Water Quality in the

Lower Susquehanna River Basin

Pennsylvania and Maryland, 1992–95

U.S. Department of the Interior

U.S. Geological Survey Circular 1168

science for a changing world
A COORDINATED EFFORT

Coordination among agencies and organizations is an integral part of the NAWQA Program. We thank the fol

agencies and organizations who contributed to the design of the studies and helped to review data presented in this r

•Academy of Natural Sciences

•Alliance for the Chesapeake Bay

•Maryland Department of the Environment

•Maryland Geological Survey

•Pennsylvania Department of Agriculture

•Pennsylvania Department of Environmental Protection

•Pennsylvania Department of Conservation and Natural Resources

•Pennsylvania Fish and Boat Commission

•Pennsylvania State University—Environmental Resources Research Institute

•Susquehanna River Basin Commission

•Tri-County Regional Planning Commission

•U.S. Army Corps of Engineers

•U.S Environmental Protection Agency

•U.S. Department of Agriculture—Agricultural Research Service

•U.S. Department of Agriculture—Natural Resources Conservation Service

•U.S. Fish and Wildlife Service—Division of Ecological Services

•University of Maryland—Water Resources Research Center

This report summarizes work by a number of dedicated USGS scientists and technicians. It was based, in part, 

USGS reports written by the following authors: Scott W. Ator, Mark R. Beaver, Tammy M. Bickford, Matthew H

Andrew J. Gavin, Robert A. Hainly, Joan M. Kahn, Connie A. Loper, Dennis W. Risser, and Steven F. Siwiec. 

lowing are names of additional USGS personnel responsible for implementing the NAWQA Program in the Lower Su

hanna River Basin: Steven J. Bogush, Jodi S. Brandt, Harry L. Campbell III, Erika J. Clesceri, Christina L. Ha

Christine M. Herbert, Scott A. Hoffman, Michael D. Lichte, Jonathan A. Peahl, David M. Pennise, Christine A

erson, Steven J. Semick, and Naomi J. Weisbeker. This report was edited by Kim L. Wetzel, Robert J. Olmstead

Edward J. Swibas, Michael Eberle, Betty Palcsak, and Chester Zenone. The manuscript was prepared by Kim L. 

The tables on pages 30-34 were designed and built by Sarah Ryker, Jonathan Scott, and Alan Haggland.

Front cover photograph: An aerial view looking north showing the Susquehanna River at Harrisburg, Pa. The Harrisb

ropolitan area is part of a rapidly developing corridor of historically agricultural land through the middle of the study 

Harrisburg is situated in the Great Valley Section of the Ridge and Valley Physiographic Province. (Reprinted from A

Wycheck and published with permission.)

Back cover photographs: Agricultural settings in the Lower Susquehanna River Basin (left to right)—Bachman Run f

through a part of the Lebanon Valley, Lebanon County, Pa.; Cumberland Valley in Cumberland County, Pa. (Reprint

Harrisburg-Hershey-Carlisle Tourism and Convention Bureau and published with permission); Penns Creek Valley in 

County, Pa. (by Albert E. Becher).

Chief, NAWQA Program

U.S. Geological Survey

Water Resources Division

12201 Sunrise Valley Drive, M.S. 413

Reston, VA 20192

Information on the NAWQA Program is also available on the Internet via the World Wide Web.

You may connect to the NAWQA Home Page using the Universal Resources Locator (URL):

http://wwwrvares.er.usgs.gov/nawqa/nawqa_home.html

The Lower Susquehanna Study Unit’s Home Page is at URL:

http://wwwpah2o.er.usgs.gov/projects/lsus/

Lower Susquehanna River Basin

Study Unit, contact:

District Chief

U.S. Geological Survey

Water Resources Division

840 Market Street

Lemoyne, PA 17043-1584

FOR ADDITIONAL INFORMATION ON THE

NATIONAL WATER-QUALITY ASSESSMENT (NAWQA) PROGRAM:
U.S. GEOLOGICAL SURVEY CIRCULAR 1168

Water Quality in the Lower Susquehanna Riv

Basin, Pennsylvania and Maryland, 1992-95

By Bruce D. Lindsey, Kevin J. Breen, Michael D. Bilger, and

Robin A. Brightbill

CONTENTS

National Water-Quality Assessment Program 

Summary of major issues and findings 

Environmental setting and hydrologic conditions 

Major issues and findings 

Nitrate in ground water and streams 

Trends in nitrogen and phosphorus

concentrations 

Pesticides in ground water and streams 

Bacteria in ground water 

Volatile organic compounds in ground water 

Radon in ground water 

Trace elements in fish tissue and streambed

sediment 

Pesticides and other organic compounds in

fish tissue and streambed sediment 

Biological communities and stream habitat 

Water-quality conditions in a national context 

Study design and data collection 

Summary of compound detections and

concentrations 

References 

Glossary 
Library of Congress Cataloging in Publications Data

The use of firm, trade, and brand names in this report is for identification purposes only and

does not constitute endorsement by the U.S. Government

Free on application to the

U.S. Geological Survey

Information Services

Box 25286 Federal Center

Denver, CO 80225

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Thomas J. Casadevall, Acting Director

Water quality in the lower Susquehanna River Basin, Pennsylvania and

Maryland : 1992-95 / by Bruce D. Lindsey ... [et.al.].

p. cm. -- (U.S. Geological Survey circular ; 1168)

ISBN 0-607-89155-6

1. Water quality--Susquehanna River Watershed. I. Lindsey, Bruce

D., 1962- . II. Series.

TD225.S895W38 1998

363.739’42’09748--dc21 98-11347

CIP

1998
U.S. Geological Survey Circular 1168 

BEGAN IN 1991

BEGAN IN 1994

BEGAN IN 1997

NOT SCHEDULED

YET

EXPLANATION

NATIONAL WATER-QUALITY ASSESSMENT PR

Knowledge of the quality of the Nation's streams and aquifers is important

because of the implications to human and aquatic health and because of the significant costs associated with decisions involving land and water management,

conservation, and regulation. In 1991, the U.S. Congress appropriated funds for

the U.S. Geological Survey (USGS) to begin the National Water-Quality Assessment (NAWQA) Program to help meet the continuing need for sound, scientific

information on the areal extent of the water-quality problems, how these problems are changing with time, and an understanding of the effects of human

actions and natural factors on water-quality conditions.

The NAWQA Program is assessing the water-quality conditions of more than 50

of the Nation's largest river basins and aquifers, known as Study Units. Collectively, these Study Units cover about one-half of the United States and include

sources of drinking water used by about 70 percent of the U.S. Population. Comprehensive assessments of about one-third of the Study Units are ongoing at a

given time. Each Study Unit is scheduled to be revisited every decade to evaluate

changes in water-quality conditions. NAWQA assessments rely heavily on existing information collected by the USGS and many other agencies as well as the

use of nationally consistent study designs and methods of sampling and analysis.

Such consistency simultaneously provides information about the status and

trends in water-quality conditions in a particular stream or aquifer and, more

importantly, provides the basis to make comparisons among watersheds and

improve our understanding of the factors that affect water-quality conditions

regionally and nationally.

This report is intended to summarize major findings that emerged between 1992

and 1995 from the water-quality assessment of the Lower Susquehanna River

Basin Study Unit and to relate these findings to water-quality issues of regional

and national concern. The information is primarily intended for those who are

involved in water-resource management. Indeed, this report addresses many of

the concerns raised by regulators, water-utility managers, industry representatives, and other scientists, engineers, public officials, and members of stakeholder

groups who provided advice and input to the USGS during this NAWQA StudyUnit investigation. Yet, the information contained here may also interest those

who simply wish to know more about the quality of water in the rivers and aquifers in the area where they live.

Robert M. Hirsch, Chief Hydrologist

“Actual water-quality d

shows us where our ef

to protect the environm

are successful and wh

still needs to be done t

prevent pollution. We

depend on this valuabl

partnership with the U.

Geological Survey, in

cooperation with our

communities, as we

continue our work to

protect and restore

Pennsylvania’s

watersheds.”

James M. Seif

Secretary,

Pennsylvania

Department of

Environmental

Protection

“Because the

Susquehanna River

provides 90 percent of 

freshwater flow to the

upper Chesapeake Bay

maintaining and impro

water quality in the rive

key to the bay restorat

efforts. We hope this re

will be used by

government, industries

and others to improve

water quality in the rive

well as the bay.”

Paul O. Swartz

Executive Direct

Susquehanna R

Basin Commiss
2 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

SUMMARY OF MAJOR ISSUES AND FINDINGS—

Lower Susquehanna River Basin Study Unit

PENNSYLVANIA

MARYLAND

Water from 30 percent of the wells sampled and about 20 percent of the streams s

would exceed the U.S. Environmental Protection Agency (USEPA) Maximum

Contaminant Level (MCL) for nitrate-nitrogen of 10 mg/L as N (milligrams per lite

nitrogen) if not properly treated before use as drinking water (p. 8).

• Water from wells in agricultural areas underlain by limestone and crystalline bedroc

commonly exceeded the USEPA MCL for nitrate in drinking water. Water from wel

urban areas underlain by limestone bedrock and in forested and agricultural areas un

by sandstone and shale had nitrate concentrations that seldom exceeded the MCL.

• Streams in agricultural areas underlain by limestone had nitrate concentrations that, 

lessened by appropriate treatment before use as drinking water, commonly would ex

USEPA MCL. Streams in other areas did not.

• The highest nitrate concentrations in streams were generally in the winter and sprin

Nitrate concentrations in the Susquehanna River at Harrisburg were generally less than 2 mg/L, which is consi

below the MCL for nitrate in drinking water of 10 mg/L (discussed above) (p. 8).

• Concentrations of nitrate at these levels, when multiplied by the large flows of the Susquehanna River, contributed 

amounts of nitrate to the Chesapeake Bay when compared to other rivers entering the bay.

• Streams from agricultural areas underlain by limestone bedrock contributed large amounts of nitrate per unit area to 

Lower Susquehanna River when compared to streams in areas with other land uses and bedrock types.

The main nitrogen source in the Study Unit is animal manure used as an agricultural fertilizer (p. 9).

• The data collected in this study provide a baseline to evaluate the effectiveness of the Pennsylvania Nutrient Manag

law, which requires concentrated animal operations to develop and have approved nutrient-management plans by 19

• Manure-application rate may be the most important factor controlling nitrate concentrations in streams in agricultura

underlain by limestone.

The concentration of total nitrogen in the Susquehanna River’s inflow to the Chesapeake Bay has decreased i

1985-96 time period (p. 11).

• The concentration of nitrate (one component of total nitrogen) has remained unchanged during this period.

• The specific environmental circumstances that would explain the lack of change in nitrate concentration during a tim

downward trends in total nitrogen could be related to the nitrate in streams that originates in ground water or to oth

nonpoint sources.

Concentrations of pesticides in water from the wells and streams sampled rarely exceeded levels established 

drinking-water standards (p. 12-14).

• Although drinking-water standards, human-health advisory levels, and aquatic-life criteria were rarely exceeded, th

criteria have not been established for many of the pesticides that were sampled for. In addition, mixtures and degrad

products were not considered in developing the human-health criteria. Therefore, only a limited range of potential e

the occurrence of pesticides in drinking water has been assessed.

• On the basis of analyses of 577 samples collected from 169 shallow wells and 155 streams, pesticides were frequen

detected in ground water and streams; usually, more than one pesticide was detected at a time. More than 60 percent 

water samples in which pesticides were present contained more than one detectable pesticide.

• The most commonly detected pesticides were the herbicides used primarily on corn: atrazine, metolachlor, simazi

prometon, alachlor, and cyanazine.

• Detections of pesticides in water were related to pesticide use, pesticide-leaching potential, and bedrock type. Pesti

were most likely to be detected in samples from agricultural and urban areas. Limestone areas were far more likely 

pesticides in well water than areas underlain by sandstone and shale.

• Seasonal variations in pesticide concentrations in water from streams are affected by the timing of pesticide applica

the type of bedrock. The highest concentrations of pesticides in streams were seasonal pulses lasting up to several m

• Concentrations of pesticides in the Susquehanna River were generally less than 1 part per billion. The pesticides det

the Susquehanna River were similar to those detected in water from streams in agricultural areas throughout the Lo

Susquehanna River Basin.
U.S. Geological Survey Circular 1168 

SUMMARY OF MAJOR ISSUES AND FIND

Lower Susquehanna River Basin Stu

Total coliform bacteria were detected in water from nearly 70 percent of the household wells sampled, indicati

the water should not be used for drinking without treatment (p. 15).

• Fecal coliform and Escherichia coli, bacteria that indicate contamination from human or animal feces, were detecte

water from 25 and 30 percent, respectively, of the wells tested.

• Few household wells from which water was sampled were grouted, and few had sealed, sanitary caps at the top of t

casing. Lack of these protective features can enable the entry of bacteria into well water. It is uncertain whether

bacteriological contamination of well water is caused by inadequate protection of wells from surface runoff, septic-

failure, application of animal manure to fields, or other causes.

• The presence of bacteria in water from rural wells is one of the most important water-quality issues related to huma

in the Study Unit.

None of the concentrations of the volatile organic compounds detected in samples from wells used as drinkin

supplies exceeded the MCLs or Lifetime Health Advisory Levels established by the USEPA (p. 16).

• In the Great Valley near Harrisburg, Pa., volatile organic compounds were detected more frequently in an urban area 

an agricultural area.

Radon, a product of the radioactive decay of uranium, is present in ground water throughout the Lower Susqu

River Basin (p. 17).

• Radon activities in 86 percent of the 165 ground-water samples tested for radon were greater than a previously prop

standard, now under review by the USEPA, of 300 pCi/L (picocuries per liter, a measurement of radioactivity).

• More than 30 percent of the 165 ground-water samples tested for radon contained radon at activities greater than

1,000 pCi/L. The area of the Study Unit underlain by crystalline rocks of the Piedmont Physiographic Province had 

highest median ground-water radon activities, but variation in radon activities within most subunits is large.

Correlations were found between the concentrations of trace elements in streambed sediments and the

concentrations in livers of bottom-feeding fish for only 3 of 11 elements regarded as common contaminants (p

• The highest concentrations of arsenic, beryllium, cadmium, cobalt, iron, manganese, nickel, selenium, and zinc in str

sediments were at sites affected by mine drainage.

No organic contaminants were detected in whole fish at levels considered harmful to human health; however, 

contaminants in streambed sediment were detected at levels harmful to aquatic life (p. 19-21).

• Organic compounds were detected in whole-body fish tissue and streambed sediment at all 20 sites sampled, which

represented a variety of settings. Of the 28 compounds analyzed for, 12 were detected. Although some of the detect

compounds are known human health risks, an interagency work group on fish-tissue contaminants reviewed the dat

collected by the USGS, compared the data to U.S. Food and Drug Administration action levels, and concluded that n

health advisories were warranted for the fish species (white sucker or smallmouth bass) collected at any of the samp

sites.

• PCBs in fish tissue were associated with urban and industrial land use. DDT and chlordane and their degradation pro

fish tissue showed an association with agricultural land use.

• The fish-tissue data indicate that DDT and chlordane have degraded over time and that no recent influx of these com

has occurred. At four sites, concentrations of total DDT or total chlordane in streambed sediment exceeded USEPA 

guidelines for protection of aquatic life. Tier 1 guidelines for total PCBs were not exceeded at any of the sites.

• Concentrations of semivolatile organic compounds in streambed sediment exceeded the USEPA Tier 1 guidelines f

protection of aquatic life at 4 of the 21 sites.

Fish communities inhabiting the seven streams in long-term monitoring basins were related to the bedrock ty

(p. 22-23).

• The habitat characteristics that proved most influential in defining fish communities were mean channel width, mea

temperature, mean canopy angle, and suspended sediment.

