Dissolved-Oxygen Regimen of the 

Willamette River, Oregon, 

Under Conditions of Basinwide 

Secondary Treatment 

By Walter G. Hines, Stuart W. McKenzie, 

David A. Rickert, and Frank A. Rinella 

RIVER-QUALITY ASSESSMENT OF THE WlllAMETTE RIVER BASIN, OREGON 

G E 0 l 0 G I C A l S U R V E Y C I R C U l A R 7 1 5-1 

1977 
United States Department of the Interior 

THOMAS S. KLEPPE, Secretary 

Geological Survey 

V. E. McKelvey, Director 

Library of Congress Cataloging in Publication Data 

Dissolved oxygen regimen of the Willamette River, Oregon, under conditions 

of basinwide secondary treatment. 

(Geological Survey Circular 715-1) 

Bibliography: p. 137-138. 

1. Water quality--Qregon-Willamette River. 2. Water-dissolved oxygen. 

I. Hines, Walter G. II. Series: United States. Geological Survey. Circular 

715-I. 

QE75 .C5 no. 715-1 [TD224.07] 363.6'1 77-21419 

Free on application to Branch of Distribution, U.S. Geological Survey,l200 South Eads Street, Arlington, VA 22202 
FOREWORD 

The American public has identified the enhancement and protection of river 

quality as an important national goal, and recent laws have given this commitment considerable force. As a consequence, a considerable investment has been 

made in the past few years to improve the quality of theN ation's rivers. Further 

improvements will require substantial expenditures and the consumption of 

large amounts of energy. For these reasons, it is important that alternative 

plans for river-quality management be scientifically assessed in terms of their 

relative ability to produce environmental benefits. To aid this endeavor, this 

circular series presents a case history of an intensive river-quality assessment 

in the Willamette River basin, Oregon. 

The series examines approaches to and results of critical aspects of riverquality assessment. The first several circulars describe approaches for providing 

technically sound, timely information for river-basin planning and management. Specific topics include practical approaches to mathematical modeling, 

analysis of river hydrology, analysis of earth resources-river quality relations, 

and development of data-collection programs for assessing specific problems. 

The later circulars describe the application of approaches to existing or potential 

river-quality problems in the Willamette River basin. Specific topics include 

maintenance of high-level dissolved oxygen in the river, effects of reservoir 

release patterns on downstream river quality, algal growth potential, distribution of toxic metals, and the significance of erosion potential to proposed future 

land and water uses. 

Each circular is the product of a study devoted to developing resource information for general use. The circulars are written to be informative and useful to 

informed laymen, resource planners, and resource scientists. This design stems 

from the recognition that the ultimate success of river-quality assessment 

depends on the clarity and utility of approaches and results as well as their basic 

scientific validity. 

Individual circulars will be published in an alphabetical sequence in the 

Geological Survey Circular 715 series entitled "River-Quality Assessment of 

the Willamette River Basin, Oregon." 

J. S. Cragwall, Jr. 

Chief Hydrologist 

III 
Cover: Willamette River as it winds through Portland, Oregon. Photograph taken by 

Hugh Ackroyd. 
CONTENTS 

Page 

Abstract---------------------------------------------------------------------------------------- 11 

Introduction ---------------------·------------·----------·------------·--------------------- 1 

Purpose and scope ----------------------------------·------------·---------- 3 

Physical setting ---·------------·------------·-----------------------·---------- 3 

Precipitation -----------------------------------·-----------------------·---------- 4 

Streamflow -------------·------------·-----------------------·----------·-------- __ 4 

Water temperature -----------------------·------------·----------·---------- 5 

Channel morphology ________ ·----------·------------·------------------- __ 7 

Upstream Reach --------·----------·------------·--------------------- 7 

"Newberg Pool" ----------·----------·------------·------------·-------- 7 

Tidal Reach ------------------·-----------------------·------------·-------- 7 

Design of the study program ---------------·---------------------·---·------ 8 

Initial hypotheses and assumptions -------------------·------ 8 

Selection of study reaches and sampling sites ______ 9 

Importance of hydrologic stability ______________________________ 10 

Methods and procedures ------------·------------·------------·----------·------ 11 

DO-BOD studies-------·------------·------------·------------·----------·------ 15 

Nonpoint-source BOD study-----------·------------·----------·------ 18 

Nitrification study ---·-------------------------·------------·----------------- 18 

Results ---------·------------·-------------------------·----------·------------·------------·---- 18 

BOD loading --·------------·-----------------------·-------------------------·---- 18 

Point-source BOD loads ·-----------------------·------------·---- 19 

Nonpoint-source BOD loads -----------------------------·---- 20 

BOD concentrations and rates in 

Willamette River-----·------------·------------·-----------------------·---- 20 

Anomalously high BOD in the Tidal Reach -----·---- 21 

Nitrification ----·------------·------------·------------·-----------------------·---- 24 

Nitrogen loading-·------------·------------·-----------------------·---- 24 

Nitrogen concentrations in 

Willamette River-----------------------·------------·--------------- 24 

Nitrifying bacteria ____________ ·----------·------------·------------·-- 24 

Photosynthesis and respiration ------------------ ------------·-- 26 

Page 

Results-Continued 

Atmosphere reaeration ________ ·-----------------------·------------·-- 127 

River-dissolved oxygen --·-----·------------·----------·------------·---- 29 

Independent check of the DO data -------------------- 30 

DO variations at individual sites ---------------------- 30 

Synoptic DO profile --------·-----------------------·------------·-- 30 

Discussion -----·-----------------------·------------·------------·-----------------------·-- 30 

Hypothetical boat trip ------------·------------·-----------------------·-- 31 

RM 185 to 120 ---------·----------·------------·-------------------------- 31 

RM 120 to 50 -----------·-----------------------·------------·------------· 31 

RM 50 to 10 -------------·------------------------------------·------------- 32 

RM 10 to 1.5 -----------·------------·-----------------------·------------· 32 

Historical perspective ---·----------·------------·-----------------------· 32 

Conclusions -----·------------·------------·-----------------------·------------·----------- 35 

Acknowledgments ------·------------·-----------------------·------------------------ 37 

Selected references ----·------------·------------·-----------------------·----------- 37 

Supplement A-River self-purification processes ________ 40 

Carbonaceous deoxygenation --·------------·---------------------- 40 

Benthal oxygen demand -·-----------------------·---------------------- 41 

Nitrification ----------·------------·------------·-----------------------·--------- 42 

Photosynthesis and respiration ·-----------------------·--------- 42 

Atmospheric reaeration -·---·--------·-----------------------·--------- 42 

Supplement B-Field calibration of 

dissolved-oxygen meters -------------------------------·-------------------- 43 

Supplement C-Analysis of BOD -----------------·------------·------- 44 

Dilution water , --------·--------·---·------------·----------·------------·------- 44 

Inhibition of nitrification -·------------·----------·------------·------- 44 

Calibration ---·------------·----------·------------·------------------------------- 44 

Measurement of DO in BOD bottles ---·-·-·----------·----- 45 

Lee's graphical method -·-----·-----------------------·------------·----- 45 

Supplement D-Special BOD experiments -·------------·----- 46 

Supplement E-Detailed river DO and water 

temperature data ------------·----------·------------·----------------------------- 49 

ILLUSTRATIONS 

Page 

FIGURE 1. Map of Willamette River basin, showing location of river miles on main-stem Willamette River -----·---------- 12 

2. Graphs showing typical precipitation patterns at various locations, Willamette River basin -------------·---------- 5 

3. Hydrographs showing Willamette River discharge at Salem, Oreg., 1944, 1964, and 

1973 water years ------------·------------·----------·------------·------------·------------·------------·------------·-------------------------·-----------------------·---------- 6 

4. Graphs showing mean monthly and maximum and minimum daily water temperatures for the 

North Santiam, Willamette, and South Yamhill Rivers-·-------------~----------·------------·------------·------------·--------------------- 9 

5. Graph showing maximum, mean, and minimum water temperature profiles for July, 

Willamette River ------------·------------·------------·-------------------------------------------------·------------·-------------------------·------------·------------·-------- 10 

6. Map and graph showing Willamette River-distinctive morphological reaches and elevation profile________ 11 

7. Typical channel cross-sections of the Willamette River at concurrent low-flow conditions______________________________ 12 

8. Graph showing cumulative time of travel for various low flows, Willamette River-----------------------------------·-------- 13 

9. Map of the lower Willamette River system ---------·------------·------------·------------·------------·------------·------------·-----------------------·-------- 14 

10. Hydrographs showing streamflow of Willamette River at Salem for 1973 and 1974 summer periods -----,-- 16 

11. Photograph of aerated lagoon used for treatment of pulp and paper mill waste waters -·------------·------------------- 17 

v 
Page 

FIGURE 12. Graph showing comparison of measured and calculated BODult loads in the Willamette River 

during August 1974 low-flow conditions---------------------------------------------------------------------------------------------------------------------- I21 

13. Graph showing longitudinal and vertical turbidity patterns in the Tidal Reach, 

-Willamette River, August 16, 1974 -------------------------------------------------------------------------------------------------------------------------------- 25 

14. Graph showing inorganic nitrogen concentration in the Willamette River during August 12-14, 1974 ______ 25 

15. Graphs showing summertime (low-flow condition) diel DO curves at various sites on Willamette River 

and tributaries, 1929 and 1973 -------------------------------------------------------------------------------------------------------------------------------------- 28 

16. Graph showing calculated reaeration coefficients (k1) for various sites in the Willamette River 

using four different reaeration prediction methods ------------------------------------------------------------------------------------------------ 29 

17. Graph showing dissolved-oxygen concentrations measured in the Willamette River by U.S. Geological 

Survey and DEQ during 1973 summer low-flow period, July 5 to August 18------------------------------------------------ 31 

18. Graph showing dissolved-oxygen concentrations measured in the Willamette River by U.S. Geological 

Survey and DEQ during 1974 summer low-flow period, August 1-15 -------------------------------------------------------------- 32 

19. Graph showing diel dissolved oxygen and water temperature curves, Willamette River at 

Harrisburg (RM 161), August 7-9, 1973 ......... --------------------------------------------------------------------------------------------------------------- 33 

20. Graph showing diel dissolved-oxygen curves at four sites in the Tidal Reach Willamette River, 

July 24-26, 1973 -------------------------------------------------------------------------------------------------------------------------------------------------------------------- 34 

21. Graph showing composite DO profile of the Willamette River under 1973 steady low-flow conditions ______ 35 

22. Graph showing comparison of 1973 with historical DO conditions in the Willamette River for the 

summer low-flow period ------------------------------------------------------------------------------------------------------------------------·--------------------------- 36 

23. Graph showing historical average daily BOD loads to the Willamette River during dry weather periods 

24. Example of Lee's graphical method for analyzing k1 and BODult, Willamette River, RM 86.5 ---------------------- 46 

25. Example of Lee's graphical method for analyzing k1 and BODult• McKenzie River ------------------------------------------ 47 

26. Example of Lee's graphical method for analyzing k1 and BODult• pulp and paper effluent---------------------------- 48 

27. Graph showing dissolved-oxygen concentration in the Willamette River and major tributaries 

between RM 185 and 86.5, August 6-12, 1973 ----------------------------------------------------------------------------------------------------------- 49 

28. Graph showing dissolved-oxygen concentration in the Willamette River between RM 86.5 and 28.6, 

August 15-17, 1973 ------------------------------------------------------------------------------------------------------------------------------------------------------------- 50 

29. Graph showing dissolved-oxygen concentration in the Willamette River between RM 28.6 and 1.5, 

July 24-26, 1973 ------------------------------------------------------------------------------------------------------------------------------------------------------------------- 51 

30. Graph showing observed dissolved-oxygen concentration in the Willamette River between 

RM 86.5 and 6.0, August 6-7, 1974 ------------------------------------------------------------------------------------------------------------------------------- 52 

TABLES 

Page 

TABLE 1. Selected characteristics of major reservoirs, Willamette River basin, Oregon------------------------------------------------------ I7 

2. Lowest daily discharge for 7, 14, and 30 consecutive days in year ending March 31 for 

Willamette River at Salem, 1910-70 ------------------------------------------------------------------------------------------------------------------------------ 8 

3. Selected physical characteristics of the main stem Willamette River ---------------------------------------------------------------------- 13 

4. Summary of studies of the Willamette River conducted during 1973 and 1974 ---------------------------------------------------- 15 

5. BODult loading to the Willamette River from individual outfalls and tributary watersheds -------------------------- 19 

6. Reach-by-reach summary of point and nonpoint BODult loading to the Willamette River for 

summer low-flow conditions -------------------------------------------------------------------------------------------------------------------------------------------- 19 

7. BODult concentrations and BOD bottle deoxygenation rates for samples of Willamette River 

during summer low-flow periods, 1973 and 1974------------------------------------------------------------------------------------------------------ 21 

8. Inorganic nitrogen loading to the main stem Willamette River during summer 1973-74 conditions __________ 25 

9. Counts of Nitrosomonas and Nitrobacter bacteria in river water and on rock slimes, 

Willamette River August 12-14, 197 4 __________________ --------------------------- _____________________ .. ·------------------------- ________ ---------------------- 26 

10. Estimated primary production at various sites in the Willamette River during summers of 1973 

and 1974 ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 27 

VI 
SYMBOLS 

[See Supplement A for definitions and further discussion of many of the terms listed here] 

BOD-biochemical oxygen demand 

BODuu-ultimate BOD 

BODs-5-day BOD at 20°C 

BOD2o -20-day BOD at 20°C 

K1 -carbonaceous deoxygenation rate (loge) as measured in 

BOD bottle at 20°C 

k1-carbonaceous deoxygenation rate (log10) as measured 

in BOD bottle at 20°C 

kr -river carbonaceous deoxygenation rate (log10), 

adjusted to 20°C 

Kn-nitrogenous deoxygenation rate (loge) in river, 

adjusted to 20°C 

kn-nitrogenous deoxygenation rate (logw) in river, 

adjusted to 20°C 

K2-reaeration coefficient (loge) 

k2 -reaeration coefficient (logw) 

n-number of samples 

PE-BOD population equivalent=0.24 lb/day BODult 

(0.11 kg/day BODult) 

Q-stream discharge 

RM-river mile 

T -water temperature 

CONVERSION FACTORS 

Factors for converting English units to the International System of Units (SI) are given below to four significant figures. However, in the text the metric equivalents 

' are shown only to the number of significant figures consistent with the values for the English units. 

English Multiply by- Metric (Sf) 

ft (feet) 3.048xl0-1 m (meters) 

ft3/s (cubic feet per second) 2.832xl0-2 m3/s (cubic meters per second) 

in. (inches) 2.540 em (centimeters) 

2.540xl0-1 mm (millimeters) 

in.2 (square inches) 6.452 cm2 (square centimeters) 

lb (pounds) 4.535xl0-1 kg (kilograms) 

mi (miles) 1.609 km (kilometers) 

mi2 (square miles) 2.590 km2 (square kilometers) 

VII 

Dissolved-Oxygen Regimen of the Willamette River, Oregon, 

Under Conditions of Basinwide Secondary Treatment 

By Walter G. Hines, Stuart W. McKenzie, 

David A. Rickert, and Frank A. Rinella 

ABSTRACT 

For nearly half a century the Willamette River experienced 

severe dissolved-oxygen problems related to large loads of 

organically rich waste waters from industries and municipalities. Since the mid-1950's dissolved-oxygen quality has 

gradually improved owing to low-flow augmentation, the 

achievement of basinwide secondary treatment, and the use 

of other waste-management practices. As a result, summer 

dissolved-oxygen levels have increased, salmon runs have 

returned, and the overall effort is widely regarded as a 

singular water-quality success. 

To document the improved dissolved-oxygen regimen, the 

U.S. Geological Survey conducted intensive studies of the 

Willamette during the summer low-flow seasons of1973 and 

1974. During each summer the mean daily dissolved-oxygen 

levels were found to be higher than 5 milligrams per liter 

throughout the river. Because of the basinwide secondary 

tr~atment, carbonaceous deoxygenation rates were low 

(kr=0.02 to 0.06, log10). In addition, almost half of the biochemical oxygen demand entering the Willamette was from 

diffuse (nonpoint) sources rather than outfalls. These 

results indicated that point-source biochemical oxygen 

demand was no longer the primary cause of dissolvedoxygen depletion. Instead, them.ajor causes of deoxygenation were nitrification in a shallow "surface active" reach 

below Salem and an anomalous oxygen demand (believed 

to be primarily of benthal origin) in Portland Harbor. 

INTRODUCTION 

Historically, the Willamette River (fig. 1) has 

experienced severe river-quality problems due 

primarily to large loads of organic waste waters 

from pulp and paper industries and municipalities (Gleeson, 1972). During summers, critically 

low and in some cases zero dissolved oxygen 

(DO) concentrations drastically affected fish 

migration, esthetics, recreation, and other 

water uses. High fecal bacteria concentrations, 

floating and benthic sludge, sulfur odors, and 

infestations of the "sewage fungus" Sphaerotilus prevailed. 

With the gradual introduction of basinwide 

11 

secondary waste-water treatment, chemical 

recovery processes by the pulp and paper 

industries, rerouting of Portland's dry-weather 

combined sewer overflows to a new waste-water 

treatment plant on the Columbia River, and 

increased low-flow augmentation, the Willamette River has recently shown a marked 

improvement in quality. Dissolved-oxygen 

concentrations have risen dramatically, and 

migratory salmon runs and water-contact 

recreation have returned. The Willamette is 

now described as an outstanding water-quality 

success story (Starbird, 1972). 

Dissolved oxygen-biochemical oxygen demand (BOD) relations in the Willamette River 

have been studied for nearly half a century. 

Rogers, Mockmore, and Adams (1930) conducted a DO study that was remarkable 

considering the state of knowledge, sampling 

equipment, and analytical methods available 

at that time. From a series of synoptic surveys, 

Gleeson (1936) analyzed DO-BOD relations in 

the hydraulically complex Tidal Reach of the 

Willamette. (See fig. 9.) On the basis of intensive 

sampling during the summer-fall low-flow 

season, Velz (1951, 1961) made detailed DO 

mass-balance calculations and developed a 

model for estimating the response of DO 

concentrations to changes in waste load, 

streamflow, and water temperature. Throughout the 1920-75 period local and State agencies 

and industries sponsored river and waste-water 

sampling. Presently (1977), the Oregon Department of Environmental Quality (DEQ) operates 

a water-quality surveillance network (primarily 

discrete grab sampling) on the entire 187-mi 

(301 km) main stem of the Willamette. 

Despite the recent improvement in the quality 

of the river, there is continuing environmental 
w 

tn 

<( 

0 

u 

II 

INDEX MAP OF OREGON 

0 10 20 MILES 

t-1 --,-1 ----~.1--rj ----rlj I

0 10 20 30 KILOMETERS 

w 

0 

<( 

u 

Cl) 

<( 

u 

FIGURE 1.-Willamette River basin, showing location of river miles on main-stem Willamette River. 

12 
interest in the Willamette River. Locally, 

citizens, industries, and environmental regulatory agencies are concerned with the maintenance of good river quality in the face of rapid 

basin development. Nationally, engineers, 

scientists, environmental planners, and Federal resource agencies are interested in the 

documentation of factors responsible for the 

Willamette "clean up" as guidance for riverquality planning in other basins. Because of the 

unique situation of complete secondary wastewater treatment (for dry weather conditions) in 

the basin, the question of the future need for 

expensive, energy-consumptive tertiary treatment is of interest both locally and nationally. 

PURPOSE AND SCOPE 

The major intent of this circular is to provide 

the data base and interpretive insight necessary- for the understanding, explanation, and 

quantitative description of the DO regimen of 

the Willamette River. More specifically, the 

report is intended to (1) describe the DO regimen 

of the Willamette through detailed examination 

of five river self-purification processes, (2) document the reasons for the recently improved DO 

conditions, (3) discuss the nature of waste-water 

and river-water BOD under the unique conditions of basinwide secondary treatment, and (4) 

present concepts and methods useful for studies 

of large river systems such as the Willamette. 

The data, analyses, and discussion presented 

here were denved partly from an examination 

of historical hydrologic and water-quality data, 

but most importantly from a series of synoptic 

field and laboratory studies made during 1973 

and 1974. Originally, it was our intent in this 

paper to describe the cause-effect relations that 

control DO in the Willamette without resorting 

to a mathematical model. However, in order to 

sufficiently define the impacts of benthal 

oxygen demand, photosynthesis, and atmospheric reaeration, it was necessary to make 

several rough DO mass-balance calculations. 

These calculations were made by using a 

preliminary version of the Willamette Intensive 

River Quality Assessment Study (WIRQAS) DO 

model (Rickert and others, 1975). The full 

development and testing of the WIRQAS model 

will be described in Circular 715-J. Moreover, 

Circular 715-K will describe application of the 

verified model for predicting the impacts of 

alternative planning proposals on the Willamette's DO condition. 

The first section of the paper provides an 

overview of the physiography and hydrology of 

the Willamette basin. The overview serves as 

background for a detailed description of the 

streamflow, water temperature, and channel 

morphology characteristics of the main -stem 

Willamette River. The next section deals with 

the design and rationale of the synoptic study 

program. This is followed by a discussion of 

laboratory and field techniques employed in the 

studies. The "Results" section provides a 

graphically oriented summary of the data 

collected during the synoptic studies. The 

section is partitioned so as to allow a step-bystep examination of each of the five classically 

recognized self-purification processes: carbonaceous deoxygenation, benthal oxygen demand, nitrification, plant photosynthesisrespiration, and atmospheric reaeration. The 

interpretive "Discussion" section includes both 

a present-day and historical overview of the 

Willamette River DO regimen. The overviews 

are developed by taking a hypothetical boat trip 

down the 187-mile main stem of the river and by 

comparison of 1973 DO profiles with historical 

profiles. The "Conclusions" section briefly 

describes the major findings and implications 

of the study. 

