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Freshwater Environment

2015 Rating RedPie chart showing freshwater water quality components Indicator Key

About this indicator: King County's Freshwater Water Quality Index is derived from two main groupings of results describing the conditions of lakes and rivers & streams. Wetland conditions do not factor into the index at this time because of inadequate data. Due to the budget cuts, several indicators in this index have been removed from data collection since 2010.

Status: Overall below standard, though with some areas of lesser concern.

Influencing factors: The impacts of development, landowner practices in areas close to the shoreline and pollutants are the dominant drivers determining the health of freshwater bodies in King County. Less forest cover and increases in impervious surfaces result in higher stream temperatures and more urban runoff. Phosphorus from blended stormwater and wastewater that bypasses the treatment process during significant storm events, failing septic systems, pet wastes and water bird droppings reduce dissolved oxygen levels and increase water temperatures.

What you can do:

  • Properly dispose of unused pharmaceuticals, harmful chemicals and paints, instead of pouring them down the drain or allowing them to run off on the ground.
  • Minimize the use of fertilizers and pesticides by practicing natural yard care.
  • Wash your car on the grass or gravel instead of on the street or driveway, or take it to a car wash.
  • Properly dispose of or manage pet and livestock wastes.

More information about King County's Freshwater water quality is available by continuing below for these measures:



Phosphorus in Large Lakes

Graph showing major lakes total phosphorus tropic state index and the potential for nuisance algal blooms About this measure: The people of King County have made significant investments in water quality improvement and protection to lakes Washington, Sammamish and Union beginning with the diversion of wastewater effluent out of Lake Washington and Lake Sammamish in 1968.

Water quality improvements continue with efforts to:

  • Reduce the discharge of combined sewer overflows
  • Improve King County's wastewater treatment system (including construction of Brightwater treatment facility)
  • Expand effluent reuse programs

These gains in water quality are constantly threatened by increasing amounts of phosphorus entering the watersheds as a result of increased development.

Status: Lake water quality results vary annually, depending on the climate effects and biological interactions that combine to create unique conditions in each lake annually. For example, the 1994-2015 results for Lake Sammamish show phosphorus concentrations fluctuated quite a bit but for the last 12 years the TSI for phosphorus has been below 40, indicating water quality is good with a low potential for nuisance algal blooms. Phosphorus concentrations in Lake Washington were low from 1998 through 2015 indicating a low potential for nuisance algal blooms. Since 2009 phosphorus concentrations have reached the threshold of between good and moderate water quality three times. Lake Union typically has phosphorus concentrations within the moderate water quality range. In 2015 Lake Washington had incidences of toxic algae blooms above state guidance values throughout the year. (see Health and Safety section).

Lake Sammamish is the only one of the three lakes with an approved management plan that includes designated water quality goals. The 1994 plan calls for an annual mean volume weighted total phosphorus concentration (VWTP) of 22 µg/L or less. NOTE: The King County Environmental Laboratory changed the analytical methods for total phosphorus in 1998 which resulted in a low bias in lake total phosphorus compared with results prior to July 1998. There was another method change in 2007. Therefore lake phosphorus results collected after to July 1998 are adjusted for both method changes for long-term data comparisons with the 1994 management goals. Annual VWTP met the lake management goals with 17.7 µg /L and 19.1 µg/L at the north and south lake stations respectively.

Influencing factors: In this region, phosphorus is most often the nutrient that promotes algal growth in freshwater. The more phosphorus that can be stopped from entering lakes, the less chance that a potentially toxic cyanobacteria bloom will occur. Phosphorus can be managed through well-designed drainage systems, maintenance of sewer infrastructure, changing homeowner and business behaviors (appropriate landscaping practices), education and incentives, and replacing watershed septic systems with sewers. King County supported state legislation, which took effect in 2013, that banned the sale of lawn fertilizers containing phosphorus.

