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King County Water Quality Monitoring

King County monitors the ecological health of Little Bear Creek in a variety of ways, including collecting and analyzing water, sediment, and benthic invertebrate samples. Station 0478 is located at the mouth of Little Bear Creek at State Route 522 East, Woodinville Way exit, near the Prairie Market. Water quality samples have been collected monthly at the mouth since 1971. In 2002, the County began collecting water quality samples at an additional upstream site (S478) located at Snohomish 520 Bridge. Sampling at this site was discontinued due to budget cutbacks in 2008, but continued again in 2014. Beginning in 1987, sediment quality samples have been collected from Little Bear Creek. King County began collecting benthic macroinvertebrate samples in Little Bear Creek in 2002.

From time to time, additional studies have been conducted on Little Bear Creek. Click here for more information about Special Studies.


Water Shed Image Little Bear Creek originates in Snohomish County, about 1.5 miles north of Clearview, and flows 7.7 miles southward where it empties into the Sammamish River near Woodinville. The drainage basin is roughly 10,000 acres, most of which is outside of urban growth boundaries in rurally zoned areas. Approximately 80% of Little Bear Creek is within Snohomish County. The basin remains roughly 40% forested, with a current total impervious area of about 37% (Kerwin, 2002).

Land use in the upper basin is primarily rural with numerous horse farms and several riparian wetlands with active beaver ponds (King County WLRD, 2001a). Below Maltby Road, land use is predominantly suburban with the riparian zone narrow and broken throughout. The lower mainstem of the stream runs parallel to State Route 522 and through the commercial portion of downtown Woodinville before flowing into the Sammamish River. The lower portion of the creek is heavily impacted with poor quality riparian corridor and extensive suburban development (King County WLRD, 2001a).

In total, a majority of land use is developed and forested. Most of the development is low intensity and open space while forest is largely evergreen and mixed forest. Agriculture, specifically pasture/hay, lands are comprise a very small portion of the basin. Scrub, wetlands, and other (grassland and open water) also do not amount to a significant portion of land use. See Table 1 below for more details on land use.

Table 1. Total land use in the basin

Agriculture Developed Forest Scrub Wetlands Other
Total <1% 63% 34% <1% <3% <1%

The habitat quality of segments of Little Bear Creek were evaluated by King County staff from August to November 1999 (see Special Studies below). All segments except one were rated low to medium-low habitat quality, despite the presence of forested riparian buffers along many of the stream reaches. The dominance of deciduous forest in the corridor and/or the removal of large woody debris are thought to have contributed to the lower rating. Stream segment 3 (between 195th N.E. and the Snohomish/King County line) was the only reach that was rated medium-high habitat quality.


Historically, Little Bear Creek supports runs of Chinook, sockeye, kokanee, and coho salmon, and coastal cutthroat trout. Steelhead/rainbow trout are presumed to use the sub-area (Kerwin, 2002). Juvenile coho and cutthroat were sighted throughout all of the stream segments surveyed for the 1999 habitat study and spawning sockeye and coho were also observed (King County WLRD, 2001a). One Chinook redd was identified in Little Bear Creek in segment 3 during the 1999 King County WLRD spawning survey (King County WLRD, 2000). Segment 3 of Little Bear Creek is the only segment of the creek where both percent pool area and riffle qualities were high (King County WLRD, 2001a).

From 1996 to 2015, volunteers with the Salmon Watchers Program recorded fish observations at various locations in Little Bear Creek. Volunteers have consistently seen coho, sockeye, and kokanee salmon in the creek. Less commonly spotted were Chinook salmon and cutthroat trout.

Water Quality

Water quality samples are analyzed monthly for temperature, dissolved oxygen (DO), pH, conductivity, turbidity, total suspended solids, ortho-phosphorus, total phosphorus, ammonia, nitrate-nitrogen, total nitrogen, and fecal coliform (FC) bacteria. Results are compared to State water quality standards. Water quality standards are designed to protect public health and aquatic life. Comparing monitoring results to water quality standards allows an understanding of how safe the creek is for recreational contact as well as for aquatic life (see link at top of page to view current water data).

State water quality standards were revised in 2003. Little Bear Creek is now categorized as “Core Summer Salmonid Habitat” for aquatic life use and “Extraordinary Contact” for recreational use. As part of the updated water quality standards, the creek has been assigned an additional “Supplemental Spawning and Incubation Protection” temperature criteria of 13 ºC to be applied from September 15th to May 15th. Little Bear Creek is on the Washington State Department of Ecology’s (Ecology) 303(d) list for violation of water temperature, DO, and bioassessment standards (Category 5). The creek has an EPA-approved Little Bear Bacteria total maximum daily load (TMDL) plan in place and implemented for FC bacteria (Category 4a).

See Table 2 below for routine monitoring summary statistics of water quality data collected to date. If stormwater data is available for this site, it will be shown as Table 3. Historical data reviews can be found in the annual reports produced by METRO/King County DNRP.

Long-term Trends

A 25-year (1979 – 2007) trend analysis was conducted with water quality data from station 0478 in Little Bear Creek. Results indicated that water quality might have declined over this 28-year period with a significant decrease and significant increases in water temperatures, total phosphorus, and conductivity. High conductivity can suggest the presence of unidentified dissolved charged substances in the water. Water at the mouth of Little Bear Creek is becoming less acidic as indicated by the significant increase in pH. (The pH remains within acceptable range relative to the state standards.) Decreased total suspended solids (TSS), some nutrients (ortho- phosphorus, ammonia and total nitrogen), and bacteria levels indicate some improvements in water quality in the same 28-year period.

