Water Quality in the 

Delaware River Basin

Pennsylvania, New Jersey, New York, and Delaware, 1998–2001

U.S. Department of the Interior

U.S. Geological Survey

Circular 1227
Points of Contact and Additional Information

The companion Web site for NAWQA summary reports:

http://water.usgs.gov/nawqa/nawqa_sumr.html

Other NAWQA summary reports

River Basin Assessments

Acadian-Pontchartrain Drainages (Circular 1232)

Albemarle-Pamlico Drainage Basin (Circular 1157)

Allegheny and Monongahela River Basins (Circular 1202)

Apalachicola-Chattahoochee-Flint River Basin (Circular 1164)

Central Arizona Basins (Circular 1213)

Central Columbia Plateau (Circular 1144)

Central Nebraska Basins (Circular 1163)

Connecticut, Housatonic, and Thames River Basins (Circular 1155)

Cook Inlet Basin (Circular 1240)

Delmarva Peninsula (Circular 1228)

Eastern Iowa Basins (Circular 1210)

Georgia-Florida Coastal Plain (Circular 1151)

Great and Little Miami River Basins (Circular 1229) 

Great Salt Lake Basins (Circular 1236)

Hudson River Basin (Circular 1165)

Island of Oahu (Circular 1239)

Kanawha - New River Basins (Circular 1204)

Lake Erie - Lake Saint Clair Drainages (Circular 1203)

Long Island - New Jersey Coastal Drainages (Circular 1201)

Lower Illinois River Basin (Circular 1209)

Lower Susquehanna River Basin (Circular 1168)

Lower Tennessee River Basin (Circular 1233)

Las Vegas Valley Area and the Carson and Truckee River Basins (Circular 1170)

Mississippi Embayment (Circular 1208)

Mobile River Basin (Circular 1231)

New England Coastal Basins (Circular 1226)

Northern Rockies Intermontane Basins (Circular 1235)

Ozark Plateaus (Circular 1158)

Potomac River Basin (Circular 1166)

Puget Sound Basin (Circular 1216)

Red River of the North Basin (Circular 1169)

Rio Grande Valley (Circular 1162)

Sacramento River Basin (Circular 1215)

San Joaquin-Tulare Basins (Circular 1159)

Santa Ana Basin (Circular 1238)

Santee River Basin and Coastal Drainages (Circular 1206)

South-Central Texas (Circular 1212)

South Platte River Basin (Circular 1167)

Southern Florida (Circular 1207)

Trinity River Basin (Circular 1171)

Upper Colorado River Basin (Circular 1214)

Upper Illinois River Basin (Circular 1230)

Upper Mississippi River Basin (Circular 1211)

Upper Snake River Basin (Circular 1160)

Upper Tennessee River Basin (Circular 1205)

Western Lake Michigan Drainages (Circular 1156)

White River Basin (Circular 1150)

Willamette Basin (Circular 1161)

Yakima River Basin (Circular 1237)

Yellowstone River Basin (Circular 1234)

National Assessments

The Quality of Our Nation‘s Waters—Nutrients and Pesticides (Circular 1225)

Delaware River Basin contact and Web site:

USGS State Representative

U.S. Geological Survey

Water Resources Discipline

810 Bear Tavern Rd., Suite 206, W. Trenton, NJ 08628

e-mail: dc_nj@usgs.gov

http://nj.usgs.gov/nawqa/

National NAWQA Program:

Chief, NAWQA Program

U.S. Geological Survey

Water Resources Discipline

12201 Sunrise Valley Drive, M.S. 413

Reston, VA 20192

http://water.usgs.gov/nawqa/

Front cover: The Fairmount Water Works on the banks of the Schuylkill River in Philadelphia. Built in 1815 to supply clean water to 

the rapidly growing city, it was world-renowned for its innovative technology and neoclassical beauty. Today the Schuylkill River is 

still an important source of water supply for the city, and the waterworks serves as a water-interpretive center.

Back cover: Left, the Delaware Water Gap (Photograph by Dick Ludwig, courtesy Pocono Mountains Vacation Bureau, Inc.); right, 

the city of Philadelphia from Camden, New Jersey. (Photograph courtesy Delaware River Basin Commission)
U.S. Department of the Interior

U.S. Geological Survey

Water Quality in the Delaware River Basin, 

Pennsylvania, New Jersey, New York, and 

Delaware, 1998–2001

By Jeffrey M. Fischer, Karen Riva-Murray, R. Edward Hickman, 

Douglas C. Chichester, Robin A. Brightbill, Kristin M. Romanok,

and Michael D. Bilger

Circular 1227
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Library of Congress Cataloging-in-Publication Data

Water quality in the Delaware River Basin, Pennsylvania, New Jersey, New York, and

 Delaware, 1999-2001 / by Jeffrey M. Fischer ... [et al.] .

 p. cm -- (Circular ; 1227)

 Includes bibliographical references.

 ISBN 0-607-96402-2 (alk. paper)

 1. Water quality -- Delaware River Watershed (N.Y. –Del. and N.J. ) I. Fischer, Jeffrey M. 

 II. Geological Survey (U.S.) III. U.S. Geological Survey circular ; 1227

TD225.D28W38 2004

363.739’42’09749—dc22 2004041394
Contents

National Water-Quality Assessment Program ......................................................... iv

Introduction to this Report .............................................................................. vi

Summary of Major Findings .............................................................................. 1

Introduction to the Delaware River Basin ............................................................ 3

Major Findings ............................................................................................. 6

Organic Contaminants in Streambed Sediment and Fish Tissue ................................. 6

Trace-Metal Contaminants in Streambed Sediment and Fish Tissue ........................... 10

NATIONAL PERSPECTIVE – Some mercury findings in the Delaware River Basin were 

similar to those from national study ......................................................... 12

Naturally Occurring Contaminants in Ground Water ............................................. 12

Pesticides in Streams and Ground Water ......................................................... 13

VOCs in Streams and Ground Water ............................................................... 17

Nutrients in Streams and Ground Water ............................................................ 19

NATIONAL PERSPECTIVE – Nutrient concentrations span the range of national findings ... 21

Effects of urbanization and streamflow on streamwater quality and aquatic communities

in streams ....................................................................................... 22

REGIONAL PERSPECTIVE – Stream quality degrades as urbanization increases in four 

major metropolitan areas ..................................................................... 25

Study Unit Design ....................................................................................... 27

References Cited .......................................................................................... 29

Glossary ................................................................................................... 31

Appendix—Water-quality data from the Delaware River Basin in a national context ............ 33
iv

National Water-Quality Assessment Program

The quality of the Nation’s water resources is integrally linked to the long-term availability of 

water that is clean and safe for drinking and recreation and also suitable for industry, irrigation, 

and habitat for fish and wildlife. Recognizing the need for long-term, nationwide assessments 

of water resources, the U.S. Congress has appropriated funds since 1991 for the USGS to conduct the National Water-Quality Assessment (NAWQA) Program. Scientists in the NAWQA 

Program work with partners in government, research, and public interest groups to assess 

the spatial extent of water-quality conditions, how water quality changes with time, and how 

human activities and natural factors affect water quality. This information is useful for guiding 

water-management and protection strategies, research, and monitoring in different hydrologic 

and land-use settings across the Nation.

The Delaware River Basin is one of 51 water-quality assessments initiated since 1991. 

Together, the 51 major river basins and aquifer systems, referred to as “Study Units,” include 

water resources used by more than 60 percent of the population in watersheds that cover about 

one-half of the land areas of the conterminous United States. Timing of the assessments varies 

because of the program’s rotational design in which one-third of all Study Units are intensively 

investigated for 3 to 4 years, with trends assessed every 10 years. As indicated on the map, the 

Delaware River Basin is part of the third set of intensive investigations that began in 1997.

1991–95 

1994–98

1997–2001

Not yet scheduled

High Plains Regional

Ground Water Study, 

1999-2004

NAWQA Study Units— 

Assessment schedule

Delaware River Basin
What kind of water-quality information does the NAWQA Program 

provide?

Water-quality assessments by a single program cannot possibly address all of the Nation’s 

water-resource needs and issues. Therefore, it is necessary to define the context within which 

NAWQA information is most useful. 

• Total resource assessment—NAWQA assessments are long-term and interdisciplinary, and 

include information on water chemistry, hydrology, land use, stream habitat, and aquatic 

life. Assessments are not limited to a specific geographic area or water-resource problem at a 

specific time. Therefore, the findings describe the general health of the total water resource, 

as well as emerging water issues, thereby helping managers and decision makers to set priorities.

• Source-water characterization—Assessments focus on the quality of the available, untreated 

resource and thereby complement (rather than duplicate) Federal, State, and local programs 

that monitor drinking water. Findings are compared to drinking-water standards and health 

advisories as a way to characterize the resource.

• Compounds studied—Assessments focus on chemical compounds that have well-established 

methods of investigation. It is not financially or technically feasible to assess all the contaminants in our Nation’s waters. In general, the NAWQA Program investigates those pesticides, 

nutrients, volatile organic compounds, and metals that have been or are currently used 

commonly in agricultural and urban areas across the Nation. A complete list of compounds 

studied is on the NAWQA Web site at http://water.usgs.gov/nawqa.

• Detection relative to risk—Compounds are measured at very low concentrations, often 

10 to 100 times lower than Federal or State standards and health advisories. Detection of 

compounds, therefore, does not necessarily translate to risks to human health or aquatic life. 

However, these analyses are useful for identifying and evaluating emerging issues, as well as 

for tracking contaminant levels over time.

• Multiple scales—Assessments are guided by a nationally consistent study design and uniform methods of sampling and analysis. Findings thereby pertain not only to water quality 

of a particular stream or aquifer, but also contribute to the larger picture of how and why 

water quality varies regionally and nationally. This consistent, multiscale approach helps to 

determine if a water-quality issue is isolated or pervasive. It also allows direct comparisons 

of how human activities and natural processes affect water quality in the Nation’s diverse 

environmental settings. 

v
vi

Introduction to this Report

This report contains the major findings of a 1998–2001 assessment of water quality in the 

Delaware River Basin. It is one of a series of reports by the National Water-Quality Assessment 

(NAWQA) Program that present major findings in 51 major river basins and aquifer systems 

across the Nation. 

In these reports, water quality is discussed in terms of local, State, and regional issues. Conditions in a particular basin or aquifer system are compared to conditions found elsewhere and 

to selected national benchmarks, such as those for drinking-water quality and the protection of 

aquatic organisms. 

This report is intended for individuals working with water-resource issues in Federal, State, or 

local agencies, universities, public interest groups, or in the private sector. The information will 

be useful in addressing a number of current issues, such as the effects of agricultural and urban 

land use on water quality, human health, drinking water, source-water protection, hypoxia and 

excessive growth of algae and plants, pesticide registration, and monitoring and sampling strategies. This report is also for individuals who wish to know more about the quality of streams 

and ground water in areas near where they live, and how that quality compares to the quality of 

water in other areas across the Nation.

The water-quality conditions in the Delaware River Basin summarized in this report are 

discussed in detail in other reports that can be accessed from http://nj.water.usgs.gov/nawqa/

delr/. Detailed technical information, data and analyses, collection and analytical methodology, models, graphs, and maps that support the findings presented in this report, in addition to 

reports in this series from other basins, can be accessed from the national NAWQA Web site 

(http://water.usgs.gov/nawqa). 

“The work reported here is 

very relevant to the work 

done in the Division of Water, 

and specifically in the waterquality monitoring program.”

Margaret Novak, 

New York State Department of 

Environmental Conservation

A B

D E

C

A. Stream sampling (Photo by Delaware NAWQA 

 project personnel)

B. Farming in Valley and Ridge (Photo by U.S. 

 Department of Agriculture, Natural Resources 

 Conservation Service)

C. Stonefly (Photo by Lawrence E. Abele, New 

 York State Department of Environmental 

 Conservation)

D. Rafting on the Upper Delaware (Photo by 

 David B. Soete)

E. Fish community sampling (Photo by Richard 

 Spear, Pennsylvania Department of 

 Environmental Protection)
Summary of Major Findings

1

Stream and River Highlights

Stream-water quality and the health of aquatic life in 

rivers of the Delaware River Basin (hereafter, “the basin”) 

are greatly affected by human activities related to agriculture 

and urbanization. Many nutrients, pesticides, and volatile 

organic compounds (VOCs) were detected in water samples 

from streams, but concentrations of most chemical compounds were low and rarely exceeded guidelines or standards 

for drinking-water quality or aquatic-life protection. Current 

guidelines, however, do not include many of these chemicals 

nor the mixtures of compounds that commonly were detected 

in streams. Organic and trace-metal contaminants were 

detected in streambed-sediment and fish-tissue samples from 

many streams and rivers throughout the basin. Concentrations of these compounds typically were higher in samples 

from urban watersheds than in those from streams in other 

land-use settings, and streams in urban settings commonly 

failed to meet guidelines for protection of fish-eating wildlife 

and sediment-dwelling organisms. In general, urbanization in 

watersheds was associated with reduced biological diversity 

in streams and an increase in species more tolerant of disturbance.

• Environmentally persistent organochlorine compounds, 

such as DDT and polychlorinated biphenyls (PCBs), were 

detected in streambed sediment and fish tissue from many 

streams and rivers, particularly in urban areas. Concentrations at many sites exceeded guidelines established for the 

protection of fish-eating wildlife and sediment-dwelling 

organisms. (p. 6)

• Concentrations of PCBs in fish from some rivers have 

markedly declined from the 1970s or 1980s to the late 

1990s, but this decline was not seen in two of the six rivers 

studied. Concentrations in game fish collected in 1998 indicated that some rivers still warrant human-health fish-consumption advisories. (p. 8)

• Concentrations of most trace metals in streambed sediment were elevated in urban watersheds and in watersheds 

Each physiographic region of the Delaware River Basin has a 

different combination of land-use types and levels of development. Access to abundant water and good transportation routes 

have led to extensive urban and agricultural development in the 

southern half of the Study Unit.

Camden

Easton

Chester

Trenton

Reading

Allentown

Wilmington

Port Jervis

Stroudsburg

Philadelphia

APPALACHIAN

PLATEAUS

NEW ENGLAND

VALLEY AND

RIDGE

PIEDMONT

COASTAL

PLAIN

Delaware

Bay

0 20 40 KILOMETERS

0 20 40 MILES

EXPLANATION

Land use, 1992

Forest

Agriculture

Urban

Wetland

Water

Other

Study area

boundary

76°

75°

42°

41°

40°

39°

New York City

Pennsylvania

New York

Delaware

New Jersey

Maryland

STUDY UNIT

76°

80°

44°

38°

72°

Small streams Major rivers

Agricultural

Undeveloped Urban 

Selected indicators of streamwater quality

Mixed

land uses

Proportion of samples with detected concentrations 

greater than or equal to health-related national 

guidelines for drinking water, protection of aquatic life, or 

the desired goal for preventing nuisance plant growth

Proportion of samples with detected concentrations less 

than health-related national guidelines for drinking 

water, protection of aquatic life, or below the desired 

goal for preventing nuisance plant growth

Proportion of samples with no detections

1 Solvents, refrigerants, fumigants, and gasoline compounds in water.

2Chlordanes, dieldrin, DDT, and PCBs in fish tissue.

3 Byproducts of fossil-fuel combustion; components of coal and crude 

oil, in sediment.

4 Arsenic, mercury, and metals in sediment.

5 Undeveloped sites have fewer samples over a shorter time period than

the other stream types shown.

Trace

elements4

Organochlorines2

Semivolatile organics3

Pesticides –

Total

phosphorus –

Volatile

organics1 –

Nitrate – 5

5

5

5
2 Water Quality in the Delaware River Basin

• Arsenic was frequently detected in wells (about 70 percent) 

in the Piedmont clastic-rock aquifer. Concentrations in two 

of 30 wells exceeded the USEPA drinking-water standard 

of 10 micrograms per liter. (p. 13)

• Pesticides were detected in about one-half of the domestic wells sampled but were detected most frequently in 

samples from the clastic-rock aquifer of the highly urban 

Piedmont Physiographic Province. Concentrations were 

low; none exceeded USEPA drinking-water standards. 

Pesticide degradation products were detected in more wells 

and often at higher concentrations than parent compounds. 

(p. 13)

• One or more VOCs were detected in more than 85 percent 

of the domestic wells sampled in the clastic-rock aquifer in the highly urban Piedmont, but were detected less 

frequently elsewhere. Concentrations were low and none 

exceeded USEPA drinking-water standards. (p. 17)

• The median concentration of nitrate was highest in domestic wells in the Piedmont clastic-rock aquifer (2.9 milligrams per liter), but no wells in the aquifer exceeded the 

USEPA drinking-water standard of 10 milligrams per liter. 

Concentrations in two domestic wells in agricultural areas 

of the Valley and Ridge Province, however, exceeded the 

standard. (p. 19)

Major Influences on Ground Water

• Use of nutrients, pesticides, and VOCs in urban and agricultural areas

• Physical properties of soils and aquifers, and chemical 

properties of contaminants

• Naturally occurring radon and arsenic

affected by mining and industrial activities relative to concentrations in forested or agricultural watersheds. (p. 10)

• Concentrations of mercury in fish fillets exceeded humanhealth criteria and wildlife-protection guidelines at 22 and 

87 percent of the sampling sites, respectively. (p. 11) 

• Pesticides were detected in almost all streams sampled, and 

their concentrations were directly related to the percentage 

of either urban or agricultural land in the watershed. Concentrations of selected degradation products often exceeded 

concentrations of the parent pesticides. Concentrations 

were low, however, and rarely exceeded U.S. Environmental Protection Agency (USEPA) drinking-water standards or 

guidelines and occasionally exceeded those for aquatic life. 

(p. 13)

• One or more of 42 volatile organic compounds (VOCs) 

were detected in 92 percent of stream samples, but concentrations were low and did not exceed USEPA drinkingwater or aquatic-life standards or guidelines. Concentrations were highest at urban sites. (p. 17)

• Concentrations of nutrients in streams in agricultural and 

urban watersheds were elevated compared to those in forested areas. (p. 19)

• Losses of pollution-sensitive invertebrate species, decreases 

in habitat quality, and increases in chemical indicators such 

as chloride and potential pesticide toxicity were related to 

the extent of urbanization in a watershed. (p. 22)

• Streamflow, chemistry, and biota were affected by the 

extreme drought during the summer of 1999. (p. 24)

Major Influences on Streams and Rivers

• Runoff and point-source discharges from agricultural and 

urban areas

• Persistence of contaminants associated with past agricultural, urban, industrial, and mining activities

• Impoundments and diversions of water

Ground-Water Highlights

Ground-water quality in the Delaware River Basin has 

been affected by human activities and geologic characteristics. 

