Water-Quality, Bed-Sediment, and Biological Data

(October 2003 through September 2004) and 

Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana

In cooperation with the U.S. Environmental Protection Agency

Open-File Report 2005-1356

U.S. Department of the Interior

U.S. Geological Survey Printed on recycled paper Dodge and others - Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams in the Upper Clark Fork Basin, Montana Open-File Report 2005-1356

Processing suspended-sediment sample

Digesting fine-grained bed-sediment samples

Identifying aquatic insects
t samples in concentrated nitric acid to liberate

sis. Photograph by Michelle I. Hornberger,

h 11, 2005.

bed-sediment samples in concentrated nitric acid

s for analysis. Photograph by Michelle I. Hornberger, 

11, 2005.

diment sample through a sieve to determine the 

 than 0.062-millimeter diameter (silt size and

odge, U.S. Geological Survey, taken January 11, 2002.

e lowest taxonomic level (usually to species) under 

helle I. Hornberger, U.S. Geological Survey, taken 
Water-Quality, Bed-Sediment, and Biological Data

(October 2003 through September 2004) and 

Statistical Summaries of Data for Streams

in the Upper Clark Fork Basin, Montana

By Kent A. Dodge, Michelle I. Hornberger, and Jessica L. Dyke

U.S. Department of the Interior

U.S. Geological Survey

In cooperation with the 

U.S. Environmental Protection Agency

Open-File Report 2005-1356 
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2005

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For additional information write to:

Director, Montana Water Science Center

U.S. Geological Survey

3162 Bozeman Avenue

Helena, Montana 59601

World Wide Web: http://mt.water.usgs.gov/

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

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

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

endorsement by the U.S. Government.

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

reproduce any copyrighted materials contained within this report.

Suggested citation:

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2005, Water-quality, bed-sediment, and biological data (October 2003

through September 2004) and statistical summaries of data for streams in the upper Clark Fork basin, Montana: U.S.

Geological Survey Open-File Report 2005-1356, 124 p.
iii

Contents

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

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

Sampling Locations and Types of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Water-Quality Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Bed-Sediment Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Biological Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Statistical Summaries of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

References Cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure

1. Map showing location of study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Tables

1. Type and period of data collection at sampling sites in the upper Clark Fork basin, Montana . . . . . . . .4

2. Properties measured onsite and constituents analyzed in samples of water, bed sediment,

and biota from the upper Clark Fork basin, Montana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

3. Data-quality objectives for analyses of water-quality samples collected in the

upper Clark Fork basin, Montana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through

September 2004. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5-7. Daily mean streamflow and suspended-sediment data, October 2003 through September 2004, for:

5. Clark Fork at Deer Lodge, Montana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

6. Clark Fork at Turah Bridge, near Bonner, Montana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

7. Clark Fork above Missoula, Montana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

8. Analyses of field replicates for water samples, upper Clark Fork basin, Montana. . . . . . . . . . . . . . . . . . 60

9. Precision of analyses of field replicates for water samples, upper Clark Fork basin, Montana . . . . . 63

10. Precision of analyses of laboratory replicates for water samples, upper Clark Fork basin,

Montana. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

11. Recovery efficiency for analyses of laboratory-spiked deionized-water blanks. . . . . . . . . . . . . . . . . . . . 65

12. Recovery efficiency for analyses of laboratory-spiked stream samples, upper Clark Fork basin,

Montana. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

13. Analyses of field blanks for water samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
iv

14. Analyses of fine-grained bed sediment, upper Clark Fork basin, Montana, August 2004 . . . . . . . . . . . 68

15. Analyses of bulk bed sediment, upper Clark Fork basin, Montana, August 2004. . . . . . . . . . . . . . . . . . . . 69

16. Recovery efficiency for analyses of standard reference materials for bed sediment . . . . . . . . . . . . . . 70

17. Analyses of procedural blanks for bed sediment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

18. Analyses of biota, upper Clark Fork basin, Montana, August 2004 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

19. Recovery efficiency for analyses of standard reference material for biota . . . . . . . . . . . . . . . . . . . . . . . . 74

20. Analyses of procedural blanks for biota. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March

1985 through September 2004. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana,

August 1986 through August 2004. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana,

August 1993 through August 2004. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986

through August 2004 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Conversion Factors, Datum, Abbreviated WaterQuality Units, and Acronyms

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

 ̊F = (1.8 x  ̊C) + 32

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

(NGVD 29). Horizontal coordinate information is referenced to the North American Datum of 1927

(NAD 27).

Abbreviated water-quality units used in this report:

μg/g micrograms per gram

μg/L micrograms per liter

μg/mL micrograms per milliliter

μm micrometer

μS/cm microsiemens per centimeter at 25 degrees Celsius

mg/L milligrams per liter

Multiply By To obtain

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

foot (ft) 0.3048 meter (m)

gallon (gal) 3.785 liter (L)

gallon (gal) 3,785 milliliter (mL)

inch (in.) 25.4 millimeter (mm)

inch (in.) 25,400 micrometer (μm)

mile (mi) 1.609 kilometer (km)

ounce (oz) 28.35 gram (g)

part per million 1 microgram per gram (μg/g)

square mile (mi2) 2.59 square kilometer (km2)

ton per day (ton/d) 907.2 kilogram per day (kg/d)
v

Water-year definition:

A water year is the 12-month period from October 1 through September 30. It is designated by

the calendar year in which it ends.

Acronyms used in the report:

ICAPES inductively coupled argon plasma-emission

spectroscopy

RSD relative standard deviation

LRL laboratory reporting level SRM standard reference material

LT-MDL long-term method detection level USGS U.S. Geological Survey

NWQL USGS National Water Quality Laboratory,

Denver, Colo.

1U.S. Geological Survey, Menlo Park, Calif.

Water-Quality, Bed-Sediment, and Biological Data 

(October 2003 through September 2004) and

Statistical Summaries of Data for Streams

in the Upper Clark Fork Basin, Montana

By Kent A. Dodge, Michelle I. Hornberger1, and Jessica L. Dyke1

Abstract 

Water, bed sediment, and biota were sampled in streams 

from Butte to below Missoula as part of a program, conducted 

in cooperation with the U.S. Environmental Protection Agency, 

to characterize aquatic resources in the upper Clark Fork basin 

of western Montana. Sampling sites were located on the Clark 

Fork, five major tributaries, and three smaller tributaries. 

Water-quality samples were collected periodically at 17 sites 

during October 2003 through September 2004 (water year 

2004). Bed-sediment and biological samples were collected 

one time in August 2004. The primary constituents analyzed 

were trace elements associated with tailings from historical 

mining and smelting activities. This report summarizes the 

results of water-quality, bed-sediment, and biota samples collected in water year 2004 and provides statistical summaries of 

data collected since 1985.

Water-quality data for samples collected periodically from 

streams include concentrations of selected major ions, trace elements, and suspended sediment. Daily values of suspended-sediment concentration and suspended-sediment discharge were 

determined for three sites. Bed-sediment data include trace-element concentrations in the fine-grained and bulk fractions. Biological data include trace-element concentrations in wholebody tissue of aquatic benthic insects. Quality-assurance data 

are reported for analytical results of water, bed sediment, and 

biota. Statistical summaries of water-quality, bed-sediment, 

and biological data are provided for the period of record since 

1985 for each site.

Introduction

The Clark Fork originates near Warm Springs in western 

Montana at the confluence of Silver Bow and Warm Springs 

Creeks (fig. 1). Along the 148-mi reach of stream from Silver 

Bow Creek in Butte to the Clark Fork at Milltown Reservoir, 

five major tributaries enter: Warm Springs Creek, Little Blackfoot River, Flint Creek, Rock Creek, and Blackfoot River. Principal surface-water uses in the 6,000-mi2

 Clark Fork basin 

above Missoula include irrigation, stock watering, light industry, hydroelectric power generation, and habitat for trout fisheries. Current land uses primarily are cattle production, logging, 

mining, residential development, and recreation. Large-scale 

mining and smelting were prevalent land uses in the upper basin 

for more than one hundred years, but are now largely discontinued.

Deposits of copper, gold, silver, and lead ores were extensively mined, milled, and smelted in the drainages of Silver 

Bow and Warm Springs Creeks from about 1870 to 1980. Moderate- and small-scale mining also occurred in the basins of 

most of the major tributaries to the upper Clark Fork. Tailings 

derived from past mineral processing commonly contain large 

quantities of trace elements such as arsenic, cadmium, copper, 

lead, and zinc. Tailings have been eroded, mixed with stream 

sediment, transported downstream, and deposited in stream 

channels, on flood plains, and in the Warm Springs Ponds and 

Milltown Reservoir. The widely dispersed tailings continue to 

be re-eroded, transported, and redeposited along the stream 

channel and flood plain, especially during high flows. The 

occurrence of elevated trace-element concentrations in water 

and bed sediment can pose a potential risk to aquatic biota and 

human health.

Concern about the potential toxicity of trace elements to 

aquatic biota and human health has resulted in a comprehensive 

effort by State, Federal, and private entities to characterize the 

aquatic resources in the upper Clark Fork basin to guide and 

monitor remedial cleanup activities. A long-term data base was 

considered necessary to detect trends over time in order to evaluate the effectiveness of remediation. Water-quality data have 

been collected by the U.S. Geological Survey (USGS) at 

selected sites in the upper Clark Fork basin since 1985 (Lambing, 1987, 1988, 1989, 1990, 1991; Lambing and others, 1994, 

1995; and Dodge and others, 1996, 1997, 1998, 1999, 2000, 

2001, 2002, 2003, 2004). Trace-element data for bed sediment 

and biota (aquatic benthic insects) have been collected intermittently since 1986 at selected sites as part of studies on bed-sediment contamination and bioaccumulation of metals conducted 

by the USGS National Research Program (Axtmann and
2 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana

Mill Creek

Willow

Creek

Cr Silver

Bow

Opportunity

Figure 1. Location of study area.

Missoula

Butte

Anaconda

Opportunity

Galen

Warm Springs

Deer Lodge

Garrison

Goldcreek

Drummond

Bonner

Turah

Clinton

Milltown

Reservoir

Clark

Bitterroot

River

Blackfoot

River

Fork

Rock

Creek

Flint

Creek

Little

Blackfoot

River

DIVIDE

Clark Fork

Warm Springs

 Ponds

Warm Springs Creek

Silver

Bow

Creek

Blacktail

Cr

CONTINENTAL

47

Helena

Study area

M O N T A N A

Base modified from U.S. Geological 

Survey, State base map, 1:1,000,000, 

1966. North American Datum of 1927 

(NAD 27)

0 10 20 MILES

0 10 20 KILOMETERS

12353000 12340500

12340000

12334550

12334510

12331800

12331500

12324680

12324590

12324200

12323800

12323770 12323750

12323600

12323250

461903112440701

461559112443301

461415112450801

STREAMFLOW SITE TYPE

 Continuous record

 Periodic measurement

WATER QUALITY, BED SEDIMENT, 

AND BIOTA SITE TYPE

 Periodic-water quality

 Daily suspended sediment

 Once-annual bed sediment

 Once-annual biota

EXPLANATION

SITE NUMBER

461903112440701 MISCELLANEOUS SITE NUMBER

12324200

12323700

12323720

Lost Cr 12323850

o

46o

114o

113o

12323230

Racetrack
Sampling Locations and Types of Data 3

Luoma, 1991; Cain and others, 1992, 1995; Axtmann and others, 1997; Hornberger and others, 1997). In March 1993, an 

expanded sampling program for water, bed sediment, and biota 

was implemented by the USGS in cooperation with the U.S. 

Environmental Protection Agency to provide systematic, longterm monitoring to better quantify the seasonal and annual variability in selected constituents.

The purpose of this report is to present water-quality data 

for 17 sites and trace-element data for 15 bed-sediment and 15 

biological sites in the upper Clark Fork basin collected from 

October 2003 through September 2004 (water year 2004). 

Quality-assurance data are presented for water-quality, bedsediment, and biota samples. Statistical summaries also are 

provided for water-quality, bed-sediment, and biological data 

collected since 1985.

Sampling Locations and Types of Data

Sampling sites in the upper Clark Fork basin from Butte to 

below Missoula (fig. 1) are located on the Clark Fork mainstem, 

five major tributaries (Warm Springs Creek, Little Blackfoot 

River, Flint Creek, Rock Creek, and Blackfoot River), and three 

smaller tributaries (Mill Creek, Willow Creek, and Lost Creek). 

The sites, types of data collected, and period of record for each 

data type are listed in table 1. Mainstem sampling sites were 

selected to divide the upper Clark Fork into reaches of relatively 

uniform length, with each reach encompassing either a major 

tributary or depositional environment (Warm Springs Ponds 

and Milltown Reservoir). Major tributaries were sampled to 

describe water-quality, bed-sediment, and biological characteristics of important hydrologic sources in the upper basin and to 

provide reference comparisons to the mainstem. The three 

smaller tributaries were sampled to gain better spatial resolution 

on sources of metals entering the Clark Fork in an area of historical metal-processing activities near Anaconda. Water-quality data were obtained periodically at 17 sites; daily suspendedsediment data were obtained at 3 of these sites. Trace-element 

data for 15 bed-sediment and 15 biological sites were obtained 

once-annually. Continuous streamflow data were collected at 

18 sites.

A list of properties measured onsite and constituents analyzed in samples of water, bed sediment, and biota is given in 

table 2. Onsite measurements of properties, laboratory analyses 

of water, bed-sediment, and biota samples, and associated quality-assurance data for water year 2004 are listed in tables 4 

through 20 at the back of the report. Statistical summaries of 

water-quality, bed-sediment, and biological data collected 

between March 1985 and September 2004 are given in tables 

21-24 at the back of the report.

Quality assurance of data was maintained through the use 

of documented procedures designed to provide environmentally 

representative data. Acceptable performance of the procedures 

was verified with quality-control samples that were collected 

systematically to provide a measure of the accuracy, precision, 

and bias of the environmental data and to identify problems 

associated with sampling, processing, or analysis.

Water-Quality Data

Water-quality data consist of onsite measurements of 

selected stream properties and concentrations of chemical and 

physical constituents analyzed in periodically collected stream 

samples. At the 12 sites on the Clark Fork mainstem and 

smaller tributaries, samples were collected 8 times per year on 

a schedule designed to describe seasonal and hydrologic variability. At the five sites on the major tributaries, samples were 

collected 6 times during the water year. At the three daily suspended-sediment sites sampled during water year 2004 (table 

1), suspended-sediment samples were collected 2 to 9 times per 

week.

Methods

Water samples were collected from multiple verticals 

across the stream using depth- and width-integration methods 

described by Ward and Harr (1990), Edwards and Glysson 

(1999), and the USGS National Field Manual for the Collection 

of Water-Quality Data (variously dated). These methods provide a vertically and laterally discharge-weighted composite 

sample that is representative of the entire flow passing through 

the cross section of a stream. Sampling equipment consisted of 

standard USGS depth-integrating suspended-sediment samplers (DH-48, DH-81, and D-74TM), which were either constructed of plastic or coated with a non-metallic epoxy paint, 

and equipped with nylon or Teflon nozzles.

Instantaneous streamflow at the time of water sampling 

was determined at all sites, either by direct measurement or 

from stage-discharge rating tables (Rantz and others, 1982). 

Onsite measurements of specific conductance, pH, and water 

temperature were made during collection of periodic waterquality samples. Onsite sample processing, including filtration 

and preservation, was performed according to procedures 

described by Ward and Harr (1990), Horowitz and others 

(1994), and USGS (variously dated). 

