Stormwater Runoff

Stormwater 101

What is stormwater runoff?
Whenever it rains or snow melts, water flows over hard surfaces, such as rooftops, sidewalks and parking lots, and into a storm sewer system. Storm sewers consist of a series of pipes that move water quickly from city streets to lakes and the river. The water is simply transported and does not receive any treatment. In fact, these systems are so efficient that they can move a large amount of water quickly, overwhelming nearby creeks, lakes and rivers. This causes erosion and degrade habitat for fish and other aquatic life.

As water moves across the landscape, it carries sediment, debris, and pollutants that can negatively affect the health of our water resources. Excessive stormwater runoff can also cause shoreline erosion of water resources, resulting in increased sediment that accumulates in lakes and rivers and negatively impacts water clarity. CRWD works to capture and clean stormwater runoff by partnering with developers, businesses, schools, cities, and residents to build projects that allow water to soak into the soil and undergo natural filtration before flowing into our lakes and the Mississippi River.

Learn more about the rivers beneath the city

Trout Brook Storm Sewer Interceptor

Water Cycle

The natural hydrological cycle moves rainfall from the atmosphere to land, through surface and groundwater systems, to the ocean and back into the atmosphere. However, urban stormwater cycles differ considerably from natural stormwater cycles due to the high percentage of impervious surfaces in urban areas like CRWD. This limits the amount of ground infiltration that can occur and results in high levels of runoff, limited groundwater replenishment and reduced groundwater flow. The District creates and maintains stormwater Best Management Practices (BMPs) designed to modify the urban stormwater cycle to make it function more like the natural water cycle.