Besides carrying pollutants directly into rivers and streams, excessive runoff can cause dangerous erosion and life-threatening floods.


Pennsylvania abounds in natural beauty, its landscape entwined with 83,161 miles of streams and more than 3,900 lakes, reservoirs, and ponds. Water is the lifeblood of the Commonwealth, supporting vast forests, abundant fish and wildlife, and a wide array of human uses that draw more than four billion gallons of ground and surface water per day. This wealth of water is a blessing, but population growth has radically altered the natural systems that manage rainfall through transpiration, infiltration, and gradual runoff into surface waters—leading to everything from poor water quality to flooding, severe erosion, and droughts. 

When the amount of rain falling exceeds the land's ability to absorb it, the result is stormwater runoff. The volume of runoff and rate at which it flows varies with the intensity and duration of the rainfall—and with the type of land surface upon which it falls. A short light rain falling on permeable soils might produce little to no runoff, while heavy rain landing on an impervious parking lot can produce a substantial amount.

Without treatment, most of the stormwater that runs from the land into our waterways is unhealthy for people and bad for the environment. Runoff can carry chemicals, metals, bacteria, viruses, organic compounds, and other pollutants directly into creeks, lakes, rivers, and streams. And, stormwater runoff can cause severe erosion and flooding—even during a typical Pennsylvania storm.

Acknowledging the problems stormwater can create has forced us to take its management more seriously than ever before. We’re working to preserve natural cycles and find innovative ways to mimic the environmental functions that existed before we disturbed landscapes with buildings, farmlands, parking lots, and roads.

The solution lies in comprehensive stormwater management, which offers tremendous rewards to local economies, the environment, and quality of life.