FRONT COVER AND BOTTOM RIGHT ON BACK COVER:

Powder River below Burger Draw, Wyo. (site P4), July 19, 2010. 

Photograph by Gregory K. Boughton, U.S. Geological Survey.

BACK COVER, LEFT HALF AND MIDDLE RIGHT:

Powder River near Arvada, Wyo., July 22, 2010. 

Photograph by David A. Peterson, U.S. Geological Survey.

Note: The location of Arvada is shown in figure 1. This photograph was not an 

established sampling site during 2005–08, and is located between sites P8 and P9.

BACK COVER, TOP RIGHT: 

Little Powder River above Dry Creek near Weston, Wyo. (site P15), July 6, 2010. 

Photograph by Gregory K. Boughton, U.S. Geological Survey.
Assessment of Ecological Conditions and 

Potential Effects of Water Produced from 

Coalbed Natural Gas Development on 

Biological Communities in Streams of the 

Powder River Stuctural Basin, Wyoming 

and Montana, 2005–08

By David A. Peterson, Melanie L. Clark, Katharine Foster, Peter R. Wright, 

and Gregory K. Boughton

Prepared in cooperation with the Bureau of Land Management,

Montana Department of Environmental Quality,

Montana Department of Fish, Wildlife, and Parks,

U.S. Environmental Protection Agency,

Wyoming Department of Environmental Quality, and

Wyoming Game and Fish Department

Scientific Investigations Report 2010–5124

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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

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

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

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

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

Any use of trade, product, or firm names 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.

Suggested citation:

Peterson, D.A., Clark, M.L., Foster, Katharine, Wright, P.R., and Boughton, G.K., 2010, Assessment of ecological 

conditions and potential effects of water produced from coalbed natural gas development on biological communities 

in streams of the Powder River structural basin, Wyoming and Montana, 2005–08: U.S. Geological Survey Scientific 

Investigations Report 2010–5124, 84 p.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................3

Methods of Data Analysis ...................................................................................................................3

Quality Assurance.................................................................................................................................6

Assessment of Ecological Conditions ........................................................................................................6

Hydrology ...............................................................................................................................................6

Water Quality.........................................................................................................................................7

Water-Quality Characteristics...................................................................................................7

Comparisons to Aquatic-Life Criteria .......................................................................................9

State of Wyoming Aquatic-Life Criteria ........................................................................15

State of Montana Aquatic-Life Criteria.........................................................................17

Federal Aquatic-Life Criteria...........................................................................................17

Habitat ..................................................................................................................................................18

Macroinvertebrate Communities .....................................................................................................18

Macroinvertebrate Community Composition ........................................................................18

Spatial and Temporal Patterns ................................................................................................19

Main-Stem Tongue River.................................................................................................19

Main-Stem Powder River................................................................................................19

Tributaries ..........................................................................................................................26

Effects of Environmental Variables on Macroinvertebrate Communities ........................27

Main-Stem Tongue River.................................................................................................30

Tongue River Plains Tributaries......................................................................................30

Main-Stem Powder River................................................................................................30

Algal Communities..............................................................................................................................32

Standing Crop.............................................................................................................................32

Composition ................................................................................................................................34

Fish Communities................................................................................................................................39

Tongue River Drainage Basin ..................................................................................................39

Community Composition ..................................................................................................39

Community Structure .......................................................................................................40

Powder River Drainage Basin .................................................................................................42

Community Composition ..................................................................................................43

Community Structure .......................................................................................................46

Potential Effects of Water Produced from Coalbed Natural Gas Development 

on Biological Communities ...........................................................................................................48

Water Quality.......................................................................................................................................48

Macroinvertebrate Communities .....................................................................................................53

Algal Communities..............................................................................................................................54

Fish Communities................................................................................................................................54

Further Study Needs...........................................................................................................................54

Summary........................................................................................................................................................55

Acknowledgments.......................................................................................................................................56

References....................................................................................................................................................56

Appendix. Summary Statistics for Water-Quality Constituents, Powder River Structural 

Basin, Wyoming and Montana, Water Years 2005–08..............................................................59
iv

Figures

1. Location of aquatic ecology sampling sites in the Powder River structural 

basin, Wyoming and Montana, 2005–08 ...................................................................................2

2. Cumulative water production as of September 30, 2008, from coalbed natural 

gas wells in the Powder River structural basin, Wyoming and Montana...........................4

3. Streamflow at the time of ecological sampling—Mean streamflow values 

from 2005 to 2008 for sites on (A) main-stem Tongue River, and (B) mainstem Powder River; instantaneous streamflow values for selected sites on 

(C) main-stem Tongue River, and (D) main-stem Powder River, Wyoming, 

and Montana .................................................................................................................................8

4. Mean values for specific conductance, dissolved sodium, and alkalinity 

for the Tongue River and Powder River during ecological sampling events, 

Wyoming and Montana, 2005–08 .............................................................................................14

5. Similarities of macroinvertebrate community taxonomic composition within 

stream groups depicted by nonmetric multidimensional scaling ordinations, 

Powder River structural basin, Wyoming and Montana, 2007–08......................................24

6. Selected macroinvertebrate community metrics by stream group, Powder 

River structural basin, Wyoming and Montana, 2005–08.....................................................25

7. Mean values for selected macroinvertebrate community metrics by site 

and by year, main-stem Tongue River, Wyoming and Montana, 2005–08 .........................27

8. Mean values for selected macroinvertebrate metrics by site and by year, 

main-stem Powder River, Wyoming and Montana, 2005–08 ...............................................28

9. Principal components ordination showing relations among sampling sites 

based on selected environmental variables, Powder River structural basin, 

Wyoming and Montana, 2007 ...................................................................................................29

10. Selected environmental variables correlated with macroinvertebrate 

communities, Powder River structural basin, 2005–08.........................................................31

11. Similarities of algal community taxonomic composition within drainage 

basins and within habitats, depicted by nonmetric multidimensional scaling 

ordination, Powder River structural basin, Wyoming and Montana, 2007........................37

12. Algal community composition by drainage basin and habitat, Powder River 

structural basin, 2007 .................................................................................................................38

13. Relative abundance of fish by species in samples from the Tongue River 

drainage basin, Wyoming and Montana, 2005–06 and 2008................................................43

14. Selected unadjusted fish community metric values for the main-stem 

Tongue River, Wyoming and Montana, 2005–06 and 2008 ...................................................45

15. Index of Biotic Integrity scores (IBI) for fish communities of the Tongue 

River tributaries, Wyoming and Montana, 2005–06 and 2008..............................................47

16. Relative abundance of fish by species in samples from the Powder River 

drainage basin, Wyoming and Montana, 2004–06 and 2008................................................50

17. Selected unadjusted fish community metric values for the main-stem 

Powder River, Wyoming and Montana, 2004–06 and 2008...................................................52

18. Index of Biotic Integrity (IBI) scores for fish communities in selected 

Powder River tributaries, Wyoming, 2005–06 and 2008........................................................53
v

Tables

1. Ecological sampling sites on streams in the Powder River structural basin, 

Wyoming and Montana, 2005–08 ...............................................................................................5

2. Biological quality-control samples, Powder River structural basin, Wyoming 

and Montana, 2005–08 .................................................................................................................7

3. Environmental variables associated with ecological samples, Powder River 

structural basin, Wyoming and Montana, 2005–08...............................................................10

4. State and Federal criteria for the protection of aquatic life................................................15

5. Aquatic-life criteria comparison for water samples collected from study 

sites in the Powder River structural basin, Wyoming and Montana, water 

years 2005–08 ..............................................................................................................................16

6. Macroinvertebrate community metrics for streams in the Powder River 

structural basin, Wyoming and Montana, 2005–08...............................................................20

7. Analysis of variance in macroinvertebrate community metrics, main-stem 

Tongue River and main-stem Powder River, Wyoming and Montana, 2005–08 ...............26

8. Environmental variables best correlated with macroinvertebrate community 

taxonomic composition, by stream group and year, Powder River structural 

basin, Wyoming and Montana, 2005–08 .................................................................................30

9. Correlation coefficients of macroinvertebrate community metrics with 

environmental variables, main-stem Powder River, Wyoming and Montana, 

2005–08 .........................................................................................................................................32

10. Algal chlorophyll-a concentration, ash-free dry mass concentration, density, 

and biovolume, Powder River structural basin, Wyoming and Montana, 2005 

and 2007........................................................................................................................................33

11. Algal community metrics for streams in the Powder River structural basin, 

Wyoming and Montana, 2005 and 2007...................................................................................35

12. Fish abundance in samples from the Tongue River drainage basin, Wyoming 

and Montana, 2005–06 and 2008 ..............................................................................................40

13. Ecological characteristics of fish species sampled in the Powder River 

Structural Basin, Wyoming and Montana, 2005–08..............................................................42

14. Unadjusted fish community metric values for the main-stem Tongue River, 

Wyoming and Montana, 2005–06 and 2008 ............................................................................44

15. Analysis of variance in fish community metrics, main-stem Tongue River 

and main-stem Powder River, Wyoming and Montana, 2005–08 .......................................44

16. Fish community metric and Index of Biotic Integrity (IBI) scores for the Tongue 

and Powder River tributaries, Wyoming and Montana, 2005–06 and 2008 ......................46

17. Fish abundance in samples from Powder River drainage basin, Wyoming and 

Montana, 2004–06 and 2008 ......................................................................................................48

18. Unadjusted fish community metric values for the main-stem Powder River, 

Wyoming and Montana, 2004–06 and 2008 ............................................................................51
vi

Conversion Factors and Datums

Multiply By To obtain

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

acre-foot (acre-ft) 1,233 cubic meter (m3)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

micrometer (μm) 0.00003937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

cubic centimeter per square meter (cm3/m2) 0.6566 cubic inch per square foot (in3/ft2)

meter per second (m/s) 3.281 foot per second (ft/s)

milligram (mg) 0.00003527 ounce, avoirdupois (oz)

milligram per square meter (mg/m2) 0.000003278 ounce per square foot (oz/ft2)

gram per square meter (g/m2) 0.003278 ounce per square foot (oz/ft2)

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

°F=(1.8×°C)+32.

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

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

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25°C).

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

or micrograms per liter (μg/L). Concentrations of algal constituents are given in milligrams per 

square meter (mg/m2), grams per square meters (g/m2), billion cells per square meter, or cubic 

centimeters per square meter (cm3/m2).

The water year begins October 1 and ends September 30, and is designated by the year in which 

it ends. For example, water year 2005 begins October 1, 2004, and ends September 30, 2005.

Abbreviations, Initializms, and Acronyms

< less than

≤ less than or equal to

> greater than

≥ greater than or equal to

AFDM ash-free dry mass

ANOVA analysis of variance

ATG Aquatic Task Group

BLM Bureau of Land Management

CBNG coalbed natural gas

D50 diameter of the 50th percentile (median) of particles

D84 diameter of the 84th percentile of particles

IBI Index of Biotic Integrity
vii

IWG Interagency Working Group

MDEQ Montana Department of Environmental Quality

NMDS nonmetric multidimensional scaling p probability level

PC principal components

PCA principal components analysis

PRMS Powder River main stem

QC quality control

r correlation coefficient

TRMT Tongue River main stem and mountainous tributaries

TRPT Tongue River plains tributaries

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

WDEQ Wyoming Department of Environmental Quality

WGFD Wyoming Game and Fish Department

Abstract

Ongoing development of coalbed natural gas in the Powder 

River structural basin in Wyoming and Montana led to formation 

of an interagency task group to address concerns about the effects 

of the resulting production water on biological communities in 

streams of the area. The interagency task group developed a monitoring plan and conducted sampling of macroinvertebrate, algal, 

and fish communities at 47 sites during 2005–08 to document 

current ecological conditions and determine existing and potential 

effects of water produced from coalbed natural gas development 

on biological communities.

Macroinvertebrate, algal, and fish community composition 

varied between drainage basins, among sites within drainage 

basins, and by year. Macroinvertebrate communities of the 

main-stem Tongue River were characterized by higher taxa 

richness and higher abundance of Ephemeroptera, for example, 

compared to macroinvertebrate communities in plains tributaries of the Tongue River and the main-stem Powder River. Fish 

communities of the Tongue River were characterized by higher 

taxa richness and abundance of introduced species compared to 

the Powder River where native species were dominant.

Macroinvertebrate community metric values from sites 

in the middle reach of the main-stem Powder River, from 

below Willow Creek to below Crazy Woman Creek, differed 

from metric values in the upper and lower reaches of the 

Powder River. Metrics indicative of communitywide differences included measures of taxa richness, relative abundance, 

feeding mode, and tolerance. Some of the variation in the 

macroinvertebrate communities could be explained by variation in environmental variables, including physical (turbidity, embeddedness, bed substrate size, and streamflow) and 

chemical (alkalinity and specific conductance) variables. Of 

these environmental variables, alkalinity was the best indicator 

of coalbed natural gas development because of the sodiumbicarbonate signature of the production water.

Algal samples from the main-stem Powder River generally confirmed the pattern observed in the macroinvertebrate communities. Algal communities at sites in the middle 

reach of the Powder River commonly were characterized by 

dominance by a single taxon and by low biovolume of algae 

compared to other sites.

In contrast to the macroinvertebrate and algal communities, species richness of fish communities was highest 

in the middle reach of the Powder River. Although a few 

significant differences in fish metrics were determined along 

the main-stem Powder River, the differences did not correspond to the pattern observed for the macroinvertebrate and 

algae communities.

Differences in biological communities were noted 

between years, potentially due to the effects of drought. 

Macroinvertebrate community metrics, such as Diptera taxa 

richness, were significantly different in the severe drought 

year of 2006 from metric values in 2005 and 2007–08. Waterquality data collected during the study indicated that, with few 

exceptions, water-quality constituents generally did not exceed 

State or Federal acute and chronic criteria for the protection of 

aquatic life.

Introduction

Development of energy and mineral resources in the 

Powder River structural basin in northeastern Wyoming and 

southeastern Montana (fig. 1) includes coalbed natural gas, 

conventional oil and gas, and coal mining. A common theme 

of coalbed natural gas (CBNG) development is discharge of 

groundwater that commonly is saline or unsuitable for irrigation of crops and has unknown effects on the aquatic communities inhabiting streams that receive the water (Bureau of 

Land Management, 2009).

Assessment of Ecological Conditions and Potential 

Effects of Water Produced from Coalbed Natural Gas 

Development on Biological Communities in Streams 

of the Powder River Structural Basin, Wyoming and 

Montana, 2005–08

By David A. Peterson, Melanie L. Clark, Katharine Foster, Peter R. Wright, and Gregory K. Boughton
2 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Figure 1. Location of aquatic ecology sampling sites in the Powder River structural basin, Wyoming and Montana, 2005–08.

CAMPBELL

JOHNSON

CARTER

CUSTER

CROOK

ROSEBUD

TREASURE

WESTON

POWDER RIVER

BIG HORN

SHERIDAN

NATRONA

CONVERSE

NIOBRARA

WASHAKIE

BIG

HORN

FALLON

Cr

Wild Horse Creek

Dead Horse Cr

Beaver Cree

Pu

k

mpkin Creek

Willow

Cr

Creek

Salt

Yellowstone

 Tongue

 River 

Reservoir

Lake

 De 

 Smet

Tongue

Pumpkin

Creek

Otter Creek

Powder

Belle

Fourche

River

River

River

River

Creek

Creek

Clear

Woman

Crazy

River

Little

Missouri

River

River

Creek

Porcupine

Cheyenne

Cr

Creek

Hanging Woman

Powder Little

River

Powder

Black Thunder Cr

Caballo Creek

Cr

Youngs Cr

Rosebud

Squirrel

 Keyhole 

Reservoir

South Fork

Powder

R

Creek LX Bar

Creek

Bitter

Spotted Horse

Fortification

Creek

Fourmile Cr

Flying E Cr Burger Draw

Dry Fk Powder Ri v er

Prairie Dog 

Creek

25

16

90

90

90

94

94

450

59

7

39

16

14

14

14

12

212

212

85

107° 106° 105°

44°

45°

46°

Base from U.S. Geological Survey digital data, 1999–2004, 1:2,000,000 

Roads from Federal Highway Administration digital data, 2002, 1:100,000 

Albers Equal-Area Conic projection 

0 20 40 MILES

0 20 40 KILOMETERS Standard parallels 40°N and 60°N, central meridian 106°W 

Kaycee

Buffalo

Ashland

Gillette

Sheridan

Moorhead

Moorcroft

Broadus

Miles

City

Birney

Kirby

Rosebud

Monarch

Decker

Locate

Weston

Hampshire

Piney

Newcastle

C6

T7

T4

T3

T5 P11

P9

T10

T16

T15

R1

P16

P17

T18

T19

P18

P13

B2

B1

C5

C4

C3

C2

C1

P15

P14

P12

P10

P6

P5

P7 P8

P4

P2

P1

P3

T8

T9

T14

T17

T13

T2

T1

R2

T6

MONTANA

WYOMING

Sussex

Arvada

Dayton

Powder River

structural basin

boundary

T12

T11

59

50

59

192

Indian Cr

Black

Hills

Bighorn

Mountains

Helena

Powder

River

structural

basin Cheyenne

MONTANA

WYOMING

Map area

EXPLANATION

Rosebud Creek

Tongue River

Powder River

Cheyenne River

Belle Fourche

 River

Drainage basin

Aquatic ecology

 sampling site

 and number

P13
Introduction 3

A total of 44,564 CBNG wells have been permitted in 

the Wyoming part of the study area as of September 30, 2008, 

and about one-half (19,172) of those wells were producing 

water (fig. 2; Wyoming Oil and Gas Conservation Commission, 

2010). Comparison of the cumulative production data from 

2006 to those from 2008 (fig. 2) indicated that most of the 

development during 2007–08 occurred in the Powder River and 

Tongue River drainage basins. For example, cumulative water 

production in the Powder River drainage in Wyoming during 

2008 was more than twice the amount of cumulative water 

production in 2006.

Substantial CBNG resources also exist in the Montana 

part of the study area but are largely undeveloped compared 

to Wyoming. Permit data from the Montana Department 

of Environmental Quality (MDEQ) (written commun., 

2010) indicate cumulative CBNG water production as of 

October 2008 was about 19,237 acre-feet (acre-ft) from 150 

or more wells in the Tongue River drainage basin in Montana. 

At maximum development in the study area, CBNG wells are 

expected to number 60,000 in Wyoming and more than 10,000 

in Montana (Stricker and others, 2006).

To address concerns about the potential effects of 

CBNG development on cultural and natural resources, the 

U.S. Department of the Interior Bureau of Land Management 

(BLM) formed an Interagency Working Group (IWG) of 

Federal, State, and tribal agencies. The charter of the IWG 

states that it “...was established as the forum for government 

agencies to address, discuss, and find solutions to issues of 

common concern to all parties involved in permitting and 

monitoring of CBNG development” (Powder River Natural 

Gas Interagency Working Group, 2004). The IWG charter 

also provides for establishment of working groups to address 

technical issues as envisioned by the April 2003 Record of 

Decision (Bureau of Land Management, 2003). One working 

group, the Aquatic Task Group (ATG), was tasked with assessing potential effects of CBNG produced water on aquatic 

ecological resources. Agencies involved in the ATG include 

the BLM, the Wyoming Department of Environmental Quality 

(WDEQ), MDEQ, the Wyoming Game and Fish Department, 

the Montana Department of Fish, Wildlife, and Parks, and the 

U.S. Environmental Protection Agency (USEPA).

The ATG developed a monitoring plan to meet two main 

objectives: (1) establish current ecological conditions for aquatic 

biota and their habitat and (2) determine existing and potential 

effects of CBNG produced water on aquatic life (Bureau of 

Land Management, 2009). The assessment of current ecological 

conditions as of 2005–08 was performed by the U.S. Geological 

Survey (USGS) under the direction of the ATG. The determination of effects from CBNG-produced water is addressed in 

part by the current conditions data assessment, as well as by 

studies of potential effects of CBNG water on fish communities in the study area (Davis, 2008; Skaar and others, 2006) 

and a literature review of the effects of CBNG activities on fish 

communities (Davis and others, 2009). Additional information 

about CBNG development and monitoring is available from 

the BLM at http://www.wy.blm.gov/prbgroup/; the WDEQ at 

http://deq.state.wy.us/wqd/WYPDES_Permitting/WYPDES_cbm/cbm.asp; 

and the USGS at http://wy.water.usgs.gov/.

Purpose and Scope

This report is a companion report to Peterson and others 

(2009) that was prepared in cooperation with the ATG and that 

described conditions for biological communities (macroinvertebrates, algae, and fish) for 2005–06 at 47 sites (fig. 1; table 1). 

Data collection continued in 2007–08 at these same 47 sites and 

included environmental variables (water quality and habitat) and 

biological communities (macroinvertebrate and algae sampling 

in 2007 and macroinvertebrate and fish sampling in 2008), but 

the 2007–08 data had not been published previous to this report. 

The types of samples and number of sites sampled varied annually due to drought and program constraints.

The purpose of this report is to (1) assess the current 

(2005–08) ecological conditions for environmental variables 

and biological communities, using new data from 2007–08 

in conjunction with previously published data from 2005–06, 

and (2) describe potential effects of natural and anthropogenic 

environmental variables, including CBNG-produced water, on 

biological communities to the extent possible from the current 

conditions data.

For the sake of brevity, some of the previously published 

material (Peterson and others, 2009) is either omitted from 

this report or summarized and referenced. For example, the 

methods of sample collection and analysis in 2007–08 were 

the same as those used in 2005–06; therefore, descriptions of 

some collection or analytical methods that were previously 

published in Peterson and others (2009) are omitted from this 

report. Additional information about the description of the 

study area, reachwide habitat data from 2005, macroinvertebrate models from 2005–06, and seasonal fish community data 

from 2004–06 may be found in Peterson and others (2009).

Methods of Data Analysis

Biological community metrics were calculated using 

procedures and attributes described by Cuffney (2003) for macroinvertebrates, Porter (2008) for algae, and Bramblett and others 

(2005) for fish. Macroinvertebrate tolerance scores (Hilsenhoff, 

1987; Cuffney, 2003) were assigned to one of three ranges: 

intolerant, greater than or equal to (≥) 0 to less than or equal to 

(≤) 4; moderately tolerant, greater than (>) 4 to less than (<) 7; 

and tolerant, ≥7 to ≤10. Statistical comparisons of macroinvertebrate and fish community metrics were performed in S+ (TIBCO 

Software Inc., 2008) at a probability level (p) of 0.05. Following 

procedures described by Helsel and Hirsch (2002), KruskalWallis rank sum tests were used to test for significant differences 

in metrics between sites and between years, and metrics identified 

as containing significant differences were then subjected to further evaluation using analysis of variance (ANOVA) and Tukey’s 

test for multiple comparisons on rank-transformed data.
107° 106° 105°

45°

44°

43°

0 10 20 40 MILES

0 20

30

10 30 40 KILOMETERS

CAMPBELL

JOHNSON

NATRONA

CONVERSE

CROOK

SHERIDAN

WESTON

NIOBRARA

BIG HORN

POWDER RIVER CARTER

ROSEBUD

WASHAKIE

BIG

HORN

1C

1B

1A

SUMA

Base from U.S. Geological Survey digital data, 1999–2004, 1:2,000,000

Albers Equal-Area Conic projection

Standard parallels 40°N and 60°N, central meridian 106°W

North American Datum of 1983 (NAD 83) 

MONTANA

WYOMING

Belle

Fourche

River

River

River

River

Creek

Powder

Little

River

Tongue

Clear

Cr

Creek

Crazy Woman

Powder

Antelope

Dry Fork

Cheyenne

 Tongue River

Reservoir

River

Powder

Middle

Powder River

structural basin

boundary

EXPLANATION

Tongue River (Montana)

Upper Powder River

Crazy Woman Creek

Middle Powder River

Clear Creek

Production, in acre-feet

As of water 

year 2006

Little Powder River

Dry Fork Cheyenne 

Antelope Creek

Upper Cheyenne River

Upper Belle Fourche River

11,119

125,548

375

23,148

5,469

67,419

504

22,255

28,606

178,941

As of water 

year 2008

19,237

270,376

2,134

45,369

10,005

88,504

1,447

30,579

31,333

203,443

Difference

8,118

Tongue River (Wyoming)

Drainage basin

45,982 84,743 38,761

144,828

1,759

22,221

4,536

21,085

943

8,324

2,727

24,502

509,366 787,169 277,803

Coalbed natural gas well

Total

Combined well outfall point and identification code 1C

4 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Figure 2. Cumulative water production as of September 

30, 2008, from coalbed natural gas wells in the Powder River 

structural basin, Wyoming and Montana.
Table 1. Ecological sampling sites on streams in the Powder River structural basin, Wyoming and Montana, 2005–08.[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. DMS, degrees, minutes, seconds; km2, square kilometers; m, meters; P, plains; M, mountains]

Site 

number 

(fig. 1)

U.S. Geological

Survey site

identification number

Site name Abbreviated site name Latitude (DMS) Longitude (DMS) Drainag

area (km2) 

R1 06295113 Rosebud Creek at reservation boundary, near Kirby, MT Upper Rosebud Creek 45 21 40 106 59 23 319 R2 06296003 Rosebud Creek at mouth, near Rosebud, MT Rosebud Creek at mouth 46 15 53 106 28 30 3,372 T1 06299980 Tongue River at Monarch, WY Tongue River at Monarch 44 54 01 107 01 13 1,238 T2 06305700 Goose Creek near Acme, WY Goose Creek 44 53 11 106 59 18 1,070 T3 450137106595101 Youngs Creek near reservation boundary, near Decker, MT Upper Youngs Creek 45 01 37 106 59 15 56 T4 445832106551401 Youngs Creek above mouth, near Decker, MT Youngs Creek at mouth 44 58 32 106 55 14 161 T5 445957106524701 Tongue River below Youngs Creek, near Decker, MT Tongue River below Youngs Creek 44 59 57 106 52 47 3,711 T6 06306100 Squirrel Creek near Decker, MT Upper Squirrel Creek 45 03 02 106 55 24 87 T7 450047106514201 Squirrel Creek above mouth at Decker, MT Squirrel Creek at mouth 45 00 47 106 51 42 112 T8 06306250 Prairie Dog Creek near Acme, WY Prairie Dog Creek 44 59 02 106 50 21 927 T9 06306300 Tongue River at State line, near Decker, MT Tongue River at State line 45 00 32 106 50 08 3,763 T10 451607106372801 Tongue River at Prairie Dog Creek, near Decker, MT Tongue River above Hanging Woman Creek 45 16 07 106 37 28 5,208 T11 06307570 Hanging Woman Creek below Horse Creek, near Birney, MT Upper Hanging Woman Creek 45 08 04 106 29 04 831 T12 451340106295501 Hanging Woman Creek below Hay Gulch, near Birney, MT Middle Hanging Woman Creek 45 13 44 106 29 57 958 T13 06307600 Hanging Woman Creek near Birney, MT Hanging Woman Creek at mouth 45 17 57 106 30 28 1,217 T14 06307616 Tongue River at Birney Day School Bridge, near Birney, MT Tongue River at Birney Day School 45 24 42 106 27 26 6,788 T15 451732106085001 Otter Creek below Taylor Creek, near Otter, MT Upper Otter Creek 45 17 32 106 08 53 803 T16 452642106091201 Otter Creek below Tenmile Creek, near Ashland, MT Middle Otter Creek 45 26 42 106 09 12 1,331 T17 06307740 Otter Creek at Ashland, MT Otter Creek at mouth 45 35 18 106 15 17 1,831 T18 06307830 Tongue River below Brandenberg Bridge, near Ashland, MT Tongue River below Brandenberg Bridge 45 50 23 106 13 09 10,225 T19 06308400 Pumpkin Creek near Miles City, MT Pumpkin Creek 46 13 42 105 41 24 1,805 P1 434056106244101 Powder River above Lone Tree Draw, near Sussex, WY Powder River above Salt Creek 43 40 56 106 24 41 5,828 P2 434124106192401 Powder River below Salt Creek, near Sussex, WY Powder River below Salt Creek 43 41 24 106 19 24 7,980 P3 435453106104701 Powder River below Willow Creek, near Sussex, WY Powder River below Willow Creek 43 54 53 106 10 47 9,808 P4 440919106091401 Powder River above Van Houghton Draw, near Buffalo, WY Powder River below Burger Draw 44 09 19 106 09 14 11,111 P5 442538106082001 Powder River below Mitchell Draw, near Arvada, WY Powder River above Crazy Woman Creek 44 25 38 106 08 20 12,564 P6 441532106251301 Crazy Woman Creek below I-90, near Buffalo, WY Crazy Woman Creek below I-90 44 15 32 106 25 13 1,769 P7 442817106133001 Crazy Woman Creek near Upper Station, near Arvada, WY Crazy Woman Creek near mouth 44 28 17 106 13 30 2,385 P8 443025106061601 Powder River below Crazy Woman Creek, near Arvada, WY Powder River below Crazy Woman Creek 44 30 25 106 06 16 15,286 P9 444857106030401 Powder River above Ivy Creek, near Arvada, WY Powder River above Clear Creek 44 48 57 106 03 04 17,050 P10 06324000 Clear Creek near Arvada, WY Clear Creek 44 52 18 106 04 56 2,875 P11 445339106032501 Powder River below Clear Creek, near Arvada, WY Powder River below Clear Creek 44 53 39 106 03 25 20,106 P12 06324500 Powder River at Moorhead, MT Powder River at Moorhead 45 03 28 105 52 39 20,943 P13 06324710 Powder River at Broadus, MT Powder River at Broadus 45 25 37 105 24 05 22,657 P14 06324790 Little Powder River at State Hwy 59, near Gillette, WY Little Powder River at Highway 59 44 26 09 105 27 17 110 P15 06324970 Little Powder River above Dry Creek, near Weston, WY Little Powder River above Dry Creek 44 55 37 105 21 10 3,204 P16 06325000 Little Powder River at Biddle, MT Little Powder River at Biddle 45 06 17 105 19 51 3,991 P17 453209105201201 Powder River below Little Powder River, near Broadus, MT Powder River below Little Powder River 45 32 09 105 20 12 29,503 P18 06326500 Powder River near Locate, MT Powder River near Locate 46 25 48 105 18 34 33,846 C1 06364300 Porcupine Creek near Teckla, WY Porcupine Creek 43 34 41 105 20 19 204 C2 06364700 Antelope Creek near Teckla, WY Antelope Creek 43 29 08 105 13 39 2,484 C3 06365900 Cheyenne River near Dull Center, WY Cheyenne River near Dull Center 43 25 45 105 02 43 3,955 C4 06375600 Little Thunder Creek near Hampshire, WY Little Thunder Creek 43 39 20 104 54 20 606 C5 06376300 Black Thunder Creek near Hampshire, WY Black Thunder Creek 43 34 54 104 43 11 1,386 C6 06386500 Cheyenne River near Spencer, WY Cheyenne River near Spencer 43 25 20 104 07 36 13,649 B1 06425720 Belle Fourche River below Rattlesnake Creek, near Piney, WY Belle Fourche River 43 59 04 105 23 16 1,282 B2 06425900 Caballo Creek at mouth, near Piney, WY Caballo Creek 44 04 48 105 15 59 673 

1Established reach length of 3,218 meters is maximum reach length; the actual reach length varied with each site visit depending on location of random starting point and availabi
6 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Nonmetric multidimensional scaling (NMDS) ordinations 

of macroinvertebrate and algal community taxonomic data 

were prepared in PRIMER (Clarke and Gorley, 2006). Macroinvertebrate and algal abundance data were log transformed 

(log x + 1) to approximate normality. Bray-Curtis similarity 

coefficients (Bray and Curtis, 1957) were computed to determine taxonomic (dis-)similarity among samples. NMDS ordinations of the Bray-Curtis similarity coefficients were used to 

determine relations among sites on the basis of the taxonomic 

composition of the communities.

Macroinvertebrate community data from samples 

collected in riffles were tested for relations with environmental 

variables using principal components analysis (PCA) and the 

BEST routine (Clarke and Gorley, 2006). Environmental data 

were log transformed (log x + 1) and standardized prior to running PCA to identify the most important variables distinguishing the sites (highest eigenvectors) and to identify and remove 

collinear (highly correlated) variables. The environmental 

variables selected through PCA were tested for correlation 

with the taxonomic composition of the macroinvertebrate 

communities using the BEST routine in PRIMER (Clarke and 

Gorley, 2006). The BEST routine tests multiple combinations 

of the environmental variables against the Bray-Curtis similarity coefficients of the macroinvertebrate communities to determine the highest Spearman correlation coefficients (r) using 

five or fewer environmental variables.

Data for major ions were either collected at the time of 

biological sampling or, in the case of sites that are sampled 

within the water-quality monitoring network, were the most 

recently collected samples (usually within 30 days prior) at 

each site. Missing values for turbidity or dissolved oxygen 

(less than 5 percent of total observations) were estimated 

for the statistical analyses from average values at the site or 

nearby sites on the same stream.

Quality Assurance

Quality assurance for analyses of major ions, chlorophyll, 

and ash-free dry mass (AFDM) included collection and analysis of quality-control (QC) samples from selected sites. The 

relative percent difference (RPD) in constituent concentrations 

between the environmental (sample 1) and the QC (sample 2) 

samples was calculated using the formula:

RPD = absolute value ((sample 1 – sample 2)/

[(sample 1 + sample 2)/2]) × 100

The RPD for major ions in six pairs of environmental and 

QC samples was less than 5 percent, on the average. The RPD 

for chlorophyll and AFDM in four pairs of samples was less 

than 15 percent, on the average.

Quality assurance for the biological taxonomic analyses also included collection and analysis of QC samples for 

macroinvertebrates and algae. The taxonomic data do not lend 

themselves to conventional QC analyses such as RPD; therefore, the taxonomic QC samples were compared to the parent 

samples using Bray-Curtis similarity coefficients. The similarity coefficients of the macroinvertebrate and algae QC samples 

ranged from 46 to 83 percent (table 2), on a scale from 0 (no 

similarity) to 100 percent (complete similarity). The similarity coefficients between the parent and QC samples were 

higher than similarities with other environmental samples as 

shown in ordinations of the 2007–08 data in the following 

sections “Macroinvertebrate Community Composition” and 

“Composition” under the “Algal Communities” section and 

ordinations of the 2005–06 data (Peterson and others, 2009, 

their figs. 20 and 31).

Quality assurance for fish taxonomy was provided through 

voucher specimens and photographic vouchers collected as 

per the fish taxonomy quality-assurance plan (Walsh and Meador, 

1998). Voucher specimens were sent to Dr. Robert Bramblett 

at Montana State University, Bozeman, Montana, for taxonomic 

confirmation and then sent to the Museum of Southwestern 

Biology at the University of New Mexico, Albuquerque, 

New Mexico, for curation.

Assessment of Ecological Conditions

This section of the report describes the assessment of 

current (2005–08) ecological conditions, including water quality, habitat, macroinvertebrate communities, algal communities, and fish communities, for streams in the Powder River 

structural basin. A description of the hydrology of the Powder 

River structural basin also is included.

Hydrology

Streamflow data were collected for the sites listed 

in table 1 during 2005–08 and are available from 

http://waterdata.usgs.gov/wy/nwis/sw. Streams with 

mountainous headwaters (table 1), such as the Tongue River, 

Goose Creek, and Clear Creek, tended to have perennial flow 

during 2005–08, whereas streams with plains headwaters, 

such as those in the Cheyenne and Belle Fourche River drainage basins and the upper parts of Otter Creek and Hanging 

Woman Creek (Tongue River drainage basin), tended to have 

ephemeral or intermittent streamflow. Mean values of instantaneous streamflow at the time of ecological sampling during 

2005–08 from sites on the main-stem Tongue River indicated 

streamflow was less upstream from Tongue River Reservoir 

(sites T1, T5, and T9; fig. 3A) than downstream (sites T10, 

T14, and T18). Mean values of instantaneous streamflow 
Assessment of Ecological Conditions 7

from sites on the main-stem Powder River indicated more flow 

within the vicinity of Clear Creek near Arvada, Wyo. (sites P9 

and P11) to Moorhead, Mont. (site P12) than at reaches farther 

upstream or downstream (fig. 3B).

Throughout most of the study area, daily streamflow in 

the study area during 2007–08 tended to be near or above the 

long-term average values, in contrast to below-average values 

in 2005–06 (http://waterdata.usgs.gov/wy/nwis/sw/). Drought 

conditions prevailed in the study area during 2005–06 and 

for several years preceding the study (National Oceanic and 

Atmospheric Administration Satellite and Information Service, 

2005). Instantaneous values of streamflow at the time of ecological sampling (table 3) indicated substantially less streamflow in 2006 than in 2005 or 2007–08 (figs. 3C and 3D). 

During the summer of 2006, some of the sampling sites on the 

main-stem Powder River (such as sites P8, P9, P12, and P17) 

did not have flow, with only isolated pools present to sample. 

Historically, infrequent days of no flow have been documented 

on the Powder River from Arvada, Wyo., to Moorhead, Mont. 

(Ringen and Daddow, 1990), which includes sites P9, P11, 

and P12 (fig. 1) and which may be inherent to the reach under 

natural conditions.

Water Quality

Water-quality data (http://waterdata.usgs.gov/wy/nwis/qw) 

that were collected during water years 2005–08 as part of ATG 

sampling events, as well as data for samples collected at ATG 

study sites that are part of other USGS monitoring efforts, were 

compiled for 47 study sites in the five major drainage basins of 

Rosebud Creek, Tongue River, Powder River, Cheyenne River, 

and Belle Fourche River. The water year 2005–08 data were 

compared to applicable State or Federal aquatic-life criteria for 

selected water-quality constituents and are statistically summarized in the Appendix. A subset, consisting of water-quality 

data collected during ecological sampling events on the Tongue 

River and Powder River, was used to describe how conditions 

varied on the two large main-stem rivers during relatively lowflow conditions of summer.

Water-Quality Characteristics

Water-quality characteristics of streams in the Powder 

River structural basin are variable largely because of streamflow and geology (Clark and Mason, 2007). The Tongue River 

drainage basin has its headwaters in the Bighorn Mountains, 

which are characterized by relatively high precipitation, 

low evaporation, and resistant igneous, metamorphic, and 

Paleozoic-era sedimentary rocks (Clark and Mason, 2007). 

In contrast, the Powder River drainage basin has a large part 

of its headwaters in the plains, which are characterized by 

relatively low precipitation, high evaporation, and soluble 

Tertiary-age sedimentary rocks (Clark and Mason, 2007). Different basin characteristics of the Tongue River and Powder 

River are reflected in the range of mean values for specific 

conductance, dissolved sodium, and alkalinity for ATG 

sampling events during the relatively low flow conditions 

of summer (fig. 4; table 3). Specific conductance, dissolved 

sodium, and alkalinity are general indicators of water-quality 

characteristics and also have been identified as constituents of 

concern for CBNG discharges because their concentrations in 

produced water can be large (Rice and others, 2000).

Mean specific conductance values at the time of ecological sampling for the Tongue River (456 to 756 microsiemens per centimeter at 25 degrees Celsius [μS/cm]) were 

small compared to the Powder River (1,970 to 4,750 μS/cm) 

(fig. 4). Mean specific conductance values for the Tongue 

River increased from Monarch, Wyo. (site T1) to the State 

line near Decker, Mont. (site T9), with a decrease downstream 

from Tongue River Reservoir (site T10) followed by another 

increase downstream to below Otter Creek (site T18). Mean 

sodium and alkalinity values on the Tongue River generally 

had a similar spatial pattern as specific conductance, with the 

largest concentrations at site T9. Potential anthropogenic influences to water quality of the Tongue River between sites T1 

and T9 include CBNG produced water, irrigation return flows 

and diversions, treated wastewater effluent, and municipal 

stormwater runoff.

Table 2. Biological quality-control samples, Powder River structural basin, Wyoming and Montana, 2005–08.

Site

number

(fig. 1)

Abbreviated

site name

Sample

date

Sample

type

Quality

control type

Bray-Curtis

similarity

(percent)

T1 Tongue River at Monarch 8/15/2005 Macroinvertebrate Replicate 61

T1 Tongue River at Monarch 8/15/2005 Algae Replicate 51

T3 Upper Youngs Creek 6/26/2008 Macroinvertebrate Split 54

T7 Squirrel Creek at mouth 7/12/2007 Macroinvertebrate Replicate 58

T17 Otter Creek at mouth 6/19/2007 Algae Replicate 46

P6 Crazy Woman Creek below I-90 7/11/2005 Macroinvertebrate Replicate 70

P7 Crazy Woman Creek near mouth 7/12/2005 Algae Replicate 61

P9 Powder River above Clear Creek 7/29/2008 Macroinvertebrate Replicate 62

C4 Little Thunder Creek 6/13/2007 Algae Split 83

B2 Caballo Creek 6/28/2005 Algae Replicate 67
8 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Figure 3. Streamflow at the time of ecological sampling—Mean streamflow values from 2005 to 2008 for sites on (A) main-stem 

Tongue River, and (B) main-stem Powder River; instantaneous streamflow values for selected sites on (C) main-stem Tongue River, 

and (D) main-stem Powder River, Wyoming and Montana.

0

50

100

150

200

250

300

350

400

450

T1 T5 T9 T10 T14 T18

MEAN STREA

MFLO

W, IN CUBIC FEET PER SECOND 

TONGUE RIVER MAIN-STEM SITE

A

0

50

100

150

200

250

P1 P2 P3 P4 P5 P8 P9 P11 P12 P13 P17 P18

POWDER RIVER MAIN-STEM SITE

B

2005 2006 2007 2008

YEAR

2005 2006 2007 2008

YEAR

C T5 D

T9

T10

T14

P4

P5

P11

P13

450

0

50

100

150

200

250

300

350

400

INSTANTANEOUS STREAMFLOW, IN CUBIC FEET PER SECOND 

0

50

100

150

200

250
Assessment of Ecological Conditions 9

Mean specific conductance for the Powder River nearly 

doubled between sites P1 and P2 (fig. 4) near Sussex, Wyo., 

as a result of inputs from Salt Creek. No CBNG discharges 

occur upstream from sites P1 and P2 (Wyoming Department 

of Environmental Quality, written commun., 2010). The 

water quality in this reach of the Powder River is affected 

by produced water from conventional oil and gas production 

in the Salt Creek drainage basin (Clark and Mason, 2007). 

The influence of Salt Creek on the Powder River was particularly evident in mean dissolved sodium concentrations, 

which increased downstream from 284 to 797 milligrams 

per liter (mg/L) between sites P1 and P2. The influence of 

Salt Creek becomes less pronounced downstream, however, 

as indicated by a decrease in mean specific conductance and 

sodium concentrations downstream from Salt Creek (site P2) 

to site P11 downstream from Clear Creek. The decreases are 

likely due to the effects of dilution by increased streamflow. 

Among all sites, mean specific conductance and dissolved 

sodium concentrations were lower for the Powder River from 

Clear Creek near Arvada, Wyo., (site P9) to Moorhead, Mont. 

(site P12) than those for site P1, which is on the Powder 

River upstream from CBNG development. An increase in 

mean dissolved sodium concentrations was observed between 

Moorhead (site P12) and Broadus, Mont. (site P13). No 

CBNG discharges occur between sites P12 and P13 (Montana 

Department of Environmental Quality, written commun., 

2010) and thus are not associated with the increase in specific 

conductance in this reach. The spatial pattern for alkalinity 

is different than the patterns for specific conductance and 

sodium. The largest mean value for alkalinity of 583 mg/L (as 

calcium carbonate) was for the Powder River below Burger 

Draw (site P4), which receives CBNG discharges from several 

drainages upstream. This value is about three times larger than 

the mean concentration calculated for the rest of the Powder 

River sites. Overall, mean values of alkalinity for the Powder 

River were less variable when compared to mean values of 

specific conductance and dissolved sodium concentrations, 

with the exception of site P4.

Comparisons to Aquatic-Life Criteria

The State of Wyoming (Wyoming Department of 

Environmental Quality, 2007), State of Montana (Montana 

Department of Environmental Quality, 2008), and USEPA 

(U.S. Environmental Protection Agency, 2005) have established chronic and acute criteria for the protection of aquatic 

life (table 4). Aquatic life includes fish, invertebrates, amphibians, and other organisms that inhabit streams at some stage in 

their life cycles. Acute criteria are based on a 1-hour average concentration, not to be exceeded more than once every 

3 years. Chronic criteria are based on a 4-day average concentration, not to be exceeded more than once every 3 years. 

For this report, constituent concentrations were compared to 

Wyoming numeric criteria for sites that are physically located 

in Wyoming and to Montana criteria for sites that are physically located in Montana. The State of Wyoming aquatic-life 

criteria for trace elements generally are based on dissolved 

concentrations in contrast to the State of Montana aquaticlife criteria that generally are based on “total recoverable” 

(referred to as “total” in this report) concentrations. Total 

concentrations occur in water at higher concentrations than 

dissolved concentrations because total concentrations include 

particulate or colloidal phases of the constituent in addition to 

the dissolved phase. Montana ATG study sites may appear to 

have poorer water quality, therefore, compared to Wyoming 

ATG study sites because more Montana samples had concentrations that exceeded aquatic-life standards. Because dissolved and total concentrations can vary substantially for some 

trace elements, constituent concentrations for both States also 

were compared to the USEPA national recommended aquaticlife criteria for reference. Criteria for the protection of human 

health were not evaluated because the focus of this report is on 

aquatic life.

Some of the trace-element constituents that were analyzed in water-quality samples are classified as “priority 

pollutants,” which are constituents that require water-quality 

criteria to be established by the USEPA, based on section 307 

of the Federal Clean Water Act (table 4). For some constituents (arsenic, chromium [VI], mercury, and selenium), the 

toxicity threshold for acute and chronic values is the same for 

all waters. For other constituents (cadmium, chromium [III], 

lead, nickel, and zinc), the toxicity is hardness-dependent; 

therefore, sample-specific criteria were calculated for comparison. Values listed for these constituents (table 4) are for 

example only and are based on a hardness value of 100 mg/L 

(as calcium carbonate). The number of exceedances and sites 

described in this report for hardness dependent criteria were 

calculated from the hardness concentration associated with 

each individual sample. Unlike the State of Wyoming and 

State of Montana equations for copper, the USEPA national 

recommended aquatic-life criteria for dissolved copper are 

not a single hardness-dependent equation; instead, values are 

based on a complex biotic ligand model that includes pH, 

hardness, and dissolved-organic carbon (U.S. Environmental 

Protection Agency, 2007). Chromium concentrations were 

compared to criteria for both chromium (III) and chromium 

(VI) for this report; however, the laboratory analyses for 

chromium were not speciated for valence states. Dissolvedmercury concentrations were not available for comparison 

with State of Wyoming or USEPA national recommended 

criteria. Total-mercury concentrations were available and 

were used for comparison in this report because if the total 

concentration is less than dissolved criteria, then the dissolved component must also have been less. The USEPA 

national recommended aquatic-life acute criteria for selenium 

currently are under review (U.S. Environmental Protection 

Agency, 2004).
10 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Table 3. Environmental variables associated with ecological samples, Powder River structural basin, Wyoming and Montana, 2005–08. 

—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River or Powder River. m, meters; %, percent; <, less than; mm, millimeters; D50, diameter of 

the 50th percentile of particles; D84, diameter of the 84th percentile of particles; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 degrees 

Celsius; °C, degrees Celsius; mg/L, milligrams per liter; NTRU, nephelometric turbidity ratio units; NA, not applicable]

Site

number

(fig. 1)

Abbreviated site name Sample

date

Microhabitat Pebble counts Field measurements

Water

depth

(m)

Embeddedness

(%)

Velocity

(m/s)

Substrate

(% coarse)

%

<2 mm D50 D84

Streamflow 

(ft3/s)

Specific

conductance

(μS/cm)

pH

(standard 

units)

R2 Rosebud Creek at mouth 9/15/2005 0.02 54 0.16 100 NA NA NA 0.01 4,300 8.6

T1 Tongue River at Monarch 8/15/2005 0.09 36 0.42 100 NA 51 84 123 426 7.5

8/23/2006 0.10 34 0.43 100 NA NA NA 27 535 8.2

8/29/2007 0.12 20 0.59 100 10 34 73 76 427 8.4

T2 Goose Creek 8/17/2005 0.13 24 0.55 70 NA 22 64 69 653 8.3

8/22/2006 0.17 48 0.60 80 NA NA NA 22 735 8.2

9/11/2007 0.23 20 0.23 100 21 23 50 83 653 8.2

8/4/2008 0.20 32 0.59 80 39 27 55 34 705 8.6

T3 Upper Youngs Creek 6/15/2005 0.10 0 0.81 100 NA NA NA 2.3 675 8.3

6/28/2006 0.05 38 0.34 80 NA NA NA 0.36 704 8.4

6/21/2007 0.15 13 0.71 100 34 13 46 8.5 615 8.2

6/26/2008 0.20 30 0.65 100 59 <2 24 15 648 7.5

T4 Youngs Creek at mouth 6/14/2005 0.19 54 0.41 100 NA NA NA 0.99 1,690 8.4

6/27/2006 0.16 50 0.35 50 NA NA NA 0.58 1,000 8.3

T5 Tongue River below Youngs Creek 8/15/2005 0.11 24 0.94 100 NA NA NA 171 544 7.8

8/22/2006 0.11 28 0.62 80 NA NA NA 23 695 7.9

8/29/2007 0.09 33 0.69 100 15 19 40 52 569 8.4

8/22/2008 0.10 34 0.33 89 10 22 36 109 523 8.4

T7 Squirrel Creek at mouth 6/13/2005 0.08 10 0.24 100 NA NA NA 0.17 5,940 8.3

7/12/2007 0.08 10 0.31 100 37 13 30 0.39 2,310 8.1

6/25/2008 0.12 8 0.54 100 0 21 40 1.8 1,750 7.9

T8 Prairie Dog Creek 8/25/2006 0.09 44 0.32 78 NA NA NA 1.2 2,270 8.1

9/11/2008 0.27 70 1.00 100 17 54 97 43 916 8.1

T9 Tongue River at State line 9/14/2005 0.11 24 0.49 80 NA 22 43 162 655 7.6

8/24/2006 0.12 22 0.45 100 NA NA NA 11 1,060 8.4

8/28/2007 0.12 40 0.28 100 10 14 28 136 705 8.4

8/21/2008 0.16 34 0.51 100 6 22 57 136 604 8.2

T10 Tongue River above Hanging Woman Creek 8/16/2005 0.15 48 0.59 100 NA NA NA 408 363 8

8/28/2006 0.16 48 0.70 100 NA NA NA 153 540 8.2

8/28/2007 0.16 40 0.77 100 16 34 101 164 495 8.2

9/9/2008 0.21 25 0.61 100 3 43 107 406 427 8.7

T11 Upper Hanging Woman Creek 6/22/2005 0.05 68 0.00 56 NA NA NA 0.03 5,000 7.9

7/11/2007 0.05 10 0.22 100 39 7 32 0.12 4,010 8.5

T12 Middle Hanging Woman Creek 6/21/2005 0.10 2 0.19 50 NA NA NA 0.04 3,870 8.1

7/10/2007 0.10 20 0.31 100 18 14 40 0.49 3,650 8.5

T13 Hanging Woman Creek at mouth 6/23/2005 0.08 20 0.15 90 NA NA NA 0.11 2,090 7.8

7/10/2007 0.14 57 0.34 50 47 4.3 41 1.1 3,510 8.1

6/24/2008 0.17 34 0.08 100 62 <2 20 0.27 2,800 8.2

T14 Tongue River at Birney Day School 9/12/2005 0.20 46 0.58 100 NA NA NA 308 466 8.1

8/28/2006 0.17 36 0.63 100 NA NA NA 139 572 8

8/27/2007 0.18 20 0.61 100 24 14 41 359 472 8.5

8/21/2008 0.16 32 0.55 100 14 14 36 409 397 8.2

T16 Middle Otter Creek 6/20/2007 0.16 8 0.60 100 19 18 138 3.8 3,200 8

T17 Otter Creek at mouth 6/30/2005 0.12 34 0.44 100 NA NA NA 1.6 2,700 8.2

6/28/2006 0.06 68 0.22 100 NA NA NA 0.82 2,890 8.4

6/24/2008 0.16 26 0.45 100 1 14 40 2.8 3,520 8.1

T18 Tongue River below Brandenberg Bridge 9/13/2005 0.23 40 0.83 100 NA NA NA 330 503 8.3

8/31/2006 0.21 26 0.74 100 NA NA NA 81.8 684 8.4

8/27/2007 0.08 26 0.46 50 14 15 41 357 528 8.5

T19 Pumpkin Creek 6/23/2005 0.07 14 0.21 100 NA NA NA 1.1 1,140 8.4

6/18/2007 0.08 32 0.44 100 52 <2 15 12 2,630 8.3

P1 Powder River above Salt Creek 7/20/2005 0.06 36 0.36 80 NA 10 35 2.7 2,100 7.6

7/24/2006 0.07 38 0.30 50 NA NA NA 1.2 2,210 7.9

8/30/2007 0.11 30 0.63 100 37 8.4 46 17 3,470 8.2

P2 Powder River below Salt Creek 7/21/2005 0.09 48 0.35 70 NA 13 21 13 4,990 7.9

7/25/2006 0.11 22 0.50 50 NA NA NA 5.1 5,650 8.3

8/30/2007 0.09 30 0.47 50 50 <2 21 38 3,610 8.1

P3 Powder River below Willow Creek 7/19/2005 0.05 28 0.19 100 NA <4 16 9.3 4,810 8.1
Assessment of Ecological Conditions 11

Table 3. Environmental variables associated with ecological samples, Powder River structural basin, Wyoming and Montana, 2005–08. 