Existing DNRP response: King County will continue to monitor these lakes as part of its ongoing Major Lakes Ambient Monitoring Program. This program is designed to track how lakes respond over time to various activities and inputs from the watersheds through influent streams, lake nutrient cycles, ecological interactions, and seasonal or year-to-year variability in weather. The goal of 100 percent of the three major lakes being within the range of moderate to low risk of potential algal blooms was met in 2015. If the lakes begin to show serious deterioration in terms of their beneficial uses, actions will be taken to further investigate causes and plans will be made.

Priority new actions: In 2012 Washington State signed the "Clean Fertilizers, Healthier Lakes and Rivers" legislation (ESHB 1489) into law. The legislation manages the sale of phosphorus in fertilizers and provides a commonsense and cost effective approach to making sure that our lakes and rivers are clean.

Data source: The data source for this indicator comes from the King County DNRP/WLR Division's Major Lakes Monitoring Program.

Collection frequency: Samples were collected monthly ( December through February) and twice monthly (March through November) from three stations in Lake Union, two stations in Lake Sammamish and four stations in Lake Washington.

Methods for analysis: This TSI-TP measure uses summer total phosphorus concentrations measured in lakes Washington, Sammamish and Union, converted to the Trophic State Index. The Trophic State Index relates phosphorus to the amount of algae that the lake can support. The potential for nuisance algal blooms is considered low if the TSI is less than 40, moderate if between 40 and 50, and high with values above 50.

NOTE: In 1998 and 2007, the King County Environmental Lab (KCEL) made two important improvements to their methods and instrumentation for examining total and dissolved nutrients in the freshwater matrix. On July 1, 1998, KCEL began using a new digestion technique for total phosphorus and total nitrogen analysis. On January 1, 2007, the King County Environmental Lab switched the instrument used for the automated analysis of dissolved nutrients in addition to improving the digestion method for total nutrients. Long-term trend analysis assumes that values remain comparable over the time period examined, and that no bias has been introduced due to changes over time in the collection or measurement methods. The instrument and method changes significantly biased results for phosphorus and impacted comparability over time. The application of correction factors allows for comparability of data collected pre- and post- the 1998 and 2007 changes which allows for long-term trend analysis.

Data Reference:

Temperature in Large Lakes

About this measure: This indicator is the trend in annual time and volume-weighted average temperature of Lake Washington and Lake Sammamish (1993-2015). This indicator is chosen as a proxy to track the impact of climate change (natural variability and human-induced global warming) on the two largest lakes in King County.

Status: Annual average temperatures of Lake Washington and Lake Sammamish vary from year to year depending on changes in weather, particularly to changes in the regional air temperature (Mean Annual Temperature in the Atmosphere section).

No statistically significant trend in annual average lake temperature was observed in either lake over the period 1993-2015. This is primarily due to the large inter-annual variability in average lake temperature and the length of the records available to detect a statistically significant trend. Statistical analysis of temperature data for Lake Washington from 1963 to 2015 provided by the University of Washington collected as part of a long-term lake ecology study indicates a statistically significant long-term increase in annual average lake temperature of approximately 0.17°C per decade (0.31°F per decade). It should also be noted, that the average Lake Washington temperature in 2015 was the highest observed since at least 1963. There is a significant amount of synchrony in regional lake temperatures, so it is reasonable to assume that Lake Sammamish had a similar warming trend over the period 1963-2015 and also experienced the highest average temperature over at least the same time period.

Average temperature in large lakes Influencing factors: The water temperature of these two large lakes is influenced by regional climate, which in turn is influenced by global climate variability and change. Studies of long-term changes in the temperatures of large lakes throughout the world have detected the influence of human-caused warming of the atmosphere superimposed on regional scale variability. Climate variability in this region is strongly influenced by variation in Pacific Ocean circulation. Two measures of this variability that differ in the time-scales of their influence are the El Nino Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). ENSO varies from warm to cool phases on the scale of years, while PDO varies on a decadal scale.

