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Open-File Report 77-462
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"Limnological studies of the major streams in Chester County, Pennsylvania"
by B.W. Lium
The major
streams in Chester County, Pennsylvania were studied to determine
their environmental state, and to relate this condition to land-
use patterns. A biological numerical rating system on a scale of
1 to 10 was developed to classify stream conditions. One indicates
extremely toxic conditions and 10 balanced biological conditions.
The majority of the streams studied had ratings between 4 and 8,
indicating they were experiencing varying degrees of enrichment
and/or sediment deposition. The streams with high numerical ratings
were generally found in rural and agricultural areas. Streams with
low numerical rating were found mostly in areas near waste treatment
facilities or industry. Large changes in the numerical rating of
a stream were related to changes in land-use patterns.
Relationships were developed between
dissolved solids concentrations and the biological numerical ratings
of the streams. Streams with ratings from 6 to 10 had dissolved
solids concentrations of approximately 100 mg/L. At ratings of 5
to 1, the dissolved solids concentrations increased progressively
from 122 to 310 mg/L.
Chemical data for the streams were related to the dominant orders of
benthic invertebrates. The stoneflies were found to be the most sensitive
to high levels of chemical constituents. The trueflies, mayflies, and
caddis flies showed a wide tolerance to various chemical constituents.
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