National Water-Quality Assessment Program

Variability in Stream Chemistry in Relation to 

Urban Development and Biological Condition in 

Seven Metropolitan Areas of the United States, 

1999–2004

Scientific Investigations Report 2012–5170

U.S. Department of the Interior

U.S. Geological Survey
Cover. Mud Creek at Spencer Road at Appleton, Wisconsin. Photograph by Michelle A. Lutz, U.S. Geological Survey.
Variability in Stream Chemistry in Relation 

to Urban Development and Biological 

Condition in Seven Metropolitan Areas of 

the United States, 1999–2004

By Karen M. Beaulieu, Amanda H. Bell, and James F. Coles

National Water-Quality Assessment Program

Scientific Investigations Report 2012–5170

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Beaulieu, K.M., Bell, A.H., and Coles, J.F., 2012, Variability in stream chemistry in relation to urban development and 

biological condition in seven metropolitan areas of the United States, 1999–2004: U.S. Geological Survey Scientific 

Investigations Report 2012–5170, 27p., available at http://pubs.usgs.gov/sir/2012/5170/.
iii

Foreword

The U.S. Geological Survey (USGS) is committed to providing the Nation with reliable scientific 

information that helps to enhance and protect the overall quality of life and that facilitates effective 

management of water, biological, energy, and mineral resources (http://www.usgs.gov/). Information 

on the Nation’s water resources is critical to ensuring long-term availability of water that is safe for 

drinking and recreation and is suitable for industry, irrigation, and fish and wildlife. Population growth 

and increasing demands for water make the availability of that water, measured in terms of quantity 

and quality, even more essential to the long-term sustainability of our communities and ecosystems.

The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to 

support national, regional, State, and local information needs and decisions related to water-quality 

management and policy (http://water.usgs.gov/nawqa). The NAWQA Program is designed to answer: 

What is the quality of our Nation’s streams and groundwater? How are conditions changing over 

time? How do natural features and human activities affect the quality of streams and groundwater, 

and where are those effects most pronounced? By combining information on water chemistry, 

physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide 

science-based insights for current and emerging water issues and priorities. From 1991 to 2001, the 

NAWQA Program completed interdisciplinary assessments and established a baseline understanding 

of water-quality conditions in 51 of the Nation’s river basins and aquifers, referred to as Study Units 

(http://water.usgs.gov/nawqa/studies/study_units.html).

National and regional assessments are ongoing in the second decade (2001–2012) of the NAWQA 

Program as 42 of the 51 Study Units are selectively reassessed. These assessments extend the 

findings in the Study Units by determining water-quality status and trends at sites that have 

been consistently monitored for more than a decade, and filling critical gaps in characterizing the 

quality of surface water and groundwater. For example, increased emphasis has been placed on 

assessing the quality of source water and finished water associated with many of the Nation’s 

largest community water systems. During the second decade, NAWQA is addressing five national 

priority topics that build an understanding of how natural features and human activities affect water 

quality, and establish links between sources of contaminants, the transport of those contaminants 

through the hydrologic system, and the potential effects of contaminants on humans and aquatic 

ecosystems. Included are studies on the fate of agricultural chemicals, effects of urbanization on 

stream ecosystems, bioaccumulation of mercury in stream ecosystems, effects of nutrient enrichment 

on aquatic ecosystems, and transport of contaminants to public-supply wells. In addition, national 

syntheses of information on pesticides, volatile organic compounds (VOCs), nutrients, trace elements, 

and aquatic ecology are continuing.

The USGS aims to disseminate credible, timely, and relevant science information to address practical 

and effective water-resource management and strategies that protect and restore water quality. We 

hope this NAWQA publication will provide you with insights and information to meet your needs, 

and will foster increased citizen awareness and involvement in the protection and restoration of our 

Nation’s waters.

The USGS recognizes that a national assessment by a single program cannot address all waterresource issues of interest. External coordination at all levels is critical for cost-effective 

management, regulation, and conservation of our Nation’s water resources. The NAWQA Program, 

therefore, depends on advice and information from other agencies—Federal, State, regional, 

interstate, Tribal, and local—as well as nongovernmental organizations, industry, academia, and 

other stakeholder groups. Your assistance and suggestions are greatly appreciated.

William H. Werkheiser

USGS Associate Director for Water
iv

Contents

Foreword ........................................................................................................................................................iii

Conversion Factors and Abbreviations....................................................................................................vi

Abbreviations.................................................................................................................................................vi

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

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Description of the Study Areas ..........................................................................................................4

Data Collection and Characterization Methods .......................................................................................4

Watershed Land Cover ........................................................................................................................4

Stream-Chemistry Samples ................................................................................................................4

Macroinvertebrate Community Samples..........................................................................................8

Data Analysis Methods.................................................................................................................................8

Stream-Chemistry Factors ..................................................................................................................8

Relating Stream-Chemistry Factors to Urban Development .........................................................8

Relating the Biological Condition to Chloride and Pesticide Toxicity ..........................................9

Results and Discussion.................................................................................................................................9

Relations of Stream-Chemistry Factors to Urban Development.................................................10

Total Nitrogen .............................................................................................................................10

Total Phosphorus .......................................................................................................................10

Chloride........................................................................................................................................11

Pesticide Toxicity .......................................................................................................................11

Variability in Stream-Chemistry Factors .........................................................................................11

Total Nitrogen .............................................................................................................................11

Total Phosphorus .......................................................................................................................11

Chloride........................................................................................................................................11

Pesticide Toxicity .......................................................................................................................11

Relations of the Biological Condition to Chloride and Pesticide Toxicity..................................13

Chloride........................................................................................................................................13

Pesticide Toxicity .......................................................................................................................13

Comparing the Community Tolerance Index Among Study Areas..............................................13

Summary and Conclusions.........................................................................................................................15

References Cited..........................................................................................................................................15

Appendix 1. Site Summary of Total Nitrogen Concentrations, Total Phosphorus Concentrations,

Chloride Concentrations, and the Pesticide Toxicity Index.....................................................19
v

Figures

1. Map showing the location of the seven study areas where samples were collected

to analyze the chemistry of streams..........................................................................................3

2. Map showing the average annual snowfall for the United States and scatter plots

showing the relation of chloride concentrations and urban development for each of

the seven study areas sampled................................................................................................12

3. Scatter plot showing the community tolerance index compared with chloride

concentrations in the Boston, Massachusetts, study area.................................................14

Tables

1. Site information for sampled streams.......................................................................................5

2. Summary of community tolerance indices...............................................................................8

3. Summary of Spearman rho correlation coefficients between characterizations of

selected stream-chemistry factors and percentage of urban development......................9

4. Summary of Spearman rho correlation coefficients between the community

tolerance index and chloride and pesticide toxicity.............................................................10
vi

Conversion Factors and Abbreviations

SI to Inch/Pound

Multiply By To obtain

Area

square kilometer (km2

) 0.3861 square mile (mi2)

Volume

liter (L) 33.82 ounce, fluid (fl. oz)

liter (L) 0.2642 gallon (gal)

milliliter (mL) 0.0338 ounce, fluid (fl. oz)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Abbreviations

NAWQA National Water-Quality Assessment

NWQL National Water-Quality Laboratory

USGS U.S. Geological Survey
Variability in Stream Chemistry in Relation to

Urban Development and Biological Condition in

Seven Metropolitan Areas of the United States,

1999–2004

By Karen M. Beaulieu, Amanda H. Bell, and James F. Coles

Abstract

Beginning in 1999, the U.S. Geological Survey National 

Water Quality Assessment Program investigated the effects 

of urban development on stream ecosystems in nine metropolitan study areas across the United States. In seven of these 

study areas, stream-chemistry samples were collected every 

other month for 1 year at 6 to 10 sites. Within a study area, the 

sites collectively represented a gradient of urban development 

from minimally to highly developed watersheds, based on the 

percentage of urban land cover; depending on study area, the 

land cover before urban development was either forested or 

agricultural. The stream-chemistry factors measured in the 

samples were total nitrogen, total phosphorus, chloride, and 

pesticide toxicity. These data were used to characterize the 

stream-chemistry factors in four ways (hereafter referred to as 

characterizations)—seasonal high-flow value, seasonal lowflow value, the median value (representing a single integrated 

value of the factor over the year), and the standard deviation of 

values (representing the variation of the factor over the year). 

Aquatic macroinvertebrate communities were sampled at each 

site to infer the biological condition of the stream based on the 

relative sensitivity of the community to environmental stressors. A Spearman correlation analysis was used to evaluate 

relations between (1) urban development and each characterization of the stream-chemistry factors and (2) the biological 

condition of a stream and the different characterizations of 

chloride and pesticide toxicity.

Overall, the study areas where the land cover before 

urban development was primarily forested had a greater number of moderate and strong relations compared with the study 

areas where the land cover before urban development was primarily agriculture; this was true when urban development was 

correlated with the stream-chemistry factors (except chloride) 

and when chloride and pesticide toxicity was correlated with 

the biological condition. Except for primarily phosphorus in 

two study areas, stream-chemistry factors generally increased 

with urban development, and among the different characterizations, the median value typically indicated the strongest 

relations. The variation in stream-chemistry factors throughout 

the year generally increased with urban development, indicating that water quality became less consistent as watersheds 

were developed. In study areas with high annual snow fall, the 

variation in chloride concentrations throughout the year was 

particularly strongly related to urban development, likely a 

result of road salt applications during the winter. The relations 

of the biological condition to chloride and pesticide toxicity 

were calculated irrespective of urban development, but the 

overall results indicated that the relations were still stronger in 

the study areas that had been forested before urban development. The weaker relations in the study areas that had been 

agricultural before urban development were likely the results 

of biological communities having been degraded from agricultural practices in the watersheds.

Collectively, these results indicated that, compared with 

sampling a stream at a single point in time, sampling at regular 

intervals during a year may provide a more representative 

measure of water quality, especially in the areas of high urban 

development where water quality fluctuated more widely 

between samples. Furthermore, the use of “integrated” values 

of stream chemistry factors may be more appropriate when 

assessing relations to the biological condition of a stream 

because the taxa composition of a biological community typically reflects the water-quality conditions over time.

Introduction

River flow regimes show regional patterns that are, in 

part, determined by geographic variation in climate, geology, 

topography, and vegetative cover. Some streams in regions 

with little seasonal variability in precipitation have relatively 
2 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004

stable flows, while in other regions, streamflow can fluctuate 

greatly throughout the year. As urban development in a watershed increases, changes occur in the magnitude and frequency 

of high and low streamflows (Poff and others, 1997). These 

changes are often associated with increases of impervious 

cover, which reduce infiltration and decrease the time for runoff to reach a stream (Scheuler, 1994). Other effects of urban 

development include increased loading of nutrients, pesticides, 

and other contaminants to streams (Paul and Meyer, 2001) and 

a decline in the biological condition, which is often expressed 

by a loss of sensitive taxa (Booth and others, 2004).

Variability in stream chemistry occurs throughout the 

year as streams are subjected to seasonal changes and storm 

runoff events (Tate and others, 1999). Land-use practices, 

including seasonal application of nutrients and pesticides during the growing season in agricultural and in suburban areas 

(U.S. Geological Survey, 1999; Overmyer and others, 2005) 

and deicing chemicals used in colder regions of the country 

(Mullaney and others, 2009; Corsi and others, 2010) can 

elevate the levels of these chemical constituents in streams 

and groundwater. A further consequence of urban development is that the increases of impervious cover create more 

direct pathways for stream-chemistry constituents to enter the 

stream. Such changes in stream chemistry typically degrade 

biological communities (algae, macroinvertebrates, and fish), 

but it is often difficult to establish a relation between stream 

chemistry and the condition of a biological community when 

stream chemistry is highly variable over time.

