Ask the Engineer: Where Does Our Water Come From?


You turn on the faucet and water comes out but where does it come from? We here in the Pacific Northwest have it good, nature does most of the work for us. Throughout the fall and winter when water use is down, precipitation falls in the mountains and turns into snowpack. When it starts to warm up in the spring, all that snow melts and sends us a steady flow of clear, clean water.

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Spada Lake is about 25 miles east of Everett

The water that comes out of your faucet has its beginnings in the Cascade Mountains. More specifically the Sultan Basin Watershed, considered one of the nation’s purest and most abundant water sources. A watershed is simply the area of land where all of the water that is under it or drains off of it goes into the same place. That place is Spada Lake or the Spada Reservoir.
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The Spada Reservoir was created in 1964 by the City of Everett in partnership with Snohomish County PUD. A dam was constructed on the Sultan River to hold back water, 50 billion gallons of water. Rain and snow melt from the surrounding Cascade Mountains flows into Spada Reservoir. The Sultan Basin Watershed covers an area of about 84 square miles (about 10 times the City of Edmonds) and the average annual rainfall is about 165 inches, or 5 times our local rainfall.

Water transmission line near Highway 2
Water transmission line near Highway 2

From Spada Reservoir, the water travels 8 miles through a pipeline to a hydroelectric powerhouse and then to the City of Everett Treatment facility at the Chaplain Reservoir. Here the water (about 50-million gallons a day) is filtered and disinfected and then travels in four 4-foot pipes towards Everett. Three of these pipes can be seen from the trestle on Highway 2 east of Everett. Two of these transmission lines carry treated drinking water, a third carried untreated water for industrial use at Kimberly-Clark paper mill up until the plant closed in 2012. A fourth line takes a southern route and can be seen from Homeacres Road west of Snohomish.

At this point much of the water goes to serve the City of Everett but a large portion is sold off to serve the majority of the remainder of Snohomish County. Over 50 water systems obtain their water from the City of Everett to serve over half a million residents.

The Alderwood Water District obtains water from the City of Everett and provides water to the City of Edmonds*.

The City of Edmonds has over 138 miles of distribution water mains, three 1.5 million gallon reservoirs, one 3.0 million gallon reservoir, and one pumping station which all work together to bring clean water right to your faucet.

*Some parts of Edmonds are served by the Olympic View Water District, not the City’s water system.

Dustin DeKoekkoek, P.E. is a civil engineer with RH2 and designs public infrastructure projects all over the Pacific Northwest. Have a question about the topic covered here or for a future “Ask the Engineer” column? Email Dustin at [email protected] or leave a comment below. You can also connect with Dustin on LinkedIn here or Google Plus here.

3 Replies to “Ask the Engineer: Where Does Our Water Come From?”

  1. my understanding is we get water from the tolt and cedar river watersheds and woodway has it’s own wells…

    please explain – thanx!


    1. Victor – Edmonds gets its water via the Alderwood Water District as described in the article. Seattle and many other King County cities get their water through the Tolt and Cedar River watersheds. The Woodway water system is managed by the Olympic View Water and Wastewater District. Olympic View purchases most of their water from Seattle (Cedar and Tolt River watersheds) but the District also has a treated surface source located in the Town of Woodway (Deer Creek). Deer Creek provides about 40% of the Districts water. There is also a groundwater well at the treatment location on Deer Creek but I don’t believe it is online (if someone knows otherwise, please correct me). The District also has a tie-in with the City of Edmonds system (purchased from Alderwood Water via City of Everett) that would act as an emergency backup supply.


  2. Dustin,
    Huge thanks for this informative column! Protecting our water supplies through good water management and maintenance of infrastructure is something that most people do not fully appreciate.

    Many organizations are also interested in protecting the natural resources from which our drinking water flows — managing our forests, streams, and riparian areas. That subject alone is vast and is one reason why I volunteer with the Sierra Club and Carpe Diem West’s “Healthy Headwaters Alliance.”

    With “Food & Water Watch,” “Corporate Accountability International,” “The Alliance for Democracy,” “The U.N. Association,” and other groups, we work to encourage people to “Take Back the Tap” or, as the National Parks say, “Step Away from Plastic” and use reusable drinking bottles instead of plastic.

    Edmonds has been a leader in getting the public to replace plastic bags with reusable bags. I notice that many people in Edmonds are now using reusable bottles (stainless and glass are particularly good) instead of toxic plastics that require oil and energy to produce each one.

    A related issues is the “commodification” of water. When our natural resource, water, is bottled and sold for profit, the water is taken out of the watershed and often shipped to distant places.

    I urge readers to go to YouTube and watch a great video, “The Story of Stuff.” “The Story of Water” is a part of that video. If not, then type in “The Story of Water.” These are done by Annie Leonard and are “right on.”

    Thanks again for helping us understand and appreciate a resource that is a “commons,” necessary for the survival of all living things. The “commons” are those essentials that we all need to survive: air, water, and food.


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