Some of the observed long-term warming of Lake Washington and Lake Sammamish is likely due to PDO variability, which shifted from a cool to a warm phase in 1976-1977, returning to a cool phase in 1998 until a strong warm phase began in 2014-2015. The recent shift to a warm phase of the PDO, which appears to be the main pacemaker of variability in the rate of increase of global mean surface air temperature, may mean that the strong uptick in lake temperatures in 2015 is a harbinger of further increases in the near future. Without long term temperature monitoring of the kind performed by the University of Washington and King County, it will not be possible to separate the influence of natural variability from the effects of human-induced global warming on these lakes. Research has also shown that the effect of climate variability and change is not limited to lake temperature, but includes ecological changes that result from shifts in the timing of the onset of lake thermal stratification — the processes that lead to warmer lake water generally also lead to earlier thermal stratification of these lakes.

Existing DNRP response: King County will continue to monitor these lakes as part of its ongoing Major Lakes Ambient Monitoring Program. This program is designed to track how lakes respond over time to various activities and inputs from the watersheds through influent streams, lake nutrient cycles, ecological interactions, and seasonal or year-to-year variability in weather. Improved understanding of the influence of climate variability and change on lake quality will help separate changes caused by watershed activities from the influence of climate.

Priority new actions: King County is collaborating with the Global Lake Ecological Observatory Network (GLEON) to support the development of a scalable, persistent network of lake ecological observations.

Data source: The data source for this indicator comes from the King County DNRP/WLR Division’s Major Lakes Monitoring Program (1993-2015). Long-term Lake Washington temperature data (1963-2015) were also provided by Dr. Daniel Schindler, University of Washington, Seattle, WA.

Collection frequency: Analysis was based on temperature profiles that were collected monthly (December through February) and twice monthly (March through November) from a central station in Lake Sammamish and in Lake Washington.

 

Methods for analysis: Temperature profile data were interpolated to a uniform depth intervals and a lake depth-volume relationship was used to calculate volume-weighted average temperature in each lake for each year. A non-parametric Mann-Kendall trend test with an adjustment for serial correlation was performed to test for the statistical significance of the trend (p<0.05). In addition, a non-parametric trend slope was calculated (Sen slope).

Data References:

Additional References:

Arhonditsis, G.B., M.T. Brett, C.L. DeGasperi, and D.E. Schindler 2004. Effects of climatic variability on the thermal properties of Lake Washington. Limnology & Oceanography 49:256-270.

Coats, R., J. Perez-Losada, G. Schadlow, R. Richards, and C.R. Goldman. 2006. The warming of Lake Tahoe. Climatic Change 76:121-148.

Jankowski, T., D.M. Livingstone, H. BŸhrer, R. Forster, and P. Niederhauser. 2006. Consequences of the 2003 European heat wave for lake temperature profiles, thermal stability, and hypolimnetic oxygen depletion: Implications for a warmer world. Limnolnology and Oceanography 51:815-819.

Johnstone, J.A. and N.J. Mantua. 2014. Atmospheric controls on northeast Pacific temperature variability and change. Proceedings of the National Academy of Sciences 111:14360-14365.

Mantua, N.J. and S.R. Hare. The Pacific Decadal Oscillation. Journal of Oceanography 58:35-44.

O'Reilly, C.M., S.R. Alin, P-D. Pilsnier, A.S. Cohen, and B.A. McKee. 2003. Climate change decreases aquatic ecosystem productivity of Lake Tanganyika, Africa. Nature 424:766-768.

O'Reilly, C. M., S. Sharma, D. K. Gray, S. E. Hampton, J. S. Read, R. J. Rowley, P. Schneider, J. D. Lenters, P. B. McIntyre, B. M. Kraemer, et al. 2015. Rapid and highly variable warming of lake surface waters around the globe. Geophys. Res. Lett., 42, 10,773–10,781, doi:10.1002/2015GL066235.

Peeters, F., D.M. Livingstone, G-H. Goudsmit, R. Kipfer, and R. Forster. 2002. Modeling 50 years of historical temperature profiles in a large central European lake. Limnol. Oceanogr. 47:186-197.

