FRONT COVER

Yocum Creek near Oak Grove, Arkansas. Photograph courtesy of Reed Green, U.S. Geological Survey.

BACK COVER

Left: Pheasant Branch at Middleton, Wisconsin. Photograph courtesy of Michelle Lutz, U.S. Geological Survey.

Top Right: Columbia River Gorge at sunrise, looking east. Photograph courtesy of Columbia River 

USGS Interdisciplinary Science Explorer (CRUISE) Web site.

Bottom Left: Colorado River near Colorado-Utah State Line. Photograph courtesy of Nancy Bauch, 

U.S. Geological Survey.
Nutrient Trends in Streams and Rivers 

of the United States, 1993–2003

By Lori A. Sprague, David K. Mueller, Gregory E. Schwarz, and David L. Lorenz

National Water-Quality Assessment Program

Scientific Investigations Report 2008–5202

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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

reproduce any copyrighted materials contained within this report.

Suggested citation:

Sprague, L.A., Mueller, D.K., Schwarz, G.E., and Lorenz, D.L., 2009, Nutrient trends in streams and rivers of the United 

States, 1993–2003: U.S. Geological Survey Scientific Investigations Report 2008–5202, 196 p.
iii

Foreword

The U.S. Geological Survey (USGS) is committed to providing the Nation with credible 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, now 

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 condition of our Nation’s streams and ground water? How are 

conditions changing over time? How do natural features and human activities affect the quality 

of streams and ground water, 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 1991–2001, 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/studyu.html).

Multiple national and regional assessments are ongoing in the second decade (2001–2012) of 

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

the findings in the Study Units by determining 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 ground water. 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 topics 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. These topical studies are conducted in those Study Units most affected by these issues; 

they comprise a set of multi-Study-Unit designs for systematic national assessment. In addition, 

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

selected trace elements, and aquatic ecology are continuing.
iv

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.

Matthew C. Larsen

Associate Director for Water
v

Contents

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

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

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

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

Acknowledgments.........................................................................................................................................2

Approach.........................................................................................................................................................2

Site Selection.........................................................................................................................................2

Trend Analysis .......................................................................................................................................4

Concepts........................................................................................................................................4

Trends in Streamflow .........................................................................................................4

Flow-Adjusted Trends in Concentration..........................................................................4

Non-Flow-Adjusted Trends in Concentration.................................................................5

Trends in Load .....................................................................................................................5

Methods.........................................................................................................................................5

Trends in Streamflow .........................................................................................................5

Flow-Adjusted Trends in Concentration........................................................................16

Non-Flow-Adjusted Trends in Concentration...............................................................17

Trends in Load ...................................................................................................................18

Reference Values.......................................................................................................................18

Limitations...................................................................................................................................18

Factors Affecting the Trends.............................................................................................................19

Data Sources..............................................................................................................................19

Analysis of Factors Affecting Trends......................................................................................20

Regional Trends...................................................................................................................................23

Nutrient Trends in Streams and Rivers of the United States, 1993–2003............................................25

Streamflow Trends..............................................................................................................................25

Total Phosphorus ................................................................................................................................26

Trends from 1993 to 2003...........................................................................................................26

Factors Affecting the Trends....................................................................................................33

Regional Trends..........................................................................................................................69

Total Nitrogen ......................................................................................................................................69

Trends from 1993 to 2003...........................................................................................................69

Factors Affecting the Trends....................................................................................................72

Regional Trends..........................................................................................................................79

Nitrate. ..................................................................................................................................................79

Trends from 1993 to 2003...........................................................................................................79

Factors Affecting the Trends....................................................................................................82

Regional Trends..........................................................................................................................86

Trend Results Relative to Stream Nutrient Enrichment................................................................93

Implications for Management of Stream Quality ..........................................................................93

Summary and Conclusions.........................................................................................................................98

Streamflow...........................................................................................................................................98

Total Phosphorus ................................................................................................................................98

Total Nitrogen ......................................................................................................................................99

Nitrate. ................................................................................................................................................100

Trend Results Relative to Stream Nutrient Enrichment..............................................................101

Implications for Management of Stream Quality ........................................................................101
vi

References Cited........................................................................................................................................101

Appendix 1. Study-site characteristics ..............................................................................................107

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.....................128

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted

trends in concentration, and trends in load from 1993 to 2003.............................................141

Figures

1. Map showing location of study sites and major river basins (as designated 

for regional assessments in the National Water-Quality Assessment program) ..............3

2–4. Graphs showing:

 2. Flow-adjusted total nitrogen concentrations from 1985 to 2003 at site 99.................19

 3. Total phosphorus concentrations from (A) 1993 to 2003 and (B) 1993 to

early 2002 at site 184 ...........................................................................................................20

 4. Mean annual loads of total nitrogen from 1993 to 2003 at site 153 .............................21

5. Map showing trends in streamflow at selected sites in the United States ......................26

6. Map showing trends in (A) streamflow, (B) flow-adjusted and (C) non-flowadjusted trends in total phosphorus concentrations, and (D) trends in total 

phosphorus loads at selected sites in the United States.....................................................32

7–9. Graphs showing:

 7. Land use and nutrient budgets at sites in the Eastern United States.........................64

 8. Land use and nutrient budgets at sites in the Central United States .........................65

 9. Land use and nutrient budgets at sites in the Western United States.......................66

10. Maps showing changes in (A) phosphorus loading from manure, (B) phosphorus

loading from fertilizer, (C) population density, (D) nitrogen loading from manure,

(E) nitrogen loading from fertilizer, and (F) nitrogen loading from atmospheric

deposition in the United States during the study period......................................................67

11. Graphs showing relations between flow-adjusted trends in total phosphorus

concentrations and changes in phosphorus sources from 1993 to 2003 for

selected site subsets .................................................................................................................74

12. Maps showing trends in (A) streamflow, (B) flow-adjusted and (C) non-flow

adjusted trends in total nitrogen concentrations, and (D) trends in total nitrogen

loads at selected sites in the United States...........................................................................87

13. Graphs showing relations between flow-adjusted trends in total nitrogen 

concentrations and changes in nitrogen sources from 1993 to 2003 for 

selected site subsets .................................................................................................................88

14. Maps showing trends in (A) streamflow, (B) flow-adjusted and (C) non-flowadjusted trends in nitrate concentrations, and (D) trends in nitrate loads at 

selected sites in the United States ..........................................................................................92

15. Graphs showing relations between flow-adjusted trends in nitrate 

concentrations and changes in nitrogen sources from 1993 to 2003 for 

selected site subsets .................................................................................................................94

16. Graphs showing distribution of (A) flow-adjusted and (B) non-flow-adjusted 

trends in total phosphorus and total nitrogen concentrations from 1993 to 

2003 relative to the level of nutrient enrichment in the stream...........................................98
vii

Tables

1. Characteristics and trend coverage of study sites.................................................................6

2. Trends in daily mean streamflow from 1993 to 2003 .............................................................27

3. Summary of trend results for streamflow, total phosphorus, total nitrogen, 

and nitrate....................................................................................................................................33

4. Flow-adjusted trends in concentration from 1993 to 2003 ...................................................34

5. Non-flow-adjusted trends in concentration from 1993 to 2003...........................................44

6. Trends in load from 1993 to 2003...............................................................................................54

7. Results of weighted least-squares regression relating flow-adjusted trends 

to changes in nutrient sources.................................................................................................70

8. Results of the Kruskal-Wallis test relating flow-adjusted trends to changes 

in nutrient sources......................................................................................................................78

9. Results of the Tukey’s multiple comparison test of changes in source loading 

at sites with upward, downward, and nonsignificant trends..............................................80

10. Results of multiple linear regression relating flow-adjusted trends to changes 

in nutrient sources......................................................................................................................82

11. Regional trends in flow-adjusted and non-flow-adjusted concentrations from 

1993 to 2003..................................................................................................................................84

Conversion Factors

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2

) 247.1 acre

square meter (m2

) 10.76 square foot (ft2) 

square kilometer (km2

) 0.3861 square mile (mi2)

Volume

cubic meter (m3

) 0.0008107 acre-foot (acre-ft) 

Flow rate

cubic meter per second (m3

/s) 70.07 acre-foot per day (acre-ft/d) 

cubic meter per second (m3

/s) 35.31 cubic foot per second (ft3/s)

Mass

kilogram (kg) 2.205 pound avoirdupois (lb)

Yield

kilogram per square kilometer (kg/km2

) 5.710 pound avoirdupois per square mile (lb/mi2)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32.

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8.

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

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

or micrograms per liter (μg/L).
viii

Abbreviations

AR(30) autoregressive process of order 30

FA flow adjusted

GIS geographic information system

LOWESS locally weighted scatterplot smooth

NAWQA National Water-Quality Assessment Program

NFA non flow adjusted

NWIS U.S. Geological Survey National Water Information System database

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey
Abstract

Trends in streamflow and concentrations and loads of total 

phosphorus, total nitrogen, and nitrate were determined for the 

period from 1993 to 2003 in selected streams and rivers of the 

United States. Flow-adjusted trends in concentration (the trends 

that would have occurred in the absence of natural changes in 

streamflow), non-flow-adjusted trends in concentration (the 

trends resulting from both natural and human factors), and trends 

in load (trends in the nutrient mass transported downstream) were 

determined, and the results were examined spatially to determine 

whether a consistent pattern of trends occurred across groups 

of sites at multiple locations. Relations between the trends and 

changes in nutrient sources and streamflow were examined.

At the majority of sites nationwide, concentrations and 

loads of total phosphorus, total nitrogen, and nitrate did not 

change significantly from 1993 to 2003. Where significant 

changes did occur, there were more upward and fewer downward flow-adjusted trends in total phosphorus and total nitrogen 

concentrations as compared to nitrate concentrations. Increases 

in nutrient sources and(or) transport contributed to net upward 

flow-adjusted trends at 33 percent of sites for total phosphorus, 

21 percent for total nitrogen, and 12 percent for nitrate; whereas 

decreases in nutrient sources, implementation of pollution-control 

strategies, or other anthropogenic activities contributed to net 

downward flow-adjusted trends at 16 percent of sites for total 

phosphorus and total nitrogen, and 25 percent of sites for nitrate.

There were fewer upward non-flow-adjusted trends 

than upward flow-adjusted trends in total phosphorus (24 

and 33 percent of sites, respectively), total nitrogen (11 and 

21 percent, respectively), and nitrate (6 and 12 percent, respectively) concentrations. This was particularly evident at sites in 

the Central and Southwestern United States, where most of the 

downward trends in streamflow occurred as a result of drought 

conditions in the latter part of the study period. At these sites, 

the increase in source indicated by the upward flow-adjusted 

trend likely was offset by the effects of decreasing precipitation and surface runoff indicated by the downward streamflow 

trend. Without the decrease in surface runoff, in-stream concentrations at these sites probably would have been higher.

Changes in population density were related to total 

phosphorus trends at sites in undeveloped areas and total 

phosphorus and nitrate trends at sites in the Western United 

States. Changes in nonpoint-source loads were related to total 

phosphorus trends (fertilizer and manure) at sites in some agricultural areas, as well as nitrate trends (manure) at sites in the 

Central United States.

The more frequent increases in total phosphorus concentrations as compared to total nitrogen and nitrate concentrations cannot be explained easily by changes in nonpointsource loads; there were slightly more sites with increases 

in nitrogen loading from fertilizer and(or) manure than 

with increases in phosphorus loading from fertilizer and(or) 

manure. Instead, the differences may have been due in part to 

phosphorus saturation of soils in areas that have been subject to long-term manure or fertilizer application and(or) lag 

time between anthropogenic changes on the land surface and 

changes in nitrogen concentration in streams caused by the 

transport of nitrogen in ground water.

At nearly 20 percent of sites with nutrient enrichment 

over natural background conditions, anthropogenic activities contributed to net decreases in nutrient concentrations 

from 1993 to 2003, and overall nutrient quality in the streams 

improved. At sites minimally affected by human activities, 

downward trends occurred at fewer than 10 percent of sites, 

and there were over three times more upward trends than 

downward trends in total phosphorus concentrations and over 

eight times more upward trends than downward trends in total 

nitrogen concentrations.

Introduction

Nutrients are essential for plant and animal life, but in 

high concentrations they can act as contaminants in water. 

Over-enrichment of streams and rivers with nutrients contributes to the formation of algal blooms, which can interfere 

with recreational activities, lead to taste and odor problems 

in drinking water supplies, deprive deeper waters of sunlight 

needed by aquatic organisms, and reduce available habitat. 

During drinking-water treatment, chlorination of algal metabolites and decomposition products may lead to the production 

of carcinogenic trihalomethanes and haloacetic acids (Nguyen 

and others, 2005; Scully and others, 1988; Oliver and Shindler, 

1980). In addition, algal toxins harmful to animal and human 

health can be produced from blooms of selected cyanobacteria 

Nutrient Trends in Streams and Rivers of the United States, 

1993–2003

By Lori A. Sprague, David K. Mueller, Gregory E. Schwarz, and David L. Lorenz
2 Nutrient Trends in Streams and River of the United States, 1993–2003

species (Falconer, 1999; Rinehart and others, 1994; Repavich 

and others, 1990). High algal biomass also is associated 

with hypoxia (low dissolved-oxygen concentrations), which 

can contribute to the release of toxic metals from bed sediments, increased availability of toxic substances like ammonia and hydrogen sulfide, and fish kills (U.S. Environmental 

Protection Agency, 2000). In recent years, nitrate and other 

nutrients discharged from the Mississippi River Basin have 

been linked to a large zone of hypoxia in the Gulf of Mexico 

along the Louisiana-Texas coast (Turner and others, 2008; 

Donner and Scavia, 2007; Justic and others, 1993).

According to the most recent U.S. Environmental 

Protection Agency (USEPA) compilation of States’ waterquality reports under Section 305(b) of the Clean Water Act, 

nutrients were the fifth leading pollutant in rivers and streams 

nationally, affecting over 15 percent of impaired river miles 

(U.S. Environmental Protection Agency, 2007). The USEPA 

report also lists nutrients as the leading pollutant in lakes 

and reservoirs and the second leading cause of degradation 

in wetlands and estuaries. Another USEPA report, covering 

its Wadeable Streams Assessment, identifies nitrogen and 

phosphorus as the two most widespread stressors contributing 

to diminished biological quality in flowing waters across the 

Nation (U.S. Environmental Protection Agency, 2006).

Understanding how and why nutrient concentrations are 

changing over time in streams and rivers is essential for effectively managing and protecting these water resources. In 1987, 

the U.S. Geological Survey (USGS) began a study of more 

than 50 river basins and aquifers across the Nation as part of 

the National Water-Quality Assessment (NAWQA) Program. 

One of the major goals of the NAWQA Program is to determine how water-quality conditions, including concentrations 

of nutrients, are changing over time. Outside of the NAWQA 

Program, USGS (in cooperation with other Federal, State, 

Tribal, and local agencies), state environmental agencies, 

USEPA and other Federal agencies, universities, and many 

others have collected nutrient data throughout the Nation. 

Collectively, these data can provide insight into how nutrient 

concentrations have changed over time in the Nation’s streams 

and rivers and how natural features and human activities have 

contributed to those changes.

Purpose and Scope

This report describes the methods used to determine 

trends in total phosphorus, total nitrogen, and nitrate concentrations and loads for the period from 1993 to 2003 in 

streams and rivers of the United States. Flow-adjusted trends 

in concentration, non-flow-adjusted trends in concentration, 

and trends in load are presented, and the results are examined 

spatially to determine whether a consistent pattern of trends 

occurred across groups of sites at multiple locations. Relations 

between the trends and changes in nutrient sources, streamflow, and other factors are examined.

Acknowledgments

The authors wish to thank the following USGS personnel for their contributions to trend analysis and interpretation: Elaine Todd Trench, Douglas Harned, Dale Robertson, 

Richard Rebich, Nancy Bauch, Gregory Fuhrer, Daniel Wise, 

Charles Kratzer, and Dina Saleh. They also would like to 

acknowledge Kerie Hitt, Naomi Nakagaki, Jo Ann Gronberg, 

James Falcone, and David Wolock for their extensive contributions to the ancillary data compilation. Hank Johnson and 

Mary Giorgino provided helpful technical reviews.

Approach

The approach for selecting sites, calculating trends, and 

evaluating factors affecting the trends is presented in this section. 

The national trends included in this report are, to a large degree, 

taken from seven recent regional trend analyses conducted within 

the NAWQA program (these regions are referred to as “major 

river basins” in the NAWQA program; see figure 1). There were 

some differences in approach between these regional analyses. 

To the extent possible, these differences have been minimized in 

the national-level analysis; as a result, some sites included in the 

regional analyses have been removed and some new sites have 

been added for this report. More detail on the regional analyses is 

available in Lorenz and others (2008; Great Lakes, Ohio, Upper 

Mississippi, and Souris-Red-Rainy region), Sprague and others 

(2006; Missouri region), Rebich and Demcheck (2007; Lower 

Mississippi, Arkansas-White-Red, and Texas-Gulf region), and 

Wise and others (2007; Pacific Northwest region). In addition, new results for the New England and Mid-Atlantic region 

(E.C.T. Trench, U.S. Geological Survey, written commun., 

2007); South Atlantic-Gulf and Tennessee region (D.A. Harned, 

U.S. Geological Survey, written commun., 2007); Rio Grande, 

Colorado, and Great Basin region (N.J. Bauch, U.S. Geological 

Survey, written commun., 2007); and the California region 

(C.R. Kratzer, U.S. Geological Survey, written commun., 2007) 

are presented in this report.

Site Selection

Nutrient data publicly accessible through the online 

USGS National Water Information System (NWIS) database at http://waterdata.usgs.gov/usa/nwis/qw initially were 

surveyed for this study. The majority of data contained in 

the NWIS database are from water samples collected using 

standard methods described in U.S. Geological Survey (variously dated). In order to fill in spatial gaps in site coverage, 

additional data from the online USEPA STORET database 

at http://www.epa.gov/storet/dbtop.html also were surveyed 

in some regions. Sites were screened separately for total 

phosphorus as P, total nitrogen as N, and nitrite plus nitrate 

as N (hereinafter referred to as nitrate).
Approach 3

Figure 1. Location of study sites and major river basins (as designated for regional assessments in the National Water-Quality 

Assessment program).

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216 207 234

235237

236 238

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222

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212 220

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244

243 242

241 240

182 181 180

179

193

190 192

191

189

188 187

176 177

178

175

128

129

174

104105

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130

131132

108

140 185

184

183 186

141 143

144

150

161

162 159

163

160 158

157

151

156 155

153

154

71

170

171

172

169

167 168

166

165 164

148

147

136120

121

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123

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149

135 139 145

146

152

134

137

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101

133

173

103

96

97 81

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102 100 99

83

75

84 76 86 85

90

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89 72

79

80 77

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39 37

36

43 42

45 44

41

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49

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70 66

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52 54 51

50

53 55

69

68 65 64

56

62

58

57 59

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87 93

88

73

124 125

113

112

109

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111 114

118

117 116 94

115 95

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198

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CENTRAL

WESTERN

EASTERN

! Trend site (see table 1) 201

EXPLANATION

Major River Basin

New England and Mid-Atlantic

South Atlantic-Gulf and Tennessee

Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy

Missouri

Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

Rio Grande, Colorado, and Great Basin

Pacific Northwest

California

Geographic-area boundary

State boundary
4 Nutrient Trends in Streams and River of the United States, 1993–2003

Sites were selected for analysis of trends between water year 

(October 1 through September 30) 1993 and water year 2003 on 

the basis of the following minimum criteria:

•	 period of water-quality record with a beginning year 

of 1993 or earlier and an ending year of 2003 or later;

•	 approximately quarterly sampling each year;

•	 continuous daily mean discharge between 1993 and 

2003 at that site or a nearby representative site;

•	 data gaps no longer than 2 years and only during the 

middle 6 years of record;

•	 representative coverage of samples over the site’s 

hydrograph to avoid bias toward low or high 

streamflows;

•	 representative coverage over all seasons to avoid bias 

toward certain times of year.

In some regions, the data record for additional sites contained 

two time periods separated by a gap longer than 2 years. These 

sites were included for step-trend analysis on the basis of the 

following minimum criteria:

•	 3 years of sampling at the beginning and end of the 

period (1993–95 and 2001–03);

•	 approximately quarterly sampling during 1993–95 

and 2001–03;

•	 continuous daily mean discharge during 1993–95 and 

2001–03 at that site or a nearby representative site;

•	 representative coverage of samples over the site’s 

hydrograph to avoid bias toward low or high 

streamflows;

•	 representative coverage over all seasons to avoid bias 

toward certain times of year.

The final 244 sites are shown in figure 1 and listed in table 1 

along with a list of constituents used in the trend analyses for 

each site. The number of sites used in the trend analyses for each 

constituent varied depending on data availability—244 sites were 

used for streamflow, 171 sites for total phosphorus, 137 sites for 

total nitrogen, and 166 for nitrate.

Trend Analysis

Many factors affect the concentration and load (mass) 

of nutrients in a stream. When these factors vary over time, 

concentration and load will change over time as well. These 

changes can be short in duration, such as those caused by 

seasonal variability or individual precipitation events, or 

longer in duration, such as those caused by changes in nutrient 

sources in the watershed (for example, a decrease in fertilizer 

application over many years). Trends, as used in this report, 

refer to the longer duration, low-frequency changes detectable 

over many years, irrespective of the shorter duration, highfrequency changes that may occur each day, month, or year.

In the following sections, the conceptual basis for the 

four different types of trend presented in this report is first 

described in a nonmathematical way in the “Concepts” 

section. This non-technical description is followed by a 

discussion of the statistical methods used in the analysis 

of each type of trend in the “Methods” section. Finally, the 

limitations of trend analysis in general are discussed in the 

“Limitations” section.

Concepts

Trends in Streamflow

Changes in streamflow are an important influence on 

nutrient concentrations in streams. Depending on the particular nutrient sources in a watershed and how these nutrients are 

transported to the stream, increases or decreases in streamflow 

can lead to increases or decreases in concentrations. For example, if a point source such as discharge from a wastewatertreatment plant is the predominant source of nutrients to a 

stream, an increase in streamflow likely will lead to a decrease 

in concentrations as a result of dilution of the plant discharge. 

However, if a nonpoint source such as runoff from fertilized 

land area is the predominant source of nutrients to a stream, 

an increase in streamflow may lead to an increase in concentration as a result of the associated increase in precipitation 

and surface runoff. As a result, understanding how streamflow 

changes over time is critical in an assessment of how and why 

nutrient concentrations change over time.

Trends in streamflow often result from natural variability 

in climatological conditions such as precipitation and evapotranspiration. In some streams, particularly in the arid west, 

trends in streamflow also can result from variability in waterregulation operations such as diversions and reservoir storage 

and release.

Flow-Adjusted Trends in Concentration

Streamflow is not always the only influence on nutrient 

concentrations in streams. Changes in the watershed, such 

as implementation of management practices like conservation tillage or an increase or decrease in nutrient sources like 

manure, can influence nutrient transport to streams. In the 

analysis of flow-adjusted (FA) trends in concentration, the 

effects of streamflow on concentration are removed, allowing 

trends caused by other factors to be identified and the effects 

of management practices to be more directly assessed.

A FA trend in concentration implies that the streamflowconcentration relation is shifting over time. If the FA trend is 

downward, the concentration at a particular streamflow will be 

lower at the end of the time period than it was in the beginning. If streamflow is different at the end of the time period 

than at the beginning, actual concentration might be greater, 

even though the FA trend is downward. In this case, the actual 

concentration at the end of the period is less than it would have 

been in the absence of the changes in source and transport 
Approach 5

within the watershed that led to the FA trend in concentration. 

Over enough years, the annual pattern of concentration in the 

stream will shift to generally lower values.

FA trends in concentration can be complex, as there often 

are multiple and possibly counteracting anthropogenic factors 

influencing nutrient source and transport in a watershed. For 

example, population growth initially may lead to an increase in 

the nutrient load discharged from wastewater-treatment plants, 

but after several years, upgrades at the plant may lead to a 

relative decrease in the nutrient load discharged. Or, a decrease 

in fertilizer use in agricultural areas of a watershed may lead 

to decreasing nutrient loads in surface runoff, but population 

growth in other areas of the watershed may lead to an increase 

in the nutrient load discharged from wastewater-treatment 

plants. These multiple changes are not always counteracting; 

they also may supplement each other. For example, a decrease 

in fertilizer use and concurrent upgrades at wastewatertreatment plants may both contribute to decreasing nutrient 

concentrations in streams. Without detailed knowledge of all 

important factors in each watershed, it may be difficult to discern the specific cause(s) of a FA trend in concentration.

Non-Flow-Adjusted Trends in Concentration

Non-flow-adjusted (NFA) trends in concentration are 

influenced by the same anthropogenic changes in the watershed that can lead to FA trends in concentration, but they are 

also influenced by changes in streamflow. Anthropogenic 

changes in the watershed and natural changes in streamflow 

often occur concurrently and can therefore counteract or 

supplement each other. For example, if nonpoint sources are 

the predominant source of nutrients to a stream, a decrease in 

concentration resulting from the implementation of management practices may be offset by an increase in concentration 

resulting from natural increases in surface runoff and streamflow. If point sources are the predominant source of nutrients to a stream, a decrease in concentration resulting from 

treatment upgrades may be offset by the decreased in-stream 

dilution capacity resulting from a natural decrease in streamflow. In both of these examples, although climate and streamflow variability may be counteracting the effects of management practices, the strategies are still having a positive effect; 

in-stream concentrations would have been even higher in the 

absence of these management practices or treatment upgrades.

To consider the effects of both streamflow variability 

and changes in the watershed, trends in concentrations that 

are not flow adjusted are determined. These NFA trends reflect 

any and all influences on nutrient concentrations in streams, 

allowing for the assessment of the status of streams relative 

to water-quality standards and their suitability for supporting 

aquatic communities.

Some “raw” (unaltered) nutrient data sets are inappropriate for analysis of NFA trends in concentration. Monitoring 

programs often are implemented to meet multiple objectives, 

such as trend analysis, illicit-discharge detection, stormwaterrunoff evaluation, and targeted seasonal assessment (such as 

during peak fertilizer-application periods). These objectives 

can change at a site over the time period used in the trend 

analysis, resulting in changes in the timing and frequency 

of sample collection. The resulting data sets may exhibit bias 

that interferes with trend analysis. For example, an increase 

in sampling at high streamflows in support of stormwaterrunoff evaluation during the latter half of the study period may 

induce a trend that likely would be an artifact of the change in 

sampling design rather than a true change in concentration. To 

deal with these limitations in the determination of NFA trends 

in concentration, a coupled statistical modeling approach that 

simultaneously accounted for changes in streamflow and concentration was used in this study.

Trends in Load

Trends in load represent changes in the nutrient mass that 

is transported downstream from the site. An increase or decrease 

in the nutrient mass moving downstream can affect the quality 

of receiving water bodies such as lakes, reservoirs, or estuaries. 

Because loads are the product of concentration and streamflow, 

changes in either or both can lead to changes in load. The same 

sampling complications that limit the assessment of trend in raw 

concentration measurements also limit the assessment of trend 

in raw load measurements. Consequently, the coupled statistical 

modeling approach used to assess trend in concentration is also 

used to assess trend in load.

Methods

Trends in Streamflow

To determine the trend in daily mean streamflow, a model 

relating streamflow and time was defined as:

q q t t   a T 	 
T , (1)

where

q is the natural logarithm of streamflow at 

time t;

q is the mean of the natural logarithm of 

streamflow during the analysis period;

a is the coefficient to be estimated;

Tt is decimal time at time t;

and

T is the mean of decimal time during the 

analysis period.

If streamflow was upward trending, then a was positive, 

and the trend in the logarithm of streamflow was less than 

the mean value of the logarithm of streamflow for the first 

half of the analysis period and greater than the mean value 

thereafter. Note that the mean of the natural logarithm of 

streamflow, q , implicitly accounted for the intercept and 

average of the seasonal terms that are included in the streamflow model but not otherwise apparent in the formulation 

of equation 1.
6 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 1. Characteristics and trend coverage of study sites.—Continued

[ARDEQ, Arkansas Department of Environmental Quality; CADWR, California Department of Water Resources; CWS, Clean Water Services (Tualatin River 

Basin, Oregon); LADEQ, Louisiana Department of Environmental Quality; ODEQ, Oregon Department of Environmental Quality; TXCEQ, Texas Commission 

on Environmental Quality; UCD, University of California, Davis; USGS, U.S. Geological Survey; WECY, Washington State Department of Ecology; UDEQ, 

Utah Department of Environmental Quality; --, not determined or not applicable; >, greater than; ≤, less than or equal to]

Site 

number 

(figure 1)

Station

number Station name Major river basin

1 01122610 Shetucket River at South Windham, Conn. New England and Mid-Atlantic 

2 01124000 Quinebaug River at Quinebaug, Conn. New England and Mid-Atlantic 

3 01127000 Quinebaug River at Jewett City, Conn. New England and Mid-Atlantic 

4 01184000 Connecticut River at Thompsonville, Conn. New England and Mid-Atlantic 

5 01184490 Broad Brook at Broad Brook, Conn. New England and Mid-Atlantic 

6 01188090 Farmington River at Unionville, Conn. New England and Mid-Atlantic 

7 01189995 Farmington River at Tariffville, Conn. New England and Mid-Atlantic 

8 01192500 Hockanum River near East Hartford, Conn. New England and Mid-Atlantic 

9 01193500 Salmon River near East Hampton, Conn. New England and Mid-Atlantic 

10 01196500 Quinnipiac River at Wallingford, Conn. New England and Mid-Atlantic 

11 01205500 Housatonic River at Stevenson, Conn. New England and Mid-Atlantic 

12 01208500 Naugatuck River at Beacon Falls, Conn. New England and Mid-Atlantic 

13 01208990 Saugatuck River near Redding, Conn. New England and Mid-Atlantic 

14 01209710 Norwalk River at Winnipauk, Conn. New England and Mid-Atlantic 

15 01357500 Mohawk River at Cohoes, N.Y. New England and Mid-Atlantic 

16 01377000 Hackensack River at Rivervale, N.J. New England and Mid-Atlantic 

17 01382500 Pequannock River at Macopin Intake Dam, N.J. New England and Mid-Atlantic 

18 01387500 Ramapo River near Mahwah, N.J. New England and Mid-Atlantic 

19 01389500 Passaic River at Little Falls, N.J. New England and Mid-Atlantic 

20 01391500 Saddle River at Lodi, N.J. New England and Mid-Atlantic 

21 01394500 Rahway River near Springfield, N.J. New England and Mid-Atlantic 

22 01395000 Rahway River at Rahway, N.J. New England and Mid-Atlantic 

23 01396660 Mulhockaway Creek at Van Syckel, N.J. New England and Mid-Atlantic 

24 01398000 Neshanic River at Reaville, N.J. New England and Mid-Atlantic 

25 01402000 Millstone River at Blackwells Mills, N.J. New England and Mid-Atlantic 

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. New England and Mid-Atlantic 

27 01408000 Manasquan River at Squankum, N.J. New England and Mid-Atlantic 

28 01408500 Toms River near Toms River, N.J. New England and Mid-Atlantic 

29 01409500 Batsto River at Batsto, N.J. New England and Mid-Atlantic 

30 01411500 Maurice River at Norma, N.J. New England and Mid-Atlantic 

31 01438500 Delaware River at Montague, N.J. New England and Mid-Atlantic 

32 01443500 Paulins Kill at Blairstown, N.J. New England and Mid-Atlantic 

33 01463500 Delaware River at Trenton, N.J. New England and Mid-Atlantic 

34 01467150 Cooper River at Haddonfield, N.J. New England and Mid-Atlantic 

35 01477120 Raccoon Creek near Swedesboro, N.J. New England and Mid-Atlantic 

36 01491000 Choptank River near Greensboro, Md. New England and Mid-Atlantic 

37 01578310 Susquehanna River at Conowingo, Md. New England and Mid-Atlantic 

38 01594440 Patuxent River near Bowie, Md. New England and Mid-Atlantic 

39 01614500 Conococheague Creek at Fairview, Md. New England and Mid-Atlantic 

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. New England and Mid-Atlantic 

41 01668000 Rappahannock River near Fredericksburg, Va. New England and Mid-Atlantic 

42 01673000 Pamunkey River near Hanover, Va. New England and Mid-Atlantic 

43 01674500 Mattaponi River near Beulahville, Va. New England and Mid-Atlantic 

44 02035000 James River at Cartersville, Va. New England and Mid-Atlantic 

45 02041650 Appomattox River at Matoaca, Va. New England and Mid-Atlantic 

46 02085000 Eno River at Hillsborough, N.C. South Atlantic-Gulf and Tennessee 

47 02089500 Neuse River at Kinston, N.C. South Atlantic-Gulf and Tennessee 

48 02091500 Contentnea Creek at Hookerton, N.C. South Atlantic-Gulf and Tennessee 

49 0210215985 Cape Fear River at State Highway 42 near Brickhaven, N.C. South Atlantic-Gulf and Tennessee 

50 02175000 Edisto River near Givhans, S.C. South Atlantic-Gulf and Tennessee 

51 02198500 Savannah River near Clyo, Ga. South Atlantic-Gulf and Tennessee 

52 02213700 Ocmulgee River near Warner Robins, Ga. South Atlantic-Gulf and Tennessee 
Approach 7

Table 1. Characteristics and trend coverage of study sites.—Continued

[ARDEQ, Arkansas Department of Environmental Quality; CADWR, California Department of Water Resources; CWS, Clean Water Services (Tualatin River 

Basin, Oregon); LADEQ, Louisiana Department of Environmental Quality; ODEQ, Oregon Department of Environmental Quality; TXCEQ, Texas Commission 

on Environmental Quality; UCD, University of California, Davis; USGS, U.S. Geological Survey; WECY, Washington State Department of Ecology; UDEQ, 

Utah Department of Environmental Quality; --, not determined or not applicable; >, greater than; ≤, less than or equal to.]

Site 

number 

(figure 1)

Data source

Drainage 

area, 

in square 

kilometers

Percent of 

drainage

area in the

United States

Land cover in the basin,

in percent1

Land-use

classification3

Constituent included 

for trend analysis

Urban Agriculture

Rangeland Forest Other2

Total

phosphorus

Total

nitrogen Nitrate

1 USGS 1,065 100.0 10.3 10.9 0.0 73.6 5.2 Mixed X X X

2 USGS 392 100.0 11.0 7.4 0.1 75.5 6.1 Mixed X X X

3 USGS 1,839 100.0 9.4 11.3 0.1 73.3 5.9 Mixed X X X

4 USGS 25,049 98.8 5.0 8.3 0.2 81.0 4.3 Mixed X X X

5 USGS 38 100.0 13.1 39.0 0.0 45.9 2.0 Mixed X X X

6 USGS 978 100.0 5.2 4.8 0.0 84.0 6.0 Mixed -- X X

7 USGS 1,493 100.0 13.4 6.7 0.0 74.8 5.1 Mixed X X X

8 USGS 191 100.0 44.5 11.1 0.0 40.5 3.9 Urban X X X

9 USGS 271 100.0 11.1 12.4 0.1 71.7 4.8 Mixed -- X X

10 USGS 286 100.0 56.6 1.0 0.0 38.8 3.6 Urban X X X

11 USGS 3,993 100.0 12.2 13.5 0.0 69.9 4.3 Mixed X X X

12 USGS 674 100.0 26.5 9.9 0.0 58.9 4.6 Urban X X X

13 USGS 54 100.0 21.4 4.4 0.0 70.7 3.4 Mixed X X X

14 USGS 85 100.0 50.7 2.8 0.0 44.2 2.3 Urban X X X

15 USGS 9,113 100.0 5.9 27.2 0.0 65.1 1.9 Mixed X X X

16 USGS 145 100.0 78.5 0.3 0.0 13.6 7.6 Urban X X X

17 USGS 164 100.0 5.7 0.8 0.0 87.7 5.8 Mixed X X X

18 USGS 312 100.0 25.4 0.9 0.0 70.2 3.6 Urban X X X

19 USGS 1,998 100.0 39.3 2.2 0.0 53.9 4.6 Urban X X X

20 USGS 146 100.0 93.2 0.5 0.0 5.7 0.5 Urban X X X

21 USGS 67 100.0 80.5 0.4 0.0 18.4 0.6 Urban -- X X

22 USGS 107 100.0 89.9 0.2 0.0 9.3 0.6 Urban X X X

23 USGS 30 100.0 3.1 25.4 0.0 71.2 0.2 Mixed -- X X

24 USGS 66 100.0 8.5 59.8 0.0 31.5 0.2 Mixed X X X

25 USGS 664 100.0 25.1 33.0 0.0 40.6 1.3 Mixed X X X

26 USGS 2,074 100.0 19.4 33.3 0.0 45.6 1.7 Mixed X X X

27 USGS 114 100.0 27.7 24.3 0.0 44.9 3.1 Urban X -- --

28 USGS 320 100.0 21.0 4.7 0.0 68.8 5.5 Mixed X -- --

29 USGS 176 100.0 2.3 12.1 0.0 82.8 2.8 Undeveloped -- X X

30 USGS 270 100.0 23.4 27.6 0.0 47.7 1.3 Mixed X -- --

31 USGS 9,016 100.0 2.4 9.8 0.0 85.0 2.8 Undeveloped X X X

32 USGS 327 100.0 9.1 25.4 0.0 61.2 4.4 Mixed X X X

33 USGS 17,580 100.0 5.6 16.2 0.0 75.1 3.1 Mixed X X X

34 USGS 47 100.0 69.9 6.4 0.0 20.1 3.6 Urban X X X

35 USGS 67 100.0 9.2 64.3 0.0 26.1 0.4 Mixed X X X

36 USGS 295 100.0 2.8 48.5 0.0 48.0 0.6 Mixed X X X

37 USGS 70,103 100.0 3.5 28.0 0.0 66.5 2.1 Mixed X X X

38 USGS 907 100.0 32.4 32.8 0.0 31.3 3.5 Mixed X X X

39 USGS 1,309 100.0 3.6 56.8 0.0 38.3 1.3 Agricultural X X X

40 USGS 29,999 100.0 5.1 33.4 0.0 59.8 1.6 Mixed X X X

41 USGS 4,135 100.0 4.7 34.7 0.0 59.4 1.2 Mixed X X X

42 USGS 2,795 100.0 2.7 23.0 0.0 69.1 5.2 Undeveloped X X X

43 USGS 1,560 100.0 2.2 18.6 0.0 73.8 5.4 Undeveloped X X X

44 USGS 16,201 100.0 3.9 15.0 0.0 79.3 1.9 Undeveloped X X X

45 USGS 3,478 100.0 2.0 19.8 0.0 74.3 3.8 Undeveloped X X X

46 USGS 171 100.0 8.7 23.5 0.0 66.6 1.2 Mixed X X --

47 USGS 7,022 100.0 12.1 28.7 0.0 56.8 2.4 Mixed -- X --

48 USGS 1,909 100.0 4.3 41.9 0.0 52.7 1.2 Mixed -- X --

49 USGS -- -- -- -- -- -- -- -- -- X --

50 USGS 7,077 100.0 2.0 31.8 0.0 60.0 6.2 Mixed -- -- X

51 USGS 25,510 100.0 4.3 18.1 0.0 69.5 8.1 Undeveloped X -- --

52 USGS 6,891 100.0 20.8 12.8 0.0 63.3 3.1 Mixed X X --
8 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 1. Characteristics and trend coverage of study sites.—Continued

[ARDEQ, Arkansas Department of Environmental Quality; CADWR, California Department of Water Resources; CWS, Clean Water Services (Tualatin River 

Basin, Oregon); LADEQ, Louisiana Department of Environmental Quality; ODEQ, Oregon Department of Environmental Quality; TXCEQ, Texas Commission 

on Environmental Quality; UCD, University of California, Davis; USGS, U.S. Geological Survey; WECY, Washington State Department of Ecology; UDEQ, 

Utah Department of Environmental Quality; --, not determined or not applicable; >, greater than; ≤, less than or equal to]

Site 

number 

(figure 1)

Station

number Station name Major river basin

53 02215500 Ocmulgee River at Lumber City, Ga. South Atlantic-Gulf and Tennessee 

54 02223600 Oconee River at Interstate 16, near Dublin, Ga. South Atlantic-Gulf and Tennessee 

55 02226010 Altamaha River near Gardi, Ga. South Atlantic-Gulf and Tennessee 

56 02226582 Satilla River at GA 15&121, near Hoboken, Ga. South Atlantic-Gulf and Tennessee 

57 02271500 Josephine Creek near De Soto City, Fla. South Atlantic-Gulf and Tennessee 

58 02295420 Payne Creek near Bowling Green, Fla. South Atlantic-Gulf and Tennessee 

59 02296750 Peace River at Arcadia, Fla. South Atlantic-Gulf and Tennessee 

60 02300700 Bullfrog Creek near Wimauma, Fla. South Atlantic-Gulf and Tennessee 

61 02301300 South Prong Alafia River near Lithia, Fla. South Atlantic-Gulf and Tennessee 

62 02302500 Blackwater Creek near Knights, Fla. South Atlantic-Gulf and Tennessee 

63 02303000 Hillsborough River near Zephyrhills, Fla. South Atlantic-Gulf and Tennessee 

64 02314500 Suwannee River at U.S. 441, at Fargo, Ga. South Atlantic-Gulf and Tennessee 

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. South Atlantic-Gulf and Tennessee 

66 02335870 Sope Creek near Marietta, Ga. South Atlantic-Gulf and Tennessee 

67 02338000 Chattahoochee River near Whitesburg, Ga. South Atlantic-Gulf and Tennessee 

68 02344040 Chattahoochee River near Steam Mill, Ga. South Atlantic-Gulf and Tennessee 

69 02353000 Flint River at Newton, Ga. South Atlantic-Gulf and Tennessee 

70 02388520 Oostanaula River at Rome, Ga. South Atlantic-Gulf and Tennessee 

71 02492000 Bogue Chitto River near Bush, La. South Atlantic-Gulf and Tennessee 

72 03353637 Little Buck Creek near Indianapolis, Ind. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

74 04063700 Popple River near Fence, Wis. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

75 04073468 Green Lake Inlet at County Highway A near Green Lake, Wis. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

76 04087000 Milwaukee River at Milwaukee, Wis. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

77 0422026250 Northrup Creek at North Greece, N.Y. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

78 04232034 Irondequoit Creek at Railroad Mills near Fishers, N.Y. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

79 0423204920 East Branch Allen Creek at Pittsford, N.Y. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

80 0423205025 Irondequoit Creek at Empire Boulevard at Rochester, N.Y. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

81 05114000 Souris River near Sherwood, N. Dak. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

82 05120000 Souris River near Verendrye, N. Dak. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

83 05287890 Elm Creek near Champlin, Minn. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

84 05427718 Yahara River at Windsor, Wis. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

85 05427948 Pheasant Branch at Middleton, Wis. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

86 054310157 Jackson Creek Tributary near Elkhorn, Wis. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

87 05500000 South Fabius River near Taylor, Mo. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

88 05514500 Cuivre River near Troy, Mo. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

89 05525500 Sugar Creek at Milford, Ill. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

90 05531500 Salt Creek at Western Springs, Ill. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

91 05532500 Des Plaines River at Riverside, Ill. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

92 05540275 Spring Brook at 87th Street near Naperville, Ill. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

93 05586100 Illinois River at Valley City, Ill. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

94 07018100 Big River near Richwoods, Mo. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

95 07022000 Mississippi River at Thebes, Ill. Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

96 06088500 Muddy Creek at Vaughn, Mont. Missouri

97 06178000 Poplar River at International Boundary, Mont. Missouri

98 06274300 Bighorn River at Basin, Wyo. Missouri

99 06329500 Yellowstone River near Sidney, Mont. Missouri

100 06338490 Missouri River at Garrison Dam, N. Dak. Missouri

101 06461500 Niobrara River near Sparks, Nebr. Missouri

102 06468250 James River above Arrowwood Lake near Kensal, N. Dak. Missouri

103 06713500 Cherry Creek at Denver, Colo. Missouri
Approach 9

Table 1. Characteristics and trend coverage of study sites.—Continued

[ARDEQ, Arkansas Department of Environmental Quality; CADWR, California Department of Water Resources; CWS, Clean Water Services (Tualatin River 

Basin, Oregon); LADEQ, Louisiana Department of Environmental Quality; ODEQ, Oregon Department of Environmental Quality; TXCEQ, Texas Commission 

on Environmental Quality; UCD, University of California, Davis; USGS, U.S. Geological Survey; WECY, Washington State Department of Ecology; UDEQ, 

Utah Department of Environmental Quality; --, not determined or not applicable; >, greater than; ≤, less than or equal to.]

Site 

number 

(figure 1)

Data source

Drainage 

area, 

in square 

kilometers

Percent of 

drainage

area in the

United States

Land cover in the basin,

in percent1

Land-use

classification3

Constituent included 

for trend analysis

Urban Agriculture

Rangeland Forest Other2

Total

phosphorus

Total

nitrogen Nitrate

53 USGS 13,582 100.0 12.0 22.7 0.0 59.4 5.9 Mixed X X --

54 USGS 11,517 100.0 3.1 18.9 0.0 72.0 5.9 Undeveloped X -- --

55 USGS 35,220 100.0 6.0 24.3 0.0 62.9 6.8 Mixed X -- --

56 USGS 3,487 100.0 1.9 32.0 0.0 56.2 10.0 Mixed X -- --

57 USGS 301 100.0 30.0 13.8 14.7 20.1 21.4 Urban -- X --

58 USGS 317 100.0 3.0 21.9 25.0 18.5 31.6 Undeveloped X X --

59 USGS 3,436 100.0 10.9 26.7 26.1 21.4 14.9 Mixed X X --

60 USGS 74 100.0 10.4 42.7 23.1 19.7 4.2 Mixed X X --

61 USGS 277 100.0 3.7 19.4 25.7 18.1 33.1 Undeveloped X X --

62 USGS 226 100.0 35.4 14.4 24.4 17.4 8.4 Urban X X --

63 USGS 546 100.0 28.0 12.8 21.1 26.6 11.6 Urban X -- --

64 USGS 3,322 100.0 0.3 1.0 0.2 86.2 12.2 Undeveloped X -- --

65 USGS 3,864 100.0 3.1 49.7 0.3 39.8 7.1 Mixed X X X

66 USGS 80 100.0 62.3 0.0 0.0 37.4 0.3 Urban X -- X

67 USGS 6,251 100.0 23.0 9.7 0.0 63.5 3.8 Mixed -- X --

68 USGS 21,974 100.0 10.4 13.3 0.0 70.2 6.1 Mixed X -- --

69 USGS 14,899 100.0 4.0 30.7 0.0 59.6 5.7 Mixed X -- --

70 USGS 20 100.0 61.5 7.7 0.0 26.0 4.8 Urban X -- --

71 USGS and

LADEQ

3,071 100.0 1.8 34.2 0.0 62.1 1.9 Mixed X X X

72 USGS 45 100.0 78.8 19.3 0.0 1.8 0.1 Urban X X X

73 USGS 527,229 100.0 5.4 37.7 0.1 54.7 2.1 Mixed X X X

74 USGS 363 100.0 0.1 3.4 0.6 92.6 3.3 Undeveloped X X X

75 USGS 122 100.0 9.0 76.8 1.2 9.1 4.0 Mixed X -- --

76 USGS 1,805 100.0 11.3 64.9 0.7 21.0 2.1 Mixed X X X

77 USGS 23 100.0 26.3 49.0 0.0 24.5 0.2 Mixed X -- --

78 USGS 98 100.0 5.8 58.3 0.0 34.6 1.3 Mixed X -- --

79 USGS 23 100.0 43.6 44.4 0.0 11.5 0.5 Mixed X -- --

80 USGS 391 100.0 47.8 32.3 0.0 19.0 0.9 Mixed X -- --

81 USGS 22,759 14.2 0.0 9.9 3.6 0.0 0.7 -- X X X

82 USGS 28,840 31.9 0.3 21.2 8.8 0.1 1.4 -- X X X

83 USGS 222 100.0 13.7 52.1 0.0 14.6 19.6 Mixed X -- --

84 USGS 185 100.0 8.3 87.2 0.5 3.5 0.4 Mixed X -- --

85 USGS 47 100.0 12.3 82.8 0.5 4.2 0.2 Mixed X -- --

86 USGS 11 100.0 42.9 53.8 0.3 1.4 1.6 Mixed X -- --

87 USGS 1,560 100.0 1.6 67.9 4.1 25.4 1.1 Agricultural X -- --

88 USGS 2,439 100.0 1.0 72.7 2.6 23.3 0.4 Agricultural X -- X

89 USGS 1,159 100.0 0.8 97.3 0.3 1.5 0.1 Agricultural X -- --

90 USGS 291 100.0 82.3 2.2 3.2 9.6 2.7 Urban X -- --

91 USGS 1,634 100.0 54.4 28.9 1.9 11.9 2.9 Mixed X -- --

92 USGS 25 100.0 97.9 0.0 0.0 0.2 1.9 Urban X X X

93 USGS 69,165 100.0 8.6 77.9 0.8 10.8 2.0 Mixed X -- --

94 USGS 1,909 100.0 2.3 21.2 1.0 73.9 1.7 Undeveloped X -- --

95 USGS 1,839,670 98.5 1.8 43.5 36.4 13.2 3.7 Mixed X X X

96 USGS 662 100.0 0.4 72.4 27.0 0.1 0.1 Agricultural -- -- X

97 USGS 929 2.0 0.0 0.8 0.8 0.0 0.5 -- X X --

98 USGS 34,249 100.0 0.2 3.6 81.5 9.1 5.7 Undeveloped -- -- X

99 USGS 177,139 100.0 0.2 8.4 72.4 14.3 4.7 Undeveloped X X X

100 USGS 468,774 94.1 0.2 19.7 58.7 12.0 3.5 Undeveloped -- X X

101 USGS 21,667 100.0 0.2 11.9 83.7 0.5 3.6 Undeveloped X X X

102 USGS 3,019 100.0 0.3 68.0 26.0 0.9 4.7 Agricultural -- X X

103 USGS 1,063 100.0 15.2 8.7 70.9 4.6 0.7 Mixed -- X X
10 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 1. Characteristics and trend coverage of study sites.—Continued

[ARDEQ, Arkansas Department of Environmental Quality; CADWR, California Department of Water Resources; CWS, Clean Water Services (Tualatin River 

Basin, Oregon); LADEQ, Louisiana Department of Environmental Quality; ODEQ, Oregon Department of Environmental Quality; TXCEQ, Texas Commission 

on Environmental Quality; UCD, University of California, Davis; USGS, U.S. Geological Survey; WECY, Washington State Department of Ecology; UDEQ, 

Utah Department of Environmental Quality; --, not determined or not applicable; >, greater than; ≤, less than or equal to]

Site 

number 

(figure 1)

Station

number Station name Major river basin

104 06752260 Cache La Poudre River at Fort Collins, Colo. Missouri

105 06752280 Cache La Poudre River above Boxelder Creek, near Timnath, Colo. Missouri

106 06753990 Lonetree Creek near Greeley, Colo. Missouri

107 06754000 South Platte River near Kersey, Colo. Missouri

108 06775900 Dismal River near Thedford, Nebr. Missouri

109 06800000 Maple Creek near Nickerson, Nebr. Missouri

110 06805500 Platte River at Louisville, Nebr. Missouri

111 06817700 Nodaway River near Graham, Mo. Missouri

112 06818000 Missouri River at St. Joseph, Mo. Missouri

113 06902000 Grand River near Sumner, Mo. Missouri

114 06905500 Chariton River near Prairie Hill, Mo. Missouri

115 06921070 Pomme De Terre River near Polk, Mo. Missouri

116 06926510 Osage River below St. Thomas, Mo. Missouri

117 06930800 Gasconade River above Jerome, Mo. Missouri

118 06934500 Missouri River at Hermann, Mo. Missouri

119 07047942 L’Anguille River near Colt, Ark. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

120 07053250 Yocum Creek near Oak Grove, Ark. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

121 07056000 Buffalo River near St Joe, Ark. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

122 07060500 White River at Calico Rock, Ark. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

123 07060710 North Sylamore Creek near Fifty Six, Ark. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

124 07066110 Jacks Fork above Two River, Mo. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

125 07068000 Current River at Doniphan, Mo. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

126 07077500 Cache River at Patterson, Ark. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

127 07077700 Bayou DeView near Morton, Ark. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

128 07103700 Fountain Creek near Colorado Springs, Colo. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

129 07103780 Monument Creek above North Gate Boulevard at United States Air Force 

Academy, Colo.

Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

130 07105500 Fountain Creek at Colorado Springs, Colo. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

131 07105530 Fountain Creek below Janitell Road below Colorado Springs, Colo. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

132 07106300 Fountain Creek near Pinon, Colo. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

133 07106500 Fountain Creek at Pueblo, Colo. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

134 07189000 Elk River near Tiff City, Mo. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

135 07195500 Illinois River near Watts, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

136 07195865 Sager Creek near West Siloam Springs, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

137 07196000 Flint Creek near Kansas, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

138 07196500 Illinois River near Tahlequah, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

139 07197000 Baron Fork at Eldon, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

140 07227500 Canadian River near Amarillo, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

141 07239450 North Canadian River near Calumet, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

142 07241000 North Canadian River below Lake Overholser near Oklahoma City, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

143 07241520 North Canadian River at Britton Road at Oklahoma City, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

144 07241550 North Canadian River near Harrah, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

145 07247015 Poteau River at Loving, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

146 07247250 Black Fork below Big Creek near Page, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

147 07247345 Black Fork at Hodgen, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

148 07247650 Fourche Maline near Leflore, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

149 07263620 Arkansas River at David D. Terry Lock and Dam below Little Rock, Ark. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

150 07331000 Washita River near Dickson, Okla. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

151 07355500 Red River at Alexandria, La. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

152 07362000 Ouachita River at Camden, Ark. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

153 07373420 Mississippi River near St Francisville, La. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf
Approach 11

Table 1. Characteristics and trend coverage of study sites.—Continued

[ARDEQ, Arkansas Department of Environmental Quality; CADWR, California Department of Water Resources; CWS, Clean Water Services (Tualatin River 

Basin, Oregon); LADEQ, Louisiana Department of Environmental Quality; ODEQ, Oregon Department of Environmental Quality; TXCEQ, Texas Commission 

on Environmental Quality; UCD, University of California, Davis; USGS, U.S. Geological Survey; WECY, Washington State Department of Ecology; UDEQ, 

Utah Department of Environmental Quality; --, not determined or not applicable; >, greater than; ≤, less than or equal to.]

Site 

number 

(figure 1)

Data source

Drainage 

area, 

in square 

kilometers

Percent of 

drainage

area in the

United States

Land cover in the basin,

in percent1

Land-use

classification3

Constituent included 

for trend analysis

Urban Agriculture

Rangeland Forest Other2

Total

phosphorus

Total

nitrogen Nitrate

104 USGS 2,921 100.0 1.0 1.8 32.3 59.3 5.7 Undeveloped -- -- X

105 USGS 3,223 100.0 2.9 2.8 34.2 54.1 6.1 Undeveloped -- -- X

106 USGS 1,478 100.0 0.9 23.1 74.7 0.4 1.0 Undeveloped X X X

107 USGS 25,016 100.0 8.1 13.3 38.5 34.5 5.7 Mixed X X X

108 USGS 72 100.0 0.0 1.1 72.0 12.8 14.2 Undeveloped -- X X

109 USGS 954 100.0 0.4 96.7 1.4 1.1 0.5 Agricultural X X X

110 USGS 220,908 100.0 1.5 25.5 61.5 8.1 3.6 Mixed X X X

111 USGS 3,927 100.0 1.5 86.6 5.5 5.4 0.9 Agricultural X X X

112 USGS 1,081,420 97.5 0.7 30.8 54.4 8.1 3.5 Mixed X X X

113 USGS 17,950 100.0 1.7 73.9 6.2 16.9 1.2 Agricultural X X X

114 USGS 4,897 100.0 1.9 68.0 5.4 22.1 2.6 Agricultural X X X

115 USGS 713 100.0 1.0 65.1 2.0 31.4 0.7 Agricultural X X X

116 USGS 37,908 100.0 1.3 55.6 7.9 31.5 3.7 Agricultural -- X X

117 USGS 6,649 100.0 1.1 36.7 1.1 60.3 0.8 Mixed -- -- X

118 USGS 1,344,910 98.0 0.9 35.8 49.2 9.0 3.1 Mixed X X X

119 USGS 1,375 100.0 1.1 82.0 0.0 15.8 1.1 Agricultural -- -- X

120 USGS 134 100.0 1.8 71.3 0.3 25.8 0.7 Agricultural X X X

121 USGS and

ARDEQ

2,149 100.0 0.3 10.8 0.6 87.5 0.8 Undeveloped -- -- X

122 USGS 25,815 100.0 2.1 30.6 0.8 63.2 3.3 Mixed -- -- X

123 USGS 150 100.0 0.0 2.0 0.1 97.8 0.2 Undeveloped -- -- X

124 USGS 1,121 100.0 0.5 19.2 0.4 79.6 0.4 Undeveloped -- X X

125 USGS 5,317 100.0 0.2 13.5 0.3 85.5 0.4 Undeveloped -- X X

126 USGS 6,678 100.0 1.2 49.3 1.2 47.0 1.2 Mixed -- -- X

127 USGS 1,079 100.0 2.8 77.1 0.0 18.4 1.8 Agricultural -- -- X

128 USGS 268 100.0 6.8 0.3 16.6 71.6 4.7 Mixed -- -- X

129 USGS 214 100.0 9.8 1.3 31.0 57.1 0.8 Mixed -- -- X

130 USGS 961 100.0 21.1 0.7 26.6 49.5 2.1 Mixed -- -- X

131 USGS 1,072 100.0 23.8 0.6 24.6 49.0 2.0 Mixed -- -- X

132 USGS 2,209 100.0 18.6 2.6 50.4 27.1 1.4 Mixed -- -- X

133 USGS 2,414 100.0 17.9 2.6 53.3 24.9 1.4 Mixed -- -- X

134 USGS 2,201 100.0 2.8 43.3 2.1 51.0 0.8 Mixed X X X

135 USGS 1,635 100.0 10.7 61.7 0.2 26.3 1.1 Mixed X X X

136 USGS 50 100.0 24.5 65.6 0.1 9.3 0.4 Mixed X X X

137 USGS 300 100.0 6.2 66.9 0.5 25.4 1.1 Mixed X X X

138 USGS 2,454 100.0 7.4 56.2 0.9 34.3 1.2 Mixed X X X

139 USGS 808 100.0 1.4 46.0 0.7 51.3 0.6 Mixed X X X

140 USGS 49,290 100.0 0.3 5.2 83.5 10.6 0.4 Undeveloped -- -- X

141 USGS 34,298 100.0 0.5 43.4 54.7 1.0 0.5 Mixed -- -- X

142 USGS 34,968 100.0 0.7 43.8 53.9 1.0 0.6 Mixed -- -- X

143 USGS 35,447 100.0 1.4 43.5 53.4 1.1 0.6 Mixed -- -- X

144 USGS 35,713 100.0 1.5 43.4 53.3 1.2 0.6 Mixed -- -- X

145 USGS 697 100.0 0.8 25.1 0.0 71.5 2.6 Mixed X X X

146 USGS 245 100.0 0.1 6.2 0.0 93.0 0.8 Undeveloped -- X X

147 USGS 511 100.0 0.2 5.7 0.0 92.4 1.7 Undeveloped -- X X

148 USGS 633 100.0 1.4 19.0 0.0 79.1 0.5 Undeveloped X X X

149 USGS 408,729 100.0 1.7 31.1 50.7 14.5 2.0 Mixed X X X

150 USGS 18,590 100.0 1.0 36.4 51.5 9.3 1.8 Mixed X X X

151 USGS 560 100.0 12.3 68.3 0.0 16.8 2.5 Mixed X X X

152 USGS 13,943 100.0 1.4 13.8 0.0 80.7 4.1 Undeveloped X X X

153 USGS 2,965,463 99.1 2.4 41.0 29.6 22.9 3.2 Mixed X X X
12 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 1. Characteristics and trend coverage of study sites.—Continued

[ARDEQ, Arkansas Department of Environmental Quality; CADWR, California Department of Water Resources; CWS, Clean Water Services (Tualatin River 

Basin, Oregon); LADEQ, Louisiana Department of Environmental Quality; ODEQ, Oregon Department of Environmental Quality; TXCEQ, Texas Commission 

on Environmental Quality; UCD, University of California, Davis; USGS, U.S. Geological Survey; WECY, Washington State Department of Ecology; UDEQ, 

Utah Department of Environmental Quality; --, not determined or not applicable; >, greater than; ≤, less than or equal to]

Site 

number 

(figure 1)

Station

number Station name Major river basin

154 07375500 Tangipahoa River at Robert, La. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

155 07376000 Tickfaw River at Holden, La. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

156 07381495 Atchafalaya River at Melville, La. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

157 07386980 Vermilion River at Perry, La. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

158 08030500 Sabine River near Ruliff, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

159 08032000 Neches River near Neches, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

160 08033500 Neches River near Rockland, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

161 08051500 Clear Creek near Sanger, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

162 08064100 Chambers Creek near Rice, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

163 08065350 Trinity River near Crockett, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

164 08136500 Concho River at Paint Rock, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

165 08143600 Pecan Bayou near Mullin, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

166 08147000 Colorado River near San Saba, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

167 08155200 Barton Creek at State Highway 71 near Oak Hill, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

168 08155240 Barton Creek at Lost Creek Boulevard near Austin, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

169 08159000 Onion Creek at U.S. Highway 183, Austin, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

170 08162000 Colorado River at Wharton, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

171 08162500 Colorado River near Bay City, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

172 08181800 San Antonio River near Elmendorf, Tex. Lower Mississippi, Arkansas-White-Red, and Texas-Gulf

173 08251500 Rio Grande near Lobatos, Colo. Rio Grande, Colorado, and Great Basin 

174 09058000 Colorado River near Kremmling, Colo. Rio Grande, Colorado, and Great Basin 

175 09163500 Colorado River near Colorado-Utah State Line Rio Grande, Colorado, and Great Basin 

176 09211200 Green River below Fontenelle Reservoir, Wyo. Rio Grande, Colorado, and Great Basin 

177 09217010 Green River below Green River, Wyo. Rio Grande, Colorado, and Great Basin 

178 09261000 Green River at Dinosaur National Monument Utah 149 Crossing, Utah Rio Grande, Colorado, and Great Basin 

179 09380000 Colorado River at Lees Ferry, Ariz. Rio Grande, Colorado, and Great Basin 

180 09403600 Kanab Creek at U.S. 89 Crossing, Utah Rio Grande, Colorado, and Great Basin 

181 09413500 Virgin River below First Narrows, Utah Rio Grande, Colorado, and Great Basin 

182 09415000 Virgin River at Littlefield, Ariz. Rio Grande, Colorado, and Great Basin 

183 09448500 Gila River at Head of Safford Valley, near Solomon, Ariz. Rio Grande, Colorado, and Great Basin 

184 09498500 Salt River near Roosevelt, Ariz. Rio Grande, Colorado, and Great Basin 

185 09508500 Verde River below Tangle Creek, above Horseshoe Dam, Ariz. Rio Grande, Colorado, and Great Basin 

186 09522000 Colorado River at Northerly International Boundary, above Morelos 

Dam, Ariz.

Rio Grande, Colorado, and Great Basin 

187 10038000 Bear River below Smiths Fork, near Cokeville, Wyo. Rio Grande, Colorado, and Great Basin 

188 10126000 Bear River near Corinne at Utah 83 Crossing, Utah Rio Grande, Colorado, and Great Basin 

189 10131000 Chalk Creek at U.S. 189 Crossing, Utah Rio Grande, Colorado, and Great Basin 

190 10154200 Provo River above Woodland at U.S. Geological Survey Gage 

Number 10154200, Utah

Rio Grande, Colorado, and Great Basin 

191 10155000 Provo River at Bridge 2.5 miles East of Hailstone Junction, Utah Rio Grande, Colorado, and Great Basin 

192 10155500 Provo River above Confluence with Snake Creek at McKeller 

Bridge, Utah

Rio Grande, Colorado, and Great Basin 

193 10189000 East Fork Sevier River at Utah 62 Crossing East of Kingston, Utah Rio Grande, Colorado, and Great Basin 

194 10336580 Upper Truckee River at South Upper Truckee Road near Meyers, Calif. Rio Grande, Colorado, and Great Basin 

195 103366092 Upper Truckee River at Highway 50 above Meyers, Calif. Rio Grande, Colorado, and Great Basin 

196 10336610 Upper Truckee River at South Lake Tahoe, Calif. Rio Grande, Colorado, and Great Basin 

197 10336698 Third Creek near Crystal Bay, Nev. Rio Grande, Colorado, and Great Basin 

198 103366993 Incline Creek above Tyrol Village near Incline Village, Nev. Rio Grande, Colorado, and Great Basin 

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. Rio Grande, Colorado, and Great Basin 

200 10336700 Incline Creek near Crystal Bay, Nev. Rio Grande, Colorado, and Great Basin 
Approach 13

Table 1. Characteristics and trend coverage of study sites.—Continued

[ARDEQ, Arkansas Department of Environmental Quality; CADWR, California Department of Water Resources; CWS, Clean Water Services (Tualatin River 

Basin, Oregon); LADEQ, Louisiana Department of Environmental Quality; ODEQ, Oregon Department of Environmental Quality; TXCEQ, Texas Commission 

on Environmental Quality; UCD, University of California, Davis; USGS, U.S. Geological Survey; WECY, Washington State Department of Ecology; UDEQ, 

Utah Department of Environmental Quality; --, not determined or not applicable; >, greater than; ≤, less than or equal to.]

Site 

number 

(figure 1)

Data source

Drainage 

area, 

in square 

kilometers

Percent of 

drainage

area in the

United States

Land cover in the basin,

in percent1

Land-use

classification3

Constituent included 

for trend analysis

Urban Agriculture

Rangeland Forest Other2

Total

phosphorus

Total

nitrogen Nitrate

154 USGS and

LADEQ

1,675 100.0 3.4 33.4 0.0 61.3 1.9 Mixed X X X

155 LADEQ 1,028 100.0 1.6 18.5 0.0 76.6 3.3 Undeveloped X X X

156 USGS 240,628 100.0 1.6 34.9 22.0 37.9 3.5 Mixed X X X

157 USGS and

LADEQ

1,129 100.0 16.6 69.2 0.2 10.0 4.0 Mixed X X X

158 TXCEQ 24,171 100.0 2.9 26.7 0.1 61.8 8.5 Mixed -- -- X

159 USGS 2,991 100.0 4.5 45.9 0.0 44.1 5.5 Mixed -- -- X

160 USGS 9,425 100.0 2.9 28.9 0.0 62.6 5.7 Mixed -- -- X

161 USGS 763 100.0 0.3 37.9 45.8 15.2 0.9 Mixed -- -- X

162 USGS 2,136 100.0 2.7 77.0 5.5 12.3 2.5 Agricultural -- -- X

163 USGS 35,967 100.0 9.6 49.6 16.0 19.8 5.1 Mixed -- -- X

164 USGS 16,698 100.0 1.2 11.6 85.4 0.9 0.9 Undeveloped -- -- X

165 TXCEQ 5,387 100.0 1.7 13.8 75.0 7.4 2.1 Undeveloped X -- --

166 TXCEQ 74,658 100.0 1.2 19.0 75.4 3.0 1.4 Undeveloped X -- --

167 USGS 232 100.0 4.1 1.6 42.7 50.5 1.0 Undeveloped -- -- X

168 USGS 279 100.0 6.5 1.4 40.0 50.9 1.2 Mixed -- -- X

169 TXCEQ 839 100.0 17.3 6.2 34.9 40.5 1.0 Mixed X -- --

170 TXCEQ 102,705 100.0 1.7 17.0 68.3 11.4 1.6 Undeveloped X -- --

171 TXCEQ 103,310 100.0 1.8 17.3 68.0 11.4 1.6 Undeveloped X -- --

172 USGS 4,528 100.0 19.1 16.2 21.1 41.6 2.0 Mixed -- -- X

173 USGS 11,876 100.0 0.3 8.4 50.9 34.3 6.1 Undeveloped X X --

174 USGS 46,230 100.0 0.8 4.2 33.5 54.8 6.7 Undeveloped -- -- X

175 USGS 46,274 100.0 0.7 4.2 33.6 54.8 6.7 Undeveloped -- -- X

176 USGS 10,862 100.0 0.1 4.2 66.6 17.7 11.4 Undeveloped -- X --

177 USGS 25,220 100.0 0.2 2.1 83.4 8.3 5.9 Undeveloped X -- X

178 UDEQ 66,056 100.0 0.2 2.6 74.1 19.4 3.8 Undeveloped X -- --

179 USGS 280,074 100.0 0.3 2.2 63.8 27.5 6.2 Undeveloped -- X --

180 UDEQ 503 100.0 0.1 0.6 69.0 29.4 0.9 Undeveloped X -- --

181 UDEQ 10,304 100.0 0.7 0.7 69.4 23.2 5.9 Undeveloped -- -- X

182 USGS 12,571 100.0 0.6 0.7 69.5 22.4 6.8 Undeveloped X X --

183 USGS 20,424 100.0 0.1 0.3 56.2 42.8 0.6 Undeveloped X -- --

184 USGS 11,103 100.0 0.3 0.0 31.1 67.8 0.8 Undeveloped X -- --

185 USGS 14,243 100.0 1.1 0.3 50.7 47.2 0.6 Undeveloped X -- --

186 USGS 624,016 99.5 0.9 2.0 68.7 22.9 5.0 Undeveloped X -- --

187 USGS 6,336 100.0 0.2 6.8 74.3 16.3 2.4 Undeveloped -- -- X

188 UDEQ 18,312 100.0 0.7 18.3 60.6 16.2 4.2 Undeveloped X -- --

189 UDEQ 661 100.0 0.1 1.2 48.9 49.4 0.4 Undeveloped -- -- X

190 UDEQ 420 100.0 0.0 0.0 18.8 79.9 1.3 Undeveloped -- -- X

191 UDEQ 568 100.0 0.0 2.3 22.5 74.2 1.0 Undeveloped -- -- X

192 UDEQ 726 100.0 1.4 4.3 24.9 68.4 0.9 Undeveloped -- -- X

193 UDEQ 3,119 100.0 0.2 0.8 51.4 44.7 2.9 Undeveloped X -- --

194 USGS 37 100.0 0.0 0.0 26.7 67.0 6.3 Undeveloped -- -- X

195 USGS 102 100.0 1.9 0.0 22.1 71.9 4.1 Undeveloped -- -- X

196 USGS 140 100.0 7.8 0.0 20.1 68.8 3.2 Mixed -- X --

197 USGS 16 100.0 17.7 0.0 29.5 45.1 7.7 Mixed -- -- X

198 USGS 7 100.0 0.0 0.0 33.9 65.7 0.4 Undeveloped -- -- X

199 USGS 12 100.0 4.8 0.0 27.0 67.7 0.4 Undeveloped -- X X

200 USGS 17 100.0 13.0 0.0 19.9 66.7 0.3 Mixed -- -- X
14 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 1. Characteristics and trend coverage of study sites.—Continued

[ARDEQ, Arkansas Department of Environmental Quality; CADWR, California Department of Water Resources; CWS, Clean Water Services (Tualatin River 

Basin, Oregon); LADEQ, Louisiana Department of Environmental Quality; ODEQ, Oregon Department of Environmental Quality; TXCEQ, Texas Commission 

on Environmental Quality; UCD, University of California, Davis; USGS, U.S. Geological Survey; WECY, Washington State Department of Ecology; UDEQ, 

Utah Department of Environmental Quality; --, not determined or not applicable; >, greater than; ≤, less than or equal to]

Site 

number 

(figure 1)

Station

number Station name Major river basin

201 10336740 Logan House Creek near Glenbrook, Nev. Rio Grande, Colorado, and Great Basin 

202 10336760 Edgewood Creek at Stateline, Nev. Rio Grande, Colorado, and Great Basin 

203 01A050 Nooksack River at Brennan, Wash. Pacific Northwest 

204 03A060 Skagit River near Mount Vernon, Wash. Pacific Northwest 

205 07A090 Snohomish River at Snohomish, Wash. Pacific Northwest 

206 09A080 Green River at Tukwila, Wash. Pacific Northwest 

207 09A190 Green River at Kanaskat, Wash. Pacific Northwest 

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. Pacific Northwest 

209 10350 Willamette River at Eastbound Highway 20 Bridge at Albany, Oreg. Pacific Northwest 

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. Pacific Northwest 

211 10386 Middle Fork Willamette at Jasper Bridge, Oreg. Pacific Northwest 

212 10411 Deschutes River at Deschutes River Park, Oreg. Pacific Northwest 

213 10555 Willamette River at Marion Street at Salem, Oreg. Pacific Northwest 

214 10611 Willamette River at Hawthorne Bridge, Oreg. Pacific Northwest 

215 10616 Columbia River at Marker number 47 upstream of Willamette 

River, Oreg.

Pacific Northwest 

216 10A070 Puyallup River at Meridian Street, Wash. Pacific Northwest 

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. Pacific Northwest 

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. Pacific Northwest 

219 11478 John Day River at Service Creek, Oreg. Pacific Northwest 

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. Pacific Northwest 

221 12413470 South Fork Coeur D‘Alene River near Pinehurst, Idaho Pacific Northwest 

222 12419000 Spokane River near Post Falls, Idaho Pacific Northwest 

223 13154500 Snake River at King Hill, Idaho Pacific Northwest 

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho Pacific Northwest 

225 13351000 Palouse River at Hooper, Wash. Pacific Northwest 

226 14201300 Zollner Creek near Mt. Angel, Oreg. Pacific Northwest 

227 14211720 Willamette River at Portland, Oreg. Pacific Northwest 

228 14246900 Columbia River at Beaver Army Terminal near Quincy, Oreg. Pacific Northwest 

229 16A070 Skokomish River near Potlatch, Wash. Pacific Northwest 

230 32A070 Walla Walla River near Touchet, Wash. Pacific Northwest 

231 3701002 Tualatin River at Weiss Bridge, Oreg. Pacific Northwest 

232 37016120 Tualatin River at Springhill Road Bridge at Dilley, Oreg. Pacific Northwest 

233 37A090 Yakima River at Kiona, Wash. Pacific Northwest 

234 45A070 Wenatchee River at Wenatchee, Wash. Pacific Northwest 

235 45A110 Wenatchee River near Leavenworth, Wash. Pacific Northwest 

236 48A070 Methow River near Pateros, Wash. Pacific Northwest 

237 49A070 Okanogan River at Malott, Wash. Pacific Northwest 

238 54A120 Spokane River at Riverside State Park, Wash. Pacific Northwest 

239 61A070 Columbia River at Northport, Wash. Pacific Northwest 

240 11264500 Merced River at Happy Isles Bridge near Yosemite, Calif. California

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. California

242 11290000 Tuolumne River at Modesto, Calif. California

243 11303500 San Joaquin River near Vernalis, Calif. California

244 11447650 Sacramento River at Freeport, Calif. California

1

Land-use characteristics for the drainage area in the United States. Data are from an enhanced version of the U.S. Geological Survey 1992 National Land 

Cover Dataset (Nakagaki and Wolock, 2005).

2

“Other” includes open water, wetlands, tundra, bare rock/sand/clay, perennial ice/snow, quarries/strip mines/gravel pits, and transitional.

3

Agricultural: >50 percent agricultural land and ≤5 percent urban land; Urban: >25 percent urban land and ≤25 percent agricultural land; Undeveloped: 

≤5 percent urban land and ≤25 percent agricultural land; Mixed - all other combinations of urban, agricultural, and undeveloped land (Gilliom and others, 2006).
Approach 15

Table 1. Characteristics and trend coverage of study sites.—Continued

[ARDEQ, Arkansas Department of Environmental Quality; CADWR, California Department of Water Resources; CWS, Clean Water Services (Tualatin River 

Basin, Oregon); LADEQ, Louisiana Department of Environmental Quality; ODEQ, Oregon Department of Environmental Quality; TXCEQ, Texas Commission 

on Environmental Quality; UCD, University of California, Davis; USGS, U.S. Geological Survey; WECY, Washington State Department of Ecology; UDEQ, 

Utah Department of Environmental Quality; --, not determined or not applicable; >, greater than; ≤, less than or equal to.]

Site 

number 

(figure 1)

Data source

Drainage 

area, 

in square 

kilometers

Percent of 

drainage

area in the

United States

Land cover in the basin,

in percent1

Land-use

classification3

Constituent included 

for trend analysis

Urban Agriculture

Rangeland Forest Other2

Total

phosphorus

Total

nitrogen Nitrate

201 USGS 5 100.0 0.0 0.0 6.5 93.5 0.0 Undeveloped -- X X

202 USGS 15 100.0 19.6 0.0 11.9 68.3 0.2 Mixed -- X --

203 WECY 1,908 100.0 3.0 11.7 3.5 69.3 12.4 Undeveloped X -- --

204 WECY 6,024 100.0 1.3 1.4 9.2 71.2 17.0 Undeveloped X -- --

205 WECY 4,438 100.0 4.0 2.5 6.5 77.3 9.7 Undeveloped X -- X

206 WECY 1,236 100.0 22.6 4.4 3.2 57.2 12.6 Mixed X -- --

207 WECY 616 100.0 0.2 0.0 3.4 77.2 19.2 Undeveloped X -- X

208 ODEQ -- -- -- -- -- -- -- -- X X X

209 ODEQ 12,567 100.0 3.8 16.2 4.4 71.8 3.9 Undeveloped X X X

210 ODEQ 8,886 100.0 2.6 3.9 4.8 84.0 4.7 Undeveloped X X X

211 ODEQ 3,487 100.0 1.0 1.2 4.1 89.1 4.7 Undeveloped X -- --

212 ODEQ 27,768 100.0 0.7 5.2 47.9 43.5 2.6 Undeveloped X X --

213 ODEQ 19,112 100.0 3.8 18.2 4.3 69.9 3.7 Undeveloped X X X

214 ODEQ 28,937 100.0 5.5 23.1 3.7 64.5 3.3 Mixed X X --

215 ODEQ -- -- -- -- -- -- -- -- X X X

216 WECY 2,381 100.0 6.2 2.9 3.5 70.2 17.2 Mixed X -- --

217 ODEQ 1,078 100.0 10.4 34.2 4.5 46.6 4.4 Mixed X X X

218 ODEQ 139 100.0 75.6 13.9 0.7 9.6 0.2 Urban X X X

219 ODEQ 13,289 100.0 0.1 1.8 37.6 59.7 0.8 Undeveloped X X --

220 ODEQ -- -- -- -- -- -- -- -- X X --

221 USGS 738 100.0 2.5 0.1 12.7 83.3 1.4 Undeveloped X X --

222 USGS 10,162 100.0 1.4 4.1 6.2 80.4 7.9 Undeveloped X X --

223 USGS 92,942 100.0 0.5 17.4 59.2 16.6 6.3 Undeveloped X X --

224 USGS 7,184 100.0 0.8 0.5 48.8 43.2 6.7 Undeveloped X X X

225 USGS 6,379 100.0 1.5 72.5 14.9 9.6 1.5 Agricultural X X X

226 USGS 39 100.0 1.1 95.2 0.8 2.6 0.3 Agricultural -- -- X

227 USGS 28,937 100.0 5.5 23.1 3.7 64.5 3.3 Mixed X X --

228 USGS 582,736 100.0 0.9 12.0 45.6 36.4 5.0 Undeveloped X X X

229 WECY 339 100.0 0.4 1.3 1.8 80.6 16.0 Undeveloped X -- X

230 WECY 4,365 100.0 2.0 56.1 23.6 17.8 0.4 Agricultural X -- --

231 CWS 1,838 100.0 19.8 33.9 0.8 43.3 2.1 Mixed X X --

232 CWS 327 100.0 1.2 22.2 0.5 73.3 2.7 Undeveloped X X --

233 WECY 14,536 100.0 2.1 15.0 41.9 36.3 4.7 Undeveloped X -- --

234 WECY 3,440 100.0 0.6 1.4 18.7 70.1 9.3 Undeveloped X -- X

235 WECY 1,721 100.0 0.1 0.2 12.0 75.1 12.6 Undeveloped X -- X

236 WECY 4,657 100.0 0.4 0.8 28.0 65.6 5.2 Undeveloped X -- --

237 WECY 4,500 100.0 1.0 5.0 48.8 41.2 4.1 Undeveloped X -- X

238 WECY 12,951 100.0 3.5 13.3 7.8 68.6 6.8 Undeveloped X -- X

239 WECY -- -- -- -- -- -- -- -- X -- X

240 USGS 468 100.0 0.0 0.0 43.7 40.0 16.4 Undeveloped -- -- X

241 USGS, UCD,

CADWR

28 100.0 0.3 95.3 3.5 0.0 1.0 Agricultural X X X

242 USGS, UCD, 

CADWR

4,760 100.0 2.8 4.3 33.9 48.5 10.7 Undeveloped X X X

243 USGS, CADWR 19,030 100.0 3.1 22.1 34.8 33.8 6.3 Undeveloped X X X

244 USGS, UCD 61,693 100.0 2.4 13.0 29.5 52.2 2.8 Undeveloped X X X
16 Nutrient Trends in Streams and River of the United States, 1993–2003

The streamflow residual was assumed to follow an autoregressive process of order 30 [AR(30)] (Fuller, 1996). The 

streamflow model was estimated using maximum-likelihood 

estimation methods as used by the AUTOREG procedure in 

SAS 9, version 1, release 2 (SAS Institute Inc., 2004). For some 

sites, serial correlation in the residuals was not fully removed by 

the AR(30) model. Significant residual serial correlation could 

invalidate the standard error of the streamflow trend coefficient, 

although the practical importance of this effect for the statistical 

significance of the trend was likely to be small.

The trend in streamflow over the analysis period 

(between t

1

, 1993, and t

2

, 2003), τq, was defined as:

 q t t t t  
 q q    
 a T 	 T 2 1 2 1 . (2)

The trend in streamflow (expressed as the percentage change 

from 1993 to 2003), %Δq, was defined as:

%∆= − q e( ) q 100 1 W , (3)

where

e is Euler’s number (the base of the natural 

logarithm).

The 95-percent confidence interval of the trend was calculated 

by use of the standard deviation of τq (given by the product of 

(Tt

2

– Tt

1

) and the standard error of a); trend results were considered significant if the p-value was less than or equal to 0.05.

Flow-Adjusted Trends in Concentration

To determine the FA trend in concentration, a concentration model relating the logarithm of nutrient concentrations to 

various functions of streamflow, decimal time, and season was 

used. An abstract representation of the model is given by:

ct = b0 + m(qt)bq + h(Tt)bT + xtbx + Et, (4)

where

ct is the natural logarithm of constituent 

concentration at time t;

b0 is the intercept;

m(.) and h(.) are multi-element vector functions of q and T;

qt is natural logarithm of streamflow at time t;

bq, bT and bx are vector-valued coefficients to be estimated;

Tt is decimal time at time t;

xt is a vector of ancillary predictors of season, 

such as the sine and cosine functions of 

decimal time;

and

Et is an independent and identically normally 

distributed random error.

Depending on the form of a given concentration model, the 

multi-element vector function of the logarithm of streamflow, 

m(.), consisted of the logarithm of streamflow and(or) the 

square of the logarithm of streamflow, and the multi-element 

vector function of decimal time, h(.), consisted of first- and(or) 

second-order polynomial terms and(or) step functions of decimal time. Because of the inclusion of the streamflow function 

in equation 4, the resulting trend in concentration was inherently flow adjusted.

The concentration model was fit separately for each 

constituent at each site. The dependent variable was always 

the logarithm of concentration, and the independent variables 

were various functions of daily mean streamflow, decimal 

time, and season. All possible combinations of these variables 

were examined, and the best model was selected on the basis 

of the Akaike Information Criteria (Akaike, 1981). Step trends 

were evaluated with an additional binary variable designating samples as residing in either the “early” or the “late” 

period. Residuals from the best-fit model were examined for 

homoscedasticity and normality, two fundamental assumptions of linear models; if either assumption was violated, the 

model was rejected. The final models always included, at a 

minimum, log of streamflow (to ensure that the resulting time 

trend was flow adjusted) and decimal time (to ensure that a 

trend over time could be calculated). In addition, sine of time 

and cosine of time (to account for seasonality) always were 

present together if either were selected. The concentration 

model was estimated using either ordinary least squares if the 

concentration data contained no censored observations or the 

maximum-likelihood estimation method if censored observations were present. The maximum-likelihood estimation bias 

adjustment required estimates of the detection level even for 

uncensored observations; the detection level was set equal 

to either the maximum of the median detection level for all 

censored observations across all study sites or to a minimum 

reported uncensored value.

The FA trend in concentration over the analysis period 

(between t1

, 1993, and t2, 2003), τFA, was defined as the change 

in the trend component of equation 4:

 FA t t T  
  ̈hT hT b a ·

1 ( ) ( ) 2 1

^

, (5)

where

bT

^

is the sample estimate for the trend 

coefficient, bT.

The FA trend in concentration (expressed as the percentage 

change from 1993 to 2003), %∆FAC, was defined as:

% () ∆FAC e FA = − 100 1 W . (6) 

The standard error of τFA, denoted S(τFA), is given by

S h FA T h t t T V b h T t T h Tt  	    	 
  	  ̈

a ·1  	  	 
  	  ̈a ·1

a

2 1 2 1

^

, (7)

where

V(bT

^

) is the covariance matrix for bT

^

.
Approach 17

The 95-percent confidence interval of the trend was calculated 

using the Student’s t distribution (Helsel and Hirsch, 2002),

95 percent confidence interval =

τFA ± α(0.975, DF)S(τFA), (8)

where

	(0.975,DF) is the 0.975 quantile of the Student’s t

distribution with DF degrees of freedom 

(DF equals the number of observations 

minus the number of estimated coefficients 

in equation 4).

Trend results were considered significant if the two-tailed 

p-value, also based on the Student’s t distribution, was less 

than or equal to 0.05.

Non-Flow-Adjusted Trends in Concentration

NFA trends in concentration were derived from the decimal time and streamflow coefficients from the concentration 

model (bT and bq

) in equation 4 and the decimal time coefficient 

from the streamflow model (a) in equation 1. The NFA trend in 

concentration during a given period t, c

t

, was defined as:

c b m q b h T b xb   t = +0 ( )tq tT x + ( ) + , (9)

where

x is an average, over period t, of the nonstreamflow/non-trend variables in the 

concentration model.

The average of the error term is absent because it is set to its 

expected value of zero. Note that in forming the estimate of c

t

, 

the trend in the logarithm of streamflow (qt) was substituted 

for the actual logarithm of streamflow in the function m(.). 

This implied that variations in streamflow not reflected in the 

trend did not determine the proposed measure of the trend in 

concentration. Because of the nonlinearity of the function m(.), 

this might have led to a bias in the evaluation of the trend in 

concentration if streamflows were becoming more or less variable over time.

The NFA trend in concentration over the analysis period 

(between t1

, 1993, and t2, 2003), τNFA, was defined as:

 NFA t t t t q

t t

c c mq mq b

hT hT

 
   	 
  	  ̈

a

© ·

1

 ̧

«

¬

­

o

»

1⁄4

  	 
 

    2 1 2 1

2 1 	  ̈

a

© ·

1

 ̧

«

¬

­

o

»

1⁄4

  	  
  	


   	  	 


 ̈

a

©

©

©

·

1

 ̧

 ̧

 ̧

b ,

m q a T T

m q a T T

T

t

t

2

1

,

b

hT hT b

q

t t T

«

¬

®

­

®

o

»

®

1⁄4

®

  	 
  	  ̈

a

© ·

1

 ̧

«

¬

­

o

»

1⁄4 2 1

^

^

^

^

^

^

(10)

where

bq

^

, bT

^ , and a

^ are sample estimates of the bq

, bT and a

coefficients in equations 1 and 4. 

The NFA trend in concentration (expressed as the percentage 

change from 1993 to 2003), %ΔNFAC, was defined as:

%∆NFAC e NFA = − 100 1 ( ) W . (11)

The estimate of the NFA trend in concentration was 

obtained by substituting sample estimates for the population 

values of a, bq

, and bT in equation 10. In general, the transformation of the estimated values of τNFA into real space, 

through the exponential function appearing in equation 11, 

induces a small degree of bias. No correction of this bias was 

applied here in order to ensure agreement between the sign of 

%ΔNFAC and the sign of the test statistic used to evaluate the 

statistical significance of the trend.

A statistical test of the null hypothesis that trend is 

zero can be undertaken by forming t-statistics from the 

estimates of τNFA and dividing by the standard error. The 

standard error of τNFA was complicated to derive owing to the 

nonlinear manner in which the streamflow trend coefficient 

and the concentration and streamflow coefficients interact in 

the determination of the trend in concentration. An approximation to the standard error suitable for large samples (30 

or more) was obtained by taking a first-order Taylor approximation of the trend estimate from equation 10 with respect 

to the streamflow and concentration model coefficients. 

The vector of combined streamflow and trend coefficients 

from the concentration model was represented by b b b  q T [ ] a a a, 

and the covariance matrix of this vector was represented 

by Vb

. Under the plausible assumption that streamflow was 

exogenous with respect to concentration, meaning that 

changes in streamflow caused changes in concentration but 

changes in concentration did not cause changes in streamflow, 

the covariance between the estimated values of a and b was 

zero. Consequently, the standard error of τNFA, denoted as σNFA,

was defined as:

V NFA a V b

m

a

b

q = AV A ∂

∂





 



 + ′ ∆ 2

, (12)

where

Va is the variance of the estimated streamflow trend 

coefficient, a;

∂∆

∂ = ∂+ −∂ − ∂+ −∂

m

a

mq aT T

a

mq aT T

a

t t ( ( )) ( ( )) 2 1 ; (13)

and

A mq aT T hT

mq aT T hT

t t

t t

= +− { } ( ) ( ) ( )

− +− { } ( ) ( ) ( )

2 2

1 1 ; (14)

and

A' is the transposition of A.
18 Nutrient Trends in Streams and River of the United States, 1993–2003

In large samples, the t-statistic τNFA / σNFA follows standard normal distribution. Therefore, the two-sided p-value for 

significance of the trend was calculated as:

p NFA NFA = − ( ) 

  2 1 Φ W V , (15)

where

p is the two-sided p-value for significance 

of the trend;

and

Φ(.) is the standard-normal cumulative 

distribution. 

NFA trend results were considered significant if p was less 

than or equal to 0.05. The 95-percent confidence interval of 

the trend was calculated by use of σNFA.

Trends in Load

The non-flow-adjusted trend in concentration depended 

on the decimal time and streamflow coefficients from the 

concentration model and the decimal time coefficient from the 

streamflow model. The trend in load during a given period t, 

L

t , was similarly defined, but included an additional term to 

reflect the direct effect streamflow had on the determination 

of load.

L q aT T b mq aT T b 

h T b xb

t t t q

tT x

=+ − ( ) ++ + − ( ) ( )

+ ( ) +

0

, (16)

The trend in load over the analysis period (between t1, 1993, 

and t2

, 2003), τL, was defined as the change in the trend in 

load, L

t , evaluated using sample estimates of the coefficients:

 L t t

t t q

t

a T T

m q a T T m q a T T b

h T

 
  	

   	  	 
 
   	  	 
  ̈

a

© ·

1

 ̧



2 1

2 1

2  	 
  	  ̈

a

© ·

1

 ̧ h T b t T 1 .

^

^ ^

^

^

(17)

The trend in load (expressed as the percentage change from 

1993 to 2003), %∆L, was defined as:

%∆L e L = − 100 1 ( ) W . (18)

The standard error of τL, denoted as σL, was defined as:

V L a V tt b

m

a

b

q = T T AV A ∂

∂

+ − ( ) 



 



 + ′ ∆

2 1

2

. (19)

In large samples, the t-statistic τL/σL is distributed standard 

normal. Therefore, the two-sided p-value for significance of 

the trend was calculated as:

p L L = − ( ) 



 



 2 1 Φ W V . (20)

The 95-percent confidence interval of the trend was calculated 

by use of σL

; trend results were considered significant if p was 

less than or equal to 0.05.

Reference Values

Ambient streamflows, concentrations, and loads vary 

throughout the Nation, and a given percentage increase or 

decrease may be more notable in one stream location than 

another. For example, a 100-percent increase in nitrate 

concentrations in a stream with an ambient concentration of 

0.001 mg/L may have less of an environmental impact than a 

100-percent increase in a stream with an ambient concentration of 5 mg/L. As a result, reference values for streamflow, 

concentration, and load representing the ambient initial conditions at each site are presented with the trend results. Because 

the season and flow conditions at the time of the first sample 

in the record differed among sites, the concentration and 

streamflow values from these initial samples were not used as 

reference values. Instead, the reference values were modeled 

as the streamflow, concentration, or load that would have been 

observed on the first day of the period of record under average 

hydrologic and seasonal conditions. The reference values for 

concentration (Cr

) in mg/L, load (Lr) in kg/day, and streamflow 

(qr

) in m3/s were defined as:

C e r

ct = 

1

, (21)

L e r

Lt = 

1 , (22)

and

q

L

C r

r

r

= × 0.011574. (23)

The estimated reference concentration and load are based on 

sample estimates of the coefficients used to evaluate c

t

1

 and L

t

1

. 

Due to the nonlinearity of the exponential function appearing in equations 21 and 22, and because the sample estimates 

of the estimates of c

t

1

 and L

t

1

 are approximately normally 

distributed, Cr and Lr and will be biased upward by the factors e ct var 

1 ( ) ( ) 2

 and e Lt var 

1 ( ) ( ) 2

. To correct this bias, equations 21 

and 22 were multiplied by retransformation factors equal to 

e ct - var 

1 ( ) ( ) 2 and e Lt - var 

1 ( ) ( ) 2 , respectively, where var( c

t

1

) and var(L

t

1

) 

are the variances of c

t

1

 and L

t

1

, computed from terms that are 

similar in form to the terms appearing inside the radicals of 

equations 12 and 19.

Limitations

The statistical procedures used in this report to evaluate 

trends assume that the trend is monotonic–that is, the population of observations increases or decreases over time, with no 

substantial reversals in direction. Major changes in the factors 

affecting in-stream concentrations could lead to nonmonotonic 

trends that would not be detected. For example, the effects 

of decreases in fertilizer use over many years may eventually 
Approach 19

be offset by the effects of increases in population density and 

concomitant increases in loading from wastewater-treatment 

plants. Typically, the longer the period of record, the more likely 

it is that different factors will be contributing to large changes in 

in-stream concentrations and the more likely it is that nonmonotonic trends will be present. A nonmonotonic trend in FA total 

nitrogen concentrations occurred at Site 99 (Yellowstone River 

near Sidney, Mont.) between 1985 and 2003; concentrations 

decreased from 1985 to 1992, then increased between 1993 and 

2003 (fig. 2). The latter trend will be the only change reflected 

in the trend results in this report. Similar longer term, nonmonotonic trends likely occurred at other sites as well.

For a valid comparison of trends at multiple sites, the data 

record at all sites must be concurrent (Hirsch and others, 1991). 

To maximize the number and coverage of sites nationally and 

to include data from a long enough period to detect changes 

in concentration but not so long as to encounter numerous 

nonmonotonic trends, a period of record from 1993 to 2003 

was used in this report. Trend results are reported here not as 

the year-to-year variation during the period of record, but as the 

overall change between the start date and the end date based 

on modeled load, concentration, or streamflow. As a result, the 

magnitude and significance of each individual trend is sensitive 

to conditions at the start and end of the record; the trend from 

1993 to 2003 might be different from a trend during a different 

period, such as 1985 to 2003 or 1993 to 2001. For example, the 

record of total phosphorus concentrations at site 184 (Salt River 

near Roosevelt, Ariz.) shows large increases in 2002 and 2003 

(fig. 3A). These increases likely were due in large part to runoff 

after the Rodeo-Chediski fire, which burned 1,890 km2

 of the 

White Mountain Apache Indian Reservation, Apache-Sitgreaves 

National Forest, and Tonto National Forest in June and July of 

2002; over 1,170 km2

 of the burned area was in the Salt River 

drainage (Arizona Game and Fish Department, 2006). The 

FA total phosphorus trend from 1993 to 2003 at site 184 was 

upward approximately 4,680 percent. The record of total phosphorus concentrations between 1993 and early 2002 (pre-burn) 

shows no evidence of an increase of similar magnitude (fig. 3B). 

The FA trend from 1993 to 2001 also was upward, but smaller 

in magnitude. The total phosphorus data for site 184 demonstrate how the use of different periods of record can lead to different, yet equally valid, trend results. Therefore, it is important 

to always consider the period of record when using and comparing any trend results.

In addition, during any period of record, there may be 

periods of shorter duration (for example, a day, season, or year) 

when relative extremes in concentration or load occur. Because 

the trend in this report represents the overall change from 1993 

to 2003 and not the variability within that period, extremes in concentration or load between 1993 and 2003 may not be reflected in 

the trend result. However, these extremes may have contributed to 

important changes in water quality or ecosystem function during 

some shorter period between 1993 and 2003. For example, mean 

annual load of total nitrogen at site 153 (Mississippi River near 

St. Francisville, La.) was substantially lower during 2000 than 

during any other year from 1993 to 2003 (fig. 4); this low load 

corresponded to the relatively smaller extent of the hypoxic zone 

in the Gulf of Mexico in 2000 (Rabalais and others, 2002). To 

relate nutrient concentrations or loads to changes in certain waterquality or ecosystem end points, it may be necessary to look not 

only at the overall trends, but at changes occurring during periods 

of shorter duration.

Factors Affecting the Trends

Nutrient concentrations and loads can be affected by 

temporal and spatial changes in nutrient sources and landscape characteristics. To aid in interpreting the nutrient trends, 

important nutrient sources and landscape characteristics were 

determined for each site.

Data Sources

Geographic information system (GIS) software (ESRI, 

2005) was used for spatial overlay analyses of the drainagearea polygons (or equivalent raster representation thereof) 

with digital thematic maps of nutrient sources and landscape characteristics. The spatial resolution of the thematic 

characteristics varied according to the scale or resolution of 

the source data. For many of the thematic characteristics, a 

time series of digital maps was available that was analyzed 

by a corresponding series of spatial overlays to produce 

a temporal series of basin characteristics. When drainage 

basins only partially extended into one or more counties, 

county-level data were apportioned according to the amount 

of agricultural or urban land contained within the drainage 

basin, as described by Nakagaki and Wolock (2005). The 

nutrient sources and landscape characteristics included 

EXPLANATION

Non-monotonic trend line

1993–2003 period of record

 used in this report

–1.0

–0.5

0

0.5

1.0

1985 1990 1995 2000 2005

FLOW-ADJUSTED CONCENTRATION OF TOTAL NITROGEN,

AS BASE-10 LOGARITHM OF MILLIGRAMS PER LITER

Figure 2. Flow-adjusted total nitrogen concentrations from 1985 

to 2003 at site 99. Modified from Sprague and others, 2006.
20 Nutrient Trends in Streams and River of the United States, 1993–2003

atmospheric deposition for nitrogen, fertilizer source loads 

for nitrogen and phosphorus, manure source loads for nitrogen 

and phosphorus, population density, land use, the base-flow 

index (estimated percentage base flow of total flow), presence of subsurface (tile) drains, mean basin slope, and mean 

annual precipitation.

Data for nitrogen in atmospheric deposition were derived 

from 1-km resolution grids of atmospheric deposition that 

were based on data from the National Atmospheric Deposition 

Program. Fertilizer and manure data were based on countylevel estimates assigned to specified land uses within each 

county and then summed for the area within each drainage 

basin; data included nitrogen and phosphorus in commercial 

fertilizers used on farms and in urban settings and nitrogen 

and phosphorus in livestock manure. More detail on atmospheric deposition, fertilizer, and manure data generation can 

be found in Ruddy and others (2006). In addition, the fertilizer 

data used in this report (version date October 21, 2008) contain a correction for a processing error in the non-farm versus 

farm allocation in Ruddy and others (2006) (J.M. Gronberg 

and N.E. Spahr, U.S. Geological Survey, written commun., 

2008). The population data were derived from a 30-m resolution grid of census block groups and population counts that 

were based on the 1990 and 2000 census of population and 

housing (U.S. Census Bureau, 1991, 2000). The source for land 

cover information was an enhanced version of the USGS 1992 

National Land Cover Dataset (Nakagaki and Wolock, 2005). 

The 30-m resolution satellite-imagery-based land-cover data 

were used to compile basin percentages by land classification. The base-flow index, mean basin slope, and mean annual 

precipitation were characterized by the average of the grid-cell 

data values in the drainage basin. Base flow, the component 

of streamflow that can be attributed to ground-water discharge 

into streams, was estimated from the national base-flow index 

1-km resolution dataset developed by Wolock (2003). Mean 

basin slope was derived from the USGS National Elevation 

Dataset (U.S. Geological Survey, 2003) gridded at 100-m 

resolution. The source for precipitation data was the 1-km 

resolution gridded data from the Daymet conterminous United 

States database (Thorton and Running, 1999); these data only 

were available through 1997. The basin area with subsurface 

(tile) drains was derived from 30-m resolution grids of 1992 

National Resources Inventory parameters compiled by the 

Natural Resources Conservation Service (U.S. Department 

of Agriculture, 1995, 2001).

Point-source discharge likely is an important source of 

nutrients to some streams. However, consistent and comprehensive national estimates of annual nitrogen and phosphorus 

loading from point sources were not available for the period of 

record. Therefore, point sources were not evaluated directly in 

this study. Urban point sources were evaluated indirectly using 

population density as a surrogate; non-urban point sources such 

as pulp and paper mills had no available surrogate. Selected 

data on the implementation of management practices are 

available in the 1992 and 1997 National Resources Inventory 

(U.S. Department of Agriculture, 1995, 2001); however, similar 

data are not available after 1997. In addition, several potentially 

influential conservation practices that had been present in the 

1992 National Resources Inventory, including conservation 

tillage systems, irrigation land management, irrigation land 

leveling, and subsurface drains, were no longer present in the 

1997 National Resources Inventory. Therefore, changes in the 

implementation of management practices were not evaluated 

directly in this study. More comprehensive data on point-source 

loading and the implementation of management practices likely 

would have improved the interpretation of trends in this report.

Analysis of Factors Affecting Trends

To help explain the factors affecting the trends over 

time, FA trends in concentration were compared to changes in 

nutrient sources during the same period. FA trends were used 

in this analysis because the effects of streamflow on concentration had been removed, allowing the effects of changes 

in nutrient sources over time to be more directly assessed. 

Figure 3. Total phosphorus concentrations from (A) 1993 to 2003 

and (B) 1993 to early 2002 at site 184. Note different y-axis scales. TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER

1993

1994

19951996199719981999

20002001

2002

0

1

2

3

4

1993199419951996199719981999

2000

200120022003

0

10

20

30

40

A

B
Approach 21

Nutrient sources included atmospheric deposition of nitrogen 

annually from 1993 to 2003; fertilizer inputs of phosphorus 

and nitrogen annually from 1993 to 2003; manure inputs 

of phosphorus and nitrogen in 1992, 1997, and 2002; and 

population density (a surrogate for urban sources of nutrients) 

in 1990 and 2000. The effects of changes in streamflow were 

assessed separately through a comparison of FA and NFA 

trends in the general discussion of trend results.

The goal of this analysis was not to explain all factors 

affecting each trend at individual sites—that was beyond 

the scope of this study. Rather, the goal was to identify on a 

broader scale those individual factors potentially affecting 

trends at a group of related sites. Groups of approximately 30 

or more related sites were selected so as to minimize within 

group variability. These site groups were:

1. Eastern United States, including

•	 New England and Mid-Atlantic NAWQA major river 

basin and

•	 South Atlantic-Gulf and Tennessee NAWQA major 

river basin; 

2. Central United States, including 

•	 Great Lakes, Ohio, Upper Mississippi, and Souris-RedRainy NAWQA major river basin,

•	 Missouri NAWQA major river basin, and

•	 Lower Mississippi, Arkansas-White-Red, and TexasGulf NAWQA major river basin; 

3. Western United States, including

•	 Rio Grande, Colorado, and Great Basin NAWQA 

major river basin,

•	 Pacific Northwest NAWQA major river basin, and

•	 California NAWQA major river basin;

4. undeveloped land-use classification (table 1);

5. greater than 40 percent agricultural land use in the basin;

6. greater than 10 percent urban land use in the basin;

7. base-flow index (estimated percentage base flow of total 

flow) greater than 50;

8. basin area with subsurface (tile) drains greater than 10 km2;

9. mean basin slope greater than 10 percent;

10. mean annual precipitation greater than 130 cm;

11. mean annual precipitation less than 80 cm;

12. reference streamflow greater than 100 m3/s;

13. reference streamflow less than 3 m3/s;

14. high source loading from atmospheric deposition (median 

annual yield from 1993 to 2003 greater than 500 kg/km2

for nitrogen);

15. high source loading from fertilizer (median annual yield 

from 1993 to 2003 greater than 2,000 kg/km2 for nitrogen 

and greater than 300 kg/km2

 for phosphorus); and 

16. high source loading from manure (median annual load 

from 1992 to 2002 greater than 1,200 kg/km2 for nitrogen 

and greater than 300 kg/km2

 for phosphorus).

Ancillary data used in grouping sites are presented in Appendix 1.

Figure 4. Mean annual loads of total nitrogen from 1993 to 2003 at site 153.

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

5.0*108

7.0*108

9.0*108

1.1*109

1.3*109

1.5*109

MEAN ANNUAL TOTAL NITROGEN LOAD,

IN KILOGRAMS PER YEAR

EXPLANATION

Standard error of the load estimate
22 Nutrient Trends in Streams and River of the United States, 1993–2003

To use the nutrient source data in these comparisons, a 

single number representing the percentage change in a given 

source over the study period (or the portion of the study 

period with available source data) was generated for each site 

(Appendix 1). When a source data series had annual observations (for example, the annual data series for fertilizer), the 

Sen slope estimate—calculated as the median of all possible 

pairwise slopes (Helsel and Hirsch, 1992)—was determined for 

that series at each site, divided by the initial value in the time 

series for that site to obtain a percentage, and then multiplied by 

11 (the number of years in the study period). When an explanatory data series had only two or three observations (for example, 

1990 and 2000 estimates of population density), the percentage 

change between the first year and the last year was determined 

for each site. When the value for the first year was zero, the percentage change value was treated as missing, because a meaningful percentage change could not be determined.

At sites with more than 50 percent of their drainage 

areas extending into Canada or Mexico, computed basin 

characteristics were based on the land area contained within 

the conterminous United States and thus were not representative of the characteristics of the full drainage areas. These 

sites—81 (Souris River near Sherwood, N. Dak.; 14.2 percent of drainage area in the United States), 82 (Souris River 

near Verendrye, N. Dak.; 31.9 percent of drainage area in the 

United States), and 97 (Poplar River at International Boundary, 

Mont.; 2.0 percent of drainage area in the United States)—

were excluded from the comparison of FA trends and changes 

in nutrient sources, though they are included in the maps and 

discussion of general trend results. In addition, drainage areas 

were not delineated for sites 49 (Cape Fear River at State 

Highway 42 near Brickhaven, N.C.), 208 (Willamette River 

at SP&S Railroad Bridge, Oreg.), 215 (Columbia River at 

Marker number 47 upstream of Willamette River, Oreg.), 220 

(Umatilla River at Westland Road at Hermiston, Oreg.), and 

239 (Columbia River at Northport, Wash.). These sites also 

were excluded from the comparison of FA trends and changes 

in nutrient sources, though they are included in the maps and 

general discussion of trend results. Finally, the FA trend in 

total phosphorus concentrations at site 184 (Salt River near 

Roosevelt, Ariz.) was an order of magnitude higher than any 

other FA trend in total phosphorus concentrations. As discussed earlier, in June and July of 2002, the Rodeo-Chediski 

fire burned over 1,170 km2

 in the Salt River drainage (Arizona 

Game and Fish Department, 2006); runoff from the burned 

area likely was a primary factor in the large increase in total 

phosphorus concentrations. Because a probable contributor to 

this outlier trend value could be determined and was different from other explanatory variables being examined, this site 

was excluded from the comparison of FA trends and changes 

in nutrient sources; however, it is included in the maps and 

general discussion of trend results.

Three methods were used to compare FA trends and 

changes in nutrient sources—weighted-least squares (bivariate) regression, the Kruskal-Wallis test, and multiple linear 

regression. Each of the three methods offers relative benefits 

and drawbacks; none are entirely suited to this application.

With weighted least-squares regression, each trend value 

can be weighted so that values known with more confidence 

(those with less variance) have a greater weight in the regression than values that are known with less confidence (those 

with greater variance) (Helsel and Hirsch, 1992). In this way, 

trends with less variance have a stronger effect on the regression. For this study, weights in the weighted least-squares 

regression were based on the inverse of the variance of the FA 

trend estimates and the mean squared error of the regression 

model for each constituent at each site:

w

s i

i ei

= +

1

2 2 V , (24)

where

wi is the weight for each site-constituent 

combination i;

si

2 is the variance of the FA trend estimate;

and

Vei

2 is the mean squared error of the regression 

model.

Relations were considered significant if the p-value was less 

than or equal to 0.05.

The weighted least-squares regression models were verified for normality and homoscedasticity of the residuals; results 

from models exhibiting heteroscedasticity or departure from a 

normal distribution were excluded. In addition, Cook’s distance 

was used to screen for the presence of influential observations. 

When Cook’s distance was greater than 2.4 (Helsel and Hirsch, 

1992), and(or) when extreme outliers were identified through 

visual inspection of the scatterplots, the results were excluded. 

Both untransformed data and transformed data initially were 

examined in the weighted-least squares procedure. Because 

of the large number of zero and negative values in both the 

response and explanatory data sets, an inverse hyperbolic sine 

transform was employed (Burbidge and others, 1988). Residuals 

from the models with transformed variables often were substantially less normal and(or) homoscedastic than the residuals 

from corresponding models using untransformed variables; as 

a result, untransformed variables were used exclusively in the 

final regression analyses reported here.

One disadvantage of the weighted least-squares regression 

(and the multiple linear regression described later in this section) is that it requires a linear distribution in the data used to fit 

the model and normality and homoscedasticity in the residuals. 

In addition, all trends are assumed equal with respect to their 

probability of being different from zero—that is, non-significant 

trends are not distinguished from significant trends. The alphalevel of 0.05 used for statistical significance in this study is 

somewhat arbitrary and without specific theoretical basis; it is 

one of several alpha-levels conventionally used in hypothesis 

testing. Some have argued that fixed alpha-levels are unnecessarily restrictive and provide results that are relatively uninformative (for example, Anderson and others, 2000).

The non-parametric Kruskal-Wallis test can discriminate between non-significant and significant trends. For the 

Kruskal-Wallis test, the FA trends in each of the 16 site groups 
Approach 23

were classified into three categories: significantly upward, 

significantly downward, and non-significant. The corresponding changes in nutrient sources at the sites within each of 

those classifications were then compared using the KruskalWallis test to determine whether the changes in source differed 

among the three trend classifications. If a significant (p-value 

less than or equal to 0.05, based on the chi-square distribution) 

difference was detected using the Kruskal-Wallis test, a posthoc Tukey’s multiple comparison test was used on the ranks 

of the data to evaluate pairwise differences in medians. The 

Kruskal-Wallis test does not require a specific data distribution 

and is not sensitive to outliers; therefore, it can be used with 

data sets that might not be appropriate for use in parametric 

tests such as linear regression (Helsel and Hirsch, 1992). However, if the assumptions of these parametric tests can be met, 

non-parametric tests like Kruskal-Wallis may have less power 

to detect real effects. In addition, the Kruskal-Wallis test cannot incorporate the errors in the trend estimates, giving equal 

weight to all estimates.

For the groups that included sites in the Eastern, Central, 

and Western United States and sites in the undeveloped landuse classification, sample sizes were large enough to permit 

the evaluation of multiple explanatory variables using multiple 

linear regression. FA trends in total phosphorus were evaluated 

in relation to changes in population density and phosphorus 

loading from fertilizer and manure. FA trends in total nitrogen 

and nitrate were evaluated in relation to changes in population 

density and nitrogen loading from atmospheric deposition, 

fertilizer, and manure. The most parsimonious model based 

on Akaike’s Information Criterion was identified in a stepwise 

manner using the stepAIC function implemented in the MASS 

library (Venables and Ripley, 2002) of S-plus (Insightful 

Corporation, 2005). The final best-fit models were verified 

for normality and homoscedasticity of the residuals; results 

from models exhibiting heteroscedasticity or departure from a 

normal distribution were excluded. As with the weighted-least 

squares bivariate regression, both untransformed and transformed (using an inverse hyperbolic sine transform) response 

and explanatory variables were evaluated initially, but because 

residuals from the models with transformed variables often 

were substantially less normal and(or) homoscedastic than 

the residuals from corresponding models using untransformed 

variables, untransformed variables were used exclusively in 

the final multiple linear regression analyses reported here.

Although the explanatory factors identified through these 

three methods have a significant relation to the FA nutrient 

trends, the specific cause-and-effect relations responsible for 

the observed relations are not always clear, and inferences 

regarding causes should be considered as hypotheses.

Regional Trends

Consistent trends in nutrient concentrations may be 

present across a given area of the Nation. These areas may 

be defined in various ways, including geographically (for 

example, Eastern, Central, or Western United States), by 

major landscape features (for example, agricultural or urban 

land area), or by site characteristic (for example, mean annual 

streamflow). The areas may be spatially contiguous or related 

by some physical characteristic, though spatially disjointed. 

Regional FA and NFA trends in concentration were examined 

using the Regional Seasonal Kendall test—the Regional 

Kendall test (Helsel and Frans, 2006) modified to account 

for seasonality. The Regional Kendall test computes a test 

for trend for all sites within a region by computing a score 

for each site and adding the scores to compute the total for 

the region (Helsel and Frans, 2006). The Regional Seasonal 

Kendall test takes this procedure one step further by computing a score for each season at each site and totaling those 

scores for the region. The Regional Seasonal Kendall test 

was built into the statistical program ESTREND (Schertz 

and others, 1991) recoded in S-plus version 7.0 (Insightful 

Corporation, 2005).

The Mann-Kendall test statistic S is calculated for a site 

by comparing each (t, y) data pair, where t is time and y is 

the response variable of interest, to all other (t, y) data pairs 

in a pairwise fashion, and subtracting the number of data 

pairs where y decreases as t increases (M) from the number 

of data pairs where y increases as t increases (P), with ties 

not counted (Helsel and Hirsch, 1992).

S = P – M. (25)

With n data pairs, the variance of S is

Var S nn n ( ) = ( )( ) − + 12 5

18 , (26)

If there are ties, an adjustment is made to the computation of 

variance (Helsel and Hirsch, 1992).