Water samples were analyzed for the constituents listed in 

table 2. The terms “filtered” and “unfiltered recoverable” 

replace the terms “dissolved” and “total recoverable,” respectively, which were used in the past. The trace elements (arsenic, 

cadmium, copper, iron, lead, manganese, and zinc) were analyzed for filtered (0.45-μm pore size) and unfiltered recoverable 

concentrations by the USGS National Water Quality Laboratory (NWQL) in Denver, Colo. Calcium and magnesium also 

were determined in filtered samples to enable calculation of 

hardness. Filtered concentrations of arsenic, cadmium, copper, 

lead, manganese, and zinc were analyzed by inductively coupled plasma-mass spectrometry (Faires, 1993; Garbarino, 

1999). Filtered concentrations of calcium, magnesium, and iron 

were analyzed by inductively coupled plasma-atomic emission
4 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana

Table 1. Type and period of data collection at sampling sites in the upper Clark Fork basin, Montana. [Abbreviations: P, present. Symbol: --, no data]

Site

number 

(fig. 1)

Site name

Continuousrecord

streamflow

Periodic 

water quality1 Daily suspended sediment

Once annual

Fine-grained bed 

sediment2

Bulk bed 

sediment2 Biota2

12323230 Blacktail Creek at Harrison Avenue, at Butte -- 03/93-08/95,

 12/96-08/03

-- -- -- --

12323250 Silver Bow Creek below Blacktail Creek, at Butte 10/83-P 03/93-08/95,

 12/96-P

-- -- -- --

12323600 Silver Bow Creek at Opportunity 07/88-P 03/93-08/95,

 12/96-P

03/93-09/95 07/92-P 08/93-08/95,

 08/97-P

07/92, 08/94,

 08/95, 08/97-P

12323700 Mill Creek at Opportunity 04/03-P 03/03-P -- -- -- --

12323720 Willow Creek at Opportunity 04/03-P 03/03-P -- -- -- --

12323750 Silver Bow Creek at Warm Springs 03/72-09/79, 

04/93-P

03/93-P 04/93-09/95 07/92-P 08/93, 08/95-P 07/92-P

12323770 Warm Springs Creek at Warm Springs 10/83-P 03/93-P -- 08/95, 08/97, 08/99,

 08/02

08/95, 08/97, 08/99, 

08/02

08/95, 08/97, 

08/99, 08/02

12323800 Clark Fork near Galen 07/88-P 07/88-P -- 08/87, 08/91-P 08/93-P 08/87, 08/91-P

12323850 Lost Creek near Galen 04/03-P 03/03-P -- -- -- --

461415112450801 Clark Fork below Lost Creek, near Galen -- -- -- 08/96-P 08/96-P 08/96-P

461559112443301 Clark Fork near Racetrack -- -- -- 08/96-P 08/96-P 08/96-P

461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack -- -- -- 08/96-P 08/96-P 08/96-P

12324200 Clark Fork at Deer Lodge 10/78-P 03/85-P 03/85-08/86, 04/87-

03/03, 08/03-P

08/86, 08/87, 08/90-P 08/93-P 08/86, 08/87, 08/90-P

12324590 Little Blackfoot River near Garrison 10/72-P 03/85-P -- 08/86, 08/87, 08/94,

 08/98, 08/01, 08/04

08/94, 08/98, 08/01, 

08/04

08/87, 08/94, 08/98,

 08/01, 08/04

12324680 Clark Fork at Goldcreek 10/77-P 03/93-P -- 07/92-P 08/93-P 07/92-P

12331500 Flint Creek near Drummond 08/90-04/03, 

08/03-P

03/85-P -- 08/86, 08/89, 07/92-P 08/93-P 08/86, 07/92-P

12331800 Clark Fork near Drummond 04/93-P 03/93-P -- 08/86, 08/87, 08/91-P 08/93-P 08/86, 08/91-P

12334510 Rock Creek near Clinton 10/72-P 03/85-P -- 08/86, 08/87, 08/89,

 08/91-99, 08/01-P

08/93-99, 08/01-P 08/87, 08/91-99, 08/01-P

12334550 Clark Fork at Turah Bridge, near Bonner 03/85-P 03/85-P 03/85-03/03, 08/03-P 08/86, 08/91-P 08/93-P 08/86, 08/91-P12340000 Blackfoot River near Bonner 10/39-P 03/85-P 07/86-04/87, 06/88-

09/95

08/86, 08/87, 08/91,

 08/93-96, 08/98-01,

09/03

08/93, 08/94, 08/99-

01, 09/03

08/86, 08/87, 08/91, 08/93, 

08/96, 08/98, 09/00, 09/03

12340500 Clark Fork above Missoula 03/29-P 07/86-P3 07/86-04/87, 06/88-

01/96, 03/96-03/03, 

08/03-P

08/97-P 08/97-P 08/97-P

12353000 Clark Fork below Missoula4 10/29-P 03/85-09/95 -- 08/86, 08/90-P 08/93-P 08/86, 08/90-P

1Onsite measurements of stream properties and laboratory analyses of selected major ions, trace elements, and suspended sediment. Prior to March 1993, laboratory analyses included only trace elements and suspended sediment, with the 

exception of Clark Fork below Missoula. 2Laboratory analyses of trace elements.

3Prior to October 1989, water-quality data for Clark Fork above Missoula only included suspended-sediment data. 4Bed sediment and biota sampled about 30 miles downstream from streamflow-gaging station to conform to previous sampling location.
Water-Quality Data 5

Table 2. Properties measured onsite and constituents analyzed in samples of water, bed sediment, and biota from the

upper Clark Fork basin, Montana.

Water Bed Sediment Biota

Property Constituent Constituent Constituent

Streamflow Hardness (calculated) Arsenic Arsenic

Specific conductance Calcium Cadmium Cadmium

pH Magnesium Chromium Chromium

Temperature Arsenic Copper Copper

Cadmium Iron Iron

Copper Lead Lead

Iron Manganese Manganese

Lead Nickel Nickel

Manganese Silver Zinc

Zinc Zinc

Suspended sediment

spectrometry (Fishman, 1993). Unfiltered recoverable concentrations of trace elements were determined from unfiltered samples that were first digested with dilute hydrochloric acid 

(Hoffman and others, 1996) and then analyzed for arsenic by 

graphite furnace-atomic absorption spectrometry (Jones and 

Garbarino, 1999) and for cadmium, copper, iron, lead, manganese, and zinc by inductively coupled plasma-mass spectrometry (Garbarino and Struzeski, 1998). 

Water samples also were collected from multiple verticals 

for analysis of suspended sediment whenever periodic waterquality samples were collected. These samples were analyzed 

for suspended-sediment concentration and the percentage of 

suspended-sediment mass finer than 0.062-mm diameter (silt 

size and smaller) by the USGS Montana Water Science Center 

sediment laboratory in Helena, Mont., according to methods 

described by Guy (1969) and Lambing and Dodge (1993).

Suspended-sediment samples for the three daily suspended 

sediment sites were collected by local contract observers using 

the depth-integration method at a single vertical near midstream. The samples were analyzed for suspended-sediment 

concentration and were used to determine daily mean suspended-sediment concentrations according to methods 

described by Porterfield (1972).

Results

Water-quality data for samples collected periodically during water year 2004 are presented in table 4. Daily mean 

streamflow, daily mean suspended-sediment concentration, and 

daily suspended-sediment discharge for water year 2004 at the 

three daily suspended-sediment stations are reported in tables 5 

through 7, along with monthly summary statistics and annual 

totals for streamflow and sediment load.

Quality Assurance

Quality-assurance procedures used for the collection and 

field processing of water-quality samples are described by 

Ward and Harr (1990), Knapton and Nimick (1991), Horowitz 

and others (1994), Edwards and Glysson (1999), and USGS 

(variously dated). Standard procedures used by the NWQL for 

internal sample handling and quality assurance are described by 

Friedman and Erdmann (1982), Jones (1987), and Pritt and 

Raese (1995). Quality-assurance procedures used by the Science Center sediment laboratory are described by Lambing and 

Dodge (1993).

The quality of analytical results reported for water-quality 

samples was evaluated by quality-control samples that were 

submitted from the field and analyzed concurrently in the laboratory with routine samples. These quality-control samples 

consisted of replicates, spikes, and blanks which provide quantitative information on the precision and bias of the overall field 

and laboratory process. Each type of quality-control sample 

was submitted at a proportion equivalent to about 5 percent of 

the total number of water-quality samples. Therefore, the total 

number of quality-control samples represented about 15 percent 

of the total number of water-quality samples.

In addition to quality-control samples submitted from the 

field, internal quality-assurance practices at the NWQL are performed systematically to provide quality control of analytical 

procedures (Pritt and Raese, 1995). These internal practices 

include analyses of quality-control samples such as calibration 

standards, standard reference water samples, replicate samples, 

deionized-water blanks, or spiked samples at a proportion 

equivalent to at least 10 percent of the sample load. The 

NWQL participates in a blind-sample program where standard 

reference water samples prepared by the USGS Branch of Quality Systems are routinely inserted into the sample line for each 

analytical method at a frequency proportional to the sample 
6 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana

load. The laboratory also participates in external evaluation 

studies twice-yearly with the U.S. Environmental Protection 

Agency, the Canadian Center for Inland Water, and the USGS 

Branch of Quality Systems to assess analytical performance.

Replicate data can be obtained in different ways to provide 

an assessment of precision (reproducibility) of analytical 

results. Replicate samples are two or more samples considered 

to be essentially identical in composition. Replicate samples 

can be obtained in the field (field replicate) by either repeating 

the collection process to obtain two or more independent composite samples, or by splitting a single composite sample into 

two or more subsamples. The individual replicate samples are 

then analyzed separately. Likewise, a single sample can be analyzed two or more times in the laboratory to obtain a measure of 

analytical variability (laboratory replicate).

Precision of analytical results for field replicates is 

affected by numerous sources of variability within the field and 

laboratory environments, including sample collection, sample 

processing, and sample analysis. To provide data on precision 

for samples exposed to all sources of variability, replicate 

stream samples for chemical analysis were obtained in the field 

by splitting a composite stream sample, and replicate stream 

samples for suspended-sediment analysis were obtained in the 

field by concurrently collecting two independent cross-sectional samples. Analyses of these field replicates indicate the 

reproducibility of environmental data that are affected by the 

combined variability potentially introduced by field and laboratory processes.

Analytical precision was evaluated with laboratory replicates, which exclude field sources of variability. Two independent analyses were made of an individual sample selected randomly in the laboratory from the group of samples comprising 

each analytical run. A separate analysis of the sample was made 

at the beginning and end of each analytical run to provide information on the reproducibility of laboratory analytical results 

independent of possible variability caused by field collection 

and processing of samples.

Spiked samples are used to evaluate bias, which measures 

the ability of an analytical method to accurately quantify a 

known amount of analyte added to a sample. Because some 

constituents in stream water can potentially interfere with the 

analysis of a targeted analyte, it is important to determine 

whether such effects are causing biased (consistently high or 

low) results. Deionized-water blanks and aliquots of stream 

samples were spiked in the laboratory with known amounts of 

the same trace elements analyzed in water samples. Analyses 

of spiked blanks indicate if the spiking procedure and analytical 

method are within control for a water matrix that is presumably 

free of chemical interference. Analyses of spiked aliquots of 

stream samples indicate if the chemical matrix of the stream 

water interferes with the analytical measurement and whether 

these interferences could contribute significant bias to reported 

trace-element concentrations for stream samples.

Blank samples of deionized water were routinely analyzed 

to identify the presence and magnitude of contamination that 

potentially could bias analytical results. The particular type of 

blank sample routinely tested was a “field” blank. Field blanks 

are aliquots of deionized water that are certified as trace-element free and are processed through the sampling equipment 

used to collect stream samples. These blanks are then subjected 

to the same processing (sample splitting, filtration, preservation, transportation, and laboratory handling) as stream samples. Blank samples are analyzed for the same constituents as 

those of stream samples to identify whether any detectable concentrations exist.

All water samples were handled in accordance with chainof-custody procedures that provide documentation of sample 

identity, shipment, receipt, and laboratory handling. All routine 

and quality-control samples submitted from a sampling episode 

were stored in a secure area of the NWQL and analyzed as a discrete sample group, independent of other samples submitted to 

the NWQL. Therefore, the quality-control data apply solely to 

the analytical results for stream samples reported herein and 

provide a direct measure of data quality for this monitoring program.

Data-quality objectives (table 3) were established for 

water-quality data as part of the study plan for the expanded 

long-term monitoring program that was initiated in 1993. The 

objectives identify analytical requirements of detectability and 

serve as a guide for identifying questionable data by establishing acceptable limits for precision and bias of laboratory results. 

Comparisons of quality-control data to data-quality objectives 

are used to evaluate whether sampling and analytical procedures are producing environmentally representative data in a 

consistent manner. Data that did not meet the objectives were 

evaluated for acceptability. If necessary, additional quality-control samples were submitted and corrective action was taken.

The NWQL uses a statistically based convention for establishing minimum laboratory reporting levels for analytical 

results and for reporting low-concentration data (Childress and 

others, 1999). Quality-control data are collected by the NWQL 

on a continuing basis to determine long-term method detection 

levels (LT-MDLs) and laboratory reporting levels (LRLs). 

These values are re-evaluated each year and, consequently, can 

change from year to year. The methods are designed to limit the 

possible occurrence of a false positive or false negative error to 

1 percent or less. Accordingly, concentrations are reported as 

less than the LRL for samples in which the analyte was either 

not detected or did not pass identification criteria. Analytes that 

are detected at concentrations between the LT-MDL and LRL 

and that pass identification criteria are estimated. Estimated 

concentrations are noted with a remark code of "E." These data 

need to be used with the understanding that their uncertainty is 

greater than that of data reported without the "E" remark code.

The precision of analytical results for a constituent can be 

determined by estimating a standard deviation of the differences between replicate measurements for several sets of samples. These replicate measurements may consist either of individual analyses of a pair of samples considered to be essentially 

identical (field replicates) or multiple analyses of an individual 

sample (laboratory replicates). The differences in concentration between replicate analyses can be used to estimate a stan-
Water-Quality Data 7

dard deviation according to the following equation (Taylor, 

1987):

(1)

where

S = standard deviation of the difference in concentration between replicate analyses,

d = difference in concentration between each pair of 

replicate analyses, and

k = number of pairs of replicate analyses.

Precision also can be expressed as a relative standard deviation (RSD), in percent, which is computed from the standard 

deviation and the mean concentration for all the replicate analyses. Expressing precision relative to a mean concentration 

standardizes comparison of precision among individual constituents. The RSD, in percent, is calculated according to the following equation (Taylor, 1987):

(2)

where

RSD = relative standard deviation,

S = standard deviation, and

x = mean of all replicate concentrations.

Paired analyses of field replicates are presented in table 8. 

The precision estimated for each constituent based on these

S Σd2

2k --------=

RSD S

x = -- × 100

Table 3. Data-quality objectives for analyses of water-quality samples collected in

the upper Clark Fork basin, Montana.

[Abbreviations: μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. 

Symbol: --, not determined]

Constituent

Data-quality objectives

Detectability Precision Bias

Laboratory

reporting

level

Maximum relative 

standard deviation of 

laboratory replicate 

analyses,

 in percent

Maximum 

deviation of

spike recovery,

in percent

Calcium, filtered 0.01 mg/L 20 --

Magnesium, filtered .008 mg/L 20 --

Arsenic, filtered .2 μg/L 20 25

Arsenic, unfiltered recoverable 2 μg/L 20 25

Cadmium, filtered .04 μg/L 20 25

Cadmium, unfiltered recoverable .04 μg/L 20 25

Copper, filtered .4 μg/L 20 25

Copper, unfiltered recoverable .6 μg/L 20 25

Iron, filtered 6 μg/L 20 25

Iron, unfiltered recoverable 9 μg/L 20 25

Lead, filtered .08 μg/L 20 25

Lead, unfiltered recoverable .06 μg/L 20 25

Manganese, filtered .2 μg/L 20 25

Manganese, unfiltered recoverable .2 μg/L 20 25

Zinc, filtered .6 μg/L 20 25

Zinc, unfiltered recoverable 2 μg/L 20 25

Sediment, suspended, percent finer than 0.062 mm 1 percent -- --

Sediment, suspended 1 mg/L -- --
8 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana

Spike recovery, in percent spiked sample concentration unspiked sample concentration –

spike concentration = ---------------------------------------------------------------------------------------------------------------------------------------------------- × 100 (3)

paired results, which include both field and laboratory sources 

of variability, is reported in table 9. Data-quality objectives for 

precision are not directly applicable to field replicates because 

of the inability to determine whether the variability results from 

field sample collection and processing, or laboratory handling 

and analysis. However, the precision for field replicate analyses is calculated to illustrate overall reproducibility of environmental data that incorporates both field and laboratory sources 

of variability. The data-quality objective used to indicate 

acceptable precision of results for field replicates was a maximum relative standard deviation of 20 percent (table 3). Precision estimates for field replicate analyses were within the 20-

percent relative standard deviation limit for all constituents 

(table 9).

Analytical precision for chemical constituents based on 

laboratory replicate analyses of individual samples, which 

includes only laboratory sources of variability, is reported in 

table 10. Statistics for analytical precision of laboratory-replicate analyses are based on unrounded values stored in laboratory data files. The data-quality objective for analytical precision of laboratory-replicate analyses was a maximum relative 

standard deviation of 20 percent (table 3). Precision estimates 

for laboratory-replicate analyses were less than the 20-percent 

relative standard deviation limit for all constituents (table 10); 

thus, the data-quality objectives for precision were met. Recovery efficiency for analyses of constituents is determined by 

analyses of an unspiked sample and a spiked aliquot of the same 

sample. The data-quality objective for acceptable spike recovery of trace elements in water samples was a maximum deviation of 25 percent from a theoretical 100-percent recovery of 

added constituent (table 3). At the laboratory, a spiked deionized-water blank and a spiked aliquot of a stream sample were 

prepared and analyzed along with the original unspiked sample. 

The differences between the spiked and unspiked sample concentrations were determined and used to compute recovery, in 

percent, according to equation 3 below.

If the spike recovery for a trace element was outside a 

range of 75 to 125 percent, the instrument was recalibrated and 

the entire sample set and spiked samples were reanalyzed for 

that particular trace element until recoveries were improved to 

the extent possible. Results of recovery efficiency for individual trace elements in spiked deionized-water blanks and spiked 

stream samples are presented in tables 11 and 12, respectively. 

The mean spike recovery for deionized-water samples spiked 

with trace elements (table 11) ranged from 96.0 to 102 percent. 

The 95-percent confidence intervals (Taylor, 1987) for the 

mean spike recovery for each constituent analyzed in deionized-water samples (table 11) did not exceed a 25-percent deviation from an expected 100-percent recovery, except for filtered 

arsenic (75.0-127). No adjustments were made to filtered 

arsenic analytical results because this minor exceedance was 

only 2 percent over the 25-percent spike recovery limit and the 

mean spike recovery (101 percent) was very good. The mean 

spike recovery for spiked stream samples (table 12) ranged 

from 93.8 to 112 percent. The 95-percent confidence intervals 

for the mean of spike recovery for each constituent analyzed in 

stream samples (table 12) did not exceed a 25-percent deviation 

from an expected 100-percent recovery, except for filtered iron 

(91.2-130 percent). No adjustments were made to the analytical 

results for filtered iron because this minor exceedance was only 

5 percent over the 25-percent spike recovery limit and the mean 

spike recovery (111 percent) was acceptable.