Robertson, D.M. and R.A. Ragotzkie. 1990. Changes in the thermal structure of moderate to large sized lakes in response to changes in air temperature. Aquatic Sciences 52(4):360-380.

Romare, P., D.E. Schindler, M.D. Scheuerell, J.M. Scheuerell, A.H. Litt, and J.H. Shepherd. 2005. Variation in spatial and temporal gradients in zooplankton spring development: the effect of climatic factors. Freshwater Biol. 50:1007-1021.

Schnieder, P. and S.J. Hook. 2010. Space observations of inland water bodies show rapid surface warming since 1985. Geophysical Research Letters 37, L22405, doi:10.1029/2010GL045059.

Trenberth, K.E. 2015. Has there been a hiatus? Science 349:691-692.

Verberg, P., R.E. Heckey, and H. Kling. 2003. Ecological consequences of a century of warming in Lake Tanganyika. Science 301:505-507.

Winder, M and D.E. Shindler. 2004a. Climate change uncouples trophic interactions in an aquatic ecosystem. Ecology 85:2100-2106.

Winder, M. and D.E. Schindler. 2004b. Climatic effects on the phenology of lake processes. Global Change Biology 10:1844-1856.

Phosphorus in Small Lakes

Graph showing Harmful Algal Bloom Watch at King County Small Lakes About this indicator: DNRP's goal is to maintain all customary beneficial uses of county lakes. In this region, high concentrations of the nutrient phosphorus are often correlated with increased algal growth. Thus, if the amount of phosphorus entering lakes is controlled or reduced, algal blooms are likely to decrease or remain relatively stable. Algal blooms can be a nuisance because they can form scums on a lake's surface, as well as occasionally give a foul odor and taste to the water. When a bloom dies off, decomposition can deplete the oxygen levels available for other aquatic life. In some circumstances, cyanobacteria (bluegreen algae) blooms can become toxic to mammals.

Phosphorus concentrations in lake water can indicate the potential for nuisance or toxic algal blooms that impact lakes. This information can facilitate allocation of limited county resources toward restoring lakes with indications of serious degradation. This indicator uses summer total phosphorus concentrations converted to Trophic State Indicators (TSI-TP) to assess conditions. Trophic State Indicators relate phosphorus to the amount of algae that the lake can support. Values below 50 have low to moderate potential for nuisance algae blooms; values above 50 have a higher potential.

Status: There is a data gap in this indicator between 2008 and 2014 due to funding constraints. Funding was restored in 2014, and in 2015, 36 lakes were monitored and incorporated into this indicator. About 91 percent of the lakes monitored have good water quality with low potential for nuisance algal blooms.

Influencing factors: Overall lake water quality varies annually and is affected by many site-specific factors in addition to phosphorus. Phosphorus from human sources and activities can be managed through drainage system design, improved sewer service, and encouraging homeowners through education and incentives to use best management practices. Although large amounts of algae may relate to changes in conditions, abundance per se may not always reduce beneficial uses. However, a trend toward increased TSI-TP over time is probably due to changes in the watershed and should be investigated.

Existing DNRP response: DNRP restored small lake monitoring in 2014 after budget cuts in 2009 reduced the program.

Phosphorus in Small Lakes
Phosphorus in Small Lakes
2015 Findings
Download the PDF version.

Data source: The source used for this indicator is the King County DNRP WLR Division's Small Lakes Program and the LIMS Database.

Collection frequency: DNRP restored small lake monitoring in 2014 after budget cuts in 2009 reduced the program.

Methods for analysis: This indicator uses summer phosphorus concentrations converted to Trophic State Indicators (TSI-TP) to assess conditions. Trophic State Indicators relate phosphorus to the amount of algae that the lake can support. Values below 50 have low or moderate potential for nuisance algae blooms; values above 50 have a higher potential.

Data Reference:

Stream Temperature

About this indicator: This indicator is based on the stream temperature standards established by the state of Washington. The stream temperature standards were established for the protection of designated beneficial uses — particularly for the protection of freshwater spawning, rearing and migration habitat for salmon. For this particular indicator, the focus is on the moving average of the daily maximum stream temperature based on continuous (every 15 minutes) observations of stream temperature conducted at routine monitoring locations by King County, the U.S. Geological Survey and the Seattle District of the U.S. Army Corps of Engineers.

