Water Quality

Deer Lake’s wild beauty and the health of its fisheries depend on the cleanliness of the lake’s water and Deer Lake has always been comparatively pristine compared to its peers. Unfortunately, the long term trend of Deer Lake’s water quality is not good. While their are many ways to measure the health of a lake, one that serves as a good general proxy is water clarity as measured by a secchi disk. Over more-or-less the past decade (from 2015 to 2022), the water clarity decreased by an average of between 5 to 14 inches of clarity annually, resulting in a total clarity loss of around 3 to 8 feet.

Causes of Water Quality Reduction

While there are many possible reasons for the decrease in lake clarity, the most likely culprit remains phosphorous runoff entering the lake. Increases in the level of phosphorus in a lake creates additional nutrients for light-blocking algae. As these algae decay, they use oxygen in the water. Deoxyginated water makes a lake less hospitable for marine life, thus depleting fisheries. On a more visceral level, algal blooms also make lake water slicker to swim in and less clean lakes can be homes to bacteria that cause ear infections. This happened to Lake Eerie in the 70s and again recently, making drinking water in nearby Toledo unsafe.

What Deer Lake Property Owners Can Do to Help

The Minnesota Department of Natural Resources publishes a shoreline guide that has in-depth information about water quality management, but the takeaways for homeowners on Deer Lake are essentially twofold.

First, you can regularly inspect your septic system and encourage your neighbors to inspect theirs. As of this writing, there are nearly 70 properties on Deer Lake with septic tanks that have no record of inspection in the past 15 years. Of those uninspected, perhaps half are likely leaking. If your septic system has not been inspected in the past 15 years, Itasca county has a number licensed inspectors who can examine it for compliance. For homeowners needing to replace a septic system, Itasca county offers low interest loans. None of us want to swim in what’s leaking from a septic system. Talk to your neighbors and friends on the lake. Leaking septics affect us all.

The second thing you can do to prevent phosphorus runoff is to manage your shoreline. For the purposes of water clarity, the ideal is to leave your shoreline wild or else create shoreline buffers around your waterfront. Certainly this won’t work for everyone on the lake, but the more native planting you can do, the better. You can also avoid using fertilizer anywhere near the lake front.

What Visitors Can do to Help

The primary thing that visitors can do to help Deer Lake’s water quality is to have any watercraft you bring onto the lake inspected for Aquatic Invasive Species(AIS) at the the public access shore station. For more information, see our AIS page.

Deer Lake Association