Water-Resources Investigations Report 03–4327

Prepared in cooperation with the

Bureau of Land Management, Vale District Office, Vale, Oregon

U.S. Department of the Interior

U.S. Geological Survey

Reconnaissance of Chemical and Biological

Quality in the Owyhee River from the Oregon

State Line to the Owyhee Reservoir, Oregon,

2001–02

Version 1.0
Cover: Owyhee River confluence with Little Owyhee River, Idaho, facing downstream. Photo by

Dorene E. MacCoy, U.S. Geological Survey.
Reconnaissance of Chemical and 

Biological Quality in the Owyhee 

River from the Oregon State Line 

to the Owyhee Reservoir, Oregon, 

2001–02

By Mark A. Hardy, Terry R. Maret, and David L. George

Prepared in cooperation with the

Bureau of Land Management, Vale District Office, Vale, Oregon

Water-Resources Investigations Report 03-4327

U.S. Department of the Interior

U.S. Geological Survey

Version 1.0
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey Bureau of Land Management

Charles G. Groat, Director Kathleen Clarke, Director

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

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

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

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

endorsement by the U.S. Government.

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

reproduce any copyrighted materials contained within this report.

Hardy, M.A., Maret, T.R., and George, D.L., 2004, Reconnaissance of Chemical and Biological Quality in the Owyhee 

River from the Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02: U.S. Geological Survey WaterResources Investigations Report 03 –4327, 48 p.
Contents iii

Contents

Contents

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

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

Purpose and scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Environmental setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Methods of sample collection and analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Water and stream-bottom samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Biological community samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Quality assurance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Chemical and biological quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Suspended sediment and turbidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Dissolved oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Major ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Nutrients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Trace elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Benthic invertebrate communities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Periphyton communities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

References cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Figures

1. Map showing location of Owyhee River drainage basin, Nevada, Idaho, and 

Oregon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Map showing location of sampling sites in the Owyhee River study area, Oregon. . . . 5

3–5. Graphs showing:

3. Flow-duration curve for 1949–2002 and sampling periods for the Owyhee River 

near Rome, Oregon, site OR4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4. Water temperature in the Owyhee River and selected tributaries, Oregon, April 

through September 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5. Suspended sediment concentrations, instantaneous loads, and turbidity in the 

Owyhee River and selected tributaries, Oregon, 2001 and 2002 . . . . . . . . . . . . . . . 11

6. Diagram showing stiff patterns representing major ions in the Owyhee River and 

selected tributaries, Oregon, 2001 and 2002. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
iv Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

7–12. Graphs showing:

7. Nitrogen concentrations and instantaneous loads in the Owyhee River and 

selected tributaries, Oregon, during spring runoff in 2001 and 2002 . . . . . . . . . . . 16

8. Phosphorus concentrations and instantaneous loads in the Owyhee River 

and selected tributaries, Oregon, during spring runoff in 2001 and 2002 . . . . . . . 17

9. Trace element concentrations in stream-bottom materials from the Owyhee 

River and selected tributaries, Oregon, in relation to concentrations in 

regional streams sampled by Rinella and others (1994). . . . . . . . . . . . . . . . . . . . . . 19

10. Aluminum concentrations in stream-bottom materials less than 62.5 micrometers in diameter from the Owyhee River and selected tributaries, Oregon. . . 20

11. Mercury concentrations in stream-bottom materials less than 62.5 micrometers in diameter from the Owyhee River and selected tributaries, Oregon. . . 21

12. Number of macroinvertebrate and Ephemeroptera, Plecoptera, and 

Trichoptera (EPT) taxa collected at sites in the Owyhee River and selected

tributaries, Oregon, June through July 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

13. Diagram showing summary of water-quality issues for the Owyhee River and 

selected tributaries, Oregon, 2001 and 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Tables

1. Description of sampling sites on the Owyhee River and selected tributaries, 

Oregon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Land use/cover and mineable deposits in the Owyhee River study area, Oregon . . . . 4

3. Onsite measurements and chemical analyses of water and bottom-material 

samples collected from the Owyhee River and selected tributaries, Oregon, 

2001 and 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4. Chemical analyses of duplicate water samples collected from the Owyhee River 

and selected tributaries, Oregon, 2001 and 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5. Mass ratios of dissolved inorganic nitrogen to orthophosphorus as phosphorus for 

sites on the Owyhee River and selected tributaries, Oregon, 2001 and 2002 . . . . . . . . 15

6. Concentrations and loads of total nitrogen and phosphorus at site OR1, 2001 and 

2002, in relation to estimated average discharge to Lake Owyhee, Oregon, 

1996–98 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

7. Stream-bottom materials less than 62.5 micrometers in diameter enriched in trace 

element concentrations, Owyhee River and selected tributaries, Oregon . . . . . . . . . . 22

8. Benthic invertebrate metric results for the Owyhee River and selected tributaries,

Oregon, June through July 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9. Benthic invertebrate abundance in the Owyhee River and selected tributaries, 

Oregon, June through July 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

10. Microhabitat characteristics and periphyton results for the Owyhee River and 

selected tributaries, Oregon, June through July 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Contents v

Conversion Factors, Datum, and Other Abbreviated Units

Temperature is given in degrees Celsius (°C), which can be converted to degrees 

Fahrenheit (°F) by use of the following equation:

°F=(1.8) (°C)+32

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 

1929 (NGVD of 1929)—a geodetic datum derived from a general adjustment of the firstorder level nets of the United States and Canada, formerly called Sea Level Datum of 

1929. 

Other Abbreviated Units

g gram 

L liter 

μg/g microgram per gram 

μg/L microgram per liter 

μm micrometer 

μS/cm microsiemens per centimeter 

mg/L milligram per liter 

mL milliliter 

mm millimeter (multiply by 0.03937 to obtain inch)

MPN/100 mL most probable number per 100 milliliters 

m2 square meter (multiply by 3.281 to obtain square foot)

Multiply By To obtain

cubic foot per second (ft3/s)

foot (ft)

inch (in.)

inch per year (in/yr)

mile (mi)

pound per day (lb/d)

square mile (mi2)

ton per day (ton/d)

0.02832

0.3048

25.4

25.4

1.609

0.4536

2.590

907.2

cubic meter per second (m3/s)

meter (m)

millimeter (mm)

millimeter per year (mm/yr)

kilometer (km)

kilogram per day (kg/d)

square kilometer (km2)

metric ton per day
[This page intentionally left blank]
Reconnaissance of Chemical and Biological 

Quality in the Owyhee River from the Oregon 

State Line to the Owyhee Reservoir, Oregon, 

2001–02

By Mark A. Hardy, Terry R. Maret, and David L. George

Abstract

The Owyhee River drains an extremely rugged and 

sparsely populated landscape in northern Nevada, southwestern Idaho, and eastern Oregon. Most of the segment between 

the Oregon State line and Lake Owyhee is part of the National 

Wild and Scenic Rivers System, and few water-quality data 

exist for evaluating environmental impacts. As a result, the 

U.S. Geological Survey, in cooperation with the Bureau of 

Land Management, assessed this river segment to characterize 

chemical and biological quality of the river, identify where 

designated beneficial uses are met and where changes in 

stream quality occur, and provide data needed to address 

activities related to environmental impact assessments and 

Total Maximum Daily Loads. Water-quality issues identified 

at one or more sites were water temperature, suspended sediment, dissolved oxygen, pH, nutrients, trace elements, fecal 

bacteria, benthic invertebrate communities, and periphyton 

communities.

Generally, summer water temperatures routinely 

exceeded Oregon's maximum 7-day average criteria of 

17.8 degrees Celsius. The presence of few coldwater taxa 

in benthic invertebrate communities supports this observation. 

Suspended-sediment concentrations during summer base flow 

were less than 10 milligrams per liter (mg/L). Dissolved solids 

concentrations ranged from 46 to 222 mg/L, were highest during base flow, and tended to increase in a downstream direction. Chemical compositions of water samples indicated that 

large proportions of upland-derived water extend to the lower 

reaches of the study area during spring runoff. Dissolved fluoride and arsenic concentrations were highest during base flow 

and may be a result of geothermal springs discharging to the 

river. No dissolved selenium was detected. 

Upstream from the Rome area, spring runoff concentrations of suspended sediment ranged from 0 to 52 mg/L, and all 

except at the Three Forks site were typically below 20 mg/L. 

Stream-bottom materials from the North Fork Owyhee River, 

an area with no mines, were enriched with nine trace elements, which indicates that this basin may be a natural source 

of these elements.

Near Rome, the part of the study area not included in the 

National Wild and Scenic Rivers System, land-use impacts 

resulted in elevated populations of Escherichia coli bacteria 

(E. coli) during base flow and elevated concentrations of 

nitrogen and phosphorus during spring runoff. Sites in this 

area had the highest numbers of benthic invertebrates; the fewest Ephemeroptera, Plecoptera, and Trichoptera taxa; and the 

highest Hilsenhoff Biotic Index scores. These results suggest 

degraded stream quality. Periphyton communities at sites in 

this area approached nuisance levels and could cause significant dissolved oxygen depletions and pH values that exceed 

Oregon’s recommended criteria. Stream-bottom materials 

from Jordan Creek were enriched with mercury and manganese, which probably were ultimately caused by past mining 

in that basin.

Below Crooked Creek, elevated suspended sediment 

concentrations (142 mg/L), phosphorus concentrations 

(0.23 mg/L), and E. coli populations (370 most probable 

number per 100 milliliters) during the largest spring runoff 

event could be the result of inputs at the lower end of Jordan 

Valley and (or) inputs from Crooked Creek. The New Zealand 

Mud Snail, a highly competitive gastropod introduced to the 

Snake River in the 1980s, was collected just downstream from 

the Crooked Creek confluence.

Introduction

The Owyhee River flows from northern Nevada, through 

southwestern Idaho, and into eastern Oregon (fig. 1), draining 

about 10,950 mi2 of extremely rugged and remote landscape. 

From the Idaho-Oregon State line to Lake Owyhee, excluding 

14 mi in the Rome area, the river has been designated part of 

the National Wild and Scenic Rivers System. The Vale District 

of the Bureau of Land Management (BLM) is required to 
2 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

Jordan

Creek

Rock

Creek

 Boulder

Creek

Louse

Creek

Antelope

Creek

Rattlesnake

Creek

Dry

Creek Crooked

Creek

Palomino

Creek

Field

Creek

Toppin

Creek

Tent

Creek

Battle

Creek

Deep

Creek

Pole

Creek

Blue Creek

Indian

Creek

Deep

Creek

 Bull

Run

Silver Creek

Sheep

Creek

Fourmile Creek

Chimney

Creek

Lake

Creek

Ranch Creek

Calico Creek

Dry Creek

Cow Creek

Bull Creek

Birch

Creek

Owyhee

River

North

Fork

Middle Fork

Owyhee River

Owyhee River

West

River

Owyhee

Little

South

Fork

Owyhee

River

Little

Owyhee

River

Owyhee

River

Owyhee

River

Snake

River

East

Antelope

Reservoir

Lake

Owyhee

Upper

Cow Lake

Lower

Cow Lake

Wild Horse

Reservoir

Owyhee

dam

China

dam

11

18

95

78

95

51

51

43

11

11A

11

201

Jordan

Valley

Burns

Junction

Riddle

Owyhee

White

Rock

Rome

Three

Forks

42° 30' 42° 30'

116° 00'

43° 00' 43° 00'

116° 30'

117° 00'

117° 30'

118° 00'

42° 00' 42° 00'

117° 00'

116° 30'

116° 00'

117° 30'

118° 00'

117° 00'

43° 43 30' ° 30'

41° 30'

41° 30'

0

0

20 40 60 80 MILES

20 80 KILOMETERS 40 60

IDAHO

NEVADA

OREGON

Owyhee River

drainage

basin

Base from U.S. Geological Survey digital data,

1:2,000,000, 1999;

Transverse Mercator projection, Zone 10,

Longitude of central meridian: -117° 00'

Latitude of origin: 42° 00'

False easting (meters): 500,000.0

False northing (meters): 0.0

Figure 1. Location of Owyhee River drainage basin, Nevada, Idaho, and Oregon.
Environmental Setting 3

Table 1. Description of sampling sites on the Owyhee River and selected tributaries, Oregon

[Site locations shown in figure 2; No., number; USGS, U.S. Geological Survey; °, degrees; ', minutes; ", seconds]

Site No. Site name

USGS site

identification No. Latitude Longitude

OR7 Owyhee River at State Line near Three Forks . . . . . . . . . . . . . . . . . . . . . 422015117024000 42°20'15" 117°02'40"

OR6 Owyhee River above West Little Owyhee River. . . . . . . . . . . . . . . . . . . . 422650117121800 42°26'50" 117°12'18"

WLO1 West Little Owyhee River at mouth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422649117121900 42°26'49" 117°12'19"

OR5 Owyhee River at Three Forks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13177900 42°32'40" 117°10'11"

NF1 North Fork Owyhee River at mouth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13177920 42°32'39" 117°10'06"

OR4 Owyhee River near Rome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425017117374900 42°50'17" 117°37'49"

JC1 Jordan Creek near Rome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13180600 42°51'51" 117°38'19"

OR3 Owyhee River below Crooked Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425442117432100 42°54'42" 117°43'21"

OR2 Owyhee River above Bull Creek near Crowley. . . . . . . . . . . . . . . . . . . . . 430631117425900 43°06'31" 117°42'59"

OR1 Owyhee River above Lake Owyhee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13182000 43°13'34" 117°29'46"

ensure that its land-management actions do not impair the 

beneficial uses of this segment of the Owyhee River. Because 

access to the river is so limited, few data have been collected 

to determine beneficial uses that the river could support or to 

contribute to other activities related to the Total Maximum 

Daily Loads (TMDLs) process required by the Clean Water 

Act. The U.S. Geological Survey (USGS), in cooperation with 

the BLM, performed a reconnaissance study during 2001–02 

that would provide data to help address these TMDL-related 

issues.

Purpose and Scope

This report describes a water-quality reconnaissance of 

the river segment between the Oregon State line and Lake 

Owyhee conducted to characterize chemical and biological 

quality, identify where major changes in water quality occur, 

and provide data that will help define beneficial uses and support TMDL-related activities. Stream discharge and samples 

of water were collected at 10 river and tributary sites (table 1) 

during two spring runoff events and during a summer base 

flow. Samples of stream-bottom materials, periphyton communities, and benthic invertebrate communities were collected 

at nine of these sites during summer base flow. Sample analyses included major ions, nutrients, and fecal-indicator bacteria 

in water; selected trace elements in stream-bottom materials; 

chlorophyll-a content and biomass of periphyton communities; and species identification and enumeration of benthic 

invertebrate communities.

Acknowledgments

The authors gratefully recognize the efforts of the 

following USGS staff for collecting water, sediment, and 

biological samples; measuring streamflows; and arranging 

for delivery of time-dependent samples from field crews to 

processing laboratories: Joe Bunt, Bill Damschen, Ross Dickinson, Jack Doyle, Dorene MacCoy, Deb Parliman, Alvin 

Sablan, and Jim Schaefer. Special thanks also go to Jack 

Wenderoth, Brian Bidding, and Justin Robinson for arranging 

the safe and efficient helicopter transport of workers and 

equipment into the Owyhee River canyons.

Environmental Setting

Environmental Setting

The 5,005-mi2 study area is in Malheur County in southeastern Oregon and represents about 46 percent of the entire 

Owyhee River watershed. It lies within the Owyhee upland 

physiographic region, where elevations range from about 

9,000 to about 2,500 ft above sea level at Lake Owyhee. The 

upper elevations of this region are characterized by granitic 

mountains that are partially covered with forest. The middle 

elevations are characterized by rhyolite and basalt in rolling 

plateaus, typically shallow soils, and shrub or grass cover. 

Most of the river flows through deep canyons that cannot be 

accessed by overland vehicles. Numerous geothermal springs 

discharge along the Owyhee River in several sections of the 

canyons.

Climate in the watershed is semiarid, and average annual 

precipitation is about 9.8 in/yr, mostly as snow in the upper 

elevations. From 1961 to 1990, yearly precipitation at the 
4 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

Rome weather station averaged 7.75 in., and mean monthly 

temperature ranged from 71.8°F (22.1°C) in July to 28.8°F 

(1.7°C) in January. On the basis of data from the USGS gaging 

station operated from 1949 through 2002, stream discharge at 

the Owyhee River near Rome ranged from 42 to 55,700 ft3/s, 

and annual mean flow was 954 ft3/s.