While observed exceedances of the stream temperature standard suggest impairment of designated uses, the Washington State Department of Ecology makes this determination under the Clean Water Act Sections 303(d) and 305(b) based on data collected by Ecology and additional data submitted by others. The result of Ecology's assessment includes placement of stream segments in one of five categories that range from Category 1 (meets standards) to Category 5 (polluted waters that require a Water Cleanup Plan — also known as a Total Maximum Daily Load (TMDL). Stream temperature TMDLs typically include the collection of additional data and the development of a stream temperature model to establish the magnitude of impairment relative to an idealized condition where riparian vegetation (and sometimes other factors) is restored to its maximum historic potential. King County has submitted historical temperature data to Ecology for their current (2012) freshwater quality assessment and 303(d) list which was approved by the Environmental Protection Agency.

Status: Continuous temperature data from 89 stream and river sites within or draining to King County were measured and the moving 7-day average of the daily maximum temperature was calculated for 2015 and all other years for which data were available going back as far as 2000.

This indicator suggests that many streams and rivers throughout the county exceed the 16°C standard established for the protection of core summer salmonid habitat, with the exception of a few streams found in rural areas and streams within the urban growth boundary dominated by cold groundwater inputs and/or intact riparian cover.

A stream temperature TMDL has been completed for the Bear-Evans Creek Basin, Newaukum Creek, the mainstem Green River below Howard Hanson Dam and the Snoqualmie River; and a temperature TMDL is under development for the Soos Creek Basin.

Influencing factors: Extensive development can substantially alter the extent of riparian shade that moderates daily peak stream temperatures. Development can also alter summer low flows through reduced groundwater recharge from impervious areas and by water management activities within the basin such as groundwater extraction and export via potable water supply and regional wastewater conveyance systems. Development induced increases in high flows combined with the loss of riparian tree cover can also cause the stream to become wider and shallower, which also contributes to higher peak stream temperatures. Climate change, particularly predicted increases in air temperature are expected to result in warmer stream conditions without substantial investment in restoring riparian shade and summer flow conditions.

Existing DNRP response: King County has a range of regulatory, educational, and on-the-ground programs to reduce the impacts of development on streams and protect and restore riparian vegetation. More attention is also being paid to how development and basin water management activities affect summer stream flow and approaches are being explored to restore and improve flows in streams where historical flow declines have been observed.

Priority new actions: The potential extent of impairment of streams for the designated use as core summer salmon habitat highlights the need for a more comprehensive and coordinated approach to identifying stream reaches that would most benefit from measures such as riparian shade restoration and improved summer stream flows. As noted in the Streams Water Quality Index, King County will work with Ecology, Puget Sound Partnership, and other regional stakeholders to advocate a regional scale water quality assessment, cleanup planning and implementation effort. A recent effort to develop a Puget Sound-wide stream temperature model (NorWeST;Isaak et al., 2015) might reasonably provide a foundation for such an effort.

Stream Temperature
Stream Temperature
2015 Findings
Download the PDF version.

Data source: The data source for this indicator comes from King County DNRP/WLR Division's Science and Technical Support Section, the U.S. Geological Survey, and the Seattle District Corps of Engineers.

Collection frequency: Continuous temperature (every 15 to 60 minutes) from 89 stream and river sites within or draining to King County was measured and the moving 7-day average of the daily maximum temperature was calculated for 2015.

Methods for analysis: The moving 7-day average of the daily maximum temperature (7-DADMax) was calculated by finding the daily maximum temperature each day and calculating a centered moving average over a seven day window. The maximum 2015 7-DADMax was compared to the 16° temperature standard for the protection of core summer salmonid habitat — the appropriate standard for the monitored streams.

