Freshwater Quality
21% of stream and river segments that were assessed in 2010 were listed as impaired
Indicator Leads: Markus Van Prause, Washington State Department of Ecology, Ken Koch, Washington State Department of Ecology, and Jo Wilhelm, King County
Data last updated on March 6, 2014
Photo Credit: Dan Bennett

Importance to Puget Sound recovery

The rivers and streams that flow into Puget Sound are the lifeblood of our region’s ecosystems and our health, economy, and quality of life. Yet only 64% of the major rivers in Puget Sound meet water quality goals.

Clean water is vital to people and to healthy fish and wildlife populations. When our rivers and streams pick up pollutants, toxic contaminants, or excessive sediments and nutrients, it adversely affects the health of our watersheds, marine waters, swimming beaches, and shellfish beds.

Three key indicators help us monitor the health of Puget Sound: the number of impaired waters, the Water Quality Index, and the Benthic Index of Biotic Integrity. Under the federal Clean Water Act of 1972, waters that fail to meet water quality standards are considered impaired. The Water Quality Index integrates complex water quality data into a readily understood scale. The Benthic Index of Biotic Integrity measures the abundance and diversity of macroinvertebrates in a streambed. Also known as stream bugs, these creatures are a critical part of the aquatic food web and are sensitive to changes in the environment.

Is there progress? Indicators and targets

What are the indicators?

There are three indicators of freshwater quality: the Water Quality Index, the number of impaired waters and the Benthic Index of Biotic Integrity.

Water Quality Index

The Water Quality Index for rivers and streams combines eight measures of water quality. Expectations for four of the component measures (dissolved oxygen, pH, temperature, and fecal coliform bacteria) are tied to the State’s Water Quality Standards for protecting aquatic life and contact recreation. The other four measures (nitrogen, phosphorus, suspended sediment, and turbidity) do not have numeric standards. Toxics are not included in the index.

Index values are based on monthly monitoring at individual stations. The index values range from 1 to 100; a higher number is indicative of better water quality. However, a particular station may receive a good Water Quality Index score, and yet have water quality impaired by parameters not included in the index. Similarly, some locations may have poor Water Quality Index scores based on measures that do not have Water Quality Standards.

Number of impaired waters

Impaired waters are segments of streams, rivers, or lakes that do not meet the State of Washington’s Water Quality Standards for bacteria, dissolved oxygen, temperature, toxics, or other pollutants. Cool, clean water is a key ingredient for a healthy Puget Sound. When lakes and streams have a reduced ability to support native species and human uses, then they are listed as Impaired.

The Washington State Department of Ecology reviews data from a variety of sources every four years to identify impairments. The data used to list segments as impaired must meet rigorous data quality standards as outlined in Washington’s Water Quality Policy 1-11.

Under the Federal Clean Water Act of 1972, waters are considered impaired when they fail to meet water quality standards or minimum requirements for certain uses. Every two years, states are required to prepare a list of water bodies that do not meet water quality standards. This list is called the 303(d) list, because the process is described in Section 303(d) of the Clean Water Act. To achieve this goal, the State of Washington established water quality standards designed to protect and restore water quality for drinking, recreation, and habitat for fish and other aquatic life.

More than one segment of a river can be listed as impaired, and a single segment can be listed for more than one pollutant. Once a segment is listed as impaired, a plan must be created and implemented to control pollution or improve water quality. The effects of these restoration programs can take many years to have a positive impact.

Benthic Index of Biotic Integrity

The Benthic Index of Biotic Integrity (B-IBI) describes the biological condition of stream sites and their surrounding habitat based on the diversity and relative abundance of the benthic (bottom dwelling) macroinvertebrates living there, such as mayfly larvae, stonefly larvae, caddisfly larvae, worms, beetles, snails, dragonfly larvae, and many others.

Ten measures of biological condition are scored and summarized as the B-IBI, which ranges from a score of 10, indicating a very poor stream condition, to 50, indicating excellent condition.

Benthic Index of Biotic Integrity data are routinely collected and reported by more than 20 local jurisdictions, tribes, and other state and federal organizations in Puget Sound for a variety of reasons. The Washington Department of Ecology samples 50 randomly selected stream and river sites every four years to get an unbiased estimate of regional conditions. Snohomish and King counties also randomly select stream sites to estimate regional condition using the B-IBI.

What are the targets?
2020 target
  • At least half of all monitored stations should score 80 or above on the Water Quality Index.
  • Reduce the number of “impaired” waters.
  • Protect small streams that are currently ranked “excellent” by the Benthic Index of Biotic Integrity for biological condition; and improve and restore streams ranked “fair” so their average scores become “good.”
Interim targets

Interim targets have not been set for these indicators

Is there progress?

