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Webster Lake has no public access boat launch. Lake users should keep a close eye on aquatic plants growing nearshore to catch infestations of Eurasian milfoil, Brazilian elodea or other aquatic noxious weeds.

Vital Statistics

Watershed Area acres
Lake surface area 10 acres
Maximum depth feet
Mean depth feet
Public Park No
Boat Ramp No
Fish Present


Webster Lake was monitored in 1996 and 1997 and then resumed in 2020. The key takeaways from the 2020 monitoring season are:

• Further monitoring is needed to identify any long-term trends. • Webster Lake had fairly clear water, with moderate nutrient concentrations and algal growth. • No algal blooms were reported for toxin testing in 2020.

Historic profile data indicated that thermal stratification might be somewhat unstable through summer, but the sediments do release phosphorus into the deep water. Nitrogen to phosphorus ratios were generally below 20:1 late in the summer, which favors bluegreens over other species of algae.

Please see below for a link to the full 2020 Webster Lake Monitoring Report.

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This bathymetric map shows contour lines of equal depth, similar to a topographic map would for mountains and valleys. The red 'X' marks the location where water quality samples are taken.
This map shows the area of the watershed relative to the area of the lake. Generally speaking, the larger a watershed is relative to a lake, the greater the influence land use practices on lake water quality.

Click image to enlarge

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Water Quality Data  

Through a combination of efforts by volunteer lake monitors and King County staff, data relating to physical, chemical, and biological aspects of the lake have been collected for most lakes. The King County Lake Stewardship Program analyzes data to track long-term water quality trends in small lakes in western King County.

View or Download Data
Use this tool to view or download data from the lake in tabular format. You can define date ranges and select which parameters to view or download.

Chart Data
Use the charting tool to look at graphs showing single parameters for a single water year at a time.

Water quality over time
A common method of tracking water quality trends in lakes is by calculating the “trophic state index” (TSI) (Carlson, 1977) and testing the values for positive or negative trends over time. TSI indicators predict the biological productivity of the lake based on water clarity (Secchi) and concentrations of total phosphorus (TP) and chlorophyll a (Chlor). Generally at least 8 years of data without major lake management activities are needed to have confidence in a significant trend.

The average of these three TSI indicators during the growing season can be used to place lakes in one of three broad categories:
<40 = oligotrophic (low productivity),
40 to 50 = mesotrophic (moderate productivity)
>50 = eutrophic (highly productive).

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Reports and Related Links

2020 Webster Lake Monitoring Report

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For questions about lakes in King County, please contact or call the Water and Land Resources Division front desk at 206-477-4800.