Data Reference: Stream temperature data from King County's Hydrologic Information Center web page

Booth, D.B., K.A. Kraseski and C.R. Jackson. 2013. Local-scale and watershed-scale determinants of summertime urban stream temperatures. Hydrological Processes DOI: 10.1002/hyp.9810.

Ecology. 2000 (revised 2002). Evaluating Standards for Protecting Aquatic Life in Washington's Surface Water Quality Standards. Temperature Criteria. Draft Discussion Paper and Literature Summary. Washington State Department of Ecology, Olympia, WA. Publication No. 00-10-070.

Isaak, D., D. Nagel, M. Groce, S. Wenger, E. Peterson, J. Ver Hoef, C. Luce, S. Hostetler, J. Dunham, J. Kershner, B. Roper, D. Nagel, D. Horan, G. Chandler, S. Parkes, S. Wollrab, C. Breshears, N. Bernklau, S. Chandler. 2015. A thermal map for all Washington streams and NorWeST:

Poole, G.C. and C.H. Berman. 2001. An Ecological perspective on In-Stream temperature: Natural heat dynamics and mechanisms of human-caused thermal degradation. Environmental Management 27(6):787-802.

Torgersen. C.E., J.L. Ebersole and D.M. Keenan. 2012. Primer for Identifying Cold-Water Refuges to Protect and Restore Thermal Diversity in Riverine Landscapes. EPA 910-C-12-001. U.S. Environmental Protection Agency, Region 10, Seattle, WA.

U.S. Environmental Protection Agency. 2003. EPA Region 10 Guidance for Pacific Northwest State and Tribal Temperature Water Quality Standards. EPA 910-B-03-002. Region 10 Office of Water, Seattle, WA.


Streams Water Quality Index

Graph showing Percent stream stations in WRIA 8 & 9 with moderate to high concern WQI ratingsAbout this indicator: King County's Streams Water Quality Index (WQI) integrates key factors into a single number that can be compared over time and across locations. This index compares monthly temperature, pH, fecal coliform bacteria, dissolved oxygen, turbidity, total suspended solids, and nutrients (phosphorus and nitrogen) relative to state standards and guidelines. This index was originally based on the Oregon Water Quality Index and work by the Washington Department of Ecology. In 2009, Ecology modified the WQI to reflect revised state water quality rules for the protection of native fish and aquatic resources. In addition to modifications for revised state criteria, the WQI was further modified in 2009 by Ecology to more directly reflect conditions in Puget Sound lowland streams. For purposes of year-to-year comparison, results from previous years were recalculated using the new Puget Sound Lowland Stream WQI.

Due to budget cuts in 2009, the Stream and River Monitoring Program in WRIAs 8 and 9 was significantly reduced from 63 sites on three rivers and twenty-eight streams to 24 sites on three rivers and eighteen streams. Four of these 24 stream sites are Vashon Island streams that are monitored through funding sources not associated with the Ambient Stream and River Monitoring Program. The 2009 Ambient Stream and River Monitoring Program reductions represented a significant gap in a long-term data set for many stream stations that have been monitored since the inception of Metro's monitoring programs in the early 1970s. In late 2011, through a different funding source, 12 sites in WRIA 7 were added to the Stream and River Monitoring Program and are now included in this index. In early 2013 KC Council added enough funds to reinstate 20 routine stream sites. Beginning in 2014 KC Council again added funds to add an additional 14 routine stream sites back into the program, bringing the total sites reported here to 71.

Status: The 2014-15 WQI scores indicated that 76 percent of the 71 sampling sites were of moderate or high water quality concern (poor to moderate water quality) and 24 percent were rated of "low concern" (good water quality). Thirteen of the 17 sites rated "high concern" are in WRIA 8 — Bear, North and Thornton Creeks (high fecal coliform bacteria), Kelsey Creek and the Sammamish River (high fecal bacteria, low dissolved oxygen); both sites on Evans Creek (low dissolved oxygen); Pipers Creek (high fecal coliform bacteria, high nitrogen), Forbes Creek (low dissolved oxygen, high phosphorus), Tibbets Creek (low dissolved oxygen, high nitrogen), and McAleer (high phosphorus and nitrogen). In WRIA 9 four sites rated "high concern", Mileta and Mill Creeks (low dissolved oxygen, high nitrogen), Rock Creek (low dissolved oxygen, high phosphorus), and Springbrook Creeks (high fecal bacteria, high phosphorus, low dissolved oxygen).