Because of the length and scope of the paper, 

those interested primarily in findings and 

implications may wish, at least initially, to 

forego much of the detailed technical discussion 

and to concentrate on the "Discussion" and 

"Conclusions" sections. For the more technically oriented reader, the report includes 

several supplements. The supplements serve to 

summarize the field and laboratory data and 

methods and to present background discussion 

on the quantification of river self-purification 

processes. 

13 

PHYSICAL SETTING 

The Willamette River drains an 11,460 mi2 

(29,800 km2) area in northwestern Oregon (fig. 

1). The basin is bounded on the north by the 

Columbia River, on the south by the Calapooya 
Mountains, and on the east and west by the 

Cascade and Coast Ranges. Within the basin 

are the State's three largest cities, Portland, 

Salem, and Eugene, and approximately 1.4 

million people (1970 census), representing 70 

percent of the State's population. The basin 

supports an important timber, agricultural, 

industrial, and recreational economy and an 

extensive fish and wildlife habitat. Two-thirds 

of the land is forested. Timbering is centered 

primarily in the Cascade Range, with lesser 

activity in the Coast Range. The middle part of 

the basin is occupied by the 3,500-mi2 (9,050 

km2) Willamette Valley. The valley is covered 

with farmlands that produce large crops of 

grass seed, vegetables, berries, hops, mint, and 

turkeys. Almost all of the limited agricultural 

irrigation is by sprinklers, and virtually no 

irrigation return flow directly reaches the 

Willamette River or its tributaries. 

The main stem of the Willamette flows 

northward for 187 mi (300 km) through the 

Willamette Valley from a point near Eugene to 

its confluence with the Columbia at Portland. 

The 135-mi (217 km) reach of the river between 

Eugene and a point just south of Newberg has a 

shallow, meandering alluvial channel. Through 

the next 25.5 mi (41.0 km) the Willamette flows 

within well-defined banks in a deep, slowmoving reach known as the "Newberg Pool." 

Near Oregon City, the river flows over a 

basaltic sill which creates the 50-ft (15 m) high 

Willamette Falls. The 26.5 mi ( 42.6 km) reach 

below the falls is subject to nonsaline tidal 

effects transmitted from the Pacific via the 

Columbia River. 

PRECIPITATION 

The Willamette Basin has a modified marine 

climate characterized by wet, cloudy winters 

and clear, dry summers. Daily average temperatures range from 35°F (1. 7°C) to 83°F (28°C) on 

the valley floor and from 20°F (-6.7°C) to 75°F 

(24°C) at the crest of the Cascade Range 

(Willamette Basin Task Force, 1969, p. 11-10). 

Seventy percent of the annual precipitation 

occurs from November through March, only 

about 5 percent from June through August. In 

some years, no precipitation falls for 30-60 days 

or more during the summer and early fall. These 

seasonal dry periods have a great impact on the 

I4 

summer-fall streamflow and quality of the 

Willamette. 

In the Willamette Valley most of the 

precipitation occurs as rain. However, as 

elevation increases, snowfall makes up an 

increasingly larger percentage of annual 

precipitation, particularly in the rugged terrain 

above 3,000 ft in the Cascade Range. (Only a 

few peaks reach this elevation in the Coast 

Range.) The heavy winter snowpack, coupled 

with the excellent water-storage and yield 

characteristics of the volcanic rocks, provide 

the Cascade tributaries, and thus the Willamette, with unusually high summer baseflows 

(Velz, 1951, p. 25). 

Mean annual precipitation for the Willamette 

Basin is 63 in. (1,600 mm), but large variations 

occur owing to elevation and topography. The 

Willamette Valley floor usually receives about 

40 in. (1,020 mm) per year, whereas several 

locations on the west slope of the Cascade 

Range receive more than 130 in. (3,330 mm) per 

year. Typical precipitation patterns are shown 

in figure 2. 

STREAMFLOW 

Most of the streamflow conveyed by the 

Willamette occurs in the November to March 

period as a result of persistent winter rainstorms and spring snowmelt. Post-March 

snowmelt in the High Cascades (above 5,000 ft 

or 1,500 m) tends to prolong the runoff season 

into June or early July. 

The seasonal flow patterns of the river are 

illustrated by the hydrographs in figure 3. The 

1944 hydrograph is typical of natural runoff 

patterns prior to large-scale reservoir regulation, whereas the 1964 and 1973 hydrographs 

reflect postregulation patterns. 

As summarized in table 1, streamflow 

regulation began with construction and operation of three reservoirs (in the period 1941-49) 

on tributaries in the Coast Range and 

Calapooya Mountains. However, it was not 

until after water year 1952 (after construction of 

Detroit and Lookout Point reservoirs on 

Cascade Range tributaries) that reservoir 

regulation had a significant impact on low-flow 

patterns of the main-stem Willamette. A review 

of post 1952 low-flow duration data (table 2) 

shows that reservoir releases have greatly 

augmented flows during the summer-fall period. 
45 

40 

C/) 35 w 

I 

(.) 

z 

; 30 

z 

0 

i= 25 <t: 

ID.. 

(.) 

~ 2D D.. 

>-...J 

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1- 15 z 

0 

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10 

5 

Valsitz, crest of Coast Range 

EXPLANATION 

B

Maximun 

Average 

Minimum 

1000 

C/) 

a:: 

LLI 

1-

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...J 

750 :!! 

~ 

z 

0 

1-

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15 

10 

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200 

C/) 

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w 

5ol--..----r----.----r===t----r~.--,...---F=;---r--+-O 

:!! 

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1- 15 

z 

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Three Lynx, Lower Cascade Range 

z 

0 

1-

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500 w 

a: 

250 

D.. 

>-

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1-

z 

0 

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FIGURE 2.-Typical precipitation patterns at various locations, Willamette River basin. Precipitation at Three Lynx 

station is not representative of that in higher Cascades which is similar to that shown for Valsitz. (Adapted from 

Willamette Basin Task Force, Appendix B, 1969, p. 11-15.) 

(All of the 7-, 14-, and 30-day low flows in table 2 

occurred during the July-October low-flow 

period.) Prior to 1953, the average annual 

consecutive 30-day low flow was 3,670 ft3 Is 

(103 m3 /s) and ranged from 2,570 to 5,020 ft3 /s 

(72.8 to 142 m3/s). Between 1953 and 1970 the 

average consecutive 30-day low flow was 6,010 

ft3 /s (170 m3/s) and ranged from 5,290 to 7,400 

ft3/s (150 to 210 m3/s). 

Analysis of streamflow data from tributaries 

shows that Cascade tributaries (Clackamas, 

Santiam, McKenzie, and Middle Fork Willamette Rivers) contribute the major part of the 

annual streamflow in the Willamette, and more 

than 95 percent during the dry summer-fall 

months (Willamette Basin Task Force, Appendix B, 1969). 

WATER TEMPERATURE 

Water temperatures in the Willamette and all 

15 

major tributaries reach a maximum during the 

July-August period (fig. 4), coinciding with the 

onset of low-flow conditions. During this period 

there is a tendency for increasing water 

temperature in the downstream direction 

despite the cooling effects of the McKenzie, 

Santiam, and Clackamas Rivers (fig. 5). The 

reach above RM 120 often has cooler water 

temperatures than naturally expected because 

of the release of cool bottom waters from the 

Lookout Point-Dexter Reservoir complex on the 

Middle Fork of the Willamette River (fig. 1). 

Reservoirs on the other tributaries are far 

enough from the Willamette to allow cool 

release flows to reach ambient temperature 

before confluence with the main stem Willamette. Thus, except in the reach above RM 120 

(and expecially above RM 172) reservoir 

regulation has little effect on summer water 

temperature of the Willamette. 
100,000 

1000 

10,000 

100 

1000 

0 

0 100,000 z 

0 z u 0 w u IJ) 

w a: IJ) w a:: 0.. 

w 1000 IJ) 0.. a: I- w w I- w w ~ ~ u u ll) 10,000 ll) 

::::> ::::> u u ~ z w· w· c.::> 

a: 100 c.::> <{ a: ::c <{ 

u ::c IJ) u 0 IJ) 

0 

1000 

100,000 

1000 

10,000 

100 

FIGURE 3.-Willamette River discharge at Salem, Oreg., 1944, 1964, and 1973 

water years. Note the recurrent nature or the July, August, and September 

low-flow periods even after large-scale streamflow regulation began 

in 1953. 

16 
TABLE 1.-Selected information for the 13 reservoirs in the Willamette River basin reservoir system 

Control 

pomt 

number' Reservoir name Strear.. name 

Useable 

capacity 

lacre-ftl 

Dram age 

area 

lmi 2 1 

Date Authonzed 

regulatwn purpose 

began or use 2 

10 

11 

24 

12 

Hills Creek ____________ __ Middle Fork Willamette River ______________ 240,000 389 Aug. 1961 FC,N,I,P Lookout Point ___________ _ ------------ ________ do_ ___________ 349,000 911 Nov. 1953 FC,N,I,P Dexter3 _________________ _ ______________________ do_ 4,800 911 Nov 1953 RR,P Fall Creek _____________ __ Fall Creek ltnbutarv to 

Middle Fork Wilhimette River!. 115,000 184 Jan 1966 FC,N,I 13 

14 

Cottage Grove __________ __ Coast Fork Willamette River_________________ 30,100 104 Oct. 1942 FC,N,I Dorena ________________ -- Row River !tributary to Coast Fork Willamette River!. 70,500 265 Oct. 1949 FC,N,I 15 

16 

18 

23 

25 

21 

22 

Cougar ________________ __ South Fork McKenzie River __ __ __ __ __ _ _ __ __ __ 165,000 208 Sep 1963 FC,N,I,P Blue River ltnbutarv to McKenzie River/ ______ 85,000 88 Oct. 1968 FC,N,I 

Long Tom River __ _-__ __ __ __ __ __ __ __ _ _ __ _ _ __ __ 110.000 

Blue River ____________ _ Fern Ridge ____________ __ 252 Nov 1941 FC.N,I Detroit _________________ _ North Santiam River__________ ______ 340,000 438 Jan. 1953 FC,N,I,P Big Cliff' ______________ __ ______________________ do__________ 2.400 438 Jan. 1953 RR,P Green Peter _____________ _ Middle Santiam River __ __ _ 333,000 277 Oct. 1966 FC,N,I,P Foster ________ _ South Santiam River_______ ____________ 33,200 494 Dec 1966 RR.FC,P 

'See figure 1. 2FC, flood control; N, navigation; I, Irrigation; P, power; RR, reregulatwn. 3Small reregulating reservoir. 

CHANNEL MORPHOLOGY 

The Willamette River comprises three distinctive morphological reaches (fig. 6). Summary data for the three reaches are included in 

figures 7 and 8 and in table 1. Figure 7 shows 

typical channel cross sections, figure 8 indicates approximate reach-to-reach times of 

travel for variou'3 streamflows, and table 3 

includes information about bed materials and 

other pertinent channel data. 

UPSTREAM REACH 

The Upstream Reach, stretching from above 

Eugene to near Newberg, is shallow, fast 

moving, and relatively turbulent. The bed is 

composed largely of cobbles and gravels that 

provide ample substrate for periphytic biological growths. 

Although U.S. Army Corps of Engineers 

channel projects have straightened the course 

of the river in many segments, there are still 

numerous meanders, islands, and side channels. At low flow, gravel bars are visible and in 

some places the river is so shallow that small 

pleasure boats may run aground. The shallow 

channel of the Upstream Reach contrasts 

markedly with that of the "Newberg Pool" and 

Tidal Reach (fig. 7). 

As shown in figure 8 and table 3, velocity in 

the Upstream Reach during low-flow conditions is 10-20 times that of either of the two 

. downstream reaches. During floods, velocity is 

sufficiently high to transport large quantities of 

cobbles and gravel as bedload. 

17 

"NEWBERG POOL" 

The deep, slow-moving "Newberg Pool" extends for 25.5mi (41.0 km) from above Newberg 

to the Willamette Falls. The elevation profile 

(fig. 6), channel geometry (fig. 7), and the 

appearance of fine sediments as bed rna terial 

(table 3) indicate that the "Pool" is predominantly a depositional reach. Travel time is 

strikingly long during low-flow conditions. (See 

table 3 and fig. 8.) 

During summer, most of the flow at the 

downstream end of the "Pool" at Willamette 

Falls is diverted through power generation 

turbines, navigation locks, oroverafishladder. 

These operations cause mild fluctuations in 

wate!" levels and flow velocities throughout the 

length of the "Pool." A series of water-surface 

elevation measurements made during the 1973 

and 1974 studies indicates that the "Pool" 

behaves like a long -stilling basin behind a weir, 

with a backwater effect measurable as far upstream as RM 50. 

TIDAL REACH 

The lower 26.5 mi ( 43 km) of the river is also a 

deep, slow-moving reach. Moreover, the reach is 

affected by tides and, during spring and early 

summer, by backwater from the Columbia 

River (Velz, 1961, p. 15-16; Gleeson, 1936). Parts 

of the Tidal Reach are dredged to maintain a 40 

ft deep navigation channel (fig. 7) from the 

mouth to about RM 14. The segment between 

RM 17 and 5 is a busy shipping corridor known 

as Portland Harbor. 
TABLE 2.-Lowest daily discharge for 7, 14, and 30 consecutive 

days in year ending March 31 for Willamette River at Salem, 

Oreg., 1910-701 

Lowest da1ly discharge in cubic feet per second 

Year 7 days 14 days 30 days 

Period of minor low-flow regulation 

1910 ---------------- 3,750 3,780 3,850 

1911 ---------------- 3,750 3,800 4,050 

1912 ---------------- 4,570 4,750 5,020 

1913 ---------------- 4,240 4,360 4,840 

1914 ---------------- 3,510 3,540 3,640 

1915 ---------------- 3,420 3,480 3,500 

--------------------

1923 ---------------- 3,920 3,980 

1924 ---------------- 2,990 3,070 

1925 ---------------- 3,020 3,070 

1926 ---------------- 3,130 3,140 

1927 ---------------- 3,730 3,730 

1928 ---------------- 3,400 3,500 

1929 ---------------- 3,190 3,190 

1930 ---------------- 2,860 2,860 

1931 ---------------- 2,520 2,580 

1932 ---------------- 3,170 3,170 

1933 ---------------- 3,750 4,020 

1934 ---------------- 2,830 2,860 

1935 ---------------- 3,140 3,220 

1936 ---------------- 3,080 3,090 

1937 ---------------- 3,800 4,000 

1938 ---------------- 3,250 3,270 

1939 ---------------- 2,940 3,060 

1940 ---------------- 2,520 2,520 

1941 ---------------- 3,140 3,210 

1942 ---------------- 2,980 3,160 

1943 ---------------- 4,200 4,300 

1944 ---------------- 2,750 2,830 

1945 ---------------- 3,170 3,300 

1946 ---------------- 3,650 3,770 

1947 ---------------- 3,800 3,940 

1948 ---------------- 4,400 4,670 

1949 ---------------- 3,670 3,730 

1950 ---------------- 4,100 4,260 

1951 ---------------- 4,080 4,200 

1952 ---------------- 3,560 3,750 

Period of major low-flow regulation 

1953 ---------------- 5,320 

1954 ---------------- 6,160 

1955 ---------------- 6,160 

1956 ---------------- 5,950 

1957 ---------------- 5,380 

1958 ---------------- 5,680 

1959 ---------------- 5,410 

1960 ---------------- 5,510 

1961 ---------------- 5,780 

1962 ---------------- 5,740 

1963 ---------------- 5,490 

1964 ---------------- 6,470 

1965 ---------------- 5,360 

1966 ---------------- 5,030 

1967 ---------------- 5,340 

1968 ---------------- 5,840 

1969 ---------------- 6,940 

1970 ---------------- 6,610 

5,430 

6,290 

6,160 

6,000 

5,440 

5,720 

5,440 

5,580 

5,800 

5,880 

5,650 

6,640 

5,400 

5,130 

5,340 

5,870 

7,360 

6,610 

4,210 

3,160 

3,220 

3,190 

3,860 

3,560 

3,240 

2,920 

2,640 

3,170 

4,360 

2,900 

3,350 

3,130 

4,110 

3,410 

3,170 

2,570 

3,390 

3,220 

4,360 

2,880 

3,390 

3,830 

4,310 

4,880 

3,880 

4,610 

4,360 

3,980 

5,770 

6,560 

6,280 

6,150 

5,670 

5,830 

5,460 

5,680 

5,840 

6,090 

5,790 

6,740 

5,460 

5,290 

5,420 

5,950 

7,400 

6,770 

'For example, the 1930 data are from Apnl 1, 1929, to March 31, 1930. 

During summer low-flow conditions, water in 

the Tidal Reach moves very slowly downstream, although tidal effects cause periodic 

flow reversals and local eddy currents. Hydrau18 

lies are most complex in the lower IO mi (I6 km) 

where, depending on tide- and river-stage 

conditions, Columbia River water may move 

upstream and intermix with Willamette water. 

(During I973-74 studies we found Columbia 

water as far upstream as RM 6. (See fig. 9)) The 

downstream movement of intermixed water can 

be either through the lower several miles of the 

Willamette and out the mouth, or through 

Multnomah Channel. Particularly during late 

summer, Columbia River water has a higher 

concentration of dissolved solids (typically I20 

mg/l as opposed to the Willamette's 80 mg/l) 

and is commonly several degrees cooler than 

Willamette River water. Columbia water is, 

therefore, denser than Willamette water and for 

the first several miles can move upstream as a 

distinct bottom wedge. 

DESIGN OF THE STUDY PROGRAM 

Design of the study program was based on the 

fundamental philosophy (Hines and others, 

I975, I976) that explanation and understanding of river-quality phenomena are best 

developed through repetitive, synoptic studies 

rather than year-round monitoring data. The 

program included three major elements: (I) a 

reconnaissance study including preliminary 

river sampling, review of existing data, and 

development of hypotheses concerning the 

relative roles, importance, and interactions of 

self-purification processes and hydrologic factors; (2) intensive field and laboratory studies; 

and (3) data analysis to test the hypotheses. 

INITIAL HYPOTHESES AND ASSUMPTIONS 

Based on reconnaissance work (Rickert and 

others, 1976) during the period January to June 

I973, four major hypotheses had been 

developed concerning the DO regimen of the 

Willamette River. Each hypothesis was either 

refuted or substantiated by later findings of the 

study. 

(I) Carbonaceous deoxygenation is the primary process affecting DO depletion in the 

Willamette River (refuted). 

(2) Photosynthesis and plant respiration. 

have little impact on the day-to-day average DO 

concentration of the river (substantiated). 

(3) Nitrification is not a significant oxygendemanding process in the river (refuted). 

(4) Benthal oxygen demand is no longer a 
North Santiam River 

at Niagara 

Willamette River 

at Salem 

South Yamhill River 

near Willamina 

Maximum 

25 

(I) 

=> 

Ci) 

..J 

w 

(.) 20 Cl) 

w 

w 

a: 

(!) 

w 

0 

~ 15 

w' 

a: 

::> 

1-

<t: 

a: 10 w 

Q. 

::!: 

w 

1-

5 

0 

JFMAMJJASOND JFMAMJJASOND JFMAMJJASON 

FIGURE 4.-Mean monthly and maximum and minimum daily water temperatures for the North Santiam, 

Willamette, and South Yamhill Rivers. (Adapted from Willamette Basin Task Force, Appendix B, 1969.) 

significant oxygen-demanding process in the 

river (substantiated except for lower segment of 

Portland Harbor). 

The major underlying assumption for the 

river studies.is that DO depletion has been and 

will continue to be a river-quality problem only 

during the recurring low-flow summer-fall 

period. Existing surveillance data (public files, 

DEQ, Portland, Oreg.)showthatDOconcentrations in the river are at or near saturation for the 

remainder of the yearly cycle. 

SELECTION OF STUDY REACHES AND SAMPLING SITES 

The time, location, and general nature of 

studies are outlined in table 4 and are 

subsequently described in detail. Spatially, the 

studies focused on the lower 86.5 mi (139 km) of 

river where DO problems have been prevalent 

in the past. In general, study segments were 

selected to conform with the three distinctive 

morphological reaches of the Willamette (fig. 6). 

Logistical considerations, the location of major 

waste-water discharges (particularly in the 

I9 

Salem area), and the need for hydrologic control 

from fixed-stream gages somewhat modified 

the selection of segments solely on the basis of 

morphology. 

Individual sampling sites were selected 

primarily on the basis of waste-water outfall 

and tributary locations, traveltime between 

sites, and the availability of boat launches and 

bridge measuring sites. Information for site 

selection was derived from: 

(I) Detailed examination of 1:12,000 high 

resolution black and white photographs of the 

Willamette River channel supplied by the 

Portland District, U.S. Army Corps of 

Engineers. 

(2) Channel geometry data obtained from 

channel soundings and maps furnished by the 

Portland District, U.S. Army Corps of Engineers. 

(3) Traveltime data from dye-tracer tests 

conducted by the Geological Survey (Harris, 

1968). 

( 4) Historic waste-loading information sup-
RIVER Kl LOMETERS ABOVE MOUTH 

Coast Fork Marys Luckiamute Tualatin 

Willamette River River River River 

Fall McKenzie Long Tom Calapooia Santi am Molalla Clackamas 

Creek River River River River River River 

0 

V'J 25 :::::> 

V'J 

...J 

w 

(.) 

w 

~ 20 ~ 

a: 

(!) 

w 

Cl 

~ 15 

ui 

a: 

:::::> 

1-

<( 10 a: 

w 

a.. 

w 

~ EXPLANATION 

1-

a: 5 --- Natural conditions w 

1- ------ Regulated conditions 

<( 

~ 

0 

200 150 100 50 0 

RIVER Ml LES ABOVE MOUTH 

FIGURE 5.-Maximum, mean, and minimum water temperature profiles for July, Willamette River. Profiles upstream 

of RM 187 are for Middle Fork Willamette River. Note that below RM 125 reservoir regulation does not change 

the naturally occurring temperature regimen. (Adapted from Willamette Basin Task Force, Appendix B, 1969.) 

plied by DEQ. 

