HISTORICAL TRENDS AND CONCENTRATIONS OF
FECAL COLIFORM BACTERIA IN THE BRANDYWINE BASIN,
CHESTER COUNTY, PENNSYLVANIA
USGS Water-Resources Investigation Report 01-4026
NEED FOR THE PROJECT
Concentrations of fecal coliform bacteria in water samples
collected from the Brandywine Creek from March to October at
U.S. Geological Survey stream-water quality monitoring stations
are consistently above 200 organisms per 100 milliliters, which is the
bathing-water criteria established by the U.S. Environmental
Protection Agency. The Brandywine Creek flows through the heart
of Chester County and is widely used for recreation and drinking water.
The aesthetic, recreational, and ecological health of the creek are
degraded because of the high concentration of fecal coliform bacteria.
Bacteria concentrations in stormflow are typically greater
than in baseflow and during storm events can reach 50,000 organisms per
100 milliliters and higher.
- Evaluate trends in fecal bacteria concentration data collected since 1972
- Determine the fecal bacteria concentration in the Brandywine Creek and its major tributaries
- Identify potential subbasin sources for fecal bacteria contamination
- Determine bacteria concentrations at different flow regimes and seasons and identify the hydrologic conditions associated with elevated concentrations of bacteria
- Determine the relation between land use and fecal bacteria concentration
- Determine the concentration of Escherichia Coli (E. coli) bacteria, which are an indicator of intestinal pathogens that cause human diseases
DESIGN OF SAMPLING NETWORK
bacteria were used as the primary indicator of bacterial
contamination in this study because they were used in data
collection from 1972-97, they are present in water when bacterial
pathogens from fecal contamination are present, and they are present in
higher concentrations than pathogens and so are easily detected. Fecal
coliform bacteria are easy to culture and are typically harmless to
humans. Escherichia coli (E. coli) bacteria were used as a
secondary indicator of bacterial contamination. E. coli are found in
smaller concentrations than fecal coliform bacteria and are more
difficult to culture, but are a better indicator of the presence of
intestinal pathogens that cause human diseases. E. coli samples were
collected along with fecal coliform samples at selected sites.
A network of 40 sites was established in the Brandywine Basin for bacteria sampling.
These stations were sampled at baseflow (low flow) in 1998 and both baseflow and storm flow
in 1999. All stations were sampled for fecal coliform
bacteria, and selected stations were sampled for E. coli bacteria.