• Fish populations were healthier in the three freestone streams than in the four limestone streams. The fish populatio

influenced by agricultural activity in the agricultural settings, but the influence of agriculture on fish communities i

to habitat degradation rather than nutrients in the water.
4 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

Urban or built-u

EXPLANATIO

LAND USE

PHYSIOGRAP

BOUNDARY

Agricultural land

Rangeland

Forest land

Water

Wetland

Barren land

0

0

50 MILES

50 KILOMETERS

41°00'

78°30'

76°00'

40°00'

Blue Ridge

Piedmont

NORTHUMBERLAND

CENTRE UNION

SCHUYLKILL

SNYDER

BERKS

MIFFLIN

DAUPHIN JUNIATA

PERRY

HUNTINGDON LEBANON

BLAIR

CHESTER

LANCASTER

CUMBERLAND

YORK

FRANKLIN

BEDFORD ADAMS

FULTON

CECIL

BALTIMORE CARROLL

Ridge

and Valley

PENNSYLVANIA

MARYLAND

HARFORD

In the Lower Susquehanna River

Basin Study Unit, land use is

47 percent agricultural, 47 percent forested, and 4 percent urban; 2 percent

of the area is water bodies or barren

land (Mitchell and others, 1977; see

map above). The well-drained areas

with rolling hills and valleys in the

southern part of the basin contain most

of the population and some of the most

productive agricultural land in the

Nation. These agricultural and urban

areas commonly are areas underlain by

carbonate (limestone) bedrock.

The study area was subdivided on

the basis of land use, physiography,

and bedrock type to assess the effect of

these characteristics on water quality.

Thermoelectric,

public supply, and

industrial and

mining are the

largest water

uses in the Lower

Susquehanna

River Basin.

Rural homeowners depend

chiefly on ground

water for

domestic supply.

ENVIRONMENTAL SETTING AND HYDROLOGIC CONDITIONS

Major water issues in the Stud

include the effects of agricultu

use on water quality and groun

contamination in areas underla

limestone bedrock. These issu

used to prioritize the selection 

environmental settings for stud

ser and Siwiec, 1996).

Water used for public suppl

largely from surface water, and 

about 25 percent of the water u

public supply comes from gro

water sources (see graph at lef

In 1990, more than 1.2 million 

used public-supplied water. In 

tion, 800,000 rural homeowne

depended on water from wells 

domestic (household) supply. 

electric cooling, industrial and 

and public-supply withdrawals 

major uses of water. Withdraw

thermoelectric cooling are mu

greater than withdrawals for o

uses. The water-quality degrad

return flows from water used f

ing primarily involves increase

water temperature.

Agricultural activity on the land surface is one important factor affecting water quality in the Lower Susquehanna River Basin.

2,658

2,871

2,424

TOTAL

PUBLIC

DOMESTIC

COMMERCIAL

INDUSTRIAL

IRRIGATION AND

LIVESTOCK

THERMOGROUND WATER

SURFACE WATER

(800)

(1,221)

POPULATION

SERVED, IN

THOUSANDS

PERCENTAGE OF TOTAL

ESTIMATED WATER

WATER WITHDRAWALS,

0

50

100

150

200

250

8

7

6

5

4

3

2

1

0

IN MILLION GALLONS PER DAY

WATER WITHDRAWALS

SUPPLY

AND MINING

ELECTRIC

SUPPLY

(85%)

WITHDRAWALS IN 1990
U.S. Geological Survey Circular 1168 

Mean annual precipitation in the

Lower Susquehanna River Basin

Study Unit ranges from 38 to

48 inches (see figure at right). The

precipitation is generally less in the

center of the basin because of storm

patterns; however, the entire Study

Unit receives enough rainfall so that

irrigation is not common except in

periods of drought. The precipitation is distributed fairly evenly

throughout the year. About

45 percent of the precipitation is

contributed by storms in May

through September during the

growing season, and much of this

precipitation is used by plants. Most

of the remaining 55 percent occurs

when vegetation is dormant; therefore, this precipitation is more

available to infiltrate into bedrock

and enter ground-water systems.

The hydrologic conditions during

the study were variable, including

wet and dry years. This information

is important in the interpretation of

the water-quality data collected. For

example, the nitrate loads were calculated for 1994, a wet year, and

may provide a higher estimate for

loads than would have been calculated during a year with more

normal flow. The spring of 1993 and

1994 and the summer of 1994 were

periods of greater than normal precipitation and streamflow (see

figure below). Heavy winter snowstorms in these years caused high

flows in the spring. The snowmelt

from the winter of 1993 caused a

record high average streamflow of 

250,100 cubic feet per second from the

Susquehanna River to the Chesapeake

Bay during April of that year. Higher

than normal flows were observed

throughout 1994, when streamflow in

the Susquehanna River at Harrisburg was 42 percent greater t

normal. The summer of 1993 a

of 1995 were dry periods. Drou

larations were in effect for most 

counties in the Study Unit in Se

1995.

ENVIRONMENTAL SETTING AND HYDROLOGIC COND

The Lower Susquehanna River Basin has a temperate climate, with adequate precip

for the crops grown in the area. (Modified from Risser and Siwiec, 1996.)

Higher than normal flows were observed throughout 1994, when streamflow in the Susquehanna River at Harrisburg was 42 percent 

than normal. Drought declarations were in effect for most of the counties in the Study Unit in September 1995.

INTERQUARTILE RANGE (MIDDLE

500,000

400,000

300,000

200,000

0

SUSQUEHANNA RIVER AT HARRISBURG, PA.

STREAMFLOW, IN CUBIC

100,000

FEET PER SECOND

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A 

LINE OF EQUAL

WEATHER STATI

40

MEAN MONTHLY

NEWPORT, PA.

78°30' 76°00'

41°00'

39°30'

0 50 MILES

0 50 KILOMETERS

42

44

40

EVERETT

38

38

40

40

42

44

46

48

NEWPORT

HARRISBURG

YORK 38

40

40

44

38

46

44

42

42

44

46

EXPLANATION

PRECIPITATION,

IN INCHES

4.0

3.0

2.0

1.0

0

J F M A M J J A S O N D

MEAN ANNUAL

PRECIPITATION

1951 TO 1980—

Interval is 2 inche

1992 1993 1994 1995

DAILY STREAMFLOW,

WATER YEARS 1993-95 50 PERCENT OF THE VALUES)

OF HISTORICAL STREAMFLOW,

WATER YEARS 1900-95
6 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

Environmental subunit

name and number

Physiographic

province

(section)

Bedrock

type

Dominant

land use

Long-term

monitoring basin

(stream type)

Groun

stud

Piedmont crystalline (1) Piedmont Igneous and metamorphic

(crystalline)

Agriculture Muddy Creek

(freestone)

Subunit 

Piedmont limestone

agricultural (2)

Piedmont Limestone and dolomite Agriculture Mill Creek

(limestone)

Land-us

Great Valley limestone

agricultural (3)

Ridge & Valley

(Great Valley)

Limestone and dolomite Agriculture Bachman Run

(limestone)

Land-us

Great Valley limestone

urban (4)

Ridge & Valley

(Great Valley)

Limestone and dolomite Urban Cedar Run

(limestone)

Land-us

Appalachian Mountain

limestone agricultural (5)

Ridge & Valley

(Appalachian Mountain)

Limestone and dolomite Agriculture Kishacoquillas

Creek (limestone)

Land-us

Appalachian Mountain

sandstone and shale

agricultural (6)

Ridge & Valley

(Appalachian Mountain)

Sandstone and shale Agriculture East Mahantango

Creek (freestone)

Subunit 

Appalachian Mountain

sandstone and shale

forested (7)

Ridge & Valley

(Appalachian Mountain)

Sandstone and shale Forest Bobs Creek

(freestone)

Sampled 

of subun

survey

Water quality in the Lower Susquehanna River Basin is affected by

diverse geologic conditions and landuse factors. The intense agricultural

activity, in conjunction with the importance of the Lower Susquehanna River

Basin as a major source of freshwater

to the Chesapeake Bay, makes runoff

of nitrogen one of the most important

water-quality issues. Contamination of

stream water and ground water by pesticides and other organic chemicals,

which are used in agricultural and

urban areas, is another important issue.

Much of the rural population, which

relies on ground water for household

water supply, is in areas underlain by

limestone bedrock. The shallow limestone aquifers in valleys of primarily

agricultural land use are vulnerable to

contamination by activities on the land

surface. The effect of urban and mining land uses on water quality are also

important issues.

Drinking-water standards

(U.S. Environmental Protection

Agency, 1996a) apply only to waters

used for public supply that have been

filtered and treated (finished water).

The NAWQA Program is designed to

assess natural waters, not finished

waters. The standards were only used

in this report to place the observed

concentrations in samples from wells

used as household drinking-water supplies and samples from streams into a

common frame of reference. Aquaticlife criteria (U.S. Environmental Protection Agency, 1996b) and other

measures were used to assess the ecological health of the streams. Selected

ecological data for invertebrates and

algae have not been analyzed and are

not included in the major findings.

Major findings for nutrients, pesticides, selected contaminants in ground

water, contaminants in fish tissue and

streambed sediment, fish-community

structure and health, and stream habitat

are presented to illustrate the quality of

the water resources.

The study was designed to address

natural and human factors affecting

water quality. The design was an integrated assessment of water quality

including stream-water chemistry,

stream-water ecology, and groundwater chemistry. Some assessments

involved large geographic areas of the

Study Unit (basinwide studies),

whereas other assessments focused on

specific environmental settings (subunit studies). From the 14 major

environmental settings based on land

use, bedrock type, and physiography,

7 subunits (see table below and map on

page 7) were selected to provide the

basis for assessing the effects of land

use and bedrock type on water quality.

Long-term monitoring sites (see

table below and map on page 7) were

established in one stream in each of the

seven subunits to evaluate the temporal

variation in stream-water chemistry

and ecology. To assess stream-water

chemistry, samples were colle

monthly to weekly at each of th

long-term monitoring sites for 

of 316 samples over the study 

Most of the samples were coll

when flow was low and domin

ground water (base flow). Rela

few stormflow samples were c

at the long-term monitoring si

therefore, issues such as the tr

of phosphorus and ammonia, w

are predominantly transported 

storms, cannot be assessed. Th

3 years of data collection are n

cient to detect trends in the wa

quality conditions, but these da

as a baseline for future studies

Detailed ecological studies of 

invertebrates, and algae also to

at each of these seven long-ter

toring sites. The structure and h

the fish community were asses

characteristics of the stream ha

were analyzed.

Basinwide studies were don

determine ecological condition

the occurrence of contaminant

Streambed-sediment samples w

collected at 21 sites, and fish-t

samples were collected at 20 s

These sites (see map on page 2

included all of the long-term m

ing sites except for Bobs Cree

Cedar Run. Studies of biologic

munities and stream habitat we

at an additional 45 sites (see m

page 28).

MAJOR ISSUES AND FINDINGS
U.S. Geological Survey Circular 1168 

EXPLANATION

PENNSYLVANIA

MARYLAND

0

0

50 MILES

50 KILOMETERS

10 20 30 40

10 20 30 40

41°00'

78°30' 76°00'

39°30'

Juniata

River

PHYSIOGRAPHIC

BOUNDARY

STUDY AREA

BOUNDARY

LONG-TERM MONITORING

SITE AND SUBUNIT NUMBER

Great

Valley

Section

Appalachian

Mountain

Section

Blue

Ridge

Province Piedmont

Ridge and Province

Valley Province

Kishacoquillas

Creek

Bobs

Creek

Cedar

Run

East

Mahantango

Creek

Bachman

Run

Mill

Creek

Muddy

Creek

Chesapeake

Bay

Susquehanna

Susquehanna

River

WestBranch

LEBANON

MARIETTA

NEWPORT

HARRISBURG

DANVILLE

LEWISBURG

SUNBURY

LANCASTER

CONESTOGA

YORK

HAVRE DE GRACE

ALTOONA

Conowingo Dam

River

1

2

2

4

3

7

5 6

Piedmont limestone

agricultural (2)

Great Valley limestone

agricultural (3)

Appalachian Mountain

limestone agricultural (5)

Appalachian Mountain

sandstone and shale

forested (7)

Appalachian Mountain

sandstone and shale

agricultural (6)

Great Valley limestone

urban (4)

Piedmont crystalline (1)

SUBUNIT NAME AND NUMBER

Susquehanna

River

Synoptic studies were done to evaluate the conditions of a selected area

during a specific time period. Subunit

studies also enhanced the understanding of processes such as those that

influence the relation between groundwater quality and stream-water quality.

The subunit-synoptic sampling sites

were located within the colored areas

on the map below; individual sites for

ground-water and stream-water synoptic studies are shown on the site maps

on page 28. Wells or streams within

the subunits were sampled to determine the variations in water quality

among areas of different bedrock type,

land use, and physiography. Synoptic

studies of stream-water chemistry took

place at 187 sites and were focused

geographically on individual subunits

or on basinwide issues.

Synoptic studies of the chemical

and bacterial quality of ground water

were done in the subunits by collecting

well-water samples at 169 sites.

Ground-water sampling was done as a

land-use study (collecting samples

from an area of a single land-use type)

or as a subunit survey (collecting samples from all land uses within a

selected aquifer). The sandstone and

shale subunit survey was limited geographically to the eastern area of the

basin and included parts of the forested

and agricultural subunits. Only six

subunit-synoptic studies of ground

water were done. For data-analysis

purposes, however, the samples from

the forested and agricultural ar

the sandstone and shale subuni

were considered separately to 

comparisons to the seven surfa

water subunits. Not all issues w

studied in each subunit; for ex

bacteriological studies were no

in the urban subunit. Moreove

analyses were done at each of 

sites, so the number of sample

able for data analysis varies.

An outline of the sampling 

given in the table on page 29. 

of the sampling for studies of 

quality are given in Siwiec and 

(1997). Data from this study a

lished in Durlin and Schaffstal

1996, 1997).

MAJOR ISSUES AND FI

The study design was based on a combination of land use, physiography, and bedrock type. This map and table (page 6)

illustrate and describe the subunits that formed the basis of the study. The subunits are the colored areas; streams used as

long-term monitoring basins are labeled.
8 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

Wells and streams in the Lower Susquehanna River Basin Study Unit were

sampled, and the waters were analyzed

for nitrate and other forms of nitrogen.

Nitrate was the dominant form of

nitrogen in the water. Nitrate was

detected in 98 percent of the samples,

and 92 percent had concentrations of

nitrate that were above 0.3 mg/L (milligram per liter as N, or part per

million). In addition to human health

effects of drinking water with nitrate

concentrations greater than 10 mg/L,

nitrate can stimulate excessive growth

of algae in lakes and streams at concentrations as low as 0.3 mg/L. The

nitrate studies focused on describing

the concentrations in seven major subunits (Lindsey, Loper, and Hainly,

1997). Nitrate analyses from 161 wells

and 156 stream sites were completed

for this study. Data from other studies

of nitrogen in the Susquehanna River

(Hainly and Loper, 1997) were used to

supplement USGS data to describe

trends in concentrations.

Spatial Distribution of

Nitrate Concentrations

Water from 30 percent of the wells

sampled and about 20 percent of the

streams sampled would exceed the U.S.

Environmental Protection Agency

(USEPA) Maximum Contaminant

Level (MCL) for nitrate-nitrogen

of 10 mg/L if not properly treated

before use as drinking water. Most of

the samples representing sources of

drinking water were the samples collected from wells used for household

supply. Ground waters in agricultural

areas were most likely to have nitrate

concentrations that exceeded drinkingwater standards, though not all agricultural areas were the same. Land use

and bedrock type accounted for most

of the variation in nitrate concentrations in ground water (see graph on

page 9). Ground-water nitrate concentrations were highest in agricultural

areas underlain by limestone, where

45 percent of the samples exceeded the

MCL. Waters from 36 percent of the

wells in agricultural areas underlain

by crystalline bedrock also had nitrate

concentrations greater than 10 mg/L.

Water from wells in urban areas

underlain by limestone and in forested

and agricultural areas underla

sandstone and shale had nitra

centrations that seldom exceed

MCL.

Streams in agricultural area

underlain by limestone had nit

concentrations that, if not less

appropriate treatment before u

drinking water, commonly wou

exceed the USEPA MCL. Strea

other areas did not. Some stre

limestone areas have nitrate co

tions of 10 mg/L or more year 

In limestone areas, streams we

monly fed by springs that disc

ground water containing high 

trations of nitrate. Water from

tributaries in limestone areas, 

Mill Creek (see graph on botto

page 10), had nitrate concentra

near 10 mg/L with some seaso

tuation. In limestone and other 

the highest nitrate concentratio

generally in the winter and spr

Seasonally high concentration

nitrate are an issue for some w

pliers. Suppliers of drinking w

regularly monitor nitrate

concentration.

Nitrate concentrations in th

quehanna River at Harrisburg 

generally less than 2 mg/L, wh

considerably below the MCL f

nitrate in drinking water of 10 

Concentrations of nitrate at th

els, when multiplied by the lar

of the Susquehanna River, con

Nitrate in drinking water at levels

in excess of 10 mg/L can result in

methemoglobinemia (blue-baby

syndrome) in bottle-fed infants

up to 6 months old. The Centers

for Disease Control and Prevention (1996) studied several cases

in Indiana where pregnant

women who were drinking water

with nitrate concentrations in the

range of 20 to 30 mg/L had

multiple miscarriages. The link

between nitrate and miscarriages

was suggestive but not conclusive in that study.

