Land Use, Organochlorine Compound 

Concentrations, and Trends in 

Benthic-Invertebrate Communities in 

Selected Stream Basins in 

Chester County, Pennsylvania

By Mark A. Hardy, Kirn L. Wetzel, and Craig R. Moore

U.S. GEOLOGICAL SURVEY 

Water-Resources Investigations Report 94-4060

Prepared in cooperation with

CHESTER COUNTY WATER RESOURCES AUTHORITY

Lemoyne, Pennsylvania 

1995
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Gordon P. Eaton, Director

For additional information 

write to:

District Chief

U.S. Geological Survey

840 Market Street

Lemoyne, Pennsylvania 17043-1586

Copies of this report may be 

purchased from:

U.S. Geological Survey

Earth Science Information Center

Open-File Reports Section

Box 25286, MS 517

Denver Federal Center

Denver, Colorado 80225
CONTENTS

Page

Abstract......................................................................... 1

Introduction...................................................................... 2

Purpose and scope ............................................................ 2

Network description and previous investigations...................................... 2

Description of study area........................................................ 5

Acknowledgments............................................................. 5

Land use........................................................................ 6

Categories................................................................... 6

Summary of changes........................................................... 7

Organochlorine compounds ........................................................ 12

Icedale Lake sediment cores.................................................... 12

Core dating.............................................................. 13

Compounds in core segments ............................................... 16

Stream-bottom materials....................................................... 16

Benthic-invertebrate communities.................................................... 22

Relations among land use, benthic-invertebrate communities, and organochlorine compounds ... 24 

Summary and conclusions ......................................................... 26

References cited................................................................. 27

Appendix: Brillouin's diversity index, maximum diversity, minimum diversity, and relative 

evenness, by site............................................................... 29

ILLUSTRATIONS 

Figure 1. Map showing location of sampling sites in Chester County, Pa. .....................3

2-4. Graphs showing:

2. Relation between annual peak flows and annual sediment discharge at

Brandywine Creek at Chadds Ford, 1964-78 ............................. 14

3. Depth profile of ratio of cesium-137 and silt-clay fraction in bottom materials

of Icedale Lake, Chester County, Pa. ................................... 14

4. Depth profiles of ratios of selected organochlorine compounds and organic

carbon in bottom materials of Icedale Lake, Chester County, Pennsylvania ..... 17
CONTENTS-Continued

Page

TABLES 

Table 1. Drainage areas of sampling sites for major streams in Chester County, Pennsylvania... .4

2. Changes in land use within drainage areas of selected stream sites in

Chester County, Pa., 1967-87 .............................................7

3. Change in land use for Icedale Lake Basin, Chester County, Pa., 1967-87............ 12

4. Concentrations of carbon and organochlorine compounds, Cesium-137 activities, 

and silt and clay sized particles in bottom materials at selected depths from 

Icedale Lake, Chester County, Pa., September 1988 .......................... 15

5. Concentrations of organochlorine compounds on unsorted streambed materials

in Chester County, Pennsylvania, October 1985 through November 1987 ..........18

6. Concentrations of organochlorine compounds exceeding or equalling 15 micrograms 

per kilogram on unsorted streambed materials in Chester County, Pa., 

October 1985 through November 1987 .....................................21

7. Comparison of pesticide concentrations at paired sites with increasing residential

land use .............................................................21

8. Values of slope, tau, p, and level of confidence from seasonal Kendall test of

diversity index......................................................... 23

CONVERSION FACTORS AND ABBREVIATED WATER-QUALITY UNITS

Multiply By To obtain

inch (in.) 2.54 centimeter

square mile (mi2) 2.590 square kilometer

cubic foot per second (fr^/s) 0.02832 cubic meter per second

Abbreviated water-ualit units used in this reort

micrometer ( 

micrograms per kilogram (|ag/kg) 

picocurie per gram (pCi/g) 

grams per kilogram (g/kg)

iv
LAND USE, ORGANOCHLORINE COMPOUND CONCENTRATIONS, 

AND TRENDS IN BENTHIC-INVERTEBRATE COMMUNITIES

IN SELECTED STREAM BASINS 

IN CHESTER COUNTY, PENNSYLVANIA

By Mark A. Hardy, Kirn L Wetzel, and Craig R. Moore

ABSTRACT

Land use was analyzed for the drainage areas of 26 stream sites in Chester County, 

Pa., that cover a total area of 227 square miles or about 30 percent of the county. The most 

significant land-use changes during 1967-87 were decreased agricultural land use, increased 

residential land use, and increased commercial and industrial land use.

Bulk samples of stream-bottom materials were collected at 42 sites in the study area 

from October 1985 through November 1987 and analyzed for content of organochlorine 

pesticides and polychlorinated biphenyls (RGB's). Organochlorine compounds and (or) PCB's 

were detected in streambed materials collected at 40 of the 42 sites sampled. The most 

enriched compounds (greater than 15 micrograms per kilogram) were PCB's, chlordane, and 

DOT plus its breakdown products. Data suggest that chlordane residues are closely 

associated with residential land use. PCB residues are closely associated with industrial and 

commercial land use.

Cores of lakebed sediments from the site of Icedale Lake, a drained reservoir on the 

West Branch Brandywine Creek, indicate that DOT was the first organochlorine pesticide to 

enter the Brandywine Creek; concentrations peaked in the late 1940's and early 1950's. As 

DOT influx subsequently decreased, influxes of chlordane and dieldrin increased and peaked 

in the mid-1960's, before the Chester County biological monitoring program. Influx of all 

pesticides appears to have decreased significantly since the 1960's.

Upward trends in Brillouin's diversity index for benthic-invertebrate communities were 

found at 45 of 46 stream sites in Chester County. The upward trends were statistically 

significant at the 99-percent confidence level at 30 sites. Trends at only four sites were not 

statistically significant at the 90-percent confidence level.

Contingency analyses showed that the relation between the Kendall slope estimator for 

trend and the increases in residential land use of 12 percent or greater were significant at the 

95-percent confidence level. The contingency tables also showed that the relation between 

diversity indices of less than 2.25 and organochlorine-compound concentrations greater than 

45 micrograms per kilogram was significant at the 95-percent confidence level.

ABSTRACT 1
INTRODUCTION

Chester County, in southeastern Pennsylvania, is being rapidly urbanized. Former 

agricultural land is being converted to residential developments, commercial areas, and 

industrial and corporate parks. This urban growth is affecting the quality of streams in 

Chester County. A study by Moore (1987) showed that the diversity of benthic-invertebrate 

communities increased at 44 of 46 sites and decreased at 2 sites from 1970-80. Subsequent 

sampling of stream-bottom sediments at one of the two sites where the diversity decreased 

revealed elevated concentrations of pesticides and other organic compounds. A study by Sloto 

(1987) showed that the more rapidly a basin in eastern Chester County changed from rural to 

suburban, the faster the diversity index increased. Both studies suggest that changes in 

diversity may be related to organochlorine compounds in stream-bottom sediment, and that 

this relation also can be affected by land use.

Information is needed to improve the understanding of the relations among land use 

and changes in land use, organochlorine-compound concentrations, and benthic-invertebrate 

diversity indexes so that Chester County planners and developers can maintain 

improvements in diversity index already observed (Moore, 1987). In 1988, a study to obtain 

such information was begun by the U.S. Geological Survey (USGS) in cooperation with the 

Chester County Water Resources Authority (CCWRA).

Purpose and Scope

This report describes (1) land-use changes in relation to the trends in diversity indexes 

of benthic-macroinvertebrate communities, (2) the detection and concentrations of 

organochlorine compounds in stream-bottom sediments in relation to diversity indexes, and 

(3) the distribution of organochlorine compounds in stream-bottom sediments at 42 stream 

sites in the study area.

The information in this report is based on data collected at 51 sites on 16 major streams 

in Chester County. The data record for 39 of these sites is continuous for 1970-88. Streambottom sediments were analyzed for organochlorine compounds during 1985-87 at 42 sites. 

Changes in land use from 26 drainage areas during 1967-87, obtained from the Chester 

County Planning Commission (CCPC), were quantified and compared to diversity trends at 

26 stream sites in the county. Concentrations of organochlorine compounds were compared to 

diversity indexes of benthic-invertebrate samples collected at 42 stream sites in the county.

Network Description and Previous Investigations

In 1969, a limnological monitoring program began to evaluate water quality of selected 

Chester County streams by use of physical, chemical, and (beginning in 1970) benthicinvertebrate data. The program is a cooperative effort of the USGS, the CCWRA, and the 

Chester County Board of Commissioners. The project was conceived by Luna B. Leopold, 

former Chief Hydrologist, USGS, and Robert G. Struble, former Executive Director of the 

CCWRA. The major goal of the program is to further the understanding of stream changes in 

response to urbanization (Lium, 1977, p.6). Some changes have occurred since the creation of 

the network. Early analysis of the data resulted in discontinuance of nine sites (sites 7,8,9,11, 

18,25,35,41, and 43). At two sites (sites 16 and 39), quantitative data collection replaced 

qualitative collections after 1979. One new site (site 51) was added in 1983. The locations of the 

51 sampling sites are shown in figure 1, and drainage areas are listed in table 1. This network 

of sampling sites and the biological, physical, and chemical data collected for this program are 

the basis for this investigation.

2 INTRODUCTION
s.

I

6

"w

O)

0)

INTRODUCTION 3
Table 1. Drainage areas of sampling sites for major streams in Chester County, 

Pennsylvania

[-, land-use data not available]

Site 

number

1

2

3

4

5

6 

7

8

9

10

41

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

51

Drainage area 

(square miles)

Picketing Creek

3.09

5.98

21.2

27.5

31.4

Stonv Run

2.00 

4.07

Pigeon Creek

4.20

6.97

12.0

French Creek

5.06

11.7

12.4

19.9

46.1

59.1

70.7

Darby Creek

5.15

Crum Creek

6.16

10.1

Ridley Creek

4.22

9.71

Chester Creek

.63

5.77

10.4

4.28

19.2

Land-use data 

available

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

-

Site Drainage area Land-use data 

number (square miles) available

26

27

28

29

30

31

32

33

34

35

37

38

45

46

36

39

42

43

44

47

48

40

49

50

Red Clav Creek

10.2

9.79 Yes

White Clav Creek

11.3 Yes

9.94

9.92

Elk Creek 

11.1

10.0

Octoraro Creek

11.8

10.5 Yes

32.9

West Branch Brandywine Creek

37.3

134.

11.8 Yes

22.6

East Branch Brandvwine Creek

60.6

123.

16.5

4.36

16.1 Yes

4.26 Yes

5.98

Brandywine Creek

291

Valley Creek

6.45 Yes

12.7 Yes

A report by Moore (1989) contains the physical, chemical, and biological data for this 

investigation for 1969-80. This superceded an earlier report by Lium (1976) that contained 

much of the same data for 1969-74. The physical and chemical data for the 1974-88 water 

years1 also have been published in the USGS annual water resources data reports for 

Pennsylvania (U.S. Geological Survey, 1975-89) and are available in USGS computer files.

Lium (1977) developed a biotic index that uses a 10-point rating scale to determine the 

environmental condition of streams at the 50 sites from his previous (1976) report. Most 

streams studied had ratings indicating they were experiencing variable degrees of nutrient 

enrichment and (or) sediment deposition. Large changes in the numerical rating of a stream 

were related to changes in land-use patterns.

1 Water year is the 12-month period October 1 through September 30 and is designated 

by the calendar year in which it ends.

4 INTRODUCTION
In 1967-68, a study was conducted in the Picketing Creek and East Branch Brandywine 

Creek Basins by Miller and others (1971). Their study examined and documented existing 

hydrologic conditions in these two small basins so that the effects of future urbanization in the 

basins could be studied by comparison with their data. These two basins are among the areas 

studied in this investigation.

Moore (1987) evaluated the biological monitoring of stream-water quality in Chester 

County. This study showed statistically valid upward trends in Brillouin's diversity index 

during 1970-80 at 27 sites studied where improved environmental quality was indicated. 

However, few trends were detected in the physical and chemical data because of a high degree 

of variability in the data. Both Lium (1977) and Moore (1987) observed that total dissolved 

solids correlated significantly with biotic index and diversity index.

An investigation by Sloto (1987) described the effects of urbanization on water quality 

in eastern Chester County. Sloto observed that basins that had a greater change in land use, 

from undeveloped to developed, surprisingly had a greater increase in diversity index. Sloto 

postulated that the increase may be caused by the banning of certain pesticides, a decreasing 

use of pesticides in urbanizing basins, (and) or flushing or burial of older pesticidecontaminated sediments.

