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King County Water Quality Monitoring

The Watershed Resource Inventory Area 7 (WRIA 7) Routine Streams Monitoring Program was established during 2011 and consists of twelve sampling sites that are distributed throughout the Snoqualmie and Skykomish watersheds. Historically in King County, routine streams monitoring has been centered on WRIA 8 (Lake Washington/Cedar/Sammamish) and WRIA 9 (Green-Duwamish). However, in 2011, a Surface Water Management (SWM) fee increase allowed King County to expand its regular water quality monitoring efforts to include the King County portions of the WRIA 7 drainage. Objectives of this program are focused on quantifying long-term water quality trends to help inform the management of salmon recovery efforts, land use regulation, and to prepare for expected increases in climate variability.

King County collects monthly water quality samples on Cherry Creek just upstream of the NE Cherry Valley Road bridge on the southern edge of Cherry Valley. King County is not currently conducting benthic macroinvertebrate or stream sediment monitoring in the WRIA 7 Routine Streams Monitoring Program.

Watershed

Water Shed Image

Cherry Creek is an east-to-west oriented stream that enters the Snoqualmie River just north of Duvall, approximately seven miles upstream of the river’s confluence with the Skykomish River near Monroe. The routine sampling location receives drainage from approximately 8314 acres of the overall subbasin. The subbasin spans the border between King and Snohomish Counties, with roughly 70% of basin area in King County. Slightly less than 3% of the subbasin lies within the City of Duvall.

Water Quality

Water quality samples are analyzed monthly for temperature, dissolved oxygen, pH, conductivity, turbidity, total suspended solids, ortho-phosphorus, total phosphorus, ammonia, nitrate-nitrogen, total nitrogen, and fecal coliform 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. Cherry Creek is now categorized as “Core Summer Salmonid Habitat” for aquatic life use and “Primary Contact” for recreational use under the 2003 rules. Two reaches of Cherry Creek are listed on the 2012 Washington State Department of Ecology's (Ecology) 303(d) list for violations of fecal coliform bacteria (Category 4A) and pH (Category 5) standards.

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. To see how Cherry Creek ratings compare with other stream sites, visit the Water Quality Index page.

Table 1. Routine monitoring summary statistics for this station from 2011 to 2017
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)8211.28.813.411.11.2
Temperature (°C)8210.33.017.910.34.1
Turbidity (NTU)711.630.345.631.261.30
pH817.396.928.127.360.26
Conductivity (mSIEMS/cm)8256.433.1101.047.419.2
Total Suspended Solids (mg/L)823.380.6027.101.724.20
Ortho-Phosphorus (mg/L)810.00630.00230.02410.00460.0040
Total Phosphorus (mg/L)810.01360.00530.02870.01340.0050
Ammonia (mg/L)820.00620.00230.02130.00570.0032
Nitrate (mg/L)820.51120.16901.05000.45350.2487
Total Nitrogen (mg/L)810.63270.30701.28000.56000.2592
Fecal Coliform(CFU/100ML)822812101933

Hydrology

King County operates multiple stream and rain gages in the Cherry Creek watershed. There is a stream gage located at the water quality monitoring site (05A). A tributary that flows into Cherry Creek just upstream of 05A is also gaged near its mouth (05B) and on its east (05B2e) and west (05B2w) forks. A rain gage (05u) is located further upstream on the mainstem of Cherry Creek just below Kelly Road NE.

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 web page.

While King County is not conducting benthic macroinvertebrate monitoring on Cherry Creek as part of the WRIA 7 Routine Streams Monitoring, King County did collect benthic samples at two locations on Cherry Creek in 2010 (Roads, at 05A) and 2012 (DNRP, at 05B). To see this data, please visit the Puget Sound Benthos webpage.