2006 Results
In 2006 Fawn Lake had excellent water quality for this region of the state (NCHF Ecoregion), receiving an overall A grade. This mesotrophic lake has some of the clearest water in the county. In 2006 it had the second highest average total phosphorus of any year monitored, but this average was driven up by one very high reading on August 14. That was also the day with the lowest transparency and highest chlorophyll-a (though still quite low). ACD staff’s subjective observations of the lake’s physical characteristics and recreational suitability were that conditions were excellent for swimming and boating throughout the summer. The water was crystal clear or at worse had “some algae.”
Trend Analysis
Nine years of water quality data have been collected by the Minnesota Pollution Control Agency (1988) and the Anoka Conservation District (1997-2006). Water quality has significantly improved from 1988 to 2006 (repeated measures MANOVA with response variables TP, Cl-a, and Secchi depth, F2,6=6.92, p=0.03). The trend is driven by poorer quality, specifically high chlorophyll-a, in 1988. If 1988 data is excluded from the analysis, no changes in water quality have occurred.
Discussion
This lake’s water quality future lies with the actions of the lakeshore homeowners. Because the lake has such a small watershed each lakeshore lot comprises a significant portion of the watershed. Poor practices on a few lots could result in noticeable changes to the lake. Some ways to protect the lake include lakeshore buffers of native vegetation, washing cars on the grass not driveways, keeping yard waste out of the lake, using phosphorus-free fertilizers. Soil testing on nearby lakes and throughout the metro has found that soil phosphorus fertility is high, and lawns do not benefit from additional phosphorus.