National Water-Quality Assessment Program

Nutrient and Suspended-Sediment Transport and Trends in the 

Columbia River and Puget Sound Basins, 1993–2003

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2007–5186
Cover: Photograph of Columbia River Gorge at sunrise, looking east. 

(Photograph courtesy of Columbia River USGS Interdisciplinary Science 

Explorer (CRUISE) website.)

Insets (from left to right): Mount Rainier, Washington. (Photograph by Jeremy 

Woodhouse through Getty Images, date unknown.)

Hop fields near Moxee, Washington. (Photograph taken by Hank Johnson, U.S. 

Geological Survey, 2001.)

Seattle, Washington skyline. (Photograph by Jeremy Woodhouse through 

Getty Images, date unknown.)
Nutrient and Suspended-Sediment Transport and 

Trends in the Columbia River and Puget Sound 

Basins, 1993–2003

By Daniel R. Wise, Frank A. Rinella, III, Joseph F. Rinella, Greg J. Fuhrer, Sandra S. Embrey, 

Gregory M. Clark, Gregory E. Schwarz, and Steven Sobieszczyk

National Water-Quality Assessment Program

Scientific Investigations Report 2007–5186

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

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Suggested citation:

Wise, D.R., Rinella, F.A., III, Rinella, J.F., Fuhrer, G.J., Embrey, S.S., Clark, G.E., Schwarz, G.E., Sobieszczyk, S., 2007, 

Nutrient and suspended-sediment transport and trends in the Columbia River and Puget Sound Basins, 1993–2003: 

U.S. Geological Survey Scientific Investigations Report 2007–5186, 116 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 to 2001, the NAWQA Program 

completed interdisciplinary assessments and established a baseline understanding of water-quality conditions in 51 

of the Nation’s river basins and aquifers, referred to as Study Units (http://water.usgs.gov/nawqa/studyu.html). 

In the second decade of the Program (2001–2012), a major focus is on regional assessments of water-quality 

conditions and trends. These regional assessments are based on major river basins and principal aquifers, which 

encompass larger regions of the country than the Study Units. Regional assessments extend the findings in the Study 

Units by filling critical gaps in characterizing the quality of surface water and ground water, and by determining 

status and trends at sites that have been consistently monitored for more than a decade. In addition, the regional 

assessments continue to build an understanding of how natural features and human activities affect water quality. 

Many of the regional assessments employ modeling and other scientific tools, developed on the basis of data 

collected at individual sites, to help extend knowledge of water quality to unmonitored, yet comparable areas within 

the regions. The models thereby enhance the value of our existing data and our understanding of the hydrologic 

system. In addition, the models are useful in evaluating various resource-management scenarios and in predicting 

how our actions, such as reducing or managing nonpoint and point sources of contamination, land conversion, and 

altering flow and (or) pumping regimes, are likely to affect water conditions within a region.

Other activities planned during the second decade include continuing national syntheses of information on pesticides, 

volatile organic compounds (VOCs), nutrients, selected trace elements, and aquatic ecology; and continuing national 

topical studies on the fate of agricultural chemicals, effects of urbanization on stream ecosystems, bioaccumulation of 

mercury in stream ecosystems, effects of nutrient enrichment on stream ecosystems, and transport of contaminants 

to public-supply wells.

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 water-resource 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.

 Robert M. Hirsch

Associate Director for Water
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Contents

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

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

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

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

Description of Columbia River and Puget Sound Basins ........................................................................2

Columbia River Basin ...........................................................................................................................2

Puget Sound Basin ...............................................................................................................................4

Data Sources..................................................................................................................................................4

Discrete Water-Quality Samples........................................................................................................5

Daily Mean Streamflow .......................................................................................................................5

Methods of Analysis......................................................................................................................................8

Load Estimation.....................................................................................................................................8

Selection of Analysis Period...............................................................................................................8

Criteria for Site Selection ..................................................................................................................10

Data Assumptions and Censoring Process....................................................................................11

Influence of Sampling and Analytical Techniques........................................................................11

Trends in Streamflow, Load, and Concentration ...........................................................................13

Non-Flow-Adjusted Trend in Concentration..........................................................................16

Trend in Load ..............................................................................................................................16

Flow-Adjusted Trend in Concentration...................................................................................16

Trend in Streamflow ..................................................................................................................17

Interpretation of Trends ............................................................................................................17

Estimation of Point-Source Nutrient Loads....................................................................................17

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins ....19

Summary of Direct Point-Source Nutrient Discharges to Columbia River and Largest 

Tributaries...............................................................................................................................20

Columbia River System ......................................................................................................................20

Willamette River System ...................................................................................................................29

Snake River System............................................................................................................................37

Puget Sound Basin .............................................................................................................................37

Nutrients and Suspended-Sediment Yields.............................................................................................42

Regional Patterns in Yields................................................................................................................42

Influence of Point Sources................................................................................................................45

Influence of Catchment Characteristics on Nutrient and Suspended-Sediment Yields ........48

Trends in Nutrients and Suspended-Sediment, 1993–2003...................................................................49

Trends in Streamflow .........................................................................................................................50

General Patterns in Concentration Trends .....................................................................................51

Total Nitrogen ......................................................................................................................................52

Total Phosphorus ................................................................................................................................54

Suspended Sediment .........................................................................................................................56

Trends in Relation to Changes in Nutrient Sources and Landscape Characteristics.............59
vi

Summary and Conclusions.........................................................................................................................60

Transport of Nutrients and Suspended-Sediment.........................................................................60

Trends in Nutrients and Suspended-Sediment, 1993–2003..........................................................61

Acknowledgments.......................................................................................................................................62

References Cited..........................................................................................................................................62

Appendix A. Results of Loadest Modeling, Flow-Weighted Concentrations, Yields, 

Drainage Areas, and Mean Annual Streamflows for Total Nitrogen, Total 

Phosphorus, and Suspended Sediment for Water Years 1997, 2000, and 2001....................75

Appendix B. Methodology for Computing Trends in Annual Streamflow, Trends in 

Load, and Flow- and Non-Flow-Adjusted Trends in Concentration.....................................113

References Cited........................................................................................................................................115

Contents—Continued

Figures

Figure 1. Map showing Columbia River and Puget Sound Basins and locations of 

water-quality monitoring site............................................................... 3

Figure 2. Graph showing daily mean discharge for the Columbia River at Beaver Army 

Terminal, Oregon, water years 1993–2003 ................................................ 4

Figure 3. Graph showing annual mean daily streamflow in the Willamette River at 

Portland, Oregon, water years 1973–2003 ................................................ 9

Figure 4. Graph showing daily mean streamflow in the Willamette River at Portland, 

Oregon, water years 1993–2003............................................................ 9

Figure 5. Graph showing comparison of monthly mean streamflow during water year 

2000 with mean monthly streamflow during water years 1973–2003 for the 

Willamette River at Portland, Oregon ................................................... 10

Figure 6. Graph showing statistical distribution of the 91 delineated catchment 

drainage areas in the Columbia River and Puget Sound basins ..................... 12

Figure 7. Graphs showing relations between concentrations of total nitrogen and 

suspended sediment and discharge for Willamette River at Portland, Oregon, 

water years 1993–2003 ..................................................................... 14

Figure 8. Graphs showing examples of data smoothing demonstrating temporal variability 

of daily mean streamflow and instantaneous total nitrogen concentrations for 

Willamette River at Portland, Oregon, water years 1993–2003 ........................ 15

Figure 9. Maps showing estimated point-source loads divided into quartiles for total 

nitrogen and total phosphorus, Columbia River basin, water year 2000 ............ 18

Figure 10. Pie diagrams showing estimated discharges from point sources to the 

Columbia River that exceed the 75th percentile of all point sources for total 

nitrogen and total phosphorus, water year 2000 ....................................... 19

Figure 11. Maps showing locations of sampling sites in the Columbia River and its

tributaries and selected point sources discharging directly to the Columbia 

River, Oregon and Washington, water year 2000 ....................................... 21

Figure 12. Graphs showing annual mean discharge of total nitrogen loads in the 

Columbia River, and relative total nitrogen load contributions from Columbia 

River monitored tributaries and point sources, Oregon and Washington, 

water year 2000 .............................................................................. 23
vii

Figures—Continued

Figure 13. Graphs showing annual mean discharge of total phosphorus loads in the 

Columbia River, and relative total phosphorus load contributions from 

Columbia River monitored tributaries and point sources, Oregon and 

Washington, water year 2000 ............................................................ 24

Figure 14. Graphs showing annual mean discharge of suspended-sediment loads in the 

Columbia River and relative suspended-sediment load contributions from 

Columbia River monitored tributaries, Oregon and Washington, water year 

2000 .......................................................................................... 28

Figure 15. Maps showing locations of sampling sites in the Willamette River and its 

tributaries, and selected point sources discharging directly to the Willamette 

River, Oregon, water year 2000 ............................................................ 30

Figure 16. Graphs showing annual mean discharge of total nitrogen loads in the 

Willamette River and relative total nitrogen load contributions from 

Willamette River monitored tributaries and point sources, Oregon, water 

year 2000 .................................................................................... 34

Figure 17. Graphs showing annual mean discharge of total phosphorus loads in the 

Willamette River and relative total phosphorus contributions from Willamette 

River monitored tributaries and point sources, Oregon, water year 2000 ............ 35

Figure 18. Graphs showing Annual mean discharge of suspended-sediment loads in the 

Willamette River and relative suspended-sediment load contributions from 

Willamette River monitored tributaries, Oregon, water year 2000..................... 36

Figure 19. Maps showing locations of sampling sites in the Snake River and its 

tributaries, and selected point sources discharging directly to the Snake 

River, Washington, Oregon, Idaho, and Wyoming, water year 2000 .................. 38

Figure 20. Graphs showing annual mean discharge of total nitrogen, total phosphorus, 

and suspended sediment loads in the Snake River, Wyoming, Idaho, and 

Washington, water year 2000 ............................................................ 40

Figure 21. Maps showing locations of sampling sites in Puget Sound tributaries, and 

selected point sources discharging directly to the Puget Sound and its major 

tributaries, Washington, water year 2000 ................................................ 41

Figure 22. Pie diagrams showing contribution of monitored tributary and estimated 

point-source loads of total nitrogen, total phosphorus, and suspended 

sediment to the Puget Sound basin, Washington, water year 2000 .................. 42

Figure 23. Piper diagram showing land use for the 91 catchments with delineated 

drainage areas for the Columbia River and Puget Sound Basins, calendar 

year 2000 .................................................................................... 43

Figure 24. Maps showing estimated annual catchment yields divided into quartiles for 

total nitrogen, total phosphorus, and sediment for the Columbia River and 

Puget Sound Basins, water year 2000 ................................................... 44

Figure 25. Maps showing estimated annual point-source loads as a percentage of 

annual in stream loads for total nitrogen and total phosphorus, Columbia 

River and Puget Sound basins, water year 2000 ....................................... 46

Figure 26. Piper diagram showing summary of annual nutrient load to delineated 

catchments for total nitrogen and total phosphorus in the Columbia River 

and Puget Sound Basins, water year 2000 and calendar year 2002 .................. 47

Figure 27. Graphs showing distribution of flow-adjusted trends in concentration of total 

nitrogen in percentage per year and milligrams per liter per year, Columbia 

River and Puget Sound basins, water years 1993–2003................................. 51
viii

Figures—Continued

Figure 28. Graphs showing distribution of flow-adjusted trends in concentration of total 

phosphorous in percentage per year and milligrams per liter per year, 

Columbia River and Puget Sound basins, water years 1993–2003..................... 51

Figure 29. Graphs showing distribution of flow-adjusted trends in concentration of 

suspended sediment in percentage per year and milligrams per liter per year, 

Columbia River and Puget Sound basins, for water years 1993–2003 ............... 52

Figure 30. Map showing flow-adjusted trends in concentration of total nitrogen, 

Columbia River and Puget Sound basins, water years 1993–2003..................... 54

Figure 31. Map showing flow-adjusted trends in concentrations of total phosphorus, 

Columbia River and Puget Sound basins, water years 1993–2003..................... 56

Figure 32. Map showing flow-adjusted trends in concentration of suspended sediment, 

Columbia River and Puget Sound basins, water years 1993–2003..................... 58

Figure 33. Graph showing measured suspended-sediment concentrations, Hood River, 

Oregon, water years 1993–2003............................................................ 58

Tables

Table 1. Description of water-quality monitoring sites in the Columbia and Puget

Sound River Basins ........................................................................ 6

Table 2. Streamflow sites used for nutrient and suspended-sediment load

computations in the Columbia River and Puget Sound basins for selected

water years ................................................................................. 10

Table 3. Rules for computing total nitrogen concentration from total Kjeldahl nitrogen

and dissolved nitrite plus nitrate as nitrogen............................................. 12

Table 4. Comparison of total nitrogen, total phosphorus, and suspended-sediment

loads based on sampling results from co-located sites operated by U.S.

Geological Survey and other agencies ................................................... 13

Table 5. Industrial categories contributing to total nitrogen and total phosphorus

loads in the Columbia and Puget Sound basins.......................................... 18

Table 6. Quartile ranges for total nitrogen and total phosphorus point-source loads in

the Columbia and Puget Sound basins, water year 2000 .............................. 19

Table 7. Accounting for annual mean streamflow in the main stem of the Columbia

River, water year 2000 ..................................................................... 22

Table 8. Annual mean discharge of total nitrogen, total phosphorus, and suspended

sediment loads in the Columbia River, monitored Columbia River tributaries,

and point sources discharging directly to the Columbia River, Oregon and

Washington, water year 2000 ............................................................ 25

Table 9. Relative discharge of total nitrogen, total phosphorus, and suspended

sediment loads from three major tributaries to Columbia River between

Vernita Bridge, Washington, and Warrendale, Oregon, water year 2000 ............ 29
ix

Tables—Continued

Table 10. Mean annual discharge of total nitrogen, total phosphorus, and suspended

sediment loads in the Willamette River, monitored Willamette River

tributaries, and point sources discharging directly to the Willamette River,

Oregon, water year 2000 .................................................................. 31

Table 11. Accounting for annual mean streamflow in the Willamette River, Oregon,

water year 2000 .............................................................................. 33

Table 12. Annual mean discharges of total nitrogen, total phosphorus, and suspended

sediment loads in the Snake River, monitored Snake River tributaries, and

point sources discharging directly to the Snake River, Wyoming, Idaho, and

Washington, water year 2000 ............................................................ 39

Table 13. Summary of annual yields for total nitrogen, total phosphorus, and suspended

sediment in the Columbia River and Puget Sound basins, water years 1997,

2000, and 2001 .............................................................................. 43

Table 14. Quartile ranges for total nitrogen, total phosphorus, and suspended sediment

annual yields for the Columbia River and Puget Sound basins, water year

2000 .......................................................................................... 45

Table 15. Summary of total point-source annual nutrient loads as a percentage of

predicted instream annual loads, Columbia River and Puget Sound basins,

water year 2000 .............................................................................. 46

Table 16. Results from multiple linear regression of catchment characteristics on

catchment yields in the Columbia River and Puget Sound basins, water year

2000 .......................................................................................... 49

Table 17. Number of sites with significant decreasing, increasing, or no flow-adjusted

trend in concentration by collecting/analyzing agency in the Columbia River

and Puget Sound basins, water years 1993–2003 ....................................... 50

Table 18. Summary of flow-adjusted trends in concentration of total nitrogen, total

phosphorus, and suspended sediment in the Columbia River and Puget Sound

basins, water years 1993–2003 ............................................................ 52

Table 19. Flow-adjusted trends in concentration, non-flow-adjusted trends in

concentration, and trends in annual loads for total nitrogen in the Columbia

River and Puget Sound basins, water years 1993–2003................................. 53

Table 20. Flow-adjusted trends in concentration, non-flow-adjusted trends in

concentration, and trends in annual loads for total phosphorus in the

Columbia River and Puget Sound basins, water years 1993–2003..................... 55

Table 21. Flow-adjusted trends in concentration, non-flow-adjusted trends in

concentration, and trends in annual loads for suspended sediment in the

Columbia River and Puget Sound basins, water years 1993–2003..................... 57

Table 22. Summary of sources and stream annual loads for total nitrogen and total

phosophorus in the Columbia River and Puget Sound basins, water year 2000

and calendar year 2002 ..................................................................... 64
x

Conversion Factors, Vertical Datums, and Abbreviations 

and Acronyms

Conversion Factors 

Multiply By To obtain

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

mile (mi) 1.609 kilometer (km)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

pound per day (lb/d) 0.4536 kilogram per day (kg/d)

pound per year (lb/yr) 0.4536 kilogram per year (kg/yr)

pound per year per square mile [(lb/yr)/mi2

] 0.1751 kilogram per year per square kilometer

square mile (mi2

) 2.590 square kilometer (km2)

ton per day (ton/d) 0.9072 metric ton per day

ton per year (ton/yr) 0.9072 metric ton per year

ton per year per square mile [(ton/yr)/mi2

] 0.3503 metric ton per year per square kilometer

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

Datums

Vertical coordinate information is referenced to the North American Vertical Datum 1988 (NAVD 

88).

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

Projections are from the Lambert Conformal Conic (Oregon Lambert Projection).
xi

Conversion Factors, Vertical Datums, and 

Abbreviations and Acronyms—Continued

Abbreviations and Acronyms

Abbreviations and 

Acronyms Meaning

AMLE Adjusted Maximum Likelihood Estimation

CWS Clean Water Service

CY calendar year

DMR Discharge Monitoring Report

Exchange Pacific Northwest Water-Quality Exchange

FATC flow-adjusted trend in concentration

NAWQA National Water-Quality Assessment

NFATC non-flow-adjusted trend in concentration

NPDES National Pollution Discharge Elimination System

NWIS National Water Information System

ODEQ Oregon Department of Environmental Quality

ORWD Oregon Water Resources Division

Pcode parameter code

PCS Permit Compliance System

RM river mile

SIC standard industrial classification

SS suspended sediment

STORET STOret and RETrieval

TKN total Kjeldahl nitrogen

TMDL Total Maximum Daily Load

TN total nitrogen as N

TP total phosphorus as P

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

WDOE Washington State Department of Ecology

WWTP wastewater treatment plant

WY water year
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Abstract

This study focused on three areas that might be of interest 

to water-quality managers in the Pacific Northwest: (1) 

annual loads of total nitrogen (TN), total phosphorus (TP) and 

suspended sediment (SS) transported through the Columbia 

River and Puget Sound Basins, (2) annual yields of TN, 

TP, and SS relative to differences in landscape and climatic 

conditions between subbasin catchments (drainage basins), 

and (3) trends in TN, TP, and SS concentrations and loads in 

comparison to changes in landscape and climatic conditions 

in the catchments. During water year 2000, an average 

streamflow year in the Pacific Northwest, the Columbia River 

discharged about 570,000 pounds per day of TN, about 55,000 

pounds per day of TP, and about 14,000 tons per day of SS 

to the Pacific Ocean. The Snake, Yakima, Deschutes, and 

Willamette Rivers contributed most of the load discharged 

to the Columbia River. Point-source nutrient loads to the 

catchments (almost exclusively from municipal wastewater 

treatment plants) generally were a small percentage of the 

total in-stream nutrient loads; however, in some reaches of the 

Spokane, Boise, Walla Walla, and Willamette River Basins, 

point sources were responsible for much of the annual instream nutrient load. Point-source nutrient loads generally 

were a small percentage of the total catchment nutrient loads 

compared to nonpoint sources, except for a few catchments 

where point-source loads comprised as much as 30 percent 

of the TN load and as much as 80 percent of the TP load. 

The annual TN and TP loads from point sources discharging 

directly to the Puget Sound were about equal to the annual 

loads from eight major tributaries.

Yields of TN, TP, and SS generally were greater in 

catchments west of the Cascade Range. A multiple linear 

regression analysis showed that TN yields were significantly 

(p < 0.05) and positively related to precipitation, atmospheric 

nitrogen load, fertilizer and manure load, and point-source 

load, and were negatively related to average slope. TP yields 

were significantly related positively to precipitation, and pointsource load and SS yields were significantly related positively 

to precipitation.

Forty-eight percent of the available monitoring sites 

for TN had significant trends in concentration (2 increasing, 

19 decreasing), 32 percent of the available sites for TP had 

significant trends in concentration (7 increasing, 9 decreasing), 

and 40 percent of the available sites for SS had significant 

trends in concentration (4 increasing, 15 decreasing). The 

trends in load followed a similar pattern, but with fewer sites 

showing significant trends. The results from this study indicate 

that inputs from nonpoint sources of nutrients probably have 

decreased over time in many of the catchments. Despite 

the generally small contribution of point-source nutrient 

loads, they still may have been partially responsible for the 

significant decreasing trends for nutrients at sites where the 

total point-source nutrient loads to the catchments equaled a 

substantial proportion of the in-stream load.

Introduction

Water-resource managers in the Pacific Northwest need 

information regarding the status of and trends in regional 

water-quality conditions. This information is useful in 

watershed planning, such as Total Maximum Daily Load 

(TMDL) development required by the Clean Water Act. Many 

streams in the Pacific Northwest have levels of nutrients 

(nitrogen and phosphorus) and suspended sediment that are 

elevated enough to cause adverse ecological effects, including 

excessive aquatic plant growth, reduced water clarity, 

reduced stream dissolved oxygen, and altered stream habitat. 

In addition, water-resource managers need information on 

the important sources of nutrients and sediment delivered 

to streams. This is especially true with regard to TMDL 

development, because source reduction is the main tool 

available to lower in-stream pollutant loads. There also is a 

need to quantify the relative contributions from tributaries and 

direct anthropogenic discharges (wastewater-treatment plants 

and industrial facilities) to the total nutrient and sediment load 

in the major rivers of the Pacific Northwest and, ultimately, to 

the Pacific Ocean.

Nutrient and Suspended-Sediment Transport and 

Trends in the Columbia River and Puget Sound 

Basins, 1993–2003

By Daniel R. Wise, Frank A. Rinella III, Joseph F. Rinella, Greg J. Fuhrer, Sandra S. Embrey, 

Gregory M. Clark, Gregory E. Schwarz, and Steven Sobieszczyk
To determine the extent of nutrient and sediment concerns 

in our Nation’s streams, analysis of the information collected 

during Cycle I of the U.S. Geological Survey’s (USGS) 

National Water-Quality Assessment Program (NAWQA) 

basin-specific water-quality studies in the United States, along 

with other Federal, State, and local agency studies, were 

assessed regionally (Gilliom and others, 2001). The addition 

of other agency data greatly extended our ability to understand 

contaminant occurrence and transport, especially during times 

of declining funding. This study is the culmination of a similar 

effort to assess the trends and the transport of total nitrogen 

(TN), total phosphorus (TP), and suspended sediment (SS), 

to provide water-quality managers in the Pacific Northwest 

the information they need to effectively develop watershed 

improvement plans. The work done for this study can be a 

resource to support future investigations by regional waterquality managers and will be the foundation for a more 

detailed and rigorous regional water-quality modeling effort 

by the USGS that will assess both pollutant transport and load 

allocation.

Purpose and Scope

This report summarizes (1) patterns in nutrient and 

suspended-sediment loads and yields and (2) trends in 

concentrations and loads in relation to landscape, management 

practices, and climate in the Columbia River and Puget 

Sound Basins during an 11-year period, water years (WYs) 

1993 through 2003. (A water year begins on October 1 of the 

previous calendar year and ends on September 30). The report 

focuses on:

•	 Annual loads of TN, TP, and SS over a range of flow in 

the Columbia River and Puget Sound Basins, including 

transport along the main-stem Columbia River and two 

of its major tributaries, and to Puget Sound;

•	 Annual yields (loads divided by catchment areas) 

of TN, TP, and SS and relating differences in yields 

to differences in landscape and climatic conditions 

between the catchments;

•	 Trends in concentrations and loads of TN, TP, and SS 

in the Columbia River and Puget Sound Basins; and

•	 The relation of trends in concentrations and loads to 

changes in landscape, management practices, and 

climatic conditions.

Description of Columbia River and 

Puget Sound Basins

Columbia River Basin

The Columbia River and its tributaries form the dominant 

water system in the Pacific Northwest (fig. 1). The main 

stem of the Columbia rises in Columbia Lake (not shown in 

fig. 1) on the west slope of the Rocky Mountains in Canada. 

After winding 1,942 km, of which 664 km are in Canada, the 

Columbia River flows into the Pacific Ocean near Astoria, 

Oregon. The river drains an area of about 567,000 km2 in 

Washington, Oregon, Idaho, Montana, Wyoming, Nevada, 

and Utah (fig. 1). An additional 99,700 km2 of the basin is in 

Canada.

Geographically, the Columbia River Basin borders the 

Rocky Mountains to the east and north, the Coast Range on 

the west and southwest, and the Great Basin to the southeast. 

The Columbia River flows through the basin from Canada’s 

Rocky Mountains and ultimately becomes the border between 

Oregon and Washington. Along the way, several major 

tributaries feed into the Columbia. The three largest basins are 

the Snake River (267,000 km2), the Clark Fork-Pend Oreille 

River (64,700 km2), and the Kootenai River (46,600 km2). 

Other contributing basins include the Willamette River (29,000 

km2), the Yakima River (16,100 km2), the Payette River (8,390 

km2), and the Cowlitz River (6,220 km2) (Foundation for 

Water and Energy Education, 2000).

The hydrologic cycle of the Columbia River reflects a 

unique relation between water flow and topography in the 

basin. In the United States, only the Missouri-Mississippi 

River system has annual runoff greater than that of the 

Columbia River. Precipitation, sunlight, and air temperature 

in the basin can vary from one year to the next and largely 

determine how much water the river will carry from year 

to year. West of the Cascade Mountains, precipitation falls 

largely as rain during the winter months, whereas in the 

Cascade Range and eastward, winter precipitation is mostly 

snow. Deep snow in the mountains eventually is released to 

the river during early to mid-spring. About 30 percent of the 

streamflow in the Columbia River occurs between January and 

March (primarily from rainfall) and about 30 percent occurs 

between April and June (from a combination of rainfall and 

melting snow). These values are based on the record of daily 

mean discharge for the Columbia River near the mouth at 

Beaver Army Terminal (fig. 2).

2 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
OR19-0072_fig01

Study area

See Figure 19

for detail

See Figure 11

for detail

See 

Figure 21

for detail

See 

Figure 15

for detail

Snake River

Boise

Salem

Seattle

Portland

Spokane

Columbia River

Columbia R

Willamette River

Yakima River

USNK

PUGT

NROK

CCPT

YAKI

CCYK

WILL

OREGON

WASHINGTON

IDAHO

CANADA

MONTANA

NEVADA UTAH

W YOMING

Astoria Pacific Ocean

3

2

5

6

1

8

4

57

39

63

98

95

12

17

41 26

10

43

42

13 14

11

45

77

80

69

71 74

75

54

73

70

64

46

76 78

86

87

79

52

53

60

61

56

81

47

50

83

84

8885

72

58

68

55

48

49

51

59

38

44

15 94

92

96

93

91

90 89

99

97

100

62

65

66

67

82

16 18

7

9

 Snake

River 

126° 125° 120° 115° 110° 109°

41°

45°

49°

123°30' 123°00' 122°30'

45°00'

45°30'

Willamette River

Columbia River 40

37

33

31

23

19 18

20

21

36 34 35

32

28

24

30 29

25

27

22

17

16

15 14

0 200 MILES

0 200 KILOMETERS

0 20 MILES

0 20 KILOMETERS

EXPLANATION

NAWQA study unit

Central Columbia Plateau/Yakima River Basin (combined unit)

Central Columbia Plateau

Yakima River Basin

Northern Rockies Intermontain Basin

Puget Sound Basin

Upper Snake River Basin

Willamette Basin

Water-quality sampling sites—Number refers to site number in table 1 

CCYK

 CCPT

 YAKI

NROK

PUGT

USNK

WILL

18

Basemap modified from U.S. Geological Survey digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, central meridian 120°30’ W

Figure 1. Columbia River and Puget Sound Basins and locations of water-quality monitoring sites. (Map index numbers refer to 

sites listed in table 1.)

Description of Columbia River and Puget Sound Basins 3
The population of the Columbia River Basin in the 

United States is about 4.6 million people (2000 census); this 

number is more than 20 percent greater than that recorded 

during the 1990 census, indicating that substantial growth is 

occurring in parts of the basin (U.S. Census Bureau, 2001). 

Land use of the basin in the United States is predominately 

forested (87 percent), with urban and agricultural land use 

comprising the remaining 2 and 11 percent of the basin, 

respectively. Land cover percentages are based on the 

enhanced National Land Cover Dataset (1992), further revised 

with 2000 population density by block group to indicate recent 

(2000) urban development (U.S. Geological Survey, 2006).

The two priorities for management of the Columbia 

River dam system historically have been hydroelectric power 

generation and flood control. Hydroelectric generation 

projects on the Columbia River provide upwards of 50 percent 

of the Pacific Northwest Region’s electrical power needs 

(Bonneville Power Administration, 2005). Other uses, such as 

irrigation, navigation, and recreation, are largely carried out in 

the context of meeting the two main priorities. Enforcement of 

Federal environmental laws related to endangered fish species 

also have resulted in the National Marine Fisheries Service’s 

indicating that anadromous fish recovery should receive 

priority over all river uses except flood control (Foundation for 

Water and Energy Education, 2000).

Puget Sound Basin

The Puget Sound Basin is a 13,500 km2 area located 

mostly in western Washington, but also encompasses parts 

of British Columbia (fig. 1). The area consists mostly 

of mountains and coastal lowlands. In all, 12 major and 

numerous minor tributaries drain to the Puget Sound and 

adjoining waters. The streams and rivers in the basin drain 

three physiographic providences (1) the Olympic Mountains in 

the west, (2) the Cascade Range in the east, and (3) centrally, 

the Puget Lowlands (Ebbert and others, 2000). About 70 

percent of the population in Washington (4 million people) 

resides in the Puget Sound Basin, primarily in the metropolitan 

areas of Seattle, Tacoma, Everett, Bellingham, and Olympia. 

The population is expected to increase by 1.1 million by the 

year 2020 (Staubitz, 1994).

The Puget Sound has a Pacific Coast marine climate 

characterized by wet, cool winters and dry, warm summers. 

Annual precipitation can vary from 16 to 53 in/yr in the 

lowland areas to upwards of 60 to 200 in/yr in the mountains 

(Staubitz, 1994). Streams with headwaters in the mountains 

generally have the highest monthly flows in December and 

January, typically associated with winter rains, and in May 

and June as a result of spring snowmelt. Streams originating 

in the lowlands typically have the highest flows in January 

and February. The land use of the basin is predominately 

forested (75 percent), with urban and agricultural land use 

encompassing 11 and 6 percent, respectively. The remaining 

land is covered by lakes, reservoirs, glaciers, and shorelands. 

Historically, roughly 56 percent of the 810 Mgal/d of water 

used in the basin has been supplied by surface water and the 

rest from ground water (Staubitz, 1994). Excluding water 

used for hydroelectric power generation, 41 percent of the 

water was used for domestic purposes in 1995, with irrigation, 

industry, commerce, and livestock using the remaining 11, 30, 

9, and 1 percent of the water, respectively (Ebbert and others, 

2000).

Data Sources

The historical water-quality and streamflow data used in 

this study were obtained from the USGS and other Federal, 

State, and local agencies. The two main types of data were 

(1) results of discrete intermittent collections of nutrient and 

SS samples from river and stream locations in the Columbia 

River and Puget Sound Basins in Oregon, Washington, and 

OR19-0072_fig02

MONTH

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

DAILY MEAN DISCHARGE, IN CUBIC FEET PER SECOND

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

Figure 2. Daily mean discharge for the Columbia 

River at Beaver Army Terminal, Oregon, water years 

1993–2003.

4 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Idaho, and (2) continuous measurements of streamflow at 

locations where the water-quality samples were collected 

or from nearby streamflow stations. Combining data from 

these agencies was important because no single agency had 

data of sufficient quantity or quality to be used alone for the 

analysis (Hirsch and others, 2006). To aid in explaining the 

trends in nutrients and sediment, and the spatial patterns in 

yields, ancillary information on individual stream catchments 

also was compiled (Hirsch and others, 2006). This ancillary 

information included basin climate, hydrology, drainage area, 

land cover, population and road densities, National Resources 

Inventory of agricultural management practices, ecoregions, 

nutrient ecoregions, hydrologic landscapes, physiographic 

divisions, bedrock and surficial geology, as well as catchmentspecific estimates for atmospheric deposition, fertilizer, and 

manure loads (provided to the study by the USGS NAWQA 

Pesticide Synthesis Workgroup [http://ca.water.usgs.gov/

pnsp/]). A technique described by Nakagaki and Wolock 

(2005) was used to reapportion the county-level ancillary data 

to the individual drainage areas upstream of the water-quality 

site used in the analysis.

Discrete Water-Quality Samples

Of the 100 water-quality sites used in our analysis, 36 

sites were operated by the USGS (fig. 1, table 1). Figure 1

shows the NAWQA study areas in the Columbia River and 

Puget Sound Basins (the USGS sites considered for this 

analysis were not restricted to these areas). As part of the 

USGS program of disseminating water data to the public, a 

distributed network of computers and fileservers is maintained 

for the storage and retrieval of water data collected through its 

activities at about 1.4 million sites. This system is called the 

National Water Information System (NWIS). Many types of 

data are stored in NWIS, including site information, timeseries (stage, streamflow, precipitation, and chemical), peak 

flow, ground water levels, water-quality data, and wateruse data (U.S. Geological Survey, 1998). The USGS uses 

the 5-digit parameter code system developed by the U.S. 

Environmental Protection Agency (USEPA) in the 1960s for 

its STORET (STOrage and RETrieval) system. The parameter 

codes (Pcodes) are used to identify each measured constituent 

in the record, defined by a set of attributes.

Additional water-quality data were retrieved from 

monitoring sites operated by various local, State, and Federal 

environmental quality agencies. Data from 26 sites were 

obtained from the Washington State Department of Ecology 

(WDOE) through their River and Stream Water-Quality 

Network database (Washington State Department of Ecology, 

2004). The goal of the WDOE network is to provide timely 

water-quality data for various purposes, including evaluation 

of the status of and trends in stream water quality statewide. 

Data from another 23 water-quality sites were obtained from 

the Pacific Northwest Water-Quality Exchange (Exchange) 

and from the Oregon Department of Environmental Quality 

(Gregory Pettit, Oregon Department of Environmental 

Quality, written commun., 2006). The Exchange comprises 

a number of related information management projects that 

collectively seek to facilitate the aggregation of and access 

to a comprehensive source of data related to water quality 

in the Pacific Northwest. (Pacific Northwest Water Quality 

Exchange, 2006). All 23 sites were operated by the Oregon 

Department of Environmental Quality (ODEQ). Data from an 

additional 13 sites were retrieved from a database maintained 

by Clean Water Services (CWS) (Janice Miller, Clean Water 

Services, written commun., 2005). CWS provides wastewater 

treatment and management of surface-water resources for the 

712 mi2

 Tualatin River basin, in northwestern Oregon (Clean 

Water Services, 2006). Data from the remaining two sites 

were retrieved from the USEPA STORET data management 

system (U.S. Environmental Protection Agency, 2006b). These 

sites were operated by the Bureau of Reclamation in eastern 

Oregon (table 1).

Daily Mean Streamflow

The 100 daily mean streamflow files were obtained from 

several data sources: (1) 80 streamflow files were retrieved 

from the USGS NWIS database; (2) 7 streamflow files from 

the Oregon Water Resources Division (OWRD) database 

(Oregon Water Resources Division, 2006); (3) 10 streamflow 

files from the Washington County, Oreg., Watermaster 

(Washington County, Oregon, 2006); and (4) 3 streamflow 

files from the Bureau of Reclamation Hydromet database 

(Bureau of Reclamation, 2006).

Data Sources 5
Table 1. Description of water-quality monitoring sites in the Columbia and Puget Sound River Basins. 

[Figure 1 shows site location by Map index No. Abbreviations: CWS, Clean Water Services; ODEQ, Oregon Department of Environmental Quality; USBR, 

Bureau of Reclamation; USGS, U.S. Geological Survey; WDOE, Washington State Department of Ecology; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; km2, square kilometer; NA , not available]

Map 

index

No.

Site No. Agency Site name

Drainage 

area

(km2

)

Trend

sites

Load

sites

1 10729 ODEQ Owyhee River at Hwy 201 Bridge (Owyhee), OR NA X

2 MAL113 USBR North Fork Malheur River approximately 2 miles upstream of Beulah 

Reservoir, OR

880 X

3 MAL144 USBR Malheur River at Ford Street (1.1 miles) upstream of Bully Creek, OR 12,000 X

4 10386 ODEQ Middle Fork Willamette River at Jasper Bridge, OR 3,490 X X

5 10663 ODEQ Mohawk River at Hill Road, OR 460 X

6 10376 ODEQ McKenzie River at Coburg Road, OR NA X

7 10355 ODEQ Willamette River at Hwy 99E (Harrisburg), OR 8,890 X X

8 11140 ODEQ Long Tom River at Stow Pit Road (Monroe), OR 1,080 X X

9 12657 ODEQ McKenzie River at Hwy 126 downstream of Clear Lake, OR 239 X

10 10508 ODEQ Deschutes River at Lower Bridge, OR 5,440 X X

11 10350 ODEQ Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 12,600 X X

12 11490 ODEQ Powder River at Hwy 7 (Baker City), OR 902 X

13 11478 ODEQ John Day River at Service Creek, OR 13,300 X X

14 10555 ODEQ Willamette River at Marion Street (Salem), OR 19,100 X X

15 14200400 USGS Little Abiqua Creek near Scotts Mills, OR 25.5 X X

16 14201300 USGS Zollner Creek near Mt. Angel, OR 38.9 X X

17 10640 ODEQ Pudding River at Hwy 211 (Woodburn), OR 818 X

18 13070 ODEQ Clackamas River at Mciver Park (Upper Boat Ramp), OR 1,760 X

19 3701002 CWS Tualatin River at Weiss Bridge, OR 1,840 X X

20 3840012 CWS Fanno Creek at Durham Road, OR 80.7 X

21 14206950 USGS Fanno Creek near Durham, OR 80.7 X

22 3701715 CWS Tualatin River at Cherry Grove, OR 97.3 X

23 11321 ODEQ Johnson Creek at SE 17th Avenue (Portland), OR 139 X X

24 3701333 CWS Tualatin River at Farmington Bridge Road, OR 1,460 X

25 3701612 CWS Tualatin River at Springhill Road Bridge (Dilley), OR 327 X X

26 11386 ODEQ John Day River at Hwy 206, OR NA X

27 3805048 CWS Scoggins Creek below Hagg Lake at Stimson Bridge, OR 103 X

28 3701391 CWS Tualatin River at Rood Bridge Road, OR 1,230 X

29 3701528 CWS Tualatin River at Golf Course Road, OR 561 X

30 3810015 CWS Gales Creek at New Hwy 47, OR 195 X

31 10611 ODEQ Willamette River at Hawthorne Bridge (Portland), OR 28,900 X X

32 3820012 CWS Rock Creek at Hwy 8, OR 193 X

33 14211720 USGS Willamette River at Portland, OR 28,900 X X

34 3850006 CWS Dawson Creek at Brookwood, OR 9.66 X

35 3824020 CWS Bronson Creek at Bronson Park downstream of Sunset Hwy, OR 10.2 X

36 3824072 CWS Bronson Creek at Saltzman, OR 5.23 X

37 10332 ODEQ Willamette River at SP&S Railroad Bridge, OR NA X X

38 14128910 USGS Columbia River at Warrendale, OR 616,000 X

39 10411 ODEQ Deschutes River at Deschutes River Park, OR 27,800 X X

40 10616 ODEQ Columbia River at Marker #47 (upstream of Willamette River), OR NA X X

41 10406 ODEQ Umatilla River at Hwy 11 (Pendleton), OR 1,150 X

42 12012 ODEQ Hood River at footbridge downstream of I-84, OR NA X X

43 11489 ODEQ Umatilla River at Westland Road (Hermiston), OR NA X X

44 14246900 USGS Columbia River at Beaver Army Terminal near Quincy, OR 658,000 X X

45 27D090 WDOE East Fork Lewis River near Dollar Corner, WA 405 X

46 32A070 WDOE Walla Walla River near Touchet, WA 4,370 X X

47 13353200 USGS Snake River at Burbank, WA 262,000 X

48 37A090 WDOE Yakima River at Kiona, WA 14,500 X X

49 12510500 USGS Yakima River at Kiona, WA 14,500 X

50 12505450 USGS Granger Drain at Granger, WA 160 X

6 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index

No.

Site No. Agency Site name

Drainage 

area

(km2

)

Trend

sites

Load

sites

51 12472900 USGS Columbia River at Vernita Bridge near Priest Rapids Dam, WA 67,800 X X

52 13351000 USGS Palouse River at Hooper, WA 6,380 X X

53 34A070 WDOE Palouse River at Hooper, WA 6,380 X X

54 41A070 WDOE Crab Creek near Beverly, WA 999 X X

55 12471400 USGS Lind Coulee Wastway at SR 17 near Warden, WA 1,840 X

56 13A060 WDOE Deschutes River at East Street Bridge, WA 267 X X

57 10A070 WDOE Puyallup River at Meridian Street, WA 2,380 X X

58 12108500 USGS Newaukum Creek near Black Diamond, WA 71.1 X

59 12464770 USGS Crab Creek at Rocky Ford Road near Ritzville, WA 1,190 X

60 12061500 USGS Skokomish River near Potlatch, WA 339 X

61 16A070 WDOE Skokomish River near Potlatch, WA 339 X X

62 12112600 USGS Big Soos Creek above Hatchery near Auburn, WA 173 X

63 09A190 WDOE Green River at Kanaskat, WA 616 X X

64 45A070 WDOE Wenatchee River at Wenatchee, WA 3,440 X X

65 12113375 USGS Springbrook Creek at Tukwila, WA 51.7 X

66 09A080 WDOE Green River at Tukwila, WA 1,240 X X

67 12113390 USGS Duwamish River at Golf Course at Tukwila, WA 1,190 X

68 12056500 USGS North Fork Skokomish River below Staircase Rapids near Hoodport, WA 147 X

69 46A070 WDOE Entiat River near Entiat, WA 1,070 X

70 45A110 WDOE Wenatchee River near Leavenworth, WA 1,720 X X

71 16C090 WDOE Duckabush River near Brinnon, WA 172 X X

72 12128000 USGS Thorton Creek near Seattle, WA 29.2 X

73 54A120 WDOE Spokane River at Riverside State Park, WA 13,000 X X

74 07D050 WDOE Snoqualmie River near Monroe, WA 1,770 X X

75 07C070 WDOE Skykomish River at Monroe, WA 1,980 X X

76 07A090 WDOE Snohomish River at Snohomish, WA 4,440 X X

77 53A070 WDOE Columbia River at Grand Coulee, WA 28,900 X X

78 48A070 WDOE Methow River near Pateros, WA 4,660 X X

79 49A070 WDOE Okanogan River at Malott, WA 4,500 X X

80 48A140 WDOE Methow River at Twisp, WA 3,430 X X

81 03A060 WDOE Skagit River near Mount Vernon, WA 6,020 X X

82 03B050 WDOE Samish River near Burlington, WA 223 X

83 12213140 USGS Nooksack River at Brennan, WA 2,020 X

84 01A050 WDOE Nooksack River at Brennan, WA 1,910 X X

85 12210700 USGS Nooksack River at North Cedarville, WA 1,520 X

86 12400520 USGS Columbia River at Northport, WA 156,000 X

87 61A070 WDOE Columbia River at Northport, WA 156,000 X X

88 12212100 USGS Fishtrap Creek at Flynn Road at Lynden, WA 98.6 X

89 13092747 USGS Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 623 X X

90 13094000 USGS Snake River near Buhl, ID 76,100 X

91 13154500 USGS Snake River at King Hill, ID 92,900 X X

92 13203510 USGS Boise River below Diversion Dam near Boise, ID 6,980 X

93 13206000 USGS Boise River at Glenwood, ID 7,180 X X

94 13238322 USGS North Fork Payette River below Fischer Creek near McCall, ID 220 X

95 12414900 USGS St. Maries River near Santa, ID 706 X

96 12414500 USGS St. Joe River at Calder, ID 2,680 X

97 12413470 USGS South Fork Coeur d’Alene River near Pinehurst, ID 738 X X

98 12413000 USGS North Fork Coeur d’Alene River at Enaville, ID 2,330 X

99 12419000 USGS Spokane River near Post Falls, ID 10,200 X X

100 13010065 USGS Snake River at Flagg Ranch, WY 1,320 X

Table 1. Description of water-quality monitoring sites in the Columbia and Puget Sound River Basins. —Continued

[Figure 1 shows site location by Map index No. Abbreviations: CWS, Clean Water Services; ODEQ, Oregon Department of Environmental Quality; USBR, 

Bureau of Reclamation; USGS, U.S. Geological Survey; WDOE, Washington State Department of Ecology; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; km2, square kilometer; NA , not available]

Data Sources 7
Methods of Analysis

Load Estimation

Annual mean loads for TN, TP, and SS were estimated 

using the USGS computer program Load Estimator, or 

LOADEST (Runkel and others, 2004). LOADEST uses a 

seven-parameter linear regression model that incorporates 

flow, time, and seasonal terms to estimate loads of mass over 

specified time periods (for this study, annual loads). The 

calibration and estimation procedures within LOADEST 

are based on three statistical estimation methods. However, 

the Adjusted Maximum Likelihood Estimation (AMLE) 

was most often used since the method is more appropriate 

when the calibration data set (time series of streamflow and 

concentration data) contains censored data. Once the model 

was calibrated, continuous daily mean values of streamflow 

were used as the independent variable to produce the annual 

load results for the specified years of interest (for this study, 

WYs 1997, 2000, and 2001). Mean load estimates, along 

with standard errors, and 95 percent confidence intervals 

were computed. The LOADEST output also included 

diagnostic tests and warnings to assist the user in determining 

the appropriate estimation method and in interpreting the 

estimated loads. LOADEST is available as a USGS module 

(David Lorenz, USGS library for S-PLUS, version 6.1, for 

Windows—Release 2.1) to the S-PLUS statistical software 

package (Insightful Corporation, 2002).

The focus of the load computations for the specified 

years of interest was two-fold:

•	 Transport of TN, TP, and SS in the Columbia River, 

Willamette River, Snake River and to the Puget Sound 

over a range of annual hydrologic conditions, and

•	 TN, TP, and SS yields for the Pacific Northwest 

for WY 2000, and relating differences in yields to 

differences in landscape and climatic conditions 

between catchments to understand how landscape and 

climate influence the transport of TN, TP, and SS.

Results of the LOADEST modeling are in appendix A. 

Included in the appendix are annual loads, annual average 

flow-weighted concentrations (defined as the annual load 

divided by the cumulative annual streamflow), annual yields 

(defined as the annual load divided by catchment drainage 

area) for TN, TP, and SS, and annual mean streamflow.

Selection of Analysis Period

The selection of the 11-year (WY 1993–2003) 

common time period for analysis of trends in streamflow, 

concentrations, and loads was based on a rigorous analysis of 

the temporal distribution of available USGS and non-USGS 

streamflow and water-quality datasets to optimize the number 

of sites spatially and temporally available for the analysis. An 

examination of annual mean streamflows for WY 1973–2003 

in the Willamette Basin (fig. 3) illustrate how streamflows 

for WY 1993–2003 were representative of mean (average), 

high-flow, and low-flow years for the longer time period. This 

allowed the examination of water-quality trends and loads 

over a diverse and variable daily mean streamflow regime 

(Hirsch and others, 2006). The common time period occurred 

when the availability of ancillary data describing landscape, 

management practices, and climatic conditions were more 

accurately detailed. This ancillary information was important 

to the completion of the second and fourth study objectives. 

Attempts to extend the analysis period either forward or 

backward in time resulted in the loss of some sites considered 

important to the analysis. Comparison of streamflow during 

the selected 11-year period relative to the mean annual 

streamflow for WY 1973 (31 years of streamflow and waterquality data) also demonstrates the diverse nature of the 

common time period selected for the trend analysis (fig. 4).

Computation of annual mean loads of nutrients and SS 

in the Columbia and Puget Sound Basins was accomplished 

by selecting high, low, and mean streamflow years from the 

common period, WY 1993–2003. Six streamflow sites in 

Oregon, Idaho, and Washington were selected to characterize 

differences in climatic and hydrologic conditions in the eastern 

and western parts of each State within the basins (table 2). 

Although the peak daily streamflows generally occurred in 

WY 1996, the highest annual mean streamflows generally 

were during WY 1997, when streamflows ranked in the 

93rd to 100th percentile of the highest annual streamflows 

in WYs 1973–2003. The lowest annual mean streamflows 

generally were during WY 2001, when streamflows ranked 

in the 1st to 14th percentile of the lowest annual streamflows 

in WYs 1973–2003. Selection of a mean annual water year 

representative of historical annual streamflow was more 

difficult because several water years in the common time 

period had annual streamflows similar to the historical mean 

annual streamflow. During the 1993–2003 period, WY 2000 

best demonstrated monthly mean streamflows that were 

comparable to the means of the monthly streamflows from 

the historical time period (fig. 5). For these six index sites, 

the annual mean streamflows for WY 2000 ranked in the 

48th to 76th percentile of the WY 1973–2003 mean annual 

streamflows.

8 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
OR19-0072_fig03

0

10,000

20,000

30,000

40,000

50,000

60,000

1973 1975 1980 1985 1990 1995 2000 2003

WATER YEAR

ANNUAL MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND

Mean annual streamflow for 

water years 1973–2003

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

450,000

STREAMFLOW, IN CUBIC FEET PER SECOND

1993 1994 1995 1996 1997 1998

WATER YEAR

1999 2000 2001 2002 2003

Mean annual streamflow

Water years 1973-2003

(33,419 cubic feet per 

second)

Figure 3. Annual mean daily streamflow in the Willamette River at Portland, Oregon, water years 1973–2003.

Figure 4. Daily mean streamflow in the Willamette River at Portland, Oregon, water years 1993–2003.

Methods of Analysis 9
Criteria for Site Selection

Two types of data compilations were used in our analysis 

based on different minimum data requirements. The first type 

considered the selection of a consistent timeframe of daily 

mean streamflows and periodic sampling of water-quality 

constituents of a sufficient duration for the computation of 

trends in concentrations and loads of nutrients and SS. The 

minimum data requirements for the selection of sites for trends 

in concentration included:

•	 Continuous daily streamflow for WY 1993–2003 (in 

some cases, for only WY 1994–2003 to increase the 

number of sites available for the analysis);

•	 At least quarterly water-quality samples in the two 

years at the beginning and end of the time period (WY 

1993, 1994, 2002, and 2003); and

•	 At least quarterly water-quality samples in a minimum 

of 4 of the intermediate 7 water years, WY 1995—

2001.

These data requirements provided a minimum of 32 or 

more water-quality samples for each site used for the trends 

analysis (David K. Mueller, U.S. Geological Survey, written 

commun., 2005). Streamflow and water-quality data from 50 

sites (table 1) met the minimum requirements for the analysis 

of trends in concentrations and loads.

Table 2. Streamflow sites used for nutrient and suspended-sediment load computations in the Columbia River and Puget Sound basins 

for selected water years.

[All values are in cubic feet per second. Common period: Number in parenthesis beside streamflow value indicates the percentage of annual mean streamflows 

less than the 31 annual streamflows for water years 1973–2003. Abbreviations: ID, Idaho; OR, Oregon; WA, Washington]

Site No. Site name

Water years 

1973–2003

Common period

(flow percentile 

water years 1993–2003)

Mean 

annual

streamflow

Annual 

mean streamflow

(water year 2000)

Low annual 

mean streamflow

(water year 2001)

High annual 

mean streamflow

(water year 1997)

14211720 Willamette River at Portland, OR 33,400 35,100 (65) 16,000 (3) 53,700 (97)

14103000 Deschutes River at Moody, OR 5,870 6,460 (76) 4,850 (14) 7,980 (100)

12413000 North Fork Coeur d’Alene River at 

Enaville, ID

1,810 2,040 (71) 759 (3) 2,730 (93)

13154500 Snake River at King Hill, ID 11,000 9,990 (48) 7,330 (11) 17,000 (96)

12510500 Yakima River at Kiona, WA 3,400 3,770 (66) 1,530 (6) 6,090 (96)

12150800 Snohomish River nr Monroe, WA 9,320 10,500 (68) 6,300 (0) 13,300 (100)

OCT NOV DEC JAN FEB MAR APR

MONTH

MAY JUNE JULY AUG SEPT

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

STREAMFLOW, IN CUBIC FEET PER SECOND

Water year 2000

Water years 1973-2003

Figure 5. Comparison of monthly mean streamflow during water year 2000 with mean monthly streamflow during water 

years 1973–2003 for the Willamette River at Portland, Oregon.

10 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
The second type of data compilation considered the 

selection of streamflow and water-quality sites for computing 

annual loads and yields of nutrients and SS over a range of 

years. The 50 sites that met the minimum data requirements 

for the analysis of trends in concentration and loads also met 

the minimum load and yield selection requirement. However, 

these sites provided insufficient coverage of the Columbia 

River and of the Puget Sound Basins. An additional 50 sites 

were identified that met the less rigorous requirements for 

the second type of data compilation analysis. All sites for the 

second type of data compilation met the following minimum 

requirements:

•	 Daily mean streamflow data existed for WY 1997 

(high-flow year), 2000 (average-flow year), or 2001 

(low-flow year);

•	 Data were available for about 30 samples over the 

range of seasonal flow described in the 3 water years 

of interest; and

•	 Data from six or more samples were available in each 

of the 3 years (for the site to qualify for computation 

of estimated annual nutrient and suspended-sediment 

loads).

One hundred sites met the minimum requirements for the 

second type of data analysis (fig. 1, table 1). The distribution 

of drainage areas for the 91 delineated catchments used in 

this study (delineations were not available for the other 9 

sites) is shown in figure 6. The drainage areas ranged in size 

from 5 km2

 to more than 650,000 km2; and, although the 

average drainage area was about 23,500 km2, most catchment 

drainage areas (54 of 91) were between 100 and 5,000 km2. 

All sites were reviewed for compliance with various modeling 

requirements (water-quality sampling representative of the 

flow regime for the period of interest, percentage of sampling 

results censored, confidence intervals, and other statistical 

measurements of model suitability).

Data Assumptions and Censoring Process

Analyses evaluated for this study consisted of a suite 

of nitrogen, phosphorus, and SS data collected and analyzed 

by the USGS, other Federal and State agencies in Oregon, 

Washington, and Idaho, and a wastewater- and stormwatertreatment public utility in Oregon. To aid in the interpretation 

of the data, assumptions concerning varying sample collection 

protocols, equipment, and analytical techniques were made. 

A detailed discussion concerning the first two assumptions is 

presented in the next section.

•	 Differences between collection techniques using grab 

sampling versus depth-width integrating sampling were 

assumed to be minor, resulting in similar precision and 

minimal bias;

•	 Differences in analytical techniques between the 

various agency laboratories were assumed to be minor; 

and

•	 Differences in the frequency of sample collection from 

one site to another were assumed to not significantly 

bias site-to-site comparisons in concentrations, trends, 

or loads as long as the minimum data requirements for 

selection of sites were met.