—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River or Powder River. m, meters; %, percent; <, less than; mm, millimeters; D50, diameter of 

the 50th percentile of particles; D84, diameter of the 84th percentile of particles; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 degrees 

Celsius; °C, degrees Celsius; mg/L, milligrams per liter; NTRU, nephelometric turbidity ratio units; NA, not applicable]

Site

number

(fig. 1)

Field measurements Dissolved major ion concentrations

Water

temperature

(°C)

Dissolved 

oxygen 

(mg/L)

Turbidity 

(NTRU)

Site 

number

Calcium 

(mg/L)

Magnesium 

(mg/L)

Sodium 

(mg/L)

Sodium 

adsorption

ratio

Potassium 

(mg/L)

Alkalinity 

(mg/L)

Chloride 

(mg/L)

Sulfate 

(mg/L)

Fluoride 

(mg/L)

Silica 

(mg/L)

Total 

dissolved 

solids 

(mg/L)

R2 12.5 9.3 9.1 R2 73.8 183 565 8 14.4 450 23.5 1,520 0.84 0.86 2,650

T1 14.8 7.5 30 T1 44.2 19.6 8.82 0.3 1.66 167 1.11 35.5 0.19 5.28 217

19.6 7.7 14 T1 44 28.9 19.1 0.5 2.55 209 1.96 67.2 0.23 3.83 293

19.8 11.6 11 T1 46.8 20.1 9.98 0.3 1.73 185 1.42 34.6 0.15 6.58 233

T2 20.5 8.3 9 T2 54.1 34.5 20.2 0.5 3.46 194 6.37 100 0.27 6.69 343

19.7 7.3 4.5 T2 67.5 51.8 39.5 0.9 4.44 289 11.6 178 0.39 4.47 532

12 8.3 12 T2 62.8 44.5 30.8 0.7 3.86 260 9.95 141 0.32 3.87 454

25.2 10 3.8 T2 61.9 39.6 27.1 0.7 3.74 239 10 135 0.29 3.52 425

T3 19 7.6 62 T3 55.1 38.2 12.8 0.3 4.61 293 1.97 53.2 0.59 13.8 356

22 7.2 85 T3 62.5 51.1 17.2 0.4 7.17 373 1.58 30.4 0.66 18.8 413

18 8 42 T3 65.6 36.8 10.5 0.3 3.96 312 1.66 38.2 0.49 17.7 362

19.5 7.3 59 T3 67.8 41.8 12.4 0.3 5.55 336 1.58 38.6 0.51 16.9 387

T4 12 8.1 33 T4 108 149 112 1.6 14.9 422 4.05 623 0.76 14.8 1,280

19.5 9.2 18 T4 70.5 79.2 44.7 0.9 9.1 376 2.47 194 0.71 12.6 639

T5 19 8.2 48 T5 56.9 31.9 20.2 0.5 2.77 210 3.35 83.3 0.26 8.54 334

19 7.3 12 T5 49 41.9 33.3 0.8 3.98 227 6.73 145 0.29 4.72 421

19 11.4 7 T5 56.5 33.2 20.6 0.5 2.81 219 3.88 90.7 0.24 5.75 345

19 8.1 5 T5 44.8 29.5 19.3 0.5 2.94 192 3.59 84.3 0.23 1.64 301

T7 13 9.7 6.8 T7 153 463 835 7.6 20 590 12.7 3330 0.73 7.68 5,180

20 NA 1.2 T7 86.4 184 199 2.8 12.1 530 4.75 880 0.57 4.21 1,690

19.5 7.7 14 T7 92.2 146 113 1.7 9.23 485 3.64 587 0.52 9.29 1,250

T8 15.3 9.1 10 T8 157 136 202 2.9 11.4 370 7.77 1040 0.41 13.4 1,790

15.3 8.8 91 T8 72.4 39.4 33.5 0.8 4.24 198 2.48 220 0.21 10.2 501

T9 13.6 8.4 12 T9 54.2 35.7 30.8 0.8 2.92 208 3.53 136 0.29 4.89 393

24.1 10.8 4.4 T9 49.9 46 51.6 1.3 4.32 227 6.96 200 0.47 4.44 500

21 10.3 8.6 T9 59.1 33 27.7 0.7 3.02 203 4.16 126 0.3 7.39 382

25 9.7 24 T9 52.6 28.1 26.3 0.7 2.85 224 4.24 109 0.3 3.53 361

T10 20 8 13 T10 37.2 17 14.7 0.5 1.92 130 1.46 54.4 0.18 3.61 209

18.5 7.5 0.6 T10 36.2 28.8 36.5 1.1 3.62 170 3.4 111 0.3 0.67 322

19 6.7 3.4 T10 48.6 24.2 23.9 0.7 2.91 174 2.7 87.6 0.24 3.14 298

15 9 5 T10 39.6 19.4 19.7 0.6 2.44 152 2.16 71.4 0.22 5.47 252

T11 22.5 NA 10 T11 140 249 732 8.6 18.3 492 18 2,450 0.84 4.39 3,900

24.5 NA 14 T11 90.1 210 695 9.2 17.9 366 15.8 2,050 0.74 1.22 3,300

T12 24.5 NA 9 T12 81.8 200 546 7.4 18 414 19.2 1,800 0.85 2.1 2,920

27.5 NA 1.4 T12 98.5 166 554 7.9 16.5 415 17.9 1,710 0.84 2.54 2,810

T13 20.3 NA 7 T13 77.4 113 259 4.4 12 572 5.7 611 1.38 16.5 1,440

19 8.3 9.5 T13 124 160 483 6.8 19.3 528 16.4 1,460 1.04 7.65 2,580

25.5 11.9 4 T13 93.6 138 376 5.8 16.5 518 13.4 1,150 1.06 9.33 2,110

T14 18.5 8.3 10 T14 44.9 22.3 21.2 0.6 2.54 160 2.23 81.7 0.23 2.02 273

23.5 10.5 NA T14 33.7 29 35.6 1.1 3.5 175 3.39 116 0.3 1.81 328

22.5 8.5 7 T14 33.6 16.9 14.9 0.5 2.41 124 1.75 56.6 0.19 6.27 207

24.5 8.2 14 T14 34.7 15.4 14.5 0.5 2.16 128 1.61 51.6 0.17 5.57 203

T16 19.5 7.5 2.5 T16 129 196 391 5.1 19.4 502 10.7 1,440 0.66 7.43 2,490

T17 18 5.3 97 T17 87.3 180 442 6.2 20.1 592 12.3 1,260 0.95 14.2 2,370

22.2 5 79 T17 55.8 141 394 6.4 19 579 11.4 1,020 1 10.6 2,000

21.5 5.9 21 T17 84.8 147 406 6.2 19.7 490 12.1 1,290 0.78 6.44 2,260

T18 14.5 9.3 16 T18 45 23.6 23.7 0.7 2.87 156 2.51 89.6 0.24 1.81 283

17.8 8.6 NA T18 38.9 32.4 44.5 1.3 3.75 190 4.05 142 0.33 4.61 385

20 8 11 T18 42.1 21.8 25.7 0.8 2.94 165 2.53 95.6 0.24 5.7 296

T19 29.4 NA 158 T19 32 14.5 181 6.7 8.69 214 3.49 294 0.41 9.93 673

21 8.7 69 T19 64.2 65.8 334 7 10.4 281 6.58 853 0.34 8.1 1,510

P1 21.8 7.4 4.7 P1 175 74.7 209 3.3 7.33 177 92.5 722 0.48 11.9 1,400

28.5 6.8 19 P1 170 70.8 213 3.5 8.14 225 93.3 798 0.46 4.93 1,490

27 10.5 380 P1 287 89.4 430 5.7 14.2 181 139 1,610 0.83 7.03 2,680

P2 23 7.7 16 P2 113 75.4 932 17 20.1 288 943 1,070 1.39 7.97 3,340

32.7 7.3 12 P2 140 79 906 15 28.7 175 915 1,310 1.99 4.46 3,490

22.1 10.2 370 P2 177 69.7 554 8.9 15.6 238 444 1,030 1.03 12.5 2,450

P3 24.3 7.2 2.9 P3 183 111 843 12 19.8 187 733 1,330 0.96 9.27 3,350
12 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Table 3. Environmental variables associated with ecological samples, Powder River structural basin, Wyoming and Montana, 2005–08. 

—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River or Powder River. m, meters; %, percent; <, less than; mm, millimeters; D50, diameter of 

the 50th percentile of particles; D84, diameter of the 84th percentile of particles; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 degrees 

Celsius; °C, degrees Celsius; mg/L, milligrams per liter; NTRU, nephelometric turbidity ratio units; NA, not applicable]

Site

number

(fig. 1)

Abbreviated site name Sample

date

Microhabitat Pebble counts Field measurements

Water

depth

(m)

Embeddedness

(%)

Velocity

(m/s)

Substrate

(% coarse)

%

<2 mm D50 D84

Streamflow 

(ft3/s)

Specific

conductance

(μS/cm)

pH

(standard 

units)

P3 Powder River below Willow Creek 7/26/2006 0.05 26 0.17 50 NA NA NA 0.22 4,650 7.8

8/24/2007 0.09 48 0.43 100 39 7.5 21 55 4,830 8.3

7/21/2008 0.07 36 0.31 100 0 15 35 84 2,980 8.4

P4 Powder River below Burger Draw 7/22/2005 0.08 36 0.21 100 NA 27 60 7.9 4,600 7.9

7/27/2006 0.07 22 0.41 90 NA NA NA 2.2 3,210 8.7

8/22/2007 0.07 10 0.64 100 40 16 44 17 3,750 8

7/23/2008 0.12 20 0.40 90 23 47 76 94 2,860 8.4

P5 Powder River above Crazy Woman Creek 7/13/2005 0.07 60 0.34 50 NA <4 12 25 3,500 8.8

7/28/2006 0.07 14 0.31 50 NA NA NA 1.7 2,960 8.1

8/23/2007 0.06 30 0.33 80 56 <2 21 30 3,190 8.2

7/24/2008 0.07 32 0.57 100 12 18 47 99 2,810 8.2

P6 Crazy Woman Creek below I-90 7/11/2005 0.08 14 0.38 50 NA 6.5 21 37 777 7.9

8/20/2007 0.05 30 0.20 100 20 14 42 0.29 1,740 8.2

P7 Crazy Woman Creek near mouth 7/12/2005 0.24 15 0.66 50 NA 43 133 40 894 7.7

8/21/2007 0.06 20 0.40 100 54 <2 32 0.11 1,930 7.9

8/20/2008 0.15 42 0.55 100 15 23 49 15 1,770 8

P8 Powder River below Crazy Woman Creek 7/23/2005 0.17 64 0.53 100 NA <4 32 99 2,050 8.1

8/21/2007 0.09 10 0.44 100 43 14 38 26 3,270 8.4

7/25/2008 0.04 16 0.23 86 48 5 21 159 2,380 8.3

P9 Powder River above Clear Creek 7/24/2005 0.12 74 0.41 100 NA NA NA 149 2,280 7.7

7/26/2007 0.11 30 0.38 50 79 <2 17 102 1,250 8.1

7/29/2008 0.08 68 0.34 100 61 <2 32 188 2,680 8.4

P10 Clear Creek 9/13/2005 0.10 34 0.45 90 NA 29 89 35 1,200 8

8/21/2006 0.08 22 0.51 80 NA NA NA 1.7 1,840 8

9/10/2007 0.11 30 0.46 50 17 22 44 98 972 8.4

8/5/2008 0.10 21 0.47 89 10 28 55 91 1,170 8.3

P11 Powder River below Clear Creek 7/25/2005 0.11 24 0.41 50 NA NA NA 92 1,940 8.2

8/3/2006 0.04 42 0.25 50 NA NA NA 0.2 2,260 8.1

7/26/2007 0.08 26 0.45 90 37 12 57 183 1,270 8.2

7/30/2008 0.18 62 0.67 100 29 33 78 139 2,410 8.3

P12 Powder River at Moorhead 7/26/2005 0.11 46 0.31 100 NA NA NA 76 1,930 8.4

7/26/2007 0.09 30 0.59 50 38 14 60 252 2,430 8.2

7/30/2008 0.06 22 0.42 86 26 14 47 204 2,890 8.2

P13 Powder River at Broadus 7/19/2005 0.17 2 0.63 90 NA NA NA 111 1,690 8.3

8/2/2006 0.07 69 0.38 100 NA NA NA 1.1 4,750 8.1

7/25/2007 0.11 11 0.57 100 41 11 47 29 3,090 8.1

7/31/2008 0.15 15 0.64 100 22 26 53 222 2,230 8.4

P14 Little Powder River at Highway 59 8/8/2007 0.24 50 0.30 100 7 15 55 1.2 2,050 8.1

P15 Little Powder River above Dry Creek 6/13/2005 0.11 30 0.60 100 NA <4 21 3.8 3,480 6.8

6/23/2006 0.09 14 0.45 100 NA NA NA 0.23 3,380 8.1

8/7/2007 0.11 16 0.53 100 19 12 29 4.4 4,190 8

8/18/2008 0.10 42 0.47 100 12 13 33 5.1 3,550 7.7

P16 Little Powder River at Biddle 6/27/2005 0.21 18 0.67 100 NA NA NA 7.6 2,720 7.9

8/9/2007 0.20 26 0.55 100 28 5.8 19 8.1 4,090 8.1

P17 Powder River below Little Powder River 7/21/2005 0.10 34 0.30 70 NA NA NA 85 1,820 8.4

7/25/2007 0.07 32 0.41 50 62 <2 35 50 3,180 8.2

P18 Powder River near Locate 7/22/2005 0.12 44 0.40 80 NA NA NA 90 1,970 8.3

7/24/2007 0.11 12 0.54 100 36 13 54 48 2,470 8.1

C3 Cheyenne River near Dull Center 6/27/2005 0.05 34 0.10 70 NA <4 5.3 0 3,070 8.1

C4 Little Thunder Creek 6/9/2005 0.02 32 0.05 100 NA <4 13 0.02 1,950 7.7

C6 Cheyenne River near Spencer 6/6/2005 0.04 40 0.20 100 NA <4 14 6.4 3,910 8

6/15/2007 0.10 34 0.40 50 53 <2 9.8 9.2 4,550 8.1

B1 Belle Fourche River 6/29/2005 0.07 40 0.17 50 NA <4 6.5 1 3,360 8.8
Assessment of Ecological Conditions 13

Table 3. Environmental variables associated with ecological samples, Powder River structural basin, Wyoming and Montana, 2005–08. 

—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River or Powder River. m, meters; %, percent; <, less than; mm, millimeters; D50, diameter of 

the 50th percentile of particles; D84, diameter of the 84th percentile of particles; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 degrees 

Celsius; °C, degrees Celsius; mg/L, milligrams per liter; NTRU, nephelometric turbidity ratio units; NA, not applicable]

Site

number

(fig. 1)

Field measurements Dissolved major ion concentrations

Water

temperature

(°C)

Dissolved 

oxygen 

(mg/L)

Turbidity 

(NTRU)

Site 

number

Calcium 

(mg/L)

Magnesium 

(mg/L)

Sodium 

(mg/L)

Sodium 

adsorption

ratio

Potassium 

(mg/L)

Alkalinity 

(mg/L)

Chloride 

(mg/L)

Sulfate 

(mg/L)

Fluoride 

(mg/L)

Silica 

(mg/L)

Total 

dissolved 

solids 

(mg/L)

P3 27.1 11.4 18 P3 213 105 643 9 18 160 548 1,550 0.76 3.02 3,180

20.1 8.1 690 P3 176 83.8 821 13 21.2 205 728 1,240 1.19 12.4 3,210

25.3 7.5 86 P3 142 64.3 405 7.1 11.3 209 344 880 0.65 9.11 1,980

P4 20.7 8 4.1 P4 115 100 866 14 21.2 318 537 1,260 0.83 6.66 3,100

24.7 13.9 84 P4 13.9 29.1 715 25 25.7 1,540 69.6 210 1.62 5.01 1,990

18.6 8.1 72 P4 153 77.6 624 10 17.5 251 419 1,130 1 8.74 2,580

23 7.8 120 P4 135 62.5 407 7.3 11.9 224 287 871 0.61 8.16 1,920

P5 26.1 6.6 28 P5 122 72.6 524 9.3 13.1 233 365 1,070 0.68 8.15 2,320

21.7 8.7 5.8 P5 78.8 50 516 11 13.4 342 212 894 0.92 4.32 1,980

18.7 8.1 190 P5 133 68.9 517 9.1 14.8 202 316 1,010 0.84 7.82 2,190

29.5 6.3 150 P5 135 56.8 392 7.1 12.2 225 264 871 0.67 7.42 1,870

P6 20.8 7 58 P6 79.9 40.5 51.2 1.2 2.28 122 3.49 318 0.27 10.6 580

22.2 7.1 11 P6 168 106 181 2.7 8.69 207 11 958 0.33 7.4 1,560

P7 22.7 7 120 P7 82.5 40.7 58.3 1.3 2.82 145 3.87 309 0.21 12 596

19.8 7.9 13 P7 168 87.8 165 2.6 9.72 188 8.92 913 0.35 3.42 1,470

22.8 8.8 18 P7 157 83.9 136 2.2 4.46 215 8.62 795 0.3 5.79 1,320

P8 21.4 5.9 960 P8 232 46.3 97.8 1.5 12.6 92 36.1 866 0.4 7.45 1,350

28.3 6.7 230 P8 140 70.5 532 9.2 15.7 194 326 1,060 0.87 8.51 2,270

21.9 8 170 P8 134 57.2 309 5.6 9.98 212 191 783 0.56 7.5 1,620

P9 24 5.6 1,000 P9 287 77.5 130 1.8 12.1 101 41.4 1,120 0.42 8.88 1,740

25 7.8 2,000 P9 82.7 37.4 171 3.9 8.49 132 68.9 510 0.76 7.04 966

21.4 7.7 460 P9 148 65.9 352 6 10.7 224 224 931 0.61 8.08 1,870

P10 13.6 8 4.3 P10 105 47.8 52.5 1.1 4.53 195 4.52 351 0.22 6.55 689

20.4 8.2 12 P10 168 101 159 2.4 9.75 261 6.02 878 0.3 7.19 1,490

15 10.3 4.2 P10 97.7 41.3 51.9 1.1 4.98 165 2.75 363 0.23 3.68 663

22.4 7.5 8.4 P10 68.3 28 38 1 2.56 141 2.55 236 0.14 4.82 467

P11 21.2 7.4 420 P11 206 59.8 143 2.3 9.54 132 61.8 867 0.39 6.64 1,430

21.1 7.2 7.6 P11 163 119 227 3.3 11.9 159 45.5 1,090 0.39 1.1 1,750

24 6.8 1690 P11 93.8 41.2 128 2.8 7.36 149 37.3 481 0.55 6.52 884

22.3 7.9 230 P11 135 59.2 302 5.5 9.16 205 191 808 0.52 6.63 1,630

P12 18.2 8 619 P12 79.9 36.1 118 2.8 4.17 153 59 350 0.28 7.21 747

23.5 6.9 NA P12 109 53.1 352 6.9 11 188 185 793 0.7 7.35 1,630

29 9.8 110 P12 141 79.4 331 5.5 10.5 200 169 996 0.49 6.47 1,850

P13 22.5 8.2 18 P13 130 59.3 188 3.4 6.54 198 72.9 608 0.31 9.86 1,190

27 9.5 3.3 P13 304 162 639 7.4 18.5 250 235 2,220 0.33 11.4 3,740

28 7.4 3 P13 190 102 428 6.2 13.4 219 179 1,290 0.5 11.5 2,340

26.5 8.1 100 P13 143 60.3 253 4.5 8.81 220 130 777 0.48 8.46 1,510

P14 20.8 11.2 2.8 P14 144 89.7 201 3.2 22.6 259 88.6 704 0.68 9.7 1,420

P15 13.6 7.5 120 P15 189 145 528 7 21.4 344 87.9 1,540 0.7 11.2 2,730

19.5 8.8 96 P15 131 83.7 337 5.6 15.9 280 83.5 1,080 0.61 7.06 1,910

25.8 10.3 14 P15 194 138 636 8.5 21.8 391 47.9 1,940 0.75 15.2 3,220

24.8 9.3 35 P15 158 104 508 7.7 19.6 367 38 1,520 0.63 10.4 2,570

P16 17.5 6.4 810 P16 152 84.8 354 5.7 22 246 52.2 1,240 0.86 7.51 2,060

21 6.8 23 P16 219 141 625 8.1 34 324 82.3 1,990 1.03 12.7 3,300

P17 28.5 5.8 22 P17 136 62.6 206 3.7 7.37 201 76.1 664 0.33 10.8 1,280

32.5 11.1 10 P17 164 97.8 466 7.1 16.2 236 119 1,400 0.56 13.3 2,420

P18 21.3 7.3 NA P18 94.9 35.3 165 3.7 5.56 185 65 488 0.32 11 977

22 7.9 3.6 P18 115 60.3 337 6.3 10.6 226 93.2 926 0.42 14 1,690

C3 21.3 5.3 4.8 C3 252 155 395 4.8 20 284 28.4 1,780 0.63 5.14 2,800

C4 14.3 8.1 41 C4 64.9 52.4 255 5.7 NA NA NA NA NA NA NA

C6 20.4 7.2 163 C6 323 132 970 11 11.1 281 108 2,750 0.52 8.35 4,460

20.4 7.8 37 C6 195 90.6 653 9.7 12.6 284 99 1,900 0.62 6.58 3,130

B1 16.6 8.1 3.8 B1 112 151 341 5 9.92 90 15.7 1,490 0.58 0.37 2,180
14 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Figure 4. Mean values for specific conductance, dissolved sodium, and alkalinity for the Tongue River and Powder 

River during ecological sampling events, Wyoming and Montana, 2005–08.

Other water-quality constituents are classified by the 

USEPA as nonpriority pollutants, which do not require criteria 

to be established. Nonpriority pollutants evaluated for this 

report include pH, chloride, aluminum, iron, and manganese. The USEPA has determined that results of toxicity and 

bioconcentration tests for total-chloride concentrations are 

essentially equivalent to results for dissolved-chloride concentrations (U.S. Environmental Protection Agency, 1988); 

therefore, dissolved-chloride concentrations were used for 

comparison in this report. The State of Wyoming has established acute and chronic chloride criteria for streams other 

than the Powder River downstream from Salt Creek. Because 

Salt Creek contributes high chloride concentrations to the 

Powder River, a site-specific criterion was established for 

the Powder River downstream from Salt Creek (Wyoming 

Department of Environmental Quality, 2007).

0

T1 T5 T9 T10 T14 T18

ALKALINITY, IN MILLIGRAMS PER LITER AS 

CALCIUM CARBONATE 

TONGUE RIVER SITE

0

P1 P2 P3 P4 P5 P8 P9 P11 P12 P13 P17 P18

POWDER RIVER SITE

0

100

200

300

400

500

600

700

800

SPECIFIC CONDUCTANCE, IN 

MICROSIEMENS

PER CENTIMETER

AT 25 DEGREES CELSIUS 

0

5

10

15

20

25

30

35

40

DISSOLVED SODIUM, IN MILLIGRA

MS PER LITER 

50

100

150

200

250

0

1,000

2,000

3,000

4,000

5,000

100

200

300

400

500

600

700

800

900

100

200

300

400

500

600

700

0
Assessment of Ecological Conditions 15

Table 4. State and Federal criteria for the protection of aquatic life.

[State of Wyoming criteria are listed in Wyoming Department of Environmental Quality (2007); State of Montana criteria are listed in Montana Department of 

Environmental Quality (2008); Federal criteria are listed in U.S. Environmental Protection Agency (2005); --, not available; concentrations for all consitutents 

in micrograms per liter, unless otherwise noted; mg/L, milligrams per liter]

Constituent

State of Wyoming State of Montana U.S. Environmental Protection Agency

Aquatic-life

acute value

Aquatic-life

chronic value

Aquatic-life

acute value

Aquatic-life

chronic value

Aquatic-life

acute value

Aquatic-life

chronic value

Priority pollutants

Arsenic, dissolved 340 150 -- -- 340 150

Arsenic, total -- -- 340 150 -- --

Cadmium, dissolved 12.0 1.25 -- -- 12.0 1.25

Cadmium, total -- -- 12.1 1.27 -- --

Chromium (III), dissolved 1569.8 174.1 -- -- 1570 174

Chromium (III), total -- -- 11,804 186 -- --

Chromium (VI), dissolved 16 11 -- -- 16 11

Chromium (VI), total -- -- 16 11 -- --

Copper, dissolved 113.4 19.0 -- -- 55.9 --

Copper, total -- -- 114 19.3 -- --

Lead, dissolved 164.6 12.5 -- -- 165 12.5

Lead, total -- -- 182 13.2 -- --

Mercury, dissolved 1.4 .77 -- -- 1.4 .77

Mercury, total -- -- 1.7 .91 -- --

Nickel, dissolved 1468.2 152.0 -- -- 1470 152

Nickel, total -- -- 1469 152.2 -- --

Selenium, dissolved 20 -- -- -- -- --

Selenium, total -- 5.0 20 5.0 (6) 5.0

Zinc, dissolved 1117.2 1118.1 -- -- 1120 1120

Zinc, total -- -- 1120 1120 -- --

Nonpriority pollutants

pH (standard units) -- 6.5–9.0 -- -- -- 6.5–9.0

Chloride, total(mg/L) 2860,000 2230,000 -- -- 860,000 230,000

Chloride, total(mg/L) 3984,000 -- -- -- -- --

Aluminum, dissolved 750 487 750 87 -- --

Aluminum, total -- -- -- -- 750 87

Iron, dissolved -- 1,000 -- -- -- --

Iron, total -- -- -- 1,000 -- 1,000

Manganese, dissolved 3,110 1,462 -- -- -- --

1

Value is hardness dependent. Value listed is for example only and is based on a hardness of 100 mg/L (as calcium carbonate).

2

Value applies to the Powder River upstream from Salt Creek and other streams.

3

Value applies to the Powder River downstream from Salt Creek.

4

Criterion only applies to samples with pH less than 7 and hardness less than 50 mg/L (as calcium carbonate).

5

Copper criteria have a complex formula; value listed is for sample pH of 8, hardness value of 40 mg/L (as calcium carbonate), and dissolved-organic carbon 

of 2–16 mg/L (U.S. Environmental Protection Agency, 2007).

6

The Federal aquatic-life acute criteria for selenium currently are under review (U.S. Environmental Protection Agency, 2004).

State of Wyoming Aquatic-Life Criteria

Water-quality constituents from 24 ATG study sites in 

Wyoming for water years 2005–08 were compared to State of 

Wyoming aquatic-life criteria (table 4). Concentrations of dissolved arsenic, dissolved cadmium, dissolved chromium (III), 

dissolved chromium (VI), dissolved copper, dissolved lead, total 

mercury, dissolved nickel, and dissolved zinc were less than 

aquatic-life acute and chronic criteria in all samples (table 5). 

Dissolved selenium concentrations were less than the acute 

criterion in all samples. Total selenium concentrations exceeded 

the chronic criterion in two samples collected from Caballo 

Creek (site B2) in the Belle Fourche River drainage basin.

A few samples had concentrations of nonpriority pollutants that were higher than aquatic-life criteria. One pH 

sample (9.8) for Porcupine Creek (site C1) in the Cheyenne 

River drainage basin was outside the chronic criterion range 

(table 5). Three samples from the Little Powder River above 

Dry Creek (site P15) had dissolved-chloride concentrations 

higher than the chronic criterion. Dissolved-chloride concentrations in all samples collected from sites on the Powder 

River downstream from Salt Creek were less than the sitespecific acute criterion for the Powder River. Dissolved-iron 

concentrations exceeded the chronic criterion in four samples 

from Antelope Creek (site C2) and seven samples from 
Table 5. Aquatic-life criteria comparison for water samples collected from study sites in the Powder River structural basin, Wyoming and Montana, [number of samples, number of samples greater than criterion or standard/total number of samples collected; --, not applicable] Constituent State of Wyoming State of Montana U.S. Environmen

Acute Chronic Acute Chronic Acute 

Number of samples Sites with exceedances Number of samples Sites with exceedances Number of samples Sites with exceedances Number of samples Sites with exceedances Number of samples Sites with exceedances 

Arsenic, dissolved 0/380 -- 0/380 -- -- -- -- -- 0/620 -- Arsenic, total -- -- -- -- 0/253 -- 0/253 -- -- -- Cadmium, dissolved 0/46 -- 0/46 -- -- -- -- -- 0/153 -- 

Cadmium, total -- -- -- -- 6/207 T19, P18 24/207 T19, P12, P18 -- -- Chromium (III), dissolved 0/3 -- 0/3 -- -- -- -- -- 0/35 -- 

Chromium (III), total -- -- -- -- 0/207 -- 4/207 T19, P18 -- -- 

Chromium (VI), dissolved 0/3 -- 0/3 -- -- -- -- -- 0/35 -- Chromium (VI), total -- -- -- -- 28/207 T19, P12, P18 36/207 T19, P12, P18 -- -- 

Copper, dissolved 0/43 -- 0/43 -- -- -- -- -- 5/150 T19 

Copper, total -- -- -- -- 24/207 T19, P12, P18 35/207 T9, T19, P12, P18 -- -- 

Lead, dissolved 0/44 -- 0/44 -- -- -- -- -- 0/151 -- 

Lead, total -- -- -- -- 7/207 T19, P18 36/207 T9, T19, P12, P18 -- -- 

Mercury, total 0/24 -- 0/24 -- 0/55 -- 0/55 -- 0/79 -- Nickel, dissolved 0/44 -- 0/44 -- -- -- -- -- 0/151 -- Nickel, total -- -- -- -- 2/207 T19 8/207 T19, P18 -- -- 

Selenium , dissolved 0/52 -- -- -- -- -- -- -- -- -- 

Selenium , total -- -- 2/382 B2 0/289 -- 1/289 P12 -- -- 

Zinc, dissolved 0/43 -- 0/43 -- -- -- -- -- 0/144 -- Zinc, total -- -- -- -- 11/207 T19, P12, P18 11/207 T19, P12, P18 -- -- pH 1/517 C1 -- -- -- -- -- -- 3/1,045 T11, T12, C1 

Chloride, dissolved 0/450 -- 3/450 P15 -- -- -- -- 2/1,001 P2 

Chloride, dissolved (Powder River) 0/27 -- -- -- -- -- -- -- -- -- 

Aluminum, dissolved 0/52 -- -- -- 0/136 -- 0/136 -- -- -- 

Aluminum, total -- -- -- -- -- -- -- -- 160/623 R1, R2, T1, T

T8, T9, T14, T17, T18, T19

P10, P12, P15

C1, C3, C5, C6, B1 

Iron, dissolved -- -- 11/380 C2, C3 -- -- -- -- -- -- 

Iron, total -- -- -- -- -- -- 111/232 R1, R2, T9, T14, 

T17, T18, T19, 

P12, P18

-- -- 

Manganese, dissolved 3/380 C2, B1 16/380 C2, C3, C6, B1 -- -- -- -- -- -- 
Assessment of Ecological Conditions 17

the Cheyenne River near Dull Center (site C3). Dissolvedmanganese concentrations exceeded the acute criterion in two 

samples from Antelope Creek (site C2) and one sample from 

the Belle Fourche River (site B1). Dissolved-manganese concentrations exceeded the chronic criterion in 10 samples from 

Antelope Creek (site C2), 3 samples from the Cheyenne River 

near Dull Center (site C3), 1 sample from the Cheyenne River 

near Spencer (site C6), and 2 samples from the Belle Fourche 

River (site B1).

State of Montana Aquatic-Life Criteria

Water-quality constituents from 23 ATG study sites in 

Montana for water years 2005–08 were compared to State of 

Montana aquatic-life criteria (table 4). Concentrations of total 

arsenic and total mercury were less than aquatic-life acute 

and chronic criteria in all samples (table 5).

Concentrations of other priority pollutants exceeded aquaticlife criteria in some samples. Total-cadmium concentrations 

exceeded acute criteria in four samples from Pumpkin Creek in 

the Tongue River drainage basin (site T19) and two samples from 

the Powder River near Locate (site P18). Total-cadmium concentrations exceeded chronic criteria that were calculated for seven 

samples from Pumpkin Creek (site T19); eight samples from the 

Powder River at Moorhead (site P12); and nine samples from the 

Powder River near Locate (site P18).

No samples had concentrations of chromium (III) higher 

than the applicable aquatic-life acute criteria (table 5). Totalchromium concentrations exceeded chromium (III) chronic 

criteria in three samples from Pumpkin Creek (site T19) and 

one sample from the Powder River near Locate (site P18). Totalchromium concentrations exceeded the chromium (VI) acute 

criterion in 5 samples from Pumpkin Creek (site T19), 10 samples 

from the Powder River at Moorhead (site P12), and 13 samples 

from the Powder River near Locate (site P18). Total-chromium 

concentrations exceeded the chromium (VI) chronic criterion in 

5 samples from Pumpkin Creek (site T19), 12 samples from the 

Powder River at Moorhead (site P12), and 19 samples from the 

Powder River near Locate (site P18); however, these comparisons 

assume that all of the chromium was present in the +6 valence 

state, which would not be typical for stream conditions.

Total-copper concentrations exceeded aquatic-life acute 

criteria in seven samples from Pumpkin Creek (site T19), eight 

samples from the Powder River at Moorhead (site P12), and 

nine samples from the Powder River near Locate (site P18, 

table 5). Total-copper concentrations exceeded chronic criteria 

in 1 sample from the Tongue River at State line (site T9), 8 

samples from Pumpkin Creek (site T19), 9 samples from the 

Powder River at Moorhead (site P12), and 17 samples from 

the Powder River near Locate (site P18).

Total-lead concentrations exceeded aquatic-life acute 

criteria that were calculated for samples in four samples from 

Pumpkin Creek (site T19) and three samples from the Powder 

River near Locate (site P18). Total-lead concentrations exceeded 

chronic criteria in 2 samples from the Tongue River at State line 

(site T9), 7 samples from Pumpkin Creek (site T19), 10 samples 

from the Powder River at Moorhead (site P12), and 17 samples 

from the Powder River near Locate (site P18).

Total-nickel concentrations exceeded acute criteria in 

two samples from Pumpkin Creek (site T19). Total-nickel concentrations exceeded chronic criteria that were calculated for 

samples in five samples from Pumpkin Creek (site T19) and 

three samples from the Powder River near Locate (site P18). 

No samples had a total-selenium concentration higher than 

the aquatic-life acute criterion. The total-selenium concentration exceeded the chronic criterion in one sample from the 

Powder River at Moorhead (site P12). Total-zinc concentrations exceeded aquatic-life acute and chronic criteria in six 

samples from Pumpkin Creek (site T19), one sample from the 

Powder River at Moorhead (site P12), and four samples from 

the Powder River near Locate (site P18).

For nonpriority pollutants, no samples had dissolvedaluminum concentrations higher than aquatic-life acute or chronic 

criteria. Total-iron concentrations exceeded the chronic criterion 

in 1 sample from upper Rosebud Creek (site R1), 6 samples from 

Rosebud Creek at mouth (site R2), 4 samples from the Tongue 

River at State line (site T9), 3 samples from the Tongue River 

at Birney Day School (site T14), 7 samples from Otter Creek 

at mouth (site T17), 2 samples from the Tongue River below 

Brandenberg Bridge (site T18), 8 samples from Pumpkin Creek 

(site T19), 40 samples from the Powder River at Moorhead 

(site P12), and 40 samples from the Powder River near Locate 

(site P18) (table 5).

Federal Aquatic-Life Criteria

Concentrations of dissolved arsenic, dissolved cadmium, dissolved chromium (III), dissolved chromium (VI), 

total mercury, dissolved nickel, and dissolved zinc were less 

than USEPA national recommended aquatic-life acute and 

chronic criteria in all samples (table 5). Five samples from 

Pumpkin Creek (site T19), with low hardness values, exceeded 

the applicable dissolved-copper acute criterion of 5.9 μg/L. 

Dissolved-lead concentrations in all samples were less than the 

USEPA national recommended aquatic-life acute and chronic 

criteria except for one sample from Pumpkin Creek (site T19) 

that exceeded the chronic criterion. Total-selenium concentrations exceeded the chronic criterion in one sample from the 

Powder River at Moorhead (site P12) and two samples from 

Caballo Creek (site B2).

Some samples had concentrations of nonpriority pollutants that exceeded aquatic-life criteria (table 5). Three measurements of pH, one at each of the upper Hanging Woman 

Creek (site T11), middle Hanging Woman Creek (site T12), 

and Porcupine Creek (site C1) sites, exceeded 9.0 standard 

units. Dissolved-chloride concentrations exceeded the acute 

criterion in two samples from Powder River below Salt Creek 

(P2). Dissolved-chloride concentrations exceeded the chronic 

criterion in three samples from the Powder River below 

Salt Creek (P2), four samples from the Powder River above 
18 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Pumpkin Creek (site P3), three samples from the Powder 

River below Burger Draw (site P4), three samples from the 

Powder River above Crazy Woman Creek (site P5), two samples from the Powder River below Crazy Woman Creek (P8), 

one sample from the Powder River at Moorhead (site P12), 

one sample from the Powder River at Broadus (site P13), 

and three samples from the Little Powder River above Dry 

Creek (site P15). Unlike the States of Wyoming and Montana, 

the USEPA national recommended aquatic-life criteria for 

aluminum are based on total concentrations. Total-aluminum 

concentrations exceeded the chronic criterion, acute criterion, or both (table 5) at all 21 sites that had analyses for total 

aluminum (sites R1, R2, T1, T2, T8, T9, T13, T14, T17, T18, 

T19, P10, P12, P15, C1, C2, C3, C5, C6, B1, and B2). Totaliron concentrations exceeded the chronic criterion at 13 of the 

14 sites that had analyses for total iron (sites R1, R2, T1, T2, 

T8, T9, T14, T17, T18, T19, P12, P15, and P18).

Habitat

Among all sites, embeddedness of the substrate, measured in conjunction with macroinvertebrate sampling in 

riffles during 2005–08, ranged from 0 to 74 percent (table 3). 

The values for embeddedness and other microhabitat data—

water depth, velocity, and coarse substrate (fraction of gravel 

or larger size particles)—listed in table 3 represent mean 

values from five points accompanying each macroinvertebrate 

sample. Among all sites, microhabitat substrate ranged from 

50 percent to 100 percent coarse substrate during 2005–08.

Pebble counts indicated a wide variation in particle 

size percentiles among sites during 2007–08. For example, 

the D84, or diameter of the 84th percentile of particles, ranged 

from 5.3 to 138 millimeters (mm) (table 3). Pebble-count 

data for the D50, or diameter of the 50th percentile (median) 

of particles, and the percentage less than 2 mm (smallest size 

measured) also are listed in table 3. The pebble-count data 

were collected from transects bankfull to bankfull across 

riffles according to methods by Wolman (1954) and therefore represent a slightly different aspect of the riffles than 

the microhabitat substrate measurements that were collected 

at an average depth of 0.4 feet (ft; 0.11 meter) in riffles 

according to methods by Moulton and others (2002). The 

microhabitat and pebble-count data were collected as indicators of physical variables potentially affecting macroinvertebrate communities.

Macroinvertebrate Communities

Macroinvertebrate taxonomic data from 2005–08 are 

available at: http://wy.water.usgs.gov/projects/atg/htms/

data.htm. Most of the taxa identified were Chironomidae 

(midges:Diptera), Ephemeroptera (mayflies), and Trichoptera 

(caddisflies). Other identified taxa, though generally rarer, 

included Coleoptera (beetles), noninsects (such as worms: 

Oligochaeta, and snails:Gastropoda), Odonata (dragonflies and 

damselflies), and Plecoptera (stoneflies). The total number of 

taxa (taxa richness) in the ATG samples ranged from 5 taxa in 

Pumpkin Creek (site T19, 2005) to 47 taxa in Hanging Woman 

Creek (site T11, 2005) (table 6).

Macroinvertebrate Community Composition

Three stream groups of sites with relatively similar 

taxonomic composition were identified: Tongue River 

main stem and mountainous tributaries (TRMS), Tongue 

River plains tributaries (TRPT), and Powder River main 

stem (PRMS). NMDS ordinations for 2007–08 (fig. 5) and 

2005–06 (Peterson and others, 2009) indicated the same 

general stream groups for all 4 years of sampling, with a few 

sites that were sometimes outliers. The TRMS group generally contained sites sampled on the main-stem Tongue River 

(sites T1, T5, T9, T10, T14, and T18) and tributaries originating in the Bighorn Mountains: Goose Creek (site T2), Crazy 

Woman Creek (sites P6 and P7), and Clear Creek (site P10). 

The TRPT group generally contained sites on Youngs Creek 

(sites T3 and T4), Squirrel Creek (site T7), Prairie Dog Creek 

(site T8), Hanging Woman Creek (sites T11–T13), Otter Creek 

(sites T16 and T17), and Pumpkin Creek (site T19). Prairie 

Dog Creek (site T8) plotted with the TRMS group although 

the headwaters are in the plains (table 1). The PRMS group 

generally contained sites P1–P5, P8, P9, P11–P13, P17, and 

P18. Sampling sites on Rosebud Creek (site R2), the Little 

Powder River (sites P14–P16), the Cheyenne River drainage 

basin (sites C3, C4, and C6), and the Belle Fourche River 

(site B1) tended to be outliers to the stream groups. Some of 

the sites, particularly the outliers, are not shown in figure 5 

because they were sampled only in 2005 or 2006 (Peterson 

and others, 2009).

Taxa richness at sites in the TRMS group ranged from 

17 to 41 taxa per sample during 2005–08 (table 6), with a 

mean of 29 taxa per sample. Diptera, Ephemeroptera, and 

Trichoptera dominated in terms of taxa richness, although 

on the average, relative abundance was dominated by 

Ephemeroptera (46 percent), Trichoptera (21 percent), and 

Diptera (12 percent). Ephemeroptera taxa richness and relative 

abundance of Ephemeroptera individuals tended to be higher 

at sites in the TRMS group than in the TRPT or PRMS groups 

(fig. 6). The Ephemeroptera Baetis, Fallceon quilleri, and

Tricorythodes were the most abundant macroinvertebrates in 

the TRMS group. The most common functional feeding mode 

at sites in the TRMS group was the collector-gatherers (mean 

of 59 percent), with smaller proportions of filter-collectors 

(mean of 26 percent) and scrapers (mean of 9 percent). Other 

functional feeding modes such as predators and omnivores 

accounted for the remainder. The proportion of intolerant 

macroinvertebrates averaged 53 percent and generally was 

higher in the TRMS group than the TRPT or PRMS groups 
Assessment of Ecological Conditions 19

(fig. 6). The 2007 sample from the main-stem Tongue River 

above Hanging Woman Creek (site T10) was an outlier to the 

TRMS group in the ordination (fig. 5) because the community 

was composed primarily of noninsects and Diptera, such as the 

snail Physa, the scud Hyallela, and the blackfly Simulium that 

are tolerant organisms (2 percent intolerant, table 6). Site T10 

plotted within ordinations of the TRMS group during 2005–06 

(Peterson and others, 2009) and 2008. The macroinvertebrate communities at site T10 might be affected by Tongue 

River Reservoir upstream as noted in the section “Spatial and 

Temporal Patterns.”

Taxa richness at sites in the TRPT group was dominated by Diptera, with a mean of 16 Diptera taxa compared 

to a mean of 30 taxa total per sample during 2005–08. The 

Diptera also predominated in terms of relative abundance 

(table 6), accounting for an average of 52 percent of the 

macroinvertebrates. Although most of the Diptera taxa were 

Chironomidae, the blackfly larvae Simulium were common and sometimes numerically dominant. Trichoptera 

larvae, such as Cheumatopsyche and Hydropsyche, also were 

abundant in some of the TRPT samples. Macroinvertebrate 

communities in the TRPT group were characterized by distinctively lower relative abundance of intolerant macroinvertebrates than the TRMS or PRMS groups (fig. 6).

Taxa richness in the PRMS group ranged from 9 to 38 

taxa and averaged 22 taxa per sample. Taxa richness in the 

PRMS group tended to be lower than in the TRMS or TRPT 

groups (fig. 6). Diptera dominated the taxa richness (average of 9 taxa per sample) and relative abundance (average 

of 45 percent per sample) of the PRMS group. The proportion 

of filterer-collectors was relatively high in the PRMS group, 

due in part to the dominance of the blackfly larvae Simulium

in many of the samples. Macroinvertebrate communities in the 

PRMS group tended to be intermediate to those of the TRMS 

and TRPT groups in terms of Ephemeroptera taxa richness, 

relative abundance of Ephemeroptera, and relative abundance 

of intolerant macroinvertebrates.

Taxa richness in macroinvertebrate communities of 

the Little Powder River (sites P14–P16) was dominated by 

Diptera, whereas Trichoptera predominated in terms of relative 

abundance (table 6). Communities of the Little Powder River 

also were characterized by high relative abundance of filterercollectors and low relative abundance of intolerant macroinvertebrates. Communities at sites on Rosebud Creek 

(sites R1 and R2) and in the Cheyenne (sites C1–C6) and Belle 

Fourche River (B1 and B2) drainage basins were characterized 

by low taxa richness, high proportions of filterer-collectors, 

and low proportions of intolerant macroinvertebrates; Diptera 

and noninsects often predominated in terms of taxa richness 

and relative abundance (table 6). Intermittent flow conditions, 

such as in the Cheyenne and Belle Fourche River drainage 

basins, and high specific-conductance values and flooding 

common to plains streams (Wangsness and Peterson, 1980) 

create a harsh environment for macroinvertebrate communities, regardless of anthropogenic effects.

Spatial and Temporal Patterns

Data from the main-stem Tongue River and main-stem 

Powder River were analyzed using ANOVA to examine spatial 

patterns, such as differences by site in the downstream direction, 

and temporal patterns, which were differences by year. A brief 

discussion of spatial and temporal patterns at sites on tributaries 

also is presented, but the tributaries did not have sufficient data 

for analysis using ANOVA. Therefore, the site groupings in this 

section are slightly different from the groupings used to describe 

macroinvertebrate community composition.

Main-Stem Tongue River

Results of ANOVA using the Tukey method for analysis of 

metric data from main-stem Tongue River sites T1, T5, T9, T10, 

T14, and T18 are listed in table 7. Macroinvertebrate community metrics did not vary significantly among main-stem Tongue 

River sites, with one exception. During 2005–08, the relative 

abundance of noninsects in the Tongue River above Hanging 

Woman Creek (site T10) was significantly different (p < 0.05) 

from that of the Tongue River at sites T9, T14, and T18. As 

shown in figure 7, the mean relative abundance of noninsects 

during 2005–08 was higher at site T10 (about 16 percent) than 

at other sites on the main-stem Tongue River (4 percent or 

less). The macroinvertebrate communities at site T10 might be 

affected by Tongue River Reservoir, which is on the main-stem 

Tongue River about 9 air-miles upstream from site T10. The 

mean relative abundance of Trichoptera decreased from site T1 

to site T9 (fig. 7).

The ANOVA also indicated significant variation (p < 0.05) 

between years in the relative abundance of macroinvertebrates in 

the scraper feeding mode (table 7). The mean relative abundance 

of scrapers was higher in 2006 than other years (fig. 7). Though 

not significant at p < 0.05, the proportion of intolerant macroinvertebrates also was higher in 2006 (mean 72 percent) than in 

other years (mean 44–52 percent; fig. 7). The extended drought 

that was particularly severe in 2006 might be at least partly 

responsible for year-to-year differences in the metric values.

