• Lake Twelve had fairly clear water, with moderate nutrient concentration and low algal growth.
• Lake Twelve continues to have contrasting trends. Decreasing nitrogen and chlorophyll concentrations, and deeper Secchi depths (clearer water), all suggest the water quality has been improving. In contrast, phosphorus concentrations have been increasing, an indicator of declining water quality. Further analysis (and likely more data) is needed before making any management recommendations based on these trend results.
• An algal bloom was sampled for toxin testing in July. No algal toxins were detected in this sample.
• Investigate potential sources of phosphorus that may be leading to increasing trend.
• Continue to monitor nearshore plants to catch garden loosestrife, a regulated Class B noxious weed that has been identified near Lake Twelve. 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).