More than 91 percent of the land cover is sagebrush 

shrubland and grassland (table 2 ). Vegetation along the river is 

generally too sparse to shade the water. The area is sparsely 

populated; most of the population and development are in the 

Rome area and near Jordan Creek and its tributaries. Primary 

historical and current land uses that may affect water quality 

are grazing, mining, and farming. Although livestock are 

grazed throughout the watershed, farming is concentrated in 

the Rome area and Jordan Creek Basin, and mining is concentrated in the Jordan Creek Basin (table 2 ). Historical gold and 

silver mining has caused significant mercury contamination in 

the Jordan Creek watershed (Koerber, 1995). This mining and 

naturally occurring cinnabar and geothermal springs contribute to the problem of mercury pollution and bioaccumulation 

by fish in the Owyhee Reservoir (Craft and others, 2000). 

Methods of Sample Collection and 

Analysis

Methods of Sample Collection and Analysis

Ten sampling sites (fig. 2 and table 1 ) on the river and 

selected tributaries were chosen to represent stream quality at 

the upstream boundary of the BLM management unit and near 

major tributary confluences or areas of possible land-use 

impacts. Flow conditions representing summer base flow and 

spring runoff in 2001 were targeted for sampling to bracket a 

large range of flow conditions (fig. 3 ). Because of low runoff 

in 2001, spring runoff was sampled again in 2002 to provide a 

better approximation of normal runoff conditions. 

A helicopter was used to gain access and transport boats 

and other equipment to 5 of the 10 sites. Sites OR5, NF1, 

OR4, JC1, and OR1 were visited by truck. In spring, travel to 

some of these sites was delayed until the remote dirt roads on 

the plateaus and steep roads into the canyons were passable. 

When transporting sampling personnel to new sites, helicopter 

pilots delivered samples from the previous site to runners who, 

in turn, arranged for delivery of samples for time-dependent 

analyses (such as nutrients and bacteria) to appropriate laboratories. The different methods used to access sites, variable 

flight schedules of helicopters, and weather-related delays for 

overland travel prevented sites from being sampled routinely 

in downstream order, and spring flow conditions sometimes 

changed significantly before all sites could be sampled. Because of these problems, an additional sample was collected at 

the bridge crossing at site OR4 during the 2002 spring runoff 

to capture a particularly high but short-term discharge. No 

bridges were located at the other sites, and safety risks were 

considered too great for sampling such high flows by using the 

inflatable watercraft that could be transported to these sites.

Table 2. Land use/cover and mineable deposits in the Owyhee River study area, Oregon

[Site locations shown in figure 2 ; No., number; mi2, square miles; land use/cover in percent; land use/cover modified from the National Land Cover Dataset, 1992 

(http://edc.usgs.gov/products/landcover.html)]

Site No.

Area

(mi2) Water/Ice Forest Shrubland Grassland Developed Cultivated Barren Wetland

No. of 

significant 

deposits

No. of 

significant 

deposits 

per mi2

OR7 4,977 0.22 2.17 84.61 10.41 0.08 1.96 0.07 0.47 304 0.061

OR6 5,041 .22 2.15 84.74 10.34 .08 1.94 .07 .46 304 .060

WLO1 310 .09 .35 96.55 2.84 0 .01 .14 .01 1 .003

OR5 5,723 .20 1.92 85.00 9.85 .07 2.46 .08 .41 306 .053

NF1 335 .36 25.77 68.16 4.98 0 .37 .02 .33 0 0

OR4 6,401 .22 3.13 84.08 9.48 .07 2.53 .08 .42 310 .048

JC1 1,273 .66 15.50 65.71 7.74 .21 5.57 3.48 1.13 162 .127

OR3 9,072 .25 4.39 82.23 8.97 .09 3.02 .58 .46 493 .054

OR2 9,433 .25 4.23 82.37 8.99 .09 2.91 .71 .46 496 .053

OR1 9,982 .23 4.00 82.73 8.98 .08 2.79 .68 .49 503 .050
Methods of Sample Collection and Analysis 5

OR1

EXPLANATION

Sampling site and identification

 number—site descriptions

 shown in table 1

Bull Creek

Birch

Creek

Jordan

Creek

Antelope

Creek

Rattlesnake

Creek

Dry

Creek Crooked

Creek

Palomino

Creek

Owyhee

River

West

River

Owyhee

Little

Owyhee

River

Snake River

North Fork

Owyhee River

River

Owyhee

Middle Fork

Owyhee River

Antelope

Reservoir

Lake

Owyhee

Owyhee

dam

Jordan

Valley

Rome

Three

Forks

OR1

OR2

OR3

JC1

OR4

NF1

OR7

WLO1 OR6

OR5

117° 00'

117° 30'

43° 30'

118° 00'

43° 00'

118° 00'

42° 30'

117° 30'

42° 00' 42° 00'

117° 00'

42° 30'

43° 00'

43° 30'

117° 00'

0

0

10 20 30 MILES

10 20 30 KILOMETERS

Figure 2. Location of sampling sites in the Owyhee River study area, Oregon.
6 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

PERCENT OF TIME FLOW EQUALED OR EXCEEDED

MEAN DAILY DISCHARGE, IN 

CUBIC FEET PER SECOND

Site OR4

10,000

30,000

6,000

3,000

1,000

600

100

300

0.1 0.5 1 2 5 10 20 30 60 40 50 70 80 90 95 98 99 99.5

60

10

30

99.9

June 2001

Base-flow

sampling

April 2002

runoff

sampling

April 2001

runoff

sampling

Figure 3. Flow-duration curve for 1949–2002 and sampling periods for the Owyhee River near Rome, Oregon, site OR4. (Site

location shown in figure 2)

Water and Stream-Bottom Samples

Water samples for analyses of chemical constituents and 

suspended sediment were collected and processed using 

depth-integrating samplers, the equal-width-increment method, 

and a modified clean-sampling procedure described by Wilde 

and others (1999). At the time of sample collections, temperature, pH, dissolved oxygen, and specific conductance were 

measured instream at the center of flow by using calibrated 

electrometric meters. In addition, when each site was sampled, 

stream discharge was measured using either a Price AA or 

pygmy current meter or an Acoustic Doppler Current Profiler 

(ADCP). All samples analyzed for “dissolved” constituents 

were filtered through 0.45-μm capsule filters that are certified 

to be free from contamination. Suspended sediment was analyzed at the USGS Sediment Laboratory at Vancouver, Washington, by using the methods of Guy (1969). Chemical constituents in water were analyzed at the USGS National Water 

Quality Laboratory (NWQL) by using the methods of Fishman and Friedman (1989) and Fishman (1993). 

Samples for analyses of E. coli bacteria were collected 

instream at the center of flow by using sterilized bottles. The 

samples were analyzed at the Idaho State Department of Welfare, Bureau of Laboratories, by using the Colilert Quantitray 

method (a most-probable-number technique) described by the 

American Public Health Association (1998).

Silt- and clay-sized stream-bottom samples were collected and sieved during summer base flow by the methods 

described by Radtke (1997). Particles less than 62.5 μm in 

diameter were isolated for analysis by sieving through nonmetallic sieves using native river water. All samples were 

analyzed at the USGS Environmental Geochemistry Laboratory by using a complete-digestion method described by 

Briggs and Meier (1999). 

Hourly water-temperature data from April through 

September 2001 were collected by deploying calibrated, selflogging microthermistors. The thermistors were deployed 

after elevated spring runoff had subsided to ensure that the 

equipment would remain submerged during summer base 

flow.

Biological Community Samples

Benthic invertebrate communities were sampled during 

base flow conditions from June 25 through July 11, 2001. Five 

riffle areas were selected at each site and sampled using a 

Slack rectangular kick-net sampler equipped with a 425-μm 

mesh net (Cuffney and others, 1993). At each riffle, large 

gravel and cobbles within a 0.25-m2 sample area in front of 

the net were brushed to dislodge organisms. The sample area 

then was disturbed by kicking in the loose gravels for 30 seconds. Each sample was elutriated onsite by repeated washing 

into a 425-μm mesh sieve. After processing, the five samples 
Methods of Sample Collection and Analysis 7

were composited (total sample area of 1.25 m2) in 1-L plastic 

jars, fixed with 10 percent buffered formalin, and shipped to 

EcoAnalysts in Moscow, Idaho, for taxonomic processing. At 

EcoAnalysts, samples were sorted and organisms were identified and counted to the lowest practical taxonomic level 

(genus or species for most taxa). 

Semiquantitative epilithic periphyton samples were collected and processed using protocols developed by the USGS 

National Water-Quality Assessment (NAWQA) Program to 

estimate and compare biomass chlorophyll-a and ash-free dry 

weight among sites (Porter and others, 1993). Epilithic periphyton samples were collected adjacent to each of the five 

benthic invertebrate sample locations. Five rocks were 

sampled at each site by using a 30-mL syringe fitted with 

an O-ring to form a watertight seal against a rock surface. Periphyton within the syringe barrel were dislodged with a small 

brush and collected with a hand pipette. Samples were composited into a sample jar and stirred, and an aliquot of 10 mL 

was filtered through a 0.7-μm glass-fiber filter. Filters were 

wrapped in aluminum foil, placed in a glass vial, and frozen 

until they were processed at the Bureau of Reclamation Pacific 

Northwest Regional Laboratory in Boise, Idaho. Biomass and 

chlorophyll-a were determined following procedures described by the American Public Health Association (1995). 

Chlorophyll-a concentrations were determined using spectrophotometry and corrected for phaeophytin, a degradation 

product of chlorophyll.

Microhabitat data were collected at each site where invertebrates and periphyton were collected following procedures outlined by Fitzpatrick and others (1998). Depth, velocity, and percent open canopy were measured. Velocities were 

measured at 0.6 of the stream depth using a Marsh-McBirney 

flowmeter. Percent open canopy was measured using a clinometer to measure left and right angles above horizon obstructions. Dominant substrate, percent substrate fines, and 

percent filamentous algae coverage were estimated visually to 

the nearest 10 percent. Percent substrate embeddedness was 

categorized into one of five groups as outlined by Fitzpatrick 

and others (1998). A mean value for each habitat variable was 

calculated to represent a riffle sample site. 

Quality Assurance

Temperature, pH, dissolved oxygen, and specific conductance were measured at the center of flow where the stream 

appeared to be well mixed. At seven sites, measurements were 

made at five sections across the stream to determine whether 

properties in some parts of the stream might differ significantly from those in the center of flow. In these cross sections, 

values of pH always agreed to within 0.1 unit, temperatures 

always agreed to within 0.3°C, and specific conductance values always agreed within 1 μS/cm. At all but one site, dissolved oxygen concentrations agreed to within 0.07 mg/L. 

Variation of dissolved oxygen concentrations across Jordan 

Creek was 0.9 mg/L (or less than 8 percent of the 11.4 mg/L at 

the center of flow) in April 2001. These data indicate that 

onsite measurements made at the center of flow closely represented the conditions in the entire cross section. Because samples were collected using depth- and width-integrating techniques, water-chemistry analyses were not affected significantly by stream cross-section variations.

Extensive quality control procedures used at NWQL 

and USGS Environmental Geochemistry Laboratory included 

verifying the condition of reagents and equipment, managing 

samples, participating in internal and external performance 

evaluation studies, internal and external audits, data verifications, protocols for continuously monitoring quality control 

data, and chemical logic checks. These procedures are summarized in reports by Pritt and Raese (1995), Friedman and 

Erdmann (1982), and Arbogast (1990). Most chemical logic 

checks met data requirements. Cation-anion balances were all 

within 5 percent, and only one analysis reported a dissolved 

organic plus ammonium nitrogen concentration higher than 

the total organic plus ammonium nitrogen concentration (see 

the June 2001 sample for site OR4 in table 3, back of report). 

This discrepancy was within the criteria established for variation of duplicate samples (explained in the following paragraphs) and, therefore, was considered acceptable.

In addition to these laboratory procedures, blank and 

duplicate samples were submitted to the NWQL. One field 

blank sample was collected at streamside during each of the 

three sampling events in April and June 2001 and April 2002 

to help verify that sampling environment, equipment, and processing were not significantly contaminating samples. Samples were collected by passing about 2 L of certified analytefree water through all sampling and processing equipment 

used for routine sample collection. The samples were analyzed for major ions, nutrients, arsenic, and selenium. Results 

for all analyses were below laboratory reporting limits, except 

for a calcium detection of 0.022 mg/L. This concentration is 

nearly 190 times lower than the lowest calcium concentration 

measured during the reconnaissance. These results indicate 

that sampling environment, equipment, and processing did not 

significantly contaminate environmental samples.

Six pairs of duplicate samples were collected and submitted to the laboratory for analysis of major ions, nutrients, 

arsenic, and selenium (table 4 ). Duplicate sample analyses 

were considered acceptable if the relative percent difference 

(RPD = {|S-D| / [(S + D)/2]}x100; where S = result of sample 

analysis and D = result of duplicate sample analysis) met the 

following criteria:

All duplicate chemical analyses met these criteria, which 

suggests that analytical data were of high precision.

Sample concentration Maximum allowed variation

0–5 times reporting limit +(-) 1 reporting limit

>5–20 times reporting limit

Greater of 2 reporting limits 

or 20 percent RPD

>20 times reporting limit 10 percent RPD
Table 4. Chemical analyses of duplicate water samples collected from the Owyhee River and selected tributaries, Oregon, 2001 and 2002[Site locations shown in figure 2; No., number; fltrd, filtered; mg/L, milligrams per liter; ANC, acid neutralizing capacity; unfltrd, unfiltered; pt, point; CaCO3, calcium carbonat

phosphorus; μg/L, micrograms per liter; <, less than; E, estimated value] Site No. Date Time Calcium, water, fltrd, mg/L (00915) Magnesium, water, fltrd, mg/L (00925) Potassium, water, fltrd, mg/L (00935) Sodium, water, fltrd, mg/L (00930) ANC, water, unfltrd, fixed end pt, lab, mg/L as CaCO3 (90410) Chloride, water, fltrd, mg/L (00940) Fluoride, water, fltrd, mg/L (00950) Silica, water, fltrd, mg/L (00955) Sulfate, water, fltrd, mg/L (00945) Resid

water, 

sum of con

mg/

(7030

OR7 06-27-01 0820 0815 23.4 23.7 8.64 8.71 5.14 4.91 30.4 30.7 137 137 8.12 8.21 1.8 1.8 19.3 19.2 14.8 14.7 194 194 OR6 04-15-02 1610 1605 11.6 11.7 2.93 2.97 2.53 2.45 9.05 9.25 5253 3.75 3.93 .5 .6 23.4 23.1 6.8 6.8 9293 WLO1 04-10-01 1455 1450 8.15 8.11 2.19 2.18 1.86 1.78 8.87 8.88 3939 5.07 4.70 .3.3 15.9 15.8 5.6 5.5 7171 NF1 04-11-02 1405 1400 4.30 4.11 1.73 1.67 1.25 1.29 3.34 3.22 2525 .90 .84 E.1 E.1 24.6 24.6 1.4 1.3 5352 OR4 04-04-01 1245 1250 14.3 14.3 3.74 3.71 2.41 2.38 12.0 11.9 6162 3.92 3.95 .7.7 25.2 25.0 8.6 8.7 108 108 OR2 06-28-01 1220 1215 20.8 21.0 5.95 5.99 4.77 4.81 41.5 40.7 129 129 11.3 11.2 2.0 2.0 32.5 32.3 23.6 23.8 221 221 Site No. Date Time Ammonia + org-N, water, fltrd, mg/L as N (00623) Ammonia + org-N, water, unfltrd, mg/L as N (00625) Ammonia, water, fltrd, mg/L as N (00608) Nitrite + nitrate, water, fltrd, mg/L as N (00631) Nitrite, water, fltrd, mg/L as N (00613) Orthophos- phate, water, fltrd, mg/L as P (00671) Phosphorus, water, unfltrd, mg/L (00665) Arsenic, water, fltrd, 

μg/L

(01000)

Arsenic,

water, 

unfltrd,

μg/L

(01002)

OR7 06-27-01

08200815

0.29

.28

0.34

.34

E.03E.03

<0.05

<.05

0.009

.008

E0.01

<.02

<0.06

<.06

66

66

OR6 04-15-02

16101605

.31.32

.48.49

<.04<.04

.07.07

<.008<.008

.03.03

.09.08

23

33

WLO1 04-10-01

14551450

E.09E.10

.15.18

<.04<.04

<.05<.05

<.006<.006

E.02E.02

E.03E.03

E1E1

E1E1

NF1 04-11-02

14051400

.22.17

.31.33

<.04<.04

.08.08

<.008<.008

E.01E.01

E.05E.05

<2<2

<2<2

OR4 04-04-01

12451250

.20.20

.40.37

<.04<.04

.10.10

<.006<.006

.02

E.02

E.04E.05

33

33

OR2 06-28-01

12201215

.23.22 

.33.30

E.02E.02

.30.30

.010.010

<.02<.02

E.04

<.06

1111

1010
Chemical and Biological Quality 9

A duplicate benthic invertebrate sample was collected 

using a 300-subsample count method (Moulton and others, 

2000) at site OR6 and submitted to the USGS Biological Unit, 

Denver. Total abundance was comparable—14,833 to 17,449 

individuals/m2. However, only 22 taxa were common between 

both samples. Of the 64 distinct taxa identified by both laboratories, 41 and 46 taxa were identified by the contract and the 

USGS laboratories, respectively. Eleven taxa identified by the 

USGS laboratory were not identified by the contract laboratory in any of the other invertebrate samples collected during 

this study. These results are consistent with an interlaboratory 

comparison by Maret and others (2001) that also revealed 

large differences between invertebrate contract laboratories 

and suggest that use of the same laboratory for routine biological monitoring and assessment programs is necessary to 

ensure analytical consistency. 

