Watershed and Stormwater Basics

What is Stormwater Runoff?

Stormwater gushes from an outfall on the Mississippi River in late winter.
Dirty rainwater discharges from a stormwater outfall in Northeast Minneapolis. The Mississippi River is lined with drain pipes like these, which take all the water that runs off our streets and yards and carry it to the river via local stormsewers.

Have you ever thought about where all the water goes from rain and melting snow? In the city, it can’t soak into the ground the way it does in nature. There are too many hard surfaces like streets and buildings. Instead, all that stormwater becomes runoff that goes into storm drains.

Storm drains — those little metal grates in the street — are a direct pipeline to rivers, lakes and streams. Unlike the water you flush down the drain in your house, stormwater doesn’t get filtered at a water treatment plant. It goes directly from the street to the nearest available waterbody. And it carries with it whatever pollution it picks up along the way.

Think about all the bad things that accumulate on our streets, yards and parking lots. Gas, oil, bacteria, chemicals, pet waste, trash, dirt — all of these things get washed down the storm drains and into our rivers and lakes. Even things like grass clippings and leaves, which are harmless if left on your yard, become potent sources of phosphorus and other nutrients that pollute our waters, creating algae and killing fish.

Because of this, urban stormwater runoff is a major source of water pollution. In the MWMO watershed, almost all of our stormwater drains directly into the Mississippi River — an important source of drinking water, recreation, and natural habitat. The way we use our land and the choices we make every day have an impact on this vital resource, both for us and for the people downstream.

The MWMO protects and improves water quality in the river by partnering with local communities to better manage our stormwater runoff through projects and infrastructure. But you have a role to play, too. There are many simple things you can do at home and in your yard that will help protect our water quality and habitat.


What is a Watershed?

A watershed is the area of land that drains to a particular lake, river or other waterbody. Watersheds can be as small as bathtubs or as big as whole countries.

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Urban Water Pollutants

Stormwater runoff carries a wide variety of pollutants from our lands into our rivers, lakes and wetlands. Learn about the variety of pollutants commonly found in our watershed, why their harmful and how they’re monitored and regulated.

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Climate Change and Stormwater

Increased precipitation and warmer winters cause problems for water quality and habitat in our watershed. Learn about the causes and local impacts of climate change and what we can do to help our communities adapt.

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