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Vital Statistics

Watershed Area 1777 acres
Lake surface area 53 acres
Maximum depth 43 feet
Mean depth 18 feet
Public Park N
Boat Ramp Yes, no gas engines
Fish Present bass, stocked rainbow, cutthro


Volunteers monitored Lake Margaret from 2000 -2008 and resumed in 2014. This lake is lightly colored, poorly buffered against pH change, and fairly low in primary productivity (threshold mesotrophic) with very good water quality. There may be an increase in productivity over time, but the data gap prevents validation. Lake Margaret is a source of domestic water for homes nearby, making water quality of paramount concern. Thermal stratification is stable in summer, but there is little phosphorus release to deep water. Nitrogen to phosphorus ratios in the upper water are above 25:1, which does not favor bluegreens. No toxic events have been reported to-date. Lake Margaret has a public access boat launch, and residents should watch for early infestations of noxious weeds such as Eurasian watermilfoil. Filamentous green algae has been reported as a nuisance.

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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

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