A duplicate periphyton community sample was collected 

to evaluate variation in chlorophyll-a concentration and biomass. Chlorophyll-a concentrations for the duplicate samples 

were 40 and 52 mg/m2 (RPD of 26 percent), and biomass 

concentrations were 18 and 34 g/m2 (RPD of 61 percent). 

These are normal variations for filamentous algae samples 

and are caused primarily by difficulties in homogenizing such 

samples. 

Chemical and Biological Quality

Chemical and Biological Quality

Water Temperature

Temperature is a property of water that affects the entire 

river ecosystem, and increases in stream temperatures are 

known to adversely affect some communities. Concentrations 

of other regulated water-quality parameters, such as dissolved 

oxygen and un-ionized ammonia, also affect stream biota and 

are dependent on water temperature. Despite maximum watertemperature criteria that have been established for many 

streams, recent data show that temperatures of streams not significantly influenced by human activities may naturally exceed 

these criteria and still support healthy biological communities 

(Essig, 1998). 

Continuous water-temperature data were collected from 

the Owyhee River and selected tributaries from April through 

September 2001 (fig. 4). Data for site OR5 are missing 

because the deployed instrument was vandalized. Temperatures were highest in early July through early August and lowest in late September. Maximum temperatures ranged from 

25.1° to 30.9°C, and maximum 7-day average temperatures 

ranged from 24.2° to 28.9°C. These temperatures exceeded 

Oregon’s recommended maximum temperature of 17.8°C for 

water that supports salmonid fish rearing (Oregon Department 

of Environmental Quality, 2002). These high water temperatures probably explain the absence or low abundance of coldwater invertebrate taxa in the study area (see section, “Benthic 

Invertebrates”). Summer temperatures generally were highest 

in the central part of the study area (sites NF1, OR4, and JC1) 

and just upstream from Lake Owyhee (site OR1). The 

increases in minimum temperatures at sites OR2 and OR1 

imply that geothermal inputs, reradiation from canyon walls, 

or other factors could affect stream temperatures in the lower 

reaches of the study area. The missing data at site OR5 might 

have given insight into effects from upstream geothermal 

springs. Collecting continuous temperature throughout cold 

seasons might help better define the influence of geothermal 

springs on Owyhee River temperatures.

Suspended Sediment and Turbidity

Suspended sediment in streams is fragmentary material 

that originates mostly from weathering of rocks. Because certain contaminants such as some trace elements and pesticides 

preferentially partition onto sediment, their distribution 

through the watershed often is controlled primarily by sediment transport, and their exposure to biota is most significant 

in zones where the sediment accumulates. In addition to contaminant transport, high concentrations of suspended sediment 

can affect stream communities by reducing light penetration 

and increasing scouring action. When stream discharges wane, 

large amounts of suspended sediment can settle and suffocate 

bottom-dwelling organisms. Delivery of fluvial sediment into 

reservoirs also results in accumulations that reduce reservoir 

volumes. 

Suspended sediment concentrations at all sites were 

higher during spring runoff than during base flow (fig. 5), 

owing to resuspension and transport of particulate and streambottom materials during increased stream velocities and to 

additional particulate materials from overland runoff and bank 

erosion. During base flow, concentrations were less than 10 

mg/L at all sites. During the 2001 spring runoff, concentrations were 52 and 41 mg/L at sites OR5 and JC1 and less than 

20 mg/L at all other sites. During the 2002 spring runoff, distributions of suspended sediment concentrations upstream 

from site OR4 were similar to those during the 2001 runoff. 

However, lower basin concentrations at sites OR4, JC1, OR3, 

and OR2 during this period commonly exceeded 50 mg/L and 

were as high as 142 mg/L at site OR3, below Crooked Creek. 

Sediment concentrations can vary widely during runoff 

events, so individual samples may not represent the most 

extreme concentrations. For the 2002 spring runoff event, flow 

was highest before the canyon could be accessed by helicopter 

on April 15. In an attempt to measure the highest flow possible, samples were collected on April 3 at site OR4, the only 

site in the study area with a bridge crossing. Suspended sediment in this sample was more than 5 times higher (134 mg/L) 

than that in the April 12 sample. Streamflow on April 3 was 

5,490 ft3/s, representing flows exceeded about 4 percent of the 

time; streamflow on April 12 was 2,510 ft3/s, representing 

flows exceeded about 10 percent of the time (fig. 3). As a 

result, it is likely that the spring runoff samples collected at 

several other sites do not represent the highest concentrations 

of suspended sediment that occurred at those sites. 

Instantaneous loads of sediment in the Owyhee River 

were highest during the 2002 spring runoff in the lower basin 
10 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

Owyhee River maximum temperature

Owyhee River maximum 7-day average temperature

Owyhee River minimum temperature

Tributary maximum temperature

Tributary maximum 7-day average temperature

Tributary minimum temperatureNo Data

(Instrument vandalized)

No Data

(Instrument vandalized)

Oregon maximum 7-day average

recommended temperature for surface water

SITES

WATER TEMPERATURE, IN DEGREES CELSIUS

OR6 WLO1

(tributary)

OR5 OR4 NF1

(tributary)

JC1 OR3 OR1

(tributary)

OR7 OR2

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

Figure 4. Water temperature in the Owyhee River and selected tributaries, Oregon, April through September 2001. (Site

locations shown in figure 2)
Chemical and Biological Quality 11

12 April

3 April

12 April

3 April

12 April

3 April

Runoff April 2001—Owyhee River site

Runoff April 2001—Tributary site

Runoff April 2002—Owyhee River site

Runoff April 2002—Tributary site

Base flow June 2001—Owyhee River site

Base flow June 2001—Tributary site

SITES

SUSPENDED SEDIMENT CONCENTR

ATION,

IN MILLIGRAMS PER LITER

TURBIDIT

Y, IN NEPHELOMETRIC 

TURBIDITY UNITS (NTU)

INS

TAN

TANEOUS SUSPENDED SEDIMENT

LOAD, IN

TONS PER D

AY

OR6 WLO1

(tributary)

OR5 NF1 OR4

(tributary)

JC1 OR3 OR1

(tributary)

OR7 OR2

160

140

120

100

80

60

40

20

0

100

90

80

70

60

50

40

30

20

10

0

2,250

2,000

1,750

1,500

1,250

1,000

750

500

250

0

Figure 5. Suspended sediment concentrations, instantaneous loads, and turbidity in the Owyhee River and selected

tributaries, Oregon, 2001 and 2002. (Site locations shown in figure 2)
12 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

at sites OR3, OR2, and OR1; loads discharged by tributaries 

WLO1, NF1, and JC1 did not contribute significantly to Owyhee River loads (fig. 5). It is not known whether the large sediment loads in the lower basin in 2002 were the result of 

increased stream-channel scouring, or whether some unique 

event such as bank caving may have caused an abnormally 

high rate of sediment recruitment.

Turbidity, an optical measurement of light scattering, 

sometimes is used as a low-cost surrogate for monitoring suspended sediment. In addition to suspended sediment, turbidity 

measurements are affected by phytoplankton populations, 

water color, sediment color, and other factors. Increases in turbidity during spring runoff between sites OR6 and OR5, and 

between OR4 and OR3 (fig. 5) exceeded Oregon’s recommended 10-percent cumulative increase. As discussed previously, the sources of sediment that probably caused these 

turbidity increases are unknown but may have been the result 

of natural processes during high flows of fairly short duration. 

The spatial and temporal variations for turbidity measurements were similar to those for suspended sediment concentrations (fig. 5), which suggests that turbidity measurements 

could be an effective method for monitoring sediment in the 

Owyhee River. Recent development of a variety of instream 

instruments has allowed effective continuous monitoring and 

real-time reporting of turbidity measurements. However, 

turbidity measurement methods vary enough that they often 

cannot be compared (even if they are reporting the same measurement units), and the instream instruments make measurements only at a single point in the stream. As a result, a 

relation between USGS laboratory turbidity measurements 

(of integrated samples) and sediment concentrations was not 

developed for this reconnaissance because the relation probably could not be applied to measurements made by the typical 

instream methods.

Dissolved Oxygen

Nearly all stream fauna depend on adequate dissolved 

oxygen, though different organisms have different minimum 

requirements. Generally, reproducing salmonid fishes have 

some of the highest dissolved oxygen requirements. Oxygen 

solubility in water is inversely related to temperature, so that 

at high temperatures, the saturated dissolved oxygen concentrations may be far lower than those at cold temperatures. 

Oxygen dissolves in water primarily by dissolution from the 

atmosphere in turbulent stream zones and by photosynthesis 

by suspended and attached algal communities. During daylight, dissolved oxygen concentrations can become supersaturated as a result of algal photosynthesis. Respiration by stream 

organisms and decomposition of organic materials are two 

major ways that dissolved oxygen is depleted in water. 

Excluding a concentration of 4.7 mg/L at the West Little 

Owyhee River during the June base flow (when water in this 

tributary was not flowing to the Owyhee River and probably 

consisted entirely of ground-water seepage), concentrations of 

dissolved oxygen ranged from 7.7 to 12.2 mg/L (table 3 ). 

These concentrations exceeded the minimum single-observation criterion (5.5 mg/L) recommended for warmwater aquatic 

life (Oregon Department of Environmental Quality, 2002). 

Although few concentrations equaled or exceeded 11 mg/L, 

the minimum single-observation criterion recommended for 

salmonid spawning (Oregon Department of Environmental 

Quality, 2002), most were within 95 to 133 percent of saturated conditions.

Predawn oxygen concentrations at two sites near Rome 

may have been low, but it is not known whether criteria were 

violated. Significant oxygen supersaturation at site OR4 (161 

percent during the June base flow) suggests that this particularly slow-moving reach might experience excess phytoplankton production. Respiration by these communities can cause 

significant oxygen depletion during nighttime periods when 

photosynthesis is not occurring. In addition, the benthic invertebrate community at this site had the highest total number of 

organisms and the highest numbers of filter-feeding caddisflies (see section, “Benthic Invertebrate Communities”), 

which suggests that organic loading and subsequent decomposition also may contribute to oxygen depletion at this site. 

Also near Rome, the extensive filamentous periphyton community observed at site JC1 had significantly higher biomass 

and chlorophyll-a content than all other communities measured, and this condition also might result in nighttime depletions of dissolved oxygen. An instrumentation breakdown 

prevented measuring dissolved oxygen at this site during the 

June base flow. However, the large numbers of tolerant invertebrate taxa at this site (including oligochaetes, which are particularly tolerant of low dissolved oxygen) and lowest 

numbers of sensitive Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa suggest that low dissolved oxygen concentrations could be common in Jordan Creek.

Solubility of oxygen may be reduced further at elevated 

water temperatures that are common in July and August. At 

the maximum single-observation and 7-day mean temperatures (30.9° and 27.7°C) (fig. 4) and the lowest barometric 

pressure (647 mm mercury) measured during this study, saturated dissolved oxygen concentrations are 6.3 and 6.6 mg/L. 

These calculated concentrations still exceed the minimum 

concentrations recommended for warmwater aquatic life. 

pH

The amount and behavior of many chemicals in water 

and the health of many aquatic biological communities are 

affected by pH. The pH of uncontaminated river water generally ranges from 6.5 to 8.5 (Hem, 1985). Photosynthesis by 

aquatic plants generally increases pH during the day, and respiration by plants and animals generally decreases pH at night.

The pH at all sites ranged from 7.4 to 9.1 (table 3 ). Only 

one pH measurement (site JC1 during June base flow) 

exceeded 9, the maximum recommended for Oregon water 

(Oregon Department of Environmental Quality, 2002). Measurements at the other sites during base flow (ranging from 7.7 

to 8.9) generally were the highest recorded for each site, and 
Chemical and Biological Quality 13

some were close to the maximum criteria. Consumption of 

carbon dioxide by the summer photosynthetic activity of phytoplankton and periphyton, combined with the naturally basic 

high-bicarbonate water in the basin, is the likely cause of these 

elevated pH values. At site JC1, the biomass (79 g/m2) and 

chlorophyll-a content (86 mg/m2) of the extensive filamentous 

periphyton community were the highest measured in the study 

area. At site OR4, a pH of 8.9 and supersaturation of dissolved 

oxygen suggest that vigorous photosynthetic activity by phytoplankton sometimes might induce pH values to exceed criteria. It is likely that pH at all these sites decreased significantly 

at nighttime when reduced photosynthetic activity, combined 

with respiration, increased carbon dioxide in the streams.

Major Ions

Major ions in water are those composing most of the dissolved solids in water and normally include calcium, magnesium, sodium, potassium, chloride, fluoride, bicarbonate, and 

sulfate. They dissolve in water having contact with naturally 

occurring minerals in the basin, and the proportions of their 

concentrations in water (water type) often reflect the geology 

of the basin. Some land uses also contribute selected major 

ions and, thus, affect the water type in a basin. 

Major ions were compared using the patterns (Stiff, 

1951) shown in figure 6. The relative sizes of these patterns 

distinguish differences in dissolved solids concentrations, and 

the shapes distinguish variations in major ion compositions. 

At each site except North Fork, concentrations of dissolved 

solids were about 2 to 6 times higher during base flow (ranging from 94 to 222 mg/L) than during spring runoff (ranging 

from 46 to 133 mg/L). In contrast, dissolved solids concentrations were similar on the North Fork Owyhee River during 

base flow and spring runoff (ranging from 52 to 70 mg/L). 

Major ion compositions ranged from calcium-bicarbonate-dominated to sodium-bicarbonate-dominated water types 

(fig. 6). Water types at tributary sites WLO1 and NF1 were 

fairly consistent during all sampling events. At Owyhee River 

sites and Jordan Creek, water types differed during base and 

runoff flows. Water in the Owyhee River generally became 

increasingly dominated by sodium in a downstream direction.

The concentrations of dissolved solids and extent of 

sodium domination probably reflect the predominant sources 

of water composing streamflow. Water derived from the upper 

elevations in the basin (such as the North Fork Owyhee River 

and the West Little Owyhee River) tends to be low in dissolved solids and dominated by calcium, sodium, and bicarbonate. These characteristics probably reflect contact with 

feldspars in the granite composing the upland areas. Water 

derived from lower elevations likely includes ground-water 

seepage from arid soils, rhyolite, basalt, and evaporite minerals that contribute high concentrations of sodium bicarbonate. 

Mariner and others (1994) also reported that geothermal 

springs near the Owyhee River contribute sodium-bicarbonate-dominated water. As a result, sodium-dominated water 

measured at most Owyhee River sites during base flow suggests that most streamflow was contributed by ground-water 

seepage in the low-elevation parts of the basin. In contrast, the 

calcium- and sodium-codominated water measured at downstream Owyhee River sites during spring runoff suggests that 

a large proportion of streamflow was derived from high-elevation snowmelt.

All sodium concentrations measured in the Owyhee 

River and tributaries were too low to present undesirable cation exchange effects for irrigation use. However, dissolved 

solids concentrations during base flow were high enough to 

present a medium salinity hazard for irrigation (Hem, 1985, 

p. 217–218).

Fluoride concentrations were generally less than 1 mg/L 

in tributaries and during spring runoff at Owyhee River sites 

(table 3 ). However, concentrations ranged from 1.7 to 2.4 

mg/L during base flow at Owyhee River sites. Both the volcanic rocks in the basin and geothermal springs near and in the 

river may be sources of fluoride (Hem, 1985, p. 21) that are 

least diluted during base-flow conditions. Mariner and others 

(1994) reported concentrations of fluoride in the geothermal 

springs near the river as high as 29 mg/L, more than 16 times 

the concentration measured during base flow at site OR7, the 

farthest upstream site in the study area. Such high concentrations might make fluoride a good surrogate ion to use to help 

estimate the volume of hot water that geothermal springs contribute to the Owyhee River.

Nutrients

Nitrogen and phosphorus are nutrients that are essential 

to aquatic plant growth, and high nutrient concentrations can 

cause undesirably high amounts of instream plant growth. In 

instances when one nutrient (such as nitrogen) is present in 

large concentrations but the other (phosphorus) is in short supply, plant communities can develop only as long as the shortsupply nutrient (called the limiting nutrient) is available. Common sources of nitrogen and phosphorus to streams include 

naturally occurring geologic and organic materials and contamination by fertilizers, sewage, and animal wastes. In addition, nitrogen can be “fixed” directly from the atmosphere by 

some organisms such as blue-green algae. Igneous rocks commonly contain relatively high concentrations of phosphorus 

compared with concentrations in other rocks (Hem, 1985, 

p. 3).