(5) Observations of river currents and mixing 

phenomenon made during reconnaissance 

sampling in late spring 1973. 

IMPORTANCE OF HYDROLOGIC STABILITY 

Studies were designed to coincide with 

relatively stable low-flow conditions; that is, a 

relatively prolonged period (""' 10 days) of 

steady stream flow not affected by preceding 

storm runoff. This consideration is particularly 

important because the quantification of selfpurification processes is accomplished with 

mathematical equations and models based 

largely on assumptions of a steady state 

system. In the Willamette River, these assumptions are (with rare exceptions) reasonably met 

only during the extended periods of hydrologic 

stability experienced during summer. 

As shown in figure 10, streamflow in the 

Willamette River and major tributaries was'low 

and relatively steady throughout the 1973 and 

110 

197 4 summer study periods. The Willamette 

Basin had an unusually light snowpack and 

winter-spring rainfall in 1973, and runoff into 

reservoirs was considerably below normal. 

Note that in 1973, a steady low-flow period 

began about July 5 and, except for a minor rise 

between July 20 and 25, persisted at about 6,000 

ft3/s (170 m3/s) until August 17, when reservoir 

releases increased streamflow above 7,000 ft3 Is 

(200 m3/s). In 1974 a heavy winter snowpack 

and late spring rainfall prolonged the runoff 

period until early August, and stable low-flow 

conditions (approximately 6,800 ft3/s or 190 

m3/s) lasted only from August 1 until August 

14. 

During the periods of study in 1973 and 1974, 

the accounting of gaged flows from all 

upstream tributaries consistently resulted in 

excellent checks (within 7 percent) with flows 

recorded at the three Willamette River gages at 

Harrisburg (RM 161), Albany (RM 134) and 

Salem (RM 85). The Salem gage was used as the 

reference gage for all studies because of the 
(A) 

'\ 

s 

( 3 135m (217 km) 

187 (301 km) 

( 

\ 

0 30 MILES 

I 11 11 

0 50 KILOMETERS 

300 200 100 0 

DISTANCE, IN RIVER KILOMETERS ABOVE MOUTH 

FIGURE 6.-Willamette River, Oreg. A, Distinctive morphological reaches. B, Elevation profile. 

capability to correlate flows at Salem with those 

observed at any other downstream location on 

the main stem Willamette. This could be done 

during the stable low-flow period because no 

major diversions or inflows, other than gaged 

tributaries, occur downstream of Salem. Because of reservoir regulation and a relatively 

homogeneous basinwide seasonal runoff regimen, major tributaries were also at a condition 

of stable low flow. Thus, average daily 

streamflow values at any point on the main 

Ill 

stem Willamette could be computed by a simple 

flow-routing procedure. 

METHODS AND PROCEDURES 

In general, methods were selected from 

standard practices and techniques documented 

in sanitary engineering and limnological 

literature. However, several modifications 

evolved from experimentation and practical 

experience during the course of study. As a 

guide for future river studies, discarded 
River mile 119 (Upstream Reach) River mile 40.8C"Newberg Pool .. ) 0 

'~__./"' ~~------------------------~~ 0 

10 

!- 5 Cl) 

a: w 

w 20 w 

!- u. w 

Discharge= 3 5280 ft /s 

(150m%) 

~ 

r.' 

!- 30 Q. 

w 

c 

~ 

~ 

r.' 

!-

Discharge= 6100 tt% 10 Q. 

w 

(173m%) 

c 

40 

50 L-------L-----~------~------~15 

River mile 9.2 (Tidal Reach) 

10 

20 

!-

w 

w 

u. 

~ 30 

r.' 

!-

Q. 

w 

c 40 

0 200 400 

I 

0 100 

600 800 FEET 

I 

200 METERS 

5 

10 

15 

Cl) 

a: 

w 

!-

w 

~ 

~ 

r.' 

!-

Q. 

w 

Cl 

FIGURE 7.-Typical channel cross-sections of the Willamette River at concurrent low-flow conditions. 

methods and the advantages of those finally 

selected are briefly described. Two of the most 

important methods, the air-calibration technique for field calibration of DO meters and the 

laboratory BOD analysis, are explained in 

detail in Supplements Band C. 

During the course of the study, more than 

2,500 20-day BOD tests were made on samples 

112 

of river and waste waters of the Willamette 

River basin using the specially designed BOD 

procedure. In addition, experiments were 

conducted to evaluate the reliability of the 

laboratory BOD procedure and to further 

quantify and isolate particular factors responsible for several types of anomalous 

readings (artifacts) noticed during the labora-
RIVER KILOMETERS ABOVE MOUTH 

Portland 

V) 

> 

<( 

0 

~ 

w 

> 

<( 

a: 

1-

LL 

0 

w 

~ 

j: 

20 

10 

0 

187 

EXPLANATION 

Willamette River discharge at 

Salem, in cubic feet per second 

2600 

----4900 

7000 

150 100 50 

RIVER Ml LES ABOVE MOUTH 

FIGURE B.-Cumulative time of travel for various low flows, Willamette River. 

TABLE 3.-Selected physical characteristics of the main stem Willamette River 

[See fig. 6 for location of reaches. Characteristics refer to summer low-flow conditions of 6x103ft3/s at Salem] 

Representative Approximate 

Approximate midchannel traveltime 

Length bed slope water depth total in reach 

Reach (mi) (ftlmi) Bed material (ft) Velocity (hr) 

Tidal 26.5 <0.1 Intermixed clay, sand, and 40 1

0.11 240 

Reach. gravel. 

"Newberg 25.5 .12 Intermixed clay, sand, and 

Pool." gravel with some cobbles. 

Upstream 135 2.8 Mostly cobbles and gravel. 

Reach. 

1Calculated by volume displacement method using channel croBB-sectional data. 2Calculated from dye study conducted by U.S. Geological Survey (Harris, 1968). 

25 1 .27 94 

7 22.0 68 

0 

0 

tory work. A brief summary of the special 

experiments and their results is offered in 

Supplement D. 

meter, 1 referred to hereafter as DO meter, and 

the Martek Mark II multichannel water quality 

analyzer, referred to hereafter as DO monitor. 

The basic instruments used for river DO and 

water temperature measurement were the YSI 

(Yellow Springs Instruments) model 54 oxygen 

I13 

1 Mentioned brand names do not imply endorsement by the Geological 

Survey. 
Rivermile6.0~ (St Johns Bridge) 

0 

I I 

0 

1 

N 

I 

I I • 

5 MILES 

I I 

I I 

I I 

l I 

8 KILOMETERS 

FIGURE 9.-Lower Willamette River system. During low-flow conditions, Columbia River water commonly moves 

upstream beyond St. Johns Bridge as a distinct bottom wedge of denser water. Depending on variations in 

tides and river flows, the subsequent discharge of mixed Columbia-Willamette water may be out the mouth 

of the Willamette, through Multnomah Channel, or a combination of the two. 

The DO meters included calibrated 50ft (15m) 

cables and Clark-type polarographic probes. 

The DO monitors were each equipped with 305 

ft (100m) of calibrated cable with depth sensor. 

114 

DO meters were field calibrated every 2-3 

hours using the air calibration technique 

described in Supplement B. This technique 

proved quick and accurate throughout the 2-
TABLE 4.-Summary of studies of the Willamette River 

conducted during 1973 and 1974 

Description 

Reconnaissance 

(review of historical data, 

preliminary sampling, 

methods testing, formulation of pl1'liminary 

hypotheses) 

Date Sampling sites 

Jan.-July Numerous sites throughout 187-

1973 mi main stem, major tributaries, and waste-water 

outfalls. 

DO-BOD study, RM 26.5-0 July 24-26, RM's 28.6, 25.5, 21.1, 16.8, 12.8, 

1973 7 .0, 6.0, 3.5, 1.5; all major tributaries just above main-stem 

confluence; all major wastewater outfalls. 

DO-BOD study, RM 187-86.5 August 6-12, RM's 185, 161, 134, 120, 96, 86.5, 

1973 McKenzie River, RM 7.1; 

Santiam River, RM 6; all major 

waste-water outfalls. 

DO-BOD study, 86.5-26.5 August 15-18, RM's 86.5, 72, 50.0, 46.0, 39.0, 

1973 34.0, 28.6, plus all major tributaries just above main-stem 

confluence; all major wastewater outfalls. 

Nonpoint-source study of June-Aug. Coast Fork Willamette River 

BOD and nutrient loading. 1974 RM's 6.4 and 29.5; Middle Fork 

Willamette River RM 8; 

McKenzie River, RM's 7.1 and 

14.9; South Santiam RM's 7.6 

and 23.3; Clackamas River 

RM0.5. 

DO-BOD study, RM 86.5-0 August 6-7, RM's 86.5, 72.0, 50.0, 39.0, 28.6, 

1974 21.0, 12.8, 10, 7.0, 6.0; all major 

tributaries just above mainstem confluence: all major 

waste-water outfalls. 

Nitrification study, RM August 12-14, RM's 120, 114, 86.5, 72.0, 60.0, 

120-0. 1974 55.0, 50.0, 39.0, 28.6, 12.8, 7.0, 

all tributaries just above mainstem confluence; all major 

waste-water outfalls. 

year study period and evolved from dissatisfaction with the originally attempted field Winkler 

calibration. The Winkler technique was particularly cumbersome. In addition to delicate 

glassware, it. required the use of distilled water 

because of possible analytical interferences in 

river water caused by the presence of low concentrations of reduced sulfur compounds discharged in waste waters from the pulp and 

paper mills. Winkler calibrations proved time 

consuming, difficult under field conditions, and 

resulted in consistently poor calibration quality 

control as determined from analysis of fieldcrew calibration records. 

DO-BOD STUDIES 

The three studies below RM 86.5 employed 5-8 

field crews with boats, 5-8 DO meters, and 4 DO 

monitors (usually in a fixed position). During 

the DO-BOD study of the Upstream Reach 

between RM 185 and 86.5, DO monitors were 

installed at each site described in table 4, except 

at RM 161, where a permanently installed 

Geological Survey water-quality instrument 

(Honeywell Model II) was already in place 

(operated by the Oregon District Geological 

Survey, WRD). Reconnaissance sampling had 

shown DO concentrations in this reach to be 

near saturation and homogeneous in cross 

section, but subject to diel variations owing to 

photosynthesis by periphytic algae (see fig. 15). 

Thus, the single point continuously recording 

DO monitors could be used to advantage with 

only a minimal need for manual sampling. This 

was an important logistical consideration in 

this long, relatively inaccessible reach. 

Each study reach was sampled from dawn 

until dusk for 2-6-day periods of steady low 

flow. During the three DO-BOD studies below 

RM 86.5 (table 4), 100-350 discrete DO and 

water temperature measurements were made 

with the DO probe at each sampling site. (The 

number of measurements varied owing to 

channel configuration and type ofinstruments 

used.) Every 2 hours, from approximately 6:00 

a.m. to 9:00p.m., vertical sampling traverses for 

DO and water temperature were made from 

boats. Depending on channel geometry, vertical 

measurements were made at water surface 3, 6, 

10, 15, 20, 30, 40, and 50ft (water surface 1, 2, 3, 

5, 6, 9, 12, and 16m), with duplicate readings at 

0.6 channel depth. At most sites additional 

vertical traverses were made 2 or 3 times each 

day at 3 horizontal locations to check for horizontal homogeniety. 

At most sites, river BOD samples were 

collected every 4 hours at mid-channel at 0.6 

channel depth with a 4-liter Scott-modified Van 

Dorn bottle. (Reconnaissance sampling had 

shown this procedure to give representative 

average daily BOD values owing to the 

relatively good mixing.) This procedure resulted 

in 12-20 BOD samples per study from each site. 

At the sampling site farthest upstream in each 

study reach, preliminary sampling was begun 

2-7 days before intensive sampling to check for 

antecedent stability of the DO regimen and to 

insure the absence of anomalous in-river BOD 

concentrations. This was important for establishing reliable boundary conditions for future 

modeling work. Moreover, had nonstable 

conditions been noted, the synoptic study would 

have been deferred until a later date. 

115 

River BOD samples were placed in clean 300-

ml BOD bottles and immediately packed in ice. 
40~------------~r---------------~---------------.---------------, 

35 

900 

Cl 

2 

830 

w 

(I) Cl 

a: 

w 

0.. 

800 2 

0 

u 1-

w w 

(I) 

w a: LL w 

5:2 25 m 

0.. 

700 (I) 

0:: ::::> IJJ u 1- LL 

0 

w 

~ 

(I) u Cl 

2 

~ 20 ::::> 

0 

:::c 

600 iii 

::::> 

u 

~ 

w· 1-

~ 500 (!) 

a: 

<( 

w· 

(!) 

~ 15 

:::c 1974 u 

(I) 

Cl 

:::c 

u 400 (I) 

0 

10 

7 

5 

JUNE JULY AUGUST SEPTEMBER 

FIGURE 10.-Hydrographs showing streamflow ofWillamette River at Salem for 1973 and 1974 summer periods. 

The samples were gathered at predetermined 

locations and delivered by truck to the Geological Survey laboratory in Portland. Initial 

readings in the laboratory were made 2-8 hours 

after sample collection. 

BOD samples from tributaries and municipal 

and industrial waste-water outfalls were collected once or twice daily. Tributaries were grab 

sampled just above confluence with the 

Willamette main stem. Municipal effluents 

were composited over 24-hour periods to 

determine daily average BODult loads. In 

I16 

contrast, pulp and paper mill effluents were 

grab sampled because all of the effluents are 

discharged from aerated lagoons (fig. 11) 

having detention times greater than 10 days. 

The long detention times made it possible to 

reliably determine daily BODult loads on a grab 

sample basis. All waste-water sampling began 

2-7 days prior to each river study to insure 

detection of any unusual antecedent conditions. 

Waste-water samples were collected by DEQ 

field crews with cooperation from each municipality and industry. The National Council for 
FIGURE 11.-Aerated lagoon used for treatment of pulp and paper mill waste waters. Boise Cascade Corp. plant (Salem) 

is at upper left corner, Willamette River in foreground. 

Air and Stream Improvement (NCASI), a 

technical service organization of United States 

wood products industries, also cooperated in the 

sampling effort. The waste-water BOD samples 

were packed in ice and delivered daily to the 

Geological Survey laboratory in Portland. Two 

or three dilutions, using fresh Willamette River 

wat~r for dilution water, were made for each 

sample and three dilution water BOD's 

("blanks" or controls) were begun each day. 

Initial DO readings on the diluted waste-water 

samples were made within 8 hours of sample 

collection. 

All river- and waste-BOD samples were 

incubated at 20±.1 oc for 20 days. Using the BOD 

probe-reaeration technique (see Supplement C), 

DO measurements were made at 0.5, 1, 2, 3, 4, 5, 

6, 7, 10, 15, and 20dayintervals. Lee's graphical 

method (Supplement C) was used to calculate 

deoxygenation rate (k1) and BODult· Lee's 

method was selected over other available 

methods because it allowed manual graphical 

inspection of all data points and direct 

comparison to the assumed "first-order decay" 

carbonaceous deoxygenation model. A computerized modification of the Reed-Theriault 

technique (Theriault, 1927) was also tried but 

discarded as giving unrealistic k1 results 

because of "overweighting" of anomalous early 

readings that occurred in some samples during 

the 0-3 day time interval (See Supplement C). 

The anomalous readings were believed due to 

DO supersaturation (common in tributary and 

Upstream Reach samples), excessive algal 

respiration caused by incubation in the dark, or 

lags in the onset of bacterial oxidation. 

With the exception of the 1973 river BOD 

samples, allylthiourea (Tuffey, 1973) was added 

to all waste-water and river BOD samples to 

inhibit nitrification and permit independent 

determination of the carbonaceous deoxygenation rate. Because nitrification was in fact 

shown to have occurred in the uninhibited 1973 

nver BOD samples, BOD results from these 

117 
samples were adjusted as described in table 7. 

These adjusted results were consistent with 

though not considered as reliable or definitiv~ as, the 1974 inhibited BOD samples. 

Water samples for nitrogen, phosphorus, and 

silica analyses were collected with Van Dorn 

samplers from most DO-BOD sampling sites for 

use in algal studies. Nitrogen, phosphorus, and 

organic carbon analyses were also conducted 

on aliquots of the BOD samples from most 

waste-water treatment plants. Algal studies 

conducted concurrently with the DO-BOD 

studies provided information on light penetration, algal cell counts (phytoplankton and 

periphyton), light-and-dark bottle primary production, and algal growth potential under conditions of nutrient enrichment. Certain of the 

results of the algal studies are presented subsequently. A detailed discussion is presented 

elsewhere (Rickert and others, 1977). 

NONPOINT-SOURCE BOD STUDY 

Results of the 1973 DO-BOD studies showed 

that river BODult concentrations of < 3.0 mg/1 

were common in all reaches above RM 86.5 and 

that river deoxygenation rates were probably in 

the rangekr=0.02-0.06. This suggested that the 

river BOD regimen was approaching a nearpristine condition characterized by loading 

only from land runoff and seepage (both 

considered to be minor during low-flow conditions) and instream primary production. To 

further analyze this condition, a study of 

diffuse-source BOD loading was undertaken. 

The major Willamette River tributaries were 

grab sampled on three separate days during 

summer 1974 for BOD, nitrogen, and phosphorus (table 4). Sampling sites were located 

above and below major point sources of pollution as determined from reconnaissance work 

in each tributary basin. The Middle Fork 

Willamette River and the Clackamas River (fig. 

1) were sampled at only one location (near their 

mouths) because no major point sources of 

pollution are known to exist in either river 

during summer low-flow conditions. Ten BOD 

analyses, plus analyses for nitrogen and 

phosphorus, were conducted on each sample. 

Point and nonpoint source BOD loads are 

summarized in table 6. Summary of nitrogen 

and phosphorus nonpoint loadings are given 

elsewhere (Rickert and others, 1977, p. G7). 

118 

NITRIFICATION STUDY 

Results of 1973 DO-BOD studies strongly 

suggested that nitrification was occurring in 

the river between RM 120 and 55. A large 

oxygen depletion, not attributable to carbonaceous BOD loadings, was evident in this reach 

(see fig. 14). The depletion was coincident with a 

rapid conversion of ammonium to nitrate ion in 

the river. Because this condition had not been 

anticipated in 1973, a special study of nitrification was planned and undertaken in August 

1974. 

During three consecutive days of low steady 

flow (August 6-8, 1974), samples were collected 

by rapid downstream boat cruises and bridge 

sampling at the river sites shown in table 4. All . 

major waste-water outfalls were also sampled, 

and together with the river water samples, were 

analyzed for ammonia-, nitrite-, and nitratenitrogen concentration. River and waste-water 

samples were chilled, brought to the laboratory 

within 12 hours, and analyzed using the 

distillation-Nesslerization method for ammania-N (NH4-N), the Brucine method for nitrateN (N03-N), and the diazotization method for 

nitrite-N (N02-N). Duplicate samples were sent 

to the Geological Survey's central laboratory in 

Salt Lake City, Utah, for check analysis by 

methods described by Brown, Skougstad, and 

Fishman (1970). 

Dawn to dusk DO measurements were made 

August 7 and 8 between RM 86.5 and 50, where 

the rapid oxygen depletion had been noted 

during 1973. Concurrent with the DO measurements, analyses for Nitrosomonas and Nitrobacter bacteria were conducted on samples 

obtained from water and rock slimes using 

techniques described by Ehrlich (1975) and 

Tuffey (1973). 

RESULTS 

BOD LOADING 

Total BODult input to the main stem 

Willamette River in the summer of 1973 and 

1974 was approximately 170,000 lb/day (77,000 

kg/day). This value is based on average 

(measured) 1973-7 4 BOD loads from tributaries ' municipalities, and industries (table 5). Of this 

total, 55 percent was from known point sources 

(municipal and industrial outfalls), and 45 

percent from diffuse sources (table 6). Almost all 
TABLE 5.-BODult loading to the Willamette River from individual outfalls and tributary watersheds 

[Calculated loadings are based on 1974low-flow conditions (6,800 ft3/s or 190 m3/s Salem gage)] 

Location ofload 

(RM) 

Description of waste-water 

load or tributary 

187 

184 

178 

175 

148 

132.1 

132 

131 

120 

118 

116 

108 

107.9 

95.4 

85.0 

78.2 

55.0 

50.3 

49.8 

35.8 

33.0 

28.4 

28.0 

27.6 

25.2 

24.8 

24.1 

20.3 

20.1 

18.4 

Confluence of Middle and Coast Forks .................. . 

Springfield STP .............................................................. . 

Eugene STP ...................................................................... . 

McKenzie River ............................................................. . 

Wood products industry ............................................. . 

Marys River .................................................................... . 

Corvallis STP ................................................................ .. 

Calapooya River ........................................................... . 

Albany STP ...................................................................... . 

Combined effluent of metals and wood products 

industries ...................................................................... . 

Santiam River ................................................................ . 

Luckiamute River .......................................................... . 

Independence STP and Ash Creek ......................... . 

Wood products industry ............................................. . 

Salem STP ......................................................................... . 

Yamhill River ................................................................... . 

Newberg STP ................................................................ . 

Wood products industry ............................................. . 

Molalla River .................................................................... . 

CanbySTP ...................................................................... . 

Tualatin River ................................................................ . 

Wood products industry .............................................. . 

................. do .......................................................................... . 

Oregon City STP ........................................................... . 

Clackamas River .............................................................. . 

West Linn Stp ................................................................... . 

Tryon Creek STP ........................................................... . 

Oak Lodge STP ............................................................... . 

Milwaukie STP -·····-·····-··············-··············-······················· 

Total ...................................................................................................... . 