The Seasonal Kendall test accounts for seasonality by 

calculating S within each of m seasons separately (Helsel and 

Hirsch, 1992).

Sk = =

∑SS

S

m

1

, (27)

where

Sk is the Seasonal Kendall test statistic;

m is the number of seasons;

and

SS is the Mann-Kendall test statistic for each of 

the S=1 to m seasons.

Sk

 is asymptotically normal with mean of 0 and variance, 

Var(SK), of

Var S Var S Cov S S K S

S

m

S Q

Q S

m

S

m

( ) = ( ) + = = = +

−

∑ ∑ ∑ 1 1 1

1

2 (, ), (28)

where

Var(SS) is the variance of SS;

and

Cov(SS, SQ) is the covariance between seasons S and Q.
24 Nutrient Trends in Streams and River of the United States, 1993–2003

The covariance is computed as described in Hirsch and Slack 

(1984), building on work by Dietz and Killeen (1981), and 

accounts for serial dependence. When serial dependence exists, 

the null hypothesis of no trend will tend to be more frequently 

rejected than it should be unless serial dependence is accounted 

for by computing the covariance between seasons.

The Regional Kendall test substitutes location for season 

in the Seasonal Kendall test and computes the Mann-Kendall 

test statistic, SL

, for each of n locations (Helsel and Frans, 

2006). The overall regional test statistic SR is computed following equation 27, with SL

 substituted for SS, and the variance of SR is computed following equation 28, again with 

SL

 substituted for SS (Douglas and others, 2000). When the 

product of the number of sites and the number of years is 

more than about 25, the distribution of SR will be approximately normal (Helsel and Frans, 2006). Calculating the 

variance following equation 28 accounts for spatial correlation 

among the sites (Douglas and others, 2000), which may occur 

when closely spaced sites repeatedly sample one portion of a 

defined region. Just as with serial dependence, when spatial 

correlation exists, the null hypothesis of no regional trend 

will tend to be more frequently rejected than it should be 

unless the spatial correlation is accounted for by computing 

the covariance between sites.

The Regional Seasonal Kendall test incorporates the 

features of both the Seasonal Kendall test and the Regional 

Kendall Test. The overall regional and seasonal test statistic, 

ST , is the sum of the individual Mann-Kendall test statistics, 

SSL, from each of the m seasons at each of the n locations.

S S T SL

L

n

S

m

= ==

∑∑ 11

(29)

The variance of ST , Var(ST), is computed from the covariance 

between each season at each site, as with the Seasonal Kendall 

test, and between each site for each season.

Var S Var S

Cov S S

T SL

L

n

S

m

SL QL

L

n

Q S

m

S

m

( ) = ( )

+

==

= = + =

−

∑∑

∑∑

11

111

1

2 (, ) ∑

+ ∑∑∑ = = +

−

=

2 11

1

1

Cov S S SL SK

K L

n

L

n

S

m

(, )

, (30)

where

Var(SSL) is the variance of SSL ;

Cov(SSL, SQL) is the covariance between seasons S and Q

at location L;

and

Cov(SSL, SSK) is the covariance between locations L and K

in season S.

The remaining covariance is assumed to be equal to zero.

The variance of ST

 can be used to compute the test 

statistic ZT

 and p-value of the normal approximation for the 

Regional Seasonal Kendall test, with a continuity correction 

for ST

.

Z

S

Var S

S

Var S

T

T

T

T

T






 	



 	

«

¬

®

®

®

­

®

®

®

1

0

1

if ST is greater than 0

if ST is equal to 0

if ST is less than 0

(31)

The null hypothesis of the Regional Seasonal Kendall test 

is that there is no regional trend. Rejection of the null hypothesis will occur when a trend in the same direction occurs at 

many of the individual locations. Failure to reject the null 

hypothesis may result from a lack of trend at most locations or 

from trends in opposite directions at different locations cancelling one another out. A general increase or decrease at an individual location occurring in the same direction as the regional 

pattern provides support for a significant regional trend, even 

if the trend at that individual location is not significant on its 

own (Helsel and Frans, 2006). Regional trend results were 

considered significant if the p-value was less than or equal to 

0.10. The higher alpha value (as compared to the 0.05 value 

used in other statistical analyses herein) was used because 

of the potential loss of power resulting from the recensoring 

process described in the following paragraph.

For the Regional Seasonal Kendall test, FA concentrations were calculated as residuals from a locally weighted 

scatterplot smooth (LOWESS) of log-transformed concentrations on log-transformed streamflow with a span of 0.75. A 

maximum of 5 percent censoring was accepted in the LOWESS 

flow-adjustment. For the NFA analysis, concentrations were 

recensored to the highest detection limit for each constituent 

among all sites, and a maximum of 50 percent censoring was 

accepted. This involved some loss of information and possibly 

loss of power to detect true trends (Helsel and Hirsch, 1992).

 For both NFA and FA concentrations, the number of 

seasons was set to four (October–December, January–March, 

April–June, July–September), the highest annual sampling frequency inclusive of the largest number of sites. A small number 

of sites had an average annual sampling frequency less than four 

and were excluded from the Regional Seasonal Kendall analysis, including sites 61 (South Prong Alafia River near Lithia, 

Fla.), 97 (Poplar River at International Boundary, Mont.), 106 

(Lonetree Creek near Greeley, Colo.), and 169 (Onion Creek at 

U.S. Highway 183, Austin, Tex.) for total phosphorus; sites 61, 

97, 106, and 179 (Colorado River at Lees Ferry, Ariz.) for total 

nitrogen; and sites 106, 159 (Neches River near Neches, Tex.), 

160 (Neches River near Rockland, Tex.), 163 (Trinity River 

near Crockett, Tex.), and 174 (Colorado River near Kremmling, 

Colo.) for nitrate. When multiple observations occurred in a 

single season at a site, the observation closest to the midpoint of 

that season was used. The same 16 site groups that were used in 

the analysis of factors affecting the trends over time were used 

in the Regional Seasonal Kendall analysis.

A similar regional analysis also could have been done for 

streamflow and nutrient loads. In this study, trends in streamflow were determined only at sites used in the analysis of trends 

in concentration and load. The main goal of the analysis was 
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 25

to determine changes in streamflow at sites where changes in 

nutrient concentrations and loads also would be determined, so 

that the effects of changes in streamflow on changes in nutrient 

concentrations and loads could be evaluated. A more complete 

regional and national analysis of streamflow trends would include 

additional sites with long-term streamflow records that may not 

have appropriate long-term records of nutrient concentrations. In 

addition, to use the Regional Seasonal Kendall test on nutrient 

loads, monthly or annual load estimates for each site and constituent would be required. However, in this study, the trends in load 

were determined using sample estimates of the coefficients in 

equation 17; they were not determined through a two-stage process involving estimation of monthly or annual loads followed by 

some independent test for trend. Therefore, load estimates were 

not needed and were not generated. Even if they had been, such 

a two-stage process would not account for the fact that loads are 

estimated with sampling error; as a result, hypothesis tests based 

on the estimated covariance matrix of the second-stage trend test 

would be biased.

Nutrient Trends in Streams and Rivers 

of the United States, 1993–2003

FA trends in concentration (the trends that would have 

occurred in the absence of natural changes in streamflow), 

NFA trends in concentration (the trends resulting from both 

natural and anthropogenic factors), and trends in load (trends 

in the nutrient mass transported downstream) from 1993 to 

2003 are presented in the following sections for total phosphorus, total nitrogen, and nitrate. Because the interpretation of 

these trends can be improved by understanding how streamflow has changed during the same period, trends in streamflow 

are presented first. The nutrient trends follow, and they are 

evaluated spatially to determine whether a consistent pattern 

of trends occurred across groups of sites at multiple locations. 

Relations between the trends and temporal changes in streamflow and nutrient sources then are examined.

General geographic areas are used periodically in the 

following sections to group results; these geographic areas 

(table 1, fig. 1, appendix 1) are categorized as follows:

•	 Eastern—the New England and Mid-Atlantic 

(Northeast) and South Atlantic-Gulf and Tennessee 

(Southeast) NAWQA major river basins.

•	 Central—the Great Lakes, Ohio, Upper Mississippi, 

and Souris-Red-Rainy; Missouri; and Lower 

Mississippi, Arkansas-White-Red, and Texas-Gulf 

NAWQA major river basins.

•	 Western—the Rio Grande, Colorado, and Great 

Basin (Southwest); Pacific Northwest; and California 

(Southwest) NAWQA major river basins.

The site coverage in some portions of these geographic areas 

was sparse. Results are discussed below in terms of the sites 

included in the analysis; care should be taken with spatial 

extrapolation of these results to unrepresented areas.

Streamflow Trends

Significant (p-value less than or equal to 0.05) trends in 

streamflow occurred at 56 (23 percent) of the 244 sites from 

1993 to 2003 (fig. 5, table 2, Appendix 2). At all but two sites, 

these trends were downward. These downward trends primarily 

occurred at sites in the Central and Southwestern United States 

and parts of the Southeastern United States. At sites in these 

three areas, trends overall were either downward or nonsignificant. Trends at sites in the Northeastern and Northwestern 

United States were almost entirely nonsignificant.

Drought conditions in the latter part of the study period 

likely were the predominant influence contributing to the 

widespread downward trends in streamflow at sites in the 

Southeastern, Central, and Southwestern United States. The 

Southeastern United States experienced unusually dry conditions each year between 1998 and 2002 (National Oceanic 

and Atmospheric Administration, 2002). Snowpack in the 

Rocky Mountains, a large source of water to rivers on both 

sides of the continental divide, was less than the long-term 

average between 2000 and 2003 (U.S. Army Corps of 

Engineers, 2006; U.S. Department of Agriculture, 2007). 

Statewide precipitation levels in Colorado between July 2001 

and June 2002 and in Nebraska between December 2001 and 

July 2002 were at the lowest level of any single year since 

1895 (National Oceanic and Atmospheric Administration, 

2002). From 2000 to 2003, moderate to severe drought conditions were observed in parts of Missouri (National Oceanic 

and Atmospheric Administration, 2003). Prolonged belowaverage precipitation in the Southwestern United States 

from 1998 to 2002 resulted in values of the Palmer Drought 

Index—an index of the scope, severity, and frequency of 

protracted periods of abnormally dry or wet weather—during 

2002 that were at the lowest level observed in 100 years 

(National Oceanic and Atmospheric Administration, 2002). 

In 2002, Colorado, Arizona, and Nevada experienced the 

driest September through August on record and Utah experienced the driest January through August on record (National 

Oceanic and Atmospheric Administration, 2002). In 2003, 

below-average precipitation and above-average temperatures 

contributed to persistent or worsening drought conditions in 

the Central and Southwestern United Sates (National Oceanic 

and Atmospheric Administration, 2003). In addition, aboveaverage precipitation occurred early in the trend period in the 

Central United States—the worst floods on record in southern 

Wisconsin, Iowa, Missouri, and Illinois occurred between June 

and August of 1993, and January through July 1993 was the 

wettest period in the upper Mississippi River Basin and the 

second wettest in the Missouri River Basin since 1895 (Bell 

and Janowiak, 1995). Precipitation in 2003 was near average 

in the Northwestern United States and above average in most 

states east of the Mississippi River, where North Carolina, 

Virginia, and Maryland experienced the wettest year on record 

(National Oceanic and Atmospheric Administration, 2003).

This analysis of streamflow trends included only sites 

used in the analysis of trends in one or more nutrient constituents. The main goal of the analysis was to determine changes in 
26 Nutrient Trends in Streams and River of the United States, 1993–2003

streamflow at sites where changes in nutrient concentrations and 

loads also would be determined, so that the effects of changes 

in streamflow on changes in nutrient concentrations and loads 

could be evaluated. A comprehensive national analysis of 

streamflow trends would include additional sites with long-term 

streamflow records that may not have appropriate long-term 

records of nutrient concentrations. Because not all sites shown 

in figure 5 were included in the trend analyses for each constituent (see table 1), maps showing trends in concentration and load 

for each constituent are presented together in the following sections with maps showing trends in streamflow from figure 5 at 

only those sites included in the analyses for that constituent.

Total Phosphorus

Trends from 1993 to 2003

Significant (p-value less than or equal to 0.05) FA trends 

in total phosphorus concentrations occurred at 84 (49 percent) of 171 sites from 1993 to 2003 (fig. 6B, tables 3 and 

4, Appendix 3). Downward FA trends only occurred at 27 

(16 percent) of the sites, indicating that at the majority of 

sites, changes in phosphorus use, implementation of pollutioncontrol strategies, or other anthropogenic activities were 

not contributing to significant decreases in total phosphorus 

concentrations in streams, or any reductions that occurred 

were offset by other anthropogenic activities in the watershed 

that increased concentrations. Upward FA trends occurred at 

57 (33 percent) of the sites, indicating increases in phosphorus 

sources and(or) transport at one-third of the sites. At sites in 

the Northeastern, Central, and Southwestern United States, 

FA trends in total phosphorus concentrations were generally 

upward or nonsignificant (fig. 6B). At sites in the Southeastern 

and Northwestern United States, FA trends were a mixture of 

upward, downward, and nonsignificant.

There were fewer significant NFA trends than FA trends 

in total phosphorus concentrations; NFA trends were significant at 69 (40 percent) of 171 sites from 1993 to 2003 

(fig. 6C, tables 3 and 5, Appendix 3). Downward NFA trends 

only occurred at 28 (16 percent) of the sites, indicating that 

at the majority of sites, total phosphorus concentrations in 

streams were not decreasing significantly. However, total 

phosphorus concentrations in streams were increasing at only 

about one-quarter of the sites—upward NFA trends occurred 

at 41 (24 percent) of the 171 sites. At the majority of sites 

(60 percent) nationwide, total phosphorus concentrations 

in streams were not changing significantly. At sites in the 

Northeastern and Central United States, NFA trends in total 

phosphorus concentrations were generally upward or nonsignificant (fig. 6C). At sites in the Southeastern and Western 

United States, NFA trends were a mixture of upward, downward, and nonsignificant.

The primary difference between the number of significant FA and NFA trends was a smaller number of upward 

NFA trends. In particular, relatively fewer upward NFA trends 

than upward FA trends occurred at sites in the Central and 

Southwestern United States, where most of the significant 

(downward) trends in streamflow occurred (fig. 6A). The 

upward FA trends at these sites (fig. 6B) indicate that phosphorus sources may have been increasing between 1993 and 2003. 

The downward trends in streamflow at many of these sites 

likely resulted from a decrease in precipitation during drought 

conditions in the latter part of the study period, which would 

have contributed to a decrease in surface runoff. The increase 

in source indicated by the upward FA trend likely was offset 

by the effects of decreasing surface runoff indicated by the 

downward streamflow trend, resulting in fewer upward NFA 

trends. Without the decrease in streamflow and associated 

surface runoff at these sites, in-stream concentrations probably 

would have been higher.

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EXPLANATION

Direction of trend

Upward

Downward

No significant trend

Magnitude of trend (percent from 1993 to 2003)

Less than or equal to 33.0

33.1–66.0

Greater than or equal to 66.1

Reference streamflow (cubic meters per second)

Less than or equal to 8.49

8.50–84.99

Greater than or equal to 85.0

Figure 5. Trends in streamflow at selected sites in the United States.
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 27

Table 2. Trends in daily mean streamflow from 1993 to 2003.—Continued

[See Appendix 2 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Streamflow

station

number

Reference

streamflow,

in cubic

meters per

second1

Trend, in percent from 

1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

1 01122610 Shetucket River at South Windham, Conn. 01122610 13.70 –20.09 35.75 –52.96 0.407

2 01124000 Quinebaug River at Quinebaug, Conn. 01124000 5.00 –24.00 36.50 –57.68 0.358

3 01127000 Quinebaug River at Jewett City, Conn. 01127000 22.25 –3.74 63.17 –43.21 0.887

4 01184000 Connecticut River at Thompsonville, Conn. 01184000 379.66 –10.12 25.25 –35.51 0.529

5 01184490 Broad Brook at Broad Brook, Conn. 01184490 0.63 –18.36 15.06 –42.07 0.247

6 01188090 Farmington River at Unionville, Conn. 01188090 16.17 –24.01 16.08 –50.25 0.204

7 01189995 Farmington River at Tariffville, Conn. 01189995 27.44 –25.45 13.76 –51.15 0.173

8 01192500 Hockanum River near East Hartford, Conn. 01192500 3.15 –21.67 12.63 –45.52 0.188

9 01193500 Salmon River near East Hampton, Conn. 01193500 2.95 –11.31 56.45 –49.72 0.679

10 01196500 Quinnipiac River at Wallingford, Conn. 01196500 4.80 –7.19 39.65 –38.32 0.720

11 01205500 Housatonic River at Stevenson, Conn. 01205500 43.66 –4.82 86.90 –51.53 0.886

12 01208500 Naugatuck River at Beacon Falls, Conn. 01208500 10.84 –13.16 35.79 –44.46 0.536

13 01208990 Saugatuck River near Redding, Conn. 01208990 0.47 17.58 164.94 –47.82 0.696

14 01209710 Norwalk River at Winnipauk, Conn. 01209710 0.87 –0.88 93.23 –49.16 0.979

15 01357500 Mohawk River at Cohoes, N.Y. 01357500 91.16 23.29 89.21 –19.66 0.338

16 01377000 Hackensack River at Rivervale, N.J. 01377000 1.72 –23.87 20.21 –51.78 0.242

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 01382500 0.42 –46.63 100.42 –85.79 0.352

18 01387500 Ramapo River near Mahwah, N.J. 01387500 2.80 14.67 151.39 –47.69 0.732

19 01389500 Passaic River at Little Falls, N.J. 01389500 14.48 –18.58 139.20 –72.29 0.708

20 01391500 Saddle River at Lodi, N.J. 01391500 1.90 4.46 81.35 –39.83 0.877

21 01394500 Rahway River near Springfield, N.J. 01394500 0.47 17.68 78.33 –22.34 0.443

22 01395000 Rahway River at Rahway, N.J. 01395000 0.65 10.34 89.87 –35.87 0.722

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 01396660 0.32 4.20 93.78 –43.97 0.897

24 01398000 Neshanic River at Reaville, N.J. 01398000 0.33 3.03 175.69 –61.50 0.953

25 01402000 Millstone River at Blackwells Mills, N.J. 01402000 6.82 –14.34 37.97 –46.82 0.524

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 01403300 18.39 –17.31 43.06 –52.20 0.497

27 01408000 Manasquan River at Squankum, N.J. 01408000 1.54 –16.44 25.75 –44.48 0.389

28 01408500 Toms River near Toms River, N.J. 01408500 5.09 –10.02 31.26 –38.31 0.584

29 01409500 Batsto River at Batsto, N.J. 01409500 2.99 –23.58 13.30 –48.46 0.181

30 01411500 Maurice River at Norma, N.J. 01411500 3.47 1.18 76.11 –41.87 0.967

31 01438500 Delaware River at Montague, N.J. 01438500 108.40 6.27 63.49 –30.92 0.782

32 01443500 Paulins Kill at Blairstown, N.J. 01443500 3.94 –20.60 65.47 –61.90 0.538

33 01463500 Delaware River at Trenton, N.J. 01463500 240.81 0.93 63.68 –37.76 0.970

34 01467150 Cooper River at Haddonfield, N.J. 01467150 0.59 –28.62 –3.38 –47.26 0.029

35 01477120 Raccoon Creek near Swedesboro, N.J. 01477120 0.82 –12.68 38.60 –44.98 0.565

36 01491000 Choptank River near Greensboro, Md. 01491000 1.89 43.84 332.25 –52.13 0.517

37 01578310 Susquehanna River at Conowingo, Md. 01578310 764.53 –21.03 32.07 –52.78 0.368

38 01594440 Patuxent River near Bowie, Md. 01594440 7.69 1.20 92.75 –46.87 0.971

39 01614500 Conococheague Creek at Fairview, Md. 01614500 13.51 –38.33 33.36 –71.48 0.219

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 01646580 213.18 –25.99 108.51 –73.73 0.569

41 01668000 Rappahannock River near Fredericksburg, Va. 01668000 32.46 –42.69 73.75 –81.09 0.325

42 01673000 Pamunkey River near Hanover, Va. 01673000 17.17 –46.94 59.54 –82.35 0.259

43 01674500 Mattaponi River near Beulahville, Va. 01674500 9.31 –53.89 96.74 –89.19 0.296

44 02035000 James River at Cartersville, Va. 02035000 147.16 –34.78 38.64 –69.32 0.267

45 02041650 Appomattox River at Matoaca, Va. 02041650 18.95 –36.08 99.23 –79.49 0.440

46 02085000 Eno River at Hillsborough, N.C. 02085000 0.54 0.82 201.95 –66.34 0.988

47 02089500 Neuse River at Kinston, N.C. 02089500 48.43 23.45 172.20 –44.01 0.602

48 02091500 Contentnea Creek at Hookerton, N.C. 02091500 10.21 52.67 283.87 –39.28 0.368

49 0210215985 Cape Fear River at State Highway 42 near Brickhaven, N.C. 02102500 49.27 –6.35 101.73 –56.52 0.867

50 02175000 Edisto River near Givhans, S.C. 02175000 67.39 –51.00 18.36 –79.71 0.113

51 02198500 Savannah River near Clyo, Ga. 02198500 384.30 –51.95 –5.97 –75.45 0.032

52 02213700 Ocmulgee River near Warner Robins, Ga. 02213700 49.94 –40.36 –4.21 –62.87 0.033

53 02215500 Ocmulgee River at Lumber City, Ga. 02215500 147.53 –47.60 14.40 –76.00 0.105

54 02223600 Oconee River at Interstate 16, near Dublin, Ga. 02223500 113.18 –59.99 –9.57 –82.30 0.028

55 02226010 Altamaha River near Gardi, Ga. 02226000 336.17 –51.45 23.90 –80.98 0.131

56 02226582 Satilla River at GA 15&121, near Hoboken, Ga. 02226500 10.70 –68.11 73.46 –94.14 0.186

57 02271500 Josephine Creek near De Soto City, Fla. 02271500 0.86 –3.83 270.94 –75.07 0.955
28 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 2. Trends in daily mean streamflow from 1993 to 2003.—Continued

[See Appendix 2 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Streamflow

station

number

Reference

streamflow,

in cubic

meters per

second1

Trend, in percent from 

1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

58 02295420 Payne Creek near Bowling Green, Fla. 02295420 2.34 –41.53 119.85 –84.45 0.427

59 02296750 Peace River at Arcadia, Fla. 02296750 14.38 –35.78 183.72 –85.46 0.559

60 02300700 Bullfrog Creek near Wimauma, Fla. 02300700 0.61 –25.78 42.03 –61.22 0.368

61 02301300 South Prong Alafia River near Lithia, Fla. 02301300 1.60 –41.87 211.34 –89.15 0.526

62 02302500 Blackwater Creek near Knights, Fla. 02302500 0.95 –59.09 112.22 –92.11 0.287

63 02303000 Hillsborough River near Zephyrhills, Fla. 02303000 3.68 –14.21 127.43 –67.64 0.758

64 02314500 Suwannee River at U.S. 441, at Fargo, Ga. 02314500 17.03 –83.56 –22.23 –96.52 0.023

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 02318500 8.10 –18.20 339.98 –84.79 0.815

66 02335870 Sope Creek near Marietta, Ga. 02335870 0.92 –37.34 7.60 –63.51 0.090

67 02338000 Chattahoochee River near Whitesburg, Ga. 02338000 115.56 –48.48 –10.88 –70.22 0.018

68 02344040 Chattahoochee River near Steam Mill, Ga. 02343801 260.33 –28.21 21.34 –57.53 0.216

69 02353000 Flint River at Newton, Ga. 02353000 168.15 –46.12 4.10 –72.11 0.066

70 02388520 Oostanaula River at Rome, Ga. 02388500 67.45 –11.15 55.96 –49.38 0.681

71 02492000 Bogue Chitto River near Bush, La. 02492000 47.14 –31.18 5.95 –55.29 0.090

72 03353637 Little Buck Creek near Indianapolis, Ind. 03353637 0.30 –47.86 28.18 –78.79 0.156

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 03611500 6,996.15 –18.06 20.92 –44.47 0.316

74 04063700 Popple River near Fence, Wis. 04063700 2.66 –35.22 –9.96 –53.39 0.010

75 04073468 Green Lake Inlet at County Highway A near Green 

Lake, Wis.

04073468 0.95 –44.81 7.95 –71.79 0.083

76 04087000 Milwaukee River at Milwaukee, Wis. 04087000 10.89 –29.12 6.87 –52.99 0.100

77 0422026250 Northrup Creek at North Greece, N.Y. 0422026250 0.21 58.64 165.31 –5.14 0.079

78 04232034 Irondequoit Creek at Railroad Mills near Fishers, N.Y. 04232034 0.90 –26.71 –1.44 –45.51 0.040

79 0423204920 East Branch Allen Creek at Pittsford, N.Y. 0423204920 0.15 –20.40 19.78 –47.10 0.274

80 0423205025 Irondequoit Creek at Empire Boulevard at Rochester, N.Y. 0423205025 3.07 –20.92 9.11 –42.69 0.153

81 05114000 Souris River near Sherwood, N. Dak. 05114000 0.15 935.99 9,496.68 11.84 0.040

82 05120000 Souris River near Verendrye, N. Dak. 05120000 1.22 84.53 678.32 –56.25 0.404

83 05287890 Elm Creek near Champlin, Minn. 05287890 0.72 –60.06 8.68 –85.32 0.072

84 05427718 Yahara River at Windsor, Wis. 05427718 0.75 –36.21 –19.03 –49.74 <0.001

85 05427948 Pheasant Branch at Middleton, Wis. 05427948 0.09 –9.68 23.68 –34.05 0.525

86 054310157 Jackson Creek Tributary near Elkhorn, Wis. 054310157 0.04 –8.53 67.45 –50.03 0.773

87 05500000 South Fabius River near Taylor, Mo. 05500000 5.14 –85.60 –55.45 –95.34 0.001

88 05514500 Cuivre River near Troy, Mo. 05514500 5.06 –61.49 23.05 –87.95 0.107

89 05525500 Sugar Creek at Milford, Ill. 05525500 5.13 –56.05 39.65 –86.17 0.163

90 05531500 Salt Creek at Western Springs, Ill. 05531500 3.85 –3.42 30.52 –28.54 0.821

91 05532500 Des Plaines River at Riverside, Ill. 05532500 16.79 –21.88 14.94 –46.91 0.210

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 05540275 0.18 –40.47 22.19 –71.00 0.158

93 05586100 Illinois River at Valley City, Ill. 05586100 824.87 –59.42 –31.58 –75.93 0.001

94 07018100 Big River near Richwoods, Mo. 07018100 15.97 –61.09 –33.55 –77.21 0.001

95 07022000 Mississippi River at Thebes, Ill. 07022000 8,873.13 –54.17 –35.15 –67.62 0.000

96 06088500 Muddy Creek at Vaughn, Mont. 06088500 2.26 –8.24 10.67 –23.92 0.369

97 06178000 Poplar River at International Boundary, Mont. 06178000 0.11 –17.28 140.85 –71.59 0.728

98 06274300 Bighorn River at Basin, Wyo. 06274300 55.72 –54.76 –9.76 –77.32 0.024

99 06329500 Yellowstone River near Sidney, Mont. 06329500 338.31 –49.57 –21.70 –67.52 0.002

100 06338490 Missouri River at Garrison Dam, N. Dak. 06338490 510.45 10.16 102.10 –39.96 0.755

101 06461500 Niobrara River near Sparks, Nebr. 06461500 22.26 –5.33 6.04 –15.49 0.344

102 06468250 James River above Arrowwood Lake near Kensal, N. Dak. 06468250 0.33 127.28 1,477.31 –67.25 0.406

103 06713500 Cherry Creek at Denver, Colo. 06713500 0.61 40.29 158.97 –24.00 0.279

104 06752260 Cache La Poudre River at Fort Collins, Colo. 06752260 1.29 –43.47 70.82 –81.29 0.312

105 06752280 Cache La Poudre River above Boxelder Creek, near 

Timnath, Colo.

06752280 0.85 –62.36 74.41 –91.88 0.212

106 06753990 Lonetree Creek near Greeley, Colo. 06753990 0.41 –93.30 –80.20 –97.74 <0.001

107 06754000 South Platte River near Kersey, Colo. 06754000 26.64 –46.40 10.26 –73.95 0.090

108 06775900 Dismal River near Thedford, Nebr. 06775900 6.03 6.81 12.00 1.85 0.007

109 06800000 Maple Creek near Nickerson, Nebr. 06800000 3.44 –71.28 –42.92 –85.55 <0.001

110 06805500 Platte River at Louisville, Nebr. 06805500 324.79 –61.40 –44.36 –73.23 <0.001

111 06817700 Nodaway River near Graham, Mo. 06817700 28.76 –90.02 –74.40 –96.11 <0.001

112 06818000 Missouri River at St. Joseph, Mo. 06818000 1,821.07 –43.38 –20.12 –59.87 0.001
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 29

Table 2. Trends in daily mean streamflow from 1993 to 2003.—Continued

[See Appendix 2 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Streamflow

station

number

Reference

streamflow,

in cubic

meters per

second1

Trend, in percent from 

1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

113 06902000 Grand River near Sumner, Mo. 06902000 100.76 –89.05 –63.62 –96.71 <0.001

114 06905500 Chariton River near Prairie Hill, Mo. 06905500 38.02 –88.81 –61.04 –96.79 0.001

115 06921070 Pomme De Terre River near Polk, Mo. 06921070 4.02 –72.43 –30.84 –89.01 0.006

116 06926510 Osage River below St. Thomas, Mo. 06926510 387.34 –84.61 –56.94 –94.50 <0.001

117 06930800 Gasconade River above Jerome, Mo. 06930800 62.90 –67.50 –44.51 –80.97 <0.001

118 06934500 Missouri River at Hermann, Mo. 06934500 3,945.46 –63.20 –43.52 –76.02 <0.001

119 07047942 L'Anguille River near Colt, Ark. 07047942 6.03 52.18 217.98 –27.17 0.264

120 07053250 Yocum Creek near Oak Grove, Ark. 07053250 1.09 –58.98 –36.26 –73.60 <0.001

121 07056000 Buffalo River near St Joe, Ark. 07056000 12.99 –49.76 0.41 –74.86 0.051

122 07060500 White River at Calico Rock, Ark. 07060500 363.03 –68.03 –42.08 –82.35 <0.001

123 07060710 North Sylamore Creek near Fifty Six, Ark. 07060710 0.63 –55.02 –24.15 –73.33 0.003

124 07066110 Jacks Fork above Two River, Mo. 07066000 13.93 –53.92 –32.31 –68.64 <0.001

125 07068000 Current River at Doniphan, Mo. 07068000 91.97 –48.45 –29.10 –62.52 <0.001

126 07077500 Cache River at Patterson, Ark. 07077500 15.65 –19.39 81.46 –64.19 0.603

127 07077700 Bayou DeView near Morton, Ark. 07077700 2.02 189.77 832.53 –9.96 0.075

128 07103700 Fountain Creek near Colorado Springs, Colo. 07103700 0.52 –46.90 37.19 –79.44 0.191

129 07103780 Monument Creek above North Gate Boulevard at 

United States Air Force Academy, Colo.

07103780 0.22 –14.33 116.13 –66.04 0.743

130 07105500 Fountain Creek at Colorado Springs, Colo. 07105500 1.64 –30.06 86.76 –73.81 0.476

131 07105530 Fountain Creek below Janitell Road below Colorado 

Springs, Colo.

07105530 3.31 –10.10 62.13 –50.15 0.723

132 07106300 Fountain Creek near Pinon, Colo. 07106300 3.42 4.53 134.55 –53.41 0.914

133 07106500 Fountain Creek at Pueblo, Colo. 07106500 3.70 –2.33 120.06 –56.65 0.955

134 07189000 Elk River near Tiff City, Mo. 07189000 20.69 –64.28 –35.45 –80.23 0.001

135 07195500 Illinois River near Watts, Okla. 07195500 16.58 –48.67 –18.72 –67.59 0.004

136 07195865 Sager Creek near West Siloam Springs, Okla. 07195865 0.41 –20.34 40.30 –54.78 0.431

137 07196000 Flint Creek near Kansas, Okla. 07196000 2.78 –51.59 –18.07 –71.40 0.007

138 07196500 Illinois River near Tahlequah, Okla. 07196500 24.71 –50.46 –18.63 –69.83 0.006

139 07197000 Baron Fork at Eldon, Okla. 07197000 8.15 –62.23 –33.05 –78.69 0.001

140 07227500 Canadian River near Amarillo, Tex. 07227500 2.21 –82.32 –27.94 –95.66 0.016

141 07239450 North Canadian River near Calumet, Okla. 07239450 4.42 –35.88 129.54 –82.09 0.495

142 07241000 North Canadian River below Lake Overholser near 

Oklahoma City, Okla.

07241000 6.65 –78.87 21.32 –96.32 0.081

143 07241520 North Canadian River at Britton Road at Oklahoma 

City, Okla.

07241520 10.47 –55.77 19.54 –83.64 0.108

144 07241550 North Canadian River near Harrah, Okla. 07241550 15.39 –47.86 2.36 –73.44 0.059

145 07247015 Poteau River at Loving, Okla. 07247015 1.86 –33.36 67.93 –73.55 0.389

146 07247250 Black Fork below Big Creek near Page, Okla. 07247250 1.60 –59.00 41.80 –88.15 0.159

147 07247345 Black Fork at Hodgen, Okla. 07247250 1.60 –59.00 41.80 –88.15 0.159

148 07247650 Fourche Maline near Leflore, Okla. 07247500 1.32 –68.28 –12.35 –88.52 0.027

149 07263620 Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Ark.

07263450 1,188.45 –61.89 –16.38 –82.63 0.016

150 07331000 Washita River near Dickson, Okla. 07331000 66.07 –72.26 –45.80 –85.80 <0.001

151 07355500 Red River at Alexandria, La. 07355500 793.30 –16.56 64.45 –57.66 0.601

152 07362000 Ouachita River at Camden, Ark. 07362000 132.49 –15.66 57.59 –54.86 0.593

153 07373420 Mississippi River near St Francisville, La. 07373420 16,338.57 –33.22 –9.58 –50.67 0.009

154 07375500 Tangipahoa River at Robert, La. 07375500 26.72 –29.02 13.68 –55.68 0.154

155 07376000 Tickfaw River at Holden, La. 07376000 7.73 –37.56 –0.96 –60.64 0.045

156 07381495 Atchafalaya River at Melville, La. 07381495 6,980.76 –34.21 –11.91 –50.86 0.005

157 07386980 Vermilion River at Perry, La. 07386980 22.17 4.35 100.34 –45.65 0.898

158 08030500 Sabine River near Ruliff, Tex. 08030500 167.84 –9.30 114.59 –61.66 0.824

159 08032000 Neches River near Neches, Tex. 08032000 11.64 –20.75 91.41 –67.19 0.605

160 08033500 Neches River near Rockland, Tex. 08033500 35.28 –8.84 155.19 –67.44 0.860

161 08051500 Clear Creek near Sanger, Tex. 08051500 1.26 –90.37 9.92 –99.16 0.060

162 08064100 Chambers Creek near Rice, Tex. 08064100 0.99 –17.89 596.90 –90.33 0.857

163 08065350 Trinity River near Crockett, Tex. 08065350 141.53 –43.85 22.10 –74.18 0.145

164 08136500 Concho River at Paint Rock, Tex. 08136500 2.11 –98.97 –96.44 –99.70 <0.001
30 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 2. Trends in daily mean streamflow from 1993 to 2003.—Continued

[See Appendix 2 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Streamflow

station

number

Reference

streamflow,

in cubic

meters per

second1

Trend, in percent from 

1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

165 08143600 Pecan Bayou near Mullin, Tex. 08143600 0.76 –45.27 80.44 –83.40 0.322

166 08147000 Colorado River near San Saba, Tex. 08147000 6.88 –53.55 5.81 –79.61 0.068

167 08155200 Barton Creek at State Highway 71 near Oak Hill, Tex. 08155200 0.05 453.02 11365.96 –73.33 0.269

168 08155240 Barton Creek at Lost Creek Boulevard near Austin, Tex. 08155240 0.08 279.80 4489.77 –68.57 0.294

169 08159000 Onion Creek at U.S. Highway 183, Austin, Tex. 08159000 0.11 455.32 3367.86 –11.07 0.067

170 08162000 Colorado River at Wharton, Tex. 08162000 35.53 35.94 224.70 –43.09 0.490

171 08162500 Colorado River near Bay City, Tex. 08162500 31.98 12.32 211.47 –59.50 0.823

172 08181800 San Antonio River near Elmendorf, Tex. 08181800 7.94 67.48 218.94 –12.06 0.117

173 08251500 Rio Grande near Lobatos, Colo. 08251500 12.90 –81.28 –29.61 –95.02 0.013

174 09058000 Colorado River near Kremmling, Colo. 09058000 27.37 –35.18 7.93 –61.07 0.096

175 09163500 Colorado River near Colorado-Utah State Line 09163500 200.30 –55.41 –26.99 –72.77 0.001

176 09211200 Green River below Fontenelle Reservoir, Wyo. 09211200 40.17 –34.67 18.22 –63.89 0.160

177 09217010 Green River below Green River, Wyo. 09217000 40.91 –37.33 23.63 –68.23 0.178

178 09261000 Green River at Dinosaur National Monument 

Utah 149 Crossing, Utah

09261000 106.68 –40.94 2.99 –66.13 0.064

179 09380000 Colorado River at Lees Ferry, Ariz. 09380000 389.40 –7.28 40.07 –38.62 0.719

180 09403600 Kanab Creek at U.S. 89 Crossing, Utah 09403600 0.29 –37.81 –17.94 –52.86 0.001

181 09413500 Virgin River below First Narrows, Utah 09413500 6.09 –74.85 –43.69 –88.76 0.001

182 09415000 Virgin River at Littlefield, Ariz. 09415000 7.54 –63.34 –35.27 –79.23 0.001

183 09448500 Gila River at Head of Safford Valley, near Solomon, Ariz. 09448500 9.82 –66.40 –18.62 –86.13 0.016

184 09498500 Salt River near Roosevelt, Ariz. 09498500 15.01 –63.86 –11.16 –85.30 0.027

185 09508500 Verde River below Tangle Creek, above Horseshoe 

Dam, Ariz.

09508500 10.51 –54.20 –26.76 –71.36 0.001

186 09522000 Colorado River at Northerly International Boundary, above 

Morelos Dam, Ariz.

09522000 82.21 –23.84 46.47 –60.40 0.414

187 10038000 Bear River below Smiths Fork, near Cokeville, Wyo. 10038000 9.04 –47.38 50.22 –81.57 0.230

188 10126000 Bear River near Corinne at Utah 83 Crossing, Utah 10126000 25.37 –29.35 250.61 –85.76 0.671

189 10131000 Chalk Creek at U.S. 189 Crossing, Utah 10131000 1.55 –53.57 4.23 –79.32 0.063

190 10154200 Provo River above Woodland at U.S. Geological Survey 

Gage Number 10154200, Utah

10154200 4.03 –37.45 –9.13 –56.95 0.014

191 10155000 Provo River at Bridge 2.5 miles East of Hailstone 

Junction, Utah

10155000 5.33 –46.37 –12.59 –67.10 0.012

192 10155500 Provo River above Confluence with Snake Creek at 

McKeller Bridge, Utah

10155500 3.78 84.10 242.36 –1.00 0.054

193 10189000 East Fork Sevier River at Utah 62 Crossing East of 

Kingston, Utah

10189000 1.38 –21.32 18.71 –47.85 0.253

194 10336580 Upper Truckee River at South Upper Truckee Road near 

Meyers, Calif.

10336580 0.45 –36.45 60.70 –74.87 0.338

195 103366092 Upper Truckee River at Highway 50 above Meyers, Calif. 103366092 1.09 –29.28 90.85 –73.80 0.494

196 10336610 Upper Truckee River at South Lake Tahoe, Calif. 10336610 1.40 –37.31 121.64 –82.27 0.469

197 10336698 Third Creek near Crystal Bay, Nev. 10336698 0.20 –45.98 34.05 –78.23 0.184

198 103366993 Incline Creek above Tyrol Village near Incline Village, Nev. 103366993 0.08 4.75 291.76 –71.99 0.945

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 103366995 0.12 –13.03 235.54 –77.46 0.839

200 10336700 Incline Creek near Crystal Bay, Nev. 10336700 0.22 –37.05 50.64 –73.69 0.299

201 10336740 Logan House Creek near Glenbrook, Nev. 10336740 0.01 108.69 1442.99 –71.77 0.471

202 10336760 Edgewood Creek at Stateline, Nev. 10336760 0.09 23.04 240.54 –55.54 0.690

203 01A050 Nooksack River at Brennan, Wash. 01A050 84.12 5.89 51.03 –25.76 0.752

204 03A060 Skagit River near Mount Vernon, Wash. 03A060 404.73 0.62 42.81 –29.11 0.972

205 07A090 Snohomish River at Snohomish, Wash. 07A090 199.53 –0.96 49.78 –34.50 0.964

206 09A080 Green River at Tukwila, Wash. 09A080 26.82 –11.36 41.13 –44.32 0.611

207 09A190 Green River at Kanaskat, Wash. 09A190 17.07 –12.83 42.44 –46.65 0.584

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 10332 763.65 –15.07 32.23 –45.45 0.470

209 10350 Willamette River at Eastbound Highway 20 Bridge 

at Albany, Oreg.

10350 328.47 –15.28 33.55 –46.26 0.475

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 10355 264.32 –11.27 36.57 –42.35 0.587
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 31

At sites in the Northeastern, Southeastern, and 

Northwestern United States, where there were few trends in 

streamflow from 1993 to 2003, FA and NFA trends generally were similar. Sites with upward FA trends may have 

experienced an increase in phosphorus sources between 1993 

and 2003; sites with downward FA trends may have experienced a decrease in phosphorus sources and(or) reductions due 

to the implementation of pollution control strategies. With no 

trend in streamflow at these sites, and thus no trend in surface 

runoff or in-stream dilution capacity, NFA trends generally 

were similar and a product of these same influences.

Trends in loads of total phosphorus from 1993 to 

2003 were a reflection of the combined influence of changes 

in streamflow and changes in concentration. At the majority of sites (81 percent) nationwide, there was no significant 

trend in the load of total phosphorus being transported to 

downstream locations (fig. 6D, tables 3 and 6, Appendix 3). 

Upward trends in load occurred at only 7 (4 percent) of the 

171 sites; these few sites primarily were in the Northeastern 

and Northwestern United States. Downward trends in load 

occurred at 25 (15 percent) of the sites, primarily in the 

Central and Southeastern United States. In the Northeast, 

Southeast, and Northwest, trends in load were similar to trends 

in streamflow at the majority of sites. However, the change 

in concentration was large enough to be the primary influence at several sites, and load changed correspondingly. In 

the Central and Southwestern United States, there were more 

frequent differences between the streamflow and load trends; 

at these sites, changes in concentration likely were the primary 

influence on changes in load. At some of these sites, the trend 

Table 2. Trends in daily mean streamflow from 1993 to 2003.—Continued

[See Appendix 2 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Streamflow

station

number

Reference

streamflow,

in cubic

meters per

second1

Trend, in percent from 

1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

211 10386 Middle Fork Willamette at Jasper Bridge, Oreg. 10386 99.38 –8.72 40.64 –40.75 0.679

212 10411 Deschutes River at Deschutes River Park, Oreg. 10411 158.52 0.20 35.51 –25.91 0.990

213 10555 Willamette River at Marion Street at Salem, Oreg. 10555 529.99 –15.02 32.63 –45.55 0.474

214 10611 Willamette River at Hawthorne Bridge, Oreg. 10611 762.85 –15.07 32.23 –45.45 0.470

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

10616 4,894.24 –7.19 43.70 –40.06 0.738

216 10A070 Puyallup River at Meridian Street, Wash. 10A070 72.70 10.27 55.78 –21.94 0.579

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 11140 9.18 –26.08 35.80 –59.77 0.330

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. 11321 1.56 –22.97 23.38 –51.91 0.278

219 11478 John Day River at Service Creek, Oreg. 11478 34.15 –45.76 5.22 –72.04 0.070

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. 11489 5.84 21.56 115.88 –31.55 0.505

221 12413470 South Fork Coeur D'Alene River near Pinehurst, Idaho 12413470 9.21 –2.39 81.63 –47.54 0.939

222 12419000 Spokane River near Post Falls, Idaho 12419000 110.76 –12.79 70.84 –55.48 0.690

223 13154500 Snake River at King Hill, Idaho 13154500 301.51 –20.44 33.54 –52.60 0.387

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 13206000 19.48 –0.64 166.07 –62.90 0.990

225 13351000 Palouse River at Hooper, Wash. 13351000 6.06 24.77 259.47 –56.69 0.682

226 14201300 Zollner Creek near Mt. Angel, Oreg. 14201300 0.19 –45.62 20.68 –75.50 0.134

227 14211720 Willamette River at Portland, Oreg. 14211720 757.47 –15.07 32.23 –45.45 0.470

228 14246900 Columbia River at Beaver Army Terminal near Quincy, Oreg. 14246900 6,587.22 –12.72 31.75 –42.18 0.517

229 16A070 Skokomish River near Potlatch, Wash. 16A070 19.57 11.40 66.53 –25.49 0.599

230 32A070 Walla Walla River near Touchet, Wash. 32A070 7.37 –4.11 60.90 –42.85 0.874

231 3701002 Tualatin River at Weiss Bridge, Oreg. 3701002 21.27 2.58 97.90 –46.83 0.940

232 37016120 Tualatin River at Springhill Road Bridge at Dilley, Oreg. 3701612 6.88 14.16 110.47 –38.08 0.671

233 37A090 Yakima River at Kiona, Wash. 37A090 73.14 11.07 141.37 –48.89 0.791

234 45A070 Wenatchee River at Wenatchee, Wash. 45A070 54.59 –4.41 89.86 –51.88 0.897

235 45A110 Wenatchee River near Leavenworth, Wash. 45A110 52.97 –4.41 89.86 –51.88 0.897

236 48A070 Methow River near Pateros, Wash. 48A070 23.48 –16.02 51.52 –53.46 0.562

237 49A070 Okanogan River at Malott, Wash. 49A070 68.39 –37.95 19.28 –67.72 0.152

238 54A120 Spokane River at Riverside State Park, Wash. 54A120 122.44 –6.57 77.83 –50.91 0.836

239 61A070 Columbia River at Northport, Wash. 61A070 2,582.28 2.06 39.37 –25.26 0.898

240 11264500 Merced River at Happy Isles Bridge near Yosemite, Calif. 11264500 4.81 –45.22 40.19 –78.60 0.209

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. 11274538 0.60 –20.65 103.40 –69.04 0.630

242 11290000 Tuolumne River at Modesto, Calif. 11290000 24.03 –21.12 184.87 –78.16 0.717

243 11303500 San Joaquin River near Vernalis, Calif. 11303500 97.35 –17.66 141.06 –71.88 0.723

244 11447650 Sacramento River at Freeport, Calif. 11447650 627.66 –5.87 65.43 –46.44 0.833

1

Reference value is the streamflow that would have been observed on the first day of the period of record under average hydrologic and seasonal conditions.
32 Nutrient Trends in Streams and River of the United States, 1993–2003

Figure 6. Trends in (A) streamflow, (B) flow-adjusted and (C) non-flow-adjusted trends in total phosphorus concentrations, and 

(D) trends in total phosphorus loads at selected sites in the United States.

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A Streamflow

B Flow-adjusted D Load

C Non-flow-adjusted

Reference streamflow (cubic meters per second)

Less than or equal to 8.49

8.50–84.99

Greater than or equal to 85.0

Reference load (kilograms per day)

Less than or equal to 19.52

19.53–663.57

Greater than or equal to 663.58

Reference concentration (milligrams per liter)

Less than or equal to 0.0698

0.0699–0.1750

Greater than or equal to 0.1751

Reference concentration (milligrams per liter)

Less than or equal to 0.0698

0.0699–0.1750

Greater than or equal to 0.1751

EXPLANATION

(applies to A–D)

Upward

Downward

No significant trend

Direction of trend

Magnitude of trend (percent from 1993 to 2003)

Less than or equal to 33.0

33.1–66.0

# Greater than or equal to 66.1

#

#

!

#

#

#

#

#
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 33

in concentration was greater in magnitude than the trend in 

streamflow. At other sites, particularly those with agricultural 

or urban influences, the reference concentration was relatively 

large and the reference streamflow was relatively small.

Factors Affecting the Trends

Land use and phosphorus budgets for each site in the 

Eastern, Central, and Western United States are shown in 

figures 7, 8, and 9, respectively. Land use is shown as a percentage of the basin area in part A of each figure. Median phosphorus loads from manure and fertilizer between 1993 and 2003 are 

shown as percentages of their combined total load in part B of 

each figure and as absolute loads, normalized to the basin area, 

in part D of each figure. There likely were additional sources of 

phosphorus in these basins that are not shown in the phosphorus 

budgets; currently (2008), national-scale, consistently derived 

phosphorus source data that cover the period from 1993 to 2003 

are available only for manure and fertilizer.

At sites in the Eastern United States, fertilizer often was a 

larger source of phosphorus than manure, particularly at more 

urbanized sites (fig. 7). At sites with relatively high percentages of agricultural land use, manure often was a larger or 

comparable source of phosphorus. The total source loads of 

phosphorus, including both manure and fertilizer, were highest 

at sites with relatively high percentages of agricultural land 

use. At sites in the Central United States, fertilizer generally was a larger source of phosphorus than manure in the 

Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 

NAWQA major river basin; manure generally was a larger 

source in the Missouri and Lower Mississippi, ArkansasWhite-Red, and Texas-Gulf NAWQA major river basins 

(figs. 1 and 8). Across the Central United States, the total 

source loads of phosphorus were highest at sites with relatively high percentages of agricultural land use. At sites in the 

Western United States, manure generally was a larger source 

of phosphorus than fertilizer in the Southwest, particularly 

the Rio Grande, Colorado, and Great Basin NAWQA major 

river basin, where the percentage of rangeland in the basins 

was high (figs. 1 and 9). Total source loads of phosphorus at 

these sites, however, were relatively low. Total source loads of 

phosphorus were higher at sites in the Pacific Northwest and 

California, where fertilizer and manure loads generally were 

comparable. As in the Eastern and Central United States, the 

total source loads of phosphorus in the West were highest at 

sites with relatively high percentages of agricultural land use.

Nutrients in fertilizer typically are more mobile than 

the organically complexed nutrients in manure (Withers and 

others, 2001; Nichols and others, 1994; Edwards and Daniel, 

1994). As a result, changes in source loads of fertilizer may 

have a greater or more immediate effect on in-stream nutrient 

concentrations than changes in source loads of manure, even 

in areas where source loads of manure are greater. In addition, it is not uncommon for urban land use to be concentrated 

closer to monitoring sites than agricultural land use. At these 

sites, changes in urban loads may have a greater or more 

immediate effect on in-stream nutrient concentrations than 

changes in agricultural loads.

Changes in phosphorus loading from manure and fertilizer and changes in population density during the study period 

are shown on a county-level basis in figure 10, parts A–C. 

Decreases in phosphorus loading from manure were widespread throughout the nation (fig. 10A). Small increases also 

were common, particularly in the Eastern and Central United 

States. Large increases in phosphorus loading from fertilizer 

were more widespread in the Central (particularly west of 

the Mississippi River) and Western United States (fig. 10B). 

In the Eastern United States, decreases in phosphorus loading from fertilizer were more widespread and often greater 

in magnitude than decreases in phosphorus loading from 

manure. Population density increases were widespread in the 

Southeastern and Western United States (fig. 10C).

Table 3. Summary of trend results for streamflow, total phosphorus, total nitrogen, and nitrate.

Trend type Number of sites Number (and percentage) of sites with trends

Upward Downward Nonsignificant

Streamflow 244 2 (1) 54 (22) 188 (77)

Total phosphorus

Concentration, flow-adjusted 171 57 (33) 27 (16) 87 (51)

Concentration, non-flow-adjusted 171 41 (24) 28 (16) 102 (60)

Load 171 7 (4) 25 (15) 139 (81)

Total nitrogen

Concentration, flow-adjusted 137 29 (21) 22 (16) 86 (63)

Concentration, non-flow-adjusted 137 15 (11) 22 (16) 100 (73)

Load 137 2 (1) 34 (25) 101 (74)

Nitrate

Concentration, flow-adjusted 166 20 (12) 42 (25) 104 (63)

Concentration, non-flow-adjusted 166 10 (6) 45 (27) 111 (67)

Load 166 5 (3) 51 (31) 110 (66)
34 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 4. Flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site 

number 

(figure 1)

Station 

number Station name

Reference 

concentration, 

in milligrams 

per liter1

Trend, in percent from 

1993 to 2003

p-value Modeled 

estimate

Upper 

95-percent 

CI

Lower 

95-percent 

CI

Total phosphorus

1 01122610 Shetucket River at South Windham, Conn. 0.021 61.1 154.4 2.0 0.044

2 01124000 Quinebaug River at Quinebaug, Conn. 0.036 20.4 88.0 –22.9 0.418

3 01127000 Quinebaug River at Jewett City, Conn. 0.046 81.3 168.8 22.3 0.004

4 01184000 Connecticut River at Thompsonville, Conn. 0.033 26.9 90.0 –15.3 0.250

5 01184490 Broad Brook at Broad Brook, Conn. 0.092 –6.5 26.3 –30.8 0.662

7 01189995 Farmington River at Tariffville, Conn. 0.087 38.5 78.2 7.7 0.013

8 01192500 Hockanum River near East Hartford, Conn. 0.364 –19.9 0.6 –36.2 0.059

10 01196500 Quinnipiac River at Wallingford, Conn. 0.241 –20.3 1.6 –37.6 0.071

11 01205500 Housatonic River at Stevenson, Conn. 0.021 10.6 189.5 –57.8 0.839

12 01208500 Naugatuck River at Beacon Falls, Conn. 0.227 61.1 121.3 17.3 0.004

13 01208990 Saugatuck River near Redding, Conn. 0.012 25.2 326.5 –63.2 0.720

14 01209710 Norwalk River at Winnipauk, Conn. 0.030 44.0 94.3 6.7 0.018

15 01357500 Mohawk River at Cohoes, N.Y. 0.034 7.9 64.9 –29.4 0.727

16 01377000 Hackensack River at Rivervale, N.J. 0.065 14.8 93.3 –31.8 0.607

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 0.025 –54.1 67.6 –87.4 0.245

18 01387500 Ramapo River near Mahwah, N.J. 0.120 –0.9 34.0 –26.8 0.951

19 01389500 Passaic River at Little Falls, N.J. 0.372 8.8 32.8 –10.9 0.413

20 01391500 Saddle River at Lodi, N.J. 0.369 120.1 216.1 53.2 <0.001

22 01395000 Rahway River at Rahway, N.J. 0.071 34.1 83.5 –2.0 0.074

24 01398000 Neshanic River at Reaville, N.J. 0.042 23.2 177.4 –45.3 0.616

25 01402000 Millstone River at Blackwells Mills, N.J. 0.195 25.9 66.4 –4.8 0.114

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 0.160 10.8 41.1 –13.0 0.407

27 01408000 Manasquan River at Squankum, N.J. 0.099 9.8 78.4 –32.5 0.709

28 01408500 Toms River near Toms River, N.J. 0.024 32.2 271.5 –53.0 0.599

30 01411500 Maurice River at Norma, N.J. 0.014 –14.4 217.9 –76.9 0.818

31 01438500 Delaware River at Montague, N.J. 0.041 –45.3 52.7 –80.4 0.256

32 01443500 Paulins Kill at Blairstown, N.J. 0.025 7.7 124.2 –48.2 0.843

33 01463500 Delaware River at Trenton, N.J. 0.057 –10.8 26.2 –36.9 0.521

34 01467150 Cooper River at Haddonfield, N.J. 0.198 0.1 42.8 –29.9 0.996

35 01477120 Raccoon Creek near Swedesboro, N.J. 0.117 29.8 83.2 –8.0 0.142

36 01491000 Choptank River near Greensboro, Md. 0.045 91.1 157.7 41.6 <0.001

37 01578310 Susquehanna River at Conowingo, Md. 0.021 78.6 134.7 35.9 <0.001

38 01594440 Patuxent River near Bowie, Md. 0.116 40.7 78.9 10.6 0.006

39 01614500 Conococheague Creek at Fairview, Md. 0.114 26.3 73.4 –8.0 0.150

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 0.030 95.6 186.3 33.6 0.001

41 01668000 Rappahannock River near Fredericksburg, Va. 0.033 51.2 102.2 13.0 0.006

42 01673000 Pamunkey River near Hanover, Va. 0.066 80.4 112.0 53.5 <0.001

43 01674500 Mattaponi River near Beulahville, Va. 0.059 0.3 14.1 –11.9 0.968

44 02035000 James River at Cartersville, Va. 0.100 –2.9 20.1 –21.5 0.789

45 02041650 Appomattox River at Matoaca, Va. 0.047 –6.7 8.3 –19.6 0.362

46 02085000 Eno River at Hillsborough, N.C. 0.025 42.2 134.8 –13.9 0.173

51 02198500 Savannah River near Clyo, Ga. 0.093 14.3 47.9 –11.7 0.311

52 02213700 Ocmulgee River near Warner Robins, Ga. 0.177 –47.9 –27.8 –62.4 <0.001

53 02215500 Ocmulgee River at Lumber City, Ga. 0.117 –34.9 –16.0 –49.5 0.001

54 02223600 Oconee River at Interstate 16, near Dublin, Ga. 0.135 –26.4 –7.4 –41.5 0.010

55 02226010 Altamaha River near Gardi, Ga. 0.106 –17.0 –2.1 –29.7 0.029

56 02226582 Satilla River at GA 15&121, near Hoboken, Ga. 0.140 19.4 49.2 –4.4 0.121

58 02295420 Payne Creek near Bowling Green, Fla. 0.620 37.6 69.2 11.8 0.004

59 02296750 Peace River at Arcadia, Fla. 0.940 –6.0 10.9 –20.3 0.464

60 02300700 Bullfrog Creek near Wimauma, Fla. 0.227 14.4 34.3 –2.6 0.104

61 02301300 South Prong Alafia River near Lithia, Fla. 0.954 –36.0 –13.8 –52.5 0.005
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 35

Table 4. Flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site 

number 

(figure 1)

Station 

number Station name

Reference 

concentration, 

in milligrams 

per liter1

Trend, in percent from 

1993 to 2003

p-value Modeled 

estimate

Upper 

95-percent 

CI

Lower 

95-percent 

CI

Total phosphorus—Continued

62 02302500 Blackwater Creek near Knights, Fla. 0.807 –36.5 –19.2 –50.0 <0.001

63 02303000 Hillsborough River near Zephyrhills, Fla. 0.323 –44.5 –23.9 –59.5 0.001

64 02314500 Suwannee River at U.S. 441, at Fargo, Ga. 0.066 –73.9 –61.7 –82.2 <0.001

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 0.150 21.1 45.6 0.7 0.044

66 02335870 Sope Creek near Marietta, Ga. 0.017 –2.9 64.3 –42.6 0.913

68 02344040 Chattahoochee River near Steam Mill, Ga. 0.085 –55.7 –31.6 –71.3 <0.001

69 02353000 Flint River at Newton, Ga. 0.049 –9.9 20.6 –32.7 0.487

70 02388520 Oostanaula River at Rome, Ga. 0.217 –55.8 –42.8 –65.8 <0.001

71 02492000 Bogue Chitto River near Bush, La. 0.070 49.2 99.8 11.4 0.009

72 03353637 Little Buck Creek near Indianapolis, Ind. 0.024 29.8 87.3 –10.0 0.165

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 0.082 82.2 124.0 48.1 <0.001

74 04063700 Popple River near Fence, Wis. 0.027 –18.3 40.3 –52.5 0.465

75 04073468 Green Lake Inlet at County Highway A near Green 

Lake, Wis.

0.134 –24.4 –15.7 –32.3 <0.001

76 04087000 Milwaukee River at Milwaukee, Wis. 0.083 26.9 54.9 3.9 0.021

77 0422026250 Northrup Creek at North Greece, N.Y. 0.402 –35.5 –23.3 –45.7 <0.001

78 04232034 Irondequoit Creek at Railroad Mills near Fishers, N.Y. 0.070 –19.9 5.2 –39.0 0.111

79 0423204920 East Branch Allen Creek at Pittsford, N.Y. 0.090 –15.5 0.1 –28.6 0.052

80 0423205025 Irondequoit Creek at Empire Boulevard at Rochester, N.Y. 0.068 52.6 68.6 38.1 <0.001

81 05114000 Souris River near Sherwood, N. Dak. 0.424 –35.8 –8.0 –55.1 0.018

82 05120000 Souris River near Verendrye, N. Dak. 0.264 –15.2 18.7 –39.4 0.341

83 05287890 Elm Creek near Champlin, Minn. 0.139 42.0 77.2 13.7 0.002

84 05427718 Yahara River at Windsor, Wis. 0.149 8.2 28.2 –8.7 0.364

85 05427948 Pheasant Branch at Middleton, Wis. 0.390 –62.6 –56.2 –68.1 <0.001

86 054310157 Jackson Creek Tributary near Elkhorn, Wis. 0.129 –12.2 9.2 –29.4 0.242

87 05500000 South Fabius River near Taylor, Mo. 0.102 63.7 134.3 14.4 0.008

88 05514500 Cuivre River near Troy, Mo. 0.136 15.7 77.9 –24.7 0.508

89 05525500 Sugar Creek at Milford, Ill. 0.060 66.0 165.1 4.0 0.037

90 05531500 Salt Creek at Western Springs, Ill. 1.019 46.2 81.8 17.6 0.001

91 05532500 Des Plaines River at Riverside, Ill. 0.517 62.0 96.6 33.4 <0.001

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 0.079 –11.5 26.8 –38.2 0.508

93 05586100 Illinois River at Valley City, Ill. 0.264 110.3 172.5 62.3 <0.001

94 07018100 Big River near Richwoods, Mo. 0.032 2.0 64.7 –36.8 0.936

95 07022000 Mississippi River at Thebes, Ill. 0.230 102.1 159.4 57.4 <0.001

97 06178000 Poplar River at International Boundary, Mont. 0.029 –17.5 53.8 –55.7 0.548

99 06329500 Yellowstone River near Sidney, Mont. 0.075 60.8 229.4 –21.5 0.197

101 06461500 Niobrara River near Sparks, Nebr. 0.121 38.8 85.8 3.7 0.031

106 06753990 Lonetree Creek near Greeley, Colo. 0.325 –16.9 89.5 –63.5 0.662

107 06754000 South Platte River near Kersey, Colo. 0.636 26.7 49.0 7.6 0.005

109 06800000 Maple Creek near Nickerson, Nebr. 0.207 290.4 473.1 165.9 <0.001

110 06805500 Platte River at Louisville, Nebr. 0.313 188.4 294.6 110.7 <0.001

111 06817700 Nodaway River near Graham, Mo. 0.327 102.5 250.2 17.1 0.013

112 06818000 Missouri River at St. Joseph, Mo. 0.216 68.3 146.9 14.7 0.009

113 06902000 Grand River near Sumner, Mo. 0.202 193.7 383.1 78.5 <0.001

114 06905500 Chariton River near Prairie Hill, Mo. 0.207 36.4 129.6 –19.0 0.246

115 06921070 Pomme De Terre River near Polk, Mo. 0.047 9.3 64.4 –27.3 0.669

118 06934500 Missouri River at Hermann, Mo. 0.187 233.3 422.7 112.5 <0.001

120 07053250 Yocum Creek near Oak Grove, Ark. 0.039 47.9 90.4 14.9 0.003

134 07189000 Elk River near Tiff City, Mo. 0.041 231.1 374.1 131.2 <0.001

135 07195500 Illinois River near Watts, Okla. 0.112 117.4 211.0 51.9 <0.001

136 07195865 Sager Creek near West Siloam Springs, Okla. 0.495 66.3 158.7 6.8 0.029
36 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 4. Flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site 

number 

(figure 1)

Station 

number Station name

Reference 

concentration, 

in milligrams 

per liter1

Trend, in percent from 

1993 to 2003

p-value Modeled 

estimate

Upper 

95-percent 

CI

Lower 

95-percent 

CI

Total phosphorus—Continued

137 07196000 Flint Creek near Kansas, Okla. 0.092 111.2 160.4 71.3 <0.001

138 07196500 Illinois River near Tahlequah, Okla. 0.063 135.6 190.3 91.1 <0.001

139 07197000 Baron Fork at Eldon, Okla. 0.028 67.4 140.2 16.6 0.006

145 07247015 Poteau River at Loving, Okla. 0.106 –9.5 34.3 –39.0 0.622

148 07247650 Fourche Maline near Leflore, Okla. 0.051 17.9 60.0 –13.1 0.293

149 07263620 Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Ark.

0.081 78.7 121.7 43.9 <0.001

150 07331000 Washita River near Dickson, Okla. 0.201 140.7 277.7 53.4 <0.001

151 07355500 Red River at Alexandria, La. 0.095 –25.1 –5.4 –40.6 0.017

152 07362000 Ouachita River at Camden, Ark. 0.041 –26.6 27.8 –57.9 0.279

153 07373420 Mississippi River near St Francisville, La. 0.175 50.4 87.9 20.3 <0.001

154 07375500 Tangipahoa River at Robert, La. 0.112 16.0 56.6 –14.1 0.335

155 07376000 Tickfaw River at Holden, La. 0.074 57.1 117.3 13.6 0.008

156 07381495 Atchafalaya River at Melville, La. 0.146 71.8 105.6 43.6 <0.001

157 07386980 Vermilion River at Perry, La. 0.297 1.2 26.0 –18.8 0.918

165 08143600 Pecan Bayou near Mullin, Tex. 0.205 0.0 88.4 –47.0 0.999

166 08147000 Colorado River near San Saba, Tex. 0.077 –68.0 8.1 –90.5 0.072

169 08159000 Onion Creek at U.S. Highway 183, Austin, Tex. 0.076 –93.9 –71.3 –98.7 0.001

170 08162000 Colorado River at Wharton, Tex. 0.269 –5.9 47.1 –39.8 0.791

171 08162500 Colorado River near Bay City, Tex. 0.291 –26.1 26.3 –56.7 0.274

173 08251500 Rio Grande near Lobatos, Colo. 0.079 52.9 96.9 18.6 0.002

177 09217010 Green River below Green River, Wyo. 0.026 51.1 186.1 –20.2 0.210

178 09261000 Green River at Dinosaur National Monument 

Utah 149 Crossing, Utah

0.062 –34.8 55.5 –72.6 0.338

180 09403600 Kanab Creek at U.S. 89 Crossing, Utah 0.035 232.7 656.8 46.2 0.005

182 09415000 Virgin River at Littlefield, Ariz. 0.106 463.4 1200.6 144.0 <0.001

183 09448500 Gila River at Head of Safford Valley, near 

Solomon, Ariz.

0.122 216.0 730.0 20.3 0.024

184 09498500 Salt River near Roosevelt, Ariz. 0.013 4678.5 14832.1 1428.8 <0.001

185 09508500 Verde River below Tangle Creek, above Horseshoe 

Dam, Ariz.

0.023 166.7 493.8 19.8 0.019

186 09522000 Colorado River at Northerly International Boundary, 

above Morelos Dam, Ariz.

0.280 –85.9 –65.2 –94.3 <0.001

188 10126000 Bear River near Corinne at Utah 83 Crossing, Utah 0.188 –50.7 –29.9 –65.3 <0.001

193 10189000 East Fork Sevier River at Utah 62 Crossing East 

of Kingston, Utah

0.085 –3.4 37.7 –32.2 0.849

203 01A050 Nooksack River at Brennan, Wash. 0.021 37.9 104.2 –6.9 0.112

204 03A060 Skagit River near Mount Vernon, Wash. 0.015 5.5 112.6 –47.6 0.880

205 07A090 Snohomish River at Snohomish, Wash. 0.009 26.3 123.2 –28.5 0.423

206 09A080 Green River at Tukwila, Wash. 0.025 19.2 59.3 –10.8 0.238

207 09A190 Green River at Kanaskat, Wash. 0.005 254.0 606.4 77.4 <0.001

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 0.070 –7.6 9.1 –21.7 0.355

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

0.075 –18.8 –3.0 –32.1 0.023

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 0.046 –2.6 18.5 –20.0 0.790

211 10386 Middle Fork Willamette at Jasper Bridge, Oreg. 0.028 –13.8 3.5 –28.1 0.117

212 10411 Deschutes River at Deschutes River Park, Oreg. 0.080 –8.9 29.5 –35.9 0.606

213 10555 Willamette River at Marion Street at Salem, Oreg. 0.064 –18.6 –4.1 –30.9 0.015

214 10611 Willamette River at Hawthorne Bridge, Oreg. 0.082 –22.9 –13.6 –31.2 <0.001

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

0.040 –21.9 –1.9 –37.9 0.039
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 37

Table 4. Flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site 

number 

(figure 1)

Station 

number Station name

Reference 

concentration, 

in milligrams 

per liter1

Trend, in percent from 

1993 to 2003

p-value Modeled 

estimate

Upper 

95-percent 

CI

Lower 

95-percent 

CI

Total phosphorus—Continued

216 10A070 Puyallup River at Meridian Street, Wash. 0.036 79.6 176.1 16.8 0.009

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 0.081 –21.7 –2.0 –37.4 0.037

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. 0.090 –7.8 11.1 –23.6 0.397

219 11478 John Day River at Service Creek, Oreg. 0.041 –19.2 10.5 –40.9 0.187

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. 0.104 –36.8 –13.8 –53.7 0.005

221 12413470 South Fork Coeur D'Alene River near Pinehurst, Idaho 0.011 93.0 235.6 11.0 0.022

222 12419000 Spokane River near Post Falls, Idaho 0.011 –37.3 87.4 –79.0 0.405

223 13154500 Snake River at King Hill, Idaho 0.068 –13.2 7.2 –29.8 0.191

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 0.083 36.3 98.7 –6.4 0.110

225 13351000 Palouse River at Hooper, Wash. 0.195 –54.4 –37.0 –67.0 <0.001

227 14211720 Willamette River at Portland, Oreg. 0.061 13.5 37.0 –6.1 0.192

228 14246900 Columbia River at Beaver Army Terminal near 

Quincy, Oreg.

0.031 14.8 75.2 –24.8 0.523

229 16A070 Skokomish River near Potlatch, Wash. 0.009 104.8 265.9 14.6 0.017

230 32A070 Walla Walla River near Touchet, Wash. 0.112 –4.2 21.3 –24.3 0.724

231 3701002 Tualatin River at Weiss Bridge, Oreg. 0.175 –32.0 –24.2 –39.1 <0.001

232 37016120 Tualatin River at Springhill Road Bridge 

at Dilley, Oreg.

0.039 –41.9 –29.4 –52.2 <0.001

233 37A090 Yakima River at Kiona, Wash. 0.102 3.1 23.1 –13.7 0.740

234 45A070 Wenatchee River at Wenatchee, Wash. 0.004 53.4 274.4 –37.2 0.349

235 45A110 Wenatchee River near Leavenworth, Wash. 0.004 13.5 154.5 –49.4 0.759

236 48A070 Methow River near Pateros, Wash. 0.003 99.5 292.6 1.3 0.048

237 49A070 Okanogan River at Malott, Wash. 0.017 16.2 111.7 –36.3 0.626

238 54A120 Spokane River at Riverside State Park, Wash. 0.019 39.9 123.2 –12.4 0.162

239 61A070 Columbia River at Northport, Wash. 0.011 –33.5 24.5 –64.5 0.205

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. 0.183 16.2 55.8 –13.4 0.319

242 11290000 Tuolumne River at Modesto, Calif. 0.074 –4.9 26.0 –28.3 0.726

243 11303500 San Joaquin River near Vernalis, Calif. 0.274 –3.2 11.8 –16.2 0.660

244 11447650 Sacramento River at Freeport, Calif. 0.039 59.6 121.8 14.9 0.006

Total nitrogen

1 01122610 Shetucket River at South Windham, Conn. 0.603 6.2 31.2 –14.1 0.581

2 01124000 Quinebaug River at Quinebaug, Conn. 0.530 34.8 60.2 13.4 0.001

3 01127000 Quinebaug River at Jewett City, Conn. 0.913 –4.3 12.3 –18.4 0.590

4 01184000 Connecticut River at Thompsonville, Conn. 0.624 2.6 21.1 –13.1 0.766

5 01184490 Broad Brook at Broad Brook, Conn. 4.259 –2.2 5.9 –9.7 0.585

6 01188090 Farmington River at Unionville, Conn. 0.270 37.6 103.3 –6.9 0.115

7 01189995 Farmington River at Tariffville, Conn. 1.018 10.4 29.7 –5.9 0.229

8 01192500 Hockanum River near East Hartford, Conn. 3.480 –4.5 10.2 –17.3 0.526

9 01193500 Salmon River near East Hampton, Conn. 0.436 16.4 58.7 –14.6 0.341

10 01196500 Quinnipiac River at Wallingford, Conn. 3.208 –4.2 7.4 –14.5 0.462

11 01205500 Housatonic River at Stevenson, Conn. 0.661 12.1 41.3 –11.0 0.338

12 01208500 Naugatuck River at Beacon Falls, Conn. 2.492 –52.9 –43.6 –60.7 <0.001

13 01208990 Saugatuck River near Redding, Conn. 0.307 40.1 106.2 –4.8 0.094

14 01209710 Norwalk River at Winnipauk, Conn. 0.642 24.3 46.3 5.7 0.009

15 01357500 Mohawk River at Cohoes, N.Y. 1.048 –10.1 1.1 –20.1 0.078

16 01377000 Hackensack River at Rivervale, N.J. 1.032 10.4 37.0 –11.0 0.372

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 0.500 23.2 73.4 –12.5 0.239

18 01387500 Ramapo River near Mahwah, N.J. 1.537 0.4 20.9 –16.6 0.965

19 01389500 Passaic River at Little Falls, N.J. 3.357 –19.1 –4.7 –31.3 0.013

20 01391500 Saddle River at Lodi, N.J. 5.794 26.4 56.6 2.1 0.037
38 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 4. Flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site 

number 

(figure 1)

Station 

number Station name

Reference 

concentration, 

in milligrams 

per liter1

Trend, in percent from 

1993 to 2003

p-value Modeled 

estimate

Upper 

95-percent 

CI

Lower 

95-percent 

CI

Total nitrogen—Continued

21 01394500 Rahway River near Springfield, N.J. 1.727 –0.3 23.4 –19.5 0.978

22 01395000 Rahway River at Rahway, N.J. 1.407 –0.1 25.0 –20.2 0.993

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 1.090 –13.5 7.2 –30.2 0.193

24 01398000 Neshanic River at Reaville, N.J. 1.753 –14.9 26.0 –42.5 0.423

25 01402000 Millstone River at Blackwells Mills, N.J. 2.902 8.1 34.4 –13.1 0.490

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 2.316 11.0 26.6 –2.7 0.125

29 01409500 Batsto River at Batsto, N.J. 0.386 –10.3 23.9 –35.1 0.513

31 01438500 Delaware River at Montague, N.J. 0.487 –23.2 –1.2 –40.3 0.046

32 01443500 Paulins Kill at Blairstown, N.J. 0.958 7.7 36.1 –14.8 0.540

33 01463500 Delaware River at Trenton, N.J. 1.277 –18.3 –3.7 –30.6 0.018

34 01467150 Cooper River at Haddonfield, N.J. 0.921 5.1 29.4 –14.7 0.644

35 01477120 Raccoon Creek near Swedesboro, N.J. 1.658 6.9 30.0 –12.1 0.507

36 01491000 Choptank River near Greensboro, Md. 1.457 23.5 36.6 11.7 <0.001

37 01578310 Susquehanna River at Conowingo, Md. 1.526 –8.5 0.6 –16.8 0.067

38 01594440 Patuxent River near Bowie, Md. 2.078 0.6 9.1 –7.2 0.883

39 01614500 Conococheague Creek at Fairview, Md. 5.429 1.3 10.4 –7.0 0.763

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 2.010 –12.0 1.2 –23.5 0.075

41 01668000 Rappahannock River near Fredericksburg, Va. 0.577 44.3 69.3 23.0 <0.001

42 01673000 Pamunkey River near Hanover, Va. 0.653 31.9 45.5 19.5 <0.001

43 01674500 Mattaponi River near Beulahville, Va. 0.623 16.2 26.3 7.0 <0.001

44 02035000 James River at Cartersville, Va. 0.478 21.5 38.4 6.7 0.004

45 02041650 Appomattox River at Matoaca, Va. 0.587 14.1 24.6 4.5 0.004

46 02085000 Eno River at Hillsborough, N.C. 0.664 17.9 40.0 –0.7 0.064

47 02089500 Neuse River at Kinston, N.C. 1.493 –36.1 –26.9 –44.2 <0.001

48 02091500 Contentnea Creek at Hookerton, N.C. 1.242 –11.1 –2.9 –18.5 0.010

49 0210215985 Cape Fear River at State Highway 42 near Brickhaven, N.C. 1.363 1.2 37.4 –25.4 0.939

52 02213700 Ocmulgee River near Warner Robins, Ga. 1.350 –5.5 27.2 –29.8 0.710

53 02215500 Ocmulgee River at Lumber City, Ga. 0.965 –16.4 1.1 –30.8 0.068

57 02271500 Josephine Creek near De Soto City, Fla. 0.889 36.4 61.5 15.1 0.001

58 02295420 Payne Creek near Bowling Green, Fla. 1.696 –10.3 15.3 –30.2 0.401

59 02296750 Peace River at Arcadia, Fla. 1.780 –2.1 13.1 –15.3 0.771

60 02300700 Bullfrog Creek near Wimauma, Fla. 0.782 22.1 49.5 –0.3 0.056

61 02301300 South Prong Alafia River near Lithia, Fla. 1.056 2.6 29.7 –18.9 0.832

62 02302500 Blackwater Creek near Knights, Fla. 1.693 –16.5 6.5 –34.6 0.152

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 1.005 36.0 57.5 17.4 <0.001

67 02338000 Chattahoochee River near Whitesburg, Ga. 1.386 11.8 37.7 –9.2 0.297

71 02492000 Bogue Chitto River near Bush, La. 0.819 16.5 103.3 –33.2 0.592

72 03353637 Little Buck Creek near Indianapolis, Ind. 1.079 –2.8 15.9 –18.6 0.749

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 1.344 20.4 44.1 0.7 0.044

74 04063700 Popple River near Fence, Wis. 0.453 26.3 47.2 8.4 0.003

76 04087000 Milwaukee River at Milwaukee, Wis. 1.724 31.9 48.4 17.2 <0.001

81 05114000 Souris River near Sherwood, N. Dak. 2.076 –18.0 10.9 –39.4 0.201

82 05120000 Souris River near Verendrye, N. Dak. 1.507 0.6 39.0 –27.2 0.970

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 1.615 –32.2 –12.4 –47.5 0.004

95 07022000 Mississippi River at Thebes, Ill. 3.227 13.7 36.7 –5.5 0.176

97 06178000 Poplar River at International Boundary, Mont. 0.613 7.6 44.1 –19.6 0.625

99 06329500 Yellowstone River near Sidney, Mont. 0.606 51.2 114.0 6.8 0.022

100 06338490 Missouri River at Garrison Dam, N. Dak. 0.193 39.8 131.3 –15.5 0.197

101 06461500 Niobrara River near Sparks, Nebr. 0.441 67.8 138.6 18.0 0.005

102 06468250 James River above Arrowwood Lake near Kensal, N. Dak. 1.518 5.4 36.7 –18.7 0.692

103 06713500 Cherry Creek at Denver, Colo. 3.828 –44.3 –30.7 –55.3 <0.001
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 39

Table 4. Flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site 

number 

(figure 1)

Station 

number Station name

Reference 

concentration, 

in milligrams 

per liter1

Trend, in percent from 

1993 to 2003

p-value Modeled 

estimate

Upper 

95-percent 

CI

Lower 

95-percent 

CI

Total nitrogen—Continued

106 06753990 Lonetree Creek near Greeley, Colo. 9.761 –42.3 –22.1 –57.3 0.001

107 06754000 South Platte River near Kersey, Colo. 6.215 7.6 16.6 –0.6 0.074

108 06775900 Dismal River near Thedford, Nebr. 0.717 –5.5 10.1 –18.8 0.473

109 06800000 Maple Creek near Nickerson, Nebr. 6.015 34.2 71.4 5.0 0.020

110 06805500 Platte River at Louisville, Nebr. 2.642 60.2 105.0 25.2 <0.001

111 06817700 Nodaway River near Graham, Mo. 5.273 –4.4 48.8 –38.6 0.841

112 06818000 Missouri River at St. Joseph, Mo. 3.257 –43.7 –27.5 –56.2 <0.001

113 06902000 Grand River near Sumner, Mo. 1.723 21.4 83.2 –19.6 0.358

114 06905500 Chariton River near Prairie Hill, Mo. 1.607 –17.0 24.5 –44.7 0.369

115 06921070 Pomme De Terre River near Polk, Mo. 0.544 36.1 116.2 –14.4 0.196

116 06926510 Osage River below St. Thomas, Mo. 0.752 –7.3 24.9 –31.2 0.620

118 06934500 Missouri River at Hermann, Mo. 2.025 22.5 58.4 –5.2 0.124

120 07053250 Yocum Creek near Oak Grove, Ark. 2.529 89.9 138.3 51.3 <0.001

124 07066110 Jacks Fork above Two River, Mo. 0.448 6.6 31.5 –13.5 0.549

125 07068000 Current River at Doniphan, Mo. 0.426 –20.8 –3.9 –34.7 0.020

134 07189000 Elk River near Tiff City, Mo. 1.721 36.6 63.2 14.3 0.001

135 07195500 Illinois River near Watts, Okla. 2.523 5.8 32.4 –15.4 0.621

136 07195865 Sager Creek near West Siloam Springs, Okla. 6.666 11.3 46.3 –15.4 0.448

137 07196000 Flint Creek near Kansas, Okla. 1.882 63.1 83.2 45.1 <0.001

138 07196500 Illinois River near Tahlequah, Okla. 1.723 20.5 41.2 2.8 0.023

139 07197000 Baron Fork at Eldon, Okla. 1.033 40.7 83.1 8.2 0.012

145 07247015 Poteau River at Loving, Okla. 0.439 16.8 53.8 –11.3 0.271

146 07247250 Black Fork below Big Creek near Page, Okla. 0.315 –5.0 41.4 –36.1 0.802

147 07247345 Black Fork at Hodgen, Okla. 0.322 5.9 49.0 –24.7 0.744

148 07247650 Fourche Maline near Leflore, Okla. 0.610 9.4 36.6 –12.4 0.430

149 07263620 Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Ark.

0.842 8.5 29.9 –9.3 0.373

150 07331000 Washita River near Dickson, Okla. 0.988 72.5 124.8 32.3 <0.001

151 07355500 Red River at Alexandria, La. 0.715 7.7 23.5 –6.1 0.292

152 07362000 Ouachita River at Camden, Ark. 0.312 52.9 127.0 2.9 0.040

153 07373420 Mississippi River near St Francisville, La. 2.096 –5.0 11.7 –19.2 0.534

154 07375500 Tangipahoa River at Robert, La. 0.909 –10.2 15.4 –30.1 0.402

155 07376000 Tickfaw River at Holden, La. 0.873 –3.0 26.3 –25.5 0.820

156 07381495 Atchafalaya River at Melville, La. 1.776 –5.6 8.6 –17.9 0.424

157 07386980 Vermilion River at Perry, La. 1.888 –16.8 1.3 –31.7 0.070

173 08251500 Rio Grande near Lobatos, Colo. 0.440 14.3 46.8 –11.0 0.298

176 09211200 Green River below Fontenelle Reservoir, Wyo. 0.230 28.9 76.9 –6.1 0.119

179 09380000 Colorado River at Lees Ferry, Ariz. 0.368 5.6 40.6 –20.8 0.713

182 09415000 Virgin River at Littlefield, Ariz. 0.841 194.4 382.6 79.6 <0.001

196 10336610 Upper Truckee River at South Lake Tahoe, Calif. 0.210 8.0 30.0 –10.3 0.418

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 0.304 –4.8 23.6 –26.7 0.713

201 10336740 Logan House Creek near Glenbrook, Nev. 0.313 –21.3 –1.5 –37.2 0.038

202 10336760 Edgewood Creek at Stateline, Nev. 0.328 –34.6 –20.9 –46.0 <0.001

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 0.967 –22.0 6.0 –42.6 0.118

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

0.791 –50.0 –35.8 –61.0 <0.001

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 0.430 –49.5 –33.9 –61.3 <0.001

212 10411 Deschutes River at Deschutes River Park, Oreg. 0.316 –24.4 1.1 –43.5 0.064

213 10555 Willamette River at Marion Street at Salem, Oreg. 0.912 –51.9 –41.3 –60.6 <0.001

214 10611 Willamette River at Hawthorne Bridge, Oreg. 1.171 –39.1 –24.9 –50.5 <0.001

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

0.459 –28.4 6.0 –51.6 0.101
40 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 4. Flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site 

number 

(figure 1)

Station 

number Station name

Reference 

concentration, 

in milligrams 

per liter1

Trend, in percent from 

1993 to 2003

p-value Modeled 

estimate

Upper 

95-percent 

CI

Lower 

95-percent 

CI

Total nitrogen—Continued

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 1.009 –45.0 –27.8 –58.1 <0.001

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. 4.554 –30.4 –23.5 –36.6 <0.001

219 11478 John Day River at Service Creek, Oreg. 0.293 –36.8 –9.1 –56.1 0.016

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. 2.665 –38.5 –18.8 –53.4 0.001

221 12413470 South Fork Coeur D'Alene River near Pinehurst, Idaho 0.230 16.7 53.7 –11.4 0.276

222 12419000 Spokane River near Post Falls, Idaho 0.138 14.0 61.6 –19.5 0.462

223 13154500 Snake River at King Hill, Idaho 1.480 –5.4 4.1 –14.1 0.259

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 0.565 22.7 47.5 2.1 0.032

225 13351000 Palouse River at Hooper, Wash. 1.724 2.3 21.9 –14.2 0.800

227 14211720 Willamette River at Portland, Oreg. 0.781 –2.4 14.3 –16.7 0.760

228 14246900 Columbia River at Beaver Army Terminal near 

Quincy, Oreg.

0.473 –7.2 10.6 –22.1 0.406

231 3701002 Tualatin River at Weiss Bridge, Oreg. 2.701 6.4 13.5 –0.3 0.064

232 37016120 Tualatin River at Springhill Road Bridge at Dilley, Oreg. 0.553 –33.8 –24.1 –42.2 <0.001

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. 2.839 2.5 31.7 –20.3 0.849

242 11290000 Tuolumne River at Modesto, Calif. 0.378 128.5 170.8 92.8 <0.001

243 11303500 San Joaquin River near Vernalis, Calif. 2.012 1.9 13.5 –8.6 0.737

244 11447650 Sacramento River at Freeport, Calif. 0.238 48.8 95.5 13.2 0.005

Nitrate

1 01122610 Shetucket River at South Windham, Conn. 0.393 –18.2 3.2 –35.2 0.093

2 01124000 Quinebaug River at Quinebaug, Conn. 0.260 10.3 34.2 –9.4 0.331

3 01127000 Quinebaug River at Jewett City, Conn. 0.481 –19.5 14.1 –43.3 0.226

4 01184000 Connecticut River at Thompsonville, Conn. 0.327 5.1 24.5 –11.2 0.562

5 01184490 Broad Brook at Broad Brook, Conn. 3.743 –0.9 8.2 –9.2 0.838

6 01188090 Farmington River at Unionville, Conn. 0.183 –28.6 –8.1 –44.6 0.012

7 01189995 Farmington River at Tariffville, Conn. 0.641 1.9 15.3 –9.9 0.767

8 01192500 Hockanum River near East Hartford, Conn. 2.545 –3.3 17.5 –20.4 0.735

9 01193500 Salmon River near East Hampton, Conn. 0.297 –25.6 20.8 –54.2 0.237

10 01196500 Quinnipiac River at Wallingford, Conn. 2.625 –14.9 –4.3 –24.3 0.008

11 01205500 Housatonic River at Stevenson, Conn. 0.342 13.0 51.7 –15.9 0.421

12 01208500 Naugatuck River at Beacon Falls, Conn. 1.055 –19.4 –2.8 –33.1 0.027

13 01208990 Saugatuck River near Redding, Conn. 0.120 –5.1 82.3 –50.6 0.876

14 01209710 Norwalk River at Winnipauk, Conn. 0.392 –1.2 28.3 –23.9 0.928

15 01357500 Mohawk River at Cohoes, N.Y. 0.689 –11.8 3.5 –24.9 0.127

16 01377000 Hackensack River at Rivervale, N.J. 0.461 –26.3 8.8 –50.0 0.132

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 0.184 21.2 124.5 –34.5 0.544

18 01387500 Ramapo River near Mahwah, N.J. 1.292 0.2 25.6 –20.0 0.986

19 01389500 Passaic River at Little Falls, N.J. 2.719 –28.0 –12.0 –41.0 0.002

20 01391500 Saddle River at Lodi, N.J. 4.463 31.1 61.2 6.7 0.013

21 01394500 Rahway River near Springfield, N.J. 1.356 1.8 34.4 –22.9 0.900

22 01395000 Rahway River at Rahway, N.J. 0.867 10.1 55.6 –22.1 0.588

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 0.931 –20.5 0.3 –37.0 0.059

24 01398000 Neshanic River at Reaville, N.J. 1.430 –16.8 58.3 –56.3 0.577

25 01402000 Millstone River at Blackwells Mills, N.J. 2.410 –2.0 20.6 –20.3 0.851

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 1.878 9.0 27.4 –6.7 0.280

29 01409500 Batsto River at Batsto, N.J. 0.168 –60.9 –36.3 –76.1 0.001

31 01438500 Delaware River at Montague, N.J. 0.295 –43.7 –18.9 –60.9 0.004

32 01443500 Paulins Kill at Blairstown, N.J. 0.795 4.6 67.9 –34.9 0.854

33 01463500 Delaware River at Trenton, N.J. 1.003 –24.2 –10.1 –36.1 0.002

34 01467150 Cooper River at Haddonfield, N.J. 0.349 –26.5 3.8 –48.0 0.084

35 01477120 Raccoon Creek near Swedesboro, N.J. 1.398 –27.9 2.3 –49.2 0.070
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 41

Table 4. Flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site 

number 

(figure 1)

Station 

number Station name

Reference 

concentration, 

in milligrams 

per liter1

Trend, in percent from 

1993 to 2003

p-value Modeled 

estimate

Upper 

95-percent 

CI

Lower 

95-percent 

CI

Nitrate—Continued

36 01491000 Choptank River near Greensboro, Md. 1.291 8.4 24.6 –5.8 0.262

37 01578310 Susquehanna River at Conowingo, Md. 1.299 –22.5 –13.1 –30.9 <0.001

38 01594440 Patuxent River near Bowie, Md. 1.434 –10.1 –1.9 –17.7 0.018

39 01614500 Conococheague Creek at Fairview, Md. 4.995 –7.8 0.2 –15.2 0.057

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 1.807 –34.0 –18.8 –46.4 <0.001

41 01668000 Rappahannock River near Fredericksburg, Va. 0.312 24.6 73.0 –10.2 0.189

42 01673000 Pamunkey River near Hanover, Va. 0.282 0.6 15.8 –12.6 0.932

43 01674500 Mattaponi River near Beulahville, Va. 0.155 14.6 38.1 –4.9 0.153

44 02035000 James River at Cartersville, Va. 0.219 –18.1 5.3 –36.3 0.121

45 02041650 Appomattox River at Matoaca, Va. 0.142 –18.8 –0.4 –33.8 0.046

50 02175000 Edisto River near Givhans, S.C. 0.099 –25.9 11.4 –50.7 0.153

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 0.374 34.3 64.1 9.9 0.005

66 02335870 Sope Creek near Marietta, Ga. 0.523 –6.3 9.8 –20.1 0.422

71 02492000 Bogue Chitto River near Bush, La. 0.243 139.0 343.6 28.7 0.007

72 03353637 Little Buck Creek near Indianapolis, Ind. 0.862 –36.2 –19.8 –49.3 <0.001

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 1.030 –8.0 16.9 –27.6 0.495

74 04063700 Popple River near Fence, Wis. 0.045 12.4 71.6 –26.5 0.591

76 04087000 Milwaukee River at Milwaukee, Wis. 0.673 92.2 181.0 31.4 0.001

81 05114000 Souris River near Sherwood, N. Dak. 0.047 –14.7 104.8 –64.4 0.724

82 05120000 Souris River near Verendrye, N. Dak. 0.147 –61.7 24.9 –88.3 0.116

88 05514500 Cuivre River near Troy, Mo. 0.329 37.6 305.4 –53.3 0.565

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 0.842 –51.7 –30.1 –66.7 <0.001

95 07022000 Mississippi River at Thebes, Ill. 2.367 0.7 31.2 –22.6 0.956

96 06088500 Muddy Creek at Vaughn, Mont. 2.327 –49.8 –27.9 –65.1 <0.001

98 06274300 Bighorn River at Basin, Wyo. 0.288 –47.7 –19.3 –66.1 0.006

99 06329500 Yellowstone River near Sidney, Mont. 0.171 –10.0 123.1 –63.7 0.820

100 06338490 Missouri River at Garrison Dam, N. Dak. 0.135 –73.2 –55.6 –83.8 <0.001

101 06461500 Niobrara River near Sparks, Nebr. 0.262 51.9 131.0 –0.1 0.055

102 06468250 James River above Arrowwood Lake near Kensal, N. Dak. 0.071 –74.2 –14.7 –92.2 0.029

103 06713500 Cherry Creek at Denver, Colo. 2.735 –46.6 –35.0 –56.2 <0.001

104 06752260 Cache La Poudre River at Fort Collins, Colo. 0.293 –73.6 –56.5 –84.0 <0.001

105 06752280 Cache La Poudre River above Boxelder Creek, near 

Timnath, Colo.

0.576 –13.4 30.9 –42.7 0.497

106 06753990 Lonetree Creek near Greeley, Colo. 6.915 –56.3 –40.4 –68.0 <0.001

107 06754000 South Platte River near Kersey, Colo. 4.974 2.7 11.4 –5.4 0.533

108 06775900 Dismal River near Thedford, Nebr. 0.458 7.7 25.1 –7.3 0.335

109 06800000 Maple Creek near Nickerson, Nebr. 6.192 –29.7 5.2 –53.0 0.089

110 06805500 Platte River at Louisville, Nebr. 1.487 9.7 108.4 –42.3 0.779

111 06817700 Nodaway River near Graham, Mo. 3.433 52.4 407.1 –54.2 0.494

112 06818000 Missouri River at St. Joseph, Mo. 1.951 –62.9 –37.1 –78.1 <0.001

113 06902000 Grand River near Sumner, Mo. 0.431 51.2 297.9 –42.6 0.404

114 06905500 Chariton River near Prairie Hill, Mo. 0.420 80.7 286.0 –15.4 0.130

115 06921070 Pomme De Terre River near Polk, Mo. 0.215 126.1 470.8 –10.5 0.088

116 06926510 Osage River below St. Thomas, Mo. 0.352 –59.5 –18.1 –80.0 0.015

117 06930800 Gasconade River above Jerome, Mo. 0.416 –0.7 49.1 –33.8 0.974

118 06934500 Missouri River at Hermann, Mo. 1.399 –29.6 11.6 –55.6 0.138

119 07047942 L'Anguille River near Colt, Ark. 0.451 –46.1 –6.6 –68.9 0.032

120 07053250 Yocum Creek near Oak Grove, Ark. 2.245 109.0 195.9 47.6 <0.001

121 07056000 Buffalo River near St Joe, Ark. 0.067 67.3 151.7 11.3 0.015

122 07060500 White River at Calico Rock, Ark. 0.241 28.2 81.9 –9.6 0.169

123 07060710 North Sylamore Creek near Fifty Six, Ark. 0.064 –2.3 30.5 –26.9 0.873
42 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 4. Flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site 

number 

(figure 1)

Station 

number Station name

Reference 

concentration, 

in milligrams 

per liter1

Trend, in percent from 

1993 to 2003

p-value Modeled 

estimate

Upper 

95-percent 

CI

Lower 

95-percent 

CI

Nitrate—Continued

124 07066110 Jacks Fork above Two River, Mo. 0.290 22.7 53.9 –2.2 0.081

125 07068000 Current River at Doniphan, Mo. 0.282 –13.2 5.1 –28.3 0.150

126 07077500 Cache River at Patterson, Ark. 0.256 –17.5 39.7 –51.3 0.479

127 07077700 Bayou DeView near Morton, Ark. 0.153 69.9 222.4 –10.5 0.117

128 07103700 Fountain Creek near Colorado Springs, Colo. 0.750 –5.8 14.7 –22.6 0.555

129 07103780 Monument Creek above North Gate Boulevard at United 

States Air Force Academy, Colo.

0.127 282.0 708.1 80.5 0.001

130 07105500 Fountain Creek at Colorado Springs, Colo. 1.563 8.6 25.1 –5.7 0.254

131 07105530 Fountain Creek below Janitell Road below Colorado 

Springs, Colo.

1.665 45.2 68.9 24.8 <0.001

132 07106300 Fountain Creek near Pinon, Colo. 5.192 –48.4 –35.0 –59.0 <0.001

133 07106500 Fountain Creek at Pueblo, Colo. 5.306 –55.1 –50.0 –59.7 <0.001

134 07189000 Elk River near Tiff City, Mo. 1.572 46.4 76.1 21.7 <0.001

135 07195500 Illinois River near Watts, Okla. 2.450 –17.7 13.4 –40.3 0.236

136 07195865 Sager Creek near West Siloam Springs, Okla. 6.241 11.5 49.4 –16.8 0.469

137 07196000 Flint Creek near Kansas, Okla. 1.871 59.6 79.5 42.0 <0.001

138 07196500 Illinois River near Tahlequah, Okla. 1.684 2.6 24.0 –15.1 0.791

139 07197000 Baron Fork at Eldon, Okla. 1.033 35.0 78.2 2.2 0.037

140 07227500 Canadian River near Amarillo, Tex. 0.173 515.1 1605.0 121.9 0.001

141 07239450 North Canadian River near Calumet, Okla. 0.084 –32.6 58.2 –71.3 0.366

142 07241000 North Canadian River below Lake Overholser near 

Oklahoma City, Okla.

0.249 –47.1 –1.6 –71.6 0.046

143 07241520 North Canadian River at Britton Road 

at Oklahoma City, Okla.

0.601 –28.4 19.1 –56.9 0.201

144 07241550 North Canadian River near Harrah, Okla. 1.176 0.0 44.8 –31.0 0.998

145 07247015 Poteau River at Loving, Okla. 0.088 45.8 161.3 –18.6 0.209

146 07247250 Black Fork below Big Creek near Page, Okla. 0.063 124.0 263.5 38.0 0.002

147 07247345 Black Fork at Hodgen, Okla. 0.033 109.8 281.3 15.5 0.018

148 07247650 Fourche Maline near Leflore, Okla. 0.093 8.4 76.4 –33.3 0.745

149 07263620 Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Ark.

0.382 –50.8 –12.6 –72.3 0.018

150 07331000 Washita River near Dickson, Okla. 0.366 17.6 178.9 –50.4 0.714

151 07355500 Red River at Alexandria, La. 0.155 –43.1 –9.9 –64.1 0.018

152 07362000 Ouachita River at Camden, Ark. 0.126 2.9 62.8 –35.0 0.903

153 07373420 Mississippi River near St Francisville, La. 1.562 –15.4 3.1 –30.6 0.100

154 07375500 Tangipahoa River at Robert, La. 0.366 –13.6 6.2 –29.6 0.168

155 07376000 Tickfaw River at Holden, La. 0.301 –13.9 6.7 –30.4 0.175

156 07381495 Atchafalaya River at Melville, La. 1.123 –16.0 5.1 –32.9 0.129

157 07386980 Vermilion River at Perry, La. 0.376 27.9 91.3 –14.4 0.233

158 08030500 Sabine River near Ruliff, Tex. 0.078 –31.8 –0.9 –53.1 0.047

159 08032000 Neches River near Neches, Tex. 0.135 –9.4 57.1 –47.7 0.727

160 08033500 Neches River near Rockland, Tex. 0.184 8.9 74.3 –31.9 0.722

161 08051500 Clear Creek near Sanger, Tex. 0.122 67.4 219.6 –12.4 0.122

162 08064100 Chambers Creek near Rice, Tex. 0.254 –16.4 57.9 –55.7 0.582

163 08065350 Trinity River near Crockett, Tex. 1.673 –2.3 66.3 –42.6 0.932

164 08136500 Concho River at Paint Rock, Tex. 11.897 –93.4 –76.6 –98.1 <0.001

167 08155200 Barton Creek at State Highway 71 near Oak Hill, Tex. 0.042 5.0 83.9 –40.0 0.864

168 08155240 Barton Creek at Lost Creek Boulevard near Austin, Tex. 0.063 54.9 132.9 2.9 0.039

172 08181800 San Antonio River near Elmendorf, Tex. 8.417 13.3 51.2 –15.0 0.396
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 43

Table 4. Flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site 

number 

(figure 1)

Station 

number Station name

Reference 

concentration, 

in milligrams 

per liter1

Trend, in percent from 

1993 to 2003

p-value Modeled 

estimate

Upper 

95-percent 

CI

Lower 

95-percent 

CI

Nitrate—Continued

174 09058000 Colorado River near Kremmling, Colo. 0.121 –0.2 49.5 –33.3 0.994

175 09163500 Colorado River near Colorado-Utah State Line 0.579 –9.2 10.7 –25.5 0.343

177 09217010 Green River below Green River, Wyo. 0.070 –10.1 32.5 –38.9 0.594

181 09413500 Virgin River below First Narrows, Utah 0.901 29.8 84.3 –8.6 0.148

187 10038000 Bear River below Smiths Fork, near Cokeville, Wyo. 0.089 –39.3 –10.9 –58.7 0.013

189 10131000 Chalk Creek at U.S. 189 Crossing, Utah 0.253 –17.9 19.3 –43.5 0.303

190 10154200 Provo River above Woodland at U.S. Geological Survey 

Gage Number 10154200, Utah

0.112 98.6 207.9 28.1 0.003

191 10155000 Provo River at Bridge 2.5 miles East of Hailstone 

Junction, Utah

0.039 301.6 649.6 115.1 <0.001

192 10155500 Provo River above Confluence with Snake Creek at 

McKeller Bridge, Utah

0.463 –54.8 –36.5 –67.8 <0.001

194 10336580 Upper Truckee River at South Upper Truckee Road near 

Meyers, Calif.

0.009 2.1 39.2 –25.1 0.894

195 103366092 Upper Truckee River at Highway 50 above 

Meyers, Calif.

0.014 –21.3 –2.2 –36.7 0.032

197 10336698 Third Creek near Crystal Bay, Nev. 0.017 –67.9 –56.7 –76.2 <0.001

198 103366993 Incline Creek above Tyrol Village near Incline Village, Nev. 0.013 10.3 45.9 –16.6 0.491

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 0.019 2.4 26.6 –17.2 0.829

200 10336700 Incline Creek near Crystal Bay, Nev. 0.021 –0.7 21.7 –18.9 0.949

201 10336740 Logan House Creek near Glenbrook, Nev. 0.004 70.7 396.2 –41.3 0.328

205 07A090 Snohomish River at Snohomish, Wash. 0.236 –7.0 10.2 –21.6 0.401

207 09A190 Green River at Kanaskat, Wash. 0.084 –4.0 32.2 –30.2 0.805

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 0.587 –24.1 6.9 –46.1 0.121

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

0.348 –39.8 –20.0 –54.6 0.001

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 0.153 –27.0 –10.3 –40.7 0.003

213 10555 Willamette River at Marion Street at Salem, Oreg. 0.473 –44.2 –30.8 –54.9 <0.001

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

0.152 30.3 94.9 –12.9 0.203

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 0.161 –22.9 54.5 –61.6 0.467

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. 4.288 –29.6 –20.8 –37.5 <0.001

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 0.446 –11.8 17.2 –33.6 0.390

225 13351000 Palouse River at Hooper, Wash. 1.113 –12.2 27.8 –39.7 0.499

226 14201300 Zollner Creek near Mt. Angel, Oreg. 8.370 25.0 54.2 1.3 0.039

228 14246900 Columbia River at Beaver Army Terminal near 

Quincy, Oreg.

0.289 –33.2 –11.5 –49.5 0.006

229 16A070 Skokomish River near Potlatch, Wash. 0.105 –59.7 –47.4 –69.1 <0.001

234 45A070 Wenatchee River at Wenatchee, Wash. 0.064 1.2 25.8 –18.6 0.916

235 45A110 Wenatchee River near Leavenworth, Wash. 0.026 7.6 57.9 –26.7 0.709

237 49A070 Okanogan River at Malott, Wash. 0.023 7.6 87.5 –38.3 0.796

238 54A120 Spokane River at Riverside State Park, Wash. 0.346 47.9 86.7 17.2 0.001

239 61A070 Columbia River at Northport, Wash. 0.056 0.5 19.1 –15.2 0.956

240 11264500 Merced River at Happy Isles Bridge near Yosemite, Calif. 0.053 –50.6 –16.3 –70.8 0.010

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. 2.006 5.3 36.8 –18.9 0.698

242 11290000 Tuolumne River at Modesto, Calif. 0.254 125.8 173.3 86.5 <0.001

243 11303500 San Joaquin River near Vernalis, Calif. 0.987 4.8 15.4 –4.8 0.335

244 11447650 Sacramento River at Freeport, Calif. 0.147 –32.4 –10.0 –49.2 0.008

1

Reference value is the concentration that would have been observed on the first day of the period of record under average hydrologic and seasonal conditions.
44 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 5. Non-flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

concentration,

in milligrams

per liter1

Trend, in percent from 1993 to 2003

Modeled p-value

estimate

Upper

95-percent 

CI

Lower

95-percent

CI

Total phosphorus

1 01122610 Shetucket River at South Windham, Conn. 0.021 66.7 166.4 4.3 0.033

2 01124000 Quinebaug River at Quinebaug, Conn. 0.036 24.2 94.9 –20.9 0.347

3 01127000 Quinebaug River at Jewett City, Conn. 0.046 81.6 169.9 22.2 0.003

4 01184000 Connecticut River at Thompsonville, Conn. 0.033 28.0 91.3 –14.3 0.228

5 01184490 Broad Brook at Broad Brook, Conn. 0.092 –17.0 19.2 –42.3 0.312

7 01189995 Farmington River at Tariffville, Conn. 0.087 55.8 110.8 15.1 0.004

8 01192500 Hockanum River near East Hartford, Conn. 0.364 –8.1 24.8 –32.3 0.590

10 01196500 Quinnipiac River at Wallingford, Conn. 0.241 –18.1 9.1 –38.5 0.173

11 01205500 Housatonic River at Stevenson, Conn. 0.021 10.3 188.7 –57.8 0.841

12 01208500 Naugatuck River at Beacon Falls, Conn. 0.227 74.8 163.2 16.1 0.007

13 01208990 Saugatuck River near Redding, Conn. 0.012 26.6 326.9 –62.5 0.704

14 01209710 Norwalk River at Winnipauk, Conn. 0.030 43.9 95.6 5.8 0.020

15 01357500 Mohawk River at Cohoes, N.Y. 0.034 13.9 76.5 –26.5 0.559

16 01377000 Hackensack River at Rivervale, N.J. 0.065 20.7 104.4 –28.7 0.484

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 0.025 –53.1 67.0 –86.8 0.242

18 01387500 Ramapo River near Mahwah, N.J. 0.120 –6.9 48.7 –41.7 0.763

19 01389500 Passaic River at Little Falls, N.J. 0.372 19.3 101.4 –29.3 0.509

20 01391500 Saddle River at Lodi, N.J. 0.369 115.1 241.7 35.4 0.001

22 01395000 Rahway River at Rahway, N.J. 0.071 35.7 87.2 –1.7 0.063

24 01398000 Neshanic River at Reaville, N.J. 0.042 23.8 184.0 –46.0 0.614

25 01402000 Millstone River at Blackwells Mills, N.J. 0.195 34.3 89.1 –4.7 0.092

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 0.160 21.4 73.2 –14.9 0.285

27 01408000 Manasquan River at Squankum, N.J. 0.099 –4.7 71.7 –47.1 0.872

28 01408500 Toms River near Toms River, N.J. 0.024 29.1 269.6 –54.9 0.634

30 01411500 Maurice River at Norma, N.J. 0.014 –14.1 221.7 –77.1 0.821

31 01438500 Delaware River at Montague, N.J. 0.041 –43.9 57.1 –80.0 0.271

32 01443500 Paulins Kill at Blairstown, N.J. 0.025 4.5 116.1 –49.4 0.905

33 01463500 Delaware River at Trenton, N.J. 0.057 –10.7 26.2 –36.9 0.520

34 01467150 Cooper River at Haddonfield, N.J. 0.198 –3.7 37.1 –32.3 0.835

35 01477120 Raccoon Creek near Swedesboro, N.J. 0.117 27.9 80.9 –9.6 0.164

36 01491000 Choptank River near Greensboro, Md. 0.045 113.6 235.0 36.1 0.001

37 01578310 Susquehanna River at Conowingo, Md. 0.021 64.5 127.5 18.9 0.003

38 01594440 Patuxent River near Bowie, Md. 0.116 41.0 84.2 7.9 0.012

39 01614500 Conococheague Creek at Fairview, Md. 0.114 14.5 63.0 –19.6 0.454

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 0.030 76.4 196.4 5.0 0.032

41 01668000 Rappahannock River near Fredericksburg, Va. 0.033 6.7 125.6 –49.6 0.866

42 01673000 Pamunkey River near Hanover, Va. 0.066 82.3 113.6 55.5 <0.001

43 01674500 Mattaponi River near Beulahville, Va. 0.059 –6.9 12.2 –22.8 0.451

44 02035000 James River at Cartersville, Va. 0.100 –11.0 15.1 –31.2 0.375

45 02041650 Appomattox River at Matoaca, Va. 0.047 –13.5 10.1 –32.0 0.238

46 02085000 Eno River at Hillsborough, N.C. 0.025 42.4 144.6 –17.1 0.200

51 02198500 Savannah River near Clyo, Ga. 0.093 42.2 91.4 5.6 0.020

52 02213700 Ocmulgee River near Warner Robins, Ga. 0.177 –38.3 –11.8 –56.9 0.008

53 02215500 Ocmulgee River at Lumber City, Ga. 0.117 –40.4 –23.2 –53.8 <0.001

54 02223600 Oconee River at Interstate 16, near Dublin, Ga. 0.135 –20.3 0.4 –36.7 0.054

55 02226010 Altamaha River near Gardi, Ga. 0.106 –9.2 11.0 –25.7 0.347

56 02226582 Satilla River at GA 15&121, near Hoboken, Ga. 0.140 48.0 118.5 0.3 0.049

58 02295420 Payne Creek near Bowling Green, Fla. 0.620 31.4 66.8 3.5 0.025

59 02296750 Peace River at Arcadia, Fla. 0.940 –3.8 15.4 –19.8 0.676

60 02300700 Bullfrog Creek near Wimauma, Fla. 0.227 7.9 32.4 –12.1 0.469
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 45

Table 5. Non-flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

concentration,

in milligrams

per liter1

Trend, in percent from 1993 to 2003

Modeled p-value

estimate

Upper

95-percent 

CI

Lower

95-percent

CI

Total phosphorus—Continued

61 02301300 South Prong Alafia River near Lithia, Fla. 0.954 –39.2 –14.7 –56.7 0.004

62 02302500 Blackwater Creek near Knights, Fla. 0.807 –40.3 –22.1 –54.3 <0.001

63 02303000 Hillsborough River near Zephyrhills, Fla. 0.323 –49.8 2.7 –75.5 0.059

64 02314500 Suwannee River at U.S. 441, at Fargo, Ga. 0.066 –71.0 –57.7 –80.0 <0.001

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 0.150 29.9 140.8 –30.0 0.407

66 02335870 Sope Creek near Marietta, Ga. 0.017 –26.2 38.8 –60.7 0.346

68 02344040 Chattahoochee River near Steam Mill, Ga. 0.085 –54.8 –31.0 –70.3 <0.001

69 02353000 Flint River at Newton, Ga. 0.049 –20.7 8.0 –41.7 0.141

70 02388520 Oostanaula River at Rome, Ga. 0.217 –55.1 –41.0 –65.7 <0.001

71 02492000 Bogue Chitto River near Bush, La. 0.070 38.2 86.6 2.3 0.035

72 03353637 Little Buck Creek near Indianapolis, Ind. 0.024 0.0 66.7 –40.0 0.999

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 0.082 60.9 121.2 17.0 0.003

74 04063700 Popple River near Fence, Wis. 0.027 –26.0 33.5 –58.9 0.318

75 04073468 Green Lake Inlet at County Highway A near Green 

Lake, Wis.

