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King County Water Quality Monitoring

King County has monitored the ecological health of the George Davis Creek (often called Eden Creek) basin in a variety of ways, including collecting and analyzing water, sediment, and benthic invertebrate samples. From 1987 - 2008, water quality samples were collected monthly from Station A690. The station is located at 635 East Lake Sammamish Shore Lane and downstream from the railroad tracks. Water quality sampling resumed at this site in 2014. Sediment samples were collected from the creek as part of the Streams Sediment Monitoring Program starting in 1987. King County began collecting benthic macroinvertebrate samples in George Davis Creek in 2002.

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

Watershed

Water Shed Image George Davis Creek is in the Inglewood subbasin on the northeast side of Lake Sammamish within the City of Sammamish, Washington.

Total land use in the basin is dominated by developed land, mostly low intensity and open space, along with some forest. There is no agriculture in the area and scrub and wetlands make up less than 10% of the area. Other land uses (barren lands, grassland, and open water) also constitute a small amount of the basin. See Table 1 below for more details on land use.

Table 1. Total land use in the basin

Developed Forest Scrub Wetlands Other
Total 67% 24% 2% 5% <2%

Fisheries

Only about 100 feet of George Davis Creek is currently accessible to kokanee and provides potential spawning habitat as the connection between George Davis Creek and Lake Sammamish is highly altered.

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. George Davis 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, portions of George Davis Creek have been assigned an additional “Supplemental Spawning and Incubation Protection” temperature criteria of 16 ºC. The creek is listed on the Washington State Department of Ecology's (Ecology) 303(d) list for violation of FC bacteria standards (Category 5).

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.

To view charts of current water quality data, please visit the Data Download webpage.

Water Quality Index

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

Table 1. Routine monitoring summary statistics for this station from 1987 to 2018
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)20511.28.713.011.20.8
Temperature (°C)2379.82.181.09.45.2
Turbidity (NTU)2402.880.2845.001.484.87
pH2357.606.618.607.630.26
Conductivity (mSIEMS/cm)184131.670.0168.0137.024.6
Total Suspended Solids (mg/L)2407.660.50274.002.7021.06
Ortho-Phosphorus (mg/L)2400.02070.00900.04590.02190.0070
Total Phosphorus (mg/L)2400.03350.01220.18900.03030.0188
Ammonia (mg/L)2400.01160.00200.04220.00610.0113
Nitrate (mg/L)2391.99250.90402.85002.08000.3768
Total Nitrogen (mg/L)2382.10960.68203.05002.20500.4097
Fecal Coliform(CFU/100ML)23874076024124

Table 2. Storm water monitoring summary statistics for this station from 1987 to 2018
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)1911.410.112.611.30.6
Temperature (°C)299.07.411.88.81.2
Turbidity (NTU)2946.790.90820.003.30158.41
pH297.446.808.007.500.28
Conductivity (mSIEMS/cm)15100.055.0135.091.024.9
Total Suspended Solids (mg/L)29152.141.702990.0010.00559.94
Ortho-Phosphorus (mg/L)290.02150.01090.05350.01520.0120
Total Phosphorus (mg/L)290.14420.01572.01000.03730.3757
Ammonia (mg/L)290.05900.02400.13300.04200.0436
Nitrate (mg/L)291.78490.90302.19001.79000.2895
Total Nitrogen (mg/L)292.08120.97503.84002.03000.5044
Fecal Coliform(CFU/100ML)292300410032758

Hydrology

King County is not currently operating any stream, rain, or temperature gages in George Davis Creek.

Stream Sediment

Sediment data were collected from George Davis Creek as part of the Stream Monitoring Program starting in 1987. Data were compiled and analyzed for the years 1987 through 2002. Data were analyzed for trends, correlations, and were compared to State water quality standards sediment quality guidelines. No significant trends were identified during data analysis for any of the parameters tested. Results indicate that George Davis Creek sediments did not exceed any sediment quality guidelines. Of the 27 streams monitored in King County, George Davis Creek had the 10th lowest metals concentration.

Benthic Invertebrates

Special Studies

George Davis Creek Fish Passage Culvert Project

The City of Sammamish is conducting a feasibility study. The goal is to build a new fish passable culvert under East Lake Sammamish Parkway, remove other fish passage barriers, and daylight the creek from its mouth to the east side of East Lake Sammamish Parkway. The creek drains the Inglewood Basin to Lake Sammamish and its riparian corridor is mostly undeveloped with ideal habitat for kokanee and other salmon species. Fish passage window construction is planned for summer 2020.

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 for future generations.