High or low bias is indicated if the confidence interval 

does not include 100 percent recovery, thereby indicating a consistent deviation in one direction. All laboratory-spiked deionized-water blank samples (table 11) had confidence intervals 

for percent recovery that included 100 percent, except filtered 

cadmium (95.6-99.2 percent). The 95-percent confidence intervals for percent recovery in all laboratory-spiked stream samples (table 12) included 100 percent, except unfiltered recoverable arsenic (106-118), filtered copper (93.8-97.0), unfiltered 

recoverable copper (89.5-98.1), and unfiltered recoverable zinc 

(91.0-97.8) percent. In most instances, the indicated biases for 

these four constituents were small. Both the 95-percent confidence interval (106-118) and mean (112) percent recoveries for 

unfiltered recoverable arsenic in laboratory-spiked stream samples indicate a persistent, moderate bias. In contrast, the 95-percent confidence interval (93.6-110) and mean (102) percent 

recoveries for unfiltered recoverable arsenic in laboratoryspiked deionized water blanks indicate no bias. Thus, it appears 

that the moderate bias is not necessarily caused by the analytical 

method, but might be a result of analytical interference from the 

chemical matrix of the stream samples. Because the mean spike 

recoveries for all constituents met data-quality objectives, no 

adjustments were made to analytical results for stream samples 

on the basis of spike recoveries.

Analytical results for field blanks are presented in table 13. 

A field blank with constituent concentrations equal to or less 

than the LRL for the analytical method indicates that the entire 

process of sample collection, field processing, and laboratory 

analysis is presumably free of significant contamination. If 

detectable concentrations in field blanks were equal to or 

greater than twice the LRL (which has a measurement precision 

generally equal to twice the LT-MDL), the concentrations were 

noted during data review. Analytical results from the field 

blank for the next sample set were evaluated for a consistent 

trend that may indicate systematic contamination. Sporadic, 

infrequent exceedances of twice the LRL probably represent 

random contamination or instrument calibration error that is not 

persistent in the process and which is not likely to cause significant positive bias in a long-term record of analytical results. 

However, if concentrations for a particular constituent 
Bed-Sediment Data 9

exceeded twice the LRL in field blanks from two consecutive 

field trips, blank samples were collected from individual components of the processing sequence and were submitted for 

analysis in order to identify the source of contamination.

Trace-element concentrations in field blanks were almost 

always less than the LRL. Only one blank had a concentration 

of filtered cadmium (0.07 μg/L) that was greater than the LRL 

of 0.04 μg/L. This sample was collected through a D-74TM 

sampler, which produced results less than the LRL for all of the 

other trace elements. No adjustments were made to water-quality sample results based on this single minor detection. 

Bed-Sediment Data

Bed-sediment data consist of analyses of trace-element 

concentrations in the fine-grained and bulk (fine-grained plus 

coarse-grained) fractions of the bed-sediment sample. Bed-sediment samples were collected once-annually during low, stable 

flow conditions and the same season (typically August) as previous samples to facilitate data comparisons among years.

Methods

Bed-sediment samples were collected in August 2004 

using protocols described by E.V. Axtmann (U.S. Geological 

Survey, written commun., 1994). Samples were collected from 

the surfaces of streambed deposits in low-velocity areas near 

the edge of the stream using an acid-washed polypropylene 

scoop. Whenever possible, samples were collected from both 

sides of the stream. Three composite samples of fine-grained 

bed sediment and one composite sample of bulk bed sediment 

were collected at each site.

Individual samples of fine-grained bed sediment were collected by scooping material from the surfaces of three to five 

randomly selected deposits along pool or low-velocity areas. 

The three to five individual samples were combined to form a 

single composite sample. This collection process was repeated 

three times to obtain three composite samples. Each composite 

sample was wet-sieved onsite through a 0.064-mm nylon-mesh 

sieve using ambient stream water. The fraction of bed sediment 

in each composite sample that was finer than 0.064 mm was 

transferred to an acid-washed 500-mL polyethylene bottle and 

transported to the laboratory on ice.

Individual samples of bulk bed sediment also were collected by scooping material from the surfaces of three to five 

randomly selected deposits along pool or low-velocity areas. 

The individual unsieved samples were composited into an acidwashed polyethylene bottle to form a single composite sample, 

each of which were then transported to the laboratory on ice. 

Because the streambed at most sampling locations is predominantly gravel and cobble, deposits were selected where gravel 

and cobble could be excluded from the samples. Generally, 

bulk bed-sediment samples were composed of particles smaller 

than about 10 mm in diameter.

Bed-sediment samples were processed and analyzed at the 

USGS National Research Program laboratory in Menlo Park, 

Calif. Fine-grained and bulk bed-sediment samples were ovendried at 60oC and ground using an acid-washed ceramic mortar 

and pestle. Single aliquots of approximately 0.6 g of sediment 

from each of the three composite fine-grained bed-sediment 

samples were digested using a hot, concentrated, nitric acid 

reflux according to methods described by Luoma and Bryan 

(1981). An additional aliquot was analyzed from one of the 

sieved replicate samples at each station. A single aliquot was 

similarly digested from the composite bulk sediment sample. 

After a digestion period of up to two weeks, the aliquots were 

evaporated to dryness on a hot plate. The dry residue was 

reconstituted in 10 mL of 0.6N (normal) hydrochloric acid. The 

reconstituted aliquots then were filtered through a 0.45-μm filter using a syringe and in-line disposable filter cartridge. The 

filtrate was diluted to a 1:5, 1:10, or 1:20 ratio with 0.6N hydrochloric acid. These final solutions were analyzed for arsenic, 

cadmium, chromium, copper, iron, lead, manganese, nickel, 

and zinc using inductively coupled argon plasma-emission 

spectroscopy (ICAPES). The smallest concentration of a constituent that can be reliably reported for a given analytical 

method is termed the minimum reporting level.

Results

Concentrations of trace elements measured in samples of 

fine-grained and bulk bed sediment collected during August 

2004 are summarized in tables 14 and 15, respectively. Liquidphase concentrations, in μg/mL, that were analyzed in the 

reconstituted aliquots of digested bed sediment were converted 

to solid-phase concentrations, in μg/g, using the following 

equation:

 μg/g = (4)

The reported solid-phase concentrations in tables 14 and 

15 are the mean of all analyses for replicate aliquots from each

composite sample collected at the site. Because the conversion 

from liquid-phase to solid-phase concentration is dependent on 

both the dilution ratio and the dry weight of the sample, minimum reporting levels for some trace elements might differ 

among stations and among years.

Quality Assurance

The protocols for field collection and processing of bedsediment samples are designed to prevent contamination from 

metal sources. Non-metallic sampling and processing equipment was acid-washed and rinsed with deionized water prior to 

the first sample collection. Nylon-mesh sieves were washed in 

a laboratory-grade detergent and rinsed with deionized water. 

All equipment received a final rinse onsite with stream water. 

μg/mL volume of digested sample, in mL ×

dry weight of sample, in g dilution ratio × ----------------------------------------------------------------------------------------------------------
10 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana

Sampling equipment used at more than one site was rinsed 

between sites with 10-percent nitric acid, deionized water, and 

stream water. Separate sieves were used at each site and, therefore, did not require between-site cleaning. Bed-sediment samples were collected sequentially at sites along an increasing 

concentration gradient to minimize effects from potential siteto-site carryover contamination.

Quality assurance of analytical results for bed-sediment 

samples included laboratory instrument calibration with standard solutions and analysis of quality-control samples designed 

to identify the presence and magnitude of bias (E.V. Axtmann, 

U.S. Geological Survey, written commun., 1994). Qualitycontrol samples consisted of standard reference materials and 

procedural blanks. Each type of quality-control sample was 

analyzed in a proportion equivalent to about 10 percent of the 

total number of bed-sediment samples.

Standard reference materials (SRMs) are commercially 

prepared materials that have certified concentrations of trace 

elements. Analyses of SRMs are used to indicate the ability of 

the method to accurately measure a known quantity of a constituent. Multiple analyses of the SRMs are made to derive a mean 

and 95-percent confidence interval for recovery. Recovery efficiency for trace-element analyses of SRMs for bed sediment is 

summarized in table 16. Two SRMs consisting of agricultural 

soils representing low and high concentrations of trace elements 

were analyzed to test recovery efficiency for a range of concentrations generally similar to those occurring in the bed sediment 

of streams in the upper Clark Fork basin. The digestion process 

used to analyze bed-sediment samples is not a “total” digestion 

(does not liberate elements associated with crystalline lattices); 

therefore, 100-percent recovery may not be achieved for elements strongly bound to the sediment. The percent recovery of 

trace elements for SRM analyses that use less than a total digestion is useful to indicate which trace elements display strong 

sediment-binding characteristics in the SRM and whether analytical recovery is consistent between multiple sets of analyses.

Although data-quality objectives have not been established for bed sediment, percent recoveries for individual trace 

elements shown in table 16 illustrate analytical performance. 

Mean SRM recoveries for the low-concentration standard 

(SRM 2709) ranged from 83.7 to 98.6 percent of the certified 

concentrations for cadmium, iron, lead, manganese, nickel, and 

zinc. Mean recoveries were lower for arsenic, chromium, and 

copper (63.0, 66.7, and 71.2 percent, respectively). Percent 

recoveries for arsenic, cadmium, copper, iron, lead, manganese, 

and zinc in the high-concentration standard (SRM 2711) ranged 

from 83.3 to 95.9 percent of the certified concentration. Chromium and nickel had lower recoveries (56.5 and 75.7 percent, 

respectively) for the high-concentration SRM, possibly due to 

the strong binding nature of these elements to sediment. The 

generally small range of variation (less than 10 percent for most 

constituents) for the 95-percent confidence interval indicates 

good reproducibility of multiple analyses of the SRMs. No 

adjustments were made to trace-element concentrations in bedsediment samples on the basis of recovery efficiencies.

Procedural blanks for bed-sediment samples consisted of 

the same reagents used for sample digestion and reconstitution. 

Concentrated nitric acid used for sample digestion was heated 

and evaporated to dryness. After evaporation, 0.6N hydrochloric acid was added to the dry residue. Procedural blanks, therefore, represent the same chemical matrix and exposure to analytical materials and handling as the reagents used to digest and 

reconstitute bed-sediment samples. Analytical results of procedural blanks for bed sediment (table 17) are reported as a liquidphase concentration, in μg/mL, which is equivalent to parts per 

million. A procedural blank was prepared and analyzed concurrently with bed-sediment samples for each site. Concentrations of trace elements in all procedural blanks were below the 

minimum reporting level; thus, no contamination bias was indicated and no adjustments to the data were necessary.

Biological Data

Biological data consist of analyses of trace-element concentrations in the whole-body tissue of aquatic benthic insects. 

Insect samples were collected once-annually at the same sites 

and dates as bed-sediment samples (table 1), allowing for a 

direct comparison of biological data with bed-sediment data 

among the years.

Methods

Insect samples were collected using protocols described in 

Hornberger and others (1997). Immature stages of benthic 

insects were collected using a large nylon-mesh kick net. A single riffle at each station was sampled repeatedly until an adequate number of individual insects were collected to provide 

sufficient mass for analysis. Targeted taxa for collection were 

the Order Trichoptera (caddisflies) and the Order Plecoptera 

(stoneflies).

Two caddisfly species of the genus Hydropsyche were targeted for collection in this study due to their occurrence at most, 

but not all, sites: Hydropsyche cockerelli and Hydropsyche 

occidentalis. In a few instances, Hydropsyche tana were collected. Hydropsyche species that could not be positively identified were considered to belong to the morosa group and are 

categorized as Hydropsyche spp. or Hydropsyche morosa group 

(in previous reports). The caddisfly Arctopsyche grandis and 

the stonefly Claasenia sabulosa were collected where available 

to represent additional insect taxa that are commonly distributed in the upper Clark Fork basin. In addition, the caddisfly 

group Brachycentrus spp. was sometimes collected when targeted taxa were not available.

Samples of each taxon were sorted by genus in the field 

and placed in acid-washed plastic containers. Samples were 

frozen on dry ice within 30 minutes of collection in a small 

amount of ambient stream water. Between 1986 and 1998, 

macroinvertebrate containers were kept on ice to allow the 

insects to evacuate their gut contents for a period of 6 to 8 hours. 
Statistical Summaries of Data 11

Excess water was drained and insects were frozen for transport 

to the laboratory. In order to reduce the possibility of metal loss 

through intracellular breakdown during depuration, samples 

were frozen on dry ice in the field between 1999 and 2004. A 

comparison of immediately frozen versus depurated samples 

showed that while no significant difference occurred for most 

metals, concentrations of copper in the depurated macroinvertebrate samples were about 20 percent lower than those which 

were immediately frozen. The data were not adjusted for this 

difference.

Insect samples were processed and analyzed at the USGS 

National Research Program laboratory in Menlo Park, Calif. 

Insects were thawed and rinsed with ultra-pure deionized water 

to remove particulate matter and then sorted to their lowest possible taxonomic level. If large numbers of specimens had been 

collected at a site, similar-sized individuals were composited 

into replicate subsamples. Subsamples were placed in tared 

scintillation vials and oven-dried at 70οC. Subsamples were 

weighed to obtain a final dry weight and digested by reflux 

using concentrated nitric acid (Cain and others, 1992). After 

digestion, insect samples were evaporated to dryness on a hot 

plate. The dry residue was reconstituted in 0.6N hydrochloric 

acid, filtered through a 0.45-μm filter, and analyzed undiluted 

by ICAPES for arsenic, cadmium, chromium, copper, iron, 

lead, manganese, nickel, and zinc. The smallest concentration 

of a constituent that can be reliably reported for a given analytical method is termed the minimum reporting level.

Results

Concentrations of trace elements in whole-body tissue of 

aquatic insects collected during August 2004 are summarized in 

table 18. The variability in the number of composite samples 

among species and among sites reflects differences in insect 

abundance, with the number of composite samples increasing 

with the relative abundance of insects. Liquid-phase concentrations analyzed in the reconstituted samples were converted to 

solid-phase concentrations using equation 4. As with bed sediment, minimum reporting levels may differ among sites as a 

result of variable sample weights. In general, the smaller the 

biological sample weight (a function of insect abundance), the 

higher the minimum reporting level. Therefore, higher minimum reporting levels do not necessarily imply a higher traceelement concentration in tissue.

Quality Assurance

The protocols for field collection and processing of biota 

samples are designed to prevent contamination from metal 

sources. Non-metallic nets, sampling equipment, and processing equipment were employed in all sample collection. Equipment was acid-washed and rinsed in ultra-pure deionized water 

prior to the first sample collection. Nets and equipment were 

thoroughly rinsed in ambient stream water at each new mainstem site. New nets were used for all tributary sites. Biota samples were collected sequentially at sites along an increasing 

concentration gradient to minimize effects from potential siteto-site carryover contamination.

Quality assurance of analytical results for biota samples 

included laboratory instrument calibration with standard solutions and analyses of quality-control samples designed to quantify precision and to identify the presence and magnitude of 

bias. Quality-control samples consisted of a SRM and procedural blanks. Each type of quality-control sample was analyzed 

in a proportion equivalent to about 10 to 20 percent of the total 

number of biota samples.

Recovery efficiency for trace-element analyses of the 

SRM for biota is summarized in table 19. The reference material tested was lobster hepatopancreas. Data-quality objectives 

have not been established for analytical recovery in biota, but 

percent recoveries are shown to illustrate analytical performance. Mean SRM recoveries ranged from 92.1 to 106 percent 

of the certified concentrations for arsenic, cadmium, chromium, 

copper, iron, manganese, and zinc. Lower mean recoveries 

were measured for nickel (82.5 percent) and lead (70.4 percent). 

The low mean recovery for lead was attributed to the low certified concentration in the SRM, resulting in 6 of the 12 analyses 

having concentrations less than the minimum reporting level. 

With the exception of chromium and lead, both of which had 

low certified concentrations in the SRM, the range of variation 

generally was small (less than about 10 percent) for the 95-percent confidence interval, thereby indicating good reproducibility of multiple analyses of the SRM. No adjustments were made 

to trace-element concentrations in biota samples on the basis of 

recovery efficiencies.

Procedural blanks for biota consisted of the same reagents 

used to digest and reconstitute tissue of aquatic insects and were 

analyzed undiluted. Analytical results of procedural blanks for 

biota (table 20) are reported as a liquid-phase concentration, in

μg/mL, which is equivalent to parts per million. A procedural 

blank was prepared and analyzed concurrently with biota samples for each site. Concentrations of trace elements in all procedural blanks were less than the minimum reporting level; 

thus, no contamination bias was indicated and no adjustments to 

the data were necessary. 

Statistical Summaries of Data

Statistical summaries of water-quality, bed-sediment, and 

biological data are provided in tables 21-24 for the period of 

record at each site since 1985. The summaries include the 

period of record, number of samples, and maximum, minimum, 

mean, and median concentrations.

Statistical summaries of water-quality data (table 21) are 

based on results of cross-sectional samples collected periodically by the USGS during the period of record for each site. The 

summaries do not include data for supplemental single-vertical 

samples collected during several years by a contract observer at 

Clark Fork at Turah Bridge, near Bonner; Blackfoot River near 
12 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana

Bonner; and Clark Fork above Missoula. Inclusion of results 

for supplemental samples that targeted high-flow conditions or 

maintenance drawdowns of Milltown Reservoir would disproportionately skew the long-term statistics at these three sites relative to the other sites in the network. Statistical summaries of 

fine-grained and bulk bed-sediment (tables 22 and 23, respectively) and biological data (table 24) are based on results of 

samples collected once-annually during the indicated years. 