Nutrients, pesticides, and VOCs were frequently detected, but 

typically less frequently and at lower concentrations than in 

streams. In general, the number of manmade contaminants 

detected and their concentrations increased with the degree 

of development in each region studied. Concentrations of 

naturally occurring radon and arsenic exceeded existing or 

proposed drinking-water standards. Concentrations of most 

other chemical compounds detected were low and did not 

exceed most drinking-water-quality standards or guidelines.

• Concentrations of radon exceeded the proposed USEPA 

drinking-water standard of 300 picocuries per liter in nearly 

all wells sampled. (p. 12)

Selected indicators of ground-water quality

Domestic-supply wells

Valley and Ridge

clastic rock

Glaciofluvial

aquifers

Piedmont

clastic rock

Proportion of samples with detected concentrations 

greater than or equal to health-related national 

guidelines for drinking water

Proportion of samples with detected concentrations less 

than health-related national guidelines for drinking water

Proportion of samples with no detections

1 Solvents, refrigerants, fumigants, and gasoline compounds.

Radon

Nitrate

Arsenic

Pesticides

Volatile

organics1
Introduction to the Delaware River Basin

3

The Delaware River originates in the Catskill Mountains 

and flows south more than 200 miles to the Delaware Estuary, which extends from near Trenton, N.J., to the Delaware 

Bay (fig. 1). The Lehigh and Schuylkill Rivers are two of the 

Delaware’s major tributaries. The 12,700-mi2 (square mile) 

basin includes parts of four States: Pennsylvania (50 percent 

of the basin), New Jersey (23 percent), New York (19 percent), 

and Delaware (8 percent). The Delaware River Basin NAWQA 

Figure 1. Physical differences across the Study Unit influence 

hydrologic conditions, land development, and population distribution. More than 80 percent of the Delaware River Basin population 

lives in the Piedmont and Coastal Plain Physiographic Provinces.

Camden

Easton

Trenton

Reading

Allentown

Wilmington

Port Jervis

Stroudsburg

Philadelphia

Schuylkill R

Neshaminy C

F

r

rench Cr

Tulpehocken Cr

Brandywine Cr

Delaware R

Lehigh River

Jordan Cr

R accoon Cr

Cooper R

Lehigh River

East Branch Delaware R

West Bra nch Delaware R

Delaware R

De l a w a r e

E s t u a r y

Pocono

Plateau

Great Valley

Triassic

Lowlands

Piedmont

Uplands

Catskill

Mountains

Delaware

Bay

0 20 40 KILOMETERS

0 20 40 MILES

EXPLANATION

Physiographic Province

Appalachian Plateaus

Valley and Ridge

New England

Piedmont

Coastal Plain

Subprovince boundary

Northern limit of KirkwoodCohansey aquifer system

Southern extent of most

recent glaciation

Basin boundary

Study area boundary

76°

75°

42°

41°

40°

39°

Population 

3%

33%

47%

3%

Area

21%

5%

35%

19%

20%

14%

Study Unit encompasses the entire watershed except for a 770-

mi2 area of the Coastal Plain in Delaware (this area is part of 

another Study Unit).

More than 7.5 million people live in the basin (2000 Census), and another 8 million people outside the basin rely on the 

Delaware River and its tributaries for their water supply. Land 

use in the basin is about 50 percent forest, 35 percent agriculture, and 5 percent urban (fig. 2). About 80 percent of the 

basin’s population lives within about 20 miles of the Delaware 

Estuary. Since 1970, the suburban population has grown as 

much as 50 percent or more, whereas the overall population 

of the basin has increased less than 15 percent. Most of this 

suburban development has replaced previously forested or 

agricultural land.

Highly varied physiography and land uses 

influence water quality

The Delaware River Basin consists of five physiographic 

provinces (fig. 1), which differ considerably with respect to 

topography, geology, and hydrology. Physical differences have 

created characteristic patterns of land development in each 

province, and water-quality issues are related to these patterns 

of development. North and west of the Delaware Estuary, 

folded and faulted siliciclastic, carbonate, and metamorphic 

bedrock are found, whereas the Coastal Plain southeast of the 

estuary is composed of layered, unconsolidated sand and clay 

(fig. 3). Glaciation of the northern one-half of the basin during the Pleistocene Epoch stripped soil from the hilltops and 

deposited unconsolidated fill in the valleys of the Appalachian 

Plateaus, New England, and Valley and Ridge Physiographic 

Provinces.

The Appalachian Plateaus Province consists of 1,000- to 

4,000-foot-high uplands composed of gently folded sandstones, shales, and conglomerates. Rivers have carved deep, 

narrow valleys through the rock, and hydroelectric dams are 

interspersed throughout the province. Three reservoirs in the 

Catskill Mountains provide drinking water to residents of New 

York City, and outflows are regulated to maintain required 

flows on the Delaware River for downstream users. Although 

the Appalachian Plateaus cover the northern one-third of the 

basin, only about 3 percent of the basin population lives there, 

and 85 percent of the land is forested (figs. 1 and 2). The 

aesthetic and recreational qualities of this relatively undeveloped region attract millions of outdoor-recreation enthusiasts, 

who temporarily, but substantially, increase local populations. 

In addition, the recent development of transportation corridors has spurred rapid population growth, particularly in the 

Pocono Plateau region. Nearly all residents of the Appalachian 

Plateaus rely on wells for drinking water, and septic systems 

are commonly used for wastewater disposal away from towns. 

Water-quality issues include preserving the health of the exist-
4 Water Quality in the Delaware River Basin

ing ecosystem and the quality of the 

water as development occurs. Effects 

of reservoir releases and diversions on 

downstream users and biota also are a 

concern.

The Valley and Ridge Province 

consists primarily of sandstones and 

shales (clastic rocks) that have been 

folded into extensive ridges and valleys that trend southwest to northeast. 

Topographic relief from ridgetop to 

valley bottom can exceed 1,200 feet. An 

extensive sequence of carbonate rocks 

forms the southern boundary with the 

New England Province, an upland ridge 

composed of metamorphosed shales and 

carbonate rocks. The Valley and Ridge 

and New England Provinces account 

for about 26 percent of the Study Unit 

and about 17 percent of the population 

(fig. 1). Most of the developed land 

is along the valley floors, whereas the 

ridges are primarily forested. More than 

one-third of the land in these provinces 

is used for agriculture. Valley floors 

often contain extensive agricultural 

development (often more than 50 percent farmland). Corn is the major crop, 

but dairy, poultry, and swine production 

are important in the southwest corner of 

the Valley and Ridge Province, where 

manure from these livestock operations 

is commonly applied to farm fields. 

These provinces are less than 7 percent 

urban land. Major cities straddle either 

the Lehigh or Schuylkill Rivers and sit 

upon the productive carbonate aquifer of 

the Great Valley. Water-quality concerns in this region include the effects 

of urban and agricultural activities on 

streams and ground-water resources, 

the effects of industrial and municipal 

discharges on larger rivers, and the need 

for continued mitigation of past coal 

mining effects near the headwaters of 

the Lehigh and Schuylkill Rivers.

The Piedmont Province is a highly 

urbanized lowland region of rolling 

hills and valleys with two distinct rock 

types. In the southwest Uplands Section, 

metamorphic and igneous rocks such 

as schist, gneiss, and granite predominate, and small areas of carbonate rock 

are present. In the northeast Lowlands 

Section, clastic rocks such as sandstones 

and shale are the primary rock type, and 

diabase intrusions form resistant hills. 

The Piedmont contains 47 percent of the 

basin’s population and is the most highly 

developed province in the Study Unit 

(figs. 1 and 2). Agricultural and urban 

development account for more than 50 

percent of the land use in the region. 

Currently, about one-third of the land 

in the Piedmont is used for agriculture, 

but much of this land is being converted 

rapidly to suburban housing. Agriculture lands are located primarily north 

and west of Philadelphia. Farm crops 

consist mainly of grasses and corn, but 

mushroom and horse farms are also 

common, particularly in the western part 

of the Piedmont. Urban development is 

centered on the Philadelphia metropolitan area, but cities have developed all 

along the estuary, which serves as both 

a transportation corridor and a source 

of water supply. Rivers and the estuary are used extensively for municipal 

and industrial water supply, wastewater 

discharges, and recreation. The area’s 

long history of agricultural and industrial development, and the associated 

discharge of treated wastewater and 

runoff of nonpoint-source pollution, 

have degraded river and estuarine water 

quality. Overuse of ground water has led 

to the declaration of a “ground-water 

protection area” in the Philadelphia area.

The Coastal Plain Province is 

an area of low relief southeast of the 

Delaware Estuary. Sediments are 

composed of slightly dipping layers 

of unconsolidated clay, silt, sand, and 

gravel that thicken and reach a depth of 

6,000 feet to the southeast. The sands 

and gravels store large quantities of 

water, which are relied upon for most of 

the industrial, municipal, domestic, and 

agricultural supply in the province. The 

Coastal Plain contains 33 percent of the 

basin’s population (fig. 1). Agricultural 

development accounts for more than 

25 percent of the land use in the Coastal 

Plain. Farms grow a wide variety of 

fruit, vegetable, and row crops. Urban 

and industrial development is centered 

on Camden, but urban growth is occurring throughout the region and currently accounts for about 22 percent of 

the land use. Excessive ground-water 

withdrawals have led to concerns about 

Figure 3. Physical and chemical differences between the many types of rock 

in the Delaware Basin are some of the 

factors that control water availability and 

vulnerability to contamination.

Figure 2. Land use differs among, and within, physiographic provinces and is a primary 

factor affecting the quality of water and aquatic life. Agriculture is an important land use 

in all regions south of the Appalachian Plateaus. Parts of the Piedmont and Coastal Plain 

Provinces are highly urbanized.

0 20 40 60 80 100

COASTAL PLAIN

PIEDMONT

NEW ENGLAND

VALLEY AND RIDGE

APPALACHIAN PLATEAUS

BASINWIDE

PERCENTAGE OF TOTAL AREA

*Primarily water and wetlands,

 except in the Valley and

 Ridge Province where it also

 includes mined land

EXPLANATION

Forest

Agriculture

Urban

Other*

Land use

EXPLANATION

76°

75°

42°

41°

40°

39°

Appalachian

Plateaus

Valley and

Ridge

New

England

Piedmont

Coastal

Plain Rock Type

Carbonate

Clastic

Coal

Metamorphic and igneous

Unconsolidated sediment

Physiographic province boundary

Southern extent of most recent glaciation

0 20 40 KILOMETERS

0 20 40 MILES
Introduction 5

STREAMFLOW, IN CUBIC

FEET PER SECOND

10,000

1,000

100

10

1

01472157 FRENCH CREEK NEAR PHOENIXVILLE, PA.

Shaded band is 25 to 75 percentile flows; period of record is 1968 to 2001

Streamflow during the study period

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 S

1998 1999 2000 2001

Figure 4. Streamflow in French Creek near Phoenixville, Pennsylvania, reflects the 

extreme drought during the summer of 1999, close to normal precipitation in 2000, and 

generally dry conditions in 2001.

PRECIPITATION 1999 2000 2001

Yearly total 40.8 43.1 39.8

Yearly departure –3.4 –1.1 –4.4

Summer departure –8.5 2.8 0.2

Table 1. Precipitation (in inches) during 

the 1999–2001 sampling period was well 

below the 30-year mean of 44.06 inches at 

Allentown, Pennsylvania, and the drought 

in the summer of 1999 was one of the most 

severe on record for the basin.

saltwater intrusion and have resulted in 

mandated reductions in ground-water 

pumpage and increased withdrawals 

from the Delaware Estuary. In addition to the widespread occurrence of 

contaminants associated with current 

agricultural, industrial, and urban land 

uses, past agricultural practices have left 

some streams contaminated with longdiscontinued pesticides.

Extremes in precipitation 

occurred during the study

The Delaware River Basin has a 

temperate climate, with seasonal and 

average yearly variations generally 

reflecting variations in topography. 

Average yearly temperature ranges from 

about 45°F (degrees Fahrenheit) in 

the north to 56°F in the south. Average annual precipitation ranges from 

50 inches in the north to 42 inches in the 

south and is typically distributed evenly 

throughout the year (Jenner and Lins, 

1991).

Precipitation and streamflow were 

below normal during much of the 1999–

2001 data-collection period (table 1 

and fig. 4). Drought emergencies were 

declared by all four basin states during 

the extremely dry summer of 1999. At 

times, the flows of many streams were 

less than 20 percent of their 30-year 

average. Hurricane Floyd produced 

considerable amounts of rain across 

the basin in September 1999. Although 

this provided relief from the drought, it 

also caused major flooding and scouring 

of stream channels. Precipitation and 

streamflow were close to normal during 

2000. The yearly rainfall deficit in 2001 

was similar to that in 1999, but the summer deficit was smaller. These varying 

climatic conditions affected some water 

quality and stream biota (p. 24).

The Delaware River Basin is a 

vital source of drinking water

The Delaware River Basin supplies large quantities of water to two 

of the Nation’s largest metropolitan 

areas—New York City and Philadelphia. 

Approximately 620 Mgal/d (million 

gallons per day) is exported from the 

basin to New York City, and another 100 

Mgal/d is exported to northeastern New 

Jersey. About 4 billion gallons of water 

is used in the Study Unit each day, but 

more than one-half of this amount is for 

power generation. Public supply, industrial supply, and irrigation account for 

about 25, 15, and 1 percent, respectively, 

of the total water use.

Approximately 1 billion gallons of 

water is used each day within the Study 

Unit for public and domestic supply. 

Streams and rivers supply about 75 

percent of this total. Most large cities on 

major rivers and the non-saline parts of 

the estuary (above Philadelphia) depend 

largely on surface water, primarily from 

the Delaware, Schuylkill, Lehigh, and 

Brandywine Rivers. Each physiographic 

province has a distinct pattern of drinking-water use (fig. 5). For example, 

most public and domestic supply in the 

Coastal Plain comes from its highly productive sand and gravel aquifers. Similarly, the highly productive glaciofluvial 

aquifer system in the Appalachian Plateaus, New England, and the Valley and 

Ridge Provinces is an important source 

of water for public and domestic supply. 

A large amount of water used for public 

supply in the Valley and Ridge Province 

is from a highly productive carbonate 

aquifer, although most public drinking 

water in the Valley and Ridge, as well 

as the Piedmont Province, is supplied 

by streams and rivers (fig. 5). Residents 

in most sparsely populated areas of all 

provinces in the basin depend on wells 

for domestic drinking-water supplies.

Figure 5. Drinking-water sources differ 

among physiographic provinces. Estimates 

do not include water exported from the 

basin.

Appalachian Plateaus Valley and Ridge

plus New England

Piedmont Coastal Plain

(24) (210)

(444) (349)

Public supply - Surface water

Public supply - Ground water

Self supplied domestic - Ground water

Estimated drinking-water use, in millions of gallons per day (444)

EXPLANATION
6 Water Quality in the Delaware River Basin

Major Findings

The quality of surface and ground 

water in the Delaware River Basin is 

affected by a complex combination 

of natural factors (for example, geology, precipitation, and streamflow) and 

human factors (for example, land use, 

chemical use, and water diversions). The 

Delaware River Basin NAWQA study 

was designed to describe water-quality 

conditions (including ecological health 

and distribution of contaminants) in 

selected settings within the basin and to 

identify the effects of natural and human 

factors on observed conditions. Streamwater studies were conducted throughout the basin, but ecological studies 

were largely focused on the Piedmont 

Province and the Pocono Plateau region 

of the Appalachian Plateaus. Groundwater studies were conducted in the 

clastic-rock aquifers of the Piedmont 

and the Valley and Ridge Provinces and 

the glaciofluvial aquifers in the northern 

one-half of the basin.

Organochlorine pesticides and 

industrial compounds were widely 

detected in streambed sediments and 

fish tissue

One or more organochlorine 

pesticides or industrial compounds 

were detected in all streambed-sediment and fish-tissue samples throughout the Delaware River Basin, even 

though the manufacture and permitted 

use of these compounds were stopped 

or restricted more than 20 years before 

the current study. The most commonly 

detected organochlorine compounds 

were DDTs, PCBs, chlordanes, and 

dieldrin. PCBs, chlordanes, and dieldrin 

were detected more frequently in fish 

tissue than in streambed sediment (fig. 

6). For instance, PCBs were detected 

in 84 percent of the fish samples but in 

only 21 percent of the streambed-sediment samples. This result indicates that 

these compounds persist in the physical environment at concentrations less 

than laboratory detection limits, and are 

bioaccumulated to detectable concentrations by fish and other organisms. 

For example, concentrations of DDT in 

whole fish (white sucker, Catostomus 

Study Methods

The Study Unit Design presented 

on pages 27 and 28 of this report 

describes the methods used to 

obtain results discussed in this 

report.

Figure 6. Although their use has been 

discontinued for decades, DDT, PCBs, 

chlordane, and dieldrin were frequently 

detected in fish. Lower rates of detection 

in streambed sediment for most compounds indicates that they are present in 

the environment at concentrations below 

laboratory detection limits and increase 

through the food chain to detectable levels 

in fish.

Streambed sediment

Fish tissue

EXPLANATION

PERCENT DETECTION

0 20 40 60 80 100

DDT

PCBs

Chlordane

Dieldrin

Figure 7. Streams in urban areas are more 

likely to have detectable concentrations of 

one or more organochlorine contaminants 

in fish tissue and streambed sediment than 

are streams in agricultural and forested 

watersheds. Concentrations in urban areas 

are also more likely to exceed guidelines 

for the protection of fish-eating wildlife 

and sediment-dwelling organisms. PCBs 

exceeded these guidelines most frequently.

DETECTIONS IN FISH TISSUE

DDT

PCBs

Chlordane

Dieldrin

DDT

PCBs

Chlordane

Dieldrin

DETECTIONS IN BED SEDIMENT

0 20 40 60 80 100

0 20 40 60 80 100

PERCENT DETECTION

Forest Agriculture

Urban Large river

EXPLANATION

Percentage of sites at which concentrations

exceeded guidelines for protection of fisheating wildlife

Percentage of sites exceeding Threshold

Effect Concentration

Percentage of sites exceeding Probable

Effect Concentration

Not detected *

*

*

*

*

*

*

*

*

commersoni) were 2 to 30 times those 

in streambed sediments from the same 

sites; and the median ratio was 18:1.

DDT, the most frequently detected 

organochlorine compound, was found in 

fish tissue and (or) streambed sediments 

from more than 80 percent of wadeable streams in forested, agricultural, 

and urban watersheds (fig. 7), and from 

all four of the large rivers sampled. 

