雨水 is water that flows down gutters and into storm drains when it rains. During dry weather, water also flows into gutters and storm drains as a result of pavement washing, runoff from excess lawn irrigation, residential car washing and other activities.
Unlike the wastewater that flows through the sanitary sewer system, stormwater is released directly to our local waterways. Because of this, urban runoff (also called nonpoint source pollution) remains the nation's largest source of water pollution, according to the U.S. Environmental Protection Agency.