Because not all sites were sampled for bed sediment and biota 

every year, the data for some sites do not represent a consecutive annual record.

Statistics for bed-sediment data (tables 22 and 23) are 

based on the mean trace-element concentrations determined for 

each year from the averaged results of analyses of composite 

samples. Therefore, the number of samples for bed sediment 

represents the number of years that the constituent was analyzed. In contrast, statistics for biological data (table 24) are 

based on individual analyses for each composite sample collected, rather than on a single mean concentration for each year. 

Also, the number of samples for arsenic for both bed sediment 

and biota is smaller than the other trace elements because it was 

only recently (2003) included for analysis. 

Differences in the number of biota composite samples 

among species reflect differences in species abundance, both 

within and between sites and among years. As a result, the statistics for biota describe a wider range of variation in traceelement concentrations than would be evident if results from 

individual composite samples were averaged. The abundance 

of aquatic insects at a particular site in a given year limits the 

biomass of the sample which, in turn, may result in variable 

minimum reporting levels. Where minimum reporting levels 

vary among years, differences in concentration over time are 

difficult to determine, especially when a large percentage of the 

samples have concentrations less than minimum reporting levels.

The presence or absence of insect species at a given site 

can vary among years and may result in different taxa being 

analyzed in the long-term period of record. Because Hydropsyche insects were not sorted to the species level during 1986-

89, statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some 

sites, statistics for the Hydropsyche morosa group are based on 

the combined results for two or more species because these 

samples could not be clearly identified to the species level, but 

the individual insects had morosa characteristics.

References Cited

Axtmann, E.V., Cain, D.J., and Luoma, S.N., 1997, Effect of 

tributary inflows on the distribution of trace metals in finegrained sediment and benthic insects of the Clark Fork River, 

Montana: Environmental Science and Technology, v. 31, no. 

3, p. 750-758.

Axtmann, E.V., and Luoma, S.N., 1991, Large scale distribution of metal contamination in the fine-grained sediment of 

the Clark Fork River, Montana: Applied Geochemistry, v. 6, 

no. 6, p. 75-88.

Cain, D.J., Luoma, S.N., and Axtmann, E.V., 1995, Influence of 

gut content in immature aquatic insects on assessments of

environmental metal contamination: Canadian Journal of 

Fisheries and Aquatic Sciences, v. 52, no. 12, p. 2736-2746.

Cain, D.J., Luoma, S.N., Carter, J.L., and Ferd, S.V., 1992, 

Aquatic insects as bioindicators of trace element contamination in cobble-bottom rivers and streams: Canadian Journal 

of Fisheries and Aquatic Sciences, v. 49, no. 10, p. 2141-

2154.

Childress, C.T., Foreman, W.T., Connor, B.F., and Maloney, 

T.J., 1999, New reporting procedures based on long-term 

method detection levels and some considerations for interpretations of water-quality data provided by the U.S. Geological Survey National Water Quality Laboratory: U.S. Geological Survey Open-File Report 99-193, 19 p.

Dodge, K.A., Hornberger, M.I., and Axtmann, E.V., 1996, 

Water-quality, bed-sediment, and biological data (October 

1994 through September 1995) and statistical summaries of 

data for streams in the upper Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 96-432, 109 p.

Dodge, K.A., Hornberger, M.I., and Axtmann, E.V., 1997, 

Water-quality, bed-sediment, and biological data (October 

1995 through September 1996) and statistical summaries of 

data for streams in the upper Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 97-552, 91 p.

Dodge, K.A., Hornberger, M.I., and Axtmann, E.V., 1998, 

Water-quality, bed-sediment, and biological data (October 

1996 through September 1997) and statistical summaries of 

data for streams in the upper Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 98-407, 102 p.

Dodge, K.A., Hornberger, M.I., and Bouse, R.M., 1999, Waterquality, bed-sediment, and biological data (October 1997 

through September 1998) and statistical summaries of data 

for streams in the upper Clark Fork basin, Montana: U.S. 

Geological Survey Open-File Report 99-251, 102 p.

Dodge, K.A., Hornberger, M.I., and David, C.P.C., 2000, 

Water-quality, bed-sediment, and biological data (October 

1998 through September 1999) and statistical summaries of 

data for streams in the upper Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 00-370, 102 p.

Dodge, K.A., Hornberger, M.I., and David, C.P.C., 2001, 

Water-quality, bed-sediment, and biological data (October 

1999 through September 2000) and statistical summaries of 

data for streams in the upper Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 01-379, 95 p.

Dodge, K.A., Hornberger, M.I., and David, C.P.C., 2002, 

Water-quality, bed-sediment, and biological data (October 

2000 through September 2001) and statistical summaries of 

data for streams in the upper Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 02-358, 94 p.

Dodge, K.A., Hornberger, M.I., and Lavigne, I.R., 2003, Waterquality, bed-sediment, and biological data (October 2001 
References Cited 13

through September 2002) and statistical summaries of data 

for streams in the upper Clark Fork basin, Montana: U.S. 

Geological Survey Open-File Report 03-356, 95 p.

Dodge, K.A., Hornberger, M.I., and Lavigne, I.R., 2004, Waterquality, bed-sediment, and biological data (October 2002 

through September 2003) and statistical summaries of data 

for streams in the upper Clark Fork basin, Montana: U.S. 

Geological Survey Open-File Report 2004-1340, 107 p.

Edwards, T.K., and Glysson, G.D., 1999, Field methods for 

measurement of fluvial sediment: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, chap. 

C2, 89 p. [Available online at http://water.usgs.gov/pubs/

twri.]

Faires, L.M., 1993, Methods of analysis by the U.S. Geological 

Survey National Water Quality Laboratory—Determination 

of metals in water by inductively coupled plasma-mass spectrometry: U.S. Geological Survey Open-File Report 92-634, 

28 p. 

Fishman, M.J., ed., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and 

fluvial sediments: U.S. Geological Survey Open-File Report 

93-125, 217 p.

Friedman, L.C., and Erdmann, D.E., 1982, Quality assurance 

practices for the chemical and biological analyses of water 

and fluvial sediments: U.S. Geological Survey Techniques 

of Water-Resources Investigations, book 5, chap. A6, 181 p. 

[Available online at http://water.usgs.gov/pubs/twri.]

Garbarino, J.R., 1999, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of dissolved arsenic, boron, lithium, selenium, strontium, thallium, and vanadium using inductively coupled 

plasma-mass spectrometry: U.S. Geological Survey OpenFile Report 99-093, 31 p.

Garbarino, J.R., and Struzeski, T.M., 1998, Methods of analysis 

by the U.S. Geological Survey National Water Quality Laboratory—Determination of elements in whole-water digests 

using inductively coupled plasma-optical emission spectrometry and inductively coupled plasma-mass spectrometry: 

U.S. Geological Survey Open-File Report 98-165, 101 p.

Guy, H.P., 1969, Laboratory theory and methods for sediment 

analysis: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. C1, 58 p. [Available 

online at http://water.usgs.gov/pubs/twri.]

Helsel, D.R., and Cohn, T.A., 1988, Estimation of descriptive 

statistics for multiply censored water quality data: Water 

Resources Research, v. 24, no. 12, p. 1997-2004.

Hoffman, G.L., Fishman, M.J., and Garbarino, J.R., 1996, 

Methods of analysis by the U.S. Geological Survey National 

Water Quality Laboratory—In-bottle acid digestion of 

whole-water samples: U.S. Geological Survey Open-File 

Report 96-225, 28 p.

Hornberger, M.I., Lambing, J.H., Luoma, S.N., and Axtmann, 

E.V., 1997, Spatial and temporal trends of trace metals in surface water, bed sediment, and biota of the upper Clark Fork 

basin, Montana, 1985-95: U.S. Geological Survey Open-File 

Report 97-669, 84 p.

Horowitz, A.J., Demas, C.R., Fitzgerald, K.K., Miller, T.L., and 

Rickert, D.A., 1994, U.S. Geological Survey protocol for the 

collection and processing of surface-water samples for the 

subsequent determination of inorganic constituents in filtered 

water: U.S. Geological Survey Open-File Report 94-539,

57 p.

Jones, B.E., 1987, Quality control manual of the U.S. Geological Survey’s National Water Quality Laboratory: U.S. Geological Survey Open-File Report 87-457, 17 p.

Jones, S.R., and Garbarino, J.R., 1999, Methods of analysis by 

the U.S. Geological Survey National Water Quality Laboratory—Determination of arsenic and selenium in water and 

sediment by graphite furnace-atomic absorption spectrometry: U.S. Geological Survey Open-File Report 98-639, 39 p.

Knapton, J.R., and Nimick, D.A., 1991, Quality assurance for 

water-quality activities of the U.S. Geological Survey in 

Montana: U.S. Geological Survey Open-File Report 91-216, 

41 p.

Lambing, J.H., 1987, Water-quality data for the Clark Fork and 

selected tributaries from Deer Lodge to Milltown, Montana, 

March 1985 through June 1986: U.S. Geological Survey 

Open-File Report 87-110, 48 p.

Lambing, J.H., 1988, Water-quality data (July 1986 through 

September 1987) and statistical summaries (March 1985 

through September 1987) for the Clark Fork and selected 

tributaries from Deer Lodge to Missoula, Montana: U.S. 

Geological Survey Open-File Report 88-308, 55 p.

Lambing, J.H., 1989, Water-quality data (October 1987 through 

September 1988) and statistical summaries (March 1985 

through September 1988) for the Clark Fork and selected 

tributaries from Galen to Missoula, Montana: U.S. Geological Survey Open-File Report 89-229, 51 p.

Lambing, J.H., 1990, Water-quality data (October 1988 through 

September 1989) and statistical summaries (March 1985 

through September 1989) for the Clark Fork and selected 

tributaries from Galen to Missoula, Montana: U.S. Geological Survey Open-File Report 90-168, 68 p.

Lambing, J.H., 1991, Water-quality and transport characteristics of suspended sediment and trace elements in streamflow 

of the upper Clark Fork basin from Galen to Missoula, Montana, 1985-90: U.S. Geological Survey Water-Resources 

Investigations Report 91-4139, 73 p.

Lambing, J.H., and Dodge, K.A., 1993, Quality assurance for 

laboratory analysis of suspended-sediment samples by the 

U.S. Geological Survey in Montana: U.S. Geological Survey 

Open-File Report 93-131, 34 p.

Lambing, J.H., Hornberger, M.I., Axtmann, E.V., and Dodge, 

K.A., 1995, Water-quality, bed-sediment, and biological data 

(October 1993 through September 1994) and statistical summaries of data for streams in the upper Clark Fork basin, 

Montana: U.S. Geological Survey Open-File Report 95-429, 

104 p.

Lambing, J.H., Hornberger, M.I., Axtmann, E.V., and Pope, 

D.A., 1994, Water-quality, bed-sediment, and biological data 
14 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana

(October 1992 through September 1993) and statistical summaries of water-quality data (March 1985 through September 

1993) for streams in the upper Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 94-375, 85 p.

Luoma, S.N., and Bryan, G.W., 1981, A statistical assessment 

of the form of trace metals in oxidized estuarine sediments 

employing chemical extractants: Science of the Total Environment, v. 17, no. 17, p. 167-196.

Porterfield, George, 1972, Computation of fluvial-sediment discharge: U.S. Geological Survey Techniques of WaterResources Investigations, book 3, chap. C3, 66 p. [Available 

online at http://water.usgs.gov/pubs/twri.]

Pritt, J.W., and Raese, J.W., eds., 1995, Quality assurance/

quality control manual—National Water Quality Laboratory: 

U.S. Geological Survey Open-File Report 95-443, 35 p.

Rantz, S.E., and others, 1982, Measurement and computation of 

streamflow: U.S. Geological Survey Water-Supply Paper 

2175, 2 v., 631 p.

Taylor, J.K., 1987, Quality assurance of chemical measurements: Chelsea, Mich., Lewis Publishers, 328 p.

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 online at http://water.usgs.gov/

pubs/twri.]

Ward, J.R., and Harr, C.A., eds., 1990, Methods for collection 

and processing of surface-water and bed-material samples for 

physical and chemical analyses: U.S. Geological Survey 

Open-File Report 90-140, 71 p.
DATA 15

DATA
16 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.

[Abbreviations: ft3/s, cubic feet per second; oC, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at

25o

C; mg/L, milligrams per liter; mm, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level; --, no data]

12323250--SILVER BOW CREEK BELOW BLACKTAIL CREEK, AT BUTTE, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

17... 0955 18 7.6 614 9.0 200 55.0 14.6 3.8

MAR 2004

17... 0725 18 7.6 578 3.5 200 56.7 13.6 3.7

APR

20... 0825 18 7.5 535 5.5 170 47.9 12.0 4.7

MAY

17... 0915 18 7.6 526 9.5 180 50.6 12.2 3.4

JUN

01... 1525 17 7.7 571 18.0 190 54.7 13.4 4.6

13... 0755 15 7.7 609 20.0 220 62.7 14.6 3.3

JUL

19... 0845 15 7.6 612 14.5 200 56.9 13.8 4.9

AUG

20... 0815 15 7.6 580 13.5 200 59.0 13.4 4.6

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

 filtered

(μg/L)

NOV 2003

17... 5 0.46 1.02 3.2 25.5 20 490 0.20

MAR 2004

17... 6 1.06 1.29 8.8 29.9 61 390 .30

APR

20... 5 1.07 1.13 15.7 26.3 46 430 .23

MAY

17... 4 1.02 1.19 18.3 35.3 32 430 .22

JUN

01... 6 .87 1.07 12.4 21.2 14 320 .13

13... 5 1.54 1.78 15.0 29.1 17 370 .12

JUL

19... 5 1.27 1.29 15.1 24.7 22 130 .22

AUG

20... 5 2.02 1.90 23.9 27.8 26 130 .18
TABLE 4 17

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323250--SILVER BOW CREEK BELOW BLACKTAIL CREEK, AT BUTTE, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

17... 4.68 286 319 182 227 94 15 0.73

MAR 2004

17... 2.69 495 505 268 278 81 8 .39

APR

20... 2.29 427 445 242 247 88 11 .53

MAY

17... 2.01 388 436 227 245 92 8 .39

JUN

01... 1.72 383 404 162 186 84 6 .28

13... 1.33 505 555 326 346 82 5 .20

JUL

19... .85 352 326 314 308 92 3 .12

AUG

20... .74 365 350 478 473 75 3 .12
18 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323600--SILVER BOW CREEK AT OPPORTUNITY, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

17... 1220 E25 8.4 566 .5 210 60.1 13.9 9.9

MAR 2004

16... 1540 35 8.8 518 7.0 190 55.0 12.0 12.1

APR

20... 1110 43 8.7 485 6.5 180 52.7 11.5 15.6

MAY

17... 1140 38 8.4 483 9.5 180 54.0 11.6 10.8

JUN

01... 1325 35 8.8 463 15.0 170 51.9 10.8 12.2

13... 1040 30 8.6 499 12.0 180 54.3 11.1 12.1

JUL

19... 1205 21 9.1 583 20.5 210 62.3 13.7 20.7

AUG

20... 1100 16 8.7 633 17.0 240 71.6 15.0 16.0

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

17... 17 .76 1.49 25.1 130 7 900 .20

MAR 2004

16... 15 .85 1.18 46.2 107 15 500 .33

APR

20... 16 .57 1.04 25.4 78.0 12 600 .22

MAY

17... 17 .42 1.08 22.1 94.5 14 840 .30

JUN

01... 18 .28 .75 20.0 70.1 20 470 .24

13... 17 .27 .80 18.5 68.4 12 450 .29

JUL

19... 22 .47 1.12 35.5 103 11 360 .31

AUG

20... 24 1.57 3.04 67.2 216 7 460 .27
TABLE 4 19

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323600--SILVER BOW CREEK AT OPPORTUNITY, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

17... 26.9 286 446 237 392 91 23 E1.6

MAR 2004

16... 13.1 423 446 129 228 83 10 .95

APR

20... 14.5 451 548 123 256 85 18 2.1

MAY

17... 19.4 428 644 115 283 90 21 2.2

JUN

01... 12.5 266 342 50.9 169 89 12 1.1

13... 12.2 264 342 81.8 203 88 13 1.1

JUL

19... 9.81 239 288 49.7 201 70 8 .45

AUG

20... 14.7 594 633 204 517 57 12 .52
20 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323700--MILL CREEK AT OPPORTUNITY, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

17... 1055 3.6 8.1 219 1.0 97 26.8 7.31 18.5

MAR 2004

16... 1435 2.9 8.2 221 4.5 100 27.9 7.68 16.2

APR

20... 0930 1.8 8.0 184 5.5 79 22.3 5.64 13.9

MAY

17... 1015 4.6 7.9 133 7.0 55 15.4 3.94 18.5

JUN

01... 1250 15 7.8 110 10.0 48 14.0 3.18 18.0

13... 0920 34 7.8 88 8.5 39 11.6 2.44 16.2

JUL

19... 1045 3.8 7.9 136 16.0 59 17.1 3.93 30.5

AUG

20... 0935 1.9 7.9 167 14.5 75 21.4 5.11 28.9

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

17... 20 .10 .13 1.8 2.8 44 110 E.08

MAR 2004

16... 16 .08 .08 2.0 3.0 17 70 E.05

APR

20... 16 .08 .09 2.3 3.5 36 80 E.04

MAY

17... 22 .07 .10 3.0 4.2 48 130 .13

JUN

01... 22 .06 .11 3.1 4.9 38 150 .13

13... 21 .07 .12 3.0 5.3 35 160 .14

JUL

19... 30 .07 .08 2.8 4.1 74 130 .19

AUG

20... 31 .07 .10 2.7 3.1 84 150 .15
TABLE 4 21

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323700--MILL CREEK AT OPPORTUNITY, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

