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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 Morton

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Vital Statistics

Watershed Area 250 acres
Lake surface area 66 acres
Maximum depth 23 feet
Mean depth 15 feet
Public Park No
Boat Ramp Yes
Fish Present bass, stocked rainbow


Volunteer monitoring began at Lake Morton in the early 1980s and continued through 2008. It was discontinued in 2009, but has resumed in 2014. In 2008, the data indicated this lake was lightly colored and fairly low in primary productivity (oligotrophic - mesotrophic) with very good water quality. Phosphorus has remained stable since 1998.

Profile data suggested that thermal stratification was not stable through summer, and phosphorus concentrations did not build up in deep water. Nitrogen to phosphorus ratios remained above 20:1 through summer, which indicated that other algae were favored over bluegreens.

Lake Morton has a public access boat launch, and residents watch for early infestations of Eurasian milfoil and other noxious weeds.

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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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