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Lake Washington
King County, Washington
Lake Washington water quality monitoring data
Overview of the lake including water quality graphs and data, and general metrics and statistics characterizing Lake Washington.
Lake Washington story
The big picture story about Lake Washington, its problems with phosphorus pollution and factors that degrade the lake's water quality.
Greening your shoreline
A tool for lakeshore property owners on Lake Washington and Lake Sammamish to improve shorelines for people and salmon.
Water quality data
Swimming beach bacteria and algal toxin levels, and water temperature
Contains a map depicting the locations of current swimming beach sampling stations in King County. To view the current bacteria and temperature data, either click on the map or select from the list of beaches. It also contains links to archived data.
Real-time combined sewer overflow status
Look up the status of sewer overflows along Lake Washington and other locations in the Seattle area.
Tributary stream water quality data
- Cedar River
- Coal Creek
- Fairweather Creek
- Forbes Creek
- Juanita Creek
- Kelsey Creek
- Lyon Creek
- May Creek
- McAleer Creek
- Thornton Creek
- Yarrow Creek
Parks, trails and recreation
Boating regulations fact sheet
Boating restrictions, equipment requirements, safety, aquatic weed, and other related information. (Washington State marine laws also affect King County boaters.)
Burke Gilman Trail
This trail runs more than 18 miles from Shilshole Bay in the City of Seattle to the City of Bothell where it intersects the Sammamish River Trail.
Drainage basin information
Cedar River-Lake Washington Watershed
Cedar River - Lake Washington watershed map
Drainage map displaying streams, lakes, drainage divides, major roads and cities in the area that drains to Lake Washington and out the Hiram M. Chittenden Locks, except for the Sammamish Watershed area. The map is in Acrobat format. File size is 445 Kb.
Salmon and salmon recovery
Salmon restoration in the greater Lake Washington watershed
Salmon plans, volunteer and funding opportunities, news and other information.
Salmon in the greater Lake Washington watershed
Fish distribution and Salmon Watcher observation maps.
Salmon Watcher Program
Salmonid species information and illustrations of fish that you may see in your stream.
Studies/reports
Estimating toxics loadings to the Lake Washington Watershed
Lake Washington has fish with some of the highest concentrations of polychlorinated biphenyls (PCBs) measured across the state. This report answers key questions.
Lake Washington Existing Conditions Report: A report on Lake Washington water quality
Water quality trends and conditions in Lake Washington from 1990 to 2001. Summarizes lake conditions and how Lake Washington has responded to human activities that have changed the watershed.
Sediment Quality Evaluation in Lake Sammamish, Lake Union, and Lake Washington, Washington State
The Sediment Quality Triad (SQT) approach to sediment quality evaluation was used to characterize and assess the extent of altered benthic invertebrate assemblages, sediment contamination and toxicity.
Water Quality Monitoring of Five Mercer Island Drainage Basins from 2008 - 2010
Monitoring results of projects to minimize degraded runoff into Lake Washington, remove silt and control erosion.
Aquatic ecosystem responses to changing climate in the three major lakes routinely monitored by King County.
Highway 520 Bridge Storm Water Runoff Study
Part of a comprehensive evaluation of current and future water quality conditions in Lake Washington to support informed decision-making.
Lake Washington Shoreline Master Programs - by jurisdiction
For questions about Lake Washington, please contact Debra Bouchard, Water Quality Planner or Curtis DeGasperi, Lead Hydrologist, King County Science and Technical Support Section.
News and announcements
Jun. 29, 2022
External report, KING5 News
As King County beaches get busy, scientists monitoring water quality