17... .26 7.3 8 7.7 8 82 2 .02

MAR 2004

16... .19 5.0 6 3.2 2 80 1 .01

APR

20... .14 10.6 10 4.4 4 83 1 .00

MAY

17... .41 7.7 11 4.5 5 90 2 .02

JUN

01... .73 5.5 11 3.5 5 84 5 .20

13... .93 4.9 12 3.9 5 73 5 .46

JUL

19... .43 11.7 13 2.2 2 80 1 .01

AUG

20... .29 12.9 14 3.3 3 90 1 .01
22 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323720--WILLOW CREEK AT OPPORTUNITY, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

17... 1135 5.7 8.1 308 5.0 130 38.9 9.03 12.0

MAR 2004

16... 1515 6.6 8.2 292 7.0 130 38.0 9.00 13.5

APR

20... 1015 5.7 8.1 280 5.0 120 36.1 7.59 13.3

MAY

17... 1050 16 8.0 371 8.5 170 47.4 12.0 89.0

JUN

01... 1410 20 8.4 314 16.0 140 41.2 10.1 81.0

13... 0950 21 8.1 321 10.0 150 44.4 10.5 75.7

JUL

19... 1115 8.3 8.1 320 13.5 140 40.7 9.11 21.8

AUG

20... 1010 6.3 7.9 308 12.0 140 40.6 9.04 15.6

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

17... 13 .08 .06 2.0 5.7 16 140 .09

MAR 2004

16... 12 .09 .05 2.7 4.2 18 100 .13

APR

20... 16 E.03 .06 2.6 5.0 29 130 E.07

MAY

17... 96 .09 .16 11.5 18.9 65 330 .21

JUN

01... 87 .05 .07 6.9 10.0 22 130 .12

13... 79 .05 .07 5.8 7.8 35 100 .11

JUL

19... 21 E.04 .04 2.9 3.6 7 30 <.08

AUG

20... 16 E.03 E.03 2.4 2.8 7 40 E.04
TABLE 4 23

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323720--WILLOW CREEK AT OPPORTUNITY, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

17... 1.43 20.2 26 3.4 7 96 4 .06

MAR 2004

16... .69 44.6 46 4.0 4 92 3 .05

APR

20... 1.02 45.5 43 3.8 7 78 4 .06

MAY

17... 2.86 39.9 60 19.8 30 85 13 .56

JUN

01... 1.14 16.7 23 5.8 10 92 5 .27

13... .68 16.6 20 5.0 7 87 3 .17

JUL

19... .27 4.1 5 1.8 2 82 1 .02

AUG

20... .29 15.9 15 2.3 3 80 1 .02
24 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323750--SILVER BOW CREEK AT WARM SPRINGS, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

17... 1325 42 9.1 626 4.0 270 75.2 18.8 26.5

MAR 2004

16... 1700 44 8.8 586 5.0 250 72.8 16.8 12.5

APR

20... 1200 50 8.8 600 9.5 250 73.8 17.1 12.2

MAY

17... 1245 62 9.1 493 10.5 220 64.5 15.2 24.1

JUN

01... 1145 77 9.0 454 12.5 190 55.5 13.6 34.5

13... 1125 76 8.7 354 12.5 150 43.9 10.5 34.1

JUL

19... 1330 30 9.2 540 22.5 240 70.4 16.2 32.4

AUG

20... 1205 27 9.1 568 18.5 260 75.3 17.1 32.3

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

17... 27 E.04 .07 3.7 6.6 E6 110 E.04

MAR 2004

16... 13 .11 .14 5.2 6.9 7 180 <.08

APR

20... 16 E.04 .10 3.3 5.9 11 200 E.05

MAY

17... 30 E.03 .13 4.9 10.4 35 370 .11

JUN

01... 43 E.04 .13 4.9 8.3 24 260 E.07

13... 44 E.03 .10 4.1 7.9 34 220 .12

JUL

19... 35 E.03 .08 3.5 5.7 8 150 <.08

AUG

20... 35 E.03 .07 3.4 5.5 11 170 E.04
TABLE 4 25

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323750--SILVER BOW CREEK AT WARM SPRINGS, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

17... .49 65.7 95 3.5 7 64 3 .34

MAR 2004

16... .96 164 178 5.9 9 90 2 .24

APR

20... .88 247 304 3.5 9 90 4 .54

MAY

17... 1.73 88.9 265 2.2 15 90 8 1.3

JUN

01... 1.10 125 214 2.0 11 84 6 1.2

13... 1.17 104 173 2.9 10 86 6 1.2

JUL

19... .62 39.6 102 .9 5 79 4 .32

AUG

20... .71 58.5 104 2.2 6 78 3 .22
26 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323770--WARM SPRINGS CREEK AT WARM SPRINGS, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

17... 1305 17 8.6 431 2.0 220 66.1 12.6 5.4

APR 2004

20... 1220 42 8.6 340 7.0 170 51.5 10.3 3.9

MAY

17... 1220 27 8.5 339 8.0 180 53.7 10.1 5.3

JUN

01... 1125 32 8.4 312 10.0 150 47.2 8.02 5.3

JUL

19... 1255 26 8.5 311 18.0 150 45.8 7.61 8.8

AUG

20... 1140 22 8.4 362 14.5 180 58.2 8.98 7.6

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

 filtered

(μg/L)

NOV 2003

17... 6 E.03 .04 2.3 7.8 E5 100 <.08

APR 2004

20... 5 <.04 E.03 2.6 5.6 10 60 <.08

MAY

17... 7 E.03 E.03 3.0 6.1 14 70 <.08

JUN

01... 6 E.03 E.04 3.2 8.1 11 90 <.08

JUL

19... 9 E.03 E.04 3.3 7.5 10 80 <.08

AUG

20... 8 E.04 .06 3.7 7.7 7 80 <.08
TABLE 4 27

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323770--WARM SPRINGS CREEK AT WARM SPRINGS, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

17... .36 229 235 1.5 3 71 10 .46

APR 2004

20... .29 84.0 94 1.1 2 62 2 .23

MAY

17... .28 71.2 95 1.2 E2 78 2 .15

JUN

01... .43 42.2 83 1.1 2 72 4 .35

JUL

19... .41 23.3 67 .9 E2 67 2 .14

AUG

20... .43 83.9 147 1.7 3 81 2 .12
28 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323800--CLARK FORK NEAR GALEN, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

17... 1420 59 8.9 575 4.0 260 74.2 17.1 19.6

MAR 2004

17... 0835 87 8.3 514 3.5 230 67.9 14.0 7.9

APR

20... 1320 93 8.7 486 8.0 220 64.5 14.0 12.9

MAY

17... 1405 89 8.9 451 10.5 210 62.1 13.8 17.5

JUN

01... 1035 116 8.7 428 10.5 190 54.2 12.4 23.9

13... 1310 143 8.6 307 12.5 140 41.0 8.03 21.2

JUL

19... 1440 49 8.7 442 20.5 210 61.2 12.8 19.4

AUG

20... 1310 39 8.7 495 18.5 240 70.9 14.4 20.2

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

17... 20 .04 .06 3.9 8.2 E6 110 <.08

MAR 2004

17... 8 .07 .12 4.0 11.9 7 290 <.08

APR

20... 11 E.04 .07 3.5 7.0 8 130 <.08

MAY

17... 21 E.03 .09 4.7 9.3 23 220 E.07

JUN

01... 31 .04 .09 4.8 10.2 20 230 E.06

13... 26 E.03 .08 4.2 10.4 21 200 E.07

JUL

19... 20 E.03 .07 4.3 7.7 7 100 <.08

AUG

20... 21 E.03 .07 4.9 7.9 E5 110 <.08
TABLE 4 29

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323800--CLARK FORK NEAR GALEN, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

17... .61 82.2 107 3.0 8 75 2 .32

MAR 2004

17... 2.19 181 228 6.7 13 77 9 2.1

APR

20... .66 131 149 3.5 8 78 4 1.0

MAY

17... 1.01 67.1 151 1.8 8 86 6 1.4

JUN

01... 1.04 90.0 172 2.4 10 82 6 1.9

13... 1.06 51.9 123 1.7 9 81 7 2.7

JUL

19... .55 48.1 85 .9 4 82 3 .40

AUG

20... .62 54.2 90 1.9 5 83 3 .32
30 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323850--LOST CREEK NEAR GALEN, MONT. 

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

17... 1450 49 8.6 585 4.5 300 86.0 19.6 8.3

MAR 2004

17... 0900 47 8.4 633 4.5 320 91.5 21.1 15.5

APR

20... 1355 20 8.5 607 8.5 300 87.1 19.7 9.9

MAY

17... 1335 2.0 8.5 707 14.0 300 78.9 24.7 11.7

JUN

01... 1005 1.8 8.4 682 11.5 280 73.5 23.5 8.8

13... 1245 1.5 8.5 623 15.5 250 64.3 22.3 7.7

JUL

19... 1420 1.7 8.4 576 24.5 220 54.8 20.4 8.2

AUG

20... 1250 1.8 8.4 608 19.5 260 67.3 21.3 6.6

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

17... 8 <.04 .05 1.5 6.7 8 170 <.08

MAR 2004

17... 16 E.03 .08 2.5 12.1 9 280 E.04

APR

20... 12 E.03 .06 2.6 7.8 E5 160 <.08

MAY

17... 12 E.03 E.03 3.3 4.4 11 70 <.08

JUN

01... 9 E.03 E.03 2.9 4.1 13 50 <.08

13... 8 E.02 E.02 2.8 3.9 E6 40 <.08

JUL

19... 8 E.02 .04 2.6 4.0 <6 40 <.08

AUG

20... 6 <.04 E.03 -- 4.3 11 20 .19
TABLE 4 31

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12323850--LOST CREEK NEAR GALEN, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

17... .59 7.5 13 1.7 5 32 22 2.9

MAR 2004

17... 1.18 17.1 25 2.4 5 83 13 1.6

APR

20... .69 14.8 19 2.4 5 51 34 1.8

MAY

17... .13 10.2 12 1.1 E1 61 17 .09

JUN

01... .10 10.9 12 1.2 E1 48 24 .12

13... .08 4.1 6 .8 <2 19 14 .06

JUL

19... .12 2.7 5 E.4 E1 60 4 .02

AUG

20... E.04 1.9 2 .9 E1 86 27 .13
32 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12324200--CLARK FORK AT DEER LODGE, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

17... 1540 182 8.6 533 3.5 240 71.3 16.0 11.5

MAR 2004

17... 1005 204 8.4 533 5.0 240 71.7 15.9 11.3

APR

20... 1505 179 8.6 520 9.0 240 69.9 15.3 15.4

MAY

17... 1505 106 8.5 499 12.5 240 70.2 14.5 10.9

JUN

01... 0855 146 8.2 497 10.5 220 65.0 14.5 17.7

13... 1415 155 8.6 385 15.5 170 51.4 10.8 18.1

JUL

19... 1540 51 8.6 490 22.5 210 62.0 13.3 17.8

AUG

20... 1415 40 8.4 535 20.0 240 73.4 13.9 14.7

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered

(μg/L)

NOV 2003

17... 13 .04 .14 4.6 21.8 E5 350 <.08

MAR 2004

17... 12 .06 .18 5.5 30.3 E6 470 E.06

APR

20... 13 E.03 .09 5.4 15.8 8 230 E.04

MAY

17... 13 E.04 .10 5.6 14.2 10 190 E.06

JUN

01... 25 .06 .18 6.1 26.5 11 380 E.07

13... 23 E.03 .12 6.2 19.9 8 230 E.06

JUL

19... 17 E.02 .14 7.0 10.9 E4 60 <.08

AUG

20... 16 E.04 .10 6.6 14.2 <6 160 <.08
TABLE 4 33

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12324200--CLARK FORK AT DEER LODGE, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

17... 2.48 38.9 81 6.1 25 77 15 7.4

MAR 2004

17... 3.52 61.3 119 6.6 29 76 23 13

APR

20... 1.86 41.2 66 4.1 16 76 12 5.8

MAY

17... 1.32 37.3 70 4.9 14 88 8 2.3

JUN

01... 2.97 36.4 126 4.9 26 88 16 6.3

13... 1.97 25.0 85 2.4 16 87 11 4.6

JUL

19... .52 8.1 21 .9 7 92 10 1.4

AUG

20... 1.35 34.1 116 2.6 13 66 19 2.1
34 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12324590--LITTLE BLACKFOOT RIVER NEAR GARRISON, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

19... 0810 61 8.2 286 3.5 140 40.0 8.87 4.4

APR 2004

20... 1605 168 8.3 213 7.5 96 28.3 6.06 6.2

MAY

17... 1615 141 8.4 246 12.0 110 34.0 7.11 4.6

JUN

01... 1700 249 8.3 231 15.0 110 31.4 6.51 4.9

JUL

19... 1645 73 8.7 281 23.0 130 38.8 8.01 6.5

AUG

20... 1520 20 8.6 332 22.0 160 47.4 10.4 6.5

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

19... 4 <.04 <.04 .6 1.1 E5 120 <.08

APR 2004

20... 5 <.04 <.04 1.2 1.9 20 240 E.05

MAY

17... 5 <.04 <.04 1.1 1.6 14 200 <.08

JUN

01... 5 <.04 E.03 1.1 1.7 18 220 <.08

JUL

19... 7 <.04 <.04 .9 1.2 7 60 <.08

AUG

20... 6 <.04 <.04 1.1 1.6 E5 80 <.08

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

19... .20 7.8 24 E.5 E1 79 4 .66

APR 2004

20... .56 8.0 22 .9 3 85 8 3.6

MAY

17... .43 8.7 22 .8 2 86 8 3.0

JUN

01... .46 8.2 22 1.1 3 73 10 6.7

JUL

19... .08 9.6 16 <.6 <2 88 2 .39

AUG

20... .08 12.7 31 E.5 <2 84 3 .16
TABLE 4 35

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12324680--CLARK FORK AT GOLDCREEK, MONT. 

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

18... 0815 317 8.3 474 2.0 220 64.7 14.2 8.6

MAR 2004

17... 1145 432 8.6 445 5.5 210 61.0 12.8 8.8

APR

20... 1710 360 8.6 394 8.5 180 52.7 11.7 7.3

MAY

18... 0720 286 8.3 398 10.0 190 54.7 12.0 8.9

JUN

02... 1140 507 8.5 351 12.5 150 46.8 9.05 8.8

13... 1535 607 8.7 298 15.5 130 40.6 7.64 9.8

JUL

20... 1355 206 8.6 425 20.5 200 58.7 12.1 12.0

AUG

20... 1555 100 8.8 459 23.0 210 64.0 13.2 13.6

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

18... 10 E.03 .12 3.0 17.3 E4 290 <.08

MAR 2004

17... 9 .04 .14 4.6 23.2 8 450 E.05

APR

20... 10 E.02 .07 4.1 11.5 E6 240 <.08

MAY

18... 10 E.03 .05 4.3 6.5 8 80 <.08

JUN

02... 10 E.02 .07 3.6 10.4 10 270 E.04

13... 12 <.04 .09 3.9 12.9 10 280 E.05

JUL

20... 12 E.02 .06 4.2 8.1 8 130 <.08

AUG

20... 14 <.04 .04 4.7 6.8 <6 70 <.08
36 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12324680--CLARK FORK AT GOLDCREEK, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

18... 2.07 21.0 79 5.6 21 86 13 11

MAR 2004

17... 2.81 23.4 80 3.4 23 81 23 27

APR

20... 1.30 14.4 46 2.3 12 87 11 11

MAY

18... .38 18.3 27 2.9 6 83 2 1.5

JUN

02... 1.24 17.5 61 2.1 11 94 12 16

13... 1.57 11.5 59 1.5 15 86 15 25

JUL

20... .72 15.0 45 1.4 7 69 7 3.9

AUG

20... .41 7.7 44 .7 5 72 7 1.9
TABLE 4 37

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12331500--FLINT CREEK NEAR DRUMMOND, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

18... 0910 111 8.4 345 2.5 160 44.1 13.2 6.2

APR 2004

21... 0735 88 8.4 305 3.0 140 38.6 11.4 10.9

MAY

18... 0810 8.3 8.3 398 9.0 200 54.9 14.4 9.7

JUN

02... 1235 39 8.5 403 13.5 190 53.1 12.8 9.0

14... 1125 134 8.4 288 11.0 140 38.3 10.4 8.1

AUG

23... 0955 57 8.2 501 12.5 240 64.6 18.7 12.3

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

 filtered

 (μg/L)

NOV 2003

18... 7 <.04 E.03 .7 1.9 E6 180 E.05

APR 2004

21... 10 <.04 .04 1.2 4.7 9 250 .09

MAY

18... 11 <.04 E.02 1.1 1.4 15 90 .09

JUN

02... 11 <.04 E.02 1.3 1.8 14 130 .11

14... 13 <.04 .05 1.2 3.0 17 270 .21

AUG

23... 15 <.04 .07 1.7 2.8 42 480 .12

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

18... 2.56 22.2 64 1.3 8 93 8 2.4

APR 2004

21... 3.17 33.0 77 1.8 10 88 12 2.9

MAY

18... .80 78.6 97 1.6 4 90 4 .09

JUN

02... 1.60 55.8 85 1.2 5 87 7 .74

14... 5.28 30.0 101 1.7 14 84 15 5.4

AUG

23... 4.27 75.0 269 1.7 14 89 26 4.0
38 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12331800--CLARK FORK NEAR DRUMMOND, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