Main-Stem Powder River

Macroinvertebrate community metrics on the mainstem Powder River indicated differences at sites in the middle 

reach from other sites on the main-stem Powder River. The 

ANOVA tests indicated one or more metrics varied significantly 

(p < 0.05) at sites P3–P5 and P8 (the middle reach, from below 

the Willow Creek to below the Crazy Woman Creek confluences) from metrics at sites P9, P11, P12, P13, and P18 (the 

lower reach) from above the confluence with Clear Creek to 

Locate, Mont.; table 7). Graphical presentation of the mean 

values during 2005–08 for five metrics (fig. 8) shows that values 

from the middle reach (sites P3–P5 and P8) and to a lesser 

extent, site P2, were notably different than values at other sites 

on the main-stem Powder River both upstream (site P1) and 
20 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Table 6. Macroinvertebrate community metrics for streams in the Powder River structural basin, Wyoming and Montana, 2005–08.

—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. %, percent]

Site

number

(fig. 1)

Abbreviated site name Sample

date

Taxa richness

Total Ephemeroptera 

richness

Trichoptera 

richness

Diptera

richness

R2 Rosebud Creek at mouth 9/15/2005 28 4 2 9

T1 Tongue River at Monarch 8/15/2005 35 8 8 7

8/23/2006 34 7 7 10

8/29/2007 27 6 8 4

T2 Goose Creek 8/17/2005 26 8 4 6

8/22/2006 29 6 4 11

9/11/2007 32 8 5 6

8/4/2008 23 7 3 6

T3 Upper Youngs Creek 6/15/2005 35 1 6 15

6/28/2006 37 2 5 17

6/21/2007 30 2 3 15

6/26/2008 40 2 6 20

T4 Youngs Creek at mouth 6/14/2005 39 2 2 22

6/27/2006 35 2 3 19

T5 Tongue River below Youngs Creek 8/15/2005 30 7 4 9

8/22/2006 32 7 6 9

8/29/2007 32 8 6 10

8/21/2008 30 11 5 8

T7 Squirrel Creek at mouth 6/13/2005 39 2 1 25

7/12/2007 29 4 3 18

6/25/2008 12 1 2 8

T8 Prairie Dog Creek 8/25/2006 28 2 5 12

9/11/2008 25 6 5 5

T9 Tongue River at State line 9/14/2005 31 5 7 13

8/24/2006 33 6 5 9

8/28/2007 29 11 3 10

8/21/2008 28 9 4 8

T10 Tongue River above Hanging Woman Creek 8/16/2005 31 6 5 9

8/28/2006 24 4 4 6

8/28/2007 41 3 1 19

9/9/2008 30 7 8 4

T11 Upper Hanging Woman Creek 6/22/2005 47 1 0 33

7/11/2007 28 1 3 12

T12 Middle Hanging Woman Creek 6/21/2005 44 2 2 23

7/10/2007 31 4 2 19

T13 Hanging Woman Creek at mouth 6/23/2005 40 3 0 21

7/10/2007 35 4 3 18

6/27/2008 34 2 0 22

T14 Tongue River at Birney Day School 9/12/2005 24 7 6 5

8/28/2006 30 9 6 7

8/27/2007 32 9 9 7

8/21/2008 32 7 8 8

T16 Middle Otter Creek 6/20/2007 8 0 1 5

T17 Otter Creek at mouth 6/30/2005 31 1 3 16

6/28/2006 26 2 4 13

6/24/2008 31 1 4 17

T18 Tongue River below Brandenberg Bridge 9/13/2005 30 7 5 11

8/31/2006 38 10 8 11

8/27/2007 23 10 3 6

T19 Pumpkin Creek 6/23/2005 5 0 1 4

6/18/2007 9 1 2 6

P1 Powder River above Salt Creek 7/20/2005 38 7 3 24

7/24/2006 34 7 3 19

8/30/2007 17 5 4 4
Assessment of Ecological Conditions 21

Table 6. Macroinvertebrate community metrics for streams in the Powder River structural basin, Wyoming and Montana, 2005–08.

—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. %, percent]

Site

number

(fig. 1)

Taxa relative abundance Functional feeding mode relative abundance Tolerance

Ephemeroptera 

abundance

(%)

Trichoptera 

abundance

(%)

Diptera

abundance

(%)

Noninsect 

abundance

(%)

Collectorgatherer

abundance

(%)

Filterercollector

abundance

(%)

Scraper

abundance

(%)

Intolerant 

macroinvertebrates 

(%)

R2 2 19 15 14 23 19 39 4

T1 76 14 2 3 79 12 4 26

32 33 10 3 51 12 26 49

53 39 4 2 49 39 9 41

T2 57 16 2 10 72 15 5 41

42 7 7 1 75 6 12 47

54 29 5 4 57 29 8 56

50 29 17 1 51 44 2 38

T3 34 3 47 11 44 50 3 7

37 33 9 5 58 34 5 31

37 5 44 5 52 39 0 9

29 30 23 10 45 34 7 30

T4 12 7 30 41 57 19 10 1

6 15 27 45 52 30 11 1

T5 44 30 5 2 62 31 4 54

25 17 6 12 61 15 18 69

41 24 7 0 63 24 6 70

68 14 13 1 69 21 4 48

T7 1 1 79 15 59 25 4 0

2 4 85 9 4 64 1 4

4 1 95 0 4 95 0 0

T8 20 32 10 0 48 35 13 56

7 79 2 1 15 80 2 87

T9 69 14 12 0 74 17 3 28

39 13 4 9 71 11 7 79

85 3 11 1 78 5 10 43

64 7 10 0 78 8 8 51

T10 26 19 17 12 56 15 19 38

7 10 3 9 77 12 10 85

11 0 36 36 38 21 20 2

60 12 17 7 64 24 4 53

T11 0 0 65 24 58 4 19 0

47 4 25 22 71 19 2 2

T12 4 4 36 48 40 7 29 2

9 32 42 16 20 36 8 35

T13 2 0 32 56 38 12 31 1

6 3 75 6 29 25 5 12

8 0 68 19 22 47 18 0

T14 67 26 1 0 66 26 7 72

46 36 3 0 48 37 12 82

63 17 11 1 68 17 12 74

34 28 21 1 51 40 3 50

T16 0 0 100 0 1 99 0 0

T17 1 51 41 3 9 79 3 3

0 23 69 7 7 90 1 11

0 48 42 4 11 77 5 35

T18 39 37 16 0 40 38 7 48

55 23 4 0 58 20 18 69

82 10 3 0 73 11 11 83

T19 0 0 100 0 0 99 0 0

0 3 97 0 0 99 0 1

P1 18 28 48 4 46 33 6 30

32 26 36 1 50 37 1 38

20 68 5 0 24 71 2 31
22 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Table 6. Macroinvertebrate community metrics for streams in the Powder River structural basin, Wyoming and Montana, 2005–08.

—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. %, percent]

Site

number

(fig. 1)

Abbreviated site name Sample

date

Taxa richness

Total Ephemeroptera 

richness

Trichoptera 

richness

Diptera

richness

P2 Powder River below Salt Creek 7/21/2005 20 4 3 12

7/25/2006 33 4 3 21

8/30/2007 35 6 5 18

P3 Powder River below Willow Creek 7/19/2005 21 5 1 12

7/26/2006 28 4 4 13

8/24/2007 21 3 3 12

7/21/2008 9 1 2 4

P4 Powder River below Burger Draw 7/22/2005 17 4 2 9

7/27/2006 24 1 4 14

8/22/2007 10 3 2 3

7/23/2008 10 1 2 6

P5 Powder River above Crazy Woman Creek 7/13/2005 16 5 2 6

7/28/2006 21 5 4 9

8/23/2007 18 4 3 7

7/24/2008 9 3 2 3

P6 Crazy Woman Creek below I-90 7/11/2005 34 8 4 12

8/20/2007 25 4 5 5

P7 Crazy Woman Creek near mouth 7/12/2005 17 6 3 4

8/21/2007 28 5 4 12

8/20/2008 26 7 3 12

P8 Powder River below Crazy Woman Creek 7/23/2005 34 4 2 24

8/21/2007 17 4 2 6

7/25/2008 16 7 1 5

P9 Powder River above Clear Creek 7/24/2005 32 6 1 21

7/26/2007 34 10 4 12

7/29/2008 23 9 2 7

P10 Clear Creek 9/13/2005 17 6 4 3

8/21/2006 34 5 6 12

9/10/2007 31 5 4 15

8/5/2008 28 9 5 9

P11 Powder River below Clear Creek 7/25/2005 26 12 3 6

8/3/2006 24 3 4 9

P11 Powder River below Clear Creek 7/26/2007 29 8 5 10

7/30/2008 21 12 2 4

P12 Powder River at Moorhead 7/26/2005 29 7 5 13

7/26/2007 20 7 3 7

7/30/2008 21 8 3 4

P13 Powder River at Broadus 7/19/2005 10 5 1 3

8/2/2006 28 4 6 12

7/25/2007 18 7 3 4

7/31/2008 12 6 2 2

P14 Little Powder River at Highway 59 8/8/2007 29 1 2 10

P15 Little Powder River above Dry Creek 6/13/2005 12 2 2 6

6/23/2006 29 2 4 15

8/7/2007 19 4 3 8

8/18/2008 21 3 2 8

P16 Little Powder River at Biddle 6/27/2005 37 2 3 22

8/9/2007 26 4 3 11

P17 Powder River below Little Powder River 7/21/2005 20 6 3 8

7/25/2007 26 9 3 8

P18 Powder River near Locate 7/22/2005 9 4 2 2

7/24/2007 14 4 3 3

C3 Cheyenne River near Dull Center 6/27/2005 28 2 2 18

C4 Little Thunder Creek 6/9/2005 16 1 0 11

C6 Cheyenne River near Spencer 6/6/2005 18 1 1 12

6/15/2007 7 0 0 7

B1 Belle Fourche River 6/29/2005 17 1 1 8
Assessment of Ecological Conditions 23

Table 6. Macroinvertebrate community metrics for streams in the Powder River structural basin, Wyoming and Montana, 2005–08.

—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. %, percent]

Site

number

(fig. 1)

Taxa relative abundance Functional feeding mode relative abundance Tolerance

Ephemeroptera 

abundance

(%)

Trichoptera 

abundance

(%)

Diptera

abundance

(%)

Noninsect 

abundance

(%)

Collectorgatherer

abundance

(%)

Filterercollector

abundance

(%)

Scraper

abundance

(%)

Intolerant 

macroinvertebrates 

(%)

P2 9 5 86 0 13 59 3 3

6 10 83 0 57 29 0 10

20 44 26 2 29 52 2 16

P3 16 10 74 0 12 76 7 16

14 57 26 1 18 73 1 19

5 59 35 0 8 90 0 5

0 10 89 0 0 98 0 2

P4 9 46 45 0 12 71 0 14

1 36 56 5 5 78 5 8

3 2 94 0 4 96 0 4

0 4 95 0 1 99 0 1

P5 12 18 69 1 13 85 0 15

8 59 20 0 17 64 1 31

6 50 42 1 9 84 1 7

1 2 97 0 1 99 0 1

P6 53 23 15 5 59 32 4 31

14 32 2 1 53 31 10 49

P7 5 6 86 0 6 92 0 4

23 45 13 2 36 46 4 30

37 37 22 0 37 45 3 36

P8 6 20 70 3 24 51 0 9

2 9 88 1 2 95 0 2

4 2 89 1 4 90 1 5

P9 11 4 80 2 21 31 1 10

62 22 11 1 62 27 2 61

60 4 34 0 59 32 1 59

P10 74 20 0 0 79 20 1 94

18 42 9 4 45 42 9 74

60 10 14 4 69 12 5 73

43 21 7 1 57 21 14 63

P11 49 32 16 0 40 49 10 52

5 67 11 3 23 69 3 37

P11 59 28 5 2 64 27 4 57

53 23 16 1 52 39 8 66

P12 34 32 29 3 37 49 3 30

69 5 23 0 69 23 3 66

38 5 55 1 38 57 1 41

P13 66 1 33 0 66 34 0 66

15 55 27 2 24 54 6 19

51 26 20 0 54 42 1 55

56 4 39 0 55 44 0 55

P14 6 8 7 58 64 12 10 18

P15 1 2 95 0 2 96 0 1

1 91 4 1 3 91 1 15

2 88 8 1 3 91 0 7

8 73 13 0 10 79 1 10

P16 3 47 36 2 13 58 8 7

38 23 26 3 39 28 7 34

P17 59 18 21 0 69 26 1 61

20 36 40 1 23 65 2 22

P18 74 7 19 0 74 25 0 74

21 73 3 0 19 77 0 26

C3 3 0 44 51 35 18 42 0

C4 1 0 98 1 3 95 0 0

C6 0 0 98 1 2 94 1 0

0 0 100 0 8 48 0 0

B1 0 1 78 19 20 77 0 1
24 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Figure 5. Similarities of macroinvertebrate community taxonomic composition within stream groups depicted by nonmetric 

multidimensional scaling ordinations, Powder River structural basin, Wyoming and Montana, 2007–08.

C6

P1

P10

P11

P12

P13

P14

P15

P16

P17

P18

P2

P3

P4

P5

P6

P7

P8

P9

T1

T10

T11

T13

T14

T16

T18

T2

T3

T5

T7

T7R

T9

P10

P11

P12

P13

P15

P3

P4

P5

P7

P8

P9R

P9

T10

T13

T14

T17

T2

T3

T3S

T5

T7

T8

T9

Stream

EXPLANATION

Tributary

Powder River

 main stem

Tongue River

 main stem

Replicate

Split

R

S

Powder River 

main-stem group

Tongue River main-stem and 

mountainous tributaries group

Tongue River plains 

tributaries group

Powder River 

main-stem group Tongue River main-stem and 

mountainous tributaries group

Tongue River plains 

tributaries group

2007

2008

–1.5

–1

–0.5

0

NONMETRIC MULTIDIMENSIONAL SCALING AXIS 1

NONMETRIC MULTIDIMENSIONAL SCALING AXIS 2

0.5

1 T19

1.5

2

–3 –2.5 –2 –1.5 –1 –0.5 0 0.5 1 1.5 2

T12

–1.5

–1

–0.5

0

NONMETRIC MULTIDIMENSIONAL SCALING AXIS 2

0.5

1

1.5

2
Assessment of Ecological Conditions 25

Figure 6. Selected macroinvertebrate community metrics by stream group, Powder River structural basin, Wyoming and Montana, 2005–08.

0

20

40

60

80

EPHEMEROPTERA ABUNDANCE, IN PERCENT

TRMS TRPT PRMS

0

10

20

30

40

50

TAXA RICHNESS

0

2

4

6

8

10

12

EPHEMEROPTERA TAXA RICHNESS

0

20

40

60

80

100

FILTERER-COLLECTOR ABUNDANCE, IN PERCENT

0

20

40

60

80

100

INTOLERANT MACROINVERTEBRATES, IN PERCENT

TRMS TRPT PRMS

TRMS TRPT PRMS

TRMS TRPT PRMS

TRMS TRPT PRMS

Tongue River main stem and mountainous tributaries group (35 samples)

EXPLANATION 

Data value less than or equal to 1.5 times the interquartile range 

 outside the quartile

75th percentile

Median

25th percentile

TRMS

TRPT Tongue River plains tributaries group (24 samples)

PRMS Powder River main-stem group (39 samples) 

Interquartile range

Outlier data value greater than 1.5 times the interquartile range 

 outside the quartile
26 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Table 7. Analysis of variance in macroinvertebrate community metrics, main-stem Tongue River and main-stem Powder River, 

Wyoming and Montana, 2005–08.

[Significance tested by Tukey method at probability level less than 0.05]

Metric

Main-stem Tongue River

(sites T1, T5, T9, T10, T14, and T18)

Main-stem Powder River

(sites P1-P5, P8, P9, P11-P13, P17, P18)

Significant differences

between sites

Significant differences

between years

Significant differences

between sites

Significant differences

between years

Taxa richness None None None 2006 to 2008

Ephemeroptera taxa richness None None P4 to P9, P4 to P11, 

P4 to P12

None

Trichoptera taxa richness None None None 2005 to 2006, 

2005 to 2007, 

2006 to 2008, 

2007 to 2008

Diptera taxa richness None None None 2005 to 2008, 

2006 to 2007, 

2006 to 2008

Ephemeroptera relative abundance None None P4 to P9, P4 to P12, 

P4 to P13, P4 to P18, 

P8 to P12, P8 to P13

None

Trichoptera relative abundance None None None 2006 to 2008, 

2007 to 2008

Diptera relative abundance None None P4 to P11, P8 to P11, 

P8 to P18

None

Noninsect relative abundance T10 to T9, T10 to T14, 

T10 to T18

None None None

Dominant taxa percent None None None None

Collector-gatherer relative abundance None None P3 to P13, P4 to P9, 

P4 to P11, P4 to P12, 

P4 to P13, P5 to P13

None

Filterer-collector relative abundance None None P3 to P9, P4 to P9, 

P5 to P9

None

Scraper relative abundance None 2006 to 2008 None None

Intolerant relative abundance None None P3 to P11, P4 to P11, 

P4 to P12, P4 to P13, 

P8 to P11, P8 to P13

None

downstream (sites P9, P11–P13, P17, and P18). Metric values for Ephemeroptera taxa richness, Ephemeroptera relative 

abundance, and intolerant macroinvertebrate relative abundance 

tended to be lower, whereas Diptera relative abundance and 

filterer-collector relative abundance tended to be higher, at sites 

P3–P5 and P8 than at other sites on the main-stem Powder 

River (fig. 8). The affected metrics included measures of taxa 

richness, taxa relative abundance, feeding modes, and tolerance, 

which were indicative of communitywide differences.

Taxa richness, Trichoptera taxa richness, Diptera taxa 

richness, and relative abundance of Trichoptera varied significantly (p < 0.05) by year during 2005–08 (table 7). As shown 

in figure 8, using Diptera taxa richness as an example, the 

metric values in 2006 were higher than in 2005 and 2007–08. 

Taxa richness and the Trichoptera metrics also were higher 

in 2006 than the other years. As noted for the main-stem 

Tongue River, the extended drought and severe low-flow 

conditions in 2006 might be at least partly the cause of the 

year-to-year variation in metric values from the main-stem 

Powder River.

Tributaries

Macroinvertebrate communities at sites on tributaries 

sometimes showed variation between 2006 and other years 

(2005, 2007–08) that resembled the patterns observed on the 

Tongue River and Powder River. For example, metrics with 

higher values in 2006 than other years included Diptera taxa 

richness and scraper abundance in Goose Creek (site T2), taxa 

richness and Trichoptera abundance in Clear Creek (site P10), 

and taxa richness and Diptera richness in the Little Powder 

River (site P15; table 6). Comparison of metrics from upper 

Youngs Creek (site T3) to lower Youngs Creek (site T4) 

indicated lower relative abundance of Ephemeroptera and 

higher relative abundance of noninsects at the lower site 

compared to the upper site, but these data should be used with 

caution because only 2 years (2005–06) of data were available from site T4 and may reflect natural spatial variation 

with lower elevation and increased drainage area. Metrics for 

the lower site on Squirrel Creek (site T7) indicated relatively 

low taxa richness in 2008 compared to 2005 and 2007. The 
Assessment of Ecological Conditions 27

Figure 7. Mean values for selected macroinvertebrate community metrics by site and by year, main-stem Tongue River, Wyoming 

and Montana, 2005–08.

macroinvertebrate communities at site T7 might be affected 

by intermittent streamflow. The upper site on Squirrel Creek 

(site T6) did not have sufficient riffle habitat for sampling; 

therefore, no metric data are available for comparison with 

the lower site. Interpretation of data from other tributaries, 

such as Crazy Woman Creek, Hanging Woman Creek, and 

Otter Creek is limited by the small number of samples available and variability in community composition, which in turn 

might be related to intermittent streamflow at some of the sites 

and natural spatial variation.

Effects of Environmental Variables 

on Macroinvertebrate Communities

Analysis of environmental variables during 2005–08 

(table 3) indicated grouping of sites, similar to the TRMS, TRPT, 

and PRMS stream groups observed for the macroinvertebrate 

communities. The PCA ordination of sites and environmental 

variables from 2007 is shown in figure 9 as an example. Sites on 

the main-stem Tongue River tended to group along the right side 

of the ordination (positive correlation with principal components 

0

2

4

6

8

10

12

14

16

18

MEAN RELATIVE

ABUNDANCE OF NONINSECTS, IN PERCENT 

0

5

10

15

20

25

30

MEAN RELATIVE

ABUND

ANCE OF TRICHOPTER

A, IN PERCENT 

0

2

4

6

8

10

12

14

16

MEAN RELATIVE

ABUND

ANCE OF SCRAPER FEEDING MODE, IN PERCENT

ME

AN RELATIVE

ABUND

ANCE OF INTOLERANT

MACROINVERTEBRATES, IN PERCENT 

T1 T5 T9 T10 T14 T18

SITE SITE

T1 T5 T9 T10 T14 T18

2005 2006 2007 2008

0

10

20

30

40

50

60

70

80

2005 2006 2007 2008

YEAR YEAR
28 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Figure 8. Mean values for selected macroinvertebrate metrics by site and by year, main-stem Powder River, Wyoming and 

Montana, 2005–08.

0

1

2

3

4

5

6

7

8

9

10

MEAN EPHEMEROPTER

A TAXA RICHNESS 

0

10

20

30

40

50

60

MEAN RELATIVE

ABUND

ANCE OF EPHEMEROPTER

A,

IN PERCENT 

0

10

20

30

40

50

60

70

80

90

MEAN RELATIVE

ABUNDANCE OF DIPTER

A, IN PERCENT 

0

10

20

30

40

50

60

70

80

90

100

MEAN REL

ATIVE

ABUND

ANCE OF FILTERER COLLECTORS,

IN PERCENT 

-

0

10

20

30

40

50

60

P1 P2 P3 P4 P5 P8 P9 P11 P12 P13 P17 P18

MEAN RELATIVE

ABUNDANCE OF INTOLERANT

M

ACROINVERTEBRATES, IN PERCENT

SITE

0

2

4

6

8

10

12

14

16

2005 2006 2007 2008

MEAN DIPTERA TAXA RICHNESS

YEAR

P1 P2 P3 P4 P5 P8 P9 P11 P12 P13 P17 P18

SITE
Assessment of Ecological Conditions 29

Figure 9. Principal components ordination showing relations among sampling sites based on selected environmental 

variables, Powder River structural basin, Wyoming and Montana, 2007.

Particle diameter, 84th percentile

Streamflow

Specific conductance

Fluoride

Alkalinity

Turbidity

Water temperature

Embeddedness

Substrate

Silica

pH

−4 −2 0 2 4

PRINCIPAL COMPONENTS AXIS 1

−4

−2

0

2

4

T7

PRINCIPAL COMPONENTS AXIS 2

T1

T2

T5

T7

T9

T10

T11

T12

T13

T14

T16

T18

T19

P1

P2

P3

P4

P5

P7

P8

P9

P10

P11

P12

P13,P14

P15

P16

P17

T3,P18,P6

C6

Site groups

Tongue River main stem and mountainous tributaries

Tongue River plains tributaries

Powder River main stem

Not assigned

EXPLANATION 

T13

T18

P9

C6
30 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Table 8. Environmental variables best correlated with 

macroinvertebrate community taxonomic composition, by stream 

group and year, Powder River structural basin, Wyoming and 

Montana, 2005–08.

[D84, diameter of the 84th percentile of particles]

Year

Spearman 

correlation 

coefficient

Environmental variables

Main-stem Tongue River

2005 0.52 Streamflow, specific conductance, 

dissolved oxygen

2006 0.21 Streamflow

2007 0.89 Specific conductance, dissolved oxygen, 

pH, turbidity

2008 0.77 Streamflow, specific conductance, dissolved 

oxygen, pH, and water temperature

Tongue River plains tributaries

2005 0.47 Streamflow and specific conductance

2006 0.54 Specific conductance, dissolved oxygen, 

and substrate

2007 0.61 Streamflow and specific conductance

2008 0.66 Dissolved oxygen, embeddedness, and 

water temperature

Main-stem Powder River 

2005 0.38 alkalinity and pH

2006 0.70 turbidity, embeddedness, and 

water temperature

2007 0.56 turbidity, embeddedness, D84, specific 

conductance, and fluoride

2008 0.50 turbidity, embeddedness, D84, alkalinity, 

and streamflow

(PC) axis 1; fig. 9), whereas sites on plains tributaries to the 

Tongue River tended to have positive correlation with PC axis 2 

(upper left), and sites on the main-stem Powder River tended to 

have negative correlation with PC axis 2 (lower left). The 2007 

eigenvectors indicated PC axis 1 was correlated with chemical variables such as specific conductance and fluoride; PC axis 

2 was correlated with physical variables such as turbidity and 

embeddedness. PCA ordinations for 2005–06 and 2008 showed 

similar results to those for 2007, due to similarities in values of 

environmental variables within the stream groups.

Given the differences in environmental variables between 

stream groups and differences in the number of sites sampled 

per year, PCA ordinations were repeated separately by stream 

group (TRMS, TRPT, and PRMS) and by year. Collinear variables were removed on a stepwise basis for each stream group 

and year, but in general, the pebble count measure, D84, was 

used as an indicator of the D50 and percent substrate less than 

2 mm; instantaneous streamflow was used as an indicator of 

microhabitat depth and velocity, and specific conductance was 

used as an indicator of major ions including sodium, potassium, chloride, sulfate, and total dissolved solids. Calcium, 

magnesium, and alkalinity were often but not always correlated with specific conductance. The selected environmental 

variables that produced the best correlation with the macroinvertebrate community taxonomy data using the BEST routine (Clarke and Gorley, 2006) are listed in table 8.

Main-Stem Tongue River

The macroinvertebrate communities at sites along the 

main-stem Tongue River tended to be best correlated with 

streamflow, specific conductance, and dissolved-oxygen 

concentrations during 2005–08. Spearman correlation coefficients between the macroinvertebrate taxonomy data and 

environmental variables identified through PCA ranged from 

0.21 in 2006 to 0.89 in 2007 (table 8). The correlation with 

streamflow might be attributed to the effects of consistently 

higher streamflow downstream from Tongue River Reservoir 

(sites T10, T14, and T18) than upstream from the reservoir (sites T1, T5, and T9; fig. 3A). Low streamflow during 

the drought year of 2006 (fig. 3C) might be a factor in the 

relatively low correlation coefficient of 0.21 for that year. 

Correlation of macroinvertebrate communities with specific 

conductance and dissolved-oxygen concentrations might 

also reflect the effects of Tongue River Reservoir. Specificconductance values at sites upstream from the reservoir 

increased from site T1 to T9 and tended to be higher upstream 

from the reservoir than downstream (fig. 4). Dissolved-oxygen 

concentrations tended to be lower downstream from the 

reservoir than upstream (fig. 10), although it should be noted 

that diel changes in dissolved-oxygen concentration were 

not measured.

Tongue River Plains Tributaries

Among all years, macroinvertebrate communities at 

sampling sites on plains tributaries to the Tongue River 

generally were best correlated with streamflow, specific 

conductance, and dissolved-oxygen concentrations (table 8). 

In 2005 for example, Hanging Woman Creek (sites T11–T13) 

had lower streamflow than other plains tributary sites such 

as Youngs Creek (sites T3 and T4), Squirrel Creek (site T7), 

Otter Creek (site T17), and Pumpkin Creek (site T19) and 

had higher specific-conductance values than most other plains 

tributary sites (fig. 10) perhaps due to higher intermittency 

in this system. The pattern of lower streamflow and higher 

specific conductance in Hanging Woman Creek than other 

plains tributaries also was repeated in 2007. Embeddedness, 

which was correlated with macroinvertebrate communities 

during 2008, ranged from less than 10 percent in Squirrel 

Creek (site T7) to 70 percent in Prairie Dog Creek (site T8) 

during 2008 (table 3).

Main-Stem Powder River

Macroinvertebrate communities at sites along the mainstem Powder River were correlated with turbidity and embeddedness in 2006–08, as well as other variables including D84, 

alkalinity, specific conductance, and streamflow in one or 
Assessment of Ecological Conditions 31

Figure 10. Selected environmental variables correlated with macroinvertebrate communities, Powder River structural basin, 2005–08.

0

2

4

6

8

10

12

14

T1 T5 T9 T10 T14 T18

DISSOLVED OXYGEN CONCENTRATION,

IN

MILLIGRAMS PER LITER 

Main-stem Tongue River, 2007

0

0.5

1

1.5

2

2.5

T3 T4 T7 T11 T12 T13 T17 T19

STREA

MFLO

W, IN CUBIC FEET PER SECOND 

Tongue River plains tributaries, 2005

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

T3 T4 T7 T11 T12 T13 T17 T19

SPECIFIC CONDUCTANCE, IN MICROSIEMENS 

PER CENTIMETER AT 25 DEGREES CELSIUS 

Tongue River plains tributaries, 2005

0

50

100

150

200

250

300

350

400

450

500

P3 P4 P5 P8 P9 P11 P12 P13

TURBIDITY, IN NEPHELOMETRIC TURBIDITY RATIO UNITS 

Main-stem Powder River,

2008

0

1,000

2,000

3,000

4,000

5,000

6,000

P1 P2 P3 P4 P5 P8 P9 P11 P12 P13 P17 P18

SPECIFIC CONDUCTANCE, IN MICROSIEMENS 

PER CENTIMETER AT 25 DEGREES CELSIUS 

Main-stem Powder River, 2007

0

50

100

150

200

250

P3 P4 P5 P8 P9 P11 P12 P13

STREA

MFLO

W, IN CUBIC FEET PER SECOND 

Main-stem Powder River, 2008
32 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

more years during 2005–08 (table 8). Embeddedness (table 3) 

and turbidity (fig. 10) varied inconsistently with downstream 

direction along the main-stem Powder River. Turbidity values 

were correlated with streamflow in 2005 (r = 0.71) and 2007 

(r = 0.82) but not in 2006 or 2008. Alkalinity concentrations, 

which were correlated with the macroinvertebrate communities in 2005 and 2008, were consistently higher in the Powder 

River below Burger Draw (site P4) than at other sites on the 

Powder River during 2005–08 (fig. 4; table 3). The Powder 

River at site P4 receives CBNG discharges from several drainages upstream. Specific conductance and dissolved-fluoride 

concentrations, which were correlated with the macroinvertebrate communities in 2007, reached maximum values in 2007 

in the Powder River below Willow Creek (site P3; fig. 10 and 

table 3). Streamflow, which was correlated with macroinvertebrate communities in 2008, generally increased in the downstream direction along the main-stem Powder River in 2008 

(fig. 10).

The BEST routine also was used to test if the environmental variables correlated with the macroinvertebrate communities of the middle reach of the Powder River (sites P3, 

P4, P5, and P8) were the same as those in the upper and lower 

reaches. The environmental data were renormalized, PCAs 

recalculated, and BEST correlation coefficients were recomputed using data from those four sites. The analyses confirmed 

that the environmental variables affecting the macroinvertebrate communities of the middle reach generally were the 

same as those affecting the upper and lower reaches.

As an additional test of the relations between macroinvertebrate communities and environmental variables in the 

main-stem Powder River, environmental variables from the 

PCA and BEST analyses were tested for correlation with the 

macroinvertebrate metrics (table 9). The maximum correlation 

coefficients occurred with streamflow and specific conductance. The relative abundance of Ephemeroptera increased 

with streamflow (r = 0.58) and decreased with specific 

conductance (r = –0.56). The relative abundance of intolerant 

macroinvertebrates also decreased with increasing specific 

conductance (r = –0.58). The relative abundance of Trichoptera decreased with streamflow (r = –0.52).

The correlations observed between the environmental 

variables and the macroinvertebrate taxonomy and metrics 

indicate that variation in the macroinvertebrate communities 

can be partially explained by variation in the environmental 

variables that were measured. Other potential causes for variation in the macroinvertebrate communities include natural 

population dynamics, sampling techniques, environmental 

variables that were not measured, and fluctuations in the measured environmental variables beyond those observed at the 

time of sampling.

Algal Communities

Algal data are available from 2005 and 2007 for standing crop (http://waterdata.usgs.gov/wy/nwis/qw) and algae taxonomy (http://wy.water.usgs.gov/projects/atg/htms/data.htm). 

This section describes the algal data in terms of standing crop, 

community composition, and community traits that include 

autecological or environmental indicators. Algal samples were 

collected from riffles where available and from pools at sites 

where riffles were unavailable. The reader should be aware 

that differences in substrate (riffles compared to pools) can 

affect algal biovolume and abundance of specific taxa; however, algal relations with physical and chemical environment 

(autecology) are not significantly affected by differences in 

substrate (Potapova and Charles, 2005).

Standing Crop

Concentrations of chlorophyll-a and ash-free dry mass 

(AFDM) in algae samples collected during 2005 and 2007 

generally were small (table 10), indicating a relatively small 

amount of algal biomass in riffles. Median concentrations 

Table 9. Correlation coefficients of macroinvertebrate community metrics with environmental variables, main-stem Powder River, 

Wyoming and Montana, 2005–08.

Metric Embeddedness

SubstrateStreamflow

Specific 

conduc-

 tance

pH

Water

tempera-

 ture

Dissolved

oxygen

Turbidity Alkalinity Fluoride

Taxa richness 0.36 –0.39 –0.15 –0.03 –0.42 0.09 0.06 0.41 –0.05 0.09

Ephemeroptera richness 0.13 –0.24 0.43 –0.43 –0.11 0.04 –0.11 0.35 –0.32 –0.36

Trichoptera richness 0.05 –0.31 –0.27 0.06 –0.07 0.05 0.43 0.20 0.16 0.08

Diptera richness 0.38 –0.24 –0.30 0.15 –0.45 0.02 –0.05 0.25 0.04 0.26

Ephemeroptera abundance –0.02 –0.10 0.58 –0.56 0.11 0.00 –0.17 0.33 –0.21 –0.44

Trichoptera abundance 0.03 –0.16 –0.52 0.19 –0.18 –0.16 0.41 –0.05 0.10 0.02

Diptera abundance –0.01 0.24 –0.06 0.34 0.07 0.14 –0.20 –0.23 0.08 0.35

Noninsect abundance 0.25 0.00 –0.16 –0.23 –0.04 –0.16 0.26 0.17 0.42 –0.05

Collector-gatherer abundance –0.03 –0.26 0.40 –0.47 –0.03 0.15 –0.23 0.29 –0.25 –0.30

Filterer-collector abundance –0.23 0.25 –0.36 0.40 0.22 –0.08 0.22 –0.36 0.20 0.24

Scraper abundance 0.21 –0.04 –0.05 –0.05 –0.11 –0.15 0.13 0.08 0.13 –0.08

Intolerant abundance –0.03 –0.17 0.47 –0.58 0.07 –0.01 –0.13 0.24 –0.19 –0.47
Assessment of Ecological Conditions 33

Table 10. Algal chlorophyll-a concentration, ash-free dry mass concentration, density, and biovolume, Powder River structural basin, 

Wyoming and Montana, 2005 and 2007.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River or Powder River. mg, milligrams; m2, square meter; g, grams; cm3, cubic centimeters; 

NA, not analyzed or not available]

Site

number

(fig. 1)

Abbreviated site name Sample

date Habitat Chlorophyll-a(mg/m2)

Ash-free

dry mass

(g/m2)

Algal

density

(billion cells/m2)

Algal

biovolume

(cm3/m2)

R1 Upper Rosebud Creek 7/9/2007 Pool NA NA 3.29 2.46

R2 Rosebud Creek at mouth 7/23/2007 Pool NA NA 2.26 0.33

T1 Tongue River at Monarch 8/15/2005 Riffle 3.9 9.3 NA NA

8/29/2007 Riffle 2.3 5.4 3.71 1.36

T2 Goose Creek 8/17/2005 Riffle 2.1 5.2 NA NA

9/11/2007 Riffle 44.1 21.6 3.86 3.84

T3 Upper Youngs Creek 6/21/2007 Riffle 17.8 12.7 3.87 0.61

T4 Youngs Creek at mouth 6/21/2007 Pool NA NA 2.16 0.02

T5 Tongue River below Youngs Creek 8/29/2007 Riffle 24.4 22.2 5.12 1.99

T6 Upper Squirrel Creek 7/11/2007 Pool NA NA 4.34 0.13

T7 Squirrel Creek at mouth 7/12/2007 Riffle 1.5 3.7 2.55 1.63

T8 Prairie Dog Creek 9/11/2007 Pool NA NA 3.07 0.35

T9 Tongue River at State line 9/14/2005 Riffle 47.1 49.4 NA NA

8/28/2007 Riffle 19.4 17.2 4.12 1.91

T10 Tongue River above Hanging Woman Creek 8/28/2007 Riffle 12.7 14.5 5.03 1.40

T11 Upper Hanging Woman Creek 7/11/2007 Riffle 11.0 12.3 3.73 0.75

T12 Middle Hanging Woman Creek 7/10/2007 Riffle 16.1 23.4 5.25 3.35

T13 Hanging Woman Creek at mouth 7/10/2007 Riffle 39.7 25.0 5.88 3.28

T14 Tongue River at Birney Day School 8/27/2007 Riffle 1.8 5.7 3.88 2.58

T15 Upper Otter Creek 6/20/2007 Pool NA NA 2.31 0.13

T16 Middle Otter Creek 6/20/2007 Riffle 10.1 17.8 3.62 1.10

T17 Otter Creek at mouth 6/19/2007 Pool NA NA 2.57 0.21

T18 Tongue River below Brandenberg Bridge 8/27/2007 Riffle 5.5 6.2 3.43 0.73

T19 Pumpkin Creek 6/18/2007 Riffle 0.6 3.8 2.49 0.06

P1 Powder River above Salt Creek 7/20/2005 Riffle 10.1 12.4 NA NA

8/30/2007 Riffle 18.3 14.1 4.04 0.13

P2 Powder River below Salt Creek 7/21/2005 Riffle 18.1 23.3 NA NA

8/30/2007 Riffle 16.6 13.1 4.11 0.11

P3 Powder River below Willow Creek 7/19/2005 Riffle 2.9 17.4 NA NA

8/24/2007 Riffle 6.2 15.2 3.94 0.01

P4 Powder River below Burger Draw 7/22/2005 Riffle 10.5 22.0 NA NA

8/22/2007 Riffle 1.0 4.5 2.46 0.0002

P5 Powder River above Crazy Woman Creek 7/13/2005 Riffle 0.7 3.5 NA NA

8/23/2007 Riffle 0.9 5.0 3.14 0.0002

P6 Crazy Woman Creek below I-90 7/11/2005 Riffle 1.6 21.0 NA NA

8/20/2007 Riffle 17.1 24.7 3.98 0.22

P7 Crazy Woman Creek near mouth 7/12/2005 Riffle 1.4 6.1 NA NA

8/21/2007 Riffle 18.1 22.7 3.98 0.62

P8 Powder River below Crazy Woman Creek 7/23/2005 Riffle 10.5 11.7 NA NA

8/21/2007 Riffle 5.8 13.9 3.39 0.02

P9 Powder River above Clear Creek 7/24/2005 Riffle 7.3 33.7 NA NA

7/26/2007 Riffle 1.3 18.6 2.99 0.01

P10 Clear Creek 9/13/2005 Riffle 12.3 21.8 NA NA

9/10/2007 Riffle 15.2 18.0 3.96 0.67

P11 Powder River below Clear Creek 7/25/2005 Riffle 54.1 22.0 NA NA

7/26/2007 Riffle 8.4 25.1 3.32 0.0002

P12 Powder River at Moorhead 7/26/2005 Riffle 71.3 61.6 NA NA

7/26/2007 Riffle 4.0 32.2 3.87 0.02

P13 Powder River at Broadus 7/25/2007 Riffle 0.5 25.1 4.23 0.43

P14 Little Powder River at Highway 59 8/8/2007 Riffle 443 87.7 3.55 0.51

P15 Little Powder River above Dry Creek 6/13/2005 Riffle 2.7 13.0 NA NA

8/7/2007 Riffle 5.5 11.6 3.22 0.16

P16 Little Powder River at Biddle 8/9/2007 Riffle 4.4 4.1 2.47 0.02

P17 Powder River below Little Powder River 7/25/2007 Riffle 0.2 326 3.70 0.63

P18 Powder River near Locate 7/24/2007 Riffle 4.0 6.3 2.99 0.15
34 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

of chlorophyll-a were 4.6 milligrams per square meter 

(mg/m2) in 2005 and 6.2 mg/m2 in 2007. For comparison, all 

chlorophyll-a concentrations in this study, with the exception 

of one, were less than the 100–150 mg/m2 concentration range 

associated with nuisance algal conditions (Stevenson and 

others, 1996). The exception was the chlorophyll-a concentration of 443 mg/m2

 from the Little Powder River at site P14 

in 2007 (table 10) that might have been influenced by lessthan-optimal availability of riffle habitat for sampling. Median 

concentrations of AFDM were 14.5 grams per square meter 

(g/m2) in 2005 and 2007. AFDM concentrations were less than 

100 g/m2 in all samples with the exception of the 2007 sample 

from the Powder River below Little Powder River (site P17), 

which contained 326 g/m2 (table 10) due to senescent algae 

or other organic matter in the sample. Concentrations of 

chlorophyll-a and AFDM at ATG sites generally were similar 

to concentrations from the lower main-stem Yellowstone River 

and less than concentrations from the upper and middle mainstem Yellowstone River and tributaries (Peterson and Porter, 

2002). Environmental variables affecting algal populations 

include nutrients, substrate, and light penetration (Stevenson 

and others, 1996).

Some of the measures of standing crop collected during 2007 (table 10) were moderately correlated with each 

other after removal of the outliers described previously. 

Chlorophyll-a concentrations were significantly (p <0.05) 

correlated with AFDM (r = 0.50), algal density (r = 0.66), 

and algal biovolume (r = 0.65). AFDM concentrations were 

significantly correlated with algal density (r = 0.62, p < 0.05) 

but not biovolume. Algal density was correlated with algal 

biovolume in samples from riffles (r = 0.59, p <0.05) but not 

in samples from pools.

The highest values of algal density in riffle samples 

occurred in the Tongue River drainage basin, at sites such as 

Hanging Woman Creek (sites T12 and T13) and the main-stem 

Tongue River (sites T5 and T10). Those sites also contained 

relatively high algal biovolume, as did Goose Creek (site T2) 

and Tongue River at site T14 (table 10). The lowest values of 

density from riffles occurred at various sites such as the mainstem Powder River (site P4), Little Powder River (site P16), 

and Pumpkin Creek (site T19). The lowest values of biovolume from riffle samples occurred on the main-stem Powder 

River (sites P3, P4, P5, P8, P9, P11, and P12), which include 

the middle reach. Algal communities in pools tended to have 

moderate densities and low biovolume values compared to 

communities in riffles.

Composition

Diatoms (Bacillariophyta) dominated the algal communities in terms of taxa richness, but green algae (Chlorophyta) 

and blue-green algae (Cyanophyta, cyanobacteria) dominated 

in terms of relative abundance (table 11). Algal taxa richness 

in both riffle and pool habitats generally was higher in 2005 

than in 2007. For example, the 2005 riffle samples contained 

a mean of 66 taxa per sample, of which 57 were diatoms, 

whereas in 2007, riffle samples contained a mean of 41 taxa 

per sample, of which 31 were diatoms. Compared to the riffle 

samples, the pool samples contained similar numbers for sample taxa richness and diatom taxa richness, as well as similar 

differences in taxa richness between 2005 and 2007. The green 

and blue-green algae each averaged a few taxa per sample in 

riffles and pools. Among all samples, green algae averaged 

26 percent of the relative abundance in 2005 and 67 percent 

in 2007; blue-green algae averaged 60 percent of the relative 

abundance in 2005 and 17 percent in 2007. Other types of 

algae that were less commonly identified in the algal communities included euglenoids (Euglenophyta), yellow-green algae 

(Chrysophyta), cryptomonads (Cryptophyta), dinoflagellates 

(Pyrrhophyta), and red algae (Rhodophyta).

Table 10. Algal chlorophyll-a concentration, ash-free dry mass concentration, density, and biovolume, Powder River structural basin, 

Wyoming and Montana, 2005 and 2007.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River or Powder River. mg, milligrams; m2, square meter; g, grams; cm3, cubic centimeters; 

NA, not analyzed or not available]

Site

number

(fig. 1)

Abbreviated site name Sample

date Habitat Chlorophyll-a(mg/m2)

Ash-free

dry mass

(g/m2)

Algal

density

(billion cells/m2)

Algal

biovolume

(cm3/m2)

C1 Porcupine Creek 6/12/2007 Pool NA NA 2.08 0.36

C2 Antelope Creek 6/14/2007 Pool NA NA 3.44 0.09

C3 Cheyenne River near Dull Center 6/27/2005 Riffle 4.7 16 NA NA

6/14/2007 Pool NA NA 2.26 0.12

C4 Little Thunder Creek 6/22/2005 Riffle 4.6 7.7 NA NA

6/13/2007 Pool NA NA 2.74 0.13

C5 Black Thunder Creek 6/13/2007 Pool NA NA 3.50 0.01

C6 Cheyenne River near Spencer 6/21/2005 Riffle 0.6 6.1 NA NA

6/15/2007 Riffle 4.0 11 2.99 0.45

B1 Belle Fourche River 6/29/2005 Riffle 1.2 9.3 NA NA

6/12/2007 Pool NA NA 0.65 0.05

B2 Caballo Creek 6/11/2007 Pool NA NA 2.74 0.09
Table 11. Algal community metrics for streams in the Powder River structural basin, Wyoming and Montana, 2005 and 2007.—Continued[Shaded cells indicate main-stem sampling sites on the Tongue River or Powder River. %, percent; NA, not available]

Site

number 

(fig. 1)

Abbreviated site name Habitat Sample date

Taxa richness and relative abundance 

Sample

taxa

richness

Diatom

taxa

richness

Diatom

abundance

(%)

Blue-green

algae taxa

richness

Blue-green

algae

abundance

(%)

Green

algae taxa

richness

Green

algae

abundance

(%)

S

to

(%

R1 Upper Rosebud Creek Pool 7/9/2007 87 67 46 5 15 10 17 R2 Rosebud Creek at mouth Pool 7/23/2007 41 28 15 2 2 7 46 T1 Tongue River at Monarch Riffle 8/15/2005 43 34 2 4 64 5 34 N

Riffle 8/29/2007 40 23 13 4 54 8 19 

T2 Goose Creek Riffle 8/17/2005 49 39 6 5 51 5 42 N

Riffle 9/11/2007 54 43 54 4 34 4 4 

T3 Upper Youngs Creek Riffle 6/21/2007 51 42 6 1 <1 5 33 T4 Youngs Creek at mouth Pool 6/21/2007 59 53 1 2 4 1 92 T5 Tongue River below Youngs Creek Riffle 8/29/2007 53 42 15 3 33 6 50 T6 Upper Squirrel Creek Pool 7/11/2007 21 17 1 2 3 1 54 T7 Squirrel Creek at mouth Riffle 7/12/2007 45 29 16 6 17 7 65 T8 Prairie Dog Creek Pool 8/16/2005 95 82 8 5 58 6 31 N

Pool 9/11/2007 66 56 10 3 12 5 67 

T9 Tongue River at State line Riffle 9/14/2005 73 58 44 5 37 9 19 N

Riffle 8/28/2007 63 49 17 6 72 6 7 

T10 Tongue River above Hanging Woman Creek Riffle 8/28/2007 34 24 11 2 17 7 72 T11 Upper Hanging Woman Creek Riffle 7/11/2007 27 13 16 4 17 6 63 T12 Middle Hanging Woman Creek Riffle 7/10/2007 66 55 32 4 15 6 52 T13 Hanging Woman Creek at mouth Riffle 7/10/2007 63 50 11 4 27 5 56 T14 Tongue River at Birney Day School Riffle 8/27/2007 34 21 8 3 20 8 70 T15 Upper Otter Creek Pool 6/20/2007 73 64 5 2 4 6 90 T16 Middle Otter Creek Riffle 6/20/2007 72 63 2 4 17 4 22 T17 Otter Creek at mouth Pool 6/19/2007 60 48 4 3 14 3 63 T18 Tongue River below Brandenberg Bridge Riffle 8/27/2007 60 42 15 6 15 7 63 T19 Pumpkin Creek Riffle 6/18/2007 26 17 1 4 20 1 77 P1 Powder River above Salt Creek Riffle 7/20/2005 69 59 3 5 77 5 20 N

Riffle 8/30/2007 33 23 5 3 19 4 71 

P2 Powder River below Salt Creek Riffle 7/21/2005 42 34 29 4 41 3 30 N

Riffle 8/30/2007 41 29 1 2 18 5 75 

P3 Powder River below Willow Creek Riffle 7/19/2005 63 53 3 4 77 6 20 N

Riffle 8/24/2007 27 22 <1 1 37 2 62 1

P4 Powder River below Burger Draw Riffle 7/22/2005 56 47 26 3 25 6 49 N

Riffle 8/22/2007 1 0 0 0 0 1 100 1

P5 Powder River above Crazy Woman Creek Riffle 7/13/2005 92 81 1 3 65 6 33 N

Riffle 8/23/2007 1 0 0 0 0 1 100 1

P6 Crazy Woman Creek below I-90 Riffle 7/11/2005 115 106 11 4 54 4 34 N

Riffle 8/20/2007 69 58 4 4 27 5 68 

P7 Crazy Woman Creek near mouth Riffle 7/12/2005 78 72 <1 3 92 3 8 N

Riffle 8/21/2007 72 59 2 6 17 5 79 
Table 11. Algal community metrics for streams in the Powder River structural basin, Wyoming and Montana, 2005 and 2007.—Continued [Shaded cells indicate main-stem sampling sites on the Tongue River or Powder River. %, percent; NA, not available] Site number (fig. 1) Abbreviated site name Habitat Sample date Taxa richness and relative abundance 

Sample taxa richness Diatom taxa richness Diatom abundance (%) Blue-green algae taxa richness Blue-green algae abundance (%) Green algae taxa richness Green algae abundance (%) S

to

(%

P8 Powder River below Crazy Woman Creek Riffle 7/23/2005 68 57 1 6 81 5 18 N

Riffle 8/21/2007 46 37 <1 1 1 4 96 

P9 Powder River above Clear Creek Riffle 7/24/2005 96 82 9 5 58 8 32 N

Riffle 7/26/2007 6 0 0 0 0 3 98 1

P10 Clear Creek Riffle 9/13/2005 56 47 22 3 47 5 26 N

Riffle 9/10/2007 55 42 9 3 15 7 73 

P11 Powder River below Clear Creek Riffle 7/25/2005 58 50 1 4 81 4 18 N

Riffle 7/26/2007 1 0 0 0 0 1 100 1

P12 Powder River at Moorhead Riffle 7/26/2005 79 69 3 5 73 4 23 N

Riffle 7/26/2007 5 0 0 2 1 2 92 1

P13 Powder River at Broadus Riffle 7/25/2007 46 35 3 2 14 6 79 P14 Little Powder River at Highway 59 Pool 6/14/2005 56 51 56 3 34 2 10 N

Riffle 8/8/2007 43 34 10 3 19 3 58 

P15 Little Powder River above Dry Creek Riffle 6/13/2005 25 20 <1 3 90 2 8 N

Riffle 8/7/2007 37 27 3 4 15 3 75 

P16 Little Powder River at Biddle Riffle 8/9/2007 29 17 1 5 11 6 87 P17 Powder River below Little Powder River Riffle 7/25/2007 85 73 4 2 9 6 84 P18 Powder River near Locate Riffle 7/24/2007 48 38 6 4 35 3 51 C1 Porcupine Creek Pool 6/15/2005 80 74 25 3 49 3 26 N

Pool 6/12/2007 47 34 5 3 27 6 65 

C2 Antelope Creek Pool 6/8/2005 60 47 26 3 30 8 43 N

Pool 6/14/2007 44 34 2 3 9 4 87 

C3 Cheyenne River near Dull Center Riffle 6/27/2005 56 48 9 3 60 5 31 N

Pool 6/14/2007 56 47 4 2 23 3 69 

C4 Little Thunder Creek Riffle 6/22/2005 66 61 1 4 98 1 1 N

Pool 6/13/2007 52 46 4 3 15 2 78 

C5 Black Thunder Creek Pool 6/7/2005 74 59 11 4 40 9 48 N

Pool 6/13/2007 17 11 <1 2 4 2 92 

C6 Cheyenne River near Spencer Riffle 6/21/2005 74 67 17 3 50 2 32 N

Riffle 6/15/2007 26 18 6 2 15 4 78 

B1 Belle Fourche River Riffle 6/29/2005 69 64 9 3 78 2 13 N

Pool 6/12/2007 51 40 4 2 19 4 74 

B2 Caballo Creek Pool 6/28/2005 86 77 33 4 44 5 23 N

Pool 6/11/2007 39 30 2 4 12 2 83 
Assessment of Ecological Conditions 37

The taxonomic composition of the algal communities showed similarities within river drainage basins and by 

habitat. NMDS ordinations of the Bray-Curtis similarity 

coefficients for algal taxonomic data from 2007 (fig. 11) and 

2005 (Peterson and others, 2009) indicated two general groups 

of sites corresponding with riffle samples: (1) a Tongue River 

drainage basin group that included sites on the main stem, 

Tongue River plains tributaries, and Clear Creek; and (2) a 

Powder River drainage basin group that included sites on the 

main-stem Powder River, Crazy Woman Creek, and the Little 

Powder River. Samples collected from pool habitats in various 

drainage basins formed a third group of sites.