The chemical and physical parameters used in this study 

included:

•	 Dissolved nitrite plus nitrate as N [STORET Pcode: 

00631],

•	 Total Kjeldahl nitrogen as N (TKN) [STORET Pcode: 

00625],

•	 Total nitrogen as N (TN) [STORET Pcode: 00600],

•	 Total phosphorus as P (TP) [STORET Pcode: 00665], 

and

•	 Suspended-sediment or nonfilterable solids (SS) 

[STORET Pcode: 80154 or 00530]

The above parameters were used to model loads, and 

trends in concentrations and loads, for TN, TP, and SS in the 

Columbia River and Puget Sound Basins for WYs 1993–2003. 

Where direct measurements of TN were not available, TN was 

computed from the sum of TKN and nitrite plus nitrate, using 

the rules outlined in table 3. The most common analytical 

reporting levels during WY1993–2003 were 0.2 mg/L for 

TKN and 0.05 mg/L for nitrite plus nitrate. In recent years, 

some slightly lower TKN and nitrite plus nitrate reporting 

levels were measured at some USGS and non-USGS sites; 

however, the rules were not changed significantly because it 

affected only a small number of the more pristine TN sites.

Influence of Sampling and Analytical 

Techniques

To produce a data set with adequate spatial and temporal 

coverage, it was necessary to include water-quality results 

from non-USGS as well as USGS data bases. As mentioned 

in the previous section, the validity of this approach 

partly rested on two assumptions: (1) differences between 

collection techniques using grab sampling (non-USGS) 

versus depth-width integrating sampling (USGS) were 

minor during typical flow regimes; and (2) differences in 

analytical techniques between various agency laboratories 

were minor. The WDOE compared their water-quality data 

to water-quality data collected during the same months by 

the USGS for two stations that also are included in this 

study (Hallock, 2005). The ranges for data collection were 

Methods of Analysis 11
September 1982 through September 1994 for the Yakima 

River at Kiona, Wash. (Kiona), and December 1992 through 

September 2002 for the Palouse River at Hooper, Wash. 

(Hooper). USGS SS concentrations were significantly greater 

than the WDOE suspended-solids concentrations at Kiona 

on the basis of the central tendency of the data, but the 

difference in concentrations was not large and might have 

been due to differences in analytical techniques. In addition, 

concentrations were not significantly different between the 

two agencies’ data from the Hooper site. However, even a 

small bias at high concentrations and during high-flow periods 

for constituents positively correlated with flow (for example, 

SS and TP), caused fluxes to be magnified. SS and TP fluxes 

calculated from WDOE data were equal to 80 percent of the 

fluxes calculated from USGS data at Kiona and 50 percent of 

the USGS fluxes at Hooper.

Martin and others (1992) compared water-quality data 

collected concurrently using surface-grab and depth-width 

integrating sampling. Although concentrations of dissolved 

constituents were not consistently different, concentrations 

of SS and constituents associated with sediment were 

significantly lower in the surface-grab samples than in the 

depth-width integrated samples, and the magnitude of the 

differences generally increased with streamflow. Gray and 

others (2000) evaluated 3,235 paired samples of suspendedsediment (used by USGS) and total suspended-solids (used 

by the ODEQ and WDOE) and concluded that data resulting 

from the suspended-sediment techniques were more reliable, 

but that the methods may be comparable when the amount of 

sand-sized material is less than about 25 percent. Comparisons 

of concurrent nutrient samples (TN and TP) using standard 

USGS methods of analysis and methods of analysis used by 

non-USGS laboratories were not available.

DRAINAGE AREA, IN SQUARE KILOMETERS

< 100 100 - 1,000 1,000 - 5,000 5,000 - 10,000 10,000 - 15,000 15,000 - 100,000 > 100,000

NUMBER OF SITES

0

5

10

15

20

25

30

All sites (91)

Trend sites (45)

Table 3. Rules for computing total nitrogen concentration from total Kjeldahl nitrogen and dissolved nitrite plus nitrate as nitrogen.

[Concentrations are in milligrams per liter. A notation of “Value(nitrite plus nitrate) greater than or equal to (≥) 0.05” means that the concentration (value) of 

the combined sum of the nitrite plus nitrate species is greater than or equal to 0.05 milligrams per liter. 0.05 is the detection limit selected for nitrite plus nitrate, 

0.025 is one-half this value; 0.2 is the detection limit for TKN, and 0.1 is one-half this value. Abbreviations: TN, total nitrogen; TKN, total Kjeldahl nitrogen; 

<, less than]

Case No. Nitrite plus nitrate TKN Condition TN

1 <0.05 <0.20 Nitrite plus nitrate is <0.05 and TKN is <0.20 <0.25

2 Value(nitrite plus nitrate) ≥ 0.05 Value(TKN) ≥ 0.2 Value(nitrite plus nitrate) ≥ 0.05 and 

Value(TKN) ≥ 0.2

Value(nitrite plus nitrate) + 

Value(TKN)

3a <0.05 Value(TKN) ≥ 0.2 Value(TKN) + 0.025 < 0.25 <0.25

3b <0.05 Value(TKN) ≥ 0.2 Value(TKN) + 0.025 ≥ 0.25 Value(TKN) + 0.025

4a Value(nitrite plus nitrate) ≥ 0.05 <0.20 Value(nitrite plus nitrate) + 0.1 < 0.25 <0.25

4b Value(nitrite plus nitrate) ≥ 0.05 <0.20 Value(nitrite plus nitrate) + 0.1 ≥ 0.25 Value(nitrite plus nitrate) 

+ 0.1

5 Missing Missing Nitrite plus nitrate is missing or TKN is missing Missing

Figure 6. Statistical distribution of the 91 delineated catchment drainage areas in the Columbia River and Puget 

Sound basins.

12 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
For this study, comparisons also were made between 

model-predicted annual loads from a minimum of three 

co-located sites for the 3 water years of interest—high flow 

in 1997 (three sites), mean flow in 2000 (three sites), and low 

flow in 2001 (four sites). Table 4 summarizes the results of 

these comparisons by showing the predicted annual non-USGS 

load as a percentage of the predicted annual USGS load. The 

water-quality data used for the predictions were not collected 

concurrently, but all data were collected between WYs 1993 

and 2003. For TN, the differences between the USGS and nonUSGS loads generally were small (less than 10 percent) for all 

3 years. However, for TP and SS, the non-USGS loads were 

less than the USGS load at all the sites in 1997 and 2000 (as 

low as 38 percent for TP and 31 percent for SS). As expected, 

SS was the most sensitive to sampling methodology and (or) 

laboratory procedures with regard to loads.

Results from other studies and the comparison of our 

co-located sites showed that surface-grab samples were biased 

low for elevated concentrations of sediment by as much as 

70 percent and biased low for total phosphorous associated 

with high-flow conditions by as much as 60 percent. This 

deficiency might compromise load calculations if a stream is 

further stratified (fine particles and less mass near the top and 

heavy particles and more mass near the bottom). However, 

the results also showed that no persistent bias existed for 

total nitrogen (the differences were less than 8 percent). The 

value of using non-USGS load data to fill the spatial gaps 

in the USGS data outweighed the potential underestimation 

problems for TP and SS loads.

Trends in Streamflow, Load, and Concentration

Changes over time in the concentration and load of a 

constituent can be used to evaluate the potential effects on 

water quality of changes in pollution sources or management 

activities in a watershed. However, the concentration 

and load of a constituent in a stream is influenced by the 

volumetric flow at the time of sampling (for example, higher 

concentrations and loads are generally associated with higher 

flows). This association is stronger for sediment and sedimentadsorbed constituents, like phosphorus, than for constituents 

that tend to dissolve in water, such as nitrate. However, an 

inverse relation may occur when a stream’s major source of 

nutrients is from point sources.

The relations of discharge to total nitrogen and discharge 

to suspended-sediment concentrations for Willamette River 

at Portland (fig. 1, site 33) for WY 1993–2003 are shown 

in figure 7. A locally weighted scatter plot smoothing 

(LOWESS) curve was fit to the data to indicate the relation 

between the parameters in the plots. Changes over time 

(trends) in the measured concentrations for a constituent 

(referred to as non-flow-adjusted trends in concentration) 

give an indication of water-quality changes streams have 

undergone. This is important with regard to possible effects 

on biota (for example, eutrophication). However, to determine 

whether a stream has experienced a trend in water quality due 

to changes in catchment activities, the effect of streamflow 

may need to be removed from the measured concentrations 

(because the streamflow itself might exhibit a trend). This is 

done by calculating the flow-adjusted trend in concentration, 

which gives insight into whether a trend in measured 

concentrations is potentially caused by management activities 

or reflects a trend in streamflow due to climatological or 

hydrological changes.

A detailed description of the method used in this study 

for estimating trends in streamflow, load, and concentration is 

provided in appendix B. Trends in load and concentration are 

defined as the model-estimated, smoothed trend in load and 

concentration over the period of water-quality record, divided 

by the length of record.

Smoothing of data is necessary when a measured variable 

is slowly varying and also influenced by random noise. In such 

a case, it is sometimes useful to replace each measured value 

with some kind of local average of the surrounding data points, 

thus reducing the level of variation without biasing the value 

of interest. An example of data smoothing (using a LOWESS 

curve) is shown in figure 8 which contains the measured 

daily mean streamflow and total nitrogen concentrations for 

the Willamette River at Portland for water years 1993–2003. 

Although LOWESS smoothing was used as an example in 

these plots, a different data smoothing routine was used for the 

analytical aspects of this study (see appendix B).

Table 4. Comparison of total nitrogen, total phosphorus, and 

suspended-sediment loads based on sampling results from 

co-located sites operated by U.S. Geological Survey and other 

agencies. 

[Values represent the ratio of predicted non-USGS (U.S. Geological Survey) 

load to predicted USGS load (expressed as a percentage). Abbreviations: 

TN, total nitrogen; TP, total phosphorus; SS, suspended sediment; OR, 

Oregon; WA, Washington; –, insufficient data]

Site name

Load

(percentage USGS)

TN TP SS

Water year 1997

Willamette River at Portland, OR 94.2 96.0 34.0

Palouse River at Hooper, WA 95.4 38.3 31.4

Yakima River at Kiona, WA 92.6 75.3 53.9

Water year 2000

Willamette River at Portland, OR 94.6 101 48.0

Palouse River at Hooper, WA 98.5 76.1 70.1

Yakima River at Kiona, WA 92.4 91.9 80.2

Water year 2001

Willamette River at Portland, OR 106 108 70.0

Palouse River at Hooper, WA 93.6 120 103

Yakima River at Kiona, WA 94.8 95.9 104

Fanno Creek at Durham Road, OR 101 93.8 –

Methods of Analysis 13
OR19-0072_fig07

STREAMFLOW, IN CUBIC FEET PER SECOND

0 25,000 50,000 75,000 100,000 125,000 150,000

TOTAL NITROGEN, IN MILLIGRAMS PER LITER

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER

0

100

200

300

400

Suspended sediment

Total nitrogen

LOWESS line

LOWESS line

Figure 7. Relations between concentrations of total nitrogen and suspended sediment and discharge 

for Willamette River at Portland, Oregon, water years 1993–2003. (LOWESS, locally weighted scatter plot 

smoothing.)

14 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
OR19-0072_fig08

Total nitrogen

Daily mean streamflow

0

100,000

200,000

300,000

400,000

500,000

DAILY MEAN STREAMFLOW, IN CUBIC FEET PER SECOND TOTAL NITROGEN CONCENTRATION, IN MILLIGRAMS PER LITER

0.0

0.5

1.0

1.5

2.0

WATER YEAR

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

LOWESS line

LOWESS line

Figure 8. Examples of data smoothing demonstrating temporal variability of daily mean streamflow and 

instantaneous total nitrogen concentrations for Willamette River at Portland, Oregon, water years 1993–2003. 

(LOWESS, locally weighted scattered plot smoothing.)

Methods of Analysis 15
Because the water-quality record for most sites does not 

include enough data to assess trends in load and concentration, 

a mathematical model is needed to “fill in” the gaps in the 

water-quality record by estimating concentrations based 

on streamflow. The model-estimated trend in load and 

concentration is determined by fitting separate trend models 

for streamflow and water-quality concentration. The model 

for trend in streamflow relates the natural logarithm of 

daily mean streamflow to an intercept, a linear trend term 

(measured by time expressed as a decimal, such as 1995.5), 

and sine and cosine seasonal factors (also functions of 

decimal time). In this study, the trend was based on all daily 

streamflow measurements available over the analysis period 

WY 1993–2003 (except for the four sites where the record 

started in WY 1994). Below is a summary of the methods 

used to calculate non-flow-adjusted trend in concentration, 

trend in load, flow-adjusted trend in concentration, and trend 

in streamflow. Appendix B contains a formal description of 

the methods described below, with additional discussion of the 

estimation of the streamflow and water-quality models, and an 

explanation of the associated statistical tests for trend.

Non-Flow-Adjusted Trend in Concentration

The water-quality model used to determine nonflowadjusted trend in concentration (percent per year), estimated 

from all water-quality measurements collected during 

the analysis period, is represented by the following linear 

equation:

c b m q b h T b x b e

c

t t q t T t x t

t

= +0 ( ) + ( ) + + ,

where:

is the natural logarithm of a constituent

concentration in period ;

is an in

t

b0 tercept value;

q is the natural logarithm of streamflow;

T

t

t is decimal time;

x is vectors of ancillary predictors such t as

sine and cosine functions of decimal

time to account for seasonality;

b b q T , , bx is coefficients determined from model

fitting;

(.) is multi-element vector function 

consist

m

ing of the natural logarithm 

of streamflow and the squareof 

the natural logarithm of streamflow;

h(.) is multi-element vector function consisting 

of the second order polynomial and step 

functions of decimal time; and

e is random e t rror term.

(1)

The smoothed trend in the natural logarithm of 

water-quality concentration (non-flow-adjusted trend in 

concentration) is determined by the streamflow and time trend 

components of the water-quality model (equation 1), where 

the smoothed trend in the natural logarithm of streamflow is 

substituted for the actual natural logarithm of streamflow in 

the model. The smoothed trend in the natural logarithm of 

streamflow is given by the following equation:





q q a T T

q

t t

t

= + ( ) − ,

where:

is smoothed trend in the natural logarithm of 

flow in the period t;

q is average of the natural logarithm of flow over

the trend period;

T is average, or midpoint, of the decimal time over

the trend period;

T is decimal time; and

a is coefficient determined from the model fitting.

(2)

Non-flow-adjusted trend in concentration is obtained by 

transforming the model-estimated, smoothed water-quality 

trend from logarithmic space to real space, computing the 

percentage change corresponding to the first and last dates 

of the water-quality record period, and normalizing by the 

decimal time length of this period.

Trend in Load

Trend in load (percent per year) is computed in a similar 

manner as non-flow-adjusted trend in concentration, except 

that the smoothed trend in the natural logarithm of streamflow 

is added to the smoothed trend in the natural logarithm of 

water quality prior to retransformation to real space (addition 

in logarithmic space is equivalent to multiplication in real 

space).

Flow-Adjusted Trend in Concentration

The estimation of flow-adjusted trend in concentration 

(percent per year) is similar to the approach used for nonflow-adjusted trend in concentration, except the streamflow 

component of the water-quality model is not included in the 

determination of the smoothed water-quality trend. Otherwise, 

the estimation methods are the same; that is, although flow is 

used to estimate the parameters of the water-quality model, 

implying that the trend parameters of the model exclude the 

effects of trend in flow, the flow component of the model is 

held constant and, therefore, does not enter into the evaluation 

of flow-adjusted trend.

16 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Trend in Streamflow

The estimation of the trend in streamflow is based on 

the smoothed streamflow trend corresponding to the simple 

linear function of decimal time described by equation 2. The 

conversion of this smoothed trend to a trend estimate follows 

the same procedure described for non-flow-adjusted trend in 

adjusted concentration—the only difference is the period of 

the trend is taken to be the beginning and ending dates for 

the flow record within the analysis period, rather than the 

beginning and ending dates of the water-quality record.

Interpretation of Trends

Trend results also are reported as unit trends (for 

example, kilograms per day per year for load or milligrams 

per liter per year for concentration). The unit trends in load 

and concentration are determined by multiplying the load and 

concentration trend estimates (expressed as rates rather than 

percentages) by the appropriate reference values of load and 

concentration. The reference value for the natural logarithm 

of concentration is obtained by evaluating the water-quality 

model given by equation 1 at reference conditions consistent 

with the trend in water quality at the beginning of the waterquality period of record. These conditions include setting 

the natural logarithm of streamflow to the smoothed trend 

value given by equation 2 to the first day of the water-quality 

period, setting the trend term to the decimal equivalent of 

the first day of the water-quality period, and setting the sine 

and cosine seasonal factors to their average values over the 

full water-quality period. The natural logarithm value of the 

reference concentration is transformed to real space and a 

multiplicative retransformation factor is applied to correct for 

statistical bias arising from sample error in the water-quality 

model coefficients (see appendix B for additional details). The 

reference load is computed similarly, except that the natural 

logarithm of streamflow trend, as determined by the linear 

streamflow equation evaluated at the starting date of the waterquality period, is added to the natural logarithm value of the 

reference concentration prior to transformation to real space. 

In addition, a conversion factor is used to convert the result to 

the appropriate load units. The same reference concentration is 

used to derive non-flow-adjusted unit trend and flow-adjusted 

unit trend in concentration, and the same reference load is 

used in the evaluation of unit trend in load.

If streamflow demonstrates no trend over time, the nonflow-adjusted and flow-adjusted trends concentration will be 

equivalent. Because the water-quality model used to derive 

these trends includes streamflow as a predictor, the estimates 

of trend are immune to bias arising from preferential waterquality sampling during high-streamflow events. Care should 

be taken, however, in interpolating or extrapolating these 

trend estimates within or beyond a site’s period of record, or 

in making comparisons of trend across sites with different 

periods of record. Due to the possible nonlinearity of trend, as 

may arise from nonlinear specifications of the water-quality 

model streamflow or trend components, trends of shorter 

duration within the water-quality period of record, or trends 

occurring outside this period could be different from the trends 

reported here. In addition, the method used to evaluate trend 

is sensitive to changes in the variability of streamflow and to 

changes in the unexplained variability of water quality (both 

changes may potentially cause trends in water quality arising 

from nonlinearity in the specification of the water-quality 

model). Accommodation of these properties of the variance in 

the data effects awaits future research.

Estimation of Point-Source Nutrient Loads

Annual TN and TP point-source loads were estimated 

for WY 2000 for the 91 delineated catchments (9 sites did 

not have delineated catchments). SS point-source loads were 

assumed to be negligible compared to in-stream SS loads 

and, therefore, were not estimated. Facility-specific average 

discharge, TN concentrations, and TP concentrations for WY 

2000 were used to estimate the annual nutrient loads from 

each point source. Point sources without a measured discharge 

were assigned a discharge equal to the design flow rate. 

When WY 2000 nutrient concentrations were not available, 

facility-specific values for water years that were as close 

as possible to WY 2000 were used instead in an attempt to 

represent typical WY 2000 operations. When facility-specific 

nutrient concentrations were not available, region-wide 

average concentrations for the applicable standard industrial 

classification (SIC) category were used. When region-wide 

average nutrient concentrations for a SIC category were 

not available or the regional data set was not large enough, 

national typical concentrations for the applicable SIC code 

were used (obtained from the USEPA [Gerard McMahan, U.S. 

Geological Survey, written commun., 2006]). Loads were not 

calculated for facilities without a measured discharge, design 

discharge, or any available nutrient concentrations (sitespecific, regional average, or typical national). In most cases, 

TN was not measured directly, so the components of TN (total 

Kjeldahl nitrogen [TKN] and dissolved nitrite plus nitrate as 

N) were summed to obtain a TN concentration. If the average 

WY 2000 value for a measured component of TN or TP was 

greater than the region-wide average for TN or TP, the facilityspecific average value for the component was used (since 

the values for TN and TP cannot be less than their individual 

components). Water-quality and discharge monitoring reports 

were obtained directly from the facilities or from the USEPA 

Permit Compliance System (PCS) (U.S. Environmental 

Protection Agency, 2006a), a database containing State 

discharge monitoring reports (DMRs) (NPDES Discharge 

Monitoring Reports) submitted by the facilities.

All municipal wastewater-treatment plants (WWTPs) 

designated as major sources (design flow greater than 

1.0 Mgal/d) were included in the analysis. The potential 

underestimation of loads caused by not including the minor 

WWTPs was determined by estimating the minor WWTPs 

Methods of Analysis 17
contribution to the total annual discharge for all of the 

facilities in the Columbia Basin. If all the minor WWTPs 

were operating at 1.0 Mgal/d (an unlikely situation), they 

would comprise about 20 percent of the total annual WWTP 

discharge (and load). However, if all the minor WWTPs were 

operating at 0.5 Mgal/d (probably still a high estimate), they 

would comprise about 12 percent of the total annual WWTP 

discharge (and load). All non-WWTP facilities in the PCS 

falling under the SIC categories in table 5 were included in the 

analysis (regardless of size). The USEPA has determined that 

these SIC categories are large sources of industrial nutrient 

loads (Tetra Tech, Inc., 1998).

Locations of the 140 point sources with estimated TN 

loads and 130 point sources with estimated TP loads in the 

catchments included in this study for WY 2000 are shown in 

figure 9. Point sources discharging directly to the Puget Sound 

are not shown in figure 9, but are discussed in the section 

describing that system. The sources are color-coded and 

sized to represent their relative loads based on the quartiles 

for annual TN and TP loads. Table 6 shows the ranges for 

the annual WY 2000 point-source load quartiles. The point 

sources with the largest nutrient loads were located around 

major population centers (lower Columbia River Basin, 

Willamette River Basin, Snake River Plain, near Spokane, 

Yakima River Basin, and the confluence of the Yakima, Snake, 

and Columbia Rivers).

Table 5. Industrial categories contributing to total nitrogen and 

total phosphorus loads in the Columbia and Puget Sound basins.

[From documentation of Phase I and Phase II activities and U.S. 

Environmental Protection Agency Permit Compliance System. Abbreviation:

SIC, standard industrial classification]

Industrial category SIC code

Plastics materials and resins 2821 

Nitrogenous fertilizers 2873 

Primary aluminum 3334 

Wet corn milling 2046 

Blast furnaces and steel mills 3312 

Industrial inorganic chemicals, 2819 

Petroleum refining 2911 

Meat packing plants 2011 

Paper mills 2621 

Pulp mills 2611

Paints and allied products 2851 

Primary nonferrous metals 3339 

Paperboard mills 2631

Poultry slaughtering and processing 2015

OR19-0072_fig09

124° 120° 115°

110°

42°

45°

49°

124° 120° 115°

110°

42°

45°

49°

0 250 KILOMETERS

0 250 MILES

EXPLANATION

Total phosphorus load—Estimated in 

pounds per year

 Quartile 1 0 to 10,000

 Quartile 2 10,001 to 22,100

 Quartile 3 22,101 to 48,000

 Quartile 4 More than 48,000

EXPLANATION

Total nitrogen load—Estimated in 

pounds per year

 Quartile 1 0 to 40,000

 Quartile 2 40,001 to 90,500

 Quartile 3 90,501 to 173,000

 Quartile 4 More than 173,000

Total phosphorus

130 sites

Total nitrogen

140 sites

Basemap modified from U.S. Geological Survey digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, central meridian 120°30’ W

Figure 9. Estimated point-source loads divided into quartiles for 

total nitrogen and total phosphorus, Columbia River basin, water 

year 2000.

18 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Transport of Nutrients and SuspendedSediment in Columbia River and Puget 

Sound Basins

Water year 2000 was selected to compare the discharges 

of TN, TP, and SS in the Columbia River and Puget Sound 

Basins. The discharge was the annual mean load in WY 

2000, expressed in units of pounds per day for TN and TP, 

and tons per day for SS. Annual mean load is defined as 

the average load for each day of one year. WY 2000 was 

selected because it represented a typical or average stream 

flow condition in the Pacific Northwest (see earlier section of 

report titled “Selection of Analysis Period”). The following 

three sections provide detailed descriptions of the load and 

transport of nutrients and sediment in the Columbia River, 

Willamette River, and Snake Rivers. Estimated annual mainstem, monitored tributary, and point-source loads for the three 

river systems are included in tables 8, 9, and 10. Although 

only the tributaries for which loads were calculated could be 

included in the analysis, the tables and the information shown 

in figures 11 through 21 provide some insight into the relative 

contribution of tributary and point source loads to rivers.

In WY 2000, the Snake, Yakima, Deschutes, and 

Willamette Rivers contributed most of the load discharged 

to the Columbia River, while point-source loads to the river 

(almost exclusively from municipal wastewater treatment 

plants) generally equaled a small percentage of the total 

in-stream nutrient load. Annual loads from point sources 

discharging directly to the Columbia River in WY 2000 

represented about 6 percent and 9 percent, respectively, of the 

estimated annual mean TN and TP load near the mouth of the 

river at Beaver Army Terminal (site 44, fig. 1). These loads 

also were equal to 10 percent and 14 percent, respectively, 

of the combined annual mean TN and TP loads discharged 

from the Snake, Yakima, Deschutes, and Willamette Rivers. 

Annual WY 2000 TN and TP loads from the largest point 

sources discharging directly to the Columbia River, which 

are in the fourth quartile in figure 9 (defined as those with 

loads exceeding 75 percent of the loads from all the facilities) 

are shown in figure 10. The City of Portland’s WWTP is the 

largest point-source discharger in the Columbia Basin. The 

annual TN and TP loads from this facility, which discharges 

directly to the Columbia River instead of the Willamette River, 

equaled 2.3 percent and 2.9 percent, respectively, of the annual 

in-stream TN and TP load at Beaver Army Terminal (site 44, 

table 1) in water year 2000.

Table 6. Quartile ranges for total nitrogen and total phosphorus 

point-source loads in the Columbia and Puget Sound basins, 

water year 2000.

[All loads are in pounds per year. Abbreviations: TN, total nitrogen; TP, total 

phosphorus]

Pointsource 

loads

Quartile range

1st 2nd 3rd 4th

TN 550–38,500 44,900–90,500 90,900–173,000 175,000–6,310,000

TP 26.0–9,070 10,300–22,100 22,300–48,000 49,200–899,000

Total phosphorus

(in pounds per day)

Total nitrogen

(in pounds per day)

City of Portland 

WWTP (1,590)

City of St. Helens

WWTP (781)

City of Camas

WWTP (408)

City of Vancouver

West WWTP (361)

City of Gresham 

WWTP (184)

City of Richland 

WWTP (179)

Fort James 

Camas (163)

Salmon Creek (163)

Boise Cascade 

Wallula (160)

City of Kennewick WWTP (149)

City of Portland 

Wastewater Treatment Plant (WWTP)

 (13,400)

City of St. Helens

WWTP (3,310)

City of Gresham 

WWTP (2,890)

Agrium US

Game Farm 

(2,390) 

Agrium US Bowlse Road (910)

City of Camas

WWTP (1,730)

City of Vancouver 

West WWTP (1,730) 

City of Kennewick 

WWTP (1,470)

City of Wenatchee 

WWTP (1,040)

City of Richland 

WWTP (936)

Figure 10. Estimated discharges from point sources to the 

Columbia River that exceed the 75th percentile of all point sources 

for total nitrogen and total phosphorus, water year 2000.

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 19
Columbia River System

Six water-quality monitoring stations were used to 

assess nutrient and sediment transport on the main stem of the 

Columbia River. Stations in Washington were at Northport 

(RM 735, fig. 1, site 86), Grand Coulee (RM 596; fig. 1, 

site 77), and Vernita Bridge near Priest Rapids Dam (RM 

388, fig. 1, site 51). Stations in Oregon were at Warrendale 

(RM 189; fig. 1., site 38), river marker 47 upstream of the 

Willamette River (RM 103; fig. 1, site 40), and Beaver Army 

Terminal (RM 54; fig. 1, site 44). In addition, 11 water-quality 

stations located on or near the mouths of Columbia River 

tributaries and 35 point sources discharging directly to the 

Columbia River, were used to assess nutrient and sediment 

load to the main stem of the river (fig. 11).

In WY 2000, the Columbia River discharged an 

average of 570,000 lb/d of TN to the Pacific Ocean (on the 

basis of the annual mean load at Columbia River at Beaver 

Army Terminal, fig. 1, site 44). In addition, an average of 

nearly 55,000 lb/d of TP, and about 14,000 ton/d of SS were 

discharged at Beaver Army Terminal. Tributary inputs to 

the Columbia River downstream of this site were small and 

did not appreciably affect the estimated load (Fuhrer and 

others, 1996). Nutrient and suspended-sediment discharges 

from the Columbia River represent contributions to the main 

Annual point-source loads of TN and TP discharged 

directly to the Willamette River were 11 percent and 36 

percent, respectively, of the annual mean load discharged 

from the Willamette to the Columbia River. Combining the 

nutrient load from the City of Portland’s WWTP with the 

point-source nutrient load to the Willamette River increased 

these contributions to the Columbia River to 18 and 42 

percent, respectively. Because most of the City of Portland 

lies within the Willamette Basin, these percentages represent 

the Willamette Basin’s total contribution to the Columbia 

River in WY 2000. Annual point-source loads of TN and TP 

discharged directly to the Snake River were 2 and 12 percent, 

respectively, of the annual mean load discharged from the 

Snake to the Columbia River. Although the drainage area 

for the Snake River is about 9 times larger than that for the 

Willamette, the Snake River’s point-source contribution to the 

Columbia River was about one half of the Willamette River’s 

contribution. The predicted annual mean loads for each of 

the main-stem sites on the Columbia River, the Willamette 

River, and the Snake River, as well as for sites located near 

the mouths of the Puget Sound tributaries for WY 2000 are 

included in appendix A. Further details regarding these loads 

are described in the following sections. An interpretation 

of nutrient and sediment transport in relation to landscape 

characteristics can be found in the section titled “Nutrient and 

Suspended-Sediment Yields”.

Summary of Direct Point-Source Nutrient Discharges to Columbia River and 

Largest Tributaries

Annual loads from point sources discharging directly to the Columbia River in WY 2000 

represented about 6 percent and 9 percent, respectively, of the annual mean TN and TP load near the 

mouth of the Columbia River at Beaver Army Terminal (site 44, fig. 1). These point-source loads also 

were small compared to annual mean loads discharged from the Snake and Willamette Rivers to the 

Columbia River. Annual WY 2000 TN and TP loads from the largest point sources discharging directly 

to the Columbia River (those in the fourth quartile in figure 9, or with loads exceeding 75 percent of the 

loads from all the facilities) are shown in figure 10. The City of Portland’s WWTP is the largest pointsource discharger in the basin. The annual TN and TP loads from this facility, which discharges directly 

to the Columbia River instead of the Willamette River, equaled 2.3 percent and 2.9 percent, respectively, 

of the annual in-stream TN and TP load at Beaver Army Terminal (site 44, table 1) in water year 2000.

Annual point-source loads of TN discharged directly to the Willamette River were 11 percent 

of the annual mean load discharged to the Columbia River from the Willamette River, and the annual 

point-source loads of TP were 36 percent of the annual mean load discharged to the Columbia River. 

Aggregating the nutrient load from the City of Portland’s WWTP with the point-source nutrient load to 

the Willamette River increased the contributions to 18 and 42 percent, respectively. These percentages 

represent the total contribution of the Willamette Basin to the Columbia River in WY 2000. The 

population density (based on 2000 census data) was six times greater in the Willamette Basin compared 

to the population density in the Columbia River Basin overall.

Annual point-source discharges of TN and TP made up 2 and 12 percent, respectively, of the annual 

mean load discharged from the Snake River to the Columbia River. Although the Snake River drainage 

area is greater than the Willamette River drainage area, the Snake River point-source contribution to the 

Columbia River was considerably less than that of the Willamette River.

20 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
OR19-0072_fig11

124° 123° 122° 121° 120° 119° 118°

46°

47°

48°

124° 123° 122° 121° 120° 119° 118°

46°

47°

48°

49°

49°

0 100 MILES

0 100 KILOMETERS

39 37

26

43

40

77

69

73

64

46

78

79

47

86

49

51

38

44

37 39

26

43

40

77

69

73

64

46

78

79

47

86

49

51

38

44

Columbia River

Columbia River

Pacific Ocean Pacific Ocean

31

33

31

33

EXPLANATION

Total phosphorus loads—Estimated in pounds 

per year

Estimated in-stream load—See table 1 for

 map identification number

 Quartile 1 0 to 40,000

 Quartile 2 40,001 to 160,000

 Quartile 3 160,001 to 750,000

 Quartile 4 More than 750,000

Estimated point source load

 Quartile 1 0 to 10,000

 Quartile 2 10,001 to 22,100

 Quartile 3 22,101 to 48,000

 Quartile 4 More than 48,000

EXPLANATION

Total nitrogen loads—Estimated in pounds per year

Estimated in-stream load—See table 1 for map

 identification number

 Quartile 1 0 to 407,500

 Quartile 2 407,501 to 1,000,000

 Quartile 3 1,000,001 to 6,790,000

 Quartile 4 More than 6,790,000

 Load not calculated

Estimated point source load

 Quartile 1 0 to 40,000

 Quartile 2 40,001 to 90,500

 Quartile 3 90,501 to 173,000

 Quartile 4 More than 173,000

Basemap modified from U.S. Geological Survey digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, central meridian 120°30’ W

Figure 11. Locations of sampling sites in the Columbia River and its tributaries and selected point sources discharging directly 

to the Columbia River, Oregon and Washington, water year 2000.

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 21
stem over a distance of 700 river miles, but permanent losses 

and temporary storage also occur during transport over this 

distance. Nitrogen and phosphorus, important nutrients in 

aquatic ecosystems, are removed by plants and other forms 

of aquatic life. Nitrogen also can be lost to the atmosphere 

as a gas (denitrification), and nitrogen and phosphorus 

can be incorporated into the streambed sediment as a solid 

through settling of algae and sediment particles. All these 

processes can affect the transport of nutrients through rivers 

and to estuaries. Therefore, the total quantity of nutrients 

delivered to the Columbia River is not conservative and may 

not necessarily exit through the Columbia estuary. Similarly, 

sediment (and sorbed nutrients) can become trapped behind 

main-stem dams and delivered to the surrounding land through 

irrigation diversions.

Water-quality stations along the main stem of the 

Columbia River were used to delineate five reaches for 

analysis (table 7). An attempt to account for the streamflow 

was made on each of these reaches by summing the monitored 

streamflow contributions to the reach by the tributaries and 

comparing that value to the accumulation of flow at the end 

of the reach (table 7). This exercise was not done to account 

for the gain and loss in streamflow within each reach: such 

an accounting would require information from all streamflow 

management actions and natural processes that divert 

water, return water, or otherwise consume water (including 

evaporative losses). Instead, the accounting was performed 

to provide some perspective on the tributary discharges of 

TN, TP, and SS for the monitored tributaries (those meeting 

the screening criteria for load estimation). This accounting 

provided a basic understanding of a tributary’s significance 

as a nutrient or suspended-sediment source. Although the 

sum of the measured tributary inflows for reach 1 was nearly 

equal to the gain within this reach during WY 2000, the 

total contribution from tributary inflows was actually greater 

than the gain if the diversion of irrigation water from the 

reach was included (annual mean of about 3,700 ft3

/s for 

WY 2000 for the diversion at Grand Coulee Dam). In reach 

2, the total contribution from tributary streamflow also was 

greater than the gain in streamflow over the reach. The results 

on the flow accounting for reaches 1 and 2 indicate that the 

Columbia River may have been losing water to the regional 

ground-water system between Northport and Grand Coulee. 

A load balance was determined to be appropriate for reaches 

3 and 4 because these reaches had no monitored tributary 

inputs. A load balance for reach 5 also was appropriate, with 

some caution regarding SS. An earlier study of the lower 

Columbia River (Fuhrer and others, 1996) determined that, 

except for the Willamette River, the streamflow and nutrient 

load contributions from the tributaries in this reach generally 

were minor (less than 5 percent in aggregate of the mainstem values). The one exception was the SS load from the 

Cowlitz River (the second largest tributary in the reach), 

which was about 22 percent of the main-stem SS load and was 

comparable to the load from the Willamette River. Because 

the Cowlitz River did not meet the screening criteria for load 

estimation, contributions of SS from this tributary were not 

considered in the load balance.

Discharge of TN and TP increased in reach 1, a distance 

of 139 river miles from Northport to Grand Coulee (fig. 12

and 13, and table 8). In this reach, the discharge of TN from 

the Spokane River accounted for nearly two-thirds of the 

gain in the annual mean load of TN (fig. 12) and slightly less 

than one-third of the gain in the annual load of TP (fig. 13). 

Table 7. Accounting for annual mean streamflow in the main stem of the Columbia River, water year 2000. 

[Abbreviations: OR, Oregon; WA, Washington; ft3/s, cubic foot per second; NA, indicates an assumption was made that no flow accumulation was in the reach]

Map 

index 

No.

Main-stem 

site name 

and reach

Reach River mile

Annual mean 

streamflow

(ft3

/s)

Gain 

in 

reach 

(ft3

/s)

Sum of measured 

annual mean 

tributary inflows 

(ft3

/s)

Measured tributary 

inflows as 

percentage of 

main-stem gain

86 Northport, WA 735 106,000

1 7,800 7,020 90.0

77 Grand Coulee, WA 596 113,000

2 6,600 8,270 125

51 Vernita Bridge, WA 388 120,000

3 65,400 59,700 91.2

38 Warrendale, OR 189 185,000

4 0 0 NA

40 Upstream of Willamette 

River, OR

103 185,000

5 46,500 35,100 75.5

44 Beaver Army 

Terminal, OR

54 232,000

22 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
OR19-0072_fig12

Reach 1 Reach 2 Reach 3 Reach 4 Reach 5

Relative total nitrogen load contributions

Annual mean discharge of total nitrogen loads

0

100,000

200,000

300,000

0

100,000

200,000

50,000

150,000

250,000

300,000

400,000

500,000

600,000

700 600 500 400 300 200 100

RIVER MILE

TOTAL NITROGEN LOAD, IN POUNDS PER DAY

Northport, WA (86)

Grand Coulee, WA (77)

Vernita Bridge near Priest Rapids Dam, WA (51)

Warrendale, OR (38)

Upstream of Wilamette R., OR (40)

Beaver Army Terminal, OR (44)

Numbers in parentheses indicate map identification No.

Change in total nitrogen load

Total nitrogen load from measured tributaries

Total nitrogen load from measured point sources

Tributary and point sources are stacked to show the 

sum of tributary and point-source contributions.

Figure 12. Annual mean discharge of total nitrogen loads in the Columbia River, and relative total nitrogen load 

contributions from Columbia River monitored tributaries and point sources, Oregon and Washington, water year 

2000. (Vertical scales on graphs are identical.)

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 23
OR19-0072_fig13

Reach 1 Reach 2 Reach 3 Reach 4 Reach 5

Relative total phosphorus load contributions

Annual mean discharge of total phosphorus loads

0

10,000

20,000

30,000

0

10,000

20,000

5,000

-5,000

15,000

25,000

30,000

40,000

50,000

60,000

700 600 500 400 300 200 100

RIVER MILE

TOTAL PHOSPHORUS LOAD, IN POUNDS PER DAY

Northport, WA (86)

Grand Coulee, WA (77)

Vernita Bridge near Priest Rapids Dam, WA (51)

Warrendale, OR (38)

Upstream of Wilamette R., OR (40)

Beaver Army Terminal, OR (44)

Numbers in parentheses indicate map identification No.

Change in total phosphorus load

Total phosphorus load from measured tributaries

Total phosphorus load from measured point sources

Tributary and point sources are stacked to show the 

sum of tributary and point-source contributions.

Figure 13. Annual mean discharge of total phosphorus loads in the Columbia River, and relative total phosphorus 

load contributions from Columbia River monitored tributaries and point sources, Oregon and Washington, water 

year 2000. (Vertical scales on graphs are identical.)

24 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Table 8. Annual mean discharge of total nitrogen, total phosphorus, and suspended sediment loads in the Columbia River, monitored 

Columbia River tributaries, and point sources discharging directly to the Columbia River, Oregon and Washington, water year 2000.

[Bold type indicates start of reach (see figure 12); shaded rows indicate monitoring site (see table 1); italicized type indicates point-source discharge source. 

Abbreviations: WA, Washington; OR, Oregon; ft3/s, cubic foot per second; -, not applicable]

Map 

index 

No.

Site

No. Site name

River mile Annual mean 

streamflow (ft3

/s)

Total nitrogen load

(pounds per day, estimated)

Columbia 

River Tributaries Point 

source 

Columbia 

River

Tributary 

inflowing

Columbia 

River 

Tributary

inflowing 

Point 

source 

86 12400520 Columbia River at Northport, WA 

(reach 1)

735 – – 106,000 – 75,700 – –

73 54A120 Spokane River at Riverside State Park 639 66 – – 7,020 – 21,600 –

WA0020281 Town of Coulee Dam Wastewater Treatment 

Plant

– – 604 – .31 – – 24.7

77 53A070 Columbia River at Grand Coulee (reach 2) 596 – – 113,000 – 111,000 – –

WA0021008 Brewster Wastewater Treatment Plant – – 530 – .47 – – 65.6

79 49A070 Okanogan River at Malott 532 2,930 2,780

78 48A070 Methow River near Pateros 524 5 1,440 1,100

69 46A070 Entiat River near Entiat 522 315

64 45A070 Wenatchee River at Wenatchee 465 1 3,370 2,780

WA0023949 Wenatchee Wastewater Treatment Plant – – 465 – 5.12 – – 1,040

WA0020621 East Wenatchee Douglas County Wastewater 

Treatment Plant

– – 464 – 2.02 – – 161

WA0002976 K.B. Alloys, Inc. – – 463 – .47 – – 21.3

WA0000680 Alcoa, Inc. Wenatchee Works – – 462 – 1.70 – – 78.1

51 12472900 Columbia River at Vernita Bridge near 

Priest Rapids Dam, WA (reach 3)

388 – – 120,000 – 144,000 – –

49 12510500 Yakima River at Kiona, WA 335 30 – – 3,770 – 21,000 –

WA0020419 Richland Wastewater Treatment Plant – – 337 – 9.52 – – 936

WA0044784 Kennewick Wastewater Treatment Plant – – 328 – 7.90 – – 1,460

WA0044962 Pasco Wastewater Treatment Plant – – 328 – 4.18 – – 500

WA0003671 Agrium US, Inc. Bowles Road – – 322 – 38.8 – – 918

WA0003727 Agrium US, Inc. Game Farm – – 322 – 101 – – 2,390

WA0003697 Boise Cascade Wallula – – 312 – 46.7 – – 352

47 13353200 Snake River at Burbank, WA 324 9 – – 46,600 – 171,000 –

46 32A070 Walla Walla River near Touchet 315 5 – – 572 – 2,430 –

43 11489 Umatilla River at Westland Road 

(Hermiston)

289 9 – – 545 – 3,980 –

26 11386 John Day River at Hwy 206 216 40 – – 1,770 – NA –

WA0000540 Columbia Gorge Aluminum Company – – 208 – 5.74 – – 263

39 10411 Deschutes River at Deschutes River Park 205 1 – – 6,450 – 10,600 –

OR0001708 Northwest Aluminum Co. – – 190 – 10.40 – – 473

OR0020885 City of The Dalles Wastewater Treatment 

Plant

– – 190 – 3.88 – – 309

WA0022373 Bingen Wastewater Treatment Plant – – 169 – 2.79 – – 223

OR0020788 City of Hood River Wastewater Treatment 

Plant

– – 169 – 1.80 – – 143

38 14128910 Columbia River at Warrendale, OR 

(reach 4)

143 – – 185,000 –– 424,000 – – 

WA0037427 Washougal Wastewater Treatment Plant – – 122 – 2.02 – – 161

WA0000256 Fort James Camas L.L.C. – – 121 – 47.6 – – 359

WA0020249 City of Camas Wastewater Treatment Plant – – 118 – 21.7 – – 1,730

OR0000060 Reynolds Metals Co. – – 119 – 4.57 – – 209

OR0026131 City of Gresham Wastewater Treatment Plant – – 118 – 18.1 – – 2,890

WA0000264 Boise Cascade Vancouver – – 106 – 5.42 – – 40.9

OR0026905 City of Portland Wastewater Treatment Plant – – 106 – 109 – – 13,400

WA0024350 Vancouver West Wastewater Treatment Plant – – 105 – 19.2 – – 1,730

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 25
Map 

index 

No.

Site No. Site Name

Total phosphorus load

(pounds per day, estimated)

Suspended sediment load

(tons per day, estimated)

Columbia

River

Tributary

inflowing

Point 

source

Columbia 

River

Tributary 

inflowing

Point 

source

86 12400520 Columbia River at Northport, WA 

(reach 1)

3,140 – – 928 – –

73 54A120 Spokane River at Riverside State Park – 1,870 – – 201 –

WA0020281 Town of Coulee Dam Wastewater Treatment 

Plant

– – 5.83 – – –

77 53A070 Columbia River at Grand Coulee (reach 2) 9,880 – – 393 – –

WA0021008 Brewster Wastewater Treatment Plant – – 8.74 – – –

79 49A070 Okanogan River at Malott – 659 – – 242 –

78 48A070 Methow River near Pateros – 166 – – 32.9 –

69 46A070 Entiat River near Entiat – 74 – – 18.1 –

64 45A070 Wenatchee River at Wenatchee – 420 – – 127 –

WA0023949 Wenatchee Wastewater Treatment Plant – – 96.2 – – –

WA0020621 East Wenatchee Douglas County Wastewater 

Treatment Plant

– – 37.9 – – –

WA0002976 K.B. Alloys, Inc. – – – – – –

WA0000680 Alcoa, Inc. Wenatchee Works – – – – – –

51 12472900 Columbia River at Vernita Bridge near Priest 

Rapids Dam, WA (reach 3)

8,220 – – 906 – –

49 12510500 Yakima River at Kiona, WA – 2,630 – – 468 –

WA0020419 Richland Wastewater Treatment Plant – – 179 – – –

WA0044784 Kennewick Wastewater Treatment Plant – – 149 – – –

WA0044962 Pasco Wastewater Treatment Plant – – 78.7 – – –

WA0003671 Agrium US, Inc. Bowles Road – – 37.6 – – –

WA0003727 Agrium US, Inc. Game Farm – – 97.7 – – –

WA0003697 Boise Cascade Wallula – – 160 – – –

47 13353200 Snake River at Burbank, WA – 13,300 – – 1,220 –

46 32A070 Walla Walla River near Touchet – 499 – – 162 –

43 11489 Umatilla River at Westland Road 

(Hermiston)

– 379 – – 70.2 –

26 11386 John Day River at Hwy 206 – 808 – – 120 –

WA0000540 Columbia Gorge Aluminum Company –

39 10411 Deschutes River at Deschutes River Park – 3,170 – – 192 –

OR0001708 Northwest Aluminum Co. – – – – – –

OR0020885 City of The Dalles Wastewater Treatment Plant – – 72.9 – – –

WA0022373 Bingen Wastewater Treatment Plant – – 52.5 – – –

OR0020788 City of Hood River Waste Water Treatment 

Plant

– – 33.8 – – –

38 14128910 Columbia River at Warrendale, OR 

(reach 4)

30,400 – – 3,560 – –

WA0037427 Washougal Wastewater Treatment Plant – – 37.9 – – –

WA0000256 Fort James Camas L.L.C. – – 163 – – –

WA0020249 City of Camas Wastewater Treatment Plant – – 408 – – –

OR0000060 Reynolds Metals Co. – – – – – –

OR0026131 City of Gresham Wastewater Treatment Plant – – 184 – – –

WA0000264 Boise Cascade Vancouver – – 18.6 – – –

OR0026905 City of Portland Wastewater Treatment Plant – – 1,590 – – –

WA0024350 Vancouver West Wastewater Treatment Plant – – 361 – – –

Table 8. Annual mean discharge of total nitrogen, total phosphorus, and suspended sediment loads in the Columbia River, monitored 

Columbia River tributaries, and point sources discharging directly to the Columbia River, Oregon and Washington, water year 2000.—

Continued

[Bold type indicates start of reach (see figure 12); shaded rows indicate monitoring site (see table 1); italicized type indicates point-source discharge source. 

Abbreviations: WA, Washington; OR, Oregon; ft3/s, cubic foot per second; –, not applicable]

26 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site

No. Site name

River mile Annual mean 

streamflow (ft3

/s)

Total nitrogen load

(pounds per day, estimated)

Columbia 

River Tributaries Point 

source 

Columbia 

River

Tributary 

inflowing

Columbia 

River 

Tributary

inflowing 

Point 

source 

40 10616 Columbia River at Marker #47 (upstream 

of Willamette River) (reach 5)

102 – – 185,000 – 455,000 – – 

37 10332 Willamette River at SP&S Railroad Bridge 101 7 – – 35,100 – 157,000 –

31 10611 Willamette River at Hawthorne Bridge 101 13 – – 35,100 – 152,000 –

33 14211720 Willamette River at Portland, OR 101 13 – – 35,100 – 160,000 –

WA0000299 Evergreen Aluminum L.L.C. – – 100 – 1.40 – – 63.9

WA0023639 Salmon Creek Wastewater Treatment Plant – – 95 – 8.68 – – 734

OR0020834 City of Saint Helens Wastewater Treatment 

Plant

– – 86 – 41.5 – – 3,310

OR0001635 Dyno Nobel, Inc. – – 84 – .12 – – 2.94

WA0000353 Chemtrade Performance Chemical – – 75 – 4.65 – – 47.6

WA0000078 Longview Fibre Longview – – 59 – 39.2 – – 296

WA0000086 Chinook Ventures, Inc. Longview – – 58 – 5.42 – – 248

WA0000124 Weyerhaeuser Longview – – 58 – 24.0 – – 181

WA0037311 Longview Wastewater Treatment Plant – – 56 – 7.75 – – 618

44 14246900 Columbia River at Beaver Army Terminal 

near Quincy, OR 

54 – – 232,000 – 572,000 – – 

Table 8. Annual mean discharge of total nitrogen, total phosphorus, and suspended sediment loads in the Columbia River, monitored 

Columbia River tributaries, and point sources discharging directly to the Columbia River, Oregon and Washington, water year 2000.—

Continued

[Bold type indicates start of reach (see figure 12); shaded rows indicate monitoring site (see table 1); italicized type indicates point-source discharge source. 

Abbreviations: WA, Washington; OR, Oregon; ft3/s, cubic foot per second; –, not applicable]

Map 

index 

No.

Site No. Site Name

Total phosphorus load

(pounds per day, estimated)

Suspended sediment load

(tons per day, estimated)

Columbia

River

Tributary

inflowing

Point 

source

Columbia 

River

Tributary 

inflowing

Point 

source

40 10616 Columbia River at Marker #47 (upstream of 

Willamette River) (reach 5)

43,800 – – 4,800 – –

37 10332 Willamette River at SP&S Railroad Bridge – 18,100 – – 1,440 –

31 10611 Willamette River at Hawthorne Bridge – 16,500 – – 1,340 –

33 14211720 Willamette River at Portland, OR – 16,300 – – 2,780 –

WA0000299 Evergreen Aluminum L.L.C. – – – – – –

WA0023639 Salmon Creek Wastewater Treatment Plant – – 163 – – –

OR0020834 City of Saint Helens Wastewater Treatment Plant – – 781 – – –

OR0001635 Dyno Nobel, Inc. – – – – – –

WA0000353 Chemtrade Performance Chemical – – 5.26 – – –

WA0000078 Longview Fibre Longview – – 135 – – –

WA0000086 Chinook Ventures, Inc. Longview – – – – – –

WA0000124 Weyerhaeuser Longview – – 82.4 – – –

WA0037311 Longview Wastewater Treatment Plant – – 146 – – –

44 14246900 Columbia River at Beaver Army Terminal 

near Quincy, OR

54,600 – – 14,600 – –

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 27
OR19-0072_fig14

Reach 1 Reach 2 Reach 3 Reach 4 Reach 5

Relative total suspended-sediment load contributions

Annual mean discharge of total suspended-sediment loads

0

2,000

4,000

6,000

0

4,000

8,000

2,000

-2,000

6,000

10,000

12,000

8,000

10,000

12,000

14,000

16,000

700 600 500 400 300 200 100

RIVER MILE

SUSPENDED-SEDIMENT LOAD, IN TONS PER DAY

Northport, WA (86)

Grand Coulee, WA (77)

Vernita Bridge near Priest Rapids Dam, WA (51)

Warrendale, OR (38)

Beaver Army Terminal, OR (44)

Upstream of Wilamette R., OR (40)

Numbers in parentheses indicate map identification No.

Change in suspended-sediment load

Total suspended-sediment load from measured tributaries

Figure 14. Annual mean discharge of suspended-sediment loads in the Columbia River and relative suspendedsediment load contributions from Columbia River monitored tributaries, Oregon and Washington, water year 2000. 

(Vertical scales on graphs are identical.)

Point-source contributions of TN and TP in this reach, 

however, were negligible. The SS discharged at Northport 

decreased by more than 40 percent in reach 1 to downstream 

of Grand Coulee, likely the result of sediment deposition in 

the backwater impoundment behind Grand Coulee (Lake 

Roosevelt) and irrigation diversions (table 8 and fig. 14). The 

discharges in reach 2 increased for TN and SS, and decreased 

for TP (figs. 12, 13, and 14). Point-source discharges of TN 

and TP to the main stem in this reach were negligible.

Several large tributaries join the Columbia River in reach 

3, which has a length of more than 200 river miles between 

Vernita Bridge and Warrendale. Most of these tributaries 

were monitored and, in aggregate, accounted for 91 percent 

of the gain in streamflow within the reach. The tributaries 

in reach 3 accounted for 74 percent of the TN discharged 

to the reach (excluding the John Day River), 92 percent of 

the TP, and 78 percent of the SS. These percentages can be 

viewed qualitatively by comparing the relative heights of 

the paired bar graphs for reach 3 in figures 12, 13, and 14. 

28 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
The major monitored tributaries discharging to this reach 

are the Yakima River, the Snake River, and the Deschutes 

River (table 8). In aggregate, the contributions of these three 

tributaries accounted for at least 94 percent of the TN, TP, and 

SS discharged to reach 3 from all of the monitored tributaries, 

with the Snake River by far the largest (table 9). As with 

reaches 1 and 2, point-source discharges of TN and TP to the 

main stem were small by comparison.

Reach 4 was different from the other reaches in that 

it had only minor tributary inputs, the most notable being 

the Sandy River (which was not included in the analysis). 

Reach 4 is affected primarily by point-source contributions 

(table 8). This reach spans about 41 river miles between 

Warrendale (immediately downstream of Bonneville Dam) 

and Marker 47 (located upstream of the confluence of the 

Willamette and Columbia Rivers). Within this reach, the 

point-source discharge of TN represented most of the nitrogen 

gain (figure 12), whereas the relative contribution for TP was 

notable, but smaller (figure 13).

Reach 5 began at Marker 47 and ended at Beaver Army 

Terminal (river mile 53.8). The gain within the reach for both 

TN and TP was less than the discharge of TN and TP from the 

Willamette River (figures 12 and 13). Without some in-stream 

loss or storage (for example, biological uptake or settling), the 

discharge of nutrients from the Willamette River should not 

have contributed more than the total of the gain in nutrients 

in this reach, especially since the tributary discharges from 

the Cowlitz River, Kalama River, and the Lewis River were 

not included in the analysis. Aside from the possibility of 

in-stream loss or storage, a reason for the discrepancy between 

TN and TP load and gain in this reach is not apparent. The 

discharge of SS from the Willamette represented slightly less 

than one third of the SS gain within the reach. This was to be 

expected considering the SS inputs from the other tributaries 

in this reach (particularly the Cowlitz River).