0.134 –27.3 –18.0 –35.5 <0.001

76 04087000 Milwaukee River at Milwaukee, Wis. 0.083 23.3 50.2 1.2 0.038

77 0422026250 Northrup Creek at North Greece, N.Y. 0.402 –41.3 –28.5 –51.9 <0.001

78 04232034 Irondequoit Creek at Railroad Mills near Fishers, N.Y. 0.070 –31.8 –6.9 –50.1 0.016

79 0423204920 East Branch Allen Creek at Pittsford, N.Y. 0.090 –19.2 –2.4 –33.1 0.027

80 0423205025 Irondequoit Creek at Empire Boulevard at Rochester, N.Y. 0.068 41.6 63.3 22.8 <0.001

81 05114000 Souris River near Sherwood, N. Dak. 0.424 –42.8 –9.8 –63.7 0.016

82 05120000 Souris River near Verendrye, N. Dak. 0.264 –13.7 21.5 –38.7 0.399

83 05287890 Elm Creek near Champlin, Minn. 0.139 16.5 58.1 –14.2 0.327

84 05427718 Yahara River at Windsor, Wis. 0.149 –37.9 –12.3 –56.0 0.007

85 05427948 Pheasant Branch at Middleton, Wis. 0.390 –64.7 –55.3 –72.1 <0.001

86 054310157 Jackson Creek Tributary near Elkhorn, Wis. 0.129 –15.5 18.3 –39.6 0.327

87 05500000 South Fabius River near Taylor, Mo. 0.102 –15.8 39.0 –49.0 0.501

88 05514500 Cuivre River near Troy, Mo. 0.136 –23.0 46.5 –59.5 0.426

89 05525500 Sugar Creek at Milford, Ill. 0.060 23.0 128.5 –33.8 0.513

90 05531500 Salt Creek at Western Springs, Ill. 1.019 49.4 99.1 12.1 0.006

91 05532500 Des Plaines River at Riverside, Ill. 0.517 84.0 143.4 39.1 <0.001

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 0.079 –19.2 17.5 –44.5 0.265

93 05586100 Illinois River at Valley City, Ill. 0.264 112.3 171.1 66.3 <0.001

94 07018100 Big River near Richwoods, Mo. 0.032 –11.7 37.5 –43.3 0.581

95 07022000 Mississippi River at Thebes, Ill. 0.230 26.2 73.1 –7.9 0.148

97 06178000 Poplar River at International Boundary, Mont. 0.029 –20.6 55.0 –59.4 0.499

99 06329500 Yellowstone River near Sidney, Mont. 0.075 6.3 118.5 –48.3 0.868

101 06461500 Niobrara River near Sparks, Nebr. 0.121 33.5 80.4 –1.3 0.061

106 06753990 Lonetree Creek near Greeley, Colo. 0.325 –73.0 –35.5 –88.7 0.003

107 06754000 South Platte River near Kersey, Colo. 0.636 34.6 59.6 13.5 0.001

109 06800000 Maple Creek near Nickerson, Nebr. 0.207 105.8 237.0 25.7 0.004

110 06805500 Platte River at Louisville, Nebr. 0.313 89.4 161.3 37.2 <0.001

111 06817700 Nodaway River near Graham, Mo. 0.327 –36.2 27.3 –68.0 0.203

112 06818000 Missouri River at St. Joseph, Mo. 0.216 23.4 81.2 –16.0 0.284

113 06902000 Grand River near Sumner, Mo. 0.202 12.9 119.5 –41.9 0.720

114 06905500 Chariton River near Prairie Hill, Mo. 0.207 –42.8 13.8 –71.2 0.112

115 06921070 Pomme De Terre River near Polk, Mo. 0.047 –22.8 20.9 –50.7 0.258

118 06934500 Missouri River at Hermann, Mo. 0.187 64.5 169.3 0.5 0.048

120 07053250 Yocum Creek near Oak Grove, Ark. 0.039 18.9 52.9 –7.5 0.176

134 07189000 Elk River near Tiff City, Mo. 0.041 280.3 433.1 171.2 <0.001
46 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 5. Non-flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

concentration,

in milligrams

per liter1

Trend, in percent from 1993 to 2003

Modeled p-value

estimate

Upper

95-percent 

CI

Lower

95-percent

CI

Total phosphorus—Continued

135 07195500 Illinois River near Watts, Okla. 0.112 110.3 206.8 44.1 <0.001

136 07195865 Sager Creek near West Siloam Springs, Okla. 0.495 94.5 250.7 7.9 0.027

137 07196000 Flint Creek near Kansas, Okla. 0.092 79.7 130.6 40.1 <0.001

138 07196500 Illinois River near Tahlequah, Okla. 0.063 80.4 139.7 35.7 <0.001

139 07197000 Baron Fork at Eldon, Okla. 0.028 6.5 64.0 –30.9 0.777

145 07247015 Poteau River at Loving, Okla. 0.106 –13.6 29.7 –42.4 0.481

148 07247650 Fourche Maline near Leflore, Okla. 0.051 –0.6 39.0 –28.9 0.971

149 07263620 Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Ark.

0.081 47.4 91.5 13.4 0.004

150 07331000 Washita River near Dickson, Okla. 0.201 19.8 109.7 –31.5 0.526

151 07355500 Red River at Alexandria, La. 0.095 –30.4 –0.1 –51.5 0.050

152 07362000 Ouachita River at Camden, Ark. 0.041 –27.2 26.5 –58.1 0.260

153 07373420 Mississippi River near St Francisville, La. 0.175 45.7 82.0 16.6 0.001

154 07375500 Tangipahoa River at Robert, La. 0.112 1.6 43.7 –28.2 0.929

155 07376000 Tickfaw River at Holden, La. 0.074 46.0 103.3 4.9 0.025

156 07381495 Atchafalaya River at Melville, La. 0.146 52.7 85.9 25.4 <0.001

157 07386980 Vermilion River at Perry, La. 0.297 1.9 30.1 –20.3 0.882

165 08143600 Pecan Bayou near Mullin, Tex. 0.205 –3.2 81.1 –48.2 0.920

166 08147000 Colorado River near San Saba, Tex. 0.077 –69.1 2.4 –90.7 0.055

169 08159000 Onion Creek at U.S. Highway 183, Austin, Tex. 0.076 –91.7 –61.7 –98.2 0.001

170 08162000 Colorado River at Wharton, Tex. 0.269 –3.1 52.1 –38.3 0.890

171 08162500 Colorado River near Bay City, Tex. 0.291 –24.9 30.6 –56.8 0.310

173 08251500 Rio Grande near Lobatos, Colo. 0.079 25.8 66.8 –5.2 0.111

177 09217010 Green River below Green River, Wyo. 0.026 90.3 281.9 –5.2 0.070

178 09261000 Green River at Dinosaur National Monument 

Utah 149 Crossing, Utah

0.062 –43.8 33.1 –76.2 0.190

180 09403600 Kanab Creek at U.S. 89 Crossing, Utah 0.035 135.1 451.5 0.2 0.049

182 09415000 Virgin River at Littlefield, Ariz. 0.106 58.4 336.2 –42.5 0.373

183 09448500 Gila River at Head of Safford Valley, near Solomon, Ariz. 0.122 –26.9 230.6 –83.8 0.684

184 09498500 Salt River near Roosevelt, Ariz. 0.013 514.5 5184.4 –28.6 0.098

185 09508500 Verde River below Tangle Creek, above Horseshoe 

Dam, Ariz.

0.023 35.8 234.2 –44.9 0.506

186 09522000 Colorado River at Northerly International Boundary, 

above Morelos Dam, Ariz.

0.280 –88.7 –67.6 –96.1 <0.001

188 10126000 Bear River near Corinne at Utah 83 Crossing, Utah 0.188 –48.3 –22.2 –65.6 0.002

193 10189000 East Fork Sevier River at Utah 62 Crossing East of 

Kingston, Utah

0.085 –8.5 32.7 –36.9 0.639

203 01A050 Nooksack River at Brennan, Wash. 0.021 43.5 129.1 –10.1 0.130

204 03A060 Skagit River near Mount Vernon, Wash. 0.015 6.0 123.6 –49.7 0.878

205 07A090 Snohomish River at Snohomish, Wash. 0.009 26.0 125.1 –29.5 0.435

206 09A080 Green River at Tukwila, Wash. 0.025 18.6 58.5 –11.3 0.250

207 09A190 Green River at Kanaskat, Wash. 0.005 244.0 597.2 69.7 0.001

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 0.070 –7.3 9.6 –21.6 0.372

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

0.075 –20.1 –4.4 –33.2 0.014

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 0.046 –4.9 17.6 –23.2 0.641

211 10386 Middle Fork Willamette at Jasper Bridge, Oreg. 0.028 –15.3 3.7 –30.8 0.107

212 10411 Deschutes River at Deschutes River Park, Oreg. 0.080 –8.9 29.5 –35.9 0.604

213 10555 Willamette River at Marion Street at Salem, Oreg. 0.064 –20.6 –5.4 –33.3 0.010

214 10611 Willamette River at Hawthorne Bridge, Oreg. 0.082 –21.7 –11.6 –30.5 <0.001

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

0.040 –24.8 3.1 –45.1 0.077
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 47

Table 5. Non-flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

concentration,

in milligrams

per liter1

Trend, in percent from 1993 to 2003

Modeled p-value

estimate

Upper

95-percent 

CI

Lower

95-percent

CI

Total phosphorus—Continued

216 10A070 Puyallup River at Meridian Street, Wash. 0.036 87.4 196.4 18.5 0.007

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 0.081 –21.5 –2.2 –36.9 0.031

218 11321 Johnson Creek at Southeast 17th Avenue 

at Portland, Oreg.

0.090 –10.3 8.5 –25.9 0.261

219 11478 John Day River at Service Creek, Oreg. 0.041 –32.8 –2.8 –53.5 0.035

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. 0.104 –33.7 –6.6 –52.9 0.019

221 12413470 South Fork Coeur D'Alene River near Pinehurst, Idaho 0.011 94.5 250.1 8.1 0.027

222 12419000 Spokane River near Post Falls, Idaho 0.011 –36.0 93.6 –78.8 0.430

223 13154500 Snake River at King Hill, Idaho 0.068 –8.9 14.4 –27.5 0.422

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 0.083 37.0 199.8 –37.4 0.431

225 13351000 Palouse River at Hooper, Wash. 0.195 –51.7 –26.2 –68.4 0.001

227 14211720 Willamette River at Portland, Oreg. 0.061 13.8 37.2 –5.5 0.173

228 14246900 Columbia River at Beaver Army Terminal near 

Quincy, Oreg.

0.031 7.8 70.6 –31.9 0.748

229 16A070 Skokomish River near Potlatch, Wash. 0.009 112.2 282.8 17.7 0.012

230 32A070 Walla Walla River near Touchet, Wash. 0.112 –4.5 21.2 –24.7 0.707

231 3701002 Tualatin River at Weiss Bridge, Oreg. 0.175 –31.9 –23.6 –39.4 <0.001

232 37016120 Tualatin River at Springhill Road Bridge at Dilley, Oreg. 0.039 –40.9 –27.2 –52.0 <0.001

233 37A090 Yakima River at Kiona, Wash. 0.102 3.8 24.8 –13.7 0.693

234 45A070 Wenatchee River at Wenatchee, Wash. 0.004 52.5 272.8 –37.6 0.354

235 45A110 Wenatchee River near Leavenworth, Wash. 0.004 12.3 156.4 –50.8 0.783

236 48A070 Methow River near Pateros, Wash. 0.003 95.3 280.8 0.1 0.050

237 49A070 Okanogan River at Malott, Wash. 0.017 –2.1 89.8 –49.6 0.949

238 54A120 Spokane River at Riverside State Park, Wash. 0.019 42.1 131.9 –13.0 0.160

239 61A070 Columbia River at Northport, Wash. 0.011 –33.2 25.4 –64.5 0.209

241 11274538 Orestimba Creek at River Road near Crows 

Landing, Calif.

0.183 15.8 54.8 –13.4 0.324

242 11290000 Tuolumne River at Modesto, Calif. 0.074 2.0 63.7 –36.4 0.934

243 11303500 San Joaquin River near Vernalis, Calif. 0.274 –2.4 13.2 –15.9 0.748

244 11447650 Sacramento River at Freeport, Calif. 0.039 57.9 122.4 12.1 0.009

Total nitrogen

1 01122610 Shetucket River at South Windham, Conn. 0.603 10.4 39.2 –12.4 0.403

2 01124000 Quinebaug River at Quinebaug, Conn. 0.530 44.3 81.0 15.0 0.002

3 01127000 Quinebaug River at Jewett City, Conn. 0.913 –4.0 13.6 –18.8 0.638

4 01184000 Connecticut River at Thompsonville, Conn. 0.624 4.9 25.4 –12.4 0.604

5 01184490 Broad Brook at Broad Brook, Conn. 4.259 0.1 9.4 –8.5 0.988

6 01188090 Farmington River at Unionville, Conn. 0.270 41.6 109.4 –4.2 0.081

7 01189995 Farmington River at Tariffville, Conn. 1.018 23.0 53.8 –1.6 0.069

8 01192500 Hockanum River near East Hartford, Conn. 3.480 5.5 29.7 –14.2 0.614

9 01193500 Salmon River near East Hampton, Conn. 0.436 13.8 58.4 –18.3 0.445

10 01196500 Quinnipiac River at Wallingford, Conn. 3.208 –1.3 20.4 –19.1 0.895

11 01205500 Housatonic River at Stevenson, Conn. 0.661 12.1 41.2 –11.0 0.333

12 01208500 Naugatuck River at Beacon Falls, Conn. 2.492 –49.3 –31.7 –62.3 <0.001

13 01208990 Saugatuck River near Redding, Conn. 0.307 40.3 106.5 –4.6 0.085

14 01209710 Norwalk River at Winnipauk, Conn. 0.642 24.3 47.0 5.1 0.011

15 01357500 Mohawk River at Cohoes, N.Y. 1.048 –9.1 2.5 –19.4 0.120

16 01377000 Hackensack River at Rivervale, N.J. 1.032 13.5 41.5 –9.0 0.261

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 0.500 21.5 69.4 –12.8 0.250

18 01387500 Ramapo River near Mahwah, N.J. 1.537 –5.3 39.2 –35.6 0.781

19 01389500 Passaic River at Little Falls, N.J. 3.357 –12.2 39.4 –44.7 0.582

20 01391500 Saddle River at Lodi, N.J. 5.794 24.5 66.9 –7.2 0.144
48 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 5. Non-flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

concentration,

in milligrams

per liter1

Trend, in percent from 1993 to 2003

Modeled p-value

estimate

Upper

95-percent 

CI

Lower

95-percent

CI

Total nitrogen—Continued

21 01394500 Rahway River near Springfield, N.J. 1.727 0.9 25.5 –18.8 0.934

22 01395000 Rahway River at Rahway, N.J. 1.407 –0.1 25.2 –20.3 0.993

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 1.090 –13.6 7.2 –30.3 0.184

24 01398000 Neshanic River at Reaville, N.J. 1.753 –14.2 39.0 –47.0 0.534

25 01402000 Millstone River at Blackwells Mills, N.J. 2.902 11.7 42.0 –12.2 0.368

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 2.316 16.4 40.5 –3.7 0.116

29 01409500 Batsto River at Batsto, N.J. 0.386 –22.1 12.0 –45.9 0.178

31 01438500 Delaware River at Montague, N.J. 0.487 –23.2 –1.2 –40.2 0.040

32 01443500 Paulins Kill at Blairstown, N.J. 0.958 4.7 34.2 –18.4 0.720

33 01463500 Delaware River at Trenton, N.J. 1.277 –18.3 –3.7 –30.6 0.016

34 01467150 Cooper River at Haddonfield, N.J. 0.921 0.9 24.3 –18.2 0.936

35 01477120 Raccoon Creek near Swedesboro, N.J. 1.658 8.9 33.6 –11.3 0.415

36 01491000 Choptank River near Greensboro, Md. 1.457 22.4 35.8 10.2 <0.001

37 01578310 Susquehanna River at Conowingo, Md. 1.526 –9.4 –0.3 –17.6 0.042

38 01594440 Patuxent River near Bowie, Md. 2.078 0.5 11.0 –9.0 0.921

39 01614500 Conococheague Creek at Fairview, Md. 5.429 –3.7 8.3 –14.3 0.530

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 2.010 –18.7 10.5 –40.2 0.186

41 01668000 Rappahannock River near Fredericksburg, Va. 0.577 17.5 82.1 –24.2 0.471

42 01673000 Pamunkey River near Hanover, Va. 0.653 27.0 42.6 13.1 <0.001

43 01674500 Mattaponi River near Beulahville, Va. 0.623 10.1 25.2 –3.1 0.140

44 02035000 James River at Cartersville, Va. 0.478 1.8 42.5 –27.3 0.918

45 02041650 Appomattox River at Matoaca, Va. 0.587 11.9 23.6 1.3 0.027

46 02085000 Eno River at Hillsborough, N.C. 0.664 18.0 48.3 –6.1 0.155

47 02089500 Neuse River at Kinston, N.C. 1.493 –36.8 –27.3 –45.1 <0.001

48 02091500 Contentnea Creek at Hookerton, N.C. 1.242 –11.5 –3.4 –18.9 0.006

49 0210215985 Cape Fear River at State Highway 42 near 

Brickhaven, N.C.

1.363 0.8 37.2 –26.0 0.961

52 02213700 Ocmulgee River near Warner Robins, Ga. 1.350 6.7 44.8 –21.4 0.679

53 02215500 Ocmulgee River at Lumber City, Ga. 0.965 –7.5 14.8 –25.4 0.481

57 02271500 Josephine Creek near De Soto City, Fla. 0.889 37.2 78.2 5.6 0.018

58 02295420 Payne Creek near Bowling Green, Fla. 1.696 –5.1 26.9 –29.0 0.726

59 02296750 Peace River at Arcadia, Fla. 1.780 –3.7 12.4 –17.4 0.635

60 02300700 Bullfrog Creek near Wimauma, Fla. 0.782 19.0 46.8 –3.6 0.106

61 02301300 South Prong Alafia River near Lithia, Fla. 1.056 7.2 40.6 –18.4 0.618

62 02302500 Blackwater Creek near Knights, Fla. 1.693 –20.7 2.8 –38.7 0.080

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 1.005 41.4 103.0 –1.5 0.060

67 02338000 Chattahoochee River near Whitesburg, Ga. 1.386 43.6 89.8 8.5 0.011

71 02492000 Bogue Chitto River near Bush, La. 0.819 –10.9 67.8 –52.7 0.720

72 03353637 Little Buck Creek near Indianapolis, Ind. 1.079 –15.5 9.7 –35.0 0.205

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 1.344 17.4 41.3 –2.4 0.089

74 04063700 Popple River near Fence, Wis. 0.453 12.3 33.5 –5.4 0.185

76 04087000 Milwaukee River at Milwaukee, Wis. 1.724 28.9 45.0 14.5 <0.001

81 05114000 Souris River near Sherwood, N. Dak. 2.076 –24.5 7.4 –46.9 0.118

82 05120000 Souris River near Verendrye, N. Dak. 1.507 4.0 45.5 –25.7 0.821

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 1.615 –38.8 –18.2 –54.3 0.001

95 07022000 Mississippi River at Thebes, Ill. 3.227 –13.0 6.0 –28.6 0.166

97 06178000 Poplar River at International Boundary, Mont. 0.613 4.6 46.3 –25.2 0.791

99 06329500 Yellowstone River near Sidney, Mont. 0.606 25.7 77.5 –11.0 0.194

100 06338490 Missouri River at Garrison Dam, N. Dak. 0.193 40.7 133.3 –15.1 0.185

101 06461500 Niobrara River near Sparks, Nebr. 0.441 61.9 132.0 13.0 0.009

102 06468250 James River above Arrowwood Lake near Kensal, N. Dak. 1.518 4.8 36.6 –19.6 0.728

103 06713500 Cherry Creek at Denver, Colo. 3.828 –49.8 –32.8 –62.5 <0.001
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 49

Table 5. Non-flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

concentration,

in milligrams

per liter1

Trend, in percent from 1993 to 2003

Modeled p-value

estimate

Upper

95-percent 

CI

Lower

95-percent

CI

Total nitrogen—Continued

106 06753990 Lonetree Creek near Greeley, Colo. 9.761 –10.6 23.2 –35.1 0.493

107 06754000 South Platte River near Kersey, Colo. 6.215 27.4 57.1 3.3 0.023

108 06775900 Dismal River near Thedford, Nebr. 0.717 4.8 24.4 –11.6 0.588

109 06800000 Maple Creek near Nickerson, Nebr. 6.015 –11.3 21.3 –35.1 0.454

110 06805500 Platte River at Louisville, Nebr. 2.642 11.2 44.6 –14.5 0.428

111 06817700 Nodaway River near Graham, Mo. 5.273 –72.1 –46.9 –85.3 <0.001

112 06818000 Missouri River at St. Joseph, Mo. 3.257 –47.7 –34.4 –58.3 <0.001

113 06902000 Grand River near Sumner, Mo. 1.723 –39.8 2.1 –64.5 0.060

114 06905500 Chariton River near Prairie Hill, Mo. 1.607 –42.1 –12.0 –61.9 0.011

115 06921070 Pomme De Terre River near Polk, Mo. 0.544 –6.2 57.9 –44.3 0.810

116 06926510 Osage River below St. Thomas, Mo. 0.752 –30.8 –5.6 –49.3 0.020

118 06934500 Missouri River at Hermann, Mo. 2.025 –12.3 13.0 –32.0 0.311

120 07053250 Yocum Creek near Oak Grove, Ark. 2.529 69.2 111.8 35.2 <0.001

124 07066110 Jacks Fork above Two River, Mo. 0.448 1.3 23.4 –16.8 0.897

125 07068000 Current River at Doniphan, Mo. 0.426 –29.7 –15.6 –41.5 <0.001

134 07189000 Elk River near Tiff City, Mo. 1.721 0.1 27.2 –21.2 0.993

135 07195500 Illinois River near Watts, Okla. 2.523 –4.0 22.2 –24.5 0.742

136 07195865 Sager Creek near West Siloam Springs, Okla. 6.666 18.3 61.5 –13.3 0.289

137 07196000 Flint Creek near Kansas, Okla. 1.882 51.6 73.1 32.7 <0.001

138 07196500 Illinois River near Tahlequah, Okla. 1.723 –9.2 17.4 –29.8 0.459

139 07197000 Baron Fork at Eldon, Okla. 1.033 2.8 41.9 –25.5 0.865

145 07247015 Poteau River at Loving, Okla. 0.439 13.4 50.3 –14.4 0.380

146 07247250 Black Fork below Big Creek near Page, Okla. 0.315 –10.6 33.7 –40.2 0.585

147 07247345 Black Fork at Hodgen, Okla. 0.322 –2.9 38.9 –32.1 0.874

148 07247650 Fourche Maline near Leflore, Okla. 0.610 2.1 28.0 –18.5 0.856

149 07263620 Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Ark.

0.842 1.7 22.0 –15.2 0.852

150 07331000 Washita River near Dickson, Okla. 0.988 27.3 71.2 –5.4 0.111

151 07355500 Red River at Alexandria, La. 0.715 4.7 24.4 –11.8 0.599

152 07362000 Ouachita River at Camden, Ark. 0.312 52.9 127.0 3.0 0.035

153 07373420 Mississippi River near St Francisville, La. 2.096 –7.9 7.4 –21.1 0.295

154 07375500 Tangipahoa River at Robert, La. 0.909 –29.0 6.3 –52.6 0.097

155 07376000 Tickfaw River at Holden, La. 0.873 –26.1 7.3 –49.1 0.112

156 07381495 Atchafalaya River at Melville, La. 1.776 –9.6 3.8 –21.3 0.153

157 07386980 Vermilion River at Perry, La. 1.888 –16.9 1.3 –31.8 0.066

173 08251500 Rio Grande near Lobatos, Colo. 0.440 26.3 61.2 –1.0 0.060

176 09211200 Green River below Fontenelle Reservoir, Wyo. 0.230 23.6 70.6 –10.4 0.197

179 09380000 Colorado River at Lees Ferry, Ariz. 0.368 5.8 40.9 –20.6 0.701

182 09415000 Virgin River at Littlefield, Ariz. 0.841 34.0 150.6 –28.4 0.360

196 10336610 Upper Truckee River at South Lake Tahoe, Calif. 0.210 4.6 28.1 –14.6 0.666

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 0.304 –8.9 50.0 –44.7 0.714

201 10336740 Logan House Creek near Glenbrook, Nev. 0.313 –2.6 81.2 –47.6 0.934

202 10336760 Edgewood Creek at Stateline, Nev. 0.328 –28.8 12.8 –55.1 0.148

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 0.967 –21.7 6.8 –42.6 0.122

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

0.791 –48.9 –34.5 –60.2 <0.001

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 0.430 –49.0 –33.3 –61.0 <0.001

212 10411 Deschutes River at Deschutes River Park, Oreg. 0.316 –24.4 1.1 –43.5 0.059

213 10555 Willamette River at Marion Street at Salem, Oreg. 0.912 –51.3 –40.7 –60.0 <0.001

214 10611 Willamette River at Hawthorne Bridge, Oreg. 1.171 –38.6 –24.5 –50.0 <0.001

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

0.459 –28.4 6.2 –51.7 0.097
50 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 5. Non-flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

concentration,

in milligrams

per liter1

Trend, in percent from 1993 to 2003

Modeled p-value

estimate

Upper

95-percent 

CI

Lower

95-percent

CI

Total nitrogen—Continued

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 1.009 –43.3 –25.6 –56.9 <0.001

218 11321 Johnson Creek at Southeast 17th Avenue at 

Portland, Oreg.

4.554 –26.6 –16.2 –35.7 <0.001

219 11478 John Day River at Service Creek, Oreg. 0.293 –37.9 –10.9 –56.7 0.010

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. 2.665 –43.1 –18.4 –60.3 0.002

221 12413470 South Fork Coeur D'Alene River near Pinehurst, Idaho 0.230 17.7 67.3 –17.2 0.365

222 12419000 Spokane River near Post Falls, Idaho 0.138 15.7 65.2 –19.0 0.423

223 13154500 Snake River at King Hill, Idaho 1.480 2.0 23.9 –16.0 0.842

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 0.565 23.1 95.7 –22.6 0.381

225 13351000 Palouse River at Hooper, Wash. 1.724 6.8 39.7 –18.5 0.634

227 14211720 Willamette River at Portland, Oreg. 0.781 –3.6 13.1 –17.7 0.654

228 14246900 Columbia River at Beaver Army Terminal near 

Quincy, Oreg.

0.473 –9.0 8.9 –24.0 0.305

231 3701002 Tualatin River at Weiss Bridge, Oreg. 2.701 6.0 17.9 –4.6 0.277

232 37016120 Tualatin River at Springhill Road Bridge at Dilley, Oreg. 0.553 –32.0 –18.4 –43.4 <0.001

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. 2.839 6.0 40.6 –20.2 0.688

242 11290000 Tuolumne River at Modesto, Calif. 0.378 171.5 600.0 5.3 0.039

243 11303500 San Joaquin River near Vernalis, Calif. 2.012 9.0 60.5 –26.0 0.664

244 11447650 Sacramento River at Freeport, Calif. 0.238 49.3 96.3 13.5 0.004

Nitrate

1 01122610 Shetucket River at South Windham, Conn. 0.393 –12.4 16.6 –34.1 0.365

2 01124000 Quinebaug River at Quinebaug, Conn. 0.260 20.0 56.4 –8.0 0.179

3 01127000 Quinebaug River at Jewett City, Conn. 0.481 –19.3 14.8 –43.3 0.233

4 01184000 Connecticut River at Thompsonville, Conn. 0.327 8.5 31.7 –10.7 0.412

5 01184490 Broad Brook at Broad Brook, Conn. 3.743 3.9 17.1 –7.8 0.528

6 01188090 Farmington River at Unionville, Conn. 0.183 –22.8 2.1 –41.6 0.070

7 01189995 Farmington River at Tariffville, Conn. 0.641 18.1 50.9 –7.6 0.184

8 01192500 Hockanum River near East Hartford, Conn. 2.545 9.9 44.4 –16.3 0.497

9 01193500 Salmon River near East Hampton, Conn. 0.297 –26.1 20.4 –54.6 0.224

10 01196500 Quinnipiac River at Wallingford, Conn. 2.625 –11.7 11.5 –30.1 0.296

11 01205500 Housatonic River at Stevenson, Conn. 0.342 12.7 51.5 –16.2 0.430

12 01208500 Naugatuck River at Beacon Falls, Conn. 1.055 –13.4 16.3 –35.5 0.340

13 01208990 Saugatuck River near Redding, Conn. 0.120 –6.3 80.4 –51.3 0.845

14 01209710 Norwalk River at Winnipauk, Conn. 0.392 –1.3 30.6 –25.5 0.926

15 01357500 Mohawk River at Cohoes, N.Y. 0.689 –10.1 6.0 –23.8 0.206

16 01377000 Hackensack River at Rivervale, N.J. 0.461 –20.9 18.9 –47.4 0.260

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 0.184 30.1 139.2 –29.2 0.397

18 01387500 Ramapo River near Mahwah, N.J. 1.292 –6.4 46.7 –40.3 0.774

19 01389500 Passaic River at Little Falls, N.J. 2.719 –20.1 42.6 –55.2 0.448

20 01391500 Saddle River at Lodi, N.J. 4.463 28.7 76.6 –6.2 0.118

21 01394500 Rahway River near Springfield, N.J. 1.356 3.0 36.5 –22.3 0.838

22 01395000 Rahway River at Rahway, N.J. 0.867 9.7 55.3 –22.6 0.604

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 0.931 –20.8 0.7 –37.7 0.057

24 01398000 Neshanic River at Reaville, N.J. 1.430 –15.2 107.3 –65.3 0.717

25 01402000 Millstone River at Blackwells Mills, N.J. 2.410 3.1 33.6 –20.5 0.817

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 1.878 15.6 45.5 –8.1 0.214

29 01409500 Batsto River at Batsto, N.J. 0.168 –60.7 –36.6 –75.6 <0.001

31 01438500 Delaware River at Montague, N.J. 0.295 –44.0 –19.3 –61.2 0.002

32 01443500 Paulins Kill at Blairstown, N.J. 0.795 –1.1 62.3 –39.7 0.965

33 01463500 Delaware River at Trenton, N.J. 1.003 –24.2 –9.9 –36.3 0.002

34 01467150 Cooper River at Haddonfield, N.J. 0.349 –32.2 –3.7 –52.3 0.030

35 01477120 Raccoon Creek near Swedesboro, N.J. 1.398 –26.1 6.0 –48.4 0.100
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 51

Table 5. Non-flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

concentration,

in milligrams

per liter1

Trend, in percent from 1993 to 2003

Modeled p-value

estimate

Upper

95-percent 

CI

Lower

95-percent

CI

Nitrate—Continued

36 01491000 Choptank River near Greensboro, Md. 1.291 3.2 26.4 –15.8 0.763

37 01578310 Susquehanna River at Conowingo, Md. 1.299 –23.4 –14.0 –31.8 <0.001

38 01594440 Patuxent River near Bowie, Md. 1.434 –10.3 5.2 –23.6 0.181

39 01614500 Conococheague Creek at Fairview, Md. 4.995 –9.5 –1.2 –17.1 0.026

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 1.807 –41.7 –6.5 –63.7 0.025

41 01668000 Rappahannock River near Fredericksburg, Va. 0.312 –29.6 130.1 –78.5 0.561

42 01673000 Pamunkey River near Hanover, Va. 0.282 6.7 26.6 –10.1 0.457

43 01674500 Mattaponi River near Beulahville, Va. 0.155 23.2 54.0 –1.5 0.068

44 02035000 James River at Cartersville, Va. 0.219 –43.6 14.0 –72.1 0.111

45 02041650 Appomattox River at Matoaca, Va. 0.142 –13.9 10.5 –32.8 0.240

50 02175000 Edisto River near Givhans, S.C. 0.099 14.7 122.3 –40.8 0.685

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 0.374 49.4 274.1 –40.3 0.391

66 02335870 Sope Creek near Marietta, Ga. 0.523 –11.3 4.9 –25.0 0.162

71 02492000 Bogue Chitto River near Bush, La. 0.243 85.4 262.6 –5.3 0.071

72 03353637 Little Buck Creek near Indianapolis, Ind. 0.862 –41.7 –24.4 –54.9 <0.001

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 1.030 –8.9 15.9 –28.5 0.447

74 04063700 Popple River near Fence, Wis. 0.045 14.0 72.5 –24.7 0.535

76 04087000 Milwaukee River at Milwaukee, Wis. 0.673 49.8 141.6 –7.2 0.098

81 05114000 Souris River near Sherwood, N. Dak. 0.047 41.2 313.1 –51.7 0.528

82 05120000 Souris River near Verendrye, N. Dak. 0.147 –56.3 52.0 –87.4 0.193

88 05514500 Cuivre River near Troy, Mo. 0.329 –30.4 162.4 –81.5 0.593

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 0.842 –59.4 –36.8 –73.9 <0.001

95 07022000 Mississippi River at Thebes, Ill. 2.367 –24.5 –1.7 –42.0 0.037

96 06088500 Muddy Creek at Vaughn, Mont. 2.327 –49.1 –26.8 –64.7 <0.001

98 06274300 Bighorn River at Basin, Wyo. 0.288 –5.9 80.3 –50.8 0.856

99 06329500 Yellowstone River near Sidney, Mont. 0.171 –47.7 29.8 –78.9 0.162

100 06338490 Missouri River at Garrison Dam, N. Dak. 0.135 –72.6 –53.5 –83.8 <0.001

101 06461500 Niobrara River near Sparks, Nebr. 0.262 51.4 130.8 –0.7 0.054

102 06468250 James River above Arrowwood Lake near Kensal, N. Dak. 0.071 –67.1 25.7 –91.4 0.104

103 06713500 Cherry Creek at Denver, Colo. 2.735 –56.4 –33.7 –71.3 <0.001

104 06752260 Cache La Poudre River at Fort Collins, Colo. 0.293 –65.4 –28.5 –83.3 0.004

105 06752280 Cache La Poudre River above Boxelder Creek, near 

Timnath, Colo.

0.576 15.1 111.6 –37.4 0.651

106 06753990 Lonetree Creek near Greeley, Colo. 6.915 –1.9 50.4 –36.0 0.931

107 06754000 South Platte River near Kersey, Colo. 4.974 24.5 57.8 –1.7 0.069

108 06775900 Dismal River near Thedford, Nebr. 0.458 8.2 25.8 –7.0 0.308

109 06800000 Maple Creek near Nickerson, Nebr. 6.192 –47.0 –22.1 –63.9 0.001

110 06805500 Platte River at Louisville, Nebr. 1.487 –62.0 –22.5 –81.4 0.008

111 06817700 Nodaway River near Graham, Mo. 3.433 –92.8 –62.2 –98.6 0.002

112 06818000 Missouri River at St. Joseph, Mo. 1.951 –66.8 –47.0 –79.2 <0.001

113 06902000 Grand River near Sumner, Mo. 0.431 –74.7 –10.7 –92.8 0.033

114 06905500 Chariton River near Prairie Hill, Mo. 0.420 –62.0 19.1 –87.9 0.097

115 06921070 Pomme De Terre River near Polk, Mo. 0.215 –21.4 151.1 –75.4 0.685

116 06926510 Osage River below St. Thomas, Mo. 0.352 –79.9 –58.2 –90.3 <0.001

117 06930800 Gasconade River above Jerome, Mo. 0.416 –50.0 –19.0 –69.1 0.005

118 06934500 Missouri River at Hermann, Mo. 1.399 –49.0 –23.7 –65.9 0.001

119 07047942 L'Anguille River near Colt, Ark. 0.451 –51.3 –11.8 –73.1 0.018

120 07053250 Yocum Creek near Oak Grove, Ark. 2.245 86.8 158.1 35.1 <0.001

121 07056000 Buffalo River near St Joe, Ark. 0.067 23.4 105.1 –25.8 0.418

122 07060500 White River at Calico Rock, Ark. 0.241 –20.0 20.8 –47.0 0.289

123 07060710 North Sylamore Creek near Fifty Six, Ark. 0.064 –12.5 16.5 –34.3 0.360

124 07066110 Jacks Fork above Two River, Mo. 0.290 17.0 42.6 –3.9 0.118
52 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 5. Non-flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

concentration,

in milligrams

per liter1

Trend, in percent from 1993 to 2003

Modeled p-value

estimate

Upper

95-percent 

CI

Lower

95-percent

CI

Nitrate—Continued

125 07068000 Current River at Doniphan, Mo. 0.282 –27.3 –12.5 –39.6 0.001

126 07077500 Cache River at Patterson, Ark. 0.256 –15.4 45.2 –50.7 0.545

127 07077700 Bayou DeView near Morton, Ark. 0.153 63.4 201.1 –11.4 0.116

128 07103700 Fountain Creek near Colorado Springs, Colo. 0.750 5.6 36.9 –18.5 0.681

129 07103780 Monument Creek above North Gate Boulevard at 

United States Air Force Academy, Colo.

0.127 303.8 813.7 78.5 0.001

130 07105500 Fountain Creek at Colorado Springs, Colo. 1.563 22.3 74.9 –14.4 0.269

131 07105530 Fountain Creek below Janitell Road below Colorado 

Springs, Colo.

1.665 50.7 95.1 16.4 0.002

132 07106300 Fountain Creek near Pinon, Colo. 5.192 –48.5 –34.7 –59.4 <0.001

133 07106500 Fountain Creek at Pueblo, Colo. 5.306 –55.0 –46.9 –61.8 <0.001

134 07189000 Elk River near Tiff City, Mo. 1.572 2.9 33.9 –20.9 0.829

135 07195500 Illinois River near Watts, Okla. 2.450 –20.0 12.1 –42.8 0.195

136 07195865 Sager Creek near West Siloam Springs, Okla. 6.241 20.1 69.5 –14.8 0.296

137 07196000 Flint Creek near Kansas, Okla. 1.871 51.9 72.6 33.7 <0.001

138 07196500 Illinois River near Tahlequah, Okla. 1.684 –23.2 1.7 –42.0 0.065

139 07197000 Baron Fork at Eldon, Okla. 1.033 0.3 39.3 –27.8 0.988

140 07227500 Canadian River near Amarillo, Tex. 0.173 264.3 960.6 25.1 0.018

141 07239450 North Canadian River near Calumet, Okla. 0.084 –44.1 53.4 –79.6 0.259

142 07241000 North Canadian River below Lake Overholser near 

Oklahoma City, Okla.

0.249 –45.7 2.5 –71.3 0.059

143 07241520 North Canadian River at Britton Road at Oklahoma 

City, Okla.

0.601 4.1 99.5 –45.7 0.904

144 07241550 North Canadian River near Harrah, Okla. 1.176 56.4 180.7 –12.8 0.134

145 07247015 Poteau River at Loving, Okla. 0.088 35.4 147.2 –25.9 0.324

146 07247250 Black Fork below Big Creek near Page, Okla. 0.063 80.8 220.3 2.0 0.043

147 07247345 Black Fork at Hodgen, Okla. 0.033 76.7 233.4 –6.4 0.079

148 07247650 Fourche Maline near Leflore, Okla. 0.093 –24.2 33.8 –57.0 0.340

149 07263620 Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Ark.

0.382 –56.3 –20.6 –75.9 0.007

150 07331000 Washita River near Dickson, Okla. 0.366 –56.9 14.2 –83.7 0.090

151 07355500 Red River at Alexandria, La. 0.155 –46.2 –10.8 –67.5 0.016

152 07362000 Ouachita River at Camden, Ark. 0.126 0.9 60.6 –36.6 0.969

153 07373420 Mississippi River near St Francisville, La. 1.562 –20.8 –4.1 –34.6 0.017

154 07375500 Tangipahoa River at Robert, La. 0.366 –30.8 –0.2 –52.0 0.049

155 07376000 Tickfaw River at Holden, La. 0.301 –32.3 –6.8 –50.8 0.017

156 07381495 Atchafalaya River at Melville, La. 1.123 –20.2 –0.9 –35.7 0.041

157 07386980 Vermilion River at Perry, La. 0.376 26.6 95.2 –17.9 0.286

158 08030500 Sabine River near Ruliff, Tex. 0.078 –30.0 8.5 –54.9 0.110

159 08032000 Neches River near Neches, Tex. 0.135 –6.8 63.7 –46.9 0.807

160 08033500 Neches River near Rockland, Tex. 0.184 11.6 92.1 –35.1 0.691

161 08051500 Clear Creek near Sanger, Tex. 0.122 –44.5 106.6 –85.1 0.380

162 08064100 Chambers Creek near Rice, Tex. 0.254 –22.1 110.3 –71.1 0.622

163 08065350 Trinity River near Crockett, Tex. 1.673 23.8 126.4 –32.3 0.489

164 08136500 Concho River at Paint Rock, Tex. 11.897 –99.5 –97.9 –99.9 <0.001

167 08155200 Barton Creek at State Highway 71 near Oak Hill, Tex. 0.042 52.2 263.0 –36.2 0.344

168 08155240 Barton Creek at Lost Creek Boulevard near Austin, Tex. 0.063 99.2 272.1 6.6 0.031

172 08181800 San Antonio River near Elmendorf, Tex. 8.417 –17.0 34.5 –48.8 0.449

174 09058000 Colorado River near Kremmling, Colo. 0.121 –31.6 23.4 –62.1 0.207
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 53

Table 5. Non-flow-adjusted trends in concentration from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

concentration,

in milligrams

per liter1

Trend, in percent from 1993 to 2003

Modeled p-value

estimate

Upper

95-percent 

CI

Lower

95-percent

CI

Nitrate—Continued

175 09163500 Colorado River near Colorado-Utah State Line 0.579 20.5 54.5 –6.1 0.143

177 09217010 Green River below Green River, Wyo. 0.070 6.2 67.0 –32.5 0.796

181 09413500 Virgin River below First Narrows, Utah 0.901 165.0 347.3 56.9 <0.001

187 10038000 Bear River below Smiths Fork, near Cokeville, Wyo. 0.089 –40.1 –15.2 –57.7 0.004

189 10131000 Chalk Creek at U.S. 189 Crossing, Utah 0.253 14.4 88.1 –30.4 0.596

190 10154200 Provo River above Woodland at U.S. Geological 

Survey Gage Number 10154200, Utah

0.112 116.0 239.6 37.4 0.001

191 10155000 Provo River at Bridge 2.5 miles East of Hailstone 

Junction, Utah

0.039 337.2 700.0 138.9 <0.001

192 10155500 Provo River above Confluence with Snake Creek at 

McKeller Bridge, Utah

0.463 –65.2 –46.2 –77.6 <0.001

194 10336580 Upper Truckee River at South Upper Truckee Road 

near Meyers, Calif.

0.009 11.0 57.4 –21.8 0.560

195 103366092 Upper Truckee River at Highway 50 above Meyers, Calif. 0.014 –21.6 –2.5 –36.9 0.029

197 10336698 Third Creek near Crystal Bay, Nev. 0.017 –67.8 –56.9 –75.9 <0.001

198 103366993 Incline Creek above Tyrol Village near Incline 

Village, Nev.

0.013 10.1 46.8 –17.5 0.514

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 0.019 4.0 34.8 –19.8 0.767

200 10336700 Incline Creek near Crystal Bay, Nev. 0.021 –1.3 20.5 –19.1 0.901

201 10336740 Logan House Creek near Glenbrook, Nev. 0.004 38.4 323.3 –54.8 0.569

205 07A090 Snohomish River at Snohomish, Wash. 0.236 –7.0 10.8 –21.9 0.419

207 09A190 Green River at Kanaskat, Wash. 0.084 –2.7 34.4 –29.5 0.870

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 0.587 –24.1 7.3 –46.3 0.118

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

0.348 –38.2 –17.6 –53.6 0.001

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 0.153 –25.8 –8.1 –40.1 0.006

213 10555 Willamette River at Marion Street at Salem, Oreg. 0.473 –42.9 –28.9 –54.1 <0.001

215 10616 Columbia River at Marker number 47 upstream 

of Willamette River, Oreg.

0.152 28.4 93.8 –14.9 0.234

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 0.161 –13.4 77.7 –57.8 0.694

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. 4.288 –25.6 –13.2 –36.2 <0.001

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 0.446 –11.5 48.2 –47.2 0.642

225 13351000 Palouse River at Hooper, Wash. 1.113 –5.8 56.8 –43.4 0.820

226 14201300 Zollner Creek near Mt. Angel, Oreg. 8.370 12.2 44.0 –12.6 0.368

228 14246900 Columbia River at Beaver Army Terminal near 

Quincy, Oreg.

0.289 –35.2 –13.3 –51.5 0.003

229 16A070 Skokomish River near Potlatch, Wash. 0.105 –59.6 –47.4 –69.0 <0.001

234 45A070 Wenatchee River at Wenatchee, Wash. 0.064 3.4 53.4 –30.3 0.868

235 45A110 Wenatchee River near Leavenworth, Wash. 0.026 5.1 77.7 –37.8 0.853

237 49A070 Okanogan River at Malott, Wash. 0.023 8.5 87.0 –37.1 0.769

238 54A120 Spokane River at Riverside State Park, Wash. 0.346 56.4 178.1 –12.1 0.128

239 61A070 Columbia River at Northport, Wash. 0.056 0.7 19.7 –15.3 0.938

240 11264500 Merced River at Happy Isles Bridge near Yosemite, Calif. 0.053 –50.6 –17.7 –70.4 0.007

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. 2.006 10.9 54.5 –20.5 0.543

242 11290000 Tuolumne River at Modesto, Calif. 0.254 170.7 635.3 –0.4 0.051

243 11303500 San Joaquin River near Vernalis, Calif. 0.987 17.1 117.4 –36.9 0.617

244 11447650 Sacramento River at Freeport, Calif. 0.147 –31.7 –7.7 –49.5 0.013

1

Reference value is the concentration that would have been observed on the first day of the period of record under average hydrologic and seasonal conditions. 
54 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 6. Trends in load from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

load,

in kilograms

per day1

Trend,

in percent from 1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

Total phosphorus

1 01122610 Shetucket River at South Windham, Conn. 24.7 33.7 152.9 –29.3 0.372

2 01124000 Quinebaug River at Quinebaug, Conn. 15.4 –5.3 86.7 –52.0 0.874

3 01127000 Quinebaug River at Jewett City, Conn. 87.8 75.0 228.8 –6.9 0.082

4 01184000 Connecticut River at Thompsonville, Conn. 1,067.5 15.2 90.0 –30.1 0.578

5 01184490 Broad Brook at Broad Brook, Conn. 5.0 –31.6 25.7 –62.8 0.221

7 01189995 Farmington River at Tariffville, Conn. 207.1 16.6 65.9 –18.1 0.394

8 01192500 Hockanum River near East Hartford, Conn. 99.4 –27.7 –5.0 –45.0 0.020

10 01196500 Quinnipiac River at Wallingford, Conn. 99.8 –24.0 8.1 –46.5 0.127

11 01205500 Housatonic River at Stevenson, Conn. 78.3 5.2 242.2 –67.7 0.933

12 01208500 Naugatuck River at Beacon Falls, Conn. 212.5 52.2 119.1 5.7 0.024

13 01208990 Saugatuck River near Redding, Conn. 0.5 48.3 553.1 –66.3 0.602

14 01209710 Norwalk River at Winnipauk, Conn. 2.3 42.6 214.6 –35.4 0.379

15 01357500 Mohawk River at Cohoes, N.Y. 270.9 38.7 169.9 –28.7 0.336

16 01377000 Hackensack River at Rivervale, N.J. 9.7 –7.6 74.3 –51.0 0.806

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 0.9 –74.7 50.9 –95.8 0.131

18 01387500 Ramapo River near Mahwah, N.J. 28.9 6.5 77.8 –36.2 0.811

19 01389500 Passaic River at Little Falls, N.J. 467.2 –2.5 78.7 –46.8 0.935

20 01391500 Saddle River at Lodi, N.J. 60.4 124.3 246.3 45.2 <0.001

22 01395000 Rahway River at Rahway, N.J. 4.0 49.4 193.2 –23.9 0.243

24 01398000 Neshanic River at Reaville, N.J. 1.2 27.5 416.9 –68.5 0.734

25 01402000 Millstone River at Blackwells Mills, N.J. 113.9 15.9 69.0 –20.6 0.444

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 255.1 0.7 44.9 –30.0 0.969

27 01408000 Manasquan River at Squankum, N.J. 13.1 –20.2 91.9 –66.8 0.614

28 01408500 Toms River near Toms River, N.J. 10.5 16.4 265.1 –62.9 0.794

30 01411500 Maurice River at Norma, N.J. 4.3 –13.1 282.5 –80.3 0.852

31 01438500 Delaware River at Montague, N.J. 379.5 –40.4 94.0 –81.7 0.390

32 01443500 Paulins Kill at Blairstown, N.J. 8.6 –16.8 148.0 –72.1 0.742

33 01463500 Delaware River at Trenton, N.J. 1,193.6 –9.9 63.5 –50.4 0.731

34 01467150 Cooper River at Haddonfield, N.J. 10.1 –30.7 12.2 –57.2 0.136

35 01477120 Raccoon Creek near Swedesboro, N.J. 8.3 12.1 105.5 –38.9 0.712

36 01491000 Choptank River near Greensboro, Md. 7.1 205.9 1,211.1 –28.6 0.132

37 01578310 Susquehanna River at Conowingo, Md. 1,396.0 30.3 172.5 –37.7 0.482

38 01594440 Patuxent River near Bowie, Md. 76.5 42.7 214.3 –35.2 0.378

39 01614500 Conococheague Creek at Fairview, Md. 132.9 –27.5 85.7 –71.7 0.503

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 549.2 31.1 445.9 –68.5 0.709

41 01668000 Rappahannock River near Fredericksburg, Va. 89.8 –38.7 278.1 –90.0 0.599

42 01673000 Pamunkey River near Hanover, Va. 98.5 –3.0 188.3 –67.4 0.956

43 01674500 Mattaponi River near Beulahville, Va. 46.9 –56.9 110.9 –91.2 0.299

44 02035000 James River at Cartersville, Va. 1,282.6 –41.8 46.9 –76.9 0.252

45 02041650 Appomattox River at Matoaca, Va. 75.7 –44.6 110.0 –85.4 0.385

46 02085000 Eno River at Hillsborough, N.C. 1.2 43.6 471.3 –63.9 0.608

51 02198500 Savannah River near Clyo, Ga. 3,076.5 –30.5 15.3 –58.1 0.159

52 02213700 Ocmulgee River near Warner Robins, Ga. 765.1 –63.1 –42.1 –76.4 <0.001

53 02215500 Ocmulgee River at Lumber City, Ga. 1,473.5 –68.6 –21.9 –87.4 0.013

54 02223600 Oconee River at Interstate 16, near Dublin, Ga. 1,321.5 –67.8 –30.6 –85.0 0.004

55 02226010 Altamaha River near Gardi, Ga. 3,075.5 –55.7 1.5 –80.6 0.054

56 02226582 Satilla River at GA 15&121, near Hoboken, Ga. 129.0 –52.3 89.4 –88.0 0.293

58 02295420 Payne Creek near Bowling Green, Fla. 122.8 –22.7 225.4 –81.6 0.726

59 02296750 Peace River at Arcadia, Fla. 1,179.6 –38.0 152.9 –84.8 0.505

60 02300700 Bullfrog Creek near Wimauma, Fla. 11.9 –19.7 76.3 –63.4 0.584
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 55

Table 6. Trends in load from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

load,

in kilograms

per day1

Trend,

in percent from 1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

Total phosphorus—Continued

61 02301300 South Prong Alafia River near Lithia, Fla. 127.3 –64.5 124.6 –94.4 0.271

62 02302500 Blackwater Creek near Knights, Fla. 66.1 –75.3 43.3 –95.8 0.119

63 02303000 Hillsborough River near Zephyrhills, Fla. 102.8 –56.9 122.0 –91.6 0.314

64 02314500 Suwannee River at U.S. 441, at Fargo, Ga. 97.3 –95.2 –78.4 –98.9 <0.001

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 107.9 6.4 218.3 –64.4 0.912

66 02335870 Sope Creek near Marietta, Ga. 1.3 –52.8 27.9 –82.5 0.140

68 02344040 Chattahoochee River near Steam Mill, Ga. 1,917.0 –67.4 –38.0 –82.9 0.001

69 02353000 Flint River at Newton, Ga. 714.8 –56.9 –0.9 –81.3 0.048

70 02388520 Oostanaula River at Rome, Ga. 1,266.1 –60.0 –31.3 –76.7 0.001

71 02492000 Bogue Chitto River near Bush, La. 286.0 –4.7 72.2 –47.3 0.872

72 03353637 Little Buck Creek near Indianapolis, Ind. 0.6 –46.7 92.0 –85.2 0.336

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 49,089.7 32.1 155.8 –31.8 0.409

74 04063700 Popple River near Fence, Wis. 6.1 –51.2 –1.4 –75.8 0.046

75 04073468 Green Lake Inlet at County Highway A near Green Lake, Wis. 11.0 –59.0 –17.5 –79.6 0.012

76 04087000 Milwaukee River at Milwaukee, Wis. 77.8 –11.1 41.8 –44.3 0.621

77 0422026250 Northrup Creek at North Greece, N.Y. 7.2 –8.7 39.1 –40.1 0.672

78 04232034 Irondequoit Creek at Railroad Mills near Fishers, N.Y. 5.4 –49.4 –15.3 –69.8 0.010

79 0423204920 East Branch Allen Creek at Pittsford, N.Y. 1.2 –35.3 7.5 –61.0 0.093

80 0423205025 Irondequoit Creek at Empire Boulevard at Rochester, N.Y. 18.0 12.7 72.8 –26.5 0.585

81 05114000 Souris River near Sherwood, N. Dak. 5.5 439.6 4,189.7 –32.1 0.111

82 05120000 Souris River near Verendrye, N. Dak. 28.1 55.5 571.7 –64.0 0.554

83 05287890 Elm Creek near Champlin, Minn. 8.7 –52.2 59.8 –85.7 0.230

84 05427718 Yahara River at Windsor, Wis. 9.7 –59.9 –30.1 –77.0 0.001

85 05427948 Pheasant Branch at Middleton, Wis. 3.1 –68.1 –46.9 –80.8 <0.001

86 054310157 Jackson Creek Tributary near Elkhorn, Wis. 0.5 –22.5 85.3 –67.6 0.567

87 05500000 South Fabius River near Taylor, Mo. 45.1 –87.1 –41.4 –97.2 0.008

88 05514500 Cuivre River near Troy, Mo. 60.8 –69.5 62.7 –94.3 0.165

89 05525500 Sugar Creek at Milford, Ill. 26.4 –44.3 176.3 –88.8 0.474

90 05531500 Salt Creek at Western Springs, Ill. 338.8 44.5 83.9 13.5 0.003

91 05532500 Des Plaines River at Riverside, Ill. 749.7 45.0 88.3 11.7 0.005

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 1.2 –51.3 19.8 –80.2 0.117

93 05586100 Illinois River at Valley City, Ill. 18,788.7 –10.9 55.1 –48.8 0.682

94 07018100 Big River near Richwoods, Mo. 43.6 –64.5 –25.6 –83.1 0.006

95 07022000 Mississippi River at Thebes, Ill. 176,092.9 –41.5 6.6 –67.9 0.080

97 06178000 Poplar River at International Boundary, Mont. 0.3 –34.2 172.2 –84.1 0.564

99 06329500 Yellowstone River near Sidney, Mont. 2,177.1 –46.1 42.2 –79.6 0.212

101 06461500 Niobrara River near Sparks, Nebr. 232.7 26.4 79.2 –10.9 0.189

106 06753990 Lonetree Creek near Greeley, Colo. 11.3 –98.2 –89.8 –99.7 <0.001

107 06754000 South Platte River near Kersey, Colo. 1,454.4 –25.7 40.4 –60.6 0.361

109 06800000 Maple Creek near Nickerson, Nebr. 61.0 –36.9 82.3 –78.2 0.395

110 06805500 Platte River at Louisville, Nebr. 8,767.3 –26.0 33.8 –59.0 0.320

111 06817700 Nodaway River near Graham, Mo. 806.1 –93.2 –70.3 –98.5 <0.001

112 06818000 Missouri River at St. Joseph, Mo. 33,847.8 –29.7 31.4 –62.4 0.270

113 06902000 Grand River near Sumner, Mo. 1,754.8 –87.2 –26.3 –97.8 0.021

114 06905500 Chariton River near Prairie Hill, Mo. 663.6 –93.4 –60.4 –98.9 0.003

115 06921070 Pomme De Terre River near Polk, Mo. 16.3 –78.2 –26.9 –93.5 0.014

118 06934500 Missouri River at Hermann, Mo. 63,637.4 –38.3 40.2 –72.9 0.249

120 07053250 Yocum Creek near Oak Grove, Ark. 3.7 –50.8 –11.3 –72.7 0.018

134 07189000 Elk River near Tiff City, Mo. 73.3 38.2 151.9 –24.1 0.290

135 07195500 Illinois River near Watts, Okla. 160.9 8.5 99.6 –41.0 0.792
56 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 6. Trends in load from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

load,

in kilograms

per day1

Trend,

in percent from 1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

Total phosphorus—Continued

136 07195865 Sager Creek near West Siloam Springs, Okla. 17.7 55.9 149.2 –2.5 0.064

137 07196000 Flint Creek near Kansas, Okla. 22.1 –12.4 72.0 –55.4 0.700

138 07196500 Illinois River near Tahlequah, Okla. 133.8 –10.0 83.5 –55.9 0.772

139 07197000 Baron Fork at Eldon, Okla. 19.5 –59.4 –0.2 –83.5 0.049

145 07247015 Poteau River at Loving, Okla. 17.2 –41.8 71.2 –80.2 0.326

148 07247650 Fourche Maline near Leflore, Okla. 5.7 –67.9 5.5 –90.2 0.061

149 07263620 Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Ark.

8,280.0 –42.4 48.3 –77.6 0.253

150 07331000 Washita River near Dickson, Okla. 1,137.5 –66.3 2.5 –88.9 0.055

151 07355500 Red River at Alexandria, La. 6,494.3 –41.9 54.7 –78.1 0.277

152 07362000 Ouachita River at Camden, Ark. 464.8 –38.4 43.7 –73.6 0.262

153 07373420 Mississippi River near St Francisville, La. 247,836.4 –2.5 44.5 –34.2 0.899

154 07375500 Tangipahoa River at Robert, La. 258.7 –27.8 47.6 –64.7 0.372

155 07376000 Tickfaw River at Holden, La. 49.4 –8.3 70.2 –50.6 0.784

156 07381495 Atchafalaya River at Melville, La. 89,521.1 1.0 52.4 –33.0 0.961

157 07386980 Vermilion River at Perry, La. 565.1 6.2 132.2 –51.4 0.879

165 08143600 Pecan Bayou near Mullin, Tex. 13.5 –45.3 110.1 –85.7 0.380

166 08147000 Colorado River near San Saba, Tex. 45.6 –85.0 –36.3 –96.5 0.010

169 08159000 Onion Creek at U.S. Highway 183, Austin, Tex. 0.7 –56.9 4,58.4 –96.7 0.519

170 08162000 Colorado River at Wharton, Tex. 826.8 29.7 257.2 –52.9 0.614

171 08162500 Colorado River near Bay City, Tex. 803.2 –16.1 187.6 –75.5 0.780

173 08251500 Rio Grande near Lobatos, Colo. 86.6 –75.8 5.9 –94.5 0.060

177 09217010 Green River below Green River, Wyo. 90.0 20.3 140.9 –39.9 0.602

178 09261000 Green River at Dinosaur National Monument 

Utah 149 Crossing, Utah

571.6 –66.3 1.0 –88.7 0.052

180 09403600 Kanab Creek at U.S. 89 Crossing, Utah 0.9 50.3 288.2 –41.8 0.401

182 09415000 Virgin River at Littlefield, Ariz. 68.0 –41.2 154.6 –86.4 0.477

183 09448500 Gila River at Head of Safford Valley, near Solomon, Ariz. 103.9 –75.3 138.6 –97.4 0.227

184 09498500 Salt River near Roosevelt, Ariz. 16.9 127.0 4,158.2 –87.9 0.584

185 09508500 Verde River below Tangle Creek, above Horseshoe 

Dam, Ariz.

20.6 –36.8 106.1 –80.6 0.447

186 09522000 Colorado River at Northerly International Boundary, 

above Morelos Dam, Ariz.

1,985.5 –91.4 –61.7 –98.1 0.001

188 10126000 Bear River near Corinne at Utah 83 Crossing, Utah 411.5 –63.4 50.4 –91.1 0.163

193 10189000 East Fork Sevier River at Utah 62 Crossing East of 

Kingston, Utah

10.1 –27.9 33.7 –61.1 0.299

203 01A050 Nooksack River at Brennan, Wash. 152.5 51.9 212.6 –26.2 0.256

204 03A060 Skagit River near Mount Vernon, Wash. 517.6 6.7 169.4 –57.8 0.891

205 07A090 Snohomish River at Snohomish, Wash. 152.9 24.8 170.1 –42.3 0.574

206 09A080 Green River at Tukwila, Wash. 58.5 5.2 84.7 –40.1 0.860

207 09A190 Green River at Kanaskat, Wash. 7.4 200.1 649.7 20.1 0.019

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 4,604.1 –21.1 24.9 –50.1 0.312

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

2,126.5 –32.1 14.2 –59.6 0.144

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 1,037.8 –15.5 45.9 –51.0 0.546

211 10386 Middle Fork Willamette at Jasper Bridge, Oreg. 238.6 –22.6 33.4 –55.1 0.356

212 10411 Deschutes River at Deschutes River Park, Oreg. 1,096.0 –8.7 44.9 –42.5 0.699

213 10555 Willamette River at Marion Street at Salem, Oreg. 2,912.6 –32.3 15.0 –60.1 0.149

214 10611 Willamette River at Hawthorne Bridge, Oreg. 5,385.0 –33.3 0.2 –55.6 0.051

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

16,869.6 –30.1 38.8 –64.8 0.306
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 57

Table 6. Trends in load from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

load,

in kilograms

per day1

Trend,

in percent from 1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

Total phosphorus—Continued

216 10A070 Puyallup River at Meridian Street, Wash. 228.7 106.5 298.1 7.1 0.030

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 63.9 –41.7 9.7 –69.0 0.095

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. 12.0 –30.6 19.6 –59.7 0.188

219 11478 John Day River at Service Creek, Oreg. 118.8 –63.3 –8.9 –85.2 0.031

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. 51.7 –19.7 73.9 –62.9 0.578

221 12413470 South Fork Coeur D'Alene River near Pinehurst, Idaho 8.6 89.9 278.2 –4.6 0.068

222 12419000 Spokane River near Post Falls, Idaho 107.9 –44.1 92.7 –83.8 0.357

223 13154500 Snake River at King Hill, Idaho 1,759.9 –27.4 13.8 –53.6 0.163

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 141.8 36.1 118.5 –15.2 0.202

225 13351000 Palouse River at Hooper, Wash. 101.6 –40.1 129.4 –84.3 0.455

227 14211720 Willamette River at Portland, Oreg. 3,996.4 –3.1 54.4 –39.1 0.896

228 14246900 Columbia River at Beaver Army Terminal near Quincy, Oreg. 17,761.9 –5.7 95.1 –54.4 0.875

229 16A070 Skokomish River near Potlatch, Wash. 15.9 136.2 416.5 8.0 0.031

230 32A070 Walla Walla River near Touchet, Wash. 71.2 –8.4 67.1 –49.8 0.776

231 3701002 Tualatin River at Weiss Bridge, Oreg. 319.9 –30.2 41.1 –65.4 0.317

232 37016120 Tualatin River at Springhill Road Bridge at Dilley, Oreg. 23.3 –32.5 38.3 –67.1 0.283

233 37A090 Yakima River at Kiona, Wash. 645.6 15.2 167.0 –50.3 0.742

234 45A070 Wenatchee River at Wenatchee, Wash. 17.7 45.9 371.6 –54.9 0.528

235 45A110 Wenatchee River near Leavenworth, Wash. 20.5 7.4 246.0 –66.7 0.905

236 48A070 Methow River near Pateros, Wash. 6.3 64.2 317.9 –35.5 0.298

237 49A070 Okanogan River at Malott, Wash. 98.8 –39.1 79.3 –79.3 0.368

238 54A120 Spokane River at Riverside State Park, Wash. 195.0 32.8 161.6 –32.6 0.412

239 61A070 Columbia River at Northport, Wash. 2,516.8 –31.9 41.3 –67.1 0.303

241 11274538 Orestimba Creek at River Road near Crows 

Landing, Calif.

9.5 –7.7 145.6 –65.3 0.873

242 11290000 Tuolumne River at Modesto, Calif. 146.6 –18.9 101.1 –67.3 0.651

243 11303500 San Joaquin River near Vernalis, Calif. 2,217.1 –19.6 126.3 –71.4 0.680

244 11447650 Sacramento River at Freeport, Calif. 2,100.3 48.8 208.8 –28.3 0.286

Total nitrogen

1 01122610 Shetucket River at South Windham, Conn. 713.2 –11.5 42.9 –45.2 0.618

2 01124000 Quinebaug River at Quinebaug, Conn. 228.7 10.0 75.4 –31.0 0.689

3 01127000 Quinebaug River at Jewett City, Conn. 1,755.0 –7.5 51.7 –43.6 0.758

4 01184000 Connecticut River at Thompsonville, Conn. 20,452.8 –5.6 28.3 –30.6 0.712

5 01184490 Broad Brook at Broad Brook, Conn. 233.2 –17.5 11.2 –38.8 0.206

6 01188090 Farmington River at Unionville, Conn. 377.6 8.6 85.1 –36.2 0.761

7 01189995 Farmington River at Tariffville, Conn. 2,412.9 –7.9 25.2 –32.2 0.598

8 01192500 Hockanum River near East Hartford, Conn. 947.7 –17.1 6.9 –35.7 0.149

9 01193500 Salmon River near East Hampton, Conn. 111.0 1.2 110.3 –51.3 0.974

10 01196500 Quinnipiac River at Wallingford, Conn. 1,328.9 –8.4 19.9 –30.0 0.524

11 01205500 Housatonic River at Stevenson, Conn. 2,492.3 6.8 114.3 –46.7 0.852

12 01208500 Naugatuck River at Beacon Falls, Conn. 2,334.6 –55.9 –42.0 –66.4 <0.001

13 01208990 Saugatuck River near Redding, Conn. 12.6 64.5 301.9 –32.7 0.275

14 01209710 Norwalk River at Winnipauk, Conn. 48.4 23.2 154.1 –40.3 0.572

15 01357500 Mohawk River at Cohoes, N.Y. 8,255.2 10.7 72.1 –28.8 0.652

16 01377000 Hackensack River at Rivervale, N.J. 153.1 –13.1 37.1 –45.0 0.545

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 18.3 –34.4 157.8 –83.3 0.546

18 01387500 Ramapo River near Mahwah, N.J. 371.2 8.3 73.7 –32.4 0.740

19 01389500 Passaic River at Little Falls, N.J. 4,200.5 –28.2 36.9 –62.4 0.314

20 01391500 Saddle River at Lodi, N.J. 953.1 29.9 94.0 –13.1 0.202

21 01394500 Rahway River near Springfield, N.J. 70.7 18.4 92.9 –27.4 0.499

22 01395000 Rahway River at Rahway, N.J. 79.3 10.0 96.1 –38.3 0.746
58 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 6. Trends in load from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

load,

in kilograms

per day1

Trend,

in percent from 1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

Total nitrogen—Continued

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 30.5 –10.0 68.2 –51.9 0.741

24 01398000 Neshanic River at Reaville, N.J. 50.7 –11.6 227.3 –76.1 0.853

25 01402000 Millstone River at Blackwells Mills, N.J. 1,709.8 –3.9 46.6 –37.1 0.852

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 3,680.5 –3.5 47.2 –36.7 0.870

29 01409500 Batsto River at Batsto, N.J. 99.8 –40.1 16.2 –69.1 0.129

31 01438500 Delaware River at Montague, N.J. 4,559.0 –18.4 34.3 –50.4 0.423

32 01443500 Paulins Kill at Blairstown, N.J. 325.7 –16.7 94.6 –64.3 0.673

33 01463500 Delaware River at Trenton, N.J. 26,572.9 –17.5 36.2 –50.0 0.452

34 01467150 Cooper River at Haddonfield, N.J. 47.0 –27.4 7.3 –50.8 0.108

35 01477120 Raccoon Creek near Swedesboro, N.J. 117.8 –4.6 47.0 –38.0 0.832

36 01491000 Choptank River near Greensboro, Md. 237.3 75.3 407.3 –39.5 0.301

37 01578310 Susquehanna River at Conowingo, Md. 100,777.9 –28.2 22.7 –58.0 0.226

38 01594440 Patuxent River near Bowie, Md. 1,380.1 1.7 82.3 –43.3 0.955

39 01614500 Conococheague Creek at Fairview, Md. 6,336.5 –39.0 37.7 –73.0 0.234

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 37,023.5 –39.6 122.2 –83.6 0.448

41 01668000 Rappahannock River near Fredericksburg, Va. 1,618.4 –32.4 208.8 –85.2 0.613

42 01673000 Pamunkey River near Hanover, Va. 968.7 –32.4 116.5 –78.9 0.510

43 01674500 Mattaponi River near Beulahville, Va. 501.5 –49.0 139.4 –89.1 0.393

44 02035000 James River at Cartersville, Va. 6,074.1 –33.4 93.8 –77.1 0.456

45 02041650 Appomattox River at Matoaca, Va. 961.9 –28.4 134.5 –78.1 0.581

46 02085000 Eno River at Hillsborough, N.C. 30.8 19.0 314.0 –65.8 0.785

47 02089500 Neuse River at Kinston, N.C. 6,248.6 –22.4 63.1 –63.1 0.503

48 02091500 Contentnea Creek at Hookerton, N.C. 1,095.9 33.7 226.2 –45.2 0.524

49 0210215985 Cape Fear River at State Highway 42 near Brickhaven, N.C. 5,800.4 –5.5 122.4 –59.8 0.897

52 02213700 Ocmulgee River near Warner Robins, Ga. 5,825.2 –36.2 0.8 –59.5 0.054

53 02215500 Ocmulgee River at Lumber City, Ga. 12,295.7 –51.3 –4.1 –75.2 0.037

57 02271500 Josephine Creek near De Soto City, Fla. 66.0 32.0 314.5 –58.0 0.635

58 02295420 Payne Creek near Bowling Green, Fla. 343.5 –44.1 84.8 –83.1 0.340

59 02296750 Peace River at Arcadia, Fla. 2,210.8 –37.9 187.6 –86.6 0.542

60 02300700 Bullfrog Creek near Wimauma, Fla. 41.0 –11.5 83.4 –57.2 0.743

61 02301300 South Prong Alafia River near Lithia, Fla. 146.0 –37.4 193.5 –86.6 0.553

62 02302500 Blackwater Creek near Knights, Fla. 139.6 –67.2 86.4 –94.2 0.209

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 703.5 15.9 345.8 –69.9 0.830

67 02338000 Chattahoochee River near Whitesburg, Ga. 13,838.9 –23.8 10.2 –47.3 0.148

71 02492000 Bogue Chitto River near Bush, La. 3,334.4 –38.6 54.5 –75.6 0.300

72 03353637 Little Buck Creek near Indianapolis, Ind. 27.7 –55.0 32.2 –84.7 0.146

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 812,588.8 –3.6 54.3 –39.7 0.879

74 04063700 Popple River near Fence, Wis. 104.0 –25.9 14.0 –51.8 0.173

76 04087000 Milwaukee River at Milwaukee, Wis. 1,621.8 –7.1 43.3 –39.8 0.740

81 05114000 Souris River near Sherwood, N. Dak. 26.3 612.1 5,638.1 –11.6 0.065

82 05120000 Souris River near Verendrye, N. Dak. 159.0 87.3 735.8 –58.0 0.411

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 25.2 –63.1 –11.0 –84.7 0.027

95 07022000 Mississippi River at Thebes, Ill. 2,473,864.5 –59.7 –34.3 –75.2 <0.001

97 06178000 Poplar River at International Boundary, Mont. 5.7 –13.2 201.6 –75.0 0.824

99 06329500 Yellowstone River near Sidney, Mont. 17,700.9 –36.3 21.1 –66.5 0.169

100 06338490 Missouri River at Garrison Dam, N. Dak. 8,511.6 54.9 250.1 –31.5 0.293

101 06461500 Niobrara River near Sparks, Nebr. 848.9 53.4 128.4 3.0 0.035

102 06468250 James River above Arrowwood Lake near Kensal, N. Dak. 43.5 135.9 1,506.8 –65.4 0.381

103 06713500 Cherry Creek at Denver, Colo. 203.1 –30.8 9.0 –56.0 0.113

106 06753990 Lonetree Creek near Greeley, Colo. 347.6 –93.9 –84.3 –97.6 <0.001
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 59

Table 6. Trends in load from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

load,

in kilograms

per day1

Trend,

in percent from 1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

Total nitrogen—Continued

107 06754000 South Platte River near Kersey, Colo. 14,303.8 –29.6 15.7 –57.2 0.166

108 06775900 Dismal River near Thedford, Nebr. 373.4 11.9 36.1 –8.0 0.262

109 06800000 Maple Creek near Nickerson, Nebr. 1,789.4 –72.8 –32.8 –89.0 0.005

110 06805500 Platte River at Louisville, Nebr. 74,129.1 –56.5 –24.8 –74.9 0.003

111 06817700 Nodaway River near Graham, Mo. 13,102.7 –97.0 –87.0 –99.3 <0.001

112 06818000 Missouri River at St. Joseph, Mo. 512,446.0 –70.2 –53.5 –80.9 <0.001

113 06902000 Grand River near Sumner, Mo. 15,003.1 –93.2 –66.0 –98.6 0.001

114 06905500 Chariton River near Prairie Hill, Mo. 5,279.4 –93.3 –70.6 –98.5 <0.001

115 06921070 Pomme De Terre River near Polk, Mo. 188.8 –73.6 –7.5 –92.4 0.037

116 06926510 Osage River below St. Thomas, Mo. 25,153.3 –89.0 –63.4 –96.7 <0.001

118 06934500 Missouri River at Hermann, Mo. 690,237.8 –67.1 –40.0 –82.0 <0.001

120 07053250 Yocum Creek near Oak Grove, Ark. 239.0 –30.0 20.0 –59.1 0.195

124 07066110 Jacks Fork above Two River, Mo. 539.4 –52.7 –25.9 –69.8 0.001

125 07068000 Current River at Doniphan, Mo. 3,386.9 –63.4 –44.9 –75.7 <0.001

134 07189000 Elk River near Tiff City, Mo. 3,076.2 –63.6 –20.9 –83.3 0.011

135 07195500 Illinois River near Watts, Okla. 3,615.6 –50.4 –12.2 –72.0 0.016

136 07195865 Sager Creek near West Siloam Springs, Okla. 236.8 –5.2 53.5 –41.4 0.829

137 07196000 Flint Creek near Kansas, Okla. 452.7 –26.2 32.8 –59.0 0.311

138 07196500 Illinois River near Tahlequah, Okla. 3,678.5 –54.7 –7.9 –77.7 0.029

139 07197000 Baron Fork at Eldon, Okla. 727.1 –60.8 –13.1 –82.3 0.021

145 07247015 Poteau River at Loving, Okla. 70.8 –23.9 109.7 –72.4 0.598

146 07247250 Black Fork below Big Creek near Page, Okla. 43.7 –62.8 45.4 –90.5 0.155

147 07247345 Black Fork at Hodgen, Okla. 44.5 –59.6 60.9 –89.8 0.199

148 07247650 Fourche Maline near Leflore, Okla. 69.4 –67.0 –2.5 –88.8 0.045

149 07263620 Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Ark.

86,502.2 –60.2 –8.2 –82.8 0.031

150 07331000 Washita River near Dickson, Okla. 5,642.1 –64.2 –15.5 –84.8 0.019

151 07355500 Red River at Alexandria, La. 49,016.7 –12.5 92.7 –60.3 0.740

152 07362000 Ouachita River at Camden, Ark. 3,570.6 29.4 167.7 –37.4 0.487

153 07373420 Mississippi River near St Francisville, La. 2,958,811.0 –38.4 –11.8 –57.0 0.008

154 07375500 Tangipahoa River at Robert, La. 2,098.0 –49.5 15.5 –78.0 0.106

155 07376000 Tickfaw River at Holden, La. 582.4 –53.6 0.0 –78.5 0.050

156 07381495 Atchafalaya River at Melville, La. 1,071,142.5 –39.6 –15.2 –57.0 0.004

157 07386980 Vermilion River at Perry, La. 3,615.4 –13.4 66.5 –54.9 0.667

173 08251500 Rio Grande near Lobatos, Colo. 489.8 –75.7 –15.6 –93.0 0.026

176 09211200 Green River below Fontenelle Reservoir, Wyo. 797.3 –18.7 66.4 –60.3 0.571

179 09380000 Colorado River at Lees Ferry, Ariz. 12,388.6 –1.6 58.8 –39.0 0.947

182 09415000 Virgin River at Littlefield, Ariz. 547.7 –50.3 49.2 –83.4 0.213

196 10336610 Upper Truckee River at South Lake Tahoe, Calif. 25.4 –33.7 150.8 –82.4 0.545

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 3.1 –20.7 370.9 –86.6 0.799

201 10336740 Logan House Creek near Glenbrook, Nev. 0.2 101.6 2,527.9 –84.5 0.593

202 10336760 Edgewood Creek at Stateline, Nev. 2.7 –12.6 267.9 –79.2 0.854

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 63,781.1 –33.3 12.7 –60.5 0.131

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

22,459.5 –56.6 –31.3 –72.6 <0.001

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 9,822.5 –54.7 –27.1 –71.8 0.001

212 10411 Deschutes River at Deschutes River Park, Oreg. 4,325.5 –24.3 15.3 –50.3 0.195

213 10555 Willamette River at Marion Street at Salem, Oreg. 41,756.6 –58.5 –35.2 –73.4 <0.001

214 10611 Willamette River at Hawthorne Bridge, Oreg. 77,155.4 –47.7 –16.9 –67.1 0.006
60 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 6. Trends in load from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

load,

in kilograms

per day1

Trend,

in percent from 1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

Total nitrogen—Continued

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

193,915.3 –33.4 19.2 –62.8 0.171

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 800.3 –57.9 –23.2 –76.9 0.005

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. 613.9 –43.2 –17.0 –61.1 0.003

219 11478 John Day River at Service Creek, Oreg. 865.5 –66.1 –27.2 –84.2 0.006

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. 1,344.9 –31.0 6.7 –55.4 0.095

221 12413470 South Fork Coeur D'Alene River near Pinehurst, Idaho 183.1 14.9 85.4 –28.8 0.570

222 12419000 Spokane River near Post Falls, Idaho 1,320.8 1.0 101.7 –49.4 0.978

223 13154500 Snake River at King Hill, Idaho 38,562.4 –18.7 16.0 –43.0 0.254

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 951.1 22.3 117.9 –31.4 0.495

225 13351000 Palouse River at Hooper, Wash. 903.2 32.4 360.3 –61.9 0.659

227 14211720 Willamette River at Portland, Oreg. 51,090.1 –17.9 34.4 –49.8 0.433

228 14246900 Columbia River at Beaver Army Terminal near Quincy, Oreg. 269,349.9 –20.4 30.5 –51.4 0.366

231 3701002 Tualatin River at Weiss Bridge, Oreg. 4,963.9 8.8 93.6 –38.9 0.775

232 37016120 Tualatin River at Springhill Road Bridge at Dilley, Oreg. 328.8 –22.4 63.7 –63.2 0.506

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. 148.3 –15.5 92.3 –62.9 0.688

242 11290000 Tuolumne River at Modesto, Calif. 784.8 115.7 207.6 51.3 <0.001

243 11303500 San Joaquin River near Vernalis, Calif. 16,922.7 –10.0 80.0 –55.0 0.766

244 11447650 Sacramento River at Freeport, Calif. 12,908.4 40.7 153.7 –22.0 0.257

Nitrate

1 01122610 Shetucket River at South Windham, Conn. 466.0 –29.7 7.8 –54.2 0.106

2 01124000 Quinebaug River at Quinebaug, Conn. 109.8 –7.8 41.7 –40.1 0.710

3 01127000 Quinebaug River at Jewett City, Conn. 907.9 –22.2 39.7 –56.7 0.400

4 01184000 Connecticut River at Thompsonville, Conn. 10,733.3 –2.4 29.8 –26.6 0.868

5 01184490 Broad Brook at Broad Brook, Conn. 205.1 –14.3 11.3 –34.1 0.246

6 01188090 Farmington River at Unionville, Conn. 255.1 –40.5 –13.3 –59.2 0.007

7 01189995 Farmington River at Tariffville, Conn. 1,508.4 –11.2 12.1 –29.6 0.318

8 01192500 Hockanum River near East Hartford, Conn. 687.6 –13.3 11.7 –32.7 0.271

9 01193500 Salmon River near East Hampton, Conn. 74.5 –34.1 39.7 –68.9 0.277

10 01196500 Quinnipiac River at Wallingford, Conn. 1,078.3 –17.8 2.8 –34.3 0.086

11 01205500 Housatonic River at Stevenson, Conn. 1,289.9 7.4 127.4 –49.3 0.852

12 01208500 Naugatuck River at Beacon Falls, Conn. 973.7 –24.4 –0.3 –42.7 0.048

13 01208990 Saugatuck River near Redding, Conn. 4.8 9.3 186.4 –58.3 0.856

14 01209710 Norwalk River at Winnipauk, Conn. 28.9 –2.2 116.2 –55.7 0.957

15 01357500 Mohawk River at Cohoes, N.Y. 5,427.1 9.4 74.9 –31.6 0.707

16 01377000 Hackensack River at Rivervale, N.J. 68.6 –39.5 1.0 –63.7 0.054

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 6.8 –29.8 155.8 –80.7 0.592

18 01387500 Ramapo River near Mahwah, N.J. 312.8 7.1 67.0 –31.3 0.761

19 01389500 Passaic River at Little Falls, N.J. 3,429.6 –34.7 13.3 –62.3 0.130

20 01391500 Saddle River at Lodi, N.J. 735.0 34.3 93.4 –6.7 0.113

21 01394500 Rahway River near Springfield, N.J. 55.5 20.8 102.9 –28.1 0.476

22 01395000 Rahway River at Rahway, N.J. 48.9 20.8 123.6 –34.8 0.548

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 26.1 –17.5 49.6 –54.5 0.526

24 01398000 Neshanic River at Reaville, N.J. 40.5 –12.7 385.2 –84.3 0.877

25 01402000 Millstone River at Blackwells Mills, N.J. 1,404.9 –11.0 27.9 –38.1 0.528

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 2,988.1 –4.1 43.0 –35.7 0.839

29 01409500 Batsto River at Batsto, N.J. 43.6 –69.8 –44.5 –83.5 <0.001

31 01438500 Delaware River at Montague, N.J. 2,761.8 –40.6 1.0 –65.0 0.055

32 01443500 Paulins Kill at Blairstown, N.J. 269.5 –21.3 117.2 –71.4 0.644

33 01463500 Delaware River at Trenton, N.J. 20,884.3 –23.5 23.1 –52.5 0.269
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 61

Table 6. Trends in load from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

load,

in kilograms

per day1

Trend,

in percent from 1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

Nitrate—Continued

34 01467150 Cooper River at Haddonfield, N.J. 17.8 –51.2 –19.3 –70.5 0.005

35 01477120 Raccoon Creek near Swedesboro, N.J. 99.3 –35.2 7.3 –60.8 0.092

36 01491000 Choptank River near Greensboro, Md. 211.9 47.8 281.9 –42.8 0.420

37 01578310 Susquehanna River at Conowingo, Md. 85,810.9 –39.3 4.6 –64.8 0.072

38 01594440 Patuxent River near Bowie, Md. 955.5 –9.3 50.9 –45.5 0.708

39 01614500 Conococheague Creek at Fairview, Md. 5,844.6 –42.7 22.8 –73.2 0.152

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 33,032.7 –56.7 86.7 –89.9 0.262

41 01668000 Rappahannock River near Fredericksburg, Va. 842.3 –59.5 289.6 –95.8 0.434

42 01673000 Pamunkey River near Hanover, Va. 426.2 –43.2 54.8 –79.2 0.269

43 01674500 Mattaponi River near Beulahville, Va. 127.2 –43.0 113.5 –84.8 0.405

44 02035000 James River at Cartersville, Va. 2,747.3 –63.1 54.0 –91.1 0.172

45 02041650 Appomattox River at Matoaca, Va. 235.0 –44.9 50.4 –79.8 0.245

50 02175000 Edisto River near Givhans, S.C. 576.7 –43.0 –5.9 –65.5 0.028

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 278.3 22.4 172.6 –45.0 0.620

66 02335870 Sope Creek near Marietta, Ga. 41.7 –43.2 3.4 –68.8 0.064

71 02492000 Bogue Chitto River near Bush, La. 993.5 27.8 227.6 –50.2 0.610

72 03353637 Little Buck Creek near Indianapolis, Ind. 22.2 –68.9 –13.9 –88.8 0.025

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 623,006.8 –25.2 19.7 –53.3 0.226

74 04063700 Popple River near Fence, Wis. 10.4 –24.8 25.8 –55.0 0.277

76 04087000 Milwaukee River at Milwaukee, Wis. 629.2 8.0 136.3 –50.6 0.847

81 05114000 Souris River near Sherwood, N. Dak. 0.6 1,219.4 21,128.4 –18.0 0.069

82 05120000 Souris River near Verendrye, N. Dak. 15.2 –21.2 530.1 –90.2 0.822

88 05514500 Cuivre River near Troy, Mo. 143.6 –72.4 152.3 –97.0 0.254

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 13.1 –75.5 –32.7 –91.1 0.006

95 07022000 Mississippi River at Thebes, Ill. 1,815,610.3 –65.0 –40.9 –79.3 <0.001

96 06088500 Muddy Creek at Vaughn, Mont. 455.3 –53.3 –30.7 –68.5 <0.001

98 06274300 Bighorn River at Basin, Wyo. 1,385.5 –56.3 –32.8 –71.5 <0.001

99 06329500 Yellowstone River near Sidney, Mont. 4,962.6 –73.5 –16.4 –91.6 0.024

100 06338490 Missouri River at Garrison Dam, N. Dak. 5,929.0 –69.8 –25.0 –87.8 0.010

101 06461500 Niobrara River near Sparks, Nebr. 504.1 43.4 122.2 –7.5 0.107

102 06468250 James River above Arrowwood Lake near Kensal, N. Dak. 1.9 –25.9 1081.4 –95.4 0.832

103 06713500 Cherry Creek at Denver, Colo. 146.0 –39.9 –19.1 –55.3 0.001

104 06752260 Cache La Poudre River at Fort Collins, Colo. 32.7 –80.4 –58.0 –90.8 <0.001

105 06752280 Cache La Poudre River above Boxelder Creek, near 

Timnath, Colo.

42.3 –56.2 38.1 –86.1 0.159

106 06753990 Lonetree Creek near Greeley, Colo. 248.1 –93.3 –85.0 –97.0 <0.001

107 06754000 South Platte River near Kersey, Colo. 11,468.1 –31.2 10.0 –57.0 0.118

108 06775900 Dismal River near Thedford, Nebr. 238.9 15.4 35.4 –1.6 0.077

109 06800000 Maple Creek near Nickerson, Nebr. 1,851.1 –83.8 –60.8 –93.3 <0.001

110 06805500 Platte River at Louisville, Nebr. 41,578.2 –85.2 –61.0 –94.3 <0.001

111 06817700 Nodaway River near Graham, Mo. 8,367.0 –99.3 –91.4 –99.9 <0.001

112 06818000 Missouri River at St. Joseph, Mo. 306,902.8 –81.1 –65.0 –89.8 <0.001

113 06902000 Grand River near Sumner, Mo. 3,650.1 –97.1 –71.5 –99.7 0.002

114 06905500 Chariton River near Prairie Hill, Mo. 1,363.0 –95.6 –58.9 –99.5 0.006

115 06921070 Pomme De Terre River near Polk, Mo. 73.3 –77.9 45.0 –96.6 0.116

116 06926510 Osage River below St. Thomas, Mo. 11,602.8 –96.8 –85.2 –99.3 <0.001

117 06930800 Gasconade River above Jerome, Mo. 2,262.0 –83.4 –58.3 –93.4 <0.001

118 06934500 Missouri River at Hermann, Mo. 477,034.2 –80.9 –62.4 –90.2 <0.001

119 07047942 L'Anguille River near Colt, Ark. 234.9 –26.5 61.7 –66.5 0.445

120 07053250 Yocum Creek near Oak Grove, Ark. 212.2 –22.7 38.9 –57.0 0.389
62 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 6. Trends in load from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

load,

in kilograms

per day1

Trend,

in percent from 1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

Nitrate—Continued

121 07056000 Buffalo River near St Joe, Ark. 75.2 –37.4 82.3 –78.5 0.390

122 07060500 White River at Calico Rock, Ark. 7,572.9 –73.8 –36.1 –89.2 0.003

123 07060710 North Sylamore Creek near Fifty Six, Ark. 3.5 –60.1 –23.7 –79.1 0.005

124 07066110 Jacks Fork above Two River, Mo. 349.2 –45.4 –14.6 –65.1 0.008

125 07068000 Current River at Doniphan, Mo. 2,237.4 –62.2 –41.7 –75.4 <0.001

126 07077500 Cache River at Patterson, Ark. 346.6 –29.3 55.5 –67.9 0.388

127 07077700 Bayou DeView near Morton, Ark. 26.7 353.1 1,463.1 31.3 0.017

128 07103700 Fountain Creek near Colorado Springs, Colo. 33.8 –43.6 24.7 –74.5 0.157

129 07103780 Monument Creek above North Gate Boulevard at United 

States Air Force Academy, Colo.

2.4 246.7 791.7 34.8 0.010

130 07105500 Fountain Creek at Colorado Springs, Colo. 221.8 –13.8 65.4 –55.1 0.654

131 07105530 Fountain Creek below Janitell Road below Colorado 

Springs, Colo.

476.5 35.8 103.0 –9.2 0.136

132 07106300 Fountain Creek near Pinon, Colo. 1,533.4 –46.3 14.8 –74.8 0.109

133 07106500 Fountain Creek at Pueblo, Colo. 1,698.0 –56.0 –13.1 –77.7 0.018

134 07189000 Elk River near Tiff City, Mo. 2,808.9 –62.6 –16.6 –83.2 0.016

135 07195500 Illinois River near Watts, Okla. 3,516.5 –58.7 –26.1 –76.9 0.003

136 07195865 Sager Creek near West Siloam Springs, Okla. 222.0 –3.7 53.5 –39.6 0.873

137 07196000 Flint Creek near Kansas, Okla. 450.8 –26.0 31.0 –58.2 0.301

138 07196500 Illinois River near Tahlequah, Okla. 3,597.3 –61.7 –21.1 –81.4 0.009

139 07197000 Baron Fork at Eldon, Okla. 728.8 –61.8 –15.6 –82.7 0.017

140 07227500 Canadian River near Amarillo, Tex. 33.1 –33.7 417.8 –91.5 0.695

141 07239450 North Canadian River near Calumet, Okla. 31.9 –63.9 162.5 –95.0 0.314

142 07241000 North Canadian River below Lake Overholser near 

Oklahoma City, Okla.

143.1 –88.4 –28.4 –98.1 0.020

143 07241520 North Canadian River at Britton Road at Oklahoma City, Okla. 543.7 –53.6 –6.2 –77.1 0.032

144 07241550 North Canadian River near Harrah, Okla. 1,563.3 –18.0 23.6 –45.6 0.344

145 07247015 Poteau River at Loving, Okla. 14.1 –9.2 208.6 –73.3 0.878

146 07247250 Black Fork below Big Creek near Page, Okla. 8.6 –24.7 270.7 –84.7 0.727

147 07247345 Black Fork at Hodgen, Okla. 4.6 –26.5 254.6 –84.7 0.702

148 07247650 Fourche Maline near Leflore, Okla. 10.4 –75.5 –0.7 –93.9 0.049

149 07263620 Arkansas River at David D. Terry Lock and Dam below 

Little Rock, Ark.

39,163.4 –82.9 –51.5 –94.0 0.001

150 07331000 Washita River near Dickson, Okla. 2,068.8 –87.9 –48.6 –97.1 0.004

151 07355500 Red River at Alexandria, La. 10,592.5 –55.1 21.7 –83.4 0.115

152 07362000 Ouachita River at Camden, Ark. 1,444.2 –14.6 94.7 –62.5 0.708

153 07373420 Mississippi River near St Francisville, La. 2,204,310.2 –47.0 –21.2 –64.4 0.002

154 07375500 Tangipahoa River at Robert, La. 846.8 –50.8 9.5 –77.9 0.082

155 07376000 Tickfaw River at Holden, La. 201.3 –57.4 –12.2 –79.4 0.021

156 07381495 Atchafalaya River at Melville, La. 687,594.0 –47.2 –22.2 –64.2 0.001

157 07386980 Vermilion River at Perry, La. 724.2 32.0 147.4 –29.5 0.386

158 08030500 Sabine River near Ruliff, Tex. 1,136.0 –36.3 28.4 –68.3 0.207

159 08032000 Neches River near Neches, Tex. 135.7 –25.4 87.6 –70.3 0.534

160 08033500 Neches River near Rockland, Tex. 561.9 2.2 140.3 –56.6 0.961

161 08051500 Clear Creek near Sanger, Tex. 13.2 –94.3 101.9 –99.8 0.115

162 08064100 Chambers Creek near Rice, Tex. 21.8 –35.8 1,108.6 –96.6 0.767

163 08065350 Trinity River near Crockett, Tex. 20,455.8 –28.8 38.7 –63.5 0.318

164 08136500 Concho River at Paint Rock, Tex. 2,164.9 –100.0 –99.9 –100.0 <0.001

167 08155200 Barton Creek at State Highway 71 near Oak Hill, Tex. 0.2 693.9 29,857.9 –79.0 0.263
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 63

Table 6. Trends in load from 1993 to 2003.—Continued

[See Appendix 3 for more detail on the trend model. CI, confidence interval; <, less than. Bold p-values indicate statistical significance at the α=0.05 level.]

Site

number

(figure 1)

Station

number Station name

Reference

load,

in kilograms

per day1

Trend,

in percent from 1993 to 2003

p-value Modeled

estimate

Upper

95-percent

CI

Lower

95-percent

CI

Nitrate—Continued

168 08155240 Barton Creek at Lost Creek Boulevard near Austin, Tex. 0.4 637.6 13,902.3 –61.2 0.183

172 08181800 San Antonio River near Elmendorf, Tex. 5,777.2 38.2 101.8 –5.3 0.094

174 09058000 Colorado River near Kremmling, Colo. 284.9 –55.5 24.2 –84.0 0.122

175 09163500 Colorado River near Colorado-Utah State Line 10,028.4 –45.9 –22.2 –62.4 0.001

177 09217010 Green River below Green River, Wyo. 248.9 –32.9 19.0 –62.2 0.173

181 09413500 Virgin River below First Narrows, Utah 473.6 –32.8 10.7 –59.1 0.119

187 10038000 Bear River below Smiths Fork, near Cokeville, Wyo. 69.8 –68.1 –3.6 –89.4 0.043

189 10131000 Chalk Creek at U.S. 189 Crossing, Utah 34.0 –46.4 –5.1 –69.7 0.032

190 10154200 Provo River above Woodland at U.S. Geological Survey 

Gage Number 10154200, Utah

39.0 35.6 132.9 –21.0 0.269

191 10155000 Provo River at Bridge 2.5 miles East of Hailstone 

Junction, Utah

18.0 137.0 391.4 14.3 0.020

192 10155500 Provo River above Confluence with Snake Creek at 

McKeller Bridge, Utah

151.3 –36.3 4.4 –61.1 0.073

194 10336580 Upper Truckee River at South Upper Truckee Road near 

Meyers, Calif.

0.4 –29.1 58.9 –68.3 0.404

195 103366092 Upper Truckee River at Highway 50 above Meyers, Calif. 1.3 –44.3 53.3 –79.8 0.258

197 10336698 Third Creek near Crystal Bay, Nev. 0.3 –82.5 –55.2 –93.1 <0.001

198 103366993 Incline Creek above Tyrol Village near Incline Village, Nev. 0.1 15.2 309.7 –67.6 0.827

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 0.2 –9.4 201.1 –72.7 0.872

200 10336700 Incline Creek near Crystal Bay, Nev. 0.4 –37.5 53.1 –74.5 0.304

201 10336740 Logan House Creek near Glenbrook, Nev. 0.0 186.3 1,474.1 –47.9 0.226

205 07A090 Snohomish River at Snohomish, Wash. 4,071.6 –7.8 38.5 –38.6 0.694

207 09A190 Green River at Kanaskat, Wash. 123.5 –15.1 46.3 –50.7 0.556

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 38,708.1 –35.4 12.7 –62.9 0.124

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

9,869.7 –47.5 –16.2 –67.0 0.007

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 3,494.3 –34.0 0.1 –56.5 0.051

213 10555 Willamette River at Marion Street at Salem, Oreg. 21,656.5 –51.3 –25.2 –68.3 0.001

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

63,995.8 19.3 129.4 –37.9 0.596

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 128.5 –35.7 39.1 –70.3 0.262

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. 578.3 –42.4 –15.8 –60.6 0.004

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 750.9 –12.1 62.2 –52.4 0.680

225 13351000 Palouse River at Hooper, Wash. 577.5 16.9 383.5 –71.7 0.829

226 14201300 Zollner Creek near Mt. Angel, Oreg. 134.4 –38.7 59.3 –76.4 0.315

228 14246900 Columbia River at Beaver Army Terminal near Quincy, Oreg. 164,026.5 –43.3 0.1 –67.9 0.050

229 16A070 Skokomish River near Potlatch, Wash. 177.0 –55.1 –27.3 –72.2 0.001

234 45A070 Wenatchee River at Wenatchee, Wash. 302.1 –1.1 49.5 –34.6 0.957

235 45A110 Wenatchee River near Leavenworth, Wash. 117.0 0.5 204.1 –66.8 0.993

237 49A070 Okanogan River at Malott, Wash. 138.1 –32.4 56.2 –70.8 0.359

238 54A120 Spokane River at Riverside State Park, Wash. 3,664.7 46.2 89.3 12.9 0.004

239 61A070 Columbia River at Northport, Wash. 12,434.4 2.7 50.4 –29.8 0.889

240 11264500 Merced River at Happy Isles Bridge near Yosemite, Calif. 21.9 –72.7 –21.4 –90.5 0.016

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. 105.3 –11.6 88.6 –58.6 0.750

242 11290000 Tuolumne River at Modesto, Calif. 529.0 115.1 197.6 55.4 <0.001

243 11303500 San Joaquin River near Vernalis, Calif. 8,323.0 –3.5 54.0 –39.5 0.881

244 11447650 Sacramento River at Freeport, Calif. 7,982.7 –35.7 10.2 –62.4 0.108

1

Reference value is the load that would have been observed on the first day of the period of record under average hydrologic and seasonal conditions.
64 Nutrient Trends in Streams and River of the United States, 1993–2003

Figure 7. Land use and nutrient budgets at sites in the Eastern United States. Note there likely were additional nutrient 

sources that are not shown here; currently (2008), national-scale, consistently derived source data for the period from 

1993 to 2003 are available only for manure, fertilizer, and atmospheric deposition.

Atmospheric deposition (median

 from 1993 to 2003)

Fertilizer (median from 1993 to 2003)

Manure (median from 1992 to 2002)

Fertilizer (median from 1993 to 2003)

Manure (median from 1992 to 2002)

Urban

Agriculture

Rangeland

Forest

Other

EXPLANATION

Land Use

Phosphorus

Nitrogen

0

5,000

10,000

15,000

20,000

25,000

0

1,000

0

20

40

2,000

3,000

4,000

5,000

60

80

100

0

20

40

60

80

100

0

MEDIAN ANNUAL SOURCE LOAD IN BASIN,

IN PERCENT

MEDIAN ANNUAL SOURCE LOAD IN BASIN, 

IN KILOGRAMS PER SQUARE KILOMETER

20

40

60

80

100

LAND USE IN BASIN,

IN PERCENT

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

SITE NUMBER

A

B

C

D

E
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 65

Figure 8. Land use and nutrient budgets at sites in the Central United States. Note there likely were additional nutrient 

sources that are not shown here; currently (2008), national-scale, consistently derived source data for the period from 

1993 to 2003 are available only for manure, fertilizer, and atmospheric deposition. LAND USE IN BASIN, IN PERCENT

0

20

40

60

80

100

0

20

40

60

80

100

0

20

40

60

80

100

SITE NUMBER

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99 100

101

102

103 104

105 106107 108

109 110111

112

113 114

115 116117 118119 120121

122

123 124125 126127 128129 130

131

132

133 134

135 136

137 138139 140

141

142

143 144

145 146 147 148 149 150151

152 153 154 155 156 157 158 159 160

161

162 163 164 165 166 167 168 169 170

171

172

A

B

C

D

E

0

5,000

10,000

15,000

20,000

25,000

0

1,000

2,000

3,000

4,000

5,000

MEDIAN ANNUAL SOURCE LOAD IN BASIN,

IN PERCENT

MEDIAN ANNUAL SOURCE LOAD IN BASIN, 

IN KILOGRAMS PER SQUARE KILOMETER

Atmospheric deposition (median

 from 1993 to 2003)

Fertilizer (median from 1993 to 2003)

Manure (median from 1992 to 2002)

Fertilizer (median from 1993 to 2003)

Manure (median from 1992 to 2002)

Urban

Agriculture

Rangeland

Forest

Other

EXPLANATION

Land Use

Phosphorus

Nitrogen
66 Nutrient Trends in Streams and River of the United States, 1993–2003

Figure 9. Land use and nutrient budgets at sites in the Western United States. Note there likely were additional nutrient 

sources that are not shown here; currently (2008), national-scale, consistently derived source data for the period from 1993 

to 2003 are available only for manure, fertilizer, and atmospheric deposition. LAND USE IN BASIN, IN PERCENT

0

20

40

60

80

100

0

20

40

60

80

100

0

20

40

60

80

100 A

B

C

D

E

0

1,000

2,000

3,000

4,000

5,000

0

5,000

10,000

15,000

20,000

25,000

MEDIAN ANNUAL SOURCE LOAD IN BASIN,

IN PERCENT

MEDIAN ANNUAL SOURCE LOAD IN BASIN, 

IN KILOGRAMS PER SQUARE KILOMETER

SITE NUMBER

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

Atmospheric deposition (median

 from 1993 to 2003)

Fertilizer (median from 1993 to 2003)

Manure (median from 1992 to 2002)

Fertilizer (median from 1993 to 2003)

Manure (median from 1992 to 2002)

Urban

Agriculture

Rangeland

Forest

Other

EXPLANATION

Land Use

Phosphorus

Nitrogen
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 67

EXPLANATION

–100.00 to –50.00

–49.99 to –10.00

–9.99 to 10.00

10.01 to 50.00

50.01 to 200.00

Greater than 200

Percent change, by county

Phosphorus loading from fertilizer,

1993 to 2003

B

Phosphorus loading from manure,

1992 to 2002

A

Population density,

1990 to 2000 

C

Nitrogen loading from fertilizer,

1993 to 2003 

E

Nitrogen loading from atmospheric deposition,

1993 to 2003

F

D Nitrogen loading from manure,

1992 to 2002 

Figure 10. Changes in (A) phosphorus loading from manure, (B) phosphorus loading from fertilizer, (C) population density, (D) nitrogen 

loading from manure, (E) nitrogen loading from fertilizer, and (F) nitrogen loading from atmospheric deposition in the United States 

during the study period.
68 Nutrient Trends in Streams and River of the United States, 1993–2003

Several significant (p-value less than or equal to 0.05) 

relations were identified through the weighted-least squares 

regression analysis relating FA trends in total phosphorus concentrations to changes in nutrient sources (table 7 and fig. 11). 

Note the R2

 value for these relations was low, indicating that 

a substantial portion of the variability in FA trends in total 

phosphorus concentration was not explained by the changes 

in the source data. At undeveloped sites, total phosphorus 

trends were positively related to changes in population density 

(fig. 11D). This relation indicates that increases in population density may be a factor contributing to increasing total 

phosphorus concentrations in streams in undeveloped areas, 

possibly as a result of increased loading from septic systems 

and point sources and(or) runoff from construction sites and 

fertilized lawns. Relations between total phosphorus trends 

and changes in population density were not as strong for sites 

with greater agricultural or urban influences (fig. 11E and F); 

the effects of increasing population may be greater or more 

discernable at sites less subject to loading from other nutrient 

sources such as fertilizer or manure. Similar positive relations 

between total phosphorus trends and changes in population 

density occurred at sites in the Western United States, at sites 

with mean basin slope greater than 10 percent, and at semiarid/arid sites with mean annual precipitation less than 80 cm 

(fig. 11C, I, and K); many of the sites in these groups also 

were classified as undeveloped. In the case of the Western and 

semi-arid/arid sites, the effects of increases in population density also may be greater or more discernable because of lower 

in-stream dilution capacity.

At sites with greater than 40 percent agricultural land 

use in the basin, total phosphorus trends were positively 

related to changes in phosphorus loading from fertilizer and 

manure (fig. 11E). These relations indicate that increases in 

the land application of fertilizer and manure may be factors 

contributing to increasing total phosphorus concentrations in 

streams in some agricultural areas. Likewise, decreases in the 

land application of fertilizer and manure may be contributing to decreases (or smaller increases) in total phosphorus 

concentrations in streams in other agricultural areas. A similar 

relation between total phosphorus trends and changes in phosphorus loading from fertilizer occurred at sites in the Central 

United States (fig. 11B) and at sites with high loading from 

atmospheric deposition (fig. 11N)—many of these sites had 

substantial agricultural land use in the basin.

At sites with greater than 10 km2

 of the basin area containing subsurface (tile) drains, total phosphorus trends were 

negatively related to changes in population density (fig. 11H). 

This relation indicates that increases in population density may 

be a factor contributing to decreases (or smaller increases) 

in total phosphorus concentrations in streams in areas where 

phosphorus transport may be influenced by subsurface tile 

drains. In general, phosphorus is transported through the 

subsurface in much smaller amounts than nitrogen owing to 

phosphorus sorption on soils and subsoils. However, phosphorus sorption in the subsurface can be reduced when tile drains 

are present; tile drains accelerate water movement to streams 

and therefore can decrease the contact time between the water 

and the subsoil (Gentry and others, 2007; Heathwaite and Dils, 

2000; Sims and others, 1998). The sites in this group were 

located throughout the United States, but many had more than 

20 percent agricultural land use in the basin. It is possible that 

conversion of agricultural land to urban land, and a concomitant reduction in fertilizer and(or) manure application, may 

have contributed to a net reduction in phosphorus transport 

to streams, thereby decreasing in-stream total phosphorus 

concentrations. However, fertilizer and manure loads did not 

decrease consistently at these sites (fig. 11H); in addition, 

land-use/land-cover data for the United States for the early 

1990’s period and the early 2000s period currently (2008) 

are not comparably derived and, as a result, land-use change 

cannot be evaluated directly. 

The Kruskal-Wallis and Tukey’s analyses identified 

several additional site groups where changes in nutrient 

sources were different between sites with upward, downward, 

and nonsignificant FA trends in total phosphorus concentrations (tables 8 and 9). At sites in the Eastern United States, 

changes in phosphorus loading from fertilizer differed between 

sites with upward, downward, and nonsignificant FA trends, 

but these differences were no longer significant in the post-hoc 

Tukey’s analysis. At sites with greater than 10 percent urban 

land cover in the basin, the decrease in phosphorus loading 

from manure was greater at sites with nonsignificant trends 

than at sites with downward trends, indicating that other factors likely were more important in affecting the downward 

trends. At sites with high source loading from atmospheric 

deposition, the increase in population density was greater 

at sites with nonsignificant trends than at sites with upward 

trends, indicating that other factors likely were more 

important in affecting the upward trends.

The results from the weighted-least squares regression 

and Kruskal-Wallis analyses largely were consistent with 

results from multiple linear regression when FA trends in total 

phosphorus concentrations were related to changes in population density and source loading from fertilizer and manure at 

sites in the Eastern, Central, and Western United States and 

at sites classified as having undeveloped land use (table 10A). 

The one exception was the model for sites in the Eastern 

United States—the variation in trends at these sites was best 

described by changes in source loading from manure, though 

the overall model was not significant (table 10A). The variation in trends in the Central United States was best described 

by changes in source loading from fertilizer alone; additional 

source variables did not improve the model (table 10A). The 

fertilizer coefficient was positive, indicating that total phosphorus trends at sites in the Central United States generally 

increased as source loading from fertilizer increased and 

decreased as source loading from fertilizer decreased. The 

variation in trends in the Western United States was best 

described by changes in population density alone; additional 

source variables did not improve the model (table 10A). 

The population-density coefficient was positive, indicating 

that total phosphorus trends at sites in the Western United 
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 69

States generally increased as population density increased 

and decreased as population density decreased. The variation 

in trends at undeveloped sites was best explained by changes 

in population density and source loading from manure. The 

manure coefficient, however, was not significant; changes in 

source loading from manure did not account for a significant 

amount of variation in total phosphorus trends at undeveloped 

sites. The population-density coefficient was significant and 

positive, indicating that total phosphorus trends at undeveloped sites generally increased as population density increased 

and decreased as population density decreased. The multiple 

R2

 value for each model was low—a substantial portion of 

the variability in FA trends in total phosphorus concentration 

at these sites was not explained by changes in the available 

source data.

Regional Trends

Upward regional trends in FA total phosphorus concentrations occurred at sites in the Central United States, sites 

with greater than 40 percent agricultural land use in the basin, 

and sites with high source loading from manure (table 11). 

There were, however, no significant regional trends in NFA 

total phosphorus concentrations at these sites, likely reflecting the effects of decreasing streamflow at many of the sites. 

For the other site groups, a combination of a lack of trend 

at many locations and trends in opposite directions at other 

locations cancelling one another out resulted in nonsignificant 

regional trends.

Total Nitrogen

Trends from 1993 to 2003

Significant (p-value less than or equal to 0.05) FA trends 

in total nitrogen concentrations only occurred at 51 (37 percent) 

of 137 sites from 1993 to 2003 (fig. 12B, tables 3 and 4, 

Appendix 3). Downward FA trends occurred at 22 (16 percent) 

of the sites, indicating that changes in nitrogen use, implementation of pollution-control strategies, or other anthropogenic 

activities contributed to significant decreases in total nitrogen 

concentrations in some streams. In many other streams, any 

such changes that occurred were offset by other anthropogenic 

activities in the watershed that increased concentrations. 

Upward FA trends occurred at 29 (21 percent) of the sites, 

indicating that increases in nitrogen sources and(or) transport 

at these sites may have been contributing to increased total 

nitrogen concentrations in streams. FA trends in total nitrogen 

concentrations generally were downward or nonsignificant at 

sites in the Northwestern United States (fig. 12B). At sites in 

the Eastern, Central, and Southwestern United States, FA trends 

were a mixture of upward, downward, and nonsignificant.

There were fewer significant NFA trends than FA trends 

in total nitrogen concentrations; NFA trends were significant 

at 37 (27 percent) of 137 sites from 1993 to 2003 (fig. 12C, 

tables 3 and 5, Appendix 3). At the majority of sites (73 percent) 

nationwide, total nitrogen concentrations in streams were not 

changing significantly. At sites where concentrations were 

changing significantly, more NFA trends were downward than 

upward. Downward NFA trends occurred at 22 (16 percent) of 

the sites, and upward NFA trends occurred at 15 (11 percent) of 

the sites. NFA trends in total nitrogen concentrations generally 

were downward or nonsignificant at sites in the Northwestern 

United States (fig. 12C). At sites in others areas of the United 

States, NFA trends were a mixture of upward, downward, 

and nonsignificant.

The primary difference between the number of significant 

FA and NFA trends was a smaller number of upward NFA 

trends. In particular, relatively fewer upward NFA trends than 

upward FA trends occurred at sites in the Central United States, 

where many of the significant (downward) trends in streamflow 

occurred (fig. 12A). At these sites, the upward FA trends indicate that nitrogen sources may have been increasing between 

1993 and 2003, while the downward trends in streamflow 

indicate that precipitation and surface runoff were decreasing, 

likely as a result of drought conditions in the latter part of the 

study period. The increase in source indicated by the upward 

FA trend likely was offset by the effects of decreasing surface 

runoff indicated by the downward streamflow trend, resulting 

in fewer upward NFA trends. In this case, in-stream concentrations probably would have been higher without the decrease 

in streamflow and associated surface runoff. At other sites, a 

downward FA trend in total nitrogen concentrations occurred 

along with a downward trend in streamflow; in this case, the 

decrease in source indicated by the downward FA trend likely 

was supplemented by the effects of decreasing surface runoff.

At sites in other parts of the United States, where there 

were few trends in streamflow from 1993 to 2003, FA and NFA 

trends generally were similar. Sites with upward FA trends may 

have experienced an increase in nitrogen sources between 1993 

and 2003; sites with downward FA trends may have experienced 

a decrease in nitrogen sources and(or) reductions due to the 

implementation of pollution-control strategies. With no trend in 

streamflow at these sites, NFA trends generally were similar and 

a product of the same influences.

Trends in loads of total nitrogen from 1993 to 2003 were 

a reflection of the combined influence of changes in streamflow and changes in concentration. At the majority of sites 

(74 percent) nationwide, there was no significant trend in the 

load of total nitrogen being transported to downstream locations (fig. 12D, tables 3 and 6, Appendix 3). Upward trends in 

load occurred at only 2 (1 percent) of the 137 sites. Downward 

trends in load occurred at 34 (25 percent) of the sites, primarily in the Central United States. Throughout the United States, 

trends in load were similar to trends in streamflow at the 

majority of sites. However, the change in concentration was 

large enough to be the primary influence at numerous sites, 

and load changed correspondingly.

There were fewer upward FA and NFA trends in total 

nitrogen concentrations (21 and 11 percent, respectively) than 

in total phosphorus concentrations (33 and 24 percent, respectively). In contrast, the percentage of downward FA and NFA 
70 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 7. Results of weighted least-squares regression relating flow-adjusted trends to changes in nutrient sources.—Continued

[--, not applicable; NN, model exhibited heteroscedasticity, departure from a normal distribution, or outliers were present; <, less than; R2, coefficient 

of determination. Bold p-values indicate statistical significance at the α=0.05 level.]

