How does lawn runoff act as a non-point source of pollution?

Lawn runoff serves as a non-point source of pollution primarily because it involves the movement of water from various landscapes, such as residential lawns, during rainfall or irrigation. As rainwater flows over these areas, it can pick up contaminants like fertilizers and pesticides that have been applied to the grass and soil. These chemicals then enter local water bodies without a distinct, identifiable source, which is the hallmark of non-point source pollution.

In contrast, direct discharge of wastewater typically originates from specific facilities like treatment plants, which classifies it as a point source pollution. Contributions to sewage overflow are also associated with specific systems rather than dispersed land use practices. While increased sedimentation rates from runoff can be a concern, the direct mechanism of contaminants being carried by rainwater is what distinctly categorizes lawn runoff in this context.