Point source 

(lb/d)2· 3 

240 

3,100 

8,650 

56,200 

4,100 

2,900 

120 

3,100 

240 

1,100 

960 55,000 

120 

960 

13,000 

11,800 

720 

100 

7,200 

500 

70 

4,300 

11,100 

5,000 

240 

240 

170 

430 

430 

240 

92,300 

Nonpoint 

source 

(lb/d)4 

21,600 

(19,200 Middle) 

30,500 

120 

240 

13,000 

120 

720 

980 

960 

9,400 

77,640 

NoTEs.-STP, sewage treatment plant; e, estimated from Oregon DEQ routine surveillance data 

'Only sources with BODult loads greater than 100 lb/d shown in table. 

Total 

(lb/d) 

21,800 

3,100 

8,650 

36,700 

4,100 

2,900 

240 

3,100 

480 

1,100 

960 

18,000 

240 

960 

13,000 

11,800 

1,440 

100 

7,200 

1,480 

70 

5,260 

11,100 

5,000 

240 

9,640 

170 

430 

430 

240 

169,900 

Average 

Average carbonaceous 

BODwt deoxygenation 

concentration rate, k1 (mg/1) (d•l) 

2.1 0.04 

74 .06 

92 .06 

2.1 .05 

22 .06 

300 .04 

e5 .04 

52 .06 

4.8 .03 

24 .06 

36 .05 

2.2 .03 

e5 .06 e50 .02 

85 .06 

60 .05 

4.9 .06 

22 .06 

90 .07 

2.1 .04 

32 .05 

25 .06 

70 .06 

27 .05 

13 .06 

1.3 .07 

30 .06 

13 .05 

26 .06 

21 .06 

2All point-source BODwt data above RM 85 based on 1973 samples. All point-source data below RM 85 based on 1974 samples except discharges with loads less 

than 500 lb/d which were sampled only in 1973. 3Below RM 85 municipalities and industries with BODwt loads greater than 1,000 lb/d were generally samples 5-10 times. Above RM 85 municipalities and 

industries were generally sampled 1-4 times. Tributaries were sampled 5-10 times. 4Nonpoint-source data from June to August 1974 samples (see table 4) of major tributaries and estimates for minor tributaries. 5Point-source loads primarily from upstream wood products industries. 

TABLE 6.-Reach-by-reach summary of point and nonpoint BODult loading to the Willamette River for summer low-flow 

conditions 

[Calculations based on 1974low-flow conditions (6,800 ft3 /s or 190 m3/s Salem gage) and 1973-74 average dry weather waste-water loads] 

BODwt loading to main stem Willamette River 

Point sources' Nonpoint sources2 

(municipal and industrial outfalls) (tributaries) Totallaoding 

Percentage Percentage 

Lb/d of Percentage Lb/d of total Percentage Lb/d Percentage 

River reach of point source of total of diffuse source of total of of 

(RM) BODult loading loading BODult loading loading BODwt total 

187-52 ········-------------.................... 62,000 68 37 67,000 86 39 129,000 76 

53-26.5 ········································· 28,000 30 17 2,000 2 1 30,000 18 

26.5-0 ........................................... 2,000 2 1 9,000 12 5 11,000 6 

Total .............................. 92,000 100 55 78,000 100 45 170,000 100 

'Outfalls discharging directly to main stem Willamette River plus flow-routed point-source loads discharged into tributaries. 2Based on BODult concentrations measured in Cascade tributaries above waste-water outfalls plus estimated nonpointcontributions from minor tributaries (that 

is, those with flows less than 100 ft3/s or 28 m3/s). 

the nonpoint-source BODwt inputs enter the 

main stem Willamette from major tributaries 

rather than by direct overland runoff or 

seepage. 

119 

POINT-SOURCE BOD LOADS 

The 92,000-lb/d (42,000 kg/d) load from point 

sources includes 56,000 lb/d (25,000 kg/d) or 61 

percent from industrial outfalls and 36,000lb/d 
(16,000 kg/d) or 39 percent from municipal 

outfalls. The BOD load from the industrial 

outfalls is virtually all from wood-products 

industries. The BODult load from municipal 

outfalls includes an unknown proportion 

(perhaps as much as 30 percent) from seasonal 

canning operations and other small industries 

connected to municipal sewer systems. 

The deoxygenation rates (kt =0.04-0.08) of 

carbonaceous material measured in pointsource waste-water discharges (all of which 

receives some form of secondary biological 

treatment) contrast with rates of kt =0.10-0.14, 

previously measured in BOD tests of raw or 

primary-treated waste water (Velz, 1951, 1961). 

These low rates indicate that the basic 

biochemical character of waste-water effluents 

in the basin is different from that of several 

decades ago. The carbonaceous material remaining in waste waters after secondary treatment is well oxidized and more resistant to biochemical decay than theraworprimary-treated 

waste waters previously discharged. As described in the following sections ("NonpointSource BOD Loads" and "BOD Concentrations 

and Rates in Willamette River"), this basic 

change in the biochemical nature of wastewater effluents is also reflected in the deoxygenation phenomena that occur in tributaries 

and the main stem Willamette. 

NONPOINT-SOURCE BOD LOADS 

Approximately 93 percent of the 77 ,000-lb/ d 

(35,000 kg/d) nonpoint-source BODult input 

was from four major Cascade Range tributaries: Middle Fork Willamette (19,000 lb/d or 

8,600 kg/d), McKenzie (31,000 lb/d or 14,000 

kg/d), Santiam (13,000 lb/d or 6,000 kg/d) and 

the Clackamas (9,400 lb/ d or 4,200 kg/ d). These 

tributary BODult loads appear large; however, 

this is deceptive because it is the large volume of 

streamflow in each tributary, rather than high 

BODult concentrations, that causes the large 

loads. Indeed, BODult concentrations are 

remarkably low, ranging only from 1.3 to 2.1 

mg/1 in samples taken upstream of all wastewater outfalls. Considering the deoxygenation 

rates of kt =0.02-0.06, these data are indicative 

of near-pristine conditions. Even below wastewater outfalls, no tributary BODult concentrations greater than 3.0 mg/1 were measured. 

Because of low streamflow, the smaller 

Cascade Range tributaries (Molalla, Pudding, 

120 

and Calapooya Rivers) and all the Coast Range 

tributaries contribute only minor BODult loads 

to the Willamette River from nonpoint sources. 

Furthermore, nonpoint-source BODult loads 

from areas adjacent to the main stem Willamette are minimal during low-flow summer 

conditions because of the absence of rains, land 

wash, and irrigation return flows. This is 

substantiated by a BODult mass-balance calculation described below. 

BOD CONCENTRATIONS AND RATES IN 

WILLAMETTE RIVER 

BODult concentrations were low throughout 

the main stem Willamette River during the 1973 

and 1974 studies (table 7). Measured values 

ranged from 1.6 mg/1 at RM 7.0 to 4.5 mg/l at 

RM 72 (both values noted during August 6-7, 

1974). Measured deoxygenation rates (in BOD 

bottles) varied from kt =0.02 to 0.06, with the 

majority of rates at or near kt =0.04. 

To evaluate the compatability of the 

laboratory-determined BOD data with observed 

river deoxygenation, a series of DO and BOD 

mass-balance calculations were made using a 

preliminary version of the DO model described 

in Circular 715-J. These calculations were then 

analyzed in conjunction with measured nitrification and suspected benthal oxygen demand 

(described subsequently). The analysis led to 

the adoption of river deoxygenation rates of 

kr=0.06 for the Upstream Reach (RM 187-52) 

and kr=0.03 for the "Newberg Pool" and Tidal 

Reach. While the kr=0.06 and 0.03 do not match 

exactly the k1 =O.O~}l 1 verage calculated from the 

BOD tests, they are within the measured range 

of 0.02-0.06 derived from the individual BOD 

samples tested in the laboratory. Moreover, the 

higher reaction rate for the shallow "surface 

active" Upstream Reach is consistent with the 

phenomenon of biological extraction and 

accumulation by the periphytic biofilms (see 

Supplement A) that are prevalent in this reach. 

Similarly, the lower deoxygenation rate determined for the deep, pooled reaches below RM 52 

is consistent with the relatively small surfaceto-volume ratio (smaller than the BOD bottle) 

and slow mixing of these reaches. 

A graphical summary of the computed 

BODult mass balance using the adopted kr 

values is shown in figure 12 for comparison 

with measured BODult concentrations. Considering the limitations in measuring BOD at 
TABLE 7.-BODult concentrations and BOD bottle deoxygenation rates for samples of Willamette 

River during summer low-flow periods, 1973 and 1974 (see table 4 for sampling dates)l 

1973 1974 

Average2 Average3 

Sampling Number BODult Average Number BODult Concentration Average 

site of concentration kt of concentration range kt 

(RM) samples (mg/1) (d·l) samples (mg/1) (mg/1) (d·l) 

185 5 2.3 0.04 

161 ------------------ 2 2.8 .05 

134 -----------·------- 6 3.0 .03 

120 ....... ______________ 7 3.0 .04 

86.5 -··········-·-··- 18 3.3 .04 14 2.4 1.7-3.0 0.04 

72 ····---------------· 17 4.2 .06 13 3.4 2.8-4.5 .04 

50 ········-----------· 17 3.7 .04 14 2.9 2.3-3.8 .04 

34 -----·-·-----------· 17 3.6 .04 

28.6 -·----·····-····-· 40 3.2 .04 6 2.5 2.0-3.1 .04 

25.5 ··-··--·-··-·····- 15 3.4 .04 

16.8 ····-···-··-······ 12 3.6 .04 

12.8 ··-··--------·--- 27 3.2 .04 15 2.6 2.1-3.3 .04 

7.0 ··-·········---·· 23 3.1 .04 13 2.3 1.6-3.1 .05 

1All BODwt data calculated from 20-day 20°C BOD tests. See Supplements C and D for methods. 

2Allylthiourea (nitrification inhibitor) was not routinely added to 1973 BOD samples. Data for 1973 are estimates based on ratios of 

inhibited to uninhibited BOD's obtained from reconnaissance sampling in early summer 1973. For this reason, concentration ranges (as shown for 1974 data) are not given. 

3lnhibited with allylthiourea every 5 days. 

187 175 

Albany 

120 

Salem 

86 

Newberg 

50 

RIVER Ml LES ABOVE MOUTH 

Willamette Falls 

26.5 

1----Portland Harbor----

17 13 7 

>-

<( 

0 

a: ~~--.---L-.-~---rL----r-----,------r---~.-----~--~-r----~-----,r-----.---~~100 ~ 

EXPLANATION 

2 4 6 8 10 12 

(/) 

80 ~ a: 

(!) 

0 60 ...J 

~ 

u. 

0 

(/) 

40 ~ 

<( 

(/) 

;::) 

0 

I 

1-

z 

TIME OF TRAVEL, IN DAYS 

FIGURE 12.-Comparison ofmeasured and calculated BODult loads in the Willamette River, during August 1974low-flow 

conditions. Estimated rates of inriver carbonaceous deoxygenation (kr) shown at top of graph. 

such low concentrations there is remarkably 

good agreement between computed and measured BOD along the entire segment from 

Eugene to Willamette Falls (RM 187-26.5). 

There is, however, an anomalous deviation 

through the Tidal Reach (in the deep Portland 

Harbor between RM 12.8 and 7.0) where 

121 

measured values of BODult are higher than 

computed by approximately 30 percent (see fig. 

12). 

ANOMALOUSLY HIGH BOD IN THE TIDAL REACH 

Prior to 1970, there were large loads of suspended organic solids reaching the Willamette 
from pulp and paper mills and, in Portland 

Harbor, from combined-sewer overflow. These 

materials were believed to be responsible for a 

significant summertime benthal oxygen demand in the "Newberg Pool" and the Tidal 

Reach (Velz, 1951, 1961). During 1970, benthal 

respirometer studies of the lower Willamette 

suggested a benthal oxygen demand of27,000 to 

54,000 lb/ d (12,000 to 24,000 kg/ d) in the 

subreach between RM 13 and 7 (Sainsbury, 

1970). Since 1970, industrial process alterations 

and new aerated waste-water treatment 

lagoons at the pulp and paper mills have 

effected a large reduction in the loading of 

suspended organic materials. Furthermore, the 

dry weather combined-sewer overflows of 

Portland had been rerouted for discharge to a 

new secondary-treatment plant on the Columbia River. 

Thus, because the original sources ofbenthal 

deposits had been largely eliminated by 1972, it 

was anticipated that the benthal demand would 

be greatly reduced by 1973. This notion was 

supported by DO data collected by DEQ during 

the low flow period of 1972 and by the 

Geological Survey reconnaissance data collected during spring 1973. Indeed, the summer 

1973 data substantiated that the benthal 

oxygen demand of previous years no longer 

existed in the "Newberg Pool," although an 

anomalous demand still existed in the Tidal 

Reach below RM 12.8. Based on the BODult 

mass-balance computations (fig. 12), the demand was estimated to be approximately 30,000 

lb/d (13,000 kg/d). To further study the 

anomalous demand, a series of riverbed 

samples was collected by dredge hauls between 

RM 18 and 0. Microscopic examination of the 

sediments showed a predominance of clay-sized 

particles, cellulosic organic matter, and diatoms. The material was dark and slightly 

odorous but did not contain wood fibers as 

found in the earlier samples by Sainsbury 

(1970). 

Further evidence concerning the nature of 

the demand was developed through laboratory 

investigation. A series of modified BOD tests 

was conducted on slurried samples of bed 

materials from the affected segment of Portland 

Harbor. The tests indicated an initial oxygen 

demand of 5-10 mg-02/gm of dry sediment. In 

most samples, this demand occurred within 

I22 

2-4 minutes following mixing in the BOD bottle. 

Mter measurement of the initial demand, each 

sample was reaerated and measured for 20 days 

using the probe-reaeration technique described 

in Supplement C. The BODuu values of these 

samples ranged from 3 to 6 mg-02/ gm of dry 

sediment, or approximately 50 percent of the 

initial oxygen demand. The deoxygenation 

rates of the slurried BOD samples (after .the 

initial demand) varied between k1 =0.03 and 

0.06. As previously described this is within the 

same range of rates exhibited by the majority of 

river water samples. 

During the period August 14-18, 1974, a U.S. 

Geological Survey oceanographic research 

team from Menlo Park, Calif., studied the water 

quality of the lower Columbia River system 

(independent of our synoptic studies of the 

Willamette River). Part of the work included 

longitudinal and vertical sampling traverses in 

the Tidal Reach (below RM 20). Results of the 

turbidity and DO measurements are most 

pertinent to the discussion here: 

(1) In segment RM 13-1.5, there was a marked 

stratification of turbidity with depth and 

transient turbidity "jumps" (such as shown in 

fig. 13). Turbidity patterns appeared to change, 

possibly owing to tides, ship traffic, and 

dredging operations. For example, during two 

of the three sampling cruises high turbidity 

readings (rather than the low readings shown 

in fig. 13) were noted between RM 10 and 1.5. 

(2) DO stratification was found in the 

segment RM 13-1.5. Between RM 5.0 and 1.5 

highest DO concentrations were found in 

bottom waters. As described previously, this 

water is composed of cool, high-DO Columbia 

River water that moves as a bottom wedge 

either upstream or downstream in the Willamette, depending on tidal phase. Farther upstream, between RM 5.0 and 13, the stratification was opposite to that found between RM 5.0 

and 1.5. There, the entire water column was 

composed of Willamette River water, the low 

DO concentrations in bottom waters apparently resulting from inplace oxygen demand. Stratification patterns similar to those 

described above had also been noted earlier in 

1973 and 1974 (for example, see fig. 29). 

The conditions described above suggest that 

the anomalous oxygen demand is partly, if not 

largely, of benthal origin. However, other 
40 30 

RIVER KILOMETERS ABOVE MOUTH 

20 10 0 

70 

>- 60 

1-

Ci 

co 

a: 

:::> 

1-

w 

> 

~ 50 

<( 

_J 

w 

a: 

40 

EXPLANATION 

DEPTH, IN FEET 

0-3 

7 

----- 16 

33 

3QL---------~~----------~----------~----------~--------~ 

25 20 15 10 5 0 

RIVER Ml LES ABOVE MOUTH 

FIGURE 13.-Longitudinal and vertical turbidity patterns in the Tidal Reach, Willamette River, 

August 16, 1974. Relative turbidity measurements were made by a recording lysometer. Measurements are not in standard Jackson Turbidity Units but can be used to depict relative site-to-site 

turbidity differences. 

factors are ·undoubtedly involved to some 

degree. 

As discussed elsewhere (Rickert and others, 

1977), planktonic algae carried from shallower 

upstream waters spend a major part of their 

transit time in the deep Tidal Reach below the 

euphotic zone of 2-3 m. This is particularly the 

case in the lowermost segment of the Tidal 

Reach below RM 13. In this segment, primary 

productivity measurements (Rickert and others, 

1977) suggest that water column oxygen 

consumption due to algal respiration may 

exceed total oxygen production by photosynthesis. Another factor that may be 

responsible, in part, for the anomalous oxygen 

demand is waste-water discharges from ships 

and the few remaining submerged combinedsewer outfalls. 

All of these factors are currently (1977) under 

123 

further investigation by the Oregon District of 

the Geological Survey. 

Based on the results of the 1973-74 synoptic 

studies and data collected during the ongoing 

follow-up study (Steven E. Mellor, oral 

commun., U.S. Geological Survey, Portland, 

Oreg.), the anomalous oxygen demand in the 

Portland Harbor (approximately 30,000 lb/ d 

(13,000 kg/ d) between RM 12.8 and 5.0) has been 

tentatively proportioned as follows: 

(1) 1/4-1/3 due to "inplace" benthal oxygen 

demand. 

(2) 1/4-1/3 due to excess algal respiration 

(that is, 02 consumption due to respiration is 

greater than photosynthetic 02 production). 

(3) 1/4-1/2 due to an unknown combination 

of (a) sewer overflows, (b) ship discharges, (c) 

navigation dredging and gravel mining, and (d) 

resuspension of benthal materials by tidal 
currents and propwash. 

These estimates are tentative and may be 

refined by results of the ongoing research. 

NITRIFICATION 

Preliminary analyses of 1973 DO-BOD data 

indicated that carbonaceous deoxygenation 

could not cause the 20-30 percent decrease in 

DO saturation (2-3 mg/l) measured between 

RM 120 and 50 (see fig. 21). Because this 

segment is shallow and swift moving, fine-sized 

benthal deposits are not present. Thus, rather 

than benthal oxygen demand, nitrification was 

suspected as the cause of this DO depletion. 

However, it was not until September 1973 when 

the results of chemical analyses of waste-water 

and river samples were received that 

nitrification was confirmed as the cause of the 

oxygen depletion. Analyses of waste-water 

samples indicated high concentrations of NH4-

N in several industrial effluents. Furthermore, 

DEQ monitoring data indicated NH4-N 

concentrations of nearly 1 mg/1 just below 

Salem, with a conversion of NH4-N to N02-N 

and NOa-N proceeding in the downstream 

direction. 

NITROGEN LOADING 

Estimates of nitrogen loads entering the 

Willamette River during low-flow conditions 

from waste-water outfalls (point sources) and 

tributaries (nonpoint sources) are shown in 

table 8. The estimates are based on NH4-N, 

N02-N, and NOa-N analyses of samples 

collected during the summers of 1973-7 4. Most 

of the major municipalities and industries were 

sampled 5-10 times, and the major tributaries 

(Middle Fork, McKenzie, Santiam, and 

Clackamas) 2-4 times; minor industries, 

municipalities, and tributaries were sampled 1-

3 times. Table 8 clearly shows for low-flow 

conditions that most of the nitrogen in the river 

(approximately 80 percent) comes from 

municipal and industrial waste-water discharged to the Upstream Reach. Analyses 

showed that approximately 90 percent of this 

nitrogen was in the form NH4-N and, thus, 

potentially subject to nitrification once 

discharged to the river. 

By far the largest known NH4-N source in the 

Upstream Reach was at RM 85 where a wood 

vroducts industry discharged 16,000-30,000 

lb/d (7,300-13,600 kg/d) of NH4-N during the 

summers of 1973 and 1974. 

NITROGEN CONCENTRATIONS IN 

WILLAMETTE RIVER 

Observations of NH4-N, N02-N, and NOa-N 

in the river during the August 12-14, -1974 

nitrification study are shown in figure 14. The 

data indicate a rapid conversion of NH4-N to 

NOa-N between RM 120 and 50. The conversion 

is particularly apparent between RM 86.5 and 

55. Below RM 55 in the deep "Newberg Pool" 

and Tidal Reach, nitrification is not indicated 

either by nitrogen analysis or by the DO profile 

(fig. 21). Above RM 120 the absence of 

significant nitrification is (despite the 

availability of a cobbly substrate for nitrifier 

biofilm growth) suggested by the low nitrogen 

concentrations and the lack of DO depletion 

(fig. 21). 

Because rapid oxygen depletion (fig. 21) was 

most evident in the segment RM 86-55, the field 

data were used to calculate a nitrification rate 

coefficient, kn· Using the rate of appearance of 

NOa-N as a basis (fig.14), a value of kn =0.7was 

estimated as the effective, inriver rate of 

nitrification. (See Supplement A, "Nitrification" for discussion of first order equation.) 

Nitrate-N appearance was used as the basis for 

the kn calculation (instead ofNH4-N disappearance) because very little NOa-N enters the 

segment RM 86.5-55 from waste-water outfalls 

or tributaries. Also, no major tributaries enter 

the Willamette in this segment, and flow is 

essentially constant throughout. Thus, increases in river NOa-N concentrations should 

be attributable to conversion from NH4-N. 

(Nitrogen losses to algal assimilation or 

denitrification were assumed to be minor.) 

NITRIFYING BACTERIA 

The occurrence of nitrification in a shallow, 

surface-active reach and the contrasting absence in a deep, slow-moving reach is consistent 

with recent work by Tuffey, Hunter, and 

Matulewich (1974). They noted that nitrification in shallow, swift-flowing reaches would 

occur by virtue of an attached, rather than a 

suspended community of nitrifying organisms. 

