What is Stormwater? Stormwater is precipitation that does not soak into the ground. Imagine a raindrop falling from the sky. It first flows over your rooftop, across the lawn and down your driveway. It makes its way along the sidewalk and into the road. At this point in the stormwater cycle, the raindrop is no longer traveling alone; it has picked up some pesticides and fertilizer from your lawn, a bit of bacteria from your pet’s waste, as well as some petroleum and oil from your driveway. Don’t forget about the sediment from the road or the gum wrapper and cigarette butts from the sidewalk. As the raindrop continues down the road, it might flow directly into your local river or lake, or it might go through a ditch or a storm drain. If it flows into a storm drain it continues to flow through an underground network of pipes, where it discharges, untreated, into your local swimming hole.