Algal communities at sites in the Tongue River drainage 

basin group contained an average of 50 taxa per sample in 2007. 

Taxa richness in the Tongue River drainage basin group was 

high compared to the Powder River drainage basin group and 

similar to the pool group (fig. 12). Green algae tended to be the 

most abundant algae in both the Tongue River and Powder River 

drainage basin groups, but the Tongue River drainage basin group 

generally contained more blue-green algae and less green algae 

than the Powder River drainage basin group. The most abundant 

taxa in the Tongue River drainage basin group were Aphanocapsa

and Oscillatoria (blue-green algae) and Chlorella (green algae). 

The proportion of algae that are capable of fixing atmospheric 

nitrogen tended to be low throughout the study area but was highest in the Tongue River drainage basin group (fig. 12). The relative abundance of nitrogen fixers ranged from 0 percent at most 

sites to 18 percent in Goose Creek (site T2; table 11). The ability 

to fix atmospheric nitrogen gives a competitive edge to nitrogen 

fixers when dissolved-nitrogen concentrations are low or ratios of 

nitrogen to phosphorus are low (Porter, 2008). Given that Goose 

Creek receives treated sewage effluent from the city of Sheridan 

(Wyoming Department of Environmental Quality, 2009), the 

proportion of nitrogen fixers at site T2 might be a reflection of 

low ratios of nitrogen to phosphorus. The chlorophyll-a concentration in Goose Creek in 2007 was relatively high at 44.1 mg/m2

(table 10). In 2005, the relative abundance of nitrogen fixers and 

the chlorophyll-a concentration at Goose Creek were comparatively low (Peterson and others, 2009).

Taxa richness of algal communities in the Powder 

River drainage basin group in 2007 ranged from 1 to 85 taxa 

(table 11). The green alga Chlorella composed 92–100 percent 

Figure 11. Similarities of algal community taxonomic composition within drainage basins and within habitats, 

depicted by nonmetric multidimensional scaling ordination, Powder River structural basin, Wyoming and 

Montana, 2007.

EXPLANATION

B1

B2

C1

C2 C3

C4

C4S

C5

C6

P1

P10

P12

P13

P17

P15

P6 P16

P18

P2

P3

P4, P5, P11 P8

P7

P14

P9

R1

R2

T1

T10

T11

T12

T13

T14

T15

T16

T17

T17R

T18

T19

T2

T3

T4

T5

T6

T7

T8

T9

Habitat

 Pool

 Riffle

Powder River group

Tongue River group

Pool group

–1

–0.8

–0.6

–0.4

–0.2

0

0.2

NONMETRIC MULTIDIMENSIONAL SCALING AXIS 2

0.4

0.6

0.8

1

NONMETRIC MULTIDIMENSIONAL SCALING AXIS 1

–2 –1 0 1 2 3
38 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Figure 12. Algal community composition by drainage basin and habitat, Powder River structural basin, 2007.

TRG PRG POOLS

GROUP

TRG PRG POOLS

GROUP

0

Tongue River drainage basin (15 samples)

EXPLANATION 

Data value less than or equal to 1.5 times the interquartile range 

 outside the quartile

75th percentile

Median

25th percentile

TRG

PRG Powder River drainage basin (17 samples)

POOLS Pools, various drainage basins (14 samples) 

Interquartile range

Outlier data value greater than 1.5 times the interquartile range 

 outside the quartile

TAXA RICHNESS

0

20

40

60

80

0

10

20

30

40

0

20

40

60

80

100

RELATIVE ABUNDANCE OF SESTONIC ALGAE, 

IN PERCENT

RELATIVE ABUNDANCE OF BLUE-GREEN ALGAE, 

IN PERCENT

RELATIVE ABUNDANCE OF GREEN ALGAE, 

IN PERCENT

RELATIVE ABUNDANCE OF NITROGEN-FIXING ALGAE, 

IN PERCENT

0

5

10

15

20

20

40

60

80

100
Assessment of Ecological Conditions 39

of the algal abundance at sites P4, P5, P9, P11, and P12 in 2007, 

which includes the middle reach (sites P3–P5 and P8), causing these sites to be outliers from the NMDS ordination of the 

Powder River drainage basin group (fig. 11). For comparison, 

in 2005, the algal communities at sites P2 and P4 on the mainstem Powder River were dominated by a single species, the 

diatom Achnanthes minutissima (Peterson and others, 2009). 

Low algal taxa richness can be an indicator of effects to the 

community if sensitive species are stressed by natural or other 

factors (Barbour and others, 1999). The relative abundance 

of Achnanthes minutissima may increase in response to metal 

toxicity, nutrient enrichment, scouring, or grazing (Bahls, 

1993). Chlorella is a cosmopolitan sestonic algae (planktonic 

or suspended) (Porter, 2008), which helps explain the generally 

higher relative abundance of sestonic algae in the Powder River 

drainage basin group than in the Tongue River drainage basin 

group (fig. 12). The dominance of sestonic algae might result 

from the influence of pools and slow-moving reaches upstream 

from the sample-collection points, as indicated by the similarities between the Powder River and pool groups (fig. 12). The 

relative abundance of eutrophic algae, which are either tolerant of or dependent on high nutrient concentrations, tended to 

be higher in the Powder River drainage basin group (average 

of 91 percent) than in the Tongue River drainage basin group 

(average of 74 percent).

The pool group contained sites from multiple river drainage basin basins; the common variable among these sites was 

that algae samples were collected from pools rather than riffles. 

Algal communities were dominated by green algae, including Chlorella, and blue-green algae such as Aphanocapsa. The 

relative abundance of sestonic algae was high in the pool group 

(fig. 12), consistent with the depositional habitat from which the 

samples were collected.

Fish Communities

Fish communities were sampled at 12 sites in the Tongue 

River drainage basin and at 11 sites in the Powder River drainage basin in 2008, and results for these sites are presented along 

with results from previous fish community sampling reported by 

Peterson and others (2009). Results for sites that were sampled 

previously (Peterson and others, 2009) but not in 2008 are not 

included in this report.

Tongue River Drainage Basin

Fish communities were sampled at 12 of the 19 sites on 

the main-stem Tongue River and Tongue River tributaries during 2005–06 and 2008 (table 12), except for Squirrel Creek at 

mouth (site T7), which was not sampled in 2006 because the 

sample reach was dry. The remaining seven sites in the Tongue 

River drainage basin were sampled in 2005–06 but not in 

2008; results for these seven sites were presented previously by 

Peterson and others (2009) and are not described in this report.

Community Composition

Twenty-nine species of fish were identified in samples 

collected from the Tongue River drainage basin during 

2005–06 and 2008 (table 12). More than one-half of the species (15) identified in the Tongue River drainage basin were 

native, including seven minnows (Cyprinidae), five suckers 

(Catostomidae), two catfish (Ictaluridae), and one sauger 

(Percidae; table 13). Introduced fish species included eight 

sunfishes (Centrarchidae), three minnows, two catfishes, and 

yellow perch (Percidae).

Smallmouth bass accounted for 28 percent of the relative abundance of fish captured in the main-stem Tongue 

River (fig. 13), with white sucker (11 percent), yellow bullhead (11 percent), and rock bass (10 percent) also abundant. 

In contrast, smallmouth bass composed only 9 percent of the 

fish captured in the tributaries to the Tongue River (fig. 13). 

Fathead minnow were the most common fish in the tributaries, 

where they composed 42 percent of the relative abundance of 

fish captured. Fathead minnow were relatively uncommon in 

the main-stem Tongue River, where they were among 16 of 

23 species that composed 10 percent of the other fish captured 

(fig. 13). Fish communities of the main-stem Tongue River 

also contained yellow bullhead (11 percent; fig. 13), common 

carp (8 percent), shorthead redhorse (8 percent), and spottail 

shiner (8 percent) that were uncommon in the tributaries.

Fish species richness was greatest at sampling sites on the 

main-stem Tongue River. Samples from Tongue River at State 

line (T9) contained 18 species in 2005, 17 species in 2006, 

and 14 species in 2008 (table 12). Reduction in the number of 

species captured for each sampling year can be from normal 

year-to-year variation, increased turbidity (table 3), changes in 

sampling efficiency, or a combination of these and unknown 

factors. Sampling on the Tongue River below Youngs Creek 

(site T5), Tongue River above Hanging Woman Creek 

(site T10), and Tongue River at Birney Day School (site T14) 

resulted in the collection of 10 to 14 species each year. The 

Tongue River Reservoir, on the main stem between sites T9 

and T10 (fig. 1), appears to affect the fish community of the 

river. Open-water species, such as spottail shiner and yellow 

perch (Baxter and Stone, 1995), were identified only at sites 

upstream from the reservoir at the Tongue River below Youngs 

Creek (site T5), Tongue River at State line (site T9), and 

Prairie Dog Creek (site T8). Black crappie and white crappie, 

also known as open-water species, were found in small numbers upstream and downstream from Tongue River Reservoir. 

Sauger was collected at Tongue River at State line (site T9) 

in 2008 but was not collected at any other sampling site in the 

Tongue River drainage basin. Mountain sucker was collected 

only at Upper Youngs Creek (site T3) in 2005 and 2008.

Tributary streams with relatively large numbers of fish 

species in all three sampling years were Goose Creek (site T2) 

and Prairie Dog Creek (site T8). Numbers of fish species collected at Goose Creek (site T2) were 11 in 2005, 8 in 2006, and 

10 in 2008. Nine species were collected at Prairie Dog Creek 
40 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

(site T8) in 2005, and 10 species were collected in 2006 and 

2008. The numbers of fish species sampled at Youngs Creek 

at mouth (site T4), Upper Squirrel Creek (site T6), Hanging 

Woman Creek at mouth (T13), and Otter Creek at mouth (T17) 

were somewhat variable from year to year.

With a few exceptions, fish communities sampled in all 

3 years appeared to be similar on the basis of species richness. 

At Squirrel Creek at mouth (site T7), five fish species were 

collected in 2005 and two species were collected in 2008. 

The lack of fish species collected in 2008 may be the result of 

drought conditions in 2006, indicating fish species have yet 

to fully repopulate the site. Only one species was identified in 

2006 at Hanging Woman Creek at mouth (site T13) presumably because 2006 was a drier year when compared to the other 

sampling years, and suitable habitat was not present for other 

species (table 3). Otherwise, the number of fish species found at 

site T13 increased overall from four species collected in 2005 to 

seven species collected in 2008. Otter Creek at mouth (site T17) 

showed a decrease in the number of fish species identified for 

each year with six species collected in 2005, five species collected in 2006, and three species collected in 2008.

The total abundance of fish collected at the 12 sites was 

3,826 individuals in 2005, 5,705 in 2006, and 2,562 in 2008. 

Although 2006 was a drier year, the mean number of species 

collected per site was similar for the 3 years: 8.1 species in 

2005, 7.7 species in 2006, and 8.1 species in 2008. The largest increases in fish abundance from 2005 to 2008 were for 

sand shiners, fathead minnow, lake chub, and golden shiner. 

The largest decreases in fish abundance from 2005 to 2008 

were for common carp, channel catfish, and white sucker. The 

difference in abundance between years is probably related to 

normal year-to-year variation.

Community Structure

The structure and integrity of the fish community were 

assessed using the Index of Biotic Integrity (IBI) developed 

for small prairie streams in Montana (Bramblett and others, 

Table 12. Fish abundance in samples from the Tongue River drainage basin, Wyoming and Montana, 2005–06 and 2008.

[Shaded cells indicate main-stem sampling sites on the Tongue River]

Site

number

(fig. 1)

Abbreviated site name Sample

date

Black

bullhead

Black

crappie

BluegillBrassy

minnow

Channel

catfish

Common

carp

Creek

chub

Fathead

minnow

Flathead

chub

Golden

shiner

Green

sunfish

Lake

chub

T2 Goose Creek 8/22/2005 3 0 0 0 0 18 0 1 0 0 3 0

8/22/2006 15 0 0 0 0 30 0 0 0 0 3 0

8/8/2008 5 0 0 0 0 21 0 0 0 0 13 0

T3 Upper Youngs Creek 6/15/2005 0 0 0 0 0 0 6 2 0 0 0 0

6/28/2006 0 0 0 0 0 0 62 15 0 0 0 0

6/26/2008 0 0 0 0 0 0 19 0 0 0 0 0

T4 Youngs Creek at mouth 6/14/2005 0 0 0 1 0 0 0 22 0 0 0 0

6/27/2006 0 0 0 54 0 0 9 104 0 0 0 4

6/26/2008 2 0 0 2 0 2 14 1 0 0 2 0

T5 Tongue River below Youngs Creek 8/29/2005 108 3 0 0 0 43 0 17 0 0 42 0

8/24/2006 10 0 0 0 0 129 0 0 4 0 5 0

9/11/2008 5 0 0 0 0 5 0 1 0 0 5 0

T6 Upper Squirrel Creek 6/16/2005 0 0 0 0 0 0 19 0 0 0 0 0

6/29/2006 0 0 0 1 0 0 10 83 0 0 0 0

6/25/2008 0 0 0 0 0 1 0 20 0 0 0 134

T7 Squirrel Creek at mouth 6/13/2005 1 0 0 0 0 0 8 3 0 0 0 1

6/25/2008 0 0 0 0 0 1 0 1 0 0 0 0

T8 Prairie Dog Creek 8/26/2005 13 0 0 0 0 1 0 0 0 0 0 0

8/25/2006 0 0 0 0 0 8 168 0 0 0 1 0

9/10/2008 9 0 0 0 0 0 0 0 1 0 1 0

T9 Tongue River at State line 8/25/2005 30 25 4 1 6 89 9 0 2 0 1 0

8/28/2006 13 3 0 0 9 99 51 0 3 0 6 0

9/10/2008 6 0 0 0 0 8 0 4 0 17 0 0

T10 Tongue River above Hanging 

Woman Creek

8/30/2005 0 9 0 0 10 21 0 0 0 0 1 0

8/29/2006 0 0 0 0 7 24 0 0 0 0 0 0

9/9/2008 0 0 0 0 9 7 0 0 0 0 0 0

T13 Hanging Woman Creek at mouth 6/23/2005 0 0 0 0 0 0 0 85 0 0 17 0

6/26/2006 0 0 0 0 0 0 0 266 0 0 0 0

6/24/2008 0 0 0 0 0 4 0 199 0 130 8 0

T14 Tongue River at Birney Day School 8/31/2005 0 0 0 0 18 35 0 0 0 0 0 0

8/30/2006 2 0 0 0 63 35 0 0 0 2 17 0

9/8/2008 0 3 0 0 12 17 0 0 0 0 1 0

T17 Otter Creek at mouth 6/30/2005 0 0 1 114 0 31 0 360 0 0 0 0

6/28/2006 1 0 0 0 0 122 0 931 0 0 6 0

6/24/2008 0 0 0 0 0 0 0 382 0 0 10 0
Assessment of Ecological Conditions 41

2005). IBI scores consist of 10 metrics, some of which 

are adjusted by the drainage area. Because the IBI was not 

intended for use in rivers with large drainage areas, raw 

and unadjusted fish community metric values were evaluated 

for the main-stem Tongue River (table 14).

Testing using ANOVA with the Tukey method was 

performed to determine statistical differences in fish community metrics between sites and by year for the main-stem 

Tongue River. Results show significant differences (p < 0.05) 

among sites for percentage of invertivorous cyprinid individuals and percentage of native individuals (table 15). The 

Tongue River Reservoir on the main stem between Tongue 

River at State line (site T9) and Tongue River above Hanging 

Woman Creek (site T10) appears to affect the fish communities of the river. As shown in figure 14, the number of 

benthic invertivorous species and percentage of invertivorous cyprinids were higher upstream from the reservoir than 

downstream; these metrics are expected to decline as human 

Table 12. Fish abundance in samples from the Tongue River drainage basin, Wyoming and Montana, 2005–06 and 2008.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River]

Site

number

(fig. 1)

Largemouth

bass

Longnose 

dace

Longnose

sucker

Mountain 

sucker

Pumpkinseed

River 

carpsucker

Rock

bass

Sand

shiner Sauger

Shorthead 

redhorse

Smallmouth 

bass

Spottail 

shiner

StonecatWhite 

crappie

White 

sucker

Yellow 

bullhead

Yellow 

perch

Total

number

of species

T2 6 3 0 0 0 0 314 0 0 31 288 0 69 0 37 0 0 11

0 8 0 0 0 0 203 0 0 0 186 0 65 0 51 0 0 8

1 2 0 0 0 0 325 0 0 22 59 0 6 0 10 0 0 10

T3 0 69 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 4

0 32 0 0 0 0 0 0 0 0 0 0 0 0 8 0 0 4

0 14 0 1 0 0 0 0 0 0 0 0 0 0 4 0 0 4

T4 0 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3

0 7 0 0 0 0 0 0 0 0 0 0 0 0 10 0 0 6

0 3 0 0 0 0 0 0 0 0 0 0 0 0 5 0 0 8

T5 0 6 4 0 0 0 93 0 0 56 412 77 2 0 125 0 0 13

0 31 4 0 4 0 116 0 0 58 217 148 11 0 57 178 0 14

0 3 1 0 0 0 23 0 0 26 98 27 1 0 10 19 0 13

T6 0 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2

0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 4

0 11 0 0 0 0 0 0 0 0 0 0 0 0 11 0 0 5

T7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 5

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2

T8 0 0 3 0 0 0 10 0 0 0 2 1 56 0 9 4 0 9

0 5 4 0 0 0 5 0 0 13 26 0 1 0 56 0 0 10

0 2 5 0 0 0 3 0 0 3 0 0 19 0 17 14 0 10

T9 0 5 0 0 0 0 34 0 0 42 264 40 10 1 102 0 1 18

0 13 1 0 34 0 55 0 0 95 234 150 46 0 119 301 0 17

0 3 0 0 20 0 10 0 1 14 148 42 5 0 14 17 0 14

T10 0 0 0 0 0 6 41 0 0 21 39 0 12 0 18 21 0 11

0 1 0 0 0 1 52 0 0 42 60 0 23 0 57 24 0 10

0 0 1 0 0 1 5 0 0 55 32 0 18 0 7 3 0 10

T13 0 0 0 0 0 0 0 0 0 0 0 0 1 0 6 0 0 4

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1

0 1 0 0 0 0 0 0 0 11 0 0 0 0 2 0 0 7

T14 0 2 0 0 0 19 61 0 0 37 21 0 16 8 62 38 0 11

0 19 4 0 0 9 69 0 0 39 138 0 46 0 111 39 0 14

0 0 0 0 0 9 33 0 0 20 94 0 19 0 18 17 0 11

T17 0 0 0 0 0 0 0 10 0 0 0 0 0 0 6 0 0 6

0 0 0 0 0 0 0 43 0 0 0 0 0 0 0 0 0 5

0 0 0 0 0 0 0 115 0 0 0 0 0 0 0 0 0 3

influence increases (Bramblett and others, 2005). The number 

of native catostomid and ictalurid species, number of longlived native species, and percentage of native individuals 

generally were higher downstream than upstream from the the 

reservoir; these metrics also are expected to decline as human 

influence increases (Bramblett and others, 2005). The causes 

are unknown as to why the metrics are inconsistent with 

regard to human influence upstream and downstream from the 

reservoir, but might be related to fish migration from Tongue 

River Reservoir.

Of the small plains streams that were sampled, the 

fish communities from Youngs Creek (sites T3 and T4) and 

Squirrel Creek (sites T6 and T7 in 2005) had some of the 

highest IBI scores in the study area (table 16). The highest observed IBI score of 96 occurred at site T3 on upper 

Youngs Creek in 2008 (fig. 15). IBI scores from sites on lower 

Youngs Creek (site T4) and Squirrel Creek (sites T6 and T7 

in 2005) also were relatively high and ranged from 66 to 84, 
42 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

although scores decreased in Youngs Creek from site T3 to 

site T4 in all 3 years of sampling (table 16). Squirrel Creek 

at mouth (site T7) had a marked decrease in the IBI score 

from 2005 to 2008, presumably because the site was dry in 

2006 and effects were still being seen in 2008. Goose Creek 

(site T2) and Otter Creek at mouth (site T17) had downward 

trends in IBI score from 2005 to 2008 (fig. 15). Prairie Dog 

Creek (site T8) had IBI scores ranging from 59 to 78 with 

a mean of 69. Hanging Woman Creek at mouth (site T13) 

had some of lowest IBI scores ranging from 40 to 46 with 

a mean of 43.

Powder River Drainage Basin

Fish communities were sampled on the main-stem Powder 

River and Powder River tributaries at 11 of 18 sites during 

2004–06 and 2008. The remaining seven sites in the Powder 

River drainage basin were sampled in 2004–06 but not in 2008; 

results for these seven sites were presented previously by 

Peterson and others (2009) and are not described in this report. 

For sites that had multiple sample dates during 2004–05, the 

sample date closest to the 2008 sample date was chosen for comparisons between years.

Table 13. Ecological characteristics of fish species sampled in the Powder River Structural Basin, Wyoming and Montana, 2005–08.

[Modified from Bramblett and others, 2005. Trophic category: IN, invertivore; HB, herbivore; OM, omnivore; IC, invertivore-carnivore; CA, carnivore. Feeding 

habitat: WC, water column; BE, benthic; GE, generalist. Reproductive class: LO, litho-obligate; TR, tolerant reproductive strategists; --, not determined or not 

available; General tolerance: INT, intolerant; MOD, moderate; TOL, tolerant. Origin: N, native; I, introduced. mm, millimeters; NA, not applicable because 

species generally lives less than 3 years]

Family Common

name

Scientific name Trophic

category

Feeding

habitat

Reproductive

class

General

tolerance Origin

Length at

3 years

(mm)

Acipenseridae Shovelnose sturgeon Scapirhynchus platorynchus IN BE -- -- N --

Cyprinidae lake chub Couesius plumbeus IN WC -- MOD N 140

common carp Cyprinus carpio OM BE -- TOL I 381

western silvery minnow Hybognathus argyritis HB BE -- MOD N 94

brassy minnow Hybognathus hankinsoni HB BE -- MOD N 81

plains minnow Hybognathus placitus HB BE -- MOD N 94

sturgeon chub Macrhybopsis gelida IN BE LO INT N 50

golden shiner Notemigonus crysoleucas OM WC -- MOD I 102

spottail shiner Notropis hudsonius IN WC LO MOD I 85

sand shiner Notropis stramineus OM GE LO MOD N 61

fathead minnow Pimephales promelas OM GE TR TOL N 76

flathead chub Platygobio gracilis IN GE -- MOD N 140

longnose dace Rhinicthys cataractae IN BE LO INT N 71

creek chub Semotilus atromaculatus IC GE LO MOD N 114

Catostomidae river carpsucker Carpiodes carpio OM BE LO MOD N 229

longnose sucker Catostomus catostomus IN BE LO MOD N 216

white sucker Catostomus commersonii OM BE LO TOL N 229

mountain sucker Catostomus platyrhynchus HB BE LO MOD N 102

shorthead redhorse Moxostoma macrolepidotum IN BE LO MOD N 254

Ictaluridae black bullhead Ameiurus melas IC BE TR TOL I 152

yellow bullhead Ameiurus natalis IC BE TR MOD I 254

channel catfish Ictalurus punctatus IC BE TR MOD N 254

stonecat Noturus flavus IC BE LO INT N 140

Cyprinodontidae northern plains killifish Fundulus kansae OM GE -- TOL I 81

Centrarchidae rock bass Ambloplites rupestris IC GE TR MOD I 89

green sunfish Lepomis cyanellus IC GE -- TOL I 102

pumpkinseed Lepomis gibbosus IC GE LO MOD I 89

bluegill Lepomis macrochirus IC GE LO MOD I 102

smallmouth bass Micropterus dolomieu IC GE TR MOD I 154

largemouth bass Micropterus salmoides IC GE TR MOD I 140

white crappie Pomoxis annularis IC WC TR MOD I 152

black crappie Pomoxis nigromaculatus IC WC TR MOD I 203

Percidae yellow perch Perca flavescens IC WC -- MOD I 140

sauger Sander canadensis IC GE LO MOD N 279
Assessment of Ecological Conditions 43

Community Composition

Twenty-four species of fish were identified in samples 

collected during 2004–06 and 2008 (table 17). Out of the 

those species identified, 17 were native, including 8 minnows 

(Cyprinidae), 4 suckers (Catostomidae), 2 catfish (Ictaluridae), 

1 goldeye (Hiodontidae), 1 shovelnose sturgeon (Acipenseridae) 

and 1 sauger (Percidae). Introduced fish species included four 

sunfishes (Centrarchidae), one minnow, one catfish, and one 

northern plains killifish (Cyprinodontidae).

Sand shiner were the most common fish in the Powder 

River drainage basin, accounting for 63 percent of the relative 

abundance of fish captured in the main-stem Powder River 

and 48 percent in the tributaries to the Powder River (fig. 16). 

Flathead chub composed 22 percent of the fish in the main-stem 

Powder River and 6 percent in the tributaries. Hybognathus spp. 

composed 5 percent of the fish in the main-stem Powder River 

but were uncommon in the tributaries, whereas white sucker and 

rock bass were more common in the tributaries than in the main 

stem (fig. 16). Of the two species of Hybognathus identified, the 

plains minnow (H. placitus) was more common than the western silvery minnow (H. argyritis; table 17) that is a Wyoming 

species of concern (Wyoming Game and Fish Department, written commun. 2008). In total, 21 fish species were captured from 

the main-stem Powder River during 2004–06 and 2008, and 20 

species were captured from the tributaries to the Powder River 

during 2004–06 and 2008.

Fish species richness on the main-stem Powder River 

tended to be relatively high in the middle reach of the Powder 

River (sites P3–P5 and P8). Richness was highest at Powder 

River downstream from Burger Draw (P4) with 11 species in 2005, 10 species in 2006, and 13 species collected 

in 2008 (table 17). Other sites on the main-stem Powder 

River with high species richness were Powder River above 

Pumpkin Creek (site P3), which contained 8 to 12 species, 

and Powder River above Crazy Woman Creek (site P5), 

which contained 7 to 11 species. Four fish species were 

identified on the main-stem Powder River and not in tributary streams. Bluegill was collected only at Powder River 

below Burger Draw (site P4) in 2008. Mountain sucker 

was collected only at Powder River above Pumpkin Creek 

(site P3) in 2004. Shovelnose sturgeon was collected at 

Powder River at Broadus (site P13) in 2008. Sturgeon chub, 

which is a Wyoming species of concern (Wyoming Game 

and Fish Department, written commun. 2008), was collected at Powder River above Crazy Woman Creek (site P5) 

in 2006 and Powder River at Moorhead (site P12) in 2006 

and 2008.

The tributary stream in the Powder River with relatively large numbers of fish species in 3 sampling years was 

Clear Creek (site P10) with 14, 14, and 11 species in 2005, 

2006, and 2008, respectively. Clear Creek (site P10) was 

the only tributary where sauger was collected in the 3 years 

of sampling.

The total abundance of fish collected at the 11 sites 

was 6,114 in 2004, 9,462 in 2005, 23,786 in 2006, and 2,629 

individuals collected in 2008. A possible cause for the large 

number of fish caught in 2006 is that the drought concentrated the fish in smaller areas, making them easier to catch. 

Figure 13. Relative abundance of fish by species in samples from the Tongue River drainage basin, Wyoming and Montana, 2005–06 

and 2008.

Smallmouth bass

28 percent

White sucker

11 percent

Yellow bullhead

11 percent

Rock bass

10 percent

Common carp

8 percent

Shorthead redhorse

8 percent

Spottail shiner

8 percent

Stonecat

3 percent

Black bullhead

3 percent

Other

10 percent

Main-stem Tongue River

Fathead minnow

42 percent

Rock bass

15 percent

Smallmouth bass

9 percent

Creek chub

5 percent

Common carp

4 percent

White sucker

4 percent

Stonecat

4 percent

Longnose dace

3 percent

Brassy minnow

3 percent

Sand shiner

3 percent

Other

8 percent

Tongue River tributaries
Table 14. Unadjusted fish community metric values for the main-stem Tongue River, Wyoming and Montana, 2005–06 and 2008. [Metric definitions from Bramblett and others (2005)] Site number (fig. 1) Abbreviated site name Sample date Number of Percentage of Native species Native families Native catostomid and ictalurid species Benthic invertivorous species Native long-lived species Tolerant individuals Invertivorous cyprinid individuals Litho-obligate reproductive guild individuals 

T5 Tongue River below Youngs Creek 8/29/2005 6 3 4 3 4 34 8 27 

8/24/2006 6 3 4 3 4 21 19 32 

9/11/2008 6 3 4 3 8 12 13 30 

T9 Tongue River at State line 8/25/2005 8 3 4 2 4 33 8 32 

8/28/2006 8 3 5 3 3 19 18 41 9/10/2008 6 4 3 2 8 16 15 32 

T10 Tongue River above Hanging Woman Creek 8/30/2005 5 3 5 1 5 20 0 29 

8/29/2006 6 3 5 2 6 28 0 43 

9/9/2008 6 2 6 2 9 10 0 59 

T14 Tongue River at Birney Day School 8/31/2005 6 3 5 2 5 31 1 43 

8/30/2006 7 3 6 3 7 28 3 38 

9/8/2008 5 2 5 1 9 36 0 27 

Table 15. Analysis of variance in fish community metrics, main-stem Tongue River and main-stem Powder River, Wyoming and Montana, 2005–08. [Significance tested by Tukey method at probablility level less than 0.05; data for Powder River also include samples collected during 2004] Metric Main-stem Tongue River Main-stem P

Significant differences between sites Significant differences between years Significant differences between sites 

Number of native species None None None Number of native families None None None Number of native catostomid and ictalurid species None None None Number of benthic invertivorous species None None None Number of native species with long lived individuals None None None Percentage of tolerant individuals None None P3 to P8, P11 to P13 Percentage of invertivorous cyprinid individuals T10 to T5, T10 to T9, T14 to 

T5, T14 to T9

None None 

Percentage of litho-obligate reproductive guild individuals None None None Percentage of tolerant reproductive guild individuals None None None Percentage of native individuals T10 to T5, T10 to T9, T14 to 

T5

None P11 to P13 
Assessment of Ecological Conditions 45

Figure 14. Selected unadjusted fish community metric values for the main-stem Tongue River, Wyoming and Montana, 2005–06 and 2008.

0

1

2

3

4

5

6

7

T5 T9 T10 T14

NUMBER OF NATIVE CATOSTOMID AND 

ICTALURID SPECIES 

0

0.5

1

1.5

2

2.5

3

3.5

T5 T9 T10 T14

NUMBER OF BENTHIC INVERTIVOROUS SPECIES 

0

1

2

3

4

5

6

7

8

9

10

T5 T9 T10 T14

NUMBER OF NATIVE LONG-LIVED SPECIES

0

2

4

6

8

10

12

14

16

18

20

T5 T9 T10 T14

PERCENTAGE OF INVERTIVOROUS CYPRINID 

INDIVIDUALS 

0

10

20

30

40

50

60

70

T5 T9 T10 T14

PERCENTAGE OF NATIVE INDIVIDUALS

2005

2006

2008

EXPLANATION
46 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Table 16. Fish community metric and Index of Biotic Integrity (IBI) scores for the Tongue and Powder River tributaries, Wyoming and 

Montana, 2005–06 and 2008. 

[Metric definitions from Bramblett and others (2005)]

Site

number

(fig.1)

Abbreviated site name Sample

date

Species richness and composition scores

Number of

species

Number of

families

Number of native

catostomid and

ictalurid species

Percentage of 

tolerant individuals

T2 Goose Creek 8/22/2005 6.1 7.6 7.2 9.2

8/22/2006 5.0 7.6 6.2 8.1

8/8/2008 5.5 7.6 7.2 8.9

T3 Upper Youngs Creek 6/15/2005 9.4 8.1 9.6 9.7

6/28/2006 9.4 8.1 9.6 7.9

6/26/2008 9.4 8.1 10.0 8.9

T4 Youngs Creek at mouth 6/14/2005 7.5 5.4 6.9 2.0

6/27/2006 9.1 7.2 8.0 3.6

6/26/2008 8.6 7.2 8.0 5.9

T6 Upper Squirrel Creek 6/16/2005 7.7 5.9 7.9 10.0

6/29/2006 8.8 7.7 9.0 0.6

6/25/2008 8.8 7.7 9.0 8.1

T7 Squirrel Creek at mouth 6/13/2005 8.5 7.5 8.6 6.2

6/25/2008 6.8 5.7 0.0 0.0

T8 Prairie Dog Creek 8/26/2005 5.2 5.9 7.5 7.5

8/25/2006 6.8 7.7 8.6 7.6

9/10/2008 6.8 7.7 8.6 6.1

T13 Hanging Woman Creek at mouth 6/23/2005 4.8 7.5 6.0 0.0

6/26/2006 3.7 3.8 3.8 0.0

6/24/2008 5.4 5.6 6.0 3.7

T17 Otter Creek at mouth 6/30/2005 4.8 5.3 4.2 2.0

6/28/2006 3.7 3.5 3.2 0.0

6/24/2008 3.7 3.5 0.0 1.8

P7 Crazy Woman Creek near mouth 7/14/2005 5.0 7.0 4.9 8.5

8/1/2006 6.1 7.0 6.0 6.5

8/20/2008 8.4 8.8 8.2 8.8

P10 Clear Creek 8/24/2005 7.6 10.0 7.9 8.0

8/21/2006 7.6 10.0 6.8 9.4

8/5/2008 6.4 10.0 7.9 9.3

P15 Little Powder River above Dry Creek 6/23/2005 5.2 6.7 4.5 4.5

6/23/2006 6.3 6.7 5.5 9.3

8/19/2008 6.9 8.6 6.6 8.4

Although the number of individuals varied among years, the 

mean number of species collected per site was similar between 

sampled years: 8.8 species in 2005, 9.6 species in 2006, and 

9.1 species in 2008. The mean number of species collected 

per site in 2004 was 10, but only five sites were sampled in 

that year.

Community Structure

The Index of Biotic Integrity (IBI) developed for small 

prairie streams in Montana (Bramblett and others, 2005) was 

applied to the fish community data from the tributary streams 

of the Powder River by using the same metrics used for the 

Tongue River tributaries. Because the IBI was not intended for 

use in rivers with large drainage areas, raw and unadjusted fish 

community metric values were evaluated for the main-stem 

Powder River (table 18).

Results of ANOVA with the Tukey method show that 

there was no significant difference for fish community metrics 

among sites or years in the main-stem Powder River except for 

percentage of tolerant individuals and the percentage of native 

individuals (table 15). The percentage of tolerant individuals 

generally was higher at sites P3 and P4 than at sites farther 

downstream, and the percentage of native individuals generally was higher at sites P5, P8, P9, P11, and P12 than at other 

sites on the main-stem Powder River (fig. 17).

The fish community at Crazy Woman Creek near mouth 

(site P7) had the highest IBI score, 81 in 2008, among the 

Powder River tributaries that were sampled (table 16). IBI 

scores from Clear Creek (site P10) and Little Powder River 

above Dry Creek (site P15) also had relatively high IBI scores 

ranging from 62 to 70 for site P10 and from 59 to 72 for 

two of three scores for site P15. The IBI scores for the Little 

Powder River above Dry Creek (site P15) trended upward 

from 2005 to 2008 with scores ranging from 45 to 72 (fig. 18 

and table 16), with a mean of 59. Crazy Woman Creek above 

mouth (site P7) had IBI scores ranging from 61 to 81 with a 

mean of 67. Clear Creek (site P10) had relatively static IBI 

scores from 2005 to 2008 (fig. 18).
Assessment of Ecological Conditions 47

Table 16. Fish community metric and Index of Biotic Integrity (IBI) scores for the Tongue and Powder River tributaries, Wyoming and 

Montana, 2005–06 and 2008.—Continued 

[Metric definitions from Bramblett and others (2005)]

Site

number

(fig.1)

Trophic composition scores Reproductive guild composition scores Fish abundance and composition scores

Percentage of

invertivorous

cyprinid individuals

Number of 

benthic

invertivorous

species

Percentage of

litho-obligate

reproductive 

guild”individuals

Percentage of tolerant 

reproducetive guild 

individuals

Percentage of

native individuals

Number of native

species with 

long-lived

individuals

IBI

Score

T2 0.1 8.2 2.2 9.0 1.8 7.6 59

0.2 6.5 2.7 8.2 2.2 7.6 54

0.1 8.2 1.0 0.4 0.9 10.0 50

T3 10.0 10.0 10.0 0.3 10.0 10.0 87

10.0 10.0 10.0 1.5 10.0 10.0 87

10.0 10.0 10.0 10.0 10.0 10.0 96

T4 2.8 10.0 2.5 8.6 10.0 9.9 66

1.5 10.0 1.7 6.3 10.0 9.9 67

7.5 10.0 8.6 8.9 8.1 9.9 83

T6 10.0 10.0 10.0 0.0 10.0 9.9 81

1.4 9.5 1.4 9.9 10.0 8.9 67

10.0 10.0 1.5 8.7 9.9 10.0 84

T7 8.8 9.0 7.8 3.3 9.3 9.5 78

0.0 0.0 0.0 4.3 5.0 9.5 10

T8 0.1 6.8 8.4 3.3 6.9 7.8 59

8.3 10.0 10.0 1.2 8.6 8.9 78

0.6 10.0 7.5 6.0 6.4 10.0 70

T13 0.0 4.6 0.8 8.9 8.4 5.3 46

0.0 4.6 0.0 10.0 10.0 4.3 40

0.0 8.0 0.5 3.6 6.0 5.3 44

T17 0.0 3.8 0.4 7.8 9.4 3.6 41

0.0 3.8 0.5 9.6 8.8 4.6 38

0.0 0.0 2.7 1.4 9.8 5.6 29

P7 3.2 5.0 9.9 0.0 10.0 7.2 61

1.5 5.0 10.0 0.4 9.9 8.2 61

1.1 6.7 10.0 8.9 9.9 10.0 81

P10 0.3 4.7 6.2 4.4 6.2 10.0 65

3.5 6.4 6.2 2.4 7.7 10.0 70

0.4 6.4 3.8 3.3 4.8 10.0 62

P15 0.4 2.8 6.2 3.7 8.0 3.6 45

0.5 4.5 10.0 0.3 9.5 6.7 59

0.1 6.2 9.0 8.5 9.2 8.7 72

Figure 15. Index of Biotic Integrity scores (IBI) for fish communities of the Tongue River tributaries, 

Wyoming and Montana, 2005–06 and 2008.

0

20

40

60

80

100

T2 T3 T4 T6 T7 T8 T13 T17

IBI SCORE

SITE

2005

2006

2008

EXPLANATION
48 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Potential Effects of Water Produced 

from Coalbed Natural Gas Development 

on Biological Communities

The ecological data presented in this report were collected to identify current conditions (2005–08) for aquatic 

biota and their habitat. Although no specific discharges of 

CBNG effluent were addressed in this study, a synthesis of 

the water-quality, macroinvertebrate, algal, and fish data is 

presented addressing existing and potential effects of CBNG 

produced water on biological communities.

Water production associated with CBNG development 

during 2005–08 tended to be largest in the Powder and Tongue 

River drainage basins in Wyoming. Among all of the drainages 

in the study area, the upper Powder River drainage basin had 

the largest increase between 2006 and 2008 in the amount of 

CBNG water production (fig. 2). For example, water production for the upper Powder River drainage basin in Wyoming 

during 2008 was more than twice as much compared to 

production prior to that time. It should be noted, however, that 

not all of the production water reaches the streams because of 

various methods of treatment and disposal.

Water Quality

Most water produced during CBNG development in 

Wyoming is discharged into constructed reservoirs or surface drainages where the water may infiltrate, become part 

of the ambient streamflow, or evaporate. Concerns have been 

expressed regarding the quality of some waters produced 

during CBNG development and effects produced waters 

may have on water quality in streams that drain the CBNGdevelopment area. Sodium and bicarbonate are the dominant 

Table 17. Fish abundance in samples from Powder River drainage basin, Wyoming and Montana, 2004–06 and 2008.

[Shaded cells indicate main-stem sampling sites on the Powder River. *, Hybognathus spp. represents genus level identifications in the field; subsamples 

of Hybognathus spp. were retained from selected samples for laboratory identification, and are subdivided by species, either plains minnow or western 

silvery minnow. L, species that were only identified in larval fish samples; the total number of species includes laboratory identification of larval fish and 

Hybognathus spp.]

Site

number

(fig.1)

Abbreviated site name Sample

date

Black

bullhead

BluegillChannel

catfish

Common

carp

Creek

chub

Fathead

minnow

Flathead

chub

GoldeyeGreen

sunfish

Hybognathus

spp.*

P3 Powder River below Willow Creek 8/9/2004 0 0 14 1 0 33 223 1 0 24

8/10/2005 0 0 9 0 0 2 703 0 0 26

7/26/2006 0 0 9 0 0 1 161 0 0 8

7/21/2008 14 0 8 0 0 2 61 0 0 24

P4 Powder River below Burger Draw 8/19/2005 0 0 46 1 0 2 272 3 0 174

7/27/2006 0 0 10 0 0 13 1,079 1 0 259

7/24/2008 2 1 1 0 0 1 54 0 2 308

P5 Powder River above Crazy Woman Creek 7/13/2004 0 0 20 0 0 1 587 0 0 328

7/13/2005 0 0 16 0 0 3 470 3 2 245

7/28/2006 0 0 61 0 0 3 2,384 0 0 96

7/23/2008 0 0 3 0 0 0 116 1 0 4

P7 Crazy Woman Creek near mouth 7/14/2005 0 0 0 0 0 10 0 0 0 0

8/1/2006 0 0 9 6 0 16 15 0 4 0

8/20/2008 1 0 13 0 0 4 5 1 0 7

P8 Powder River below Crazy Woman Creek 8/4/2004 0 0 40 0 1 0 343 0 0 173

8/18/2005 0 0 27 0 0 2 335 0 0 76

8/2/2006 0 0 41 7 2 1 118 2 0 51

7/28/2008 0 0 10 0 0 0 112 0 0 48

P9 Powder River above Clear Creek 8/5/2004 0 0 24 0 L 0 78 0 0 8

7/24/2005 0 0 131 0 0 9 21 0 0 9

8/4/2006 0 0 166 4 0 2 324 1 1 80

7/29/2008 0 0 20 0 0 0 118 0 9 19

P10 Clear Creek 8/24/2005 0 0 9 29 0 22 8 15 2 0

8/21/2006 0 0 4 14 5 0 128 6 2 0

8/5/2008 0 0 46 22 0 0 9 27 0 0

P11 Powder River below Clear Creek 8/6/2004 0 0 31 0 0 L 157 1 0 17

7/25/2005 0 0 228 1 0 8 43 0 0 0

8/3/2006 0 0 2 0 0 0 112 0 0 0

7/30/2008 0 0 8 0 0 0 26 0 0 1

P12 Powder River at Moorhead 7/18/2005 0 0 0 0 0 0 36 2 0 2

8/2/2006 0 0 105 1 0 0 218 12 0 0

7/31/2008 0 0 11 0 0 1 53 0 1 9

P13 Powder River at Broadus 7/19/2005 0 0 2 0 0 0 13 0 0 4

8/2/2006 0 0 8 0 0 0 416 0 4 0

8/1/2008 0 0 0 0 0 0 21 1 0 27

P15 Little Powder River at Highway 59 6/23/2005 12 0 2 5 3 56 3 0 27 0

6/23/2006 3 0 4 3 0 8 1 0 18 2

8/19/2008 0 0 16 0 0 12 0 1 17 10
Potential Effects of Water Produced from Coalbed Natural Gas Development on Biological Communities 49

Table 17. Fish abundance in samples from Powder River drainage basin, Wyoming and Montana, 2004-06 and 2008.—Continued

[Shaded cells indicate main-stem sampling sites on the Powder River. *, Hybognathus spp. represents genus level identifications in the field; subsamples 

of Hybognathus spp. were retained from selected samples for laboratory identification, and are subdivided by species, either plains minnow or western 

silvery minnow. L, species that were only identified in larval fish samples; the total number of species includes laboratory identification of larval fish and 

Hybognathus spp.]

Site

number

(fig.1)

Plains

minnow*

Western

silvery

minnow*

Longnose

dace

Mountain

sucker

Northern

plains

killifish

River

carpsucker

Rock

bass

Sand

shiner Sauger

Shorthead

redhorse

Shovelnose

sturgeon

Smallmouth

bass

Stonecat

Sturgeon

chub

White

sucker

Total

number

of species

P3 24 0 28 1 27 8 0 487 0 0 0 0 1 0 0 12

26 0 17 0 80 70 0 847 0 0 0 0 1 0 1 10

0 0 24 0 164 50 0 4,486 0 0 0 0 4 0 0 9

24 0 0 0 5 1 0 51 0 0 0 0 0 0 0 8

P4 166 8 52 0 197 68 0 685 0 0 0 0 0 0 0 11

0 0 70 0 43 46 0 3,789 0 0 0 0 2 0 0 10

188 120 18 0 8 5 0 123 0 0 0 0 3 0 0 13

P5 319 9 15 0 8 6 0 1,294 0 0 0 0 1 0 0 10

245 0 2 0 4 136 0 1,668 0 1 0 0 0 0 0 11

0 0 17 0 20 75 0 3,104 0 0 0 0 0 2 0 9

4 0 0 0 1 21 0 68 0 0 0 0 0 0 0 7

P7 0 0 3 0 0 0 0 33 0 0 0 0 1 0 8 5

0 0 67 0 0 0 0 402 0 0 0 0 9 0 227 9

0 7 11 0 0 0 0 129 0 3 0 1 1 0 16 13

P8 173 0 33 0 0 2 0 933 0 1 0 0 12 0 0 9

0 0 29 0 15 4 0 875 0 0 0 0 0 0 0 8

0 0 14 0 3 182 0 1,903 0 3 0 0 0 0 0 12

48 0 0 0 1 9 0 160 0 0 0 0 0 0 0 6

P9 8 0 1 0 1 2 0 446 0 0 0 0 2 0 0 9

0 0 0 0 0 4 0 370 0 0 0 0 0 0 0 6

0 0 0 0 0 25 0 794 0 0 0 0 0 0 0 9

10 9 0 0 1 4 0 192 0 0 0 0 2 0 0 9

P10 0 0 0 0 0 13 91 71 2 40 0 22 32 0 19 14

0 0 1 0 0 0 76 192 1 12 0 33 45 0 13 14

0 0 0 0 0 29 96 0 2 25 0 56 14 0 0 11

P11 17 0 2 0 0 3 0 687 0 0 0 1 7 0 0 10

0 0 0 0 0 25 0 404 0 0 0 1 17 0 L 10

0 0 4 0 0 3 0 289 0 0 0 0 3 0 0 6

1 0 0 0 0 0 0 18 0 0 0 0 1 0 0 5

P12 1 1 11 0 0 0 0 14 0 0 0 0 0 0 0 6

0 0 6 0 0 116 0 283 0 2 0 0 1 4 0 10

9 0 2 0 0 1 0 9 0 0 0 0 12 1 0 10

P13 4 0 246 0 6 0 0 39 0 0 0 0 0 1 0 7

0 0 55 0 28 43 0 559 0 0 0 0 0 0 0 7

19 8 16 0 0 1 0 64 0 0 1 0 0 0 0 8

P15 0 0 0 0 0 0 0 95 0 0 0 0 0 0 13 9

2 0 19 0 0 5 0 453 0 0 0 0 0 0 4 11

0 10 1 0 0 1 0 150 0 4 0 0 0 0 3 10

ions in coalbed waters (Rice and others, 2000) in contrast to 

area stream waters, which typically have a larger ambient 

percentage of calcium, magnesium, and sulfate (Clark and 

Mason, 2007). The primary constituents of concern in CBNG 

produced water are sodium, sodium-adsorption ratio, specific 

conductance, and dissolved solids because large values for 

these constituents have the potential to negatively affect the 

water for irrigation uses (Brown and Johnston, 2005).

The potential effects of CBNG discharges on biological communities include several aspects of water quality. 

