Urban runoff happens year round, even in dry weather. If people over water their lawns and gardens, the runoff spills into the storm drains. This sends fertilizers and pesticides into our streams. When people wash their cars, the dirty, soapy water ends up there too. Some people even use the storm drains to illegally dump paint, oil, and antifreeze. They do not know or do not care how their actions pollute our streams and impact our water quality.

The second kind of "used water" is runoff. Runoff from towns and cities like Sacramento is called urban runoff. Urban runoff carries pollutants washed from our houses, yards, cars, and driveways into street gutters and down the storm drains. From here another set of underground pipes takes it straight to our streams. Even small amounts of pollutants in urban runoff are enough to pollute the streams.