To test this idea in the Willamette River, 

enumerations were made of nitrifying bacteria 

in water samples and in biological slimes 

124 
TABLE B.-Inorganic nitrogen loading to the main stem Willamette River during summer 1973-74 conditions 

Total inorganic nitrogen1 loading 

Municipal or industrial outfall2 (point sources) Tributaries3 (nonpoint-source components only) Combined 

------------------- River reach Lb/d Percentage Percentage Lb/d Percentage Percentage Percentage Lb/d 

asN in reach of total asN in reach of total of total as N 

Upstream reach 

(RM 187-52) --·--·····-· .. 30,()()()4 93 80 2,400 7 6 86 32,000 

"Newberg Pool" 

(RM 52-26.5) ________ , _______________ 2,800 82 7 600 18 2 9 3,400 

Tidal reach 

(RM 26.5-0) ····--··--------------- 1,600 84 4 300 16 5 1,900 

Total. 91 9 

1Approximately 90 percent of the nitrogen from municipal and industrial outfalls and 40 percent of the nitrogen from tributaries is in the NHl-N form. 

20utfalls discharging either directly to Willamette River or into Middle Fork, McKenzie, Santiam, or Clackamas Rivers less than 20 mi from confluence with 

Willamette. 

3Estimated from nitrogen concentrations measured in tributaries above waste-water outfalls. 

•Nitrogen mass-balance calculations based on measured loadings and inriver concentrations indicate the possibility of up to 12,000 additionallb/d ofNH4+-N 

entering this reach, most probably in the Albany-Millersburg area. DEQ is currently (1977) studying the nitrogen loading in the Upstream Reach in more detail. 

RIVER MILES ABOVE MOUTH 

a: 

L.U 

Albany 

120 

Salem 

86 

Newberg 

50 

Willamette Falls 

26.5 

1----Portland Harbor--------• 

17 13 7 

t1.4 

..J 

0: 

L.U 

a.. 1.2 en 

~ 

<( 

0: 

~ 1.0 ..J 

..J 

..,....,-----

-- ---- z 

~ .8 ~ ..,...., -- -------- NO~ 

z· I --------- 0 I 

i= .6 

<( 

0: 

tz .4 L.U 

() 

z 

0 

() .2 

z 

L.U 

<!) 

0 0 0: 

t 0 2 4 6 8 

z TIME OF TRAVEL, IN DAYS 

FIGURE 14.-lnorganic nitrogen concentration in the Willamette River during August 12-14, 1974. Breaks in 

lines indicate sampling locations. Each point is an average of three samples. 

scraped from bottom rocks (table 9). Nitrosomonas concentrations were >1 most probable number (MPN)/ml in all water samples. In 

slimes, Nitrosomonas concentrations were > 1 

MPN/mg above RM 86 and 1-4MPN/mg in 

samples collected between RM 86 and 55 (the 

active zone of nitrification). (Shortly below RM 

55, the deep "Newberg Pool" begins, and few 

bottom rocks are available for attachment of 

biological slimes.) Nitrobacter enumerations 

were also made. In the zone of nitrification the 

I25 

counts ranged from > 1 to 4 MPN/ml in water 

samples and from 3-50 MPN/mg in slimes. The 

combined bacteriological data, though not 

absolutely definite, tend to support the 

hypothesis that nitrification occurred in slimes 

attached to rocks rather than in flowing water. 

An interesting sidelight of the bacterial 

enumerations relates to the notion thatnitrifier 

counts in streambed slimes must be 103MPN/ 

mg or greater in order to cause a significant 

nitrification-induced oxygen demand (see Tuf-
TABLE 9.-Counts of Nitrosomonas and Nitrobacter 

bacteria in river water and on rock slimes, Willamette 

River, August 12-14, 1974 

Sampling site 

(RM) 

120 (above Albany) 

114 (below Albany 

and Conser 

Slough) .................. . 

86.5 ---------------------········ 

79{right side ......... . 

left side ............ . 

72 ········-··------------------·· 

60 ----------------------------·· 

55 ----------------------------· 

50 ------------------------------

39 --------·---------------------

28.6 ----------------------------

12.8 ---------·------------------

7.0 -·························· 

River water1 Rock slimes2, 3 

Nitrosomonas Nitrobacter Nitrosomonas Nitrobacter 

(MPN/ml) (MPN/ml) (MPN/mg) (MPN/mg) 

-<1 -<1 <1 

<1 <1 <1 2 

<1 1 <1 50 

<1 4 4 4 

<1 <1 

<1 1 3 3 

<1 430 1 6 

<1 90 2 20 

-<1 1 

<1 230 

<1 1 

<1 1 

<1 1 

1Most probable number (MPN) from "Standard Methods" (American Public 

Health Association and others, 1971, p. 676) 3-tube dilution technique. 

2Calculated from dry weight of slurry. Rock slimes were obtained from 

scrapings of randomly sampled river rocks. Scraped slimes were suspended in a 

small volume of river water, subsampled, and incubated using the 3-tube 

dilution technique. Details of the methodology are described by Tuffey (1973) 

and Ehrlich (1975). 

3Below RM 55, the river channel is deep and slow moving with few rocks for 

attachment and growth of nitrifiers. Although nitrifiers are undoubtedly 

present in bottom muds, their impact on the DO regimen is insignificant because of the low rate of renewal between the mud-water interface. 

fey, 1973). The 1974 data, and more recent 

nitrifier counts made in 1976 (D. A. Dunnette, 

written comm., DEQ, Portland, Oreg., 1977), do 

not support this notion. Instead, we hypothesize 

that there is no threshold number of streambed 

nitrifiers necessary to induce high-rate nitrification. We believe concentrations lower than 

103MPN/mg can induce p.igh-rate nitrification 

if the reach is relatively gravelly or cob bly (high 

surface to volume ratio) and well mixed. Such 

conditions, which prevail in the Upstream 

Reach of the Willamette (fig. 7; table 3), allow a 

rapid renewal of NH4-N with a large area of 

streambed to which nitrifiers are attached. 

PHOTOSYNTHESIS AND RESPIRATION 

The amount of oxygen produced by a 

community of aquatic plants during a 24-hour 

period is an estimate of net primary production. 

Oxygep production occurs only during daylight 

hours of the 24-hour period. Therefore, if the 24-

hour net primary production is positive, 

photosynthesis is presumably producing more 

oxygen than is being consumed by plant 

respiration. If net primary production is 

negative, respiration is consuming more oxygen than is being produced by photosynthesis. 

I26 

The amount of oxygen consumed (respiration) 

during a 24-hour period added to the amount of 

oxygen produced (net primary production) is an 

estimate of gross primary production. This 

calculation assumes that the rate of respiration 

is the same in the light ~sin the dark. __ Phytoplankton production was measured at 

various sites in the Willamette River (table 10) 

using either the diel-curve method or the lightand-dark bottle technique (Slack and others, 

1973). For the light-and-dark bottle method, net 

production was determined from gross production by subtracting community respiration as 

calculated from inriver BOD concentrations 

and deoxygenation rates (see "BOD Concentrations and Rates in Willamette River"). This 

approach was used so that net production could 

be calculated for the entire water column as well 

as the euphotic zone. 

The values summarized in table 10 must be 

considered only as approximations. This interpretive limitation results from (1) the many 

assumptions involved in primary production 

tests and (2) the lack of reliable methodology for 

accurately partioning plant respiration from 

total community respiration. Because of these 

difficulties and because of the limited number of 

tests conducted, it is impossible to analyze the 

production data in table 10 with regard to 

temporal and spatial patterns. Overall, however, the production data do suggest that values 

for net water column primary production are 

fairly low in magnitude (positive or negative) 

and clustered near zero. In itself, this distribution of values suggests that there is an 

approximate riverwide balance of oxygen 

produced by photosynthesis and oxygen consumed by plant respiration. (Indeed, this possibility has been substantiated by subsequent 

application of the WIRQAS DO model to all 

oxygen-related data presented in this report. 

See Circular 715-J for further details). 

The notion of an approximate daily average 

oxygen balance between plant photosynthesis 

and respiration appears to be plausible, at least 

for long segments of the river. However, as 

previously described (see "Anomalously High 

BOD in Tidal Reach) there may be local 

exceptions. Also, as shown in Supplement E 

(figs. 27-30), photosynthesis induces diel variations in DO concentrations, particularly at the 

shallow sampling sites above RM 52 and in the 

euphotic zone of several sites below RM 52. Diel 
TABLE 10.-Estimated primary production at various sites in the Willamette River, during summers of 1973 and 1974 

Primary production in g-02/m2/d 

---------------- Diel curve method Light-dark BOD method 

River mile 

1612 --···············-·-·--············· 

86.52 ···-···-···········-··-······-·· 

12.83 ··-·············--· ··········-· 

12.83 ··········--··-· ............... . 

12.83 ···············-····-············ 

12.83 --····--·····-·····-··--···-·-···· 

7.03 ····-······---······-··········-· 

7.0 -··············-·-················ 

7.0 -···········-·······-·--·--······ 

Date 

8/09173 

8/15173 

7/05174 

8/05174 

8/06174 

9/19174 

7/25173 

9/17174 

9/19174 

Gross in Net in 

water column water column 

3.7 -1.2 

2.7 -l.O 

1.7 0.1 

Gross in Net ineuphotic zone euphotic zone water columnt 

1.8 1.3 0.1 

1.9 1.4 .2 

1.6 1.5 .3 

1.7 1.4 .4 

4.4 3.7 .7 

2.0 1.3 -1.7 

NoTES.-See Rickert and others (1977) for further discussion of data in table. All measurements made during relatively steady low-flow 

conditions. 

•Calculated from detailed channel geometry measurements assuming an effective respiration rate of 0.03/d. 2Entire water column in euphotic zone (effective channel depth <6 ft or 2m). 3Euphotic zone (depth to 1 percent light transmittance) varied between 6-10ft (2-3m). 

variations in DO due to photosynthesis are not 

new to the Willamette River as evidenced by 

comparison of diel DO curves from 1929 with 

1973 (fig. 15). 

ATMOSPHERIC REAERA TION 

Atmospheric reaeration is the transfer of 

oxygen from the atmosphere to river water 

under conditions of a DO deficit (see Supplement A). Reaeration is commonly described in 

mathematical terms by the reaeration equation: 

where 

dC 

- =K2(Cs -C) dt 

C=river DO concentration, 

Cs=DO saturation concentration at prevailing river water temperature, 

Cs-C=DO deficit, 

K2=reaeration coefficient, proportional to 

stream depth and velocity 

in the form 

(velocity)a . . K2 ; a and b are emp1ncal 

(depth)b 

coefficients, and 

t=time. 

The rate at which a river can be reaerated at 

any location for a particular DO deficit is 

reflected by the reaeration coefficient, K2. This 

coefficient, is in effect a measure of the river's 

127 

reach-to-reach "reaeration potential" as controlled largely by cross-sectional velocity and 

channel morphology. Although K2 is not 

directly measurable, reach-to-reach estimates 

can be made from velocity and channel 

geometry data. 

Several common forms of the reareation 

equation were used to calculate k2 values for 

different sites on the Willamette River (fig. 16). 

Note that the calculated values exhibit a 

consistent difference of one to two orders of 

magnitude between the shallow Upstream 

Reach (RM 187-52) and the deep "Newberg 

Pool" (RM 52-26.5). This relationship reflects 

the expected higher "reaeration potential" of 

the Upstream Reach due to higher velocities 

and shallower depths. (Note that only Velz k2 

values are shown for the Tidal Reach (RM 26.5-

0) because the other equations have not been 

calibrated for tidal rivers.) 

Above RM 54, the Churchill (1962), Bennett 

and Rathbun (1971), and Krenke! and Orlob 

(1962) equations predict higher reaeration 

coefficients than the Velz (1970) graphical 

technique. However, in the deep, slow-moving 

Newberg Pool, the pattern is reversed. Because 

the predictive accuracy of the individual 

equations can be fully evaluated only through 

mass-balance computations involving all the 

significant self-purification processes, equation 

predictions were examined through preliminary use of the WIRQAS DO model. The results 

showed that only the Velz technique provided 

reasonable reaeration inputs for the Willamette 

River (that is, inputs that resulted in good 
10 

Coast Fork Wi llamette River 

/,_ 

/ """" ' 9 

8 

10 

~ "-. 

a: 

w 

9 

8 

9 

~ .. 

......____. 

... ~ 

~~ 

/ " / 

/ RM 186 ' - /v 

/ """"' 

/ ' 1"-----fl' ' RM 184 

t:: 8 ...J 

a: 

w 

Q. 

~ 10 

<( 

a: 

(.!) 9 ...J 

...J 

~~ 

~ 

~ 

I 

/ ' \ v McKenzie River ' 

... .... 

~~ 

~ 

(A) 1929 

10 8 

RM 131 - / 9 

............._ ' 7 

~ 

-""' 8 - 6 

... ..., ... , ·~ ~ ~ 

,.-..... 

/_ ' 9 6 

/ "\. 

./ Sant iam River 

8 5 

7 4 

..... ....,.,--........ .. ~ 

_, ..... v 

"-.... ~ RM 95 

>· .. 

1-......... 

9 

8 

5 

> ... , .... .. ~ 4 

8 .. .......__ -i-"""' 

RM 86.5 ,.,..-- 7 4 

~ 8 6 

~ 0 

z 

12 24 0 12 

3 

24 0 

0 

i= 

<( 

a: 

1-

z 

w 

() 

z 

0 

() 12 

z 

w 

(.!) 

~ 11 

0 

Cl 

w 10 

> 

...J 

0 

~ 9 

Cl 

12 

11 

10 

9 

....... 

I" 

8 

0 

-

j~ - / " " RM 185 

~I" 

/~ 

/ ' \. 

I \ 

v \ 

McKenzie River '\ 

12 24 

TIME, IN HOURS 

(B) 1973 

~ / RM134 ,........__, 

I 

I 

' ../ Santiam River 8-~---=~---+----~--~ 

9 

8 

7 

7 

6 

9 ... ~ ..... 8 

./ 

- RM96 

7 

8r---~~---r----+---~ 

.. ~ 

~ .. 

... 

RM 86.5 

0 12 

6 

24 0 

TIME, IN HOURS 

-

-

__. t-... 

v ~ ' 

RM 72 

I" 

............_ l---'" 

RM 39 

~ .... 

I" 

~ r-...... ""--/ ' 

RM 25.5 

... 

... ~ 

- - ~ ............... 

RM 17 

12 24 

~ r-....... 

/r 

L 

RM 72 

> 

- ...... RM 34 

"I'-

RM 25.5 

.....,. ~ ~ 

- ~ 

RM 17 ./ 

12 24 

FIGURE 15.-Summertime (low-flow condition) diel DO curves at various sites on the Willamette River and tributaries (A) 1929 and (B) 1973. 1929 data from Rogers, Mockmore, and Adams (1930); 1973 data collected by 

U.S. Geological Survey, see figures 27, 28, 29, and 30. 

128 
agreement with observed conditions). The 

reasons for the apparent inability of the other 

equations to describe reaeration in the Willamette system are unknown. 

RIVER-DISSOLVED OXYGEN 

The cumulative effect of the individual 

deoxygenation and reoxygenation processes 

described above is reflected in the temporal and 

spatial pattern of DO concentrations observed 

in the river. River DO data from the 1973-74 

synoptic surveys were collated by date, time, 

sampling site, depth, and cross-channel position. Concurrently collected water temperature 

RIVER KILOMETERS ABOVE MOUTH 

300 

2.0 

1.0 

0.5 

0.2 

> 0.1 

<( 

0 

[[ 

w 

Q. 

0 0.05 

w -

en 

<( 

m 

C\1 

.lie 

0.02 

0.002 

250 

161 

200 150 

River data for k2 calculations 

River Effective Average velocity 

mile depth (ft) (ft/sec) 

185 

161 

134 

120 

95 

86.5 

72.0 

60.0 

54.0 

50.0 

46.0 

38.0 

34.0 

28.0 

25.5 

21.3 

16.8 

12.8 

7.0 

4.5 

5.4 

8.0 

5.5 

6.2 

6.8 

4.8 

7.0 

13.2 

21.6 

27.8 

31.3 

30.8 

33.2 

16.2 

55.2 

39.4 

39.6 

41.8 

134 120 

3.2 

3.2 

2.7 

2.6 

3.0 

2.8 

3.4 

3.6 

.84 

.61 

.39 

.40 

.29 

.23 

.86 

.31 

.25 

.23 

.12 

100 

Krenkel and Orlob (1962) 

RIVER MILES ABOVE MOUTH 

50 11.3 

FIGURE 16.-Calculated reaeration coefficients (k2) for various sites in the Willamette River, using four different reaeration 

prediction methods. 

129 
data were used to convert DO concentration to 

percent saturation. A detailed graphical summary of all these data is given in figures 27-30, 

Supplement E. Selected results from the 

summary are highlighted below in order to (1) 

permit a comparison of Geological Survey data 

with independently collected data of the DEQ, 

(2) define DO conditions typical of individual 

sites in each of the three distinctive morphological reaches (fig. 6), and (3) present a representative average daily DO profile of the 187-mi (300 

km) main stem Willamette River for steady, 

summer low-flow conditions. 

INDEPENDENT CHECK OF THE DO DATA 

Average DO concentrations and concentration ranges for each sampling site studied 

during July and August 1973 and August 1974 

are shown in figures 17 and 18. Also shown are 

independently collected DO data from the 

Oregon DEQ river surveillance program(public 

files, DEQ, Portland, Oreg.). The DEQ data 

were segregated to include only those samples 

collected during periods of relatively stable low 

flow. Note that there is relatively good agreement between the two data sets. 

DO VARIATIONS AT INDIVIDUAL SITES 

Sampling sites less than 15ft ( 4.8 m) in depth 

(all sites above RM 50) showed no measurable 

DO variability with depth. However, the deeper 

sites in the "Newberg Pool" (particularly RM 

39) and the Tidal Reach (RM 12.8, 7.0, and 6.0) 

showed slight DO and water temperature 

variations with depth (figs. 28-30). Highest DO 

concentrations in these deep reaches were 

generally in the near-surface waters (upper 10ft 

or 3.2 m), and the lowest concentrations were in 

near-bottom waters, particularly below 20 ft (6 

m). Exceptions occurred at RM 3.5 and 1.5 (fig. 

29) where the bottom inflow of cool, high-DO 

Columbia River water caused a reversal of this 

general pattern. 

Above RM 50, horizontal DO variations of up 

to 25 percent saturation were noted at several 

sites because of the photosynthetic activity of 

periphytic algae. However, these variations 

were observed only in shallow ( > 3 ft or 1 m), 

slow-moving parts of the flow out of the main 

channel. Slight horizontal variations (less than 

5 percent saturation) were also found at sites in 

the lower part of the Tidal Reach (RM 3.5 and 

130 

1.5) where waters from the Willamette and 

Columbia intermix. 

Diel variations in DO and water temperature 

were striking in the shallow upstream sites 

(above RM 50) but were relatively minor at sites 

in the "Newberg Pool" and Tidal Reach (figs. 

27 -30). A detailed example of diel DO and water 

temperature variability (RM 161) is shown in 

figure 19.The DO and temperaturecurvesatRM 

161 (and all other sites above RM 50) reflect 

photosynthesis and respiration by periphytic 

diatoms and a response to diel air temperature 

changes. Of particular interest in figure 19 is 

the impact of day-to-day solar radiation 

patterns. August 7 and 8, 1973, were hot and 

sunny, but August 9 was cooler and partly 

cloudy. _ DO variations observed during July 24-26, 

1973, at four sites in the Tidal Reach (RM 16.8, 

12.8 at 6-m depth and RM 7.0 at 6- and 1-m 

depths) are shown in figure 20. (Note that the 

data at RM 7.0 show DO concentrations in the 

near-surface waters to be higher than those in 

deeper water.) Examined as a whole, the four 

curves in figure 20 show a gradual DO depletion 

between RM 16.8 and 7.0 but an upward trend in 

DO concentration at each site for each 

successive day of measurement. July 24, 1973, 

was preceded by a week of cloudy weather that 

caused a reduced level of photosynthetic 

activity, but the July 24-26 period was hot, 

sunny, and, on July 25 and 26, windy. (No 

quantitative solar radiation or wind data are 

available for inclusion here.) These factors 

apparently led to increases in photosynthetic 

oxygen production and atmospheric reaeration 

for each successive day. 

SYNOPTIC DO PROFILE 

A DO profile of the Willamette, using the 

average daily DO concentrations obtained from 

the 1973 U.S. Geological Survey data, is 

presented in figure 21. The profile is constructed 

with time of travel on the horizontal axis to 

permit examination of the rate of change in DO 

concentration in the downstream direction. The 

profile also includes some brief notes relative to 

the predominant factors controlling DO concentrations in various segments of the river. 

DISCUSSION 

The DO regimen of the Willamette can be 
RIVER KILOMETERS ABOVE MOUTH 

300 250 200 150 100 60 45 30 15 0 

z 

0 

i= 

<( 

110 

~ 100 :::> 

1-

<( 

en 

1-

z 

~ 90 

~ 

w 

0.. 

z 

z 80 w 

C) 

>-

X 

0 

~ 70 

> ...J 

0 

en 

en 

0 60 

EXPLANATION 

Max. J 

Avg. T USGS 

Min. 

Max. T 

I 

Avg. * DEQ I Min . .a. 

150 

T 

100 50 30 20 10 0 

RIVER MILES ABOVE MOUTH 

FIGURE 17.-Dissolved oxygen concentrations measured in the Willamette River by U.S. Geological Survey and DEQ 

during 1973 summer low-flow period, July 5 to August 18. Note break in scale below RM 30. 

conveniently examined and explained by 

taking a hypothetical downriver excursion 

while referring to the DO profile in figure 21. 

HYPOTHETICAL BOAT TRIP 

Assume that the boat travels at the average 

velocity of the river and that observers in the 

boat can obtain daily average DO concentrations by sampling at a single point in each cross 

section at any time of day. 

