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Vital Statistics

Watershed Area 310 acres
Lake surface area 50 acres
Maximum depth 45 feet
Mean depth 22 feet
Public Park No
Boat Ramp Yes, no gas engines
Fish Present bass, stocked rainbow


Volunteers monitored Shadow Lake from the 1980s-2008 and resumed in 2014. This lake is moderately colored, lightly buffered against pH change, and moderate in primary productivity (mesotrophic) with good water quality, remaining steady over time. Nutrients also show no trends.

Thermal stratification is stable in summer, but sedimentary phosphorus release adds little to deep water concentrations. Nitrogen to phosphorus ratios in the upper water are above 25:1 before fall, which does not favor cyanobacteria. Shadow was monitored for cyanotoxins from 2009-2011, but levels were consistently below the detection limit. Shadow Lake has a public access boat launch. Eurasian watermilfoil has been found in the lake since 1995, but populations do not appear to be increasing. Residents should track the milfoil population and watch for infestations of other noxious weeds.

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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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