Description of Study Area

The study area is in the southeastern corner of Pennsylvania near Philadelphia (fig. 1) in 

the Piedmont Physiographic Province. General topography of the area is broad, gently rolling 

hills having low to moderate relief. Nearly 95 percent of Chester County (720 mr) is drained 

by the streams included in the study (fig 1). All streams sampled originate within the 

boundaries of the county, except for short reaches in the headwaters of the West Branch 

Brandywine, French, and Octoraro Creeks. Octoraro Creek forms part of the western 

boundary of the county, and its headwaters lie in both Chester and Lancaster Counties (fig. 1).

The population of Chester County doubled between 1950 and 1980 (Sloto, 1987) and 

increased another 10 percent from 1980 to 1987 to 348,484 persons. Population projections by 

the CCPC indicate that by the year 2010, the county will have more than 418,000 persons 

(Chestef County Planning Commission, written commun., 1988).

Some areas, particularly in the eastern half of the county, have undergone more rapid 

growth. Several townships in the county have population increases ranging from 53 to 

145 percent from 1970 to 1980. These townships, along with six others in the county, are 

expected to increase 50 percent or more over their 1980 populations by the year 2010 (Chester 

County Planning Commission, written commun., 1988).

Acknowledgments

The cooperation of the Chester County Board of Commissioners, the Chester County 

Water Resources Authority, Chester County Planning Commission, and the Chester County 

Health Department is gratefully acknowledged. The authors are particularly indebted to 

Robert E. Walker and the staff of the Chester County Planning Commission for graciously 

allowing us to use their resources and facilities during the course of the study. Special thanks 

are extended to David C. Yaeck, former Executive Director of the Chester County Resources 

Authority, and Dr. Robin Vannote, Stroud Water Research Center, for their particular interest 

throughout the study. The authors also would like to thank all the individuals who provided 

assistance and information essential to the successful completion of this study.

INTRODUCTION 5
LAND USE

Drainage basins of 26 sites were selected for land-use analysis (table 1). These basins 

were selected to provide good areal coverage of Chester County and to represent the widest 

possible range of dominant land-use categories. Basins selected on French, Pickering, Ridley, 

and East Branch Chester Creeks comprise series of concatenated drainage areas representing 

progressively larger parts of the stream basin. These are referred to as "nested systems" in this 

report and allow observations of changing land use within individual watersheds. Land-use 

analyses were not performed for sites in the lower reaches of the Brandywine Creek Basin. 

These basins are quite large and heterogeneous, thus making it more difficult to separate the 

effects of differing land use. In addition, the lower Brandywine Creek Basin also contains 

many major point-source discharges that can mask the effects of land use in the basin.

Categories

Land-use classifications are from land-use maps prepared by the CCPC (1972; 1987). 

The seven land-use classifications used in this report are combinations with slight 

modifications of the 15 categories used by the CCPC.

Residential land use combines CCPC's Medium Density (single-family detached homes 

on lots less than 1 acre) and High Density (two-family dwellings, townhouses, apartments, 

and mobile homes) categories. For the purpose of this study, homes included in CCPC's Low 

Density residential category were placed in either the Open Space or Agricultural categories 

on the basis of the surrounding land use.

Commercial land use combines CCPC's Commercial, General (retail and wholesale 

trade, and professional, personal, and business services); Commercial, Office Park (office and 

corporate park development); and Institutional (health, educational, governmental, and 

religious facilities, excluding cemeteries, which were placed in the Open Space category).

Industrial land use combines CCPC's Industrial, Limited (light assembly, warehouse, 

and research and developmental facilities); Industrial, Manufacturing (processing, fabrication, 

or assembly of raw materials or component parts); Transportation/Communications/Utilities 

(rail, air, and highway transportation; communication facilities; and utility facilities); and 

Mining/Quarry (mining, quarrying, and other extractive operations).

Open space combines CCPC's Recreational Lands (parks, playgrounds, and related 

facilities, but excluding golf courses), Woodlands (tree masses in excess of 10 acres), Water 

Bodies (lakes and reservoirs in excess of 50 acres), Other Land (floodplain land, land which is 

awaiting development, vacant, unused, or otherwise undefined), and cemeteries. The 

woodlands are primarily composed of deciduous hardwoods such as red and black oak, tulip 

poplar, beech, sugar maple, and chestnut oak; and are situated on steep, less productive soils 

(Lium, 1977).

Agricultural lands were divided into three categories in CCPC's 1967 classification 

system: Agriculture (row crops), Pasture (pasture or meadow lands), and Specialized 

Agriculture (orchards, nurseries, tree farms, and mushroom farms). For the purpose of this 

study, the same categories for agricultural lands were used with one modification. Golf 

courses were included in the Specialized Agriculture category as opposed to Open Space 

(recreation land). Because of the heavy applications of fertilizers, insecticides, and herbicides, 

golf courses more closely approximate a specialized form of agriculture. Major crops are hay, 

winter wheat, corn, garden crops, and mushrooms. Livestock raised primarily include dairy 

and beef cattle, and horses.

6 LAND USE
Summary of Changes

Land use was analyzed for the 26 drainage areas covering a total area of 227 mi2 or 

about 30 percent of the county (table 2), Overall, the most significant land-use changes for 

these basins during 1967-87 were (1) decreased agricultural land use (ranging from 2.5 to 

52.6 percent; median 14.2 percent); (2) increased residential land use (ranging from 4.0 to 

42.9 percent; median 20.8 percent); and (3) increased commercial and industrial land use 

(ranging from 0 to 20.0 percent; median 3.0 percent). These changes were greatest in the 

northeastern half of the study area, including East Branch Brandywine Creek but excluding 

French and Darby Creeks.

Pasture and open space decreased in some basins and increased in others. Decreases for 

both categories generally were the result of residential, industrial, or commercial 

development. Increases in pasture seem to be a result of converted agricultural land use. 

Increases in open space seem to be a result of converted pasture and (or) agricultural land use.

The nested systems represented increases in residential land use ranging from 10.3 to 

42.9 percent; and decreases in residential land use ranging from 5.0 to 34.8 percent. In the 

Pickering Creek and East Branch Chester Creek nested systems, land-use changes were not 

uniform. In Pickering Creek, the increase in residential land use was about 15 percent less for 

the site 1 drainage area than the other four downstream drainage areas. Agricultural land use 

progressively decreased by about 6 percent from the site 1 to the site 3 drainage areas. In East 

Branch Chester Creek, the increase in residential land use was about 13 percent greater for the 

site 24 drainage area (the most downstream site) than for the other two sites. The decrease in 

agricultural land use was about 11 percent less for the site 22 drainage area than for the other 

two downstream sites. In addition, open space increased 17 percent within this drainage area 

but decreased for the two downstream sites.

Table 2. Changes in land use within drainage areas of selected stream sites in Chester County, Pa., 

1967-87

[Bounding may account for differences.]

1967

Land-use 

category

Open space

Agricultural

Pasture

Residential

Commercial

Open space

Agricultural

Pasture

Residential

Commercial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Square 

miles

0.80

1.57

.58

.14

.00

1.50

2.82

1.30

.36

.00

6.09

9.47

4.83

.09

.60

.00

.12

Percentage 

of drainage 

area

Sitel

25.8

50.8

18.8

4.6

.0

Site 2

25.1

47.2

21.8

5.9

.0

Site3

28.7

44.7

22.8

.4

2.8

.0

.6

Square 

miles

0.67

1.07

.67

.46

.22

1.23

1.64

1.00

1.88

.23

4.99

4.78

4.10

.06

6.23

.23

.81

1987

Percentage 

of drainage 

area

21.7

34.6

21.7

14.9

7.1

20.6

27.4

16.7

31.4

3.8

23.5

22.6

19.3

.3

29.4

1.1

3.8

Change

Square 

miles

-0.13

-.50

.09

.32

.22

-.27

-1.18

-.30

1.52

.23

-1.10

-4.69

-.73

-.03

5.63

.23

.69

Percentage 

of drainage 

area

-4.2

-16.2

2.9

10.4

7.1

-4.5

-19.7

-5.0

25.4

3.8

-5.2

-22.1

-3.4

-.1

26.6

1.1

3.3

LAND USE 7
Table 2. Changes in land use within drainage areas of selected stream sites in Chester County, Pa., 

1967-87 Continued

[Bounding may account for differences.]

1967

Land-use 

category

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Residential

Commercial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Square 

miles

8.01

12.29

6.09

.11

.86

.00

.14

9.62

13.60

6.76

.11

1.10

.00

.21

.23

1.34

.40

.03

.00

3.69

4.82

2.59

.20

.64

.06

4.54

3.94

3.63

.05

.24

.00

.00

15.54

4.22

3.19

.29

.00

24.99

11.66

8.76

.11

.87

.03

.00

Percentage 

of drainage 

area

Site 4

29.1

44.7

22.1

.4

3.1

.0

.5

SiteS

30.6

43.3

21.5

.3

3.5

.0

.7

SiteS

11.6

67.2

19.8

1.4

.0

Site 10

30.8

40.2

21.6

1.7

5.3

.5

Site 12

36.6

31.8

29.3

.4

1.9

.0

.0

Site 13

66.9

18.2

13.7

1.2

.0

Site 14

53.5

25.3

19.0

.2

1.9

.1

.0

Square 

miles

6.87

6.66

5.38

.06

7.47

.23

.83

8.03

6.97

6.22

.06

8.92

.23

.97

.23

.87

.32

.02

.56

3.27

3.62

.63

.16

4.16

.16

4.58

3.21

2.90

.03

1.56

.00

.12

15.03

3.07

2.33

2.69

.12

24.14

9.10

5.99

.03

6.34

.38

.12

1987

Percentage 

of drainage 

area

25.0

24.2

19.6

.2

27.2

.8

3.0

25.6

22.2

19.8

.2

28.4

.7

3.1

11.5

43.5

16.0

1.0

28.0

27.2

30.2

5.2

1.3

34.7

1.3

36.9

25.9

23.4

.2

12.6

.0

1.0

64.7

13.2

10.0

11.6

.5

52.4

19.7

13.0

.1

13.8

.8

.3

Change

Square 

miles

-1.14

-5.63

-.71

-.05

6.61

.23

.69

-1.59

-6.63

-.54

-.05

7.82

.23

.76

.00

-1.05

.08

-.01

.56

-.42

-1.20

-1.96

-.04

3.52

.10

.04

-.73

-.73

-.02

1.32

.00

.12

-.51

-1.15

-.86

2.40

.12

.85

-2.56

-2.77

-.08

5.47

.35

.12

Percentage 

of drainage 

area

-4.2

-20.5

-2.6

-.2

24.0

.8

2.5

-5.1

-21.1

-1.7

-.2

24.9

.7

2.4

.0

-52.6

-4.0

-.5

28.0

-3.5

-10.0

-16.3

-.3

29.3

.8

.3

-5.9

-5.9

-.2

10.6

.0

1.0

-2.2

-5.0

-3.7

10.3

.5

-1.8

-5.6

-6.0

-.2

11.9

.8

.3

8 LAND USE
Table 2. Changes in land use within drainage areas of selected stream sites in Chester County, Pa., 

1967-87 Continued

[Bounding may account for differences.]

1967

Land-use 

category

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Residential

Industrial

Commercial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Residential

Commercial

Open space

Agricultural

Pasture

Residential

Commercial

Industrial

Square 

miles

27.36

15.20

11.80

.13

1.14

.03

.00

.97

.31

.78

2.85

.00

.24

2.63

1.24

1.97

.51

3.21

.54

1.10

1.58

.63

.18

.61

.12

.00

2.17

4.09

1.60

.21

1.46

.18

.00

.02

.12

.36

.56

.00

1.14

1.56

1.21

1.86

.00

.00

Percentage 

of drainage 

area

Site 15

49.2

27.3

21.2

.2

2.0

.1

.0

Site 17

18.8

6.0

15.2

55.3

.0

4.7

Site 19

26.1

12.2

19.5

5.3

31.8

5.1

26.0

37.4

15.1

4.2

14.4

2.9

.0

Site 21

22.4

42.1

16.5

2.1

15.1

1.8

.0

3ile_22

1.9

11.3

34.0

52.8

.0

19.8

27.0

21.0

32.2

.0

.0

Square 

miles

27.61

12.29

7.38

.03

9.32

.40

.12

.70

.01

.15

3.89

.02

.38

1.97

.65

.32

.54

6.01

.61

.94

.11

.33

.17

2.42

.16

.09

1.63

.92

1.23

.18

5.29

.27

.19

.20

.00

.05

.78

.03

.76

.24

.66

3.06

.16

.89

1987

Percentage 

of drainage 

area

48.3

21.5

12.9

.0

16.3

.7

.2

13.6

.2

2.9

75.5

.4

7.34

19.5

6.4

3.2

5.4

59.5

6.0

22.3

2.6

7.8

4.0

57.4

3.8

2.0

16.8

9.4

12.6

1.8

54.5

2.8

2.0

18.9

.0

4.7

73.6

2.8

13.2

4.2

11.4

53.0

2.8

15.4

Change

Square 

miles

0.24

-2.92

-4.41

-.10

8.18

.38

.12

-.27

-.30

-.63

1.04

-.02

.14

-.66

-.59

-1.65

.03

2.80

.07

-.16

-1.47

-.30

-.01

1.81

.04

.09

-.54

-3.17

-.37

-.03

3.83

.09

.19

.18

-.12

-.31

.22

.03

-.38

-1.32

-.55

1.20

.16

.89

Percentage 

of drainage 

area

-0.9

-5.8

-8.3

-.2

14.3

.7

.2

-5.2

-5.8

-12.2

20.2

.4

2.7

-6.5

-5.8

-16.3

.3

27.7

.7

-3.8

-34.8

-7.1

-.2

42.9

1.0

2.1

-5.6

-32.6

-3.8

-.3

39.4

.9

2.0

17.0

-11.3

-29.2

20.8

2.8

-6.6

-22.9

-9.5

20.8

2.8

15.4

LAND USE 9
Table 2. Changes in land use within drainage areas of selected stream sites in Chester County, Pa., 

1967-87 Continued

[Bounding may account for differences.]

