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You are here:   Home → Natural Environment → 303d Listed Watercourses
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Indicator: 303d Listed Watercourses

Data and Data Discussion provided by Sustainable Seattle

Figure 2. Puget Sound Water Bodies on the 303(d) list.

Figure 1. State-wide Pollutant Parameters

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Upstream Indicators
  •   Urbanization and Impervious Surface Changes --- The number of acres of urban land, clear-cut, and regenerating forest have increased in King County since 1986. Acres of grass and deciduous, mixed and coniferous forest have decreased. Acres of rural forests and privately owned working forests have declined in recent years  (view data graph)
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Downstream Indicators
  •   Drinking Water Quality --- Seattle Public Utilities (SPU) regularly tests its water for 179 compounds, including metals, chemical contaminants and disease-causing organisms. From 2001 through 2008, SPU-supplied water easily met all state and federal drinking water standards. No compounds were detected above allowable levels.  (view data graph)
  •   Wild Salmon --- Many of Puget Sound's salmon stocks have experienced substantial declines over the past 50-100 years due to overfishing, dams, and habitat degradation. Although the number of mature, adult chinook salmon returning to their stream of origin were almost twice in 2006 as high as 2005 levels, they comprised only 25 percent of the long-term chinook population target.  (view data graph)
  •   Fecal Coliform at Swimming Beaches --- Status: High bacterial counts at several beaches monitored in Lake Washington (Juanita, Magnusson Off Leash Park, Gene Coulon, and Meydenbauer) during the 2007 summer season resulted in swimming beach closures. Bacteria levels were low in Green Lake for the fifth year in a row while Lake Sammamish remained fairly consistent, with slight variability from year to year. The 2008 target and long-term outcome for swimming beaches on large lakes is that none of the testing sites violate both parts of the Washington Department of Health fecal coliform bacteria target which is a geometric mean of 200 colonies per 100 ml with no single sample exceeding 1000 colonies per100 ml.   (view data graph)
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Sustainability Snapshot:

Clean water is essential for healthy ecosystems and for the long-term protection of human, plant and animal health. Unsustainable land use practices, manufacturing processes, commercial and residential activities can all contribute to poor water quality. One of the best methods we have for protecting our region's water quality is our state's regular assessment of waterbodies. These waterbodies are labeled impaired by the Department of Ecology based on an assessment every two years. Most of these impairments are the result of toxic contamination, pathogens, low dissolved oxygen and high temperatures. Identifying these problems not only tells where specific clean up actions may be needed but also where ongoing sources of pollutants should be investigated and addressed.

Sustainability Trend:

Although approximately 50% of watercourses included on the 1998 Washington State 303(d) list have been de-listed, the total number of listed water segments has increased in the past decade. The most significant increase in listings has occurred with regards to temperature.

Data Discussion

The Indicator Defined

Measure of amount of stream miles and acres of lakes of 303d-listed water bodies. A waterbody or segment of a waterbody is added to the 303d list because it is not meeting water quality standards or because water quality is threatened.

Data Interpretation/Evaluation

Washington State contains approximately 73,886 miles of rivers and streams, 4,174 lakes, and 2,943 square miles of marine estuaries. The latest  Water Quality Assessment (2004) assessed approximately 30,000 water segments, which is nearly 13 times the number of segments assessed in 1998. The 2004 assessment represented 5% (approximately 4000 miles) of all streams , and 3% (approximately 881) of the total lakes and marine grids.

Of the key pollutants causing 303(d) listing, temperature accounted for the majority of listings (33%), followed by fecal coliform (29%) and other pollutants such as metals or toxics (17%) (Figure 1).  Dissolved oxygen, pH, and phosphorus were also listed as key pollutants, but caused only a small number of listings.

As a result of the 2004 statewide assessment, approximately 50% of waters included on the 1998 303(d) list were removed from the list based on updated guidance and/or new data.  However, new listings were added, leading to an increase by approximately 725 water body segments and 166 new water bodies since 1998. In total, 14% of waters assessed were included on the 2004 303(d) list. Of the main pollutant parameters causing 303(d) listings, the most significant increase occurred with temperature.  This is likely the result of increased efforts to monitor habitat for salmon, which were listed as threatened under the Endangered Species Act in 1999. 

The Columbia Basin and Puget Lowland Ecosystems accounted for the majority of 303(d) listings.  Listed water course segments within the Puget Sound region are shown in Figure 2.

Water bodies listed on the state's 303(d) list are categorized according to the Water Resource Inventory Area (WRIA) they fall within. King County encompasses portions of WRIAs 7,8,9,10, and 15.  You can check the 303(d) of any water in the state by following the link provided below. 

Data Source and Limitations

Data were obtained from the Washington State Department of Ecology using their 2004 Water Quality Assessment for Washington State.  Data from the 2008 assessment have been collected but not published as of October 4, 2008.  Therefore, above results may be somewhat out-of-date.  It is difficult to determine whether this indicator is getting worse or better, as the increase in the number of listed watercourses over the past decade appears to be largely the result of increased monitoring.

Washington State Department of Ecology's 303(d) homepage can be accessed at  http://www.ecy.wa.gov/programs/wq/303d/

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