The widespread detection of DDT in a 

variety of land-use settings results in 

part from its historical use in controlling many types of insect pests in farms, 

homes, and forests. The degradation 

Organic Contaminants in 

Streambed Sediment and Fish 

Tissue

Many organic chemicals and trace 

metals that are released into the environment are more likely to be detected 

in streambed sediment or fish tissue 

than in water because of their chemical properties. These chemicals are 

of concern because they can interfere 

with the growth and reproduction of 

aquatic organisms. Also, many of these 

compounds can be bioaccumulated 

(increased in concentration as they move 

up the food chain) and can pose health 

risks to humans and wildlife consumers 

of aquatic biota.
Major Findings 7

product p,p'-DDE was the most commonly detected form of DDT. Concentrations of DDT in fish tissue and 

streambed sediment (fig. 8), like its 

detection frequencies, were typically 

highest in urban watersheds and large 

rivers and lowest in forested watersheds. 

Residual contamination of recently 

urbanized land from former agricultural 

applications also may have a bearing on 

these findings.

Total PCBs were widely detected 

in fish tissue from wadeable streams in 

all land-use settings (fig. 7) and from all 

four of the large rivers sampled. Detections in streambed sediment, however, 

were limited to streams in urban settings 

and large rivers downstream from major 

population centers. PCB concentrations 

were strongly related to the intensity 

of urbanization in a watershed because 

of the historical use of PCBs in industrial and electrical applications and the 

disposal of PCB-laden equipment in 

landfills and industrial sites near urban 

centers.

Chlordanes and dieldrin were 

detected in fish-tissue samples collected 

from every stream in urban watersheds, 

from more than one-half the streams in 

agricultural watersheds, and from three 

of the four large rivers sampled. These 

organochlorine compounds also were 

detected in streambed sediment from 

more than 60 percent of the urban and 

large-river sites (fig. 7). Both of these 

pesticides, as well as aldrin (which 

degrades to dieldrin), were commonly 

applied around and inside houses, apartment buildings, and commercial buildings for control of termites, carpenter 

ants, and other insect pests. Therefore, 

concentrations and detection frequencies 

of both were highly correlated with the 

percentage of urban land in the watershed. Chlordane and dieldrin also were 

detected in agricultural settings, but 

concentrations were much lower than in 

urban areas (fig. 8). This may be because 

the registration of these compounds for 

agricultural use was canceled a decade 

before it was canceled for use in urban 

areas, or because they were not applied 

as heavily in agricultural areas.

Concentrations of organochlorine 

compounds in streambed sediment 

and fish tissue exceeded guidelines 

for protection of wildlife at many sites

Concentrations of PCBs in whole 

fish exceeded guidelines developed for 

the protection of fish-eating wildlife 

(Newell and others, 1987) at 52 percent 

of the sites. Concentrations of dieldrin 

and DDT also exceeded this guideline 

(at 16 and 12 percent of sites, respectively). Guidelines were exceeded 

most frequently, and often for multiple 

compounds, at urban and large-river 

sites downstream from urban or industrial areas (fig. 7). Therefore, fish in 

streams in urban watersheds are most 

likely to contain multiple organochlorine 

compounds at concentrations thought to 

affect the health of fish-eating wildlife. 

Concentrations of DDT and (or) PCBs 

in fish tissue exceeded guidelines for the 

protection of fish-eating wildlife at some 

agricultural sites, but no guidelines were 

exceeded in fish tissue collected from 

forested watersheds. Concentrations of 

PCBs in fish from the four large-river 

sites (Lehigh River near Glendon, Pa.; 

Schuylkill River at Philadelphia, Pa.; 

and the Delaware River at Trenton, 

N.J., and at Port Jervis, N.Y.) exceeded 

fish-eating wildlife guidelines, and the 

guideline for dieldrin was exceeded at 

the Schuylkill River at Philadelphia.

Streambed sediments in many 

urban settings may be harmful to 

sediment-dwelling organisms. At many 

urban sites, concentrations of multiple 

co-occurring organochlorines exceeded 

A Few Notes About Fish-Tissue and Streambed-Sediment Analyses

Analyses for organochlorine compounds in fish tissue were done on composite 

samples of five to eight whole white suckers (Catostomus commersoni) from 

each of 25 sites; whole common carp (Cyprinus carpio) samples also were 

collected at five sites, and smallmouth bass fillets (Micropterus dolomieu) 

were collected at three sites. Concentrations of DDT and chlordane in fish 

tissue and streambed sediment were each calculated as the sum of the concentrations of the major components of the technical pesticide mixture plus 

degradation products. Total PCBs were determined by comparison to mixed 

aroclor standards. Normalization of organochlorine concentrations in fish tissue to lipid (fat) content and of those in streambed sediment to organic carbon 

content did not alter the findings presented here.

Figure 8. Concentrations of DDT, PCBs, 

chlordane, and dieldrin in fish tissue 

(whole white sucker) and streambed 

sediment were highest in urban areas. 

Guidelines for protecting fish-eating 

wildlife and sediment-dwelling organisms 

were most frequently exceeded in urban 

areas. Concentrations less than laboratory 

detection limits are not shown.

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8 Water Quality in the Delaware River Basin

sediment-quality guidelines (see box, 

p. 9). One or more organochlorine 

compounds were detected at every urban 

site. Fewer than 20 percent of these 

sites had concentrations below a TEC 

(Threshold Effect Concentration — see 

box on p. 9). Concentrations of DDT 

or chlordanes in sediment exceeded 

the TEC in more than 80 percent of the 

streams in urban watersheds, and PCBs 

exceeded this threshold at more than 

one-half the sites (fig. 7). Furthermore, 

concentrations of PCBs exceeded the 

PEC (Probable Effect Concentration 

— see box on p. 9) at 55 percent of 

urban sites, and concentrations of chlordanes exceeded the PEC at 18 percent 

of urban sites. The Schuylkill River at 

Philadelphia was the only large-river 

site at which a PEC was exceeded (for 

PCBs). No TEC was exceeded at any 

other large-river site.

PCB concentrations in fish tissue 

from some rivers declined markedly 

from 1969 to 1998 but remain above 

fish-consumption advisory levels

An analysis of PCB concentration 

data from historical and recent fish collections from six reaches of four major 

Figure 9. PCB concentrations in fish tissue 

from the Delaware River at Trenton have 

declined over the last 25 years. Declines 

also were seen on the upper Delaware 

River, Brandywine Creek, and upper 

Schuylkill River. Declines were not as 

apparent on the lower Schuylkill and lower 

Lehigh Rivers (Riva-Murray and others, 

2003).

Standards and Guidelines Used in This Report 

Water-quality standards and guidelines generally are maximum acceptable 

concentrations of contaminants in water, sediment, or fish tissue above which 

adverse effects on humans, aquatic life, or fish-eating wildlife are thought 

to occur. Regulatory agencies use these guidelines for evaluating whether 

measured concentrations may be harmful. Given the large number of potential contaminants and exposure pathways, no single source of standards or 

guidelines is available. The following standards and guidelines were used in 

this report to evaluate contaminant concentrations measured in surface water, 

ground water, streambed sediments, and fish tissue:

Current standards and guidelines cannot completely evaluate risks to humans 

or aquatic life because (1) standards or guidelines have not been established 

for many compounds, (2) mixtures of compounds are not considered, (3) 

effects of seasonal exposure to high concentrations have not been evaluated, 

and (4) other potential effects (such as endocrine disruption) have not yet been 

addressed.

Standard or 

guideline Medium Source 

Human 

health 

Drinking 

water

U.S. Environmental Protection Agency (2002a, 2003) 

— Maximum contaminant levels, risk-specific doses, and 

lifetime health advisories

Aquatic 

life— plants 

and animals

Surface 

water

U.S. Environmental Protection Agency (2002b, 2003)

Canadian Council of Ministers of the Environment (2001)

International Joint Commission, United States and Canada 

(1978)

Sedimentdwelling 

organisims 

Streambed 

sediment

Consensus based (MacDonald and others, 2000)

 

Fish-eating 

wildlife

Fish tissue 

(whole fish)

N.Y. State Department of Environmental Conservation 

(Newell and others, 1987)

U.S. Fish and Wildlife Service (Eisler, 1987) 

Human 

health

Fish tissue 

(edible 

flesh)

Great Lakes Fish Consumption Advisory (Anderson and 

others, 1993)

U.S. Environmental Protection Agency (2001) 

rivers indicates that PCB concentrations 

in fish from four of these reaches (the 

upper and lower Delaware River, Brandywine Creek, and the upper Schuylkill 

River) declined during the past 20 to 30 

years (fig. 9). The analysis considered 

total PCB concentrations determined 

by comparable methods in whole 

white suckers and in edible portions of 

American eel (Anguilla rostrata), as 

well as several other species. Limited 

data from the lower Lehigh River and 

lower Schuylkill River indicate less 

improvement in these reaches (RivaMurray and others, 2003). PCB concentrations in game-fish fillets collected in 

1998 from the lower Delaware, Lehigh, 

and Schuylkill Rivers, however, still 

exceeded the lowest fish-consumption 

advisory level for humans (Anderson 

and others, 1993). In addition, PCB 

concentrations in whole white suckers 

and common carp from these three river 

sections and the upper Delaware River 

(the only four river reaches with trend 

data at which whole-fish samples were 

collected during 1998) exceeded the 

guideline for protection of fish-eating 

wildlife (Newell and others, 1987). ������������������������ ���������������������� ������������

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Major Findings 9

Semivolatile organic compounds are 

widespread in streambed sediments

One or more semivolatile organic 

compounds (SVOCs) were detected in 

streambed sediments from 95 percent of 

the streams sampled. SVOCs for which 

analyses were conducted as part of this 

study include three broad groups: PAHs 

(polycyclic aromatic hydrocarbons), 

phthalates, and phenols. Compounds 

from all three groups were detected at 

46 percent of the stream sites sampled. 

Some of these compounds are probable human carcinogens, are endocrine 

disruptors, and (or) are toxic to aquatic 

organisms. Once SVOCs enter the water, 

they are quickly adsorbed onto particulate matter and are deposited on stream 

bottoms, where they remain stable and 

persist (Neff, 1985).

PAHs, which are formed and 

released into the atmosphere during 

the incomplete combustion of wood, 

coal, and fossil fuel, were detected 

How are contaminated sediments evaluated? 

Screening values known as effect concentrations are used to indicate when 

concentrations of contaminant in streambed sediments are likely to cause 

adverse effects in sediment-dwelling organisms. The Threshold Effect Concentration (TEC) is an estimate of the concentration of a contaminant in sediment below which adverse biological effects rarely occur. The Probable Effect 

Concentration (PEC) is an estimate of the concentration of a contaminant in 

sediment above which adverse biological effects commonly occur (MacDonald and others, 2000). Therefore, adverse biological effects are expected to be 

rare if streambed-sediment concentrations are less than the TEC, occasional if 

concentrations are between the TEC and the PEC, and frequent if concentrations exceeds the PEC.

Sediment-quality guidelines apply to whole-sediment samples, whereas samples collected as part of the NAWQA Program were sieved at 63 micrometers. 

Finer grained sediments commonly have higher contaminant concentrations 

than do whole-sediment samples. Therefore, comparison of NAWQA data to 

guidelines may overestimate toxicity somewhat.

Figure 10. Semivolatile organic compounds 

were widely detected in streambed sediments from all land-use settings except 

agricultural areas. The reasons for high 

rates of detections in some forested settings are not clear.

0 20 40 60 80 100

Phthalates

PAHs

Phenols

PERCENT DETECTION

Forest

Agriculture

Urban

Large rivers

(Sediment guidelines have not been established for phenols

or phthalates)

Percentage of sites exceeding Probable Effect

Concentration

Percentage of sites exceeding Threshold Effect

Concentration

EXPLANATION

More information on PCB trends in the Delaware River Basin are in the following 

report: 

Trends in concentrations of polychlorinated biphenyls in fish tissue from selected sites in the 

Delaware River Basin in New Jersey, New York, and Pennsylvania, 1969–98, by Karen RivaMurray and others: U.S. Geological Survey Water-Resources Investigations Report 01–4066 at 

http://ny.usgs.gov/pubs/wri/wri014066/

in 90 percent of streambed-sediment 

samples collected. The most frequently 

detected PAH compound was pyrene, 

which was detected at 87 percent of 

the sampling sites. Seven other PAH 

compounds were detected at more than 

75 percent of the sites (see Appendix). PAHs were detected in all stream 

samples collected in forested and urban 

settings and in 55 percent of the samples 

collected in agricultural settings (fig. 

10). Total PAH concentrations were 

below the TEC at 33 percent of the 

sampling sites, were between the TEC 

and PEC at 49 percent of sites, and were 

greater than the PEC at 18 percent of the 

sampling sites. The effects of urban land 

use are indicated by increasing PAH 

concentrations with increasing urban 

land cover and population density. The 

TEC was exceeded most frequently at 

urban and large-river sites (fig. 10), and 

the PEC was exceeded at 46 percent of 

the urban and 17 percent of the forested 

sites. Median concentration and percentage of sites exceeding the TEC were 

relatively high in samples from largeriver sites because these rivers drain 

major population and industrial centers.

Phthalates, which are used in the 

manufacture of plastic products and 

adhesives, were detected in 72 percent of streambed-sediment samples. 

Detection frequency and total phthalate 

median concentration were highest in 

samples from urban sites and lowest in 

samples from agricultural sites (fig. 11). 

Concentrations are likely higher at urban 

and large-river sites as a result of industrial discharges, or disposal by incineration or in landfills. Phthalate detections 

in forested settings were not expected. 

There are no sediment-quality guidelines 

for phthalates, so the potential effects of 

phthalates on sediment-dwelling organisms cannot be assessed.

Phenols are used as disinfectants 

and in chemical production, and they 

occur in combustion products. P-cresol, 

the only phenol detected of the five 

compounds analyzed for, was detected 

in 54 percent of the samples. Although 

p-cresol use is greatest in urban areas, 

median concentrations and frequencies 

of detection were higher at large-river 

and forested sites than at agricultural 

or urban sites (fig. 11). There are no 

sediment-quality guidelines for phenols, 
10 Water Quality in the Delaware River Basin

ence in high concentrations in many 

streams throughout the Study Unit indicates that sediment-dwelling organisms 

may be at risk from streambed sediments contaminated by multiple trace 

metals (fig. 12). The median number of 

TECs exceeded for metals was six, and 

at least three TECs were exceeded at 

all sites. Concentrations of chromium, 

lead, nickel, and zinc most frequently 

exceeded a PEC (each at about 20 percent of all sites sampled).

Concentrations of each trace-metal 

contaminant (except arsenic) generally 

were highest in streams draining watersheds that are associated either with 

historical or current industrial activities. 

Because many of these metals are associated with industrial processes and disposal practices, and because of the high 

population density and long history of 

industrial activity in the basin, this finding is not unexpected. Yet some streams 

in forested areas also contained elevated 

concentrations of some trace metals. 

Many of the forested sites at which levels of cadmium and zinc were elevated 

are in the headwaters of the Lehigh and 

Schuylkill Rivers, where coal was mined 

extensively from the 1870s to the 1950s. 

Moreover, concentrations of cadmium 

Figure 12. Many metals exceeded the 

Threshold Effect Concentration (TEC), the 

concentration at which adverse biological 

effects are expected to begin, in streambed sediments in all land-use settings. 

Streambed sediments of urban streams are 

likely to contain multiple metal contaminants at concentrations that may be harmful to sediment-dwelling organisms.

Health Effects of Methylmercury 

Methylmercury, the biologically active and toxic form of mercury, is a potent 

neurotoxin to humans and wildlife. It can cause neurological damage, mental 

retardation, blindness, deafness, kidney malfunction, and even death. The 

developing fetus is especially vulnerable to harmful effects of methylmercury. 

Consumption of contaminated fish and shellfish is a primary route of transmission of methylmercury to humans. Methylmercury is also harmful to wildlife 

that regularly consume contaminated fish and other organisms, particularly 

because it becomes increasingly concentrated as it is transferred up the food 

chain. This “bioaccumulation” can cause very high levels of mercury in top 

predator fish, which then pose health risks to humans and wildlife consumers. 

In 2001, the U.S. Environmental Protection Agency lowered the maximum 

advisable concentration of mercury in fish and shellfish to 0.3 micrograms per 

gram of edible tissue to protect consumers in the general population. Many 

States have much more stringent advisories for children, pregnant women, 

and women who are considering becoming pregnant. The sources of mercury 

and the environmental processes favoring its methylation are subjects of current research by the USGS and other agencies. Additional information about 

methylmercury is on the World Wide Web at URLs http://minerals.usgs.gov/

mercury and http://www.epa.gov/waterscience/criteria/methylmercury/

factsheet.html

so the potential effects of phenols on 

sediment-dwelling organisms cannot be 

assessed.

PAHs, phthlates, and phenols were 

detected more frequently at forested 

sites than at agricultural sites, and 

median concentrations tended to be 

higher than concentrations in agricultural areas (figs. 10 and 11). The reasons 

for these findings are not clear. Possible 

explanations may include local sources 

where wood or trash is burned, large leaf 

areas in forests scavenging chemicals 

from the air, and preferential deposition 

from regional atmospheric sources to 

forests that are topographically higher 

than agricultural lands.

Trace-Metal Contaminants in 

Streambed Sediment and Fish 

Tissue

Sediment-dwelling organisms may 

be at risk from multiple trace-metal 

contaminants in sediment

Trace metals that are contaminants 

of concern, including arsenic, cadmium, 

chromium, copper, lead, mercury, nickel, 

and zinc, were detected in streambed 

sediment at all 39 sites sampled in the 

basin. Although these trace metals occur 

naturally in the environment, their presFigure 11. Higher median concentrations 

of phthalates and polycyclic aromatic 

hydrocarbons at urban and large-river 

streambed-sediment sampling sites reflect 

the high rate of use and disposal of these 

compounds in these settings.

100 1,000 10,000 100,000

CONCENTRATION, IN MICROGRAMS

PER KILOGRAM

Phenols

PAHs

Phthalates

EXPLANATION

Sample concentration

Large rivers

Urban

Agriculture

Forest

Median

Probable Effect Concentration

Threshold Effect Concentration

0

10

20

30

40

50

60

70

80

90

100

PERCENTAGE OF SITES

EXCEEDING TEC

0

10

20

30

40

50

PERCENTAGE OF SITES

EXCEEDING PEC

Forest Agriculture Urban

Dominant land use

EXPLANATION

ARSENIC

CADMIUM

CHROMIUM

COPPER

MERCURY

LEAD

 NICKEL

ZINC
Major Findings 11

and zinc were highest at the two stream 

sites on the Lehigh River near a metals 

smelter (PECs were exceeded at both 

sites). The next highest concentrations 

of these elements were at the downstream site on the Delaware River at 

Trenton, N.J. Past contamination of the 

Schuylkill River by lead and other metals is also well documented (Stamer and 

others, 1985). Concentrations of trace 

metals were typically lowest in streams 

draining agricultural areas.

