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Vital Statistics

Watershed Area 8120 acres
Lake surface area 279 acres
Maximum depth 58 feet
Mean depth 26 feet
Public Park Yes
Boat Ramp Yes, outboard restriction
Fish Present stocked rainbow, bass


Volunteers monitored Lake Sawyer in the 1980s through 2014.This lake in Black Diamond is clear, moderately buffered against pH change, and low to moderate in primary productivity (borderline mesotrophic) with very good water quality. Productivity appears to have stabilized after wastewater diversion in the early 1990s and has remained steady since 2008. A lake management plan was completed by King County in 2000. Thermal stratification is stable in summer, and a small amount of sedimentary phosphorus release adds to deep water concentrations. Nitrogen to phosphorus ratios in the upper water during summer are often above 25:1, but can sometimes favor cyanobacteria. Sawyer was monitored for cyanotoxins from 2009-2011, but values have been below detection levels. Lake Sawyer has a public access boat launch and a history of Eurasian watermilfoil infestation with little control, for which a management plan is being prepared.

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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

Lake Sawyer Community Club

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