U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the Bureau of Land Management, U.S. Department of the Interior, Wyoming 

Department of Environmental Quality, Wyoming Game and Fish Department, U.S. Environmental Protection 

Agency, Montana Department of Environmental Quality, and Montana Department of Fish, Wildlife, and Parks

Ecological Assessment of Streams in the Powder River 

Structural Basin, Wyoming and Montana, 2005–06

Scientific Investigations Report 2009–5023
Hanging Woman Creek below Horse Creek, Wyo. (site T11), June 22, 2005. 

Photograph by Seth Davidson, U.S. Geological Survey.

Cheyenne River near Spencer, Wyo. (site C6), 

June 22, 2005. Photograph by Kendra Remley, 

U.S. Geological Survey.

Youngs Creek near Crow Indian Reservation 

boundary, Mont. (site T3), June 14, 2005. 

Photograph by Peter Wright, U.S. Geological 

Survey.

Cheyenne River near Dull Center, Wyo., 

(site C3), June 19, 2006. Photograph by Greg 

Boughton, U.S. Geological Survey.

Front cover photographs:
Ecological Assessment of Streams in the 

Powder River Structural Basin, Wyoming 

and Montana, 2005–06

By David A. Peterson, Peter R. Wright, Gordon P. Edwards, Jr., Eric G. Hargett, 

David L. Feldman, Jeremy R. Zumberge, and Paul Dey

Prepared in cooperation with the Bureau of Land Management, U.S. Department 

of the Interior, Wyoming Department of Environmental Quality, Wyoming Game 

and Fish Department, U.S. Environmental Protection Agency, Montana Department of Environmental Quality, and Montana Department of Fish, Wildlife, and 

Parks

Scientific Investigations Report 2009–5023

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

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

This and other USGS information products are available at http://store.usgs.gov/

U.S. Geological Survey 

Box 25286, Denver Federal Center 

Denver, CO 80225

To learn about the USGS and its information products visit http://www.usgs.gov/

1-888-ASK-USGS

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., 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.
iii

Preface

The work described in this report was performed under the direction of a multiagency Aquatic 

Task Group (ATG) formed to address issues related to development of coalbed natural gas in 

northeastern Wyoming and southeastern Montana. In addition to the multiagency participation 

in design and sampling, the multiple aspects of aquatic ecology led to a collaborative multiagency effort on this report. The sampling was conducted by the U.S. Geological Survey (USGS), 

with the exception of sampling on the main stem of the Powder River in Wyoming that was 

coordinated with personnel from the Wyoming Game and Fish Department (WGFD). Personnel 

from the WGFD collected fish samples and conducted much of the habitat work at eight sampling sites on the Powder River in Wyoming. Gordon Edwards, Jr., of the WGFD is the author of 

the report sections describing the Powder River fish community and Powder River habitat. Peter 

Wright of the USGS is the author of the habitat section that encompasses all of the streams, 

including some habitat data collected by the USGS from the Powder River. Peter Wright and 

Dave Peterson condensed and rewrote habitat mapping information from a WGFD administrative 

report by Paul Dey after Mr. Dey took a different job assignment within WGFD. Dave Peterson of 

the USGS authored the fish section on other streams of the study area, as well as the sections 

on algae and macroinvertebrate communities with the exception of the sections on macroinvertebrate models and indices. Eric Hargett and Jeremy Zumberge of the Wyoming Department of 

Environmental Quality and David Feldman of the Montana Department of Environmental Quality 

authored the report sections on macroinvertebrate models and indices. Other members of the 

ATG helped to improve the report through comments during the review process. Thank you to 

everyone for their collaboration and cooperative spirit.
iv

Contents

Preface ...........................................................................................................................................................iii

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

Introduction.....................................................................................................................................................2

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

Description of the Study Area ............................................................................................................5

Geographic Setting......................................................................................................................5

Climate and Hydrology................................................................................................................5

 Land and Water Use.................................................................................................................10

Water Quality..............................................................................................................................10

Acknowledgments..............................................................................................................................11

Methods of Sample Collection and Analysis ..........................................................................................11

Habitat ..................................................................................................................................................11

Basinwide Habitat Assessment ..............................................................................................11

Main-Stem Powder River Habitat Assessment ....................................................................15

Water Chemistry .................................................................................................................................17

Macroinvertebrates and Algae ........................................................................................................17

Fish Communities................................................................................................................................19

Basinwide Fish Community Assessment ...............................................................................19

Main-Stem Powder River Fish Community Assessment.....................................................19

Ancillary Investigations .....................................................................................................................20

Ecological Assessment...............................................................................................................................21

Habitat Assessment............................................................................................................................21

Habitat Characteristics of Streams in the Powder River Structural Basin......................21

Channel Characteristics ..................................................................................................21

Substrate Characteristics ...............................................................................................29

Riparian Characteristics..................................................................................................29

Reach Characteristics .....................................................................................................35

Habitat Characteristics of the Main-Stem Powder River in Wyoming ............................38

Macroinvertebrate Community Assessment .................................................................................48

Community Characteristics at Sites with Riffles ..................................................................48

Community Composition ..................................................................................................48

Effect of Environmental Variables on Macroinvertebrate Communities .................53

Modeling and Metric Indices ..................................................................................................58

Wyoming Observed/Expected Index Biological Condition ........................................58

Tongue River Drainage............................................................................................58

Powder River Drainage...........................................................................................58

Belle Fourche and Cheyenne River Drainages...................................................63

Wyoming Stream Integrity Index Biological Condition...............................................64

Tongue River Drainage............................................................................................64

Powder River Drainage...........................................................................................64

Belle Fourche and Cheyenne River Drainages...................................................66

Montana Observed/Expected Biological Condition....................................................66
v

Tongue River Drainage............................................................................................66

Powder River Drainage...........................................................................................66

Rosebud Creek .........................................................................................................70

Montana Multimetric Index Biological Condition ......................................................70

Tongue River Drainage............................................................................................70

Powder River Drainage...........................................................................................72

Rosebud Creek .........................................................................................................72

Comparison of Model and Multimetric Results ...........................................................72

Macroinvertebrate Community Composition in Multiple Habitats ....................................72

Ancillary Macroinvertebrate Data..........................................................................................76

Algal Community Assessment ..........................................................................................................78

Standing Crop.............................................................................................................................78

Community Composition ...........................................................................................................78

Effect of Environmental Variables on Algal Communities...................................................84

Ancillary Algal Data...................................................................................................................84

Fish Community Assessment ............................................................................................................85

Fish Communities of the Tongue, Cheyenne, and Belle Fourche Rivers 

and Tributaries ..............................................................................................................85

Spatial and Temporal Distribution of Fish.....................................................................85

Fish Community Structure ...............................................................................................86

Fish Communities of the Main-Stem Powder River .............................................................96

Spatial Distribution of Fish ..............................................................................................96

Temporal Distribution of Fish ........................................................................................107

Fish Distribution by Habitat Type..................................................................................110

Fish Community Structure .............................................................................................110

Implications.................................................................................................................................................119

Summary......................................................................................................................................................120

References Cited........................................................................................................................................123

Appendixes .................................................................................................................................................129

Figures

1–2. Maps showing:

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

Structural Basin, Wyoming and Montana, 2005–06.......................................................3

2. Cumulative water production as of October 2006 from coalbed 

natural gas wells in the Powder River Structural Basin, Wyoming ............................4

3. Streamflow hydrographs showing historical mean 

daily flow and daily mean flow for water years 2005 and 2006.............................................9

4. Photographs of sample reach on Hanging Woman Creek near 

Birney, Mont., showing the difference in water levels for sampling dates 

in 2005 and 2006 ..........................................................................................................................10

5–18. Graphs showing:

5. Streambank angle, bankfull height, bankfull width, and incised height 

by stream drainage, Powder River Structural Basin, 2005 .........................................25
vi

6. Width-to-depth ratios by stream drainage, Powder River Structural 

Basin, 2005 ..........................................................................................................................26

7. Geomorphic channel units as a percentage of reach at 27 sampling 

sites, Powder River Structural Basin, 2005 ...................................................................26

8. Presence of fish cover identified in the Powder River Structural Basin, 

2005 ......................................................................................................................................28

9. Particle-size distribution of reachwide streambed substrate data, by 

stream, Powder River Structural Basin, 2005 ...............................................................32

10. Cumulative particle-size distributions of riffle pebble counts collected 

at sites on the Tongue River and tributaries, main-stem Powder River, 

tributaries to the Powder River, and Cheyenne and Belle Fourche Rivers 

and tributaries, Powder River Structural Basin, 2005..................................................33

11. Percentages of legacy tree types identified at study reaches, 

Powder River Structural Basin, 2005..............................................................................35

12. Distribution of invasive plant species identified in study reaches, 

Powder River Structural Basin, 2005..............................................................................36

13. Examples of longitudinal survey data, Porcupine Creek near Teckla, 

Wyo., 2005 ...........................................................................................................................39

14. Mean percentages of silt, sand, and gravel observed at sites sampled 

during flow in the main-stem Powder River, Wyoming, 2004–06...............................43

15. Mean percentage of substrate size by habitat type surveyed during 

flow in the main-stem Powder River, Wyoming, 2004–06............................................44

16. Mean stream velocity of habitat units categorized as pool, riffle, run, 

or shoal during periods of sample collection on the main-stem 

Powder River, Wyoming, 2004–06 ...................................................................................45

17. Fish cover at sampling sites on the main-stem Powder River, Wyoming, 

2004–06 ................................................................................................................................45

18. Habitat types determined from global positioning system mapping in 

2005 and from transects in 2006 at eight sampling sites on the main-stem 

Powder River, Wyoming....................................................................................................46

19. Maps showing habitat composition at varying flows in May, July, and 

August 2005 for a segment of the Powder River below Clear Creek, Wyoming ..............47

20–22. Diagrams showing:

20. Similarities of macroinvertebrate communities within stream 

drainages depicted by nonmetric multidimensional scaling ordination, 

Powder River Structural Basin, 2005..............................................................................52

21. Similarities of macroinvertebrate communities within stream 

drainages depicted by nonmetric multidimensional scaling ordination, 

Powder River Structural Basin, 2006..............................................................................53

22. Principal components analysis showing relations among sampling sites 

based on selected environmental variables, Powder River Structural 

Basin, 2005 ..........................................................................................................................57

23–30. Graphs showing:

23. Wyoming observed/expected model and Wyoming Stream Integrity 

Index scores for macroinvertebrate samples collected in Wyoming and 

adjacent areas of Montana, 2005–06 .............................................................................62
vii

24. Regression of selected macroinvertebrate metrics using scores 

of the Wyoming Stream Integrity Index for sites in the Tongue and 

Powder River drainages in Wyoming and adjacent areas of 

Montana, 2005–06..............................................................................................................65

25. Montana observed/expected model and Montana multimetric index 

scores for macroinvertebrate samples collected in Montana and 

adjacent areas of Wyoming, 2005–06.............................................................................69

26. Regression of selected macroinvertebrate metrics compared to 

Montana observed/expected model scores and Montana multimetric 

index scores for sampling sites in the Tongue and Powder River 

drainages in Montana and adjacent areas of Wyoming, 2005–06 ............................71

27. Macroinvertebrate taxa richness, functional groups, and tolerance 

for sampling sites with both richest-targeted habitat and qualitative 

multihabitat samples, and for sites with only qualitative multihabitat 

samples, Powder River Structural Basin, 2005–06.......................................................75

28. Macroinvertebrate community composition in National Water-Quality 

Assessment samples from the Little Powder River above Dry Creek, 

1999–2007 ............................................................................................................................77

29. Chlorophyll-a and ash-free dry mass concentrations in algae samples, 

Powder River Structural Basin, 2005..............................................................................79

30. Relative abundance of algal divisions by site, Powder River Structural 

Basin, 2005 ..........................................................................................................................82

31. Diagram showing algal communities depicted by nonmetric multidimensional 

scaling ordination, Powder River Structural Basin, 2005.....................................................83

32–39. Graphs showing:

32. Chlorophyll-a and ash-free dry mass concentrations in ancillary algae 

samples, Powder River Structural Basin, 2001–07.......................................................85

33. Relative abundance of fish by species in samples from the Tongue, 

Cheyenne, and Belle Fourche Rivers and tributaries, 2005–06..................................95

34. Relative abundance of fish taxa in samples from the main-stem 

Powder River, Wyoming and Montana, 2004–06 ........................................................107

35. Rarefaction curves relating species richness to fish community samples 

for sampling sites on the main-stem Powder River, Wyoming and Montana, 

and the South Fork of the Powder River, Wyoming, 2004–06 ...................................108

36. Longitudinal distribution of selected fish species in the main-stem 

Powder River, Wyoming, 2004–06 .................................................................................109

37. Fish species composition in monthly (May–October) samples at eight 

sampling sites on the main-stem Powder River, Wyoming, 2004 ............................111

38. Species composition of fish community during pre-high flow, post-high 

flow, and low-flow conditions for eight sampling sites on the main-stem 

Powder River in Wyoming and one sampling site in Montana, 2005 ......................112

39. Mean percentage of fish observations per sampling period within 

connected aquatic habitat types for eight sampling sites on the main-stem 

Powder River in Wyoming and one sampling site in Montana, 2004–06................113
viii

Tables

1. Aquatic ecology sampling sites and selected characteristics, Powder River 

Structural Basin, Wyoming and Montana, 2005–06................................................................6

2. Types of aquatic ecology measurements and samples by site, Powder 

River Structural Basin, Wyoming and Montana, 2005–06....................................................12

3. Substrate codes, numbers, and size classes.........................................................................14

4. Components of bank-stability index ........................................................................................15

5. Habitat types used to classify aquatic habitat in the main-stem Powder 

River, Wyoming and Montana, 2005–06 ..................................................................................16

6. Sampling sites with ancillary data for macroinvertebrates and algae, 

Powder River Structural Basin, Wyoming and Montana.....................................................21

7. Summary of channel characteristics measured at sampling sites in the 

Powder River Structural Basin, Wyoming and Montana, 2005...........................................22

8. Fish cover identified during habitat sampling, Powder River Structural Basin, 

Wyoming and Montana, 2005 ...................................................................................................27

9. Statistical summary of reachwide substrate data, Powder River Structural 

Basin, Wyoming and Montana, 2005 .......................................................................................30

10. Riparian vegetative structure and percentages of mean areal vegetative 

cover identified by semiquantitative visual estimates, Powder River 

Structural Basin, Wyoming and Montana, 2005 ....................................................................34

11. Bank-stability index and scores for sites sampled in the Powder River 

Structural Basin, Wyoming and Montana, 2005 ....................................................................36

12. Proximity-weighted human riparian disturbance values, Powder River 

Structural Basin, Wyoming and Montana, 2005 ....................................................................40

13. Wetted stream widths observed at sites on the main-stem Powder River, 

Wyoming, 2004–06 ......................................................................................................................42

14. Mean, maximum, and residual pool depths observed at sites on the 

main-stem Powder River, Wyoming, 2004–06 ........................................................................42

15. Macroinvertebrate metrics for samples collected from riffles, Powder River 

Structural Basin, Wyoming and Montana, 2005–06..............................................................49

16. Environmental variables tested for correlation with macroinvertebrate 

communities, Powder River Structural Basin, Wyoming and Montana, 2005..................55

17. Eigenvectors from principal components analysis of environmental variables, 

Powder River Structural Basin, Wyoming and Montana, 2005...........................................57

18. Scores from the Wyoming observed/expected model and the Wyoming 

Stream Integrity Index metrics for macroinvertebrate samples collected 

at riffles in streams in Wyoming and adjacent areas of Montana, 2005–06.....................59

19. Scores from the Montana observed/expected model and the Montana 

multimetric index for macroinvertebrate samples collected at 

riffles in streams in Montana and adjacent areas of Wyoming, 2005–06 .........................67

20. Macroinvertebrate community metrics for sampling sites where qualitative 

multihabitat samples were the primary macroinvertebrate sample 

type, Powder River Structural Basin, Wyoming and Montana, 2005–06...........................73

21. Algal taxa richness and diatom metrics from periphyton samples, Powder 

River Structural Basin, Wyoming and Montana, 2005..........................................................80

22. Fish abundance in samples from the Tongue, Cheyenne, and Belle Fourche 

Rivers and tributaries, Wyoming and Montana, 2005–06.....................................................87
ix

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

Structural Basin, Wyoming and Montana, 2005–06..............................................................94

24. Fish community metric scores and Index of Biotic Integrity scores for 

the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming 

and Montana, 2005–06 ...............................................................................................................97

25. Fish abundance in samples from the main-stem Powder River, Wyoming 

and Montana, 2004–06 .............................................................................................................101

26. Fish community metric scores and Index of Biotic Integrity scores for 

the main-stem Powder River, Wyoming and Montana, 2005–06 ......................................114

27. Mean values of microhabitat measurements collected at macroinvertebrate 

sampling sites in riffles, Powder River Structural Basin, Wyoming and 

Montana, 2005–06.....................................................................................................................130

28. Onsite measurements of physical and chemical characteristics collected 

in conjunction with biological samples, Powder River Structural Basin, 

Wyoming and Montana, 2005–06 ...........................................................................................132

29. Total numbers of fish by sampling site collected by the Wyoming Game and 

Fish Department at sites on the main-stem Powder River, Wyoming, 2004–06 .............135

30. Total numbers of fish by sampling site collected by the U.S. Geological Survey 

at sites on the main-stem Powder River, Montana, 2005–06.............................................136

31. Larval fish collected by the Wyoming Game and Fish Department from 

eight sampling sites on the main-stem Powder River, Wyoming, 2004–05 .....................137

Conversion Factors and Datums

Multiply By To obtain

centimeter (cm) 0.3937 inch (in.)

micron (μm) 0.00003937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

meter (m) 1.094 yard (yd) 

square centimeter (cm2) 0.1550 square inch (in2)

square meter (m2) 10.76 square foot (ft2) 

square kilometer (km2) 0.3861 square mile (mi2)

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

milligram (mg) 0.00003527 ounce, avoirdupois (oz)

milligram per square meter (mg/m2) 0.0003795 ounce per square foot (oz/ft2)

gram (g) 0.03527 ounce, avoirdupois (oz)

gram per square meter (g/m2) 0.3795 ounce per square foot (oz/ft2)

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

cubic foot per second (ft3/s) 0.3048 cubic meter per second (m3/s)

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

°F=(1.8×°C)+32.
x

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).

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 and Acronyms

< less than

> greater than

≤ less than or equal to

g/m2 gram per square meter

mg/m2 milligram per square meter

ρ Spearman’s rho

AFDM ash-free dry mass

ANOVA analysis of variance

ATG Aquatic Task Group

BLM Bureau of Land Management

CBNG coalbed natural gas

DTH depositional-targeted habitat

EMAP Environmental Monitoring and Assessment Program

EPT Ephemeroptera, Plecoptera, and Trichoptera

GIS geographic information system

GPS global positioning system
xi

IBI Index of Biotic Integrity

IWG Interagency Working Group

MDEQ Montana Department of Environmental Quality

MFWP Montana Department of Fish, Wildlife, and Parks

MMI multimetric index

n number of measurements/samples

NAWQA National Water-Quality Assessment Program

NMDS Nonmetric multidimensional scaling

NWIS National Water Information System

NWQL National Water Quality Laboratory

O/E observed/expected

P probability level

PCA principal components analysis

PRB Powder River Structural Basin

QMH qualitative multihabitat

r correlation coefficient

R2 coefficient of determination

RTH richest-targeted habitat

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

UTM Universal Transverse Mercator

W/D width/depth ratio (bankfull width/bankfull depth)

WDEQ Wyoming Department of Environmental Quality

WGFD Wyoming Game and Fish Department

WSA Warm-water Stream Assessment

WSII Wyoming Stream Integrity Index

WWSC Wyoming Water Science Center

Ecological Assessment of Streams in the Powder River 

Structural Basin, Wyoming and Montana, 2005–06

By David A. Peterson1, Peter R. Wright1, Gordon P. Edwards, Jr.2, Eric G. Hargett3, David L. Feldman4, 

Jeremy R. Zumberge3, and Paul Dey2

Abstract

Energy and mineral development, particularly coalbed 

natural gas development, is proceeding at a rapid pace in 

the Powder River Structural Basin (PRB) in northeastern 

Wyoming. Concerns about the potential effects of development led to formation of an interagency working group of 

primarily Federal and State agencies to address these issues in 

the PRB in Wyoming and in Montana where similar types of 

resources exist but are largely undeveloped. Under the direction of the interagency working group, an ecological assessment of streams in the PRB was initiated to determine the 

current status (2005–06) and to establish a baseline for future 

monitoring. 

The ecological assessment components include assessment of stream habitat and riparian zones as well as assessments of macroinvertebrate, algal, and fish communities. All 

of the components were sampled at 47 sites in the PRB during 

2005. A reduced set of components, consisting primarily 

of macroinvertebrate and fish community assessments, was 

sampled in 2006. Related ecological data, such as habitat and 

fish community data collected from selected sites in 2004, also 

are included in this report. 

The stream habitat assessment included measurement of 

channel features, substrate size and embeddedness, riparian 

vegetation, and reachwide characteristics. The width-to-depth 

ratio (bankfull width/bankfull depth) tended to be higher 

at sites on the main-stem Powder River than at sites on the 

main-stem Tongue River and at sites on tributary streams. 

The streambed substrate particle size was largest at sites on 

the main-stem Tongue River and smallest at sites on small 

tributary streams such as Squirrel Creek and Otter Creek. Total 

vegetative cover at the ground level, understory, and canopy 

layers ranged from less than 40 percent at a few sites to more 

than 90 percent at many of the sites. A bank-stability index 

indicated that sites in the Tongue River drainage were less at 

risk of bank failure than sites on the main-stem Powder River. 

Macroinvertebrate communities showed similarity at the 

river-drainage scale. Macroinvertebrate communities at sites 

with mountainous headwaters and snowmelt-driven hydrology, 

such as Clear Creek, Crazy Woman Creek, and Goose Creek, 

showed similarity with communities from the main-stem 

Tongue River. The data also indicated similarity among sites 

on the main-stem Powder River and among small tributaries 

of the Tongue River. Data analyses using macroinvertebrate 

observed/expected models and multimetric indices developed 

by the States of Wyoming and Montana indicated a tendency 

toward declining biological condition in the downstream 

direction along the Tongue River. Biological condition for the 

main-stem Powder River generally improved downstream, 

from below Salt Creek to near the Wyoming/Montana border, 

followed by a general decline downstream from the border 

to the confluence with the Yellowstone River. The biological 

condition generally was not significantly different between 

2005 and 2006, although streamflow was less in 2006 because 

of drought. 

Algal communities showed similarity at the 

river-drainage scale with slight differences from the pattern 

observed in the macroinvertebrate communities. Although the 

algal communities from Clear Creek and Goose Creek were 

similar to those from the main-stem Tongue River, as was true 

of the macroinvertebrate communities, the algal communities from Crazy Woman Creek had more similarity to those 

of main-stem Powder River sites than to the Tongue River 

sites, contrary to the macroinvertebrates. Ordination of algal 

communities, as well as diatom metrics including salinity 

and dominant taxa, indicated substantial variation at two sites 

along the main stem of the Powder River. 

Fish communities of the PRB were most diverse in the 

Tongue River drainage. In part due to the effects of Tongue 

River Reservoir, 15 species of fish were found in the Tongue 

River drainage that were not found in the Cheyenne, Belle 

Fourche, or Little Powder River drainages. The number of 

introduced species and relative abundance of introduced 

species of fish were higher in the Tongue River and other 

drainages than at sites on the main-stem Powder River. 

Although non-native species were identified in the Powder 

1

 U.S. Geological Survey.

2

 Wyoming Game and Fish Department.

3

 Wyoming Department of Environmental Quality.

4

 Montana Department of Environmental Quality.
2 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

River, the native fish community is largely intact. Western 

silvery minnow and sturgeon chub—species of special 

concern—were identified only at sites on the main-stem 

Powder River and were most common in the Montana segment 

of the main stem. Fish and habitat sampling on the main-stem 

Powder River indicated affinity of some species for certain 

habitats such as pools, runs, riffles, backwaters, or shoals. 

Aquatic Task Group (ATG), was tasked with assessing potential effects on aquatic ecological resources. 

The ATG developed a monitoring plan to meet two 

main objectives: (1) establish current conditions for aquatic 

biota and their habitat and (2) determine existing and potential effects of CBNG-produced water on aquatic life (Wright 

and others, 2006). The sample collection conducted during 

2005–06 and described in this report was conducted under 

the direction of the ATG to help meet objective 1 of their 

monitoring plan. Results from sampling by the Wyoming 

Game and Fish Department (WGFD) during 2004 and by the 

U.S. Geological Survey (USGS) during 1980–2007 also are 

described in this report to help meet objective 1. 

At the time the ATG was formed, CBNG development 

was occurring at a rapid pace in Wyoming, precluding the 

possibility of designing a regional monitoring plan useful 

for establishing a baseline of predevelopment conditions. 

Although it is too late to establish a true baseline, the data 

collected as part of this ecological assessment can be used to 

identify the current ecological status of streams in the PRB. 

The ecological assessment of streams in the PRB in Wyoming 

and Montana was performed by the USGS in cooperation 

with the BLM, Wyoming Department of Environmental 

Quality (WDEQ), WGFD, U.S. Environmental Protection 

Agency (USEPA), MDEQ, and the Montana Department of 

Fish, Wildlife, and Parks (MFWP). In light of CBNG activity 

planned for future years, this “current condition” (2005–06) 

information will provide scientists and decisionmakers in the 

public and private sectors data to make scientifically sound 

decisions related to ATG objective 2. Other work under the 

direction of the ATG, related to objective 2, includes ongoing 

studies of potential effects of CBNG water on fish communities in the PRB (Davis and others, 2006a; Skaar and others, 

2006), and a literature review of the effects of CBNG activities 

on fish communities (Davis and others, 2006b). 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 

The primary purpose of this report is to describe the 

ecological assessment of streams in the PRB in northeastern 

Wyoming and southeastern Montana. Characteristics of the 

habitat and biological communities (macroinvertebrates, algae, 

and fish) are based on samples collected at 47 sites during 

2005–06. Fish and habitat data collected from sites on the 

main stem of the Powder River in Wyoming and at one miscellaneous site on the South Fork of the Powder River during 

2004 also are presented as well as macroinvertebrate and algal 

data from 1980–2007. 

Introduction

Development of energy and mineral resources in 

the Powder River Structural Basin (PRB) in northeastern 

Wyoming and southeastern Montana (fig. 1) currently (2008) 

includes rapid expansion of coalbed natural gas (CBNG) 

development in Wyoming. Conventional oil and gas development and coal mining also occur in the PRB. A common 

theme of CBNG development is discharge of ground water 

that (1) often is saline or otherwise is unsuitable to use for 

crop irrigation and (2) has unknown effects on the aquatic 

communities inhabiting streams that receive the water (http://

www.wy.blm.gov/prbgroup/). 

A total of 41,096 CBNG wells have been permitted 

in the Wyoming part of the PRB as of October 2006; about 

one-half (21,018) of those wells have produced water (fig. 2; 

Wyoming Oil and Conservation Commission, 2008). CBNG 

development is concentrated along a north-south trending 

belt associated with the coal fields in the Cheyenne, Belle 

Fourche, and Powder River drainages but also occurs in the 

Tongue River drainage. Substantial CBNG resources also 

exist in the Montana part of the PRB but are largely undeveloped compared to Wyoming. Permit data from the Montana 

Department of Environmental Quality (MDEQ) indicate 

cumulative CBNG water production as of October 2006 was 

about 11,100 acre-feet (acre-ft) from 150 or more wells in the 

Tongue River drainage in Montana. At maximum development in the PRB, 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 Bureau of 

Land Management (BLM), U.S. Department of the Interior, 

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 and 

Environmental Impact Statement. One working group, the 
Spotted HorseCr

Wild Horse Creek

Dead Horse Cr

Beaver Cree

Pu

k

mpkin Creek

Willow

Cr

Creek

Salt

Yellowstone

CAMPBELL

JOHNSON

CARTER

CUSTER

CROOK

ROSEBUD

TREASURE

WESTON

POWDER RIVER

BIG HORN

SHERIDAN

NATRONA

CONVERSE

NIOBRARA

WASHAKIE

BIG

HORN

FALLON

 Tongue

 River 

Reservoir

Lake

 De 

 Smet

Tongue

P u m p k in 

Creek 

Otter Creek

Powder

Belle 

F o u r c h e 

River

River

River 

River

Creek

Creek 

Clear

Woman

C ra zy 

River

Little

M issouri 

River

River 

Creek

Porcupine

Cheyenne

Cr

Creek

Hanging Woman

Powder

Little

River

Pow

der

Black Thunder Cr

Caballo Creek

Cr

Youngs Cr

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

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 Squirrel

 Keyhole 

Reservoir

South Fork

Powder

59

50

59

R

192

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

Miscellaneous site 

 sampled in 2004

P13

Figure 1. Location of aquatic ecology sampling sites in the Powder River Structural Basin, Wyoming and Montana, 2005–06.

Introduction 3
Powder River

Structural Basin

boundary

0 10 20 30 40 MILES

0 10 20 30 40 KILOMETERS

 Lake

De 

Smet

Belle

Fourche

River

River

River

River

Creek

Cheyenne

Powder

Little

River

Tongue

Clear

Creek

Creek

Woman

Crazy

Powder

Antelope Cheyenne

Dry

Fork

River

EXPLANATION

Upper Tongue River

Upper Powder River

Crazy Woman Creek

Middle Powder River

Clear Creek

Drainage basin

Water

production,

in acre-feet

Little Powder River

Dry Fork Cheyenne 

Antelope Creek

Upper Cheyenne River

Upper Belle Fourche River

45,982

125,548

375

23,148

5,469

67,419

504

22,255

28,606

178,941

Coalbed natural gas well

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 

107° 106°30’ 106° 105°30’ 105°

45°

44°30’

44°

43°30’

43°

CAMPBELL

JOHNSON

CROOK

WESTON

POWDER RIVER

BIG HORN

SHERIDAN

CONVERSE

NIOBRARA

WASHAKIE

NATRONA

MONTANA

WYOMING

BIG HORN

Figure 2. Cumulative water production as of October 2006 from coalbed natural gas wells in the Powder River Structural Basin, 

Wyoming. (Data from Wyoming Oil and Gas Commission, 2008.)

4 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Introduction 5

Description of the Study Area

The PRB includes the namesake Powder River drainage 

as well as the Tongue River and Rosebud Creek drainages 

and upstream parts of the Cheyenne and Belle Fourche River 

drainages (fig. 1). This section of the report describes the 

geographic setting, climate and hydrology, land and water use, 

and water quality of the PRB.

Geographic Setting

Elevations in the study area range from about 

727 meters (m) above the National Geodetic Vertical Datum 

of 1929 (NGVD 29) at the Powder River near the confluence 

with the Yellowstone River in Montana to more than 3,990 m 

in the Bighorn Mountains in Wyoming. The study area lies 

within the Northwestern Great Plains ecoregion, although 

some of the streams originate in the Middle Rockies ecoregion or the Wyoming Basin ecoregion (Woods and others, 

2002; Chapman and others, 2003). Stream origins are listed 

in table 1 as either mountain (Middle Rockies ecoregion) 

or plains (Northwestern Great Plains and Wyoming Basin 

ecoregions). The predominant vegetation in the study area is 

short and mixed grass prairie that includes shrubs (sagebrush 

and rabbit brush) and scattered trees (Knight, 1994; Bailey, 

1995). The landscape is characterized by undulating to highly 

dissected plains, sheer-sided buttes, and rugged badlands along 

some river valleys (Bailey, 1995; McNab and others, 2005). 

Headwater streams in the western parts of the Tongue and 

Powder River drainages flow across igneous and metamorphic rocks of Precambrian age (Lindner-Lunsford and others, 

1992; Zelt and others, 1999; Clark and Mason, 2007). As these 

streams continue downslope across the foothills to the plains, 

they flow across uplifted Paleozoic-era marine sandstone 

and limestone deposits, Mesozoic era sandstone and shale, 

and then Tertiary-age sedimentary rocks of the Wasatch and 

Fort Union Formations (Hembree and others, 1952; LindnerLunsford and others, 1992). 

Some of the plains streams sampled as part of this assessment 

had intermittent streamflow, meaning they had flow during 

part of the year. Intermittent streams often have perennial 

pools that are sustained by ground water but may not have 

flow between the pools during part of the year. In contrast, 

some plains streams with mountain headwaters have perennial 

flow and rarely go dry, even during periods of drought, with 

streamflow sustained by snowmelt and ground-water discharge 

(Lindner-Lunsford and others, 1992). 

Many of the streams in the study area have diversion 

dams that are used for irrigation withdrawals, and numerous small impoundments have been built on small tributary 

streams. The largest reservoir in the study area is Tongue 

River Reservoir, located between sampling sites T9 and T10 

on the main-stem Tongue River (fig. 1). The storage capacity 

of Tongue River Reservoir is about 68,040 acre-ft (Zelt and 

others, 1999). The main-stem Powder River is free flowing 

(no dams) as are the Cheyenne and the Belle Fourche Rivers 

within the study area. 

Data described in this report generally were collected 

during the summer months (June through September) of 2005 

and 2006. By the summer of 2005, the States of Wyoming and 

Montana were in the 6th year of drought (National Oceanic 

Atmospheric Administration Satellite and Information 

Service, 2005). As a result of this drought, with the exception 

of short-term storms, mean daily flows during both 2005 and 

2006 were substantially less than the long-term mean. Streamflow data from three sampling sites are shown in figure 3 to 

illustrate the severity of the drought and the annual variability 

of streamflow conditions in the study area. In general, streamflow during the 2006 was considerably less than during the 

2005 as shown by the hydrographs for the Powder River at 

Moorhead (site P12, fig. 3A), Cheyenne River near Spencer 

(site C6, fig. 3B), and Tongue River at State line (site T9, 

fig. 3C). The Powder River between Sussex, Wyo. (site P2, 

fig. 1), and Moorhead, Mont. (site P12, fig. 1), is a losing 

reach (river loses more water to aquifer and evaporation than it 

gains), and although the Powder River is considered perennial, 

it historically has periods when it does not flow (Ringen and 

Daddow, 1990). During 2006, however, some of the reaches 

on the Powder River, like many of the small streams (fig. 4), 

had no flow, which left isolated pools to sample. 

In spite of the ongoing 6-year long drought, streamflow 

in 2005 in the Tongue River at State line (site T9, fig. 3C) 

was closer to the long-term mean streamflow than were many 

of the streams in the study area. The 2005 streamflow in the 

Tongue River was affected by intense rainfall; for example, the 

monthly total precipitation for Dayton, Wyo. (near Monarch, 

fig. 1) in May 2005 was 160 mm, more than twice the longterm monthly average of 77 mm (Western Region Climate 

Center, 2009). The above-average precipitation in 2005 helped 

sustain streamflow later in the year, but the streamflow in 2006 

was considerably less than the long-term mean streamflow and 

more similar to other drought-affected streams in the study 

area (fig. 3C). 

Climate and Hydrology

The study area is semiarid (McNab and others, 2005). 

Precipitation is quite variable and comes in the form of rain 

and snow, with most precipitation falling as rain during 

the spring and summer months. Average annual precipitation generally is less than 500 millimeters (mm; Western 

Region Climate Center, 2009). Temperatures vary widely 

with extremely cold winters and hot summers. For example, 

climatic records from Broadus, Mont., show a recorded low 

temperature of -44 degrees Celsius (°C), a high of 42°C, and a 

mean annual temperature of 7.5°C during 1948–2007 (Western 

Regional Climate Center, 2007).

Flow in plains streams is quite variable throughout the 

study area because of the high variability of precipitation. 
Table 1. Aquatic ecology sampling sites and selected characteristics, Powder River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. DMS, degrees, minutes, seconds; km2, square kilometers; m, meters; M, mountains; P, plains]

 Site 

number 

(fig. 1)

U.S. Geological Survey 

site identification 

number

Site name Abbreviated site name Latitude (DMS) Longitude (DMS) Drainage area (km2

)

 Elevation 

(m)

Stream 

origin

Reach length

(m)

R1 06295113 Rosebud Creek at Reservation 

Boundary, near Kirby, MT

upper Rosebud Creek 45 21 40 106 59 23 319 1,152

P 200

R2 06296003 Rosebud Creek at mouth, near 

Rosebud, MT

Rosebud Creek at mouth 46 15 53 106 28 30 3,372 756

P 200

T1 06299980 Tongue River at Monarch, WY Tongue River at Monarch 44 54 01 107 01 13 1,238 1,103

M 970

T2 06305700 Goose Creek near Acme, WY Goose Creek 44 53 11 106 59 18 1,070 1,103

M 640

T3 450137106595101 Youngs Creek near Reservation 

Boundary, near Decker, MT

upper Youngs Creek 45 01 37 106 59 15 56 1,155

P 200

T4 445832106551401 Youngs Creek above mouth, near 

Decker, MT

Youngs Creek at mouth 44 58 32 106 55 14 161 1,088

P 200

T5 445957106524701 Tongue River below Youngs 

Creek, near Decker, MT

Tongue River below Youngs 

Creek

44 59 57 106 52 47 3,711 1,058

M 1,000

T6 06306100 Squirrel Creek near Decker, MT upper Squirrel Creek 45 03 02 106 55 24 87 1,122

P 200

T7 450047106514201 Squirrel Creek above mouth at 

Decker, MT

Squirrel Creek at mouth 45 00 47 106 51 42 112 972

P 200

T8 06306250 Prairie Dog Creek near Acme, 

WY

Prairie Dog Creek 44 59 02 106 50 21 927 1,052

P 170

T9 06306300 Tongue River at State line, near 

Decker, MT

Tongue River at State line 45 00 32 106 50 08 3,763 1,045

M 1,000

T10 451607106372801 Tongue River at Prairie Dog 

Creek, near Decker, MT

Tongue River above Hanging 

Woman Creek

45 16 07 106 37 28 5,208 890

M 1,000

T11 06307570 Hanging Woman Creek below 

Horse Creek, near Birney, MT

upper Hanging Woman Creek 45 08 04 106 29 04 831 954

P 200

T12 451340106295501 Hanging Woman Creek below 

Hay Gulch, near Birney, MT

middle Hanging Woman Creek 45 13 44 106 29 57 958 997

P 200

T13 06307600 Hanging Woman Creek near 

Birney, MT

Hanging Woman Creek at mouth 45 17 57 106 30 28 1,217 960

P 200

T14 06307616 Tongue River at Birney Day 

School Bridge, near Birney, MT

Tongue River at Birney Day 

School

45 24 42 106 27 26 6,788 933

M 1,000

T15 451732106085001 Otter Creek below Taylor Creek, 

near Otter, MT

upper Otter Creek 45 17 32 106 08 53 803 991

P 200

6 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 1. Aquatic ecology sampling sites and selected characteristics, Powder River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. DMS, degrees, minutes, seconds; km2, square kilometers; m, meters; M, mountains; P, plains]

 Site 

number 

(fig. 1)

U.S. Geological Survey 

site identification 

number

Site name Abbreviated site name Latitude (DMS) Longitude (DMS) Drainage area (km2) Elevation (m) Stream origin Reach length (m)

T16 452642106091201 Otter Creek below Tenmile 

Creek, near Ashland, MT

middle Otter Creek 45 26 42 106 09 12 1,331 945 P 200

T17 06307740 Otter Creek at Ashland, MT Otter Creek at mouth 45 35 18 106 15 17 1,831 889 P 200T18 06307830 Tongue River below Brandenberg 

Bridge, near Ashland, MT

Tongue River below Brandenberg 

Bridge

45 50 23 106 13 09 10,225 841 M 1,000

T19 06308400 Pumpkin Creek near Miles City, 

MT

Pumpkin Creek 46 13 42 105 41 24 1,805 759 P 200

P1 434056106244101 Powder River above Lone Tree 

Draw, near Sussex, WY

Powder River above Salt Creek 43 40 56 106 24 41 5,828 1,350 P 13,218

P2 434124106192401 Powder River below Salt Creek, 

near Sussex, WY

Powder River below Salt Creek 43 41 24 106 19 24 7,980 1,338 P 13,218

P3 435453106104701 Powder River below Willow 

Creek, near Sussex, WY

Powder River above Pumpkin 

Creek

43 54 53 106 10 47 9,808 1,311 P 13,218

P4 440919106091401 Powder River above Van Houghton Draw, near Buffalo, WY Powder River below Burger Draw 44 09 19 106 09 14 11,111 1,216 P 13,218P5 442538106082001 Powder River below Mitchell 

Draw, near Arvada, WY

Powder River above Crazy 

Woman Creek

44 25 38 106 08 20 12,564 1,152 P 13,218

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 1,280 M 340

P7 442817106133001 Crazy Woman Creek near Upper 

Station, near Arvada, WY

Crazy Woman Creek near mouth 44 28 17 106 13 30 2,385 1,167 M 490

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 1,134 P 13,218

P9 444857106030401 Powder River above Ivy Creek, 

near Arvada, WY

Powder River above Clear Creek 44 48 57 106 03 04 17,050 1,062 P 13,218

P10 06324000 Clear Creek near Arvada, WY Clear Creek 44 52 18 106 04 56 2,875 1,069 M 750P11 445339106032501 Powder River below Clear Creek, 

near Arvada, WY

Powder River below Clear Creek 44 53 39 106 03 25 20,106 1,059 P 13,218

P12 06324500 Powder River at Moorhead, MT Powder River at Moorhead 45 03 28 105 52 39 20,943 1,021 P 13,218P13 06324710 Powder River at Broadus, MT Powder River at Broadus 45 25 37 105 24 05 22,657 919 P 13,218P14 06324790 Little Powder River at State 

Hwy 59, near Gillette, WY

Little Powder River at 

Highway 59

44 26 09 105 27 17 110 1,250 P 200

Introduction 7
Table 1. Aquatic ecology sampling sites and selected characteristics, Powder River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. DMS, degrees, minutes, seconds; km2, square kilometers; m, meters; M, mountains; P, plains]

 Site 

number 

(fig. 1)

U.S. Geological Survey 

site identification 

number

Site name Abbreviated site name Latitude (DMS) Longitude (DMS) Drainage area (km2

)

 Elevation 

(m)

Stream 

origin

Reach length

(m)

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 1,039

P 240

P16 06325000 Little Powder River at Biddle, 

MT

Little Powder River at Biddle 45 06 17 105 19 51 3,991 991

P 200

P17 453209105201201 Powder River below Little Powder River, near Broadus, MT Powder River below Little Pow- der River 45 32 09 105 20 12 29,503 908

P 13,218

P18 06326500 Powder River near Locate, MT Powder River near Locate 46 25 48 105 18 34 33,846 727

P 13,218

C1 06364300 Porcupine Creek near Teckla, 

WY

Porcupine Creek 43 34 41 105 20 19 204 1,428

P 200

C2 06364700 Antelope Creek near Teckla, WY Antelope Creek 43 29 08 105 13 39 2,484 1,366

P 280

C3 06365900 Cheyenne River near Dull Center, 

WY

Cheyenne River near Dull Center 43 25 45 105 02 43 3,955 1,314

P 320

C4 06375600 Little Thunder Creek near Hampshire, WY Little Thunder Creek 43 39 20 104 54 20 606 1,341

P 200

C5 06376300 Black Thunder Creek near Hampshire, WY Black Thunder Creek 43 34 54 104 43 11 1,386 1,244

P 200

C6 06386500 Cheyenne River near Spencer, 

WY

Cheyenne River near Spencer 43 25 20 104 07 36 13,649 1,105

P 220

B1 06425720 Belle Fourche River below 

Rattlesnake Creek, near Piney, WY

Belle Fourche River 43 59 04 105 23 16 1,282 1,384

P 200

B2 06425900 Caballo Creek at mouth, near 

Piney, WY

Caballo Creek 44 04 48 105 15 59 673 1,335

P 200

1Established reach length of 3,218 m is maximum reach length; the actual reach length varied each time site was visited depending on location of random starting point and availability of expected habitat 

types.

8 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
0

500

1,000

1,500

2,000

2,500

3,000

3,500

STREAMFLOW, IN CUBIC FEET PER SECOND

A Powder River at Moorhead, Mont. (site P12)

DATE

10/1 11/1 12/1 1/1 2/1 3/1 4/1 5/1 6/1 7/1 8/1 9/1

0

1,000

2,000

3,000

4,000

5,000

Historical mean daily

2005 daily mean

2006 daily mean

C Tongue River at State line near Decker, Mont. (site T9)

EXPLANATION

STREAMFLOW, IN CUBIC FEET PER SECOND

DATE

10/1 11/1 12/1 1/1 2/1 3/1 4/1 5/1 6/1 7/1 8/1 9/1

STREAMFLOW, IN CUBIC FEET PER SECOND

0

200

400

600

800

B Cheyenne River near Spencer, Wyo. (site C6)

DATE

10/1 11/1 12/1 1/1 2/1 3/1 4/1 5/1 6/1 7/1 8/1 9/1

10/1

10/1

10/1

Figure 3. Streamflow hydrographs showing historical mean daily flow and daily mean flow for water years 2005 and 2006 

for A, Powder River at Moorhead, Mont. (site P12); B, Cheyenne River near Spencer, Wyo. (site C6); and C, Tongue River at 

State line near Decker, Mont. (site T9).

Introduction 9
Figure 4. Photographs of sample reach on Hanging Woman Creek near Birney, Mont. (site T13), 

showing the difference in water levels for sampling dates in 2005 and 2006.

June 23, 2005 June 26, 2006

Photograph by Stacy M. Kinsey, U.S. Geological Survey. Photograph by Michael J. Sweat, U.S. Geological Survey.

10 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

 Land and Water Use

Although few small communities are in the PRB, the 

predominant land uses are agricultural and mineral related. 

As of 2000, the largest city in the study area is Gillette, Wyo., 

with an estimated population of 19,646 (U.S. Census Bureau, 

2007). The primary agricultural uses in the study area are 

livestock production and irrigated and dryland crop production 

(Zelt and others, 1999). CBNG production followed by coal 

mining and conventional oil and gas are the dominant mineralrelated land uses. Although limited, some timber production 

occurs in the Bighorn Mountains and in forested areas of the 

downstream Tongue and Powder River drainages (Zelt and 

others, 1999). 

The following brief summary of water use in the Tongue 

and Powder River drainages in Wyoming is drawn from HKM 

Engineering, Inc. and others (2002). Irrigated crop production, primarily associated with production of livestock forage, 

uses the largest percentage of surface water in the Tongue and 

Powder River drainages in Wyoming. About 194,000 acre-ft 

of water, or approximately 87 percent of all surface-water 

use, is for irrigation. The remaining 13 percent of surfacewater use is for municipal supply. Industries with the largest 

water demands in the Tongue and Powder River drainages in 

Wyoming include conventional oil and gas production and 

CBNG development. Together these industries use approximately 68,000 acre-ft of ground water per year. Industry 

accounts for about 93 percent of the ground-water use in the 

area, followed by domestic use (6 percent), municipal use 

(<1 percent), and agricultural use (<1 percent). 

Wastewater effluent from municipal treatment plants 

enters some of the streams in the study area, primarily in 

Sheridan County in the Tongue River drainage (fig. 1). The 

town of Sheridan, for example, discharges effluent to Goose 

Creek, and smaller towns such as Dayton and Ranchester 

discharge effluent to the Tongue River (Wyoming Department of Environmental Quality, 2009). The total population of Sheridan County in 2007 was estimated to be 27,207 

(U.S. Census Bureau, 2009). Other towns include Buffalo, 

that discharges effluent to Clear Creek approximately 

80 kilometers upstream from the nearest sampling site, and 

Gillette, that discharges to a tributary of the Belle Fourche 

River downstream from the nearest sampling site.

Water Quality

Water-quality information in this section is drawn from 

Clark and Mason (2007) unless otherwise specified. Chemical characteristics of surface water are dependent upon many 

variables, including the sources of the water (snowmelt, 

rainfall, or ground-water discharge), stream hydrology, and the 

characteristics of the geologic formations the water traverses. 

Because of the wide range of environmental settings (chemical, ecological, hydrological, and physical characteristics) in 

the study area, water-quality characteristics throughout the 

area are quite variable. Water types in the PRB ranged from 

magnesium calcium bicarbonate type water for some sites 

in the Tongue River drainage to sodium sulfate type water at 

many sites in the Powder, Cheyenne, and Belle Fourche River 
Methods of Sample Collection and Analysis 11

drainages (Lee and others, 1981; Ringen and Daddow, 1990; 

Clark and Mason, 2007). Generally, streams with headwaters 

in the mountains have smaller major ion and dissolved-solids 

concentrations than streams with headwaters in the plains 

(Lindner-Lunsford and others, 1992), and concentrations of 

dissolved constituents become larger as water flows downstream. Two exceptions to this are worth noting and occur 

in the Powder River between Arvada, Wyo., and Moorhead, 

Mont., and in the Belle Fourche River. In the Powder River 

between Arvada and Moorhead, the decrease in dissolvedsolids concentrations can be attributed to inflows from Clear 

Creek that have smaller dissolved-solids concentrations 

(Hembree and others, 1952; Ringen and Daddow, 1990; Clark 

and Mason, 2007). Smaller downstream concentrations in 

the Belle Fourche River likely are because of differences in 

geology and changes in water quality of tributaries as the 

Belle Fourche River approaches the Black Hills and Keyhole 

Reservoir (fig. 1).

Water quality of the Powder River has been affected 

by discharges from conventional oil and gas production in 

the Salt Creek drainage. Salt Creek has large concentrations 

of dissolved solids, chloride, and sodium due to discharges 

from conventional oil and gas production (Clark and Mason, 

2007). Concentrations of chloride frequently were larger than 

the State of Wyoming chronic criterion for aquatic life of 

230 milligrams per liter (Wyoming Department of Environmental Quality, 2001) in the Powder River below Salt Creek 

(site P2), Powder River below Burger Draw (near site P4), 

and Powder River at Arvada (downstream from sites P5 and 

P8), and to a lesser extent, in the Little Powder River above 

Dry Creek (site P15; Clark and Mason, 2007). The reach of 

the Powder River from Salt Creek to Clear Creek has been 

listed by the WDEQ as chloride impaired, and the reach of 

the Powder River from Salt Creek to Crazy Woman Creek has 

been listed as selenium impaired (Wyoming Department of 

Environmental Quality, 2006). 

Acknowledgments

Greg Boughton, Kendra Remley, Stacy Kinsey, Tom 

Cleasby, Billy Justus, Jodi Norris, Pete McCarthy, Fred Bailey, 

Laura Hallberg, Seth Davidson, Mike Sweat, Ty Blacklock, 

John Tertuliani, Rick Hubbell, Jon Mason, and others with the 

USGS and Travis Cundy, Dave Zafft, Bud Stewart, and others 

with the WGFD assisted with data collection. Travis Cundy 

also participated in the habitat data analysis from sites on the 

main-stem Powder River in Wyoming. Many private landowners, as well as the Anadarko Corporation (The Woodlands, 

Texas), allowed access to sampling sites. 

Colleague reviews by Stephen Porter (Texas State 

University), Jim Petersen (USGS), and Robert Bramblett 

(Montana State University) improved the quality of the 

manuscript. Other members of the ATG, including David 

Zafft (WGFD), and Joe Platz (BLM), also provided helpful 

comments. Merry Gamper (USGS) helped compile the ancillary macroinvertebrate and algal data. Sue Roberts (USGS) 

created the illustrations and performed layout work. Laura 

Hallberg (USGS) performed the geographic information 

system (GIS) analysis.

Methods of Sample Collection and 

Analysis

A total of 47 sampling sites (fig. 1; table 1) were chosen 

for sampling by the ATG on the basis of prioritization with 

respect to existing and potential CBNG development and 

availability of existing data and using professional judgment to 

identify and fill in data gaps. All of the sites were sampled in 

2005, the first year of the ATG study. The number of sampling 

sites was reduced to 39 sites during 2006, and the scope of 

sampling at each site was smaller in 2006 than 2005 (table 2) 

partially because of drought and partially because of study 

constraints. 

Sampling and measurement techniques described in this 

section are drawn primarily from the USGS National WaterQuality Assessment Program (NAWQA) protocols for algae 

and macroinvertebrates and the USEPA Environmental Monitoring and Assessment Program (EMAP) protocols for habitat 

and fish community. Protocols used by the WGFD for habitat 

and fish community assessment on the main-stem Powder 

River also are described in this section. 

Habitat

The description of habitat assessment methods is divided 

into two parts because of differences in methodology. The first 

section, “Basinwide Habitat Assessment,” describes habitat 

assessment methods used by the USGS to collect data for 

all 47 sampling sites, which includes sites on the main-stem 

Powder River. The second section, “Main-Stem Powder River 

Habitat Assessment,” describes habitat assessment methods 

used by the WGFD to collect data at eight sites on the mainstem Powder River in Wyoming. 

Basinwide Habitat Assessment

Habitat assessments were conducted by USGS personnel in 2005 using the EMAP transect-based survey technique 

(Peck and others, 2003) at each of the 47 sites sampled for 

aquatic biota. The standard sampling reach length was defined 

as 40 wetted channel widths and ranged from a minimum of 

200 m to a maximum of 1,000 m with the exception of reaches 

on the main-stem Powder River that were 3,218 m (table 1). 

At each site, 11 equally spaced transects were established 

for measurements, and at each transect, five points including 

the edge of water were measured for features such as depth, 

substrate, and embeddedness. Reachwide mean values were 
Table 2. Types of aquatic ecology measurements and samples by site, Powder River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Data collected by U.S. Geological Survey except as indicated by footnotes. Shaded cells indicate main-stem sites on the Tongue or Powder River. GPS, global positioning system; X, data were collected; A, attempted to collect sample, but reach was dry or did not have enough wetted area to sample; --, data were not collected]

Site 

number 

(fig. 1)

Abbreviated site name

Habitat 

transects and 

 cross sections

Longitudinalsurvey 

profiles

GPS 

mapping Algae Macroinvertebrate community Fish community Major ion samples

2005 2005 2006 2005 2006 2005 2006

R1 upper Rosebud Creek

X -- -- --

X

X

X

X -- --

R2 Rosebud Creek at mouth

X -- -- --

X --

X -- -- --

T1 Tongue River at Monarch

X

X --

X

X

X

X

X -- --

T2 Goose Creek

X

X --

X

X

X

X

X -- --

T3 upper Youngs Creek

X -- -- --

X

X

X

X

X

X

T4 Youngs Creek at mouth

X -- -- --

X

X

X

X

X

X

T5 Tongue River below Youngs Creek

X -- -- --

X

X

X

X

X

X

T6 upper Squirrel Creek

X -- -- --

X

X

X

X

X

X

T7 Squirrel Creek at mouth

X -- -- --

X

A

X

A

X

A

T8 Prairie Dog Creek

X

X --

X

X

X

X

X -- --

T9 Tongue River at State line

X

X --

X

X

X

X

X -- --

T10 Tongue River above Hanging Woman 

Creek

X -- -- --

X

X

X

X

X

X

T11 upper Hanging Woman Creek

X -- -- --

X

X

X

X

X

X

T12 middle Hanging Woman Creek

X -- -- --

X

X

X

X

X

X

T13 Hanging Woman Creek at mouth

X -- -- --

X

X

X

X -- --

T14 Tongue River at Birney Day School

X -- -- --

X

X

X

X -- --

T15 upper Otter Creek

X -- -- --

X

X

X

X

X

X

T16 middle Otter Creek

X -- -- --

X

A

X

A

X

A

T17 Otter Creek at mouth

X -- -- --

X

X

X

X -- --

T18 Tongue River below Brandenberg Bridge

X -- -- --

X

X

X

X -- --

T19 Pumpkin Creek

X -- -- --

X --

X -- -- --

P1 Powder River above Salt Creek

X --

X

X

X

X

X1 X1 X

X

P2 Powder River below Salt Creek

X --

X

X

X

X

X1 X1 X

X

P3 Powder River above Pumpkin Creek

X --

X

X

X

X

X1 X1 X

X

12 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 2. Types of aquatic ecology measurements and samples by site, Powder River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Data collected by U.S. Geological Survey except as indicated by footnotes. Shaded cells indicate main-stem sites on the Tongue or Powder River. GPS, global positioning system; X, data were collected; A, attempted to collect sample, but reach was dry or did not have enough wetted area to sample; --, data were not collected]

Site 

number 

(fig. 1)

Abbreviated site name

Habitat 

transects and 

 cross sections

Longitudinalsurvey 

profiles

GPS 

mapping Algae Macroinvertebrate community Fish community Major ion samples

2005 2005 2006 2005 2006 2005 2006

P4 Powder River below Burger Draw X -- X X X X X1 X1 X XP5 Powder River above Crazy Woman Creek X -- X X X X X1 X1 X XP6 Crazy Woman Woman Creek below I-90 X X X X X X X X X XP7 Crazy Woman Creek near mouth X X X X X X X X X XP8 Powder River below Crazy Woman Creek X -- X X X X X1 X1 X XP9 Powder River above Clear Creek X -- X X X X X1 X1 X X

P10 Clear Creek X X -- X X X X X -- --P11 Powder River below Clear Creek X -- X X X X X1 X1 X XP12 Powder River at Moorhead X -- X X X X X X -- --P13 Powder River at Broadus X -- -- X X X X X XP14 Little Powder River at Highway 59 X X -- X X X X X X XP15 Little Powder River above Dry Creek X X -- X X X X X -- --P16 Little Powder River at Biddle X -- -- -- X -- X -- X --P17 Powder River below Little Powder River X -- -- -- X X X X X XP18 Powder River near Locate X -- -- -- X -- X -- --

C1 Porcupine Creek X X -- X X X X X -- --C2 Antelope Creek X2 X2 -- X X X X X -- --C3 Cheyenne River near Dull Center X2 X2 -- X X X X X -- --C4 Little Thunder Creek X X -- X X X X X -- --C5 Black Thunder Creek X2 X2 -- X X A X A -- --C6 Cheyenne River near Spencer X2 X2 -- X X X X X -- --B1 Belle Fourche River X X -- X X X X X -- --B2 Caballo Creek X X -- X X A X A -- --

1Data were collected by the Wyoming Game and Fish Department.2Data were collected by the Wyoming Department of Environmental Quality.