Concentrations of arsenic were 

elevated at sites in the western part of 

the Coastal Plain in the basin. Arsenic 

concentrations in streambed sediment 

from three of four western Coastal Plain 

streams were higher than at any other 

sites sampled throughout the basin, and 

concentrations exceeded the PEC at 

these three sites. Comparison of these 

findings with other sediment data from 

U.S. Geological Survey’s National 

Water Information System database and 

the National Uranium Resource Evaluation Program indicates that elevated 

concentrations of arsenic in the Coastal 

Plain were confined to the area where 

many geologic formations crop out 

west of the Kirkwood-Cohansey aquifer 

system (fig. 1). Whether these elevated 

arsenic concentrations are related to 

natural sources in clays or are a result of 

past use of arsenate pesticides (Murphy 

and Aucott, 1998) or other human disturbances is not clear.

Mercury levels in fish are of concern 

to health of humans and wildlife

Elevated concentrations of 

mercury were found in fish fillets 

throughout the Delaware River Basin 

(fig. 13). Concentrations of total 

mercury exceeded the human health 

criterion of 0.3 μg/g (micrograms per 

gram) set by the USEPA (2001) at 22 

percent of the 31 sites sampled, and 

exceeded the 0.1 μg/g guideline set by 

the U.S. Fish and Wildlife Service for 

protecting fish-eating wildlife (Eisler, 

1987) at 87 percent of the sites sampled. 

These levels were exceeded at sites in 

Figure 14. Formation of methylmercury (methylation efficiency), the bioavailable and toxic 

form of mercury, was much higher in forested settings than in other land-use settings. 

This helps explain why some fish-fillet samples from forested areas contained mercury 

concentrations as high as those found in urban areas, even though total mercury concentrations in water and sediment were higher in urban areas.

both urban and forested settings, and the 

wildlife guideline was exceeded at some 

agricultural sites.

Concentrations of total mercury 

in water and streambed sediment were 

lowest in forested settings (fig. 14) and 

highest in urban settings; however, 

the methylation efficiency (concentration of methylmercury divided by total 

mercury) was higher in forested settings 

than the urban settings (fig. 14). Methylmercury is the most bioavailable form of 

mercury (U.S. Environmental Protection 

Agency, 1997), and higher methylation 

rates in the forests, where the natural 

environment may be more conducive to 

the methylation process, contribute to 

the elevated concentrations in fish fillets 

at these sites (Brightbill and others, 

2003). The primary source of mercury at 

forested sites is atmospheric deposition 

from incinerators, coal-fired powerFigure 13. Mercury concentrations in smallmouth bass fillets sometimes exceeded the 

human health criterion and often exceeded 

the fish-eating wildlife-protection guideline.

More information on mercury in the Delaware River Basin is in the following 

report: 

Total mercury and methylmercury in game fish fillets, water, and bed sediment from selected 

streams in the Delaware River Basin, New Jersey, New York, and Pennsylvania, 1998–2001, by 

R.A. Brightbill and others: U.S. Geological Survey Water-Resources Investigations Report 03–4183 

at http://pa.water.usgs.gov/reports/wrir03-4183/ TOTAL MERCURY, IN

NANOGRAMS PER LITER (WATER) OR

NANOGRAMS PER GRAM (SEDIMENT)

0.1

1

10

100

Water

Bed sediment

PERCENTAGE OF TOTAL MERCUR

Y

AS METHYLMERCUR

Y

0.01

0.1

1

10

100

FOREST

AGRICULTURE

URBAN

FOREST

AGRICULTURE

URBAN

0.4

0.3

0.2

0.1

0

FISH FILLET MERCURY CONCENTRATION,

IN MICROGRAMS PER GRAM

FOREST

AGRICULTURE

URBAN

LARGE RIVER

U.S. Environmental Protection

Agency human health criterion

U.S. Fish and Wildlife Service

fish-eating wildlife guideline
12 Water Quality in the Delaware River Basin

plants and other fossil-fuel combustion 

sources. The presence of high total mercury concentrations in sediment in some 

urban settings indicates additional local 

inputs, but lower methylation efficiencies or other processes in urban regions 

limit uptake in fish. The high methylation rate in forests and low rate in urban 

areas could explain why concentrations 

of mercury in fish from both forested 

and urban settings were similar.

Naturally Occurring Contaminants in Ground Water

Of the 23 trace elements (see 

Appendix) analyzed for in domestic 

wells in the clastic-rock aquifers of the 

Piedmont and Valley and Ridge Provinces and the glaciofluvial aquifers, only 

the concentrations of arsenic and radon 

exceeded established drinking-water 

standards or guidelines. Some trace 

elements are vital to human and aquatic 

organisms; yet some can be toxic at high 

concentrations. Although trace elements 

can occur naturally, they can be mobilized as a result of human activities that 

change subsurface geochemical conditions. Trace elements from contaminated 

materials emplaced at the surface also 

can leak into aquifers.

beta radiation, were analyzed for and 

detected in wells in the clastic-rock 

aquifers of the Piedmont and Valley 

and Ridge. Many of these compounds 

are short-lived (decaying in a matter 

of days) but nevertheless are a concern 

because particles emitted in the decay 

process can cause genetic damage and 

cancers. Alpha radiation was detected in 

72 percent of the wells sampled in the 

Piedmont and 8 percent of the wells in 

Radon concentrations in most wells 

exceeded proposed drinking-water 

standard

In the Delaware River Basin, concentrations of radon (a naturally occurring gas, see box on p.13) were greater 

than 300 pCi/L (picocuries per liter), the 

proposed drinking-water standard for 

public water-supply systems, in more 

than 96 percent of the domestic wells 

sampled. The standard was exceeded in 

all the wells sampled in the Piedmont 

clastic-rock and glaciofluvial aquifers 

and in 90 percent of the wells in the 

Valley and Ridge clastic-rock aquifer. 

Concentrations ranged from 60 to 6,020 

pCi/L (fig. 15); the median concentration 

was highest in the Piedmont clastic-rock 

aquifer (1,820 pCi/L), followed by the 

Valley and Ridge clastic-rock aquifer 

(1,400 pCi/L) and the glaciofluvial 

aquifers (1,011 pCi/L). Because radon 

is produced naturally by the radioactive 

decay of uranium in rocks, concentrations in the Delaware Basin were similar 

to those in nearby NAWQA Study Units 

that sampled wells in the Appalachian 

Mountains but exceeded concentrations 

in most other areas of the country.

Other forms of radioactive materials in water have also been identified as 

health risks. Some of these elements, 

such as radium-224, radium-226, 

and radium-228, as well as alpha and 

Figure 15. Radon concentrations exceeded 

the proposed 300-pCi/L drinking-water 

standard for public water suppliers in 

almost all domestic wells sampled.

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

CONCENTRATION OF RADON,

IN PICOCURIES PER LITER 

Piedmont clastic rocks

Valley and Ridge clastic rocks

Glaciofluvial deposits

Median concentration

Proposed maximum contaminant level

EXPLANATION

Some mercury findings in the Delaware River Basin were similar to those 

from national study

Mercury concentrations in fish 

fillets in the Delaware River Basin 

ranked eighth highest among concentrations measured in 20 NAWQA 

Study Units that were sampled as 

part of a National pilot program 

(Brumbaugh and others, 2001). A 

geometric mean concentration of 

0.26 μg/g total mercury in fillets was 

calculated for the basin using data 

from this study combined with data 

from more recently collected samples. 

The geometric means across the 

Nation ranged from 0.03 to 3.34 μg/g. 

National findings on the relation of 

mercury concentrations to land-use 

patterns were similar to those in the 

Delaware River Basin. Total mercury concentrations in both water 

and sediment were higher at urban 

sites than at forested or agricultural 

sites. Similarly, median methylation 

efficiencies were lower at urban sites 

than at forested sites (Krabbenhoft 

and others, 1999). Findings from 

the national study, which included a 

wide range of environmental settings, 

also indicated that methylation is 

related to the percentage of wetlands 

in a watershed and is enhanced by 

environmental variables such as the 

presence of sulfate, organic matter, 

and dissolved oxygen. However, 

similar relations were not observed 

in the Delaware River Basin study. 

The factors affecting methylation 

rates in different environmental settings is an area of current research 

(http://minerals.usgs.gov/mercury/).
Major Findings 13

the Valley and Ridge clastic rocks, and 

exceeded the 15-pCi/L drinking-water 

standard in 10 and 3 percent of the 

domestic wells in each aquifer, respectively. Beta radiation was detected in 

41 percent of the wells sampled in the 

Piedmont and 30 percent of the wells in 

the Valley and Ridge clastic rocks, but 

did not exceed the 15-pCi/L standard. 

One or more of the different radium 

isotopes were detected in all of the wells 

sampled. The 5-pCi/L drinking-water 

standard for radium-226 plus radium228 was exceeded in 3 percent of the 

wells in the Piedmont and none of the 

wells in the Valley and Ridge clasticrock aquifer. Results in the Piedmont 

were similar to those reported by Szabo 

and Zapecza (1991) for public-supply 

wells.

Arsenic concentrations in Piedmont 

wells can exceed drinking-water 

standards

Arsenic was detected in more than 

70 percent of the domestic wells sampled in the Piedmont clastic-rock aquifer 

but in only 20 and 6 percent of the wells 

in the in the Valley and Ridge clasticrock and glaciofluvial aquifers, respecThe most commonly detected 

pesticides in surface water and in ground 

water were the herbicides atrazine, 

metolachlor, and simazine (fig. 17). 

Atrazine and metolachlor, two of the 

most heavily applied pesticides in 

agricultural areas of the basin (Gianessi 

and Marcelli, 2000), were detected in 

more streams (over 70 percent) and 

wells (almost 30 percent) than any other 

pesticide. Simazine also was frequently 

detected in streams (about 70 percent) 

and wells (about 7 percent) in various 

land-use settings throughout the basin. 

Also commonly detected in streams (but 

less frequently in ground water) was 

the herbicide prometon, which is used 

on road and utility rights-of-way, and 

the insecticides diazinon and carbaryl, 

which are commonly used to control 

residential and household pests. The 

most widely detected pesticides in the 

basin are also among the most widely 

detected pesticides nationwide (Larson 

and others, 1999).

Although similar pesticides were 

detected in surface water and ground 

water, they typically were detected 

less frequently in ground water. This 

difference can be attributed to the slow 

rate of water movement through the 

subsurface—recently applied pesticides 

are less likely to be detected in wells 

because they are still in transit. Slow 

water movement in the subsurface and 

intimate contact with the sediment 

tively (fig. 16). The median concentration for arsenic was 2.8 μg/L in samples 

from the Piedmont clastic-rock aquifer 

and less than 1.0 μg/L in the Valley and 

Ridge clastic-rock aquifer and glaciofluvial aquifers. Arsenic concentrations in 

samples from two domestic wells in the 

Piedmont exceeded the 10-μg/L drinking-water standard. Arsenic in the clastic 

rocks of the Piedmont is from natural 

sources, and its occurrence is related to 

ancient depositional environments and 

current geochemical conditions (Serfes 

and others, 2004). Arsenic in high concentrations is a human health concern 

because it can contribute to cancers 

of the skin, bladder, and other organs 

(National Research Council, 1999).

Pesticides in Streams and 

Ground Water

Pesticides include a wide variety 

of chemicals that are used to control 

undesirable plants (herbicides), insects 

(insecticides), molds (fungicides), and 

other agricultural, urban, or forest pests. 

Concerns about the potential effects of 

pesticides on human health, as well as 

on aquatic and terrestrial ecosystems, 

have led to a wide range of monitoring 

and management programs by State and 

Federal agencies. However, the types 

and amounts of pesticides used changes 

over time and many compounds are 

transformed once they are applied. Data 

collected in a consistent manner over 

time are needed to assess the implications of these changes. 

Pesticides were detected in most 

streams and in many wells sampled

One or more pesticides were 

detected in 93 percent of samples from 

94 stream and river sites and in 43 

percent of 76 domestic wells sampled. 

Of the 43 pesticides for which analyses 

were conducted, 28 were detected in 

stream samples and 15 were detected in 

wells. The number of pesticides detected 

in stream samples ranged from 0 to 13, 

and the number of pesticides detected in 

well samples ranged from 0 to 7.

More Information on Radon 

Radon is a colorless and odorless 

gas that is produced naturally by 

the radioactive decay of uranium 

in rocks and soils. Airborne radon 

has been identified as a leading cause of lung cancer. The 

USEPA has identified ground 

water as a source of radon in 

homes and recommends testing 

of well water, especially in areas 

where radon concentrations are 

known to be elevated, such as the 

bedrock areas of the Delaware 

River Basin. Additional information about radon can be found 

on the World Wide Web at URLs 

http://energy.cr.usgs.gov/radon/

radonhome.html and 

http://www.epa.gov/iaq/radon/.

Figure 16. Arsenic was detected much 

more frequently and at higher concentrations in samples from wells in the Piedmont 

clastic-rock aquifer than in those from 

wells in other parts of the Delaware River 

Basin. Data were censored to a common 

reporting limit of 1.0 micrograms per liter.

0 20 40 60 80

Piedmont

clastic rocks

Valley and Ridge

clastic rocks

Glaciofluvial

deposits

PERCENT DETECTION

Percentage of wells exceeding 10-μg/L

drinking-water standard

EXPLANATION
14 Water Quality in the Delaware River Basin

also increases the likelihood that a 

transported pesticide will stick to soil 

(adsorb), break down (degrade), or 

become a gas (volatilize).

Chemical properties of pesticides 

determine how they transform and 

interact and may explain why some 

widely used pesticides were detected 

less frequently than others. For instance, 

pendimethalin was frequently detected 

in streams in the spring, rarely detected 

in streams in the late summer, and never 

detected in ground water (fig. 17). The 

tendency for this chemical to attach 

to organic matter in soil, rather than 

dissolve in water, in large part limits 

its movement and detection in ground 

water. Also, some pesticides, such as 

alachlor, break down rapidly and are 

more likely to be found as degradation 

products than as the parent compound.

Pesticide degradation products were 

detected more frequently and often 

at higher concentrations than parent 

compounds

Many pesticides are unstable and 

can degrade into other compounds. Samples were analyzed for deethylatrazine 

(for all sites) and several degradation 

products of metolachlor, alachlor, and 

acetochlor (for all ground-water sites 

and two surface-water sites – Tulpehocken Creek, Pa., and the Schuylkill 

River at Philadelphia). Seven of 10 degradation products analyzed for in both 

ground-water and surface-water samples 

were detected. Degradation products of 

atrazine, metolachlor, and alachlor were 

some of the most frequently detected 

pesticide compounds in surface water 

and ground water, and concentrations 

were often higher than parent compounds (fig. 18). These results indicate 

that many more pesticide compounds 

are present in surface water and ground 

water than are detected in routine analyses that are designed to measure only 

parent compounds.

Deethylatrazine was the most 

frequently detected degradation product. It was the most frequently detected 

pesticide compound in ground water and 

the second most frequently detected pesticide compound in surface water. Typically it was detected in about the same 

percentage of samples and at about the 

same concentrations as atrazine, its parent compound. However, concentrations 

of both atrazine and deethylatrazine typically were lower in ground water than 

in surface water. Deethylatrazine was 

detected in 79 percent of surface-water 

samples collected in the spring, with 

a median concentration of 0.053 μg/L 

(micrograms per liter). In ground water 

it was detected in 39 percent of the wells 

sampled, with a median concentration 

below the detection limit (0.002 μg/L). 

In the Piedmont clastic rock aquifer, 

deethylatrazine had a median concentration of 0.004 μg/L and was detected in 

60 percent of the wells (a rate twice that 

of atrazine ).

Degradation products of metolachlor, alachlor, and acetochlor were 

detected at much higher concentrations 

than parent compounds, particularly 

in ground water. Degradation products 

were detected in 43 of 76 wells, whereas 

parent compounds were detected in 

only 33 wells, even though the parent 

compounds had lower detection limits 

(fig. 18). In particular, metolachlor ethane sulfonic acid (ESA) was detected in 

37 percent of the wells, at concentrations 

between 0.05 and 10.4 μg/L, whereas 

metolachlor (the parent compound) was 

detected in 3 percent of the wells, at 

concentrations above 0.05 μg/L. Results 

for the two stream sites where acetanilide herbicide degradation products 

were sampled were similar to results for 

ground-water samples.

Figure 17. Thirteen different pesticides were detected in more than 10 percent of streams 

sampled, and nine different pesticides were detected in more than 5 percent of wells 

sampled. Typically, the same pesticides were detected in streams and ground water in 

the basin, although almost all pesticides were detected less frequently in ground water.

0 10 20 30 40 50 60 70 80 90 100

PERCENTAGE OF SAMPLES IN WHICH

PESTICIDE WAS DETECTED

Metribuzin

Alachlor

Cyanazine

Trifluralin

Chlorpyrifos

Tebuthiuron

Acetochlor

Pendimethalin

Diazinon

Carbaryl

Prometon

Simazine

Metolachlor

Atrazine

Ground-water sampling sites (n=74)

Not detected

Base-flow stream sampling sites, August - September (n=74)

Base-flow stream sampling sites, May - June (n=84)

*

*

*

*

*

*

* *
Major Findings 15

Pesticide concentrations rarely 

exceeded standards or guidelines 

for drinking water and sometimes 

exceeded those for the protection of 

aquatic life

Concentrations of pesticides in 

surface water and ground water rarely 

exceeded drinking-water standards or 

guidelines (see box on p. 8). No drinking-water standards or guidelines were 

exceeded in any of the 76 homeowner 

wells sampled. Of the 531 stream samples collected at 94 sites, only 7 samples 

from 6 sites contained pesticides at concentrations that exceeded one or more 

drinking-water standard or guideline. 

These exceedances (for atrazine, simazine, or dieldrin) were found in stream 

samples collected from the Piedmont 

Province in the summer of 2000. 

Pesticide concentrations in 6 percent of the stream samples (29 samples 

collected at 11 sites) exceeded aquaticlife guidelines (see box on p. 8) for one 

or more of five pesticides. Diazinon was 

the pesticide that most often exceeded 

its aquatic-life guideline (in 19 samples 

collected at 7 sites). Of the 19 exceedances, 15 were from multiple samples 

collected at three sites: Little Neshaminy 

Creek, Pa.; Cooper River, N.J.; and 

Raccoon Creek, N.J. (see fig. 39A). 