Site group

Loading from atmospheric deposition Loading from fertilizer

Number of

samples R2 p-value Slope

coefficient

Standard

error of 

slope

coefficient

Number of

samples R2 p-value Slopecoefficient

Standard

error of

slope

coefficient

Total phosphorus

Eastern United States -- -- -- -- -- 60 0.020 0.284 –0.166 0.154

Central United States -- -- -- -- -- 57 0.160 0.002 0.207 0.064

Western United States -- -- -- -- -- 46 0.000 0.900 –0.008 0.065

Undeveloped land-use classification -- -- -- -- -- 58 0.000 0.894 0.008 0.060

Greater than 40 percent agricultural land use 

in the basin

-- -- -- -- -- 38 0.213 0.004 0.252 0.081

Greater than 10 percent urban land use 

in the basin

-- -- -- -- -- 51 0.001 0.821 –0.043 0.186

Base-flow index greater than 50 -- -- -- -- -- 67 0.007 0.512 0.054 0.081

Basin area with subsurface drains greater than 

10 square kilometers

-- -- -- -- -- 46 0.042 0.172 0.081 0.058

Mean basin slope greater than 10 percent -- -- -- -- -- 50 0.000 0.889 –0.009 0.062

Mean annual precipitation greater than 

130 centimeters

-- -- -- -- -- 51 0.004 0.677 –0.050 0.119

Mean annual precipitation less than 80 centimeters -- -- -- -- -- 34 0.081 0.103 0.097 0.058

Reference streamflow greater than 100 cubic 

meters per second

-- -- -- -- -- 40 0.003 0.726 0.025 0.070

Reference streamflow less than 3 cubic meters 

per second

-- -- -- -- -- 42 0.007 0.592 0.089 0.165

High source loading from atmospheric deposition -- -- -- -- -- 54 0.084 0.034 0.193 0.089

High source loading from fertilizer -- -- -- -- -- 54 0.005 0.595 0.051 0.095

High source loading from manure -- -- -- -- -- 46 0.068 0.081 0.120 0.067

Total nitrogen

Eastern United States 56 0.066 0.056 –0.180 0.092 56 0.000 0.891 0.073 0.531

Central United States 45 0.083 0.055 –0.120 0.061 45 0.001 0.875 –0.031 0.195

Western United States 29 0.125 0.060 0.105 0.054 28 0.008 0.651 0.065 0.141

Undeveloped land-use classification 41 0.036 0.233 0.083 0.068 40 0.008 0.583 0.086 0.155

Greater than 40 percent agricultural land use 

in the basin

28 0.241 0.008 –0.240 0.084 28 0.005 0.711 0.097 0.259

Greater than 10 percent urban land use 

in the basin

41 0.034 0.251 –0.103 0.088 41 0.007 0.616 0.287 0.568

Base-flow index greater than 50 42 NN NN NN NN 41 0.002 0.804 –0.090 0.361

Basin area with subsurface drains greater than 

10 square kilometers

38 0.047 0.191 0.095 0.072 38 0.000 0.908 –0.023 0.193

Mean basin slope greater than 10 percent 38 0.132 0.025 0.129 0.055 37 0.002 0.769 0.052 0.176

Mean annual precipitation greater than 

130 centimeters

41 0.057 0.134 0.105 0.069 41 0.011 0.512 0.213 0.322

Mean annual precipitation less than 80 centimeters 27 0.037 0.334 0.059 0.060 26 0.000 0.984 0.005 0.233

Reference streamflow greater than 100 cubic 

meters per second

35 0.142 0.025 0.198 0.085 35 0.007 0.625 –0.097 0.196

Reference streamflow less than 3 cubic meters 

per second

41 0.017 0.413 –0.067 0.081 40 0.000 0.911 0.052 0.458

High source loading from atmospheric deposition 43 0.064 0.101 –0.142 0.085 43 0.027 0.292 0.267 0.250

High source loading from fertilizer 32 0.032 0.330 –0.097 0.098 32 0.000 0.961 –0.016 0.315

High source loading from manure 37 0.126 0.031 –0.175 0.078 37 NN NN NN NN

Nitrate

Eastern United States 46 0.002 0.775 –0.023 0.078 46 0.001 0.817 –0.129 0.554

Central United States 78 0.049 0.051 –0.046 0.023 78 0.027 0.151 0.099 0.068

Western United States 37 0.007 0.623 0.020 0.041 33 0.010 0.576 –0.082 0.145

Undeveloped land-use classification 57 0.006 0.572 0.019 0.033 53 0.003 0.722 0.036 0.101

Greater than 40 percent agricultural land use 

in the basin

39 0.124 0.028 –0.118 0.052 39 0.028 0.309 0.108 0.105
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 71

Table 7. Results of weighted least-squares regression relating flow-adjusted trends to changes in nutrient sources.—Continued

[--, not applicable; NN, model exhibited heteroscedasticity, departure from a normal distribution, or outliers were present; <, less than; R2, coefficient 

of determination. Bold p-values indicate statistical significance at the α=0.05 level.]

Site group

Loading from manure Population density

Number of

samples R2 p-value Slope

coefficient

Standard

error of 

slope

coefficient

Number of

samples R2 p-value Slopecoefficient

Standard

error of

slope

coefficient

Total phosphorus

Eastern United States 60 NN NN NN NN 60 0.002 0.718 –0.015 0.042

Central United States 57 0.062 0.061 0.090 0.047 57 0.006 0.566 0.020 0.034

Western United States 46 0.009 0.527 –0.021 0.033 46 0.315 <0.001 0.170 0.038

Undeveloped land-use classification 58 0.026 0.228 –0.043 0.035 58 0.357 <0.001 0.182 0.033

Greater than 40 percent agricultural land use 

in the basin

38 0.140 0.021 0.100 0.042 38 0.031 0.289 0.049 0.046

Greater than 10 percent urban land use 

in the basin

51 NN NN NN NN 51 0.018 0.353 –0.052 0.056

Base-flow index greater than 50 67 0.014 0.340 –0.033 0.034 67 NN NN NN NN

Basin area with subsurface drains greater than 

10 square kilometers

46 0.004 0.668 0.017 0.039 46 0.157 0.006 –0.070 0.024

Mean basin slope greater than 10 percent 50 0.005 0.616 –0.016 0.032 50 0.315 <0.001 0.161 0.034

Mean annual precipitation greater than 

130 centimeters

51 0.008 0.534 –0.050 0.081 51 NN NN NN NN

Mean annual precipitation less than 80 centimeters 34 0.000 0.933 –0.002 0.026 34 0.124 0.041 0.083 0.039

Reference streamflow greater than 100 cubic 

meters per second

40 0.003 0.745 0.015 0.045 40 0.060 0.129 –0.050 0.032

Reference streamflow less than 3 cubic meters 

per second

42 NN NN NN NN 42 0.077 0.075 0.126 0.069

High source loading from atmospheric deposition 54 NN NN NN NN 54 NN NN NN NN

High source loading from fertilizer 54 0.001 0.816 –0.016 0.070 54 0.039 0.155 –0.064 0.044

High source loading from manure 46 0.017 0.392 0.035 0.040 46 0.016 0.396 0.030 0.035

Total nitrogen

Eastern United States 56 NN NN NN NN 56 0.002 0.774 0.026 0.091

Central United States 45 NN NN NN NN 45 0.000 0.899 –0.013 0.105

Western United States 29 0.028 0.384 0.069 0.078 29 NN NN NN NN

Undeveloped land-use classification 41 0.000 0.929 –0.007 0.081 41 NN NN NN NN

Greater than 40 percent agricultural land use 

in the basin

28 0.010 0.609 0.067 0.130 28 0.066 0.186 0.232 0.171

Greater than 10 percent urban land use 

in the basin

41 NN NN NN NN 41 0.094 0.052 –0.236 0.117

Base-flow index greater than 50 42 0.009 0.558 0.050 0.085 42 NN NN NN NN

Basin area with subsurface drains greater than 

10 square kilometers

38 0.019 0.407 –0.094 0.112 38 0.049 0.180 –0.103 0.075

Mean basin slope greater than 10 percent 38 0.001 0.845 0.018 0.091 38 NN NN NN NN

Mean annual precipitation greater than 

130 centimeters

41 0.006 0.640 0.086 0.183 41 0.004 0.694 –0.032 0.081

Mean annual precipitation less than 80 centimeters 27 0.000 0.924 –0.009 0.093 27 NN NN NN NN

Reference streamflow greater than 100 cubic 

meters per second

35 0.029 0.330 0.086 0.087 35 0.022 0.397 –0.079 0.092

Reference streamflow less than 3 cubic meters 

per second

41 NN NN NN NN 41 0.032 0.263 –0.169 0.149

High source loading from atmospheric deposition 43 NN NN NN NN 43 0.019 0.377 –0.095 0.107

High source loading from fertilizer 32 0.001 0.846 0.047 0.237 32 0.088 0.098 –0.296 0.174

High source loading from manure 37 0.004 0.703 –0.044 0.115 37 NN NN NN NN

Nitrate

Eastern United States 46 NN NN NN NN 46 0.000 0.938 0.006 0.072

Central United States 78 0.059 0.033 0.108 0.050 78 0.024 0.172 0.054 0.039

Western United States 37 0.009 0.572 0.029 0.050 37 NN NN NN NN

Undeveloped land-use classification 57 0.040 0.135 0.060 0.040 57 NN NN NN NN

Greater than 40 percent agricultural land use 

in the basin

39 0.017 0.427 0.047 0.059 39 NN NN NN NN
72 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 7. Results of weighted least-squares regression relating flow-adjusted trends to changes in nutrient sources.—Continued

[--, not applicable; NN, model exhibited heteroscedasticity, departure from a normal distribution, or outliers were present; <, less than; R2, coefficient 

of determination. Bold p-values indicate statistical significance at the α=0.05 level.]

Site group

Loading from atmospheric deposition Loading from fertilizer

Number of

samples R2 p-value Slope

coefficient

Standard

error of 

slope

coefficient

Number of

samples R2 p-value Slopecoefficient

Standard

error of

slope

coefficient

Nitrate—Continued

Greater than 10 percent urban land use 

in the basin

39 0.028 0.309 –0.073 0.070 39 0.001 0.850 0.097 0.508

Base-flow index greater than 50 58 0.008 0.492 0.030 0.043 54 0.001 0.831 –0.053 0.247

Basin area with subsurface drains greater than 

10 square kilometers

33 0.050 0.213 0.082 0.064 33 0.031 0.327 –0.137 0.138

Mean basin slope greater than 10 percent 54 0.007 0.554 0.020 0.033 50 0.000 0.891 0.017 0.122

Mean annual precipitation greater than 

130 centimeters

38 0.002 0.768 0.016 0.055 37 0.031 0.294 –0.294 0.276

Mean annual precipitation less than 80 centimeters 43 0.003 0.708 0.011 0.030 42 0.021 0.361 0.104 0.113

Reference streamflow greater than 100 cubic 

meters per second

30 0.010 0.608 0.054 0.104 30 0.088 0.112 –0.312 0.190

Reference streamflow less than 3 cubic meters 

per second

54 0.002 0.761 –0.010 0.033 51 0.000 0.886 0.027 0.184

High source loading from atmospheric deposition 44 0.000 0.982 0.002 0.070 44 0.002 0.781 0.061 0.216

High source loading from fertilizer 34 0.017 0.459 –0.050 0.066 34 0.016 0.472 0.129 0.178

High source loading from manure 42 0.088 0.057 –0.111 0.057 42 NN NN NN NN

trends was similar for total nitrogen concentrations and total 

phosphorus concentrations (16 percent for all). The greater 

number of upward total phosphorus trends at these sites cannot 

be explained easily by changes in nonpoint-source loading of 

nitrogen and phosphorus from 1993 to 2003; during this period, 

there were slightly more sites with increases in nitrogen loading 

from fertilizer and(or) manure than there were sites with increases 

in phosphorus loading from these two sources (appendix 1). One 

alternate possibility is that soils are at or approaching phosphorus 

saturation in areas that have been subject to long-term manure 

or fertilizer application (Sharpley and others, 1996). Because the 

amount of phosphorus in surface runoff can increase with the 

phosphorus content of soils (Davis and others, 2005; Pote and 

others, 1996), over time, a greater proportion of the phosphorus 

load applied to the land surface may be reaching streams, particularly in agricultural areas. Another possibility is that a substantial 

source of nitrate in some streams is ground water (Sprague and 

others, 2006; Bachman and others, 1998). Because of the time 

required for ground water to travel to streams, there may be a lag 

between changes in nitrogen use, implementation of pollutioncontrol strategies, or other anthropogenic activities on the land 

surface and changes in total nitrogen concentration in streams. As 

a result, trends in total nitrogen concentrations from 1993 to 2003 

may have been influenced by changes that took place on the land 

surface prior to 1993.

Factors Affecting the Trends

Land use and nitrogen budgets for each site in the 

Eastern, Central, and Western United States are shown in 

figures 7, 8, and 9, respectively. Land use is shown as a 

percentage of the basin area in part A of each figure. Median 

nitrogen loads from manure, fertilizer, and atmospheric 

deposition between 1993 and 2003 are shown as percentages 

of their combined total load in part C of each figure and as 

absolute loads, normalized to the basin area, in part E of each 

figure. There likely were additional sources of nitrogen in 

these basins that are not shown in the nitrogen budgets; currently (2008), national-scale, consistently derived nitrogen 

source data that cover the period from 1993 to 2003 are available only for manure, fertilizer, and atmospheric deposition.

At sites in the Eastern United States, fertilizer often was a 

larger source of nitrogen than manure (fig. 7). In the Northeast 

(New England and Mid-Atlantic NAWQA major river basin in 

fig. 1), atmospheric deposition often was the largest source of 

nitrogen, particularly at sites with minimal urban or agricultural development and small total loads. The total source loads 

of nitrogen, including manure, fertilizer, and atmospheric 

deposition, were highest at sites with relatively high percentages of agricultural land use. At sites in the Central United 

States, fertilizer generally was a larger source of nitrogen 

than manure in the Great Lakes, Ohio, Upper Mississippi, 

and Souris-Red-Rainy NAWQA major river basin; manure 

generally was a comparable or larger source in the Missouri 

and Lower Mississippi, Arkansas-White-Red, and Texas-Gulf 

NAWQA major river basins (figs. 1 and 8). Atmospheric 

deposition was a large source of nitrogen at sites with minimal urban or agricultural development and small total loads. 

Across the Central United States, the total source loads of 

nitrogen were highest at sites with relatively high percentages of agricultural land use. At sites in the Western United 

States, manure generally was a larger source of nitrogen 

than fertilizer in the Southwest, particularly the Rio Grande, 

Colorado, and Great Basin NAWQA major river basin, where 

the percentage of rangeland in the basins was high (figs. 1 and 
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 73

Table 7. Results of weighted least-squares regression relating flow-adjusted trends to changes in nutrient sources.—Continued

[--, not applicable; NN, model exhibited heteroscedasticity, departure from a normal distribution, or outliers were present; <, less than; R2, coefficient 

of determination. Bold p-values indicate statistical significance at the α=0.05 level.]

Site group

Loading from manure Population density

Number of

samples R2 p-value Slope

coefficient

Standard

error of 

slope

coefficient

Number of

samples R2 p-value Slopecoefficient

Standard

error of

slope

coefficient

Nitrate—Continued

Greater than 10 percent urban land use 

in the basin

39 NN NN NN NN 39 0.071 0.102 –0.151 0.090

Base-flow index greater than 50 58 0.002 0.739 –0.017 0.051 58 NN NN NN NN

Basin area with subsurface drains greater than 

10 square kilometers

33 0.005 0.709 –0.026 0.070 33 0.000 0.909 0.007 0.062

Mean basin slope greater than 10 percent 54 0.009 0.484 0.039 0.056 54 NN NN NN NN

Mean annual precipitation greater than 

130 centimeters

38 NN NN NN NN 38 0.006 0.644 0.046 0.099

Mean annual precipitation less than 80 centimeters 43 0.000 0.978 –0.002 0.058 43 0.018 0.387 0.060 0.068

Reference streamflow greater than 100 cubic 

meters per second

30 0.023 0.423 –0.090 0.111 30 0.066 0.169 0.139 0.098

Reference streamflow less than 3 cubic meters 

per second

54 NN NN NN NN 54 0.011 0.450 0.049 0.064

High source loading from atmospheric deposition 44 NN NN NN NN 44 NN NN NN NN

High source loading from fertilizer 34 0.097 0.073 0.266 0.143 34 0.010 0.569 –0.066 0.114

High source loading from manure 42 0.027 0.295 0.061 0.058 42 NN NN NN NN

9). Total source loads of nitrogen at these sites, however, were 

relatively low. Total source loads of nitrogen were higher at 

sites in the Pacific Northwest and California, where fertilizer 

was a comparable or larger source of nitrogen than manure. As 

in the Eastern and Central United States, atmospheric deposition often was a large source of nitrogen at sites with minimal 

urban or agricultural development and small total loads in the 

West, and the total source loads of nitrogen were highest at 

sites with relatively high percentages of agricultural land use.

Changes in nitrogen loading from manure, fertilizer, and 

atmospheric deposition during the study period are shown 

on a county-level basis in figure 10, parts D–F. Decreases in 

nitrogen loading from manure were widespread throughout the 

nation (fig. 10D). Small increases also were common, particularly in the Eastern and Central United States. Large increases 

in nitrogen loading from fertilizer were more widespread in 

the Central (particularly west of the Mississippi River) and 

Western United States (fig. 10E). In the Eastern United States, 

decreases in nitrogen loading from fertilizer were more widespread and often greater in magnitude than decreases in nitrogen loading from manure. Nitrogen loading from atmospheric 

deposition decreased or increased only slightly in many parts 

of the United States (fig. 10F). Larger increases in nitrogen 

loading from atmospheric deposition occurred in parts of the 

Southeast, the Southwest, and northern parts of the Central 

United States.

Several significant (p-value less than or equal to 0.05) 

relations were identified through the weighted-least squares 

regression analysis relating FA trends in total nitrogen concentration to changes in nutrient sources (table 7 and fig. 13). 

Note the R2

 value for these relations was low, indicating that 

a substantial portion of the variability in FA trends in total 

nitrogen concentration was not explained by the changes in 

the source data. Changes in nitrogen loading from atmospheric 

deposition were significantly related to FA trends in total 

nitrogen concentrations at sites with greater than 40 percent 

agricultural land use in the basin (fig. 13E), at sites with mean 

basin slope greater than 10 percent (fig. 13I), at sites with reference streamflow values greater than 100 m3

/s (fig. 13L), and 

at sites with high loading from manure (fig. 13P). Although 

a negative relation was observed at sites with greater than 

40 percent agricultural land use in the basin and at sites with 

high loading from manure, changes in loading from atmospheric deposition likely had little impact on trends in total 

nitrogen at these sites because nitrogen loading from atmospheric deposition was small compared to that from fertilizer 

and(or) manure (figs. 7–9).

The Kruskal-Wallis and Tukey’s analyses identified several additional site groups where changes in nutrient sources 

were different between sites with upward, downward, and nonsignificant FA trends in total nitrogen concentrations (tables 8 

and 9). At sites in the Eastern United States, changes in nitrogen loading from atmospheric deposition differed between 

sites with upward, downward, and nonsignificant FA trends, 

but these differences were no longer significant in the posthoc Tukey’s analysis. At sites with high source loading from 

fertilizer, changes in nitrogen loading from fertilizer differed 

between sites with upward, downward, and nonsignificant 

FA trends, but these differences were no longer significant 

in the post-hoc Tukey’s analysis. At sites with high source 

loading from manure, nitrogen loading from fertilizer generally decreased at sites with downward trends and generally 

increased at sites with upward and nonsignificant trends. At 

sites with reference streamflow values greater than 100 m3

/s, 

the decrease in loading from manure was greater at sites with 

downward trends than at sites with nonsignificant trends.
74 Nutrient Trends in Streams and River of the United States, 1993–2003

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present

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400

500

–200

–100

0

100

200

300

400

500

–200

–100

0

100

200

300

400

500

–200

–100

0

100

200

300

400

500

–100 100 200

–100 –60 –20 –20 0 20 40 60 80 100

–50 150

–80 –40

–100 –50 0 50 100 150

–80 –40 0 20 60 –60 –20 40 80

–60 –40 –20 0 20 40 60 80 100 –80 –60 –40 –20 0 20 –60 –40 –20 0 20 6040 80 100

–80 –60 –40 –20 0 20 40 60 80 100 –80 –40–60 –20 0 20 40 60 80 100

0 20 40

0 50 0–10 10 20 30 40 50 60

0 20 40 60

FLOW-ADJUSTED TREND IN TOTAL PHOSPHORUS CONCENTRATION, IN PERCENT

n

60

r2

0.02

pvalue

0.284

n

57

r2

0.16

pvalue

0.002

n

46

r2

0.000

pvalue

0.900

n

46

pvalue

0.527

n

57

pvalue

0.061

n

58

pvalue

0.894

n

58

pvalue

0.228

CHANGE IN POPULATION DENSITY,

IN PERCENT

CHANGE IN PHOSPHORUS LOADING

FROM FERTILIZER, IN PERCENT

CHANGE IN PHOSPHORUS LOADING

FROM MANURE, IN PERCENT

r2

0.000

r2

0.026

r2

0.009

r2

0.062

n

60

pvalue

NN

r2

NN

n

60

pvalue

0.718

r2

0.002

n

57

pvalue

0.566

r2

0.006

n

46

pvalue

<0.001

r2

0.315

n

58

pvalue

<0.001

r2

0.357

A Eastern United States

B Central United States

C Western United States

D Undeveloped Land-Use Classification

Figure 11. Relations between flow-adjusted trends in total phosphorus concentrations and changes in phosphorus sources from 

1993 to 2003 for selected site subsets.
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 75

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present

–100

0

100

200

300

–100

0

100

200

300

–200

–150

–100

–50

0

50

100

150

–100

–150

–200

–50

0

50

100

150

–100

0

100

200

300

–100

–150

–200

–50

0

50

100

150

–100

0

100

200

300

400

500

–100

0

100

200

300

400

500

–100

0

100

200

300

400

500

–200

–100

0

100

200

300

–200

–100

0

100

200

300

–200

–100

0

100

200

300

–60 20

–100 0 100 –20 0 20 40 60 80 100

–40 40

–50 50

–80 –40 –20 200 –60 6040 80

–100 –50 0 50 100 150

–100 –50 0 50 100 150 –80 –60 –40 –20 0 20 40 60 0 20 40 60 80 100

–60 –40 –20 0 20 40 60 80 –60 –20–40 0 –20 –10 0 10 20 30 40 50

150 200

–20 0 –60 –40 –20 0 20 40 60

20 40 60

FLOW-ADJUSTED TREND IN TOTAL PHOSPHORUS CONCENTRATION, IN PERCENT

n

38

r2

0.213

pvalue

0.004

n

51

r2

0.001

pvalue

0.821

n

67

r2

0.007

pvalue

0.512

n

67

pvalue

0.340

n

51

pvalue

NN

n

46

pvalue

0.172

n

46

pvalue

0.668

CHANGE IN POPULATION DENSITY,

IN PERCENT

CHANGE IN PHOSPHORUS LOADING

FROM FERTILIZER, IN PERCENT

CHANGE IN PHOSPHORUS LOADING

FROM MANURE, IN PERCENT

r2

0.042

r2

0.004

r2

0.014

r2

NN

n

38

pvalue

0.021

r2

0.140

n

38

pvalue

0.289

r2

0.031

n

51

pvalue

0.353

r2

0.018

n

67

pvalue

NN

r2

NN

n

46

pvalue

0.006

r2

0.157

E Greater Than 40 Percent Agricultural Land Use in the Basin

F Greater Than 10 Percent Urban Land Use in the Basin

G Base-Flow Index Greater Than 50

H Basin Area With Subsurface Drains Greater Than 10 Square Kilometers

Figure 11—Continued. Relations between flow-adjusted trends in total phosphorus concentrations and changes in phosphorus 

sources from 1993 to 2003 for selected site subsets.
76 Nutrient Trends in Streams and River of the United States, 1993–2003

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present

–200

–100

0

100

200

300

400

500

–200

–100

0

100

200

300

400

500

–200

–100

0

100

200

300

400

500

–200

–100

0

100

200

300

–200

–100

0

100

200

300

–200

–100

0

100

200

300

–200

–100

0

100

200

300

400

500

–200

–100

0

100

200

300

400

500

–200

–100

0

100

200

300

400

500

–100

–50

0

50

100

150

200

250

–100

–50

0

50

100

150

200

250

–100

–50

0

50

100

150

200

250

–80

–100 0 20 –20 0 20 40 50 60 100

–60 20

–80 –60 –40 –20

–60 –20 0 4020 –40 8060 100

–100 –50 0 50 100 150

–60 –40 –20 0 20 40 60 80 –50 –40 –20 –10 –30 0 10 20 –60 –40 –20 0 20 40 60 80 100

–60 –40 –20 0 20 40 60 80 –60 –20–40 0 –20 –10 0 10 20 30 40 50

40 60

–40 –20 0 0 20 40 60 80 100

20 40 60

FLOW-ADJUSTED TREND IN TOTAL PHOSPHORUS CONCENTRATION, IN PERCENT

n

50

r2

0.000

pvalue

0.889

n

51

r2

0.004

pvalue

0.677

n

34

r2

0.081

pvalue

0.103

n

34

pvalue

0.933

n

51

pvalue

0.534

n

40

pvalue

0.726

n

40

pvalue

0.745

CHANGE IN

POPULATION DENSITY,

IN PERCENT

CHANGE IN PHOSPHORUS

LOADING FROM FERTILIZER,

IN PERCENT

CHANGE IN PHOSPHORUS

LOADING FROM MANURE,

IN PERCENT

r2

0.003

r2

0.003

r2

0.000

r2

0.008

n

50

pvalue

0.616

r2

0.005

n

50

pvalue

<0.001

r2

0.315

n

51

pvalue

NN

r2

NN

n

34

pvalue

0.041

r2

0.124

n

40

pvalue

0.129

r2

0.060

I Mean Basin Slope Greater Than 10 Percent

J Mean Annual Precipitation Greater Than 130 Centimeters

K Mean Annual Precipitation Less Than 80 Centimeters

L Reference Streamflow Greater Than 100 Cubic Meters Per Second

Figure 11—Continued. Relations between flow-adjusted trends in total phosphorus concentrations and changes in phosphorus 

sources from 1993 to 2003 for selected site subsets.
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 77

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present

–100

–200

0

100

200

300

–200

–100

0

200

100

300

–200

–100

0

100

200

300

–100

–200

0

100

200

300

–200

–100

0

100

200

300

–200

–100

0

100

200

300

–100

0

100

200

300

–100

0

100

200

300

–100

0

100

200

300

–100

0

100

200

300

–100

0

100

200

300

–100

0

100

200

300

–100

–100 100 150 –20 0 20 40 60 80 100

–50

–50 0 50

–100 –50 0 50 100 150

–100 –50 0 50 100

–100 –50 0 50 100 –100 –80 –40 –20 –60 0 20 40 0 20 40 60 80 100

–60–80 –40 –20 0 20 40 60 80 –40 –20 0 –60 –40 –20 0 20 40 60

200

0 50 100 150 200 0 20 40 60 80 100

20 40 60

–60 –40 –20

–60 –40 –20

FLOW-ADJUSTED TREND IN TOTAL PHOSPHORUS CONCENTRATION, IN PERCENT

n

42

r2

0.007

pvalue

0.592

n

54

r2

0.084

pvalue

0.034

n

54

r2

0.005

pvalue

0.595

n

54

pvalue

0.816

n

54

pvalue

NN

n

46

pvalue

0.081

n

46

pvalue

0.392

CHANGE IN

POPULATION DENSITY,

IN PERCENT

CHANGE IN PHOSPHORUS

LOADING FROM FERTILIZER,

IN PERCENT

CHANGE IN PHOSPHORUS

LOADING FROM MANURE,

IN PERCENT

r2

0.068

r2

0.017

r2

0.001

r2

NN

n

42

pvalue

NN

r2

NN

n

42

pvalue

0.075

r2

0.077

n

54

pvalue

NN

r2

NN

n

54

pvalue

0.155

r2

0.039

n

46

pvalue

0.396

r2

0.016

M References Streamflow Less Than 3 Cubic Meters Per Second

N High Source Loading From Atmospheric Deposition

O High Source Loading From Fertilizer

P High Source Loading From Manure

Figure 11—Continued. Relations between flow-adjusted trends in total phosphorus concentrations and changes in phosphorus 

sources from 1993 to 2003 for selected site subsets.
78 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 8. Results of the Kruskal-Wallis test relating flow-adjusted trends to changes in nutrient sources.—Continued

[--, not applicable. Bold p-values indicate statistical significance at the α=0.05 level.]

Site group

Loading from 

atmospheric deposition Loading from fertilizer Loading from manure Population density

Chi

square p-value Chisquare p-value Chisquare p-value Chisquare p-value

Total phosphorus

Eastern United States -- -- 6.40 0.041 5.72 0.057 2.46 0.293

Central United States -- -- 7.23 0.027 3.06 0.217 0.15 0.929

Western United States -- -- 0.94 0.625 2.54 0.281 1.11 0.574

Undeveloped land-use classification -- -- 3.40 0.182 1.05 0.590 1.92 0.382

Greater than 40 percent agricultural land 

use in the basin

-- -- 7.29 0.026 3.19 0.203 0.83 0.662

Greater than 10 percent urban land use 

in the basin

-- -- 2.80 0.246 7.50 0.023 3.50 0.173

Base-flow index greater than 50 -- -- 2.26 0.324 2.61 0.271 0.51 0.774

Basin area with subsurface drains greater 

than 10 square kilometers

-- -- 1.42 0.493 2.75 0.252 6.24 0.044

Mean basin slope greater than 10 percent -- -- 5.19 0.075 1.30 0.523 0.88 0.643

Mean annual precipitation greater than 

130 centimeters

-- -- 1.81 0.405 2.07 0.356 0.08 0.962

Mean annual precipitation less than 

80 centimeters

-- -- 4.84 0.089 2.00 0.368 2.36 0.307

Reference streamflow greater than 

100 cubic meters per second

-- -- 0.96 0.620 2.90 0.234 4.20 0.123

Reference streamflow less than 3 cubic 

meters per second

-- -- 3.34 0.189 2.40 0.302 4.17 0.124

High source loading from atmospheric 

deposition 

-- -- 6.01 0.049 0.35 0.840 7.17 0.028

High source loading from fertilizer -- -- 2.86 0.239 0.22 0.898 4.63 0.099

High source loading from manure -- -- 1.80 0.407 5.00 0.082 0.31 0.857

Total nitrogen

Eastern United States 6.32 0.042 2.30 0.317 2.13 0.345 1.72 0.422

Central United States 5.45 0.065 2.98 0.225 5.29 0.071 0.52 0.769

Western United States 4.17 0.124 0.49 0.782 2.51 0.285 1.09 0.581

Undeveloped land-use classification 2.38 0.305 0.11 0.946 1.35 0.508 3.24 0.198

Greater than 40 percent agricultural land 

use in the basin

6.73 0.034 2.91 0.233 3.42 0.181 2.92 0.232

Greater than 10 percent urban land use 

in the basin

0.87 0.648 1.61 0.448 0.61 0.736 4.92 0.085

Base-flow index greater than 50 1.72 0.423 0.34 0.844 5.48 0.065 0.78 0.677

Basin area with subsurface drains greater 

than 10 square kilometers

1.96 0.376 0.68 0.712 0.21 0.901 2.35 0.310

Mean basin slope greater than 10 percent 7.41 0.025 0.08 0.963 2.18 0.336 1.82 0.402

Mean annual precipitation greater than 

130 centimeters

3.17 0.205 1.29 0.525 0.54 0.764 0.25 0.881

Mean annual precipitation less than 

80 centimeters

0.45 0.800 0.47 0.790 2.41 0.299 0.40 0.818

Reference streamflow greater than 

100 cubic meters per second

5.73 0.057 1.82 0.402 8.51 0.014 0.95 0.623

Reference streamflow less than 3 cubic 

meters per second

4.76 0.092 2.88 0.236 2.03 0.363 2.82 0.245

High source loading from atmospheric 

deposition 

3.01 0.222 1.53 0.466 1.84 0.398 0.48 0.785

High source loading from fertilizer 2.25 0.325 6.09 0.047 0.34 0.845 5.78 0.056

High source loading from manure 10.96 0.004 8.36 0.015 1.37 0.503 2.22 0.330
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 79

The non-significant relations between FA trends in total 

nitrogen concentrations and changes in nutrient sources were 

informative as well. None of the relations that were significant in the weighted-least squares regression analysis for total 

phosphorus were found to be significant for total nitrogen. In 

addition, none of the additional differences between sites with 

upward, downward, and nonsignificant FA trends that were 

significant in the Kruskal-Wallis analysis for total phosphorus 

were found to be significant for total nitrogen. As discussed 

earlier, a substantial source of nitrate in some streams is 

ground water (Sprague and others, 2006; Bachman and others, 

1998), and ground-water travel times of months, years, or 

decades can lead to a lag between changes in nitrogen use on 

the land surface and changes in total nitrogen concentration 

in streams. As a result, trends in total nitrogen concentrations 

from 1993 to 2003 may be influenced by changes that took 

place on the land surface prior to 1993; these changes would 

not be reflected in the contemporaneous ancillary data used 

here. Nitrogen typically is transported through ground water to 

a greater extent than phosphorus, which sorbs more readily to 

soil; therefore, nitrogen trends in streams are more likely to be 

affected by ground-water lag times than are phosphorus trends.

The multiple linear regression results provided limited 

additional insights when FA trends in total nitrogen concentrations were related to changes in population density and source 

loading from atmospheric deposition, fertilizer, and manure 

at sites in the Eastern, Central, and Western United States and 

at sites classified as having undeveloped land use (table 10B). 

The models for sites in the Eastern United States and for undeveloped sites were not significant, and the models for sites in 

the Central and Western United States violated assumptions of 

normality and(or) homoscedasticity (table 10B).

Regional Trends

There were no significant regional trends in FA or NFA 

total nitrogen concentrations (table 11). This likely resulted 

from a combination of a lack of trend at many locations and 

trends in opposite directions at other locations cancelling one 

another out.

Nitrate

Trends from 1993 to 2003

Significant (p-value less than or equal to 0.05) FA trends 

in nitrate concentrations occurred at 62 (37 percent) of 166 

sites from 1993 to 2003 (fig. 14B, tables 3 and 4, Appendix 3). 

There were more downward FA trends in nitrate concentrations 

Table 8. Results of the Kruskal-Wallis test relating flow-adjusted trends to changes in nutrient sources.—Continued

[--, not applicable. Bold p-values indicate statistical significance at the α=0.05 level.]

Site group

Loading from 

atmospheric deposition Loading from fertilizer Loading from manure Population density

Chi

square p-value Chisquare p-value Chisquare p-value Chisquare p-value

Nitrate

Eastern United States 1.20 0.548 1.61 0.448 1.05 0.591 0.67 0.716

Central United States 11.06 0.004 2.84 0.242 5.51 0.064 5.80 0.055

Western United States 3.00 0.223 0.88 0.644 2.72 0.257 0.51 0.776

Undeveloped land-use classification 1.59 0.451 0.98 0.614 4.42 0.109 1.70 0.427

Greater than 40 percent agricultural land 

use in the basin

6.24 0.044 1.07 0.587 0.34 0.842 5.43 0.066

Greater than 10 percent urban land use 

in the basin

7.19 0.027 0.79 0.672 2.09 0.352 1.50 0.472

Base-flow index greater than 50 1.41 0.493 0.01 0.997 1.33 0.514 3.43 0.180

Basin area with subsurface drains greater 

than 10 square kilometers

5.21 0.074 2.94 0.230 2.29 0.318 3.43 0.180

Mean basin slope greater than 10 percent 2.15 0.342 0.22 0.898 2.07 0.356 2.14 0.342

Mean annual precipitation greater than 

130 centimeters

1.21 0.546 1.89 0.389 9.16 0.010 1.04 0.594

Mean annual precipitation less than 

80 centimeters

0.01 0.993 1.07 0.585 2.92 0.232 0.56 0.755

Reference streamflow greater than 

100 cubic meters per second

1.73 0.421 3.20 0.202 1.80 0.406 1.13 0.568

Reference streamflow less than 3 cubic 

meters per second

6.97 0.031 2.41 0.300 4.05 0.132 1.34 0.512

High source loading from atmospheric 

deposition 

2.06 0.357 0.66 0.719 1.88 0.391 3.30 0.192

High source loading from fertilizer 1.46 0.483 0.08 0.962 2.51 0.285 0.06 0.970

High source loading from manure 5.63 0.060 3.75 0.153 0.03 0.984 1.55 0.460
80 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 9. Results of the Tukey's multiple comparison test of changes in source loading at sites with upward, downward, and 

nonsignificant trends.

[Only those groups with significant differences in the Kruskal-Wallis test are shown (see table 8). Letters indicate significantly different group medians.]

Site group Nutrient source

Median change in source, in percent over period of record

Sites with upward

flow-adjusted trends

in concentration

Sites with downward

flow-adjusted trends

in concentration

Sites with nonsignificant

flow-adjusted trends

in concentration

Total phosphorus

Eastern United States Loading from fertilizer –14.5

a

–3.9

a

–32.5

a

Central United States Loading from fertilizer 7.7

a

–43.9

ab

–15.4

b

Greater than 40 percent agricultural land 

use in the basin

Loading from fertilizer 9.6

a

–43.9

ab

–49.0

b

High source loading from atmospheric 

deposition 

Loading from fertilizer –17.3

a

–49.0

a

–49.0

a

Greater than 10 percent urban land use in 

the basin

Loading from manure –26.9

ab

–17.0

a

–31.4

b

Basin area with subsurface drains greater 

than 10 square kilometers

Population density 8.3

a

23.2

b

13.4

ab

High source loading from atmospheric 

deposition 

Population density 5.2

a

11.5

ab

11.5

b

Total nitrogen

Eastern United States Loading from atmospheric 

deposition

–26.9

a

–15.4

a

–20.6

a

Greater than 40 percent agricultural land 

use in the basin

Loading from atmospheric 

deposition

–21.5

a

9.6

a

–6.3

a

Mean basin slope greater than 10 percent Loading from atmospheric 

deposition

–14.0

ab

–23.5

a

–14.2

b

High source loading from manure Loading from atmospheric 

deposition

–21.6

a

9.6

b

–7.5

a

High source loading from fertilizer Loading from fertilizer –7.0

a

–10.2

a

10.9

a

High source loading from manure Loading from fertilizer 2.8

a

–52.3

b

4.4

a

Reference streamflow greater than 

100 cubic meters per second

Loading from manure –3.5

ab

–13.9

a

–0.4

b

Nitrate

Central United States Loading from atmospheric 

deposition

–17.4

a

–1.5

b

–3.8

b

Greater than 40 percent agricultural land 

use in the basin

Loading from atmospheric 

deposition

–21.0

a

0.1

b

–2.8

ab

Greater than 10 percent urban land use 

in the basin

Loading from atmospheric 

deposition

–7.3

a

–7.2

a

–21.0

a

Reference streamflow less than 3 cubic 

meters per second

Loading from atmospheric 

deposition

–16.9

ab

–3.5

a

–16.3

b

Mean annual precipitation greater than 

130 centimeters

Loading from manure 41.2

a

–23.8

ab

–29.5

b
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 81

than in total phosphorus or total nitrogen concentrations—42 

(25 percent) of the sites had downward FA trends in nitrate 

concentrations, indicating that changes in nitrogen use, implementation of pollution-control strategies, or other anthropogenic activities likely were contributing to decreases in nitrate 

concentrations in one-quarter of the study streams. There were 

fewer upward FA trends in nitrate concentrations than in total 

phosphorus or total nitrogen concentrations—20 (12 percent) 

of the sites had upward FA trends in nitrate concentrations, 

indicating that increases in sources and(or) transport at these 

sites may have been contributing to increased nitrate concentrations in streams. FA trends in nitrate concentrations generally were downward or nonsignificant at sites in the Eastern 

and Western United States (fig. 14B). At sites in the Central 

United States, FA trends were a mixture of upward, downward, 

and nonsignificant.

There were fewer significant NFA trends than FA trends 

in nitrate concentrations; NFA trends were significant at 

55 (33 percent) of 166 sites from 1993 to 2003 (fig. 14C, 

tables 3 and 5, Appendix 3). At the majority of sites (67 

percent) nationwide, nitrate concentrations in streams were 

not changing significantly. At sites where concentrations were 

changing significantly, more NFA trends were downward than 

upward. Downward NFA trends occurred at 45 (27 percent) of 

the sites, and upward NFA trends occurred at 10 (6 percent) 

of the sites. NFA trends in nitrate concentrations generally 

were downward or nonsignificant at sites in the Eastern and 

Western United States (fig. 14C). At sites in the Central 

United States, NFA trends were a mixture of upward, downward, and nonsignificant.

The majority of the differences between the FA and NFA 

trends in nitrate concentrations occurred at sites in the Central 

United States, where many of the significant (downward) 

trends in streamflow occurred (fig. 14A). In particular, there 

were numerous sites with non-significant FA trends and downward NFA trends. At other sites, there were upward FA tends 

and upward, downward, or nonsignificant NFA trends. The 

downward trends in streamflow at many of these same sites 

likely resulted from a decrease in precipitation during drought 

conditions in the latter part of the study period. At sites with 

non-significant FA trends, there was little net change in inputs 

of nitrate from land application or loading from ground water 

between 1993 and 2003; a decrease in runoff at these sites 

probably contributed to downward NFA trends. At sites with 

upward FA trends, inputs of nitrate from land application or 

loading from ground water may have been increasing between 

1993 and 2003. With a decrease in runoff, NFA trends were 

divided between non-significant (when the increase in source 

was offset by the effects of decreasing surface runoff), downward (when the increase in source was less than the effects 

of decreasing surface runoff), or upward (when the increase 

in source was greater than the effects of decreasing surface 

runoff). In all three cases, in-stream concentrations probably 

would have been higher without the decrease in streamflow 

and associated surface runoff.

Trends in loads of nitrate from 1993 to 2003 were a 

reflection of the combined influence of changes in streamflow 

and changes in concentration. At the majority of sites (66 

percent) nationwide, there was no significant trend in the load 

of nitrate being transported to downstream locations (fig. 14D, 

tables 3 and 6, Appendix 3). Upward trends in load occurred 

at only 5 (3 percent) of the sites. Downward trends in load 

occurred at 51 (31 percent) of the sites; a large number were 

in the Central United States, although numerous downward 

trends occurred in other parts of the United States as well. 

Trends in load were similar to trends in streamflow at the 

majority of sites nationwide. However, the change in concentration was large enough to be the primary influence at many 

sites, and load changed correspondingly.

There were more downward and fewer upward trends 

in nitrate concentrations as compared to total phosphorus 

and total nitrogen. The discrepancy between trends in nitrate 

concentrations and trends in total phosphorus concentrations 

cannot be explained by changes in sources alone; from 1993 to 

2003, there were slightly more sites with increases in nitrogen 

loading from fertilizer and(or) manure than there were sites 

with increases in phosphorus loading from these two sources 

(appendix 1). The discrepancy between trends in nitrate 

concentrations and trends in total nitrogen concentrations also 

cannot be explained easily by changes in sources, as the source 

data currently (2008) available do not distinguish between 

nitrate and other forms of nitrogen. Because inorganic nitrogen 

in fertilizer typically is more mobile than the organically complexed nitrogen in manure, it can be hypothesized that trends 

in nitrate concentrations were affected more by changes in 

source loads of fertilizer than manure, whereas trends in total 

nitrogen concentrations were affected by changes in source 

loads of both fertilizer and manure. However, from 1993 to 

2003, there were more sites with increases in nitrogen loading 

from fertilizer than there were sites with increases in nitrogen loading from manure. The discrepancy between trends in 

nitrate concentrations and trends in total phosphorus and total 

nitrogen concentrations instead may be tied to the relatively 

greater transport of nitrate in ground water. Because nitrate 

is more soluble than phosphorus and other forms of nitrogen, 

it is more readily leached through the soil, and because it is 

more stable in ground water under aerobic conditions and less 

likely to sorb to aquifer materials than phosphorus and other 

forms of nitrogen, it is more mobile in ground water (Nolan 

and Stoner, 2000). Therefore, the lag time between changes 

in use, implementation of pollution-control strategies, or other 

anthropogenic activities on the land surface and changes in 

in-stream concentrations may have had the greatest impact on 

nitrate trends. As a result, trends in nitrate concentrations from 

1993 to 2003 may have been influenced to a greater degree 

than trends in total phosphorus and total nitrogen by changes 

that took place on the land surface prior to 1993. Because 

ground-water residence times can vary substantially among 

river basins (Michel, 1992), it is difficult to link the trends in 

in-stream nitrate concentrations from 1993 to 2003 to changes 

on the land surface during any particular earlier year(s).
82 Nutrient Trends in Streams and River of the United States, 1993–2003

Factors Affecting the Trends

Fewer significant (p-value less than or equal to 0.05) 

relations were identified through the weighted-least squares 

regression and Kruskal-Wallis analyses relating FA trends 

in nitrate concentrations to changes in nutrient sources 

(tables 7–9; fig. 15) than were identified for total phosphorus or total nitrogen. At sites with greater than 40 percent agricultural land use in the basin, nitrate trends were 

negatively related to changes in nitrogen loading from atmospheric deposition (fig. 15E). However, changes in loading 

from atmospheric deposition likely had little impact on trends 

in nitrate at these sites because nitrogen loading from atmospheric deposition was small compared to that from fertilizer 

and manure (figs. 7–9). In the Central United States, where 

many sites had substantial agricultural land use in the basin, 

Table 10. Results of multiple linear regression relating flow-adjusted trends to changes in nutrient sources.

[Note model explanatory terms are in units of percent change from 1993 to 2003. --, explanatory term not in best fit model; NN, model exhibited heteroscedasticity 

or departure from a normal distribution; <, less than; R2, coefficient of determination.]

(A) Total phosphorus

Site group

Model coefficients Standardized model coefficients Model coefficient standard error

Intercept

Population

density

Phosphorus

loading

from

fertilizer

Phosphorus

loading

from

manure

Population

density

Phosphorus

loading

from

fertilizer

Phosphorus

loading

from

manure

Intercept

Population

density

Phosphorus

loading 

from

fertilizer

Phosphorus

loading

from

manure

Eastern United States 7.693 -- -- –0.223 -- -- –0.194 5.290 -- -- 0.148

Central United States 54.536 -- 0.771 -- -- 0.369 -- 8.467 -- 0.239 --

Western United States –19.144 1.853 -- -- 0.550 -- -- 12.416 0.412 -- --

Undeveloped land-use 

classification

–26.857 1.997 -- –0.737 0.562 -- –0.152 10.721 0.345 -- 0.397

Site group Model coefficient p-value

Degrees

of freedom

Residual

standard

error

Model

p-value

Multiple

R2 Intercept

Population 

density

Phosphorus

loading

from

fertilizer

Phosphorus

loading

from

manure

Eastern United States 0.151 -- -- 0.137 58 57.957 0.137 0.021

Central United States <0.001 -- 0.002 -- 55 90.297 0.002 0.144

Western United States 0.130 <0.001 -- -- 44 91.104 <0.001 0.299

Undeveloped land-use 

classification

0.015 <0.001 -- 0.068 55 78.957 <0.001 0.373

(B) Total nitrogen

Site group

Model coefficients Standardized model coefficients

Intercept

Population

density

Nitrogen

loading from

atmospheric

deposition

Nitrogen

loading from

fertilizer

Nitrogen

loading from

manure

Population

density

Nitrogen

loading from

atmospheric

deposition

Nitrogen

loading from

fertilizer

Nitrogen

loading from

manure

Eastern United States –2.755 -- –0.366 -- -- -- –0.244 -- --

Central United States NN NN NN NN NN NN NN NN NN

Western United States NN NN NN NN NN NN NN NN NN

Undeveloped land-use 

classification

7.574 0.380 0.573 -- -- 0.231 0.218 -- --

Site group

Model coefficient standard error Model coefficient p-value

Degrees

of freedom

Residual

standard

error

Model

p-value

Multiple

R2 Intercept

Population

density

Nitrogen

loading

from

atmospheric

deposition

Nitrogen

loading

from

fertilizer

Nitrogen

loading

from

manure

Intercept

Population

density

Nitrogen

loading

from

atmospheric

deposition

Nitrogen

loading

from

fertilizer

Nitrogen

loading

from

manure

Eastern United States 4.085 -- 0.188 -- -- 0.503 -- 0.056 -- -- 54 36.128 0.056 0.048

Central United States NN NN NN NN NN NN NN NN NN NN NN NN NN NN

Western United States NN NN NN NN NN NN NN NN NN NN NN NN NN NN

Undeveloped land-use 

classification

8.817 0.269 0.369 -- -- 0.396 0.166 0.129 -- -- 38 69.069 0.188 0.036
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 83

nitrate trends were positively related to changes in nitrogen 

loading from manure (fig. 15B). This relation indicates that 

increases in the land application of manure may be a factor 

contributing to increasing nitrate concentrations in streams in 

some areas of the Central United States. Likewise, decreases 

in the land application of manure may be contributing to 

decreases (or smaller increases) in nitrate concentrations in 

streams in other areas of the Central United States. A similar 

relation was not seen with changes in nitrogen loading from 

fertilizer (fig. 15B). Nitrate originating from manure sources 

may experience relatively more transport through surface runoff and less through ground water than nitrate originating from 

fertilizer sources; with less ground-water transport, there may 

have been less of a lag between changes in manure applications and changes in in-stream nitrate concentrations. Note 

the R2

 value for these significant relations was low, indicating that a substantial portion of the variability in FA trends in 

nitrate concentration was not explained by the changes in the 

source data.

The Kruskal-Wallis and Tukey’s analyses identified several additional site groups where changes in nutrient sources 

were different between sites with upward, downward, and 

nonsignificant FA trends in nitrate concentration (tables 8 and 

9). Changes in nitrogen loading from atmospheric deposition 

differed between sites with upward, downward, and nonsignificant FA trends in nitrate concentrations at sites in the Central 

United States (where decreases in loading from atmospheric 

deposition were greater at sites with upward trends than at 

sites with downward trends), sites with greater than 10 percent 

urban land use in the basin (where the differences were no 

longer significant in the post-hoc Tukey’s analysis), and sites 

with reference streamflow less than 3 m3

/s (where decreases 

in loading from atmospheric deposition were smaller at sites 

with downward trends than at sites with nonsignificant trends). 

The counterintuitive results indicate that other factors likely 

were more important than changes in loading from atmospheric deposition in affecting the trends at these sites. In 

particular, changes in loading from atmospheric deposition 

probably had little impact on trends in nitrate at sites in the 

Central United States (where nitrate trends were found to be 

positively related to changes in nitrogen loading from manure 

in the weighted-least squares regression analysis), because 

nitrogen loading from atmospheric deposition was small compared to that from agricultural nonpoint sources (figs. 7–9). 

In addition, at sites with mean annual precipitation greater 

than 130 centimeters, increases in loading from manure were 

greater at sites with upward FA trends than at sites with nonsignificant FA trends.

Most of the relations that were significant for total nitrogen in the weighted least-squares regression analysis and the 

additional differences between sites with upward, downward, 

and nonsignificant FA trends that were significant for total 

nitrogen in the Kruskal-Wallis analysis were not found to 

be significant for nitrate. Many of these differences were in 

relations with changes in nitrogen loading from atmospheric 

deposition, which includes both nitrate and ammonium. 

Trends in total nitrogen concentrations may have been affected 

by changes in ammonium deposition as well as nitrate deposition, and the magnitude and direction of these changes were 

not always similar (Lehmann and others, 2005).

Table 10. Results of multiple linear regression relating flow-adjusted trends to changes in nutrient sources.—Continued

[Note model explanatory terms are in units of percent change from 1993 to 2003. --, explanatory term not in best fit model; NN, model exhibited heteroscedasticity or departure from a normal distribution; <, less than; R2

, coefficient of determination.]

(C) Nitrate

Site group

Model coefficients Standardized model coefficients

Intercept

Population

density

Nitrogen

loading from

atmospheric

deposition

Nitrogen

loading

from

fertilizer

Nitrogen

loading

from

manure

Population

density

Nitrogen

loading from

atmospheric

deposition

Nitrogen

loading from

fertilizer

Nitrogen

loading from

manure

Eastern United States –6.224 -- -- -- -- -- -- -- --

Central United States NN NN NN NN NN NN NN NN NN

Western United States –15.603 0.597 0.682 -- -- 0.589 0.136 -- --

Undeveloped land-use 

classification

NN NN NN NN NN NN NN NN NN

Site group

Model coefficient standard error Model coefficient p-value

Degrees

of freedom

Residual

standard

error

Model

p-value

Multiple

R2 Intercept

Population

density

Nitrogen

loading

from

atmospheric

deposition

Nitrogen

loading

from 

fertilizer

Nitrogen

loading

from

manure

Intercept

Population

density

Nitrogen

loading

from

atmospheric

deposition

Nitrogen

loading

from

fertilizer

Nitrogen

loading

from

manure

Eastern United States 3.270 -- -- -- -- 0.063 -- -- -- -- 45 38.300 -- <0.001

Central United States NN NN NN NN NN NN NN NN NN NN NN NN NN NN

Western United States 13.449 0.155 0.597 -- -- 0.254 <0.001 0.261 -- -- 34 66.635 0.002 0.268

Undeveloped land-use 

classification

NN NN NN NN NN NN NN NN NN NN NN NN NN NN
84 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 11. Regional trends in flow-adjusted and non-flow-adjusted concentrations from 1993 to 2003.—Continued

[FA, flow adjusted; NFA, non flow adjusted; ST, overall regional and seasonal test statistic. Bold p-values indicate statistical significance at the α=0.10 level.]

Site group Concentration

type

Number

of sites

Number

of seasons ST

Variance

of ST

Seasonal

covariance

of ST

Regional

covariance

of ST

p-value

Total phosphorus

Eastern United States FA 40 4 345 23,816 6,927 299,209 0.549

NFA 58 4 –37 21,167 9,155 629,828 0.965

Central United States FA 38 4 1099 20,607 9,855 325,905 0.066

NFA 56 4 297 26,186 9,255 628,203 0.716

Western United States FA 29 4 –444 18,150 3,738 164,610 0.305

NFA 51 4 –493 16,809 2,615 491,884 0.491

Undeveloped land-use classification FA 28 4 –118 16,485 719 147,139 0.773

NFA 56 4 –304 17,625 2,896 553,277 0.689

Greater than 40 percent agricultural 

land use in the basin

FA 27 4 820 15,177 8,485 152,807 0.051

NFA 37 4 346 18,430 8,117 279,017 0.533

Greater than 10 percent urban land 

use in the basin

FA 34 4 121 19,614 8,669 201,259 0.802

NFA 49 4 –217 20,901 10,613 453,296 0.756

Base-flow index greater than 50 FA 34 4 153 20,798 4,682 209,725 0.754

NFA 61 4 –288 20,205 4,329 659,967 0.729

Basin area with subsurface drains 

greater than 10 square kilometers

FA 32 4 749 18,666 5,754 225,047 0.134

NFA 43 4 –12 18,175 5,065 351,002 0.986

Mean basin slope greater than 

10 percent

FA 27 4 –60 16,638 2,046 134,340 0.880

NFA 48 4 –357 15,150 2,847 428,014 0.594

Mean annual precipitation greater 

than 130 centimeters

FA 31 4 –130 18,745 4,329 168,778 0.768

NFA 47 4 –333 16,258 5,305 412,681 0.614

Mean annual precipitation less than 

80 centimeters

FA 23 4 71 12,814 2,971 93,821 0.833

NFA 35 4 –237 16,128 3,282 215,329 0.626

Reference streamflow greater than 

100 cubic meters per second

FA 28 4 178 17,426 5,173 173,993 0.690

NFA 41 4 –195 15,279 3,079 325,233 0.741

Reference streamflow less than 

3 cubic meters per second

FA 25 4 242 14,256 4,127 110,138 0.501

NFA 40 4 13 16,745 4,125 285,692 0.983

High source loading from fertilizer FA 35 4 462 19,865 7,076 225,367 0.359

NFA 49 4 –1 24,192 6,039 446,539 1.000

High source loading from manure FA 36 4 964 20,149 8,897 274,577 0.081

NFA 43 4 424 20,310 8,630 360,341 0.498

Total nitrogen

Eastern United States FA 51 4 29 30,240 5,240 544,149 0.971

NFA 56 4 –57 33,158 10,781 655,919 0.947

Central United States FA 40 4 829 21,312 5,385 303,090 0.149

NFA 46 4 –147 24,954 5,965 411,648 0.826

Western United States FA 18 4 –162 10,777 4,637 66,762 0.574

NFA 31 4 –616 16,542 6,157 207,000 0.199

Undeveloped land-use classification FA 22 4 299 11,696 1,160 85,731 0.343

NFA 40 4 –205 20,880 5,419 285,262 0.715

Greater than 40 percent agricultural 

land use in the basin

FA 28 4 606 15,837 4,743 148,510 0.141

NFA 28 4 –4 16,091 5,769 144,224 0.994
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 85

Table 11. Regional trends in flow-adjusted and non-flow-adjusted concentrations from 1993 to 2003.—Continued

[FA, flow adjusted; NFA, non flow adjusted; ST, overall regional and seasonal test statistic. Bold p-values indicate statistical significance at the α=0.10 level.]

Site group Concentration

type

Number

of sites

Number

of seasons ST

Variance

of ST

Seasonal

covariance

of ST

Regional

covariance

of ST

p-value

Total nitrogen—Continued

Greater than 10 percent urban land 

use in the basin

FA 38 4 –51 21,358 5,675 262,684 0.926

NFA 41 4 –88 23,039 5,855 336,252 0.886

Base-flow index greater than 50 FA 26 4 623 14,483 2,300 138,549 0.115

NFA 39 4 51 20,158 6,364 288,791 0.929

Basin area with subsurface drains 

greater than 10 square kilometers

FA 32 4 25 18,834 5,993 194,580 0.959

NFA 37 4 –669 21,784 10,061 261,486 0.217

Mean basin slope greater than 

10 percent

FA 22 4 194 12,939 3,627 100,910 0.573

NFA 36 4 –325 19,144 7,211 269,299 0.551

Mean annual precipitation greater 

than 130 centimeters

FA 26 4 –250 15,299 2,649 131,131 0.519

NFA 39 4 –471 23,239 7,043 305,073 0.417

Mean annual precipitation less than 

80 centimeters

FA 23 4 328 12,257 1,836 93,030 0.318

NFA 27 4 –201 13,648 2,625 120,199 0.588

Reference streamflow greater than 

100 cubic meters per second

FA 25 4 35 15,416 3,345 128,925 0.930

NFA 34 4 –738 20,314 6,472 237,378 0.152

Reference streamflow less than 

3 cubic meters per second

FA 35 4 413 19,662 6,475 229,485 0.415

NFA 41 4 192 21,811 6,355 309,551 0.742

High source loading from atmospheric 

deposition 

FA 39 4 27 23,965 4,609 318,509 0.965

NFA 43 4 –357 26,141 7,533 366,265 0.573

High source loading from fertilizer FA 31 4 –17 17,839 6,074 168,901 0.971

NFA 32 4 –516 18,723 6,139 187,973 0.264

High source loading from manure FA 34 4 478 18,445 7,849 234,086 0.350

NFA 35 4 –265 19,010 9,607 238,353 0.609

Nitrate

Eastern United States FA 41 4 –608 25,341 3,294 369,081 0.336

NFA 46 4 –512 26,593 5,622 450,335 0.462

Central United States FA 40 4 –296 22,379 10,607 271,849 0.593

NFA 74 4 –612 35,891 15,551 1,023,978 0.556

Western United States FA 34 4 –461 20,811 7,541 225,189 0.361

NFA 39 4 –211 13,030 4,307 286,969 0.703

Undeveloped land-use classification FA 37 4 –635 22,482 8,041 250,719 0.232

NFA 55 4 –344 19,857 7,266 548,688 0.651

Greater than 40 percent agricultural 

land use in the basin

FA 22 4 123 12,097 4,062 87,109 0.704

NFA 37 4 –159 20,202 7,271 256,751 0.767

Greater than 10 percent urban land 

use in the basin

FA 35 4 –438 20,414 7,239 223,485 0.383

NFA 39 4 –262 21,175 6,375 294,733 0.646

Base-flow index greater than 50 FA 44 4 –514 26,279 9,911 365,991 0.419

NFA 55 4 –298 22,115 8,762 592,909 0.707

Basin area with subsurface drains 

greater than 10 square kilometers

FA 24 4 –452 14,525 6,283 109,703 0.212

NFA 33 4 –657 18,199 9,121 219,918 0.187
86 Nutrient Trends in Streams and River of the United States, 1993–2003

Table 11. Regional trends in flow-adjusted and non-flow-adjusted concentrations from 1993 to 2003.—Continued

[FA, flow adjusted; NFA, non flow adjusted; ST, overall regional and seasonal test statistic. Bold p-values indicate statistical significance at the α=0.10 level.]

Site group Concentration

type

Number

of sites

Number

of seasons ST

Variance

of ST

Seasonal

covariance

of ST

Regional

covariance

of ST

p-value

Nitrate—Continued

Mean basin slope greater than 

10 percent

FA 41 4 –565 24,784 9,381 309,693 0.336

NFA 52 4 –222 20,504 9,405 521,462 0.766

Mean annual precipitation greater 

than 130 centimeters

FA 27 4 –543 16,856 3,278 143,265 0.180

NFA 36 4 –357 17,577 4,715 250,209 0.495

Mean annual precipitation less than 

80 centimeters

FA 29 4 –820 16,328 8,004 149,670 0.050

NFA 42 4 –477 19,639 8,417 331,003 0.427

Reference streamflow greater than 

100 cubic meters per second

FA 25 4 –507 15,961 6,663 132,804 0.199

NFA 32 4 –793 17,010 8,449 217,745 0.108

Reference streamflow less than 

3 cubic meters per second

FA 34 4 –350 20,345 6,675 217,435 0.480

NFA 55 4 –112 22,334 6,155 543,341 0.883

High source loading from atmospheric 

deposition 

FA 33 4 –413 20,345 3,801 222,603 0.407

NFA 44 4 –522 25,643 6,455 381,911 0.418

High source loading from fertilizer FA 19 4 –382 10,923 3,210 58,821 0.158

NFA 34 4 –483 19,154 7,273 222,842 0.334

High source loading from manure FA 24 4 128 13,414 4,310 116,792 0.729

NFA 38 4 –370 20,162 8,396 284,541 0.510

None of the relations that were significant for total 

phosphorus in the weighted least-squares regression analysis were found to be significant for nitrate or total nitrogen, and none of the additional differences between sites 

with upward, downward, and nonsignificant FA trends that 

were significant for total phosphorus in the Kruskal-Wallis 

analysis were found to be significant for nitrate or total 

nitrogen. As with total nitrogen, with nitrate this may be 

due to the greater lag between changes in nutrient use on 

the land surface and changes in in-stream concentrations 

as compared to total phosphorus.

The multiple linear regression results provided limited 

additional insight when FA trends in nitrate concentrations 

were related to changes in population density and source 

loading from atmospheric deposition, fertilizer, and manure 

at sites in the Eastern, Central, and Western United States and 

at sites classified as having undeveloped land use (table 10C). 

The model for sites in the Eastern United States included only 

the intercept term, indicating that no combination of available source variables explained more variability in nitrate 

trends than random variation alone. The models for sites 

in the Central United States and for sites classified as having undeveloped land use violated assumptions of normality 

and(or) homoscedasticity (table 10C). The best-fit model for 

sites in the Western United States was significant and included 

changes in population density and source loading from atmospheric deposition (table 10C). The atmospheric-deposition 

coefficient, however, was not significant; changes in source 

loading form atmospheric deposition did not account for a 

significant amount of variation in nitrate trends at sites in the 

Western United States. The coefficient for population density was positive; nitrate trends at sites in the Western United 

States generally increased as population density increased, 

and decreased as population density and source loading from 

atmospheric deposition decreased. The multiple R2

 value for 

this model was low, however, indicating that much of the 

variability in FA trends in nitrate concentrations at sites in the 

Western United States was not explained by changes in the 

available source data.

Regional Trends

A downward regional trend in FA nitrate concentrations 

occurred at sites with mean annual precipitation less than 

80 cm (table 11). For the other site groups, a combination of 

a lack of trend at many locations and trends in opposite directions at other locations cancelling one another out resulted in 

nonsignificant regional trends.
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 87

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A Streamflow C Non-flow-adjusted

B Flow-adjusted D Load

Reference streamflow (cubic meters per second)

Less than or equal to 8.49

8.50–84.99

Greater than or equal to 85.0

Reference concentration (milligrams per liter)

Less than or equal to 0.62

Greater than or equal to 1.50

0.63–1.49

848.86–13,102.68

Reference load (killigrams per day)

Less than or equal to 848.85

Greater than or equal to 13,102.69

Reference concentration (milligrams per liter)

Less than or equal to 0.62

Greater than or equal to 1.50

0.63–1.49

#

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!

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EXPLANATION

(applies to A–D)

Upward

Downward

No significant trend

Direction of trend

Magnitude of trend (percent from 1993 to 2003)

Less than or equal to 33.0

33.1–66.0

Greater than or equal to 66.1

Figure 12. Trends in (A) streamflow, (B) flow-adjusted and (C) non-flow adjusted trends in total nitrogen concentrations, and (D) trends 

in total nitrogen loads at selected sites in the United States.
88 Nutrient Trends in Streams and River of the United States, 1993–2003

Figure 13. Relations between flow-adjusted trends in total nitrogen concentrations and changes in nitrogen sources from 1993 to 2003 

for selected site subsets.

–100

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0

20

40

60

–100

–50

0

50

100

150

200

250

–100

–50

0

50

100

150

200

250

–60

–20

–40

20

0

40

60

80

100

–60

–40

–20

0

20

40

60

–40 –30 –20 –10 0 10 20

–30 –10 10 20 40 –20 0 30

–40 –30 –10–20 0 10 20

–40 –20 0 20 40

–100 –50 0 100 15050 200 300250

–100 –50 0 50 100 150

–40 –20 0 20 40 60 80 100

–50 0 50 100 150 0 20 40 60

–60

–60 –40 –20

–40 –20 0 20 40

–100 –80 –60 –40 –20 0 20 40 60

–50–100 0 50 100 150 200 250

0 20 40 60 80 100 120 140

–50

–20

0 50 100 150

–60 –40 –20 0 20 40 60 80 100

–10 10 20 30 40 50 60 0

n

56

pvalue

NN

r2

NN

n

56

r2

0.066

pvalue

0.056

n

56

pvalue

0.891

r2

0.000

n

45

r2

0.083

pvalue

0.055

n

45

pvalue

0.875

r2

0.001

n

45

pvalue

NN

r2

NN

n

29

r2

0.125

pvalue

0.060

n

28

pvalue

0.651

r2

0.008

n

29

pvalue

0.384

r2

0.028

n

41

pvalue

0.233

n

40

pvalue

0.583

r2

0.036

r2

0.008

n

41

pvalue

0.929

r2

0.000

n

56

pvalue

0.774

r2

0.002

n

45

pvalue

0.899

r2

0.000

n

29

pvalue

NN

r2

NN

n

41

pvalue

NN

r2

NN

CHANGE IN NITROGEN

LOADING FROM MANURE,

IN PERCENT

CHANGE IN

POPULATION DENSITY,

IN PERCENT

CHANGE IN NITROGEN LOADING

FROM ATMOSPHERIC DEPOSITION,

IN PERCENT

CHANGE IN NITROGEN

LOADING FROM FERTILIZER,

IN PERCENT

FLOW-ADJUSTED TREND IN TOTAL NITROGEN CONCENTRATION, IN PERCENT

A Eastern United States

B Central United States

C Western United States

D Undeveloped Land-Use Classification

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 89

Figure 13 —Continued. Relations between flow-adjusted trends in total nitrogen concentrations and changes in nitrogen sources from 

1993 to 2003 for selected site subsets.

–60

–40

–20

0

20

40

60

–40

–20

0

20

40

60

80

100

–60

–20

–40

0

20

60

40

–20

–40

0

20

40

60

80

100

–60

–40

–20

0

40

20

60

–40

–20

40

20

0

60

80

100

–60

–20

–40

0

20

40

60

–40

–20

40

20

0

60

80

100

–100

–50

0

50

100

150

200

250

–100

–50

0

50

100

150

200

250

–100

–50

0

50

100

150

200

250

–100

–50

0

50

100

150

200

250

–60

–40

–20

0

20

40

60

80

0

–60

–40

–20

20

40

60

80

–60

–40

–20

0

20

40

60

80

–60

–40

–20

0

20

40

60

80

–30 –20 –10 0 10

–40 –20 –10 10 20 –30 0

–40 –20 0 20 40

–40 –30 –20 –10 0 10 20

–60 –40 –20 40 80 0 20 60 100 120

–100 0 100 200 300

–50 0 50 100 150 200 250 300

–60 –40 –20 0 20 40 60 80 0 20 40 60 80

–60

–40 –20

–40 –20 0 20 40

–100 –50 0 50 100 150 200 250

–40 –30 –20 –10 0 10 20 30 40

0 10 20 30 40

–20

–10

0 20 40 60 80 100 120 140

–20 0 20 40 60 80 100

–60 –40 –20 20 40 60 0

n

28

pvalue

0.609

r2

0.010

n

28

r2

0.241

pvalue

0.008

n

28

pvalue

0.711

r2

0.005

n

41

r2

0.034

pvalue

0.251

n

41

pvalue

0.616

r2

0.007

n

41

pvalue

NN

r2

NN

n

42

r2

NN

pvalue

NN

n

41

pvalue

0.804

r2

0.002

n

42

pvalue

0.558

r2

0.009

n

38

pvalue

0.191

n

38

pvalue

0.908

r2

0.047

r2

0.000

n

38

pvalue

0.407

r2

0.019

n

28

pvalue

0.186

r2

0.066

n

41

pvalue

0.052

r2

0.094

n

42

pvalue

NN

r2

NN

n

38

pvalue

0.180

r2

0.049

CHANGE IN NITROGEN

LOADING FROM MANURE,

IN PERCENT

CHANGE IN

POPULATION DENSITY,

IN PERCENT

CHANGE IN NITROGEN LOADING

FROM ATMOSPHERIC DEPOSITION,

IN PERCENT

CHANGE IN NITROGEN

LOADING FROM FERTILIZER,

IN PERCENT

FLOW-ADJUSTED TREND IN TOTAL NITROGEN CONCENTRATION, IN PERCENT

E Greater Than 40 Percent Agricultural Land Use in the Basin

F Greater Than 10 Percent Urban Land Use in the Basin

G Base-Flow Index Greater Than 50

H Basin Area With Subsurface Drains Greater Than 10 Square Kilometers

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present
90 Nutrient Trends in Streams and River of the United States, 1993–2003

Figure 13 —Continued. Relations between flow-adjusted trends in total nitrogen concentrations and changes in nitrogen sources from 

1993 to 2003 for selected site subsets.

–60

–40

–20

0

20

40

60

–60

–20

–40

0

20

60

40

–60

–40

–20

0

40

20

60

–60

–20

–40

0

20

40

60

–100

–50

0

50

100

150

200

250

–100

–50

0

50

100

150

200

250

–100

–50

0

50

100

150

200

250

–100

–50

0

50

100

150

200

250

–50

0

50

100

150

200

250

–50

0

50

100

150

200

250

–50

0

50

100

150

200

250

–50

0

50

100

150

200

250

–60

–40

–20

0

20

40

60

80

–60

–40

–20

0

20

40

60

80

–60

–40

–20

0

20

40

60

80

–60

–40

–20

0

20

40

60

80

–40 –20 –10 10 20 –30 0 –50 0 10050 150 200 250 –80 –60 –40 –20 0 20 40 60 –20 –10 0 10 20 30 40 50

–40 –30 –20 –10 0 10 20 –50 0 50 100 150 –60 –40 –20 0 20 40 60 0 20 40 60 80 100 140120

–30 –20 –10 0 10 20 –50 0 50 100 150 –40 –30 –20 –10 0 10 20 30 40 –50 0 50 100 150

–40 –30 –20 –10 0 10 20 –60 –40 –20 20 40 60 80 0 100 120 –40 –30 –20 –10 0 10 20 30 –1 –20 0 0 10 20 30 40 50

n

38

pvalue

0.845

r2

0.001

n

38

r2

0.132

pvalue

0.025

n

37

pvalue

0.769

r2

0.002

n

41

r2

0.057

pvalue

0.134

n

41

pvalue

0.512

r2

0.011

n

41

pvalue

0.640

r2

0.006

n

27

r2

0.037

pvalue

0.334

n

26

pvalue

0.984

r2

0.000

n

27

pvalue

0.924

r2

0.000

n

35

pvalue

0.025

n

35

pvalue

0.625

r2

0.142

r2

0.007

n

35

pvalue

0.330

r2

0.029

n

38

pvalue

NN

r2

NN

n

41

pvalue

0.694

r2

0.004

n

27

pvalue

NN

r2

NN

n

35

pvalue

0.397

r2

0.022

CHANGE IN NITROGEN

LOADING FROM MANURE,

IN PERCENT

CHANGE IN

POPULATION DENSITY,

IN PERCENT

CHANGE IN NITROGEN LOADING

FROM ATMOSPHERIC DEPOSITION,

IN PERCENT

CHANGE IN NITROGEN

LOADING FROM FERTILIZER,

IN PERCENT

FLOW-ADJUSTED TREND IN TOTAL NITROGEN CONCENTRATION, IN PERCENT

I Mean Basin Slope Greater Than 10 Percent

J Mean Annual Precipitation Greater Than 130 Centimeters

K Mean Annual Precipitation Less Than 80 Centimeters

L Reference Streamflow Greater Than 100 Cubic Meters Per Second

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 91

Figure 13 —Continued. Relations between flow-adjusted trends in total nitrogen concentrations and changes in nitrogen sources from 

1993 to 2003 for selected site subsets.

–60

–40

–20

0

20

40

60

80

100

–60

–40

–20

0

20

40

60

80

100

–60

–40

–20

0

20

40

60

80

100

–60

–40

–20

0

20

40

60

80

100

–60

–40

–20

0

20

40

60

–60

–40

–20

0

20

40

60

–60

–40

–20

0

20

40

60

–60

–40

–20

0

20

40

60

–60

–40

–20

0

20

40

60

80

–60

–40

–20

0

20

40

60

80

–60

–40

–20

0

20

40

60

80

–60

–40

–20

0

20

40

60

80

–60

–40

–20

0

20

40

60

80

100

–60

–40

–20

0

20

40

60

80

100

–60

–40

–20

0

20

40

60

80

100

–60

–40

–20

0

20

40

60

80

100

–40 –20 –100 0 100 200 300 –100 –50 0 50 100 150 200 250 –50 0 50 100 150

–40 –30 –20 –10 0 10 –80–60 –40 –20 0 20 40 80 10060 –100 –50 0 50 100 200 250 150

–40 –30 –20 –10 0 10 –100 –50 0 50 100 150 –100 –50 0 50 100 –60 –40 –20 0 20 40 60 10080

–40 –30 –20 –10 0 10 20 –100 –50 0 50 100 150 200 250 300 –40 –20 0 20 40 60 80 –60 –40 –20 0 20 40 60

0 20 40

–20 0 20 40 60 80 100

n

41

pvalue

NN

r2

NN

n

41

r2

0.017

pvalue

0.413

n

40

pvalue

0.911

r2

0.000

n

43

r2

0.064

pvalue

0.101

n

43

pvalue

0.292

r2

0.027

n

43

pvalue

NN

r2

NN

n

32

r2

0.032

pvalue

0.330

n

32

pvalue

0.961

r2

0.000

n

32

pvalue

0.846

r2

0.001

n

37

pvalue

0.031

n

37

pvalue

NN

r2

0.126

r2

NN

n

37

pvalue

0.703

r2

0.004

n

41

pvalue

0.263

r2

0.032

n

43

pvalue

0.377

r2

0.019

n

32

pvalue

0.098

r2

0.088

n

37

pvalue

NN

r2

NN

CHANGE IN NITROGEN

LOADING FROM MANURE,

IN PERCENT

CHANGE IN

POPULATION DENSITY,

IN PERCENT

CHANGE IN NITROGEN LOADING

FROM ATMOSPHERIC DEPOSITION,

IN PERCENT

CHANGE IN NITROGEN

LOADING FROM FERTILIZER,

IN PERCENT

FLOW-ADJUSTED TREND IN TOTAL NITROGEN CONCENTRATION, IN PERCENT

M Reference Streamflow Less Than 3 Cubic Meters Per Second

N High Source Loading From Atmospheric Deposition

O High Source Loading From Fertilizer

P High Source Loading From Manure

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present
92 Nutrient Trends in Streams and River of the United States, 1993–2003

Figure 14. Trends in (A) streamflow, (B) flow-adjusted and (C) non-flow-adjusted trends in nitrate concentrations, and (D) trends in nitrate 

loads at selected sites in the United States.

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Reference concentration (milligrams per liter)

Less than or equal to 0.24

0.25–1.05

Greater than or equal to 1.06

Reference concentration (milligrams per liter)

Less than or equal to 0.24

0.25–1.05

Greater than or equal to 1.06

Reference streamflow (cubic meters per second)

Less than or equal to 8.49

8.50–84.99

Greater than or equal to 85.0

Reference load (kilograms per day)

Less than or equal to 248.13

248.14–3,516.55

Greater than or equal to 3,516.56

#

#

#

!

#

#

#

#

#

EXPLANATION

(applies to A–D)

Upward

Downward

No significant trend

Direction of trend

Magnitude of trend (percent from 1993 to 2003)

Less than or equal to 33.0

33.1–66.0

Greater than or equal to 66.1

A Streamflow B Flow-adjusted

C Non-flow adjusted D Load
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 93

Trend Results Relative to Stream 

Nutrient Enrichment

The Federal Clean Water Act requires states and authorized tribes to adopt water-quality criteria that protect designated uses of their waters (U.S. Environmental Protection 

Agency, 2000). As a starting point for development of more 

refined nutrient criteria, USEPA has developed recommended 

criteria for total phosphorus and total nitrogen concentrations 

in streams in 14 nutrient ecoregions (U.S. Environmental 

Protection Agency, 2002). These recommended ecoregional 

nutrient criteria “represent stream conditions that have minimal impacts caused by human activities” (U.S. Environmental 

Protection Agency, 2000).

At each trend site, the reference concentrations of total 

phosphorus and total nitrogen divided by USEPA’s recommended nutrient criteria in the respective ecoregion provide an 

enrichment ratio—an approximation of the degree of nutrient 

enrichment in 1993—for that site (Appendix 1). An enrichment ratio less than one indicates that the reference concentration was below USEPA’s recommended nutrient criteria for 

that ecoregion. An enrichment ratio greater than one indicates 

that nutrient enrichment over natural background conditions 

may have been present, with increasing ratios indicating 

greater relative enrichment. Because of the small number of 

sites with an enrichment ratio less than one (potentially a key 

group of sites representing minimally affected conditions), 

these ratios were not used in the statistical analyses reported 

on previously. Rather, they are described qualitatively here to 

provide some perspective on changes in nutrient concentrations at minimally affected sites as compared to more enriched 

sites during the study period.

Generally, more downward trends (FA and NFA) 

occurred at sites with enrichment ratios greater than one as 

compared to sites with ratios less than one (fig. 16). At nearly 

20 percent of the more enriched sites, anthropogenic activities contributed to net decreases in nutrient concentrations 

from 1993 to 2003, and overall nutrient quality in the stream 

improved. The number of downward trends did not increase 

consistently as the enrichment ratio increased, however, 

despite the nutrient management strategies that may have 

been targeted to the most enriched sites.

Downward trends occurred at fewer than 10 percent 

of sites with enrichment ratios less than one—those sites 

that were likely to be minimally affected by anthropogenic activities. At half or more of these sites, FA and NFA 

trends in total phosphorus and total nitrogen concentrations 

were nonsignificant (fig. 16), indicating that anthropogenic 

activities did not contribute to significant net changes in 

concentrations from 1993 to 2003, and overall nutrient quality in the stream was maintained. At the remaining sites with 

enrichment ratios less than one, there were over three times 

as many upward than downward trends (FA and NFA) in 

total phosphorus concentrations and over eight times as many 

upward than downward trends in total nitrogen concentrations 

(fig. 16).

Implications for Management 

of Stream Quality

Nationwide, anthropogenic increases in nutrient 

sources and(or) transport contributed to increasing concentrations at 33 percent of stream sites for total phosphorus, 21 percent for total nitrogen, and 12 percent for nitrate between 1993 

and 2003. At sites in the Central and Southwestern United 

States, where drought conditions occurred in the latter part 

of the study period, these increases often were offset by the 

effects of naturally decreasing precipitation and surface runoff 

transporting nutrients to the stream. Without the decrease in 

precipitation and surface runoff, stream concentrations and 

loads at these sites probably would have been higher than were 

observed. The decrease in precipitation between 1993 and 

2003, however, will not continue indefinitely—for example, 

precipitation levels in the Upper Mississippi River Basin from 

December 2007 through May 2008 were the second highest 

since 1895, and record precipitation during June 2008 caused 

widespread flooding in Iowa, Wisconsin, Indiana, Illinois, 

and Missouri and numerous flash floods in Missouri and Ohio 

(National Oceanic and Atmospheric Administration, 2008). 

Future water-quality conditions in the Nation’s streams will 

depend on both natural and anthropogenic changes, and consideration of the full range of possible climatic conditions can 

inform future water-quality management decisions.

The more frequent increases in total phosphorus concentrations as compared to total nitrogen and nitrate concentrations may have been due in part to phosphorus saturation of 

soils in areas that have been subject to long-term manure or 

fertilizer application and(or) lag times between changes in 

nitrogen inputs on the land surface and changes in nitrogen 

concentrations in streams caused by the transport of nitrogen 

in ground water. In the case of ground-water lag times, the full 

effect of current changes in nitrogen inputs on the land surface 

may not be realized for years or decades (Stålnacke and 

others, 2003). Knowledge of ground-water travel times will 

contribute to the proper assessment of the potential and actual 

effects of management strategies aimed at reducing stream 

nitrogen concentrations.

While modest gains have been made in nutrient quality in some heavily impacted streams, nutrient enrichment 

has increased in many streams that were least impacted in 

1993. The Nation’s least-impacted streams are increasingly 

being affected by population growth, and new strategies 

designed to reduce these effects may need to be integrated 

with ongoing actions to improve nutrient quality in heavily 

impacted streams.
94 Nutrient Trends in Streams and River of the United States, 1993–2003

Figure 15. Relations between flow-adjusted trends in nitrate concentrations and changes in nitrogen sources from 1993 to 2003 for 

selected site subsets.

–100

–50

0

50

100

150

–100

–50

0

50

100

150

–100

–50

0

50

100

150

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50

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150

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100

200

300

400

500

600

–200

–100

0

100

200

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400

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600

–200

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100

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400

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600

–200

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0

100

200

300

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600

–100

0

100

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300

400

–100

0

100

200

300

400

–100

0

100

200

300

400

–100

0

100

200

300

400

–200

–100

0

100

200

300

400

500

600

–200

–100

0

100

200

300

400

500

600

–200

–100

0

100

200

300

400

500

600

–200

–100

0

100

200

300

400

500

600

–40 –30 –20 –10 0 10 20 –50 0 50 100 150 200 250 300 –100 –50 0 50 100 150 200 250 –10 0 10 20 30 40 50 60

–40 –30 –20 –10 0 10 20 30 40 –100 –50 0 50 100 150 –100 –80 –60 –40 –20 0 20 40 60 –60 –40 –20 0 20 40 60 80 100

–40 –30 –20 –10 0 10 –100 –50 0 50 100 150 –40 –30 –20 –10 0 10 20 –50 0 50 100 200150 250 300

–40 –20 0 20 40 –100 –50 0 50 100 150 –60 –40 –20 0 20 40 60 –50 0 50 100 150 200 250 300

n

46

pvalue

NN

r2

NN

n

46

r2

0.002

pvalue

0.775

n

46

pvalue

0.817

r2

0.001

n

78

r2

0.049

pvalue

0.051

n

78

pvalue

0.151

r2

0.027

n

78

pvalue

0.033

r2

0.059

n

37

r2

0.007

pvalue

0.623

n

33

pvalue

0.576

r2

0.010

n

37

pvalue

0.572

r2

0.009

n

57

pvalue

0.572

n

53

pvalue

0.722

r2

0.006

r2

0.003

n

57

pvalue

0.135

r2

0.040

n

46

pvalue

0.938

r2

0.000

n

78

pvalue

0.172

r2

0.024

n

37

pvalue

NN

r2

NN

n

57

pvalue

NN

r2

NN

CHANGE IN NITROGEN

LOADING FROM MANURE,

IN PERCENT

CHANGE IN

POPULATION DENSITY,

IN PERCENT

CHANGE IN NITROGEN LOADING

FROM ATMOSPHERIC DEPOSITION,

IN PERCENT

CHANGE IN NITROGEN

LOADING FROM FERTILIZER,

IN PERCENT

FLOW-ADJUSTED TREND IN NITRATE CONCENTRATION, IN PERCENT

A Eastern United States

B Central United States

C Western United States

D Undeveloped Land-Use Classification

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 95

Figure 15—Continued. Relations between flow-adjusted trends in nitrate concentrations and changes in nitrogen sources from 1993 

to 2003 for selected site subsets.

–150

–100

–50

0

50

100

150

200

–150

–100

–50

0

50

100

150

200

–150

–100

–50

0

50

100

150

200

–150

–100

–50

0

50

100

150

200

–100

–50

0

50

100

–100

–50

0

50

100

–100

–50

0

50

100

–100

–50

0

50

100

–100

0

100

200

300

400

–100

0

100

200

300

400

–100

0

100

200

300

400

–100

0

100

200

300

400

–100

–50

0

50

100

–100

–50

0

50

100

–100

–50

0

50

100

–100

–50

0

50

100

–30 –20 –10 0 10 20 –60 –40 –20 0 20 40 60 80 100 120 –40 –30 –20 –10 0 10 20 30 –60 –40 –20 0 20 40 60

–40 –30 –20 –10 0 10 20 –100 0 100 200 300 –100 –50 0 50 100 150 200 250 –20 0 20 40 60 80 100

–100 –50 0 50 100 150 200 250 300 –60 –40 –20 0 20 40 –50 0 50 100 150 200 250 300

–30 –20 –10 0 10 20 –40 –20 0 20 40 60 80 –30 –20 –10 0 10 20 –10 0 10 20 30 40

–40 –20 0 20 40

n

39

pvalue

0.427

r2

0.017

n

39

r2

0.124

pvalue

0.028

n

39

pvalue

0.309

r2

0.028

n

39

r2

0.028

pvalue

0.309

n

39

pvalue

0.850

r2

0.001

n

39

pvalue

NN

r2

NN

n

58

r2

0.008

pvalue

0.492

n

54

pvalue

0.831

r2

0.001

n

58

pvalue

0.739

r2

0.002

n

33

pvalue

0.213

n

33

pvalue

0.327

r2

0.050

r2

0.031

n

33

pvalue

0.709

r2

0.005

n

39

pvalue

NN

r2

NN

n

39

pvalue

0.102

r2

0.071

n

58

pvalue

NN

r2

NN

n

33

pvalue

0.909

r2

0.000

CHANGE IN NITROGEN

LOADING FROM MANURE,

IN PERCENT

CHANGE IN

POPULATION DENSITY,

IN PERCENT

CHANGE IN NITROGEN LOADING

FROM ATMOSPHERIC DEPOSITION,

IN PERCENT

CHANGE IN NITROGEN

LOADING FROM FERTILIZER,

IN PERCENT

FLOW-ADJUSTED TREND IN NITRATE CONCENTRATION, IN PERCENT

E Greater than 40 Percent Agricultural Land Use in the Basin

F Greater Than 10 Percent Urban Land Use in the Basin

G Base-Flow Index Greater Than 50

H Basin Area With Subsurface Drains Greater Than 10 Square Kilometers

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present
96 Nutrient Trends in Streams and River of the United States, 1993–2003

Figure 15—Continued. Relations between flow-adjusted trends in nitrate concentrations and changes in nitrogen sources from 1993 

to 2003 for selected site subsets.

–100

0

100

200

300

400

–100

0

100

200

300

400

–100

0

100

200

300

400

–100

0

100

200

300

400

–100

–50

0

50

100

150

–100

–50

0

50

100

150

–100

–50

0

50

100

150

–100

–50

0

50

100

150

–200

–100

0

100

200

300

400

500

600

–200

–100

0

100

200

300

400

500

600

–200

–100

0

100

200

300

400

500

600

–200

–100

0

100

200

300

400

500

600

–100

–80

–60

–40

–20

0

20

40

60

–100

–80

–60

–40

–20

0

20

40

60

–100

–80

–60

–40

–20

0

20

40

60

–100

–80

–60

–40

–20

0

20

40

60

–40 –30 –20 –10 0 10 20 –100 –50 0 50 100 150 –60 –40 –20 0 604020 0 50 100 150 200 250 300

–40 –30 –20 –10 0 10 20 –50 0 50 100 150 200 250 –100–80 –60 –40 –20 0 20 40 60 –20 0 20 40 60 80 100

–40 –30 –20 –10 0 10 20 –100 –50 0 50 100 150 –60 –40 –20 0 20 40 –50 0 50 100 150

–40 –30 –20 –10 0 10 20 –60 –20–40 0 20 40 60 80 100120 –40 –30 –20 –10 0 10 20 –20 –10 0 10 20 40 50 30

n

54

pvalue

0.484

r2

0.009

n

54

r2

0.007

pvalue

0.554

n

50

pvalue

0.891

r2

0.000

n

38

r2

0.002

pvalue

0.768

n

37

pvalue

0.294

r2

0.031

n

38

pvalue

NN

r2

NN

n

43

r2

0.003

pvalue

0.708

n

42

pvalue

0.361

r2

0.021

n

43

pvalue

0.978

r2

0.000

n

30

pvalue

0.608

n

30

pvalue

0.112

r2

0.010

r2

0.088

n

30

pvalue

0.423

r2

0.023

n

54

pvalue

NN

r2

NN

n

38

pvalue

0.644

r2

0.006

n

43

pvalue

0.387

r2

0.018

n

30

pvalue

0.169

r2

0.066

CHANGE IN NITROGEN

LOADING FROM MANURE,

IN PERCENT

CHANGE IN

POPULATION DENSITY,

IN PERCENT

CHANGE IN NITROGEN LOADING

FROM ATMOSPHERIC DEPOSITION,

IN PERCENT

CHANGE IN NITROGEN

LOADING FROM FERTILIZER,

IN PERCENT

FLOW-ADJUSTED TREND IN NITRATE CONCENTRATION, IN PERCENT

I Mean Basin Slope Greater than 10 Percent

J Mean Annual Precipitation Greater Than 130 Centimeters

K Mean Annual Precipitation Less Than 80 Centimeters

L Reference Streamflow Greater Than 100 Cubic Meters Per Second

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present
Nutrient Trends in Streams and Rivers of the United States, 1993–2003 97

Figure 15—Continued. Relations between flow-adjusted trends in nitrate concentrations and changes in nitrogen sources from 1993 

to 2003 for selected site subsets.

–200

–100

0

100

200

300

400

500

600

–200

–100

0

100

200

300

400

500

600

–200

–100

0

100

200

300

400

500

600

–200

–100

0

100

200

300

400

500

600

–100

–50

0 0

50

100

–100

–50

50

100

–100

–50

0

50

100

–100

–50

0

50

100

–150

–100

–50

0

50

100

–150

–100

–50

0

50

100

–150

–100

–50

0

50

100

–150

–100

–50

0

50

100

–100

–50

0

50

100

150

200

–100

–50

0

50

100

150

200

–100

–50

0

50

100

150

200

–100

–50

0

50

100

150

200

–40 –20 0 20 40 –100 0 100 200 300 –100 –50 0 50 100 150 200 250 –50 0 50 100 150

–10–20–30–40 0 10 –20–40–60–80 0 20 40 60 80 100 –50–100 0 50 100 150 200 250 –20 0 20 40 60 80 100

–30 –20 –10 0 10 20 –100 –50 0 50 100 150 –100 –80 –60 –40 –20 0 20 40 –60 –40 –20 0 20 40 60 80 100

–40 –30 –20 –10 0 10 20 30 –50 0 50 100 150 200 250 300 –30 –20 –10 0 10 20 30 40 –60 –40 –20 0 20 40 60

n

54

pvalue

NN

r2

NN

n

54

r2

0.002

pvalue

0.761

n

51

pvalue

0.886

r2

0.000

n

44

r2

0.000

pvalue

0.982

n

44

pvalue

0.781

r2

0.002

n

44

pvalue

NN

r2

NN

n

34

r2

0.017

pvalue

0.459

n

34

pvalue

0.472

r2

0.016

n

34

pvalue

0.073

r2

0.097

n

42

pvalue

0.057

n

42

pvalue

NN

r2

0.088

r2

NN

n

42

pvalue

0.295

r2

0.027

n

54

pvalue

0.450

r2

0.011

n

44

pvalue

NN

r2

NN

n

34

pvalue

0.569

r2

0.010

n

42

pvalue

NN

r2

NN

CHANGE IN NITROGEN

LOADING FROM MANURE,

IN PERCENT

CHANGE IN

POPULATION DENSITY,

IN PERCENT

CHANGE IN NITROGEN LOADING

FROM ATMOSPHERIC DEPOSITION,

IN PERCENT

CHANGE IN NITROGEN

LOADING FROM FERTILIZER,

IN PERCENT

FLOW-ADJUSTED TREND IN NITRATE CONCENTRATION, IN PERCENT

M Reference Streamflow Less Than 3 Cubic Meters Per Second

N High Source Loading From Atmospheric Deposition

O High Source Loading From Fertilizer

P High Source Loading From Manure

EXPLANATION

Error bars showing variance of the trend estimate

r2 Coefficient of determination

pvalue p-value of the regression

n Number of samples

NN Model exhibited heteroscedasticity, departure from

 a normal distribution, or outliers were present
98 Nutrient Trends in Streams and River of the United States, 1993–2003

Summary and Conclusions

In 1987, the U.S. Geological Survey (USGS) began a 

study of more than 50 river basins and aquifers across the 

Nation as part of the National Water-Quality Assessment 

(NAWQA) Program. One of the major goals of the NAWQA 

Program is to determine how water-quality conditions, 

including concentrations and loads of nutrients, are changing 

over time. Outside of the NAWQA Program, USGS (in cooperation with other Federal, State, Tribal, and local agencies), 

state environmental agencies, the U.S. Environmental Protection Agency and other federal agencies, universities, and many 

others have collected nutrient data throughout the Nation. 

Collectively, these data can provide insight into how nutrient 

concentrations have changed over time in the Nation’s streams 

and rivers and how natural features and human activities have 

contributed to those changes.

This report describes the methods and results of a study 

to determine trends in total phosphorus, total nitrogen, and 

nitrate concentrations and loads for the period from 1993 

to 2003 in selected streams and rivers of the United States. 

Flow-adjusted (FA) trends in concentration (the trends that 

would have occurred in the absence of natural changes in 

streamflow), non-flow-adjusted (NFA) trends in concentration 

(the trends resulting from both natural and human factors), 

and trends in load (trends in the nutrient mass transported 

downstream) were determined, and the results were examined 

spatially to determine whether a consistent pattern of trends 

occurred across groups of sites at multiple locations. Relations 

between the trends and changes in nutrient sources, streamflow, and other factors were examined.

Streamflow

At the majority of sites nationwide, streamflow did not 

change significantly from 1993 to 2003. Significant trends 

in streamflow occurred at 23 percent of the sites; at all but 

two sites, the trends were downward. These downward trends 

primarily occurred at sites in Central and Southwestern 

United States and parts of the Southeastern United States, 

likely as a result of drought conditions in the latter part of 

the study period.

Total Phosphorus

Downward FA trends in total phosphorus concentrations 

occurred at 16 percent of the sites nationwide, indicating that 

at the majority of sites, changes in phosphorus use, implementation of pollution-control strategies, or other anthropogenic 

activities were not contributing to significant decreases in 

total phosphorus concentrations in streams, or any reductions 

that occurred were offset by other anthropogenic activities 

in the watershed that increased concentrations. Upward FA 

trends in total phosphorus concentrations were more numerous; increases in phosphorus sources and(or) transport at 

33 percent of the sites may have been contributing to increased 

total phosphorus concentrations in streams. Upward NFA 

trends were fewer, with total phosphorus concentrations in 

streams increasing at 24 percent of sites. Downward NFA 

trends only occurred at 16 percent of the sites. At the majority 

of sites, total phosphorus concentrations in streams were not 

changing significantly. FA trends in total phosphorus concentrations were generally upward or nonsignificant at sites in the 

Northeastern, Central, and Southwestern United States, and 

NFA trends in total phosphorus concentrations were generally upward or nonsignificant at sites in the Northeastern and 

Central United States. Elsewhere, trends were upward, downward, and nonsignificant.

Figure 16. Distribution of (A) flow-adjusted and (B) non-flowadjusted trends in total phosphorus and total nitrogen concentrations 

from 1993 to 2003 relative to the level of nutrient enrichment in 

the stream.

Nonsignificant

Downward

Upward

EXPLANATION

> Greater than

0

20

40

60

80

100

0–1 1.1–2 2.1–3 >3 0–1 1.1–2 2.1–3 >3

0

20

40

60

80

100

Total phosphorus Total nitrogen

ENRICHMENT RATIO

PERCENT OF SITES PERCENT OF SITES

0–1 1.1–2 2.1–3 >3 0–1 1.1–2 2.1–3 >3

ENRICHMENT RATIO

Total phosphorus Total nitrogen

A Flow-adjusted trends

B Non-flow-adjusted trends
Summary and Conclusions 99

Relatively fewer upward NFA trends than upward FA trends 

occurred at sites in the Central and Southwestern United States, 

where most of the significant (downward) trends in streamflow 

occurred. In these areas, the increase in source indicated by the 

upward FA trend likely was offset by the effects of decreasing 

surface runoff indicated by the downward streamflow trend, 

leading to fewer upward NFA trends. Total phosphorus concentrations at sites in the Central and Southwestern United States were 

probably lower than they would have been without the decrease in 

streamflow and associated surface runoff. Trends in loads of total 

phosphorus from 1993 to 2003 were a reflection of the combined 

influence of changes in streamflow and changes in concentration. 

At the majority of sites (81 percent) nationwide, there was no 

significant trend in the load of total phosphorus being transported 

to downstream locations. Upward trends in load occurred at only 

4 percent of sites; downward trends in load occurred at 15 percent 

of sites, primarily in the Central and Southeastern United States.

Several significant relations between FA trends in total 

phosphorus concentrations and changes in nutrient sources 

were identified, although these relations did not explain all of 

the variability in the trends. At undeveloped sites, total phosphorus trends were positively related to changes in population 

density, indicating that increases in population density may 

have been one factor contributing to increasing total phosphorus concentrations in streams in undeveloped areas, possibly 

as a result of increased loading from septic systems and point 

sources and(or) runoff from construction sites and fertilized lawns. At sites with greater than 40 percent agricultural 

land use in the basin, total phosphorus trends were positively 

related to changes in phosphorus loading from fertilizer and 

manure. These relations indicate that increases in the land 

application of fertilizer and manure may have been factors 

contributing to increasing total phosphorus concentrations 

in streams in some agricultural areas. Likewise, decreases in 

the land application of fertilizer and manure may have been 

contributing to decreases (or smaller increases) in total phosphorus concentrations in streams in other agricultural areas. A 

similar relation between total phosphorus trends and changes 

in phosphorus loading from fertilizer occurred at sites in the 

Central United States and at sites with high loading from 

atmospheric deposition—many of these sites had substantial 

agricultural land use in the basin. At sites with greater than 

10 km2

 of the basin area containing subsurface (tile) drains, 

total phosphorus trends were negatively related to changes in 

population density.

Additional analyses comparing source changes at sites 

with upward, downward, and nonsignificant FA trends in total 

phosphorus concentrations indicated that at sites with greater 

than 10 percent urban land cover in the basin, the decrease in 

phosphorus loading from manure was greater at sites with nonsignificant trends than at sites with downward trends—at these 

sites, other factors likely were more important in affecting 

the downward trends. At sites with high source loading from 

atmospheric deposition, the increase in population density was 

greater at sites with nonsignificant trends than at sites with 

upward trends—at these sites, other factors likely were more 

important in affecting the upward trends.

Upward regional trends in FA total phosphorus concentrations occurred at sites in the Central United States, sites 

with greater than 40 percent agricultural land use in the basin, 

and sites with high source loading from manure. There were, 

however, no significant regional trends in NFA total phosphorus concentrations at these sites, likely reflecting the effects of 

decreasing streamflow at many of the sites.

Total Nitrogen

Downward FA trends in total nitrogen concentrations 

occurred at 16 percent of the sites, indicating that at the 

majority of sites, changes in nitrogen use, implementation 

of pollution-control strategies, or other anthropogenic activities were not contributing to significant decreases in total 

nitrogen concentrations in streams, or any reductions that 

occurred were offset by other anthropogenic activities in the 

watershed that increased concentrations. Upward FA trends in 

total nitrogen concentrations were more numerous; increases 

in nitrogen sources and(or) transport at 21 percent of the 

sites may have been contributing to increased total nitrogen 

concentrations in streams. In contrast, more NFA trends were 

downward than upward—downward NFA trends occurred at 

16 percent of sites, whereas upward NFA trends occurred at 

11 percent of sites. FA and NFA trends in total nitrogen concentrations generally were downward or nonsignificant at sites 

in the Northwestern United States. Elsewhere, trends were a 

mixture of upward, downward, and nonsignificant.

Relatively fewer upward NFA trends than upward FA 

trends occurred at sites in the Central United States, where 

many of the significant (downward) trends in streamflow 

occurred. At these sites, the increase in source indicated by the 

upward FA trend likely was offset by the effects of decreasing 

surface runoff indicated by the downward streamflow trend, 

resulting in fewer upward NFA trends. Total nitrogen concentrations at sites in the Central United States were probably lower 

than they would have been without the decrease in streamflow 

and associated surface runoff. Trends in loads of total nitrogen 

from 1993 to 2003 were a reflection of the combined influence of changes in streamflow and changes in concentration. 

At the majority of sites (74 percent) nationwide, there was no 

significant trend in the load of total nitrogen being transported 

to downstream locations. Upward trends in load occurred at 

only 1 percent of sites; downward trends in load occurred at 

25 percent of sites, primarily in the Central United States.

There were fewer upward trends in total nitrogen concentrations than in total phosphorus concentrations. This 

difference cannot be explained easily by changes in nonpointsource loading of nitrogen and phosphorus from 1993 to 

2003—during this period, there were slightly more sites with 

increases in nitrogen loading from fertilizer and(or) manure 

than there were sites with increases in phosphorus loading from these two sources. One alternate possibility may 

be that soils are at or approaching phosphorus saturation in 

areas that have been subject to long-term manure or fertilizer 

application; over time, a greater proportion of the phosphorus 
100 Nutrient Trends in Streams and River of the United States, 1993–2003

load applied to the land surface may be reaching streams in 

these areas. Another possibility is that a substantial source 

of nitrogen in some streams is ground water. Because of the 

time required for ground water to travel to streams, there may 

be a lag between changes in nitrogen use, implementation of 

pollution-control strategies, or other anthropogenic activities 

on the land surface and changes in total nitrogen concentration 

in streams. As a result, trends in total nitrogen concentrations 

from 1993 to 2003 may be influenced to a greater degree than 

trends in total phosphorus concentrations by changes that took 

place on the land surface prior to 1993.

Several significant relations between FA trends in total 

nitrogen concentrations and changes in nutrient sources were 

identified, although these relations did not explain all of the 

variability in the trends. Changes in nitrogen loading from 

atmospheric deposition were significantly related to trends in 

total nitrogen concentrations at sites with greater than 40 percent agricultural land use in the basin, at sites with mean basin 

slope greater than 10 percent, at sites with high streamflows, 

and at sites with high loading from manure. Although a negative relation was observed at sites with greater than 40 percent 

agricultural land use in the basin and at sites with high loading 

from manure, changes in loading from atmospheric deposition 

likely had little impact on trends in total nitrogen at these sites 

because nitrogen loading from atmospheric deposition was 

small compared to that from fertilizer and(or) manure.

Additional analyses comparing source changes at sites 

with upward, downward, and nonsignificant FA trends in total 

nitrogen concentrations indicated that at sites with high source 

loading from manure, nitrogen loading from fertilizer generally decreased at sites with downward trends and generally 

increased at sites with upward and nonsignificant trends. At 

sites with high streamflows, the decrease in loading from 

manure was greater at sites with downward trends than at sites 

with nonsignificant trends.

There were no significant regional trends in FA or NFA 

total nitrogen concentrations. This likely resulted from a 

combination of a lack of trend at many locations and trends in 

opposite directions at other locations cancelling one another out.

Nitrate

There were more downward FA trends in nitrate 

concentrations than in total phosphorus or total nitrogen 

concentrations—25 percent of sites had downward FA trends in 

nitrate concentrations, indicating that changes in nitrogen use, 

implementation of pollution-control strategies, or other anthropogenic activities likely were contributing to decreases in nitrate 

concentrations in one-quarter of the study streams. There were 

fewer upward FA trends in nitrate concentrations than in total 

phosphorus or total nitrogen concentrations—12 percent of sites 

had upward FA trends in nitrate concentrations, indicating that 

increases in sources and(or) transport at these sites may have 

been contributing to increased nitrate concentrations in streams. 

More NFA trends in nitrate concentrations were downward 

than upward—downward NFA trends occurred at 27 percent of 

sites, whereas upward NFA trends occurred at 6 percent of sites. 

FA and NFA trends in nitrate concentrations generally were 

downward or nonsignificant at sites in the Eastern and Western 

United States and mixed at sites in the Central United States.

There were numerous sites with non-significant FA 

trends and downward NFA trends at sites in the Central United 

States, where many of the significant (downward) trends in 

streamflow occurred. At these sites, there likely was little net 

change in inputs of nitrate from land application or ground 

water between1993 and 2003; a decrease in runoff at these 

sites probably contributed to the downward NFA trends. As 

a result, nitrate concentrations at sites in the Central United 

States were probably lower than they would have been without 

the decrease in streamflow and associated surface runoff. 

Trends in loads of nitrate from 1993 to 2003 were a reflection of the combined influence of changes in streamflow and 

changes in concentration. At the majority of sites (66 percent) 

nationwide, there was no significant trend in the load of nitrate 

being transported to downstream locations. Upward trends in 

load occurred at only 3 percent of sites; downward trends in 

load occurred at 31 percent of sites, a large number of which 

were in the Central United States.

There were more downward and fewer upward trends in 

nitrate concentrations as compared to total phosphorus and 

total nitrogen. Nitrate is more readily leached through the soil 

and is more mobile in ground water than phosphorus and other 

forms of nitrogen. Therefore, the lag time between changes in 

use, implementation of pollution-control strategies, or other 

anthropogenic activities on the land surface and changes in 

in-stream concentrations may have had a greater impact on 

nitrate trends. As a result, trends in nitrate concentrations from 

1993 to 2003 may have been influenced by changes that took 

place on the land surface prior to 1993 to a greater degree than 

trends in total phosphorus and total nitrogen.

Several significant relations between FA trends in nitrate 

concentrations and changes in nutrient sources were identified, 

although these relations did not explain all of the variability in 

the trends. Fewer significant relations between FA trends and 

changes in nutrient sources were identified for nitrate than for 

total phosphorus or total nitrogen. In the Central United States, 

where many sites had substantial agricultural land use in the 

basin, nitrate trends were positively related to changes in nitrogen loading from manure. This relation indicates that increases 

in the land application of manure may have been a factor 

contributing to increasing nitrate concentrations in streams in 

some areas of the Central United States. Likewise, decreases 

in the land application of manure may have been contributing 

to decreases (or smaller increases) in nitrate concentrations in 

streams in other areas of the Central United States. In addition, 

nitrate trends at sites in the Western United States generally 

increased as population density increased and decreased as 

population density decreased.
References Cited 101

Additional analyses comparing source changes at sites 

with upward, downward, and nonsignificant FA trends in 

nitrate concentrations also found relations with changes in 

nitrogen loading from atmospheric deposition at sites in 

the Central United States (where decreases in loading from 

atmospheric deposition were greater at sites with upward 

trends than at sites with downward trends), and sites with low 

streamflows (where decreases in loading from atmospheric 

deposition were smaller at sites with downward trends than at 

sites with nonsignificant trends). The counterintuitive results 

indicate that other factors likely were more important than 

changes in loading from atmospheric deposition in affecting 

the trends at these sites. At sites with mean annual precipitation greater than 130 centimeters, increases in loading from 

manure were greater than at sites with upward FA trends than 

at sites with nonsignificant FA trends.

A downward regional trend in FA nitrate concentrations 

occurred at sites with mean annual precipitation less than 

80 cm. The absence of additional regional trends in nitrate 

concentrations likely resulted from a combination of a lack 

of trend at many locations and trends in opposite directions 

at other locations cancelling one another out.

Trend Results Relative to Stream 

Nutrient Enrichment

Generally, more downward trends occurred at sites with 

nutrient enrichment above natural background conditions as 

compared to sites minimally affected by anthropogenic activities. At nearly 20 percent of sites with nutrient enrichment 

over natural background conditions, anthropogenic activities contributed to net decreases in nutrient concentrations 

from 1993 to 2003, and overall nutrient quality in the stream 

improved. At sites minimally affected by anthropogenic activities, downward trends occurred at fewer than 10 percent of 

sites, and there were over three times as many upward than 

downward trends in total phosphorus concentrations and over 

eight times as many upward than downward trends in total 

nitrogen concentrations.

Implications for Management 

of Stream Quality

While modest gains have been made in nutrient 

quality in some heavily impacted streams, nutrient enrichment has increased in many streams that were least impacted 

in 1993. The Nation’s least-impacted streams are increasingly being affected by population growth, and new strategies 

designed to reduce these effects may need to be integrated 

with ongoing actions to improve nutrient quality in heavily 

impacted streams. In addition, future water-quality conditions 

will depend on both natural and anthropogenic changes, and 

consideration of the full range of possible climatic conditions 

can inform future water-quality management decisions.

