Kelsey Creek Site 0444

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King County Water Quality Monitoring

King County monitors the ecological health of Kelsey Creek in a variety of ways including collecting and analyzing water, sediment, and benthic invertebrate samples. Since 1976 water quality samples have been collected monthly from two sites along on the creek. Station 0444 (previously referred to as Mercer Slough in some reports) is located at the mouth of Kelsey creek at the gauging station located off Interstate 405, under the trestle near the Richards Road exit. Station D444 is located at the footbridge in the northeast quarter of Kelsey Creek Park. Sediment samples have been collected from Kelsey Creek as part of the Streams Sediment Monitoring Program starting in 1987. Benthic invertebrates were sampled from the creek in 2002 and 2003.

From time to time additional studies will be conducted on Kelsey Creek. Click here for more information about these Special Studies of Kelsey Creek.

Kelsey Creek Watershed

The Kelsey Creek basin comprises approximately 10,870 acres and has several streams draining west into the east channel of Lake Washington at Interstate 90. The basin includes over 19 miles of open stream encompassing Mercer Slough, Sturtevant Creek, Kelsey Creek, Valley Creek, the West Tributary, Goff Creek, Richards Creek, East Creek, and Sunset Creek. The mainstem of Kelsey Creek originates in the Phantom and Larsen Lake wetlands. Historically, the creek originated from Phantom Creek and Phantom Lake, but early pioneers redirected the Phantom Lake outlet to Lake Sammamish in the late 1880s (KCM 1993).

Land use in the Kelsey Creek basin is 37 percent single family residential, 22 percent open space, 13 percent multi-family residential, 13 percent public roads, 8 percent commercial/office, 6 percent institutional/government, <1 percent industrial, and mixed use (Kerwin 2001). Kelsey Creek Park, within the central part of the City of Bellevue encompasses 150 acres of forest and wetland habitat.

The Kelsey Creek basin area is considered to have reached built-out conditions and future development will be predominantly redeveloping existing properties. An analysis of vegetation in 2000 found 7 percent forest canopy, 38 percent green vegetation, and the rest of the watershed in unvegetated land cover such as impervious area and bare soils.

Fisheries

The suitability of Kelsey Creek for salmonids was rated as “fair” overall in 1989 (Metro 1990). Impacts from high stormwater flows and sedimentation were cited as the primary factors for declining conditions. Numerous hydrology studies have been done on Kelsey Creek. The University of Washington evaluated the hydrologic impacts of human development in the Kelsey Creek basin using historical land development patterns (Richey et al, 1981). They found that the monthly average volume of flow had increased only slightly with urban development but the storm peaks increased two to three times over the same historical period (Kerwin 2001). The City of Bellevue now operates six in-stream, regional detention facilities.

Volunteers with the Salmon Watcher Program have been observing salmon at various locations throughout the basin since 1996. Chinook, coho, and sockeye salmon have been consistently observed in the basin. Less commonly seen are cutthroat trout and chum salmon. Issaquah Hatchery coho stock are planted at various life history stages throughout the basin (Kerwin 2001).

The City of Bellevue sponsored juvenile fish surveys in four of the sub-basins in 1996 and 1997 (Kerwin 2001). In 1996, eight fish species were observed in the Kelsey Creek basin: cutthroat, coho, rainbow, sculpins, lamprey, dace, sucker, and bluegill. Coho were observed at all sampling locations, but numbers were low, averaging seven coho per 50-meter reach. Cutthroat trout were present in fairly high numbers in all sampling locations. Similar findings were noted, when the study was replicated in 1997.

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 bacteria (FC). 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. Kelsey Creek is considered a “Class AA” water body under the 1997 rules. As the 2003 rules become effective Kelsey Creek is categorized as “Core Salmon Migration and Rearing Habitat” for aquatic life 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 through May 15th. Kelsey Creek is designated as “Primary Contact” for recreational use. Both sampling sites in Kelsey Creek are listed on the 2004 Washington Department of Ecology’s (Ecology) 303(d) list for violation of dissolved oxygen (DO), temperature, and fecal coliform (FC) bacteria standards.

The water quality in Kelsey Creek was characterized as fair in 1989 (Metro 1990). The creek was described as having been impacted by high storm flows that resulted in degraded spawning habitats. To view charts of current data for Kelsey Creek, visit the links above.

Long-term Trends

A 25-year (1979 – 2004) trend analysis was conducted with baseflow water quality data showed some significant changes in the water quality since 1979. Water quality declined during this time period as indicated by significant increases in water temperatures and conductivity at both sampling sites. Other indications of declining water quality are a decrease in DO and pH at the mouth (0444) and an increase in nitrate-nitrogen upstream (D444). Decreased total suspended solids (TSS), and ortho-phosphorus at both sites indicate some improvements in water quality in the same 25-year period. In addition, ammonia and nitrate-nitrogen, and fecal coliform bacteria decreased at the mouth of the creek.

Water Quality Index

A Water Quality Index (WQI) rating system was developed by the State Department of Ecology that evaluates several water quality parameters and gives a single rating of “high,” “moderate,” or “low” water quality concern. Both Kelsey Creek stations have been rated “high” concern during the last six water years with one exception- station D444 in 2000-01 rated “moderate” concern. The “high” concern ratings were based on high bacteria, high nutrients, high summer temperatures and low summer DO. To see how Kelsey Creek ratings compare with other stream sites, visit the Water Quality Index page.

A review of the water year 2007 data shows the following violations of State water quality standards:

 

Stream Sediment

Sediment data were collected from Kelsey Creek as part of the Stream Monitoring Program from 1987 through 2002. Data were analyzed for trends, correlations, and were compared to sediment quality guidelines. No significant rends were identified during data analysis for any o f the parameters tested. Results indicate that Kelsey Creek sediments exceeded one sediment quality guidelines (arsenic). Of the 27 streams monitored in King County, Kelsey Creek had the 10th highest metals concentration.

Benthic Invertebrates

The County also monitors stream health by collecting samples of benthic invertebrates from selected streams as part of King County's Benthic Invertebrate Program. Benthic invertebrates are an important link in the food chain for fish in the creek and are an excellent indicator of stream health. In both 2002 and 2003, benthic invertebrate samples were collected, analyzed, and benthic invertebrate index scores (BIBI) were calculated for Kelsey Creek.

BIBI scores from both years indicate that conditions in Kelsey Creek were very poor for benthic invertebrates. About 90 to 98 percent of the species found in Kelsey Creek are tolerant of degraded conditions. No individuals of species that are long lived were found and only one individual that was considered sensitive to degraded conditions was found during both years. Longer-lived species tend to take longer to reproduce and along with sensitive species are among the first to disappear when a stream ecosystem is altered by human activity such as urbanization.

Special Studies

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. Visit the WRIA 8 Web page to see how this creek is part of this WRIA 8 planning process