18... 1015 501 8.4 490 4.5 230 64.8 16.1 8.4

MAR 2004

17... 1250 613 8.4 471 7.5 220 64.2 14.9 9.0

APR

21... 0840 505 8.3 435 7.0 200 57.8 13.8 12.0

MAY

18... 0900 308 8.4 484 12.5 240 68.8 15.8 9.2

JUN

02... 1325 608 8.5 436 15.5 200 58.6 13.3 10.4

13... 1645 855 8.4 370 16.0 170 49.1 11.3 10.6

JUL

20... 1250 298 8.4 525 20.5 250 70.4 17.1 12.8

AUG

23... 1045 235 8.2 578 15.5 280 81.1 19.5 12.1

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

18... 8 E.03 .10 2.6 11.1 <6 220 <.08

MAR 2004

17... 9 E.04 .14 4.5 19.7 7 460 .09

APR

21... 10 E.03 .12 4.1 13.7 E5 310 E.04

MAY

18... 10 E.02 .04 4.4 5.8 E6 40 E.05

JUN

02... 12 E.02 .08 4.7 10.4 E6 180 E.06

13... 14 <.04 .14 4.2 19.0 10 450 .10

JUL

20... 12 E.02 .06 3.6 6.7 E4 100 E.05

AUG

23... 12 E.03 .07 3.8 7.7 E3 130 E.04
TABLE 4 39

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12331800--CLARK FORK NEAR DRUMMOND, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

18... 1.63 12.9 63 4.1 17 86 11 15

MAR 2004

17... 3.24 20.8 88 4.2 25 82 26 43

APR

21... 2.04 14.2 62 9.1 18 89 14 19

MAY

18... .29 11.1 16 3.2 5 81 2 1.7

JUN

02... 1.19 15.8 49 2.6 12 90 9 15

13... 3.45 15.6 97 2.9 26 89 23 53

JUL

20... .80 11.0 41 1.7 7 64 8 6.4

AUG

23... .98 6.8 45 2.9 11 86 7 4.4
40 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12334510--ROCK CREEK NEAR CLINTON, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

18... 1140 197 8.2 144 2.5 66 17.1 5.76 .6

APR 2004

21... 1005 432 7.8 106 4.5 47 12.4 3.84 .8

MAY

18... 1035 748 7.9 87 8.0 37 9.52 3.18 .5

JUN

02... 1515 1,020 8.2 83 12.5 35 9.37 2.85 .6

JUL

20... 1140 455 8.3 133 16.5 60 16.4 4.71 .7

AUG

23... 1110 279 8.4 139 14.0 63 16.7 5.07 .8

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

 filtered

(μg/L)

NOV 2003

18... <2 <.04 <.04 E.2 <.6 E6 20 <.08

APR 2004

21... E1 <.04 <.04 .5 E.6 17 60 E.05

MAY

18... <2 <.04 <.04 E.4 E.5 28 100 <.08

JUN

02... <2 E.04 .06 .7 1.5 23 110 <.08

JUL

20... <2 <.04 <.04 E.4 E.5 10 60 <.08

AUG

23... <2 <.04 <.04 .7 <.6 13 90 <.08
TABLE 4 41

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12334510--ROCK CREEK NEAR CLINTON, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

18... <.06 .6 1 <.6 <2 82 1 .53

APR 2004

21... <.06 1.0 2 E.4 <2 81 2 2.3

MAY

18... .08 1.1 5 E.4 <2 75 4 8.1

JUN

02... .14 1.3 5 .6 3 74 6 17

JUL

20... E.05 1.7 5 <.6 <2 57 4 4.9

AUG

23... E.05 2.9 9 <.6 <2 80 5 3.8
42 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12334550--CLARK FORK AT TURAH BRIDGE, NEAR BONNER, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

18... 1310 739 8.5 402 3.0 190 53.8 13.7 5.8

MAR 2004

17... 1410 930 8.5 381 6.0 180 51.3 12.4 6.5

APR

21... 1125 1,080 8.1 304 6.5 130 38.5 9.12 4.6

MAY

18... 1145 1,110 8.4 224 10.0 99 28.2 6.93 3.1

JUN

02... 1705 1,860 8.6 230 15.0 100 29.0 6.75 4.4

14... 0925 1,950 8.2 239 12.0 100 30.5 6.83 5.2

JUL

20... 1020 768 8.4 301 18.0 140 37.9 10.6 4.9

AUG

23... 1335 540 8.3 317 14.0 150 40.8 11.2 4.6

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

18... 6 E.02 .06 2.0 6.5 E3 110 <.08

MAR 2004

17... 6 E.02 .11 3.4 13.5 7 350 E.06

APR

21... 6 <.04 .06 2.7 8.1 8 190 .09

MAY

18... 3 <.04 E.03 1.7 3.1 15 110 <.08

JUN

02... 4 <.04 .06 2.5 6.3 11 180 E.05

14... 6 <.04 .10 2.4 10.9 12 300 E.07

JUL

20... 6 <.04 E.04 2.1 4.1 E6 80 <.08

AUG

23... 4 <.04 .04 1.8 4.1 <6 120 <.08
TABLE 4 43

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12334550--CLARK FORK AT TURAH BRIDGE, NEAR BONNER, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

18... .87 3.2 30 3.1 12 86 6 12

MAR 2004

17... 2.33 8.4 65 5.0 20 86 21 53

APR

21... 1.16 5.6 31 2.3 12 82 11 32

MAY

18... .32 3.5 11 1.8 4 68 6 18

JUN

02... .81 4.8 24 1.5 9 67 12 60

14... 1.90 6.7 54 2.7 19 75 18 95

JUL

20... .47 3.3 21 1.6 5 79 7 15

AUG

23... .58 4.4 24 3.1 8 77 8 12
44 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12340000--BLACKFOOT RIVER NEAR BONNER, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

18... 1445 523 8.5 260 3.0 130 34.0 12.1 1.0

APR 2004

21... 1340 2,350 8.2 175 7.0 86 22.9 7.04 1.1

MAY

18... 1320 2,400 8.5 183 11.0 92 24.4 7.54 .8

JUN

03... 0720 3,150 8.2 174 12.0 88 23.6 7.14 .8

JUL

20... 0720 957 8.4 239 17.5 120 30.5 10.8 1.2

AUG

23... 1445 694 8.7 246 14.5 130 31.1 11.7 1.3

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead,

filtered

(μg/L)

NOV 2003

18... <2 <.04 <.04 .6 .8 <6 30 <.08

APR 2004

21... <2 <.04 <.04 .7 1.0 10 90 E.05

MAY

18... <2 <.04 <.04 .6 .7 7 70 <.08

JUN

03... <2 <.04 <.04 .6 1.1 8 140 <.08

JUL

20... E2 <.04 E.02 .7 1.0 E4 70 <.08

AUG

23... E1 <.04 <.04 .4 E.3 <6 40 <.08
TABLE 4 45

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12340000--BLACKFOOT RIVER NEAR BONNER, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

18... .07 .8 2 1.5 E2 95 2 2.8

APR 2004

21... .08 2.4 8 E.6 <2 85 6 38

MAY

18... .10 1.7 7 E.3 <2 81 5 32

JUN

03... .18 1.4 12 .8 E1 86 10 85

JUL

20... .13 1.4 8 E.3 E1 75 4 10

AUG

23... E.05 1.4 5 .7 <2 72 2 3.7
46 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12340500--CLARK FORK ABOVE MISSOULA, MONT.

Date Time

Streamflow, 

instantaneous

(ft3

/s)

pH,

onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water

(

oC)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered

(μg/L)

NOV 2003

18... 1600 1,360 8.6 338 2.5 160 44.6 12.8 3.7

MAR 2004

17... 1525 1,800 8.4 317 5.5 150 41.9 11.4 3.8

APR

21... 1535 3,340 8.4 219 7.5 100 28.2 7.75 3.2

MAY

18... 1505 3,360 8.3 196 10.5 94 25.7 7.31 1.6

JUN

03... 0850 4,920 8.2 195 12.5 110 29.2 7.91 2.2

14... 0715 4,980 8.2 205 12.5 96 26.8 7.13 2.7

JUL

20... 0850 1,660 8.3 263 19.5 130 32.9 10.5 3.5

AUG

23... 1635 1,220 8.4 282 16.0 140 36.2 11.8 3.2

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered

(μg/L)

NOV 2003

18... 4 <.04 .04 2.8 5.8 E4 100 <.08

MAR 2004

17... 4 <.04 .07 4.2 9.8 19 230 .09

APR

21... 3 <.04 E.04 2.1 5.7 11 130 E.05

MAY

18... E2 <.04 E.02 1.2 2.6 12 90 E.05

JUN

03... 2 <.04 .05 1.7 5.8 16 200 E.04

14... 3 <.04 .06 1.5 6.6 12 230 E.05

JUL

20... 5 <.04 .14 1.5 13.9 16 400 .10

AUG

23... 4 <.04 .06 1.4 4.5 E3 140 <.08
TABLE 4 47

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2003 through September 2004.—Continued

12340500--CLARK FORK ABOVE MISSOULA, MONT.—Continued

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

NOV 2003

18... .53 9.7 17 2.3 8 93 4 15

MAR 2004

17... 1.16 31.6 48 7.7 15 93 12 58

APR

21... .55 17.1 22 1.0 6 93 7 63

MAY

18... .32 10.8 16 1.8 6 89 5 45

JUN

03... .82 14.2 27 2.1 9 87 14 186

14... 1.11 15.0 36 1.9 11 92 13 175

JUL

20... 2.33 37.7 67 .8 25 91 24 108

AUG

23... .64 11.9 25 1.0 9 82 9 30
48 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

 

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2003 through September 

2004.

[Abbreviations: ft3/s, cubic feet per second; e, estimated; mg/L, milligrams per liter; ton/d, tons per day. Symbol: --, no data or value computed]

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

OCTOBER NOVEMBER DECEMBER

1 133 21 7.5 e130 10 3.5 206 16 8.9

2 135 16 5.8 161 11 4.8 217 16 9.4

3 128 14 4.8 170 14 6.4 221 16 9.5

4 127 14 4.8 e160 16 6.9 209 16 9.0

5 131 14 5.0 e150 16 6.5 200 16 8.6

6 133 14 5.0 e150 17 6.9 214 17 9.8

7 129 13 4.5 e150 18 7.3 210 17 9.6

8 132 14 5.0 162 18 7.9 196 17 9.0

9 135 14 5.1 164 18 8.0 187 17 8.6

10 143 14 5.4 184 16 7.9 190 17 8.7

11 150 14 5.7 189 13 6.6 198 16 8.6

12 155 14 5.9 185 12 6.0 196 15 7.9

13 156 14 5.9 178 11 5.3 196 14 7.4

14 157 14 5.9 171 11 5.1 202 13 7.1

15 156 13 5.5 179 11 5.3 194 12 6.3

16 159 13 5.6 177 11 5.3 180 11 5.3

17 157 13 5.5 180 14 6.8 197 10 5.3

18 149 14 5.6 182 10 4.9 181 9 4.4

19 147 14 5.6 199 9 4.8 180 9 4.4

20 149 14 5.6 203 10 5.5 190 9 4.6

21 150 14 5.7 184 10 5.0 188 9 4.6

22 152 13 5.3 e170 10 4.6 e170 9 4.1

23 153 12 5.0 e160 11 4.8 e170 9 4.1

24 143 13 5.0 e170 11 5.0 178 9 4.3

25 142 13 5.0 e180 11 5.3 182 8 3.9

26 144 14 5.4 192 11 5.7 177 8 3.8

27 142 14 5.4 192 11 5.7 169 10 4.6

28 140 14 5.3 198 14 7.5 156 12 5.1

29 159 13 5.6 210 16 9.1 e150 12 4.9

30 180 11 5.3 212 16 9.2 e140 12 4.5

31 e130 10 3.5 -- -- -- e130 12 4.2

 TOTAL 4,496 -- 166.2 5,292 -- 183.6 5,774 -- 200.5

 MEAN 145 14 5.4 176 13 6.1 186 13 6.5

 MAX 180 21 7.5 212 18 9.2 221 17 9.8

 MIN 127 10 3.5 130 9 3.5 130 8 3.8
TABLE 5 49

 

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2003 through September 

2004.—Continued

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e150 11 4.5 182 36 18 199 18 9.7

2 e150 12 4.9 189 29 15 198 16 8.6

3 e140 12 4.5 184 24 12 193 17 8.9

4 e120 12 3.9 182 22 11 199 20 11

5 e110 13 3.9 184 21 10 198 18 9.6

6 e120 14 4.5 172 20 9.3 198 20 11

7 e130 15 5.3 183 18 8.9 198 20 11

8 e140 17 6.4 179 17 8.2 233 36 23

9 e150 18 7.3 179 17 8.2 267 64 46

10 165 19 8.5 178 18 8.7 265 47 34

11 166 20 9.0 179 22 11 235 28 18

12 e160 19 8.2 164 24 11 224 27 16

13 e160 18 7.8 171 24 11 225 24 15

14 165 17 7.6 183 24 12 215 20 12

15 e180 16 7.8 183 24 12 212 22 13

16 175 14 6.6 177 24 11 210 26 15

17 e170 12 5.5 178 24 12 206 24 13

18 e170 10 4.6 195 34 18 211 29 17

19 176 9 4.3 204 43 24 208 23 13

20 181 8 3.9 195 38 20 190 24 12

21 e170 8 3.7 189 34 17 185 23 11

22 e190 8 4.1 181 29 14 185 25 12

23 185 9 4.5 186 25 13 182 23 11

24 192 12 6.2 195 23 12 186 20 10

25 189 22 11 210 22 12 188 20 10

26 180 36 17 205 22 12 188 16 8.1

27 181 46 22 203 22 12 185 14 7.0

28 187 48 24 201 21 11 181 18 8.8

29 191 49 25 197 21 11 179 19 9.2

30 209 48 27 -- -- -- 176 20 9.5

31 193 43 22 -- -- -- 181 24 12

TOTAL 5,145 -- 285.5 5,408 -- 365.3 6,300 -- 425.4

MEAN 166 20 9.2 186 25 13 203 24 14

MAX 209 49 27 210 43 24 267 64 46

MIN 110 8 3.7 164 17 8.2 176 14 7.0
50 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

 

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2003 through September 

2004.—Continued

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 201 25 14 152 11 4.5 144 15 5.8

2 233 32 20 145 12 4.7 128 11 3.8

3 219 27 16 131 10 3.5 115 10 3.1

4 216 26 15 128 10 3.5 111 11 3.3

5 211 22 13 108 8 2.3 135 12 4.4

6 209 23 13 119 10 3.2 157 17 7.2

7 217 22 13 128 10 3.5 187 21 11

8 209 23 13 112 7 2.1 175 18 8.5

9 223 23 14 108 7 2.0 168 19 8.6

10 212 20 11 104 8 2.2 160 23 9.9

11 197 15 8.0 114 8 2.5 232 37 23

12 188 18 9.1 119 8 2.6 196 22 12

13 182 15 7.4 1148 2.5 159 11 4.7

14 181 14 6.8 101 7 1.9 144 9 3.5

15 177 15 7.2 87 15 3.5 136 9 3.3

16 173 12 5.6 84 8 1.8 138 9 3.4

17 172 10 4.6 100 9 2.4 135 8 2.9

18 175 10 4.7 107 8 2.3 124 7 2.3

19 176 10 4.8 121 9 2.9 120 7 2.3

20 179 12 5.8 114 9 2.8 126 7 2.4

21 179 11 5.3 112 11 3.3 120 6 1.9

22 172 11 5.1 146 19 7.5 105 7 2.0

23 167 11 5.0 180 42 20 97 8 2.1

24 161 10 4.3 180 35 17 93 7 1.8

25 159 10 4.3 162 22 9.6 95 9 2.3

26 157 10 4.2 148 13 5.2 102 14 3.9

27 152 20 8.2 143 11 4.2 110 14 4.2

28 164 12 5.3 147 12 4.8 139 14 5.3

29 177 9 4.3 172 26 12 122 12 4.0

30 162 7 3.1 166 21 9.4 120 11 3.6

31 -- -- -- 156 24 10 -- -- --

TOTAL 5,600 -- 255.1 4,008 -- 159.7 4,093 -- 156.5

MEAN 187 16 8.5 129 13 5.2 136 13 5.2

MAX 233 32 20 180 42 20 232 37 23

MIN 15273.1 847 1.8 936 1.8
TABLE 5 51

 

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2003 through September 

2004.—Continued

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

JULY AUGUST SEPTEMBER

1 142 12 4.6 37 22 2.2 75 20 4.0

2 103 12 3.3 38 19 1.9 77 19 4.0

3 93 12 3.0 39 18 1.9 81 20 4.4

4 92 12 3.0 33 20 1.8 76 20 4.1

5 93 13 3.3 34 20 1.8 83 21 4.7

6 86 12 2.8 35 20 1.9 87 22 5.2

7 82 12 2.7 33 19 1.7 90 22 5.3

8 82 13 2.9 32 16 1.4 90 23 5.6

9 83 12 2.7 30 14 1.1 89 23 5.5

10 80 10 2.2 30 15 1.2 89 23 5.5

11 77 7 1.5 29 20 1.6 85 23 5.3

12 70 5 .95 33 26 2.3 92 22 5.5

13 68 5 .92 29 29 2.3 113 20 6.1

14 66 4 .71 28 30 2.3 119 19 6.1

15 61 4 .66 27 28 2.0 113 18 5.5

16 57 3 .46 28 22 1.7 111 18 5.4

17 48 3 .39 31 18 1.5 111 18 5.4

18 46 7 .87 34 17 1.6 112 18 5.4

19 48 11 1.4 38 18 1.8 128 20 6.9

20 47 8 1.0 41 21 2.3 149 23 9.3

21 53 6 .86 42 24 2.7 152 23 9.4

22 48 4 .52 40 29 3.1 143 17 6.6

23 47 3 .38 59 29 4.6 142 13 5.0

24 45 4 .49 73 24 4.7 139 12 4.5

25 45 6 .73 83 20 4.5 138 11 4.1

26 38 14 1.4 90 18 4.4 135 11 4.0

27 47 22 2.8 94 19 4.8 134 11 4.0

28 38 25 2.6 88 20 4.8 133 12 4.3

29 39 26 2.7 83 20 4.5 129 11 3.8

30 39 26 2.7 81 21 4.6 128 11 3.8

31 37 26 2.6 81 21 4.6 -- -- --

TOTAL 2,000 -- 57.14 1,473 -- 83.6 3,343 -- 158.7

MEAN 64.5 11 1.8 47.5 21 2.7 111 18 5.3

MAX 142 26 4.6 94 30 4.8 152 23 9.4

MIN 37 3 .38 27 14 1.1 75 11 3.8

TOTAL FOR WATER YEAR 2004:

STREAMFLOW--52,932 ft3

/s

SEDIMENT LOAD--2,497.24 tons
52 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

 

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2003 

through September 2004.

