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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.

Lake Killarney

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Vital Statistics

Watershed Area 185 acres
Lake surface area 31 acres
Maximum depth 15 feet
Mean depth 9 feet
Public Park Y
Boat Ramp Yes, no gas engines
Fish Present Bass, stocked rainbow


Volunteer monitoring began at Lake Killarney in the late 1980s and continued through 2008. It was discontinued in 2009, but has resumed in 2014. In 2008, the data indicated that this lake, partly in Federal Way, was lightly colored and fairly high in primary productivity (borderline eutrophic) with fair to good water quality. There were no statistically significant trends over time.

Profile data suggested that thermal stratification was not stable through summer, and sedimentary phosphorus release did not build up in deep water. Nitrogen to phosphorus ratios varied close to 20:1, which indicated that at times bluegreens might be favored over other algae.

Lake Killarney has a public boat launch and in the past has been heavily infested with milfoil. Though herbicide treatments were successful, residents should keep an eye on aquatic plants growing nearshore to catch early new infestations.

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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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