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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 the Skykomish River along the Stevens Pass Highway, just west of the town of Skykomish . King County is not currently conducting benthic macroinvertebrate or stream sediment monitoring in the WRIA 7 Routine Streams Monitoring Program.


Water Shed Image

Approximately 109,000 acres of the combined Foss, Tye, Beckler, and South Fork Skykomish rivers drain King County portions of the upper south fork Skykomish above our sampling site. Possibly owing to the relatively large extent of forest in the basin, some of the healthiest aquatic habitat remaining in King County is in the Skykomish River drainage (King County WLRD, 2001). {/p>


Despite the high quality habitat, the population of Chinook salmon is listed as “threatened” under the Endangered Species Act (ESA). It is estimated that Chinook in the basin are at about 3.5% of their historic abundance (Snohomish County, 2004). In addition, there are four listed bull trout populations – North Fork Skykomish, Troublesome Creek, Salmon Creek, and South Fork Skykomish – each have populations estimated at less than 100 individuals. By contrast, the basin produces between 25-50% of coho salmon in Puget Sound (Snohomish County, 2004).

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. The Skykomish River is now categorized as “Core Summer Salmonid Habitat” for aquatic life use and “Extraordinary Contact” for recreational use under the 2003 rules. 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 July 1st. The Skykomish River is listed on the 2012 Washington State Department of Ecology's (Ecology) 303(d) list for violations of dissolved oxygen and temperature standards (Category 5). However, these violations far downstream of King County's water quality monitoring station.

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 Skykomish River ratings compare with other stream sites, visit the Water Quality Index page.

Table 1. Routine monitoring summary statistics for this station from 2011 to 2018
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)8611.59.113.511.71.0
Temperature (°C)868.00.319.46.54.6
Turbidity (NTU)762.580.2621.701.084.07
Conductivity (mSIEMS/cm)8632.217.545.032.36.6
Total Suspended Solids (mg/L)873.980.5031.501.406.35
Ortho-Phosphorus (mg/L)870.00290.00050.03350.00120.0056
Total Phosphorus (mg/L)860.01000.00510.02810.00760.0066
Ammonia (mg/L)870.00290.00200.00760.00270.0009
Nitrate (mg/L)870.08200.01300.31500.06930.0652
Total Nitrogen (mg/L)860.13810.05200.37900.11850.0764
Fecal Coliform(CFU/100ML)87413636


King County is not currently operating any stream, rain, or temperature gages on the Skykomish River. However the US Geological Survey does operate a stream gage on the Skykomish near Gold Bar, WA (12134500).

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 the Skykomish River as part of the WRIA 7 Routine Streams Monitoring, the Washington Department of Ecology collected benthic samples on the North Fork and mainstem of the Skykomish River in 2009 and 2012. To see this data, please visit the Puget Sound Benthos webpage.