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Appendixes

Appendix 1 107

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Station

number Station name

Drainage area,

in square

kilometers

Percent of

drainage area in 

the United States

Area of

United States

1 01122610 Shetucket River at South Windham, Conn. 1,065.4 100.0 Eastern

2 01124000 Quinebaug River at Quinebaug, Conn. 392.0 100.0 Eastern

3 01127000 Quinebaug River at Jewett City, Conn. 1,838.7 100.0 Eastern

4 01184000 Connecticut River at Thompsonville, Conn. 25,049.5 98.8 Eastern

5 01184490 Broad Brook at Broad Brook, Conn. 38.1 100.0 Eastern

6 01188090 Farmington River at Unionville, Conn. 977.8 100.0 Eastern

7 01189995 Farmington River at Tariffville, Conn. 1,493.0 100.0 Eastern

8 01192500 Hockanum River near East Hartford, Conn. 190.7 100.0 Eastern

9 01193500 Salmon River near East Hampton, Conn. 271.3 100.0 Eastern

10 01196500 Quinnipiac River at Wallingford, Conn. 285.8 100.0 Eastern

11 01205500 Housatonic River at Stevenson, Conn. 3,993.4 100.0 Eastern

12 01208500 Naugatuck River at Beacon Falls, Conn. 674.4 100.0 Eastern

13 01208990 Saugatuck River near Redding, Conn. 53.8 100.0 Eastern

14 01209710 Norwalk River at Winnipauk, Conn. 85.1 100.0 Eastern

15 01357500 Mohawk River at Cohoes, N.Y. 9,113.4 100.0 Eastern

16 01377000 Hackensack River at Rivervale, N.J. 145.3 100.0 Eastern

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 164.2 100.0 Eastern

18 01387500 Ramapo River near Mahwah, N.J. 312.1 100.0 Eastern

19 01389500 Passaic River at Little Falls, N.J. 1,997.6 100.0 Eastern

20 01391500 Saddle River at Lodi, N.J. 146.5 100.0 Eastern

21 01394500 Rahway River near Springfield, N.J. 67.1 100.0 Eastern

22 01395000 Rahway River at Rahway, N.J. 107.3 100.0 Eastern

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 30.4 100.0 Eastern

24 01398000 Neshanic River at Reaville, N.J. 66.0 100.0 Eastern

25 01402000 Millstone River at Blackwells Mills, N.J. 663.9 100.0 Eastern

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 2,074.2 100.0 Eastern

27 01408000 Manasquan River at Squankum, N.J. 114.1 100.0 Eastern

28 01408500 Toms River near Toms River, N.J. 319.9 100.0 Eastern

29 01409500 Batsto River at Batsto, N.J. 176.5 100.0 Eastern

30 01411500 Maurice River at Norma, N.J. 270.2 100.0 Eastern

31 01438500 Delaware River at Montague, N.J. 9,016.4 100.0 Eastern

32 01443500 Paulins Kill at Blairstown, N.J. 326.7 100.0 Eastern

33 01463500 Delaware River at Trenton, N.J. 17,579.8 100.0 Eastern

34 01467150 Cooper River at Haddonfield, N.J. 47.0 100.0 Eastern

35 01477120 Raccoon Creek near Swedesboro, N.J. 67.4 100.0 Eastern

36 01491000 Choptank River near Greensboro, Md. 295.0 100.0 Eastern

37 01578310 Susquehanna River at Conowingo, Md. 70,103.1 100.0 Eastern

38 01594440 Patuxent River near Bowie, Md. 906.6 100.0 Eastern

39 01614500 Conococheague Creek at Fairview, Md. 1,309.5 100.0 Eastern

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 29,998.8 100.0 Eastern

41 01668000 Rappahannock River near Fredericksburg, Va. 4,134.7 100.0 Eastern

42 01673000 Pamunkey River near Hanover, Va. 2,795.0 100.0 Eastern

43 01674500 Mattaponi River near Beulahville, Va. 1,560.2 100.0 Eastern

44 02035000 James River at Cartersville, Va. 16,200.6 100.0 Eastern

45 02041650 Appomattox River at Matoaca, Va. 3,477.7 100.0 Eastern

46 02085000 Eno River at Hillsborough, N.C. 171.4 100.0 Eastern

47 02089500 Neuse River at Kinston, N.C. 7,021.5 100.0 Eastern

48 02091500 Contentnea Creek at Hookerton, N.C. 1,908.6 100.0 Eastern

49 0210215985 Cape Fear River at State Highway 42 near Brickhaven, N.C. -- -- Eastern

50 02175000 Edisto River near Givhans, S.C. 7,077.1 100.0 Eastern

51 02198500 Savannah River near Clyo, Ga. 25,509.8 100.0 Eastern

52 02213700 Ocmulgee River near Warner Robins, Ga. 6,891.2 100.0 Eastern

53 02215500 Ocmulgee River at Lumber City, Ga. 13,581.9 100.0 Eastern

54 02223600 Oconee River at Interstate 16, near Dublin, Ga. 11,517.1 100.0 Eastern

55 02226010 Altamaha River near Gardi, Ga. 35,220.1 100.0 Eastern

56 02226582 Satilla River at GA 15&121, near Hoboken, Ga. 3,486.9 100.0 Eastern

57 02271500 Josephine Creek near De Soto City, Fla. 301.1 100.0 Eastern

58 02295420 Payne Creek near Bowling Green, Fla. 316.8 100.0 Eastern

59 02296750 Peace River at Arcadia, Fla. 3,436.0 100.0 Eastern

60 02300700 Bullfrog Creek near Wimauma, Fla. 73.8 100.0 Eastern

61 02301300 South Prong Alafia River near Lithia, Fla. 277.3 100.0 Eastern
108 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Station

number Station name

Drainage area,

in square

kilometers

Percent of

drainage area in 

the United States

Area of

United States

62 02302500 Blackwater Creek near Knights, Fla. 226.4 100.0 Eastern

63 02303000 Hillsborough River near Zephyrhills, Fla. 546.1 100.0 Eastern

64 02314500 Suwannee River at U.S. 441, at Fargo, Ga. 3,322.2 100.0 Eastern

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 3,863.7 100.0 Eastern

66 02335870 Sope Creek near Marietta, Ga. 79.5 100.0 Eastern

67 02338000 Chattahoochee River near Whitesburg, Ga. 6,250.6 100.0 Eastern

68 02344040 Chattahoochee River near Steam Mill, Ga. 21,974.1 100.0 Eastern

69 02353000 Flint River at Newton, Ga. 14,899.4 100.0 Eastern

70 02388520 Oostanaula River at Rome, Ga. 20.5 100.0 Eastern

71 02492000 Bogue Chitto River near Bush, La. 3,071.5 100.0 Eastern

72 03353637 Little Buck Creek near Indianapolis, Ind. 44.6 100.0 Central

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 527,228.9 100.0 Central

74 04063700 Popple River near Fence, Wis. 362.6 100.0 Central

75 04073468 Green Lake Inlet at County Highway A near Green Lake, Wis. 122.3 100.0 Central

76 04087000 Milwaukee River at Milwaukee, Wis. 1,805.2 100.0 Central

77 0422026250 Northrup Creek at North Greece, N.Y. 22.6 100.0 Central

78 04232034 Irondequoit Creek at Railroad Mills near Fishers, N.Y. 97.6 100.0 Central

79 0423204920 East Branch Allen Creek at Pittsford, N.Y. 22.9 100.0 Central

80 0423205025 Irondequoit Creek at Empire Boulevard at Rochester, N.Y. 391.0 100.0 Central

81 05114000 Souris River near Sherwood, N. Dak. 22,758.7 14.2 Central

82 05120000 Souris River near Verendrye, N. Dak. 28,839.6 31.9 Central

83 05287890 Elm Creek near Champlin, Minn. 222.1 100.0 Central

84 05427718 Yahara River at Windsor, Wis. 184.7 100.0 Central

85 05427948 Pheasant Branch at Middleton, Wis. 47.0 100.0 Central

86 054310157 Jackson Creek Tributary near Elkhorn, Wis. 11.1 100.0 Central

87 05500000 South Fabius River near Taylor, Mo. 1,560.2 100.0 Central

88 05514500 Cuivre River near Troy, Mo. 2,439.3 100.0 Central

89 05525500 Sugar Creek at Milford, Ill. 1,158.8 100.0 Central

90 05531500 Salt Creek at Western Springs, Ill. 290.6 100.0 Central

91 05532500 Des Plaines River at Riverside, Ill. 1,634.2 100.0 Central

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 24.7 100.0 Central

93 05586100 Illinois River at Valley City, Ill. 69,164.6 100.0 Central

94 07018100 Big River near Richwoods, Mo. 1,909.5 100.0 Central

95 07022000 Mississippi River at Thebes, Ill. 1,839,670.0 98.5 Central

96 06088500 Muddy Creek at Vaughn, Mont. 661.9 100.0 Central

97 06178000 Poplar River at International Boundary, Mont. 929.1 2.0 Central

98 06274300 Bighorn River at Basin, Wyo. 34,249.0 100.0 Central

99 06329500 Yellowstone River near Sidney, Mont. 177,139.1 100.0 Central

100 06338490 Missouri River at Garrison Dam, N. Dak. 468,773.8 94.1 Central

101 06461500 Niobrara River near Sparks, Nebr. 21,666.8 100.0 Central

102 06468250 James River above Arrowwood Lake near Kensal, N. Dak. 3,019.2 100.0 Central

103 06713500 Cherry Creek at Denver, Colo. 1,063.2 100.0 Central

104 06752260 Cache La Poudre River at Fort Collins, Colo. 2,920.8 100.0 Central

105 06752280 Cache La Poudre River above Boxelder Creek, near Timnath, Colo. 3,222.6 100.0 Central

106 06753990 Lonetree Creek near Greeley, Colo. 1,477.9 100.0 Central

107 06754000 South Platte River near Kersey, Colo. 25,015.6 100.0 Central

108 06775900 Dismal River near Thedford, Nebr. 71.6 100.0 Central

109 06800000 Maple Creek near Nickerson, Nebr. 953.9 100.0 Central

110 06805500 Platte River at Louisville, Nebr. 220,907.8 100.0 Central

111 06817700 Nodaway River near Graham, Mo. 3,927.0 100.0 Central

112 06818000 Missouri River at St. Joseph, Mo. 1,081,419.7 97.5 Central

113 06902000 Grand River near Sumner, Mo. 17,950.5 100.0 Central

114 06905500 Chariton River near Prairie Hill, Mo. 4,897.5 100.0 Central

115 06921070 Pomme De Terre River near Polk, Mo. 712.6 100.0 Central

116 06926510 Osage River below St. Thomas, Mo. 37,907.8 100.0 Central

117 06930800 Gasconade River above Jerome, Mo. 6,649.3 100.0 Central

118 06934500 Missouri River at Hermann, Mo. 1,344,910.2 98.0 Central

119 07047942 L'Anguille River near Colt, Ark. 1,374.9 100.0 Central

120 07053250 Yocum Creek near Oak Grove, Ark. 134.1 100.0 Central

121 07056000 Buffalo River near St Joe, Ark. 2,149.4 100.0 Central

122 07060500 White River at Calico Rock, Ark. 25,815.4 100.0 Central
Appendix 1 109

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Station

number Station name

Drainage area,

in square

kilometers

Percent of

drainage area in 

the United States

Area of

United States

123 07060710 North Sylamore Creek near Fifty Six, Ark. 150.0 100.0 Central

124 07066110 Jacks Fork above Two River, Mo. 1,120.5 100.0 Central

125 07068000 Current River at Doniphan, Mo. 5,317.2 100.0 Central

126 07077500 Cache River at Patterson, Ark. 6,677.9 100.0 Central

127 07077700 Bayou DeView near Morton, Ark. 1,079.2 100.0 Central

128 07103700 Fountain Creek near Colorado Springs, Colo. 268.1 100.0 Central

129 07103780 Monument Creek above North Gate Boulevard at United States Air Force Academy, Colo. 214.2 100.0 Central

130 07105500 Fountain Creek at Colorado Springs, Colo. 961.4 100.0 Central

131 07105530 Fountain Creek below Janitell Road below Colorado Springs, Colo. 1,072.1 100.0 Central

132 07106300 Fountain Creek near Pinon, Colo. 2,208.9 100.0 Central

133 07106500 Fountain Creek at Pueblo, Colo. 2,414.2 100.0 Central

134 07189000 Elk River near Tiff City, Mo. 2,200.7 100.0 Central

135 07195500 Illinois River near Watts, Okla. 1,634.7 100.0 Central

136 07195865 Sager Creek near West Siloam Springs, Okla. 49.7 100.0 Central

137 07196000 Flint Creek near Kansas, Okla. 300.1 100.0 Central

138 07196500 Illinois River near Tahlequah, Okla. 2,454.3 100.0 Central

139 07197000 Baron Fork at Eldon, Okla. 808.5 100.0 Central

140 07227500 Canadian River near Amarillo, Tex. 49,289.7 100.0 Central

141 07239450 North Canadian River near Calumet, Okla. 34,298.2 100.0 Central

142 07241000 North Canadian River below Lake Overholser near Oklahoma City, Okla. 34,968.2 100.0 Central

143 07241520 North Canadian River at Britton Road at Oklahoma City, Okla. 35,447.1 100.0 Central

144 07241550 North Canadian River near Harrah, Okla. 35,712.9 100.0 Central

145 07247015 Poteau River at Loving, Okla. 696.6 100.0 Central

146 07247250 Black Fork below Big Creek near Page, Okla. 245.5 100.0 Central

147 07247345 Black Fork at Hodgen, Okla. 511.3 100.0 Central

148 07247650 Fourche Maline near Leflore, Okla. 633.2 100.0 Central

149 07263620 Arkansas River at David D. Terry Lock and Dam below Little Rock, Ark. 408,729.4 100.0 Central

150 07331000 Washita River near Dickson, Okla. 18,589.7 100.0 Central

151 07355500 Red River at Alexandria, La. 560.5 100.0 Central

152 07362000 Ouachita River at Camden, Ark. 13,943.0 100.0 Central

153 07373420 Mississippi River near St Francisville, La. 2,965,462.6 99.1 Central

154 07375500 Tangipahoa River at Robert, La. 1,674.8 100.0 Central

155 07376000 Tickfaw River at Holden, La. 1,028.0 100.0 Central

156 07381495 Atchafalaya River at Melville, La. 240,627.8 100.0 Central

157 07386980 Vermilion River at Perry, La. 1,128.9 100.0 Central

158 08030500 Sabine River near Ruliff, Tex. 24,171.0 100.0 Central

159 08032000 Neches River near Neches, Tex. 2,990.7 100.0 Central

160 08033500 Neches River near Rockland, Tex. 9,424.9 100.0 Central

161 08051500 Clear Creek near Sanger, Tex. 763.4 100.0 Central

162 08064100 Chambers Creek near Rice, Tex. 2,135.6 100.0 Central

163 08065350 Trinity River near Crockett, Tex. 35,967.2 100.0 Central

164 08136500 Concho River at Paint Rock, Tex. 16,698.0 100.0 Central

165 08143600 Pecan Bayou near Mullin, Tex. 5,387.3 100.0 Central

166 08147000 Colorado River near San Saba, Tex. 74,658.5 100.0 Central

167 08155200 Barton Creek at State Highway 71 near Oak Hill, Tex. 232.4 100.0 Central

168 08155240 Barton Creek at Lost Creek Boulevard near Austin, Tex. 278.8 100.0 Central

169 08159000 Onion Creek at U.S. Highway 183, Austin, Tex. 839.4 100.0 Central

170 08162000 Colorado River at Wharton, Tex. 102,705.4 100.0 Central

171 08162500 Colorado River near Bay City, Tex. 103,310.5 100.0 Central

172 08181800 San Antonio River near Elmendorf, Tex. 4,528.5 100.0 Central

173 08251500 Rio Grande near Lobatos, Colo. 11,875.7 100.0 Western

174 09058000 Colorado River near Kremmling, Colo. 46,230.3 100.0 Western

175 09163500 Colorado River near Colorado-Utah State Line 46,274.0 100.0 Western

176 09211200 Green River below Fontenelle Reservoir, Wyo. 10,862.1 100.0 Western

177 09217010 Green River below Green River, Wyo. 25,220.0 100.0 Western

178 09261000 Green River at Dinosaur National Monument Utah 149 Crossing, Utah 66,055.9 100.0 Western

179 09380000 Colorado River at Lees Ferry, Ariz. 280,073.6 100.0 Western

180 09403600 Kanab Creek at U.S. 89 Crossing, Utah 502.9 100.0 Western

181 09413500 Virgin River below First Narrows, Utah 10,303.6 100.0 Western

182 09415000 Virgin River at Littlefield, Ariz. 12,571.5 100.0 Western

183 09448500 Gila River at Head of Safford Valley, near Solomon, Ariz. 20,424.0 100.0 Western
110 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Station

number Station name

Drainage area,

in square

kilometers

Percent of

drainage area in 

the United States

Area of

United States

184 09498500 Salt River near Roosevelt, Ariz. 11,102.9 100.0 Western

185 09508500 Verde River below Tangle Creek, above Horseshoe Dam, Ariz. 14,242.6 100.0 Western

186 09522000 Colorado River at Northerly International Boundary, above Morelos Dam, Ariz. 624,015.9 99.5 Western

187 10038000 Bear River below Smiths Fork, near Cokeville, Wyo. 6,335.6 100.0 Western

188 10126000 Bear River near Corinne at Utah 83 Crossing, Utah 18,311.9 100.0 Western

189 10131000 Chalk Creek at U.S. 189 Crossing, Utah 661.2 100.0 Western

190 10154200 Provo River above Woodland at U.S. Geological Survey Gage Number 10154200, Utah 419.8 100.0 Western

191 10155000 Provo River at Bridge 2.5 miles East of Hailstone Junction, Utah 568.3 100.0 Western

192 10155500 Provo River above Confluence with Snake Creek at McKeller Bridge, Utah 726.2 100.0 Western

193 10189000 East Fork Sevier River at Utah 62 Crossing East of Kingston, Utah 3,119.0 100.0 Western

194 10336580 Upper Truckee River at South Upper Truckee Road near Meyers, Calif. 36.8 100.0 Western

195 103366092 Upper Truckee River at Highway 50 above Meyers, Calif. 101.6 100.0 Western

196 10336610 Upper Truckee River at South Lake Tahoe, Calif. 139.7 100.0 Western

197 10336698 Third Creek near Crystal Bay, Nev. 15.6 100.0 Western

198 103366993 Incline Creek above Tyrol Village near Incline Village, Nev. 7.4 100.0 Western

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 11.7 100.0 Western

200 10336700 Incline Creek near Crystal Bay, Nev. 17.3 100.0 Western

201 10336740 Logan House Creek near Glenbrook, Nev. 5.4 100.0 Western

202 10336760 Edgewood Creek at Stateline, Nev. 14.5 100.0 Western

203 01A050 Nooksack River at Brennan, Wash. 1,907.8 100.0 Western

204 03A060 Skagit River near Mount Vernon, Wash. 6,024.1 100.0 Western

205 07A090 Snohomish River at Snohomish, Wash. 4,438.0 100.0 Western

206 09A080 Green River at Tukwila, Wash. 1,235.7 100.0 Western

207 09A190 Green River at Kanaskat, Wash. 615.6 100.0 Western

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. -- -- Western

209 10350 Willamette River at Eastbound Highway 20 Bridge at Albany, Oreg. 12,567.2 100.0 Western

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 8,886.4 100.0 Western

211 10386 Middle Fork Willamette at Jasper Bridge, Oreg. 3,487.2 100.0 Western

212 10411 Deschutes River at Deschutes River Park, Oreg. 27,768.3 100.0 Western

213 10555 Willamette River at Marion Street at Salem, Oreg. 19,112.2 100.0 Western

214 10611 Willamette River at Hawthorne Bridge, Oreg. 28,936.9 100.0 Western

215 10616 Columbia River at Marker number 47 upstream of Willamette River, Oreg. -- -- Western

216 10A070 Puyallup River at Meridian Street, Wash. 2,381.1 100.0 Western

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 1,077.9 100.0 Western

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. 138.8 100.0 Western

219 11478 John Day River at Service Creek, Oreg. 13,288.9 100.0 Western

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. -- -- Western

221 12413470 South Fork Coeur D'Alene River near Pinehurst, Idaho 738.0 100.0 Western

222 12419000 Spokane River near Post Falls, Idaho 10,162.1 100.0 Western

223 13154500 Snake River at King Hill, Idaho 92,942.4 100.0 Western

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 7,184.4 100.0 Western

225 13351000 Palouse River at Hooper, Wash. 6,378.8 100.0 Western

226 14201300 Zollner Creek near Mt. Angel, Oreg. 38.9 100.0 Western

227 14211720 Willamette River at Portland, Oreg. 28,936.9 100.0 Western

228 14246900 Columbia River at Beaver Army Terminal near Quincy, Oreg. 582,735.9 100.0 Western

229 16A070 Skokomish River near Potlatch, Wash. 339.4 100.0 Western

230 32A070 Walla Walla River near Touchet, Wash. 4,365.4 100.0 Western

231 3701002 Tualatin River at Weiss Bridge, Oreg. 1,838.2 100.0 Western

232 37016120 Tualatin River at Springhill Road Bridge at Dilley, Oreg. 326.6 100.0 Western

233 37A090 Yakima River at Kiona, Wash. 14,536.2 100.0 Western

234 45A070 Wenatchee River at Wenatchee, Wash. 3,440.5 100.0 Western

235 45A110 Wenatchee River near Leavenworth, Wash. 1,720.9 100.0 Western

236 48A070 Methow River near Pateros, Wash. 4,656.9 100.0 Western

237 49A070 Okanogan River at Malott, Wash. 4,499.6 100.0 Western

238 54A120 Spokane River at Riverside State Park, Wash. 12,950.9 100.0 Western

239 61A070 Columbia River at Northport, Wash. -- -- Western

240 11264500 Merced River at Happy Isles Bridge near Yosemite, Calif. 468.0 100.0 Western

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. 27.9 100.0 Western

242 11290000 Tuolumne River at Modesto, Calif. 4,759.9 100.0 Western

243 11303500 San Joaquin River near Vernalis, Calif. 19,029.9 100.0 Western

244 11447650 Sacramento River at Freeport, Calif. 61,692.7 100.0 Western
111 Nutrient Trends in Streams and River of the United States, 1993–2003 Appendix 1 111

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Land cover in the basin, in percent1

Land-use

classification3

Base-flow

index,

in percent

Area with

subsurface

(tile) drains

Mean

basin slope,

in percent Urban Agriculture Rangeland Forest Other2

1 10.3 10.9 0.0 73.6 5.2 Mixed 51.6 0.0 6.0

2 11.0 7.4 0.1 75.5 6.1 Mixed 52.9 0.7 6.8

3 9.4 11.3 0.1 73.3 5.9 Mixed 52.9 1.8 5.1

4 5.0 8.3 0.2 81.0 4.3 Mixed 47.6 14.7 11.6

5 13.1 39.0 0.0 45.9 2.0 Mixed 52.9 0.0 4.2

6 5.2 4.8 0.0 84.0 6.0 Mixed 47.6 0.0 9.0

7 13.4 6.7 0.0 74.8 5.1 Mixed 48.7 0.0 7.9

8 44.5 11.1 0.0 40.5 3.9 Urban 52.4 0.0 5.1

9 11.1 12.4 0.1 71.7 4.8 Mixed 52.6 0.0 6.0

10 56.6 1.0 0.0 38.8 3.6 Urban 49.8 0.0 5.3

11 12.2 13.5 0.0 69.9 4.3 Mixed 48.0 2.7 9.8

12 26.5 9.9 0.0 58.9 4.6 Urban 47.7 0.0 8.0

13 21.4 4.4 0.0 70.7 3.4 Mixed 48.1 0.2 8.1

14 50.7 2.8 0.0 44.2 2.3 Urban 47.1 0.2 5.5

15 5.9 27.2 0.0 65.1 1.9 Mixed 45.5 139.3 7.9

16 78.5 0.3 0.0 13.6 7.6 Urban 47.7 0.0 4.6

17 5.7 0.8 0.0 87.7 5.8 Mixed 44.6 0.0 11.2

18 25.4 0.9 0.0 70.2 3.6 Urban 44.8 0.1 10.8

19 39.3 2.2 0.0 53.9 4.6 Urban 43.9 0.1 7.4

20 93.2 0.5 0.0 5.7 0.5 Urban 47.5 0.0 4.3

21 80.5 0.4 0.0 18.4 0.6 Urban 30.4 0.0 5.2

22 89.9 0.2 0.0 9.3 0.6 Urban 28.8 0.0 3.8

23 3.1 25.4 0.0 71.2 0.2 Mixed 49.5 0.0 7.1

24 8.5 59.8 0.0 31.5 0.2 Mixed 30.8 0.0 3.3

25 25.1 33.0 0.0 40.6 1.3 Mixed 37.7 0.9 1.9

26 19.4 33.3 0.0 45.6 1.7 Mixed 40.5 0.9 4.2

27 27.7 24.3 0.0 44.9 3.1 Urban 50.3 1.4 1.0

28 21.0 4.7 0.0 68.8 5.5 Mixed 60.9 0.9 1.4

29 2.3 12.1 0.0 82.8 2.8 Undeveloped 68.6 0.0 0.4

30 23.4 27.6 0.0 47.7 1.3 Mixed 64.8 0.0 0.4

31 2.4 9.8 0.0 85.0 2.8 Undeveloped 43.5 31.8 15.6

32 9.1 25.4 0.0 61.2 4.4 Mixed 54.9 0.0 6.6

33 5.6 16.2 0.0 75.1 3.1 Mixed 47.6 38.1 10.0

34 69.9 6.4 0.0 20.1 3.6 Urban 43.8 0.0 1.4

35 9.2 64.3 0.0 26.1 0.4 Mixed 58.2 0.0 1.5

36 2.8 48.5 0.0 48.0 0.6 Mixed 54.9 4.8 0.1

37 3.5 28.0 0.0 66.5 2.1 Mixed 44.9 359.3 11.6

38 32.4 32.8 0.0 31.3 3.5 Mixed 54.0 0.6 3.6

39 3.6 56.8 0.0 38.3 1.3 Agricultural 48.2 1.9 7.9

40 5.1 33.4 0.0 59.8 1.6 Mixed 43.8 65.1 11.7

41 4.7 34.7 0.0 59.4 1.2 Mixed 45.1 4.2 8.0

42 2.7 23.0 0.0 69.1 5.2 Undeveloped 43.2 3.4 3.1

43 2.2 18.6 0.0 73.8 5.4 Undeveloped 43.5 0.2 2.6

44 3.9 15.0 0.0 79.3 1.9 Undeveloped 46.8 5.0 13.7

45 2.0 19.8 0.0 74.3 3.8 Undeveloped 45.0 0.0 3.6

46 8.7 23.5 0.0 66.6 1.2 Mixed 31.4 0.0 2.9

47 12.1 28.7 0.0 56.8 2.4 Mixed 34.0 101.1 2.1

48 4.3 41.9 0.0 52.7 1.2 Mixed 39.4 23.8 1.0

49 -- -- -- -- -- -- -- -- --

50 2.0 31.8 0.0 60.0 6.2 Mixed 69.8 127.3 1.3

51 4.3 18.1 0.0 69.5 8.1 Undeveloped 58.8 34.8 4.6

52 20.8 12.8 0.0 63.3 3.1 Mixed 48.5 0.0 3.9

53 12.0 22.7 0.0 59.4 5.9 Mixed 47.8 12.4 3.0

54 3.1 18.9 0.0 72.0 5.9 Undeveloped 51.2 2.1 3.8

55 6.0 24.3 0.0 62.9 6.8 Mixed 47.1 22.6 2.9

56 1.9 32.0 0.0 56.2 10.0 Mixed 33.8 2.0 0.7

57 30.0 13.8 14.7 20.1 21.4 Urban 52.2 1.1 0.4

58 3.0 21.9 25.0 18.5 31.6 Undeveloped 43.0 0.0 0.2

59 10.9 26.7 26.1 21.4 14.9 Mixed 47.4 4.4 0.3

60 10.4 42.7 23.1 19.7 4.2 Mixed 35.8 0.0 0.3

61 3.7 19.4 25.7 18.1 33.1 Undeveloped 41.6 0.0 0.3
112 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Land cover in the basin, in percent1

Land-use

classification3

Base-flow

index,

in percent

Area with

subsurface

(tile) drains

Mean

basin slope,

in percent Urban Agriculture Rangeland Forest Other2

62 35.4 14.4 24.4 17.4 8.4 Urban 40.0 0.0 0.4

63 28.0 12.8 21.1 26.6 11.6 Urban 39.2 0.0 0.3

64 0.3 1.0 0.2 86.2 12.2 Undeveloped 33.5 0.0 0.0

65 3.1 49.7 0.3 39.8 7.1 Mixed 42.1 43.9 1.1

66 62.3 0.0 0.0 37.4 0.3 Urban 49.7 0.0 4.1

67 23.0 9.7 0.0 63.5 3.8 Mixed 56.5 0.0 6.7

68 10.4 13.3 0.0 70.2 6.1 Mixed 53.3 1.9 4.6

69 4.0 30.7 0.0 59.6 5.7 Mixed 53.8 12.5 2.5

70 61.5 7.7 0.0 26.0 4.8 Urban 42.6 0.0 1.6

71 1.8 34.2 0.0 62.1 1.9 Mixed 41.6 0.0 1.8

72 78.8 19.3 0.0 1.8 0.1 Urban 23.6 1.8 0.8

73 5.4 37.7 0.1 54.7 2.1 Mixed 33.4 36,591.3 8.9

74 0.1 3.4 0.6 92.6 3.3 Undeveloped 68.3 0.0 1.6

75 9.0 76.8 1.2 9.1 4.0 Mixed 51.2 3.4 1.6

76 11.3 64.9 0.7 21.0 2.1 Mixed 47.5 147.0 2.1

77 26.3 49.0 0.0 24.5 0.2 Mixed 51.0 0.7 1.1

78 5.8 58.3 0.0 34.6 1.3 Mixed 53.3 5.2 3.3

79 43.6 44.4 0.0 11.5 0.5 Mixed 52.1 0.6 2.6

80 47.8 32.3 0.0 19.0 0.9 Mixed 52.9 11.7 3.1

81 0.0 9.9 3.6 0.0 0.7 -- 25.1 0.0 1.2

82 0.3 21.2 8.8 0.1 1.4 -- 25.4 0.0 1.3

83 13.7 52.1 0.0 14.6 19.6 Mixed 52.9 0.0 1.5

84 8.3 87.2 0.5 3.5 0.4 Mixed 58.3 7.5 1.7

85 12.3 82.8 0.5 4.2 0.2 Mixed 56.2 2.7 2.7

86 42.9 53.8 0.3 1.4 1.6 Mixed 44.5 1.4 0.8

87 1.6 67.9 4.1 25.4 1.1 Agricultural 14.1 0.0 2.4

88 1.0 72.7 2.6 23.3 0.4 Agricultural 11.2 0.0 2.1

89 0.8 97.3 0.3 1.5 0.1 Agricultural 33.8 239.3 0.3

90 82.3 2.2 3.2 9.6 2.7 Urban 33.6 0.4 0.9

91 54.4 28.9 1.9 11.9 2.9 Mixed 36.5 94.9 0.8

92 97.9 0.0 0.0 0.2 1.9 Urban 38.7 3.2 0.5

93 8.6 77.9 0.8 10.8 2.0 Mixed 36.2 16,132.9 1.0

94 2.3 21.2 1.0 73.9 1.7 Undeveloped 29.3 0.0 5.9

95 1.8 43.5 36.4 13.2 3.7 Mixed 43.3 59,053.9 4.3

96 0.4 72.4 27.0 0.1 0.1 Agricultural 66.6 0.0 2.3

97 0.0 0.8 0.8 0.0 0.5 -- 17.9 0.0 2.7

98 0.2 3.6 81.5 9.1 5.7 Undeveloped 54.8 52.9 11.5

99 0.2 8.4 72.4 14.3 4.7 Undeveloped 52.6 93.2 10.8

100 0.2 19.7 58.7 12.0 3.5 Undeveloped 48.5 105.3 8.7

101 0.2 11.9 83.7 0.5 3.6 Undeveloped 71.6 0.0 2.9

102 0.3 68.0 26.0 0.9 4.7 Agricultural 24.9 0.0 0.7

103 15.2 8.7 70.9 4.6 0.7 Mixed 44.4 0.0 4.4

104 1.0 1.8 32.3 59.3 5.7 Undeveloped 62.2 0.8 17.7

105 2.9 2.8 34.2 54.1 6.1 Undeveloped 62.2 1.4 16.6

106 0.9 23.1 74.7 0.4 1.0 Undeveloped 59.7 5.2 2.7

107 8.1 13.3 38.5 34.5 5.7 Mixed 61.7 37.4 13.3

108 0.0 1.1 72.0 12.8 14.2 Undeveloped 81.6 0.0 12.5

109 0.4 96.7 1.4 1.1 0.5 Agricultural 41.3 12.2 3.2

110 1.5 25.5 61.5 8.1 3.6 Mixed 58.5 108.0 5.0

111 1.5 86.6 5.5 5.4 0.9 Agricultural 33.4 97.4 3.6

112 0.7 30.8 54.4 8.1 3.5 Mixed 47.0 3,369.6 5.8

113 1.7 73.9 6.2 16.9 1.2 Agricultural 16.2 187.5 3.3

114 1.9 68.0 5.4 22.1 2.6 Agricultural 20.5 12.4 3.4

115 1.0 65.1 2.0 31.4 0.7 Agricultural 34.1 0.0 3.7

116 1.3 55.6 7.9 31.5 3.7 Agricultural 23.8 0.0 3.2

117 1.1 36.7 1.1 60.3 0.8 Mixed 32.1 0.0 5.8

118 0.9 35.8 49.2 9.0 3.1 Mixed 43.4 3,902.9 5.1

119 1.1 82.0 0.0 15.8 1.1 Agricultural 27.7 0.1 0.5

120 1.8 71.3 0.3 25.8 0.7 Agricultural 36.8 0.0 5.5

121 0.3 10.8 0.6 87.5 0.8 Undeveloped 29.1 0.0 16.9

122 2.1 30.6 0.8 63.2 3.3 Mixed 37.1 0.0 9.6
Appendix 1 113

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Land cover in the basin, in percent1

Land-use

classification3

Base-flow

index,

in percent

Area with

subsurface

(tile) drains

Mean

basin slope,

in percent Urban Agriculture Rangeland Forest Other2

123 0.0 2.0 0.1 97.8 0.2 Undeveloped 35.0 0.0 13.7

124 0.5 19.2 0.4 79.6 0.4 Undeveloped 46.2 0.0 7.3

125 0.2 13.5 0.3 85.5 0.4 Undeveloped 44.5 0.0 8.2

126 1.2 49.3 1.2 47.0 1.2 Mixed 34.9 0.0 4.1

127 2.8 77.1 0.0 18.4 1.8 Agricultural 31.6 0.0 0.5

128 6.8 0.3 16.6 71.6 4.7 Mixed 49.5 0.0 26.7

129 9.8 1.3 31.0 57.1 0.8 Mixed 51.5 0.0 12.7

130 21.1 0.7 26.6 49.5 2.1 Mixed 50.2 0.0 15.6

131 23.8 0.6 24.6 49.0 2.0 Mixed 50.0 0.0 16.2

132 18.6 2.6 50.4 27.1 1.4 Mixed 49.1 0.0 10.7

133 17.9 2.6 53.3 24.9 1.4 Mixed 48.8 0.0 10.0

134 2.8 43.3 2.1 51.0 0.8 Mixed 47.7 0.0 6.0

135 10.7 61.7 0.2 26.3 1.1 Mixed 40.4 0.0 4.1

136 24.5 65.6 0.1 9.3 0.4 Mixed 45.2 0.0 1.5

137 6.2 66.9 0.5 25.4 1.1 Mixed 45.6 0.0 3.2

138 7.4 56.2 0.9 34.3 1.2 Mixed 41.2 0.0 4.7

139 1.4 46.0 0.7 51.3 0.6 Mixed 37.4 0.0 6.5

140 0.3 5.2 83.5 10.6 0.4 Undeveloped 30.1 0.0 5.3

141 0.5 43.4 54.7 1.0 0.5 Mixed 21.3 0.0 1.2

142 0.7 43.8 53.9 1.0 0.6 Mixed 21.6 0.0 1.2

143 1.4 43.5 53.4 1.1 0.6 Mixed 21.7 0.0 1.2

144 1.5 43.4 53.3 1.2 0.6 Mixed 21.7 0.0 1.2

145 0.8 25.1 0.0 71.5 2.6 Mixed 19.7 0.0 8.2

146 0.1 6.2 0.0 93.0 0.8 Undeveloped 20.0 0.0 15.1

147 0.2 5.7 0.0 92.4 1.7 Undeveloped 19.8 0.0 12.6

148 1.4 19.0 0.0 79.1 0.5 Undeveloped 15.3 0.0 8.1

149 1.7 31.1 50.7 14.5 2.0 Mixed 26.4 45.0 3.6

150 1.0 36.4 51.5 9.3 1.8 Mixed 26.1 14.3 2.7

151 12.3 68.3 0.0 16.8 2.5 Mixed 38.4 0.0 0.3

152 1.4 13.8 0.0 80.7 4.1 Undeveloped 22.5 0.0 5.0

153 2.4 41.0 29.6 22.9 3.2 Mixed 38.5 95,810.1 4.9

154 3.4 33.4 0.0 61.3 1.9 Mixed 37.3 0.0 1.6

155 1.6 18.5 0.0 76.6 3.3 Undeveloped 30.9 0.0 1.1

156 1.6 34.9 22.0 37.9 3.5 Mixed 23.2 64.1 2.2

157 16.6 69.2 0.2 10.0 4.0 Mixed 19.8 0.0 0.2

158 2.9 26.7 0.1 61.8 8.5 Mixed 19.8 0.0 1.9

159 4.5 45.9 0.0 44.1 5.5 Mixed 22.3 0.0 2.7

160 2.9 28.9 0.0 62.6 5.7 Mixed 21.9 0.0 2.4

161 0.3 37.9 45.8 15.2 0.9 Mixed 12.4 0.0 3.0

162 2.7 77.0 5.5 12.3 2.5 Agricultural 11.8 0.0 1.6

163 9.6 49.6 16.0 19.8 5.1 Mixed 12.6 0.0 1.8

164 1.2 11.6 85.4 0.9 0.9 Undeveloped 29.3 0.0 1.7

165 1.7 13.8 75.0 7.4 2.1 Undeveloped 9.0 0.0 2.2

166 1.2 19.0 75.4 3.0 1.4 Undeveloped 18.7 0.0 1.4

167 4.1 1.6 42.7 50.5 1.0 Undeveloped 31.5 0.0 4.7

168 6.5 1.4 40.0 50.9 1.2 Mixed 30.8 0.0 5.1

169 17.3 6.2 34.9 40.5 1.0 Mixed 34.9 0.0 3.3

170 1.7 17.0 68.3 11.4 1.6 Undeveloped 23.4 0.0 2.0

171 1.8 17.3 68.0 11.4 1.6 Undeveloped 23.3 0.0 2.0

172 19.1 16.2 21.1 41.6 2.0 Mixed 40.7 0.0 5.1

173 0.3 8.4 50.9 34.3 6.1 Undeveloped 63.2 18.9 15.8

174 0.8 4.2 33.5 54.8 6.7 Undeveloped 65.6 6.1 22.2

175 0.7 4.2 33.6 54.8 6.7 Undeveloped 65.6 6.1 22.2

176 0.1 4.2 66.6 17.7 11.4 Undeveloped 65.2 0.0 12.3

177 0.2 2.1 83.4 8.3 5.9 Undeveloped 60.4 0.0 8.3

178 0.2 2.6 74.1 19.4 3.8 Undeveloped 59.4 0.0 9.9

179 0.3 2.2 63.8 27.5 6.2 Undeveloped 57.6 6.5 14.4

180 0.1 0.6 69.0 29.4 0.9 Undeveloped 77.7 0.0 12.9

181 0.7 0.7 69.4 23.2 5.9 Undeveloped 70.6 0.0 14.5

182 0.6 0.7 69.5 22.4 6.8 Undeveloped 68.0 0.0 15.0

183 0.1 0.3 56.2 42.8 0.6 Undeveloped 52.1 0.0 17.2
114 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Land cover in the basin, in percent1

Land-use

classification3

Base-flow

index,

in percent

Area with

subsurface

(tile) drains

Mean

basin slope,

in percent Urban Agriculture Rangeland Forest Other2

184 0.3 0.0 31.1 67.8 0.8 Undeveloped 47.4 0.0 16.8

185 1.1 0.3 50.7 47.2 0.6 Undeveloped 32.5 0.0 11.5

186 0.9 2.0 68.7 22.9 5.0 Undeveloped 44.6 55.8 12.0

187 0.2 6.8 74.3 16.3 2.4 Undeveloped 64.7 0.0 12.5

188 0.7 18.3 60.6 16.2 4.2 Undeveloped 73.3 3.2 15.2

189 0.1 1.2 48.9 49.4 0.4 Undeveloped 63.7 0.0 17.8

190 0.0 0.0 18.8 79.9 1.3 Undeveloped 66.7 0.0 19.6

191 0.0 2.3 22.5 74.2 1.0 Undeveloped 67.2 0.2 18.3

192 1.4 4.3 24.9 68.4 0.9 Undeveloped 68.4 1.1 18.0

193 0.2 0.8 51.4 44.7 2.9 Undeveloped 72.2 0.0 14.8

194 0.0 0.0 26.7 67.0 6.3 Undeveloped 65.8 0.0 23.9

195 1.9 0.0 22.1 71.9 4.1 Undeveloped 67.1 0.0 25.7

196 7.8 0.0 20.1 68.8 3.2 Mixed 67.6 0.0 22.4

197 17.7 0.0 29.5 45.1 7.7 Mixed 73.9 0.0 25.9

198 0.0 0.0 33.9 65.7 0.4 Undeveloped 73.8 0.0 23.0

199 4.8 0.0 27.0 67.7 0.4 Undeveloped 74.2 0.0 23.9

200 13.0 0.0 19.9 66.7 0.3 Mixed 74.1 0.0 23.1

201 0.0 0.0 6.5 93.5 0.0 Undeveloped 73.7 0.0 20.1

202 19.6 0.0 11.9 68.3 0.2 Mixed 74.4 0.0 24.4

203 3.0 11.7 3.5 69.3 12.4 Undeveloped 58.4 2.2 29.6

204 1.3 1.4 9.2 71.2 17.0 Undeveloped 60.4 3.7 45.2

205 4.0 2.5 6.5 77.3 9.7 Undeveloped 57.2 9.7 33.0

206 22.6 4.4 3.2 57.2 12.6 Mixed 61.2 14.5 20.4

207 0.2 0.0 3.4 77.2 19.2 Undeveloped 59.1 0.0 33.8

208 -- -- -- -- -- -- -- -- --

209 3.8 16.2 4.4 71.8 3.9 Undeveloped 54.4 54.8 20.6

210 2.6 3.9 4.8 84.0 4.7 Undeveloped 59.2 6.4 24.9

211 1.0 1.2 4.1 89.1 4.7 Undeveloped 65.3 0.7 27.3

212 0.7 5.2 47.9 43.5 2.6 Undeveloped 76.0 0.0 10.0

213 3.8 18.2 4.3 69.9 3.7 Undeveloped 54.1 158.9 20.3

214 5.5 23.1 3.7 64.5 3.3 Mixed 53.8 638.5 18.0

215 -- -- -- -- -- -- -- -- --

216 6.2 2.9 3.5 70.2 17.2 Mixed 61.5 8.7 28.8

217 10.4 34.2 4.5 46.6 4.4 Mixed 37.6 6.1 10.5

218 75.6 13.9 0.7 9.6 0.2 Urban 46.7 1.3 5.6

219 0.1 1.8 37.6 59.7 0.8 Undeveloped 59.7 0.0 18.9

220 -- -- -- -- -- -- -- -- --

221 2.5 0.1 12.7 83.3 1.4 Undeveloped 65.6 0.0 38.3

222 1.4 4.1 6.2 80.4 7.9 Undeveloped 63.9 3.0 28.4

223 0.5 17.4 59.2 16.6 6.3 Undeveloped 76.4 0.0 12.2

224 0.8 0.5 48.8 43.2 6.7 Undeveloped 71.4 0.0 30.3

225 1.5 72.5 14.9 9.6 1.5 Agricultural 46.4 18.0 7.9

226 1.1 95.2 0.8 2.6 0.3 Agricultural 50.8 4.0 1.4

227 5.5 23.1 3.7 64.5 3.3 Mixed 53.8 638.5 18.0

228 0.9 12.0 45.6 36.4 5.0 Undeveloped 67.3 130.4 17.3

229 0.4 1.3 1.8 80.6 16.0 Undeveloped 52.0 0.0 34.2

230 2.0 56.1 23.6 17.8 0.4 Agricultural 60.7 0.0 15.1

231 19.8 33.9 0.8 43.3 2.1 Mixed 48.3 159.5 10.5

232 1.2 22.2 0.5 73.3 2.7 Undeveloped 49.4 16.6 16.2

233 2.1 15.0 41.9 36.3 4.7 Undeveloped 67.1 14.8 17.2

234 0.6 1.4 18.7 70.1 9.3 Undeveloped 68.7 0.0 40.5

235 0.1 0.2 12.0 75.1 12.6 Undeveloped 67.5 0.0 41.6

236 0.4 0.8 28.0 65.6 5.2 Undeveloped 68.1 0.0 36.0

237 1.0 5.0 48.8 41.2 4.1 Undeveloped 67.3 0.0 20.3

238 3.5 13.3 7.8 68.6 6.8 Undeveloped 63.0 13.7 24.2

239 -- -- -- -- -- -- -- -- --

240 0.0 0.0 43.7 40.0 16.4 Undeveloped 59.6 0.0 36.5

241 0.3 95.3 3.5 0.0 1.0 Agricultural 27.6 0.0 0.1

242 2.8 4.3 33.9 48.5 10.7 Undeveloped 53.5 0.0 27.9

243 3.1 22.1 34.8 33.8 6.3 Undeveloped 44.5 114.0 20.3

244 2.4 13.0 29.5 52.2 2.8 Undeveloped 55.7 12.0 19.0
Appendix 1 115

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Reference streamflow,

in cubic meters

per second

Mean annual

precipitation,

in centimeters

Median annual source yield, in kilograms per square kilometer

Nitrogen in

atmospheric deposition

Nitrogen

in fertilizer

Nitrogen

in manure

Phosphorus

in fertilizer

Phosphorus

in manure

1 13.70 132.4 480 323 578 55 123

2 5.00 129.4 481 339 221 67 52

3 22.25 131.6 456 369 672 66 168

4 379.66 119.3 497 222 261 48 50

5 0.63 123.2 486 1,281 1,504 215 286

6 16.17 133.1 523 149 109 26 21

7 27.44 131.9 515 392 126 65 25

8 3.15 127.8 486 636 416 108 78

9 2.95 136.5 489 758 870 130 249

10 4.80 131.2 517 720 11 99 2

11 43.66 128.1 564 280 327 50 64

12 10.84 137.1 538 361 274 59 55

13 0.47 136.0 592 295 55 43 12

14 0.87 133.5 592 606 35 84 8

15 91.16 119.5 645 470 828 112 149

16 1.72 129.2 590 1,310 6 213 1

17 0.42 133.2 597 201 19 37 4

18 2.80 135.4 589 361 27 63 5

19 14.48 132.4 607 839 38 154 8

20 1.90 129.3 595 1,872 13 324 3

21 0.47 134.0 586 1,771 3 303 1

22 0.65 131.8 579 1,805 2 309 1

23 0.32 130.3 537 745 314 134 75

24 0.33 125.3 528 1,787 739 324 176

25 6.82 122.9 525 1,652 264 382 61

26 18.39 127.0 536 1,376 369 274 87

27 1.54 124.1 526 1,921 299 384 58

28 5.09 122.5 500 548 51 91 10

29 2.99 117.7 499 727 130 133 27

30 3.47 116.9 499 2,576 360 472 95

31 108.40 121.0 578 126 370 31 73

32 3.94 120.8 569 521 488 125 103

33 240.81 122.9 579 535 344 129 73

34 0.59 119.7 499 2,362 38 408 8

35 0.82 117.8 499 4,569 489 821 142

36 1.89 113.7 508 4,010 1,191 702 322

37 764.53 110.2 596 712 1,296 174 321

38 7.69 114.2 566 1,720 459 343 111

39 13.51 108.6 630 1,899 3,865 466 969

40 213.18 106.8 540 969 2,066 245 582

41 32.46 111.6 486 996 1,485 282 427

42 17.17 110.8 538 857 732 240 216

43 9.31 111.1 505 806 284 224 75

44 147.16 114.6 515 333 688 93 207

45 18.95 112.0 519 622 1,247 177 368

46 0.54 123.3 489 1,262 921 270 238

47 48.43 120.0 507 2,538 1,676 547 657

48 10.21 119.8 498 4,370 3,142 924 1,285

49 49.27 -- -- -- -- -- --

50 67.39 123.4 348 1,420 826 258 249

51 384.30 130.1 412 611 1,170 150 356

52 49.94 125.1 385 383 572 113 163

53 147.53 121.6 365 1,025 521 284 150

54 113.18 122.2 385 495 1,601 139 484

55 336.17 121.7 363 1,007 893 272 270

56 10.70 130.2 302 2,516 1,536 714 484

57 0.86 126.0 356 1,801 593 311 190

58 2.34 140.4 358 2,450 1,605 438 495

59 14.38 134.2 354 3,007 1,925 524 582

60 0.61 137.4 358 5,904 3,236 993 1,046

61 1.60 141.2 357 2,248 1,536 383 486
116 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Reference streamflow,

in cubic meters

per second

Mean annual

precipitation,

in centimeters

Median annual source yield, in kilograms per square kilometer

Nitrogen in

atmospheric deposition

Nitrogen

in fertilizer

Nitrogen

in manure

Phosphorus

in fertilizer

Phosphorus

in manure

62 0.95 136.7 336 2,308 1,474 376 479

63 3.68 136.7 329 1,667 1,221 273 388

64 17.03 133.5 299 63 31 19 9

65 8.10 128.8 308 3,944 721 1,082 211

66 0.92 139.8 425 128 0 30 0

67 115.56 146.3 445 278 2,063 82 642

68 260.33 135.6 385 556 862 139 266

69 168.15 125.7 362 1,646 655 447 185

70 67.45 142.6 504 337 525 92 140

71 47.14 166.7 468 1,558 1,860 179 484

72 0.30 109.0 592 3,287 98 717 26

73 6,996.15 123.8 560 2,021 964 412 290

74 2.66 82.5 405 29 48 7 12

75 0.95 85.9 544 2,941 2,372 642 473

76 10.89 88.3 601 2,147 1,921 480 384

77 0.21 89.9 593 1,480 311 363 58

78 0.90 85.9 562 1,432 629 396 121

79 0.15 87.0 572 1,702 302 394 56

80 3.07 86.9 574 1,604 346 363 65

81 0.15 38.0 173 1,905 274 291 77

82 1.22 41.1 203 2,631 323 386 99

83 0.72 83.0 496 2,960 850 545 185

84 0.75 91.5 608 3,728 2,490 790 562

85 0.09 94.2 604 3,656 2,556 801 545

86 0.04 93.6 577 2,846 1,251 615 293

87 5.14 100.9 516 3,289 1,231 597 400

88 5.06 107.7 519 3,882 1,296 694 412

89 5.13 97.7 603 8,152 388 1,420 130

90 3.85 96.4 644 2,382 9 573 2

91 16.79 93.6 650 2,498 263 491 57

92 0.18 96.8 645 3,170 91 569 22

93 824.87 98.8 589 6,045 630 1,081 219

94 15.97 118.5 559 503 814 89 257

95 8,873.13 65.0 364 2,397 1,029 356 318

96 2.26 33.2 90 2,241 714 442 224

97 0.11 32.1 129 632 209 127 59

98 55.72 35.3 100 560 260 64 76

99 338.31 41.6 120 414 373 59 112

100 510.45 41.3 120 517 365 87 111

101 22.26 47.1 300 915 904 102 274

102 0.33 47.2 321 2,857 469 450 141

103 0.61 48.3 246 254 382 45 108

104 1.29 57.0 262 106 271 14 74

105 0.85 55.4 262 167 324 22 87

106 0.41 39.2 282 1,283 1,964 173 534

107 26.64 51.2 300 672 819 99 221

108 6.03 55.2 397 146 618 17 158

109 3.44 78.2 532 7,645 3,702 860 1,178

110 324.79 51.7 343 2,058 1,139 232 344

111 28.76 92.9 556 4,300 1,805 628 603

112 1,821.07 48.4 254 1,359 792 204 247

113 100.76 98.4 557 2,009 1,493 346 478

114 38.02 102.3 560 1,981 1,503 311 483

115 4.02 116.0 490 1,897 2,939 348 838

116 387.34 113.1 550 2,012 1,620 320 507

117 62.90 119.3 494 1,271 1,663 235 450

118 3,945.46 55.3 301 1,711 894 243 279

119 6.03 126.6 496 6,580 102 896 29

120 1.09 118.0 464 1,402 7,958 173 2,524

121 12.99 127.0 411 325 543 39 164

122 363.03 120.3 444 881 1,939 144 597
Appendix 1 117

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Reference streamflow,

in cubic meters

per second

Mean annual

precipitation,

in centimeters

Median annual source yield, in kilograms per square kilometer

Nitrogen in

atmospheric deposition

Nitrogen

in fertilizer

Nitrogen

in manure

Phosphorus

in fertilizer

Phosphorus

in manure

123 0.63 129.5 384 76 228 10 69

124 13.93 122.4 514 641 794 116 236

125 91.97 126.3 536 430 543 78 161

126 15.65 123.0 572 3,450 502 498 154

127 2.02 126.0 499 6,068 121 825 36

128 0.52 58.9 208 42 91 12 23

129 0.22 57.0 205 87 144 19 42

130 1.64 55.4 208 106 152 32 44

131 3.31 55.0 209 118 147 37 42

132 3.42 49.6 213 166 283 36 83

133 3.70 48.4 213 162 283 35 83

134 20.69 118.2 493 899 3,859 152 1,190

135 16.58 125.3 484 1,638 7,876 226 2,498

136 0.41 123.8 484 1,975 7,786 305 2,447

137 2.78 123.1 485 1,656 6,975 217 2,218

138 24.71 124.7 484 1,481 6,569 199 2,079

139 8.15 129.8 484 1,384 4,074 162 1,271

140 2.21 44.5 211 325 472 38 140

141 4.42 52.8 348 2,196 2,062 249 601

142 6.65 53.5 349 2,229 2,056 254 599

143 10.47 54.1 351 2,228 2,037 256 593

144 15.39 54.4 351 2,221 2,028 256 591

145 1.86 137.8 490 316 2,629 42 818

146 1.60 149.7 483 104 560 12 174

147 1.60 145.3 485 108 470 12 146

148 1.32 137.1 473 494 945 56 292

149 1,188.45 73.0 369 1,594 1,289 187 373

150 66.07 89.0 418 1,825 1,585 204 466

151 793.30 156.7 433 4,266 1,054 469 286

152 132.49 145.4 485 275 1,075 39 338

153 16,338.57 80.1 405 2,215 1,008 342 309

154 26.72 171.3 472 1,899 1,849 205 428

155 7.73 177.3 471 651 746 80 189

156 6,980.76 111.3 410 1,304 1,226 153 358

157 22.17 164.6 433 3,926 750 462 233

158 167.84 133.1 419 968 1,325 108 390

159 11.64 116.0 394 2,109 1,627 231 492

160 35.28 122.4 363 1,271 1,107 141 334

161 1.26 101.8 359 1,521 1,721 164 506

162 0.99 99.9 375 2,982 1,483 319 396

163 141.53 102.9 376 1,965 1,405 225 418

164 2.11 51.7 208 347 502 37 123

165 0.76 75.7 303 772 1,003 81 290

166 6.88 54.4 228 960 581 108 155

167 0.05 89.6 294 222 638 34 191

168 0.08 89.3 295 301 555 50 166

169 0.11 89.8 295 625 603 87 174

170 35.53 61.5 236 926 682 105 191

171 31.98 61.8 237 955 685 109 193

172 7.94 80.0 248 1,085 634 147 188

173 12.90 57.0 179 597 289 79 88

174 27.37 61.4 197 175 317 23 93

175 200.30 61.5 198 175 318 23 93

176 40.17 49.2 104 164 283 18 86

177 40.91 37.1 109 89 176 10 52

178 106.68 42.8 142 98 196 12 56

179 389.40 42.6 143 86 195 12 57

180 0.29 45.5 111 17 47 4 15

181 6.09 40.5 118 30 93 7 28

182 7.54 39.8 116 27 85 6 25

183 9.82 50.0 109 17 122 3 36
118 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Reference streamflow,

in cubic meters

per second

Mean annual

precipitation,

in centimeters

Median annual source yield, in kilograms per square kilometer

Nitrogen in

atmospheric deposition

Nitrogen

in fertilizer

Nitrogen

in manure

Phosphorus

in fertilizer

Phosphorus

in manure

184 15.01 62.4 94 1 40 0 12

185 10.51 53.1 105 11 138 2 40

186 82.21 38.5 123 165 164 26 44

187 9.04 50.8 141 216 545 31 165

188 25.37 59.3 214 447 741 95 194

189 1.55 69.7 136 25 442 5 122

190 4.03 85.2 148 0 88 0 24

191 5.33 80.3 150 42 222 9 54

192 3.78 77.0 153 69 327 16 77

193 1.38 41.6 108 23 116 5 33

194 0.45 131.8 88 0 46 0 12

195 1.09 123.2 87 13 46 2 13

196 1.40 116.6 86 40 50 6 14

197 0.20 107.0 72 128 142 21 35

198 0.08 96.4 69 0 126 0 31

199 0.12 92.0 69 37 104 6 26

200 0.22 91.0 69 80 71 13 18

201 0.01 74.0 71 0 3 0 1

202 0.09 70.6 70 74 63 12 19

203 84.12 213.3 178 765 1,635 79 300

204 404.73 202.5 181 217 211 22 45

205 199.53 219.6 157 148 381 18 79

206 26.82 179.4 130 469 639 72 114

207 17.07 214.1 133 2 39 0 8

208 763.65 -- -- -- -- -- --

209 328.47 168.0 90 1,374 302 176 78

210 264.32 172.4 95 227 109 29 30

211 99.38 167.0 93 66 54 8 15

212 158.52 65.1 102 315 230 38 67

213 529.99 174.1 93 1,768 340 226 84

214 762.85 170.3 125 2,332 452 290 110

215 4,894.24 -- -- -- -- -- --

216 72.70 202.0 123 205 387 24 81

217 9.18 155.1 80 1,893 659 244 177

218 1.56 147.1 233 3,153 521 401 136

219 34.15 57.0 68 26 191 3 60

220 5.84 -- -- -- -- -- --

221 9.21 132.8 110 15 7 3 2

222 110.76 116.3 110 165 33 33 9

223 301.51 52.1 112 1,436 597 284 148

224 19.48 80.5 97 81 129 16 38

225 6.06 57.4 111 3,269 256 375 77

226 0.19 120.7 152 14,477 1,775 1,892 383

227 757.47 170.3 125 2,332 452 290 110

228 6,587.22 68.4 105 752 337 111 90

229 19.57 350.7 109 79 45 8 13

230 7.37 63.7 84 3,620 378 373 112

231 21.27 139.1 186 3,396 530 424 117

232 6.88 167.0 163 1,834 377 240 86

233 73.14 76.1 138 1,402 743 145 185

234 54.59 131.1 165 255 15 27 4

235 52.97 155.3 174 32 9 3 2

236 23.48 90.9 175 44 148 5 46

237 68.39 51.1 162 283 199 29 61

238 122.44 105.7 110 513 101 81 28

239 2,582.28 -- -- -- -- -- --

240 4.81 98.5 204 0 64 0 16

241 0.60 32.3 174 10,687 13,627 1,689 3,063

242 24.03 93.8 203 492 792 79 193

243 97.35 70.9 175 2,426 2,571 380 571

244 627.66 101.7 115 993 337 154 94
Appendix 1 119

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Change in source load from 1993 to 2003, in percent

Population

density

Nitrogen loading from

atmospheric deposition

Nitrogen loading

from fertilizer

Nitrogen loading

from manure

Phosphorus loading

from fertilizer

Phosphorus loading

from manure

1 6.5 –32.0 243.4 –33.8 130.0 –38.1

2 3.1 –36.3 8.3 –31.6 –33.2 –35.1

3 5.2 –31.4 56.1 –44.8 5.3 –54.7

4 2.2 –25.9 19.2 –14.4 –32.5 –10.4

5 4.3 –35.5 295.5 –25.2 146.3 –21.3

6 6.4 –24.0 49.1 –25.2 –6.6 –18.4

7 5.0 –24.6 52.1 –29.5 8.5 –25.0

8 2.6 –25.8 128.2 –26.1 97.1 –22.3

9 16.7 –27.5 170.7 –57.4 51.4 –69.1

10 1.3 –23.5 66.7 –33.3 61.6 –28.5

11 7.1 –22.7 42.9 –21.0 –10.8 –13.5

12 1.4 –27.3 75.8 –30.1 39.6 –22.1

13 7.2 –13.6 86.6 –26.1 81.7 –26.8

14 10.2 –13.5 74.0 –26.2 73.7 –26.9

15 –2.9 –4.2 –27.3 –15.1 –52.7 –6.2

16 2.9 –15.6 2.5 239.6 –17.1 162.4

17 11.8 –12.3 9.9 –29.5 –51.4 –39.9

18 23.1 –16.3 1.0 –34.7 –29.2 –36.8

19 11.3 –13.2 13.3 –43.9 –63.6 –50.5

20 4.8 –12.8 9.6 –95.2 –67.1 –94.8

21 8.8 –16.1 5.3 –73.8 –77.6 –55.9

22 5.4 –21.8 0.9 –79.2 –78.7 –64.6

23 18.8 –19.6 –6.6 –35.4 –48.6 –34.9

24 13.8 –21.4 –5.1 –35.4 –48.0 –34.9

25 29.2 –21.3 –40.9 –27.9 –69.3 –30.4

26 23.5 –20.6 –23.4 –34.3 –70.5 –35.8

27 22.4 –20.4 –24.6 –12.9 –86.1 –15.0

28 27.9 –26.1 77.4 –18.6 8.2 –15.6

29 –5.1 –36.9 –12.3 –17.9 –56.3 –16.3

30 9.4 –33.5 –9.0 –18.6 –58.0 –26.0

31 10.0 –20.0 –20.0 –14.0 –56.6 –1.8

32 10.3 –21.1 –45.0 –32.7 –71.6 –26.8

33 11.1 –17.7 –31.7 –19.1 –59.3 –12.1

34 2.9 –27.5 –2.5 –38.4 –71.6 –35.8

35 52.9 –27.6 –9.0 –10.7 –59.6 –22.9

36 8.6 –26.9 –7.4 14.4 –42.7 12.8

37 3.7 0.9 –12.3 0.5 –57.5 4.6

38 23.8 –23.5 29.0 –34.2 –14.5 –36.9

39 8.3 –1.1 –11.7 20.4 –59.7 31.6

40 21.1 –16.1 3.5 5.1 –34.1 6.7

41 22.7 –26.3 –0.9 –5.0 –16.8 –8.4

42 35.3 –37.3 –2.8 –12.1 –17.5 –12.0

43 30.4 –33.3 3.0 –4.7 –9.6 –4.9

44 8.7 –30.1 –1.4 –5.0 –16.5 –5.6

45 26.7 –36.7 0.8 7.8 –12.2 10.2

46 19.6 9.0 –47.0 –7.8 –19.8 –1.7

47 35.8 8.1 –52.3 61.7 –28.3 70.2

48 18.4 9.6 –52.5 30.5 –30.0 36.4

49 -- -- -- -- -- --

50 13.0 11.8 –11.9 8.0 –23.3 4.2

51 14.3 –20.1 –13.9 41.2 7.7 41.1

52 33.7 17.7 –21.3 1.6 6.2 4.1

53 30.9 6.4 –43.9 9.9 –21.7 10.2

54 28.1 3.8 –27.9 13.9 2.5 14.4

55 28.8 –7.7 –38.5 11.4 –15.0 10.7

56 14.3 –14.3 –43.5 8.4 –16.5 –0.8

57 21.5 –11.5 21.2 3.0 13.5 6.8

58 44.4 –6.9 –5.1 12.1 –10.1 13.2

59 13.6 –11.1 4.8 13.6 –3.9 14.6

60 5.5 –6.5 12.4 –26.2 6.8 –31.3

61 0.0 –7.5 21.5 –7.7 12.9 –10.1
120 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Change in source load from 1993 to 2003, in percent

Population

density

Nitrogen loading from

atmospheric deposition

Nitrogen loading

from fertilizer

Nitrogen loading

from manure

Phosphorus loading

from fertilizer

Phosphorus loading

from manure

62 11.3 –9.1 2.7 –13.5 –6.0 –17.1

63 20.6 –9.2 10.5 –16.8 –4.9 –20.7

64 0.0 –20.7 –39.2 17.4 –2.8 13.0

65 15.2 –20.5 –39.3 –5.0 –9.6 –19.2

66 13.7 18.1 –34.7 –96.3 –85.9 –100.0

67 34.6 –1.5 0.3 –1.0 25.2 –1.1

68 28.1 7.0 –15.3 2.9 8.7 0.9

69 23.7 1.2 –36.8 29.4 –13.2 23.9

70 18.8 4.9 –47.3 13.8 –37.6 –1.4

71 4.8 –21.1 –17.2 32.0 –50.2 51.9

72 30.9 –0.5 20.7 –78.7 –8.2 –84.6

73 8.0 –7.6 –6.6 –1.9 –20.0 –3.7

74 0.0 38.0 –19.0 –27.9 –66.7 –26.4

75 0.0 7.0 13.1 –20.2 –43.9 –21.3

76 2.0 1.8 7.3 –12.6 –49.6 –13.2

77 4.2 3.1 –23.8 –32.7 –54.0 –26.4

78 27.3 7.5 –39.7 6.4 –58.6 10.2

79 4.8 6.0 –27.0 –37.3 –53.1 –31.4

80 5.4 6.4 –26.5 –18.6 –52.4 –14.2

81 0.0 32.9 96.6 20.7 101.4 4.6

82 0.0 25.8 43.7 22.5 56.2 18.4

83 47.9 –7.6 –7.0 –43.4 9.6 –43.6

84 29.4 –0.7 14.3 –24.1 –49.9 –26.9

85 52.2 –1.1 –6.3 –21.0 –60.3 –22.8

86 27.5 –1.5 –16.9 –47.6 –70.3 –51.6

87 0.0 –1.5 24.3 –4.4 21.2 –14.1

88 12.5 –20.8 8.0 –9.7 3.0 –17.2

89 –14.3 –15.4 –16.9 –31.7 –14.6 –35.3

90 5.9 –3.6 –30.2 –63.9 –27.6 –71.4

91 11.1 –2.2 –0.1 –25.0 –29.4 –27.2

92 84.5 0.5 –69.5 –100.0 –35.2 –100.0

93 10.4 –13.4 –23.7 –19.6 –17.1 –23.1

94 7.7 –10.4 –14.1 –0.5 –14.6 –1.5

95 5.6 –4.0 4.2 –3.7 6.7 –4.7

96 –33.3 –3.4 –48.4 –17.7 –41.1 –16.5

97 0.0 22.9 234.2 15.7 181.2 19.1

98 0.0 –5.9 12.0 –11.5 6.6 –8.4

99 0.0 11.0 –9.7 –10.3 –12.6 –8.5

100 0.0 11.6 14.3 –4.9 10.0 –4.7

101 0.0 –4.9 26.5 –3.7 62.8 –4.9

102 –50.0 –6.0 –32.8 –9.7 –22.8 –10.6

103 46.3 –1.5 –5.4 –22.6 –29.6 –27.6

104 20.0 –3.5 –41.0 –21.2 –26.1 –26.6

105 14.8 0.3 –39.3 –21.8 –21.7 –27.3

106 0.0 11.9 –30.9 –10.4 –1.1 –16.1

107 30.7 4.4 –32.1 –19.7 –10.6 –25.3

108 0.0 10.3 144.4 35.6 215.7 6.5

109 0.0 –11.4 –2.0 –6.9 45.9 –8.5

110 28.6 –3.5 –11.4 –0.8 26.9 –6.6

111 0.0 –3.8 4.5 –18.1 6.7 –27.0

112 16.7 1.1 19.4 –2.0 35.1 –4.3

113 0.0 –1.7 18.4 4.6 20.4 1.9

114 0.0 –7.6 13.0 5.5 14.3 5.3

115 28.6 –14.3 2.5 7.0 1.0 10.8

116 16.7 –7.5 9.4 10.7 14.6 12.1

117 8.3 –8.1 16.8 3.3 14.6 8.6

118 14.3 –6.0 14.8 –0.7 32.0 –3.6

119 6.7 10.0 6.6 5.8 25.7 14.1

120 25.0 –16.7 15.8 12.0 33.3 10.7

121 0.0 –17.9 13.0 17.1 23.5 –1.1

122 27.8 –14.1 12.4 9.5 16.7 9.9
Appendix 1 121

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Change in source load from 1993 to 2003, in percent

Population

density

Nitrogen loading from

atmospheric deposition

Nitrogen loading

from fertilizer

Nitrogen loading

from manure

Phosphorus loading

from fertilizer

Phosphorus loading

from manure

123 0.0 –11.8 71.7 8.1 99.4 6.0

124 16.7 –2.0 10.8 8.5 9.7 11.0

125 0.0 2.0 11.1 9.4 9.8 13.4

126 20.0 9.5 12.9 21.1 23.0 15.2

127 10.3 7.4 2.4 12.3 23.0 –3.7

128 16.7 –7.5 –6.1 –40.3 –50.2 –33.2

129 65.9 –6.5 –2.5 –41.0 –38.0 –39.1

130 34.9 –7.3 –1.8 –45.1 –50.1 –43.2

131 26.8 –7.3 –8.9 –45.1 –50.9 –42.9

132 28.5 –7.5 –14.5 –39.8 –41.2 –37.9

133 26.9 –6.9 –17.1 –39.2 –41.3 –37.6

134 50.0 –23.2 40.3 13.2 41.6 9.0

135 47.2 –18.2 16.1 4.2 50.4 2.9

136 25.2 –20.7 2.1 15.3 34.1 14.7

137 30.4 –23.3 4.8 22.8 21.4 23.2

138 45.5 –21.5 17.0 6.8 40.2 5.8

139 30.0 –21.7 –6.7 –11.8 –12.0 –14.2

140 0.0 6.3 11.8 –3.3 –14.5 –11.1

141 0.0 7.6 –10.4 29.8 –25.5 31.5

142 20.0 7.9 –10.1 29.3 –22.7 30.8

143 0.0 8.1 –10.2 29.1 –22.8 30.6

144 7.7 8.2 –10.1 29.1 –22.0 30.6

145 11.1 –18.4 57.3 35.1 77.2 34.3

146 33.3 –18.8 38.8 41.2 43.1 40.7

147 33.3 –16.9 31.7 47.0 28.0 47.0

148 0.0 –10.8 1.6 16.0 –16.1 17.2

149 14.3 –7.4 4.2 11.3 8.7 8.2

150 0.0 3.4 –14.0 14.9 –30.0 12.6

151 –13.5 3.5 102.1 13.3 75.6 –11.1

152 16.7 –18.7 9.7 4.0 33.9 –8.1

153 8.7 –1.0 6.0 –0.4 –0.5 –2.0

154 11.1 –18.3 –8.0 3.4 –30.1 19.3

155 16.7 –17.9 –26.3 –6.0 –41.4 6.9

156 8.3 6.5 0.5 17.9 –12.7 14.3

157 13.7 –0.1 43.8 4.9 25.0 6.2

158 10.0 9.1 –13.9 17.8 –29.6 23.8

159 18.2 10.5 –8.1 3.2 –25.3 4.8

160 14.3 5.2 –13.2 5.9 –26.3 5.7

161 33.3 25.1 –8.2 16.1 –25.7 14.1

162 32.1 9.9 6.5 4.7 –12.2 –3.2

163 29.3 17.7 –5.2 9.9 –22.3 7.4

164 0.0 –4.2 18.8 –40.6 0.2 –38.7

165 0.0 14.0 4.7 –13.9 –9.9 –16.8

166 0.0 –8.1 –20.1 –26.5 –28.3 –27.1

167 100.0 –31.1 –29.9 –8.0 –40.9 –11.3

168 80.6 –31.4 –22.4 –7.8 –42.2 –11.1

169 42.7 –33.1 –6.6 –13.3 –15.6 –16.8

170 23.1 –10.2 –17.1 –17.8 –28.0 –19.6

171 23.1 –10.6 –16.4 –17.2 –27.9 –18.9

172 17.0 –19.8 –14.0 –4.0 –23.4 –15.7

173 0.0 –1.5 –26.4 –20.1 3.0 –37.1

174 40.0 –21.7 –54.3 –31.8 –38.3 –34.3

175 40.0 –21.6 –53.5 –31.4 –37.8 –34.0

176 0.0 –4.1 62.0 –17.4 55.3 –33.2

177 0.0 –19.9 50.1 –24.4 35.8 –32.4

178 0.0 –22.2 17.3 –15.3 15.2 –16.7

179 50.0 –19.1 –36.8 –25.0 –36.1 –27.4

180 100.0 –16.5 –20.8 –19.9 –10.0 –18.8

181 80.0 –0.1 14.3 –15.3 32.5 –15.4

182 100.0 –0.3 13.0 –16.6 28.0 –16.4

183 0.0 18.9 –1.4 –23.5 –15.7 –27.0
122 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Change in source load from 1993 to 2003, in percent

Population

density

Nitrogen loading from

atmospheric deposition

Nitrogen loading

from fertilizer

Nitrogen loading

from manure

Phosphorus loading

from fertilizer

Phosphorus loading

from manure

184 50.0 20.7 –89.0 –63.5 –55.7 –66.5

185 66.7 5.2 –4.6 –23.4 24.3 –41.8

186 50.0 –8.2 –1.6 –19.7 22.6 –26.7

187 0.0 –32.8 –10.6 –10.9 –10.0 –21.7

188 14.3 –50.5 20.0 –6.2 31.8 –9.8

189 100.0 –35.3 –56.0 9.7 –72.7 12.8

190 200.0 –35.0 0.0 –9.7 0.0 –5.2

191 300.0 –35.6 –51.1 –15.8 –63.5 –8.7

192 71.4 –36.3 –32.4 –26.4 –33.9 –19.1

193 0.0 –11.4 –35.2 –3.2 –24.8 –12.8

194 85.7 –14.1 0.0 –4.9 0.0 11.0

195 62.5 –15.1 38.7 –16.0 12.6 –1.5

196 23.8 –16.3 81.8 –18.0 43.3 –3.9

197 18.6 –25.3 17.9 –26.2 7.0 –27.5

198 57.1 –21.6 0.0 –26.1 0.0 –27.6

199 51.6 –21.6 5.3 –26.2 –2.0 –27.4

200 39.1 –22.0 41.1 –26.2 18.9 –27.6

201 133.3 –22.1 0.0 –31.3 0.0 –60.0

202 67.9 –22.9 –1.4 –30.7 –5.9 –42.5

203 29.4 –7.1 –26.0 –1.4 –41.7 5.8

204 16.7 –7.9 –39.6 –23.9 –55.2 –24.7

205 43.5 –11.2 –17.8 –31.5 –27.4 –29.5

206 24.3 –14.0 –21.8 –39.0 –15.8 –35.0

207 100.0 –15.3 –34.8 –23.7 –43.0 –16.9

208 -- -- -- -- -- --

209 13.8 –28.2 18.8 –18.3 –14.3 –21.8

210 11.8 –37.2 19.3 –23.8 –9.7 –27.7

211 0.0 –38.8 23.4 –23.1 –13.3 –26.7

212 50.0 –26.8 46.2 –13.5 15.9 –10.7

213 13.8 –22.8 24.4 –13.7 –10.0 –16.7

214 23.2 –31.5 40.6 –10.8 4.9 –14.9

215 -- -- -- -- -- --

216 26.8 –12.4 5.5 –47.3 –2.9 –52.7

217 13.3 –23.5 24.5 –25.0 –6.3 –29.1

218 17.4 –5.0 31.9 –32.2 15.6 –34.3

219 0.0 –26.0 –15.3 –11.6 –42.9 –12.4

220 -- -- -- -- -- --

221 0.0 10.8 –11.2 –56.2 –37.1 –65.7

222 37.5 8.9 –27.8 –30.5 –7.3 –43.8

223 25.0 –23.5 –13.5 24.8 18.3 12.8

224 20.0 –38.0 2.9 10.7 0.9 5.3

225 10.0 5.8 –21.9 –28.7 –21.3 –41.7

226 10.9 –21.0 52.9 –6.8 15.2 –8.2

227 23.2 –31.5 40.6 –10.8 4.9 –14.9

228 40.0 –12.1 –11.1 4.7 –2.6 –2.2

229 50.0 –25.5 134.1 –2.2 90.2 –3.6

230 7.1 –4.1 –48.1 –10.2 –54.1 –13.9

231 40.0 –6.7 58.2 –21.0 19.2 –25.4

232 0.0 –16.1 69.4 –5.1 32.6 –10.0

233 12.5 –16.8 –10.6 8.5 –28.7 –1.7

234 50.0 –11.5 33.7 –38.0 7.0 –41.8

235 0.0 –12.7 32.9 –38.4 7.7 –42.0

236 0.0 –11.5 –44.9 –9.4 –57.0 –11.2

237 25.0 –12.6 –44.2 –11.0 –56.1 –12.4

238 22.2 7.9 –27.5 –22.0 –14.3 –28.3

239 -- -- -- -- -- --

240 100.0 –1.5 0.0 –2.0 0.0 11.5

241 –42.9 –27.5 68.2 3.6 69.5 –0.2

242 12.5 –3.9 73.5 4.5 67.5 2.3

243 18.2 2.3 60.3 18.0 69.5 16.1

244 13.3 –24.1 37.1 –15.4 35.0 –16.3
Appendix 1 123

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Reference concentration

of total phosphorus,

in milligrams per liter

USEPA recommended

ecoregional

nutrient criteria

for total phosphorus,

in milligrams per liter

Enrichment

ratio for total

phosphorus4

Reference

concentration

of total nitrogen,

in milligrams per liter

USEPA recommended

ecoregional

nutrient criteria

for total nitrogen,

in milligrams per liter

Enrichment

ratio for total

nitrogen4

1 0.021 0.031 0.668 0.603 0.710 0.849

2 0.036 0.031 1.146 0.530 0.710 0.746

3 0.046 0.031 1.464 0.913 0.710 1.286

4 0.033 0.031 1.042 0.624 0.710 0.878

5 0.092 0.031 2.943 4.259 0.710 5.999

6 -- -- -- 0.270 0.710 0.381

7 0.087 0.031 2.796 1.018 0.710 1.434

8 0.364 0.031 11.662 3.480 0.710 4.902

9 -- -- -- 0.436 0.710 0.613

10 0.241 0.031 7.713 3.208 0.710 4.518

11 0.021 0.031 0.665 0.661 0.710 0.931

12 0.227 0.031 7.252 2.492 0.710 3.510

13 0.012 0.031 0.398 0.307 0.710 0.432

14 0.030 0.031 0.970 0.642 0.710 0.904

15 0.034 0.033 1.044 1.048 0.540 1.941

16 0.065 0.031 2.082 1.032 0.710 1.454

17 0.025 0.010 2.493 0.500 0.380 1.315

18 0.120 0.031 3.826 1.537 0.710 2.165

19 0.372 0.037 10.174 3.357 0.690 4.865

20 0.369 0.031 11.800 5.794 0.710 8.161

21 -- -- -- 1.727 0.690 2.503

22 0.071 0.037 1.953 1.407 0.690 2.039

23 -- -- -- 1.090 0.690 1.580

24 0.042 0.037 1.139 1.753 0.690 2.540

25 0.195 0.037 5.339 2.902 0.690 4.207

26 0.160 0.037 4.374 2.316 0.690 3.357

27 0.099 0.031 3.167 -- -- --

28 0.024 0.031 0.763 -- -- --

29 -- -- -- 0.386 0.710 0.544

30 0.014 0.031 0.455 -- -- --

31 0.041 0.010 4.072 0.487 0.380 1.281

32 0.025 0.010 2.527 0.958 0.310 3.089

33 0.057 0.031 1.836 1.277 0.710 1.799

34 0.198 0.031 6.343 0.921 0.710 1.298

35 0.117 0.031 3.738 1.658 0.710 2.336

36 0.045 0.031 1.437 1.457 0.710 2.052

37 0.021 0.037 0.581 1.526 0.690 2.211

38 0.116 0.037 3.174 2.078 0.690 3.012

39 0.114 0.010 11.450 5.429 0.310 17.514

40 0.030 0.037 0.823 2.010 0.690 2.913

41 0.033 0.037 0.897 0.577 0.690 0.836

42 0.066 0.037 1.802 0.653 0.690 0.947

43 0.059 0.037 1.601 0.623 0.690 0.903

44 0.100 0.037 2.743 0.478 0.690 0.692

45 0.047 0.037 1.279 0.587 0.690 0.851

46 0.025 0.037 0.696 0.664 0.690 0.963

47 -- -- -- 1.493 0.690 2.164

48 -- -- -- 1.242 0.690 1.800

49 -- -- -- 1.363 0.690 1.975

50 -- -- -- -- -- --

51 0.093 0.040 2.316 -- -- --

52 0.177 0.037 4.846 1.350 0.690 1.957

53 0.117 0.037 3.195 0.965 0.690 1.398

54 0.135 0.037 3.696 -- -- --

55 0.106 0.040 2.647 -- -- --

56 0.140 0.040 3.489 -- -- --

57 -- -- -- 0.889 0.900 0.987
124 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Reference concentration

of total phosphorus,

in milligrams per liter

USEPA recommended

ecoregional

nutrient criteria

for total phosphorus,

in milligrams per liter

Enrichment

ratio for total

phosphorus4

Reference

concentration

of total nitrogen,

in milligrams per liter

USEPA recommended

ecoregional

nutrient criteria

for total nitrogen,

in milligrams per liter

Enrichment

ratio for total

nitrogen4

58 0.620 0.040 15.493 1.696 0.900 1.884

59 0.940 0.040 23.496 1.780 0.900 1.977

60 0.227 0.040 5.683 0.782 0.900 0.869

61 0.954 0.040 23.854 1.056 0.900 1.173

62 0.807 0.040 20.172 1.693 0.900 1.881

63 0.323 0.040 8.081 -- -- --

64 0.066 0.040 1.652 -- -- --

65 0.150 0.037 4.101 1.005 0.690 1.456

66 0.017 0.037 0.459 -- -- --

67 -- -- -- 1.386 0.690 2.009

68 0.085 0.037 2.331 -- -- --

69 0.049 0.037 1.346 -- -- --

70 0.217 0.010 21.727 -- -- --

71 0.070 0.040 1.745 0.819 0.900 0.910

72 0.024 0.076 0.312 1.079 2.180 0.495

73 0.082 0.037 2.233 1.344 0.690 1.948

74 0.027 0.010 2.663 0.453 0.380 1.192

75 0.134 0.033 4.073 -- -- --

76 0.083 0.033 2.509 1.724 0.540 3.193

77 0.402 0.033 12.188 -- -- --

78 0.070 0.033 2.110 -- -- --

79 0.090 0.033 2.726 -- -- --

80 0.068 0.033 2.056 -- -- --

81 0.424 0.076 5.561 2.076 2.180 0.952

82 0.264 0.076 3.461 1.507 2.180 0.691

83 0.139 0.033 4.217 -- -- --

84 0.149 0.033 4.507 -- -- --

85 0.390 0.033 11.812 -- -- --

86 0.129 0.033 3.916 -- -- --

87 0.102 0.037 2.777 -- -- --

88 0.136 0.037 3.712 -- -- --

89 0.060 0.076 0.780 -- -- --

90 1.019 0.076 13.359 -- -- --

91 0.517 0.076 6.778 -- -- --

92 0.079 0.076 1.038 1.615 2.180 0.741

93 0.264 0.037 7.211 -- -- --

94 0.032 0.010 3.159 -- -- --

95 0.230 0.037 6.303 3.227 0.690 4.677

96 -- -- -- -- -- --

97 0.029 0.067 0.435 0.613 0.880 0.697

98 -- -- -- -- -- --

99 0.075 0.023 3.252 0.606 0.560 1.081

100 -- -- -- 0.193 0.560 0.345

101 0.121 0.023 5.261 0.441 0.560 0.788

102 -- -- -- 1.518 2.180 0.696

103 -- -- -- 3.828 0.880 4.350

104 -- -- -- -- -- --

105 -- -- -- -- -- --

106 0.325 0.067 4.846 9.761 0.880 11.092

107 0.636 0.067 9.487 6.215 0.880 7.063

108 -- -- -- 0.717 0.560 1.280

109 0.207 0.076 2.711 6.015 2.180 2.759

110 0.313 0.076 4.099 2.642 2.180 1.212

111 0.327 0.076 4.290 5.273 2.180 2.419
Appendix 1 125

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Reference concentration

of total phosphorus,

in milligrams per liter

USEPA recommended

ecoregional

nutrient criteria

for total phosphorus,

in milligrams per liter

Enrichment

ratio for total

phosphorus4

Reference

concentration

of total nitrogen,

in milligrams per liter

USEPA recommended

ecoregional

nutrient criteria

for total nitrogen,

in milligrams per liter

Enrichment

ratio for total

nitrogen4

112 0.216 0.076 2.829 3.257 2.180 1.494

113 0.202 0.037 5.530 1.723 0.690 2.498

114 0.207 0.037 5.655 1.607 0.690 2.329

115 0.047 0.010 4.696 0.544 0.310 1.754

116 -- -- -- 0.752 0.310 2.425

117 -- -- -- -- -- --

118 0.187 0.037 5.128 2.025 0.690 2.935

119 -- -- -- -- -- --

120 0.039 0.010 3.884 2.529 0.310 8.157

121 -- -- -- -- -- --

122 -- -- -- -- -- --

123 -- -- -- -- -- --

124 -- -- -- 0.448 0.310 1.446

125 -- -- -- 0.426 0.310 1.375

126 -- -- -- -- -- --

127 -- -- -- -- -- --

128 -- -- -- -- -- --

129 -- -- -- -- -- --

130 -- -- -- -- -- --

131 -- -- -- -- -- --

132 -- -- -- -- -- --

133 -- -- -- -- -- --

134 0.041 0.010 4.078 1.721 0.310 5.550

135 0.112 0.010 11.232 2.523 0.310 8.140

136 0.495 0.010 49.503 6.666 0.310 21.503

137 0.092 0.010 9.206 1.882 0.310 6.070

138 0.063 0.010 6.276 1.723 0.310 5.559

139 0.028 0.010 2.786 1.033 0.310 3.331

140 -- -- -- -- -- --

141 -- -- -- -- -- --

142 -- -- -- -- -- --

143 -- -- -- -- -- --

144 -- -- -- -- -- --

145 0.106 0.010 10.574 0.439 0.310 1.417

146 -- -- -- 0.315 0.310 1.017

147 -- -- -- 0.322 0.310 1.037

148 0.051 0.037 1.384 0.610 0.690 0.885

149 0.081 0.128 0.634 0.842 0.760 1.108

150 0.201 0.037 5.497 0.988 0.690 1.432

151 0.095 0.128 0.746 0.715 0.760 0.941

152 0.041 0.037 1.112 0.312 0.690 0.452

153 0.175 0.128 1.371 2.096 0.760 2.758

154 0.112 0.040 2.793 0.909 0.900 1.010

155 0.074 0.040 1.842 0.873 0.900 0.970

156 0.146 0.128 1.144 1.776 0.760 2.337

157 0.297 0.128 2.317 1.888 0.760 2.484

158 -- -- -- -- -- --

159 -- -- -- -- -- --

160 -- -- -- -- -- --

161 -- -- -- -- -- --

162 -- -- -- -- -- --

163 -- -- -- -- -- --

164 -- -- -- -- -- --

165 0.205 0.037 5.607 -- -- --
126 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Reference concentration

of total phosphorus,

in milligrams per liter

USEPA recommended

ecoregional

nutrient criteria

for total phosphorus,

in milligrams per liter

Enrichment

ratio for total

phosphorus4

Reference

concentration

of total nitrogen,

in milligrams per liter

USEPA recommended

ecoregional

nutrient criteria

for total nitrogen,

in milligrams per liter

Enrichment

ratio for total

nitrogen4

166 0.077 0.023 3.337 -- -- --

167 -- -- -- -- -- --

168 -- -- -- -- -- --

169 0.076 0.067 1.135 -- -- --

170 0.269 0.128 2.104 -- -- --

171 0.291 0.128 2.271 -- -- --

172 -- -- -- -- -- --

173 0.079 0.022 3.592 0.440 0.380 1.157

174 -- -- -- -- -- --

175 -- -- -- -- -- --

176 -- -- -- 0.230 0.380 0.604

177 0.026 0.022 1.167 -- -- --

178 0.062 0.022 2.834 -- -- --

179 -- -- -- 0.368 0.380 0.969

180 0.035 0.022 1.616 -- -- --

181 -- -- -- -- -- --

182 0.106 0.022 4.835 0.841 0.380 2.212

183 0.122 0.022 5.596 -- -- --

184 0.013 0.010 1.302 -- -- --

185 0.023 0.010 2.274 -- -- --

186 0.280 0.022 12.776 -- -- --

187 -- -- -- -- -- --

188 0.188 0.022 8.581 -- -- --

189 -- -- -- -- -- --

190 -- -- -- -- -- --

191 -- -- -- -- -- --

192 -- -- -- -- -- --

193 0.085 0.010 8.492 -- -- --

194 -- -- -- -- -- --

195 -- -- -- -- -- --

196 -- -- -- 0.210 0.120 1.746

197 -- -- -- -- -- --

198 -- -- -- -- -- --

199 -- -- -- 0.304 0.120 2.536

200 -- -- -- -- -- --

201 -- -- -- 0.313 0.120 2.612

202 -- -- -- 0.328 0.120 2.735

203 0.021 0.010 2.098 -- -- --

204 0.015 0.010 1.480 -- -- --

205 0.009 0.010 0.891 -- -- --

206 0.025 0.010 2.523 -- -- --

207 0.005 0.010 0.503 -- -- --

208 0.070 0.047 1.485 0.967 0.310 3.118

209 0.075 0.047 1.599 0.791 0.310 2.553

210 0.046 0.047 0.970 0.430 0.310 1.387

211 0.028 0.047 0.591 -- -- --

212 0.080 0.022 3.657 0.316 0.380 0.831

213 0.064 0.047 1.358 0.912 0.310 2.942

214 0.082 0.047 1.738 1.171 0.310 3.776

215 0.040 0.047 0.855 0.459 0.310 1.479

216 0.036 0.010 3.640 -- -- --

217 0.081 0.047 1.718 1.009 0.310 3.255

218 0.090 0.047 1.910 4.554 0.310 14.689

219 0.041 0.010 4.058 0.293 0.120 2.444
Appendix 1 127

Appendix 1. Study-site characteristics.—Continued

[--, not determined or not applicable; USEPA, U.S. Environmental Protection Agency]

Site

number 

(figure 1)

Reference concentration

of total phosphorus,

in milligrams per liter

USEPA recommended

ecoregional

nutrient criteria

for total phosphorus,

in milligrams per liter

Enrichment

ratio for total

phosphorus4

Reference

concentration

of total nitrogen,

in milligrams per liter

USEPA recommended

ecoregional

nutrient criteria

for total nitrogen,

in milligrams per liter

Enrichment

ratio for total

nitrogen4

220 0.104 0.022 4.742 2.665 0.380 7.013

221 0.011 0.010 1.088 0.230 0.120 1.919

222 0.011 0.010 1.126 0.138 0.120 1.150

223 0.068 0.022 3.100 1.480 0.380 3.896

224 0.083 0.022 3.788 0.565 0.380 1.487

225 0.195 0.022 8.896 1.724 0.380 4.537

226 -- -- -- -- -- --

227 0.061 0.047 1.298 0.781 0.310 2.518

228 0.031 0.010 3.134 0.473 0.120 3.944

229 0.009 0.010 0.943 -- -- --

230 0.112 0.022 5.107 -- -- --

231 0.175 0.047 3.724 2.701 0.310 8.714

232 0.039 0.047 0.832 0.553 0.310 1.784

233 0.102 0.022 4.669 -- -- --

234 0.004 0.022 0.175 -- -- --

235 0.004 0.010 0.444 -- -- --

236 0.003 0.022 0.142 -- -- --

237 0.017 0.022 0.773 -- -- --

238 0.019 0.010 1.873 -- -- --

239 0.011 0.010 1.129 -- -- --

240 -- -- -- -- -- --

241 0.183 0.047 3.890 2.839 0.310 9.160

242 0.074 0.047 1.573 0.378 0.310 1.220

243 0.274 0.047 5.821 2.012 0.310 6.490

244 0.039 0.047 0.828 0.238 0.310 0.768

1

Land use characteristics for the drainage area in the United States.

2

"Other" includes open water, wetlands, tundra, bare rock/sand/clay, perennial ice/snow, quarries/strip mines/gravel pits, and transitional.

3

Agricultural: > 50 percent agricultural land and ≤ 5 percent urban land; Urban: > 25 percent urban land and ≤ 25 percent agricultural land; Undeveloped: 

≤ 5 percent urban land and ≤ 25 percent agricultural land; Mixed - all other combinations of urban, agricultural, and undeveloped land (Gilliom and others, 2006).

4

Enrichment ratio: the reference concentration of total phosphorus or total nitrogen divided by the U.S. Environmental Protection Agency’s recommended 

nutrient criteria (U.S. Environmental Protection Agency, 2002) in the respective ecoregion.
128 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Station

number Station name Streamflowstation number

Reference

streamflow,

in cubic feet

per second

Reference

streamflow,

in cubic meters

per second

1 01122610 Shetucket River at South Windham, Conn. 01122610 483.77 13.70

2 01124000 Quinebaug River at Quinebaug, Conn. 01124000 176.52 5.00

3 01127000 Quinebaug River at Jewett City, Conn. 01127000 785.58 22.25

4 01184000 Connecticut River at Thompsonville, Conn. 01184000 13,407.74 379.66

5 01184490 Broad Brook at Broad Brook, Conn. 01184490 22.38 0.63

6 01188090 Farmington River at Unionville, Conn. 01188090 570.91 16.17

7 01189995 Farmington River at Tariffville, Conn. 01189995 968.91 27.44

8 01192500 Hockanum River near East Hartford, Conn. 01192500 111.30 3.15

9 01193500 Salmon River near East Hampton, Conn. 01193500 104.22 2.95

10 01196500 Quinnipiac River at Wallingford, Conn. 01196500 169.35 4.80

11 01205500 Housatonic River at Stevenson, Conn. 01205500 1,541.71 43.66

12 01208500 Naugatuck River at Beacon Falls, Conn. 01208500 382.89 10.84

13 01208990 Saugatuck River near Redding, Conn. 01208990 16.77 0.47

14 01209710 Norwalk River at Winnipauk, Conn. 01209710 30.79 0.87

15 01357500 Mohawk River at Cohoes, N.Y. 01357500 3,219.33 91.16

16 01377000 Hackensack River at Rivervale, N.J. 01377000 60.63 1.72

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 01382500 14.98 0.42

18 01387500 Ramapo River near Mahwah, N.J. 01387500 98.72 2.80

19 01389500 Passaic River at Little Falls, N.J. 01389500 511.42 14.48

20 01391500 Saddle River at Lodi, N.J. 01391500 67.23 1.90

21 01394500 Rahway River near Springfield, N.J. 01394500 16.72 0.47

22 01395000 Rahway River at Rahway, N.J. 01395000 23.04 0.65

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 01396660 11.42 0.32

24 01398000 Neshanic River at Reaville, N.J. 01398000 11.82 0.33

25 01402000 Millstone River at Blackwells Mills, N.J. 01402000 240.78 6.82

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 01403300 649.45 18.39

27 01408000 Manasquan River at Squankum, N.J. 01408000 54.29 1.54

28 01408500 Toms River near Toms River, N.J. 01408500 179.65 5.09

29 01409500 Batsto River at Batsto, N.J. 01409500 105.60 2.99

30 01411500 Maurice River at Norma, N.J. 01411500 122.56 3.47

31 01438500 Delaware River at Montague, N.J. 01438500 3,828.23 108.40

32 01443500 Paulins Kill at Blairstown, N.J. 01443500 139.02 3.94

33 01463500 Delaware River at Trenton, N.J. 01463500 8,504.29 240.81

34 01467150 Cooper River at Haddonfield, N.J. 01467150 20.86 0.59

35 01477120 Raccoon Creek near Swedesboro, N.J. 01477120 29.02 0.82

36 01491000 Choptank River near Greensboro, Md. 01491000 66.58 1.89

37 01578310 Susquehanna River at Conowingo, Md. 01578310 26,999.08 764.53

38 01594440 Patuxent River near Bowie, Md. 01594440 271.43 7.69

39 01614500 Conococheague Creek at Fairview, Md. 01614500 477.02 13.51

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 01646580 7,528.21 213.18

41 01668000 Rappahannock River near Fredericksburg, Va. 01668000 1,146.30 32.46

42 01673000 Pamunkey River near Hanover, Va. 01673000 606.25 17.17

43 01674500 Mattaponi River near Beulahville, Va. 01674500 328.88 9.31

44 02035000 James River at Cartersville, Va. 02035000 5,196.79 147.16

45 02041650 Appomattox River at Matoaca, Va. 02041650 669.32 18.95

46 02085000 Eno River at Hillsborough, N.C. 02085000 18.93 0.54

47 02089500 Neuse River at Kinston, N.C. 02089500 1,710.44 48.43

48 02091500 Contentnea Creek at Hookerton, N.C. 02091500 360.73 10.21

49 0210215985 Cape Fear River at State Highway 42 near Brickhaven, N.C. 02102500 1,739.98 49.27

50 02175000 Edisto River near Givhans, S.C. 02175000 2,379.70 67.39

51 02198500 Savannah River near Clyo, Ga. 02198500 13,571.33 384.30

52 02213700 Ocmulgee River near Warner Robins, Ga. 02213700 1,763.69 49.94

53 02215500 Ocmulgee River at Lumber City, Ga. 02215500 5,209.86 147.53

54 02223600 Oconee River at Interstate 16, near Dublin, Ga. 02223500 3,996.93 113.18

55 02226010 Altamaha River near Gardi, Ga. 02226000 11,871.78 336.17
Appendix 2 129

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Station

number Station name Streamflowstation number

Reference

streamflow,

in cubic feet

per second

Reference

streamflow,

in cubic meters

per second

56 02226582 Satilla River at GA 15&121, near Hoboken, Ga. 02226500 377.80 10.70

57 02271500 Josephine Creek near De Soto City, Fla. 02271500 30.37 0.86

58 02295420 Payne Creek near Bowling Green, Fla. 02295420 82.79 2.34

59 02296750 Peace River at Arcadia, Fla. 02296750 507.75 14.38

60 02300700 Bullfrog Creek near Wimauma, Fla. 02300700 21.46 0.61

61 02301300 South Prong Alafia River near Lithia, Fla. 02301300 56.53 1.60

62 02302500 Blackwater Creek near Knights, Fla. 02302500 33.69 0.95

63 02303000 Hillsborough River near Zephyrhills, Fla. 02303000 129.96 3.68

64 02314500 Suwannee River at U.S. 441, at Fargo, Ga. 02314500 601.58 17.03

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 02318500 286.14 8.10

66 02335870 Sope Creek near Marietta, Ga. 02335870 32.58 0.92

67 02338000 Chattahoochee River near Whitesburg, Ga. 02338000 4,080.95 115.56

68 02344040 Chattahoochee River near Steam Mill, Ga. 02343801 9,193.59 260.33

69 02353000 Flint River at Newton, Ga. 02353000 5,938.05 168.15

70 02388520 Oostanaula River at Rome, Ga. 02388500 2,381.84 67.45

71 02492000 Bogue Chitto River near Bush, La. 02492000 1,664.91 47.14

72 03353637 Little Buck Creek near Indianapolis, Ind. 03353637 10.49 0.30

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 03611500 247,066.83 6,996.15

74 04063700 Popple River near Fence, Wis. 04063700 93.81 2.66

75 04073468 Green Lake Inlet at County Highway A near Green Lake, Wis. 04073468 33.51 0.95

76 04087000 Milwaukee River at Milwaukee, Wis. 04087000 384.42 10.89

77 0422026250 Northrup Creek at North Greece, N.Y. 0422026250 7.28 0.21

78 04232034 Irondequoit Creek at Railroad Mills near Fishers, N.Y. 04232034 31.78 0.90

79 0423204920 East Branch Allen Creek at Pittsford, N.Y. 0423204920 5.29 0.15

80 0423205025 Irondequoit Creek at Empire Boulevard at Rochester, N.Y. 0423205025 108.46 3.07

81 05114000 Souris River near Sherwood, N. Dak. 05114000 5.18 0.15

82 05120000 Souris River near Verendrye, N. Dak. 05120000 43.14 1.22

83 05287890 Elm Creek near Champlin, Minn. 05287890 25.56 0.72

84 05427718 Yahara River at Windsor, Wis. 05427718 26.54 0.75

85 05427948 Pheasant Branch at Middleton, Wis. 05427948 3.23 0.09

86 054310157 Jackson Creek Tributary near Elkhorn, Wis. 054310157 1.43 0.04

87 05500000 South Fabius River near Taylor, Mo. 05500000 181.50 5.14

88 05514500 Cuivre River near Troy, Mo. 05514500 178.57 5.06

89 05525500 Sugar Creek at Milford, Ill. 05525500 181.04 5.13

90 05531500 Salt Creek at Western Springs, Ill. 05531500 135.94 3.85

91 05532500 Des Plaines River at Riverside, Ill. 05532500 592.90 16.79

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 05540275 6.39 0.18

93 05586100 Illinois River at Valley City, Ill. 05586100 29,129.99 824.87

94 07018100 Big River near Richwoods, Mo. 07018100 563.98 15.97

95 07022000 Mississippi River at Thebes, Ill. 07022000 313,351.60 8,873.13

96 06088500 Muddy Creek at Vaughn, Mont. 06088500 79.97 2.26

97 06178000 Poplar River at International Boundary, Mont. 06178000 3.78 0.11

98 06274300 Bighorn River at Basin, Wyo. 06274300 1,967.85 55.72

99 06329500 Yellowstone River near Sidney, Mont. 06329500 11,947.18 338.31

100 06338490 Missouri River at Garrison Dam, N. Dak. 06338490 18,026.30 510.45

101 06461500 Niobrara River near Sparks, Nebr. 06461500 785.96 22.26

102 06468250 James River above Arrowwood Lake near Kensal, N. Dak. 06468250 11.72 0.33

103 06713500 Cherry Creek at Denver, Colo. 06713500 21.69 0.61

104 06752260 Cache La Poudre River at Fort Collins, Colo. 06752260 45.63 1.29

105 06752280 Cache La Poudre River above Boxelder Creek, near Timnath, Colo. 06752280 30.06 0.85

106 06753990 Lonetree Creek near Greeley, Colo. 06753990 14.55 0.41

107 06754000 South Platte River near Kersey, Colo. 06754000 940.63 26.64

108 06775900 Dismal River near Thedford, Nebr. 06775900 212.97 6.03

109 06800000 Maple Creek near Nickerson, Nebr. 06800000 121.59 3.44

110 06805500 Platte River at Louisville, Nebr. 06805500 11,469.82 324.79
130 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Station

number Station name Streamflowstation number

Reference

streamflow,

in cubic feet

per second

Reference

streamflow,

in cubic meters

per second

111 06817700 Nodaway River near Graham, Mo. 06817700 1,015.57 28.76

112 06818000 Missouri River at St. Joseph, Mo. 06818000 64,310.44 1,821.07

113 06902000 Grand River near Sumner, Mo. 06902000 3,558.24 100.76

114 06905500 Chariton River near Prairie Hill, Mo. 06905500 1,342.71 38.02

115 06921070 Pomme De Terre River near Polk, Mo. 06921070 141.91 4.02

116 06926510 Osage River below St. Thomas, Mo. 06926510 13,678.79 387.34

117 06930800 Gasconade River above Jerome, Mo. 06930800 2,221.23 62.90

118 06934500 Missouri River at Hermann, Mo. 06934500 139,332.46 3,945.46

119 07047942 L'Anguille River near Colt, Ark. 07047942 213.05 6.03

120 07053250 Yocum Creek near Oak Grove, Ark. 07053250 38.63 1.09

121 07056000 Buffalo River near St Joe, Ark. 07056000 458.89 12.99

122 07060500 White River at Calico Rock, Ark. 07060500 12,820.44 363.03

123 07060710 North Sylamore Creek near Fifty Six, Ark. 07060710 22.21 0.63

124 07066110 Jacks Fork above Two River, Mo. 07066000 491.80 13.93

125 07068000 Current River at Doniphan, Mo. 07068000 3,247.85 91.97

126 07077500 Cache River at Patterson, Ark. 07077500 552.80 15.65

127 07077700 Bayou DeView near Morton, Ark. 07077700 71.37 2.02

128 07103700 Fountain Creek near Colorado Springs, Colo. 07103700 18.42 0.52

129 07103780 Monument Creek above North Gate Boulevard at United States Air Force 

Academy, Colo.

07103780 7.68 0.22

130 07105500 Fountain Creek at Colorado Springs, Colo. 07105500 58.03 1.64

131 07105530 Fountain Creek below Janitell Road below Colorado Springs, Colo. 07105530 116.94 3.31

132 07106300 Fountain Creek near Pinon, Colo. 07106300 120.71 3.42

133 07106500 Fountain Creek at Pueblo, Colo. 07106500 130.80 3.70

134 07189000 Elk River near Tiff City, Mo. 07189000 730.81 20.69

135 07195500 Illinois River near Watts, Okla. 07195500 585.65 16.58

136 07195865 Sager Creek near West Siloam Springs, Okla. 07195865 14.52 0.41

137 07196000 Flint Creek near Kansas, Okla. 07196000 98.34 2.78

138 07196500 Illinois River near Tahlequah, Okla. 07196500 872.49 24.71

139 07197000 Baron Fork at Eldon, Okla. 07197000 287.82 8.15

140 07227500 Canadian River near Amarillo, Tex. 07227500 78.12 2.21

141 07239450 North Canadian River near Calumet, Okla. 07239450 156.02 4.42

142 07241000 North Canadian River below Lake Overholser near Oklahoma City, Okla. 07241000 234.81 6.65

143 07241520 North Canadian River at Britton Road at Oklahoma City, Okla. 07241520 369.81 10.47

144 07241550 North Canadian River near Harrah, Okla. 07241550 543.37 15.39

145 07247015 Poteau River at Loving, Okla. 07247015 65.85 1.86

146 07247250 Black Fork below Big Creek near Page, Okla. 07247250 56.66 1.60

147 07247345 Black Fork at Hodgen, Okla. 07247250 56.51 1.60

148 07247650 Fourche Maline near Leflore, Okla. 07247500 46.49 1.32

149 07263620 Arkansas River at David D. Terry Lock and Dam below Little Rock, Ark. 07263450 41,969.83 1,188.45

150 07331000 Washita River near Dickson, Okla. 07331000 2,333.19 66.07

151 07355500 Red River at Alexandria, La. 07355500 28,015.06 793.30

152 07362000 Ouachita River at Camden, Ark. 07362000 4,678.67 132.49

153 07373420 Mississippi River near St Francisville, La. 07373420 576,991.28 16,338.57

154 07375500 Tangipahoa River at Robert, La. 07375500 943.50 26.72

155 07376000 Tickfaw River at Holden, La. 07376000 272.81 7.73

156 07381495 Atchafalaya River at Melville, La. 07381495 246,523.35 6,980.76

157 07386980 Vermilion River at Perry, La. 07386980 782.85 22.17

158 08030500 Sabine River near Ruliff, Tex. 08030500 5,927.29 167.84

159 08032000 Neches River near Neches, Tex. 08032000 411.19 11.64

160 08033500 Neches River near Rockland, Tex. 08033500 1,245.79 35.28

161 08051500 Clear Creek near Sanger, Tex. 08051500 44.48 1.26

162 08064100 Chambers Creek near Rice, Tex. 08064100 35.08 0.99

163 08065350 Trinity River near Crockett, Tex. 08065350 4,997.95 141.53

164 08136500 Concho River at Paint Rock, Tex. 08136500 74.38 2.11
Appendix 2 131

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Station

number Station name Streamflowstation number

Reference

streamflow,

in cubic feet

per second

Reference

streamflow,

in cubic meters

per second

165 08143600 Pecan Bayou near Mullin, Tex. 08143600 26.92 0.76

166 08147000 Colorado River near San Saba, Tex. 08147000 242.83 6.88

167 08155200 Barton Creek at State Highway 71 near Oak Hill, Tex. 08155200 1.84 0.05

168 08155240 Barton Creek at Lost Creek Boulevard near Austin, Tex. 08155240 2.77 0.08

169 08159000 Onion Creek at U.S. Highway 183, Austin, Tex. 08159000 3.92 0.11

170 08162000 Colorado River at Wharton, Tex. 08162000 1,254.86 35.53

171 08162500 Colorado River near Bay City, Tex. 08162500 1,129.38 31.98

172 08181800 San Antonio River near Elmendorf, Tex. 08181800 280.56 7.94

173 08251500 Rio Grande near Lobatos, Colo. 08251500 455.47 12.90

174 09058000 Colorado River near Kremmling, Colo. 09058000 966.42 27.37

175 09163500 Colorado River near Colorado-Utah State Line 09163500 7,073.37 200.30

176 09211200 Green River below Fontenelle Reservoir, Wyo. 09211200 1,418.71 40.17

177 09217010 Green River below Green River, Wyo. 09217000 1,444.65 40.91

178 09261000 Green River at Dinosaur National Monument Utah 149 Crossing, Utah 09261000 3,767.24 106.68

179 09380000 Colorado River at Lees Ferry, Ariz. 09380000 13,751.49 389.40

180 09403600 Kanab Creek at U.S. 89 Crossing, Utah 09403600 10.07 0.29

181 09413500 Virgin River below First Narrows, Utah 09413500 214.94 6.09

182 09415000 Virgin River at Littlefield, Ariz. 09415000 266.28 7.54

183 09448500 Gila River at Head of Safford Valley, near Solomon, Ariz. 09448500 346.76 9.82

184 09498500 Salt River near Roosevelt, Ariz. 09498500 529.91 15.01

185 09508500 Verde River below Tangle Creek, above Horseshoe Dam, Ariz. 09508500 371.09 10.51

186 09522000 Colorado River at Northerly International Boundary, above Morelos 

Dam, Ariz.