[Abbreviations: ft3/s, cubic feet per second; e, estimated; mg/L, milligrams per liter; ton/d, tons per day. Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

OCTOBER NOVEMBER DECEMBER

1 516 6 8.4 e660 9 16 760 10 21

2 538 6 8.7 686 9 17 755 10 20

3 543 7 10 752 9 18 769 10 21

4 580 9 14 761 8 16 766 8 17

5 612 10 17 e680 8 15 715 6 12

6 618 11 18 e650 8 14 756 7 14

7 621 12 20 e650 8 14 779 7 15

8 615 11 18 e660 9 16 766 7 14

9 619 9 15 e700 11 21 734 7 14

10 626 7 12 782 11 23 703 6 11

11 635 6 10 822 10 22 718 9 17

12 650 6 11 811 9 20 721 8 16

13 673 7 13 767 8 17 726 8 16

14 678 7 13 732 8 16 740 7 14

15 688 8 15 724 8 16 730 6 12

16 710 8 15 742 7 14 677 5 9.1

17 730 8 16 774 7 15 679 5 9.2

18 706 8 15 747 7 14 e660 6 11

19 682 8 15 755 7 14 e560 8 12

20 669 8 14 791 8 17 e600 9 15

21 682 8 15 781 8 17 e700 9 17

22 690 9 17 e700 8 15 e680 7 13

23 697 9 17 e630 8 14 e600 6 9.7

24 707 9 17 e700 8 15 e610 6 9.9

25 690 9 17 710 8 15 e720 7 14

26 709 8 15 709 8 15 686 8 15

27 711 8 15 725 8 16 656 8 14

28 723 8 16 694 9 17 e600 6 9.7

29 809 9 20 755 9 18 e520 6 8.4

30 876 9 21 766 10 21 e460 6 7.5

31 777 9 19 -- -- -- e420 6 6.8

TOTAL 20,780 -- 467.1 21,816 -- 498 20,966 -- 415.3

MEAN 670 8 15 727 8 17 676 7 13

MAX 876 12 21 822 11 23 779 10 21

MIN 516 6 8.4 630 7 14 420 5 6.8
TABLE 6 53

 

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2003 

through September 2004.—Continued

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e450 6 7.3 659 7 12 686 17 31

2 e500 5 6.8 621 7 12 688 16 30

3 e460 5 6.2 603 7 11 682 15 28

4 e440 6 7.1 614 7 12 662 13 23

5 e350 6 5.7 639 6 10 675 10 18

6 e230 7 4.3 624 6 10 671 10 18

7 e240 11 7.1 613 6 9.9 653 10 18

8 e300 14 11 629 6 10 770 24 50

9 e400 14 15 642 6 10 1,610 330 1,430

10 e550 13 19 633 6 10 1,580 198 845

11 e580 11 17 625 6 10 1,460 98 386

12 e600 9 15 e580 6 9.4 1,190 53 170

13 e600 9 15 e520 7 9.8 1,190 44 141

14 e620 8 13 e530 7 10 1,130 38 116

15 e640 8 14 569 8 12 987 26 69

16 648 8 14 619 8 13 943 25 64

17 e650 8 14 635 8 14 935 23 58

18 e630 8 14 659 8 14 992 26 70

19 631 15 26 697 10 19 1,090 31 91

20 652 16 28 731 16 32 1,070 27 78

21 656 13 23 710 14 27 938 20 51

22 645 10 17 671 14 25 912 21 52

23 636 9 15 654 14 25 936 23 58

24 650 8 14 662 15 27 998 24 65

25 666 7 13 710 15 29 1,050 24 68

26 643 6 10 763 15 31 1,050 23 65

27 636 5 8.6 735 16 32 1,010 19 52

28 639 6 10 710 16 31 957 17 44

29 652 7 12 695 16 30 911 17 42

30 685 7 13 -- -- -- 895 16 39

31 695 7 13 -- -- -- 910 18 44

TOTAL 17,374 -- 408.1 18,752 -- 507.1 30,231 -- 4,314

MEAN 560 9 13 647 10 17 975 41 139

MAX 695 16 28 763 16 32 1,610 330 1,430

MIN 230 5 4.3 520 6 9.4 653 10 18
54 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

 

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2003 

through September 2004.—Continued

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 997 19 51 1,120 11 33 2,010 16 87

2 1,060 19 54 1,100 11 33 1,900 12 62

3 1,040 21 59 1,180 10 32 1,810 12 59

4 1,010 22 60 1,300 16 56 1,780 14 67

5 1,070 25 72 1,420 25 96 1,830 17 84

6 1,120 28 85 1,510 24 98 1,950 25 132

7 1,200 31 100 1,520 22 90 2,020 21 115

8 1,230 32 106 1,540 19 79 1,900 15 77

9 1,300 32 112 1,530 17 70 1,830 13 64

10 1,300 31 109 1,440 12 47 1,930 25 130

11 1,230 24 80 1,410 8 30 2,430 57 374

12 1,160 23 72 1,360 8 29 2,450 51 337

13 1,160 21 66 1,250 5 17 2,120 27 155

14 1,220 25 82 1,170 5 16 1,930 19 99

15 1,290 23 80 1,090 5 15 1,750 16 76

16 1,250 18 61 1,040 5 14 1,610 14 61

17 1,190 20 64 1,140 8 25 1,480 12 48

18 1,150 18 56 1,150 7 22 1,390 10 38

19 1,110 16 48 1,350 9 33 1,400 11 42

20 1,080 15 44 1,400 10 38 1,400 13 49

21 1,070 12 35 1,380 10 37 1,310 12 42

22 1,030 12 33 1,420 11 42 1,220 11 36

23 963 12 31 1,670 18 81 1,140 10 31

24 933 13 33 1,770 20 96 1,090 9 26

25 936 12 30 1,690 14 64 1,030 8 22

26 932 10 25 1,610 11 48 1,000 8 22

27 923 10 25 1,690 13 59 1,020 8 22

28 1,090 15 44 1,850 19 95 1,170 12 38

29 1,280 18 62 2,130 31 178 1,160 10 31

30 1,180 12 38 2,180 27 159 1,120 8 24

31 -- -- -- 2,100 22 125 -- -- --

TOTAL 33,504 -- 1,817 45,510 -- 1,857 48,180 -- 2,450

MEAN 1,117 20 61 1,468 14 60 1,606 17 82

MAX 1,300 32 112 2,180 31 178 2,450 57 374

MIN 923 10 25 1,040 5 14 1,000 8 22
TABLE 6 55

 

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2003 

through September 2004.—Continued

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

JULY AUGUST SEPTEMBER

1 1,040 7 20 506 7 9.6 571 8 12

2 996 7 19 490 7 9.3 599 8 13

3 949 6 15 490 7 9.3 595 7 11

4 923 6 15 511 8 11 585 7 11

5 942 5 13 511 9 12 582 6 9.4

6 918 4 9.9 534 10 14 576 6 9.3

7 905 4 9.8 530 9 13 569 6 9.2

8 884 4 9.5 513 8 11 573 6 9.3

9 855 3 6.9 491 7 9.3 568 6 9.2

10 830 3 6.7 465 6 7.5 553 6 9.0

11 845 5 11 445 6 7.2 543 6 8.8

12 834 5 11 434 5 5.9 592 7 11

13 809 4 8.7 412 5 5.6 770 12 25

14 784 4 8.5 395 6 6.4 831 12 27

15 749 5 10 386 7 7.3 793 9 19

16 717 5 9.7 374 7 7.1 767 8 17

17 691 4 7.5 374 7 7.1 749 8 16

18 692 5 9.3 419 8 9.1 753 8 16

19 713 6 12 451 8 9.7 808 9 20

20 762 7 14 452 8 9.8 980 17 45

21 776 8 17 436 7 8.2 999 17 46

22 705 9 17 438 7 8.3 983 16 42

23 669 8 14 527 10 14 946 15 38

24 659 8 14 620 12 20 971 14 37

25 643 9 16 631 12 20 969 12 31

26 623 9 15 668 11 20 931 10 25

27 605 9 15 694 10 19 904 10 24

28 565 8 12 681 10 18 887 10 24

29 540 8 12 655 9 16 891 10 24

30 529 8 11 614 8 13 882 10 24

31 520 6 8.4 586 8 13 -- -- --

TOTAL 23,672 -- 377.9 15,733 -- 350.7 22,720 -- 622.2

MEAN 764 6 12 508 8 11 757 10 21

MAX 1,040 9 20 694 12 20 999 17 46

MIN 520 3 6.7 374 5 5.6 543 6 8.8

TOTAL FOR WATER YEAR 2004:

STREAMFLOW--319,238 ft3

/s

SEDIMENT LOAD--14,084.4 tons
56 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

 

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2003 through

September 2004.

[Abbreviations: ft3/s, cubic feet per second; e, estimated; mg/L, milligrams per liter; ton/d, tons per day. Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

OCTOBER NOVEMBER DECEMBER

1 994 7 19 1,070 5 14 1,270 5 17

2 1,010 7 19 1,140 5 15 1,270 5 17

3 1,020 7 19 1,250 4 14 1,290 7 24

4 1,030 7 19 1,190 4 13 1,290 7 24

5 1,060 7 20 1,160 4 13 1,250 6 20

6 1,060 7 20 1,060 4 11 1,250 5 17

7 1,070 6 17 1,100 4 12 1,280 6 21

8 1,050 6 17 1,150 5 16 1,270 7 24

9 1,040 6 17 1,280 6 21 1,260 7 24

10 1,040 6 17 1,390 6 23 1,170 6 19

11 1,060 6 17 1,430 7 27 1,180 7 22

12 1,100 6 18 1,370 7 26 1,240 8 27

13 1,130 6 18 1,330 7 25 1,230 8 27

14 1,120 7 21 1,260 6 20 1,220 10 33

15 1,150 7 22 1,220 4 13 1,240 10 33

16 1,190 7 22 1,220 4 13 1,170 11 35

17 1,180 7 22 1,270 4 14 1,120 10 30

18 1,170 7 22 1,310 4 14 1,140 8 25

19 1,130 7 21 1,260 4 14 e1,000 5 14

20 1,130 7 21 1,280 6 21 e950 4 10

21 1,120 6 18 1,330 8 29 e1,000 4 11

22 1,100 6 18 1,270 5 17 e1,200 4 13

23 1,110 6 18 1,110 4 12 e1,100 4 12

24 1,110 6 18 1,160 3 9.4 e1,000 4 11

25 1,110 5 15 1,240 3 10 e1,100 4 12

26 1,110 5 15 1,230 3 10 1,220 4 13

27 1,130 5 15 1,230 3 10 1,130 4 12

28 1,150 5 16 1,190 3 9.6 1,020 4 11

29 1,320 5 18 1,220 4 13 e950 5 13

30 1,390 5 19 1,350 5 18 e900 6 15

31 1,270 5 17 -- -- -- e800 6 13

 TOTAL 34,654 -- 575 37,070 -- 477 35,510 -- 599

 MEAN 1,118 6 19 1,236 5 16 1,145 6 19

 MAX 1,390 7 22 1,430 8 29 1,290 11 35

 MIN 994 5 15 1,060 3 9.4 800 4 10
TABLE 7 57

 

 

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2003 through

September 2004.—Continued

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e850 6 14 1,140 4 12 1,150 5 16

2 e950 6 15 1,080 4 12 1,130 5 15

3 e1,000 6 16 1,040 4 11 1,140 4 12

4 e850 6 14 1,050 4 11 1,120 5 15

5 e700 6 11 1,090 4 12 1,080 10 29

6 e600 7 11 1,050 4 11 1,140 4 12

7 e500 7 9.4 1,070 4 12 1,100 6 18

8 e700 7 13 1,070 4 12 1,180 9 29

9 e800 7 15 1,090 4 12 2,100 46 261

10 e900 6 15 1,070 4 12 2,360 49 312

11 e1,000 6 16 1,060 4 11 2,520 38 259

12 e1,100 6 18 1,010 4 11 2,000 31 167

13 e1,050 6 17 938 4 10 2,020 23 125

14 e1,050 5 14 818 4 8.8 2,070 16 89

15 e1,050 5 14 1,000 3 8.1 1,810 12 59

16 e1,100 5 15 1,110 4 12 1,780 12 58

17 e1,100 5 15 1,080 5 15 1,780 12 58

18 e1,100 5 15 1,110 5 15 1,890 13 66

19 e1,100 5 15 1,160 6 19 2,160 14 82

20 e1,100 4 12 1,200 6 19 2,190 15 89

21 e1,150 5 16 1,170 6 19 2,000 11 59

22 e1,150 5 16 1,130 6 18 1,900 10 51

23 e1,150 5 16 1,100 7 21 2,030 11 60

24 e1,150 5 16 1,100 7 21 2,250 12 73

25 1,140 5 15 1,150 7 22 2,420 12 78

26 1,090 5 15 1,220 8 26 2,460 12 80

27 1,060 5 14 1,230 9 30 2,460 11 73

28 1,070 6 17 1,200 9 29 2,400 10 65

29 1,140 6 18 1,160 8 25 2,330 11 69

30 1,200 5 16 -- -- -- 2,260 12 73

31 1,190 4 13 -- -- -- 2,280 12 74

TOTAL 31,090 -- 456.4 31,696 -- 456.9 58,510 -- 2,526

MEAN 1,003 6 15 1,093 5 16 1,887 15 81

MAX 1,200 7 18 1,230 9 30 2,520 49 312

MIN 500 4 9.4 818 3 8.1 1,080 4 12
58 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2003 through

September 2004.—Continued

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 2,560 12 83 3,940 12 128 5,350 13 188

2 2,690 12 87 3,940 10 106 5,080 12 165

3 2,650 12 86 4,240 10 114 4,900 12 159

4 2,610 12 85 4,780 15 194 4,950 11 147

5 2,770 11 82 5,260 20 284 5,290 13 186

6 3,020 12 98 5,710 27 416 5,820 19 299

7 3,360 13 118 5,780 28 437 6,050 18 294

8 3,720 14 141 5,850 27 426 5,580 14 211

9 4,000 17 184 5,910 26 415 5,160 16 223

10 3,920 15 159 5,630 23 350 5,130 16 222

11 3,740 14 141 5,400 18 262 5,730 23 356

12 3,660 12 119 4,940 14 187 5,710 21 324

13 3,710 11 110 4,480 11 133 5,280 16 228

14 4,060 12 132 4,070 9 99 4,880 12 158

15 4,310 14 163 3,780 7 71 4,550 10 123

16 4,270 16 184 3,530 6 57 4,270 8 92

17 4,080 16 176 3,520 6 57 3,960 7 75

18 3,830 11 114 3,450 5 47 3,750 6 61

19 3,650 10 99 3,740 6 61 3,710 5 50

20 3,440 11 102 3,950 7 75 3,680 5 50

21 3,360 10 91 4,010 7 76 3,410 5 46

22 3,230 9 78 4,450 9 108 3,270 5 44

23 2,990 10 81 5,110 12 166 3,180 5 43

24 3,020 9 73 5,240 12 170 3,040 6 49

25 3,110 8 67 4,930 10 133 3,100 8 67

26 3,130 8 68 4,700 9 114 3,130 7 59

27 3,310 7 63 4,750 10 128 3,170 5 43

28 3,890 11 116 5,080 12 165 3,370 10 91

29 4,360 13 153 5,600 14 212 3,270 11 97

30 4,210 14 159 5,750 18 279 3,200 8 69

31 -- -- -- 5,560 15 225 -- -- --

TOTAL 104,660 -- 3,412 147,080 -- 5,695 130,970 -- 4,219

MEAN 3,489 12 114 4,745 13 184 4,366 11 141

MAX 4,360 17 184 5,910 28 437 6,050 23 356

MIN 2,560 7 63 3,450 5 47 3,040 5 43
59 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