Willamette River System

Four water-quality monitoring stations in Oregon were 

used to assess nutrient and sediment transport on the main 

stem of the Willamette River (fig. 15): Harrisburg, (RM 161, 

fig. 1, site 7), Albany (RM 119, fig. 1, site 11), Salem (RM 

84, fig. 1, site 14), and Portland (RM 13, fig. 1, site 33). 

In addition, 6 water-quality stations on Willamette River 

tributaries and 20 point sources were used to assess nutrient 

and sediment load to the river.

The Willamette River discharged an annual mean load 

of 160,000 lb/d of TN (table 10), 16,300 lb/d of TP, and 

2,780 ton/d of SS to the Columbia River in WY 2000 (on 

the basis of annual mean loads at Portland, Oreg.; fig. 1, site 

33). These contributions represented discharges from all 

tributaries and point sources, ground-water systems, and the 

environmental processing of nutrients as Willamette waters 

flowed to the Columbia River. As was done with the main 

stem of the Columbia River, an accounting of streamflow 

gains was made for the reaches defined by the main-stem 

sites on the Willamette River (table 11). None of the reaches 

had tributaries that accounted for more than one-half the 

streamflow gain (table 11). Discharge of TN, TP, and SS 

increased steadily down the main stem, with the largest 

increase occurring in reach 3 between Salem and Portland 

(figs. 16, 17, and 18). Because they accounted for so little of 

the streamflow gain, the discharge of TN, TP, and SS from the 

six monitored tributaries to the Willamette River accounted for 

only a small part (within their respective reaches) of the gain 

in TN, TP, and SS in reaches 1 through 3 (figs. 16, 17, and 18).

Reach 1 spans a distance of 42 river miles and is 

bounded upstream by Harrisburg and downstream by Albany 

(fig. 17). About 10 river miles upstream from Harrisburg, 

the Willamette River receives point-source runoff from the 

Eugene/Springfield Water Pollution Control Facility and 

non-point source runoff from the McKenzie River. These two 

sources, with about equal annual TP loads, accounted for 59 

percent of the annual mean TP load discharge at Harrisburg 

(table 10). Contributions of TN from the Eugene/Springfield 

WWTP represented 32 percent of the load at Harrisburg. In 

reach 1, the Willamette River receives urban runoff from 

Corvallis, as well as discharge from the Corvallis WWTP. 

It also receives nonpoint-source runoff from the Long Tom 

River, in addition to the Calapooya River and Mary’s River 

(the latter two of which were not included in the analysis). 

Table 9. Relative discharge of total nitrogen, total phosphorus, 

and suspended sediment loads from three major tributaries 

to Columbia River between Vernita Bridge, Washington, and 

Warrendale, Oregon, water year 2000.

[Discharge expressed as a percentage of all measured tributary loads for the 

reach]

Discharge

Load (percentage)

Snake River Yakima River Deschutes River

Total nitrogen 82.8 10.2 5.10

Total phosphorus 65.5 13.0 15.6

Suspended sediment 82.8 10.2 5.10

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 29
OR19-0072_fig15 Pacific Ocean Pacific Ocean

124°00' 123°00' 122°00'

44°30'

45°00'

45°30'

124°00' 123°00' 122°00'

44°30'

45°00'

45°30'

0 50 MILES

0 50 KILOMETERS

6

8

7

37

18

19

17

23

14

11

6

8

7

37

18

19

17

23

14

11

Willamette River

Willamette River

Columbia River 

Columbia River 

31

33

31

33

EXPLANATION

Total phosphorus loads—Estimated in pounds per year

Estimated in-stream load—See table 1 for map

 identification number

 Quartile 1 0 to 40,000

 Quartile 2 40,001 to 160,000

 Quartile 3 160,001 to 750,000

 Quartile 4 More than 750,000

Estimated point source load

 Quartile 1 0 to 10,000

 Quartile 2 10,001 to 22,100

 Quartile 3 22,101 to 48,000

 Quartile 4 More than 48,000

EXPLANATION

Total nitrogen loads—Estimated in pounds per year

Estimated in-stream load—See table 1 for map

 identification number

 Quartile 1 0 to 407,500

 Quartile 2 407,501 to 1,000,000

 Quartile 3 1,000,001 to 6,790,000

 Quartile 4 More than 6,790,000

 Load not calculated

Estimated point source load

 Quartile 1 0 to 40,000

 Quartile 2 40,001 to 90,500

 Quartile 3 90,501 to 173,000

 Quartile 4 More than 173,000

Basemap modified from U.S. Geological Survey digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, central meridian 120°30’ W

Figure 15. Locations of sampling sites in the Willamette River and its tributaries, and selected point sources 

discharging directly to the Willamette River, Oregon, water year 2000.

30 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Table 10. Mean annual discharge of total nitrogen, total phosphorus, and suspended sediment loads in the Willamette River, monitored 

Willamette River tributaries, and point sources discharging directly to the Willamette River, Oregon, water year 2000.

[Bold type indicates start of reach (see figure 16); shaded rows indicate monitoring site (see table 1); italicized type indicates point-source discharge source. 

Abbreviations: WA, Washington; OR, Oregon; ft3/s, cubic foot per second; –, not applicable]

Map 

index 

No.

Site No. Site name

River mile Annual mean 

streamflow (ft3

/s)

Total nitrogen load

(pounds per day, estimated)

Willamette 

River

TributariesPoint 

source 

Willamette 

River

Tributary 

inflowing

Willamette 

River

Tributary 

inflowing

Point 

source 

OR0020559 City of Cottage Grove Wastewater 

Treatment Plant

– – 187 – 2.87 – – 160

OR0031224 Eugene/Springfield Water Pollution 

Control Facility

– – 172 – 62.6 – – 4,980

6 10376 McKenzie River at Coburg Road – 172 – – 5,070 – – –

7 10355 Willamette River at Hwy 99E 

(Harrisburg) (reach 1)

161 – – 11,300 – 15,800 – –

OR0033405 Fort James Operating Co. – – 148 – 5.12 – – 38.6

OR0001074 Pope & Talbot, Inc. – – 147 – 17.6 – – 133

8 11140 Long Tom River at Stow Pit Road 

(Monroe)

– 146 – 743 – 3,040

OR0000299 Evanite Fiber Corp. – – 20 – 1.02 – – 33.8

OR0026361 City of Corvallis Wastewater Treatment 

Plant

– – 20 – 16.4 – – 602

11 10350 Willamette River at Albany 

(Eastbound Hwy 20 Bridge) 

(reach 2)

119 – – 14,200 – 38,100 – –

OR0028801 City of Albany Wastewater Treatment 

Plant

– – 117 – 12.2 – – 580

OR0000442 Weyerhaeuser Co. – – 116 – 8.06 – – 319

OR0001112 Tdy Industries, Inc. – – 116 – 3.21 – – 148

14 10555 Willamette River at Marion Street 

(Salem) (reach 3)

84 – 23,700 – 65,900 – –

OR0026409 City of Salem Wastewater Treatment 

Plant

– – 83 – 64.6 – – 5,920

OR0032352 City of Newberg Wastewater Treatment 

Plant

– – – – 4.34 – – 346

OR0000558 SP Newsprint – – – – 10.1 – – 76.0

17 10640 Pudding River at Hwy 211 (Woodburn) – 36 – – 825 – 11,700 –

OR0022764 Wilsonville, City of – – – – 2.99 – – 154

OR0020214 Canby City Wastewater Treatment Plant – – 34 – 1.60 – – 127

19 3701002 Tualatin River at Weiss Bridge – 28 – – 1,410 – 16,600 –

OR0000566 Blue Heron Paper Co. – – 28 – 4.57 – – 58.0

OR0000787 West Linn Paper Co. – – 28 – 4.57 – – 34.5

OR0031259 Tri-City Service District – – 25 – 12.6 – – 994

18 13070 Clackamas River at Mciver Park (upper 

boat ramp)

– 25 – 2,830 – – –

OR0026891 Tryon Creek Wastewater Treatment Plant – – 20 – 12.80 – 1,200

OR0026221 Kellogg Creek Wastewater Treatment 

Plant

– – 19 – 12.60 – 1,000

23 11321 Johnson Creek at SE 17th Avenue 

(Portland)

– 18 – – 69 – 1,300 –

31 10611 Willamette River at Hawthorne 

Bridge

13 – – 35,100 – 152,000 – –

33 14211720 Willamette River at Portland, OR 13 – – 35,100 – 160,000 – –

OR0001597 Atofina Chemicals, Inc. – – 7 12.5 – 128

37 10332 Willamette River at SP&S Railroad 

Bridge

7 –– – 35,100 – 157,000 – –

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 31
Table 10. Mean annual discharge of total nitrogen, total phosphorus, and suspended sediment loads in the Willamette River, monitored 

Willamette River tributaries, and point sources discharging directly to the Willamette River, water year 2000.—Continued

[Bold type indicates start of reach (see figure 16); shaded rows indicate monitoring site (see table 1); italicized type indicates point-source discharge source. 

Abbreviations: WA, Washington; OR, Oregon; ft3/s, cubic foot per second; -, not applicable]

Map 

index 

No.

Site No. Site name

Total phosphorus load

(pounds per day, estimated)

Suspended sediment load

(tons per day, estimated)

Willamette 

River

Tributary 

inflowing

Point 

source

Willamette 

River

Tributary 

inflowing

Point 

source 

OR0020559 City of Cottage Grove Wastewater 

Treatment Plant

– – 53.9 – – –

OR0031224 Eugene/Springfield Water Pollution Control 

Facility

– – 1,130 – – –

6 10376 Mckenzie River at Coburg Road – 1,200 – – 88.1 –

7 10355 Willamette River at Hwy 99E 

(Harrisburg) (reach 1)

3,980 – – 227 – –

OR0033405 Fort James Operating Co. – – 28.1 – – –

OR0001074 Pope & Talbot, Inc. – – 60.4 – – –

8 11140 Long Tom River at Stow Pit Road 

(Monroe)

– 337 – – 60.3 –

OR0000299 Evanite Fiber Corp. – – 3.51 – – –

OR0026361 City Of Corvallis Wastewater Treatment 

Plant

– – 1,650 – – –

11 10350 Willamette River at Albany 

(Eastbound Hwy. 20 Bridge) 

(reach 2)

6,140 – – 521 – –

OR0028801 City of Albany Wastewater Treatment 

Plant

– – 237 – – –

OR0000442 Weyerhaeuser Co. – – 68.2 – – –

OR0001112 Tdy Industries, Inc. – – – – – –

14 10555 Willamette River at Marion Street 

(Salem) (reach 3)

9,360 – – 1,050 – –

OR0026409 City of Salem Wastewater Treatment 

Plant

– – 1,220 – – –

OR0032352 City of Newberg Wastewater Treatment 

Plant

– – 81.6 – – –

OR0000558 Sp Newsprint – – 701 – – –

17 10640 Pudding River at Hwy. 211 (Woodburn) – 575 – – 27.5 –

OR0022764 Wilsonville, City of – – 31.1 – – –

OR0020214 Canby City Wastewater Treatment Plant – – 30.0 – – –

19 3701002 Tualatin River at Weiss Bridge – 1,160 – – –

OR0000566 Blue Heron Paper Co. – – 27.0 – – –

OR0000787 West Linn Paper Co. – – 15.7 – – –

OR0031259 Tri-City Service District – – 236 – – –

18 13070 Clackamas River At Mciver Park (upper 

boat ramp)

– 450 – 264

OR0026891 Tryon Creek Wastewater Treatment Plant – – 143 – – –

OR0026221 Kellogg Creek Wastewater Treatment 

Plant

– – 236 – – –

23 11321 Johnson Creek at SE 17th Avenue 

(Portland)

– 47 – – 3.74 –

31 10611 Willamette River at Hawthorne 

Bridge

16,500 – – 1,340 – –

33 14211720 Willamette River at Portland, OR 16,300 – 2,780 –

OR0001597 Atofina Chemicals, Inc. – 14.1 – –

37 10332 Willamette River at SP&S Railroad 

Bridge

18,100 – – 1,440 – –

32 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Table 11. Accounting for annual mean streamflow in the Willamette River, Oregon, water year 2000.

[Abbreviation: ft3/s, cubic foot per second]

Map 

index 

No.

Main-stem site 

name and reach Reach River mile

Annual mean 

streamflow 

(ft3

/s)

Gain in 

reach 

(ft3/s)

Sum of measured 

annual mean 

tributary inflows 

(ft3

/s)

Measured tributary 

inflows as 

percentage of 

main-stem gain

7 Harrisburg 161 11,300

1 2,820 743 26.3

11 Albany 119 14,200

2 9,590 0 0

14 Salem 84 23,700

3 11,300 5,130 45.4

33 Portland 13 35,100

The annual load of TP discharged to the Willamette River 

from the City of Corvallis’ WWTP represented 27 percent of 

annual mean load in the Willamette River at Albany (about 

5 times the annual mean load discharged from the Long Tom 

River), and 80 percent of the increase in TP annual mean load 

between Harrisburg and Albany. However, the annual TN load 

from the city’s WWTP was less than 2 percent of the annual 

mean load in this reach. Although tributary inflow increased 

streamflow by only 25 percent in the reach from Harrisburg 

to Albany, the tributaries, nonpoint-source runoff, and point 

source discharges were responsible for increasing the annual 

mean TN load by nearly 140 percent, increasing the annual 

mean TP load by about 11 percent, and increasing the annual 

mean SS load by 130 percent.

Reach 2 covered the 35 river miles between Albany 

and Salem, where annual mean streamflow increased by 

nearly 10,000 ft3/s owing to inputs from the Luckiamute 

River, the Santiam River, and several smaller streams (none 

were included in the analysis). Within reach 2, TN and TP 

from point sources discharging directly to the Willamette 

River were small and negligible in comparison to tributary 

discharges of TN and TP (table 10, fig. 16 and 17). Therefore, 

discharges from the Luckiamute River and the Santiam River, 

although not measured directly, were likely important sources 

of nutrients and SS to the Willamette.

In the more than 70 river miles from Salem to Portland 

(reach 3), the Willamette River receives discharges from 

point sources resulting from high-density urbanization in 

Portland and the surrounding metropolitan areas, as well 

as Salem. This reach also is affected by nonpoint sources, 

principally agricultural runoff. Annual mean streamflow 

in reach 3 increased by 11,300 ft3/s. About 45 percent of 

this increase was from monitored tributaries. This reach 

also received tributary inputs from the Yamhill and Molalla 

Rivers (not included in the analysis), Pudding, Tualatin, and 

Clackamas Rivers, in addition to several small creeks. In this 

reach, monitored tributaries and point sources accounted for 

nearly one-half the 85,600 lb/d gain of annual mean TN load 

and about 70 percent of the 7,000 pounds per day gain in 

annual mean TP load. The largest annual mean loads of TN 

were from the Tualatin River (16,600 lb/d) and the Pudding 

River (11,700 lb/d). Annual mean point-source loads within 

this reach (which did not include the City of Portland’s main 

WWTP) equaled almost 10,000 lb/d of TN. The largest pointsource annual mean load of TN was 5,900 lb/d from the City 

of Salem’s WWTP. Of the tributaries with estimated SS loads, 

the Clackamas River was the largest monitored tributary in 

the entire Willamette basin. However, the estimated load from 

the Clackamas River may have been biased low because of 

interagency differences in field sampling protocols. Annual 

mean point-source loads within the reach equaled about 

2,700 lb/d of TP.

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 33
OR19-0072_fig16

Reach 1 Reach 2 Reach 3

Relative total nitrogen load contributions

Annual mean discharge of total nitrogen loads

0

120,000

140,000

0

20,000

60,000

40,000

80,000

100,000

20,000

60,000

40,000

80,000

100,000

160,000

180,000

180 160 140 120 100 80 60 40 20 0

RIVER MILE

TOTAL NITROGEN LOAD, IN POUNDS PER DAY

Salem, OR (14)

Portland, OR (33)

Albany, OR (11)

Harrisburg, OR (7)

Numbers in parentheses indicate map identification No.

Change in total nitrogen load

Total nitrogen load from measured tributaries

Total nitrogen load from measured point sources

Tributary and point sources are stacked to show the 

sum of tributary and point-source contributions.

Figure 16. Annual mean discharge of total nitrogen loads in the Willamette River and relative total nitrogen load 

contributions from Willamette River monitored tributaries and point sources, Oregon, water year 2000. (Vertical 

scales on graphs are identical.)

34 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
OR19-0072_fig17

Reach 1 Reach 2 Reach 3

0

12,000

14,000

0

2,000

6,000

4,000

8,000

10,000

2,000

6,000

4,000

8,000

10,000

16,000

18,000

180 160 140 120 100 80 60 40 20 0

RIVER MILE

Relative total phosphorus load contributions

Annual mean discharge of total phosphorus loads

TOTAL PHOSPHORUS LOAD, IN POUNDS PER DAY

Salem, OR (14)

Portland, OR (33)

Harrisburg, OR (7)

Albany, OR (11)

Numbers in parentheses indicate map identification No.

Change in total phosphorus load

Total phosphorus load from measured tributaries

Total phosphorus load from measured point sources

Tributary and point sources are stacked to show the 

sum of tributary and point-source contributions.

Figure 17. Annual mean discharge of total phosphorus loads in the Willamette River and relative total phosphorus 

contributions from Willamette River monitored tributaries and point sources, Oregon, water year 2000. (Vertical scales 

on graphs are identical.)

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 35
OR19-0072_fig18

Reach 1 Reach 2 Reach 3

Numbers in parentheses indicate map identification No.

Salem, OR (14)

Portland, OR (33)

Albany, OR (11)

Harrisburg, OR (7)

0

1,500

2,000

0

500

1,000

1,500

2,000

500

1,000

2,500

3,000

180 160 140 120 100 80 60 40 20 0

RIVER MILE

Relative total suspended-sediment load contributions

Annual mean discharge of total suspended-sediment loads

SUSPENDED-SEDIMENT LOAD, IN TONS PER DAY SUSPENDED-SEDIMENT LOAD, IN TONS PER DAY

Change in suspended-sediment load

Total suspended-sediment load from measured tributaries

Figure 18. Annual mean discharge of suspended-sediment loads in the Willamette River and relative suspendedsediment load contributions from Willamette River monitored tributaries, Oregon, water year 2000. (Vertical scales on 

graphs are identical.)

36 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Snake River System

The Snake River travels more than 1,000 river miles 

from its headwaters and drains parts of Oregon, Washington, 

Idaho, and Wyoming. Its drainage basin represents about 42 

percent of the Columbia Basin’s drainage area. The uppermost 

site for load estimation was the Snake River at Flagg Ranch, 

WY. (RM 1,050, fig. 1, site 100); the lowermost site was the 

Snake River at Burbank, WA (RM 8.7, fig. 1, site 47). Two 

intermediate sites were at Snake River at Buhl, ID (RM 597, 

fig. 1, site 90) and Snake River at King Hill, ID (RM 546, 

fig. 1, site 91) [fig. 19].

The Snake River was a major source of nutrients and 

sediment to the Columbia River, discharging an annual mean 

load of 171,000 lb/d of TN, 13,300 lb/d of TP, and 1,220 

ton/d of SS (table 12). Characterizing nutrient and sediment 

deliveries from tributaries to the Snake River was difficult 

because only 2 of the 32 major Snake River tributaries met 

the screening criteria for estimating loads. Although waterquality records were available for several tributaries, most 

water-quality data were only seasonal instead of the required 

coverage throughout the water year. The annual mean load 

of TN, TP, and SS increased 151 fold, 50 fold, and 9 fold, 

respectively, from the headwaters at Flagg Ranch to the mouth 

(fig. 20). In reach 2, between Buhl and King Hill, a distance 

of 51 mi, streamflow and TN discharge nearly doubled, TP 

increased by slightly more than one-third, and SS remained 

essentially unchanged. The Snake River between Buhl 

and King Hill received a large amount of nutrient-rich and 

sediment-free ground-water discharge, in addition to some 

phosphorus discharges from aquaculture activities. These 

sources could explain the patterns in streamflow, nutrients, and 

sediment observed in this reach.

Puget Sound Basin

Nutrient and sediment delivery to Puget Sound was 

assessed by using water-quality monitoring stations near the 

mouths of 8 major tributaries and estimated nutrient loads 

from 28 point sources. Figure 21 shows the location of waterquality stations on 8 major tributaries to the Sound and the 2 

point sources that discharge directly to those tributaries (but 

not directly to the Sound). The water-quality stations were 

on the Duckabush River near Brinnon, Wash. (fig. 1, site 71), 

the Skokomish River near Potlatch, Wash. (fig. 1, site 61), the 

Deschutes River at East Street Bridge, Wash. (fig. 1, site 56), 

the Puyallup River at Meridan Street, Wash. (fig. 1, site 57), 

the Duwamish River at Golf course at Tukwilla, Wash. (fig. 1, 

site 67), the Snohomish River at Snohomish, Wash. (fig. 1, site 

76), the Skagit River near Mount Vernon, Wash. (fig. 1, site 

81), and the Nooksack River at Brennan, Wash. (fig. 1, site 

84). The areas draining to these eight tributaries account for 

about 50 percent of the surface area of the Puget Sound basin. 

A study by Embrey and Inkpen (1998) determined that these 

tributaries delivered 65 percent of the surface-water inflow 

and accounted for about 75 percent of the inorganic nitrogen 

(nitrite plus nitrate nitrogen and ammonia nitrogen) and TP 

loads to the Puget Sound. In WY 2000, the total discharge of 

these tributaries to Puget Sound equaled 61,000 lb/d of TN, 

13,000 lb/d of TP, and 11,500 ton/d of SS (fig. 22).

Figure 22 shows the WY 2000 monitored tributary and 

estimated point-source loads of TN, TP, and SS discharged 

to the Puget Sound. The contribution of nutrients to the eight 

monitored tributaries from point sources located within their 

catchments was very small (six tributaries had no direct 

point-source contributions and the estimated point-source 

contribution to the other two tributaries was never more than 

6 percent of the predicted in-stream load for WY 2000). 

However, the sum of the nutrient loads from point sources 

discharging either directly to the Puget Sound or very close 

to the mouths of tributaries was comparable to the sum of the 

monitored tributary loads. Point sources contributed almost 

50 percent of the annual TN and TP load discharged to the 

Sound in WY 2000, with WWTPs accounting for more than 

90 percent of the point-source load. The largest tributary loads 

of TN in WY 2000 were from the Snohomish River and the 

Skagit River. Together, they accounted for about 57 percent 

of the total monitored tributary TN load to the Sound. With 

the addition of the TN load from the Nooksack River, the 

contribution increased to 77 percent of the total TN load. The 

Skagit River was the single largest tributary contributor to 

the Sound for TP, accounting for more than 31 percent of the 

monitored tributary load. These tributaries are on the east side 

of the Sound, in areas where the intensity of urbanization and 

agricultural activity is greatest.

Monitored WY 2000 tributary nutrient loads to the 

Puget Sound were only a fraction of those discharged from 

the Columbia River. The TN and TP loads from all of the 

monitored Puget Sound tributaries were equal to about 11 

percent and 24 percent of the TN and TP load, respectively, at 

the Columbia River at Beaver Army Terminal, Oreg. (fig. 1, 

site 44). The smaller loads are because Puget Sound’s drainage 

area is only one-seventh of the Columbia River Basin and the 

sum of the mean streamflow for the eight monitored tributaries 

in WY 2000 was about 17 percent of the value in the 

Columbia River at Beaver Army Terminal. However, the total 

annual mean SS load discharged from all monitored tributaries 

to the sound (fig. 22) represented about three-quarters of the 

annual mean SS load discharged from the Columbia River.

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 37
OR19-0072_fig19

47

93

91

90 89

100

47

93

91

90 89

100

120° 119° 118° 117° 116° 115° 114° 113° 112° 111° 110°

43°

44°

45°

46°

120° 119° 118° 117° 116° 115° 114° 113° 112° 111° 110°

43°

44°

45°

46°

River

River

Snake

Snake

Columbia River

Columbia River

WASHINGTON

WASHINGTON

OREGON

IDAHO

OREGON

IDAHO

IDAHO

MONTANA

IDAHO

MONTANA

WYOMING WYOMING

0 100 MILES

0 100 KILOMETERS

EXPLANATION

Total phosphorus loads—Estimated in pounds per year

Estimated in-stream load—Table 1 contains 

 mapping number identification

 Quartile 1 0 to 40,000

 Quartile 2 40,001 to 160,000

 Quartile 3 160,001 to 750,000

 Quartile 4 More than 750,000

Estimated point source load

 Quartile 1 0 to 10,000

 Quartile 2 10,001 to 22,100

 Quartile 3 22,101 to 48,000

 Quartile 4 More than 48,000

EXPLANATION

Toal nitrogen loads—Estimated in pounds per year

Estimated in-stream load—Table 1 contains 

 mapping number identification

 Quartile 1 0 to 407,500

 Quartile 2 407,501 to 1,000,000

 Quartile 3 1,000,001 to 6,790,000

 Quartile 4 More than 6,790,000

Estimated point source load

 Quartile 1 0 to 40,000

 Quartile 2 40,001 to 90,500

 Quartile 3 90,501 to 173,000

 Quartile 4 More than 173,000

Basemap modified from U.S. Geological Survey digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, central meridian 120°30’ W

Figure 19. Locations of sampling sites in the Snake River and its tributaries, and selected point sources 

discharging directly to the Snake River, Washington, Oregon, Idaho, and Wyoming, water year 2000.

38 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Table 12. Annual mean discharges of total nitrogen, total phosphorus, and suspended sediment loads in the Snake River, monitored 

Snake River tributaries, and point sources discharging directly to the Snake River, Wyoming, Idaho, and Washington, water year 2000.

[Bold type indicates start of reach (see figure 20); shaded rows indicate monitoring site (see table 1); italicized type indicates point-source discharge source. 

Abbreviations: ID, Idaho; WA, Washington; WY, Wyoming; ft3/s, cubic foot per second; –, not applicable]

Map 

index 

No.

Site No. Site name

River mile location Annual mean 

streamflow (ft3

/s)

Total nitrogen 

(pounds per day, estimated)

Snake 

River

TributariesPoint 

source 

Snake 

River

Tributary 

inflowing

Snake 

River

Tributary

inflowing

Point 

source

100 13010065 Snake River at Flagg Ranch, 

WY (reach 1)

1,050 – – 839 – 1,130 – –

ID0021261 Idaho Falls, City of – – 798 – 15.20 – – 265

ID0020044 Blackfoot, City of – – 764 – 1.71 – – 221

ID0020095 Burley, City of – – 652 – 2.02 – – 143

ID0021270 Twin Falls, City of – – 608 – 11.9 – – 1,670

ID0020168 Jerome, City of – – 608 – 2.17 – – 305

89 13092747 Rock Creek above Hwy 30/93 

crossing at Twin Falls, ID

– 606 – – 115 – 1,370 –

90 13094000 Snake River near Buhl, ID 

(reach 2)

597 – – 4,660 – 42,300 – –

91 13154500 Snake River at King Hill, ID 

(reach 3)

546 – – 9,990 – 82,200 – –

93 13206000 Boise River at Glenwood, ID – 392 – – 865 – 2,040 –

OR0020621 Ontario, City of – – 372 – 3.04 – – 123

ID0020290 Weiser, City of – – 352 – 2.79 – – 223

47 13353200 Snake River at Burbank, WA 

(reach 4)

9 – – 46,600 – 171,000 – –

ID0001163 Potlatch Corp. – – 39 – 57.2 – – 431

WA0021113 Clarkston Wastewater Treatment 

Plant

– – 38 – 4.03 – – 322

Map 

index 

No.

Site No. Site name

Total phosphorus

(pounds per day, estimated)

Suspended sediment 

(tons per day, estimated)

Snake 

River

Tributary

inflowing

Point 

source

Snake 

River 

Tributary

inflowing

Point 

source

100 13010065 Snake River At Flagg Ranch, 

WY (reach 1)

266 – – 137 – –

ID0021261 Idaho Falls, City of – – 90.0 – – –

ID0020044 Blackfoot, City of – – 35.5 – – –

ID0020095 Burley, City of – – 83.1 – – –

ID0021270 Twin Falls, City of – – 727 – – –

ID0020168 Jerome, City of – – 229 – – –

89 13092747 Rock Creek above Hwy 30/93 

crossing at Twin Falls, ID

– 55.1 – – 17.6 –

90 13094000 Snake River near Buhl, ID 

(reach 2)

2,690 – – 362 – –

91 13154500 Snake River at King Hill, ID 

(reach 3)

3,710 – – 354 – –

93 13206000 Boise River at Glenwood, ID – 458 – – 22.1 –

OR0020621 Ontario, City of – – 51.4 – – –

ID0020290 Weiser, City of – – 60.9 – – –

47 13353200 Snake River at Burbank, WA 

(reach 4)

13,300 – – 1,220 – –

ID0001163 Potlatch Corp. – – 231 – – –

WA0021113 Clarkston Wastewater Treatment 

Plant

– – 75.8 – – –

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 39
OR19-0072_fig20

0

0

12,000

14,000

20,000

0

1,200

1,000

1,400

200

600

400

800

4,000

8,000

10,000

2,000

6,000

80,000

140,000

40,000

100,000

160,000

60,000

120,000

180,000

RIVER MILE

Annual mean discharge of total nitrogen loads

TOTAL PHOSPHORUS LOAD, IN POUNDS PER DAY TOTAL NITROGEN LOAD, IN POUNDS PER DAY SUSPENDED-SEDIMENT LOAD, IN TONS PER DAY

Numbers in parentheses indicate map identification No.

Annual mean discharge of total phosphorus loads

Annual mean discharge of suspended-sediment loads

1000 800 600 400 200 0

Flagg Ranch, WY (100)

King Hill, ID (91)

Buhl, ID (90)

Burbank, WA (47)

Reach 1

Reach 2

Reach 3

Figure 20. Annual mean discharge of total nitrogen, total phosphorus, and suspended sediment loads in the 

Snake River, Wyoming, Idaho, and Washington, water year 2000.

40 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
OR19-0072_fig21 Pacific Ocean Pacific Ocean

124° 123° 122° 121°

47°

48°

49°

124° 123° 122° 121°

47°

48°

49°

0 50 MILES

0 50 KILOMETERS

56

84

71

76

61 57

81

67

56

84

71

76

61 57

81

67

Puget Sound

Puget Sound

EXPLANATION

Total phosphorus loads—Estimated in pounds per year

Estimated in-stream load—See table 1 for map

 identification number

 Quartile 1 0 to 40,000

 Quartile 2 40,001 to 160,000

 Quartile 3 160,001 to 750,000

 Quartile 4 More than 750,000

Estimated point source load

 Quartile 1 0 to 10,000

 Quartile 2 10,001 to 22,100

 Quartile 3 22,101 to 48,000

 Quartile 4 More than 48,000

EXPLANATION

Total nitrogen loads—Estimated in pounds per year

Estimated in-stream load—See table 1 for map

 identification number

 Quartile 1 0 to 407,500

 Quartile 2 407,501 to 1,000,000

 Quartile 3 1,000,001 to 6,790,000

 Quartile 4 More than 6,790,000

Estimated point source load

 Quartile 1 0 to 40,000

 Quartile 2 40,001 to 90,500

 Quartile 3 90,501 to 173,000

 Quartile 4 More than 173,000

Basemap modified from U.S. Geological Survey digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, central meridian 120°30’ W

Figure 21. Locations of sampling sites in Puget Sound tributaries, and selected point sources discharging directly to the Puget 

Sound and its major tributaries, Washington, water year 2000.

Transport of Nutrients and Suspended-Sediment in Columbia River and Puget Sound Basins 41
OR19-0072_fig22

Total phosphorus

(in pounds per year)

Total nitrogen

(in pounds per year)

Suspended-sediment

(in tons per year)

Point sources (54,700)

Duckabush 

River (121)

Deschutes 

River (1,700)

Snohomish River 

(19,000)

Nooksack River (12,400) Puyallup River (6,500)

Skagit River (15,700)

Duwamish R

(5,200)

Skokomish 

River (638)

Point sources (10,700)

Nooksack River (2,940)

Skagit River (4,070)

Snohomish

River

(1,820)

Duwamish

River (726)

Puyallup River (2,750)

Deschutes 

River (178)

Skokomish 

River (396)

Duckabush 

River (48.4)

Duckabush

River (19.3) Skokomish R. (450)

Deschutes

River (69.9)

Puyallup River (3,760)

Duwamish

River (267)

Snohomish

River (899)

Skagit River (3,700)

Nooksack River (2,300)

Figure 22. Contribution of monitored 

tributary and estimated point-source loads 

of total nitrogen, total phosphorus, and 

suspended sediment to the Puget Sound 

basin, Washington, water year 2000.

Nutrients and Suspended-Sediment 

Yields

Regional Patterns in Yields

Yields are useful when making comparisons between 

catchments because the yield calculation normalizes loads 

for catchment area (for example, pounds per square mile of 

catchment). This provides a measure of the “intensity” of 

pollutant sources, which is useful for watershed management. 

Although drainage areas were available for 91 of the 100 

catchments, WY 2000 yield estimates were made for only 

70, 81, and 65 catchments for TN, TP, and SS, respectively, 

because of either a lack of adequate data to build a model or 

poor model performance. Basic land-use characteristics for 

the 91 delineated catchments are shown in figure 23. The 

catchments tended to have large percentages of forested and 

undeveloped land and small percentages of agricultural and 

urban land. The amount of agricultural and urban land in onehalf of the catchments was less than 5 percent and 2 percent 

of the total land area, respectively, whereas the amount of 

forested or undeveloped land in one-half of the catchments 

was greater than 86 percent of the total land area. However, 

some catchments included relatively large areas of agricultural 

and urban land: in eight catchments, agricultural areas made 

up more than 50 percent of the total land area; and in five 

catchments, urban areas made up more than 50 percent of the 

42 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
total land area. Appendix A contains the predicted yields for 

WY 1997, 2000, and 2001 for TN, TP, and SS, and table 13

summarizes the annual yields for the 3 water years. For TN, 

TP, and SS, respectively, the median yields were 2.2, 2.7, and 

3.8 times greater in 1997 (the high-flow year) compared to 

2000 and 2.2, 2.4, and 5.0 times greater in 2000 compared to 

2001 (the low-flow year).

The values for yields and annual catchment nutrient 

loads were not normally distributed. For these variables, the 

log-transformed (base 10) values were used when relations 

between catchment yields and catchment characteristics were 

evaluated. This transformation resulted in approximately 

normally-distributed values. The two-sided Pearson’s 

correlation coefficient (r) was calculated for all comparisons. 

The Pearson’s correlation coefficient expresses the similarity 

between two sets of data. The significance of each correlation 

coefficient (p-value) also was calculated. A 5 percent 

significance level was selected.

Figure 24 shows the TN, TP, and SS yields estimated for 

the 91 catchments. In this figure, catchments are represented 

by the monitoring station location (catchment outlet). Table 14

shows the ranges for the WY 2000 yield quartiles used in 

figure 24. TP yields were highly correlated with SS yields 

(r=0.84, p≤0.05), whereas TN yields were less correlated 

with SS yields (r=0.65, p≤0.05). This reflects the fact that 

phosphorus can adsorb onto and be transported by soil 

particles, whereas the predominant species of nitrogen do 

not exhibit this property as strongly. TN yields were highly 

correlated with TP yields (r=0.81, p≤0.05), which probably 

is explained by the similarities in the sources of nitrogen and 

phosphorus in the catchments. The yields for TN, TP and SS 

generally were greater on the western side of the Cascade 

Mountains (the Willamette River and the Puget Sound basins) 

compared to the eastern side of the Cascade Mountains (t-test 

p-value = 0.00 for all three constituents). The median yield 

(untransformed) for the western-side catchments was 5.6 times 

greater for TN, 4.6 times greater for TP, and 5.8 times greater 

for SS than the median yield for the eastern-side catchments. 

The western side of the Cascades experiences much more 

precipitation and surface runoff than the eastern side. When 

the annual mean streamflows for WY 2000 were normalized 

for catchment area, the median value for the western-side 

catchments was 4.7 times greater than the value for the 

eastern-side catchments, and the two groups were significantly 

different. This probably explains most of the difference in 

the regional pattern for yields, because stream loads (and 

yields) are dependent on flow and, therefore, should be highly 

correlated with spatial patterns in precipitation.

OR19-0072_fig23

0

10

20

30

40

50

60

70

80

90

100 0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

PERCENT URBAN LAND

PERCENT FORESTED AND OTHER NON-DEVELOPED LAND

PERCENT AGRICULTURAL LAND

Figure 23. Land use for the 91 catchments with delineated 

drainage areas for the Columbia River and Puget Sound 

Basins, calendar year 2000. Trend sites are designated with 

red circles, whereas all circled sites were used for load 

estimates.

Table 13. Summary of annual yields for total nitrogen, total 

phosphorus, and suspended sediment in the Columbia River and 

Puget Sound basins, water years 1997, 2000, and 2001.

[Abbreviations: TN, total nitrogen; TP, total phosphorus; SS, suspended 

sediment; lb/yr/mi2, pound per year per square mile; ton/yr/mi2, ton per year 

per square mile]

Yields

TN

(lb/yr/mi2

)

TP

 (lb/yr/mi2)

SS

(ton/yr/mi2)

Water year 1997 (high flow year)

Count 66 67 63

Minimum 292 58.4 1.72

Median 3,790 490 132

Maximum 81,900 3,780 13,500

Water year 2000 (average flow year)

Count 70 81 65

Minimum 177 16.8 1.57

Median 1,740 180 35

Maximum 32,300 1,460 1490

Water year 2001 (low flow year)

Count 71 81 64

Minimum 79.9 9.51 .23

Median 803 74.6 6.82

Maximum 7,210 433 194

Nutrients and Suspended-Sediment Yields 43
OR19-0072_fig24

124° 120° 115°

110°

42°

45°

49°

124° 120° 115°

110°

42°

45°

49°

124° 120° 115°

110°

42°

45°

49°

0 250 KILOMETERS

0 250 MILES

EXPLANATION

Total phosphorus yield—Estimated in 

pounds per square mile per year

Quartile 1 0 to 80

Quartile 2 81 to 180

Quartile 3 181 to 390

Quartile 4 More than 390

EXPLANATION

Suspended-sediment yield—Estimated 

in tons per square mile per year

Quartile 1 0 to 8.00

Quartile 2 8.1 to 35.0

Quartile 3 35.1 to 95.0

Quartile 4 More than 95.0

EXPLANATION

Total nitrogen yield—Estimated in 

pounds per square mile per year

Quartile 1 0 to 660

Quartile 2 661 to 1,750

Quartile 3 1,751 to 4,050

Quartile 4 More than 4,050

Suspended

sediment

65 sites

Total phosphorus

81 sites

Total nitrogen

70 sites

Basemap modified from U.S. Geological Survey digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, central meridian 120°30’ W

Figure 24. Estimated annual catchment yields divided into quartiles for total nitrogen, total phosphorus, and sediment for the Columbia 

River and Puget Sound Basins, water year 2000.

Notable exceptions to the regional pattern in yields were 

Granger Drain in the lower Yakima Basin, Granger, Wash. 

(fig. 1, site 50), which was in the 4th quartile for TN and SS 

yields and in the 3rd quartile for TP yields, and the Snake 

River at Flagg Ranch, Wyo., WY 2000 (fig. 1, site 100), 

which was in the 4th quartile for SS yields. The Granger Drain 

catchment contains intensive agricultural activity that relies 

almost exclusively on irrigation during the growing season. 

In addition, the agricultural activity is near the drain. With 

60 percent agricultural land, it was the 6th most agricultural 

catchment of the 91 catchments with land-use data. This 

probably explains the relatively high yields for this catchment. 

The catchment characteristics available for the Snake River 

at Flagg Ranch, Wyo., could not explain the high SS yield for 

WY 2000. Of the remaining 14 catchments in the 4th quartile 

for SS yield, 13 were in the Puget Sound watershed, and 1 was 

in the upper Willamette Basin.

44 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Influence of Point Sources

Thirty-one of the 70 delineated catchments with annual 

in-stream TN loads predicted for WY 2000 had non-zero 

estimates for annual WY 2000 point-source TN load, and 

31 of the 81 delineated catchments with annual in-stream 

TP loads predicted for WY 2000 had non-zero estimates for 

annual WY 2000 point-source TP load. The catchments with 

point-source nutrient loads of zero could have contained 

nutrient point sources, but these point sources either were 

not identified in the available data bases or did not meet the 

criteria for inclusion in the analysis. Table 22 (at back of 

report) lists the total WY 2000 estimated point-source TN and 

TP loads for the catchments. Estimated annual point-source 

loads as a percentage of the annual in-stream loads are also 

listed in table 22. For each catchment, the annual loads for all 

point sources were expressed as a percentage of the annual 

in-stream WY 2000 nutrient load at the catchment outlet. 

Because nutrients can undergo many transformations in a 

stream (for example, settling or uptake by plants), a direct 

comparison between point-source and annual in-stream load in 

a catchment is not possible. However, a determination of the 

relative importance of point-sources in a catchment is possible. 

Using this approach allowed for the following statement—

During WY 2000, the estimated annual point-source load 

for TN in catchment A was at least X percent of the annual 

in-stream TN load at the outlet of catchment A.

The annual point-source nutrient loads in the catchments 

ranged from zero to 85 percent of the predicted annual 

in-stream TN loads and 98 percent of the predicted annual 

in-stream TP loads. The annual point-source loads from 

industrial sources (not WWTPs) generally were a small 

percentage of the annual in-stream loads (less than 5 percent). 

The one exception was the Spokane River (fig. 1, site 73), 

where the annual TP loads from paper mills were 17 percent 

of the annual in-stream load. Figure 25 shows the point-source 

nutrient loads for each catchment as a percentage of the annual 

in-stream load. In this figure, the catchments are represented 

by the location of the monitoring station. The percentage of 

the annual in-stream load is represented by four symbol size 

classes: less than 25 percent, 25–50 percent, 50–75 percent, 

and greater than 75 percent (table 15 shows the number of 

sites with these percentages for TN and TP).

The one catchment with point-source annual TN loads 

greater than 75 percent of the annual in-stream load, the Walla 

Walla River near Touchet, Wash. (fig. 1, site 46), contained 

a WWTP that discharged relatively large annual loads of 

TN (ranking 13th of 140 TN point sources). Five of the six 

catchments with annual point-source TN loads between 25 

and 50 percent of the annual in-stream loads were in the more 

developed areas of the basin (the Willamette basin, Spokane, 

and Boise). Although no sites with point-source contributions 

were in the Seattle-Tacoma area, this does not mean that the 

streams in that area are necessarily free from point-source 

effects. Rather, the results likely reflect the lack of waterquality sampling sites downstream of major point sources 

in the area. The other catchment in this group contained the 

WWTP for Page, Idaho, which ranked 61st of 140 TN point 

sources.

As with TN, the one catchment where annual pointsource TP loads were greater than 75 percent of the annual 

in-stream load, the Spokane River (fig. 1, site 73), contained a 

WWTP that discharged relatively large annual loads (ranking 

5th of 130 sources for TP). One of the two catchments with 

point-source annual TP loads between 50 and 75 percent of the 

annual in-stream loads, another Spokane River site (fig. 1, site 

99), contained WWTPs that discharged relatively large annual 

loads of TP (if they were aggregated into one point-source, 

they would rank 14th of 130 TP point sources). The other 

catchment in this group contained the WWTP for Page, Idaho 

(fig.1, site 97), which ranked 63rd of 130 TP point sources. All 

15 catchments with annual point-source TP loads between 25 

and 50 percent of the annual in-stream loads were in some of 

the more developed areas (Willamette River/lower Columbia 

River basins, Spokane River, Snake River Plain, and lower 

Yakima River/lower Snake River/Colombia River confluence). 

No sites with annual TP point-source loads between 25 and 50 

percent were in the Seattle-Tacoma area.

Table 14. Quartile ranges for total nitrogen, total phosphorus, 

and suspended sediment annual yields for the Columbia River and 

Puget Sound basins, water year 2000.

[All TN and TP loads are in pounds per year per square mile; suspendedsediment loads are in tons per year per square mile. Abbreviations: TN, total 

nitrogen, TP, total pohosphorus, SS, suspended sediment]

Yields

Quartile range

1st 2nd 3rd 4th

TN 177–651 663–1,710 1,780–4,050 4,050–32,300

TP 16.8–78.6 83.6–180 190–387 390–1,460

SS 1.57–6.68 8.89–35.0 35.0–90.7 97.6–1,490

Nutrients and Suspended-Sediment Yields 45
OR19-0072_fig25

124° 120° 115°

110°

42°

45°

49°

124° 120° 115°

110°

42°

45°

49°

123°

30'

123°

00'

122°

30'

122°

00'

123°

30'

123°

00'

122°

30'

122°

00'

44°00'

44°30'

45°00'

45°30'

44°00'

44°30'

45°00'

45°30'

7

38 28

24 19

17

14

11

7

38 28

24 19

17

14

11

31

33

31

33

0 250 KILOMETERS

0 250 MILES

0 20 KM

0 20 MILES

0 20 KM

0 20 MILES

EXPLANATION

Estimated point source contribution

None

Less than 25%

25–50%

50–75%

More than 75%

Total nitrogen Total phosphorus

7

73

77 79

64

46

57

81

84

44

38 47

93

91

90

51

9997 67

14

11 7

73

77

79

64

46

57

81

84

44

38

47

93

91

90

51

99 97 67

14

11

48

49

48

49

52

53

52

53

Basemap modified from U.S. Geological Survey 

digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, 

central meridian 120°30’ W

Figure 25. Estimated annual point-source loads as a percentage of annual in stream loads for total nitrogen and total 

phosphorus, Columbia River and Puget Sound basins, water year 2000.

Table 15. Summary of total point-source annual nutrient loads as 

a percentage of predicted instream annual loads, Columbia River 

and Puget Sound basins, water year 2000.

[Abbreviations: TN, total nitrogen; TP, toal phosphorus; <, less than; >, 

greater than]

Constituent

Number of sites with total annual point-source 

catchment nutrient loads (percent)

< 25 25 – 50 50 – 75 > 75 

TN 24 6 0 1

TP 13 15 2 1

sources), the annual WY 2000 TN load for all estimated point 

sources in the Columbia River basin was 11.8 percent of the 

annual in-stream TN load, and the estimated annual TP pointsource load was 22.5 percent of the annual in-stream TP load. 

These results indicate that, in large catchments with a wellmixed land-use profile, nonpoint sources, such as fertilizer, 

manure, and atmospheric deposition, are responsible for most 

in-stream load. The 12 largest catchments generally had a 

diverse mix of urban and agricultural land (1–6.5 percent 

urban [mean of 3.1 percent] and 1.8–22.7 percent agricultural 

[mean of 13.7 percent]). The annual point-source loads for 

these catchments, as a percentage of annual in-stream loads, 

ranged from 0 to 22.6 percent for TN (mean of 8.9 percent) 

and from 0 to 42.1 percent for TP (mean of 26.2 percent). 

For these catchments, all annual point-source loads were less 

than the mean value of 27 percent for the catchments with an 

estimated point-source TN load, and all but one annual pointsource load were less than the mean value of 39 percent for the 

catchments with an estimated point-source TP load.

Table 22 shows the predicted annual in-stream TN and 

TP loads and the estimated annual TN and TP loads from 

point sources for WY 2000, and the estimated annual fertilizer 

and manure nitrogen and phosphorus loads and atmospheric 

nitrogen deposition for calendar year (CY) 2002. The data 

for CY 2002 were used because manure data were available 

The results from the point-source analysis showed that 

streams away from major population centers and large point 

sources can still be significantly affected by point sources, 

if the annual in-stream load is relatively low. The results 

also showed that streams downstream from many large point 

sources are not necessarily largely affected by those upstream 

point sources. An example of this was the Columbia River at 

Beaver Army Terminal (fig. 1, site 44). Although this waterquality station is the integrator site for the Columbia River 

basin (the site is downstream of a large and complex drainage 

basin and contains multiple environmental settings and point 

46 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
for that year but not CY 2000. Table 22 also includes (1) 

annual point-source loads expressed as a percentage of the 

annual in-stream load, (2) annual fertilizer and manure loads 

expressed as a percentage of the annual in-stream load, 

(3) annual atmospheric nitrogen deposition expressed as a 

percentage of the annual in-stream load, (4) annual pointsource loads expressed as a percentage of the annual fertilizer 

and manure loads, (5) annual point-source TN load expressed 

as a percentage of the annual atmospheric deposition of 

nitrogen, and (6) annual point-source TN loads expressed as a 

percentage of the land-applied nitrogen loads.

Relative allocations of annual TN and TP loads to the 

catchments from fertilizer and manure, point sources, and 

atmospheric deposition (nitrogen only) are shown in figure 26. 

For TN, values ranged from near 0 to nearly 100 percent 

for both fertilizer and manure (median of 86 percent) and 

atmospheric deposition (median of 12 percent), and from 0 to 

close to 50 percent for point sources (median of 0 percent). 

For TP, values ranged from near 0 to close to 100 percent for 

fertilizer and manure, and from 0 to close to 80 percent for 

point sources (median of 0 percent). However, 60 of the 91 

catchments had no estimated point-source TN or TP loads. 

The sites are generally located at the left sides of each plot, 

indicating that the estimated point source loads tended to be a 

small percentage of total TN and TP loads in the catchments 

compared to fertilizer and manure application and atmospheric 

deposition.

One catchment, the South Fork Coeur d’Alene River 

(fig. 1, site 97), had annual point-source TP loads greater than 

the total land-applied phosphorus loads, and 10 catchments 

had annual point-source TP loads greater than 10 percent of 

the land-applied phosphorus loads. Annual point-source loads 

for TP in the South Fork Coeur d’Alene River were equal to 

60 percent of the annual in-stream load (the median value 

was 10.5 percent for all 31 catchments with point-source TP 

loads). Higher values of annual point-source nutrient loads 

as a percentage of annual land-applied loads were positively 

related to higher values of annual point-source nutrient 

loads as a percentage of annual in-stream loads. In smaller, 

urbanized catchments, point sources tended to contribute 

more to the total nutrient load than in larger, less urbanized 

catchments.

Total nitrogen Total phosphorus

0

10

20

30

40

50

60

70

80

90

100 0

10

20

30

40

50

60

70

80

90

100

PERCENT FROM POINT SOURCES, IN WATER YEAR 2000

0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100

0

10

20

30

40

50

60

70

80

90

100 0

10

20

30

40

50

60

70

80

90

100

PERCENT FROM POINT SOURCES, IN WATER YEAR 2000

PERCENT FROM MANURE, IN CALENDAR YEAR 2002

PERCENT FROM ATMOSPHERIC DEPOSITION, IN CALENDAR YEAR 2002

PERCENT FROM FERTILIZER AND MANURE, IN CALENDAR YEAR 2002

PERCENT FROM FERTILIZER, IN CALENDAR YEAR 2002 

Figure 26. Summary of annual nutrient load to delineated catchments for total nitrogen and total phosphorus in the Columbia River 

and Puget Sound Basins, water year 2000 and calendar year 2002. Trend sites are designated with red circles, whereas all circled 

sites were used for load estimates.

Nutrients and Suspended-Sediment Yields 47
Influence of Catchment Characteristics on 

Nutrient and Suspended-Sediment Yields

A multiple linear regression of catchment yields 

(the response variable) on catchment characteristics (the 

explanatory variables) was performed to determine which 

characteristics best explained the variability in TN, TP, 

and SS yields. Seven explanatory variables were used 

in the regressions for TN and TP: (1) percentage of the 

catchment land area categorized as urban; (2) percentage 

of the catchment land area categorized as agricultural; (3) 

mean slope for the catchment in percent; (4) mean annual 

precipitation for the catchment for 1980–1997; (5) annual load 

of nitrogen or phosphorus to the catchment from fertilizer 

and manure application (CY 2002), normalized for catchment 

area and log-transformed; (6) annual load of nitrogen to 

the catchment from atmospheric deposition (CY 2002), 

normalized for catchment area and log transformed; and (7) 

annual load of nitrogen or phosphorus to the catchment from 

point sources (WY 2000), normalized for catchment area 

and log-transformed. The linear model selected provided 

the best estimate of the response variable using some linear 

combination of the explanatory variables, based on the model 

standard error (a measure of the differences between the 

measured and the predicted values). The linear model took the 

form: Y = aX1

 + bX2 + cX3 + dX4 + eX5 + fX6 + gX7, 

where Y was the predicted yield, X1- X7 were values for the 

catchment characteristics, and a–g were the coefficients. 

The statistically significant predictive capability of each 

explanatory variable in the presence of the other variables was 

provided by the p-values. The magnitude of each regression 

coefficient indicated the response of the yields to a particular 

catchment characteristic. The results from the multiple linear 

regressions are summarized in table 16. Also, included in the 

table are standardized regression coefficients. To obtain these 

coefficients, all variables (response and explanatory) were 

standardized before fitting the multiple regression equation 

by subtracting the mean for that variable and dividing by the 

standard deviation. Each standardized regression coefficient 

represents the change in the response of yield in standardized 

units to a unit change in the standardized explanatory 

variable (for example, one standard deviation unit change 

in precipitation corresponds to some standard deviation unit 

change in yield). Because standardized regression coefficients 

are independent of scale units, they are useful in interpreting 

the results from multiple linear regressions.

Although average annual precipitation was the major 

explanatory factor for TN, TP, and SS yields, the relation 

was slightly stronger for TP (on the basis of the standardized 

regression coefficients). However, precipitation was only one 

factor that influenced catchment yields; for TN and TP yields 

another important factor was the amount of nutrients applied 

to the catchments from point and nonpoint sources. The results 

from this analysis showed that, although a unit change in 

point-source loads of phosphorus tended to have about twice 

the effect on TP yields as a unit change in nonpoint-source 

loads (fertilizer and manure), a unit change in point-source 

loads of nitrogen tended to have only about two-thirds the 

effect on TN yields as a unit change in nonpoint-source 

loads (fertilizer and manure or atmospheric deposition). The 

decrease in TN and TP yields with an increase in mean slope 

may have been an indication of the importance of topography 

and subsurface flow paths on nutrient delivery to streams. 

These results might indicate, for example, that greater 

overland flow and nutrient transport and delivery occurred 

in catchments dominated by relatively flat topography. 

However, slope also could have been acting as a surrogate 

for the percentage of forested land in the catchments because 

mean slope was strongly correlated with the percentage of 

forested land. Land use in the catchments also was a factor 

that influenced nutrient yields—the percentage of agricultural 

land influenced TN, TP, and SS yields (about as much as 

point-source loads for TN yields), whereas the percentage 

of urban and agricultural land influenced TP yields (with 

the percentage of urban land having a stronger influence). 

The analysis described above provided an estimation of the 

factors affecting nutrient and sediment transport in some of 

the catchments of the Pacific Northwest. A more complete 

analysis would include many more water-quality monitoring 

sites, all the catchments, and a more rigorous geospatial 

statistical approach. A study is planned that will incorporate 

all of those components. This study will use the SPARROW 

model to estimate nutrient and sediment sources and transport 

in the surface waters of the Pacific Northwest that have been 

mapped on the RF1 hydrologic network (U.S. Environmental 

Protection Agency, 1996). The SPARROW model makes 

these estimates by correlating water-quality data with data 

on pollutant sources (for example, atmospheric deposition, 

fertilizers, and human and animal wastes) and climatic 

and hydrogeologic properties (for example, precipitation, 

topography, vegetation, soils, and water routing) that affect 

contaminant transport (Schwarz and others, 2006). Much of 

the data collected for the study described in this report will be 

used in the upcoming SPARROW study.