In 1999, the U.S. Geological Survey (USGS) began an 

investigation of the effects of urban development on stream 

ecosystems as part of the National Water-Quality Assessment 

Program (NAWQA). Study areas were in nine major metropolitan areas across the United States. In these studies, urban 

development was defined as the conversion from rural land 

cover of forest or agricultural land use to urban land cover of 

residential and commercial land use (Couch and Hamilton, 

2002). Within each study area, the selected sites had watershed areas of similar size and were in a region where natural 

variability was constrained to a single level III ecoregion, as 

measured by climate, soils, and elevation (Omernik, 1987). 

Each study area contained 28 to 30 sites that represented a 

gradient of urban development, from minimally to highly 

developed, as measured by the percentage of urban land cover 

in the watershed. Information collected at each site included 

data from two stream chemistry samples (one during seasonal high-flow conditions and one during seasonal low-flow 

conditions), a stream habitat survey, and an assessment of the 

biological communities (algal, macroinvertebrate, and fish). 

Additional information on study design and study area characteristics has been summarized by the USGS (U.S. Geological 

Survey, undated).

The investigation of the effects of urban development on 

stream ecosystems was based on a short-term (1 year) synoptic 

design that produced high spatial resolution in the information 

collected at each study area by sampling many sites within the 

study area. A consequence of this synoptic design, however, is 

that many sites were sampled over a short time interval at the 

expense of collecting multiple samples at fewer sites (Gilliom 

and others, 1995). Because stream chemistry varies seasonally and annually (Tate and others, 1999), the “typical” or 

midrange water-quality conditions may not be characterized 

accurately with data from only one or two samples. Furthermore, variations in stream chemistry over the course of 1 year 

are generally integrated by the aquatic macroinvertebrate community so that the biological condition of a stream may not be 

characteristic of water-quality conditions at a particular point 

in time (Barbour and others, 1989). However, the condition of 

the macroinvertebrate community can provide comprehensive 

information about the health of a stream that might not be 

captured with a single stream-chemistry sample.

In seven of the nine study areas (fig. 1), additional 

stream-chemistry samples were collected generally every other 

month for 1 year at a subset of 6 to 10 sites. Stream-chemistry 

factors measured in the samples included total nitrogen, total 

phosphorus, chloride, and pesticide toxicity. Because values 

of a factor often vary with time of year a sample is collected, 

each factor was characterized four separate ways to account 

for variation throughout the year (hereafter referred to as 

characterizations)—the seasonal high-flow value, the seasonal 

low-flow value, the median value (representing an “integrated” 

value), and the standard deviation of values (representing the 

variation among values). Additionally, a community tolerance 

index for macroinvertebrates was used to infer the biological 

condition for each site.

Purpose and Scope

The purpose of this report is to evaluate how variation 

in stream chemistry relates to urban development and to the 

biological condition of streams in seven metropolitan study 

areas of the United States. This report focuses on four streamchemistry factors—total nitrogen, total phosphorus, chloride, 

and pesticide toxicity—and explores how the strength of the 

relation of these factors to urban development and the aquatic 

biological condition often depends on how the values of the 

factors are characterized. The objectives of this report are to 

(1) describe how relations between urban development and 

stream-chemistry factors can depend on the time of year or 

how frequently over the course of 1 year stream-chemistry 

samples are collected and how the values of the factors are 

characterized, and (2) identify characterizations of chloride 

and pesticide toxicity values that have the strongest relations 

to the biological condition of a stream. Specific questions that 

are addressed in this report are the following:

• In describing the response of stream-chemistry factors 

to urban development, are the strongest relations based 

on factors measured from a seasonal high-flow sample, 

a seasonal low-flow sample, or the annual integrated 

value of all samples? (see Relations of Stream-Chemistry Factors to Urban Development section)
Introduction 

3

Base from the National LandCover Database 2001(Multi-Resolution LandCharacteristics Consortium, 2001).

EXPLANATION

Land cover categories, from National Land Cover Database 2001

Developed

Developed, open spaceDeveloped, low intensityDeveloped, medium intensityDeveloped, high intensity

Water

Open waterPerennial ice and snow

Barren

Barren land (rock, sand, and clay)

U.S. Geological Survey study areas

Forest

Deciduous forestEvergreen forestMixed forest

Shrubland

Dwarf scrubShrub and scrub

Wetlands

Woody wetlandsEmergent herbaceous wetlands

Herbaceous

Grassland and herbaceousSedge and herbaceousLichensMoss

Planted and cultivated

Pasture and hayCultivated crops

Milwaukee

Atlanta

Raleigh

Denver

Boston

Dallas

Portland

500 KILOMETERS

0

0

500 MILES

Figure 1. The location of the seven study areas where samples were collected to analyze the chemistry of streams.
4 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004

• As the percentage of urban development increases in 

a watershed, do the stream-chemistry factors show 

greater variance among samples collected throughout 

the year? (see Variability in Stream-Chemistry Factors 

section)

• Is the loss of sensitive macroinvertebrate taxa more 

strongly related to contaminant values measured from 

a seasonal high-flow sample, a seasonal low-flow 

sample, or the annual integrated value of all samples? 

(see Relations of the Biological Condition to Chloride 

and Pesticide Toxicity section)

Description of the Study Areas

Study areas were located in seven major metropolitan 

areas across the United States, including Portland, Oregon; 

Atlanta, Georgia; Raleigh, North Carolina; Boston, Massachusetts; Denver, Colorado; Dallas, Texas; and Milwaukee, 

Wisconsin. In the Portland, Atlanta, Raleigh, and Boston study 

areas, the land cover before urban development was primarily 

forested; in the Denver, Dallas, and Milwaukee study areas, 

the land cover before urban development was primarily agricultural (table 1). Studies were conducted in the Boston study 

area during 1999–2000, in the Atlanta, Raleigh, and Denver 

study areas during 2002–2003, and in the Portland, Dallas, 

and Milwaukee study areas during 2003–2004. Sixty-one 

sites were sampled among these seven study areas. Additional 

information on individual studies can be found for Portland in 

Waite and others (2008), for Atlanta in Gregory and Calhoun 

(2007), for Raleigh in Giddings and others (2007), for Boston 

in Coles and others (2004), for Denver in Sprague and others 

(2006), for Dallas in Moring (2009), and for Milwaukee in 

Richards and others (2010).

Data Collection and Characterization 

Methods

Within a study area, the sites collectively represented 

a gradient of urban development from minimally to highly 

developed watersheds, based on the percentage of urban land 

cover. This gradient of land cover—from forested or agricultural to urban land—represents a “space-for-time substitution” (Pickett, 1989) where the network of sites in essence 

represents a single watershed as it transitions from low to high 

urban development over time. For each site, stream-chemistry 

factors included measured concentrations of total nitrogen, 

total phosphorus, chloride, and total pesticides, the latter of 

which was used to calculate the relative pesticide toxicity of 

the water sample. Macroinvertebrate samples were collected 

at each site and were used to calculate a community tolerance 

index for assessing the biological condition of each site.

Watershed Land Cover

Percentages of urban, forest, and agriculture land cover 

were calculated using the aggregated 2001 National Land 

Cover Database categories (Multi-Resolution Land Characteristics Consortium, 2001; Falcone and others, 2007). Because 

urban development occurred with the conversion of land that 

generally had been forested (Portland, Atlanta, Raleigh, and 

Boston) or agricultural (Denver, Dallas, and Milwaukee), 

the study areas are grouped by their land cover before urban 

development. The 61 sites that were selected among the seven 

study areas are listed in order of increasing percentage of 

urban development in their respective study areas in table 1.

Stream-Chemistry Samples

Stream chemistry was sampled at sites usually every 

other month for a year, but sites in the Boston study area were 

sampled at least 10 times during the year. Samples were collected and processed using standard USGS protocols (U.S. 

Geological Survey, variously dated) and were analyzed with 

the use of standard USGS methods at the USGS National 

Water-Quality Laboratory (NWQL) in Lakewood, Colo., to 

measure concentrations of stream-chemistry factors (Fishman 

and Friedman, 1989; Fishman, 1993; Zaugg and others, 1995). 

The data from these samples are reported in Giddings and others (2009). Data selected for this report were concentrations of 

total nitrogen, total phosphorus, chloride, and total pesticides, 

except that pesticides were not evaluated in samples from the 

Boston study area. Additionally, total pesticide concentrations 

were converted to a pesticide toxicity index (described below), 

which was considered more relevant to the biological condition of streams.

Quantifying pesticide toxicity.—A pesticide toxicity index 

specific to cladocerans (a type of aquatic invertebrate used in 

testing contaminant toxicity) was used to calculate the potential total toxicity of all pesticides that were detected in the 

water samples (Munn and Gilliom, 2001; Munn and others, 

2006; Giddings and others, 2009). This index combines information on exposure of aquatic biota to pesticides (measured 

concentrations of pesticides in water) with toxicity estimates 

(results from laboratory toxicity studies) to produce a relative 

pesticide toxicity value for a sample. While the pesticide toxicity index (hereafter referred to as pesticide toxicity) does not 

indicate whether a water sample is toxic, the index value can 

be used to rank or compare the relative potential toxicity of 

different samples and to evaluate the relations between urban 

development and pesticide toxicity on biological communities, such as the macroinvertebrates. A zero value indicates 

that pesticides used in the calculation of the pesticide toxicity 

index were not detected. A value of 1.00 E-1 would indicate 

relatively high potential toxicity, whereas a value of 1.00 E-4 

would be potentially a thousand times less toxic (appendix 1).
Data Collection and Characterization Methods 

5

Table 1. Site information for sampled streams.—Continued[Includes U.S. Geological Survey (USGS) site identification, site name, and site short name, watershed drainage area, percentage of land cover, and community tolerance index. Study areas are grouped by land cover before urban development (Portland, Atlanta, Raleigh and Boston, under forest and shrubland and Denver, Dallas, and Milwaukee under agriculture) and listed from west to east. Sites within each study area are listed by increasing percentage of urban land. ID, identification number; %, percentage; km2, square kilometers; Oreg., Oregon; Ga., Georgia; N.C. North Carolina; Mass., Massachusetts; Colo., Colorado; Tex., Texas; Wis., Wisconsin]

USGS site ID USGS site name Site short code

Watershed 

drainage 

area (km2)

Urban 

land

(%)

Forest

and 

shrubland 

(%)

Agriculture and 

grassland 

(%)

Other 

(%)