1967

Land-use 

category

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Open space

Agricultural

Pasture

Residential

Industrial

Square 

miles

2.01

2.53

2.58

.24

2.96

.08

.00

1.69

2.61

3.81

.31

1.24

.09

.04

2.32

4.47

3.91

.33

.24

.00

.04

2.22

5.86

1.84

.12

.37

.06

.03

6.47

6.09

3.73

.36

2.65

.62

.38

2.38

5.59

3.57

.08

.18

2.06

1.71

.39

.05

.05

Percentage 

of drainage 

area

Site 24

19.3

24.3

24.8

2.3

28.5

.8

.0

Site 27

17.3

26.7

38.9

3.2

12.7

.9

.4

Site 28

20.5

39.5

34.6

2.9

2.1

.0

.4

Site 34

21.1

55.8

17.5

1.1

3.5

.6

.3

Site 44

31.9

30.0

18.4

1.8

13.1

3.1

1.9

Site 45

20.2

47.4

30.2

.7

1.5

Site 47

48.4

40.1

9.2

1.2

1.2

Square 

miles

1.14

.28

.92

.12

6.52

.51

.91

1.70

2.20

2.83

.34

2.34

.19

.19

2.64

4.19

2.96

.32

.85

.24

.10

2.09

4.84

1.02

.09

1.97

.42

.07

4.76

1.88

2.29

.26

8.19

1.56

1.36

2.30

5.09

3.28

.00

1.13

1.60

.22

1.33

1.08

.03

1987

Percentage 

of drainage 

area

11.0

2.7

8.8

1.2

62.7

4.9

8.8

17.4

22.5

28.9

3.5

23.9

1.9

1.9

23.4

37.1

26.2

2.8

7.5

2.1

.9

19.9

46.1

9.7

.9

18.8

4.0

.7

23.4

9.3

11.3

1.3

40.3

7.7

6.6

19.5

43.1

27.8

.0

9.6

37.6

5.2

31.2

25.4

.7

Change

Square 

miles

-0.87

-2.25

-1.66

-.12

3.56

.43

.91

.01

-.41

-.98

.03

1.10

.10

.15

.32

-.28

-.95

-.01

.61

.24

.06

-.13

-1.02

-.82

-.03

1.60

.36

.04

-1.71

-4.21

-1.44

-.10

5.54

.94

.98

-.08

-.50

-.29

-.08

.95

-.46

-1.49

.94

1.03

-.02

Percentage 

of drainage 

area

-8.4

-21.6

-16.0

-1.2

34.2

4.1

8.8

.1

-4.2

-10.0

.3

11.2

1.0

1.5

2.8

-2.5

-8.4

-.1

5.4

2.1

.5

-1.2

-9.7

-7.8

-.3

15.2

3.4

.4

-10.6

-26.2

-8.9

-.6

34.4

5.8

6.1

-.7

-4.2

-2.5

-.7

8.0

-10.8

-35.0

22.1

24.1

-.5

10 LAND USE
Table 2. Changes in land use within drainage areas of selected stream sites in Chester County, Pa., 

1967-87 Continued

[Hounding may account for differences.]

1967

Land-use 

category

Open space

Agricultural

Pasture

Residential

Commercial

Industrial

Open space

Agricultural

Pasture

Specialized agriculture

Residential

Commercial

Industrial

Square 

miles

1.35

.98

1.04

2.36

.18

.54

3.07

4.01

1.73

.44

2.74

.26

.47

Percentage 

of drainage 

area

Site 49

20.9

15.2

16.1

36.6

2.8

8.4

Site 50

24.1

31.5

13.6

3.5

21.5

2.0

3.7

Square 

miles

1.37

.19

.62

2.62

.40

1.25

3.33

.35

.60

.52

4.62

.62

2.66

1987

Percentage 

of drainage 

area

21.2

3.0

9.6

40.6

6.2

19.4

26.2

2.8

4.7

4.1

36.4

4.9

21.0

Change

Square 

miles

0.02

-.79

-.42

.26

.22

.71

.26

-3.66

-1.13

.08

1.88

.36

2.19

Percentage 

of drainage 

area

0.3

-12.2

-6.5

4.0

3.4

11.0

2.0

-28.8

-8.9

.6

14.8

2.8

17.2

LAND USE 11
ORGANOCHLORINE COMPOUNDS 

Icedale Lake Sediment Cores

Accumulated sediments at the site of Icedale Lake, a drained reservoir on West Branch 

Brandywine Creek (fig. 1), provided an opportunity to examine relative influx of 

organochlorine compounds to the stream over time. The lake was a small reservoir built in 

1913 to allow wintertime ice production. In 1984, a breach in the dam drained the reservoir, 

leaving a large amount of accumulated sediment. Like most basins in the study area, the 

Icedale Lake Basin has experienced increased residential development and subsequent 

decreases in agricultural land use, pasture, and open space (table 3).

Three cores of accumulated sediments were collected by driving 6-in. diameter PVC 

pipe into the old lake bed. Resistance to driving by rock or gravel was considered to be the 

bottom of the accumulated sediment. The cores were extruded from the pipes in 2-cm 

segments. The outermost part of each extruded core segment was removed to minimize 

smearing problems, and the central part was analyzed for lead-210 and cesium-137 activities, 

silt and clay content, and concentrations of selected organochlorine compounds and organic 

carbon. The radioactive elements were analyzed at a contract laboratory according to the 

methods of the National Council on Radiation Protection and Measurements (1985) and the 

American Society for Testing and Materials (1987). The silt and clay contents were determined 

at the USGS Pennsylvania District Sediment Laboratory by sieving technique. Analyses of 

organic carbon and organochlorine compounds were performed by the USGS National WaterQuality Laboratory according to the methods of Wershaw and others (1987, p. 17-22 and SI35). Compaction errors for the three cores were small and ranged from 0 to 4 percent of the 

core depths. Therefore, data from same depth segments in each core were considered 

comparable.

Table 3. Change in land use for Icedale Lake Basin, Chester County, Pa., 1967-87

Land-use 

category

Open space 

Cropland 

Pasture

Residential

Commercial

Industrial

Square 

miles

6.38 

9.98

2.45

.80

.00

.08

1967

Percentage 

of drainage 

area

32.4 

50.7 

12.5

4.1

.0

.4

Square 

miles

5.46 

8.89 

1.99

3.14

.07

.26

1987

Percentage 

of drainage 

area

27.6 

44.9 

10.1

15.8

.3

.3

Change

Square 

miles

-0.92 

-1.09 

-.46

2.34

.07

.18

Percentage 

of drainage 

area

-4.8 

-5.8 

-2.4

11.8

.3

.9

12 ORGANOCHLORINE COMPOUNDS
Core Dating

Estimates of the times of deposition for core segments were made by estimating the 

amount of annual sediment loads for the Brandywine Creek at Chadds Ford. Because the 

accuracy of these estimates could be affected by unknown changes in sediment transport 

caused by land-use changes (table 3), the estimates were compared to cesium-137 activities in 

the core segments. Although lead-210 data also were collected for dating purposes, activities 

were less than 1.25 pCi/g in all core segments and were considered too small and variable for 

dating purposes.

The USGS streamflow-gagmg station at Chadds Ford (fig. 1) has streamflow data from 

1912 to 1955 and continuously since 1963. Suspended-sediment data were collected from 1964 

to 1978. Assuming that peak-flow events transported most sediment to the lake, annual 

sediment loads for the period of record (1964-78) were correlated (r=0.76, p=<0.05) with the 

annual peak discharges exceeding 6,000 ft3 /s (fig. 2). By use of this relation, annual sediment 

loads were calculated for all years that the lake existed except for 1956-63, when discharge 

data were not collected. About 10 percent of the sediment discharged to the lake during the 

period of missing record. The amount of sediment discharged for individual years was 

divided by the total sediment discharged from 1913 to 1984 and multiplied by the core depth 

to assign approximate deposition years to the core. The depth of the shallowest core (32 cm) 

was used as total depth because the deeper cores (40 and 50 cm) are thought to represent lowelevation areas of the lakebed that might have accumulated disproportionately large amounts 

of sediment in the early period of the reservoir's existence.

Cesium-137 fallout is a product of atmospheric nuclear detonations. Activities in the 

core segments (table 4) were used to determine the reasonability of the calculated deposition 

years. Because metals like cesium (which has a high affinity for sediment attachment) have 

disproportionately higher concentrations on fine particles compared to coarse particles, the 

core-segment activities were normalized for silt and clay content according to methods used 

by Horowitz (1991, p. 84) and compared to the calculated deposition periods in figure 3. The 

largest cesium-137 peak on figure 3 (at 9-13 cm) is considered representative of cesium-137 

deposition to the basin during the highest fallout period from 1959 to 1966 (Ritchie and others, 

1973). This suggests a lag time of about 2 or 3 years for transport to the reservoir and is 

considered reasonable for this analysis. The sharp decrease (at 7 cm) and secondary peak (at 

5 cm) also correlate on a 2- to 3-year lag time with the low fallout rate in 1967 and subsequent 

increase reported by Ritchie and others (1973).

ORGANOCHLORINE COMPOUNDS 13
120,000

100,000

OT 

I

LLJ 

O

tr

i 

o

80,000

- 60,000 o

LLJ OT

o 

z

<

40,000

20,000

y = (125,873) log x - 446,974 

Correlation coefficient = 0.7582 Figure 2. Relation between annual 

peak flows and annual sediment 

discharge at Brandywine Creek at 

Chadds Ford, 1964-78

1,000 10,000 100,000

ANNUAL PEAK DISCHARGE, IN CUBIC FEET PER SECOND

Figure 3. Depth profile of ratio of 

cesium-137 and silt-clay fraction in 

bottom materials of Icedale Lake, 

Chester County, Pa.