Methods of Sample Collection and Analysis 13
Table 3. Substrate codes, numbers, and size classes.

[mm, millimeter; <, less than; >, greater than]

Substrate Substrate 

code

Substrate 

number

Substrate size 

(mm)

Fines FN 1 <0.06

Sand SA 2 0.06 to 2

Gravel (fine) GF 2.5 >2 to 16

Gravel (coarse) GC 3.5 >16 to 64

Cobble CB 4 >64 to 250

Boulder (small) SB 5 >250 to 4,000

Boulder (large) XB 5 >250 to 4,000

Bedrock (rough) RR 6 >4,000

Bedrock (smooth) RS 6 >4,000

Concrete RC 6 >4,000

Hardpan HP 6 >4,000

14 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

calculated from the transect values, including depths of zero at 

the edge of water if the banks were less than vertical.

Channel dimensions, bank characteristics, and in-stream 

fish cover were evaluated at each of the cross-section transects. 

Bankfull depth measurements described in this report are 

the height of bankfull stage as measured from the bottom of 

the thalweg (the line connecting the lowest or deepest points 

along a streambed). When thalweg data were collected in 

conjunction with transect measurements, the thalweg depth 

measured at each transect was added to its corresponding 

bankfull height above water surface to determine bankfull 

depth. When thalweg data were collected independently from 

transect measurements, a reach mean was determined for 

bankfull height above water surface and thalweg depth, and 

then these reach means were added to produce the bankfull 

depths from thalweg. The width/depth ratio (W/D; Rosgen, 

1996) was calculated as the mean bankfull width divided by 

the mean bankfull depth. Incised height was measured as the 

distance from the water surface to the level of the first terrace. 

Stream incision values given in this report represent the 

incised height above the bottom of the thalweg, calculated by 

adding the incised height above the water surface to the reach 

mean thalweg depth. Fish cover was recorded as a semiquantitative observation of filamentous algae, aquatic macrophytes, 

large woody debris, brush, live trees or roots, overhanging 

vegetation, undercut banks, and boulders. Areal coverage 

of each fish-cover type was estimated for a 10-m segment 

of the stream at each cross-section transect by estimating 

cover classes ranging from “0” (absent) to “4” (>75 percent; 

Peck and others, 2003). Fish-cover estimates can exceed 

100 percent when all categories are added together because of 

the ranges used for observations. At each site, a sketch of the 

reach was drawn, and photographic points were established to 

assist in documenting channel, bank, and riparian conditions 

and as a reference for possible long-term comparisons. 

Substrate size and embeddedness were measured along 

the transects at all sites; additionally, the substrate size was 

estimated for an additional 50 particles along the thalweg 

profile at sites in Montana. Substrate measurements were 

recorded as a code that represented a substrate size range or 

class. Substrate statistics presented in this report were calculated according to methods described by Kaufmann and others 

(1999) by assigning a numeric value to each class, representing the logarithm of the midpoint diameter of each size class 

(table 3). Bedrock is operationally defined in this report as 

rock, concrete, or hardpan greater than 4,000 mm in diameter. Embeddedness of particles was estimated to the nearest 

10 percent at the transects (55 points per site). 

In addition to the reachwide substrate characteristics 

collected as part of the EMAP procedures, pebble counts were 

collected following procedures outlined in Wolman (1954). 

Wolman pebble counts were collected at one riffle and one 

pool, if present, at all Wyoming sites and sites T9 (Tongue 

River at State line) and P12 (Powder River at Moorhead). At 

each riffle or pool, at least 100 particles were measured at 

evenly spaced intervals across the stream starting at bankfull. 

Particle size was measured using a U.S. SAH-97 Hand Held 

Particle Size Analyzer (gravelometer) and tallied by standard 

1⁄2 phi Wentworth size classes (Potyondy and Bunte, 2002). 

Cumulative distribution curves for the pebble count data were 

generated using a spreadsheet developed by J.P. Potyondy 

(U.S. Department of Agriculture, Forest Service) and K. Bunte 

(Colorado State University, written commun., 2007). 

Several measures of riparian vegetation were collected 

at each cross-section transect. Canopy density, the area of 

the sky bracketed by vegetation (Peck and others, 2003), was 

measured in six locations (four directions mid-stream and 

at each bank). Reachwide mean values of canopy density 

were calculated separately for mid-stream and bank densiometer measurements and reported as a percentage of possible 

density, as much as 100 percent (Kaufmann and others, 1999). 

Riparian vegetation type and cover were visually estimated 

for three vegetative layers—ground cover (<0.5 m high), 

understory (0.5 to 5 m high), and canopy (>5 m high)—using 

classes of 0 percent (absent), less than 10 percent (sparse), 10 

to 40 percent (moderate), 40 to 75 percent (dense), and more 

than 75 percent (very dense). Reachwide vegetative cover was 

calculated by averaging the midpoint values (0, 5, 25, 57.5, 

and 87.5 percent) of the classes observed while onsite. One 

“legacy” tree, generally the largest tree in or near the riparian 

zone, was chosen for each transect. Information recorded for 

each tree included type, the taxonomic group (if possible), 

estimated height, diameter at breast height, and distance from 

the wetted edge of the stream. Study personnel also noted 

the presence, if any, of eight specific invasive plant species, 

also referred to as target species—Canada thistle (Cirsium 

arvense), leafy spurge (Euphorbia esula), musk thistle 

(Carduus nutans), English ivy (Hedera helix), Russian olive 

(Elaeagnus angustifolia), salt cedar (Tamarix spp.), cheatgrass 

(Bromus tectorum), and common burdock (Arctium minus). 
Table 4. Components of bank-stability index (from Fitzpatrick and 

others, 1998).

[>, greater than; ≤, less than or equal to; <, less than]

Bank characteristics

 (unit of measurement) Measurement Score

Angle (degrees) 0–30 1

31–60 2

>60 3

Vegetative cover (percent) >80 1

50–80 2

20≤50 3

<20 4

Height (meters) 0–1 1

1.1–2 2

2.1–3 3

3.1–4 4

>4 5

Substrate (category) Bedrock, artificial 1

Boulder, cobble 3

Silt 5

Sand 8

Gravel/sand 10

Methods of Sample Collection and Analysis 15

tive Fish and Wildlife Research Unit in Laramie, Wyoming 

(Quist and others, 2004). The WSA provides standardized 

methods to describe baseline aquatic habitat conditions within 

specific habitat types at a local level. Two additional aquatic 

habitat assessment approaches were used in 2005 and 2006, 

in conjunction with modified WSA methods, to quantify the 

availability of each habitat type within study reaches. Aquatic 

habitat types were mapped with high-precision GPS units in 

2005. A transect-based survey technique was adapted from 

EMAP methods and implemented in 2006 to increase efficiency, objectivity, and repeatability (Peck and others, 2003). 

The primary aquatic habitat types were defined as pool, 

riffle, run, backwater, and shoal (table 5). One other habitat 

type, isolated pool, was recorded where it occurred but was 

not considered a primary habitat type. To encompass all 

available habitat types, the reach length at each site was set 

to 3,218 m (the typical distance of two meander lengths as 

estimated from aerial photographs) instead of using the reachlength criteria provided in the WSA. Sampling of the entire 

3,218 m at each site was not feasible, however, because of 

time and personnel constraints, and therefore, the reach was 

divided into eight starting points, evenly spaced downstream 

(402 m apart) from the upstream end of each reach. One of 

the eight starting points was chosen at random, and sampling 

progressed downstream until two units of each primary habitat 

type (pool, riffle, run, backwater, and shoal) were sampled 

Reach characteristics that were documented included 

bank stability and riparian disturbance. Bank-stability scores 

were calculated from bank angle, vegetative cover, bank 

height, and bank substrate (Fitzpatrick and others, 1998). Site 

scores for each category (table 4) were summed to determine 

the bank-stability index with a possible range of 4 to 22. Bankstability scores that range from 4 to 7 are considered stable, 8 

to 10 are at risk, 11 to 15 are unstable, and 16 to 22 are very 

unstable (Fitzpatrick and others, 1998). Eleven human landuse activities (wall or dam; building; pavement; road; intake or 

outlet pipe; trash or landfill; park or lawn; row crops; pasture, 

range, or hayfield; logging operations; and mining activity) 

were recorded at each transect along with the proximity of 

each to the riparian zone. Proximity weighted disturbance 

indices were calculated by weighting the total number of 

observances of each land-use activity as follows: observations 

in the channel or on the bank were weighted 1.5; observations 

within the 10- by 10-m riparian sample plot were weighted 

1.0; and observations behind or adjacent to the riparian sample 

plot were weighted 0.667 (Kaufmann and others, 1999). 

Additional survey data were collected at many of the 

47 sites. In both Wyoming and Montana, at least two cross 

sections, one through a riffle and one through a pool, in each 

reach were identified with rebar when possible and surveyed 

using a transit or total station. In Wyoming, longitudinal 

profiles were conducted at many sites (table 2) profiling the 

streambed, water surface, bankfull stage and low terraces, if 

any, as described by Harrelson and others (1994). Longitudinal 

profiles were conducted using either surveying equipment or a 

high-resolution global positioning system (GPS). Collection of 

additional data varied between States due to study scope.

Statistical tests of the data, such as the Wilcoxon rank 

sum test (Helsel and Hirsch, 2002), were calculated in S-Plus, 

version 7.0 (Insightful Corp., 2005). The probability level (P) 

used to determine significance was 0.05 unless specified 

otherwise. 

Main-Stem Powder River Habitat Assessment

Aquatic habitat assessments were conducted by WGFD 

personnel during 2004–06 at eight sites on the main-stem 

Powder River in Wyoming (sites P1–P5, P8, P9, and P11; 

fig. 1). Data collected during 2004 from a miscellaneous site 

on the South Fork Powder River (Wyoming Game and Fish 

Department, 2007) also are included in this report. 

Three approaches to habitat assessment were used 

during 2004–06 to better describe the homogenous, shifting 

sand habitats of the Powder River. The quantity of various 

habitat types, fish species presence, and relative abundance of 

fish inhabiting each habitat type were considered important 

variables to help assess potential changes in habitat availability as a result of possible changes in streamflow from CBNG 

activities. 

The first and primary approach applied during 2004–06 

was adapted from the Warm-water Stream Assessment 

(WSA) methodology developed by the Wyoming Coopera-
Table 5. Habitat types used to classify aquatic habitat in the main-stem Powder River, Wyoming and Montana, 2005–06.

[≥, greater than or equal to]

Habitat type Description

Pool Relatively deep, slow-moving water with a predominance of fine substrate. Little to no surface disturbance. Formed by 

scour (mid-channel scour, scour against a streambank, scour below or adjacent to a log, boulder, or other obstruction) 

or beaver activity. Usually shorter than the active channel width. Pools required RPD1 ≥ 0.31 meter. 

Riffle Relatively shallow, fast-moving water with a predominance of coarse substrate (≥25 percent gravel and cobble). Obvious surface turbulence. Gravel and cobble in the Powder River often were ≥25 percent embedded. Cross-sectional 

profiles were usually broad and uniform. 

Run Uniform depth and flow with little or no surface turbulence and homogenous features. Variable, but predominantly fine 

substrate. Often longer than the active channel width. Deeper than riffles with few flow obstructions (such as boulders 

and logs). Scarce structure. 

Backwater Located along a channel margin, island, or within a mid-channel bar. Predominantly fine substrate. Partially connected 

to the main channel, usually at just one end. Negligible flow. No surface turbulence. Scoured at high flows and 

remains after flows recede. 

Shoal Very shallow, flowing water, generally less than 10 centimeters deep. Predominantly sand substrate with occasional 

embedded gravel or cobble. Formed as flow recedes and cuts across mid-channel and stream margin deposits such as 

point bars. 

Isolated pool Disconnected from streamflow but within the active channel. Isolated pools are usually associated with gravel bars and 

may be sustained by subsurface flow during late summer. Substrate is highly variable. 

1

The residual pool depth (RPD) is the difference between the maximum pool depth and the pool tail crest (PTC). The PTC is the deepest point at the downstream margin of a pool where the pool transitions into another habitat unit—analogous to the spout on a pitcher. The RPD is similar to the distance from the 

bottom of a pitcher’s spout to the pitcher’s base.

16 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

(2 units times five habitat types equals ten units total per reach 

if all habitat types were present in the reach). If the bottom of 

the reach was encountered before two units of each available 

habitat type were sampled, sampling resumed at the upstream 

end of the same reach. 

The length, mean width, and geographical coordinates 

of the approximate center of each sampled habitat unit were 

recorded. Runs longer than about 100 m were recorded as such 

rather than measured. Wetted stream width was recorded on a 

line bisecting each habitat unit, perpendicular to streamflow. 

Velocity was measured using dye or a floating object in pools, 

riffles, runs, and shoals. 

The aerial coverage (percentage of total area) of substrate 

and cover types was visually estimated within about 5-percent 

accuracy for each habitat unit (Quist and others, 2004). The 

minimum size of a patch of substrate or cover required to 

record its presence was 0.21 square meters (m2). A “trace” of 

substrate or cover was recorded where it was present but visually estimated to be less than 5 percent of the total area of a 

habitat type. Substrate types were roughly defined as silt, sand, 

gravel, cobble, boulder, or bedrock. Cover types were classified as aquatic vegetation, woody debris, undercut banks, and 

overhead cover according to Quist and others (2004). 

Habitat types were sampled on a monthly basis from 

May through October in 2004 to capture seasonal variation. After sampling was completed in 2004, it was noted 

that major changes in aquatic habitat were affected by three 

major streamflow periods. In 2005, sites were sampled three 

times—during pre-high flows, post-high flows, and low flows. 

Sampling was reduced further to a single sampling at each site 

in 2006 during the low-flow period. The low-flow period was 

considered the most valuable for assessing the effects of flow 

augmentation from CBNG development on aquatic habitat and 

the fish community. 

During the spring and summer of 2005, high-resolution 

GPS mapping was added to the modified WSA habitat 

sampling and was used to estimate the distribution of habitat 

types and total area of each habitat type throughout a range 

of streamflow. Working cooperatively, USGS and WGFD 

personnel used high-resolution GPS units to map pools, riffles, 

runs, shoals, backwater, isolated pools, and islands at each 

reach during three different flow conditions in May, July, and 

August. Two to three individuals mapped habitat features at 

each site over the course of a single day. Mapping involved 

walking the edge of water on both banks and the perimeter 

of identified habitat types within the channel and recording 

coordinates as needed to delineate each habitat unit. Habitat 

units estimated to be smaller than 10 m2 were not mapped. 

Streamflow was measured at each survey reach during or 

immediately after completion of mapping so that relations 

between streamflow and relative amounts of available habitat 

types (table 5) could be tested. Geographic information system 

(GIS) programs were used to generate maps of habitat units. 

Additional information about surveying equipment, methods, 

and results is available from the Wyoming Game and Fish 

Department (2007).
Methods of Sample Collection and Analysis 17

In 2006, a transect-based approach modeled after the 

EMAP protocol (Peck and others, 2003) was added to the 

modified WSA habitat assessment. At each site, as many as 

30 transects were established at even intervals throughout a 

reach length of about 111 m. At each transect, a GPS location 

was recorded, and wetted width was measured and divided 

by four to identify three locations for depth and habitat-type 

observations. The widths of shoals and islands were excluded 

from wetted width calculations. The widths of the dry emergent sandbars associated with shoals were included in the 

point-sample spacing calculations along each transect, which 

allowed depth measurements to occur on dry shoal areas. The 

widths of islands were excluded from point-sample spacing 

calculations to ensure no sample points were on islands. 

Measurements also were collected at left and right water’s 

edge for a total of five measurement locations per transect. 

The predominant habitat type was noted for each point along 

the transect. After transect measurements were completed, 

the number and location of pools, riffles, and backwater in the 

study reach were recorded by collecting a GPS point in the 

center of each habitat while returning upstream through the 

reach. 

Water Chemistry

During 2005 and 2006, onsite water-quality measurements of specific conductance, pH, water temperature, and 

dissolved oxygen were collected at each site using a multiprobe instrument. Turbidity measurements were made using 

a portable turbidity meter. Instruments were calibrated and 

measurements collected following procedures outlined in the 

USGS National Field Manual for the Collection of WaterQuality Data (U.S. Geological Survey, variously dated). 

Many sites chosen for ecological sampling also were 

part of a USGS water-chemistry monitoring network. At sites 

not included in the network, a grab sample was collected 

and processed in accordance with the USGS National Field 

Manual for the Collection of Water-Quality Data (U.S. 

Geological Survey, variously dated). Water-quality samples 

were sent to the USGS National Water Quality Laboratory 

(NWQL) in Denver for analysis of major ions. Two replicate 

samples were collected and analyzed for major ions. Results 

of the major ion analyses were published in the annual data 

reports for Wyoming and Montana and can be retrieved from 

the Web at http://pubs.usgs.gov/wdr/. Water-quality results, 

including onsite measurements, also are available on the Web 

at http://waterdata.usgs.gov/nwis.

Specific conductance, water temperature, and turbidity 

were collected by the WGFD in conjunction with fish and 

habitat assessments performed at the eight main-stem Powder 

River sites in Wyoming. Additional surface-water temperatures were recorded sporadically during the sample collection 

in an attempt to approximate daily maximum water temperature. The data for specific conductance, water temperature, and 

turbidity collected by the WGFD are available upon request to 

WGFD, Casper, Wyo.

Macroinvertebrates and Algae

Two types of macroinvertebrate samples were collected 

in 2005–06 that followed NAWQA protocols described by 

Moulton and others (2002). The first was the richest-targeted 

habitat (RTH) sample collected at sites where riffles were 

present (about three-fourths of the sites). RTH samples are 

intended to represent the habitat with highest taxa richness. 

Each RTH macroinvertebrate sample was a composite of five 

0.25-m2 samples collected from multiple riffles, where available, with a Slack sampler equipped with 500-micron (μm) 

mesh. The second type of macroinvertebrate sample was a 

qualitative multihabitat (QMH) sample collected at all sites 

and that served as the primary sample at sites where riffles 

were absent. QMH samples are intended to represent the taxa 

that are present throughout the sample reach. Each QMH 

sample was a timed collection (1-hour) from all of the multiple 

habitats identified in the sample reach, such as woody snags, 

macrophytes, pool sediment, and riffles. 

Macroinvertebrate samples were sent to the Buglab at 

Utah State University in Logan for taxonomic identification 

under BLM contract. A reference collection of identified 

macroinvertebrates is maintained at the Buglab. Identification 

of Chironomidae was subcontracted to Rhithron Associates, 

Inc. in Missoula, Mont. Replicate samples were collected at 

two sites and processed in the same manner as the environmental samples. 

Algae samples were collected at 26 sites within Wyoming 

and near the Wyoming-Montana State line during the summer 

of 2005 following NAWQA protocols described by Moulton 

and others (2002; table 2). Similar to the RTH habitat for 

macroinvertebrates, riffles were designated as RTH habitat for 

algae and were sampled where present (20 sites). The algae 

sample from riffles was a composite sample of 25 collections 

of periphyton scraped from rocks using an SG–92 sampler 

(cylinder with brush) to delineate a known area. At six of the 

sampling sites, no riffles were present, and therefore, the algae 

sample at those sites was collected from depositional-targeted 

habitat (DTH) in the euphotic zone of pools (Moulton and 

others, 2002). 

Algae samples were homogenized at each site, and 

aliquots were withdrawn for taxonomic identification and 

enumeration. At sites with riffles, aliquots also were withdrawn for analysis of chlorophyll-a and ash-free dry mass 

(AFDM). Algal taxonomy samples were sent to Ecoanalysts, 

Inc., Moscow, Idaho, for identification and enumeration 

under BLM contract. Chlorophyll-a and AFDM samples 

were preserved on dry ice and sent to the USGS NWQL for 

analysis. Algae DTH samples from pools were not analyzed 

for either chlorophyll-a or AFDM. Replicate samples of algae 

were collected at three sites for quality-assurance purposes and 
18 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

analyzed following the same procedures as the environmental 

samples. 

Macroinvertebrate and algal community data were 

analyzed in PRIMER (Clarke and Gorley, 2006). Macroinvertebrate abundance data were log transformed to approximate 

normality. Algal abundance data were transformed to relative 

abundance for analysis of diatoms and soft algae, and to presence/absence data for analysis of combined diatoms and soft 

algae in each sample, due to lack of density or biovolume data 

for the algae samples. Bray-Curtis similarity coefficients (Bray 

and Curtis, 1957) were computed to determine (dis-)similarity 

among samples. The similarity data then were used in nonmetric multidimensional scaling (NMDS) ordinations to determine 

relations among sites. Macroinvertebrate and algal metrics 

were calculated using procedures and attributes described by 

Cuffney (2003) and Porter (2008). 

Macroinvertebrate and algal community data also were 

tested for relations with environmental variables, including 

geographic, habitat, and water-quality variables. Geographic 

variables selected for testing with the biological communities 

were location (northing and easting), drainage area, elevation, and proximity-weighted human riparian disturbance. The 

geographic variables used in the PCA overlap with variables 

used in the Wyoming and Montana observed/expected (O/E) 

models, such as location (latitude and longitude), elevation, 

and drainage area (Hargett and others, 2007). 

Because the number of habitat and water-quality variables was too large to assess directly against the biological data, the habitat and water-quality data sets were each 

assessed separately through principal components analysis 

(PCA; Clarke and Gorley, 2006). Prior to running the PCA, 

the environmental data were transformed as needed and 

standardized. Habitat variables were selected from the EMAP 

reachwide measurements and from microhabitat variables that 

were measured at the point of the macroinvertebrate sample 

collections. Variables were tested for collinearity, and those 

that were highly correlated with the selected variables were 

removed from the analysis. Streamflow and water-quality 

variables were analyzed in a manner similar to habitat variables. Water-quality variables included onsite measurements 

of specific conductance, pH, water temperature, turbidity, 

and dissolved oxygen that were collected with the biological samples and major ion data. At sites where water samples 

were collected for analysis of major ions as part of this study, 

those major ion data were used. At other sites that are part of 

the USGS monitoring network (about one-half of the ATG 

sites), the major ion data collected for the network were 

retrieved from the USGS’s National Water Information System 

(NWIS). The major ion data selected from NWIS generally 

were from the sample collected most recently in time (within 

30 days) before collection of the biological sample. Alkalinity 

was automatically selected as a variable of interest because 

of potential toxicity of bicarbonate (Skaar and others, 2006) 

and use of alkalinity in the Wyoming O/E model (Hargett and 

others, 2007). 

The final set of environmental variables was analyzed 

using PCA to determine relations among the variables and 

sites and then tested for correlation with the macroinvertebrate 

communities using the BEST routine in PRIMER (Clarke and 

Gorley, 2006). The BEST routine tests multiple iterations of 

various combinations of the environmental variables to determine which combination of environmental variables is best 

correlated with the biological data as indicated by maximum 

values of Spearman’s rho (ρ). 

The O/E models and multimetric indices (MMIs) developed by the State of Wyoming (Hargett and others, 2005, 

2007) and the State of Montana (Montana Department of 

Environmental Quality, 2006) also were used to evaluate the 

macroinvertebrate data. Similar to other multivariate predictive models such as RIVPACS (Moss and others, 1987; Wright 

and others, 1993; Clarke and others, 2003) and its derivatives, the Wyoming and Montana O/E models are statewide 

macroinvertebrate-based predictive models that provide an 

assessment of biological condition by comparing the macroinvertebrate taxa observed at a site of unknown biological 

condition to the indigenous macroinvertebrate taxa expected to 

occur in the absence of human stress. Predictor variables, such 

as site latitude and longitude, substrate type, precipitation, air 

temperature, drainage area, elevation, and geology were used 

to construct the models. The expected macroinvertebrate taxa 

were derived from an appropriate set of reference sites that 

were minimally or least affected by human stress. The deviation of the observed from the expected taxa, known as the O/E 

score, is a measure of the compositional similarity expressed 

in units of taxa richness, and thus, is a community-level 

measure of biological condition. O/E scores near 1 indicate 

a favorable biological condition similar to expected conditions, whereas O/E scores less than 1 indicate some degree of 

biological degradation as a result of the absence of expected 

taxa. 

The MMIs developed by the States of Wyoming and 

Montana are similar in design to other MMIs such as the 

Index of Biotic Integrity (IBI; Kerans and Karr, 1994) in that 

both are regionally calibrated macroinvertebrate-based indices 

designed to evaluate the biological condition of wadeable 

perennial streams in Wyoming and Montana (Hargett and 

Zumberge, 2006; Montana Department of Environmental 

Quality, 2006). The Wyoming Stream Integrity Index (WSII) 

is an aggregation of seven individual indices developed for 

seven bioregions delineated within Wyoming. Similarly, three 

individual MMIs were developed for three bioregions in the 

State of Montana. The MMIs developed by Wyoming and 

Montana for their respective “Plains” bioregions were used 

in the evaluation of macroinvertebrate data collected at ATG 

sampling sites. Core macroinvertebrate metrics (for example, 

composition, structure, tolerance, and functional guilds) 

with moderate to high discrimination efficiencies (degree of 

separation between metric values of reference and degraded 

sites) within and across bioregions, a relatively consistent 

mode of response to human disturbance across bioregions, and 
Methods of Sample Collection and Analysis 19

no redundancy with other metrics were incorporated into the 

WSII and MMI. 

Biological condition as summarized by the Wyoming 

Plains WSII is calculated from seven metrics—Ephemeroptera 

richness, Trichoptera richness, total taxa, percentage of 

Trichoptera individuals (less Hydropsychidae) within the 

community, percentage of Ephemeroptera individuals (less 

Baetidae) within the community, percentage of collectorgatherer individuals, and the Hilsenhoff Biotic Index (Hilsenhoff, 1987). Most members of the families Baetidae and 

Hydropsychidae are considered tolerant to environmental 

stressors. Similarly, seven metrics compose the Montana 

MMI—Ephemeroptera, Trichoptera, and Plecoptera richness; 

percentage of Tanypodinae individuals within the community; 

percentage of Orthocladiinae individuals of the total Chironomid population within the community; predator taxa richness; 

and the percentage of collector/filterers. 

The majority of metrics from both indices (WSII and 

MMI) are expected to decline with increasing perturbation. 

The exceptions that are expected to increase with increasing 

perturbation are percentage of collector-gatherers, Hilsenhoff 

Biotic Index (Hilsenhoff, 1987), percentage of Orthocladiinae 

of the total Chironomid population within the community, and 

percentage of collector/filterers. The final index score for both 

the Wyoming and Montana MMI models is a mean of the individual metric scores where final scores decline with increased 

perturbation. 

Fish Communities

The methods used to collect fish samples varied depending on the site. EMAP methods (Peck and others, 2003) were 

used at all sites except on the main stem of the Powder River 

where modified WSA methods (Quist and others, 2004) were 

used. 

Fish community data from all of the sites were assessed 

using an IBI developed for small plains streams in Montana 

(Bramblett and others, 2005). The IBI contains 10 metrics 

that measure various aspects of community structure—species 

richness and composition, trophic composition, reproductive guilds, and fish abundance and condition. The IBI score 

assigned to a fish sample can range from 0 (worst) to 100 

(best) as determined by summing the scores from each of the 

10 individual metrics with scores that can range from 0 to 

10. As outlined by Bramblett and others (2005), creek chubs 

were included with invertivorous cyprinids, and the IBI score 

was manually set to 10 for any sample with less than 10 fish 

because the sample might not accurately reflect environmental 

conditions. Although the IBI was not intended for use in rivers 

with a drainage area as large as that of the Tongue River or 

Powder River, the IBI can be used to compare fish community 

structure among sites and between years within the main-stem 

Tongue River or Powder River (Bob Bramblett, Montana State 

University, written commun., May 27, 2008). The IBI scores 

from the Tongue and Powder Rivers should not, however, be 

compared to the smaller plains streams for which the IBI was 

designed. 

Basinwide Fish Community Assessment

Near the time of macroinvertebrate and algal sampling, 

fish communities at 35 sites (excluding those on the main-stem 

Powder River) were sampled by USGS once per year following EMAP techniques described by Peck and others (2003). 

Seining was the primary fish-collection method, although electrofishing from a boat or barge was used at sites on the main 

stem of the Tongue River and some of the larger tributaries. 

The reach length for fish sampling was defined as 40 times the 

mean wetted channel width, with a minimum reach length set 

at 200 m and maximum at 1,000 m. Multiple seine hauls were 

completed within each reach to determine relative abundance 

of fish species. 

Voucher specimens of fish, particularly Cyprinidae 

(minnows), were collected as per the fish taxonomy quality-assurance plan (Walsh and Meador, 1998) and sent to 

Dr. Robert Bramblett at Montana State University in Bozeman 

for taxonomic confirmation. The Museum of Southwestern 

Biology at the University of New Mexico in Albuquerque 

was selected as the long-term repository for the fish-voucher 

specimens. 

Main-Stem Powder River Fish Community 

Assessment

Fish community samples from 12 sites on the main-stem 

Powder River were collected following modified WSA protocols. WGFD collected the samples at eight main-stem Powder 

River sites and one miscellaneous site on the South Fork 

Powder River in Wyoming, and USGS collected the samples at 

four main-stem Powder River sites in Montana. Fish sampling 

at the sites in Wyoming generally occurred on the same 

schedule as the modified WSA aquatic habitat surveys—six 

times in sampling conducted by the WGFD in 2004 (Wyoming 

Game and Fish Department, 2007) and three times in 2005 and 

once in 2006 for the study described in this report. Exceptions 

to the general pattern of sampling in Wyoming were that the 

South Fork of the Powder River was sampled only in 2004 and 

the site below Burger Draw was sampled in 2005–06 but not in 

2004. Fish sampling at the four main-stem Powder River sites 

in Montana occurred at site P12, twice in 2005 and once in 

2006; sites P13 and P17, once each in 2005 and in 2006; and 

site P18, once in 2005. 

The WSA fish sampling methodology documents basic 

presence and absence information for fish species and was 

designed as a framework for comparing current fish assemblages with expected unaltered native communities and for 

interpreting fish community changes (Quist and others, 2004). 

The seining methods used in this study, however, are best 

suited to small-bodied fish. Large-bodied fish known to be 

present in the main-stem Powder River, such as adult sauger 
20 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

(Sander canadense), shovelnose sturgeon (Scaphirhynchus 

platorynchus), and others, were not targeted by seining, and 

therefore, their abundance in samples might not be reflective 

of their true relative abundance in the river. The distribution 

of large-bodied fishes in the main-stem Powder River was 

addressed separately (Wyoming Game and Fish Department, 

2007). Each habitat unit sampled was seined repeatedly until 

no new species were captured (minimum of two seine hauls). 

Data from individual seine hauls were recorded separately. All fish were identified using characteristics determined 

onsite from dichotomous keys (Brown, 1971; Baxter and 

Stone, 1995; Pflieger, 1997) and enumerated by species or 

group. The smallest and largest individuals of each species 

or group sampled from each habitat unit were measured for 

total length. Fish vouchers were retained for identification or 

confirmation from sites in Wyoming and Montana, although 

the sampling process differed slightly between the States in 

part because the 6.4-mm mesh-opening size of the seines 

used by USGS at Montana sites was larger than the 4.8-mm 

mesh-opening size of the seines used by WGFD at Wyoming 

sites. At Wyoming sites, groups of juvenile fish (age-0) too 

small for field identification and groups of the genus Hybognathus were retained for laboratory identification. All age-0 

fish and subsamples of Hybognathus spp. (number of samples 

(n) ≤20) collected in Wyoming were retained and identified at 

the Larval Fish Laboratory at Colorado State University, Fort 

Collins, Colo. Voucher specimens of each species present at 

Wyoming sites were curated by the Museum of Southwestern Biology in Albuquerque. At the Montana sites, voucher 

specimens of each species, including Hybognathus spp., also 

were retained, but the vouchers were sent to Montana State 

University in Bozeman for species verification. Larval fish 

were treated as part of regular samples at Montana sites. All 

fish that were retained were fixed in a 10-percent formalin 

solution. 

Rarefaction curves were developed for all sites on the 

main-stem Powder River to allow consistent and standardized methods for comparison of species richness among sites 

despite varied sampling effort (Kwak and Peterson, 2007). 

Effort was roughly equal among surveys, but the number of 

surveys varied among some sites because of the addition or 

deletion of sites during study years and minor sample scheduling irregularities within the cumulative data set. For example, 

site P4 was not sampled in 2004, and site P5 was sampled 

an additional time in 2004. Therefore, the rarefaction technique was used to evaluate expected species richness among 

sites using all data, standardized to equal effort. Rarefaction 

extrapolates species richness from a given sample to lesser 

sample sizes on the basis of species composition within a 

given sample. 

The overall slope of a rarefaction curve relates a general 

trend among data for a site that indicates the “thoroughness” 

of sampling species diversity (Kwak and Peterson, 2007). 

Steep rarefaction curves indicate relatively high species 

diversity and (or) that the sampling effort was inadequate to 

accurately reflect species richness. Flat rarefaction curves indicate relatively low species diversity and (or) that the species 

assemblage was sampled thoroughly with the effort expended. 

The results of applying the rarefaction technique also provide 

a visual representation of sampling efficiency as it relates to 

identifying species richness at all sites. These data are useful 

for determining the sampling effort required for adequate 

monitoring and future research.

Data distributions were tested for normality, using the 

Shapiro-Wilk normality test (Helsel and Hirsch, 2002), before 

performing analysis of variance (ANOVA). The equality of the 

variances in the ANOVA was tested using Bartlett’s test. The 

analyses were performed in Statistix, version 7 (http://www.

statistix.com/) at P <0.05 to indicate significance. 

Ancillary Investigations

For comparative purposes, emphasis was placed on 

ancillary samples collected from ATG sites under low-flow, 

summer conditions using collection and analysis methods as 

similar as possible to those used for the ATG investigation. 

Ancillary data were available from three programs—NAWQA, 

the USGS Wyoming Water Science Center (WWSC) monitoring network (network), and a 1980–81 WWSC project investigation (project; table 6). 

Macroinvertebrate and algae samples from the NAWQA 

Program for 1999-2007 and the WWSC monitoring network 

for 2002 generally were collected following the same 

NAWQA protocols used for collection of the ATG samples. 

The 1999 NAWQA chlorophyll-a data were omitted from this 

report because the laboratory analytical method was different 

than that used for the remainder of the samples. The ancillary 

data from the WWSC monitoring network are available from 

the USGS ATG project Web site (http://wy.water.usgs.gov/). 

Macroinvertebrate samples from the 1980–81 investigative project were collected with a Surber sampler following 

methods described by Peterson (1990). The 1980–81 periphyton samples were collected by scraping algae from areas of 

hard surfaces present in the reach, such as rocks and logs. 

Ancillary data from the 1980–81 project used in this report, 

as well as other algae and macroinvertebrate data collected for 

the 1980–81 project from other sites in the PRB, are available 

from the ATG project Web site (http://wy.water.usgs.gov/). 
Table 6. Sampling sites with ancillary data for macroinvertebrates and algae, Powder River Structural 

Basin, Wyoming and Montana.

[Network, Wyoming Water Science Center monitoring network; Project, Wyoming Water Science Center project; NAWQA, 

National Water-Quality Assessment Program]

Site number (fig. 1) Abbreviated stream name Sampling program Dates of ancillary data

T9 Tongue River at State line Network 2002

P10 Clear Creek Network 2002

P14 Little Powder River at Highway 59 Project 1980–81

P15 Little Powder River above Dry Creek Project and NAWQA 1980–81, 1999–2007

P18 Powder River near Locate NAWQA 1999

C3 Cheyenne River near Dull Center Project 1980–81

1

C6 Cheyenne River at Riverview Network 2002

B1 Belle Fourche River Project 1980–81

1

Ancillary data site is located at U.S. Geological Survey gaging station 06386400 (http://waterdata.usgs.gov/nwis), several 

kilometers upstream from site C6.

Ecological Assessment 21

Ecological Assessment

The ecological assessment consists of four main parts: 

habitat, macroinvertebrates, algae, and fish communities. The 

“Implications” section that follows the ecological assessment 

includes comparison among selected biological communities. 

Habitat Assessment

Results of habitat measurements collected at all 

47 sampling sites in the PRB and including the main-stem 

Powder River followed the EMAP protocol or a modified 

version of it and are described in the section “Habitat Characteristics of Streams in the Powder River Structural Basin.” 

Results of habitat measurements collected at eight sites on the 

main-stem Powder River followed a modified WSA protocol 

and are presented in the section “Habitat Characteristics of the 

Main-Stem Powder River in Wyoming.”

Habitat Characteristics of Streams in the Powder 

River Structural Basin

Reach-scale habitat measurements collected at all 

47 sampling sites in the PRB are described in this section, 

but the reader should be aware that methods used at the 12 

sites along the main-stem Powder River varied slightly from 

methods used at the other 35 sites and could affect results for 

these 12 sites. 

Channel Characteristics

The geometry of a stream channel is a function of streamflow (quantity and frequency), streambed and bank materials 

and composition (vegetative cover), and the character of the 

sediment transported through the stream section (Leopold and 

others, 1992). Any changes of these variables can cause modifications to the channel characteristics. 

Mean wetted widths in the study area (table 7) ranged 

from 0.90 m at Squirrel Creek at mouth (site T7) to 52.4 m 

at Powder River below Little Powder River (site P17). Mean 

wetted widths on the Cheyenne and Belle Fourche Rivers and 

including all of the tributaries were less than 10 m except at 

the two largest tributaries, Goose Creek (site T2, 16.4 m) and 

Clear Creek (site P10, 19.7 m). Mean wetted width generally 

increased in the downstream direction along the Tongue and 

Powder Rivers. The Tongue River had an increase of about 

6 m between sites T1 (Tongue River at Monarch, mean wetted 

width = 19.0 m) and T18 (Tongue River below Brandenberg 

Bridge, mean wetted width = 25.4 m), and the Powder River 

had the greatest increase in mean wetted width of about 37 m 

between sites P1 (Powder River above Salt Creek, mean 

wetted width = 14.1 m) and P18 (Powder River near Locate, 

mean wetted width = 51.1 m). 

Mean water depths ranged from a minimum of 2.3 centimeter (cm) at Caballo Creek (site B2) to a maximum of 55 cm 

at Prairie Dog Creek (site T8). Caballo Creek had no flow 

during sampling, and the reach only had two shallow pools 

making up less than 50 percent of its length. Prairie Dog Creek 

had the maximum mean water depth because of nearly vertical 

bank angles along almost the entire reach in contrast to other 

sites with sloping banks and water depths of zero at the ends 

of the transects. 

Mean thalweg depths were deepest on the main-stem 

Tongue River with a mean of 88 cm for depths from six sites. 

Although several tributary stream sites have shallow mean 

thalweg depths, the mean thalweg depth for tributary streams 

was 39 cm, which is 3 cm deeper than the mean thalweg depth 

of 36 cm on the Powder River. Although all the stream reaches 

included in this study were considered wadeable, some pools 
Table 7. Summary of channel characteristics measured at sampling sites in the Powder River Structural Basin, Wyoming and Montana, 2005.—Continued

[m, meter; cm, centimeter; m/km, meters/kilometers; NC, measurements not collected; NA, measurement not available due to missing data; NA1, measurements not collected properly]

Site 

number 

(fig. 1)

Mean 

wetted 

width

(m)

Mean 

water 

depth

(cm)

Mean 

thalweg 

depth

(cm)

Maximum 

measured 

depth

(cm)

Mean 

bank 

angle

(degrees)

Median 

bank 

angle

(degrees)

Mean 

bankfull 

height

above 

thalweg

(m)

Mean 

bankfull 

height 

above water surface 

(m)

Mean 

bankfull 

width

(m)

Width-todepth 

ratio

Mean 

incised 

height

above 

thalweg 

(m)

Mean 

incised 

height

(m)

Mid-stream 

canopy 

density

(percent)

Bank 

canopy 

density

(percent)

Reach 

gradient

(m/km)

Main-stem Tongue River

T1 19.0 35 63 177 47 16 0.98 0.35 22.3 22.9 1.58 0.95 17 81 2.50

T5 30.0 35 88 142 30 23 1.42 .54 37.1 26.2 3.04 2.16 .3 8.6 7.51

T9 34.3 35 77 173 30 25 1.36 .59 36.8 27.0 2.12 1.35 .4 59 .73

T10 29.2 39 101 205 35 23 1.64 .64 33.1 20.1 2.34 1.34 .0 7.5 1.44

T14 26.7 37 186 200 46 39 1.56 .70 27.1 17.4 2.87 2.01 3.7 78 1.03

T18 25.4 44 112 210 48 33 1.92 .80 33.2 17.3 3.08 1.95 7.1 63 1.08

Main-stem Powder River

P1 14.1 7.5 22 91 11 7 1.35 1.13 34.7 25.7 1.77 1.55 0.4 5.2 0.93

P2 15.0 7.5 23 53 11 7 1.49 1.26 42.7 28.6 1.93 1.70 .6 5.7 21.1

P3 26.6 4.3 20 43 19 14 1.38 1.17 42.4 30.8 1.78 1.58 .5 2.7 .30

P4 21.9 6.5 26 53 7 4 1.03 .77 46.2 45.0 1.61 1.35 .4 3.6 1.36

P5 37.7 8.7 32 60 22 10 1.25 .93 40.1 32.2 2.97 2.65 .7 2.9 .33

P8 41.4 17 29 84 34 24 1.13 .84 51.9 45.7 1.59 1.30 .0 3.9 2.90

P9 29.4 20 41 80 26 27 .92 .51 41.7 45.2 1.38 .97 .4 7.0 21.0

P11 37.5 28 49 200 27 22 1.54 1.05 50.8 33.1 2.24 1.75 .1 5.0 21.0

P12 47.0 18 37 130 11 8 .94 .58 61.4 65.0 1.41 1.04 1.7 37 21.3

P13 30.8 23 60 152 22 15 1.69 1.09 52.4 31.0 2.50 1.90 .0 3.7 21.0

P17 52.4 9.0 50 125 31 33 1.76 1.26 74.5 42.2 2.30 1.80 .0 .3 20.9

P18 51.1 14 40 79 13 11 1.53 1.14 75.7 49.3 2.22 1.83 .0 .2 21.0

Cheyenne and Belle Fourche Rivers, Rosebud Creek, and all tributary streams

R1 4.40 28 66 113 39 41 1.03 0.37 5.50 5.35 1.90 1.25 56 90 0.40

R2 4.97 13 26 59 32 21 .59 .34 7.23 12.2 1.07 .82 34 78 .87

T2 16.4 28 62 129 37 31 1.27 .65 20.4 16.0 1.72 1.10 5.8 76 7.51

T3 2.20 15 31 50 40 33 .74 .43 4.35 5.89 1.28 .96 14 15 8.45

T4 1.85 19 31 45 22 23 .95 .64 5.94 6.23 1.85 1.54 5.1 6.2 4.81

T6 1.64 14 27 51 20 15 .57 .31 4.12 7.17 .90 .64 3.5 1.6 2.42

22 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 7. Summary of channel characteristics measured at sampling sites in the Powder River Structural Basin, Wyoming and Montana, 2005.—Continued

[m, meter; cm, centimeter; m/km, meters/kilometers; NC, measurements not collected; NA, measurement not available due to missing data; NA1, measurements not collected properly]

Site 

number 

(fig. 1)

Mean 

wetted 

width

(m)

Mean 

water 

depth

(cm)

Mean 

thalweg 

depth

(cm)

Maximum 

measured 

depth

(cm)

Mean 

bank 

angle

(degrees)

Median 

bank 

angle

(degrees)

Mean 

bankfull 

height

above 

thalweg

(m)

Mean 

bankfull 

height 

above water surface 

(m)

Mean 

bankfull 

width

(m)

Width-todepth 

ratio

Mean 

incised 

height

above 

thalweg 

(m)

Mean 

incised 

height

(m)

Mid-stream 

canopy 

density

(percent)

Bank 

canopy 

density

(percent)

Reach 

gradient

(m/km)

Cheyenne and Belle Fourche Rivers, Rosebud Creek, and all tributary streams—Continued

T7 0.90 11 18 40 63 61 0.48 0.30 2.82 5.86 0.86 0.68 1.1 4.3 7.21

T8 4.34 55 78 117 97 84 1.19 .41 5.03 4.22 1.57 .79 9.1 99 1.91

T11 3.39 17 31 55 65 68 .71 .40 5.97 8.42 .96 .65 23 55 5.15

T12 2.67 17 24 78 47 34 .64 .40 5.37 8.39 1.61 1.37 1.4 6.8 6.15

T13 5.63 19 32 72 70 70 .72 .40 7.15 9.96 1.52 1.20 11 55 1.85

T15 3.37 12 125 45 24 20 .66 .41 6.94 10.5 3.66 NA1 8.6 13 1.11

T16 5.45 14 134 55 32 32 .71 .36 8.70 12.2 3.71 NA1 14 15 1.75

T17 5.55 28 58 56 70 90 .62 .05 5.98 9.58 3.62 NA1 3.1 43 .40

T19 6.19 10 25 93 29 21 .65 .40 11.2 17.3 .82 .57 5.0 18 3.00

C1 4.36 12 22 64 44 38 .82 .60 11.3 13.9 1.17 .95 .1 1.1 4.51

C2 7.53 21 30 75 50 64 .66 .36 16.2 24.5 .66 .36 2.9 5.9 42.1

C3 9.97 14 NC 58 50 43 NA .72 18.9 NA NA 1.21 1.5 5.0 41.44

C4 3.40 17 52 101 42 24 1.20 .68 12.0 9.99 1.20 .68 .1 1.5 6.82

C5 3.44 13 NC 50 53 43 NA .83 3.92 NA NA 2.60 3.8 8.3 41.18

C6 7.37 11 NC 59 23 18 NA .39 11.7 NA NA .61 .4 1.8 41.37

B1 5.95 14 5.9 64 39 34 .47 .41 11.9 25.5 1.04 .98 .2 3.7 1.42

B2 8.33 2.3 1.1 19 16 8 .63 .62 17.6 28.0 1.49 1.48 4.0 7.2 .83

P6 8.57 13 68 153 75 81 1.72 1.05 12.0 6.97 2.58 1.90 2.4 8.0 1.25

P7 9.01 31 58 110 41 40 1.48 .90 12.2 8.22 2.06 1.47 .2 5.8 3.74

P10 19.7 25 63 155 34 25 1.24 .61 24.6 19.8 2.34 1.71 3.5 53 1.44

P14 2.55 21 31 55 61 68 .82 .51 5.36 6.58 2.19 1.88 5.0 8.1 3.08

P15 6.01 32 52 98 61 60 1.37 .85 9.08 6.64 1.89 1.37 .6 9.4 1.26

P16 5.35 41 61 101 67 90 1.58 .97 7.48 4.74 .87 .26 .8 7.0 .35

1Indicates this number was calculated with an incomplete data set because of nonwadeable pools.2Estimate from U.S. Geological Survey 1:24,000-scale topographic maps.3Used the bankfull height, which is the minimum this measurement can be.4Measurements collected by Wyoming Department of Environmental Quality.

Ecological Assessment 23
24 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

were not wadeable, and measurements were not collected. The 

mean thalweg depths associated with these nonwadeable pools 

are noted in table 7 and are biased low. 

The slope or angle of a streambank is important when 

determining the ability of a bank to resist erosion. Generally, the steeper the angle of the bank, the more prone it is to 

erosion and even failure. However, many other variables such 

as bank-material composition, stratigraphy, bank vegetation, 

and root density contribute to streambank stability (Rosgen, 

1996). Mean bank angles (table 7) ranged from 7 degrees for 

the Powder River below Burger Draw (site P4) to 97 degrees 

for Prairie Dog Creek (site T8). Sites on the main-stem 

Powder River (sites P1-P5, P8, P9, P11-P13, P17, and P18) 

generally had the shallowest bank angles, whereas tributaries 

to the Powder River (sites P6, P7, P10, and P14-P16) had the 

steepest angles (fig. 5). Although the ranges of bank angles 

varied, the sites on the main-stem Tongue River (sites T1, T5, 

T9, T10, T14, and T18), Tongue River tributaries (sites T2-T4, 

T6-8, T11-T13, T15-T17, and T19) and Rosebud Creek and 

the Cheyenne and Belle Fourche River drainages (sites R1, 

R2, C1-C6, B1, and B2) all had median bank angles (fig. 5) of 

approximately 40 degrees.

Mean bankfull height above thalweg ranged from about 

0.5 m at several of the tributary sites (table 7) to about 1.92 m 

at Tongue River below Brandenberg Bridge (site T18). The 

tributaries to the Tongue River and the category including 

Rosebud Creek and the Cheyenne and Belle Fourche Rivers 

had the lowest median bankfull height (near 0.7 m; fig. 5), 

whereas the Tongue River, Powder River, and Powder River 

tributaries all had median bankfull heights almost twice as 

high, near 1.4 m. 

Mean bankfull widths (table 7) ranged from 2.82 m at 

Squirrel Creek at mouth (site T7) to 75.7 m at Powder River 

near Locate (site P18). Mean bankfull widths at tributary sites 

were less than 20 m except at Goose Creek (site T2) and Clear 

Creek (site P10), which had mean bankfull widths of 20.4 and 

24.6 m, respectively. The main-stem Powder River had the 

greatest variability in bankfull width (fig. 5), ranging from 

34.7 m at Powder River above Salt Creek (site P1) to 75.7 m at 

Powder River near Locate (site P18). 

The geometry of stream channels can be described using 

a ratio of mean width to mean depth (W/D) as related to the 

channel cross section at bankfull stage (Rosgen, 1996). The 

W/D ratio varies with channel slope, streamflow, channel 

roughness, erosion resistance of bed and bank material, and 

degree of entrenchment. Channel geometry is directly affected 

by changes in streamflow and sediment regimes. Thus, the 

W/D ratio can be symptomatic of both natural and humaninduced changes to the stream’s flow and sediment regimes 

but cannot by itself be used as an indicator of specific stressors. Using reach means for bankfull height above thalweg and 

bankfull width, W/D ratios ranged from 4.22 at Prairie Dog 

Creek (site T8) to 65.0 at Powder River at Moorhead (site P12; 

table 7). W/D ratios generally were lowest at tributary sites 

and highest on the main-stem Powder River (fig. 6). The mainstem Powder River had large variability in W/D ratios, often 

having ratio differences of 10 or more between sites (table 7). 

Variations in the W/D ratio can indicate differences in streamflow and (or) sediment load among stream reaches (Chorley, 

1984). 

Stream incision, or the vertical distance between the 

thalweg and the level of the first terrace above the active flood 

plain, can be a fairly sensitive indicator of changes within a 

drainage because stream channels naturally incise (downcut) 

and aggrade (raise streambed by sediment deposition) as 

weather patterns change and variations occur in annual flows 

and sediment loads (Peck and others, 2003). The balance that 

stream systems naturally achieve can be altered by external 

factors such as human activities that increase or decrease the 

“natural” sediment supply or the stream’s ability to transport 

sediment (Chorley and others, 1984). Although channel stability may not be evident at the time of sampling, monitoring 

the incision over time will provide an indication of whether a 

stream reach is eroding or aggrading. Stream incision heights 

above thalweg (table 7) ranged from a mean of 0.66 m at 

Antelope Creek (site C2) to about 3 m at Tongue River below 

Youngs Creek (site T5) and Tongue River below Brandenberg 

Bridge (site T18). The main-stem Tongue River (fig. 5) had 

the highest median incision height (about 2.5 m), whereas 

Tongue River tributaries had the lowest median incision height 

(about 1.0 m). Powder River tributaries had a median incised 

height of about 2.1 m, which is about 0.2 m higher than the 

median incised height on the main-stem Powder River.

Geomorphic units (riffles, runs, pools) were recorded 

at 27 sampling sites during habitat data collection and 

are presented in figure 7 as a percentage of reach. Of the 

27 sites where geomorphic units were measured, four sites or 

15 percent did not have a riffle present within the reach, two 

sites did not have a run, and two sites had no pools.

The main-stem Powder River generally had the least 

total fish cover, whereas fish cover was variable among the 

tributary streams (table 8). Total fish-cover percentages at 

sites on the main-stem Powder River ranged from 1.0 percent 

for the Powder River below Crazy Woman Creek (site P8) to 

20.1 percent above Pumpkin Creek (site P3). Among other 

streams in the study area, the largest percentages of fish cover 

occurred in Rosebud Creek (sites R1 and R2), two of the 

three sites on Otter Creek (sites T15 and T16), and the Little 

Powder River at Highway 59 (site P14). The Little Powder 

River drainage had the greatest variability in total fish cover 

with a maximum of 122 percent cover at Little Powder River 

at Highway 59 (site P14), decreasing to 18 percent at Little 

Powder River above Dry Creek (site P15) and 10 percent at 

Biddle (site P16). 

Aquatic macrophytes, brushy debris, overhanging vegetation, undercut banks, and boulders were the most common fish 

cover identified (fig. 8). Manmade structures were the least 

common fish cover (fig. 8) and were noted at only seven sites, 

four of which were on the main-stem Tongue River. Filamentous algae were identified at many sites on the Tongue River 

and its tributaries but were rarely noted at sites in other drainages. Filamentous algae need a stable substrate and flow to 
Figure 5. Streambank angle, bankfull height, bankfull width, and incised height by stream drainage, Powder River Structural Basin, 

2005.

