What Stormwater Is

Stormwater is water from precipitation that flows across the ground and pavement when it rains or when snow and ice melt. The water seeps into the ground or drains into what we call storm sewers. These are the drains you see at street corners or at low points on the sides of streets. Collectively, the draining water is called stormwater runoff.


Rain is an important part of nature's water cycle, but there are times it can do more damage than good. Problems related to stormwater runoff can include:

  • Flooding caused by too much stormwater flowing over hardened surfaces such as roads and parking lots, instead of soaking into the ground.
  • Increases in spending on maintaining storm drains and the storm sewer system that become clogged with excessive amounts of dirt and debris.
  • Decreases in sport fish populations because stormwater carries sediment and pollutants that degrade important fish habitat.
  • More expensive treatment technologies to remove harmful pollutants carried by stormwater into our drinking water supplies.
  • Closed beaches due to high levels of bacteria carried by stormwater that make swimming unsafe.

Protecting Our Health and Environment

We can help rain restore its good reputation while protecting our health and environment while saving money for ourselves and our community. Continue reading to find out how.

Restoring Rain's Reputation & What Everyone Can Do to Help

Rain by nature is important for replenishing drinking water supplies, recreation, and healthy wildlife habitats. It only becomes a problem when pollutants from our activities like car maintenance, lawn care, and dog walking are left on the ground for rain to wash away. Here are some of the most important ways to prevent stormwater pollution:

  • Properly dispose of hazardous substances such as used oil, cleaning supplies and paint - never pour them down any part of the storm sewer system, and report anyone who does!
  • Use pesticides, fertilizers, and herbicides properly and efficiently to prevent excess runoff.
  • Look for signs of soil and other pollutants, such as debris and chemicals, leaving construction sites in stormwater runoff or tracked into roads by construction vehicles. Report poorly managed construction sites that could impact stormwater runoff to us.
  • Install innovative stormwater practices on residential property, such as rain barrels or rain gardens, which capture stormwater and keep it on site instead of letting it drain away into the storm sewer system.
  • Report any discharges from stormwater outfalls during times of dry weather - a sign that there could be a problem with the storm sewer system.
  • Pick up after pets and dispose of their waste properly. No matter where pets make a mess - in a back yard or at the park - stormwater runoff can carry pet waste from the land to the storm sewer system to a stream.
  • Store materials that could pollute stormwater indoors, and use containers for outdoor storage that do not rust or leak to eliminate exposure of materials to stormwater.

Storm Water is "Good Rain Gone Wrong"

Stormwater becomes a problem when it picks up debris, chemicals, dirt, and other pollutants as it flows or when it causes flooding and erosion of stream banks. Stormwater travels through a system of pipes and roadside ditches that make up storm sewer systems. It eventually flows directly to a lake, river, stream, wetland or coastal water. All of the pollutants stormwater carries along the way empty into our waters, too, because stormwater does not get treated! View the following pollutants:

  • Pet wastes left on the ground get carried away by stormwater, contributing harmful bacteria, parasites, and viruses to our water.
  • Vehicles drip fluids such as the following onto paved areas where stormwater runoff carries them through our storm drains and into our water:
    • Antifreeze
    • Brake Fluids
    • Gasoline
    • Grease
    • Oil, etc.
  • Chemicals used to grow and maintain beautiful lawns and gardens, if not used properly, can run off into the storm drains when it rains or when we water our lawns and gardens.
  • Waste from chemicals and materials used in construction can wash into the storm sewer system when it rains. Soil that erodes from construction sites causes environmental degradation, including harming fish and shellfish populations that are important for recreation and our economy.