Influencing factors: Generally stream water quality in King County is impacted by increased urbanization in our region — primarily stormwater runoff. However, the unusually high temperatures and drought during the 2014-15 water year affected stream temperatures and dissolved oxygen concentrations, and is reflected in the lower WQI rankings at some sites. Thirteen of the 71 streams monitored had declining WQI scores compared with the last year sampled — seven sites dropped their rating since they were last monitored in 2008 and six sites dropped their ranking since the 2013-14 water year. Sites on Little Bear, McAleer, and Mill Creek and the Sammamish River all dropped from "moderate concern" to "high concern". Sites on the Middle Fork of the Snoqualmie and Shingle Mill Creek dropped from "low concern" to "moderate concern". Six sites had improved WQI scores this last year – sites on Bear, Juanita, Longfellow, Lyon and Swamp Creeks went from "high concern" to "moderate concern", and Eibright Creek went from "moderate concern" to low concern". Stormwater, illicit connections, homeless encampments, combined sewer overflows (CSOs), waterfowl and pet wastes are the most likely sources of bacteria in urban streams. Poor livestock manure management and failing septic systems can be a potential source of bacteria in agricultural and suburban areas. In wetlands, wildlife excrement and stagnant water conditions can lead to elevated bacteria counts. High phosphorus concentrations are found in fecal material and elevated concentrations are often linked to similar sources as bacteria. In addition, elevated phosphorus concentrations are linked to areas undergoing development primarily due to erosion.

Low dissolved oxygen concentrations can be associated with low flows, wetlands, high temperatures (colder water holds more oxygen), and high levels of organic matter (bacteria use up oxygen in the process of decomposing).

Existing DNRP response: King County is responsible for preserving water quality and preventing and repairing damage to its waterways and water bodies. Attention is given to high concern sites to improve water quality. This can involve properly maintaining facilities, constructing or engineering solutions, identifying where or how pollutants are entering the stream, and/or educating adjacent property owners about the impacts of pesticides and fertilizers on streams.

Priority new actions: Results from 2014-15 King County's Streams Water Quality Index highlight the need for a comprehensive and coordinated approach to resolving in-stream flow management, since lower summer flows and increased stormwater runoff inflate every water quality measurement of the index. In 2015, King County worked with local jurisdictions and Washington State Department of Ecology on in-depth bacterial investigations for White Center, Juanita, Thornton, Issaquah, Newaukum and Boise Creeks. In 2016, efforts will be focused on further identifying sources in all of these basins and in Pipers Creek. King County will work with the Puget Sound Partnership to advocate a coordinated effort in the planning at a regional scale.

Map showing streams water quality index
Streams Water Quality Index
2015 Findings
Download the PDF version.

Data source: The data source for this indicator comes from the King County DNRP/WLR Division's Science, Monitoring and Data Management Section.

Collection frequency: This index is based on the Oregon Water Quality Index and work done by the Washington Department of Ecology. In 2009, Ecology modified the WQI to reflect revised state water quality rules for the protection of native fish and aquatic resources. In addition to modifications for revised state criteria, the WQI was further modified by Ecology to more directly reflect conditions in Puget Sound lowland streams. For purposes of year-to-year comparison, results for all samples beginning with the 2000 water year were recalculated using the new Puget Sound Lowland WQI. Due to budget cuts, the number of stations was reduced from 56 to 20 in the Lake Washington and Green-Duwamish drainage basins. In addition, four streams on Vashon Island and 12 sites in WRIA 7 are part of this index through a different funding source. In early 2013 KC Council added enough funds to reinstate 20 routine stream sites, bringing the total sites reported here to 57 sites. Beginning in 2014 KC Council again added funds to add an additional 14 routine stream sites back into the program. A site at the mouth of Boise Creek was added in December 2014 but is not included in this report as there needs to be a 12 month period of record to calculate the WQI. Samples are collected monthly for temperature, pH, fecal coliform bacteria, dissolved oxygen, turbidity, total suspended solids, and nutrients (phosphorus and nitrogen) relative to state standards.