Total nitrogen (N) concentrations (combined concentrations of total ammonia plus organic N and nitrite plus nitrate 

N, table 4 ) ranged from 0.14 to 2.6 mg/L; most concentrations 

were less than the 1.9 mg/L national median for 179 basins 

sampled as part of the NAWQA Program from 1991 to 2001 

(accessed April 2003 at http://water.usgs.gov/nawqa/

nutrients/datasets/nutconc2000/#SW). Concentrations were 

highest (exceeding 0.9 mg/L) in the lower reaches of the study 

area at sites OR4, JC1, OR3, and OR2. All ammonia concentrations were at or below the laboratory reporting limit of 0.05 

mg/L as N. 

Nitrogen concentrations were generally lowest and uniform at all sites during June base flow (table 3). All concentra- 
14 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

Figure 6. Stiff patterns representing major ions in the Owyhee River and selected tributaries, Oregon, 2001 and 2002.

(Site locations shown in figure 2 )

Na + K

Ca

Mg

Cl + F

HCO3

SO4

321 2 0 3 1

MILLIEQUIVALENTS PER LITER

OR7

OR6

OR5

OR4

OR3

OR2

OR1

WLO1

NF1

JC1

SITES JUNE 2001

BASE FLOW

APRIL 2001

RUNOFF

APRIL 2002

RUNOFF

OWYHEE RIVER

WEST LITTLE

OWYHEE RIVER

JORDAN

CREEK

NORTH FORK

OWYHEE RIVER
Chemical and Biological Quality 15

tions of total N were less than 0.7 mg/L, and inorganic nitrogen concentrations (combined concentrations of ammonia as 

N and nitrite plus nitrate as N) were all less than or only 

slightly greater than the 0.3 mg/L concentration considered 

essential to stimulate algal growth when adequate phosphorus 

is present (Mackenthun, 1969). Conditions during the 2001 

spring runoff were nearly the same as those during base flow 

(fig. 7), possibly as a result of the small amount of precipitation that the basin received during the preceding winter.

During the 2002 spring runoff, concentrations of organic 

and particulate nitrogen were high at all sites, and concentrations were highest near and downstream from Rome (fig. 7). 

Concentrations peaked at site OR4 and gradually decreased 

downstream at sites OR3, OR2, and OR1. A comparison between dissolved and total ammonia plus organic N concentrations (table 3 ) indicates that most of the high downstream concentrations were associated with organic particles, possibly 

dislodged periphyton and materials flushed from adjacent 

lands. The nitrogen concentration at site OR4 on April 12 was 

more than 3 times higher than on April 3, when discharge 

exceeded the April 12 discharge (fig. 7). This suggests that 

these elevated concentrations might be of short duration during runoff periods.

Total nitrogen concentrations were higher at Jordan 

Creek than at other tributary sites during all sampling events 

(fig. 7 and table 3 ). This basin has the greatest amounts of cultivated and developed land cover in the study area (table 2). 

Although the large populations of periphyton (see section, 

"Periphyton Communities ") at the site demonstrate that nutrients are enriched at the site, measurements of inorganic nitrogen during both spring runoff events only slightly exceeded 

the 0.3 mg/L concentration considered necessary for stimulating algal growth. This suggests that the periphyton community 

might already have incorporated nitrogen from the stream 

water and also might obtain nitrogen from ground-water seepage or stream-bottom materials. Instantaneous loads of nitrogen transported by Jordan Creek were small (about 7 to 15 

percent) compared with those transported by the Owyhee 

River just upstream from the Jordan Creek confluence (site 

OR4) (fig. 7).

Total phosphorus concentrations ranged from <0.06 to 

0.23 mg/L (table 3 ). Most concentrations were less than the 

0.18 mg/L national median for 179 basins sampled as part 

of the NAWQA Program from 1991 to 2001 (accessed April 

2003 at http://water.usgs.gov/nawqa/nutrients/datasets/

nutconc2000/#SW). The highest concentrations equaled or 

exceeded 0.1 mg/L and were measured in the lower reaches of 

the study area at sites OR5, OR4, JC1, OR3, OR2, and OR1.

During base flow, total phosphorus and orthophosphate 

concentrations were typically below laboratory reporting limits, and all total phosphorus concentrations were less than the 

0.1 mg/L maximum concentration recommended for preventing nuisance biological growth in flowing water (Mackenthun, 

1969). 

During spring runoff, orthophosphate concentrations 

generally remained near laboratory reporting limits, but concentrations of organic plus particulate phosphorus were higher 

than those during base flow (fig. 8). The spatial concentration 

pattern for phosphorus mimicked that for suspended sediment 

(fig. 5), which suggests that much of the phosphorus was 

transported on inorganic particles contributed by land adjacent 

to the river and tributaries. Total phosphorus concentrations in 

the Owyhee River equaled or exceeded 0.1 mg/L at sites OR4, 

OR3, OR2, and OR1 during the 2002 spring runoff and only at 

site OR5 during the smaller-than-normal 2001 runoff. The 

concentration at site OR4 on April 12, 2002, was less than half 

that on April 3 when discharge was higher. This suggests that 

such elevated concentrations might be of short duration.

The only tributary where total phosphorus concentrations exceeded 0.1 mg/L during both spring runoff events was 

Jordan Creek (fig. 8). Large populations of periphyton at the 

site support this measurement of enriched nutrient concentrations. Despite enriched phosphorus concentrations, instantaneous loads of phosphorus transported by Jordan Creek were 

about 25 to 34 percent of those transported by the Owyhee 

River just upstream from the Jordan Creek confluence (site 

OR4) (fig. 8). Similar to suspended sediment loads, the high 

phosphorus load at site OR3 in April 2002 (about 10 times that 

at Jordan Creek) suggests that cultivated and developed lands 

downstream from the Jordan Creek confluence and (or) input 

from Crooked Creek also may contribute significant amounts 

of phosphorus to the Owyhee River.

Nutrient limitation appears to vary within the study area. 

For samples containing either nitrogen or phosphorus concentrations equal to or exceeding the algal production criteria of 

0.3 and 0.1 mg/L, respectively, mass ratios of dissolved inorganic nitrogen to dissolved orthophosphate as P (N:P) were 

calculated to give some insight into nutrients that may limit 

primary productivity (table 5 ). Ryding and Rast (1989) indicated that, on the basis of a preferential uptake ratio by algae, 

N:P exceeding 7.2 may indicate phosphorus limitation, and 

N:P less than 7.2 may indicate nitrogen limitation. Ratios for 

water in the upper study area (upstream from Rome) and just 

upstream from Lake Owyhee (site OR1) were low, which sugTable 5. Mass ratios of dissolved inorganic nitrogen to orthophosphorus as phosphorus for sites on the Owyhee River and 

selected tributaries, Oregon, 2001 and 2002

[Site locations shown in figure 2; No., number; ratios shown for sites where 

concentrations of inorganic nitrogen or total phosphorus exceeded 0.3 or 0.1 

milligrams per liter, respectively]

Site No.

2001 2002

June April April

OR5 1.5

OR4 3.3

JC1 10.3 11.3

OR3 11

OR2 16 10.5

OR1 4.7
16 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

Organic and particulate nitrogen

Total nitrogen—Owyhee River site

Total nitrogen—Tributary site

Dissolved nitrite plus nitrate as

 nitrogen—Owyhee River site

Dissolved nitrite plus nitrate as

 nitrogen—Tributary site

12 April

3 April

April 2002—Owyhee River site

April 2002—Tributary site

April 2001—Owyhee River site

April 2001—Tributary site

12 April

3 April

SITES

NITROGEN CONCENTRATION, IN

MILLIGRAMS PER LITER

NITROGEN CONCENTRATION, IN

MILLIGRAMS PER LITER

APRIL 2002

APRIL 2001

INSTANTANEOUS TOTAL NITROGEN

LOAD, IN TONS PER DAY

OR6 WLO1

(tributary)

OR5 OR4 NF1

(tributary)

JC1 OR3 OR1

(tributary)

OR7 OR2

3.0

2.5

2.0

1.5

1.0

0.5

0

3.0

2.5

2.0

1.5

1.0

0.5

0

20.0

17.5

15.0

12.5

10.0

7.5

5.0

2.5

0

Figure 7. Nitrogen concentrations and instantaneous loads in the Owyhee River and selected tributaries, Oregon, during

spring runoff in 2001 and 2002. (Site locations shown in figure 2 )
Chemical and Biological Quality 17

Organic and particulate phosphorus

Total phosphorus—Owyhee River site

Total phosphorus—Tributary site

Dissolved orthophosphate as

 phosphorus—Owyhee River site

Dissolved orthophosphate as

 phosphorus—Tributary site

12 April

3 April

April 2002—Owyhee River site

April 2002—Tributary site

April 2001—Owyhee River site

April 2001—Tributary site

12 April

3 April

SITES

PHOSPHORUS CONCENTRATION, IN

MILLIGRAMS PER LITER

PHOSPHORUS CONCENTRATION, IN

MILLIGRAMS PER LITER

APRIL 2002

APRIL 2001

INSTANTANEOUS TOTAL PHOSPHORUS

LOAD, IN POUNDS PER DAY

OR6 WLO1

(tributary)

OR5 OR4 NF1

(tributary)

JC1 OR3 OR1

(tributary)

OR7 OR2

0.25

0.20

0.15

0.10

0.05

0

0.25

0.20

0.15

0.10

0.05

0

5,000

4,500

4,000

3,500

3,000

2,500

2,000

1,500

1,000

500

0

Figure 8. Phosphorus concentrations and instantaneous loads in the Owyhee River and selected tributaries, Oregon,

during spring runoff in 2001 and 2002. (Site locations shown in figure 2 )
18 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

gests nitrogen limitation (table 5). Ratios for water at sites on 

the Owyhee River and Jordan Creek between these areas were 

high, which suggests phosphorus limitation. Nutrient limitation can change over time and in response to changing hydrologic conditions. Also, the reservoir of nutrients contained in 

periphytic communities and stream-bottom materials is not 

considered in these ratios. As a result, a comprehensive assessment of nutrient limitation would require significantly more 

sampling than this reconnaissance provides.

Concentrations and loads of nitrogen and phosphorus 

discharged to Lake Owyhee by the Owyhee River were estimated by Craft and others (2000) by using data collected near 

Rome, Oregon, during 1996–98. A comparison of these data 

with the instantaneous measurements made closer to the lake 

for this reconnaissance at site OR1 is shown in table 6. 

Concentrations of nitrogen and phosphorus in the summer and phosphorus concentrations in the spring at site OR1 

compared fairly well (within 15 percent) with the concentrations estimated by Craft and others (2000). However, spring 

nitrogen concentrations for this reconnaissance were about 39 

to 62 percent higher than those estimated. Additional sources 

of nitrogen between Rome and site OR1, differences in sampling techniques (grab samples used by Craft and others versus flow-integrated samples used for this reconnaissance), and 

streamflow volumes exceeding those used by Craft and others 

probably account for some of the concentration differences.

Loads of nitrogen in summer during this reconnaissance 

were about 86 percent higher than the estimated loads. Higher 

stream discharges at site OR1, compared with those used by 

Craft and others, probably account for most of these load differences. The April 2002 loads of both nitrogen and phosphorus were within about 10 percent of the estimated loads. However, April 2001 nitrogen and phosphorus loads were about 62 

and 72 percent, respectively, lower than the estimated loads. 

These low loads almost certainly were caused by the low 

spring discharge in the Owyhee River in 2001.

Trace Elements 

Trace elements include many metallic and some nonmetallic elements that typically are present in water at concentrations far below 1 mg/L. Some of these elements can be toxic 

to aquatic life, whereas others are essential micronutrients that 

are beneficial in small concentrations but toxic in larger concentrations. Because trace elements are not degradable, their 

concentrations can be magnified in the upper trophic levels of 

food chains, such as fish. Some geologic formations are naturally rich sources of trace elements to streams, and many land 

uses such as mining, industry, agriculture, and urban areas discharge trace elements to streams.

Transport of trace elements in streams is often sporadic 

and difficult to capture without collecting large numbers of 

samples. Because many trace elements, especially metals, 

have low solubilities and are preferentially incorporated into 

sediments, samples of stream-bottom materials often contain 

Maximum value

75th percentile value

Median value

25th percentile value

Minimum value

Data from Owyhee River and tributaries

Data from Rinella and others, 1994

Bulk sediment Threshold Effects Level (TEL) for aquatic biota

 according to Washington State Department of Ecology (Batts

 and Cubbage, 1995)

Bulk sediment Probable Effects Level (PEL) for aquatic biota

 according to Washington State Department of Ecology (Batts

 and Cubbage, 1995)

No analyte detected at reporting limits (RL) shown

Analyte detected when all other measurements were below

 detection limits

EXPLANATION

for figure 9

RL

RL

Table 6. Concentrations and loads of total nitrogen and phosphorus at site OR1, 2001 and 2002, in relation to estimated average discharge to 

Lake Owyhee, Oregon, 1996–98

[Site locations shown in figure 2; summer, June base flow; spring, April runoff; N, nitrogen; P, phosphorus; mg/L, milligrams per liter; lb/d, pounds per day; 

<, less than]

Summer

total N 

concentration

(mg/L)

Spring

total N 

concentration 

(mg/L)

Summer

total N 

load

(lb/d)

Spring

total N load

(lb/d)

Summer

total P 

concentration 

(mg/L)

Spring

total P 

concentration 

(mg/L)

Summer

total P 

load

(lb/d)

Spring

total P

load

(lb/d)

Average discharge to

Lake Owyhee 

(Craft and others, 2000) . . . . 0.6 0.445 417 11,995 0.0325 0.095 30 1,900

Site OR1. . . . . . . . . . . . . . . . . . . . .51

.72 (2001)

.62 (2002) 776

4,508 (2001)

11,038 (2002) < .06

.086 (2001)

.096 (2002) < 90

0,538 (2001)

1,709 (2002)
6,0001,0003,000

600100

6010

63

0.060.03

30

300

0.01

1

0.60.30.1

Arsenic Barium Beryllium Bismuth Cadmium Cerium ChromiumCopper Cobalt Europium GalliumGold LanthanumLithium Manganese Molybdenum NeodymiumNickel NiobiumSeleniumSilver Strontium ThoriumTin Uranium Vanadium Ytterbium Yttrium 

Zinc

LeadMercury Scandium

CONCENTRATION, IN MICROGRAMS PER GRAM

ELEMENTS IN STREAM-BOTTOM MATERIALS LESS THAN 62.5 MICROMETERS IN DIAMETER

RLRL

RLRL RL

RL

RLRL

RLRL

RLRL

RL

RL RL

Figure 9. Trace element concentrations in stream-bottom materials from the Owyhee River and selected tributaries, Oregon, in relation to c

streams sampled by Rinella and others (1994).
20 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

time-integrated accumulations of metals that are better indicators of impacted areas than are water samples. 

During this reconnaissance, concentrations of 39 trace 

elements on stream-bottom materials were analyzed to help 

determine zones of the basin that were significant sources of 

trace elements. Because of their large surface area, fine sediments tend to accumulate higher concentrations of trace metals than do coarse sediments (Horowitz, 1991, p. 20–21). As a 

result, only stream-bottom materials less than 62.5 μm in 

diameter were collected and analyzed for this study, which 

allowed data from the different sites to be compared. In addition, water samples were analyzed for two nonmetallic trace 

elements—arsenic and selenium—that have stream health 

implications and that frequently are dissolved in water of the 

Western United States.

As part of an investigation of stream quality associated 

with the Owyhee and Vale irrigation projects in southeastern 

Oregon and southwestern Idaho, Rinella and others (1994) 

analyzed most of the same elements in stream-bottom materials as were analyzed for this study. Rinella and others also 

used the same sampling and analytical techniques as were 

used in this study. In general, concentration ranges of most 

elements collected for this reconnaissance were similar to 

those reported for the irrigation studies (fig. 9). However, for 

nearly half of the trace elements analyzed for this reconnaissance (arsenic, barium, cerium, copper, gallium, lanthanum, 

lead, lithium, mercury, neodymium, niobium, thorium, titanium, uranium, yttrium, and zinc), more than 75 percent of the 

concentrations exceeded the median concentrations reported 

for the irrigation studies. This may be because samples for this 

reconnaissance were collected in areas of the watershed that 

were closer to geologic formations naturally enriched with 

trace elements, as evidenced by the number of mines that have 

been developed in the upper basin. 

Probability plots of data from all sites were used to 

determine samples that were enriched with trace elements 

relative to samples from other sites in the basin (Velz, 1970, 

p. 522–542; Rickert and others, 1977, p. F13–F18; Hardy, 

1984, p. 17–20). Concentrations that plotted on a straight line 

were considered “background” concentrations. Concentrations that plotted significantly above the background line were 

considered enriched concentrations that belonged to a different statistical population. A plot for aluminum as an example 

of an ubiquitous metal that was not enriched at any particular 

site is shown in figure 10. In contrast, a plot for mercury as an 

example of a metal that was enriched at two sites is shown in 

figure 11.

