Stormwater (stormwater, runoff, urban drool…) is generated from rain and snowmelt events that flow over land or impervious surfaces, such as paved streets, parking lots, and building rooftops, and does not soak into the ground. Stormwater is often considered a nuisance because it mobilizes pollutants like trash, chemicals, oils, and dirt/sediment that can harm our rivers, streams, lakes, and coastal waters. In most cases, stormwater flows untreated directly to water bodies through sewer systems, contributing a major source of pollution to rivers, lakes, and the ocean. Watch these videos to learn "What the heck is stormwater runoff?" and "Where Does Stormwater Go?".

Storm water discharges in California are regulated through National Pollutant Discharge Elimination System (NPDES) permits. The Federal Clean Water Act (Clean Water Act) prohibits certain discharges of storm water containing pollutants except in compliance with a National Pollutant Discharge Elimination System (NPDES) permit. The NPDES storm water program regulates some stormwater discharges from three potential sources: municipal separate storm sewer systems (MS4s), construction activities, and industrial activities.

However, storm water may also act as a resource and recharge to groundwater when properly managed. The Water Boards are actively involved in initiatives to improve the management of storm water as a resource.  With the focus on storm water as a resource for local landscape and agricultural irrigation, and groundwater recharge. To protect these resources, municipalities, communities, construction companies, industries, and others, use stormwater controls, known as best management practices (BMPs). These BMPs filter out pollutants and/or prevent pollution by controlling it at its source.

  • Low Impact Development (LID) refers to systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration or use of stormwater in order to protect water quality and associated aquatic habitat. Unlike traditional storm water management that collects and conveys storm water runoff through storm drains, pipes, or other conveyances to a centralized storm water facility, LID takes a different approach by using site design and storm water management to maintain the site’s pre-development runoff rates and volumes.
  • Green Infrastructure (GI) refers to the management of wet weather flows using these processes, and to refer to the patchwork of natural areas that provide habitat, flood protection, cleaner air, and cleaner water. This expands the low impact development approach to a larger community scale and presents similar sustainable opportunities to local governments and regional projects.

Monitoring and tracking storm water quality helps us understand how well these programs, activities by permittees, and/or best management practices are working.


National Pollutant Discharge Elimination System (NPDES) Stormwater Program

Storm Water Management in California

Strategy to Optimize Resource Management of Stormwater (STORMS)

California Stormwater Quality Association (CASQA)


After the Storm - A Citizen's Guide to Understanding Stormwater

What is Stormwater?

Central Coast Stormwater, California 

The Napa Countywide Stormwater Pollution Prevention Program (NCSPPP) is a joint effort of the County of Napa, cities of American Canyon, Napa, St. Helena and Calistoga, and the Town of Yountville to: 

  • Prevent stormwater pollution
  • Protect and enhance water quality in creeks and wetlands
  • Preserve beneficial uses of local waterways
  • Comply with State and federal regulations

Though the entities of the NCSPPP carry out their own individual stormwater pollution prevention programs, the NCSPPP provides for the coordination and consistency of approaches between the individual participants and documents their efforts in annual reports.

For Eco-Friendly pest management practices, a website called, Our Water Our World has been developed to assist consumers in managing home and garden pests in a way that helps protect our water. Among other things, this website offers:

  • Assorted fact sheets/forma informativas on specific pests and methods to manage them without using hazardous materials.
  • Pocket guide to less toxic products for managing common pests.
  • Information on where to buy less toxic pesticides, including fungicides and herbicides.
  • A list of products by brand name that are considered less toxic alternatives to more conventional pesticides.
  • A list of products by the pest they target.
  • An Ask the Expert feature that allows you to ask a specific question and receive a personal reply.

Report stormwater pollution