RM 185 TO 120 

The trip would begin at Eugene-Springfield 

and proceed downriver to RM 120 (Albany), a 

distance of 65 mi (105 km), in 1-1/3 days. DO 

concentrations throughout this segment are 

consistently near 100 percent oxygen saturation, or about 9.4 mg/1 at the prevailing average 

water temperature of 18-19°C. The McKenzie 

River enters the Willamette at RM 175 but, with 

a DO concentration of 100 percent saturation, 

131 

does not cause any measurable change in DO 

conditions. The impact on DO concentration of 

waste-water loads from municipalities and 

industries in Eugene-Springfield, Corvallis, 

and other smaller communities is discernible 

only in the immediate vicinity of outfalls. 

Because of the relatively light loading of 

ammonia in this segment, nitrification is 

insignificant, and the high atmospheric reaeration capability of the shallow, fast moving 

segment quickly counterbalances the relatively 

slow rate of carbonaceous deoxygenation. 

RM 120 TO 50 

During the next 1-2/3 days the boat travels 70 

river miles (103 km) from Albany to Newberg. 

Beginning at RM 114, DO concentrations begin 

to decrease slowly and then to decrease rapidly 

below Salem (RM 85). Between RM 120 and 50, 

DO concentrations decline approximately 30 

percent from near 100 percent to 70 percent, a 
RIVER KILOMETERS ABOVE MOUTH 

100 00 0 

z 

Q 100 

1-

c:( 

a: 

::::> 

1-

c:( 

(/) 

1-

z 

w 

0 

a: 

w 

0.. 

z 

-, 80 

z 

w 

(.!) 

> 

X 

0 

Cl 

w 

> ..J 

0 

(/) 

(/) 

Ci 

80 60 

I 

I 

I 

I 

I 

I 

I 

.J. 

EXPLANATION 

Max. I 

Avg. l USGS 

Min. 

Max • .,. 

I 

Avg. t DEQ 

Min. 

40 

T 

I 

I 

I 

I 

I 

6 

I 

I 

I 

I 

I 

I 

I 

.... 

20 0 

RIVER MILES ABOVE MOUTH 

FIGURE 18.-Dissolved oxygen concentrations measured in the Willamette River by U.S. Geological Survey and DEQ 

during 1974 summer low-flow period, August 1-15. 

drop of approximately 2.5 mg/1 at the prevailing water temperatures. The decrease is due to 

large industrial ammonia loads that induce the 

growth of nitrifying bacteria on the cobhly, 

diatom-encrusted river bottom. The bacterially 

induced nitrification proceeds at a high rate, 

outpacing the capacity of the river in this reach 

to produce DO by atmospheric reaeration. 

RM 50 TO 10 

The next 40 river miles, (64 km) require a 

traverse time of about 8 days. DO variations in 

this segment are minor relative to the large DO 

decrease between RM 120 and 50. The observed 

DO variations include (I) an approximate 5 

percent increase in saturation caused by 

at Willamette Falls and the inflow of cool, 

highly oxygented water from the Clackamas 

River, (2) a slight decline in percent saturation 

between RM 21 and 12.8 resuting from 

carbonaceous deoxygenation, and (3) a 

somewhat sharper decline between RM 12.8 and 

10 owing to the additive effects of carbonaceous 

deoxygenation and the anomalous oxygen 

demand. Because the rate of carbonaceous 

deoxygenation is slow, the total reaeration 

effectively balances deoxygenation in this 

132 

segment and keeps DO concentrations at a 

relatively stable level. 

RM 10 TO 1.5 

During the next 6 days the boat progresses 

only 8.5 mi (14 km). Despite the slow net downstream movement, the boat moves erratically 

owing to once-or-twice daily flow reversals and 

strong eddy currents induced by tidal effects. 

Between RM 10 and 6 the river often appears 

turbid, and there is a gradual decrease in DO 

concentration (7 percent) which results primarily from the anomalous demand. From RM 6._9 

to 3.5, DO concentrations remain fairly 

constant (approximately 63 percent saturation 

or 5.4 mg/1). In the vicinity of RM 3.5, near the 

entrance to Multnomah Channel (see fig. 10), 

DO concentrations begin to rise sharply owing 

to mixing with the Columbia River. At RM 1.5, 

approximately 1-1/2 days travel time from RM 

3.5, the DO concentration has risen to 7 4 

percent saturation. Concentrations continue to 

rise, finally reaching 97 percent saturation at 

the Columbia River confluence. 

HISTORICAL PERSPECTIVE 

The 1973 DO profile is compared with 
30 

a: 

120 12 w 28 

1-

...J 

a: 

w 

0.. 

z en en 0 ~ :::> 

i= 110 Percent DO saturation 11 <( 26 (j) 

<( a: ...J 

a: (.!) w 

:::> ...J (.) 

1- ...J {/) 

<( ~ w en w 

1- ~ a: 

z 24 ~ ~ 100 10 z· a 

a: 0 

w i= ~ 0.. <( u.i ~ a: a: 1- :::> z z w 1- w 90 9 (.) (.!) 22 ~ z 

>- 0 w X (.) 0.. 

0 ~ 

a 

z w w 1- w (.!) a: > >- ...J w 

0 X 20 ~ en 80 8 0 en a 3: 

c w 

> ...J 

0 

en 

en Water temperature 7 70 a 18 

16 

TIME, tN HOURS 

FIGURE 19.-Di~l dissolved oxygen and water temperature curves, Willamette River at Harrisburg (RM 161), August 7-9, 

1973. August 7 and 8 were bright, sunny days; August 9 was partly cloudy. 

historical DO conditions in figure 22. Similarities among the profiles include the zone of DO 

recovery below RM 5.0 caused by mixing with 

Columbia River water, a DO low point probably 

due to benthal oxygen demand between RM 10 

and 5, and a DO increase (at least in several of 

the profiles) immediately below RM 26.5 caused 

by reaeration at Willamette Falls and the inflow 

of the Clackamas River. 

The DO profiles do not reflect any simple time 

trend, although there is a clear pattern of recent 

improvement as shown by the 1968-73 profiles. 

In general, the improvement in DO conditions 

is attributable to the reduction in BOD loads 

(fig. 23) and related benthal deposits, and, after 

1954, to increased flows in summer and fall 

I33 

from reservoir flow augmentation (table 2). 

Interestingly, the 1971 DO profile tends to be 

higher than the 1973 profile despite the fact that 

secondary waste-water treatment plants were 

not all in operation until 1972. This apparent 

anomaly can be explained by the higher 

augmented flows during summer 1971 and the 

fact that during 1968-71, pulp and paper mills 

were on a program whereby highly concentrated wastes were stored and discharged to the 

river only during high-flow conditions. 

Despite the general improvement in recent 

DO conditions, Horowitz and Bazel (1974, p. 77-

122) analyzed historical DEQ river BOD5 data 

and concluded that BOD5 concentrations had 

not changed significantly between 1954 and 
0:: 

w 

1-

_. 

0:: 7 w 

Cl. 

Cl) 

~ 

<( 

0:: 

(!) 

_. 

_. 

~ 

~ 

z 

0 

~ 

~ 6 1-

z 

w 

(.) 

z 

0 

(.) 

~ f"'-1~ 

/

/"-- ( ""' I r, // 

\ ,j .,.,,." -,,"~ I / ., 

) .,.," .._, ;._ .,,' 

z 

w 

(!) 

>-

X 

0 

'--- .,----·"'~ ~ r 

../'-~---" '~ \I 

I 

Cl 

w .,.-~/ EXPLANATION 

> _. 

~5 Cl) 

Cl 

0 6 12 18 24 6 12 18 24 

TIME, IN HOURS 

RM 16.8 (depth, 20ft ) 

RM 12.8 (depth, 20 ft ) 

RM 7.0(depth, 3ft) 

RM 7.0 (depth, 20ft) 

6 12 18 24 

FIGURE 20.-Diel dissolved oxygen curves at four sites in the Tidal Reach Willamette River, July 24-26, 1973. 

1971. This suggested that reductions in BOD 

loading had not occurred and, thus, that BOD 

removal could not be cited as a major cause of 

improved DO conditions. They discussed 

several reasons for this paradox, emphasizing 

river sampling problems and the inaccuracies 

of the Winkler method (used by DEQ) for 

measurement of DO. (The Winkler method is 

subject to interferences by reduced chemical 

compounds, including sulfite, that were sometimes present in significant quantities in the 

river below pulp mill waste-water outfalls.) 

A confounding factor not discussed by 

Horowitz and Bazel is that river deoxygenation 

rates have decreased markedly between the 

1950's and the 1970's. In the early 1950's, Velz 

(1951) found kr's in the range of 0.10-0.14, as 

contrasted with the prevailing 1973-74 k,'s of 

0.02-0.06. Assuming first order BOD decay and 

134 

a k,.=0.04, only 40 percent ofBODult was utilized 

in 5 days under 1973-74 conditions as opposed 

to the 76 percent exerted at a k7=0.12 under 

1950's conditions. Thus, depending on k 7 and 

the time of travel between an outfall and the 

sampling site, 1954 and 1971 river BOD5 samples from a common site may give equivalent 

results in terms of concentration. However, 

because of the higher rate of deoxygenation, the 

1954 BOD5 sample reflects more upstream 

oxygen depletion than the 1971 sample. 

The above example underscores the inadequacies of the BOD5 test and the need for 

determining deoxygenation rates and BODult 

concentrations from a long-term BOD test 

(Supplement C). Without this information, 

determination of DO and BOD time trends are 

exceedingly difficult, and q uan tita ti ve analysis 

of the DO regimen is subject to gross errors. 
RIVER MILES ABOVE MOUTH 

187 134 86.5 50 39 34 28.6 17 12.8 10 7.0 6.0 3.5 1.5 0 

z 

0 

i= 

<( 

~ 100 

1-

<( 

(/) 

1-

z 90 w 

(.) 

[[ 

w 

Q. 

~ 80 

z 

w 

(!) 

>- 70 

X 

0 

0 

w 

> 60 _J 

0 

(/) 

(/) 

0 50 

Reaeration at Willamette Falls 

~ 

I 

Nitrifi- )-- 02 demand~ -cat; on -

1 

atmosp""''c ,ea.,at;on 

Discharge at Sa•em=6000 ft3fs (170 m3Jsl 

DO recovery 

~' 

Suspected benthic --L-f o 2 demand --,~Mixing with the _ I • Columbia River 

I I 

I I 

0 5 10 

TIME OF TRAVEL, IN DAYS 

15 

FIGURE 21.-Composite DO profile of the Willamette River under 1973 steady low-flow conditions. The profile is 

plotted on a time-of-travel basis to emphasize the relative rates that DO is removed or added in various reaches. 

Major controlling factors are noted for appropriate reaches. 

CONCLUSIONS 

1. Dissolved-oxygen concentrations in the 

Willamette River have increased dramatically 

during the last two decades. The improvement 

has resulted primarily from basinwide secondary waste-water treatment, removal of Portland's dry-weather combined sewer overflows 

from the Tidal Reach, increased low-flow 

augmentation from storage reservoirs, and 

chemical recovery processes at pulp and paper 

mills (Gleeson, 1972). Besides the high DO 

concentrations, the present-day (1977) DO 

regimen of the Willamette also reflects certain 

recently evolved phenomena (see below) that 

may occur in other rivers as basin wide 

secondary treatment becomes more prevalent. 

2. Augmented summer streamflows provide 

a large source of DO-rich water and reduce the 

detention time of oxygen-demanding materials 

in the river. The chemical recovery processes at 

the pulp and paper mills have effectively 

reduced the discharge of oxygen-demanding 

wood fibers and sulfite. During the 1973-74 

summer studies, DO concentrations were above 

5.0 mg/l throughout the river with the exception 

of bottom waters isolated in deep sections of 

Portland Harbor. As in past years, the lowest 

135 

DO concentrations in the Willamette continue 

to occur during summer low-flow conditions in 

the Portland Harbor between river mile (RM) 

7.0 and 3.0. 

3. Discharge of carbonaceous waste waters, 

historically the major cause of severe DO 

depletion in the Willamette, has been dramatically reduced. Concentrations ofBODultin the 

river were consistently less than 4 mg/l. 

Moreover, 45 percent of the BODult in the river 

during 1974 low-flow conditions was from 

nonpoint (diffuse) sources and in-stream production, rather than from waste-water outfalls. 

Equally as important as the reduction in BOD 

loads is the fact that the carbonaceous material 

in effluents from the secondary waste-water 

treatment plants is now relatively stable. Thus, 

the material is oxidixed more slowly in the river 

(k,=0.02-0.06) than the material previously 

discharged in primary waste-water effluents 

(k,=0.10-0.14). 

4. The low levels of BODult and the reduced 

rate of carbonaceous deoxygenation imply 

strongly the need for long-term BOD determinations, in lieu of the traditional BOD5 test, 

as a basis for DO-BOD studies in rivers 

receiving secondary waste-water effluents. This 

concept, though recognized for decades by 
RIVER KILOMETERS ABOVE MOUTH 

1-Portland-1 

Salem Newberg Harbor 

a: 

w 

!:: 8 ....1 

a: 

w 

a.. 

(I) 

~ 

<( 

a: 

(!) 6 ....1 

....1 

~ 

~ 

z· 

w 

(!) 4 

> X 

0 

Cl 

w 

> ....1 

0 

~ 2 

Cl 

150 100 0 

0~------~---------L--------~--------~------~ 100 80 60 40 20 0 

RIVER MILES ABOVE MOUTH 

FIGURE 22.-Comparison of 1973 with historical DO conditions in the Willamette River for the summer low-flow period. (Historical data are adapted 

from Gleeson, 1972.) 

researchers, has generally not been incorporated in the design of river-quality monitoring 

or effluent standards programs. 

5. DO conditions in the Willamette would be 

even better were it not for the presence of two 

significant oxygen-demanding processes: (1) 

nitrification, carried on by periphytic nitrifying 

bacteria in a shallow, cobblyreach between RM 

120 and 52.5, and (2) an anomalous oxygen 

demand in the deeper part of Portland Harbor 

below RM 13 that is probably due primarily to 

benthal deposits. Of the two, nitrification has 

the larger impact on river DO concentrations, 

causing a 10-20 percent reduction in DO 

concentration between RM 86.5 and 52.5 during 

summer low-flow conditions. Nitrification was 

not documented during past river sampling 

despite sizable ammonia loads from pulp and 

paper mills since 1955. Whether or not the onset 

I36 

of nitrification is related to the reduction in 

carbonaceous loads by secondary treatment is 

uncertain. 

6. Algal growth and primary production in 

the river have probably increased during the 

last several decades. However, studies (Rickert 

and others, 1977) suggest that the algal regime 

is in a stable state, with no suggestion of 

"blooms" or a shift from the historically 

predominant diatom assemblage. Primary 

production measurements indicate that photosynthesis and respiration by aquatic plants 

during summer conditions can result in a small 

net production of DO in some reaches. However, 

photosynthesis and total community (plants 

and animals) respiration result in an approximate balance between oxygen production and 

oxygen consumption over much of the river. A 

possible exception to this balance may occur in 
~3-

z 

w 

_. 

<( 

> 

:::> 

0 - w 

z 

0 

1-

<( 

_. 

=>2ra.. 

0 

a.. 

u. 

0 

U) 

z 

0 r-

_. 

_. 

~ 

~ 

61rz 

0 

<( 

EXPLANATION 

0Total 

-

0 Industrial 

fm Municipal 

-

-

-

-

-

~ o.__r---~~~····=·.~· ~ ..... ='_::: ... ==··; ... =.:l·:~::l __ ~~~m·=; .... ·=~. :~ .... =!:;.::·:_~.:.::·::~ .. .... =:.:l;::·:· __ ~~-f~~--~~---~--~~~-~--~~~-=~--~- I I I lla 

1930 1954 1963 1967 1970 1973-74 

FIGURE 23.-Historical average daily BOD loads to the Willamette River during dry 

BODult (lb/d) BODult (kb/d) weatherperiods.Apopulationequivalent= 0.

24 = O.ll .(1930-

70 data adapted from Gleeson, p. 70; 1973-7 4 data from U.S. Geological Survey 

synoptic studies (see table 5). 

the deeper reaches of Portland Harbor. Here, 

algae transported from upstream spend long 

periods of time in a respiratory phase (02 consumption > 02 production) because of the 

relatively shallow depth ("'10ft or 3m) of the 

euphotic zone in comparison to the total depth 

of the water column (-- 40 ft or 12 m). 

ACKNOWLEDGMENTS 

We wish to acknowledge the aid and 

encouragement of the Non-Federal Advisory 

Committee on Water Data for Public Use. Our 

special thanks go to the members of the 

Advisory Committee's Ad Hoc Working Group 

on River Quality Assessment. During the 

Willamette Study, the group included Howard 

B. Brown, Robert A. Canham, Edward J. 

Cleary, Laurence R. Jahn, John E. Kinney, 

137 

Walter A. Lyon, John A. Roller, and Clarence J. 

Velz. The personal inspiration and insights of 

Velz were invaluable in writing this report. 

Timothy L. Miller and Joseph F. Rinella aided 

greatly with field and laboratory work and with 

many of the calculations and ideas. Alex E. 

Gonsalves and Brandon Burch did the work on 

the 30 technical illustrations. We also wish to 

acknowledge the helpful review suggestions of 

David H. Peterson, Doyle W. Stephens, Keith V. 

Slack, Warren C. Westgarth, and Glenn D. 

Carter. 

SELECTED REFERENCES 

American Public Health Association and others, 1969, 

Glossary of water and wastewater control engineering: 

Am. Public Health Assoc., 387 p. 

--1971, Standard methods for the examination of water 

and wastewater [13th ed.]: New York, Am. Public 

Health Assoc., 874 p. 
Bennett, J. P., and Rathbun, R. E., 1972, Reaeration in 

open-channel flow: U.S. Geol. Survey Prof. Paper 737, 

75 p. 

Brown, Eugene, Skougstad, M. W., and Fishman, M. J., 

1970, Methods for collection and analysis of water 

samples for dissolved minerals and gases: U.S. Geol. 

Survey Techniques Water Resources Inv., book 5, 

chap. AI, 160 p. 

Churchill, M. A., Elmore, H. L., and Buchingham, R. A., 

1962, The prediction of stream reaeration rates: Internat. Jour. Air and Water Pollution, v. 6, p. 467-504. 

Ehrlich, G. G., 1975, Nitrifying bacteria (most probable 

number method): U.S. Geol. Survey Quality of Water 

Branch Tech. Memo. 75.13, January 24, 1975. 

Gleeson, G. W., 1936, A sanitary survey of the Willamette 

River from Sellwood Bridge to the Columbia River: 

Oregon State Univ., Corvallis, Eng. Expt. Sta. Bull. 

Series 6, 103 p. 

--1972, The return of a river, the Willamette River, 

Oreg.: Advisory Comm. on Environmental Sci. and 

Technology and Water Resources Inst., Oregon State 

Univ., Corvallis, 103 p. 

Harris, D. D., 1968, Travel rates of water from selected 

streams in the Willamette River basin: U.S. Geol. 

Survey Hydrol. Inv. Atlas HA-273, 2 sheets. 

Hines, W. G., Rickert, D. A., McKenzie, S. W., and Bennett, 

J.P., 1975, Formulation and use of practical models for 

river-quality assessment: U.S. Geol. Survey Circ. 

715-B, 13 p. 

Hines, W. G., Rickert, D. A., and McKenzie, S. W., 1976, 

Hydrologic analysis and river quality data programs: 

U.S. Geol. Survey Circ. 715-D, 20 p. 

Horowitz, Jerome, and Bazel, L. A., 1974, Evaluation of 

water quality standards in California, Maryland, Ohio, 

and Oregon: Case studies, 1965-72: Prepared by 

Enviro Control, Inc., Rockville, Md., for U.S. Environmental Protection Agency, Div. Water Planning, Contract No. 68-01-184, 106 p. 

Krenkel, P. A., and Orlob, G. T., 1962, Turbulent diffusion 

and the reaeration coefficient: Jour. Sanitary Eng., 

Div. Am. Soc. Civil Engineers, v. 88, no. SA-2, p. 53-83. 

Lee, J. D., 1951, Sewage and Industrial Wastes: v. 23, 

no. 2, p. 164. 

Merryfield, Fred and Wilmot, W. G., 1945, progress report 

on pollution of Oregon streams: Oregon State Univ., 

Corvallis, Eng. Expt. Sta. Bull. Series 19, 53 p. 

Phelps, E. G., 1944, Stream sanitation: New York, John 

Wiley & Sons, Inc., 209 p. 

Rickert, D. A., and Hines, W. G., 1975, A practical framework for river-quality assessment: U.S. Geol. Survey 

Circ. 715-A, 17 p. 

Rickert, D. A., Hines, W. G., and McKenzie, S. W., 1975, 

138 

Planning implications of dissolved-oxygen depletion in 

the Willamette River, Oregon, in William Whipple, Jr. 

ed., Urbanization and water quality control: Minneapolis, Am. Water Resources Assoc., p. 70-84. 

--1976, Project development and data programs for 

assessing the quality of the Willamette River, Oregon: 

U.S. Geol. Survey Circ. 715-C, 31 p. 

Rickert, D. A., Petersen, Richard, McKenzie, S. W., Hines, 

W. G., and Wille, S. A., 1977, Algal conditions and the 

potential for future algal problems in the Willamette 

River, Oreg.: U.S. Geol. Survey Circ. 715-G, 39 p. 

Rogers, H. S., Mockmore, C. A., and Adams, C. D., 1930, 

A sanitary survey of the Willamette Valley: Oregon 

State Univ., Corvallis, Eng. Expt. Sta. Bull. Series 2, 

55p. 

Sainsbury, J. B., 1970, Benthal deposits of the Willamette 

River, Oregon: Dept. Environmental Quality rept., 

Portland, Oreg. 43 p. 

