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King County Water Quality Monitoring

The Water Resource Inventory Area (WRIA) 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.

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

Watershed

Water Shed Image

Cherry Creek is an east-to-west oriented stream that enters the Snoqualmie River just north of the City of Duvall, Washington, approximately seven miles upstream of the river’s confluence with the Skykomish River near the City of Monroe, Washington. 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.

Land use in the basin is predominantly forest and scrub. Forest consists of evergreen, mixed, and deciduous. There are roughly the same amounts of developed lands and wetlands. Developed is mostly open space. Currently, there is no agriculture in 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 5% 73% 13% 4% 5%

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. Cherry Creek is now categorized as “Spawning, Rearing and Migration Habitat” for aquatic life use and “Primary Contact” for recreational use. As part of the updated water quality standards, portions of Cherry Creek have been assigned an additional “Supplemental Spawning and Incubation Protection” temperature criteria of 16 °C. Two reaches of Cherry Creek are listed on the Washington State Department of Ecology's (Ecology) 303(d) list for violations of pH standards (Category 5). The creek has two types of EPA-approved total maximum daily load (TMDL) plans in place and implemented: a Snoqualmie River Watershed Multiparameter TMDL for FC bacteria and DO; as well as a Snoqualmie River Watershed Temperature TMDL (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.

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 Cherry Creek ratings compare with other stream sites, visit the Water Quality Index webpage.

Table 1. Routine monitoring summary statistics for this station from 2011 to 2019
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)10111.38.813.411.21.1
Temperature (°C)10110.13.017.910.04.2
Turbidity (NTU)901.720.3411.901.291.65
pH1007.416.928.697.360.29
Conductivity (mSIEMS/cm)10156.331.3101.046.719.6
Total Suspended Solids (mg/L)1013.530.6034.001.665.04
Ortho-Phosphorus (mg/L)1000.00610.00210.02410.00460.0039
Total Phosphorus (mg/L)1000.01380.00530.03160.01340.0052
Ammonia (mg/L)1010.00580.00210.02130.00550.0030
Nitrate (mg/L)1010.47900.11901.05000.39500.2402
Total Nitrogen (mg/L)1000.60020.24301.28000.50950.2497
Fecal Coliform(CFU/100ML)1012812101833

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 webpage.

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.

Special Studies

2017 Snoqualmie River Juvenile Yearling Chinook Habitat Use and Distribution

The Snoqualmie River supports a population of wild Chinook salmon which is one of two Chinook populations in the Snohomish River Watershed. This 2017 pilot study looks to organize relevant information on yearling Chinook to evaluate distribution and habitat use specific to this life history type in the Snoqualmie Watershed.

Hot Water and Low Flow: The Summer of 2015 in the Snoqualmie River Watershed

This report summarizes water temperatures measured during the summer of 2015 in the Snoqualmie River watershed. Temperatures were considerably higher than normal and flows were at a record low across the watershed. This work emphasizes the value of addressing water temperature issues at a site- and basin-scale to build watershed resiliency for salmon.

Snoqualmie Watershed Forum Ten-Year Status Report (2005-2015): Real Progress, Real Challenges

The report summarizes progress, trends and challenges in habitat restoration and habitat protection in the Snoqualmie watershed during the first ten years of implementation following completion of the Salmon Plan. Progress towards riparian restoration in Cherry Creek exceeded the 10-year goal by 185%. Additionally, Cherry Creek, as well as other Snoqualmie River tributaries, experienced exceptionally high water temperatures. Such conditions can have important implications for salmon in the future.

Snohomish Basin Protection Plan

With funding from the U.S. Environmental Protection Agency, watershed partners developed the Snohomish Basin Protection Plan to identify strategies to prevent the degradation of hydrologic processes that support salmon or salmon habitat, and also provide numerous other services, such as flood control, clean drinking water and irrigation supplies. The report identifies geographic areas that are important to the goal of protecting hydrology, and examines new and existing tools to help support that goal. Through the protection of hydrology, the SBPP aims to ultimately protect habitat quality, quantity, and heterogeneity for fish and wildlife.

Lower Cherry Creek and Lower Ames Creek Watersheds Dissolved Oxygen Study

Dissolved oxygen (DO) concentrations have frequently failed to meet Washington State water quality standards in the Snoqualmie River flood plain Agricultural Production District (APD) reaches of Cherry and Ames Creeks. However, Cherry and Ames Creeks are not on the federal Clean Water Act Section 303(d) list for DO because the data were yet to be verified for the most recent 2008 water quality assessment.

This study was conducted in order to: (1) characterize DO concentrations, (2) identify possible mechanisms that influence DO, and (3) provide information about the possibility of low DO coinciding with high groundwater-to-surface-water ratios during late spring following long periods of soil saturation.