Communtiy 

tolerance 

index

Portland, Oreg., study area

14205400 East Fork Dairy Creek near Meacham Corner, Oreg. POR_efdar 87.54 0.53 86.92 7.96 4.59 4.20

452231122200000 Deep Creek near Sandy, Oreg. POR_deep 31.36 4.38 59.76 35.04 0.82 4.19

455122122310600 Rock Creek near Battleground, Wash. POR_rocwa 26.08 7.51 62.46 19.32 10.71 4.93

454549122295800 Salmon Creek near Battleground, Wash. POR_salmo 58.84 13.21 70.76 10.73 5.30 4.22

452414122213200 Tickle Creek near Boring, Oreg. POR_tickl 34.08 19.03 37.36 43.15 0.46 4.83

452337122243500 North Fork Deep Creek at Barton, Oreg. POR_nfdep 37.01 27.06 13.07 58.47 1.40 5.82

454510122424900 Whipple Creek near Salmon Creek, Wash. POR_whipp 22.17 37.56 22.77 33.22 6.45 4.98

452526122364400 Kellogg Creek at Milwaukie, Oreg. POR_kello 34.11 81.00 11.02 6.16 1.82 5.73

445551123015800 Pringle Creek at Salem, Oreg. POR_pring 24.79 88.71 2.40 8.04 0.85 5.69

450022123012400 Claggett Creek at Keizer, Oreg. POR_clagg 24.84 97.81 0.10 1.87 0.22 6.66

Atlanta, Ga., study area

02338523 Hillabahatchee Creek at Thaxton Road, near Franklin,Ga. ATL_hil 43.22 2.81 74.77 19.97 2.45 5.08

02337395 Dog River at North Helton Road, near Winston, Ga. ATL_dog 109.08 13.45 62.18 20.31 4.06 5.67

02344480 Shoal Creek near Griffin, Ga. ATL_sho 53.40 22.91 49.43 22.01 5.65 6.15

02344737 Whitewater Creek at Willow Pond Road near Fayetteville, Ga. ATL_whw 110.50 25.08 47.82 18.32 8.78 6.45

02344797 White Oak Creek at Cannon Road, near Raymond, Ga. ATL_who 112.68 25.73 50.76 15.85 7.66 6.30

02334885 Suwanee Creek at Suwanee, Ga. ATL_suw 122.10 42.56 39.51 12.10 5.83 6.58

02336968 Noses Creek at Powder Springs Road,Powder Springs, Ga. ATL_nos 114.79 43.08 41.82 11.39 3.71 6.28

02336635 Nickajack Creek at US 78/278, near Mableton, Ga. ATL_nic 80.69 66.17 27.80 3.47 2.56 6.32

02335870 Sope Creek near Marietta, Ga. ATL_sop 79.54 72.51 23.32 2.54 1.63 6.83

Raleigh, N.C., study area

02097464 Morgan Creek near White Cross, N.C. RAL_morgan 21.45 5.19 70.77 23.06 0.98 5.59

0208500600 Cates Creek near Hillsborough, N.C. RAL_cates 10.88 20.00 64.77 14.76 0.47 5.63

0208726370 Richlands Creek at Schenk Forest near Cary, N.C. RAL_rschen 11.24 60.14 26.73 12.90 0.23 6.77

02087580 Swift Creek near Apex, N.C. RAL_swift 54.26 72.19 21.09 4.49 2.23 6.83
6 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004 Table 1. Site information for sampled streams.—Continued [Includes U.S. Geological Survey (USGS) site identification, site name, and site short name, watershed drainage area, percentage of land cover, and community tolerance index. Study areas are grouped by land cover before urban development (Portland, Atlanta, Raleigh and Boston, under forest and shrubland and Denver, Dallas, and Milwaukee under agriculture) and listed from west to east. Sites within each study area are listed by increasing percentage of urban land. ID, identification number; %, percentage; km2, square kilometers; Oreg., Oregon; Ga., Georgia; N.C. North Carolina; Mass., Massachusetts; Colo., Colorado; Tex., Texas; Wis., Wisconsin] USGS site ID USGS site name Site short code Watershed drainage area (km2

)

Urban 

land

(%)

Forest

and 

shrubland 

(%)

Agriculture and 

grassland 

(%)

Other 

(%)

Communtiy 

tolerance 

index

0208726995 Hare Snipe Creek at SR 1822 near Leesville, N.C. RAL_hare 16.01 76.09 20.03 1.62 2.26 6.79

0208725055 Black Creek at Weston Parkway near Cary, N.C. RAL_black 8.99 78.96 16.72 4.03 0.29 6.66

0208730725 Beaverdam Creek at Glenwood Aveue at Raleigh, N.C. RAL_swprng 7.98 94.16 5.19 0.32 0.33 6.68

0208732610 Pigeon House Branch at Crabtree Boulevard at Raleigh, N.C. RAL_pigeon 11.37 98.41 1.14 0.45 0.00 6.85

Boston, Mass., study area

01095220 Stillwater River near Sterling, Mass. BOS_stil 78.70 3.16 75.83 9.29 11.72 4.24

01109000 Wading River (head of Threemile River) near Norton, Mass. BOS_wade 113.40 23.49 51.08 6.27 19.16 5.28

01105000 Neponset River at Norwood, Mass. BOS_nepo 84.90 38.56 41.27 4.93 15.24 5.39

01101500 Ipswich River at South Middleton, Mass. BOS_ipsw 115.30 43.29 31.05 3.62 22.04 5.55

01102345 Saugus River at Saugus Ironworks at Saugus, Mass. BOS_saug 60.40 64.45 20.03 1.94 13.58 5.82

01102500 Aberjona River (head of Mystic River) at Winchester, Mass. BOS_aber 58.20 76.43 16.20 2.05 5.32 6.79

Denver, Colo., study area

413659104370001 Bear Creek above Little Bear Cr, near Phillips, Wyo. DEN_brphil 458.59 1.46 1.96 95.03 1.55 5.48

403308105001601 Boxelder Creek at mouth, near Fort Collins, Colo. DEN_boxel 558.64 4.42 0.69 89.15 5.74 6.58

403048105042701 Fossil Creek at College Ave, at Fort Collins, Colo. DEN_fossil 26.68 16.60 1.94 79.52 1.94 6.54

393948105053501 Bear Creek below Estes Road at Lakewood, Colo. DEN_breste 62.95 38.01 3.83 55.25 2.91 5.89

394919105074601 Ralston Creek above Simms at Arvada Colo. DEN_ralst 25.46 41.40 4.07 47.10 7.43 6.19

400217105123701 Boulder Creek below 61st Street, near Boulder, Colo. DEN_bould 87.61 49.38 7.75 38.79 4.08 5.12

06713500 Cherry Creek at Denver, Colo. DEN_cherry 80.92 79.61 2.14 11.36 6.89 6.75

394409105020501 Lakewood Gulch above Knox Street at Denver, Colo. DEN_lakew 40.75 89.26 1.90 8.64 0.20 6.36

394921105015701 Little Dry Creek below Lowell Street near Westminster, Colo. DEN_litdry 18.30 90.37 2.41 6.80 0.42 6.33

Dallas, Tex., study area

08063595 South Prong Creek at FM 876 near Waxahachie, Tex. DFW_sprong 53.41 2.28 25.80 70.90 1.02 6.30

08063565 Mill Creek at Lowell Road near Milford, Tex. DFW_mill 80.37 2.80 24.52 71.87 0.81 6.05

08063555 S Fk Chambers Creek near CR 102 near Maypearl, Tex. DFW_sfkcha 291.37 3.34 21.75 73.38 1.53 6.72

08052740 Doe Branch at Fishtrap Road near Prosper, Tex. DFW_doe 94.53 6.71 9.23 83.20 0.86 7.32

08064695 Tehuacana Creek at Rural Road 27 near Wortham, Tex. DFW_tehuac 164.70 6.94 32.98 59.71 0.37 6.96
Data Collection and Characterization Methods 

7

Table 1. Site information for sampled streams.—Continued[Includes U.S. Geological Survey (USGS) site identification, site name, and site short name, watershed drainage area, percentage of land cover, and community tolerance index. Study areas are grouped by land cover before urban development (Portland, Atlanta, Raleigh and Boston, under forest and shrubland and Denver, Dallas, and Milwaukee under agriculture) and listed from west to east. Sites within each study area are listed by increasing percentage of urban land. ID, identification number; %, percentage; km2, square kilometers; Oreg., Oregon; Ga., Georgia; N.C. North Carolina; Mass., Massachusetts; Colo., Colorado; Tex., Texas; Wis., Wisconsin]

USGS site ID USGS site name Site short code

Watershed 

drainage 

area (km2)

Urban 

land

(%)

Forest

and 

shrubland 

(%)

Agriculture and 

grassland 

(%)

Other 

(%)

Communtiy 

tolerance 

index

08061780 Buffalo Creek near Trinity Road at Forney, Tex. DFW_buftri 88.16 15.16 16.78 64.48 3.58 6.93

08057475 Parsons Slough near Davis Road near Crandall, Tex. DFW_parsn 115.72 21.28 25.04 42.70 10.98 7.28

08057431 Fivemile Creek near Simpson Stuart Road, Dallas, Tex. DFW_5mile 108.99 61.60 25.29 12.67 0.44 7.05

08057200 White Rock Creek at Greenville Ave, Dallas, Tex. DFW_white 173.01 83.94 5.66 9.96 0.44 7.08

Milwaukee, Wis., study area

040853145 Black Creek at Curran Road near Denmark, Wis. MGB_blak 56.13 3.23 16.66 73.32 6.79 6.77

04085188 Rio Creek at Pheasant Road near Rio Creek, Wis. MGB_rioc 55.81 3.53 9.60 78.24 8.63 6.41

040851325 Baird Creek at Superior Road at Green Bay, Wis. MGB_bair 52.01 5.48 4.58 85.26 4.68 5.93

04081897 Sawyer Creek at Westhaven Road at Oshkosh, Wis. MGB_sawy 30.60 13.80 2.96 81.34 1.90 6.71

04087258 Pike River at Cth A near Kenosha, Wis. MGB_pikr 100.29 27.32 5.19 64.74 2.75 5.57

04087030 Menomonee River at Menomonee Falls, Wis. MGB_meno 87.85 30.39 12.50 45.49 11.62 6.01

04084429 Mud Creek at Spencer Road at Appleton, Wis. MGB_mudc 33.28 58.83 4.44 35.49 1.24 6.23

04087204 Oak Creek at South Milwaukee, Wis. MGB_oakc 66.79 62.93 11.17 21.83 4.07 6.43

040869415 Lincoln Creek at 47th Street at Milwaukee, Wis. MGB_linc 25.96 97.56 2.10 0.10 0.24 6.74

04087118 Honey Creek near Portland Avenue at Wauwatosa, Wis. MGB_hony 27.74 99.06 0.75 0.00 0.19 7.14
8 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004

Macroinvertebrate Community Samples

Two types of macroinvertebrate samples were collected 

along the designated sampling reach for the stream at each 

site, according to NAWQA methods (Cuffney and others, 

1993; Moulton and others, 2002). A quantitative sample was 

collected from locations in the stream where the maximum 

taxa richness was likely to occur, generally from rocks in 

riffle areas or submerged woody snags. A qualitative sample 

also was collected from multiple locations along the sampling 

reach, and included areas such as riffles, undercut banks, 

aquatic vegetation beds, and depositional substrates. Identification of macroinvertebrates in these samples was done at 

NWQL. Together, these two sample types were used to create 

a comprehensive list of macroinvertebrate taxa observed at 

each site, which provided the biological data used in this 

report.

Characterizing the biological condition.—A community 

tolerance index for macroinvertebrates was used to characterize the biological condition for each site based on the taxa that 

occurred in the sampling reach (tables 1 and 2). The community tolerance index represents an average of the pollution-tolerance values for all taxa in the macroinvertebrate community 

and was calculated with the USGS invertebrate data analysis 

system (Cuffney, 2003). The values range from 0 (most sensitive) to 10 (most tolerant), and therefore, the index values typically increase when sensitive macroinvertebrate taxa are being 

lost from the community. The macroinvertebrate community 

data are available in Giddings and others (2009).

Data Analysis Methods

For each stream site described in this report (table 1), 

the stream-chemistry factors and each characterization are 

reported in appendix 1. Data were analyzed with SYSTAT 12 

(SYSTAT Software, Inc., 2007), and the figures were created 

using TIBCO Software Inc. S–Plus (Insightful Corporation, 

2005).

Stream-Chemistry Factors

At each site, each stream-chemistry factor (total nitrogen, 

total phosphorus, chloride, and pesticide toxicity) was characterized four different ways—the seasonal high-flow value, the 

seasonal low-flow value, the median value, and the standard 

deviation of values. Seasonal high-flow values were from the 

sample collected during the time of year when average climatic conditions reflect frequent precipitation events or snowmelt that results in sustained high flows (typically spring). 

