by Sara Swenson
It may seem like a land home to 10,000 lakes and the headwaters of the Mississippi River doesn’t need to worry about water. But water quality is an important concern for our state and a responsibility for all Minnesotans. By understanding how water flows around us, we can take actions that have a positive effect on our Minnesota waters and all waters downstream.
Water Quality Dynamics
Runoff. Every drop of water is at some stage of the water cycle—that is, some stage of a journey. It is important to consider both where water goes when it leaves your property and also how fast it gets there. For example, rain that falls on impervious surfaces such as roads, driveways, parking lots, rooftops, etc. is going to travel to its next destination much faster than rain that falls on pervious soil and seeps into the ground. Stormwater that does not infiltrate into the soil becomes surface runoff that flows into ditches, gutters, storm drains, etc., and ends up in surface waters like lakes and streams. Runoff is of particular concern in urban environments, where plentiful impervious surfaces increase runoff volumes and speeds. Excess runoff can cause flooding, erode soil, and carry pollutants into surface waters.
Pollutants. Materials found in eroded soils and on impervious surfaces are washed downslope along with runoff, accumulating along the way (and reaching waters in larger quantities the faster they are borne by runoff). These materials—such as sediment, pet waste, gas and oil, sand, salt, metal residue, pesticides, fertilizers, organic debris, etc.—then act as pollutants that impair water quality. Nutrients (especially nitrogen and phosphorus) also act as pollutants for lakes when introduced in excessive amounts. Phosphorus is of particular concern for lake water quality, as it absorbs more strongly into soil than nitrogen, contributing to lake eutrophication through soil erosion and runoff. Eutrophication (or hyper-eutrophication) is the process by which an aquatic ecosystem is enriched with high concentrations of nutrients and becomes a system characterized by turbid (murky) waters, frequent algal blooms, and severe oxygen depletion. Eutrophication is a natural process, but is accelerated by human activities that increase nutrient loading to surface waters, creating problems for organisms (including us!) that used to rely on them.
Best Management Practices
What can you do to help Minnesota waters? Best Management Practices (BMPs) are practices that have been developed in the agricultural, forest management, and construction fields for reducing the negative environmental impacts of their activities. BMPs also exist for residents who want to have a more positive impact on local waters. Best Management Practices for water quality use two main strategies: reducing runoff volumes and reducing phosphorus concentrations.
Reduce Runoff. Runoff leaving your property can be reduced or prevented by increasing infiltration, storage, or evaporation of water.
- Increase infiltration on your property by minimizing impervious surfaces—pave patios with flagstones or decay-resistant wood blocks that leave spaces for water to infiltrate the soil below, use permeable pavements, or choose a gravel driveway.
- Use rain barrels to collect and store rainwater that flows from your rooftops and gutters. Storing this water decreases the flow of runoff leaving your yard immediately after a storm and provides a supply for watering your garden or other later use.
- Plant rain gardens of native plants in depressions where runoff can collect. Rain garden plants soak up water, preventing excess runoff (and carried pollutants) from washing into storm drains and reaching surface waters.
Reduce Phosphorus. Phosphorus can be found in organic materials and sediment as well as synthetic household products and chemical fertilizers (though Minnesota Statute 18C.60 restricts the use of fertilizers containing phosphorus). To protect water quality, it is important to reduce phosphorus loading to surface waters.
- Practice responsible lawn care. Prevent soil erosion by paying special attention to slopes and areas of exposed soil, which present a higher risk of erosion. Minimize or avoid the use of chemical fertilizers by having your soil tested to determine its need (if any) for fertilizer, planting native vegetation, or using appropriate amounts of compost or manure instead of chemicals.
- Know your household products. Read the labels of household products, including hand soaps and dishwashing and laundry detergents. Consider alternatives with lower levels of phosphorus or other hazardous ingredients.
- Protect storm drains. Do not let phosphorus sources or other hazardous materials get into storm drains. Nutrients found in pet waste, yard waste, leaves, or other organic materials can pollute surface waters. Likewise, sweep up driveway pollutants like sand or road salt instead of washing them into the street.
Twin Cities Water Quality
The most important strategy for improving water quality is to be mindful of the water you use—where it comes from, and where it goes when you are done with it. This perspective is useful for a single yard or on a much larger scale, like the Twin Cities projects described below.
Maplewood Mall Retrofit. Recognizing that the Maplewood Mall represented a major source of impervious surfaces and phosphorus loading to the Ramsey-Washington Metro Watershed District’s Kohlman Lake, the District and the Mall collaborated on a project to reduce Maplewood Mall’s impact on local water quality. The Maplewood Mall Retrofit involves the addition of rain gardens, permeable pavement, and tree trenches to the property, along with an educational display for mall visitors.
Master Water Stewards. The Master Water Stewards program is a joint effort by the Freshwater Society and the Minnehaha Creek Watershed District in the west metro. The program trains volunteers to educate residents about actions they can take to improve local water quality.
Sara C Swenson is a recent graduate from the University of Minnesota Twin Cities with a B.S. in Environmental Sciences, Policy, and Management (concentrated in Environmental Education and Communication) and a minor in Spanish. She has studied biology and conservation in the Galápagos Islands and the effects of tourism on coral reef ecosystems in Belize, is well-versed in Minnesota’s Environmental Review process, and has a longstanding interest in environmental policy and communication.