Slack, K. V., Averett, R. C., Greeson, P. E., and Lipscomb, 

R. G., 1973, Methods for collection and analysis of 

aquatic biological and microbiological samples: U.S. 

Geol. Survey Techniques Water Resources Inv. book 5, 

chap. 4, 165 p. 

Starbird, E. A., 1972, A river restored: Oregon's Willamette: 

Natl. Geog., v. 141, no. 6, p. 817-834. 

Theriault, E. J., 1927, The oxygen demand of polluted 

waters, I: U.S. Public Health Service Bull. 173. 

Tuffey, T. J., 1973, The detection and study of nitrification 

in streams and estuaries: Ph.D thesis submitted to the 

Graduate School, Rutgers Univ., New Brunswick, N.J., 

180 p. 

Tuffey, T. J., Hunter, J. V., and Matulewich, V. A., 1974, 

Zones of nitrification: Water Resources Bull., v. 10, 

no. 3, p. 555-563. 

Velz, C. J., 1951, Report on natural purification capacities, 

Willamette River: Natl. Council for Stream Improvement of the Pulp, Paper, and Paperboard Industries, 

Inc.: School of Public Health, Michigan Univ., Ann 

Arbor, 80 p. 

--1961, Supplementary report on lovrer Willamette 

River waste assimilation capacity: Natl. Council for 

Stream Improvement of the Pulp, Paper, and Paperboard Industries, Inc.: School of Public Health, 

Michigan Univ., Ann Arbor, 28 p. 

--1970, Applied stream sanita.tion: New York, John 

Wiley & Sons, Inc., 619 p. 

Wezernak, C. T., and Gannon, J. J., 1967, Oxygen-nitrogen 

relationships in autotrophic nitrification: Applied 

Microbiology, v. 15, no. 5, p. 1211-1215. 

Willamette Basin Task Force, 1969, Hydrology, Willamette 

Basin Comprehensive Study, Appendix B: Pacific 

Northwest River Basins Comm. Rept., 163 p. 
SUPPLEMENTAL INFORMATION 
SUPPLEMENT ARIVER SELF-PURIFICATION PROCESSES 

In the natural setting, self-purification capacity is not a fixed quantity but rather a range in 

potential that varies from season to season and 

through each reach of the river. Moreover, selfpurification processes occur within a river and, 

thus, are subservient to it's physical character-that character being largely defined by 

the interplay of streamflow, water temperature, 

and channel morphology. 

In broad terms, self-purification has been 

defined (American Public Health Association 

and others, 1969) as "The natural processes 

occuring in a stream or other water body that 

result in the reduction of bacteria, satisfaction 

of BOD (biochemical oxygen demand), stabilization of organic constituents, replacement of 

depleted dissolved oxygen, and the return of the 

stream biota to normal." 

With regard to the DO regimen of rivers, the 

processes of most interest are: 

(1) Carbonaceous deoxygenation via microbial oxidation of dissolved or suspended organic 

matter (as used here, analogous to BOD). 

(2) Benthal oxygen demand, caused by 

oxidation of settled organic or reduced -chemical 

materials. 

(3) Nitrification, caused by microbial oxidation of ammonium to nitrite and nitrate ions. 

(4) Photosynthesis (oxygen production) and 

respiration (oxygen consumption) by aquatic 

plants. 

(5) Atmospheric reaeration. 

Atmospheric reaeration and photosynthesis 

are commonly termed "DO sources"; the other 

processes are called "DO sinks." 

CARBON A CEO US DEOXYGENATION 

Carbonaceous deoxygenation is the process 

by which aquatic organisms, in the course of 

respiration and synthesis (or growth), oxidize 

organic carbon. Dissolved oxygen is consumed 

in the process and waste products, predominantly carbon dioxide and water, are emitted. 

When a large quantity of oxidizable carbonaceous material is present, as in rivers polluted 

with sewage, severe oxygen depletion may 

develop. All stream organisms, including 

bacteria, fungi, protozoa, zooplankton, phytoplankton, periphyton, macro-invertebrates, 

rooted plants, and fish are involved in the 

I40 

process. However, it is usually assumed that a 

mixed group of heterotrophic bacteria are 

primarily responsible for carbonaceous deoxygenation. 

The quantitative determination of carbonaceous deoxygenation in rivers is commonly 

based on "Phelps Law" (Phelps, 1944): "The 

rate of biochemical oxidation of organic matter 

is proportional to the remaining concentration 

of unoxidized substance, measured in terms of 

oxidizability." In mathematical form the 

expression is: 

dL -- = K1L dt 

which may be integrated to 

Lt Lt logeJ: =- K1t or log10 L = -0.43K1t= -kt 

and 

_!:_t = 10-klt 

L 

where Lis the initial oxidizability at time zero 

(the initial total amount of oxidizable matter) 

and Lt is the corresponding oxidizability at 

time t. The term Lt I L is the fraction of 

oxidizable organic matter remaining, and 

conversely, (1 -Ltl L) is the fraction that has 

been oxidized. 

ln the simplest cases, the rate of oxidation in 

the river is approximated by the empirical 

constant k1. A typical k1, corresponding to rates 

found for many primary domestic sewage 

effluents and their receiving waters, is 0.1 at 

20°C. As with most biochemical reaction rates, 

the rate of oxidation increases with increasing 

temperature and decreases with decreasing 

temperature. For a k1 = 0.1 and 20°C the 

oxidizable matter is reduced by a constant 

percentage, 20.6 percent (not a constant 

amount), each day and is 99 percent oxidized at 

the end of 20 days. 

In many rivers, actual deoxygenation rates 

vary from rates determined by the standard 

laboratory BOD test (American Public Health 

Association and others, 1971, p. 489-495). The 

reason for this is often related to the morphology of the river channel. In shallow, cobbly 

reaches, biological growth attached to the· 

streambed extracts organic matter from the 

flowing water, performing in a manner similar 

to that of a biological trickling filter. Other 
rivers may perform as natural activated sludge 

systems with the growth dispersed as biological 

floc throughout the water column. In both 

instances the effect on the river is removal of 

BOD in excess of that normally expected in the 

time of travel through the reach. 

This accelerated removal of BOD has been 

termed "biological extraction" (Velz, 1970) and 

is relatively independent of normal carbonaceous deoxygenation. In biological extraction, 

the removed BOD is not oxidized at the instant 

of extraction but is merely transferred from the 

flowing stream by biophysical contact with the 

biological growth (biofilm). If extraction and 

biofilm accumulation continue uninterrupted 

by a scouring freshet, a steady state is 

approached and the daily BOD satisfied within 

the biofilm equals the BOD extracted. For the 

steady-state condition, the impact on river DO 

can be quantified using first-order decay 

kinetics. The first-order kinetics are employed 

by reducing the two processes to a single 

composite process having a higher deoxygenation rate than that calculated for carbonaceous deoxygenation alone. For conditions 

other than steady state, it is necessary to deal 

with normal satisfaction in transit and to 

consider separately the oxygen demand from 

the biofilm accumulation. This nonsteady-state 

situation is quite difficult to simulate accurately 

in a quantitative manner. 

Because extraction is a function of contact 

opportunity of the biological growth with the 

flowing stream, highest rates occur in shallow, 

swift-flowing reaches with high surface-tovolume ratios and rapid mixing. The extraction 

rate is also influenced by the biochemical 

nature of the BOD. For example, the introduction of waste waters with high concentrations of oxidizable carbon can result in rapid 

extraction. In contrast, the oxidized carbonaceous materials found in effluents of secondary-treatment systems are less suitable as 

sources of immediate food energy for biological 

organisms; therefore, extraction rates tend to be 

lower. 

BENTHAL OXYGEN DEMAND 

In slow-moving reaches, reduced river velocity allows settling of suspended organic 

materials. If such materials are continuously 

deposited without disturbance by a scouring 

141 

freshet, accumulation continues until the 

material added to the deposit per day is equal to 

that oxidized in the accumulation per day (Velz, 

1970, p. 162-178). Under these steady-state 

conditions a high, relatively constant oxygen 

demand will occur. For accumulations less than 

the steady-state level, the oxygen demand is 

correspondingly less. During winter, cold 

temperatures drastically reduce the rate of 

decomposition of the depositing materials, and 

excessive accumulation of the materials may 

occur. If such accumulations are not scoured by 

spring floods, they may exercise a heavy 

demand on oxygen resources (in excess of that 

under steady-state conditions) during subsequent periods of high temperature. 

For quantitative determination it is necessary to make a distinction between organic 

deposits arising principally from (1) recently 

deposited raw or poorly treated municipal and 

industrial waste water and (2) older accumulations of partly oxidized organic river sediments 

derived from soil erosion, land wash, and dead 

terrestrial or aquatic vegetation. The latter is 

referred to as a benthal deposit, and the former 

as a sludge deposit. In many instances both 

types of accumulation occur simultaneously, 

although the decomposition rates of the two 

deposits can be quite different. 

Sludge deposits undergo decomposition of a 

semianaerobic character, with reduced oxygendemanding end products readily leaching in to 

the stream. Fresh sludge deposits may produce 

large quantities of gas that result in sludge 

boils, inducing a process of resuspension and 

redeposition until decomposition is essentially 

complete. In contrast, benthal deposits of 

organic river sediments tend to be less active 

with much slower reaction rates. However, if 

extensive and relatively recent, such deposits 

may still depress the level of DO in reaches that 

are relatively stagnant. 

Quantitative studies of benthal deoxygenation in rivers usually require difficult in situ 

benthal respirometer measurements coupled 

with a study of the origin and hydraulic 

behavior of the deposited materials. Other 

pertinent information can be obtained from DO 

sampling (preferably longitudinal, horizontal, 

and vertical traverses), channel geometry 

measurements, and bottom sampling with 

dredges. Modified BOD tests, using slurried 
benthic material, are also useful for understanding the nature of the deposited material. 

NITRIFICATION 

Nitrification is the biochemical oxidation of 

ammonium to nitrite and nitrate ion by 

Nitrosomonas and Nitrobacter bacteria. Dissolved oxygen is consumed by the bacteria in 

the process according to the following chemical 

equations: 

+ Nitrosomonas 

NH4 + 1% 02 ~========• 

and 

Nitrobacter 

N02-+11202 ~======~ 

Approximately 4.3 mg of dissolved oxygen is 

required for each milligram of ammonium-N 

oxidized to nitrate-N (Wezernak and Gannon, 

1967). 

In unpolluted waters, ammonium ion concentrations are usually very low, and nitrification 

cannot significantly affect the DO concentration. However, in rivers receiving large loads of 

ammonia, nitrification can be a major cause of 

deoxygenation. 

Several mathematical expressions have been 

formulated for describing nitrification. The 

first-order decay expression, 

dN =-K N dt n , 

where 

N = concentration of ammonia-nitrogen 

Kn =rate constant, 

is the most commonly employed in practical 

application. Note that the expression is 

mathematically identical to the forementioned 

expression for the oxidation of organic matter. 

Studies by Tuffey (1973) suggest that nitrification in rivers may not be as prevalent as 

commonly assumed. His conclusions suggest 

that nitrification of sufficient intensity to cause 

rapid oxygen depletion is almost always 

restricted to (1) shallow "surface active" 

reaches with good opportunity for attached 

growths of nitrifiers or (2) tidal rivers or 

estuarine embayments with very long detention 

142 

times and abundant suspended matter to serve 

as a nitrifier-attachment substrate. 

PHOTOSYNTHESIS AND RESPIRATION 

Photosynthesis is the process by which 

plants, in the presence of sunlight, water, 

carbon dioxide, and nutrients, grow and synthesize organic matter while giving off oxygen 

(6C02 + 6H20 ligh~ C6H1206 + 602). Resnutnents 

piration is the process by which living organisms use oxygen and organic matter and 

release oxidation products, primarily carbon 

dioxide and water. 

When present in large numbers, aquatic 

plants (phytoplankton, periphyton, and rooted 

plants) may be a significant source of DO 

during daylight hours. However, all aquatic 

organisms, including plants, are constantly 

respiring. At night when no oxygen is produced, 

plant respiration can cause a large decrease in 

river DO concentrations. The resulting diel 

variations in DO concentrations are usually 

most pronounced in (1) shallow reaches where 

periphytic algae or rooted plants are abundant 

or in (2) the euphotic zone of deep relatively 

stagnant reaches. 

The rate of photosynthesis is usually determined by measuring the amount of oxygen 

produced or the amount of carbon dioxide 

consumed. Conversely, the rate of respiration is 

determined by measuring the amount of oxygen 

consumed or the amount of carbon dioxide 

produced. 

Three common methods for studying photosynthesis and respiration are documented by 

Slack, Averett, Greeson, and Lipscomb (1973, p. 

92-122). The methods are characterized by the 

following general approaches: (1) in situ 

bioassay tests using the concept of light- and 

dark-bottle incubation, (2) in situ light- and 

dark-enclosures similar to (1) except that the 

method is usually employed in shallow reaches 

where periphytic growth is prevalent, and (3) 

intensive diel DO measurements made at 

different points in the river (the diel curve 

method). 

ATMOSPHERIC REAERA TION 

As atmospheric gas, oxygen dissolves in river 

water as a function of: 

1. The solubility of oxygen in water, which 
depends on: 

a. The partial pressure of oxygen in the atmosphere above the river. This can 

usually be considered constant for a 

particular altitude and temperature 

condition. 

b. The water temperature. As water temperature increases the solubility of 

oxygen decreases and vice versa. 

c. The concentration of dissolved solids or 

presence of surface films. This is usually not an important consideration 

except in saline coastal waters or in 

grossly polluted rivers. 

2. The rate of solution of oxygen, which is controlled by: 

a. The degree of undersaturation (or oxygen deficit) of the water. For example, 

fresh water at 20°C and 760 mm pressure has an oxygen saturation value 

of approximately 9.2 mg/1. If the river 

water contains only 7.2 mg/1 of dissolved oxygen, it has an oxygen deficit of 2.0 mg/1. The rate of solution is 

directly proportional to the magnitude of the oxygen deficit. 

b. The temperature of the water. At higher 

temperatures oxygen will dissolve 

more quickly even though the total 

amount of oxygen that can potentially dissolve decreases. 

c. The relative exposure of the river surface to the atmosphere. For example, 

if the river is ice covered, the water 

surface is prevented from contacting 

the atmosphere, and no atmospheric 

oxygen enters solution. In contrast, 

windy conditions tend to increase 

the rate of reaeration. 

3. The rate of dispersion of dissolved or gaseous 

oxygen under the water surface, which 

is by: 

a. Molecular diffusion. In entirely quiescent water, the rate of dispersion is 

controlled entirely by molecular diffusion, which is responsible for the solution of oxygen from molecule to molecule of water. The rate is proportional 

to the difference in DO concentration 

between any two points (the concentration gradient). Reaeration would 

be a very slow process if molecular 

diffusion were not aided by mixing. 

b. Mixing. Rivers are never quiescent. 

Mixing phenomena induced by 

streamflow and channel configuration play an important part in dispersing dissolved and gaseous oxygen to 

the subsurface. Mixing does not alter 

the basic function of molecular diffusion. It is well established that no 

amount of mixing per se can cause 

solution-solution occurs at the molecular level owing to diffusion. However, by constantly renewing the airwater interface and the contact between saturated and under-saturated 

molecules of water, mixing increases 

the opportunity for molecular diffusion. Thus, if all other factors were 

equal and the same oxygen deficit 

were present, a shallow, fast-moving 

reach would be reaerated faster than 

a deep, slow-moving pool. 

Reaeration is a complex dynamic process 

whose quantification is based on empirical 

equations and intensive field data. The most 

commonly used form of equation is 

where 

C= dissolved oxygen concentration 

C8 =dissolved oxygen saturation value at 

the particular temperature 

C8 -C= dissolved oxygen deficit 

K2 =the reaeration coefficient proportional 

to stream depth and velocity. 

The reaeration coefficient cannot be measured directly in sizeable stream systems, and 

even the reach-to-reach measurement of Cs-C 

requires intensive fieldwork. The ability to 

estimate reaeration is, thus, largely related to 

the ability to account for streamflow, water 

temperature, channel morphology, and oxygen 

deficit on a systematic, segment-to-segment 

basis. 

I43 

SUPPLEMENT B-FIELD CALIBRATION 

OF DISSOLVED-OXYGEN METERS 

The DO meter selected for use during the 

study was the YSI model 54 with a 50-ft DO and 

temperature probe (model 5419). During the 
summer of 1973, a series of tests were made to 

compare calibrations using the Winkler (wet 

chemical) method (American Public Health 

Association and others, 1971, p. 474-481) with 

the YSI calibration chamber (model 5075) 

method. The tests led to selection of the 

calibration chamber method as the standard 

procedure for field calibration. The basic 

procedure is outlined below: 

1. All meters are turned on at least 1 hour 

before calibration to achieve electronic stability 

and are left on until all measurements are 

completed for the day. 

2. Prior to calibration, the probe and membrane are checked for general condition and for 

gas bubbles inside the membrane. A loose 

membrane or gas bubbles were found to cause 

erratic DO readings. 

3. Meters are shielded from direct sunlight 

and wind to avoid the heating and cooling of 

meter circuitry. DO readings were observed to 

change with exposure of the meter case to direct 

sunlight, cold, wind, or early-morning dew. 

Field experience suggested that uncontrolled 

heating and cooling could cause errors in DO 

measurements approaching 1.0 mg/l. 

4. The DO probe is inserted into the 

calibration chamber and sealed with the 

probe's rubber gasket. Calibration is accomplished with the chamber and probe immersed 

in water or in air after a 5-10 minute equilibration period. The advantage of water calibration 

is that the chamber is immersed in the river and 

calibration is made under the same conditions 

for which the meter is to be used. However, 

when the chamber is immersed in water, it must 

be checked for leakage into the calibration 

chamber. Such leakage was found to cause 

erroneous calibrations. In air, the chamber can 

be used only with the newer model YSI DO 

probes that have the thermister located 

adjacent to the DO membrane. The advantages 

of the air calibration technique are its relative 

speed and ease. When using the chamber in air, 

it must be shielded from direct sunlight and 

wind to prevent calibration errors resulting 

from large fluctuations in temperature. 

5. During the 5-10 minute equilibration 

period, meter stability is checked by switching 

back and forth between the temperature and 

DO modes until readings are repetitive. Then, 

with the probe still in the calibration chamber, 

144 

the meter is set at the DO saturation value using 

a standard DO saturation table. 

6. Step 5 is repeated before each sampling 

traverse or at about 2-hour intervals. 

SUPPLEMENT C-ANALYSIS OF BOD 

The laboratory BOD tests provided data for 

calculating BODult and carbonaceous deoxygenation rate, k1. The test utilized a YSI DO 

meter (model 54) with a self-stirring probe 

(model 542a). Approximately 2,500 BOD samples were analyzed in 1973-7 4 using the method 

described below. 

DILUTION WATER 

Willamette River water was used as dilution 

water for the BOD test of waste waters because 

(1) the water has a ready-made bacterial "seed" 

acclimated to the types of waste waters entering 

the river, (2) the BODult concentration ("background") was low, and (3) there were sufficient 

nutrients and no known interferences due to 

toxic materials. Fresh dilution water was 

collected daily, and at least three BOD tests 

were made on each batch. 

INHIBITION OF NITRIFICATION 

To measure only the carbonaceous oxygen 

demand in the BOD test, it was necessary to use 

1-allyl-2-thiourea as an inhibitor. Allylthiourea 

was selected over other available inhibitors on 

the basis of discussion with researchers having 

recent experience. Stock solutions were made 

every 14 days and added to the BOD bottle on 

incubation days 0, 5, 10, and 15 to provide an 

approximate active concentration of 0.5 mg/1 

in the BOD sample (Tuffey, 1973). 

CALIBRATION 

Meters and BOD probes were turned on at 

least 1 hour before calibration and left on until 

the end of the day. To obtain accurate results 

over a wide range of DO concentrations and 

among several BOD probes, the wand on each 

self-stirring mechanism was adjusted to form a 

circle three-fourths in. (1.9 em) in diameter 

(measured with a rule in back of the moving 

band). Prior to calibration, each probe was 

checked for holes or wrinkles in the membrane 

and for air bubbles under the membrane. 

Calibrations were made using distilled water 

stored at room temperature in a 14 gallon 
carboy. Triplicate analyses of DO were made 

each day on the distilled water by the Winkler 

method. If the range of values from the three 

tests was less than 0.10 mg/1, the average value 

was ·used to calibrate the meters. If the range 

was greater than 0.10 mg/1, the calibration was 

repeated. A record was kept on the calibration of 

each meter. Throughout each day, the meters 

were checked for drift and, if necessary, 

recalibrated against the distilled water standard. When not in use, the probes were stored in 

BOD bottles filled with distilled water. 

MEASUREMENT OF DO IN BOD BOTTLES 

The initial reading of the BOD test was taken 

after the river or waste-water sample had 

warmed to 20±1 °C and the DO reading had 

stabilized. After the first reading, the DO was 

measured at increments of 1/2, 1, 2, 3, 4, 5, 6, 8, 

10, 12, 15, and 20 days. This schedule of measurements was selected to provide an adequate 

distribution of data points to define accurately a 

time trend of BOD exertion. The BOD measurement procedure included (1) removal of a plastic 

cap which prevented evaporization of the water 

seal around the glass stopper of the BOD bottle, 

(2) pouring off the water seal, (3) rinsing the 

BOD probe with distilled water, (4) removing 

the glass stopper, (5) inserting the probe such 

that no aeration occurred in the BOD bottle, (6) 

turning on the stirring mechanism, (7) waiting 

1-2 minutes for the probe to equilibrate, (8) 

recording the date, time, and DO reading on a 

data sheet, (9) removing the probe and 

replacing the glass stopper and water seal, and 

(10) replacing the plastic cap on the BOD bottle 

and returning the bottle to the incubator. 

