What is stormwater?

Stormwater is water that naturally falls from the sky. Stormwater runoff is generated when precipitation from rain events flows over land or impervious surfaces and does not percolate into the ground.

What is stormwater pollution and how is it created?

Where does rain go after it falls? If you live in the city, runoff from your yard and driveway probably flows into the street where it drops into storm drains … but then where does it go?

Many people think that water for the storm drain system is treated at a wastewater treatment plant and all of the pollutants are removed. In truth, urban runoff flows untreated through the storm drain system directly into creeks and rivers.

As the runoff flows over the land or impervious surfaces (paved streets, parking lots and building rooftops), it accumulates debris, chemicals, sediment or other pollutants that could adversely affect water quality. Anything thrown, swept or poured into the street, gutter or storm drain flows directly into our creeks without treatment or filtering.

Stormwater pollution is runoff that has picked up pollutants as it flows over the land and through the storm drain system – a network of channels, gutters, and pipes that collect runoff from city streets, neighborhoods, farms, construction sites and parking lots and empties into our local waterways.

Sonoma Water’s stormwater management plan incorporates appropriate activities and best management practices for activities related to its flood control and general fund activities to prevent stormwater pollution. 

What you can do to prevent stormwater pollution:

  • Keep litter, pet wastes, leaves and debris out of street gutters and storm drains—these outlets drain directly to creeks, rivers and lakes.
  • Use eco-friendly lawn and garden chemicals and apply them sparingly and according to directions.
  • Adjust your sprinkler heads to prevent water draining off your lawn and down the gutter. Reduce sprinkler run-time, remember to water at night, and don’t be a gutter flooder.
  • Dispose of used oil, antifreeze, paints and other household chemicals properly—not in storm drains. Sonoma County residents can find out more about ways to dispose of these hazardous materials on the website.
  • Clean up spilled brake fluid, oil, grease and antifreeze and dispose properly. Do not hose them into the street where they can pollute local creeks, rivers and lakes.
  • Direct car wash water to landscape areas instead of going down the gutter and into the storm drain system.
  • Control soil erosion on your property by planting ground cover and stabilizing erosion-prone areas.
  • Have your septic system inspected and pumped, at a minimum every three to five years, so that it operates properly.
  • Use chemical-free pest management options as described in Our Water Our World fact sheets found in many local nurseries.

Stormwater Resource Plans

Sonoma Water is currently involved in a collaborative process to create Stormwater Resource Plans in order to prioritize and implement multi-benefit stormwater projects which consider climate change resiliency, groundwater management, and flood protection, among other factors.

Report a non-stormwater spill

Everyone can do their part to prevent storm water pollution. Click here to report non-stormwater spills or dumping.

Stormwater resources

For more information

For more information about Sonoma Water's Stormwater program, please contact Kevin Booker via email at or via phone at (707) 521-1865.