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Vital Statistics

Watershed Area 331 acres
Lake surface area 19 acres
Maximum depth 31 feet
Mean depth 16 feet
Public Park Y
Boat Ramp Car top boats
Fish Present Bass


Volunteer monitoring began at Bitter Lake in the 1980s and continued from 1997 through 2008 when it was discontinued. The collected data indicated this city lake (Seattle) was nearly colorfree and moderate in primary productivity (mesotrophic), with good water quality, and that it remained stable over time with no significant trends found.

Thermal stratification appeared stable through the summer, and sedimentary phosphorus release added to deep water concentrations. Nitrogen to phosphorus ratios were occasionally below 20:1, which generally favored algae other than bluegreens. Bluegreen species were occasionally present, but never common.

Bitter Lake has no public access boat ramp, but car top boats can be launched through the city park. Residents should monitor aquatic plants growing nearshore to catch early infestations of Eurasian milfoil, Brazilian elodea, or other noxious aquatic 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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For questions about lakes in King County, please contact or call the Water and Land Resources Division front desk at 206-477-4800.