UJ

O

^ 8 ~

tr 

I

10

8: 12

uJ 14 o

16

18

20

-1980

-1975

-1945

0 .002.004.006.008.010.012.014.016.018

RATIO OF CESIUM-137 ACTIVITY,

IN PICOCURIES PER GRAM TO

SILT-CLAY CONTENT, IN PERCENT

14 ORGANOCHLORINE COMPOUNDS
Table 4. Concentrations of carbon and organochlorine compounds, Cesium-137 activities, and silt and clay 

sized particles in bottom materials at selected depths from Icedale Lake, Chester County, Pa., September 

1988

[cm, centimeter; ng/kg, microgram per kilogram; g/kg, gram per kilogram; <, less than; pCi/g, picoCurie 

per gram; urn, micrometer]

Depth 

(cm)

0-2 

2-4

4-6

6-8

8-10

10-12

12-14

14-16

16-18

18-20

20-22

22-24

24-26

26-28

28-30

Aldrin, Chlordane, ODD, DDE, DOT, Dieldrin, Endosulfan, Endrin, PCB, PCN, 

total total total total total total total total total total 

(ng/kg) (ng/kg) (ng/kg) (ng/kg) (ng/kg) (ng/kg) (ng/kg) (ng/kg) (ng/kg) (ng/kg)

<0.1 4.0 0.8 

- <.l 3.0 .6

<.l 3.0 .6

<.l 3.0 .6

<.l 4.0 .8

<.l 4.0 1.2

<.l 3.0 1.8

<.l 2.0 2.9

<.l 2.0 3.4

<.l 2.0 2.5

<.l 1.0 1.0

<.l <1.0 .3

<.l <1.0 <.l

<.l <1.0 <.l

<.l <1.0 <.l

1.9 

2.1

2.1

2.1

2.5

2.9

3.4

3.6

4.1

2.9

1.4

.5

.1

.1

.1

clO 0.4 <0.1 

clO .4 <.l

clO .3 <.l

clO .3 <.l

clO .4 <.l

clO .4 <.l

clO .3 <.l

clO .2 <.l

clO .1 <.l

clO <.l <.l

clO <.l <.l

clO <.l <.l

<.l <.l <.l

<.l <.l <.l

<.l <.l <.l

<0.1 5 

<.l 6

<.l 5

<.l 5

<.l 7

<.l 3

<.l 7

<.l 6

<.l 7

<.l 4

<.l 3

<.l 3

<.l <1

<.l <1

<.l <1

Jo

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

Heptachlor, 

total 

(ng/kg)

<0.1

<.i

<.i

<.i

<.i

<.i

<.i

<.i

<.i

<.i

<.i

<.i

<.i

<.i

Depth 

(cm)

0-2 

2-4

4-6

6-8

8-10

10-12

12-14

14-16

16-18

18-20

20-22

22-24

24-26

26-28

28-30

Heptachlor Methepoxide, ' oxychlor, 

total to total 

(ng/kg) y (ng/kg)

<0.1 <0.1 <0.1

<.l <.l <.l

<-l <.l <.l

<.l <.l <.l

<.l <.l <.l

<-l <-l <.l

<-l <.l <.l

<.l <.l <.l

<.l <.l <-l

<.l <.l <.l

<.l <.l <-l

<-l <.l <.l

<.l <.l <-l

<.l <.l <.l

Mirex, 

total 

(no/kg)

<0.1

<.l

<.l

<.l

<.l

<.l

<.l

<.l

<.l

<.l

<.l

<.l

<.l

<.l

Perthane, Toxaphene, 

total total 

(ng/kg) (^g/kg)

<1.00 <10 

1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

<1.00 <10

ca*°n, £sr+-

in°Snic organic, 5 35 C) asC) £

<0.1 31 

<.l 27

<.l 24

<.l 23

<.l 21

<.l 23

<.l 25

<.l 25

<.l 25

<.l 24

<.l 22

<.l 24

<.l 28

<.l 32

<.l 29

Cesium 

137, 

total 

(pCi/g)

0.236 

.315

.415

.386

.528

.550

.526

.194

.046

<.020

-

-

Grain size 

<63nm 

percent 

of total

25 

28

27

29

32

34

38

34

26

32

30

27

30

31

31

ORGANOCHLORINE COMPOUNDS 15
Compounds in Core Segments

Five organochlorine compounds chlordane, dieldrin (a commercial insecticide and 

biodegradation product of aldrin), PCB's, ODD, and DDE were detected in the Icedale Lake 

core and represent primary-use compounds or degradation products that are resistant to further 

decomposition in the natural environment (Callahan and others, 1979). DDD and DDE typically 

reflect biodegradation of DOT (Johnsen, 1976). Because these nonionic organic compounds have 

a strong tendency to partition into organic material in the presence of water (Smith and others, 

1988, p. 27-28), ratios of their concentrations and concentrations of organic carbon were used to 

normalize the data for more meaningful comparisons. The highest ratios suggest the periods of 

greatest influx of organochlorine compounds to the lake. Figure 3 compares these ratios for the 

detected compounds. Generally, data suggest the influx of the detected compounds was smaller 

in recent years than in the past, although only DDD, the compound most likely to be 

biodegraded (Johnsen, 1976), had recent ratios nearly as low as the oldest ones. Although DDT 

was not detected, the ratios of DDE and DDD suggest that the greatest effects of this pesticide 

were in the late 1940's to early 1950's, shortly after commercial production began in the United 

States. Influxes of chlordane and dieldrin seem to increase after 1950, while those of DDE and 

DDD decrease, suggesting that DDT use was gradually replaced by chlordane and dieldrin. The 

influx of chlordane and dieldrin appears to be greatest in the mid 1960's, corresponding closely 

with the peak farm use of aldrin and dieldrin (1966) and chlordane (1971) reported by Gilliom 

and others (1985, p. 7). This usage peaked just before the biological monitoring program began in 

Chester County.

Two peaks are present for PCB's, one in the late 1950's and the other in the late 1960's. It is 

not known if this is related to use of PCB's as a pesticide extender (National Research Council, 

1979, p. 3-4) or any of the many other wide-ranging historical uses for these compounds. 

Although greatest regional concentrations are commonly in industrial areas, atmospheric 

discharges (volatilization, incineration, etc.) contribute to their very widespread distribution 

(Smith and others, 1988, p. 30-32).

Stream-Bottom Materials

Bulk samples of stream-bottom materials were collected at 42 sites in the study area from 

October 1985 through November 1987 and analyzed for content of organochlorine pesticides and 

PCB's (table 5). The samples were collected from the top 2 cm of the stream bottom in depositional areas of the stream by use of stainless-steel scoops according to the methods of Wershaw 

and others (1987, p. 7-8). Analyses were performed by the USGS National Water-Quality Laboratory according to the methods of Wershaw and others (1987, p. 31-35).

The most frequently detected compounds were PCB's, chlordane, DDT, DDD, DDE, 

dieldrin, heptachlor epoxide, methoxychlor, and lindane (table 5). In a few instances, the 

minimum reporting levels1 exceeded those typically reported or no values are reported for some 

compounds. This is a result of interference caused by high concentrations of other target or 

nontarget compounds and the resulting subsample dilutions that sometimes must be made 

during analysis. Organochlorine compounds were detected at every site except one (site 46) 

located in the northwestern part of the study area. Methoxychlor was detected at only three sites 

(sites 1,39, and 49). Land-use analysis was done for the drainage areas of two of these three sites 

(sites 1 and 49). The data show that drainage areas for these sites were among the four areas 

having the greatest commercial land use in 1987 (greater than 6 percent). Methoxychlor is usually 

associated only with agricultural activities, has a short half-life compared to other 

organochlorine pesticides, and is rarely detected in the stream-bottom materials in stream basins 

where this pesticide is used (Gilliom and others, 1985, p. 9). Detection of methoxychlor at these 

sites might be a result of commercial construction activities on former agricultural lands.

1 The smallest measured concentration of a constituent that may be reliably reported using a 

given analytical method.

16 ORGANOCHLORINE COMPOUNDS
tr 

01

01 

O

01

Q 

1

O 

tr

LL

t

01 

Q

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

CHLORDANE

-1980

-1945

DIELDRIN

-1980

-1945

PC

0 .04 .08 .12 .16 .20 0 .04 .08 .12 .16 0 .005 .010 .015 .020 0 

RATIOS OF ORGANOCHLORINE-COMPOUND CONCENTRATIONS, IN MICROGRAMS PER KILOGRA

TO ORGANIC-CARBON CONCENTRATION, IN GRAMS PER KILOGRAM

Figure 3. Depth profiles of ratios of selected organochlorine compounds and organic carbon in bottom materials of Icedale 

Chester County, Pennsylvania
Table 5. Concentrations of organochlorine compounds on unsorted streambed materials of streams in 

Chester County, Pennsylvania, October 1985 through November 1987

[All values are in micrograms per kilogram; <, less than]

Site 

number

1 

2

3

4

5

6

10

12

13

14

15

16

17

19

20

21

22

23

24

26

27

28

29

30

31

32

33

34

36

37

38

39

40

42

44

45

46

47

48

49

50

51

- *"«'

10-09-87 <0.1 

10-07-86 <.l

10-08-86 <.l

10-07-85 <.l

10-06-86 <.l

10-11-85 <.l

10-11-85 <.l

10-10-85 <.l

10-22-86 <.l

10-11-85 <.l

12-05-86 <.l

10-09-85 <.l

11-14-86 <.l

10-09-86 <.l

10-15-85 <.l

10-09-86 <.l

10-15-86 <.l

10-15-86 <,!

10-16-85 <1

10-18-85 <.l

11-18-86 <.l

10-25-85 <.l

12-02-86 <.l

10-25-85 <.l

10-28-86 <.l

10-17-85 <.l

11-20-86 <.l

10-24-85 <.!

10-21-85 <.l

11-17-86 <.l

10-22-85 <.l

11-03-86 <.l

10-30-85 <.l

10-23-85 <.l

10-31-85 <.l

10-30-86 <.l

10-29-85 <.l

10-29-86 <.l

10-29-86 .1

11-16-87 <10

10-09-85 <.l

10-16-86 <.l

Chlordane, 

total

2.0

<1.0

<1.0

<1.0

6.0

<1.0

<1.0

<1.0

6.0

1.0

5.0

<1.0

7.0

7.0

<1.0

30

<1.0

7,0

5,0

-

<1.0

<1.0

<1.0

29

1.0

4.0

<1.0

<1.0

<1.0

3.0

32

3.0

<1.0

4.0

4.0

<1.0

<1.0

1.0

13

5.0

110

ODD, 

total

0.3

.3

<.l

<.l

.4

<.l

.3

1.2

<.l

<.l

<.l

.8

.1

.6

.1

.8

.3

<.l

36

-

6.3

1.1

-

3.2

.8

3.1

.1

.1

.2

.6

4.4

3.6

<.l

.4

.6

<.l

 4

.3

.3

1.7

5.0

DDE, 

total

0.2

.5

.4

-

.4

1.0

.1

.4

1.1

.6

.2

<.l

1.7

.3

.6

.1

1.6

.6

.3

22

-

2.8

1.2

.4

7.4

1.0

4.8

<.l

.2

.3

.2

4.1

2.5

.2

<.l

Zl

<,1

. ' . . 1.8

<10

1.7

2.1

DOT, 

total

<1.0

-

<.l

.3

<.l

<.l

.4

<.!

<.l

<.l

<.l

1.0

2.2

<.l

<.l

1.3

<1

<1

61

-

.4

1.3

<.l

.8

3.1

3J

.2

<.l

<.l

<.l

1.3

<.l

<.l

<.l

<.l

<,1

<.l

<.l

<10

3.2

1.2

Dieldrin, 

total

<0.1

<.l

.1

<.l

.3

<.l

4.8

.3

.1

.1

.2

2.7

.1

.3

<.l

.5

.4

.1

<.l

.1

.1

<.l

.9

<.l

1.2

< !

<.l

f>

.1

3.2

<.l

<.l

.3

.7

<.l

. .:. .4 

- : ' .*.. 

.- ' ''''J .': '

.1

.6

Endosulfan, Endrin, PCB, 

total total total

<.2 <.l <5

.1 <.l <1

<.l <.l 9

.3 <.l <1

<.l <.l 3

<.l <.l <1

 cl .1 <1

<.l <.l <1

<1 <.l 12

<.l <.l 3

<.l <.l 5

<.l <.l 95

<.l <.l 7

<.l <.l 5

<.l <.l <1

<.l <.l 8

<.l <1 4

<.l <.l 2

<.l <,1 38

<.l <.l 1,400

<.l <.l <1

<.l <.l 3

<.l <.l <1

<.l <.l <1

<.l <.l <1

<.l ,3 3

<1 <.l <1

<.l <,1 <1

<,1 <.l 6

<.l <.l 11

.2 <.l 14

<.l <.l 6

<.l <.l <1

<.l <.l 40

<.l <.l <1

<.l <1 <1

 cl ' <!' 3

' : <1 :', .: ',<,! . . <1

<! <1 S40

<.l <.l 18

<.l <.l 73

18 ORGANOCHLORINE COMPOUNDS
Table 5. Concentrations of organochlorine compounds on unsorted streambed materials of streams in 

Chester County, Pennsylvania, October 1985 through November 1987 Continued

[All values are in micrograms per kilogram; <, less than]