Increases in sodium bicarbonate concentrations in streams 

to potentially toxic levels as a result of CBNG produced 

water inputs are of concern to aquatic life (Bureau of Land 

Management, 2003). Larval fish that were exposed to sodium 

bicarbonate had lower hatch and survival rates compared 

to controls for both acute and chronic exposures (Skaar 

and others, 2006). Coalbed waters, which have a relatively 

constant temperature compared to streams, have the potential 

to increase or decrease stream temperature depending on the 

time of year. Turbidity associated with coalbed waters may 

be lower than the natural stream turbidity; however, increased 

concentrations of suspended sediment resulting from indirect 

CBNG-development activities such as road construction and 

channel erosion may increase stream turbidity. Increased 

sedimentation also has potential to affect substrate and spawning habitat. Coalbed waters typically are anoxic and reducing, 

which increases the solubility of some trace elements, including iron, manganese, and barium (Rice and others, 2000). The 

discharge of anoxic coalbed waters to streams could affect 

dissolved-oxygen concentrations of streams and affect the 

precipitation of selected trace elements, particularly iron and 

manganese. Data collected from ATG sites indicated that iron 

and manganese concentrations were higher than the chronic 

and, in a few cases, the acute aquatic-life criteria. The mobilization of other trace elements, including arsenic and selenium, 

in basin sediments from the addition of coalbed waters to the 
50 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Figure 16. Relative abundance of fish by species in samples from the Powder River 

drainage basin, Wyoming and Montana, 2004–06 and 2008.

Sand shiner

63 percent

Flathead chub

22 percent

Hybognathus spp.

5 percent

Channel catfish

3 percent

River carpsucker

2 percent

Longnose dace

2 percent

Northern plains killifish 

2 percent

Other

1 percent

Sand shiner

48 percent

White sucker

9 percent

Rock bass

8 percent

Flathead chub

6 percent

Fathead minnow

4 percent

Smallmouth bass

3 percent

Channel catfish

3 percent

Longnose dace

3 percent

Stonecat

3 percent

Shorthead redhorse

3 percent

Other

10 percent

Main-stem Powder River

Powder River tributaries
Table 18. Unadjusted fish community metric values for the main-stem Powder River, Wyoming and Montana, 2004–06 and 2008. [Metric definitions from Bramblett and others (2005)] Site number (fig. 1) Abbreviated site name Sample date Number of Percentage of Native species Native families Native catostomid and ictalurid species Bbenthic invertivorous species Native long-lived species Tolerant individuals Invertivorous cyprinid individuals Litho-obligat

reproductive guild individu

P3 Powder River below Willow Creek 8/9/2004 11 4 4 1 4 7.2 29.6 61.9 

8/10/2005 9 3 4 1 4 4.7 41.0 53.3 7/26/2006 7 3 3 1 5 3.4 3.8 93.0 7/21/2008 6 3 2 0 3 12.7 36.7 31.3 

P4 Powder River below Burger Draw 8/19/2005 10 4 2 1 6 13.3 21.6 53.9 

7/27/2006 8 4 3 1 7 1.1 21.6 73.6 7/24/2008 9 3 3 1 5 3.2 13.6 28.3 

P5 Powder River above Crazy Woman Creek 7/13/2004 9 3 3 1 3 0.4 26.6 58.2 

7/13/2005 9 4 3 2 5 0.4 18.5 71.0 7/28/2006 7 3 2 2 5 0.4 41.7 55.5 7/23/2008 6 4 2 0 1 0.5 54.2 42.1 

P8 Powder River below Crazy Woman Creek 8/4/2004 9 3 4 2 6 0.0 24.5 63.8 

8/18/2005 7 3 2 1 4 1.2 26.7 66.6 

8/2/2006 10 4 3 2 5 0.5 5.8 90.5 

7/28/2008 5 3 2 0 1 0.3 32.9 49.7 

P9 Powder River above Clear Creek 8/5/2004 8 3 3 1 5 0.2 14.1 80.2 

7/24/2005 6 3 2 0 2 1.7 3.9 68.8 

8/4/2006 7 4 2 0 6 0.5 23.2 58.7 

7/29/2008 7 3 3 0 3 2.7 32.3 54.2 

P11 Powder River below Clear Creek 8/6/2004 9 4 3 1 6 0.0 17.5 77.3 

7/25/2005 9 3 4 0 5 1.2 5.9 61.3 

8/3/2006 6 3 3 1 2 0.0 28.1 72.4 

7/30/2008 5 2 2 0 0 0 48.1 35.2 

P12 Powder River at Moorhead 7/18/2005 6 2 0 1 1 0.0 72.3 41.5 

8/2/2006 10 4 4 3 7 0.1 30.5 56.7 

7/31/2008 9 3 3 2 5 2 56.0 25.0 

P13 Powder River at Broadus 7/19/2005 6 2 1 2 2 1.9 83.6 92.0 

8/2/2006 5 3 2 1 1 2.9 42.3 59.0 8/1/2008 8 4 1 2 6 0 28.2 63.4 
52 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Figure 17. Selected unadjusted fish community metric values for the main-stem Powder River, Wyoming and Montana, 2004–06 and 

2008.

80

85

90

95

100

105

P3 P4 P5 P8 P9 P11 P12 P13

PERCENTAGE OF NATIVE INDIVIDUALS

0

2

4

6

8

10

12

P3 P4 P5 P8 P9 P11 P12 P13

NUMBER OF NATIVE SPECIES

2005

2004

2006

2008

EXPLANATION

0

2

4

6

8

10

12

14

P3 P4 P5 P8 P9 P11 P12 P13

PERCENTAGE OF TOLERANT INDIVIDUALS

0

10

20

30

40

50

60

70

80

90

PERCENTAGE OF INVERTIVOROUS CYPRINID INDIVIDUALS 

P3 P4 P5 P8 P9 P11 P12 P13

0

5

10

15

20

25

30

35

P3 P4 P5 P8 P9 P11 P12 P13

PERCENTAGE OF TOLERANT REPRODUCTIVE 

GUILD INDIVIDUALS 
Potential Effects of Water Produced from Coalbed Natural Gas Development on Biological Communities 53

surface also has been identified as a potential water-quality 

concern (Brinck and others, 2008). Nutrient cycling in streams 

also may be affected by inputs of coalbed waters, which can 

contain elevated concentrations of ammonia. Increases in 

inputs of inorganic nitrogen could increase the potential for 

eutrophication (Smith and others, 2009).

Macroinvertebrate Communities

Macroinvertebrate communities of the main-stem Tongue 

River indicated some differences in community composition 

in the downstream direction. For example, the relative abundance of noninsects at a site on the main-stem Tongue River 

downstream from Tongue River Reservoir during 2005–08 

was significantly different from other sites on the main stem 

upstream and downstream from the reservoir. Given the differences in water quality from upstream to downstream from the 

reservoir, the differences in macroinvertebrate communities 

might be attributable to the effects of the reservoir rather than 

the effects of CBNG development.

Macroinvertebrate community composition in the middle 

reach of the main-stem Powder River, from below the confluence with Willow Creek to below the Crazy Woman Creek 

confluence, differed from communities in the upper and lower 

reaches of the Powder River. Macroinvertebrate community 

metric values at sampling sites in the middle reach during 

2005–08 were significantly different (ANOVA, p < 0.05) from 

metric values at other sites on the main-stem Powder River. 

The affected metrics included taxa richness, relative abundance, feeding modes, and tolerance, which were indicative 

of communitywide differences. Ephemeroptera taxa richness, 

Ephemeroptera relative abundance, and intolerant macroinvertebrate relative abundance tended to be lower, whereas Diptera 

relative abundance and filterer-collector relative abundance 

tended to be higher, in the middle reach of the Powder River 

than in other reaches.

Potential causes of the observed pattern in macroinvertebrate communities of the main-stem Powder River include 

natural influences, coalbed natural gas development, and other 

development such as conventional oil and gas development in 

the Salt Creek drainage. For example, chloride concentrations 

in the Powder River downstream from Salt Creek sometimes 

exceeded USEPA acute and chronic criteria for the protection 

of aquatic life but not WDEQ site-specific criteria. Testing 

of relations between environmental variables and the macroinvertebrate taxonomy and metrics from the Powder River 

indicated some of the variation in the macroinvertebrate communities could be explained by variation in the environmental 

variables. The environmental variables that best correlated 

with the macroinvertebrates communities included physical variables (turbidity, embeddedness, D84, and streamflow) 

and chemical variables (alkalinity and specific conductance). 

The Powder River is known for its relatively high transport 

of fine sediment (Lowry and others, 1986), which in turn can 

affect turbidity, embeddedness, and D84. Of the environmental 

variables correlated with the macroinvertebrate communities, 

alkalinity perhaps is the best indicator of potential CBNG 

produced water influences because of the sodium-bicarbonate 

signature of CBNG water (Rice and others, 2000). Mean 

alkalinity concentrations at the time of ecological sampling 

were about 200 mg/L throughout the main-stem Powder River 

from upstream from Salt Creek to Locate, near the mouth at 

the Yellowstone River, with the exception of site P4, which is 

downstream from Burger Draw (fig. 4). The alkalinity concentrations in the Powder River below Burger Draw (site P4) 

ranged from 224 mg/L in 2008 to 1,540 mg/L during the 

drought year of 2006, with a mean near 600 mg/L. This site 

receives CBNG discharges from several upstream drainages.

Given that macroinvertebrate communities integrate 

responses to environmental variables over a longer time 

period than instantaneous samples, it is likely that the macroinvertebrate communities in the middle reach of the Powder 

River from Willow Creek to below the Crazy Woman Creek 

confluence are responding to variation in the measured 

environmental variables beyond those observed at the time 

of sampling or to other environmental variables that were not 

measured. Water production from CBNG development in the 

Powder River drainage more than doubled from 2006 to 2008. 

Discharge of CBNG produced water is a logical explanation 

for the observed patten in macroinvertebrate communities 

of the main-stem Powder River, but further study would be 

needed for confirmation as described in the section “Further 

Study Needs.”

Figure 18. Index of Biotic Integrity (IBI) scores for fish communities 

in selected Powder River tributaries, Wyoming, 2005–06 and 2008.

0

10

20

30

40

50

60

70

80

90

P7 P10 P15

IBI SCORE

SITE

2005

2006

2008

EXPLANATION
54 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Algal Communities

Similar to the pattern observed for the macroinvertebrates, the algal communities of the main-stem Powder River 

in 2005 and 2007 indicated differences in communities of the 

middle reach from those in the upper or lower reaches. Algal 

communities in the middle reach often were characterized by 

dominance by a single taxon and by low biovolume of algae 

compared to the upper and lower reaches of the Powder River.

Fish Communities

Fish species richness was relatively high in the middle 

reach of the main-stem Powder River, the same reach where 

macroinvertebrate and algal communities appeared to be 

anomalous. Although a few significant differences in fish 

metrics along the main-stem Powder River were noted, the 

differences did not correspond to the pattern observed for the 

macroinvertebrate and algae communities.

The Powder River fish assemblage has been described as 

largely intact as a result of the relatively unperturbed state of the 

river (Hubert, 1993). More recently, Senecal (2009) derived a 

reference fish assemblage for the Powder River on the basis of 

1964–80 sampling data and compared the reference fish assemblage dataset to more current sampling data from 1994 and 2008. 

The reference fish assemblage using the combined 1964–80 

dataset was composed predominantly of flathead chub, followed 

by Hybognathus spp. and sturgeon chub (Senecal, 2009). In 

contrast, the 2008 fish assemblage was dominated by sand shiners, Hybognathus spp., flathead chub, river carpsucker, channel 

catfish, and longnose dace (Senecal, 2009). The differences 

between the reference fish assemblage and the more recent fish 

assemblages were due to decreases in proportions of previously 

common species, such as sturgeon chub, and increases in proportions of two species, sand shiners and northern plains killifish. 

Senecal (2009) states that care must be taken with the results 

because the datasets used in the reference fish assemblage were 

collected at different times by different investigators, and lack of 

standardization across datasets may have contributed to discrepancies. However, results presented in this report are similar to 

those as presented by Senecal (2009). Slight differences in the 

relative abundance in the 2005–06 and 2008 samples, in order 

of dominance, were sand shiner, flathead chub, Hybognathus spp., 

channel catfish, river carpsucker, longnose dace, and northern 

plains killifish. Reasons for the increase in abundance of sand 

shiners are unclear.

A study conducted by Davis (2008) indicated mixed results 

of the effects of CBNG development on fish assemblages in the 

Powder River Basin during 2005–06. For example, species richness and IBI scores were similar between developed and undeveloped sites, and no strong relations existed between overall 

IBI scores or most IBI metric scores and the number or density 

of CBNG wells in a drainage area. Other evidence, however, 

indicated that CBNG-produced water may negatively affect fish 

assemblages. Conductivity was, on average, higher in streams 

with CBNG-produced water and was negatively related to 

biotic integrity. Bicarbonate, one of the primary salts in product 

water, appeared to be harmful to some species of fish. Altered 

flow regimes may present the biggest direct effect from CBNG 

effluent on fish assemblages (Davis, 2008; Senecal, 2009), and 

potential effects of CBNG development may be more apparent during wet years when more sensitive fish assemblages are 

present. Also, toxicity testing (Skaar and others, 2006) indicates 

that larval fish are more sensitive to CBNG effects than the 

adult and juvenile fish that were collected during this study.

Further Study Needs

The anomalous patterns of macroinvertebrate and 

algal communities in the middle reach of the main-stem 

Powder River are worthy of further study to help assess 

the natural or anthropogenic factors affecting the anomalous patterns. One approach to further study would be 

establishment of paired sampling sites upstream and 

downstream from known CBNG discharge points. As an 

aid to selecting potential sampling sites, water-quality 

and streamflow data from the current USGS monitoring network (http://wy.water.usgs.gov/) were evaluated. 

Fifteen tributaries to the Powder River in Wyoming are 

currently (2010) sampled in cooperation with the WDEQ. 

Instantaneous streamflow values indicate that other than 

the perennial tributaries (Salt Creek, Crazy Woman Creek, 

and Clear Creek) bracketed during this study, Pumpkin 

Creek (in Johnson County), Beaver Creek, and Wild Horse 

Creek (fig. 1) contribute the largest amount of streamflow 

to the Powder River. Although streamflow in Pumpkin, 

Beaver, and Wildhorse Creeks often was small compared to 

streamflow in the Powder River, these streams are of interest for biological monitoring because specific-conductance 

values and alkalinity concentrations measured in the tributaries commonly were higher than those measured in the 

Powder River. Permit data on file with the WDEQ indicate 

other tributaries, such as Indian Creek and Flying E Creek, 

also contribute treated and untreated CBNG discharges 

to the Powder River. One or more future biological monitoring sites could be located upstream from Willow Creek 

to help determine a reference condition upstream from 

CBNG discharges. Consideration to defining the spatial 

extent of the effects of tributaries and whether the effects 

are cumulative with distance downstream also may be 

warranted.

Additional analysis of data from the water-quality 

monitoring network in the Powder River and Tongue River 

drainage basins would be useful in determining long-term 

trends in water quality. Specific conductance in the Tongue 

River increased from Monarch (site T1) to the State line 

(site T9; fig. 4), but it is not known if the increase is due to 

effects of CBNG discharges or other influences such as irrigation return flows and discharge of treated sewage effluent. 

Long-term ecological monitoring also may be considered to 

identify trends and natural variability in biological communities in the Tongue and Powder River Basins.
Summary 55

Summary

In response to concerns about the effects of coalbed natural 

gas development (CBNG) on streams of the Powder River structural basin in Wyoming and Montana, an interagency Aquatic 

Task Group (ATG) was formed in 2004. Participants in the ATG 

included the Bureau of Land Management (BLM), the Montana 

Department of Environmental Quality (MDEQ), Montana Fish, 

Wildlife, and Parks, the U.S. Environmental Protection Agency 

(USEPA), the Wyoming Department of Environmental Quality 

(WDEQ), the Wyoming Game and Fish Department, and the 

U.S. Geological Survey (USGS). The ATG developed a monitoring plan to (1) establish current ecological conditions for aquatic 

biota and their habitat and (2) determine existing and potential 

effects of CBNG-produced water on aquatic life. The sample collection performed by the USGS during 2005–08 and described in 

this report was conducted under the direction of the ATG to meet 

objective 1 of the monitoring plan and, to the extent possible, 

objective 2.

Samples for environmental variables (water quality and 

habitat) and biological communities (macroinvertebrates, 

algae, and fish) were collected from 47 sites in 2005–08. The 

types of samples and number of sites sampled varied annually 

due to drought and program constraints.

Current ecological conditions (2005–08) are described in 

this report for water quality, habitat, macroinvertebrates, algae, 

and fish communities. Water-quality data collected during 

water years 2005–08 indicated most constituents generally 

did not exceed acute or chronic criteria for the protection of 

aquatic life set by the States of Wyoming and Montana and the 

USEPA. Comparison of data from sites in Wyoming to WDEQ 

criteria indicated that pH and concentrations of selenium, 

iron, and manganese at a few sites in the Cheyenne and Belle 

Fourche River drainage basins exceeded criteria. Chloride 

concentrations exceeded the WDEQ chronic criterion in a 

few samples from the Little Powder River. Chloride concentrations were relatively high in the main-stem Powder River 

downstream from Salt Creek but did not exceed the WDEQ 

site-specific acute chloride criterion. Comparison of waterquality data from sites in Montana to MDEQ criteria indicated numerous exceedances for trace elements, particularly 

in samples from Pumpkin Creek and the main-stem Powder 

River at Moorhead and Locate, Montana.

Macroinvertebrate communities showed similarities 

within stream groups. Macroinvertebrate community composition at sites on the main-stem Tongue River and mountainous 

tributaries such as Clear Creek (TRMS group) were characterized by high Ephemeroptera taxa richness, high relative 

abundance of Ephemeroptera, dominance of the collectorgatherer feeding mode, and a high proportion of intolerant 

macroinvertebrates compared to communities at sites on the 

Tongue River plains tributaries (TRPT group) and main-stem 

Powder River (PRMS group). Among the Tongue River sites, 

the Tongue River above Hanging Woman Creek contained 

significantly (p < 0.05) different (higher) relative abundance 

of noninsects than other sites on the main-stem Tongue River 

during 2005–08, perhaps due to the influence of Tongue River 

Reservoir. The relative abundance of the scraper feeding mode 

at sites on the main-stem Tongue River was significantly different (higher) in 2006 than in 2005 or 2007–08. Significant 

differences between 2006 and other years also were noted for 

metrics including Diptera taxa richness and relative abundance 

of Trichoptera at sites on the main-stem Powder River and 

some tributaries. Streamflow and climatic data indicated 2006 

was a particularly severe year of a multiyear drought in the 

study area.

Macroinvertebrate community composition varied 

significantly (p < 0.05) among sites on the main-stem Powder 

River during 2005–08. Macroinvertebrate community metric 

values from sites in the middle reach of the main-stem Powder 

River, from below Willow Creek to below Crazy Woman 

Creek, differed from metric values in the upper and lower 

reaches of the Powder River. Metric values for Ephemeroptera 

taxa richness, Ephemeroptera relative abundance, and intolerant macroinvertebrate relative abundance tended to be lower, 

whereas Diptera relative abundance and filterer-collector relative abundance tended to be higher at sites in the middle reach 

of the main-stem Powder River than at upstream and downstream sites on the main-stem Powder River. The affected 

metrics included measures of taxa richness, relative abundance, feeding modes, and tolerance, which were indicative 

of communitywide differences.

Algal samples from the main-stem Powder River generally confirmed the pattern observed in the macroinvertebrate 

communities. Algal communities in the middle reach of the 

Powder River often were characterized by dominance of a single 

taxon and low biovolume compared to other sites in the study 

area, which might be indicative of anthropogenic disturbances. 

Diatoms composed the majority of the taxa identified in 2005 and 

2007, whereas green and blue-green algae commonly dominated 

in terms of relative abundance at sites throughout the study area.

Fish communities of the main-stem Tongue River and 

tributaries contained 29 fish species, of which 15 were native, 

during 2005–06 and 2008. Communities at the main-stem Tongue 

River sites were dominated by smallmouth bass, white sucker, 

yellow bullhead, and rock bass. Significant differences in fish 

Index of Biotic Integrity metrics from the Tongue River upstream 

from Hanging Woman Creek to those from other sites on the 

main-stem Tongue River might have been related to fish migration from Tongue River Reservoir. Fish Index of Biotic Integrity 

scores from upper Youngs Creek and upper Squirrel Creek were 

among the highest in the study area.

Fish communities of the main-stem Powder River and 

tributaries contained 24 fish species, of which 17 were native. The 

most abundant fish were native species including sand shiner and 

flathead chub. Species richness on the main-stem Powder River 

was highest downstream from Burger Draw, where 13 species 

were collected in 2008. Although a few significant differences 

in fish metrics along the main-stem Powder River were noted, 

the differences did not correspond to the pattern observed for the 

macroinvertebrate and algae communities.
56 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Potential causes of the anomalous pattern in macroinvertebrate communities of the middle reach of the main-stem Powder 

River include natural influences, discharge of production water 

from CBNG development, and other human activities. Relations 

between environmental variables and the macroinvertebrate 

taxonomy and metrics from the Powder River indicated some 

of the variation in the macroinvertebrate communities could be 

explained by variation in physical variables (specifically, turbidity, embeddedness, particle size, and streamflow) and chemical 

variables (alkalinity, pH, and specific conductance). Of those 

environmental variables, alkalinity perhaps is the best indicator 

of CBNG development because of the sodium-bicarbonate signature of CBNG water. Mean alkalinity concentrations at the time 

of biological sampling were similar throughout the main-stem 

Powder River, with the exception of the site downstream from 

Burger Draw in Wyoming that had a relatively high mean alkalinity concentration, perhaps due to the influences of several CBNG 

discharges upstream. Given that macroinvertebrate communities 

integrate responses to environmental variables over a longer time 

period than instantaneous samples, it is likely that the macroinvertebrate communities in the middle Powder River reach between 

the Willow and Crazy Woman Creek confluences are responding to variation in the measured environmental variables beyond 

those observed at the time of sampling, or to other environmental 

variables that were not measured. The recent (2006–08) large 

increase in CBNG production in the Powder River drainage is a 

logical explanation for the observed patten in macroinvertebrate 

communities of the main-stem Powder River, but further study 

would be needed for confirmation.

The fish community composition of the main-stem Powder 

River observed in this study was similar to that observed by other 

investigators during about the same timeframe but may represent a departure from historical (1964–80) conditions. Potential 

causes for the departure include natural variation and the effects 

of resource development. Toxicity testing by other investigators 

indicates larval fish are more sensitive to sodium bicarbonate 

from CBNG discharges in the study area than the adult and juvenile fish that were sampled during this study.

In conclusion, the assessment of the current condition 

(2005–08) of biological communities in the Powder River 

structural basin indicated anomalous conditions for macroinvertebrate and algal communities in the middle reach of the Powder 

River compared to the upper and lower reaches. The anomalous conditions occurred at the lower trophic levels represented 

by macroinvertebrates and algae, whereas the higher trophic 

levels represented by the fish community generally did not vary 

significantly along the Powder River during 2005–08. Although 

CBNG development might have led to the observed patterns, 

further study of macroinvertebrate and algal communities in the 

middle reach of the Powder River is needed for confirmation. The 

sampling design proposed for further study is based on paired 

sampling locations, upstream and downstream from CBNG 

discharge points.

Acknowledgments

Seth Davidson, Chris Murray, Dan Sturgis, Tom Cleasby, 

and others with the USGS assisted with data collection in 

2007–08. Many private landowners, as well as the Anadarko 

Corporation (The Woodlands, Texas), allowed access to 

sampling sites. Colleague reviewers were Daren Carlisle and 

Jill Frankforter, USGS. Eric Hargett (WDEQ), Dave Feldman 

(MDEQ), Rod McNeil (MDEQ), and several other representatives of ATG agencies provided helpful comments and 

discussion. Laura Hallberg, USGS, provided Geographic 

Information System (GIS) analyses.

References

Bahls, L.L., 1993, Periphyton bioassessment methods for 

Montana streams: Helena, Montana Department of Environmental Quality, 31 p. plus appendixes.

Barbour, M.T., Gerritsen, J., Snyder, B.D., and Stribling, J.B., 

1999, Rapid bioassessment protocols for use in streams and 

wadeable rivers—Periphyton, benthic macroinvertebrates, 

and fish (2d ed.): U.S. Environmental Protection Agency, 

Office of Water, EPA 841–B–99–002, variable pagination.

Baxter, G.T., and Stone, M.D., 1995, Fishes of Wyoming: 

Cheyenne, Wyoming Game and Fish Department Bulletin 

no. 4, 290 p.

Bramblett, R.G., Johnson, T.R., Zale, A.V., and Heggem, 

D.G., 2005, Development and evaluation of a fish assemblage index of biotic integrity for northwestern Great Plains 

streams: Transactions of the American Fisheries Society, 

v. 134, p. 624–640.

Bray, J.R., and Curtis, J.T., 1957, An ordination of the upland 

forest communities of southern Wisconsin: Ecological 

Monographs, v. 27, p. 325–349.

Brinck, E.L, Drever, J.I., and Frost, C.D., 2008, The geochemical evolution of water coproduced with coalbed natural 

gas in the Powder River Basin, Wyoming: Environmental 

Geosciences, v. 15, no. 4, p. 153–171.

Brown, T.H., and Johnston, Chris, 2005, Assessment of the 

environmental impacts of coalbed natural gas development 

in the Powder River Basin—Use of coalbed natural gasproduced water for cropland irrigation, in Zoback, M.D., 

ed., Western Resources Project final report—Produced 

groundwater associated with coalbed natural gas production in the Powder River Basin: Wyoming State Geological 

Survey Report of Investigations no. 55, chap. 3, p. 71–85.
References 57

Bureau of Land Management, 2003, Record of decision and 

resource management plan amendments for the Powder 

River Basin oil and gas project, WY–070–02–065, 

Buffalo Field Office, Wyoming, April 2003 [variously 

paged], accessed February 16, 2010, at http://www.blm.gov/

pgdata/etc/medialib/blm/wy/information/NEPA/

prb-rod.Par.71614.File.dat/00rod.pdf.

Bureau of Land Management, 2009, Powder River Basin 

Interagency Working Group, accessed on September 21, 

2009, at http://www.wy.blm.gov/prbgroup/.

Clark, M.L., and Mason, J.P., 2007, Water-quality characteristics for sites in the Tongue, Powder, Cheyenne, and Belle 

Fourche River drainage basins, Wyoming and Montana, 

water years 2001–05, with temporal patterns of selected 

long-term water-quality data: U.S. Geological Survey 

Scientific Investigations Report 2007–5146, 65 p.

Clarke, K.R., and Gorley, R.N., 2006, PRIMER v6: 

Plymouth, United Kingdom, Plymouth Marine Laboratory, 

PRIMER–E Ltd., 190 p.

Cuffney, T.C., 2003, User’s manual for the National WaterQuality Assessment Program invertebrate data analysis system (IDAS) software—Version 3: U.S. Geological Survey 

Open-File Report 2003–172, 103 p.

Davis, W.N., 2008, Effects of coalbed natural gas development 

on fish assemblages in tributary streams in Powder River 

Basin, Montana and Wyoming: Bozeman, Montana State 

University, Master’s thesis, 137 p., 26 figs.

Davis, W.N., Bramblett, R.G., Zale, A.V., and Endicott, C.L., 

2009, A review of the potential effects of coal bed natural 

gas development activities on fish assemblages of the Powder River Geologic Basin: Reviews in Fisheries Science, 

v. 17, no. 3, p. 402–422.

Helsel, D.R., and Hirsch, R.M., 2002, Statistical methods in 

water resources: U.S. Geological Survey Techniques of 

Water Resources Investigations, book 4, chap. A3, 522 p.

Hilsenhoff, W.L., 1987, An improved index of organic stream 

pollution: Great Lakes Entomologist, v. 20, p. 31–39.

Hubert, W. A., 1993, The Powder River: a relatively pristine 

stream on the Great Plains, in Hesse, L.W., Stalnaker, C.B. 

Benson, N.G. and Zuboy, J.R., eds., Restoration planning 

for the rivers of the Mississippi River ecosystem: Washington, D.C., National Biological Survey, Biological Report 19, 

p. 387–395.

Lowry, M.E., Wilson, J.F., and others, 1986, Hydrology of 

Area 50, Northern Great Plains and Rocky Mountain Coal 

Provinces, Wyoming and Montana: U.S. Geological Survey 

Water-Resources Investigations Open-File Report 83–545, 

137 p.

Montana Department of Environmental Quality, 2008, Montana numeric water quality standards: Montana Department 

of Environmental Quality, Circular DEQ–7, 42 p., accessed 

May 27, 2010, at http://www.deq.mt.gov/wqinfo/Standards/

PDF/CompiledDEQ7.pdf.

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

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

invertebrate, and fish communities as part of the National 

Water-Quality Assessment Program: U.S. Geological Survey 

Open-File Report 2002–150, 75 p.

National Oceanic and Atmospheric Administration, Satellite and Information Service, 2005, Climate of 2005—

June, Wyoming Division 4 Drought, Regional overview/

paleo perspective, accessed October 26, 2007, at 

http://www.ncdc.noaa.gov/oa/climate/research/2005/jun/

st048dv04pcp200506.html.

Peterson, D.A., and Porter, S.D., 2002, Biological and chemical indicators of eutrophication in the Yellowstone River 

and major tributaries during August, 2000: National Water 

Quality Monitoring Council, Proceedings of the 2002 

National Water Quality Monitoring Conference, Madison, 

Wisc., May 20–23, 14 p.

Peterson, D.A., Wright, P.R., Edwards, G.P., Jr., Hargett, E.G., 

Feldman, D.L., Zumberge, J.R., and Dey, Paul, 2009, Ecological assessment of streams in the Powder River structural 

basin, Wyoming and Montana, 2005–06: U.S. Geological 

Survey Scientific Investigations Report 2009–5023, 139 p.

Porter, S.D., 2008, Algal attributes—An autecological classification of algal taxa collected by the National Water-Quality 

Assessment Program: U.S. Geological Survey Data Series 329, 

http://pubs.usgs.gov/ds/ds329.

Potapova, M., and Charles, D.F., 2005, Choice of substrate in 

algae-based water-quality assessment: Journal of the North 

American Benthological Society, v. 24, no. 2, p. 415–427.

Powder River Natural Gas Interagency Working Group, 2004, 

Charter: Buffalo, Wyo., Bureau of Land Management, 15 p., 

accessed April 1, 2008, at http://www.wy.blm.gov/prbgroup/

pdfs/charter061504.pdf.

Rice, C.A., Ellis, M.S., and Bullock, J.H., Jr., 2000, Water coproduced with coalbed methane in the Powder River Basin, 

Wyoming—Preliminary compositional data: U.S. Geological Survey Open-File Report 2000–372, 20 p.

Ringen, B.H., and Daddow, P.B., 1990, Hydrology of the Powder River alluvium between Sussex, Wyoming, and Moorhead, Montana: U.S. Geological Survey Water-Resources 

Investigations Report 89–4002, 48 p.
58 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Senecal, A.C., 2009, Fish assemblage structure and flow 

regime of the Powder River, Wyoming—An assessment of 

the potential effects of flow augmentation related to energy 

development: Laramie, University of Wyoming, Master’s 

thesis, 237 p., 37 figs.

Skaar, Don, Farag, A.M., and Harper, D., 2006, Toxicity 

of sodium bicarbonate to fish from coal-bed natural gas 

production in the Tongue and Powder River drainages, 

Montana and Wyoming: U.S. Geological Survey Fact 

Sheet 2006–3092, 4 p.

Smith, R.L., Repert, D.A., and Hart, C.P., 2009, Geochemistry of inorganic nitrogen in waters released from coal-bed 

natural gas production wells in the Powder River Basin, 

Wyoming: Environmental Science and Technology, v. 43, 

no. 7, p. 2348–2354.

Stevenson, R.J., Bothwell, M.L., and Lowe, R.L., 1996, Algal 

ecology: San Diego, Calif., Academic Press, 753 p.

Stricker, G.D., Flores, R.M., McGarry, D.E., Stillwell, D.P., 

Hoppe, D.J., Stillwell, C.R., Ochs, A.M., Ellis, M.S., 

Osvald, K.S., Taylor, S.L., Thorvaldson, M.C., Trippi, M.H., 

Grose, S.D., Crockett, F.J., and Shariff, A.J., 2006, Gas 

desorption and adsorption isotherm studies of coals in the 

Powder River Basin, Wyoming and adjacent basins in Wyoming and North Dakota: U.S. Geological Survey Open-File 

Report 2006–1174, 21 p., accessed September 21, 2009, at 

http://pubs.usgs.gov/of/2006/1174/.

TIBCO Software Inc., 2008, Tibco Spotfire S+ version 8.1.1: 

Palo Alto, California.

U.S. Environmental Protection Agency, 1988, Ambient water 

quality criteria for chloride: Office of Water, EPA 440/5–

88–001, February 1988, 39 p., accessed November 15, 

2009, at http://www.epa.gov/waterscience/criteria/library/

ambientwqc/chloride1988.pdf.

U.S. Environmental Protection Agency, 2004, Draft aquatic 

life water quality criteria for selenium-2004: Office of 

Water, EPA–822–D–04–001, accessed November 15, 2009, 

at http://www.epa.gov/waterscience/criteria/selenium/pdfs/

complete.pdf.

U.S. Environmental Protection Agency, 2005, National recommended water quality criteria, accessed November 15, 2009, at 

http://www.epa.gov/waterscience/criteria/wqctable/index.html.

U.S. Environmental Protection Agency, 2007, Aquatic life 

ambient freshwater quality criteria - copper: Office of 

Water, EPA–822–R–07–001, February 2007, accessed 

November 15, 2009, at http://www.epa.gov/waterscience/

criteria/copper/2007/criteria-full.pdf.

Walsh, S.J., and Meador, M.R., 1998, Guidelines for quality assurance and quality control of fish taxonomic data 

collected as part of the National Water-Quality Assessment 

Program: U.S. Geological Survey Water-Resources Investigations Report 98–4239, 33 p.

Wangsness, D.J., and Peterson, D.A., 1980, Behavioral and 

catastrophic drift of invertebrates in two streams in northeastern Wyoming: U.S. Geological Survey Open-File 

Report 80–1101, 13 p.

Wolman, 1954, A method for sampling coarse riverbed 

material: Transactions of the American Geophysical Union, 

v. 35, p. 951–956.

Wyoming Department of Environmental Quality, 2007, Water 

quality rules and regulations, chapter 1, Wyoming surface 

water quality standards: Wyoming Department of Environmental Quality, Water Quality Division, [variously paged], 

accessed November 15, 2009, at http://soswy.state.wy.us/

Rules/RULES/6547.pdf.

Wyoming Department of Environmental Quality, 2009, 

National Pollutant Discharge Elimination System (NPDES) 

Program; Wyoming Department of Environmental Quality 

database, accessed January 28, 2009, at http://deq.state.wy.us/

wqd/npdes/.

Wyoming Oil and Gas Conservation Commission, 2010, Coal 

bed methane wells: digital data, accessed February 8, 2010, 

at: http://wogcc.state.wy.us/.
Appendix 59

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

R1 06295113 Streamflow, in cubic feet per second 33 0.02 8.545 1.05 5.6 10.95 51

R1 06295113 Turbidity, nephelometric turbidity ratio units 1 -- -- -- -- -- 6

R1 06295113 Dissolved oxygen, in mg/L 31 5.3 9.245 7.6 9.1 10.7 12.5

R1 06295113 Dissolved oxygen, percent saturation 31 64 93.32 88 99 101 115

R1 06295113 pH, in standard units 32 7.9 8.28 8.1 8.3 8.4 8.6

R1 06295113 Specific conductance, at 25 degrees Celsius, in μS/cm 31 791 960.8 882 944 1,020 1,170

R1 06295113 Temperature, water deg C 33 0 10.70 3.75 10 16.25 25.5

R1 06295113 Hardness, in mg/L as CaCO3 32 390 505.9 470 510 550 610

R1 06295113 Calcium, dissolved, in mg/L 32 53.5 74.03 67.75 76.2 80.5 89.3

R1 06295113 Magnesium, dissolved, in mg/L 32 59.2 78.05 69.15 80.9 84.175 94.5

R1 06295113 Potassium, dissolved, in mg/L 32 6.04 8.362 7.062 7.935 9.352 12.1

R1 06295113 Sodium-adsorption ratio (unitless) 32 0.4 0.672 0.5 0.6 0.875 1

R1 06295113 Sodium, dissolved, in mg/L 32 20.1 35.40 26.2 31.9 46.675 52.6

R1 06295113 Alkalinity, in mg/L as CaCO3 32 285 432.7 382.25 414.5 490 565

R1 06295113 Chloride, dissolved, in mg/L 32 2.54 3.811 3.117 3.72 4.538 6

R1 06295113 Fluoride, dissolved, in mg/L 32 0.52 0.703 0.582 0.665 0.85 0.93

R1 06295113 Silica, dissolved, in mg/L 32 2.14 13.66 11.175 13.9 16.275 21.6

R1 06295113 Sulfate, dissolved, in mg/L 32 83.5 143.8 122.5 137 174.75 204

R1 06295113 Dissolved solids, calculated, in mg/L 31 474 617.9 561 627 670 765

R1 06295113 Dissolved solids, tons/day 31 0.04 12.87 1.81 7.58 13.9 77.2

R1 06295113 *Ammonia, dissolved, in mg/L as N 10 -- 0.012 0.006 0.008 0.012 0.044

R1 06295113 **Nitrate plus nitrite, dissolved, in mg/L as N 14 -- -- -- -- -- 0.018

R1 06295113 *Nitrite, dissolved, in mg/L as N 14 -- 0.001 0.001 0.001 0.001 0.003

R1 06295113 Orthophosphate, dissolved, in mg/L as P 14 0.004 0.01 0.007 0.009 0.014 0.026

R1 06295113 Phosphorus, total, in mg/L 14 0.023 0.041 0.03 0.038 0.05 0.072

R1 06295113 Total nitrogen, total, in mg/L 14 0.27 0.424 0.338 0.435 0.505 0.58

R1 06295113 Aluminum, dissolved, in μg/L 22 0.9 3.045 1.4 2.2 4.25 9.8

R1 06295113 Aluminum, total, in μg/L 22 10 123.8 40.5 84 136 865

R1 06295113 Arsenic, dissolved, in μg/L 22 0.58 1.425 0.877 1.35 1.775 3.3

R1 06295113 Arsenic, total, in μg/L 22 0.87 1.608 1.1 1.7 2 2.4

R1 06295113 Barium, dissolved, in μg/L 22 62 94.55 84 94.5 105.5 128

R1 06295113 Barium, total, in μg/L 22 70.1 98.04 85.575 95.3 114.25 135

R1 06295113 **Beryllium, dissolved, in μg/L 22 -- -- -- -- -- <0.06

R1 06295113 **Beryllium, total, in μg/L 22 -- -- -- -- -- 0.09

R1 06295113 **Cadmium, dissolved, in μg/L 8 -- -- -- -- -- <0.04

R1 06295113 **Cadmium, total, in μg/L 8 -- -- -- -- -- <0.04

R1 06295113 *Chromium, dissolved, in μg/L 8 -- 0.071 0.045 0.068 0.088 0.12

R1 06295113 *Chromium, total, in μg/L 8 -- 0.348 0.253 0.325 0.477 0.5

R1 06295113 Copper, dissolved, in μg/L 8 0.9 2.287 1 2.25 3.3 4.7

R1 06295113 Copper, total, in μg/L 8 0.9 2.062 1.325 1.6 3.15 4.3

R1 06295113 Iron, dissolved, in μg/L 22 11 22.82 15 19.5 28.5 67

R1 06295113 Iron, total, in μg/L 22 35 392.3 165.25 280.5 474 2,340

R1 06295113 Lead, dissolved, in μg/L 8 0.07 0.191 0.07 0.13 0.3 0.56

R1 06295113 Lead, total, in μg/L 8 0.09 0.211 0.105 0.16 0.332 0.41

R1 06295113 Manganese, dissolved, in μg/L 22 3.3 32.02 8.25 33.25 41.6 83.7

R1 06295113 Manganese, total, in μg/L 22 4.4 45.76 10.775 41.4 58.65 167

R1 06295113 Nickel, dissolved, in μg/L 8 1.35 2.255 1.41 1.7 3.362 4.7

R1 06295113 Nickel, total, in μg/L 8 1.1 2.305 1.56 2.36 3.148 3.23

R1 06295113 Selenium, dissolved, in μg/L 22 0.05 0.284 0.2 0.275 0.3 0.9

R1 06295113 Selenium, total, in μg/L 22 0.1 0.353 0.27 0.29 0.348 1.1

R1 06295113 Zinc, dissolved, in μg/L 7 1.7 4.771 3 5.1 5.5 8

R1 06295113 *Zinc, total, in μg/L 8 -- 2.236 1.142 2 2.375 6

R1 06295113 Suspended sediment, <0.0625 mm, percent 32 40 70.13 56.25 71.5 81.75 96

R1 06295113 Suspended sediment, in mg/L 32 18 58.25 31.75 47 83.5 137

R1 06295113 Suspended sediment, tons/day 32 0 1.940 0.102 0.35 2.35 16

R2 06296003 Streamflow, in cubic feet per second 14 0.08 37.50 0.285 8.9 36 226

R2 06296003 Turbidity, nephelometric turbidity ratio units 1 -- -- -- -- -- 45

R2 06296003 Dissolved oxygen, in mg/L 9 7.6 10.08 8.7 9.5 11.65 13.1

R2 06296003 Dissolved oxygen, percent saturation 9 92 98.56 96.5 99 100 105

R2 06296003 pH, in standard units 11 8.2 8.46 8.3 8.5 8.6 8.8
60 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

R2 06296003 Specific conductance, at 25 degrees Celsius, in μS/cm 14 427 2,245 1,768 2,315 2,923 3,500

R2 06296003 Temperature, water deg C 14 0 11.82 3.25 11 19.25 30

R2 06296003 Hardness, in mg/L as CaCO3 11 35 688.5 670 790 870 1,100

R2 06296003 Calcium, dissolved, in mg/L 11 8.77 75.34 68.8 79.5 95.3 131

R2 06296003 Magnesium, dissolved, in mg/L 11 3.18 121.9 120 139 149 196

R2 06296003 Potassium, dissolved, in mg/L 11 4.24 11.65 11.5 12.3 14.4 16.2

R2 06296003 Sodium-adsorption ratio (unitless) 11 2.8 4.800 3 3.9 6.2 8.6

R2 06296003 Sodium, dissolved, in mg/L 11 76.1 269.2 166 203 399 565

R2 06296003 Alkalinity, in mg/L as CaCO3 11 118 400.8 384 430 452 629

R2 06296003 Chloride, dissolved, in mg/L 11 1.27 13.35 8.92 12.6 16.5 31

R2 06296003 Fluoride, dissolved, in mg/L 11 0.36 0.653 0.61 0.7 0.73 0.84

R2 06296003 Silica, dissolved, in mg/L 11 0.86 7.511 4.47 6.68 10.9 16.5

R2 06296003 Sulfate, dissolved, in mg/L 11 70.9 833.4 617 802 1,180 1,520

R2 06296003 Dissolved solids, calculated, in mg/L 11 244 1,573 1,230 1,550 2,220 2,650

R2 06296003 Dissolved solids, tons/day 11 1.1 85.10 18 64.3 154 201

R2 06296003 **Ammonia, dissolved, in mg/L as N 3 -- -- -- -- -- 0.011

R2 06296003 **Nitrate plus nitrite, dissolved, in mg/L as N 3 -- -- -- -- -- <0.016

R2 06296003 **Nitrite, dissolved, in mg/L as N 3 -- -- -- -- -- <0.002

R2 06296003 **Orthophosphate, dissolved, in mg/L as P 3 -- -- -- -- -- <0.006

R2 06296003 Phosphorus, total, in mg/L 3 0.038 -- -- -- -- 0.172

R2 06296003 Total nitrogen, total, in mg/L 3 0.42 -- -- -- -- 1.11

R2 06296003 Aluminum, dissolved, in μg/L 10 1.5 8.690 2.3 3.3 7.25 48.8

R2 06296003 Aluminum, total, in μg/L 10 228 12,618 309.25 983.5 16,705 59,800

R2 06296003 Arsenic, dissolved, in μg/L 10 0.76 1.040 0.8 0.95 1.325 1.5

R2 06296003 **Arsenic, total, in μg/L 10 -- 3.170 1.075 1.6 4.15 11

R2 06296003 Barium, dissolved, in μg/L 10 23 80.00 39.25 71 121 147

R2 06296003 Barium, total, in μg/L 10 47.5 314.9 65.125 129.5 339 1,440

R2 06296003 **Beryllium, dissolved, in μg/L 10 -- -- -- -- -- <0.12

R2 06296003 *Beryllium, total, in μg/L 10 -- 1.889 0.03 0.103 1.862 11.4

R2 06296003 **Cadmium, dissolved, in μg/L 4 -- -- -- -- -- <0.08

R2 06296003 **Cadmium, total, in μg/L 4 -- -- -- -- -- <0.08

R2 06296003 **Chromium, dissolved, in μg/L 4 -- -- -- -- -- 1.5

R2 06296003 Chromium, total, in μg/L 4 0.5 -- -- -- -- 4

R2 06296003 Copper, dissolved, in μg/L 4 4.3 -- -- -- -- 9.1

R2 06296003 Copper, total, in μg/L 4 4.6 -- -- -- -- 15.8

R2 06296003 *Iron, dissolved, in μg/L 10 -- 174.2 3.718 8.308 32.507 1,630

R2 06296003 Iron, total, in μg/L 10 261 14,257 410 1,115 18,310 70,100

R2 06296003 **Lead, dissolved, in μg/L 4 -- -- -- -- -- 0.13

R2 06296003 Lead, total, in μg/L 4 0.38 -- -- -- -- 4.02

R2 06296003 Manganese, dissolved, in μg/L 10 0.8 23.80 2.175 15.35 38.15 83.5

R2 06296003 Manganese, total, in μg/L 10 43.6 368.1 59.525 99.8 403 1,870

R2 06296003 Nickel, dissolved, in μg/L 4 4.45 -- -- -- -- 5.33

R2 06296003 Nickel, total, in μg/L 4 3.84 -- -- -- -- 10.3

R2 06296003 Selenium, dissolved, in μg/L 10 0.09 0.748 0.298 0.53 1.225 1.8

R2 06296003 Selenium, total, in μg/L 10 0.31 1.073 0.328 0.715 1.925 2.7

R2 06296003 Zinc, dissolved, in μg/L 4 3.5 -- -- -- -- 8.2

R2 06296003 Zinc, total, in μg/L 4 4 -- -- -- -- 18

R2 06296003 Suspended sediment, <0.0625 mm, percent 10 76 94.70 92.75 99 99 99

R2 06296003 Suspended sediment, in mg/L 10 80 1,980 87 165 1,895 11,900

R2 06296003 Suspended sediment, tons/day 10 0.05 908.7 1.143 5.95 1,035 4,970

T1 06299980 Streamflow, in cubic feet per second 50 32 321.6 71.5 111 234.25 2,520

T1 06299980 Turbidity, nephelometric turbidity ratio units 1 -- -- -- -- -- 14

T1 06299980 Dissolved oxygen, in mg/L 49 6.8 10.40 8.95 10.1 11.6 15

T1 06299980 Dissolved oxygen, percent saturation 49 80 102.8 94 99 110.5 159

T1 06299980 pH, in standard units 49 7.7 8.26 8 8.3 8.5 8.7

T1 06299980 Specific conductance, at 25 degrees Celsius, in μS/cm 50 186 372.3 292.75 407.5 441 535

T1 06299980 Temperature, water deg C 50 0 9.736 3.625 9 15.5 26

T1 06299980 Hardness, in mg/L as CaCO3 49 84 178.9 140 200 210 250

T1 06299980 Calcium, dissolved, in mg/L 49 22.1 42.38 35.1 46.6 50.35 57.7

T1 06299980 Magnesium, dissolved, in mg/L 49 7.04 17.70 12.6 19.9 21.25 28.9
Appendix 61

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T1 06299980 Potassium, dissolved, in mg/L 49 0.72 1.543 1.175 1.37 1.665 4.2

T1 06299980 Sodium-adsorption ratio (unitless) 49 0.1 0.318 0.2 0.3 0.4 0.7

T1 06299980 Sodium, dissolved, in mg/L 49 2.45 9.867 6 9.98 12.65 25.5

T1 06299980 Alkalinity, in mg/L as CaCO3 49 81 158.0 125.5 178 187 212

T1 06299980 Chloride, dissolved, in mg/L 49 0.54 1.442 1.04 1.35 1.75 3.6

T1 06299980 Fluoride, dissolved, in mg/L 49 0.08 0.162 0.14 0.17 0.19 0.23

T1 06299980 Silica, dissolved, in mg/L 49 3.63 6.464 5.29 6.58 7.55 9.54

T1 06299980 Sulfate, dissolved, in mg/L 49 8.26 41.52 22.55 44.3 55.25 110

T1 06299980 Dissolved solids, calculated, in mg/L 46 103 213.4 160.5 235 255 332

T1 06299980 Dissolved solids, tons/day 46 25.3 150.0 54.8 70.8 126 1,140

T1 06299980 Dissolved solids, residue on evaporation, in mg/L 11 114 231.0 187 252 274 310

T1 06299980 *Ammonia, dissolved, in mg/L as N 18 -- 0.013 0.005 0.007 0.012 0.085

T1 06299980 *Nitrate plus nitrite, dissolved, in mg/L as N 18 -- 0.048 0.008 0.016 0.064 0.222

T1 06299980 *Nitrite, dissolved, in mg/L as N 18 -- 0.002 0.001 0.001 0.002 0.004

T1 06299980 *Orthophosphate, dissolved, in mg/L as P 18 -- 0.009 0.003 0.005 0.009 0.039