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

44 6 13 12 6 7

MEAN BANKFULL WIDTH, IN 

METERS

0

20

40

60

80

100

47 6 13 12 6 10

0

0.5

1.0

1.5

2.0

2.5

44 6 13 12 6 7

0

20

40

60

80

100

120

47 6 13 12 6 10

ALL SITES

MAIN-STEM TONGUE RIVER

TONGUE RIVER TRIBUTARIES

MAIN-STEM POWDER RIVER

POWDER RIVER TRIBUTARIES

ROSEBUD CREEK,

CHEYENNE RIVER, AND 

BELLE FOURCHE RIVER

ALL SITES

MAIN-STEM TONGUE RIVER

TONGUE RIVER TRIBUTARIES

MAIN-STEM POWDER RIVER

POWDER RIVER TRIBUTARIES

ALL SITES

MAIN-STEM TONGUE RIVER

TONGUE RIVER TRIBUTARIES

MAIN-STEM POWDER RIVER

POWDER RIVER TRIBUTARIES

ALL SITES

MAIN-STEM TONGUE RIVER

TONGUE RIVER TRIBUTARIES

MAIN-STEM POWDER RIVER

POWDER RIVER TRIBUTARIES

ROSEBUD CREEK,

CHEYENNE RIVER, AND 

BELLE FOURCHE RIVER

MEAN BANK ANGLE, IN DEGREES

MEAN BANKFULL HEIGHT ABOVE THALWEG, IN METERS MEAN INCISED BANK HEIGHT ABOVE THALWEG, IN METERS

ROSEBUD CREEK,

CHEYENNE RIVER, AND 

BELLE FOURCHE RIVER

ROSEBUD CREEK,

CHEYENNE RIVER, AND 

BELLE FOURCHE RIVER

10 Number of values 

EXPLANATION 

Data value less than or equal to 1.5 times the 

 interquartile range outside the quartile

75th percentile

Median

25th percentile

Outlier data value less than or equal to 3 and 

 more than 1.5 times the interquartile range 

 outside the quartile

Outlier data value greater than 3 times the 

 interquartile range outside the quartile

Interquartile range

Ecological Assessment 25
0

10

20

30

40

50

60

70

80

90

100

R1

R2

T1

T2T3T4

T5

T6

T7T8

T9

T10

T11T12

T13

T14

T15

T16

T17

T18

T19

P10

P13

P12

P17

P18

C2

GEOMORPHIC UNITS, PERCENTAGE OF REACH

Pool

Run

Riffle

EXPLANATION

SITE NUMBER

Figure 6. Width-to-depth ratios by stream drainage, Powder River Structural Basin, 2005.

TRIBUTARY

SITES

WIDTH-TO-DEPTH RATIO

0

10

20

30

40

50

60

70

80

Number of values 

EXPLANATION 

Data value less than or equal to 1.5 times the 

 interquartile range outside the quartile

75th percentile

Median

25th percentile

MAIN-STEM

TONGUE 

RIVER

MAIN-STEM

POWDER 

RIVER

6 12 26

44

Interquartile range

Outlier data value less than or equal to 3 and 

 more than 1.5 times the interquartile range 

 outside the quartile

ALL SITES

44

Figure 7. Geomorphic channel units as a percentage of reach at 27 sampling sites, Powder River Structural Basin, 2005.

26 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 8. Fish cover identified during habitat sampling, Powder River Structural Basin, Wyoming and Montana, 2005.—Continued

[Total fish cover may exceed 100 percent due to use of range categories during sampling]

Site 

number

(fig. 1)

Fish cover, in percent

Filamentous 

algae

Aquatic 

macrophytes

Woody 

debris

Brushy 

debris

Live trees 

or roots

Overhanging 

vegetation

Under-cut 

banks Boulders

Manmade 

structures

Total fish 

cover 

Main-stem Tongue River

T1 0 21.0 4.6 5.8 5.4 7.9 6.3 8.8 5.6 65.4

T5 5.0 5.0 .5 1.4 1.8 3.6 0 0 0 17.3

T9 0 25.0 2.3 0 0 4.5 1.8 8.6 2.7 44.9

T10 13.2 13.6 .0 0 0 4.1 .5 5.0 .9 37.3

T14 2.7 5.0 3.0 3.7 4.3 11.7 2.7 0 0 33.1

T18 5.0 6.8 4.1 5.0 8.6 20.2 3.2 0 .5 53.4

Main-stem Powder River

P1 0 0.5 0 1.0 1.0 1.0 0.5 9.3 0 13.3

P2 0 0 1.0 8.5 0 2.5 0 0 0 12.0

P3 0 0 8.4 8.9 0 2.3 0 .5 0 20.1

P4 0 8.0 0 .5 0 0 0 .5 0 9.0

P5 0 .5 .5 0 0 .5 .5 0 .5 2.5

P8 0 0 .0 .5 0 0 .5 .0 0 1.0

P9 0 0 2.5 2.5 0 0 0 0 0 5.0

P11 0 0 .5 1.0 0 0 .5 8.0 0 10.0

P12 0 0 0 1.3 0 0 0 9.7 0 11.0

P13 0 .6 1.3 0 0 1.9 0 9.1 0 12.9

P17 0 0 4.4 .6 0 0 0 0 0 5.0

P18 0 .6 0 0 0 0 0 8.1 0 8.7

Cheyenne and Belle Fourche Rivers, Rosebud Creek, and all tributary streams

R1 6.4 68.0 14.8 29.1 17.7 25.5 0 0 0 161.5

R2 .9 12.3 0 1.4 7.3 43.4 .9 44.5 0 110.7

T2 0 6.8 .5 2.7 2.3 1.4 .5 19.8 0 34.0

T3 4.1 18.2 3.6 10.2 1.8 14.8 .5 .9 0 54.1

T4 0 33.2 0 2.3 0 57.5 .5 0 0 93.5

T6 5.0 82.0 0 .5 0 0 .0 0 0 87.5

T7 0 9.3 0 .9 0 13.6 1.4 0 0 25.2

T8 0 0 0 0 0 6.8 5.0 6.1 0 17.9

T11 .5 41.1 0 .5 5.9 19.5 2.7 2.3 0 72.5

T12 6.4 54.3 0 .5 0 17.0 3.2 0 0 81.4

T13 14.8 36.8 0 1.4 .9 17.0 2.3 0 0 73.2

T15 4.5 29.1 0 62.3 0 64.1 .9 0 8.0 168.9

T16 82.0 13.4 .5 3.6 0 70.7 0 5.5 0 175.7

T17 5.0 20.0 1.4 5.9 .5 12.5 2.7 .9 0 48.9

T19 5.0 5.0 0 0 0 0 0 0 0 10.0

C1 0 50.9 0 0 .5 0 .5 0 0 51.9

Ecological Assessment 27
Figure 8. Presence of fish cover identified in the Powder River Structural Basin, 2005.

0

5

10

15

20

25

30

35

40

Filamentous 

algae

Aquatic 

macrophytes

Woody 

debris

Brushy 

debris

Roots Overhanging 

vegetation

Undercut 

banks

Boulders Manmade 

structures

FISH COVER CATEGORIES

NUMBER OF SITES WHERE COVER TYPE OCCURRED

Rosebud Creek and Cheyenne

 and Belle Fourche Rivers

Powder River tributaries

Main-stem Powder River

Tongue River tributaries

Main-stem Tongue River

EXPLANATION

Table 8. Fish cover identified during habitat sampling, Powder River Structural Basin, Wyoming and Montana, 2005.—Continued

[Total fish cover may exceed 100 percent due to use of range categories during sampling]

Site 

number

(fig. 1)

Fish cover, in percent

Filamentous 

algae

Aquatic 

macrophytes

Woody 

debris

Brushy 

debris

Live trees 

or roots

Overhanging 

vegetation

Under-cut 

banks Boulders

Manmade 

structures

Total fish 

cover 

Cheyenne and Belle Fourche Rivers, Rosebud Creek, and all tributary streams—Continued

C2 0 87.5 0 2.3 0 0.5 0.5 0 0 90.8

C3 0 28.0 0 2.3 0 0 1.8 .9 0 33.0

C4 0 22.0 0 .9 0 .9 7.3 20.9 0 52.0

C5 0 15.5 0 0 0 0 1.4 .5 0 17.4

C6 0 15.0 .0 1.8 .5 .5 .5 .5 0 18.8

B1 0 77.3 0 0 0 0 3.2 0 0 80.5

B2 0 22.7 2.7 13.9 0 .5 .9 0 0 40.7

P6 0 2.3 .9 2.3 .5 3.2 4.5 2.3 0 16.0

P7 0 8.2 0 0 0 2.7 2.3 4.1 0 17.3

P10 0 5.0 0 0 .9 2.7 1.8 14.8 0 25.2

P14 0 87.5 0 8.4 8.6 17.0 0 .5 0 122.0

P15 0 4.5 0 1.4 3.6 .5 5.5 2.3 .5 18.3

P16 1.8 0 0 .5 0 4.5 2.3 .9 0 10.0

28 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Ecological Assessment 29

thrive, so it is not surprising that they are mostly absent in the 

Powder River where homogenous mobile silt and sand are the 

dominant substrates and in the Cheyenne and Belle Fourche 

drainages where flow often is intermittent.

Substrate Characteristics

Streambed substrate is an important variable to consider 

when evaluating aquatic habitat. Although substrates are relatively sensitive to human effects, they are not affected greatly 

by small changes in flow as are the other variables determining aquatic habitat (Fitzpatrick and Giddings, 1995). Substrate 

size and embeddedness should be similar between annual 

visits unless there has been some major change to the system. 

This change could be of human origin or could be natural, 

such as recent major flooding. If sampling occurs before a 

stream has time to reach equilibrium after flooding, then variability in the data likely will be because of timing of sampling 

with respect to flooding and not necessarily human-induced 

change (Fitzpatrick and Giddings, 1995). 

The number of substrate size estimates collected under 

the EMAP protocol generally was either 55 particles from 

the transect data or 105 particles if both transect particles 

and intermediate points between transects were measured. 

To determine the validity of comparing reachwide substrate 

data from sites with 55 measured particles to those with 

105 measured particles, a Wilcoxon rank sum test was 

conducted using data from each of the 26 sites with complete 

data sets. All of the P values were greater than 0.05; therefore, 

the null hypothesis that the two data sets (55 or 105 measurements) were not different from each other was accepted. 

Therefore, discussion of reachwide substrate data includes all 

of the available data for each site. 

Substrate size varied considerably among sites (table 9). 

Median streambed substrate size classes were sand at 20 sites, 

fines at 15 sites, fine gravel at 7 sites, and coarse gravel at 

5 sites. Sites with fines as the median substrate size were 

located on tributaries to the Tongue and Powder Rivers or 

in the Rosebud, Cheyenne, and Belle Fourche drainages. 

Coarse gravel was the median substrate class at three sites on 

the main-stem Tongue River (sites T1, T5, and T10) and at 

Rosebud Creek at mouth (site R2) and Goose Creek (site T2). 

Fines were present at nearly all 47 sites ( <0.06 mm; table 9), 

whereas bedrock was noted at only six sites ( >4,000 mm; 

table 9). Little Thunder Creek (site C4) had a relatively 

large proportion of bedrock, as shown in table 9 by the large 

numbers for the D75, D84, and Bedrock categories. Substrate 

data for nine different streams were plotted using box plots 

and are presented in figure 9. The Tongue River had the coarsest substrates overall, whereas Squirrel and Otter Creeks had 

the finest substrates. Seventy-five percent of the substrate 

found at sites on the main-stem Powder River was sand to fine 

gravel. 

Pebble counts indicated riffles measured on streams in 

the Tongue River drainage (fig. 10A) had median particle 

sizes that ranged from about 20 to 50 mm (coarse gravel, 

table 3). Median particle size from riffles measured on the 

main-stem Powder River (fig. 10B), and its tributaries (fig. 

10C) had median values ranging from <4 mm (the minimum 

particle size measured) to almost 60 mm (coarse gravel). The 

median substrate values were <4 mm for riffles at all sites on 

the Cheyenne and Belle Fourche Rivers and tributaries (fig. 

10D). Although pebble counts were performed at both pools 

and riffles, the pool substrates tended to be all fine material, 

<4 mm, and therefore the pool data are not shown. 

The degree to which coarse streambed substrates are 

surrounded by fine sediment and sand is called embeddedness. 

Most coarse substrates are naturally embedded to some degree 

dependent on stream characteristics such as gradient, flow 

regime, and geology. However, as interstitial spaces between 

coarse substrates fill and substrates become more embedded, 

the habitat area available to many algae, macroinvertebrates, 

and fish decreases. Embeddedness alone is not a good measure 

of stress in streams that naturally have predominantly fine 

substrates and hence high embeddedness. Mean embeddedness 

ranged from 50 percent at Tongue River at Monarch (site T1) 

to 100 percent at upper Squirrel Creek (site T6), Porcupine 

Creek (site C1), and Caballo Creek (site B2; table 9). Embeddedness on the Tongue River increased in the downstream 

direction and then decreased below Tongue River Reservoir 

(located between sites T9 and T10), indicating that the reservoir is acting as a sediment trap. 

For this study, soft sediment at each thalweg measurement point was defined as fine gravel and smaller (≤16 mm 

diameter). The presence of soft sediment was measured at 

32 sites (table 9) and ranged from 1 percent at Tongue River 

at Monarch (site T1) to 100 percent at 17 sites. The mean 

presence of soft sediment was 84.5 percent. The 1 percent 

noted at site T1 seems unusually small compared to the rest of 

the data, but site T1 had a large median substrate (median of 

about 51 mm in fig. 10A) and the lowest mean embeddedness, 

indicating it had less fine substrates than other sites. 

Riparian Characteristics

Along all streambanks is a corridor or transition zone 

between the aquatic and terrestrial systems. This corridor most 

often is referred to as the riparian zone. Generally, riparian 

zones with complex, multi-layered vegetation are considered 

healthier than zones with simple, single-layered vegetation. 

When a riparian zone is healthy, it performs many critical 

functions. Riparian vegetation holds soils along streambanks 

(thus reducing erosion), intercepts surface flow (thus encouraging ground-water recharge and sustained late-summer 

flows), and reduces flooding while filtering sediment, excess 

nutrients, and other potential contaminants. Trees, shrubs, 

and herbaceous plants provide stream shading, which helps 

to control stream temperature variations. Riparian vegetation 

also provides food, in the form of leaf litter, seeds, insects, and 

deadfall for the aquatic system. This litter and deadfall also 

can provide additional habitat to the system. For this study, 

riparian characteristics were assessed through measurements 
Table 9. Statistical summary of reachwide substrate data, Powder River Structural Basin, Wyoming and Montana, 2005.—Continued

[N, number of substrate measurements used to calculate statistics; soft sediment, percentage presence of sediment less than or equal to (≤) 16 millimeters in diameter; <, less than; mm, millimeters; >, greater than. Bank substrate was calculated using substrate measured at stream margin. Substrate size classes: 1, fines <0.06 mm; 2, sand 0.06–2 mm; 2.5, fine gravel >2 to 16 mm; 3.5, coarse gravel >16 to 64 mm; 4, cobble >64 to 250 mm; 5, boulders >250 to 4,000 mm; 6, bedrock >4,000 mm; NM, not measured]

Site 

number 

(fig. 1)

N 

values

Soft 

sediment 

(percentage 

presence)

Streambed substrate Bank substrate

Mean embeddedness 

(percent)

Percentile Fraction

Mean 

(class) 25th (class) 50th (median) (class) 75th (class) 84th (class) <0.06 mm 0.06–2 mm 

≤2 mm 

≤16 mm >16 mm Bedrock 

Main-stem Tongue River

T1 104 1 50 2.00 3.50 4.00 4.00 0.20 0.03 0.24 0.29 0.71 0 2.25T5 105 96 69 1.50 3.50 3.50 3.50 .33 .16 .49 .58 .40 0 1.32T9 105 42 76 1.00 2.00 3.50 3.50 .33 .24 .56 .69 .31 0 1.59

T10 94 90 55 2.00 3.50 3.88 4.00 .17 .11 .28 .31 .69 0 2.61T14 103 100 71 1.00 2.00 3.50 4.00 .35 .19 .53 .57 .43 0 1.30T18 100 100 56 2.00 2.50 3.50 3.50 .07 .31 .38 .51 .49 0 2.07

Main-stem Powder River

P1 50 NM 69 2.00 2.00 2.50 2.50 0.14 0.47 0.56 0.88 0.12 0 2.10P2 50 100 72 2.00 2.50 3.50 3.50 .04 .38 .42 .68 .32 0 2.50P3 55 NM 86 2.00 2.00 2.50 3.50 .05 .67 .73 .82 .18 0 2.55P4 50 100 70 2.00 2.00 3.50 3.50 0 .52 .52 .70 .30 0 3.03P5 55 NM 92 1.00 2.00 2.00 2.00 .49 .42 .91 .98 .02 0 1.27P8 50 100 90 1.00 2.00 2.00 2.00 .36 .48 .84 .86 .12 0 1.45P9 50 NM 98 1.00 2.00 2.00 2.00 .36 .56 .92 .92 .08 0 1.23

P11 50 100 78 2.00 2.00 3.50 3.58 .24 .36 .60 .72 .28 0 1.63P12 39 100 65 1.00 2.00 4.00 4.00 .30 .20 .50 .58 .38 .03 2.33P13 75 81.82 71 2.00 2.00 3.50 3.50 .08 .50 .58 .65 .32 .03 2.44P17 75 76.62 94 2.00 2.00 2.00 2.00 .10 .78 .88 .98 ..02 0 1.97P18 75 100 64 2.00 2.50 3.50 4.00 .03 .42 .45 .55 .45 0 3.19

Cheyenne and Belle Fourche Rivers, Rosebud Creek, and all tributary streams

R1 104 100 99 1.00 1.00 1.00 1.00 1.00 0 1.00 1.00 0 0 1.00R2 105 88 62 3.00 3.50 4.00 4.00 .24 0 .24 .29 .71 0 2.57

T2 105 43 58 2.00 3.50 4.00 5.00 .07 .16 .24 .27 .69 .04 2.00T3 105 100 90 1.00 2.00 2.00 2.50 .40 .42 .82 .95 .04 0 1.41T4 105 100 99 1.00 1.00 1.00 1.00 .95 .04 .98 1.00 0 0 1.00

30 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 9. Statistical summary of reachwide substrate data, Powder River Structural Basin, Wyoming and Montana, 2005.—Continued

[N, number of substrate measurements used to calculate statistics; soft sediment, percentage presence of sediment less than or equal to (≤) 16 millimeters in diameter; <, less than; mm, millimeters; >, greater than. Bank substrate was calculated using substrate measured at stream margin. Substrate size classes: 1, fines <0.06 mm; 2, sand 0.06–2 mm; 2.5, fine gravel >2 to 16 mm; 3.5, coarse gravel >16 to 64 mm; 4, cobble >64 to 250 mm; 5, boulders >250 to 4,000 mm; 6, bedrock >4,000 mm; NM, not measured]

Site 

number 

(fig. 1)

N 

values

Soft 

sediment 

(percentage 

presence)

Streambed substrate Bank substrate

Mean embeddedness 

(percent)

Percentile Fraction

Mean 

(class) 25th (class) 50th (median) (class) 75th (class) 84th (class) <0.06 mm 0.06–2 mm ≤2 mm ≤16 mm >16 mm Bedrock 

Cheyenne and Belle Fourche Rivers, Rosebud Creek, and all tributary streams—Continued

T6 105 100 100 1.00 1.00 1.00 1.00 1.00 0 1.00 1.00 0 0 1.00T7 105 45 91 1.00 1.00 1.38 2.50 .82 0 .82 .91 .07 0 1.00T8 105 69 73 2.00 2.00 3.50 4.00 .07 .53 .60 .75 .25 0 1.89

T11 105 100 88 1.00 1.00 3.50 3.50 .67 .04 .71 .76 .24 0 1.14T12 105 100 91 1.00 2.00 2.50 3.50 .38 .33 .71 .78 .18 0 1.64T13 105 100 95 1.00 1.00 1.00 1.00 .85 .02 .87 .91 .09 0 1.16T15 105 89 87 1.00 1.00 2.50 3.50 .73 0 .73 .76 .24 0 1.18T16 105 87 94 1.00 1.00 1.00 1.00 .83 .02 .85 .85 .15 0 1.20T17 105 100 83 1.00 1.00 2.00 2.00 .62 .13 .75 .82 .18 0 1.50T19 105 100 65 1.00 2.50 3.50 3.50 .35 .09 .44 .56 .44 0 1.84

P6 55 NM 77 1.00 1.00 2.50 2.86 .51 .15 .65 .84 .16 0 1.30P7 55 NM 81 1.00 2.00 3.50 4.00 .38 .22 .60 .62 .38 0 1.64

P10 105 39 65 1.00 2.50 4.00 4.00 .29 .20 .49 .56 .40 .04 1.77P14 54 NM 93 1.00 1.00 2.00 2.00 .62 .22 .84 .89 .09 0 1.27P15 55 NM 86 1.00 1.00 2.00 2.50 .51 .25 .76 .93 .07 0 1.64P16 105 96 76 1.00 2.50 3.50 3.50 .35 .02 .37 .55 .45 0 1.77

C1 55 NM 100 1.00 2.00 2.00 2.00 .44 .56 1.00 1.00 0 0 1.68C2 55 60 99 1.00 1.00 1.00 2.00 .76 .22 .98 1.00. 0 0 1.25C3 55 NM 90 1.00 2.00 2.00 2.50 .47 .31 .78 .89 .11 0 1.50C4 55 NM 53 2.00 2.50 5.50 6.00 .20 .18 .38 .53 .22 .25 3.11C5 55 NM 83 2.00 2.00 2.25 2.50 .13 .62 .75 .95 .05 0 1.75C6 55 NM 71 2.00 2.00 2.50 2.50 .18 .36 .55 .85 .07 .07 1.86B1 55 NM 96 1.00 1.00 1.50 2.00 .75 .18 .93 .98 .02 0 1.14B2 55 NM 100 1.00 1.00 1.00 1.00 1.00 0 1.00 1.00 0 0 1.00

Ecological Assessment 31
SUBSTRATE CLASS COARSE GRAVEL

COBBLE

BOULDERS

BEDROCK

FINES

SAND

FINE GRAVEL

209 609 207 209 314 307 671 110 213

213 Number of values 

EXPLANATION 

Data value less than or equal to 

 1.5 times the interquartile range 

 outside the quartile

75th percentile

Median

25th percentile

Outlier data value greater than 

 3 times the interquartile range 

 outside the quartile

Outlier data value less than or 

 equal to 3 and more than 1.5 times 

 the interquartile range outside 

 the quartile

ROSEBUD CREEK

TONGUE RIVER

YOUNGS CREEK

SQUIRREL CREEK

HANGING WOMAN CREEK

OTTER CREEK

POWDER RIVER

CRAZY WOMAN CREEK

LITTLE POWDER RIVER

Interquartile 

 range

Figure 9. Particle-size distribution of reachwide streambed substrate data, by stream, Powder River Structural Basin, 2005.

32 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

of density of vegetative (canopy) cover, vegetation complexity, 

identification of legacy trees, and presence of invasive species. 

Mid-stream canopy density ranged from zero percent 

cover at sites T10, P8, P13, P17, and P18 to 56 percent cover 

at upper Rosebud Creek (site R1; table 7). Although measurements of mid-stream canopy density indicated less density at 

the large river sites on the main-stem Powder River (mean = 

<1 percent) and Tongue River (mean = 4.8 percent) than at 

tributary streams (mean = 7.5 percent) as one might expect, 19 

of the tributary sites had means of 5 percent or less, and 7 of 

those sites had means of less than 1 percent. Bank or streamside canopy density measurements ranged from 0.2 percent at 

Powder River near Locate (site P18) to 99 percent at Prairie 

Dog Creek (site T8). The main-stem Tongue River had the 

largest mean bank canopy density (about 49 percent) when 

compared to the main-stem Powder River (about 6 percent) 

and tributary sites (about 24 percent). 

Woody and non-woody vegetation were observed in the 

riparian zone at all 47 sampling sites. Non-woody vegetation 

comprised the largest percentage of vegetative cover at most of 

the sites (table 10). All of the sites surveyed had some type of 

ground vegetation, whereas two sites (Little Powder River at 

Biddle, site P16, and Antelope Creek, site C2) had no woody 

vegetation observed for either ground cover or the understory. 

Several sites had less than 10 percent total understory vegetative cover including upper Squirrel Creek (site T6), Little 

Thunder Creek (site C4), Black Thunder Creek (site C5), 

Cheyenne River near Spencer (site C6), and Powder River 

above Pumpkin Creek (site P3). Percentages of mean areal 

vegetative cover for the canopy were generally small with only 

eight sites having combined total percentages of 10 percent 

or more. Four sites, upper Rosebud Creek (site R1), Rosebud 

Creek at mouth (site R2), Powder River at Broadus (site P13), 

and upper Youngs Creek (site T3), had canopies with percentages of mean areal vegetative cover larger than 20 percent. 

Eighteen sites had summed mean areal vegetative cover 

greater than 100 percent (table 10); eight of these sites had 

little or no bare ground. Summed mean areal vegetative cover 

and bare ground or duff were inversely correlated (ρ = –0.76).

Nine different tree types were identified as legacy trees 

(fig. 11). Cottonwoods composed 65 percent of the legacy 

trees, and boxelder trees were the second most common. 
Figure 10. Cumulative particle-size distributions of riffle pebble counts collected at sites on the 

A, Tongue River and tributaries; 

B, main-stem Powder River; 

C, tributaries to the 

Powder River; and 

D, Cheyenne and Belle Fourche Rivers and tributaries, Powder River Structural Basin, 2005.

B1

C3C4C5C6

0

908070605040302010

110100

1 10 100 1,000

PARTICLE SIZE, IN MILLIMETERS

CUMULATIVE PERCENT FINER THAN INDICATED SIZE

C

1 10 100 1,000

PARTICLE SIZE, IN MILLIMETERS

0

908070605040302010

110100

CUMULATIVE PERCENT FINER THAN INDICATED SIZE

P6

Site number

P7P10

P14

P15

0

908070605040302010

110100

0

908070605040302010

110100

1 10 100 1,000

PARTICLE SIZE, IN MILLIMETERS

CUMULATIVE PERCENT FINER THAN INDICATED SIZE

BD

P1P2P3P4

P5P8

Site number

1 10 100 1,000

PARTICLE SIZE, IN MILLIMETERS

CUMULATIVE PERCENT FINER THAN INDICATED SIZE T1T2T8T9 Site number

A

Site number

Ecological Assessment 33
Table 10. Riparian vegetative structure and percentages of mean areal vegetative cover identified by semiquantitative visual 

estimates, Powder River Structural Basin, Wyoming and Montana, 2005.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. <, less than; m, meter; >, greater than; DBH, diameter at breast height. Total 

vegetative cover may exceed 100 percent due to use of range categories during sampling]

Site 

number 

(fig. 1)

Bare/duff 

(percent)

Mean areal vegetative cover (percent) Sum of 

mean 

areal 

vegetative 

cover 

(percent)

Total 

vegetative 

cover 

(percent)

Ground cover, <0.5 m Understory, 0.5–5 m Canopy, >5 m

Nonwoody Woody Nonwoody Woody Small trees, 

<0.3 m DBH

Large trees, 

>0.3 m DBH

R1 0 37 12 71 42 24 7 192 100

R2 1 46 27 52 33 36 .5 193 99

T1 11 8 6 19 44 4 1 81 89

T2 14 11 5 22 28 1 0 68 86

T3 14 34 8 50 10 8 14 123 86

T4 .5 88 7 21 6 .5 1 124 100

T5 5 30 6 45 9 2 1 94 95

T6 36 50 1 7 2 0 0 60 64

T7 .5 86 1 23 1 0 0 111 100

T8 0 24 17 40 22 0 .2 104 100

T9 20 15 3 44 6 1 0 68 80

T10 6 47 5 47 5 8 3 116 94

T11 10 60 3 52 7 4 0 126 90

T12 0 58 4 52 7 3 1 125 100

T13 1 58 1 58 3 4 1 124 99

T14 9 45 17 43 22 13 4 144 91

T15 8 80 0 77 9 1 .2 167 92

T16 8 80 0 40 2 0.2 1 123 92

T17 9 53 17 10 12 1 0 93 91

T18 14 35 17 37 23 5 5 122 86

T19 20 25 4 17 3 2 4 54 80

P1 45 8 7 6 23 0.3 0 43 55

P2 40 10 6 6 21 7 3 52 60

P3 43 33 2 1 3 0 1 39 58

P4 43 14 5 14 10 1 1 44 57

P5 61 12 4 8 13 0 .2 36 39

P6 37 28 7 14 8 .5 10 66 63

P7 37 37 3 14 5 0 1 59 63

P8 27 32 11 6 13 2 1 65 73

P9 38 8 5 18 23 0 .3 53 62

P10 32 26 .2 31 2 1 .2 60 68

P11 22 30 6 22 7 .3 .3 66 78

P12 26 12 4 32 8 2 2 59 74

P13 15 38 5 23 20 29 2 116 85

P14 2 32 2 36 6 8 .2 84 98

34 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Figure 11. Percentages of legacy tree types identified at study 

reaches, Powder River Structural Basin, 2005.

Willow

6 percent 

Pine

1 percent

Elm

1 percent

Russian olive

3 percent

Ash

5 percent

Juniper

1 percent

Spruce 

1 percent

Boxelder

18 percent

Cottonwood

65 percent

Table 10. Riparian vegetative structure and percentages of mean areal vegetative cover identified by semiquantitative visual 

estimates, Powder River Structural Basin, Wyoming and Montana, 2005.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. <, less than; m, meter; >, greater than; DBH, diameter at breast height. Total 

vegetative cover may exceed 100 percent due to use of range categories during sampling]

Site 

number 

(fig. 1)

Bare/duff 

(percent)

Mean areal vegetative cover (percent) Sum of 

mean 

areal 

vegetative 

cover 

(percent)

Total 

vegetative 

cover 

(percent)

Ground cover, <0.5 m Understory, 0.5–5 m Canopy, >5 m

Nonwoody Woody Nonwoody Woody Small trees, 

<0.3 m DBH

Large trees, 

>0.3 m DBH

P15 10 59 1 10 2 0.2 0 71 90

P16 2 88 0 11 0 3 0 101 98

P17 18 51 13 31 13 2 .3 111 83

P18 23 52 7 42 4 0 1 105 78

C1 8 49 1 34 .2 0 0 85 92

C2 6 76 0 .2 0 3 .2 80 94

C3 33 41 4 6 6 1 .5 59 67

C4 6 68 4 1 3 0 0 76 94

C5 55 35 4 0 2 0 0 42 45

C6 64 22 3 1 6 0 0 32 36

B1 39 32 5 18 3 0 0 59 61

B2 18 53 5 11 9 0 0 77 82

Ecological Assessment 35

Of the eight species that were targeted for this study, 

cheatgrass and Canada thistle were the most commonly 

noted invasive plants in the riparian zone at the sampling 

sites. Cheatgrass and Canada thistle were identified at 35 

and 26 percent of the sites, respectively (fig. 12). One target 

species, English ivy, was not observed by study personnel. 

Reach Characteristics

Bank-stability scores, computed according to Fitzpatrick 

and others (1998), indicated the streambanks tended to be 

more stable at sites on tributaries in the Tongue River drainage 

than at sites on tributaries in the Powder River drainage and 

the main-stem Powder River. Low index scores for bank 

angle, vegetative cover, bank height, and substrate resulted in 

relatively small bank-stability scores (more stable) for Tongue 

River tributary sites (table 11). Bank-stability scores were 

mixed for sites on the main-stem Tongue River. Streambanks 

at sites in the Cheyenne and Belle Fourche River drainages 

were relatively stable (small bank-stability scores) with the 

exception of Little Thunder Creek (site C4), which was tied 

with Tongue River above Hanging Woman Creek (site T10) 

and sites on the Powder River (sites P2-P4 and P18) with 

maximum scores of 15 (least stable). The narrative ratings of 

“at risk” (25 sites) or “unstable” (22 sites) in table 11 provide 

a relative indicator of current bank conditions; however, observations of erosion or bank slumping also should be considered 

when evaluating bank stability.
Musk thistle

4 percent

Common burdock

2 percent

Russian olive

8 percent

Leafy spurge

11 percent

Salt cedar

14 percent

Canada thistle

26 percent

Cheat grass

35 percent

Figure 12. Distribution of invasive plant species identified in 

study reaches, Powder River Structural Basin, 2005.

Table 11. Bank-stability index and scores for sites sampled in the Powder River Structural Basin, Wyoming and 

Montana, 2005.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River. Bank-stability scores: 4–7 = stable; 8–10 = at risk; 11–15 = unstable; 

16–22 = very unstable; from Fitzpatrick and others, 1998]

Site number

(fig. 1)

Index scores Bank-stability 

score

Bank-stability 

rating Angle Vegetative cover Height Substrate

R1 2 1 2 5 10 At risk

R2 2 1 1 10 14 Unstable

T1 2 1 1 8 12 Unstable

T2 2 1 2 8 13 Unstable

T3 2 1 1 5 9 At risk

T4 1 1 1 5 8 At risk

T5 1 1 2 5 9 At risk

T6 1 2 1 5 9 At risk

T7 3 1 1 5 10 At risk

T8 3 1 2 5 11 Unstable

T9 1 1 2 5 9 At risk

36 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 11. Bank-stability index and scores for sites sampled in the Powder River Structural Basin, Wyoming and 

Montana, 2005.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River. Bank-stability scores: 4–7 = stable; 8–10 = at risk; 11–15 = unstable; 

16–22 = very unstable; from Fitzpatrick and others, 1998]

Site number

(fig. 1)

Index scores Bank-stability 

score

Bank-stability 

rating Angle Vegetative cover Height Substrate

T10 2 1 2 10 15 Unstable

T11 3 1 1 5 10 At risk

T12 2 1 1 5 9 At risk

T13 3 1 1 5 10 At risk

T14 2 1 2 5 10 At risk

T15 1 1 1 5 8 At risk

T16 2 1 1 5 9 At risk

T17 3 1 1 5 10 At risk

T18 2 1 2 8 13 Unstable

T19 1 2 1 5 9 At risk

P1 1 2 2 8 13 Unstable

P2 1 2 2 10 15 Unstable

P3 1 2 2 10 15 Unstable

P4 1 2 2 10 15 Unstable

P5 1 3 2 5 11 Unstable

P6 3 2 2 5 12 Unstable

P7 2 2 2 5 11 Unstable

P8 2 2 2 5 11 Unstable

P9 1 2 1 5 9 At risk

P10 2 2 2 5 11 Unstable

P11 1 2 2 5 10 At risk

P12 1 2 1 8 12 Unstable

P13 1 1 2 8 12 Unstable

P14 3 1 1 5 10 At risk

P15 3 1 2 5 11 Unstable

P16 3 1 2 5 11 Unstable

P17 2 1 2 5 10 At risk

P18 1 2 2 10 15 Unstable

C1 2 1 1 5 9 At risk

C2 2 1 1 5 9 At risk

C3 2 2 11 5 10 At risk

C4 2 1 2 10 15 Unstable

C5 2 3 11 5 11 Unstable

C6 1 3 11 5 10 At risk

B1 2 2 1 5 10 At risk

B2 1 1 1 5 8 At risk

1

Value may be underestimated because bank height was calculated using the mean water depth instead of the mean thalweg depth.

Ecological Assessment 37
38 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

Cross-sectional and longitudinal surveys along with 

mapping of habitat types were performed at several sites 

during the summer of 2005. Examples of data collected 

during a longitudinal survey at Porcupine Creek (site C1) are 

presented in figure 13 as both longitudinal-profile and plan 

views. Longitudinal survey data, from sites that are noted in 

table 2, are available upon request from the USGS WWSC in 

Cheyenne, Wyo.

Proximity-weighted human disturbance values indicated 

that the sites with the largest amount of human activities 

were Tongue River at State line (site T9) and Tongue River at 

Birney Day School (site T14), each with six human activities 

present, and Hanging Woman Creek at mouth (site T13) with 

seven observed activities (table 12). At 32 sites, two or more 

human activities were observed. The most-common land use, 

“pasture, range, or hay field,” was identified at 45 of 47 sites. 

The least-common land use, “mining,” was identified at Porcupine Creek (site C1) and Caballo Creek (site B2).

Three summary categories were added to table 12—

“agricultural” (the sum of “row crops” and “pasture, range, 

or hay field”), “nonagricultural” (the sum of all other categories), and “all types” (the sum of all categories). In the PRB, 

agricultural land-use activities were twice as likely to disturb 

sampled stream reaches as nonagricultural land-use activities 

(table 12). Powder River below Salt Creek (site P2) had the 

least riparian disturbance with an overall proximity-weighted 

disturbance value of 0.14, whereas Hanging Woman Creek at 

mouth (site T13) showed the greatest disturbance with a value 

of 3.32 (table 12). 

Habitat Characteristics of the Main-Stem 

Powder River in Wyoming 

A total of 690 habitat units were surveyed during 

72 periods of sample collection at eight sites on the main-stem 

Powder River during 2004–06. Periods of sample collections 

numbered 40 in 2004, 24 in 2005, and 8 in 2006. 

The median wetted stream width of the main-stem 

Powder River in Wyoming increased from 12.0 m above 

Salt Creek (site P1) to 32.6 m below Clear Creek (site P11, 

table 13). A wide range of wetted stream widths was observed 

at each site (table 13) and depended on the streamflow conditions at the time of sampling. 

The mean and maximum depths observed from 2004 

through 2006 varied little among sites (table 14). The mean 

of mean depths at each site ranged from 0.15 to 0.27 m. The 

mean of maximum depths observed ranged from 0.34 to 

0.49 m across all sites. The deepest maximum depths observed 

at all sites ranged from 1.10 to 2.13 m. Onsite observations 

indicate that the deepest habitats were pools scoured near 

in-stream obstructions such as large woody debris or boulders. 

Residual pool depths had a mean of 0.55 m and ranged from 

0.30 to 1.71 m (table 14). 

Sand was the most common substrate in the main-stem 

Powder River. Mean percentages of gravel were larger at the 

sites farthest upstream (sites P1 and P2) than downstream 

(fig. 14), but sand predominated at all sites other than site P1, 

which had similar proportions of gravel (41.4 percent) and 

sand (35.8 percent). The largest percentages of cobble were 

observed at sites P11 (11.7 percent) and P4 (9.4 percent). 

Bedrock generally was rare but was observed most commonly 

at sites P3-P5 and P9. Substrate categorized as bedrock was 

primarily sandstone that was scoured by the river where the 

channel was controlled by bluffs. 

Substrate varied substantially among habitat units. The 

substrate of pools, runs, and shoals in the main-stem Powder 

River was predominantly sand (mean of 67 to 74 percent, 

fig. 15). Riffles had the largest mean percentage of gravel 

(56.5 percent) and cobble (22.3 percent). Backwater had a 

consistently large percentage of silt (mean 58.3 percent) and 

sand (mean 31.2 percent). Isolated pools were dominated 

by a variable combination of silt (mean 67.5 percent) and 

sand (mean 32.5 percent). The mean water velocity in riffles 

(0.54 meters per second, m/s) was substantially greater than in 

pools (0.31 m/s) and shoals (0.20 m/s) but was similar to that 

observed in runs (0.44 m/s; fig. 16). 

Fish cover, such as vegetation and woody debris, was 

observed more frequently at upstream Powder River sites 

than at downstream sites (fig. 17). Although fish cover often 

was not abundant enough to be quantified, the presence of 

discernable cover was observed in 30 percent of surveys of 

habitat units (n = 204). Overall, the mean percentages of fish 

cover containing aquatic vegetation (1.4 percent), woody 

debris (1.6 percent), undercut bank (0.2 percent), and overhead cover (0.7 percent) were considerably smaller than the 

perceived margin of error for visual coverage estimates (about 

5 percent). However, the presence of cover was denoted as a 

trace for many habitat units where the percentage of coverage 

was smaller than could be estimated precisely. 

Zero-flow conditions were encountered during sampling 

at two sites (P8 and P9) in August 2006. Six isolated pools 

were surveyed at each site. Surface-water temperatures of the 

isolated pools during late morning ranged from 17.5 to 27.5oC 

(four measurements). In a single pool at site P9, transparency was 40 cm, and specific conductance was 6,400 μS/cm, 

which was the maximum observation during the study. The 

mean of mean depths measured in the isolated pools was 

0.18 m, and the mean of maximum depths was 0.34 m (range 

of 0.12–0.70 m). The overall substrate composition of the 

isolated pools differed slightly from that of other pools but was 

dominated by sand (88.7 percent). Cobble (5.0 percent), gravel 

(3.8 percent), bedrock (1.3 percent), and silt (0.8 percent) were 

less common in isolated pools than sand. Cover types such 

as woody debris, undercut bank, and overhead cover were 

observed in 33 percent of the isolated pools. Aquatic vegetation was not observed in any of the isolated pools surveyed. 

The aquatic habitat of isolated pools surveyed under 

intermittent conditions was fairly homogeneous and harsh, 

which concurs with the description of “isolated streambed 

pools” in other warm-water stream studies (Ostrand and 

Wilde, 2004). Most isolated pools were small and temporary, 
Figure 13. Examples of longitudinal survey data, Porcupine Creek near Teckla, Wyo. (site C1), 2005.

1,420 1,440 1,460 1,480 1,500 1,520 1,540 1,560 1,580 1,600

DISTANCE, IN METERS

1,400

1,420

1,440

1,460

1,470

1,480

1,500

1,520

1,540

1,530

1,550

DISTANCE, IN METERS

Water surface

Bankfull

Flood plain

Lower terrace

Channel center

151

150

152

153

154

155

156

0 20 40 60 80 100 120 140 160 180 200 210

Channel center

Water surface

Bankfull

Flood plain

Lower terrace

RELATIVE HEIGHT, IN METERS

DISTANCE, IN METERS

Longitudinal profile

Plan view

Ecological Assessment 39
Table 12. Proximity-weighted human riparian disturbance values, Powder River Structural Basin, Wyoming and Montana, 2005.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River. Disturbance values are weighted number of observations]

Site 

number 

(fig. 1)

Human activities Summed activities

Wall or 

dam Building Pavement Road Intake or outlet pipe Trash or landfill Park or lawn Row crops Pasture, range, or hay field Logging operations Mining activity Agricul- tural Non- agricul- tural All types 

R1 0 0.30 0 0.30 0 1.34 0.30 0 0.61 0 0 0.61 2.25 2.85R2 0 0 0 .67 0 0 0 0 .67 0 0 .67 .67 1.33

T1 .17 .11 0 .23 0 0 0 0 .17 0 0 .17 .50 .67T2 0 0 0 .33 0 0 0 0 .98 0 0 .98 .33 1.31T3 0 .09 0 .33 0 0 0 0 1.50 0 0 1.50 .43 1.93T4 0 0 0 .48 0 0 0 0 0 0 0 0 .49 .49T5 0 .07 0 .52 .58 0 0 .64 .64 0 0 1.27 1.17 2.44T6 0 .21 0 .33 0 0 0 0 1.00 0 0 1.00 .55 1.55T7 0 0 0 .33 0 .03 0 0 0 0 0 0 .37 .37T8 0 0 0 0 0 0 0 0 .67 0 0 .67 0 .67T9 .06 .07 0 .06 .14 0 0 .03 .30 0 0 .33 .33 .66

T10 .10 0 0 .67 .21 0 0 0 .67 0 0 .67 .98 1.65T11 0 .33 .0 .67 0 0 .03 0 .45 .64 0 .45 1.67 2.12T12 0 0 0 .67 0 0 0 0 .67 .64 0 .67 1.33 2.00T13 .67 .33 0 .67 0 0 .21 .11 .67 .67 0 .78 2.55 3.32T14 0 .38 0 .69 0 .62 .02 .09 .67 .00 0 .75 1.72 2.47T15 0 0 0 0 0 0 0 0 1.50 0 0 1.50 0 1.50T16 .07 0 0 .06 .20 .07 0 0 1.50 0 0 1.50 .41 1.91T17 0 .03 0 .03 0 .16 .03 0 1.50 0 0 1.50 .26 1.76T18 0 0 0 .67 0 .03 0 0 .67 0 0 .67 .70 1.37T19 0 0 0 .67 0 .03 0 0 .89 0 0 .89 .70 1.59

P1 0 0 0 0 0 0 0 0 1.18 0 0 1.18 0 1.18P2 .08 0 0 0 0 0 0 0 .07 0 0 .07 .08 .14P3 0 0 0 0 0 0 0 0 1.14 0 0 1.13 0 1.13P4 0 0 0 0 0 0 0 0 .93 0 0 .93 0 .93P5 0 0 0 0 0 0 0 0 .94 0 0 .93 0 .93

40 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 12. Proximity-weighted human riparian disturbance values, Powder River Structural Basin, Wyoming and Montana, 2005.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River. Disturbance values are weighted number of observations]

Site 

number 

(fig. 1)

Human activities Summed activities

Wall or 

dam Building Pavement Road Intake or outlet pipe Trash or landfill Park or lawn Row crops Pasture, range, or hay field Logging operations Mining activity Agricul- tural Non- agricul- tural All types 

P6 0 0 0 0 0 0 0 0 0.80 0 0 0.80 0 0.80P7 0 0 0 0 0 0 0 0 1.41 0 0 1.41 0 1.41P8 0 0 0 0 0 0 0 0 1.43 0 0 1.43 0 1.43P9 0 0 0 0 0 0 0 0 .71 0.03 0 .71 .03 .74

P10 0 0 0 .12 0 0 0 0 1.03 0 0 1.02 .12 1.15P11 0 0 0 0 0 0 0 0 .33 0 0 .33 0 .33P12 0 0 0 0 0 0 0 0 .67 0 0 .67 0 .67P13 0 .25 .21 .33 0 0 0 0 .54 0 0 .54 .79 1.33P14 0 0 0 .33 0 0 0 0 1.08 0 0 1.07 .33 1.41P15 .62 0 0 .15 0 .12 0 0 1.02 0 0 1.03 .89 1.93P16 0 0 0 0 0 0 0 0 1.50 0 0 1.50 0 1.50P17 0 .08 .08 .21 0 0 0 0 1.50 0 0 1.50 .37 1.87P18 .10 .13 0 .63 0 0 0 0 1.40 0 0 1.41 .87 2.25

C1 .67 0 0 .12 0 0 0 0 1.43 0 .67 1.43 1.45 2.88C2 0 0 0 0 0 0 0 0 1.50 0 0 1.50 0 1.50C3 0 0 0 0 0 0 0 0 1.32 0 0 1.33 0 1.33C4 .06 0 0 0 0 0 0 0 1.41 0 0 1.41 6 1.47C5 0 0 0 0 0 0 0 0 1.09 0 0 1.09 0 1.09C6 0 .05 0 0 0 0 0 0 1.48 0 0 1.48 .05 1.52B1 .06 0 0 .06 0 0 0 0 1.41 0 0 1.41 .12 1.53B2 0 0 0 0 0 0 0 0 1.25 .14 .03 1.25 .17 1.42

Ecological Assessment 41
Table 13. Wetted stream widths observed at sites on the main-stem Powder River, Wyoming, 2004–06.

[Median stream widths that do not share the same letter under homogeneous groups are statistically different (Dunn’s test, P < 0.05)]

Site number and location on 

Powder River (fig. 1)

Wetted stream width

Homogeneous groups for median stream widths Median (meters) Range (meters)

P1, above Salt Creek 12.0 1.7–39.3 A

P2, below Salt Creek 14.0 6.2–42.7 A B

P3, above Pumpkin Creek 18.0 1.2–38.8 B C

P4, below Burger Draw 20.1 4.3–52.0 C D

P5, above Crazy Woman Creek 21.6 2.1–49.4 C D

P8, below Crazy Woman Creek 26.4 1.8–52. 4 D E

P9, above Clear Creek 23.2 3.2–50.0 D

P11, below Clear Creek 32.6 6.4–59.5 E

Table 14. Mean, maximum, and residual pool depths observed at sites on the main-stem Powder River, Wyoming, 2004–06.

Site number and location on 

Powder River (fig. 1) Depth (meters) Maximum depth (meters) Residual pool depth (meters)

Mean Range Mean Range Mean Range

P1, above Salt Creek 0.21 0.03–0.67 0.46 0.03–1.22 0.55 0.34–1.01

P2, below Salt Creek .18 0.03–0.55 .46 0.03–1.16 .46 0.30–0.70

P3, above Pumpkin Creek .18 0.03–0.49 .49 0.06–1.83 .73 0.30–1.71

P4, below Burger Draw .21 0.03–0.67 .34 0.03–1.13 .52 0.34–0.73

P5, above Crazy Woman Creek .15 0.03–0.58 .40 0.03–2.13 .46 0.34–0.79

P8, below Crazy Woman Creek .27 0.03–1.16 .43 0.06–1.52 .55 0.30–1.13

P9, above Clear Creek .24 0.03–1.07 .40 0.06–1.10 .52 0.37–0.76

P11, below Clear Creek .27 0.03–0.91 .40 0.06–1.52 .52 0.52–1.01

42 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Figure 14. Mean percentages of silt, sand, and gravel observed at sites sampled during flow in the 

main-stem Powder River, Wyoming, 2004–06.

0

20

40

60

80

100

Silt

MEAN PERCENT

0

20

40

60

80

100

Sand

SITE NUMBER

P1 P2 P3 P4 P5 P8 P9 P11

0

20

40

60

80

100

Gravel

95-percent confidence interval Mean

EXPLANATION







Ecological Assessment 43
Figure 15. Mean percentage of substrate size by habitat type surveyed during flow in the main-stem Powder River, Wyoming, 2004–06.

0

20

40

60

80

100

MEAN PERCENTAGE OF HABITAT

AREA

0

20

40

60

80

100

SUBSTRATE TYPE

Silt Sand Gravel Cobble Boulder Bedrock Silt Sand Gravel Cobble Boulder Bedrock

0

20

40

60

80

100

Isolated pool

(n = 6)

95-percent confidence interval Mean

Number of habitat units

EXPLANATION







n

Riffle

(n = 137)

Run

(n = 214)

Backwater

(n = 121)

Shoal

(n = 59)

Pool

(n = 153)

44 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Figure 17. Fish cover at sampling sites on the main-stem Powder River, Wyoming, 2004–06.

0

10

20

30

40

50

60

P1 P2 P3 P4 P5 P8 P9 P11

SITE NUMBER

FISH COVER, IN PERCENT

Aquatic vegetation

Woody debris

Undercut bank

Overhead cover

Figure 16. Mean stream velocity of habitat units categorized as pool, riffle, run, or shoal during periods of sample 

collection on the main-stem Powder River, Wyoming, 2004–06.

HABITAT TYPE

Pool Riffle Run Shoal

VELOCITY, IN METERS PER SECOND

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

95-percent 

confidence 

interval

Mean velocity

EXPLANATION







Ecological Assessment 45
Figure 18. Habitat types determined from global positioning 

system mapping in 2005 and from transects in 2006 at eight 

sampling sites on the main-stem Powder River, Wyoming.

0

10

20

30

40

50

60

70

80

90

100

P1 P2 P3 P4 P5 P8 P9 P11

P1 P2 P3 P4 P5 P8 P9 P11

SITE SAMPLED IN 2006

HABITAT TYPE, IN PERCENT HABITAT TYPE, IN PERCENT

EXPLANATION

Isolated pool

Shoal

Run

Backwater

Riffle

Pool

SITE SAMPLED IN 2005

0

20

40

60

80

100

46 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

probably lasting less than a week. However, some isolated 

pools, such as one at the end of the stream reach at site P5, 

were fairly large and recurred from one year to the next. 

High-resolution GPS units were used to map stream 

habitat types at main-stem Powder River sites in Wyoming 

during three different flow periods in 2005 (May, July, and 

August that generally corresponded with high, middle, and low 

flows, respectively), with the exception of Powder River above 

Pumpkin Creek (site P3) where streamflow was similar in July 

and August. Percentages of habitat types were calculated for 

each site and flow period. These values then were averaged 

for each site to identify general differences or tendencies 

among the study sites. Runs were the most extensive habitat 

feature at all the main-stem sites (fig. 18), accounting for more 

than 80 percent of the habitat at all of the sites except below 

Burger Draw (site P4). The Powder River below Clear Creek 

(site P11) had the largest percentage of pool habitat among 

the main-stem sites. Riffle habitat tended to be greater at the 

upstream Powder River sites (fig. 18) and was largest at the 

Powder River below Burger Draw (site P4). Shoal habitat was 

greatest at Powder River above Crazy Woman Creek (site P5) 

and smallest at Powder River above Salt Creek (site P1) 

and Powder River below Clear Creek (site P11). Additional 

information regarding the methodology and results of the GPS 

mapping and transect-based estimates of habitat can be found 

in Wyoming Game and Fish Department (2007). 

Analysis of habitat types mapped during the high-, 

middle-, and low-flow periods in 2005 indicated some changes 

between time periods, but none were consistent among all sites 

(Wyoming Game and Fish Department, 2007). Riffle percentages, for example, appeared to increase at some sites, decrease 

at others, and remain relatively unchanged at still other sites 

as flow declined. Shoals were more common at lower flows, 

except at the uppermost and lowermost sites where they were 

uncommon habitat types at all flows. With the exception of the 

site on the Powder River above Clear Creek (site P9) where 

pools were always a very small percentage of total wetted 

area, pools accounted for their smallest relative percentage 

of total habitat during the high-flow visit. Percentages of 

backwater habitats generally were larger during the middleor low-flow visit, except for the sites on the Powder River 

below Crazy Woman Creek (site P8), Powder River above 

Clear Creek (site P9), and Powder River below Clear Creek 

(site P11, fig. 19) where overall percentages of backwater 

were consistently small. 

In 2006, all of the Powder River sites in Wyoming were 

revisited; however, each site was sampled only once. Flow 

during sampling in 2006 was extremely low during the last 

week of July, and zero flow occurred during the first week 

of August. Data for the USGS gage at Moorhead, Mont. 

(fig. 3A), show mean daily flows were less than 1 cubic foot 

per second (ft3/s) during the 2006 sampling activities, including 1 day of no flow on August 1.
A Below Clear Creek, May 5, 2005

Discharge = 248 cubic feet per second

Shoal

Island

Backwater

Pool

Riffle

Run

B Below Clear Creek, July 25, 2005

Discharge = 91 cubic feet per second

Shoal

Island

Backwater

Pool

Riffle

Run

C Below Clear Creek, August 16, 2005

Discharge = 152 cubic feet per second

Shoal

Island

Backwater

Pool

Riffle

Run

Habitat type

Habitat type

Habitat type

0 200 400 600 FEET

0 50 100 150 METERS

0 200 400 600 FEET

0 50 100 150 METERS

0 200 400 600 FEET

0 50 100 150 METERS

Figure 19. Habitat composition at varying flows in A, May; B, July; and C, August 2005 for a 

segment of the Powder River below Clear Creek, Wyoming (site P11).

Ecological Assessment 47
48 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

environmental conditions (for example, large specific conductance values and flooding; Wangsness and Peterson, 1980) 

in streams of the PRB affect macroinvertebrate community 

composition regardless of anthropogenic effects. 

Ephemeroptera accounted for a mean of about 24 percent 

of the relative abundance of individuals in the macroinvertebrate community. Mean values for other taxonomic groups 

in the samples were 22 percent for Trichoptera, 35 percent 

for Diptera (of which more than one-half were Chironomidae), 9 percent for Coleoptera, 8 percent for noninsects, and 

0.4 percent for Odonata. The density of macroinvertebrates 

ranged from 144 to 19,592 individuals per square meter 

(individuals/m2), with a mean of 4,100 individuals/m2. The 

proportion of the single-most common taxon in each sample 

ranged from 13 to 98 percent with a mean of 43 percent. The 

proportion of the single-most dominant, or of the five most 

dominant taxa (table 15), can be used as an indicator of water 

quality because dominance is expected to increase in response 

to increasing perturbation (Barbour and others, 1999). 

Samples with the largest percentages of single dominant taxa 

were Pumpkin Creek (site T19, 98 percent), Cheyenne River 

near Spencer (site C6, 94 percent), Little Powder River above 

Dry Creek (site P15, 94 percent), and Little Thunder Creek 

(site C4, 94 percent); those four samples all were collected 

in 2005 and were dominated by blackfly larvae Simulium. 

