April showers bring … runoff?

Spring is a wet season, full of snowmelt and spring rain showers. We see puddles and streams running down roads and cutting through fields. This water that travels overland is called runoff. Runoff occurs when the ground is too saturated to allow water to infiltrate into the soil, so the excess water follows the contours of the land and “runs off” until it reaches a point where it can either soak into the ground or where it enters a larger body of water.

According to the MN DNR, snowmelt and spring runoff are major sources of replenishment for the entire hydrologic system, including groundwater. A majority of spring runoff ends up entering streams and lakes, swelling those water bodies temporarily and sometimes causing damaging flooding. However, some of the spring water also infiltrates into the soil, where it replenishes groundwater through aquifers. Groundwater flows into rivers and lakes through springs and seeps, which helps maintain the water level.

While runoff helps replenish the water level of lakes and rivers, it can be problematic. Since humans have vastly increased the amount of impervious surfaces on the land, we have also greatly increased the amount of water that becomes runoff. Unfortunately, the stream channels are not able to handle the vast increase, which causes erosion of the stream banks and flooding.

Runoff water is also often “dirty water” because it picks up the things it is flowing over, such as sediment, chemicals, and garbage. It transports these things to the lake or river, where they harm water quality. Excess nutrients, such as phosphorus and nitrogen, are two of the more problematic things that runoff water transports to surface waters. These nutrients feed algal blooms in lakes.

The best way to combat spring runoff is to do as Mother Nature does — allow infiltration. The mentality of the recent past was to get the water off the land as fast as possible.  We need to shift this thought process to allow water to infiltrate into the ground, where the soil can act as a filter to clean the water. Install rain gardens, which are specially designed to allow water to infiltrate, or vegetated swales, which are areas that you allow water to soak in, in your yard.

Contact the Chisago Soil and Water Conservation District for more information on rain gardens, vegetated swales or other ways to decrease runoff from your property. Call 651-674-2333 or visit www.chisagoswcd.org for more information.

Leave a Reply

Your email address will not be published. Required fields are marked *