Other compounds whose concentrations 

exceeded their aquatic-life guidelines 

were carbaryl (seven samples), lindane 

(two samples), atrazine (two samples), 

and chlorpyrifos (one sample). 

Because drinking-water or aquaticlife standards or guidelines have not 

been established for all pesticides and 

degradation products, some of the risks 

of pesticides to humans and aquatic life 

may be overlooked. For the 35 pesticide 

compounds detected in the basin, drinking-water standards or guidelines have 

been established for 21 and aquatic-life 

guidelines for 17 (including 7 of the 10 

most frequently detected pesticides). 

In particular, pesticide degradation 

products may be of concern because 

they are frequently detected at concentrations equal to or greater than parent 

compounds and can have similar or 

even greater toxicities than the parent 

compounds. Pesticide degradation products are not detected in routine water 

analyses that look only for parent compounds; therefore, harmful effects may 

be underestimated. Another concern is 

that none of the standards or guidelines 

take into account the possible synergistic effects of the mixtures of pesticides 

that are common in water samples. For 

instance, cumulative concentrations of 

all pesticides and degradation products 

in more than 20 percent of the domestic 

wells sampled in the Piedmont clastic 

rocks exceeded 1μg/L (fig. 19), and five 

or more compounds were detected in 

more than 18 percent of the wells. The 

combined effects of prolonged exposure 

to multiple co-occurring compounds on 

human health are unknown.

Pesticide concentrations are related 

to application rates on agricultural 

and urban lands

Concentrations of pesticides in 

streams were related to land use and 

pesticide-application rates in agricultural 

and urban settings (fig. 20). Concentrations of herbicides in stream samples 

(such as atrazine, metolachlor, and 

pendimethalin) increased with increasing amounts of agricultural land in a 

watershed. For example, concentrations of atrazine increased from about 

0.001 μg/L in a watershed with minimal 

Figure 18. Degradation products of the pesticides metolachlor, alachlor, and acetochlor 

(ethane sulfonic acids or ESA) were typically detected at higher concentrations than 

parent compounds, particularly in ground water. Deethylatrazine (a degradation product 

of atrazine) was generally detected at concentrations similar to those of its parent compound. Most of these degradation products are not routinely measured in water-quality 

studies, and their health effects are unknown.

PERCENTAGE OF SAMPLES

IN WHICH PESTICIDE OR

DEGRADATION PRODUCT WAS

ANALYZED FOR AND DETECTED

0.001 0.010 0.100 1.000 10.000

Atrazine

Metolachlor

Acetochlor

Alachlor

Deethylatrazine

Metolachlor ESA

Acetochlor ESA

Alachlor ESA

CONCENTRATION, IN MICROGRAMS PER LITER

Surface-water sample

Ground-water sample

Minimum reporting limit

Drinking-water standard

EXPLANATION

0 100

Not detected

Figure 19. Total concentrations of pesticides and degradation products in groundwater samples were consistently higher 

in the Piedmont than in other parts of the 

basin. Samples from 20 percent of the 

wells in the Piedmont clastic-rock aquifer, 

which has more agricultural and urban 

development than the other aquifers, had 

concentrations of 1.0 microgram per liter 

or more.

0

10

20

30

40

50

60

70

80

0.01 0.1 1.0

PERCENTAGE OF WELLS IN WHICH

CONCENTRATION 

WAS EXCEEDED

Piedmont clastic rocks

Valley and Ridge

clastic rocks

Glaciofluvial deposits

TOTAL CONCENTRATION OF

PESTICIDES AND DEGRADATION

PRODUCTS, IN MICROGRAMS

PER LITER
16 Water Quality in the Delaware River Basin

to no agricultural land to about 1.00 

μg/L in a basin with 70 percent agricultural land (fig. 21). Concentrations 

of atrazine generally were highest in 

the counties with the highest rates of 

application to agricultural lands (fig. 22). 

Some pesticides were used and detected 

only in a specific region. Terbacil, which 

is used extensively on peaches and 

blueberries, was frequently detected 

in streams of the Coastal Plain, where 

peaches and blueberries are major crops. 

Results of previous studies (Reiser and 

O’Brien, 1998; Stackelberg and others, 1997) also indicate that terbacil is 

present in streams and aquifers of the 

Coastal Plain. Terbacil was not detected 

in surface water or ground water elsewhere in the basin where other crops 

predominate and terbacil is not widely 

used.

Surface-water concentrations of 

four other frequently detected pesticides—prometon, diazinon, carbaryl, 

and chlorpyrifos—increased with the 

percentage of the watershed occupied by 

urban land. Concentrations of these pesticides were highest in and near Philadelphia and other urban areas (fig. 23). 

A comparison of use and detection rates 

could not be made, however, because 

few good estimates of rates of application of these pesticides in urban areas 

are available.

In general, more pesticides were 

detected in base-flow samples at urban 

sites than at agricultural sites. The 

median number of pesticides detected 

in streams at urban sites was 9, whereas 

the median at agricultural sites was 6, 

and the median at forested sites was 

1. A wider variety of pesticides, such 

as prometon, diazinon, carbaryl, and 

chlorpyrifos, are used around homes, 

lawns, and rights-of-way in urban areas 

than on farmland. Some pesticides, such 

as simazine, are used in both agricultural and urban areas. In addition, low 

concentrations of atrazine, metolachlor, 

and other pesticides that are associated 

primarily with agricultural land use were 

commonly detected at urban sites. These 

Figure 20. Concentrations of frequently 

detected pesticides reflected the land-use 

setting in which they were used. Streams 

in agricultural areas had higher concentrations of atrazine and metolachlor than 

streams in urban areas because these 

pesticides are primarily applied to crops. 

Conversely, streams in urban areas had 

higher concentrations of prometon and 

diazinon than streams in agricultural 

areas because prometon is primarily 

used along roads and diazinon is used to 

control insects around housing. Simazine 

is applied in both urban and agricultural 

areas.

0 0.05 0.1 0.15

Atrazine

Metolachlor

Simazine

Prometon

Diazinon

MEDIAN CONCENTRATION, IN

MICROGRAMS PER LITER

Agriculture

*

*

*

Urban

Below detection

limit

Figure 22. Atrazine was widely detected 

throughout the basin, but the highest 

concentrations were found in counties in 

which the highest quantities of atrazine 

were applied to agricultural land.

EXPLANATION

Atrazine concentration,

in micrograms per liter

Not detected

Less than or equal to 0.20

Greater than 0.20

Atrazine application rate

to commercial farmland,

in pounds per year per

square mile of county

Less than or equal to 10

Greater than 10 and less

than or equal to 50

Greater than 50

0 20 40 KILOMETERS

0 20 40 MILES

76°

75°

42°

41°

40°

39°

Figure 21. Concentrations of atrazine, a herbicide used on row crops, increased in streams and ground water with increasing 

agricultural land use.

pesticides may be derived from small 

areas of active farming or may represent 

residual pesticides in soils or ground 

water from previous land uses. Also, low 

concentrations of these pesticides may 

be carried into the area by rain (McConnell and others, 2002).

Results of ground-water studies, 

which were not specifically designed to 

0 10 20 30 40 50 60 70 80 90 100

0.0001

0.0010

0.0100

0.1000

1.0000

10.0000

Aquatic-life guideline

Nondetected concentations were set to 0.001 micrograms per liter

USEPA Drinking-water standard

AGRICULTURAL LAND AS A PERCENTAGE OF A DRAINAGE BASIN

(FOR STREAMWATER SAMPLES), OR AS A PERCENTAGE OF LAND

WITHIN 500 METERS OF A WELL (FOR GROUND-WATER SAMPLES)

ATRAZINE CONCENTRATION,

IN MICROGRAMS PER LITER

EXPLANATION

Streamwater samples in which atrazine was detected

Smoothed curve through all stream-water samples

Ground-water samples in which atrazine was detected

Ground-water samples in which atrazine was not

detected

Smoothed curve through all ground-water samples

Streamwater samples were collected at base flow during May and

June 1999, 2000, and 2001
Major Findings 17

lyzed for 85 VOCs. Forty-two different 

VOCs were detected in stream samples 

(170 samples collected at 10 sites), and 

26 VOCs were detected in well samples 

(one sample from each of 76 wells). 

Compounds typically detected in ground 

water also were found in surface water, 

although for most VOCs the detection 

frequency in surface water was generally 

greater (fig. 25). The most frequently 

detected classes of VOC compounds 

were chlorinated solvents and disinfection byproducts (compounds produced 

when water is treated with a disinfectant). Many components of gasoline, 

such as benzene, toluene, ethylbenzene, 

and xylenes, were detected frequently in 

surface water but were not detected in 

ground water, most likely because they 

are readily biodegraded in the subsurface. Gasoline-related compounds that 

were found most frequently in ground 

water were oxygenates such as methyl 

tert-butyl ether (MTBE) that are not 

readily biodegraded.

Although VOCs were detected 

frequently, concentrations generally 

were low. Only five VOCs (acetone, 

MTBE, toluene, chloroform, and 

trichloroethene) had median concentrations greater than 0.01 μg/L, and only 

acetone and MTBE were detected at 

concentrations greater than 1.0 μg/L. 

account for the effects of land use, were 

similar to surface-water findings. In 

general, more pesticides were detected 

in wells in the more developed southern 

part of the basin than in wells in the less 

developed northern part. A total of 12 

pesticide compounds were detected in 

well samples from the Piedmont clasticrock aquifer, 10 in samples from the 

Valley and Ridge clastic-rock aquifer, 

and 3 in samples from the glaciofluvial 

aquifers. Concentrations of atrazine and 

metolachlor generally were lowest in the 

northern part of the basin, where agriculture development is least intense. Detections of prometon, diazinon, carbaryl, 

and chlorpyrifos in ground water were 

few because these insecticides are likely 

to sorb to soil or degrade. However, 

these compounds are used and detected 

most frequently in urbanized regions 

like the Piedmont; they were detected 

less frequently in the Valley and Ridge 

and not at all in the relatively undeveloped Appalachian Plateaus.

Figure 23. Prometon, a herbicide used 

extensively on roads and other rights-ofway, was typically found in streams draining highly populated watersheds.

Prometon concentration,

in micrograms per liter

Not detected

Less than or equal to

0.015

Greater than 0.015

Population density, people

per square mile

Less than or equal 100

Greater than 100 and less

than or equal to 1,000

Greater than 1,000

EXPLANATION

0 20 40 KILOMETERS

0 20 40 MILES

76°

75°

42°

41°

40°

39°

Figure 24. Concentrations of atrazine in streams were highest during the growing season 

(May, June, and July). This pattern has been noted for many pesticides in streams nationwide (Larson and others, 1999) and has been attributed to rain washing off pesticides 

applied in the spring. Station locations are shown in figure 39.

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 S

1998 1999 2000 2001

EXPLANATION

Nongrowing season

Growing season

Less than or equal to 0.007

Greater than 0.007 and less than or equal to 0.12

Greater than 0.12 and less than 2

Atrazine concentration in streamwater, in micrograms per liter

6

1

4

3

5

8

9

10

2

7

Decreasing agricultural land use 

STATION NUMBER

Pesticide concentrations in streams 

were highest during the growing 

season

Concentrations of pesticides in 

streams were highest during the growing season, when most pesticides are 

applied. Concentrations of pesticides 

used in agricultural areas (atrazine, 

metolachlor, and acetochlor) peaked 

from May to July (fig. 24) when they are 

typically applied. In contrast, concentrations of pesticides used primarily in 

urban areas (prometon, diazinon, carbaryl, and chlorpyrifos) are elevated over 

the entire growing season because they 

are applied repeatedly to control weeds 

and insect pests. The seasonal pattern 

in agricultural pesticide concentrations 

has been noted in streams nationwide 

(Larson and others, 1999) and has been 

attributed to pesticides being washed off 

by rainstorms during the period they are 

applied.

VOCs in Streams and Ground 

Water

One or more volatile organic compounds (VOCs) were detected in 92 percent of stream samples and 59 percent of 

well samples. Water samples were ana-
18 Water Quality in the Delaware River Basin

In ground water, only chloroform and 

MTBE were detected at concentrations 

above 0.01 μg/L in more than 10 percent 

of the wells. Concentrations of VOCs 

in surface water and ground water did 

not exceed drinking-water standards 

or guidelines, and concentrations in 

surface water did not exceed aquaticlife guidelines (see box on p. 8). The 

health effects of VOCs are not completely understood, however, because 

drinking-water standards or guidelines 

have been established for only 23 of 42 

VOCs detected in surface water and 21 

of 26 VOCs detected in ground water, 

and aquatic-life guidelines have been 

established for only 10 of the 42 VOCs 

detected in streams.

VOCs were detected in streams and 

ground water in urban and agricultural areas

VOCs were detected in water 

samples collected in urban and agricultural areas, but the number of compounds detected and the frequency of 

detections were greatest in urban areas. 

This pattern of higher VOC detection in 

both surface and ground water in urban 

areas reflects a greater intensity of use 

and production of solvents, gasoline 

products, and sewage in urban areas. 

For example, the frequency of VOC 

detections was greater in wells in the 

urban Piedmont clastic-rock aquifer 

(87 percent) than in wells completed in 

either the agricultural Valley and Ridge 

clastic-rock aquifer (47 percent) or the 

less developed glaciofluvial areas farther 

north (31 percent) (figs. 25 and 26). 

Similarly, the number of VOCs detected 

was greater in the Piedmont clastic-rock 

aquifer than the other aquifers. Three or 

more VOCs were detected in 60 percent 

of the Piedmont wells, and five or more 

were detected in 33 percent of the wells. 

In contrast, three or more compounds 

were detected in only 20 percent of the 

wells in the Valley and Ridge, and only 

one well had five or more.

Analyses of surface-water samples 

also indicated that the number of VOCs 

detected and the frequency of detection 

were highest in the group of urban sites, 

intermediate in the group of agricultural 

sites, and lowest at the forested site 

(fig. 27). MTBE was the only compound 

detected at the forested site (Delaware 

River at Port Jervis, N.Y.) and was 

detected in only one of eight samples. 

In general, the same classes of compounds (solvents, gasoline, and disinfection byproducts) were detected at both 

agricultural and urban sites, but the 

frequency of detection and the number 

of compounds detected were lower at 

agricultural sites than at urban sites.

Concentrations and detection frequencies of VOCs vary seasonally

More than two-thirds of detections 

of most chlorinated solvents and gasoline-related compounds in surface water 

were in samples collected in winter and 

spring. This pattern is similar to that 

Figure 27. VOCs were frequently detected 

in streams in both urban and agricultural 

settings, but the number of VOCs detected 

was greater in urban areas.

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Figure 25. Volatile organic compounds (VOCs) were frequently detected in surface-water 

and ground-water samples, but concentrations did not exceed drinking-water standards 

or guidelines. Many of the gasoline compounds, such as benzene, were detected in 

surface water but were not detected in wells because they are readily degraded in the 

subsurface.

Figure 26. VOCs were detected in a higher 

percentage of wells in the Piedmont 

clastic-rock aquifer than in wells in other 

regions. This is likely due to higher use of 

VOCs in the heavily urban Piedmont region.

0 20 40 60 80 100

None

1 or more

3 or more

5 or more

NUMBER OF 

VOCs

DETECTED

PERCENT DETECTION

Glaciofluvial deposits (n=16)

Valley and Ridge clastic rocks (n=30)

Piedmont clastic rocks (n=30)

Number in parentheses indicates total

number of wells sampled in each aquifer.

EXPLANATION

Detections by VOC Class

0 10 20 30 40 50 60 70

TETRACHLOROETHYLENE

TRICHLOROETHYLENE

CIS-1,2-DICHLOROETHENE

1,1,1-TRICHLOROETHANE

METHYL TERT-BUTYL ETHER (MTBE)

TOLUENE

BENZENE

M&P-XYLENE

1,2,4-TRIMETHYLBENZENE

ETHYLBENZENE

O-XYLENE

CHLOROFORM

ACETONE

BROMODICHLOROMETHANE

PERCENT DETECTION

All wells Piedmont wells Surface water Not detected

Chlorinated 

solvents

Gasoline 

compounds

Disinfection

byproducts

EXPLANATION

*

*

*

*

*

*

*

*

*

*

*

*

*
Major Findings 19

reported by Reiser and O’Brien (1998) 

and can be attributed to the fact that 

VOCs are less likely to be detected in 

warm water because they become more 

volatile and are driven into the atmosphere. In contrast, at two large-river 

sites (Schuylkill River at Philadelphia 

and the Delaware River at Trenton), the 

detection frequency and concentration of 

MTBE was greater in the summer than 

in other seasons, whereas concentrations 

of other gasoline-related compounds 

showed no increase in the summer (most 

likely because they are more volatile 

and degrade more readily than MTBE). 

The use of motorized watercraft is most 

likely responsible for the summer peaks 

in MTBE concentration and detection frequency at these two sites (the 

only locations studied where motorized watercraft are used routinely). A 

similar seasonal pattern has been noted 

in lakes used for motor boating, both 

locally (Baehr and Reilly, 2001) and in 

other parts of the Nation (Boughton and 

Lico, 1998). In contrast to solvents and 

gasoline, no seasonal trends in concentrations were noted for most disinfection 

byproducts, such as chloroform and 

acetone, probably as a result of limited 

variability in point-source inputs and 

streamflow.

Nutrients in Streams and 

Ground Water

Nutrients (forms of nitrogen and 

phosphorus) are essential for plant 

growth, but elevated concentrations are 

undesirable for two reasons. First, consumption of drinking water containing 

high concentrations of some forms of 

nitrogen can reduce oxygen concentrations in the blood of infants to dangerously low levels (blue-baby syndrome). 

Second, elevated concentrations in 

surface water can degrade water quality 

by promoting excessive growth of algae 

and other aquatic plants. This growth 

can be aesthetically unpleasing; can 

interfere with recreational activities such 

as swimming, boating, and fishing; and 

can clog water intakes. When algae die 

and decay, resulting oxygen depletion 

can affect other aquatic communities 

and can produce foul odors and tastes.

Nutrients in the Delaware River 

Basin originate from point and nonpoint 

sources. Point sources are primarily 

municipal and industrial dischargers. 

Nonpoint sources are primarily related 

to application of commercial fertilizers 

and manure in agricultural settings, and 

commercial fertilizer in urban settings. 

Atmospheric deposition can also be a 

significant source of nitrogen. In areas 

without public sewers, septic-system 

leachate can contribute nitrogen to 

aquifers. Nutrients on the land surface 

are often carried into streams with storm 

runoff, or they can infiltrate into the 

ground where they can travel for months 

or years before being discharged to 

streams.