Seasonal low-flow values were from the sample collected during the time of year when average climatic conditions reflect 

few precipitation events and sustained low flows are expected 

(typically summer). The median value of each factor was 

calculated using all samples collected at a site; it represented 

Table 2. Summary of community tolerance indices

[Study areas are grouped based on type of land before urban development. 

CTI, community tolerance index; XX, not applicable]

Study area Minimum 

CTI

Maximum 

CTI

Range

Forested lands before urban development

Portland, Oregon

Atlanta, Georgia

Raleigh, North Carolina

Boston, Massachusetts

Average

Overall average

4.19

5.08

5.59

4.24

4.78

XX

6.66

6.83

6.85

6.79

6.78

XX

2.47

1.75

1.26

2.55

2.01

2.66

Agricultural lands before urban development

Denver, Colorado

Dallas, Texas

Milwaukee, Wisconsin

Average

Overall average 

5.12

6.05

5.57

5.58

XX

6.75

7.32

7.14

7.07

XX

1.63

1.27

1.57

1.49

2.20

an integrated midrange value of what might be expected over 

the course of 1 year. The standard deviation of values was 

calculated for each factor using all samples collected at a site; 

it represented the variation of a factor throughout the year 

(in other words, the extent that the factor fluctuated over the 

course of 1 year).

Relating Stream-Chemistry Factors to Urban 

Development

For this report, data were analyzed separately by study 

area to evaluate how stream-chemistry factors responded as 

the percentage of urban development increased. The analyses 

used Spearman correlations to indicate how strongly each 

stream-chemistry factor was related to urban development 

when the factors were characterized by the seasonal high-flow 

value, the seasonal low-flow value, the median value, and 

the standard deviation of values. Following the convention 

for describing results in publications on the effects of urban 

development on stream ecosystems (Cuffney and others, 

2010), the absolute rho values (|rho|) from the Spearman 

correlations were used to indicate the relative strength of the 

relations, where 0.70 or greater (|rho| ≥ 0.70) were considered a strong relation and between 0.5 and 0.70 (0.50 ≤ |rho| 

< 0.70) were considered a moderate relation. Correlations 

were considered statistically significant if the probability of 

occurrence by chance was less than 5 percent (p < 0.05); to 

indicate that a |rho| value was significant, it was displayed with 

an asterisk preceding the value (for example, |rho| = *0.72). 

While all strong correlations were statistically significant, not 
Results and Discussion 9

all moderate correlations were statistically significant, mainly 

because sample size was smaller for this analysis (6 to 10 sites 

per study area) compared with the comprehensive investigation of the effects of urban development on stream ecosystems 

(typically 30 sites per study area).

Relating the Biological Condition to Chloride 

and Pesticide Toxicity

Data were analyzed by study area to evaluate how the 

biological condition of a stream would respond to an increase 

in chloride concentrations and pesticide toxicity. The community tolerance index was compared with chloride concentrations and pesticide toxicity characterized by the seasonal high-flow value, seasonal low-flow value, and median 

value. The intent of this analysis was to indicate if the loss 

of sensitive taxa in macroinvertebrate community was more 

strongly related to a seasonal stream-chemistry value (highor low-flow) or to an integrated value (median) of chloride 

concentrations and pesticide toxicity. Additionally, these 

results were used to indicate if chloride and pesticide toxicity 

were potential stressors to the macroinvertebrate community 

in a region. The relative strength of the relations and their significance are based on the Spearman correlations procedures 

described previously.

Results and Discussion

Results that pertain to the first objective of the study (to 

describe how variation in the relations between urban development and stream-chemistry factors can depend on when 

stream-chemistry samples are collected and how their values 

are characterized) are highlighted in table 3. Results that 

pertain to the second objective (to identify characterizations of 

chloride and pesticide toxicity that have the strongest relations to the biological condition of a stream) are highlighted in 

table 4.

Table 3. Summary of Spearman rho correlation coefficients between characterizations of selected stream-chemistry factors and 

percentage of urban development.

[Values preceded by asterisk indicate a probability (p) of occurrence by chance was less than 5 percent (p<0.05). Values in bold indicate a strong relation. Values in italic indicate a moderate relation. Study areas are grouped by primary type of land cover before urban development and listed from west to east. Oreg., 

Oregon; Ga., Georgia; N.C., North Carolina; Mass., Massachusetts; Colo., Colorado; Tex., Texas; Wis., Wisconsin; ND, no data]

Forested lands before urban development Agricultural lands before urban development

Portland, 

Oreg.

Atlanta, Ga. Raleigh, N.C. Boston, 

Mass.

Denver, Colo. Dallas, Tex. Milwaukee, 

Wis.

Total nitrogen

Seasonal high flow *0.73 0.47 0.38 *0.89 0.07 0.08 0.02

Seasonal low flow 0.61 *0.70 0.69 *1.00 0.05 -0.43 -0.12

Median 0.62 *0.67 0.21 *0.94 0.05 -0.15 -0.37

Standard deviation -0.14 0.10 -0.21 *0.83 0.43 -0.42 -0.13

Total Phosphorus

Seasonal high flow 0.58 0.12 *-0.74 -0.20 0.63 0.25 *-0.68

Seasonal low flow *0.75 0.03 -0.13 *0.94 0.47 0.27 -0.50

Median *0.66 -0.07 -0.24 *0.71 0.52 0.22 *-0.70

Standard deviation *0.78 0.37 -0.62 0.09 *0.73 0.30 -0.62

Chloride

Seasonal high flow *0.76 *0.83 0.24 0.49 0.65 0.42 *0.94

Seasonal low flow 0.44 0.57 0.38 *0.83 *0.72 0.60 *0.68

Median *0.75 *0.82 0.43 *1.00 *0.90 0.45 *0.99

Standard deviation 0.50 -0.12 0.31 *0.77 *0.75 0.12 *0.96

Pesticide Toxicity

Seasonal high flow 0.56 0.63 0.33 ND 0.25 *0.77 0.25

Seasonal low flow *0.68 0.43 0.43 ND 0.28 0.50 -0.18

Median *0.67 *0.88 0.24 ND *0.73 0.63 *-0.66

Standard deviation *0.65 *0.97 0.40 ND *0.77 0.42 -0.15
10 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004

Table 4. Summary of Spearman rho correlation coefficients between the community tolerance index and chloride and pesticide 

toxicity.

[Values preceded by asterisk indicate a probability (p) of occurrence by chance was less than 5 percent (p<0.05). Values in bold indicate a strong relation. 

Values in italic indicate a moderate relation. Study areas are grouped by primary type of land cover before urban development and listed from west to east. 

Oreg., Oregon; Ga., Georgia; N.C., North Carolina; Mass., Massachusetts; Colo., Colorado; Tex., Texas; Wis., Wisconsin; ND, no data]

Forested lands before urban development Agricultural lands before urban development

Portland, Oreg. Atlanta, Ga. Raleigh, N.C. Boston, Mass. Denver, Colo. Dallas, Tex. Milwaukee, Wis.

Chloride

Seasonal High Flow *0.70 *0.83 0.38 0.49 *0.73 0.28 0.36

Seasonal Low Flow *0.66 *0.83 0.33 *0.83 0.65 0.42 0.12

Median *0.76 *0.85 0.10 *1.00 0.25 0.42 0.24

Pesticide toxicity

Seasonal High Flow *0.65 *0.90 0.57 ND 0.61 0.50 0.59

Seasonal Low Flow *0.69 0.17 0.14 ND 0.42 *0.77 0.45

Median *0.74 *0.95 0.62 ND *0.68 0.53 -0.04

development, whereas in regions where agricultural was the 

land cover before urban development, total nitrogen did not 

change significantly with urban development because total 

nitrogen concentrations were already relatively high in streams 

with low percentages of urban land as a result of agricultural 

practices.

Total Phosphorus

In contrast to the results of total nitrogen (above), moderate or strong relations between total phosphorus and urban 

development were not limited to study areas where land cover 

before urban development was forest (table 3). Furthermore, 

the moderate or strong relations were not associated with 

a particular characterization of total phosphorus, and some 

relations were negative, indicating that total phosphorus was 

decreasing with urban development. The seasonal low-flow 

value resulted in strong relations in two study areas and a 

moderate relation in one study area, whereas the seasonal 

high-flow value resulted in a strong relation in one study area 

and moderate relations in three study areas. The median values 

resulted in strong relations in two study areas and moderate 

relations in two study areas.

In the Milwaukee study area, a negative relation between 

urban development and total phosphorus was indicated with 

all three total phosphorus characterizations. The relation was 

strongest with the median value (rho = *-0.70) and suggests 

that total phosphorus concentrations decreased significantly 

in streams as land cover was converted from agricultural to 

urban. In the Raleigh study area, a negative relation also was 

indicated between urban development and total phosphorus, 

but only for the high-flow values of total phosphorus; thus, 

this apparent decline of total phosphorus concentrations with 

urban development may have been an artifact of high-flow 

conditions, such as dilution.

Relations of Stream-Chemistry Factors to Urban 

Development

Variability in stream chemistry can occur throughout the 

year as streams are subjected to seasonal changes and storm 

runoff events (Tate and others, 1999). Stream-chemistry factors depend on conditions in the watershed before collection 

of the sample, such as road salt applications (chloride inputs) 

in areas of heavy snowfalls or fertilizer applications (nutrient 

inputs) for lawn maintenance. If heavy precipitation follows 

such applications, then these chemical factors can be flushed 

into the stream; a stream sample collected soon afterwards can 

result in a spike in value, but subsequent samples often show 

much lower values. Consequently, the “typical” or midrange 

water-quality conditions may not be characterized accurately 

with data from any particular single sample. Thus, the median 

value for each of the selected stream-chemistry factors is used 

to represent an integrated value during the course of 1 year at 

a site.

Total Nitrogen

In study areas where agriculture was the predominant 

land cover before urban development, there were no moderate or strong relations indicated between total nitrogen and 

urban development (table 3). In the four study areas where 

forest was the predominant land cover before urban development, relations between total nitrogen and urban development 

were either moderate or strong in all four study areas when 

based on the seasonal low-flow value, in three study areas 

when based on the median value, and in two study areas when 

based on the high-flow value. These results indicate that the 

total nitrogen concentrations increased with urban development in regions where forest was the land cover before urban 
Results and Discussion 11

Chloride

The relations between chloride and urban development 

were notably strongest with the median value (table 3). Strong 

positive relations were indicated in all but the Dallas and 

Raleigh study areas. Unlike fertilizers and pesticides, which 

can be used extensively in both agricultural and urban areas, 

chloride use is associated primarily with urban development; 

sources include road salt, wastewater effluent, and industrial 

processes. The strongest relations (greater than 0.90) were in 

colder regions of the country and may be related to snowfall 

and subsequent road salt application.

Pesticide Toxicity

The relations between pesticide toxicity and urban development also were strongest with the median value (table 3). 

Either moderate or strong positive relations were indicated in 

all study areas except Raleigh (Boston was excluded because 

pesticide data were not collected). However, in the Milwaukee 

study area, the relation between the median pesticide toxicity 

and urban development was negative (rho = *-0.66). Similar 

to the negative relation between the median total phosphorus 

value and urban development in the Milwaukee study area, 

this response suggests that pesticide toxicity decreased significantly in streams as land cover was converted from agricultural to urban.