ALUMINUM CONCENTRATION,

IN PERCENT (DRY WEIGHT)

PERCENT PROBABILITY OF CONCENTRATION EQUAL TO

OR LESS THAN CONCENTRATION INDICATED

9

8

7

6

5

4

1 5 10 2 20 30 40 60 70 80 50 90 95 98 99

Figure 10. Aluminum concentrations in stream-bottom materials less than 62.5 micrometers in diameter from the Owyhee

River and selected tributaries, Oregon.

Sampling site with back-

 ground concentration
Chemical and Biological Quality 21

Enriched trace element concentrations are summarized 

in table 7. Only two elements, manganese and mercury, were 

enriched at site JC1, where a high density of upstream mines 

(table 1) suggests high potential for trace element mobilization. It is not known whether the wetlands and small reservoirs 

upstream from this site act to enhance concentrations of these 

trace elements or to deplete others. Nine trace elements (beryllium, cerium, copper, lanthanum, neodymium, nickel, titanium, yttrium, and zinc) were most highly enriched at site 

NF1, where no mines are located upstream. This result suggests that natural sources (such as local rocks and geothermal 

springs) might be more significant sources of some trace elements than mining activities are. Four of these trace elements 

(copper, mercury, nickel, and titanium) also were enriched farther downstream at sites OR1 and (or) OR4. It is not known 

whether the enrichments at these sites were due to additional 

sources of these metals or simply to the sites’ locations in lowgradient zones of the river that tend to accumulate fine sediments. 

The lack of selenium enrichment in sediments supports 

the water-chemistry data showing low selenium concentrations (all were below reporting limits) in stream water 

throughout the watershed. Although arsenic was not enriched 

in sediments at any site, dissolved concentrations were common and were highest during base flow at sites OR1, OR2, and 

OR3. These elevated concentrations (10 to 11 μg/L) may be 

caused by geothermal springs (Hem, 1985, p. 184–185) that 

discharge to the lower reaches of the study area, but the concentrations were well below maximum brief- and continuousexposure concentrations (340 and 150 μg/L, respectively) recommended for the protection of aquatic communities (U.S. 

Environmental Protection Agency, 2002, p. 12, Federal Register source 65FR31682).

High concentrations of some trace elements on streambottom materials can be harmful to aquatic biota living on and 

in them. Criteria for protection of biota currently do not exist 

in the United States, but the Washington State Department of 

Ecology (Batts and Cubbage, 1995) has established guidelines 

that are based on proposed criteria. These guidelines are based 

on partial digestions of bulk sediment samples. Partial digestions primarily include trace elements only in particle coatings; complete digestions include trace elements in both the 

particle coatings and the matrices. Because the analyses for 

this reconnaissance were complete digestions of fine particles, 

which tend to have a higher affinity for sorbing trace elements, 

MERCURY CONCENTRATION, IN MICROGRAMS

PER GRAM (DRY WEIGHT)

PERCENT PROBABILITY OF CONCENTRATION EQUAL TO

OR LESS THAN CONCENTRATION INDICATED

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

1 5 10 2 20 30 40 60 70 80 50 90 95 98 99

Figure 11. Mercury concentrations in stream-bottom materials less than 62.5 micrometers in diameter from the Owyhee

River and selected tributaries, Oregon.

Sampling site with back-

 ground concentration

Sampling site with enriched

 concentration

OR1

JC1

(tributary)
22 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

the analyses would be expected to yield higher trace element 

concentrations. 

Concentrations of arsenic, chromium, copper, mercury, 

and nickel exceeded the threshold-effect guidelines and the 

probable-effect guidelines at several sites in the study area 

(fig. 9). Considering that the maximum concentrations of 

arsenic and copper for this reconnaissance were less than 1.6 

times the threshold-effect guidelines, it is likely that concentrations in bulk sediment would not threaten aquatic communities. However, because the maximum concentrations of 

chromium (at sites NF1, OR4, and OR1), nickel (at site NF1), 

and mercury (at site JC1) were 2.1 to 4.9 times the thresholdeffect guidelines and also exceeded probable-effect guidelines, it is possible that concentrations in bulk sediments might 

be high enough to compromise selected populations of biota. 

Although chromium exceeded probable-effect guidelines at 

three sites, concentrations at all sites were high enough that it 

was not considered enriched at any particular site.

Bacteria

Escherichia coli bacteria (E. coli) inhabit the digestive 

tract of warmblooded animals and, therefore, are indicators 

of fecal wastes in water. Water receiving fecal contamination from warmblooded animals is considered at risk for the 

presence of pathenogenic organisms that can infect humans 

ingesting or recreating in that water. 

Populations of E. coli ranged from <1 to 370 

(MPN/100 mL) (table 3 ), all less than the maximum 406 

organisms/100 mL recommended for a single instream 

measurement before additional followup investigation is 

required (Oregon Department of Environmental Quality, 

2002). During the spring runoff and base flow in 2001, no 

populations exceeded 50 MPN/100 mL at any site. Populations were highest (32 and 50 MPN/100 mL) at Jordan 

Creek (site JC1); all other populations were less than 15 

MPN/100 mL. The high populations at Jordan Creek during 

base flow suggest a source of fecal material in the stream 

that tends to be diluted at high flows.

During the 2002 spring runoff, populations were highest 

(140 and 370 MPN/100 mL) at sites OR3 and OR2. Populations at all other sites were less than or equal to 24 MPN/100 

mL. The high bacterial populations during the 2002 spring 

runoff suggest that flushing of fecal material from adjacent 

lands in and downstream from the Rome area and Crooked 

Creek may be the primary source of bacteria in the study area. 

Table 7. Stream-bottom materials less than 62.5 micrometers in diameter enriched in trace element concentrations, Owyhee River and 

selected tributaries, Oregon

[Site locations shown in figure 2 ; No., number; blank values indicate measurements of background concentrations; μg/g, micrograms per gram; %, percent]

Trace element concentrations

Site No.

Background 

NF1 OR4 JC1 OR1 range

Barium (μg/g) . . . . . . . . . . . . . . . . . 2.6 1.6–2.1

Cerium (μg/g) . . . . . . . . . . . . . . . . . 110 53–81

Copper (μg/g) . . . . . . . . . . . . . . . . . 43 38 31–34

Lanthanum (μg/g) . . . . . . . . . . . . . . 57 27–44

Manganese (μg/g) . . . . . . . . . . . . . . 1,700 560–840

Mercury (μg/g) . . . . . . . . . . . . . . . . .86 .28 0.04–0.13

Neodymium (μg/g) . . . . . . . . . . . . . 51 26–38

Nickel (μg/g) . . . . . . . . . . . . . . . . . . 38 34 19–27

Titanium (%) . . . . . . . . . . . . . . . . . . .78 0.75 .75 0.44–0.57

Yttrium (μg/g) . . . . . . . . . . . . . . . . . 54 25–33

Zinc (μg/g). . . . . . . . . . . . . . . . . . . . 110 84–99
Chemical and Biological Quality 23

Benthic Invertebrate Communities

Various metrics described by Hayslip (1993) and Barbour and others (1999) were calculated to describe the benthic 

invertebrate assemblages at each site (table 8). A metric is an 

enumeration representing an assemblage characteristic or 

combination of characteristics that change in a predictable 

way with increased human influence (Karr and others, 1986). 

Coldwater taxa were identified using the Idaho Department of 

Environmental Quality empirically derived list (Grafe and others, 2002). There is less than a 10-percent chance that these 

taxa will be present where temperatures exceed 19°C. The 

modified Hilsenhoff Biotic Index (HBI, includes all benthic 

invertebrates) was calculated following the methods of Barbour and others (1999). Tolerance values ranging from 0 to 10 

are assigned to each taxa on the basis of tolerances to sediment and organic waste for Northwestern streams (G. Lester, 

EcoAnalysts, Moscow, Idaho, oral commun., 2002). A value 

of 0 indicates that a taxon occurs in very high quality water, 

whereas a value of 10 indicates a taxon known to occur in 

severely polluted streams. Final HBI indices also range from 

0 to 10; a rating of 0 reflects excellent water quality with no 

organic or sediment pollution, and 10 indicates severe organic 

and sediment pollution (Lydy and others, 2000). For wadeable 

streams in the Northwest, an HBI score of >5.0 indicates 

impaired water quality (B. Wisseman, Aquatic Biological 

Associates, written commun., 2002). 

Samples of benthic invertebrate communities were collected only at 9 of the 10 sampling sites. Samples were not 

collected at site WLO1 because this tributary was not flowing 

at the time of sampling. At least 120 taxa were identified in riffle samples collected from the 9 sampling sites (table 9, back 

of report). Total abundance (table 8 ) ranged from 3,616 to 

16,864 individuals/m2 at the North Fork Owyhee River (site 

NF1) and Owyhee River near Rome (site OR4), respectively. 

The associated microhabitat characteristics for each site are 

summarized in table 10 . 

Aquatic insects composed most of the benthic invertebrate assemblages sampled. Taxa collected at all sites were 

Baetis tricaudatus, Tricorythodes sp., Microcylloepus sp., 

Psephenus sp., Hydropsyche sp., Simulium sp., Polypedilum

sp., Turbellaria, and Acari. Colonies of the freshwater mussels Gonidea angulata were collected only at the Owyhee 

River at State Line (site OR7). 

There was no apparent downstream decline in the number of benthic invertebrate taxa at Owyhee River sites. Total 

Table 8. Benthic invertebrate metric results for the Owyhee River and selected tributaries, Oregon, June through July 2001

[Site locations shown in figure 2; No., number; EPT, Ephemeroptera, Plecoptera, and Trichoptera taxa; no./m2, number of individuals per square meter]

1Sum of Ephemeroptera, Plecoptera, and Trichoptera taxa.

2Obligate coldwater taxa according to Idaho Department of Environmental Quality (Grafe and others, 2002).

Metric

Site No.

OR7 OR6 0R5 NF1 OR4 JC1 OR3 OR2 OR1

Total taxa 46 40 52 42 34 46 45 35 31

Ephemeroptera taxa 11 9 11 5 13 7 10 5 10

Plecoptera taxa 0 0 02 0 000 1

Trichoptera taxa 8 7 9 5 5 4 10 9 5

EPT taxa1 19 16 20 12 18 11 20 14 16

Percent Plecoptera 0 0 0 1.55 0 0 0 0 .18

Hilsenhoff Biotic 

Index 3.91 3.80 4.32 4.48 3.57 5.52 3.77 4.46 4.06

Percent coldwater 

taxa2 0 0 .2 .2 .5 .5 0 0 .6

Abundance (no./m2) 8,457 14,833 6,396 3,616 16,864 8,134 6,039 8,144 11,733
Table 10. Microhabitat characteristics and periphyton results for the Owyhee River and selected tributaries, Oregon, June through July 2001 [Site locations shown in figure 2; values represent average of five measurements at riffle collection sites within each reach; No., number; m, meters; m/smm, millimeters; <, less than; mg, milligrams; m2, square meters; g, grams; multiply meters by 3.281 to obtain feet; multiply millimeters by 0.03937 to 

1Ash-free dry weight. 2Average of duplicates. Site No. Site name Sample date Riffle depth (m) Riffle velocity (m/s) Percent substrate fines <2mm Dominant substrate Substrate embedded- ness (percent) Open canopy (percent) Substrate covered by filamentous algae (percent) 

OR7 Owyhee River at State Line. . . . . . . . . . 06-27 0.26 0.56 10 cobble/gravel 25-50 45 40 

OR6 Owyhee River above West Little Owyhee River . . . . . . . . . 06-26 .20 .72 10 cobble/gravel 25-50 80 80 

OR5 Owyhee River at Three Forks . . . . . . . . 06-25 .24 .42 10 cobble/gravel 25-50 74 30 NF1 North Fork Owyhee River . . . . . . . . . . 06-25 .14 .40 20 gravel/sand 25-50 89 10 JC1 Jordan Creek near Rome . . . . . . . . . . . . 06-27 .18 .49 30 gravel/sand 25-50 91 60 OR4 Owyhee River near Rome . . . . . . . . . . . 07-11 .17 .64 20 cobble/gravel 25-50 91 10 OR3 Owyhee River below Crooked Creek . . 06-28 .22 .36 20 cobble/gravel 5-25 83 10 OR2 Owyhee River above Bull Creek . . . . . . 06-28 .29 .54 <10 cobble/boulder 5-25 84 0 OR1 Owyhee River above Lake Owyhee . . . 07-11 .23 .59 20 cobble/gravel 25-50 76 0 
Chemical and Biological Quality 25

taxa collected ranged from 31 to 52 at the Owyhee River 

above Lake Owyhee (site OR1) and Owyhee River at Three 

Forks (site OR5), respectively (table 8 ). Mochan and Mrazik 

(2000) sampled near site OR5 in September 1996–97 and collected 27 to 30 taxa, much fewer than the 52 taxa collected 

during this reconnaissance. Different laboratories were used 

for processing the samples, which can create inconsistencies 

in taxonomic identification, thus making comparison of results 

or detecting trends problematic (Maret and others, 2001). 

The number of EPT taxa collected in the Owyhee River 

study area is small relative to the number usually collected in 

montane forested streams, where more than 30 EPT taxa from 

riffle habitats are common (B. Wisseman, Aquatic Biological 

Associates, written commun., 2002). EPT taxa generally are 

considered intolerant of pollution, and this metric is one of the 

most widely used to evaluate water-quality conditions of 

Northwestern streams (Hayslip, 1993). The number of EPT 

taxa ranged from 11 to 20 (fig. 12 and table 8 ). The fewest 

EPT taxa (11) were collected at Jordan Creek (site JC1). 

Mochan and Mrazik (2000) collected only 13 EPT taxa at this 

site in 1996. They also reported that tolerant taxa, including B. 

tricaudatus, Tricorythodes sp., and Oligochaeta were predominant at this site. During this reconnaissance, B. tricaudatus and Oligochaeta were the most abundant taxa at site JC1. 

Oligochaete worms can tolerate low dissolved oxygen conditions well and are often abundant in areas where organic-rich 

sediment has accumulated. Site JC1 also contained the largest 

amount (30 percent) of substrate fines. These biological findings correspond with Oregon’s mean water-quality index 

score for this site, which was rated as poor for the period 

1992–97 (Mochan and Mrazik, 2000).

Plecopterans were collected only at sites NF1 and OR1, 

and they composed less than 2 percent of the total assemblage 

at these sites. As a group, Plecopterans generally are considered indicators of good water quality and habitat conditions 

because they are adversely affected by substrate embeddedness, low dissolved oxygen, warm water temperatures, and 

excessive growth of filamentous algae. Clark (1978) also 

noted that Plecopterans were absent in some benthic invertebrate samples collected in September 1976 at Owyhee River 

sites in Idaho. Reasons for their absence are unclear but are 

likely the high summer water temperatures and the abundance 

of filamentous algae at some of the sites (table 10 ). 

The HBI scores ranged from 3.57 to 5.52 at the Owyhee 

River near Rome (site OR4) and Jordan Creek near Rome (site 

JC1), respectively (table 8 ). There was no apparent downstream trend in HBI scores at sites on the Owyhee River. However, the HBI score (> 5.0) for Jordan Creek indicates waterquality impairment. 

The coldwater taxa Epeorus sp. and Perlidae were 

collected at sites OR5, NF1, JC1, and OR4, but they composed less than 1 percent of the total abundance at any one 

site (table 8 ). Because maximum water temperatures comEPT

Other

No data

collected,

dry

streambed

SITES

NUMBER OF MACROINVERTEBRATE TAXA

OR6 WLO1

(tributary)

OR5 OR4 NF1

(tributary)

JC1 OR3 OR1

(tributary)

OR7 OR2

60

50

40

30

20

10

0

Figure 12. Number of macroinvertebrate and Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa collected at sites in

the Owyhee River and selected tributaries, Oregon, June through July 2001. (Site descriptions shown in table 1; locations

shown in figure 2)
26 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

monly approached or exceeded 27°C at all sites (fig. 4), the 

lack of coldwater taxa at these sites is not surprising. 

Potamopyrgus antipodarum (New Zealand mud snail) 

was collected at site OR3 (table 9 ). This gastropod was introduced in the 1980s in the Hagerman Valley (along the Snake 

River in Gooding County, downstream from Twin Falls, 

Idaho) by aquaculture practices (Maret and others, 2001). It 

has been known to reach very high densities where water quality has been degraded (such as the middle Snake River in 

southern Idaho), and is suspected to compete with native species for food and habitat resources.