Agricultural and urban lands are 

the primary sources of nutrients in 

streams and aquifers 

Concentrations of total nitrogen 

in streams increased with the percentage of agricultural or urban land in a 

watershed. Total nitrogen increased 

with increasing amounts of agricultural 

land in watersheds in which urban 

land makes up a small part (10 percent 

or less) of the basin (fig. 28). A similar increase was seen with increasing 

urbanization in streams where agricultural land makes up a small part (about 

10 percent or less) of the basin. In 

watersheds with a mix of agricultural 

and urban land, nutrient-concentration 

increases were related to both land uses. 

In addition to land-use associations, high 

concentrations of total nitrogen were 

sometimes associated with large pointsource discharges.

In streams, the predominant forms 

of nitrogen were nitrate and organic 

nitrogen plus ammonia. Nitrate was 

detected in more than 95 percent of the 

streams sampled and often amounted 

to more than 75 percent of the total 

nitrogen in surface-water samples. Concentrations of total nitrate ranged from 

nondetectable to 10.5 mg/L as N, with 

a median of 0.87 mg/L. The drinkingwater standard for nitrate (10 mg/L as 

Figure 28. In agricultural watersheds with little urban land (10 percent or less), concentrations of nitrogen and phosphorus increase with agricultural development. In urban 

watersheds with little agricultural land (10 percent or less), concentrations of nutrients 

increase with urbanization. In watersheds with a mix of land uses, the two sources of 

nutrients are difficult to separate. Concentrations shown were measured at base flow, 

May and June 1999–2001.

0.01

0.10

1.00

10.00

TOTAL NITROGEN, IN

MILLIGRAMS PER LITER

AS NITROGEN

Streams in which

urban land makes

up 10 percent or

less of basin

Streams in which

urban land makes

up more than 10

percent of basin

Smoothed curve

through agricultural

sites

Smoothed curve

through urban sites

0 20 40 60 80 100

PERCENTAGE OF DRAINAGE BASIN COMPOSED

OF AGRICULTURAL LAND

0.001

0.010

0.100

1.000

TOTAL PHOSPHORUS, IN

MILLIGRAMS PER LITER

AS PHOSPHORUS

USEPA RECOMMENDED LIMIT

FOR TOTAL PHOSPHORUS

EXPLANATION
20 Water Quality in the Delaware River Basin

aquifer, which has the highest percentage of urban and agricultural land (over 

50 percent), followed by the Valley and 

Ridge, and glaciofluvial aquifers (fig. 

29). In the Valley and Ridge clastic-rock 

aquifer, nitrate concentrations generally were higher in the Great Valley, 

where agricultural development is much 

more extensive than elsewhere. Higher 

concentrations of nitrate in wells than 

in streams in the Piedmont and Appalachian Plateaus (fig. 29), as well as parts 

of the Valley and Ridge Provinces, indicates that ground water can be a major 

contributor of nitrate to streams during 

base flow.

Total phosphorus concentrations in stream samples ranged from 

nondetectable to 1.4 mg/L as P, with a 

median of 0.068 mg/L. Concentrations 

commonly exceeded 0.1 mg/L, a goal 

established by USEPA for minimizing 

nuisance plant growth. For example, 

total phosphorus concentrations at 5 of 

the 10 streams sampled throughout the 

year under all flow conditions exceeded 

this goal more than 50 percent of the 

time (fig. 30). Only 15 percent of the 

81 streams sampled only once or twice 

under base-flow conditions exceeded 

this goal. The lower percentage in the 

base-flow samples likely reflects the 

fact that phosphorus is often transported 

in stormwater. Concentrations of total 

phosphorus at 8 of 10 streams sampled 

routinely were higher during storms 

because phosphorus is often attached to 

sediment, and sediment concentrations 

increase during storms.

Concentrations of total phosphorus 

in streams increased with the percentage of agricultural or urban land in a 

watershed (fig. 28). Concentrations of 

phosphorus in streams in urban and agricultural settings also were more likely to 

exceed the USEPA goal for minimizing 

nuisance plant growth. Under base-flow 

conditions, phosphorus concentrations 

were highest (greater than 0.5 mg/L 

as P) in streams in which point-source 

discharges constitute a large percentage of total flow. These streams include 

Pennypack Creek, Wissahickon Creek, 

and the Lehigh and Schuylkill Rivers. 

Concentrations of dissolved phosphorus in well samples ranged from 

nondetectable to 0.317 mg/L as P, with a 

median of 0.014 mg/L. Most phosphorus 

detected in well samples was orthophosphate, which is extremely soluble. Most 

other forms of phosphorus are not very 

soluble and are filtered out by sediments 

near the surface or are taken up by 

plants. For this reason, concentrations 

of phosphorus were lower in most well 

samples than in stream samples. As with 

nitrate, differences in orthophosphate 

concentrations in each aquifer studied 

were related to differing levels of agricultural and urban development. Median 

orthophosphate concentrations were 

highest in the more urban Piedmont 

clastic rock aquifer (0.031 mg/L as P), 

followed by the agricultural Valley and 

Ridge clastic rock aquifer (0.014 mg/L 

as P), and the least developed glaciofluvial aquifers (below 0.005 mg/L as P).

Nutrients increase algal biomass and 

alter diatom communities

Algal biomass and the types of 

algal species present in streams generally are indicative of nutrient enrichment 

(elevated concentrations of nutrients) 

because algae require nutrients for 

growth and reproduction. The number and types of algae in the water or 

attached to rocks provide important 

information about a stream’s nutrient 

Figure 29. Concentrations of nitrate in 

streams and aquifers in the intensely 

developed Piedmont Province are among 

the highest in the basin. High nitrate concentrations in wells in this region indicate 

that ground water is one likely source 

of nitrates to streams during periods of 

low flow. Stream samples were collected 

May–June 1999–2001 at base flow.

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Figure 30. The percentage of stream samples in which the USEPA recommended 

limit for total phosphorus (0.1 milligrams 

per liter) was exceeded increased as the 

percentage of the watershed composed of 

urban land increased. Sites locations are 

shown in figure 39.

1

10

100

0 20 40 60 80 100

4

URBAN LAND USE, IN

PERCENTAGE OF BASIN

PERCENTAGE OF SAMPLES IN

WHICH CONCENTRATION OF

TOTAL PHOSPHORUS EXCEEDED

0.1 MILLIGRAMS PER LITER

AS PHOSPHORUS

Site number

Smoothed curve

1

2

3

4

5 6

7

8

9

10

N) was exceeded in one stream sample 

(10.5 mg/L in Tulpehocken Creek). 

Organic nitrogen plus ammonia also was 

frequently detected in streams (99 percent of samples) and usually amounted 

to about 20 percent of the total nitrogen 

in stream samples.

In ground water, more than 95 

percent of the total nitrogen was nitrate 

(a form of nitrogen that is soluble, not 

easily degraded, and unlikely to sorb to 

sediments). Concentrations of nitrate 

in wells ranged from nondetectable 

to 10.7 mg/L as N, with a median of 

1.1 mg/L. The drinking-water standard 

for nitrate (10 mg/L as N) was exceeded 

in two domestic supply wells, both in 

the Valley and Ridge Province (10.1 and 

10.7 mg/L). Nitrate was not detected in 

about 13 percent of the wells sampled 

(detection limit, 0.05 mg/L), which were 

mostly in parts of aquifers with minimal 

to no oxygen.

Differences in nitrate concentrations were related to differing levels of 

agricultural and urban development in 

each aquifer studied. The median concentration was highest in the Piedmont 
Major Findings 21

Nutrient concentrations span the range of national findings

Concentrations of nitrogen and 

phosphorus at sites sampled monthly 

in the Delaware River Basin were 

similar to or slightly higher than those 

in 479 streams sampled throughout 

the Nation (fig. 33). Flow-weighted 

mean concentrations of total nitrogen 

at sites on Tulpehocken Creek, Jordan 

Creek, and the Schuylkill River (sites 

7, 2, and 9 in fig. 33) exceeded those 

at 75 percent of the sites nationwide, 

and the mean concentration at the 

agricultural site on Tulpehocken 

Creek exceeded those at 95 percent of 

the sites. The highest mean concentration of total phosphorus in the 

basin was measured at the urban site 

at Cooper River (site 6). This value 

exceeded concentrations measured 

at 80 percent of the sites nationwide. 

In contrast, phosphorus and nitrogen 

concentrations at the forested site on 

the Delaware River at Port Jervis, 

N.Y. (site 1), were among the lowest 

measured nationally.

Concentrations of phosphorus 

and nitrogen in domestic wells from 

the Valley and Ridge clastic-rock and 

glaciofluvial aquifers of the basin 

were similar to those in other domestic wells sampled throughout the 

Nation (fig. 34). Median concentrations of nitrate and orthophosphate 

phosphorus in domestic wells in the 

Piedmont clastic-rock aquifer, however, were among the highest measured. The median nitrate concentration for the Piedmont well survey was 

greater than that found in 91 percent 

of the well surveys nationwide. The 

median concentration of orthophosphate phosphorus in the Piedmont 

clastic-rock aquifer also was high, 

exceeding concentrations measured 

in 81 percent of the wells nationwide. 

These elevated concentrations reflect 

the long history of intensive agricultural and urban development in the 

Piedmont.

Figure 33. Flow-weighted mean concentrations of total nitrogen and total phosphorus 

in stream samples from sites sampled routinely in the Delaware River Basin span the 

range of concentrations measured in 479 streams throughout the Nation. Site locations 

are shown in figure 39.

Figure 34. Median concentrations of nutrients in well samples from the Piedmont 

clastic-rock aquifers of the Delaware River Basin were greater than the median 

concentrations in most of the 94 domestic well surveys made nationwide.

0 20 40 60 80 100

0.001

0.010

0.100

1.000

10.000

MEDIAN CONCENTRATION,

IN MILLIGRAMS PER LITER

Piedmont

Piedmont

Valley and Ridge

Valley and Ridge

Glaciofluvial

Glaciofluvial

Median concentrations less than reporting limits are not shown

PERCENTAGE OF DOMESTIC WELL SURVEYS WITH MEDIAN CONCENTRATION

LESS THAN OR EQUAL TO INDICATED VALUE

Median concentration of dissolved nitrate plus nitrite (as N) of NAWQA well surveys

Median concentration of dissolved orthophosphate (as P) of NAWQA well surveys

Reporting limit for dissolved nitrate plus nitrite

Reporting limit for dissolved orthophosphate

Median concentration of dissolved nitrate plus nitrite of well survey in Delaware River Basin

Median concentration of dissolved orthophosphate of well survey in Delaware River Basin

EXPLANATION

0 20 40 60 80 100

0.01

0.10

1.00

10.00

100.00

Flow-weighted mean concentrations less than the reporting limits are not shown.

2

1 6

4

8

10

5

9

3

7

1 2 6 4

5

7

10

9

6 3

PERCENTAGE OF NAWQA ROUTINE SAMPLING SITES WITH FLOW-WEIGHTED MEAN

CONCENTRATION LESS THAN OR EQUAL TO INDICATED VALUE

FLO

W-WEIGHTED MEAN CONCENTRATION,

IN MILLIGRAMS PER LITER

EXPLANATION

6

4

Total nitrogen concentrations (as N) at NAWQA routine sampling sites

Total nitrogen concentrations at routine sampling sites in the Delaware River Basin and station number

Reporting limit for total nitrogen

Total phosphorus concentrations (as P) at NAWQA routine sampling sites

Total phosphorus concentrations at routine sampling sites in the Delaware River Basin and station number

Reporting limit for total phosphorus
22 Water Quality in the Delaware River Basin

status and whether nutrients may be 

contributing to ecological degradation. 

Furthermore, algae are a main source 

of food for certain insects, snails, other 

invertebrates, and fish and can affect the 

structure and function of invertebrate 

and fish communities.

Algae samples collected from 

rocks (periphyton) indicate that Delaware River Basin streams are affected 

by nutrient enrichment from human 

activities, although none of the stream 

samples indicated eutrophic conditions 

(having excessive plant growth from elevated nutrient concentrations). Median 

and maximum concentrations of chlorophyll-a, one indicator of algal quantity, 

were 18.6 mg/m2 (milligrams per square 

meter) and 79.8 mg/m2, respectively. 

Comparison with published values 

(Dodds and others, 1998) indicates that 

the typical wadeable stream sampled is 

mesotrophic (has a level of nutrients that 

allows for moderate plant growth).

Agricultural sources of nutrients 

appear to influence algal density (the 

number of algal cells per unit area of 

rock) because algal density increased 

with the percentage of agricultural land 

in a basin (fig. 31). This relationship is 

not straightforward because trees can 

reduce algal densities in streams by 

reducing the available sun and heat that 

algae need to grow.

Most highly urbanized basins had 

higher algal densities than less urbanized 

basins, but a clear pattern of increasing algal density with urban land use is 

not evident. This is most likely because 

of substantial scatter in the data at low 

levels of urbanization, possibly caused 

by nutrients from multiple sources and 

previous land uses. It is also possible 

that high flows and scouring of stream 

channels after rainstorms may serve 

to control algal growth in some of the 

urban streams sampled. Another factor 

influencing algal density is the presence 

of shade trees along streambanks. 

The presence and numbers of 

particular species of diatoms seemed to 

be a more sensitive indicator of nutrient 

enrichment than either chlorophyll-a or 

algal density. Increases in the percentage of diatom algae species considered 

tolerant of nutrient enrichment (Van 

Dam and others, 1994) were related to 

increases in the percentage of land used 

for agricultural and (or) urban activities 

(fig. 32). Both the algal-density and diatom-species findings indicate that algal 

communities are responding to increased 

nutrients from agricultural and urban 

land uses, and that some of the streams 

may be susceptible to further degradation if nutrient inputs increase and (or) 

stream shading is reduced.

Effects of Urbanization and 

Streamflow on Water Quality 

and Aquatic Communities in 

Streams

Stream chemistry and the health of 

aquatic communities can be affected by 

many interrelated natural and manmade 

factors. For example, aquatic communities often respond to habitat changes 

caused by flow variations but can also be 

affected by changes in water or sediment 

chemistry. Stream chemistry, in turn, can 

be affected by natural or human-induced 

variations in flow. The relative importance of these many factors on chemistry 

and biology can vary in different settings 

and can change over time.

Urbanization degrades water quality 

and ecological health

Urbanization affects the physical, 

chemical, and biological characteristics 

of streams in the Delaware River Basin. 

(For a broader geographic perspective 

on urbanization effects see page 25.) 

Stream-dwelling biota are affected by 

urbanization, as indicated by decreases 

in the numbers and relative abundances 

of pollution-sensitive invertebrate 

species as road density (an indicator 

of urbanization — see box on p. 23) 

increased (fig. 35A). This included a 

general decline in “EPT richness”—or 

numbers of mayfly (Ephemeroptera), 

stonefly (Plecoptera), and caddisfly 

(Trichoptera) taxa—with increasing 

road density. Similarly, diatoms that are 

attached to rocks in streams can be sensitive indicators of environmental disturbance. In this study, diatom species that 

are less tolerant of salt than other species 

(Van Dam and others, 1994) decreased 

with increasing road density, most likely 

because of increased salinity from road 

runoff and other urban sources. The 

loss of sensitive invertebrates and other 

biological changes that occur in streams 

in urbanized areas may be the result of 

multiple interrelated disturbances associated with urbanization. These include 

chemical inputs from point and nonpoint sources, alteration of natural flow 

regimes, and loss of suitable habitat.

Figure 32. Relative species richness of 

diatoms that are tolerant of nutrient enrichment (eutrophic) increased with increasing 

agricultural and urban land cover. This 

change in algal community structure can 

affect other biota and the stream ecosystem in general.

URBAN PLUS AGRICULTURAL LAND,

IN PERCENTAGE OF BASIN

80

100

60

40

0

0 20 40 60 80 100

EUTROPHIC DIATOM RELATIVE

RICHNESS, IN PERCENT

Smoothed curve fit

EXPLANATION

Figure 31. Algal density, an indicator of 

nutrient enrichment, increased with agricultural land use. Shading from trees can 

reduce algal densities.

0 20 40 60 80 100

EXPLANATION

105

106

107

108

TOTAL ALGAL DENSITY, IN CELLS

PER SQUARE CENTIMETER

PERCENTAGE OF WATERSHED

THAT IS AGRICULTURAL LAND

Degree of shading

More open

More shaded

Smoothed curve

More open

More shaded
Major Findings 23

Urban Factors That Were Studied

Water chemistry, physical conditions, and ecological communities were surveyed during 2000 at 28 Piedmont sites in the Philadelphia metropolitan area 

and during 2001 at 16 sites in the Pocono plateau region (fig. 39A). Effects of 

urbanization were examined by comparing physical, chemical, and biological conditions among sites having relatively low to relatively high levels of 

urbanization. Road density (miles of roads divided by square miles of watershed area) is used as an indicator of urbanization in this section of the report 

because it provides a more accurate representation of urbanization in the 

Poconos than does percentage of urban land from satellite data (which often 

do not discern developed land where there is substantial tree cover).

An increase in chloride concentration with increasing road density (fig. 

36B) indicates that invertebrate, diatom, 

and other aquatic communities may be 

responding to chemical changes associated with urban road runoff, water-softening and septic system leachate, and 

municipal and industrial wastewater. 

Chloride is an indicator of multiple 

chemical inputs and other disturbances 

associated with these sources. Concentrations of sodium, sulfate, and other 

major ions also increased with urbanization.

Pesticides that are applied to 

farms, lawns, golf courses, roadsides, 

and other settings are found in surfacewater samples in the Delaware Basin 

(see p. 15). A Pesticide Toxicity Index 

(PTI; see box on p. 24) was applied to 

pesticide concentration data collected 

during late spring and late summer in 

order to assess the potential toxicity 

of the detected pesticide mixtures to 

invertebrates and fish. Findings indicate 

increasing potential pesticide toxicity of streamwater from both sampling 

periods with increasing urbanization 

(fig. 35C shows late summer PTI for 

invertebrates). A seasonal difference was 

also seen, in that PTI from late summer samples was more closely related 

to urbanization than was PTI from late 

spring samples. This reflects the application of pesticides (primarily insecticides) throughout the summer in urban 

settings, whereas pesticides (primarily 

herbicides) are applied to agricultural 

areas primarily in the spring (see p. 15).

Nutrient concentrations were generally higher in samples from streams 

in the more urban Piedmont than in 

samples from streams in the more forested Poconos region. An urban-related 

pattern of nutrient concentrations in the 

Piedmont, however, is not clear because 

of agricultural activity in some slightly 

to moderately urbanized watersheds 

(fig. 28). However, algal biomass and 

the types of algal species present in 

streams were related to agricultural and 

urban sources of nutrients (see p. 20).