Variability in Stream-Chemistry Factors

For each of the selected stream-chemistry factors, the 

standard deviation of all samples collected in a stream was 

used to represent the variability throughout the year. Variability is small when a stream-chemistry factor shows little fluctuation among samples collected throughout the year, whereas 

a relatively large variation results when a stream-chemistry 

factor shows great fluctuation among samples collected 

throughout the year. Therefore, an increase in the standard 

deviation of a stream-chemistry factor that corresponds to 

an increase in urban development would suggest that, as a 

watershed is developed, the value of a stream-chemistry factor 

could be expected to vary more widely among samples collected throughout the year.

Total Nitrogen

Boston was the only study area where the amount of 

variation throughout the year increased significantly with 

urban development for total nitrogen (rho=*0.83; table 3). 

This result suggests that as urban development increases in 

a watershed, total nitrogen concentrations vary more widely 

among samples collected throughout the year. In the other 

study areas, the extent that total nitrogen concentrations fluctuate throughout the year remains relatively constant as urban 

land cover increases in a watershed.

Total Phosphorus

Total phosphorus showed a different pattern from total 

nitrogen in how the amount of variation throughout the year 

was related to urban development. There was no relation 

indicated in the Boston study area, but moderate or strong 

relations were indicated in four other study areas (table 3). In 

the Portland and Denver study areas, the relations were strong, 

indicating that variation of total phosphorus concentrations 

throughout the year increased with urban development. Conversely, the Raleigh and Milwaukee study areas had moderate, 

negative relations (rho = -0.62 for both study areas), which 

suggests that total phosphorus concentrations in streams varied 

less as urban development increased. As previously described, 

this response in the Milwaukee study area might be associated 

with the agricultural land cover before urban development 

where fertilizer containing phosphorus is applied to crops only 

at certain times throughout the year. The reason for the negative response in the Raleigh study area is less clear. Fitzpatrick 

and Peppler (2010) reported a strong increase in the frequency 

of high flows related to urban development in the Raleigh 

study area, and it is possible that otherwise high total phosphorus concentrations in urban streams were diluted by these 

high flows.

Chloride

The relation between variation throughout the year in 

chloride concentrations and urban development indicated a 

pattern that was closely associated with the colder regions of 

the country (fig. 2; table 3). In the three study areas where road 

salt is used extensively to maintain travel in the winter (Boston, Denver, and Milwaukee), a strong positive relation was 

indicated. (Note: The graph for Milwaukee has been charted 

on a logarithmic scale.) A moderate relation was indicated in 

the Portland study area where snowfall generally occurs only 

at the higher elevations, but even then, road salt is typically 

not used. Because the relation between the median chloride 

concentration and urban development was also strong in the 

Boston, Denver, and Milwaukee study areas, the increase in 

the variation of chloride is consistent with wintertime salt use. 

Chloride concentrations in colder regions are typically highest 

during spring snowmelt and lower throughout the rest of the 

year, and this seasonal fluctuation can account for the greater 

variability in streams with high percentages of urban land.

Pesticide Toxicity

The relations between variation throughout the year in 

pesticide toxicity and urban development did not indicate any 

discernible pattern among the study areas (table 3). The relation was moderate in the Portland study area (rho = *0.65) and 

strong in the Atlanta (rho = *0.97) and Denver (rho = *0.77) 

study areas. In these three study areas, there was general 

agreement among the relations between variation throughout 
12 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004

Urban development, in percentage of watershed area

50

1510

Atlanta, Georgia

0 20 40 60 80

Milwaukee

Atlanta

Raleigh

Denver

Boston

Dallas

Portland

U.S. Geological Survey study areasAverage annual snowfall, in inches

Less than 6.06.1 to 12.012.1 to 24.024.1 to 36.036.1 to 48.048.1 to 72.0Greater than 72.0

EXPLANATION

100 0

80604020

Dallas, Texas 100

0 20 40 60 80

Chloride concentration, in milligrams per liter

Urban development, in percentage of watershed area

Denver, Colorado

Portland, Oregon

MedianAll samplesLinear fit line

EXPLANATION

0

50

200150100

Boston, Massachusetts 250

0 20 40 60 80 100

60

241812

Raleigh, North Carolina 30

0 20 40 60 80 100

Milwaukee, Wisconsin

1

10

100

1,000

10,000

0

0 20 40 60 80 100

Urban development, in percentage of watershed area

Chloride concentration, in milligrams per liter

Chloride concentration, in milligrams per liter

0

600400200

0 20 40 60 80 100

0 20 40 60 80

50

1510

100

Figure 2. The average annual snowfall for the United States and scatter plots showing the relation of chloride concentrations and urban development for each of the seven 

study areas sampled.
Results and Discussion 13

the year in pesticide toxicity and urban development and the 

relations between the median pesticide toxicity and urban 

development. Evaluated together, these results suggest that, 

while pesticide toxicity increases with urban development 

in these study areas, levels at sites within these study areas 

that are more urban are more variable throughout the year. A 

variance throughout the year such as this could occur when 

pesticides are applied mainly during warm months, similarly 

to the variance throughout the year in chloride related to road 

salt use in winter months.

Relations of the Biological Condition to Chloride 

and Pesticide Toxicity

Elevated chloride concentrations and pesticide toxicity values in streams are known to be toxic to macroinvertebrate communities (Munn and Gilliom, 2001; Munn and 

others, 2006; Corsi and others, 2010). Because values of 

these two stream-chemistry factors can vary among samples 

collected throughout the year, it is important to determine 

characterizations of these factors as they relate to biological community condition. The community tolerance index is 

used to characterize the biological community condition with 

values ranging from 0 (highly sensitive taxa) to 10 (highly 

tolerant taxa); therefore, a positive relation of the community 

tolerance index to a stream-chemistry factor indicates loss of 

sensitive taxa and a declining stream health.

Chloride

All moderate or strong relations between the community tolerance index and chloride were positive, indicating 

that sensitive taxa were being lost and the biological condition declined as chloride concentrations increased (table 4). 

In three of the four study areas where the land cover before 

urban development was forested, the relations with the median 

value were strong. The exception was the Raleigh study area, 

where no moderate or strong relations were indicated with any 

characterization of the chloride concentrations. In study areas 

where land cover before urban development was agriculture, 

no moderate or strong relations were indicated except for Denver study area, where the relation was strong with the seasonal 

high-flow value and moderate with the seasonal low-flow 

value.

The strongest relation between the community tolerance 

index and any characterization of chloride was indicated in 

the Boston study area with the median value (rho=*1.00; fig. 

3). This finding supports the premise that the condition of the 

macroinvertebrate community reflects water-quality conditions integrated over time and is consistent with other studies 

that identified chloride as an important water-quality factor 

that can occur at concentrations harmful to aquatic life in the 

northeastern United States (Mullaney and others, 2009). Furthermore, Kashuba and others (2012) developed a Bayesian 

model for the northeastern United States that predicted how 

changes in stream habitat, hydrology, and water quality could 

degrade macroinvertebrate communities in streams of the 

region. Using the Bayesian modeling approach of analyzing 

region-specific data and eliciting information from regional 

experts, specific conductance (a surrogate for chloride in the 

region) was identified as the stream-chemistry factor that best 

predicted the condition of the macroinvertebrate communities.

Pesticide Toxicity

Relations between the community tolerance index and 

pesticide toxicity indicated moderate to strong positive relations in all study areas with at least one characterization of 

pesticide toxicity, which suggested that the biological condition declined with an increase in pesticide use (table 4). This 

finding is supported by the general purpose of pesticides: to 

eliminate plant and animal species from places such as crops, 

buildings, and lawns. Thus, when pesticides (especially insecticides) enter a stream, they can affect the macroinvertebrate 

Comparing the Community Tolerance Index 

Among Study Areas

Examining the community tolerance index 

values within each study area provides a better 

understanding of how the macroinvertebrate 

community relates to both chloride and pesticide toxicity. The community tolerance index 

minimum values (table 2) were generally lower 

in study areas where land cover before urban 

development was forested (average = 4.78) 

compared with the study areas where the land 

cover before urban development was agricultural (average = 5.58). The range of the 

community tolerance index was calculated 

by subtracting the minimum value from the 

maximum value within a study area. The average range of the community tolerance index 

was greater in study areas where the land cover 

before urban development was forested (2.66 

overall), whereas study areas where land cover 

before urban development was agricultural 

had smaller ranges (2.20 overall). The smaller 

range of community tolerance indices in study 

areas where the land cover before urban development was agricultural is consistent with less 

change in the community structure, therefore 

decreasing the potential response to chloride 

and pesticide toxicity.
14 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004

0 50 100 150 200

Chloride concentration, in milligrams per liter

0

2

4

6

8

Community tolerance index

Boston, Massachusetts 10

250

Median

All samples

EXPLANATION

Linear fit line

Figure 3. The community tolerance index compared with chloride concentrations in the Boston, Massachusetts, study area.

community. Relations based on the median value were moderate to strong in all study areas except Milwaukee.

The community tolerance index at the least urban site in 

Milwaukee was 6.77, which, for the seven study areas, is the 

highest community tolerance index among the least urban sites 

(table 1). This occurs because streams in watersheds of the 

Milwaukee study area had agricultural land cover before urban 

development, which resulted in relatively fewer sensitive 

macroinvertebrate taxa compared with streams in the other 

study areas, especially those that had watersheds with forest 

land cover before urban development; the presence of fewer 

sensitive taxa in Milwaukee study area may be related, in part, 

to widespread pesticide application in the watersheds before 

urban development. Furthermore, the presence of relatively 

few sensitive taxa in Milwaukee study area may help explain 

the lack of a relation between the community tolerance index 

and chloride in that study area (table 4). Even though the 

relation between the median chloride value and urban development was very strong in the Milwaukee study area (table 

3; rho=*0.99), the invertebrate community would not be 

particularly responsive to an increase in chloride concentrations if the sensitive taxa were already depleted.

These findings are substantiated by the results of Cuffney 

and others (2010), who reported that watersheds in the Denver, 

Dallas, and Milwaukee study areas before urban development 

had relatively few sensitive taxa in their streams because they 

had been affected by degradation from agricultural practices. 

Consequently, the expected response of a biological community to urban development and other stressors would be 

weaker in agricultural areas compared with that in forested 

areas. Thus, the relatively weak responses in the Denver, 

Dallas, and Milwaukee study areas does not mean that their 

aquatic biological communities are more resilient to increases 

in chloride and pesticides, but more likely that the biological 

condition was already degraded to some degree before the 

increases in these stressors.

Results in the Raleigh, North Carolina, study area were 

not consistent with the study areas where land cover before 

urban development was forested; the high minimum community tolerance index value (5.59) and the smallest range 
References Cited 15

(1.26) more closely approximate study areas where land cover 

before urban development was agricultural (table 2). Although 

the land cover in Raleigh is being converted from forested to 

urban, the Raleigh area was farmed in the early 1900s and then 

allowed to revert to forest (Falcone and others, 2007).

Summary and Conclusions

The U.S. Geological Survey investigated the effects 

of urban development on stream ecosystems as part of the 

National Water-Quality Assessment Program beginning in 

1999. Water quality was sampled in seven study areas across 

the United States at 61 stream sites (6 to 10 stream sites in 

each study area) along a gradient of land cover from forested 

or agricultural to urban land. Stream-chemistry samples were 

collected every other month for a year and the aquatic macroinvertebrate community was assessed. The purpose of this 

report was to evaluate how variation in stream-chemistry 

factors related to urban development and to the biological 

condition of these streams.