09522000 2,903.14 82.21

187 10038000 Bear River below Smiths Fork, near Cokeville, Wyo. 10038000 319.30 9.04

188 10126000 Bear River near Corinne at Utah 83 Crossing, Utah 10126000 895.81 25.37

189 10131000 Chalk Creek at U.S. 189 Crossing, Utah 10131000 54.87 1.55

190 10154200 Provo River above Woodland at U.S. Geological Survey Gage 

Number 10154200, Utah

10154200 142.47 4.03

191 10155000 Provo River at Bridge 2.5 miles East of Hailstone Junction, Utah 10155000 188.18 5.33

192 10155500 Provo River above Confluence with Snake Creek at McKeller Bridge, Utah 10155500 133.64 3.78

193 10189000 East Fork Sevier River at Utah 62 Crossing East of Kingston, Utah 10189000 48.66 1.38

194 10336580 Upper Truckee River at South Upper Truckee Road near Meyers, Calif. 10336580 16.00 0.45

195 103366092 Upper Truckee River at Highway 50 above Meyers, Calif. 103366092 38.45 1.09

196 10336610 Upper Truckee River at South Lake Tahoe, Calif. 10336610 49.56 1.40

197 10336698 Third Creek near Crystal Bay, Nev. 10336698 7.08 0.20

198 103366993 Incline Creek above Tyrol Village near Incline Village, Nev. 103366993 2.96 0.08

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 103366995 4.23 0.12

200 10336700 Incline Creek near Crystal Bay, Nev. 10336700 7.69 0.22

201 10336740 Logan House Creek near Glenbrook, Nev. 10336740 0.21 0.01

202 10336760 Edgewood Creek at Stateline, Nev. 10336760 3.31 0.09

203 01A050 Nooksack River at Brennan, Wash. 01A050 2,970.69 84.12

204 03A060 Skagit River near Mount Vernon, Wash. 03A060 14,292.96 404.73

205 07A090 Snohomish River at Snohomish, Wash. 07A090 7,046.18 199.53

206 09A080 Green River at Tukwila, Wash. 09A080 947.25 26.82

207 09A190 Green River at Kanaskat, Wash. 09A190 602.74 17.07

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 10332 26,967.94 763.65

209 10350 Willamette River at Eastbound Highway 20 Bridge at Albany, Oreg. 10350 11,599.72 328.47

210 10355 Willamette River at Highway 99 East at Harrisburg, Oreg. 10355 9,334.51 264.32

211 10386 Middle Fork Willamette at Jasper Bridge, Oreg. 10386 3,509.56 99.38

212 10411 Deschutes River at Deschutes River Park, Oreg. 10411 5,597.93 158.52

213 10555 Willamette River at Marion Street at Salem, Oreg. 10555 18,716.49 529.99

214 10611 Willamette River at Hawthorne Bridge, Oreg. 10611 26,939.66 762.85

215 10616 Columbia River at Marker number 47 upstream of Willamette River, Oreg. 10616 172,838.33 4,894.24

216 10A070 Puyallup River at Meridian Street, Wash. 10A070 2,567.46 72.70

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 11140 324.20 9.18
132 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Station

number Station name Streamflowstation number

Reference

streamflow,

in cubic feet

per second

Reference

streamflow,

in cubic meters

per second

218 11321 Johnson Creek at Southeast 17th Avenue at Portland, Oreg. 11321 55.11 1.56

219 11478 John Day River at Service Creek, Oreg. 11478 1,206.16 34.15

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. 11489 206.29 5.84

221 12413470 South Fork Coeur D'Alene River near Pinehurst, Idaho 12413470 325.10 9.21

222 12419000 Spokane River near Post Falls, Idaho 12419000 3,911.28 110.76

223 13154500 Snake River at King Hill, Idaho 13154500 10,647.62 301.51

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 13206000 687.95 19.48

225 13351000 Palouse River at Hooper, Wash. 13351000 214.15 6.06

226 14201300 Zollner Creek near Mt. Angel, Oreg. 14201300 6.56 0.19

227 14211720 Willamette River at Portland, Oreg. 14211720 26,749.77 757.47

228 14246900 Columbia River at Beaver Army Terminal near Quincy, Oreg. 14246900 232,625.53 6,587.22

229 16A070 Skokomish River near Potlatch, Wash. 16A070 691.14 19.57

230 32A070 Walla Walla River near Touchet, Wash. 32A070 260.41 7.37

231 3701002 Tualatin River at Weiss Bridge, Oreg. 3701002 751.09 21.27

232 37016120 Tualatin River at Springhill Road Bridge at Dilley, Oreg. 3701612 243.03 6.88

233 37A090 Yakima River at Kiona, Wash. 37A090 2,582.89 73.14

234 45A070 Wenatchee River at Wenatchee, Wash. 45A070 1,927.84 54.59

235 45A110 Wenatchee River near Leavenworth, Wash. 45A110 1,870.50 52.97

236 48A070 Methow River near Pateros, Wash. 48A070 829.26 23.48

237 49A070 Okanogan River at Malott, Wash. 49A070 2,415.34 68.39

238 54A120 Spokane River at Riverside State Park, Wash. 54A120 4,323.99 122.44

239 61A070 Columbia River at Northport, Wash. 61A070 91,192.51 2,582.28

240 11264500 Merced River at Happy Isles Bridge near Yosemite, Calif. 11264500 169.70 4.81

241 11274538 Orestimba Creek at River Road near Crows Landing, Calif. 11274538 21.35 0.60

242 11290000 Tuolumne River at Modesto, Calif. 11290000 848.47 24.03

243 11303500 San Joaquin River near Vernalis, Calif. 11303500 3,437.77 97.35

244 11447650 Sacramento River at Freeport, Calif. 11447650 22,165.47 627.66
Appendix 2 133

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Trend, in percent from 1993 to 2003 Properties of the calibration data set

Modeled

estimate

Upper

95-percent CI

Lower

95-percent CI Start date End date Number ofobservations

1 –20.09 35.75 –52.96 10/1/1992 9/30/2003 4,017

2 –24.00 36.50 –57.68 10/1/1992 9/30/2003 4,017

3 –3.74 63.17 –43.21 10/1/1992 9/30/2003 4,017

4 –10.12 25.25 –35.51 10/1/1992 9/30/2003 4,017

5 –18.36 15.06 –42.07 10/1/1992 9/30/2003 4,017

6 –24.01 16.08 –50.25 10/1/1992 9/30/2003 4,017

7 –25.45 13.76 –51.15 10/1/1992 9/30/2003 4,017

8 –21.67 12.63 –45.52 10/1/1992 9/30/2003 4,017

9 –11.31 56.45 –49.72 10/1/1992 9/30/2003 4,017

10 –7.19 39.65 –38.32 10/1/1992 9/30/2003 4,017

11 –4.82 86.90 –51.53 10/1/1992 9/30/2003 4,017

12 –13.16 35.79 –44.46 10/1/1992 9/30/2003 4,017

13 17.58 164.94 –47.82 10/1/1992 9/30/2003 4,017

14 –0.88 93.23 –49.16 10/1/1992 9/30/2003 4,017

15 23.29 89.21 –19.66 10/1/1992 9/30/2003 4,017

16 –23.87 20.21 –51.78 10/1/1992 9/30/2003 4,017

17 –46.63 100.42 –85.79 10/1/1992 9/30/2003 4,000

18 14.67 151.39 –47.69 10/1/1992 9/30/2003 4,017

19 –18.58 139.20 –72.29 10/1/1992 9/30/2003 4,017

20 4.46 81.35 –39.83 10/1/1992 9/30/2003 4,017

21 17.68 78.33 –22.34 10/1/1992 9/30/2003 4,017

22 10.34 89.87 –35.87 10/1/1992 9/30/2003 4,017

23 4.20 93.78 –43.97 10/1/1992 9/30/2003 4,017

24 3.03 175.69 –61.50 10/1/1992 9/30/2003 3,938

25 –14.34 37.97 –46.82 10/1/1992 9/30/2003 4,017

26 –17.31 43.06 –52.20 10/1/1992 9/30/2003 4,017

27 –16.44 25.75 –44.48 10/1/1992 9/30/2003 4,017

28 –10.02 31.26 –38.31 10/1/1992 9/30/2003 4,017

29 –23.58 13.30 –48.46 10/1/1992 9/30/2003 4,017

30 1.18 76.11 –41.87 10/1/1992 9/30/2003 4,017

31 6.27 63.49 –30.92 10/1/1992 9/30/2003 4,017

32 –20.60 65.47 –61.90 10/1/1992 9/30/2003 4,017

33 0.93 63.68 –37.76 10/1/1992 9/30/2003 4,017

34 –28.62 –3.38 –47.26 10/1/1992 9/30/2003 4,017

35 –12.68 38.60 –44.98 10/1/1992 9/30/2003 4,017

36 43.84 332.25 –52.13 10/1/1992 9/30/2003 4,017

37 –21.03 32.07 –52.78 10/1/1992 9/30/2003 4,017

38 1.20 92.75 –46.87 10/1/1992 9/30/2003 4,017

39 –38.33 33.36 –71.48 10/1/1992 9/30/2003 4,017

40 –25.99 108.51 –73.73 10/1/1992 9/30/2003 4,017

41 –42.69 73.75 –81.09 10/1/1992 9/30/2003 4,017

42 –46.94 59.54 –82.35 10/1/1992 9/30/2003 4,017

43 –53.89 96.74 –89.19 10/1/1992 9/30/2003 4,017

44 –34.78 38.64 –69.32 10/1/1992 9/30/2003 4,017

45 –36.08 99.23 –79.49 10/1/1992 9/30/2003 4,017

46 0.82 201.95 –66.34 10/1/1992 9/30/2003 4,017

47 23.45 172.20 –44.01 10/1/1992 9/30/2003 4,016

48 52.67 283.87 –39.28 10/1/1992 9/30/2003 4,015

49 –6.35 101.73 –56.52 10/1/1992 9/30/2003 4,017

50 –51.00 18.36 –79.71 10/1/1992 9/30/2003 4,017

51 –51.95 –5.97 –75.45 10/1/1992 9/30/2003 4,017

52 –40.36 –4.21 –62.87 10/10/1992 9/30/2003 2,527

53 –47.60 14.40 –76.00 10/1/1992 9/30/2003 4,017

54 –59.99 –9.57 –82.30 10/1/1992 9/30/2003 4,017

55 –51.45 23.90 –80.98 10/1/1992 9/30/2003 4,017

56 –68.11 73.46 –94.14 10/1/1992 9/30/2003 4,017

57 –3.83 270.94 –75.07 10/1/1992 9/30/2003 4,017

58 –41.53 119.85 –84.45 10/1/1992 9/30/2003 4,017

59 –35.78 183.72 –85.46 10/1/1992 9/30/2003 4,017

60 –25.78 42.03 –61.22 10/1/1992 9/30/2003 4,013

61 –41.87 211.34 –89.15 10/1/1992 9/30/2003 3,983
134 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Trend, in percent from 1993 to 2003 Properties of the calibration data set

Modeled

estimate

Upper

95-percent CI

Lower

95-percent CI Start date End date Number ofobservations

62 –59.09 112.22 –92.11 10/1/1992 9/30/2003 3,926

63 –14.21 127.43 –67.64 10/1/1992 9/30/2003 4,017

64 –83.56 –22.23 –96.52 10/1/1992 9/30/2003 4,017

65 –18.20 339.98 –84.79 6/1/1993 9/30/2003 3,774

66 –37.34 7.60 –63.51 10/1/1992 9/30/2003 4,017

67 –48.48 –10.88 –70.22 10/1/1992 9/30/2003 4,017

68 –28.21 21.34 –57.53 10/1/1992 9/30/2003 4,017

69 –46.12 4.10 –72.11 10/1/1992 9/30/2003 4,017

70 –11.15 55.96 –49.38 10/1/1992 9/30/2003 4,017

71 –31.18 5.95 –55.29 10/1/1992 9/30/2003 4,017

72 –47.86 28.18 –78.79 10/1/1992 9/30/2003 3,495

73 –18.06 20.92 –44.47 10/1/1992 9/30/2003 4,017

74 –35.22 –9.96 –53.39 10/1/1992 9/30/2003 4,017

75 –44.81 7.95 –71.79 10/1/1992 9/30/2003 4,009

76 –29.12 6.87 –52.99 10/1/1992 9/30/2003 4,017

77 58.64 165.31 –5.14 10/1/1992 9/30/2003 4,017

78 –26.71 –1.44 –45.51 10/1/1992 9/30/2003 4,017

79 –20.40 19.78 –47.10 10/1/1992 12/31/2002 3,744

80 –20.92 9.11 –42.69 10/1/1992 12/31/2002 3,744

81 935.99 9,496.68 11.84 10/1/1992 9/30/2003 3,935

82 84.53 678.32 –56.25 10/1/1992 9/30/2003 4,017

83 –60.06 8.68 –85.32 10/1/1992 9/30/2003 4,017

84 –36.21 –19.03 –49.74 10/1/1992 9/30/2003 4,017

85 –9.68 23.68 –34.05 10/1/1992 9/30/2003 4,017

86 –8.53 67.45 –50.03 10/1/1992 9/30/2003 4,017

87 –85.60 –55.45 –95.34 10/1/1992 9/30/2003 4,017

88 –61.49 23.05 –87.95 10/1/1992 9/30/2003 4,017

89 –56.05 39.65 –86.17 10/1/1992 9/30/2003 4,017

90 –3.42 30.52 –28.54 10/1/1992 9/30/2003 4,017

91 –21.88 14.94 –46.91 10/1/1992 9/30/2003 4,017

92 –40.47 22.19 –71.00 10/1/1992 9/30/2003 4,016

93 –59.42 –31.58 –75.93 10/1/1992 9/30/2003 4,017

94 –61.09 –33.55 –77.21 10/1/1992 9/30/2003 4,017

95 –54.17 –35.15 –67.62 10/1/1992 9/30/2003 4,017

96 –8.24 10.67 –23.92 10/1/1992 9/30/2003 4,017

97 –17.28 140.85 –71.59 10/1/1992 9/30/2003 2,615

98 –54.76 –9.76 –77.32 10/1/1992 9/30/2003 4,017

99 –49.57 –21.70 –67.52 10/1/1992 9/30/2003 4,017

100 10.16 102.10 –39.96 10/1/1992 9/30/2003 4,017

101 –5.33 6.04 –15.49 10/1/1992 9/30/2003 4,017

102 127.28 1,477.31 –67.25 11/11/1992 9/30/2003 3,839

103 40.29 158.97 –24.00 10/1/1992 9/30/2003 4,017

104 –43.47 70.82 –81.29 10/1/1992 9/30/2003 4,017

105 –62.36 74.41 –91.88 10/1/1992 9/30/2003 4,017

106 –93.30 –80.20 –97.74 3/17/1993 9/30/2003 1,546

107 –46.40 10.26 –73.95 10/1/1992 9/30/2003 4,017

108 6.81 12.00 1.85 10/1/1992 9/30/2003 4,017

109 –71.28 –42.92 –85.55 10/1/1992 9/30/2003 4,017

110 –61.40 –44.36 –73.23 10/1/1992 9/30/2003 4,017

111 –90.02 –74.40 –96.11 10/1/1992 9/30/2003 4,017

112 –43.38 –20.12 –59.87 10/1/1992 9/30/2003 4,017

113 –89.05 –63.62 –96.71 10/1/1992 9/30/2003 4,017

114 –88.81 –61.04 –96.79 10/1/1992 9/30/2003 4,017

115 –72.43 –30.84 –89.01 10/1/1992 9/30/2003 4,017

116 –84.61 –56.94 –94.50 10/1/1992 9/30/2003 4,017

117 –67.50 –44.51 –80.97 10/1/1992 9/30/2003 4,017

118 –63.20 –43.52 –76.02 10/1/1992 9/30/2003 4,017

119 52.18 217.98 –27.17 10/1/1992 9/30/2003 4,017

120 –58.98 –36.26 –73.60 4/15/1993 9/30/2003 3,821

121 –49.76 0.41 –74.86 10/1/1992 9/30/2003 4,017

122 –68.03 –42.08 –82.35 10/1/1992 9/30/2003 4,017
Appendix 2 135

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Trend, in percent from 1993 to 2003 Properties of the calibration data set

Modeled

estimate

Upper

95-percent CI

Lower

95-percent CI Start date End date Number ofobservations

123 –55.02 –24.15 –73.33 10/1/1992 9/30/2003 4,017

124 –53.92 –32.31 –68.64 10/1/1992 9/30/2003 4,017

125 –48.45 –29.10 –62.52 10/1/1992 9/30/2003 4,017

126 –19.39 81.46 –64.19 10/1/1996 9/30/2003 2,257

127 189.77 832.53 –9.96 10/1/1997 9/30/2003 1,958

128 –46.90 37.19 –79.44 10/1/1992 9/30/2003 4,017

129 –14.33 116.13 –66.04 10/1/1992 9/30/2003 4,017

130 –30.06 86.76 –73.81 10/1/1992 9/30/2003 4,017

131 –10.10 62.13 –50.15 10/1/1992 9/30/2003 4,017

132 4.53 134.55 –53.41 10/1/1992 9/30/2003 4,017

133 –2.33 120.06 –56.65 10/1/1992 9/30/2003 4,017

134 –64.28 –35.45 –80.23 10/1/1992 9/30/2003 4,017

135 –48.67 –18.72 –67.59 10/1/1992 9/30/2003 4,017

136 –20.34 40.30 –54.78 9/12/1996 9/30/2003 2,574

137 –51.59 –18.07 –71.40 10/1/1992 9/30/2003 4,017

138 –50.46 –18.63 –69.83 10/1/1992 9/30/2003 4,017

139 –62.23 –33.05 –78.69 10/1/1992 9/30/2003 4,017

140 –82.32 –27.94 –95.66 10/1/1992 9/30/2003 3,866

141 –35.88 129.54 –82.09 10/1/1992 9/30/2003 4,017

142 –78.87 21.32 –96.32 10/1/1992 9/30/2003 4,017

143 –55.77 19.54 –83.64 10/1/1992 9/30/2003 4,017

144 –47.86 2.36 –73.44 10/1/1992 9/30/2003 4,017

145 –33.36 67.93 –73.55 10/1/1992 9/30/2003 4,015

146 –59.00 41.80 –88.15 10/1/1992 9/30/2003 3,643

147 –59.00 41.80 –88.15 10/1/1992 9/30/2003 3,643

148 –68.28 –12.35 –88.52 10/1/1992 9/30/2003 3,930

149 –61.89 –16.38 –82.63 10/1/1992 9/30/2003 4,017

150 –72.26 –45.80 –85.80 10/1/1992 9/30/2003 4,017

151 –16.56 64.45 –57.66 10/1/1992 9/30/2003 3,892

152 –15.66 57.59 –54.86 10/1/1992 9/30/2003 4,017

153 –33.22 –9.58 –50.67 10/1/1992 9/30/2003 4,017

154 –29.02 13.68 –55.68 10/1/1992 9/30/2003 4,017

155 –37.56 –0.96 –60.64 10/1/1992 9/30/2003 4,017

156 –34.21 –11.91 –50.86 10/1/1992 9/30/2003 4,017

157 4.35 100.34 –45.65 10/1/1992 9/30/2003 3,358

158 –9.30 114.59 –61.66 10/1/1992 9/30/2003 4,017

159 –20.75 91.41 –67.19 10/1/1992 9/30/2003 4,017

160 –8.84 155.19 –67.44 10/1/1992 9/30/2003 4,017

161 –90.37 9.92 –99.16 10/1/1992 9/30/2003 3,464

162 –17.89 596.90 –90.33 10/1/1992 9/30/2003 3,724

163 –43.85 22.10 –74.18 10/1/1992 9/30/2003 4,017

164 –98.97 –96.44 –99.70 10/1/1992 9/30/2003 3,189

165 –45.27 80.44 –83.40 10/1/1992 9/30/2003 3,963

166 –53.55 5.81 –79.61 10/1/1992 9/30/2003 4,017

167 453.02 11,365.96 –73.33 10/1/1992 9/30/2003 3,423

168 279.80 4,489.77 –68.57 10/1/1992 9/30/2003 3,890

169 455.32 3,367.86 –11.07 10/1/1992 9/30/2003 3,238

170 35.94 224.70 –43.09 10/1/1992 9/30/2003 4,017

171 12.32 211.47 –59.50 10/1/1992 9/30/2003 4,017

172 67.48 218.94 –12.06 10/1/1992 9/30/2003 4,017

173 –81.28 –29.61 –95.02 10/1/1992 9/30/2003 4,017

174 –35.18 7.93 –61.07 10/1/1992 9/30/2003 4,017

175 –55.41 –26.99 –72.77 10/1/1992 9/30/2003 4,017

176 –34.67 18.22 –63.89 10/1/1992 9/30/2003 4,017

177 –37.33 23.63 –68.23 10/1/1992 9/30/2003 4,017

178 –40.94 2.99 –66.13 10/1/1992 9/30/2003 4,017

179 –7.28 40.07 –38.62 10/1/1992 9/30/2003 4,017

180 –37.81 –17.94 –52.86 10/1/1992 9/30/2003 4,017

181 –74.85 –43.69 –88.76 10/1/1992 9/30/2003 4,017

182 –63.34 –35.27 –79.23 10/1/1992 9/30/2003 4,017

183 –66.40 –18.62 –86.13 10/1/1992 9/30/2003 4,017
136 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Trend, in percent from 1993 to 2003 Properties of the calibration data set

Modeled

estimate

Upper

95-percent CI

Lower

95-percent CI Start date End date Number ofobservations

184 –63.86 –11.16 –85.30 10/1/1992 9/30/2003 4,017

185 –54.20 –26.76 –71.36 10/1/1992 9/30/2003 4,017

186 –23.84 46.47 –60.40 10/1/1992 9/30/2003 4,017

187 –47.38 50.22 –81.57 10/1/1992 9/30/2003 3,771

188 –29.35 250.61 –85.76 10/1/1992 9/30/2003 4,017

189 –53.57 4.23 –79.32 10/1/1992 9/30/2003 4,017

190 –37.45 –9.13 –56.95 10/1/1992 9/30/2003 4,017

191 –46.37 –12.59 –67.10 10/1/1992 9/30/2003 4,017

192 84.10 242.36 –1.00 10/1/1992 9/30/2003 4,017

193 –21.32 18.71 –47.85 10/1/1992 9/30/2003 4,017

194 –36.45 60.70 –74.87 10/1/1992 9/30/2003 4,017

195 –29.28 90.85 –73.80 10/1/1992 9/30/2003 4,017

196 –37.31 121.64 –82.27 10/1/1992 9/30/2003 4,017

197 –45.98 34.05 –78.23 10/1/1992 9/30/2003 4,017

198 4.75 291.76 –71.99 10/1/1992 9/30/2003 4,017

199 –13.03 235.54 –77.46 10/1/1992 9/30/2003 4,017

200 –37.05 50.64 –73.69 10/1/1992 9/30/2003 4,017

201 108.69 1,442.99 –71.77 10/1/1992 9/30/2003 4,017

202 23.04 240.54 –55.54 10/1/1992 9/30/2003 4,017

203 5.89 51.03 –25.76 10/1/1992 9/30/2003 4,017

204 0.62 42.81 –29.11 10/1/1992 9/30/2003 4,017

205 –0.96 49.78 –34.50 10/1/1992 9/30/2003 4,017

206 –11.36 41.13 –44.32 10/1/1992 9/30/2003 4,017

207 –12.83 42.44 –46.65 10/1/1992 9/30/2003 4,017

208 –15.07 32.23 –45.45 10/1/1992 9/30/2003 4,017

209 –15.28 33.55 –46.26 10/1/1992 9/30/2003 4,017

210 –11.27 36.57 –42.35 10/1/1992 9/30/2003 4,017

211 –8.72 40.64 –40.75 10/1/1992 9/30/2003 4,017

212 0.20 35.51 –25.91 10/1/1992 9/30/2003 4,017

213 –15.02 32.63 –45.55 10/1/1992 9/30/2003 4,017

214 –15.07 32.23 –45.45 10/1/1992 9/30/2003 4,017

215 –7.19 43.70 –40.06 10/1/1992 9/30/2003 4,017

216 10.27 55.78 –21.94 10/1/1992 9/30/2003 4,017

217 –26.08 35.80 –59.77 10/1/1992 9/30/2003 4,017

218 –22.97 23.38 –51.91 10/1/1992 9/30/2003 4,017

219 –45.76 5.22 –72.04 10/1/1992 9/30/2003 4,017

220 21.56 115.88 –31.55 10/1/1992 9/30/2003 4,017

221 –2.39 81.63 –47.54 10/1/1992 9/30/2003 4,017

222 –12.79 70.84 –55.48 10/1/1992 9/30/2003 4,017

223 –20.44 33.54 –52.60 10/1/1992 9/30/2003 4,017

224 –0.64 166.07 –62.90 10/1/1992 9/30/2003 4,017

225 24.77 259.47 –56.69 10/1/1992 9/30/2003 4,017

226 –45.62 20.68 –75.50 10/1/1993 9/30/2003 3,652

227 –15.07 32.23 –45.45 10/1/1992 9/30/2003 4,017

228 –12.72 31.75 –42.18 10/1/1992 9/30/2003 4,017

229 11.40 66.53 –25.49 10/1/1992 9/30/2003 4,017

230 –4.11 60.90 –42.85 10/1/1992 9/30/2003 4,017

231 2.58 97.90 –46.83 10/1/1992 9/30/2003 4,017

232 14.16 110.47 –38.08 10/1/1992 9/30/2003 4,017

233 11.07 141.37 –48.89 10/1/1992 9/30/2003 4,017

234 –4.41 89.86 –51.88 10/1/1992 9/30/2003 4,017

235 –4.41 89.86 –51.88 10/1/1992 9/30/2003 4,017

236 –16.02 51.52 –53.46 10/1/1992 9/30/2003 4,017

237 –37.95 19.28 –67.72 10/1/1992 9/30/2003 4,017

238 –6.57 77.83 –50.91 10/1/1992 9/30/2003 4,017

239 2.06 39.37 –25.26 10/1/1992 9/30/2003 4,017

240 –45.22 40.19 –78.60 10/1/1992 9/30/2003 4,017

241 –20.65 103.40 –69.04 10/1/1992 9/30/2003 3,898

242 –21.12 184.87 –78.16 10/1/1992 9/30/2003 4,017

243 –17.66 141.06 –71.88 10/1/1992 9/30/2003 4,017

244 –5.87 65.43 –46.44 10/1/1992 9/30/2003 4,017
Appendix 2 137

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Properties of the calibrated model

Intercept Time

coefficient

Standard error

of the intercept

Standard error of

the time coefficient

Degrees

of freedom

Log likelihood

statistic t statistic p-value ARMA 6p-value1

1 6.0792 –0.0204 0.0790 0.0246 3980 –366.8 –0.830 0.407 0.065

2 5.0466 –0.0250 0.0875 0.0272 3980 –129.7 –0.919 0.358 0.148

3 6.6524 –0.0035 0.0788 0.0245 3980 –847.5 –0.142 0.887 0.012

4 9.4572 –0.0097 0.0492 0.0154 3980 885.5 –0.630 0.529 0.005

5 3.0310 –0.0184 0.0512 0.0159 3980 –527.5 –1.159 0.247 0.589

6 6.2314 –0.0250 0.0631 0.0197 3980 179.9 –1.270 0.204 0.063

7 6.7466 –0.0267 0.0630 0.0196 3980 964.1 –1.362 0.173 0.157

8 4.5983 –0.0222 0.0543 0.0169 3980 –957.3 –1.318 0.188 0.100

9 4.5979 –0.0109 0.0847 0.0263 3980 –1,757.1 –0.414 0.679 0.023

10 5.1062 –0.0068 0.0609 0.0190 3980 –1,088.9 –0.358 0.720 0.519

11 7.3322 –0.0045 0.1007 0.0313 3980 –4,873.4 –0.144 0.886 0.000

12 5.8850 –0.0128 0.0664 0.0207 3980 –1,355.1 –0.619 0.536 0.294

13 2.9353 0.0147 0.1216 0.0377 3980 –1,680.7 0.391 0.696 0.504

14 3.4490 –0.0008 0.0998 0.0310 3980 –1,822.4 –0.026 0.979 0.631

15 8.1963 0.0190 0.0636 0.0199 3980 –1,573.4 0.958 0.338 0.013

16 4.0000 –0.0248 0.0680 0.0212 3980 –1,393.5 –1.170 0.242 0.007

17 2.4808 –0.0571 0.1988 0.0614 3963 –2,680.5 –0.930 0.352 0.270

18 4.6586 0.0125 0.1175 0.0364 3980 –1,653.4 0.342 0.732 0.537

19 6.1662 –0.0187 0.1621 0.0500 3980 –1,263.1 –0.374 0.708 0.322

20 4.2391 0.0040 0.0829 0.0256 3980 –2,629.9 0.155 0.877 0.412

21 2.8921 0.0148 0.0619 0.0193 3980 –4,448.5 0.768 0.443 0.191

22 3.1884 0.0089 0.0809 0.0252 3980 –4,731.3 0.355 0.722 0.491

23 2.4757 0.0037 0.0934 0.0288 3980 –2,781.9 0.130 0.897 0.227

24 2.4588 0.0027 0.1474 0.0457 3901 –4,367.3 0.059 0.953 0.598

25 5.4028 –0.0141 0.0708 0.0221 3980 –2,255.2 –0.637 0.524 0.210

26 6.3878 –0.0173 0.0816 0.0254 3980 –2,656.1 –0.680 0.497 0.415

27 3.9185 –0.0163 0.0613 0.0190 3980 –1,799.2 –0.861 0.389 0.078

28 5.1440 –0.0096 0.0569 0.0175 3980 2,873.6 –0.548 0.584 0.089

29 4.5504 –0.0245 0.0594 0.0183 3980 3,693.3 –1.339 0.181 0.001

30 4.8456 0.0011 0.0848 0.0257 3980 3,971.4 0.041 0.967 0.043

31 8.2944 0.0055 0.0641 0.0200 3980 725.0 0.277 0.782 0.386

32 4.8588 –0.0210 0.1102 0.0341 3980 91.1 –0.616 0.538 0.266

33 9.0734 0.0008 0.0721 0.0224 3980 1,382.6 0.038 0.970 0.693

34 2.8800 –0.0307 0.0449 0.0140 3980 –3,614.9 –2.183 0.029 0.139

35 3.3106 –0.0123 0.0696 0.0214 3980 –1,655.1 –0.575 0.565 0.086

36 4.4386 0.0331 0.1677 0.0510 3980 –738.6 0.648 0.517 0.188

37 10.1162 –0.0215 0.0764 0.0239 3980 –1,266.3 –0.900 0.368 0.000

38 5.6340 0.0011 0.0974 0.0299 3980 –1,699.4 0.036 0.971 0.019

39 6.0136 –0.0440 0.1159 0.0358 3980 –707.9 –1.229 0.219 0.232

40 8.8603 –0.0274 0.1566 0.0481 3980 546.6 –0.570 0.569 0.470

41 6.8985 –0.0506 0.1679 0.0515 3980 –1,605.3 –0.984 0.325 0.257

42 6.1949 –0.0576 0.1665 0.0511 3980 –427.7 –1.128 0.259 0.005

43 5.5627 –0.0704 0.2210 0.0673 3980 986.9 –1.046 0.296 0.011

44 8.4064 –0.0389 0.1135 0.0350 3980 134.0 –1.111 0.267 0.599

45 6.4041 –0.0407 0.1710 0.0527 3980 –707.9 –0.772 0.440 0.189

46 3.0232 0.0007 0.1655 0.0509 3980 –3,708.1 0.015 0.988 0.008

47 7.5623 0.0192 0.1192 0.0367 3979 3,457.8 0.522 0.602 0.451

48 6.1238 0.0385 0.1389 0.0428 3978 1,877.5 0.899 0.368 0.373

49 7.4737 –0.0060 0.1151 0.0356 3980 –1,068.5 –0.168 0.867 0.017

50 7.4621 –0.0649 0.1353 0.0409 3980 6,673.5 –1.585 0.113 0.040

51 9.1939 –0.0667 0.1044 0.0312 3980 7,230.8 –2.140 0.032 0.114

52 7.4596 –0.0471 0.0724 0.0220 2490 810.9 –2.138 0.033 0.150

53 8.2854 –0.0588 0.1197 0.0362 3980 6,418.6 –1.622 0.105 0.335

54 7.8935 –0.0833 0.1237 0.0378 3980 701.7 –2.202 0.028 0.400

55 9.0774 –0.0657 0.1441 0.0435 3980 7,595.5 –1.512 0.131 0.858

56 5.4846 –0.1039 0.2580 0.0786 3980 516.6 –1.323 0.186 0.291

57 3.4880 –0.0036 0.2071 0.0626 3980 1,711.5 –0.057 0.955 0.768

58 4.2192 –0.0488 0.2029 0.0615 3980 277.0 –0.794 0.427 0.464

59 6.1293 –0.0403 0.2268 0.0689 3980 2,133.8 –0.584 0.559 0.037

60 2.9402 –0.0271 0.0964 0.0301 3976 –2,471.2 –0.900 0.368 0.208

61 3.8240 –0.0493 0.2573 0.0779 3946 514.9 –0.634 0.526 0.019
138 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Properties of the calibrated model

Intercept Time

coefficient

Standard error

of the intercept

Standard error of

the time coefficient

Degrees

of freedom

Log likelihood

statistic t statistic p-value ARMA 6p-value1

62 3.1004 –0.0813 0.2488 0.0764 3889 –2,505.4 –1.064 0.287 0.011

63 4.8793 –0.0139 0.1490 0.0452 3980 1,336.8 –0.308 0.758 0.040

64 5.6355 –0.1642 0.2367 0.0721 3980 3,342.0 –2.277 0.023 0.339

65 5.6396 –0.0194 0.2592 0.0831 3737 –461.0 –0.234 0.815 0.212

66 3.3200 –0.0425 0.0811 0.0251 3980 –4,094.9 –1.695 0.090 0.171

67 8.0566 –0.0603 0.0836 0.0254 3980 –569.1 –2.372 0.018 0.000

68 8.9807 –0.0301 0.0791 0.0244 3980 –1,342.1 –1.238 0.216 0.000

69 8.4264 –0.0562 0.1001 0.0306 3980 1,809.4 –1.840 0.066 0.138

70 7.7324 –0.0107 0.0847 0.0261 3980 903.9 –0.412 0.681 0.423

71 7.2519 –0.0340 0.0645 0.0200 3980 1,724.5 –1.698 0.090 0.000

72 1.8607 –0.0592 0.1354 0.0417 3458 –4,407.2 –1.419 0.156 0.056

73 12.3350 –0.0181 0.0580 0.0181 3980 2,736.2 –1.003 0.316 0.001

74 4.3474 –0.0395 0.0489 0.0153 3980 3,362.4 –2.585 0.010 0.513

75 3.2251 –0.0541 0.1011 0.0311 3972 –1,270.1 –1.736 0.083 0.010

76 5.8022 –0.0313 0.0611 0.0191 3980 237.8 –1.643 0.100 0.056

77 2.1930 0.0420 0.0771 0.0239 3980 –1,333.5 1.759 0.079 0.011

78 3.3288 –0.0283 0.0441 0.0137 3980 –544.2 –2.056 0.040 0.364

79 1.5986 –0.0223 0.0631 0.0203 3707 –2,542.8 –1.094 0.274 0.176

80 4.6188 –0.0229 0.0499 0.0160 3707 –910.0 –1.429 0.153 0.052

81 2.4788 0.2126 0.3403 0.1033 3898 990.0 2.059 0.040 0.460

82 3.9613 0.0557 0.2189 0.0668 3980 1,140.5 0.834 0.404 0.030

83 2.8417 –0.0835 0.1500 0.0464 3980 1,739.9 –1.797 0.072 0.772

84 3.0661 –0.0409 0.0355 0.0111 3980 40.2 –3.694 0.000 0.139

85 1.1197 –0.0093 0.0466 0.0146 3980 –3,180.6 –0.635 0.525 0.344

86 0.3357 –0.0081 0.0901 0.0281 3980 –3,885.6 –0.289 0.773 0.771

87 4.3914 –0.1762 0.1685 0.0524 3980 –3,217.8 –3.363 0.001 0.027

88 4.8294 –0.0868 0.1738 0.0539 3980 –4,098.4 –1.610 0.107 0.121

89 4.9366 –0.0748 0.1740 0.0536 3980 –1,191.7 –1.394 0.163 0.153

90 4.8891 –0.0032 0.0445 0.0140 3980 –1,035.3 –0.227 0.821 0.471

91 6.2650 –0.0225 0.0573 0.0179 3980 –575.6 –1.253 0.210 0.633

92 1.6268 –0.0472 0.1070 0.0334 3979 –2,387.7 –1.414 0.158 0.065

93 9.8677 –0.0820 0.0783 0.0242 3980 4,179.1 –3.384 0.001 0.025

94 5.8984 –0.0858 0.0799 0.0248 3980 –1,541.4 –3.457 0.001 0.510

95 12.2810 –0.0710 0.0522 0.0161 3980 7,365.4 –4.404 0.000 0.153

96 4.3438 –0.0078 0.0277 0.0087 3980 1,943.7 –0.899 0.369 0.053

97 0.9736 –0.0173 0.2564 0.0496 2578 –1,007.2 –0.348 0.728 0.307

98 7.1852 –0.0721 0.1053 0.0320 3980 3,172.3 –2.252 0.024 0.092

99 9.0666 –0.0623 0.0660 0.0204 3980 4,662.9 –3.050 0.002 0.034

100 9.8307 0.0088 0.0957 0.0282 3980 6,718.5 0.312 0.755 0.010

101 6.6377 –0.0050 0.0169 0.0053 3980 5,543.6 –0.946 0.344 0.426

102 2.6235 0.0754 0.2904 0.0908 3802 1,263.7 0.831 0.406 0.364

103 3.2110 0.0308 0.0926 0.0284 3980 –1,492.5 1.082 0.279 0.028

104 3.5405 –0.0519 0.1657 0.0513 3980 –2,269.2 –1.011 0.312 0.219

105 2.9265 –0.0889 0.2327 0.0711 3980 –2,631.7 –1.249 0.212 0.576

106 1.3404 –0.2565 0.2137 0.0525 1509 –937.8 –4.888 0.000 0.011

107 6.5691 –0.0567 0.1085 0.0335 3980 1,036.1 –1.695 0.090 0.061

108 5.3912 0.0060 0.0071 0.0022 3980 8,097.7 2.718 0.007 0.710

109 4.2292 –0.1134 0.1035 0.0319 3980 –1,917.2 –3.560 0.000 0.034

110 8.8993 –0.0866 0.0546 0.0170 3980 1,857.0 –5.101 0.000 0.053

111 5.8701 –0.2096 0.1424 0.0437 3980 –1,117.1 –4.796 0.000 0.046

112 10.7954 –0.0517 0.0523 0.0160 3980 5,344.0 –3.239 0.001 0.007

113 7.2115 –0.2012 0.1814 0.0557 3980 –1,538.3 –3.610 0.000 0.406

114 6.2637 –0.1992 0.1886 0.0579 3980 –1,873.8 –3.441 0.001 0.013

115 4.3699 –0.1172 0.1376 0.0427 3980 –3,012.7 –2.746 0.006 0.466

116 8.6771 –0.1702 0.1543 0.0477 3980 –3,019.4 –3.565 0.000 0.001

117 7.1855 –0.1022 0.0798 0.0248 3980 388.3 –4.118 0.000 0.719

118 11.3697 –0.0909 0.0648 0.0199 3980 4,378.3 –4.574 0.000 0.589

119 5.5242 0.0382 0.1091 0.0342 3980 –672.5 1.117 0.264 0.114

120 3.2739 –0.0852 0.0663 0.0215 3784 –1,159.4 –3.963 0.000 0.687

121 5.8097 –0.0626 0.1033 0.0321 3980 –1,646.5 –1.948 0.051 0.006

122 8.9275 –0.1037 0.0893 0.0276 3980 –1,822.9 –3.762 0.000 0.000

123 2.7286 –0.0727 0.0777 0.0242 3980 –2,681.5 –2.996 0.003 0.407
Appendix 2 139

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Properties of the calibrated model

Intercept Time

coefficient

Standard error

of the intercept

Standard error of

the time coefficient

Degrees

of freedom

Log likelihood

statistic t statistic p-value ARMA 6p-value1

124 5.8323 –0.0705 0.0574 0.0178 3980 –322.6 –3.948 0.000 0.007

125 7.7686 –0.0603 0.0476 0.0148 3980 2,198.7 –4.075 0.000 0.023

126 6.3821 –0.0308 0.1883 0.0592 2220 952.8 –0.521 0.603 0.635

127 3.7680 0.1774 0.3254 0.0994 1921 –2,057.4 1.784 0.075 0.000

128 2.5983 –0.0576 0.1463 0.0440 3980 1,271.7 –1.307 0.191 0.344

129 1.9386 –0.0141 0.1414 0.0429 3980 503.8 –0.328 0.743 0.910

130 3.8610 –0.0325 0.1510 0.0456 3980 –1,257.6 –0.714 0.476 0.024

131 4.6931 –0.0097 0.0896 0.0274 3980 –156.3 –0.354 0.723 0.039

132 4.7906 0.0040 0.1226 0.0375 3980 –1,697.4 0.108 0.914 0.004

133 4.8406 –0.0021 0.1232 0.0377 3980 –1,530.5 –0.057 0.955 0.232

134 6.1105 –0.0936 0.0884 0.0275 3980 –400.5 –3.410 0.001 0.597

135 6.0534 –0.0606 0.0685 0.0213 3980 –1,253.2 –2.844 0.004 0.332

136 2.5791 –0.0323 0.0852 0.0410 2537 –1,326.3 –0.788 0.431 0.787

137 4.2448 –0.0660 0.0787 0.0244 3980 –798.2 –2.702 0.007 0.203

138 6.4394 –0.0639 0.0740 0.0230 3980 64.5 –2.774 0.006 0.264

139 5.2092 –0.0885 0.0853 0.0266 3980 –1,408.6 –3.334 0.001 0.149

140 3.5054 –0.1575 0.2097 0.0652 3829 –3,149.4 –2.417 0.016 0.089

141 4.8674 –0.0404 0.1933 0.0592 3980 –829.7 –0.683 0.495 0.014

142 4.7854 –0.1414 0.2701 0.0811 3980 –2,243.1 –1.743 0.081 0.391

143 5.5101 –0.0742 0.1509 0.0461 3980 –2,622.3 –1.608 0.108 0.036

144 5.9694 –0.0592 0.1016 0.0313 3980 –1,215.6 –1.892 0.059 0.014

145 4.0195 –0.0369 0.1375 0.0429 3978 –3,341.8 –0.861 0.389 0.072

146 3.1806 –0.0811 0.1869 0.0576 3606 –3,493.2 –1.408 0.159 0.010

147 3.1806 –0.0811 0.1869 0.0576 3606 –3,493.2 –1.408 0.159 0.010

148 3.2008 –0.1044 0.1509 0.0472 3893 –3,637.5 –2.214 0.027 0.906

149 10.2105 –0.0877 0.1172 0.0365 3980 –3,908.5 –2.406 0.016 0.006

150 7.1617 –0.1166 0.0999 0.0311 3980 –887.3 –3.753 0.000 0.942

151 10.1738 –0.0165 0.1021 0.0315 3855 –937.7 –0.523 0.601 0.156

152 8.3662 –0.0155 0.0935 0.0290 3980 105.2 –0.534 0.593 0.027

153 13.0773 –0.0367 0.0455 0.0141 3980 9,864.2 –2.612 0.009 0.883

154 6.7007 –0.0312 0.0706 0.0219 3980 318.8 –1.426 0.154 0.110

155 5.3961 –0.0428 0.0687 0.0214 3980 –146.6 –2.001 0.045 0.147

156 12.2294 –0.0381 0.0438 0.0135 3980 6,865.2 –2.812 0.005 0.006

157 6.5903 0.0039 0.0970 0.0303 3321 –3,311.4 0.128 0.898 0.003

158 8.6258 –0.0089 0.1302 0.0400 3980 2,471.4 –0.222 0.824 0.000

159 5.9286 –0.0211 0.1335 0.0409 3980 1,858.1 –0.517 0.605 0.164

160 7.0786 –0.0084 0.1551 0.0478 3980 1,402.7 –0.176 0.860 0.383

161 2.4460 –0.2128 0.3745 0.1130 3427 –3,164.6 –1.884 0.060 0.144

162 3.2789 –0.0179 0.3229 0.0992 3687 –3,670.4 –0.181 0.857 0.173

163 8.2294 –0.0525 0.1164 0.0360 3980 1,467.3 –1.456 0.145 0.126

164 1.9644 –0.4160 0.1864 0.0575 3152 –3,082.0 –7.230 0.000 0.004

165 3.0401 –0.0548 0.1785 0.0554 3926 –3,143.7 –0.990 0.322 0.330

166 5.1708 –0.0697 0.1229 0.0382 3980 –1,679.1 –1.826 0.068 0.870

167 1.1718 0.1555 0.4672 0.1407 3386 –2,484.2 1.106 0.269 0.185

168 1.7003 0.1214 0.3803 0.1156 3853 –2,164.0 1.050 0.294 0.457

169 1.7398 0.1559 0.2779 0.0850 3201 –4,240.1 1.834 0.067 0.004

170 7.2854 0.0279 0.1315 0.0404 3980 54.3 0.691 0.490 0.193

171 7.1081 0.0106 0.1536 0.0473 3980 –1,514.8 0.223 0.823 0.010

172 5.8834 0.0469 0.0970 0.0299 3980 –1,225.5 1.569 0.117 0.287

173 5.3169 –0.1524 0.2032 0.0614 3980 2,909.7 –2.480 0.013 0.199

174 6.6923 –0.0394 0.0771 0.0237 3980 5,240.7 –1.667 0.096 0.014

175 8.4754 –0.0734 0.0747 0.0229 3980 5,920.9 –3.210 0.001 0.902

176 7.0528 –0.0387 0.0906 0.0275 3980 6,946.5 –1.407 0.160 0.242

177 7.0340 –0.0425 0.1044 0.0315 3980 6,446.9 –1.348 0.178 0.253

178 7.9704 –0.0479 0.0845 0.0258 3980 5,786.5 –1.856 0.064 0.422

179 9.4725 –0.0069 0.0642 0.0191 3980 4,658.6 –0.359 0.719 0.000

180 2.1280 –0.0432 0.0413 0.0129 3980 253.6 –3.358 0.001 0.422

181 4.6820 –0.1255 0.1221 0.0374 3980 –1,234.6 –3.356 0.001 0.557

182 5.1140 –0.0912 0.0859 0.0264 3980 –85.6 –3.460 0.001 0.020

183 5.3916 –0.0992 0.1341 0.0410 3980 266.7 –2.416 0.016 0.001

184 5.9085 –0.0926 0.1365 0.0417 3980 810.0 –2.218 0.027 0.044
140 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003.—Continued

[CI, confidence interval; ARMA, autoregressive moving average]

Site

number 

(figure 1)

Properties of the calibrated model

Intercept Time

coefficient

Standard error

of the intercept

Standard error of

the time coefficient

Degrees

of freedom

Log likelihood

statistic t statistic p-value ARMA 6p-value1

185 5.5569 –0.0710 0.0701 0.0218 3980 313.0 –3.260 0.001 0.042

186 7.8597 –0.0248 0.1000 0.0303 3980 3,521.2 –0.816 0.414 0.309

187 5.5172 –0.0584 0.1679 0.0487 3734 4,468.2 –1.200 0.230 0.005

188 6.5833 –0.0316 0.2527 0.0743 3980 246.9 –0.425 0.671 0.192

189 3.5982 –0.0698 0.1241 0.0375 3980 1,626.3 –1.860 0.063 0.705

190 4.7320 –0.0427 0.0555 0.0173 3980 3,415.1 –2.462 0.014 0.066

191 4.9306 –0.0567 0.0727 0.0227 3980 3,274.4 –2.500 0.012 0.798

192 5.1656 0.0555 0.0934 0.0288 3980 3,653.9 1.928 0.054 0.004

193 3.7705 –0.0218 0.0611 0.0191 3980 1,871.7 –1.143 0.253 0.488

194 2.5430 –0.0412 0.1416 0.0430 3980 984.2 –0.958 0.338 0.168

195 3.5008 –0.0315 0.1518 0.0461 3980 1,621.5 –0.684 0.494 0.115

196 3.7220 –0.0425 0.1945 0.0586 3980 621.0 –0.725 0.469 0.475

197 1.6544 –0.0560 0.1401 0.0422 3980 3,111.8 –1.328 0.184 0.122

198 1.0477 0.0042 0.2154 0.0612 3980 3,911.5 0.069 0.945 0.070

199 1.3650 –0.0127 0.2236 0.0626 3980 3,611.7 –0.203 0.839 0.006

200 1.8046 –0.0421 0.1346 0.0405 3980 3,252.3 –1.040 0.299 0.003

201 –1.1104 0.0669 0.3244 0.0928 3980 1,811.6 0.721 0.471 0.595

202 1.2736 0.0189 0.1678 0.0472 3980 1,652.7 0.399 0.690 0.009

203 8.0251 0.0052 0.0532 0.0165 3980 215.2 0.316 0.752 0.128

204 9.5743 0.0006 0.0528 0.0162 3980 2,315.2 0.035 0.972 0.029

205 8.8489 –0.0009 0.0620 0.0192 3980 856.4 –0.045 0.964 0.060

206 6.8042 –0.0110 0.0699 0.0216 3980 2,104.8 –0.508 0.611 0.499

207 6.3468 –0.0125 0.0735 0.0228 3980 1,506.2 –0.548 0.584 0.025

208 10.1065 –0.0149 0.0667 0.0205 3980 4,348.3 –0.723 0.470 0.212

209 9.2654 –0.0151 0.0687 0.0211 3980 4,245.1 –0.714 0.475 0.002

210 9.0744 –0.0109 0.0649 0.0200 3980 3,206.2 –0.544 0.587 0.040

211 8.1157 –0.0083 0.0647 0.0201 3980 2,807.2 –0.414 0.679 0.000

212 8.6243 0.0002 0.0466 0.0140 3980 6,263.9 0.013 0.990 0.000

213 9.7451 –0.0148 0.0671 0.0207 3980 4,217.7 –0.717 0.474 0.621

214 10.1065 –0.0149 0.0667 0.0205 3980 4,348.3 –0.723 0.470 0.212

215 12.0165 –0.0068 0.0686 0.0203 3980 3,138.3 –0.335 0.738 0.000

216 7.9014 0.0089 0.0518 0.0160 3980 659.1 0.555 0.579 0.158

217 5.6307 –0.0275 0.0906 0.0282 3980 –171.4 –0.974 0.330 0.269

218 3.8598 –0.0237 0.0707 0.0219 3980 –948.0 –1.086 0.278 0.687

219 6.7924 –0.0556 0.1010 0.0307 3980 2,684.7 –1.809 0.070 0.175

220 5.3769 0.0178 0.0850 0.0266 3980 –478.4 0.666 0.505 0.069

221 5.7531 –0.0022 0.0944 0.0288 3980 2,076.5 –0.076 0.939 0.015

222 8.2109 –0.0124 0.1021 0.0312 3980 4,097.1 –0.399 0.690 0.000

223 9.1554 –0.0208 0.0808 0.0240 3980 6,573.1 –0.866 0.387 0.149

224 6.5155 –0.0006 0.1500 0.0457 3980 4,268.2 –0.013 0.990 0.654

225 5.4657 0.0201 0.1644 0.0491 3980 1,215.1 0.410 0.682 0.066

226 1.6263 –0.0609 0.1231 0.0407 3615 –2,035.2 –1.498 0.134 0.207

227 10.1065 –0.0149 0.0667 0.0205 3980 4,348.3 –0.723 0.470 0.212

228 12.2844 –0.0124 0.0639 0.0191 3980 4,004.8 –0.647 0.517 0.000

229 6.5780 0.0098 0.0600 0.0187 3980 –676.0 0.526 0.599 0.000

230 5.5318 –0.0038 0.0781 0.0240 3980 1,165.5 –0.159 0.874 0.282

231 6.6311 0.0023 0.0994 0.0305 3980 3,306.9 0.076 0.940 0.005

232 5.5698 0.0120 0.0921 0.0284 3980 1,446.2 0.424 0.671 0.184

233 7.9252 0.0095 0.1205 0.0360 3980 4,299.4 0.265 0.791 0.686

234 7.5247 –0.0041 0.1050 0.0318 3980 3,531.8 –0.129 0.897 0.000

235 7.5247 –0.0041 0.1050 0.0318 3980 3,531.8 –0.129 0.897 0.000

236 6.6382 –0.0159 0.0900 0.0274 3980 5,662.4 –0.580 0.562 0.817

237 7.5576 –0.0434 0.0997 0.0303 3980 5,220.2 –1.431 0.152 0.309

238 8.3219 –0.0062 0.0984 0.0299 3980 5,409.7 –0.207 0.836 0.075

239 11.4358 0.0019 0.0476 0.0145 3980 5,849.6 0.128 0.898 0.105

240 4.8270 –0.0547 0.1427 0.0436 3980 1,301.4 –1.255 0.209 0.042

241 2.8587 –0.0210 0.1402 0.0437 3861 –4,392.0 –0.482 0.630 0.122

242 6.5405 –0.0216 0.1974 0.0596 3980 2,118.3 –0.362 0.717 0.003

243 8.0070 –0.0177 0.1668 0.0498 3980 6,155.2 –0.355 0.723 0.021

244 9.9586 –0.0055 0.0858 0.0262 3980 5,852.1 –0.210 0.833 0.027

1

ARMA 6 p-value is the p-value for the joint significance of serial correlation for the lag-21 through lag-26 residuals.
Appendix 3 141

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Station 

number Station name

Reference

concentration,

in milligrams

per liter

Reference

load, in

kilograms

per day

Flow-adjusted trend in concentration from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value t-statistic

Total phosphorus

1 01122610 Shetucket River at South Windham, Conn. 0.021 24.7 61.1 154.4 2.0 0.044 2.043

2 01124000 Quinebaug River at Quinebaug, Conn. 0.036 15.4 20.4 88.0 –22.9 0.418 0.814

3 01127000 Quinebaug River at Jewett City, Conn. 0.046 87.8 81.3 168.8 22.3 0.004 2.960

4 01184000 Connecticut River at Thompsonville, Conn. 0.033 1,067.5 26.9 90.0 –15.3 0.250 1.155

5 01184490 Broad Brook at Broad Brook, Conn. 0.092 5.0 –6.5 26.3 –30.8 0.662 –0.439

7 01189995 Farmington River at Tariffville, Conn. 0.087 207.1 38.5 78.2 7.7 0.013 2.535

8 01192500 Hockanum River near East Hartford, Conn. 0.364 99.4 –19.9 0.6 –36.2 0.059 –1.909

10 01196500 Quinnipiac River at Wallingford, Conn. 0.241 99.8 –20.3 1.6 –37.6 0.071 –1.829

11 01205500 Housatonic River at Stevenson, Conn. 0.021 78.3 10.6 189.5 –57.8 0.839 0.205

12 01208500 Naugatuck River at Beacon Falls, Conn. 0.227 212.5 61.1 121.3 17.3 0.004 2.946

13 01208990 Saugatuck River near Redding, Conn. 0.012 0.5 25.2 326.5 –63.2 0.720 0.360

14 01209710 Norwalk River at Winnipauk, Conn. 0.030 2.3 44.0 94.3 6.7 0.018 2.384

15 01357500 Mohawk River at Cohoes, N.Y. 0.034 270.9 7.9 64.9 –29.4 0.727 0.350

16 01377000 Hackensack River at Rivervale, N.J. 0.065 9.7 14.8 93.3 –31.8 0.607 0.519

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 0.025 0.9 –54.1 67.6 –87.4 0.245 –1.178

18 01387500 Ramapo River near Mahwah, N.J. 0.120 28.9 –0.9 34.0 –26.8 0.951 –0.062

19 01389500 Passaic River at Little Falls, N.J. 0.372 467.2 8.8 32.8 –10.9 0.413 0.824

20 01391500 Saddle River at Lodi, N.J. 0.369 60.4 120.1 216.1 53.2 0.000 4.267

22 01395000 Rahway River at Rahway, N.J. 0.071 4.0 34.1 83.5 –2.0 0.074 1.832

24 01398000 Neshanic River at Reaville, N.J. 0.042 1.2 23.2 177.4 –45.3 0.616 0.503

25 01402000 Millstone River at Blackwells Mills, N.J. 0.195 113.9 25.9 66.4 –4.8 0.114 1.613

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 0.160 255.1 10.8 41.1 –13.0 0.407 0.832

27 01408000 Manasquan River at Squankum, N.J. 0.099 13.1 9.8 78.4 –32.5 0.709 0.376

28 01408500 Toms River near Toms River, N.J. 0.024 10.5 32.2 271.5 –53.0 0.599 0.530

30 01411500 Maurice River at Norma, N.J. 0.014 4.3 –14.4 217.9 –76.9 0.818 –0.232

31 01438500 Delaware River at Montague, N.J. 0.041 379.5 –45.3 52.7 –80.4 0.256 –1.152

32 01443500 Paulins Kill at Blairstown, N.J. 0.025 8.6 7.7 124.2 –48.2 0.843 0.199

33 01463500 Delaware River at Trenton, N.J. 0.057 1,193.6 –10.8 26.2 –36.9 0.521 –0.644

34 01467150 Cooper River at Haddonfield, N.J. 0.198 10.1 0.1 42.8 –29.9 0.996 0.005

35 01477120 Raccoon Creek near Swedesboro, N.J. 0.117 8.3 29.8 83.2 –8.0 0.142 1.483

36 01491000 Choptank River near Greensboro, Md. 0.045 7.1 91.1 157.7 41.6 0.000 4.240

37 01578310 Susquehanna River at Conowingo, Md. 0.021 1,396.0 78.6 134.7 35.9 0.000 4.159

38 01594440 Patuxent River near Bowie, Md. 0.116 76.5 40.7 78.9 10.6 0.006 2.785

39 01614500 Conococheague Creek at Fairview, Md. 0.114 132.9 26.3 73.4 –8.0 0.150 1.445

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 0.030 549.2 95.6 186.3 33.6 0.001 3.447

41 01668000 Rappahannock River near Fredericksburg, Va. 0.033 89.8 51.2 102.2 13.0 0.006 2.785

42 01673000 Pamunkey River near Hanover, Va. 0.066 98.5 80.4 112.0 53.5 0.000 7.165

43 01674500 Mattaponi River near Beulahville, Va. 0.059 46.9 0.3 14.1 –11.9 0.968 0.040

44 02035000 James River at Cartersville, Va. 0.100 1,282.6 –2.9 20.1 –21.5 0.789 –0.268

45 02041650 Appomattox River at Matoaca, Va. 0.047 75.7 –6.7 8.3 –19.6 0.362 –0.912

46 02085000 Eno River at Hillsborough, N.C. 0.025 1.2 42.2 134.8 –13.9 0.173 1.376

51 02198500 Savannah River near Clyo, Ga. 0.093 3,076.5 14.3 47.9 –11.7 0.311 1.017

52 02213700 Ocmulgee River near Warner Robins, Ga. 0.177 765.1 –47.9 –27.8 –62.4 0.000 –3.922

53 02215500 Ocmulgee River at Lumber City, Ga. 0.117 1,473.5 –34.9 –16.0 –49.5 0.001 –3.304

54 02223600 Oconee River at Interstate 16, near Dublin, Ga. 0.135 1,321.5 –26.4 –7.4 –41.5 0.010 –2.620

55 02226010 Altamaha River near Gardi, Ga. 0.106 3,075.5 –17.0 –2.1 –29.7 0.029 –2.214

56 02226582 Satilla River at GA 15&121, near Hoboken, Ga. 0.140 129.0 19.4 49.2 –4.4 0.121 1.564

58 02295420 Payne Creek near Bowling Green, Fla. 0.620 122.8 37.6 69.2 11.8 0.004 3.020

59 02296750 Peace River at Arcadia, Fla. 0.940 1,179.6 –6.0 10.9 –20.3 0.464 –0.736

60 02300700 Bullfrog Creek near Wimauma, Fla. 0.227 11.9 14.4 34.3 –2.6 0.104 1.641

61 02301300 South Prong Alafia River near Lithia, Fla. 0.954 127.3 –36.0 –13.8 –52.5 0.005 –2.942

62 02302500 Blackwater Creek near Knights, Fla. 0.807 66.1 –36.5 –19.2 –50.0 0.000 –3.700
142 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Station 

number Station name

Reference

concentration,

in milligrams

per liter

Reference

load, in

kilograms

per day

Flow-adjusted trend in concentration from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value t-statistic

Total phosphorus—Continued

63 02303000 Hillsborough River near Zephyrhills, Fla. 0.323 102.8 –44.5 –23.9 –59.5 0.001 –3.653

64 02314500 Suwannee River at U.S. 441, at Fargo, Ga. 0.066 97.3 –73.9 –61.7 –82.2 0.000 –6.866

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 0.150 107.9 21.1 45.6 0.7 0.044 2.031

66 02335870 Sope Creek near Marietta, Ga. 0.017 1.3 –2.9 64.3 –42.6 0.913 –0.109

68 02344040 Chattahoochee River near Steam Mill, Ga. 0.085 1,917.0 –55.7 –31.6 –71.3 0.000 –3.671

69 02353000 Flint River at Newton, Ga. 0.049 714.8 –9.9 20.6 –32.7 0.487 –0.700

70 02388520 Oostanaula River at Rome, Ga. 0.217 1,266.1 –55.8 –42.8 –65.8 0.000 –6.222

71 02492000 Bogue Chitto River near Bush, La. 0.070 286.0 49.2 99.8 11.4 0.009 2.684

72 03353637 Little Buck Creek near Indianapolis, Ind. 0.024 0.6 29.8 87.3 –10.0 0.165 1.395

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 0.082 49,089.7 82.2 124.0 48.1 0.000 5.680

74 04063700 Popple River near Fence, Wis. 0.027 6.1 –18.3 40.3 –52.5 0.465 –0.733

75 04073468 Green Lake Inlet at County Highway A near Green 

Lake, Wis.

0.134 11.0 –24.4 –15.7 –32.3 0.000 –5.016

76 04087000 Milwaukee River at Milwaukee, Wis. 0.083 77.8 26.9 54.9 3.9 0.021 2.337

77 0422026250 Northrup Creek at North Greece, N.Y. 0.402 7.2 –35.5 –23.3 –45.7 0.000 –4.985

78 04232034 Irondequoit Creek at Railroad Mills near Fishers, N.Y. 0.070 5.4 –19.9 5.2 –39.0 0.111 –1.596

79 0423204920 East Branch Allen Creek at Pittsford, N.Y. 0.090 1.2 –15.5 0.1 –28.6 0.052 –1.951

80 0423205025 Irondequoit Creek at Empire Boulevard at 

Rochester, N.Y.

0.068 18.0 52.6 68.6 38.1 0.000 8.317

81 05114000 Souris River near Sherwood, N. Dak. 0.424 5.5 –35.8 –8.0 –55.1 0.018 –2.418

82 05120000 Souris River near Verendrye, N. Dak. 0.264 28.1 –15.2 18.7 –39.4 0.341 –0.960

83 05287890 Elm Creek near Champlin, Minn. 0.139 8.7 42.0 77.2 13.7 0.002 3.099

84 05427718 Yahara River at Windsor, Wis. 0.149 9.7 8.2 28.2 –8.7 0.364 0.908

85 05427948 Pheasant Branch at Middleton, Wis. 0.390 3.1 –62.6 –56.2 –68.1 0.000 –12.242

86 054310157 Jackson Creek Tributary near Elkhorn, Wis. 0.129 0.5 –12.2 9.2 –29.4 0.242 –1.172

87 05500000 South Fabius River near Taylor, Mo. 0.102 45.1 63.7 134.3 14.4 0.008 2.694

88 05514500 Cuivre River near Troy, Mo. 0.136 60.8 15.7 77.9 –24.7 0.508 0.666

89 05525500 Sugar Creek at Milford, Ill. 0.060 26.4 66.0 165.1 4.0 0.037 2.123

90 05531500 Salt Creek at Western Springs, Ill. 1.019 338.8 46.2 81.8 17.6 0.001 3.423

91 05532500 Des Plaines River at Riverside, Ill. 0.517 749.7 62.0 96.6 33.4 0.000 4.874

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 0.079 1.2 –11.5 26.8 –38.2 0.508 –0.664

93 05586100 Illinois River at Valley City, Ill. 0.264 18,788.7 110.3 172.5 62.3 0.000 5.624

94 07018100 Big River near Richwoods, Mo. 0.032 43.6 2.0 64.7 –36.8 0.936 0.081

95 07022000 Mississippi River at Thebes, Ill. 0.230 176,092.9 102.1 159.4 57.4 0.000 5.524

97 06178000 Poplar River at International Boundary, Mont. 0.029 0.3 –17.5 53.8 –55.7 0.548 –0.606

99 06329500 Yellowstone River near Sidney, Mont. 0.075 2,177.1 60.8 229.4 –21.5 0.197 1.297

101 06461500 Niobrara River near Sparks, Nebr. 0.121 232.7 38.8 85.8 3.7 0.031 2.206

106 06753990 Lonetree Creek near Greeley, Colo. 0.325 11.3 –16.9 89.5 –63.5 0.662 –0.439

107 06754000 South Platte River near Kersey, Colo. 0.636 1,454.4 26.7 49.0 7.6 0.005 2.848

109 06800000 Maple Creek near Nickerson, Nebr. 0.207 61.0 290.4 473.1 165.9 0.000 6.952

110 06805500 Platte River at Louisville, Nebr. 0.313 8,767.3 188.4 294.6 110.7 0.000 6.616

111 06817700 Nodaway River near Graham, Mo. 0.327 806.1 102.5 250.2 17.1 0.013 2.525

112 06818000 Missouri River at St. Joseph, Mo. 0.216 33,847.8 68.3 146.9 14.7 0.009 2.661

113 06902000 Grand River near Sumner, Mo. 0.202 1,754.8 193.7 383.1 78.5 0.000 4.243

114 06905500 Chariton River near Prairie Hill, Mo. 0.207 663.6 36.4 129.6 –19.0 0.246 1.169

115 06921070 Pomme De Terre River near Polk, Mo. 0.047 16.3 9.3 64.4 –27.3 0.669 0.429

118 06934500 Missouri River at Hermann, Mo. 0.187 63,637.4 233.3 422.7 112.5 0.000 5.241

120 07053250 Yocum Creek near Oak Grove, Ark. 0.039 3.7 47.9 90.4 14.9 0.003 3.037

134 07189000 Elk River near Tiff City, Mo. 0.041 73.3 231.1 374.1 131.2 0.000 6.534

135 07195500 Illinois River near Watts, Okla. 0.112 160.9 117.4 211.0 51.9 0.000 4.249

136 07195865 Sager Creek near West Siloam Springs, Okla. 0.495 17.7 66.3 158.7 6.8 0.029 2.252

137 07196000 Flint Creek near Kansas, Okla. 0.092 22.1 111.2 160.4 71.3 0.000 7.000
Appendix 3 143

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Station 

number Station name

Reference

concentration,

in milligrams

per liter

Reference

load, in

kilograms

per day

Flow-adjusted trend in concentration from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value t-statistic

Total phosphorus—Continued

138 07196500 Illinois River near Tahlequah, Okla. 0.063 133.8 135.6 190.3 91.1 0.000 8.032

139 07197000 Baron Fork at Eldon, Okla. 0.028 19.5 67.4 140.2 16.6 0.006 2.793

145 07247015 Poteau River at Loving, Okla. 0.106 17.2 –9.5 34.3 –39.0 0.622 –0.495

148 07247650 Fourche Maline near Leflore, Okla. 0.051 5.7 17.9 60.0 –13.1 0.293 1.060

149 07263620 Arkansas River at David D. Terry Lock and Dam 

below Little Rock, Ark.

0.081 8,280.0 78.7 121.7 43.9 0.000 5.262

150 07331000 Washita River near Dickson, Okla. 0.201 1,137.5 140.7 277.7 53.4 0.000 3.822

151 07355500 Red River at Alexandria, La. 0.095 6,494.3 –25.1 –5.4 –40.6 0.017 –2.425

152 07362000 Ouachita River at Camden, Ark. 0.041 464.8 –26.6 27.8 –57.9 0.279 –1.093

153 07373420 Mississippi River near St Francisville, La. 0.175 247,836.4 50.4 87.9 20.3 0.000 3.586

154 07375500 Tangipahoa River at Robert, La. 0.112 258.7 16.0 56.6 –14.1 0.335 0.968

155 07376000 Tickfaw River at Holden, La. 0.074 49.4 57.1 117.3 13.6 0.008 2.731

156 07381495 Atchafalaya River at Melville, La. 0.146 89,521.1 71.8 105.6 43.6 0.000 5.907

157 07386980 Vermilion River at Perry, La. 0.297 565.1 1.2 26.0 –18.8 0.918 0.103

165 08143600 Pecan Bayou near Mullin, Tex. 0.205 13.5 –0.0 88.4 –47.0 0.999 –0.001

166 08147000 Colorado River near San Saba, Tex. 0.077 45.6 –68.0 8.1 –90.5 0.072 –1.835

169 08159000 Onion Creek at U.S. Highway 183, Austin, Tex. 0.076 0.7 –93.9 –71.3 –98.7 0.001 –3.540

170 08162000 Colorado River at Wharton, Tex. 0.269 826.8 –5.9 47.1 –39.8 0.791 –0.266

171 08162500 Colorado River near Bay City, Tex. 0.291 803.2 –26.1 26.3 –56.7 0.274 –1.105

173 08251500 Rio Grande near Lobatos, Colo. 0.079 86.6 52.9 96.9 18.6 0.002 3.282

177 09217010 Green River below Green River, Wyo. 0.026 90.0 51.1 186.1 –20.2 0.210 1.266

178 09261000 Green River at Dinosaur National Monument 

Utah 149 Crossing, Utah

0.062 571.6 –34.8 55.5 –72.6 0.338 –0.964

180 09403600 Kanab Creek at U.S. 89 Crossing, Utah 0.035 0.9 232.7 656.8 46.2 0.005 2.866

182 09415000 Virgin River at Littlefield, Ariz. 0.106 68.0 463.4 1,200.6 144.0 0.000 4.050

183 09448500 Gila River at Head of Safford Valley, near 

Solomon, Ariz.

0.122 103.9 216.0 730.0 20.3 0.024 2.335

184 09498500 Salt River near Roosevelt, Ariz. 0.013 16.9 4,678.5 14,832.1 1,428.8 0.000 6.651

185 09508500 Verde River below Tangle Creek, above Horseshoe 

Dam, Ariz.

0.023 20.6 166.7 493.8 19.8 0.019 2.402

186 09522000 Colorado River at Northerly International Boundary, 

above Morelos Dam, Ariz.

0.280 1,985.5 –85.9 –65.2 –94.3 0.000 –4.253

188 10126000 Bear River near Corinne at Utah 83 Crossing, Utah 0.188 411.5 –50.7 –29.9 –65.3 0.000 –3.940

193 10189000 East Fork Sevier River at Utah 62 Crossing East of 

Kingston, Utah

0.085 10.1 –3.4 37.7 –32.2 0.849 –0.191

203 01A050 Nooksack River at Brennan, Wash. 0.021 152.5 37.9 104.2 –6.9 0.112 1.601

204 03A060 Skagit River near Mount Vernon, Wash. 0.015 517.6 5.5 112.6 –47.6 0.880 0.151

205 07A090 Snohomish River at Snohomish, Wash. 0.009 152.9 26.3 123.2 –28.5 0.423 0.804

206 09A080 Green River at Tukwila, Wash. 0.025 58.5 19.2 59.3 –10.8 0.238 1.187

207 09A190 Green River at Kanaskat, Wash. 0.005 7.4 254.0 606.4 77.4 0.000 3.586

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 0.070 4,604.1 –7.6 9.1 –21.7 0.355 –0.934

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

0.075 2,126.5 –18.8 –3.0 –32.1 0.023 –2.301

210 10355 Willamette River at Highway 99 East at 

Harrisburg, Oreg.

0.046 1,037.8 –2.6 18.5 –20.0 0.790 –0.267

211 10386 Middle Fork Willamette at Jasper Bridge, Oreg. 0.028 238.6 –13.8 3.5 –28.1 0.117 –1.592

212 10411 Deschutes River at Deschutes River Park, Oreg. 0.080 1,096.0 –8.9 29.5 –35.9 0.606 –0.519

213 10555 Willamette River at Marion Street at Salem, Oreg. 0.064 2,912.6 –18.6 –4.1 –30.9 0.015 –2.459

214 10611 Willamette River at Hawthorne Bridge, Oreg. 0.082 5,385.0 –22.9 –13.6 –31.2 0.000 –4.480

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

0.040 16,869.6 –21.9 –1.9 –37.9 0.039 –2.121

216 10A070 Puyallup River at Meridian Street, Wash. 0.036 228.7 79.6 176.1 16.8 0.009 2.667

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 0.081 63.9 –21.7 –2.0 –37.4 0.037 –2.140
144 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Station 

number Station name

Reference

concentration,

in milligrams

per liter

Reference

load, in

kilograms

per day

Flow-adjusted trend in concentration from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value t-statistic

Total phosphorus—Continued

218 11321 Johnson Creek at Southeast 17th Avenue at 

Portland, Oreg.

0.090 12.0 –7.8 11.1 –23.6 0.397 –0.854

219 11478 John Day River at Service Creek, Oreg. 0.041 118.8 –19.2 10.5 –40.9 0.187 –1.335

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. 0.104 51.7 –36.8 –13.8 –53.7 0.005 –2.900

221 12413470 South Fork Coeur D›Alene River near Pinehurst, Idaho 0.011 8.6 93.0 235.6 11.0 0.022 2.329

222 12419000 Spokane River near Post Falls, Idaho 0.011 107.9 –37.3 87.4 –79.0 0.405 –0.836

223 13154500 Snake River at King Hill, Idaho 0.068 1,759.9 –13.2 7.2 –29.8 0.191 –1.315

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 0.083 141.8 36.3 98.7 –6.4 0.110 1.614

225 13351000 Palouse River at Hooper, Wash. 0.195 101.6 –54.4 –37.0 –67.0 0.000 –4.761

227 14211720 Willamette River at Portland, Oreg. 0.061 3,996.4 13.5 37.0 –6.1 0.192 1.311

228 14246900 Columbia River at Beaver Army Terminal near 

Quincy, Oreg.

0.031 17,761.9 14.8 75.2 –24.8 0.523 0.641

229 16A070 Skokomish River near Potlatch, Wash. 0.009 15.9 104.8 265.9 14.6 0.017 2.422

230 32A070 Walla Walla River near Touchet, Wash. 0.112 71.2 –4.2 21.3 –24.3 0.724 –0.354

231 3701002 Tualatin River at Weiss Bridge, Oreg. 0.175 319.9 –32.0 –24.2 –39.1 0.000 –6.917

232 37016120 Tualatin River at Springhill Road Bridge at 

Dilley, Oreg.

0.039 23.3 –41.9 –29.4 –52.2 0.000 –5.456

233 37A090 Yakima River at Kiona, Wash. 0.102 645.6 3.1 23.1 –13.7 0.740 0.332

234 45A070 Wenatchee River at Wenatchee, Wash. 0.004 17.7 53.4 274.4 –37.2 0.349 0.940

235 45A110 Wenatchee River near Leavenworth, Wash. 0.004 20.5 13.5 154.5 –49.4 0.759 0.307

236 48A070 Methow River near Pateros, Wash. 0.003 6.3 99.5 292.6 1.3 0.048 1.998

237 49A070 Okanogan River at Malott, Wash. 0.017 98.8 16.2 111.7 –36.3 0.626 0.489

238 54A120 Spokane River at Riverside State Park, Wash. 0.019 195.0 39.9 123.2 –12.4 0.162 1.407

239 61A070 Columbia River at Northport, Wash. 0.011 2,516.8 –33.5 24.5 –64.5 0.205 –1.274

241 11274538 Orestimba Creek at River Road near Crows 

Landing, Calif.

0.183 9.5 16.2 55.8 –13.4 0.319 0.999

242 11290000 Tuolumne River at Modesto, Calif. 0.074 146.6 –4.9 26.0 –28.3 0.726 –0.350

243 11303500 San Joaquin River near Vernalis, Calif. 0.274 2,217.1 –3.2 11.8 –16.2 0.660 –0.441

244 11447650 Sacramento River at Freeport, Calif. 0.039 2,100.3 59.6 121.8 14.9 0.006 2.786

Total nitrogen

1 01122610 Shetucket River at South Windham, Conn. 0.603 713.2 6.2 31.2 –14.1 0.581 0.553

2 01124000 Quinebaug River at Quinebaug, Conn. 0.530 228.7 34.8 60.2 13.4 0.001 3.381

3 01127000 Quinebaug River at Jewett City, Conn. 0.913 1,755.0 –4.3 12.3 –18.4 0.590 –0.540

4 01184000 Connecticut River at Thompsonville, Conn. 0.624 20,452.8 2.6 21.1 –13.1 0.766 0.298

5 01184490 Broad Brook at Broad Brook, Conn. 4.259 233.2 –2.2 5.9 –9.7 0.585 –0.549

6 01188090 Farmington River at Unionville, Conn. 0.270 377.6 37.6 103.3 –6.9 0.115 1.603

7 01189995 Farmington River at Tariffville, Conn. 1.018 2,412.9 10.4 29.7 –5.9 0.229 1.213

8 01192500 Hockanum River near East Hartford, Conn. 3.480 947.7 –4.5 10.2 –17.3 0.526 –0.636

9 01193500 Salmon River near East Hampton, Conn. 0.436 111.0 16.4 58.7 –14.6 0.341 0.962

10 01196500 Quinnipiac River at Wallingford, Conn. 3.208 1,328.9 –4.2 7.4 –14.5 0.462 –0.739

11 01205500 Housatonic River at Stevenson, Conn. 0.661 2,492.3 12.1 41.3 –11.0 0.338 0.968

12 01208500 Naugatuck River at Beacon Falls, Conn. 2.492 2,334.6 –52.9 –43.6 –60.7 0.000 –8.145

13 01208990 Saugatuck River near Redding, Conn. 0.307 12.6 40.1 106.2 –4.8 0.094 1.708

14 01209710 Norwalk River at Winnipauk, Conn. 0.642 48.4 24.3 46.3 5.7 0.009 2.623

15 01357500 Mohawk River at Cohoes, N.Y. 1.048 8,255.2 –10.1 1.1 –20.1 0.078 –1.775

16 01377000 Hackensack River at Rivervale, N.J. 1.032 153.1 10.4 37.0 –11.0 0.372 0.902

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 0.500 18.3 23.2 73.4 –12.5 0.239 1.195

18 01387500 Ramapo River near Mahwah, N.J. 1.537 371.2 0.4 20.9 –16.6 0.965 0.044

19 01389500 Passaic River at Little Falls, N.J. 3.357 4,200.5 –19.1 –4.7 –31.3 0.013 –2.543

20 01391500 Saddle River at Lodi, N.J. 5.794 953.1 26.4 56.6 2.1 0.037 2.151

21 01394500 Rahway River near Springfield, N.J. 1.727 70.7 –0.3 23.4 –19.5 0.978 –0.028

22 01395000 Rahway River at Rahway, N.J. 1.407 79.3 –0.1 25.0 –20.2 0.993 –0.009
Appendix 3 145

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Station 

number Station name

Reference

concentration,

in milligrams

per liter

Reference

load, in

kilograms

per day

Flow-adjusted trend in concentration from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value t-statistic

Total nitrogen—Continued

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 1.090 30.5 –13.5 7.2 –30.2 0.193 –1.322

24 01398000 Neshanic River at Reaville, N.J. 1.753 50.7 –14.9 26.0 –42.5 0.423 –0.806

25 01402000 Millstone River at Blackwells Mills, N.J. 2.902 1,709.8 8.1 34.4 –13.1 0.490 0.697

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 2.316 3,680.5 11.0 26.6 –2.7 0.125 1.548

29 01409500 Batsto River at Batsto, N.J. 0.386 99.8 –10.3 23.9 –35.1 0.513 –0.660

31 01438500 Delaware River at Montague, N.J. 0.487 4,559.0 –23.2 –1.2 –40.3 0.046 –2.056

32 01443500 Paulins Kill at Blairstown, N.J. 0.958 325.7 7.7 36.1 –14.8 0.540 0.617

33 01463500 Delaware River at Trenton, N.J. 1.277 26,572.9 –18.3 –3.7 –30.6 0.018 –2.412

34 01467150 Cooper River at Haddonfield, N.J. 0.921 47.0 5.1 29.4 –14.7 0.644 0.464

35 01477120 Raccoon Creek near Swedesboro, N.J. 1.658 117.8 6.9 30.0 –12.1 0.507 0.667

36 01491000 Choptank River near Greensboro, Md. 1.457 237.3 23.5 36.6 11.7 0.000 4.114

37 01578310 Susquehanna River at Conowingo, Md. 1.526 100,777.9 –8.5 0.6 –16.8 0.067 –1.839

38 01594440 Patuxent River near Bowie, Md. 2.078 1,380.1 0.6 9.1 –7.2 0.883 0.147

39 01614500 Conococheague Creek at Fairview, Md. 5.429 6,336.5 1.3 10.4 –7.0 0.763 0.302

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 2.010 37,023.5 –12.0 1.2 –23.5 0.075 –1.793

41 01668000 Rappahannock River near Fredericksburg, Va. 0.577 1,618.4 44.3 69.3 23.0 0.000 4.505

42 01673000 Pamunkey River near Hanover, Va. 0.653 968.7 31.9 45.5 19.5 0.000 5.500

43 01674500 Mattaponi River near Beulahville, Va. 0.623 501.5 16.2 26.3 7.0 0.000 3.548

44 02035000 James River at Cartersville, Va. 0.478 6,074.1 21.5 38.4 6.7 0.004 2.938

45 02041650 Appomattox River at Matoaca, Va. 0.587 961.9 14.1 24.6 4.5 0.004 2.932

46 02085000 Eno River at Hillsborough, N.C. 0.664 30.8 17.9 40.0 –0.7 0.064 1.882

47 02089500 Neuse River at Kinston, N.C. 1.493 6,248.6 –36.1 –26.9 –44.2 0.000 –6.511

48 02091500 Contentnea Creek at Hookerton, N.C. 1.242 1,095.9 –11.1 –2.9 –18.5 0.010 –2.630

49 0210215985 Cape Fear River at State Highway 42 near 

Brickhaven, N.C.

1.363 5,800.4 1.2 37.4 –25.4 0.939 0.077

52 02213700 Ocmulgee River near Warner Robins, Ga. 1.350 5,825.2 –5.5 27.2 –29.8 0.710 –0.374

53 02215500 Ocmulgee River at Lumber City, Ga. 0.965 12,295.7 –16.4 1.1 –30.8 0.068 –1.844

57 02271500 Josephine Creek near De Soto City, Fla. 0.889 66.0 36.4 61.5 15.1 0.001 3.589

58 02295420 Payne Creek near Bowling Green, Fla. 1.696 343.5 –10.3 15.3 –30.2 0.401 –0.847

59 02296750 Peace River at Arcadia, Fla. 1.780 2,210.8 –2.1 13.1 –15.3 0.771 –0.293

60 02300700 Bullfrog Creek near Wimauma, Fla. 0.782 41.0 22.1 49.5 –0.3 0.056 1.931

61 02301300 South Prong Alafia River near Lithia, Fla. 1.056 146.0 2.6 29.7 –18.9 0.832 0.213

62 02302500 Blackwater Creek near Knights, Fla. 1.693 139.6 –16.5 6.5 –34.6 0.152 –1.454

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 1.005 703.5 36.0 57.5 17.4 0.000 4.091

67 02338000 Chattahoochee River near Whitesburg, Ga. 1.386 13,838.9 11.8 37.7 –9.2 0.297 1.048

71 02492000 Bogue Chitto River near Bush, La. 0.819 3,334.4 16.5 103.3 –33.2 0.592 0.538

72 03353637 Little Buck Creek near Indianapolis, Ind. 1.079 27.7 –2.8 15.9 –18.6 0.749 –0.320

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 1.344 812,588.8 20.4 44.1 0.7 0.044 2.032

74 04063700 Popple River near Fence, Wis. 0.453 104.0 26.3 47.2 8.4 0.003 2.998

76 04087000 Milwaukee River at Milwaukee, Wis. 1.724 1,621.8 31.9 48.4 17.2 0.000 4.597

81 05114000 Souris River near Sherwood, N. Dak. 2.076 26.3 –18.0 10.9 –39.4 0.201 –1.291

82 05120000 Souris River near Verendrye, N. Dak. 1.507 159.0 0.6 39.0 –27.2 0.970 0.037

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 1.615 25.2 –32.2 –12.4 –47.5 0.004 –2.972

95 07022000 Mississippi River at Thebes, Ill. 3.227 2,473,864.5 13.7 36.7 –5.5 0.176 1.362

97 06178000 Poplar River at International Boundary, Mont. 0.613 5.7 7.6 44.1 –19.6 0.625 0.492

99 06329500 Yellowstone River near Sidney, Mont. 0.606 17,700.9 51.2 114.0 6.8 0.022 2.331

100 06338490 Missouri River at Garrison Dam, N. Dak. 0.193 8,511.6 39.8 131.3 –15.5 0.197 1.304

101 06461500 Niobrara River near Sparks, Nebr. 0.441 848.9 67.8 138.6 18.0 0.005 2.884

102 06468250 James River above Arrowwood Lake near 

Kensal, N. Dak.

1.518 43.5 5.4 36.7 –18.7 0.692 0.398

103 06713500 Cherry Creek at Denver, Colo. 3.828 203.1 –44.3 –30.7 –55.3 0.000 –5.243

106 06753990 Lonetree Creek near Greeley, Colo. 9.761 347.6 –42.3 –22.1 –57.3 0.001 –3.595
146 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Station 

number Station name

Reference

concentration,

in milligrams

per liter

Reference

load, in

kilograms

per day

Flow-adjusted trend in concentration from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value t-statistic

Total nitrogen—Continued

107 06754000 South Platte River near Kersey, Colo. 6.215 14,303.8 7.6 16.6 –0.6 0.074 1.802

108 06775900 Dismal River near Thedford, Nebr. 0.717 373.4 –5.5 10.1 –18.8 0.473 –0.722

109 06800000 Maple Creek near Nickerson, Nebr. 6.015 1,789.4 34.2 71.4 5.0 0.020 2.354

110 06805500 Platte River at Louisville, Nebr. 2.642 74,129.1 60.2 105.0 25.2 0.000 3.748

111 06817700 Nodaway River near Graham, Mo. 5.273 13,102.7 –4.4 48.8 –38.6 0.841 –0.201

112 06818000 Missouri River at St. Joseph, Mo. 3.257 512,446.0 –43.7 –27.5 –56.2 0.000 –4.460

113 06902000 Grand River near Sumner, Mo. 1.723 15,003.1 21.4 83.2 –19.6 0.358 0.923

114 06905500 Chariton River near Prairie Hill, Mo. 1.607 5,279.4 –17.0 24.5 –44.7 0.369 –0.902

115 06921070 Pomme De Terre River near Polk, Mo. 0.544 188.8 36.1 116.2 –14.4 0.196 1.303

116 06926510 Osage River below St. Thomas, Mo. 0.752 25,153.3 –7.3 24.9 –31.2 0.620 –0.499

118 06934500 Missouri River at Hermann, Mo. 2.025 690,237.8 22.5 58.4 –5.2 0.124 1.550

120 07053250 Yocum Creek near Oak Grove, Ark. 2.529 239.0 89.9 138.3 51.3 0.000 5.530

124 07066110 Jacks Fork above Two River, Mo. 0.448 539.4 6.6 31.5 –13.5 0.549 0.602

125 07068000 Current River at Doniphan, Mo. 0.426 3,386.9 –20.8 –3.9 –34.7 0.020 –2.362

134 07189000 Elk River near Tiff City, Mo. 1.721 3,076.2 36.6 63.2 14.3 0.001 3.429

135 07195500 Illinois River near Watts, Okla. 2.523 3,615.6 5.8 32.4 –15.4 0.621 0.496

136 07195865 Sager Creek near West Siloam Springs, Okla. 6.666 236.8 11.3 46.3 –15.4 0.448 0.765

137 07196000 Flint Creek near Kansas, Okla. 1.882 452.7 63.1 83.2 45.1 0.000 8.236

138 07196500 Illinois River near Tahlequah, Okla. 1.723 3,678.5 20.5 41.2 2.8 0.023 2.301

139 07197000 Baron Fork at Eldon, Okla. 1.033 727.1 40.7 83.1 8.2 0.012 2.545

145 07247015 Poteau River at Loving, Okla. 0.439 70.8 16.8 53.8 –11.3 0.271 1.109

146 07247250 Black Fork below Big Creek near Page, Okla. 0.315 43.7 –5.0 41.4 –36.1 0.802 –0.251

147 07247345 Black Fork at Hodgen, Okla. 0.322 44.5 5.9 49.0 –24.7 0.744 0.328

148 07247650 Fourche Maline near Leflore, Okla. 0.610 69.4 9.4 36.6 –12.4 0.430 0.794

149 07263620 Arkansas River at David D. Terry Lock and Dam 

below Little Rock, Ark.

0.842 86,502.2 8.5 29.9 –9.3 0.373 0.895

150 07331000 Washita River near Dickson, Okla. 0.988 5,642.1 72.5 124.8 32.3 0.000 4.030

151 07355500 Red River at Alexandria, La. 0.715 49,016.7 7.7 23.5 –6.1 0.292 1.059

152 07362000 Ouachita River at Camden, Ark. 0.312 3,570.6 52.9 127.0 2.9 0.040 2.103

153 07373420 Mississippi River near St Francisville, La. 2.096 2,958,811.0 –5.0 11.7 –19.2 0.534 –0.623

154 07375500 Tangipahoa River at Robert, La. 0.909 2,098.0 –10.2 15.4 –30.1 0.402 –0.841

155 07376000 Tickfaw River at Holden, La. 0.873 582.4 –3.0 26.3 –25.5 0.820 –0.229

156 07381495 Atchafalaya River at Melville, La. 1.776 1,071,142.5 –5.6 8.6 –17.9 0.424 –0.802

157 07386980 Vermilion River at Perry, La. 1.888 3,615.4 –16.8 1.3 –31.7 0.070 –1.834

173 08251500 Rio Grande near Lobatos, Colo. 0.440 489.8 14.3 46.8 –11.0 0.298 1.047

176 09211200 Green River below Fontenelle Reservoir, Wyo. 0.230 797.3 28.9 76.9 –6.1 0.119 1.573

179 09380000 Colorado River at Lees Ferry, Ariz. 0.368 12,388.6 5.6 40.6 –20.8 0.713 0.369

182 09415000 Virgin River at Littlefield, Ariz. 0.841 547.7 194.4 382.6 79.6 0.000 4.281

196 10336610 Upper Truckee River at South Lake Tahoe, Calif. 0.210 25.4 8.0 30.0 –10.3 0.418 0.812

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 0.304 3.1 –4.8 23.6 –26.7 0.713 –0.369

201 10336740 Logan House Creek near Glenbrook, Nev. 0.313 0.2 –21.3 –1.5 –37.2 0.038 –2.088

202 10336760 Edgewood Creek at Stateline, Nev. 0.328 2.7 –34.6 –20.9 –46.0 0.000 –4.381

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 0.967 63,781.1 –22.0 6.0 –42.6 0.118 –1.590

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

0.791 22,459.5 –50.0 –35.8 –61.0 0.000 –5.436

210 10355 Willamette River at Highway 99 East at 

Harrisburg, Oreg.

0.430 9,822.5 –49.5 –33.9 –61.3 0.000 –4.988

212 10411 Deschutes River at Deschutes River Park, Oreg. 0.316 4,325.5 –24.4 1.1 –43.5 0.064 –1.885

213 10555 Willamette River at Marion Street at Salem, Oreg. 0.912 41,756.6 –51.9 –41.3 –60.6 0.000 –7.192

214 10611 Willamette River at Hawthorne Bridge, Oreg. 1.171 77,155.4 –39.1 –24.9 –50.5 0.000 –4.647

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

0.459 193,915.3 –28.4 6.0 –51.6 0.101 –1.670
Appendix 3 147

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Station 

number Station name

Reference

concentration,

in milligrams

per liter

Reference

load, in

kilograms

per day

Flow-adjusted trend in concentration from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value t-statistic

Total nitrogen—Continued

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 1.009 800.3 –45.0 –27.8 –58.1 0.000 –4.302

218 11321 Johnson Creek at Southeast 17th Avenue at 

Portland, Oreg.

4.554 613.9 –30.4 –23.5 –36.6 0.000 –7.535

219 11478 John Day River at Service Creek, Oreg. 0.293 865.5 –36.8 –9.1 –56.1 0.016 –2.471

220 11489 Umatilla River at Westland Road at Hermiston, Oreg. 2.665 1,344.9 –38.5 –18.8 –53.4 0.001 –3.431

221 12413470 South Fork Coeur D›Alene River near Pinehurst, 

Idaho

0.230 183.1 16.7 53.7 –11.4 0.276 1.096

222 12419000 Spokane River near Post Falls, Idaho 0.138 1,320.8 14.0 61.6 –19.5 0.462 0.739

223 13154500 Snake River at King Hill, Idaho 1.480 38,562.4 –5.4 4.1 –14.1 0.259 –1.134

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 0.565 951.1 22.7 47.5 2.1 0.032 2.178

225 13351000 Palouse River at Hooper, Wash. 1.724 903.2 2.3 21.9 –14.2 0.800 0.254

227 14211720 Willamette River at Portland, Oreg. 0.781 51,090.1 –2.4 14.3 –16.7 0.760 –0.305

228 14246900 Columbia River at Beaver Army Terminal near 

Quincy, Oreg.

0.473 269,349.9 –7.2 10.6 –22.1 0.406 –0.835

231 3701002 Tualatin River at Weiss Bridge, Oreg. 2.701 4,963.9 6.4 13.5 –0.3 0.064 1.859

232 37016120 Tualatin River at Springhill Road Bridge at 

Dilley, Oreg.

0.553 328.8 –33.8 –24.1 –42.2 0.000 –5.946

241 11274538 Orestimba Creek at River Road near Crows 

Landing, Calif.

2.839 148.3 2.5 31.7 –20.3 0.849 0.190

242 11290000 Tuolumne River at Modesto, Calif. 0.378 784.8 128.5 170.8 92.8 0.000 9.533

243 11303500 San Joaquin River near Vernalis, Calif. 2.012 16,922.7 1.9 13.5 –8.6 0.737 0.336

244 11447650 Sacramento River at Freeport, Calif. 0.238 12,908.4 48.8 95.5 13.2 0.005 2.851

Nitrate

1 01122610 Shetucket River at South Windham, Conn. 0.393 466.0 –18.2 3.2 –35.2 0.093 –1.694

2 01124000 Quinebaug River at Quinebaug, Conn. 0.260 109.8 10.3 34.2 –9.4 0.331 0.978

3 01127000 Quinebaug River at Jewett City, Conn. 0.481 907.9 –19.5 14.1 –43.3 0.226 –1.220

4 01184000 Connecticut River at Thompsonville, Conn. 0.327 10,733.3 5.1 24.5 –11.2 0.562 0.580

5 01184490 Broad Brook at Broad Brook, Conn. 3.743 205.1 –0.9 8.2 –9.2 0.838 –0.206

6 01188090 Farmington River at Unionville, Conn. 0.183 255.1 –28.6 –8.1 –44.6 0.012 –2.610

7 01189995 Farmington River at Tariffville, Conn. 0.641 1,508.4 1.9 15.3 –9.9 0.767 0.297

8 01192500 Hockanum River near East Hartford, Conn. 2.545 687.6 –3.3 17.5 –20.4 0.735 –0.339

9 01193500 Salmon River near East Hampton, Conn. 0.297 74.5 –25.6 20.8 –54.2 0.237 –1.197

10 01196500 Quinnipiac River at Wallingford, Conn. 2.625 1,078.3 –14.9 –4.3 –24.3 0.008 –2.703

11 01205500 Housatonic River at Stevenson, Conn. 0.342 1,289.9 13.0 51.7 –15.9 0.421 0.811

12 01208500 Naugatuck River at Beacon Falls, Conn. 1.055 973.7 –19.4 –2.8 –33.1 0.027 –2.253

13 01208990 Saugatuck River near Redding, Conn. 0.120 4.8 –5.1 82.3 –50.6 0.876 –0.157

14 01209710 Norwalk River at Winnipauk, Conn. 0.392 28.9 –1.2 28.3 –23.9 0.928 –0.090

15 01357500 Mohawk River at Cohoes, N.Y. 0.689 5,427.1 –11.8 3.5 –24.9 0.127 –1.534

16 01377000 Hackensack River at Rivervale, N.J. 0.461 68.6 –26.3 8.8 –50.0 0.132 –1.536

17 01382500 Pequannock River at Macopin Intake Dam, N.J. 0.184 6.8 21.2 124.5 –34.5 0.544 0.612

18 01387500 Ramapo River near Mahwah, N.J. 1.292 312.8 0.2 25.6 –20.0 0.986 0.018

19 01389500 Passaic River at Little Falls, N.J. 2.719 3,429.6 –28.0 –12.0 –41.0 0.002 –3.216

20 01391500 Saddle River at Lodi, N.J. 4.463 735.0 31.1 61.2 6.7 0.013 2.578

21 01394500 Rahway River near Springfield, N.J. 1.356 55.5 1.8 34.4 –22.9 0.900 0.126

22 01395000 Rahway River at Rahway, N.J. 0.867 48.9 10.1 55.6 –22.1 0.588 0.546

23 01396660 Mulhockaway Creek at Van Syckel, N.J. 0.931 26.1 –20.5 0.3 –37.0 0.059 –1.932

24 01398000 Neshanic River at Reaville, N.J. 1.430 40.5 –16.8 58.3 –56.3 0.577 –0.561

25 01402000 Millstone River at Blackwells Mills, N.J. 2.410 1,404.9 –2.0 20.6 –20.3 0.851 –0.190

26 01403300 Raritan River at Queens Bridge at Bound Brook, N.J. 1.878 2,988.1 9.0 27.4 –6.7 0.280 1.085

29 01409500 Batsto River at Batsto, N.J. 0.168 43.6 –60.9 –36.3 –76.1 0.001 –3.763

31 01438500 Delaware River at Montague, N.J. 0.295 2,761.8 –43.7 –18.9 –60.9 0.004 –3.088

32 01443500 Paulins Kill at Blairstown, N.J. 0.795 269.5 4.6 67.9 –34.9 0.854 0.186

33 01463500 Delaware River at Trenton, N.J. 1.003 20,884.3 –24.2 –10.1 –36.1 0.002 –3.184
148 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Station 

number Station name

Reference

concentration,

in milligrams

per liter

Reference

load, in

kilograms

per day

Flow-adjusted trend in concentration from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value t-statistic

Nitrate—Continued

34 01467150 Cooper River at Haddonfield, N.J. 0.349 17.8 –26.5 3.8 –48.0 0.084 –1.749

35 01477120 Raccoon Creek near Swedesboro, N.J. 1.398 99.3 –27.9 2.3 –49.2 0.070 –1.834

36 01491000 Choptank River near Greensboro, Md. 1.291 211.9 8.4 24.6 –5.8 0.262 1.125

37 01578310 Susquehanna River at Conowingo, Md. 1.299 85,810.9 –22.5 –13.1 –30.9 0.000 –4.375

38 01594440 Patuxent River near Bowie, Md. 1.434 955.5 –10.1 –1.9 –17.7 0.018 –2.386

39 01614500 Conococheague Creek at Fairview, Md. 4.995 5,844.6 –7.8 0.2 –15.2 0.057 –1.912

40 01646580 Potomac River at Chain Bridge, at Washington, D.C. 1.807 33,032.7 –34.0 –18.8 –46.4 0.000 –3.918

41 01668000 Rappahannock River near Fredericksburg, Va. 0.312 842.3 24.6 73.0 –10.2 0.189 1.318

42 01673000 Pamunkey River near Hanover, Va. 0.282 426.2 0.6 15.8 –12.6 0.932 0.086

43 01674500 Mattaponi River near Beulahville, Va. 0.155 127.2 14.6 38.1 –4.9 0.153 1.433

44 02035000 James River at Cartersville, Va. 0.219 2,747.3 –18.1 5.3 –36.3 0.121 –1.553

45 02041650 Appomattox River at Matoaca, Va. 0.142 235.0 –18.8 –0.4 –33.8 0.046 –2.003

50 02175000 Edisto River near Givhans, S.C. 0.099 576.7 –25.9 11.4 –50.7 0.153 –1.440

65 02318500 Withlacoochee River at U.S. 84, near Quitman, Ga. 0.374 278.3 34.3 64.1 9.9 0.005 2.887

66 02335870 Sope Creek near Marietta, Ga. 0.523 41.7 –6.3 9.8 –20.1 0.422 –0.805

71 02492000 Bogue Chitto River near Bush, La. 0.243 993.5 139.0 343.6 28.7 0.007 2.761

72 03353637 Little Buck Creek near Indianapolis, Ind. 0.862 22.2 –36.2 –19.8 –49.3 0.000 –3.839

73 03612500 Ohio River at Dam 53 near Grand Chain, Ill. 1.030 623,006.8 –8.0 16.9 –27.6 0.495 –0.684

74 04063700 Popple River near Fence, Wis. 0.045 10.4 12.4 71.6 –26.5 0.591 0.539

76 04087000 Milwaukee River at Milwaukee, Wis. 0.673 629.2 92.2 181.0 31.4 0.001 3.369

81 05114000 Souris River near Sherwood, N. Dak. 0.047 0.6 –14.7 104.8 –64.4 0.724 –0.355

82 05120000 Souris River near Verendrye, N. Dak. 0.147 15.2 –61.7 24.9 –88.3 0.116 –1.591

88 05514500 Cuivre River near Troy, Mo. 0.329 143.6 37.6 305.4 –53.3 0.565 0.578

92 05540275 Spring Brook at 87th Street near Naperville, Ill. 0.842 13.1 –51.7 –30.1 –66.7 0.000 –3.854

95 07022000 Mississippi River at Thebes, Ill. 2.367 1,815,610.3 0.7 31.2 –22.6 0.956 0.055

96 06088500 Muddy Creek at Vaughn, Mont. 2.327 455.3 –49.8 –27.9 –65.1 0.000 –3.725

98 06274300 Bighorn River at Basin, Wyo. 0.288 1,385.5 –47.7 –19.3 –66.1 0.006 –2.929

99 06329500 Yellowstone River near Sidney, Mont. 0.171 4,962.6 –10.0 123.1 –63.7 0.820 –0.228

100 06338490 Missouri River at Garrison Dam, N. Dak. 0.135 5,929.0 –73.2 –55.6 –83.8 0.000 –5.115

101 06461500 Niobrara River near Sparks, Nebr. 0.262 504.1 51.9 131.0 –0.1 0.055 1.954

102 06468250 James River above Arrowwood Lake near 

Kensal, N. Dak.

0.071 1.9 –74.2 –14.7 –92.2 0.029 –2.220

103 06713500 Cherry Creek at Denver, Colo. 2.735 146.0 –46.6 –35.0 –56.2 0.000 –6.219

104 06752260 Cache La Poudre River at Fort Collins, Colo. 0.293 32.7 –73.6 –56.5 –84.0 0.000 –5.208

105 06752280 Cache La Poudre River above Boxelder Creek, near 

Timnath, Colo.

0.576 42.3 –13.4 30.9 –42.7 0.497 –0.681

106 06753990 Lonetree Creek near Greeley, Colo. 6.915 248.1 –56.3 –40.4 –68.0 0.000 –5.210

107 06754000 South Platte River near Kersey, Colo. 4.974 11,468.1 2.7 11.4 –5.4 0.533 0.626

108 06775900 Dismal River near Thedford, Nebr. 0.458 238.9 7.7 25.1 –7.3 0.335 0.973

109 06800000 Maple Creek near Nickerson, Nebr. 6.192 1,851.1 –29.7 5.2 –53.0 0.089 –1.713

110 06805500 Platte River at Louisville, Nebr. 1.487 41,578.2 9.7 108.4 –42.3 0.779 0.282

111 06817700 Nodaway River near Graham, Mo. 3.433 8,367.0 52.4 407.1 –54.2 0.494 0.686

112 06818000 Missouri River at St. Joseph, Mo. 1.951 306,902.8 –62.9 –37.1 –78.1 0.000 –3.678

113 06902000 Grand River near Sumner, Mo. 0.431 3,650.1 51.2 297.9 –42.6 0.404 0.837

114 06905500 Chariton River near Prairie Hill, Mo. 0.420 1,363.0 80.7 286.0 –15.4 0.130 1.527

115 06921070 Pomme De Terre River near Polk, Mo. 0.215 73.3 126.1 470.8 –10.5 0.088 1.726

116 06926510 Osage River below St. Thomas, Mo. 0.352 11,602.8 –59.5 –18.1 –80.0 0.015 –2.515

117 06930800 Gasconade River above Jerome, Mo. 0.416 2,262.0 –0.7 49.1 –33.8 0.974 –0.032

118 06934500 Missouri River at Hermann, Mo. 1.399 477,034.2 –29.6 11.6 –55.6 0.138 –1.493

119 07047942 L›Anguille River near Colt, Ark. 0.451 234.9 –46.1 –6.6 –68.9 0.032 –2.201

120 07053250 Yocum Creek near Oak Grove, Ark. 2.245 212.2 109.0 195.9 47.6 0.000 4.152

121 07056000 Buffalo River near St Joe, Ark. 0.067 75.2 67.3 151.7 11.3 0.015 2.473
Appendix 3 149

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Station 

number Station name

Reference

concentration,

in milligrams

per liter

Reference

load, in

kilograms

per day

Flow-adjusted trend in concentration from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value t-statistic

Nitrate—Continued

122 07060500 White River at Calico Rock, Ark. 0.241 7,572.9 28.2 81.9 –9.6 0.169 1.394

123 07060710 North Sylamore Creek near Fifty Six, Ark. 0.064 3.5 –2.3 30.5 –26.9 0.873 –0.160

124 07066110 Jacks Fork above Two River, Mo. 0.290 349.2 22.7 53.9 –2.2 0.081 1.770

125 07068000 Current River at Doniphan, Mo. 0.282 2,237.4 –13.2 5.1 –28.3 0.150 –1.448

126 07077500 Cache River at Patterson, Ark. 0.256 346.6 –17.5 39.7 –51.3 0.479 –0.715

127 07077700 Bayou DeView near Morton, Ark. 0.153 26.7 69.9 222.4 –10.5 0.117 1.621

128 07103700 Fountain Creek near Colorado Springs, Colo. 0.750 33.8 –5.8 14.7 –22.6 0.555 –0.593

129 07103780 Monument Creek above North Gate Boulevard at 

United States Air Force Academy, Colo.

0.127 2.4 282.0 708.1 80.5 0.001 3.505

130 07105500 Fountain Creek at Colorado Springs, Colo. 1.563 221.8 8.6 25.1 –5.7 0.254 1.146

131 07105530 Fountain Creek below Janitell Road below Colorado 

Springs, Colo.

1.665 476.5 45.2 68.9 24.8 0.000 4.820

132 07106300 Fountain Creek near Pinon, Colo. 5.192 1,533.4 –48.4 –35.0 –59.0 0.000 –5.624

133 07106500 Fountain Creek at Pueblo, Colo. 5.306 1,698.0 –55.1 –50.0 –59.7 0.000 –14.605

134 07189000 Elk River near Tiff City, Mo. 1.572 2,808.9 46.4 76.1 21.7 0.000 4.044

135 07195500 Illinois River near Watts, Okla. 2.450 3,516.5 –17.7 13.4 –40.3 0.236 –1.192

136 07195865 Sager Creek near West Siloam Springs, Okla. 6.241 222.0 11.5 49.4 –16.8 0.469 0.730

137 07196000 Flint Creek near Kansas, Okla. 1.871 450.8 59.6 79.5 42.0 0.000 7.831

138 07196500 Illinois River near Tahlequah, Okla. 1.684 3,597.3 2.6 24.0 –15.1 0.791 0.265

139 07197000 Baron Fork at Eldon, Okla. 1.033 728.8 35.0 78.2 2.2 0.037 2.116

140 07227500 Canadian River near Amarillo, Tex. 0.173 33.1 515.1 1,605.0 121.9 0.001 3.492

141 07239450 North Canadian River near Calumet, Okla. 0.084 31.9 –32.6 58.2 –71.3 0.366 –0.907

142 07241000 North Canadian River below Lake Overholser near 

Oklahoma City, Okla.

0.249 143.1 –47.1 –1.6 –71.6 0.046 –2.011

143 07241520 North Canadian River at Britton Road at Oklahoma 

City, Okla.

0.601 543.7 –28.4 19.1 –56.9 0.201 –1.286

144 07241550 North Canadian River near Harrah, Okla. 1.176 1,563.3 –0.0 44.8 –31.0 0.998 –0.002

145 07247015 Poteau River at Loving, Okla. 0.088 14.1 45.8 161.3 –18.6 0.209 1.267

146 07247250 Black Fork below Big Creek near Page, Okla. 0.063 8.6 124.0 263.5 38.0 0.002 3.263

147 07247345 Black Fork at Hodgen, Okla. 0.033 4.6 109.8 281.3 15.5 0.018 2.432

148 07247650 Fourche Maline near Leflore, Okla. 0.093 10.4 8.4 76.4 –33.3 0.745 0.327

149 07263620 Arkansas River at David D. Terry Lock and Dam 

below Little Rock, Ark.

0.382 39,163.4 –50.8 –12.6 –72.3 0.018 –2.419

150 07331000 Washita River near Dickson, Okla. 0.366 2,068.8 17.6 178.9 –50.4 0.714 0.368

151 07355500 Red River at Alexandria, La. 0.155 10,592.5 –43.1 –9.9 –64.1 0.018 –2.406

152 07362000 Ouachita River at Camden, Ark. 0.126 1,444.2 2.9 62.8 –35.0 0.903 0.123

153 07373420 Mississippi River near St Francisville, La. 1.562 2,204,310.2 –15.4 3.1 –30.6 0.100 –1.654

154 07375500 Tangipahoa River at Robert, La. 0.366 846.8 –13.6 6.2 –29.6 0.168 –1.386

155 07376000 Tickfaw River at Holden, La. 0.301 201.3 –13.9 6.7 –30.4 0.175 –1.368

156 07381495 Atchafalaya River at Melville, La. 1.123 687,594.0 –16.0 5.1 –32.9 0.129 –1.527

157 07386980 Vermilion River at Perry, La. 0.376 724.2 27.9 91.3 –14.4 0.233 1.200

158 08030500 Sabine River near Ruliff, Tex. 0.078 1,136.0 –31.8 –0.9 –53.1 0.047 –2.008

159 08032000 Neches River near Neches, Tex. 0.135 135.7 –9.4 57.1 –47.7 0.727 –0.350

160 08033500 Neches River near Rockland, Tex. 0.184 561.9 8.9 74.3 –31.9 0.722 0.357

161 08051500 Clear Creek near Sanger, Tex. 0.122 13.2 67.4 219.6 –12.4 0.122 1.560

162 08064100 Chambers Creek near Rice, Tex. 0.254 21.8 –16.4 57.9 –55.7 0.582 –0.552

163 08065350 Trinity River near Crockett, Tex. 1.673 20,455.8 –2.3 66.3 –42.6 0.932 –0.086

164 08136500 Concho River at Paint Rock, Tex. 11.897 2,164.9 –93.4 –76.6 –98.1 0.000 –4.222

167 08155200 Barton Creek at State Highway 71 near Oak Hill, Tex. 0.042 0.2 5.0 83.9 –40.0 0.864 0.171

168 08155240 Barton Creek at Lost Creek Boulevard near 

Austin, Tex.

0.063 0.4 54.9 132.9 2.9 0.039 2.099

172 08181800 San Antonio River near Elmendorf, Tex. 8.417 5,777.2 13.3 51.2 –15.0 0.396 0.852
150 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Station 

number Station name

Reference

concentration,

in milligrams

per liter

Reference

load, in

kilograms

per day

Flow-adjusted trend in concentration from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value t-statistic

Nitrate—Continued

174 09058000 Colorado River near Kremmling, Colo. 0.121 284.9 –0.2 49.5 –33.3 0.994 –0.008

175 09163500 Colorado River near Colorado-Utah State Line 0.579 10,028.4 –9.2 10.7 –25.5 0.343 –0.951

177 09217010 Green River below Green River, Wyo. 0.070 248.9 –10.1 32.5 –38.9 0.594 –0.536

181 09413500 Virgin River below First Narrows, Utah 0.901 473.6 29.8 84.3 –8.6 0.148 1.460

187 10038000 Bear River below Smiths Fork, near Cokeville, Wyo. 0.089 69.8 –39.3 –10.9 –58.7 0.013 –2.547

189 10131000 Chalk Creek at U.S. 189 Crossing, Utah 0.253 34.0 –17.9 19.3 –43.5 0.303 –1.036

190 10154200 Provo River above Woodland at U.S. Geological 

Survey Gage Number 10154200, Utah

0.112 39.0 98.6 207.9 28.1 0.003 3.067

191 10155000 Provo River at Bridge 2.5 miles East of Hailstone 

Junction, Utah

0.039 18.0 301.6 649.6 115.1 0.000 4.365

192 10155500 Provo River above Confluence with Snake Creek at 

McKeller Bridge, Utah

0.463 151.3 –54.8 –36.5 –67.8 0.000 –4.581

194 10336580 Upper Truckee River at South Upper Truckee Road 

near Meyers, Calif.

0.009 0.4 2.1 39.2 –25.1 0.894 0.133

195 103366092 Upper Truckee River at Highway 50 above 

Meyers, Calif.

0.014 1.3 –21.3 –2.2 –36.7 0.032 –2.162

197 10336698 Third Creek near Crystal Bay, Nev. 0.017 0.3 –67.9 –56.7 –76.2 0.000 –7.433

198 103366993 Incline Creek above Tyrol Village near Incline 

Village, Nev.

0.013 0.1 10.3 45.9 –16.6 0.491 0.690

199 103366995 Incline Creek at Highway 28 at Incline Village, Nev. 0.019 0.2 2.4 26.6 –17.2 0.829 0.216

200 10336700 Incline Creek near Crystal Bay, Nev. 0.021 0.4 –0.7 21.7 –18.9 0.949 –0.065

201 10336740 Logan House Creek near Glenbrook, Nev. 0.004 0.0 70.7 396.2 –41.3 0.328 0.981

205 07A090 Snohomish River at Snohomish, Wash. 0.236 4,071.6 –7.0 10.2 –21.6 0.401 –0.842

207 09A190 Green River at Kanaskat, Wash. 0.084 123.5 –4.0 32.2 –30.2 0.805 –0.247

208 10332 Willamette River at SP&S Railroad Bridge, Oreg. 0.587 38,708.1 –24.1 6.9 –46.1 0.121 –1.579

209 10350 Willamette River at Eastbound Highway 20 Bridge at 

Albany, Oreg.

0.348 9,869.7 –39.8 –20.0 –54.6 0.001 –3.505

210 10355 Willamette River at Highway 99 East at 

Harrisburg, Oreg.

0.153 3,494.3 –27.0 –10.3 –40.7 0.003 –2.990

213 10555 Willamette River at Marion Street at Salem, Oreg. 0.473 21,656.5 –44.2 –30.8 –54.9 0.000 –5.337

215 10616 Columbia River at Marker number 47 upstream of 

Willamette River, Oreg.

0.152 63,995.8 30.3 94.9 –12.9 0.203 1.288

217 11140 Long Tom River at Stow Pit Road at Monearoe, Oreg. 0.161 128.5 –22.9 54.5 –61.6 0.467 –0.734

218 11321 Johnson Creek at Southeast 17th Avenue at 

Portland, Oreg.

4.288 578.3 –29.6 –20.8 –37.5 0.000 –5.852

224 13206000 Boise River at Glenwood Bridge near Boise, Idaho 0.446 750.9 –11.8 17.2 –33.6 0.390 –0.865

225 13351000 Palouse River at Hooper, Wash. 1.113 577.5 –12.2 27.8 –39.7 0.499 –0.678

226 14201300 Zollner Creek near Mt. Angel, Oreg. 8.370 134.4 25.0 54.2 1.3 0.039 2.085

228 14246900 Columbia River at Beaver Army Terminal near 

Quincy, Oreg.

0.289 164,026.5 –33.2 –11.5 –49.5 0.006 –2.813

229 16A070 Skokomish River near Potlatch, Wash. 0.105 177.0 –59.7 –47.4 –69.1 0.000 –6.705

234 45A070 Wenatchee River at Wenatchee, Wash. 0.064 302.1 1.2 25.8 –18.6 0.916 0.105

235 45A110 Wenatchee River near Leavenworth, Wash. 0.026 117.0 7.6 57.9 –26.7 0.709 0.374

237 49A070 Okanogan River at Malott, Wash. 0.023 138.1 7.6 87.5 –38.3 0.796 0.259

238 54A120 Spokane River at Riverside State Park, Wash. 0.346 3,664.7 47.9 86.7 17.2 0.001 3.300

239 61A070 Columbia River at Northport, Wash. 0.056 12,434.4 0.5 19.1 –15.2 0.956 0.055

240 11264500 Merced River at Happy Isles Bridge near 

Yosemite, Calif.

0.053 21.9 –50.6 –16.3 –70.8 0.010 –2.623

241 11274538 Orestimba Creek at River Road near Crows 

Landing, Calif.

