Life in a Watershed

Minnesota, land of 10,000 lakes, birthplace of the Mississippi and many other rivers - all of which are fed by the dozens of overlapping watersheds in our communities.

We all live in a watershed, and we all contribute to the health of the lakes, rivers and groundwater in our watershed and beyond. A watershed is the area across or under which water flows on its way to lakes, rivers, streams and groundwater. Any area of land is made up of overlapping basins. Water flows to the lowest point in each of these basins - usually a lake, stream, pond or river. This basin is a watershed, and can come in many different shapes and sizes. The Mississippi River watershed, for example, is composed of hundreds of smaller watersheds. Waters from over thirty different states flow into the Mississippi. The waters of Minnesota flow into three major watersheds: north to Hudson Bay via the Red River; east to the Atlantic Ocean via the Great Lakes Basin and St. Lawrence Seaway; and south to the Gulf of Mexico via the Mississippi River. Minneapolis and St. Paul, of course, contribute to the Mississippi River watershed.

Many years ago, the Twin Cities area was composed of oak savannah, broadleaf forests, tallgrass prairie, and marshlands - nature's water treatment plants. With development, however, much of the land has been covered by structures, concrete, asphalt and agricultural tiling. All of these modifications prevent rainwater from being absorbed into the ground. Instead of filtering through the soil or marsh plants, water flows over these surfaces and into storm drains, absorbing pollutants along the way and depositing them into lakes, rivers and streams. In our area, this means that oil spilled in your driveway will eventually wash directly into the Mississippi.

By the time the Mississippi River reaches the Twin Cities, its waters are already polluted. Where the river reaches the Gulf of Mexico, pollutants carried by its waters cause a "dead zone" seven thousand square miles wide during the summer months. The dead zone is an area of hypoxia, where oxygen levels in the water are low, and little plant or animal life can grow there. Scientists believe that hypoxia in the Gulf is caused by excessive nutrients carried in the rivers' waters. Overabundant nutrients cause excessive growth of algae, which chokes out sunlight and decreases the amount of oxygen in the water, making it virtually impossible for fish and other aquatic life to live in the area. Due also in part to over-fishing, this dead zone has doubled in size since 1993.

The major sources of pollution in the Mississippi River and other watersheds are urban runoff and agricultural and lawn runoff. Primary pollutants include: phosphates from industrial and home detergents; excessive nitrogen and phosphorus from agriculture and lawn fertilizers; petroleum products from industrial spills, road runoff, improper disposal and recreational boating; pesticides and herbicides from agriculture and landscaping; sediment from erosion; and trash and debris from dumping, storm drains and flooding.

Although Minnesotans enjoy only a few snow-free months, our yards contribute to local water quality all year round. Every time rain falls or snow melts, water winds its way off the roofs and down the sidewalks, through the yards and streets, down storm drains and then directly into the nearest body of water.