48 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Trends in Nutrients and SuspendedSediment, 1993–2003

For this study, trend sites were selected based on the 

availability of data collected from 1993 to 2003, meaning that 

data for each site generally were available for most seasons in 

each year during this period. Consequently, data for the sites 

were not necessarily statistically representative of waterquality trends in each of the Pacific Northwest states. The 

results represent conditions at the sites used in this study and 

should not be extrapolated to other areas in each of the states. 

Table 17 shows the breakdown of the trend sites by collecting/

analyzing agency. There were 11 USGS sites, 14 ODEQ 

sites, 23 WDOE sites, 2 CWS sites, and, depending on the 

constituent, 18–20 sites in Oregon, 20–25 sites in Washington, 

and 4–5 sites in Idaho. Figure 6 shows the distribution 

of drainage areas for the 45 trend sites with delineated 

catchments (indicated by blue bars). Delineated drainage areas 

ranged from 25 to 658,000 km2

, although most catchments had 

drainage areas between 1,000 and 5,000 square km2

. Only two 

catchments had drainage areas less than 100 km2, and only one 

had a drainage area greater than 100,000 km2. Consequently, 

the trend results were not necessarily representative of 

conditions occurring in the smallest and largest basins.

The distribution of land use for the trend sites with 

delineated catchments is shown in figure 23 (red circles). Total 

agricultural land use ranged from 0 to 95 percent, with most 

sites less than 20 percent; total urban land use ranged from 0.5 

to 60 percent, with most sites less than 10 percent; and total 

forest land use ranged from 4 to 100 percent, with most sites 

greater than 70 percent. The many forested watersheds in the 

study area, especially in the mountainous parts of the basin 

where rainfall is high and nutrient concentrations are relatively 

low, likely provided dilution of nutrient concentrations from 

point sources and agricultural runoff downstream. Depending 

on forest activities, the forested areas also may have 

contributed significantly to the suspended-sediment loads, 

especially during winter storms and high-flow, snow-melt 

periods.

Table 16. Results from multiple linear regression of catchment characteristics on catchment yields in the Columbia River and Puget 

Sound basins, water year 2000.

[Abbreviations: TN, total nitrogen; TP, total phosphorus; SS, suspended sediment; CY, calendar year; WY, water year; kg/km2, kilogram per square 

kilometer; cm, centimeter; NA, not available]

Catchment characteristic Coefficient 

unit

Yield (kg/km2

)

TN TP

p-value Regression 

coefficient

Standardized 

regression 

coefficient

p-value Regression 

coefficient

Standardized 

regression 

coefficient

Urban land Percent 0.471 0.002 0.078 0.085 0.004 0.186

Agricultural land Percent .055 .005 .202 .167 .003 .142

Mean slope Percent .028 -.013 -.341 .094 -.008 -.220

Mean annual precipitation (CY 1980–97) cm .000 .414 .650 .000 .453 .800

CY 2002 fertilizer and manure application log(kg/km2

) .045 .179 .279 .142 .102 .159

CY 2002 atmospheric deposition log(kg/km2

) .000 .962 .301 NA NA NA

WY 2000 point-source loading log(kg/km2

) .011 .108 .186 .000 .228 .258

Catchment characteristic Coefficient 

unit

Yields (kg/km2

)

SS

p-value Regression 

coefficient

Standardized 

regression 

coefficient

Urban land Percent 0.519 0.004 0.105

Agricultural land Percent .057 .008 .246

Mean slope Percent .762 -.003 -.051

Mean annual precipitation (CY 1980–97) cm .000 .006 .667

CY 2002 fertilizer and manure application log(kg/km2

) NA NA NA

CY 2002 atmospheric deposition log(kg/km2

) NA NA NA

WY 2000 point-source loading log(kg/km2

) NA NA NA

Trends in Nutrients and Suspended-Sediment, 1993–2003 49
For the statistical trend analysis used in this study, 

the null hypothesis being tested is “There is not a trend 

in the constituent concentrations for either flow-adjusted 

trend in concentrations (FATC) or non-flow-adjusted trend 

in concentration (NFATC) at a site.” A type 1 error in the 

analyses occurs if the null hypothesis is rejected when it is 

true. For this study, the tolerable probability level—level 

of significance—for committing a type 1 error was set at 

p=0.05; that is, there is a 5-percent chance of rejecting the null 

hypothesis when it is true (Ott, 1993). As p becomes smaller, 

the data show more evidence for rejecting the null hypothesis. 

For example, at p=0.20, there is a 20-percent chance of 

rejecting the null hypothesis when it is true, and at a p≤0.051, 

there is only a 0.1-percent chance of rejecting the null 

hypothesis when it is true. The time span from 1993–2003 for 

assessing trends in this report is relatively short, considering 

that the data used in this analysis could be far fewer than 12 

samples per year (for example, as few as 56 samples over 

an 11 year period). Given the paucity of the data, significant 

trends could have actually existed in the streams even when 

the reported p-level in this report was computed to be greater 

than 0.05 because the amount of data analyzed may have 

been insufficient to reveal the significant trend. In an attempt 

to compensate for the relatively small data sets, the direction 

of the trends in the basin that were not significant (p>0.05) 

also are mentioned in the text to further paint a picture of 

basin-wide trends. Although not significant, the majority of 

these trends often were consistent with the direction of the 

significant trends; thereby indicating that the patterns in trends 

could be wider spread throughout the basin, and might have 

been apparent if more data had been available for analysis.

Trends in Streamflow

Only streamflow at 2 of the 50 sites: Crab Creek near 

Beverly, Wash. (fig. 1, site 54) and Rock Creek above Hwy 

30/93 crossing at Twin Falls, Idaho, (site 89), had significant 

trends (decreasing). Unlike the data from most sites, which 

extended from October 1992 through September 2003, the 

streamflow data for these sites began in October 1993 (WY 

1994). Three of the other four sites with streamflow data 

starting in WY 1994 rather than WY 1993 also showed 

a decreasing (but not significant) trend in streamflow. A 

re-analysis of all trends in streamflow, using WYs 1994 

through 2003, showed only one additional site, the Okanogan 

Table 17. Number of sites with significant decreasing, increasing, or no flow-adjusted trend in 

concentration by collecting/analyzing agency in the Columbia River and Puget Sound basins, water years 

1993–2003. 

[Abbreviations: CWS, Clean Water Services; FATC, flow-adjusted trend in concentration; ODEQ, Oregon Department of 

Environmental Quality; WDOE, Washington State Department of Ecology; USGS, U.S. Geological Survey]

Constituent

Number of sites with 

data for trend testing

Number of sites with 

decreasing FATC

USGS ODEQ WDOE CWS Total sites USGS ODEQ WDOE CWS Total sites

(percent)

Total nitrogen 11 13 18 2 44 1 9 8 1 19

(43)

Total phosphorus 11 14 23 2 50 1 6 0 2 9

(18)

Suspended 

sediment

11 14 23 0 48 8 1 6 0 15

(31)

Constituent

Number of sites with 

increasing FATC

Number of sites 

with no FATC

USGS ODEQ WDOE CWS Total sites 

(percent) USGS ODEQ WDOE CWS Total sites(percent)

Total nitrogen 2 0 0 0 2

(5)

8 4 10 1 23

(52)

Total phosphorus 1 0 6 0 7

(14)

9 8 17 0 34

(68)

Suspended 

sediment

0 4 0 0 4

(8)

3 9 17 0 29

(60)

50 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
River at Malott, Wash. (fig. 1, site 79), with a significant 

trend in streamflow (decreasing). In addition, changing the 

analytical time period did not substantially change the results 

for flow-adjusted trend in concentration, nonflow-adjusted 

trend in concentration, or trend in load. Except at the two 

sites where there was a trend in streamflow, any site showing 

a FATC could only show a significant NFATC that was in the 

same direction (increasing or decreasing).

General Patterns in Concentration Trends

Because significant NFATC occurred at about 90 percent 

of the sites with significant FATC for all three constituents, 

and the values for the NFATC and FATC were generally close 

in magnitude, only the results for FATC are presented in this 

section. Overall distributions of FATC for TN, TP, and SS, 

expressed in percentage per year and milligrams per liter per 

year, are shown in figures 27, 28, and 29. The figures show 

distributions for the sites where the FATC was significant (p

< 0.05) and the sites where it was not significant. Although 

many sites showed relatively large FATC for TN based on 

percentage change, more than 90 percent of the sites had 

relatively small FATC for TN based on absolute change in 

concentration (≤ 0.05 mg/L/yr). Most sites showed relatively 

small FATC for TP based on both percentage change and 

absolute change in concentration (≤ 0.003 mg/L/yr). Although 

many sites showed relatively large FATC for SS based on 

percentage change, more than 90 percent of the sites had 

relatively small FATC for SS based on absolute change in 

concentration (≤ 2 mg/L/yr).

The numbers of sites with significant FATC for TN, TP, 

and SS are shown in table 17. Unless indicated otherwise, all 

the FATC results presented in the remainder of this section 

were significant (some FATC results that were not significant 

also are described to provide a more complete picture of the 

patterns in trends). For most catchments, the net change in 

nonhydrologic characteristics (land use and other human 

activities) was not great enough to cause any FATC for TN 

(52 percent), TP (68 percent), or SS (60 percent) during this 

relatively short time period (WY’s 1993–2003). However, 

some nonhydrologic changes might still have occurred in 

these catchments, but either they cancelled out (for example, 

FLOW-ADJUSTED TREND IN TOTAL NITROGEN CONCENTRATION,

IN PERCENT PER YEAR

Less

than -4

-4 to -2 -2 to 0 0 to 2 2 to 4 More

than 4

NUMBER OF SITES

0

5

10

15

20

FLOW-ADJUSTED TREND IN TOTAL NITROGEN CONCENTRATION,

IN MILLIGRAMS PER LITER PER YEAR

Less

than -0.10

-0.10 to

-0.05

-0.05 to

0.00

0.00 to

0.05

0.05 to

0.10

More

than 0.10

NUMBER OF SITES

0

5

10

15

20

25

30

35

A

B

Trend significant at p ≤0.05

Trend not significant

Negative

Positive

Negative

Positive

FLOW-ADJUSTED TREND IN TOTAL PHOSPHORUS CONCENTRATION,

IN PERCENT PER YEAR

Less

than -8

-4 to -8 -4 to 0 0 to 4 4 to 8 More

than 8

NUMBER OF SITES

FLOW-ADJUSTED TREND IN TOTAL PHOSPHORUS CONCENTRATION,

IN MILLIGRAMS PER LITER PER YEAR

Less

than -0.005

-0.005 to

-0.003

-0.003 to

0.00

0.000 to

0.003

0.003 to

0.005

More

than 0.005

NUMBER OF SITES

A

B

0

5

10

15

20

25

30

0

5

10

15

20

25

Trend significant at p ≤0.05

Trend not significant

Figure 27. Distribution of flow-adjusted trends in 

concentration of total nitrogen in percentage per year and 

milligrams per liter per year, Columbia River and Puget 

Sound basins, water years 1993–2003.

Figure 28. Distribution of flow-adjusted trends in 

concentration of total phosphorous in percentage per year 

and milligrams per liter per year, Columbia River and Puget 

Sound basins, water years 1993–2003.

Trends in Nutrients and Suspended-Sediment, 1993–2003 51
decreasing nonpoint source loads and increasing point-source 

loads) or were too far upstream to have much effect on water 

quality. Although a few sites had increasing FATC for TN, TP, 

and (or) SS (5, 14, and 8 percent of the sites, respectively), 

more sites showed decreasing FATC (43, 18, and 31 percent of 

the sites for TN, TP, and SS, respectively).

Some differences in trend results were observed among 

the agencies (table 17), which might have been due to each 

agency having sampled sites with different land uses and 

hydrologic characteristics, using different sampling protocols 

and (or) laboratory methods, and targeted sampling of 

problem areas by the State regulatory agencies. For example, 

USGS data showed decreasing FATC for SS at 73 percent 

of sites (8 of the 11 sampled), whereas ODEQ and WDOE 

data showed decreasing FATC for SS at 7 and 26 percent 

of sites, respectively. In addition, decreasing FATC for TP 

were measured at only one USGS site and no WDOE sites, 

compared to 43 percent of the ODEQ sites (table 17). In 

all three states, the number of decreasing FATC frequently 

exceeded the number of increasing FATC, except for TP in 

Idaho and Washington (table 18).

Total Nitrogen

Complete results from the trend analysis for TN are 

shown in table 19, and figure 30 shows the FATC for TN at 

each available trend site in the study area. Figure 30 indicates 

whether there was a significant FATC at each site and, if 

there was, shows the direction of the trend and indicates its 

magnitude in percentage per year and milligrams per liter 

per year (some sites with relatively large percentage change 

in FATC had small changes in concentration). Twenty-one 

(48 percent) of the 44 sites had FATC for TN (2 increasing, 

19 decreasing, and 6 sites had insufficient water-quality data 

to determined trends). Trends in load for TN were observed 

at 10 sites (all decreasing), and 77 percent of the sites had 

decreasing (but not necessarily significant) FATC and trends 

in load for TN. The decreasing trends in load for TN generally 

corresponded to decreasing FATC but not decreasing trends 

in streamflow, indicating that the decreasing loads resulted 

solely from decreasing FATC. However, at Rock Creek (fig. 1, 

site 89) the decreasing trend in load for TN may have been 

caused by the decreasing FATC and (or) the decreasing trend 

in streamflow.

Figure 29. Distribution of flow-adjusted trends in 

concentration of suspended sediment in percentage per year 

and milligrams per liter per year, Columbia River and Puget 

Sound basins, for water years 1993–2003.

Negative

Positive

FLOW-ADJUSTED TREND IN SUSPENDED-SEDIMENT CONCENTRATION,

IN PERCENT PER YEAR

Less

than -8

-4 to -8 -4 to 0 0 to 4 4 to 8 More

than 8

NUMBER OF SITES

FLOW-ADJUSTED TREND IN SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER PER YEAR

Less

than -4

-2 to

-4

-2 to 0 0 to 2 2 to 4 More

than 4

NUMBER OF SITES

A

B

0

5

10

15

20

25

0

5

10

15

20

25

30

Trend significant at p ≤0.05

Trend not significant

Table 18. Summary of flow-adjusted trends in concentration of 

total nitrogen, total phosphorus, and suspended sediment in the 

Columbia River and Puget Sound basins, water years 1993–2003.

[FATC, Flow-adjusted trend in concentration]

Constituent

Sites with

Total

number 

of sites

Significant 

increasing

FATC

Significant 

decreasing

FATC

No 

significant 

FATC

Idaho

Total nitrogen 1 1 3 5

Total phosphorus 1 0 4 5

Suspended sediment 0 4 1 5

Oregon

Total nitrogen 1 10 8 19

Total phosphorus 0 8 12 20

Suspended sediment 4 4 10 18

Washington

Total nitrogen 0 8 12 20

Total phosphorus 6 1 18 25

Suspended sediment 0 7 18 25

Summary

Total nitrogen 2 19 23 44

Total phosphorus 7 9 34 50

Suspended sediment 4 15 29 48

52 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Table 19. Flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in annual loads for total 

nitrogen in the Columbia River and Puget Sound basins, water years 1993–2003. 

[Sites can be located in figure 1 by the Map index No. Bold values indicate trends significant at a less than or equal to 0.05 p-level. Abbreviations: FATC, flowadjusted trends in concentration; NFATC, non-flow-adjusted trends in concentration]

Map 

index

No.

Site 

No.

Water quality FATC NFATC Load trend

Start date End date Number of 

observations

Number of 

observations

 below

reporting 

limit

Percent 

per year

Milligrams 

per liter 

per year

Percent 

per year

Milligrams 

per liter 

per year

Percent 

per year

Kilograms 

per day 

per year

7 10355 10-20-92 08-12-03 126 57 -4.58 -0.020 -4.53 -0.020 -5.06 -497

8 11140 10-20-92 08-12-03 55 0 -4.16 -.042 -4.01 -.040 -5.36 -42.9

10 10508 11-01-93 09-22-03 69 49 -2.55 -.005 -2.57 -.005 -2.43 -9.70

11 10350 10-21-92 08-12-03 126 22 -4.63 -.037 -4.53 -.036 -5.24 -1,180

13 11478 10-14-92 09-03-03 63 32 -3.38 -.010 -3.48 -.010 -6.07 -52.5

14 10555 10-21-92 08-12-03 128 10 -4.81 -.044 -4.74 -.043 -5.41 -2,260

15 14200400 10-14-93 09-03-03 98 1 -.17 -.001 -.580 -.003 -2.40 -.564

16 14201300 10-04-93 09-03-03 129 0 2.40 .221 1.10 .102 -3.97 -5.88

19 3701002 10-05-92 09-29-03 404 0 .58 .016 .550 .015 .798 39.6

23 11321 10-28-92 08-11-03 56 0 -2.82 -.128 -2.47 -.112 -4.00 -24.6

25 3701612 10-01-92 09-29-03 430 80 -3.07 -.017 -2.91 -.016 -2.04 -6.69

31 10611 10-21-92 08-11-03 132 0 -3.61 -.042 -3.57 -.042 -4.42 -3,400

33 14211720 11-16-92 09-10-03 145 1 -.225 -.002 -.330 -.003 -1.65 -845

37 10332 10-21-92 08-06-03 57 0 -2.04 -.020 -2.012 -.019 -3.09 -1,970

39 10411 10-26-92 08-18-03 63 19 -2.26 -.007 -2.261 -.007 -2.25 -97.2

40 10616 10-21-92 08-06-03 57 13 -2.63 -.012 -2.630 -.012 -3.10 -6,000

42 12012 06-21-93 08-18-03 60 16 -3.34 -.013 -3.35 -.013 -3.63 -27.0

43 11489 10-26-92 08-18-03 76 0 -3.56 -.095 -3.98 -.106 -2.87 -38.6

44 14246900 11-19-92 09-08-03 118 22 -.665 -.003 -0.832 -.004 -1.89 -5,080

46 32A070 10-11-93 09-10-03 118 0 -3.81 -.043 -3.84 -.044 -4.07 -30.2

48 37A090 10-12-93 09-10-03 119 0 -2.23 -.026 -2.40 -.028 -1.64 -128

51 12472900 11-17-92 09-25-03 70 52 -2.21 -.005 -2.20 -.005 -2.48 -1,580

52 13351000 12-21-92 09-03-03 164 0 .214 .004 .631 .011 3.03 27.4

53 34A070 10-04-93 09-09-03 116 0 -1.53 -.023 -1.08 -.017 .905 7.24

54 41A070 10-12-93 09-10-03 117 0 -.624 -.012 .167 .003 -2.82 -36.9

57 10A070 10-27-93 09-24-03 118 0 -2.70 -.008 -2.70 -.007 -2.02 -36.0

61 16A070 10-25-93 09-23-03 118 1 -5.00 -.005 -5.00 -.005 -4.48 -7.48

63 09A190 10-18-93 09-24-03 119 1 -.762 -.001 -.666 -.001 -1.76 -3.27

64 45A070 10-12-93 09-08-03 118 0 -2.54 -.004 -2.43 -.004 -2.73 -19.9

66 09A080 10-20-93 09-24-03 117 0 -2.47 -.013 -2.35 -.012 -3.15 -38.2

70 45A110 10-12-93 09-08-03 114 3 -2.14 -.001 -2.23 -.001 -2.54 -7.98

71 16C090 10-25-93 09-23-03 115 13 .736 .000 .658 .000 .256 .067

73 54A120 10-05-93 09-08-03 118 0 1.84 .008 2.36 .011 1.62 76.7

76 07A090 10-19-93 09-22-03 120 0 -1.00 -.003 -.996 -.003 -1.07 -55.6

78 48A070 10-13-93 09-09-03 119 0 -1.88 -.003 -1.26 -.002 -2.55 -7.78

79 49A070 10-13-93 09-09-03 117 0 -2.12 -.003 -2.17 -.003 -4.94 -42.7

81 03A060 10-19-93 09-22-03 118 1 .079 .000 .090 .000 .147 6.60

84 01A050 10-19-93 09-23-03 118 0 -.005 -.000 -.021 -.000 .512 12.8

87 61A070 10-06-93 09-07-03 119 0 -1.45 -.002 -1.45 -.002 -1.29 -402

89 13092747 10-14-93 09-23-03 105 0 -1.93 -.038 .129 .003 -4.53 -29.4

91 13154500 11-04-92 09-24-03 138 0 -.487 -.007 .193 .003 -1.71 -658

93 13206000 11-02-92 09-16-03 93 6 2.09 .012 2.12 .012 2.05 19.5

97 12413470 11-18-92 09-08-03 115 47 1.541 .004 1.63 .004 1.38 2.52

99 12419000 10-07-92 09-03-03 111 88 1.288 .002 1.44 .002 .091 1.20

Trends in Nutrients and Suspended-Sediment, 1993–2003 53
Seven sites in the Willamette River Basin had decreasing 

FATC for TN: the Willamette River main-stem sites at 

Harrisburg (fig. 1, site 7), Albany (fig. 1, site 11), Salem 

(fig. 1, site 14), and Portland (fig. 1, site 31), and tributary 

sites on the Long Tom River (fig. 1, site 8), Johnson Creek 

(fig. 1, site 23) and the Tualatin River (fig. 1, site 25). 

Although not significant, the FATC at Little Abiqua Creek 

(fig. 1, site 15), the Willamette River at Portland (fig. 1, site 

33), and the Willamette River at SP&S Railroad Bridge (fig. 1, 

site 37) also were decreasing.

Other sites in Oregon, Washington, and Idaho with 

decreasing FATC for TN were in catchments with a wide 

range of agricultural activity, covering as little as 0.8 percent 

to as much as 56 percent. The two sites with increasing FATC 

for TN had different land-use profiles. Agricultural land 

covered 95 percent of the catchment for Zollner Creek near 

Mt. Angel, Oreg. (fig. 1, site 16), whereas agricultural land 

covered only 0.5 percent of the catchment for the Boise River 

at Glenwood, Idaho (fig. 1, site 93). However, the Boise River 

at this location received a large point-source load of nitrogen 

(estimated to be about 40 percent of the in-stream TN load), 

which indicates that changes in point-source load could have 

been responsible for the increasing FATC for TN.

OR19-0072_fig30

124° 120° 115°

110°

42°

45°

49°

123°30' 123° 122°30' 122°

45°

45°15'

45°30'

45°45'

0 250 KILOMETERS

0 250 MILES

0 20 KM

0 20 MILES

EXPLANATION

Flow-adjusted trends in concentrations

Direction of trend—Table 1 contains mapping 

 number identification

 Upward

 Downward

 No significant trend

Magnitude of trend, in percent per year

 More than 4 

 2.01–4.00

 0.00–2.00

Magnitude of trend, in milligrams per liter per year

 More than 0.10

 0.051–0.10

 0–0.05

16

Total nitrogen

Basemap modified from U.S. Geological Survey 

digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, 

central meridian 120°30’ W

37

33

40

23

31

14

16

15

8 7

4

57

39

84

63

10

43

42

13

14

11

71

54

73

70

64

46

66

78

87

48

61

81

51 44

93

91

89

9997

79

76

19

25

25

52

53

Figure 30. Flow-adjusted trends in concentration of total nitrogen, Columbia River and Puget Sound basins, water years 1993–2003.

Total Phosphorus

Complete results from the trend analysis for TP are 

shown in table 20, and figure 31 shows the FATC for TP at 

each available trend site in the study area. Sixteen (32 percent) 

of the 50 sites had significant FATC for TP (7 increasing 

and 9 decreasing). Trend in load for TP was observed at six 

sites (3 increasing and 3 decreasing). The number of sites 

with decreasing FATC for TP was about one-half of those for 

TN. Much of this difference can be attributed to the WDOE 

data, which showed eight sites with decreasing FATC for TN 

but no sites with decreasing FATC for TP (table 17). About 

50 percent of the sites had decreasing (but not necessarily 

significant) FATC and trend in load for TP.

Six sites in the Willamette River Basin, Oregon: 

Willamette main-stem sites at Albany (fig. 1, site 11), Salem 

(fig. 1, site 14), and Portland (fig. 1, site 31), and tributary 

sites on the Long Tom River (fig. 1, site 8) and the Tualatin 

River (fig. 1, sites 19 and 25) had decreasing FATC for 

TP. The four other sites in the Willamette River Basin had 

decreasing (but not significant) FATC for TP. Increasing 

FATC for TP was measured in the Puget Sound at four sites: 

Deschutes River (fig. 1, site 56), Green River (fig. 1, site 63), 

54 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Table 20. Flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in annual loads for total 

phosphorus in the Columbia River and Puget Sound basins, water years 1993–2003. 

[Sites can be located in figure 1 by the Map index No. Bold values indicate trends significant at a less than or equal to 0.05 p-level. Abbreviations: FATC, flowadjusted trends in concentration; NFATC, non-flow-adjusted trends in concentration]

Map 

index

No.

Site No.

Water quality FATC NFATC Load trend

Start date End date Number of 

observations

Number of 

observations

 below

reporting 

limit

Percent 

per year

Milligrams 

per liter 

per year

Percent 

per year

Milligrams 

per liter 

per year

Percent 

per year

Kilograms 

per day 

per year

4 10386 10-20-92 08-12-03 57 0 -1.27 -0.000 -1.42 -0.000 -2.09 -4.99

7 10355 10-20-92 08-12-03 130 0 -.244 -.000 -.457 -.000 -1.43 -14.9

8 11140 10-20-92 08-12-03 56 0 -2.01 -.002 -1.99 -.002 -3.85 -2.46

10 10508 11-01-93 09-22-03 69 0 1.13 .001 1.17 .001 1.39 2.12

11 10350 10-21-92 08-12-03 129 0 -1.74 -.001 -1.86 -.001 -2.97 -63.2

13 11478 10-14-92 09-03-03 64 0 -1.76 -.001 -3.01 -.001 -5.82 -6.91

14 10555 10-21-92 08-12-03 129 0 -1.72 -.001 -1.90 -.001 -2.99 -87.1

15 14200400 10-14-93 09-03-03 99 19 6.36 .001 6.01 .001 2.92 .019

16 14201300 10-04-93 09-03-03 129 0 -1.31 -.004 -2.16 -.006 -5.75 -.264

19 3701002 10-05-92 09-29-03 423 0 -2.92 -.005 -2.91 -.005 -2.75 -8.79

23 11321 10-28-92 08-11-03 57 0 -.726 -.001 -.958 -.001 -2.84 -.341

25 3701612 10-01-92 09-29-03 449 92 -3.81 -.001 -3.72 -.001 -2.96 -.689

31 10611 10-21-92 08-11-03 133 0 -2.12 -.002 -2.00 -.002 -3.08 -166

33 14211720 11-16-92 09-10-03 145 0 1.24 .001 1.28 .001 -.284 -11.3

37 10332 10-21-92 08-06-03 57 0 -.704 -.000 -.680 -.000 -1.95 -89.9

39 10411 10-26-92 08-18-03 64 0 -.823 -.001 -.823 -.001 -.806 -8.84

40 10616 10-21-92 08-06-03 57 0 -2.03 -.001 -2.30 -.001 -2.79 -471

42 12012 06-21-93 08-18-03 60 0 3.988 .001 3.71 .001 3.12 2.08

43 11489 10-26-92 08-18-03 75 0 -3.41 -.004 -3.12 -.003 -1.82 -.940

44 14246900 11-19-92 09-08-03 118 6 1.37 .000 .725 .000 -.524 -93.0

46 32A070 10-05-92 09-10-03 128 0 -.381 -.000 -.409 -.000 -.766 -.545

48 37A090 10-12-92 09-10-03 130 0 .280 .000 .347 .000 1.39 8.98

51 12472900 11-17-92 09-25-03 70 38 11.17 .001 10.9 .001 10.1 151

52 13351000 12-21-92 09-03-03 164 0 -5.08 -.010 -4.83 -.009 -3.74 -3.80

53 34A070 10-06-92 09-09-03 126 0 -1.22 -.001 -1.34 -.001 .586 .246

54 41A070 10-12-93 09-10-03 116 0 -1.34 -.001 -.672 -.000 -3.42 -1.67

56 13A060 10-26-92 09-22-03 120 1 7.87 .001 7.70 .001 7.01 .829

57 10A070 10-27-92 09-24-03 130 3 7.30 .003 8.01 .003 9.76 22.3

61 16A070 10-28-92 09-23-03 130 25 9.61 .001 10.3 .001 12.5 1.98

63 09A190 10-19-92 09-24-03 131 34 23.2 .001 22.3 .001 18.3 1.35

64 45A070 10-12-92 09-08-03 127 34 4.90 .000 4.82 .000 4.21 .745

66 09A080 10-21-92 09-24-03 128 1 1.76 .000 1.70 .000 .474 .277

70 45A110 10-12-92 09-08-03 126 50 1.24 .000 1.13 .000 .675 .138

71 16C090 10-25-93 09-23-03 115 65 1.06 .000 .939 .000 .527 .016

73 54A120 10-06-92 09-08-03 130 8 3.65 .001 3.85 .001 3.00 5.85

74 07D050 10-19-92 09-22-03 119 19 4.86 .001 4.69 .001 4.06 2.89

75 07C070 10-19-92 09-22-03 117 48 -.050 -.000 .177 .000 1.11 .436

76 07A090 10-19-92 09-22-03 131 27 2.41 .000 2.38 .000 2.27 3.47

77 53A070 10-14-92 09-08-03 119 56 -1.19 -.000 -1.19 -.000 -1.20 -27.9

78 48A070 10-13-92 09-09-03 129 53 9.12 .000 8.74 .000 5.89 .371

79 49A070 10-13-92 09-09-03 126 9 1.48 .000 -.196 -.000 -3.58 -3.54

80 48A140 10-13-92 09-09-03 118 53 13.9 .000 13.3 .000 9.50 .422

81 03A060 10-21-92 09-22-03 130 24 .508 .000 0.552 .000 .612 3.17

84 01A050 10-20-92 09-23-03 128 3 3.46 .001 3.99 .001 4.75 7.25

87 61A070 10-07-92 09-07-03 132 69 -3.07 -.000 -3.04 -.000 -2.92 -73.5

89 13092747 10-14-93 09-23-03 106 0 -.158 -.000 -1.44 -.001 -5.38 -1.46

91 13154500 11-04-92 09-24-03 136 0 -1.21 -.001 -.804 -.001 -2.50 -44.0

93 13206000 11-02-92 09-16-03 93 1 3.34 .003 3.40 .003 3.32 4.71

97 12413470 11-18-92 09-08-03 117 8 8.61 .001 8.75 .001 8.32 .719

99 12419000 10-07-92 09-03-03 112 22 -3.42 -.000 -3.30 -.000 -4.04 -4.36

Trends in Nutrients and Suspended-Sediment, 1993–2003 55
Puyallup River (fig. 1, site 57), and Skokomish River (fig. 1, 

site 61). In these catchments, more than 14 percent of the land 

cover was urban, and less than 9 percent was agriculture. In 

the eastern side of the Columbia Basin, increasing FATCs for 

TP were observed in the Methow River (fig. 1, sites 78 and 80) 

and South Fork Coeur d’Alene River (fig. 1, site 97). These 

catchments were predominately forested with low agricultural 

and urban use. Twenty-two of the 24 sites with increasing (but 

not necessarily significant) FATC for TP were in catchments 

with less than 15 percent agricultural land, whereas the FATC 

for TP at 14 sites in catchments with more than about 15 

percent agricultural land generally decreased (one-half were 

significant). Increasing FATC for TP was measured (but not 

significant) at two larger integrator sites (the Columbia River 

at Vernita Bridge [fig. 1, site 51] and the Willamette River at 

Portland [fig. 1, site 33], located in catchments with 18.4 and 

22.7 percent agricultural land, respectively).

Suspended Sediment

Complete results from the trend analysis for SS are 

shown in table 21, and figure 32 shows the FATC for SS 

at each available trend site in the study area. Nineteen (40 

percent) of the 48 sites had significant FATC for SS (4 

increasing, 15 decreasing, and 2 sites had insufficient waterquality data to determine trends). Trend in load for SS was 

observed at seven sites (one increasing, six decreasing). More 

than 65 percent of the sites had decreasing (but not necessarily 

significant) FATC and trend in load for SS. All six sites with 

decreasing trends in load for SS also had decreasing FATC 

for SS, and one site with an increasing trend in load for SS 

also had an increasing FATC for SS. Five of the six sites with 

decreasing trend in load for SS had no trend in streamflow, 

indicating that the decreasing FATC for SS at these sites 

was the cause of the decreasing trend in load. At the sixth 

site, Rock Creek [fig. 1, site 89]), both FATC and trend in 

streamflow were decreasing, meaning that either could have 

contributed to the decreasing trend in load at this site.

Significant increasing FATC for SS were measured at 

four sites: Long Tom River (fig. 1, site 8, with an average 

increase of 0.6 mg/L/yr from 1993 to 2003) and Hood 

River (fig. 1, site 42, 1.1 mg/L/yr), which are agricultural 

catchments; Deschutes River (fig. 1, site 10, 0.1 mg/L/year), 

a predominately forested and undeveloped catchment; and 

Willamette River at Salem (fig. 1, site 14, 0.2 mg/L/yr), 

which integrates runoff from a mix of forested, agricultural, 

and urban lands. The increasing FATC for SS in the Hood 

River (fig. 33) was most likely the result of high elevation 

rain on Mt. Hood in late September, early October 2000. 

The rain caused a glacial outwash of sediment that filled the 

Hood River channel and took several years to wash out. This 

increase in trend probably will not continue at this site, unless 

another glacial outwash occurs.

OR19-0072_fig31

124° 120° 115°

110°

42°

45°

49°

123°30' 123° 122°30' 122°

45°

45°15'

45°30'

45°45'

0 250 KILOMETERS

0 250 MILES

0 20 KM

0 20 MILES

EXPLANATION

Flow-adjusted trends in concentrations

Direction of trend—Table 1 contains mapping 

 number identification

 Upward

 Downward

 No significant trend

Magnitude of trend, in percent per year

 More than 8 

 4.01 - 8.00

 0.00 - 4.00

Magnitude of trend, in milligrams per liter per year

 More than 0.005

 0.0026 - 0.005

 0 - 0.0025

57

Total phosphorus

Basemap modified from U.S. Geological Survey 

digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, 

central meridian 120°30’ W

37

33

40

23

31

14

16

15

8 7

4

57

39

84

63

10

43

42

13

14

11

71

54

73

70

64

46

66

56

78

87

48

52

53

61

81

51 44

93

91

89

99

97

79

80

76 77 75

74

19

25

25

Figure 31. Flow-adjusted trends in concentrations of total phosphorus, Columbia River and Puget Sound basins, water years 1993–2003.

56 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Table 21. Flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in annual loads for suspended 

sediment in the Columbia River and Puget Sound basins, water years 1993–2003. 

[Sites can be located in figure 1 by the Map index No. Bold values indicate trends significant at a less than or equal to 0.05 p-level. Abbreviations: FATC, flowadjusted trends in concentration; NFATC, non-flow-adjusted trends in concentration]

Map 

index

No.

Site No.

Water quality FATC NFATC Load trend

Start date End date Number of 

observations

Number of 

observations

 below

reporting 

limit

Percent 

per year

Milligrams 

per liter 

per year

Percent 

per year

Milligrams 

per liter 

per year

Percent 

per year

Kilograms 

per day 

per year

4 10386 10-20-92 08-12-03 60 4 2.16 0.034 1.58 0.025 0.653 88.9

7 10355 10-20-92 08-12-03 128 0 3.28 .061 2.23 .042 .958 405

8 11140 10-20-92 08-12-03 59 0 11.4 .581 10.0 .509 5.07 202

10 10508 11-01-93 09-22-03 68 6 5.98 .092 6.16 .094 6.47 211

11 10350 10-21-92 08-12-03 127 0 1.48 .070 .335 .016 -1.11 -1,470

13 11478 10-14-92 09-03-03 62 0 2.15 .068 -.932 -.029 -4.68 -429

14 10555 10-21-92 08-12-03 126 0 4.74 .186 3.16 .124 1.32 2,340

15 14200400 10-14-93 09-03-03 98 1 -6.58 -.355 -7.04 -.380 -7.63 -19.9

16 14201300 100-4-93 09-03-03 130 1 -4.48 -.608 -5.94 -.806 -7.82 -16.8

23 11321 10-28-92 08-11-03 59 0 2.28 .093 1.53 .063 -.907 -4.96

31 10611 10-21-92 09-09-03 132 0 .607 .030 -.179 -.009 -1.52 -4,960

33 14211720 11-16-92 09-10-03 144 0 -3.15 -.343 -3.79 -.412 -4.60 -32,500

37 10332 10-21-92 08-06-03 60 0 .651 .031 .038 .002 -1.34 -4,180

39 10411 10-26-92 08-18-03 63 0 3.80 .204 3.85 .207 3.87 2,820

40 10616 10-21-92 08-06-03 57 0 -1.14 -.069 -1.94 -.117 -2.46 -61,700

42 12012 06-21-93 08-18-03 67 4 76.0 1.07 72.4 1.02 68.8 1,770

43 11489 10-26-92 08-18-03 99 0 -4.15 -.283 -3.26 -.221 -1.99 -66.5

44 14246900 11-19-92 09-08-03 142 1 1.77 .243 -.480 -.066 -1.58 -121,000

46 32A070 10-05-92 09-10-03 128 0 -6.31 -3.43 -6.35 -3.45 -6.47 -2,230

48 37A090 10-12-92 09-10-03 132 0 -4.89 -1.27 -4.44 -1.15 -3.93 -6,230

51 12472900 11-17-92 09-25-03 70 2 -.547 -.012 -.669 -.014 -1.01 -5,900

52 13351000 12-21-92 09-03-03 171 0 -8.26 -8.27 -8.04 -8.04 -7.72 -3,870

53 34A070 10-06-92 09-09-03 129 0 -6.00 -2.16 -5.55 -2.00 -4.67 -829

54 41A070 10-12-93 09-10-03 117 0 -1.33 -.344 .439 .113 -2.63 -454

56 13A060 10-26-92 09-22-03 119 2 -.113 -.005 -.519 -.025 -.872 -26.1

57 10A070 10-27-92 09-24-03 131 0 4.03 1.89 6.13 2.88 7.69 22,500

61 16A070 10-28-92 09-23-03 131 9 -3.90 -.161 -3.19 -.132 -2.52 -174

63 09A190 10-19-92 09-24-03 131 10 -1.84 -.034 -2.36 -.043 -3.22 -86.5

64 45A070 10-12-92 09-08-03 128 1 -2.04 -.063 -2.19 -.068 -2.49 -355

66 09A080 10-21-92 09-24-03 129 0 -1.51 -.137 -2.09 -.190 -2.89 -601

70 45A110 10-12-92 09-08-03 128 18 -2.62 -.072 -2.83 -.078 -3.11 -388

71 16C090 10-25-93 09-23-03 116 42 3.98 .046 3.36 .039 2.86 25.1

73 54A120 10-06-92 09-08-03 132 9 -.558 -.014 -.779 -.020 -1.33 -348

74 07D050 10-19-92 09-22-03 119 1 .167 .012 -.273 -.020 -.680 -318

75 07C070 10-19-92 09-22-03 117 3 -5.46 -.286 -5.18 -.271 -4.79 -1,620

76 07A090 10-19-92 09-22-03 131 1 -1.81 -.122 -1.88 -.127 -1.95 -2,240

77 53A070 10-14-92 09-08-03 119 51 -1.60 -.016 -1.60 -.017 -1.61 -3,920

78 48A070 10-13-92 09-09-03 130 21 -2.96 -.074 -3.33 -.083 -4.26 -214

79 49A070 10-13-92 09-09-03 127 3 -1.75 -.197 -4.34 -.489 -6.16 -4,000

80 48A140 10-13-92 090-9-03 118 24 -1.32 -.020 -1.73 -.027 -2.98 -78.1

81 03A060 10-21-92 09-22-03 130 1 -1.74 -.421 -1.67 -.403 -1.63 -13,600

84 01A050 10-20-92 09-23-03 128 0 -.752 -.216 .016 .005 .553 1,140

87 61A070 10-07-92 09-07-03 132 14 -.986 -.019 -.852 -.016 -.682 -2,910

89 13092747 10-14-93 09-23-03 106 0 -6.03 -4.29 -7.95 -5.67 -8.92 -2,070

91 13154500 11-04-92 09-24-03 135 0 -6.10 -1.53 -6.60 -1.65 -7.12 -45,500

93 13206000 11-02-92 09-16-03 92 0 -6.84 -1.44 -6.85 -1.44 -6.87 -2,270

97 12413470 11-18-92 09-08-03 208 0 -5.58 -.225 -5.60 -.226 -5.69 -180

99 12419000 11-10-92 09-03-03 75 1 -3.00 -.053 -3.18 -.056 -3.94 -660

Trends in Nutrients and Suspended-Sediment, 1993–2003 57
Decreasing FATC for SS were measured at four of the 

five sites in Idaho: Boise River (fig. 1, site 93), Snake River 

(fig. 1, site 91), Rock Creek (fig. 1, site 89), and South Fork 

Coeur d’Alene River (fig. 1, site 97). The fifth site, the 

Spokane River (fig. 1, site 99), also had a decreasing (but not 

significant) FATC for SS. Three sites in the Willamette River 

Basin had significant decreasing FATC for SS: Willamette 

River at Portland (fig. 1, site 33), Zollner Creek (fig. 1, site 

16), and Little Abiqua Creek (fig. 1, site 15). Two sites had 

significant increasing FATC for SS: Long Tom River (fig. 1, 

site 8) and Willamette River at Salem (fig. 1, site 14). Six 

sites in the Willamette River Basin had increasing (but not 

significant) FATC for SS: Middle Fork Willamette River 

(fig. 1, site 4), Willamette River at Harrisburg (fig. 1, site 7), 

Albany (fig. 1, site 11), Hawthorne Bridge (fig. 1, site 31), 

and SP&S Railroad Bridge (fig. 1, site 37), and Johnson Creek 

(fig. 1, site 23).

Decreasing FATC for SS were measured at three of the 

four sites with the largest percentages of agricultural land, 

ranging from about 42 to 95 percent: Zollner Creek (fig. 1, 

site 16, 95.2 percent agricultural land); Palouse River (fig. 1, 

sites 52 and 53, 72.5 percent); and Walla Walla River (fig. 1, 

site 46, 56.1 percent). One site (Crab Creek [fig. 1, site 54, 

42.2 percent]), showed decreasing FATC for SS that was not 

significant. The Walla Walla River, Palouse River, and Crab 

Creek are in southeastern Washington, and Zollner Creek is 

in the Willamette River Basin, Oregon. Other than at these 

four sites, the percentage of agricultural land in a basin did not 

appear to be related to the increasing or decreasing FATC for 

SS.

OR19-0072_fig32

124° 120° 115°

110°

42°

45°

49°

123°30' 123° 122°30' 122°

45°

45°15'

45°30'

45°45'

37

33

40

23

31

14

16

15

0 250 KILOMETERS

0 250 MILES

0 20 KM

0 20 MILES

EXPLANATION

Flow-adjusted trends in concentrations

Direction of trend—Table 1 contains mapping 

 number identification

 Upward

 Downward

 No significant trend

Magnitude of trend, in percent per year

 More than 8 

 4.01 - 8.00

 0.00 - 4.00

Magnitude of trend, in milligrams per liter per year

 More than 4

 2.01 - 4.00

 0 - 2.00

14

Suspended sediment

Basemap modified from U.S. Geological Survey 

digital data, 1983 (1:100,000). 

Lambert Conformal Conic projection

Standard parallels 43°N and 45°N, 

central meridian 120°30’ W

8 7

4

57

39

84

63

10

43 42

13

16

15

14

71

54

73

70 64

46

66

56

78

87

48

52

53

61

81

51 44

93

91

89

99

97

79

80

77 7675

74

11

Figure 32. Flow-adjusted trends in concentration of suspended sediment, Columbia River and Puget Sound basins, water years 

1993–2003.

Figure 33. Measured suspended-sediment 

concentrations, Hood River, Oregon, water years 

1993–2003.

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 

WATER YEAR

SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

1

10

100

1000

10,000

58 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Trends in Relation to Changes in Nutrient 

Sources and Landscape Characteristics

Ancillary data on (1) nitrogen and phosphorus loads for 

fertilizer and manure use for farm and on-farm applications, 

(2) nitrogen loads from atmospheric deposition, and (3) 

nitrogen and phosphorus loads from point sources (table 22) 

were acquired for 45 trend catchments. For this study, pointsource nutrient loads were estimated only for CY 2000, and 

total fertilizer and manure applications were estimated only 

for CYs 1992, 1997, and 2002, because manure estimates 

were available only for those 3 years. Because of the scarcity 

of nutrient data from point sources for the 1993–2003 period, 

temporal changes in point-source input trends generally were 

not assessed in this report; however, the relative importance 

of point-source discharges, on the basis of CY 2000 data, 

is addressed in relation to their potential effect on the trend 

results.

Estimates of point- and nonpoint-source contributions of 

nitrogen and phosphorus are shown in table 22 and figure 26. 

Point-source loads could have an immediate effect on water 

quality and trends, because the effluent generally is piped 

directly into the stream, whereas the transport of nutrients 

from nonpoint sources (for example, land applications of 

inorganic fertilizers and manure) generally is delayed by 

the timing of erosional processes or by way of seepage 

into the ground water, which eventually discharges to the 

streams. Nutrients from nonpoint sources first contact the 

land surface (for example, impervious surfaces, soil particles, 

and vegetation) and their transport to the stream is delayed 

by sorption, biological uptake, and (or) degassing to the 

atmosphere (for example, denitrification). Eventually, part 

of the nonpoint-source nutrients will flow into the streams, 

but the process could take hours to decades depending on 

the characteristics of the flow path. Soluble nitrate fertilizer 

not taken up by plants likely will move through the soils into 

the ground water and gradually seep back to the stream. In 

contrast, phosphorus fertilizer is more likely to adsorb to 

soils and erode to streams during periods of intense irrigation 

or precipitation events, especially during high-flow years. 

Therefore, land-applied nutrients will likely show a temporal 

delay in being transported to streams. To some extent, the 

transport to streams of atmospheric nitrogen also may be 

delayed; however, during the cold, wet winters in the Pacific 

Northwest when the soils are saturated and biological uptake 

is minimal, transport of atmospheric nitrogen is likely to be 

greater during the large rainfall/snowmelt events.

Of the 43 trend sites with in-stream and point-source 

TN load estimates, point-source loads accounted for less 

than 25 percent of the in-stream nitrogen load at 37 sites (86 

percent). Of the 44 sites with in-stream and point-source TP 

load estimates, point-source loads accounted for less than 25 

percent of the in-stream phosphorus load at 31 (70 percent) 

of the sites (table 22). Assuming that (1) a point-source load 

accounted for 25 percent (or less) of the in-stream load for 

a catchment, and (2) a decreasing trend in the in-stream 

nutrient load was 3–4 percent per year (which was typical), 

the decrease in the point-source load would have to be 12–16 

percent or more per year to account for the decreasing trend 

observed in the stream. Over an 11 year period, this would 

equal 132–176 percent. Because point-source nutrient loads 

in most catchments during this period probably increased 

due to increases in population, a decrease in point-source 

loads of this magnitude does not seem likely. Consequently, 

in catchments with point-source loads equal to less than 25 

percent of the in-stream load, the trends observed were not 

likely caused solely by reduced point-source nutrient loads. 

If this study had focused on seasonal rather than annual 

trends, the effect of point-source nutrient discharges might 

have been apparent during periods of low flows, because this 

is when point-source loads can often contribute a larger part 

to the in-stream nutrient load. Additionally, seasonal trends 

would not necessarily be consistent with the annual trend 

results shown in this report. For example, FATC for TN during 

summer low flows might have been increasing at a number of 

sites because of increasing populations, rather than generally 

decreasing (as was shown in the annual data).

Results from this study indicate that nonpoint-source 

loads of nutrients probably have decreased over time in many 

of the catchments. Some data for the Willamette River Basin 

support this hypothesis. Between 1991 and 2000 the sum of 

the annual average flows for the largest nutrient point sources 

in the basin (those contributing close to 90 percent of the 

total measured point-source flow in 2000) increased from 199 

Mgal/d (Tetra Tech, Inc., 1992) to 233 Mgal/d, an increase 

of 17.3 percent. This increase in total annual average flow 

corresponded to an increase in population in the basin during 

this period. In addition, the estimated total annual TP load 

from a subset of these sources increased by 130 percent from 

the early 1990’s (Tetra Tech, Inc., 1992) to 2000. Although 

this subset represented only 37 percent of the total TP load in 

2000, the trend indicates that total TP load from point sources 

in the Willamette River Basin increased overall since the early 

1990’s.

Point sources generally accounted for less than 20 

percent of the total load (from point and nonpoint sources) of 

nitrogen and phosphorus to the trend-site catchments (fig. 26). 

Except for a few sites, point-source loads were equivalent to 

less than 10 percent of the land-applied nutrients in fertilizers 

and manure. In all the trend-site catchments, nonpoint sources 

of nutrients from land applications of fertilizers and manure 

exceeded point-source loads and, generally, even nitrogen 

loads due solely to atmospheric deposition exceeded pointsource loads. The few exceptions are shown in table 22.

In spite of the generally small contribution of pointsource nutrient loads, they still may have been partially 

responsible for the significant trends at several sites assessed 

in this study, especially those sites where the point-source 

nutrient loads exceeded 25 percent of the in-stream load. 

These sites were the Willamette River at Highway 99E, 

Oreg. (Harrisburg) (fig. 1, site 7), the Walla Walla River 

near Touchet, Wash. (fig. 1, site 46), and the Boise River at 

Trends in Nutrients and Suspended-Sediment, 1993–2003 59
Glenwood, Idaho (fig. 1, site 93) for TN, and the Willamette 

River at Albany (fig. 1, site 11), at Marion Street (Salem) 

(fig. 1, site 14), and at Hawthorne Bridge (Portland) (fig. 1, 

site 31), and the South Fork Coeur d’Alene River near 

Pinehurst, Idaho (fig. 1, site 97) for TP. The catchment for 

the Boise River site had the following characteristics: (1) the 

point-source TN load was 40 percent of the in-stream load, 

(2) the population increased by about 20 percent from 1990 

to 2000 (about 2 percent per year), and (3) the FATC for TN 

was significant at 2.1 percent per year. These observations 

indicate that a possible increase in nitrogen load from point 

sources could have accounted for the increasing FATC for TN. 

Although the FATC for TP at this site was not significant, it 

did increase by 3.3 percent per year, indicating that a possible 

increase in phosphorus load from point sources could have 

accounted for the increasing FATC for TP. Except for the 

limited data for the Willamette River basin, temporal pointsource data were not available from 1993 through 2003 to 

accurately assess water-quality trends throughout the region in 

relation to changes in point-source loads.

Sixteen of the 19 sites with decreasing FATC for TN 

also had decreasing annual loads of atmospheric nitrogen in 

their catchments between CY’s 1992 and 2002 (ancillary data 

were not available for three of the catchments). However, 

no consistent temporal pattern in the load of nitrogen from 

fertilizers and manure was observed across the 16 catchments 

during this time period. Zollner Creek near Mt Angel, OR 

(fig. 1, site 16) and the Boise River at Glenwood, ID (fig. 1, 

site 93) were the two sites that showed increasing FATC for 

TN. More than 99 percent of the nitrogen in the Zollner Creek 

catchment came from land-applied fertilizers and manure, 

which also had an upward trend in nitrogen application from 

1992 to 2002. The increasing FATC for TN in the Boise 

River catchment could not be explained with the available 

fertilizer and manure data. However, as discussed above, the 

increasing FATC for TN and TP at this site might have been 

due to the influence of point sources. Although data on annual 

phosphorus loads from fertilizers and manure were available 

for 13 of the 15 sites having FATC for TP, the trends could 

not be explained by the annual patterns in the application 

of phosphorus from fertilizers and manure. However, the 

limited data on point sources showing large increases in TP 

loads to the Willamette River Basin between 1991 and 2000 

strongly indicate that an overall decrease in nonpoint-source 

phosphorus load was the reason for the decreasing significant 

FATC for TP at the three lower Willamette River sites.

Summary and Conclusions

In 1991, the U.S. Geological Survey (USGS) 

implemented the National Water-Quality Assessment 

(NAWQA) Program to support national, regional, State, 

and local information needs and decisions related to waterquality management and policy (http://water.usgs.gov/

nawqa). NAWQA was designed to answer the following 

types of questions: What is the condition of our streams? 

What are the factors (contaminant sources, loads, and yields) 

affecting the conditions? Is the water quality changing over 

time? From 1991 to 2001, the NAWQA Program completed 

interdisciplinary assessments and established a baseline 

understanding of water-quality conditions in 51 of the Nation’s 

river basins and aquifers. In the Pacific Northwest, the 

NAWQA Program has collected long-term water-quality data 

for the Columbia River and Puget Sound Basins in Oregon, 

Washington, and Idaho. In addition, other Federal, State, and 

local agencies also have collected water-quality data in these 

areas. For this study, multiagency data were compiled and 

used to provide insights into the recent status of water-quality 

conditions in the Pacific Northwest; how these conditions have 

changed over time; and how natural features and (or) human 

activities may have contributed to these changes.

This study examined three topics that might be of 

interest to water-resource managers in the Pacific Northwest: 

(1) Annual loads of total nitrogen (TN), total phosphorus 

(TP), and suspended sediment (SS) transported through the 

Columbia River and Puget Sound Basins were estimated for 

water years 1997 (high-flow), 2000 (average-flow), and 2001 

(low-flow); (2) Annual yields (loads divided by catchment 

areas) of TN, TP, and SS for water year 2000 were compared 

to differences in landscape and climatic conditions between 

sub-basin catchments; and (3) Trends in TN, TP, and SS 

concentrations and loads were calculated for WY 1993–2003 

and compared to changes in landscape and climatic conditions 

in the catchments. Trends in concentrations were determined 

in two ways: (1) flow-adjusted trend in concentration (FATC) 

was used to determine water-quality trends in the absence of 

trends in natural streamflow and (2) non-flow adjusted trend in 

concentration (NFATC) was used to express the overall trend 

of exposure to biota resulting from natural and anthropogenic 

changes. Depending on the constituent, annual loads were 

estimated for as many as 88 water-quality sites; annual yields 

were estimated for as many as 81 catchments; and trends 

were estimated for as many as 50 water-quality sites. The 

catchments ranged in size from 5 km2

 to more than 650,000 

km2, with most sites between 100 and 10,000 km2. Although 

the catchments tended to have large percentages of forested 

and undeveloped land and small percentages of agricultural 

and urban land, there were a few catchments where 

agricultural and/or urban land made up most of the watershed.