2.006 105.3 5.3 36.8 –18.9 0.698 0.389

242 11290000 Tuolumne River at Modesto, Calif. 0.254 529.0 125.8 173.3 86.5 0.000 8.362

243 11303500 San Joaquin River near Vernalis, Calif. 0.987 8,323.0 4.8 15.4 –4.8 0.335 0.964

244 11447650 Sacramento River at Freeport, Calif. 0.147 7,982.7 –32.4 –10.0 –49.2 0.008 –2.683
Appendix 3 151

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Non-flow-adjusted trend in concentration from 1993 to 2003 Trend in load from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Total phosphorus

1 66.7 166.4 4.3 0.033 0.239 33.7 152.9 –29.3 0.372 0.325

2 24.2 94.9 –20.9 0.347 0.230 –5.3 86.7 –52.0 0.874 0.347

3 81.6 169.9 22.2 0.003 0.202 75.0 228.8 –6.9 0.082 0.322

4 28.0 91.3 –14.3 0.228 0.205 15.2 90.0 –30.1 0.578 0.255

5 –17.0 19.2 –42.3 0.312 0.185 –31.6 25.7 –62.8 0.221 0.311

7 55.8 110.8 15.1 0.004 0.154 16.6 65.9 –18.1 0.394 0.180

8 –8.1 24.8 –32.3 0.590 0.156 –27.7 –5.0 –45.0 0.020 0.139

10 –18.1 9.1 –38.5 0.173 0.146 –24.0 8.1 –46.5 0.127 0.179

11 10.3 188.7 –57.8 0.841 0.491 5.2 242.2 –67.7 0.933 0.602

12 74.8 163.2 16.1 0.007 0.209 52.2 119.1 5.7 0.024 0.186

13 26.6 326.9 –62.5 0.704 0.620 48.3 553.1 –66.3 0.602 0.756

14 43.9 95.6 5.8 0.020 0.157 42.6 214.6 –35.4 0.379 0.404

15 13.9 76.5 –26.5 0.559 0.223 38.7 169.9 –28.7 0.336 0.340

16 20.7 104.4 –28.7 0.484 0.269 –7.6 74.3 –51.0 0.806 0.324

17 –53.1 67.0 –86.8 0.242 0.648 –74.7 50.9 –95.8 0.131 0.911

18 –6.9 48.7 –41.7 0.763 0.239 6.5 77.8 –36.2 0.811 0.262

19 19.3 101.4 –29.3 0.509 0.267 –2.5 78.7 –46.8 0.935 0.309

20 115.1 241.7 35.4 0.001 0.236 124.3 246.3 45.2 0.000 0.222

22 35.7 87.2 –1.7 0.063 0.164 49.4 193.2 –23.9 0.243 0.344

24 23.8 184.0 –46.0 0.614 0.424 27.5 416.9 –68.5 0.734 0.714

25 34.3 89.1 –4.7 0.092 0.175 15.9 69.0 –20.6 0.444 0.193

26 21.4 73.2 –14.9 0.285 0.181 0.7 44.9 –30.0 0.969 0.186

27 –4.7 71.7 –47.1 0.872 0.301 –20.2 91.9 –66.8 0.614 0.448

28 29.1 269.6 –54.9 0.634 0.537 16.4 265.1 –62.9 0.794 0.583

30 –14.1 221.7 –77.1 0.821 0.674 –13.1 282.5 –80.3 0.852 0.756

31 –43.9 57.1 –80.0 0.271 0.525 –40.4 94.0 –81.7 0.390 0.602

32 4.5 116.1 –49.4 0.905 0.370 –16.8 148.0 –72.1 0.742 0.557

33 –10.7 26.2 –36.9 0.520 0.177 –9.9 63.5 –50.4 0.731 0.304

34 –3.7 37.1 –32.3 0.835 0.180 –30.7 12.2 –57.2 0.136 0.246

35 27.9 80.9 –9.6 0.164 0.177 12.1 105.5 –38.9 0.712 0.309

36 113.6 235.0 36.1 0.001 0.230 205.9 1211.1 –28.6 0.132 0.743

37 64.5 127.5 18.9 0.003 0.165 30.3 172.5 –37.7 0.482 0.376

38 41.0 84.2 7.9 0.012 0.136 42.7 214.3 –35.2 0.378 0.403

39 14.5 63.0 –19.6 0.454 0.180 –27.5 85.7 –71.7 0.503 0.480

40 76.4 196.4 5.0 0.032 0.265 31.1 445.9 –68.5 0.709 0.728

41 6.7 125.6 –49.6 0.866 0.382 –38.7 278.1 –90.0 0.599 0.928

42 82.3 113.6 55.5 0.000 0.081 –3.0 188.3 –67.4 0.956 0.556

43 –6.9 12.2 –22.8 0.451 0.095 –56.9 110.9 –91.2 0.299 0.810

44 –11.0 15.1 –31.2 0.375 0.131 –41.8 46.9 –76.9 0.252 0.472

45 –13.5 10.1 –32.0 0.238 0.123 –44.6 110.0 –85.4 0.385 0.680

46 42.4 144.6 –17.1 0.200 0.276 43.6 471.3 –63.9 0.608 0.705

51 42.2 91.4 5.6 0.020 0.152 –30.5 15.3 –58.1 0.159 0.258

52 –38.3 –11.8 –56.9 0.008 0.182 –63.1 –42.1 –76.4 0.000 0.229

53 –40.4 –23.2 –53.8 0.000 0.130 –68.6 –21.9 –87.4 0.013 0.465

54 –20.3 0.4 –36.7 0.054 0.118 –67.8 –30.6 –85.0 0.004 0.392

55 –9.2 11.0 –25.7 0.347 0.102 –55.7 1.5 –80.6 0.054 0.423

56 48.0 118.5 0.3 0.049 0.199 –52.3 89.4 –88.0 0.293 0.704

58 31.4 66.8 3.5 0.025 0.122 –22.7 225.4 –81.6 0.726 0.733

59 –3.8 15.4 –19.8 0.676 0.093 –38.0 152.9 –84.8 0.505 0.717

60 7.9 32.4 –12.1 0.469 0.105 –19.7 76.3 –63.4 0.584 0.401

61 –39.2 –14.7 –56.7 0.004 0.173 –64.5 124.6 –94.4 0.271 0.941

62 –40.3 –22.1 –54.3 0.000 0.136 –75.3 43.3 –95.8 0.119 0.898

63 –49.8 2.7 –75.5 0.059 0.366 –56.9 122.0 –91.6 0.314 0.836

64 –71.0 –57.7 –80.0 0.000 0.191 –95.2 –78.4 –98.9 0.000 0.764
152 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Non-flow-adjusted trend in concentration from 1993 to 2003 Trend in load from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Total phosphorus—Continued

65 29.9 140.8 –30.0 0.407 0.315 6.4 218.3 –64.4 0.912 0.559

66 –26.2 38.8 –60.7 0.346 0.322 –52.8 27.9 –82.5 0.140 0.508

68 –54.8 –31.0 –70.3 0.000 0.215 –67.4 –38.0 –82.9 0.001 0.328

69 –20.7 8.0 –41.7 0.141 0.157 –56.9 –0.9 –81.3 0.048 0.425

70 –55.1 –41.0 –65.7 0.000 0.139 –60.0 –31.3 –76.7 0.001 0.276

71 38.2 86.6 2.3 0.035 0.153 –4.7 72.2 –47.3 0.872 0.302

72 0.0 66.7 –40.0 0.999 0.261 –46.7 92.0 –85.2 0.336 0.654

73 60.9 121.2 17.0 0.003 0.162 32.1 155.8 –31.8 0.409 0.337

74 –26.0 33.5 –58.9 0.318 0.301 –51.2 –1.4 –75.8 0.046 0.359

75 –27.3 –18.0 –35.5 0.000 0.061 –59.0 –17.5 –79.6 0.012 0.357

76 23.3 50.2 1.2 0.038 0.101 –11.1 41.8 –44.3 0.621 0.238

77 –41.3 –28.5 –51.9 0.000 0.101 –8.7 39.1 –40.1 0.672 0.215

78 –31.8 –6.9 –50.1 0.016 0.159 –49.4 –15.3 –69.8 0.010 0.263

79 –19.2 –2.4 –33.1 0.027 0.096 –35.3 7.5 –61.0 0.093 0.259

80 41.6 63.3 22.8 0.000 0.073 12.7 72.8 –26.5 0.585 0.218

81 –42.8 –9.8 –63.7 0.016 0.232 439.6 4,189.7 –32.1 0.111 1.058

82 –13.7 21.5 –38.7 0.399 0.174 55.5 571.7 –64.0 0.554 0.747

83 16.5 58.1 –14.2 0.327 0.156 –52.2 59.8 –85.7 0.230 0.616

84 –37.9 –12.3 –56.0 0.007 0.176 –59.9 –30.1 –77.0 0.001 0.284

85 –64.7 –55.3 –72.1 0.000 0.121 –68.1 –46.9 –80.8 0.000 0.259

86 –15.5 18.3 –39.6 0.327 0.172 –22.5 85.3 –67.6 0.567 0.445

87 –15.8 39.0 –49.0 0.501 0.256 –87.1 –41.4 –97.2 0.008 0.773

88 –23.0 46.5 –59.5 0.426 0.328 –69.5 62.7 –94.3 0.165 0.853

89 23.0 128.5 –33.8 0.513 0.316 –44.3 176.3 –88.8 0.474 0.817

90 49.4 99.1 12.1 0.006 0.147 44.5 83.9 13.5 0.003 0.123

91 84.0 143.4 39.1 0.000 0.143 45.0 88.3 11.7 0.005 0.133

92 –19.2 17.5 –44.5 0.265 0.191 –51.3 19.8 –80.2 0.117 0.459

93 112.3 171.1 66.3 0.000 0.125 –10.9 55.1 –48.8 0.682 0.283

94 –11.7 37.5 –43.3 0.581 0.226 –64.5 –25.6 –83.1 0.006 0.378

95 26.2 73.1 –7.9 0.148 0.161 –41.5 6.6 –67.9 0.080 0.306

97 –20.6 55.0 –59.4 0.499 0.342 –34.2 172.2 –84.1 0.564 0.724

99 6.3 118.5 –48.3 0.868 0.367 –46.1 42.2 –79.6 0.212 0.495

101 33.5 80.4 –1.3 0.061 0.154 26.4 79.2 –10.9 0.189 0.178

106 –73.0 –35.5 –88.7 0.003 0.444 –98.2 –89.8 –99.7 0.000 0.871

107 34.6 59.6 13.5 0.001 0.087 –25.7 40.4 –60.6 0.361 0.324

109 105.8 237.0 25.7 0.004 0.252 –36.9 82.3 –78.2 0.395 0.541

110 89.4 161.3 37.2 0.000 0.164 –26.0 33.8 –59.0 0.320 0.302

111 –36.2 27.3 –68.0 0.203 0.352 –93.2 –70.3 –98.5 0.000 0.753

112 23.4 81.2 –16.0 0.284 0.196 –29.7 31.4 –62.4 0.270 0.319

113 12.9 119.5 –41.9 0.720 0.339 –87.2 –26.3 –97.8 0.021 0.893

114 –42.8 13.8 –71.2 0.112 0.351 –93.4 –60.4 –98.9 0.003 0.912

115 –22.8 20.9 –50.7 0.258 0.229 –78.2 –26.9 –93.5 0.014 0.618

118 64.5 169.3 0.5 0.048 0.252 –38.3 40.2 –72.9 0.249 0.419

120 18.9 52.9 –7.5 0.176 0.128 –50.8 –11.3 –72.7 0.018 0.301

134 280.3 433.1 171.2 0.000 0.172 38.2 151.9 –24.1 0.290 0.306

135 110.3 206.8 44.1 0.000 0.193 8.5 99.6 –41.0 0.792 0.311

136 94.5 250.7 7.9 0.027 0.301 55.9 149.2 –2.5 0.064 0.239

137 79.7 130.6 40.1 0.000 0.127 –12.4 72.0 –55.4 0.700 0.345

138 80.4 139.7 35.7 0.000 0.145 –10.0 83.5 –55.9 0.772 0.363

139 6.5 64.0 –30.9 0.777 0.220 –59.4 –0.2 –83.5 0.049 0.459

145 –13.6 29.7 –42.4 0.481 0.207 –41.8 71.2 –80.2 0.326 0.550

148 –0.6 39.0 –28.9 0.971 0.171 –67.9 5.5 –90.2 0.061 0.606

149 47.4 91.5 13.4 0.004 0.134 –42.4 48.3 –77.6 0.253 0.483

150 19.8 109.7 –31.5 0.526 0.285 –66.3 2.5 –88.9 0.055 0.567
Appendix 3 153

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Non-flow-adjusted trend in concentration from 1993 to 2003 Trend in load from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Total phosphorus—Continued

151 –30.4 –0.1 –51.5 0.050 0.185 –41.9 54.7 –78.1 0.277 0.499

152 –27.2 26.5 –58.1 0.260 0.282 –38.4 43.7 –73.6 0.262 0.432

153 45.7 82.0 16.6 0.001 0.113 –2.5 44.5 –34.2 0.899 0.201

154 1.6 43.7 –28.2 0.929 0.177 –27.8 47.6 –64.7 0.372 0.365

155 46.0 103.3 4.9 0.025 0.169 –8.3 70.2 –50.6 0.784 0.315

156 52.7 85.9 25.4 0.000 0.100 1.0 52.4 –33.0 0.961 0.210

157 1.9 30.1 –20.3 0.882 0.125 6.2 132.2 –51.4 0.879 0.399

165 –3.2 81.1 –48.2 0.920 0.319 –45.3 110.1 –85.7 0.380 0.686

166 –69.1 2.4 –90.7 0.055 0.611 –85.0 –36.3 –96.5 0.010 0.739

169 –91.7 –61.7 –98.2 0.001 0.778 –56.9 458.4 –96.7 0.519 1.307

170 –3.1 52.1 –38.3 0.890 0.230 29.7 257.2 –52.9 0.614 0.517

171 –24.9 30.6 –56.8 0.310 0.282 –16.1 187.6 –75.5 0.780 0.629

173 25.8 66.8 –5.2 0.111 0.144 –75.8 5.9 –94.5 0.060 0.753

177 90.3 281.9 –5.2 0.070 0.355 20.3 140.9 –39.9 0.602 0.354

178 –43.8 33.1 –76.2 0.190 0.439 –66.3 1.0 –88.7 0.052 0.559

180 135.1 451.5 0.2 0.049 0.435 50.3 288.2 –41.8 0.401 0.484

182 58.4 336.2 –42.5 0.373 0.517 –41.2 154.6 –86.4 0.477 0.748

183 –26.9 230.6 –83.8 0.684 0.770 –75.3 138.6 –97.4 0.227 1.156

184 514.5 5,184.4 –28.6 0.098 1.098 127.0 4,158.2 –87.9 0.584 1.496

185 35.8 234.2 –44.9 0.506 0.460 –36.8 106.1 –80.6 0.447 0.603

186 –88.7 –67.6 –96.1 0.000 0.539 –91.4 –61.7 –98.1 0.001 0.761

188 –48.3 –22.2 –65.6 0.002 0.208 –63.4 50.4 –91.1 0.163 0.721

193 –8.5 32.7 –36.9 0.639 0.190 –27.9 33.7 –61.1 0.299 0.315

203 43.5 129.1 –10.1 0.130 0.239 51.9 212.6 –26.2 0.256 0.368

204 6.0 123.6 –49.7 0.878 0.381 6.7 169.4 –57.8 0.891 0.473

205 26.0 125.1 –29.5 0.435 0.296 24.8 170.1 –42.3 0.574 0.394

206 18.6 58.5 –11.3 0.250 0.148 5.2 84.7 –40.1 0.860 0.287

207 244.0 597.2 69.7 0.001 0.361 200.1 649.7 20.1 0.019 0.467

208 –7.3 9.6 –21.6 0.372 0.085 –21.1 24.9 –50.1 0.312 0.234

209 –20.1 –4.4 –33.2 0.014 0.091 –32.1 14.2 –59.6 0.144 0.265

210 –4.9 17.6 –23.2 0.641 0.109 –15.5 45.9 –51.0 0.546 0.279

211 –15.3 3.7 –30.8 0.107 0.103 –22.6 33.4 –55.1 0.356 0.278

212 –8.9 29.5 –35.9 0.604 0.179 –8.7 44.9 –42.5 0.699 0.236

213 –20.6 –5.4 –33.3 0.010 0.089 –32.3 15.0 –60.1 0.149 0.270

214 –21.7 –11.6 –30.5 0.000 0.061 –33.3 0.2 –55.6 0.051 0.207

215 –24.8 3.1 –45.1 0.077 0.161 –30.1 38.8 –64.8 0.306 0.350

216 87.4 196.4 18.5 0.007 0.234 106.5 298.1 7.1 0.030 0.335

217 –21.5 –2.2 –36.9 0.031 0.112 –41.7 9.7 –69.0 0.095 0.322

218 –10.3 8.5 –25.9 0.261 0.097 –30.6 19.6 –59.7 0.188 0.277

219 –32.8 –2.8 –53.5 0.035 0.188 –63.3 –8.9 –85.2 0.031 0.464

220 –33.7 –6.6 –52.9 0.019 0.175 –19.7 73.9 –62.9 0.578 0.394

221 94.5 250.1 8.1 0.027 0.300 89.9 278.2 –4.6 0.068 0.351

222 –36.0 93.6 –78.8 0.430 0.565 –44.1 92.7 –83.8 0.357 0.631

223 –8.9 14.4 –27.5 0.422 0.116 –27.4 13.8 –53.6 0.163 0.229

224 37.0 199.8 –37.4 0.431 0.400 36.1 118.5 –15.2 0.202 0.242

225 –51.7 –26.2 –68.4 0.001 0.216 –40.1 129.4 –84.3 0.455 0.685

227 13.8 37.2 –5.5 0.173 0.095 –3.1 54.4 –39.1 0.896 0.237

228 7.8 70.6 –31.9 0.748 0.234 –5.7 95.1 –54.4 0.875 0.371

229 112.2 282.8 17.7 0.012 0.301 136.2 416.5 8.0 0.031 0.399

230 –4.5 21.2 –24.7 0.707 0.121 –8.4 67.1 –49.8 0.776 0.307

231 –31.9 –23.6 –39.4 0.000 0.059 –30.2 41.1 –65.4 0.317 0.359

232 –40.9 –27.2 –52.0 0.000 0.106 –32.5 38.3 –67.1 0.283 0.366
154 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Non-flow-adjusted trend in concentration from 1993 to 2003 Trend in load from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Total phosphorus—Continued

233 3.8 24.8 –13.7 0.693 0.094 15.2 167.0 –50.3 0.742 0.429

234 52.5 272.8 –37.6 0.354 0.456 45.9 371.6 –54.9 0.528 0.599

235 12.3 156.4 –50.8 0.783 0.421 7.4 246.0 –66.7 0.905 0.597

236 95.3 280.8 0.1 0.050 0.341 64.2 317.9 –35.5 0.298 0.477

237 –2.1 89.8 –49.6 0.949 0.338 –39.1 79.3 –79.3 0.368 0.550

238 42.1 131.9 –13.0 0.160 0.250 32.8 161.6 –32.6 0.412 0.346

239 –33.2 25.4 –64.5 0.209 0.322 –31.9 41.3 –67.1 0.303 0.372

241 15.8 54.8 –13.4 0.324 0.148 –7.7 145.6 –65.3 0.873 0.499

242 2.0 63.7 –36.4 0.934 0.241 –18.9 101.1 –67.3 0.651 0.463

243 –2.4 13.2 –15.9 0.748 0.076 –19.6 126.3 –71.4 0.680 0.528

244 57.9 122.4 12.1 0.009 0.175 48.8 208.8 –28.3 0.286 0.372

Total nitrogen

1 10.4 39.2 –12.4 0.403 0.118 –11.5 42.9 –45.2 0.618 0.244

2 44.3 81.0 15.0 0.002 0.116 10.0 75.4 –31.0 0.689 0.238

3 –4.0 13.6 –18.8 0.638 0.086 –7.5 51.7 –43.6 0.758 0.252

4 4.9 25.4 –12.4 0.604 0.091 –5.6 28.3 –30.6 0.712 0.157

5 0.1 9.4 –8.5 0.988 0.046 –17.5 11.2 –38.8 0.206 0.152

6 41.6 109.4 –4.2 0.081 0.200 8.6 85.1 –36.2 0.761 0.272

7 23.0 53.8 –1.6 0.069 0.114 –7.9 25.2 –32.2 0.598 0.157

8 5.5 29.7 –14.2 0.614 0.106 –17.1 6.9 –35.7 0.149 0.130

9 13.8 58.4 –18.3 0.445 0.169 1.2 110.3 –51.3 0.974 0.373

10 –1.3 20.4 –19.1 0.895 0.101 –8.4 19.9 –30.0 0.524 0.137

11 12.1 41.2 –11.0 0.333 0.118 6.8 114.3 –46.7 0.852 0.355

12 –49.3 –31.7 –62.3 0.000 0.152 –55.9 –42.0 –66.4 0.000 0.139

13 40.3 106.5 –4.6 0.085 0.197 64.5 301.9 –32.7 0.275 0.456

14 24.3 47.0 5.1 0.011 0.086 23.2 154.1 –40.3 0.572 0.369

15 –9.1 2.5 –19.4 0.120 0.061 10.7 72.1 –28.8 0.652 0.225

16 13.5 41.5 –9.0 0.261 0.113 –13.1 37.1 –45.0 0.545 0.233

17 21.5 69.4 –12.8 0.250 0.170 –34.4 157.8 –83.3 0.546 0.698

18 –5.3 39.2 –35.6 0.781 0.197 8.3 73.7 –32.4 0.740 0.241

19 –12.2 39.4 –44.7 0.582 0.236 –28.2 36.9 –62.4 0.314 0.329

20 24.5 66.9 –7.2 0.144 0.150 29.9 94.0 –13.1 0.202 0.205

21 0.9 25.5 –18.8 0.934 0.111 18.4 92.9 –27.4 0.499 0.249

22 –0.1 25.2 –20.3 0.993 0.115 10.0 96.1 –38.3 0.746 0.295

23 –13.6 7.2 –30.3 0.184 0.110 –10.0 68.2 –51.9 0.741 0.319

24 –14.2 39.0 –47.0 0.534 0.246 –11.6 227.3 –76.1 0.853 0.668

25 11.7 42.0 –12.2 0.368 0.123 –3.9 46.6 –37.1 0.852 0.216

26 16.4 40.5 –3.7 0.116 0.096 –3.5 47.2 –36.7 0.870 0.215

29 –22.1 12.0 –45.9 0.178 0.185 –40.1 16.2 –69.1 0.129 0.338

31 –23.2 –1.2 –40.2 0.040 0.128 –18.4 34.3 –50.4 0.423 0.254

32 4.7 34.2 –18.4 0.720 0.127 –16.7 94.6 –64.3 0.673 0.433

33 –18.3 –3.7 –30.6 0.016 0.084 –17.5 36.2 –50.0 0.452 0.256

34 0.9 24.3 –18.2 0.936 0.107 –27.4 7.3 –50.8 0.108 0.199

35 8.9 33.6 –11.3 0.415 0.104 –4.6 47.0 –38.0 0.832 0.220

36 22.4 35.8 10.2 0.000 0.053 75.3 407.3 –39.5 0.301 0.542

37 –9.4 –0.3 –17.6 0.042 0.048 –28.2 22.7 –58.0 0.226 0.273

38 0.5 11.0 –9.0 0.921 0.051 1.7 82.3 –43.3 0.955 0.298

39 –3.7 8.3 –14.3 0.530 0.060 –39.0 37.7 –73.0 0.234 0.415

40 –18.7 10.5 –40.2 0.186 0.157 –39.6 122.2 –83.6 0.448 0.665

41 17.5 82.1 –24.2 0.471 0.224 –32.4 208.8 –85.2 0.613 0.775

42 27.0 42.6 13.1 0.000 0.059 –32.4 116.5 –78.9 0.510 0.594

43 10.1 25.2 –3.1 0.140 0.065 –49.0 139.4 –89.1 0.393 0.789
Appendix 3 155

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Non-flow-adjusted trend in concentration from 1993 to 2003 Trend in load from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Total nitrogen—Continued

44 1.8 42.5 –27.3 0.918 0.172 –33.4 93.8 –77.1 0.456 0.545

45 11.9 23.6 1.3 0.027 0.051 –28.4 134.5 –78.1 0.581 0.605

46 18.0 48.3 –6.1 0.155 0.117 19.0 314.0 –65.8 0.785 0.636

47 –36.8 –27.3 –45.1 0.000 0.071 –22.4 63.1 –63.1 0.503 0.379

48 –11.5 –3.4 –18.9 0.006 0.044 33.7 226.2 –45.2 0.524 0.455

49 0.8 37.2 –26.0 0.961 0.158 –5.5 122.4 –59.8 0.897 0.436

52 6.7 44.8 –21.4 0.679 0.156 –36.2 0.8 –59.5 0.054 0.233

53 –7.5 14.8 –25.4 0.481 0.110 –51.3 –4.1 –75.2 0.037 0.345

57 37.2 78.2 5.6 0.018 0.134 32.0 314.5 –58.0 0.635 0.584

58 –5.1 26.9 –29.0 0.726 0.148 –44.1 84.8 –83.1 0.340 0.610

59 –3.7 12.4 –17.4 0.635 0.079 –37.9 187.6 –86.6 0.542 0.782

60 19.0 46.8 –3.6 0.106 0.107 –11.5 83.4 –57.2 0.743 0.371

61 7.2 40.6 –18.4 0.618 0.139 –37.4 193.5 –86.6 0.553 0.788

62 –20.7 2.8 –38.7 0.080 0.132 –67.2 86.4 –94.2 0.209 0.887

65 41.4 103.0 –1.5 0.060 0.184 15.9 345.8 –69.9 0.830 0.687

67 43.6 89.8 8.5 0.011 0.143 –23.8 10.2 –47.3 0.148 0.188

71 –10.9 67.8 –52.7 0.720 0.323 –38.6 54.5 –75.6 0.300 0.471

72 –15.5 9.7 –35.0 0.205 0.133 –55.0 32.2 –84.7 0.146 0.550

73 17.4 41.3 –2.4 0.089 0.095 –3.6 54.3 –39.7 0.879 0.240

74 12.3 33.5 –5.4 0.185 0.088 –25.9 14.0 –51.8 0.173 0.220

76 28.9 45.0 14.5 0.000 0.060 –7.1 43.3 –39.8 0.740 0.221

81 –24.5 7.4 –46.9 0.118 0.180 612.1 5,638.1 –11.6 0.065 1.065

82 4.0 45.5 –25.7 0.821 0.171 87.3 735.8 –58.0 0.411 0.763

92 –38.8 –18.2 –54.3 0.001 0.148 –63.1 –11.0 –84.7 0.027 0.449

95 –13.0 6.0 –28.6 0.166 0.101 –59.7 –34.3 –75.2 0.000 0.249

97 4.6 46.3 –25.2 0.791 0.171 –13.2 201.6 –75.0 0.824 0.635

99 25.7 77.5 –11.0 0.194 0.176 –36.3 21.1 –66.5 0.169 0.328

100 40.7 133.3 –15.1 0.185 0.258 54.9 250.1 –31.5 0.293 0.416

101 61.9 132.0 13.0 0.009 0.183 53.4 128.4 3.0 0.035 0.203

102 4.8 36.6 –19.6 0.728 0.135 135.9 1,506.8 –65.4 0.381 0.979

103 –49.8 –32.8 –62.5 0.000 0.149 –30.8 9.0 –56.0 0.113 0.232

106 –10.6 23.2 –35.1 0.493 0.164 –93.9 –84.3 –97.6 0.000 0.479

107 27.4 57.1 3.3 0.023 0.107 –29.6 15.7 –57.2 0.166 0.254

108 4.8 24.4 –11.6 0.588 0.087 11.9 36.1 –8.0 0.262 0.100

109 –11.3 21.3 –35.1 0.454 0.160 –72.8 –32.8 –89.0 0.005 0.461

110 11.2 44.6 –14.5 0.428 0.134 –56.5 –24.8 –74.9 0.003 0.280

111 –72.1 –46.9 –85.3 0.000 0.328 –97.0 –87.0 –99.3 0.000 0.752

112 –47.7 –34.4 –58.3 0.000 0.115 –70.2 –53.5 –80.9 0.000 0.227

113 –39.8 2.1 –64.5 0.060 0.270 –93.2 –66.0 –98.6 0.001 0.819

114 –42.1 –12.0 –61.9 0.011 0.213 –93.3 –70.6 –98.5 0.000 0.755

115 –6.2 57.9 –44.3 0.810 0.266 –73.6 –7.5 –92.4 0.037 0.639

116 –30.8 –5.6 –49.3 0.020 0.159 –89.0 –63.4 –96.7 0.000 0.613

118 –12.3 13.0 –32.0 0.311 0.130 –67.1 –40.0 –82.0 0.000 0.307

120 69.2 111.8 35.2 0.000 0.114 –30.0 20.0 –59.1 0.195 0.275

124 1.3 23.4 –16.8 0.897 0.101 –52.7 –25.9 –69.8 0.001 0.229

125 –29.7 –15.6 –41.5 0.000 0.093 –63.4 –44.9 –75.7 0.000 0.209

134 0.1 27.2 –21.2 0.993 0.122 –63.6 –20.9 –83.3 0.011 0.396

135 –4.0 22.2 –24.5 0.742 0.123 –50.4 –12.2 –72.0 0.016 0.292

136 18.3 61.5 –13.3 0.289 0.159 –5.2 53.5 –41.4 0.829 0.246

137 51.6 73.1 32.7 0.000 0.068 –26.2 32.8 –59.0 0.311 0.300

138 –9.2 17.4 –29.8 0.459 0.131 –54.7 –7.9 –77.7 0.029 0.362

139 2.8 41.9 –25.5 0.865 0.164 –60.8 –13.1 –82.3 0.021 0.406

145 13.4 50.3 –14.4 0.380 0.144 –23.9 109.7 –72.4 0.598 0.517

146 –10.6 33.7 –40.2 0.585 0.205 –62.8 45.4 –90.5 0.155 0.695
156 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Non-flow-adjusted trend in concentration from 1993 to 2003 Trend in load from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Total nitrogen—Continued

147 –2.9 38.9 –32.1 0.874 0.183 –59.6 60.9 –89.8 0.199 0.705

148 2.1 28.0 –18.5 0.856 0.115 –67.0 –2.5 –88.8 0.045 0.552

149 1.7 22.0 –15.2 0.852 0.093 –60.2 –8.2 –82.8 0.031 0.427

150 27.3 71.2 –5.4 0.111 0.151 –64.2 –15.5 –84.8 0.019 0.438

151 4.7 24.4 –11.8 0.599 0.088 –12.5 92.7 –60.3 0.740 0.403

152 52.9 127.0 3.0 0.035 0.201 29.4 167.7 –37.4 0.487 0.371

153 –7.9 7.4 –21.1 0.295 0.079 –38.4 –11.8 –57.0 0.008 0.183

154 –29.0 6.3 –52.6 0.097 0.206 –49.5 15.5 –78.0 0.106 0.423

155 –26.1 7.3 –49.1 0.112 0.190 –53.6 –0.0 –78.5 0.050 0.392

156 –9.6 3.8 –21.3 0.153 0.071 –39.6 –15.2 –57.0 0.004 0.173

157 –16.9 1.3 –31.8 0.066 0.101 –13.4 66.5 –54.9 0.667 0.333

173 26.3 61.2 –1.0 0.060 0.124 –75.7 –15.6 –93.0 0.026 0.635

176 23.6 70.6 –10.4 0.197 0.164 –18.7 66.4 –60.3 0.571 0.365

179 5.8 40.9 –20.6 0.701 0.146 –1.6 58.8 –39.0 0.947 0.244

182 34.0 150.6 –28.4 0.360 0.319 –50.3 49.2 –83.4 0.213 0.561

196 4.6 28.1 –14.6 0.666 0.103 –33.7 150.8 –82.4 0.545 0.678

199 –8.9 50.0 –44.7 0.714 0.254 –20.7 370.9 –86.6 0.799 0.909

201 –2.6 81.2 –47.6 0.934 0.317 101.6 2,527.9 –84.5 0.593 1.310

202 –28.8 12.8 –55.1 0.148 0.235 –12.6 267.9 –79.2 0.854 0.733

208 –21.7 6.8 –42.6 0.122 0.158 –33.3 12.7 –60.5 0.131 0.268

209 –48.9 –34.5 –60.2 0.000 0.127 –56.6 –31.3 –72.6 0.000 0.234

210 –49.0 –33.3 –61.0 0.000 0.137 –54.7 –27.1 –71.8 0.001 0.242

212 –24.4 1.1 –43.5 0.059 0.149 –24.3 15.3 –50.3 0.195 0.215

213 –51.3 –40.7 –60.0 0.000 0.101 –58.5 –35.2 –73.4 0.000 0.227

214 –38.6 –24.5 –50.0 0.000 0.105 –47.7 –16.9 –67.1 0.006 0.236

215 –28.4 6.2 –51.7 0.097 0.201 –33.4 19.2 –62.8 0.171 0.297

217 –43.3 –25.6 –56.9 0.000 0.139 –57.9 –23.2 –76.9 0.005 0.307

218 –26.6 –16.2 –35.7 0.000 0.068 –43.2 –17.0 –61.1 0.003 0.193

219 –37.9 –10.9 –56.7 0.010 0.184 –66.1 –27.2 –84.2 0.006 0.390

220 –43.1 –18.4 –60.3 0.002 0.184 –31.0 6.7 –55.4 0.095 0.222

221 17.7 67.3 –17.2 0.365 0.179 14.9 85.4 –28.8 0.570 0.244

222 15.7 65.2 –19.0 0.423 0.182 1.0 101.7 –49.4 0.978 0.353

223 2.0 23.9 –16.0 0.842 0.099 –18.7 16.0 –43.0 0.254 0.181

224 23.1 95.7 –22.6 0.381 0.237 22.3 117.9 –31.4 0.495 0.295

225 6.8 39.7 –18.5 0.634 0.137 32.4 360.3 –61.9 0.659 0.636

227 –3.6 13.1 –17.7 0.654 0.081 –17.9 34.4 –49.8 0.433 0.251

228 –9.0 8.9 –24.0 0.305 0.092 –20.4 30.5 –51.4 0.366 0.252

231 6.0 17.9 –4.6 0.277 0.054 8.8 93.6 –38.9 0.775 0.294

232 –32.0 –18.4 –43.4 0.000 0.093 –22.4 63.7 –63.2 0.506 0.381

241 6.0 40.6 –20.2 0.688 0.144 –15.5 92.3 –62.9 0.688 0.419

242 171.5 600.0 5.3 0.039 0.483 115.7 207.6 51.3 0.000 0.181

243 9.0 60.5 –26.0 0.664 0.198 –10.0 80.0 –55.0 0.766 0.354

244 49.3 96.3 13.5 0.004 0.140 40.7 153.7 –22.0 0.257 0.301

Nitrate

1 –12.4 16.6 –34.1 0.365 0.146 –29.7 7.8 –54.2 0.106 0.218

2 20.0 56.4 –8.0 0.179 0.135 –7.8 41.7 –40.1 0.710 0.219

3 –19.3 14.8 –43.3 0.233 0.180 –22.2 39.7 –56.7 0.400 0.299

4 8.5 31.7 –10.7 0.412 0.099 –2.4 29.8 –26.6 0.868 0.146

5 3.9 17.1 –7.8 0.528 0.061 –14.3 11.3 –34.1 0.246 0.133

6 –22.8 2.1 –41.6 0.070 0.143 –40.5 –13.3 –59.2 0.007 0.192

7 18.1 50.9 –7.6 0.184 0.125 –11.2 12.1 –29.6 0.318 0.119

8 9.9 44.4 –16.3 0.497 0.139 –13.3 11.7 –32.7 0.271 0.129
Appendix 3 157

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Non-flow-adjusted trend in concentration from 1993 to 2003 Trend in load from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Nitrate—Continued

9 –26.1 20.4 –54.6 0.224 0.249 –34.1 39.7 –68.9 0.277 0.384

10 –11.7 11.5 –30.1 0.296 0.119 –17.8 2.8 –34.3 0.086 0.114

11 12.7 51.5 –16.2 0.430 0.151 7.4 127.4 –49.3 0.852 0.383

12 –13.4 16.3 –35.5 0.340 0.150 –24.4 –0.3 –42.7 0.048 0.141

13 –6.3 80.4 –51.3 0.845 0.334 9.3 186.4 –58.3 0.856 0.491

14 –1.3 30.6 –25.5 0.926 0.143 –2.2 116.2 –55.7 0.957 0.405

15 –10.1 6.0 –23.8 0.206 0.084 9.4 74.9 –31.6 0.707 0.239

16 –20.9 18.9 –47.4 0.260 0.208 –39.5 1.0 –63.7 0.054 0.261

17 30.1 139.2 –29.2 0.397 0.311 –29.8 155.8 –80.7 0.592 0.659

18 –6.4 46.7 –40.3 0.774 0.229 7.1 67.0 –31.3 0.761 0.227

19 –20.1 42.6 –55.2 0.448 0.296 –34.7 13.3 –62.3 0.130 0.281

20 28.7 76.6 –6.2 0.118 0.161 34.3 93.4 –6.7 0.113 0.186

21 3.0 36.5 –22.3 0.838 0.144 20.8 102.9 –28.1 0.476 0.265

22 9.7 55.3 –22.6 0.604 0.177 20.8 123.6 –34.8 0.548 0.314

23 –20.8 0.7 –37.7 0.057 0.122 –17.5 49.6 –54.5 0.526 0.304

24 –15.2 107.3 –65.3 0.717 0.456 –12.7 385.2 –84.3 0.877 0.875

25 3.1 33.6 –20.5 0.817 0.132 –11.0 27.9 –38.1 0.528 0.185

26 15.6 45.5 –8.1 0.214 0.117 –4.1 43.0 –35.7 0.839 0.204

29 –60.7 –36.6 –75.6 0.000 0.244 –69.8 –44.5 –83.5 0.000 0.310

31 –44.0 –19.3 –61.2 0.002 0.187 –40.6 1.0 –65.0 0.055 0.271

32 –1.1 62.3 –39.7 0.965 0.253 –21.3 117.2 –71.4 0.644 0.518

33 –24.2 –9.9 –36.3 0.002 0.089 –23.5 23.1 –52.5 0.269 0.243

34 –32.2 –3.7 –52.3 0.030 0.180 –51.2 –19.3 –70.5 0.005 0.257

35 –26.1 6.0 –48.4 0.100 0.184 –35.2 7.3 –60.8 0.092 0.257

36 3.2 26.4 –15.8 0.763 0.104 47.8 281.9 –42.8 0.420 0.484

37 –23.4 –14.0 –31.8 0.000 0.059 –39.3 4.6 –64.8 0.072 0.278

38 –10.3 5.2 –23.6 0.181 0.082 –9.3 50.9 –45.5 0.708 0.260

39 –9.5 –1.2 –17.1 0.026 0.045 –42.7 22.8 –73.2 0.152 0.388

40 –41.7 –6.5 –63.7 0.025 0.241 –56.7 86.7 –89.9 0.262 0.745

41 –29.6 130.1 –78.5 0.561 0.604 –59.5 289.6 –95.8 0.434 1.155

42 6.7 26.6 –10.1 0.457 0.087 –43.2 54.8 –79.2 0.269 0.512

43 23.2 54.0 –1.5 0.068 0.114 –43.0 113.5 –84.8 0.405 0.673

44 –43.6 14.0 –72.1 0.111 0.359 –63.1 54.0 –91.1 0.172 0.728

45 –13.9 10.5 –32.8 0.240 0.127 –44.9 50.4 –79.8 0.245 0.512

50 14.7 122.3 –40.8 0.685 0.338 –43.0 –5.9 –65.5 0.028 0.256

65 49.4 274.1 –40.3 0.391 0.468 22.4 172.6 –45.0 0.620 0.408

66 –11.3 4.9 –25.0 0.162 0.086 –43.2 3.4 –68.8 0.064 0.306

71 85.4 262.6 –5.3 0.071 0.342 27.8 227.6 –50.2 0.610 0.480

72 –41.7 –24.4 –54.9 0.000 0.132 –68.9 –13.9 –88.8 0.025 0.520

73 –8.9 15.9 –28.5 0.447 0.123 –25.2 19.7 –53.3 0.226 0.240

74 14.0 72.5 –24.7 0.535 0.211 –24.8 25.8 –55.0 0.277 0.262

76 49.8 141.6 –7.2 0.098 0.244 8.0 136.3 –50.6 0.847 0.400

81 41.2 313.1 –51.7 0.528 0.548 1,219.4 21,128.4 –18.0 0.069 1.417

82 –56.3 52.0 –87.4 0.193 0.636 –21.2 530.1 –90.2 0.822 1.061

88 –30.4 162.4 –81.5 0.593 0.677 –72.4 152.3 –97.0 0.254 1.129

92 –59.4 –36.8 –73.9 0.000 0.225 –75.5 –32.7 –91.1 0.006 0.516

95 –24.5 –1.7 –42.0 0.037 0.135 –65.0 –40.9 –79.3 0.000 0.267

96 –49.1 –26.8 –64.7 0.000 0.186 –53.3 –30.7 –68.5 0.000 0.201

98 –5.9 80.3 –50.8 0.856 0.332 –56.3 –32.8 –71.5 0.000 0.219

99 –47.7 29.8 –78.9 0.162 0.463 –73.5 –16.4 –91.6 0.024 0.586

100 –72.6 –53.5 –83.8 0.000 0.269 –69.8 –25.0 –87.8 0.010 0.464

101 51.4 130.8 –0.7 0.054 0.215 43.4 122.2 –7.5 0.107 0.224
158 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Non-flow-adjusted trend in concentration from 1993 to 2003 Trend in load from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Nitrate—Continued

102 –67.1 25.7 –91.4 0.104 0.684 –25.9 1,081.4 –95.4 0.832 1.413

103 –56.4 –33.7 –71.3 0.000 0.214 –39.9 –19.1 –55.3 0.001 0.151

104 –65.4 –28.5 –83.3 0.004 0.371 –80.4 –58.0 –90.8 0.000 0.388

105 15.1 111.6 –37.4 0.651 0.311 –56.2 38.1 –86.1 0.159 0.586

106 –1.9 50.4 –36.0 0.931 0.218 –93.3 –85.0 –97.0 0.000 0.409

107 24.5 57.8 –1.7 0.069 0.121 –31.2 10.0 –57.0 0.118 0.239

108 8.2 25.8 –7.0 0.308 0.077 15.4 35.4 –1.6 0.077 0.081

109 –47.0 –22.1 –63.9 0.001 0.197 –83.8 –60.8 –93.3 0.000 0.449

110 –62.0 –22.5 –81.4 0.008 0.364 –85.2 –61.0 –94.3 0.000 0.493

111 –92.8 –62.2 –98.6 0.002 0.848 –99.3 –91.4 –99.9 0.000 1.239

112 –66.8 –47.0 –79.2 0.000 0.239 –81.1 –65.0 –89.8 0.000 0.315

113 –74.7 –10.7 –92.8 0.033 0.644 –97.1 –71.5 –99.7 0.002 1.173

114 –62.0 19.1 –87.9 0.097 0.583 –95.6 –58.9 –99.5 0.006 1.141

115 –21.4 151.1 –75.4 0.685 0.593 –77.9 45.0 –96.6 0.116 0.958

116 –79.9 –58.2 –90.3 0.000 0.373 –96.8 –85.2 –99.3 0.000 0.779

117 –50.0 –19.0 –69.1 0.005 0.246 –83.4 –58.3 –93.4 0.000 0.471

118 –49.0 –23.7 –65.9 0.001 0.205 –80.9 –62.4 –90.2 0.000 0.344

119 –51.3 –11.8 –73.1 0.018 0.303 –26.5 61.7 –66.5 0.445 0.402

120 86.8 158.1 35.1 0.000 0.165 –22.7 38.9 –57.0 0.389 0.299

121 23.4 105.1 –25.8 0.418 0.259 –37.4 82.3 –78.5 0.390 0.546

122 –20.0 20.8 –47.0 0.289 0.210 –73.8 –36.1 –89.2 0.003 0.454

123 –12.5 16.5 –34.3 0.360 0.146 –60.1 –23.7 –79.1 0.005 0.330

124 17.0 42.6 –3.9 0.118 0.101 –45.4 –14.6 –65.1 0.008 0.228

125 –27.3 –12.5 –39.6 0.001 0.095 –62.2 –41.7 –75.4 0.000 0.220

126 –15.4 45.2 –50.7 0.545 0.275 –29.3 55.5 –67.9 0.388 0.403

127 63.4 201.1 –11.4 0.116 0.312 353.1 1,463.1 31.3 0.017 0.632

128 5.6 36.9 –18.5 0.681 0.132 –43.6 24.7 –74.5 0.157 0.405

129 303.8 813.7 78.5 0.001 0.417 246.7 791.7 34.8 0.010 0.482

130 22.3 74.9 –14.4 0.269 0.182 –13.8 65.4 –55.1 0.654 0.333

131 50.7 95.1 16.4 0.002 0.132 35.8 103.0 –9.2 0.136 0.205

132 –48.5 –34.7 –59.4 0.000 0.121 –46.3 14.8 –74.8 0.109 0.387

133 –55.0 –46.9 –61.8 0.000 0.084 –56.0 –13.1 –77.7 0.018 0.347

134 2.9 33.9 –20.9 0.829 0.134 –62.6 –16.6 –83.2 0.016 0.409

135 –20.0 12.1 –42.8 0.195 0.172 –58.7 –26.1 –76.9 0.003 0.297

136 20.1 69.5 –14.8 0.296 0.176 –3.7 53.5 –39.6 0.873 0.238

137 51.9 72.6 33.7 0.000 0.065 –26.0 31.0 –58.2 0.301 0.291

138 –23.2 1.7 –42.0 0.065 0.143 –61.7 –21.1 –81.4 0.009 0.368

139 0.3 39.3 –27.8 0.988 0.168 –61.8 –15.6 –82.7 0.017 0.404

140 264.3 960.6 25.1 0.018 0.545 –33.7 417.8 –91.5 0.695 1.048

141 –44.1 53.4 –79.6 0.259 0.515 –63.9 162.5 –95.0 0.314 1.012

142 –45.7 2.5 –71.3 0.059 0.324 –88.4 –28.4 –98.1 0.020 0.928

143 4.1 99.5 –45.7 0.904 0.332 –53.6 –6.2 –77.1 0.032 0.360

144 56.4 180.7 –12.8 0.134 0.298 –18.0 23.6 –45.6 0.344 0.209

145 35.4 147.2 –25.9 0.324 0.307 –9.2 208.6 –73.3 0.878 0.624

146 80.8 220.3 2.0 0.043 0.292 –24.7 270.7 –84.7 0.727 0.813

147 76.7 233.4 –6.4 0.079 0.324 –26.5 254.6 –84.7 0.702 0.802

148 –24.2 33.8 –57.0 0.340 0.290 –75.5 –0.7 –93.9 0.049 0.713

149 –56.3 –20.6 –75.9 0.007 0.304 –82.9 –51.5 –94.0 0.001 0.532

150 –56.9 14.2 –83.7 0.090 0.496 –87.9 –48.6 –97.1 0.004 0.735

151 –46.2 –10.8 –67.5 0.016 0.258 –55.1 21.7 –83.4 0.115 0.508

152 0.9 60.6 –36.6 0.969 0.237 –14.6 94.7 –62.5 0.708 0.420

153 –20.8 –4.1 –34.6 0.017 0.098 –47.0 –21.2 –64.4 0.002 0.202
Appendix 3 159

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Non-flow-adjusted trend in concentration from 1993 to 2003 Trend in load from 1993 to 2003

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Modeled

estimate,

in percent

from 1993

to 2003

Upper

95-percent

CI, in

percent

from 1993

to 2003

Lower

95-percent

CI, in

percent

from 1993

to 2003

p-value Standard 

error

Nitrate—Continued

154 –30.8 –0.2 –52.0 0.049 0.187 –50.8 9.5 –77.9 0.082 0.408

155 –32.3 –6.8 –50.8 0.017 0.163 –57.4 –12.2 –79.4 0.021 0.369

156 –20.2 –0.9 –35.7 0.041 0.110 –47.2 –22.2 –64.2 0.001 0.198

157 26.6 95.2 –17.9 0.286 0.221 32.0 147.4 –29.5 0.386 0.320

158 –30.0 8.5 –54.9 0.110 0.224 –36.3 28.4 –68.3 0.207 0.357

159 –6.8 63.7 –46.9 0.807 0.287 –25.4 87.6 –70.3 0.534 0.471

160 11.6 92.1 –35.1 0.691 0.277 2.2 140.3 –56.6 0.961 0.436

161 –44.5 106.6 –85.1 0.380 0.670 –94.3 101.9 –99.8 0.115 1.820

162 –22.1 110.3 –71.1 0.622 0.507 –35.8 1,108.6 –96.6 0.767 1.498

163 23.8 126.4 –32.3 0.489 0.308 –28.8 38.7 –63.5 0.318 0.340

164 –99.5 –97.9 –99.9 0.000 0.703 –100.0 –99.9 –100.0 0.000 1.155

167 52.2 263.0 –36.2 0.344 0.444 693.9 29,857.9 –79.0 0.263 1.852

168 99.2 272.1 6.6 0.031 0.319 637.6 13,902.3 –61.2 0.183 1.502

172 –17.0 34.5 –48.8 0.449 0.247 38.2 101.8 –5.3 0.094 0.193

174 –31.6 23.4 –62.1 0.207 0.301 –55.5 24.2 –84.0 0.122 0.523

175 20.5 54.5 –6.1 0.143 0.127 –45.9 –22.2 –62.4 0.001 0.186

177 6.2 67.0 –32.5 0.796 0.231 –32.9 19.0 –62.2 0.173 0.292

181 165.0 347.3 56.9 0.000 0.267 –32.8 10.7 –59.1 0.119 0.254

187 –40.1 –15.2 –57.7 0.004 0.178 –68.1 –3.6 –89.4 0.043 0.564

189 14.4 88.1 –30.4 0.596 0.254 –46.4 –5.1 –69.7 0.032 0.291

190 116.0 239.6 37.4 0.001 0.231 35.6 132.9 –21.0 0.269 0.276

191 337.2 700.0 138.9 0.000 0.308 137.0 391.4 14.3 0.020 0.372

192 –65.2 –46.2 –77.6 0.000 0.223 –36.3 4.4 –61.1 0.073 0.251

194 11.0 57.4 –21.8 0.560 0.178 –29.1 58.9 –68.3 0.404 0.412

195 –21.6 –2.5 –36.9 0.029 0.111 –44.3 53.3 –79.8 0.258 0.517

197 –67.8 –56.9 –75.9 0.000 0.148 –82.5 –55.2 –93.1 0.000 0.478

198 10.1 46.8 –17.5 0.514 0.147 15.2 309.7 –67.6 0.827 0.647

199 4.0 34.8 –19.8 0.767 0.133 –9.4 201.1 –72.7 0.872 0.613

200 –1.3 20.5 –19.1 0.901 0.102 –37.5 53.1 –74.5 0.304 0.457

201 38.4 323.3 –54.8 0.569 0.570 186.3 1,474.1 –47.9 0.226 0.870

205 –7.0 10.8 –21.9 0.419 0.089 –7.8 38.5 –38.6 0.694 0.208

207 –2.7 34.4 –29.5 0.870 0.164 –15.1 46.3 –50.7 0.556 0.277

208 –24.1 7.3 –46.3 0.118 0.177 –35.4 12.7 –62.9 0.124 0.284

209 –38.2 –17.6 –53.6 0.001 0.146 –47.5 –16.2 –67.0 0.007 0.238

210 –25.8 –8.1 –40.1 0.006 0.109 –34.0 0.1 –56.5 0.051 0.213

213 –42.9 –28.9 –54.1 0.000 0.112 –51.3 –25.2 –68.3 0.001 0.219

215 28.4 93.8 –14.9 0.234 0.210 19.3 129.4 –37.9 0.596 0.333

217 –13.4 77.7 –57.8 0.694 0.367 –35.7 39.1 –70.3 0.262 0.394

218 –25.6 –13.2 –36.2 0.000 0.079 –42.4 –15.8 –60.6 0.004 0.193

224 –11.5 48.2 –47.2 0.642 0.263 –12.1 62.2 –52.4 0.680 0.313

225 –5.8 56.8 –43.4 0.820 0.260 16.9 383.5 –71.7 0.829 0.724

226 12.2 44.0 –12.6 0.368 0.128 –38.7 59.3 –76.4 0.315 0.487

228 –35.2 –13.3 –51.5 0.003 0.148 –43.3 0.1 –67.9 0.050 0.290

229 –59.6 –47.4 –69.0 0.000 0.135 –55.1 –27.3 –72.2 0.001 0.245

234 3.4 53.4 –30.3 0.868 0.201 –1.1 49.5 –34.6 0.957 0.211

235 5.1 77.7 –37.8 0.853 0.268 0.5 204.1 –66.8 0.993 0.565

237 8.5 87.0 –37.1 0.769 0.278 –32.4 56.2 –70.8 0.359 0.428

238 56.4 178.1 –12.1 0.128 0.294 46.2 89.3 12.9 0.004 0.132

239 0.7 19.7 –15.3 0.938 0.088 2.7 50.4 –29.8 0.889 0.194

240 –50.6 –17.7 –70.4 0.007 0.261 –72.7 –21.4 –90.5 0.016 0.539

241 10.9 54.5 –20.5 0.543 0.169 –11.6 88.6 –58.6 0.750 0.387

242 170.7 635.3 –0.4 0.051 0.510 115.1 197.6 55.4 0.000 0.166

243 17.1 117.4 –36.9 0.617 0.316 –3.5 54.0 –39.5 0.881 0.238

244 –31.7 –7.7 –49.5 0.013 0.154 –35.7 10.2 –62.4 0.108 0.275
160 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibration data set Properties of the calibrated model

Start

date

End

date

Number of

observations

Number of

censored

observations

Median

number

of days

between

successive

samples

Maximum

number

of days

between

successive

samples

Model

calibration

method

Model

specification1 Intercept

Log

streamflow

coefficient

Log

streamflow

squared

coefficient

Total phosphorus

1 11/10/1992 9/3/2003 105 7 34.5 113 AMLE 8 2.421 –1.828 0.138

2 10/20/1992 9/4/2003 106 5 35 88 AMLE 9 –1.970 –0.590 0.047

3 11/10/1992 9/3/2003 104 2 35 91 AMLE 9 0.174 –0.989 0.070

4 11/16/1992 9/25/2003 153 4 25 74 AMLE 8 15.971 –3.989 0.206

5 3/25/1993 9/15/2003 94 0 32 580 OLS 8 –3.061 –0.229 0.141

7 11/19/1992 9/23/2003 91 0 44 139 OLS 9 7.081 –2.474 0.154

8 11/19/1992 9/17/2003 108 0 33 85 OLS 3 1.591 –0.573 --

10 10/16/1992 9/16/2003 90 0 44 77 OLS 9 2.162 –0.876 0.049

11 11/13/1992 7/8/2003 53 9 69.5 142 AMLE 3 –4.129 0.046 --

12 11/18/1992 9/10/2003 91 0 42.5 78 OLS 9 0.418 0.200 –0.067

13 10/14/1992 7/28/2003 58 13 75 189 AMLE 7 –4.429 0.066 --

14 10/14/1992 9/30/2003 196 13 15 79 AMLE 8 –4.370 0.513 –0.060

15 4/8/1993 8/4/2003 138 3 28 115 AMLE 8 10.097 –3.553 0.234

16 11/12/1992 8/27/2003 48 2 86 156 AMLE 9 –1.696 –0.624 0.055

17 11/9/1992 8/27/2003 50 10 90 122 AMLE 3 –3.931 –0.033 --

18 10/27/1992 8/20/2003 47 0 90 183 OLS 8 2.847 –1.679 0.130

19 10/29/1992 8/12/2003 82 0 28 414 OLS 8 –1.890 0.785 –0.101

20 2/9/1993 8/13/2003 49 0 85.5 127 OLS 9 –1.204 1.015 –0.185

22 11/24/1992 9/4/2003 49 1 80 133 AMLE 8 –2.234 –0.277 0.062

24 11/5/1992 9/4/2003 76 9 47 131 AMLE 9 –3.372 –0.395 0.113

25 2/17/1993 8/5/2003 47 0 84 148 OLS 5 6.332 –2.458 0.187

26 11/18/1992 9/9/2003 110 0 29 133 OLS 8 10.934 –3.477 0.234

27 10/28/1992 9/3/2003 50 3 84 119 AMLE 9 –7.117 1.115 –0.040

28 11/25/1992 8/21/2003 51 17 78 128 AMLE 9 –14.259 3.636 –0.331

30 11/17/1992 8/19/2003 50 12 71 496 AMLE 7 –5.583 0.270 --

31 10/19/1992 9/3/2003 49 11 81 132 AMLE 9 1.270 –1.737 0.130

32 10/21/1992 9/2/2003 50 4 84 119 AMLE 8 –1.771 –0.897 0.106

33 10/22/1992 9/4/2003 94 0 35 119 OLS 8 24.946 –6.163 0.341

34 11/18/1992 8/7/2003 86 0 35 120 OLS 8 –1.047 –0.523 0.111

35 11/30/1992 8/7/2003 82 0 35 124 OLS 8 –0.627 –0.956 0.162

36 11/3/1992 9/16/2003 185 6 20 86 AMLE 9 –3.989 0.112 0.022

37 11/18/1992 9/24/2003 255 11 14 79 AMLE 8 5.929 –2.243 0.129

38 11/17/1992 9/19/2003 295 0 11 63 OLS 9 –3.034 0.016 0.015

39 4/15/1993 9/3/2003 278 0 8 56 OLS 8 –1.485 –0.427 0.054

40 11/18/1992 9/20/2003 150 3 26 208 AMLE 9 1.473 –1.340 0.096

41 10/19/1992 9/23/2003 341 1 10 405 AMLE 8 –3.626 –0.558 0.087

42 10/14/1992 9/25/2003 413 0 7 42 OLS 9 –0.920 –0.573 0.045

43 10/14/1992 9/24/2003 410 0 7 63 OLS 9 –3.368 0.010 0.008

44 10/28/1992 9/25/2003 358 0 9 60 OLS 9 5.486 –2.171 0.142

45 10/8/1992 9/25/2003 417 0 8.5 42 OLS 9 –2.749 –0.370 0.043

46 10/8/1992 8/21/2003 83 55 47 179 AMLE 9 –3.712 –0.017 0.034

51 10/1/1992 6/24/2003 115 11 28 344 AMLE 9 1.923 –0.630 0.018

52 10/20/1992 9/11/2003 87 7 32 415 AMLE 9 –20.344 5.285 –0.389

53 10/28/1992 9/25/2003 132 14 28 141 AMLE 9 –7.464 0.974 –0.051

54 10/28/1992 9/11/2003 123 5 28 259 AMLE 9 –7.821 1.432 –0.097

55 10/21/1992 9/17/2003 119 5 28 400 AMLE 9 –2.077 –0.015 –0.006

56 10/29/1992 9/22/2003 123 2 28 300 AMLE 9 –1.400 –0.032 –0.015

58 10/29/1992 9/8/2003 60 0 61 272 OLS 9 –0.641 0.060 0.003

59 10/28/1992 9/25/2003 82 0 35 315 OLS 9 –0.156 0.053 –0.009

60 10/21/1992 9/10/2003 103 0 31.5 153 OLS 9 –1.986 0.270 –0.012

61 10/21/1992 9/10/2003 63 0 56 162 OLS 9 –0.102 –0.201 0.039

62 10/26/1992 9/9/2003 64 0 56 152 OLS 9 –0.771 –0.005 0.012

63 10/26/1992 9/9/2003 64 1 56 160 AMLE 9 –8.183 2.032 –0.140

64 10/21/1992 9/24/2003 125 84 28 180 AMLE 9 –2.983 –0.304 0.022
Appendix 3 161

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibration data set Properties of the calibrated model

Start

date

End

date

Number of

observations

Number of

censored

observations

Median

number

of days

between

successive

samples

Maximum

number

of days

between

successive

samples

Model

calibration

method

Model

specification1 Intercept

Log

streamflow

coefficient

Log

streamflow

squared

coefficient

Total phosphorus—Continued

65 6/3/1993 9/3/2003 140 0 25 210 OLS 9 1.692 –0.939 0.052

66 3/9/1993 9/9/2003 167 73 17 135 AMLE 9 –4.909 0.032 0.089

68 10/22/1992 9/10/2003 123 34 28 237 AMLE 9 –1.585 –0.316 0.014

69 11/5/1992 9/10/2003 78 14 28 1,503 AMLE 9 –3.598 –0.063 0.016

70 10/28/1992 9/3/2003 125 1 28 258 AMLE 9 3.714 –1.310 0.075

71 10/13/1992 9/23/2003 98 0 35 70 OLS 3 –4.000 0.206 --

72 1/15/1993 9/2/2003 154 58 21 182 AMLE 9 –3.901 0.072 0.083

73 10/20/1992 9/9/2003 124 0 21 177 OLS 8 4.692 –1.760 0.097

74 3/4/1993 9/15/2003 110 51 21 1,541 AMLE 3 –4.734 0.236 --

75 1/8/1993 8/20/2003 662 9 4 49 AMLE 8 –1.938 –0.208 0.042

76 4/6/1993 9/16/2003 168 5 20 127 AMLE 8 0.518 –1.099 0.103

77 1/4/1993 7/21/2003 606 4 2 62 AMLE 9 –0.530 –0.867 0.147

78 1/3/1993 7/21/2003 496 95 3 78 AMLE 7 –4.630 0.541 --

79 1/3/1993 12/16/2002 545 44 3 64 AMLE 8 –2.637 –0.027 0.074

80 1/4/1993 12/30/2002 1,313 177 3 31 AMLE 8 –2.757 –0.240 0.062

81 3/8/1993 9/26/2003 85 1 36 147 AMLE 9 –1.627 –0.310 0.045

82 2/17/1993 9/11/2003 71 1 46 142 AMLE 9 –0.697 –0.584 0.074

83 1/19/1993 9/25/2003 198 4 14 107 AMLE 9 –2.933 0.578 –0.063

84 1/4/1993 9/26/2003 775 23 2 54 AMLE 9 –7.761 2.537 –0.207

85 1/4/1993 9/26/2003 738 1 2 157 AMLE 5 –2.142 0.691 –0.051

86 1/4/1993 9/15/2003 855 47 1 42 AMLE 8 –2.269 0.455 –0.030

87 1/6/1993 9/3/2003 115 18 29 272 AMLE 8 –3.562 0.185 0.020

88 1/6/1993 9/3/2003 59 4 62 440 AMLE 7 –4.236 0.440 --

89 1/5/1993 8/14/2003 96 9 34 741 AMLE 8 –2.304 –0.551 0.095

90 1/11/1993 8/20/2003 112 0 28 694 OLS 9 7.048 –2.137 0.152

91 1/8/1993 8/20/2003 92 0 35 694 OLS 9 8.396 –2.244 0.136

92 1/5/1993 9/23/2003 122 31 32 72 AMLE 9 –3.211 0.123 0.018

93 1/14/1993 8/18/2003 127 0 28 131 OLS 9 –20.667 4.046 –0.206

94 1/19/1993 9/4/2003 63 45 58.5 469 AMLE 5 0.535 –1.538 0.144

95 11/11/1992 9/10/2003 141 0 23.5 131 OLS 3 –8.884 0.612 --

97 10/15/1992 8/13/2003 46 17 63 250 AMLE 8 –3.985 0.019 0.073

99 10/8/1992 9/9/2003 113 9 27 197 AMLE 7 –8.059 0.609 --

101 10/7/1992 9/9/2003 70 0 43 176 OLS 8 –76.708 21.784 –1.586

106 4/13/1993 9/24/2003 74 0 20 2,131 OLS 810 –2.998 0.501 –0.030

107 4/7/1993 9/23/2003 131 0 28 456 OLS 7 0.364 –0.102 --

109 4/15/1993 9/16/2003 129 0 27 615 OLS 5 –2.359 –0.037 0.068

110 11/13/1992 9/19/2003 150 0 22 210 OLS 7 –4.846 0.448 --

111 11/10/1992 7/24/2003 94 2 31 433 AMLE 7 –4.354 0.515 --

112 11/10/1992 9/24/2003 119 0 29 433 OLS 7 –7.402 0.552 --

113 11/12/1992 9/9/2003 111 1 29 433 AMLE 8 –6.610 0.986 –0.038

114 11/12/1992 9/11/2003 94 6 35 433 AMLE 7 –4.345 0.403 --

115 11/17/1992 9/8/2003 84 23 43 493 AMLE 8 –2.870 –0.429 0.081

118 11/24/1992 9/9/2003 131 1 22 138 AMLE 3 –9.624 0.720 --

120 4/26/1993 9/3/2003 126 34 28 119 AMLE 8 –2.272 –0.831 0.167

134 11/18/1992 9/9/2003 96 3 34 874 AMLE 9 1.531 –1.206 0.088

135 10/7/1992 9/2/2003 103 1 31.5 358 AMLE 8 1.622 –1.192 0.103

136 10/16/1996 8/28/2003 58 0 42 91 OLS 8 3.031 –1.942 0.240

137 10/6/1992 8/31/2003 98 0 35 353 OLS 8 –2.022 –0.265 0.058

138 10/14/1992 9/3/2003 118 5 30 327 AMLE 8 –2.066 –0.516 0.070

139 10/13/1992 9/3/2003 105 37 33 355 AMLE 8 –3.789 –0.382 0.082

145 11/18/1992 8/4/2003 89 0 48 127 OLS 5 –2.573 0.014 0.013

148 10/14/1992 8/5/2003 72 4 52 120 AMLE 8 –3.216 –0.013 0.025

149 12/17/1992 9/2/2003 92 0 33 156 OLS 9 0.227 –0.762 0.047
162 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibration data set Properties of the calibrated model

Start

date

End

date

Number of

observations

Number of

censored

observations

Median

number

of days

between

successive

samples

Maximum

number

of days

between

successive

samples

Model

calibration

method

Model

specification1 Intercept

Log

streamflow

coefficient

Log

streamflow

squared

coefficient

Total phosphorus—Continued

150 10/21/1992 9/3/2003 98 0 33 411 OLS 7 –5.447 0.550 --

151 10/27/1992 9/23/2003 122 2 29 76 AMLE 8 –2.820 –0.352 0.038

152 11/17/1992 8/27/2003 60 21 63 156 AMLE 3 –3.737 0.048 --

153 10/14/1992 9/23/2003 139 0 22 106 OLS 5 –82.855 12.366 –0.470

154 10/12/1992 9/23/2003 132 0 28 43 OLS 7 –4.780 0.388 --

155 11/16/1992 9/23/2003 98 0 35 70 OLS 3 –3.275 0.158 --

156 11/19/1992 9/24/2003 142 0 21 102 OLS 5 –45.724 6.914 –0.271

157 10/12/1992 8/13/2003 108 0 28 126 OLS 8 0.394 –0.645 0.061

165 11/18/1992 4/16/2003 55 1 63 182 AMLE 7 –1.769 0.056 --

166 11/18/1992 4/16/2003 58 12 63 182 AMLE 5 1.341 –1.769 0.176

169 10/13/1992 4/24/2003 56 22 62 305 AMLE 5 –3.862 –0.079 0.059

170 10/14/1992 4/2/2003 70 0 56 183 OLS 3 –2.041 0.099 --

171 10/14/1992 4/2/2003 55 1 62 253 AMLE 3 –2.386 0.143 --

173 10/27/1992 8/20/2003 78 1 36 169 AMLE 8 –4.425 0.638 –0.049

177 10/30/1992 8/15/2003 65 6 57.5 112 AMLE 8 26.004 –7.828 0.519

178 10/28/1992 7/1/2003 80 5 47 174 AMLE 7 –5.351 0.290 --

180 5/5/1993 9/16/2003 92 5 36 217 AMLE 5 –2.466 –1.251 0.484

182 10/21/1992 9/3/2003 61 5 63 116 AMLE 7 –8.551 1.279 --

183 10/8/1992 9/10/2003 55 3 71 181 AMLE 8 –12.425 2.453 –0.102

184 10/27/1992 8/1/2003 96 29 32 199 AMLE 8 –21.185 4.018 –0.166

185 10/27/1992 7/29/2003 76 18 36 218 AMLE 7 –8.515 0.884 --

186 10/22/1992 8/19/2003 74 12 45 156 AMLE 9 –6.931 0.005 0.053

188 10/20/1992 9/23/2003 88 0 42 169 OLS 9 –0.649 –0.233 0.007

193 10/14/1992 9/17/2003 88 1 42 273 AMLE 9 –3.967 0.381 –0.020

203 10/20/1992 9/23/2003 128 3 28 64 AMLE 9 20.789 –6.708 0.462

204 10/21/1992 9/22/2003 130 24 28 70 AMLE 8 54.977 –13.093 0.722

205 10/19/1992 9/22/2003 131 27 28 64 AMLE 9 14.900 –4.552 0.272

206 10/21/1992 9/24/2003 128 1 28 63 AMLE 9 10.082 –3.950 0.294

207 10/19/1992 9/24/2003 131 34 28 63 AMLE 9 –2.440 –0.737 0.075

208 10/21/1992 8/6/2003 57 0 69.5 113 OLS 8 24.079 –5.270 0.259

209 10/21/1992 8/12/2003 129 0 30 84 OLS 9 12.711 –3.445 0.191

210 10/20/1992 8/12/2003 130 0 30 62 OLS 8 15.363 –4.269 0.246

211 10/20/1992 8/12/2003 57 0 70.5 105 OLS 5 10.364 –3.658 0.238

212 10/26/1992 8/18/2003 64 0 63 175 OLS 5 67.553 –16.251 0.942

213 10/21/1992 8/12/2003 129 0 30 84 OLS 9 18.191 –4.505 0.239

214 10/21/1992 8/11/2003 133 0 29 84 OLS 9 27.947 –5.959 0.289

215 10/21/1992 8/6/2003 57 0 69.5 113 OLS 8 165.710 –28.614 1.210

216 10/27/1992 9/24/2003 130 3 28 63 AMLE 8 25.568 –7.666 0.513

217 10/20/1992 8/12/2003 56 0 71 105 OLS 9 –1.111 –0.599 0.052

218 10/28/1992 8/11/2003 57 0 69 204 OLS 8 –0.239 –1.251 0.175

219 10/14/1992 9/3/2003 64 0 63 176 OLS 5 –1.639 –0.821 0.083

220 10/26/1992 8/18/2003 75 0 56 158 OLS 8 –2.348 –0.291 0.050

221 11/18/1992 9/8/2003 117 8 27 216 AMLE 9 9.727 –4.371 0.350

222 10/7/1992 9/3/2003 112 22 27 216 AMLE 8 6.915 –2.664 0.153

223 11/4/1992 9/24/2003 136 0 28 84 OLS 8 40.473 –9.217 0.491

224 11/2/1992 9/16/2003 93 1 35 130 AMLE 5 6.938 –2.127 0.109

225 12/21/1992 9/3/2003 164 0 27 118 OLS 8 –1.324 –0.497 0.069

227 11/16/1992 9/10/2003 145 0 27 91 OLS 9 31.739 –6.845 0.337

228 11/19/1992 9/8/2003 118 6 28 195 AMLE 8 70.349 –12.467 0.526

229 10/28/1992 9/23/2003 130 25 28 63 AMLE 9 –0.100 –1.543 0.142

230 10/5/1992 9/10/2003 128 0 28 62 OLS 8 4.075 –2.340 0.217

231 10/5/1992 9/29/2003 423 0 7 29 OLS 9 –4.364 0.628 –0.043

232 10/1/1992 9/29/2003 449 92 7 29 AMLE 9 –1.010 –0.900 0.092
Appendix 3 163

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibration data set Properties of the calibrated model

Start

date

End

date

Number of

observations

Number of

censored

observations

Median

number

of days

between

successive

samples

Maximum

number

of days

between

successive

samples

Model

calibration

method

Model

specification1 Intercept

Log

streamflow

coefficient

Log

streamflow

squared

coefficient

Total phosphorus—Continued

233 10/12/1992 9/10/2003 130 0 28 63 OLS 8 7.713 –2.583 0.167

234 10/12/1992 9/8/2003 127 34 28 91 AMLE 9 5.819 –2.761 0.191

235 10/12/1992 9/8/2003 126 50 28 67 AMLE 9 3.785 –2.423 0.177

236 10/13/1992 9/9/2003 129 53 28 65 AMLE 9 2.631 –2.228 0.177

237 10/13/1992 9/9/2003 126 9 28 91 AMLE 9 2.512 –2.021 0.157

238 10/6/1992 9/8/2003 130 8 28 63 AMLE 9 6.597 –2.143 0.115

239 10/7/1992 9/7/2003 132 69 28 43 AMLE 3 –6.975 0.202 --

241 12/15/1992 9/17/2003 261 0 10.5 211 OLS 7 –1.688 0.015 --

242 1/21/1993 9/17/2003 156 0 14 212 OLS 7 –0.575 –0.306 --

243 10/2/1992 9/12/2003 333 0 9 44 OLS 9 –5.806 1.085 –0.070

244 12/16/1992 9/23/2003 202 1 14 160 AMLE 7 –4.836 0.182 --

Total nitrogen

1 11/10/1992 9/3/2003 104 0 34 113 OLS 5 2.803 –0.896 0.059

2 10/20/1992 9/4/2003 104 1 34 175 AMLE 3 0.812 –0.252 --

3 11/10/1992 9/3/2003 102 0 35 184 OLS 3 0.547 –0.098 --

4 11/16/1992 9/25/2003 153 1 25 74 AMLE 7 1.534 –0.210 --

5 3/25/1993 9/15/2003 94 0 32 580 OLS 8 2.065 –0.286 0.028

6 11/19/1992 7/2/2003 59 11 72.5 173 AMLE 3 –0.459 –0.109 --

7 11/19/1992 9/23/2003 89 0 43 173 OLS 9 4.161 –0.881 0.038

8 11/19/1992 9/17/2003 107 0 32.5 131 OLS 7 3.182 –0.415 --

9 11/9/1992 7/17/2003 58 6 77 186 AMLE 9 –2.819 0.571 –0.040

10 10/16/1992 9/16/2003 88 0 44 185 OLS 7 3.203 –0.401 --

11 11/13/1992 7/8/2003 53 0 69.5 142 OLS 7 –0.392 0.005 --

12 11/18/1992 9/10/2003 89 0 42 173 OLS 9 6.322 –1.310 0.066

13 10/14/1992 7/28/2003 56 7 76 189 AMLE 3 –1.046 0.011 --

14 10/14/1992 9/30/2003 195 4 15 97 AMLE 8 –1.074 0.368 –0.045

15 4/8/1993 8/4/2003 137 0 28 115 OLS 8 2.773 –0.734 0.048

16 11/12/1992 8/27/2003 46 0 89 156 OLS 5 1.509 –0.610 0.064

17 11/9/1992 8/27/2003 50 1 90 122 AMLE 8 –0.900 0.229 –0.042

18 10/27/1992 8/20/2003 48 0 89 187 OLS 5 4.421 –1.284 0.091

19 10/29/1992 8/12/2003 82 0 28 414 OLS 8 0.635 0.580 –0.080

20 11/4/1992 8/13/2003 50 0 86 127 OLS 5 0.003 1.251 –0.192

21 11/18/1992 8/28/2003 50 0 83 126 OLS 3 0.331 0.076 --

22 11/24/1992 9/4/2003 48 0 84 133 OLS 8 0.672 –0.208 0.033

23 11/5/1992 8/5/2003 50 0 83 145 OLS 3 0.094 –0.031 --

24 11/5/1992 9/4/2003 74 1 47 183 AMLE 5 –0.588 0.568 –0.055

25 11/19/1992 8/5/2003 48 0 85 148 OLS 3 2.305 –0.219 --

26 11/18/1992 9/9/2003 112 0 29 133 OLS 8 5.553 –1.198 0.074

29 11/24/1992 8/19/2003 49 5 83.5 138 AMLE 5 –6.375 1.802 –0.139

31 10/19/1992 9/3/2003 50 1 79 132 AMLE 8 15.918 –4.055 0.245

32 10/21/1992 9/2/2003 50 0 84 119 OLS 8 –1.956 0.676 –0.057

33 10/22/1992 9/4/2003 94 0 35 119 OLS 5 6.762 –1.452 0.080

34 11/18/1992 8/7/2003 86 0 35 120 OLS 8 –0.159 –0.067 0.033

35 11/30/1992 8/7/2003 82 0 35 134 OLS 8 1.753 –0.591 0.068

36 11/3/1992 9/16/2003 184 0 20 86 OLS 7 0.591 –0.027 --

37 11/18/1992 9/24/2003 255 0 14 79 OLS 7 –0.030 0.040 --

38 11/17/1992 9/19/2003 260 0 13 63 OLS 9 0.777 0.040 –0.012

39 4/15/1993 9/3/2003 278 0 8 56 OLS 9 –0.824 0.657 –0.046

40 11/18/1992 9/20/2003 150 1 26 208 AMLE 9 –7.050 1.431 –0.066

41 10/19/1992 9/23/2003 331 1 11 405 AMLE 5 –2.322 0.170 0.015

42 10/14/1992 9/20/2003 399 0 8 45 OLS 9 –0.457 –0.041 0.008

43 10/14/1992 9/24/2003 391 0 8 68 OLS 9 –1.055 0.063 0.001

44 10/28/1992 9/25/2003 349 0 10 60 OLS 9 –3.101 0.128 0.017
164 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibration data set Properties of the calibrated model

Start

date

End

date

Number of

observations

Number of

censored

observations

Median

number

of days

between

successive

samples

Maximum

number

of days

between

successive

samples

Model

calibration

method

Model

specification1 Intercept

Log

streamflow

coefficient

Log

streamflow

squared

coefficient

Total nitrogen—Continued

45 10/8/1992 9/25/2003 413 0 8 42 OLS 9 –0.277 –0.174 0.017

46 10/8/1992 8/21/2003 87 0 46.5 122 OLS 9 –1.013 0.154 –0.002

47 12/16/1992 9/2/2003 128 0 28 162 OLS 9 –2.051 0.676 –0.048

48 12/16/1992 9/2/2003 146 0 23 162 OLS 9 –0.625 0.309 –0.026

49 10/5/1992 6/23/2003 83 0 46.5 106 OLS 9 –1.849 0.442 –0.025

52 10/20/1992 9/11/2003 85 0 33 415 OLS 9 –22.408 6.514 –0.468

53 10/28/1992 9/25/2003 119 0 28 387 OLS 9 0.935 –0.115 –0.003

57 10/29/1992 9/3/2003 61 0 57 224 OLS 9 1.105 –0.406 0.037

58 10/29/1992 9/8/2003 60 0 61 272 OLS 9 0.664 –0.069 –0.004

59 10/28/1992 9/25/2003 89 0 32 315 OLS 9 –1.327 0.555 –0.043

60 10/21/1992 9/10/2003 103 0 31.5 153 OLS 9 –0.368 0.112 –0.004

61 10/21/1992 9/10/2003 63 0 56 162 OLS 9 0.299 –0.047 –0.004

62 10/26/1992 9/9/2003 63 0 58 152 OLS 9 0.067 0.170 –0.018

65 6/3/1993 9/3/2003 123 0 27 210 OLS 9 2.284 –0.593 0.035

67 3/11/1993 9/8/2003 114 0 28 566 OLS 9 9.713 –1.863 0.092

71 10/13/1992 9/23/2003 97 5 35 70 AMLE 5 –12.313 2.611 -0.130

72 1/15/1993 9/2/2003 154 0 21 182 OLS 7 –0.470 0.223 --

73 10/20/1992 9/9/2003 124 0 21 177 OLS 7 –1.210 0.128 --

74 3/4/1993 9/15/2003 110 1 21 1,541 AMLE 9 –2.756 0.754 –0.054

76 4/6/1993 9/16/2003 164 0 21 127 OLS 7 0.254 0.071 --

81 3/8/1993 9/26/2003 85 1 36 147 AMLE 9 0.426 –0.121 0.015

82 2/17/1993 9/11/2003 71 0 46 142 OLS 7 0.209 0.056 --

92 1/5/1993 9/23/2003 121 0 33.5 72 OLS 7 –0.080 0.204 --

95 11/11/1992 9/10/2003 141 0 23 131 OLS 8 –32.946 5.202 –0.198

97 10/15/1992 8/13/2003 46 0 63 250 OLS 8 –0.799 0.024 0.049

99 10/8/1992 9/9/2003 113 1 27 197 AMLE 7 –2.853 0.272 --

100 10/6/1992 8/28/2003 61 0 49 567 OLS 3 –2.129 0.067 --

101 10/7/1992 9/9/2003 68 0 42 259 OLS 7 –4.954 0.658 --

102 11/23/1992 8/25/2003 86 0 41 157 OLS 7 0.463 –0.007 --

103 4/12/1993 9/22/2003 96 0 16 2,041 OLS 510 2.711 –0.759 0.068

106 4/13/1993 9/24/2003 73 0 20 2,131 OLS 710 2.146 –0.164 --

107 4/7/1993 9/23/2003 132 0 28 456 OLS 8 3.404 –0.157 –0.010

108 11/3/1992 9/8/2003 61 0 34.5 765 OLS 8 249.550 –94.239 8.883

109 4/15/1993 9/16/2003 132 0 27 615 OLS 7 0.254 0.350 --

110 11/13/1992 9/19/2003 152 0 22 163 OLS 3 –2.439 0.389 --

111 11/10/1992 7/24/2003 107 0 29 238 OLS 8 –4.893 1.512 –0.082

112 11/10/1992 9/24/2003 132 0 29 58 OLS 8 9.387 –1.711 0.085

113 11/12/1992 9/9/2003 125 1 29 92 AMLE 7 –2.015 0.322 --

114 11/12/1992 9/11/2003 107 1 35 90 AMLE 7 –0.823 0.167 --

115 11/17/1992 9/8/2003 90 1 44 146 AMLE 5 –0.926 –0.171 0.053

116 11/17/1992 9/3/2003 67 0 60 97 OLS 7 –1.844 0.159 --

118 11/24/1992 9/9/2003 132 0 22 138 OLS 7 –3.242 0.341 --

120 4/26/1993 9/3/2003 125 2 28 119 AMLE 7 0.747 0.130 --

124 11/12/1992 9/5/2003 70 2 56 539 AMLE 7 –1.186 0.067 --

125 11/12/1992 9/10/2003 118 6 29 465 AMLE 7 –2.451 0.184 --

134 11/18/1992 9/9/2003 96 0 34 874 OLS 8 –5.055 1.534 –0.101

135 10/7/1992 9/2/2003 102 1 32 358 AMLE 8 –1.860 0.769 –0.051

136 10/16/1996 8/28/2003 58 0 42 91 OLS 3 2.694 –0.278 --

137 10/6/1992 8/31/2003 99 0 35 353 OLS 9 0.447 0.180 –0.009

138 10/14/1992 9/3/2003 118 0 30 327 OLS 8 –5.427 1.435 –0.080

139 10/13/1992 9/3/2003 105 0 33 355 OLS 9 –2.062 0.614 –0.028

145 10/13/1992 8/4/2003 85 1 48.5 127 AMLE 9 –0.377 –0.099 0.022

146 10/15/1992 8/5/2003 74 23 50 196 AMLE 8 –1.199 –0.060 0.018
Appendix 3 165

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibration data set Properties of the calibrated model

Start

date

End

date

Number of

observations

Number of

censored

observations

Median

number

of days

between

successive

samples

Maximum

number

of days

between

successive

samples

Model

calibration

method

Model

specification1 Intercept

Log

streamflow

coefficient

Log

streamflow

squared

coefficient

Total nitrogen—Continued

147 10/14/1992 8/5/2003 71 20 50 196 AMLE 8 –1.266 –0.016 0.016

148 10/14/1992 8/5/2003 72 0 52 120 OLS 7 –0.679 0.061 --

149 12/17/1992 9/2/2003 92 0 33 156 OLS 8 0.470 –0.194 0.013

150 10/21/1992 9/3/2003 99 0 33.5 411 OLS 9 –0.871 0.126 0.008

151 10/27/1992 9/23/2003 123 0 29 76 OLS 8 0.371 –0.290 0.022

152 11/17/1992 8/27/2003 60 9 63 156 AMLE 7 –0.927 –0.004 --

153 10/14/1992 9/23/2003 134 0 21 106 OLS 8 –52.498 8.067 –0.306

154 10/12/1992 9/23/2003 131 6 28 71 AMLE 5 –13.282 3.203 –0.188

155 11/16/1992 9/23/2003 97 7 35 71 AMLE 5 –10.657 3.271 –0.249

156 2/23/1993 9/24/2003 134 0 21 102 OLS 8 –44.611 7.282 –0.294

157 10/12/1992 8/13/2003 108 0 28 126 OLS 7 0.753 –0.031 --

173 10/27/1992 8/20/2003 78 1 36 169 AMLE 7 –0.383 –0.061 --

176 11/6/1992 9/3/2003 108 8 35 113 AMLE 3 –2.074 0.100 --

179 12/18/1992 6/24/2003 62 0 61 176 OLS 3 –0.688 –0.030 --

182 10/21/1992 9/3/2003 61 0 63 116 OLS 8 –7.981 2.329 –0.150

196 12/16/1992 9/2/2003 274 0 8 127 OLS 9 –1.687 –0.268 0.045

199 10/21/1992 9/5/2003 235 0 13 84 OLS 9 –2.566 0.298 0.007

201 10/22/1992 9/4/2003 221 0 14 170 OLS 9 –1.656 0.258 –0.018

202 10/21/1992 9/4/2003 261 0 12 70 OLS 9 –2.573 0.483 –0.025

208 10/21/1992 8/6/2003 57 0 69.5 113 OLS 9 11.693 –2.383 0.116

209 10/21/1992 8/12/2003 126 22 31 84 AMLE 9 8.871 –1.982 0.100

210 10/20/1992 8/12/2003 126 57 33 70 AMLE 9 8.170 –2.047 0.109

212 10/26/1992 8/18/2003 63 19 63 175 AMLE 5 81.687 –19.241 1.116

213 10/21/1992 8/12/2003 128 10 30 84 AMLE 9 13.816 –2.926 0.145

214 10/21/1992 8/11/2003 132 0 29 84 OLS 9 8.089 –1.641 0.079

215 10/21/1992 8/6/2003 57 13 69.5 113 AMLE 7 –0.957 0.001 --

217 10/20/1992 8/12/2003 55 0 72 116 OLS 9 1.501 –0.597 0.044

218 10/28/1992 8/11/2003 56 0 69 204 OLS 9 1.636 0.145 –0.045

219 10/14/1992 9/3/2003 63 32 63 176 AMLE 5 1.011 –0.751 0.057

220 10/26/1992 8/18/2003 76 0 56 158 OLS 9 2.091 –0.014 –0.036

221 11/18/1992 9/8/2003 115 47 27 216 AMLE 9 6.314 –2.229 0.162

222 10/7/1992 9/3/2003 111 88 27 216 AMLE 5 7.135 –2.094 0.121

223 11/4/1992 9/24/2003 138 0 28 79 OLS 7 3.452 –0.332 --

224 11/2/1992 9/16/2003 93 6 35 130 AMLE 9 7.835 –2.231 0.137

225 12/21/1992 9/3/2003 164 0 27 118 OLS 9 0.434 –0.031 0.021

227 11/16/1992 9/10/2003 145 1 27 91 AMLE 9 11.450 –2.454 0.125

228 11/19/1992 9/8/2003 118 22 28 195 AMLE 9 –5.984 0.665 –0.021

231 10/5/1992 9/29/2003 404 0 7 132 OLS 9 1.421 –0.076 –0.004

232 10/1/1992 9/29/2003 430 80 7 132 AMLE 7 –1.893 0.200 --

241 12/15/1992 9/17/2003 244 0 12 686 OLS 8 1.565 –0.194 0.008

242 1/21/1993 9/17/2003 135 2 14 1666 AMLE 9 2.392 0.043 –0.060

243 11/17/1992 9/12/2003 264 0 12 483 OLS 8 –1.534 0.918 –0.079

244 12/16/1992 9/23/2003 202 22 14 160 AMLE 7 –0.713 –0.053 --

Nitrate

1 11/10/1992 9/3/2003 105 0 34.5 113 OLS 9 3.059 –1.105 0.065

2 2/10/1993 9/4/2003 104 0 34 88 OLS 5 1.826 –0.909 0.059

3 1/21/1993 9/3/2003 103 1 35 91 AMLE 8 –5.331 1.436 –0.114

4 11/16/1992 9/25/2003 153 1 25 74 AMLE 8 –3.089 0.722 –0.054

5 3/25/1993 9/15/2003 94 0 32 580 OLS 8 1.312 0.268 –0.085

6 1/15/1993 7/2/2003 60 0 69 112 OLS 7 0.065 –0.303 --

7 1/26/1993 9/23/2003 90 0 43 139 OLS 8 1.133 0.074 –0.044

8 1/14/1993 9/17/2003 107 0 32.5 85 OLS 7 3.467 –0.541 --

9 1/11/1993 7/17/2003 59 2 76.5 110 AMLE 9 –2.457 0.153 –0.011
166 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibration data set Properties of the calibrated model

Start

date

End

date

Number of

observations

Number of

censored

observations

Median

number

of days

between

successive

samples

Maximum

number

of days

between

successive

samples

Model

calibration

method

Model

specification1 Intercept

Log

streamflow

coefficient

Log

streamflow

squared

coefficient

Nitrate—Continued

10 2/18/1993 9/16/2003 88 0 44 77 OLS 7 3.529 –0.514 --

11 11/13/1992 7/8/2003 53 0 69.5 142 OLS 7 –1.429 0.056 --

12 1/25/1993 9/10/2003 90 0 42 78 OLS 9 4.184 –0.842 0.027

13 2/9/1993 7/28/2003 56 7 76 189 AMLE 7 –1.911 –0.083 --

14 2/9/1993 9/30/2003 195 4 15 79 AMLE 5 –2.017 0.472 –0.046

15 4/8/1993 8/4/2003 138 0 28 115 OLS 8 –5.096 1.048 –0.058

16 11/12/1992 8/27/2003 47 0 87 156 OLS 8 1.535 –0.954 0.087

17 11/9/1992 8/27/2003 50 3 90 122 AMLE 8 –1.565 0.122 –0.048

18 10/27/1992 8/20/2003 48 0 89 187 OLS 7 2.581 –0.504 --

19 10/29/1992 8/12/2003 83 0 28 414 OLS 8 0.088 0.781 –0.105

20 11/4/1992 8/13/2003 49 0 88 127 OLS 5 –0.608 1.497 –0.229

21 11/18/1992 8/28/2003 50 0 83 126 OLS 5 –0.720 0.647 –0.099

22 11/24/1992 9/4/2003 49 0 80 133 OLS 7 0.039 –0.043 --

23 11/5/1992 8/5/2003 50 0 83 145 OLS 3 0.055 –0.096 --

24 11/5/1992 9/4/2003 74 5 47 183 AMLE 5 –2.680 1.721 –0.213

25 2/17/1993 8/5/2003 48 0 83 148 OLS 7 2.760 –0.344 --

26 11/18/1992 9/9/2003 112 0 29 133 OLS 8 4.456 –0.859 0.043

29 11/24/1992 8/19/2003 49 6 83.5 138 AMLE 7 –2.124 –0.023 --

31 10/19/1992 9/3/2003 49 1 81 132 AMLE 8 14.722 –3.822 0.225

32 10/21/1992 9/2/2003 49 1 85 146 AMLE 9 –6.427 2.134 –0.195

33 10/22/1992 9/4/2003 94 0 35 119 OLS 7 0.501 –0.069 --

34 11/18/1992 8/7/2003 86 0 35 120 OLS 7 –1.946 0.247 --

35 11/30/1992 8/7/2003 83 0 35 124 OLS 7 0.824 –0.191 --

36 11/3/1992 9/16/2003 183 0 20 86 OLS 9 0.196 0.122 –0.029

37 11/18/1992 9/24/2003 255 0 14 79 OLS 8 –4.696 0.907 –0.042

38 11/17/1992 9/19/2003 297 0 11 63 OLS 8 0.721 0.064 –0.024

39 4/15/1993 9/3/2003 278 0 8 56 OLS 9 –0.709 0.636 –0.050

40 11/18/1992 9/20/2003 150 0 26 208 OLS 8 –17.725 3.678 –0.185

41 10/19/1992 9/23/2003 347 17 10 405 AMLE 8 –21.642 4.920 –0.284

42 10/14/1992 9/25/2003 421 0 7 45 OLS 8 –1.232 0.094 –0.015

43 10/14/1992 9/19/2003 417 5 7 45 AMLE 9 –2.456 0.203 –0.027

44 10/28/1992 9/25/2003 369 7 9 60 AMLE 9 –26.915 5.077 –0.251

45 10/8/1992 9/25/2003 420 3 8 42 AMLE 8 0.630 –0.707 0.045

50 11/19/1992 9/3/2003 125 12 28 105 AMLE 9 9.851 –2.552 0.130

65 6/3/1993 9/3/2003 140 2 25 210 AMLE 9 2.725 –0.735 0.018

66 3/9/1993 9/9/2003 165 0 19 135 OLS 9 –1.804 0.557 –0.066

71 10/13/1992 9/23/2003 98 3 35 70 AMLE 5 –32.454 7.976 –0.503

72 1/15/1993 9/2/2003 155 1 19.5 182 AMLE 8 –0.827 0.258 –0.028

73 10/20/1992 9/9/2003 132 0 21 177 OLS 7 –0.636 0.050 --

74 3/4/1993 9/15/2003 110 48 21 1,541 AMLE 7 –2.848 –0.035 --

76 4/6/1993 9/16/2003 165 9 21 127 AMLE 8 –10.858 2.924 -0.187

81 3/8/1993 9/10/2003 84 31 36 147 AMLE 7 –3.437 0.225 --

82 2/17/1993 9/11/2003 71 24 46 142 AMLE 7 –3.121 0.225 --

88 1/6/1993 9/3/2003 64 13 62 131 AMLE 7 –4.775 0.736 --

92 1/5/1993 9/23/2003 123 2 32 72 AMLE 7 –1.145 0.341 --

95 11/11/1992 9/10/2003 143 1 23 131 AMLE 8 –53.142 8.408 –0.327

96 10/20/1992 9/10/2003 96 1 35 99 AMLE 8 5.964 –2.338 0.250

98 12/17/1992 8/5/2003 44 0 84 169 OLS 8 11.184 –2.693 0.134

99 10/8/1992 9/9/2003 113 25 27 197 AMLE 8 8.494 –3.130 0.217

100 10/6/1992 8/28/2003 62 0 49 567 OLS 5 –7.858 0.806 –0.028

101 10/7/1992 9/9/2003 68 3 42 259 AMLE 7 –1.538 0.060 --

102 11/23/1992 8/25/2003 86 43 41 157 AMLE 7 –3.955 0.302 --
Appendix 3 167

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibration data set Properties of the calibrated model

Start

date

End

date

Number of

observations

Number of

censored

observations

Median

number

of days

between

successive

samples

Maximum

number

of days

between

successive

samples

Model

calibration

method

Model

specification1 Intercept

Log

streamflow

coefficient

Log

streamflow

squared

coefficient

Nitrate—Continued

103 4/12/1993 9/22/2003 96 0 16 2,041 OLS 710 2.369 –0.629 --

104 10/28/1992 9/17/2003 130 1 29 70 AMLE 3 –0.009 –0.479 --

105 10/30/1992 9/17/2003 128 1 29 71 AMLE 7 0.402 –0.294 --

106 4/13/1993 9/24/2003 73 0 20 2,131 OLS 810 2.195 –0.295 –0.003

107 4/7/1993 9/23/2003 132 0 28 456 OLS 8 1.794 0.306 –0.048

108 11/3/1992 9/8/2003 61 0 34.5 765 OLS 8 187.435 –69.842 6.480

109 4/15/1993 9/16/2003 132 1 27 615 AMLE 8 –0.502 0.736 –0.059

110 11/13/1992 9/19/2003 152 17 22 163 AMLE 8 –37.107 7.224 –0.343

111 11/10/1992 7/24/2003 108 17 29 238 AMLE 8 –17.569 4.748 –0.289

112 11/10/1992 9/24/2003 132 4 29 58 AMLE 7 –1.983 0.197 --

113 11/12/1992 9/9/2003 126 34 29 92 AMLE 8 –11.801 2.084 –0.088

114 11/12/1992 9/11/2003 107 21 35 90 AMLE 8 –13.096 3.147 –0.196

115 11/17/1992 9/8/2003 90 14 44 146 AMLE 8 –7.271 1.777 –0.108

116 11/17/1992 9/3/2003 67 9 60 97 AMLE 7 –5.093 0.380 --

117 11/17/1992 9/5/2003 121 2 31 77 AMLE 8 –16.797 3.744 –0.218

118 11/24/1992 9/9/2003 133 2 21.5 138 AMLE 7 –3.713 0.328 --

119 11/11/1992 8/25/2003 65 3 56.5 230 AMLE 9 –3.838 1.111 –0.121

120 4/26/1993 9/3/2003 126 2 28 119 AMLE 7 0.684 0.127 --

121 10/27/1992 9/1/2003 136 41 23 168 AMLE 9 –7.037 1.158 –0.061

122 11/17/1992 8/20/2003 65 2 58.5 100 AMLE 7 –5.293 0.422 --

123 11/17/1992 9/2/2003 112 30 30 121 AMLE 3 –3.192 0.141 --

124 11/12/1992 9/5/2003 77 0 56 105 OLS 9 –5.247 1.397 –0.115

125 11/12/1992 9/10/2003 132 1 29 70 AMLE 8 –14.635 3.136 –0.184

126 10/16/1997 8/25/2003 41 3 56 104 AMLE 8 –3.424 0.806 –0.076

127 11/24/1997 8/25/2003 33 2 57 169 AMLE 7 –1.749 –0.038 --

128 10/15/1992 9/3/2003 101 0 35 194 OLS 7 0.218 –0.182 --

129 10/14/1992 8/21/2003 91 8 35 194 AMLE 9 0.185 –0.284 –0.020

130 10/15/1992 7/28/2003 116 0 28 194 OLS 9 2.120 –0.330 –0.001

131 10/15/1992 7/28/2003 105 0 35 194 OLS 9 2.288 –0.136 –0.024

132 12/18/1992 7/23/2003 53 0 74 194 OLS 8 –1.738 1.342 –0.146

133 10/16/1992 7/24/2003 110 0 28 194 OLS 9 1.635 0.056 –0.022

134 11/18/1992 9/9/2003 105 0 33.5 687 OLS 8 –6.056 1.797 –0.119

135 10/7/1992 9/2/2003 103 0 31.5 358 OLS 8 –2.348 1.000 –0.079

136 10/16/1996 8/28/2003 58 0 42 91 OLS 3 2.789 –0.337 --

137 10/6/1992 8/31/2003 99 0 35 353 OLS 9 –0.272 0.528 –0.054

138 10/14/1992 9/3/2003 118 0 30 327 OLS 8 –8.041 2.208 –0.139

139 10/13/1992 9/3/2003 105 0 33 355 OLS 9 –3.525 1.172 –0.083

140 11/17/1992 9/9/2003 57 9 62 484 AMLE 9 –3.486 0.321 –0.002

141 11/17/1992 9/10/2003 131 60 28 71 AMLE 7 –4.828 0.427 --

142 10/14/1992 9/9/2003 132 22 29 49 AMLE 8 –0.773 –0.366 0.036

143 10/14/1992 9/9/2003 132 6 29 50 AMLE 9 8.665 –3.014 0.231

144 10/14/1992 9/9/2003 130 0 29 71 OLS 8 10.752 –2.780 0.175

145 10/13/1992 8/4/2003 85 16 48.5 127 AMLE 3 –3.022 0.186 --

146 10/15/1992 8/5/2003 74 17 50 196 AMLE 9 –3.480 0.469 –0.031

147 10/14/1992 8/5/2003 72 23 50 196 AMLE 9 –3.065 0.126 0.010

148 10/14/1992 8/5/2003 73 16 51.5 120 AMLE 9 –4.072 0.939 –0.094

149 12/17/1992 9/2/2003 92 13 33 156 AMLE 7 –2.616 0.124 --

150 10/21/1992 9/3/2003 99 18 33.5 411 AMLE 8 –16.016 3.328 –0.178

151 10/27/1992 9/23/2003 123 33 29 76 AMLE 8 –17.066 2.621 –0.113

152 11/17/1992 8/27/2003 60 7 63 156 AMLE 8 –15.778 3.158 –0.181

153 10/14/1992 9/23/2003 138 0 22 106 OLS 8 –64.890 9.821 –0.369

154 10/12/1992 9/23/2003 132 3 28 43 AMLE 5 –21.913 5.544 –0.365

155 11/16/1992 9/23/2003 98 2 35 70 AMLE 8 –14.412 4.324 –0.353
168 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibration data set Properties of the calibrated model

Start

date

End

date

Number of

observations

Number of

censored

observations

Median

number

of days

between

successive

samples

Maximum

number

of days

between

successive

samples

Model

calibration

method

Model

specification1 Intercept

Log

streamflow

coefficient

Log

streamflow

squared

coefficient

Nitrate—Continued

156 11/19/1992 9/24/2003 140 0 21 102 OLS 8 –42.923 6.901 –0.277

157 10/12/1992 8/13/2003 108 1 28 126 AMLE 9 –1.541 0.522 –0.058

158 10/15/1992 4/9/2003 114 45 33 125 AMLE 8 –5.106 0.828 –0.064

159 1/21/1993 8/5/2003 65 10 44 198 AMLE 8 –4.517 0.976 –0.093

160 1/22/1993 8/5/2003 64 13 49 203 AMLE 5 –15.247 4.117 –0.309

161 11/2/1992 7/15/2003 95 22 30.5 273 AMLE 8 –3.362 0.178 0.051

162 10/20/1992 8/6/2003 116 24 21 259 AMLE 7 –2.862 0.366 --

163 1/20/1993 8/4/2003 66 1 44 198 AMLE 9 –4.050 1.747 –0.132

164 11/5/1992 6/24/2003 59 5 62 362 AMLE 8 –1.341 1.050 –0.112

167 1/25/1993 9/9/2003 84 31 30 428 AMLE 7 –3.312 0.224 --

168 11/19/1992 9/3/2003 77 10 36 239 AMLE 7 –2.781 0.192 --

172 10/21/1992 9/10/2003 126 1 28 245 AMLE 3 5.642 –0.611 --

174 10/5/1992 8/20/2003 63 5 48 196 AMLE 9 –35.894 9.127 –0.617

175 10/14/1992 9/10/2003 118 0 28 147 OLS 9 –2.629 0.814 –0.069

177 10/30/1992 8/15/2003 65 16 57.5 112 AMLE 7 –0.068 –0.362 --

181 10/13/1992 9/16/2003 88 0 42 176 OLS 7 2.824 –0.520 --

187 12/15/1992 9/23/2003 71 15 36.5 210 AMLE 7 –2.784 0.021 --

189 10/20/1992 8/27/2003 112 2 35 140 AMLE 8 1.464 –1.086 0.089

190 10/20/1992 9/17/2003 111 5 31.5 184 AMLE 7 –0.960 –0.181 --

191 10/22/1992 8/12/2003 118 24 27 167 AMLE 9 2.758 –2.186 0.207

192 10/14/1992 9/17/2003 125 1 28 147 AMLE 7 0.975 –0.432 --

194 10/23/1992 9/2/2003 225 0 13 93 OLS 7 –4.128 –0.185 --

195 10/23/1992 9/2/2003 229 0 14 93 OLS 9 –4.729 0.085 -0.011

197 10/21/1992 9/5/2003 310 0 8 91 OLS 7 –4.598 –0.008 --

198 10/21/1992 9/5/2003 227 0 14 88 OLS 9 –4.089 –0.038 -0.006

199 10/21/1992 9/5/2003 236 0 13 84 OLS 7 –3.765 –0.114 --

200 10/21/1992 9/5/2003 317 0 8 76 OLS 8 –4.044 0.186 –0.047

201 10/22/1992 9/4/2003 221 1 14 170 AMLE 9 –4.637 –0.079 0.105

205 10/19/1992 9/22/2003 131 0 28 64 OLS 8 –9.752 1.968 –0.117

207 10/19/1992 9/24/2003 130 2 28 63 AMLE 8 1.757 –1.241 0.090

208 10/21/1992 8/6/2003 57 0 69.5 113 OLS 9 2.375 –0.675 0.033

209 10/21/1992 8/12/2003 129 0 30 84 OLS 9 12.629 –2.929 0.149

210 10/20/1992 8/12/2003 129 0 30 70 OLS 9 13.826 –3.455 0.182

213 10/21/1992 8/12/2003 129 0 30 84 OLS 9 16.110 –3.477 0.171

215 10/21/1992 8/6/2003 57 0 69.5 113 OLS 7 –4.179 0.200 --

217 10/20/1992 8/12/2003 56 0 71 105 OLS 8 6.051 –2.424 0.180

218 10/28/1992 8/11/2003 57 0 69 204 OLS 9 0.852 0.521 –0.095

224 11/2/1992 9/16/2003 93 1 35 130 AMLE 9 7.882 –2.398 0.150

225 12/21/1992 9/3/2003 164 8 27 118 AMLE 9 –2.721 0.795 –0.042

226 10/4/1993 9/3/2003 131 0 28 448 OLS 8 1.794 0.293 –0.035

228 11/19/1992 9/8/2003 118 1 28 195 AMLE 9 17.927 –3.424 0.148

229 10/28/1992 9/23/2003 130 2 28 64 AMLE 9 –5.599 0.779 –0.058

234 10/12/1992 9/8/2003 128 0 28 91 OLS 9 12.141 –3.321 0.188

235 10/12/1992 9/8/2003 127 27 28 67 AMLE 7 –7.606 0.526 --

237 10/13/1992 9/9/2003 127 28 28 90 AMLE 7 –3.575 –0.017 --

238 10/6/1992 9/8/2003 131 0 28 63 OLS 9 6.966 –0.968 0.009

239 10/7/1992 9/7/2003 132 0 28 43 OLS 9 –5.097 0.337 –0.010

240 11/18/1992 9/11/2003 123 6 7.5 1,741 AMLE 9 –2.711 –0.467 0.048

241 12/15/1992 9/17/2003 263 0 11 211 OLS 8 1.165 –0.066 –0.027

242 1/21/1993 9/17/2003 156 0 14 212 OLS 9 3.453 –0.314 –0.036

243 10/2/1992 9/12/2003 533 0 6 44 OLS 9 0.763 0.490 –0.066

244 12/16/1992 9/23/2003 202 8 14 160 AMLE 7 –0.349 –0.174 --
Appendix 3 169

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Sine

coefficient

Cosine

coefficient

Time

coefficient

Time

squared

coefficient

Step

trend

coefficient

Root mean

square

error

Standard

error of

intercept

Standard

error of log

streamflow

coefficient

Standard

error of log

streamflow

squared

coefficient

Standard

error of sine

coefficient

Total phosphorus

1 –0.312 –0.142 0.044 -- -- 0.558 1.578 0.531 0.044 0.133

2 –0.044 –0.148 0.008 0.019 -- 0.543 1.089 0.471 0.050 0.141

3 –0.223 –0.203 0.046 0.017 -- 0.539 1.792 0.568 0.045 0.119

4 –0.230 0.136 0.022 -- -- 0.683 5.701 1.203 0.063 0.109

5 –0.500 –0.183 –0.006 -- -- 0.471 0.889 0.531 0.077 0.091

7 –0.194 –0.082 0.022 0.013 -- 0.356 2.753 0.812 0.059 0.063

8 -- -- –0.020 -- -- 0.363 0.229 0.049 -- --

10 –0.226 –0.047 –0.013 -0.016 -- 0.344 1.437 0.550 0.052 0.064

11 -- -- 0.009 -- -- 0.720 0.956 0.126 -- --

12 –0.203 –0.092 0.053 –0.016 -- 0.455 1.983 0.677 0.057 0.090

13 –0.161 –0.690 0.021 -- -- 0.634 0.478 0.131 -- 0.213

14 –0.436 –0.668 0.033 -- -- 0.557 0.331 0.210 0.033 0.096

15 –0.378 –0.049 0.007 -- -- 0.583 3.326 0.780 0.045 0.100

16 –0.318 –0.516 0.000 0.024 -- 0.497 1.466 0.728 0.085 0.132

17 -- -- –0.072 -- -- 0.729 0.342 0.088 -- --

18 –0.210 –0.179 –0.001 -- -- 0.311 0.700 0.300 0.031 0.081

19 –0.251 –0.035 0.008 -- -- 0.255 0.631 0.219 0.018 0.046

20 –0.154 –0.176 0.086 –0.015 -- 0.378 1.389 0.670 0.080 0.090

22 –0.382 –0.205 0.027 -- -- 0.308 0.390 0.225 0.031 0.067

24 –0.169 –0.288 0.008 0.022 -- 0.776 0.310 0.187 0.030 0.169

25 -- -- 0.022 -- -- 0.296 1.089 0.393 0.035 --

26 –0.141 –0.232 0.009 -- -- 0.306 1.009 0.294 0.021 0.048

27 –0.227 –0.425 –0.009 0.036 -- 0.479 2.710 1.299 0.155 0.123

28 –0.648 –0.466 0.011 0.028 -- 0.870 13.869 5.165 0.480 0.272

30 –0.304 –0.457 –0.014 -- -- 0.848 2.088 0.428 -- 0.323

31 –0.110 –0.150 –0.068 0.027 -- 0.629 18.276 4.184 0.238 0.225

32 –0.340 –0.557 0.007 -- -- 0.554 1.787 0.723 0.072 0.172

33 –0.174 –0.110 –0.010 -- -- 0.498 5.948 1.263 0.067 0.087

34 –0.086 –0.295 0.000 -- -- 0.419 0.484 0.282 0.038 0.069

35 –0.220 –0.270 0.024 -- -- 0.396 0.649 0.329 0.039 0.076

36 –0.119 –0.384 0.053 0.011 -- 0.541 0.457 0.172 0.016 0.068

37 –0.289 0.010 0.053 -- -- 0.532 2.924 0.539 0.025 0.065

38 –0.285 –0.175 0.022 0.017 -- 0.566 1.138 0.359 0.028 0.049

39 –0.420 –0.278 0.023 -- -- 0.751 1.233 0.373 0.027 0.074

40 –0.211 –0.223 0.068 –0.010 -- 0.677 2.293 0.502 0.027 0.103

41 –0.265 –0.169 0.038 -- -- 0.631 1.149 0.298 0.019 0.063

42 –0.210 –0.025 0.049 0.010 -- 0.448 0.457 0.135 0.010 0.035

43 –0.201 –0.261 –0.003 0.007 -- 0.357 0.152 0.053 0.005 0.030

44 –0.270 –0.093 –0.010 0.013 -- 0.561 1.593 0.353 0.019 0.047

45 –0.036 0.021 –0.011 0.008 -- 0.419 0.413 0.121 0.009 0.035

46 –0.078 0.023 0.033 –0.000 -- 0.525 0.477 0.214 0.023 0.142

51 –0.047 –0.057 0.011 0.006 -- 0.359 8.123 1.710 0.090 0.056

52 0.187 0.005 –0.069 0.019 -- 0.400 6.285 1.768 0.124 0.076

53 0.006 –0.043 –0.048 0.016 -- 0.411 2.494 0.562 0.031 0.073

54 0.138 –0.022 –0.036 0.016 -- 0.345 1.914 0.485 0.030 0.058

55 0.052 –0.029 –0.025 0.015 -- 0.238 1.786 0.389 0.021 0.037

56 0.051 –0.264 0.012 0.008 -- 0.357 0.308 0.122 0.011 0.053

58 0.029 –0.028 0.030 –0.000 -- 0.215 0.226 0.114 0.014 0.047

59 –0.004 –0.086 –0.007 0.003 -- 0.201 0.289 0.092 0.007 0.032

60 –0.143 –0.161 0.015 –0.005 -- 0.233 0.126 0.066 0.008 0.035

61 0.027 –0.106 –0.041 0.001 -- 0.329 0.215 0.124 0.017 0.063

62 –0.042 –0.220 –0.045 0.007 -- 0.285 0.104 0.050 0.007 0.058

63 –0.276 –0.246 –0.057 0.006 -- 0.412 1.099 0.409 0.036 0.080
170 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Sine

coefficient

Cosine

coefficient

Time

coefficient

Time

squared

coefficient

Step

trend

coefficient

Root mean

square

error

Standard

error of

intercept

Standard

error of log

streamflow

coefficient

Standard

error of log

streamflow

squared

coefficient

Standard

error of sine

coefficient

Total phosphorus—Continued

64 0.049 –0.231 –0.135 0.023 -- 0.411 0.665 0.238 0.022 0.097

65 –0.044 –0.005 0.012 0.007 -- 0.366 0.298 0.110 0.010 0.050

66 –0.201 –0.298 0.008 –0.013 -- 0.717 1.034 0.449 0.047 0.141

68 0.070 –0.091 –0.083 0.016 -- 0.532 10.611 2.329 0.127 0.091

69 0.009 –0.063 –0.007 –0.005 -- 0.319 2.761 0.604 0.032 0.069

70 –0.157 –0.047 –0.075 0.000 -- 0.420 2.343 0.579 0.035 0.074

71 -- -- 0.037 -- -- 0.408 0.441 0.061 -- --

72 –0.387 –0.470 0.032 –0.011 -- 0.510 0.180 0.096 0.016 0.087

73 –0.150 0.121 0.055 -- -- 0.312 7.281 1.164 0.046 0.053

74 -- -- –0.019 -- -- 0.341 1.078 0.166 -- --

75 0.015 –0.406 –0.026 -- -- 0.411 0.216 0.117 0.015 0.026

76 –0.121 –0.426 0.023 -- -- 0.444 1.416 0.477 0.040 0.053

77 –0.298 –0.457 –0.053 0.020 -- 0.568 0.174 0.115 0.019 0.037

78 –0.408 –0.495 –0.021 -- -- 0.837 0.223 0.056 -- 0.069

79 –0.370 –0.375 –0.017 -- -- 0.552 0.101 0.083 0.016 0.033

80 –0.263 –0.622 0.042 -- -- 0.509 0.440 0.174 0.017 0.025

81 0.023 –0.400 –0.074 0.036 -- 0.501 0.223 0.125 0.015 0.094

82 –0.228 –0.297 –0.029 0.016 -- 0.448 0.422 0.170 0.017 0.090

83 –0.057 –0.419 0.036 –0.004 -- 0.455 0.156 0.096 0.013 0.052

84 –0.006 –0.057 0.012 –0.007 -- 0.632 0.559 0.285 0.035 0.032

85 -- -- –0.092 -- -- 0.629 0.088 0.075 0.014 --

86 –0.318 –0.208 –0.012 -- -- 0.929 0.054 0.056 0.018 0.051

87 –0.214 –0.250 0.046 -- -- 0.533 0.287 0.119 0.011 0.089

88 –0.279 –0.194 0.014 -- -- 0.484 0.231 0.045 -- 0.118

89 –0.251 –0.354 0.048 -- -- 0.589 0.607 0.239 0.022 0.134

90 –0.151 0.045 0.036 –0.001 -- 0.326 1.371 0.543 0.053 0.047

91 –0.149 0.014 0.047 –0.002 -- 0.287 1.816 0.561 0.043 0.047

92 –0.129 –0.110 –0.020 0.012 -- 0.592 0.135 0.077 0.016 0.074

93 –0.105 0.140 0.073 –0.005 -- 0.351 5.900 1.190 0.060 0.056

94 -- -- 0.002 -- -- 0.331 1.762 0.520 0.038 --

95 -- -- 0.065 -- -- 0.397 0.750 0.060 -- --

97 0.176 –0.492 –0.018 -- -- 0.539 0.251 0.069 0.015 0.230

99 0.432 –0.547 0.043 -- -- 0.906 1.425 0.156 -- 0.142

101 –0.027 –0.189 0.030 -- -- 0.376 24.862 7.361 0.545 0.101

106 0.112 –0.893 –0.123 -- 1.106 0.868 0.589 0.107 0.029 0.147

107 0.224 0.296 0.023 -- -- 0.288 0.177 0.027 -- 0.036

109 -- -- 0.131 -- -- 0.609 0.395 0.171 0.019 --

110 –0.070 –0.361 0.098 -- -- 0.518 0.606 0.067 -- 0.068

111 0.155 –0.291 0.066 -- -- 0.639 0.318 0.052 -- 0.095

112 0.380 –0.164 0.048 -- -- 0.578 1.634 0.151 -- 0.075

113 –0.043 –0.390 0.100 -- -- 0.580 1.057 0.277 0.018 0.092

114 0.194 –0.457 0.029 -- -- 0.678 0.337 0.052 -- 0.106

115 –0.441 –0.560 0.008 -- -- 0.428 0.406 0.176 0.018 0.099

118 -- -- 0.112 -- -- 0.608 1.194 0.103 -- --

120 –0.172 –0.155 0.038 -- -- 0.320 0.374 0.205 0.027 0.060

134 –0.118 –0.082 0.111 –0.000 -- 0.505 1.782 0.538 0.040 0.107

135 –0.321 –0.099 0.071 -- -- 0.529 1.425 0.411 0.029 0.085

136 –0.132 –0.030 0.074 -- -- 0.491 0.836 0.532 0.076 0.117

137 –0.119 –0.155 0.069 -- -- 0.286 0.414 0.156 0.014 0.051

138 –0.274 –0.169 0.079 -- -- 0.340 0.815 0.226 0.015 0.051

139 –0.379 –0.311 0.047 -- -- 0.445 0.962 0.293 0.022 0.092

145 -- -- –0.009 -- -- 0.537 0.191 0.094 0.010 --

148 –0.093 –0.229 0.015 -- -- 0.360 0.124 0.069 0.010 0.076
Appendix 3 171

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Sine

coefficient

Cosine

coefficient

Time

coefficient

Time

squared

coefficient

Step

trend

coefficient

Root mean

square

error

Standard

error of

intercept

Standard

error of log

streamflow

coefficient

Standard

error of log

streamflow

squared

coefficient

Standard

error of sine

coefficient

Total phosphorus—Continued

149 –0.214 0.053 0.048 0.010 -- 0.288 0.829 0.174 0.009 0.052

150 –0.262 –0.397 0.081 -- -- 0.555 0.392 0.053 -- 0.092

151 –0.066 0.125 –0.026 -- -- 0.406 4.393 0.876 0.043 0.068

152 -- -- –0.029 -- -- 0.525 0.771 0.092 -- --

153 -- -- 0.037 -- -- 0.366 17.291 2.649 0.101 --

154 –0.029 –0.138 0.014 -- -- 0.502 0.469 0.070 -- 0.066

155 -- -- 0.042 -- -- 0.458 0.285 0.053 -- --

156 -- -- 0.050 -- -- 0.304 12.288 2.015 0.083 --

157 0.152 0.028 0.001 -- -- 0.337 0.499 0.158 0.013 0.048

165 0.269 0.314 –0.000 -- -- 0.691 0.213 0.065 -- 0.135

166 -- -- –0.110 -- -- 1.165 2.161 0.800 0.072 --

169 -- -- –0.266 -- -- 1.570 0.400 0.265 0.047 --

170 -- -- –0.006 -- -- 0.584 0.612 0.085 -- --

171 -- -- –0.029 -- -- 0.591 0.542 0.074 -- --

173 0.054 –0.326 0.039 -- -- 0.331 0.475 0.190 0.018 0.059

177 0.348 –0.281 0.038 -- -- 0.699 9.119 2.498 0.170 0.156

178 0.703 –0.613 –0.040 -- -- 0.966 1.492 0.184 -- 0.198

180 -- -- 0.116 -- -- 1.031 1.513 1.205 0.232 --

182 –0.269 0.449 0.159 -- -- 0.775 0.994 0.191 -- 0.170

183 –0.858 –0.825 0.105 -- -- 0.909 2.503 0.827 0.066 0.175

184 –1.291 –1.044 0.359 -- -- 1.429 3.509 0.968 0.065 0.319

185 –0.204 –0.758 0.091 -- -- 0.773 0.766 0.126 -- 0.180

186 –0.116 –0.535 –0.201 0.046 -- 1.006 17.076 4.134 0.249 0.231

188 0.269 –0.063 –0.063 –0.003 -- 0.478 1.465 0.457 0.035 0.088

193 0.173 –0.008 –0.009 0.011 -- 0.503 1.360 0.674 0.081 0.081

203 –0.072 0.106 0.036 –0.012 -- 0.515 6.883 1.662 0.100 0.094

204 –0.121 0.128 0.005 -- -- 0.638 20.392 4.173 0.213 0.149

205 0.029 0.244 0.030 –0.017 -- 0.518 7.725 1.722 0.095 0.144

206 –0.044 0.058 0.023 –0.013 -- 0.363 2.415 0.702 0.050 0.081

207 0.010 0.023 0.126 –0.019 -- 0.511 2.770 0.844 0.063 0.146

208 –0.008 0.158 –0.007 -- -- 0.186 3.994 0.762 0.036 0.053

209 –0.011 0.184 –0.021 0.005 -- 0.289 4.767 0.984 0.051 0.046

210 –0.057 0.098 –0.002 -- -- 0.327 5.686 1.205 0.064 0.046

211 -- -- –0.014 -- -- 0.210 3.824 0.922 0.055 --

212 -- -- –0.009 -- -- 0.405 42.172 9.625 0.549 --

213 –0.058 0.142 –0.022 0.006 -- 0.266 4.297 0.846 0.041 0.045

214 0.004 0.176 –0.026 0.004 -- 0.188 2.273 0.426 0.020 0.034

215 0.075 0.176 –0.023 -- -- 0.258 32.098 5.278 0.217 0.060

216 –0.557 –0.300 0.054 -- -- 0.635 6.793 1.712 0.108 0.118

217 –0.116 0.219 –0.025 0.007 -- 0.238 0.524 0.189 0.016 0.048

218 –0.222 –0.055 –0.008 -- -- 0.205 0.581 0.297 0.037 0.053

219 -- -- –0.020 -- -- 0.363 1.107 0.340 0.025 --

220 –0.152 0.036 –0.042 -- -- 0.382 0.248 0.106 0.013 0.084

221 –0.166 0.218 0.067 –0.011 -- 0.525 2.301 0.733 0.057 0.154

222 0.209 0.340 –0.043 -- -- 0.598 5.534 1.300 0.077 0.278

223 0.076 0.027 –0.013 -- -- 0.329 14.784 3.145 0.167 0.042

224 -- -- 0.029 -- -- 0.469 1.857 0.570 0.043 --

225 –0.275 0.093 –0.073 -- -- 0.657 0.530 0.169 0.014 0.126

227 –0.054 0.191 0.006 0.009 -- 0.330 4.601 0.874 0.041 0.056

228 0.026 0.266 0.013 -- -- 0.493 37.241 5.962 0.238 0.096

229 –0.135 0.009 0.069 –0.006 -- 0.487 3.506 0.994 0.069 0.152

230 0.193 0.011 –0.004 -- -- 0.388 1.727 0.601 0.051 0.073

231 0.088 0.329 –0.038 0.005 -- 0.343 0.625 0.180 0.013 0.038
172 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Sine