This report focused on four stream-chemistry factors—

total nitrogen, total phosphorus, chloride, and pesticide toxicity—and explored how the strength in their relation to urban 

development and how the aquatic biological condition often 

depends on how the stream-chemistry factors are characterized. Because the values of factors can vary with the time of 

year a sample is collected, each factor was characterized four 

separate ways to account for variation throughout the year—

the seasonal high-flow value, the seasonal low-flow value, the 

median value (representing an annual “integrated” value), and 

the standard deviation of values (representing the amount of 

variation throughout the year among values). Additionally, a 

community tolerance index for macroinvertebrates was used 

to infer the biological condition for each site. The objectives 

of this report were to (1) describe how relations between urban 

development and stream-chemistry factors depend on when 

stream-chemistry is sampled and how their values are characterized, and (2) identify characterizations of chloride and 

pesticide toxicity values that have the strongest relations to the 

biological condition of a stream. Spearman correlations were 

used to evaluate these relations.

Stream-chemistry factors generally increased with 

urban development, with the exception of total phosphorus in 

Raleigh, North Carolina, and Milwaukee, Wisconsin, study 

areas and pesticide toxicity in the Milwaukee study area. 

Among the characterizations of stream-chemistry factors, the 

median value generally had the greatest number of strong 

relations with urban development. The variation throughout 

the year in stream-chemistry factors generally increased with 

urban development, indicating that the values of streamchemistry factors (and water-quality in general) became less 

consistent among samples as watersheds were developed. 

The study areas where the land cover before urban development was forested generally had a larger number of strong and 

moderate relations between the stream-chemistry factors and 

urban development compared to the number of relations in the 

study areas where the land cover before urban development 

was agriculture. The relations between chloride and urban 

development were the strongest of relations with the streamchemistry factors. The negative relations for total phosphorus 

and pesticide toxicity in the Milwaukee study area are likely 

the results of fertilizer and pesticide applications on agricultural crops.

The relations of community tolerance index to chloride 

and pesticide toxicity were calculated irrespective of the level 

of urban development. The overall results, however, were 

similar to results for the stream-chemistry factors and urban 

development; the forested study areas had a greater number 

of strong relations compared with the agricultural study areas. 

This response is likely due to a degraded biological community that resulted from agricultural practices in the watersheds. 

In general, the median values for chloride and pesticide toxicity provided the strongest relations of the community tolerance 

index to chloride and pesticide toxicity.

The results of this investigation indicated that, compared 

with sampling a stream at a single point in time, sampling at 

regular intervals over the course of 1 year is valuable for determining the overall water quality and for relating water quality 

to the biological condition of a stream. From these samples, 

the median value may indicate a more integrated water-quality 

condition for streams undergoing urban development.

References Cited

Barbour, M.T., Gerritsen, Jeroen, Snyder, B.D., and Stribling, J.B., 1999, Rapid bioassessment protocols for use in 

streams and wadeable rivers—Periphyton, benthic macroinvertebrates and fish (2d ed.): U.S. Environmental Protection 

Agency EPA 841–B–99–002, [variously paged], accessed 

July 17, 2012, at http://water.epa.gov/scitech/monitoring/

rsl/bioassessment/index.cfm.

Booth, D.B., Karr, J.R., Schauman, Sally, Konrad, C.P., Morley, S.A., Larson, M.G., and Burges, S.J., 2004, Reviving 

urban streams—Land use, hydrology, biology, and human 

behavior: Journal of the American Water Resources Association, v. 40, p. 1351–1364.

Coles, J.F., Cuffney, T.F., McMahon, Gerard, and Beaulieu, 

K.M., 2004, The effects of urbanization on the biological, physical, and chemical characteristics of coastal New 

England streams: U.S. Geological Survey Professional 

Paper 1695, 47 p. (Also available at http://pubs.usgs.gov/

pp/pp1695/)
16 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004

Corsi, S.R., Graczyk, D.J., Geis, S.W., Booth, N.L., and Richards, K.D., 2010, A fresh look at road salt—Aquatic toxicity 

and water-quality impacts on local, regional, and national 

scales: Environmental Science & Technology, v. 44, no. 19, 

p. 7376–7382.

Couch, Carol, and Hamilton, Pixie, 2002, Effects of urbanization on stream ecosystems: U.S. Geological Survey Fact 

Sheet FS–042–02, 2 p., available at http://pubs.usgs.gov/fs/

fs04202/.

Cuffney, T.F., 2003, User’s manual for the National WaterQuality Assessment Program Invertebrate Data Analysis 

System (IDAS) software—ver. 3: U.S. Geological Survey 

Open-File Report 03-172, 103 p.

Cuffney, T.F., Gurtz, M.E., and Meador, M.R., 1993, Methods 

for collecting benthic invertebrate samples as part of the 

National Water-Quality Assessment Program: U.S. Geological Survey Open-File Report 93–406, 66 p. (Also available 

at http://water.usgs.gov/nawqa/protocols/OFR-93-406/.)

Cuffney, T.F., Brightbill, R.A., May, J.T., and Waite, I.R., 

2010, Responses of benthic macroinvertebrates to environmental changes associated with urbanization in nine 

metropolitan areas: Ecological Applications, v. 20, no. 5, p. 

1384–1401.

Falcone, James, Stewart, Jana, Sobieszczyk, Steven, Dupree, 

Jean, McMahon, Gerard, and Buell, Gary, 2007, A comparison of natural and urban characteristics and the development of urban intensity indices across six geographic 

settings: U.S. Geological Survey Scientific Investigations 

Report 2007–5123, 43 p. plus 7 appendixes, available at 

http://pubs.usgs.gov/sir/2007/5123/.

Fishman, M.J., 1993, Methods of analysis by the U.S. Geological Survey National Water-Quality Laboratory—Determination of inorganic and organic constituents in water and 

fluvial sediments: U.S. Geological Survey OpenFile Report 

93–125, 217 p.

Fishman, M.J., and Friedman, L.C., eds., 1989, Methods for 

determination of inorganic substances in water and fluvial 

sediments: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. A1, 545 p. (Also 

available at http://pubs.usgs.gov/twri/twri5-a1/.)

Fitzpatrick, F.A., and Peppler, M.C., 2010, Relation of urbanization to stream habitat and geomorphic characteristics in 

nine metropolitan areas of the United States: U.S. Geological Survey Scientific Investigations Report 2010–5056, 29 

p., available at http://pubs.usgs.gov/sir/2010/5056/.

Giddings, E.M., Moorman, M.C., Cuffney, T.F., McMahon, 

Gerard, and Harned, D.A., 2007, Selected physical, chemical, and biological data for 30 urbanizing streams in the 

North Carolina Piedmont ecoregion, 2002–2003: U.S. 

Geological Survey Data Series 279, 14 p. (Also available at 

http://pubs.usgs.gov/ds/279/.)

Giddings, E.M.P., Bell, A.H., Beaulieu, K.M., Cuffney, T.F., 

Coles, J.F., Brown, L.R., Fitzpatrick, F.A., Falcone, James, 

Sprague, L.A., Bryant, W.L., Peppler, M.C., Stephens, Cory, 

and McMahon, Gerard, 2009, Selected physical, chemical, 

and biological data used to study urbanizing streams in nine 

metropolitan areas of the United States, 1999–2004: U.S. 

Geological Survey Data Series 423, 11 p. and data tables, 

available at http://pubs.usgs.gov/ds/423/.

Gilliom, R.J., Alley, W.M., and Gurtz, M.E., 1995, Design 

of the National Water-Quality Assessment Program—

Occurrence and distribution of water-quality conditions: U.S. Geological Survey Circular 1112, available at 

http://pubs.usgs.gov/circ/circ1112/.

Gregory, M.B., and Calhoun, D.L., 2007, Physical, chemical, 

and biological responses of streams to increasing watershed urbanization in the Piedmont ecoregion of Georgia 

and Alabama, 2003: U.S. Geological Survey Scientific 

Investigations Report 2006–5101–B, 104 p., available at 

http://pubs.usgs.gov/sir/2006/5101B/.

Insightful Corporation, 2005, S–PLUS version 7.0 for Windows: Seattle, Washington, Insightful Corporation computer 

software.

Kashuba, Roxolana, McMahon, Gerard, Cuffney, T.F., 

Qian, Song, Reckhow, Kenneth, Gerritsen, Jeroen, and 

Davies, Susan, 2012, Linking urbanization to the biological condition gradient (BCG) for stream ecosystems in the northeastern United States using a Bayesian 

network approach: U.S. Geological Survey Scientific 

Investigations Report 2012–5030, 48 p., available at 

http://pubs.usgs.gov/sir/2012/5030/.

Moring, J.B., 2009, Effects of urbanization on the chemical, 

physical, and biological characteristics of small Blackland 

Prairie streams in and near the Dallas-Fort Worth metropolitan area, Texas: U.S. Geological Survey Scientific 

Investigations Report 2006–5101–C, 31 p., available at 

http://pubs.usgs.gov/sir/2006/5101C/.

Moulton, S.R., II, Kennen, J.G., Goldstein, R.M., and 

Hambrook, J.A., 2002, Revised protocols for sampling 

algal, invertebrate, and fish communities as part of the 

National Water-Quality Assessment Program: U.S. Geological Survey Open-File Report 02–150, available at 

http://pubs.usgs.gov/of/2002/ofr-02-150/.
References Cited 17

Mullaney, J.R., Lorenz, D.L., and Arntson, A.D., 2009, 

Chloride in groundwater and surface water in areas 

underlain by the glacial aquifer system, northern 

United States: U.S Geological Survey Scientific Investigations Report 2009–5086, 41 p. (Also available at 

http://pubs.usgs.gov/sir/2009/5086/.)

Multi-Resolution Land Characteristics Consortium, 

2001, National land cover database: U.S. Geological Survey, accessed December 20, 2005, at 

http://www.mrlc.gov/mrlc2k_nlcd.asp.

Munn, M.D., and Gilliom, R.J., 2001, Pesticide toxicity index 

for freshwater aquatic organisms: U. S. Geological Survey 

Water Resources Investigation Report 01–4077, 61 p. (Also 

available at http://pubs.usgs.gov/wri/wri014077/.)

Munn, M.D., Gilliom, R.J., Moran, P.W., and Nowell, L.H., 

2006, Pesticide toxicity index for freshwater aquatic 

organisms (2d ed.): U.S. Geological Survey Scientific 

Investigations Report 2006–5148, 81 p., available at 

http://pubs.usgs.gov/sir/2006/5148/.

Omernik, J.M., 1987, Ecoregions of the conterminous United 

States: Annals of the Association of American Geographers, 

v. 77, no. 1, p. 118–125.

Overmyer, J.P., Noblet, Raymond, and Armbrust, K.L., 2005, 

Impacts of lawn-care pesticides on aquatic ecosystems in 

relation to property value: Environmental Pollution, v. 137, 

no. 2, p. 263–272.

Paul, M.J., and Meyer, J.L., 2001, Streams in the urban landscape: Annual Review of Ecology and Systematics, v. 32, p. 

333–365.

Pickett, S.T.A., 1989, Space-for-time substitution as an alternative to long-term studies, in Likens G.E, ed., Long-term 

studies in ecology—Approaches and alternatives: New 

York, Springer-Verlag, p. 110–135.

Poff, N.L., Allan, J.D., Bain, M.B., Karr, J.R., Prestegaard, 

K.L., Richter, B.D., Sparks, R.E., and Stromberg, J.C., 

1997, The natural flow regime: BioScience, v. 47, no. 11, p. 

769–784.

Richards, K.D., Scudder, B.C., Fitzpatrick, F.A., Steuer, J.J., 

Bell, A.H., Peppler, M.C., Stewart, J.S., and Harris, M.A., 

2010, Effects of urbanization on stream ecosystems along 

an agriculture-to-urban land-use gradient, Milwaukee to 

Green Bay, Wisconsin, 2003–2004: U.S. Geological Survey 

Scientific Investigations Report 2006–5101–E, 210 p., 

available at http://pubs.usgs.gov/sir/2006/5101E/.