Ground-water and stream-water qual

related to manure management and a

rates. Best-management practices, lik

manure-storage structure (concrete s

with chain-link fence) on this farm in L

County, Pa. (left), help keep manure f

applied to the fields in the winter whe

more likely to enter streams and grou

(above, photograph by Dennis W. Ris

U.S. Geological Survey).

MAJOR ISSUES AND FINDINGS—

Nitrate in Ground Water and Streams
U.S. Geological Survey Circular 1168 

large amounts of nitrate to the Chesapeake Bay when compared to other

rivers entering the bay. Although

safe for human consumption after filtration and water treatment, the

water flowing from the Susquehanna River into the Chesapeake

Bay still contained enough nitrate to

stimulate algae growth and affect the

bay ecosystem. Estimates of loads

and yields of nitrate for 1994 from

samples collected when the flow was

dominated by ground water (base

flow) showed that streams from agricultural areas underlain by

limestone bedrock contributed large

amounts of nitrate per unit area to

the Lower Susquehanna River when

compared to streams in areas with

other land uses and bedrock types.

However, streams in agricultural

areas underlain by sandstone and

shale and crystalline bedrock also

provide large amounts of nitrate to 

Susquehanna River.

The main nitrogen source in the 

Unit is animal manure used as an 

tural fertilizer. High manure-appli

rates showed a strong association 

vated nitrate concentrations in are

specific land uses and bedrock typ

Nitrogen in manure and fertilizers 

to agricultural land is essential to 

growth; however, concentrated ani

operations can produce more man

the crops grown on that farm can u

number of concentrated animal op

is increasing in some parts of the b

Improper or excess application can 

nitrate and other forms of nitrogen 

the ground water or streams. Rece

through the efforts of the Chesape

Restoration Program, many agricu

operations have voluntarily taken 

tage of new technologies to manag

manure more efficiently. The data 

lected in this study provide a base

evaluate the effectiveness of the Pe

vania Nutrient Management law, w

requires concentrated animal oper

to develop and have approved nut

management plans by 1998.

The nitrate data from the seven 

were compared to determine facto

affect nitrate movement and conce

Nitrate concentrations were highe

stream water in areas underlain by 

stone than in areas underlain by ot

MAJOR ISSUES AND FIND

Nitrate in Ground Water and S

For agricultural areas underlain by crystalline or limestone bedrock, nitrate concentrations generally were higher in ground water th

stream water. In urban areas and areas underlain by sandstone and shale, nitrate concentrations generally were higher in stream w

than in ground water.

Nitrate concentrations in ground water are highest in agricultural areas underlain by limestone bedrock, where almost half of the samples collected exceed 10 mg/L of nitrate.

Shallow bedrock depth and highly fractured bedrock in valleys underlain by limestone can

allow nitrate from manure and fertilizer to infiltrate rapidly into the ground water. NITRATE CONCENTRATION,

EXPLANATION

U.S. Environmental Protection

0

5

10

15

20

25

SAMPLE TYPE AND SUBUNIT

Minimum

Median

22 Number of samples

Maximum

Between 3 and 10

Less than 3

Greater than 10

MEDIAN CONCENTRATION

SUBUNIT

1 - Piedmont crystalline

2 - Piedmont limestone

3 - Great Valley limestone

4 - Great Valley limestone

5 - Appalachian Mountain

6 - Appalachian Mountain

sandstone and shale

7 - Appalachian Mountain

BOXPLOT

TYPE OF SAMPLING SITE

GW - Ground-water subunit

SW - Stream-water subunit

GW-SW GW-SW GW-SW GW-SW GW-SW GW-SW GW-SW

1 2 3 4 5 6 7

22

17

30

16

30

10

20 11

30

16

22

14

7 16

28

IN MILLIGRAMS PER LITER AS NITROGEN

Agency Maximum Contaminant

Level for nitrate

synoptic

synoptic

limestone agricultural

sandstone and shale

OF NITRATE (milligrams

agricultural

agricultural

agricultural

urban

agricultural

forested

per liter)
10 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

bedrock types; however, these areas

generally had the highest manureapplication rates. When an agricultural

area underlain by limestone and an

agricultural area underlain by sandstone and shale with similar manureapplication rates were compared,

nitrate concentrations in streams were

not significantly different. Manureapplication rate may be the most

important factor controlling nitrate

concentrations in streams in agricultural basins underlain by limestone. A

comparison of 41 basins in agricultural

areas underlain by limestone shows

that the manure-application rate is

strongly correlated with nitrate concentration (see graph above).

Nitrate concentrations were higher

in ground water than in streams in

agricultural areas underlain by limestone bedrock and in agricultural areas

underlain by crystalline bedrock. Conditions in these areas allow much of

the agriculturally applied nitrogen to

enter the ground water. Under certain

conditions, forested areas near streams

(riparian buffers) can remove nitrate

from the ground water before it flows

into the stream.

Nitrate concentrations were higher

in streams than in ground water in

urban areas underlain by limestone.

Streams in urban areas were affected

by point-source discharges. Nitrate

concentrations were also higher in

stream water than ground water in both

agricultural and forested areas underlain by sandstone and shale. The

conditions in the sandstone and shale

aquifers are not favorable for the

MAJOR ISSUES AND FINDINGS—

Nitrate in Ground Water and Streams

Nitrate concentrations in stream base flow decline through the summer and

increase through the fall, reaching the highest concentrations in the winter mo

20

0

5

10

15

0 400 100 200 300

SURFACE-WATER NITRATE

MILLIGRAMS PER LITER AS NITROGEN

MANURE-APPLICATION RATE, IN POUNDS

CONCENTRATION, IN

OF NITROGEN PER ACRE PER YEAR

movement of nitrate into the ground

water. Conditions in these aquifers also

were such that nitrate could change

chemically to other forms of nitrogen

(denitrification) and potentially leave

the water system and enter the atmosphere. The sandstone and shale

subunits had the lowest median nitrate

concentrations in streams and ground

water compared to the other subunits.

The relation of topography and land

use is important in understanding

nitrate occurrence. In the Ridge and

Valley Physiographic Province, where

agricultural areas are in the valleys and

forested areas are on the ridges, the

ground water under the valleys may be

mixed with water from the ridges,

which dilutes agricultural contaminants. In areas of the Piedmont

underlain by crystalline bedrock, agricultural land use is commonly on the

hilltops, and the steep hillsides are forested. There, the ground water under

the agricultural land contains contaminants from the agricultural lan

but contaminants may be abso

vegetation or diluted as the wa

passes under the forested areas 

way to the stream.

Temporal Variation in

Nitrate Concentration in S

Temporal variation in nitrat

centrations in streams during p

when storm runoff is absent (b

flow) and flow is dominated by

ground-water flow was determ

from the analyses of samples c

throughout the year at seven lo

monitoring sites (see map on p

Nitrate concentrations were co

higher in the winter months th

summer months. An example 

Mill Creek is shown below.

Statistical analysis showed t

flows in the streams were relat

high nitrate concentrations. Th

tion may have been caused by 

seasonal change in the amount 

water that flows through the gr

and carries nitrate to the stream

water transports more nitrate). 

possible explanations for this v

include the seasonal cycle in p

uptake of nitrogen and seasona

ations in uptake of nitrate by a

streams. Because no informati

available about the time for gr

water to travel from land surfa

streams, interpretation of this t

variation was not conclusive. N

concentrations in stream base 

unlikely to change quickly in r

to land-management practices 

it may take years for ground w

in aquifers underlying the basin 

into streams.

EXPLANATION

DAILY MEAN STREAMFLOW NITRATE CONCENTRATION IN SAMPLES COLLEC

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER

AS NITROGEN

DAILY MEAN STREAMFLOW

MILL CREEK NEAR LYNDON, PA. (SUBUNIT 2) 2,400

2,000

1,600

1,200

800

400

0

14

12

10

8

6

4

2

0

MAMJ J ASOND J FMAMJ J A

1993 1994

WHEN STORM RUNOFF WAS NOT PRESENT

A comparison of samples

from 41 streams in agricultural areas underlain by

limestone (subunits 2, 3,

and 5) shows a strong relation between manureapplication rate and nitrate

concentration.
U.S. Geological Survey Circular 1168 

PENNSYLVANIA

MARYLAND

0

0

50 MIL

50 KILOMETERS

10 20 30 40

10 20 30 40

41°00'

78°30' 76°

39°30'

Chesap

Ba

SUSQUEHANNA

RIVER AT

WEST BRANCH DANVILLE

SUSQUEHANNA RIVER

AT LEWISBURG

SUSQUEHANNA

RIVER AT MARIETTA

SUSQUEHANNA RIVER AT

CONOWINGO DAM

CONESTOG

RIVER AT

CONESTOG

JUNIATA RIVER

AT NEWPORT

EXPLANATION

TOTAL PHOSPHORUS

DOWNWARD TREND

NO CHANGE

UPWARD TREND

TOTAL NITROGEN

NITRATE-NITROGEN

TP

TN

NO3

TP TN NO3

Because the stream samples primarily were collected when the

flow was low and dominated by

ground water (base flow), the occurrence and trends of phosphorus and

other forms of nitrogen such as

ammonia are difficult to determine

from the NAWQA data. These

nutrients generally are associated

with storm runoff and would not be

well characterized by an analysis of

base-flow data. Therefore, data

from an ongoing study of the Susquehanna River (Langland and

others, 1998) was used to show

trends for these nutrients. The study

showed that the concentration of

total nitrogen in the Susquehanna

River at Conowingo Dam, the

river’s inflow to the Chesapeake

Bay, decreased in the 1985-96 time

period. The concentration of nitrate

(one component of total nitrogen)

remained unchanged during this

period.

The downward trends in total

nitrogen (see map and table at right)

are probably the result of large

decreases in concentrations of

ammonia and organic nitrogen—other components of total

nitrogen. The decreases in concentrations of ammonia and organic

nitrogen, and subsequent decreases

in total nitrogen, are attributed to

improvements in sewage-treatment

plants and implementation of agricultural best-management practices.

The specific environmental circumstances that would explain the lack

of change in nitrate concentration

during a time of downward trends

in total nitrogen could be related to

the nitrate in streams that originates in ground water or to other

nonpoint sources. Further study

would be needed to determine the

causes of these opposing trends.

Studies of phosphorus show that

trends in concentration have

decreased throughout the basin.

These trends are attributed to a ban

on phosphate detergents as well as

improvements in sewage-treatment

plants and implementation of agricultural practices that decrease

surface runoff.

A study of nutrient concentrations in the Susquehanna River Basin from 1985 to 1996 ind

downward trends in concentrations of total nitrogen and phosphorus (Langland and oth

1998). These trends are attributed to improvements in sewage-treatment plants, a ban o

phate detergents, and implementation of agricultural best-management practices. Nitra

component of total nitrogen, showed an upward trend at Lewisburg and no change at an

sites. Constant or increasing nitrate concentrations may be related to flow from ground 

and nonpoint sources. (Map modified from U.S. Environmental Protection Agency, 199

MAJOR ISSUES AND FIND

Trends in Nitrogen and Phosphorus Concen

The table above shows the trends in concentrations calculated by Langland and others 

illustrating the magnitude of the trends shown on the map as a percentage. The bold nu

on the table is the trend from the statistical model used to detect changes in concentratio

time (Cohn and others, 1992). The maximum and minimum results illustrate the range o

ble trends. Negative numbers indicate downward trends. The term “no change” is used in 

where it is uncertain whether the trend is upward or downward.

Site location

Percentage change in nutrien

concentrations 1985-96

minimum/trend/maximum

Total

phosphorus Total nitrogen Nitnitro

1The trend shown is for total nitrate plus nitrite nitrogen, which is a close approxim

the trend in nitrate-nitrogen.

Susquehanna River at Danville –41/–27/–10 –37/–31/–23 No c

West Branch Susquehanna River at Lewisburg No change –24/–15/–4 8/1

Juniata River at Newport –59/–51/–41 –31/–26/–21 No c

Susquehanna River at Marietta2

2The trend for Marietta is based on data from 1987 to 1996.

–47/–35/–20 –37/–30/–22 No c

Conestoga River at Conestoga –32/–20/–6 –23/–19/–14 No c

Susquehanna River at Conowingo Dam –62/–53/–42 –25/–18/–10 No c
12 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

MAJOR ISSUES AND FINDINGS—

Pesticides in Ground Water and Streams

Wells and streams in the Lower Susquehanna River Basin Study Unit were

sampled and the waters analyzed for

many of the most commonly used pesticides in the United States. The

pesticides analyzed for are soluble in

water. The samples were collected to

provide information on the spatial distribution of pesticides in ground water

and streams, as well as the seasonal

patterns of pesticides in streams

(Breen and others, 1995; Hainly and

Kahn, 1996; Hainly and Bickford,

1997).

Concentrations of pesticides in

water from the wells and streams sampled rarely exceeded levels established

as drinking-water standards. Only 10

of the measured concentrations in

untreated waters from streams

exceeded a level established as a drinking-water standard. Seasonal factors,

such as storm runoff of pesticides during the major application period in the

spring, contribute to high concentrations of pesticides in streams. Very few

storm samples were collected for this

study; however, 8 of the 10 exceedances were measured in storm-affected

samples. More work would be needed

to understand fully the high-concentration pulses of pesticides in stormflow.

None of the samples collected from

household-supply wells had concentrations that exceeded drinking-water

standards.

Guidelines for protection of aquatic

life were exceeded in samples from

nine streams. Concentrations of

malathion, chlorpyrifos, and methylazinphos exceeded guidelines for protection of aquatic life (U.S.

Environmental Protection Agency,

1991). Although no guidelines have

been established in the United States

for atrazine, cyanazine, and metolachlor, these pesticides exceeded the

Canadian guidelines for protection of

aquatic life (Canadian Council of

Resource and Environment Ministers,

1996).

Although drinking-water standards,

human-health advisory levels, and

aquatic-life criteria were rarely

exceeded, these criteria have n

established for many of the pes

that were sampled for. In addit

tures and degradation product

not considered in developing th

human-health criteria. Only a 

range of the potential effects of 

cides in drinking water has be

assessed. Therefore, it is impo

evaluate pesticide occurrence a

trends even though current stan

were rarely exceeded.

Spatial Distribution of

Pesticide Concentrations

Pesticides were detected fre

in ground water and streams; 

more than one pesticide was d

at a time. Spatial and seasonal 

of pesticide concentrations we

mented using 577 samples that 

tested for 47 herbicides or inse

A subset of the stream-water s

and all ground-water samples w

tested for an additional 38 pest

In total, nearly 40,000 analyse

centrations for individual pesti

were made on waters from 155 

sites and 169 shallow wells fro

to 1995. For this study, shallow 

were defined as those less than 

deep.

In more than 90 percent of t

ples collected, at least one pest

was detected, and two or more 

cides per sample were frequen

detected. More than 60 percen

water samples in which pesticid

WATER FROM WELLS

80 WATER FROM STREAMS

60

40

20

0

100

DIAZINON

2,4-D

CHLORPYRIFOS

CARBARYL

PENDIMETHALIN

ACETOCHLOR

DCPA

TEBUTHIURON

PROMETON

ALACHLOR

CYANAZINE

SIMAZINE

METOLACHLOR

ATRAZINE

ATRAZINE,

The timing and rate of agricultural

pesticide applications (below) were

important factors in describing the

seasonal and spatial concentration

patterns detected in ground water and

streams.

Indicators of residential, com

and industrial pesticide use 

helped to explain concentrat

patterns of pesticides not us

extensively for agricultural p

DETECTION FREQUENCY,

IN PERCENT

DESETHYL

PESTICIDE

The six most frequently detected pesticides were the same for water from wells and water

from streams.
U.S. Geological Survey Circular 1168 

MAJOR ISSUES AND FIND

Pesticides in Ground Water and S

S

A

URF CE RUNOFF

SOIL

BEDROCK

WATER TABLE

GROUND-WATER FLOW

present contained more than one

detectable pesticide. In general, measured concentrations of individual

pesticides were very low; only 22 samples of stream water and 2 samples of

ground water had concentrations that

exceeded 2 μg/L (micrograms per liter,

or parts per billion).

