How does runoff from paved surfaces reduce water quality in downstream ecosystems?

In the context of urban sprawl, the expansion of infrastructure creates vast areas of impermeable surfaces—such as roads, parking lots, and roofs—that replace natural vegetation and permeable soils. These surfaces prevent rainwater and snowmelt from being absorbed into the ground.1

As this water runs off these surfaces, it collects various chemicals present on the pavement. This runoff carries these pollutants into local waterways, directly reducing water quality and threatening downstream aquatic ecosystems. By altering natural drainage patterns and introducing contaminants, this process disrupts the health of streams and lakes, which are vital for supporting diverse aquatic life. Protecting these ecosystems from such degradation is an essential environmental responsibility.1