T1 06299980 Phosphorus, total, in mg/L 18 0.005 0.045 0.009 0.018 0.053 0.26

T1 06299980 Total nitrogen, total, in mg/L 18 0.1 0.337 0.175 0.235 0.39 1.21

T1 06299980 *Aluminum, dissolved, in μg/L 18 -- 2.309 1.252 1.628 2.425 9.6

T1 06299980 Aluminum, total, in μg/L 29 22 279.8 34.5 52 204.5 2,810

T1 06299980 Arsenic, dissolved, in μg/L 29 0.2 0.408 0.3 0.35 0.5 0.8

T1 06299980 *Arsenic, total, in μg/L 29 -- 0.66 0.457 0.56 0.755 2

T1 06299980 Barium, dissolved, in μg/L 18 25 43.11 41 44 47.25 57

T1 06299980 Barium, total, in μg/L 29 32.9 47.39 41.15 44.3 48.7 90.2

T1 06299980 **Beryllium, dissolved, in μg/L 18 -- -- -- -- -- <0.06

T1 06299980 *Beryllium, total, in μg/L 29 -- 0.044 0.015 0.029 0.046 0.32

T1 06299980 Boron, dissolved, in μg/L 15 15 32.53 30 31 35 53

T1 06299980 **Cadmium, dissolved, in μg/L 16 -- -- -- -- -- <0.04

T1 06299980 **Cadmium, total, in μg/L 16 -- -- -- -- -- 0.12

T1 06299980 Chromium, dissolved, in μg/L 1 -- -- -- -- -- 0.13

T1 06299980 *Chromium, total, in μg/L 16 -- 1.172 0.881 1 1.251 3

T1 06299980 Copper, dissolved, in μg/L 13 0.7 1.033 0.8 0.9 1.2 1.8

T1 06299980 Copper, total, in μg/L 16 0.7 1.663 1 1.15 1.7 6.9

T1 06299980 Iron, dissolved, in μg/L 29 6 20.21 13 17 29.5 41

T1 06299980 Iron, total, in μg/L 18 55 439.7 86.75 175.5 510 2,450

T1 06299980 *Lead, dissolved, in μg/L 14 -- 0.092 0.053 0.065 0.085 0.43

T1 06299980 Lead, total, in μg/L 16 0.04 0.569 0.06 0.125 0.4 5.43

T1 06299980 Lithium, dissolved, in μg/L 15 3.9 9.707 8.5 9.5 10.3 16.6

T1 06299980 Manganese, dissolved, in μg/L 29 1.8 9.948 5.2 6.1 10 34.1

T1 06299980 Manganese, total, in μg/L 18 3.1 27.51 8.1 22.75 43.825 86.6

T1 06299980 Mercury, total, ng/L 5 0.28 -- -- -- -- 3.8

T1 06299980 **Mercury, total, μg/L 3 -- -- -- -- -- <0.01

T1 06299980 Nickel, dissolved, in μg/L 15 0.23 1.163 0.47 1.09 1.79 2.27

T1 06299980 Nickel, total, in μg/L 16 0.85 1.656 0.923 1.35 2.003 5.34

T1 06299980 *Selenium, dissolved, in μg/L 18 -- 0.282 0.168 0.225 0.305 0.8

T1 06299980 Selenium, total, in μg/L 29 0.08 0.301 0.18 0.21 0.32 1.2

T1 06299980 Strontium, dissolved, in μg/L 15 93 207.3 189 217 238 253

T1 06299980 *Zinc, dissolved, in μg/L 14 -- 1.279 0.467 0.755 2.175 3.3

T1 06299980 *Zinc, total, in μg/L 16 -- 2.864 1 1.224 2.75 19

T1 06299980 Suspended sediment, <0.0625 mm, percent 33 36 85.67 78.5 91 95 99

T1 06299980 Suspended sediment, in mg/L 33 4 32.15 9.5 17 35 266

T1 06299980 Suspended sediment, tons/day 33 0.65 47.46 1.95 3.7 18 826

T2 06305700 Streamflow, in cubic feet per second 38 5.1 200.5 42.75 67.5 159 1,350

T2 06305700 Turbidity, nephelometric turbidity ratio units 2 3.8 -- -- -- -- 4.5

T2 06305700 Dissolved oxygen, in mg/L 38 6 10.86 8.925 10.5 12.875 15.9

T2 06305700 Dissolved oxygen, percent saturation 38 62 113.2 95.5 104.5 126 194

T2 06305700 pH, in standard units 37 7.8 8.31 8.05 8.3 8.55 9

T2 06305700 Specific conductance, at 25 degrees Celsius, in μS/cm 38 130 595.6 539 663 723.75 860

T2 06305700 Temperature, water deg C 38 0 11.85 5.25 10.75 19.175 28

T2 06305700 Hardness, in mg/L as CaCO3 37 57 281.9 250 320 350 420

T2 06305700 Calcium, dissolved, in mg/L 37 13.2 54.05 49.85 61.1 67.25 76.2
62 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T2 06305700 Magnesium, dissolved, in mg/L 37 5.76 35.51 29.8 39.6 44.65 56.6

T2 06305700 Potassium, dissolved, in mg/L 37 0.83 2.810 2.3 2.72 3.65 4.82

T2 06305700 Sodium-adsorption ratio (unitless) 37 0.2 0.589 0.5 0.6 0.7 1.2

T2 06305700 Sodium, dissolved, in mg/L 37 3.96 23.36 18.35 24.7 30.25 48.2

T2 06305700 Alkalinity, in mg/L as CaCO3 37 50 208.0 181.5 236 257.5 300

T2 06305700 Chloride, dissolved, in mg/L 37 0.88 6.786 4.685 6.39 8.905 18.2

T2 06305700 Fluoride, dissolved, in mg/L 37 0.07 0.271 0.24 0.29 0.33 0.4

T2 06305700 Silica, dissolved, in mg/L 37 1.25 7.339 5.45 7.66 9.265 12.6

T2 06305700 Sulfate, dissolved, in mg/L 37 13.8 111.3 95.4 118 138.5 210

T2 06305700 Dissolved solids, calculated, in mg/L 36 77 367.4 313 412.5 451.5 559

T2 06305700 Dissolved solids, tons/day 36 7.7 122.9 55.45 73.3 159.75 914

T2 06305700 *Ammonia, dissolved, in mg/L as N 17 -- 0.024 0.007 0.012 0.023 0.11

T2 06305700 *Nitrate plus nitrite, dissolved, in mg/L as N 17 -- 0.208 0.017 0.139 0.326 1.04

T2 06305700 *Nitrite, dissolved, in mg/L as N 17 -- 0.007 0.001 0.003 0.007 0.033

T2 06305700 Orthophosphate, dissolved, in mg/L as P 17 0.016 0.091 0.06 0.086 0.117 0.188

T2 06305700 Phosphorus, total, in mg/L 17 0.071 0.147 0.105 0.142 0.185 0.28

T2 06305700 Total nitrogen, total, in mg/L 17 0.31 0.637 0.415 0.52 0.85 1.44

T2 06305700 *Aluminum, dissolved, in μg/L 17 -- 2.570 0.936 1.322 2.35 14.4

T2 06305700 Aluminum, total, in μg/L 17 13 218.9 27.5 60 193 2,090

T2 06305700 Arsenic, dissolved, in μg/L 17 0.27 0.575 0.38 0.51 0.785 1.2

T2 06305700 *Arsenic, total, in μg/L 17 -- 0.893 0.56 0.72 1.148 2

T2 06305700 Barium, dissolved, in μg/L 17 18 49.71 48 52 55 60

T2 06305700 Barium, total, in μg/L 17 25.1 53.62 50.15 53.6 60.05 67.7

T2 06305700 **Beryllium, dissolved, in μg/L 17 -- -- -- -- -- 0.1

T2 06305700 **Beryllium, total, in μg/L 17 -- -- -- -- -- 0.22

T2 06305700 Boron, dissolved, in μg/L 14 46 83.79 68 80.5 97 131

T2 06305700 **Cadmium, dissolved, in μg/L 15 -- -- -- -- -- <0.04

T2 06305700 *Cadmium, total, in μg/L 15 -- 0.026 0.01 0.019 0.03 0.1

T2 06305700 Chromium, dissolved, in μg/L 1 -- -- -- -- -- 0.15

T2 06305700 *Chromium, total, in μg/L 15 -- 1.523 1 1.015 2 4

T2 06305700 Copper, dissolved, in μg/L 15 0.69 1.354 1.1 1.3 1.6 2.2

T2 06305700 Copper, total, in μg/L 15 1.2 2.347 1.5 1.9 2.7 6.7

T2 06305700 Iron, dissolved, in μg/L 17 12 32.94 16 33 47 59

T2 06305700 Iron, total, in μg/L 17 74 463.8 163 193 449.5 3,180

T2 06305700 Lead, dissolved, in μg/L 15 0.04 0.095 0.06 0.08 0.12 0.24

T2 06305700 Lead, total, in μg/L 15 0.08 0.498 0.11 0.15 0.44 3.53

T2 06305700 Lithium, dissolved, in μg/L 14 9.4 17.77 15.575 16.9 21.875 26

T2 06305700 Manganese, dissolved, in μg/L 17 6.7 28.65 12.45 21.7 40.85 67.1

T2 06305700 Manganese, total, in μg/L 17 9.3 52.54 29.75 43.9 76.75 118

T2 06305700 Mercury, total, ng/L 5 0.45 -- -- -- -- 1.01

T2 06305700 **Mercury, total, μg/L 3 -- -- -- -- -- <0.01

T2 06305700 Nickel, dissolved, in μg/L 14 0.52 1.822 0.89 1.86 2.388 3.32

T2 06305700 Nickel, total, in μg/L 15 1.1 2.198 1.55 2.1 2.58 5.21

T2 06305700 Selenium, dissolved, in μg/L 17 0.2 0.49 0.325 0.42 0.55 1.3

T2 06305700 Selenium, total, in μg/L 17 0.19 0.556 0.355 0.41 0.75 1.6

T2 06305700 Strontium, dissolved, in μg/L 14 228 444.4 429.25 455 504.25 537

T2 06305700 Zinc, dissolved, in μg/L 14 1.9 3.100 2.45 2.9 3.925 4.8

T2 06305700 Zinc, total, in μg/L 15 3 4.933 3 4 5 17

T2 06305700 Suspended sediment, <0.0625 mm, percent 31 36 76.94 64 82 88 97

T2 06305700 Suspended sediment, in mg/L 31 2 25.58 7 17 27 216

T2 06305700 Suspended sediment, tons/day 31 0.18 36.92 0.83 1.9 8.4 787

T3 450137106595101 Streamflow, in cubic feet per second 4 0.36 -- -- -- -- 15

T3 450137106595101 Turbidity, nephelometric turbidity ratio units 4 42 -- -- -- -- 85

T3 450137106595101 Dissolved oxygen, in mg/L 4 7.2 -- -- -- -- 8

T3 450137106595101 Dissolved oxygen, percent saturation 3 92 -- -- -- -- 96

T3 450137106595101 pH, in standard units 4 7.5 -- -- -- -- 8.4

T3 450137106595101 Specific conductance, at 25 degrees Celsius, in μS/cm 4 615 -- -- -- -- 704

T3 450137106595101 Temperature, water deg C 4 18 -- -- -- -- 22

T3 450137106595101 Hardness, in mg/L as CaCO3 4 290 -- -- -- -- 370

T3 450137106595101 Calcium, dissolved, in mg/L 4 55.1 -- -- -- -- 67.8
Appendix 63

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T3 450137106595101 Magnesium, dissolved, in mg/L 4 36.8 -- -- -- -- 51.1

T3 450137106595101 Potassium, dissolved, in mg/L 4 3.96 -- -- -- -- 7.17

T3 450137106595101 Sodium-adsorption ratio (unitless) 4 0.3 -- -- -- -- 0.4

T3 450137106595101 Sodium, dissolved, in mg/L 4 10.5 -- -- -- -- 17.2

T3 450137106595101 Alkalinity, in mg/L as CaCO3 4 293 -- -- -- -- 373

T3 450137106595101 Chloride, dissolved, in mg/L 4 1.58 -- -- -- -- 1.97

T3 450137106595101 Fluoride, dissolved, in mg/L 4 0.49 -- -- -- -- 0.66

T3 450137106595101 Silica, dissolved, in mg/L 4 13.8 -- -- -- -- 18.8

T3 450137106595101 Sulfate, dissolved, in mg/L 4 30.4 -- -- -- -- 53.2

T3 450137106595101 Dissolved solids, calculated, in mg/L 4 356 -- -- -- -- 413

T3 450137106595101 Dissolved solids, tons/day 4 0.4 -- -- -- -- 15.4

T4 445832106551401 Streamflow, in cubic feet per second 4 0.58 -- -- -- -- 6.1

T4 445832106551401 Turbidity, nephelometric turbidity ratio units 4 18 -- -- -- -- 58

T4 445832106551401 Dissolved oxygen, in mg/L 4 8 -- -- -- -- 9.2

T4 445832106551401 Dissolved oxygen, percent saturation 3 86 -- -- -- -- 115

T4 445832106551401 pH, in standard units 4 7.9 -- -- -- -- 8.4

T4 445832106551401 Specific conductance, at 25 degrees Celsius, in μS/cm 4 863 -- -- -- -- 1,690

T4 445832106551401 Temperature, water deg C 4 12 -- -- -- -- 21.8

T4 445832106551401 Hardness, in mg/L as CaCO3 4 420 -- -- -- -- 880

T4 445832106551401 Calcium, dissolved, in mg/L 4 70.5 -- -- -- -- 108

T4 445832106551401 Magnesium, dissolved, in mg/L 4 56.8 -- -- -- -- 149

T4 445832106551401 Potassium, dissolved, in mg/L 4 6.06 -- -- -- -- 14.9

T4 445832106551401 Sodium-adsorption ratio (unitless) 4 0.6 -- -- -- -- 1.6

T4 445832106551401 Sodium, dissolved, in mg/L 4 29.1 -- -- -- -- 112

T4 445832106551401 Alkalinity, in mg/L as CaCO3 4 359 -- -- -- -- 422

T4 445832106551401 Chloride, dissolved, in mg/L 4 2.25 -- -- -- -- 4.05

T4 445832106551401 Fluoride, dissolved, in mg/L 4 0.59 -- -- -- -- 0.76

T4 445832106551401 Silica, dissolved, in mg/L 4 12.6 -- -- -- -- 16.9

T4 445832106551401 Sulfate, dissolved, in mg/L 4 139 -- -- -- -- 623

T4 445832106551401 Dissolved solids, calculated, in mg/L 4 542 -- -- -- -- 1,280

T4 445832106551401 Dissolved solids, tons/day 4 1 -- -- -- -- 8.92

T5 445957106524701 Streamflow, in cubic feet per second 4 23 -- -- -- -- 171

T5 445957106524701 Turbidity, nephelometric turbidity ratio units 4 5 -- -- -- -- 48

T5 445957106524701 Dissolved oxygen, in mg/L 4 7.3 -- -- -- -- 11.4

T5 445957106524701 Dissolved oxygen, percent saturation 4 91 -- -- -- -- 139

T5 445957106524701 pH, in standard units 4 7.8 -- -- -- -- 8.4

T5 445957106524701 Specific conductance, at 25 degrees Celsius, in μS/cm 4 523 -- -- -- -- 695

T5 445957106524701 Temperature, water deg C 4 19 -- -- -- -- 19

T5 445957106524701 Hardness, in mg/L as CaCO3 4 230 -- -- -- -- 290

T5 445957106524701 Calcium, dissolved, in mg/L 4 44.8 -- -- -- -- 56.9

T5 445957106524701 Magnesium, dissolved, in mg/L 4 29.5 -- -- -- -- 41.9

T5 445957106524701 Potassium, dissolved, in mg/L 4 2.77 -- -- -- -- 3.98

T5 445957106524701 Sodium-adsorption ratio (unitless) 4 0.5 -- -- -- -- 0.8

T5 445957106524701 Sodium, dissolved, in mg/L 4 19.3 -- -- -- -- 33.3

T5 445957106524701 Alkalinity, in mg/L as CaCO3 4 192 -- -- -- -- 227

T5 445957106524701 Chloride, dissolved, in mg/L 4 3.35 -- -- -- -- 6.73

T5 445957106524701 Fluoride, dissolved, in mg/L 4 0.23 -- -- -- -- 0.29

T5 445957106524701 Silica, dissolved, in mg/L 4 1.64 -- -- -- -- 8.54

T5 445957106524701 Sulfate, dissolved, in mg/L 4 83.3 -- -- -- -- 145

T5 445957106524701 Dissolved solids, calculated, in mg/L 4 301 -- -- -- -- 421

T5 445957106524701 Dissolved solids, tons/day 4 25.9 -- -- -- -- 154

T6 06306100 Streamflow, in cubic feet per second 4 0.12 -- -- -- -- 2.3

T6 06306100 Turbidity, nephelometric turbidity ratio units 4 2.1 -- -- -- -- 15

T6 06306100 Dissolved oxygen, in mg/L 3 7.7 -- -- -- -- 13.2

T6 06306100 Dissolved oxygen, percent saturation 3 85 -- -- -- -- 173

T6 06306100 pH, in standard units 4 7.8 -- -- -- -- 8.5

T6 06306100 Specific conductance, at 25 degrees Celsius, in μS/cm 4 1,290 -- -- -- -- 1,570

T6 06306100 Temperature, water deg C 4 13.5 -- -- -- -- 22

T6 06306100 Hardness, in mg/L as CaCO3 4 670 -- -- -- -- 760

T6 06306100 Calcium, dissolved, in mg/L 4 85.2 -- -- -- -- 99.5
64 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T6 06306100 Magnesium, dissolved, in mg/L 4 110 -- -- -- -- 124

T6 06306100 Potassium, dissolved, in mg/L 4 7.88 -- -- -- -- 9.54

T6 06306100 Sodium-adsorption ratio (unitless) 4 0.8 -- -- -- -- 1.2

T6 06306100 Sodium, dissolved, in mg/L 4 50 -- -- -- -- 77.8

T6 06306100 Alkalinity, in mg/L as CaCO3 4 408 -- -- -- -- 514

T6 06306100 Chloride, dissolved, in mg/L 4 2.68 -- -- -- -- 3.49

T6 06306100 Fluoride, dissolved, in mg/L 4 0.43 -- -- -- -- 0.56

T6 06306100 Silica, dissolved, in mg/L 4 11.2 -- -- -- -- 21.1

T6 06306100 Sulfate, dissolved, in mg/L 4 327 -- -- -- -- 409

T6 06306100 Dissolved solids, calculated, in mg/L 4 842 -- -- -- -- 1,030

T6 06306100 Dissolved solids, tons/day 4 0.33 -- -- -- -- 5.25

T7 450047106514201 Streamflow, in cubic feet per second 3 0.17 -- -- -- -- 1.8

T7 450047106514201 Turbidity, nephelometric turbidity ratio units 3 1.2 -- -- -- -- 14

T7 450047106514201 Dissolved oxygen, in mg/L 2 7.7 -- -- -- -- 9.7

T7 450047106514201 Dissolved oxygen, percent saturation 2 96 -- -- -- -- 107

T7 450047106514201 pH, in standard units 3 7.9 -- -- -- -- 8.3

T7 450047106514201 Specific conductance, at 25 degrees Celsius, in μS/cm 3 1,750 -- -- -- -- 5,940

T7 450047106514201 Temperature, water deg C 3 13 -- -- -- -- 20

T7 450047106514201 Hardness, in mg/L as CaCO3 3 830 -- -- -- -- 2,300

T7 450047106514201 Calcium, dissolved, in mg/L 3 86.4 -- -- -- -- 153

T7 450047106514201 Magnesium, dissolved, in mg/L 3 146 -- -- -- -- 463

T7 450047106514201 Potassium, dissolved, in mg/L 3 9.23 -- -- -- -- 20

T7 450047106514201 Sodium-adsorption ratio (unitless) 3 1.7 -- -- -- -- 7.6

T7 450047106514201 Sodium, dissolved, in mg/L 3 113 -- -- -- -- 835

T7 450047106514201 Alkalinity, in mg/L as CaCO3 3 485 -- -- -- -- 590

T7 450047106514201 Chloride, dissolved, in mg/L 3 3.64 -- -- -- -- 12.7

T7 450047106514201 Fluoride, dissolved, in mg/L 3 0.52 -- -- -- -- 0.73

T7 450047106514201 Silica, dissolved, in mg/L 3 4.21 -- -- -- -- 9.29

T7 450047106514201 Sulfate, dissolved, in mg/L 3 587 -- -- -- -- 3,330

T7 450047106514201 Dissolved solids, calculated, in mg/L 3 1,250 -- -- -- -- 5,180

T7 450047106514201 Dissolved solids, tons/day 3 1.76 -- -- -- -- 6.22

T8 06306250 Streamflow, in cubic feet per second 55 0.21 29.22 13 21 38 127

T8 06306250 Turbidity, nephelometric turbidity ratio units 3 10 -- -- -- -- 120

T8 06306250 Dissolved oxygen, in mg/L 55 7.2 10.12 8 10.5 11.8 14.5

T8 06306250 Dissolved oxygen, percent saturation 53 82 103.2 93 99 109.5 165

T8 06306250 pH, in standard units 54 7.6 8.24 8.1 8.3 8.4 8.5

T8 06306250 Specific conductance, at 25 degrees Celsius, in μS/cm 55 768 1,404 1,150 1,400 1,600 2,500

T8 06306250 Temperature, water deg C 55 0 11.24 4.5 10.5 18.4 26.5

T8 06306250 Hardness, in mg/L as CaCO3 51 330 672.7 540 680 800 1,200

T8 06306250 Calcium, dissolved, in mg/L 51 65.6 128.2 106 130 153 209

T8 06306250 Magnesium, dissolved, in mg/L 51 39.4 85.64 68.2 85.7 101 167

T8 06306250 Potassium, dissolved, in mg/L 51 3.8 7.807 6.23 7.37 8.67 17.8

T8 06306250 Sodium-adsorption ratio (unitless) 51 0.6 1.361 1.1 1.3 1.5 2.9

T8 06306250 Sodium, dissolved, in mg/L 51 29.7 82.50 58.9 74.5 103 216

T8 06306250 Alkalinity, in mg/L as CaCO3 51 177 312.0 267 317 354 443

T8 06306250 Chloride, dissolved, in mg/L 51 2.08 4.773 3.85 4.71 5.57 7.97

T8 06306250 Fluoride, dissolved, in mg/L 51 0.2 0.305 0.27 0.31 0.34 0.41

T8 06306250 Silica, dissolved, in mg/L 51 6.6 12.08 10.7 12.3 14.1 16

T8 06306250 Sulfate, dissolved, in mg/L 51 213 506.2 383 491 592 1,160

T8 06306250 Dissolved solids, calculated, in mg/L 51 501 1,016 810 997 1,180 2,030

T8 06306250 Dissolved solids, tons/day 51 1.01 75.51 42.6 52.6 73.5 398

T8 06306250 Dissolved solids, residue on evaporation, in mg/L 39 526 1,072 853 1,080 1,250 2,160

T8 06306250 *Ammonia, dissolved, in mg/L as N 17 -- 0.026 0.008 0.014 0.029 0.106

T8 06306250 *Nitrate plus nitrite, dissolved, in mg/L as N 17 -- 0.268 0.063 0.24 0.431 0.729

T8 06306250 *Nitrite, dissolved, in mg/L as N 17 -- 0.002 0.001 0.002 0.003 0.005

T8 06306250 *Orthophosphate, dissolved, in mg/L as P 17 -- 0.013 0.005 0.012 0.021 0.028

T8 06306250 Phosphorus, total, in mg/L 17 0.013 0.127 0.027 0.058 0.236 0.34

T8 06306250 Total nitrogen, total, in mg/L 17 0.29 0.821 0.49 0.83 1 1.73

T8 06306250 *Aluminum, dissolved, in μg/L 17 -- 1.543 1.054 1.36 1.85 3.1

T8 06306250 Aluminum, total, in μg/L 36 35 1,084 125.25 304.5 1,550 9,480
Appendix 65

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T8 06306250 Arsenic, dissolved, in μg/L 36 0.31 0.72 0.543 0.75 0.9 1.1

T8 06306250 *Arsenic, total, in μg/L 34 -- 1.629 0.98 1.4 2 6.1

T8 06306250 Barium, dissolved, in μg/L 17 27 39.47 35 40 44 54

T8 06306250 Barium, total, in μg/L 36 37.2 58.84 45 50.35 63.375 210

T8 06306250 **Beryllium, dissolved, in μg/L 17 -- -- -- -- -- 0.12

T8 06306250 *Beryllium, total, in μg/L 36 -- 0.1 0.02 0.046 0.13 0.84

T8 06306250 Boron, dissolved, in μg/L 14 70 107.7 86.25 108.5 127.75 166

T8 06306250 **Cadmium, dissolved, in μg/L 15 -- -- -- -- -- <0.04

T8 06306250 *Cadmium, total, in μg/L 15 -- 0.056 0.02 0.033 0.08 0.18

T8 06306250 Chromium, dissolved, in μg/L 1 -- -- -- -- -- 0.22

T8 06306250 *Chromium, total, in μg/L 15 -- 3.270 2 2.7 4 9

T8 06306250 Copper, dissolved, in μg/L 15 0.57 2.757 1.9 2.7 3.4 5.1

T8 06306250 Copper, total, in μg/L 15 2.5 6.293 4 6 8.7 14.6

T8 06306250 *Iron, dissolved, in μg/L 36 -- 14.26 6 7.5 11.75 100

T8 06306250 Iron, total, in μg/L 17 136 2,553 339 800 4,365 8,170

T8 06306250 *Lead, dissolved, in μg/L 15 -- 0.093 0.048 0.068 0.093 0.33

T8 06306250 Lead, total, in μg/L 15 0.08 1.586 0.14 0.39 2.72 6.54

T8 06306250 Lithium, dissolved, in μg/L 14 17.8 32.04 23.125 30.55 40.525 62.5

T8 06306250 Manganese, dissolved, in μg/L 36 9.2 47.28 22.5 35.2 65.75 137

T8 06306250 Manganese, total, in μg/L 17 58.3 241.2 88.05 168 421 537

T8 06306250 Mercury, total, ng/L 5 0.92 -- -- -- -- 9.76

T8 06306250 **Mercury, total, μg/L 3 -- -- -- -- -- <0.01

T8 06306250 Nickel, dissolved, in μg/L 15 1 2.960 1.46 3.17 3.76 5.56

T8 06306250 Nickel, total, in μg/L 15 2.7 5.369 4 4.8 6.76 10.9

T8 06306250 Selenium, dissolved, in μg/L 17 0.23 0.874 0.63 0.78 1.15 1.7

T8 06306250 Selenium, total, in μg/L 36 0.12 0.92 0.632 0.85 1.2 2

T8 06306250 Strontium, dissolved, in μg/L 14 920 1,658 1,296 1,770 1,943 2,520

T8 06306250 *Zinc, dissolved, in μg/L 15 -- 3.065 1.2 2 2.5 15.9

T8 06306250 Zinc, total, in μg/L 15 2 9.140 3 8 12 27

T8 06306250 Suspended sediment, <0.0625 mm, percent 34 43 82.03 76.75 87 92 97

T8 06306250 Suspended sediment, in mg/L 34 21 122.4 60 84 174 431

T8 06306250 Suspended sediment, tons/day 34 0.02 12.60 1.7 4.1 14.5 119

T9 06306300 Streamflow, in cubic feet per second 67 12 530.9 137 181 347 5,430

T9 06306300 Turbidity, nephelometric turbidity ratio units 2 4.4 -- -- -- -- 24

T9 06306300 Dissolved oxygen, in mg/L 63 5.6 10.21 8.6 10.3 11.6 15.9

T9 06306300 Dissolved oxygen, percent saturation 63 76 107.9 94 105 121 164

T9 06306300 pH, in standard units 65 7.7 8.35 8.2 8.4 8.5 8.7

T9 06306300 Specific conductance, at 25 degrees Celsius, in μS/cm 67 186 594.4 455 634 730 1,060

T9 06306300 Temperature, water deg C 66 0 13.09 6.5 13.25 21.5 26.5

T9 06306300 Hardness, in mg/L as CaCO3 64 83 261.1 210 280 310 400

T9 06306300 Calcium, dissolved, in mg/L 64 20.1 53.02 44.475 55.5 63.05 78.9

T9 06306300 Magnesium, dissolved, in mg/L 64 7.83 31.23 23.025 34.2 38.475 50

T9 06306300 Potassium, dissolved, in mg/L 64 1 2.750 1.995 2.805 3.1 7.34

T9 06306300 Sodium-adsorption ratio (unitless) 64 0.2 0.719 0.5 0.7 0.875 1.5

T9 06306300 Sodium, dissolved, in mg/L 64 4.97 27.72 17.825 28.25 35.45 65.2

T9 06306300 Acid neutralizing capacity, in mg/L as CaCO3 42 81 200.2 171.25 212 235.25 273

T9 06306300 Alkalinity, in mg/L as CaCO3 64 73 193.8 161.25 206 235.75 276

T9 06306300 Chloride, dissolved, in mg/L 64 0.83 3.923 2.67 3.83 4.832 7.93

T9 06306300 Fluoride, dissolved, in mg/L 63 0.08 0.273 0.2 0.29 0.32 0.61

T9 06306300 Silica, dissolved, in mg/L 63 2.37 5.852 3.97 5.77 7.63 10.3

T9 06306300 Sulfate, dissolved, in mg/L 64 20.5 117.4 79.175 124.5 149.25 237

T9 06306300 Dissolved solids, calculated, in mg/L 60 108 364.3 270.75 385.5 451.5 571

T9 06306300 Dissolved solids, tons/day 62 26.2 357.0 160.5 188.5 333.5 3,580

T9 06306300 Dissolved solids, residue on evaporation, in mg/L 43 118 381.1 281 411 466 561

T9 06306300 *Ammonia, dissolved, in mg/L as N 20 -- 0.02 0.006 0.012 0.025 0.083

T9 06306300 *Nitrate plus nitrite, dissolved, in mg/L as N 20 -- 0.071 0.009 0.03 0.07 0.434

T9 06306300 *Nitrite, dissolved, in mg/L as N 20 -- 0.002 0.001 0.001 0.003 0.009

T9 06306300 *Orthophosphate, dissolved, in mg/L as P 20 -- 0.011 0.003 0.007 0.013 0.057

T9 06306300 Phosphorus, total, in mg/L 20 0.019 0.084 0.029 0.041 0.08 0.53

T9 06306300 Total nitrogen, total, in mg/L 20 0.22 0.483 0.282 0.355 0.425 1.99
66 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T9 06306300 *Aluminum, dissolved, in μg/L 20 -- 4.096 1.1 1.7 4.175 25.1

T9 06306300 Aluminum, total, in μg/L 29 18 536.3 70.5 140 363.5 5,810

T9 06306300 Arsenic, dissolved, in μg/L 28 0.3 0.523 0.41 0.49 0.595 0.91

T9 06306300 *Arsenic, total, in μg/L 29 -- 0.88 0.59 0.75 0.915 3

T9 06306300 Barium, dissolved, in μg/L 20 24 47.15 41 48.5 55.5 67

T9 06306300 Barium, total, in μg/L 29 35 59.01 47.5 55.3 60.3 155

T9 06306300 **Beryllium, dissolved, in μg/L 20 -- -- -- -- -- <0.06

T9 06306300 *Beryllium, total, in μg/L 29 -- 0.064 0.005 0.014 0.05 0.75

T9 06306300 Boron, dissolved, in μg/L 15 35 64.27 54 62 69 99

T9 06306300 Boron, total, in μg/L 3 61 -- -- -- -- 79

T9 06306300 **Cadmium, dissolved, in μg/L 20 -- -- -- -- -- 0.05

T9 06306300 *Cadmium, total, in μg/L 24 -- 0.034 0.006 0.015 0.022 0.35

T9 06306300 Chromium, dissolved, in μg/L 6 0.06 0.097 0.068 0.085 0.12 0.18

T9 06306300 *Chromium, total, in μg/L 24 -- 1.377 0.407 0.965 2 7

T9 06306300 Copper, dissolved, in μg/L 20 0.51 1.456 0.993 1.35 1.675 2.8

T9 06306300 *Copper, total, in μg/L 24 -- 2.572 1.325 1.75 2.2 15.2

T9 06306300 Iron, dissolved, in μg/L 29 6 25.14 12.5 19 33 80

T9 06306300 Iron, total, in μg/L 20 66 903.1 178 367 810 7,530

T9 06306300 *Lead, dissolved, in μg/L 20 -- 0.109 0.064 0.078 0.102 0.37

T9 06306300 Lead, total, in μg/L 24 0.06 1.090 0.132 0.26 0.73 10.8

T9 06306300 Lithium, dissolved, in μg/L 14 10 19.28 15.475 19.1 22.2 36.6

T9 06306300 Manganese, dissolved, in μg/L 30 0.5 15.72 7.15 11.15 24.65 52.6

T9 06306300 Manganese, total, in μg/L 20 13.7 61.66 28.7 50.25 59.675 290

T9 06306300 Mercury, total, ng/L 5 0.59 -- -- -- -- 2.35

T9 06306300 **Mercury, total, μg/L 4 -- -- -- -- -- 0.01

T9 06306300 Nickel, dissolved, in μg/L 21 0.22 1.493 0.67 1.5 2.09 3.06

T9 06306300 Nickel, total, in μg/L 24 0.63 2.400 1.2 1.82 2.395 12.1

T9 06306300 Selenium, dissolved, in μg/L 20 0.15 0.384 0.222 0.3 0.5 1

T9 06306300 Selenium, total, in μg/L 29 0.09 0.388 0.22 0.31 0.395 1.6

T9 06306300 Strontium, dissolved, in μg/L 15 219 470.2 443 508 532 567

T9 06306300 Zinc, dissolved, in μg/L 18 0.81 1.928 1.275 1.7 2.3 4.8

T9 06306300 *Zinc, total, in μg/L 24 -- 5.739 2 2.2 4.875 44

T9 06306300 Suspended sediment, <0.0625 mm, percent 56 31 79.30 69.5 85 92 99

T9 06306300 Suspended sediment, in mg/L 56 11 57.57 20.5 35.5 52.75 697

T9 06306300 Suspended sediment, tons/day 56 1.1 263.5 6.95 15.5 31.75 10,200

T10 451607106372801 Streamflow, in cubic feet per second 4 153 -- -- -- -- 408

T10 451607106372801 Turbidity, nephelometric turbidity ratio units 4 0.6 -- -- -- -- 13

T10 451607106372801 Dissolved oxygen, in mg/L 4 6.7 -- -- -- -- 9

T10 451607106372801 Dissolved oxygen, percent saturation 4 81 -- -- -- -- 101

T10 451607106372801 pH, in standard units 4 8 -- -- -- -- 8.7

T10 451607106372801 Specific conductance, at 25 degrees Celsius, in μS/cm 4 363 -- -- -- -- 540

T10 451607106372801 Temperature, water deg C 4 15 -- -- -- -- 20

T10 451607106372801 Hardness, in mg/L as CaCO3 4 160 -- -- -- -- 220

T10 451607106372801 Calcium, dissolved, in mg/L 4 36.2 -- -- -- -- 48.6

T10 451607106372801 Magnesium, dissolved, in mg/L 4 17 -- -- -- -- 28.8

T10 451607106372801 Potassium, dissolved, in mg/L 4 1.92 -- -- -- -- 3.62

T10 451607106372801 Sodium-adsorption ratio (unitless) 4 0.5 -- -- -- -- 1.1

T10 451607106372801 Sodium, dissolved, in mg/L 4 14.7 -- -- -- -- 36.5

T10 451607106372801 Alkalinity, in mg/L as CaCO3 4 130 -- -- -- -- 174

T10 451607106372801 Chloride, dissolved, in mg/L 4 1.46 -- -- -- -- 3.4

T10 451607106372801 Fluoride, dissolved, in mg/L 4 0.18 -- -- -- -- 0.3

T10 451607106372801 Silica, dissolved, in mg/L 4 0.67 -- -- -- -- 5.47

T10 451607106372801 Sulfate, dissolved, in mg/L 4 54.4 -- -- -- -- 111

T10 451607106372801 Dissolved solids, calculated, in mg/L 4 209 -- -- -- -- 322

T10 451607106372801 Dissolved solids, tons/day 4 132 -- -- -- -- 276

T11 06307570 Streamflow, in cubic feet per second 3 0 -- -- -- -- 0.12

T11 06307570 Turbidity, nephelometric turbidity ratio units 3 3.9 -- -- -- -- 14

T11 06307570 Dissolved oxygen, in mg/L 1 -- -- -- -- -- 10

T11 06307570 Dissolved oxygen, percent saturation 1 -- -- -- -- -- 123

T11 06307570 pH, in standard units 3 7.9 -- -- -- -- 9.3
Appendix 67

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T11 06307570 Specific conductance, at 25 degrees Celsius, in μS/cm 3 4,010 -- -- -- -- 5,000

T11 06307570 Temperature, water deg C 3 18.5 -- -- -- -- 24.5

T11 06307570 Hardness, in mg/L as CaCO3 3 950 -- -- -- -- 1,400

T11 06307570 Calcium, dissolved, in mg/L 3 18.9 -- -- -- -- 140

T11 06307570 Magnesium, dissolved, in mg/L 3 210 -- -- -- -- 249

T11 06307570 Potassium, dissolved, in mg/L 3 13.7 -- -- -- -- 18.3

T11 06307570 Sodium-adsorption ratio (unitless) 3 8.6 -- -- -- -- 10

T11 06307570 Sodium, dissolved, in mg/L 3 695 -- -- -- -- 732

T11 06307570 Alkalinity, in mg/L as CaCO3 3 335 -- -- -- -- 492

T11 06307570 Chloride, dissolved, in mg/L 3 15.8 -- -- -- -- 18.3

T11 06307570 Fluoride, dissolved, in mg/L 3 0.74 -- -- -- -- 0.84

T11 06307570 Silica, dissolved, in mg/L 3 1.22 -- -- -- -- 4.39

T11 06307570 Sulfate, dissolved, in mg/L 3 2,050 -- -- -- -- 2,450

T11 06307570 Dissolved solids, calculated, in mg/L 3 3,300 -- -- -- -- 3,900

T11 06307570 Dissolved solids, tons/day 2 0.32 -- -- -- -- 1.07

T12 451340106295501 Streamflow, in cubic feet per second 3 0.04 -- -- -- -- 0.49

T12 451340106295501 Turbidity, nephelometric turbidity ratio units 2 1.4 -- -- -- -- 3.1

T12 451340106295501 Dissolved oxygen, in mg/L 1 -- -- -- -- -- 14.8

T12 451340106295501 Dissolved oxygen, percent saturation 1 -- -- -- -- -- 206

T12 451340106295501 pH, in standard units 3 8.1 -- -- -- -- 9.3

T12 451340106295501 Specific conductance, at 25 degrees Celsius, in μS/cm 3 3,650 -- -- -- -- 3,970

T12 451340106295501 Temperature, water deg C 3 24.5 -- -- -- -- 27.5

T12 451340106295501 Hardness, in mg/L as CaCO3 3 930 -- -- -- -- 1,000

T12 451340106295501 Calcium, dissolved, in mg/L 3 40 -- -- -- -- 98.5

T12 451340106295501 Magnesium, dissolved, in mg/L 3 166 -- -- -- -- 213

T12 451340106295501 Potassium, dissolved, in mg/L 3 16.5 -- -- -- -- 20

T12 451340106295501 Sodium-adsorption ratio (unitless) 3 7.4 -- -- -- -- 9.2

T12 451340106295501 Sodium, dissolved, in mg/L 3 546 -- -- -- -- 662

T12 451340106295501 Alkalinity, in mg/L as CaCO3 3 323 -- -- -- -- 415

T12 451340106295501 Chloride, dissolved, in mg/L 3 17.9 -- -- -- -- 20

T12 451340106295501 Fluoride, dissolved, in mg/L 3 0.81 -- -- -- -- 0.85

T12 451340106295501 Silica, dissolved, in mg/L 3 0.41 -- -- -- -- 2.54

T12 451340106295501 Sulfate, dissolved, in mg/L 3 1,710 -- -- -- -- 1,920

T12 451340106295501 Dissolved solids, calculated, in mg/L 3 2,810 -- -- -- -- 3,070

T12 451340106295501 Dissolved solids, tons/day 3 0.32 -- -- -- -- 3.72

T13 06307600 Streamflow, in cubic feet per second 37 0 1.978 0.1 0.25 0.81 43

T13 06307600 Turbidity, nephelometric turbidity ratio units 2 4 -- -- -- -- 140

T13 06307600 Dissolved oxygen, in mg/L 37 1.5 8.289 6.65 7.9 10 13.6

T13 06307600 Dissolved oxygen, percent saturation 36 37 90.25 68.25 84.5 105.75 184

T13 06307600 pH, in standard units 36 7.6 8.10 8 8.1 8.2 8.7

T13 06307600 Specific conductance, at 25 degrees Celsius, in μS/cm 37 921 2,493 2,080 2,300 2,980 3,890

T13 06307600 Temperature, water deg C 37 0 11.91 4.25 12 18.25 28.6

T13 06307600 Hardness, in mg/L as CaCO3 35 240 771.7 660 770 930 1,000

T13 06307600 Calcium, dissolved, in mg/L 35 39.9 102.4 89.2 103 112 195

T13 06307600 Magnesium, dissolved, in mg/L 35 34 125.9 110 124 150 176

T13 06307600 Potassium, dissolved, in mg/L 35 9.47 15.32 13.2 15.3 17.1 21.6

T13 06307600 Sodium-adsorption ratio (unitless) 35 2.5 4.843 3.9 4.5 5.9 7.2

T13 06307600 Sodium, dissolved, in mg/L 35 87.2 313.7 238 273 402 530

T13 06307600 Alkalinity, in mg/L as CaCO3 35 146 566.4 535 578 607 751

T13 06307600 Chloride, dissolved, in mg/L 35 4.38 11.86 9.07 11.5 14.7 18.6

T13 06307600 Fluoride, dissolved, in mg/L 35 0.28 1.261 1.1 1.29 1.46 1.89

T13 06307600 Silica, dissolved, in mg/L 35 6.61 13.87 9.33 13.3 16.9 27

T13 06307600 Sulfate, dissolved, in mg/L 35 317 868.1 584 716 1,170 1,550

T13 06307600 Dissolved solids, calculated, in mg/L 35 591 1,792 1,440 1,630 2,210 2,730

T13 06307600 Dissolved solids, tons/day 35 0.03 6.525 0.45 1.08 5.53 68.6

T13 06307600 *Ammonia, dissolved, in mg/L as N 15 -- 0.018 0.011 0.015 0.028 0.045

T13 06307600 *Nitrate plus nitrite, dissolved, in mg/L as N 15 -- 0.026 0.009 0.014 0.026 0.141

T13 06307600 *Nitrite, dissolved, in mg/L as N 15 -- 0.002 0.001 0.001 0.002 0.005

T13 06307600 *Orthophosphate, dissolved, in mg/L as P 15 -- 0.009 0.004 0.009 0.013 0.023

T13 06307600 Phosphorus, total, in mg/L 15 0.02 0.037 0.024 0.037 0.046 0.059
68 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T13 06307600 Total nitrogen, total, in mg/L 15 0.31 0.489 0.39 0.49 0.57 0.63

T13 06307600 *Aluminum, dissolved, in μg/L 14 -- 1.660 0.875 1.107 1.85 6.5

T13 06307600 Aluminum, total, in μg/L 14 19 73.64 40.75 71 108.25 126

T13 06307600 Arsenic, dissolved, in μg/L 14 0.53 1.074 0.75 0.985 1.35 1.9

T13 06307600 *Arsenic, total, in μg/L 14 -- 1.279 0.812 1.1 1.492 2.6

T13 06307600 Barium, dissolved, in μg/L 14 18 45.07 41.75 46 49 71

T13 06307600 Barium, total, in μg/L 14 23.2 46.66 42.2 48 55.125 65.3

T13 06307600 **Beryllium, dissolved, in μg/L 14 -- -- -- -- -- <0.12

T13 06307600 **Beryllium, total, in μg/L 14 -- -- -- -- -- <0.12

T13 06307600 Boron, dissolved, in μg/L 9 197 251.4 235.5 257 265.5 294

T13 06307600 **Cadmium, dissolved, in μg/L 12 -- -- -- -- -- <0.08

T13 06307600 *Cadmium, total, in μg/L 12 -- 0.04 0.015 0.023 0.039 0.2

T13 06307600 **Chromium, dissolved, in μg/L 3 -- -- -- -- -- 0.42

T13 06307600 *Chromium, total, in μg/L 12 -- 2.485 0.678 2 3.75 6

T13 06307600 *Copper, dissolved, in μg/L 12 -- 3.012 2.175 2.7 3.125 9.5

T13 06307600 *Copper, total, in μg/L 12 -- 4.672 1.62 3.5 8.15 11.8

T13 06307600 Iron, dissolved, in μg/L 14 18 38.21 25 30.5 45.25 107

T13 06307600 Iron, total, in μg/L 14 295 484.6 331.75 430.5 626.5 772

T13 06307600 **Lead, dissolved, in μg/L 12 -- -- -- -- -- <0.24

T13 06307600 Lead, total, in μg/L 12 0.08 0.148 0.093 0.13 0.188 0.28

T13 06307600 Lithium, dissolved, in μg/L 9 61.4 95.70 86.45 100 104.5 119

T13 06307600 Manganese, dissolved, in μg/L 14 45.3 117.9 75.575 104 140.5 228

T13 06307600 Manganese, total, in μg/L 14 57.1 123.8 79.375 113.5 143.5 234

T13 06307600 Mercury, total, ng/L 4 0.65 -- -- -- -- 1.06

T13 06307600 **Mercury, total, μg/L 3 -- -- -- -- -- <0.01

T13 06307600 Nickel, dissolved, in μg/L 12 1.8 3.303 2.15 3.345 4.265 5.03

T13 06307600 Nickel, total, in μg/L 12 1.6 4.003 2.727 3.91 4.935 8.57

T13 06307600 Selenium, dissolved, in μg/L 14 0.15 0.531 0.215 0.515 0.725 1.2

T13 06307600 Selenium, total, in μg/L 14 0.14 0.551 0.22 0.36 0.925 1.2

T13 06307600 Strontium, dissolved, in μg/L 9 1,240 1,404 1,340 1,430 1,475 1,540

T13 06307600 *Zinc, dissolved, in μg/L 12 -- 3.015 1.925 2.24 3.525 6.5

T13 06307600 *Zinc, total, in μg/L 12 -- 3.085 2 2.858 4 5

T13 06307600 Suspended sediment, <0.0625 mm, percent 30 8 62.63 50.75 63 79 98

T13 06307600 Suspended sediment, in mg/L 30 17 72.20 42 61.5 98.5 171

T13 06307600 Suspended sediment, tons/day 30 0 0.632 0.018 0.025 0.055 17

T14 06307616 Streamflow, in cubic feet per second 67 63 482.7 96 227 457 3,230

T14 06307616 Turbidity, nephelometric turbidity ratio units 1 -- -- -- -- -- 14

T14 06307616 Dissolved oxygen, in mg/L 63 6.9 9.705 8.2 9.2 11 14.5

T14 06307616 Dissolved oxygen, percent saturation 61 65 102.4 95.5 102 111 137

T14 06307616 pH, in standard units 64 7.9 8.40 8.3 8.4 8.5 8.7

T14 06307616 Specific conductance, at 25 degrees Celsius, in μS/cm 67 263 583.5 436 623 715 807

T14 06307616 Temperature, water deg C 67 0 13.94 8 14 20.5 27

T14 06307616 Hardness, in mg/L as CaCO3 63 110 244.0 180 260 300 370

T14 06307616 Calcium, dissolved, in mg/L 63 26.6 47.78 35.9 49.7 56.4 69.6

T14 06307616 Magnesium, dissolved, in mg/L 63 11 30.26 19.9 33.2 38 47

T14 06307616 Potassium, dissolved, in mg/L 63 1.42 3.202 2.54 3.38 3.69 4.67

T14 06307616 Sodium-adsorption ratio (unitless) 63 0.4 0.924 0.6 1 1.2 1.4

T14 06307616 Sodium, dissolved, in mg/L 63 9.04 33.99 19.8 39.4 44.8 54.5

T14 06307616 Alkalinity, in mg/L as CaCO3 63 99 190.9 144 198 226 282

T14 06307616 Chloride, dissolved, in mg/L 63 1.15 3.685 2.23 4.04 4.83 7.59

T14 06307616 Fluoride, dissolved, in mg/L 63 0.14 0.295 0.21 0.33 0.36 0.43

T14 06307616 Silica, dissolved, in mg/L 63 0.76 3.558 1.81 3.1 5.46 7.82

T14 06307616 Sulfate, dissolved, in mg/L 63 32 121.5 73.5 142 157 184

T14 06307616 Dissolved solids, calculated, in mg/L 60 162 359.0 257.5 387 444 532

T14 06307616 Dissolved solids, tons/day 60 65.2 362.7 122.25 213.5 321.75 2,270

T14 06307616 *Ammonia, dissolved, in mg/L as N 20 -- 0.013 0.005 0.007 0.012 0.095

T14 06307616 *Nitrate plus nitrite, dissolved, in mg/L as N 20 -- 0.023 0.007 0.009 0.022 0.16

T14 06307616 *Nitrite, dissolved, in mg/L as N 20 -- 0.002 0.001 0.001 0.002 0.007

T14 06307616 *Orthophosphate, dissolved, in mg/L as P 20 -- 0.005 0.003 0.004 0.006 0.013

T14 06307616 Phosphorus, total, in mg/L 20 0.007 0.036 0.009 0.018 0.053 0.13
Appendix 69

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T14 06307616 Total nitrogen, total, in mg/L 20 0.22 0.386 0.262 0.315 0.47 0.94