The most commonly detected pesticides were the herbicides used

primarily on corn: atrazine, metolachlor, simazine, prometon, alachlor,

and cyanazine (see graph on page 12).

Metolachlor and atrazine are the two

most used agricultural pesticides in the

Study Unit. Atrazine was detected in

98 percent of the stream samples and

in 74 percent of the ground-water samples. Desethylatrazine (a breakdown

product of atrazine) was usually

detected with atrazine. Metolachlor

was detected in 95 percent of the

stream samples and in 53 percent of

the ground-water samples. Nearly half

of all the pesticides analyzed for were

not detected in any sample. Of the 45

pesticides that were detected at least

once, only 5 were detected in more

than half of the samples collected.

Average annual pesticide use for

agricultural purposes and nonagricultural (residential, commercial, and

industrial) pesticide-use indicators

were related to patterns of pesticide

concentrations in waters from wells

and streams. The timing and rate of

agricultural pesticide applications for

the high-use pesticides described a

major part of the seasonal concentration patterns observed in water from

streams and the spatial pattern

observed in water from stream

wells. Indicators of nonagricul

helped to explain concentratio

terns of pesticides not used ext

in agriculture.

Detections of pesticides we

related to pesticide use, pestic

leaching potential, and bedroc

Pesticides were most likely to 

detected in samples from agric

and urban areas. Limestone a

were far more likely to have pe

in well water than areas under

sandstone and shale. Bedrock 

influences the movement and d

charge of ground water and af

spatial patterns of pesticide co

tions, as shown in the graph to 

and in the figure below. Some 

monly used pesticides with low

leaching potential (low potenti

infiltrate into the ground with 

water), such as alachlor and cy

were detected in streams more 

than in wells because they are 

likely to be transported in surf

runoff.

To help understand how dif

in bedrock type control concen

of highly soluble pesticides in 

base flow, Study Unit personn

pared atrazine concentrations 

streams during the dry times o

year, when the flow is low and 

nated by ground water (base fl

concentrations in ground wate

shallow wells. Results differed 

erably between limestone syst

non-limestone systems. In sub

with limestone bedrock, atrazi

centrations in waters from stre

shallow wells were similar, ind

0

100

20

40

60

80

DETECTION FREQUENCY IN

ALACHLOR CYANAZINE METOLACHLOR SIMAZINE ATRAZINE

PESTICIDE AND LEACHING POTENTIAL

SANDSTONE AND SHALE

CRYSTALLINE BEDROCK

LIMESTONE

LOW MEDIUM HIGH LOW MEDIUM

GROUND WATER, IN PERCENT

In water from wells in areas of limestone bedrock, where water easily infiltrates into the

aquifer, pesticides with high leaching potential, such as atrazine, were almost always

detected. Less widely used pesticides with low leaching potential, such as cyanazine, were

rarely detected in these same areas. In areas of sandstone and shale, where the infiltration

is poor, even pesticides with high leaching potential and high use, such as atrazine, were

rarely detected in water from wells.

The amount of water that runs off the land surface or infiltrates into the

ground depends on factors such as slope and how easily water can

flow through the soil and bedrock material. In areas of limestone bedrock, where water can readily infiltrate into the ground, pesticides

were commonly detected in ground water. The same pesticides

detected in ground water were usually detected in streams during

times when the flow in the streams is sustained by flow from ground

water. In areas of sandstone and shale, where water does not easily

flow through the soil and bedrock material, the easiest pathway for the

water is to run off over the land. Pesticides were rarely detected in

ground water in these areas.
14 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

MAJOR ISSUES AND FINDINGS—

Pesticides in Ground Water and Streams

a system of ground-water flow through

large fractures and springs to the

streams. In the sandstone and shale

subunit, atrazine concentrations in well

waters were lower than concentrations

in the streams, indicating that water

reaching the stream may be flowing

from the aquifer to the stream through

a system of fractures in a shallower

layer of the aquifer than the layer penetrated by the wells. The graphs to the

right illustrate the differences between

pesticide concentrations in streams in

limestone settings and sandstone and

shale settings.

Temporal Variation in Pesticide

Concentrations in Streams

Seasonal variations in pesticide

concentrations in water from streams

are affected by the timing of pesticide

application and the type of bedrock.

The highest concentrations of pesticides were seasonal pulses lasting up

to several months (see graph at right).

Peak concentrations were smaller in a

limestone stream compared with a

stream in a sandstone and shale area.

Elevated concentrations in streams

were related to the seasonality of agricultural-use applications. The seasonal

variations in climate also were an

important factor in explaining seasonal

patterns.

Mill Creek, a limestone stream,

shows a slight rise in atrazine concentration after the major application

period because some atrazine is in runoff. Some atrazine infiltrates into the

ground water and provides constant

levels of atrazine to the stream for the

rest of the year. This is a limestone

stream pattern. Levels of atrazine

remain between 0.1 and 0.2 μg/L

because ground water provides most of

the water to the stream.

The pattern at East Mahantango

Creek, a stream in an area of sandstone

and shale, shows a pulse or increase in

atrazine concentration after application, followed by lower concentrations

throughout the rest of the year. Topography and soils in this basin favor

runoff of atrazine over leaching to the

ground water. The levels of atrazine

after the application period when the

streamflow is supplied from ground

water are lower in East Mahantango

Creek than in Mill Creek.

Pesticide Concentrations in the

Susquehanna River

Concentrations of pesticides in the

Susquehanna River were generally less

than 1 μg/L. Analyses of 11 water

samples from the Susquehanna River

at Harrisburg from June 1994 to

August 1995 indicated that mixtures of

pesticides and their degradation products were frequently present in the

river but at concentrations generally

less than 1 μg/L (see table below). The

pesticides detected at this site were

similar to those detected in wa

streams in agricultural areas t

out the Lower Susquehanna R

Basin.

Pesticides were not detected 

ples collected during synoptic 

at the main-stem Susquehanna 

Danville and were detected in 

centrations in the West Branch

Susquehanna River at Lewisbu

(upstream from the Lower Sus

hanna River Basin). This patte

indicates that the pesticides pr

the Susquehanna River at Harr

are most likely introduced by t

taries in the Lower Susquehan

Basin.

EAST MAHANTANGO CREEK AT KLINGERSTOWN, PA. (SUBUNIT 6)

A M J J A S O N D J F M

1993 1994

1

10

2

5

10

20

50

10

20

50

1,0

2,0

5,0

MILL CREEK NEAR LYNDON, PA. (SUBUNIT 2)

0.8

0

0.2

0.4

0.6

0.8

0

0.2

0.4

0.6

ATRAZINE CONCENTRATION,

IN MICROGRAMS PER LITER

1

10

2

5

10

20

50

10

20

50

1,0

2,0

5,0

MAJOR APPLICATION

PERIOD

MAJOR APPLICATION

PERIOD

ATRAZINE CONCENTRATION

EXPLANATION

DAILY MEAN STREAMFLOW

In limestone streams, such as Mill Creek, atrazine concentrations were nearly con

year round. In streams in sandstone and shale areas, such as East Mahantango C

atrazine concentrations increased significantly after the major pesticide application 

Pesticide concentrations in the Susquehanna River at Harrisburg, 1994-95, were ge

less than (<) 1 microgram per liter.

Compound

Minimum

concentration

Maximum

concentration

Med

concen

micrograms per liter (parts per billion)

Alachlor <0.002 0.730 <0.0

Atrazine .014 1.20 .0

Atrazine, desethyl .015 .118 .0

Cyanazine <.004 .280 <.0

Metolachlor .007 2.30 .0

Prometon <.018 .035 <.0

Simazine <.005 .124 .0
U.S. Geological Survey Circular 1168 

Samples from 146 householdsupply wells were analyzed for organisms indicative of fecal contamination,

including total and fecal coliform bacteria (Bickford and others, 1996). Total

coliform bacteria were detected in

water from nearly 70 percent of the

household wells sampled, indicating

that the water should not be used for

drinking without treatment. Fecal

coliforms were present in water from

about 25 percent of those same wells.

In an 88-well subset, approximately

30 percent had waters containing

Escherichia coli bacteria (E. coli).

Fecal streptococcus bacteria were

present in water from about 65 percent

of the wells sampled. Bacteriological

contamination was more likely to

occur in water from wells in agricultural areas than in water from wells in

forested areas. Water from wells in

areas underlain by limestone had

higher concentrations of bacteria than

areas with other types of bedrock.

Few household wells from which

water was sampled were grouted, and

few had sealed, sanitary caps at the

top of the casing. Lack of these protective features can enable the entry of

bacteria into well water and may have

contributed to the number of detections of bacteria. It is uncertain

whether the bacteria detected were the

result of widespread aquifer contamination or local factors. In most

counties in Pennsylvania, testing and

treatment of private wells is not

required. It is uncertain whether bacteriological contamination of well water

is caused by inadequate protection of

wells from surface runoff, septic-system failure, application of animal

manure to fields, or other causes.

Although samples were not tested

for protozoan pathogens, such as Giardia lamblia and Cryptosporidium, the

presence of fecal bacteria indicates the

potential for these protozoans and

other pathogens of fecal origin 

present in the drinking water. G

trointestinal diseases related to 

used for household-water supp

symptoms such as diarrhea an

ach cramps and commonly go

unreported. With waters from n

70 percent of the wells sample

ing one or more bacteriologica

indicators, the presence of bac

water from rural wells is one o

most important water-quality 

related to human health in the 

Unit.

MAJOR ISSUES AND FIND

Bacteria in Groun

The presence of bacteria in water from rural household wells is an important drinking-water issue. Total coliform and fecal coliform b

were detected in water from many of the wells.

Fecal contamination of water supplies is a leading cause of waterborne-dis

outbreaks. Most outbreaks shown here are from public supplies; outbreaks 

eases involving water from private household wells are usually neither iden

nor reported. The cases from public supplies illustrate the potential effects 

drinking contaminated water. All of the cases listed above except acute gas

trointestinal illness of unknown cause (AGI) are transmitted by fecal

contamination.

WATERBORNE-DISEASE CASES ASSOCIATED WITH

230

385

625

Giardia

lamblia

Shigella

sonnei

Salmonella

Cryptosporidium

parvum1

AGI2 495

1403,000 cases from outbre

2AGI - Acute gastrointestina

Source: Centers for Disease Control and

0

10

20

30

40

50

60

70

80 28

29

22

30

PERCENTAGE OF WELLS WITH TOTAL COLIFORM

22

EXPLANATION

22 NUMBER OF SAMPLES

TOTAL COLIFORM DETECTED

FECAL COLIFORM DETECTED

100

90

Less than or equal to 50 and

Less than 10

Greater than 50

PERCENTAGE OF WELLS WITH 7

SUBUNIT

1 2 3 5 6 7

SUBUNIT

1 - Piedmont crystalline agricultural

2 - Piedmont limestone agricultural

3 - Great Valley limestone agricultur

4 - Great Valley limestone urban

5 - Appalachian Mountain limestone

6 - Appalachian Mountain sandstone

 and shale agricultural

7 - Appalachian Mountain sandstone

agricultural

and shale forested

OR FECAL COLIFORM PRESENT

BACTERIA PRESENT

greater than or equal to 10

0%

DRINKING WATER—UNITED STATES 1993-94

in Milwaukee, Wis.

illness of unknown cause. F

coliforms were detected in 

drinking water in 80 percen

Prevention (1996). the cases of AGI.
16 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

EXPLANATION

Water samples for analysis of volatile organic compounds (VOCs) were

collected from 118 of the 169 wells

used in this assessment; at least 1 compound was present in water from 26 of

the 118 wells (Daly and Lindsey, 1996;

Lindsey, Breen, and Daly, 1997). Analyses for 60 VOCs at detection levels

ranging from 0.2 to 1.0 μg/L revealed

the presence of 23 compounds. These

compounds are present in commonly

used industrial solvents and degreasers

or are components of gasoline.

None of the concentrations of the

VOCs detected in samples from wells

used as drinking-water supplies

exceeded the MCLs or Lifetime Health

Advisory Levels established by the

USEPA. Methyl tert-butyl ether, a gasoline additive, was the most commonly

detected compound. Concentrations of

methyl tert-butyl ether, detected in 11

of the 118 wells, ranged from 0.2 to

51 μg/L. The 51 μg/L of methyl tertbutyl ether, detected in a monitoring

well, exceeded the lower limit of the

compound’s Lifetime Health Advisory Level. Chloroform was the second

most commonly detected compound.

Chloroform is a byproduct of using

chlorine as a disinfectant. Chloroform

also is present in septic-system effluent, and it has industrial uses. The

highest chloroform concentration

detected in a water sample was

61 μg/L.

The presence of VOCs in limestone

aquifers in the Great Valley near Harrisburg, Pa., is affected by land use as

illustrated by the graph below. VOCs

were detected more frequently in the

urban area (subunit 4) than in the

agricultural area (subunit 3). Within

the urban area, analyses of samples

from wells, springs, and a spring-fed

stream indicate that contaminated

ground water flows from springs into

the streams.

The frequency of detections of

VOCs in urban areas is likely to be a

result of the numerous urban sources

of VOCs, including spills, leaks from

underground tanks, improper disposal,

atmospheric deposition, runoff from

pavement, and leaking sewerlines.

In the rural areas in the Appalachian

Mountain subunits, no VOCs were

detected in well water (see graph

below). The low population densities

in rural areas and fewer sources of

VOCs are likely explanations for the

lack of detections of VOCs. In rural

areas, leaking storage tanks, septic systems, improper disposal, and

atmospheric deposition are potential

sources of VOCs.

Numerous sources of VOCs in urban areas are a likely explanation for the high frequency of detections in the urban subunit. In the 

area, ground water contaminated with VOCs flows from springs that feed coldwater streams known for their trout populations.

MAJOR ISSUES AND FINDINGS—

Volatile Organic Compounds in Ground Water

Underground storage tanks that con

gasoline and other fuels can be a so

VOCs in ground water. The drill rig 

above is used to install monitoring w

property owner can determine whet

leakage or contamination has occur

0

10

20

30

40

50

60

70

80

10

100

90

30

20

20

22

0%

9

0%

7

0%

PERCENTAGE OF WELLS WITH

AT LEAST ONE VOC DETECTED

SUBUNIT

1 2 3 4 5 6 7

22 NUMBER OF SAMPLES

PERCENTAGE OF WELLS

Less than or equal to 50 and

Less than 10

Greater than 50

greater than or equal to 10

WITH AT LEAST ONE

SUBUNIT

1 - Piedmont crystalline agricultural

2 - Piedmont limestone agricultural

3 - Great Valley limestone agricultur

4 - Great Valley limestone urban

5 - Appalachian Mountain limestone

6 - Appalachian Mountain sandstone

 and shale agricultural

7 - Appalachian Mountain sandstone

agricultural

and shale forested

VOC DETECTED
U.S. Geological Survey Circular 1168 

Radon, a product of the radioactive

decay of uranium, is present in ground

water throughout the Lower Susquehanna River Basin (Lindsey and Ator,

1996). Airborne radon has been cited

by the Surgeon General of the United

States as the second leading cause of

lung cancer, and the USEPA has identified ground-water supplies as possible contributing sources of indoor

radon. Radon activities in 86 percent

of the 165 ground-water samples

tested for radon were greater than a

previously proposed standard, now

under review by the USEPA, of 300

pCi/L (picocuries per liter, a measurement of radioactivity). More than

30 percent of the 165 ground-water

samples tested for radon contained

radon at activities greater than

1,000 pCi/L.

The subunit of the Study Unit underlain by crystalline rocks of the

Piedmont Physiographic Province had

the highest median radon activities in

ground water (greater than

1,000 pCi/L), but variation in radon

activities within most subunits is large.

Lower median radon activities (less

MAJOR ISSUES AND FIND

Radon in Groun

Many of the known cancer-causing agents cause only a relatively small pe

age of cancer deaths. The risk of radon can be put in perspective by comp

the risk of radon exposure to other factors that have been identified as caus

cancer. This figure accounts for all exposures to radon, not only radon in w

(not all factors are shown).