Allylthiourea was added every 5 days using a 

pipette. Glass beads were periodically added to 

the sample to compensate for the loss in sample 

water caused by the probe measurement 

procedure. The beads prevented the formation 

of air bubbles in the neck of the BOD bottle. 

If the estimated DO in the bottle would be 

below 2.0 mg/1 at the next scheduled reading, 

the sample was reaerated using an "aeration 

tube." The "aeration tube" procedure included 

(1) placing one end of the tube in the top of a 

clean, empty BOD bottle, (2) placing the other 

end in the sample bottle, (3) holding the bottles, 

·one in each hand, and reaerating by vigorous 

145 

back-and-forth shaking for about 1 minute, (4) 

allowing the sample to drain back into the 

original sample bottle, (5) returning the BOD 

probe to the sample bottle, and (6) remeasuring 

and recording the new DO concentration. 

LEE'S GRAPHICAL METHOD 

Data from the BOD tests were analyzed by 

Lee's (1951) graphical method to obtain values 

for k1 and BODult· To use the method a series of 

graphs covenng a range of k1 values was 

constructed on the basis of first-order decay 

kinetics. For each graph a linear relation was 

obtained between BOD on theY-axis and time 

(t) on the X-axis by positioning ton an arbitrary 

linear distance (such as 10 in.) in proportion to 

(1-1o-kt). A series of grids for k1 intervals of0.02 

was developed, and copies were reproduced for 

trial plots. 

The basis for using the grids·is that a time 

series of BOD values which follow a specific 

reaction rate(k1) will plot as a straight line on a 

grid constructed for that rate. Thus, to 

determine the reaction rate of a sample, 

successive trial plots of laboratory BOD are 

made on selected grids. If the first trial plot 

bends downward, it indicates that the selected 

k1 is too low; if the plot bends upward, the 

selected k1 is too high. Subsequent selection of 

plotting grids leads quickly to the best straightline fit for the data, identifying the appropriate 

BOD reaction rate, k1 (see figs. 24-26). 

Extrapolation of a single stage line to the 

right to "ultimate" time gives a direct value for 

BODult. Extrapolation of the line to the left can 

provide valuable insight into the nature of the 

BOD and the reliability of the BOD test. If the 

line intersects the Y-axis at zero time, the 

reaction has proceeded normally from initial 

incubation. An intercept above zero time 

indicates an immediate demand, with the Y 

intercept giving directly its magnitude. An 

intercept on the X-axis indicates a lag in the 

start of the reaction, and the X intercept gives 

the magnitude of the lag. 

Examples of BOD analyses by Lee's method 

for river and waste waters in the Willamette 

basin are shown in figures 24, 25, and 26. Note 

in figure 25 the method used for compensating 

the anomalous DO readings that occurred in 

several samples during the first days of 

incubation. Such readings were believed asso-
Date Time Bottle 

Source Yr Mo Day (2400) No. 

RM 86.5 74 08 06 0855 005 

DO Days of 

Date Time concentration incu- BOD 

Mo Day (2400) (mg/1) bat ion (mg/1) 

08 06 2246 7.7 

08 07 0903 7.6 0.4 0.1 

08 08 1255 7.3 1.6 .4 

08 09 1058 7.1 2.5 .6 

08 10 1100 7.0 3.5 .7 

08 11 1050 6.7 4.5 1.0 

08 12 0945 6.6 5.5 1.1 

08 14 1405 6.4 7.6 1.3 

08 16 1125 6.1 9.5 1.6 

08 18 0940 6.0 11.5 1.7 

08 21 0845 5.8 14.4 1.9 

a: 08 26 0845 5.5 19.4 2.2 

w 2.5 t 

..J 

a: 

w 

0.. 

~ 2.0 

<( 

a: 

c.? 

..J 

..J 1.5 

~ 

~ 

z 

0 1.0 BOD5=1.0 

i= BOD2o=2.2 

<( B0Dult=2.7 a: 

1- k1=0.04 

~ 0.5 (.) 

z 

0 

(.) 

0 0 

0 

co 0 2 3 4 6 8 10 12 15 20 30 

TIME, IN DAYS 

FIGURE 24.-Lee's graphical method for analyzing k1 and BODult• Willamette 

River, RM 86.5. 

ciated with either (1) supersaturation of the 

original sample (common in tributary samples) 

or (2) excessive algal respiration in the first day 

or two caused by lightless incubation of the 

sample. 

SUPPLEMENT D-SPECIAL BOD 

EXPERIMENTS 

A series of special experiments was conducted 

on BOD samples to evaluate possible methodological errors. Experiments and results are 

briefly summarized below. 

(1) Incubation in 1- and 4-liter bottles to 

evaluate the effect of a variable surface area. In 

I46 

general, incubation in large bottles with 

surface-to-volume ratios smaller than the 

standard 300-ml BOD bottle did not result in 

measurably different BOD2o or k1 values. 

(2) Settled and unsettled BOD's to examine 

the oxygen demand associated with suspended 

matter in river samples. Results indicated that 

between 10 and 30 percent of 20-day BOD was 

due to suspended matter. Microscopic examination indicated that the settleable material was 

predominantly diatoms, microbial cellular 

materials, and fine-grained inorganic river 

sediments. All BOD values reported in the main 

text are for unsettled samples. 
Date Time Bottle 

Source Yr Mo Day (2400) No. 

McKenzie R. 74 08 23 1100 272 

at Eugene 

pump 

DO Days of 

Date Time concentration incu- BOD 

Mo Day (2400) (mg/1) bat ion (mg/1) 

08 23 1721 10.4 

08 24 1055 10.1 0.7 0.3 

08 25 1030 9.6 1.7 .8 

08 26 1010 9.6 2.7 .8 

08 27 0924 9.3 3.7 1.1 

08 28 0930 9.2 4.7 1.2 

08 29 1005 9.2 5.7 1.2 

08 31 1235 9.1 7.8 1.3 

09 02 1220 8.9 9.8 1.5 

09 04 1050 8.8 11.7 1.6 

09 07 1000 8.6 14.7 1.8 

09 12 1208 8.4 19.8 2.0 

a: 

w 2.5 t 

...J 

a: 

w 

a.. 

(I) 2.0 :;:! 

<( 

a: 

(.!) 

...J 

...J 1.5 

:;:! 

~ 

z 

0 1.0 

i= BOD5=0.6 <( 

a: BOD2o=1.3 

1- BODutt=1.6 ~ 0.5 () k1=0.04 

z 

0 

() 

Cl 0 0 

co 0 2 3 4 6 8 10 12 15 20 30 

TIME, IN DAYS 

FIGURE 25.-Lee's graphical method for analyzing k1 and BODult• McKenzie 

River. Incubation of cool (l7°C), supersaturated sample at 20°C caused 

apparent immediate 0 2 demand at day zero. To correct for this, the 

measured data are fitted with a straight line to establish k 1 (slope ofline). 

A line of this slope is then drawn through zero and extrapolated to obtain 

a value of BODult· 

(3) Additions of various doses of nitrifier 

inhibitor (allylthiourea) to examine (a) efficiency of nitrification inhibition and (b) the 

impact of the inhibitor on carbonaceous 

deoxygenation. Results suggested that maintenance of a 0.5 mg/1 concentration of 

allylthiourea in the BOD bottle effectively 

stopped nitrification without a significant 

effect on carbonaceous deoxygenation. 

(4) Examination of the impact of stirring 

147 

frequency on BOD exertion. Tests included 

stirring frequencies of (a) 2-3 times per day, (b) 

the standard DO measurement schedule (see 

"Measurement of DO in BOD Bottles," Supplement C), and (c) every 5 days. Results indicated 

no significant differences in BOD2o from the 

three treatments. 

(5) Comparison of samples that were (a) 

chilled ( 4 ° C) in the field, returned to the 

laboratory, and warmed to 20°C with (b) 
Date Time Bottle Vol. diluSource Yr Mo Day (2400) No. tion water 

Pulp mill 74 06 20 1000 071 250 

waste 

DO Days of 

Date Time concentration Reaer- incu- BOD 

Mo Day (2400) (mg/1) ated D.O. bat ion (mg/1) 

06 20 1548 8.6 

06 21 1035 6.7 0.8 9.4 

06 22 0935 4.3 1.8 23.2 

06 23 0800 2.3 7.8 2.7 34.7 

06 24 0949 5.5 3.8 48.0 

06 25 0954 4.0 4.8 56.5 

06 26 1150 3.0 5.9 62.1 

06 28 1008 1.2 8.3 7.8 72.1 

06 30 1100 6.7 9.8 81.1 

07 02 1025 5.4 11.8 88.3 

07 05 0955 4.2 14.8 94.9 

07 10 0930 2.1 19.8 106.9 

120 

a: 

w 

t: 

...J 

0:::100 

w 

a. 

(/) 

::2: 

<! 

ffi 80 

...J 

...J 

::2: 

~ 60 

z' 

0 

i= BOD5=56 

<! 40 BOD2o=107 a: 

1- BODult=115 z 

w k1=0.06 (.) 

z 

0 20 (.) 

Cl 

0 

co 

0 

0 2 3 4 5 6 8 10 15 20 30 

TIME, IN DAYS 

FIGURE 26.-Lee's graphical method for analyzing k1 and BODult. pulp and 

paper effluent, Salem, Oreg. 

samples that were field incubated at ambient 

air temperature and returned (within 4 hours) to 

the laboratory. Results indicate little difference 

in k1 or BOD20 attributable to the two 

treatments. However, the chilling procedure 

was selected for standard use because of the 

148 

possibility of (a) sample temperatures > 30°C 

using the ambient air temperature incubation 

method and (b) time periods greater than 4 

hours between sampling and laboratory 

analysis. 

(6) Incubation of samples with initial super-
saturated DO concentrations. Supersaturated 

conditions were prevalent in the cool, high DO 

waters of Cascade tributaries and upstream 

segments of the Willamette. Erratic readings 

were common in these samples during the first 

several days, probably owing to air-bubble 

formation caused by sample warming and 

bubble escapement during bottle openings. A 

modification of the Lee's grid technique (fig. 25) 

was used to compensate for these and other 

discrepancies that were believed to be artifacts 

not representative of the river environment. 

The overall BOD measurement program 

yielded two major results: 

(1) The BOD probe procedure (described in 

Supplement C) was proven to be an easy, 

reliable method for analyzing large numbers of 

river and waste-water samples. This conclusion 

was verified not only by these special experimental tests but also by experience gained from 

the large number of routine BOD measurements. 

(2) The 20-day laboratory BOD test provided a 

reasonable representation of river and wastewater deoxygenation phenomena in the Willamette River system. This conclusion was substantiated by several independent analyses of 

the intensive DO balance data presented in this 

report and by subsequent application of the 

WIRQAS DO model (Circular 715-J). 

SUPPLEMENT E-DETAILED RIVER DO 

AND WATER TEMPERATURE DATA 

A synopsis of the DO and water temperature 

z RM 185 McKenzie River B..M..1.6..1 RM 134 

'0 Z- wlCD- 5 ft CD- 5 ft CD- 5 ft co-8ft 

(!)<( DO= 102 DO= 100 DO= 100 DO= 97 >-CI: n=7 n = cont n = cont n = cont x::> 

g~ 120 

T' = 19 T = 11 T = 20 T= 20 

~~ 100 

ow 80 (/)() 

(/)CI: 

-w Co_ 60 

0 12 24 0 12 24 0 12 24 0 12 

data collected on the Willamette and major 

tributaries during 1973 and 197 4 is pre sen ted in 

figures 27-30'. Figures 27-29 show data from 

1973 studies for the segments RM 185-86.5; RM 

86.5-28.6, and RM 28.6-1.5. Figure 30 summarizes 1974 data for the segment RM 86.5-6.0. 

Several of the figures include more than one 

data graph per sampling site. The multiple 

graphs are presented because the DO data were 

segregated and averaged on the basis of 

incremental water depths. This allows the 

examination of the vertical variability in DO 

and temperature that occurred at some of the 

deeper sampling sites below RM 86.5. As 

described previously in "Results," no significant cross channel (horizontal) variations were 

noted. 

Besides the basic data, the four figures also 

include complementary information on sampling site water depth, sampling method, and 

number of samples. Note that the number of 

samples varied from site to site because of differences in study duration, variations in 

channel configuration, equipment malfunctions, 

and the use (at some sites) of continuous 

monitors. The notations used in the figures are 

24 

CD-channel depth 

DO-average DO concentration in percent 

saturation 

n-number of samples 

cont-continuous monitoring 

T-average water temperature in °C. 

BM...11l ~ Saotiam Bi~!H RM 86.5 

CD- 6ft CD- 6ft CD- 5 ft c·D -7 tt 

~ I 

DO o;= 1'()2 DO= 96 DO =98 DO =94 

n = 14 n = cont n = 11 n = cont 

"T = 20 T = 19 ~ T= 20 T= 20 

,../" ~ 

1- / 

0 12 24 0 12 24 0 12 24 0 12 

~ TIME, IN HOURS 

24 

FIGURE 27.-Dissolved-oxygen concentration in the Willamette River and major tributaries between RM 185 and 86.5, August 6-

12, 1973. Each graph presents average of 3 days of sampling. No depth stratification in DO concentrations were observed 

at these stations. See text for explanation of symbols. 

149 
SAMPLING DEPTH, 0-10 FEET 

RM 86.5 RM 72 RM 50 RM46 RM 39 RM 34 B..M...2S...§ 

CD- 7ft CD- 5 ft CD- 22ft CD- 28ft CD- 31 ft CD- 31 ft CD- 25ft 

z DO= 93 DO= 82 DO= 72 DO= 74 DO= 73 -·I 

DO= 73 0 n = cont n = 108 n = 128 n = 120 n = 104 n = 102 ~ f = 19 T= 20 T' = 20 T' = 21 co"' T' = 21 T' = 21 <( .... Q). 

co .... a: "'u :::> Q) 

100 o= 1- zo 

<( u (I) 80 /' I"" 

1- ,-- z 60 _L I 

----I 

w 

u 

a: 

w 

0.. 

~ 

z SAMPLING DEPTH, MIDFLOW (MIDDLE THIRD OF WATER COLUMN) w 

CJ 

>- _!_ _!_I 

DO= 72 

_!_I I 

X DO= 93 05 = 81 DO= 71 DO= 72 DO= 71 DO= 72 

0 n = cont n = 108 n = 120 n = 101 n = cont n = 80 n = 133 

0 

w T= 19 T=20 T= 20 'T= 21 "f= 21 f = 21 f = 21 

> 

...J 100 t- t- 0 

(I) 

(I) 80 ~ ....__ t- c ,.--.. - __.,...-

60 0 I I I 

12 24 0 12 24 0 12 24 0 12 24 0 12 24 0 12 24 0 12 24 

TIME, IN HOURS 

FIGURE28.-Dissolved-oxygenconcentrationintheWillametteRiverbetweenRM86.5and28.6,August15-17, 

1973. Each graph represents average of 3 days of sampling. Several DO measurements were made at 

depths less than 20 ft (6 m) at RM 50, 46, 39, 34 and 28.6. However, results are not presented here because 

measurements were identical to those shown in "Midflow, graphs. See text for explanation of symbols. 

150 
looo4 

c:n 

....... 

RM 28.6 

c0-25ft 

100 

80 

DO= 76 

n = 104 

T = 20 

__.,...... ~ 601 I I I I 

i= 

<{ 

a: 

::> 

1-

<{ 

en 

1-

z 

w 

(.) 

a: 

w 

~ 

z 

-:.100 

z 

~ 80 

>-

00 = 76 

n = 136 

T= 20 

0 

X 60 '---L-L-"---' 

----- 0 

w 

> ..J 

0 

~ 

c 

100 I 

80 

DO= 74 

n = 150 

T' = 20 

____. 60 I I I I I 

0 12 24 0 

B.M...2U 

co -16 ft 

DO= 79 

n = 106 

T' = 21 

____....... 

DO= 79 

n =55 

T= 21 

_.....--... 

~ 

§~ 

:C. 

~E 

"' cu o"' o'- 1-2 

12 

RM 21 11 

CD -50 ft 

DO= 81 

n = 104 

T= 21 

___,......_ 

SAMPLING DEPTH, 0-10 FEET 

B.M..1U 

CD- 25ft 

co= 79 

n = 100 

T= 22 

.---

RM 12.8 

CD- 55ft I I I 

DO= 77 

n = 96 

T= 22 

__,..-

1 

RM 7.0 

C'D-'mt 

DO= 67 

n = 104 

T = 22 

B.M.6..Q 

CD- 43ft 

Oo=64 

n = 71 

T = 22 

SAMPLING DEPTH, MIDFLOW (MIDDLE THIRD OF WATER COLUMN) 

DO= 78 

n =54 

T= 21 

-

DO= 80 

n =52 

'T = 21 

1----

24 0 12 24 0 

DO= 76 

n =50 

T= 22 

-

DO= 74 

n = 46 

T= 22 

---

DO =64 

n =51 

T' = 22 

SAMPLING DEPTH, 20 FEET OR MORE 

!:"' 

0~ 

=o. 

~E .,cu 

0"' 0 ... 

1-2 

I 

DO= 73 

n = 39 

T=22 

.__,.... 

12 24 0 12 24 0 

TIME, IN HOURS 

DO= 63 

n =52 

T= 22 

12 24 0 

DO= 63 

n = 34 

T' = 22 

~ 

T 

DO= 61 

n =54 

T= 22 

~ 

12 24 0 

B.M...U 

CD- 40ft 

DO =65 

n = 72 

T' = 22 

DO =64 

n = 36 

T = 22 

T 

DO= 71 

n =54 

'T = 21 

L-...1..-.L. 

~ 

12 24 0 

B..M..1...5 

CD- 40ft 

DO= 75 

n = 104 

T' = 22 

\./'"' 

DO= 76 

n =52 

'T = 21 

~ 

DO =84 

n =53 

'T = 20 

'--. 

I 

12 24 

FIGURE 29.-Dissolved-oxygen concentration in the Willamette River between RM 28.6 and 1.5, July 24-26, 1973. Each graph represents average 

of 3 days of sampling. See text for explanation of symbols. 
......... 

CJ1 

t-:l 

100 

80 

AM- 86.5 

CD- 7ft ...,....--roo = 92 

n = 108 

T= 19 

z 60 ....._L...-...JL...--L........I 

0 

i= 

<{ 

a: 

~ 

1-

<{ 

tl) 

1-

z 

w 

u 

a: 

w 

Q. 

~.100 

z 

~ 80 

I I 

DO"' 92 

n =54 

'T = 19 

~ 

~ 60 ....._...__...__L....J 

0 

0 

w 

> ...J 

0 

tl) 

tl) 

i5 

100 ~ 

80 

60 LJ.. 

0 

s: ... oCI> 

=C. 

-5~ o"' 0 .... 

t-.E 

12 24 

AM 72 

CD- 5 ft ...--.-.-

DO= 87 

n = 98 

T= 20 

~~ 

f-

...L...l_._L 

I 

DO •87 

n = 101 

T= 20 

AM 50 

CD- 22ft 

DO= 77 

n = 72 

T = 21 

...1.._.l..._.L 

~ 

AM 39 

Co:3Tft 

DO =84 

n = 64 

'f = 22 

~ 

SAMPLING DEPTH, 0-10 FEET 

AM 28.6 AM 21.1 

CD - 25 ft CD - 50 ft 

' DO= 80 

n = 72 

'f= 2~ 

~ 

...L...l_._L 

' ' ' DO= 83 

n = 64 

T= 23 

I _.......-..._ 

..,i__L_J_ 

AM 12.8 

C~t 

I I i 

150 = 84 

n = 72 

T=24 

.,./ 

...L-J.._j_ 

AM 10 

Co:40ft 

t I I 

i50 = 84 

n = 72 

T= 24 

/' 

_L____l_ 

SAMPLING DEPTH, MIDFLOW (MIDDLE THIRD OF WATER COLUMN) 

I 

DO= 77 

n =50 

T = 21 

-

I I I 

DO= 79 

n = 72 

'T = 22 

tI 

DO =80 

n = 74 

T= 23 

I 

DO= 82 

n = 61 

T = 23 

-

I 

i50 = 80 

n = 40 

T = 24 

-

I I 

DO= 80 

n = 40 

'f= 24 

- ~ 1- _,..--- t- ---- ---- ~ .,.,...,-_ ,...._r--

0 

s: ... 0~ 

:=a. 

~E 

... m - o ... 0 0 1--

I 

12 24 0 

I 

I 

s:.., 

0~ -a. iOE 

~m 0 .... oo 1--

12 24 0 

I 1 I 

SAMPLING DEPTH, 20 FEET OR MORE 

I I I 

DO= 79 

n = 33 

"T = 22 

---.... 

-

I I 

DO= 79 

n = 18 

'f = 23 

---

I 

DO= 82 

n = 49 

"T = 23 

----

I 

00=79 

n =51 

'f= 24 

I I I I I I I I I I I I I I I ---- I I I 

t12 24 0 12 24 0 12 24 0 12 24 0 

TIME, IN HOURS 

.J.__i__j_ 

I 

150 = 78 

n =54 

'f = 24 

- __,__ 

...L....J..._J_ 

12 24 

RM7.0 

ci)':4'21t 

I I I 

00 = 79 

n = 72 

T=24 

~ f' 

...i__L_1 

I I I 

DO= 73 

n =54 

T= 23 

t- -

......__....... 

....L_1_.l 

I I I 

00=69 

n =54 

T= 23 

1'-("7" 

-

-

0 12 24 0 

AM 6.0 

C~t 

I I I 

DO= 75 

n = 68 

'f = 24 

..l..__.I.__L 

~ 

I T 

DO= 69 

n =51 

"f = 23 

1:::i:::: 

DO= 64 

n =51 

'f = 23 

12 24 

FIGURE 30.-Dissolved-oxygen concentration in the Willamette River between RM 86.5 and 6.0, August 6-7, 1974. Each graph represents average of2 days 

of sampling. See text for explanation of symbols.