Other taxa that dominated samples, but at smaller percentages, included Baetis, Traverella albertana, and Tricorythodes

(Ephemeroptera), and Cheumatopsyche (Trichoptera). 

The primary functional groups of the macroinvertebrate 

communities were gatherer-collectors (mean abundance 

of 40 percent) and filter-collectors (mean abundance of 

43 percent). Gatherer-collectors are organisms that feed by 

moving to food patches, in contrast to filterer-collectors that 

generally are stationary and obtain food by filtering particles 

from flowing water (Merritt and Cummins, 1996). The 

expected response of the percentage of gather-collectors and 

filter-collectors to perturbation is variable (Barbour and others, 

1999), but a shift in percentages can be an indicator of environmental changes. Other functional groups that were present 

in the samples, generally in small percentages, included predators, scrapers, and shredders. 

Macroinvertebrate communities showed some similarities 

within river drainages on the basis of Bray-Curtis similarity 

coefficients (fig. 20). Four groups of relatively similar sites 

were identified; Tongue River main-stem and mountainous 

tributaries; Powder River main-stem; Tongue River plains 

tributaries; and the Cheyenne and Belle Fourche Rivers. 

Replicate macroinvertebrate samples collected for qualitycontrol purposes plotted near to the parent samples indicating 

considerable similarity among parent and replicate samples 

(samples T1 and T1R; sites P6 and P6R; fig. 20). 

The Tongue River group of samples in the lower-right 

corner of figure 20 includes all of the samples collected in 

2005 from the main stem of the Tongue River as well as from 

tributaries with mountainous headwaters—Goose Creek, 

Clear Creek, and Crazy Woman Creek. Although two of 

Percentages of habitats identified during transect-based 

sampling during 2006 are presented in figure 18. Site P1 

(Powder River above Salt Creek) had larger percentages of 

pool and riffle habitat than other sites. The site on the Powder 

below Salt Creek (site P2) had the largest relative run percentage, and the Powder River above Pumpkin Creek (site P3) is 

notable for its large percentage of shoal habitat. The Powder 

River below Burger Draw (site P4) had a small percentage 

of pool habitat, the second largest riffle percentage, and the 

largest percentage of backwater habitat (fig. 18). Site P5 is 

notable for large percentages of backwater and shoals. Sites P8 

(Powder River below Crazy Woman Creek) and P9 (Powder 

River above Clear Creek) did not have streamflow, and most 

habitat types were not present (Wyoming Game and Fish 

Department, 2007).

Macroinvertebrate Community Assessment

Macroinvertebrate samples were collected from riffles 

when present in the sample reach (RTH samples) and from 

multiple habitats (qualitative, QMH samples) at each site 

regardless of whether riffles were present. These samples were 

collected during 2005–06.

Community Characteristics at Sites with Riffles

Macroinvertebrate samples were collected from riffles 

at 37 sites in 2005 and at 20 sites in 2006. Fewer sites were 

sampled in 2006 than in 2005 because of the drier conditions 

(fewer sites with flowing water) and study constraints in 2006. 

Community Composition

The number of macroinvertebrate taxa per sample (taxa 

richness) in the 2005–06 PRB data varied considerably from 

5 taxa identified in Pumpkin Creek (site T19) in 2005 to 

47 taxa identified in upper Hanging Woman Creek (site T11), 

also in 2005 (table 15). A mean of 28 macroinvertebrate taxa 

per sample was identified after removal of ambiguous taxa. 

The Chironomidae (midges, Diptera) were the most common 

group, comprising a mean of 35 percent of the taxa identified 

per sample. The Ephemeroptera (mayflies) comprised a mean 

of about 18 percent of the taxa, and the Trichoptera (caddisflies) comprised a mean of about 13 percent of the taxa identified per sample. The remainder of the taxa included Plecoptera 

(stoneflies, 1 percent), noninsects (such as snails and worms, 

8 percent), and other organisms such as Coleoptera (beetles) 

and Odonata (dragonflies and damselflies). In general, the 

proportion of Ephemeroptera, Plecoptera, and Trichoptera 

(EPT), both as number of taxa and relative abundance of 

organisms, is expected to be greater with good water-quality 

conditions, and the proportion of Chironomids and noninsects 

is expected to be greater in response to increasing perturbation 

(disturbance or decline in water quality; Barbour and others, 

1999). These are general patterns, however, and the harsh 
Table 15. Macroinvertebrate metrics for samples collected from riffles, Powder River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River. m2, square meter]

Site 

number 

(fig. 1)

Sample 

date

Taxa richness

)

2 Density (number/m

Taxa percentage abundance Functional group richness Functional group percentage abundance

Total

Ephemeroptera

Plecoptera

Trichoptera

Chironomidae

Noninsect taxa

Ephemeroptera

Plecoptera

Trichoptera

Chironomidae

Noninsects

Dominant taxon

Dominant five taxa

Predator taxa

Gatherer-collector taxa

Filterer-collector taxa

Scraper taxa

Shredder taxa

Predator

Gatherer-collector

Filterer-collector

Scraper

Shredder

R2 9/15/2005 28 4 0 2 5 3 237 2 0 19 10 14 26 70 11 10 2 3 1 18 23 19 39 0

T1 8/15/2005 35 8 0 8 5 5 2,274 76 0 14 2 3 33 81 6 15 4 5 2 3 79 12 4 2T1 8/23/2006 34 7 0 7 9 4 14,808 32 0 33 9 3 25 72 4 13 6 5 2 3 51 12 26 1T2 8/17/2005 26 8 0 4 5 4 4,394 57 0 16 1 10 27 72 5 12 4 2 1 7 72 15 5 0T2 8/22/2006 29 6 0 4 8 4 8,984 42 0 7 7 1 32 86 5 12 4 3 2 2 75 6 12 1T3 6/15/2005 35 1 0 6 11 5 3,871 34 0 3 3 11 42 86 7 12 8 3 1 2 44 50 3 0T3 6/28/2006 37 2 1 5 13 5 4,198 37 0 33 7 5 37 78 7 14 8 3 2 3 58 34 5 1T4 6/14/2005 39 2 0 2 19 6 1,537 12 0 7 19 41 24 59 5 21 4 4 1 6 57 19 10 0T4 6/27/2006 35 2 0 3 17 5 5,647 6 0 15 11 45 36 74 10 13 5 2 3 3 52 30 11 2T5 8/15/2005 30 7 0 4 7 1 8,452 44 0 30 3 2 26 77 6 9 6 4 1 1 62 31 4 1T5 8/22/2006 32 7 0 6 8 5 1,323 25 0 17 6 12 32 75 6 12 5 5 1 5 61 15 18 0T7 6/13/2005 39 2 0 1 16 4 2,571 1 0 1 49 15 25 70 15 18 1 1 2 10 59 25 4 1T8 8/25/2006 28 2 0 5 11 1 3,830 20 0 32 10 0 27 81 5 11 6 4 0 3 48 35 13 0T9 9/14/2005 31 5 1 7 12 0 7,763 69 0 14 9 0 55 76 6 13 6 3 2 3 74 17 3 1T9 8/24/2006 33 6 0 5 7 8 6,791 39 0 13 3 9 28 78 9 11 6 3 1 10 71 11 7 0

T10 8/16/2005 31 6 0 5 8 7 1,340 26 0 19 17 12 20 66 5 12 6 5 1 8 56 15 19 1T10 8/28/2006 24 4 0 4 4 4 2,338 7 0 10 1 9 68 88 5 9 4 4 0 1 77 12 10 0T11 6/22/2005 47 1 0 0 27 2 654 0 0 0 61 24 27 71 19 21 2 1 3 17 58 4 19 2T12 6/21/2005 44 2 0 2 18 5 1,907 4 0 4 31 48 28 68 15 16 4 3 2 21 40 7 29 1T13 6/23/2005 40 3 0 0 18 3 1,934 2 0 0 23 56 29 72 15 14 2 3 4 17 38 12 31 1T14 9/12/2005 24 7 0 6 4 0 7,760 67 0 26 1 0 45 79 3 10 5 4 0 1 66 26 7 0T14 8/28/2006 30 9 1 6 6 2 1,248 46 1 36 2 0 24 73 6 11 6 4 1 2 48 37 12 0T17 6/30/2005 31 1 0 3 15 4 2,806 1 0 51 13 3 46 84 6 13 6 3 0 4 9 79 3 0

Ecological Assessment 49
Table 15. Macroinvertebrate metrics for samples collected from riffles, Powder River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River. m2, square meter]

Site 

number 

(fig. 1)

Sample 

date

Taxa richness

)

2 Density (number/m

Taxa percentage abundance Functional group richness Functional group percentage abundance

Total

Ephemeroptera

Plecoptera

Trichoptera

Chironomidae

Noninsect taxa

Ephemeroptera

Plecoptera

Trichoptera

Chironomidae

Noninsects

Dominant taxon

Dominant five taxa

Predator taxa

Gatherer-collector taxa

Filterer-collector taxa

Scraper taxa

Shredder taxa

Predator

Gatherer-collector

Filterer-collector

Scraper

Shredder

T17 6/28/2006 26 2 0 4 11 4 19,592 0 0 23 7 7 57 89 3 12 6 1 1 1 7 90 1 0T18 9/13/2005 30 7 1 5 10 0 1,285 39 1 37 15 0 27 75 6 10 7 3 1 3 40 38 7 1T18 8/31/2006 38 10 2 8 10 1 1,109 55 1 23 3 0 29 65 9 14 5 9 1 3 58 20 18 0T19 6/23/2005 5 0 0 1 3 0 8,423 0 0 0 1 0 98 100 2 1 2 0 0 1 0 99 0 0

P1 7/20/2005 38 7 0 3 22 2 3,035 18 0 28 43 4 13 52 7 21 5 3 0 13 46 33 6 0P1 7/24/2006 34 7 0 3 16 1 2,422 32 0 26 34 1 21 66 9 13 5 4 1 9 50 37 1 3P2 7/21/2005 20 4 0 3 10 0 3,864 9 0 5 86 0 57 84 6 5 4 2 1 7 13 59 3 7P2 7/25/2006 33 4 0 3 17 1 6,891 6 0 10 77 0 23 69 8 13 6 1 1 6 57 29 0 3P3 7/19/2005 21 5 0 1 8 1 1,480 16 0 10 7 0 65 93 7 6 4 1 1 4 12 76 7 1P3 7/26/2006 28 4 1 4 10 1 2,869 14 0 57 19 1 53 89 7 10 5 4 1 7 18 73 1 1P4 7/22/2005 17 4 1 2 7 0 348 9 0 46 15 0 41 82 4 6 4 1 1 12 12 71 0 2P4 7/27/2006 24 1 1 4 12 1 3,826 1 0 36 52 5 41 83 6 8 4 3 1 11 5 78 5 1P5 7/13/2005 16 5 0 2 5 1 1,346 12 0 18 2 1 66 97 2 7 4 0 1 1 13 85 0 0P5 7/28/2006 21 5 1 4 6 0 275 8 0 59 15 0 37 81 5 7 5 2 2 16 17 64 1 2P6 7/11/2005 34 8 0 4 10 3 2,035 53 0 23 6 5 29 68 6 14 5 4 1 2 59 32 4 1P7 7/12/2005 17 6 0 3 2 1 5,655 5 0 6 0 0 85 95 3 6 4 1 1 2 6 92 0 0P8 7/23/2005 34 4 0 2 18 1 290 6 0 20 55 3 25 61 9 14 5 1 2 17 24 51 0 6P9 7/24/2005 32 6 0 1 17 2 144 11 0 4 45 2 21 58 8 15 3 2 2 30 21 31 1 15

P10 9/13/2005 17 6 0 4 3 1 5,069 74 0 20 0 0 62 92 2 7 4 3 0 0 79 20 1 0P10 8/21/2006 34 5 0 6 10 5 16,800 18 0 42 9 4 30 74 10 12 5 4 1 3 45 42 9 2P11 7/25/2005 26 12 0 3 4 1 3,673 49 0 32 1 0 16 67 3 12 5 4 1 1 40 49 10 0P11 8/3/2006 24 3 1 4 8 2 2,729 5 0 67 11 3 45 86 8 7 3 4 1 2 23 69 3 3P12 7/26/2005 29 7 0 5 9 1 925 34 0 32 12 3 19 79 6 9 4 7 1 2 37 49 3 9

50 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 15. Macroinvertebrate metrics for samples collected from riffles, Powder River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River. m2, square meter]

Site 

number 

(fig. 1)

Sample 

date

Taxa richness

)

2 Density (number/m

Taxa percentage abundance Functional group richness Functional group percentage abundance

Total

Ephemeroptera

Plecoptera

Trichoptera

Chironomidae

Noninsect taxa

Ephemeroptera

Plecoptera

Trichoptera

Chironomidae

Noninsects

Dominant taxon

Dominant five taxa

Predator taxa

Gatherer-collector taxa

Filterer-collector taxa

Scraper taxa

Shredder taxa

Predator

Gatherer-collector

Filterer-collector

Scraper

Shredder

P13 7/19/2005 10 5 1 1 1 0 2,646 66 0 1 0 0 65 99 3 5 2 0 0 1 66 34 0 0P13 8/2/2006 28 4 1 6 10 2 1,872 15 0 55 18 2 47 80 7 10 4 4 1 11 24 54 6 5P15 6/13/2005 12 2 0 2 5 1 10,181 1 0 2 1 0 94 99 2 5 3 1 0 0 2 96 0 0P15 6/23/2006 29 2 0 4 11 2 4,427 1 0 91 4 1 77 94 7 11 4 2 1 4 3 91 1 0P16 6/27/2005 37 2 0 3 19 3 502 3 0 47 24 2 38 66 8 17 4 3 1 9 13 58 8 0P17 7/21/2005 20 6 1 3 6 1 506 59 0 18 13 0 41 82 5 8 3 1 2 3 69 26 1 2P18 7/22/2005 9 4 1 2 1 0 8,825 74 0 7 0 0 74 100 1 5 3 0 0 0 74 25 0 0

C3 6/27/2005 28 2 0 2 16 3 2,136 3 0 0 28 51 38 84 7 14 3 1 0 4 35 18 42 0C4 6/9/2005 16 1 0 0 7 2 4,275 1 0 0 2 1 94 98 5 5 3 1 0 1 3 95 0 0C6 6/6/2005 18 1 0 1 10 1 2,708 0 0 0 4 1 94 98 5 8 2 1 1 3 2 94 1 0B1 6/29/2005 17 1 0 1 7 2 3,740 0 0 1 2 19 76 98 6 7 1 0 0 2 20 77 0 0

Ecological Assessment 51
Figure 20. Similarities of macroinvertebrate communities within stream drainages depicted by nonmetric 

multidimensional scaling ordination, Powder River Structural Basin, 2005.

B1

C3

C4 C6

P1

P10

P11

P12

P13

P15

P16

P17

P18

P2

P3

P4

P5

P6

P6R

P7

P8

P9

R2

T1

T10

T11

T12

T13

T17 T14 T18

T19

T1R T2

T3

T4

T5

T7

T9

Powder River main-stem group

Tongue River 

main-stem group 

and mountainous 

tributaries

Cheyenne and 

Belle Fourche 

Rivers group

Tongue River plains 

tributaries group

52 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

the three tributaries drain to the Powder River, the common 

variable among the three tributaries and the main stem of the 

Tongue River is their origin in the Bighorn Mountains. The 

inclusion of site P11, Powder River below Clear Creek, in 

the Tongue River group might be a reflection of the effect 

of Clear Creek on the main stem of the Powder River. The 

Tongue River group generally is characterized by relatively 

large Ephemeroptera taxa richness and relative abundance, and 

smaller percentages of Chironomidae and noninsects than the 

mean of the 2005–06 riffle samples (PRB mean). The Tongue 

River group also has a relatively large percentage of the 

gatherer-collector functional group with a mean abundance of 

60 percent. Dominant taxa in the Tongue River group include 

Ephemeroptera such as Baetis, Tricorythodes, and Fallceon 

quilleri, although caddisfly larvae such as Hydropsyche and 

Cheumatopsyche, riffle beetles Microcylloepus pusillus, and 

blackfly larvae Simulium also occur in the dominant five taxa. 

Macroinvertebrate communities from the main stem 

of the Powder River during 2005 form a group in the upper 

right corner of figure 20. The Powder River main-stem group 

is characterized by slightly fewer taxa (mean of 20 taxa per 

sample), with greater relative abundance of Ephemeroptera 

and Chironomidae, and less relative abundance of Trichoptera 

and noninsects, than the PRB mean. Filterer-collectors, such 

as Simulium and Cheumatopsyche, had a mean abundance of 

53 percent, which is larger than the PRB mean of 43 percent. 

Chironomidae, including Tanytarsus and Cricotopus, were 

among the dominant five taxa at some of the sites in the 

upstream part of the main-stem Powder River. The mayfly 

Traverella albertana dominated the 2005 samples from the 

downstream part of the Powder River (sites P13, P17, and 

P18). 

Macroinvertebrate communities from the Tongue River 

tributaries with plains origins, including Hanging Woman 

Creek, Squirrel Creek, and Youngs Creek, are somewhat 

similar to each other and form a group in the lower left of 

figure 20. The Tongue River plains tributaries group contained 

a mean of 40 taxa per sample, which is relatively large; 

noninsects and Chironomidae had a mean abundance of 

74 percent. Dominant taxa in the Tongue River plains tributaries group included snails, Physa and Lymnaea, the scud (Crustacea) Hyallela azteca, and the Chironomid Micropsectra. 

Some of the 2005 samples from the Cheyenne and Belle 

Fourche River drainages had macroinvertebrate communities 

that were somewhat similar to each other (fig. 20, left center). 

A few samples, such as from Rosebud Creek, Pumpkin Creek, 

and the Little Powder River, were either loosely or not associated with communities at other sites. 

Clustering and ordination of the 2006 macroinvertebrate 

data indicated persistence of two of the main groups observed 

from the 2005 data. The groups in the 2006 macroinvertebrate 

communities are the Tongue River and mountainous tributaries 

and the main stem of the Powder River (fig. 21). Macroinvertebrate communities in the Tongue River group contained a 
Figure 21. Similarities of macroinvertebrate communities within stream drainages depicted by nonmetric 

multidimensional scaling ordination, Powder River Structural Basin, 2006.

T9 P10 P1

P11

P13

P15

P2

P3

P4

P5

T1

T10

T14

T17

T18

T2

T3

T4

T5

T8

Tongue River main-stem and Powder River main-stem group

mountainous tributaries group

Ecological Assessment 53

smaller mean percentage of Ephemeroptera relative abundance 

in 2006 (32 percent) than in 2005 (54 percent) but were still 

slightly larger than the PRB mean (25 percent). The mean 

relative abundances of Chironomidae and noninsects in 2006 

were similar to those in 2005 and were less than the PRB 

mean. Dominant taxa in the Tongue River group for 2006 

included Tricorythodes, Microcylloepus pusillus, Chimarra

(Trichoptera: Philopotamidae), Fallceon quilleri, and Hydropsyche. As in 2005, the 2006 samples from the Tongue River 

group contained larger mean percentages of collector-gatherers 

and smaller percentages of filterer-collectors than the PRB 

mean. 

Macroinvertebrate communities from sites on the main 

stem of the Powder River generally were grouped together 

(fig. 21), but the group contained fewer sites in 2006 than 2005 

because some of the sites on the main stem had no flow (pools 

present but not riffles) in 2006. Taxa richness in the Powder 

River group was greater in 2006 (mean of 28 taxa per sample) 

than in 2005 (mean of 20 taxa per sample), and the community composition was somewhat different. The communities 

consisted of a larger mean relative abundance of Trichoptera 

and Chironomidae and smaller mean relative abundance of 

Ephemeroptera in 2006 than in 2005. Dominant taxa in 2006 

included Cheumatopsyche and Tanytarsus, similar to 2005, 

but Simulium was not among the dominant five taxa in 2006 

as it was in 2005. The difference in community composition 

between years could be a reflection of different environmental 

conditions, the different number of sites sampled, or some 

combination of those factors. The predominant functional 

group of the macroinvertebrate communities of the mainstem Powder River sites in 2006 was the filter-collector group 

(mean abundance of 57 percent), similar to 2005. The sample 

from site P5, Powder River above Crazy Woman Creek, was 

an outlier from the main-stem Powder River group in 2006, 

perhaps due to smaller taxa richness and smaller percentage 

of Chironomids at site P5 compared to other sites on the main 

stem. 

Effect of Environmental Variables on Macroinvertebrate 

Communities

Environmental variables that were assessed for effect 

on macroinvertebrate communities fell into three main 

categories—geographic, habitat, and water-quality variables. Geographic variables included location (northing and 

easting), drainage area, elevation, and the reachwide estimate 

of riparian disturbance. Habitat variables were selected from 

the reachwide measurements presented previously in this 

report in the “Habitat Characteristics of Streams in the Powder 

River Structural Basin” section and microhabitat variables 

that were measured at the point of the macroinvertebrate 

sample collections (table 27 in Appendix 1). The PCA of 

the habitat data indicated seven habitat variables were best 

suited to carry forward in further analyses. These variables 
54 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

were mean reachwide embeddedness, percentage of gravel 

or larger substrate, mean wetted width, mean bankfull height 

above water surface, microhabitat velocity, fish cover, and 

thalweg depth (table 16). Water-quality variables included 

major ions and onsite measurements of specific conductance, 

pH, water temperature, dissolved oxygen, and turbidity that 

were collected with the macroinvertebrate samples (table 28 in 

Appendix 1); streamflow was included with the water-quality 

variables because of the relation between water chemistry and 

streamflow (Clark and Mason, 2007). Variables selected on the 

basis of the PCA in the water-quality data set were streamflow, 

specific conductance, water temperature, calcium, magnesium, 

and turbidity; alkalinity also was carried forward because of 

potential toxicity of bicarbonate (Skaar and others, 2006) and 

use of alkalinity in the Wyoming O/E model (Hargett and 

others, 2007). 

The PCA analysis of the final environmental variables 

indicated the linear combinations of the variables that best 

explained the variation in the data (table 17). Streamflow and 

wetted width were strongly and positively correlated with 

PCA axis 1 as indicated by the relatively large values of the 

eigenvectors (a measure of association) for those variables 

in table 17. Specific conductance, magnesium, and alkalinity were negatively correlated with PCA axis 1. The variables 

associated with PCA axis 1 cumulatively explain 29 percent of 

the variability in the environmental data. The variables most 

strongly correlated with PCA axis 2 were calcium (positive) 

and fish cover (negative: table 17). The variables associated with PCA axis 2 explain 22 percent of the variability in 

the environmental data. Together, PCA axes 1 and 2 explain 

51 percent of the variability in the environmental data. Eigenvectors listed in table 17 also are shown in figure 22, where 

the length and direction of the vector in the figure corresponds 

to the positive or negative values in the table. Eigenvectors 

were computed for additional axes 3 to 5, but the data are not 

shown because they explained only a small amount of the variability. 

The PCA ordination also can be used to show relations among sampling sites on the basis of differences in the 

environmental variables. Main-stem sites on the Tongue and 

Powder Rivers plotted to the right (positive values) on PCA 

axis 1 (fig. 22) because of their higher streamflow and greater 

widths, whereas smaller streams with large specific conductance values and larger magnesium concentrations, such as 

Squirrel Creek (site T7) and Hanging Woman Creek (sites T11 

and T12), plotted to the left (negative values) on axis 1. Sites 

with large calcium concentrations, such as sites C3 and C6 on 

the Cheyenne River, plotted near the top of figure 22, whereas 

sites with large values for fish cover tended to plot near the 

bottom (for example, site R2 on Rosebud Creek, site T4 on 

Youngs Creek, and site T12 on Hanging Woman Creek). 

Some of the environmental variables that were important in describing variability among sites also were correlated 

with the macroinvertebrate communities. The environmental 

variables listed in table 16 were tested against the Bray-Curtis 

similarity indices of the macroinvertebrate communities, using 

the BEST routine (Clarke and Gorley, 2006). Two combinations of five environmental variables were identified that 

produced the best correlation (largest values of Spearman’s 

rho, ρ) between environmental variables and the macroinvertebrate communities. Streamflow and magnesium, which 

were correlated with PCA axis 1, were in the first combination along with drainage area, easting, and embeddedness 

(ρ = 0.66). A second combination, also using streamflow, 

drainage area, easting, and embeddedness but using specific 

conductance in place of magnesium, also indicated ρ = 0.66. 

Successive iterations from the BEST routine indicated 

substrate, thalweg depth, and alkalinity also were useful 

explanatory variables associated with slightly smaller correlation coefficients. 

The correlations of the environmental variables with the 

macroinvertebrate communities determined from the BEST 

routine also are evident to some degree from the PCA and 

NMDS ordinations. Streamflow, for example, was identified 

as an important variable from the BEST and PCA routines. 

Sites with high streamflow, such as sites T10, T14, and T18 

on the main stem of the Tongue River, were grouped together 

in the NMDS ordination (fig. 20) and plotted along the upper 

end of PCA axis 1 (fig. 22). Specific conductance, magnesium, and alkalinity were identified from the BEST and PCA 

routines. Sites in the Tongue River plains tributaries group of 

the NMDS ordination, such as Squirrel Creek and Hanging 

Woman Creek, generally had relatively large concentrations 

of magnesium and alkalinity but large specific conductance 

values were not confined to that group. 

The relations between macroinvertebrate communities 

and environmental variables described in this section should 

be considered tentative in part because they are based on only 

1 year (2005) of data. This analysis is constrained to the 2005 

data for consistency and because fewer data were collected 

during 2006 by design and because of drought. Additional 

sampling and data analysis would be required to confirm the 

patterns described and to better determine which variables 

have the most effect on the macroinvertebrate communities of 

the PRB. 
Table 16. Environmental variables tested for correlation with macroinvertebrate communities, Powder River Structural Basin, 

Wyoming and Montana, 2005.

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. UTM, Universal Transverse Mercator; km2, square kilometers; NGVD 29; 

National Geodetic Vertical Datum of 1929; Riparian disturbance index, proximity-weighted disturbance value from table 12; °C, degrees Celsius; ft3/s, cubic 

feet per second; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per liter; NTU, nephelometric turbidity units; embed, embeddedness; m, meters; 

m/s; meters per second; cm, centimeters]

Site 

number 

(fig. 1)

Northing

(UTM)

Easting

(UTM)

Drainage 

area 

(km2)

Elevation 

(meters above 

NGVD 29)

Riparian 

disturbance

index

Streamflow 

(ft3/s)

Specific 

conductance 

(μS/cm) 

Water 

temperature 

(°C)

R2 5124517.888 386333.771 3,372 756 1.33 0.01 4,300 12.5

T1 4973858.036 340495.082 1,238 1,104 .67 123 426 14.8

T2 4972252.878 342979.36 1,070 1,104 1.31 69 653 20.5

T3 4987865.115 343428.017 56 1,155 1.93 2.3 675 19

T4 4982029.167 348566.429 161 1,088 .49 0.99 1,690 12

T5 4984576.562 351846.947 3,711 1,058 2.44 171 544 19

T7 4986086.578 353305.488 112 972 .37 0.17 5,940 13

T9 4985576.746 355352.485 3,763 1,045 .66 162 655 13.6

T10 5014073.901 372568.691 5,208 890 1.65 408 363 20

T11 4998957.461 383277.047 831 954 2.12 .03 5,000 22.5

T12 5009470.727 382314.206 958 997 2.00 .04 3,870 24.5

T13 5017290.634 381784.208 1,217 960 3.32 .11 2,090 20.3

T14 5029715.78 385974.163 6,788 933 2.47 308 466 18.5

T17 5049075.745 402126.116 1,831 889 1.76 1.6 2,700 18

T18 5076962.445 405325.098 10,225 841 1.37 330 503 14.5

T19 5119648.757 446791.955 1,805 759 1.59 1.1 1,140 29.4

P1 4837546.759 386240.398 5,828 1,351 1.18 2.7 2,100 21.8

P2 4838293.577 393351.624 7,980 1,338 .14 13 4,990 23

P3 4863077.684 405281.187 9,808 1,311 1.13 9.3 4,810 24.3

P4 4889766.716 407729.405 11,111 1,216 .93 7.9 4,600 20.7

P5 4919955.969 409348.212 12,564 1,152 .93 25 3,500 26.1

P6 4901608.494 386626.475 1,769 1,280 .80 37 777 20.8

P7 4924960.865 402567.494 2,385 1,168 1.41 40 894 22.7

P8 4928773.725 412209.471 15,286 1,134 1.43 99 2,050 21.4

P9 4963029.492 416891.369 17,050 1,063 .74 149 2,280 24

P10 4969263.986 414514.112 2,875 1,069 1.15 35 1,200 13.6

P11 4971737.101 416543.372 20,106 1,059 .33 92 1,940 21.2

P12 4989743.314 430909.122 20,943 1,022 .67 76 1,930 18.2

P13 5030458.647 468600.245 22,657 920 1.33 111 1,690 22.5

P15 4974895.432 472160.404 3,204 1,040 1.93 3.8 3,480 13.6

P16 4994637.05 473972.815 3,991 991 1.50 7.6 2,720 17.5

P17 5042532.613 473714.003 29,503 909 1.87 85 1,820 28.5

P18 5141871.762 476225.295 33,846 727 2.25 90 1,970 21.3

C3 4808475.814 496335.272 39,55 1,314 1.32 0 3,070 21.3

C4 4833621.645 507615.667 606 1,341 1.47 .02 1,950 14.3

C6 4808073.951 570694.767 13,649 1,105 1.52 6.4 3,910 20.4

B1 4870218.204 468902.131 1,282 1,384 1.53 1 3,360 16.6

Ecological Assessment 55
Site 

number 

(fig. 1)

Calcium 

(mg/L)

Magnesium 

(mg/L)

Alkalinity 

(mg/L)

Turbidity 

(NTU)

Mean 

reach-wide 

embeddedness 

(percent)

Percentage of 

gravel 

or larger 

substrate

Mean 

wetted 

width 

(m)

Mean 

bankfull 

height 

(m above 

water 

surface)

Microhabitat 

velocity 

(m/s)

Reachwide fish 

cover 

(percent)

Thalweg 

depth 

(cm)

R2 73.8 183 450 9.1 62 71 5.0 0.34 0.16 111 26

T1 44.2 19.6 167 30 50 71 19.0 .35 .42 65 63

T2 54.1 34.5 194 9 58 69 16.4 .65 .55 34 62

T3 55.1 38.2 293 62 90 4 2.2 .43 .81 54 31

T4 108 149 422 33 99 0 1.8 .64 .41 94 31

T5 56.9 31.9 210 48 69 40 30.0 .54 .94 17 88

T7 153 463 590 6.8 91 7 .9 .30 .24 25 18

T9 54.2 35.7 208 12 76 31 34.3 .59 .49 45 77

T10 37.2 17 130 13 55 69 29.2 .64 .59 37 101

T11 140 249 492 10 88 24 3.4 .40 .00 73 31

T12 81.8 200 414 9 91 16 2.7 .40 .19 81 24

T13 77.4 113 572 7 95 9 5.6 .40 .15 73 32

T14 44.9 22.3 160 10 71 43 26.7 .70 .58 33 79

T17 87.3 180 592 97 83 18 5.5 .05 .44 49 58

T18 45 23.6 156 16 56 49 25.4 .80 .83 53 112

T19 32 14.5 214 158 65 44 6.2 .40 .21 10 25

P1 175 74.7 177 4.7 69 12 14.1 1.13 .36 13 22

P2 113 75.4 288 16 72 32 15.0 1.26 .35 12 23

P3 183 111 187 2.9 86 18 26.6 1.17 .19 20 20

P4 115 100 318 4.1 70 30 21.9 .77 .21 9 26

P5 122 72.6 233 28 92 2 37.7 .93 .34 3 32

P6 79.9 40.5 122 58 77 16 8.6 1.05 .38 16 68

P7 82.5 40.7 145 120 81 38 9.0 .90 .66 17 58

P8 232 46.3 92 960 90 12 41.4 .84 .53 1 29

P9 287 77.5 101 1,000 98 8 29.4 .51 .41 5 41

P10 109 46.9 154 4.3 65 40 19.7 .61 .45 25 63

P11 206 59.8 132 420 78 28 37.5 1.05 .41 10 49

P12 79.9 36.1 153 619 65 29 47.0 .58 .31 11 37

P13 130 59.3 198 18 71 25 30.8 1.09 .63 13 60

P15 189 145 344 120 86 7 6.0 .85 .60 18 52

P16 152 84.8 246 810 76 45 5.3 .97 .67 10 61

P17 136 62.6 201 22 94 3 52.4 1.26 .30 5 50

P18 122 62 212 22 64 45 51.1 1.14 .40 9 40

C3 252 155 284 4.8 90 11 10.0 .72 .10 33 30

C4 82.5 61.9 225 41 53 22 3.4 .68 .05 52 52

C6 323 139 239 163 71 7 7.4 .39 .20 19 25

B1 112 151 90 3.8 96 2 6.0 .41 .17 81 6

Table 16. Environmental variables tested for correlation with macroinvertebrate communities, Powder River Structural Basin, 

Wyoming and Montana, 2005.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River. UTM, Universal Transmercator; km2, square kilometers; NGVD 29; National 

Geodetic Vertical Datum of 1929; Riparian disturbance index, proximity-weighted disturbance value from table 12; °C, degrees Celsius; ft3/s, cubic feet per 

second; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per liter; NTU, nephelometric turbidity units; embed, embeddedness; m, meters; m/s; 

meters per second; cm, centimeters]

56 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Figure 22. Principal components analysis showing relations among sampling sites based on selected environmental variables, 

Powder River Structural Basin, 2005. Environmental variables are listed in table 16.

Northing

Easting

Drainage area

Elevation

Riparian disturbance

Water temperature

Streamflow

Specific conductance

Calcium

Magnesium

Alkalinity

Turbidity

Embeddedness

Substrate size

Wetted width

Bankfull height

Microhabitat velocity

Fish cover

Thalweg depth 

−6 −4 −2 0 2 4

PRINCIPAL COMPONENTS ANALYSIS AXIS 1

−4

−2

0

2

4

T7

PRINCIPAL COMPONENTS ANALYSIS AXIS 2

R2

T2

T3

T4

T7 T11 T12

T13

T17

T19

C3

C4

C6

B1

P6

P7

P10

P15

P16

T1

T5

T9

T10

T14

T18

P1

P2

P3

P4

P5

P8

P9

P11

P12 P13

P17

P18

Table 17. Eigenvectors from principal components analysis of environmental variables, Powder River Structural Basin, Wyoming and 

Montana, 2005.

Variable Axis 1 Axis 2

Northing 0.121 –0.291

Easting –.009 .271

Drainage area .251 .272

Elevation –.106 .241

Riparian disturbance .023 –.124

Water temperature .076 .255

Streamflow .374 .049

Specific conductance –.307 .185

Calcium –.098 .379

Magnesium –.356 –.012

Variable Axis 1 Axis 2

Alkalinity –0.308 –0.177

Turbidity .149 .122

Embeddedness –.216 .193

Substrate size .208 –.281

Wetted width .304 .171

Bankfull height .188 .278

Microhabitat velocity .275 –.135

Fish cover –.192 –.352

Thalweg depth .296 –.195

Ecological Assessment 57
58 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

Modeling and Metric Indices

The following sections present analyses of ATG macroinvertebrate data from riffle samples. Analyses included O/E 

models and MMIs developed by the States of Wyoming and 

Montana.

Wyoming Observed/Expected Index Biological Condition

Overall, the Wyoming O/E scores indicated biological 

condition was about the same in 2005 (mean = 0.54) as in 

2006 (mean = 0.56) at sites where both years of data were 

collected; the difference between years was not significant 

(P > 0.05). During 2005–06, Wyoming O/E scores ranged 

from 0 at Powder River below Salt Creek (site P2) to 0.95 at 

Crazy Woman Creek below I-90 (site P6; table 18). The wide 

variety of biologic conditions in streams sampled for this study 

is reflected in the wide range of O/E scores (fig. 23). 

Despite the variability in O/E scores, some general broadscale patterns were identified. ATG sampling sites located 

on streams with mountain origins had higher O/E scores 

compared to sites on streams with plains origins. This is not 

surprising because water from mountain streams generally 

is of high quality as a result of persistent flows, cool water 

temperatures, small concentrations of dissolved constituents, 

and low turbidity. The PCA of environmental variables and 

macroinvertebrate communities by site validated this spatial 

pattern (fig. 22). Conversely, plains-origin streams in the 

region, such as the Powder River, are characterized by large 

dissolved concentrations and turbidity attributed to the erodible soils and geology in their drainages. Flow regimes of 

plains-origin streams are dependent on springs and intense 

precipitation. For both years, O/E scores generally were 

highest in the Tongue River drainage, followed by the Powder, 

Belle Fourche, and Cheyenne River drainages, respectively. 

Higher O/E scores in the Tongue River drainage are related to 

the dominance of higher quality snowmelt-driven streams with 

mountainous headwaters compared to the other drainages. An 

evaluation of the spatial and temporal patterns at the drainage 

scale is described in the following sections.

Tongue River Drainage

Among samples collected from three sites on the main 

stem of the Tongue River (sites T1, T5, and T9), the O/E 

score decreased slightly from 2005 (mean = 0.78) to 2006 

(mean = 0.71), although the difference was not significant 

(P > 0.05; fig. 23). Overall, O/E scores were higher at site T1 

than at site T9 in both 2005 and 2006 (fig. 23), partially due to 

absence of expected mayfly (Ephemerella), caddisfly (Helicopsyche and Nectopsyche), and riffle beetle (Zaitzevia) taxa, 

which have low to moderate stressor tolerances. 

O/E scores also were computed for sites on tributaries to 

the Tongue River. Both sites on Youngs Creek (sites T3 and 

T4) had improved biological conditions on the basis of O/E 

scores from 2005 (combined mean = 0.71) to 2006 (combined 

mean = 0.81), although the improvements were not significant (P > 0.05; fig. 23). Similar to Youngs Creek, Prairie Dog 

Creek (site T8) had a relatively high O/E score of 0.74 in 

2006 (no riffle sample was collected from site T8 in 2005). 

The biological condition of Goose Creek (site T2) was similar 

in both years (O/E scores of 0.22 in 2005 and 0.21 in 2006), 

although this site had markedly lower O/E scores relative to 

sites on the Tongue River, Youngs Creek, and Prairie Dog 

Creek. At site T2, only three taxa were collected in each year 

out of 13 expected taxa in 2005 and 14 expected taxa in 2006. 

Because of Goose Creek’s flow regime and site T2’s location close to its mountain source, several less tolerant stonefly (Chloroperlidae and Pteronarcella), mayfly (Drunella, 

Ephemerella, and Rhithrogena), and caddisfly (Brachycentrus) 

taxa were expected to occur at site T2. The assemblage at 

site T2 was represented by a large percentage of taxa with 

moderate to high tolerances that include midges Microcylloepus and Rheocricotopus and the mayfly Tricorythodes. The 

PCA of environmental variables did not show site T2 separate 

from the rest of the Tongue River drainage sites (fig. 22), 

which indicates that one or more variables not represented by 

the PCA could be contributing to the low biological condition 

at site T2 on Goose Creek. 

Powder River Drainage

Among sites on the main-stem Powder River, O/E scores 

were similar in 2005 (mean = 0.44) and 2006 (mean = 0.44). 

In 2005, biological conditions appeared to improve with 

distance downstream (fig. 23), which might reflect the cumulative effects of tributary (particularly streams coming off the 

Bighorn Mountains) and spring inputs and perhaps increased 

habitat complexity. In 2006, fewer data points were available 

for the main-stem Powder River, and a downstream trend was 

not as obvious as in 2005, although the lowest O/E scores in 

2006 were for sites P1 and P2. 

Exceptions to the general pattern of improving biological condition with downstream direction on the main-stem 

Powder River include a substantial decrease in O/E scores 

in both years for the Powder River from above Salt Creek 

(site P1) to below Salt Creek (site P2). An appreciable absence 

of expected mayfly, caddisfly, beetle, and midge taxa, among 

other groups, contributed to the decrease in O/E scores for 

the Powder River below Salt Creek (site P2). Instead of the 

expected taxa, the macroinvertebrate community at site P2 

was dominated by tolerant midges such as Polypedilum and 

Tanytarsus. A large increase in specific conductance from 

site P1 to site P2 might partially explain the decline in biological condition (table 16). Analysis of the 2005 data also showed 

a decline in biological condition of the Powder River from 

below Crazy Woman Creek (site P8) to above Clear Creek 

(site P9), followed by an increase in O/E score below Clear 

Creek (site P11). Natural intermittency between sites P8 and 

P9 may have contributed to the decline in biological condition in this reach (Armentrout and Wilson, 1987). In 2006, the 
Table 18. Scores from the Wyoming observed/expected model and the Wyoming Stream Integrity Index metrics for macroinvertebrate samples collected at riffles in streams 

in Wyoming and adjacent areas of Montana, 2005–06.—Continued[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River]

Site 

number

(fig. 1)

Sampling 

date

Observed/expected score

Ephemeroptera taxa

Ephemeroptera taxa score

Trichoptera taxa

Trichoptera taxa score

Total taxa

Total taxa score

Trichoptera percentage (less 

Hydropsychidae)

Trichoptera percentage (less 

Hydropsychidae) score

Ephemeroptera percentage 

(less Baetidae)

Ephemeroptera percentage 

(less Baetidae) score

Collector-gatherer (percent)

Collector-gatherer (percent) 

score

Hilsenhoff Biotic Index

Hilsenhoff Biotic Index score

Wyoming Stream Integrity 

Index Score

R2 09/15/2005 0.67 4 50 2 22 27 64 0 0 2 4 28 82 3.64 100 46

T1 08/15/2005 .78 7 88 8 89 32 76 3 15 31 57 78 24 3.56 100 64

08/23/2006 .78 7 88 7 78 33 79 27 100 27 49 38 70 3.79 100 80

T2 08/17/2005 .22 8 100 4 44 25 60 3 13 19 35 63 41 3.61 100 56

08/22/2006 .21 6 75 4 44 29 69 6 31 32 58 53 53 4.06 100 62

T3 06/15/2005 .66 1 13 6 67 33 79 3 14 0 0 41 67 4.40 100 49

06/28/2006 .79 2 25 5 56 35 83 6 28 0 1 46 61 4.02 100 50

T4 06/14/2005 .76 2 25 2 22 34 81 3 15 1 3 56 49 4.80 100 42

06/27/2006 .82 2 25 3 33 30 71 4 19 1 2 56 49 5.66 83 40

T5 08/15/2005 .89 7 88 4 44 29 69 5 25 11 20 43 64 3.90 100 58

08/22/2006 .67 7 88 6 67 31 74 16 75 7 14 44 63 3.43 100 69

T7 06/13/2005 .45 2 25 1 11 36 86 1 6 0 1 62 43 5.68 83 36T8 08/25/2006 .74 2 25 5 56 26 62 2 7 16 30 30 80 4.15 100 51T9 09/14/2005 .67 5 63 7 78 31 74 7 31 59 100 73 30 4.13 100 68

08/24/2006 .67 6 75 6 67 33 79 12 56 9 17 44 64 3.64 100 65

T10 08/16/2005 .67 6 75 5 56 30 71 15 71 4 6 36 72 3.62 100 65

08/28/2006 .78 4 50 4 44 22 52 7 35 0 0 11 100 3.64 100 55

T11 06/22/2005 .32 1 13 0 0 46 100 0 0 0 0 72 30 4.36 100 35T12 06/21/2005 .63 2 25 2 22 42 100 1 5 4 7 67 37 4.19 100 42T13 06/23/2005 .33 3 38 0 0 40 95 0 0 0 1 67 37 4.11 100 39T14 09/12/2005 .67 7 88 6 67 24 57 2 11 55 100 55 50 3.06 100 68

08/28/2006 .67 9 100 6 67 29 69 25 100 17 32 44 63 3.57 100 76

Ecological Assessment 59
Table 18. Scores from the Wyoming observed/expected model and the Wyoming Stream Integrity Index metrics for macroinvertebrate samples collected at riffles in streams 

in Wyoming and adjacent areas of Montana, 2005–06.—Continued[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River]

Site 

number

(fig. 1)

Sampling 

date

Observed/expected score

Ephemeroptera taxa

Ephemeroptera taxa score

Trichoptera taxa

Trichoptera taxa score

Total taxa

Total taxa score

Trichoptera percentage (less 

Hydropsychidae)

Trichoptera percentage (less 

Hydropsychidae) score

Ephemeroptera percentage 

(less Baetidae)

Ephemeroptera percentage 

(less Baetidae) score

Collector-gatherer (percent)

Collector-gatherer (percent) 

score

Hilsenhoff Biotic Index

Hilsenhoff Biotic Index score

Wyoming Stream Integrity 

Index Score

T17 06/30/2005 .56 1 13 3 33 28 67 2 10 1 2 13 100 4.58 100 46

06/28/2006 .67 2 25 4 44 22 52 0 2 0 1 8 100 5.10 96 46

T18 09/13/2005 .89 7 88 5 56 30 71 1 3 26 48 49 57 3.81 100 60

08/31/2006 .78 10 100 8 89 35 83 3 17 22 40 55 51 3.81 100 69

T19 06/23/2005 .22 0 0 1 11 5 12 0 0 0 0 0 100 5.97 76 28

P1 07/20/2005 .20 7 88 3 33 35 83 5 23 7 13 45 62 4.69 100 57

07/24/2006 .27 7 88 3 33 30 71 0 1 25 46 47 60 4.24 100 57

P2 07/21/2005 0 4 50 3 33 20 48 2 12 9 17 21 90 5.66 83 48

07/25/2006 .13 4 50 3 33 28 67 6 29 5 10 59 46 5.58 85 46

P3 07/19/2005 .44 5 63 1 11 20 48 0 0 8 15 13 100 5.43 88 46

07/26/2006 .67 4 50 4 44 25 60 0 2 14 26 18 94 4.20 100 54

P4 07/22/2005 .56 4 50 2 22 17 40 0 0 2 4 13 99 4.85 100 45

07/27/2006 .45 1 13 4 44 21 50 3 13 1 2 5 100 4.92 100 46

P5 07/13/2005 .67 5 63 2 22 15 36 0 0 12 22 13 99 5.67 83 46

07/28/2006 .56 5 63 4 44 20 48 1 4 6 11 16 96 4.11 100 52

P6 07/11/2005 .95 9 100 4 44 33 79 2 8 41 76 56 49 4.08 100 65P7 07/12/2005 .84 6 75 3 33 16 38 0 1 2 4 5 100 5.62 84 48P8 07/23/2005 .67 4 50 2 22 30 71 0 0 5 9 18 94 3.78 100 50P9 07/24/2005 .44 6 75 1 11 31 74 0 0 11 19 21 90 4.98 98 53

P10 09/13/2005 .44 6 75 4 44 17 40 8 39 64 100 74 29 2.67 100 61

08/21/2006 .67 5 63 6 67 30 71 32 100 17 32 27 84 3.40 100 74

P11 07/25/2005 .78 12 100 3 33 26 62 0 1 30 56 33 77 3.94 100 61

60 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 18. Scores from the Wyoming observed/expected model and the Wyoming Stream Integrity Index metrics for macroinvertebrate samples collected at riffles in streams 

in Wyoming and adjacent areas of Montana, 2005–06.—Continued[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River]

Site 

number

(fig. 1)

Sampling 

date

Observed/expected score

Ephemeroptera taxa

Ephemeroptera taxa score

Trichoptera taxa

Trichoptera taxa score

Total taxa

Total taxa score

Trichoptera percentage (less 

Hydropsychidae)

Trichoptera percentage (less 

Hydropsychidae) score

Ephemeroptera percentage 

(less Baetidae)

Ephemeroptera percentage 

(less Baetidae) score

Collector-gatherer (percent)

Collector-gatherer (percent) 

score

Hilsenhoff Biotic Index

Hilsenhoff Biotic Index score

Wyoming Stream Integrity 

Index Score

08/03/2006 .56 3 38 4 44 20 48 1 5 3 5 11 100 4.10 100 49

P12 07/26/2005 .67 7 88 5 56 27 64 2 9 33 60 22 88 4.19 100 67P13 07/19/2005 .22 5 63 1 11 10 24 0 0 65 100 1 100 3.36 100 57

08/02/2006 .56 4 50 6 67 25 60 5 24 14 27 23 88 4.24 100 59

P15 06/13/2005 .44 2 25 2 22 12 29 0 0 1 2 2 100 5.93 77 36

06/23/2006 .67 2 25 4 44 26 62 1 4 0 0 2 100 4.00 100 48

P16 06/27/2005 .78 2 25 3 33 34 81 2 11 2 4 20 92 4.66 100 49P17 07/21/2005 .56 6 75 3 33 19 45 0 1 56 100 28 83 3.77 100 62P18 07/22/2005 .22 4 50 2 22 9 21 0 0 74 100 1 100 2.91 100 56

C3 06/27/2005 .11 2 25 2 22 28 67 0 1 2 3 75 27 3.04 100 35C4 06/09/2005 .11 1 13 0 0 15 36 0 0 1 2 3 100 6.01 75 32C6 06/06/2005 .11 1 13 1 11 18 43 0 0 0 0 2 100 5.92 77 35B1 06/29/2005 .42 1 13 1 11 16 38 1 5 0 0 20 91 6.29 69 32

Ecological Assessment 61
0

0.5

1

0

50

100

2005 2006

O/E SCORE

P1

0

0.5

1

2005 2006

O/E SCORE

0

50

100

0

0.5

1

2005 0

50

100

0

0.5

1

2005 2006 0

50

100

0

0.5

1

2005 0

0.5

1

2005 2006 0

0.5

1

2005 0

50

100

0

50

100

0

0.5

1

2005 2006 0

50

100

0

50

100

0

0.5

1

2005 2006 0

50

100

0

0.5

1

2005 2006 0

50

100

0

0.5

1

2005 2006 0

50

100

WSII SCORE

WSII SCORE

Powder River main-stem sites

P2 P3 P4 P5

P8 P9 P11 P12

O/E SCORE 0

0.5

1

0

50

100

P6

2005 0

0.5

1

2005 0

50

100

P7 P10

WSII SCORE WSII SCORE

Powder River tributary sites

0

0.5

1

2005 2006 0

50

100

0

0.5

1

2005 0

50

100

WSII SCORE

O/E SCORE

P15 P16

Tongue River main-stem sites

Tongue River tributary sites

0

0.5

1

O/E SCORE

0 0

50

100

O/E SCORE 0

0.5

1

0

50

100

T1

2005 2006

T5

0

0.5

1

0

50

100

2005 2006

0

0.5

1

0

50

100

2005 2006

T9

T2

2005 2006 0

0.5

1

50

100

2005 2006

T3 T4

Wyoming Stream Integrity Index (WSII) score

Wyoming observed/expected (O/E) model score

EXPLANATION

0

0.5

1

0

50

100

WSII SCORE

T7

2005 0 0

0.5

1

50

100

2006

T8

Figure 23. Wyoming observed/expected model and Wyoming Stream Integrity Index scores for macroinvertebrate samples collected 

in Wyoming and adjacent areas of Montana, 2005–06.

62 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Figure 23. Wyoming observed/expected model and Wyoming Stream Integrity Index 

scores for macroinvertebrate samples collected in Wyoming and adjacent areas of 

Montana, 2005–06.—Continued

Cheyenne River drainage sites

Belle Fourche River site

C3

O/E SCORE 0

0.5

1

2005 0

50

100

0

0.5

1

2005 0

50

100

0

0.5

1

2005 0

50

100

WSII SCORE

O/E SCORE 0

0.5

1

2005 0

50

100

WSII SCORE C6

B1

C4

Wyoming Stream Integrity Index (WSII) score

Wyoming observed/expected (O/E) model score

EXPLANATION

Ecological Assessment 63

O/E score in the Powder River decreased from above Pumpkin 

Creek (site P3) to below Burger Draw (site P4), then increased 

above Crazy Woman Creek (site P5). Absence of less tolerant 

mayflies (Fallceon quilleri, Leptophlebiidae, and Tricorythodes) played a large role in the decline in biological condition 

between sites P3 and P4. Many of these and other mayfly taxa 

were present at site P5, which contributed to the increase in 

the 2005 and 2006 O/E scores. 

Tributaries to the Powder River that were sampled were 

Crazy Woman Creek and Clear Creek, which have mountainous headwaters, and the Little Powder River, which has plains 

headwaters. O/E scores for Crazy Woman Creek decreased 

slightly with distance downstream from site P6 (0.94) to 

site P7 (0.84), although they were some of the highest scores 

in the study area (fig. 23). This was expected considering 

this stream’s mountain origins and mountainous headwaters 

(snowmelt-driven flow regime). However, Clear Creek 

(site P10) had a less favorable biological condition (0.45) 

than Crazy Woman Creek (sites P6 and P7) in 2005. Because 

of their common origins and flow regimes, the biological 

condition between Crazy Woman and Clear Creeks would be 

expected to be similar. The less favorable biological condition at site P10 was attributed to absence of both tolerant and 

potentially sensitive expected taxa such as the midge Orthocladius, Simuliidae (black flies), and the riffle beetle Dubiraphia. The biological-condition score at site P10 increased 

to 0.67 in 2006, although many members of the community 

remained a mixture of adaptive taxa with generally varying 

tolerances to pollution. 

Biological conditions in the Little Powder River were 

similar to biological conditions in the Powder River with 

an increase in O/E scores at Little Powder River above Dry 

Creek (site P15) from 2005 (0.44) to 2006 (0.67; fig. 23). 

The similarity in biological conditions between the Little 

Powder and Powder Rivers is expected considering their 

plains-dominated origins and largely spring-fed flow regimes 

supplemented by intense precipitation. Biological conditions 

became more favorable with distance downstream in 2005 in 

the Little Powder River from an O/E score of 0.44 above Dry 

Creek (site P15) to an O/E score of 0.78 at Biddle (site P16, 

fig. 23). Similar to the Powder River, cumulative tributary and 

spring inputs may partially explain the increase in O/E scores 

from site P15 to site P16. Collector-filterer midges and other 

fly larvae were common taxa collected at both of these Little 

Powder River sites. 

Belle Fourche and Cheyenne River Drainages

The O/E score of 0.42 for the macroinvertebrate community of the Belle Fourche River (site B1) in 2005 was similar 

to O/E scores for the Powder and Little Powder Rivers, likely 

due to similar drainage characteristics. In contrast, communities for sites C3, C4, and C6 in the Cheyenne River drainage 

had appreciably low O/E scores (0.11 for all three sites; 

fig. 23). These scores may be artificially low, however, and 

inaccurately represent the biological condition of the drainage. 

The low scores may be because of limitations of the model 

in accurately representing reference conditions in streams of 

the Cheyenne River drainage, which have a greater propensity for intermittent/ephemeral flow regimes relative to the 

Powder and Tongue River drainages. Despite model limitations, the macroinvertebrate assemblages among ATG sites in 

the Cheyenne River drainage were similar to one another and 
64 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

comparable to expected conditions derived from the literature 

for intermittent and ephemeral systems. Common macroinvertebrate fauna of intermittent and ephemeral streams consist 

of widespread opportunistic species that are tolerant of the 

naturally “harsh” environmental conditions and include small 

crustaceans, beetles, tolerant caddisflies and mayflies, and a 

large assemblage component of midges and other fly larvae 

(Zale and others, 1989; Peterson, 1990; Graham, 2002). 

Wyoming Stream Integrity Index Biological Condition

Although the relation between WSII and Wyoming 

O/E scores was poor (coefficient of determination R2 = 0.16, 

P < 0.05), the general spatiotemporal patterns of biological 

condition among ATG sites assigned by both indicators were 

similar. The relation between both indicators improved when 

data from only the 2005 sampling season were considered 

(R2 = 0.25, P < 0.05). No relation between indicator scores 

was found for the 2006 season (R2 = 0.03, P > 0.05), which 

probably is the result of a smaller data set and perhaps more 

variable environmental conditions. The range of WSII scores 

was smaller than the range of Wyoming O/E scores. During 

2005–06, WSII scores ranged from 32 at Little Thunder Creek 

(site C4) and the Belle Fourche River (site B1) to 80 at Tongue 

River at Monarch (site T1; table 18).

