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Vital Statistics

Watershed Area 573 acres
Lake surface area 17 acres
Maximum depth 14 feet
Mean depth feet
Public Park No
Boat Ramp No
Fish Present


Volunteers monitored Welcome Lake from 1996-2008 and resumed in 2014. The lake water is moderately colored, lightly buffered against pH change, and moderate in primary productivity (mesotrophic) with good water quality. Productivity decreased from 1996 through 2002, but may have increased slowly since then. The large data gap from 2009 – 2014 prevents verification. Thermal stratification is not stable in summer, so there are no increases in phosphorus or ammonia in the deep water. Nitrogen to phosphorus ratios hover around 25:1 from mid-summer through fall, which can favor cyanobacteria. However, there are no reported toxic events to-date. Welcome Lake has no public boat launch, but residents should watch for Eurasian milfoil, as well as other noxious 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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