Field Notes: a Northwest nature blog
One of the reasons many of us live in the Pacific Northwest is the natural wonders that amaze us all. On this blog Seattle Times writers and photographers will share their explorations of the natural world from snowcaps to whitecaps. Write us at firstname.lastname@example.org with your own sightings, questions and wonders to share.
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Lake Mills on the Elwha is almost history
Since 1926, the glittering blue of Lake Mills has been a landmark -- albeit an artificial one -- of the Northwest landscape.
Lake Mills, the reservoir behind Glines Canyon Dam, was actually at the root of the legal case to tear down the Elwha dams: the reservoir intruded into the boundary of Olympic National Park. While it still exists on maps and in the memories of many longtime Northwesterners, Lake Mills will soon be gone from the landscape.
Photo by Steve Ringman of the Seattle Times, taken October 1, 2010
Lake Mills has been steadily dropping since dam removal began on the river in September 2011. But, depending on weather over this weekend, it will be gone by next week. The lake is only about 8 to 10 feet deep at the deepest right now -- down from 180 feet before workers began taking down the 210 foot tall dam, now only about 70 feet high.
Lake Mills is nearly gone. Andy Ritchie, Elwha restoration project hydrologist for the National Park Service took this aerial photo in September, 2012.
Photo courtesy, National Park Service
Here is the same view, one month later, photographed by Ritchie on Oct. 15, 2012. He predicts the lake will be completely gone by next week.
Lake Mills is nearly gone.
Photo by Andy Ritichie, Elwha restoration project hydrologist, National Park Service.
Courtesy, National Park Service
The dam might be completely gone by May. The schedule depends on the downstream effect of the massive amount of sediment about to be unleashed into the river. Slower is safer.
Less than five percent of the material pent up behind the dams since Elwha Dam was built in 1910 has been released, said Andy Ritchie, Elwha restoration project hydrologist with the National Park Service, based in Port Angeles.
Glines always hoarded the biggest load of sediment -- and the two dams together trapped an estimated 24 million cubic yards of material --gravel, sand, cobble and fines that normally would have been rinsing down from the upper watershed, and distributed throughout the Elwha's 45-mile length all the way to the saltwater Strait of Juan de Fuca.
One of the most important aspects of the $325 million Elwha restoration project is restarting the river's capacity to transport that material, a natural process that shapes the river and provides habitat for everything in it.
The goal is to restart the conveyor belt without doing damage downstream. To control the release of sediment in to the middle and upper watershed, the sediment management team at the Denver office of the Bureau of Reclamation and locally in Port Angeles at the National Park Service have been carefully watching the pace of dam removal, so the river can keep up with its task of eroding out the material stuck behind the dams.
With the winter storm season getting underway, things are about to get exciting. A 70-foot wall of sediment has been advancing toward what's left of the dam, and as workers continue to take it down, that material is going to start coming out.
Any day now, cobbles and sand are about to start tumbling over the dam -- and that's not been seen before.
"We've just seen the leading edge of the torrent of sediment, just a whisper of what's to come," Ritchie said.
Elwha Dam was completely gone by last March, but it didn't have much big stuff behind it. The lower of the two dams, it trapped mostly sand and fines. It's a different story with Glines, where a stockpile of gravel and cobble is on the way.
"What we are seeing is an increase in both the concentration and the size of what is coming," Ritchie said. "The sand will speed down the river, the gravel will tumble, and the cobble will bump along. One of the big parts of this experiment is how the river will respond to sediment it hasn't seen in 80 years.
"The coarse sediment part of this experiment is about to begin."