Transport of Nutrients and Suspended-Sediment

During WY 2000, total point-source nutrient loads to the 

catchments generally were equal to a small percentage of the 

estimated in-stream loads. In 10 percent of the catchments, 

annual point-source TN loads were greater than 25 percent 

of the estimated annual in-stream TN load discharged from 

the catchment, and in 22 percent of the catchments, annual 

point-source TP loads were greater than 25 percent of the 

60 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
estimated annual in-stream TP load discharged from the 

catchment. Point-source nutrient loads generally also were a 

small percentage of the total nutrient load to the catchments 

compared to nonpoint sources, such as fertilizer and manure 

and atmospheric deposition, and loads from sources other than 

municipal wastewater treatment plants were never more than 

5 percent of the total point-source load. However, there were 

a few examples where point sources comprised as much as 30 

percent of the TN load and as much as 80 percent of the TP 

load to a catchment. In smaller urbanized catchments, point 

sources tended to contribute more of the total nutrient load 

when compared to larger catchments with less urbanization. 

Although point sources contributed very little to the in-stream 

load of TN and TP in the eight tributaries delivering most of 

the nutrients to the Puget Sound, the nitrogen and phosphorus 

loads from point sources discharging directly to the Puget 

Sound were about equal to the annual loads from those 

tributaries.

The annual mean load discharged from the Columbia 

River to the Pacific Ocean was about 570,000 pounds per day 

of TN, about 55,000 pounds per day of TP, and about 14,000 

tons per day of SS. The monitored tributaries contributing 

the most to the annual nutrient loads in the Columbia River 

were the Yakima, Snake, Deschutes, and Willamette Rivers 

(in downstream order). Total annual loads of TN and TP from 

these tributaries were equal to about 63 percent of the load 

near the mouth of the Columbia River, whereas the annual SS 

load from these four tributaries was equal to about 32 percent 

of the load near the mouth. The estimated annual loads from 

point sources discharging directly into the Columbia River 

were equal to less than 10 percent of the annual TN and TP 

loads near the mouth. Generally, direct point-source discharges 

of nutrients to the Willamette and Snake Rivers were relatively 

small when compared to the total nutrient loads these rivers 

discharged to the Columbia. However, in some reaches of the 

Willamette River, point sources were responsible for much of 

the gain in phosphorus load.

The yields of TN, TP, and SS were generally greater in 

catchments west of the Cascade Range, where precipitation 

and runoff were greater. A multiple linear regression analysis 

was performed to determine the relative importance of specific 

catchment characteristics on yields. Based on the standardized 

regression coefficients, TN yields were significantly (p < 0.05) 

and positively related to precipitation, atmospheric nitrogen 

loads, fertilizer and manure loads, point-source loads, and 

were negatively related to average slope. TP yields were 

significantly and positively related to precipitation and pointsource loads, and SS yields were significantly and positively 

related to precipitation.

Trends in Nutrients and Suspended-Sediment, 

1993–2003

For most catchments, the net change in non-hydrologic 

characteristics (land use and other human activities) was 

not great enough to cause any significant (p < 0.05) flowadjusted trend in concentration (FATC) for TN (52 percent), 

TP (68 percent), or SS (60 percent) between WY 1993–2003. 

However, some non-hydrologic changes might still have 

occurred in these catchments, but either they cancelled out (for 

example, decreasing non-point source loads and increasing 

point-source loads) or were too far upstream to have much 

effect on water quality. Twenty-one of the 44 sites available 

for TN trend analysis had significant FATC for TN (2 

increasing, 19 decreasing). Ten sites showed significant trend 

in load for TN (all decreasing), and more than 70 percent of 

the sites had decreasing (but not necessarily significant) FATC 

and trend in load for TN. Sixteen of the 50 sites available for 

TP trend analysis had significant FATC for TP (7 increasing 

and 9 decreasing). Six sites had significant trend in load for 

TP (3 increasing, 3 decreasing), and about 50 percent of the 

sites had decreasing (but not necessarily significant) FATC 

and significant trend in load for TP. Nineteen of the 48 sites 

available for SS trend analysis had significant FATC for SS 

(4 increasing, 15 decreasing). Seven sites showed significant 

trend in load for SS (1 increasing, 6 decreasing), and more 

than 65 percent of the sites had decreasing (but not necessarily 

significant) FATC and trend in load for SS. Streamflow at only 

two of the 50 trend sites had significantly decreasing trends, 

indicating that almost all trends in load resulted from FATC. 

The values for NFATC for TN, TP, and SS were similar in 

magnitude to the values for FATC.

The results from this study indicate that nonpoint sources 

of nutrients probably have decreased over time in many of 

the catchments. For the Willamette River Basin, some data 

supported this hypothesis (total annual flow and TP loads 

from the major WWTPs in the basin increased between 

1991 and 2000). Despite the generally small contribution of 

point-source nutrient loads, point sources still may have been 

partially responsible for the significant decreasing FATC 

for TN at the six sites where the total point-source nutrient 

loads to the catchments exceeded 25 percent of the in-stream 

load. Although the decreasing FATC for TP at three lower 

Willamette River sites could not be explained by the available 

data on phosphorus load from fertilizer and manure, the 

limited data on point sources showing large increases in TP 

loads to the basin between 1991 and 2000 indicate that an 

overall decrease in nonpoint-source phosphorus load may have 

been the cause.

Summary and Conclusions 61
Acknowledgments

Technical Review—Richard Alexander (U.S. Geological 

Survey, Reston, Virginia) and Stuart McKenzie (ret.) and John 

Williams (U.S. Geological Survey, Portland, Oregon).

Data Compilation—Bruce Fisher, Tana Haluska, 

Thomas Herrett, Matt Johnston, and Suzanne Miller 

(U.S. Geological Survey, Portland, Oregon), Naomi Nakagaki 

(U.S. Geological Survey, Sacramento, California), and Alan 

Rea (U.S. Geological Survey, Boise, Idaho).

Water Quality and Point-Source Data—Ranei Nomura 

and Greg Pettit (Oregon Department of Environmental 

Quality, Portland, Oregon), Carol Johnston (WA Department 

of Ecology, Olympia, Washington), Jan Miller (Clean Water 

Services, Hillsboro, Oregon), Janet Gillaspie (Oregon 

Association of Clean Water Agencies, Portland, Oregon), 

Dean Marriot (City of Portland, Oregon), Dan Hanthorne (City 

of Corvallis, Oregon), Ernie Strahm (City of McMinnville, 

Oregon), Thomas Mendes (City of Eugene, OR), and Alan 

Johnston (City of Gresham, Oregon).

Streamflow Data—Robert Harmon and Ken Stahr 

(Oregon Department of Water Resources, Salem, Oregon), and 

Darrell Hedin (Washington County, Oregon).

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Table 22. Summary of sources and stream annual loads for total nitrogen and total phosophorus in the Columbia River and Puget 

Sound basins, water year 2000 and calendar year 2002. 

[Abbreviations: TN, total nitrogen; lb, pound; ID, Idaho; OR, Oregon; WA, Washington; WY, Wyoming; NA, either an annual instream load was not calculated 

or no catchment delineation was available to base point-source and nonpoint-source loads]

Map 

index 

No.

Site 

No.

Trend 

site Site name

Water year 2000

(lb)

Calendar year 2002

(lb)

Catchment 

point-source 

TN load as a 

percentage of 

in-stream load

Estimated 

annual 

instream 

load 

Estimated 

annual total 

catchment 

point-source 

load 

Estimated 

annual nitrogen 

load from 

fertilizer 

and manure 

Estimated 

annual 

nitrogen 

load from 

atmospheric 

deposition 

Total nitrogen

1 10729 Owyhee River at Hwy 201 Bridge (Owyhee), OR 634,000 NA NA NA NA

2 MAL113 North Fork Malheur River approximately 2 miles 

upstream of Beulah Reservoir, OR

NA NA 367,000 88,500 NA

3 MAL144 Malheur River at Ford south of Vale 1.1 miles 

upstream of Bully Creek, OR

NA NA 13,000,000 1,150,000 NA

4 10386 X Middle Fork Willamette River at Jasper Bridge, OR NA NA 934,000 541,000 NA

5 10663 Mohawk River at Hill Road, OR NA NA 428,000 84,100 NA

6 10376 McKenzie River at Coburg Road, OR NA NA NA NA NA

7 10355 X Willamette River at Hwy 99E (Harrisburg), OR 5,770,000 1,920,000 6,720,000 1,440,000 33.2

8 11140 X Long Tom River at Stow Pit Road (Monroe), OR 1,110,000 0 6,380,000 226,000 .00

9 12657 McKenzie River at Hwy 126 downstream Clear 

Lake, OR

NA NA 16,700 38,700 NA

10 10508 X Deschutes River at Lower Bridge, OR 447,000 0 2,360,000 650,000 .00

11 10350 X Willamette River at Albany (Eastbound Hwy 20 

Bridge), OR

14,000,000 2,220,000 46,000,000 2,240,000 15.9

12 11490 Powder River at Hwy 7 (in Baker City), OR 78,000 0 1,110,000 93,400 .00

13 11478 X John Day River at Service Creek, OR 912,000 0 5,640,000 1,490,000 .00

14 10555 X Willamette River at Marion Street (Salem), OR 24,100,000 3,110,000 91,400,000 3,610,000 12.9

15 14200400 X Little Abiqua Creek near Scotts Mills, OR 47,000 0 23,100 6,620 .00

16 14201300 X Zollner Creek near Mt. Angel, OR 486,000 0 1,820,000 11,000 .00

17 10640 Pudding River at Hwy 211 (Woodburn), OR 43,000,000 123,000 23,600,000 211,000 2.87

18 13070 Clackamas River at Mciver Park. (Upper Boat 

Ramp), OR

NA NA 372,000 587,000 NA

19 3701002 X Tualatin River at Weiss Bridge, OR 6,060,000 1,780,000 20,600,000 603,000 29.3

20 3840012 Fanno Creek at Durham Road, OR NA NA 400,000 28,900 NA

21 14206950 Fanno Creek near Durham, OR NA NA 400,000 28,900 NA

22 3701715 Tualatin River at Cherry Grove, OR NA NA 37,400 28,400 NA

23 11321 X Johnson Creek at SE 17th Avenue (Portland), OR 476,000 0 1,410,000 52,600 .00

24 3701333 Tualatin River at Farmington Bridge Road, OR 3,840,000 1,010,000 15,000,000 473,000 26.3

25 3701612 X Tualatin River at Springhill Road Bridge (Dilley), 

OR

512,000 0 2,200,000 98,300 .00

26 11386 John Day River at Hwy 206, OR NA NA NA NA NA

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, 

OR

68,400 0 101,000 31,200 .00

28 3701391 Tualatin River at Rood Bridge Road, OR 2,630,000 1,520,000 12,400,000 392,000 5.77

29 3701528 Tualatin River at Golf Course Road, OR 934,000 0 3,770,000 171,000 .00

30 3810015 Gales Creekk at New Hwy 47, OR 308,000 0 766,000 60,400 .00

31 10611 X Willamette River at Hawthorne Bridge (Portland), 

OR

55,500,000 8,900,000 201,000,000 6,650,000 16.1

32 3820012 Rock Creek at Hwy 8, OR NA NA 1,850,000 68,100 NA

33 14211720 X Willamette River at Portland, OR 58,600,000 8,900,000 201,000,000 6,650,000 15.2

34 3850006 Dawson Creekk at Brookwood, OR 14,600 0 203,000 3,330 .00

35 3824020 Bronson Creek at Bronson Park Downstream of 

Sunset Hwy, OR

7,350 0 78,800 3,650 .00

36 3824072 Bronson Creek at Saltzman, OR 2,750 0 54,200 1,880 .00

37 10332 X Willamette River at SP&S Railroad Bridge, OR 57,400,000 NA NA NA NA

38 14128910 Columbia River at Warrendale,OR 155,000,000 14,500,000 1,260,000,000 122,000,000 9.31

39 10411 X Deschutes River at Deschutes River Park, OR 3,870,000 0 33,200,000 4,680,000 .00

64 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No.

Trend 

site Site name

Catchment

Fertilizer 

and manure 

nitrogen load 

as a percentage 

of instream 

load

Atmospheric 

nitrogen 

deposition as a 

percentage of 

instream

load

Point-source loads

(percentage)

Fertilizer 

and manure 

nitrogen 

application

Atmospheric 

nitrogen 

deposition

Total landapplied 

nitrogen

Total nitrogen—Continued

1 10729 Owyhee River at Hwy 201 Bridge (Owyhee), OR NA NA NA NA NA

2 MAL113 North Fork Malheur River approximately 2 miles 

upstream of Beulah Reservoir, OR

NA NA NA NA NA

3 MAL144 Malheur River at Ford south of Vale 1.1 miles 

upstream of Bully Creek, OR

NA NA NA NA NA

4 10386 X Middle Fork Willamette River at Jasper Bridge, OR NA NA NA NA NA

5 10663 Mohawk River at Hill Road, OR NA NA NA NA NA

6 10376 McKenzie River at Coburg Road, OR NA NA NA NA NA

7 10355 X Willamette River at Hwy 99E (Harrisburg), OR 116 25.0 28.5 133 23.5

8 11140 X Long Tom River at Stow Pit Road (Monroe), OR 575 20.3 .00 .00 .00

9 12657 McKenzie R. at Hwy 126 downstream Clear Lake, 

OR

NA NA NA NA NA

10 10508 X Deschutes River at Lower Bridge, OR 528 146 .00 .00 .00

11 10350 X Willamette River at Albany (Eastbound Hwy 20 

Bridge), OR

329 16.0 4.83 99.1 4.60

12 11490 Powder River at Hwy.7 (in Baker City), OR 1,423 120 .00 .00 .00

13 11478 X John Day River at Service Creek, OR 618 163 .00 .00 .00

14 10555 X Willamette River at Marion Street (Salem), OR 379 15.0 3.40 86.1 3.27

15 14200400 X Little Abiqua Creek near Scotts Mills, OR 49.1 14.1 .00 .00 .00

16 14201300 X Zollner Creek near Mt. Angel, OR 374 2.27 .00 .00 .00

17 10640 Pudding River at Hwy. 211 (Woodburn), OR 54.9 4.90 .52 58.3 .52

18 13070 Clackamas River at Mciver Park (Upper Boat 

Ramp), OR

NA NA NA NA NA

19 3701002 X Tualatin River at Weiss Bridge, OR 340 9.95 8.61 295 8.36

20 3840012 Fanno Creek at Durham Road, OR NA NA NA NA NA

21 14206950 Fanno Creek near Durham, OR NA NA NA NA NA

22 3701715 Tualatin River at Cherry Grove, OR NA NA NA NA NA

23 11321 X Johnson Creek at SE 17th Avenue (Portland), OR 296 11.0 .00 .00 .00

24 3701333 Tualatin River at Farmington Bridge Road, OR 391 12.3 6.75 214 6.54

25 3701612 X Tualatin River at Springhill Road Bridge (Dilley), 

OR

430 19.2 .00 .00 .00

26 11386 John Day River at Hwy 206, OR NA NA NA NA NA

27 3805048 Scoggins Creek below Hagg Lake at Stimson 

Bridge, OR

148 45.6 .00 .00 .00

28 3701391 Tualatin River at Rood Bridge Road, OR 471 14.9 1.22 388 1.18

29 3701528 Tualatin River at Golf Course Road, OR 404 18.3 .00 .00 .00

30 3810015 Gales Creekk at New Hwy 47, OR 249 19.6 .00 .00 .00

31 10611 X Willamette River at Hawthorne Bridge (Portland), 

OR

362 12.0 4.42 134 4.28

32 3820012 Rock Creek at Hwy 8, OR NA NA NA NA NA

33 14211720 X Willamette River at Portland, OR 343 11.3 4.42 134 4.28

34 3850006 Dawson Creekk at Brookwood, OR 1,390 22.9 .00 .00 .00

35 3824020 Bronson Creek at Bronson Park downstream of 

Sunset Hwy, OR

1,072 49.7 .00 .00 .00

36 3824072 Bronson Creek at Saltzman, OR 1,971 68.3 .00 .00 .00

37 10332 X Willamette River at SP&S Railroad Bridge, OR NA NA NA NA NA

38 14128910 Columbia River at Warrendale, OR 813 78.5 1.15 11.9 1.05

39 10411 X Deschutes River at Deschutes River Park, OR 858 121 .00 .00 .00

Table 22. Summary of sources and stream annual loads for total nitrogen and total phosophorus in the Columbia River and Puget 

Sound basins, water year 2000 and calendar year 2002.—Continued 

[Abbreviations: lb, pound; ID, Idaho; OR, Oregon; WA, Washington; WY, Wyoming; NA, either an annual instream load was not calculated or no catchment 

delineation was available to base point-source and nonpoint-source loads]

Table 22 65
Map 

index 

No.

Site 

No.

Trend 

site Site name

Water year 2000

(lb)

Calendar year 2002

(lb)

Catchment 

point-source 

TN load as a 

percentage of 

in-stream load

Estimated 

annual 

instream 

load 

Estimated 

annual total 

catchment 

point-source 

load 

Estimated 

annual nitrogen 

load from 

fertilizer 

and manure 

Estimated 

annual 

nitrogen 

load from 

atmospheric 

deposition 

Total nitrogen—Continued

40 10616 X Columbia River at Marker #47 (upstream of 

Willamette River), OR

167,000,000 NA NA NA NA

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 280,000 0 1,110,000 121,000 0.00

42 12012 X Hood River at footbridge downstream of I-84, OR NA NA NA NA NA

43 11489 X Umatilla River at Westland Road (Hermiston), OR 1,460,000 NA NA NA NA

44 14246900 X Columbia River at Beaver Army Terminal near 

Quincy, OR

209,000,000 24,700,000 1,270,000,000 127,000,000 11.8

45 27D090 East Fork Lewis River near Dollar Corner, WA 675,000 0 208,000 152,000 .00

46 32A070 X Walla Walla River near Touchet, WA 889,000 759,000 26,800,000 807,000 85.4

47 13353200 Snake River at Burbank, WA 62,700,000 5,000,000 692,000,000 50,600,000 7.98

48 37A090 X Yakima River at Kiona, WA 7,100,000 1,740,000 62,100,000 4,420,000 24.4

49 12510500 Yakima River at Kiona, WA 7,690,000 1,740,000 62,100,000 4,420,000 22.6

50 12505450 Granger Drain at Granger, WA 299,000 0 2,930,000 39,900 .00

51 12472900 X Columbia River at Vernita Bridge near Priest 

Rapids Dam, WA

52,900,000 3,500,000 165,000,000 21,100,000 6.63

52 13351000 X Palouse River at Hooper, WA 6,790,000 239,000 39,400,000 1,740,000 3.52

53 34A070 X Palouse River at Hooper. WA 6,690,000 239,000 39,400,000 1,740,000 3.58

54 41A070 X Crab Creek near Beverly, WA NA NA 9,680,000 255,000 NA

55 12471400 Lind Coulee Wasteway at SR 17 near Warden, WA 996,000 0 18,500,000 482,000 .00

56 13A060 X Deschutes River at E. Street Bridge, WA 633,000 0 1,040,000 76,000 .00

57 10A070 X Puyallup River at Meridian Street, WA 2,380,000 146,000 2,580,000 760,000 6.12

58 12108500 Newaukum Creek near Black Diamond, WA NA NA 812,000 22,700 NA

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 320,000 0 5,400,000 324,000 .00

60 12061500 Skokomish River near Potlatch, WA NA NA 109,000 76,100 NA

61 16A070 X Skokomish River near Potlatch, WA 234,000 0 109,000 76,100 .00

62 12112600 Big Soos Creek above hatchery near Auburn, WA NA NA 414,000 54,900 NA

63 09A190 X Green River at Kanaskat, WA 387,000 0 46,700 206,000 .00

64 45A070 X Wenatchee River at Wenatchee, WA 1,020,000 550 2,150,000 1,280,000 .05

65 12113375 Springbrook Creek at Tukwila, WA NA NA 105,000 16,000 NA

66 09A080 X Green River at Tukwila, WA 1,410,000 0 2,500,000 402,000 .00

67 12113390 Duwamish River at golf course at Tukwila, WA 1,900,000 54,300 2,460,000 389,000 2.85

68 12056500 North Fork Skokomish River below Staircase

Rapids near Hoodport, WA

NA NA 14,200 32,100 NA

69 46A070 Entiat River near Entiat, WA 115,000 0 233,000 404,000 .00

70 45A110 X Wenatchee River near Leavenworth, WA 595,000 0 157,000 664,000 .00

71 16C090 X Duckabush River near Brinnon, WA 44,200 0 35,800 38,500 .00

72 12128000 Thorton Creek near Seattle, WA 33,900 0 97,900 9,370 .00

73 54A120 X Spokane River at Riverside State Park, WA 7,900,000 2,590,000 15,000,000 3,570,000 32.8

74 07D050 X Snoqualmie River near Monroe, WA 2,950,000 0 1,820,000 635,000 .00

75 07C070 X Skykomish River at Monroe, WA 1,690,000 0 683,000 757,000 .00

76 07A090 X Snohomish River at Snohomish, WA 6,960,000 0 4,320,000 1,650,000 .00

77 53A070 X Columbia River at Grand Coulee, WA 40,600,000 2,690,000 30,100,000 8,260,000 6.62

78 48A070 X Methow River near Pateros, WA 402,000 0 1,690,000 1,800,000 .00

79 49A070 X Okanogan River at Malott, WA 1,020,000 199,000 3,710,000 1,620,000 19.5

80 48A140 X Methow River at Twisp, WA 307,000 0 1,020,000 1,340,000 .00

81 03A060 X Skagit River near Mount Vernon, WA 5,730,000 158,000 4,340,000 2,400,000 2.76

82 03B050 Samish River near Burlington, WA 557,000 0 507,000 86,300 0.00

83 12213140 Nooksack River at Brenan, WA NA NA 9,720,000 794,000 NA

84 01A050 X Nooksack River at Brennan, WA 4,540,000 54,300 9,570,000 748,000 1.20

Table 22. Summary of sources and stream annual loads for total nitrogen and total phosophorus in the Columbia River and Puget 

Sound basins, water year 2000 and calendar year 2002.—Continued 

[Abbreviations: lb, pound; ID, Idaho; OR, Oregon; WA, Washington; WY, Wyoming; NA, either an annual instream load was not calculated or no catchment 

delineation was available to base point-source and nonpoint-source loads]

66 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No.

Trend 

site Site name

Catchment

Fertilizer 

and manure 

nitrogen load 

as a percentage 

of instream 

load

Atmospheric 

nitrogen 

deposition as a 

percentage of 

instream

load

Point-source loads

(percentage)

Fertilizer 

and manure 

nitrogen 

application

Atmospheric 

nitrogen 

deposition

Total landapplied 

nitrogen

Total nitrogen—Continued

40 10616 X Columbia River at Marker #47 (upstream of 

Willamette River), OR

NA NA NA NA NA

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 396 43.3 0.00 0.00 0.00

42 12012 X Hood River at footbridge downstream of I-84, OR NA NA NA NA NA

43 11489 X Umatilla River at Westland Road (Hermiston), OR NA NA NA NA NA

44 14246900 X Columbia River at Beaver Army Terminal near 

Quincy, OR

608 60.4 1.94 19.4 1.76

45 27D090 East Fork Lewis River near Dollar Corner, WA 30.8 22.5 .00 .00 .00

46 32A070 X Walla Walla River near Touchet, WA 3,015 90.7 2.83 94.1 2.75

47 13353200 Snake River at Burbank, WA 1,104 80.8 .72 9.88 .67

48 37A090 X Yakima River at Kiona, WA 875 62.2 2.79 39.4 2.61

49 12510500 Yakima River at Kiona, WA 808 57.5 2.79 39.4 2.61

50 12505450 Granger Drain at Granger, WA 980 13.4 .00 .00 .00

51 12472900 X Columbia River at Vernita Bridge near Priest Rapids 

Dam, WA

312 40.0 2.13 16.6 1.88

52 13351000 X Palouse River at Hooper, WA 580 25.6 .61 13.7 .58

53 34A070 X Palouse River at Hooper, WA 589 26.0 .61 13.7 .58

54 41A070 X Crab Creek near Beverly, WA NA NA NA NA NA

55 12471400 Lind Coulee Wasteway at SR 17 near Warden, WA 1,857 48.4 .00 .00 .00

56 13A060 X Deschutes River at E. Street Bridge, WA 164 12.0 .00 .00 .00

57 10A070 X Puyallup River at Meridian Street, WA 108 32.1 5.65 19.2 4.36

58 12108500 Newaukum Creek near Black Diamond, WA NA NA NA NA NA

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 1,688 102 .00 .00 .00

60 12061500 Skokomish River near Potlatch, WA NA NA NA NA NA

61 16A070 X Skokomish River near Potlatch, WA 46.6 32.6 .00 .00 .00

62 12112600 Big Soos Creek above hatchery near Auburn, WA NA NA NA NA NA

63 09A190 X Green River at Kanaskat, WA 12.1 53.2 .00 .00 .00

64 45A070 X Wenatchee River at Wenatchee, WA 211 126 .03 .04 .02

65 12113375 Springbrook Creek at Tukwila, WA NA NA NA NA NA

66 09A080 X Green River at Tukwila, WA 177 28.5 .00 .00 .00

67 12113390 Duwamish River at golf course at Tukwila, WA 129 20.4 2.21 14.0 1.92

68 12056500 North Fork Skokomish River below Staircase

Rapids near Hoodport, WA

NA NA NA NA NA

69 46A070 Entiat River near Entiat, WA 203 351 .00 .00 .00

70 45A110 X Wenatchee River near Leavenworth, WA 26.4 112 .00 .00 .00

71 16C090 X Duckabush River near Brinnon, WA 81.0 87.1 .00 .00 .00

72 12128000 Thorton Creek near Seattle, WA 289 27.6 .00 .00 .00

73 54A120 X Spokane River at Riverside State Park, WA 190 45.2 17.3 72.5 14.0

74 07D050 X Snoqualmie River near Monroe, WA 61.7 21.5 .00 .00 .00

75 07C070 X Skykomish River at Monroe, WA 40.4 44.9 .00 .00 .00

76 07A090 X Snohomish River at Snohomish, WA 62.1 23.7 .00 .00 .00

77 53A070 X Columbia River at Grand Coulee, WA 74.1 20.3 8.93 32.6 7.01

78 48A070 X Methow River near Pateros, WA 420 448 .00 .00 .00

79 49A070 X Okanogan River at Malott, WA 364 159 5.36 12.3 3.73

80 48A140 X Methow River at Twisp, WA 332 436 .00 .00 .00

81 03A060 X Skagit River near Mount Vernon, WA 75.7 41.9 3.65 6.58 2.35

82 03B050 Samish River near Burlington, WA 91.0 15.5 0.00 0.00 0.00

83 12213140 Nooksack River at Brennan, WA NA NA NA NA NA

84 01A050 X Nooksack River at Brennan, WA 211 16.5 .57 7.26 .53

Table 22. Summary of sources and stream annual loads for total nitrogen and total phosophorus in the Columbia River and Puget 

Sound basins, water year 2000 and calendar year 2002.—Continued 

[Abbreviations: lb, pound; ID, Idaho; OR, Oregon; WA, Washington; WY, Wyoming; NA, either an annual instream load was not calculated or no catchment 

delineation was available to base point-source and nonpoint-source loads]

Table 22 67
Map 

index 

No.

Site 

No.

Trend 

site Site name

Water year 2000

(lb)

Calendar year 2002

(lb)

Catchment 

point-source 

TN load as a 

percentage of 

in-stream load

Estimated 

annual 

instream 

load 

Estimated 

annual total 

catchment 

point-source 

load 

Estimated 

annual nitrogen 

load from 

fertilizer 

and manure 

Estimated 

annual 

nitrogen 

load from 

atmospheric 

deposition 

Total nitrogen—Continued

85 12210700 Nooksack River at North Cedarville, WA NA NA 1,050,000 604,000 NA

86 12400520 Columbia River at Northport, WA 27,700,000 NA NA NA NA

87 61A070 X Columbia River at Northport, WA 29,400,000 NA NA NA NA

88 12212100 Fistrap Creek at Flynn Road at Lynden, WA NA NA 1,190,000 37,000 NA

89 13092747 X Rock Creek above Hwy 30/93 crossing at Twin Falls, 

ID

501,000 0 4,030,000 151,000 .00

90 13094000 Snake River near Buhl, ID 15,500,000 1,280,000 318,000,000 20,600,000 8.30

91 13154500 X Snake River at King Hill, ID 30,100,000 1,580,000 396,000,000 24,200,000 5.26

92 13203510 Boise River below Diversion Dam near Boise, 

ID

613,000 0 2,530,000 966,000 .00

93 13206000 X Boise River at Glenwood, ID 746,000 295,000 3,300,000 985,000 39.6

94 13238322 North Fork Payette River below Fisher Creek near 

McCall, ID

103,000 0 11,800 36,700 .00

95 12414900 St. Maries River near Santa, ID NA NA 115,000 192,000 NA

96 12414500 St. Joe River at Calder, ID NA NA 15,100 735,000 NA

97 12413470 X South Fork Coeur d’Alene River near Pinehurst, ID 347,000 104,000 37,900 205,000 30.0

98 12413000 North Fork Coeur d’Alene River at Enaville, ID NA NA 18,000 657,000 NA

99 12419000 X Spokane River near Post Falls, ID 2,420,000 483,000 3,890,000 2,810,000 20.0

100 13010065 Snake River at Flagg Ranch, WY 413,000 0 60,700 326,000 .00

Table 22. Summary of sources and stream annual loads for total nitrogen and total phosophorus in the Columbia River and Puget 

Sound basins, water year 2000 and calendar year 2002.—Continued 

[Abbreviations: lb, pound; ID, Idaho; OR, Oregon; WA, Washington; WY, Wyoming; NA, either an annual instream load was not calculated or no catchment 

delineation was available to base point-source and nonpoint-source loads]

Map 

index 

No.

Site 

No.

Trend 

site Site name

Catchment

Fertilizer 

and manure 

nitrogen load 

as a percentage 

of instream 

load

Atmospheric 

nitrogen 

deposition as a 

percentage of 

instream

load

Point-source loads

(percentage)

Fertilizer 

and manure 

nitrogen 

application

Atmospheric 

nitrogen 

deposition

Total landapplied 

nitrogen

Total nitrogen—Continued

85 12210700 Nooksack River at North Cedarville, WA NA NA NA NA NA

86 12400520 Columbia River at Northport, WA NA NA NA NA NA

87 61A070 X Columbia River at Northport, WA NA NA NA NA NA

88 12212100 Fistrap Creek at Flynn Road at Lynden, WA NA NA NA NA NA

89 13092747 X Rock Creek above Hwy. 30/93 crossing at Twin 

Falls, ID

804 30.2 .00 .00 .00

90 13094000 Snake River near Buhl, ID 2,052 133 .40 6.21 .38

91 13154500 X Snake River at King Hill, ID 1,316 80.3 .40 6.53 .38

92 13203510 Boise River below Diversion Dam near Boise, 

ID

413 158 .00 .00 .00

93 13206000 X Boise River at Glenwood, ID 442 132 8.95 29.9 6.89

94 13238322 North Fork Payette River below Fisher Creek near 

McCall, ID

11.5 35.7 .00 .00 .00

95 12414900 St. Maries River near Santa, ID NA NA NA NA NA

96 12414500 St. Joe River at Calder, ID NA NA NA NA NA

97 12413470 X South Fork Coeur d’Alene River near Pinehurst, ID 10.9 59.1 275 50.7 42.9

98 12413000 North Fork Coeur d’Alene River at Enaville, ID NA NA NA NA NA

99 12419000 X Spokane River near Post Falls, ID 161 116 12.4 17.2 7.21

100 13010065 Snake River at Flagg Ranch, WY 14.7 78.9 .00 .00 .00

68 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No.

Trend 

site Site name

Water year 2000

(lb)

Calendar year 

2002 (lb)

Estimated annual 

instream 

load 

Estimated annual 

total catchment 

point-source load

Phosphorus from 

fertilizer and 

manure

Total phosphorus

1 10729 Owyhee River at Hwy 201 Bridge (Owyhee) 70,500 NA NA

2 MAL113 North Fork Malheur River approximately 2 miles 

upstream of Beulah Reservoir

25,200 0 112,000

3 MAL144 Malheur River at Ford south of Vale 1.1 miles 

upstream of Bully Creek

144,000 0 2,700,000

4 10386 X Middle Fork Willamette at Jasper Bridge 271,000 0 155,000

5 10663 Mohawk River at Hill Road 35,300 0 66,500

6 10376 McKenzie River at Coburg Road 440,000 NA NA

7 10355 X Willamette River at Hwy 99E (Harrisburg) 1,460,000 449,000 984,000

8 11140 X Long Tom River at Stow Pit Road (Monroe) 124,000 0 866,000

9 12657 McKenzie R. at Hwy 126 downstream Clear Lake 38,100 0 4,300

10 10508 X Deschutes River at Lower Bridge 187,000 0 494,000

11 10350 X Willamette River at Albany (Eastbound Hwy 20 

Bridge)

2,250,000 1,090,000 5,800,000

12 11490 Powder River at Hwy.7 (in Baker City) 12,600 0 302,000

13 11478 X John Day River at Service Creek 224,000 0 1,600,000

14 10555 X Willamette River at Marion Street (Salem) 3,420,000 1,330,000 11,200,000

15 14200400 X Little Abiqua Creek near Scotts Mills, OR 1,660 0 2,790

16 14201300 X Zollner Creek near Mt. Angel, OR 13,200 0 205,000

17 10640 Pudding River at Hwy 211 (Woodburn) 210,000 53,700 2,660,000

18 13070 Clackamas River at Mciver Park (upper boat ramp) 164,000 0 64,400

19 3701002 X Tualatin River at Weiss Bridge 426,000 96,700 2,390,000

20 3840012 Fanno Creek at Durham Road NA NA 45,200

21 14206950 Fanno Creek near Durham, OR NA NA 45,200

22 3701715 Tualatin River at Cherry Grove 14,100 0 4,480

23 11321 X Johnson Creek at SE 17th Ave (Portland) 17,100 0 170,000

24 3701333 Tualatin River at Farmington Bridge Road 360,000 64,100 1,720,000

25 3701612 X Tualatin River at Springhill Road Bridge (Dilley) 46,500 0 261,000

26 11386 John Day River at Hwy 206 296,000 NA NA

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge 5,430 0 12,100

28 3701391 Tualatin River at Rood Bridge Road 174,000 11,300 1,440,000

29 3701528 Tualatin River at Golf Course Road 84,700 0 438,000

30 3810015 Gales Creekk at New Hwy 47 40,900 0 85,200

31 10611 X Willamette River at Hawthorne Bridge (Portland) 6,030,000 2,510,000 24,700,000

32 3820012 Rock Creek at Hwy 8 NA NA 209,000

33 14211720 X Willamette River at Portland, OR 5,980,000 2,510,000 24,700,000

34 3850006 Dawson Creekk at Brookwood 1,380 0 23,400

35 3824020 Bronson Creek at Bronson Park downstream of 

Sunset Hwy

712 0 8,850

36 3824072 Bronson Creek at Saltzman 269 0 6,070

37 10332 X Willamette River at SP&S Railroad Bridge 6,610,000 NA NA

38 14128910 Columbia River at Warrendale, OR 11,100,000 2,850,000 253,000,000

39 10411 X Deschutes River at Deschutes River Park 1,160,000 0 5,810,000

40 10616 X Columbia River at Marker #47 (upstream of 

Willamette River)

16,000,000 NA NA

41 10406 Umatilla River at Hwy 11 (Pendleton) 53,600 0 164,000

Table 22. Summary of sources and stream annual loads for total nitrogen and total phosophorus in the Columbia River and Puget 

Sound basins, water year 2000 and calendar year 2002.—Continued 

[Abbreviations: lb, pound; ID, Idaho; OR, Oregon; WA, Washington; WY, Wyoming; NA, either an annual instream load was not calculated or no catchment 

delineation was available to base point-source and nonpoint-source loads]

Table 22 69
Table 22. Summary of sources and stream annual loads for total nitrogen and total phosophorus in the Columbia River and Puget 

Sound basins, water year 2000 and calendar year 2002.—Continued 

[Abbreviations: lb, pound; ID, Idaho; OR, Oregon; WA, Washington; WY, Wyoming; NA, either an annual instream load was not calculated or no catchment 

delineation was available to base point-source and nonpoint-source loads]

Map 

index 

No.

Site 

No.

Trend 

site Site name

Catchment

Point-source load 

as a percentage of 

instream load

Fertilizer and manure 

phosphorus load as a 

percentage of instream 

TN load

Point-source load 

as percentage of 

fertilizer and manure 

phosphorus application

Total phosphorus

1 10729 Owyhee River at Hwy 201 Bridge (Owyhee) NA NA NA

2 MAL113 North Fork Malheur River approximately 2 miles 

upstream of Beulah Reservoir

0.00 444 0.00

3 MAL144 Malheur River at Ford south of Vale 1.1 miles 

upstream of Bully Creek

.00 1,875 .00

4 10386 X Middle Fork Willamette at Jasper Bridge .00 57.2 .00

5 10663 Mohawk River at Hill Road .00 188 .00

6 10376 McKenzie River at Coburg Road NA NA NA

7 10355 X Willamette River at Hwy 99E (Harrisburg) 30.8 67.4 45.6

8 11140 X Long Tom River at Stow Pit Road (Monroe) .00 698 .00

9 12657 McKenzie R. at Hwy 126 downstream Clear Lake .00 11.3 .00

10 10508 X Deschutes River at Lower Bridge .00 264 .00

11 10350 X Willamette River at Albany (Eastbound Hwy 20 

Bridge)

48.4 258 18.7

12 11490 Powder River at Hwy 7 (in Baker City) .00 2,397 .00

13 11478 X John Day River at Service Creek .00 714.3 .00

14 10555 X Willamette River at Marion Street (Salem) 38.9 327 11.9

15 14200400 X Little Abiqua Creek near Scotts Mills, OR .00 168 .00

16 14201300 X Zollner Creek near Mt. Angel, OR .00 1,553 .00

17 10640 Pudding River at Hwy. 211 (Woodburn) 25.5 1,267 2.01

18 13070 Clackamas River at Mciver Park (upper boat ramp) .00 39.3 .00

19 3701002 X Tualatin River at Weiss Bridge 22.7 561 4.04

20 3840012 Fanno Creek at Durham Road NA NA NA

21 14206950 Fanno Creek near Durham, OR NA NA NA

22 3701715 Tualatin River at Cherry Grove .00 31.8 .00

23 11321 X Johnson Creek at SE 17th Ave (Portland) .00 994 .00

24 3701333 Tualatin River at Farmington Bridge Road 17.8 478 3.72

25 3701612 X Tualatin River at Springhill Road Bridge (Dilley) .00 561 .00

26 11386 John Day River at Hwy 206 NA NA NA

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge .00 223 .00

28 3701391 Tualatin River at Rood Bridge Road 6.54 828 .79

29 3701528 Tualatin River at Golf Course Road .00 517 .00

30 3810015 Gales Creekk at New Hwy 47 .00 208 .00

31 10611 X Willamette River at Hawthorne Bridge (Portland) 41.7 410 10.2

32 3820012 Rock Creek at Hwy 8 NA NA NA

33 14211720 X Willamette River at Portland, OR 42.1 413 10.2

34 3850006 Dawson Creekk at Brookwood .00 1,696 .00

35 3824020 Bronson Creek at Bronson Park downstream of Sunset 

Hwy

.00 1,243 .00

36 3824072 Bronson Creek at Saltzman .00 2,254 .00

37 10332 X Willamette River at SP&S Railroad Bridge NA NA NA

38 14128910 Columbia River at Warrendale, OR 25.7 2,279 1.13

39 10411 X Deschutes River at Deschutes River Park .00 501 .00

40 10616 X Columbia River at Marker #47 (upstream of Willamette 

River)

NA NA NA

41 10406 Umatilla River at Hwy 11 (Pendleton) .00 306 .00

70 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No.

Trend 

site Site name

Water year 2000

(lb)

Calendar year 

2002 (lb)

Estimated annual 

instream 

load 

Estimated annual 

total catchment 

point-source load

Phosphorus from 

fertilizer and 

manure

Total phosphorus—Continued

42 12012 X Hood River at footbridge downstream of I-84 NA NA NA

43 11489 X Umatilla River at Westland Road (Hermiston) 139,000 NA NA

44 14246900 X Columbia River at Beaver Army Terminal near 

Quincy, OR

20,000,000 4,500,000 256,000,000

45 27D090 East Fork Lewis River near Dollar Corner 46,400 0 41,500

46 32A070 X Walla Walla River near Touchet 182,000 48,000 3,410,000

47 13353200 Snake River at Burbank, WA 4,860,000 1,220,000 159,000,000

48 37A090 X Yakima River at Kiona 885,000 313,000 9,750,000

49 12510500 Yakima River at Kiona, WA 963,000 313,000 9,750,000

50 12505450 Granger Drain at Granger, WA 23,800 0 458,000

51 12472900 X Columbia River at Vernita Bridge near Priest Rapids 

Dam, WA

3,010,000 818,000 23,800,000

52 13351000 X Palouse River at Hooper, WA 408,000 39,600 5,620,000

53 34A070 X Palouse River at Hooper 311,000 39,600 5,620,000

54 41A070 X Crab Creek near Beverly NA NA 1,270,000

55 12471400 Lind Coulee Wasteway at SR 17 near Warden, WA 48,300 0 2,340,000

56 13A060 X Deschutes River at E. Street Bridge 65,300 0 212,000

57 10A070 X Puyallup River at Meridian Street 1,006,000 34,500 437,000

58 12108500 Newaukum Creek near Black Diamond, WA NA NA 132,000

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 16,300 0 699,000

60 12061500 Skokomish River near Potlatch, WA NA NA 17,500

61 16A070 X Skokomish River near Potlatch 145,000 0 17,500

62 12112600 Big Soos Creek above hatchery near Auburn, WA NA NA 51,400

63 09A190 X Green River at Kanaskat 59,400 0 10,700

64 45A070 X Wenatchee River at Wenatchee 154,000 2,870 241,000

65 12113375 Springbrook Creek at Tukwila, WA NA NA 12,000

66 09A080 X Green River at Tukwila 223,000 0 375,000

67 12113390 Duwamish River at golf course at Tukwila, WA 266,000 12,800 369,000

68 12056500 North Fork Skokomish River below Staircase

Rapids near Hoodport, WA

12,000 0 4,000

69 46A070 Entiat River near Entiat 27,100 0 30,400

70 45A110 X Wenatchee River near Leavenworth 115,000 0 20,700

71 16C090 X Duckabush River near Brinnon 17,700 0 9,540

72 12128000 Thorton Creek near Seattle, WA 2,280 0 10,900

73 54A120 X Spokane River at Riverside State Park 685,000 675,000 2,930,000

74 07D050 X Snoqualmie River near Monroe 287,000 0 311,000

75 07C070 X Skykomish River at Monroe 194,000 0 143,000

76 07A090 X Snohomish River at Snohomish 665,000 0 779,000

77 53A070 X Columbia River at Grand Coulee 3,610,000 690,000 5,660,000

78 48A070 X Methow River near Pateros, WA 60,600 0 450,000

79 49A070 X Okanogan River at Malott, WA 241,000 46,800 739,000

80 48A140 X Methow River at Twisp 56,100 0 272,000

81 03A060 X Skagit River near Mount Vernon, WA 1,490,000 37,300 709,000

82 03B050 Samish River near Burlington 21,000 0 72,200

83 12213140 Nooksack River at Brenan, WA NA NA 1,590,000

84 01A050 X Nooksack River at Brennan 1,080,000 12,800 1,560,000

85 12210700 Nooksack River at North Cedarville, WA NA NA 179,000

86 12400520 Columbia River at Northport, WA 1,150,000 NA NA

Table 22. Summary of sources and stream annual loads for total nitrogen and total phosophorus in the Columbia River and Puget 

Sound basins, water year 2000 and calendar year 2002.—Continued 

[Abbreviations: lb, pound; ID, Idaho; OR, Oregon; WA, Washington; WY, Wyoming; NA, either an annual instream load was not calculated or no catchment 

delineation was available to base point-source and nonpoint-source loads]

Table 22 71
Table 22. Summary of sources and stream annual loads for total nitrogen and total phosophorus in the Columbia River and Puget 

Sound basins, water year 2000 and calendar year 2002.—Continued 

[Abbreviations: lb, pound; ID, Idaho; OR, Oregon; WA, Washington; WY, Wyoming; NA, either an annual instream load was not calculated or no catchment 

delineation was available to base point-source and nonpoint-source loads]

Map 

index 

No.

Site 

No.

Trend 

site Site name

Catchment

Point-source load 

as a percentage of 

instream load

Fertilizer and manure 

phosphorus load as a 

percentage of instream 

TN load

Point-source load 

as percentage of 

fertilizer and manure 

phosphorus application

Total phosphorus—Continued

42 12012 X Hood River at footbridge downstream of I-84 NA NA NA

43 11489 X Umatilla River at Westland Road (Hermiston) NA NA NA

44 14246900 X Columbia River at Beaver Army Terminal near Quincy, 

OR

22.5 1,280 1.76

45 27D090 East Fork Lewis River near Dollar Corner .00 89.4 .00

46 32A070 X Walla Walla River near Touchet 26.3 1,874 1.41

47 13353200 Snake River at Burbank, WA 25.1 3,272 .77

48 37A090 X Yakima River at Kiona 35.3 1,102 3.21

49 12510500 Yakima River at Kiona, WA 32.5 1,012 3.21

50 12505450 Granger Drain at Granger, WA .00 1,924 .00

51 12472900 X Columbia River at Vernita Bridge near Priest Rapids 

Dam, WA

27.2 791 3.43

52 13351000 X Palouse River at Hooper, WA 9.70 1,377 .70

53 34A070 X Palouse River at Hooper 12.7 1,807 .70

54 41A070 X Crab Creek near Beverly NA NA NA

55 12471400 Lind Coulee Wasteway at SR 17 near Warden, WA .00 4,845 .00

56 13A060 X Deschutes River at E. Street Bridge .00 325 .00

57 10A070 X Puyallup River at Meridian Street 3.43 43.4 7.90

58 12108500 Newaukum Creek near Black Diamond, WA NA NA NA

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA .00 4,288 .00

60 12061500 Skokomish River near Potlatch, WA NA NA NA

61 16A070 X Skokomish River near Potlatch .00 12.1 .00

62 12112600 Big Soos Creek above hatchery near Auburn, WA NA NA NA

63 09A190 X Green River at Kanaskat .00 18.0 .00

64 45A070 X Wenatchee River at Wenatchee 1.87 156 1.19

65 12113375 Springbrook Creek at Tukwila, WA NA NA NA

66 09A080 X Green River at Tukwila .00 168 .00

67 12113390 Duwamish River at golf course at Tukwila, WA 4.81 139 3.44

68 12056500 North Fork Skokomish River below Staircase

Rapids near Hoodport, WA

.00 33.3 .00

69 46A070 Entiat River near Entiat .00 112 .00

70 45A110 X Wenatchee River near Leavenworth .00 18.0 .00

71 16C090 X Duckabush River near Brinnon .00 53.9 .00

72 12128000 Thorton Creek near Seattle, WA .00 478 .00

73 54A120 X Spokane River at Riverside State Park 98.5 428 23.0

74 07D050 X Snoqualmie River near Monroe .00 108 .00

75 07C070 X Skykomish River at Monroe .00 73.7 .00

76 07A090 X Snohomish River at Snohomish .00 117 .00

77 53A070 X Columbia River at Grand Coulee 19.1 157 12.2

78 48A070 X Methow River near Pateros, WA .00 743 .00

79 49A070 X Okanogan River at Malott, WA 19.4 307 6.33

80 48A140 X Methow River at Twisp .00 485 .00

81 03A060 X Skagit River near Mount Vernon, WA 2.51 47.6 5.27

82 03B050 Samish River near Burlington .00 344 .00

83 12213140 Nooksack River at Brenan, WA NA NA NA

84 01A050 X Nooksack River at Brennan 1.19 144 .82

85 12210700 Nooksack River at North Cedarville, WA NA NA NA

86 12400520 Columbia River at Northport, WA NA NA NA

72 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No.

Trend 

site Site name

Water year 2000

(lb)

Calendar year 

2002 (lb)

Estimated annual 

instream 

load 

Estimated annual 

total catchment 

point-source load

Phosphorus from 

fertilizer and 

manure

Total phosphorus—Continued

87 61A070 X Columbia River at Northport 2,400,000 NA NA

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NA NA 19,400

89 13092747 X Rock Creek above Hwy 30/93 crossing at Twin 

Falls, ID

20,200 0 967,000

90 13094000 Snake River near Buhl, ID 985,000 410,000 79,300,000

91 13154500 X Snake River at King Hill, ID 1,360,000 534,000 97,000,000

92 13203510 Boise River below Diversion Dam near Boise, 

ID

45,500 0 721,000

93 13206000 X Boise River at Glenwood, ID 168,000 57,500 868,000

94 13238322 North Fork Payette River below Fisher Creek near 

McCall, ID

3,700 0 2,800

95 12414900 St. Maries River near Santa, ID 32,000 0 29,000

96 12414500 St. Joe River at Calder, ID 43,500 0 3,500

97 12413470 X South Fork Coeur d’Alene River near Pinehurst, 

ID

40,300 24,500 7,250

98 12413000 North Fork Coeur d’Alene River at Enaville, ID 70,800 0 4,100

99 12419000 X Spokane River near Post Falls, ID 161,000 96,700 912,000

100 13010065 Snake River at Flagg Ranch, WY 97,400 0 13,800

Map 

index 

No.

Site 

No.

Trend 

site Site name

Catchment

Point-source load 

as a percentage of 

instream load

Fertilizer and 

manure phosphorus 

load as a 

percentage of 

instream TN load

Point-source load 

as percentage 

of fertilizer and 

manure phosphorus 

application

Total phosphorus—Continued

87 61A070 X Columbia River at Northport NA NA NA

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NA NA NA

89 13092747 X Rock Creek above Hwy 30/93 crossing at Twin 

Falls, ID

0.00 4,787 0.00

90 13094000 Snake River near Buhl, ID 41.6 8,051 .52

91 13154500 X Snake River at King Hill, ID 39.4 7,132 .55

92 13203510 Boise River below Diversion Dam near Boise, 

ID

.00 1,585 .00

93 13206000 X Boise River at Glenwood, ID 34.3 517 6.63

94 13238322 North Fork Payette River below Fisher Creek near 

McCall, ID

.00 75.7 .00

95 12414900 St. Maries River near Santa, ID .00 90.6 .00

96 12414500 St. Joe River at Calder, ID .00 8.0 .00

97 12413470 X South Fork Coeur d’Alene River near Pinehurst, ID 60.8 18.0 338

98 12413000 North Fork Coeur d’Alene River at Enaville, ID .00 5.8 .00

99 12419000 X Spokane River near Post Falls, ID 60.1 566 10.6

100 13010065 Snake River at Flagg Ranch, WY .00 14.2 .00

Table 22. Summary of sources and stream annual loads for total nitrogen and total phosophorus in the Columbia River and Puget 

Sound basins, water year 2000 and calendar year 2002.—Continued 

[Abbreviations: lb, pound; ID, Idaho; OR, Oregon; WA, Washington; WY, Wyoming; NA, either an annual instream load was not calculated or no catchment 

delineation was available to base point-source and nonpoint-source loads]

Table 22 73
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74 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Appendix A. Results of Loadest Modeling, Flow-Weighted Concentrations, 

Yields, Drainage Areas, and Mean Annual Streamflows for Total Nitrogen, Total 

Phosphorus, and Suspended Sediment for Water Years 1997, 2000, and 2001
Map 

index 

No.

Site 

No. Site name Flux

(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 3,370 57,900 2,910 3,870 245 365

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NA NA NA NA NA –

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully Creek, 

OR

NA NA NA NA NA –

4 10386 Middle Fork Willamette River at Jasper Bridge, OR NA NA NA NA NA –

5 10663 Mohawk River at Hill Road, OR NA NA NA NA NA –

6 10376 McKenzie River at Coburg Road, OR NA NA NA NA NA –

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 31,200 8,240,000 25,700 37,500 3,020 365

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 5,930 345,000 4,820 7,210 612 365

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NA NA NA NA NA –

10 10508 Deschutes River at Lower Bridge, OR 1,820 73,200 1,340 2,410 273 365

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 75,100 57,300,000 60,700 92,000 8,000 365

12 11490 Powder River at Hwy 7 (Baker City), OR 279 499 237 326 22.9 365

13 11478 John Day River at Service Creek, OR 6,310 1,020,000 4,510 8,600 1,050 365

14 10555 Willamette River at Marion Street (Salem), OR 140,000 142,000,000 117,000 167,000 12,600 365

15 14200400 Little Abiqua Creek near Scotts Mills, OR 178 38.5 164 192 6.92 365

16 14201300 Zollner Creek near Mt. Angel, OR 3,370 75,900 2,800 4,020 311 365

17 10640 Pudding River at Hwy 211 (Woodburn), OR NA NA NA NA NA –

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR NA NA NA NA NA –

19 3701002 Tualatin River at Weiss Bridge, OR 25,300 406,000 23,800 26,800 763 365

20 3840012 Fanno Creek at Durham Road, OR NA NA NA NA NA –

21 14206950 Fanno Creek near Durham, OR NA NA NA NA NA –

22 3701715 Tualatin River at Cherry Grove, OR NA NA NA NA NA –

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 2,280 10,800 2,080 2,490 105 365

24 3701333 Tualatin River at Farmington Bridge Road, OR 17,200 795,000 15,400 19,150 955 365

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 2,400 13,200 2,120 2,710 150 365

26 11386 John Day River at Hwy 206, OR NA NA NA NA NA –

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 416 2,075 332 516 47.2 365

28 3701391 Tualatin River at Rood Bridge Road, OR 15,300 584,000 13,600 17,200 916 365

29 3701528 Tualatin River at Golf Course Road, OR 4,480 39,700 4,000 5,000 254 365

30 3810015 Gales Creek at New Hwy 47, OR 1,480 5,270 1,310 1,660 89.6 365

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 294,000 344,000,000 256,000 336,000 20,500 365

32 3820012 Rock Creek at Hwy 8, OR NA NA NA NA NA –

33 14211720 Willamette River at Portland, OR 312,000 420,000,000 270,000 359,000 22,500 365

34 3850006 Dawson Creek at Brookwood, OR NA NA NA NA NA –

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR NA NA NA NA NA –

36 3824072 Bronson Creek at Saltzman, OR NA NA NA NA NA –

37 10332 Willamette River at SP&S Railroad Bridge, OR 295,000 1,240,000,000 230,000 373,000 36,500 365

38 14128910 Columbia River at Warrendale, OR 514,000 997,000,000 453,000 582,000 33,000 365

39 10411 Deschutes River at Deschutes River Park, OR 29,800 899,000,000 4,070 108,000 30,000 365

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

719,000 6,260,000,000 573,000 892,000 81,500 365

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 1,180 24,700 887 1,540 167 365

42 12012 Hood River at footbridge downstream of I-84, OR 3,350 143,000 2,650 4,180 392 365

43 11489 Umatilla River at Westland Road (Hermiston), OR 5,690 204,000 4,830 6,660 468 365

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 868,000 1,110,000,000 799,000 940,000 35,900 365

45 27D090 East Fork Lewis River near Dollar Corner, WA 2,560 17,000 2,290 2,850 144 365

46 32A070 Walla Walla River near Touchet, WA 3,680 43,900 3,250 4,160 235 365

47 13353200 Snake River at Burbank, WA 310,000 180,000,000 283,000 339,000 14,300 365

48 37A090 Yakima River at Kiona, WA 27,300 1,460,000 24,800 30,000 1,300 365

49 12510500 Yakima River at Kiona, WA 29,500 4,100,000 25,600 33,800 2,070 365

50 12505450 Granger Drain at Granger, WA NA NA NA NA NA –

Table A1. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 1997.

