What is stormwater runoff?

Stormwater runoff is the rainwater and snowmelt that flows off of land and through a series of pipes and swales, finally flowing into local streams. Some stormwater runoff is absorbed into the ground and some of it evaporates; but much of it simply flows across the land. As stormwater flows across neighborhoods, parking lots, schools, and factories, it accelerates, picks up pollutants, and carries them to these streams.