• Lake Retreat had fairly clear water, with low nutrient concentrations and moderate algal growth.
• Long-term trends suggest that water quality in Lake Retreat has been declining over time, with increasing nitrogen and phosphorus concentrations, and shallower Secchi depths.
• No algal blooms were reported for toxin testing in 2023.
• Investigate potential sources of phosphorus that may be leading to increasing trend.
• Continue to monitor nearshore plants to catch purple loosestrife, a regulated Class B noxious weed that has been identified near Lake Retreat. If spotted, notify the King County Noxious Weeds Program.
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.
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).
