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Lake Geneva has Eurasian milfoil. If you visit the lake with a boat, please remove milfoil fragments from your trailer before leaving the ramp area!

Vital Statistics

Watershed Area 198 acres
Lake surface area 29 acres
Maximum depth 46 feet
Mean depth 19 feet
Public Park Yes
Boat Ramp Yes, no gas engines
Fish Present bass, stocked rainbow


Volunteers monitored Lake Geneva in the 1980s, from 1994 through 2008, and resumed in 2014. The lake is lightly colored and lightly buffered against pH change. It has moderate primary productivity (mid range mesotrophic), with good water quality, but up from 2008. Productivity may have increased since it was last monitored and should be watched carefully. Total nitrogen appears to be increasing slowly. Thermal stratification is stable in summer, and sediments release phosphorus to the deep water, while ammonia build-up signals low oxygen. Nitrogen to phosphorus ratios are largely above 25:1, which does not favor cyanobacteria. No toxic blooms have been identified in the lake. Lake Geneva has a public access boat ramp, and residents have funded efforts to control water lilies and Eurasian watermilfoil in the past. A community effort to form an LMD to fund a variety of lake management activities is underway.

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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 Geneva

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