PERCENTAGES OF CANCER DEATHS

35

30

4

2-3

2

0.5

Diet

Tobacco

Occupation

Radon

Pollution

Medical X-Rays Source: American Institute for

ATTRIBUTED TO VARIOUS FACTORS

Cancer Research (1992)

EXPLANATION

RADON, IN PICOCURIES PER LITER

SUBUNIT

10

50

100

300

500

1,000

5,000

10,000

50,000 22

Median

Minimum

Maximum

Number of samples

Less than or equal to 1,000

Greater than 1,000

MEDIAN ACTIVITY (picocuries per liter)

Land use generally does not affect

1 2 3-4 5 6-7

28

30

48

29

30

than 1,000 pCi/L) were measu

ground water in subunits unde

limestone. The median activity 

ground water in the subunit un

by sandstone and shale also wa

than 1,000 pCi/L; however, the 

mum activity was higher than 

maximum activity in any of th

units underlain by limestone. L

generally does not affect radon 

Although the ground water 

areas has higher activities of ra

ative to other areas, the only w

sure of the radon activity in wa

a well is to have it tested. In ho

where high indoor radon levels 

measured and where water is s

by a well, the USEPA recomm

testing well water as a potentia

tributing source of radon. For e

10,000 pCi/L of radon in wate

1 pCi/L of radon is released to 

in addition to any airborne rad

may enter a home through the 

ment (only 1 of the 165 ground

samples contained greater than 

pCi/L of radon). If a large perc

of the radon in the house is fro

water, the USEPA recommend

installation of a water-treatmen

tem to remove radon be consid

Homes and water supplies both 

treated to reduce radon levels.

radon activity. For this analysis, landuse types were grouped as follows:

subunits 3 and 4 were combined,

subunits 6 and 7 were combined,

subunit 1 includes 7 samples from

forested and mixed land uses.

SUBUNIT

1 - Piedmont crystalline agricultural

2 - Piedmont limestone agricultural

3 - Great Valley limestone agricultural

4 - Great Valley limestone urban

5 - Appalachian Mountain limestone

6 - Appalachian Mountain sandstone

 and shale agricultural

7 - Appalachian Mountain sandstone

agricultural

and shale forested

The activities of radon in ground water were varied but followed general patterns according

to bedrock type.

BOXPLOT

100,000
18 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

MAJOR ISSUES AND FINDINGS—

Trace Elements in Fish Tissue and Streambed Sediment

Streambed sediments and liver tissues of fish were analyzed for selected

trace elements. Trace-element analyses were not done for ground water or

surface water. Trace elements are

present naturally in water and sediments at concentrations that depend on

the type of rock where sediments originate (Hainly and others, 1994).

Concentrations can be elevated above

natural levels as a result of discharges

from wastewater-treatment plants,

industrial activity, or mining. Sediment samples from 21 sites were

analyzed. Livers from bottom-feeding

fish (white sucker) from 20 sites also

were analyzed. Livers from bottomfeeding fish species (white sucker) and

predator fish species (smallmouth bass)

were collected at 3 of the 20 sites.

Streambed sediments were analyzed

for 27 trace elements; 24 were

detected. Liver tissues of fish were analyzed for 22 trace elements; 18 were

detected.

Human-health issues were not the

focus of the trace-element studies.

Because trace-element concentrations

were determined only for fish livers

and not for edible portions, no statements about suitability of fish for

human consumption can be made. The

U.S. Food and Drug Administration

(FDA) action level for mercury is

1 part per million in the edible portion

(fillets) of fish. Mercury concentrations

in fish livers at four sites were close

enough to the FDA action level to suggest a need for further study of

mercury. Liver tissue from smallmouth

bass in the Susquehanna River at Danville and the West Branch Susquehanna

River at Lewisburg and white sucker in

Codorus Creek and the Frankstown

Branch Juniata River had mercury concentrations that ranged from 0.5 to

0.7 part per million.

Correlations were found between the

concentrations in streambed sediments

and the concentrations in livers of bottom-feeding fish for only 3 of 11

elements regarded as common contaminants. Arsenic, chromium, copper,

lead, mercury, nickel, selenium, and

zinc were not significantly correlated.

Concentrations of cadmium, silver, and

vanadium in livers from white sucker

and the concentrations of these trace

elements in streambed sediments were

correlated. Although these associaaffected by mine drainage. Stre

sediment from the Susquehann

at Danville had high to modera

high concentrations of all of th

ments. Tributaries such as the 

Branch of the Susquehanna Ri

Mahanoy Creek are affected b

drainage and have the highest 

trations of beryllium, cadmium

manganese, nickel, and zinc. T

est concentrations of lead were 

on Codorus Creek and Quittap

Creek downstream from urban 

industrial areas. Lead is also p

high concentrations in streamb

ment from Mahanoy Creek. Se

from some sites in basins in th

mont Physiographic Province t

no industrial or mining activity 

contained elevated concentrati

nickel, indicating that the bedr

that area may be a natural sour

nickel.

To better understand transpo

trace elements to the Susqueha

River from a tributary affected 

drainage, Study Unit personne

lected samples from Mahanoy 

including streambed sediment

coatings on rock surfaces, and 

sue from white suckers— and a

all these substances for trace e

(Breen and Gavin, 1995). Mos

elements being transported dow

stream were in the form of sus

particles or colloids. The coati

rock surfaces contained high c

trations of trace elements, and 

coatings could be dislodged fr

rock surfaces during storms. C

tions showed that the transport 

elements dislodged from rock 

during a storm would be small 

to the daily transport from susp

particles and colloids.

tions do not imply direct cause and

effect relations, they may indicate that

these elements travel pathways through

the aquatic system in a manner different

from the other elements.

Trace-element concentrations in liver

tissue from a predator species (smallmouth bass) and a bottom-feeding

species (white sucker) were determined

for samples from three sites. The liver

tissue of smallmouth bass had higher

concentrations of aluminum, cobalt,

iron, mercury, selenium, strontium, and

vanadium. The liver tissue of white

sucker had higher concentrations of

copper, manganese, and silver. These

differences indicate that the two fish

species may have different bioaccumulation mechanisms for these elements.

The bioavailability of trace elements

in the sediments is not clearly understood but is known to depend on such

local factors as concentration of dissolved solids and dissolved organics,

pH, hardness, and sediment load, which

also influence the prevailing chemical

forms of trace elements in aquatic systems (Neilson, 1994). Therefore, the

trace elements present in the streambed

sediment may not have been bioavailable for uptake by fish. Moreover, the

sediment samples may not have been

collected in that part of the stream

channel where the fish were most

actively in contact with the streambed.

These factors may help explain the lack

of correlation between the concentrations detected in streambed sediments

and the concentrations of the same element detected in the liver tissue of fish.

The highest concentrations of

arsenic, beryllium, cadmium, cobalt,

iron, manganese, nickel, selenium, and

zinc in streambed sediment were at sites

Livers were removed

from fish and analyzed

for trace elements.
U.S. Geological Survey Circular 1168 

MAJOR ISSUES AND FIND

Pesticides and Other Organic Compounds in Fish Tissue and Streambed S

Organochlorine Pesticides and

PCBs in Fish Tissue

Some pesticides and organic compounds were in widespread use for

nearly 40 years until banned or

restricted in the 1970’s and 1980’s

(Smith and others, 1988), when it was

learned that many of these compounds

are toxic and also accumulate in the

food chain. These compounds include

organochlorine pesticides (such as

DDT and chlordane) and polychlorinated biphenyls (PCBs, formerly used

as electrical insulators). Because of the

low chemical reactivity, resistance to

oxidation, and resistance to other

degenerative processes, residues of

these compounds have been shown to

be persistent in the environment (Great

Lakes Basin Commission, 1975).

These compounds generally are not

soluble in water but can accumulate in

the tissues of organisms that live in the

water. As a result, tissue samples of

fish are collected and analyzed for the

presence of these compounds.

Twenty sites were sampled from

1992 to 1995 to determine the occurrence and distribution of selected

organochlorine compounds. Wholebody tissue samples of white sucker

were collected at 19 of the 20 sites and

Contaminants on the land surface can be washed into streams, commonly attached 

sediment. The contaminants can enter the food chain and bioaccumulate in predato

1. Contaminants

are washed

into stream

with sediment.

2. Bottom-feeding fish and

aquatic invertebrates

bioaccumulate contaminants.

3. Predator species of fish

and fish-eating wildlife

consume prey that

have taken up

contaminants.

tion, Pennsylvania Fish and Bo

Commission, and Pennsylvania

Department of Health) reviewe

data collected by the USGS, co

the data to FDA action levels, 

cluded that no public-health ad

were warranted for the fish spe

(white sucker or smallmouth b

lected at any of the sampling s

Concentrations in the whole bo

fish and the edible portions (fil

not directly comparable. Neve

the FDA action level for huma

sumption for total chlordane

[300 μg/kg (micrograms per k

gram)], total DDT (5,000 μg/k

(U.S. Food and Drug Adminis

1992), or total PCBs (2,000 μg

(U.S. Food and Drug Adminis

1995) in the edible portion wa

exceeded in the whole-body ti

any of the sample locations. T

lection of whole fish and fillet 

future studies would aid in ide

problem sites and evaluating th

for fish-consumption advisorie

PCBs in fish tissue were ass

with urban and industrial land 

The organochlorine pesticides 

their degradation products in fi

tissue showed an association w

cultural land use. Organochlor

concentrations detected in fish 

were evaluated in terms of the 

land uses present in the basin (

tural, forested, urban) as show

smallmouth bass were collected at 5

sites. Organic compounds were

detected in whole-body fish tissue and

the streambed sediment at all 20 sites

sampled, which represented a variety of

settings. Of the 28 compounds analyzed

for, 12 were detected.

Although some of the detected compounds are known human-health risks,

an interagency work group on fishtissue contaminants (composed of representatives of the Pennsylvania

Department of Environmental ProtecOrganochlorine pesticides (many of which are now banned) are persistent in the environment.

Trace amounts are present in streambed sediment and fish. Fish are collected for study by a

team of biologists using equipment like this barge-mounted electroshocker. (Photograph by

Steven F. Siwiec, U.S. Geological Survey.)
20 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

MAJOR ISSUES AND FINDINGS—

Pesticides and Other Organic Compounds in Fish Tissue and Streambed Sediment

graph below. The two sites representing basins with a mixture of

agricultural, urban, and industrial land

uses had the highest concentrations of

total PCBs, total DDT, and total chlordane. DDT and chlordane were

associated with the highest percentages of agricultural land use. Tissue

samples from sites whose drainage

included the greatest percentage of

urban land use, although never a dominant land use, had higher total PCB

concentrations than those at sites

downstream from less urban use. Samples from sites categorized as forest

dominant (greater than 50 percent of

the basin area forested) had the lowest

number of detectable organochlorine

compounds and the lowest concentrations overall.

The fish-tissue data indicate that

DDT and chlordane have degraded

over time and that no recent influx of

these compounds has occurred. Organochlorine pesticides such as DDT and

chlordane degrade in the environment

over time into a series of breakdown

products called metabolites. The most

persistent metabolite of DDT—

p,p’- DDE—made up about 50 percent

of the total DDT detected in fish tissue.

Because the metabolite p,p’- DDE is

the most persistent, it can be expected

to be the major metabolite present late

in the degradation process. The high

percentage of p,p’- DDE indicates no

recent influx of total DDT within the

basin. Concentrations of two components of total chlordane, cis-chlordane

and trans-nonachlor, were the highest

among the chlordane components

detected in fish tissue. These are the

most abundant and persistent components of chlordane. The high

concentrations of more persistent components indicate that degradation has

taken place.

Synthetic Organic Compounds

in Streambed Sediment

At four sites, concentrations of total

DDT or total chlordane in streambed

sediment exceeded USEPA Tier 1

guidelines for protection of aquatic life

(U.S. Environmental Protection

Agency, 1996b). Tier 1 guidelines for

total PCBs were not exceeded at any of

the sites. Of the 32 compounds analyzed for, 15 were detected. The

highest concentrations were for metabolites of DDT and components of total

chlordane, more specifically, the concentrations of the p,p’- forms of DDD,

DDE, and DDT, trans-nonachlor, and

cis-nonachlor. Further analysis of the

data shows a strong correlation

between the concentrations of these

compounds and PCBs in the streambed

sediments and whole-fish tissues, indicating the possibility of a direct

contaminant pathway. For example,

the highest concentrations of total

DDT and chlordane in streambed sediments were in Quittapahilla Creek.

The fish-tissue samples at that site also

had the highest concentrations of DDT

and chlordane. Codorus Creek had the

highest concentrations of total PCBs in

both streambed sediment and fish

tissue.

The concentration patterns 

streambed sediment and fish ti

with respect to land use were s

(see graph below). Sites repres

basins with agricultural and m

urban and industrial land use h

highest concentrations of total 

total DDT, and total chlordane

representing basins with the hi

percentage of agricultural land 

showed the highest concentrat

total DDT and total chlordane

representing basins with the gr

percentage of urban and indust

use (though never dominant) h

highest concentrations of total 

Streambed sediments from the 

dominated sites had the lowest 

trations of all organochlorine

compounds and PCBs.

At most sites where DDT w

detected, the DDE/DDT ratio 

greater than 1, indicating long

degradation of the DDT. At on

FORESTED AGRICULTURAL AGRICULTURAL

LAND USE IN BASIN AND NUMBER OF SITES

0

2,000

500

1,000

1,500

0

1,200

200

400

600

800

1,000

MEDIAN CONCENTRATIONS IN FISH TISSUE AND STREAMBED SEDIMENT,

0

100

20

40

60

80

FISH (WHITE SUCKER)

STREAMBED SEDIMENT

AND INDUSTRIAL

TOTAL DDT TOTAL TOTAL PCBs

4 MIXED WITH

10 2

CHLORDANE

MIXED WITH URBAN

Median concentration

total organochlorine

pesticides and total P

white sucker tissue a

streambed sediment 

grouped by the predo

land use in the basin 

illustrate the effects o

use.

Sites representing ba

with a mixture of

agricultural, urban, a

industrial land uses h

highest concentration

total PCBs, total DDT

total chlordane. PCB

concentrations were

associated with the h

percentages of urban 

use, and DDT and

chlordane were asso

with the highest

percentages of agric

land use.

IN MICROGRAMS PER KILOGRAM

(3 large river sites

FORESTED not included)
U.S. Geological Survey Circular 1168 

MAJOR ISSUES AND FIND

Pesticides and Other Organic Compounds in Fish Tissue and Streambed S

the 21 sites did concentrations of DDT

in the sediment and DDE/DDT ratios

indicate a recent influx of DDT. At six

of the sites, data were available to

compare concentrations of organic

compounds in sediment detected in

1974 (Hollowell, 1975) to the concentrations detected in the 1992-95

NAWQA survey. At most of these

sites, total DDT and total chlordane

concentrations declined between 1974

and 1995. The concentrations of the

most persistent metabolite—p, p’-

DDE— increased at most of these

sites, illustrating the continued degradation of DDT. Concentrations of total

DDT and total PCBs increased significantly at the Codorus Creek site,

indicating a recent influx of these contaminants. This is also one of the sites

where the DDE/DDT ratio indicated a

recent influx of DDT. The evidence of

a recent influx of DDT at the Codorus

Creek site or the other two sites was

not apparent from the analysis of DDT

in fish tissue.

Concentrations of semivolatile

organic compounds (SVOCs) in

streambed sediment exceeded USEPA

Tier 1 guidelines for protection of

aquatic life at 4 of the 21 sites. All the

SVOCs that exceeded the guidelines

were polycyclic aromatic hydrocarbons (PAHs), a group of organic

compounds that result from incomplete combustion of fossil fuels, wood,

and municipal solid waste or are

present naturally in coal. A nationwide

study using NAWQA data (Lopes and

others, in press) showed concentrations of PAHs were strongly correlated

with population density, urban land

use, and toxic releases to the air.

The sites where concentrations of

PAHs exceeded Tier 1 guidelines

include Quittapahilla Creek and

Codorus Creek. These basins have

agricultural land mixed with urban and

FORESTED AGRICULTURAL AGRICULTURAL

LAND USE IN BASIN AND NUMBER OF SITES

0

1,200

200

400

600

800

1,000

 MEDIAN CONCENTRATIONS IN STREAMBED SEDIMENT,

0

500

100

200

300

400

STREAMBED SEDIMENT

AND INDUSTRIAL

SUM OF PHENOLS SUM OF PHTHALATES

4 MIXED WITH

11 2

MIXED WITH URBAN

Median concentrations for

the sum of PAHs, phthalates,

and phenols for streambed

sediment are grouped by the

predominant land use in the

basin to illustrate the effects

of land use.

Sites representing basins

with a mixture of agricultural,

urban, and industrial land

uses had the highest

concentrations of PAHs,

phthalates, and phenols.

