliest day it could begin is Monday, Maynes said.
Dam managers estimate that the water level will drop approximately 11⁄2 feet each day until the reservoir is 6 feet lower than normal, which is expected to occur by the end of this month.
Launch to be unusable
The Lake Mills boat launch will be inaccessible and unusable for the duration of the drawdown, Maynes said.
Following the drawdown, the reservoir will be allowed to refill and is expected to reach “full pool” no later than June 1.
Last fall, contractors completed a project at the Lake Mills delta to encourage erosion.
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, Maynes said.
It also left the boat launch high until rain refilled the lake basin.
Lowering the reservoir will help maximize erosion before the dams are torn down beginning Sept. 17, Maynes said.
The dam removal is part of the $327 million Elwha River Restoration Project, which is intended to revive the waterway’s severely depleted salmon run.
“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.