Site 

number

1

2

3

4

5

6

10

12

13

14

15

16

17

19

20

21

22

23

24

26

27

28

29

30

31

32

33

34

36

37

38

39

40

42

44

45

46

47

48

49

50

51

- a

10-09-87 <1.0

10-07-86 <1.0

10-08-86 <1.0

10-07-85 <1.0

10-06-86 <1.0

10-11-85 <1.0

10-11-85 <1.0

10-10-85 <1.0

10-22-86 <1.0

10-11-85 <1.0

12-05-86 <1.0

10-09-85 <1.0

11-14-86 <1.0

10-09-86 <1.0

10-15-85 <1.0

10-09-86 <1.0

10-15-86 <1.0

10-15-86 <1.0

10-16-85 <1.0

10-18-85 1.0

11-18-86 <1.0

10-25-85 <1.0

12-02-86 <1.0

10-25-85 <1.0

10-28-86 <1.0

10-17-85 <1.0

11-20-86 <1.0

10-24-85 <1.0

10-21-85 <1.0

11-17-S6 <1.0

10-22-85 <1.0

11-03-86 <1.0

10-30-85 <1.0

10-23-85 <1.0

10-31-85 <1.0

10-30-86 <1.0

10-29-85 <1.0

10-29-86 <1.0

10-29-86 <1.0

11-16-87 <1.0

10-09-85 <1.0

10-16-86 <1.0

Heptachlor, HePtachlor Lindane, Methoxychlor, 

total ^al total total

<0.1 <0.1 <0.1 2.4

<.l <.l <.l <.l

<.l 3.8 <.l <.l

<.l <.l <.l <.l

<.l <.l <.l <.l

<-l .2 V.<1 <.l

<.l <.l <.l <.l

<.l ,4 <.l <.l

<.l <;1 .1 <.l

<.l .1 <-l <<1

<.l <.l <.l <.l

<.l .1 <.l <.l

<.l <.l <.l <.l

<.l <.l <.l <.l

<.l .4 .1 <.l

<.l <.l <.l <.l

<.l .1 .1 <.l

<.l .2 <.l <.l

<-l .1 .4 <.l

<.l <.l .3 <.l

<.l <.l <.l <.l

<.l <.l <.l <.l

<.l <.l <.l <.l

<.l <.l <.l <.l

.5 <.l <.l <.l

<.l .1 <.l <.l

 Cl .1 <.l <.l

 cl <.l <.l <.l

<.l <.l <.l <.l

<.l <.l <.l <.l

<.l .1 <.l <.l

<.l <.l .2 .2

<.l <.l <.l <.l

<.l <.l <.l <.l

<.l <.l <.l <.l

<.l .1 <.l <.l

<.l <,1 <.l <.l

<.l <.l <.l <.l

<.l <,1 <1 <.l

<10 <.l <.l 13

.1 .1 <.l <.l

.1 .1 1.0 <.l

Mirex, Perthane, Toxaphene, 

total total total

<0.1 <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

.2 <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<-l <1.00 <10

«.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

.7 <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<,1 <IJOO <10

<.l <1.00 <10

<.l <1.00 <10

<.l - <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

<! <IM <10

<.l <100 <10

<.i <i.oo <io

<10 <1.00 <10

<.l <1.00 <10

<.l <1.00 <10

ORGANOCHLORINE COMPOUNDS 19
Because compound concentrations in these bulk stream-bottom samples can be 

expected to be complicated by variation in sample organic-carbon concentrations, only 

concentrations equal to or greater than 15 ug/kg were considered enriched for this study. 

Comparison of all compound concentrations by use of probability plots according to the 

methods of Velz (1970) also suggests that concentrations greater than about 15 to 20 ug/kg can 

be considered enriched over background. Table 6 summarizes results for compounds detected 

at greater than 15 ug/kg.

Only one site (site 22) had both a bottom-material sample with the concentration of 

chlordane exceeding 15 ug/kg and an analysis of drainage-area land use. This drainage area 

had the second highest residential land use (greater than 74 percent) and low agricultural land 

use (0 percent), suggesting that residential land use is, or has been, the most significant source 

of chlordane, possibly for termite control. Moore (1987, p. 28) reports that chlordane also was 

used by the mushroom industry in Chester County.

Site 26 (East Branch Red Clay Creek) was the only site having combined DDT, ODD, 

and DDE concentrations in bottom materials exceeding 15 ug/kg. Although no land-use data 

were available, the high concentrations at this site are consistent with other data suggesting 

heavy past or current use of DDT throughout the Red Clay Creek Basin (Cindy Rice, U.S. Fish 

and Wildlife Service, written commun., 1992). Unfortunately, comparisons could not be made 

to site 27 (West Branch Red Clay Creek) because elevated concentrations of PCB (1,400 ug/hg) 

at this site interfered with pesticide determinations.

Bottom-material samples from seven sites had PCB concentrations exceeding 15 ug/kg, 

but only five sites had analyses of drainage-area land use. The drainage area of four of these 

sites (sites 17,44,49, and 50) were among the six having the highest combined industrial and 

commercial land uses in 1987 (ranging from 7 to 26 percent). Although the drainage area of 

site 27 did not have high industrial and commercial land use, the extremely high PCB 

concentrations may have been caused by reported industrial contamination to the West 

Branch Red Clay Creek at Kennett Square, Pa. (Roy F. Weston, Inc., 1988, P. 3-33 to 3-36).

Three bottom-material samples from sites with drainage area land-use data (sites 5,21, 

and 23) had lower concentrations of organochlorine compounds than the samples from 

upstream sites (see table 7). The drainage areas for the downstream sites all experienced 

greater than 20 percent residential growth between 1967-87, suggesting that construction 

activities between each pair of sites may contribute sediments that have lower pesticide 

concentration than do the older sediments of the streams.

20 ORGANOCHLORINE COMPOUNDS
Table 6. Concentrations of organochlorine compounds exceeding or 

equalling 15 micrograms per kilogram on unsorted streambed materials 

in Chester County, Pa., October 1985 through November 1987

[-, concentration did not equal or exceed 15 micrograms per kilogram]

Site 

number

1 17

1 22

26

'27

31

39

144

'49

'50

51

Chlordane

-

30

-

29

32

-

110

DOT ODD ' ' PCB

95

_

119 38

1,400

-

-

40

540

18

73

1 1967 and 1987 land-use data available for the drainage area of this site.

Table 7. Comparison of pesticide concentrations at paired sites with increasing residential land use 

[Concentrations are in micrograms per kilogram; <, less than]

Sample 

location

Picketing Creek

Upstream from site 5

SiteS

Ridley Creek

Upstream from site 21

Site 21

East Branch Chester Creek

Upstream from site 23

Site 23

Combined 

Chlordane DOT, ODD, 

and ODE

2 0.5

<1 .7

7 1.2

<1 .2

30 2.9

<1 <.l

pCB Heplachlor 

epoxide

9 3.8

<1 <.l

5 .4

<1 <.l

8 .1

4 .2

Melhoxychlor

2.4

<.l

<.l

<.l

<.l

<.l

ORGANOCHLORINE COMPOUNDS 21
BENTHIC-INVERTEBRATE COMMUNITIES

Benthic-invertebrate communities were sampled annually in autumn. Samples were 

collected in riffles at each site by collecting 10 rocks between 45 and 90 mm in diameter. A 

Lium Sampler (Britton and Greeson, 1988, pp. 280-281) having a 210 (o.m mesh screen was used 

to collect the samples. Moore (1987) discusses this sampling method and its comparability to 

other techniques in greater detail.

Diversities of the invertebrate communities were determined for each sample by 

calculating Brillouin's diversity index (Brillouin, 1962). This index is commonly used by 

aquatic ecologists and, when samples are only a representative part of a larger, undefined 

community, this index most appropriately represents community diversity (Pielou, 1969; 

Kaesler and Herricks, 1976; and Zand, 1976). All organisms were identified to the genus level 

for the entire study period except for midges (Chironomidae), which were identified to only 

family level for the 1970-74 and 1981-88 periods. In order to ensure comparability for this 

study, all diversity indexes were calculated on the basis of midge identification to family level. 

Brillouin's diversity indexes for each sample for 1970-88 are given in the appendix. Diversity 

indexes as a function of time also are given in graphic form for each site. The 1978 data were 

omitted from the tables, time plots, and trend analyses because variations in the sampling 

procedures made comparisons to the other data inappropriate. Supplementary information 

also given in the appendix includes numbers of organisms and taxa and calculations of 

minimum diversity, maximum diversity, and evenness. Moore (1987, p. 11) gives detailed 

descriptions of these calculations. Generally, higher diversities were directly related to higher 

numbers of organisms and higher numbers of taxa at the genus and family levels, but not at 

the order level.

A nonparametric, distribution-free statistical test for monotonic trend with time was 

used to detect trends in the diversities at each of 46 sites. Magnitude of trend in the data was 

determined by the Kendall slope estimator (Hirsch and others, 1982). Sites previously 

dropped from the network because habitat differences resulted in data that could not be 

compared to other network sites (sites 25 and 41) and sites having only recent diversity data 

(sites 16,39, and 51) were not included in the analysis. Trend tests and estimates of the slope of 

the linear trends are presented in table 8. The diversity of benthic-invertebrate communities 

increased at 45 of 46 sites. The upward trends were significant at the 99-percent confidence 

level at 30 sites, 95- to 98-percent confidence level at 9 sites, and 90- to 94-percent confidence 

level at 3 sites (table 8). The trends in diversity indexes at sites 7,28,31, and 47 were not 

statistically significant. Sites 3 and 26, which exhibited downward diversity-index trends prior 

to 1981 (Moore, 1987), show statistically significant upward trends.

22 BENTHIC-INVERTEBRATE COMMUNITIES
Table 8. Values of slope, tau, p, and level of confidence from seasonal 

Kendall test of diversity index

[--, trend not statistically significant at the 90-percent confidence level; 

Tau, measures the degree of correlation the lower the tau value, the lower 

the correlation; p, measures the significance of the trend the higher the 

p value, the higher the probability of error]

Site 

number

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

17

18

19

20

21

22

23

24

26

27

28

29

30

31

32

33

34

35

36

37

38

40

42

43

44

45

46

47

48

49

50

Kendall 

slope 

estimator

0.08

.08

.06

.10

.09

.16

.14

.08

.11

.09

.13

.08

.06

.06

.07

.13

.13

.09

.11

.09

.09

.15

.12

.08

.01

.00

.12

.10

.08

.07

.10

.12

.10

.08

.09

.14

.15

.12

.21

.08

.07

.12

.04

.07

.10

.13

Tau

0.72

.43

.42

.67

.55

.78

.33

.44

.64

.64

.72

.68

.32

.37

.43

.85

.56

.50

.66

.56

.57

.70

.67

.39

.58

.01

.66

.70

.31

.47

.68

.59

.41

.54

.47

.71

.78

.62

.71

.55

.47

.65

.35

.46

.69

.88

P

0.00

.02

.03

.001

.01

.00

.18

.09

.01

.00

.01

.00

.09

.05

.02

.00

.03

.01

.00

.00

.00

.00

.00

.05

.00

1.00

.00

.00

.11

.02

.00

.00

.07

.00

.01

.00

.00

.00

.02

.01

.02

.00

.11

.02

.00

.00

Level of

confidence 

of significant 

trends

(percent)

99

98

97

99

99

99

91

99

99

99

99

91

95

98

99

97

99

99

99

99

99

99

95

99

99

99

98

99

99

93

99

99

99

99

99

98

99

99

99

98

99

99

BENTHIC-INVERTEBRATE COMMUNITIES 23
RELATIONS AMONG LAND USE, BENTHIC-INVERTEBRATE COMMUNITIES, 

AND ORGANOCHLORINE COMPOUNDS

Streamflow data were examined to determine if extreme hydrologic conditions would 

have significantly affected invertebrate communities for any sampling periods. Available 

discharge records from Brandywine, Darby, and French Creeks were examined for 

streamflows less than the 7-day, 10-year low flow and the two highest peak flows occurring up 

to 3 months prior to or during sampling. These extreme flows were compared to invertebratecommunity diversities and numbers of organisms. The comparisons showed no consistent 

effects that could be expected to overwhelm other factors, such as land use, for any sampling 

periods.

The trends in community diversities and changes in land use were compared. The 1988 

land-use data for 26 drainage areas primarily show increases in residential land use and 

decreases in agricultural land use since 1967. Biological data collected from sites in these 

drainage areas show positive trends in the diversity indices for the period 1970-88. These data 

were analyzed by use of contingency tables to measure any possible relation between the 

biological trends and land-use changes. The contingency analyses were based on the 

frequency with which a large percentage change in land use and a high Kendall slope 

estimator occurred together in a basin.

The contingency analyses showed that the relation between the Kendall slope estimator 

and the increases in residential land use of 12 percent or greater was significant at the 95- 

percent confidence level. The phi-coefficient (the correlation coefficient calculated on the 

observations in the contingency table) was 0.43, which shows a moderate dependence. 

Increases in residential land use greater than or equal to 12 percent occurred in 18 of the 26 

drainage areas with land-use data in Chester County.

The contingency analyses also showed that the relation between the Kendall slope 

estimators and decreases in agricultural land use of 5 percent or greater was significant at the 

95-percent confidence level. The phi-coefficient was 0.39, which again shows a moderate 

dependence. Decreases in cropland greater than or equal to 5 percent occurred in 23 of the 26 

drainage areas.