In general, habitat quality 

decreased with increasing road density 

(fig. 35D), as indicated by the USEPA’s 

qualitative assessment method (Barbour and others, 1999). Variations in 

particular physical characteristics such 

as substrate size and water temperature, however, may also be influenced 

by natural factors, such as stream size, 

slope, and geology. For example, road 

density in the Piedmont region was 

related to an increase in mean daily 

minimum water temperature and a 

decrease in the percentage of streambed 

substrate composed of cobble — two 

factors that affect aquatic biota (Allan, 

1995), but these patterns were revealed 

only when sites were limited to those 

in clastic rock settings. Responses of 

particular habitat variables to urbanization can be obscured by other complicating factors such as effects of agricultural 

activity in watersheds with low amounts 

of urbanization, the length of time an 

area has been urbanized, and the extent 

of riparian-zone (streambank and floodplain) disturbance. Some of these factors 

may account for the unusually low or 

high habitat quality scores in relation 

to levels of urbanization for some sites 

shown in figure 35D. 

Elevated concentrations of some 

organic and trace-metal contaminants 

in water, streambed sediment, and fish 

tissue are also related to the extent of 

urbanization (see p. 6 and 10). In some 

Figure 35. Biological, chemical, and physical changes in streams are associated with 

increasing urbanization (indicated here by road density). EPT richness (A) is number of 

mayfly, stonefly, and caddisfly invertebrate taxa; chloride concentrations (B) are from 

base-flow samples collected in May or June; Pesticide Toxicity Index (C) is calculated 

from concentrations in base-flow samples collected in late summer and is based on toxicity to invertebrates; habitat quality (D) is based on visual assessments of in-stream and 

streambank condition; and road density is miles of road per square mile of drainage area. ������������ ����������������� �������������� ��������������� �����

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24 Water Quality in the Delaware River Basin

cases, contaminants such as VOCs in 

surface water and SVOCs in streambed 

sediments increased with increasing 

watershed urbanization, indicating that 

currently urbanizing areas may be at risk 

for increasing concentrations of these 

contaminants. In other cases, “legacy” 

contaminants, such as organochlorine 

pesticides and PCBs, are associated primarily with older urban sites (see p. 7).

These studies suggest that continued urban growth in the basin may be 

expected to result in further changes in 

chemical, physical, and biological conditions of streams. Some of the changes 

observed in this study were similar to 

those observed in other NAWQA urbanization studies (see p. 25) and suggest 

areas for additional study and monitoring. In particular, macroinvertebrates, 

which are already routinely collected by 

many monitoring agencies, appear to be 

sensitive indicators of stream response 

to urbanization. Chemical responses 

such as potential pesticide toxicity and 

chloride (the latter which is relatively 

inexpensive to measure) also show fairly 

clear trends with urbanization. Habitat degradation appears to occur with 

urbanization, but finer scale landscape 

information may be required in order to 

more fully describe the specific physical 

changes that occur in these streams.

Highly variable annual streamflow 

affects water chemistry and aquatic 

biota

Flows in streams throughout the 

Delaware River Basin were well below 

normal in 1999 and slightly below 

normal in 2001 (fig. 4) as a result of 

lower than normal precipitation during those years. In 2000, differences in 

precipitation patterns produced abovenormal flows in northern streams and 

near-normal flows in southern streams. 

Within each year, seasonal patterns 

in flow generally corresponded with 

seasonal variation in evapotranspiration; 

highest streamflows usually occurred 

in the spring and lowest flows usually 

occurred in the late summer (fig. 4). 

Underlying geology also influenced 

the seasonal variation in flow and the 

degree to which flows were affected 

by drought. Streams flowing through 

areas of carbonate rocks and unconsolidated sediments typically had higher 

flows per unit area than streams flowing 

through areas of less permeable clastic 

rocks (fig. 36). The Catskills did not fit 

this general pattern because of greater 

precipitation and higher permeabilities 

in that region. Point-source discharges at 

some sites can also help maintain flows 

in dry years, but can adversely affect 

water quality.

The year-to-year differences in 

streamflow affected water quality in 

the basin, particularly for nutrients and 

pesticides. For instance, the concentration and number of pesticides detected at 

monthly sample sites in the wettest year, 

2000, were greater than those in other 

years (fig. 37). It is not clear whether 

this difference was due to greater washoff of pesticides in 2000, or whether 

smaller amounts of pesticides were 

applied during dry periods (when crops 

and lawns were less likely to grow). 

Total phosphorus concentrations at 

some routine sampling sites were higher 

during 1999, the drought year, than 

during 2000 or 2001. This is likely due 

to point-source discharges from wastewater-treatment plants, which made up 

a greater percentage of the streamflow 

at some of these sites. Streamwater concentrations of chloride, ammonia, and 

organic nitrogen behaved similarly to 

pesticides and usually decreased during 

dry years. Concentrations increased during dry years, however, on some streams 

with large point-source discharges.

Figure 36. During summer 1999, streamflow 

per unit area was generally higher in more 

permeable carbonate rocks and unconsolidated sediments than in less permeable 

clastic rocks. Greater precipitation in the 

Catskills also produced higher flows per 

unit area.

What is the PTI?

The Pesticide Toxicity Index (PTI; Munn and Gilliom, 2001) is the sum of 

the concentrations of all herbicides and insecticides detected after each is 

weighted by its presumed toxicity to particular forms of aquatic life. Although 

the PTI provides no information regarding a sample’s actual toxicity to invertebrates or fish, it does allow for the ranking of sites as to their relative potential toxicity. Only one of the stream samples used in the PTI calculation for the 

Delaware River Basin exceeded an aquatic-life guideline for pesticides.

Figure 37. The number of pesticides 

detected was greatest in 2000, a year with 

more precipitation than 1999 or 2001.

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1.5

0.5

2

Appalachian Plateau-Catskills

Appalachian

Plateau-Poconos

Valley and Ridge

Piedmont 

Coastal Plain

FLOW PER UNIT AREA, IN CUBIC FEET

PER SECOND PER SQUARE MILE

Clastic rocks

Carbonates

Unconsolidated

sediment

Streams with

point sources
Major Findings 25

Urbanization can degrade water quality and affect sensitive aquatic life, according to a comparison of NAWQA findings 

among studies in the major metropolitan areas of Boston (New 

England Coastal Basins), Philadelphia (Delaware River Basin), 

Dayton and Cincinnati (Great and Little Miami River Basins), 

and Chicago (upper Illinois River Basin). These studies, which 

compared conditions among streams in watersheds ranging 

from minimally to highly urbanized, showed declines in indicators of biological-community health—and increases in chemical 

indicators of human activity—with increases in percentage of 

urban land. For example, the number of benthic invertebrate 

species sensitive to pollution, such as the “EPT taxa” (mayflies [Ephemeroptera], stoneflies [Plecoptera], and caddisflies 

[Trichoptera]) generally decreased with increasing urban-land 

percentage in all four metropolitan areas. The declines in EPT 

taxa were steepest from 0 to about 20 percent urban land, and 

with the exception of Dayton/Cincinnati, the decline continues with increased urbanization. The anomalous pattern in the 

Dayton/Cincinnati area may be associated, in part, with effects 

of high percentages of agricultural land in some of its less 

urbanized watersheds, as well as the absence of study sites with 

much more than 50 percent urban land.

Over space and time, invertebrate communities integrate 

the effects of many factors, including chemical changes, physical habitat alterations, and changes in types of food available 

to invertebrate consumers. Among the chemical changes noted 

with increasing urban land in the metropolitan areas studied 

were increased chloride concentrations and increased potential 

pesticide toxicity to benthic invertebrates. Chloride sources 

include municipal and industrial discharges, septic systems, and 

road-salt runoff. Other organic and inorganic chemicals may 

be associated with chloride from these sources. The potential 

toxicity of the mixture of pesticides detected in streamwater 

increased with increasing urban land percentage, according 

to the Pesticide Toxicity Index (a measure for ranking sites 

based on summed concentrations of detected pesticides and the 

toxicity of each pesticide to benthic invertebrates [Munn and 

Gilliom, 2001]). The increase was especially pronounced at 

relatively low percentages of urban land. Contributing factors may include the amount, relative toxicity, and timing of 

pesticides—particularly insecticides—that are applied in urban 

settings.

Patterns of nitrate concentration with increasing urban 

land were not consistent among the four metropolitan areas. 

In fact, the only clear increase in nitrate concentrations with 

urbanization was in the Boston area. This is, in part, because 

nutrients in Boston-area streams are associated primarily with 

urban sources and are not affected by additional sources, such 

as fertilizers applied on agricultural land. Moreover, watersheds 

with minimal urban land in the Boston area are mainly forested, 

and nitrate concentrations in those streams were low (less than

 0.1 mg/L). In contrast, nitrate concentrations in streams decreased 

with increasing urbanization in the Dayton/Cincinnati area and 

in minimally to moderately urban settings of the Chicago area, 

whereas in the Philadelphia area they neither increased nor 

decreased; fertilizers applied to crops contribute to the higher 

nitrate concentrations in some less urbanized watersheds in these 

settings. Sewage may be a factor contributing to the high nutrient 

concentrations in some highly urban Chicago streams.

In summary, biological and chemical characteristics in 

streams respond to increases in urban land in their respective watersheds. The responses may differ in pattern and in rate, however, so 

approaches for monitoring the effects of urbanization on streams 

may need to be tailored to specific metropolitan areas. Findings 

of these NAWQA studies may help in developing and prioritizing 

optimal management strategies for a particular setting.

Stream quality degrades as urbanization increases in four major 

metropolitan areas

Selected examples of biological and chemical indicators, in 

relation to urbanization. Smoothed lines are shown in plots for 

which Spearman rank correlations were statistically significant at a probability value of less than 0.05.
26 Water Quality in the Delaware River Basin

Algae, fish, and invertebrates were 

affected by the drought

Algae, fish, and invertebrates were 

affected by the extreme drought during the summer of 1999. The extent to 

which a stream’s biota were affected 

varied with the stream’s degree of 

departure from normal flows (fig. 

38A) and the extent to which its water 

and habitat quality normally support 

species that are sensitive to pollution 

and other disturbances. Effects of the 

drought were generally more apparent in 

streams in forested or low-agricultural 

watersheds than in streams in urbanized 

basins. Biological communities in highly 

urbanized streams may be less responsive to droughts than other streams 

because their biota consist largely of 

tolerant species even in normal-flow 

years. Therefore, streams in watersheds 

that are in the early stages of urbanization could be especially vulnerable to 

landscape changes that affect minimum 

flows required to maintain healthy 

aquatic communities. These results also 

suggest that water quality and land-use 

relationships may not be as strong in a 

drought year.

Algal growth rates can increase 

during dry periods as a result of 

decreased streamflow and increased 

water temperatures and nutrient concentrations. In the Delaware River 

Basin, this was indicated by higher algal 

biovolume (a measure of the quantity 

of algae collected from a specified area 

of rocky surfaces) during the drought 

than during the more normal-flow years 

at the five streams in less-developed 

watersheds (fig. 38B). Environmental 

stress associated with drought also was 

manifested in the relative abundance 

of intolerant diatom algae growing on 

rocks or woody substrate, even where 

the drought did not produce high algal 

biovolume. At seven of eight streams 

studied, diatom species considered 

tolerant of environmental stress (Bahls, 

1993) made up higher percentages of 

total diatom densities in drought-year 

samples than in samples collected during one or both of the higher flow years 

(data not shown).

Noninsect invertebrates (such 

as worms and snails), a group that is 

generally more tolerant of environmental 

disturbance than are many insect species, exhibited higher relative richness 

(percentage of the total number of 

invertebrate species) during the drought 

year than during the normal-flow years 

at four of the sites in less-developed 

watersheds (fig. 38C). However, the two 

streams in highly urbanized settings 

(Cooper River and Little Neshaminy 

Creek) showed little variation over time 

in noninsect relative richness. Biota in 

these streams may be less responsive to 

droughts because they consist primarily of tolerant species even in normalflow years. Riffle habitats in Little 

Neshaminy Creek were devastated by 

the extreme high flows from Hurricane 

Floyd in September 1999 and another 

storm in 2000. These disturbances may 

have offset any potential recovery from 

the drought at this site.

Fish communities can be strongly 

affected by warmer water temperatures 

and loss of habitat during a drought. At 

five of six sites at which fish sampling 

was conducted during all 3 years, the 

relative abundance of the single mostcommon species (dominance) was 

higher during the drought year than 

during normal-flow years (fig. 38D). 

A similar drought effect was seen in 

northern mid-Atlantic Index of Biotic 

Integrity (IBI) scores (Daniels and others, 2002), which were lower during 

1999 than during 2000 and 2001.

Some natural factors may mitigate 

effects of the drought. For example, 

Raccoon Creek and Tulpehocken Creek 

had relatively little change in fishcommunity relative abundance, and 

lower noninsect invertebrate relative 

richness during the drought year than 

other sites. Both sites are in geologic 

settings where highly permeable underlying rocks allow for comparatively high 

streamflows to be maintained during 

the drought; these flows helped sustain 

the existing biological community. 

Additionally, good instream habitat 

and streamside vegetation seemed to 

mitigate effects of the drought at French 

Creek. Although streamflow was well 

below normal in 1999, the French Creek 

fish community was relatively diverse.

Figure 38. Physical and chemical stresses from low flows during the drought of 1999 

affected algae, invertebrate, and (or) fish communities at most sites studied. Sites are 

placed from left to right in graphs in order of increasing road density, an indicator of 

human activity.

106

107

108

109

1010

1999 2000 2001

0

10

20

30

40

50

60

70

0

5

10

15

20

25

30

35

0

25

50

75

100

125

150

250

275

1999 2000 2001

PERCENTAGE OF LONG-TERM

MEAN DAILY DISCHARGE

FOR JULY-AUGUST

NONINSECT INVERTEBRATE

RELATIVE RICHNESS,

IN PERCENT

MOST-ABUNDANT FISH

SPECIES RELATIVE

ABUNDANCE, IN PERCENT

ALGAL BIOVOLUME, IN CUBIC

MILLIMETERS PER SQUARE

CENTIMETER

Neversink River

Flat Brook

French Creek

Jordan Creek

Tulpehocken Creek

Raccoon Creek

Little Neshaminy Creek

Cooper River

Forested and low-agriculture sites Agriculture sites Urban sites

EXPLANATION

A

B

C

D
Study Unit Design 27

Study Unit Design

This study was designed to describe current water-quality and ecological conditions throughout the Delaware River Basin, 

document the occurrence and distribution of contaminants in water, sediment, and biota, and improve our understanding of the 

factors affecting water quality and ecological health (Gilliom and others, 1995).

Surface-Water Studies

Surface-water studies were designed to assess the effects of natural factors and human activities on stream chemistry and ecological communities. 

Ten streams (fig. 39A) were sampled from 1998 to 2001 at regular intervals 

and during storms to examine variations in water quality and biological communities over time. Stream surveys were conducted at more than 80 sites 

(many in the Piedmont and Pocono regions) to describe spatial distributions of 

contaminants and examine relations among land use, water quality, and (for a 

subset of sites) biological communities. These sites were sampled only once or 

twice during the study period, at base flow.

Bed-sediment and fish-tissue samples were collected throughout the basin 

(fig. 39B) to document the distribution of metals, organochlorine pesticides, 

industrial compounds, and semivolatile organic compounds. A special study 

was conducted on mercury in water, sediment, and fish.

Ground-Water Chemistry

Water-quality studies were conducted 

on domestic (household) wells in three aquifer systems: the clastic-rock aquifer of the 

Piedmont Province, the clastic-rock aquifer 

of the Valley and Ridge Province, and the 

unconsolidated glaciofluvial aquifers that 

are interfingered through the Appalachian 

Plateaus, Valley and Ridge, and New England Provinces (fig. 40). Ground water in the 

Coastal Plain sediments or in the metamorphic rocks of the Piedmont was not sampled 

because data are available from previous 

NAWQA studies of the Long Island–New 

Jersey Coastal drainages and the Lower 

Susquehanna River Basin (Ayers and others, 

2000; Lindsey and others, 1998).

Figure 40. Ground-water sampling sites 

included domestic-supply (household) wells in 

the Piedmont clastic-rock and Valley and Ridge 

clastic-rock aquifers and the unconsolidated 

glaciofluvial aquifers.

Figure 39. Stream-sampling sites included (A) surface-water routine sampling sites, 

water-quality survey sites, and ecological survey sites, and (B) streambed-sediment, 

fish-tissue, and mercury sampling sites.

Wells in the Valley and Ridge

Wells in the Piedmont

Wells in the glaciofluvial deposits

Southern extent of most recent glaciation

Glaciofluvial deposits

Valley and Ridge clastic rocks

Piedmont clastic rocks

EXPLANATION

0 20 40 KILOMETERS

0 20 40 MILES

76°

75°

42°

41°

40°

39°

EXPLANATION

Delaware

Bay

Bed-sediment

sampling site

Fish-tissue

sampling site

Mercury

sampling site

Physiographic Province

Sampling sites

Appalachian Plateaus

Valley and Ridge

New England

Piedmont

Coastal Plain

Fixed site and

site number

Surface-water

survey Site

Ecological

survey site

6

0 20 40 KILOMETERS

0 20 40 MILES

A. B.

Delaware

Bay

1

2

3

5 4

6

7

8

9

10

76°

75°

42°

41°

40°

39°

76°

75°

42°

41°

40°

39°

1 Delaware River at Port Jervis, N.Y. (I)

2 Jordan Creek near Schnecksville, Pa (A)

3 Lehigh River at Glendon, Pa (I)

4 Delaware River at Trenton, N.J. (I)

5 Little Neshaminy Creek near Neshaminy, Pa(U)

6 Cooper River at Haddonfield, N.J. (U)

7 Tulpehocken Creek near Bernville, Pa (A)

8 French Creek near Phoenixville, Pa (A)

9 Schuylkill River at Philadelphia, Pa (I)

10 Racoon Creek near Swedesboro, N.J. (A)

(I) Integrator site; (A) Agricultural site; (U) Urban site
28 Water Quality in the Delaware River Basin

Study

component What data are collected and why Number and types of sites sampled Sampling frequency and period

Stream and River Chemistry

Fixed sites Streamflow, field parameters,* major ions, nutrients, organic carbon, suspended sediment, 53 

pesticides, and 85 volatile organic contaminants 

(VOCs). Sampled to determine how concentrations 

vary over time. Indicator sites also examine landuse and regional differences.

10 sites: 4 large (>1,000 mi2) integrator basins with a mix of land uses, 

and 6 smaller indicator basins in the 

three most developed physiographic 

regions. Sites shown in figure 39.

Monthly and storm events: 

November 1998 – August 

2001. VOCs sampled quarterly, no pesticides winter 

of 2000–2001.

