Southern Minnesota Lakes: Built Different by Nature

Minnesota, the land of 10,000 lakes. When people think of Minnesota lakes, they imagine sparkling blue waters, perfect for fishing and swimming. These types of lakes are commonly found in Northern Minnesota, while Southern Minnesota lakes generally do not fit that image. A common trend is to compare our local lakes to those we see up North, however before we do that, there needs to be an understanding of why these lakes differ so greatly from each other and why they should not be compared directly against each other.

Kelly Dudley Lake in Rice County.

There are several factors that contribute to the types of lakes throughout Minnesota. Northern Lakes were formed by glaciers carving into the bedrock, while Southern Lakes were formed by prairie potholes or glacial meltwater, making Southern Lakes usually shallower than those found in Northern Minnesota. The way they were formed also leads to what type of lake bottom they have. Since Northern lakes were generally carved into bedrock, the lake bottoms are mostly made of sand and rock. Southern lake bottoms are generally made of mud. There is also a difference in the landscape surrounding the lakes. The Northern region is generally surrounded by forests and other vegetative landscapes, while Southern lakes have a large portion of their contributing watershed as agricultural land.

Other factors contribute to lake health across the state also, such as: lake shore development, in flow, water temperature, and even the amount of recreational use. All these factors contribute to the health of the lake. Southern lakes tend to have higher levels of phosphorus in the lake due to the lake bottom composition of mud, shallower depth, and the contributing landscape being a higher percentage of agriculture. High phosphorus means more plant growth in the lake, which is associated to more weeds and the green color of the lakes.

Will Southern Lakes ever be sparkling blue like Northern Lakes? They may not be able to be as clear due to the lake’s characteristics; however, they can be cleaned up and clearer than what they currently are. Some ways for lake owners to help keep their lake healthy in Southern Minnesota include: reducing lawn fertilizer use, converting lawn from turf grass to native pollinator plants, and keeping septic systems inspected and up to date. Farmers who have land that directly contributes water to lakes can implement reduced tillage practices and cover crops to help with water quality. Those who recreationally use the lakes can slow their boats down to reduce the wave action causing erosion on shorelines and to reduce the amount of muck they are stirring up on the bottom of the lakes.

Everyone can do their part in the health of our local lakes to keep them usable for generations to come. The Rice SWCD office has programs to help with the health of Southern Minnesota lakes. Please reach out to our office for more information by giving us a call at 507-332-5408. ISG, an engineering firm, holds a Southern Lakes conference every Spring in Mankato since it is recognized that Southern Lakes need to be thought of and treated differently than Northern Minnesota Lakes. Learn more about the event at https://www.isginc.com/news/the-future-of-southern-minnesota-lakes-conference-highlights-lake-solutions-new-lake-management-workshop.

Emmie Scheffler is a District Technician with the Rice Soil & Water Conservation District and is the Plan Administrator for the Cannon River Comprehensive Watershed Management Plan. She also assists landowners and farmers with the implementation of soil erosion control practices and tree windbreaks. Contact Emmie with your questions at 507-332-5408.