Periphyton Communities

Samples of epilithic periphyton communities were collected at only 9 of the 10 sampling sites. Samples were not 

collected at site WLO1 because this tributary was not flowing 

during the base-flow period. Chlorophyll-a concentrations 

were compared with proposed aggregate ecoregion criteria for 

the xeric West and with concentrations suggested as indicators 

of nuisance algal conditions (U.S. Environmental Protection 

Agency, 2000a and b). 

There was no obvious downstream trend in the chlorophyll-a and biomass (ash-free dry weight) concentrations at 

Owyhee River sites (table 10). Periphyton at sites OR7, JC1, 

and OR3 exceeded the U.S. Environmental Protection Agency 

proposed ecoregion chlorophyll-a criterion of 44 mg/m2 (U.S. 

Environmental Protection Agency, 2000a). The community 

at Jordan Creek (site JC1), where 60 percent of the riffle substrates were covered with filamentous algae, had the highest 

biomass (79 g/m2) and chlorophyll-a concentrations (86 

mg/m2). The chlorophyll-a concentration at this site approached 100 mg/m2, the concentration suggested as an indicator of nuisance algal conditions (U.S. Environmental Protection Agency, 2000b). Cladophora sp. was the predominant 

filamentous algae observed at all sites.

Summary

Summary

The Owyhee River drains about 10,950 square miles of 

extremely rugged and remote landscape in northern Nevada, 

southwestern Idaho, and eastern Oregon. The Vale District of 

the Bureau of Land Management must ensure that its landmanagement actions do not impair the beneficial uses of the 

river from the Idaho-Oregon State line to Lake Owyhee. This 

segment, excluding 14 miles in the Rome area, has been designated part of the National Wild and Scenic Rivers System.

More than 91 percent of the land cover in the watershed 

is sagebrush shrubland and grassland, and livestock grazing is 

the primary land use. The sparse human population is concentrated near Rome and along Jordan Creek and its tributaries, where mining, farming, and grazing are the predominant 

land uses. Because access to the river is so limited, few chemical and biological data are available. This reconnaissance of 

10 river and tributary sites was undertaken to describe river 

quality, determine where major changes in water quality 

occur, and provide data that will help define beneficial uses 

and support activities related to environmental impact assessments and Total Maximum Daily Loads. Water samples were 

collected during a summer base flow and two spring runoff 

events in an attempt to bracket the range of water-quality conditions. Samples of benthic invertebrate and periphyton communities and stream-bottom materials were collected and 

habitat characteristics were measured to assess integrated, 

long-term, water-quality conditions. Major water-quality 

issues are summarized in figure 13 and discussed in the 

subsequent paragraphs.

Water temperatures were highest in early July through 

early August. Maximum temperatures ranged from 25.1° to 

30.9° Celsius (C). Maximum 7-day average temperatures 

ranged from 24.2° to 28.9°C, which exceeded Oregon’s recommended maximum of 17.8°C. Summer temperatures generally were highest in the central part of the study area and just 

upstream from Lake Owyhee. 

Suspended sediment concentrations at all sites were 

higher during spring runoff than during base flow. Concentrations during base flow were less than 10 milligrams per liter 

(mg/L) at all sites. Concentrations in the upper reaches of the 

study area during both spring runoff events were typically less 

than 20 mg/L, although a peak concentration of 52 mg/L was 

measured at site OR5. However, during the highest runoff 

event (April 2002), concentrations in the lower study area at 

sites OR4, JC1, OR3, and OR2 commonly exceeded 50 mg/L 

and were as high as 142 mg/L at site OR3 below Crooked 

Creek. A second sampling during this runoff event indicates 

that these high-flow samples might not represent the highest 

concentrations that occurred. Despite elevated concentrations 

of suspended sediment in some tributaries, the loads were 

small compared with those transported by the Owyhee River. 

Spatial trends for turbidity were similar to those for suspended 

sediment.

Concentrations of dissolved oxygen in flowing water 

ranged from 7.7 to 12.2 mg/L, which exceeded Oregon’s minimum single-observation criterion (5.5 mg/L) recommended 

for warmwater aquatic life. Although few concentrations 

exceeded the minimum single-observation criterion for salmonid spawning (11 mg/L), most concentrations were within 95 

to 133 percent of saturated conditions. Significant oxygen 

supersaturation during the June base flow suggests that excess 

production by phytoplankton might occur near Rome. In addition, the presence of large periphyton populations, generally 

tolerant invertebrate communities, and organisms known to 

tolerate low oxygen conditions in Jordan Creek indicate that 

this tributary might be subject to significant dissolved oxygen 

depletions at times. Calculations show that, even during the 

warmest periods, dissolved oxygen concentrations continue to 

exceed the minimum concentration recommended for warmwater aquatic life. 

Measurements of pH ranged from 7.4 to 9.1. One 

measurement exceeded the maximum of pH 9 recommended 

for eastern Oregon streams. This high pH was measured at 
Summary 27

SITES

LOCATION

TEMPERATURE (Exceeds

 maximum 7-day average)

pH (Greater than 9)

NUTRIENTS (Nitrogen great-

 er than 0.9 milligrams per liter

 or phosphorus greater than or

 equal to 0.1 milligrams per liter)

E. COLI BACTERIA (Greater

 than 30 organisms per 100

 milliliters)

DISSOLVED OXYGEN

 (Greater than 160 percent

 saturation)

TRACE METALS (Stream-

 bottom materials enriched in or

 exceed Probable-Effect Levels

 for biota)

PERIPHYTON (Highest

 Chlorophyll-a and biomass)

SEDIMENT (Greater than

 50 milligrams per liter)

INVERTEBRATES (Fewest

 sensitive taxa)

Issue and threshold

used to evaluate

observations

OR6

WLO1

(tributary)

OR5 OR4

NF1

(tributary)

OR3 OR1

JC1

(tributary)

OR7 OR2

Owyhee

River

at State

Line

West

Little

Owyhee

River

Owyhee River

above West

Little Owyhee

River

Owyhee

River

at Three

Forks

Owyhee

River

near

Rome

North

Fork

Owyhee

River

Jordan

Creek

near

Rome

Owyhee

River

above Bull

Creek

Owyhee

River

below

Crooked Creek

Owyhee

River

at Lake

Owyhee

Base-flow issue

Spring runoff issue

Nonflow-related issue

Figure 13. Summary of water-quality issues for the Owyhee River and selected tributaries, Oregon, 2001 and 2002.

Jordan Creek and is probably a result of excess production by 

periphyton. 

For each site except North Fork, concentrations of dissolved solids were about 2 to 6 times higher during base flow 

(ranging from 94 to 222 mg/L) than during spring runoff 

(ranging from 46 to 133 mg/L). In contrast, dissolved solids 

were similar in the North Fork Owyhee River during all flow 

conditions (ranging from 52 to 70 mg/L). 

Sodium-dominated water with a high dissolved solids 

content was measured at most Owyhee River sites during base 

flow and suggests that most stream water was derived from 

ground water from low elevations. In contrast, the calciumand sodium-codominated water with a low dissolved solids 

content measured at Owyhee River sites in the lower part of 

the study area during spring runoff suggests that a large proportion of the stream water was derived from the uplands. All 

sodium concentrations measured were too low to cause undesirable cation exchange effects for irrigation use. However, 

dissolved solids concentrations during base flow were high 

enough to present a medium salinity hazard for irrigation.

Fluoride concentrations were generally less than 1 mg/L 

in tributaries and during spring runoff at Owyhee River sites 

but ranged from 1.7 to 2.4 mg/L during base flow. Because of 

the high concentrations reported in some of the geothermal 

springs along the river, fluoride concentrations might be able 

to be used to estimate the volume of hot water that these 

springs contribute to the river.

Total nitrogen concentrations ranged from 0.14 to 

2.6 mg/L, and nearly all were less than the 1.9 mg/L national 

median for 179 basins sampled as part of the National WaterQuality Assessment (NAWQA) Program. Concentrations were 

highest (exceeding 0.9 mg/L) in the lower reaches of the study 

area at sites OR4, JC1, OR3, and OR2. All ammonia concentrations were at or below laboratory reporting limits. During 

base flow, all total nitrogen concentrations (less than 0.7 mg/L) 

and inorganic nitrogen concentrations (less than or equal to 

0.3 mg/L) were generally low and uniform throughout the 
28 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

basin. Concentrations were nearly the same during the 2001 

spring runoff, possibly as a result of the small amount of precipitation that the basin received during the preceding winter.

During the 2002 spring runoff, concentrations of organic 

and particulate nitrogen were high at all sites, particularly near 

Rome where organic particles (possibly dislodged periphyton 

and materials flushed from adjacent lands) composed most of 

the total nitrogen concentrations. Significant differences 

between concentrations in two samples collected near Rome 

during this runoff event indicated that these elevated concentrations might have been of short duration. Though concentrations of nitrogen in Jordan Creek were somewhat elevated, the 

loads that the creek transported to the Owyhee River were 

only about 7 to 15 percent of those transported by the Owyhee 

River upstream from the Jordan Creek confluence.

Total phosphorus concentrations ranged from <0.06 to 

0.23 mg/L. Most concentrations were less than the 0.18 mg/L 

national median for 179 basins sampled as part of the NAWQA 

Program. Concentrations were highest (exceeding 0.1 mg/L, a 

threshold level for possible nuisance algal production) in the 

lower reaches of the study area at sites OR5, OR4, JC1, OR3, 

OR2, and OR1 during spring runoff. Significant differences 

between concentrations in two samples collected near Rome 

during the 2002 spring runoff indicated that these elevated 

concentrations might be of short duration. During base flow, 

total phosphorus and orthophosphate typically were not 

detected. During spring runoff, concentrations of organic plus 

particulate phosphorus were significantly higher than those 

during base flow and were associated with suspended sediment transport. 

Loads of phosphorus transported by Jordan Creek were 

about 25 to 34 percent of those transported by the Owyhee 

River upstream from the Jordan Creek confluence. The high 

phosphorus load at site OR3 in April 2002 suggests that cultivated and developed lands downstream from the Jordan Creek 

confluence and input from Crooked Creek also may contribute 

significant amounts of phosphorus to the Owyhee River.

Compared with estimates from an earlier study, instantaneous loads of nitrogen discharged to the reservoir were 

higher in summer during this study, whereas loads of phosphorus in April 2001 were lower. Different hydrologic conditions, sampling locations, and sampling techniques probably 

contributed to these differences.

Eleven of 39 trace elements analyzed in stream-bottom 

materials were considered enriched over background study 

area concentrations. Data suggest that Jordan Creek and the 

North Fork Owyhee River may be the main sources of these 

metals. Manganese and mercury were elevated in Jordan 

Creek, probably ultimately a result of upstream mining activities. It is not known whether small reservoirs and wetlands 

upstream from the sampling site have roles in enhancing 

concentrations of these elements and depleting concentrations 

of others. Beryllium, cerium, copper, lanthanum, neodymium, 

nickel, titanium, yttrium, and zinc were enriched at the North 

Fork Owyhee River. Though this area is not mined, naturally 

enriched geologic formations and geothermal springs in the 

drainage basin may be the sources of these elements. Chromium, mercury, and nickel in stream-bottom materials at sites 

NF1, OR4, JC1, and OR1 were considered to have the greatest 

likelihood of affecting the health of bottom-dwelling organisms. 

In water, arsenic concentrations were highest during base 

flow in the lower reaches of the study area, possibly a result of 

geothermal springs that discharge to the river, but were well 

below concentrations considered harmful to aquatic organisms. Selenium was not detected in any water samples.

Populations of Escherichia Coli bacteria ranged from 

<1 to 370 most probable number per 100 milliliters 

(MPN/100 mL), all less than the maximum of 406 organisms/100 mL recommended for a single measurement in 

Oregon freshwater. Major sources of bacteria were near and 

downstream from Rome. Populations during the spring runoff 

and base flow in 2001 were highest (32 and 50 MPN/100 mL) 

at Jordan Creek. Populations during the 2002 spring runoff 

were highest (140 to 370 MPN/100 mL) downstream from 

Crooked Creek.

Aquatic insects composed most of the benthic invertebrate assemblages sampled. Total taxa collected ranged from 

31 to 52 per site. Ephemeroptera, Plecoptera, and Trichoptera 

(EPT) taxa abundance was low compared with those in montane forested streams, ranging from 11 to 20 per site. Few Plecopterans were collected, and their absence is consistent with 

data from the Owyhee River in Idaho. High summer water 

temperatures and the abundance of filamentous algae at some 

of the sites might contribute to their low numbers. Coldwater 

taxa were rare, supporting the high summer stream temperatures that were measured. The introduced species Potamopyrgus antipodarum (New Zealand mud snail) was collected in 

the Owyhee River below Crooked Creek. This gastropod was 

introduced in the 1980s in the Hagerman Valley along the 

Snake River by aquaculture practices and is suspected to compete for resources with native species. The freshwater clam 

Gonidea angulata was collected only in the uppermost part of 

the study area at the Oregon State line. 

No spatial trends were apparent in the numbers of taxa, 

community abundance, EPT taxa, or Hilsenhoff Biotic Index 

(HBI) scores. Jordan Creek near Rome contained the fewest 

EPT taxa, was dominated by the tolerant taxa Oligochaeta

and B. tricaudatus, had the highest HBI score, and had the 

highest proportion of fine particles composing the stream bottom. The Owyhee River just upstream from Jordan Creek contained the most abundant invertebrate community. These 

measurements support the nutrient and dissolved oxygen 

results documenting significant water-quality impacts in Jordan Valley. 

No obvious spatial trends were apparent in periphyton 

communities from the Owyhee River. Cladophora sp. was the 

predominant filamentous algae observed at all sites. Communities in and near Rome and at the Oregon State line exceeded 

the EPA proposed ecoregion chlorophyll-a criterion of 44 milligrams per square meter (mg/m2). The concentration of chlorophyll-a was highest (86 mg/m2) at Jordan Creek and 
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Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A8, 48 p.

Rickert, D.A., Kennedy, V.C., McKenzie, S.W., and Hines, 

W.G., 1977, A synoptic survey of trace metals in bottom 

sediments of the Willamette River, Oregon: U.S. Geological Survey Circular 715–F, 27 p.

Rinella, F.A., Mullins, W.H., and Schuler, C.A., 1994, Reconnaissance investigation of water quality, bottom sediment, and biota associated with irrigation drainage in the 

Owyhee and Vale projects, Oregon and Idaho, 1990–91: 

U.S. Geological Survey Water-Resources Investigations 

Report 93–4156, 101 p.

Ryding, S.O., and Rast, Walter, eds., 1989, The control of 

eutrophication of lakes and reservoirs, v. 1 of Programme 

on man and the biosphere series: Cambridge University 

Press, 295 p.

Stiff, H.A., Jr., 1951, The interpretation of chemical water 

analysis by means of patterns: Journal of Petroleum 

Technology, v. 3, no. 10, p. 15–17.

U.S. Environmental Protection Agency, 2000a, National nutrient criteria development: accessed May 2001, at URL 

http://www.epa.gov/OST/standards/nutrient.html

———2000b, Nutrient criteria technical guidance manual, 

rivers and streams: accessed May 2001, at URL 

http://www.epa.gov/OST/standards/nutrient.html

———2002, National recommended water quality criteria, 

2002: U.S. Environmental Protection Agency, EPA–

822–R–02–047, 33 p.

Velz, C.J., 1970, Applied stream sanitation: New York, John 

Wiley and Sons, Inc., 619 p.

Wilde, F.D., Radtke, D.B., Gibs, J., and Iwatsubo, R.T., eds., 

1999, Collection of water samples and processing of 

water samples, in national field manual for the collection 

of water-quality data: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chaps. 