coefficient

Cosine

coefficient

Time

coefficient

Time

squared

coefficient

Step

trend

coefficient

Root mean

square

error

Standard

error of

intercept

Standard

error of log

streamflow

coefficient

Standard

error of log

streamflow

squared

coefficient

Standard

error of sine

coefficient

Total phosphorus—Continued

232 0.241 0.209 –0.044 –0.011 -- 0.482 1.033 0.361 0.031 0.046

233 –0.118 –0.010 0.003 -- -- 0.297 2.639 0.652 0.040 0.043

234 0.075 0.276 0.058 –0.040 -- 0.592 6.363 1.649 0.106 0.169

235 0.028 0.251 0.025 –0.029 -- 0.669 6.171 1.583 0.101 0.210

236 –0.003 0.126 0.080 –0.035 -- 0.586 4.546 1.222 0.081 0.159

237 0.157 0.094 0.018 –0.010 -- 0.462 5.453 1.341 0.082 0.131

238 0.246 0.762 0.038 –0.017 -- 0.583 5.577 1.321 0.078 0.129

239 -- -- –0.037 -- -- 0.737 3.302 0.289 -- --

241 –0.079 –0.517 0.014 -- -- 0.738 0.117 0.035 -- 0.067

242 –0.025 –0.587 –0.005 -- -- 0.576 0.385 0.062 -- 0.074

243 0.078 0.121 –0.008 0.010 -- 0.422 2.104 0.497 0.029 0.041

244 0.067 0.309 0.043 -- -- 0.466 0.748 0.074 -- 0.057

Total nitrogen

1 -- -- 0.006 -- -- 0.306 0.784 0.267 0.022 --

2 -- -- 0.027 -- -- 0.245 0.098 0.021 -- --

3 -- -- –0.004 -- -- 0.231 0.144 0.022 -- --

4 0.086 0.169 0.002 -- -- 0.322 0.378 0.040 -- 0.044

5 –0.025 0.114 –0.002 -- -- 0.126 0.237 0.142 0.021 0.024

6 -- -- 0.030 -- -- 0.397 0.447 0.072 -- --

7 –0.057 0.052 0.005 0.006 -- 0.221 1.709 0.504 0.037 0.039

8 0.022 0.154 –0.004 -- -- 0.226 0.175 0.037 -- 0.037

9 –0.157 –0.198 0.010 0.010 -- 0.355 0.611 0.296 0.036 0.103

10 –0.055 0.046 –0.004 -- -- 0.157 0.137 0.027 -- 0.029

11 –0.081 0.138 0.011 -- -- 0.258 0.246 0.033 -- 0.063

12 –0.009 0.010 –0.064 –0.010 -- 0.252 1.105 0.377 0.032 0.051

13 -- -- 0.031 -- -- 0.393 0.114 0.038 -- --

14 0.000 –0.087 0.020 -- -- 0.379 0.178 0.113 0.018 0.050

15 0.010 0.114 –0.010 -- -- 0.196 0.963 0.225 0.013 0.030

16 -- -- 0.009 -- -- 0.209 0.524 0.256 0.030 --

17 –0.036 0.193 0.019 -- -- 0.354 0.094 0.069 0.012 0.085

18 -- -- 0.000 -- -- 0.194 0.378 0.168 0.018 --

19 –0.059 0.046 –0.020 -- -- 0.209 0.517 0.180 0.015 0.038

20 -- -- 0.022 -- -- 0.224 0.800 0.390 0.047 --

21 -- -- –0.000 -- -- 0.224 0.111 0.038 -- --

22 0.140 –0.036 –0.000 -- -- 0.231 0.295 0.169 0.023 0.053

23 -- -- –0.013 -- -- 0.228 0.082 0.029 -- --

24 -- -- –0.015 -- -- 0.401 0.116 0.081 0.013 --

25 -- -- 0.007 -- -- 0.232 0.201 0.037 -- --

26 –0.043 0.055 0.010 -- -- 0.167 0.549 0.160 0.011 0.026

29 -- -- –0.010 -- -- 0.308 2.835 1.168 0.119 --

31 0.101 0.083 –0.024 -- -- 0.268 5.110 1.186 0.068 0.055

32 0.019 0.110 0.007 -- -- 0.239 0.633 0.256 0.025 0.053

33 -- -- –0.019 -- -- 0.237 2.568 0.551 0.029 --

34 0.028 –0.206 0.005 -- -- 0.245 0.284 0.165 0.022 0.041

35 0.235 0.064 0.006 -- -- 0.227 0.372 0.188 0.023 0.044

36 0.047 0.042 0.019 -- -- 0.198 0.054 0.011 -- 0.023

37 –0.002 0.144 –0.008 -- -- 0.224 0.166 0.016 -- 0.024

38 0.063 0.090 –0.001 0.003 -- 0.188 0.389 0.123 0.010 0.017

39 –0.176 0.005 –0.006 0.008 -- 0.190 0.313 0.095 0.007 0.019

40 –0.106 0.101 –0.015 0.005 -- 0.266 0.770 0.167 0.009 0.038

41 -- -- 0.034 -- -- 0.431 0.439 0.121 0.008 --

42 –0.164 –0.107 0.024 0.003 -- 0.270 0.281 0.083 0.006 0.022

43 –0.076 –0.190 0.009 0.009 -- 0.226 0.100 0.035 0.003 0.020
Appendix 3 173

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Sine

coefficient

Cosine

coefficient

Time

coefficient

Time

squared

coefficient

Step

trend

coefficient

Root mean

square

error

Standard

error of

intercept

Standard

error of log

streamflow

coefficient

Standard

error of log

streamflow

squared

coefficient

Standard

error of sine

coefficient

Total nitrogen—Continued

44 –0.216 –0.099 0.016 0.003 -- 0.341 0.982 0.217 0.012 0.029

45 –0.084 –0.007 0.009 0.007 -- 0.248 0.245 0.072 0.005 0.021

46 –0.061 –0.108 0.012 0.008 -- 0.245 0.107 0.058 0.007 0.046

47 –0.047 –0.002 –0.039 –0.004 -- 0.234 1.061 0.273 0.017 0.032

48 0.027 –0.039 –0.008 –0.004 -- 0.153 0.276 0.088 0.007 0.020

49 –0.043 0.175 –0.001 0.009 -- 0.419 2.398 0.615 0.039 0.077

52 0.055 0.188 –0.008 0.005 -- 0.371 5.797 1.632 0.115 0.072

53 0.050 0.064 –0.019 0.004 -- 0.267 1.613 0.365 0.020 0.042

57 –0.012 0.047 0.031 –0.004 -- 0.184 0.134 0.079 0.011 0.041

58 –0.044 –0.067 –0.014 0.007 -- 0.260 0.275 0.138 0.017 0.057

59 –0.068 –0.012 –0.004 0.003 -- 0.177 0.247 0.078 0.006 0.027

60 –0.103 0.026 0.020 –0.003 -- 0.294 0.159 0.084 0.011 0.044

61 –0.062 –0.051 0.002 0.001 -- 0.259 0.170 0.098 0.013 0.050

62 –0.084 –0.075 –0.017 –0.000 -- 0.279 0.106 0.052 0.007 0.057

65 –0.008 0.063 0.026 0.004 -- 0.283 0.243 0.090 0.008 0.040

67 –0.013 –0.050 0.016 –0.007 -- 0.330 3.515 0.844 0.050 0.047

71 -- -- 0.014 -- -- 0.776 6.958 1.851 0.122 --

72 0.009 –0.118 –0.003 -- -- 0.367 0.054 0.021 -- 0.046

73 0.213 –0.009 0.017 -- -- 0.270 0.524 0.042 -- 0.046

74 0.111 –0.001 0.029 –0.008 -- 0.317 0.990 0.422 0.044 0.045

76 0.172 0.279 0.026 -- -- 0.245 0.164 0.028 -- 0.031

81 0.173 0.168 –0.032 0.014 -- 0.407 0.177 0.096 0.012 0.070

82 0.122 0.232 0.001 -- -- 0.398 0.148 0.031 -- 0.073

92 0.157 0.196 –0.036 -- -- 0.417 0.061 0.028 -- 0.055

95 0.193 –0.028 0.012 -- -- 0.260 9.883 1.580 0.063 0.039

97 –0.034 –0.518 0.007 -- -- 0.273 0.095 0.029 0.006 0.087

99 0.273 0.270 0.038 -- -- 0.473 0.702 0.077 -- 0.074

100 -- -- 0.031 -- -- 0.566 1.779 0.180 -- --

101 0.065 0.302 0.047 -- -- 0.445 2.159 0.325 -- 0.115

102 0.173 –0.002 0.005 -- -- 0.351 0.075 0.021 -- 0.057

103 -- -- –0.070 -- 0.149 0.277 0.462 0.295 0.045 --

106 0.033 0.240 –0.133 -- 0.836 0.315 0.217 0.030 -- 0.053

107 0.042 0.330 0.007 -- -- 0.140 0.350 0.102 0.007 0.018

108 0.109 0.089 –0.005 -- -- 0.188 96.966 36.073 3.354 0.035

109 0.008 0.274 0.028 -- -- 0.377 0.152 0.033 -- 0.054

110 -- -- 0.043 -- -- 0.415 0.434 0.048 -- --

111 0.222 0.096 –0.004 -- -- 0.534 0.928 0.286 0.021 0.082

112 0.376 –0.148 –0.053 -- -- 0.382 12.536 2.285 0.104 0.047

113 0.140 –0.045 0.018 -- -- 0.577 0.300 0.041 -- 0.080

114 0.198 –0.296 –0.017 -- -- 0.556 0.293 0.046 -- 0.079

115 -- -- 0.028 -- -- 0.576 0.408 0.200 0.022 --

116 0.168 –0.027 –0.007 -- -- 0.325 0.274 0.031 -- 0.058

118 0.279 –0.078 0.019 -- -- 0.323 0.711 0.062 -- 0.042

120 0.021 0.161 0.062 -- -- 0.374 0.147 0.044 -- 0.060

124 –0.119 0.104 0.006 -- -- 0.261 0.291 0.050 -- 0.052

125 0.067 0.081 –0.022 -- -- 0.315 0.483 0.062 -- 0.056

134 –0.016 0.219 0.029 -- -- 0.255 0.856 0.263 0.020 0.050

135 0.103 0.205 0.005 -- -- 0.311 0.877 0.254 0.018 0.051

136 -- -- 0.016 -- -- 0.307 0.137 0.050 -- --

137 0.051 0.245 0.048 –0.007 -- 0.156 0.226 0.086 0.008 0.028

138 0.075 0.237 0.017 -- -- 0.253 0.685 0.189 0.013 0.039

139 0.007 0.227 0.036 –0.011 -- 0.380 0.562 0.183 0.014 0.064

145 –0.159 –0.102 0.019 –0.011 -- 0.350 0.168 0.069 0.007 0.074
174 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Sine

coefficient

Cosine

coefficient

Time

coefficient

Time

squared

coefficient

Step

trend

coefficient

Root mean

square

error

Standard

error of

intercept

Standard

error of log

streamflow

coefficient

Standard

error of log

streamflow

squared

coefficient

Standard

error of sine

coefficient

Total nitrogen—Continued

146 –0.195 –0.186 –0.005 -- -- 0.496 0.117 0.049 0.006 0.107

147 –0.279 –0.197 0.005 -- -- 0.412 0.107 0.036 0.005 0.095

148 –0.123 –0.172 0.008 -- -- 0.284 0.077 0.022 -- 0.056

149 0.111 0.093 0.008 -- -- 0.241 0.690 0.144 0.008 0.043

150 –0.135 –0.190 0.055 –0.011 -- 0.326 0.941 0.258 0.017 0.055

151 0.002 0.075 0.007 -- -- 0.226 2.388 0.478 0.024 0.034

152 0.218 –0.087 0.039 -- -- 0.401 0.572 0.069 -- 0.084

153 0.133 –0.124 –0.005 -- -- 0.240 11.571 1.770 0.068 0.045

154 -- -- –0.010 -- -- 0.382 2.197 0.611 0.042 --

155 -- -- –0.003 -- -- 0.363 1.220 0.427 0.036 --

156 0.043 –0.219 –0.005 -- -- 0.217 9.037 1.479 0.060 0.042

157 0.133 –0.199 –0.017 -- -- 0.303 0.204 0.030 -- 0.043

173 0.144 –0.094 0.012 -- -- 0.302 0.159 0.029 -- 0.054

176 -- -- 0.023 -- -- 0.471 0.590 0.082 -- --

179 -- -- 0.005 -- -- 0.325 1.046 0.109 -- --

182 –0.346 0.263 0.099 -- -- 0.481 2.801 1.052 0.098 0.099

196 0.131 0.337 –0.004 0.018 -- 0.459 0.183 0.082 0.009 0.060

199 0.175 0.222 –0.019 0.030 -- 0.569 0.165 0.159 0.039 0.067

201 0.122 0.026 –0.035 0.027 -- 0.494 0.058 0.042 0.016 0.058

202 0.045 –0.003 –0.050 0.024 -- 0.451 0.177 0.159 0.037 0.057

208 0.206 0.271 –0.028 0.012 -- 0.344 7.369 1.405 0.067 0.098

209 0.274 0.461 –0.069 0.012 -- 0.387 6.656 1.370 0.070 0.063

210 0.125 0.252 –0.067 0.010 -- 0.364 7.339 1.548 0.081 0.060

212 -- -- –0.026 -- -- 0.281 30.119 6.874 0.392 --

213 0.305 0.305 –0.074 0.015 -- 0.329 6.108 1.195 0.058 0.064

214 0.233 0.300 –0.051 0.013 -- 0.341 4.141 0.775 0.036 0.062

215 0.481 0.240 –0.031 -- -- 0.416 2.364 0.197 -- 0.100

217 0.224 0.285 –0.058 0.007 -- 0.286 0.632 0.228 0.020 0.058

218 –0.081 0.080 –0.031 –0.005 -- 0.102 0.346 0.167 0.020 0.029

219 -- -- –0.042 -- -- 0.408 1.328 0.416 0.031 --

220 –0.158 0.016 –0.041 –0.008 -- 0.341 0.227 0.095 0.011 0.076

221 –0.084 0.380 0.019 –0.008 -- 0.327 1.299 0.412 0.032 0.078

222 -- -- 0.012 -- -- 0.354 2.005 0.514 0.032 --

223 –0.071 0.197 –0.005 -- -- 0.158 0.332 0.036 -- 0.020

224 0.091 0.068 0.011 0.014 -- 0.252 1.475 0.425 0.030 0.045

225 0.056 0.370 0.009 –0.011 -- 0.356 0.304 0.092 0.007 0.072

227 0.176 0.312 –0.009 0.012 -- 0.298 4.003 0.760 0.036 0.050

228 0.305 0.478 –0.011 0.007 -- 0.240 15.470 2.486 0.100 0.047

231 –0.018 0.206 0.001 0.009 -- 0.198 0.372 0.107 0.008 0.022

232 0.364 0.286 –0.038 -- -- 0.418 0.178 0.032 -- 0.034

241 –0.031 –0.557 0.002 -- -- 0.596 0.128 0.079 0.012 0.055

242 0.069 0.054 0.092 –0.019 -- 0.313 1.534 0.477 0.036 0.045

243 0.088 0.149 0.002 -- -- 0.289 1.695 0.403 0.024 0.030

244 0.154 0.417 0.037 -- -- 0.400 0.609 0.061 -- 0.047

Nitrate

1 0.188 0.205 –0.023 0.009 -- 0.337 0.906 0.303 0.025 0.060

2 -- -- 0.009 -- -- 0.282 0.501 0.212 0.022 --

3 0.196 0.270 –0.020 -- -- 0.509 1.683 0.525 0.041 0.109

4 0.229 0.233 0.005 -- -- 0.331 2.896 0.606 0.032 0.050

5 0.035 0.123 –0.001 -- -- 0.138 0.260 0.155 0.022 0.027

6 0.196 0.284 –0.032 -- -- 0.292 0.407 0.066 -- 0.064

7 –0.006 0.081 0.002 -- -- 0.175 1.357 0.400 0.029 0.031

8 0.062 0.149 –0.003 -- -- 0.310 0.241 0.051 -- 0.051

9 0.482 0.176 –0.041 0.023 -- 0.570 0.994 0.478 0.057 0.162
Appendix 3 175

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Sine

coefficient

Cosine

coefficient

Time

coefficient

Time

squared

coefficient

Step

trend

coefficient

Root mean

square

error

Standard

error of

intercept

Standard

error of log

streamflow

coefficient

Standard

error of log

streamflow

squared

coefficient

Standard

error of sine

coefficient

Nitrate—Continued

10 –0.090 0.033 –0.015 -- -- 0.166 0.144 0.028 -- 0.030

11 0.169 0.307 0.011 -- -- 0.329 0.313 0.042 -- 0.081

12 –0.091 0.018 –0.016 –0.006 -- 0.268 1.178 0.402 0.034 0.053

13 0.608 0.122 –0.005 -- -- 0.750 0.334 0.112 -- 0.176

14 -- -- –0.001 -- -- 0.627 0.286 0.196 0.030 --

15 0.085 0.195 –0.012 -- -- 0.267 1.314 0.308 0.018 0.041

16 0.398 0.318 –0.028 -- -- 0.383 1.044 0.501 0.058 0.089

17 0.449 0.565 0.018 -- -- 0.583 0.165 0.122 0.020 0.140

18 –0.127 0.107 0.000 -- -- 0.235 0.166 0.035 -- 0.058

19 –0.019 0.152 –0.030 -- -- 0.258 0.633 0.221 0.019 0.046

20 -- -- 0.025 -- -- 0.214 0.765 0.374 0.045 --

21 -- -- 0.002 -- -- 0.292 0.462 0.296 0.044 --

22 0.286 –0.030 0.009 -- -- 0.365 0.187 0.055 -- 0.080

23 -- -- –0.021 -- -- 0.247 0.089 0.031 -- --

24 -- -- –0.017 -- -- 0.687 0.231 0.173 0.029 --

25 0.018 0.182 –0.002 -- -- 0.219 0.219 0.041 -- 0.053

26 –0.045 0.103 0.008 -- -- 0.198 0.651 0.190 0.014 0.031

29 0.411 0.667 –0.088 -- -- 0.493 0.669 0.145 -- 0.116

31 0.326 0.247 –0.053 -- -- 0.398 7.827 1.816 0.105 0.093

32 0.158 0.269 –0.003 0.016 -- 0.483 1.442 0.577 0.057 0.117

33 0.007 0.112 –0.025 -- -- 0.246 0.304 0.033 -- 0.040

34 0.089 –0.118 –0.029 -- -- 0.411 0.163 0.054 -- 0.065

35 0.260 0.067 –0.031 -- -- 0.416 0.222 0.065 -- 0.073

36 0.082 0.134 0.005 0.004 -- 0.270 0.190 0.075 0.007 0.032

37 0.046 0.248 –0.023 -- -- 0.264 1.164 0.218 0.010 0.029

38 0.143 0.100 –0.010 -- -- 0.207 0.407 0.129 0.010 0.018

39 –0.144 0.047 –0.017 0.010 -- 0.186 0.306 0.093 0.007 0.018

40 –0.128 0.243 –0.038 -- -- 0.416 1.222 0.268 0.014 0.055

41 0.173 0.154 0.020 -- -- 0.888 1.606 0.425 0.028 0.081

42 –0.008 –0.093 0.001 -- -- 0.404 0.400 0.119 0.009 0.031

43 0.284 –0.033 0.006 0.013 -- 0.510 0.229 0.078 0.007 0.044

44 –0.097 0.082 –0.022 0.006 -- 0.675 2.284 0.502 0.027 0.054

45 0.014 0.299 –0.019 -- -- 0.634 0.619 0.184 0.013 0.056

50 0.248 –0.154 –0.022 –0.010 -- 0.532 2.906 0.759 0.049 0.075

65 0.030 0.157 0.025 0.003 -- 0.431 0.354 0.131 0.011 0.062

66 0.122 –0.070 –0.006 –0.000 -- 0.343 0.211 0.111 0.013 0.044

71 -- -- 0.080 -- -- 0.815 7.009 1.877 0.125 --

72 0.124 0.016 –0.042 -- -- 0.463 0.078 0.060 0.012 0.057

73 0.353 –0.030 –0.008 -- -- 0.397 0.747 0.060 -- 0.067

74 0.888 1.188 0.011 -- -- 0.653 0.444 0.097 -- 0.114

76 0.088 1.028 0.063 -- -- 0.804 2.640 0.893 0.075 0.104

81 0.536 1.058 –0.015 -- -- 1.101 0.325 0.069 -- 0.188

82 0.520 1.154 –0.091 -- -- 1.497 0.606 0.126 -- 0.321

88 –0.023 0.740 0.030 -- -- 1.218 0.557 0.110 -- 0.257

92 0.417 0.355 –0.068 -- -- 0.596 0.087 0.041 -- 0.082

95 0.197 –0.033 0.001 -- -- 0.356 13.248 2.119 0.085 0.049

96 0.082 0.610 –0.063 -- -- 0.530 1.812 0.828 0.093 0.091

98 0.001 –0.465 –0.061 -- -- 0.401 4.986 1.342 0.090 0.086

99 0.651 1.817 –0.010 -- -- 1.045 13.320 2.860 0.153 0.146

100 -- -- –0.121 -- -- 0.560 36.418 7.364 0.372 --

101 0.036 0.915 0.038 -- -- 0.542 2.548 0.382 -- 0.136

102 0.456 1.081 –0.126 -- -- 1.389 0.348 0.087 -- 0.244
176 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Sine

coefficient

Cosine

coefficient

Time

coefficient

Time

squared

coefficient

Step

trend

coefficient

Root mean

square

error

Standard

error of

intercept

Standard

error of log

streamflow

coefficient

Standard

error of log

streamflow

squared

coefficient

Standard

error of sine

coefficient

Nitrate—Continued

103 –0.062 –0.042 –0.123 -- 0.654 0.252 0.184 0.040 -- 0.039

104 -- -- –0.122 -- -- 0.801 0.173 0.046 -- --

105 0.050 0.598 –0.013 -- -- 0.753 0.140 0.042 -- 0.084

106 –0.126 0.352 –0.133 -- 0.562 0.327 0.226 0.040 0.011 0.055

107 0.010 0.337 0.003 -- -- 0.145 0.360 0.105 0.008 0.018

108 0.077 0.227 0.007 -- -- 0.185 95.333 35.465 3.298 0.034

109 0.004 0.375 –0.034 -- -- 0.567 0.391 0.162 0.017 0.079

110 0.321 0.813 0.009 -- -- 1.075 8.829 1.900 0.102 0.142

111 0.347 0.987 0.039 -- -- 1.386 2.587 0.783 0.057 0.207

112 0.672 0.088 –0.091 -- -- 0.795 2.328 0.215 -- 0.092

113 0.550 1.086 0.038 -- -- 1.207 2.182 0.588 0.039 0.177

114 0.348 0.325 0.055 -- -- 1.130 1.610 0.510 0.040 0.170

115 –0.632 0.084 0.075 -- -- 1.175 1.158 0.522 0.054 0.246

116 0.299 0.253 –0.084 -- -- 0.788 0.711 0.080 -- 0.144

117 –0.006 0.327 –0.001 -- -- 0.624 2.644 0.691 0.044 0.095

118 0.427 0.054 –0.033 -- -- 0.606 1.289 0.112 -- 0.074

119 0.401 –0.288 –0.063 0.011 -- 0.647 0.775 0.323 0.032 0.117

120 0.045 0.161 0.071 -- -- 0.567 0.236 0.070 -- 0.102

121 –0.484 0.424 0.051 –0.007 -- 0.700 1.027 0.299 0.021 0.144

122 –0.365 –0.066 0.023 -- -- 0.404 0.490 0.055 -- 0.074

123 -- -- –0.002 -- -- 0.440 0.119 0.036 -- --

124 –0.062 0.133 0.022 –0.005 -- 0.262 1.660 0.525 0.041 0.053

125 0.142 0.139 –0.013 -- -- 0.283 2.892 0.698 0.042 0.043

126 0.611 –0.839 –0.033 -- -- 0.530 0.953 0.346 0.030 0.111

127 0.588 –0.328 0.092 -- -- 0.599 0.326 0.069 -- 0.143

128 0.085 0.176 –0.005 -- -- 0.287 0.109 0.040 -- 0.040

129 0.326 0.963 0.136 –0.030 -- 1.014 0.616 0.479 0.092 0.161

130 –0.041 0.200 0.011 –0.009 -- 0.220 0.339 0.152 0.017 0.030

131 –0.065 0.130 0.040 –0.014 -- 0.221 1.268 0.494 0.048 0.032

132 0.148 0.285 –0.062 -- -- 0.247 1.738 0.727 0.075 0.048

133 0.128 0.309 –0.073 –0.004 -- 0.155 0.364 0.145 0.015 0.021

134 –0.050 0.242 0.035 -- -- 0.270 0.875 0.268 0.020 0.049

135 0.132 0.294 –0.018 -- -- 0.465 1.371 0.396 0.028 0.076

136 -- -- 0.016 -- -- 0.328 0.146 0.054 -- --

137 0.057 0.309 0.045 –0.005 -- 0.157 0.228 0.086 0.008 0.028

138 0.088 0.307 0.002 -- -- 0.302 0.817 0.225 0.015 0.047

139 0.042 0.350 0.032 –0.009 -- 0.401 0.593 0.193 0.015 0.067

140 0.254 0.237 0.143 0.044 -- 1.210 0.640 0.266 0.033 0.243

141 0.247 1.104 –0.037 -- -- 1.287 0.577 0.109 -- 0.179

142 –0.121 0.919 –0.058 -- -- 1.025 0.497 0.219 0.024 0.134

143 –0.022 0.663 –0.038 0.015 -- 0.816 1.387 0.476 0.041 0.112

144 –0.040 0.337 –0.000 -- -- 0.598 1.949 0.627 0.050 0.081

145 -- -- 0.035 -- -- 0.836 0.197 0.040 -- --

146 –0.168 0.228 0.078 –0.009 -- 0.581 0.412 0.177 0.017 0.143

147 –0.010 0.509 0.077 –0.021 -- 0.674 0.336 0.145 0.018 0.169

148 –0.051 –0.169 0.014 –0.016 -- 0.597 0.436 0.216 0.026 0.136

149 0.719 0.420 –0.066 -- -- 0.809 0.876 0.086 -- 0.148

150 –0.490 0.373 0.015 -- -- 1.043 3.510 0.956 0.064 0.186

151 0.296 0.399 –0.052 -- -- 0.724 8.545 1.689 0.083 0.113

152 0.257 0.126 0.003 -- -- 0.524 5.801 1.415 0.086 0.104

153 0.120 –0.171 –0.015 -- -- 0.301 14.377 2.199 0.084 0.056

154 -- -- –0.013 -- -- 0.350 2.101 0.591 0.041 --
Appendix 3 177

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Sine

coefficient

Cosine

coefficient

Time

coefficient

Time

squared

coefficient

Step

trend

coefficient

Root mean

square

error

Standard

error of

intercept

Standard

error of log

streamflow

coefficient

Standard

error of log

streamflow

squared

coefficient

Standard

error of sine

coefficient

Nitrate—Continued

155 0.017 –0.102 –0.014 -- -- 0.317 1.085 0.376 0.032 0.046

156 –0.008 –0.367 –0.016 -- -- 0.352 14.447 2.366 0.097 0.064

157 –0.061 –0.485 0.026 –0.007 -- 0.644 0.918 0.292 0.024 0.094

158 0.353 0.473 –0.037 -- -- 0.516 4.127 0.982 0.058 0.083

159 –0.475 0.326 –0.009 -- -- 0.619 2.259 0.775 0.065 0.139

160 -- -- 0.008 -- -- 0.580 2.543 0.769 0.056 --

161 –0.421 0.143 0.048 -- -- 0.856 0.205 0.070 0.010 0.150

162 0.626 0.373 –0.017 -- -- 1.063 0.257 0.055 -- 0.182

163 –0.379 0.197 0.014 –0.026 -- 0.627 5.349 1.277 0.074 0.139

164 0.287 1.009 –0.255 -- -- 1.158 0.508 0.297 0.039 0.245

167 –0.401 0.078 0.005 -- -- 0.837 0.164 0.041 -- 0.139

168 –0.348 0.164 0.041 -- -- 0.531 0.114 0.030 -- 0.087

172 -- -- 0.012 -- -- 0.427 0.306 0.051 -- --

174 0.207 0.346 –0.003 0.007 -- 0.442 6.654 1.886 0.133 0.082

175 –0.271 –0.052 –0.013 0.008 -- 0.246 3.128 0.700 0.039 0.034

177 0.292 0.270 –0.010 -- -- 0.422 0.816 0.117 -- 0.080

181 –0.207 0.114 0.024 -- -- 0.432 0.266 0.056 -- 0.067

187 0.186 0.413 –0.046 -- -- 0.390 0.503 0.088 -- 0.076

189 –0.270 –0.157 –0.018 -- -- 0.573 0.552 0.273 0.033 0.090

190 0.194 0.456 0.063 -- -- 0.690 0.441 0.093 -- 0.096

191 0.835 0.804 0.122 0.015 -- 0.847 1.983 0.708 0.062 0.154

192 –0.296 0.153 –0.073 -- -- 0.558 0.342 0.066 -- 0.071

194 0.272 0.107 0.002 -- -- 0.695 0.137 0.043 -- 0.091

195 0.237 0.412 –0.025 0.006 -- 0.484 0.270 0.131 0.015 0.069

197 0.582 0.312 –0.105 -- -- 0.761 0.111 0.052 -- 0.072

198 0.983 0.190 0.012 –0.005 -- 0.611 0.131 0.138 0.039 0.069

199 0.759 0.085 0.002 -- -- 0.470 0.074 0.040 -- 0.052

200 0.704 0.166 –0.001 -- -- 0.503 0.174 0.156 0.032 0.050

201 0.598 0.434 0.058 –0.019 -- 0.647 0.446 0.218 0.084 0.331

205 0.108 0.744 –0.007 -- -- 0.285 2.803 0.631 0.035 0.044

207 0.067 0.890 –0.004 -- -- 0.489 1.758 0.552 0.043 0.080

208 0.274 0.443 –0.031 0.013 -- 0.384 8.225 1.569 0.074 0.109

209 0.504 0.628 –0.053 0.015 -- 0.461 7.597 1.568 0.081 0.073

210 0.254 0.478 –0.036 0.017 -- 0.343 5.984 1.267 0.067 0.049

213 0.468 0.480 –0.061 0.018 -- 0.348 5.609 1.104 0.054 0.059

215 0.566 0.704 0.025 -- -- 0.453 2.352 0.195 -- 0.104

217 1.266 0.763 –0.024 -- -- 0.739 1.626 0.582 0.050 0.149

218 –0.105 0.098 –0.031 –0.004 -- 0.129 0.432 0.210 0.025 0.035

224 –0.020 0.214 –0.022 0.019 -- 0.321 1.777 0.511 0.036 0.050

225 0.267 0.702 –0.006 –0.010 -- 0.744 0.638 0.194 0.016 0.141

226 –0.136 0.094 0.023 -- -- 0.361 0.055 0.042 0.008 0.065

228 0.364 0.886 –0.043 0.009 -- 0.364 19.088 3.068 0.123 0.067

229 –0.169 0.596 –0.089 0.011 -- 0.397 2.082 0.605 0.043 0.080

234 –0.063 0.126 0.009 –0.017 -- 0.361 2.044 0.535 0.035 0.055

235 0.580 0.631 0.007 -- -- 0.516 0.614 0.080 -- 0.095

237 –0.066 1.090 0.007 -- -- 0.644 0.930 0.122 -- 0.103

238 0.305 0.250 0.041 –0.011 -- 0.395 2.668 0.629 0.037 0.074

239 0.274 0.488 0.005 –0.010 -- 0.289 22.226 3.864 0.168 0.036

240 –0.121 0.086 –0.077 0.020 -- 0.362 0.508 0.228 0.025 0.222

241 –0.074 –0.591 0.005 -- -- 0.648 0.124 0.076 0.012 0.059

242 0.004 0.073 0.095 –0.024 -- 0.384 1.448 0.434 0.032 0.051

243 0.103 0.140 0.010 –0.012 -- 0.302 1.198 0.281 0.016 0.023

244 0.314 0.588 –0.036 -- -- 0.467 0.685 0.069 -- 0.049
178 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Standard

error of

cosine

coefficient

Standard

error of

time

coefficient

Standard

error of

time squared

coefficient

Standard

error of

step trend

coefficient

Standard

error of

root mean

square error

Covariance

of log of

concentration

and log of

streamflow

Variance of the

covariance of log

of concentration

and log of

streamflow

Centered

time

Total phosphorus

1 0.107 0.022 -- -- 0.069 –0.425 0.008 1/1/1998

2 0.124 0.021 0.007 -- 0.059 –0.232 0.004 1/1/1998

3 0.088 0.019 0.006 -- 0.050 –0.221 0.005 1/1/1998

4 0.093 0.019 -- -- 0.057 –0.089 0.002 1/1/1998

5 0.073 0.015 -- -- 0.035 0.128 0.002 1/1/1998

7 0.054 0.012 0.004 -- 0.027 –0.281 0.003 1/1/1998

8 -- 0.011 -- -- 0.025 –0.288 0.002 1/1/1998

10 0.054 0.012 0.004 -- 0.027 –0.287 0.003 1/1/1998

11 -- 0.046 -- -- 0.129 0.128 0.016 1/1/1998

12 0.075 0.015 0.005 -- 0.035 –0.540 0.009 1/1/1998

13 0.241 0.058 -- -- 0.121 –0.314 0.019 1/1/1998

14 0.089 0.014 -- -- 0.049 –0.171 0.004 1/1/1998

15 0.097 0.021 -- -- 0.053 0.374 0.007 1/1/1998

16 0.151 0.025 0.009 -- 0.080 –0.121 0.008 1/1/1998

17 -- 0.061 -- -- 0.147 0.065 0.041 1/1/1998

18 0.070 0.014 -- -- 0.034 –0.837 0.036 1/1/1998

19 0.043 0.009 -- -- 0.021 –0.808 0.018 1/1/1998

20 0.077 0.018 0.006 -- 0.041 –0.350 0.008 1/1/1998

22 0.063 0.015 -- -- 0.033 0.049 0.005 1/1/1998

24 0.145 0.039 0.012 -- 0.097 0.516 0.041 1/1/1998

25 -- 0.014 -- -- 0.032 –0.316 0.007 1/1/1998

26 0.041 0.011 -- -- 0.021 –0.388 0.006 1/1/1998

27 0.112 0.023 0.008 -- 0.069 0.246 0.006 1/1/1998

28 0.243 0.050 0.016 -- 0.146 –0.119 0.006 1/1/1998

30 0.252 0.062 -- -- 0.163 0.011 0.004 1/1/1998

31 0.190 0.049 0.013 -- 0.130 0.305 0.011 1/1/1998

32 0.172 0.034 -- -- 0.094 –0.087 0.011 1/1/1998

33 0.077 0.016 -- -- 0.037 0.127 0.003 1/1/1998

34 0.067 0.017 -- -- 0.033 0.149 0.003 1/1/1998

35 0.066 0.016 -- -- 0.032 0.105 0.003 1/1/1998

36 0.066 0.015 0.006 -- 0.038 0.660 0.011 1/1/1998

37 0.068 0.013 -- -- 0.038 0.576 0.005 1/1/1998

38 0.050 0.012 0.004 -- 0.024 0.139 0.002 1/1/1998

39 0.071 0.016 -- -- 0.032 0.232 0.004 1/1/1998

40 0.095 0.020 0.006 -- 0.052 0.680 0.015 1/1/1998

41 0.059 0.014 -- -- 0.035 1.294 0.013 1/1/1998

42 0.035 0.007 0.002 -- 0.016 –0.082 0.001 1/1/1998

43 0.028 0.006 0.002 -- 0.013 0.023 0.001 1/1/1998

44 0.045 0.010 0.003 -- 0.021 0.471 0.003 1/1/1998

45 0.032 0.007 0.002 -- 0.015 0.475 0.002 1/1/1998

46 0.137 0.024 0.009 -- 0.097 0.743 0.024 1/1/1998

51 0.053 0.012 0.004 -- 0.025 –0.119 0.001 1/1/1998

52 0.065 0.016 0.005 -- 0.035 –0.024 0.001 1/1/1998

53 0.054 0.012 0.004 -- 0.034 0.150 0.002 1/1/1998

54 0.051 0.011 0.003 -- 0.024 –0.008 0.001 1/1/1998

55 0.030 0.008 0.003 -- 0.014 –0.074 0.001 1/1/1998

56 0.050 0.011 0.004 -- 0.023 –0.655 0.011 1/1/1998

58 0.042 0.010 0.003 -- 0.021 0.138 0.002 1/1/1998

59 0.035 0.008 0.002 -- 0.016 –0.113 0.001 1/1/1998

60 0.035 0.007 0.003 -- 0.017 0.319 0.003 1/1/1998

61 0.062 0.014 0.005 -- 0.031 0.185 0.006 1/1/1998

62 0.054 0.012 0.004 -- 0.026 0.280 0.008 1/1/1998

63 0.077 0.015 0.006 -- 0.033 0.647 0.019 1/1/1998
Appendix 3 179

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Standard

error of

cosine

coefficient

Standard

error of

time

coefficient

Standard

error of

time squared

coefficient

Standard

error of

step trend

coefficient

Standard

error of

root mean

square error

Covariance

of log of

concentration

and log of

streamflow

Variance of the

covariance of log

of concentration

and log of

streamflow

Centered

time

Total phosphorus—Continued

64 0.086 0.018 0.008 -- 0.059 0.023 0.010 1/1/1998

65 0.047 0.010 0.004 -- 0.022 –1.351 0.031 1/1/1998

66 0.145 0.026 0.009 -- 0.101 0.851 0.013 1/1/1998

68 0.085 0.021 0.006 -- 0.064 0.032 0.001 1/1/1998

69 0.061 0.015 0.007 -- 0.040 0.369 0.005 1/1/1998

70 0.057 0.012 0.004 -- 0.027 –0.147 0.002 1/1/1998

71 -- 0.014 -- -- 0.029 0.085 0.001 1/1/1998

72 0.093 0.017 0.007 -- 0.051 1.018 0.022 1/1/1998

73 0.042 0.010 -- -- 0.020 0.318 0.002 1/1/1998

74 -- 0.026 -- -- 0.148 0.207 0.002 1/1/1998

75 0.028 0.005 -- -- 0.012 0.145 0.000 1/1/1998

76 0.049 0.010 -- -- 0.027 0.057 0.001 1/1/1998

77 0.038 0.008 0.003 -- 0.016 –0.287 0.001 1/1/1998

78 0.065 0.013 -- -- 0.034 0.199 0.001 1/1/1998

79 0.035 0.009 -- -- 0.019 0.245 0.001 1/1/1997

80 0.022 0.005 -- -- 0.010 0.070 0.000 1/1/1997

81 0.115 0.018 0.006 -- 0.036 0.300 0.025 1/1/1998

82 0.090 0.018 0.007 -- 0.036 0.306 0.016 1/1/1998

83 0.054 0.010 0.004 -- 0.026 0.436 0.006 1/1/1998

84 0.034 0.008 0.003 -- 0.018 0.400 0.001 1/1/1998

85 -- 0.007 -- -- 0.018 0.546 0.002 1/1/1998

86 0.050 0.010 -- -- 0.026 0.449 0.002 1/1/1998

87 0.073 0.017 -- -- 0.038 1.272 0.041 1/1/1998

88 0.076 0.021 -- -- 0.045 1.253 0.069 1/1/1998

89 0.096 0.023 -- -- 0.048 0.930 0.033 1/1/1998

90 0.044 0.011 0.004 -- 0.022 –0.308 0.002 1/1/1998

91 0.043 0.010 0.004 -- 0.022 –0.357 0.004 1/1/1998

92 0.080 0.017 0.007 -- 0.050 0.352 0.008 1/1/1998

93 0.049 0.013 0.004 -- 0.023 –0.130 0.001 1/1/1998

94 -- 0.023 -- -- 0.081 0.445 0.010 1/1/1998

95 -- 0.012 -- -- 0.024 0.174 0.001 1/1/1998

97 0.265 0.029 -- -- 0.081 0.799 0.107 1/1/1998

99 0.160 0.034 -- -- 0.072 0.605 0.012 1/1/1998

101 0.075 0.014 -- -- 0.033 0.034 0.000 1/1/1998

106 0.172 0.146 -- 1.227 0.075 1.092 0.068 1/1/1998

107 0.036 0.008 -- -- 0.018 –0.079 0.001 1/1/1998

109 -- 0.019 -- -- 0.038 0.604 0.013 1/1/1998

110 0.062 0.015 -- -- 0.030 0.178 0.002 1/1/1998

111 0.104 0.026 -- -- 0.049 1.013 0.033 1/1/1998

112 0.092 0.018 -- -- 0.038 0.127 0.001 1/1/1998

113 0.089 0.023 -- -- 0.039 0.997 0.031 1/1/1998

114 0.104 0.025 -- -- 0.053 1.091 0.040 1/1/1998

115 0.079 0.019 -- -- 0.043 0.395 0.020 1/1/1998

118 -- 0.021 -- -- 0.039 0.186 0.002 1/1/1998

120 0.050 0.012 -- -- 0.036 0.273 0.003 1/1/1998

134 0.081 0.017 0.006 -- 0.041 –0.326 0.007 1/1/1998

135 0.075 0.017 -- -- 0.037 0.292 0.008 1/1/1998

136 0.095 0.033 -- -- 0.048 –0.304 0.007 1/1/2000

137 0.043 0.010 -- -- 0.021 0.627 0.011 1/1/1998

138 0.043 0.010 -- -- 0.022 0.598 0.009 1/1/1998

139 0.081 0.017 -- -- 0.044 1.370 0.045 1/1/1998

145 -- 0.019 -- -- 0.041 0.700 0.029 1/1/1998

148 0.073 0.014 -- -- 0.037 0.337 0.011 1/1/1998
180 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Standard

error of

cosine

coefficient

Standard

error of

time

coefficient

Standard

error of

time squared

coefficient

Standard

error of

step trend

coefficient

Standard

error of

root mean

square error

Covariance

of log of

concentration

and log of

streamflow

Variance of the

covariance of log

of concentration

and log of

streamflow

Centered

time

Total phosphorus—Continued

149 0.043 0.011 0.003 -- 0.022 0.115 0.003 1/1/1998

150 0.080 0.021 -- -- 0.041 0.697 0.017 1/1/1998

151 0.056 0.011 -- -- 0.029 0.350 0.003 1/1/1998

152 -- 0.026 -- -- 0.102 0.045 0.004 1/1/1998

153 -- 0.010 -- -- 0.022 0.014 0.000 1/1/1998

154 0.063 0.014 -- -- 0.031 0.165 0.001 1/1/1998

155 -- 0.015 -- -- 0.033 0.113 0.002 1/1/1998

156 -- 0.008 -- -- 0.018 0.074 0.000 1/1/1998

157 0.046 0.010 -- -- 0.024 0.103 0.002 1/1/1998

165 0.141 0.031 -- -- 0.070 0.234 0.031 1/1/1998

166 -- 0.060 -- -- 0.140 0.404 0.044 1/1/1998

169 -- 0.075 -- -- 0.236 0.459 0.220 1/1/1998

170 -- 0.022 -- -- 0.050 0.066 0.003 1/1/1998

171 -- 0.026 -- -- 0.058 0.155 0.008 1/1/1998

173 0.059 0.012 -- -- 0.028 0.226 0.005 1/1/1998

177 0.152 0.030 -- -- 0.090 –0.012 0.004 1/1/1998

178 0.228 0.042 -- -- 0.109 0.558 0.017 1/1/1998

180 -- 0.040 -- -- 0.105 0.285 0.005 1/1/1998

182 0.157 0.039 -- -- 0.083 0.601 0.020 1/1/1998

183 0.226 0.045 -- -- 0.108 1.184 0.092 1/1/1998

184 0.254 0.054 -- -- 0.145 1.422 0.122 1/1/1998

185 0.180 0.038 -- -- 0.105 0.615 0.022 1/1/1998

186 0.231 0.041 0.015 -- 0.130 0.391 0.013 1/1/1998

188 0.093 0.016 0.006 -- 0.037 –0.046 0.005 1/1/1998

193 0.137 0.017 0.006 -- 0.047 0.221 0.004 1/1/1998

203 0.086 0.019 0.007 -- 0.055 0.322 0.003 1/1/1998

204 0.136 0.033 -- -- 0.072 0.218 0.002 1/1/1998

205 0.124 0.026 0.012 -- 0.062 0.218 0.002 1/1/1998

206 0.072 0.015 0.005 -- 0.040 0.063 0.001 1/1/1998

207 0.147 0.032 0.011 -- 0.076 0.213 0.003 1/1/1998

208 0.052 0.008 -- -- 0.018 0.140 0.002 1/1/1998

209 0.050 0.008 0.003 -- 0.018 0.166 0.001 1/1/1998

210 0.050 0.009 -- -- 0.021 0.167 0.001 1/1/1998

211 -- 0.009 -- -- 0.020 0.100 0.001 1/1/1998

212 -- 0.017 -- -- 0.037 0.023 0.000 1/1/1998

213 0.049 0.008 0.003 -- 0.017 0.209 0.001 1/1/1998

214 0.036 0.005 0.002 -- 0.012 0.141 0.001 1/1/1998

215 0.051 0.011 -- -- 0.025 0.125 0.001 1/1/1998

216 0.083 0.020 -- -- 0.053 0.032 0.002 1/1/1998

217 0.067 0.011 0.004 -- 0.024 0.184 0.006 1/1/1998

218 0.055 0.009 -- -- 0.020 0.014 0.001 1/1/1998

219 -- 0.015 -- -- 0.033 0.523 0.013 1/1/1998

220 0.082 0.015 -- -- 0.032 0.323 0.010 1/1/1998

221 0.102 0.027 0.008 -- 0.062 –0.192 0.006 1/1/1998

222 0.205 0.051 -- -- 0.108 –0.091 0.005 1/1/1998

223 0.041 0.010 -- -- 0.020 0.014 0.000 1/1/1998

224 -- 0.018 -- -- 0.039 –0.737 0.015 1/1/1998

225 0.093 0.015 -- -- 0.037 0.647 0.016 1/1/1998

227 0.054 0.009 0.003 -- 0.020 0.174 0.002 1/1/1998

228 0.081 0.020 -- -- 0.055 0.111 0.001 1/1/1998

229 0.167 0.027 0.008 -- 0.060 0.286 0.003 1/1/1998

230 0.062 0.011 -- -- 0.025 0.160 0.001 1/1/1998

231 0.037 0.005 0.002 -- 0.012 0.252 0.001 1/1/1998
Appendix 3 181

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Standard

error of

cosine

coefficient

Standard

error of

time

coefficient

Standard

error of

time squared

coefficient

Standard

error of

step trend

coefficient

Standard

error of

root mean

square error

Covariance

of log of

concentration

and log of

streamflow

Variance of the

covariance of log

of concentration

and log of

streamflow

Centered

time

Total phosphorus—Continued

232 0.050 0.009 0.003 -- 0.027 0.202 0.001 1/1/1998

233 0.039 0.008 -- -- 0.019 0.025 0.000 1/1/1998

234 0.150 0.037 0.017 -- 0.075 0.136 0.004 1/1/1998

235 0.173 0.036 0.016 -- 0.084 0.259 0.006 1/1/1998

236 0.221 0.032 0.013 -- 0.073 0.342 0.006 1/1/1998

237 0.158 0.028 0.009 -- 0.065 0.403 0.004 1/1/1998

238 0.117 0.022 0.008 -- 0.067 –0.015 0.005 1/1/1998

239 -- 0.029 -- -- 0.084 0.024 0.000 1/1/1998

241 0.066 0.014 -- -- 0.033 –0.108 0.005 1/1/1998

242 0.063 0.013 -- -- 0.033 –0.218 0.003 1/1/1998

243 0.033 0.007 0.003 -- 0.016 –0.060 0.000 1/1/1998

244 0.056 0.016 -- -- 0.035 0.087 0.000 1/1/1998

Total nitrogen

1 -- 0.010 -- -- 0.022 –0.246 0.002 1/1/1998

2 -- 0.008 -- -- 0.018 –0.295 0.002 1/1/1998

3 -- 0.008 -- -- 0.016 –0.107 0.001 1/1/1998

4 0.036 0.008 -- -- 0.020 –0.095 0.001 1/1/1998

5 0.019 0.004 -- -- 0.009 –0.042 0.000 1/1/1998

6 -- 0.019 -- -- 0.041 –0.060 0.001 1/1/1998

7 0.034 0.008 0.003 -- 0.017 –0.225 0.001 1/1/1998

8 0.033 0.007 -- -- 0.016 –0.191 0.001 1/1/1998

9 0.085 0.015 0.007 -- 0.037 0.106 0.003 1/1/1998

10 0.025 0.005 -- -- 0.012 –0.238 0.001 1/1/1998

11 0.050 0.011 -- -- 0.026 0.038 0.003 1/1/1998

12 0.042 0.009 0.003 -- 0.020 –0.411 0.005 1/1/1998

13 -- 0.018 -- -- 0.040 0.049 0.006 1/1/1998

14 0.038 0.008 -- -- 0.020 0.104 0.001 1/1/1998

15 0.028 0.006 -- -- 0.012 0.147 0.001 1/1/1998

16 -- 0.010 -- -- 0.023 –0.064 0.001 1/1/1998

17 0.071 0.016 -- -- 0.034 0.013 0.013 1/1/1998

18 -- 0.009 -- -- 0.021 –0.664 0.021 1/1/1998

19 0.035 0.008 -- -- 0.017 –0.625 0.011 1/1/1998

20 -- 0.010 -- -- 0.023 –0.187 0.002 1/1/1998

21 -- 0.010 -- -- 0.023 0.054 0.001 1/1/1998

22 0.046 0.011 -- -- 0.025 0.051 0.001 1/1/1998

23 -- 0.010 -- -- 0.023 –0.036 0.001 1/1/1998

24 -- 0.018 -- -- 0.032 0.751 0.023 1/1/1998

25 -- 0.010 -- -- 0.024 –0.182 0.002 1/1/1998

26 0.022 0.006 -- -- 0.011 –0.241 0.002 1/1/1998

29 -- 0.015 -- -- 0.033 0.149 0.002 1/1/1998

31 0.053 0.012 -- -- 0.027 0.131 0.002 1/1/1998

32 0.051 0.011 -- -- 0.025 0.144 0.002 1/1/1998

33 -- 0.008 -- -- 0.018 0.040 0.001 1/1/1998

34 0.039 0.010 -- -- 0.019 0.102 0.001 1/1/1998

35 0.038 0.009 -- -- 0.018 0.026 0.001 1/1/1998

36 0.021 0.005 -- -- 0.010 –0.028 0.001 1/1/1998

37 0.023 0.004 -- -- 0.010 0.111 0.000 1/1/1998

38 0.017 0.004 0.001 -- 0.008 –0.099 0.000 1/1/1998

39 0.018 0.005 0.002 -- 0.008 0.002 0.000 1/1/1998

40 0.032 0.007 0.002 -- 0.016 0.464 0.004 1/1/1998

41 -- 0.007 -- -- 0.019 0.795 0.005 1/1/1998

42 0.022 0.005 0.001 -- 0.010 0.007 0.001 1/1/1998

43 0.018 0.004 0.001 -- 0.008 0.043 0.000 1/1/1998
182 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Standard

error of

cosine

coefficient

Standard

error of

time

coefficient

Standard

error of

time squared

coefficient

Standard

error of

step trend

coefficient

Standard

error of

root mean

square error

Covariance

of log of

concentration

and log of

streamflow

Variance of the

covariance of log

of concentration

and log of

streamflow

Centered

time

Total nitrogen—Continued

44 0.028 0.006 0.002 -- 0.013 0.540 0.002 1/1/1998

45 0.019 0.004 0.001 -- 0.009 0.079 0.000 1/1/1998

46 0.042 0.008 0.003 -- 0.019 0.352 0.005 1/1/1998

47 0.032 0.007 0.002 -- 0.015 –0.107 0.001 1/1/1998

48 0.021 0.004 0.001 -- 0.009 –0.039 0.000 1/1/1998

49 0.072 0.014 0.006 -- 0.034 0.100 0.003 1/1/1998

52 0.065 0.014 0.005 -- 0.030 –0.016 0.001 1/1/1998

53 0.036 0.009 0.003 -- 0.018 –0.124 0.001 1/1/1998

57 0.035 0.008 0.003 -- 0.018 –0.294 0.005 1/1/1998

58 0.051 0.012 0.004 -- 0.025 –0.131 0.003 1/1/1998

59 0.029 0.007 0.002 -- 0.014 0.074 0.001 1/1/1998

60 0.044 0.009 0.003 -- 0.021 0.163 0.002 1/1/1998

61 0.049 0.011 0.004 -- 0.024 –0.145 0.003 1/1/1998

62 0.054 0.012 0.004 -- 0.026 0.245 0.006 1/1/1998

65 0.039 0.008 0.003 -- 0.018 –0.732 0.012 1/1/1998

67 0.044 0.011 0.004 -- 0.022 –0.164 0.001 1/1/1998

71 -- 0.026 -- -- 0.055 0.301 0.005 1/1/1998

72 0.042 0.008 -- -- 0.021 0.514 0.006 1/1/1998

73 0.036 0.008 -- -- 0.017 0.127 0.001 1/1/1998

74 0.045 0.009 0.004 -- 0.021 0.158 0.001 1/1/1998

76 0.028 0.006 -- -- 0.014 0.060 0.001 1/1/1998

81 0.090 0.015 0.005 -- 0.032 0.024 0.012 1/1/1998

82 0.080 0.016 -- -- 0.034 0.168 0.009 1/1/1998

92 0.055 0.012 -- -- 0.027 0.453 0.007 1/1/1998

95 0.042 0.009 -- -- 0.016 0.124 0.000 1/1/1998

97 0.107 0.014 -- -- 0.030 0.330 0.035 1/1/1998

99 0.078 0.016 -- -- 0.035 0.131 0.002 1/1/1998

100 -- 0.024 -- -- 0.052 0.012 0.001 1/1/1998

101 0.085 0.016 -- -- 0.039 0.064 0.000 1/1/1998

102 0.069 0.012 -- -- 0.027 0.093 0.008 1/1/1998

103 -- 0.043 -- 0.359 0.020 –0.159 0.001 1/1/1998

106 0.059 0.054 -- 0.454 0.027 –0.288 0.008 1/1/1998

107 0.020 0.004 -- -- 0.009 –0.262 0.002 1/1/1998

108 0.035 0.007 -- -- 0.018 0.008 0.000 1/1/1998

109 0.050 0.012 -- -- 0.024 0.496 0.006 1/1/1998

110 -- 0.012 -- -- 0.024 0.193 0.001 1/1/1998

111 0.082 0.021 -- -- 0.037 0.865 0.020 1/1/1998

112 0.057 0.012 -- -- 0.024 0.091 0.001 1/1/1998

113 0.087 0.019 -- -- 0.039 0.883 0.020 1/1/1998

114 0.074 0.019 -- -- 0.040 0.556 0.013 1/1/1998

115 -- 0.022 -- -- 0.044 0.823 0.026 1/1/1998

116 0.057 0.014 -- -- 0.029 0.403 0.009 1/1/1998

118 0.050 0.012 -- -- 0.020 0.145 0.001 1/1/1998

120 0.045 0.011 -- -- 0.021 0.070 0.002 1/1/1998

124 0.042 0.010 -- -- 0.021 0.005 0.001 1/1/1998

125 0.042 0.009 -- -- 0.022 0.109 0.001 1/1/1998

134 0.037 0.008 -- -- 0.019 0.248 0.003 1/1/1998

135 0.047 0.010 -- -- 0.024 0.138 0.002 1/1/1998

136 -- 0.020 -- -- 0.029 –0.189 0.002 1/1/2000

137 0.023 0.006 0.002 -- 0.011 0.194 0.002 1/1/1998

138 0.034 0.007 -- -- 0.017 0.463 0.005 1/1/1998

139 0.055 0.013 0.004 -- 0.027 0.657 0.013 1/1/1998

145 0.061 0.013 0.004 -- 0.030 0.255 0.012 1/1/1998
Appendix 3 183

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Standard

error of

cosine

coefficient

Standard

error of

time

coefficient

Standard

error of

time squared

coefficient

Standard

error of

step trend

coefficient

Standard

error of

root mean

square error

Covariance

of log of

concentration

and log of

streamflow

Variance of the

covariance of log

of concentration

and log of

streamflow

Centered

time

Total nitrogen—Continued

146 0.093 0.019 -- -- 0.052 0.074 0.031 1/1/1998

147 0.077 0.016 -- -- 0.040 –0.079 0.018 1/1/1998

148 0.050 0.010 -- -- 0.024 0.070 0.005 1/1/1998

149 0.036 0.009 -- -- 0.018 0.146 0.002 1/1/1998

150 0.047 0.013 0.004 -- 0.024 0.294 0.004 1/1/1998

151 0.032 0.006 -- -- 0.015 0.139 0.001 1/1/1998

152 0.071 0.019 -- -- 0.039 0.052 0.003 1/1/1998

153 0.031 0.008 -- -- 0.015 0.065 0.000 1/1/1998

154 -- 0.012 -- -- 0.026 0.255 0.002 1/1/1998

155 -- 0.012 -- -- 0.028 0.256 0.003 1/1/1998

156 0.029 0.007 -- -- 0.014 0.055 0.000 1/1/1998

157 0.041 0.009 -- -- 0.021 0.001 0.001 1/1/1998

173 0.052 0.012 -- -- 0.025 –0.072 0.003 1/1/1998

176 -- 0.015 -- -- 0.048 0.024 0.001 1/1/1998

179 -- 0.014 -- -- 0.030 –0.004 0.000 1/1/1998

182 0.110 0.023 -- -- 0.046 0.295 0.007 1/1/1998

196 0.043 0.009 0.003 -- 0.020 0.213 0.003 1/1/1998

199 0.064 0.012 0.005 -- 0.027 0.218 0.002 1/1/1998

201 0.056 0.011 0.005 -- 0.024 0.427 0.004 1/1/1998

202 0.043 0.009 0.004 -- 0.020 0.132 0.001 1/1/1998

208 0.098 0.015 0.005 -- 0.034 0.198 0.004 1/1/1998

209 0.070 0.012 0.004 -- 0.026 0.178 0.002 1/1/1998

210 0.065 0.013 0.004 -- 0.034 0.086 0.001 1/1/1998

212 -- 0.014 -- -- 0.033 0.033 0.000 1/1/1998

213 0.060 0.010 0.004 -- 0.021 0.184 0.002 1/1/1998

214 0.066 0.010 0.003 -- 0.021 0.213 0.002 1/1/1998

215 0.084 0.019 -- -- 0.044 0.072 0.001 1/1/1998

217 0.081 0.013 0.004 -- 0.029 0.113 0.007 1/1/1998

218 0.029 0.005 0.002 -- 0.010 –0.154 0.001 1/1/1998

219 -- 0.017 -- -- 0.050 0.060 0.005 1/1/1998

220 0.074 0.013 0.005 -- 0.029 –1.025 0.034 1/1/1998

221 0.055 0.013 0.004 -- 0.027 –0.449 0.006 1/1/1998

222 -- 0.016 -- -- 0.059 –0.280 0.004 1/1/1998

223 0.019 0.005 -- -- 0.010 –0.057 0.000 1/1/1998

224 0.069 0.009 0.003 -- 0.018 –0.490 0.007 1/1/1998

225 0.051 0.009 0.003 -- 0.020 0.838 0.012 1/1/1998

227 0.057 0.008 0.003 -- 0.018 0.246 0.002 1/1/1998

228 0.034 0.008 0.003 -- 0.017 0.066 0.000 1/1/1998

231 0.022 0.003 0.001 -- 0.007 –0.116 0.000 1/1/1998

232 0.039 0.006 -- -- 0.017 0.241 0.001 1/1/1998

241 0.060 0.012 -- -- 0.027 –0.428 0.005 1/1/1998

242 0.042 0.008 0.004 -- 0.018 –0.392 0.003 1/1/1998

243 0.025 0.005 -- -- 0.013 –0.222 0.001 1/1/1998

244 0.043 0.013 -- -- 0.026 0.037 0.000 1/1/1998

Nitrate

1 0.051 0.011 0.004 -- 0.024 –0.295 0.003 1/1/1998

2 -- 0.009 -- -- 0.020 –0.411 0.004 1/1/1998

3 0.075 0.017 -- -- 0.035 0.118 0.004 1/1/1998

4 0.041 0.008 -- -- 0.018 –0.105 0.001 1/1/1998

5 0.021 0.004 -- -- 0.010 –0.100 0.000 1/1/1998

6 0.054 0.012 -- -- 0.028 –0.059 0.001 1/1/1998

7 0.027 0.006 -- -- 0.013 –0.297 0.002 1/1/1998

8 0.045 0.009 -- -- 0.022 –0.244 0.002 1/1/1998
184 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Standard

error of

cosine

coefficient

Standard

error of

time

coefficient

Standard

error of

time squared

coefficient

Standard

error of

step trend

coefficient

Standard

error of

root mean

square error

Covariance

of log of

concentration

and log of

streamflow

Variance of the

covariance of log

of concentration

and log of

streamflow

Centered

time

Nitrate—Continued

9 0.138 0.023 0.010 -- 0.053 0.371 0.013 1/1/1998

10 0.026 0.006 -- -- 0.013 –0.327 0.003 1/1/1998

11 0.064 0.014 -- -- 0.033 0.259 0.008 1/1/1998

12 0.044 0.009 0.003 -- 0.021 –0.433 0.005 1/1/1998

13 0.174 0.032 -- -- 0.080 0.234 0.026 1/1/1998

14 -- 0.013 -- -- 0.032 0.264 0.004 1/1/1998

15 0.038 0.008 -- -- 0.016 0.169 0.001 1/1/1998

16 0.087 0.018 -- -- 0.042 –0.120 0.006 1/1/1998

17 0.119 0.029 -- -- 0.060 –0.086 0.046 1/1/1998

18 0.052 0.011 -- -- 0.025 –0.786 0.028 1/1/1998

19 0.044 0.009 -- -- 0.021 –0.742 0.016 1/1/1998

20 -- 0.010 -- -- 0.022 –0.227 0.003 1/1/1998

21 -- 0.013 -- -- 0.030 –0.005 0.001 1/1/1998

22 0.073 0.016 -- -- 0.039 0.019 0.004 1/1/1998

23 -- 0.011 -- -- 0.025 –0.117 0.002 1/1/1998

24 -- 0.030 -- -- 0.062 1.469 0.095 1/1/1998

25 0.044 0.010 -- -- 0.023 –0.266 0.004 1/1/1998

26 0.026 0.007 -- -- 0.014 –0.349 0.003 1/1/1998

29 0.098 0.023 -- -- 0.057 0.161 0.005 1/1/1998

31 0.079 0.017 -- -- 0.037 0.083 0.003 1/1/1998

32 0.104 0.022 0.008 -- 0.047 0.295 0.011 1/1/1998

33 0.038 0.008 -- -- 0.018 –0.034 0.001 1/1/1998

34 0.064 0.016 -- -- 0.032 0.191 0.002 1/1/1998

35 0.067 0.017 -- -- 0.033 –0.049 0.002 1/1/1998

36 0.030 0.007 0.002 -- 0.014 –0.352 0.003 1/1/1998

37 0.027 0.005 -- -- 0.012 0.123 0.001 1/1/1998

38 0.018 0.004 -- -- 0.009 –0.223 0.001 1/1/1998

39 0.018 0.005 0.001 -- 0.008 –0.103 0.000 1/1/1998

40 0.051 0.010 -- -- 0.024 0.633 0.011 1/1/1998

41 0.072 0.015 -- -- 0.036 1.674 0.024 1/1/1998

42 0.031 0.007 -- -- 0.014 –0.280 0.001 1/1/1998

43 0.040 0.009 0.003 -- 0.019 –0.033 0.002 1/1/1998

44 0.057 0.012 0.004 -- 0.027 0.837 0.006 1/1/1998

45 0.050 0.009 -- -- 0.024 –0.098 0.002 1/1/1998

50 0.071 0.020 0.006 -- 0.032 –0.426 0.005 1/1/1998

65 0.055 0.010 0.004 -- 0.024 –1.940 0.060 1/1/1998

66 0.039 0.008 0.003 -- 0.019 0.091 0.001 1/1/1998

71 -- 0.029 -- -- 0.055 0.165 0.004 1/1/1998

72 0.056 0.011 -- -- 0.029 0.359 0.005 1/1/1998

73 0.052 0.011 -- -- 0.025 0.140 0.001 1/1/1998

74 0.136 0.021 -- -- 0.059 –0.157 0.011 1/1/1998

76 0.093 0.019 -- -- 0.046 0.369 0.007 1/1/1998

81 0.240 0.042 -- -- 0.107 1.239 0.149 1/1/1998

82 0.320 0.057 -- -- 0.167 0.638 0.156 1/1/1998

88 0.211 0.052 -- -- 0.112 2.595 0.309 1/1/1998

92 0.079 0.018 -- -- 0.038 0.803 0.019 1/1/1998

95 0.056 0.012 -- -- 0.021 0.132 0.001 1/1/1998

96 0.145 0.017 -- -- 0.041 –0.397 0.006 1/1/1998

98 0.106 0.021 -- -- 0.045 –0.284 0.008 1/1/1998

99 0.187 0.042 -- -- 0.077 0.175 0.015 1/1/1998

100 -- 0.024 -- -- 0.052 0.037 0.001 1/1/1998

101 0.109 0.020 -- -- 0.046 0.036 0.001 1/1/1998

102 0.314 0.057 -- -- 0.167 1.235 0.191 1/1/1998
Appendix 3 185

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Standard

error of

cosine

coefficient

Standard

error of

time

coefficient

Standard

error of

time squared

coefficient

Standard

error of

step trend

coefficient

Standard

error of

root mean

square error

Covariance

of log of

concentration

and log of

streamflow

Variance of the

covariance of log

of concentration

and log of

streamflow

Centered

time

Nitrate—Continued

103 0.042 0.038 -- 0.319 0.019 –0.346 0.003 1/1/1998

104 -- 0.024 -- -- 0.056 –1.258 0.042 1/1/1998

105 0.109 0.019 -- -- 0.046 –1.199 0.039 1/1/1998

106 0.065 0.056 -- 0.472 0.028 –0.519 0.016 1/1/1998

107 0.021 0.004 -- -- 0.009 –0.314 0.002 1/1/1998

108 0.035 0.007 -- -- 0.018 –0.001 0.000 1/1/1998

109 0.080 0.020 -- -- 0.037 0.432 0.008 1/1/1998

110 0.131 0.030 -- -- 0.067 0.623 0.012 1/1/1998

111 0.224 0.057 -- -- 0.098 1.626 0.100 1/1/1998

112 0.137 0.025 -- -- 0.049 0.083 0.002 1/1/1998

113 0.178 0.046 -- -- 0.089 1.835 0.102 1/1/1998

114 0.156 0.036 -- -- 0.074 1.427 0.073 1/1/1998

115 0.190 0.044 -- -- 0.108 1.800 0.121 1/1/1998

116 0.136 0.033 -- -- 0.074 1.034 0.057 1/1/1998

117 0.086 0.019 -- -- 0.040 0.485 0.008 1/1/1998

118 0.098 0.022 -- -- 0.036 0.176 0.002 1/1/1998

119 0.117 0.027 0.009 -- 0.053 –0.098 0.023 1/1/1998

120 0.067 0.017 -- -- 0.037 0.063 0.003 1/1/1998

121 0.095 0.019 0.008 -- 0.054 0.974 0.030 1/1/1998

122 0.070 0.017 -- -- 0.035 0.265 0.005 1/1/1998

123 -- 0.014 -- -- 0.039 0.247 0.004 1/1/1998

124 0.043 0.011 0.003 -- 0.022 –0.060 0.001 1/1/1998

125 0.037 0.009 -- -- 0.017 0.096 0.000 1/1/1998

126 0.115 0.046 -- -- 0.062 0.096 0.047 1/1/1998

127 0.135 0.057 -- -- 0.068 0.057 0.053 1/1/1998

128 0.049 0.009 -- -- 0.021 –0.191 0.001 1/1/1998

129 0.157 0.034 0.016 -- 0.076 –0.361 0.022 1/1/1998

130 0.033 0.007 0.003 -- 0.015 –0.382 0.003 1/1/1998

131 0.033 0.007 0.003 -- 0.016 –0.112 0.001 1/1/1998

132 0.063 0.011 -- -- 0.025 –0.002 0.002 1/1/1998

133 0.027 0.005 0.002 -- 0.011 –0.104 0.001 1/1/1998

134 0.038 0.009 -- -- 0.019 0.271 0.003 1/1/1998

135 0.068 0.015 -- -- 0.033 –0.109 0.005 1/1/1998

136 -- 0.022 -- -- 0.031 –0.228 0.003 1/1/2000

137 0.024 0.006 0.002 -- 0.012 –0.050 0.002 1/1/1998

138 0.041 0.009 -- -- 0.020 0.352 0.005 1/1/1998

139 0.058 0.013 0.004 -- 0.029 0.400 0.010 1/1/1998

140 0.253 0.049 0.018 -- 0.118 0.385 0.111 1/1/1998

141 0.205 0.040 -- -- 0.122 0.881 0.046 1/1/1998

142 0.125 0.029 -- -- 0.067 –0.071 0.029 1/1/1998

143 0.103 0.024 0.009 -- 0.052 –0.610 0.015 1/1/1998

144 0.077 0.017 -- -- 0.038 –0.506 0.007 1/1/1998

145 -- 0.028 -- -- 0.073 0.959 0.063 1/1/1998

146 0.109 0.022 0.008 -- 0.056 1.542 0.107 1/1/1998

147 0.149 0.028 0.010 -- 0.082 1.703 0.134 1/1/1998

148 0.117 0.022 0.009 -- 0.054 1.043 0.051 1/1/1998

149 0.127 0.027 -- -- 0.071 0.676 0.030 1/1/1998

150 0.148 0.041 -- -- 0.075 0.995 0.041 1/1/1998

151 0.105 0.021 -- -- 0.051 0.434 0.007 1/1/1998

152 0.096 0.022 -- -- 0.050 0.240 0.006 1/1/1998

153 0.039 0.009 -- -- 0.018 0.093 0.000 1/1/1998

154 -- 0.010 -- -- 0.021 0.165 0.001 1/1/1998

155 0.044 0.010 -- -- 0.023 0.118 0.002 1/1/1998
186 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site 

number 

(figure 1)

Properties of the calibrated model

Standard

error of

cosine

coefficient

Standard

error of

time

coefficient

Standard

error of

time squared

coefficient

Standard

error of

step trend

coefficient

Standard

error of

root mean

square error

Covariance

of log of

concentration

and log of

streamflow

Variance of the

covariance of log

of concentration

and log of

streamflow

Centered

time

Nitrate—Continued

156 0.045 0.011 -- -- 0.021 0.054 0.000 1/1/1998

157 0.090 0.019 0.008 -- 0.043 –0.160 0.006 1/1/1998

158 0.080 0.018 -- -- 0.052 –0.148 0.005 1/1/1998

159 0.134 0.027 -- -- 0.058 –0.350 0.013 1/1/1998

160 -- 0.023 -- -- 0.056 –0.256 0.021 1/1/1998

161 0.135 0.031 -- -- 0.082 1.919 0.132 1/1/1998

162 0.156 0.030 -- -- 0.078 2.948 0.219 1/1/1998

163 0.130 0.027 0.010 -- 0.054 –0.841 0.031 1/1/1998

164 0.212 0.060 -- -- 0.102 2.312 0.463 1/1/1998

167 0.136 0.027 -- -- 0.083 1.274 0.095 1/1/1998

168 0.078 0.019 -- -- 0.049 1.158 0.062 1/1/1998

172 -- 0.013 -- -- 0.025 –0.286 0.002 1/1/1998

174 0.118 0.019 0.007 -- 0.048 0.172 0.003 1/1/1998

175 0.040 0.009 0.003 -- 0.016 –0.237 0.001 1/1/1998

177 0.083 0.018 -- -- 0.045 –0.152 0.002 1/1/1998

181 0.079 0.016 -- -- 0.033 –0.653 0.013 1/1/1998

187 0.089 0.018 -- -- 0.044 –0.015 0.003 1/1/1998

189 0.099 0.018 -- -- 0.034 –0.538 0.010 1/1/1998

190 0.145 0.021 -- -- 0.053 –0.405 0.009 1/1/1998

191 0.173 0.028 0.010 -- 0.074 0.244 0.019 1/1/1998

192 0.086 0.016 -- -- 0.034 –0.420 0.005 1/1/1998

194 0.086 0.015 -- -- 0.033 –0.386 0.008 1/1/1998

195 0.055 0.010 0.004 -- 0.023 –0.040 0.003 1/1/1998

197 0.074 0.014 -- -- 0.031 0.155 0.003 1/1/1998

198 0.074 0.013 0.005 -- 0.029 0.154 0.004 1/1/1998

199 0.051 0.010 -- -- 0.022 0.093 0.002 1/1/1998

200 0.047 0.010 -- -- 0.020 0.129 0.001 1/1/1998

201 0.322 0.055 0.021 -- 0.169 –0.048 0.005 1/1/1998

205 0.037 0.008 -- -- 0.018 0.065 0.002 1/1/1998

207 0.079 0.015 -- -- 0.033 0.170 0.005 1/1/1998

208 0.109 0.017 0.006 -- 0.038 0.287 0.006 1/1/1998

209 0.079 0.013 0.005 -- 0.029 0.265 0.003 1/1/1998

210 0.053 0.010 0.003 -- 0.022 0.139 0.001 1/1/1998

213 0.064 0.010 0.004 -- 0.022 0.254 0.002 1/1/1998

215 0.090 0.019 -- -- 0.044 0.090 0.002 1/1/1998

217 0.209 0.033 -- -- 0.073 –0.009 0.060 1/1/1998

218 0.036 0.006 0.002 -- 0.013 –0.178 0.002 1/1/1998

224 0.093 0.014 0.004 -- 0.025 –0.586 0.010 1/1/1998

225 0.106 0.018 0.007 -- 0.041 1.545 0.042 1/1/1998

226 0.066 0.011 -- -- 0.023 0.635 0.011 1/1/1998

228 0.048 0.013 0.004 -- 0.023 0.096 0.001 1/1/1998

229 0.080 0.012 0.005 -- 0.033 0.162 0.003 1/1/1998

234 0.054 0.010 0.004 -- 0.023 –0.471 0.005 1/1/1998

235 0.089 0.018 -- -- 0.054 0.507 0.009 1/1/1998

237 0.126 0.026 -- -- 0.064 –0.464 0.009 1/1/1998

238 0.053 0.011 0.004 -- 0.025 –0.553 0.006 1/1/1998

239 0.039 0.008 0.003 -- 0.018 –0.022 0.000 1/1/1998

240 0.154 0.026 0.012 -- 0.083 –0.320 0.007 1/1/1998

241 0.061 0.012 -- -- 0.029 –0.591 0.007 1/1/1998

242 0.043 0.009 0.004 -- 0.022 –0.484 0.004 1/1/1998

243 0.019 0.004 0.002 -- 0.009 –0.369 0.001 1/1/1998

244 0.048 0.014 -- -- 0.027 0.058 0.001 1/1/1998
Appendix 3 187

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site

number

(figure 1)

Properties of the calibrated model

Degrees of

freedom

Fit

statistic2

Probability

plot

correlation

coefficient3

Probability

plot

correlation

coefficient,

lower bound

Probability

plot

correlation

coefficient,

upper bound

Shapiro-Wilk

test statistic3

Shapiro-Wilk 

p-value

Total phosphorus

1 98 –83.96 0.99 0.99 0.99 0.99 0.396

2 98 –74.12 0.98 0.98 0.99 0.97 0.040

3 96 –78.89 0.96 0.95 0.97 0.94 0.000

4 146 –150.09 0.96 0.95 0.97 0.94 0.000

5 88 0.42 0.98 0.97 0.98 0.96 0.013

7 84 0.62 0.94 0.92 0.96 0.91 0.000

8 105 0.56 0.97 0.96 0.98 0.95 0.000

10 83 0.63 0.99 0.99 0.99 0.98 0.307

11 49 –55.83 0.94 0.91 0.96 0.90 0.000

12 84 0.69 0.99 0.98 0.99 0.97 0.051

13 52 –45.93 0.98 0.97 0.99 0.96 0.077

14 189 –164.40 0.96 0.95 0.97 0.93 0.000

15 131 –119.09 0.98 0.97 0.99 0.97 0.010

16 40 –32.89 0.98 0.96 0.99 0.97 0.196

17 46 –50.02 0.99 0.98 0.99 0.97 0.177

18 41 0.87 0.98 0.97 0.99 0.98 0.614

19 76 0.88 0.99 0.99 1.00 0.98 0.368

20 42 0.73 0.95 0.92 0.97 0.93 0.005

22 42 –10.77 0.98 0.97 0.99 0.96 0.111

24 68 –84.46 0.96 0.95 0.98 0.95 0.003

25 43 0.69 0.95 0.92 0.97 0.93 0.007

26 104 0.77 0.97 0.95 0.98 0.95 0.000

27 42 –31.77 0.98 0.97 0.99 0.96 0.110

28 43 –50.71 0.97 0.95 0.98 0.95 0.023

30 44 –52.18 0.95 0.92 0.97 0.92 0.002

31 41 –42.22 0.98 0.96 0.99 0.97 0.249

32 43 –38.24 0.97 0.95 0.98 0.95 0.043

33 88 0.38 1.00 0.99 1.00 0.99 0.723

34 80 0.40 0.89 0.85 0.92 0.81 0.000

35 76 0.51 0.96 0.94 0.97 0.95 0.002

36 177 –151.41 0.98 0.97 0.98 0.96 0.000

37 248 –203.19 0.98 0.98 0.98 0.97 0.000

38 288 0.23 0.98 0.97 0.98 0.96 0.000

39 272 0.21 0.99 0.99 0.99 0.98 0.001

40 142 –151.27 0.98 0.98 0.99 0.97 0.004

41 334 –325.35 1.00 0.99 1.00 0.99 0.072

42 406 0.25 0.99 0.99 0.99 0.98 0.000

43 403 0.23 0.99 0.99 0.99 0.98 0.000

44 351 0.46 0.99 0.99 0.99 0.98 0.000

45 410 0.41 0.99 0.99 0.99 0.99 0.009

46 75 –37.78 0.96 0.95 0.98 0.94 0.001

51 107 –49.93 0.99 0.99 0.99 0.99 0.291

52 79 –46.26 0.97 0.96 0.98 0.96 0.004

53 124 –73.77 0.99 0.99 0.99 0.99 0.601

54 115 –44.42 0.99 0.98 0.99 0.98 0.072

55 111 0.23 0.97 0.96 0.98 0.95 0.000

56 115 –47.15 0.93 0.91 0.95 0.88 0.000

58 53 0.33 0.99 0.99 0.99 0.98 0.395

59 75 0.22 0.99 0.99 0.99 0.98 0.151

60 96 0.65 1.00 0.99 1.00 0.99 0.915

61 56 0.30 0.95 0.92 0.97 0.92 0.000
188 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site

number

(figure 1)

Properties of the calibrated model

Degrees of

freedom

Fit

statistic2

Probability

plot

correlation

coefficient3

Probability

plot

correlation

coefficient,

lower bound

Probability

plot

correlation

coefficient,

upper bound

Shapiro-Wilk

test statistic3

Shapiro-Wilk 

p-value

Total phosphorus—Continued

62 57 0.51 0.99 0.99 1.00 0.98 0.548

63 56 –31.04 1.00 0.99 1.00 0.99 0.972

64 117 –45.13 0.99 0.99 0.99 0.97 0.019

65 133 0.80 0.99 0.99 0.99 0.99 0.138

66 159 –109.09 0.98 0.97 0.98 0.95 0.000

68 115 –88.40 0.91 0.88 0.93 0.85 0.000

69 70 –23.89 1.00 0.99 1.00 0.99 0.941

70 117 –67.55 0.99 0.99 1.00 0.99 0.544

71 95 0.14 0.96 0.95 0.97 0.94 0.000

72 146 –86.72 0.99 0.99 1.00 0.99 0.419

73 118 0.71 0.99 0.99 1.00 0.99 0.483

74 106 –23.10 0.98 0.97 0.99 0.95 0.000

75 655 –353.16 0.99 0.99 1.00 0.99 0.001

76 161 –100.71 0.99 0.99 0.99 0.98 0.025

77 598 –513.78 0.98 0.97 0.98 0.96 0.000

78 490 –565.25 0.98 0.98 0.98 0.96 0.000

79 538 –448.06 0.99 0.99 0.99 0.98 0.000

80 1,306 –966.71 0.97 0.96 0.97 0.93 0.000

81 77 –60.26 0.99 0.98 0.99 0.98 0.241

82 63 –42.54 0.98 0.96 0.98 0.97 0.048

83 190 –123.51 0.99 0.99 0.99 0.99 0.046

84 767 –746.79 0.99 0.99 0.99 0.99 0.000

85 733 –708.80 0.99 0.99 0.99 0.99 0.000

86 848 –1,135.13 0.97 0.97 0.97 0.94 0.000

87 108 –86.49 1.00 1.00 1.00 0.99 0.593

88 53 –38.49 1.00 0.99 1.00 0.99 0.995

89 89 –81.56 0.98 0.97 0.99 0.97 0.029

90 105 0.69 0.96 0.95 0.97 0.94 0.000

91 85 0.75 0.98 0.97 0.99 0.97 0.020

92 114 –99.71 0.91 0.88 0.94 0.85 0.000

93 120 0.39 0.98 0.97 0.98 0.97 0.003

94 58 –14.21 0.95 0.93 0.97 0.91 0.000

95 138 0.44 0.98 0.97 0.98 0.96 0.001

97 39 –29.51 0.99 0.98 0.99 0.96 0.149

99 107 –142.24 0.97 0.95 0.97 0.94 0.000

101 64 0.27 0.93 0.90 0.96 0.90 0.000

106 67 0.54 0.98 0.98 0.99 0.97 0.136

107 126 0.49 0.97 0.96 0.98 0.96 0.001

109 125 0.54 0.99 0.99 0.99 0.99 0.172

110 145 0.43 0.98 0.98 0.99 0.97 0.004

111 88 –89.85 0.98 0.97 0.98 0.97 0.034

112 114 0.36 0.99 0.99 0.99 0.98 0.057

113 104 –95.02 1.00 1.00 1.00 1.00 0.965

114 88 –94.12 1.00 0.99 1.00 0.99 0.674

115 77 –42.55 1.00 0.99 1.00 0.99 0.578

118 127 –122.97 0.97 0.96 0.98 0.96 0.001

120 119 –37.31 0.98 0.98 0.99 0.97 0.011

134 88 –69.03 0.99 0.99 0.99 0.98 0.071

135 96 –78.06 0.90 0.86 0.93 0.83 0.000

136 52 0.53 0.86 0.80 0.91 0.77 0.000

137 92 0.80 0.95 0.93 0.97 0.93 0.000
Appendix 3 189

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site

number

(figure 1)

Properties of the calibrated model

Degrees of

freedom

Fit

statistic2

Probability

plot

correlation

coefficient3

Probability

plot

correlation

coefficient,

lower bound

Probability

plot

correlation

coefficient,

upper bound

Shapiro-Wilk

test statistic3

Shapiro-Wilk 

p-value

Total phosphorus—Continued

138 111 –38.98 0.98 0.97 0.98 0.97 0.004

139 98 –47.01 0.99 0.99 1.00 0.99 0.676

145 85 0.26 0.99 0.99 0.99 0.98 0.134

148 65 –27.74 0.99 0.98 0.99 0.97 0.136

149 85 0.47 0.99 0.98 0.99 0.98 0.303

150 93 0.60 0.99 0.98 0.99 0.97 0.057

151 115 –59.89 0.99 0.99 0.99 0.99 0.308

152 56 –43.34 0.97 0.95 0.98 0.95 0.010

153 135 0.22 0.99 0.99 0.99 0.99 0.192

154 127 0.22 0.95 0.93 0.96 0.93 0.000

155 95 0.14 0.97 0.96 0.98 0.96 0.005

156 138 0.35 0.97 0.96 0.98 0.95 0.000

157 102 0.31 0.99 0.99 0.99 0.98 0.129

165 49 –56.32 0.99 0.98 0.99 0.97 0.271

166 53 –79.93 0.99 0.98 0.99 0.98 0.357

169 51 –74.09 0.98 0.96 0.99 0.96 0.042

170 67 0.02 0.98 0.97 0.99 0.97 0.063

171 51 –49.03 0.97 0.96 0.98 0.97 0.187

173 71 –20.85 0.99 0.99 1.00 0.99 0.738

177 58 –63.79 0.98 0.97 0.99 0.97 0.111

178 74 –109.04 0.98 0.97 0.98 0.95 0.007

180 87 –129.71 0.99 0.98 0.99 0.97 0.029

182 55 –66.74 0.99 0.99 1.00 0.99 0.946

183 48 –69.06 0.99 0.98 0.99 0.98 0.613

184 89 –133.30 1.00 0.99 1.00 0.99 0.418

185 70 –79.74 0.99 0.99 0.99 0.98 0.191

186 66 –90.63 0.98 0.98 0.99 0.97 0.076

188 81 0.25 0.97 0.96 0.98 0.96 0.012

193 80 –62.31 0.99 0.99 0.99 0.98 0.090

203 120 –90.79 0.99 0.99 0.99 0.99 0.391

204 123 –122.48 0.97 0.96 0.98 0.95 0.000

205 123 –98.20 0.98 0.97 0.98 0.97 0.002

206 120 –50.32 0.97 0.96 0.98 0.95 0.000

207 123 –90.91 0.99 0.99 0.99 0.98 0.158

208 51 0.70 0.97 0.95 0.98 0.95 0.015

209 122 0.49 0.93 0.91 0.95 0.88 0.000

210 124 0.45 0.94 0.92 0.96 0.90 0.000

211 53 0.53 0.97 0.95 0.98 0.93 0.002

212 60 0.10 0.75 0.65 0.83 0.60 0.000

213 122 0.62 0.94 0.92 0.95 0.90 0.000

214 126 0.76 0.98 0.98 0.99 0.97 0.007

215 51 0.73 0.96 0.93 0.97 0.93 0.003

216 123 –124.48 1.00 0.99 1.00 0.99 0.761

217 49 0.54 0.99 0.98 0.99 0.97 0.194

218 51 0.54 0.99 0.98 0.99 0.99 0.829

219 60 0.58 0.99 0.99 0.99 0.98 0.275

220 69 0.40 0.98 0.97 0.99 0.97 0.074

221 109 –86.96 0.99 0.99 0.99 0.99 0.245

222 105 –85.04 0.96 0.94 0.97 0.93 0.000

223 130 0.11 0.97 0.96 0.98 0.95 0.000

224 88 –56.35 0.99 0.99 0.99 0.98 0.154
190 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site

number

(figure 1)

Properties of the calibrated model

Degrees of

freedom

Fit

statistic2

Probability

plot

correlation

coefficient3

Probability

plot

correlation

coefficient,

lower bound

Probability

plot

correlation

coefficient,

upper bound

Shapiro-Wilk

test statistic3

Shapiro-Wilk 

p-value

Total phosphorus—Continued

225 158 0.44 0.99 0.99 0.99 0.98 0.054

227 138 0.58 0.98 0.97 0.98 0.97 0.002

228 111 –83.32 0.99 0.98 0.99 0.97 0.018

229 122 –83.74 0.99 0.99 0.99 0.98 0.066

230 122 0.28 0.99 0.98 0.99 0.98 0.068

231 416 0.45 0.97 0.96 0.97 0.94 0.000

232 441 –305.84 0.98 0.98 0.98 0.97 0.000

233 124 0.19 0.98 0.97 0.98 0.97 0.003

234 119 –99.78 1.00 1.00 1.00 0.99 0.690

235 118 –103.11 0.99 0.98 0.99 0.98 0.126

236 121 –94.41 1.00 1.00 1.00 1.00 0.944

237 118 –82.39 0.98 0.98 0.99 0.98 0.026

238 122 –113.58 0.97 0.96 0.98 0.95 0.000

239 128 –113.44 0.92 0.90 0.94 0.86 0.000

241 256 0.22 0.95 0.94 0.96 0.92 0.000

242 151 0.45 0.98 0.98 0.99 0.98 0.011

243 326 0.16 0.99 0.99 0.99 0.99 0.041

244 196 –127.16 0.99 0.99 0.99 0.99 0.074

Total nitrogen

1 100 0.37 0.99 0.98 0.99 0.98 0.146

2 100 –3.60 0.97 0.96 0.98 0.95 0.001

3 99 0.17 0.98 0.97 0.98 0.97 0.026

4 147 –42.97 0.91 0.88 0.93 0.84 0.000

5 88 0.42 0.98 0.97 0.98 0.97 0.017

6 55 –34.18 0.99 0.98 0.99 0.97 0.112

7 82 0.68 0.91 0.88 0.94 0.86 0.000

8 102 0.63 0.89 0.86 0.92 0.83 0.000

9 50 –23.53 1.00 0.99 1.00 0.99 0.894

10 83 0.81 0.99 0.99 1.00 0.99 0.693

11 48 0.22 0.97 0.95 0.98 0.95 0.037

12 82 0.83 0.99 0.99 1.00 0.99 0.644

13 52 –29.64 0.98 0.97 0.99 0.95 0.017

14 188 –87.30 0.97 0.97 0.98 0.95 0.000

15 131 0.42 1.00 1.00 1.00 0.99 0.716

16 42 0.19 0.95 0.92 0.97 0.92 0.003

17 43 –16.84 0.99 0.98 0.99 0.98 0.712

18 44 0.90 0.99 0.99 1.00 0.98 0.556

19 76 0.87 0.99 0.99 1.00 0.99 0.531

20 46 0.64 0.94 0.91 0.96 0.91 0.001

21 47 0.08 0.98 0.97 0.99 0.97 0.317

22 42 0.20 0.99 0.99 1.00 0.99 0.897

23 47 0.06 0.99 0.98 0.99 0.98 0.463

24 69 –36.80 0.98 0.98 0.99 0.97 0.138

25 45 0.44 0.97 0.95 0.98 0.96 0.131

26 106 0.71 0.97 0.96 0.98 0.96 0.002

29 44 –13.05 1.00 1.00 1.00 0.99 0.870

31 43 –3.31 0.99 0.99 0.99 0.99 0.824

32 44 0.38 0.95 0.92 0.97 0.93 0.005

33 90 0.16 0.99 0.99 0.99 0.98 0.171

34 80 0.41 0.99 0.99 1.00 0.99 0.889

35 76 0.30 0.93 0.89 0.95 0.88 0.000
Appendix 3 191

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site

number

(figure 1)

Properties of the calibrated model

Degrees of

freedom

Fit

statistic2

Probability

plot

correlation

coefficient3

Probability

plot

correlation

coefficient,

lower bound

Probability

plot

correlation

coefficient,

upper bound

Shapiro-Wilk

test statistic3

Shapiro-Wilk 

p-value

Total nitrogen—Continued

36 179 0.12 0.98 0.98 0.99 0.97 0.000

37 250 0.26 0.99 0.99 1.00 0.99 0.219

38 253 0.31 0.99 0.99 1.00 0.99 0.097

39 271 0.36 0.99 0.98 0.99 0.98 0.000

40 142 –13.50 0.99 0.99 0.99 0.98 0.089

41 326 –191.93 1.00 1.00 1.00 1.00 0.615

42 392 0.22 0.99 0.99 0.99 0.98 0.000

43 384 0.30 0.99 0.99 0.99 0.99 0.001

44 342 0.66 1.00 0.99 1.00 0.99 0.078

45 406 0.19 1.00 1.00 1.00 1.00 0.280

46 80 0.50 0.99 0.99 1.00 0.99 0.693

47 121 0.39 0.98 0.97 0.99 0.97 0.015

48 139 0.25 0.99 0.98 0.99 0.98 0.047

49 76 0.16 0.66 0.55 0.75 0.47 0.000

52 78 0.22 0.95 0.94 0.97 0.93 0.000

53 112 0.23 0.90 0.86 0.92 0.83 0.000

57 54 0.69 0.99 0.99 1.00 0.99 0.753

58 53 0.22 0.99 0.99 0.99 0.98 0.451

59 82 0.47 0.99 0.99 0.99 0.99 0.692

60 96 0.25 0.98 0.97 0.99 0.97 0.019

61 56 0.18 0.97 0.95 0.98 0.95 0.015

62 56 0.35 0.99 0.99 1.00 0.99 0.780

65 116 0.69 0.98 0.97 0.99 0.97 0.005

67 107 0.41 0.78 0.72 0.84 0.64 0.000

71 92 –110.46 0.78 0.71 0.84 0.64 0.000

72 149 0.48 0.98 0.98 0.99 0.98 0.007

73 119 0.40 1.00 1.00 1.00 0.99 0.547

74 102 –26.25 0.95 0.93 0.96 0.91 0.000

76 159 0.53 0.99 0.99 0.99 0.99 0.154

81 77 –41.05 0.94 0.91 0.96 0.90 0.000

82 66 0.22 0.91 0.87 0.94 0.86 0.000

92 116 0.47 0.98 0.97 0.98 0.96 0.002

95 135 0.53 0.99 0.99 0.99 0.99 0.402

97 40 0.75 0.99 0.98 0.99 0.98 0.645

99 107 –75.33 0.95 0.93 0.96 0.91 0.000

100 58 0.03 0.93 0.90 0.95 0.90 0.000

101 63 0.37 0.95 0.93 0.97 0.93 0.001

102 81 0.12 0.99 0.98 0.99 0.97 0.092

103 91 0.56 0.96 0.94 0.97 0.93 0.000

106 67 0.49 0.97 0.95 0.98 0.95 0.007

107 126 0.87 0.99 0.99 0.99 0.99 0.451

108 55 0.44 0.98 0.97 0.99 0.97 0.182

109 127 0.58 0.97 0.96 0.98 0.96 0.001

110 149 0.31 0.98 0.97 0.98 0.97 0.001

111 101 0.64 0.97 0.96 0.98 0.96 0.002

112 126 0.49 0.99 0.99 0.99 0.98 0.031

113 119 –108.38 0.96 0.95 0.97 0.94 0.000

114 101 –86.90 0.99 0.99 1.00 0.99 0.814

115 85 –75.16 0.98 0.97 0.99 0.96 0.011

116 62 0.47 0.96 0.95 0.98 0.95 0.008

118 127 0.50 0.99 0.98 0.99 0.98 0.038

120 119 –54.52 0.69 0.61 0.76 0.50 0.000

124 64 –5.71 0.98 0.98 0.99 0.98 0.204
192 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site

number

(figure 1)

Properties of the calibrated model

Degrees of

freedom

Fit

statistic2

Probability

plot

correlation

coefficient3

Probability

plot

correlation

coefficient,

lower bound

Probability

plot

correlation

coefficient,

upper bound

Shapiro-Wilk

test statistic3

Shapiro-Wilk 

p-value

Total nitrogen—Continued

125 112 –31.14 0.92 0.89 0.94 0.86 0.000

134 90 0.64 0.99 0.99 0.99 0.99 0.501

135 95 –23.83 0.82 0.75 0.86 0.69 0.000

136 55 0.38 0.88 0.82 0.92 0.81 0.000

137 92 0.76 0.96 0.95 0.97 0.95 0.000

138 112 0.78 1.00 1.00 1.00 1.00 0.991

139 98 0.64 0.94 0.92 0.96 0.91 0.000

145 77 –30.58 0.99 0.99 0.99 0.98 0.333

146 67 –54.75 0.97 0.96 0.98 0.94 0.002

147 64 –42.89 0.97 0.95 0.98 0.93 0.001

148 67 0.19 0.99 0.98 0.99 0.98 0.344

149 86 0.30 0.98 0.98 0.99 0.98 0.135

150 92 0.49 1.00 1.00 1.00 0.99 0.816

151 117 0.35 1.00 0.99 1.00 0.99 0.813

152 54 –32.57 0.99 0.99 0.99 0.98 0.534

153 128 0.38 0.99 0.99 1.00 0.98 0.085

154 126 –61.52 0.97 0.96 0.98 0.95 0.000

155 92 –40.63 0.99 0.99 1.00 0.99 0.943

156 128 0.49 0.99 0.99 0.99 0.98 0.048

157 103 0.24 0.98 0.97 0.99 0.97 0.025

173 72 –16.29 0.98 0.97 0.99 0.98 0.152

176 104 –69.14 0.96 0.94 0.97 0.93 0.000

179 59 0.00 0.98 0.98 0.99 0.98 0.290

182 55 0.63 0.98 0.97 0.99 0.97 0.216

196 267 0.32 0.98 0.98 0.99 0.97 0.000

199 228 0.31 0.98 0.98 0.99 0.97 0.000

201 214 0.39 0.99 0.98 0.99 0.98 0.001

202 254 0.30 0.99 0.98 0.99 0.98 0.000

208 50 0.45 0.99 0.99 1.00 0.99 0.945

209 118 –66.85 0.97 0.96 0.98 0.95 0.000

210 118 –55.37 0.97 0.96 0.98 0.94 0.000

212 58 –22.90 0.95 0.93 0.97 0.92 0.000

213 120 –44.45 0.99 0.98 0.99 0.98 0.041

214 125 0.48 0.90 0.87 0.92 0.83 0.000

215 51 –32.11 0.97 0.95 0.98 0.94 0.004

217 48 0.48 0.99 0.99 0.99 0.97 0.249

218 49 0.84 0.98 0.97 0.99 0.97 0.179

219 58 –35.66 0.98 0.97 0.99 0.97 0.156

220 69 0.80 0.98 0.98 0.99 0.97 0.049

221 107 –41.38 0.95 0.93 0.96 0.91 0.000

222 106 –30.94 0.93 0.90 0.95 0.88 0.000

223 133 0.64 0.89 0.85 0.91 0.82 0.000

224 85 –7.48 0.99 0.99 1.00 0.99 0.692

225 157 0.72 0.98 0.98 0.99 0.97 0.002

227 137 –29.61 0.99 0.99 0.99 0.99 0.142

228 110 –11.39 0.99 0.99 1.00 0.99 0.272

231 397 0.47 1.00 1.00 1.00 1.00 0.433

232 424 –259.96 0.96 0.95 0.96 0.92 0.000

241 238 0.40 0.98 0.98 0.99 0.97 0.000

242 127 –32.74 0.93 0.91 0.95 0.89 0.000

243 258 0.55 1.00 1.00 1.00 1.00 0.586

244 196 –108.51 1.00 1.00 1.00 0.99 0.357
Appendix 3 193

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site

number

(figure 1)

Properties of the calibrated model

Degrees of

freedom

Fit

statistic2

Probability

plot

correlation

coefficient3

Probability

plot

correlation

coefficient,

lower bound

Probability

plot

correlation

coefficient,

upper bound

Shapiro-Wilk

test statistic3

Shapiro-Wilk 

p-value

Nitrate

1 98 0.49 0.99 0.99 0.99 0.98 0.210

2 100 0.65 1.00 0.99 1.00 0.99 0.690

3 96 –75.77 0.93 0.91 0.95 0.89 0.000

4 146 –47.79 0.86 0.82 0.89 0.77 0.000

5 88 0.67 0.98 0.97 0.99 0.97 0.022

6 55 0.43 0.98 0.98 0.99 0.98 0.348

7 84 0.85 0.97 0.96 0.98 0.95 0.002

8 102 0.58 0.86 0.81 0.90 0.77 0.000

9 51 –47.34 0.99 0.99 0.99 0.99 0.852

10 83 0.88 1.00 0.99 1.00 0.99 0.726

11 48 0.48 0.97 0.95 0.98 0.95 0.036

12 83 0.79 0.99 0.99 0.99 0.99 0.571

13 50 –61.05 0.98 0.97 0.99 0.95 0.015

14 190 –186.88 0.95 0.94 0.96 0.91 0.000

15 132 0.41 0.97 0.96 0.98 0.95 0.000

16 41 0.58 0.97 0.96 0.98 0.97 0.172

17 43 –43.15 0.97 0.96 0.98 0.97 0.164

18 43 0.89 0.99 0.99 0.99 0.97 0.274

19 77 0.86 0.99 0.98 0.99 0.98 0.107

20 45 0.74 0.95 0.93 0.97 0.94 0.010

21 46 0.10 0.94 0.90 0.96 0.91 0.001

22 44 0.23 0.99 0.99 1.00 0.98 0.556

23 47 0.21 0.99 0.99 1.00 0.99 0.899

24 69 –76.59 0.97 0.96 0.98 0.96 0.018

25 43 0.70 0.91 0.86 0.95 0.87 0.000

26 106 0.75 0.99 0.98 0.99 0.98 0.151

29 43 –33.45 0.99 0.99 1.00 0.99 0.907

31 42 –22.75 0.98 0.97 0.99 0.97 0.269

32 41 –31.77 0.95 0.92 0.97 0.94 0.009

33 89 0.20 0.98 0.97 0.98 0.96 0.009

34 81 0.29 0.97 0.95 0.98 0.95 0.003

35 78 0.19 0.82 0.75 0.87 0.70 0.000

36 176 0.51 0.99 0.98 0.99 0.98 0.004

37 249 0.38 1.00 1.00 1.00 0.99 0.564

38 291 0.60 0.99 0.99 0.99 0.99 0.005

39 271 0.44 1.00 0.99 1.00 0.99 0.052

40 144 0.72 0.96 0.95 0.97 0.94 0.000

41 340 –436.92 0.92 0.90 0.93 0.86 0.000

42 415 0.20 0.97 0.97 0.98 0.95 0.000

43 409 –311.23 0.98 0.97 0.98 0.96 0.000

44 361 –374.33 0.95 0.94 0.96 0.92 0.000

45 413 –401.55 0.98 0.97 0.98 0.95 0.000

50 117 –99.39 0.97 0.97 0.98 0.96 0.001

65 132 –76.11 0.99 0.98 0.99 0.98 0.032

66 158 0.28 0.88 0.84 0.90 0.80 0.000

71 93 –115.07 0.73 0.64 0.80 0.56 0.000

72 148 –101.18 0.97 0.97 0.98 0.96 0.000

73 127 0.31 0.98 0.98 0.99 0.97 0.009

74 104 –75.70 0.98 0.98 0.99 0.96 0.005

76 158 –195.31 0.98 0.98 0.99 0.97 0.004
194 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site

number

(figure 1)

Properties of the calibrated model

Degrees of

freedom

Fit

statistic2

Probability

plot

correlation

coefficient3

Probability

plot

correlation

coefficient,

lower bound

Probability

plot

correlation

coefficient,

upper bound

Shapiro-Wilk

test statistic3

Shapiro-Wilk 

p-value

Nitrate—Continued

81 78 –101.31 0.99 0.99 0.99 0.99 0.691

82 65 –104.84 0.99 0.98 0.99 0.98 0.445

88 58 –91.42 1.00 0.99 1.00 0.99 0.669

92 117 –110.00 0.97 0.96 0.98 0.96 0.001

95 136 –54.92 0.99 0.99 0.99 0.99 0.135

96 89 –73.31 0.91 0.87 0.93 0.85 0.000

98 38 0.66 0.99 0.98 0.99 0.98 0.564

99 106 –143.98 0.98 0.98 0.99 0.98 0.061

100 58 0.33 0.98 0.97 0.99 0.97 0.103

101 62 –54.08 0.97 0.95 0.98 0.95 0.007

102 80 –97.42 0.99 0.98 0.99 0.98 0.152

103 90 0.80 1.00 1.00 1.00 0.99 0.896

104 126 –156.62 0.96 0.94 0.97 0.93 0.000

105 122 –144.49 0.87 0.83 0.90 0.78 0.000

106 66 0.72 0.94 0.91 0.96 0.91 0.000

107 126 0.90 0.99 0.98 0.99 0.98 0.087

108 55 0.48 0.91 0.86 0.94 0.86 0.000

109 125 –111.75 0.88 0.84 0.91 0.79 0.000

110 145 –220.83 0.97 0.96 0.98 0.95 0.000

111 101 –174.36 0.99 0.99 0.99 0.99 0.525

112 126 –158.62 0.92 0.90 0.94 0.87 0.000

113 119 –169.77 1.00 0.99 1.00 1.00 0.955

114 100 –147.39 0.97 0.96 0.98 0.96 0.002

115 83 –131.67 0.98 0.98 0.99 0.97 0.026

116 61 –75.56 0.99 0.98 0.99 0.99 0.605

117 114 –110.67 0.98 0.98 0.99 0.97 0.004

118 127 –120.81 0.90 0.87 0.92 0.83 0.000

119 57 –60.41 0.99 0.99 0.99 0.98 0.445

120 120 –106.35 0.58 0.48 0.67 0.36 0.000

121 128 –122.64 0.98 0.98 0.99 0.97 0.008

122 59 –32.48 0.98 0.97 0.99 0.97 0.157

123 108 –72.99 0.96 0.94 0.97 0.93 0.000

124 70 0.27 0.98 0.98 0.99 0.97 0.088

125 125 –19.85 0.99 0.98 0.99 0.98 0.066

126 34 –29.81 0.97 0.95 0.98 0.94 0.026

127 27 –28.79 1.00 0.99 1.00 0.99 0.954

128 96 0.45 0.94 0.92 0.96 0.91 0.000

129 83 –124.13 0.99 0.99 1.00 0.98 0.233

130 109 0.78 1.00 1.00 1.00 0.99 0.503

131 98 0.62 1.00 1.00 1.00 0.99 0.851

132 47 0.69 0.87 0.80 0.92 0.79 0.000

133 103 0.85 0.99 0.98 0.99 0.97 0.029

134 99 0.66 0.99 0.98 0.99 0.98 0.218

135 97 0.32 0.74 0.66 0.81 0.58 0.000

136 55 0.44 0.87 0.81 0.92 0.79 0.000

137 92 0.81 0.95 0.93 0.97 0.93 0.000

138 112 0.72 0.98 0.98 0.99 0.98 0.042

139 98 0.59 0.94 0.91 0.95 0.90 0.000

140 49 –82.06 0.98 0.97 0.99 0.96 0.041

141 125 –152.39 0.99 0.99 1.00 0.99 0.327
Appendix 3 195

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site

number

(figure 1)

Properties of the calibrated model

Degrees of

freedom

Fit

statistic2

Probability

plot

correlation

coefficient3

Probability

plot

correlation

coefficient,

lower bound

Probability

plot

correlation

coefficient,

upper bound

Shapiro-Wilk

test statistic3

Shapiro-Wilk 

p-value

Nitrate—Continued

142 125 –177.31 0.99 0.99 1.00 0.99 0.713

143 124 –159.38 0.98 0.97 0.98 0.96 0.001

144 124 0.54 0.93 0.90 0.94 0.87 0.000

145 81 –97.42 0.98 0.98 0.99 0.97 0.071

146 66 –53.72 0.97 0.95 0.98 0.95 0.005

147 64 –59.05 0.99 0.98 0.99 0.98 0.332

148 65 –53.63 0.96 0.94 0.97 0.92 0.000

149 86 –108.53 0.99 0.99 0.99 0.99 0.478

150 92 –130.87 0.99 0.99 0.99 0.99 0.656

151 116 –121.25 0.99 0.99 0.99 0.98 0.057

152 53 –45.31 0.97 0.96 0.98 0.96 0.040

153 132 0.40 1.00 0.99 1.00 0.99 0.261

154 127 –51.81 0.97 0.96 0.98 0.96 0.000

155 91 –26.32 0.97 0.96 0.98 0.95 0.001

156 134 0.43 0.99 0.99 1.00 0.99 0.181

157 100 –102.46 0.96 0.95 0.97 0.94 0.000

158 107 –76.22 1.00 0.99 1.00 0.99 0.557

159 58 –58.65 0.99 0.98 0.99 0.98 0.395

160 59 –53.21 0.96 0.94 0.97 0.94 0.006

161 88 –108.41 0.99 0.99 0.99 0.99 0.635

162 110 –153.37 0.96 0.95 0.97 0.94 0.000

163 58 –61.54 0.84 0.76 0.89 0.73 0.000

164 52 –85.32 0.96 0.94 0.98 0.94 0.010

167 78 –83.67 0.96 0.94 0.97 0.93 0.000

168 71 –59.16 0.98 0.97 0.98 0.97 0.057

172 122 –68.89 0.80 0.75 0.85 0.67 0.000

174 55 –36.65 0.99 0.99 1.00 0.98 0.597

175 111 0.73 0.99 0.98 0.99 0.97 0.012

177 59 –38.19 1.00 0.99 1.00 0.99 0.904

181 83 0.69 0.97 0.96 0.98 0.96 0.013

187 65 –36.08 0.99 0.99 1.00 0.98 0.491

189 105 –94.03 0.99 0.99 1.00 0.99 0.824

190 105 –115.54 0.95 0.94 0.97 0.93 0.000

191 110 –134.53 0.97 0.95 0.98 0.95 0.000

192 119 –102.66 0.98 0.97 0.98 0.97 0.003

194 220 0.15 1.00 1.00 1.00 0.99 0.179

195 222 0.31 0.99 0.99 0.99 0.98 0.011

197 305 0.33 0.99 0.99 1.00 0.99 0.030

198 220 0.54 0.99 0.99 0.99 0.98 0.002

199 231 0.51 0.98 0.97 0.98 0.96 0.000

200 311 0.47 0.97 0.97 0.98 0.96 0.000

201 213 –187.44 1.00 1.00 1.00 0.99 0.547

205 125 0.78 0.98 0.97 0.99 0.97 0.005

207 123 –89.76 0.98 0.97 0.99 0.96 0.002

208 50 0.56 0.99 0.98 0.99 0.98 0.634

209 122 0.61 0.96 0.95 0.97 0.94 0.000

210 122 0.60 1.00 1.00 1.00 1.00 0.983

213 122 0.67 0.99 0.99 0.99 0.99 0.219

215 52 0.71 0.99 0.98 0.99 0.99 0.797

217 50 0.62 0.98 0.97 0.99 0.98 0.505
196 Nutrient Trends in Streams and River of the United States, 1993–2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load 

from 1993 to 2003.—Continued

[CI, confidence interval; OLS, ordinary least squares; AMLE, adjusted maximum likelihood estimation]

Site

number

(figure 1)

Properties of the calibrated model

Degrees of

freedom

Fit

statistic2

Probability

plot

correlation

coefficient3

Probability

plot

correlation

coefficient,

lower bound

Probability

plot

correlation

coefficient,

upper bound

Shapiro-Wilk

test statistic3

Shapiro-Wilk 

p-value

Nitrate—Continued

218 50 0.80 0.99 0.99 0.99 0.99 0.826

224 85 –26.20 0.98 0.97 0.98 0.96 0.011

225 156 –183.66 0.96 0.95 0.97 0.94 0.000

226 125 0.53 0.99 0.99 0.99 0.98 0.071

228 110 –46.44 0.98 0.98 0.99 0.97 0.008

229 122 –57.13 0.98 0.98 0.99 0.97 0.007

234 121 0.70 0.95 0.93 0.96 0.92 0.000

235 121 –89.90 0.98 0.97 0.99 0.96 0.002

237 121 –115.26 0.98 0.97 0.98 0.97 0.008

238 124 0.73 0.97 0.96 0.98 0.96 0.001

239 125 0.67 0.98 0.98 0.99 0.97 0.007

240 115 –36.90 0.99 0.99 0.99 0.98 0.065

241 257 0.48 0.97 0.97 0.98 0.96 0.000

242 149 0.77 0.98 0.97 0.98 0.97 0.001

243 526 0.71 0.97 0.96 0.97 0.94 0.000

244 196 –134.94 0.97 0.96 0.97 0.94 0.000

1

Model specification values: (1) log streamflow; (2) log streamflow and log streamflow squared; (3) log streamflow and time; (4) log streamflow and sine/

cosine of time; (5) log streamflow, log streamflow squared, and time; (6) log streamflow, log streamflow squared, and sine/cosine of time; (7) log streamflow, 

time, and sine/cosine of time; (8) log streamflow, log streamflow squared, time, and since/cosine of time; (9) log streamflow, log streamflow squared, time, time 

squared, and sine/cosine of time.

2

Fit statistic is R-square for ordinary least squares model calibration method and the value of the likelihood function for the adjusted maximum likelihood 

model calibration method.

3

Probability plot correlations and Shapiro-Wilk tests indicate whether samples are from a normal distribution (Helsel and Hirsch, 1992).

Publishing support provided by:

Denver Publishing Service Center, Denver, Colorado

Manuscript approved for publication, October 21, 2008

Edited by Chelsea Carr

Graphics and layout by Joy Monson

For more information concerning this publication, contact:

Director, USGS Colorado Water Science Center

Box 25046, Mail Stop 415

Denver, CO 80225

(303) 236-4882

Or visit the Colorado Water Science Center Web site at:

http://co.water.usgs.gov/

This publication is available online at:

http://pubs.usgs.gov/sir/2008/5202/
Printed on recycled paper