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

76 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Table A1. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 1997.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Map 

index 

 No.

Site 

No. Site name Load

(lb/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(lb/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow

(ft3/s)

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 1,230,000 0.80 NC NA 779

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NC NC NC 880 162

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully Creek, 

OR

NC NC NC 12,000 434

4 10386 Middle Fork Willamette River at Jasper Bridge, OR NC NC NC 3,490 6,720

5 10663 Mohawk River at Hill Road, OR NC NC NC 460 883

6 10376 McKenzie River at Coburg Road, OR NC NC NC NA 6,900

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 11,400,000 .34 3,320 8,890 17,200

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 2,160,000 .91 5,200 1,080 1,210

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NC NC NC 239 688

10 10508 Deschutes River at Lower Bridge, OR 663,000 .23 316 5,440 1,460

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 27,400,000 .65 5,650 12,600 21,600

12 11490 Powder River at Hwy 7 (Baker City), OR 102,000 .33 292 902 158

13 11478 John Day River at Service Creek, OR 2,300,000 .36 449 13,300 3,230

14 10555 Willamette River at Marion Street (Salem), OR 51,200,000 .71 6,940 19,100 36,600

15 14200400 Little Abiqua Creek near Scotts Mills, OR 64,800 .68 6,590 25.5 48.7

16 14201300 Zollner Creek near Mt. Angel, OR 1,230,000 12.8 81,900 38.9 48.8

17 10640 Pudding River at Hwy 211 (Woodburn), OR NC NC NC 818 NA

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR NC NC NC 1,760 4,080

19 3701002 Tualatin River at Weiss Bridge, OR 9,240,000 1.93 13,000 1,840 2,430

20 3840012 Fanno Creek at Durham Road, OR NC NC NC 80.7 –

21 14206950 Fanno Creek near Durham, OR NC NC NC 80.7 –

22 3701715 Tualatin River at Cherry Grove, OR NC NC NC 97.3 292

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 831,000 3.09 15,500 139 137

24 3701333 Tualatin River at Farmington Bridge Road, OR 6,280,000 1.61 11,200 1,460 1,980

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 876,000 .84 6,950 327 530

26 11386 John Day River at Hwy 206, OR NC NC NC NA –

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 152,000 .42 3,810 103 182

28 3701391 Tualatin River at Rood Bridge Road, OR 5,590,000 1.62 11,800 1,230 1,760

29 3701528 Tualatin River at Golf Course Road, OR 1,640,000 .93 7,550 561 893

30 3810015 Gales Creek at New Hwy 47, OR 541,000 .82 7,180 195 335

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 107,000,000 1.01 9,610 28,900 53,800

32 3820012 Rock Creek at Hwy 8, OR NC NC NC 193 –

33 14211720 Willamette River at Portland, OR 114,000,000 1.08 10,200 28,900 53,800

34 3850006 Dawson Creek at Brookwood, OR NC NC NC 9.7 –

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR NC NC NC 10.2 –

36 3824072 Bronson Creek at Saltzman, OR NC NC NC 5.23 –

37 10332 Willamette River at SP&S Railroad Bridge (Portland), OR 108,000,000 1.02 NC NA 53,800

38 14128910 Columbia River at Warrendale, OR 188,000,000 .36 789 616,000 264,000

39 10411 Deschutes River at Deschutes River Park, OR 10,900,000 .69 1,010 27,800 7,970

40 10616 Columbia River at Marker #47 (upstream of Willamette River), OR 263,000,000 .49 NC 624,000 272,000

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 431,000 .28 968 1,150 777

42 12012 Hood River at footbridge downstream of I-84, OR 1,220,000 .41 NC NA 1,520

43 11489 Umatilla River at Westland Road (Hermiston), OR 2,080,000 1.03 NC NA 1,030

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 317,000,000 .48 1,250 658,000 338,000

45 27D090 East Fork Lewis River near Dollar Corner, WA 934,000 .50 5,980 405 957

46 32A070 Walla Walla River near Touchet, WA 1,340,000 .64 798 4,370 1,060

47 13353200 Snake River at Burbank, WA 317,000,000 .48 1,250 658,000 338,000

48 37A090 Yakima River at Kiona, WA 9,970,000 .83 1,780 14,500 6,070

49 12510500 Yakima River at Kiona, WA 5,380 .90 1,920 14,500 6,070

50 12505450 Granger Drain at Granger, WA NC NC NC 160 –

Appendix A 77
Map 

index 

No.

Site 

No. Site name Flux

(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

51 12472900 Columbia River at Vernita Bridge near 

Priest Rapids Dam, WA

162,000 462,000,000 124,000 208,000 21,800 365

52 13351000 Palouse River at Hooper, WA 54,400 15,700,000 45,900 64,000 4,630 365

53 34A070 Palouse River at Hooper, WA 51,900 46,000,000 39,300 67,300 7,150 365

54 41A070 Crab Creek near Beverly, WA 3,630 14,700 3,380 3,880 127 365

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NA NA NA NA NA –

56 13A060 Deschutes River at East Street Bridge, WA 2,370 6,810 2,200 2,550 88.1 365

57 10A070 Puyallup River at Meridian Street, WA 9,480 286,000 8,400 10,700 576 365

58 12108500 Newaukum Creek near Black Diamond, WA 1,360 5,230 1,220 1,520 77.1 365

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA NA NA NA NA NA –

60 12061500 Skokomish River near Potlatch, WA NA NA NA NA NA –

61 16A070 Skokomish River near Potlatch, WA 829 6,160 676 1,000 84.6 365

62 12112600 Big Soos Creek above Hatchery near Auburn, WA 1,350 4,540 1,210 1,490 71.9 365

63 09A190 Green River at Kanaskat, WA 1,480 13,600 1,240 1,740 128 365

64 45A070 Wenatchee River at Wenatchee, WA 4,150 54,700 3,680 4,660 251 365

65 12113375 Springbrook Creek at Tukwila, WA 257 49.3 243 272 7.60 365

66 09A080 Green River at Tukwila, WA 5,620 66,200 5,100 6,190 278 365

67 12113390 Duwamish River at Golf Course at Tukwila, WA 7,880 169,000 7,030 8,800 451 365

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

NA NA NA NA NA –

69 46A070 Entiat River near Entiat, WA 463 2,900 360 585 57.3 365

70 45A110 Wenatchee River near Leavenworth, WA 2,830 80,300 2,270 3,480 308 365

71 16C090 Duckabush River near Brinnon, WA 138 204 107 174 17.0 365

72 12128000 Thorton Creek near Seattle, WA 120 22.1 110 130 5.16 365

73 54A120 Spokane River at Riverside State Park, WA 23,300 1,240,000 21,000 25,700 1,190 365

74 07D050 Snoqualmie River near Monroe, WA 10,400 122,000 9,680 11,200 382 365

75 07C070 Skykomish River at Monroe, WA 5,310 48,900 4,840 5,830 253 365

76 07A090 Snohomish River at Snohomish, WA 23,100 938,000 21,000 25,300 1,090 365

77 53A070 Columbia River at Grand Coulee, WA 153,000 47,400,000 139,000 168,000 7,400 365

78 48A070 Methow River near Pateros, WA 1,780 12,700 1,550 2,030 122 365

79 49A070 Okanogan River at Malott, WA 5,700 194,000 4,840 6,660 465 365

80 48A140 Methow River at Twisp, WA 1,320 9,090 1,120 1,530 104 365

81 03A060 Skagit River near Mount Vernon, WA 20,500 1,180,000 18,200 22,900 1,210 365

82 03B050 Samish River near Burlington, WA 1,750 4,880 1,620 1,900 72.9 365

83 12213140 Nooksack River at Brennan, WA 21,900 2,140,000 18,900 25,100 1,570 365

84 01A050 Nooksack River at Brennan, WA 15,600 561,000 14,000 17,300 812 365

85 12210700 Nooksack River at North Cedarville, WA 10,500 1,020,000 8,490 12,800 1,100 365

86 12400520 Columbia River at Northport, WA NA NA NA NA NA –

87 61A070 Columbia River at Northport, WA 108,000 17,600,000 99,700 117,000 4,370 365

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA 2,370 8,400 2,190 2,570 95.9 365

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID NA NA NA NA NA –

90 13094000 Snake River near Buhl, ID 67,800 4,880,000 63,400 72,400 2,290 365

91 13154500 Snake River at King Hill, ID 112,000 6,330,000 107,000 117,000 2,690 365

92 13203510 Boise River below Diversion Dam near Boise, ID 6,470 382,000 5,330 7,790 628 365

93 13206000 Boise River at Glenwood, ID 6,190 245,000 5,250 7,240 507 365

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 745 7,800 572 953 97.4 365

95 12414900 St. Maries River near Santa, ID NA NA NA NA NA –

96 12414500 St. Joe River at Calder, ID NA NA NA NA NA –

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID NA NA NA NA NA –

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID NA NA NA NA NA –

99 12419000 Spokane River near Post Falls, ID NA NA NA NA NA –

100 13010065 Snake River at Flagg Ranch, WY 3,770 894,000 2,130 6,190 1,050 365

Table A1. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 1997.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

78 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

 No.

Site 

No. Site name Load

(lb/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(lb/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow

(ft3/s)

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 29,500 0.18 2,260 67,800 164,000

52 13351000 Palouse River at Hooper, WA 9,930 6.32 8,060 6,380 1,600

53 34A070 Palouse River at Hooper, WA 19,000,000 6.03 7,700 6,380 1,600

54 41A070 Crab Creek near Beverly, WA 1,320,000 2.29 3,430 999 293

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NC NC NC 1,840 –

56 13A060 Deschutes River at East Street Bridge, WA 866,000 .76 8,410 267 575

57 10A070 Puyallup River at Meridian Street, WA 346,000 .41 3,760 2,380 4,340

58 12108500 Newaukum Creek near Black Diamond, WA 498,000 3.02 18,200 71.1 83.7

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA NC NC NC 1,190 40.1

60 12061500 Skokomish River near Potlatch, WA NC NC NC 339 1,500

61 16A070 Skokomish River near Potlatch, WA 303,000 .10 2,310 339 1,500

62 12112600 Big Soos Creek above Hatchery near Auburn, WA 491,000 1.28 7,350 173 195

63 09A190 Green River at Kanaskat, WA 539,000 .20 2,270 616 1,390

64 45A070 Wenatchee River at Wenatchee, WA 1,520,000 .17 1,140 3,440 4,540

65 12113375 Springbrook Creek at Tukwila, WA 93,900 1.05 4,700 51.7 45.2

66 09A080 Green River at Tukwila, WA 2,050,000 .55 4,300 1,240 1,900

67 12113390 Duwamish River at Golf Course at Tukwila, WA 2,880,000 .68 6,240 1,190 2,150

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

NC NC NC 147 677

69 46A070 Entiat River near Entiat, WA 169,000 .12 407 1,070 700

70 45A110 Wenatchee River near Leavenworth, WA 1,030,000 .13 1,550 1,720 4,190

71 16C090 Duckabush River near Brinnon, WA 50,300 .05 757 172 507

72 12128000 Thorton Creek near Seattle, WA 43,800 1.75 3,880 29.2 12.7

73 54A120 Spokane River at Riverside State Park, WA 8,500,000 .42 1,700 13,000 10,400

74 07D050 Snoqualmie River near Monroe, WA 3,800,000 .38 5,550 1,770 5,040

75 07C070 Skykomish River at Monroe, WA 1,940,000 .18 2,530 1,980 5,580

76 07A090 Snohomish River at Snohomish, WA 8,440,000 .32 4,930 4,440 13,300

77 53A070 Columbia River at Grand Coulee, WA 55,700,000 .20 5,000 28,900 155,000

78 48A070 Methow River near Pateros, WA 650,100 .16 362 4,660 2,130

79 49A070 Okanogan River at Malott, WA 2,080,000 .21 1,200 4,500 5,120

80 48A140 Methow River at Twisp, WA 480,000 .13 363 3,430 1,920

81 03A060 Skagit River near Mount Vernon, WA 7,470,000 .17 3,210 6,020 21,800

82 03B050 Samish River near Burlington, WA 641,000 .96 7,430 223 340

83 12213140 Nooksack River at Brennan, WA 7,980,000 .42 10,200 2,020 9,720

84 01A050 Nooksack River at Brennan, WA 5,700,000 .55 7,730 1,910 5,280

85 12210700 Nooksack River at North Cedarville, WA 3,820,000 .45 6,500 1,520 4,340

86 12400520 Columbia River at Northport, WA NC NC NC 156,000 131,000

87 61A070 Columbia River at Northport, WA 39,400,000 .15 650 156,000 131,000

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA 870,000 4.03 22,700 98.6 109

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID NC NC NC 623 175

90 13094000 Snake River near Buhl, ID 24,700,000 1.14 842 76,100 11,100

91 13154500 Snake River at King Hill, ID 40,800,000 1.22 1,140 92,900 16,900

92 13203510 Boise River below Diversion Dam near Boise, ID 2,360,000 .32 877 6,980 3,690

93 13206000 Boise River at Glenwood, ID 2,260,000 .34 814 7,180 3,380

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 272,000 .33 3,200 220 416

95 12414900 St. Maries River near Santa, ID NC NC NC 706 –

96 12414500 St. Joe River at Calder, ID NC NC NC 2,680 –

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID NC NC NC 738 846

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID NC NC NC 2,330 2,740

99 12419000 Spokane River near Post Falls, ID NC NC NC 10,200 10,300

100 13010065 Snake River at Flagg Ranch, WY 1,370,000 .45 2,690 1,320 1,540

Table A1. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 1997.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 79
Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 515 3,960 401 652 64.1 365

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NA NA NA NA NA –

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NA NA NA NA NA –

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 2,060 60,700 1,620 2,590 250 365

5 10663 Mohawk River at Hill Road, OR 307 1,520 235 395 40.8 365

6 10376 McKenzie River at Coburg Road, OR 2,300 41,400 1,920 2,740 209 365

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 9,750 896,000 7,940 11,800 999 365

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 668 3,240 559 791 59.1 365

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR 124 26.9 114 135 5.35 365

10 10508 Deschutes River at Lower Bridge, OR 547 815 492 606 29.1 365

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 14,100 1,420,000 11,700 16,700 1,260 365

12 11490 Powder River at Hwy 7 (Baker City), OR 55.8 53.6 42.5 71.8 7.50 365

13 11478 John Day River at Service Creek, OR 1,750 78,400 1,250 2,396 294 365

14 10555 Willamette River at Marion Street (Salem), OR 24,400 3,950,000 20,518 28,800 2,110 365

15 14200400 Little Abiqua Creek near Scotts Mills, OR 6.38 .92 4.60 8.62 1.03 365

16 14201300 Zollner Creek near Mt. Angel, OR 155 398 111 211 25.6 365

17 10640 Pudding River at Hwy 211 (Woodburn), OR NA NA NA NA NA –

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR NA NA NA NA NA –

19 3701002 Tualatin River at Weiss Bridge, OR 2,110 9,370 1,890 2,350 117 365

20 3840012 Fanno Creek at Durham Road, OR NA NA NA NA NA –

21 14206950 Fanno Creek near Durham, OR NA NA NA NA NA –

22 3701715 Tualatin River at Cherry Grove, OR 72.2 118 51.5 98.4 12.0 365

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 189 1,960 116 292 45.0 365

24 3701333 Tualatin River at Farmington Bridge Road, OR 1,580 17,600 1,312 1,880 145 365

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 240 248 204 281 19.7 365

26 11386 John Day River at Hwy 206, OR NA NA NA NA NA –

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 29.2 142 12.3 59.0 12.2 365

28 3701391 Tualatin River at Rood Bridge Road, OR 1,070 1,830 973 1,180 51.5 365

29 3701528 Tualatin River at Golf Course Road, OR 482 541 428 540 28.5 365

30 3810015 Gales Creek at New Hwy 47, OR 235 166 204 268 16.3 365

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 41,500 2,920,000 37,910 45,400 1,910 365

32 3820012 Rock Creek at Hwy 8, OR NA NA NA NA NA –

33 14211720 Willamette River at Portland, OR 43,300 13,900,000 35,600 52,000 4,160 365

34 3850006 Dawson Creek at Brookwood, OR NA NA NA NA NA –

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR NA NA NA NA NA –

36 3824072 Bronson Creek at Saltzman, OR NA NA NA NA NA –

37 10332 Willamette River at SP&S Railroad Bridge, OR 42,500 9,730,000 36,600 49,200 3,240 365

38 14128910 Columbia River at Warrendale, OR 54,300 28,800,000 43,900 66,400 5,750 365

39 10411 Deschutes River at Deschutes River Park, OR 6,260 97,400,000 374 30,000 9,870 365

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

162,000 500,000,000 122,000 211,000 22,700 365

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 245 351 207 287 20.2 365

42 12012 Hood River at footbridge downstream of I-84, OR 803 71,600 389 1,480 282 365

43 11489 Umatilla River at Westland Road (Hermiston), OR 1,300 49,900 897 1,820 235 365

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 111,000 76,900,000 94,000 131,300 9,530 365

45 27D090 East Fork Lewis River near Dollar Corner, WA 137 506 93.7 194 25.6 365

46 32A070 Walla Walla River near Touchet, WA 774 12,600 563 1,040 121 365

47 13353200 Snake River at Burbank, WA 31,900 7,290,000 26,600 38,000 2,900 365

48 37A090 Yakima River at Kiona, WA 4,760 88,800 4,170 5,410 315 365

49 12510500 Yakima River at Kiona, WA 6,320 743,000 4,780 8,210 876 365

50 12505450 Granger Drain at Granger, WA NA NA NA NA NA –

Table A2. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound basins, water year 1997.

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

80 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Table A2. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound basins, water year 1997.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 515 3,960 401 652 64.1 365

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NA NA NA NA NA –

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NA NA NA NA NA –

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 2,060 60,700 1,620 2,590 250 365

5 10663 Mohawk River at Hill Road, OR 307 1,520 235 395 40.8 365

6 10376 McKenzie River at Coburg Road, OR 2,300 41,400 1,920 2,740 209 365

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 9,750 896,000 7,940 11,800 999 365

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 668 3,240 559 791 59.1 365

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR 124 26.9 114 135 5.35 365

10 10508 Deschutes River at Lower Bridge, OR 547 815 492 606 29.1 365

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 14,100 1,420,000 11,700 16,700 1,260 365

12 11490 Powder River at Hwy 7 (Baker City), OR 55.8 53.6 42.5 71.8 7.50 365

13 11478 John Day River at Service Creek, OR 1,750 78,400 1,250 2,396 294 365

14 10555 Willamette River at Marion Street (Salem), OR 24,400 3,950,000 20,518 28,800 2,110 365

15 14200400 Little Abiqua Creek near Scotts Mills, OR 6.38 .92 4.60 8.62 1.03 365

16 14201300 Zollner Creek near Mt. Angel, OR 155 398 111 211 25.6 365

17 10640 Pudding River at Hwy 211 (Woodburn), OR NA NA NA NA NA –

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR NA NA NA NA NA –

19 3701002 Tualatin River at Weiss Bridge, OR 2,110 9,370 1,890 2,350 117 365

20 3840012 Fanno Creek at Durham Road, OR NA NA NA NA NA –

21 14206950 Fanno Creek near Durham, OR NA NA NA NA NA –

22 3701715 Tualatin River at Cherry Grove, OR 72.2 118 51.5 98.4 12.0 365

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 189 1,960 116 292 45.0 365

24 3701333 Tualatin River at Farmington Bridge Road, OR 1,580 17,600 1,312 1,880 145 365

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 240 248 204 281 19.7 365

26 11386 John Day River at Hwy 206, OR NA NA NA NA NA –

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 29.2 142 12.3 59.0 12.2 365

28 3701391 Tualatin River at Rood Bridge Road, OR 1,070 1,830 973 1,180 51.5 365

29 3701528 Tualatin River at Golf Course Road, OR 482 541 428 540 28.5 365

30 3810015 Gales Creek at New Hwy 47, OR 235 166 204 268 16.3 365

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 41,500 2,920,000 37,910 45,400 1,910 365

32 3820012 Rock Creek at Hwy 8, OR NA NA NA NA NA –

33 14211720 Willamette River at Portland, OR 43,300 13,900,000 35,600 52,000 4,160 365

34 3850006 Dawson Creek at Brookwood, OR NA NA NA NA NA –

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR NA NA NA NA NA –

36 3824072 Bronson Creek at Saltzman, OR NA NA NA NA NA –

37 10332 Willamette River at SP&S Railroad Bridge, OR 42,500 9,730,000 36,600 49,200 3,240 365

38 14128910 Columbia River at Warrendale, OR 54,300 28,800,000 43,900 66,400 5,750 365

39 10411 Deschutes River at Deschutes River Park, OR 6,260 97,400,000 374 30,000 9,870 365

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

162,000 500,000,000 122,000 211,000 22,700 365

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 245 351 207 287 20.2 365

42 12012 Hood River at footbridge downstream of I-84, OR 803 71,600 389 1,480 282 365

43 11489 Umatilla River at Westland Road (Hermiston), OR 1,300 49,900 897 1,820 235 365

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 111,000 76,900,000 94,000 131,300 9,530 365

45 27D090 East Fork Lewis River near Dollar Corner, WA 137 506 93.7 194 25.6 365

46 32A070 Walla Walla River near Touchet, WA 774 12,600 563 1,040 121 365

47 13353200 Snake River at Burbank, WA 31,900 7,290,000 26,600 38,000 2,900 365

48 37A090 Yakima River at Kiona, WA 4,760 88,800 4,170 5,410 315 365

49 12510500 Yakima River at Kiona, WA 6,320 743,000 4,780 8,210 876 365

50 12505450 Granger Drain at Granger, WA NA NA NA NA NA –

Appendix A 81
Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 12,100 5,320,000 8,090 17,500 2,420 365

52 13351000 Palouse River at Hooper, WA 5,500 699,000 3,700 7,860 1,070 365

53 34A070 Palouse River at Hooper, WA 2,110 126,000 1,470 2,930 373 365

54 41A070 Crab Creek near Beverly, WA 156 94 137 177 10.2 365

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NA NA NA NA NA –

56 13A060 Deschutes River at East Street Bridge, WA 214 701 163 275 28.7 365

57 10A070 Puyallup River at Meridian Street, WA 3,180 400,000 2,000 4,810 723 365

58 12108500 Newaukum Creek near Black Diamond, WA 157 848 102 231 32.8 365

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA NA NA NA NA NA NA

60 12061500 Skokomish River near Potlatch, WA 893 187,000 209 2,540 632 365

61 16A070 Skokomish River near Potlatch, WA 451 15,300 243 768 135 365

62 12112600 Big Soos Creek above Hatchery near Auburn, WA 67.6 196 42.5 102 15.4 365

63 09A190 Green River at Kanaskat, WA 199 441 158 248 22.8 365

64 45A070 Wenatchee River at Wenatchee, WA 769 13,700 551 1,040 126 365

65 12113375 Springbrook Creek at Tukwila, WA 40.7 9.32 34.6 47.56 3.31 365

66 09A080 Green River at Tukwila, WA 787 4,200 657 934 70.8 365

67 12113390 Duwamish River at Golf Course at Tukwila, WA 1,000 10,600 790 1,254 119 365

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

80.2 684 34.3 161 32.9 365

69 46A070 Entiat River near Entiat, WA 152 728 103 216 28.9 365

70 45A110 Wenatchee River near Leavenworth, WA 573 10,200 390 813 109 365

71 16C090 Duckabush River near Brinnon, WA 60.3 719 23.1 130 28.0 365

72 12128000 Thorton Creek near Seattle, WA 8.25 1.98 5.48 11.94 1.66 365

73 54A120 Spokane River at Riverside State Park, WA 2,410 70,900 1,900 3,020 286 365

74 07D050 Snoqualmie River near Monroe, WA 958 9,210 762 1,190 109 365

75 07C070 Skykomish River at Monroe, WA 734 9,900 542 973 110 365

76 07A090 Snohomish River at Snohomish, WA 2,450 72,300 1,920 3,080 297 365

77 53A070 Columbia River at Grand Coulee, WA 14,500 5,740,000 10,000 20,300 2,620 365

78 48A070 Methow River near Pateros, WA 475 8,830 306 706 102 365

79 49A070 Okanogan River at Malott, WA 2,220 129,000 1,570 3,050 381 365

80 48A140 Methow River at Twisp, WA 331 4,720 208 500 75.1 365

81 03A060 Skagit River near Mount Vernon, WA 5,600 795,000 3,870 7,830 1,010 365

82 03B050 Samish River near Burlington, WA 111 280 80.5 148 17.4 365

83 12213140 Nooksack River at Brennan, WA 6,200 2,320,000 3,510 10,160 1,710 365

84 01A050 Nooksack River at Brennan, WA 5,550 1,790,000 3,120 9,160 1,550 365

85 12210700 Nooksack River at North Cedarville, WA 4,530 9,170,000 1,030 13,100 3,270 365

86 12400520 Columbia River at Northport, WA 6,770 956,000 4,970 9,000 1,030 365

87 61A070 Columbia River at Northport, WA 9,800 1,500,000 7,470 12,600 1,320 365

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA 64.0 321 34.2 110 19.5 365

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID NA NA NA NA NA –

90 13094000 Snake River near Buhl, ID 6,090 419,000 4,880 7,520 674 365

91 13154500 Snake River at King Hill, ID 7,750 346,000 6,620 9,020 612 365

92 13203510 Boise River below Diversion Dam near Boise, ID NA NA NA NA NA NA

93 13206000 Boise River at Glenwood, ID 843 12,900 638 1,090 116 365

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 19.1 3.64 15.2 23.80 2.21 365

95 12414900 St. Maries River near Santa, ID NA NA NA NA NA –

96 12414500 St. Joe River at Calder, ID NA NA NA NA NA –

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 194 626 144 255 28.2 365

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 450 77,709 286 676 100 365

99 12419000 Spokane River near Post Falls, ID NA NA NA NA NA –

100 13010065 Snake River at Flagg Ranch, WY 1,230 138,000 614 2,210 413 365

Table A2. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound basins, water year 1997.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

82 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Table A2. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound basins, water year 1997.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 12,100 5,320,000 8,090 17,500 2,420 365

52 13351000 Palouse River at Hooper, WA 5,500 699,000 3,700 7,860 1,070 365

53 34A070 Palouse River at Hooper, WA 2,110 126,000 1,470 2,930 373 365

54 41A070 Crab Creek near Beverly, WA 156 94 137 177 10.2 365

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NA NA NA NA NA –

56 13A060 Deschutes River at East Street Bridge, WA 214 701 163 275 28.7 365

57 10A070 Puyallup River at Meridian Street, WA 3,180 400,000 2,000 4,810 723 365

58 12108500 Newaukum Creek near Black Diamond, WA 157 848 102 231 32.8 365

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA NA NA NA NA NA NA

60 12061500 Skokomish River near Potlatch, WA 893 187,000 209 2,540 632 365

61 16A070 Skokomish River near Potlatch, WA 451 15,300 243 768 135 365

62 12112600 Big Soos Creek above Hatchery near Auburn, WA 67.6 196 42.5 102 15.4 365

63 09A190 Green River at Kanaskat, WA 199 441 158 248 22.8 365

64 45A070 Wenatchee River at Wenatchee, WA 769 13,700 551 1,040 126 365

65 12113375 Springbrook Creek at Tukwila, WA 40.7 9.32 34.6 47.56 3.31 365

66 09A080 Green River at Tukwila, WA 787 4,200 657 934 70.8 365

67 12113390 Duwamish River at Golf Course at Tukwila, WA 1,000 10,600 790 1,254 119 365

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

80.2 684 34.3 161 32.9 365

69 46A070 Entiat River near Entiat, WA 152 728 103 216 28.9 365

70 45A110 Wenatchee River near Leavenworth, WA 573 10,200 390 813 109 365

71 16C090 Duckabush River near Brinnon, WA 60.3 719 23.1 130 28.0 365

72 12128000 Thorton Creek near Seattle, WA 8.25 1.98 5.48 11.94 1.66 365

73 54A120 Spokane River at Riverside State Park, WA 2,410 70,900 1,900 3,020 286 365

74 07D050 Snoqualmie River near Monroe, WA 958 9,210 762 1,190 109 365

75 07C070 Skykomish River at Monroe, WA 734 9,900 542 973 110 365

76 07A090 Snohomish River at Snohomish, WA 2,450 72,300 1,920 3,080 297 365

77 53A070 Columbia River at Grand Coulee, WA 14,500 5,740,000 10,000 20,300 2,620 365

78 48A070 Methow River near Pateros, WA 475 8,830 306 706 102 365

79 49A070 Okanogan River at Malott, WA 2,220 129,000 1,570 3,050 381 365

80 48A140 Methow River at Twisp, WA 331 4,720 208 500 75.1 365

81 03A060 Skagit River near Mount Vernon, WA 5,600 795,000 3,870 7,830 1,010 365

82 03B050 Samish River near Burlington, WA 111 280 80.5 148 17.4 365

83 12213140 Nooksack River at Brennan, WA 6,200 2,320,000 3,510 10,160 1,710 365

84 01A050 Nooksack River at Brennan, WA 5,550 1,790,000 3,120 9,160 1,550 365

85 12210700 Nooksack River at North Cedarville, WA 4,530 9,170,000 1,030 13,100 3,270 365

86 12400520 Columbia River at Northport, WA 6,770 956,000 4,970 9,000 1,030 365

87 61A070 Columbia River at Northport, WA 9,800 1,500,000 7,470 12,600 1,320 365

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA 64.0 321 34.2 110 19.5 365

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID NA NA NA NA NA –

90 13094000 Snake River near Buhl, ID 6,090 419,000 4,880 7,520 674 365

91 13154500 Snake River at King Hill, ID 7,750 346,000 6,620 9,020 612 365

92 13203510 Boise River below Diversion Dam near Boise, ID NA NA NA NA NA NA

93 13206000 Boise River at Glenwood, ID 843 12,900 638 1,090 116 365

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 19.1 3.64 15.2 23.80 2.21 365

95 12414900 St. Maries River near Santa, ID NA NA NA NA NA –

96 12414500 St. Joe River at Calder, ID NA NA NA NA NA –

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 194 626 144 255 28.2 365

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 450 77,709 286 676 100 365

99 12419000 Spokane River near Post Falls, ID NA NA NA NA NA –

100 13010065 Snake River at Flagg Ranch, WY 1,230 138,000 614 2,210 413 365

Appendix A 83
Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 39.1 28.5 29.4 50.9 5.50 365

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NA NA NA NA NA –

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NA NA NA NA NA –

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 80.6 450 46.3 131 21.7 365

5 10663 Mohawk River at Hill Road, OR 71.1 650 32.3 137 27.1 365

6 10376 McKenzie River at Coburg Road, OR 267 12,900 108 556 117 365

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 1,150 66,200 709 1,780 274 365

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 121 851 72.0 191 30.5 365

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NA NA NA NA NA –

10 10508 Deschutes River at Lower Bridge, OR 9.9 2.27 7.2 13.3 1.55 365

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 2,080 239,000 1,240 3,280 523 365

12 11490 Powder River at Hwy 7 (Baker City), OR 7.01 3.03 4.2 11.1 1.78 365

13 11478 John Day River at Service Creek, OR 321 22,600 113 725 161 365

14 10555 Willamette River at Marion Street (Salem), OR 3,780 597,000 2,410 5,640 828 365

15 14200400 Little Abiqua Creek near Scotts Mills, OR 1.92 .16 1.2 2.92 .44 365

16 14201300 Zollner Creek near Mt. Angel, OR 36.9 97.2 15.3 75.3 15.6 365

17 10640 Pudding River at Hwy 211 (Woodburn), OR NA NA NA NA NA –

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR NA NA NA NA NA –

19 3701002 Tualatin River at Weiss Bridge, OR NA NA NA NA NA –

20 3840012 Fanno Creek at Durham Road, OR NA NA NA NA NA –

21 14206950 Fanno Creek near Durham, OR NA NA NA NA NA –

22 3701715 Tualatin River at Cherry Grove, OR NA NA NA NA NA –

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 69.9 4,020 10.5 244 66.4 365

24 3701333 Tualatin River at Farmington Bridge Road, OR NA NA NA NA NA –

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR NA NA NA NA NA –

26 11386 John Day River at Hwy 206, OR NA NA NA NA NA –

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR NA NA NA NA NA –

28 3701391 Tualatin River at Rood Bridge Road, OR NA NA NA NA NA –

29 3701528 Tualatin River at Golf Course Road, OR NA NA NA NA NA –

30 3810015 Gales Creek at New Hwy 47, OR NA NA NA NA NA –

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 6,430 823,000 4,600 8,770 1,070 365

32 3820012 Rock Creek at Hwy 8, OR NA NA NA NA NA –

33 14211720 Willamette River at Portland, OR 18,900 6,960,000 13,700 25,400 3,010 365

34 3850006 Dawson Creek at Brookwood, OR NA NA NA NA NA –

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR NA NA NA NA NA –

36 3824072 Bronson Creek at Saltzman, OR NA NA NA NA NA –

37 10332 Willamette River at SP&S Railroad Bridge, OR 9,300 4,440,000 5,700 14,300 2,220 365

38 14128910 Columbia River at Warrendale, OR 19,600 3,390,000 16,100 23,700 1,950 365

39 10411 Deschutes River at Deschutes River Park, OR 439 31,500 184 891 184 365

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

32,000 101,000,000 16,600 56,100 10,200 365

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 25.6 529 4.1 87.0 23.4 365

42 12012 Hood River at footbridge downstream of I-84, OR 61.1 1,100 18.4 152 35.5 365

43 11489 Umatilla River at Westland Road (Hermiston), OR 1,100 150,000 442 2,290 482 365

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 58,800 29,900,000 47,700 71,800 6,150 365

45 27D090 East Fork Lewis River near Dollar Corner, WA 33.7 83.1 16.9 60.4 11.2 365

46 32A070 Walla Walla River near Touchet, WA 477 111,000 104 1,410 355 365

47 13353200 Snake River at Burbank, WA 5,120 221,000 4,190 6,190 510 365

48 37A090 Yakima River at Kiona, WA 2,430 165,000 1,690 3,390 435 365

49 12510500 Yakima River at Kiona, WA 4,520 1,710,000 2,460 7,640 1,330 365

50 12505450 Granger Drain at Granger, WA NA NA NA NA NA –

Table A3. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 1997.

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; ton/yr, ton per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

84 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Load(ton/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(lb/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow 

(ft3/s)

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 14,300 18.6 NC NA 779

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NC NC NC 880 162

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NC NC NC 12,000 434

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 29,400 4.45 21.9 3,490 6,720

5 10663 Mohawk River at Hill Road, OR 25,900 29.9 146 460 883

6 10376 McKenzie River at Coburg Road, OR 97,500 14.4 NC NA 6,900

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 421,000 24.9 123 8,890 17,200

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 44,100 37.0 106 1,080 1,210

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NC NC NC 239 688

10 10508 Deschutes River at Lower Bridge, OR 3,610 2.51 1.72 5,440 1,460

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 760,000 35.8 157 12,600 21,600

12 11490 Powder River at Hwy 7 (Baker City), OR 2,560 16.4 7.35 902 158

13 11478 John Day River at Service Creek, OR 117,000 36.8 22.8 13,300 3,230

14 10555 Willamette River at Marion Street (Salem), OR 1,380,000 38.3 187 19,100 36,600

15 14200400 Little Abiqua Creek near Scotts Mills, OR 700 14.6 71.1 25.5 48.7

16 14201300 Zollner Creek near Mt. Angel, OR 13,500 365 13,500 38.9 48.8

17 10640 Pudding River at Hwy 211 (Woodburn), OR NC NC NC 818 –

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR NC NC NC 1,760 4,080

19 3701002 Tualatin River at Weiss Bridge, OR NC NC NC 1,840 2,430

20 3840012 Fanno Creek at Durham Road, OR NC NC NC 80.7 –

21 14206950 Fanno Creek near Durham, OR NC NC NC 80.7 –

22 3701715 Tualatin River at Cherry Grove, OR NC NC NC 97.3 292

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 25,500 190 476 139 137

24 3701333 Tualatin River at Farmington Bridge Road, OR NC NC NC 1,460 1,990

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR NC NC NC 327 530

26 11386 John Day River at Hwy 206, OR NC NC NC NA –

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR NC NC NC 103 182

28 3701391 Tualatin River at Rood Bridge Road, OR NC NC NC 1,230 1,760

29 3701528 Tualatin River at Golf Course Road, OR NC NC NC 561 893

30 3810015 Gales Creek at New Hwy 47, OR NC NC NC 195 335

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 2,350,000 44.4 210 29,000 53,800

32 3820012 Rock Creek at Hwy 8, OR NC NC NC 193 –

33 14211720 Willamette River at Portland, OR 6,890,000 130 617 29,000 53,800

34 3850006 Dawson Creek at Brookwood, OR NC NC NC 9.7 –

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR NC NC NC 10.2 –

36 3824072 Bronson Creek at Saltzman, OR NC NC NC 5.23 –

37 10332 Willamette River at SP&S Railroad Bridge, OR 3,390,000 64.1 NC NA 53,800

38 14128910 Columbia River at Warrendale, OR 7,160,000 27.6 30.1 616,000 264,000

39 10411 Deschutes River at Deschutes River Park, OR 160,000 20.4 14.9 28,800 7,970

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

11,700,000 43.7 NC NA 272,000

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 9,330 12.2 21.0 1,150 777

42 12012 Hood River at footbridge downstream of I-84, OR 22,300 14.9 NC NA 1,520

43 11489 Umatilla River at Westland Road (Hermiston), OR 401,000 397 NC NA 1,030

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 21,500,000 64.5 84.5 658,000 338,000

45 27D090 East Fork Lewis River near Dollar Corner, WA 12,300 13.1 78.7 405 957

46 32A070 Walla Walla River near Touchet, WA 174,000 166 103 4,370 1,060

47 13353200 Snake River at Burbank, WA 1,870,000 22.5 18.4 262,000 84,200

48 37A090 Yakima River at Kiona, WA 888,000 149 158 14,500 6,070

49 12510500 Yakima River at Kiona, WA 1,650,000 276 294 14,500 6,070

50 12505450 Granger Drain at Granger, WA NC NC NC 160 –

Table A3. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 1997.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; ton/yr, ton per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 85
Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 2,020 56,400 1,580 2,550 248 365

52 13351000 Palouse River at Hooper, WA 10,800 9,240,000 3,410 26,200 6,020 365

53 34A070 Palouse River at Hooper, WA 3,390 3,100,000 946 8,790 2,100 365

54 41A070 Crab Creek near Beverly, WA 33.1 6.77 27.9 38.9 2.81 365

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NA NA NA NA NA –

56 13A060 Deschutes River at East Street Bridge, WA 107 1,360 47.5 209 42.0 365

57 10A070 Puyallup River at Meridian Street, WA 3,520 3,590,000 951 9,300 2,240 365

58 12108500 Newaukum Creek near Black Diamond, WA 5.92 1.87 3.5 9.38 1.51 365

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA NA NA NA NA NA –

60 12061500 Skokomish River near Potlatch, WA 1,840 1,032,417 268 6,520 1,790 365

61 16A070 Skokomish River near Potlatch, WA 1,360 842,000 281 4,120 1,050 365

62 12112600 Big Soos Creek above Hatchery near Auburn, WA 38.8 253 14.4 85.1 18.5 365

63 09A190 Green River at Kanaskat, WA 55.0 89.2 36.2 80.0 11.2 365

64 45A070 Wenatchee River at Wenatchee, WA 406 11,400 224 680 118 365

65 12113375 Springbrook Creek at Tukwila, WA 5.39 .95 3.5 8.01 1.17 365

66 09A080 Green River at Tukwila, WA 218 943 157 295 35.3 365

67 12113390 Duwamish River at Golf Course at Tukwila, WA 525 5,910 370 725 91.0 365

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

43.6 343 14.3 103 23.3 365

69 46A070 Entiat River near Entiat, WA 43.8 61.6 28.8 63.9 8.98 365

70 45A110 Wenatchee River near Leavenworth, WA 165 1,250 102 254 39.1 365

71 16C090 Duckabush River near Brinnon, WA 34.2 1,520 3.5 139 40.9 365

72 12128000 Thorton Creek near Seattle, WA 2.39 1.22 .7 6.02 1.41 365

73 54A120 Spokane River at Riverside State Park, WA 393 13,300 202 691 126 365

74 07D050 Snoqualmie River near Monroe, WA 581 11,500 360 888 136 365

75 07C070 Skykomish River at Monroe, WA 520 18,300 261 933 174 365

76 07A090 Snohomish River at Snohomish, WA 1,520 54,300 1,050 2,130 275 365

77 53A070 Columbia River at Grand Coulee, WA 679 7,250 522 869 88.8 365

78 48A070 Methow River near Pateros, WA 204 2,330 118 328 54.0 365

79 49A070 Okanogan River at Malott, WA 961 13,600 724 1,250 134 365

80 48A140 Methow River at Twisp, WA 118 822 67.6 193 32.3 365

81 03A060 Skagit River near Mount Vernon, WA 4,550 1,130,000 2,610 7,400 1,230 365

82 03B050 Samish River near Burlington, WA 31.1 43.0 19.0 48.1 7.48 365

83 12213140 Nooksack River at Brennan, WA 6,690 1,570,000 4,340 9,880 1,420 365

84 01A050 Nooksack River at Brennan, WA 4,280 1,460,000 2,190 7,590 1,400 365

85 12210700 Nooksack River at North Cedarville, WA 7,260 11,900,000 2,220 17,900 4,150 365

86 12400520 Columbia River at Northport, WA 3,600 390,000 2,480 5,050 659 365

87 61A070 Columbia River at Northport, WA 2,100 169,000 1,390 3,040 424 365

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA 14.8 11.4 9.0 22.9 3.58 365

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID NA NA NA NA NA –

90 13094000 Snake River near Buhl, ID 2,100 219,000 1,280 3,160 482 365

91 13154500 Snake River at King Hill, ID 2,140 129,000 1,500 2,960 373 365

92 13203510 Boise River below Diversion Dam near Boise, ID 78.0 392 45.6 125 20.4 365

93 13206000 Boise River at Glenwood, ID 311 7,480 173 518 88.8 365

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID NA NA NA NA NA –

95 12414900 St. Maries River near Santa, ID NA NA NA NA NA –

96 12414500 St. Joe River at Calder, ID NA NA NA NA NA –

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID NA NA NA NA NA –

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 333 8,270 168 593 110 365

99 12419000 Spokane River near Post Falls, ID NA NA NA NA NA –

100 13010065 Snake River at Flagg Ranch, WY 1,740 245,000 881 3,100 572 365

Table A3. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 1997.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; ton/yr, ton per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

86 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Load(ton/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(lb/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow 

(ft3/s)

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 737,000 4.56 28.2 67,800 164,000

52 13351000 Palouse River at Hooper, WA 3,940,000 2,510 1,601 6,380 1,600

53 34A070 Palouse River at Hooper, WA 1,240,000 788 503 6,380 1,600

54 41A070 Crab Creek near Beverly, WA 12,100 41.9 31.3 999 293

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NC NC NC 1,840 –

56 13A060 Deschutes River at East Street Bridge, WA 39,100 69.0 380 267 575

57 10A070 Puyallup River at Meridian Street, WA 1,290,000 301 1,400 2,380 4,340

58 12108500 Newaukum Creek near Black Diamond, WA 2,160 26.2 78.8 71.1 83.7

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA NC NC NC 1,190 40.1

60 12061500 Skokomish River near Potlatch, WA 672,000 455 5,130 339 1,500

61 16A070 Skokomish River near Potlatch, WA 497,000 336 3,790 339 1,500

62 12112600 Big Soos Creek above Hatchery near Auburn, WA 14,200 73.8 212 173 195

63 09A190 Green River at Kanaskat, WA 20,100 14.6 84.4 616 1,390

64 45A070 Wenatchee River at Wenatchee, WA 148,000 33.2 112 3,440 4,540

65 12113375 Springbrook Creek at Tukwila, WA 1,970 44.2 98.6 51.7 45.2

66 09A080 Green River at Tukwila, WA 79,600 42.5 167 1,240 1,900

67 12113390 Duwamish River at Golf Course at Tukwila, WA 192,000 90.5 416 1,190 2,150

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

15,900 23.8 280 147 677

69 46A070 Entiat River near Entiat, WA 16,000 23.2 38.6 1,080 700

70 45A110 Wenatchee River near Leavenworth, WA 60,300 14.6 90.8 1,720 4,190

71 16C090 Duckabush River near Brinnon, WA 12,500 25.0 188 172 507

72 12128000 Thorton Creek near Seattle, WA 874 69.9 77.5 29.2 12.7

73 54A120 Spokane River at Riverside State Park, WA 143,000 14.1 28.7 13,000 10,400

74 07D050 Snoqualmie River near Monroe, WA 212,000 42.7 310 1,770 5,040

75 07C070 Skykomish River at Monroe, WA 190,000 34.5 248 1,980 5,580

76 07A090 Snohomish River at Snohomish, WA 555,000 42.4 324 4,440 13,300

77 53A070 Columbia River at Grand Coulee, WA 248,000 1.74 22.2 28,900 145,000

78 48A070 Methow River near Pateros, WA 74,400 35.5 41.4 4,660 2,130

79 49A070 Okanogan River at Malott, WA 351,000 69.6 202 4,500 5,120

80 48A140 Methow River at Twisp, WA 43,200 22.8 32.7 3,430 1,920

81 03A060 Skagit River near Mount Vernon, WA 1,660,000 77.3 715 6,020 21,800

82 03B050 Samish River near Burlington, WA 11,400 33.9 132 223 340

83 12213140 Nooksack River at Brennan, WA 2,440,000 255 3,130 2,020 9,720

84 01A050 Nooksack River at Brennan, WA 1,560,000 301 2,120 1,910 5,280

85 12210700 Nooksack River at North Cedarville, WA 2,650,000 621 4,500 1,530 4,340

86 12400520 Columbia River at Northport, WA 1,310,000 10.2 21.7 156,000 131,000

87 61A070 Columbia River at Northport, WA 765,000 5.95 12.7 156,000 131,000

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA 5,400 50.3 142 98.6 109

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID NC NC NC 623 175

90 13094000 Snake River near Buhl, ID 754,000 69.2 25.6 76,100 11,100

91 13154500 Snake River at King Hill, ID 782,000 46.9 21.8 92,900 16,900

92 13203510 Boise River below Diversion Dam near Boise, ID 28,500 7.83 10.6 6,980 3,690

93 13206000 Boise River at Glenwood, ID 114,000 34.1 41.0 7,180 3,380

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID NC NC NC 220 416

95 12414900 St. Maries River near Santa, ID NC NC NC 706 –

96 12414500 St. Joe River at Calder, ID NC NC NC 2,680 –

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID NC NC NC 738 846

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 122,000 45.0 135 2,320 2,740

99 12419000 Spokane River near Post Falls, ID NC NC NC 10,200 10,300

100 13010065 Snake River at Flagg Ranch, WY 635,000 419 1,240 1,320 1,540

Table A3. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 1997.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; ton/yr, ton per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 87
Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number

of 

days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 1,730 4,100 1,600 1,870 67.6 366

2 MAL113 North Fork Malheur River approximately 2 miles upstrean of 

Beulah Reservoir, OR

NA NA NA NA NA –

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NA NA NA NA NA –

4 10386 Middle Fork Willamette River at Jasper Bridge, OR NA NA NA NA NA –

5 10663 Mohawk River at Hill Road, OR NA NA NA NA NA –

6 10376 McKenzie River at Coburg Road, OR NA NA NA NA NA –

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 15,800 809,000 13,900 17,800 991 366

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 3,040 55,200 2,580 3,560 250 366

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NA NA NA NA NA –

10 10508 Deschutes River at Lower Bridge, OR 1,220 18,400 974 1,510 137 366

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 38,100 5,060,000 33,400 43,300 2,540 366

12 11490 Powder River at Hwy 7 (Baker City), OR 213 154 189 240 13.0 366

13 11478 John Day River at Service Creek, OR 2,490 58,700 2,020 3,040 260 366

14 10555 Willamette River at Marion Street (Salem), OR 65,900 10,600,000 59,000 73,400 3,670 366

15 14200400 Little Abiqua Creek near Scotts Mills, OR 129 16.0 120 138 4.66 366

16 14201300 Zollner Creek near Mt. Angel, OR 1,330 4,900 1,170 1,510 87.1 366

17 10640 Pudding River at Hwy 211 (Woodburn), OR 11,700 1,170,000 9,660 14,100 1,140 366

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR NA NA NA NA NA –

19 3701002 Tualatin River at Weiss Bridge, OR 16,600 92,800 15,800 17,300 392 366

20 3840012 Fanno Creek at Durham Road, OR NA NA NA NA NA –

21 14206950 Fanno Creek near Durham, OR NA NA NA NA NA –

22 3701715 Tualatin River at Cherry Grove, OR NA NA NA NA NA –

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 1,300 838 1,240 1,360 30.3 366

24 3701333 Tualatin River at Farmington Bridge Road, OR 10,500 180,000 9,630 11,400 460 366

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 1,400 3,170 1,250 1,560 77.8 366

26 11386 John Day River at Hwy 206, OR NA NA NA NA NA –

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 187 50.3 172 203 7.92 366

28 3701391 Tualatin River at Rood Bridge Road, OR 7,190 82,600 6,500 7,920 362 366

29 3701528 Tualatin River at Golf Course Road, OR 2,560 8,710 2,320 2,820 128 365

30 3810015 Gales Creek at New Hwy 47, OR 842 993 756 934 45.6 366

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 152,000 53,100,000 136,000 168,000 8,270 366

32 3820012 Rock Creek at Hwy 8, OR NA NA NA NA NA –

33 14211720 Willamette River at Portland, OR 160,000 38,000,000 146,000 175,000 7,340 366

34 3850006 Dawson Creek at Brookwood, OR 39.8 2.44 36.3 43.6 1.88 366

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR 20.1 .47 18.5 21.8 .84 366

36 3824072 Bronson Creek at Saltzman, OR 7.51 .05 6.96 8.09 .29 366

37 10332 Willamette River at SP&S Railroad Bridge, OR 157,000 132,000,000 134,000 182,000 12,200 366

38 14128910 Columbia River at Warrendale, OR 424,000 1,030,000,000 363,000 493,000 33,000 366

39 10411 Deschutes River at Deschutes River Park, OR 10,600 332,000 9,430 11,800 604 366

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

455,000 1,120,000,000 389,000 529,000 35,600 366

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 766 6,700 608 951 87.7 366

42 12012 Hood River at footbridge downstream of I-84, OR NA NA NA NA NA –

43 11489 Umatilla River at Westland Road (Hermiston), OR 3,980 52,400 3,530 4,480 243 366

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 572,000 423,000,000 529,000 617,000 22,300 366

45 27D090 East Fork Lewis River near Dollar Corner, WA 1,850 8,740 1,650 2,060 105 366

46 32A070 Walla Walla River near Touchet, WA 2,430 15,900 2,160 2,730 145 366

47 13353200 Snake River at Burbank, WA 171,000 56,900,000 156,000 187,000 7,970 366

48 37A090 Yakima River at Kiona, WA 19,400 489,000 17,900 21,000 780 366

49 12510500 Yakima River at Kiona, WA 21,000 817,000 19,200 22,900 955 366

50 12505450 Granger Drain at Granger, WA 816 645 766 868 26.2 366

Table A4. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 2000.