Schueler, T.R., 1994, The importance of imperviousness: 

Watershed Protection Techniques, v. 1, no. 3, p. 100–111.

Sprague, L.A., Zuellig, R.E., and Dupree, J.A., 2006, Effects 

of urbanization on stream ecosystems in the South Platte 

River basin, Colorado and Wyoming: U.S. Geological Survey Scientific Investigations Report 2006–5101–A, 139 p., 

available at http://pubs.usgs.gov/sir/2006/5101A/.

Systat Software, Inc., 2007, SYSTAT, version 12: San Jose, 

California, Systat Software, Inc.

Tate, K.W., Dahlgren, R.A., Singer, M.J., Allen-Diaz, B.H., 

and Atwill, E.R., 1999, Timing, frequency of sampling 

affect accuracy of water-quality monitoring: California 

Agriculture, v. 53, no. 6, p. 44–48.

U.S. Geological Survey, 1999, The quality of our 

nation’s waters—Nutrients and pesticides: U.S. Geological Survey Circular 1225, 82 p. (Also available at 

http://pubs.usgs.gov/circ/circ1225/.)

U.S. Geological Survey, [variously dated], National field 

manual for the collection of water-quality data: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 9, chaps. A1–A9, available at 

http://water.usgs.gov/owq/FieldManual/.

U.S. Geological Survey, [undated], Effects of 

urbanization on stream ecosystems: U.S. Geological Survey, accessed July 17, 2012, at 

http://water.usgs.gov/nawqa/urban/html/studydesign.html.

Waite, I.R., Sobieszczyk, Steven, Carpenter, K.D., Arnsberg, 

A.J., Johnson, H.M., Hughes, C.A., Sarantou, M.J., and 

Rinella, F.A., 2008, Effects of urbanization on stream ecosystems in the Willamette River basin and surrounding area, 

Oregon and Washington: U.S. Geological Survey Scientific 

Investigations Report 2006–5101–D, 62 p., available at 

http://pubs.usgs.gov/sir/2006/5101-D/.

Zaugg, S.D., Sandstrom, M.W., Smith, S.G. and Fehlberg, 

K.M., 1995, Methods of analysis by the U.S. Geological 

Survey National Water Quality Laboratory—Determination of pesticides in water by C–18 solid-phase extraction 

and capillary-column gas chromatography/mass spectrometry with selected-ion monitoring: U.S. Geological 

Survey Open-File Report 95–181, 49 p. (Also available at 

http://nwql.usgs.gov/OFR-95-181.shtml.)
This page has been left blank intentionally. 
Appendix 1. Site Summary of Total Nitrogen

Concentrations, Total Phosphorus Concentrations,

Chloride Concentrations, and the Pesticide Toxicity Index
This page has been left blank intentionally. 
Appendix 1 21

Appendix Table 1-1. Sample characterizations of total nitrogen concentrations, total phosphorus concentrations, chloride 

concentrations, and pesticide toxicity for each stream.—Continued

[Site information is listed in table 1. The data from these samples are reported in Giddings and others (2009). Values shown as a number followed with “E” 

and a negative number are the number multiplied by 10 to the power of the second number; thus, 1.04E-7 is 1.04 ×10-7 or 0.000000104. Colo., Colorado; 

Ga., Georgia; Mass., Massachusetts; N.C., North Carolina; Oreg., Oregon; Tex., Texas; Wis., Wisconsin; ID, identification number; mg/L, milligrams per 

liter; ND, no data; USGS, U.S. Geological Survey]

Site code USGS site ID Sample characterization Total nitrogen 

(mg/L)

Total phosphorus 

(mg/L)

Chloride

(mg/L)

Pesticide 

toxicity1

(unitless)

Portland, Oreg., study area

POR_efdar 14205400 Seasonal high flow 0.41 0.04 2.5 1.04E-7

Seasonal low flow 0.26 0.05 2.3 0

Median 0.39 0.03 2.3 5.30E-8

Standard deviation 0.23 0.01 0.1 6.71E-8

POR_deep 452231122200000 Seasonal high flow 0.38 0.02 1.8 1.68E-7

Seasonal low flow 0.21 0.03 2.1 0

Median 0.37 0.02 2.1 3.86E-8

Standard deviation 0.51 0.01 0.3 9.95E-7

POR_rocwa 455122122310600 Seasonal high flow 0.27 0.05 1.8 3.86E-8

Seasonal low flow 0.12 0.04 12 0

Median 0.56 0.03 2.3 1.93E-8

Standard deviation 0.60 0.01 4.2 1.47E-3

POR_salmo 454549122295800 Seasonal high flow 0.33 0.01 1.8 0

Seasonal low flow 0.11 0.02 1.9 0

Median 0.31 0.01 1.9 0

Standard deviation 0.37 0.00 0.4 9.78E-4

POR_tickl 452414122213200 Seasonal high flow 0.66 0.05 2.6 4.77E-3

Seasonal low flow 1.1 0.11 4.0 1.17E-2

Median 1.2 0.05 3.2 5.64E-3

Standard deviation 0.56 0.03 0.5 5.97E-3

POR_nfdep 452337122243500 Seasonal high flow 1.3 0.06 4.7 2.44E-2

Seasonal low flow 1.1 0.09 6.0 5.61E-3

Median 1.4 0.06 4.6 2.45E-2

Standard deviation 1.3 0.02 1.0 1.70E-2

POR_whipp 454510122424900 Seasonal high flow 0.77 0.16 7.1 2.26E-4

Seasonal low flow 0.51 0.18 7.6 0

Median 0.74 0.13 7.4 5.24E-6

Standard deviation 0.16 0.05 1.1 1.06E-3

POR_kello 452526122364400 Seasonal high flow 2.3 0.10 6.0 4.41E-4

Seasonal low flow 1.8 0.12 5.0 4.20E-7

Median 2.1 0.10 5.9 4.76E-6

Standard deviation 0.24 0.04 0.5 1.23E-3

POR_pring 445551123015800 Seasonal high flow 0.72 0.03 3.9 5.76E-6

Seasonal low flow 0.60 0.05 4.8 9.45E-6

Median 0.70 0.03 4.5 4.26E-3

Standard deviation 0.60 0.01 1.1 1.23E-3
22 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004

Appendix Table 1-1. Sample characterizations of total nitrogen concentrations, total phosphorus concentrations, chloride 

concentrations, and pesticide toxicity for each stream.—Continued

[Site information is listed in table 1. The data from these samples are reported in Giddings and others (2009). Values shown as a number followed with “E” 

and a negative number are the number multiplied by 10 to the power of the second number; thus, 1.04E-7 is 1.04 ×10-7 or 0.000000104. Colo., Colorado; 

Ga., Georgia; Mass., Massachusetts; N.C., North Carolina; Oreg., Oregon; Tex., Texas; Wis., Wisconsin; ID, identification number; mg/L, milligrams per 

liter; ND, no data; USGS, U.S. Geological Survey]

Site code USGS site ID Sample characterization Total nitrogen 

(mg/L)

Total phosphorus 

(mg/L)

Chloride 

(mg/L)

Pesticide 

toxicity1

(unitless)

POR_clagg 450022123012400 Seasonal high flow

Seasonal low flow

Median

Standard deviation

0.97

0.84

0.90

0.12

0.16

0.28

0.14

0.06

5.4

6.9

5.4

0.9

1.41E-3

1.41E-2

1.43E-2

8.41E-3

Atlanta, Ga., study area

ATL_hil

ATL_dog

ATL_sho

ATL_whw

ATL_who

ATL_suw

ATL_nos

ATL_nic

02338523

02337395

02344480

02344737

02344797

02334885

02336968

02336635

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

0.55

0.18

0.31

0.78

0.34

0.34

0.40

0.07

0.69

0.34

0.53

0.13

0.60

0.62

0.62

0.13

1.5

1.4

1.2

0.33

0.96

0.92

0.95

0.37

0.52

0.38

0.53

0.31

0.93

0.97

0.95

0.12

0.01

0.01

0.01

0.03

0.01

0.01

0.02

0.01

0.05

0.02

0.03

0.02

0.23

0.12

0.12

0.07

0.08

0.31

0.11

0.10

0.03

0.03

0.03

0.02

0.02

0.01

0.02

0.06

0.01

0.02

0.02

0.03

1.7

1.8

1.8

3.8

2.0

2.8

2.4

0.4

2.8

4.0

3.1

0.5

3.8

9.9

3.8

2.8

2.6

7.2

4.4

2.5

3.7

5.6

4.8

1.1

3.1

3.9

3.1

0.5

6.2

7.1

5.8

1.6

0

0

0

3.53E-4

1.70E-5

1.84E-3

8.37E-4

5.30E-3

1.55E-5

4.94E-6

1.45E-3

4.82E-3

1.58E-2

8.98E-6

8.53E-3

5.82E-3

4.84E-4

3.71E-3

6.56E-3

7.55E-3

1.17E-2

7.29E-6

8.53E-3

1.19E-2

4.23E-3

8.40E-4

5.37E-3

1.55E-2

5.96E-3

3.52E-3

1.24E-2

2.43E-2
Appendix 1 23

Appendix Table 1-1. Sample characterizations of total nitrogen concentrations, total phosphorus concentrations, chloride 

concentrations, and pesticide toxicity for each stream.—Continued

[Site information is listed in table 1. The data from these samples are reported in Giddings and others (2009). Values shown as a number followed with “E” 

and a negative number are the number multiplied by 10 to the power of the second number; thus, 1.04E-7 is 1.04 ×10-7 or 0.000000104. Colo., Colorado; 

Ga., Georgia; Mass., Massachusetts; N.C., North Carolina; Oreg., Oregon; Tex., Texas; Wis., Wisconsin; ID, identification number; mg/L, milligrams per 

liter; ND, no data; USGS, U.S. Geological Survey]

Site code USGS site ID Sample characterization Total nitrogen 

(mg/L)

Total phosphorus 

(mg/L)

Chloride 

(mg/L)

Pesticide 

toxicity1

(unitless)

ATL_sop 02335870 Seasonal high flow

Seasonal low flow

Median

Standard deviation

0.87

0.69

0.83

0.45

0.01

0.01

0.01

0.05

5.1

7.3

5.3

1.4

1.08E-2

7.32E-4

1.85E-2

2.42E-2

Raleigh, N.C., study area

RAL_morgan

RAL_cates

RAL_rschen

RAL_swift

RAL_hare

RAL_black

RAL_swprng

RAL_pigeon

02097464

0208500600

0208726370

02087580

0208726995

0208725055

0208730725

0208732610

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

0.86

0.70

1.0

0.83

0.29

0.35

0.31

0.06

0.90

0.67

0.60

0.35

0.75

0.66

0.67

0.17

0.80

1.7

0.88

0.37

0.44

0.75

0.24

0.24

0.90

0.89

0.83

0.11

2.2

1.6

1.8

0.33

0.07

0.10

0.10

0.11

0.03

0.02

0.02

0.01

0.06

0.03

0.03

0.24

0.05

0.05

0.05

0.01

0.05

0.03

0.04

0.02

0.04

0.08

0.02

0.02

0.01

0.03

0.02

0.01

0.03

0.03

0.03

0.01

5.4

6.2

6.1

0.8

23

10

12

4.8

100

10

10

38

8.7

5.7

5.9

1.6

20

6.6

6.5

5.4

13

4.9

7.4

2.6

18

11

11

2.9

36

21

24

5.9

2.39E-7

4.37E-6

1.64E-7

1.72E-6

7.89E-8

1.32E-3

2.03E-6

1.02E-3

1.05E-2

1.49E-3

4.53E-3

2.82E-2

3.82E-2

5.85E-3

2.87E-2

3.62E-2

1.07E-2

1.88E-2

1.68E-2

3.32E-2

3.11E-2

1.16E-1

2.55E-3

4.61E-2

4.12E-5

8.32E-3

2.23E-3

4.01E-3

5.60E-4

4.66E-5

3.04E-4

4.46E-3
24 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004

Appendix Table 1-1. Sample characterizations of total nitrogen concentrations, total phosphorus concentrations, chloride 

concentrations, and pesticide toxicity for each stream.—Continued

[Site information is listed in table 1. The data from these samples are reported in Giddings and others (2009). Values shown as a number followed with “E” 

and a negative number are the number multiplied by 10 to the power of the second number; thus, 1.04E-7 is 1.04 ×10-7 or 0.000000104. Colo., Colorado; 