IN MICROGRAMS PER KILOGRAM

(4 large river sites

FORESTED

industrial land use (see graph b

and also have the highest conce

tions of PCBs, DDT, and chlor

streambed sediment and fish tis

Concentrations of PAHs also e

guidelines at Swatara Creek, w

drains an area of significant co

ing activity, and at the Susqueh

River at Conowingo Reservoir.

The sum of PAHs was well a

the NAWQA medians even at s

little urban, industrial, or minin

use. The proximity of the Study 

major metropolitan areas of the 

eastern United States is a proba

explanation for this fact becaus

are also distributed regionally b

spheric deposition. The sum of

phthalates also was higher than 

national NAWQA median at al

sites. Phthalates are commonly 

industrial sources. The sum of 

ranged from well below the nat

median to well above the natio

median. Phenols are used in in

agricultural, and sanitation acti

and also can occur naturally.

0

20,000

5,000

10,000

15,000

SUM OF PAHs

not included)
22 Water-Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

MAJOR ISSUES AND FINDINGS—

Biological Communities and Stream Habitat

The fish community and the stream

habitat were evaluated at selected

reaches in each of the seven long-term

monitoring basins (see map on page 7)

to determine the distribution of fish

populations and the relations of fish

populations to stream habitat (Bilger

and Brightbill, in press). Studies of

fish-community composition were

done annually from June 1993 to June

1995. As with other parts of the

NAWQA study, each basin represented

an environmental subunit. Environmental characteristics for the selected

reaches consisting of instream and

riparian habitat, hydrology, and water

quality were determined.

A total of 33,143 fish were collected

from the 28 samples from multiple

reaches in the 7 basins during the

3-year intensive sampling period from

1993 to 1995. Thirty-nine species were

collected from eight families. The

Cyprinidae (minnows) were represented by the greatest number of

species (17), followed by the Centrarchidae (sunfishes) with 7 species,

and by the Percidae (perches and darters) with 4 species. The most abundant

and frequently collected species were

the blacknose dace, white sucker, and

mottled and slimy sculpins. Together,

these species made up 49 percent of

the total fish collected. Statistical analysis determined that the composition

of fish communities for each stream

did not differ between years and multiple reaches.

Fish communities inhabiting the

seven streams were related to the bedrock type. Limestone and dolomite

bedrock are associated with limestone

streams (see table on page 6). Sandstone, shale, and crystalline rocks are

associated with freestone streams (see

table on page 6). Limestone streams

were located in valley areas and

receive much of their flow from large

springs (Shaffer, 1991). Limestone

springs discharge cool water to the

stream throughout the year. The limestone (calcium carbonate) dissolved in

the spring water provides for a stable

pH. These factors make the conditions

favorable for sensitive fish such as

trout species. Limestone streams are

known for naturally low numbers of

fish species and high abundances of

aquatic plants and invertebrate life.

The valuable limestone farmland is

commonly cultivated to the edge of the

streambank, leaving little or no riparian vegetation (canopy cover). This, in

turn, affects water temperature. Agricultural areas with little or no riparian

buffers can also have increased

sedimentation.

Freestone streams tend to b

from runoff and by small feed

streams and gain water a little 

time. The flow and temperatur

these streams is more variable

stone streams do not have as m

dissolved calcium as the limes

streams and are vulnerable to c

in pH. These streams also tend 

off ridges and through areas w

topography, making the riparia

less likely to be cultivated. Alt

freestone streams do not have t

springs discharging to the stre

absence of alterations to the ri

habitat is favorable for fish

communities.

The habitat characteristics 

proved most influential in defin

communities in the seven long

monitoring basins were mean 

width, mean water temperatur

canopy angle, and suspended 

ment. These four variables com

accounted for about 79 percen

variation in the stream habitat-

relation.

Fish are sensitive to water t

ture. Warm-water streams supp

different fish communities tha

water streams. Streams with m

Limestone streams, like Bachman Run (left), are supplied by springs that have nearly constant ambient

temperatures throughout the year. Agriculture is a

dominant land use that can degrade habitat conditions

by reducing riparian vegetation and increasing sedimentation. Habitat degradation can offset the natural

benefits of having a supply of cool water from springs

Freestone streams, such as Stony Creek (right), tend

to be supplied by runoff from small streams that flow

off ridges. Riparian vegetation provides favorable

habitat conditions by shading the stream and reducing sedimentation.
U.S. Geological Survey Circular 1168 

MAJOR ISSUES AND FIND

Biological Communities and Stream 

Other Ecological Indicators

In summary, the overall ecological condition of the Lower Susquehanna River Basin appears to represe

good water quality for aquatic life and low contaminant levels. In addition to analyses of the fish communi

preliminary analysis of benthic-invertebrate communities collected and analyzed at the seven long-term

monitoring sites are mostly indicative of the natural conditions that would be expected. For example, hea

water limestone streams have fewer species than larger freestone streams. No sites had benthicinvertebrate communities that indicated adverse effects from water quality. Examination of long-term re

rospective data generated by local regulatory agencies confirms that ecological conditions in the basin a

improving. Sensitive water-quality indicators such as mayflies are now considered a local nuisance spe

cies at nighttime sporting events along the Susquehanna River at Harrisburg, Pa.

The Susquehanna Rive

Rockville Bridge at Mar

Pa., looking west. (Rep

from Alan R. Wycheck 

published with permiss

water temperatures have species found

in both the cooler and warmer streams.

Canopy angle and channel width,

which affect water temperature, influence the fish species that are able to

inhabit a stream. Canopy angle determines the amount of sunlight that

reaches the stream surface. A wide

stream can have a well-established

riparian zone, but the canopy cannot

shade the entire stream; thus, the water

temperature is typically higher than for

a smaller stream with the same type of

riparian zone.

Fish were sensitive to suspended

sediment; therefore, erosional bank

conditions also influenced fish communities. Steep, high banks with little

vegetative cover have a greater chance

of erosion during storms than lower

banks with more vegetation. Banks

consisting of finer sediment are more

erodible than banks that consist of cobbles and boulders. The more tolerant

fish species were present at sites that

were warmer and where the banks

were more eroded than at sites that

were cooler and had more stable

banks. These factors also influence the

amount of oxygen in the stream water.

Fish with high oxygen demands typically thrive in cooler waters with little

to no erosion and with fairly high oxygen concentrations. Fish with lower

oxygen demands can live in warmer

waters where lower oxygen concentrations are common.

The health or general condition of

the fish community was determined by

examining the populations of pollution-tolerant and -intolerant species,

the numbers of nonnative species, the

percentage of omnivores, and the percentage of individuals with external

anomalies. The assessment of the fish

community, based on these factors,

showed that fish populations were

healthier in the three freestone streams

than in the four limestone streams.

This may be the result of a number of

interrelated factors, such as rip

vegetation and canopy angle, w

affect temperature and sedime

The intense agricultural activit

limestone areas can have an in

on the fish community. The infl

of agriculture on fish commun

related to habitat degradation 

than nutrients in the water. Th

stone agricultural settings appe

adversely affect the fish comm

many ways. Although limeston

streams have many characteris

would support a healthy fish p

tion, changes in the land use a

the stream can adversely affec

native fish populations (Shaffe

The limestone agricultural stre

chosen for this study were cho

assess the effects of intense ag

tural activity and do not repres

fish populations of all limeston

streams.
24 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95.

Susqueh

Kishacoquillas

Creek (5)

Bobs Creek

(7) Cedar

Run (4)

East

Mahanta

Creek (6

Ba

Ru

Mu

Cr

WATER-QUALITY CONDITIONS IN A NATIONAL CONTEXT

Comparison of Stream Quality in the Lower Susquehanna River Basin

with Nationwide Findings

Seven major water-quality characteristics were evaluated for stream sites in each

NAWQA Study Unit. Summary scores for each characteristic were computed for al

that had adequate data. Scores for each site in the Lower Susquehanna River Basin 

compared with scores for all sites sampled in the 20 NAWQA Study Units during 1

Results are summarized by percentiles; higher percentile values generally indicate p

quality compared with other NAWQA sites. Water-quality conditions at each site al

compared to established criteria for protection of aquatic life. Applicable criteria are 

to nutrients and pesticides in water and semivolatile organic compounds, organochlo

pesticides, and PCBs in sediment. (Methods used to compute rankings and evaluate 

life criteria are described by Gilliom and others, in press.)

NUTRIENTS in water

Comparisons of scores based on nitrate, phosphorus, and ammonia

concentrations in streams showed that the agricultural and urban sites 

among the highest of all NAWQA Study-Unit sites (above the 75th per

Animal manure and fertilizer are the primary sources of the nitrogen. 

forested site was above the 25th percentile nationally, which may be re

atmospheric deposition of nitrogen or the small part (less than 15 perc

the basin in nonforested land use.

PESTICIDES in water

The scores based on total herbicide concentrations and total insectic

concentrations were higher than the national median at the two agricu

sites. The score for total herbicides and total insecticides was slightly 

than the national median at the urban site.

ORGANOCHLORINE PESTICIDES and PCBs in streambed

sediment and biological tissue

Comparison of scores based on total PCBs and organochlorines in fi

and streambed sediment showed two of the agricultural sites to be amo

highest of all NAWQA Study-Unit sites; the other three agricultural si

between the median and 75th percentile. The Pennsylvania interagenc

group composed of key agencies compared the data to FDA action lev

concluded that there was no evidence of concentrations in fish tissue t

would warrant human-health advisories for fish consumption. Althoug

persistent, the major compounds detected showed signs of degradation

of the five long-term monitoring sites shown here exceeded the USEPA 

sediment guidelines for total DDT, total chlordane, or total PCBs. Two 

long-term monitoring sites did not have sufficient sediment or target fi

species for sample collection.

Susquehan er n v a Ri

Harrisburg

Lancaster

York

Susquehan er n v a Ri

Harrisburg

Lancaster

York

Susquehan er n v a Ri

Harrisburg

Lancaster

York

Surface-water long-term monitoring sit

subunit numbers

RANKING OF STREAM QUALITY RELATIVE TO ALL NAWQA STREAM SITES—Darker colored

circles generally indicate poorer quality. Bold outline of circle indicates that one or more aquatic life

criteria were exceeded.

Greater than the 75th percentile

(among the highest 25 percent

of NAWQA stream sites)

Between the median and the

75th percentile

Between the 25th percentile

and the median

Less than the 25th percentile

(among the lowest 25 percent

of NAWQA stream sites)

EXPLANATION
U.S. Geological Survey Circular 1168 

WATER-QUALITY CONDITIONS IN A NATIONAL CO

Comparison of Stream Quality in the Lower Susquehanna Rive

with Nationwide F

TRACE ELEMENTS in streambed sediment

Scores based on trace-element concentrations in streambed sediments at the

five long-term monitoring sites where sediment was collected were above the

national median for all NAWQA Study Unit sites. The concentrations of trace

elements in sediment were not well correlated with concentrations in fish liver

tissue for 8 of the 11 trace elements, indicating that the elements in the

sediment may not have been bioavailable.

SEMIVOLATILE ORGANIC COMPOUNDS (SVOCs) in streambed

sediment

Comparison of SVOCs showed that the concentrations of phthalates, PAHs,

and phenols at two of the sampling sites were among the highest of all

NAWQA Study-Unit sites. Concentrations at the three other sites were above

the national median. None of the long-term monitoring sites sampled exceeded

the USEPA Tier 1 guidelines for SVOCs in streambed sediment.

STREAM-HABITAT DEGRADATION

Stream-habitat scores at six of the seven sites were ranked between the 25th

and 75th percentile nationally. Bachman Run had the poorest stream-habitat

score because of high bank erosion and minimal vegetative bank stability; it

was ranked as one of the most degraded of all NAWQA Study-Unit sites.

FISH-COMMUNITY DEGRADATION

Fish communities at five of the seven sites were ranked between the 25th

and 75th percentile nationally. East Mahantango Creek exhibited a diverse and

healthy fish community and was ranked as having one of the least degraded

fish communities of all NAWQA Study-Unit sites. The fish community at Mill

Creek scored poorly because of the high percentage of pollution-tolerant and

omnivorous species and the high incidence of anomalies; it ranked among the

poorest of all NAWQA Study-Unit sites.

Susqueh

Harrisburg

La

York

Susqueh

Harrisburg

La

York

Susque

Harrisburg

La

York

Susque

Harrisburg

La

York

CONCLUSIONS

In the Lower Susquehanna River Basin Study Unit, compared to the other NAWQA study units:

• Nutrient concentrations in streams are high and, in agricultural areas, often would exceed drinking-water standar

the water was not filtered and treated before use as a public-water supply.

• Pesticide concentrations are near the national median but would rarely exceed drinking-water standards.

• Concentrations of PCBs and organochlorine pesticides in fish tissue at some sites are among the highest; howeve

interagency work group concluded that no human-health advisories for fish consumption were warranted.
26 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95.

WATER-QUALITY CONDITIONS IN A NATIONAL CONTEXT

Comparison of Ground-Water Quality in the Lower Susquehanna River Basin

with Nationwide Findings

RANKING OF GROUND-WATER

QUALITY RELATIVE TO ALL NAWQA

GROUND-WATER STUDIES—Darker

colored circles generally indicate poorer

quality. Bold outline of circle indicates

one or more standards or criteria were

exceeded

Harrisburg

Lancaster

York

Harrisburg

Lancaster

York

NITRATE

Nitrate concentrations in agricultural areas underlain by limesto

rock were among the highest of all NAWQA Study Units, and num

drinking-water samples exceeded the drinking-water standard for 

Ground water in the subunits underlain by crystalline bedrock also 

high nitrate concentrations. Ground water in the urban subunit and 

unit underlain by sandstone and shale had nitrate concentrations c

the median when compared to all subunits representing drinking-w

aquifers in all NAWQA Study Units.

Agriculture (5)

Agriculture (3)

Agricu

A

Fores

Urban 

Mixed

Appalachian Mountain

Piedmont crystalline

Piedmont limestone

Appalachian Mountain

Great Valley limestone

Great Valley limestone

EXPLANATION

All of these subunits represent both

1

2

3

4

5

6,7

SUBUNIT SUBUNIT NAME

NUMBER

Five major water-quality characteristics were evaluated for ground-water studies in 

NAWQA Study Unit. Ground-water resources were divided into two categories:

(1) drinking-water aquifers, and (2) shallow ground water underlying agricultural o

areas. Summary scores were computed for each characteristic for all aquifers and sh

ground-water areas that had adequate data. Scores for each aquifer and shallow groun

area in the Lower Susquehanna River Basin were compared with scores for all aqui

shallow ground-water areas sampled in the 20 NAWQA Study Units during 1992–95

are summarized by percentiles; higher percentile values generally indicate poorer qu

compared with other NAWQA ground-water studies. Water-quality conditions for e

drinking-water aquifer also are compared to established drinking-water standards and 

for protection of human health. (Methods used to compute rankings and evaluate sta

and criteria are described by Gilliom and others, in press.)

Ground-water subunits for Land-use Studies an

Surveys

Greater than the 75th percentile

Between the median and the

Between the 25th percentile

Less than the 25th percentile

Insufficient data for analysis

RADON

Radon activities in limestone and crystalline subunits in the Pie

Physiographic Province were among the highest of all NAWQA S

Units. Activities in the remaining subunits were slightly above the 

percentile when compared to other subunits representing drinking

aquifers in all NAWQA Study Units.

75th percentile

and the median

shallow ground-water areas and drinkingwater aquifers. For national comparison

purposes, these subunits were compared

to the summary scores from other drinkingwater aquifers.

(mixed land use)

agricultural

agricultural

urban

limestone agricultural

sandstone and shale

(mixed land use)

(among the highest 25 percent

of NAWQA ground-water studies)

(among the lowest 25 percent

of NAWQA ground-water studies)
U.S. Geological Survey Circular 1168 

DISSOLVED SOLIDS

Scores based on concentrations of dissolved solids were above the

50th percentile for all of the subunits underlain by limestone. The subunits

underlain by crystalline bedrock and the subunit underlain by sandstone

and shale had scores for dissolved solids that were among the lowest of all

the subunits representing drinking-water aquifers in all NAWQA Study

Units.

Harrisburg

Lancas

York

Harrisburg

Lancas

York

VOLATILE ORGANIC COMPOUNDS (VOCs)

Scores based on the frequency of detections of VOCs in the Great Valley

limestone urban subunit and the Piedmont limestone agricultural subunit

were among the highest of subunits representing drinking-water aquifers in

all NAWQA Study Units; however, the frequency of detection was much

higher in the urban subunit. No VOCs were detected in the subunits in the

Appalachian Mountains, which is the more rural part of the Study Unit.