Progress toward the 2020 freshwater quality targets was mixed, at best. The total number of impaired river and stream segments was down in 2008-2010, which represents some improvement, but the trend is expected to reverse in the next round of assessments. However, freshwater quality, as measured by the Water Quality Index for streams and rivers, was slightly worse than the baseline reference. Finally, there was a net decline in the biological condition of small streams as shown by the Benthic Index of Biotic Integrity.

Water Quality Index Target Bar

Water Quality Index

There has been no progress toward the 2020 target for the Water Quality Index. Only about 27% of monitored stations were at or above the target value of 80, on average, from 2008 to 2012, indicating that they support water quality goals for conventional pollutants (toxics are not included). This number is slightly lower compared to the baseline reference established for the 2003-2007 period (29%). Furthermore, results from the trend analysis of 14 major rivers at their most downstream sites suggest that the target is not likely to be reached by 2020.

The earliest projection to meet the target for these 14 rivers would be 2025. When adjusted for differences in seasonal flows, the trend is much slower: average flow-adjusted scores of 80 are projected for 2060. Flow-adjusting accounts for the effect of flow on the parameters underlying the index.

However, this kind of estimate is a best guess due to fluctuations in drivers like the rate of population growth, global warming, and effectiveness of management activities, as well as possible long-term cycles not visible in the current 15-year dataset. For example, management tends to address the easier and more egregious problems first. As those problems get fixed, remaining problems become more difficult to correct with less effect on the water body for a given level of effort. Consequently, the rate of improvement in the index could be less, perhaps much less, than predicted by simply extending current trends.

Number of impaired waters Target Bar

Number of impaired waters

Although the number of impairments for rivers and streams decreased by 77 segments in 2010 - a step in the right direction - it does not mean that these segments now meet water quality standards. Instead, the change in number of impairments was largely due to the number of segments receiving approval for their water quality improvement project plans or pollution control programs.

Having a plan in place removes a segment from the impairment list, but does not necessarily mean that the area has been restored or that water quality standards are being met. For example, only four segments from the 2010 list were removed from the impaired list because they met water quality standards.

New data for freshwater were not reviewed in 2010; the 2012 water quality assessment will use new data and be published sometime in 2013. The number of freshwater impairments is likely to rise significantly in 2012 due to an increase in data and the number of sites assessed. Comparing the number of impairments for 2008 to 2012 will be difficult because the method used to map and count segments will change.

Benthic Index of Biotic Integrity Target Bar

Benthic Index of Biotic Integrity

No progress has been made in improving the biological condition of small streams. Overall, the biological condition of streams initially ranked as "fair" has declined, based on the Benthic Index of Biotic Integrity scores.

From 2007-2011, a total of 245 stream sites were sampled more than once. Of these, a total of 128 sites had initial B-IBI scores indicating “fair” condition (Figure 4 in Latest data and maps sections). The biological condition of most of these sites did not change. Consistent with the 2020 target, 11 of the 128 sites improved and changed categories to “good” or “excellent". However, 26 stream sites declined and changed status from “fair” to “poor” or “very poor”. The net difference in the change in status of 15 streams represents an overall decline (12%) in the biological condition of "fair" streams.

For the streams with “excellent” biological condition as rated by the B-IBI, some streams are already protected. A detailed analysis has not been done to identify which streams and watersheds should be protected for this target. The watersheds will likely be small, five to 20 square miles.

Latest data and maps


Water Quality Index

Water quality index, annual, 1994-2011

For 14 major rivers, three stations reported average WQI scores of 80 or higher during this time period (Table 1).

Freshwater Quality Index scores (averaged) for 55 sites in Puget Sound, 2008-2012

From 2008-2012, 15 of the 55 (27%) long-term monitoring stations reported average Water Quality Index scores of 80 or more, indicating that they support water quality goals for conventional pollutants (toxics are not included). This value is down from 31% relative to the 2008-2011 average reported last year. Fifteen stations had values that were “borderline” (70 – 79); 22 had “poor” scores (40 – 69); and three stations had a very poor index score (< 40) (Figure 1).

Water Quality Index scores have improved significantly in the Nisqually and Deschutes systems (1.4 and 1.6 units per year, respectively, p < 0.05). No Puget Sound basins have had significantly declining scores (p > 0.20). Stations meeting water quality goals are all in the relatively undeveloped Olympic Peninsula, except for the Snohomish River. Stations not meeting water quality goals tend to be in watersheds with more people and more agricultural development. Improvements in fecal coliform bacteria and total nitrogen index scores have also been reported.