WSII scores increased from 2005 (mean = 53) to 2006 

(mean = 56) at sites sampled in both years, although similar to 

the O/E scores, the increase was not significant (P > 0.05). The 

broad-scale pattern in WSII scores largely mimicked what was 

revealed with the Wyoming O/E scores—higher WSII scores 

for sites on mountain-origin streams compared to plains-origin 

streams and improved biological condition for the Tongue 

River drainage, followed by the Powder, Cheyenne, and Belle 

Fourche River drainages, respectively.

Youngs Creek (sites T3 and T4) were similar between 2005 

(mean = 46) and 2006 (mean = 45). The WSII score at Prairie 

Dog Creek (site T8) was 51, which was slightly higher than 

scores from Youngs Creek. The WSII score at Goose Creek 

(site T2) was similar in both years (56 in 2005 and 62 in 2006) 

and slightly higher compared to scores from Youngs and 

Prairie Dog Creeks. However, complementing the Wyoming 

O/E scores, Goose Creek had a lower WSII score relative 

to sites on the Tongue River because of small values for 

Trichopteran taxa score and percentage of Trichoptera less 

Hydropsychidae (table 18). 

Powder River Drainage

Metrics that were most important in discriminating 

between high and low WSII scores for the Powder River 

drainage were the Hilsenhoff Biotic Index (R2 = 0.50) and 

the percentage of Ephemeroptera less Baetidae (R2 = 0.47), 

both of which exhibited a linear relation with WSII scores 

(fig. 24E–F). WSII scores among sites on the main-stem 

Powder River were similar in 2005 and 2006 (mean = 50, 

P > 0.05). The 2005 WSII scores tended to increase downstream from site P4 to site P12 as seen with the Wyoming 

O/E model (fig. 23). Corroborating results from the Wyoming 

O/E index, WSII scores showed the same decline in biological condition of the Powder River from sites P1 to P2 in 

both years. The decreases in WSII scores from sites P1 to P2 

were attributed to an appreciable loss of total taxa, including Ephemeroptera (mayflies) and Trichoptera (caddisflies). 

Specific to 2006, a substantial decrease in the percentage of 

Ephemeroptera less Baetidae was another contributor to the 

decreased WSII scores from sites P1 to site P2.

Mimicking the Wyoming O/E scores, WSII scores in 

2006 for the main-stem Powder River showed an improvement 

in biological condition from sites P2 to P3, a decline from 

sites P3 to P4, followed by an improvement at site P5 (fig. 23). 

Decreases in total taxa, percentage of Ephemeroptera less 

Baetidae, and number of Ephemeroptera taxa were the primary 

metrics causing the decrease in the WSII score from site P3 

to site P4. These declines are corroborated by the absence of 

expected mayfly taxa detected by the Wyoming O/E index. 

Too few data points for 2006 are available downstream from 

site P5 in 2006 to identify a linear pattern.

Contrary to the Wyoming O/E scores, the WSII scores 

did not decrease between Powder River sites P8 and P9 

in 2005. In fact, the 2005 WSII metrics show a consistent 

downstream improvement in biological condition of the 

Powder River beginning below Burger Draw at site P4. Only 

Trichoptera taxa scores showed a decrease from site P8 to 

site P9. All other metrics used in the Plains WSII had increasing values between the two sites. The increase in metric scores 

might indicate that several expected indigenous taxa were 

intolerant to stressors acting upon the system (hence, their 

absence according to the Wyoming O/E model) and were 

replaced by more tolerant (supported by the increased Hilsenhoff Biotic Index score) congener taxa that received higher 

metric scores under the existing conditions.

Tongue River Drainage

Of the seven metrics included in the Plains WSII, the 

percentages of Trichoptera (less Hydropsychidae) (R2 = 0.59), 

Ephemeroptera taxa richness (R2 = 0.57), Hilsenhoff Biotic 

Index (R2 = 0.54), and Trichoptera taxa richness (R2 = 0.52) 

were the most important in affecting the WSII scores for the 

Tongue River drainage (fig. 24A–D). The WSII scores among 

the three sites on the main-stem Tongue River (sites T1, T5, 

and T9) increased slightly from 2005 (mean = 63) to 2006 

(mean = 71), although the difference was not significant 

(P > 0.05; fig. 23). Similar to the Wyoming O/E scores, WSII 

scores generally decreased from upstream to downstream 

for sampling sites on the Tongue River in 2006. Decreases 

in the percentages of Trichoptera less Hydropsychidae and 

Ephemeroptera less Baetidae strongly affected the downstream 

decrease in WSII scores in 2006. In 2005, increases in the 

percentages of both aforementioned metrics resulted in an 

increase in WSII scores from site T5 to site T9. 

Patterns derived from the WSII for Tongue River tributaries were similar to those obtained from the Wyoming O/E 

model. When considered together, biological conditions at 
−10 0 10 20 30 40 50 60 70

EPHEMEROPTERA (LESS BAETIDAE) (PERCENT)

30

35

40

45

50

55

60

65

70

75

80

F Powder River 

drainage

R2 = 0.47

Regression line

95-percent confidence interval

EXPLANATION

2.5 3.0 3.5 4.0 4.5 5.0

HILSENHOFF BIOTIC INDEX

5.5 6.0 6.5

E Powder River drainage

R2 = 0.50

3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 0 1 2 3 4 5 6 7 8 9

HILSENHOFF BIOTIC INDEX

0 1 2 3 4 5 6 7 8 9

EPHEMEROPTERA TAXA RICHNESS

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

TRICHOPTERA (LESS HYDROPSYCHIDAE) (PERCENT)

35

40

45

50

55

60

65

70

75

80

85

WYOMING STREAM INTEGRITY INDEX (WSII) SCORE

35

40

45

50

55

60

65

70

75

80

85

30

35

40

45

50

55

60

65

70

75

80

85

WYOMING STREAM INTEGRITY INDEX (WSII) SCORE

30

35

40

45

50

55

60

65

70

75

80

WYOMING STREAM INTEGRITY INDEX (WSII) SCORE

35

40

45

50

55

60

65

70

75

80

85

C Tongue River drainage

R2 = 0.54

B Tongue River drainage

R2 = 0.57

A Tongue River drainage

R2 = 0.59

TRICHOPTERA TAXA RICHNESS

D Tongue River drainage

R2 = 0.52

Figure 24. Regression of selected macroinvertebrate metrics using scores of the Wyoming Stream Integrity Index for sites in the 

Tongue and Powder River drainages in Wyoming and adjacent areas of Montana, 2005–06.

Ecological Assessment 65
66 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

Among the tributaries to the Powder River, the downstream difference in biological condition according to the 

WSII scores for Crazy Woman Creek sites P6 (65) to P7 (48) 

in 2005 was greater than was detected with the Wyoming 

O/E model (fig. 23). The decrease in WSII score was caused 

by decreases in the percentages of collector-gatherers, 

Ephemeroptera less Baetidae, and numbers of Ephemeroptera 

and total taxa. The WSII and O/E scores for Crazy Woman 

Creek might indicate that stressors were present to alter 

community attributes, although perhaps near the extremes 

of tolerance ranges for the majority of indigenous taxa still 

present. Unlike the Wyoming O/E score, the WSII score of 61 

for Clear Creek (site P10) in 2005 was similar to or greater 

than WSII scores for samples from Crazy Woman Creek. 

Although several expected taxa were absent at site P10, 

large percentages of non-Baetid mayflies (Acentrella, Fallceon quilleri, Leptophlebiidae, and Heptageniidae) with low 

pollution tolerances were present. An increased percentage 

of Ephemeroptera less Baetidae was found in place of the 

expected taxa, decreasing the Hilsenhoff Biotic Index value, 

and resulting in an elevated WSII score comparable to Crazy 

Woman Creek. 

Complementing scores from the Wyoming O/E model, 

WSII scores for the Little Powder River showed that biological conditions were similar to conditions in the upstream and 

middle sections of the Powder River in Wyoming, with an 

increase in WSII scores from site P15 (36) downstream to 

site P16 (49) in 2005. In addition, the WSII scores increased 

temporally from 36 in 2005 to 48 in 2006 at site P15 

(table 18). 

Belle Fourche and Cheyenne River Drainages

In general, the patterns of WSII scores for the Belle 

Fourche and Cheyenne River drainages relative to scores 

for the Powder and Tongue River drainages were similar to 

patterns from the Wyoming O/E model. The Belle Fourche 

River (site B1) WSII score of 32 was similar to WSII scores 

for the Cheyenne River drainage (site C3 = 35, site C4 = 32, 

site C6 = 35; table 18). However, as with the Wyoming 

O/E model, the biological condition of the Cheyenne River 

drainage assigned by the WSII scores may be underestimated 

due to limitations of this index in effectively evaluating intermittent water in this drainage. 

Montana Observed/Expected Biological Condition

Data from sites in Montana, as well as sites in Wyoming 

near the Montana border, are described in the following 

sections. The O/E and MMI scores are listed in table 19 along 

with scores from the individual metrics that compose the 

MMI. 

Tongue River Drainage

Overall, samples collected from sites on the mainstem Tongue River had lower scores than the samples from 

tributary sites in the Tongue River drainage as measured by 

the Montana O/E model (fig. 25). The tributary sites had less 

streamflow and smaller wetted widths than main-stem sites 

(fig. 22; table 7; table 16). The physical properties of the tributaries more closely matched the physical properties of those 

streams identified as reference streams by MDEQ that were 

used to calibrate the O/E model than did the physical properties of the main-stem sites (Suplee and others, 2005).

Within the Tongue River drainage (fig. 25), the mean 

O/E score was 0.81 in both 2005 and 2006. The Montana 

O/E model was sensitive to the mountainous headwater, 

snowmelt-driven stream settings found in the upstream part 

of the Tongue River drainage (upstream from Tongue River 

Reservoir) and scored those sites slightly higher both years; 

O/E scores ranged from 0.75 to 1.28 in 2005 and from 0.90 

to 1.41 in 2006 (table 19). The samples collected from the 

Youngs Creek sites (T3 and T4) had the highest O/E scores 

both years. Site T3 scored 1.28 in 2005 and 1.41 in 2006. Site 

T4 scored 1.26 in 2005 and 1.12 in 2006. Scores exceeding 

1.0 indicate that more taxa were observed than were expected 

on the basis of Great Plains reference sites in Montana. Scores 

from samples collected at site T5 on the main-stem Tongue 

River below Youngs Creek (0.44 in 2005 and 0.88 in 2006) 

were lower than those measured for the Tongue River at 

Monarch (site T1) and at the State line (site T9). The samples 

from the upstream part of the Tongue River drainage contained 

both tolerant taxa (for example, scuds, Hyalella azteca; black 

flies, Simulium; and snails, Physa) and potentially sensitive 

taxa (for example, riffle beetles, Dubiraphia; and caddisflies, 

Hydroptila). Different percentages of these taxa affected the 

O/E scores for the Tongue River sites. 

The O/E scores from samples collected from the mainstem Tongue River downstream from Tongue River Reservoir 

decreased from site T10 (above Hanging Woman Creek) to 

site T14 (at Birney Day School) and increased from site T14 to 

site T18 (below Brandenberg Bridge) in both 2005 and 2006. 

The O/E scores for samples from sites T10, T14, and T18 

tended to be higher in 2005 than in 2006 (table 19). The mean 

score for these three sites was 0.55 in 2005 and 0.46. The O/E 

model scores were correlated with predator taxa richness (for 

example, midges, Chironomidae; and creeping water bugs, 

Naucoridae; R2 = 0.44; fig. 26A). 

Powder River Drainage

The macroinvertebrate data collected from the eight 

sampling sites in the downstream part of the Powder and Little 

Powder River drainages showed no significant difference 

(P > 0.05) in O/E scores between 2005 and 2006. Data for six 

sites on the main-stem Powder River, starting from site P9 

above Clear Creek in Wyoming and continuing downstream to 

site P18 near the mouth, and for two sites on the Little Powder 

River are shown in figure 25. 

In 2005, the highest O/E score for sites on the mainstem Powder River was at site P9 (0.50). The 2005 O/E 

scores tended to decrease downstream from site P9, reach-
Table 19. Scores from the Montana observed/expected model and the Montana multimetric index (MMI) for macroinvertebrate samples collected at riffles in streams in 

Montana and adjacent areas of Wyoming, 2005–06.—Continued[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River; EPT, Ephemeroptera, Plecoptera, and Trichoptera]

Site 

number 

(fig. 1)

Sample date

Observed/ 

expected 

score

MMI 

score

EPT taxa 

(percent)

EPT taxa 

score 

Tanypodinae 

(percent)

Tanypodinae 

score 

Orthocladiinae 

to 

Chironomidae 

(percent)

Orthocladiinae 

to 

Chironomidae 

score

Predator 

taxa 

(percent)

Predator 

taxa 

score

Filtercollector 

(percent)

Filtercollector 

score

R2 09/15/2005 1.00 55 6.0 42.9 1.4 13.5 10.3 89.7 10.0 100.0 80.4 30.1

T1 08/15/2005 1.05 42 12.6 90.3 .1 1.3 46.2 53.8 5.0 55.6 94.0 9.2

08/23/2006 1.05 43 12.4 88.9 1.4 13.6 75.4 24.6 4.4 48.8 73.3 41.0

T2 08/17/2005 .75 44 10.2 72.7 .4 4.3 22.2 77.8 5.0 55.6 93.4 10.2

08/22/2006 .90 30 7.9 56.5 .8 8.4 74.5 25.5 4.7 52.2 95.4 7.1

T3 06/15/2005 1.28 34 5.7 40.4 .2 1.6 60.0 40.0 6.3 69.7 89.6 16.0

06/28/2006 1.41 35 6.8 48.4 1.0 10.1 64.6 35.4 6.0 67.0 89.6 16.1

T4 06/14/2005 1.26 35 4.0 28.5 1.1 10.9 56.6 43.4 6.2 68.4 84.1 24.5

06/27/2006 1.12 40 4.7 33.4 1.8 17.6 21.1 78.9 5.2 57.2 92.7 11.3

T5 08/15/2005 .44 36 9.7 69.3 .2 1.5 37.1 62.9 3.3 36.1 93.2 10.4

08/22/2006 .88 56 11.0 78.6 3.8 37.8 14.3 85.7 5.3 59.1 89.1 16.7

T7 06/13/2005 .98 35 2.6 18.2 .2 2.4 34.9 65.1 7.0 78.1 91.7 12.7T9 09/14/2005 .57 39 10.8 76.9 1.7 17.2 58.2 41.8 4.3 48.3 93.9 9.4

08/24/2006 1.00 52 9.8 70.2 1.9 19.3 19.2 80.8 6.5 72.8 90.6 14.5

T10 08/16/2005 .77 51 9.8 69.9 2.0 20.0 36.5 63.5 4.9 54.7 69.7 46.6

08/28/2006 .64 40 6.8 48.3 .2 1.6 12.5 87.5 4.8 53.5 93.1 10.6

T11 06/22/2005 .87 55 .5 3.5 5.0 50.5 7.0 93.0 9.4 100 82.9 26.3T12 06/21/2005 1.25 68 3.4 24.5 12.0 100 10.3 89.7 8.2 91.4 78.5 33.1T13 06/23/2005 .94 53 2.0 13.9 6.7 66.7 18.6 81.4 6.9 76.6 83.3 25.6T14 09/12/2005 .38 36 10.8 77.3 .0 .0 37.5 62.5 2.4 26.8 92.5 11.5

08/28/2006 .25 48 13.6 97.1 .6 6.3 13.3 86.7 3.7 41.4 93.8 9.5

T17 06/30/2005 .89 24 4.0 28.4 .1 1.4 67.1 32.9 4.5 50.1 94.2 9.0

06/28/2006 .38 22 4.0 28.4 .0 .0 54.4 45.6 3.1 34.7 98.8 1.9

T18 09/13/2005 .50 32 10.2 72.6 .6 6.5 85.4 14.6 5.3 58.4 93.4 10.2

08/31/2006 .50 56 17.1 100 .9 8.5 13.0 87.0 6.4 71.5 91.7 12.7

T19 06/23/2005 .25 23 .6 4.5 .9 9.1 12.5 87.5 1.0 10.8 98.7 2.0

P9 07/24/2005 .50 63 7.0 50.0 6.7 66.7 18.5 81.5 7.0 77.8 73.9 40.2

Ecological Assessment 67
Table 19. Scores from the Montana observed/expected model and the Montana multimetric index (MMI) for macroinvertebrate samples collected at riffles in streams in 

Montana and adjacent areas of Wyoming, 2005–06.—Continued[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River; EPT, Ephemeroptera, Plecoptera, and Trichoptera]

Site 

number 

(fig. 1)

Sample date

Observed/ 

expected 

score

MMI 

score

EPT taxa 

(percent)

EPT taxa 

score 

Tanypodinae 

(percent)

Tanypodinae 

score 

Orthocladiinae 

to 

Chironomidae 

(percent)

Orthocladiinae 

to 

Chironomidae 

score

Predator 

taxa 

(percent)

Predator 

taxa 

score

Filtercollector 

(percent)

Filtercollector 

score

P11 07/25/2005 .38 46 14.1 100 .2 1.7 16.7 83.3 2.5 27.5 89.3 16.5

08/03/2006 .50 46 7.0 49.7 1.0 10.3 5.3 94.7 6.0 66.7 94.2 9.0

P12 07/26/2005 .37 44 8.8 62.9 .3 3.2 5.6 94.4 4.5 50.2 93.3 10.3P13 07/19/2005 .12 31 4.4 31.1 .2 2.4 .0 100 1.9 21.1 98.9 1.6

08/02/2006 .50 52 8.7 62.3 1.6 16.0 7.5 92.5 5.6 62.0 81.0 29.3

P15 06/13/2005 .62 22 3.1 22.2 .1 1.2 28.6 71.4 1.2 13.6 99.9 .2

06/23/2006 .87 40 4.6 33.0 1.9 18.7 20.0 80.0 5.5 60.6 94.0 9.3

P16 06/27/2005 .87 43 4.9 34.7 5.1 51.0 59.5 40.5 6.4 70.6 89.2 16.7P17 07/21/2005 .25 44 8.6 61.4 .3 3.2 1.2 98.8 4.8 53.4 96.5 5.3P18 07/22/2005 .12 27 4.1 29.1 0 0 0 100 .7 8.2 99.9 .2

68 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Figure 25. Montana observed/expected model and Montana multimetric index scores for macroinvertebrate samples collected in 

Montana and adjacent areas of Wyoming, 2005–06.

O/E SCORE 0

0.5

1

2005 2006

O/E SCORE

0

50 0.5 50

100

0

0.5

1

2005 2006 0

50

100

0

0.5

1

2005 0

50

100

0

0.5

1

2005 0

50

100

MMI SCORE

Tongue River tributary sites

Tongue River main-stem sites

0

0.5

1

O/E SCORE

0 0

50

100

0

0.5

1

0

50

100

2005 2006 2005 2006 0

0.5

1

50

100

2005 2006 0

0.5

1

0

50

100

MMI SCORE

2006 0 0

0.5

1

50

100

2006

T1

1.25 125

0

0.5

1

O/E SCORE

0

50

100

2005 2006

T5 T9 T10 T14

T18

MMI SCORE

Montana multimetric index (MMI) score

Montana observed/expected (O/E) model score

EXPLANATION

T2

0

1

0

100

2005 2006

1.50 150 1.50 150

T3 T4

T7 T11

0.5 50

0

1

0

100

2005

1.50 150

0 0

0.5

1

0

50

100

0

0.5

1

50

100

2005 0

0.5

1

0

50

100

2005

T12

T13 T17 T19

MMI SCORE

2005 2006

Ecological Assessment 69
Little Powder River sites

0

0.5

1

2005 2006 0

50

100

0

0.5

1

2005 0

50

100

MMI SCORE

O/E SCORE

Montana multimetric index (MMI) score

Montana observed/expected (O/E) model 

 score

EXPLANATION

Powder River main-stem sites

0

0.5

1

O/E SCORE

0 0

50

100

0

0.5

1

0

50

100

2005 2005 0

0.5

1

50

100

2005 2006

0

0.5

1

O/E SCORE

O/E SCORE

0 0

50

100

0

0.5

1

0

50

100

2005 2006 2005 0

0.5

1

50

100

2005

MMI SCORE MMI SCORE

0

0.5

1

0

50

100

2005

MMI SCORE

P9 P11 P12

P13 P17 P18

P15 P16

R2

Rosebud Creek site

Figure 25. Montana observed/expected model and Montana 

multimetric index scores for macroinvertebrate samples 

collected in Montana and adjacent areas of Wyoming, 

2005–06.—Continued

70 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

ing a minimum of 0.12 at site P13 at Broadus and site P18 

near Locate. The O/E scores were related to the percentage 

of Orthocladiinae midges among the total Chironomidae 

in the samples (R2 = 0.63; fig. 26B). This diverse group of 

midges was sampled in different proportions to the total 

Chironomid numbers in the upstream part of the Powder 

drainage (site P9 = 18.5 percent; site P11 = 16.7 percent) and 

trended downward into the downstream part of the Powder 

River drainage (site P12 = 5.6 percent, site P13 = 0 percent, 

site P17 = 1.2 percent, site P18 = 0 percent). This is another 

line of evidence that demonstrates how the O/E model is 

potentially sensitive to cold-water effects in plains streams. 

Overall, the Powder River naturally maintains less abundant 

and diverse macroinvertebrate populations than other drainages in the plains (Stagliano, 2006). The O/E scores for 

samples collected from the main-stem Powder River therefore, 

might be artificially low compared to samples from other 

drainages in the plains.

Samples from both sites in the Little Powder River 

drainage (sites P15 and P16) scored relatively high using the 

O/E model in 2005 (site P15 = 0.62, site P16 = 0.87; table 19). 

Site P15 was sampled again in 2006, and the O/E score (0.87) 

was higher than in 2005. The O/E scores calculated from the 

samples collected at these sites were affected by a diverse 

macroinvertebrate community dominated by filter/collector 

taxa (for example, mayflies, Traverella; black flies, Simuliidae; and caddisflies, Hydropsyche and Cheumatopsyche).

Rosebud Creek

Macroinvertebrate riffle data were collected at one 

site (R2) within the Rosebud Creek drainage in 2005. The 

2005 O/E score was 1.00 at site R2 (table 19), indicating that 

the macroinvertebrate community at site R2 was very similar 

to communities at regional reference sites in Montana (Suplee 

and others, 2005).

Montana Multimetric Index Biological Condition 

Tongue River Drainage

Mean MMI scores at sites in the Tongue River drainage 

were higher in 2006 (mean = 42) than in 2005 (mean = 40), 

but the difference was not statistically significant (P > 0.05). 

The Tongue River MMI scores did not follow the same general 

pattern as the scores from the O/E model. The MMI scores at 

the six main-stem Tongue River sites did not show a consistent pattern in the downstream direction, whereas the O/E 

scores were highest for the main-stem sites farthest upstream 

(fig. 25). MMI scores for sites on the Tongue River tributaries 

generally were either near or lower than scores from the mainstem Tongue River sites, whereas the maximum O/E scores 

occurred at the tributary sites. The maximum MMI score of 68 

for Tongue River sites (table 19) occurred at site T12 (middle 

Hanging Woman Creek) in 2005. 
Figure 26. Regression of selected macroinvertebrate metrics compared to Montana observed/expected model scores and Montana 

multimetric index scores for sampling sites in the Tongue and Powder River drainages in Montana and adjacent areas of Wyoming, 

2005–06.

Regression line

95-percent confidence interval

EXPLANATION

PREDATOR TAXA RICHNESS

40 50 60 70 80 90 100

ORTHOCLADIINAE/TOTAL CHIRONOMIDAE SCORE (PERCENT)

MONTANA OBSERVED/EXPECTED SCORE

0 20 40 60 80 100

80

70

60

50

40

30

20

10

0

PREDATOR TAXA RICHNESS METRIC SCORE

PREDATOR TAXA RICHNESS METRIC SCORE

MONTANA PLAINS MULTIMETRIC INDEX SCORE MONTANA PLAINS MULTIMETRIC INDEX SCORE

0 10 20 30 40 50

80

90

70

60

50

40

30

20

10

FILTERER/COLLECTOR TAXA RICHNESS SCORE (PERCENT)

0 10 20 30 40

80

70

60

50

40

30

20

10

FILTERER/COLLECTOR TAXA RICHNESS SCORE (PERCENT)

A Tongue River drainage

R2

 = 0.44

B Powder River drainage

R2

 = 0.63

C Tongue River drainage

R2

 = 0.40

D Tongue River drainage

R2

 = 0.37

E Powder River drainage

R2

 = 0.79 F Powder River drainage

R2

 = 0.68

0 2 4 6 8 10

2.0

1.5

1.0

0.5

0

1.5

1.25

1

0.75

0.5

0.25

0

0 10 20 30 40 50 60 70 80

80

70

60

50

40

30

20

10

Ecological Assessment 71
72 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

The MMI model was sensitive to some of the same 

aspects of the macroinvertebrate community as the O/E 

model. The MMI scores were most correlated to the predator 

taxa richness score (R2 = 0.40; fig. 26C) and the percentage 

filterer/collector taxa richness score (R2 = 0.37; fig. 26D). The 

metrics of Tanypodinae (midge; table 19) and filterer/collector 

percentages (table 19) represent generally hardy and tolerant taxa that increase in the sample population with increased 

environmental perturbation (Kerans and Karr, 1994; Montana 

Department of Environmental Quality, 2006). Decreases in the 

percentages of these taxa within the samples caused the higher 

overall MMI scores at sites T11–T13.

Powder River Drainage

The mean of the MMI scores from samples collected 

in the Powder River drainage in Montana and adjacent areas 

of Wyoming were higher in 2006 (mean = 46) than in 2005 

(mean = 42), but the difference was not significant (P > 0.05). 

The maximum MMI score of 63 occurred at site P9 (above 

Clear Creek) on the main-stem Powder River (table 19; 

fig. 25). MMI scores for the Little Powder River samples 

appeared to be similar to those for the main-stem Powder 

River samples. The MMI score for the Little Powder River 

above Dry Creek (site P15) was higher in 2006 (40) than in 

2005 (22) due to smaller percentages of Tanypodinae and 

larger numbers of predator taxa in 2006. For the Powder River 

drainage, the MMI was more sensitive to different aspects 

of the macroinvertebrate community than those affecting the 

O/E model. Although the O/E was sensitive to the presence of 

potentially cold stenotherm Orthocladiinae (midge) taxa, the 

MMI responded to the percentage of filterers/collectors taxa 

richness (R2 = 0.79) and predator taxa richness (R2 = 0.68) 

metrics in the samples (fig. 26E–F).

Rosebud Creek

Macroinvertebrate riffle data were collected at one 

site (R2) in the Rosebud Creek drainage in 2005. The sample 

collected in 2005 had an MMI score of 55, which was relatively high compared to scores for other sites in Montana and 

adjacent areas of Wyoming (table 19). 

Comparison of Model and Multimetric Results

Analysis of the entire ATG data set with both the 

Wyoming and Montana O/E and MMI indicators was considered initially in this study. However, preliminary investigations 

revealed appreciable differences in indicator scores between 

the Wyoming and Montana indicators for the same sites. 

These differences were attributed predominantly to fundamental differences in the development and expectations of each 

State’s respective indicators in addition to application in areas 

outside the regions for which they were intended. For these 

reasons, ATG sites within Wyoming and Montana were evaluated with the respective indicators developed for that State. 

Selected sites on either side of the Wyoming/Montana State 

line that were reasonably within the geographic applicability 

of each indicator also were included in each State’s respective analysis to provide additional resolution when identifying 

spatial patterns in biological condition. Spatial and temporal 

patterns in biological condition obtained from the initial 2 

years of this study provide baseline information to augment 

future data collections of biological data. 

The general similarity in patterns of biological condition 

in the study area and at drainage scales derived from the indicators are encouraging in that these indicators, in conjunction 

with other data types and tools, can serve as suitable indicators 

of water-quality change in the ATG study area. The overall 

degree of differences in O/E scores among ATG sites generally was greater than differences in the multimetric scores for 

both the Wyoming and Montana indicators. Furthermore, the 

O/E scores sometimes showed more substantial changes in 

biological condition between sites relative to the multimetric 

indicators. This may indicate that the O/E indicators are more 

sensitive in detecting environmental change than the multimetric indicators for the ATG study area. On the other hand, 

evaluation of the multimetric scores and associated metric 

values were valuable for identifying why particular similarities 

or differences existed between the two indicator outputs.

The disagreements in biological condition as assessed 

by the Wyoming and Montana indicators primarily were 

at the drainage scale and associated with differences in the 

indicators’ responses to environmental gradients and sensitivity to the magnitude and duration of stressors. Better spatial 

and temporal patterns are more likely to emerge with additional data collections. These additional data collections may 

increase the probability of developing causal relations between 

anthropogenic stressors and changes in biological condition. 

Furthermore, it will be important to differentiate the effects of 

human activities from naturally occurring perturbations (such 

as variations in flows and drought).

Macroinvertebrate Community Composition in 

Multiple Habitats

At sites where riffles were absent, the QMH macroinvertebrate samples are the only type of macroinvertebrate 

data available (table 20). Fewer sites had riffles in 2006 than 

in 2005 because of drier conditions in 2006, and therefore, 

some sites appear in table 20 with only a QMH sample for 

1 year. As an aid to interpreting data for QMH-only sites, RTH 

and QMH data were compared at sites that had both types of 

macroinvertebrate samples. A total of 57 sample-collection 

periods in 2005–06 were used for the RTH–QMH comparison.

Total taxa richness was greater in the QMH samples than 

in the RTH samples collected at the same sites (fig. 27) as 

would be expected given that riffles and additional habitats 

such as macrophytes and pool sediment were sampled for the 

QMH sample. Pair-wise comparison of the QMH and RTH 

samples indicated total taxa richness as well as taxa richness 

of Ephemeroptera, Chironomidae, and noninsects were 
Table 20. Macroinvertebrate community metrics for sampling sites where qualitative multihabitat (QMH) samples were the primary macroinvertebrate sample type, Powder 

River Structural Basin, Wyoming and Montana, 2005–06.—Continued[Shaded cells indicate main-stem sampling sites on the Powder River]

Site 

number

(fig. 1)

Abbreviated site name Sample date Taxa richness Ephemer- optera richness Plecoptera richness Trichoptera richness Chironomi- dae richness Noninsect taxa richness Predator taxa richness Gatherer- collector taxa richness Filterer- collector taxa richness Taxa tolerance

R1 upper Rosebud Creek 06/20/2005 23 2 0 1 8 2 12 7 1 6.6R1 upper Rosebud Creek 07/12/2006 49 3 0 4 23 6 13 23 4 6.2

T6 upper Squirrel Creek 06/16/2005 46 2 0 3 27 6 12 22 4 5.8T6 upper Squirrel Creek 06/29/2006 44 2 0 1 19 6 15 15 3 6.3T8 Prairie Dog Creek 08/16/2005 27 8 0 3 2 2 7 8 3 4.5

T11 upper Hanging Woman 

Creek

06/27/2006 43 4 0 0 20 4 14 18 2 6.8

T12 middle Hanging Woman 

Creek

06/26/2006 53 4 0 4 22 5 18 22 6 6.0

T13 Hanging Woman Creek at 

mouth

06/26/2006 48 2 0 0 19 4 22 17 3 6.4

T15 upper Otter Creek 06/29/2005 31 1 0 1 14 2 15 11 3 6.1T15 upper Otter Creek 07/12/2006 45 3 0 1 16 6 16 20 4 5.9T16 middle Otter Creek 06/28/2005 46 2 0 1 23 3 19 18 3 6.8

P6 Crazy Woman Creek 

below I-90

07/31/2006 49 2 0 2 23 3 22 16 2 6.1

P7 Crazy Woman Creek near 

mouth

08/01/2006 42 2 0 2 15 3 20 11 3 6.5

P8 Powder River below 

Crazy Woman Creek

08/02/2006 40 4 1 2 19 1 16 16 2 5.6

P9 Powder River above 

Clear Creek

08/04/2006 37 2 0 3 16 1 14 14 3 5.9

P12 Powder River at Moorhead 08/02/2006 41 5 1 5 19 2 14 16 3 5.6P14 Little Powder River at 

Highway 59

06/14/2005 41 1 0 4 22 0 15 16 4 5.3

P14 Little Powder River at 

Highway 59

06/22/2006 49 2 0 2 24 4 19 19 5 6.1

P17 Powder River below 

Little Powder River

08/03/2006 52 9 1 4 17 3 17 19 4 5.6

Ecological Assessment 73
Table 20. Macroinvertebrate community metrics for sampling sites where qualitative multihabitat (QMH) samples were the primary macroinvertebrate sample type, Powder 

River Structural Basin, Wyoming and Montana, 2005–06.—Continued[Shaded cells indicate main-stem sampling sites on the Powder River]

Site 

number

(fig. 1)

Abbreviated site name Sample date Taxa richness Ephemer- optera richness Plecoptera richness Trichoptera richness Chironomi- dae richness Noninsect taxa richness Predator taxa richness Gatherer- collector taxa richness Filterer- collector taxa richness Taxa tolerance

C1 Porcupine Creek 06/15/2005 36 0 0 0 18 3 14 16 1 6.6C1 Porcupine Creek 06/22/2006 36 2 0 0 18 4 14 16 0 7.1C2 Antelope Creek 06/08/2005 39 1 0 0 21 7 11 19 4 6.6C2 Antelope Creek 06/20/2006 42 3 0 0 27 5 13 22 2 6.7C3 Cheyenne River near Dull 

Center

06/19/2006 36 2 0 0 13 4 21 12 0 7.2

C4 Little Thunder Creek 06/21/2006 44 3 0 0 24 4 15 21 1 6.7C5 Black Thunder Creek 06/07/2005 45 2 0 0 24 2 19 19 1 6.8C6 Cheyenne River near 

Spencer

06/20/2006 46 2 0 1 23 4 18 19 1 6.6

B1 Belle Fourche River 06/21/2006 18 2 0 0 5 4 8 7 0 7.1B2 Caballo Creek 06/28/2005 11 0 0 0 3 3 7 2 0 8.3

74 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
FILTERER-COLLECTOR

TRICHOPTERA CHIRONOMIDAE NONINSECTS

57 57 29 57 57 29 57 57 29 57 57 29

0

5

10

15

20

25

30

0

5

10

15

20

25

30

35

57 57 29

60

80

40

20

0

RTH PAIR QMH PAIR QMH ONLY

TOTAL TAXA RICHNESS

57 Number of values Richest-targeted habitat (riffle) samples 

 for sites with paired QMH samples 

EXPLANATION

Data value less than or equal to 1.5 times the 

 interquartile range outside the quartile

75th percentile

Median

25th percentile

Outlier data value greater than 3 times the 

 interquartile range outside the quartile

Outlier data value less than or equal to 3 

 and more than 1.5 times the interquartile 

 range outside the quartile

TAXA RICHNESS

TOLERANCE SCORE

FUNCTIONAL GROUP TAXA RICHNESS

57 57 29 57 57 29 57 57 29 57 57 29 RTH PAIR QMH PAIR QMH ONLY RTH PAIR QMH PAIR QMH ONLY RTH PAIR QMH PAIR QMH ONLY RTH PAIR QMH PAIR QMH ONLY

EPHEMEROPTERA

3

4

5

6

7

8

9

10

RTH PAIR QMH PAIR QMH ONLY

RTH PAIR

QMH PAIR

QMH ONLY

RTH PAIR

QMH PAIR

QMH ONLY

RTH PAIR

QMH PAIR

QMH ONLY

PREDATOR GATHERER-COLLECTOR

RTH PAIR

Qualitative multihabitat samples for

 sites with paired RTH samples 

QMH PAIR

Qualitative multihabitat sample (no 

 accompanying RTH sample)

QMH ONLY Interquartile range

Figure 27. Macroinvertebrate taxa richness, functional groups, and tolerance for sampling sites with both richest-targeted habitat and 

qualitative multihabitat samples, and for sites with only qualitative multihabitat samples, Powder River Structural Basin, 2005–06.

Ecological Assessment 75
76 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

significantly (P < 0.05) different between the QMH and RTH 

samples. The macroinvertebrate communities in the QMH 

samples also differed somewhat by functional groups from 

the RTH samples. The QMH samples contained significantly 

larger numbers of predator taxa and gatherer-collector taxa 

(P < 0.05) but about the same number of filterer-collector taxa 

(P > 0.05). The tolerance scores of taxa in the QMH samples 

were significantly (P < 0.05) higher than scores in the RTH 

samples (fig. 27), indicating that more organisms in the QMH 

samples were tolerant of poor water quality. 

Total taxa richness for sites with QMH-only samples 

was similar to total taxa richness for paired QMH samples 

(fig. 27). The general composition of the macroinvertebrate 

community for QMH-only samples, however, was considerably different from the composition of paired QMH samples. 

The QMH-only samples generally contained larger percentages of Chironomidae taxa and noninsect taxa, and smaller 

percentages of Ephemeroptera and Trichoptera taxa than 

the paired QMH samples. Because Ephemeroptera and 

Trichoptera generally are associated with higher waterquality and lower tolerance scores, the taxa-tolerance scores 

for the QMH-only samples were higher than scores for the 

paired QMH samples (fig. 27). The QMH-only samples also 

contained more predator taxa than the paired QMH samples 

and fewer filter-collector taxa as might be expected when 

sampling includes habitats with little or no flowing water 

needed to provide a food source for the filterer-collectors. 

Common taxa of Chironomids in the QMH-only 

samples included Procladius, Dicrotendipes, Tanytarsus, 

and Micropsectra. Common taxa of noninsects included the 

pond snail Physa, the scud or side swimmer Hyallela azteca, 

and mites (Trombidiformes). The most common genus of 

Ephemeroptera was Callibaetis. The predator functional 

group was well represented in the QMH-only samples, 

including damselfly nymphs (Coenagrionidae), water striders 

(Corixidae), and predaceous diving beetles (Dytiscidae). Plant 

piercers (herbivores) such as Haliplus and Berosus (beetles, 

Coleoptera) also were common in the QMH-only samples. 

Ancillary Macroinvertebrate Data

Data collected at ATG sites for other USGS studies were 

evaluated as ancillary data. This included ancillary macroinvertebrate data from the NAWQA Program, the WWSC 

water-quality monitoring network, and a WWSC project investigation (table 6). 

Taxa richness of macroinvertebrate samples from the 

Little Powder River (site P15) ranged from 15 to 36 taxa per 

sample in riffle samples collected during 1999–2007 under the 

NAWQA Program. Chironomidae generally had greater taxa 

richness than Ephemeroptera or Trichoptera, but Coleoptera 

and noninsects also were well represented (fig. 28). Dominant 

taxa in terms of relative abundance included caddisfly larvae 

Cheumatopsyche, mayflies Caenis and Choroterpes, blackfly larvae Simulium, riffle beetles Stenelmis and Dubiraphia, 

and Chironomids such as Ablabesmyia. The predominant 

functional groups were the gatherer-collectors and filtercollectors; a mean of about 35 to 40 percent of the macroinvertebrate individuals fell into each of those two functional 

groups. 

Macroinvertebrate samples also were collected from the 

Little Powder River at sites P15 and P14 as part of a WWSC 

project investigation during 1980–81 (Peterson, 1990). Project 

samples collected at site P15 on six dates between April 

1980 and March 1981 indicated the dominant macroinvertebrates during 1980–81 often were the same species that 

predominated in the ATG and NAWQA samples from site P15. 

Predominant species at site P15 during 1980–81 included 

Simulium, Caenis, Cheumatopsyche, and Choroterpes (Peterson, 1990). Macroinvertebrate samples also were collected 

in 1980–81 from riffles, runs, pools, and drift (timed collections of macroinvertebrates suspended in the water column) 

in the Little Powder River at Highway 59 (site P14). The ATG 

samples from site P14 were QMH samples because no riffles 

were present at the time of sampling. Some species, such as 

Hyallela azteca and Tanytarsus, were identified in both the 

ATG and project samples, whereas others, such as Caenis and 

Choroterpes, were present in the project samples but not the 

ATG samples from site P14.

Macroinvertebrate samples were collected during 

1980–81 from the Cheyenne River near Dull Center (site C3) 

and the Belle Fourche River (site B1). The predominant 

species in the 1980–81 samples from runs in the Cheyenne 

River at site C3 was the Chironomid Stictochironomus, 

whereas the predominant species in the 2005 sample from 

riffles at site C3 were the snails Physa and Lymnaea, and 

the Chironomids Micropsectra and Pseudochironomus. The 

1980–81 samples from the Belle Fourche River were collected 

primarily from the pools and were dominated by the mayfly 

Caenis and the Chironomids Limnochironomus (now taxonomically revised to Dicrotendipes) and Tanytarsus (Peterson, 

1990, p. 28). One or more of the 2005–06 samples from the 

Belle Fourche River contained the mayfly family Caenidae as 

well as Dicrotendipes and Tanytarsus. 

Ancillary data also are available from three ATG sites 

that were sampled using the NAWQA protocol for riffles; the 

Tongue River at State line (site T9) and Clear Creek (site P10) 

were sampled during 2002 as part of monitoring network 

activities, and the Powder River near Locate (site P18) was 

sampled during 1999 as part of the Yellowstone River Basin 

NAWQA study (Peterson and others, 2004). The macroinvertebrate community in the Tongue River at site T9, identified 

on the basis of the 2002 riffle sample, was a diverse assemblage dominated by Microcylloepus, Stenelmis, Simulium, 

and Fallceon quilleri. Those same taxa were present and 

sometimes dominant in the 2005 and 2006 riffle samples from 

site T9. The 2002 riffle sample from Clear Creek was dominated by Microcylloepus, Fallceon quilleri, and Simulium. The 

2005–06 riffle samples from Clear Creek at site P10 contained 

Microcylloepus and Fallceon quilleri, but not Simulium. No 

Simulium or any other members of Simuliidae were identified 

in either the riffle or qualitative samples collected from Clear 
Figure 28. Macroinvertebrate community composition in National Water-Quality Assessment samples 

from the Little Powder River above Dry Creek (site P15), 1999–2007.

0

5

10

15

20

25

30

35

40

9/29/99 7/19/01 7/10/02 7/14/03 8/25/04 8/8/06 8/7/07

SAMPLE DATE

EXPLANATION

TAXA RICHNESS

Ephemeroptera

Trichoptera

Chironomidae

Coleoptera

Non-insects

Other

Ecological Assessment 77

Creek in 2005–06. The cause is not known for the absence 

of Simulium in the 2005–06 samples given that Simulium is 

a widely distributed, common genus of blackflies. The 1999 

riffle sample from the Powder River near Locate (site P18) 

was dominated by Simulium, Cheumatopsyche, and three 

genera of Chironomids—Saetheria, Cricotopus/Orthocladius, and Cardiocladius. The Perlid stonefly Acroneuria 

abnormis was a subdominant in the 1999 Powder River 

sample and was common underneath the largest boulders 

in the riffles. The 2005 riffle sample from the Powder River 

near Locate contained some of the same species as the 1999 

sample, including Simulium, Cheumatopsyche, Saetheria, and 

Acroneuria abnormis.
78 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

Algal Community Assessment

Previous analysis of NAWQA data (Potapova and 

Charles, 2005) has shown that differences in substrate (habitat) 

can affect algal diversity, biovolume, and abundance of 

specific taxa, however, algal relations with their physical and 

chemical environment (autecology) were not significantly 

affected by differences in substrate. Results described in this 

section of the report follow the recommendations of Potapova 

and Charles (2005) for presentation of RTH data separate from 

DTH data where appropriate. 

Standing Crop

Concentrations of chlorophyll-a and AFDM generally 

were small, indicating a relatively small amount of algal 

biomass in riffles. Chlorophyll-a concentrations ranged from 

0.6 to 71.3 milligrams per square meter (mg/m2; fig. 29), with 

relatively large values observed at downstream sites on the 

main-stem Powder River below Clear Creek and at Moorhead (sites P11 and P12) and the main-stem Tongue River 

at the state line (site T9). Values for AFDM ranged from 3.5 

to 61.6 grams per square meter (g/m2), with relatively large 

values observed at sites P12 and T9. Median concentrations 

of chlorophyll-a and AFDM were 4.2 mg/m2 and 12.7 g/m2, 

respectively; chlorophyll-a and AFDM concentrations were 

positively correlated (R2 = 0.67, P < 0.05). For comparison, all 

chlorophyll-a values were less than the 100-mg/m2 seasonal 

mean target concentration to avoid nuisance algal conditions in 

the Clark Fork River in western Montana (Watson and others, 

2000). 

Community Composition

Taxa richness, the number of algal species in a sample, 

ranged from 25 in the Little Powder River above Dry Creek 

(site P15) to 115 in Crazy Woman Creek below I-90 (site P6; 

table 21). Although diatoms (Chrysophyta, Bacillariophyceae) 

contributed most to overall taxa richness, blue-green algae 

(Cyanophyta, cyanobacteria) and green algae (Chlorophyta) 

accounted for a substantial amount of periphyton standing 

crop at many sites, shown as relative (percentage) abundance 

in figure 30 and table 21. The abundance of blue-green algae 

ranged from 25 to 98 percent, whereas the abundance of 

diatoms and green algae varied from one percent to about 

50 percent among sites. The abundance of green algae and 

diatoms generally was larger in pools than riffles; however, 

several riffle sites along the main stem of the Powder and 

Tongue Rivers (table 21, sites T9, P2, and P4) were characterized by more than 50 percent abundance of diatoms and green 

algae, that are considered a more desirable food source for 

macroinvertebrates (and certain fish) than blue-green algae. 

Taxa richness and relative abundance of euglenoid (Euglenophyta) and yellow-green (Chrysophyta, Chrysophyceae) 

algae generally were low-to-absent at sites in the study area 

(table 21).

Periphyton communities also can be classified, functionally, by the abundance of periphyton (attached or benthic) taxa 

compared with the abundance of suspended (phytoplankton 

or sestonic) taxa (table 21) for diatoms and “soft” algae (algae 

exclusive of diatoms). For example, within the blue-green 

algal division, common benthic taxa included Oscillatoria, 

Lyngbya, Nostoc, and Calothrix spp., whereas common 

sestonic taxa included Microcystis, Aphanothece, Anabaena, 

and Gleocapsa spp. Similarly, within the green algal division, 

common benthic taxa included Cladophora, Rhizoclonium, 

Microspora, and Ulothrix spp., whereas common sestonic 

taxa included Oocystis, Sphaerocystis, Botryococcus, and 

Scenedesmus spp. 

Most sites in the study were dominated (more than 

75 percent abundance) by sestonic soft algae, regardless of 

whether riffles or pools were sampled (table 21). The exceptions, sites with more than 25 percent abundance of benthic 

soft algae, included primarily main-stem sites along the 

Powder River (sites P1-P3, P8, P11, and P12), Little Powder 

River at Highway 59 (site P14), and Cheyenne River near Dull 

Center (site C3). In contrast to the soft algae, diatoms were 

more than 90 percent benthic forms at all of the sites, with the 

exception of sites P5 and P8 on the main-stem Powder River 

(table 21). The presence of sestonic algae in the samples might 

be affected by phytoplankton (free-floating) algae originating 

in pools or slow-flowing reaches upstream from the sample 

collection points. 

Similarity of algal communities within river drainages 

and within specific habitats (riffles and pools) was indicated 

by NMDS ordination of Bray-Curtis similarity coefficients 

calculated from presence and absence data for diatoms and 

soft algae (fig. 31). Five groups of sites were identified that 

correspond with riffles in three river drainages (Tongue, 

Powder, and Cheyenne River groups), pools representing all 

river drainages in the study, and a small group containing only 

two riffle sites (sites P2 and P4). Site P15 (Little Powder River 

above Dry Creek) was an outlier in the ordination (fig. 31). 

The Tongue River group (fig. 31) included the mainstem Tongue River (sites T1 and T9), Goose Creek (site T2), 

and Clear Creek (site P10). A replicate sample from site T1, 

indicated as T1R in figure 31, also plotted within the Tongue 

River group, indicating high similarity with the parent sample. 

As was found with the macroinvertebrate data, the presence 

of Clear Creek in the Tongue River group likely reflects the 

commonality of mountainous headwaters and snowmelt-driven 

hydrology. In contrast to the macroinvertebrate data, however, 

algal-community structure in Crazy Woman Creek (sites P6 

and P7) was more similar to other sites in the Powder River 

drainage than to those in the Tongue River drainage. Microcystis, Aphanothece, and Oscillatoria were common bluegreen algal taxa whereas Oocystis and Sphaerocystis were 

common green algal taxa in the Tongue River group. Diatom 

communities were dominated by Cocconeis pediculus and 
Figure 29. Chlorophyll-a and ash-free dry mass concentrations in algae samples, Powder River Structural 

Basin, 2005.

0

10

20

30

40

50

60

70

80

T1 T2 T9 P1 P2 P3 P4 P5 P8 P9 P11 P12 P6 P7 P10 P15 B1 C3 C4 C6

SAMPLING SITE

CHLOROPHYLL-a, IN MILLIGRA

MS PER SQUARE METER, AND

ASH-FREE DRY M

ASS, IN GRA

MS PER SQUARE METER 

Chlorophyll-a

Ash-free dry mass

Main-stem Powder River sites

Ecological Assessment 79

Cocconeis placentula var. lineata. Cocconeis is a eutrophic 

taxon found commonly as an epiphyte (attached to plants) on 

filamentous algae or aquatic macrophytes (Prescott, 1978), 

which were relatively abundant in the Tongue River drainage 

(table 8). Predominant diatoms in Clear Creek (site P10) 

included Fragilaria construens var. venter (32 percent), Fragilaria brevistrata var. inflata (19 percent), that are halophilic 

species (tolerant to dissolved salts) that might be responding to slightly larger specific conductance values at site P10 

(1,200 μS/cm) compared with other sites in the Tongue River 

group (426–655 μS/cm; table 16). 

The Powder River group (fig. 31) included most of the 

sites on the main-stem Powder River, both sites on Crazy 

Woman Creek (sites P6 and P7, and the replicate sample P7R) 

and site B1 on the Belle Fourche River. The replicate sample 

(P7R) plotted close to the parent sample (P7) in the Powder 

River group, indicating high similarity between those two 

samples. Predominant soft algae were the blue-green algae 

Microcystis, Aphanothece, Lyngbya, and Oscillatoria and 

the green algae Oocystis, Sphaerocystis, Rhizoclonium, and 

Ulothrix. The most common diatom taxa at main-stem Powder 

River sites were Nitzchia, Caloneis, and Fragilaria, which 

are generally found in eutrophic waters with large concentrations of dissolved ions. Specific conductance values at sites 

in the Powder River group ranged from less than 1,000 μS/cm 

in Crazy Woman Creek to over 3,000 μS/cm at sites P3, P5, 

and B1. Common diatoms in Crazy Woman Creek and the 

Belle Fourche River (sites P6, P7, and B1) included species 

of Cocconeis and Fragilaria. The occurrence of nitrogenfixing algae (for example, Anabaena, Calothrix, Nostoc, and 

diatoms in the family Rhopalodiaceae (listed as “nitrogen 

fixers” diatom metric in table 21)) at many sites in the PRB 

possibly indicates nitrogen limitation. Nitrogen-fixing algae 

are capable of using atmospheric nitrogen gas as a source of 

nitrogen, and they are found commonly in aquatic systems 

with low concentrations of dissolved nitrogen or low ratios of 

nitrogen:phosphorus (Porter and others, 2008).

The Cheyenne River group of algal samples (fig. 31) 

contained four of the six sites in the Cheyenne River basin 

(sites C3–C6). All sites were dominated by sestonic bluegreen (Microcystis, Aphanothece, and Anabaena) and green 

(Oocystis) soft algal taxa. Rhizoclonium and Stigeoclonium

(benthic, filamentous green algae) accounted for 12 and 

9 percent of algal abundance, respectively, in the Cheyenne River near Dull Center (site C3). Common diatoms at 

sites in the Cheyenne River group included Fragilaria spp., 

Gomphonema spp., Epithemia spp. (nitrogen fixing diatoms), 

and Mastogloia smithii (associated with highly saline, brackish waters; Porter, 2008). Nitrogen-fixing algae accounted 

for 21 percent of the diatom community at site C6, probably 

indicative of low dissolved nitrogen concentrations (or low 

ratios of nitrogen:phosphorus) at that site. The presence of 

halophilic diatoms in the Cheyenne River group is consistent with elevated specific conductance values (1,410 to 

3,610 μS/cm) at those sites. Overall, algal community structure is similar between sites in the Cheyenne River group and 

those in the Powder River group.
Table 21. Algal taxa richness and diatom metrics from periphyton samples, Powder River Structural Basin, Wyoming and Montana, 

2005.

[Shaded cells indicate main-stem sites on the Tongue or Powder River; %, percent; <, less than; >, greater than] Site number (fig. 1) Habitat Sample date

Taxa richness and relative abundance

Sample taxa 

richness

Diatom taxa 

richness

Diatom abundance 

(%)

Blue-green algae 

richness

Blue-green algae 

abundance (%)

Green algae 

richness

Green algae 

abundance (%)

Euglenoid algae 

richness

Euglenoid algae 

abundance (%)

Yellow-green algae 

richness

Yellow-green algae 

abundance (%)

T1 Riffle 8/15/2005 43 34 2 4 64 5 34 0 0 0 0

T2 Riffle 8/17/2005 49 39 6 5 51 5 42 1 1 0 0

T8 Pool 8/16/2005 95 82 8 5 58 6 31 2 3 0 0

T9 Riffle 9/14/2005 73 58 44 5 37 9 19 1 <1 0 0

P1 Riffle 7/20/2005 69 59 3 5 77 5 20 0 0 0 0

P2 Riffle 7/21/2005 42 34 29 4 41 3 30 1 1 0 0

P3 Riffle 7/19/2005 63 53 3 4 77 6 20 0 0 0 0

P4 Riffle 7/22/2005 56 47 26 3 25 6 49 0 0 0 0

P5 Riffle 7/13/2005 92 81 1 3 65 6 33 1 <1 1 1

P6 Riffle 7/11/2005 115 106 11 4 54 4 34 1 1 0 0

P7 Riffle 7/12/2005 78 72 <1 3 92 3 8 0 0 0 0

P8 Riffle 7/23/2005 68 57 1 6 81 5 18 0 0 0 0

P9 Riffle 7/24/2005 96 82 9 5 58 8 32 1 1 0 0

P10 Riffle 9/13/2005 56 47 22 3 47 5 26 1 5 0 0

P11 Riffle 7/25/2005 58 50 1 4 81 4 18 0 0 0 0

P12 Riffle 7/26/2005 79 69 3 5 73 4 23 1 <1 0 0

P14 Pool 6/14/2005 56 51 56 3 34 2 10 0 0 0 0

P15 Riffle 6/13/2005 25 20 <1 3 90 2 8 0 0 0 0

C1 Pool 6/15/2005 80 74 25 3 49 3 26 0 0 0 0

C2 Pool 6/8/2005 60 47 26 3 30 8 43 2 1 0 0

C3 Riffle 6/27/2005 56 48 9 3 60 5 31 0 0 0 0

C4 Riffle 6/22/2005 66 61 1 4 98 1 1 0 0 0 0

C5 Pool 6/7/2005 74 59 11 4 40 9 48 2 2 0 0

C6 Riffle 6/21/2005 74 67 17 3 50 2 32 2 1 0 0

B1 Riffle 6/29/2005 69 64 9 3 78 2 13 0 0 0 0

B2 Pool 6/28/2005 86 77 33 4 44 5 23 0 0 0 0

80 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 21. Algal taxa richness and diatom metrics from periphyton samples, Powder River Structural Basin, Wyoming and Montana, 

2005.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River; %, percent; <, less than; >, greater than] Site number (fig. 1)

Soft Algae metrics Diatom metrics Benthic soft algae (%) Sestonic soft algae (%) Benthic diatoms (%) Sestonic diatoms (%) Achnanthes minutissima (%) Prefer low salinity (%) Prefer high salinity (halophilic) (%) Prefer pH near 7 (%) Prefer pH >7 (alkaliphilous) (%)

Indifferent to pH (%)

Eutrophic (%)

Nitrogen 

heterotrophs (%)

Nitrogen fixers (%)

Motile (%)

T1 15 85 100 0 1 56 44 3 95 1 92 0 19 3

T2 14 86 100 0 1 80 20 7 92 1 88 1 6 3

T8 24 76 100 0 1 81 19 19 75 6 77 14 1 33

T9 24 76 98 2 1 79 21 5 93 2 82 3 8 5

P1 65 35 100 0 0 83 17 13 86 1 63 4 33 42

P2 28 72 97 3 40 57 43 2 56 42 21 8 0 11

P3 53 47 93 7 0 87 13 23 68 8 47 8 7 46

P4 9 91 96 4 60 97 3 7 28 65 25 15 0 4

P5 7 93 85 15 1 85 15 30 65 5 46 10 1 41

P6 8 92 96 4 0 82 18 17 80 3 70 14 8 24

P7 0 100 100 0 1 84 16 32 67 2 61 4 5 14

P8 61 39 65 35 0 71 29 34 57 9 49 18 1 28

P9 17 83 98 2 0 81 19 23 62 15 52 12 1 40

P10 17 83 100 0 1 87 13 3 95 1 65 1 1 5

P11 82 18 100 0 0 94 6 16 82 1 44 3 3 11

P12 50 50 97 3 1 93 7 8 90 2 48 3 4 19

P14 39 61 96 4 2 77 23 10 88 2 82 13 1 20

P15 2 98 100 0 26 86 14 7 67 26 69 6 8 3

C1 11 89 94 6 0 71 29 8 84 7 86 17 2 32

C2 19 81 100 0 1 86 14 11 84 5 44 12 2 16

C3 32 68 100 0 0 78 22 3 94 3 40 5 6 16

C4 8 92 99 1 1 78 22 32 62 6 45 17 9 27

C5 12 88 100 0 12 76 24 14 63 23 51 2 8 39

C6 0 100 100 0 1 82 18 12 86 2 48 3 21 21

B1 5 95 99 1 0 89 11 7 88 5 73 4 0 7

B2 14 86 100 0 0 68 32 21 60 19 70 14 1 55

Ecological Assessment 81
Figure 30. Relative abundance of algal divisions by site, Powder River Structural Basin, 2005.