A4 and A5, [variously paged].
Tables 3 and 9
Table 3 33

nts and chemical analyses of water and bottom-material samples collected from the Owyhee River and selected tributaries, Oregon, 2001 and 2002 

2; bed sed, bed sediment; CaCO3, calcium carbonate; cfs, cubic feet per second; deg C, degrees Celsius; E, estimated value; E. coli, Escherichia coliform; fld, field; fltrd, fil

anic; mg/L, milligrams per liter; mL, milliliters; mm, millimeters; MPN, most probable number; nat, native water; NTU, nephelometric turbidity units; org-N, organic 

overable; std, standard; svd, sieved; tot, total; μg/g, micrograms per gram; μg/L, micrograms per liter; μm, micrometers; μS/cm, microsiemens per centimeter; unf, unfltrd, 

sieved; <, less than; >, greater than; –, no data]

Turbidity, Dis- pH, Specific

Instan- wat unf Baro- solved water, conduc- Magnes- Potastaneous lab, metric Dis- oxygen, unfltrd tance, Temper- Temper- Calcium ium, sium,

dis- Hach pres- solved percent field, wat unf ature, ature, water, water, water,

charge, 2100AN sure, oxygen, of sat- std μS/cm air, water, fltrd, fltrd, fltrd,

cfs NTU mm Hg mg/L uration units 25 deg C deg C deg C mg/L mg/L mg/L

me (00061) (99872) (00025) (00300) (00301) (00400) (00095) (00020) (00010) (00915) (00925) (00935)

600 534 13 652 10.9 101 7.8 170 4.5 5.6 17.4 4.25 2.80

815 84 1.1 – – – 8.3 314 19.0 18.0 23.7 8.71 4.91300 846 19 659 9.8 98 7.9 134 – 8.9 14.6 3.56 2.43

330 463 12 654 10.5 97 8.0 179 7.5 5.5 17.4 4.23 2.67

830 86 1.4 654 8.9 110 8.5 313 – 18.0 23.8 8.48 5.20605 1060 17 655 9.8 103 7.6 104 – 10.9 11.7 2.97 2.45

450 31 3.2 653 10.6 101 8.2 102 8.0 6.5 8.11 2.18 1.78

115 .54 1.2 655 4.7 59 7.7 141 – 18.5 11.0 3.05 3.52715 280 11 655 10.1 101 7.4 45 – 8.5 3.92 1.16 1.50

235 1260 53 660 – – 7.6 105 17.5 11.6 8.96 2.42 2.07

200 116 5.2 657 7.7 99 8.6 319 23.0 20.0 22.6 7.02 4.34230 2070 39 669 9.5 96 7.8 99 16.0 9.8 8.94 2.40 2.10

430 281 16 660 12.2 126 7.8 52 17.5 10.1 4.33 1.56 .93

415 13 6.1 647 8.5 109 8.0 81 23.0 19.0 6.80 2.50 2.07400 346 16 665 9.8 97 7.6 52 16.0 8.7 4.11 1.67 1.29

245 866 13 677 11.2 108 7.7 150 8.5 8.5 14.3 3.74 2.41

715 148 1.2 675 11.9 161 8.9 299 30.0 24.3 20.5 6.07 4.17230 5490 64 672 11.1 107 7.5 53 18.0 8.3 4.15 1.30 1.68915 2510 22 681 9.6 97 7.9 91 13.0 10.6 8.34 2.34 2.02

345 58 41 666 11.4 116 7.9 164 6.5 10.0 15.3 4.33 3.37

600 20 2.6 – – – 9.1 318 27.0 21.4 26.9 8.50 5.34210 494 41 682 9.9 101 7.8 85 14.0 11.1 7.92 2.39 1.85

145 779 9.8 676 10.1 93 7.8 171 7.5 6.5 14.4 3.70 2.61

900 191 2.9 675 8.5 106 8.3 338 23.0 20.0 21.5 6.21 4.83245 2970 96 674 9.5 93 8.1 95 – 9.0 7.89 2.27 2.22

745 923 10 – – – 8.1 180 – – 15.0 3.84 2.71

215 248 1.5 690 10.6 133 8.6 325 29.0 21.5 21.0 5.99 4.81015 3130 44 674 9.4 95 7.6 102 – 10.2 8.83 2.51 2.11

245 1170 20 688 9.8 96 7.6 140 4.5 10.0 11.3 3.16 2.46

815 287 2.4 683 8.0 101 8.5 343 23.0 21.0 20.9 6.09 4.92330 3330 30 698 8.5 86 8.0 91 – 11.9 6.96 2.07 1.94
34 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

nts and chemical analyses of water and bottom-material samples collected from the Owyhee River and selected tributaries, Oregon, 2001 and 2002—

Residue Ammonia Ammonia Nitrite Orthowater, + + + phosAlka- Chlor- Fluor- fltrd, org-N, org-N, Ammonia nitrate Nitrite phate,

odium, linity, ide, ide, Silica, Sulfate, sum of water, water, water, water, water, water,

water, lab, water, water, water, water, consti- fltrd, unfltrd, fltrd, fltrd, fltrd, fltrd,

fltrd, mg/L as fltrd, fltrd, fltrd, fltrd, tuents, mg/L mg/L mg/L mg/L mg/L mg/L

mg/L CaCO3 mg/L mg/L mg/L mg/L mg/L as N as N as N as N as N as P

00930) (90410) (00940) (00950) (00955) (00945) (70301) (00623) (00625) (00608) (00631) (00613) (00671)

3.0 74 4.85 0.7 24.1 10.5 122 0.29 0.47 <0.04 E0.03 <0.006 E0.01

30.7 137 8.21 1.8 19.2 14.7 194 .28 .34 E.03 <.05 .008 <.02

9.71 64 3.39 .4 23.2 7.5 104 .33 .45 <.04 .05 <.008 .02

3.3 74 5.00 .7 24.6 10.6 123 .21 .40 <.04 <.05 <.006 E.01

31.0 137 8.10 1.7 16.8 15.1 192 .29 .36 E.03 <.05 .009 <.02

9.25 53 3.93 .6 23.1 6.8 93 .32 .49 <.04 .07 <.008 .03

8.88 39 4.70 .3 15.8 5.5 71 E.10 .18 <.04 <.05 <.006 E.02

1.8 54 6.16 .3 18.6 7.1 94 <.10 .08 E.03 .06 .009 .024.75 23 1.47 .2 18.6 2.1 48 .20 .30 <.04 <.05 <.008 E.01

8.89 44 2.13 .4 20.3 5.1 77 .31 .72 <.04 E.03 <.006 E.02

36.6 132 9.97 2.2 21.7 17.3 201 .29 .34 <.04 .14 E.004 <.02

7.68 42 3.13 .5 21.4 5.6 78 .24 .50 <.04 .09 <.008 .03

3.82 25 .62 E.1 24.1 1.3 52 .18 .30 <.04 <.05 <.006 <.02

5.61 38 1.49 .2 26.2 2.0 70 .15 .20 <.04 <.05 <.006 <.023.22 25 .84 E.1 24.6 1.3 52 .17 .33 <.04 .08 <.008 E.01

2.0 61 3.92 .7 25.2 8.6 108 .20 .40 <.04 .10 <.006 .02

37.0 122 9.68 2.4 23.9 16.7 194 .25 .19 E.03 E.04 .007 E.02

4.34 23 1.24 .2 16.3 2.1 46 .19 .71 <.04 .10 <.008 .037.60 40 2.53 .5 22.0 4.9 75 .24 2.5 <.04 .12 <.008 .03

2.1 61 3.28 .3 25.3 15.7 118 .33 .85 <.04 .31 E.005 .03

30.8 140 6.71 .7 26.8 22.5 213 .47 .64 E.03 <.05 .009 .04

6.38 34 1.42 .3 25.3 8.6 76 .26 .57 <.04 .34 <.008 .03

6.8 71 5.24 .8 26.3 10.9 124 .22 .40 <.04 .09 <.006 E.01

43.20 138 10.8 2.2 28.2 21.5 222 .25 .34 .05 .10 .006 .05

8.20 39 3.34 .5 22.8 6.2 78 .27 .92 <.04 .22 <.008 .02

8.7 74 5.85 .9 28.1 12.4 133 .21 .37 <.04 .17 <.006 E.02

40.7 129 11.2 2.0 32.3 23.8 221 .22 .30 E.02 .30 .010 <.02

9.28 44 3.25 .6 24.0 7.2 85 .25 .70 <.04 .21 <.008 .02

3.3 56 4.17 .7 26.2 9.5 105 .23 .51 <.04 .21 <.006 .02

42.1 130 11.0 2.0 29.4 25.3 220 .21 .32 E.03 .19 .011 E.01

7.89 36 2.97 .4 21.1 5.8 72 .21 .48 <.04 .14 <.008 .03
Table 3 35

nts and chemical analyses of water and bottom-material samples collected from the Owyhee River and selected tributaries, Oregon, 2001 and 2002—

Total

E. coli, coliSus- Coli- form, Calcium, Magnes- Potas- Sodium, Sulfur,

pended lert Coli- bed sed ium, sium, bed sed bed sed

Phos- Selen- Selen- sedi- Quan- lert <62.5 μm bed sed bed sed <62.5 μm <62.5 μm

horus, Arsenic, Arsenic, ium, ium, ment titray, Quan- wet svd <62.5 μm <62.5 μm wet svd wet svd

water, water, water, water, water, concen- water, titray field, wet svd wet svd field, field,

nfltrd, fltrd, unfltrd, fltrd, unfltrd, tration, MPN/ MPN/ total, fld, tot fld, tot total, total,

mg/L μg/L μg/L μg/L μg/L mg/L 100 mL 100 mL percent percent percent percent percent

00665) (01000) (01002) (01145) (01147) (80154) (50468) (50569) (34830) (34900) (34940) (34960) (34970)

E0.05 3 3 <2 <3 12 1 730 – – – – –

<.06 6 6 <2 <3 1 <1 380 1.6 0.740 1.8 1.2 <0.10

.06 3 3 <2 <2 19 1 930 – – – – –

E.04 3 3 <2 <3 9 <1 220 – – – – –

<.06 6 6 <2 <3 1 2 1400 1.8 .720 1.8 1.2 .09

.08 3 3 <2 <2 14 2 1600 – – – – –

E.03 E1 E1 <2 <3 0 <1 770 – – – – –

<.06 <2 <2 <2 <3 0 4 >2400 – – – – –

E.04 E1 <2 <2 <2 7 4 410 – – – – –

.12 2 3 <2 <3 52 11 >2400 – – – – –

<.06 8 8 <2 <3 2 2 2600 1.7 .730 1.7 1.3 .08

.08 2 2 <2 <2 27 6 770 – – – – –

E.04 <2 <2 <2 <3 12 14 1200 – – – – –

<.06 <2 <2 <2 <3 1 6 3500 2.0 .930 1.8 1.5 <.05

E.05 <2 <2 <2 <2 21 2 1100 – – – – –

E.04 3 3 <2 <3 9 <1 650 – – – – –

<.06 8 8 <2 <3 4 4 2900 2.3 .900 1.8 1.5 .21

.16 <2 3 <2 <2 134 24 900 – – – – –.07 2 2 <2 <2 26 – – – – – – –

.17 3 4 E1 <3 41 32 1400 – – – – –

.07 6 7 <2 <3 5 50 2400 2.0 .840 1.5 1.1 .16.13 2 E2 <2 <2 51 – – – – – – –

E.04 4 4 <2 <3 11 4 1600 – – – – –

E.04 12 11 <2 <3 7 5 >2400 2.0 .900 1.8 1.3 .10

.23 2 4 <2 <2 142 370 4600 – – – – –

E.04 5 5 <2 <3 11 7 580 – – – – –

<.06 11 10 <2 <3 2 <1 >2400 2.2 .960 1.6 1.1 .14

.15 2 3 <2 <2 85 140 4600 – – – – –

.09 4 4 <2 <3 19 3 1700 – – – – –

<.06 11 10 <2 <3 8 7 4600 2.4 1.1 1.7 1.4 .07

.10 2 2 <2 <2 43 10 1600 – – – – –
36 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

nts and chemical analyses of water and bottom-material samples collected from the Owyhee River and selected tributaries, Oregon, 2001 

Phos- Total Inorg. Organic Alum- Anti- Arsenic, Barium, Beryll- Bismuth, Cadmium,

phorus, carbon, carbon, carbon, inum, mony, bed sed bed sed ium, bed sed bed sed

bed sed bed sed bed sed bed sed bed sed bed sed <62.5 μm <62.5 μm bed sed <62.5 μm <62.5 μm

62.5 μm <62.5 μm <62.5 μm <62.5 μm <62.5 μm <62.5 μm wet svd wet svd <62.5 μm wet svd wet svd

wet svd wsv nat wsv nat wsv nat wet svd wet svd field, field, wet svd field, field,

fld, tot, field, field, field, fld, tot, fld, tot, total, total, fld, tot, total, total,

percent percent percent percent percent μg/g μg/g μg/g μg/g μg/g μg/g

(34935) (49267) (49269) (49266) (34790) (34795) (34800) (34805) (34810) (34816) (34825)

– – – – – – – – – – –

0.095 2.4 0.02 2.4 6.8 1.5 7.3 880 2.0 <1 0.4– – – – – – – – – – –

– – – – – – – – – – –

.100 2.9 .07 2.8 6.6 1.4 7.5 860 1.9 <1 .4

– – – – – – – – – – –

– – – – – – – – – – –

– – – – – – – – – – –– – – – – – – – – – –

– – – – – – – – – – –

.094 2.4 .03 2.4 6.9 1.4 7.7 810 2.1 <1 .4

– – – – – – – – – – –

– – – – – – – – – – –

.092 2.2 .01 2.2 7.7 .7 6.1 730 2.6 <1 .3

– – – – – – – – – – –

– – – – – – – – – – –

.091 1.4 .03 1.4 7.2 1.1 8.1 890 1.8 <1 .3

– – – – –– – – – – – – – – – –

– – – – – – – – – – –

.180 4.2 .09 4.1 6.1 .9 8.7 660 1.6 <1 .3

– – – – – – – – – – –

– – – – – – – – – – –

.120 2.8 .04 2.8 6.6 1.0 9.1 850 1.8 <1 .3

– – – – – – – – – – –

– – – – – – – – – – –

.120 3.8 .09 3.7 5.9 .9 7.4 720 1.7 <1 .3

– – – – – – – – – – –

– – – – – – – – – – –

.089 1.7 .01 1.7 7.1 1.0 7.0 880 1.8 <1 .2

– – – – – – – – – – –
Table 3 37

nts and chemical analyses of water and bottom-material samples collected from the Owyhee River and selected tributaries, Oregon, 2001 

Cerium, Chrom- Cobalt, Copper, Europ- Gallium, Gold, Holmium, Iron, Lantha- Lead,

bed sed ium, bed sed bed sed ium, bed sed bed sed bed sed bed sed num, bed sed 

62.5 μm bed sed <62.5 μm <62.5 μm bed sed <62.5 μm <62.5 μm <62.5 μm <62.5 μm bed sed <62.5 μm

wet svd <62.5 μm wet svd wet svd <62.5 μm wet svd wet svd wet svd wet svd <62.5 μm wet svd

field, wet svd field, field, wet svd field, field, field, field, wet svd field,

total, fld, tot total, total, fld, tot, total, total, total, total, fld, tot, total,

μg/g μg/g μg/g μg/g μg/g μg/g μg/g μg/g percent μg/g μg/g

(34835) (34840) (34845) (34850) (34855) (34860) (34870) (34875) (34880) (34885) (34890)

– – – – – – – – – – –

76 58 10 32 1 18 <1 1 3.1 40 18

– – – – – – – – – – –

– – – – – – – – – – –

69 54 9 31 1 17 <1 1 3.0 37 17

– – – – – – – – – – –

– – – – – – – – – – –

– – – – – – – – – – –– – – – – – – – – – –

– – – – – – – – – – –

80 66 12 34 1 18 <1 1 3.3 41 18

– – – – – – – – – – –

– – – – – – – – – – –

110 95 18 43 2 21 <1 2 4.5 57 19

– – – – – – – – – – –

– – – – – – – – – – –

81 100 12 33 1 19 <1 1 3.9 44 17

– – – – – – – – – – –– – – – – – – – – – –

– – – – – – – – – – –

53 60 13 32 1 16 <1 <1 3.5 27 14

– – – – – – – – – – –

– – – – – – – – – – –

66 72 12 32 1 17 <1 1 3.6 36 16

– – – – – – – – – – –

– – – – – – – – – – –

59 88 12 31 1 15 <1 1 3.3 32 14

– – – – – – – – – – –

– – – – – – – – – – –

75 110 15 38 1 18 <1 1 4.2 40 16

– – – – – – – – – – –
38 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02

nts and chemical analyses of water and bottom-material samples collected from the Owyhee River and selected tributaries, Oregon, 2001 and 

Lithium, Mangan- Mercury, Molyb- Neodym- Nickel, Niobium, Scand- Selen- Silver, Strontbed sed ese, bed sed denum, ium, bed sed bed sed ium, ium, bed sed ium,

62.5 μm bed sed <62.5 μm bed sed bed sed <62.5 μm <62.5 μm bed sed bed sed <62.5 μm bed sed

wet svd <62.5 μm wet svd <62.5 μm <62.5 μm wet svd wet svd <62.5 μm <62.5 μm wet svd <62.5 μm

field, wet svd field, wet svd wet svd field, field, wet svd wet svd field, wet svd

total, fld, tot total, fld, tot fld, tot total, total, fld, tot fld, tot total, fld, tot

μg/g μg/g μg/g μg/g μg/g μg/g μg/g μg/g μg/g μg/g μg/g

(34895) (34905) (34910) (34915) (34920) (34925) (34930) (34945) (34950) (34955) (34965)

