Impervious Surfaces and Lakes: What’s the Connection?

Impervious Surfaces and Lakes: What’s the Connection?

I just returned from the annual Wisconsin Lakes Partnership Convention in Green Bay.  After giving my own talk, I attended other presentations including one on the impact of impervious surfaces on lakes.  Here is what I learned:

Impervious surfaces include hard, man-made structures like roofs, driveways, patios, and parking areas.  These surfaces negatively impact lakes much more than you might think.  Here is the problem.  When it rains, hard surfaces prevent water from soaking into lawns, gardens, and the like.  By preventing the natural filtration of water into the ground, impervious surfaces redirect it as run-off that carries various pollutants, such as pesticides; bacteria; and nutrients like phosphorous and nitrogen.  In addition, the run-off of this water causes erosion, essentially carrying soil from the land into the lake, reducing lake water clarity.

Studies in northern Minnesota a few years ago discovered that properties with clearer water had higher property values than those by less clear water when other factors were taken into account.  A Wisconsin study found that lakes surrounded by properties with less than 8 percent impervious surface had 19 different fish species present, including 6 game fish.  Properties with 8-12 percent impervious surface had 11 different fish species and 2 game fish.  Properties with greater than 12 percent impervious surface had 5 species, none of which were game fish.

The impact on wildlife is also negative.  Mallard young feed extensively on aquatic insects, but sediment reduces insect numbers, forcing the ducks to search elsewhere to raise ducklings.  Reduced water clarity can also cause loons problems, according to Wisconsin studies.

We say we love our lakes.  Let’s demonstrate that love by keeping impervious surfaces on our properties at a minimum.

Darby Nelson

Parts of this information came from a pamphlet published by the University of Wisconsin-Extension, Cooperative Extension.

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