Data from the nested systems (French, Pickering, Ridley, and East Branch Chester 

Creeks) suggest no refinements to conclusions drawn from the entire data base. All sites 

showed similar degrees of improvement in the diversity of benthic communities.

24 RELATIONS
The relation between community diversities and concentrations of organochlorine 

compounds in bottom sediments also was analyzed by use of contingency tables. 

Concentrations of chlordane, PCB's, and DOT plus its breakdown products were totaled for 

use in the analyses and compared to those diversities for biological samples collected in the 

same year. The contingency tables showed that the relation between diversity indexes of less 

than 2.25 and concentrations of organochlorine compounds greater than 45 ng/kg was 

significant at the 95-percent confidence level. The phi-coefficient was 0.37, which showed a 

moderate dependence. Concentrations of organochlorine compounds were greater than 

45 ug/kg at 5 of the 42 sites (sites 17,26,27,49, and 51).

Comparisons of the magnitude of organochlorine-compound concentrations to the 

ranking of the diversities suggest that pesticide residues could influence the benthic 

communities more than PCB residues influence them. The maximum concentrations of DOT 

plus its breakdown products and chlordane (119 and 110 ug/kg, respectively) were at sites 26 

and 51. The concentration of PCB residues at site 27 (1,400 ng/kg) was so high that it 

interfered with the detection of other pesticides. The diversities associated with these high 

concentrations were in the lowest quartile of all diversities (less than 2.39). In contrast, 

concentrations of PCB at sites 17 and 49 (95 and 540 ug/kg, respectively) were associated with 

diversities greater than 3.0 (median diversity).

Overall, the contingency-table analyses show relations that support several possible 

factors or combination of factors affecting the invertebrate communities. Sediment produced 

by new residential development might be less than that produced by the replaced agricultural 

activities, causing less stress on the communities. Decreases in agricultural land use and (or) 

changing pesticide use might translate into less pesticide influx to streams, also causing less 

stress on communities. Finally, sediment from new residential development might have lower 

pesticide concentrations associated with it than sediment from agricultural land does, 

resulting in dilution of pesticides in the streambed materials where the benthic communities 

reside. However, the moderate degree of dependence for these relations indicates that landuse changes and organochlorine compounds are probably only two of several factors that 

might cause the improvements in benthic-invertebrate communities observed in the streams 

studied. Site-specific studies would be required to verify the cause and effect relations 

suggested by this study or to identify other significant factors affecting the communities.

RELATIONS 25
SUMMARY AND CONCLUSIONS

Land use was analyzed for the drainage areas of 26 stream sites that cover about 

30 percent of Chester County. The most significant land-use changes during 1967-87 were 

decreased agricultural land use and increased residential, commercial, and industrial land 

use.

Cores of lakebed sediments at the site of Icedale Lake (a drained reservoir on West 

Branch Brandywine Creek) were collected to evaluate past influx of organochlorine pesticides 

and PCB's. Residues of ODD and DDE indicate that DOT was the first organochlorine 

insecticide entering the stream; concentrations peaked in the late 1940's and early 1950's. After 

this time, the influx of DOT decreased and those of chlordane and dieldrin increased. The 

influxes of these two insecticides peaked near the late-1960's, corresponding with reported 

national peak farm usage. Influx of PCB's seemed to be somewhat erratic; concentrations 

peaked from the late 1940's through the late 1960's. It is not known if any of the PCB influxes 

were associated with pesticide use. The core data suggest that influx of chlordane, dieldrin, 

and PCB's were greatest before the start of the biological monitoring program and decreased 

through the early 1980's, supporting the hypothesis of decreased pesticide use suggested by 

Sloto (1987).

Samples of stream-bottom material were collected at 42 sites in the study area from 

October 1985 through November 1987 and analyzed for organochlorine pesticides and PCB's. 

Organochlorine compounds were detected in streambed materials at 41 of the 42 sites 

sampled. The most enriched compounds (greater than 15 ug/kg) were PCB's, chlordane, and 

DOT plus its breakdown products. Methoxychlor was detected only in drainage areas with 

commercial land use greater than 6 percent. Chlordane concentrations exceeding 15 ug/kg 

were detected at four sites, and the only site of these four with drainage area land-use data 

had high residential land use (74 percent) and low (0 percent) agricultural land use. Four of 

the five highest PCB concentrations were within the six drainage areas with the highest 

combined industrial and commercial land use. Although the drainage area of the site with the 

highest PCB concentration included less than 4 percent total industrial and commercial land 

use, the site is located downstream of an industrial-contamination site. In the nested systems, 

pesticide and (or) PCB concentrations were lower at three downstream sites than they were at 

the upstream sites. The drainage areas of all of these sites experienced greater than 20 percent 

residential growth between 1967 and 1987.

Brillouin's diversity index was calculated for all biological samples for each site in 

Chester County. Diversity index was plotted as a function of time at each site and tested for 

trend by use of the seasonal Kendall test. Upward trends in Brillouin's diversity index were 

found at 45 of the 46 stream sites. The upward trends were significant at the 99-percent 

confidence level at 30 sites, were significant at the 95- to 98-percent confidence level at 9 sites, 

and were significant at the 90- to 94-percent confidence level at 3 sites. Trends at only four sites 

were not statistically significant at the 90-percent confidence level.

Contingency-table analyses showed that upward trends in invertebrate-community 

diversities were associated with increases in residential land use of 12 percent or greater; and 

decreases in agricultural land use of 5 percent or greater. Contingency-table analyses also 

showed that concentrations of organochlorine compounds exceeding 45 ug/kg in streambottom material were associated with community diversities less than 2.25. However, the 

moderate degree of dependence demonstrated by the contingency analyses suggests that 

additional factors also affect the communities.

26 SUMMARY AND CONCLUSIONS
REFERENCES CITED

American Society for Testing and Materials, 1987, Standard practice for high-resolution

gamma-ray spectrometry of water in Annual Book of ASTM standards: Philadelphia, 

Pa., American Society for Testing and Materials D3649-85.

Brillouin, L., 1962, Science and information theory (2nd ed.): New York, Academic Press, 

347 p.

Britton, L.J., and Greeson, P.E., eds., 1988, Methods for collection and analysis of aquatic 

biological and microbiological samples: U.S. Geological Survey Open-File 

Report 88-190, 685 p.

Callahan, M.A., Slimak, M.W., Gabel, N.W., May, I.P., Fowler, C.F., Freed, J.R., Jennings, 

Patricia, Durfee, R.L., Whitmore, F.C., Maestri, Bruno, Mabey, W.R., Holt, B.R., and 

Gould, Constance, 1979, Water-related environmental fate of 129 priority pollutants: 

U.S. Environmental Protection Agency, EPA-440/4-79-029 a, b.

Chester County Planning Commission, 1972, Existing land use 1972: West Chester, Pa., 1 

sheet, scale 1:126,720.

 1987, Existing land use 1987: West Chester, Pa., 1 sheet, scale 1:95,000.

Gilliom, R.J., Alexander, R.B., and Smith, R.A., 1985, Pesticides in the nation's rivers, 1975- 

1980, and implications for future monitoring: U.S. Geological Survey Water-Supply 

Paper 2271, 26 p.

Hirsch, R.M., Slack, J.R., and Smith, R.A., 1982, Techniques of trend analysis for monthly 

water-quality data: Water Resources Research, v. 18, no. 1, p. 107-121.

Horowitz, A.J., 1991, A primer on sediment-trace element chemistry (2nd ed.): Chelsea, 

Mich., Lewis Publishers, 136 p.

Johnsen, R.E., 1976, DOT metabolism in microbial systems: Residue Reviews, v. 61, p. 1-28.

Kaesler, R.L., and Herricks, E.E., 1976, Analysis of data from biological surveys of streams 

diversity and sample size: Water Resources Bulletin, v. 12, no. 6, p. 125-135.

Lium, B.W., 1976, Limnological data for the major streams in Chester County, Pennsylvania: 

U.S. Geological Survey Open-File Report (unnumbered), 219 p.

 1977, Limnological studies of the major streams in Chester County, Pennsylvania: U.S. 

Geological Survey Open-File Report 77-462,37 p.

Miller, R.A.,Troxell, John, and Leopold, L.B., 1971, Hydrology of two small river basins in 

Pennsylvania before urbanization: U.S. Geological Survey Professional Paper 701-A, 

57 p.

Moore, C.R., 1987, Determination of benthic-invertebrate indices and water-quality trends of 

selected streams in Chester County, Pennsylvania, 1969-80: U.S. Geological Survey 

Water-Resources Investigations Report 85-4177, 62 p.

 1989, Physical, chemical, and biological data for selected streams in Chester County, 

Pennsylvania, 1969-80: U.S. Geological Survey Open-File Report 85-686,289 p.

REFERENCES CITED 27
REFERENCES CITED Continued

National Council on Radiation Protection and Measurements, 1985, A handbook of

radioactivity measurement and procedures (2nd ed.): Washington, D.C., National 

Council on Radiation Protection Report 58,592 p.

/.""' 

National Research Council, 1979, Polychlorinated biphenyls: Washington, D.C., National

Academy of Sciences, 182 p. 

Pielou, B.C., 1969, An introduction to mathematical ecology: New York, John Wiley, 286 p.

Ritchie, J.C., McHenry, J.R., and Gill, A.C., 1973, Dating recent reservoir sediments: 

Limnology and Oceanography, v. 18, no. 2, p. 254-263.

Roy F. Weston, Inc., 1988, Synoptic report on toxic substances contamination of Red Clay 

Creek: Delaware Department of Natural Resources and Environmental Control.

Sloto, R.A., 1987, Effect of urbanization on the water resources of eastern Chester County,

Pennsylvania: U.S. Geological Survey Water-Resources Investigations Report 87-4098, 

131 p.

Smith, J.A., Witkowski, P.J., and Fusillo, T.V., 1988, Manmade organic compounds in the 

surface waters of the United States A review of current understanding: U.S. 

Geological Survey Circular 1007,92 p.

U.S. Geological Survey, 1975-89, Water resources data for Pennsylvania, 1974-88 volume 1: 

U.S. Geological Survey Water-Data Reports PA-74-1 to PA-88-1 (published annually).

Velz, C.J., 1970, Applied stream sanitation: New York, John Wiley and Sons, 619 p.

Wershaw, M.J., Fishman, M.J., Grabbe, R.R., and Lowe, L.E., 1987, Methods for the

determination of organic substances in water and fluvial sediments: U.S. Geological 

Survey Techniques of Water-Resources Investigations, book 5, chap. A3,80 p.

Zand, S.M., 1976, Indexes associated with information theory in water quality: Water 

Pollution Control Federation Journal, v. 48, no. 8, p. 2026-2031.

28 REFERENCES CITED
Appendix. Brillouin's diversity index, maximum diversity, minimum diversity,

and relative evenness, by site

29
DIVERSITY INDEX (H)

^D

11 i§ i

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DIVERSITY INDEX (H)

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e§9Si§iSsg*i, s

KJijjOJhJhJOJhJOJi »i » N^I 

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vj vj Q*\ ^ vj Q\ vj Q\ ^ Q\ ^ Q\ cji 
DIVERSITY INDEX (H)

xi In QO

NJ W NJ u NJ NJ . i-> 

MN>vOt?*.i-'! \O

JS S3 Sft Si Q 5S

i-> KJ w In bo

(JN N> Nl (JN X|

B Si

bo

M
Sites

Year

1970

1971

1972

1973

1974

1975

1976

1977

1979

1980

1981

1982

Total 

number of 

organisms

94

26

288

486

~

554

125

117

440

826

979

Total 

number 

of taxa

6

4

15

20

-

~

21

12

14

9

28

31

Brillouin's 

diversity 

index (H)

,.;:. ,.. 2.23' , -

1,65

2,39

2,32

 . : v

_

2.97

1.83

2.67

1.83

3,11

3.52

Maximum 

diversity 

(Hmax)

2.59

1.94

3.79

4.24

~

4.33

3.47

3.64

3.20

4.77

4.92

Minimum 

diversity 

(Hmin)

0.35

.54

.40

.35

~

~

.33

1.61

.75

.16

.32

.30

Evenness 

(E)

0.84

.79

.59

.51

~

~

.66

.43

.66

.55

.63

.70

x

Ld 

Q

to Q:

Q

UNSTRESSED 

COMMUNITY

INTERMEDIRTE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

37 APPENDIX
DIVERSITY INDEX (H)

-<

m

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\ 

\ 

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CT-i

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ID

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DIVERSITY INDEX (H)

8o-93£8£83B22§

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it^ 

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W vO O *^ O vO i 

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C*> bo ot to w o H-* J " bo

cS NJ o o ^o "**j ^o Wi ***4 

6

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o^j o^ o^ s

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DIVERSITY INDEX (H)

OLOLO

o^m 

3^)<

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d u>;o 

zcon 

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DIVERSITY INDEX (H)

, N> 

! o 

£

K) I W 

8§ Sv 

U1U14**-4*U14*4*W4*4*I 4^ 

k) 

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§s
DIVERSITY INDEX (H)

\^ \^ \^

£ 9§ 8?