Intensive fixed 

sites

Same data collection as above, but sampled more 

frequently for pesticides and VOCs. 

3 fixed sites: Schuylkill River, Little 

Neshaminy Creek, and Tulpehocken 

Creek.

Biweekly to monthly, and 

storm events. April 1999 

– August 2000. 

Basinwide synoptic surveySame as fixed sites, except no VOCs. To assess 

distribution of contaminants throughout the basin.

21 sites with a wide variety of land 

uses distributed throughout the basin.

Once in spring and once in 

summer 1999.

Urban stream 

synoptic surveys

Same as fixed sites, except no VOCs. Sites selected 

to assess effects of urban land use on water quality. 

Integrated with ecological synoptic surveys. 

30 sites in the Piedmont and 20 in the 

Poconos. Sites range from undeveloped to highly urbanized.

Once in spring and once in 

summer. Piedmont (2000) 

and Poconos (2001).

Agricultural 

synoptic survey

Same as fixed sites, except no VOCs. Sites selected 

to assess effects of agriculture on water quality.

10 sites. Primarily agricultural land 

use in the Valley and Ridge.

Once in spring 2000.

Contaminants in 

bed sediments

32 organochlorine pesticides, 63 semivolatile 

organic compounds (SVOCs), and 44 trace 

elements in bed sediment. Sites sampled to look at 

basinwide distributions and land-use effects.

39 sites (including all 10 fixed sites). 

Forested, agricultural, urban, and 

mining sites located throughout the 

basin.

Once in July–August 1998, 

July–August 1999, or June 

2000.

Contaminants in 

fish tissue

30 organochlorine pesticides in whole fish and 24 

trace elements in fish livers. Sites sampled to look 

at basinwide distributions and land-use effects. 

25 sites (including all 10 fixed sites). 

Forested, agricultural, and urban sites 

located throughout the basin.

Each site sampled once in 

July–August 1998 or 1999.

Mercury in sediment, fish, and 

water

Total and methylmercury in fish fillets, bed sediment, and water. To look at basinwide distributions 

and effects of human and natural factors.

31 fish-tissue, 30 streambedsediment, and 24 water column 

sites throughout the basin.

Each site sampled once 

in summer of 1998, 1999, 

2000, or 2001.

Stream and River Ecology

Fixed indicator 

sites

Surveys of fish, macroinvertebrates, algae, and 

riparian habitat. To assess ecological conditions, 

determine yearly variations, and assess land-use 

effects.

Six sites representative of agricultural and urban land uses (see chemistry 

fixed indicator sites).

Once each year in 1999, 

2000, and 2001.

Fixed integrator 

sites

Surveys of macroinvertebrates and algae. To assess 

ecological conditions at large river sites.

Four fixed integrator sites (see chemistry fixed indicator sites).Once in July 1999 or September 2001.

Urban stream 

synoptic survey

Surveys of macroinvertebrates, algae, and riparian 

habitat. To look at effects of urbanization on stream 

biota and habitat.

24 Piedmont and 16 Poconos sites 

selected along gradients of urban development. Subset of chemistry sites.

Once in July-September 

2000 (Piedmont) and 2001 

(Poconos).

Ground-Water Chemistry

Aquifer survey

Piedmont clastic 

rocks

Field parameters,* turbidity, major ions, nutrients, 

organic carbon, 17 trace elements, 53 pesticides, 

85 VOCs, and radionuclides. To provide broad 

overview of water quality.

30 wells — primarily existing openhole domestic wells 63 to 500 feet 

deep.

Once, June–November 

1999.

Aquifer survey

Valley and Ridge 

clastic rocks

Field parameters,* turbidity, major ions, nutrients, 

organic carbon, 21 trace elements, 53 pesticides, 

85 VOCs, and radionuclides. To provide broad 

overview of water quality.

30 wells — primarily existing openhole domestic wells 65 to 500 feet 

deep.

Once, April–July 2000.

Aquifer survey

glaciofluvial 

deposits 

Field parameters,* turbidity, major ions, nutrients, 

organic carbon, 21 trace elements, 53 pesticides, 

85 VOCs, and radionuclides. To provide broad 

overview of water quality.

16 wells — primarily existing openended or screened domestic wells 22 

to 213 feet deep.

Once, July–August 2001.

* Field parameters include dissolved oxygen, pH, alkalinity, specific conductance, and temperature.
References Cited 29

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//www.ijc.org/agree/quality.html#ann1.

Jenner, C.B., and Lins, H.F., 1991, Climatic atlas of the 

Delaware River Basin: U.S. Geological Survey Professional 

Paper 1392, 127 p.

Krabbenhoft, D.P., Wiener, J.G., Brumbaugh, W.G., Olson, 

M.L., DeWilde, J.F., and Sabin, T.J., 1999, A national pilot 

study of mercury contamination of aquatic ecosystems 

along multiple gradients: U.S. Geological Survey WaterResources Investigations Report 99–4018–B, 13 p.

Larson, S.J., Gilliom, R.J., and Capel, P.D., 1999, Pesticides 

in streams of the United States, initial results from the 

National Water-Quality Assessment Program: U.S. Geological Survey Water-Resources Investigations Report 98–4222, 

92 p.

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1998, Water quality in the Lower Susquehanna River Basin, 

Pennsylvania and Maryland, 1992–95: U.S. Geological 

Survey Circular 1168, 38 p.

MacDonald, D.D., Ingersoll, C.G., and Berger, T.A., 2000, 

Development and evaluation of consensus-based sediment 

quality guidelines for freshwater ecosystems: Archives of 

Environmental Contamination and Toxicology v. 39, no. 1, 

p. 20–31.
30 Water Quality in the Delaware River Basin

McConnell, L.L., Torrents, A., Kuang, Z., Merritt, D., and 

Tobash, S., 2002, Atmospheric deposition of currently-used 

pesticides to an agricultural watershed of the Chesapeake 

Bay, in Principles of environmental sampling and analysis—Two decades later, v. 42, no. 2, p. 707–713.

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for freshwater aquatic organisms: U.S. Geological Survey 

Water-Resources Investigations Report 01–4077, 61 p., 

accessed April 10, 2003, at URL http://water.usgs.gov/pubs/

wri/wri014077/.

Murphy, E.A., and Aucott, M., 1998, An assessment of the 

amounts of arsenical pesticides used historically in a 

geographic area: Science of the Total Environment, v. 218, 

p. 89–101.

National Research Council, 1999, Arsenic in drinking water: 

Washington, D.C., National Academy Press, 310 p.

National Research Council, 2000, Toxicological effects of 

methylmercury: Washington, D.C., National Academy 

Press, 344 p. 

Neff, J.M., 1985, Polycyclic aromatic hydrocarbons, in Rand, 

G.M., and Petrocelli, S.R., eds., Fundamentals of aquatic 

toxicology, Washington D.C., Hemisphere Publishing, 

chap. 14, p. 416-454.

Newell, A.J., Johnson, D.W., and Allen, L.K., 1987, Niagara 

River biota contamination project—fish flesh criteria for 

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Reiser, R.G., and O’Brien, A.K., 1998, Pesticides in streams in 

New Jersey and Long Island, New York, and relation to land 

use: U.S. Geological Survey Water-Resources Investigations Report 98–4261, p. 12.

Riva-Murray, Karen, Brightbill, R.A., and Bilger, M.D., 2003, 

Trends in concentrations of polychlorinated biphenyls in 

fish tissue from selected sites in the Delaware River Basin 

in New Jersey, New York, and Pennsylvania, 1969–98: U.S. 

Geological Survey Water-Resources Investigations Report 

01–4066, 19 p.

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Jersey Geological Survey Information Circular, 2 p.

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Occurrence of nitrate, pesticides, and volatile organic compounds in the Kirkwood-Cohansey aquifer system, southern New Jersey: U.S. Geological Survey Water-Resources 

Investigations Report 97–4241, 8 p.

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River Basin from Berne to Philadelphia, Pennsylvania: U.S. 

Geological Survey Water-Supply Paper 2256–A, 45 p.

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Glossary 31

Glossary

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. 

Aquatic-life guidelines Specific levels of water quality which, 

if reached, may adversely affect aquatic life. These are nonenforceable guidelines issued by a governmental agency or 

other institution. 

Aquatic-life criteria Water-quality guidelines for protection 

of aquatic life. Often refers to U.S. Environmental Protection 

Agency water-quality criteria for protection of aquatic organisms. See also Water-quality guidelines and Water-quality 

criteria. 

Aquifer A water-bearing layer of soil, sand, gravel, or rock 

that will yield usable quantities of water to a well. 

Base flow Sustained, low flow in a stream; ground-water 

discharge is the source of base flow in most places. 

Basin See Drainage basin. 

Bedrock General term for consolidated (solid) rock that 

underlies soils or other unconsolidated material. 

Bed sediment The material that temporarily is stationary in 

the bottom of a stream or other watercourse. 

Benthic invertebrates Insects, mollusks, crustaceans, worms, 

and other organisms without a backbone that live in, on, or 

near the bottom of lakes, streams, or oceans. 

Bioaccumulation The net accumulation of a substance by an 

organism as a result of uptake from all environmental sources, 

including gills, epithelial tissues, and dietary sources. 

Biota The animal and plant life of a particular region. 

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–). 

Clastic Rock or sediment composed principally of broken 

fragments that are derived from preexisting rocks that have 

been transported from their place of origin, as in sandstone. 

Contamination Degradation of water quality compared to 

original or natural conditions due to human activity. 

Degradation products Compounds resulting from transformation of an organic substance through chemical, photochemical, 

and(or) biochemical reactions. 

Detection limit The minimum concentration of a substance 

that can be identified, measured, and reported within 99 percent confidence that the analyte concentration is greater than 

zero; determined from analysis of a sample in a given matrix 

containing the analyte. 

Diatoms Microscopic algae having cell walls made of silica.

Discharge Rate of fluid flow passing a given point at a given 

moment in time, expressed as volume per unit of time. 

Drainage basin The portion of the surface of the Earth that 

contributes water to a stream through overland runoff, including tributaries and impoundments. 

Drinking-water standard or guideline A threshold concentration in a public drinking-water supply, designed to protect 

human health. As defined here, standards are U.S. Environmental Protection Agency regulations that specify the maximum contamination levels for public water systems required 

to protect the public welfare; guidelines have no regulatory 

status and are issued in an advisory capacity. 

Drought Commonly defined as being a time of less-than-normal or less-than-expected precipitation. 

Ecological studies Studies of biological communities and 

habitat characteristics to evaluate the effects of physical and 

chemical characteristics of water and hydrologic conditions 

on aquatic biota and to determine how biological and habitat characteristics differ among environmental settings in 

NAWQA Study Units. 

Endocrine system The collection of glands in animals that 

secrete hormones which influence growth, gender, and sexual 

maturity. 

Ground water In general, any water that exists beneath the 

land surface, but more commonly applied to water in fully 

saturated soils and geologic formations. 

Glaciofluvial Pertaining to the meltwater streams flowing 

from wasting glacier ice, and especially to the deposits and 

landforms produced by such streams.

Habitat The part of the physical environment where plants 

and animals live. 

Herbicide A chemical or other agent applied for the purpose 

of killing undesirable plants. See also Pesticide. 

Human health advisory Guidance provided by U.S. Environmental Protection Agency, State agencies, or scientific 

organizations, in the absence of regulatory limits, to describe 

acceptable contaminant levels in drinking water or edible fish. 

Index of Biotic Integrity (IBI) An aggregated number, or index, 

based on several attributes or metrics of a fish community that 

provides an assessment of biological conditions. 

Indicator sites Stream sampling sites located at outlets of 

drainage basins with relatively homogeneous land use and 

physiographic conditions; most indicator-site basins have 

drainage areas ranging from 20 to 200 square miles. 

Insecticide A substance or mixture of substances intended to 

destroy or repel insects. 

Integrator or Mixed-use site Stream sampling site located at 

an outlet of a drainage basin that contains multiple environ-
32 Water Quality in the Delaware River Basin

mental settings. Most integrator sites are on major streams 

with relatively large drainage areas. 

Invertebrate An animal having no backbone or spinal column. 

See also Benthic invertebrates. 

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 mg/L. 

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. 

Periphyton Organisms that grow on underwater surfaces; 

periphyton include algae, bacteria, fungi, protozoa, and other 

organisms. 

Pesticide A chemical applied to crops, rights-of-way, lawns, 

or residences to control weeds, insects, fungi, nematodes, 

rodents or other “pests.” 

Physiography A description of the surface features of the 

Earth, with an emphasis on the origin of landforms. 

Plankton Floating or weakly swimming organisms at the 

mercy of the waves and currents. Animals of the group are 

called zooplankton and the plants are called phytoplankton. 

Relative abundance The number of organisms of a particular 

kind present in a sample relative to the total number of organisms in the sample.

Study Unit A major hydrologic system of the United States in 

which NAWQA studies are focused. Study Units are geographically defined by a combination of ground- and surfacewater features and generally encompass more than 4,000 

square miles of land area. 

Surface water An open body of water, such as a lake, river, or 

stream. 

Survey Sampling of any number of sites during a given hydrologic condition. 

Synoptic sites Sites sampled during a short-term investigation 

of specific water-quality conditions during selected seasonal or 

hydrologic conditions to provide improved spatial resolution 

for critical water-quality conditions. 

Tolerant species Those species that are adaptable to (tolerant 

of) human alterations to the environment and often increase in 

number when human alterations occur. 

Turbidity Reduced clarity of surface water because of suspended particles, usually sediment. 

Unconsolidated deposit Deposit of loosely bound sediment 

that typically fills topographically low areas. 

Volatile organic compounds (VOCs) Organic chemicals that 

have a high vapor pressure relative to their water solubility. VOCs include components of gasoline, fuel oils, and 

lubricants, as well as organic solvents, fumigants, some inert 

ingredients in pesticides, and some byproducts of chlorine 

disinfection. 

Water-quality criteria Specific levels of water quality which, 

if reached, are expected to render a body of water unsuitable 

for its designated use. Commonly refers to water-quality criteria established by the U.S. Environmental Protection Agency. 

Water-quality criteria are based on specific levels of pollutants 

that would make the water harmful if used for drinking, swimming, farming, fish production, or industrial processes. 

Water-quality guidelines Specific levels of water quality which, if reached, may adversely affect human health or 

aquatic life. These are nonenforceable guidelines issued by a 

governmental agency or other institution. 

Water-quality standards State-adopted and U.S. Environmental Protection Agency-approved ambient standards for water 

bodies. Standards include the use of the water body and the 

water-quality criteria that must be met to protect the designated use or uses. 

Watershed See Drainage basin.
Appendix—Water-Quality Data from the Delaware River Basin 

in a National Context

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Coordination with agencies and organizations in the Delaware River Basin was integral to the 

success of this water-quality assessment. We thank those who served as members of our liaison 

committee:

Federal Agencies

National Park Service (NPS)

Natural Resources Conservation Service 

(NRCS)

U.S. Army Corp of Engineers (USACE)

U.S. Environmental Protection Agency 

(USEPA)

U.S. Fish and Wildlife Service (USFWS)

USDA Forest Service (USFS)

State Agencies

Delaware Department of Natural 

Resources and Environmental Control 

(DNREC)

Delaware Geological Survey

New Jersey Department of Agriculture

New Jersey Department of Environmental Protection (NJDEP)

New Jersey Geological Survey

New York State Department of Environmental Conservation (NYSDEC)

New York State Department of Health

Pennsylvania Department of Environmental Protection (PADEP)

Pennsylvania Fish and Boat Commission 

(PFBC)

Pennsylvania Geological Survey

Local Agencies

Chester County Water Resources 

Authority

Delaware Estuary Program

Delaware River Basin Commission 

(DRBC)

Delaware Valley Regional Planning 

Commission

Lehigh County Authority

Monroe County Planning Commission

New Jersey Pinelands Commission

New York City Department of Environmental Protection (NYCDEP)

Philadelphia Water Department

Pike County Conservation District

Upper Delaware Council

Water Resources Agency of New Castle 

County

Universities

Drexel University

University of Delaware

Other Public and Private Organizations

The Academy of Natural Sciences

Berks County Conservancy

Delaware Riverkeeper Network

The Heritage Conservancy

The Nature Conservancy

Public Service Electric and Gas Co. 

(PSE&G)

PECO Energy

Wildlands Conservancy

In addition, we thank the following individuals for contributing to this effort.

For their willingness to share knowledge and insights on the Delaware River Basin and providing advice and assistance on the 

study design: Eric Bartolacci (Monroe County), Robert Bode (NYSDEC), Janet L. Bowers (Chester County), Donald Charles (Academy of Natural Sciences), Alan C. Everett (PADEP), Thomas Fikslin (DRBC), Joseph Hoffman (Berks County Conservancy), Christopher Kocher (Wildlands Conservancy), James H. Porter (NYCDEP), Hannelore Schanzenbacher (Pike County), Jonathan H. Sharp 

(University of Delaware), Gregory Westfall (NRCS), Richard Westergaard (Gloucester County), Sheri Wills (PADEP), and Charles R. 

Wood (USGS).

For their cooperation and assistance, we thank the well owners who made their wells accessible for sampling, and the following 

individuals who helped in locating wells: DeNise Cooke (NPS), Jeannie Darling (Cornell Cooperative Extension), Bill Foley (Stokes 

State Forest), Donald Hamilton (NPS), and Frank Waksmunski (Carbon County Ground-Water Guardians).

For assisting in fish-sample collection, we thank Michael Boyer, Steven Schubert, and other personnel (including many student 

interns) from PADEP, and Richard Spear and his assistants from PFBC. We also thank land owners who provided access to 

streams.

For help on other aspects of the study, we are grateful to Robert Daniels (N.Y. State Museum), Gary Rhoades (Western Berks 

Water Authority), and Daniel Salvito (PSE&G).

Appreciation is also extended to those individuals who reviewed this report: Michael J. Brayton (USGS), Kevin Breen (USGS), Alan 

C. Everett (PADEP), Mark Hartle (PFBC), Bill Honachefsky (NJDEP), Robert K. Lewis (PA Bureau of Radiation Protection), Margaret 

Novak (NYSDEC), James H. Porter (NYCDEP), Keith W. Robinson (USGS), and Gregory Westfall (NRCS).

Finally, this study benefited greatly from the dedication and enthusiasm of many of our USGS colleagues, particularly Timothy 

D. Oden (lead technician), Brent Bohlert, John D. Byrnes, Susan Colarullo, Paul Dunne, Susan M. Edwards, Jonathan Klotz, and 

Kimberly Orlick.
Fischer and others— Water Quality in the Delaware River Basin 

U.S. Geological Survey Circular 1227

National Water-Quality Assessment (NAWQA) Program

Delaware River Basin

NAWQA

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