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Why Water Quality Changes

Why Does Water Quality Change?

Rivers, lakes and oceans are not sterile bodies of water. Not only do they contain naturally occurring organisms and bacteria, they can be contaminated by outside sources. The most frequent sources of microbial contamination are polluted storm water runoff, sewage overflows, and boating wastes. Contamination in large bodies of water is often much higher during and immediately after rainstorms, because the rainwater picks up wastes and other pollutants as it runs off lawns, farms, streets and other ground sites and into the streams. Most of the contamination in the Schuylkill River actually originates upstream from the City of Philadelphia, in the Schuylkill River Watershed.

Water quality in a river changes because it is affected by many factors including weather, climate, rainfall, industrial and sewage discharges, and accidental spills. It is strongly impacted by runoff from rain events. This is easily observed by the eye during and after storms when streams and rivers are very cloudy and look brown. When it rains, the dirt, animal waste, and other contaminants that build up on the surface of the ground or pavement are washed off into the streams and rivers. Though there is more water in the streams and rivers during storms, there are more contaminants as well. Below is an example of changes in water quality for bacteria during rainfall periods. As shown, bacteria (the red dots) increased by a factor of over 100 fold during a storm event and these increases in bacteria correspond with the rise in the water level (the blue line) and increase in stream flow during the rain event.

Hypothetical Example of Water Quality Changes in a Stream during a Storm

Image of Water Quality Changes in a Stream during a Storm

What Can I Do To Prevent Pollution?

The impacts from runoff can be addressed in many ways. In urban and suburban areas the following are possible ways to address runoff:

  • Individuals shouldn't dump oil and unused household chemicals down stormdrains, they should be disposed of properly at household hazardous waste drop-off events.
  • Minimize the use of lawn fertilizers, herbicides, and pesticides and do not use them when rain is forecasted within 24 hours of their application.
  • Landscape your property to detain and infiltrate runoff from rooftops, sidewalks, and patios.
  • Install a rain barrel or cistern to detain rooftop runoff and have it slowly drain via a soaker hose into flowerbeds or back into the stormsewer.
  • Local communities can adopt ordinances that require stormwater runoff to be infiltrated or detained from new or redeveloped areas.
  • Local communities need to adopt and enforce erosion and sedimentation control measures to prevent runoff impacts from new construction.
  • Incentives can be provided in communities to encourage businesses, schools, and owners of large impervious areas to employ techniques to reduce runoff discharge to local streams.
  • Open space can be preserved and enhanced along stream corridors to create riparian buffers that will keep the streambank stable and prevent erosion.

In agricultural areas, the following are possible ways to address runoff:

  • Riparian buffers should be created and preserved along streams to filter runoff from crop fields and livestock areas.
  • Streambank fencing should be employed to keep cattle from accessing streambank areas and alternative water sources away from the stream should be provided.
  • Manure should be managed to prevent runoff into streams and the groundwater.
  • No-till and low-till crop growth options should be employed or encouraged.
  • The above should all be performed using an incentive plan or following a conservation plan for the farm.

For more information about stormwater and water quality visit the following link.. http://www.fairmountwaterworks.com/teachers.php?sec=4&subsec=2