Number of impaired waters

Number of streams and river segments listed in each assessment category, 2008 and 2010

In the Puget Sound basin, the 2010 Water Quality Assessment showed a total of 6,957 segment and parameters combinations were assessed. A total of 1,496 river and stream segments, in 525 rivers and streams, did not meet Water Quality Standards and thus were listed as impaired.

Impairments occurred in all 19 Water Resource Inventory Areas (WRIAs) in the Puget Sound basin (Figures 5 to 7). More than 60% of the total number of listings for Puget Sound rivers and streams were in five watersheds: Nooksack (296 listings), Kitsap (194), Cedar/Sammamish (181), Duwamish-Green (132), and Lower Skagit-Samish (109). For Puget Sound lakes, 52 were listed as impaired; 48% were listed for bacteria and total phosphorus, and approximately one-half were listed for toxic chemical contamination.

The most frequently cited data for listing segments as impaired were bacteria (524 listings), dissolved oxygen (460), temperature (353), and pH (97). However, the largest number of segments (39%) could not be categorized because of insufficient data. Water Quality Standards include strict rules about the number of samples required to determine whether a segment is impaired or meeting standards.

Segments listed as waters of concern have data that indicate a problem, but not enough data to make a determination of impairment.

Sampling of streams, rivers, and lakes tends to focus in areas with known problems; therefore, not all segments have been assessed, and some impairments can be missed. Consequently, impairment data are not a complete reflection of the overall health of all streams, rivers, and lakes in Puget Sound watersheds.

In addition, selection of monitoring sites is frequently constrained by funding. Monitoring efforts are split between monitoring established sites and looking for new problems. This limits the numbers of new waters that are addressed during a cycle.

Benthic Index of Biotic Integrity

B-IBI scores category of biological condition for Puget Sound Streams, Annual, 2007-2011

Biological condition ranged from very poor to excellent for streams assessed between 2007 and 2011. The majority of streams (88%) rated very poor, poor or fair, while fewer than 12% of streams were rated as good or excellent (Figure 3).

Not surprisingly, Benthic Index of Biotic Integrity (B-IBI) scores were lower in areas with greater urban development (Figure 8). The B-IBI is highly correlated with development and component metrics respond to specific aspects of disturbance. For example, long-lived species tend to decline as stream flows become higher in wet periods and lower in dry periods. Stoneflies also decline when natural vegetation near the stream is removed. Stream invertebrates are also sensitive to sediment, toxics, increased temperatures, and loss of habitat.

B-IBI scores for 128 streams in Puget Sound, Annual, 2007-2011

For sites with repeat visits during the last five years, more sites have declined in biological condition from “fair” to “poor” or “very poor” (29%) than have improved to “good” or “excellent” condition (9%; Figure 4). These B-IBI scores were not derived from a random sample design and, therefore, do not necessarily represent the entire Puget Sound area.

For 84 sites with long-term data in King County, scores for 68 sites did not change (81%), 10 improved (12%), and six declined (7%).

River and stream segments listed as impaired for bacteria River and stream segments listed as impaired for dissolved oxygen River and stream segments listed as impaired for temperature B-IBI scores for rivers and streams in the Puget Sound watershed

What you can do

  1. Use Low Impact Development (LID) techniques to manage stormwater runoff such as natural landscaping, rain gardens, rain barrels, green roofs and permeable paving where appropriate.
  2. Let the Rain Soak In: Slow stormwater runoff by directing downspouts into lawns, beds or rain gardens. Plant more trees to help capture rainwater.
  3. Do not use pesticides on your lawn. Pesticides are poisoning some urban streams.
  4. Volunteer in your area to work with a group helping to reduce fresh water pollution.
  5. Debris and pollution from cars affect water quality. Try alternatives to driving such as public transportation, carpooling, vanpooling, walking, or biking.
  6. If you do have a car, wash your car at a commercial car wash so wastewater plants can treat the water before it enters local waterways. Learn more at Puget Sound Starts here.
  7. Dispose of oil and other auto wastes at your local recycling location or hazardous waste collection facility. Some county-based links are available here.

What our partners are doing

View Near Term Actions helping to advance this Vital Sign

Links for more information

Washington State Department of Ecology: River and Stream Water Quality Monitoring Program

Washington State Department of Ecology: Stream Biological Monitoring

United States Geological Survey: Washington Water Science Center

Northwest Indian Fisheries Commission: Coordinated Tribal Water Quality Program