Ga., Georgia; Mass., Massachusetts; N.C., North Carolina; Oreg., Oregon; Tex., Texas; Wis., Wisconsin; ID, identification number; mg/L, milligrams per 

liter; ND, no data; USGS, U.S. Geological Survey]

Site code USGS site ID Sample characterization Total nitrogen 

(mg/L)

Total phosphorus 

(mg/L)

Chloride 

(mg/L)

Pesticide 

toxicity1

(unitless)

Boston, Mass., study area

BOS_stil

BOS_wade

BOS_nepo

BOS_ipsw

BOS_saug

BOS_aber

01095220

01109000

01105000

01101500

01102345

01102500

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

0.63

0.48

0.44

0.10

0.49

0.67

0.63

0.15

0.66

0.87

0.82

0.27

0.73

1.0

0.81

0.16

0.66

1.1

1.1

0.18

2.4

2.9

2.9

0.89

0.15

0.02

0.02

0.04

0.01

0.03

0.03

0.02

0.07

0.04

0.04

0.04

0.02

0.05

0.03

0.02

0.02

0.05

0.03

0.02

0.03

0.05

0.04

0.04

9.7

20

17

11

47

56

46

9.5

47

54

48

8.6

37

56

56

12

32

110

92

32

130

120

110

35

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

ND

Denver, Colo., study area

DEN_brphil

DEN_boxel

DEN_fossil

413659104370001

403308105001601

403048105042701

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

0.25

0.20

0.49

0.17

4.4

4.6

5.4

0.59

1.6

1.5

2.0

1.0

0.01

0.01

0.00

0.00

0.02

0.03

0.03

0.02

0.04

0.02

0.02

0.02

6.2

6.5

6.2

0.8

27

27

26

2.0

38

42

53

25

0

0

0

0

2.09E-6

2.15E-6

3.47E-6

1.94E-6

5.35E-4

6.88E-6

2.71E-4

1.11E-3
Appendix 1 25

Appendix Table 1-1. Sample characterizations of total nitrogen concentrations, total phosphorus concentrations, chloride 

concentrations, and pesticide toxicity for each stream.—Continued

[Site information is listed in table 1. The data from these samples are reported in Giddings and others (2009). Values shown as a number followed with “E” 

and a negative number are the number multiplied by 10 to the power of the second number; thus, 1.04E-7 is 1.04 ×10-7 or 0.000000104. Colo., Colorado; 

Ga., Georgia; Mass., Massachusetts; N.C., North Carolina; Oreg., Oregon; Tex., Texas; Wis., Wisconsin; ID, identification number; mg/L, milligrams per 

liter; ND, no data; USGS, U.S. Geological Survey]

Site code USGS site ID Sample characterization Total nitrogen 

(mg/L)

Total phosphorus 

(mg/L)

Chloride 

(mg/L)

Pesticide 

toxicity1

(unitless)

DEN_breste

DEN_ralst

DEN_bould

DEN_cherry

DEN_lakew

DEN_litdry

393948105053501

394919105074601

400217105123701

06713500

394409105020501

394921105015701

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

0.74

1.7

1.5

0.57

0.60

2.0

1.9

0.69

0.28

0.33

0.35

0.42

2.2

2.5

2.6

1.1

ND

ND

1.1

0.56

0.74

0.86

2.1

1.3

0.03

0.14

0.03

0.05

0.07

0.09

0.03

0.04

0.02

0.02

0.03

0.07

0.18

0.19

0.19

0.04

0.06

0.06

0.02

0.02

0.04

0.05

0.03

0.20

33

40

61

73

13

29

43

110

8.3

14

62

44

86

73

89

120

64

49

100

180

54

56

74

48

1.63E-7

3.73E-7

1.01E-6

4.94E-4

0

4.57E-2

5.30E-6

1.86E-2

9.56E-8

4.22E-7

6.25E-7

4.89E-4

7.97E-2

1.91E-2

2.65E-3

3.13E-2

0

0

1.78E-3

9.71E-1

1.10E-2

9.06E-3

7.23E-3

5.74E-3

Dallas, Tex., study area

DFW_sprong

DFW_mill

DFW_sfkcha

08063595

08063565

08063555

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

1.3

3.4

1.4

0.95

1.1

0.42

0.72

0.32

0.36

4.3

0.70

1.7

0.04

0.05

0.05

0.05

0.03

0.02

0.03

0.02

0.04

0.10

0.10

0.07

13

13

13

5.9

10

26

10

8.4

55

25

52

21

7.18E-7

6.50E-6

5.83E-6

8.06E-3

2.76E-6

1.14E-6

3.74E-6

7.11E-6

4.43E-5

6.81E-4

2.08E-4

2.79E-4
26 Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004

Appendix Table 1-1. Sample characterizations of total nitrogen concentrations, total phosphorus concentrations, chloride 

concentrations, and pesticide toxicity for each stream.—Continued

[Site information is listed in table 1. The data from these samples are reported in Giddings and others (2009). Values shown as a number followed with “E” 

and a negative number are the number multiplied by 10 to the power of the second number; thus, 1.04E-7 is 1.04 ×10-7 or 0.000000104. Colo., Colorado; 

Ga., Georgia; Mass., Massachusetts; N.C., North Carolina; Oreg., Oregon; Tex., Texas; Wis., Wisconsin; ID, identification number; mg/L, milligrams per 

liter; ND, no data; USGS, U.S. Geological Survey]

Site code USGS site ID Sample characterization Total nitrogen 

(mg/L)

Total phosphorus 

(mg/L)

Chloride 

(mg/L)

Pesticide 

toxicity1

(unitless)

DFW_doe

DFW_tehuac

DFW_buftri

DFW_parsn

DFW_5mile

DFW_white

08052740

08064695

08061780

08057475

08057431

08057200

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

1.6

6.8

4.4

2.8

0.13

0.22

0.13

0.07

4.2

3.9

3.1

1.4

0.14

0.11

0.13

0.06

0.89

0.19

0.67

0.35

1.9

1.7

2.3

0.30

0.15

0.19

0.19

0.13

0.04

0.06

0.04

0.05

0.98

1.16

0.79

0.84

0.09

0.10

0.10

0.07

0.01

0.01

0.03

0.03

0.19

0.14

0.25

0.09

24

26

26

8.6

30

31

30

11

75

54

44

26

52

63

59

21

21

26

16

8.4

35

35

36

6.4

5.23E-4

8.56E-2

1.19E-2

3.39E-2

1.11E-6

4.49E-4

1.11E-6

2.27E-4

4.79E-3

8.34E-3

1.16E-2

1.06E-2

1.86E-5

7.73E-3

2.37E-5

1.01E-2

1.03E-2

1.39E-4

2.62E-2

4.59E-2

2.69E-2

9.63E-3

1.21E-2

7.10E-3

Milwaukee, Wis., study area

MGB_blak

MGB_rioc

MGB_bair

040853145

04085188

040851325

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

2.0

2.6

2.0

0.29

0.88

4.1

2.4

1.7

0.43

0.09

0.26

0.15

0.19

0.31

0.14

0.09

0.22

0.16

0.13

0.07

0.71

0.13

0.20

0.24

22

30

30

7.0

18

37

31

13

20

24

46

21

2.25E-2

3.86E-1

3.19E-2

1.45E-1

3.31E-5

1.41E-5

1.67E-5

1.07E-5

8.84E-5

5.01E-6

4.84E-5

1.25E-2
Appendix 1 27

Appendix Table 1-1. Sample characterizations of total nitrogen concentrations, total phosphorus concentrations, chloride 

concentrations, and pesticide toxicity for each stream.—Continued

[Site information is listed in table 1. The data from these samples are reported in Giddings and others (2009). Values shown as a number followed with “E” 

and a negative number are the number multiplied by 10 to the power of the second number; thus, 1.04E-7 is 1.04 ×10-7 or 0.000000104. Colo., Colorado; 

Ga., Georgia; Mass., Massachusetts; N.C., North Carolina; Oreg., Oregon; Tex., Texas; Wis., Wisconsin; ID, identification number; mg/L, milligrams per 

liter; ND, no data; USGS, U.S. Geological Survey]

Site code USGS site ID Sample characterization Total nitrogen 

(mg/L)

Total phosphorus 

(mg/L)

Chloride 

(mg/L)

Pesticide 

toxicity1

(unitless)

MGB_sawy

MGB_pikr

MGB_meno

MGB_mudc

MGB_oakc

MGB_linc

MGB_hony

04081897

04087258

04087030

04084429

04087204

040869415

04087118

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

Seasonal high flow

Seasonal low flow

Median

Standard deviation

8.7

0.14

5.1

3.5

9.8

0.57

4.1

5.1

1.3

0.43

1.2

1.2

0.97

0.23

0.82

0.28

1.2

0.74

0.74

0.20

1.0

0.32

0.79

0.50

1.9

1.2

1.2

0.46

0.07

0.15

0.09

0.05

0.12

0.12

0.10

0.09

0.09

0.18

0.07

0.07

0.19

0.11

0.09

0.05

0.10

0.07

0.04

0.03

0.05

0.19

0.09

0.07

0.08

0.10

0.08

0.03

57

27

58

45

61

32

72

54

91

220

130

56

77

130

160

76

150

150

210

570

200

93

320

1,900

170

130

240

190

1.06E-2

1.47E-3

8.00E-4

8.43E-3

8.18E-3

1.61E-5

6.60E-5

3.30E-3

1.07E-3

8.48E-7

2.82E-6

5.35E-4

1.57E-2

9.84E-6

4.54E-4

6.33E-3

1.42E-2

3.85E-2

9.07E-7

1.68E-2

5.63E-3

2.58E-7

9.14E-7

2.82E-3

1.71E-2

1.07E-2

6.17E-6

7.95E-3

1

Pesticide toxicity can be used to rank or compare the relative potential toxicity of different samples and to evaluate the relations between urban development and pesticide toxicity on biological communities, such as the macroinvertebrates (Munn and Gilliom, 2001; Munn and others, 2006; Giddings 

and others, 2009). A zero value indicates that pesticides used in the calculation of the pesticide toxicity index were not detected. A value of 1.00 E-1 

would indicate relatively high potential toxicity, whereas a value of 1.00 E-4 would be potentially a thousand times less toxic. 
This page has been left blank intentionally. 
Prepared by the Pembroke Publishing Service Center.

For more information concerning this report, contact:

Director

U.S. Geological Survey

Connecticut Water Science Center

101 Pitkin Street

East Hartford, CT 06108

dc_ct@usgs.gov

or visit our Web site at:

http://ct.water.usgs.gov
Beaulieu and others—Variability in Stream Chemistry in Seven Metropolitan Areas of the United States, 1999–2004—Scientific Investigations Report 2012–5170