The Piedmont crystalline subunit and Great Valley carbonate agricultural

subunit also had scores that indicated a low frequency of detections of

VOCs when compared to national data.

Harrisburg

Lancas

York

PESTICIDES

Pesticides were detected frequently in all the subunits except for the

Appalachian Mountain sandstone and shale subunit. The limestone agricultural, limestone urban, and crystalline agricultural subunits were ranked

as having some of the highest pesticide-detection frequencies of subunits

representing drinking-water aquifers in all NAWQA Study Units; however,

none of the detections of pesticides in water from any of the wells sampled

exceeded drinking-water standards.

CONCLUSIONS

In the Lower Susquehanna River Basin Study Unit, compared to the other NAWQA study units:

• Nitrate concentrations in waters from household wells in agricultural subunits underlain by limestone are some o

highest and represent a human-health concern.

• The number of pesticide detections was high for subunits underlain by limestone and crystalline bedrock. Pestici

concentrations did not exceed USEPA MCLs for drinking water.

WATER-QUALITY CONDITIONS IN A NATIONAL CO

Comparison of Ground-Water Quality in the Lower Susquehanna Rive

with Nationwide F
28 Water-Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

STUDY DESIGN AND DATA COLLECTION

0

0

50 MILES

50 KILOMETERS

10 20 30 40

10 20 30 40

41°00' 78°30' 76°00'

39°30'

EXPLANATION

SITE TYPE

Synoptic sites with

long-term basins

Basinwide or subu

synoptic site

Long-term monitor

basic sites

Long-term monitor

intensive sites

EXPLANATION

Basic or intensive 

of biological com

and stream habit

Synoptic studies o

biological

communities and

stream habitat

Fish tissue or strea

sediment

SITE TYPE

EXPLANATIO

Piedmont limest

agricultural (2)

Great Valley lime

agricultural (3)

Appalachian Mo

limestone agric

Appalachian Mo

sandstone and 

Great Valley

limestone urba

Piedmont crysta

(mixed land us

SUBUNIT NAME

AND NUMBER

Urban land-use 

Subunit survey

Agricultural

land-use stud

SITE TYPE

An overview of data collection is presented here. For details on the design and implementation of the study, see Siwie

others (1997).

Stream-Water Chemistry

Long-term monitoring sites were

sampled periodically to determine the

occurrence and seasonal variability of

contaminants. To determine shortterm occurrence and distribution of

concentrations over a broad-scale

area, synoptic studies were of three

designs: (1) basinwide, to define concentrations and loads of selected constituents during periods of seasonal

herbicide application; (2) within the

subunits, to determine the spatial variability in constituent concentrations

and to evaluate the representativeness

of the long-term monitoring site; or

(3) within long-term monitoring-site

basins, to describe spatial variability

in water quality due to point and nonpoint influxes of constituents.

Biological Communities,

Stream Habitat, and

Contaminants in Fish

Tissue and Streambed

Sediment

Ecological assessments included

analysis of stream habitat, fish communities, invertebrates, and algae.

Contaminants in streambed sediment

and fish tissue were analyzed at sites

on the main stem, major tributaries,

and selected smaller tributaries to

determine the occurrence and distribution of contaminants. Data on invertebrate communities and algae have not

been analyzed and are not included in

this report.

Ground-Water Chemistry

The wells shown represent three

agricultural land-use studies, one

urban land-use study, and two subunit

surveys. Most of the wells sampled

were less than 200 feet deep. Samples

from these wells generally contain

water that has infiltrated through the

ground in recent years and therefore

could be used to indicate whether

land-use practices have affected

ground-water quality. All of the aquifers sampled are used for drinkingwater supply.
U.S. Geological Survey Circular 1168 

STUDY DESIGN AND DATA COLL

SUMMARY OF DATA COLLECTION IN THE LOWER SUSQUEHANNA RIVER BASIN STUDY UNIT, 1992-95

Study component (number of sites) Types of sites sampled Sampling freq

What data were collected and why and perio

Stream-Water Chemistry

Long-term monitoring, basic sites (4)

Occurrence and seasonal variability of concentrations. Data included streamflow,

nutrients, major ions, organic carbon, suspended sediment, water temperature,

specific conductance, pH, and dissolved oxygen. In addition, 47 dissolved pesticides during synoptics and, at the site in subunit 4, 47 dissolved pesticides during

base flow and selected stormflow events.

Streams draining basins ranging from

7.72 to 71.9 square miles representing four subunits (1, 3, 5, and 7).

Monthly plus storms

Apr. 1993 – Aug. 

One site semimonth

monthly plus stor

Nov. 1994 – Aug

Long-term monitoring, intensive sites (3)

Occurrence and seasonal variability of concentrations—Data included all of the

above constituents plus 84 dissolved pesticides in all routine base-flow samples

plus selected storm samples until Sept. 1994. Data collected through Aug. 1995

at the site in subunit 4 included 47 dissolved pesticides in base-flow and selected

stormflow events. Six samples for volatile organic compounds analysis were collected at the site in subunit 4.

Streams draining basins ranging from

12.6 to 54.3 square miles representing three subunits (2, 4, and 6).

Weekly: Apr. – Sept

Semimonthly to mon

Oct. 1993 – Sept. 

One site semimonth

monthly plus stor

Nov. 1994 – Aug

Synoptic studies (187)

Short-term occurrence and distribution of concentrations were studied over a broadscale area—synoptic studies were of three designs: (1) basinwide; (2) within the

subunits; or (3) within long-term monitoring site basins. Data included streamflow, nutrients, pesticides, major ions, suspended sediment, water temperature,

specific conductance, pH, dissolved oxygen, and volatile organic compounds

(five sites in subunit 4) during low-flow conditions.

Main-stem and tributary sites for the

synoptics done in the late spring and

early summer during periods of seasonal herbicide application. For

other synoptics, sites on streams

draining basins representing the

seven subunits.

Summers of 1993, 1

1995. Most sites w

pled once. Selecte

were sampled two 

times as part of se

synoptic studies.

Biological Communities, Stream Habitat, and Contaminants in Fish Tissue and Streambed Sediment

Basic and intensive assessments (7)

Structure and function of major aquatic communities—algae, fish, and invertebrates—in three habitats (richest, depositional, and multiple) at each site; quantitatively describe habitat.Long-term monitoring sites from

stream-water chemistry component

of the study design. The three intensive long-term monitoring sites were

used for multiple-reach sampling.

One reach per site ea

1993, 1994, and 1

Two additional reach

sites in 1994.

Three additional rea

one site in 1994.

Synoptic studies (45)

Structure and function of selected aquatic communities—algae and invertebrates—in two habitats (richest and multiple) at each site; quantitatively describe

habitat. Sites were chosen to match ecological surveys by other agencies in the

1970’s and 1980’s.

Sites on main stem, major tributaries,

and selected smaller tributaries. Sites

represented selected subunits and

mixed land uses.

Once during 1993-9

Contaminants in fish tissue (20)

Occurrence and spatial distribution of concentrations of contaminants—total PCBs,

27 organochlorine pesticides, and 22 trace elements—in fish tissue (white sucker

and smallmouth bass). Whole fish were analyzed for organic contaminants; fish

livers were analyzed for trace elements.

Sites on main stem, major tributaries,

and selected smaller tributaries with

white sucker present were primary

choices.

Once at 16 sites in 1

1993, 5 in 1994, a

1995. The 1993-9

also were sample

Synoptic studies—streambed sediment (21)

Occurrence and spatial distribution of concentrations of contaminants—total PCBs,

31 organochlorine pesticides, 63 semivolatile organic compounds, forms of carbon, and 27 trace elements. Most sites were selected to match sites sampled for

contaminants in fish tissue.

Depositional zones on main stem,

major tributaries, and selected

smaller tributaries representing the

seven subunits plus an area of

anthracite coal mining.

Once at 17 sites in 1

at 4 sites in 1995

Ground-Water Chemistry

Subunit surveys (59)

Occurrence and distribution of concentrations in water from wells representing the

subunit—nutrients, major ions, 60 volatile organic compounds, 84 pesticides,

methylene blue active substances, tritium, stable isotopes of oxygen and hydrogen, bacteria (total coliform, fecal coliform, fecal streptococcus 1993-95 and

Escherichia coli 1994-95), dissolved organic carbon, uranium, and radon.

Wells used for household supply in

subunit 1 and subunits 6 and 7

combined.

One sample per well

subunits 6 and 7, 

subunit 1, 1994.

Land-use effects—agriculture (90)

Same as above. Wells used for household supply in

subunits 2, 3, and 5.

One sample per well

subunit 2, 1993; s

1994; subunit 5, 1

Land-use effects—urban (20)

Same as above. Wells in subunit 4. Well types include

monitoring (6), household (13), and

public (1).

One sample per well 
30 Water-Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

Herbicide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.001 0.01 0.1 1 10 100 1,000

The following tables summarize data collected for NAWQA studies during 1992-1995 by showing results for the Lo

hanna River Basin Study Unit compared to the NAWQA national range for each compound detected. The data were collec

variety of places and times. In order to represent the wide concentration ranges observed among Study Units, logarithmic 

used to emphasize the general magnitude of concentrations (such as 10, 100, or 1,000), rather than the precise numbers. T

data set used to construct these tables is available upon request. The groups of compounds analyzed for were selected on t

national usage of pesticides and other criteria. This summary includes compounds that may not be registered for use in Pen

Maryland. Some of the compounds analyzed for have previously been registered in Pennsylvania or Maryland, but either h

renewed or have had the registration revoked.

Concentrations of herbicides, insecticides, volatile organic compounds, and nutrients detected in ground water and streams 

Susquehanna River Basin Study Unit. [mg/L, milligrams per liter; μg/L, micrograms per liter; pCi/L, picocuries per liter; %, pe

than; - -, not measured; trade names may vary]

EXPLANATION

Range of surface-water detections in all 20 Study Units

Detection in the Lower Susquehanna River Basin Study Unit

Range of ground-water detections in all 20 Study Units

Drinking water standard or guideline a

Freshwater-chronic criterion for the protection of aquatic life a

Herbicide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.001 0.01 0.1 1 

Linuron (Lorox,

Linex)

4%

1%

MCPA (Selectyl 40,) 1%

0%

Metolachlor (Dual,

Pennant)

89%

28%

Metribuzin (Lexone,

Sencor)

4%

<1%

Napropamide

(Devrinol)

1%

1%

Oryzalin (Surflan) 0%

1%

Pebulate (Tillam) <1%

1%

Pendimethalin

(Prowl)

13%

<1%

Prometon (Pramitol) 75%

32%

Pronamide (Kerb,

propyzamid)

0%

1%

Propachlor (Ramrod,

propachlore)

1%

0%

Simazine (Aquazine,

Princep)

87%

36%

Tebuthiuron (Spike,

Tebusan)

26%

6%

Terbacilc (Sinbar) 2%

1%

Trifluralin (Treflan) 4%

<1%

Acetochlor

(Harness, Surpass)

13%

0%

Acifluorfen (Blazer,

Tackle 2S)

1%

1%

Alachlor (Lasso) 34%

5%

2,6-Diethylaniline

(Alachlor metabolite)

<1%

<1%

Atrazine (AAtrex) 96%

66%

Atrazine, Desethylc

(Atrazine metabolite)

95%

72%

Benfluralin (Balan,

Benefin)

2%

<1%

Bentazon (Basagran,

bentazone)

0%

2%

Bromacil (Hyvar X) 0%

1%

Butylate (Sutan) <1%

<1%

Cyanazine (Bladex) 33%

4%

2,4-D (Esteron,

Weedone)

10%

1%

DCPA (Dacthal) 5%

0%

Dicamba (Banvel) 1%

1%

Diuron (Karmex) 7%

3%

EPTC (Eptam) 2%

<1%
U.S. Geological Survey Circular 1168 

SUMMARY OF COMPOUND DETECTIONS AND CONCEN

Azinphos-methylc

(Guthion)

6%

0%

Carbarylc (Sevin,

Sevimol)

14%

4%

Carbofuranc

(Furadan)

6%

2%

Chlorpyrifos

(Dursban, Lorsban)

8%

0%

p,p’-DDE (p,p’-DDT

metabolite)

<1%

<1%

Diazinon

(Spectracide)

6%

<1%

Dieldrin (Panoram

D-31, Octalox)

1%

1%

Ethoprop (Mocap) 1%

0%

Fonofos (Dyfonate) <1%

0%

Malathion (malathon,

Cythion)

3%

0%

Methomyl (Lannate,

Nudrin)

1%

0%

Methyl parathion

(Penncap-M)

<1%

0%

Terbufos (Counter) <1%

0%

Volatile organic

compound

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

1,1,1-Trichloroethane --

7%

1,1-Dichloroethane --

1%

1,1-Dichloroethene

(Vinylidene chloride)

--

1%

1,2,4-Trimethylbenzene (Pseudocumene)

--

2%

1,3,5-Trimethylbenzene (Mesitylene)

--

2%

Benzene --

2%

0.01 0.1 1 10 100 1,000

Dichlorodifluoromethane (CFC 12)

--

1%

Dichloromethane

(Methylene chloride)

--

2%

Dimethylbenzenes

(Xylenes (total))

--

3%

Ethylbenzene

(Phenylethane)

--

2%

Isopropylbenzene

(Cumene)

--

1%

Methylbenzene

(Toluene)

--

2%

Naphthalene --

1%

Tetrachloromethane --

2%

total Trihalomethanes

--

11%

Trichloroethene

(TCE)

--

5%

cis-1,2-Dichloroethene

--

2%

n-Propylbenzene

(Isocumene)

--

1%

p-Isopropyltoluene

(p-Cymene)

--

1%

Volatile organic

compound

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

Methyl tert-butyl

etherd

 (MTBE)

--

11%

Tetrachloroethene

(Perchloroethene)

--

7%

0.01 0.1 1 10 100 

Volatile organic

compound

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.01 0.1 1 10 

Insecticide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.001 0.01 0.1 1 10 100 1,000
32 Water-Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

Dissolved ammonia 90%

76%

Dissolved ammonia

plus organic nitrogen

as nitrogen

55%

5%

Dissolved phosphorus as phosphorus

70%

38%

Dissolved nitrite plus

nitrate

100%

92%

Radon 222 --

100%

Other Rate

of

detection b

Concentration, in pCi/L

1 10 100 1,000 

Nutrient

(Trade or common

name)

Rate

of

detection b

Concentration, in mg/L

0.01 0.1 1 10 100 1,000 10,000 100,000

Herbicides

2,4,5-T (Fruitone A)

2,4,5-TP (Silvex, Fenoprop)

2,4-DB (Butyrac)

Bromoxynil ( Bromotril)

Chloramben (Amiben)

Clopyralid (Stinger)

Dacthal mono-acid (Dacthal

metabolite)

Dichlorprop (2,4-DP)

Dinoseb (Dinitro)

Ethalfluralin (Sonalan)

Fenuron (Fenulon)

Fluometuron (Flo-Met)

MCPB (Thistrol)

Molinate (Ordram)

Neburon (Neburyl)

Norflurazon (Evital)

Picloram (Grazon, Tordon)

Propham (Tuberite)

Thiobencarb (Bolero)

Triallate (Far-Go, Avadex)

Triclopyr (Garlon)

Insecticides

3-Hydroxycarbofuran (Carbofuran metabolite)

Aldicarb sulfone (Standak)

Aldicarb sulfoxide (Aldicarb metabolite)

Aldicarb (Temik, Ambush)

Disulfoton (Disyston)

Methiocarb (Slug-Geta)

Oxamyl (Vydate L)

Parathion (Roethyl-P)

Phorate (Thimet, Granutox)

Propargite (Comite, Omite)

Propoxur (Baygon)

alpha-HCH (alpha-lindane)

cis-Permethrin (Ambush)

gamma-HCH (Lindane)

Volatile organic

compounds

1,1,1,2-Tetrachloroethane

1,1,2,2-Tetrachloroethane

1,1,2-Trichloro-1,2,2-trifluoroethane (Freon 113, CFC

113)

1,1,2-Trichloroethane

1,1-Dichloropropene

1,2,3-Trichlorobenzene

1,2,3-Trichloropropane

1,2,4-Trichlorobenzene

1,2-Dibromo-3-chloropropane (DBCP)

1,2-Dibromoethane (EDB,

Ethylene dibromide)

1,2-Dichlorobenzene

1,2-Dichloroethane

1,2-Dichloropropane

1,3-Dichlorobenzene

1,3-Dichloropropane

1,4-Dichlorobenzene

1-Chloro-2-methylbenzene

(o-Chlorotoluene)

