Keep Our Waterways Safe This Halloween! Stormwater is water that runs off roofs, driveways, and streets into our storm drains and rivers. In the journey from our streets to our streams, stormwater picks up chemicals, trash, and other pollutants that contaminate our waterways. The water that flows in our storm drains flows directly into our waterways, without passing through a water treatment plant, so it is important that only rain goes down our storm drains. Once you and your family are done eating your delicious Halloween candy, make sure to throw the wrappers in the trash can and encourage those around you to do the same!