0

10

20

30

40

50

60

70

80

90

100

T1

T2

T8

T9

P1

P2

P3

P4

P5

P6

P7

P8

P9

P10

P11

P12

P14P15

C1

C2

C3

C4

C5C6

B1

B2

SAMPLING SITE

Yellow-green algae

Euglenoids

Green algae

Blue-green algae

Diatoms

RELATIVE ABUNDANCE, IN PERCENT

EXPLANATION

82 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

The fourth NMDS group in figure 31 consists of five 

sites from all major river basins in the study (T8, P14, C1, 

C2, and B2); the common variable among these sites is that 

algae samples were collected from pools rather than riffles. 

Consistent with the other three major-river basin groups, 

algal communities were dominated by sestonic soft algae; 

however, the abundance of green algae (10–48 percent) and 

diatoms (8–56 percent) was considerably larger than found 

in other groups, and similarly, the percentage of blue-green 

algae (30–58 percent) was relatively smaller. The replicate 

sample from Caballo Creek (B2R) plotted close to the parent 

sample (B2) indicating high similarity between those two 

samples (fig. 31). The distribution of common sestonic and 

benthic diatom taxa, as well as the percentage of halophilic 

diatoms was similar to the other three major-river basin 

groups; however, the percentage of nitrogen-fixing diatoms 

was small (less than or equal to 2 percent). Percentages of 

halophilic diatoms (table 21) were similar to the other three 

major-river basin groups, and specific conductance values in 

the pool group ranged from 775–4,240 μS/cm. The relative 

abundance of motile diatoms (16–55 percent) was relatively 

larger in the pool group than the other three major-river basin 

groups. These taxa are capable of moving through streambed 

sediments and avoiding burial by sedimentation. This finding 

is consistent with embeddedness values listed in table 9 that 

ranged from 73 percent at site T8, to 99 percent at site C2, 
Figure 31. Algal communities depicted by nonmetric multidimensional scaling ordination, Powder River Structural 

Basin, 2005.

B1

C1

C4

C6

P10

P15

P11

P2

P3 P1

P5

P9 P6

P7 P8

C2

T1

C5

T1R

T2

P14

T9

Powder River group

Tongue River 

group

Cheyenne River group

Pool group

P7R

P4

C3

B2R

B2 T8

Habitat

Riffle

Pool

P12

Ecological Assessment 83

and 100 percent at sites C1and B2, among the largest reported 

values in the NMDS algal groups. Curiously, the remaining 

pool site in the study (C5) grouped with its major river basin 

(Cheyenne).

Algal communities in the Powder River below Salt 

Creek (site P2) and below Burger Draw (site P4) were similar 

relative to one another but highly dissimilar to other site 

groups in the study (fig. 31). A similar case can be made for 

site P15 (Little Powder River above Dry Creek), which is an 

outlier to all NMDS groups. Considering the P2-P4 group, 

both sites were dominated by sestonic soft algae; however, 

the abundance of diatoms (26 to 29 percent) was larger than 

other Powder River sites as was the abundance of green algae 

(30 to 49 percent; table 21). No nitrogen-fixing algae were 

identified in the P2–P4 group. Although the percentage of 

halophilic diatoms at site P2 (43 percent; table 21) was among 

the largest in the study, the percentage of halophils at site P4 

(3 percent) was among the smallest in the study. The relative 

abundance of Mastogloia smithii in the diatom community at 

site P2 was 28 percent, indicative of elevated salinity. Specific 

conductance values at P2 (4,990 μS/cm) and P4 (4,600 μS/cm) 

were among the largest observed in the study (with site P3; 

4,800 μS/cm).

Although community structure generally was disparate 

between the P2-P4 group and site P15 outlier, one common 

element was a relatively large percentage of Achnanthes 

minutissima. The relative abundance of A. minutissima was 

60 percent of the diatom community at site P4, 40 percent 

at site P2, 26 percent at site P15, and 12 percent at site C5 

(table 21); percentages at other sites in the study were very 

small. The percentage of A. minutissima frequently has been 

used as an indicator of disturbance (Barbour and others, 

1999; Bahls and others, 1984), in part because the taxon is a 

pioneer species (with high rates of immigration on to clean 

substrates) whose abundance “has been found to be directly 

proportional to the time that has elapsed since the last scouring flow or episode of toxic pollution” (Barbour and others, 

1999, p. 6–16). Conversely, A. minutissima is known to exhibit 

a broad range of ecological tolerance (Bahls and others, 1984; 

Porter, 2008), so its use as disturbance indicator may be questionable. 

Diatom species are excellent indicators of salinity or 

specific conductance values (for example, van Dam and 

others, 1994). Diatom communities with the largest percentages of halobiontic (salt-loving; relatively high salinity) 

species occurred in the Powder River below Salt Creek 

(site P2), Tongue River at Monarch, WY (site T1), and 

Caballo Creek (site B2; table 21). Percentages of halobiontic 

diatoms ranged from 3 percent in the Powder River below 

Burger Draw (site P4) to 43 and 44 percent at sites P2 and T1. 

The salinity metric presented by van Dam and others (1994) 

is reflective of a European data set from freshwater, estuarine, 

and marine habitats, representing a wider gradient of salinity 

concentrations than found in most continental studies. Sources 
84 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

of constituents contributing to elevated specific-conductance 

values include anthropogenic sources and natural geochemical 

and soil properties in the PRB.

Diatom species also are good indicators of pH and water 

hardness. Species occurring in the Powder River structural 

basin generally reflect pH values greater than 7 (alkaliphilous). 

The abundance of alkaliphilous diatoms ranged from 28 

percent at site P4 to 95 percent at sites T1 and P10 (table 21). 

This corresponds with pH values ranging from 6.8 to 8.8 

(median = 8.0) measured during the time of biological 

sampling. Caution should be used in interpretation of single 

measurements of pH (and dissolved oxygen) at eutrophic sites 

because of considerable variability in these constituents over 

a 24-hr cycle as a result of primary productivity (for example, 

Peterson and others, 2001).

The nutrient status, as indicated by diatom communities, 

varied among river drainages. The relative abundance of eutrophic, or nutrient-rich, species was generally greater in samples 

from the Tongue River, Little Powder, and Belle Fourche River 

drainages than from the Powder and Cheyenne River drainages (table 21). The percentage of eutrophic diatoms ranged 

from 21 percent of the diatom community in the Powder River 

below Salt Creek (site P2) to 88–92 percent of the community at sites that receive wastewater-effluent discharges from 

small towns in the study area (for example, sites T1 and T2; 

table 21). Another diatom indicator of nutrient status is the 

percentage of nitrogen heterotrophs, species with requirements for organic forms of nitrogen (van Dam and others, 

1994; Porter and others, 2008). The percentage of nitrogen 

heterotrophs in samples ranged from zero (site T1) to 18 

percent (site P8) with relatively little differences among sites 

in major-river basins. Sources of organic nitrogen enrichment 

include wastewater-effluent discharges and localized uses 

of streams by livestock or wildlife. As previously described, 

many of the algal communities contained both diatom and soft 

algae nitrogen fixers, associated with either small concentrations of nitrogen or low ratios of nitrogen:phosphorus. This 

might indicate nitrogen is a limiting nutrient to algal growth in 

streams of the PRB, similar to indications from a study of the 

Yellowstone River in Montana (Peterson and Porter, 2002).

The relative abundance of motile diatoms in samples 

from riffles was greatest at sites on the main-stem Powder 

River. The percentage of motile diatoms is based on the sum 

of diatoms that are thought to be capable of movement to 

avoid sedimentation (Porter, 2008). Forty percent or more of 

the diatoms at the Powder River above Salt Creek (site P1), 

above Pumpkin Creek (site P3), above Crazy Woman Creek 

(site P5), and above Clear Creek (site P9) were motile species 

(table 21). Algae samples collected from pools, such as 

Caballo Creek (site B2), Black Thunder Creek (site C5), and 

Prairie Dog Creek (site P8) also contained large percentages 

of motile diatoms as might be expected given the depositional 

nature of the habitat.

Effect of Environmental Variables on Algal 

Communities

The environmental variables previously selected as 

indicators of geographic variables, habitat, and water quality 

(table 16) were tested for relation to the algal communities in 

the RTH (riffle) samples using the BEST routine (Clarke and 

Gorley, 2006). The five environmental variables chosen by 

the routine as best correlated with the Bray-Curtis similarity 

coefficients for the algal communities were northing, riparian disturbance, specific conductance, water temperature, and 

alkalinity (ρ = 0.58). Three of the five environmental variables 

best correlated with the algal riffle communities were related 

to water quality, and the other two were geographic variables; 

none were habitat related. A greater degree of correlation 

might have been achieved by including other variables. For 

example, nutrient concentrations are known to affect algal 

communities (Porter and others, 2008), but nutrient data 

were not collected because they were beyond the scope of 

this study. Comparison of results from the BEST routine for 

algal communities to the BEST results described previously 

for macroinvertebrate communities in the section “Effect of 

Environmental Variables on Macroinvertebrate Communities” indicates that specific conductance and alkalinity were 

explanatory variables common to both algal and macroinvertebrate communities. 

Ancillary Algal Data

Concentrations of chlorophyll-a in algae samples 

collected from the Little Powder River (site P15) for the 

NAWQA Program ranged from 3.0 to 48.5 mg/m2 during 

2001–04 and 2006–07 (fig. 32). The ATG chlorophyll data 

from 2005 are included in figure 32 for comparison. The 

median chlorophyll-a concentration was 5.5 mg/m2 at site P15 

during 2001–07. Chlorophyll-a concentrations in samples 

collected for the WWSC water-quality monitoring network 

in 2002 were 7 mg/m2 at sampling site T9 on the Tongue 

River at State line and 28.6 mg/m2 at site P10 on Clear Creek. 

Algae samples were not analyzed for chlorophyll-a during the 

WWSC project in 1980–81. 

Diatoms dominated the algal taxa identified in the 

NAWQA samples from the Little Powder River at site P15, 

constituting a mean of 91 percent of the taxa during 1999–

2006. The most common species of diatom in the NAWQA 

samples were Nitzchia inconspicua and Achnanthidium 

minutissimum. The dominance of Nitzchia inconspicua, a 

halophil, is consistent with the relatively high specific conductance values observed at this site. Blue-green algae sometimes 

dominated the NAWQA samples in terms of density and 

biovolume; the most common taxa of blue-green algae were 

Calothrix spp. (nitrogen fixers) and Homoeothrix spp. The 

predominant species of diatoms and blue-green algae differed 
Figure 32. Chlorophyll-a and ash-free dry mass concentrations 

in ancillary algae samples, Powder River Structural Basin, 

2001–07.

0

25

50

75

100

SITE P15 7/10/02SITE P15 7/14/03SITE P15 8/25/04SITE P15 6/13/05

SITE P15 8/8/06SITE P15 8/7/07

SITE T9 8/20/02

SITE P15 7/19/01SITE P10 9/17/02

SAMPLING SITE AND DATE

CHLOROPHYLL-a, IN MILLIGRAMS PER SQUARE 

METER, AND ASH-FREE DRY MASS, IN GRAMS 

PER SQUARE METER 

Chlorophyll-a

Ash-free dry mass

Ecological Assessment 85

between the NAWQA and ATG samples, but some were from 

the same families in both data sets. In contrast, blue-green 

algae were not identified in three algae samples collected 

during 1980 from periphyton at site P15 for a WWSC project. 

The lack of blue-green algae in 1980 might be because the 

samples were collected earlier in the season (April, May, and 

June) than the NAWQA samples (July through September). 

The mean number of taxa identified and the number of 

samples (n) from the Little Powder River at site P15 were 

ATG, 25 taxa (n = 1); WWSC project, 25 taxa (n = 3); and 

NAWQA, 40 taxa (n = 6). One of the predominant algae 

species in the WWSC project samples and the ATG sample 

from site P15 was the diatom Achnanthes minutissima, which 

also was common in the NAWQA samples under the newer 

synonym Achnanthidium minutissimum. Diatom species in the 

NAWQA samples generally were alkaliphilous, with optima 

greater than pH 7. Salinity optima for the diatoms were in the 

fresh-brackish category (dissolved-solids concentrations less 

than 500 mg/L) and to a lesser extent, the brackish-fresh category (dissolved-solids concentrations of 500 to 1,000 mg/L). 

Nutrient optima indicated most diatoms in the NAWQA 

samples from site P15 were either tolerant of or moderately 

dependent on large concentrations of organic nitrogen. 

NAWQA protocols were used to collect algae samples in 

2002 as part of the WWSC monitoring network at the Tongue 

River at State line (site T9), Clear Creek (site P10), and Cheyenne River at Riverview (USGS gaging station 06386400, 

several kilometers upstream from site C6). The dominant 

algae in terms of relative abundance in the riffle sample from 

the Tongue River were the blue-green algae Phormidium and 

the diatom Cocconeis pediculus. Nitrogen optima indicated 

about 76 percent of the diatoms in the Tongue River sample 

were nitrogen autotrophs that are tolerant of, but not necessarily dependent on, large concentrations of organic nitrogen. 

The 2002 riffle sample from Clear Creek was dominated by 

blue-green algae, mainly Phormidium and Oscillatoria; the 

most common diatoms were Achnanthidium minutissimum

and Encyonopsis subminuta. The diatom community from 

Clear Creek contained mostly nitrogen autotrophs, with low 

to moderate tolerance of organic nitrogen. Blue-green algae 

(Oscillatoria) also dominated the algae sample from the 

Cheyenne River, which was collected from pools due to lack 

of riffles at the site. About 64 percent of the diatoms from the 

Cheyenne River sample fell into the fresh-brackish salinity 

category. 

Algae samples were collected from the Little Powder 

River at Highway 59 (site P14), Cheyenne River near Dull 

Center (site C3), and the Belle Fourche River (site B1) during 

a WWSC project investigation in 1980. Algae samples from 

the Little Powder River were dominated by the diatoms 

Nitzchia dissipata and Gomphonema spp. during April and 

May, the diatom Amphora perpusilla in June, and the bluegreen algae Anabaena during August. Motile species of 

diatoms dominated in the algae samples from the Cheyenne 

River, including Surirella ovata in April, Nitzchia constricta

and Nitzchia palea in May, and Nitzchia acicularis in June. 

Algal communities sampled in the Belle Fourche River were 

dominated by the halophilic diatom Fragilaria construens 

venter in April and August and by Navicula gregaria in June. 

The periphyton algae samples from the WWSC project sites 

typically each contained 20 to 30 species of algae. 

Fish Community Assessment

The results of the fish community assessment are organized by river drainage because of differences in sampling 

methods. For convenience, the term “tributaries” is used to 

encompass all streams not specifically named in the section 

title. 

Fish Communities of the Tongue, Cheyenne, and 

Belle Fourche Rivers and Tributaries

Fish communities were sampled at 35 sites during 2005; 

28 of the same sites were sampled during 2006. The number of 

sites sampled in 2006 was smaller than in 2005 because of dry 

sample reaches (sites T7, T16, C5, and B2) and study limitations at other sites (sites R2, T19, and P16). 

Spatial and Temporal Distribution of Fish

A total of 36 species of fish were identified in samples 

collected during 2005 and 2006 (table 22). Ecological characteristics of those 36 fish species, as well as of 2 fish species 

identified only in the main-stem Powder River, are listed in 

table 23. About one-half of the species (17) identified in the 

Tongue, Cheyenne, and Belle Fourche Rivers and tributaries 
86 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

were native, including eight minnows (Cyprinidae) and all 

five suckers (Catostomidae). Introduced fish species included 

eight sunfishes (Centrarchidae), two topminnows (Cyprinodontidae), northern pike (Esocidae), and yellow perch (Percidae). Other fish identified included goldeye (Hiodontidae, 

native) and catfishes (Ictaluridae, two native species and two 

introduced species), and sauger (Percidae, native). The fishes 

sampled generally were warm-water species, although trout 

(Salmonidae) were captured in the Tongue River at Monarch 

(site T1). Site T1 is located at the boundary between the coldwater and warm-water fishery as defined by WGFD and might 

be considered a transition zone on the basis of the presence of 

both cold- and warm-water species. 

Fathead minnows were the most common fish in 

the collective samples during 2005–06 and comprised 16 

percent of the relative abundance of fish captured (fig. 33). 

Smallmouth bass and sand shiner each comprised more 

than 10 percent of the fish, whereas rock bass, white sucker, 

common carp, green sunfish, and shorthead redhorse each 

comprised 5 percent or more of the fish. The other 27 species 

comprised 24 percent of the fish captured.

Fish species richness was greatest at sampling sites on 

the Tongue River. Samples from the Tongue River at State 

line (site T9) contained 18 species in 2005 and 17 species 

in 2006 (table 22), whereas other sites on the Tongue River 

(sites T1, T5, T10, T14, and T18) contained 10 to 16 species. 

The Tongue River Reservoir on the main stem between 

sites T9 and T10 appears to affect the fish communities 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—sites T5 and T9 on the Tongue 

River and site T8 on Prairie Dog Creek. Black crappie and 

white crappie, also known as open-water species, were found 

in small numbers in the Tongue River upstream and downstream from Tongue River Reservoir. Farther downstream 

from the reservoir, in the Tongue River below Brandenberg 

Bridge (site T18), the fish community shifted toward a warmwater community adapted to turbid water and large rivers, as 

indicated by larger numbers of flathead chub, channel catfish, 

and river carpsucker (Baxter and Stone, 1995). 

A total of 15 species of fish were identified in the main 

stem of the Tongue River and its tributaries that were not 

identified in the Cheyenne and Belle Fourche Rivers and their 

tributaries, nor in Rosebud Creek or the Little Powder River. 

Additionally, of those 15 species, only one—the mountain 

sucker—was identified in samples from the main-stem Powder 

River. Several of the 15 species were open-water species as 

noted previously. Some native species, such as the brassy 

minnow and lake chub, were found only in the Tongue River 

drainage, as were introduced species such as the yellow 

bullhead and golden shiner. Of the 31 species of fish identified in samples from the Tongue River drainage in 2005–06, 

16 species were introduced. Introduced fish comprised 51 

percent of the total abundance of fish in samples from the 

Tongue River drainage and included smallmouth bass, rock 

bass, common carp, and green sunfish. 

Tributary streams with relatively large numbers of fish 

species in both 2005 and 2006 were Goose Creek (site T2), 

Prairie Dog Creek (site T8), Clear Creek (site P10), and Little 

Powder River above Dry Creek (site P15). Fourteen species of 

fish were collected in both 2005 and 2006 from Clear Creek, 

including sauger in both years. Sauger, which is a species of 

concern, were not collected at any of the other 34 sampling 

sites. The number of species per sample was smallest in small 

intermittent streams such as Rosebud Creek (site R1), Porcupine Creek (site C1), and the Belle Fourche River (site B1). 

The fish community at site R1 was atypical because northern 

pike (an efficient carnivore) was the only species captured 

there in 2005, and no fish were captured during the 2006 

sampling. Site R1 also was the only site where northern pike 

were observed. Only one species of fish (fathead minnow) was 

collected at Porcupine Creek in 2005–06, and two and three 

species of fish were captured from the Belle Fourche River in 

2005 and 2006, respectively. 

Fish communities sampled in 2006 appeared to be similar 

to those in 2005 on the basis of taxa richness and abundance. 

Although 2006 was a drier year and fish habitat appeared to be 

reduced (figs. 3 and 4), the mean number of species collected 

was similar between the years. Using data from sites sampled 

in both years, a mean of 6.9 species per site was sampled 

in 2005, and a mean of 7.1 species per site was sampled in 

2006. The total abundance of fish collected from those sites 

was 7,132 fish in 2005 and 11,638 fish in 2006. The largest 

increases in fish abundance from 2005 to 2006 were for sand 

shiner, fathead minnow, and common carp, but the differences in abundance between years might be related to normal 

year-to-year variation or perhaps due to more efficient capture 

related to reduction in the available habitat associated with 

smaller flows. 

Fish Community Structure

The structure and integrity of the fish community were 

assessed using the Index of Biotic Integrity (IBI) developed 

for prairie streams in Montana (Bramblett and others, 2005). 

As noted in the methods section of this report, IBI scores for 

the main-stem Tongue River are presented for comparative 

purposes among the main-stem sites and between years, and 

should not be compared directly to the scores from the small 

plains streams. 

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) had some of the highest IBI 

scores in this study (table 24). The highest observed IBI score 

of 87 occurred at site T3 on upper Youngs Creek in both 2005 

and 2006 (table 24). IBI scores from sites on lower Youngs 

Creek (site T4) and Squirrel Creek (sites T6 and T7) also were 

relatively high and ranged from 66 to 81. Other sites with IBI 

scores greater than 60 in both years were Crazy Woman Creek 

near mouth (site P7), Clear Creek (site P10), and the Little 

Powder River at Highway 59 (site P14). 
Table 22. Fish abundance in samples from the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River. Numbers indicate the number of individuals]

Site number

(fig. 1)

Abbreviated site 

name

Sample date

Black bullhead

Black crappie

Bluegill

Brassy minnow

Brown trout

Channel catfish

Common carp

Creek chub

Fathead minnow

Flathead chub

Golden shiner

Goldeye

Green sunfish

Lake chub

Largemouth bass

Longnose dace

R1 upper Rosebud 

Creek

06/20/05 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 008/22/06 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

R2 Rosebud Creek 

at mouth

09/14/05 1 0 0 0 0 1 2 0 21 2 0 0 6 0 0 0

T1 Tongue River at 

Monarch

08/23/05 2 0 0 0 3 0 26 0 1 0 0 0 22 0 0 008/23/06 1 0 0 0 1 0 20 0 0 0 0 0 15 0 0 2

T2 Goose Creek 08/22/05 3 0 0 0 0 0 18 0 1 0 0 0 3 0 6 3

08/22/06 15 0 0 0 0 0 30 0 0 0 0 0 3 0 0 8

T3 upper Youngs 

Creek

06/15/05 0 0 0 0 0 0 0 6 2 0 0 0 0 0 0 6906/28/06 0 0 0 0 0 0 0 62 15 0 0 0 0 0 0 32

T4 Youngs Creek at 

mouth

06/14/05 0 0 0 1 0 0 0 0 22 0 0 0 0 0 0 606/27/06 0 0 0 54 0 0 0 9 104 0 0 0 0 4 0 7

T5 Tongue River 

below Youngs Creek

08/29/05 108 3 0 0 0 0 43 0 17 0 0 0 42 0 0 608/24/06 10 0 0 0 0 0 129 0 0 4 0 0 5 0 0 31

T6 upper Squirrel 

Creek

06/16/05 0 0 0 0 0 0 0 19 0 0 0 0 0 0 0 1006/29/06 0 0 0 1 0 0 0 10 83 0 0 0 0 0 0 0

T7 Squirrel Creek 

at mouth

06/13/05 1 0 0 0 0 0 0 8 3 0 0 0 0 1 0 0

T8 Prairie Dog 

Creek

08/26/05 13 0 0 0 0 0 1 0 0 0 0 0 0 0 0 008/25/06 0 0 0 0 0 0 8 168 0 0 0 0 1 0 0 5

Ecological Assessment 87
Table 22. Fish abundance in samples from the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River. Numbers indicate the number of individuals]

Site number

(fig. 1)

Abbreviated site 

name

Sample date

Black bullhead

Black crappie

Bluegill

Brassy minnow

Brown trout

Channel catfish

Common carp

Creek chub

Fathead minnow

Flathead chub

Golden shiner

Goldeye

Green sunfish

Lake chub

Largemouth bass

Longnose dace

T9 Tongue River at 

State line

08/25/05 30 25 4 1 0 6 89 9 0 2 0 0 1 0 0 508/28/06 13 3 0 0 0 9 99 51 0 3 0 0 6 0 0 13

T10 Tongue River 

above Hanging Woman Creek

08/30/05 0 9 0 0 0 10 21 0 0 0 0 0 1 0 0 008/29/06 0 0 0 0 0 7 24 0 0 0 0 0 0 0 0 1

T11 upper Hanging 

Woman Creek

06/22/05 0 0 0 3 0 0 0 0 0 0 0 0 52 0 0 006/27/06 0 0 0 8 0 0 4 0 6 0 0 0 24 0 0 0

T12 middle Hanging 

Woman Creek

06/21/05 0 0 0 0 0 0 0 0 0 0 0 0 8 0 0 006/26/06 0 0 0 0 0 0 0 0 7 0 0 0 18 0 0 0

T13 Hanging Woman 

Creek at mouth

06/23/05 0 0 0 0 0 0 0 0 85 0 0 0 17 0 0 006/26/06 0 0 0 0 0 0 0 0 266 0 0 0 0 0 0 0

T14 Tongue River at 

Birney Day School

08/31/05 0 0 0 0 0 18 35 0 0 0 0 0 0 0 0 2

T14 Tongue River at 

Birney Day School

08/30/06 2 0 0 0 0 63 35 0 0 0 2 0 17 0 0 19

T15 upper Otter 

Creek

06/29/05 0 0 0 12 0 0 0 0 0 0 0 0 0 12 0 0

07/12006 0 0 0 1 0 0 0 0 0 0 0 0 0 4 0 0

T16 middle Otter 

Creek

06/28/05 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

88 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 22. Fish abundance in samples from the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River. Numbers indicate the number of individuals]

Site number

(fig. 1)

Abbreviated site 

name

Sample date

Black bullhead

Black crappie

Bluegill

Brassy minnow

Brown trout

Channel catfish

Common carp

Creek chub

Fathead minnow

Flathead chub

Golden shiner

Goldeye

Green sunfish

Lake chub

Largemouth bass

Longnose dace

T17 Otter Creek at 

mouth

06/30/05 0 0 1 114 0 0 31 0 360 0 0 0 0 0 0 006/28/06 1 0 0 0 0 0 122 0 931 0 0 0 6 0 0 0

T18 Tongue River 

below Brandenberg Bridge

09/01/05 0 1 0 0 0 19 18 0 5 237 0 0 54 0 0 1908/31/06 0 0 0 0 0 55 81 0 11 136 0 0 4 0 0 9

T19 Pumpkin Creek 06/24/05 0 0 0 0 0 1 0 0 36 4 0 2 0 0 0 0

P6 Crazy Woman 

Creek below I-90

07/14/05 0 0 0 0 0 0 0 0 0 5 0 2 0 0 0 007/31/06 0 0 0 0 0 6 330 0 2 0 0 7 0 0 0 4

P7 Crazy Woman 

Creek near mouth

07/14/05 0 0 0 0 0 0 0 0 0 10 0 0 0 0 0 308/01/06 0 0 0 0 0 9 6 0 16 15 0 0 4 0 0 67

P10 Clear Creek 08/24/05 0 0 0 0 0 9 29 0 22 8 0 15 2 0 0 0

08/21/06 0 0 0 0 0 4 14 5 0 128 0 6 2 0 0 1

P14 Little Powder 

River at Highway 59

06/23/05 0 0 0 0 0 0 0 0 27 0 0 0 0 0 0 006/22/06 0 0 0 0 0 0 0 0 0 0 0 0 6 0 0 18

P15 Little Powder 

River above Dry Creek

06/23/05 12 0 0 0 0 2 5 3 56 3 0 0 27 0 0 006/23/06 3 0 0 0 0 4 3 0 8 1 0 0 18 0 0 19

P16 Little Powder 

River at Biddle

06/27/05 2 0 0 0 0 2 2 2 50 0 0 0 4 0 0 0

Ecological Assessment 89
Table 22. Fish abundance in samples from the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River. Numbers indicate the number of individuals]

Site number

(fig. 1)

Abbreviated site 

name

Sample date

Black bullhead

Black crappie

Bluegill

Brassy minnow

Brown trout

Channel catfish

Common carp

Creek chub

Fathead minnow

Flathead chub

Golden shiner

Goldeye

Green sunfish

Lake chub

Largemouth bass

Longnose dace

C1 Porcupine Creek 06/20/05 0 0 0 0 0 0 0 0 373 0 0 0 0 0 0 0

06/22/06 0 0 0 0 0 0 0 0 20 0 0 0 0 0 0 0

C2 Antelope Creek 06/20/05 0 0 0 0 0 0 1 0 69 0 0 0 356 0 0 0

06/20/06 3 0 0 0 0 0 0 0 0 0 0 0 335 0 0 0

C3 Cheyenne River 

near Dull Center

06/22/05 1 0 0 0 0 0 3 0 2 0 0 0 40 0 0 006/19/06 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

C4 Little Thunder 

Creek

06/2205 16 0 0 0 0 0 1 0 36 0 0 0 14 0 0 0

06/21/06 15 0 0 0 0 0 3 0 200 0 0 0 13 0 0 0

C5 Black Thunder 

Creek

06/21/05 1 0 0 0 0 0 0 0 2 0 0 0 1 0 0 0

C6 Cheyenne River 

near Spencer

06/21/05 1 0 0 0 0 0 4 0 20 0 0 0 33 0 0 006/20/06 0 0 0 0 0 0 0 0 8 0 0 0 1 0 0 0

B1 Belle Fourche 

River

06/24/05 0 0 0 0 0 0 0 0 25 0 0 0 0 0 0 006/21/06 0 0 0 0 0 0 22 0 58 0 0 0 0 0 0 0

B2 Caballo Creek 06/23/05 0 0 0 0 0 0 3 0 13 0 0 0 0 0 0 0

90 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 22. Fish abundance in samples from the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River. Numbers indicate the number of individuals]

Site num-ber

(fig. 1)

Sample date

Longnose sucker

Mountain sucker

Northern pike

Northern plains 

killifish

Plains minnow

Plains topminnow

Pumpkinseed

Rainbow trout

River carpsucker

Rock bass

Sand shiner

Sauger

- Shorthead red

horse

Smallmouth bass

Spottail shiner

Stonecat

White crappie

White sucker

Yellow bullhead

Yellow perch

Total number of 

species

R1 6/20/2005 0 0 11 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1

8/22/2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

R2 9/14/2005 0 0 0 0 0 0 0 0 0 0 13 0 0 0 0 0 0 4 0 0 8

T1 8/23/2005 11 0 0 0 0 0 0 1 0 240 0 0 57 93 0 13 0 46 0 0 12

8/23/2006 20 0 0 0 0 0 0 0 0 369 0 0 67 559 0 53 0 68 0 0 11

T2 8/22/2005 0 0 0 0 0 0 0 0 0 314 0 0 31 288 0 69 0 37 0 0 11

8/22/2006 0 0 0 0 0 0 0 0 0 203 0 0 0 186 0 65 0 51 0 0 8

T3 6/15/2005 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4

6/28/2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 0 0 4

T4 6/14/2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3

6/27/2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 10 0 0 6

T5 8/29/2005 4 0 0 0 0 0 0 0 0 93 0 0 56 412 77 2 0 125 0 0 13

8/24/2006 4 0 0 0 0 0 4 0 0 116 0 0 58 217 148 11 0 57 178 0 14

T6 6/16/2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2

6/29/2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 4

T7 6/13/2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 5T8 8/26/2005 3 0 0 0 0 0 0 0 0 10 0 0 0 2 1 56 0 9 4 0 9

8/25/2006 4 0 0 0 0 0 0 0 0 5 0 0 13 26 0 1 0 56 0 0 10

T9 8/25/2005 0 0 0 0 0 0 0 0 0 34 0 0 42 264 40 10 1 102 0 1 18

8/28/2006 1 0 0 0 0 0 34 0 0 55 0 0 95 234 150 46 0 119 301 0 17

T10 8/30/2005 0 0 0 0 0 0 0 0 6 41 0 0 21 39 0 12 0 18 21 0 11

8/29/2006 0 0 0 0 0 0 0 0 1 52 0 0 42 60 0 23 0 57 24 0 10

T11 6/22/2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 3

6/27/2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4

T12 6/21/2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1

6/26/2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 3

Ecological Assessment 91
Table 22. Fish abundance in samples from the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River. Numbers indicate the number of individuals]

Site num-ber

(fig. 1)

Sample date

Longnose sucker

Mountain sucker

Northern pike

Northern plains 

killifish

Plains minnow

Plains topminnow

Pumpkinseed

Rainbow trout

River carpsucker

Rock bass

Sand shiner

Sauger

- Shorthead red

horse

Smallmouth bass

Spottail shiner

Stonecat

White crappie

White sucker

Yellow bullhead

Yellow perch

Total number of 

species

T13 6/23/2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 6 0 0 4T13 6/26/2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1T14 8/31/2005 0 0 0 0 0 0 0 0 19 61 0 0 37 21 0 16 8 62 38 0 11

8/30/2006 4 0 0 0 0 0 0 0 9 69 0 0 39 138 0 46 0 111 39 0 14

T15 6/29/2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 0 0 3

7/12/2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2

T16 6/28/2005 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 1 0 0 2T17 6/30/2005 0 0 0 0 0 0 0 0 0 0 10 0 0 0 0 0 0 6 0 0 6

6/28/2006 0 0 0 0 0 0 0 0 0 0 43 0 0 0 0 0 0 0 0 0 5

T18 9/1/2005 4 0 0 0 0 0 3 0 51 1 0 0 81 8 0 7 0 95 9 0 16

8/31/2006 1 0 0 0 0 0 0 0 155 1 1 0 354 24 0 4 0 214 2 0 15

T19 6/24/2005 0 0 0 0 0 0 0 0 1 0 162 0 0 0 0 0 0 0 0 0 6

P6 7/14/2005 0 0 0 0 0 0 0 0 0 0 20 0 0 0 0 0 0 0 0 0 3

7/31/2006 0 0 0 0 0 0 0 0 4 0 160 0 10 30 0 9 0 156 0 0 11

P7 7/14/2005 0 0 0 0 0 0 0 0 0 0 33 0 0 0 0 1 0 8 0 0 5

8/1/2006 0 0 0 0 0 0 0 0 0 0 402 0 0 0 0 9 0 227 0 0 9

P10 8/24/2005 0 0 0 0 0 0 0 0 13 91 71 2 40 22 0 32 0 19 0 0 14

8/21/2006 0 0 0 0 0 0 0 0 0 76 192 1 12 33 0 45 0 13 0 0 14

P14 6/23/2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1

6/22/2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 3

P15 6/23/2005 0 0 0 0 0 0 0 0 0 0 95 0 0 0 0 0 0 13 0 0 9

6/23/2006 0 0 0 0 2 0 0 0 5 0 453 0 0 0 0 0 0 4 0 0 11

P16 6/27/2005 0 0 0 0 0 0 0 0 0 0 226 0 1 0 0 1 0 11 0 0 10

C1 6/20/2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1

6/22/2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1

C2 6/20/2005 0 0 0 0 0 160 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4

92 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 22. Fish abundance in samples from the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue River. Numbers indicate the number of individuals]

Site num-ber

(fig. 1)

Sample date

Longnose sucker

Mountain sucker

Northern pike

Northern plains 

killifish

Plains minnow

Plains topminnow

Pumpkinseed

Rainbow trout

River carpsucker

Rock bass

Sand shiner

Sauger

- Shorthead red

horse

Smallmouth bass

Spottail shiner

Stonecat

White crappie

White sucker

Yellow bullhead

Yellow perch

Total number of 

species

6/20/2006 0 0 0 0 0 192 0 0 0 0 0 0 0 0 0 0 0 1 0 0 4

C3 6/22/2005 0 0 0 14 0 7 0 0 0 0 8 0 0 0 0 0 0 24 0 0 8

6/19/2006 0 0 0 18 0 14 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2

C4 6/22/2005 0 0 0 3 0 0 0 0 0 0 12 0 0 0 0 0 0 6 0 0 7

6/21/2006 0 0 0 21 0 0 0 0 0 0 69 0 0 0 0 0 0 5 0 0 7

C5 6/21/2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3C6 6/21/2005 0 0 0 37 2 6 0 0 1 0 34 0 0 0 0 0 0 2 0 0 10C6 6/20/2006 0 0 0 66 1 0 0 0 0 0 14 0 0 0 0 0 0 1 0 0 6B1 6/24/2005 0 0 0 0 0 0 0 0 0 0 74 0 0 0 0 0 0 0 0 0 2

6/21/2006 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 3

B2 6/23/2005 0 0 0 0 0 0 0 0 0 0 78 0 0 0 0 0 0 0 0 0 3

Ecological Assessment 93
Table 23. Ecological characteristics of fish species sampled in the Powder River Structural Basin, Wyoming and Montana, 

2005–06.—Continued

[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 

toleranceOrigin

Length at 

3 years 

(mm)

Hiodontidae Goldeye Hiodon alosoides IN WC LO INT N 259

Cyprinidae Lake chub Couesius plumbeus IN WC -- MOD N 140

Common carp Cyprinus carpio OM BE -- TOL I 381

Western silvery 

minnow1

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 chub1 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

Esocidae northern pike Esox lucius CA WC -- MOD I 457

Salmonidae rainbow trout Oncorhynchus mykiss IC WC LO INT I 279

brown trout Salmo trutta IC WC LO INT I 305

94 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Figure 33. Relative abundance of fish by species in samples from 

the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, 

2005–06.

Fathead minnow

16 percent

Smallmouth bass

14 percent

Sand shiner

11 percent

Rock bass

9 percent

White 

sucker

9 percent Common carp

6 percent

Green sunfish

6 percent

Shorthead 

redhorse

5 percent

Other

24 percent

Table 23. Ecological characteristics of fish species sampled in the Powder River Structural Basin, Wyoming and Montana, 

2005–06.—Continued

[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 

toleranceOrigin

Length at 

3 years 

(mm)

Cyprinodontidae Northern plains 

killifish

Fundulus kansae OM GE -- TOL I 81

Plains topminnow

Fundulus sciadicus IN GE -- MOD I NA

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

1

Identified only in the main-stem Powder River.

Ecological Assessment 95

Fish communities in other small plains streams included 

Hanging Woman Creek (sites T11–T13) that received IBI 

scores ranging from 10 to 46, with a mean score of 31. 

Scores for Otter Creek (sites T15–T17) ranged from 10 to 60, 

with a mean of 32. Scores for the Cheyenne River drainage 

(sites C1–C6) ranged from 10 to 53, with a mean of 30. All of 

the fish samples from sites in the Cheyenne and Belle Fourche 

River drainages received metric scores of 0 for the percentage 

of invertivorous cyprinids (table 24). Most of the sites in the 

Cheyenne River drainage did, however, support plains topminnow and northern plains killifish that might occupy a similar 

ecological niche as the invertivorous cyprinids, but because 

these species are introduced, their presence lowers IBI scores. 

Fish communities of the main-stem Tongue River sites 

received IBI scores ranging from 49 to 63. The lowest scores 

from sites on the main-stem Tongue River in 2005 and again 

in 2006 were at site T10, downstream from Tongue River 

Reservoir. Scores increased in the downstream direction 

from the reservoir, from site T10 to site T18, in both years. 

The highest IBI scores for the main-stem Tongue River fish 

communities were from site T1 at Monarch. The IBI scores for 

site T1 might be affected by the presence of cold-water species 
96 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

for which the IBI was not designed (Bob Bramblett, Montana 

State University, oral commun., Dec. 2007). 

Fish Communities of the Main-Stem Powder 

River

In total, 134,938 fish were collected during 80 surveys 

by the WGFD and the USGS on the main-stem Powder River 

in Wyoming and Montana, representing a total of six families 

and 21 species (table 25). Of the 21 fish species identified, 

15 were native, and 6 were introduced. Native fish species 

included 8 minnows (Cyprinidae), 4 suckers (Catostomidae), 

3 catfish (Ictaluridae), and 1 goldeye (Hiodontidae). Introduced species included 3 sunfishes (Centrarchidae), 1 killifish 

(Cyprinidontidae), 1 catfish, and 1 minnow. Sand shiners 

(61 percent), flathead chub (21 percent), Hybognathus spp. 

(8 percent), northern plains killifish (4 percent), and longnose 

dace (2 percent) dominated the total catch when data from all 

sampling periods were combined (fig. 34; tables 29 and 30 in 

Appendix 2). Northern plains killifish was the most abundant 

and widespread introduced species and was present at nearly 

all of the sites. All other introduced species (common carp, 

green sunfish, smallmouth bass, rock bass, and black bullhead) were uncommon and collectively comprised less than 

1 percent of the total catch.

Spatial Distribution of Fish

Fish species richness per sample ranged from a minimum 

of 4 species, collected in the Powder River below Crazy 

Woman Creek (site P8) on August 31, 2004, to a maximum 

of 13 species, collected in the Powder River above Salt Creek 

(site P1) on July 20, 2005, and the Powder River above 

Pumpkin Creek (P3) on September 7, 2004 (table 25). The 

mean number of fish species ranged from 6.0 species per 

sample at the South Fork Powder River (miscellaneous site) 

to 10.1 species per sample at the Powder River at Moorhead 

(site P12; table 25). 

When considering the total number of species identified 

at each site during all of the sampling periods, the Powder 

River above Crazy Woman Creek (site P5) had the greatest richness of 17 species. At least 15 species in total were 

observed at five (sites P1, P5, P8, P9, and P11) of the eight 

sites in Wyoming. The largest total species count among sites 

in Montana was observed at Moorhead (site P12, 14 species). 

The total species counts by site might be affected by differences in sampling frequency given that sites in Wyoming 

generally were sampled nine times each, whereas sites in 

Montana were sampled one to three times each. Patton 

(1997) showed that increased sampling effort can increase 

species counts, but recommended that the target level of 

species richness be set to 90 percent or some value less 

than 100 percent of all species present because of diminishing returns at increased levels of effort. Rarefaction curves 

described in the following paragraph were calculated to help 

explain the relation between sampling effort and species abundance for this study. 

Rarefaction curves plotted for the main-stem Powder 

River sampling sites indicated that the site with the maximum 

overall species richness, site P5, had a relatively flat curve, 

indicating that the fish community is reasonably represented in the overall sample (fig. 35). The least expected 

species richness for the main-stem sites occurred at Broadus 

(site P13), and the maximum expected species richness 

occurred at Moorhead (site P12). The rarefaction curves were 

steepest for the Powder River above Salt Creek (site P1), 

below Clear Creek (site P11), at Moorhead (site P12), and 

below Little Powder River (site P17), which indicates that 

either the species diversity of the fish community is underrepresented in the samples or that the greatest species diversity 

was present at those sites regardless of sampling effort. Similar 

to the species richness counts, interpretation of the rarefaction 

curves might be affected by differences in sampling frequency 

at sites.

Native fish predominated in the main-stem Powder 

River, both in terms of number of species and abundance 

(tables 23 and 25). The native fish community at all mainstem sites included flathead chub, sand shiner, and channel 

catfish. Minnows in the genus Hybognathus also were found at 

nearly every site. Other native fish species identified in small 

numbers included shorthead redhorse, river carpsucker, white 

sucker, and goldeye. This core community of fish species 

identified in the main-stem Powder River is well adapted to 

life in turbid water, shifting substrates, and wide variations in 

streamflow (Hubert, 1993). 

The distribution of fish species appeared to shift longitudinally along the main-stem Powder River in Wyoming. 

White sucker, mountain sucker, northern plains killifish, 

and longnose dace were more common at the upstream sites 

(sites P1–P3) than downstream sites (sites P8–P11; fig. 36); 

mountain sucker were not collected downstream from site P3. 

Other fish species, such as channel catfish and stonecat, were 

more common at the downstream sites (particularly sites P9 

and P11) than the upstream sites. River carpsucker and 

goldeye, which are large-bodied species, tended to be more 

common at the downstream sites than upstream sites. The 

longitudinal distribution might be related to changes in habitat, 

water quality, and streamflow in the downstream direction or 

by migration from the Yellowstone River (Hubert, 1993).

Introduced species of fish generally were rare in the 

main-stem Powder River. Northern plains killifish were the 

most common introduced fish species and were observed in 

small numbers at all sites except near Locate (site P18) where 

the number of sampling periods (1) was fewest. Green sunfish 

(n = 17) were found at three sites in Wyoming and two sites 

in Montana. Common carp (n = 39) were found at six sites in 

Wyoming and two sites in Montana. Smallmouth bass (n = 3) 

and rock bass (n = 1) were identified only in the Powder River 

below Clear Creek (site P11) where common carp and northern plains killifish also were noted.
Table 24. Fish community metric scores and Index of Biotic Integrity (IBI) scores for the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 

2005–06.—Continued[Metric definitions from Bramblett and others (2005). Shaded cells indicate main-stem sampling sites on the Tongue River; indv., individuals]

Site 

number 

(fig. 1)

Abbreviated site name Sample date

Species richness and composition scores Trophic composition scores Reproductive guild composition scores Fish abundance and composition scores

IBI score

Number of native 

species

Number of native 

families

- Number of native ca

tostomid and ictalurid 

species

Percentage of tolerant 

indv.

Percentage of invertivorous cyprinid indv.

Number of benthic 

invertivorous species

Percentage of lithoobligate reproductive 

guild indv.

Percentage of tolerant 

reproducetive guild 

indv.

Percentage of native 

indv.

- Number of native spe

cies with long-lived 

indv.

R1 upper Rosebud Creek 06/20/2005 0 0 0 10.0 0 0 0 10.0 0 0 20R2 Rosebud Creek at mouth 09/14/2005 4.6 6.7 4.4 2.8 .5 2.7 4.1 5.2 8.2 3.5 43

T1 Tongue River at Monarch 08/23/2005 5.9 7.5 8.1 8.0 0 8.0 3.1 7.4 2.5 8.3 59

08/23/2006 5.9 7.5 8.1 9.1 0 9.7 2.2 9.0 1.8 9.4 63

T2 Goose Creek 08/22/2005 6.1 7.6 7.2 9.2 .1 8.2 2.2 9.0 1.8 7.6 59

08/22/2006 5.0 7.6 6.2 8.1 .2 6.5 2.7 8.2 2.2 7.6 54

T3 upper Youngs Creek 06/15/2005 9.4 8.1 9.6 9.7 10.0 10.0 10.0 .3 10.0 10.0 87

06/28/2006 9.4 8.1 9.6 7.9 10.0 10.0 10.0 1.5 10.0 10.0 87

T4 Youngs Creek at mouth 06/14/2005 7.5 5.4 6.9 2.0 2.8 10.0 2.5 8.6 10.0 9.9 66

06/27/2006 9.1 7.2 8.0 3.6 1.5 10.0 1.7 6.3 10.0 9.9 67

T5 Tongue River below 

Youngs Creek

08/29/2005 5.0 6.6 6.4 6.4 1.2 7.6 3.3 7.3 2.1 6.4 5208/24/2006 5.0 6.6 6.4 7.8 2.6 7.6 3.9 6.1 1.7 6.4 54

T6 upper Squirrel Creek 06/16/2005 7.7 5.9 7.9 10.0 10.0 10.0 10.0 .0 10.0 9.9 81

06/29/2006 8.8 7.7 9.0 .6 1.4 9.5 1.4 9.9 10.0 8.9 67

T7 Squirrel Creek at mouth 06/13/2005 8.5 7.5 8.6 6.2 8.8 9.0 7.8 3.3 9.3 9.5 78T8 Prairie Dog Creek 08/26/2005 5.2 5.9 7.5 7.5 .1 6.8 8.4 3.3 6.9 7.8 59

08/25/2006 6.8 7.7 8.6 7.6 8.3 10.0 10.0 1.2 8.6 8.9 78

T9 Tongue River at State 

line

08/25/2005 6.1 6.6 6.4 6.5 1.2 5.9 3.8 6.1 2.7 6.4 5208/28/2006 6.1 6.6 7.5 8.0 2.4 7.6 5.0 5.7 2.7 5.4 57

Ecological Assessment 97
Table 24. Fish community metric scores and Index of Biotic Integrity (IBI) scores for the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 

2005–06.—Continued[Metric definitions from Bramblett and others (2005). Shaded cells indicate main-stem sampling sites on the Tongue River; indv., individuals]

Site 

number 

(fig. 1)

Abbreviated site name Sample date

Species richness and composition scores Trophic composition scores Reproductive guild composition scores Fish abundance and composition scores

IBI score

Number of native 

species

Number of native 

families

- Number of native ca

tostomid and ictalurid 

species

Percentage of tolerant 

indv.

Percentage of invertivorous cyprinid indv.

Number of benthic 

invertivorous species

Percentage of lithoobligate reproductive 

guild indv.

Percentage of tolerant 

reproducetive guild 

indv.

Percentage of native 

indv.

- Number of native spe

cies with long-lived 

indv.

T10 Tongue River above 

Hanging Woman Creek

08/30/2005 4.0 6.3 7.0 7.9 0 3.6 3.5 6.9 3.4 6.9 4908/29/2006 4.5 6.3 7.0 7.1 0 5.3 5.1 5.6 4.5 7.9 53

T11 upper Hanging Woman 

Creek

06/22/2005 4.7 5.9 5.5 0 0 5.3 .4 .0 .9 6.0 2906/27/2006 4.7 4.1 4.4 1.4 0 5.3 0 1.6 3.3 4.9 30

T12 middle Hanging Woman 

Creek

06/21/2005 3.4 2.1 4.2 0 0 5.0 0 0 0 4.7 11006/26/2006 4.6 5.8 5.2 0 0 5.0 .9 2.9 3.3 4.7 33

T13 Hanging Woman Creek 

at mouth

06/23/2005 4.8 7.5 6.0 0 0 4.6 .8 8.9 8.4 5.3 4606/26/2006 3.7 3.8 3.8 0 0 4.6 0 10.0 10.0 4.3 40

T14 Tongue River at Birney 

Day School

08/31/2005 4.2 6.1 6.6 6.8 .1 4.8 5.2 5.2 4.9 6.4 5008/30/2006 4.8 6.1 7.6 7.1 .4 6.5 4.6 6.0 4.9 8.5 56

T15 upper Otter Creek 06/29/2005 6.6 6.7 7.0 7.4 5.2 7.1 3.0 0 10.0 6.7 60

07/12/2006 6.0 4.9 5.9 10.0 10.0 7.1 0 0 10.0 6.7 110

T16 middle Otter Creek 06/28/2005 5.4 6.3 6.2 7.4 0 6.2 10.0 0 10.0 5.8 110T17 Otter Creek at mouth 06/30/2005 4.8 5.3 4.2 2.0 0 3.8 .4 7.8 9.4 3.6 41

06/28/2006 3.7 3.5 3.2 0 0 3.8 .5 9.6 8.8 4.6 38

T18 Tongue River below 

Brandenberg Bridge

09/01/2005 5.3 5.8 7.0 7.0 5.7 5.7 5.1 .8 8.5 6.7 5808/31/2006 5.9 5.8 7.0 6.9 1.9 5.7 8.5 1.0 8.9 7.7 59

98 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 24. Fish community metric scores and Index of Biotic Integrity (IBI) scores for the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 

2005–06.—Continued[Metric definitions from Bramblett and others (2005). Shaded cells indicate main-stem sampling sites on the Tongue River; indv., individuals]

Site 

number 

(fig. 1)

Abbreviated site name Sample date

Species richness and composition scores Trophic composition scores Reproductive guild composition scores Fish abundance and composition scores

IBI score

Number of native 

species

Number of native 

families

- Number of native ca

tostomid and ictalurid 

species

Percentage of tolerant 

indv.

Percentage of invertivorous cyprinid indv.

Number of benthic 

invertivorous species

Percentage of lithoobligate reproductive 

guild indv.

Percentage of tolerant 

reproducetive guild 

indv.

Percentage of native 

indv.

- Number of native spe

cies with long-lived 

indv.

T19 Pumpkin Creek 06/24/2005 5.9 9.0 5.3 8.2 0.3 3.8 9.7 2.0 10.0 7.7 62

P6 Crazy Woman Creek 

below I-90

07/14/2005 4.3 5.3 3.2 10.0 2.5 3.9 9.8 0 10.0 6.7 5607/31/2006 7.6 9.0 8.6 2.8 .1 7.3 5.9 .6 5.0 8.7 56

P7 Crazy Woman Creek 

near mouth

07/14/2005 5.0 7.0 4.9 8.5 3.2 5.0 9.9 0 10.0 7.2 6108/01/2006 6.1 7.0 6.0 6.5 1.5 5.0 10.0 .4 9.9 8.2 61

P10 Clear Creek 08/24/2005 7.6 10.0 7.9 8.0 .3 4.7 6.2 4.4 6.2 10.0 65

08/21/2006 7.6 10.0 6.8 9.4 3.5 6.4 6.2 2.4 7.7 10.0 70

P14 Little Powder River at 

Highway 59

06/23/2005 8.1 6.5 9.0 0 0 10.0 0 10.0 10.0 10.0 6406/22/2006 8.7 8.3 10.0 6.7 9.5 10.0 9.3 0 7.7 10.0 80

P15 Little Powder River 

above Dry Creek

06/23/2005 5.2 6.7 4.5 4.5 .4 2.8 6.2 3.7 8.0 3.6 4506/23/2006 6.3 6.7 5.5 9.3 .5 4.5 10.0 .3 9.5 6.7 59

P16 Little Powder River at 

Biddle

06/27/2005 5.5 6.5 6.3 7.6 .1 4.1 9.7 2.0 9.7 5.3 57

C1 Porcupine Creek 06/20/2005 6.0 5.2 6.6 0 0 7.9 0 10.0 10.0 7.4 53

06/22/2006 6.0 5.2 6.6 0 0 7.9 0 10.0 10.0 7.4 53

C2 Antelope Creek 06/20/2005 2.7 3.2 2.7 2.3 0 3.2 0 1.3 1.2 3.0 20

06/20/2006 2.7 3.2 3.8 3.2 0 3.2 0 .1 0 3.0 19

C3 Cheyenne River near 

Dull Center

06/22/2005 3.2 4.7 4.1 1.0 0 2.4 3.9 .3 3.4 3.2 2606/19/2006 1.6 1.0 2.0 4.0 0 2.4 0 0 0 2.2 13

Ecological Assessment 99
Table 24. Fish community metric scores and Index of Biotic Integrity (IBI) scores for the Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, Wyoming and Montana, 

2005–06.—Continued[Metric definitions from Bramblett and others (2005). Shaded cells indicate main-stem sampling sites on the Tongue River; indv., individuals]

Site 

number 

(fig. 1)

Abbreviated site name Sample date

Species richness and composition scores Trophic composition scores Reproductive guild composition scores Fish abundance and composition scores

IBI score

Number of native 

species

Number of native 

families

- Number of native ca

tostomid and ictalurid 

species

Percentage of tolerant 

indv.

