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
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
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,
- 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..