T14 06307616 *Aluminum, dissolved, in μg/L 20 -- 2.511 1.106 2.15 3.075 7

T14 06307616 Aluminum, total, in μg/L 20 8 165.9 20.25 43 166.25 990

T14 06307616 Arsenic, dissolved, in μg/L 20 0.6 0.9 0.738 0.83 0.952 1.6

T14 06307616 *Arsenic, total, in μg/L 20 -- 1.228 0.978 1.198 1.475 1.7

T14 06307616 Barium, dissolved, in μg/L 20 30 51.70 43.5 54.5 59.75 63

T14 06307616 Barium, total, in μg/L 20 40 56.59 50.325 56.95 62.7 72.9

T14 06307616 **Beryllium, dissolved, in μg/L 20 -- -- -- -- -- <0.06

T14 06307616 *Beryllium, total, in μg/L 20 -- 0.037 0.024 0.034 0.045 0.09

T14 06307616 Boron, dissolved, in μg/L 14 43 69.29 60 69.5 82 88

T14 06307616 **Cadmium, dissolved, in μg/L 18 -- -- -- -- -- 0.05

T14 06307616 *Cadmium, total, in μg/L 18 -- 0.017 0.004 0.009 0.02 0.09

T14 06307616 Chromium, dissolved, in μg/L 4 0.07 -- -- -- -- 0.19

T14 06307616 *Chromium, total, in μg/L 18 -- 1.280 0.729 1 1.9 3

T14 06307616 Copper, dissolved, in μg/L 18 0.63 1.969 0.972 1.4 2.65 5.8

T14 06307616 *Copper, total, in μg/L 18 -- 2.405 1.375 1.75 3.05 7.2

T14 06307616 Iron, dissolved, in μg/L 20 4 16.75 11.25 15 22.75 33

T14 06307616 Iron, total, in μg/L 20 39 369.3 71.5 124 421.5 1,960

T14 06307616 *Lead, dissolved, in μg/L 18 -- 0.09 0.05 0.067 0.113 0.24

T14 06307616 *Lead, total, in μg/L 18 -- 0.323 0.044 0.065 0.368 1.67

T14 06307616 Lithium, dissolved, in μg/L 14 10.9 22.76 19.85 22.65 26.1 29.5

T14 06307616 Manganese, dissolved, in μg/L 20 3.3 10.42 5.8 7.65 17.15 25.2

T14 06307616 Manganese, total, in μg/L 20 7.5 43.42 12.225 32.7 60.45 157

T14 06307616 Mercury, total, ng/L 5 0.18 -- -- -- -- 1.25

T14 06307616 **Mercury, total, μg/L 3 -- -- -- -- -- <0.01

T14 06307616 Nickel, dissolved, in μg/L 17 0.79 1.611 0.935 1.7 2.05 3.33

T14 06307616 Nickel, total, in μg/L 18 0.84 2.143 1.597 2.06 2.592 3.9

T14 06307616 Selenium, dissolved, in μg/L 20 0.17 0.346 0.28 0.345 0.393 0.6

T14 06307616 *Selenium, total, in μg/L 20 -- 0.381 0.262 0.33 0.398 0.9

T14 06307616 Strontium, dissolved, in μg/L 14 300 504.2 439.75 498.5 600.25 611

T14 06307616 Zinc, dissolved, in μg/L 15 0.5 2.223 1 1.4 3.8 5.8

T14 06307616 *Zinc, total, in μg/L 18 -- 2.145 1 1.715 2 7.1

T14 06307616 Suspended sediment, <0.0625 mm, percent 56 28 77.71 73.5 81 87 92

T14 06307616 Suspended sediment, in mg/L 56 2 28.25 12.25 22 37.5 132

T14 06307616 Suspended sediment, tons/day 56 0.34 66.96 3.5 9.9 28.75 1,150

T15 451732106085001 Streamflow, in cubic feet per second 3 0.1 -- -- -- -- 1.4

T15 451732106085001 Turbidity, nephelometric turbidity ratio units 3 2.4 -- -- -- -- 5.5

T15 451732106085001 Dissolved oxygen, in mg/L 3 7.8 -- -- -- -- 18.4

T15 451732106085001 Dissolved oxygen, percent saturation 2 96 -- -- -- -- 177

T15 451732106085001 pH, in standard units 3 7.7 -- -- -- -- 8.6

T15 451732106085001 Specific conductance, at 25 degrees Celsius, in μS/cm 3 3,470 -- -- -- -- 4,000

T15 451732106085001 Temperature, water deg C 3 19 -- -- -- -- 26.5

T15 451732106085001 Hardness, in mg/L as CaCO3 3 1,200 -- -- -- -- 1,500

T15 451732106085001 Calcium, dissolved, in mg/L 3 91.2 -- -- -- -- 159

T15 451732106085001 Magnesium, dissolved, in mg/L 3 233 -- -- -- -- 257

T15 451732106085001 Potassium, dissolved, in mg/L 3 18.3 -- -- -- -- 20.3

T15 451732106085001 Sodium-adsorption ratio (unitless) 3 5.2 -- -- -- -- 5.9

T15 451732106085001 Sodium, dissolved, in mg/L 3 418 -- -- -- -- 516

T15 451732106085001 Alkalinity, in mg/L as CaCO3 3 464 -- -- -- -- 583

T15 451732106085001 Chloride, dissolved, in mg/L 3 9.39 -- -- -- -- 14

T15 451732106085001 Fluoride, dissolved, in mg/L 3 0.64 -- -- -- -- 0.77

T15 451732106085001 Silica, dissolved, in mg/L 3 12.9 -- -- -- -- 14.3

T15 451732106085001 Sulfate, dissolved, in mg/L 3 1,390 -- -- -- -- 1,950

T15 451732106085001 Dissolved solids, calculated, in mg/L 3 2,480 -- -- -- -- 3,270

T15 451732106085001 Dissolved solids, tons/day 3 0.75 -- -- -- -- 12.4

T16 452642106091201 Streamflow, in cubic feet per second 2 0.26 -- -- -- -- 3.8

T16 452642106091201 Turbidity, nephelometric turbidity ratio units 2 2.5 -- -- -- -- 4.4

T16 452642106091201 Dissolved oxygen, in mg/L 2 6.4 -- -- -- -- 7.5

T16 452642106091201 Dissolved oxygen, percent saturation 1 -- -- -- -- -- 83

T16 452642106091201 pH, in standard units 2 8 -- -- -- -- 8.8
70 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T16 452642106091201 Specific conductance, at 25 degrees Celsius, in μS/cm 2 3,200 -- -- -- -- 3,600

T16 452642106091201 Temperature, water deg C 2 19.5 -- -- -- -- 21.5

T16 452642106091201 Hardness, in mg/L as CaCO3 2 1,100 -- -- -- -- 1,100

T16 452642106091201 Calcium, dissolved, in mg/L 2 52 -- -- -- -- 129

T16 452642106091201 Magnesium, dissolved, in mg/L 2 196 -- -- -- -- 246

T16 452642106091201 Potassium, dissolved, in mg/L 2 19.4 -- -- -- -- 19.4

T16 452642106091201 Sodium-adsorption ratio (unitless) 2 5.1 -- -- -- -- 6.1

T16 452642106091201 Sodium, dissolved, in mg/L 2 391 -- -- -- -- 475

T16 452642106091201 Alkalinity, in mg/L as CaCO3 2 438 -- -- -- -- 502

T16 452642106091201 Chloride, dissolved, in mg/L 2 10.7 -- -- -- -- 12.9

T16 452642106091201 Fluoride, dissolved, in mg/L 2 0.65 -- -- -- -- 0.66

T16 452642106091201 Silica, dissolved, in mg/L 2 1.16 -- -- -- -- 7.43

T16 452642106091201 Sulfate, dissolved, in mg/L 2 1,440 -- -- -- -- 1,730

T16 452642106091201 Dissolved solids, calculated, in mg/L 2 2,490 -- -- -- -- 2,800

T16 452642106091201 Dissolved solids, tons/day 2 1.97 -- -- -- -- 25.6

T17 06307740 Streamflow, in cubic feet per second 45 0.15 3.247 1 1.7 3.05 33

T17 06307740 Turbidity, nephelometric turbidity ratio units 3 21 -- -- -- -- 79

T17 06307740 Dissolved oxygen, in mg/L 42 5 9.343 7.35 8.3 10.075 22.2

T17 06307740 Dissolved oxygen, percent saturation 40 64 96.40 81.25 95.5 106 171

T17 06307740 pH, in standard units 43 7.9 8.39 8.3 8.4 8.5 8.9

T17 06307740 Specific conductance, at 25 degrees Celsius, in μS/cm 45 1,730 2,841 2,510 2,880 3,115 3,700

T17 06307740 Temperature, water deg C 45 0 14.16 7.5 14 22 29

T17 06307740 Hardness, in mg/L as CaCO3 43 480 822.1 720 820 910 1,100

T17 06307740 Calcium, dissolved, in mg/L 43 50.1 79.69 67.3 79 87.5 122

T17 06307740 Magnesium, dissolved, in mg/L 43 84 151.1 132 151 165 206

T17 06307740 Potassium, dissolved, in mg/L 43 11.7 18.88 17.4 18.6 20.4 25.8

T17 06307740 Sodium-adsorption ratio (unitless) 43 4.6 6.005 5.5 6.1 6.4 6.9

T17 06307740 Sodium, dissolved, in mg/L 43 233 396.4 334 406 443 520

T17 06307740 Alkalinity, in mg/L as CaCO3 43 350 549.8 508 554 592 807

T17 06307740 Chloride, dissolved, in mg/L 43 7.12 11.79 10.1 11.7 13.1 16.1

T17 06307740 Fluoride, dissolved, in mg/L 43 0.58 0.9 0.83 0.91 0.97 1.2

T17 06307740 Silica, dissolved, in mg/L 43 5.8 10.77 8.02 9.9 14 22.3

T17 06307740 Sulfate, dissolved, in mg/L 43 624 1,102 903 1,070 1,290 1,600

T17 06307740 Dissolved solids, calculated, in mg/L 43 1,230 2,102 1,820 2,110 2,300 2,850

T17 06307740 Dissolved solids, tons/day 43 0.68 19.19 5.26 9.96 17.1 162

T17 06307740 *Ammonia, dissolved, in mg/L as N 20 -- 0.025 0.006 0.011 0.031 0.127

T17 06307740 *Nitrate plus nitrite, dissolved, in mg/L as N 20 -- 0.062 0.009 0.016 0.045 0.423

T17 06307740 *Nitrite, dissolved, in mg/L as N 20 -- 0.003 0.001 0.001 0.003 0.011

T17 06307740 *Orthophosphate, dissolved, in mg/L as P 20 -- 0.006 0.004 0.005 0.007 0.013

T17 06307740 Phosphorus, total, in mg/L 20 0.016 0.063 0.031 0.054 0.093 0.185

T17 06307740 Total nitrogen, total, in mg/L 20 0.31 0.737 0.562 0.755 0.91 1.29

T17 06307740 *Aluminum, dissolved, in μg/L 19 -- 1.984 1.5 1.8 2.112 4.9

T17 06307740 Aluminum, total, in μg/L 19 37 349.5 104 299 522 1,020

T17 06307740 Arsenic, dissolved, in μg/L 19 0.69 2.227 1.2 1.4 1.7 7.5

T17 06307740 *Arsenic, total, in μg/L 19 -- 2.458 1.3 1.7 2.3 8.2

T17 06307740 Barium, dissolved, in μg/L 19 11 33.21 25 31 39 61

T17 06307740 Barium, total, in μg/L 19 11.2 41.14 29 38 50.4 76.8

T17 06307740 **Beryllium, dissolved, in μg/L 19 -- -- -- -- -- <0.12

T17 06307740 *Beryllium, total, in μg/L 19 -- 0.047 0.034 0.04 0.06 0.1

T17 06307740 Boron, dissolved, in μg/L 14 357 495.6 407 498 541.5 744

T17 06307740 *Cadmium, dissolved, in μg/L 17 -- 0.026 0.02 0.023 0.03 0.04

T17 06307740 *Cadmium, total, in μg/L 17 -- 0.034 0.02 0.03 0.05 0.06

T17 06307740 **Chromium, dissolved, in μg/L 3 -- -- -- -- -- 0.45

T17 06307740 *Chromium, total, in μg/L 17 -- 3.381 1.068 3 5.5 9

T17 06307740 *Copper, dissolved, in μg/L 17 -- 3.893 1.3 3.3 4.9 11.3

T17 06307740 *Copper, total, in μg/L 17 -- 6.654 3.4 5.4 7.7 20.1

T17 06307740 *Iron, dissolved, in μg/L 19 -- 20.40 12.82 16.646 28 43

T17 06307740 Iron, total, in μg/L 19 220 849.4 361 802 1,100 2,220

T17 06307740 *Lead, dissolved, in μg/L 17 -- 0.085 0.051 0.07 0.095 0.26

T17 06307740 Lead, total, in μg/L 17 0.05 0.801 0.22 0.67 1.14 2.24
Appendix 71

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T17 06307740 Lithium, dissolved, in μg/L 14 80 111.1 94.1 107.5 128.75 162

T17 06307740 Manganese, dissolved, in μg/L 19 6.5 49.53 11.4 49.6 68.5 137

T17 06307740 Manganese, total, in μg/L 19 55.7 108.3 69.2 89.7 141 208

T17 06307740 Mercury, total, ng/L 6 0.5 2.367 1.415 1.935 3.613 4.94

T17 06307740 **Mercury, total, μg/L 3 -- -- -- -- -- <0.01

T17 06307740 Nickel, dissolved, in μg/L 17 1.4 3.502 2.61 3.06 4.41 7.94

T17 06307740 Nickel, total, in μg/L 17 2.58 4.911 3.75 4.3 6.15 8.61

T17 06307740 Selenium, dissolved, in μg/L 19 0.61 1.075 0.75 1 1.4 1.9

T17 06307740 Selenium, total, in μg/L 19 0.45 1.126 0.82 0.94 1.5 2.1

T17 06307740 Strontium, dissolved, in μg/L 14 1,120 1,675 1,325 1,695 1,978 2,430

T17 06307740 *Zinc, dissolved, in μg/L 17 -- 2.844 1.8 2.6 3.8 5.4

T17 06307740 *Zinc, total, in μg/L 17 -- 5.782 3 6 7 13

T17 06307740 Suspended sediment, <0.0625 mm, percent 38 45 81.63 73.5 82 95.25 98

T17 06307740 Suspended sediment, in mg/L 38 26 95.84 45 97.5 137 186

T17 06307740 Suspended sediment, tons/day 38 0.01 0.591 0.17 0.36 0.67 3.4

T18 06307830 Streamflow, in cubic feet per second 53 60 376.3 98.5 194 382.5 2,360

T18 06307830 Turbidity, nephelometric turbidity ratio units 1 -- -- -- -- -- 6.8

T18 06307830 Dissolved oxygen, in mg/L 50 7.4 10.03 8.375 9.3 11.125 16.5

T18 06307830 Dissolved oxygen, percent saturation 50 76 105.1 100.75 104 111 132

T18 06307830 pH, in standard units 52 8 8.42 8.3 8.5 8.5 8.7

T18 06307830 Specific conductance, at 25 degrees Celsius, in μS/cm 53 337 689.4 570.5 730 835 926

T18 06307830 Temperature, water deg C 53 0 14.59 7.75 15 23 29

T18 06307830 Hardness, in mg/L as CaCO3 52 150 273.3 222.5 280 327.5 380

T18 06307830 Calcium, dissolved, in mg/L 52 32.5 51.16 43.5 50.7 58.675 69.8

T18 06307830 Magnesium, dissolved, in mg/L 52 16.2 35.41 26.35 35.8 43.9 51.7

T18 06307830 Potassium, dissolved, in mg/L 52 2.24 4.067 3.453 3.945 4.807 7.31

T18 06307830 Sodium-adsorption ratio (unitless) 52 0.5 1.235 0.925 1.35 1.5 1.8

T18 06307830 Sodium, dissolved, in mg/L 52 13.5 47.97 32.375 51.5 62.475 80.4

T18 06307830 Alkalinity, in mg/L as CaCO3 52 115 208.7 176.75 218.5 245.5 288

T18 06307830 Chloride, dissolved, in mg/L 52 1.69 4.276 3.155 4.835 5.405 5.9

T18 06307830 Fluoride, dissolved, in mg/L 52 0.17 0.327 0.26 0.34 0.39 0.45

T18 06307830 Silica, dissolved, in mg/L 52 1.41 4.732 3.572 4.555 5.775 7.58

T18 06307830 Sulfate, dissolved, in mg/L 52 53.5 159.5 122.75 167 206.75 241

T18 06307830 Dissolved solids, calculated, in mg/L 52 196 432.8 347.5 456 535.75 602

T18 06307830 Dissolved solids, tons/day 52 89.3 352.3 145.25 231.5 317.25 1,930

T18 06307830 *Ammonia, dissolved, in mg/L as N 18 -- 0.007 0.005 0.006 0.008 0.028

T18 06307830 **Nitrate plus nitrite, dissolved, in mg/L as N 18 -- -- -- -- -- 0.27

T18 06307830 *Nitrite, dissolved, in mg/L as N 18 -- 0.002 0.001 0.001 0.002 0.013

T18 06307830 **Orthophosphate, dissolved, in mg/L as P 18 -- -- -- -- -- 0.007

T18 06307830 Phosphorus, total, in mg/L 18 0.007 0.049 0.014 0.023 0.045 0.3

T18 06307830 Total nitrogen, total, in mg/L 18 0.17 0.423 0.245 0.305 0.425 1.36

T18 06307830 *Aluminum, dissolved, in μg/L 17 -- 2.531 1.211 2 3.8 6.1

T18 06307830 Aluminum, total, in μg/L 17 44 452.3 88.5 151 370.5 3,550

T18 06307830 Arsenic, dissolved, in μg/L 17 0.6 0.828 0.695 0.8 0.885 1.3

T18 06307830 *Arsenic, total, in μg/L 17 -- 1.349 0.99 1.1 1.45 3

T18 06307830 Barium, dissolved, in μg/L 17 46 55.65 50 55 60.5 68

T18 06307830 Barium, total, in μg/L 17 51.5 65.88 55.4 58.5 69.85 140

T18 06307830 **Beryllium, dissolved, in μg/L 17 -- -- -- -- -- <0.06

T18 06307830 *Beryllium, total, in μg/L 17 -- 0.081 0.037 0.05 0.093 0.4

T18 06307830 Boron, dissolved, in μg/L 14 56 90.14 69 87 114 123

T18 06307830 **Cadmium, dissolved, in μg/L 15 -- -- -- -- -- <0.04

T18 06307830 **Cadmium, total, in μg/L 15 -- -- -- -- -- 0.17

T18 06307830 Chromium, dissolved, in μg/L 1 -- -- -- -- -- 0.14

T18 06307830 *Chromium, total, in μg/L 15 -- 1.896 1 1.103 2.05 8

T18 06307830 Copper, dissolved, in μg/L 15 0.61 1.938 1.3 1.8 2.6 3.4

T18 06307830 Copper, total, in μg/L 15 1.1 3.320 1.5 2 4.6 13.1

T18 06307830 *Iron, dissolved, in μg/L 17 -- 12.75 4.279 10 14.5 64

T18 06307830 Iron, total, in μg/L 17 120 902.5 189.5 365 593.5 6,880

T18 06307830 *Lead, dissolved, in μg/L 15 -- 0.096 0.06 0.075 0.16 0.2

T18 06307830 Lead, total, in μg/L 15 0.1 0.879 0.15 0.27 0.48 6.98
72 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T18 06307830 Lithium, dissolved, in μg/L 14 14.5 23.89 19.675 23.25 26.3 42.6

T18 06307830 Manganese, dissolved, in μg/L 17 1 8.041 3.4 7 10.8 24.9

T18 06307830 Manganese, total, in μg/L 17 12.3 63.73 16.25 33 63.5 397

T18 06307830 Mercury, total, ng/L 5 0.83 -- -- -- -- 2.02

T18 06307830 **Mercury, total, μg/L 3 -- -- -- -- -- <0.01

T18 06307830 Nickel, dissolved, in μg/L 15 0.89 2.016 1.4 2.03 2.7 3.47

T18 06307830 Nickel, total, in μg/L 15 1.54 2.899 1.86 2.29 2.93 10.7

T18 06307830 Selenium, dissolved, in μg/L 17 0.16 0.318 0.25 0.29 0.39 0.61

T18 06307830 *Selenium, total, in μg/L 17 -- 0.437 0.275 0.37 0.435 1.4

T18 06307830 Strontium, dissolved, in μg/L 14 346 580.7 499.75 587 684.25 787

T18 06307830 Zinc, dissolved, in μg/L 15 0.39 2.393 0.9 1.6 3 9.4

T18 06307830 Zinc, total, in μg/L 15 1 4.407 2 2 3 27

T18 06307830 Suspended sediment, <0.0625 mm, percent 45 46 82.84 77.5 86 90 96

T18 06307830 Suspended sediment, in mg/L 45 3 65.69 23 37 56.5 513

T18 06307830 Suspended sediment, tons/day 45 0.57 126.4 7.55 13 36 1,570

T19 06308400 Streamflow, in cubic feet per second 37 0.01 44.25 0.23 2.5 13.35 584

T19 06308400 Dissolved oxygen, in mg/L 36 6 9.644 7.925 9.4 11.35 14.2

T19 06308400 Dissolved oxygen, percent saturation 35 71 96.63 87 97 102 121

T19 06308400 pH, in standard units 36 7.9 8.39 8.2 8.35 8.6 9

T19 06308400 Specific conductance, at 25 degrees Celsius, in μS/cm 37 263 1,270 509.5 1,010 1,650 4,430

T19 06308400 Temperature, water deg C 37 0 12.96 5.25 13 19.75 30

T19 06308400 Hardness, in mg/L as CaCO3 37 4 181.5 36 110 205 970

T19 06308400 Calcium, dissolved, in mg/L 37 0.97 31.97 8.695 24.8 38.35 132

T19 06308400 Magnesium, dissolved, in mg/L 37 0.366 24.64 2.99 11.9 26.2 167

T19 06308400 Potassium, dissolved, in mg/L 37 1.48 7.578 4.42 7.23 8.91 22.4

T19 06308400 Sodium-adsorption ratio (unitless) 37 2.6 8.332 6.05 7.7 10 15

T19 06308400 Sodium, dissolved, in mg/L 37 35.9 221.3 96.05 180 304.5 745

T19 06308400 Alkalinity, in mg/L as CaCO3 37 80 210.4 115 185 287 435

T19 06308400 Chloride, dissolved, in mg/L 37 0.91 4.370 1.74 3.18 5.76 14.5

T19 06308400 Fluoride, dissolved, in mg/L 37 0.17 0.405 0.33 0.4 0.47 0.66

T19 06308400 Silica, dissolved, in mg/L 36 0.74 7.469 6.543 7.665 8.672 12.9

T19 06308400 Sulfate, dissolved, in mg/L 37 40.2 450.1 134 294 588 2,090

T19 06308400 Dissolved solids, calculated, in mg/L 37 157 874.8 344 640 1,120 3,420

T19 06308400 Dissolved solids, tons/day 37 0.04 38.25 0.445 3.49 27.85 554

T19 06308400 *Ammonia, dissolved, in mg/L as N 14 -- 0.017 0.008 0.013 0.017 0.082

T19 06308400 *Nitrate plus nitrite, dissolved, in mg/L as N 14 -- 0.383 0.019 0.113 0.465 2.27

T19 06308400 *Nitrite, dissolved, in mg/L as N 14 -- 0.009 0.002 0.004 0.018 0.024

T19 06308400 *Orthophosphate, dissolved, in mg/L as P 14 -- 0.022 0.004 0.007 0.013 0.171

T19 06308400 Phosphorus, total, in mg/L 14 0.045 0.584 0.06 0.271 0.902 2.6

T19 06308400 Total nitrogen, total, in mg/L 14 0.68 2.436 0.858 1.74 3.89 7

T19 06308400 Aluminum, dissolved, in μg/L 14 1.6 9.364 1.85 10.3 14.825 18.9

T19 06308400 Aluminum, total, in μg/L 14 124 17,083 352.25 5,865 34,275 63,900

T19 06308400 Arsenic, dissolved, in μg/L 14 0.78 1.200 0.97 1.2 1.425 1.6

T19 06308400 *Arsenic, total, in μg/L 14 -- 5.618 1.316 2.7 7.95 29

T19 06308400 Barium, dissolved, in μg/L 14 13 66.71 21.5 56.5 77.25 247

T19 06308400 Barium, total, in μg/L 14 65 382.1 93.175 153.5 667.25 1,310

T19 06308400 **Beryllium, dissolved, in μg/L 14 -- -- -- -- -- <0.12

T19 06308400 *Beryllium, total, in μg/L 14 -- 2.313 0.064 0.435 4.755 8.73

T19 06308400 Boron, dissolved, in μg/L 10 46 144.0 53.75 121 259.5 274

T19 06308400 *Cadmium, dissolved, in μg/L 13 -- 0.034 0.023 0.03 0.041 0.06

T19 06308400 *Cadmium, total, in μg/L 13 -- 0.666 0.029 0.2 1.565 2.2

T19 06308400 Chromium, dissolved, in μg/L 3 0.14 -- -- -- -- 0.5

T19 06308400 *Chromium, total, in μg/L 13 -- 27.83 1.4 11 47 123

T19 06308400 Copper, dissolved, in μg/L 13 2.3 7.815 5.25 6 11.05 17

T19 06308400 Copper, total, in μg/L 13 4.4 51.25 8.4 19.5 102.1 159

T19 06308400 *Iron, dissolved, in μg/L 14 -- 36.85 9.889 23 52.5 147

T19 06308400 Iron, total, in μg/L 14 94 21,353 385.75 5,340 42,275 97,700

T19 06308400 *Lead, dissolved, in μg/L 13 -- 0.383 0.128 0.18 0.43 1.68

T19 06308400 Lead, total, in μg/L 13 0.23 41.52 0.795 13.5 77.35 181

T19 06308400 Lithium, dissolved, in μg/L 10 3.1 15.28 4.575 9 28.325 38.5
Appendix 73

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

T19 06308400 Manganese, dissolved, in μg/L 14 0.7 5.279 1.825 4.2 6.425 15.9

T19 06308400 Manganese, total, in μg/L 14 25.8 401.3 44.2 91.05 760.25 1,620

T19 06308400 Mercury, total, ng/L 4 2.65 -- -- -- -- 357

T19 06308400 **Mercury, total, μg/L 2 -- -- -- -- -- 0.474

T19 06308400 Nickel, dissolved, in μg/L 13 3.1 5.742 4.3 6.08 7.18 7.88

T19 06308400 Nickel, total, in μg/L 13 3.2 51.78 6.875 18 102.3 186

T19 06308400 Selenium, dissolved, in μg/L 14 0.41 1.447 0.68 1.2 1.925 3.5

T19 06308400 Selenium, total, in μg/L 14 0.44 1.505 0.673 1.2 1.95 3.6

T19 06308400 Strontium, dissolved, in μg/L 10 23 494.5 131 216 993.5 1,610

T19 06308400 *Zinc, dissolved, in μg/L 13 -- 7.891 2.05 2.582 13.2 34.5

T19 06308400 Zinc, total, in μg/L 13 3.9 152.1 5.05 48 312.5 603

T19 06308400 Suspended sediment, <0.0625 mm, percent 33 89 97.79 98.5 99 99 99

T19 06308400 Suspended sediment, in mg/L 33 12 3,600 58 666 5,505 20,100

T19 06308400 Suspended sediment, tons/day 33 0 694.1 0.055 2.7 131.5 12,400

P1 434056106244101 Streamflow, in cubic feet per second 3 1.2 -- -- -- -- 17

P1 434056106244101 Turbidity, nephelometric turbidity ratio units 3 6.7 -- -- -- -- 380

P1 434056106244101 Dissolved oxygen, in mg/L 3 6.7 -- -- -- -- 10.5

P1 434056106244101 Dissolved oxygen, percent saturation 2 101 -- -- -- -- 156

P1 434056106244101 pH, in standard units 3 7.8 -- -- -- -- 8.2

P1 434056106244101 Specific conductance, at 25 degrees Celsius, in μS/cm 3 2,090 -- -- -- -- 3,470

P1 434056106244101 Temperature, water deg C 3 27 -- -- -- -- 32.8

P1 434056106244101 Hardness, in mg/L as CaCO3 3 710 -- -- -- -- 1,100

P1 434056106244101 Calcium, dissolved, in mg/L 3 170 -- -- -- -- 287

P1 434056106244101 Magnesium, dissolved, in mg/L 3 70.8 -- -- -- -- 89.4

P1 434056106244101 Potassium, dissolved, in mg/L 3 7.33 -- -- -- -- 14.2

P1 434056106244101 Sodium-adsorption ratio (unitless) 3 3.3 -- -- -- -- 5.7

P1 434056106244101 Sodium, dissolved, in mg/L 3 209 -- -- -- -- 430

P1 434056106244101 Alkalinity, in mg/L as CaCO3 3 177 -- -- -- -- 225

P1 434056106244101 Chloride, dissolved, in mg/L 3 92.5 -- -- -- -- 139

P1 434056106244101 Fluoride, dissolved, in mg/L 3 0.46 -- -- -- -- 0.83

P1 434056106244101 Silica, dissolved, in mg/L 3 4.93 -- -- -- -- 11.9

P1 434056106244101 Sulfate, dissolved, in mg/L 3 722 -- -- -- -- 1,610

P1 434056106244101 Dissolved solids, calculated, in mg/L 3 1,400 -- -- -- -- 2,680

P1 434056106244101 Dissolved solids, tons/day 3 4.64 -- -- -- -- 125

P2 434124106192401 Streamflow, in cubic feet per second 3 5.1 -- -- -- -- 38

P2 434124106192401 Turbidity, nephelometric turbidity ratio units 3 12 -- -- -- -- 370

P2 434124106192401 Dissolved oxygen, in mg/L 3 7.3 -- -- -- -- 10.2

P2 434124106192401 Dissolved oxygen, percent saturation 2 118 -- -- -- -- 138

P2 434124106192401 pH, in standard units 3 7.8 -- -- -- -- 8.3

P2 434124106192401 Specific conductance, at 25 degrees Celsius, in μS/cm 3 3,610 -- -- -- -- 5,650

P2 434124106192401 Temperature, water deg C 3 22.1 -- -- -- -- 32.7

P2 434124106192401 Hardness, in mg/L as CaCO3 3 590 -- -- -- -- 730

P2 434124106192401 Calcium, dissolved, in mg/L 3 113 -- -- -- -- 177

P2 434124106192401 Magnesium, dissolved, in mg/L 3 69.7 -- -- -- -- 79

P2 434124106192401 Potassium, dissolved, in mg/L 3 15.6 -- -- -- -- 28.7

P2 434124106192401 Sodium-adsorption ratio (unitless) 3 8.9 -- -- -- -- 17

P2 434124106192401 Sodium, dissolved, in mg/L 3 554 -- -- -- -- 932

P2 434124106192401 Alkalinity, in mg/L as CaCO3 3 175 -- -- -- -- 288

P2 434124106192401 Chloride, dissolved, in mg/L 3 444 -- -- -- -- 943

P2 434124106192401 Fluoride, dissolved, in mg/L 3 1.03 -- -- -- -- 1.99

P2 434124106192401 Silica, dissolved, in mg/L 3 4.46 -- -- -- -- 12.5

P2 434124106192401 Sulfate, dissolved, in mg/L 3 1,030 -- -- -- -- 1,310

P2 434124106192401 Dissolved solids, calculated, in mg/L 3 2,450 -- -- -- -- 3,490

P2 434124106192401 Dissolved solids, tons/day 3 48.3 -- -- -- -- 253

P3 435453106104701 Streamflow, in cubic feet per second 4 0.22 -- -- -- -- 84

P3 435453106104701 Turbidity, nephelometric turbidity ratio units 4 3.1 -- -- -- -- 690

P3 435453106104701 Dissolved oxygen, in mg/L 4 6.2 -- -- -- -- 11.4

P3 435453106104701 Dissolved oxygen, percent saturation 3 106 -- -- -- -- 172

P3 435453106104701 pH, in standard units 4 7.8 -- -- -- -- 8.4

P3 435453106104701 Specific conductance, at 25 degrees Celsius, in μS/cm 4 2,980 -- -- -- -- 4,940
74 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

P3 435453106104701 Temperature, water deg C 4 20.1 -- -- -- -- 29.1

P3 435453106104701 Hardness, in mg/L as CaCO3 4 620 -- -- -- -- 960

P3 435453106104701 Calcium, dissolved, in mg/L 4 142 -- -- -- -- 213

P3 435453106104701 Magnesium, dissolved, in mg/L 4 64.3 -- -- -- -- 111

P3 435453106104701 Potassium, dissolved, in mg/L 4 11.3 -- -- -- -- 21.2

P3 435453106104701 Sodium-adsorption ratio (unitless) 4 7.1 -- -- -- -- 13

P3 435453106104701 Sodium, dissolved, in mg/L 4 405 -- -- -- -- 843

P3 435453106104701 Alkalinity, in mg/L as CaCO3 4 160 -- -- -- -- 209

P3 435453106104701 Chloride, dissolved, in mg/L 4 344 -- -- -- -- 733

P3 435453106104701 Fluoride, dissolved, in mg/L 4 0.65 -- -- -- -- 1.19

P3 435453106104701 Silica, dissolved, in mg/L 4 3.02 -- -- -- -- 12.4

P3 435453106104701 Sulfate, dissolved, in mg/L 4 880 -- -- -- -- 1,550

P3 435453106104701 Dissolved solids, calculated, in mg/L 4 1,980 -- -- -- -- 3,350

P3 435453106104701 Dissolved solids, tons/day 4 1.89 -- -- -- -- 476

P4 440919106091401 Streamflow, in cubic feet per second 4 2.2 -- -- -- -- 94

P4 440919106091401 Turbidity, nephelometric turbidity ratio units 4 3.2 -- -- -- -- 120

P4 440919106091401 Dissolved oxygen, in mg/L 4 7.5 -- -- -- -- 13.9

P4 440919106091401 Dissolved oxygen, percent saturation 3 102 -- -- -- -- 198

P4 440919106091401 pH, in standard units 4 8 -- -- -- -- 8.7

P4 440919106091401 Specific conductance, at 25 degrees Celsius, in μS/cm 4 2,860 -- -- -- -- 4,610

P4 440919106091401 Temperature, water deg C 4 18.6 -- -- -- -- 30.3

P4 440919106091401 Hardness, in mg/L as CaCO3 4 150 -- -- -- -- 700

P4 440919106091401 Calcium, dissolved, in mg/L 4 13.9 -- -- -- -- 153

P4 440919106091401 Magnesium, dissolved, in mg/L 4 29.1 -- -- -- -- 100

P4 440919106091401 Potassium, dissolved, in mg/L 4 11.9 -- -- -- -- 25.7

P4 440919106091401 Sodium-adsorption ratio (unitless) 4 7.3 -- -- -- -- 25

P4 440919106091401 Sodium, dissolved, in mg/L 4 407 -- -- -- -- 866

P4 440919106091401 Alkalinity, in mg/L as CaCO3 4 224 -- -- -- -- 1,540

P4 440919106091401 Chloride, dissolved, in mg/L 4 69.6 -- -- -- -- 537

P4 440919106091401 Fluoride, dissolved, in mg/L 4 0.61 -- -- -- -- 1.62

P4 440919106091401 Silica, dissolved, in mg/L 4 5.01 -- -- -- -- 8.74

P4 440919106091401 Sulfate, dissolved, in mg/L 4 210 -- -- -- -- 1,260

P4 440919106091401 Dissolved solids, calculated, in mg/L 4 1,920 -- -- -- -- 3,100

P4 440919106091401 Dissolved solids, tons/day 4 12.1 -- -- -- -- 487

P5 442538106082001 Streamflow, in cubic feet per second 4 1.7 -- -- -- -- 99

P5 442538106082001 Turbidity, nephelometric turbidity ratio units 4 5.8 -- -- -- -- 190

P5 442538106082001 Dissolved oxygen, in mg/L 4 5.9 -- -- -- -- 8.7

P5 442538106082001 Dissolved oxygen, percent saturation 3 97 -- -- -- -- 115

P5 442538106082001 pH, in standard units 4 7.8 -- -- -- -- 8.2

P5 442538106082001 Specific conductance, at 25 degrees Celsius, in μS/cm 4 2,810 -- -- -- -- 3,550

P5 442538106082001 Temperature, water deg C 4 18.7 -- -- -- -- 32.9

P5 442538106082001 Hardness, in mg/L as CaCO3 4 400 -- -- -- -- 620

P5 442538106082001 Calcium, dissolved, in mg/L 4 78.8 -- -- -- -- 135

P5 442538106082001 Magnesium, dissolved, in mg/L 4 50 -- -- -- -- 72.6

P5 442538106082001 Potassium, dissolved, in mg/L 4 12.2 -- -- -- -- 14.8

P5 442538106082001 Sodium-adsorption ratio (unitless) 4 7.1 -- -- -- -- 11

P5 442538106082001 Sodium, dissolved, in mg/L 4 392 -- -- -- -- 524

P5 442538106082001 Alkalinity, in mg/L as CaCO3 4 202 -- -- -- -- 342

P5 442538106082001 Chloride, dissolved, in mg/L 4 212 -- -- -- -- 365

P5 442538106082001 Fluoride, dissolved, in mg/L 4 0.67 -- -- -- -- 0.92

P5 442538106082001 Silica, dissolved, in mg/L 4 4.32 -- -- -- -- 8.15

P5 442538106082001 Sulfate, dissolved, in mg/L 4 871 -- -- -- -- 1,070

P5 442538106082001 Dissolved solids, calculated, in mg/L 4 1,870 -- -- -- -- 2,320

P5 442538106082001 Dissolved solids, tons/day 4 9.19 -- -- -- -- 500

P6 441532106251301 Streamflow, in cubic feet per second 3 0 -- -- -- -- 37

P6 441532106251301 Turbidity, nephelometric turbidity ratio units 3 11 -- -- -- -- 240

P6 441532106251301 Dissolved oxygen, in mg/L 3 6.8 -- -- -- -- 8.8

P6 441532106251301 Dissolved oxygen, percent saturation 2 96 -- -- -- -- 114

P6 441532106251301 pH, in standard units 3 7.9 -- -- -- -- 8.2

P6 441532106251301 Specific conductance, at 25 degrees Celsius, in μS/cm 3 827 -- -- -- -- 3,500
Appendix 75

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

P6 441532106251301 Temperature, water deg C 3 19.7 -- -- -- -- 25.4

P6 441532106251301 Hardness, in mg/L as CaCO3 3 370 -- -- -- -- 1,700

P6 441532106251301 Calcium, dissolved, in mg/L 3 79.9 -- -- -- -- 290

P6 441532106251301 Magnesium, dissolved, in mg/L 3 40.5 -- -- -- -- 245

P6 441532106251301 Potassium, dissolved, in mg/L 3 2.28 -- -- -- -- 13

P6 441532106251301 Sodium-adsorption ratio (unitless) 3 1.2 -- -- -- -- 3.5

P6 441532106251301 Sodium, dissolved, in mg/L 3 51.2 -- -- -- -- 334

P6 441532106251301 Alkalinity, in mg/L as CaCO3 3 122 -- -- -- -- 207

P6 441532106251301 Chloride, dissolved, in mg/L 3 3.49 -- -- -- -- 21.8

P6 441532106251301 Fluoride, dissolved, in mg/L 3 0.27 -- -- -- -- 0.45

P6 441532106251301 Silica, dissolved, in mg/L 3 1.61 -- -- -- -- 10.6

P6 441532106251301 Sulfate, dissolved, in mg/L 3 318 -- -- -- -- 2,050

P6 441532106251301 Dissolved solids, calculated, in mg/L 3 580 -- -- -- -- 3,060

P6 441532106251301 Dissolved solids, tons/day 2 1.22 -- -- -- -- 57.3

P7 442817106133001 Streamflow, in cubic feet per second 4 0 -- -- -- -- 40

P7 442817106133001 Turbidity, nephelometric turbidity ratio units 4 13 -- -- -- -- 120

P7 442817106133001 Dissolved oxygen, in mg/L 4 6.7 -- -- -- -- 8.8

P7 442817106133001 Dissolved oxygen, percent saturation 3 84 -- -- -- -- 118

P7 442817106133001 pH, in standard units 4 7 -- -- -- -- 8

P7 442817106133001 Specific conductance, at 25 degrees Celsius, in μS/cm 4 891 -- -- -- -- 3,410

P7 442817106133001 Temperature, water deg C 4 17.6 -- -- -- -- 27.2

P7 442817106133001 Hardness, in mg/L as CaCO3 4 370 -- -- -- -- 1,400

P7 442817106133001 Calcium, dissolved, in mg/L 4 82.5 -- -- -- -- 295

P7 442817106133001 Magnesium, dissolved, in mg/L 4 40.7 -- -- -- -- 152

P7 442817106133001 Potassium, dissolved, in mg/L 4 2.82 -- -- -- -- 27

P7 442817106133001 Sodium-adsorption ratio (unitless) 4 1.3 -- -- -- -- 3.1

P7 442817106133001 Sodium, dissolved, in mg/L 4 58.3 -- -- -- -- 262

P7 442817106133001 Alkalinity, in mg/L as CaCO3 4 145 -- -- -- -- 390

P7 442817106133001 Chloride, dissolved, in mg/L 4 3.87 -- -- -- -- 30

P7 442817106133001 Fluoride, dissolved, in mg/L 4 0.21 -- -- -- -- 0.51

P7 442817106133001 Silica, dissolved, in mg/L 4 3.42 -- -- -- -- 12

P7 442817106133001 Sulfate, dissolved, in mg/L 4 309 -- -- -- -- 1,440

P7 442817106133001 Dissolved solids, calculated, in mg/L 4 596 -- -- -- -- 2,450

P7 442817106133001 Dissolved solids, tons/day 3 0.44 -- -- -- -- 64.1

P8 443025106061601 Streamflow, in cubic feet per second 4 0 -- -- -- -- 159

P8 443025106061601 Turbidity, nephelometric turbidity ratio units 4 17 -- -- -- -- 960

P8 443025106061601 Dissolved oxygen, in mg/L 4 5.3 -- -- -- -- 8

P8 443025106061601 Dissolved oxygen, percent saturation 3 82 -- -- -- -- 105

P8 443025106061601 pH, in standard units 4 7 -- -- -- -- 8.4

P8 443025106061601 Specific conductance, at 25 degrees Celsius, in μS/cm 4 1,760 -- -- -- -- 3,990

P8 443025106061601 Temperature, water deg C 4 21.9 -- -- -- -- 28.3

P8 443025106061601 Hardness, in mg/L as CaCO3 4 570 -- -- -- -- 1,100

P8 443025106061601 Calcium, dissolved, in mg/L 4 134 -- -- -- -- 290

P8 443025106061601 Magnesium, dissolved, in mg/L 4 46.3 -- -- -- -- 97.6

P8 443025106061601 Potassium, dissolved, in mg/L 4 9.98 -- -- -- -- 15.7

P8 443025106061601 Sodium-adsorption ratio (unitless) 4 1.5 -- -- -- -- 9.2

P8 443025106061601 Sodium, dissolved, in mg/L 4 97.8 -- -- -- -- 596

P8 443025106061601 Alkalinity, in mg/L as CaCO3 4 92 -- -- -- -- 332

P8 443025106061601 Chloride, dissolved, in mg/L 4 36.1 -- -- -- -- 348

P8 443025106061601 Fluoride, dissolved, in mg/L 4 0.4 -- -- -- -- 0.87

P8 443025106061601 Silica, dissolved, in mg/L 4 7.45 -- -- -- -- 8.51

P8 443025106061601 Sulfate, dissolved, in mg/L 4 783 -- -- -- -- 1,460

P8 443025106061601 Dissolved solids, calculated, in mg/L 4 1,350 -- -- -- -- 3,010

P8 443025106061601 Dissolved solids, tons/day 3 158 -- -- -- -- 695

P9 444857106030401 Streamflow, in cubic feet per second 4 0 -- -- -- -- 188

P9 444857106030401 Turbidity, nephelometric turbidity ratio units 4 20 -- -- -- -- 2,000

P9 444857106030401 Dissolved oxygen, in mg/L 4 5.2 -- -- -- -- 7.8

P9 444857106030401 Dissolved oxygen, percent saturation 3 68 -- -- -- -- 109

P9 444857106030401 pH, in standard units 4 7.7 -- -- -- -- 8.4

P9 444857106030401 Specific conductance, at 25 degrees Celsius, in μS/cm 4 1,250 -- -- -- -- 2,680
76 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

P9 444857106030401 Temperature, water deg C 4 21.4 -- -- -- -- 29

P9 444857106030401 Hardness, in mg/L as CaCO3 4 360 -- -- -- -- 1,100

P9 444857106030401 Calcium, dissolved, in mg/L 4 82.7 -- -- -- -- 287

P9 444857106030401 Magnesium, dissolved, in mg/L 4 37.4 -- -- -- -- 100

P9 444857106030401 Potassium, dissolved, in mg/L 4 8.37 -- -- -- -- 12.1

P9 444857106030401 Sodium-adsorption ratio (unitless) 4 1.8 -- -- -- -- 6.2

P9 444857106030401 Sodium, dissolved, in mg/L 4 130 -- -- -- -- 472

P9 444857106030401 Alkalinity, in mg/L as CaCO3 4 101 -- -- -- -- 592

P9 444857106030401 Chloride, dissolved, in mg/L 4 41.4 -- -- -- -- 224

P9 444857106030401 Fluoride, dissolved, in mg/L 4 0.42 -- -- -- -- 0.88

P9 444857106030401 Silica, dissolved, in mg/L 4 7.04 -- -- -- -- 9.86

P9 444857106030401 Sulfate, dissolved, in mg/L 4 510 -- -- -- -- 1,210

P9 444857106030401 Dissolved solids, calculated, in mg/L 4 966 -- -- -- -- 2,560

P9 444857106030401 Dissolved solids, tons/day 3 266 -- -- -- -- 951

P10 06324000 Streamflow, in cubic feet per second 98 0.24 172.1 51 78.5 104 2,230

P10 06324000 Turbidity, nephelometric turbidity ratio units 2 8.4 -- -- -- -- 12

P10 06324000 Dissolved oxygen, in mg/L 97 7 10.46 8.55 10.6 12.2 14.4

P10 06324000 Dissolved oxygen, percent saturation 96 77 104.0 96 102 109 162

P10 06324000 pH, in standard units 98 7.7 8.23 8.1 8.2 8.4 8.8

P10 06324000 Specific conductance, at 25 degrees Celsius, in μS/cm 98 175 1,010 861.25 1,010 1,170 2,020

P10 06324000 Temperature, water deg C 98 0 10.32 0.075 9.75 18.125 30

P10 06324000 Hardness, in mg/L as CaCO3 96 67 440.0 352.5 450 527.5 840

P10 06324000 Calcium, dissolved, in mg/L 96 17.7 101.0 81.375 105 121 170

P10 06324000 Magnesium, dissolved, in mg/L 96 5.49 45.69 36.025 46.1 54.825 101

P10 06324000 Potassium, dissolved, in mg/L 96 1.13 4.381 3.65 4.12 4.965 9.75

P10 06324000 Sodium-adsorption ratio (unitless) 96 0.3 1.137 1 1.1 1.2 2.4

P10 06324000 Sodium, dissolved, in mg/L 96 6.53 56.71 44.875 55.6 65.275 159

P10 06324000 Alkalinity, in mg/L as CaCO3 96 48 183.5 154 189 217 301

P10 06324000 Chloride, dissolved, in mg/L 96 0.69 3.489 3.013 3.67 4.202 6.02

P10 06324000 Fluoride, dissolved, in mg/L 96 0.06 0.192 0.18 0.2 0.22 0.3

P10 06324000 Silica, dissolved, in mg/L 94 0.63 6.913 4.608 6.72 9.315 13.7

P10 06324000 Sulfate, dissolved, in mg/L 96 32.9 360.1 287 349.5 415.25 878

P10 06324000 Dissolved solids, calculated, in mg/L 94 100 691.9 566.25 695.5 803 1,490

P10 06324000 Dissolved solids, tons/day 96 1.04 188.7 116.25 158 196 1,330

P10 06324000 Dissolved solids, residue on evaporation, in mg/L 96 90 750.6 622.25 744.5 875.75 1,660

P10 06324000 Ammonia, dissolved, in mg/L as N 1 -- -- -- -- -- <0.04

P10 06324000 Nitrate plus nitrite, dissolved, in mg/L as N 1 -- -- -- -- -- <0.06

P10 06324000 Nitrite, dissolved, in mg/L as N 1 -- -- -- -- -- <0.008

P10 06324000 Orthophosphate, dissolved, in mg/L as P 1 -- -- -- -- -- <0.02

P10 06324000 Total nitrogen, total, in mg/L 1 -- -- -- -- -- 0.32

P10 06324000 Aluminum, total, in μg/L 96 16 325.6 40.75 64.5 128.25 8,820

P10 06324000 Arsenic, dissolved, in μg/L 94 0.22 0.526 0.4 0.5 0.62 0.87

P10 06324000 Arsenic, total, in μg/L 72 0.34 0.917 0.62 0.81 1.1 3.1

P10 06324000 Barium, total, in μg/L 96 25 42.15 32.75 36.35 45.15 197

P10 06324000 *Beryllium, total, in μg/L 96 -- 0.05 0.014 0.027 0.05 0.83

P10 06324000 Iron, dissolved, in μg/L 94 4 28.62 16 23 40 102

P10 06324000 Manganese, dissolved, in μg/L 94 3.9 19.26 10 14.6 21.85 106

P10 06324000 Selenium, total, in μg/L 96 0.09 0.568 0.403 0.495 0.65 1.3

P11 445339106032501 Streamflow, in cubic feet per second 4 0.2 -- -- -- -- 183

P11 445339106032501 Turbidity, nephelometric turbidity ratio units 4 7.5 -- -- -- -- 1,690

P11 445339106032501 Dissolved oxygen, in mg/L 4 6.8 -- -- -- -- 7.9

P11 445339106032501 Dissolved oxygen, percent saturation 3 92 -- -- -- -- 105

P11 445339106032501 pH, in standard units 4 8.1 -- -- -- -- 8.4

P11 445339106032501 Specific conductance, at 25 degrees Celsius, in μS/cm 4 1,270 -- -- -- -- 2,410

P11 445339106032501 Temperature, water deg C 4 21.1 -- -- -- -- 24

P11 445339106032501 Hardness, in mg/L as CaCO3 4 400 -- -- -- -- 900

P11 445339106032501 Calcium, dissolved, in mg/L 4 93.8 -- -- -- -- 206

P11 445339106032501 Magnesium, dissolved, in mg/L 4 41.2 -- -- -- -- 119

P11 445339106032501 Potassium, dissolved, in mg/L 4 7.36 -- -- -- -- 11.9

P11 445339106032501 Sodium-adsorption ratio (unitless) 4 2.3 -- -- -- -- 5.5
Appendix 77

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

P11 445339106032501 Sodium, dissolved, in mg/L 4 128 -- -- -- -- 302

P11 445339106032501 Alkalinity, in mg/L as CaCO3 4 132 -- -- -- -- 205

P11 445339106032501 Chloride, dissolved, in mg/L 4 37.3 -- -- -- -- 191

P11 445339106032501 Fluoride, dissolved, in mg/L 4 0.39 -- -- -- -- 0.55

P11 445339106032501 Silica, dissolved, in mg/L 4 1.1 -- -- -- -- 6.64

P11 445339106032501 Sulfate, dissolved, in mg/L 4 481 -- -- -- -- 1,090

P11 445339106032501 Dissolved solids, calculated, in mg/L 4 884 -- -- -- -- 1,750

P11 445339106032501 Dissolved solids, tons/day 4 0.94 -- -- -- -- 613

P12 06324500 Streamflow, in cubic feet per second 98 0 375.0 90.75 192 297 5,220

P12 06324500 Turbidity, nephelometric turbidity ratio units 2 41 -- -- -- -- 110

P12 06324500 Dissolved oxygen, in mg/L 98 6.2 10.24 8.675 9.9 11.9 15.7

P12 06324500 Dissolved oxygen, percent saturation 98 75 102.1 97 101.5 106.25 148