Percentage of invertivorous cyprinid indv.

Number of benthic 

invertivorous species

Percentage of lithoobligate reproductive 

guild indv.

Percentage of tolerant 

reproducetive guild 

indv.

Percentage of native 

indv.

- Number of native spe

cies with long-lived 

indv.

C4 Little Thunder Creek 06/22/2005 5.7 6.2 5.9 0.9 0 5.9 2.5 6.7 6.1 7.5 47

06/21/2006 5.7 6.2 5.9 1.7 0 5.9 2.7 7.5 8.4 6.5 51

C5 Black Thunder Creek 06/21/2005 3.5 3.7 3.6 0 0 4.3 0 8.5 5.0 4.1 110C6 Cheyenne River at 

Spencer

06/21/2005 2.7 3.7 2.2 2.7 0 .1 3.2 1.7 4.2 2.1 2306/20/2006 2.2 3.7 1.1 1.2 0 .1 2.0 1.0 2.6 1.1 15

B1 Belle Fourche River 06/24/2005 4.2 3.7 3.7 7.3 0 4.5 9.0 2.9 10.0 4.2 50

06/21/2006 4.2 3.7 3.7 0 0 4.5 .1 8.1 7.3 5.2 37

B2 Caballo Creek 06/23/2005 5.0 4.3 4.7 8.2 0 5.7 10.0 1.6 9.7 6.3 55

1An IBI score of 10 was assigned because less than 10 fish were present in sample.

100 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 25. Fish abundance in samples from the main-stem Powder River, Wyoming and Montana, 2004–06.—Continued

[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

Number of fish

Black bullhead

Channel catfish

Common carp

Creek chub

Fathead minnow

Flathead chub

Goldeye

Green sunfish

Hybognathus spp.1

P1 Powder River above 

Salt Creek

06/07/04 0 0 0 1 14 717 0 0 38

07/08/04 0 0 0 1 3 466 0 0 48

08/10/04 0 0 0 0 0 460 0 0 22

09/09/04 0 0 0 0 13 403 0 0 18

10/13/04 0 0 0 0 7 214 0 0 4

05/07/05 0 0 0 0 21 72 0 0 2

07/20/05 0 3 0 20 2 402 1 0 0

08/12/05 1 1 0 0 0 139 0 0 7

07/24/06 0 0 0 0 47 427 0 0 0

P2 Powder River below 

Salt Creek

06/08/04 0 0 0 0 1 452 0 0 330

07/09/04 0 1 0 0 1 107 0 0 57

08/11/04 0 1 2 0 3 553 1 0 55

09/08/04 0 2 0 0 5 459 1 0 28

10/14/04 0 0 0 0 0 140 1 0 2

05/09/05 0 0 0 0 L 133 0 0 41

07/21/05 0 0 0 0 9 810 0 0 246

08/11/05 0 8 0 0 7 363 0 0 119

07/25/06 0 0 0 0 35 2,641 0 2 132

P3 Powder River above 

Pumpkin Creek

07/07/04 0 1 0 0 7 396 1 0 287

08/09/04 0 14 1 0 33 223 1 0 24

09/07/04 0 5 3 0 2 466 0 0 34

10/12/04 0 5 0 0 20 359 0 0 74

05/08/05 0 0 0 0 0 51 0 0 23

07/19/05 0 1 3 0 2 631 1 0 506

08/10/05 0 9 0 0 2 703 0 0 26

07/26/06 0 9 0 0 1 161 0 0 8

P4 Powder River below 

Burger Draw

05/03/05 0 3 1 0 0 135 0 0 49

07/22/05 0 73 4 0 5 172 0 0 838

08/19/05 0 46 1 0 2 272 3 0 174

07/27/06 0 10 0 0 13 1,079 1 0 259

Ecological Assessment 101
Table 25. Fish abundance in samples from the main-stem Powder River, Wyoming and Montana, 2004–06.—Continued

[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

Number of fish

Black bullhead

Channel catfish

Common carp

Creek chub

Fathead minnow

Flathead chub

Goldeye

Green sunfish

Hybognathus spp.1

P5 Powder River above 

Crazy Woman 

Creek

05/20/04 0 8 0 0 30 272 4 0 80

06/02/04 0 4 0 0 0 456 2 0 94

07/13/04 0 20 0 0 1 587 0 0 328

08/02/04 0 12 L 0 2 584 0 0 258

09/08/04 0 12 0 0 1 1,101 0 0 183

10/12/04 0 0 0 1 L 684 0 0 185

04/26/05 0 4 0 0 231 165 0 0 427

07/13/05 0 16 0 0 3 470 3 2 245

P5 Powder River above 

Crazy Woman 

Creek

08/24/05 0 12 0 0 2 412 0 0 207

07/28/06 0 61 0 0 3 2,384 0 0 96

P8 Powder River below 

Crazy Woman 

Creek

06/07/04 0 12 0 0 0 302 7 0 882

07/06/04 0 7 0 0 3 232 0 0 89

08/04/04 0 40 0 1 0 343 0 0 173

08/31/04 0 1 0 0 0 144 0 0 5

10/05/04 0 35 0 0 1 387 0 0 447

05/02/05 0 8 0 0 0 93 0 0 60

07/23/05 0 4 0 0 0 54 0 0 227

08/18/05 0 27 0 0 2 335 0 0 76

08/02/06 0 41 7 2 1 118 2 0 51

P9 Powder River above 

Clear Creek

06/09/04 0 5 1 0 0 156 3 0 91

07/07/04 0 12 0 0 0 108 0 0 4

08/05/04 0 24 0 L 0 78 0 0 8

08/31/04 0 28 0 4 3 355 0 1 10

10/04/04 0 12 0 0 5 100 0 0 467

05/04/05 0 10 0 0 0 209 0 0 0

07/24/05 0 131 0 0 9 21 0 0 9

08/17/05 0 191 0 0 8 67 0 0 6

08/04/06 0 166 4 0 2 324 1 1 80

102 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 25. Fish abundance in samples from the main-stem Powder River, Wyoming and Montana, 2004–06.—Continued

[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

Number of fish

Black bullhead

Channel catfish

Common carp

Creek chub

Fathead minnow

Flathead chub

Goldeye

Green sunfish

Hybognathus spp.1

P11 Powder River below 

Clear Creek

06/10/04 0 16 0 0 0 188 4 0 387

07/08/04 0 35 2 0 0 207 3 0 253

08/06/04 0 31 0 0 L 157 1 0 17

09/01/04 0 4 0 0 0 178 3 0 32

10/06/04 0 3 2 0 1 88 1 0 699

05/05/05 0 35 0 0 0 248 0 0 2

07/25/05 0 228 1 0 8 43 0 0 0

08/16/05 0 90 0 0 10 8 1 0 72

08/03/06 0 2 0 0 0 112 0 0 0

P12 Powder River at 

Moorhead

05/06/05 0 34 0 0 0 167 0 0 8

07/18/05 0 0 0 0 0 36 2 0 2

08/02/06 0 105 1 0 0 218 12 0 0

P13 Powder River at 

Broadus

07/19/05 0 2 0 0 0 13 0 0 4

08/02/06 0 8 0 0 0 416 0 4 0

P17 Powder River below 

Little Powder 

River

07/20/05 0 2 0 0 0 3 0 0 98

08/03/06 0 12 6 0 2 62 1 7 63

P18 Powder River near 

Locate

07/21/05 0 3 0 0 1 47 5 0 0

(2) South Fork Powder 

River

05/26/04 0 0 0 0 0 224 0 0 455

06/29/04 0 0 0 4 0 431 0 0 214

08/03/04 0 0 0 2 0 210 0 0 35

09/01/04 0 0 0 3 0 342 0 0 22

09/29/04 0 0 0 1 0 303 0 0 72

Ecological Assessment 103
Table 25. Fish abundance in samples from the main-stem Powder River, Wyoming and Montana, 2004–06.—Continued

[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) Sample date

Number of fish

Plains minnow1

Western silvery 

minnow1

Longnose dace

Mountain sucker

Northern plains 

killifish

River carpsucker

Rock bass

Sand shiner

Shorthead redhorse

Smallmouth bass

Stonecat

Sturgeon chub

White sucker

Species richness

P1 06/07/2004 38 0 0 L 85 0 0 378 0 0 0 0 4 8

07/08/2004 48 0 4 1 26 0 0 186 0 0 0 0 0 8

08/10/2004 22 0 141 103 116 0 0 235 1 0 0 0 1 8

09/09/2004 18 0 31 341 207 0 0 469 0 0 0 0 0 7

10/13/2004 4 0 29 33 125 0 0 315 0 0 0 0 0 7

05/07/2005 2 0 15 12 36 0 0 391 0 0 0 0 0 7

07/20/2005 0 0 15 L 20 106 0 1,216 0 0 1 0 L 13

08/12/2005 7 0 225 20 624 7 0 838 0 0 6 0 3 11

07/24/2006 0 0 628 14 142 4 0 5,078 0 0 3 0 5 9

Mean 8.7

P2 06/08/2004 0 0 0 0 70 0 0 552 0 0 0 0 3 6

07/09/2004 57 0 1 L 9 2 0 254 0 0 0 0 0 9

08/11/2004 0 0 104 80 139 3 0 1,065 0 0 0 0 1 11

09/08/2004 28 0 78 25 217 10 0 1,832 0 0 0 0 7 11

10/14/2004 2 0 24 11 38 0 0 141 0 0 0 0 1 8

05/09/2005 41 0 86 32 12 0 0 353 0 0 0 0 1 8

07/21/2005 246 0 142 16 23 7 0 1,612 0 0 0 0 3 9

08/11/2005 119 0 135 8 810 38 0 1,354 0 0 0 0 4 10

07/25/2006 0 0 472 13 123 10 0 5,020 0 0 0 0 2 10

Mean 9.1

P3 07/07/2004 287 0 5 2 21 2 0 827 0 0 0 0 0 10

08/09/2004 24 0 28 1 27 8 0 487 0 0 1 0 0 12

09/07/2004 30 4 42 1 238 2 0 433 0 0 1 0 1 13

10/12/2004 74 0 11 1 671 15 0 2,513 0 0 1 0 0 10

05/08/2005 23 0 36 0 3 0 0 82 0 0 0 0 0 5

07/19/2005 497 9 22 3 12 9 0 589 0 0 0 0 0 12

08/10/2005 26 0 17 0 80 70 0 847 0 0 1 0 1 10

07/26/2006 0 0 24 0 164 50 0 4,486 0 0 4 0 0 9

Mean 10.1

P4 05/03/2005 49 0 54 0 7 1 0 505 0 0 0 0 0 8

07/22/2005 0 0 102 0 83 31 0 1,471 0 0 0 0 0 9

08/19/2005 166 8 52 0 197 68 0 685 0 0 0 0 0 11

07/27/2006 0 0 70 0 43 46 0 3,789 0 0 2 0 0 10

Mean 9.5

104 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 25. Fish abundance in samples from the main-stem Powder River, Wyoming and Montana, 2004–06.—Continued

[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) Sample date

Number of fish

Plains minnow1

Western silvery 

minnow1

Longnose dace

Mountain sucker

Northern plains 

killifish

River carpsucker

Rock bass

Sand shiner

Shorthead redhorse

Smallmouth bass

Stonecat

Sturgeon chub

White sucker

Species richness

P5 05/20/2004 0 0 0 0 3 1 0 252 0 0 0 0 1 8

06/02/2004 0 0 3 0 4 2 0 1,019 1 0 0 0 0 9

07/13/2004 319 9 15 0 8 6 0 1,294 0 0 1 0 0 10

08/02/2004 258 0 16 0 35 14 0 1,381 0 0 3 0 0 10

09/08/2004 181 2 6 0 36 3 0 4,677 0 0 0 0 0 9

10/12/2004 185 0 7 0 96 5 0 2,638 0 0 0 0 0 8

04/26/2005 0 0 13 0 4 102 0 1,398 0 0 0 0 0 8

07/13/2005 245 0 2 0 4 136 0 1,668 1 0 0 0 0 11

08/24/2005 207 0 22 0 54 3 0 968 0 0 4 0 0 9

07/28/2006 0 0 17 0 20 75 0 3,104 0 0 0 2 0 9

Mean 9.1

P8 06/07/2004 662 221 1 0 4 21 0 1,361 0 0 0 0 0 10

07/06/2004 89 0 19 0 6 18 0 1,026 0 0 0 0 0 8

08/04/2004 173 0 33 0 0 2 0 933 1 0 12 0 0 9

08/31/2004 5 0 0 0 0 0 0 467 0 0 0 0 0 4

10/05/2004 447 0 28 0 16 5 0 2,596 0 0 4 0 0 9

05/02/2005 56 4 3 0 1 1 0 298 0 0 0 0 0 8

07/23/2005 0 0 7 0 0 11 0 498 0 0 3 1 0 8

08/18/2005 0 0 29 0 15 4 0 875 0 0 0 0 0 8

08/02/2006 0 0 14 0 3 182 0 1,903 3 0 0 0 0 12

Mean 8.4

P9 06/09/2004 90 1 0 0 0 5 0 587 0 0 0 0 0 8

07/07/2004 4 0 2 0 0 5 0 760 0 0 1 0 0 7

08/05/2004 8 0 1 0 1 2 0 446 0 0 2 0 0 9

08/31/2004 8 2 3 0 0 13 0 1,181 2 0 0 0 2 12

10/04/2004 467 0 1 0 23 0 0 1,497 0 0 0 0 0 7

05/04/2005 0 0 2 0 0 1 0 330 0 0 0 0 0 5

07/24/2005 0 0 0 0 0 4 0 370 0 0 0 0 0 6

08/17/2005 6 0 2 0 0 44 0 475 0 0 0 0 0 7

08/04/2006 0 0 0 0 0 25 0 794 0 0 0 0 0 9

Mean 7.8

Ecological Assessment 105
Table 25. Fish abundance in samples from the main-stem Powder River, Wyoming and Montana, 2004–06.—Continued

[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) Sample date

Number of fish

Plains minnow1

Western silvery 

minnow1

Longnose dace

Mountain sucker

Northern plains 

killifish

River carpsucker

Rock bass

Sand shiner

Shorthead redhorse

Smallmouth bass

Stonecat

Sturgeon chub

White sucker

Species richness

P11 06/10/2004 387 0 0 0 0 29 0 317 19 0 6 0 0 8

07/08/2004 253 0 0 0 0 7 0 687 0 0 33 0 0 8

08/06/2004 17 0 2 0 0 3 0 687 0 1 7 0 0 10

09/01/2004 32 0 0 0 6 1 0 1,465 0 0 1 0 0 8

10/06/2004 698 1 4 0 7 2 0 2,222 0 0 1 0 0 12

05/05/2005 0 0 3 0 2 5 0 472 0 0 17 0 0 8

07/25/2005 0 0 0 0 0 25 0 404 0 1 17 0 L 10

08/16/2005 0 0 0 0 L 257 1 311 0 1 1 0 0 11

08/03/2006 0 0 4 0 0 3 0 289 0 0 3 0 0 6

Mean 9.0

P12 05/06/2005 8 0 3 0 1 6 0 18 0 0 9 0 0 8

07/18/2005 1 1 11 0 0 0 0 14 0 0 0 0 0 6

08/02/2006 0 0 6 0 0 116 0 283 2 0 1 4 0 10

Mean 8.0

P13 07/19/2005 4 0 246 0 6 0 0 39 0 0 0 1 0 7

08/02/2006 0 0 55 0 28 43 0 559 0 0 0 0 0 7

Mean 7.0

P17 07/20/2005 0 98 0 0 2 4 0 170 0 0 0 2 0 7

08/03/2006 0 63 0 0 55 369 0 477 0 0 0 18 0 11

Mean 9.0

P18 07/21/2005 0 0 0 0 0 1 0 8 0 0 0 3 0 7

Mean 7.0

(

2

) 05/26/2004 0 0 13 0 3 0 0 35 0 0 0 0 0 5

06/29/2004 0 0 10 0 52 0 0 67 0 0 0 0 1 7

08/03/2004 0 0 17 0 214 0 0 115 0 0 0 0 0 6

09/01/2004 0 0 14 0 501 0 0 199 0 0 0 0 1 7

09/29/2004 0 0 3 0 413 0 0 86 0 0 0 0 0 6

Mean 6.2

1

Hybognathus spp. represents genus-level onsite identifications. Subsamples of Hybognathus spp. were retained from selected samples for laboratory identification and are subdivided by species, either plains minnow or western silvery minnow.

2

Miscellaneous site sampled by Wyoming Game and Fish Department (2004).

106 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Figure 34. Relative abundance of fish taxa in samples from the 

main-stem Powder River, Wyoming and Montana, 2004–06.

Sand shiner

61 percent Flathead chub

21 percent

Other

1 percent

Channel catfish

1 percent

River carpsucker

2 percent

Longnose dace

2 percent

Northern plains 

killifish

4 percent

Hybognathus spp.

8 percent

Ecological Assessment 107

Laboratory identification of adult Hybognathus spp. 

samples from main-stem sites in Wyoming indicated 

98.8 percent were plains minnow (n = 1,457), 1.2 percent were 

western silvery minnow (n = 17), and a single Hybognathus 

spp. specimen collected at site P5 was identified meristically 

(by relating body parts) as a plains minnow X western silvery 

minnow hybrid. No Hybognathus spp. specimens collected 

in the main-stem Powder River in Wyoming were identified as brassy minnow. Plains minnow were common at all 

Wyoming sites, but western silvery minnow were not collected 

at the two sites farthest upstream, sites P1 and P2. Occurrences of western silvery minnow were sporadic among the 

other six Wyoming sites (sites P3–P11). Counts of western 

silvery minnow from Wyoming sites were less than 10 fish per 

sample, except for 221 western silvery minnow collected in 

June 2004 from site P8 below Crazy Woman Creek (table 25). 

Occurrences of western silvery minnow were unique to the 

main-stem Powder River; the species was not identified at any 

of the sites on the Tongue, Cheyenne, Belle Fourche Rivers or 

tributaries. 

Laboratory identification of Hybognathus spp. (n = 175) 

from main-stem Powder River sites in Montana indicated 

43 percent plains minnow and 57 percent western silvery 

minnow. Occurrences of both species were relatively 

infrequent at the four Montana sites but were most common 

at the Powder River below Little Powder River (site P17; 

table 25). 

Sturgeon chub were collected infrequently from the 

main-stem Powder River but were most common in Montana. 

Sturgeon chub were collected in one sample each from two 

sites in Wyoming, sites P5 and P8. The largest numbers of 

sturgeon chub were observed in the Powder River below Little 

Powder River (site P17), but sturgeon chub also were identified from sites P12, P13, and P18 on the main-stem Powder 

River in Montana. Similar to the distribution of the western 

silvery minnow, sturgeon chub were collected only from the 

main-stem Powder River and not from other drainages in the 

PRB. 

Identification of larval fish (n = 6,846) at the Larval 

Fish Laboratory, Fort Collins, Colo., showed that age-0 fish 

in the main-stem Powder River were primarily sand shiner 

(60 percent), plains minnow (17 percent), and flathead chub 

(17 percent). The remainder of species collectively accounted 

for 6 percent of the larval fish identified and less than 

2 percent individually. Identification of larval fish at the laboratory also included four relatively uncommon species (mountain sucker, white sucker, fathead minnow, and creek chub) 

and one dominant species (northern plains killifish) during 

nine sampling periods (table 31 in Appendix 2). However, 

these occurrences did not add to the overall list of species 

observed at those sites at older age classes. Only in the case 

of common carp at the P5 site and white sucker at the P11 site 

did the identification of larval fish detect additional species 

that were not identified onsite at the time of sampling. 

Temporal Distribution of Fish

Changes in species composition were notable among data 

collected monthly from May through October 2004 at sites 

on the main-stem Powder River in Wyoming (fig. 37). It was 

notable that the total sample size was substantially smaller in 

May (n = 1,381) than in all other months (n = 9,833–17,678) 

although sampling effort was approximately equal among 

months. The percentage of sand shiner in the total monthly 

catch increased from 21 percent in May to 70 percent in 

October. Conversely, the percentages of flathead chub and 

Hybognathus spp. decreased from 36 and 39 percent, respectively, in May to 12 and 11 percent, respectively, in October. 

These trends may be explained in part by the growth of 

age-0 sand shiner to a size large enough to be captured by 

seining in late summer and early fall. The largest percentage 

of fathead minnow (2.2 percent) was observed in May, and 

fathead minnow were observed less frequently during all other 

months. Northern plains killifish were a smaller percentage 

of the total catch during May through June (0.4–2.3 percent) 

than during August through September (4.4–11 percent). The 

largest percentages of longnose dace were observed during 

August (2.9 percent) and September (1.2 percent). Mountain 

suckers were not observed during May and June but were a 

noteworthy percentage of the September sample (2.4 percent). 

The largest percentage of channel catfish was observed 
Figure 35. Rarefaction curves relating species richness to fish community samples for sampling sites on the main-stem Powder 

River, Wyoming and Montana, and the South Fork of the Powder River, Wyoming, 2004–06.

0 200 400 600 800 1,000 1,200 1,400

3

4

5

6

7

8

9

10

11

12

SAMPLE SIZE (INDIVIDUALS)

SPECIES RICHNESS

South Fork Powder River (miscellaneous site)

P12

P11

P1

P9

P17

P3

P8

P2

P4

P5

P13

P18

108 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
0

20

40

60

0

20

40

60

0

20

40

60

0

20

40

60

0

20

40

60

0

20

40

60

PERCENTAGE OF TOTAL CATCH

SITE

P1 P2 P3 P4 P5 P8 P9 P11

White sucker

Mountain sucker

Sand shiner

Northern plains 

 killifish

Hybognathus spp.

Longnose dace

Channel catfish

Stonecat

River carpsucker

Goldeye

Fathead minnow

Flathead chub

Figure 36. Longitudinal distribution of selected fish species in the main-stem Powder River, Wyoming, 2004–06.

Ecological Assessment 109
110 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

in August (1.3 percent). Species such as river carpsucker, 

stonecat, goldeye, shorthead redhorse, white sucker, creek 

chub, common carp, green sunfish, and smallmouth bass were 

collected but never accounted for more than 1 percent of a 

total monthly sample. 

Temporal changes in species composition during pre-high 

(May), post-high (June/July), and low streamflow conditions 

(August/September) in 2005 also were examined using data 

from all sites in Wyoming and one site in Montana (site P12). 

It was notable that the total sample size during pre-high 

streamflow (n = 6,547) was substantially less than the samples 

sizes during post-high (n = 14,563) and low-flow conditions 

(n = 51,410), although the sampling effort was approximately 

equal during the three sampling periods. Sand shiners consistently dominated samples and accounted for 55–64 percent of 

the total catch (fig. 38). The percentage of flathead chub in the 

total catch also was consistently large among three flow conditions (19–20 percent). Northern plains killifish accounted for 

a slightly smaller percentage of the total catch during pre-high 

(1.0 percent) and post-high flow (1.0 percent) than during lowflow conditions (4.7 percent). The percentages of longnose 

dace (3.3–3.8 percent) and river carpsucker (1.8–2.8 percent) 

were similar among different flow conditions. Substantially 

larger percentages of Hybognathus spp. were collected during 

pre-high (9.3 percent) and post-high (15 percent) flow than 

during low-flow (2.6 percent) conditions. Fathead minnows 

accounted for a notable percentage of the catch (3.8 percent) 

only during pre-high streamflow sampling. The largest 

percentage of channel catfish (3.2 percent) was collected 

during post-high streamflow. Species such as mountain sucker, 

stonecat, goldeye, sturgeon chub, common carp, creek chub, 

white sucker, green sunfish, and shorthead redhorse also were 

observed less frequently than the aforementioned species 

during all flow periods with percentages of species composition less than 1 percent. Mountain sucker and stonecat were 

present during all flow periods; however, goldeye, sturgeon 

chub, creek chub, green sunfish, and shorthead redhorse only 

were collected during the post-high and low-flow periods. 

Fish Distribution by Habitat Type

Associations among fish species and habitat types were 

explored by plotting the mean number of observations (occurrences) per habitat type for each species during individual 

surveys (fig. 39). This facilitated the calculation of confidence 

intervals needed to infer potential differences in distribution 

of fishes among available habitat types that were sampled. 

Data points from all sampling periods were aggregated. The 

percentages of channel catfish and goldeye observations from 

pools were larger than all other habitat types. Goldeye (n = 63) 

were never sampled from riffles, backwater, or shoals. Stonecats and mountain sucker were collected in larger percentages 

in pools, runs, and riffles than in backwater and shoals. River 

carpsucker occurred more often in pool, run, and backwater 

habitats than in either riffle or shoal habitats. Although the 

overall abundance of white sucker was relatively low (n = 41), 

the percentages of white sucker found in pools and runs were 

larger than in riffles, backwater, and shoals. The percentages 

of Hybognathus spp. observed in pools and runs were significantly larger than that observed for other habitat types. The 

percentage of longnose dace observations was larger in riffles 

than in other habitats, but a substantial percentage of longnose 

dace also occurred in pools and runs. Flathead chub, sand 

shiner, and fathead minnow were most commonly observed in 

pools and runs, whereas northern plains killifish preferred runs 

and backwater. 

Fish Community Structure

The Index of Biotic Integrity (IBI) developed for small 

plains streams of eastern Montana by Bramblett and others 

(2005) was applied to the fish community data from the 

main-stem Powder River, using the same metrics and caveats 

applied to data from the Tongue, Cheyenne, and Belle Fourche 

Rivers and tributaries. IBI scores for fish communities in the 

main-stem Powder River ranged from 38 to 64 (table 26). 

The mean IBI score for all of the sampling sites and dates 

during 2004–06 was 50. Individual mean IBI scores by site 

(table 26) were lowest below the Little Powder River (site P17, 

mean = 43) and highest above Pumpkin Creek (site P3, 

mean = 53). The IBI scores at site P17 and other sites on the 

main-stem of the Powder River in Montana might be biased 

(low) because the drainage area adjustment built into some of 

the metrics by Bramblett and others (2005) has not been thoroughly tested for drainage areas as large as the lower Powder 

River. 

The IBI scores for main-stem sites in Wyoming during 

2005–06 were tested for differences between years and 

between sites. The 2005-06 data were selected as an appropriate subset because of consistency in sampling methods 

and to facilitate comparisons among a variety of data types, 

although three fish surveys were conducted at each site in 

2005 compared to just one survey per site in 2006. The IBI 

subset appeared normally distributed, which was verified by 

the Shapiro-Wilk normality test (P > 0.05). An ANOVA with 

IBI value as the dependent variable, the site as the independent 

variable, and year as a covariate was applied to the subset of 

IBI values. Year was not significant as a covariate (P > 0.05) 

and was removed. A second ANOVA revealed no statistical 

differences (P > 0.05) in IBI values among Wyoming sites 

during 2005–06. Bartlett’s test showed that variances were 

equal (P > 0.05) for the second test. 

The drainage areas for the seven sites on the main-stem 

Powder River below Crazy Woman Creek (including and 

downstream from site P8) exceeded the largest drainage areas 

used by Bramblett and others (2005) in the development of 

the IBI. Mean IBI scores for those seven downstream sites 

were less than or equal to 50, whereas mean scores from the 

five upstream most sites (P1–P5) were slightly higher than 

50 (table 26). The IBI values for the main-stem Powder River 

reported herein should be interpreted cautiously within the 

context of drainage-size effects on species richness that may 
Figure 37. Fish species composition in monthly (May–October) samples at eight sampling sites on the main-stem Powder River, 

Wyoming, 2004.

2.2

4.4

Channel catfish

Fathead minnow

59 58

61

70

12

11

46

21

5.7

5.0

2.9

1.3

1.5

1.1

26

1.6

0

10

20

30

40

50

60

70

80

90

100

MAY JUNE JULY AUG. SEPT. OCT.

MONTH OF 2004

PERCENTAGE OF TOTAL CATCH

Other

Longnose dace

Northern plains killifish

Mountain sucker

Flathead chub

Sand shiner

Hybognathus spp.

2.6

11

2.4

1.2

0.5

22

12

3.4

25

2.3

1.9

22

29

39

36

2.4

EXPLANATION

Ecological Assessment 111
Figure 38. Species composition of fish community during pre-high flow, post-high flow, and low-flow conditions for eight sampling 

sites on the main-stem Powder River in Wyoming and one sampling site in Montana, 2005.

1.0

19

1.0

19

3.3

9.3

1.8

59

55

64

0

10

20

30

40

50

60

70

80

90

100

PRE-HIGH STREAMFLOW POST-HIGH STREAMFLOW

2005 STREAMFLOW PERIOD

LOW STREAMFLOW

Fathead minnow

Channel catfish

Other Northern plains killifish

Longnose dace

River carpsucker Flathead chub

Sand shiner

Hybognathus

EXPLANATION

PERCENTAGE OF TOTAL CATCH

3.5

4.7

20

2.8

1.6

2.6

0.6

15

2.3

3.8

3.2

0.9

3.8

1.4

1.1

112 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
0

20

40

60

80

100

POOL RUN RIFFLE BACKWATER SHOAL

0

20

40

60

80

100

0

20

40

60

80

100

MEAN PERCENTAGE OF OBSERVATIONS

0

20

40

60

80

100

0

20

40

60

80

100

0

20

40

60

80

100

HABITAT TYPE

Hybognathus

White sucker

Stonecat

Sand shiner

River carpsucker

Northern plains killifish

Mountain sucker

Longnose dace

Fathead minnow

Goldeye

Flathead chub

Channel catfish

POOL RUN RIFFLE BACKWATER SHOAL

95-percent confidence interval Mean

EXPLANATION







Figure 39. Mean percentage of fish observations per sampling period within connected aquatic habitat types for eight sampling sites 

on the main-stem Powder River in Wyoming and one sampling site in Montana, 2004–06.

Ecological Assessment 113
Table 26. Fish community metric scores and Index of Biotic Integrity (IBI) scores for the main-stem Powder River, Wyoming and Montana, 2005–06.—Continued

[Metric definitions from Bramblett and others (2005). SD, standard deviation; indv., individuals; NA, not applicable]

Site 

number 

(fig. 1)

Abbreviated site 

name

Sample 

date

Species richness and composition scores Trophic composition scores Reproductive guild composition scores Fish abundance and composition scores

IBI 

score

Mean 

IBI score 

for site 

(SD)

Number of native 

species

Number of native 

families

Number of native 

catostomid and 

ictalurid species

- Percentage of toler

ant indv.

Percentage of invertivorous cyprinid 

indv.

Number of 

- benthic invertivo

rous species

Percentage of litho-

- obligate reproduc

tive guild indv.

Percentage of 

tolerant reproductive 

guild indv.

Percentage of 

native indv.

Number of native 

species with 

long-lived indv.

P1 Powder River above 

Salt Creek

06/07/2004 5.0 4.4 3.5 9.1 8.0 1.7 3.7 0.1 9.3 2.6 4707/08/2004 5.0 4.4 2.4 9.6 8.8 3.4 3.1 0 9.7 5.6 5208/10/2004 5.0 4.4 4.6 8.9 7.7 5.1 4.2 0 8.9 7.7 5609/09/2004 4.4 4.4 2.4 8.4 4.0 3.4 4.1 .1 8.6 2.6 4210/13/2004 4.4 4.4 2.4 8.1 4.6 3.4 5.7 .1 8.3 4.6 4605/07/2005 4.4 4.4 2.4 8.9 2.2 3.4 8.9 .4 9.3 1.5 4607/20/2005 7.7 8.1 6.8 9.9 3.4 3.4 9.2 0 9.9 5.6 6408/12/2005 6.1 6.2 6.8 6.4 2.7 3.4 7.0 0 6.7 6.7 5207/24/2006 5.5 6.2 5.7 9.7 2.3 3.4 10.0 .1 9.8 5.6 58 52 (7.0)

P2 Powder River below 

Salt Creek

06/08/2004 2.9 4.1 2.0 9.4 4.4 1.1 4.8 0 9.5 2.0 4007/09/2004 5.1 6.0 4.1 9.8 3.4 2.8 7.2 .1 9.8 4.1 5208/11/2004 6.2 7.8 5.2 9.2 4.5 2.8 7.1 0 9.3 9.2 6109/08/2004 6.2 7.8 5.2 9.1 2.8 2.8 8.7 0 9.2 9.2 6110/14/2004 4.5 6.0 3.0 8.8 6.3 2.8 5.6 0 8.9 4.1 5005/09/2005 4.5 4.1 3.0 9.8 4.6 2.8 8.1 0 9.8 4.1 5107/21/2005 5.1 4.1 4.1 9.9 4.6 2.8 7.4 0 9.9 6.1 5408/11/2005 5.7 6.0 5.2 6.9 2.4 2.8 6.5 .1 7.2 5.1 4807/25/2006 4.5 4.1 4.1 9.8 5.1 2.8 7.9 0 9.9 6.1 54 52 (6.5)

114 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 26. Fish community metric scores and Index of Biotic Integrity (IBI) scores for the main-stem Powder River, Wyoming and Montana, 2005–06.—Continued

[Metric definitions from Bramblett and others (2005). SD, standard deviation; indv., individuals; NA, not applicable]

Site 

number 

(fig. 1)

Abbreviated site 

name

Sample 

date

Species richness and composition scores Trophic composition scores Reproductive guild composition scores Fish abundance and composition scores

IBI 

score

Mean 

IBI score 

for site 

(SD)

Number of native 

species

Number of native 

families

Number of native 

catostomid and 

ictalurid species

- Percentage of toler

ant indv.

Percentage of invertivorous cyprinid 

indv.

Number of 

- benthic invertivo

rous species

Percentage of litho-- obligate reproduc

tive guild indv.

Percentage of 

tolerant reproductive 

guild indv.

Percentage of 

native indv.

Number of native 

species with 

long-lived indv.

P3 Powder River above 

Pumpkin Creek

07/07/2004 5.4 7.7 3.8 9.8 3.6 2.4 6.5 .1 9.9 2.7 5208/09/2004 6.5 7.7 4.9 9.2 4.1 2.4 7.5 .6 9.7 4.7 5709/07/2004 7.0 5.8 6.0 7.9 5.7 2.4 4.7 .1 8.0 5.8 5310/12/2004 5.4 5.8 4.9 8.0 1.4 2.4 8.3 .1 8.2 4.7 4905/08/2005 2.6 5.8 .6 9.8 6.1 2.4 7.3 0 9.9 2.7 4707/19/2005 6.5 7.7 3.8 9.9 5.0 2.4 4.2 0 9.9 7.8 5708/10/2005 5.4 5.8 4.9 9.5 5.6 2.4 6.4 .1 9.5 4.7 5407/26/2006 4.3 5.8 3.8 9.6 .5 2.4 10.0 .0 9.7 5.8 52 53 (3.6)

P4 Powder River below 

Burger Draw

05/03/2005 4.1 5.7 2.5 9.9 3.4 2.2 8.9 .0 9.9 3.5 5007/22/2005 4.1 5.7 2.5 9.6 1.4 2.2 7.0 .3 9.7 4.5 4708/19/2005 5.8 7.6 2.5 8.6 3.0 2.2 6.5 .4 8.7 6.6 5207/27/2006 4.7 7.6 3.6 9.9 3.0 2.2 8.9 .0 9.9 7.6 57 52 (4.3)

Implications 115
Table 26. Fish community metric scores and Index of Biotic Integrity (IBI) scores for the main-stem Powder River, Wyoming and Montana, 2005–06.—Continued

[Metric definitions from Bramblett and others (2005). SD, standard deviation; indv., individuals; NA, not applicable]

Site 

number 

(fig. 1)

Abbreviated site 

name

Sample 

date

Species richness and composition scores Trophic composition scores Reproductive guild composition scores Fish abundance and composition scores

IBI 

score

Mean 

IBI score 

for site 

(SD)

Number of native 

species

Number of native 

families

Number of native 

catostomid and 

ictalurid species

- Percentage of toler

ant indv.

Percentage of invertivorous cyprinid 

indv.

Number of 

- benthic invertivo

rous species

Percentage of litho-

- obligate reproduc

tive guild indv.

Percentage of 

tolerant reproductive 

guild indv.

Percentage of 

native indv.

Number of native 

species with 

long-lived indv.

P5 Powder River above 

Crazy Woman Creek

05/20/2004 3.9 7.5 3.4 9.4 5.7 .2 4.8 .7 10.0 3.3 4906/02/2004 3.9 7.5 3.4 10.0 4.0 3.6 7.8 0 10.0 5.3 5607/13/2004 5.1 5.6 3.4 10.0 3.7 1.9 7.0 .1 10.0 3.3 5008/02/2004 5.1 5.6 3.4 9.8 3.6 1.9 7.4 .1 9.9 4.3 5109/08/2004 4.5 5.6 2.3 9.9 2.5 1.9 9.4 0 9.9 4.3 5110/12/2004 3.9 5.6 1.3 9.7 2.6 1.9 8.8 0 9.7 5.3 4904/26/2005 3.4 5.6 2.3 8.9 1.0 1.9 7.8 1.1 10.0 5.3 4807/13/2005 5.1 7.5 3.4 10.0 2.5 3.6 8.6 .1 10.0 5.3 5608/24/2005 4.5 5.6 3.4 9.6 3.5 1.9 7.1 .1 9.7 5.3 5107/28/2006 3.9 5.6 2.3 10.0 5.7 3.6 6.7 .1 10.0 5.3 53 51 (2.8)

P8 Powder River below 

Crazy Woman Creek

06/07/2004 4.2 7.3 2.0 10.0 1.6 1.6 6.5 .1 10.0 1.9 4507/06/2004 3.7 5.5 2.0 9.9 2.5 1.6 9.2 .1 10.0 0 4408/04/2004 4.8 5.5 4.2 10.0 3.4 3.3 7.7 .3 10.0 6.0 5508/31/2004 2.0 3.6 1.0 10.0 3.2 0 9.1 0 10.0 0 3910/05/2004 4.2 5.5 3.1 9.9 1.6 1.6 9.0 .1 10.0 0 4505/02/2005 3.7 5.5 2.0 10.0 2.8 1.6 7.9 .2 10.0 .9 4407/23/2005 3.7 5.5 3.1 10.0 1.1 3.3 7.8 .1 10.0 5.0 4908/18/2005 3.7 5.5 2.0 9.9 3.7 1.6 8.0 .2 9.9 4.0 4808/02/2006 5.4 7.3 3.1 9.9 .8 3.3 10.0 .2 10.0 5.0 55 47 (5.3)

116 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Table 26. Fish community metric scores and Index of Biotic Integrity (IBI) scores for the main-stem Powder River, Wyoming and Montana, 2005–06.—Continued

[Metric definitions from Bramblett and others (2005). SD, standard deviation; indv., individuals; NA, not applicable]

Site 

number 

(fig. 1)

Abbreviated site 

name

Sample 

date

Species richness and composition scores Trophic composition scores Reproductive guild composition scores Fish abundance and composition scores

IBI 

score

Mean 

IBI score 

for site 

(SD)

Number of native 

species

Number of native 

families

Number of native 

catostomid and 

ictalurid species

- Percentage of toler

ant indv.

Percentage of invertivorous cyprinid 

indv.

Number of 

- benthic invertivo

rous species

Percentage of litho-- obligate reproduc

tive guild indv.

Percentage of 

tolerant reproductive 

guild indv.

Percentage of 

native indv.

Number of native 

species with 

long-lived indv.

P9 Powder River above 

Clear Creek

06/09/2004 4.1 7.2 1.9 10.0 2.5 .0 8.5 .1 10.0 4.8 4907/07/2004 3.5 5.4 3.0 10.0 1.7 1.3 10.0 .2 10.0 2.7 4808/05/2004 4.1 5.4 3.0 10.0 1.9 1.3 9.7 .5 10.0 4.8 5108/31/2004 5.8 5.4 4.0 10.0 3.1 3.1 9.1 .2 10.0 3.8 5410/04/2004 3.0 5.4 .8 9.9 .7 1.3 8.6 .1 9.9 0 4005/04/2005 2.4 5.4 1.9 10.0 5.3 1.3 7.3 .2 10.0 1.7 4607/24/2005 3.0 5.4 1.9 9.8 .5 .0 8.3 2.9 10.0 1.7 4408/17/2005 3.5 5.4 1.9 9.9 1.2 1.3 7.9 2.9 10.0 .7 4508/04/2006 3.5 7.2 1.9 9.9 3.2 .0 7.1 1.4 10.0 5.8 50 47 (4.4)

P11 Powder River below 

Clear Creek

06/10/2004 3.9 7.1 3.8 10.0 2.7 1.0 4.7 .2 10.0 4.5 4807/08/2004 3.9 7.1 2.7 10.0 2.3 .0 7.2 .3 10.0 4.5 4808/06/2004 4.4 7.1 2.7 10.0 2.4 1.0 9.3 .4 10.0 5.5 5309/01/2004 3.3 7.1 2.7 10.0 1.4 .0 10.0 0 10.0 2.5 4710/06/2004 5.5 7.1 2.7 10.0 .4 1.0 8.9 0 10.0 3.5 4905/05/2005 3.3 5.3 2.7 10.0 4.4 1.0 7.6 .5 10.0 3.5 4807/25/2005 4.4 5.3 3.8 9.9 .8 0 7.4 3.7 10.0 4.5 5008/16/2005 3.9 7.1 2.7 9.9 .1 0 9.1 1.5 10.0 1.4 4608/03/2006 2.8 5.3 2.7 10.0 3.9 1.0 8.7 .1 10.0 1.4 46 48 (2.2)

Implications 117
Table 26. Fish community metric scores and Index of Biotic Integrity (IBI) scores for the main-stem Powder River, Wyoming and Montana, 2005–06.—Continued

[Metric definitions from Bramblett and others (2005). SD, standard deviation; indv., individuals; NA, not applicable]

Site 

number 

(fig. 1)

Abbreviated site 

name

Sample 

date

Species richness and composition scores Trophic composition scores Reproductive guild composition scores Fish abundance and composition scores

IBI 

score

Mean 

IBI score 

for site 

(SD)

Number of native 

species

Number of native 

families

Number of native 

catostomid and 

ictalurid species

- Percentage of toler

ant indv.

Percentage of invertivorous cyprinid 

indv.

Number of 

- benthic invertivo

rous species

Percentage of litho-

- obligate reproduc

tive guild indv.

Percentage of 

tolerant reproductive 

guild indv.

Percentage of 

native indv.

Number of native 

species with 

long-lived indv.

P12 Powder River at 

Moorhead

05/06/2005 3.3 5.2 2.6 10.0 9.5 1.0 1.8 1.6 10.0 4.4 4907/18/2005 2.7 3.4 0 10.0 9.9 1.0 5.0 0 10.0 .3 4208/02/2006 5.5 7.1 3.7 9.9 4.1 4.4 6.8 1.6 10.0 6.5 59 50 (8.5)

P13 Powder River at 

Broadus

07/19/2005 2.6 3.3 .3 9.8 10.0 2.5 10.0 .1 9.8 1.2 50

P13 08/02/2006 2.1 5.2 1.4 9.7 5.8 .8 7.1 .1 9.7 .2 42 46 (5.4)P17 Powder River below 

Little Powder River

07/20/2005 2.3 5.0 1.0 9.9 .2 .3 7.6 .1 9.9 1.8 38

P17 Powder River below 

Little Powder River

08/03/2006 3.9 6.8 1.0 9.6 7.6 .3 5.0 .1 9.7 2.8 45 41 (4.5)

P18 Powder River near 

Locate

07/21/2005 2.6 6.7 .8 9.8 10.0 .1 3.0 .7 10.0 0 44 44 (NA)

(

1

) South Fork Powder 

River

05/26/2004 4.2 3.4 3.1 10.0 4.5 5.5 .8 0 10.0 6.6 4806/29/2004 5.3 5.3 4.2 9.3 7.8 5.5 1.3 0 9.3 6.6 5508/03/2004 4.8 3.4 3.1 6.2 5.3 5.5 2.7 0 6.4 4.6 4209/01/2004 5.3 5.3 4.2 5.1 4.6 5.5 2.4 0 5.4 6.6 4409/29/2004 4.8 3.4 3.1 5.0 4.8 5.5 1.2 0 5.3 5.6 39 46 (6.1)

1Miscellaneous site sampled by Wyoming Game and Fish Department (2004).

118 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06
Implications 119

not be adequately accommodated by the metric normalizations for drainage area. Stagliano (2006) reported a mean IBI 

score of 60 for sites on the middle Powder River in Montana 

and noted that the input metrics with the lowest score included 

adjustments for drainage area. Further work and testing of an 

IBI for large plains streams would be beneficial to the assessment of fish communities of the Powder and Tongue Rivers. 

Implications

Ongoing development of CBNG and other resources 

has the potential to affect biological communities in streams 

of the PRB, but predevelopment data on biological condition have not been available at the basin scale. Although this 

report provides a snapshot of current conditions (2005–06), 

this section of the report describes patterns in the data that 

bear further scrutiny. Most sampling sites were located in the 

Tongue and Powder River drainages (fig. 1), areas of current 

and anticipated CBNG development (fig. 2); therefore, the 

following implications apply only to those rivers and areas of 

development. 

Macroinvertebrate and fish communities of the mainstem Tongue River are affected by many environmental 

variables including the mountainous origins of the river and, 

therefore, the water in Tongue River Reservoir. Scores from 

the Wyoming macroinvertebrate O/E model and the multimetric WSII indicated the biological condition of the Tongue 

River was slightly better at Monarch (site T1, nearest to the 

mountains) than at site T9 at the State line in both 2005 and 

2006; the biological condition at site T5 below Youngs Creek 

tended to be intermediate to the condition at sites T1 and T9 

(fig. 23). For comparison, the Montana macroinvertebrate 

O/E model scores also indicated the biological condition of 

the Tongue River was slightly better at site T1 than at site T9 

during 2005–06, but Montana O/E scores were lower for 

site T5 than for either site T1 or site T9 (fig. 25). The Montana 

MMI (multimetric index) indicated relatively stable biological conditions from site T1 to site T9 in 2005 and a slight 

improvement from site T1 to site T9 in 2006. Scores of the 

Montana O/E model and MMI for the Tongue River sites 

downstream from Tongue River Reservoir (sites T10, T14, and 

T18) were in about the same range as scores for sites upstream 

from the reservoir. 

Fish communities of the main-stem Tongue River were 

dominated by warm-water species, but trout were collected 

at Monarch (site T1; table 22). Open-water fish species, such 

as black crappie, were captured at sites T5, T9, and T10 and 

probably are associated with the Tongue River Reservoir. 

Scores from the Index of Biotic Integrity (IBI) for fish indicated a slight decrease from site T1 to site T9 in both 2005 

and 2006. The variety of water-quality effects in the upstream 

Tongue River drainage, including natural change in water 

quality with distance from the mountains as well as municipal, urban, agricultural, and industrial development, makes it 

difficult to determine from the current data whether CBNG 

development has any role in the apparent decline in biological 

condition. 

Biological data available for the main-stem Powder River 

include algae, macroinvertebrates, and fish communities at 

eight sites in Wyoming and four sites in Montana. The algae 

data collected in 2005 indicated two sites were distinctly 

different from other sites on the Powder River. Algae samples 

from the main stem of the Powder River below Salt Creek 

(site P2) and below Burger Draw (site P4) were outliers to 

the main-stem sample group in an NMDS ordination (fig. 31) 

and with regard to some of the algal metrics (table 21). For 

example, diatom communities at sites P2 and P4 were dominated by a single taxon, Achnanthes minutissima, whereas 

diatom communities at sites P1 and P3, upstream from sites P2 

and P4, respectively, contained much smaller percentages 

of A. minutissima. The diatom community at site P2 had the 

largest percentages of halobiontic (salt loving) species of any 

of the sites in this study, whereas the sample from site P4 indicated relatively low salinity (salt) conditions. 

Some differences among macroinvertebrate communities 

at sites on the main-stem Powder River were noted, although 

the NMDS ordination indicated sites P2 and P4 were similar 

to other sites on the main-stem Powder River in both 2005 

(fig. 20) and 2006 (fig. 21). The Wyoming O/E macroinvertebrate model indicated a general improvement in biological 

condition from upstream to downstream on the Powder River 

in 2005, but declines in condition were noted from site P1 to 

site P2 in 2005 and 2006, from site P8 (below Crazy Woman 

Creek) to site P9 (above Clear Creek) in 2005, and from 

site P11 (below Clear Creek) to site P12 (Moorhead) in 2005 

(fig. 23). The Wyoming WSII showed a decline in biological 

condition from site P1 to site P2 in 2005 and 2006, similar to 

the results from the O/E model. 

Fish communities in the Powder River changed longitudinally from larger percentages of mountain sucker, white 

sucker, northern plains killifish, and longnose dace at sites 

farthest upstream to larger percentages of channel catfish, 

stonecat, river carpsucker, and goldeye at the sites farthest 

downstream in Wyoming (fig. 36). An ANOVA of fish IBI 

scores (table 26) indicated no significant differences among 

Wyoming sites. 

Differences in patterns observed from the algal, macroinvertebrate, and fish data from the Powder River might be a 

reflection of different time scales for response to environmental effects. For example, life cycles can be measured in days 

for algae, and therefore algal communities would respond to 

environmental effects more quickly than macroinvertebrates 

with life cycles measured in months, which in turn might 

respond more quickly than species of fish with life cycles 

measured in years. Differences among the biota in ability 

to respond to environmental perturbations might also play 

a role in explaining patterns observed in the Powder River. 

The Powder River below Salt Creek is on the WDEQ 303d 

list for impaired water because of large chloride concentra-
120 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

tions associated with discharges from conventional oil and 

gas development in the Salt Creek Basin (Wyoming Department of Environmental Quality, 2006); the WDEQ report also 

describes the need for additional monitoring of the main-stem 

Powder River downstream from Pumpkin Creek, which enters 

the Powder River between sites P3 and P4, due to CBNG 

development. 

Summary

Development of energy and mineral resources in 

the Powder River Structural Basin (PRB) of northeastern Wyoming and southeastern Montana includes rapid 

expansion of coalbed natural gas (CBNG) development in 

Wyoming. Concerns about the potential effects of development on cultural and natural resources led to the formation 

of the Aquatic Task Group (ATG), which is an interagency 

working group of primarily Federal and State agencies 

formed to address these issues in the PRB in Wyoming and 

Montana, where similar types of resources exist but are largely 

undeveloped. Under the direction of the ATG, an ecological assessment of streams in the PRB was performed by 

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

of Land Management (BLM), Wyoming Department of 

Environmental Quality (WDEQ), Wyoming Game and Fish 

Department (WGFD), U.S. Environmental Protection Agency 

(USEPA), Montana Department of Environmental Quality 

(MDEQ), and Montana Department of Fish, Wildlife, and 

Parks (MFWP) to determine current (2005–06) status and to 

establish a baseline for future monitoring. 

The primary purpose of this report is to describe the 

ecological assessment of streams in the PRB in northeastern 

Wyoming and southeastern Montana. Habitat characteristics 

and condition of macroinvertebrate, algal, and fish communities are based on samples collected at 47 sites during 2005–06. 

The results of habitat and fish sampling at eight sites on the 

main-stem Powder River in Wyoming and at one miscellaneous site on the South Fork Powder River during 2004 also 

are presented. Macroinvertebrate and algae data collected at 

ATG sites from various investigations during 1980–2007 also 

are presented for comparison with the ATG data. 

Habitat measurements, including characterization of 

stream channels, substrate, riparian features, and reach-scale 

features, were made by the U.S. Geological Survey (USGS) 

following Environmental Monitoring and Assessment Program 

(EMAP) protocols at all 47 sites during 2005. Channel 

characteristics measured included features such as wetted 

width, bankfull width, thalweg depth, and bankfull height. The 

bankfull width/depth ratios generally were smallest at tributary sites and largest at main-stem Powder River sites. Sites 

on the main-stem Tongue River tended to have the highest 

median incision height, whereas Tongue River tributaries had 

the lowest median incision height. Rosebud Creek, as well as 

some of the sites on Otter Creek, had the largest percentages 

of fish cover. The Powder River had small percentages of fish 

cover compared to other streams. 

Reachwide substrate data indicated the Tongue River 

had the coarsest substrates, whereas Squirrel and Otter Creeks 

had the finest substrates. Reachwide substrate embeddedness ranged from 50 percent in the Tongue River at Monarch 

to 100 percent at sites on upper Squirrel Creek, Porcupine 

Creek, and Caballo Creek. Streamside (bank) canopy density 

measurements indicated the main-stem Tongue River sites had 

greater mean canopy density than main-stem Powder River 

and tributary sites. Scores of the bank-stability index indicated streambanks at sites on the main-stem Tongue River in 

Montana and tributaries to the Tongue River were more stable 

than streambanks at sites on the main-stem Powder River and 

tributaries. Sites with the largest proximity-weighted human 

riparian disturbance scores included Hanging Woman Creek, 

Porcupine Creek, Rosebud Creek, and the Tongue River. The 

most commonly noted riparian disturbance was pasture, range, 

or hay fields that were noted at 45 of 47 sites. 

Habitat characteristics of eight sites on the main-stem 

Powder River in Wyoming also were surveyed by the WGFD, 

using three approaches to provide data that might be useful in 

assessing the availability of habitat types and their respective 

fish communities with regard to changes in streamflow such as 

from CBNG activities. Modified Warm-water Stream Assessment (WSA) protocols were used to quantify habitat types, 

starting in 2004. In addition, ground-based, high-resolution 

global positioning system (GPS) mapping of habitat types 

was used in 2005, and EMAP-style transects were used in 

2006. Habitat types that were measured at each site included 

riffle, run, pool, shoal, and backwater. Characteristics such 

as area, depth, substrate, and velocity were recorded for each 

habitat unit. The predominant aquatic habitat in the main-stem 

Powder River was shallow runs with low stream velocity, 

sand substrate, and little fish cover. Riffles and shoals were 

subdominant habitat types, depending on the site and the 

streamflow. 

Macroinvertebrate communities were sampled following National Water-Quality Assessment (NAWQA) protocols. 

Riffles were the preferred sampling habitat and were sampled 

at 37 sites in 2005 and at 20 sites in 2006. Nonmetric multidimensional scaling (NMDS) ordinations indicated similarity 

of macroinvertebrate communities within river drainages. 

One group of similar sites included sites on the main-stem 

Tongue River as well as sites on other streams with mountainous headwaters—Goose Creek, Clear Creek, and Crazy 

Woman Creek. Macroinvertebrate communities of the Tongue 

River group were characterized by relatively large percentages of Ephemeroptera taxa richness and relative abundance 

and smaller percentages of Chironomidae and noninsects 

compared to other sampling sites in the PRB. Sites on the 

main-stem Powder River in Wyoming and Montana formed 

a second group of similar sites characterized by slightly 

fewer taxa, greater relative abundance of Ephemeroptera and 

Chironomidae, and less relative abundance of Trichoptera 

and noninsects than other sampling sites. A third group of 
Summary 121

similar sites in the ordination was Tongue River tributary sites 

representing streams with plains origins, including Hanging 

Woman Creek, Squirrel Creek, and Youngs Creek. The Tongue 

River tributaries group was characterized by a relatively large 

number of taxa with large percentages of Chironomids and 

noninsects. Geographic, habitat, and water-quality variables 

were selected by principal components analysis (PCA) to 

test for correlation with the macroinvertebrate communities. 

