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King County Water Quality Monitoring

King County monitors the ecological health of the Laughing Jacobs Creek basin in a variety of ways, including collecting and analyzing water quality samples. Water quality samples are collected from one station, LSIN9. Monthly monitoring began in 2014. The station is located near the mouth of Ravensdale Creek where it cross SE 312th Street.

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


A major tributary to Lake Sawyer, the fourth largest natural lake in King County, the Ravensdale Creek basin flows from Ravensdale Lake through the Henry’s Ridge Area and the Black Diamond Natural Area. The basin comprises 30% of Lake Sawyer’s 13 square miles and contains 16 wetlands (King County, 2000). It enters the southeastern portion of Lake Sawyer in the Lake Sawyer Regional Park. Within the Ravensdale Creek drainage lies a portion of the Ravensdale community.

Land use in the Ravensdale Creek basin is primarily evergreen and mixed forest. There is some development, which ranges mostly between low to medium intensity and open space. However, there is less developed land than scrub land. Scrub is approximately one-fifth of the basin followed by other land uses (barren land, grass land, and open water). In comparison, wetland and agriculture make a little over 5% and less than 1%, respectively, of the basin. See Table 1 below for more details on land use.

Table 1. Total land use in the basin


Ravensdale Creek is known to have coho salmon, which travel through Lake Sawyer to the Ravensdale Creek system to spawn.

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. Ravensdale Creek is now categorized as "Core Summer Salmonid Habitat" for aquatic life use and "Primary Contact" for recreational use. As part of the updated water quality standards, portions of Ravensdale Creek have been assigned an additional “Supplemental Spawning and Incubation Protection” temperature criteria of 16 °C. Ravensdale Creek is currently listed on the Washington State Ecology (Ecology’s) 303(d) list for violation of water temperature and bioassessment 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 (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 WQI ratings for other stream sites, please visit the Water Quality Index webpage.

Table 1. Routine monitoring summary statistics for this station from 2014 to 2019
Agriculture Developed Forest Scrub Wetlands Other
Total <1% 14% 41% 22% 6% 17%
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)5810.67.712.610.70.9
Temperature (°C)5810.63.717.89.63.6
Turbidity (NTU)581.110.4412.400.831.58
Conductivity (mSIEMS/cm)58108.195.3124.0107.06.9
Total Suspended Solids (mg/L)581.770.5026.401.203.62
Ortho-Phosphorus (mg/L)580.00210.00070.00770.00170.0013
Total Phosphorus (mg/L)580.00900.00510.03960.00830.0049
Ammonia (mg/L)580.00500.00240.02270.00460.0027
Nitrate (mg/L)580.39470.03301.10000.39550.2814
Total Nitrogen (mg/L)580.51220.12801.32000.50000.2743
Fecal Coliform(CFU/100ML)5810185515

Table 2. Storm water monitoring summary statistics for this station from 2014 to 2019
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)211.110.711.411.10.5
Temperature (°C)
Turbidity (NTU)0     
Conductivity (mSIEMS/cm)2105.0104.0106.0105.01.4
Total Suspended Solids (mg/L)31.000.801.201.000.28
Ortho-Phosphorus (mg/L)30.00170.00080.00300.00120.0012
Total Phosphorus (mg/L)30.01940.00610.04450.00760.0218
Ammonia (mg/L)30.00330.00250.00500.00250.0014
Nitrate (mg/L)30.36170.02600.57800.48100.2947
Total Nitrogen (mg/L)30.62170.57900.64600.64000.0371
Fecal Coliform(CFU/100ML)3172361417


King County operates a stream gage on Ravensdale Creek: Lake Sawyer Inflow #3 (09d).

Stream Sediment

Stream sediment data is not currently collected from Ravensdale Creek. Two sediment samples were collected in 2008 for a property characterization. However, the samples were not part of the monitoring program.

Special Studies

Lake Sawyer Management Plan

Since the mid-1980s, Lake Sawyer has experienced water quality degradation due to watershed loading. Modeling of future water quality indicates development within the watershed leading to further degradation. King County Surface Water Management, with assistance from ENTRANCO and funding by the Washington State Department of Ecology, published a study that details a water quality management approach to lessen the impacts of land use changes. As a major inflow to Lake Sawyer, Ravensdale Creek is included in the report.