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

88 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number

of 

days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 1,730 4,100 1,600 1,870 67.6 366

2 MAL113 North Fork Malheur River approximately 2 miles upstrean of 

Beulah Reservoir, OR

NA NA NA NA NA –

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NA NA NA NA NA –

4 10386 Middle Fork Willamette River at Jasper Bridge, OR NA NA NA NA NA –

5 10663 Mohawk River at Hill Road, OR NA NA NA NA NA –

6 10376 McKenzie River at Coburg Road, OR NA NA NA NA NA –

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 15,800 809,000 13,900 17,800 991 366

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 3,040 55,200 2,580 3,560 250 366

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NA NA NA NA NA –

10 10508 Deschutes River at Lower Bridge, OR 1,220 18,400 974 1,510 137 366

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 38,100 5,060,000 33,400 43,300 2,540 366

12 11490 Powder River at Hwy 7 (Baker City), OR 213 154 189 240 13.0 366

13 11478 John Day River at Service Creek, OR 2,490 58,700 2,020 3,040 260 366

14 10555 Willamette River at Marion Street (Salem), OR 65,900 10,600,000 59,000 73,400 3,670 366

15 14200400 Little Abiqua Creek near Scotts Mills, OR 129 16.0 120 138 4.66 366

16 14201300 Zollner Creek near Mt. Angel, OR 1,330 4,900 1,170 1,510 87.1 366

17 10640 Pudding River at Hwy 211 (Woodburn), OR 11,700 1,170,000 9,660 14,100 1,140 366

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR NA NA NA NA NA –

19 3701002 Tualatin River at Weiss Bridge, OR 16,600 92,800 15,800 17,300 392 366

20 3840012 Fanno Creek at Durham Road, OR NA NA NA NA NA –

21 14206950 Fanno Creek near Durham, OR NA NA NA NA NA –

22 3701715 Tualatin River at Cherry Grove, OR NA NA NA NA NA –

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 1,300 838 1,240 1,360 30.3 366

24 3701333 Tualatin River at Farmington Bridge Road, OR 10,500 180,000 9,630 11,400 460 366

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 1,400 3,170 1,250 1,560 77.8 366

26 11386 John Day River at Hwy 206, OR NA NA NA NA NA –

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 187 50.3 172 203 7.92 366

28 3701391 Tualatin River at Rood Bridge Road, OR 7,190 82,600 6,500 7,920 362 366

29 3701528 Tualatin River at Golf Course Road, OR 2,560 8,710 2,320 2,820 128 365

30 3810015 Gales Creek at New Hwy 47, OR 842 993 756 934 45.6 366

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 152,000 53,100,000 136,000 168,000 8,270 366

32 3820012 Rock Creek at Hwy 8, OR NA NA NA NA NA –

33 14211720 Willamette River at Portland, OR 160,000 38,000,000 146,000 175,000 7,340 366

34 3850006 Dawson Creek at Brookwood, OR 39.8 2.44 36.3 43.6 1.88 366

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR 20.1 .47 18.5 21.8 .84 366

36 3824072 Bronson Creek at Saltzman, OR 7.51 .05 6.96 8.09 .29 366

37 10332 Willamette River at SP&S Railroad Bridge, OR 157,000 132,000,000 134,000 182,000 12,200 366

38 14128910 Columbia River at Warrendale, OR 424,000 1,030,000,000 363,000 493,000 33,000 366

39 10411 Deschutes River at Deschutes River Park, OR 10,600 332,000 9,430 11,800 604 366

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

455,000 1,120,000,000 389,000 529,000 35,600 366

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 766 6,700 608 951 87.7 366

42 12012 Hood River at footbridge downstream of I-84, OR NA NA NA NA NA –

43 11489 Umatilla River at Westland Road (Hermiston), OR 3,980 52,400 3,530 4,480 243 366

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 572,000 423,000,000 529,000 617,000 22,300 366

45 27D090 East Fork Lewis River near Dollar Corner, WA 1,850 8,740 1,650 2,060 105 366

46 32A070 Walla Walla River near Touchet, WA 2,430 15,900 2,160 2,730 145 366

47 13353200 Snake River at Burbank, WA 171,000 56,900,000 156,000 187,000 7,970 366

48 37A090 Yakima River at Kiona, WA 19,400 489,000 17,900 21,000 780 366

49 12510500 Yakima River at Kiona, WA 21,000 817,000 19,200 22,900 955 366

50 12505450 Granger Drain at Granger, WA 816 645 766 868 26.2 366

Table A4. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 2000.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 89
Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number

of 

days

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 144,000 121,000,000 123,000 168,000 11,400 366

52 13351000 Palouse River at Hooper, WA 18,500 983,000 16,300 21,000 1,210 366

53 34A070 Palouse River at Hooper, WA 18,300 1,860,000 15,400 21,500 1,540 366

54 41A070 Crab Creek near Beverly, WA NA NA NA NA NA –

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA 2,720 4,320 2,590 2,860 69.3 366

56 13A060 Deschutes River at East Street Bridge, WA 1,730 2,250 1,630 1,830 52.5 366

57 10A070 Puyallup River at Meridian Street, WA 6,500 89,800 5,880 7,170 330 366

58 12108500 Newaukum Creek near Black Diamond, WA NA NA NA NA NA –

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 874 911 810 942 33.9 366

60 12061500 Skokomish River near Potlatch, WA NA NA NA NA NA –

61 16A070 Skokomish River near Potlatch, WA 638 3,070 527 766 61.0 366

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NA NA NA NA NA –

63 09A190 Green River at Kanaskat, WA 1,060 7,480 874 1,270 101 366

64 45A070 Wenatchee River at Wenatchee, WA 2,780 12,600 2,540 3,030 124 366

65 12113375 Springbrook Creek at Tukwila, WA NA NA NA NA NA –

66 09A080 Green River at Tukwila, WA 3,850 25,500 3,510 4,210 179 366

67 12113390 Duwamish River at Golf Course at Tukwila, WA 5,200 59,700 4,680 5,770 278 366

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

NA NA NA NA NA –

69 46A070 Entiat River near Entiat, WA 315 836 259 379 30.5 366

70 45A110 Wenatchee River near Leavenworth, WA 1,630 11,500 1,400 1,880 122 366

71 16C090 Duckabush River near Brinnon, WA 121 154 94.8 152 14.5 366

72 12128000 Thorton Creek near Seattle, WA 92.7 8.17 86.5 99.2 3.20 366

73 54A120 Spokane River at Riverside State Park, WA 21,600 764,000 19,800 23,500 952 366

74 07D050 Snoqualmie River near Monroe, WA 8,060 62,600 7,520 8,630 282 366

75 07C070 Skykomish River at Monroe, WA 4,610 40,500 4,170 5,090 235 366

76 07A090 Snohomish River at Snohomish, WA 19,000 574,000 17,400 20,800 878 366

77 53A070 Columbia River at Grand Coulee, WA 111,000 16,900,000 102,000 120,000 4,540 366

78 48A070 Methow River near Pateros, WA 1,100 2,170 1,000 1,200 50.8 366

79 49A070 Okanogan River at Malott, WA 2,780 15,700 2,520 3,060 138 366

80 48A140 Methow River at Twisp, WA 838 1,730 751 932 46.2 366

81 03A060 Skagit River near Mount Vernon, WA 15,700 561,000 14,000 17,500 879 366

82 03B050 Samish River near Burlington, WA 1,520 2,240 1,420 1,620 51.0 366

83 12213140 Nooksack River at Brennan, WA NA NA NA NA NA –

84 01A050 Nooksack River at Brennan, WA 12,400 266,000 11,300 13,500 567 366

85 12210700 Nooksack River at North Cedarville, WA NA NA NA NA NA –

86 12400520 Columbia River at Northport, WA 75,700 288,000,000 47,700 114,000 17,100 366

87 61A070 Columbia River at Northport, WA 80,300 4,290,000 76,000 84,700 2,230 366

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NA NA NA NA NA –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 1,370 838 1,310 1,430 31.5 366

90 13094000 Snake River near Buhl, ID 42,300 1,120,000 40,100 44,500 1,120 366

91 13154500 Snake River at King Hill, ID 82,200 1,330,000 79,600 84,900 1,340 366

92 13203510 Boise River below Diversion Dam near Boise, ID 1,670 8,420 1,490 1,870 95.9 366

93 13206000 Boise River at Glenwood, ID 2,040 6,670 1,870 2,210 87.5 366

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 281 1,590 205 375 43.5 366

95 12414900 St. Maries River near Santa, ID NA NA NA NA NA –

96 12414500 St. Joe River at Calder, ID NA NA NA NA NA –

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 947 1,940 855 1,050 49.1 366

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID NA NA NA NA NA –

99 12419000 Spokane River near Post Falls, ID 6,600 327,000 5,510 7,850 600 366

100 13010065 Snake River at Flagg Ranch, WY 1,130 30,900 763 1,610 216 366

Table A4. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 2000.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

90 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number

of 

days

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 144,000 121,000,000 123,000 168,000 11,400 366

52 13351000 Palouse River at Hooper, WA 18,500 983,000 16,300 21,000 1,210 366

53 34A070 Palouse River at Hooper, WA 18,300 1,860,000 15,400 21,500 1,540 366

54 41A070 Crab Creek near Beverly, WA NA NA NA NA NA –

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA 2,720 4,320 2,590 2,860 69.3 366

56 13A060 Deschutes River at East Street Bridge, WA 1,730 2,250 1,630 1,830 52.5 366

57 10A070 Puyallup River at Meridian Street, WA 6,500 89,800 5,880 7,170 330 366

58 12108500 Newaukum Creek near Black Diamond, WA NA NA NA NA NA –

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 874 911 810 942 33.9 366

60 12061500 Skokomish River near Potlatch, WA NA NA NA NA NA –

61 16A070 Skokomish River near Potlatch, WA 638 3,070 527 766 61.0 366

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NA NA NA NA NA –

63 09A190 Green River at Kanaskat, WA 1,060 7,480 874 1,270 101 366

64 45A070 Wenatchee River at Wenatchee, WA 2,780 12,600 2,540 3,030 124 366

65 12113375 Springbrook Creek at Tukwila, WA NA NA NA NA NA –

66 09A080 Green River at Tukwila, WA 3,850 25,500 3,510 4,210 179 366

67 12113390 Duwamish River at Golf Course at Tukwila, WA 5,200 59,700 4,680 5,770 278 366

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

NA NA NA NA NA –

69 46A070 Entiat River near Entiat, WA 315 836 259 379 30.5 366

70 45A110 Wenatchee River near Leavenworth, WA 1,630 11,500 1,400 1,880 122 366

71 16C090 Duckabush River near Brinnon, WA 121 154 94.8 152 14.5 366

72 12128000 Thorton Creek near Seattle, WA 92.7 8.17 86.5 99.2 3.20 366

73 54A120 Spokane River at Riverside State Park, WA 21,600 764,000 19,800 23,500 952 366

74 07D050 Snoqualmie River near Monroe, WA 8,060 62,600 7,520 8,630 282 366

75 07C070 Skykomish River at Monroe, WA 4,610 40,500 4,170 5,090 235 366

76 07A090 Snohomish River at Snohomish, WA 19,000 574,000 17,400 20,800 878 366

77 53A070 Columbia River at Grand Coulee, WA 111,000 16,900,000 102,000 120,000 4,540 366

78 48A070 Methow River near Pateros, WA 1,100 2,170 1,000 1,200 50.8 366

79 49A070 Okanogan River at Malott, WA 2,780 15,700 2,520 3,060 138 366

80 48A140 Methow River at Twisp, WA 838 1,730 751 932 46.2 366

81 03A060 Skagit River near Mount Vernon, WA 15,700 561,000 14,000 17,500 879 366

82 03B050 Samish River near Burlington, WA 1,520 2,240 1,420 1,620 51.0 366

83 12213140 Nooksack River at Brennan, WA NA NA NA NA NA –

84 01A050 Nooksack River at Brennan, WA 12,400 266,000 11,300 13,500 567 366

85 12210700 Nooksack River at North Cedarville, WA NA NA NA NA NA –

86 12400520 Columbia River at Northport, WA 75,700 288,000,000 47,700 114,000 17,100 366

87 61A070 Columbia River at Northport, WA 80,300 4,290,000 76,000 84,700 2,230 366

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NA NA NA NA NA –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 1,370 838 1,310 1,430 31.5 366

90 13094000 Snake River near Buhl, ID 42,300 1,120,000 40,100 44,500 1,120 366

91 13154500 Snake River at King Hill, ID 82,200 1,330,000 79,600 84,900 1,340 366

92 13203510 Boise River below Diversion Dam near Boise, ID 1,670 8,420 1,490 1,870 95.9 366

93 13206000 Boise River at Glenwood, ID 2,040 6,670 1,870 2,210 87.5 366

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 281 1,590 205 375 43.5 366

95 12414900 St. Maries River near Santa, ID NA NA NA NA NA –

96 12414500 St. Joe River at Calder, ID NA NA NA NA NA –

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 947 1,940 855 1,050 49.1 366

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID NA NA NA NA NA –

99 12419000 Spokane River near Post Falls, ID 6,600 327,000 5,510 7,850 600 366

100 13010065 Snake River at Flagg Ranch, WY 1,130 30,900 763 1,610 216 366

Table A4. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 2000.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 91
Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 193 151 168 219 13.0 366

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

69.0 21.3 59.9 79.0 4.87 366

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

393 613 344 447 26.3 366

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 741 1,160 673 815 36.3 366

5 10663 Mohawk River at Hill Road, OR 96.5 87.2 78.3 118 10.1 366

6 10376 McKenzie River at Coburg Road, OR 1,200 2,030 1,110 1,300 49.9 366

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 3,980 27,600 3,600 4,380 200 366

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 337 465 295 385 23.0 366

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR 104 10.6 97.6 111 3.44 366

10 10508 Deschutes River at Lower Bridge, OR 510 322 474 547 18.7 366

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 6,140 70,500 5,570 6,760 305 366

12 11490 Powder River at Hwy 7 (Baker City), OR 34.3 10.2 28.2 41.4 3.37 366

13 11478 John Day River at Service Creek, OR 612 2,480 511 727 55.1 366

14 10555 Willamette River at Marion Street (Salem), OR 9,360 152,000 8,510 10,300 449 366

15 14200400 Little Abiqua Creek near Scotts Mills, OR 4.54 .34 3.40 5.95 .65 366

16 14201300 Zollner Creek near Mt. Angel, OR 36.0 5.88 30.0 42.8 3.26 366

17 10640 Pudding River at Hwy 211 (Woodburn), OR 575 3,490 462 706 62.4 366

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR 449 4,900 317 619 77.3 366

19 3701002 Tualatin River at Weiss Bridge, OR 1,170 1,500 1,070 1,270 50.9 366

20 3840012 Fanno Creek at Durham Road, OR NA NA NA NA NA –

21 14206950 Fanno Creek near Durham, OR NA NA NA NA NA –

22 3701715 Tualatin River at Cherry Grove, OR 38.5 21.1 28.8 50.4 5.51 366

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 46.7 8.76 40.7 53.2 3.17 366

24 3701333 Tualatin River at Farmington Bridge Road, OR 983 3,380 858 1,120 67.5 366

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 127 36.6 111 145 8.52 366

26 11386 John Day River at Hwy 206, OR 808 12,000 598 1,070 120 366

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 14.8 5.96 10.4 20.6 2.63 366

28 3701391 Tualatin River at Rood Bridge Road, OR 474 223 439 512 18.7 366

29 3701528 Tualatin River at Golf Course Road, OR 232 87.1 209 257 12.1 365

30 3810015 Gales Creek at New Hwy 47, OR 112 32.3 96.1 129 8.50 366

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 16,500 190,000 15,500 17,500 504 366

32 3820012 Rock Creek at Hwy 8, OR NA NA NA NA NA –

33 14211720 Willamette River at Portland, OR 16,300 483,000 14,700 18,100 854 366

34 3850006 Dawson Creek at Brookwood, OR 3.78 .01 3.57 4.00 .11 366

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR 1.95 .00 1.81 2.09 .07 366

36 3824072 Bronson Creek at Saltzman, OR .74 .00 .65 .82 .04 366

37 10332 Willamette River at SP&S Railroad Bridge, OR 18,100 383,000 16,800 19,400 680 366

38 14128910 Columbia River at Warrendale, OR 30,400 5,430,000 25,700 35,600 2,550 366

39 10411 Deschutes River at Deschutes River Park, OR 3,170 41,300 2,770 3,610 216 366

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

43,800 3,810,000 39,900 48,000 2,080 366

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 146 81.1 128 166 9.76 366

42 12012 Hood River at footbridge downstream of I-84, OR NA NA NA NA NA –

43 11489 Umatilla River at Westland Road (Hermiston), OR 379 925 318 448 33.2 366

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 54,600 9,360,000 48,100 61,800 3,490 366

45 27D090 East Fork Lewis River near Dollar Corner, WA 127 483 83.5 185 26.0 366

46 32A070 Walla Walla River near Touchet, WA 499 2,510 398 617 56.2 366

47 13353200 Snake River at Burbank, WA 13,300 1,130,000 11,200 15,600 1,130 366

48 37A090 Yakima River at Kiona, WA 2,420 6,230 2,240 2,600 91.1 366

49 12510500 Yakima River at Kiona, WA 2,630 22,300 2,330 2,960 159 366

50 12505450 Granger Drain at Granger, WA 65.0 14.5 57.5 73.1 3.97 366

Table A5. Results of loadest modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound basins, water year 2000.

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

92 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Load(lb/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(lb/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow 

(ft3/s)

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 70,500 0.21 NC NA 166

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

25,200 .10 74.0 880 134

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

144,000 .24 31.1 12,000 302

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 271,000 .03 201 3,490 4,200

5 10663 Mohawk River at Hill Road, OR 35,300 .03 198 460 554

6 10376 McKenzie River at Coburg Road, OR 440,000 .04 NC NA 5,070

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 1,460,000 .07 423 8,890 11,300

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 124,000 .08 296 1,080 743

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR 38,100 .04 412 239 515

10 10508 Deschutes River at Lower Bridge, OR 187,000 .08 88.6 5,440 1,250

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 2,250,000 .08 462 12,600 14,200

12 11490 Powder River at Hwy 7 (Baker City), OR 12,600 .06 36.0 902 109

13 11478 John Day River at Service Creek, OR 224,000 .07 43.5 13,300 1,680

14 10555 Willamette River at Marion Street (Salem), OR 3,420,000 .07 463 19,100 23,700

15 14200400 Little Abiqua Creek near Scotts Mills, OR 1,660 .02 168 25.5 37.1

16 14201300 Zollner Creek near Mt. Angel, OR 13,200 .36 875 38.9 18.4

17 10640 Pudding River at Hwy 211 (Woodburn), OR 210,000 .13 664 818 825

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR 164,000 .03 241 1,760 2,830

19 3701002 Tualatin River at Weiss Bridge, OR 426,000 .15 599 1,840 1,410

20 3840012 Fanno Creek at Durham Road, OR NC NC NC 80.7 –

21 14206950 Fanno Creek near Durham, OR NC NC NC 80.7 –

22 3701715 Tualatin River at Cherry Grove, OR 14,100 .05 374 97.3 148

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 17,100 .12 318 139 69.3

24 3701333 Tualatin River at Farmington Bridge Road, OR 360,000 .16 638 1,460 1,130

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 46,500 .06 368 327 392

26 11386 John Day River at Hwy 206, OR 296,000 .08 NC NA 1,770

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 5,430 .02 136 103 111

28 3701391 Tualatin River at Rood Bridge Road, OR 174,000 .09 365 1,230 972

29 3701528 Tualatin River at Golf Course Road, OR 84,700 .07 391 561 610

30 3810015 Gales Creek at New Hwy 47, OR 40,900 .09 543 195 221

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 6,030,000 .09 539 28,900 35,100

32 3820012 Rock Creek at Hwy 8, OR NC NC NC 193 –

33 14211720 Willamette River at Portland, OR 5,980,000 .09 533 28,900 35,100

34 3850006 Dawson Creek at Brookwood, OR 1,380 .13 370 9.66 5.44

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR 712 .11 180 10.2 3.36

36 3824072 Bronson Creek at Saltzman, OR 269 .14 133 5.23 1.00

37 10332 Willamette River at SP&S Railroad Bridge, OR 6,610,000 .10 NC NA 35,100

38 14128910 Columbia River at Warrendale, OR 11,100,000 .03 46.6 616,000 185,000

39 10411 Deschutes River at Deschutes River Park, OR 1,160,000 .09 108 27,800 6,450

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

16,000,000 .05 NC NA 177,000

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 53,600 .05 120 1,150 518

42 12012 Hood River at footbridge downstream of I-84, OR NC NC NC NA 1,030

43 11489 Umatilla River at Westland Road (Hermiston), OR 139,000 .13 NC NA 545

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 20,000,000 .04 78.5 658,000 232,000

45 27D090 East Fork Lewis River near Dollar Corner, WA 46,400 .03 296 405 771

46 32A070 Walla Walla River near Touchet, WA 182,000 .16 108 4,370 572

47 13353200 Snake River at Burbank, WA 4,860,000 .05 47.9 262,000 46,600

48 37A090 Yakima River at Kiona, WA 885,000 .12 157 14,500 3,770

49 12510500 Yakima River at Kiona, WA 963,000 .13 171 14,500 3,770

50 12505450 Granger Drain at Granger, WA 23,800 .30 384 160 40.4

Table A5. Results of loadest modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound basins, water year 2000.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 93
Map 

index 

No.

Site 

No. Site name Flux(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 8,220 1,360,000 6,040 10,900 1,250 366

52 13351000 Palouse River at Hooper, WA 1,110 10,600 869 1,410 138 366

53 34A070 Palouse River at Hooper, WA 849 7,180 677 1,050 95.8 366

54 41A070 Crab Creek near Beverly, WA NA NA NA NA NA –

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA 132 390 96.5 176 20.4 366

56 13A060 Deschutes River at East Street Bridge, WA 178 310 143 220 19.7 366

57 10A070 Puyallup River at Meridian Street, WA 2,750 317,000 1,650 4,300 680 366

58 12108500 Newaukum Creek near Black Diamond, WA NA NA NA NA NA –

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 44.5 12.1 37.1 53.1 4.09 366

60 12061500 Skokomish River near Potlatch, WA NA NA NA NA NA –

61 16A070 Skokomish River near Potlatch, WA 396 5,030 262 576 80.4 366

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NA NA NA NA NA –

63 09A190 Green River at Kanaskat, WA 162 283 128 203 19.2 366

64 45A070 Wenatchee River at Wenatchee, WA 420 1,550 339 514 44.7 366

65 12113375 Springbrook Creek at Tukwila, WA NA NA NA NA NA –

66 09A080 Green River at Tukwila, WA 608 3,420 488 749 66.5 366

67 12113390 Duwamish River at Golf Course at Tukwila, WA 726 6,850 550 942 100 366

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

32.8 31.8 19.8 51.3 8.10 366

69 46A070 Entiat River near Entiat, WA 74.1 84.3 56.7 95.2 9.83 366

70 45A110 Wenatchee River near Leavenworth, WA 314 1,270 243 399 40.0 366

71 16C090 Duckabush River near Brinnon, WA 48.4 145 27.5 79.2 13.3 366

72 12128000 Thorton Creek near Seattle, WA 6.24 .44 4.85 7.90 .78 366

73 54A120 Spokane River at Riverside State Park, WA 1,870 25,600 1,550 2,250 179 366

74 07D050 Snoqualmie River near Monroe, WA 784 5,890 624 973 89.2 366

75 07C070 Skykomish River at Monroe, WA 531 4,040 403 688 73.0 366

76 07A090 Snohomish River at Snohomish, WA 1,820 32,000 1,450 2,250 206 366

77 53A070 Columbia River at Grand Coulee, WA 9,880 1,340,000 7,510 12,800 1,340 366

78 48A070 Methow River near Pateros, WA 166 280 132 206 19.0 366

79 49A070 Okanogan River at Malott, WA 659 2,240 558 772 54.6 366

80 48A140 Methow River at Twisp, WA 153 380 115 200 21.8 366

81 03A060 Skagit River near Mount Vernon, WA 4,070 605,000 2,480 6,310 985 366

82 03B050 Samish River near Burlington, WA 57.4 67.6 42.3 76.1 8.65 366

83 12213140 Nooksack River at Brennan, WA NA NA NA NA NA –

84 01A050 Nooksack River at Brennan, WA 2,940 154,000 2,130 3,970 471 366

85 12210700 Nooksack River at North Cedarville, WA NA NA NA NA NA –

86 12400520 Columbia River at Northport, WA 3,140 512,000 1,950 4,790 729 366

87 61A070 Columbia River at Northport, WA 6,550 359,000 5,340 7,950 666 366

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NA NA NA NA NA –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 55.1 2.53 51.5 59.0 1.91 366

90 13094000 Snake River near Buhl, ID 2,690 30,200 2,340 3,080 187 366

91 13154500 Snake River at King Hill, ID 3,710 16,500 3,430 4,000 145 366

92 13203510 Boise River below Diversion Dam near Boise, ID 124 1,120 70.8 203 34.0 366

93 13206000 Boise River at Glenwood, ID 458 686 404 517 28.7 366

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 10.1 .96 8.03 12.6 1.16 366

95 12414900 St. Maries River near Santa, ID 87.3 213 61.0 121 15.4 366

96 12414500 St. Joe River at Calder, ID 119 263 88.6 156 17.4 366

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 110 61.2 91.9 131 10.0 366

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 193 828 127 282 39.5 366

99 12419000 Spokane River near Post Falls, ID 439 1,180 367 521 39.3 366

100 13010065 Snake River at Flagg Ranch, WY 266 2,290 167 402 60.2 366

Table A5. Results of loadest modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound basins, water year 2000.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

94 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Load(lb/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(lb/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow 

(ft3/s)

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 3,010,000 0.01 115 67,800 120,000

52 13351000 Palouse River at Hooper, WA 408,000 .28 165 6,380 736

53 34A070 Palouse River at Hooper, WA 311,000 .21 126 6,380 736

54 41A070 Crab Creek near Beverly, WA NC NC NC 999 –

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA 48,300 .12 67.7 1,840 209

56 13A060 Deschutes River at East Street Bridge, WA 65,300 .07 632 267 449

57 10A070 Puyallup River at Meridian Street, WA 1,010,000 .15 1,090 2,380 3,430

58 12108500 Newaukum Creek near Black Diamond, WA NC NC NC 71.1 61.9

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 16,300 .13 35.4 1,190 61.6

60 12061500 Skokomish River near Potlatch, WA NC NC NC 339 1,310

61 16A070 Skokomish River near Potlatch, WA 145,000 .06 1,100 339 1,310

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NC NC NC 173 124

63 09A190 Green River at Kanaskat, WA 59,400 .03 249 616 953

64 45A070 Wenatchee River at Wenatchee, WA 154,000 .02 115 3,440 3,370

65 12113375 Springbrook Creek at Tukwila, WA NC NC NC 51.7 45.6

66 09A080 Green River at Tukwila, WA 223,000 .08 465 1,240 1,400

67 12113390 Duwamish River at Golf Course at Tukwila, WA 266,000 .08 575 1,190 1,590

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

12,000 .01 211 147 535

69 46A070 Entiat River near Entiat, WA 27,100 .03 65.2 1,070 522

70 45A110 Wenatchee River near Leavenworth, WA 115,000 .02 172 1,720 3,190

71 16C090 Duckabush River near Brinnon, WA 17,700 .02 266 172 432

72 12128000 Thorton Creek near Seattle, WA 2,280 .11 202 29.2 10.5

73 54A120 Spokane River at Riverside State Park, WA 685,000 .05 137 13,000 7,030

74 07D050 Snoqualmie River near Monroe, WA 287,000 .04 418 1,770 3,930

75 07C070 Skykomish River at Monroe, WA 194,000 .02 253 1,980 4,620

76 07A090 Snohomish River at Snohomish, WA 665,000 .03 387 4,440 10,500

77 53A070 Columbia River at Grand Coulee, WA 3,610,000 .02 323 28,900 113,000

78 48A070 Methow River near Pateros, WA 60,600 .02 33.6 4,660 1,440

79 49A070 Okanogan River at Malott, WA 241,000 .04 138 4,500 2,930

80 48A140 Methow River at Twisp, WA 56,100 .02 42.3 3,430 1,310

81 03A060 Skagit River near Mount Vernon, WA 1,490,000 .04 639 6,020 17,500

82 03B050 Samish River near Burlington, WA 21,000 .04 243 223 288

83 12213140 Nooksack River at Brennan, WA NC NC NC 2,020 4,250

84 01A050 Nooksack River at Brennan, WA 1,080,000 .13 1,460 1,910 4,250

85 12210700 Nooksack River at North Cedarville, WA NC NC NC 1,520 –

86 12400520 Columbia River at Northport, WA 1,150,000 .01 19.0 156,000 106,000

87 61A070 Columbia River at Northport, WA 2,400,000 .01 39.8 156,000 106,000

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NC NC NC 98.6 –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 20,200 .09 83.6 623 115

90 13094000 Snake River near Buhl, ID 985,000 .11 33.4 76,100 4,670

91 13154500 Snake River at King Hill, ID 1,360,000 .07 37.7 92,900 9,990

92 13203510 Boise River below Diversion Dam near Boise, ID 45,500 .02 16.8 6,980 1,300

93 13206000 Boise River at Glenwood, ID 168,000 .10 60.2 7,180 865

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 3,700 .01 43.4 220 231

95 12414900 St. Maries River near Santa, ID 32,000 .04 117 706 391

96 12414500 St. Joe River at Calder, ID 43,500 .01 42.0 2,680 2,380

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 40,300 .03 141 738 584

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 70,800 .02 78.6 2,330 2,030

99 12419000 Spokane River near Post Falls, ID 161,000 .01 40.9 10,200 6,850

100 13010065 Snake River at Flagg Ranch, WY 97,400 .06 190 1,320 839

Table A5. Results of loadest modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound basins, water year 2000.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 95
Map 

index 

No.

Site 

No. Site name Flux

(ton/d)

Variance

(ton/d)

Lower 95

(ton/d)

Upper 95

(ton/d)

SEP

(ton/d)

Number 

of

 days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 30.8 11.2 24.4 38.3 3.54 366

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NA NA NA NA NA –

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NA NA NA NA NA –

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 32.8 21.4 24.2 43.5 4.94 366

5 10663 Mohawk River at Hill Road, OR 20.4 34.2 10.4 36.1 6.62 366

6 10376 McKenzie River at Coburg Road, OR 88.1 393 51.4 141 23.2 366

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 227 594 173 293 30.9 366

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 60.3 120 40.2 87.1 12.0 366

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NA NA NA NA NA –

10 10508 Deschutes River at Lower Bridge, OR 9.04 1.11 7.08 11.4 1.09 366

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 521 2,760 402 664 67.0 366

12 11490 Powder River at Hwy 7 (Baker City), OR 4.61 .61 3.20 6.42 0.82 366

13 11478 John Day River at Service Creek, OR 64.3 139 42.1 94.1 13.3 366

14 10555 Willamette River at Marion Street (Salem), OR 1,050 11,400 816 1,320 129 366

15 14200400 Little Abiqua Creek near Scotts Mills, OR .93 .03 0.58 1.42 0.22 366

16 14201300 Zollner Creek near Mt. Angel, OR 3.07 .13 2.15 4.24 0.53 366

17 10640 Pudding River at Hwy 211 (Woodburn), OR 27.5 11.6 21.1 35.3 3.63 366

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR 264 73,500 29.2 1,040 300 366

19 3701002 Tualatin River at Weiss Bridge, OR NA NA NA NA NA –

20 3840012 Fanno Creek at Durham Road, OR NA NA NA NA NA –

21 14206950 Fanno Creek near Durham, OR NA NA NA NA NA –

22 3701715 Tualatin River at Cherry Grove, OR NA NA NA NA NA –

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 3.74 .55 2.30 5.75 0.88 366

24 3701333 Tualatin River at Farmington Bridge Road, OR NA NA NA NA NA –

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR NA NA NA NA NA –

26 11386 John Day River at Hwy 206, OR 120 706 71.9 189 30.1 366

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR NA NA NA NA NA –

28 3701391 Tualatin River at Rood Bridge Road, OR NA NA NA NA NA –

29 3701528 Tualatin River at Golf Course Road, OR NA NA NA NA NA –

30 3810015 Gales Creek at New Hwy 47, OR NA NA NA NA NA –

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 1,340 8,180 1,110 1,600 124 366

32 3820012 Rock Creek at Hwy 8, OR NA NA NA NA NA –

33 14211720 Willamette River at Portland, OR 2,780 29,500 2,340 3,270 239 366

34 3850006 Dawson Creek at Brookwood, OR NA NA NA NA NA –

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR NA NA NA NA NA –

36 3824072 Bronson Creek at Saltzman, OR NA NA NA NA NA –

37 10332 Willamette River at SP&S Railroad Bridge, OR 1,440 14,900 1,180 1,740 143 366

38 14128910 Columbia River at Warrendale, OR 3,560 116,000 2,930 4,300 351 366

39 10411 Deschutes River at Deschutes River Park, OR 192 642 144 250 27.2 366

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

4,800 138,000 4,050 5,650 410 366

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 8.04 3.26 4.90 12.5 1.94 366

42 12012 Hood River at footbridge downstream of I-84, OR NA NA NA NA NA –

43 11489 Umatilla River at Westland Road (Hermiston), OR 70.2 101 49.1 97.3 12.3 366

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 14,600 746,000 12,700 16,700 1,040 366

45 27D090 East Fork Lewis River near Dollar Corner, WA 27.9 76.8 11.5 57.3 11.9 366

46 32A070 Walla Walla River near Touchet, WA 162 3,880 65.3 336 70.5 366

47 13353200 Snake River at Burbank, WA 1,220 9,750 1,020 1,450 108 366

48 37A090 Yakima River at Kiona, WA 375 872 311 449 35.2 366

49 12510500 Yakima River at Kiona, WA 468 2,730 366 589 56.9 366

50 12505450 Granger Drain at Granger, WA 18.1 8.88 12.8 24.9 3.11 366

Table A6. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 2000.

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; ton/d, ton per day; ton/yr, ton per year; mg/L, milligram per liter; ton/mi2/yr, ton per square mile per year; km2, square kilometer; ft3/s, cubic foot per 

second; NA, not available; NC, not calculated; –, not applicable]

96 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Load

(ton/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(ton/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow 

(ft3/s)

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 11,300 68.7 NC NA 166

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NC NC NC 880 134

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NC NC NC 12,000 302

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 12,000 2.89 8.89 3,490 4,200

5 10663 Mohawk River at Hill Road, OR 7,470 13.7 41.9 460 554

6 10376 McKenzie River at Coburg Road, OR 32,300 6.45 NC NA 5,070

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 83,100 7.43 24.2 8,890 11,300

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 22,100 30.1 52.9 1,080 743

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NC NC NC 239 515

10 10508 Deschutes River at Lower Bridge, OR 3,310 2.69 1.57 5,440 1,250

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 191,000 13.6 39.2 12,600 14,200

12 11490 Powder River at Hwy 7 (Baker City), OR 1,690 15.7 4.83 902 109

13 11478 John Day River at Service Creek, OR 23,500 14.2 4.57 13,300 1,680

14 10555 Willamette River at Marion Street (Salem), OR 383,000 16.3 51.8 19,100 23,700

15 14200400 Little Abiqua Creek near Scotts Mills, OR 342 9.34 34.7 25.5 37.1

16 14201300 Zollner Creek near Mt. Angel, OR 1,120 61.8 74.6 38.9 18.4

17 10640 Pudding River at Hwy 211 (Woodburn), OR 10,100 12.4 31.7 818 825

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR 96,400 34.5 141 1,760 2,830

19 3701002 Tualatin River at Weiss Bridge, OR NC NC NC 1,840 1,410

20 3840012 Fanno Creek at Durham Road, OR NC NC NC 80.7 –

21 14206950 Fanno Creek near Durham, OR NC NC NC 80.7 –

22 3701715 Tualatin River at Cherry Grove, OR NC NC NC 97.3 148

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 1,370 20.0 25.4 139 69.3

24 3701333 Tualatin River at Farmington Bridge Road, OR NC NC NC 1,460 1,130

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR NC NC NC 327 392

26 11386 John Day River at Hwy 206, OR 44,000 25.2 NC NA 1,770

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR NC NC NC 103 111

28 3701391 Tualatin River at Rood Bridge Road, OR NC NC NC 1,230 972

29 3701528 Tualatin River at Golf Course Road, OR NC NC NC 561 610

30 3810015 Gales Creek at New Hwy 47, OR NC NC NC 195 221

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 490,000 14.2 43.8 28,900 35,100

32 3820012 Rock Creek at Hwy 8, OR NC NC NC 193 –

33 14211720 Willamette River at Portland, OR 1,020,000 29.3 90.7 28,900 35,100

34 3850006 Dawson Creek at Brookwood, OR NC NC NC 9.66 5.44

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR NC NC NC 10.2 3.36

36 3824072 Bronson Creek at Saltzman, OR NC NC NC 5.23 1.00

37 10332 Willamette River at SP&S Railroad Bridge, OR 527,000 15.2 NC NA 35,100

38 14128910 Columbia River at Warrendale, OR 1,300,000 7.13 5.47 616,000 185,000

39 10411 Deschutes River at Deschutes River Park, OR 70,200 11.0 6.53 27,800 6,450

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

1,760,000 10.0 NC NA 177,000

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 2,940 5.75 6.59 1,150 518

42 12012 Hood River at footbridge downstream of I-84, OR NC NC NC NA 1,030

43 11489 Umatilla River at Westland Road (Hermiston), OR 25,700 47.7 NC NA 545

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 5,350,000 23.4 21.0 658,000 232,000

45 27D090 East Fork Lewis River near Dollar Corner, WA 10,200 13.4 65.2 405 771

46 32A070 Walla Walla River near Touchet, WA 59,100 105 35.0 4,370 572

47 13353200 Snake River at Burbank, WA 447,000 9.72 4.40 262,000 46,600

48 37A090 Yakima River at Kiona, WA 137,000 36.9 24.4 14,500 3,770

49 12510500 Yakima River at Kiona, WA 171,000 46.1 30.4 14,500 3,770

50 12505450 Granger Drain at Granger, WA 6,630 166 107 160 40.4

Table A6. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 2000.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; ton/d, ton per day; ton/yr, ton per year; mg/L, milligram per liter; ton/mi2/yr, ton per square mile per year; km2, square kilometer; ft3/s, cubic foot per 

second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 97
Map 

index 

No.

Site 

No. Site name Flux

(ton/d)

Variance

(ton/d)

Lower 95

(ton/d)

Upper 95

(ton/d)

SEP

(ton/d)

Number 

of

 days

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 906 2,450 805 1,020 54.2 366

52 13351000 Palouse River at Hooper, WA 363 3,360 189 634 115 366

53 34A070 Palouse River at Hooper, WA 254 2,640 144 418 70.5 366

54 41A070 Crab Creek near Beverly, WA NA NA NA NA NA –

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA 65.7 898 24.7 143 31.0 366

56 13A060 Deschutes River at East Street Bridge, WA 69.9 353 36.2 123 22.3 366

57 10A070 Puyallup River at Meridian Street, WA 3,760 4,760,000 807 11,200 2,840 366

58 12108500 Newaukum Creek near Black Diamond, WA NA NA NA NA NA –

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 7.35 3.16 3.38 14.0 2.76 366

60 12061500 Skokomish River near Potlatch, WA NA NA NA NA NA –

61 16A070 Skokomish River near Potlatch, WA 450 37,300 157 1,030 229 366

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NA NA NA NA NA –

63 09A190 Green River at Kanaskat, WA 38.5 60.2 22.8 60.8 9.76 366

64 45A070 Wenatchee River at Wenatchee, WA 127 325 90.8 174 21.2 366

65 12113375 Springbrook Creek at Tukwila, WA NA NA NA NA NA –

66 09A080 Green River at Tukwila, WA 164 944 105 246 36.3 366

67 12113390 Duwamish River at Golf Course at Tukwila, WA 267 2,060 172 397 57.7 366

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

16.3 18.5 6.90 32.9 6.77 366

69 46A070 Entiat River near Entiat, WA 18.1 5.01 13.5 23.7 2.60 366

70 45A110 Wenatchee River near Leavenworth, WA 66.9 75.1 48.9 89.2 10.3 366

71 16C090 Duckabush River near Brinnon, WA 19.3 145 4.38 56.0 14.0 366

72 12128000 Thorton Creek near Seattle, WA 1.04 .04 .64 1.61 .25 366

73 54A120 Spokane River at Riverside State Park, WA 201 1,460 125 308 46.8 366

74 07D050 Snoqualmie River near Monroe, WA 385 3,780 256 559 77.6 366

75 07C070 Skykomish River at Monroe, WA 287 4,100 159 478 82.0 366

76 07A090 Snohomish River at Snohomish, WA 899 14,600 641 1,230 150 366

77 53A070 Columbia River at Grand Coulee, WA 393 531 344 447 26.3 366

78 48A070 Methow River near Pateros, WA 32.9 13.2 25.1 42.4 4.41 366

79 49A070 Okanogan River at Malott, WA 242 365 200 291 23.3 366

80 48A140 Methow River at Twisp, WA 22.3 6.44 16.8 29.0 3.13 366

81 03A060 Skagit River near Mount Vernon, WA 3,700 1,450,000 1,540 7,550 1,570 366

82 03B050 Samish River near Burlington, WA 31.1 43.1 18.5 49.2 7.89 366

83 12213140 Nooksack River at Brennan, WA NA NA NA NA NA –

84 01A050 Nooksack River at Brennan, WA 2,300 162,000 1,480 3,410 496 366

85 12210700 Nooksack River at North Cedarville, WA NA NA NA NA NA –

86 12400520 Columbia River at Northport, WA 928 11,600 728 1,170 112 366

87 61A070 Columbia River at Northport, WA 729 1,660 643 824 46.1 366

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NA NA NA NA NA –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 17.6 3.25 13.8 22.1 2.12 366

90 13094000 Snake River near Buhl, ID 362 4,470 247 514 68.5 366

91 13154500 Snake River at King Hill, ID 354 581 306 409 26.3 366

92 13203510 Boise River below Diversion Dam near Boise, ID 16.8 5.09 12.5 22.2 2.47 366

93 13206000 Boise River at Glenwood, ID 22.1 9.21 16.1 29.6 3.45 366

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID NA NA NA NA NA –

95 12414900 St. Maries River near Santa, ID NA NA NA NA NA –

96 12414500 St. Joe River at Calder, ID 36.2 60.3 23.0 54.4 8.04 366

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 34.6 21.0 19.0 58.1 10.1 366

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 102 628 44.5 201 40.7 366

99 12419000 Spokane River near Post Falls, ID 36.5 10.2 30.0 43.9 3.56 366

100 13010065 Snake River at Flagg Ranch, WY 137 593 82.0 215 34.1 366

Table A6. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 2000.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; ton/d, ton per day; ton/yr, ton per year; mg/L, milligram per liter; ton/mi2/yr, ton per square mile per year; km2, square kilometer; ft3/s, cubic foot per 

second; NA, not available; NC, not calculated; –, not applicable]

98 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Load

(ton/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(ton/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow 

(ft3/s)

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 332,000 2.80 12.6 67,800 120,000

52 13351000 Palouse River at Hooper, WA 133,000 183 53.8 6,380 736

53 34A070 Palouse River at Hooper, WA 93,100 128 37.7 6,380 736

54 41A070 Crab Creek near Beverly, WA NC NC NC 999 –

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA 24,100 117 33.7 1,840 209

56 13A060 Deschutes River at East Street Bridge, WA 25,600 57.8 248 267 449

57 10A070 Puyallup River at Meridian Street, WA 1,380,000 407 1,490 2,380 3,430

58 12108500 Newaukum Creek near Black Diamond, WA NC NC NC 71.1 61.9

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 2,690 44.2 5.85 1,190 61.6

60 12061500 Skokomish River near Potlatch, WA NC NC NC 339 1,310

61 16A070 Skokomish River near Potlatch, WA 165,000 128 1,250 339 1,310

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NC NC NC 173 124

63 09A190 Green River at Kanaskat, WA 14,100 15.0 59.1 616 953

64 45A070 Wenatchee River at Wenatchee, WA 46,600 14.0 35.0 3,440 3,370

65 12113375 Springbrook Creek at Tukwila, WA NC NC NC 51.7 45.6

66 09A080 Green River at Tukwila, WA 60,200 43.6 126 1,240 1,400

67 12113390 Duwamish River at Golf Course at Tukwila, WA 97,800 62.5 211 1,190 1,590

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

5,970 11.3 105 147 535

69 46A070 Entiat River near Entiat, WA 6,610 12.8 15.9 1,070 522

70 45A110 Wenatchee River near Leavenworth, WA 24,500 7.76 36.7 1,720 3,190

71 16C090 Duckabush River near Brinnon, WA 7,080 16.6 106 172 432

72 12128000 Thorton Creek near Seattle, WA 380 36.7 33.6 29.2 10.5

73 54A120 Spokane River at Riverside State Park, WA 73,700 10.6 14.7 13,000 7,030

74 07D050 Snoqualmie River near Monroe, WA 141,000 36.3 206 1,770 3,930

75 07C070 Skykomish River at Monroe, WA 105,000 23.0 137 1,980 4,620

76 07A090 Snohomish River at Snohomish, WA 329,000 31.8 191 4,440 10,500

77 53A070 Columbia River at Grand Coulee, WA 144,000 1.29 12.9 28,900 113,000

78 48A070 Methow River near Pateros, WA 12,000 8.48 6.68 4,660 1,440

79 49A070 Okanogan River at Malott, WA 88,700 30.6 50.9 4,500 2,930

80 48A140 Methow River at Twisp, WA 8,160 6.33 6.15 3,430 1,310

81 03A060 Skagit River near Mount Vernon, WA 1,360,000 78.5 581 6,020 17,500

82 03B050 Samish River near Burlington, WA 11,400 40.1 132 223 288

83 12213140 Nooksack River at Brennan, WA NC NC NC 2,020 4,250

84 01A050 Nooksack River at Brennan, WA 840,000 200 1,140 1,910 4,250

85 12210700 Nooksack River at North Cedarville, WA NC NC NC 1,520 –

86 12400520 Columbia River at Northport, WA 340,000 3.26 5.63 156,000 106,000

87 61A070 Columbia River at Northport, WA 267,000 2.56 4.43 156,000 106,000

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NC NC NC 98.6 –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 6,460 56.9 26.8 623 115

90 13094000 Snake River near Buhl, ID 133,000 28.8 4.50 76,100 4,670

91 13154500 Snake River at King Hill, ID 130,000 13.1 3.60 92,900 9,990

92 13203510 Boise River below Diversion Dam near Boise, ID 6,150 4.80 2.28 6,980 1,300

93 13206000 Boise River at Glenwood, ID 8,090 9.47 2.91 7,180 865

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID NC NC NC 220 231

95 12414900 St. Maries River near Santa, ID NC NC NC 706 391

96 12414500 St. Joe River at Calder, ID 13,300 5.64 12.8 2,680 2,380

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 12,700 21.9 44.3 738 584

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 37,300 18.6 41.4 2,330 2,030

99 12419000 Spokane River near Post Falls, ID 13,400 1.97 3.39 10,200 6,850

100 13010065 Snake River at Flagg Ranch, WY 50,100 60.5 97.6 1,320 839

Table A6. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 2000.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; ton/d, ton per day; ton/yr, ton per year; mg/L, milligram per liter; ton/mi2/yr, ton per square mile per year; km2, square kilometer; ft3/s, cubic foot per 

second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 99
Map 

index 

No.

Site

No. Site name Flux

(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of

days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 1,380 2,870 1,270 1,490 56.5 365

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NA NA NA NA NA –

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NA NA NA NA NA –

4 10386 Middle Fork Willamette River at Jasper Bridge, OR NA NA NA NA NA –

5 10663 Mohawk River at Hill Road, OR NA NA NA NA NA –

6 10376 McKenzie River at Coburg Road, OR NA NA NA NA NA –

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 7,550 232,000 6,610 8,600 508 365

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 767 2,660 666 880 54.8 365

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NA NA NA NA NA –

10 10508 Deschutes River at Lower Bridge, OR 806 7,720 646 993 88.7 365

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 17,000 1,330,000 14,700 19,500 1,230 365

12 11490 Powder River at Hwy 7 (Baker City), OR 121 46.2 107 135 7.28 365

13 11478 John Day River at Service Creek, OR 1,120 11,200 917 1,360 114 365

14 10555 Willamette River at Marion Street (Salem), OR 28,600 2,360,000 25,500 32,000 1,640 365

15 14200400 Little Abiqua Creek near Scotts Mills, OR 48.2 1.29 45.6 50.9 1.34 365

16 14201300 Zollner Creek near Mt. Angel, OR 296 179 266 329 16.1 365

17 10640 Pudding River at Hwy 211 (Woodburn), OR 3,440 98,300 2,850 4,120 326 365

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR NA NA NA NA NA –

19 3701002 Tualatin River at Weiss Bridge, OR 6,070 18,200 5,770 6,380 155 365

20 3840012 Fanno Creek at Durham Road, OR 122 5.88 115 128 3.16 365

21 14206950 Fanno Creek near Durham, OR 120 18.5 111 131 5.20 365

22 3701715 Tualatin River at Cherry Grove, OR 62.3 17.9 53.5 72.2 4.76 365

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 815 263 783 849 17.0 365

24 3701333 Tualatin River at Farmington Bridge Road, OR 4,240 34,200 3,870 4,630 193 365

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 290 147 263 319 14.5 365

26 11386 John Day River at Hwy 206, OR NA NA NA NA NA –

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 59.5 12.8 52.6 67.1 3.68 365

28 3701391 Tualatin River at Rood Bridge Road, OR 1,160 2,840 1,040 1,290 62.3 365

29 3701528 Tualatin River at Golf Course Road, OR 482 381 437 530 23.8 365

30 3810015 Gales Creek at New Hwy 47, OR 139 25.3 127 151 6.14 365

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 63,200 10,900,000 56,600 70,500 3,560 365

32 3820012 Rock Creek at Hwy 8, OR 217 23.0 205 229 6.24 365

33 14211720 Willamette River at Portland, OR 59,500 6,790,000 54,200 65,300 2,840 365

34 3850006 Dawson Creek at Brookwood, OR 11.3 .13 10.4 12.3 .48 365

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR 5.91 .03 5.51 6.33 .21 365

36 3824072 Bronson Creek at Saltzman, OR 1.50 .00 1.39 1.62 .06 365

37 10332 Willamette River at SP&S Railroad Bridge, OR 65,100 35,200,000 54,000 77,800 6,090 365

38 14128910 Columbia River at Warrendale, OR 514,000 996,000,000 453,000 582,000 33,000 365

39 10411 Deschutes River at Deschutes River Park, OR 7,070 172,000 6,270 7,950 430 365

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

266,000 877,000,000 212,000 331,000 30,400 365

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 498 2,180 405 607 51.6 365

42 12012 Hood River at footbridge downstream of I-84, OR 917 6,460 764 1,090 83.9 365

43 11489 Umatilla River at Westland Road (Hermiston), OR 3,070 33,700 2,710 3,470 194 365

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 316,000 234,000,000 286,000 349,000 16,000 365

45 27D090 East Fork Lewis River near Dollar Corner, WA 781 836 720 847 32.4 365

46 32A070 Walla Walla River near Touchet, WA 788 1,090 718 864 37.2 365

47 13353200 Snake River at Burbank, WA NA NA NA NA NA –

48 37A090 Yakima River at Kiona, WA 9,990 210,000 9,060 11,000 491 365

49 12510500 Yakima River at Kiona, WA 10,500 203,000 9,640 11,500 476 365

50 12505450 Granger Drain at Granger, WA 644 303 609 680 18.1 365

Table A7. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 2001.

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

100 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Load

(lb/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(lb/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow 

(ft3/s)

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 502,000 2.27 NC NA 112

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NC NC NC 880 67.1

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NC NC NC 12,000 94.6

4 10386 Middle Fork Willamette River at Jasper Bridge, OR NC NC NC 3,490 2,400

5 10663 Mohawk River at Hill Road, OR NC NC NC 460 193

6 10376 McKenzie River at Coburg Road, OR NC NC NC NA 2,900

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 2,760,000 .24 803 8,890 5,820

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 280,000 .64 673 1,080 221

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NC NC NC 239 260

10 10508 Deschutes River at Lower Bridge, OR 294,000 .17 140 5,440 883

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 6,210,000 .47 1,280 12,600 6,750

12 11490 Powder River at Hwy 7 (Baker City), OR 44,000 .37 126 902 60.3

13 11478 John Day River at Service Creek, OR 410,000 .24 79.9 13,300 877

14 10555 Willamette River at Marion Street (Salem), OR 10,400,000 .47 1,420 19,100 11,200

15 14200400 Little Abiqua Creek near Scotts Mills, OR 17,600 .49 1,790 25.5 18.1

16 14201300 Zollner Creek near Mt. Angel, OR 108,000 11.4 7,210 38.9 4.83

17 10640 Pudding River at Hwy 211 (Woodburn), OR 1,260,000 1.91 3,980 818 334

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR NC NC NC 1,760 1,500

19 3701002 Tualatin River at Weiss Bridge, OR 2,210,000 2.62 3,120 1,840 429

20 3840012 Fanno Creek at Durham Road, OR 44,400 1.17 1,420 80.7 19.3

21 14206950 Fanno Creek near Durham, OR 44,000 1.16 1,410 80.7 19.3

22 3701715 Tualatin River at Cherry Grove, OR 22,800 .18 606 97.3 65.5

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 298,000 3.91 5,550 139 38.7

24 3701333 Tualatin River at Farmington Bridge Road, OR 1,550,000 2.58 2,750 1,460 305

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 106,000 .41 839 327 130

26 11386 John Day River at Hwy 206, OR NC NC NC NA 916

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 21,700 .22 545 103 50.0

28 3701391 Tualatin River at Rood Bridge Road, OR 424,000 .93 894 1,230 231

29 3701528 Tualatin River at Golf Course Road, OR 176,000 .58 811 561 155

30 3810015 Gales Creek at New Hwy 47, OR 50,700 .43 674 195 60.6

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 23,100,000 .73 2,070 28,900 16,000

32 3820012 Rock Creek at Hwy 8, OR 79,200 1.06 1,060 193 37.8

33 14211720 Willamette River at Portland, OR 21,700,000 .69 1,940 28,900 16,000

34 3850006 Dawson Creek at Brookwood, OR 4,120 1.16 1,100 9.7 1.80

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR 2,160 .82 547 10.2 1.34

36 3824072 Bronson Creek at Saltzman, OR 548 1.39 272 5.23 0.20

37 10332 Willamette River at SP&S Railroad Bridge, OR 23,800,000 .75 NC NA 16,000

38 14128910 Columbia River at Warrendale, OR 188,000,000 .81 NC 616,000 118,000

39 10411 Deschutes River at Deschutes River Park, OR 2,580,000 .27 241 27,800 4,850

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

97,200,000 .44 NC NA 112,000

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 182,000 .27 409 1,150 343

42 12012 Hood River at footbridge downstream of I-84, OR 335,000 .31 NC NA 541

43 11489 Umatilla River at Westland Road (Hermiston), OR 1,120,000 1.53 NC NA 372

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 115,000,000 .42 454 658,000 140,000

45 27D090 East Fork Lewis River near Dollar Corner, WA 285,000 .35 1,820 405 411

46 32A070 Walla Walla River near Touchet, WA 288,000 .36 171 4,370 409

47 13353200 Snake River at Burbank, WA NC NC NC 262,000 24,700

48 37A090 Yakima River at Kiona, WA 3,650,000 1.21 650 14,500 1,530

49 12510500 Yakima River at Kiona, WA 3,850,000 1.28 686 14,500 1,530

50 12505450 Granger Drain at Granger, WA 235,000 4.32 3,810 160 27.6

Table A7. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 2001.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 101
Map 

index 

No.