55 JS 55 VI 

OS <J1 *. 

W <J1 KJ

^O C>J ^O

OS so t-*

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KJ KJ KJ I-J1 

ftsOKJOOi 00 

W ts> C*3 W W C*J W W W OJ O3 W 

ftUlOfiUlbokjboWQois>fi 

KJOf>OOH4|sJfiOBfiOSlKJ

00 00 KJ VI H^ fi i^ KJ v] OJ fi SO 

>O v^ »~k v] H^ <"^ |^ >o t~k ip- >o V]

00 bJ

01 KJ KJ KJ *» x

SO ^4 t^ "^1 V 

OS t£fc OS 

KJ so O 
Site 14

Year

1970

1971

1972

1973

1974

1975

1976

1977

1979

1980

1981

1982

1983

1984

1985

1986

1987

19881

Total 

number of 

organisms

58

34

643

225

189

-

362

747

96

615

1,763

1,543

1,427

1,719

421

1,419

1,328

2,589

Total 

number 

oftaxa

8

6

27

15

16

-

27

27

16

26

35

29

40

31

24

32

31

33

Brillouin's 

diversity 

index (H)

2.23

1,88

3.00

1.73

2.79

-

2.91

3.04

2.44

3.37

3.42

2.88

3.63

3.20

3.33

3.32

2.03

3.72

Maximum 

diversity 

(Hmax)

2.79

2.54

4.77

3.71

4.01

-

4.65

4.74

3.61

4.68

5.09

4.81

5.31

4.93

4.53

4.96

4.97

5.03

Minimum 

diversity 

(Hmin)

0.70

.74

.38

.48

.60

~

.61

.33

1.01

.38

.21

.19

.29

.19

.47

.23

.23

.14

Evenness

(E)

0.73

.63

.60

.39

.64

-

.57

.61

.55

.70

.66

.58

.66

.64

.70

.65

.38

.73

1 Sampled upstream riffle because of bridge construction.

UNSTRESSED 

COMMUNITY

INTERMEDIRTE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

43 APPENDIX
DIVERSITY INDEX (H)

\O vO vO

* * * 1

s

W K)

O VO

K) 

K)

hi W W C*> K> W K»

S.J xj \o {& Qo o OJ

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VO k)

vO p-i

do K)

a §

w M w 

w *» yi

bi In

oo o s; 
t)

I

g 

x

DIVERSITY INDEX (H)

^O 

Ul 

ifj

^.^.^.^.

l-> O\ W

1-1 ON 

(^ Cjl JSk ON 

U1 U1 OO i >
DIVERSITY INDEX (H)

\o \o

00 ^J

fe ^

O i »

<jj l_>

K) *K 

i-iyii-

U)U)U)U)OJOJWK)K>NJK)K)N

,^*K*K*K*K*K*K^.OJ*K*>*>OJOJ 

>->N>UN>N>CngNgjfo^fou!->U 
DIVERSITY INDEX (H)

oo

VD v£> vO 

vj

! !

KJ KJ i-» K> KJ , , 

^ vD W ^O Ol W t i 

W W JsJ KJ W W ! I 

&^Oibvh-*Opl 

85 ^ fe

l-> Dl vO W

.

vO

! 1

ife 2 
Site 19

Year

1970

1971

1972

1973

1974

1975

1976

1977

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

Total 

number of 

organisms

88

45

219

120

67

-

363

835

131

417

994

1,628

526

1,220

571

912

1,286

1,987

Total 

number 

of taxa

9

6

8

17

14

~

25

27

12

16

38

35

30

26

28

28

33

24

Brillouin's 

diversity 

index (H)

1.87

1.90

1.64

2.66

2.55

-

3.16

2.85

2.72

3.16

3.61

3.38

3.12

3.07

2.85

2.85

3-91

2.01

Maximum 

diversity 

(Hmax)

3.18

2.50

2.95

3.76

3.73

-

4.57

4.79

3.63

3.88

5.14

5.11

4.85

4.73

4.73

4.78

5.08

4.59

Minimum 

diversity 

(Hmin)

0.58

.60

.25

.91

1.15

-

.56

.30

.59

.31

.37

.22

.50

.21

.43

.29

.26

.13

Evenness 

(E)

0.50

.68

.51

.61

.54

-

.65

.57

.70

.80

.68

.65

.60

.63

.56

.57

.76

.42

UNSTRESSED 

COMMUNITY

INTERMEDIRTE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

APPENDIX 48
DIVERSITY INDEX (H)

00 ^O ^ ^ 00

^q "sj » * o <ji

oo ^3 \o o o

Nl Nl

it^ O i-> N)

Cp 

>^ 

VO

! 

U>K)» iK)KJK)K)^-»^-»t i» iK), 

ooN^DH^ho^o^ioo^aixio! 

Od O3 O^ I^J ^y ^j ^j (y(j 

Q\ ^O ON 

en O oo 2 ^ £

K

fe S

Ss te a

a S

v] o\ 

l-> W

In 
DIVERSITY INDEX (H)

\Q ^O

00 00 £ £ £

U> SJ i->

VI V] V] V? 

vj O\ Ul *»

t » ON ON 00 ON 

ON N> ON * ! N>

hj » *

ON U1 

Ul SI >->>->

! 00 

COOJCiJCOOJCiJLONJtOCol )_

H** C#) O Ot i ' i i V] Cjl i& 

uii^KJKJtoyicxo &

Ol tfy t/j ^j ^fy j |^ 

ON S>JOO<4ONO<JOOJ^ONJON \O 

ON ^^ 00 "^-J 00 fO ON fO ^^J ^3 00 Ol ^O 

I"1 ! . 

I 'hjJ-*I 'OhJt 'hjJ i Jp*. O It*. O

t i |sj \o ^ 00 O ^ tt>» 00 **>J ^-! Ol ^* 

fessfefe^'f
Site 22

Year

1970

1971

1972

1973

1974

1975

1976

1977

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

Total 

number of 

organisms

59

43

520

144

13

~

703

162

179

247

323

465

319

516

247

340

1,307

1,027

Total 

number 

of taxa

5

7

17

11

4

-

21

12

10

16

25

20

22

21

13

21

33

19

Brillouin's 

diversity 

index (H)

1.83

2.04

2.36

2.34

1.42

-

2.41

2.34

1.57

2.77

3.44

3.32

3.20

3.21

3.21

3.17

3.47

3.06

Maximum 

diversity 

(Hmax)

2.37

2.53

4.07

3.28

1.71

-

4.36

3.52

3.37

3.92

4.68

4.23

4.39

4.36

3.54

4.25

5.03

4.18

(Hmin)

0.40

.74

.28

.49

.83

-

.27

.50

.37

.48

.62

.36

.54

.35

.38

.49

.25

.18

Evenness

0.73

.73

.55

.66

.67

-

.52

.61

.40

.67

.70

.77

.69

.71

.89

.71

.57

.72

UNSTRESSED 

COMMUNITY

INTERMEDIRTE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

51 APPENDIX
DIVERSITY INDEX (H)

W K> i-» O

VO VO VO 

K> W

V*» ^j Xq ^j )_* £^

OP tf^ o vi o vo

ON vo iS W K> O

w

W v*i KJ OJ C/J W frj

Q *4 5> ON W !- VO

2K |s3 * i-1 <F ON po

*>. *>. *>. *>. *> w

S

VOH^CJIOOVO^^O 

KJK>Gl K>

J-> t-> w KJ k> Kj >-> k> '*» w w In 

O<J1K>*>-OCJIOO<J1WK>OO 

s;

^^ G\ Cjl ^v 

W K> OO ifeDIVERSITY INDEX (H)

£ $

_iN>i-'i->N>N>Wi->N>

2« bl O >> > N> bl Vl Vg 

ONvjNjOlWUlvj^DKj

i? N "^ 

K

OJ N> N> I ' I ' N) I ' , I ' 

oK3oovooi->oo! <M

OJWWN)WWN)WNJN)N>»-' ! NJ 

^jk yt ^^ .Ob: ^5 *&---- f"O i^ t« ^ ^ ON ^p QD 

*> *»

23

W N> OO OO

ip.t^iUMj^i^! w 

5l W OJ NJ W OO vC 

!-" ! 

O i-> i-> <g 
Site 26

Year

1970

1971

1972

1973

1974

1975

1976

1977

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

Total 

number of 

organisms

61

7

181

473

--

-

826

1,463

239

468

1,047

281

578

2,397

625

34

575

919

Total 

number 

of taxa

2

3

5

12

~

-

12

13

4

4

14

16

17

12

16

10

17

11

Brillouln's 

diversity 

index (H)

0.25

.77

1.52

1.34

~

-

1.90

1.23

.90

.35

2.21

2.90

1.73

.85

2.03

1.92

2.08

1.77

Maximum 

diversity 

(Hmax)

1.03

1.33

2.27

3.55

-

-

3.60

3.70

2.02

1.97

3.82

3.96

3.98

3.59

3.92

3.00

4.11

3.45

Minimum 

diversity 

(Hmin)

0.10

.77

.17

.21

~

.13

.09

.10

.06

.12

.43

.25

.05

.22

1.30

.25

.11

Evenness

(E)

0.16

0

.64

.34

.51

.32

.41

.15

.56

.70

.39

.23

.49

.37

.47

.50

UNSTRESSED 

COMMUNITY

INTERMEDIRTE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

APPENDIX 54
Site 27

Year

1970

1971

1972

1973

1974

1975

1976

1977

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

Total 

number of 

organisms

182

30

177

108

-

60

172

70

29

556

210

776

84

459

327

107

267

543

Total 

number 

of taxa

1

4

5

6

-

9

12

5

8

3

11

13

11

10

18

10

15

17

Brillouin's 

diversity 

index (H)

0

1.19

.90

1.19

-

1.91

1.75

1.10

1.83

1.01

1.51

2.42

2.45

1.88

2.31

1.90

2.61

2.75

Maximum 

diversity 

(Hmax)

0

1.95

2.30

2.44

-

3.11

3.48

2.15

2.83

1.58

3.32

3.71

3.39

3.35

4.04

3.31

3.92

4.13

Minimum 

diversity 

(Hmin)

0

.49

.17

.31

-

.78

.47

.35

1.13

.03

.37

.15

.75

.17

.43

.56

.42

.27

Evenness 

(E)

0

.48

.35

.41

-

.48

.43

.41

.41

.63

.39

.64

.64

.54

.52

.49

.63

.64

UNSTRESSED 

COMMUNITY

INTERMEOIRTE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

55 APPENDIX
Site 28

Year

1970

1971

1972

1973

1974

1975

1976

1977

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

Total 

number of 

organisms

76

26

202

293

-

-

820

935

855

1,188

836

1,298

1,358

928

1,007

1,026

4,216

2,599

Total 

number 

of taxa

4

6

10

10

-

-

18

23

27

17

18

23

18

16

21

19

19

19

Brillouin's 

diversity 

index (H)

0.87

2,04

2.18

2.34

~

-

3.05

2.65

3.45

2.91

3.06

2.74

2.56

1.96

2.51

2,33

2.02

2.31

Maximum 

diversity 

(Hmax)

1.88

2.34

3.22

3.26

-

~

4.16

4.52

4.75

4.11

4.14

4.50

4.15

3.93

4.42

4.18

4.26

4.26

Minimum 

diversity 

(Hmin)

0.25

.88

.34

.25

-

~

.20

.23

.30

.14

.20

.18

.13

.16

.20

.18

.05

.08

Evenness 

(E)

0.38

.79

.64

.70

-

-

.72

.56

.71

.70

.73

.59

.60

.48

.55

.54

.47

.53

UNSTRESSED 

COMMUNITY

INTERMEDIRTE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

APPENDIX 56
Site 29

Year

1970

1971

1972

1973

1974

1975

1976

1977

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

Total 

number of 

organisms

61

13

677

290

156

-

174

283

84

1,376

778

1,698

832

1,742

1,276

905

1317

3,469

Total 

number 

of taxa

6

3

15

6

6

-

12

12

13

14

16

19

17

19

25

24

23

21

Brillouin's 

diversity 

index (H)

0.95

1.05

2.25

.85

1.44

-

1.97

2.32

2.03

1.77

2.82

2.43

2.82

2.54

2.77

3.07

2.56

2.74

Maximum 

diversity 

(Hmax)

2.42

1.44

3.84

2.56

2.48

-

3.52

3.56

3.53

3.78

4.00

4.23

4.12

4.25

4.57

4.59

4.48

4.37

Minimum 

diversity 

(Hmin)

0.48

.56

.19

.14

.23

-

.47

.32

.90

.10

.18

.11

.19

.11

.19

.25

.17

.07

Evenness 

(E)

0.24

.55

.56

.29

.54

-

.49

.62

.43

.45

.69

.56

.67

.59

.59

.65

.55

.62

UNSTRESSED 

COMMUNITY

INTERMEDIRTE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

57 APPENDIX
DIVERSITY INDEX (H)

\^ \^

00 00

00 ^J

To

N>

\^ \^

00 00

To 00 W

o w ^"*

^.^.^.^.^.^.^.^.WW4^ifc.w! 