1-Chloro-4-methylbenzene

(p-Chlorotoluene)

2,2-Dichloropropane

Bromobenzene

Bromochloromethane

Bromome

Chloroben

Chloroeth

Chloroeth

ride)

Dibromom

Ethenylbe

Hexachlor

cis-1,3-Di

tert-Butylb

trans-1,2-D

trans-1,3-D

Nutrient

No non-de

Herbicides, insecticides, volatile organic compounds, and nutrients not detected in ground and surface waters of the Lowe

River Basin Study Unit.

a

 Selected water-quality standards and guidelines (Gilliom and others, in press).

b Rates of detection are based on the number of analyses and detections in the Study Unit, not on national data. Rates of detection for h

insecticides were computed by only counting detections equal to or greater than 0.01 μg/L in order to facilitate equal comparisons 

pounds, which had widely varying detection limits. For herbicides and insecticides, a detection rate of “<1%” means that all detect

0.01 μg/L, or the detection rate rounds to less than one percent. For other compound groups, all detections were counted and minim

its for most compounds were similar to the lower end of the national ranges shown. Method detection limits for all compounds in t

summarized in Gilliom and others (in press).

c

 Detections of these compounds are reliable, but concentrations are determined with greater uncertainty than for the other compounds 

as estimated values (Zaugg and others, 1995).

d The guideline for methyl tert-butyl ether is between 20 and 40 μg/L; if the tentative cancer classification C is accepted, the lifetime he

be 20 μg/L (Gilliom and others, in press).

e

 Selected sediment-quality guidelines (Gilliom and others, in press).
U.S. Geological Survey Circular 1168 

SUMMARY OF COMPOUND DETECTIONS AND CONCEN

1,2-Dichlorobenzene --

14%

1,2-Dimethylnaphthalene

--

43%

1,4-Dichlorobenzene --

24%

1,6-Dimethylnaphthalene

--

52%

1-Methyl-9Hfluorene

--

48%

1-Methylphenanthrene

--

67%

1-Methylpyrene --

76%

2,2-Biquinoline --

24%

2,3,6-Trimethylnaphthalene

--

52%

2,6-Dimethylnaphthalene

--

100%

2-Ethylnaphthalene --

53%

2-Methylanthracene --

71%

3,5-Dimethylphenol --

10%

4,5-Methylenephenanthrene

--

90%

9H-Carbazole --

52%

9H-Fluorene --

76%

Acenaphthene --

52%

Acenaphthylene --

100%

Concentrations of semivolatile organic compounds, organochlorine compounds, and trace elements detected in fish tissue 

streambed sediment of the Lower Susquehanna River Basin Study Unit. [μg/g, micrograms per gram; μg/kg, micrograms p

%, percent; <, less than; - -, not measured; trade names may vary]

EXPLANATION

Range of detections in fish and clam tissue in all 20 Study Units

Detection in streambed sediment in the Lower Susquehanna River Basin Study Unit

Range of detections in streambed sediment in all 20 Study Units

Guideline for the protection of aquatic life e

Detection in fish tissue in the Lower Susquehanna River Basin Study Unit

Semivolatile organic

compound

Rate of

detection b

Concentration, in μg/kg

0.1 10 100 1,000 10,000 100,000 1

Semivolatile organic

compound

Rate of

detection b

Concentration, in μg/kg

0.1 10 100 1,1

Acridine --

52%

Anthracene --

100%

Anthraquinone --

76%

Azobenzene --

5%

Benz[ a ]anthracene --

90%

Benzo[ a ]pyrene --

100%

Benzo[ b ]fluoranthene

--

100%

Benzo[g,h,i] perylene --

81%

Benzo[ k ]fluoranthene

--

100%

Butylbenzylphthalate --

81%

Chrysene --

100%

Di- n -butylphthalate --

90%

Di- n -octylphthalate --

24%

Dibenz[ a,h ]

anthracene

--

57%

Dibenzothiophene --

62%

Diethylphthalate --

33%

Dimethylphthalate --

19%

Fluoranthene --

100%
34 Water-Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

Semivolatile organic compounds, organochlorine compounds, and trace elements not detected in fish tissue and streambed 

the Lower Susquehanna River Basin Study Unit.

total-Chlordane 82%

43%

DCPA (dacthal,

chlorthal-dimethyl)

10%

0%

p,p’-DDE 100%

81%

total-DDT 100%

86%

Dieldrin (Panoram

D-31, Octalox)

29%

24%

Arsenic 51%

100%

Cadmium 90%

100%

Chromium 67%

100%

Copper 100%

100%

Lead 31%

100%

Mercury 74%

100%

Nickel 56%

100%

Selenium 100%

100%

Zinc 100%

100%

Organochlorine

compound

(Trade or

common name)

Rate

of

detection b

Concentration, in μg/kg

0.01 0.1 1 10 100 1,000 10,000 100,000

Organochlorine

compound

(Trade or

common name)

Rate

of

detection b

Concentration, in μg/kg

0.01 0.1 1 10 100 

Indeno[1,2,3- cd ]

pyrene

--

90%

Isoquinoline --

24%

Naphthalene --

48%

N-Nitrosodiphenylamine

--

10%

Phenanthrene --

100%

Phenanthridine --

24%

Phenol --

86%

Pyrene --

100%

Quinoline --

24%

bis(2-Ethylhexyl)phthalate

--

100%

p-Cresol --

95%

Semivolatile organic

compound

Rate of

detection b

Concentration, in μg/kg

0.1 10 100 1,000 10,000 100,000 1

Endosulfan I (alphaendosulfann)

--

19%

beta-HCH (betaBHC, beta)

5%

5%

gamma-HCH

(lindane)

5%

0%

Heptachlor epoxide 2%

5%

Hexachlorobenzene 2%

--

PCB, total 83%

5%

Pentachloroanisole 12%

0%

Trace element Rate

of

detection b

Concentration, in μg/g

0.01 0.1 1 10 1

Semivolatile organic

compounds

1,2,4-Trichlorobenzene

1,3-Dichlorobenzene

2,4-Dinitrotoluene

2,6-Dinitrotoluene

2-Chloronaphthalene

2-Chlorophenol

4-Bromophenyl-phenylether

4-Chloro-3-methylphenol

4-Chlorophenyl-phenylether

Benzo [c] cinnoline

C8-Alkylphenol

Isophorone

N-Nitrosodi-n-propylamine

Nitrobenzene

Pentachloronitrobenzene

bis (2-Chloroethoxy)methane

Organochlorine

compounds

Aldrin (HHDN, Octalene)

Chloroneb (Tersan SP)

Endrin

Heptachlor

Isodrin

Mirex (Dechlorane)

Toxaphene (Camphechlor)

alpha-HCH (alpha-BHC,

alpha-lindane)

cis-Permethrin (Ambush,

Pounce)

delta-HCH (d

o,p’-Methoxy

p,p’-Methoxy

trans-Permeth

Pounce)

Trace elem

No non-detect
U.S. Geological Survey Circular 1168 

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U.S. Geological Survey Circular 1168 

GLO

The terms in this glossary were compiled from numerous sources. Some

definitions have been modified and

may not be the only valid ones for

these terms.

Algae–Chlorophyll-bearing nonvascular, primarily aquatic species that

have no true roots, stems, or leaves;

most algae are microscopic, but

some species can be as large as vascular plants.

Anomalies–As related to fish, externally visible skin or subcutaneous

disorders, including deformities,

eroded fins, lesions, and tumors.

Aquatic life criteria–Water-quality

guidelines for protection of aquatic

life. Often refers to U.S. Environmental Protection Agency waterquality criteria for protection of

aquatic organisms. See also Waterquality criteria.

Aquifer–A water-bearing layer of soil,

sand, gravel, or rock that will yield

usable quantities of water to a well.

Atmospheric deposition–The transfer

of substances from the air to the

surface of the Earth, either in wet

form (rain, fog, snow, dew, frost,

hail) or in dry form (gases, aerosols, particles).

Background concentration–A concentration of a substance in a particular

environment that is indicative of

minimal influence by human

(anthropogenic) sources.

Base flow–Sustained, low flow in a

stream; ground-water discharge is

the source of base flow in most

places.

Bedrock–General term for consolidated

(solid) rock that underlies soils or

other unconsolidated material.

Best management practice (BMP)–An

agricultural practice that has been

determined to be an effective, practical means of preventing or

reducing nonpoint source pollution.

Bioaccumulation–The biological

sequestering of a substance at a

higher concentration than that at

which it occurs in the surrounding

environment or medium. Also, the

process whereby a substance enters

organisms through the gills, epithelial tissues, dietary, or other

sources.

Bioavailability–The capacity of a

chemical constituent to be taken up

by living organisms either through

physical contact or ingestion.

Breakdown product–A compound

derived by chemical, biological, or

physical action upon a pesticide.

The breakdown is a natural process

that may result in a more or less

toxic and a more or less persistent

compound.

Carbonate rocks–Rocks (such as limestone or dolostone) that are

composed primarily of minerals

(such as calcite and dolomite) containing the carbonate ion (CO3

2-).

Community–In ecology, the species

that interact in a common area.

Concentration–The amount or mass of

a substance present in a given volume or mass of sample. Usually

expressed as microgram per liter

(water sample) or micrograms per

kilogram (sediment or tissue

sample).

Concentrated animal operation–Operation where the animal density

exceeds two animal units per acre

on an annual basis as defined for

the Pennsylvania nutrient management legislation. An animal unit is

1,000 pounds of live weight.

Contamination–Degradation of water

quality compared to original or natural conditions due to human

activity.

Crystalline rocks–Rocks (igneous or

metamorphic) consisting wholly of

crystals or fragments of crystals.

Criterion–A standard rule or test on

which a judgment or decision can

be based.

Degradation products–Compounds

resulting from transformation of an

organic substance through chemical, photochemical, and(or)

biochemical reactions.

Denitrification–A process by which oxidized forms of nitrogen such as

nitrate (NO3

-

) are reduced to form

nitrites, nitrogen oxides, ammonia,

or free nitrogen; commonly brought

about by the action of denitrifying

bacteria and usually resulting in the

escape of nitrogen to the air.

Detection limit–The concentration

below which a particular analytical

method cannot determine, with a

high degree of certainty, a

concentration.

Drainage basin–The portion o

face of the earth that contr

water to a stream through o

runoff, including tributarie

impoundments.

Drinking-water standard or g

line–A threshold concentra

public drinking-water supp

designed to protect human 

As defined here, standards 

U.S. Environmental Protec

Agency regulations that sp

maximum contamination l

public water systems requi

protect the public welfare; 

lines have no regulatory st

are issued in an advisory c

Ecosystem–The interacting pop

tions of plants, animals, an

microorganisms occupying 

plus their physical environ

Environmental setting–Land a

acterized by a unique comb

of natural and human-relat

tors, such as row-crop culti

glacial-till soils.

Eutrophication–The process by 

water becomes enriched w

nutrients, most commonly 

phorus and nitrogen.

FDA action level–A regulatory 

recommended by the U.S. 

mental Protection Agency 

enforcement by the FDA w

ticide residues occur in foo

commodities for reasons o

the direct application of th

cide. Action levels are set 

inadvertent pesticide residu

resulting from previous leg

accidental contamination. 

to edible portions of fish an

fish in interstate commerce

Fish community–See Commu

Herbicide–A chemical or other 

that applied for the purpos

ing of undesirable plants. S

Pesticide.

Human health advisory level–

ance provided by U.S. Env

mental Protection Agency, 

agencies, or scientific orga

tions, in the absence of reg

limits, to describe acceptab

taminant levels in drinking 

edible fish.

Insecticide–A substance or mix

substances intended to prev

destroy, or repel insects.
38 Water Quality in the Lower Susquehanna River Basin, Pennsylvania and Maryland, 1992-95

GLOSSARY

Leaching–The removal of materials in

solution from soil or rock to ground

water; refers to movement of pesticides or nutrients from land surface

to ground water.

Load–A general term that refers to a

material or constituent in solution,

in suspension, or in transport; usually expressed in terms of mass or

volume.

Maximum Contaminant Level

(MCL)–The maximum permissible level of a contaminant in water

that is delivered to any user of a

public water system. MCL’s are

enforceable standards established

by the U.S. Environmental Protection Agency.

Median–The middle or central value in a

distribution of data ranked in order

of magnitude. The median is also

known as the 50th percentile.

Micrograms per liter (μg/L)–A unit

expressing the concentration of

constituents in solution as weight

(micrograms) of solute per unit volume (liter) of water; equivalent to

one part per billion in most streamwater and ground water. One

thousand micrograms per liter

equals 1 milligram per liter.

Milligrams per liter (mg/L)–A unit

expressing the concentration of

chemical constituents in solution as

weight (milligrams) of solute per

unit volume (liter) of water; equivalent to one part per million in most

streamwater and ground water. One

thousand micrograms per liter

equals 1 mg/L.

Nitrate–An ion consisting of nitrogen

and oxygen (NO3

-

). Nitrate is a

plant nutrient and is very mobile in

soils.

Nonpoint source–A pollution source

that cannot be defined as originating from discrete points such as

pipe discharge. Areas of fertilizer

and pesticide applications, atmospheric deposition, manure, and

natural inputs from plants and trees

are types of nonpoint source pollution. See also Point source.

Nutrient–Element or compound essential for animal and plant growth.

Common nutrients in fertilizer

include nitrogen, phosphorus, and

potassium.

Occurrence and distribution assessment–Characterization of the

broad-scale spatial and temporal

distributions of water-quality conditions in relation to major

contaminant sources and background conditions for surface water

and ground water.

Organochlorine compound–Synthetic

organic compound containing chlorine. As generally used, the term

refers to compounds containing

mostly or exclusively carbon,

hydrogen, and chlorine. Examples

include organochlorine insecticides, polychlorinated biphenyls,

and some solvents containing

chlorine.

Organochlorine insecticide–A class of

organic insecticides containing a

high percentage of chlorine.

Includes dichlorodiphenylethanes

(such as DDT), chlorinated cyclodienes (such as chlordane), and

chlorinated benzenes (such as lindane). Most organochlorine

insecticides were banned because

of their carcinogenicity, tendency to

bioaccumulate, and toxicity to

wildlife.

Organochlorine pesticide–See Organochlorine insecticide.

Pesticide–A chemical applied to crops,

rights of way, lawns, or residences

to control weeds, insects, fungi,

nematodes, rodents, and other

“pests.” See also Herbicide,

Insecticide.

Point source–A source at a discrete

location such as a discharge pipe,

drainage ditch, well, or concentrated livestock operation. See also

Nonpoint source.

Riparian–The area adjacent to a stream

or river with a high density, diversity, and productivity of plant and

animal species relative to nearby

uplands.

Species diversity–An ecological concept that incorporates both the

number of species in a particular

sampling area and the evenness

with which individuals are 

uted among the various spe

Species (taxa) richness–The nu

species (taxa) present in a 

area or sampling unit.

Synoptic sites–Sites sampled du

short-term investigation of 

water-quality conditions du

selected seasonal or hydro

conditions to provide impr

spatial resolution for critic

quality conditions.

Tier 1 sediment guideline–Thr

concentration above which 

a high probability of advers

on aquatic life from sedim

tamination, determined by 

modified procedures from 

U.S. Environmental Protec

Agency (1996b).

Trace element–An element fou

only minor amounts (conc

tions less than 1.0 milligra

liter) in water or sediment; 

arsenic, cadmium, chromiu

per, lead, mercury, nickel, 

Volatile organic compounds (V

Organic chemicals that hav

vapor pressure relative to t

water solubility. VOCs inc

components of gasoline, fu

and lubricants, as well as o

solvents, fumigants, some 

ingredients in pesticides, a

byproducts of chlorine disi

Water-quality criteria–Specifi

of water quality which, if r

are expected to render a bo

water unsuitable for its des

use. Commonly refers to w

quality criteria established 

U.S. Environmental Protec

Agency. Water-quality crit

based on specific levels of 

ants that would make the w

harmful if used for drinkin

ming, farming, fish produc

industrial processes.

Yield–The mass of a material or 

uent transported by a river 

specified period of time div

the drainage area of the riv
Lindsey and others • Water Quality in the Lower Susquehanna River Basin

USGS Circular 1168 • 1998

Susquehanna River Lancaster

Harrisburg

York

National Water-Quality Assessment (NAWQA) Program

Lower Susquehanna River Basin

NAWQA