Site

No. Site name Flux

(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of

days

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 92,200 91,000,000 74,600 113,000 9,740 365

52 13351000 Palouse River at Hooper, WA 4,180 53,700 3,690 4,720 264 365

53 34A070 Palouse River at Hooper, WA 3,910 76,900 3,350 4,540 305 365

54 41A070 Crab Creek near Beverly, WA 2,570 4,460 2,430 2,720 72.5 365

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NA NA NA NA NA –

56 13A060 Deschutes River at East Street Bridge, WA 695 240 663 729 16.9 365

57 10A070 Puyallup River at Meridian Street, WA 3,470 17,900 3,190 3,760 146 365

58 12108500 Newaukum Creek near Black Diamond, WA NA NA NA NA NA –

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 250 54.3 234 265 7.95 365

60 12061500 Skokomish River near Potlatch, WA NA NA NA NA NA –

61 16A070 Skokomish River near Potlatch, WA 259 189 230 291 15.6 365

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NA NA NA NA NA –

63 09A190 Green River at Kanaskat, WA 474 510 424 528 26.5 365

64 45A070 Wenatchee River at Wenatchee, WA 1,510 3,610 1,390 1,650 66.3 365

65 12113375 Springbrook Creek at Tukwila, WA NA NA NA NA NA –

66 09A080 Green River at Tukwila, WA 2,170 6,490 2,000 2,350 88.1 365

67 12113390 Duwamish River at Golf Course at Tukwila, WA 2,930 17,000 2,660 3,220 143 365

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

NA NA NA NA NA –

69 46A070 Entiat River near Entiat, WA 166 169 140 195 13.8 365

70 45A110 Wenatchee River near Leavenworth, WA 660 1,890 563 770 52.9 365

71 16C090 Duckabush River near Brinnon, WA 55.2 13.8 46.7 64.8 4.63 365

72 12128000 Thorton Creek near Seattle, WA 68.8 4.01 64.3 73.4 2.31 365

73 54A120 Spokane River at Riverside State Park, WA 15,400 576,000 13,900 17,000 802 365

74 07D050 Snoqualmie River near Monroe, WA 4,790 20,400 4,490 5,110 157 365

75 07C070 Skykomish River at Monroe, WA 2,350 5,900 2,180 2,530 90.6 365

76 07A090 Snohomish River at Snohomish, WA 10,900 136,000 10,100 11,800 427 365

77 53A070 Columbia River at Grand Coulee, WA 72,200 9,010,000 66,000 78,800 3,260 365

78 48A070 Methow River near Pateros, WA 600 594 549 653 26.5 365

79 49A070 Okanogan River at Malott, WA 1,140 2,190 1,040 1,250 53.1 365

80 48A140 Methow River at Twisp, WA 428 345 388 470 21.1 365

81 03A060 Skagit River near Mount Vernon, WA 7,130 115,000 6,420 7,890 373 365

82 03B050 Samish River near Burlington, WA 769 251 735 804 17.4 365

83 12213140 Nooksack River at Brennan, WA NA NA NA NA NA –

84 01A050 Nooksack River at Brennan, WA 6,740 74,400 6,180 7,350 299 365

85 12210700 Nooksack River at North Cedarville, WA NA NA NA NA NA –

86 12400520 Columbia River at Northport, WA NA NA NA NA NA –

87 61A070 Columbia River at Northport, WA 54,300 2,300,000 51,200 57,500 1,620 365

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NA NA NA NA NA –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 1,050 502 1,000 1,100 24.5 365

90 13094000 Snake River near Buhl, ID 29,700 741,000 27,900 31,500 897 365

91 13154500 Snake River at King Hill, ID 66,500 1,210,000 64,100 68,900 1,230 365

92 13203510 Boise River below Diversion Dam near Boise, ID 947 4,600 818 1,090 69.5 365

93 13206000 Boise River at Glenwood, ID 1,620 4,680 1,480 1,770 72.1 365

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 133 478 91.8 185 24.0 365

95 12414900 St. Maries River near Santa, ID NA NA NA NA NA –

96 12414500 St. Joe River at Calder, ID NA NA NA NA NA –

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 472 606 422 525 26.3 365

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID NA NA NA NA NA –

99 12419000 Spokane River near Post Falls, ID 2,590 41,900 2,190 3,040 216 365

100 13010065 Snake River at Flagg Ranch, WY 525 7,000 339 776 112 365

Table A7. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 2001.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

102 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Load

(lb/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(lb/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow 

(ft3/s)

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 33,700,000 0.21 1,290 67,800 80,700

52 13351000 Palouse River at Hooper, WA 1,530,000 2.96 620 6,380 262

53 34A070 Palouse River at Hooper, WA 1,430,000 2.77 580 6,380 262

54 41A070 Crab Creek near Beverly, WA 939,000 2.37 2,430 999 201

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NC NC NC 1,840 –

56 13A060 Deschutes River at East Street Bridge, WA 254,000 .72 2,460 267 178

57 10A070 Puyallup River at Meridian Street, WA 1,270,000 .27 1,380 2,380 2,350

58 12108500 Newaukum Creek near Black Diamond, WA NC NC NC 71.1 33.7

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 91,100 1.72 199 1,190 26.8

60 12061500 Skokomish River near Potlatch, WA NC NC NC 339 646

61 16A070 Skokomish River near Potlatch, WA 94,600 .07 722 339 646

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NC NC NC 173 71.9

63 09A190 Green River at Kanaskat, WA 173,000 .15 728 616 573

64 45A070 Wenatchee River at Wenatchee, WA 552,000 .18 416 3,440 1,590

65 12113375 Springbrook Creek at Tukwila, WA NC NC NC 51.7 29.7

66 09A080 Green River at Tukwila, WA 793,000 .47 1,660 1,240 851

67 12113390 Duwamish River at Golf Course at Tukwila, WA 1,070,000 .56 2,320 1,190 965

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

NC NC NC 147 300

69 46A070 Entiat River near Entiat, WA 60,600 .15 146 1,070 209

70 45A110 Wenatchee River near Leavenworth, WA 241,000 .08 363 1,720 1,570

71 16C090 Duckabush River near Brinnon, WA 20,100 .04 303 172 229

72 12128000 Thorton Creek near Seattle, WA 25,100 1.57 2,220 29.2 8.11

73 54A120 Spokane River at Riverside State Park, WA 5,620,000 .95 1,120 13,000 3,010

74 07D050 Snoqualmie River near Monroe, WA 1,750,000 .36 2,560 1,770 2,440

75 07C070 Skykomish River at Monroe, WA 858,000 .16 1,120 1,980 2,690

76 07A090 Snohomish River at Snohomish, WA 3,990,000 .32 2,330 4,440 6,310

77 53A070 Columbia River at Grand Coulee, WA 26,400,000 .18 2,360 28,900 74,400

78 48A070 Methow River near Pateros, WA 219,000 .19 122 4,660 576

79 49A070 Okanogan River at Malott, WA 418,000 .16 240 4,500 1,330

80 48A140 Methow River at Twisp, WA 156,000 .16 118 3,430 508

81 03A060 Skagit River near Mount Vernon, WA 2,600,000 .13 1,120 6,020 10,500

82 03B050 Samish River near Burlington, WA 281,000 .90 3,260 223 158

83 12213140 Nooksack River at Brennan, WA NC NC NC 2,020 2,540

84 01A050 Nooksack River at Brennan, WA 2,460,000 .49 3,340 1,910 2,540

85 12210700 Nooksack River at North Cedarville, WA NC NC NC 1,520 –

86 12400520 Columbia River at Northport, WA NC NC NC 156,000 74,000

87 61A070 Columbia River at Northport, WA 19,800,000 .14 329 156,000 74,000

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NC NC NC 98.6 –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 383,000 2.50 1,590 623 77.7

90 13094000 Snake River near Buhl, ID 10,800,000 2.56 368 76,100 2,150

91 13154500 Snake River at King Hill, ID 24,300,000 1.68 676 92,900 7,330

92 13203510 Boise River below Diversion Dam near Boise, ID 346,000 .21 128 6,980 817

93 13206000 Boise River at Glenwood, ID 592,000 .60 213 7,180 503

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 48,400 .19 570 220 132

95 12414900 St. Maries River near Santa, ID NC NC NC 706 155

96 12414500 St. Joe River at Calder, ID NC NC NC 2,680 1,130

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 172,000 .38 604 738 232

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID NC NC NC 2,330 763

99 12419000 Spokane River near Post Falls, ID 945,000 .18 241 10,200 2,690

100 13010065 Snake River at Flagg Ranch, WY 192,000 .18 375 1,320 528

Table A7. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

nitrogen in the Columbia River and Puget Sound basins, water year 2001.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 103
Map 

index 

No.

Site 

No. Site name Flux

(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 137 95.7 118 158 10.3 365

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

29.5 2.31 26.5 32.8 1.60 365

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

128 34.4 116 141 6.43 365

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 332 146 307 357 12.8 365

5 10663 Mohawk River at Hill Road, OR 18.8 1.18 16.6 21.1 1.15 365

6 10376 McKenzie River at Coburg Road, OR 600 393 560 643 21.1 365

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 1,470 3,330 1,350 1,600 64.2 365

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 87.1 23.9 77.2 97.8 5.27 365

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR 58.0 7.77 52.6 63.8 2.85 365

10 10508 Deschutes River at Lower Bridge, OR 364 124 342 388 11.8 365

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 2,270 10,300 2,060 2,490 108 365

12 11490 Powder River at Hwy 7 (Baker City), OR 16.7 1.91 14.0 19.9 1.50 365

13 11478 John Day River at Service Creek, OR 231 160 202 262 15.5 365

14 10555 Willamette River at Marion Street (Salem), OR 3,050 14,600 2,800 3,310 130 365

15 14200400 Little Abiqua Creek near Scotts Mills, OR 1.75 .03 1.41 2.15 0.19 365

16 14201300 Zollner Creek near Mt. Angel, OR 6.01 .09 5.31 6.77 0.37 365

17 10640 Pudding River at Hwy 211 (Woodburn), OR 196 306 163 234 18.3 365

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR 160 129 139 185 11.8 365

19 3701002 Tualatin River at Weiss Bridge, OR 313 159 285 342 14.7 365

20 3840012 Fanno Creek at Durham Road, OR 14.3 .14 13.3 15.3 .50 365

21 14206950 Fanno Creek near Durham, OR 15.2 .59 13.7 16.8 .79 365

22 3701715 Tualatin River at Cherry Grove, OR 6.17 .23 5.19 7.28 .54 365

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 18.8 .37 17.5 20.2 .67 365

24 3701333 Tualatin River at Farmington Bridge Road, OR 366 846 309 431 31.2 365

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 26.1 1.40 23.4 28.9 1.41 365

26 11386 John Day River at Hwy 206, OR 213 541 164 270 27.1 365

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 6.47 .62 4.96 8.29 0.85 365

28 3701391 Tualatin River at Rood Bridge Road, OR 96.8 10.9 89.5 104 3.81 365

29 3701528 Tualatin River at Golf Course Road, OR 38.3 2.50 34.8 42.1 1.86 365

30 3810015 Gales Creek at New Hwy 47, OR 11.8 .17 10.8 12.8 .50 365

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 6,320 28,500 5,970 6,680 182 365

32 3820012 Rock Creek at Hwy 8, OR 28.5 .18 27.5 29.6 .55 365

33 14211720 Willamette River at Portland, OR 5,850 72,700 5,300 6,440 292 365

34 3850006 Dawson Creek at Brookwood, OR 1.12 .00 1.06 1.18 .03 365

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR .70 .00 .66 .74 .02 365

36 3824072 Bronson Creek at Saltzman, OR .16 .00 .14 .17 .01 365

37 10332 Willamette River at SP&S Railroad Bridge, OR 6,610 66,900 6,100 7,150 268 365

38 14128910 Columbia River at Warrendale, OR 14,800 2,800,000 11,700 18,500 1,740 365

39 10411 Deschutes River at Deschutes River Park, OR 2,230 17,300 1,970 2,520 140 365

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

21,900 2,050,000 19,200 24,900 1,460 365

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 91.0 24.6 80.5 102 5.59 365

42 12012 Hood River at footbridge downstream of I-84, OR 191 1,370 122 285 41.8 365

43 11489 Umatilla River at Westland Road (Hermiston), OR 205 216 176 238 16.0 365

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 26,800 4,550,000 22,600 31,500 2,270 365

45 27D090 East Fork Lewis River near Dollar Corner, WA 42.5 18.8 33.6 53.0 4.95 365

46 32A070 Walla Walla River near Touchet, WA 125 38.7 112 140 6.96 365

47 13353200 Snake River at Burbank, WA NA NA NA NA NA NA

48 37A090 Yakima River at Kiona, WA 930 1,210 858 1,010 38.1 365

49 12510500 Yakima River at Kiona, WA 970 2,330 874 1,070 50.8 365

50 12505450 Granger Drain at Granger, WA 33.6 3.17 30.0 37.4 1.88 365

Table A8. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound Basins, water year 2001.

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

104 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site No. Site name Load

(lb/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(lb/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow 

(ft3/s)

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 50,000 0.23 NC NA 112

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

10,800 .08 31.7 880 67.1

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

46,700 .25 10.1 12,000 94.6

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 121,000 .03 89.9 3,490 2,400

5 10663 Mohawk River at Hill Road, OR 6,850 .02 38.5 460 193

6 10376 McKenzie River at Coburg Road, OR 219,000 .04 NC NA 2,900

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 537,000 .05 157 8,890 5,820

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 31,800 .07 76.4 1,080 221

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR 21,200 .04 229 239 260

10 10508 Deschutes River at Lower Bridge, OR 133,000 .08 63.3 5,440 883

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 827,000 .06 171 12,600 6,750

12 11490 Powder River at Hwy 7 (Baker City), OR 6,110 .05 17.5 902 60.3

13 11478 John Day River at Service Creek, OR 84,200 .05 16.4 13,300 877

14 10555 Willamette River at Marion Street (Salem), OR 1,110,000 .05 151 19,100 11,200

15 14200400 Little Abiqua Creek near Scotts Mills, OR 640 .02 65.0 25.5 18.1

16 14201300 Zollner Creek near Mt. Angel, OR 2,190 .23 146 38.9 4.83

17 10640 Pudding River at Hwy 211 (Woodburn), OR 71,500 .11 226 818 334

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR 58,500 .02 86.0 1,760 1,500

19 3701002 Tualatin River at Weiss Bridge, OR 114,000 .14 161 1,840 429

20 3840012 Fanno Creek at Durham Road, OR 5,210 .14 167 80.7 19.3

21 14206950 Fanno Creek near Durham, OR 5,550 .15 178 80.7 19.3

22 3701715 Tualatin River at Cherry Grove, OR 2,250 .02 60.0 97.3 65.5

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 6,870 .09 128 139 38.7

24 3701333 Tualatin River at Farmington Bridge Road, OR 134,000 .22 237 1,460 305

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR 9,510 .04 75.4 327 130

26 11386 John Day River at Hwy 206, OR 77,600 .04 NC NA 916

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR 2,360 .02 59.2 103 50.0

28 3701391 Tualatin River at Rood Bridge Road, OR 35,300 .08 74.6 1,230 231

29 3701528 Tualatin River at Golf Course Road, OR 14,000 .05 64.6 561 155

30 3810015 Gales Creek at New Hwy 47, OR 4,310 .04 57.3 195 60.6

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 2,310,000 .07 207 28,900 16,000

32 3820012 Rock Creek at Hwy 8, OR 10,400 .14 140 193 37.8

33 14211720 Willamette River at Portland, OR 2,140,000 .07 191 28,900 16,000

34 3850006 Dawson Creek at Brookwood, OR 409 .12 110 9.7 1.80

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR 257 .10 65.1 10.2 1.34

36 3824072 Bronson Creek at Saltzman, OR 57.1 .15 28.3 5.23 .20

37 10332 Willamette River at SP&S Railroad Bridge, OR 2,410,000 .08 NC NA 16,000

38 14128910 Columbia River at Warrendale, OR 5,410,000 .02 NC 616,000 118,000

39 10411 Deschutes River at Deschutes River Park, OR 815,000 .09 76.0 27,800 4,850

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

8,010,000 .04 NC NA 112,000

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 33,200 .05 74.6 1,150 343

42 12012 Hood River at footbridge downstream of I-84, OR 69,600 .07 NC NA 541

43 11489 Umatilla River at Westland Road (Hermiston), OR 74,900 .10 NC NA 372

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 9,780,000 .04 38.5 658,000 140,000

45 27D090 East Fork Lewis River near Dollar Corner, WA 15,500 .02 99.2 405 411

46 32A070 Walla Walla River near Touchet, WA 45,800 .06 27.2 4,370 409

47 13353200 Snake River at Burbank, WA NC NC NC 262,000 24,700

48 37A090 Yakima River at Kiona, WA 340,000 .11 60.5 14,500 1,530

49 12510500 Yakima River at Kiona, WA 354,000 .12 63.1 14,500 1,530

50 12505450 Granger Drain at Granger, WA 12,300 .23 199 160 27.6

Table A8. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound Basins, water year 2001.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 105
Map 

index 

No.

Site 

No. Site name Flux

(lb/d)

Variance

(lb/d)

Lower 95

(lb/d)

Upper 95

(lb/d)

SEP

(lb/d)

Number 

of 

days

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 4,370 833,000 2,810 6,490 943 365

52 13351000 Palouse River at Hooper, WA 204 367 163 253 22.9 365

53 34A070 Palouse River at Hooper, WA 245 539 199 299 25.6 365

54 41A070 Crab Creek near Beverly, WA 102 25.0 91.5 113 5.45 365

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NA NA NA NA NA –

56 13A060 Deschutes River at East Street Bridge, WA 36.4 3.30 32.7 40.4 1.97 365

57 10A070 Puyallup River at Meridian Street, WA 1,090 9,110 890 1,320 111 365

58 12108500 Newaukum Creek near Black Diamond, WA NA NA NA NA NA –

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 13.0 .63 11.4 14.8 0.86 365

60 12061500 Skokomish River near Potlatch, WA NA NA NA NA NA –

61 16A070 Skokomish River near Potlatch, WA 85.1 28.7 73.4 98 6.34 365

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NA NA NA NA NA –

63 09A190 Green River at Kanaskat, WA 74.0 27.0 63.0 86.5 6.00 365

64 45A070 Wenatchee River at Wenatchee, WA 138 142 113 168 14.1 365

65 12113375 Springbrook Creek at Tukwila, WA NA NA NA NA NA –

66 09A080 Green River at Tukwila, WA 210 107 188 233 11.7 365

67 12113390 Duwamish River at Golf Course at Tukwila, WA 291 413 247 340 23.7 365

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

8.75 1.77 6.15 12.1 1.52 365

69 46A070 Entiat River near Entiat, WA 22.3 4.88 17.8 27.5 2.47 365

70 45A110 Wenatchee River near Leavenworth, WA 105 132 80.7 134 13.5 365

71 16C090 Duckabush River near Brinnon, WA 13.9 2.27 10.8 17.7 1.77 365

72 12128000 Thorton Creek near Seattle, WA 4.67 .23 3.61 5.95 .60 365

73 54A120 Spokane River at Riverside State Park, WA 821 6,290 666 1,000 85.5 365

74 07D050 Snoqualmie River near Monroe, WA 311 332 272 355 21.1 365

75 07C070 Skykomish River at Monroe, WA 185 200 155 218 16.2 365

76 07A090 Snohomish River at Snohomish, WA 677 2,100 581 786 52.4 365

77 53A070 Columbia River at Grand Coulee, WA 5,310 411,000 4,000 6,910 742 365

78 48A070 Methow River near Pateros, WA 46.9 18.0 37.6 57.7 5.14 365

79 49A070 Okanogan River at Malott, WA 204 191 173 240 17.2 365

80 48A140 Methow River at Twisp, WA 42.4 22.3 32.2 54.9 5.78 365

81 03A060 Skagit River near Mount Vernon, WA 970 4,500 824 1,130 78.9 365

82 03B050 Samish River near Burlington, WA 24.0 3.17 20.4 28.1 1.95 365

83 12213140 Nooksack River at Brennan, WA NA NA NA NA NA –

84 01A050 Nooksack River at Brennan, WA 668 1,830 568 780 54.3 365

85 12210700 Nooksack River at North Cedarville, WA NA NA NA NA NA –

86 12400520 Columbia River at Northport, WA NA NA NA NA NA –

87 61A070 Columbia River at Northport, WA 4,040 208,000 3,160 5,080 490 365

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NA NA NA NA NA –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 32.0 1.04 29.8 34.3 1.16 365

90 13094000 Snake River near Buhl, ID 1,580 14,600 1,340 1,840 127 365

91 13154500 Snake River at King Hill, ID 2,920 11,800 2,690 3,160 120 365

92 13203510 Boise River below Diversion Dam near Boise, ID 74.5 580 38.0 132 24.3 365

93 13206000 Boise River at Glenwood, ID 402 807 346 464 30.2 365

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 5.18 .28 4.00 6.61 .67 365

95 12414900 St. Maries River near Santa, ID 25.5 14.5 18.3 34.6 4.17 365

96 12414500 St. Joe River at Calder, ID 51.3 35.5 39.4 65.8 6.75 365

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 48.2 13.7 40.8 56.6 4.04 365

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 32.8 8.06 25.2 42.0 4.31 365

99 12419000 Spokane River near Post Falls, ID 152 140 128 181 13.5 365

100 13010065 Snake River at Flagg Ranch, WY 126 501 76.0 198 31.2 365

Table A8. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound Basins, water year 2001.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

106 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site No. Site name Load

(lb/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(lb/mi2

/yr)

Drainage 

area

(km2

)

Annual 

mean flow 

(ft3/s)

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 1,590,000 0.01 60.9 67,800 80,700

52 13351000 Palouse River at Hooper, WA 74,600 .14 30.3 6,380 262

53 34A070 Palouse River at Hooper, WA 89,400 .17 36.3 6,380 262

54 41A070 Crab Creek near Beverly, WA 37,100 .09 96.3 999 201

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NC NC NC 1,840 –

56 13A060 Deschutes River at East Street Bridge, WA 13,300 .04 129 267 178

57 10A070 Puyallup River at Meridian Street, WA 398,000 .09 433 2,380 2,350

58 12108500 Newaukum Creek near Black Diamond, WA NC NC NC 71.1 33.7

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 4,760 .09 10.4 1,190 26.8

60 12061500 Skokomish River near Potlatch, WA NC NC NC 339 646

61 16A070 Skokomish River near Potlatch, WA 31,100 .02 237 339 646

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NC NC NC 173 71.9

63 09A190 Green River at Kanaskat, WA 27,000 .02 114 616 573

64 45A070 Wenatchee River at Wenatchee, WA 50,500 .02 38.1 3,440 1,590

65 12113375 Springbrook Creek at Tukwila, WA NC NC NC 51.7 29.7

66 09A080 Green River at Tukwila, WA 76,500 .05 160 1,240 851

67 12113390 Duwamish River at Golf Course at Tukwila, WA 106,000 .06 230 1,190 965

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

3,200 .01 56.3 147 300

69 46A070 Entiat River near Entiat, WA 8,140 .02 19.6 1,070 209

70 45A110 Wenatchee River near Leavenworth, WA 38,200 .01 57.5 1,720 1,570

71 16C090 Duckabush River near Brinnon, WA 5,080 .01 76.5 172 229

72 12128000 Thorton Creek near Seattle, WA 1,710 .11 151 29.2 8.11

73 54A120 Spokane River at Riverside State Park, WA 300,000 .05 59.9 13,000 3,010

74 07D050 Snoqualmie River near Monroe, WA 114,000 .02 166 1,770 2,440

75 07C070 Skykomish River at Monroe, WA 67,400 .01 88.0 1,980 2,690

76 07A090 Snohomish River at Snohomish, WA 247,000 .02 144 4,440 6,310

77 53A070 Columbia River at Grand Coulee, WA 1,940,000 .01 174 28,900 74,400

78 48A070 Methow River near Pateros, WA 17,100 .02 9.5 4,660 576

79 49A070 Okanogan River at Malott, WA 74,500 .03 42.9 4,500 1,330

80 48A140 Methow River at Twisp, WA 15,500 .02 11.7 3,430 508

81 03A060 Skagit River near Mount Vernon, WA 354,000 .02 152 6,020 10,500

82 03B050 Samish River near Burlington, WA 8,760 .03 102 223 158

83 12213140 Nooksack River at Brennan, WA NC NC NC 2,020 2,540

84 01A050 Nooksack River at Brennan, WA 244,000 .05 331 1,910 2,540

85 12210700 Nooksack River at North Cedarville, WA NC NC NC 1,520 –

86 12400520 Columbia River at Northport, WA NC NC NC 156,000 74,000

87 61A070 Columbia River at Northport, WA 1,470,000 .01 24.4 156,000 74,000

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NC NC NC 98.6 –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 11,700 .08 48.5 623 77.7

90 13094000 Snake River near Buhl, ID 576,000 .14 19.6 76,100 2,150

91 13154500 Snake River at King Hill, ID 1,060,000 .07 29.7 92,900 7,330

92 13203510 Boise River below Diversion Dam near Boise, ID 27,200 .02 10.1 6,980 817

93 13206000 Boise River at Glenwood, ID 147,000 .15 52.9 7,180 503

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID 1,890 .01 22.3 220 132

95 12414900 St. Maries River near Santa, ID 9,320 .03 34.2 706 155

96 12414500 St. Joe River at Calder, ID 18,700 .01 18.1 2,680 1,130

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 17,600 .04 61.8 738 232

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 12,000 .01 13.3 2,330 763

99 12419000 Spokane River near Post Falls, ID 55,600 .01 14.2 10,200 2,690

100 13010065 Snake River at Flagg Ranch, WY 46,100 .04 90.1 1,320 528

Table A8. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for total 

phosphorus in the Columbia River and Puget Sound Basins, water year 2001.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; lb/d, pound per day; lb/yr, pound per year; mg/L, milligram per liter; lb/mi2/yr, pound per square mile per year; km2, square kilometer; ft3/s, cubic foot 

per second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 107
Map 

index 

No.

Site 

No. Site name Flux

(ton/d)

Variance

(ton/d)

Lower 95

(ton/d)

Upper 95

(ton/d)

SEP

(ton/d)

Number 

of 

days

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 24.0 7.82 18.7 30.3 2.95 365

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NA NA NA NA NA –

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NA NA NA NA NA –

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 12.8 1.49 10.3 15.6 1.34 365

5 10663 Mohawk River at Hill Road, OR 1.82 .05 1.38 2.36 .25 365

6 10376 McKenzie River at Coburg Road, OR 15.0 2.75 11.9 18.8 1.77 365

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 38.0 8.05 32.1 44.6 3.18 365

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 8.77 1.06 6.63 11.4 1.21 365

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NA NA NA NA NA –

10 10508 Deschutes River at Lower Bridge, OR 5.58 .25 4.60 6.70 .54 365

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 91.0 37.6 77.6 106 7.27 365

12 11490 Powder River at Hwy 7 (Baker City), OR 1.62 .06 1.13 2.24 .28 365

13 11478 John Day River at Service Creek, OR 17.5 4.28 12.9 23.4 2.69 365

14 10555 Willamette River at Marion Street (Salem), OR 156 173 129 187 14.6 365

15 14200400 Little Abiqua Creek near Scotts Mills, OR .19 .00 .14 .25 .03 365

16 14201300 Zollner Creek near Mt. Angel, OR .18 .00 .14 .22 .02 365

17 10640 Pudding River at Hwy 211 (Woodburn), OR 7.43 .48 6.05 9.02 .76 365

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR 5.48 .25 4.47 6.65 .56 365

19 3701002 Tualatin River at Weiss Bridge, OR NA NA NA NA NA –

20 3840012 Fanno Creek at Durham Road, OR NA NA NA NA NA –

21 14206950 Fanno Creek near Durham, OR 1.45 .07 .96 2.11 .29 365

22 3701715 Tualatin River at Cherry Grove, OR NA NA NA NA NA –

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR .72 .00 .59 0.87 .07 365

24 3701333 Tualatin River at Farmington Bridge Road, OR NA NA NA NA NA –

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR NA NA NA NA NA –

26 11386 John Day River at Hwy 206, OR 27.6 18.1 18.2 40.1 5.59 365

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR NA NA NA NA NA –

28 3701391 Tualatin River at Rood Bridge Road, OR NA NA NA NA NA –

29 3701528 Tualatin River at Golf Course Road, OR NA NA NA NA NA –

30 3810015 Gales Creek at New Hwy 47, OR NA NA NA NA NA –

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 228 129 202 256 13.8 365

32 3820012 Rock Creek at Hwy 8, OR NA NA NA NA NA –

33 14211720 Willamette River at Portland, OR 326 323 288 368 20.3 365

34 3850006 Dawson Creek at Brookwood, OR NA NA NA NA NA –

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR NA NA NA NA NA –

36 3824072 Bronson Creek at Saltzman, OR NA NA NA NA NA –

37 10332 Willamette River at SP&S Railroad Bridge, OR 237 208 208 269 15.5 365

38 14128910 Columbia River at Warrendale, OR 904 28,300 617 1,280 169 365

39 10411 Deschutes River at Deschutes River Park, OR 88.6 122 67.7 114 11.8 365

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

1,430 15,700 1,190 1,700 131 365

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 4.26 .53 2.86 6.12 .84 365

42 12012 Hood River at footbridge downstream of I-84, OR 24.0 82.2 8.50 54.3 12.0 365

43 11489 Umatilla River at Westland Road (Hermiston), OR 21.5 6.87 15.8 28.7 3.30 365

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 3,600 68,400 3,070 4,200 288 365

45 27D090 East Fork Lewis River near Dollar Corner, WA 4.09 .18 3.05 5.37 .59 365

46 32A070 Walla Walla River near Touchet, WA 23.4 15.6 15.7 33.5 4.56 365

47 13353200 Snake River at Burbank, WA NA NA NA NA NA –

48 37A090 Yakima River at Kiona, WA 46.8 16.9 38.7 56.1 4.45 365

49 12510500 Yakima River at Kiona, WA 44.9 13.2 37.8 53.0 3.88 365

50 12505450 Granger Drain at Granger, WA 6.60 0.79 4.91 8.67 0.96 365

Table A9. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 2001.

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; ton/d, ton per day; ton/yr, ton per year; mg/L, milligram per liter; ton/mi2/yr, ton per square mile per year; km2, square kilometer; ft3/s, cubic foot per 

second; NA, not available; NC, not calculated; –, not applicable]

108 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Load

(ton/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(ton/mi2

/yr)

Drainage 

area

(ft3

/s)

Annual 

mean flow 

(ft3/s)

1 10729 Owyhee River at Hwy. 201 Bridge (Owyhee), OR 8,750 79.4 NC NA 112

2 MAL113 North Fork Malheur River approximately 2 miles upstream of 

Beulah Reservoir, OR

NC NC NC 880 67.1

3 MAL144 Malheur River at Ford Street (1.1 miles) upstream of Bully 

Creek, OR

NC NC NC 12,000 94.6

4 10386 Middle Fork Willamette River at Jasper Bridge, OR 4,660 1.98 3.46 3,490 2,400

5 10663 Mohawk River at Hill Road, OR 665 3.50 3.74 460 193

6 10376 McKenzie River at Coburg Road, OR 5,490 1.92 NC NA 2,900

7 10355 Willamette River at Hwy 99E (Harrisburg), OR 13,900 2.42 4.04 8,890 5,820

8 11140 Long Tom River at Stow Pit Road (Monroe), OR 3,200 14.7 7.69 1,080 221

9 12657 McKenzie River at Hwy 126 downstream of Clear Lake, OR NC NC NC 239 260

10 10508 Deschutes River at Lower Bridge, OR 2,040 2.34 .97 5,440 883

11 10350 Willamette River at Albany (Eastbound Hwy 20 Bridge), OR 33,200 5.00 6.85 12,600 6,750

12 11490 Powder River at Hwy 7 (Baker City), OR 590 9.96 1.69 902 60.3

13 11478 John Day River at Service Creek, OR 6,410 7.40 1.25 13,300 877

14 10555 Willamette River at Marion Street (Salem), OR 57,000 5.16 7.72 19,100 11,200

15 14200400 Little Abiqua Creek near Scotts Mills, OR 67.6 3.89 6.86 25.5 18.1

16 14201300 Zollner Creek near Mt. Angel, OR 65.7 13.8 4.38 38.9 4.83

17 10640 Pudding River at Hwy 211 (Woodburn), OR 2,710 8.25 8.58 818 334

18 13070 Clackamas River at Mciver Park (Upper Boat Ramp), OR 2,000 1.35 2.94 1,760 1,500

19 3701002 Tualatin River at Weiss Bridge, OR NC NC NC 1840 429

20 3840012 Fanno Creek at Durham Road, OR NC NC NC 80.7 19.3

21 14206950 Fanno Creek near Durham, OR 529 27.9 17.0 80.7 19.3

22 3701715 Tualatin River at Cherry Grove, OR NC NC NC 97.3 65.5

23 11321 Johnson Creek at SE 17th Avenue (Portland), OR 262 6.90 4.89 139 38.7

24 3701333 Tualatin River at Farmington Bridge Road, OR NC NC NC 1460 305

25 3701612 Tualatin River at Springhill Road Bridge (Dilley), OR NC NC NC 327 130

26 11386 John Day River at Hwy 206, OR 10,100 11.2 NC NA 916

27 3805048 Scoggins Creek below Hagg Lake at Stimson Bridge, OR NC NC NC 103 50.0

28 3701391 Tualatin River at Rood Bridge Road, OR NC NC NC 1,230 231

29 3701528 Tualatin River at Golf Course Road, OR NC NC NC 561 155

30 3810015 Gales Creek at New Hwy 47, OR NC NC NC 195 60.6

31 10611 Willamette River at Hawthorne Bridge (Portland), OR 83,200 5.28 7.45 28,900 16,000

32 3820012 Rock Creek at Hwy 8, OR NC NC NC 193 37.8

33 14211720 Willamette River at Portland, OR 119,000 7.55 10.7 28,900 16,000

34 3850006 Dawson Creek at Brookwood, OR NC NC NC 9.7 1.80

35 3824020 Bronson Creek at Bronson Park downstream of Sunset Hwy, OR NC NC NC 10.2 1.34

36 3824072 Bronson Creek at Saltzman, OR NC NC NC 5.23 .20

37 10332 Willamette River at SP&S Railroad Bridge, OR 86,500 5.49 NC NA 16,000

38 14128910 Columbia River at Warrendale, OR 330,000 2.84 1.39 616,000 118,000

39 10411 Deschutes River at Deschutes River Park, OR 32,300 6.77 3.02 27,800 4,850

40 10616 Columbia River at Marker #47 (upstream of Willamette River), 

OR

521,000 4.73 NC NA 112,000

41 10406 Umatilla River at Hwy 11 (Pendleton), OR 1,560 4.60 3.49 1,150 343

42 12012 Hood River at footbridge downstream of I-84, OR 8,770 16.4 NC NA 541

43 11489 Umatilla River at Westland Road (Hermiston), OR 7,850 21.4 NC NA 372

44 14246900 Columbia River at Beaver Army Terminal near Quincy, OR 1,320,000 9.53 5.18 658,000 140,000

45 27D090 East Fork Lewis River near Dollar Corner, WA 1,490 3.69 9.6 405 411

46 32A070 Walla Walla River near Touchet, WA 8,530 21.2 5.06 4,370 409

47 13353200 Snake River at Burbank, WA NC NC NC 262000 24,700

48 37A090 Yakima River at Kiona, WA 17,100 11.3 3.04 14,500 1,530

49 12510500 Yakima River at Kiona, WA 16,400 10.9 2.92 14,500 1,530

50 12505450 Granger Drain at Granger, WA 2,410 88.7 39.0 160 27.6

Table A9. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 2001.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; ton/d, ton per day; ton/yr, ton per year; mg/L, milligram per liter; ton/mi2/yr, ton per square mile per year; km2, square kilometer; ft3/s, cubic foot per 

second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 109
Map 

index 

No.

Site 

No. Site name Flux

(ton/d)

Variance

(ton/d)

Lower 95

(ton/d)

Upper 95

(ton/d)

SEP

(ton/d)

Number 

of 

days

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 511 2,340 421 616 49.7 365

52 13351000 Palouse River at Hooper, WA 20.8 9.57 13.0 31.7 4.82 365

53 34A070 Palouse River at Hooper, WA 21.5 9.74 14.6 30.5 4.09 365

54 41A070 Crab Creek near Beverly, WA 24.2 3.02 20.7 28.2 1.91 365

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NA NA NA NA NA –

56 13A060 Deschutes River at East Street Bridge, WA 1.92 .01 1.65 2.22 .14 365

57 10A070 Puyallup River at Meridian Street, WA 489 5,380 305 743 112 365

58 12108500 Newaukum Creek near Black Diamond, WA NA NA NA NA NA –

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA .29 0.00 .21 0.41 .05 365

60 12061500 Skokomish River near Potlatch, WA NA NA NA NA NA –

61 16A070 Skokomish River near Potlatch, WA 11.6 1.19 8.49 15.6 1.81 365

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NA NA NA NA NA –

63 09A190 Green River at Kanaskat, WA 5.09 .10 4.19 6.12 .49 365

64 45A070 Wenatchee River at Wenatchee, WA 36.2 22.2 25.2 50.5 6.47 365

65 12113375 Springbrook Creek at Tukwila, WA NA NA NA NA NA –

66 09A080 Green River at Tukwila, WA 30.9 3.60 26.1 36.3 2.60 365

67 12113390 Duwamish River at Golf Course at Tukwila, WA 57.2 34.6 44.6 72.2 7.04 365

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

1.88 .07 1.21 2.79 .40 365

69 46A070 Entiat River near Entiat, WA 3.63 .18 2.62 4.91 .59 365

70 45A110 Wenatchee River near Leavenworth, WA 21.0 5.81 15.0 28.5 3.44 365

71 16C090 Duckabush River near Brinnon, WA 1.65 .04 1.00 2.57 .40 365

72 12128000 Thorton Creek near Seattle, WA .65 .01 .39 1.02 .16 365

73 54A120 Spokane River at Riverside State Park, WA 44.9 40.7 30.1 64.4 8.77 365

74 07D050 Snoqualmie River near Monroe, WA 78.9 20.1 65.9 93.6 7.08 365

75 07C070 Skykomish River at Monroe, WA 41.9 12.6 33.4 51.8 4.71 365

76 07A090 Snohomish River at Snohomish, WA 165 122 138 196 14.6 365

77 53A070 Columbia River at Grand Coulee, WA 209 202 180 241 15.6 365

78 48A070 Methow River near Pateros, WA 7.46 .62 5.45 9.96 1.15 365

79 49A070 Okanogan River at Malott, WA 64.5 22.2 51.9 79.2 6.99 365

80 48A140 Methow River at Twisp, WA 5.06 .26 3.64 6.87 .83 365

81 03A060 Skagit River near Mount Vernon, WA 385 1,310 307 477 43.4 365

82 03B050 Samish River near Burlington, WA 6.36 .45 4.87 8.16 .84 365

83 12213140 Nooksack River at Brennan, WA NA NA NA NA NA –

84 01A050 Nooksack River at Brennan, WA 329 512 259 412 38.9 365

85 12210700 Nooksack River at North Cedarville, WA NA NA NA NA NA –

86 12400520 Columbia River at Northport, WA NA NA NA NA NA –

87 61A070 Columbia River at Northport, WA 380 413 337 427 23.1 365

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NA NA NA NA NA –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 5.21 .20 4.31 6.25 .49 365

90 13094000 Snake River near Buhl, ID 108 306 77.2 147 18.0 365

91 13154500 Snake River at King Hill, ID 190 158 165 219 13.7 365

92 13203510 Boise River below Diversion Dam near Boise, ID 10.4 2.18 7.65 13.9 1.59 365

93 13206000 Boise River at Glenwood, ID 6.70 .71 5.10 8.65 .91 365

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID NA NA NA NA NA –

95 12414900 St. Maries River near Santa, ID NA NA NA NA NA –

96 12414500 St. Joe River at Calder, ID 11.7 4.77 7.87 16.9 2.30 365

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 3.30 .10 2.47 4.33 .48 365

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 7.27 .96 4.68 10.8 1.57 365

99 12419000 Spokane River near Post Falls, ID 11.4 .90 9.39 13.7 1.10 365

100 13010065 Snake River at Flagg Ranch, WY 46.5 70.1 25.1 79.1 13.9 365

Table A9. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 2001.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; ton/d, ton per day; ton/yr, ton per year; mg/L, milligram per liter; ton/mi2/yr, ton per square mile per year; km2, square kilometer; ft3/s, cubic foot per 

second; NA, not available; NC, not calculated; –, not applicable]

110 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Map 

index 

No.

Site 

No. Site name Load

(ton/yr)

Flow-weighted 

concentration

(mg/L)

Yield

(ton/mi2

/yr)

Drainage 

area

(ft3

/s)

Annual 

mean flow 

(ft3/s)

51 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam, WA 187,000 2.35 7.13 67,800 80,700

52 13351000 Palouse River at Hooper, WA 7,590 29.4 3.08 6,380 262

53 34A070 Palouse River at Hooper, WA 7,830 30.4 3.18 6,380 262

54 41A070 Crab Creek near Beverly, WA 8,840 44.6 22.9 999 201

55 12471400 Lind Coulee Wastway at SR 17 near Warden, WA NC NC NC 1,840 –

56 13A060 Deschutes River at East Street Bridge, WA 701 4.00 6.81 267 178

57 10A070 Puyallup River at Meridian Street, WA 178,000 77.1 194 2,380 2,350

58 12108500 Newaukum Creek near Black Diamond, WA NC NC NC 71.1 33.7

59 12464770 Crab Creek at Rocky Ford Road near Ritzville, WA 108 4.01 .23 1,190 26.8

60 12061500 Skokomish River near Potlatch, WA NC NC NC 339 646

61 16A070 Skokomish River near Potlatch, WA 4,250 6.66 32.4 339 646

62 12112600 Big Soos Creek above Hatchery near Auburn, WA NC NC NC 173 71.9

63 09A190 Green River at Kanaskat, WA 1,860 3.29 7.81 616 573

64 45A070 Wenatchee River at Wenatchee, WA 13,200 8.44 10.0 3,440 1,590

65 12113375 Springbrook Creek at Tukwila, WA NC NC NC 51.7 29.7

66 09A080 Green River at Tukwila, WA 11,300 13.5 23.7 1,240 851

67 12113390 Duwamish River at Golf Course at Tukwila, WA 20,900 22.0 45.3 1,190 965

68 12056500 North Fork Skokomish River below Staircase Rapids near 

Hoodport, WA

685 2.32 12.1 147 300

69 46A070 Entiat River near Entiat, WA 1,330 6.44 3.20 1,070 209

70 45A110 Wenatchee River near Leavenworth, WA 7,650 4.96 11.5 1,720 1,570

71 16C090 Duckabush River near Brinnon, WA 603 2.67 9.07 172 229

72 12128000 Thorton Creek near Seattle, WA 237 29.7 21.0 29.2 8.11

73 54A120 Spokane River at Riverside State Park, WA 16,400 5.53 3.28 13,000 3,010

74 07D050 Snoqualmie River near Monroe, WA 28,800 12.0 42.1 1,770 2,440

75 07C070 Skykomish River at Monroe, WA 15,300 5.77 20.0 1,980 2,690

76 07A090 Snohomish River at Snohomish, WA 60,300 9.69 35.2 4,440 6,310

77 53A070 Columbia River at Grand Coulee, WA 76,200 1.04 6.83 28,900 74,400

78 48A070 Methow River near Pateros, WA 2,720 4.80 1.51 4,660 576

79 49A070 Okanogan River at Malott, WA 23,500 18.0 13.5 4,500 1,330

80 48A140 Methow River at Twisp, WA 1,850 3.69 1.40 3,430 508

81 03A060 Skagit River near Mount Vernon, WA 141,000 13.6 60.5 6,020 10,500

82 03B050 Samish River near Burlington, WA 2,320 14.9 26.9 223 158

83 12213140 Nooksack River at Brennan, WA NC NC NC 2,020 2,540

84 01A050 Nooksack River at Brennan, WA 120,000 48.0 163 1,910 2,540

85 12210700 Nooksack River at North Cedarville, WA NC NC NC 1,520 –

86 12400520 Columbia River at Northport, WA NC NC NC 156,000 74,000

87 61A070 Columbia River at Northport, WA 139,000 1.90 2.3 156,000 74,000

88 12212100 Fishtrap Creek at Flynn Road at Lynden, WA NC NC NC 98.6 –

89 13092747 Rock Creek above Hwy 30/93 crossing at Twin Falls, ID 1,900 24.9 7.91 623 77.7

90 13094000 Snake River near Buhl, ID 39,500 18.6 1.34 76,100 2,150

91 13154500 Snake River at King Hill, ID 69,400 9.61 1.94 92,900 7,330

92 13203510 Boise River below Diversion Dam near Boise, ID 3,800 4.72 1.41 6,980 817

93 13206000 Boise River at Glenwood, ID 2,450 4.94 0.88 7,180 503

94 13238322 North Fork Payette River below Fischer Creek near McCall, ID NC NC NC 220 132

95 12414900 St. Maries River near Santa, ID NC NC NC 706 155

96 12414500 St. Joe River at Calder, ID 4,290 3.84 4.14 2,680 1,130

97 12413470 South Fork Coeur d’ Alene River near Pinehurst, ID 1,210 5.27 4.23 738 232

98 12413000 North Fork Coeur d’ Alene River at Enaville, ID 2,650 3.53 2.96 2,330 763

99 12419000 Spokane River near Post Falls, ID 4,160 1.57 1.06 10,200 2,690

100 13010065 Snake River at Flagg Ranch, WY 17,000 32.7 33.2 1,320 528

Table A9. Results of LOADEST modeling, flow-weighted concentrations, yields, drainage areas, and mean annual streamflows for 

suspended sediment in the Columbia River and Puget Sound basins, water year 2001.—Continued

[Flux, estimate of average daily load for water year. Variance, variance of the flux. Lower 95, lower estimate of 95 percent confidence interval for flux. Upper 

95, upper estimate of 95 percent confidence interval for flux. Abbreviations: SEP, standard error of prediction; ID, Idaho; OR, Oregon; WA, Washington; WY, 

Wyoming; ton/d, ton per day; ton/yr, ton per year; mg/L, milligram per liter; ton/mi2/yr, ton per square mile per year; km2, square kilometer; ft3/s, cubic foot per 

second; NA, not available; NC, not calculated; –, not applicable]

Appendix A 111
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112 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Appendix B. Methodology for Computing Trends in Annual Streamflow, Trends 

in Load, and Flow- and Non-Flow-Adjusted Trends in Concentration

The non-flow adjusted trend estimates are derived 

from parameter estimates, and associated covariances, 

obtained from a model of flow and model of water-quality 

concentration, both models being estimated in logarithm 

space. The model of flow consists of an intercept, a linear 

trend term (decimal time), sine and cosine functions of 

decimal time (the seasonal component of flow), and a serially 

correlated error term; the flow residual is assumed to follow 

a 30-order autoregressive (AR(30)) process. The flow model 

is estimated using maximum likelihood methods as employed 

by the SAS AUTOREG procedure (SAS Institute, 1989). The 

high order autoregressive process is necessary to remove as 

much serial correlation as possible from the residuals, thereby 

reducing bias in the estimated coefficient covariance matrix of 

the flow model.

The water-quality model relates the natural logarithm of 

contaminant concentration to various predictors. An abstract 

representation of the model is given by

c b m q b h T b x b e

c

t t q t T t x t

t

= +0 ( ) + ( ) + + ,

where:

is the natural logarithm of contaminant 

concentration in period ; 

is natur

t

qt al logarithm of streamflow; 

T is decimal time, in years;

xt is a vector of ancillary predictors such 

as the sine andcosine functions of 

decimal time;

e is an independent an t d identically

 normalllydistributed random error;

m(.) and (.) are multi-element vector functions of

 and ; an

h

q T d 

, , and are associated coefficients to be

est

b b b b 0 q T x

imated. 

(B1)

The multi-element vector function of the natural logarithm of 

streamflow, m(.), consists of the natural logarithm of flow and 

the square of the natural logarithm of flow; the multi-element 

vector function of decimal time, h(.), consists of second-order 

polynomial terms and step functions of decimal time.

The water-quality model estimates values using either 

ordinary least squares, if the water-quality data contain no 

censored observations, or the maximum likelihood method, 

if censored observations are present. The exact methods 

differ slightly from those employed by LOADEST (Runkel 

and others, 2004) and small discrepancies can be expected 

in the coefficient and covariance estimates. In particular, 

LOADEST uses exact analytic derivatives to estimate 

the covariance and maximum likelihood bias adjustment, 

whereas the method employed in this model uses a numerical 

central-difference approach. The maximum likelihood bias 

adjustment requires estimates of the detection level even for 

uncensored observations. If the detection level is not supplied, 

a default detection level is used that equals the maximum 

of the parameter’s median detection level for all censored 

observations across all stations or the reported, uncensored 

value.

The estimate of non-flow adjusted trend (NFAT) is based 

on the flow and trend coefficients from the water quality 

model (bq and bT), and the coefficient on decimal time in the 

flow model, subsequently denoted a. Let t

1

 and t

2

 define the 

beginning and ending dates of the trend period (in this case, 

the dates of the first and last water-quality sample collected 

during the analysis period October 1, 1992, to September 30, 

2004). The trend in the natural logarithm of flow in period t, 

qt , is given by

q q  a T T

q T

t t = + ( ) − ,

where:

 and are the averages of the natural logarithm of 

flow and decimal time over the trend period.

(B2)

If flow is upward trending, then a will be positive and trend 

in the natural logarithm of flow will be less than the mean 

value of the natural logarithm of flow for the first one-half of 

the analysis period and greater than the mean value thereafter. 

Note that the average of the natural logarithm of flow, 

q , implicitly accounts for the intercept and average of the 

seasonal terms that are included in the flow model but not 

otherwise apparent in the formulation of equation (B2).
The full trend in water quality in period t, c

t

, is defined as

c b   m q b h T b xb t t q t T x

x

= + ( ) + + ( ) 0 ,

where:

 is an average, over the trend period to 

 of the non-flow/no

t t 1 2 ,

n-trend variables in the

 

water-quality modelgiven in equation 1,

 

and the average of the error term is absent

 

because it is set to its expected value of zero.

(B3)

Note that in forming this estimate of c

t

, the trend in the natural 

logarithm of flow is substituted for the actual natural logarithm 

of flow in the function m(.). This implies that variations 

in streamflow not reflected in trend do not determine the 

proposed measure of full trend in water quality. Because of the 

nonlinearity of the function m(.), this might lead to a bias in 

the evaluation of full water-quality trend if flows are becoming 

more or less variable over time.

The full trend in water-quality concentration, τc

, over the 

trend period, t

1

 to t

2

, is given by

τ c t t

t t q t t T

t

c c

mq mq b h T h T b

m q a T

= −

= ( ) ( ) − ( ) + ( ) ( ) − ( )

= +

 

 

2 1

2 1 2 1

2 ( ( ) ( ) − − + ( ) ( ) − )

+( ) ( ) − ( )

T m q a T T b

hT hT b

t q

t t T

1

2 1 .

(B4)

The full trend in water-quality concentration depends 

on the trend and flow coefficients from the water-quality 

model, bq and bT, as well as the trend coefficient a from the 

streamflow model. The trend in load, τL, is similarly defined 

but includes an additional term to reflect the direct effect 

streamflow has on the determination of load

τ L t t

t t q

t t

a T T

m q a T T m q a T T b

hT hT

= − ( )

+ + ( ( ) ( ) − − + ( ) ( ) − )

+ ( ) − (

2 1

2 1

2 1 ( )) bT .

(B5)

The full trend, expressed in percent per year, is given by

Percent Trend 100

exp

where:

 is either o

= ( ) ( ) −

−

τ

τ τ

1

2 1 T T t t

c

,

r τ . L

(B6)

The estimator of full trend is obtained by evaluating the 

coefficients a, bq

 and bT in (B4) and (B5) at their estimated 

values, where the water-quality parameter estimates are 

obtained using the adjusted maximum likelihood method 

(Cohn, 2005). Generally, the transformation of the estimated 

values of τc or τL into real space, via the exponential function 

appearing in (B6), induces a small degree of bias. No 

correction of this bias was applied in this case to ensure 

agreement between the sign of the percent trend and the sign 

of the test statistic used to evaluate the statistical significance 

of trend

A statistical test of the null hypothesis that trend is zero 

can be undertaken by forming t-statistics from the estimates 

of either τc or τL, and dividing by their respective standard 

error. Standard errors of the estimated values of τc and τL 

are complicated to derive owing to the nonlinear manner 

in which the flow trend coefficient and the water-quality 

flow coefficients interact in the determination of full trend. 

An approximation to the standard error, which is suitable 

for large samples, is obtained by taking a first-order Taylor 

approximation of the full trend estimate (either equation (B4)

or (B5)) with respect to the flow and water-quality model 

coefficients. Let b b b = { } q r  ́  ́  ́ represent the vector of 

combined flow and trend coefficients from the water-quality 

model and let Vb be the covariance matrix of this vector. Under 

the plausible assumption that streamflow is exogenous with 

respect to water quality, meaning that changes in streamflow 

cause changes in water quality but changes in water quality do 

not cause changes in streamflow, the covariance between the 

estimated values of a and b is zero. Consequently, the standard 

error of τc and τL, denoted σc and σL, are given by

σ c a V b

m

a

b

q = AV A ∂

∂





 



 + ′ ∆ 2

, (B7)

and

σ L a t t b

a

V m

a

b

q

T T AV A

V

= ∂

∂

+ − ( ) 



 



 + ′ ∆

2 1

2

,

where 

is the variance of the estimated flow trend 

coefficient, , a

(B8)

 ∂

∂ =

∂ + ( ) ( ) −

∂ −

∂ + ( ) ( ) −

∂

∆m

a

m q a T T

a

m q a T T

a

t t 2 1 (B9)

and

 

 

A m q a T T h T

m q a T T h T

t t

t t

= + { } ( ) ( ) − ( )

− + { } ( ) ( ) − ( )

2 2

1 1

(B10)

114 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
In large samples, the t-statistics τc /σc and τc /σc are 

distributed standard normal. Therefore, the two-sided p-value 

for significance of trend is given by

p

c c L L

= − 2 1( ) Φ( )

Φ

τ σ

τ σ τ σ τ σ

,

where:

is either / or / , and 

(.) isthe standard normal cumulative distribution.

(B11)

The unit trend is the change in concentration or load 

over a given period, expressed in the units of concentration 

or load, divided by the length of the period, expressed in 

years. Both the unit trend in concentration and the unit trend 

in load are based on trend-denominated variations in the 

logarithm-transformed water-quality and flow models given 

in equations (B1) and (B2). The unit trend in concentration, 

denoted τ c

u

, is given by

t

t c

u t t

t t

t

c

t t

c c

T T

c

T T = ( ) − ( ) − = ( ) ( ) −

−





exp exp

exp   exp  2 1

2 1

1

2 1

1 











,

where 

is given by equation (B3), and 

is given

c

t

tc by equation (B4).

(B12)

The units of τ c

u

 are milligrams per liter per year (mg/L-1/y-1). 

A similar expression applies to the determination of the unit 

trend in load, τ L

u ,

t

t L

u

t t

L

t t

k c q T T

k

= + ( ) ( ) −

−















 exp

exp   , 1 1

2 1

1

where 

 is a conversion factor that expresses in units

of kilograms 

tL

u

per year per year (kg/y ), and

 is given by equation

-2

qt

1 (B2), evaluated at the date

of the first water-quality sample in the analysis 

 period.

(B13)

The estimators of τ c

u

 and τ L

u

, given by (B12) and (B13), 

are based on the sample estimates of τc and τL described above, 

and on estimates of c

t

1

 and qt

1

, given in equations (B3) and 

(B2), with coefficients evaluated at their sample estimates 

(see above), and with the period set to t

1

, the date of the first 

water-quality sample in the analysis period. A correction was 

applied to account for the transformation bias arising from the 

exponential transformation of c

t

1

 in equation (B12) and c q   t t 1 1 +

in (B13). The correction was applied only to these terms, 

and not to the terms involving τc and τL , because correction 

of the latter could affect the sign of the unit trend estimate as 

compared to the sign of the test statistic used to statistically 

evaluate the significance of trend. The transformation bias 

correction is based on a first-order Taylor approximation that 

linearizes the expressions for c

t

1

 and c q   t t 1 1 + with respect to 

all model coefficients. The estimation of the variance of c

t

1

and c q   t t 1 1 + then follows by evaluating the quadratic form 

implied by this linearization, similar to the quadratic forms 

appearing inside the square-root radicals in equations (B7)

and (B8) above, employing the estimated variance of a and 

the covariance matrix of the estimated values of b0, bq, bT and 

bx. Let the estimated variances of c

t

1

 and c q   t t 1 1 + be denoted 

V ct



1 ( ) and V ct



1 ( ). Under the assumption that the estimated 

coefficients are approximately normally distributed, as occurs 

in large samples, the transformation bias correction is obtained 

by multiplying the expressions for τ c

u

 and τ L

u

 by the respective 

factors exp / ( ) −V c( ) t



1 2 and exp / ( ) − + V c( ) q t t  

1 1 2 .

References Cited

Cohn, T.A., 2005, Estimating contaminant loads in rivers—An 

application of adjusted maximum likelihood to type 1 

censored data: Water Resources Research, v. 41, no. 7, 

W07003.

Runkel, R.L., Crawford, C.G., and Cohn, T.A., 2004, Load 

estimator (LOADEST)—A FORTRAN program for 

estimating constituent loads in streams and rivers: U.S. 

Geological Survey Techniques and Methods Book 4, Chap. 

A5, 69 p.

SAS Institute, Inc., 1989, SAS version 6, original copyright, 

1989: SAS Institute, Inc., Cary, N.C.

Appendix B 115
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116 Nutrient and Suspended-Sediment Transport and Trends, Columbia River and Puget Sound Basins, 1993–2003
Manuscript approved for publication August 30, 2007

Prepared by the USGS Publishing Network, 

Publishing Service Center, Tacoma, Washington

Bill Gibbs 

Debra Grillo

Donita Parker

Bobbie Jo Richey

Sharon Wahlstrom

For more information concerning the research in this report, contact the 

Director, Oregon Water Science Center

U.S. Geological Survey

2130 SW 5th Avenue

Portland, Oregon 97201

http://or.water.usgs.gov
Printed on recycled paper

Wise and others— Nutrient and Suspended-Sediment Transport and Trends in the Columbia River and Puget Sound Basins, 1993–2003— SIR 2007–5186