– – – – – – – – – – –

33 780 0.07 0.9 36 20 23 10 0.5 0.4 240

– – – – – – – – – – –

– – – – – – – – – – –

33 840 .08 .7 32 19 21 9 .5 .4 240

– – – – – – – – – – –

– – – – – – – – – – –

– – – – – – – – – – –– – – – – – – – – – –

– – – – – – – – – – –

34 700 .07 .9 36 23 22 10 .4 .3 240

– – – – – – – – – – –

– – – – – – – – – – –

31 780 .05 1.1 51 38 28 14 .3 .4 220

– – – – – – – – – – –

– – – – – – – – – – –

33 600 .04 1.1 38 25 25 12 .4 .4 290

– – – – – – – – – – –– – – – – – – – – – –

– – – – – – – – – – –

27 1700 .86 1.1 26 27 18 10 .9 .5 220

– – – – – – – – – – –

– – – – – – – – – – –

32 760 .13 1.0 31 26 18 11 .5 .3 240

– – – – – – – – – – –

– – – – – – – – – – –

37 630 .13 1.3 28 27 20 10 .6 .3 220

– – – – – – – – – – –

– – – – – – – – – – –

39 560 .28 1.0 35 34 22 13 .4 .4 290

– – – – – – – – – – –
Table 3 39

nts and chemical analyses of water and bottom-material samples collected from the Owyhee River and selected tributaries, Oregon, 

Tant- Thall- Thorium Tin, Titan- Vanad- Ytterb- Yttrium, Zinc, Uranium

alum, ium, bed sed bed sed ium, ium, ium, bed sed bed sed bed sed

bed sed bed sed <62.5 μm <62.5 μm bed sed bed sed bed sed <62.5 μm <62.5 μm <62.5 μm

62.5 μm <62.5 μm wet svd wet svd <62.5 μm <62.5 μm <62.5 μm wet svd wet svd wet svd

wet svd dry svd field, field, wsv nat wet svd wet svd field, field, field,

fld, tot total, total, total, rec, fld, tot fld, tot total, total, total

μg/g μg/g μg/g μg/g percent μg/g μg/g μg/g μg/g μg/g

(34975) (04064) (34980) (34985) (49274) (35005) (35015) (35010) (35020) (35000)

– – – – – – – – – –

2 <1 12 3 0.460 82 3 30 93 3.8– – – – – – – – – –

– – – – – – – – – –

1 <1 11 3 .440 74 2 28 91 3.0– – – – – – – – – –

– – – – – – – – – –

– – – – – – – – – –– – – – – – – – – –

– – – – – – – – – –

<1 <1 12 3 .510 85 3 33 90 4.0

– – – – – – – – – –

– – – – – – – – – –

2 <1 15 4 .750 120 5 54 110 4.8– – – – – – – – – –

– – – – – – – – – –

1 <1 12 3 .780 120 3 32 97 3.6– – – – – – – – – –– – – – – – – – – –

– – – – – – – – – –

<1 <1 8 2 .550 94 2 25 91 2.1

– – – – – – – – – –

– – – – – – – – – –

<1 <1 11 3 .560 98 3 29 89 3.0

– – – – – – – – – –

– – – – – – – – – –

<1 <1 10 2 .570 97 2 26 84 3.0

– – – – – – – – – –

– – – – – – – – – –

1 <1 12 3 .750 120 3 32 99 3.4– – – – – – – – – –
Table 9 40

e abundance in the Owyhee River and selected tributaries, Oregon, June through July, 2001

2 ; abundance reported in number of individuals per square meter (no./m2); USGS, U.S. Geological Survey: ID, identification]

Owyhee River

at

State Line 

Owyhee River 

above

West Little 

Owyhee River

Owyhee River 

above

West Little 

Owyhee River

Owyhee 

River

at

Three 

Forks

North 

Fork 

Owyhee 

River

Jordan 

Creek

Owyhee River 

near

Rome

Owyhee River

below

Crooked Creek

Owyhee River

above

Bull Creek

Owyhee 

River

above

Lake 

Owyhee

422015117024000 422650117121800 422650117121800 13177900 13177920 13180600 42501711737900 425442117432100 430631117425900 13182000

OR7 OR6 OR6c OR5 NF1 JC1 OR4 OR3 OR2 OR1

154 0 0 84 0 0 96 405 512 149

0 0 151 0 0 16 192 0 0 0

92 27 0 24 0 0 640 512 208 1,216

554 2,605 8,215 0 0 0 0 0 0 0

2,708 3,812 1,360 672 512 1,223 2,624 1,045 1,520 2,518

0 0 0 132 0 0 64 107 0 210 0 0 24 0 0 0 0 0 0

31 82 0 300 0 16 32 0 0 015 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 64 0 0 0

46 82 0 12 8 0 0 0 0 43

15 0 0 0 0 0 128 53 0 85

46 521 50 612 328 505 3,168 331 0 64

0 0 50 0 0 16 32 0 0 43

0 0 101 0 0 0 0 0 0 0

0 0 0 0 0 0 64 11 0 0
41 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02 

e abundance in the Owyhee River and selected tributaries, Oregon, June through July, 2001—Continued 

0 0 0 24 8 0 0 0 0 0

0 0 151 0 0 0 0 0 0 0

1,231 1,892 706 48 0 0 0 11 0 0

0 27 0 0 0 16 128 96 32 405

215 247 706 228 16 82 192 672 208 1,259

15 0 0 0 0 0 0 0 0 0

0 0 0 24 0 0 0 0 0 0

0 0 0 0 0 0 32 0 0 0

0 0 0 12 0 0 32 0 0 0

0 0 0 0 0 0 0 0 0 21

0 0 50 0 0 16 0 0 0 0

92 27 0 12 0 0 128 64 0 43

0 0 10 24 0 0 0 0 0 0

0 0 0 0 40 0 0 0 0 0

0 0 0 0 0 0 0 0 0 21

0 0 0 0 16 0 0 0 0 0

Owyhee River

at

State Line 

Owyhee River 

above

West Little 

Owyhee River

Owyhee River 

above

West Little 

Owyhee River

Owyhee 

River

at

Three 

Forks

North 

Fork 

Owyhee 

River

Jordan 

Creek

Owyhee River 

near

Rome

Owyhee River

below

Crooked Creek

Owyhee River

above

Bull Creek

Owyhee 

River

above

Lake 

Owyhee

422015117024000 422650117121800 422650117121800 13177900 13177920 13180600 42501711737900 425442117432100 430631117425900 13182000

OR7 OR6 OR6c OR5 NF1 JC1 OR4 OR3 OR2 OR1
Table 9 42

e abundance in the Owyhee River and selected tributaries, Oregon, June through July, 2001—Continued

15 0 50 84 8 261 32 21 0 0

15 0 101 0 0 0 0 0 0 0

0 0 0 0 32 0 0 0 0 0

323 439 504 336 8 603 1,248 139 352 512

0 55 50 0 88 0 0 0 0 0

0 0 0 0 16 0 0 0 0 0

0 0 0 0 0 16 0 0 0 0

77 137 101 84 24 16 32 32 64 85

0 0 0 36 0 16 0 0 0 0

108 137 101 84 80 16 0 11 16 0

0 0 0 0 0 0 0 0 496 128

0 0 0 216 8 49 3,200 885 736 1,152

108 55 101 12 0 0 448 96 256 192

0 0 0 0 0 0 0 0 16 0

31 110 50 852 0 65 0 21 0 0

46 82 0 156 112 408 1,536 213 1,152 1,664

0 0 101 0 0 0 0 0 16 0

Owyhee River

at

State Line 

Owyhee River 

above

West Little 

Owyhee River

Owyhee River 

above

West Little 

Owyhee River

Owyhee 

River

at

Three 

Forks

North 

Fork 

Owyhee 

River

Jordan 

Creek

Owyhee River 

near

Rome

Owyhee River

below

Crooked Creek

Owyhee River

above

Bull Creek

Owyhee 

River

above

Lake 

Owyhee

422015117024000 422650117121800 422650117121800 13177900 13177920 13180600 42501711737900 425442117432100 430631117425900 13182000

OR7 OR6 OR6c OR5 NF1 JC1 OR4 OR3 OR2 OR1
43 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02 

e abundance in the Owyhee River and selected tributaries, Oregon, June through July, 2001—Continued

108 603 0 12 0 0 0 0 0 0

15 110 0 0 0 16 0 11 0 0

0 0 50 12 0 0 0 0 0 0

0 0 0 0 0 0 0 43 400 0

15 0 0 0 0 0 0 0 0 0

0 0 0 24 0 0 0 0 0 0

46 0 0 0 0 0 0 11 16 0

0 0 0 252 8 0 128 21 0 0

62 55 50 0 48 0 0 53 0 0

0 0 0 0 8 0 0 0 0 0

0 55 0 12 8 0 256 107 48 213

15 0 0 0 0 0 0 0 0 0

15 27 0 36 0 0 0 32 32 64

0 0 202 0 0 0 0 0 0 0

0 0 0 0 8 0 0 0 0 0

0 0 0 0 0 16 0 0 0 0

123 165 0 12 24 33 0 32 16 0

0 0 0 0 40 0 0 0 0 0

Owyhee River

at

State Line 

Owyhee River 

above

West Little 

Owyhee River

Owyhee River 

above

West Little 

Owyhee River

Owyhee 

River

at

Three 

Forks

North 

Fork 

Owyhee 

River

Jordan 

Creek

Owyhee River 

near

Rome

Owyhee River

below

Crooked Creek

Owyhee River

above

Bull Creek

Owyhee 

River

above

Lake 

Owyhee

422015117024000 422650117121800 422650117121800 13177900 13177920 13180600 42501711737900 425442117432100 430631117425900 13182000

OR7 OR6 OR6c OR5 NF1 JC1 OR4 OR3 OR2 OR1
Table 9 44

e abundance in the Owyhee River and selected tributaries, Oregon, June through July, 2001—Continued

0 0 0 0 0 0 0 0 16 0

15 0 2 0 16 0 0 0 0 0

185 1,179 555 60 664 196 288 21 80 107

0 0 0 0 32 0 0 0 0 0

0 0 50 0 0 0 0 0 0 0

0 0 0 0 0 0 32 0 0 0

0 0 0 0 0 0 0 0 80 0

0 0 151 0 0 0 0 0 0 0

0 0 0 0 16 0 0 0 0 0

308 192 252 240 0 228 0 75 448 171

292 192 756 12 40 98 0 21 16 64

0 0 0 12 0 33 0 0 0 0

0 27 0 0 8 0 0 0 0 00 0 0 0 0 0 0 21 0 0

0 0 0 0 32 0 0 0 0 0

0 0 0 0 0 897 0 0 0 0

15 0 0 0 0 33 0 0 0 0

Owyhee River

at

State Line 

Owyhee River 

above

West Little 

Owyhee River

Owyhee River 

above

West Little 

Owyhee River

Owyhee 

River

at

Three 

Forks

North 

Fork 

Owyhee 

River

Jordan 

Creek

Owyhee River 

near

Rome

Owyhee River

below

Crooked Creek

Owyhee River

above

Bull Creek

Owyhee 

River

above

Lake 

Owyhee

422015117024000 422650117121800 422650117121800 13177900 13177920 13180600 42501711737900 425442117432100 430631117425900 13182000

OR7 OR6 OR6c OR5 NF1 JC1 OR4 OR3 OR2 OR1
45 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02 

e abundance in the Owyhee River and selected tributaries, Oregon, June through July, 2001—Continued 

ued 

0 0 50 0 0 0 0 0 0 0 

0 0 50 48 32 0 0 0 0 0 

15 0 0 24 0 33 64 0 512 448 

15 55 0 144 160 33 32 64 0 0

15 27 0 0 0 0 0 0 0 0

0 0 101 0 0 0 0 0 0 0

123 82 302 36 440 130 480 64 16 341

0 0 0 72 0 261 0 0 0 0

15 165 0 0 56 65 64 43 16 0

31 27 0 0 24 0 0 11 48 149

0 0 50 0 8 0 0 0 0 0

154 603 302 0 8 0 0 0 0 0

0 0 50 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 16 0

46 0 0 180 64 0 64 32 0 0

0 0 0 12 0 16 0 11 32 0

62 274 0 348 224 98 0 149 0 0

0 0 0 0 0 0 0 11 0 0

Owyhee River

at

State Line 

Owyhee River 

above

West Little 

Owyhee River

Owyhee River 

above

West Little 

Owyhee River

Owyhee 

River

at

Three 

Forks

North 

Fork 

Owyhee 

River

Jordan 

Creek

Owyhee River 

near

Rome

Owyhee River

below

Crooked Creek

Owyhee River

above

Bull Creek

Owyhee 

River

above

Lake 

Owyhee

422015117024000 422650117121800 422650117121800 13177900 13177920 13180600 42501711737900 425442117432100 430631117425900 13182000

OR7 OR6 OR6c OR5 NF1 JC1 OR4 OR3 OR2 OR1
Table 9 46

e abundance in the Owyhee River and selected tributaries, Oregon, June through July, 2001—Continued

0 0 50 12 0 16 160 32 80 210 0 0 0 0 0 32 32 16 21

0 0 0 0 0 49 0 0 0 0

123 110 302 72 0 1,859 128 139 160 107

154 110 353 12 48 65 480 43 64 0

0 0 0 0 0 0 0 11 0 0

169 0 0 0 0 0 0 0 0 0

15 0 0 12 8 0 0 0 0 0

31 27 4 0 0 0 0 53 0 0

0 0 50 0 0 0 0 0 0 0

0 0 101 0 0 0 0 0 0 0

Owyhee River

at

State Line 

Owyhee River 

above

West Little 

Owyhee River

Owyhee River 

above

West Little 

Owyhee River

Owyhee 

River

at

Three 

Forks

North 

Fork 

Owyhee 

River

Jordan 

Creek

Owyhee River 

near

Rome

Owyhee River

below

Crooked Creek

Owyhee River

above

Bull Creek

Owyhee 

River

above

Lake 

Owyhee

422015117024000 422650117121800 422650117121800 13177900 13177920 13180600 42501711737900 425442117432100 430631117425900 13182000

OR7 OR6 OR6c OR5 NF1 JC1 OR4 OR3 OR2 OR1
47 Reconnaissance of Chemical and Biological Quality, Owyhee River, Oregon State Line to the Owyhee Reservoir, Oregon, 2001–02 

e abundance in the Owyhee River and selected tributaries, Oregon, June through July, 2001—Continued 

0 0 0 0 0 196 0 0 0 0

0 0 0 0 0 49 0 0 0 0

0 0 0 24 0 0 0 0 0 0

0 0 0 0 0 16 0 0 0 0

0 0 0 0 0 16 0 0 0 0

0 0 0 60 0 0 0 0 0 0

0 0 0 0 0 49 0 0 0 0

0 0 0 0 0 16 0 0 0 0

15 0 0 48 0 0 0 0 0 0

31 0 50 0 0 0 0 0 0 0

0 0 0 0 0 0 0 21 0 0

0 0 50 0 0 0 0 0 0 0

0 55 0 132 0 0 0 0 0 43

0 55 0 36 0 16 64 11 0 0

Owyhee River

at

State Line 

Owyhee River 

above

West Little 

Owyhee River

Owyhee River 

above

West Little 

Owyhee River

Owyhee 

River

at

Three 

Forks

North 

Fork 

Owyhee 

River

Jordan 

Creek

Owyhee River 

near

Rome

Owyhee River

below

Crooked Creek

Owyhee River

above

Bull Creek

Owyhee 

River

above

Lake 

Owyhee

422015117024000 422650117121800 422650117121800 13177900 13177920 13180600 42501711737900 425442117432100 430631117425900 13182000

OR7 OR6 OR6c OR5 NF1 JC1 OR4 OR3 OR2 OR1
Table 9 48

e abundance in the Owyhee River and selected tributaries, Oregon, June through July, 2001—Continued

ng to Idaho Division of Environmental Quality (Grafe and others, 2002).

ate sample analyzed by the USGS lab, Denver.

ate - 1/2 split. 

62 27 101 324 32 179 320 128 112 107

0 0 0 0 0 49 0 0 0 0

215 274 706 24 256 33 160 11 336 256

15 0 0 0 0 0 0 0 0 0

8,457 14,833 17,449 6,396 3,616 8,134 16,864 6,039 8,144 11,733

Owyhee River

at

State Line 

Owyhee River 

above

West Little 

Owyhee River

Owyhee River 

above

West Little 

Owyhee River

Owyhee 

River

at

Three 

Forks

North 

Fork 

Owyhee 

River

Jordan 

Creek

Owyhee River 

near

Rome

Owyhee River

below

Crooked Creek

Owyhee River

above

Bull Creek

Owyhee 

River

above

Lake 

Owyhee

422015117024000 422650117121800 422650117121800 13177900 13177920 13180600 42501711737900 425442117432100 430631117425900 13182000

OR7 OR6 OR6c OR5 NF1 JC1 OR4 OR3 OR2 OR1
Hardy, Mark A., Maret, Terry R., and George, David L. -- Reconnaissance of Chemical and Biological Quality in the Owyhee River from the

Oregon State Line to the Owyhee Reservoir, Oregon, 2001-02 --U.S. Geological Survey Water-Resources Investigations Report 03-4327