M OI i->
DIVERSITY INDEX (H)

S3

1 1 1 1

£ K

N> N>

f~\ i_a

^J W

W Ul

£ w

8 S

££gggg§33§§§

00 CJl To ^ * "*^ 00 vO ^3 H-* 

)^- j^ ^_1 "Vj ^_a j^ S^ (JJ ^^ \^ 

jj\ \^ QJI j^ ^j s^j ^j s^q QJI \^ j J 

K) K> N) K) K) K> H- i hJk-i , 

K)K)K)OJK)K>^hJft>.^l t 

 ^ ^h bo o bo tn J-* ^j KJ >-* 

^O ho (5* k 1 j^ tJfi ^3 GN ^3 t^ 

hJCJlON*^ONONI 'hJON"^! 

v]OWCJiON s^K)i-iO s^ 

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hJ CJi ON vO 00 00 s*] \o vO 00 

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ON CJi ON ON CJi CJi "^ ON CJi 00 

OJ ^3 ^5 ON ^O to CJi v] ^O ^O 
DIVERSITY INDEX (H)

\o \o \o \o \o \o \o 

OOOOSISISISIS

N>

K O (Jl I N) O 

NJKJCONJK)N)N)WN; 

^3 Nj ^.i j^3 QQ \£ sjj ^^ ^i

K> N>

?5 fe

>P>.|P>.|P>.|P>.|P>.|P>.|P>.|P>.M! >F>.>F>.! 

^DWyiN)^oS^D>^W N) W 

o

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O SI N> N> O a
DIVERSITY INDEX (H)

00 00 Op 00 00 00 00 Si*J Si*J xJ Si*J Si*J Si*J 

OsOifrWN)i-JO\OOOMOsCJii^

a s 

^->cn^noooNNOi^i-> 

§

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ol

v] 

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i-> 

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£

4^ 4^ W K) ! 4^ ! !WW

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00 N>

tn 

en

Ol V] NO O O

ON ON CJl ON 

NO NO OO Ol

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H-> ro *.

G 

! 

£ 
DIVERSITY INDEX (H)

SO SO so so so so so so 

OOXiasyii^WKJl->

os

O1 oo OJ So ! ! o 

OJN>K>OJK>OJK>i ' h-> . , 

l iU>OOOU>N)H^N)Osso i i

OJ OJ OJ NJ NJ OJ

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*> Os KJ O X] XI 

OssoUlXIpDUlOWUlpKJ 

O t^ W ^ Ol W NJ Ol X| i^ t »

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xi 

so 

1 1

S

i-i k> KJ i i k> i-j I ' o OJ k> OJ 

yixioo^.oJ*».o^DOJK) K> 

Os Os Ol ON Os XI Os lo XI 

OOWsOi^Osi II^ISJH^

OJ 

OO 
s

>"U

I

D 

X

DIVERSITY INDEX (H)

O W

1-» ^-* ( *

^C *^ K) ! OO

N> 

N) K> K> 

vj

vo

N 

S

CO CO *^ CO ! CO 

1 .

!_> kj !-> kj !-> '*>. tn 

ui ui o i-> i^ \o o\
DIVERSITY INDEX (H)

00 vi ON en Jp> CP

^ ^-> K> 00 ^O 00

\o oo oj en en w

CO iK Co K) K) VO

fO CfcJ CfcJ CfcJ CfcJ W 

^ 1-1 |_> O to I-1

N3 W KJ W KJ JO

Ol' ^^ K2 ^R CO fp>

o> w o i-1 w en

o> en en vi -vi KJ

Ol O^ Ol O^ H^ Ol 

*sj H-i Qo H-1 h<J O^

SS§S5SS2

:».,..,

KJKji-ii_iKJKJKji_i

22S$gS2^^o
£

>"0 

"0

o

X

DIVERSITY INDEX (H)

OOOOOOOOOOOO 

OO^OxU1*»W

.

O OO V] i^ h-> N)

vO 

OO VJVJVJ

OxU1*

N> O\ lU >-> 

>-> Ov O W 

*> *> *> *> *> *> *>. N> ro 

ro ro ^ Vo ro In 
Site 38

Year

1970

1971

1972

1973

1974

1975

1976

1977

1979

1980

1981

1982

1983

1984

1985

1986

19871

1988

Total 

number of 

organisms

58

26

507

-

-

277

196

52

52

464

605

1,653

1,104

1,406

1,079

775

402

1,941

Total 

number 

of taxa

2

2

11

-

-

11

10

10

4

13

31

21

27

22

24

24

23

22

Brillouin's 

diversity 

index (H)

0.18

.83

1.55

-

-

1.60

1.71

1.83

.85

2.40

2.95

2.87

3.21

2.61

2.24

3.09

3.20

2.84

Maximum 

diversity 

(Hmax)

0.94

.90

3.39

-

-

3.37

3.30

3.01

1.84

3.70

4.90

4.40

4.78

4.48

4.62

4.52

4.46

4.43

Minimum 

diversity 

(Hmin)

0.10

.18

.18

-

-

.29

.35

.97

.33

.23

.46

.13

.24

.16

.21

.28

.47

.12

(E)

0.10

.91

.43

~

-

.42

.46

.42

.35

.63

.56

.64

.66

.57

.46

.66

.69

.63

1 Sampled upstream riffle because of bridge construction.

UNSTRESSED 

COMMUNITY

INTERMEDIflTE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

APPENDIX 66
en 

^i

>

T3 

T3

m 

g

X

DIVERSITY INDEX (H)

o

oc/>

12 PI

inS

^o

W

h-> t-> NJ 
Site 40

Year

1970

1971

1972

1973

1974

1975

1976

1977

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

Total 

number of 

organisms

-

133

653

246

717

460

103

132

549

650

1,663

1,016

1,441

999

428

1,049

1,819

Total 

number 

of taxa

~

~

8

11

10

16

13

15

18

10

23

30

32

24

25

36

37

25

Brillouin's 

diversity 

index (H)

-

-

1.77

1.34

1,66

1.74

2.08

2.48

3.13

2.53

3.28

3.28

3.23

2.86

3.41

3.92

3.53

3.64

Maximum 

diversity 

(Hmax)

-

-

2.99

3.43

3.31

4.02

3.66

3.91

3.96

3.35

4.45

4.88

5.00

4.52

4.68

5.19

5.14

4.65

Minimum 

diversity 

(Hmin)

~

0.37

.14

.29

.20

.23

.90

.90

.15

.32

.19

.30

.17

.24

.71

.34

.14

Evenness 

(E)

--

0.53

.36

.46

.40

.54

.53

.73

.74

.72

.66

.62

.62

.72

.72

.66

.78

'UNSTRESSED 

COMMUNITY

INTERMEDIRTE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

APPENDIX 68
DIVERSITY INDEX (H)

* $

Ol

00 00 00 

K> » O

KJ 00 \O *~J Ol t"^ *"~* \O it^ Ol ^^ 

QJ H- » t » t »

O> 00 *. 0\

w to

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^O1 ' OO j^ ttk ^sl ' 

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Ul Ul Ul Ul Ul

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S o w !-i o

Ul .fe. W W 

*i_> '»-" bo bo 

K> N) O\ W W 

i-> Ul K> K> Ul as

£ a

tn

o\
DIVERSITY INDEX (H)

i>°

\d5

%

zrm 

:;o 

:=z

-in

- a 

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zmi 'CO 

MO)

OO

- -

M \£> 00 W 1-"

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WKJKJf-'t

k> >->

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OO

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OO

-

W

OO

8
T3

I 

D 

X

DIVERSITY INDEX (H)

m 

>

23

NJ W K> K> K)
DIVERSITY INDEX (H)

\o V«O

"ON ^-* ON

W NJ i-1 

K> ON \O

U>

^ ^ ^ .^ ^ _*. .^ _*. CO CJ CO 

6

ON
-o

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rn

g 

x

DIVERSITY INDEX (H)

m 

>

70

O <-n Ln 

KJKJKJKJKJi 'i '

it^cnoJi 'i '^JO\

S a fe S S ^ 85

H^ 1 1 

N W >-i W 1-1 

oo i-" 

1-1 W K> 

VO OO 1-1 

O\a\OOJ
DIVERSITY INDEX (H)

o

m

ocn

O-!

un 

d en 

zcn

cz ^> 

z;z

 urn

ID 

 -a 

m

TJ "D

m

D 

X

2!
Site 48

Year

1973

1974

1975

1976

1977

1979

1980

1981

1982 

19831

1984 

19851

19861

1987

1988

Total 

number of 

organisms

218

188

749

518

583

166

624

1,307

2,525 

733

1,648 

684

604

1,139

1,985

1 Sampled upstream

5 i 

4 _.. ........

^_^

X 3 -....-.. 

LJ

O

z

t

cn LJ 2 ~ -------- -- 

Q

1 -

n I

! i 1

 «r

i i i

Total 

number 

of taxa

14

17

28

23

21

21

16

43

35 

32

24 

28

28

31

32

Brillouin's 

diversity 

index (H)

2.59

2.58

2.89

3.15

2.88

2.47

3.10

4.10

3.21 

3.61

3.04 

3.43

3.62

3.15

3.43

Maximum 

diversity 

(Hmax)

3.76

3.86

4.81

4.48

4.40

4.41

3.91

5.37

5.08 

5.03

4.58 

4.75

4.77

4.96

4.94

Minimum ._ diversity Eve""ess 

(Hmin) ( '

0.46 0.65

.64 .60

.34 .57

.38 .67

.31 .63

.88 .45

.22 .78

.33 .75

.15 .62 

.40 .69

.15 .65 

.37 .70

.41 .74

.27 .61

.17 .68

riffle because of bridge construction.

-jar ^

1 1

1 1

AAv^

Vl... ......J-C

----------------------------------

----------------

UNSTRESSED COMMUNITY

INTERMEDIFITE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

YEAR

75 APPENDIX
DIVERSITY INDEX (H)

l

h-> i-> >-> S> N> h->

g a h-> K) N> >-> h-> h->

>-> O

sj 3\

NI

p\

fONIfO

xi -^4 KJ

fO

K-"

OJOOONIOi-iOJOJOOOOON

hj ^O CJ1 ^ CJ1 O) ^ I 1 OO i^ CJ1 

I ' I ' I i OJ 

i^ h-> U1 h-i

M 

OJ

V] vq 

00 01
Site 50

Year

1973

1974

1975

1976

1977

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

Total 

number of 

organisms

25

153

534

849

1,003

263

1,412

2,201

3,155

1,744

2,058

1,362

1,824

1,623

2,277

Total 

number 

of taxa

2

8

10

14

13

9

12

20

20

16

21

19

19

22

15

Brillouin's 

diversity 

index (H)

0.19

1.42

1,89

1.73

. 1,65

1.98

2,64

2.51

2,67

2.66

2.68

' 2.77 :>;: ,;'.

2.77

:' 3.13 ','C 

2.78

Maximum 

diversity 

(Hmax)

1.04

2.88

3.30

3.81

3.66

3.10

3.59

4.29

4.33

3.96

4.35

4.25

4.20

4.47

3.92

Minimum 

diversity 

(Hmin)

0.19

.33

.15

.15

.12

.24

.08

.10

.07

.09

.11

.14

.11

.14

.07

Evenness 

(E)

0

.43

.55

.43

.43

.61

.73

.58

.61

.66

.61

.64

.65

.69

.71

UNSTRESSED 

COMMUNITY

INTERMEDIATE 

COMMUNITY

STRESSED 

COMMUNITY

SEVERELY 

STRESSED 

COMMUNITY

^ &*>

YEAR

77 APPENDIX
DIVERSITY INDEX (H)

oc

%

 Sfr ^

*>

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*> 

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*>

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i-HD^ ^D i-HD ^LD

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3 a

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vo T-> 

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