The Cedar River Watershed not only quenches the thirst of the City of Seattle and lights its homes, it also bears witness to our changing cultural values and climate change. A couple of years ago, I toured the Cedar River Watershed with a group I belong to, the Pacific Northwest Chapter of the Association of Women Geoscientists (PNW-AWG). Seattle City Light’s Pierre LaBarge led the trip. During the tour, he discussed numerous aspects of the watershed including climate change and snowpack, the town of Cedar Falls, Mason Dam, the dam’s reservoir (Chester Morse Lake) and its seepage, and the surrounding forest’s restoration. Finally, he took us to the Cedar Falls waterfall. Note to PNW-AWG members: if this looks familiar, a lot of this is taken from an early draft of my article in the newsletter that followed the trip.
Climate Change and Cedar River Watershed Layout
This model of the Cedar River Watershed occupies the Watershed’s visitor center.
The group met at the Cedar River Watershed’s Education Center, which housed a relief model of the Cedar River Watershed. Using the model, LaBarge pointed out the watershed’s boundaries, water, snowpack, and highest peaks; then discussed climate change and potential effects to the snowpack and Seattle water supply.
According to LeBarge during that June 2012 tour, by 2050, the average winter freezing level is expected to rise to 4500 feet above sea level (ft asl), instead of the current 3500 ft asl. The highest peak, Meadow Mountain, stands 5414 ft asl. This will result in a much lower snowpack.
The Town of Cedar Falls
Building within historic Cedar Falls. I reckon the traffic cone in the window is new.
LaBarge next drove us through the town of Cedar Falls, which was considered the birthplace of Seattle City Light. Founded as Moncton as a railroad town in 1907, the Moncton railroad depot was renamed Cedar Falls in 1912. Moncton was flooded in 1915 (explained later), but Cedar Falls, a Seattle City Light town, peaked during the late 1920s and 1930s. Seattle City Light employees lived there until the 1990s. The town was a tourist destination until September 11, 2001.
When Moncton was originally settled, it was on a natural prairie by a lake. The lake once consisted of a seasonal wetland with camas. It predated Mason Dam by five years. The Cedar River Watershed had changed quite a bit.
LaBarge drove us from Cedar Falls to Mason Dam, the only barrier on the Cedar River upstream from Ballard Locks in Seattle. This dam’s construction directly impacted the town of Moncton, and continues to affect Cedar Falls to this day. The underlying geology was (and is) the key to the problem.
The south side of the dam is anchored in andesite and basalt bedrock, and its reservoir’s north side consists of soft silts within glacial till.
The basalt on the north side had seepage issues. Designers could not find an impenetrable layer within the till. Mason Dam’s construction began in 1912 and ended in 1914, but the problems were not noticed until six to eight weeks after the reservoir filled.
Water seeped through the soft silts of the reservoir’s north side. Water gushed out of the hills, flooding the town of Mocton. Seattle City Light condemned the town. They attempted to cement the seepage; and in 1918, they deemed the reservoir sealed.
However, a heavy rain soon swelled the reservoir. On December 23, 1918, a washout and slide flooded Cedar River and destroyed the town of Edgewick and its sawmills. The Box Leak Blowout (or Curse) resulted in no loss of life. The night watchmen woke community members.
Due the resultant lawsuit, the court ruled that the reservoir (Chester Morse Lake) could never be filled to full capacity. Dozens of piezometers now permeate the moraine to monitor head in the Cedar River Watershed’s reservoir.
Chester Morse Lake
LaBarge drove us to our next destination, which was higher up the watershed along the shores of Chester Morse Lake. Along the roadway to our stop, we saw submerged land and trees. We climbed out of the vehicle at a picnic area with a view of anchored floating stations and surrounding forest, both of which were topics of the stop.
Anchored Floating Stations
Anchored floating stations are along the perimeter of Chester Morse Lake in case of drought affecting the Cedar River Watershed. They are only turned on when levels are so low, Seattle City Light needs to pump water out of the lake. Despite the pumps, the stations operate mostly via gravity. They require a two month deployment.
Seattle City Light has never had to operate the stations. However, they have been within days of flipping the switch.
Surrounding Forest: Habitat Restoration
The City of Seattle owns 99% of the lands within the Cedar River Watershed. They manage the forest to support the water supply.
During the late 1800s and early 1900s, much of the watershed had been logged. Attempts at reforestation occurred, but frequent fires destroyed them. In 1924, Seattle City Light hired a University of Washington forestry specialist to design a plan to replant and replace the forest. The plan included hiring a forester on a permanent basis to manage it.
During the latter part of the twentieth century, forest practices shifted gradually from harvest to habitat rehabilitation. This transition resulted from Seattle residents’ willingness to pay more for water, and the presence of a variety of endangered species within the watershed that needed protection. During the early part of the twentieth century, Seattle City Light wanted to harvest the forests for additional revenue. Now its goal is to grow old growth habitat for restoration and to hold the snowpack.
Lastly: Cedar Falls (the Waterfall)
The last stop on the Cedar River Watershed trip was scenic, though the drive was education. Along the road, seeps from Chester Morse Lake through glacial till were shown to us. They were the small waterfalls spilling from the roadsides along the way. Cedar Falls itself was quite lovely.
Want to Learn More and Go On a Field Trip Yourself?
The Cedar River Watershed’s Education Center holds regular tours throughout the summer. Their website also contains an abundance of information and historic photographs. This is the website’s URL: http://www.seattle.gov/util/EnvironmentConservation/Education/CedarRiverWatershed/ProgramsTours/index.htm.
Cedar River Watershed: Utility & Environment by Shari Maria Silverman is licensed under a Creative Commons Attribution 4.0 International License.