Water Quality Index

A Water Quality Index (WQI) rating system was developed by Ecology that evaluates several water quality parameters and gives a single rating of “high,” “moderate,” or “low” water quality concern. To see how these ratings compare with other stream sites, please visit the Water Quality Index webpage.

Table 1. Routine monitoring summary statistics for this station from 1971 to 2024
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)34610.97.113.611.01.1
Temperature (°C)4849.
Turbidity (NTU)4504.590.3056.602.806.42
Conductivity (mSIEMS/cm)310151.656.0200.2154.923.8
Total Suspended Solids (mg/L)4858.380.80115.004.4013.58
Ortho-Phosphorus (mg/L)4850.02700.00700.19000.02480.0122
Total Phosphorus (mg/L)4840.05900.02730.57000.05110.0348
Ammonia (mg/L)4850.02700.00480.24200.02250.0231
Nitrate (mg/L)4850.83000.35402.50000.73000.3343
Total Nitrogen (mg/L)4071.11140.52102.37001.05000.3553
Fecal Coliform(CFU/100ML)4524005230001301417

Table 2. Storm water monitoring summary statistics for this station from 1971 to 2024
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)4210.98.813.510.91.3
Temperature (°C)589.
Turbidity (NTU)5221.852.1997.0015.0020.92
Conductivity (mSIEMS/cm)28130.888.0177.0131.024.7
Total Suspended Solids (mg/L)6046.094.60194.0030.5042.54
Ortho-Phosphorus (mg/L)600.03160.01540.16200.02630.0237
Total Phosphorus (mg/L)600.13740.02980.47900.10650.0945
Ammonia (mg/L)600.03620.01200.11000.02900.0221
Nitrate (mg/L)600.80420.39902.30000.69350.3566
Total Nitrogen (mg/L)581.41030.71402.90001.37500.4222
Fecal Coliform(CFU/100ML)60212535190007053785


King County maintains streamflow and temperature gages on Little Bear Creek:

  • Streamflow: SR 202 (30A), 233rd PL SE Snohomish County (30B), above tributary 0083 Snohomish County (30C)
  • Water temperature: North side of bridge off Maltby Rd at river mile (RM) 5 (30E)

Stream Sediment

Sediment samples were collected from eight stations about a mile apart, along a nine mile reach of Little Bear Creek in the summer of 2004 (see map). Additional samples were collected at the legacy site (0478) from 2004 - 2010. Concentrations of detected chemicals in all samples were below all sediment quality guidelines, suggesting little potential for adverse effects in sediment-dwelling organisms. The low chemical concentrations found in Little Bear Creek suggest that current pollution control efforts in the basin should be focused on maintaining current water and sediment quality.

Benthic Invertebrates

Benthic macroinvertebrates are small animals visible to the naked eye (macro) that lack a backbone (invertebrate) and live in or around the streambed (benthic). This group includes aquatic insects (such as mayflies and dragonflies), crustaceans, clams, snails, and worms. Benthic macroinvertebrates are of interest to scientists and water resource managers because they are an excellent indicator of the biological health of stream ecosystems and are a critical component of the food web in aquatic communities. Scientists quantify the composition and diversity of benthic macroinvertebrate populations in a stream to compare the biologic integrity of different streams. King County has utilized benthic macroinvertebrate sampling to assess biological health of numerous creeks across the county (see map).

For more information about benthic macroinvertebrates and King County’s Benthic Macroinvertebrate Program, please visit the King County Stream Bug Monitoring webpage. To see the benthic macroinvertebrate data for Little Bear Creek, please visit the Puget Sound Stream Benthos webpage.

Special Studies

Habitat Inventory and Assessment of Three Sammamish River Tributaries: North, Swamp and Little Bear Creeks

From August to November 1999, King County conducted habitat assessment on North, Swamp, and Little Bear creeks. These streams are the three major northern tributaries to the Sammamish River. The Little Bear Creek habitat assessment took place from its confluence with the Sammamish River to 180th St. S.E. in Snohomish County and 371 meters of the Great Dane tributary.

The results of these habitat assessments indicate that the channel and habitat structure of a number of the segments in all three streams are frequently degraded relative to values from published "properly functioning conditions" for the Puget Sound or the Pacific Northwest region. These data provide important baseline information for any restoration projects that might occur in the basins, as well as for monitoring changes in habitat quality. These assessments may be used for limiting factor analysis for the threatened Chinook salmon as well as other salmonid species in these basins.

Little Bear Creek Fish Barrier Removal

The Adopt-A-Stream Foundation is working on the removal of a culvert as well as construction of riparian and in-stream habitat improvements. This project is partially funded by a King County Waterworks Grant.

205th Street Culvert Repair

In 2000, Snohomish County Surface Water Management improved fish survival through streambed erosion control measures, pool building, and culvert repair. Fish cover and other habitat features were provided. This project was partially funded by a King County Waterworks Grant.

Small Streams Toxicity/Pesticide Study

In 1999, King County conducted a pesticide study on Lyon, Juanita, and Lewis creeks. In 2000 the study was repeated at Lyon, Swamp, and Little Bear creeks. In 2001, Big Bear and Issaquah Creeks were sampled. And in 2002, North, Little Bear, and the 124th street Creeks were sampled. Rock Creek was tested for pesticides in 1999 and then it was used as the reference stream for toxicity testing during each year of the study. The County collected samples for pesticides, other organics, metals, suspended solids, and toxicity (Ceriodaphnia dubia, and Selenastrum capricornutum).

Water Resources Inventory Area (WRIA) 8

In WRIA 8, citizens, scientists, businesses, environmentalists and governments are cooperating on protection and restoration projects and have developed a science-based plan to conserve salmon today and for future generations. Please visit the WRIA 8 webpage to see how this creek is part of this WRIA 8 planning process.