EVALUATION OF STREAM CONDITIONS
USING BIOLOGICAL AND WATER-QUALITY DATA,
CHESTER COUNTY, PENNSYLVANIA

This project is being done in cooperation with the Chester County Water Resources Authority.

NEED FOR THE PROJECT

The Stream Conditions of Chester County Biological Monitoring Network has been used to collect biological and chemical data from 51 sites on the major streams in the County since 1970. The data from 1981-97 had not been formally analyzed and reported. An analysis of the data using biometric techniques was needed to provide the County with information on the current and past surface-water-quality conditions. This information is needed in support of the County's Landscapes Program. Since the Stream Conditions of Chester County Biological Monitoring Network was established in 1970, Chester County has continued to undergo rapid urbanization as agricultural land is converted to residential, commercial, and industrial areas. These changes in land use have caused many changes in the stream systems including streamflow, sedimentation, nutrients loads, and pesticides concentrations. The effect urbanization has had on surface-water quality can be documented in the biological samples collected over the past 27 years. In addition, new methods of analyzing macroinvertebrate data have been developed since the data from 1970-80 were analyzed. These new techniques need to be applied to the data so that an evaluation of the County's surface-water quality can be made to determine the affects of past environmental and land use practices.

PROJECT OBJECTIVES

• Determine trends in the benthic macroinvertebrate communities at each station
• Determine trends in water-quality chemical data at each station
• Evaluate the water-quality conditions at each site using benthic macroinvertebrate data
• Relate bottom-sediment and water-chemistry data to biological data

APPROACH

Literature review

A literature search was conducted to obtain the latest information available on the evaluation of water quality using benthic macroinvertebrate data. This included current methods being used by the U.S. Environmental Protection Agency, state and local governments, and other federal agencies.


Data base creation

A new data base was created to store the data generated from the identification of macroinvertebrate samples. The Stream Conditions of Chester County Biological Monitoring Network has generated a large amount of data that is now available in a flexible interactive data base. This data base is compatible with software used to analyze the data.


Trend analysis

Brillouin's Diversity Index was calculated at all stations for 1981-97. The Stream Conditions of Chester County Biological Monitoring Network has used Brillouin's Diversity Index as the main method of evaluation. Brillouin's Diversity index is based on the different kinds of organisms (taxa) present in a community and their relative abundances. In general, diversity is high if a community has many taxa and their abundances are evenly distributed; diversity is low if the taxa are few and their abundances are unevenly distributed. Brillouin's Diversity Index is retained as measure of water-quality for this study. Kendall's tau test for trend was applied to the Brillouin's Diversity Index values. Hilsenhoff's Biotic Index will be calculated at all stations from 1981-97. Hilsenhoff's Biotic Index was calculated back to 1981 so that it can be compared to Brillouin's Diversity Index. Hilsenhoff's Biotic Index is based on tolerance values assigned to individual organisms. The tolerance values used were obtained from the New York State Department of Environmental Conservation macroinvertebrate rankings. Organisms are given a tolerance value based on their ability to withstand organic pollutants. Chemical results for selected parameters were evaluated for trends using Kendall's tau test at each station from 1981-97.


Calculation of biometrics Data

Data analysis used a multimetric approach. Each metric measures a different part of community structure and has a different response to environmental stress. The mulitimetric approach increases the chance that an environmental stress will be detected. The following metrics were calculated: Brillouin's Diversity Index, Hilsenhoff's Biotic Index,  taxa richness, percent dominate taxa (relative abundance), and EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa, percent EPT. The classification system developed by The New York State Department of Environmental Conservation was used to determine functional feeding groups and assign IBI and tolerant-facultative-intolerant values. The metrics were calculated on the data for 1981-97.


Analysis of chemical data

Results from bottom-sediment sampling for metals and pesticides were compared with USEPA or other available standards. Trends in biological measures were compared to chemical values to determine if relations are present between them.


Rating of sites

Using the information from all the biometrics calculated, streams or portions of streams that are considered of high quality or biologically stressed are identified.

REPORTS RESULTING FROM THIS PROJECT

FACT SHEETS:

Reif, A.G., 2002, Assessment of stream quality using biological indicies at selected sites in the Schuylkill River Basin, Chester County, Pennsylvania, 1981-97: U.S. Geological Survey Fact Sheet FS-114-02, 4 p. [ PDF file ]

Reif, A.G., 2002, Assessment of stream quality using biological indicies at selected sites in the Big Elk and Octoraro Creek Basins, Chester County, Pennsylvania, 1981-97: U.S. Geological Survey Fact Sheet FS-115-02, 4 p. [ PDF file ]

Reif, A.G., 2002, Assessment of stream quality using biological indicies at selected sites in the Delaware River Basin, Chester County, Pennsylvania, 1981-97: U.S. Geological Survey Fact Sheet FS-116-02, 4 p. [ PDF file ]

Reif, A.G., 2002, Assessment of stream quality using biological indicies at selected sites in the Brandywine Creek Basin, Chester County, Pennsylvania, 1981-97: U.S. Geological Survey Fact Sheet FS-117-02, 4 p. [ PDF file ]

Reif, A.G., 2002, Assessment of stream quality using biological indicies at selected sites in the Red Clay and White Clay Creek Basins, Chester County, Pennsylvania, 1981-97: U.S. Geological Survey Fact Sheet FS-118-02, 4 p. [ PDF file ]

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