2005 Results:
In 2005 Ham Lake had above-average water quality for this region of the state (NCHF Ecoregion), receiving an overall B grade. The lake is slightly eutrophic. Chlorophyll-a and Secchi depths in recent years have been similar to all other monitored years. The average total phosphorus levels in 2004 and 2005 have been the highest ever recorded, but both of these averages are driven by a single high reading each year which may likely be a contaminated sample. The 2005 errant phosphorus sample (180 ug/L on June 15) was retested to ensure it was not a lab error, and the result was the same. The high reading could be due to chance introduction of a contaminant into the bottle, contamination during bottle handling, or may in fact be an accurate measurement of lake conditions. For both 2004 and 2005, if the single high phosphorus sample is ignored, then the year’s average is similar to all previous years. ACD staff’s subjective observations of the lake included that the lake was nearly crystal clear in early spring, and progressed to having “some” algae mid to late summer. The lake had no or minimal problems for swimmers and boaters due to water quality, but an abundance of curly leaf pondweed hampers aquatic recreation in the spring.
Trend Analysis:
Eleven years of water quality data have been collected by the Minnesota Pollution Control Agency (between 1984 and 1997) and the Anoka Conservation District (between 1998 and 2005). Lake water quality has fluctuated from “A” to “C” water quality grades, but there is no significant long-term trend (repeated measures MANOVA with response variables TP, Cl-a, and Secchi depth, F 2,8=0.90, p=0.44).
Discussion:
Current threats to lake water quality include runoff from residential areas, curly leaf pondweed, and perhaps sediment disturbance by high-powered boats and jet-skis. The City of Ham Lake is working on measures to reduce pollution from failing septic systems. To address curly leaf pondweed p rob lems, low-dose whole-lake treatments with herbicides might be effective. In addition to these water quality issues, some local anglers feel that fishing on this lake has declined since the establishment of the County Park and associated boat ramp due to an increase in users.