Non-Point Sources of contaminants are less obvious than Point Sources, but they are responsible for a whopping 96% of water quality impairments throughout Pennsylvania!


That’s right: according to PA DEP, the overwhelming majority of impaired watersheds are polluted by nonpoint sources, including acid mine drainage, atmospheric deposition, improperly operating on-lot sewage systems (septic systems), earth moving, stream hydro-modification, improper timber harvesting, and more.

Some Non-Point Sources to be considered include:

  • Agricultural areas
  • Roads and highways
  • Railways
  • Pipeline systems
  • Commercial properties
  • Residential properties and development
  • Septic Systems (onlot wastewater systems)
Amongst these various non-point sources, it’s runoff from rainfall and snowmelt–STORMWATER–that is the most common pathway for contaminants to get into raw water supplies.

Stormwater Runoff: trash and debris in dirty waterway

Unfortunately, the problems associated with stormwater aren‘t limited to major storms; they more often result from the average rainfall event. Human activities have changed the landscape so dramatically that nature’s system for dealing with runoff no longer works.

Consider the path rainfall takes when it hits the ground: it either soaks into the ground to become groundwater, evaporates, or flows over the surface of the land. This overland runoff—stormwater—feeds our surface waters, but it also carries sediments, chemicals, automobile oil, trash, and other natural and not-so-natural debris along with it. Groundcover, trees, soil, wetlands, and a wide range of other landscape features act as buffers and barriers that slow the runoff, trap or filter out pollutants, and enable infiltration and evaporation to occur. The more we alter the landscape, the more we affect this natural cycle. When we grade and cut and pave and build, the resulting impervious surfaces allow polluted runoff to flow into waterways more quickly, leaving less water to re-absorp into the ground. That, in turn, affects stream flow—and the aquifers we depend on for drinking water in many parts of the state.

The following videos look at some of the problems caused by runoff—and some of the ways communities are working to bring it under control.

More detail on stormwater runoff is available here >>

Past Development Catches Up with Municipalities When it Rains from GreenTreks Network on Vimeo.

Townships that were formed more than 30 years ago are finding themselves increasingly dealing with flooding and water quality problems because rainwater has nowhere to go. They’re trying to remedy that by using public spaces to get water back into the ground…

Restoring Plum Run: Turning Red Streams to Blue from GreenTreks Network on Vimeo.

Clean water is vital. In Chester County, Pennsylvania, people are working together to restore the health of their drinking water sources. A red stream is an impaired stream that does not meet water quality standards. A blue stream has a clean bill of health. Watch as Plum Run, part of the Brandywine River Watershed, is transformed from a red stream into a blue stream. Through creating a level floodplain to reduce erosion, planting trees, and removing grass that's so compacted that it's practically a parking lot, Plum Run is restored to a much healthier stream.

For an in-depth look at everything Stormwater—from a more detailed discussion of the Hydrologic Cycle to an interactive presentation that shows how developers can implement Low Impact Development techniques to a comprehensive look at how local, State, and federal regulatory requirements work—visit .

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