Watersheds 101

Watersheds 101

I have spoken to 69 groups and organizations about lakes.  I first like to get a sense of my audience’s knowledge base, so I typically start by asking, “How many of you live on a watershed?”  If the group is a lake association, nearly all blurt out the answer, “We all do!”  Other audiences are puzzled by the question.

The truth is, to understand lakes one must first understand watersheds.

When rain falls and snow melts, some of the water soaks into the ground, increasing soil moisture and adding volume to groundwater.  The remainder of the water that does not soak in is called runoff.  A watershed is simply that area of land across which runoff flows into lakes and streams.

Some watersheds are small, perhaps a few hundred acres in size.  Others can be tens of thousands of acres or more.

As this water flows, it carries with it oil drips from parked cars, pesticides and lawn fertilizers, discarded toxic chemicals, sand and soil particles laden with phosphorus, etc.

The amount of nasty material delivered to a lake off its watershed has a major impact on the water quality of a lake. Runoff from many miles up watersheds can have significant negative impact on lakes. Effective lake protection requires reducing the flow of harmful substances contained in runoff.

That could be done by redirecting runoff away from impervious surfaces.  Several months ago I chose such an option.  Part of our lawn slopes directly toward a storm drain, where water with its nasty materials will eventually enter water bodies.  I removed a small section of grass, dug a bowl-shaped depression in line with the storm sewer grate, and planted native flowers in the depression.  Now when it rains, runoff water sinks into my ‘bowl,’ where it soaks into the soil rather than flow into the storm sewer en route to a water body.

Three side benefits emerged from my little rain garden.  I have less lawn to mow, my new plants are far more attractive than lawn grass, and I feel better knowing I have helped protect a water body, to boot!

Darby Nelson

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