Water quality tips for winter
You can help improve the water quality of our city's lakes, rivers and streams -- even in winter. Here are a few lake- and river-conscious tips to keep in mind before the snow melts:
Runoff washes grass clippings, leaves, fertilizer and other pollutants off hard surfaces such as sidewalks and driveways and carries them into our storm-sewer system. To reduce runoff from melting snow, direct your downspouts onto your lawn and away from hard surfaces.
Phosphorus is a food source for all plants -- including algae, small green plants that live in lakes and streams. Increases in phosphorus lead to increased algae growth. Large amounts of algae in lakes are called "blooms" or "scums" and harm lakes by blocking sunlight and preventing other aquatic plants from growing. As algae die and decay, algae also take away much-needed oxygen from fish.
Recently, the City of Minneapolis passed an ordinance restricting the sale and use of lawn fertilizers containing phosphorus. The purpose of this ordinance is to reduce phosphorus pollution of our lakes, creeks and rivers. The ordinance concerns only lawn fertilizer and does not regulate the phosphorus level in fertilizers for flower and vegetable gardens.
Of the three nutrients in turf fertilizers, nitrogen, phosphorus and potassium, the amount of phosphorus needed by grass is much less than that of nitrogen or potassium. Additionally, metro area soils are already high in phosphorus, making lawn fertilizer applications of phosphorus overkill. Nitrogen, the nutrient that makes lawns green, may not be needed if grass clippings are left on the lawn, as grass clippings are a nitrogen source.
Healthy lawns benefit urban water quality by soaking up rainwater and decreasing the amount of storm-water runoff into lakes and rivers. Only 10 percent of the rain falling on lawns, green space and trees results in runoff; however, 90 percent of the rain falling on streets, driveways, roofs and other hard surfaces results in runoff.
Healthy soil is the key to a thriving lawn and garden. As soon as the ground thaws, take a soil test to determine your soil type and what amendments you may need to improve it. Soil tests are available for a small fee through the U of M's Hennepin County Extension Office at 374-8400.
Oftentimes soil improvement can be accomplished through the addition of organic matter such as compost. Core aeration of your lawn in the fall will also help improve your soil, particularly if it is compacted from heavy use. Aeration helps water reach the roots of the grass plant and minimize water runoff.
Organic mulches such as partially decomposed compost, shredded leaves or grass clippings improve your soil structure by adding organic matter to the soil as they decompose. Using organic mulches on gardens, trees and shrubs reduces weed growth, conserves soil moisture and moderates soil temperature.
Washing your vehicle in your driveway or on the street contributes to runoff. Soap and petroleum products washed off your car flow directly into the storm-sewer system that sends them, un-treated, directly into our city lakes and streams. However, water from carwashes goes into the sanitary sewer system and is treated at wastewater treatment plants.