Methods for analysis: This water quality index will generate a number ranging from 1 to 100. Higher numbers reflect better water quality. The index uses data for temperature, pH, fecal coliform bacteria, dissolved oxygen, turbidity, total suspended solids, and nutrients (phosphorus and nitrogen) relative to state standards required to maintain beneficial uses. For nutrient and sediment measures, where the state standards are not specific, results are expressed relative to expected conditions in a given eco-region. The multiple water quality parameters are combined and results aggregated over the water year to produce a single score for each sample station.

In general, stations scoring 80 and above meet expectations and are of "low concern," scores 40 to 80 indicate "moderate concern," and water quality at stations with scores below 40 do not meet expectations and are of "high concern." 72 stations in WRIA 8 and 9, and 12 stations in WRIA 7 are currently being monitored monthly. Data can be downloaded from the website.

Data Reference:



Nitrates in Groundwater on Vashon-Maury Islands

Graph showing groundwater nitrate index

About this indicator: King County has been tracking groundwater quality on Vashon-Maury Island since 2001. Nitrate is used to track groundwater quality because it is a good indicator of changes caused by human activities, such as land-use development. King County's goal is to ensure high water quality through effective land-use and on-site septic regulations.

The groundwater quality indicator uses a nitrate index, defined as the maximum concentration of the annual sampling results divided by the maximum contaminant level (MCL) of Nitrate (10 mg/L). This method yields one number. The closer this index gets to 1 (or over 1) the greater concern. The nitrate index for 2015 is above 0.5 with a value of 0.64. The nitrate index has varied from 0.64 to 0.36 since 2001.

Status: Of the 22 well/spring sites monitored, all have tested below the drinking water standard (Maximum Contaminant Level, MCL of 10 mg/L) and all but one site are less than 5 mg per liter of nitrate present. Less than half the sites tested have seen above average nitrate increases since testing began.

Influencing factors: Poor drainage systems, improperly maintained septic systems and improper fertilizer use can increase nitrate levels.

Existing DNRP response: King County plans to continue monitoring Vashon's wells and springs annually for nitrate concentrations.

Priority new actions: Additional locations have been sought to increase our understanding of island aquifers. King County intends to produce Vashon-Maury Island-wide water table, contour maps with seasonal variability that will be reported every year.

Map showing nitrates in groundwater on vashon-maury islands Nitrates in Groundwater on Vashon-Maury Islands
2015 Findings

Data source: The data source for this indicator comes from the King County DNRP/WLR Division's Groundwater Protection Program.

Collection frequency: King County has been monitoring nitrate concentrations and water level measurements on Vashon-Maury Island since 2001. During 2015, 22 well/springs sites were sampled for nitrate concentration (mg/L) on an annual basis (once a year).

Methods for analysis: In previous indicator reports (Measuring for Results), for the time period of 2001- through 2005, four groundwater quality levels designations for nitrate concentrations existed and were defined as "above 5 mg/L", "1 to 5 mg/L", "0.1 to 1 mg/L" and "below 0.1 mg/L". Averages for nitrate concentrations were compared to previous years' data and designated as "Above Average", "Same as Average" or "Below Average". The rating was based on a combination of average nitrate concentrations and the trend for the data. The groundwater quality indicator was redeveloped in 2006 to use a nitrate index, defined as the maximum concentration of the annual sampling results divided by the maximum contaminant level (MCL) of Nitrate (10 mg/L). This method yields one number. The closer this index gets to 1 (or over 1) the greater concern.

Data Reference:

Groundwater Maps and Reports

Most recent report: Vashon-Maury Island Water Resources — A Retrospective of Contributions & Highlights