Polluted stormwater runoff largely happens anywhere people use or alter the land. Developed areas in general, with their increased runoff, concentrated numbers of people and animals, construction and other activities, are a major contributor to pollution, as are agricultural activities. As such people going about their daily lives are a large source of stormwater pollutants.
Most people are unaware of the impact they have on water quality. Some common examples include over fertilizing lawns, excessive pesticide use, not picking up pet waste, using too much salt to de-ice driveways, letting oil drip out of their vehicles and littering.