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King County Small Lakes Information and Data


If you have question on this site, please contact Sally Abella
(206) 477-4605.

Horseshoe Lake

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Vital Statistics

Watershed Area 256 acres
Lake surface area 10 acres
Maximum depth Not Available
Mean depth Not Available
Public Park N
Boat Ramp N
Fish Present Not Available

Overview

Volunteer monitoring began at Horseshoe Lake in water year 2000 and continued from 2002 through 2008, after which it was discontinued. The data indicated that this rural lake was lightly colored and moderate to high in primary productivity (mesotrophic to eutrophic), with good to fair water quality. There wasan upward trend in productivity with good correlation over the years of measurement.

The lake is too shallow for profile sampling, and thermal stratification was unstable over summer. Nitrogen to phosphorus ratios were above 20:1, which generally favors other algae over bluegreens.

Horseshoe Lake has no public access boat launch, and widely fluctuating annual water levels may make invasion by noxious aquatic weeds unlikely over the long term. The lake level is generally thought to reflect groundwater levels in winter and a perched water table in summer.

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Maps

bathymetric map lake watershed map
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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