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Jerry Wilkes enjoys a drink on his Devil Track Lake dock. Photo submitted by Ann Mershon
You probably don’t think about the water quality of our lake as you sit quietly on your dock in the evening with a nice glass of Pinot something. You listen to the waves gently lapping on the shore as you watch the moon rise. You think pleasant self-satisfied thoughts about your good fortune. I do the same. It’s mighty nice, and I feel very lucky to be here—but there is cause for concern.
How did we get this data?
The Cook County Soil and Water Conservation District has recently released a summary report covering 10 years of water monitoring of Devil Track Lake by local volunteers. Sophisticated equipment allows the volunteers to measure temperature, dissolved oxygen, electrical conductivity and pH at meter increments from the surface to the bottom of the lake. Water samples are analyzed by a lab in Duluth for calcium, phosphorus and chlorophyll-a. Additionally, water clarity is measured with a Secchi disk. The lake is tested monthly from May through September at a cost of approximately $300/ season. This cost has been absorbed by the county, but beginning this year it will have to be covered by the Devil Track Lake Property Owners’ Association. This is money well spent.
What does the data say?
While this data is complex, it can be collated into a single numerical index called the Trophic State Index (TSI). This allows water quality comparisons from month to month, year to year and lake to lake throughout Minnesota. A TSI of 30 or less indicates a very clear, cold, deep, well-oxygenated lake which would be attractive to cold water sport fish. A TSI of 80 indicates algae scum, green water, summer fish kills, low oxygen, rough fish and higher temperature. Low TSI lakes are called oligotrophic and high TSI lakes are called eutrophic. Devil Track lies between these extremes with a TSI of 42 and is called mesotrophic, fully supportive of swimming, fishing, boating as well as aesthetically pleasing.
At this time, Devil Track is in relatively good condition—BUT it has a 10-year history of gradually INCREASING TSI levels. This decline in water quality is slow, but it is consistent and statistically significant. If the decline continues at the present rate, the lake will slide into the early stages of eutrophication in about 10 years. This is serious! Studies have established a high correlation between lake water quality and surrounding property values. It is obviously in all our best interests to stop and even reverse this trend.
Why is this happening?
Studies of the Devil Track watershed feeding the lake reveal good water quality, so the watershed is not the source of unwanted nutrients and sediment. This means the probable source of our difficulties are the properties around the lake and the personal habits of the people who live there. As Pogo so famously said, “We have seen the enemy and they are us.”
What can you do?
Have your septic system pumped every three years. This is, in fact, state law. The county is working to develop a system to monitor compliance.
If your septic system has been inspected and determined to be NOT in compliance, have it brought up to code. Low interest loans are available to help with the cost. If your system hasn’t been inspected for a number of years, have it checked at your next pump out.
Leave an unmowed strip of lawn about 15’ wide at the water’s edge. This prevents the sluicing of runoff and sediments directly into the lake. The county offers grants for the professional planting of such buffers with native plants.
ABSOLUTELY do not fertilize your lawn! The nitrates and phosphates from the fertilizer inevitably leach into the lake and cause large spikes in algal growth.
Don’t flush unwanted or out-of-date medications down your toilet. These compounds eventually get into the groundwater and are disruptive even in low concentrations. Don’t use soaps or detergents directly in the lake. No washing your hair OR your dog.
If you use your boat in other lakes, follow best practices for washing and draining at both ends of your trip.
Finally, the effects of global warming are greatest further from the equator. Lakes in our area are showing significant rises in temperature. This effect by itself can cause greater algal growth and limit the species of fish which can tolerate this new environment. So, be a good world citizen and do your best to lower your carbon footprint.
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