Star Lake

Vital Statistics
Overview
Maps
Water Quality Data
Reports and Related Links

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Star Lake has a public access boat launch, and the lake has been treated for Eurasian milfoil in the past. Residents should watch aquatic plants growing nearshore to catch new infestations of this or other aquatic noxious weeds.

Vital Statistics

Watershed Area	376 acres
Lake surface area	34 acres
Maximum depth	50 feet
Mean depth	25 feet
Public Park	No
Boat Ramp	Yes, no gas engines
Fish Present	bass, stocked rainbow

Overview

Volunteer monitoring began at Star Lake in the 1980s and continued with few gaps through 2008, after which it was discontinued.

The key takeaways from the 2025 monitoring season are:

• Star Lake was last monitored in the Lake Stewardship Program from 1996 through 2008. • Star lake has very clear water with low nutrient concentrations and low algal growth. • Long-term trends suggest that water quality in Star Lake has been improving over time, with decreasing chlorophyll-a and nitrogen concentrations, and deeper Secchi depths (clearer water). • Nitrogen-to-phosphorus (N:P) ratios were above 25 for most of the monitoring season. This indicates a low likelihood for the algal community to be dominated by cyanobacteria (which have the ability to produce toxins). • No algal blooms were reported for toxin testing in 2025.

Maps

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

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).

Reports and Related Links

2024 Water Quality Plot

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