The BEST routine indicated macroinvertebrate communities 

were best correlated with easting, drainage area, streamflow, 

specific conductance, magnesium concentration, percentage 

embeddedness, and alkalinity. 

The macroinvertebrate data from the 2005–06 riffle 

samples also were analyzed using modeling and metric indices 

developed independently by the State of Wyoming and the 

State of Montana. The Wyoming observed/expected (O/E) 

model and Wyoming Stream Integrity Index (WSII) indicated 

that samples from sites on streams originating in the mountains had higher scores than those originating in the plains. 

For both 2005 and 2006, the O/E and WSII scores generally 

were highest in the Tongue River drainage followed by the 

Powder River drainage and then the Belle Fourche and Cheyenne River drainages. A general gradual downstream decline 

in biological condition was noted on the main-stem Tongue 

River upstream of Tongue River Reservoir. Among main-stem 

Powder River sites in Wyoming and near the State line, the 

O/E and WSII scores indicated a general increase in biological 

condition in the downstream direction, with the exception of 

declines in biological condition from upstream to downstream 

at Salt Creek and between Crazy Woman Creek and Clear 

Creek. Low scores were assigned to samples from the Cheyenne and Belle Fourche River drainages. Low O/E and WSII 

scores in the Cheyenne drainage may be because of limitations 

of the models in accurately representing reference conditions for streams in this drainage that have a greater tendency 

towards intermittent/ephemeral flow regimes compared to the 

Powder and Tongue River drainages. The Wyoming O/E and 

WSII scores were not significantly different between years. 

Similar to the Wyoming O/E model, the Montana O/E 

model indicated higher scores for sites on streams with mountainous origins than those with plains origins. The Montana 

O/E scores for samples from the main-stem Tongue River 

were lower than scores for samples from tributaries of the 

Tongue River. This might be, in part, because the tributaries 

more closely matched the physical properties of those streams 

identified by MDEQ as reference streams used to calibrate the 

O/E model. The Montana O/E scores trended downward in 

the downstream direction along the main-stem Tongue River 

as opposed to the Montana Multimetric Index (MMI) scores 

that did not show a distinct trend downstream. The Montana 

O/E and MMI scores from the Tongue River and Powder River 

drainages generally were higher in 2006 than in 2005, but 

the differences were not statistically significant. The Powder 

River MMI scores were most affected by the presence of 

filterer-collectors and predator taxa, whereas the O/E scores 

were sensitive to the presence of potentially cold stenotherm 

Orthocladiinae (Chironomidae) taxa. 

Analysis of the ATG macroinvertebrate data set with both 

the Wyoming and Montana O/E models and MMIs indicated 

appreciable differences in model scores between the Wyoming 

and Montana models for the same sites. The differences in 

scores were attributed to fundamental differences in the way 

the States designed their tools, including selection of relevant 

metrics and choice of reference sites, that resulted in differences in the models’ responses to environmental gradients 

and sensitivity to the magnitude and duration of stressors. In 

spite of those differences, the O/E models and MMIs generally showed similar patterns in biological condition at the 

study-area and drainage-basin scales. The results indicate that 

O/E indicators might be more sensitive in detecting environmental change than the MMIs, but the MMIs were valuable 

for identifying particular similarities or differences between 

the macroinvertebrate communities. Additional data collection 

and analysis are needed to confirm and further define these 

patterns for both Wyoming and Montana. Given the regional 

scale of the drainage basins and development issues, development of biological indicators at a regional scale might provide 

additional insights and understanding of the processes affecting biological communities. 

Qualitative multihabitat (QMH) samples of the macroinvertebrates were collected at all of the ATG sites, including 

sites where no riffles were present. The QMH samples exhibited significantly larger values than richest targeted habitat 

(RTH), or riffle, samples in terms of taxa tolerance scores, 

total taxa richness, and taxa richness of Ephemeroptera, 

Chironomidae, and noninsects. Ancillary data from other 

USGS studies also were evaluated. For example, comparison 

of macroinvertebrate samples collected a site on the Little 

Powder River during a 1980–81 Wyoming Water Science 

Center (WWSC) project investigation, NAWQA samples 

collected during 1999–2007, and ATG samples collected 

during 2005–06 indicated the same macroinvertebrate taxa 

often dominated the samples collected at the site during all 

three studies. 

Algal samples were collected from sites in Wyoming 

and near the Wyoming-Montana State line during 2005. An 

NMDS ordination of the algal data indicated similarity of algal 

communities within the Tongue River drainage, the main-stem 

Powder River, and the Cheyenne River drainage. The groups 

of sites determined to be most similar for the algal communities generally were similar to the groups determined for the 

macroinvertebrate communities, with some exceptions. Algal 

samples from Crazy Woman Creek were more similar to those 

from the main-stem Powder River, whereas macroinvertebrate samples from Crazy Woman Creek were more similar 

to those in the Tongue River group. Samples from sites on the 

main-stem Powder River below Salt Creek (site P2) and below 

Burger Draw (site P4) were outliers to the main-stem group in 

the ordination and with regard to some of the diatom metrics 

related to Achnanthes minutissima and salinity. Diatom 

communities at sites P2 and P4 were dominated by a single 
122 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

taxon, Achnanthes minutissima, which is sometimes used as 

an indicator of disturbance. The diatom community at site P2 

had the largest relative abundance of halobiontic (salt loving) 

species of any of the sites, which may reflect tributary inflows 

from Salt Creek. 

Algal data were tested for correlation with environmental variables using the BEST routine, similar to the analysis 

of the macroinvertebrate communities. The algal communities were best correlated with northing, riparian disturbance, 

specific conductance, water temperature, and alkalinity. The 

environmental variables correlated with both the algal and 

macroinvertebrate communities were specific conductance 

and alkalinity. Although nutrients were beyond the scope of 

this study, collection of nutrient data in conjunction with any 

future sampling of algae might help define environmental 

variables affecting the algal communities. 

Algal data from other programs also were evaluated 

where available for ATG sites. For example, NAWQA samples 

were collected at the Little Powder River above Dry Creek 

during 1999–2006. Diatoms generally dominated in those 

samples, although blue-green algae also were common. Algal 

data also were available from the WWSC water-quality monitoring network during 2002 and from a WWSC project investigation during 1980 for some of the ATG sites. For example, 

diatoms in the genus Cocconeis dominated in the 2002 and the 

2005 samples from the Tongue River at the State line. 

Fish community samples were collected by the USGS 

following EMAP protocols at 35 sites in the Tongue, Cheyenne, and Belle Fourche River drainages as well as tributaries to the Powder River during 2005–06. Fish community 

samples were collected following modified WSA protocols 

by the WGFD at eight sites on the main-stem Powder River in 

Wyoming during 2004–06 and by the USGS at four sites on 

the main-stem Powder River in Montana during 2005–06. A 

total of 36 fish species were identified in the samples from the 

Tongue, Cheyenne, and Belle Fourche Rivers and tributaries, 

of which about one-half were native species including eight 

species of minnows (Cyprinidae) and five species of suckers 

(Catostomidae). A total of 16 native and 5 introduced species 

were identified in samples from the main-stem Powder River 

in Wyoming and Montana. 

Fourteen species of fish were collected in samples from 

the Tongue River drainage that were not collected in samples 

from any of the other drainages, including the main-stem 

Powder River. Many of the fish species unique to the Tongue 

River drainage appeared to be associated with Tongue River 

Reservoir as indicated by the presence of open-water species 

such as spottail shiner, yellow perch, black crappie, and 

white crappie. Other species captured only in the Tongue 

River drainage included brassy minnow, lake chub, golden 

shiner, and yellow bullhead. Native species, such as fathead 

minnow, sand shiner, white sucker, and shorthead redhorse 

were the most abundant fish in the Tongue, Cheyenne, and 

Belle Fourche Rivers and tributaries, but introduced species, 

such as smallmouth bass, rock bass, common carp, and green 

sunfish, also were common in the Tongue River drainage 

and some tributaries. Tributary streams with relatively large 

numbers of fish species in 2005–06 were Clear Creek, Little 

Powder River, Prairie Dog Creek, and Goose Creek. The 

number of species per sample was smallest in small, intermittent streams such as Rosebud Creek, Porcupine Creek, and the 

Belle Fourche River. Fish species sampled in 2006 appeared 

to be similar to those sampled in 2005 in spite of notably drier 

conditions during 2006. 

Fish abundance in the main-stem Powder River was 

dominated by native species such as sand shiner, flathead 

chub, and plains minnow. Although northern plains killifish 

were common, other introduced fish were relatively rare in 

the main-stem Powder River. Two species of fish, the sturgeon 

chub and western silvery minnow, were identified in samples 

from the main-stem Powder River that were not found in 

samples from any of the other sites in this study. The sturgeon chub and western silvery minnow are species of special 

concern to the States of Wyoming and Montana. Sturgeon 

chub were documented more often at the Montana sampling 

sites than the Wyoming sites, potentially indicating more 

favorable conditions in the Montana part of the Powder River 

than in Wyoming. Laboratory confirmation of Hybognathus

spp. from the Powder River sites in Wyoming indicated that 

99 percent of the voucher specimens were plains minnow 

(H. placitus) and 1 percent were western silvery minnow 

(H. argyritis), whereas laboratory confirmation of Hybognathus spp. from Montana sites indicated 43 percent were plains 

minnow and 57 percent were western silvery minnow. Both 

sturgeon chub and western silvery minnow generally were rare 

in the samples. 

Monthly sampling from May through October 2004 

at main-stem Powder River sites in Wyoming indicated the 

percentage of sand shiner in the overall catch increased 

substantially from May through October in concert with a 

substantial decrease in the percentage of flathead chub and 

Hybognathus spp. These trends may be explained in part by 

the recruitment of age-0 sand shiner to the sampling equipment by late summer and early fall. This shift in species 

composition was not repeated in 2005 when samples were 

collected pre-high flow, post-high flow, and during low flow. 

Samples collected early in the year contained noticeably fewer 

fish than samples collected later in the year despite equal 

sampling effort in both 2004 and 2005. 

Comparison of fish species by habitat indicated some 

associations in the main-stem Powder River. Channel catfish 

and goldeye, for example, were found significantly more often 

in pools than in riffles, backwater, or shoals. The percentages 

of Hybognathus spp. were significantly larger in runs and 

pools than in riffles, backwaters, or shoals. Flathead chubs 

were found more often in pools and runs than in other habitats. 

Data for other species also are available.

The structure and integrity of the fish communities was 

assessed using an Index of Biotic Integrity (IBI) developed 

for small plains streams in Montana. The highest IBI scores, 

associated with best condition, among the small plains streams 

were from Youngs Creek, Squirrel Creek, Clear Creek, Little 
Summary 123

Powder River, and Crazy Woman Creek. The lowest IBI scores 

among the small plains streams, using mean values, occurred 

in the Hanging Woman Creek, Otter Creek, Cheyenne River, 

and Belle Fourche River drainages. Small intermittent streams 

such as those in the Cheyenne River drainage have naturally 

small numbers of fish species, and therefore, the IBI scores 

might be biased toward lower values. Of the six sites on the 

main-stem Tongue River, the lowest IBI scores in both 2005 

and 2006 were at the site downstream from the Tongue River 

Reservoir, but these data should be used with caution because 

the IBI was not designed for larger rivers such as the Tongue 

River and Powder River. An analysis of variance of the IBI 

scores from main-stem Powder River sites in Wyoming indicated no significant difference between sites or between years 

(2005–06). 

The data collected for habitat, algae, macroinvertebrates, 

and fish from streams of the PRB indicate substantial variation in habitat characteristics and biological communities from 

one river drainage to another and in the downstream direction 

within river drainages. Differences in the algal communities at sampling sites on the Powder River below Salt Creek 

and below Burger Draw from other sampling sites as determined from the ordination and various diatom metrics were 

supported in part by the macroinvertebrate data. Wyoming O/E 

and WSII scores were quite low at sites in the Powder River 

below Salt Creek. The macroinvertebrate ordination, however, 

showed the macroinvertebrate communities below Salt Creek 

and Burger Draw were generally similar to other sites on the 

main-stem Powder River. The ANOVA of fish community IBI 

scores from the main-stem Powder River in Wyoming did not 

indicate significant differences among the sites. In combination, these data might indicate that the algal communities 

respond to different environmental variables, or at a different 

time scale, than the macroinvertebrate or fish communities.

These data provide a snapshot of conditions in streams of 

the PRB during 2005–06 and can be used in conjunction with 

future monitoring to assess the effects of coalbed natural gas 

and other development. Additional data analysis tools, such 

as development of regional macroinvertebrate O/E and MMI 

models, and calibration of a fish IBI for large plains rivers also 

may warrant further investigation.

References Cited

Armentrout, G.W., Jr., and Wilson, J.F., Jr., 1987, An assessment of low flows in streams in northeastern Wyoming: 

U.S. Geological Survey Water-Resources Investigations 

Report 85–4246, 30 p.

Bahls, L.L., Weber, E.E., and Jarvie, J.O., 1984, Ecology and 

distribution of major diatom ecotypes in the southern Fort 

Union coal region of Montana: U.S. Geological Survey 

Professional Paper 1289, 151 p.

Bailey, R.G., 1995, Description of the ecoregions of the 

United States (2d ed.): U.S. Department of Agriculture, 

Forest Service Miscellaneous Publication No. 1391 (rev.), 

108 p., 1 pl. in pocket.

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 (2nd 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, Wyo.: Wyoming Game and Fish Department 

Bulletin Number 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. 

Brown, C.J.D., 1971, Fishes of Montana: Bozeman, Mont., 

Big Sky Books, Montana State University, 207 p.

Chapman, S.S., Bryce, S.A., Omernik, J.M., Despain, D.G., 

Zumberge, J., and Conrad, M., 2003, Ecoregions of Wyoming (color poster with map, descriptive text, summary 

tables, and photographs): Reston, Va., U.S. Geological Survey, scale 1:1,400,000, accessed October 2, 2007, at http://

www.epa.gov/wed/pages/ecoregions/wy_eco.htm

Chorley, R.J., Schumm, S.A., and Sugden, D.E., 1984, Geomorphology: New York, Methuen & Co., 605 p.

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.

Clarke, R.T., Wright, J.F., and Furse, M.T., 2003, RIVPACS 

models for predicting the expected macroinvertebrate fauna 

and assessing the ecological quality of rivers: Ecological 

Modeling, v. 160, p. 219–233.

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 03–172, 103 p.
124 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

Davis, W.N., Bramblett, R.G., and Zale, A.V., 2006a, Effects 

of coalbed natural gas development on fish assemblages in 

the Powder River Basin, 2005: Bozeman, Montana Cooperative Fishery Research Unit, 3 p. 

Davis, W.N., Bramblett, R.G., and Zale, A.V., 2006b, The 

effects of coalbed natural gas activities on fish assemblages—a review of the literature: Bozeman, Montana 

Cooperative Fishery Research Unit, 47 p.

Fitzpatrick, F.A., and Giddings, E.M., 1995, Stream habitat 

characteristics of fixed sites in the Western Lake Michigan 

drainages, Wisconsin and Michigan, 1993–95: 

U.S. Geological Survey Water-Resources Investigations 

Report 95–4211–B, 58 p.

Fitzpatrick, F.A., Waite, I.R., D’Arconte, P.J., Meador, M.R., 

and Gurtz, M.E., 1998, Revised methods for characterizing 

stream habitat in the National Water-Quality Assessment 

Program: U.S. Geological Survey Water-Resources Investigations Report 98–4052, 67 p.

Graham, T.B., 2002, Climate change and ephemeral pool 

ecosystems—potholes and vernal pools as potential indicator systems: U.S. Geological Survey Biological Resources 

Division, accessed December 19, 2007, at http://geochange.

er.usgs.gov/sw/impacts/biology/vernal/.

Hargett, E.G., and Zumberge, J.R., 2006, Redevelopment of 

the Wyoming Stream Integrity Index (WSII) for assessing 

the biological condition of wadeable streams of Wyoming: 

Wyoming Department of Environmental Quality, Water 

Quality Division Report, 70 p.

Hargett, E.G., Zumberge, J.R., and Hawkins, C.P., 2005, 

Development of a RIVPACS model for wadeable streams of 

Wyoming: Wyoming Department of Environmental Quality, 

Water Quality Division Report, 64 p.

Hargett, E.G., Zumberge, J.R., Hawkins, C.P., and Olson, J.R., 

2007, Development of a RIVPACS-type predictive model 

for bioassessment of wadeable streams in Wyoming: Ecological Indicators, v. 7, p. 807–826.

Harrelson, C.C., Rawlins, C.L., and Potyondy, J.P., 1994, 

Stream channel reference sites—an illustrated guide to 

field technique: Fort Collins, Colo., U.S. Department 

of Agriculture, Forest Service, Rocky Mountain Forest 

and Range Experimentation Station, General Technical 

Report RM–245, 61 p.

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.

Hembree, C.H., Colby, B.R., Swensen, H.A., and Davis, J.R., 

1952, Sedimentation and chemical quality of water in the 

Powder River drainage basin, Wyoming and Montana: U.S. 

Geological Survey Circular 170, 99 p.

Hilsenhoff, W.L., 1987, An improved index of organic stream 

pollution: Great Lakes Entomologist, v. 20, p. 31–39.

HKM Engineering, Inc., Lord Consulting, and Watts and 

Associates, 2002, Powder/Tongue River Basin Plan—executive summary: Available on the Web, accessed March 16, 

2008, at http://censtats.census.gov/data/WY/1605631855.

pdf

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 J. R. 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.

Insightful Corp., 2005, S-Plus 7.0 for Windows—professional 

developer: Palo Alto, California, TIBCO Software, Inc.

Kaufmann, P.R., Levine, P., Robison, E.G., Seeliger, C., and 

Peck, D.V., 1999, Quantifying physical habitat in wadeable streams: U.S. Environmental Protection Agency, 

EPA/620/R–99/003, 102 p.

Kerans, B.L., and Karr, J.R., 1994, A benthic index of biotic 

integrity (B-IBI) for rivers of the Tennessee Valley: Ecological Applications, v. 4, p. 768–785.

Knight, D.H., 1994, Mountains and plains—the ecology of 

Wyoming landscapes: New Haven and London, Yale University Press, 338 p.

Kwak, T.J., and Peterson, J.T., 2007, Community indices, 

parameters, and comparisons, in Guy, C.S., and Brown, 

M.L., eds., Analysis and interpretation of freshwater 

fisheries data: Bethesda, Md., American Fisheries Society, 

p. 677–763. 

Lee, R.W., Slagle, S.E., and Stimson, J.R., 1981, Magnitude 

and chemical quality of base flow of Otter Creek, Tongue 

River, and Rosebud Creek, southeastern Montana, October 

26–November 5, 1977: U.S. Geological Survey WaterResources Investigations, Open-File Report 80–1298, 25 p.

Leopold, L.B., Wolman, M.G., and Miller, J.P., 1992, Fluvial 

processes in geomorphology: Mineola, N.Y., Dover Publications, Inc., 522 p.

Lindner-Lunsford, J.B., Parrett, Charles, Wilson, J.F., Jr., and 

Eddy-Miller, C.A., 1992, Chemical quality of surface water 

and mathematical simulation of the surface-water system, 

Powder River drainage basin, northeastern Wyoming and 

southeastern Montana: U.S. Geological Survey WaterResources Investigations Report 91–4199, 85 p.

Lowe, R.L., 1974, Environmental requirements and pollution tolerance of freshwater diatoms: U.S. Environmental 

Protection Agency, EPA–670/4–74–005, 333 p.
References Cited 125

McNab, W.H., Cleland, D.T., Freeouf, J.A., Keys, J.E., Jr., 

Nowacki, G.J., and Carpenter, C.A., compilers, 2005, 

Description of ecological subregions—sections of the conterminous United States: Washington, D.C., U.S. Department of Agriculture, Forest Service, 80 p., [CD-ROM].

Merritt, R.W., and Cummins, K.W., 1996, An introduction to 

the aquatic insects of North America (3d ed.): Dubuque, 

Iowa, Kendall/Hunt Publishing Co., 862 p. 

Montana Department of Environmental Quality, 2006, Sample 

collection, sorting and taxonomic identification of benthic 

macroinvertebrates: Water Quality Planning Bureau, Standard Operating Procedure (WQPBWQM-009), 32 p.

Moss, D., Furse, M.T., Wright, J.F., and Armitage, P.D., 1987, 

The prediction of the macroinvertebrate fauna of unpolluted 

running water sites in Great Britain using environmental 

data: Freshwater Biology, v. 17, p. 41–52.

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 02–150, 75 p. 

National Oceanic 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

Ostrand, K.G., and Wilde, G.R., 2004, Changes in prairie 

stream fish assemblages restricted to isolated streambed 

pools: Transactions of the American Fisheries Society, v. 

133, p. 1329–1338. 

Patton, T.M., 1997, Distribution and status of fishes in the 

Missouri River drainage in Wyoming—implications for 

identifying conservation areas: Laramie, University of Wyoming, doctoral dissertation, 173 p.

Peck, D.V., Lazorchak, J.M., and Klemm, D.J., eds., 2003, 

Environmental Monitoring and Assessment Program—surface waters—Western Pilot Study field operations manual 

for wadeable streams: Washington, D.C., U.S. Environmental Protection Agency, 258 p.

Peterson, D.A., 1990, Invertebrate communities of small 

streams in northeastern Wyoming: U.S. Geological Survey 

Water-Resources Investigation Report 85–4287, 45 p. 

Peterson, D.A., Miller, K.A., Bartos, T.T., Clark, M.L., 

Porter, S.D., and Quinn, T.L., 2004, Water quality in the 

Yellowstone River Basin, Wyoming, Montana, and North 

Dakota, 1999–2001: U.S. Geological Survey Circular 1234, 

34 p., available on the Web at http://pubs.usgs.gov/

circ/2004/1234/.

Pflieger, W.L., 1997, The fishes of Missouri, revised edition: 

Jefferson City, Missouri Department of Conservation, 371 p.

Porter, S.D., 2008, Algal attributes—An autecological classification of algal taxa collected by the National WaterQuality Assessment Program: U.S. Geological Survey Data 

Series 329, available on the Web at http://pubs.usgs.gov/ds/

ds329

Porter, S.D., Mueller, D.K., Spahr, N.E., Munn. M.D., and 

Dubrovsky, N.M,, 2008, Efficacy of algal metrics for assessing nutrient and organic enrichment in flowing waters: 

Freshwater Biology, v. 53, p. 1036-1054. 

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. 

Potyondy, J.P., and Bunte, K., 2002, Sampling with the 

US SAH–97 Hand-held Particle Size Analyzer: Federal 

Interagency Sedimentation Project, 6 p., available on the 

Web at http://fisp.wes.army.mil/Instructions %20US_SAH97_040412.pdf

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

Prescott, G.W., 1978, How to know the freshwater algae: 

Dubuque, Iowa, Wm. C. Brown Co., 293 p. 

Quist, M.C., Hubert, W.A., and Rahel, F.J., 2004, Warmwater 

stream assessment manual: Cheyenne, Wyoming Game and 

Fish Department, 190 p. 

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 00–372, 22 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.

Rosgen, D.L., 1996, Applied river morphology: Pagosa 

Springs, Colo., Wildland Hydrology, 342 p.

Skaar, D., Farag, A., 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. 

Stagliano, D., 2006, Aquatic surveys and assessment within 

the Middle Powder River watershed: U.S. Bureau of Land 

Management Report (ESA010009), 37 p., accessed Dec.13, 

2007, at http://mtnhp.org/Reports/Mid_Powd_Riv_Water_

Assess.pdf
126 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

Stoner, D.L., 1993, Microbial transformation of organic 

nitrogen and sulfur in low rank coals, in Crawford, D.L. ed., 

Microbial transformations of low rank coals: Ann Arbor, 

Mich., CRC Press, 223 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., available on the Web at http://

pubs.usgs.gov/of/2006/1174/.

Suplee, M., Sada de Suplee, R., Feldman, D., and Laidlaw, T., 

2005, Identification and assessment of Montana reference 

streams—a follow-up and expansion of the 1992 Benchmark Biology Study: Helena, Montana Department of 

Environmental Quality, Planning Prevention and Assistance 

Division, Water Quality Planning Bureau, Water Quality 

Standards Section, 41 p. 

U.S. Census Bureau, 2007, 2000 Census: digital data available 

on the Web, accessed March, 16, 2007, at http://censtats.

census.gov/data/WY/1605631855.pdf

U.S. Census Bureau, 2009, American fact finder: digital data 

available on web, accessed January 28, 2009 at http://

factfinder.census.gov/home/saff/main.html?_lang=en

U.S. Geological Survey, 2008, NAWQA data warehouse 

home: Information available on the Web, accessed June 6, 

2008, at http://water.usgs.gov/nawqa/data

U.S. Geological Survey, variously dated, National field manual 

for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chaps. A1–A9, available on the Web, accessed 

March 10, 2008 at http://pubs.water.usgs.gov/twri9A

Van Dam, H., Mertens, A., and Sinkeldam, J., 1994, A coded 

checklist and ecological indicator values of freshwater diatoms from the Netherlands: Netherlands Journal of Aquatic 

Ecology, v. 28, no. 1, p. 117–133.

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.

Watson, V.J., Ingman, G., and Anderson, B., 2000, Appendix 

A. Case studies, in U.S. Environmental Protection Agency, 

Nutrient criteria technical guidance manual—rivers and 

streams: EPA–B22–B–00–002, p. A–19 to A–23. 

Western Regional Climate Center, 2007, Broadus, Montana: digital data available on the Web, accessed October, 

26, 2007, at http://www.wrcc.dri.edu/cgi-bin/cliGCStT.

pl?mt1127

Western Regional Climate Center, 2009, Digital data available 

on the Web, accessed January 28, 2009, at http://www.wrcc.

dri.edu/.

Wolman, M.G., 1954, A method for sampling coarse riverbed 

material: Transactions of the American Geophysical Union, 

v. 35, p. 951–956.

Woods, A.J., Omernik, J.M., Nesser, J.A., Shelden, J., 

Comstock, J.A., and Azevedo, S.H., 2002, Ecoregions of 

Montana (2d ed.) (color poster with map, descriptive text, 

summary tables, and photographs): U.S. Environmental Protection Agency, map scale 1:1,500,000, accessed October 

17, 2007, at http://www.epa.gov/wed/pages/ecoregions/

mt_eco.htm#Ecoregions%20denote

Wright, J.F., Furse, M.T., and Armitage, P.D., 1993, 

RIVPACS—a technique for evaluating the biological quality 

of rivers in the U.K.: European Water Pollution Control, 

v. 3, p. 15–25.

Wright, P.R., Peterson, D.A., and Hallberg. L.L., 2006, Data 

collection for the assessment of aquatic communities in 

northeastern Wyoming and southeastern Montana, 2005: 

U.S. Geological Survey Fact Sheet 2006–3047, 6 p. 

Wyoming Department of Environmental Quality, 2001, Water 

quality rules and regulations—Chapter 1, Wyoming Surface 

Water Quality Standards: Cheyenne, 23 p. plus appendixes. 

Wyoming Department of Environmental Quality, 2006, 

Wyoming’s 2006 305(b) State water quality assessment 

report and 2006 303(d) list of waters requiring TMDLs: 

Cheyenne, Water Quality Division, 107 p., accessed 

August 3, 2008, at http://deq.state.wy.us/wqd/watershed/

Downloads/305b/2006/2006_305b_.pdf

Wyoming Department of Environmental Quality, 2009, 

National Pollutant Discharge Elimination System (NPDES) 

Program; digital data accessed January 28, 2009 at http://

deq.state.wy.us/wqd/npdes/.

Wyoming Game and Fish Department, 2007, Annual fisheries progress report on the 2006 work schedule: Cheyenne, 

Wyoming Game and Fish Department, 451p.
References Cited 127

Wyoming Oil and Gas Conservation Commission, 2008, Coal 

bed methane wells: digital data accessed July 21, 2008 at: 

http://wogcc.state.wy.us/crms.cfm

Zale, A.V., Leslie, D.M., Jr., Fisher, W.L., and Merrifield, 

S.G., 1989, The physicochemistry, flora, and fauna of intermittent prairie streams—a review of the literature: U.S. Fish 

and Wildlife Service, Biological Report 89(5), 44 p.

Zelt, R.B., Boughton, G.K., Miller, K.A., Mason, J.P., and 

Gianakos, L.M., 1999, Environmental setting of the Yellowstone River basin, Montana, North Dakota, and Wyoming: 

U.S. Geological Survey Water-Resources Investigations 

Report 98–4269, 112 p., available on the Web at http://pubs.

usgs.gov/wri/wri984269/.

Appendixes
130 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

Appendix 1. Supporting Data for Macroinvertebrates

Table 27. Mean values of microhabitat measurements collected at macroinvertebrate sampling sites in riffles, Powder River 

Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River; m/s, meters per second; E, estimate]

Site 

number 

(fig. 1)

Abbreviated site name Sample date Mean depth 

(meters)

Mean 

embeddedness 

(percent)

Mean velocity 

(m/s)

Gravel or larger 

substrate 

(percent)

R2 Rosebud Creek at mouth 09/15/2005 0.02 54 0.16 100

T1 Tongue River at Monarch 08/15/2005 .09 36 .42 100

08/23/2006 .10 34 .43 100

T2 Goose Creek 08/17/2005 .13 24 .55 70

08/22/2006 .17 48 .60 80

T3 upper Youngs Creek 06/15/2005 .10 0 .81 100

06/28/2006 .05 38 .34 80

T4 Youngs Creek at mouth 06/14/2005 .19 54 .41 100

06/27/2006 .16 50 .35 50

T5 Tongue River below Youngs 

Creek

08/15/2005 .11 24 .94 100

08/22/2006 .11 28 .62 80

T7 Squirrel Creek at mouth 06/13/2005 .08 10 .24 100

T8 Prairie Dog Creek 08/25/2006 .09 44 .32 78

T9 Tongue River at State line 09/14/2005 .11 24 .49 80

08/24/2006 .12 22 .45 100

T10 Tongue River above 

Hanging Woman Creek

08/16/2005 .15 48 .59 100

08/28/2006 .16 48 .70 100

T11 upper Hanging Woman 

Creek

06/22/2005 .05 68 0 56

T12 middle Hanging Woman 

Creek

06/21/2005 .10 2 .19 50

T13 Hanging Woman Creek near 

Birney, MT

06/23/2005 .08 20 .15 90

T14 Tongue River at Birney Day 

School

09/12/2005 .20 46 .58 100

08/28/2006 .17 36 .63 100

T17 Otter Creek at mouth 06/30/2005 .12 34 .44 100

06/28/2006 .06 68 .22 100

T18 Tongue River below Brandenberg Bridge09/13/2005 .23 40 .83 100

08/31/2006 .21 26 .74 100

T19 Pumpkin Creek 06/23/2005 .07 14 .21 100

P1 Powder River above Salt 

Creek

07/20/2905 .06 36 .36 80

07/24/2006 .07 38 .30 50
Appendix 1. Supporting Data for Macroinvertebrates 131

Table 27. Mean values of microhabitat measurements collected at macroinvertebrate sampling sites in riffles, Powder River 

Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sampling sites on the Tongue or Powder River; m/s, meters per second; E, estimate]

Site 

number 

(fig. 1)

Abbreviated site name Sample date Mean depth 

(meters)

Mean 

embeddedness 

(percent)

Mean velocity 

(m/s)

Gravel or larger 

substrate 

(percent)

P2 Powder River below Salt 

Creek

07/21/2005 0.09 48 0.35 70

07/25/2006 .11 22 .50 50

P3 Powder River above Pumpkin Creek07/19/2005 .05 28 .19 100

07/26/2006 .05 26 .17 50

P4 Powder River below Burger 

Draw

07/22/2005 .08 36 .21 100

07/27/2006 .07 22 .41 90

P5 Powder River above Crazy 

Woman Creek

07/13/2005 .07 60 .34 50

07/28/2006 .07 14 .31 50

P6 Crazy Woman Creek below 

I-90

07/11/2005 .08 14 .38 50

P7 Crazy Woman Creek near 

mouth

07/12/2005 .24 15 .66 50

P8 Powder River below Crazy 

Woman Creek

07/23/2005 .17 64 .53 100

P9 Powder River above Clear 

Creek

07/24/2005 .12 74 .41 100

P10 Clear Creek 09/13/2005 .10 34 .45 90

08/21/2006 .08 22 .51 80

P11 Powder River below Clear 

Creek

07/25/2005 .11 24 .41 E50

08/03/2006 .04 42 .25 50

P12 Powder River at Moorhead 07/26/2005 .11 46 .31 100

P13 Powder River at Broadus 07/19/2005 .17 2 .63 90

08/02/2006 .07 69 .38 100

P15 Little Powder River above 

Dry Creek

06/13/2005 .11 30 .60 100

06/23/2006 .09 14 .45 100

P16 Little Powder River at 

Biddle

06/27/2005 .21 18 .67 100

P17 Powder River below Little 

Powder River

07/21/2005 .10 34 .30 70

P18 Powder River near Locate 07/22/2005 .12 44 .40 80

C3 Cheyenne River near Dull 

Center

06/27/2005 .05 34 .10 70

C4 Little Thunder Creek 06/09/2005 .02 32 .05 100

C6 Cheyenne River near 

Spencer

06/06/2005 .04 40 .20 100

B1 Belle Fourche River 06/29/2005 .07 40 .17 50
132 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

Table 28. Onsite measurements of physical and chemical characteristics collected in conjunction with biological samples, Powder 

River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River; μS/cm, microsiemens per centimeter at 25°C; NC, not collected or missing]

Site number 

(fig. 1) Sample date

Streamflow 

(cubic feet per 

second)

Specific 

conductance 

(μS/cm)

pH 

(standard 

units)

Water 

temperature 

(degrees 

Celsius)

Dissolved 

oxygen 

(milligrams 

per liter)

Turbidity 

(nephelometric 

turbidity units)

R1 06/20/2005 5.6 1,079 7.7 21.2 NC 3.0

07/12/2006 .37 985 7.2 20.0 6.8 .9

R2 09/15/2005 .01 4,300 8.6 12.5 9.3 9.1

T1 08/15/2005 123 426 7.5 14.8 7.5 30

08/23/2006 27 535 8.2 19.6 7.7 14

T2 08/17/2005 69 653 8.3 20.5 8.3 9.0

08/22/2006 22 735 8.2 19.7 7.3 4.5

T3 06/14/2005 2.3 675 8.3 19.0 7.6 62

06/28/2006 .36 704 8.4 22.0 7.2 85

T4 06/14/2005 .99 1,690 8.4 12.0 8.1 33

06/27/2006 .58 1,000 8.3 19.5 9.2 18

T5 08/15/2005 171 544 7.8 19.0 8.2 48

08/24/2006 23 695 7.9 19.0 7.3 12

T6 06/16/2005 .12 1,570 7.8 14.0 7.7 2.1

06/29/2006 .12 1,480 8.0 13.5 7.8 3

T7 06/13/2005 .17 5,940 8.3 13.0 9.7 6.8

T8 08/16/2005 45 775 8.1 18.8 7.2 120

08/25/2006 1.2 2,270 8.1 15.3 9.1 10

T9 09/14/2005 162 655 7.6 13.6 8.4 12

08/24/2006 11 1,060 8.4 24.1 10.8 4.4

T10 08/16/2005 408 363 8.0 20.0 8.0 13

08/29/2006 153 540 8.2 18.5 7.5 .6

T11 06/22/2005 .03 5,000 7.9 22.5 NC 10

06/27/2006 0 4,500 9.3 18.5 10.0 3.9

T12 06/21/2005 .04 3,870 8.1 24.5 NC 9.0

06/26/2006 .06 3,970 9.3 26.0 14.8 3.1

T13 06/23/2005 .11 2,090 7.8 20.3 NC 7.0

06/26/2006 0 3,890 8.1 14.5 1.5 140

T14 09/12/2005 308 466 8.1 18.5 8.3 10

08/28/2006 139 572 8.0 23.5 10.5 NC

T15 06/29/2005 .75 3,470 7.7 19.0 7.8 5.5

07/12/2006 .1 3,510 8.6 26.5 12.1 3.2

T16 06/28/2005 .26 3,600 8.8 21.5 6.4 4.4

T17 06/30/2005 1.6 2,700 8.2 18.0 5.3 97

06/28/2006 .82 2,890 8.4 22.2 5.0 79

T18 09/14/2005 330 503 8.3 14.5 9.3 16

08/03/2006 81.8 684 8.4 17.8 8.6 NC
Appendix 1. Supporting Data for Macroinvertebrates 133

Table 28. Onsite measurements of physical and chemical characteristics collected in conjunction with biological samples, Powder 

River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River; μS/cm, microsiemens per centimeter at 25°C; NC, not collected or missing]

Site number 

(fig. 1) Sample date

Streamflow 

(cubic feet per 

second)

Specific 

conductance 

(μS/cm)

pH 

(standard 

units)

Water 

temperature 

(degrees 

Celsius)

Dissolved 

oxygen 

(milligrams 

per liter)

Turbidity 

(nephelometric 

turbidity units)

T19 06/23/2005 1.1 1,140 8.4 29.4 NC 158

P1 07/20/2005 2.7 2,100 7.6 21.8 7.4 4.7

P1 07/24/2006 1.2 2,210 7.9 28.5 6.8 19

P2 07/21/2005 13 4,990 7.9 23.0 7.7 16

07/25/2006 5.1 5,650 8.3 32.7 7.3 12

P3 07/19/2005 9.3 4,810 8.1 24.3 7.2 2.9

07/26/2006 0.22 4,650 7.8 27.1 11.4 18

P4 07/22/2005 7.9 4,600 7.9 20.7 8.0 4.1

07/27/2006 2.2 3,210 8.7 24.7 13.9 84

P5 07/13/2005 25 3,500 8.8 26.1 6.6 28

07/28/2006 1.7 2,960 8.1 21.7 8.7 5.8

P6 07/11/2005 37 777 7.9 20.8 7.0 58

07/31/2006 0 3,500 8.1 19.7 8.8 28

P7 07/12/2005 40 894 7.7 22.7 7.0 120

08/01/2006 0 3,410 7.0 17.6 6.8 97

P8 07/23/2005 99 2,050 8.1 21.4 5.9 960

08/02/2006 0 3,990 7.3 22.6 6.1 15

P9 07/24/2005 149 2,280 7.7 24.0 5.6 1000

08/04/2006 0 2,360 7.7 21.6 5.2 20

P10 09/13/2005 35 1,200 8.0 13.6 8.0 4.3

08/21/2006 1.7 1,840 8.0 20.4 8.2 12

P11 07/25/2005 92 1,940 8.2 21.2 7.4 420

08/03/2006 0.2 2,260 8.1 21.1 7.2 7.6

P12 07/26/2005 76 1,930 8.4 18.2 8.0 619

08/02/2006 0 4,300 8.3 16.0 6.2 41

P13 07/19/2005 111 1,690 8.3 22.5 8.2 18

08/02/2006 1.1 4,750 8.1 27.0 9.5 3.3

P14 06/14/2005 0.73 2,080 8.1 11.2 9.5 7.3

06/22/2006 0.27 2,060 8.5 22.8 10.0 1.5

P15 06/13/2005 3.8 3,480 6.8 13.6 7.5 120

06/23/2006 0.23 3,380 8.1 19.5 8.8 96

P16 06/27/2005 7.6 2,720 7.9 17.5 6.4 810

P17 07/20/2005 85 1,820 8.4 28.5 5.8 22

08/03/2006 .01 3,010 8.1 25.0 8.3 4.2

P18 07/22/2005 90 1,970 8.3 21.3 7.3 NC

C1 06/15/2005 .33 3,110 8.1 19.4 7.8 5.0

06/22/2006 .12 3,690 9.8 17.9 10.6 1.8
134 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06

Table 28. Onsite measurements of physical and chemical characteristics collected in conjunction with biological samples, Powder 

River Structural Basin, Wyoming and Montana, 2005–06.—Continued

[Shaded cells indicate main-stem sites on the Tongue or Powder River; μS/cm, microsiemens per centimeter at 25°C; NC, not collected or missing]

Site number 

(fig. 1) Sample date

Streamflow 

(cubic feet per 

second)

Specific 

conductance 

(μS/cm)

pH 

(standard 

units)

Water 

temperature 

(degrees 

Celsius)

Dissolved 

oxygen 

(milligrams 

per liter)

Turbidity 

(nephelometric 

turbidity units)

C2 06/08/2005 0.09 3,050 7.8 14.1 7.2 9.3

06/20/2006 0 2,840 7.8 29.1 5.1 4.2

C3 06/27/2005 0 3,070 8.1 21.3 5.3 4.8

06/19/2006 0 6,560 8.1 30.6 6.4 49.4

C4 06/22/2005 .02 1,950 7.7 14.3 8.1 41

06/21/2006 0 6,370 8.9 15.6 5.6 19

C5 06/07/2005 0 1,410 8.1 20.2 6.5 48

C6 06/06/2005 6.4 3,910 8.0 20.4 7.2 163

06/20/2006 0 7,100 8.0 20.6 6.5 3.4

B1 06/29/2005 1 3,360 8.8 16.6 8.1 3.8

06/21/2006 .5 4,960 7.8 29.8 8.1 5.7

B2 06/28/2005 0 4,240 8.0 21.7 10.0 160
Appendix 2. Supporting Data for Fish 135

Appendix 2. Supporting Data for Fish

Table 29. Total numbers of fish by sampling site collected by the Wyoming Game and Fish Department at sites on the main-stem 

Powder River, Wyoming, 2004–06.

[Location of sampling sites shown in figure 1. SFP, South Fork Powder River; n, number of sampling periods]

Species

Total numbers of fish at sampling sites (percent of total catch1)

Site SFP2

(n=5)

Site P1 

(n=9)

Site P2 

(n=9)

Site P3 

(n=8)

Site P4 

(n=4)

Site P5 

(n=10)

Site P8 

(n=9)

Site P9 

(n=9)

Site P11 

(n=9) Overall

Sand shiner 502 

(12.4)

9,106 

(57.6)

12,183 

(56.2)

10,264 

(64.4)

6,450 

(62.3)

18,399 

(63.9)

9,957 

(68.1)

6,440 

(69.3)

6,854 

(65.3)

80,155 

(61.2)

Flathead chub 1,510 

(37.2)

3,300 

(20.9)

5,658 

(26.1)

2,990 

(18.8)

1,658 

(16.0)

7,115 

(24.7)

2,008 

(13.7)

1,418 

(15.3)

1,229 

(11.7)

26,886 

(20.5)

Hybognathus spp. 798 

(19.6)

139 (0.9) 1,010 

(4.7)

982 (6.2) 1,320 

(12.8)

2,103 

(7.3)

2,010 

(13.7)

675 (7.3) 1,462 

(13.9)

10,499 

(8.0)

Northern plains 

killifish

1,183 

(29.1)

1,381 

(8.7)

1,441 

(6.6)

1,216 

(7.6)

330 (3.2) 264 (0.9) 45 (0.3) 24 (0.3) 15 

(0.1)

5,899 

(4.5)

Longnose dace 57 

(1.4)

1,088 

(6.9)

1,042 

(4.8)

185 (1.2) 278 (2.7) 101 (0.4) 134 (0.9) 11 

(0.1)

13 

(0.1)

2,909 

(2.2)

River carpsucker 0 117 (0.7) 70 

(0.3)

156 (1.0) 146 (1.4) 347 (1.2) 244 (1.7) 99 

(1.1)

332 (3.2) 1,511 

(1.2)

Channel catfish 0 4 12 

(0.1)

44 

(0.3)

132 (1.3) 149 (0.5) 175 (1.2) 579 (6.2) 444 (4.2) 1,539 

(1.2)

Mountain sucker 0 524 (3.3) 185 (0.9) 8 (0.1) 0 0 0 0 0 717 (0.5)

Fathead minnow 0 107 (0.7) 61 

(0.3)

67 

(0.4)

20 

(0.2)

273 (0.9) 7 27 (0.3) 19 

(0.2)

581 (0.4)

Stonecat 0 10 

(0.1)

0 8 (0.1) 2 8 19 

(0.1)

3 86 

(0.8)

136 (0.1)

Goldeye 0 1 3 3 4 9 9 

(0.1)

4 13 

(0.1)

46 

White sucker 2 13 

(0.1)

22 

(0.1)

2 0 1 0 2 0 42

Creek chub 10 

(0.2)

22 

(0.1)

0 0 0 1 3 4 0 40

Common carp 0 0 2 7 6 

(0.1)

7 5 

(0.1)

5 32 

Sturgeon chub 0 0 0 0 0 2 1 0 0 3 

Northern redhorse 0 1 0 0 0 2 4 2 19 

(0.2)

28 

Green sunfish 0 0 2 0 0 2 0 2 0 6

Smallmouth bass 0 0 0 0 0 0 0 0 3 3

Black bullhead 0 1 0 0 0 0 0 0 0 1

Rock bass 0 0 0 0 0 0 0 0 1 1 

Total 4,062 15,814 21,691 15,932 10,346 28,776 14,623 9,295 10,495 131,034

1

Percentage of total catch not listed if less than 0.1 percent.

2

Miscellanous site location.
136 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06 Table 30. Total numbers of fish by sampling site collected by the U.S. Geological Survey at sites on the main-stem Powder River, Montana, 2005–06. [Location of sampling sites shown in figure 1. n, number of sampling periods] Species Total numbers of fish Overall Percentage of total Site P12 (n=3) Site P13 (n=2) Site P17 (n=2) Site P18 (n=1) Count Percentage of total Count Percentage of total Count Percentage of total Count Percentage of total Sand shiner 315 29.7 598 42.0 647 47.8 8 11.8 1,568 40.2 Flathead chub 421 39.8 429 30.1 65 4.8 47 69.1 962 24.6 River carpsucker 122 11.5 43 3.0 373 27.6 1 1.5 539 13.8 Longnose dace 20 1.9 301 21.1 0 0 0 0 321 8.2 Channel catfish 139 13.1 10 .7 14 1.0 3 4.4 166 4.3 Western silvery minnow 1 .1 0 .0 98 7.2 0 0 99 2.5 Northern plains killifish 1 .1 34 2.4 57 4.2 0 0 92 2.4 Plains minnow 9 .8 4 .3 63 4.7 0 0 76 1.9 Sturgeon chub 4 .4 1 .1 20 1.5 3 4.4 28 .7 Goldeye 14 1.3 0 .0 1 .1 5 7.4 20 .5 Green sunfish 0 .0 4 .3 7 .5 0 0 11 .3 Stonecat 10 .9 0 0 0 0 0 0 10 .3 Common carp 1 .1 0 0 6 .4 0 0 7 .2 Fathead minnow 0 .0 0 0 2 .1 1 1.5 3 .1 Shorthead redhorse 2 .2 0 0 0 0 0 0 2 .1 Total 1,059 99.91 1,424 100.0 1,353 99.9 68 100.1 3,904 100.1

1Total percentage not equal to 100.0 due to rounding
Appendix 2. Supporting Data for Fish 137

Table 31. Larval fish collected by the Wyoming Game and Fish Department from eight sampling sites on the main-stem Powder River, Wyoming, 2004–05.—Continued[CKC, creek chub; CRP, common carp; FHC, flathead chub; PMN, plains minnow; LND, longnose dace; SDS, sand shiner; MTS, mountain sucker; RCS, river carpsucker; SHR, shorthead redhorse; WHS, white sucker; CCF, channel catfish; STC, stonecat; PKF, northern plains killifish]

Site 

number

(fig. 1)

Sample date

Number of fish collected

Total

CKC CRP FHC FHM PMN LND SDS MTS RCS SHR WHS CCF STC PKF

P1 06/07/2004 1 0 2 1 0 0 1 1 0 0 0 0 0 2 8

07/08/2004 0 0 7 0 0 0 52 0 0 0 0 0 0 0 5908/10/2004 0 0 0 0 1 0 3 0 0 0 0 0 0 0 409/09/2004 0 0 0 0 0 0 10 0 0 0 0 0 0 0 1010/13/2004 0 0 0 0 0 0 11 0 0 0 0 0 0 0 1107/20/2005 0 0 376 1 1 35 940 3 32 0 2 0 0 17 1,40708/12/2005 0 0 0 0 0 0 65 0 0 0 0 0 0 4 69

Total 1 0 385 2 2 35 1,082 4 32 0 2 0 0 23 1,568

P2 07/09/2004 0 0 258 0 0 13 505 34 0 0 3 0 0 1 814

09/08/2004 0 0 1 0 0 0 7 0 0 0 0 0 0 0 810/14/2004 0 0 0 0 0 0 1 0 0 0 0 0 0 1 205/09/2005 0 0 1 1 0 0 2 0 0 0 0 0 0 0 407/21/2005 0 0 25 0 0 1 36 22 5 0 0 0 0 5 9408/10/2005 0 0 0 0 0 0 1 0 0 0 0 0 0 0 108/11/2005 0 0 7 0 0 0 408 0 1 0 0 0 0 63 479

Total 0 0 292 1 0 14 960 56 6 0 3 0 0 70 1,402

P3 07/07/2004 0 0 1 2 0 0 6 0 0 0 0 0 0 0 9

08/09/2004 0 0 0 0 0 0 15 0 0 0 0 0 0 0 1510/12/2004 0 0 1 3 0 0 15 0 0 0 0 0 0 0 1907/19/2005 0 0 1 0 0 1 16 0 2 0 0 0 0 3 2308/10/2005 0 0 9 0 0 0 240 0 0 0 0 0 0 6 255

Total 0 0 12 5 0 1 292 0 2 0 0 0 0 9 321
138 Ecological Assessment of Streams in the Powder River Structural Basin, Wyoming and Montana, 2005–06 Table 31. Larval fish collected by the Wyoming Game and Fish Department from eight sampling sites on the main-stem Powder River, Wyoming, 2004–05.—Continued [CKC, creek chub; CRP, common carp; FHC, flathead chub; PMN, plains minnow; LND, longnose dace; SDS, sand shiner; MTS, mountain sucker; RCS, river carpsucker; SHR, shorthead redhorse; WHS, white sucker; CCF, channel catfish; STC, stonecat; PKF, northern plains killifish] Site number (fig. 1) Sample date Number of fish collected Total CKC CRP FHC FHM PMN LND SDS MTS RCS SHR WHS CCF STC PKF P4 07/13/2004 0 0 0 6 0 2 18 0 0 0 0 0 0 0 26 05/03/2005 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 08/19/2005 0 0 6 0 0 0 227 0 0 0 0 0 0 3 236 Total 0 0 7 6 0 2 245 0 0 0 0 0 0 3 263 P5 07/13/2004 0 0 1 0 0 0 16 0 0 0 0 0 0 3 20 07/23/2004 0 0 36 0 21 0 17 0 0 0 0 0 0 0 74 08/02/2004 0 2 4 17 0 0 282 0 14 0 0 0 0 3 322 09/08/2004 0 0 10 1 94 0 66 0 0 0 0 0 0 0 171 09/09/2004 0 0 10 1 250 0 62 0 0 0 0 0 0 0 323 10/11/2004 1 0 2 2 0 4 111 0 0 0 0 0 0 2 122 07/13/2005 0 0 71 6 0 1 5 0 2 0 0 0 0 0 85 07/23/2005 0 0 53 11 5 2 0 11 0 0 0 0 0 82 08/24/2005 0 0 0 1 1 0 55 0 0 0 0 0 0 0 57 Total 1 2 187 28 377 10 616 0 27 0 0 0 0 8 1,256 P8 06/04/2004 0 0 0 0 31 0 44 0 0 0 0 0 0 0 75 06/08/2004 0 0 0 0 1 0 66 0 0 0 0 0 0 0 67 07/06/2004 0 0 0 3 0 0 0 0 0 0 0 0 0 0 3 08/04/2004 0 0 2 0 3 0 19 0 0 0 0 0 0 0 24 08/31/2004 0 0 0 0 44 0 9 0 0 0 0 0 0 0 53 10/05/2004 0 0 2 2 25 0 105 0 0 0 0 0 0 0 134 05/02/2005 0 0 0 0 10 0 2 0 0 0 0 0 0 0 12 08/18/2005 0 0 99 1 33 17 21 0 0 0 0 0 0 0 172

Total 0 0 103 6 147 17 266 0 1 0 0 0 0 0 540
Appendix 2. Supporting Data for Fish 139

Table 31. Larval fish collected by the Wyoming Game and Fish Department from eight sampling sites on the main-stem Powder River, Wyoming, 2004–05.—Continued[CKC, creek chub; CRP, common carp; FHC, flathead chub; PMN, plains minnow; LND, longnose dace; SDS, sand shiner; MTS, mountain sucker; RCS, river carpsucker; SHR, shorthead redhorse; WHS, white sucker; CCF, channel catfish; STC, stonecat; PKF, northern plains killifish]

Site 

number

(fig. 1)

Sample date

Number of fish collected

Total

CKC CRP FHC FHM PMN LND SDS MTS RCS SHR WHS CCF STC PKF

P9 06/09/2004 0 0 1 0 0 0 21 0 0 0 0 0 0 0 22

07/07/2004 0 0 0 0 0 0 15 0 0 0 0 0 0 0 1508/05/2004 1 9 0 51 0 80 0 0 0 0 1 0 0 14208/08/2004 0 0 0 0 52 0 50 0 0 0 0 0 0 0 10208/31/2004 0 0 0 0 88 0 20 0 0 1 0 0 0 0 10910/04/2004 0 0 3 1 114 0 86 0 0 0 0 0 0 1 20507/24/2005 0 0 17 9 37 0 51 0 6 0 0 2 0 0 12208/17/2005 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1

Total 1 0 30 10 342 0 324 0 6 1 0 3 0 1 718

P11 06/10/2004 0 0 0 0 22 0 13 0 0 0 0 0 0 0 35

07/08/2004 0 0 26 0 1 0 34 0 0 0 0 0 0 0 6108/06/2004 0 0 52 1 65 0 168 0 0 0 0 0 1 0 28709/01/2004 0 0 0 0 96 0 24 0 0 0 0 0 0 0 12010/01/2004 0 0 0 0 1 0 0 0 0 0 0 0 0 0 110/06/2004 0 0 1 0 92 0 13 0 0 0 0 0 0 0 10605/05/2005 0 0 0 0 3 0 0 0 0 0 0 0 0 0 307/25/2005 0 0 25 6 14 0 12 0 5 0 3 0 0 0 6508/16/2005 0 0 39 2 5 0 33 0 20 0 0 0 0 1 100

 Total 0 0 143 9 299 0 297 0 25 0 3 0 1 1 778

Overall 3 2 1,159 67 1,167 79 4,082 60 99 1 8 3 1 115 6,846
Publishing support provided by:

Helena Publishing Service Center

For more information concerning this publication, contact:

Director, Wyoming Water Science Center

U.S. Geological Survey

2617 East Lincolnway Avenue, Suite B

Cheyenne, Wyoming 82001

(307) 778-2931

Or visit the Wyoming Water Science Center Web site at:

http://wy.water.usgs.gov
Otter Creek Creek at Ashland, Mont. (site T17), June 30, 2005. 

Photograph by John Tertuliani, U.S. Geological Survey.

Back cover photographs:

Little Powder River above Dry Creek, Wyo. 

(site P15), June 23, 2006. Photograph by Greg 

Boughton, U.S. Geological Survey.

Powder River below Mitchell Draw, Wyo. 

(site P5), July 28, 2006. Photograph by Greg 

Boughton, U.S. Geological Survey.

Hanging Woman Creek below Horse Creek, 

Wyo. (site T11), June 22, 2005. Photograph by 

Seth Davidson, U.S. Geological Survey.
Author—Spine Title—Scientific Investigations Report 2008–XXXX

Printed on recycled paper

Peterson and others—Ecological Assessment of Streams in the Powder River Structural Basin, Wyo. and Mont., 2005–06—SIR 2009–5023