P12 06324500 pH, in standard units 97 7.6 8.29 8.2 8.3 8.4 8.7

P12 06324500 Specific conductance, at 25 degrees Celsius, in μS/cm 98 500 1,855 1,525 1,855 2,083 4,300

P12 06324500 Temperature, water deg C 98 0 10.77 0 11.5 17.625 30

P12 06324500 Hardness, in mg/L as CaCO3 96 140 500.5 432.5 520 570 1,000

P12 06324500 Calcium, dissolved, in mg/L 96 33.6 111.8 94.85 114.5 130 180

P12 06324500 Magnesium, dissolved, in mg/L 96 13.8 53.83 43.125 54.25 60.55 148

P12 06324500 Potassium, dissolved, in mg/L 96 2.65 8.060 6.97 7.97 8.86 19.2

P12 06324500 Sodium-adsorption ratio (unitless) 96 1.5 4.183 3.45 4.2 4.6 9

P12 06324500 Sodium, dissolved, in mg/L 96 46.7 218.6 162.5 217.5 257 520

P12 06324500 Acid neutralizing capacity, in mg/L as CaCO3 91 119 276.7 201 265 327 697

P12 06324500 Alkalinity, in mg/L as CaCO3 96 81 227.6 176.5 216.5 259.75 441

P12 06324500 Chloride, dissolved, in mg/L 96 10 103.7 70.325 104 127.5 232

P12 06324500 Fluoride, dissolved, in mg/L 96 0.23 0.524 0.44 0.54 0.62 0.99

P12 06324500 Silica, dissolved, in mg/L 96 0.4 7.314 5.795 7.06 9.04 14.1

P12 06324500 Sulfate, dissolved, in mg/L 96 129 595.5 476.5 567.5 665.5 1,640

P12 06324500 Dissolved solids, calculated, in mg/L 96 302 1,237 979.75 1,255 1,428 2,650

P12 06324500 Dissolved solids, tons/day 96 4.29 916.9 383.25 640.5 1,045 8,880

P12 06324500 Dissolved solids, residue on evaporation, in mg/L 96 314 1,310 1,060 1,315 1,495 2,820

P12 06324500 *Ammonia, dissolved, in mg/L as N 95 -- 0.041 0.008 0.015 0.065 0.221

P12 06324500 *Nitrate plus nitrite, dissolved, in mg/L as N 95 -- 0.301 0.058 0.222 0.462 2.33

P12 06324500 *Nitrite, dissolved, in mg/L as N 95 -- 0.006 0.001 0.002 0.007 0.078

P12 06324500 *Orthophosphate, dissolved, in mg/L as P 95 -- 0.006 0.004 0.005 0.007 0.021

P12 06324500 Phosphorus, total, in mg/L 96 0.01 0.318 0.068 0.192 0.398 4

P12 06324500 Total nitrogen, total, in mg/L 96 0.31 1.187 0.69 0.86 1.168 9.41

P12 06324500 Aluminum, total, in μg/L 96 43 7,035 983.25 3,555 7,620 52,400

P12 06324500 Arsenic, dissolved, in μg/L 96 0.17 0.746 0.59 0.7 0.87 1.7

P12 06324500 Arsenic, total, in μg/L 60 0.72 4.655 1.2 3.1 6.45 19.5

P12 06324500 Barium, total, in μg/L 96 37.5 162.4 60.5 92.2 164.75 910

P12 06324500 *Beryllium, total, in μg/L 96 -- 0.69 0.07 0.315 0.68 5.92

P12 06324500 Boron, total, in μg/L 48 58 199.6 164 197.5 223.75 392

P12 06324500 Cadmium, total, in μg/L 48 0.01 0.521 0.062 0.18 0.445 5

P12 06324500 Chromium, total, in μg/L 48 0.26 12.00 1.425 5.3 11.25 74.2

P12 06324500 Copper, total, in μg/L 48 1.2 20.56 5.45 10.5 25.15 102

P12 06324500 *Iron, dissolved, in μg/L 96 -- 6.425 4 5.155 7.258 44

P12 06324500 Iron, total, in μg/L 48 86 17,606 1,470 6,910 14,700 121,000

P12 06324500 Lead, total, in μg/L 48 0.12 16.29 1.35 5.83 14 134

P12 06324500 Manganese, dissolved, in μg/L 96 0.3 4.175 1.625 3.45 5.55 30.2

P12 06324500 Manganese, total, in μg/L 48 14.4 371.1 38.125 124.5 356.75 3,330

P12 06324500 Mercury, total, μg/L 4 0.016 -- -- -- -- 0.182

P12 06324500 Nickel, total, in μg/L 48 1.8 23.15 5.083 9.375 19.35 149

P12 06324500 Selenium, total, in μg/L 96 0.33 1.937 1.2 1.5 2.275 11.3

P12 06324500 Zinc, total, in μg/L 48 2 67.70 6.875 26.25 67.75 418

P12 06324500 Suspended sediment, <0.0625 mm, percent 91 45 89.44 85 96 98 99

P12 06324500 Suspended sediment, in mg/L 91 11 1,044 179 417 866 11,000

P12 06324500 Suspended sediment, tons/day 91 0.02 2,884 44 208 740 102,000

P13 06324710 Streamflow, in cubic feet per second 4 1.1 -- -- -- -- 222

P13 06324710 Turbidity, nephelometric turbidity ratio units 4 3 -- -- -- -- 100

P13 06324710 Dissolved oxygen, in mg/L 4 7.4 -- -- -- -- 9.5
78 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

P13 06324710 Dissolved oxygen, percent saturation 3 108 -- -- -- -- 136

P13 06324710 pH, in standard units 4 8.1 -- -- -- -- 8.4

P13 06324710 Specific conductance, at 25 degrees Celsius, in μS/cm 4 1,690 -- -- -- -- 4,750

P13 06324710 Temperature, water deg C 4 22.5 -- -- -- -- 28

P13 06324710 Hardness, in mg/L as CaCO3 4 570 -- -- -- -- 1,400

P13 06324710 Calcium, dissolved, in mg/L 4 130 -- -- -- -- 304

P13 06324710 Magnesium, dissolved, in mg/L 4 59.3 -- -- -- -- 162

P13 06324710 Potassium, dissolved, in mg/L 4 6.54 -- -- -- -- 18.5

P13 06324710 Sodium-adsorption ratio (unitless) 4 3.4 -- -- -- -- 7.4

P13 06324710 Sodium, dissolved, in mg/L 4 188 -- -- -- -- 639

P13 06324710 Alkalinity, in mg/L as CaCO3 4 198 -- -- -- -- 250

P13 06324710 Chloride, dissolved, in mg/L 4 72.9 -- -- -- -- 235

P13 06324710 Fluoride, dissolved, in mg/L 4 0.31 -- -- -- -- 0.5

P13 06324710 Silica, dissolved, in mg/L 4 8.46 -- -- -- -- 11.5

P13 06324710 Sulfate, dissolved, in mg/L 4 608 -- -- -- -- 2,220

P13 06324710 Dissolved solids, calculated, in mg/L 4 1,190 -- -- -- -- 3,740

P13 06324710 Dissolved solids, tons/day 4 11.1 -- -- -- -- 907

P14 06324790 Streamflow, in cubic feet per second 2 0.27 -- -- -- -- 1.2

P14 06324790 Turbidity, nephelometric turbidity ratio units 2 1.5 -- -- -- -- 2.8

P14 06324790 Dissolved oxygen, in mg/L 2 10 -- -- -- -- 11.2

P14 06324790 Dissolved oxygen, percent saturation 1 -- -- -- -- -- 147

P14 06324790 pH, in standard units 2 8.1 -- -- -- -- 8.5

P14 06324790 Specific conductance, at 25 degrees Celsius, in μS/cm 2 2,050 -- -- -- -- 2,060

P14 06324790 Temperature, water deg C 2 20.8 -- -- -- -- 22.8

P14 06324790 Hardness, in mg/L as CaCO3 3 730 -- -- -- -- 1,100

P14 06324790 Calcium, dissolved, in mg/L 3 144 -- -- -- -- 239

P14 06324790 Magnesium, dissolved, in mg/L 3 89.7 -- -- -- -- 115

P14 06324790 Potassium, dissolved, in mg/L 3 22.6 -- -- -- -- 38.8

P14 06324790 Sodium-adsorption ratio (unitless) 3 1.5 -- -- -- -- 3.2

P14 06324790 Sodium, dissolved, in mg/L 3 106 -- -- -- -- 201

P14 06324790 Alkalinity, in mg/L as CaCO3 3 146 -- -- -- -- 259

P14 06324790 Chloride, dissolved, in mg/L 3 41.3 -- -- -- -- 88.6

P14 06324790 Fluoride, dissolved, in mg/L 3 0.68 -- -- -- -- 0.93

P14 06324790 Silica, dissolved, in mg/L 3 9.7 -- -- -- -- 23.4

P14 06324790 Sulfate, dissolved, in mg/L 3 704 -- -- -- -- 1,030

P14 06324790 Dissolved solids, calculated, in mg/L 3 1,420 -- -- -- -- 1,690

P14 06324790 Dissolved solids, tons/day 2 1.14 -- -- -- -- 4.57

P15 06324970 Streamflow, in cubic feet per second 50 0.02 10.80 1.35 3.1 10.175 95

P15 06324970 Turbidity, nephelometric turbidity ratio units 2 35 -- -- -- -- 96

P15 06324970 Dissolved oxygen, in mg/L 49 4.6 10.14 8.65 10.5 12.1 13.6

P15 06324970 Dissolved oxygen, percent saturation 48 55 102.8 95.25 101.5 112 136

P15 06324970 pH, in standard units 50 7.6 8.12 8 8.1 8.3 8.5

P15 06324970 Specific conductance, at 25 degrees Celsius, in μS/cm 50 500 3,116 2,285 3,310 3,945 5,170

P15 06324970 Temperature, water deg C 50 0 10.99 0.5 12.2 19.5 24.8

P15 06324970 Hardness, in mg/L as CaCO3 48 81 800.4 565 865 990 1,400

P15 06324970 Calcium, dissolved, in mg/L 48 18.7 154.5 111.5 161 187.5 298

P15 06324970 Magnesium, dissolved, in mg/L 48 8.24 100.6 69.275 111.5 125.75 186

P15 06324970 Potassium, dissolved, in mg/L 48 6.53 18.21 15.35 18.5 21.3 28.3

P15 06324970 Sodium-adsorption ratio (unitless) 48 1.9 6.748 5.325 7 8 10

P15 06324970 Sodium, dissolved, in mg/L 48 54.5 445.1 326 479.5 589.25 836

P15 06324970 Acid neutralizing capacity, in mg/L as CaCO3 47 98 357.2 276 370 420 728

P15 06324970 Alkalinity, in mg/L as CaCO3 48 82 347.2 263 361.5 410.25 734

P15 06324970 Chloride, dissolved, in mg/L 48 6.75 69.70 38.1 52.6 79.425 298

P15 06324970 Fluoride, dissolved, in mg/L 48 0.21 0.662 0.555 0.675 0.748 1.09

P15 06324970 Silica, dissolved, in mg/L 48 1.92 9.288 7.483 9.12 11.15 15.2

P15 06324970 Sulfate, dissolved, in mg/L 48 138 1,334 901.75 1,395 1,770 2,420

P15 06324970 Dissolved solids, calculated, in mg/L 48 299 2,340 1,625 2,525 3,033 4,200

P15 06324970 Dissolved solids, tons/day 48 0.2 54.88 8.868 24.9 62.975 422

P15 06324970 Dissolved solids, residue on evaporation, in mg/L 48 324 2,485 1,725 2,635 3,188 4,400

P15 06324970 *Ammonia, dissolved, in mg/L as N 38 -- 0.018 0.009 0.012 0.02 0.128
Appendix 79

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

P15 06324970 *Nitrate plus nitrite, dissolved, in mg/L as N 38 -- 0.052 0.014 0.027 0.05 0.49

P15 06324970 *Nitrite, dissolved, in mg/L as N 38 -- 0.002 0.001 0.001 0.002 0.012

P15 06324970 *Orthophosphate, dissolved, in mg/L as P 38 -- 0.009 0.004 0.006 0.009 0.102

P15 06324970 Total nitrogen, total, in mg/L 38 0.33 0.836 0.46 0.565 0.928 3.95

P15 06324970 Aluminum, total, in μg/L 48 91 1,564 242.5 430 1,435 33,900

P15 06324970 Arsenic, dissolved, in μg/L 48 0.43 0.93 0.69 0.84 1.1 2.3

P15 06324970 *Arsenic, total, in μg/L 47 -- 1.725 1 1.3 1.8 15.4

P15 06324970 Barium, total, in μg/L 48 27.8 87.12 44.525 64.95 85.275 582

P15 06324970 *Beryllium, total, in μg/L 48 -- 0.236 0.058 0.081 0.138 6.27

P15 06324970 Boron, total, in μg/L 48 55 214.6 148.5 194.5 261.25 615

P15 06324970 *Cadmium, total, in μg/L 47 -- 0.088 0.021 0.04 0.05 2.2

P15 06324970 *Chromium, total, in μg/L 47 -- 2.027 0.6 0.86 1.7 39

P15 06324970 *Copper, total, in μg/L 47 -- 10.18 2.35 6.4 12.8 96.9

P15 06324970 *Iron, dissolved, in μg/L 48 -- 18.21 9.139 14 18.024 136

P15 06324970 Iron, total, in μg/L 47 18 1,768 325 748 1,430 36,500

P15 06324970 Lead, total, in μg/L 47 0.13 4.346 0.32 0.83 2.69 130

P15 06324970 Manganese, dissolved, in μg/L 48 1.1 134.2 69.15 118.5 175.5 508

P15 06324970 Manganese, total, in μg/L 48 66.5 201.2 115.25 182.5 224.75 664

P15 06324970 Nickel, total, in μg/L 47 1.9 7.214 3.6 5.77 7.3 73

P15 06324970 Selenium, total, in μg/L 48 0.28 0.958 0.535 0.64 1.35 2.5

P15 06324970 *Zinc, total, in μg/L 47 -- 17.27 3.9 7 12 410

P15 06324970 Suspended sediment, <0.0625 mm, percent 25 55 89.76 83 96 98 100

P15 06324970 Suspended sediment, in mg/L 45 35 308.2 72 128 157 7,750

P15 06324970 Suspended sediment, tons/day 45 0 13.43 0.47 1.2 4.1 322

P16 06325000 Streamflow, in cubic feet per second 2 7.6 -- -- -- -- 8.1

P16 06325000 Turbidity, nephelometric turbidity ratio units 2 23 -- -- -- -- 810

P16 06325000 Dissolved oxygen, in mg/L 2 6.4 -- -- -- -- 6.8

P16 06325000 Dissolved oxygen, percent saturation 2 76 -- -- -- -- 87

P16 06325000 pH, in standard units 2 7.9 -- -- -- -- 8.1

P16 06325000 Specific conductance, at 25 degrees Celsius, in μS/cm 2 2,720 -- -- -- -- 4,090

P16 06325000 Temperature, water deg C 2 17.5 -- -- -- -- 21

P16 06325000 Hardness, in mg/L as CaCO3 2 730 -- -- -- -- 1,100

P16 06325000 Calcium, dissolved, in mg/L 2 152 -- -- -- -- 219

P16 06325000 Magnesium, dissolved, in mg/L 2 84.8 -- -- -- -- 141

P16 06325000 Potassium, dissolved, in mg/L 2 22 -- -- -- -- 34

P16 06325000 Sodium-adsorption ratio (unitless) 2 5.7 -- -- -- -- 8.1

P16 06325000 Sodium, dissolved, in mg/L 2 354 -- -- -- -- 625

P16 06325000 Alkalinity, in mg/L as CaCO3 2 246 -- -- -- -- 324

P16 06325000 Chloride, dissolved, in mg/L 2 52.2 -- -- -- -- 82.3

P16 06325000 Fluoride, dissolved, in mg/L 2 0.86 -- -- -- -- 1.03

P16 06325000 Silica, dissolved, in mg/L 2 7.51 -- -- -- -- 12.7

P16 06325000 Sulfate, dissolved, in mg/L 2 1,240 -- -- -- -- 1,990

P16 06325000 Dissolved solids, calculated, in mg/L 2 2,060 -- -- -- -- 3,300

P16 06325000 Dissolved solids, tons/day 2 42.1 -- -- -- -- 72.5

P17 453209105201201 Streamflow, in cubic feet per second 3 0.01 -- -- -- -- 85

P17 453209105201201 Turbidity, nephelometric turbidity ratio units 3 4.2 -- -- -- -- 22

P17 453209105201201 Dissolved oxygen, in mg/L 3 5.8 -- -- -- -- 11.1

P17 453209105201201 Dissolved oxygen, percent saturation 2 84 -- -- -- -- 112

P17 453209105201201 pH, in standard units 3 8.1 -- -- -- -- 8.4

P17 453209105201201 Specific conductance, at 25 degrees Celsius, in μS/cm 3 1,820 -- -- -- -- 3,180

P17 453209105201201 Temperature, water deg C 3 25 -- -- -- -- 32.5

P17 453209105201201 Hardness, in mg/L as CaCO3 3 600 -- -- -- -- 830

P17 453209105201201 Calcium, dissolved, in mg/L 3 136 -- -- -- -- 189

P17 453209105201201 Magnesium, dissolved, in mg/L 3 62.6 -- -- -- -- 97.8

P17 453209105201201 Potassium, dissolved, in mg/L 3 7.37 -- -- -- -- 16.2

P17 453209105201201 Sodium-adsorption ratio (unitless) 3 3.7 -- -- -- -- 7.1

P17 453209105201201 Sodium, dissolved, in mg/L 3 206 -- -- -- -- 466

P17 453209105201201 Alkalinity, in mg/L as CaCO3 3 201 -- -- -- -- 289

P17 453209105201201 Chloride, dissolved, in mg/L 3 76.1 -- -- -- -- 128

P17 453209105201201 Fluoride, dissolved, in mg/L 3 0.33 -- -- -- -- 0.56
80 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

P17 453209105201201 Silica, dissolved, in mg/L 3 10.8 -- -- -- -- 15.4

P17 453209105201201 Sulfate, dissolved, in mg/L 3 664 -- -- -- -- 1,400

P17 453209105201201 Dissolved solids, calculated, in mg/L 3 1,280 -- -- -- -- 2,420

P17 453209105201201 Dissolved solids, tons/day 3 0.06 -- -- -- -- 326

P18 06326500 Streamflow, in cubic feet per second 50 0.2 501.1 90 168.5 401 4,300

P18 06326500 Dissolved oxygen, in mg/L 44 7.2 10.46 8.55 10.35 12.1 15

P18 06326500 Dissolved oxygen, percent saturation 43 76 99.07 94 100 105 133

P18 06326500 pH, in standard units 49 7.6 8.28 8.2 8.3 8.4 8.7

P18 06326500 Specific conductance, at 25 degrees Celsius, in μS/cm 49 634 2,060 1,760 2,050 2,485 3,580

P18 06326500 Temperature, water deg C 50 0 9.566 0 8.5 18 26

P18 06326500 Hardness, in mg/L as CaCO3 48 120 510.4 422.5 535 590 860

P18 06326500 Calcium, dissolved, in mg/L 48 29.6 113.4 96.9 117 132.5 197

P18 06326500 Magnesium, dissolved, in mg/L 48 11.8 55.28 43.725 60.05 67.875 98.2

P18 06326500 Potassium, dissolved, in mg/L 48 3.16 8.922 7.812 8.565 10.29 14.2

P18 06326500 Sodium-adsorption ratio (unitless) 48 2.2 5.260 4.425 5.05 5.7 9.4

P18 06326500 Sodium, dissolved, in mg/L 48 65.2 273.3 212.5 257.5 343 520

P18 06326500 Acid neutralizing capacity, in mg/L as CaCO3 46 124 309.3 234.5 287.5 345.75 738

P18 06326500 Alkalinity, in mg/L as CaCO3 48 101 242.4 196 225 262.25 500

P18 06326500 Chloride, dissolved, in mg/L 48 20.9 95.09 65.05 103 123.25 185

P18 06326500 Fluoride, dissolved, in mg/L 48 0.26 0.481 0.41 0.475 0.55 0.78

P18 06326500 Silica, dissolved, in mg/L 48 3.3 9.315 7.125 8.8 11.15 16.2

P18 06326500 Sulfate, dissolved, in mg/L 48 149 732.1 579.25 714 925.25 1,320

P18 06326500 Dissolved solids, calculated, in mg/L 48 388 1,434 1,198 1,395 1,758 2,590

P18 06326500 Dissolved solids, tons/day 48 1.24 1,274 431 650.5 1,448 7,670

P18 06326500 *Ammonia, dissolved, in mg/L as N 48 -- 0.025 0.006 0.012 0.035 0.162

P18 06326500 *Nitrate plus nitrite, dissolved, in mg/L as N 48 -- 0.32 0.071 0.258 0.434 2.36

P18 06326500 *Nitrite, dissolved, in mg/L as N 48 -- 0.003 0.001 0.002 0.003 0.043

P18 06326500 *Orthophosphate, dissolved, in mg/L as P 48 -- 0.009 0.004 0.005 0.008 0.115

P18 06326500 Phosphorus, total, in mg/L 48 0.008 0.455 0.05 0.175 0.55 5.37

P18 06326500 Total nitrogen, total, in mg/L 48 0.27 1.624 0.46 0.895 1.588 14.2

P18 06326500 *Arsenic, total, in μg/L 48 -- 5.765 1.4 2.85 8 23.6

P18 06326500 Barium, total, in μg/L 48 40.2 253.9 64.575 106.2 249.5 1,700

P18 06326500 Boron, total, in μg/L 48 50 199.1 159 193 220 544

P18 06326500 *Cadmium, total, in μg/L 48 -- 0.626 0.04 0.15 0.608 5.74

P18 06326500 *Chromium, total, in μg/L 48 -- 18.26 1.25 4.2 18.175 184

P18 06326500 *Copper, total, in μg/L 48 -- 35.27 4.4 12.8 31.375 368

P18 06326500 Iron, total, in μg/L 48 59 22,594 1,615 5,225 23,375 186,000

P18 06326500 Lead, total, in μg/L 48 0.09 27.07 1.112 4.29 20.825 383

P18 06326500 Manganese, total, in μg/L 48 7.7 593.9 37.825 151 591.25 6,020

P18 06326500 **Mercury, total, μg/L 4 -- -- -- -- -- 0.289

P18 06326500 Nickel, total, in μg/L 48 0.32 37.09 4.502 10.65 29.025 402

P18 06326500 Selenium, total, in μg/L 48 0.16 1.780 0.918 1.6 2.4 4.7

P18 06326500 Zinc, total, in μg/L 48 1.6 95.45 7 24 100.5 960

P18 06326500 Suspended sediment, <0.0625 mm, percent 47 28 86.13 81 89 96 99

P18 06326500 Suspended sediment, in mg/L 47 16 2,326 182 411 2,270 22,700

P18 06326500 Suspended sediment, tons/day 47 0.07 8,990 40 224 1,520 166,000

C1 06364300 Streamflow, in cubic feet per second 21 0 0.279 0.03 0.12 0.175 2.6

C1 06364300 Turbidity, nephelometric turbidity ratio units 2 1.8 -- -- -- -- 13

C1 06364300 Dissolved oxygen, in mg/L 17 5.3 9.594 8.4 9.7 10.8 13.1

C1 06364300 Dissolved oxygen, percent saturation 14 43 95.14 89.75 98 104 124

C1 06364300 pH, in standard units 17 7.8 8.31 8.15 8.2 8.35 9.8

C1 06364300 Specific conductance, at 25 degrees Celsius, in μS/cm 16 2,240 3,128 2,768 2,975 3,488 5,080

C1 06364300 Temperature, water deg C 17 0 9.353 1 5.5 18.25 23.5

C1 06364300 Hardness, in mg/L as CaCO3 15 470 587.3 480 580 690 800

C1 06364300 Calcium, dissolved, in mg/L 15 60.9 99.52 78.1 96.2 115 142

C1 06364300 Magnesium, dissolved, in mg/L 15 58.9 82.05 67.5 80.1 97.5 109

C1 06364300 Potassium, dissolved, in mg/L 15 6.98 9.666 7.72 8.86 10.3 14.6

C1 06364300 Sodium-adsorption ratio (unitless) 15 6.7 8.587 7.5 8.7 9.6 11

C1 06364300 Sodium, dissolved, in mg/L 15 359 476.6 406 460 551 625

C1 06364300 Alkalinity, in mg/L as CaCO3 15 257 376.7 325 360 429 543
Appendix 81

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

C1 06364300 Chloride, dissolved, in mg/L 15 12.6 18.85 15.7 17.4 22.8 26.4

C1 06364300 Fluoride, dissolved, in mg/L 15 0.9 1.252 1.1 1.19 1.39 1.79

C1 06364300 Silica, dissolved, in mg/L 15 0.16 2.207 0.55 1.9 3.08 5.45

C1 06364300 Sulfate, dissolved, in mg/L 15 890 1,205 983 1,180 1,290 1,800

C1 06364300 Dissolved solids, calculated, in mg/L 15 1,580 2,122 1,790 2,080 2,380 2,920

C1 06364300 Dissolved solids, tons/day 15 0.13 1.132 0.45 0.9 1.38 4.79

C1 06364300 Dissolved solids, residue on evaporation, in mg/L 15 1,610 2,215 1,880 2,170 2,490 3,190

C1 06364300 Aluminum, total, in μg/L 15 55 246.9 99 174 377 754

C1 06364300 Arsenic, dissolved, in μg/L 15 1.3 2.127 1.7 2 2.3 4.5

C1 06364300 Arsenic, total, in μg/L 8 2.1 2.450 2.125 2.25 2.825 3.2

C1 06364300 Barium, total, in μg/L 15 19.5 51.13 26.3 51.4 74.5 101

C1 06364300 **Beryllium, total, in μg/L 15 -- -- -- -- -- <0.12

C1 06364300 *Iron, dissolved, in μg/L 15 -- 28.91 12 28 31 117

C1 06364300 Manganese, dissolved, in μg/L 15 47.2 150.8 72.9 118 166 515

C1 06364300 Selenium, total, in μg/L 15 0.1 0.759 0.14 0.21 1.5 1.8

C2 06364700 Streamflow, in cubic feet per second 51 0 0.029 0 0 0.07 0.12

C2 06364700 Turbidity, nephelometric turbidity ratio units 3 2.4 -- -- -- -- 9.3

C2 06364700 Dissolved oxygen, in mg/L 23 3.4 6.426 5.1 5.6 7.5 11.6

C2 06364700 Dissolved oxygen, percent saturation 20 41 68.25 46.5 61 79.75 166

C2 06364700 pH, in standard units 23 7.1 7.55 7.3 7.6 7.7 8.1

C2 06364700 Specific conductance, at 25 degrees Celsius, in μS/cm 23 1,820 2,994 2,910 3,090 3,130 3,200

C2 06364700 Temperature, water deg C 23 0.5 10.55 3.5 9.5 15 29.1

C2 06364700 Hardness, in mg/L as CaCO3 20 730 1,332 1,300 1,300 1,400 1,500

C2 06364700 Calcium, dissolved, in mg/L 20 192 317.7 308.5 321.5 336.25 361

C2 06364700 Magnesium, dissolved, in mg/L 20 61.1 132.2 132.25 136 138.75 151

C2 06364700 Potassium, dissolved, in mg/L 20 14.7 19.54 18.775 19.8 20.9 21.7

C2 06364700 Sodium-adsorption ratio (unitless) 20 1.9 3.050 2.825 3.15 3.275 3.7

C2 06364700 Sodium, dissolved, in mg/L 20 121 257.2 239.5 268 282.75 308

C2 06364700 Alkalinity, in mg/L as CaCO3 20 320 388.9 353.5 396 417.5 438

C2 06364700 Chloride, dissolved, in mg/L 20 7.62 20.39 19.725 21.05 22.45 23.3

C2 06364700 Fluoride, dissolved, in mg/L 20 0.64 0.712 0.673 0.71 0.738 0.79

C2 06364700 Silica, dissolved, in mg/L 20 15.3 19.09 17.6 18.75 20.95 24.4

C2 06364700 Sulfate, dissolved, in mg/L 20 655 1,442 1,420 1,480 1,530 1,570

C2 06364700 Dissolved solids, calculated, in mg/L 20 1,280 2,442 2,395 2,525 2,580 2,620

C2 06364700 Dissolved solids, tons/day 20 0.04 0.524 0.312 0.56 0.728 0.92

C2 06364700 Dissolved solids, residue on evaporation, in mg/L 20 1,390 2,676 2,665 2,735 2,830 2,850

C2 06364700 *Ammonia, dissolved, in mg/L as N 12 -- 0.025 0.02 0.026 0.032 0.034

C2 06364700 **Nitrate plus nitrite, dissolved, in mg/L as N 12 -- -- -- -- -- <0.06

C2 06364700 **Nitrite, dissolved, in mg/L as N 12 -- -- -- -- -- <0.008

C2 06364700 *Orthophosphate, dissolved, in mg/L as P 12 -- 0.01 0.007 0.009 0.013 0.015

C2 06364700 Total nitrogen, total, in mg/L 12 0.24 0.379 0.29 0.325 0.447 0.7

C2 06364700 Aluminum, total, in μg/L 20 11 38.40 15.25 39 55.75 119

C2 06364700 Arsenic, dissolved, in μg/L 20 0.42 0.646 0.505 0.62 0.7 1.1

C2 06364700 *Arsenic, total, in μg/L 12 -- 0.907 0.778 0.89 0.983 1.3

C2 06364700 Barium, total, in μg/L 20 22.4 40.29 24.85 27.35 34 192

C2 06364700 **Beryllium, total, in μg/L 20 -- -- -- -- -- <0.18

C2 06364700 Iron, dissolved, in μg/L 20 14 431.6 25 207.5 592.5 1,700

C2 06364700 Manganese, dissolved, in μg/L 20 402 1,735 1,045 1,545 2,100 4,850

C2 06364700 *Selenium, total, in μg/L 20 -- 0.741 0.135 0.22 1.475 2.4

C3 06365900 Streamflow, in cubic feet per second 50 0 0.103 0 0.01 0.04 4.3

C3 06365900 Turbidity, nephelometric turbidity ratio units 2 6 -- -- -- -- 49

C3 06365900 Dissolved oxygen, in mg/L 30 5.1 7.547 6.475 7.85 8.575 9.7

C3 06365900 Dissolved oxygen, percent saturation 26 41 70.96 63.75 71.5 80.25 95

C3 06365900 pH, in standard units 31 7.2 7.69 7.5 7.8 7.9 8.1

C3 06365900 Specific conductance, at 25 degrees Celsius, in μS/cm 29 263 3,814 3,275 3,870 4,185 6,560

C3 06365900 Temperature, water deg C 31 0 7.158 0 3.5 12.9 30.6

C3 06365900 Hardness, in mg/L as CaCO3 29 65 1,448 1,250 1,500 1,650 2,100

C3 06365900 Calcium, dissolved, in mg/L 29 16.2 322.6 277 332 371.5 479

C3 06365900 Magnesium, dissolved, in mg/L 29 6.01 157.0 136.5 162 181.5 226

C3 06365900 Potassium, dissolved, in mg/L 29 8.49 18.65 15 20 21.85 28.1
82 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

C3 06365900 Sodium-adsorption ratio (unitless) 29 0.9 4.886 4.45 4.9 5.4 7.1

C3 06365900 Sodium, dissolved, in mg/L 29 17.1 435.5 372 438 502 732

C3 06365900 Alkalinity, in mg/L as CaCO3 29 46 337.8 299.5 340 399.5 458

C3 06365900 Chloride, dissolved, in mg/L 29 3.28 27.17 26.15 28.3 31.05 34.4

C3 06365900 Fluoride, dissolved, in mg/L 29 0.18 0.632 0.59 0.64 0.69 0.86

C3 06365900 Silica, dissolved, in mg/L 29 3.67 12.46 9.235 12.2 15.6 22.2

C3 06365900 Sulfate, dissolved, in mg/L 29 64.4 1,966 1,655 1,950 2,265 3,100

C3 06365900 Dissolved solids, calculated, in mg/L 29 148 3,142 2,670 3,220 3,510 4,860

C3 06365900 Dissolved solids, tons/day 28 0.02 0.344 0.14 0.26 0.377 2.05

C3 06365900 Dissolved solids, residue on evaporation, in mg/L 29 175 3,415 2,905 3,430 3,845 5,180

C3 06365900 Aluminum, total, in μg/L 29 4 599.0 22 35 64.5 16,100

C3 06365900 Arsenic, dissolved, in μg/L 29 0.45 0.729 0.525 0.59 0.95 1.4

C3 06365900 *Arsenic, total, in μg/L 20 -- 1.190 0.762 0.965 1.3 3.9

C3 06365900 Barium, total, in μg/L 29 14.8 39.17 20.25 25.6 30.8 258

C3 06365900 **Beryllium, total, in μg/L 29 -- -- -- -- -- 1.33

C3 06365900 Iron, dissolved, in μg/L 29 16 594.7 42 533 972.5 2,540

C3 06365900 Manganese, dissolved, in μg/L 29 36.5 848.6 429 777 1,063 2,350

C3 06365900 Selenium, total, in μg/L 29 0.07 0.674 0.18 0.26 1.3 2.4

C4 06375600 Streamflow, in cubic feet per second 51 0 0.458 0 0 0.01 13

C4 06375600 Turbidity, nephelometric turbidity ratio units 3 19 -- -- -- -- 42

C4 06375600 Dissolved oxygen, in mg/L 14 3.4 7.371 5.475 7.7 9.325 10.8

C4 06375600 Dissolved oxygen, percent saturation 11 46 88.55 67 93 112 124

C4 06375600 pH, in standard units 14 7.5 8.18 7.68 8.2 8.48 8.9

C4 06375600 Specific conductance, at 25 degrees Celsius, in μS/cm 14 232 1,798 858.75 1,610 2,075 6,370

C4 06375600 Temperature, water deg C 14 8 17.84 14.225 19 21.7 24.1

C4 06375600 Hardness, in mg/L as CaCO3 11 59 339.7 160 350 550 720

C4 06375600 Calcium, dissolved, in mg/L 11 13.1 65.97 34.7 64.9 114 130

C4 06375600 Magnesium, dissolved, in mg/L 11 6.47 42.51 16.6 42.8 63.8 94.9

C4 06375600 Sodium-adsorption ratio (unitless) 11 0.9 4.264 2 4.3 5.8 8.3

C4 06375600 Sodium, dissolved, in mg/L 11 15.2 195.7 57.3 183 277 508

C4 06375600 Dissolved solids, residue on evaporation, in mg/L 11 145 1,046 394 987 1,380 2,460

C4 06375600 **Ammonia, dissolved, in mg/L as N 9 -- -- -- -- -- 0.046

C4 06375600 **Nitrate plus nitrite, dissolved, in mg/L as N 9 -- -- -- -- -- 0.36

C4 06375600 **Nitrite, dissolved, in mg/L as N 9 -- -- -- -- -- 0.019

C4 06375600 **Orthophosphate, dissolved, in mg/L as P 9 -- -- -- -- -- <0.02

C4 06375600 Total nitrogen, total, in mg/L 9 0.64 1.211 0.76 1.04 1.405 2.78

C5 06376300 Streamflow, in cubic feet per second 51 0 1.520 0 0 0 24

C5 06376300 Turbidity, nephelometric turbidity ratio units 2 48 -- -- -- -- 3,310

C5 06376300 Dissolved oxygen, in mg/L 12 5 7.850 6.55 7.7 8.85 11.3

C5 06376300 Dissolved oxygen, percent saturation 10 69 93.30 85.25 87.5 102.75 124

C5 06376300 pH, in standard units 12 7.5 7.98 7.73 7.95 8.28 8.5

C5 06376300 Specific conductance, at 25 degrees Celsius, in μS/cm 12 197 510.8 226.5 424 723.75 1,410

C5 06376300 Temperature, water deg C 12 0.5 16.79 15.55 17.35 22.15 24.4

C5 06376300 Hardness, in mg/L as CaCO3 10 40 113.1 47.75 104 162.5 240

C5 06376300 Calcium, dissolved, in mg/L 10 8.9 26.39 11.225 24.2 37.35 58.5

C5 06376300 Magnesium, dissolved, in mg/L 10 4.23 11.48 4.86 10.59 16.725 23.3

C5 06376300 Potassium, dissolved, in mg/L 10 4.22 7.485 5.493 7.595 9.023 11.1

C5 06376300 Sodium-adsorption ratio (unitless) 10 0.9 1.720 1.1 1.75 2.3 2.4

C5 06376300 Sodium, dissolved, in mg/L 10 14.1 43.20 20.575 38.45 63.475 84.9

C5 06376300 Alkalinity, in mg/L as CaCO3 10 34 80.20 44.5 75.5 121.25 139

C5 06376300 Chloride, dissolved, in mg/L 10 0.84 3.954 1.872 3.82 5.905 7.72

C5 06376300 Fluoride, dissolved, in mg/L 10 0.2 0.27 0.228 0.265 0.303 0.36

C5 06376300 Silica, dissolved, in mg/L 10 0.68 5.217 3.257 5.455 6.948 8.74

C5 06376300 Sulfate, dissolved, in mg/L 10 42.2 130.4 50.725 106.65 198.75 288

C5 06376300 Dissolved solids, calculated, in mg/L 10 113 276.5 123.75 257 394.75 555

C5 06376300 Dissolved solids, tons/day 10 0.05 4.286 0.225 1.88 9.032 15.9

C5 06376300 Dissolved solids, residue on evaporation, in mg/L 10 134 307.9 162.75 282.5 427.5 590

C5 06376300 Aluminum, total, in μg/L 10 117 10,456 4,793 10,650 14,725 25,800

C5 06376300 Arsenic, dissolved, in μg/L 10 0.49 0.781 0.623 0.76 0.903 1.2

C5 06376300 Arsenic, total, in μg/L 8 0.93 3.741 2.525 3.9 4.575 6.4
Appendix 83

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

C5 06376300 Barium, total, in μg/L 10 71.1 195.1 112.5 170 263.25 426

C5 06376300 *Beryllium, total, in μg/L 10 -- 1.011 0.298 0.965 1.528 2.79

C5 06376300 Iron, dissolved, in μg/L 10 5 34.30 15.5 27 51.25 98

C5 06376300 Manganese, dissolved, in μg/L 10 1.1 6.530 1.4 3 10.925 18.8

C5 06376300 Selenium, total, in μg/L 10 0.57 1.213 0.8 1.05 1.825 2.1

C6 06386500 Streamflow, in cubic feet per second 44 0 5.893 0.012 0.12 1.275 121

C6 06386500 Turbidity, nephelometric turbidity ratio units 2 3.4 -- -- -- -- 160

C6 06386500 Dissolved oxygen, in mg/L 35 4.6 8.903 7.6 8.7 10.4 11.6

C6 06386500 Dissolved oxygen, percent saturation 33 43 99.21 88.5 102 110.5 149

C6 06386500 pH, in standard units 35 7.6 8.07 7.9 8.1 8.3 8.4

C6 06386500 Specific conductance, at 25 degrees Celsius, in μS/cm 36 541 4,497 3,498 4,995 5,515 7,100

C6 06386500 Temperature, water deg C 36 0 13.75 2.125 13.5 23.85 30.5

C6 06386500 Hardness, in mg/L as CaCO3 34 120 1,015 772.5 1,100 1,300 1,700

C6 06386500 Calcium, dissolved, in mg/L 34 31.1 236.7 178.5 247.5 307.75 407

C6 06386500 Magnesium, dissolved, in mg/L 34 10.7 102.0 79.25 112 129.75 171

C6 06386500 Potassium, dissolved, in mg/L 34 6.36 11.74 10.45 11.85 13.45 15.3

C6 06386500 Sodium-adsorption ratio (unitless) 34 2.3 9.594 7.625 10.5 11.25 14

C6 06386500 Sodium, dissolved, in mg/L 34 59 719.3 500.75 815 917.25 1,190

C6 06386500 Alkalinity, in mg/L as CaCO3 34 87 258.7 240.25 262.5 285.5 397

C6 06386500 Chloride, dissolved, in mg/L 34 5.27 88.75 65.6 97 110.75 148

C6 06386500 Fluoride, dissolved, in mg/L 34 0.3 0.564 0.53 0.57 0.623 0.72

C6 06386500 Silica, dissolved, in mg/L 34 1.79 7.235 5.507 7.44 9.14 10.8

C6 06386500 Sulfate, dissolved, in mg/L 34 150 2,193 1,593 2,485 2,815 3,490

C6 06386500 Dissolved solids, calculated, in mg/L 34 329 3,513 2,583 3,930 4,500 5,590

C6 06386500 Dissolved solids, tons/day 34 0.11 18.57 0.535 3.995 16.825 181

C6 06386500 Dissolved solids, residue on evaporation, in mg/L 34 363 3,737 2,858 4,125 4,743 5,990

C6 06386500 **Ammonia, dissolved, in mg/L as N 2 -- -- -- -- -- <0.04

C6 06386500 **Nitrate plus nitrite, dissolved, in mg/L as N 2 -- -- -- -- -- <0.06

C6 06386500 **Nitrite, dissolved, in mg/L as N 2 -- -- -- -- -- <0.008

C6 06386500 **Orthophosphate, dissolved, in mg/L as P 2 -- -- -- -- -- <0.02

C6 06386500 Total nitrogen, total, in mg/L 2 0.53 -- -- -- -- 0.6

C6 06386500 Aluminum, total, in μg/L 34 18 1,875 71.25 130.5 428 34,400

C6 06386500 Arsenic, dissolved, in μg/L 34 0.46 0.976 0.637 0.735 1.225 2.2

C6 06386500 *Arsenic, total, in μg/L 28 -- 1.671 0.905 1.1 1.7 10.3

C6 06386500 Barium, total, in μg/L 34 17.3 59.57 22.325 27.75 61.05 513

C6 06386500 *Beryllium, total, in μg/L 34 -- 0.261 0.03 0.065 0.122 4.36

C6 06386500 *Iron, dissolved, in μg/L 34 -- 22.22 11.965 16.381 19.84 140

C6 06386500 Manganese, dissolved, in μg/L 34 5.7 407.0 176.75 383.5 536.5 1,620

C6 06386500 Selenium, total, in μg/L 34 0.13 1.027 0.558 0.67 1.2 3.3

B1 06425720 Streamflow, in cubic feet per second 50 0 1.291 0 0.58 1.8 11

B1 06425720 Turbidity, nephelometric turbidity ratio units 2 4.3 -- -- -- -- 5.7

B1 06425720 Dissolved oxygen, in mg/L 36 2.1 8.256 7.4 8.45 9.8 12.3

B1 06425720 Dissolved oxygen, percent saturation 34 17 82.03 68 87 97.5 136

B1 06425720 pH, in standard units 37 7.5 8.08 7.8 8.1 8.3 8.8

B1 06425720 Specific conductance, at 25 degrees Celsius, in μS/cm 37 1,760 3,068 2,630 2,920 3,335 6,210

B1 06425720 Temperature, water deg C 37 0 7.457 0 4.5 14.65 29.8

B1 06425720 Hardness, in mg/L as CaCO3 35 560 946.9 800 890 1,100 2,200

B1 06425720 Calcium, dissolved, in mg/L 35 65.2 174.4 134 162 195 394

B1 06425720 Magnesium, dissolved, in mg/L 35 67.4 124.5 107 120 137 300

B1 06425720 Potassium, dissolved, in mg/L 29 8.47 13.66 11.3 12.6 15.3 26.7

B1 06425720 Sodium-adsorption ratio (unitless) 35 3.7 5.429 4.8 5.4 6.1 7.6

B1 06425720 Sodium, dissolved, in mg/L 35 200 385.2 319 372 445 825

B1 06425720 Alkalinity, in mg/L as CaCO3 29 90 295.5 227 282 314.5 778

B1 06425720 Chloride, dissolved, in mg/L 29 10.2 23.51 17.5 20.4 28.5 62.1

B1 06425720 Fluoride, dissolved, in mg/L 29 0.51 0.786 0.69 0.78 0.875 1.21

B1 06425720 Silica, dissolved, in mg/L 29 0.37 2.489 1.245 1.83 3.07 9.68

B1 06425720 Sulfate, dissolved, in mg/L 29 745 1,480 1,285 1,450 1,585 3,180

B1 06425720 Dissolved solids, calculated, in mg/L 29 1,270 2,388 2,110 2,260 2,600 5,270

B1 06425720 Dissolved solids, tons/day 29 0.9 10.57 3.195 8.08 12.2 40.6

B1 06425720 Dissolved solids, residue on evaporation, in mg/L 35 1,370 2,550 2,150 2,450 2,810 5,720
84 Assessment of Ecological Conditions and Potential Effects of Water, Wyoming and Montana, 2005–08

Appendix. Summary statistics for water-quality constituents, Powder River structural basin, Wyoming and Montana, 

water years 2005–08.—Continued

[--, value cannot be calculated; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; CaCO3, calcium carbonate; 

as N, as nitrogen; as P, as phosphorus; μg/L, micrograms per liter; ng/L, nanograms per liter; mm, millimeters; *, constituent statistics were estimated using a log-probability 

regression; **, too many non-detected constituent concentrations to estimate statistics with log-probablity regression]

Site

number

(fig. 1)

Site

identification

number

Constituent Sample

size

Minimum Mean 25th

percentile Median 75thpercentile

Maximum

B1 06425720 Aluminum, total, in μg/L 29 3 165.6 66.5 98 155 1,820

B1 06425720 Arsenic, dissolved, in μg/L 29 0.46 0.955 0.705 0.81 1.045 2

B1 06425720 Arsenic, total, in μg/L 26 0.77 1.325 1 1.25 1.5 2.7

B1 06425720 Barium, total, in μg/L 29 20 37.61 29.8 35.1 42.95 81.5

B1 06425720 **Beryllium, total, in μg/L 29 -- -- -- -- -- 0.15

B1 06425720 Iron, dissolved, in μg/L 29 15 56.48 26 47 81 185

B1 06425720 Manganese, dissolved, in μg/L 29 40.1 394.1 106.5 165 312.5 4,090

B1 06425720 Selenium, total, in μg/L 29 0.13 0.479 0.215 0.32 0.565 1.8

B2 06425900 Streamflow, in cubic feet per second 51 0 0.541 0 0 0.2 4.8

B2 06425900 Turbidity, nephelometric turbidity ratio units 2 21 -- -- -- -- 160

B2 06425900 Dissolved oxygen, in mg/L 20 4.7 9.505 8.2 9.85 11.125 12.4

B2 06425900 Dissolved oxygen, percent saturation 19 58 93.16 86 94 101 137

B2 06425900 pH, in standard units 21 7.8 8.19 8 8.2 8.3 8.6

B2 06425900 Specific conductance, at 25 degrees Celsius, in μS/cm 21 1,100 2,865 2,155 2,480 3,315 5,370

B2 06425900 Temperature, water deg C 21 0 8.819 1.5 8.8 15.3 23.9

B2 06425900 Hardness, in mg/L as CaCO3 19 340 981.1 670 820 1,100 2,200

B2 06425900 Calcium, dissolved, in mg/L 19 67.1 175.7 124 148 208 392

B2 06425900 Magnesium, dissolved, in mg/L 19 40.9 133.2 84.7 109 162 300

B2 06425900 Potassium, dissolved, in mg/L 19 7.93 20.44 14.6 18 22.8 42.7

B2 06425900 Sodium-adsorption ratio (unitless) 19 2.3 4.279 3.5 4.4 4.9 6.4

B2 06425900 Sodium, dissolved, in mg/L 19 110 313.8 218 272 366 640

B2 06425900 Alkalinity, in mg/L as CaCO3 19 161 303.9 214 292 340 778

B2 06425900 Chloride, dissolved, in mg/L 19 10.9 46.50 29.7 45.2 63.2 81.5

B2 06425900 Fluoride, dissolved, in mg/L 19 0.53 0.943 0.78 0.86 1.1 1.84

B2 06425900 Silica, dissolved, in mg/L 19 0.15 3.798 0.9 3.2 6.14 11

B2 06425900 Sulfate, dissolved, in mg/L 19 384 1,309 810 1,110 1,580 3,210

B2 06425900 Dissolved solids, calculated, in mg/L 19 730 2,184 1,520 1,820 2,510 4,780

B2 06425900 Dissolved solids, tons/day 19 0.28 5.603 0.93 2.06 10.1 18.8

B2 06425900 Dissolved solids, residue on evaporation, in mg/L 19 761 2,394 1,640 2,030 2,840 5,280

B2 06425900 *Ammonia, dissolved, in mg/L as N 13 -- 0.023 0.012 0.017 0.025 0.067

B2 06425900 **Nitrate plus nitrite, dissolved, in mg/L as N 13 -- -- -- -- -- <0.06

B2 06425900 **Nitrite, dissolved, in mg/L as N 13 -- -- -- -- -- <0.002

B2 06425900 *Orthophosphate, dissolved, in mg/L as P 13 -- 0.006 0.004 0.005 0.007 0.012

B2 06425900 Total nitrogen, total, in mg/L 13 0.45 0.687 0.49 0.59 0.935 1.09

B2 06425900 Aluminum, total, in μg/L 19 45 173.8 76 115 208 697

B2 06425900 Arsenic, dissolved, in μg/L 19 0.55 1.204 0.69 1.1 1.5 3.3

B2 06425900 Arsenic, total, in μg/L 13 0.66 1.241 0.785 1.2 1.7 2.3

B2 06425900 Barium, total, in μg/L 19 23.4 49.03 35.7 44.3 62.3 84.3

B2 06425900 **Beryllium, total, in μg/L 19 -- -- -- -- -- <0.18

B2 06425900 *Iron, dissolved, in μg/L 19 -- 28.64 16 24 38 70

B2 06425900 Manganese, dissolved, in μg/L 19 6.1 76.89 15 55.9 109 258

B2 06425900 Selenium, total, in μg/L 19 0.39 2.245 0.56 1.7 2.5 11.6

Publishing support provided by: 

Denver Publishing Service Center, Denver, Colorado

Manuscript approved for publication, June 9, 2010

For more information concerning this publication, contact:

Center Director, USGS Wyoming Water Science Center

2617 E. Lincolnway, Suite B.

Cheyenne, WY 82001

(307) 778-2931

Or visit the Wyoming Water Science Center Web site at:

http://wy.water.usgs.gov/index.html

This publication is available online at

http://pubs.usgs.gov/sir/2010/5124
Printed on recycled paper