 

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2003 through

September 2004.—Continued

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

Mean 

concentration

(mg/L)

Discharge 

(ton/d)

JULY AUGUST SEPTEMBER

1 3,010 6 49 1,180 28 89 1,190 4 13

2 2,860 6 46 1,150 25 78 1,190 3 9.6

3 2,660 5 36 1,130 22 67 1,220 4 13

4 2,570 4 28 1,140 21 65 1,170 3 9.5

5 2,580 4 28 1,150 20 62 1,190 4 13

6 2,510 4 27 1,150 22 68 1,160 3 9.4

7 2,400 4 26 1,160 20 63 1,140 3 9.2

8 2,360 4 25 1,130 17 52 1,130 4 12

9 2,200 4 24 1,110 16 48 1,130 3 9.2

10 2,160 4 23 1,070 17 49 1,140 5 15

11 2,140 4 23 1,010 17 46 1,080 4 12

12 2,100 6 34 993 15 40 1,130 4 12

13 1,990 6 32 958 14 36 1,310 5 18

14 1,880 7 36 917 12 30 1,530 7 29

15 1,830 7 35 867 10 23 1,470 6 24

16 1,790 7 34 826 7 16 1,430 6 23

17 1,790 7 34 832 5 11 1,370 6 22

18 1,720 9 42 830 4 9.0 1,360 6 22

19 1,690 16 73 864 4 9.3 1,420 7 27

20 1,690 24 110 1,020 6 17 1,660 7 31

21 1,700 30 138 987 6 16 1,790 7 34

22 1,600 33 143 960 6 16 1,700 7 32

23 1,530 36 149 1,130 7 21 1,660 7 31

24 1,470 41 163 1,270 7 24 e1,660 7 31

25 1,430 42 162 1,350 7 26 e1,650 6 27

26 1,390 41 154 1,350 8 29 e1,600 6 26

27 1,360 40 147 1,380 6 22 e1,570 6 25

28 1,310 42 149 1,370 6 22 e1,550 5 21

29 1,260 43 146 1,330 5 18 1,550 5 21

30 1,210 36 118 1,280 4 14 1,540 5 21

31 1,190 29 93 1,220 4 13 -- -- --

TOTAL 59,380 -- 2,327 34,114 -- 1,099.3 41,690 -- 601.9

MEAN 1,915 18 75 1,100 12 35 1,390 5 20

MAX 3,010 43 163 1,380 28 89 1,790 7 34

MIN 1,190 4 23 826 4 9.0 1,080 3 9.2

TOTAL FOR WATER YEAR 2004:

STREAMFLOW--746,424 ft3

/s

SEDIMENT LOAD--22,444.5 tons
60 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 8. Analyses of field replicates for water samples, upper Clark Fork basin, Montana.

[Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbol: <, less than laboratory reporting level]

Site

number

(fig. 1)

Site name Date Time

Hardness,

 filtered

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium,

filtered 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable

(μg/L)

12340500 Clark Fork above Missoula 11/18/03 1600 160 44.6 12.8 3.7 4

Clark Fork above Missoula 11/18/03 1605 170 45.0 13.0 3.8 4

12323600 Silver Bow Creek at Opportunity 03/16/04 1540 190 55.0 12.0 12.1 15

Silver Bow Creek at Opportunity 03/16/04 1545 180 53.9 12.1 12.1 14

12323750 Silver Bow Creek at Warm Springs 04/20/04 1200 250 73.8 17.1 12.2 16

Silver Bow Creek at Warm Springs 04/20/04 1205 260 73.9 17.4 12.1 15

12324200 Clark Fork at Deer Lodge 05/17/04 1505 240 70.2 14.5 10.9 13

Clark Fork at Deer Lodge 05/17/04 1510 240 71.2 14.7 11.0 14

12334550 Clark Fork at Turah Bridge, near Bonner 06/02/04 1705 100 29.0 6.75 4.4 4

Clark Fork at Turah Bridge, near Bonner 06/02/04 1710 100 28.9 6.91 4.5 5

12331800 Clark Fork near Drummond 06/13/04 1645 170 49.1 11.3 10.6 14

Clark Fork near Drummond 06/13/04 1650 170 49.5 11.5 10.8 14

12323700 Mill Creek at Opportunity 07/19/04 1045 59 17.1 3.93 30.5 30

Mill Creek at Opportunity 07/19/04 1050 60 17.4 4.00 30.7 31

12334510 Rock Creek near Clinton 08/23/04 1110 63 16.7 5.07 .8 <2

Rock Creek near Clinton 08/23/04 1115 63 16.8 5.06 .7 <2
TABLE 8 61

Table 8. Analyses of field replicates for water samples, upper Clark Fork basin, Montana.—Continued

Station 

number Date

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

recoverable

(μg/L)

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

12340500 11/18/03 <0.04 0.04 2.8 5.8 E4 100 <0.08 0.53

11/18/03 <.04 .04 2.9 5.8 <6 80 <.08 .54

12323600 03/16/04 .85 1.18 46.2 107 15 500 .33 13.1

03/16/04 .87 1.20 46.9 96.0 16 510 .32 13.2

12323750 04/20/04 E.04 .10 3.3 5.9 11 200 E.05 .88

04/20/04 E.04 .10 3.4 6.2 12 200 E.05 .90

12324200 05/17/04 E.04 .10 5.6 14.2 10 190 E.06 1.32

05/17/04 .04 .10 5.7 14.1 11 190 E.07 1.33

12334550 06/02/04 <.04 .06 2.5 6.3 11 180 E.05 .81

06/02/04 <.04 .06 2.5 7.9 10 180 E.05 .84

12331800 06/13/04 <.04 .14 4.2 19.0 10 450 .10 3.45

06/13/04 E.02 .14 4.3 18.8 10 440 .10 3.52

12323700 07/19/04 .07 .08 2.8 4.1 74 130 .19 .43

07/19/04 .06 .09 2.8 4.0 74 130 .18 .39

12334510 08/23/04 <.04 <.04 .7 <.6 13 90 <.08 E.05

08/23/04 <.04 <.04 E.3 <.6 14 100 <.08 .07
62 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 8. Analyses of field replicates for water samples, upper Clark Fork basin, Montana.—Continued

Station 

number Date

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc,

filtered

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

12340500 11/18/03 9.7 17 2.3 8 93 4

11/18/03 9.9 18 2.5 8 90 4

12323600 03/16/04 423 446 129 228 83 10

03/16/04 428 449 130 228 81 10

12323750 04/20/04 247 304 3.5 9 90 4

04/20/04 246 307 3.5 10 93 3

12324200 05/17/04 37.3 70 4.9 14 88 8

05/17/04 37.4 69 4.7 14 91 10

12334550 06/02/04 4.8 24 1.5 9 67 12

06/02/04 4.8 24 2.4 9 67 12

12331800 06/13/04 15.6 97 2.9 26 89 23

06/13/04 15.7 97 3.0 26 89 23

12323700 07/19/04 11.7 13 2.2 2 80 1

07/19/04 11.6 13 2.1 3 83 1

12334510 08/23/04 2.9 9 <.6 <2 80 5

08/23/04 2.7 9 <.6 E1 79 5
TABLE 9 63

Table 9. Precision of analyses of field replicates for water samples, upper Clark Fork

 basin, Montana.

[Abbreviations: μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter]

Constituent and reporting unit

Number of 

replicate 

pairs

Standard 

deviation1, 

in listed units

Relative 

standard 

deviation,

in percent

Calcium, filtered, mg/L 8 0.41 0.91

Magnesium, filtered, mg/L 8 .13 1.2

Arsenic, filtered, μg/L 8 .09 .84

Arsenic, unfiltered recoverable, μg/L 8 .56 4.6

Cadmium, filtered, μg/L 8 .01 4.1

Cadmium, unfiltered recoverable, μg/L 8 .01 2.6

Copper, filtered, μg/L 8 .21 2.4

Copper, unfiltered recoverable, μg/L 8 2.8 14

Iron, filtered, μg/L 8 .61 3.3

Iron, unfiltered recoverable, μg/L 8 6.6 2.9

Lead, filtered, μg/L 8 .00 4.1

Lead, unfiltered recoverable, μg/L 8 .03 1.3

Manganese, filtered, μg/L 8 1.3 1.4

Manganese, unfiltered recoverable, μg/L 8 1.1 .91

Zinc, filtered, μg/L 8 .35 1.9

Zinc, unfiltered recoverable, μg/L 8 .35 .95

Sediment, suspended, percent finer than 0.062 mm 8 1.6 1.9

Sediment, suspended, mg/L 8 .56 6.6

1

Standard deviation is calculated using one-half the laboratory reporting level for censored values.
64 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 10. Precision of analyses of laboratory replicates for water samples, upper Clark Fork basin, Montana.

[Abbreviations: μg/L, micrograms per liter; mg/L, milligrams per liter]

Constituent and reporting unit

Number of 

replicate 

pairs

Standard 

deviation1,

in listed units

Relative 

standard 

deviation,

in percent

Within 

limits2

of dataquality 

objective

Calcium, filtered, mg/L 7 0.21 0.61 Yes

Magnesium, filtered, mg/L 7 .15 1.7 Yes

Arsenic, filtered, μg/L 7 .19 1.8 Yes

Arsenic, unfiltered recoverable, μg/L 7 1.2 10 Yes

Cadmium, filtered, μg/L 7 .01 2.6 Yes

Cadmium, unfiltered recoverable, μg/L 7 .02 3.7 Yes

Copper, filtered, μg/L 7 .07 .55 Yes

Copper, unfiltered recoverable, μg/L 7 .12 .36 Yes

Iron, filtered, μg/L 7 .22 1.2 Yes

Iron, unfiltered recoverable, μg/L 7 2.6 1.2 Yes

Lead, filtered, μg/L 7 .00 3.2 Yes

Lead, unfiltered recoverable, μg/L 7 .03 .72 Yes

Manganese, filtered, μg/L 7 1.3 1.3 Yes

Manganese, unfiltered recoverable, μg/L 7 1.5 .92 Yes

Zinc, filtered, μg/L 7 .48 1.8 Yes

Zinc, unfiltered recoverable, μg/L 7 1.2 1.3 Yes

1Standard deviation is calculated using laboratory reporting level for censored values.

2Data-quality objective for an acceptable level of precision is a maximum relative standard deviation of 20 percent for

laboratory replicate analyses (table 3).
TABLE 11 65

Table 11. Recovery efficiency for analyses of laboratory-spiked deionized-water blanks.

[Abbreviation: μg/L, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent 

confidence 

interval for spike 

recovery,

in percent

Mean spike 

recovery,

in percent

Within 

limits1

of dataquality 

objective

Arsenic, filtered, μg/L 5 75.0-127 101 Yes

Arsenic, unfiltered recoverable, μg/L 5 93.6-110 102 Yes

Cadmium, filtered, μg/L 5 95.6-99.2 97.4 Yes

Cadmium, unfiltered recoverable, μg/L 5 98.6-101 100 Yes

Copper, filtered, μg/L 5 92.7-105 98.9 Yes

Copper, unfiltered recoverable, μg/L 5 95.4-104 99.6 Yes

Iron, filtered, μg/L 5 88.8-103 96.1 Yes

Iron, unfiltered recoverable, μg/L 5 96.3-106 101 Yes

Lead, filtered, μg/L 5 91.9-100 96.0 Yes

Lead, unfiltered recoverable, μg/L 5 97.3-100 98.9 Yes

Manganese, filtered, μg/L 5 90.6-107 98.6 Yes

Manganese, unfiltered recoverable, μg/L 5 92.3-106 99.1 Yes

Zinc, filtered, μg/L 5 91.7-112 102 Yes

Zinc, unfiltered recoverable, μg/L 5 96.3-104 100 Yes

1Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).
66 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 12. Recovery efficiency for analyses of laboratory-spiked stream samples, upper Clark Fork basin, Montana.

[Abbreviation: μg/L, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent 

confidence 

interval for 

spike recovery, 

in percent

Mean spike 

recovery,

in percent

Within limits1

of dataquality 

objective

Arsenic, filtered, μg/L 5 86.9-108 97.3 Yes

Arsenic, unfiltered recoverable, μg/L 5 106-118 112 Yes

Cadmium, filtered, μg/L 5 94.2-108 101 Yes

Cadmium, unfiltered recoverable, μg/L 5 100-103 101 Yes

Copper, filtered, μg/L 5 93.8-97.0 95.4 Yes

Copper, unfiltered recoverable, μg/L 5 89.5-98.1 93.8 Yes

Iron, filtered, μg/L 5 91.2-130 111 Yes

Iron, unfiltered recoverable, μg/L 5 99.5-108 104 Yes

Lead, filtered, μg/L 5 93.0-104 98.7 Yes

Lead, unfiltered recoverable, μg/L 5 98.6-102 100 Yes

Manganese, filtered, μg/L 5 91.8-100 96.0 Yes

Manganese, unfiltered recoverable, μg/L 5 89.8-117 103 Yes

Zinc, filtered, μg/L 5 95.3-105 100 Yes

Zinc, unfiltered recoverable, μg/L 5 91.0-97.8 94.4 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).
TABLE 13 67

 

Table 13. Analyses of field blanks for water samples.

[Abbreviations; oC, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25oC; mg/L, milligrams per liter.

Symbol: <, less than laboratory reporting level]

Date Time

pH,

onsite 

(standard 

units)

Specific 

conductance,

onsite

(μS/cm)

Calcium, 

filtered

(mg/L)

Magnesium,

filtered

(mg/L)

Arsenic, 

filtered

(μg/L)

Arsenic, 

unfiltered 

recoverable

(μg/L)

Cadmium, 

filtered

(μg/L)

Cadmium, 

unfiltered 

(μg/L)

NOV 2003

18... 0915 5.6 2 E0.01 <0.008 <0.2 <2 <0.04 <0.04

MAR 2004

15... 1100 5.6 2 .02 <.008 <.2 <2 .07 <.04

APR

21... 1500 5.5 2 E.01 <.008 <.2 <2 <.04 <.04

MAY

17... 1900 5.6 1 .01 <.008 <.2 <2 <.04 <.04

JUN

01... 0600 5.6 2 E.01 <.008 <.2 <2 <.04 <.04

13... 1200 5.5 1 .01 <.008 <.2 <2 <.04 <.04

JUL

19... 1200 5.7 1 .01 <.008 <.2 <2 <.04 <.04

AUG

23... 0600 5.5 2 E.01 <.008 <.2 <2 <.04 <.04

Date

Copper, 

filtered

(μg/L)

Copper, 

unfiltered 

recoverable

(μg/L)

Iron, 

filtered

(μg/L)

Iron, 

unfiltered 

(μg/L)

Lead,

filtered

(μg/L)

Lead, 

unfiltered 

recoverable

(μg/L)

Manganese, 

filtered

(μg/L)

Manganese, 

unfiltered 

(μg/L)

Zinc, 

filtered

(μg/L)

Zinc, 

unfiltered 

recoverable

(μg/L)

NOV 2003

18... <0.4 <0.6 <6 <9 <0.08 <0.06 <0.2 <0.2 <0.6 <2

MAR 2004

15... <.4 <.6 <6 <9 <.08 <.06 <.2 <.2 E.4 <2

APR

21... <.4 <.6 <6 <9 <.08 <.06 <.2 <.2 <.6 <2

MAY

17... <.4 <.6 <6 <9 <.08 <.06 <.2 <.2 <.6 <2

JUN

01... <.4 <.6 <6 <9 <.08 <.06 <.2 <.2 E.4 <2

13... <.4 <.6 <6 <9 <.08 <.06 <.2 <.2 E.5 <2

JUL

19... <.4 <.6 <6 <9 <.08 <.06 <.2 <.2 <.6 <2

AUG

23... <.4 <.6 <6 <9 E.07 <.06 <.2 <.2 <.6 <2
68 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 14. Analyses of fine-grained bed sediment, upper Clark Fork basin, Montana, August 2004.[Fine-grained bed sediment is material less than 0.064 millimeter in diameter. Reported concentrations are the mean of all analyses for replicate aliquots from each composite sample. 

Abbreviation: μg/g, micrograms per gram of dry sample weight. Symbol: <, less than minimum reporting level]

Site number

(fig. 1) Site name

Number 

of composite 

samples

Concentration, in μg/g

Arsenic Cad- mium Chro- mium Cop- per Iron Lead Manga- nese Nickel Zinc

12323600 Silver Bow Creek at Opportunity 3 163 43.9 20.8 4,510 31,200 481 7,620 14.9 10,10012323750 Silver Bow Creek at Warm Springs 3 177 11.4 15.9 346 31,700 75 12,900 18.5 1,10012323800 Clark Fork near Galen 3 119 5.2 19.5 838 24,000 92 11,900 13.9 999461415112450801 Clark Fork below Lost Creek, near Galen 3 92 5.8 20.5 1,150 24,400 127 5,570 11.7 1,160461559112443301 Clark Fork near Racetrack 3 56 5.2 19.0 940 21,200 103 3,990 10.3 999461903112440701 Clark Fork at Demspey Creek diversion, 

near Racetrack 

3 58 4.4 17.8 721 20,600 92 3,990 8.7 902

12324200 Clark Fork at Deer Lodge 3 49 3.8 20.2 683 21,100 103 2,460 11.5 84612324590 Little Blackfoot River near Garrison 3 12 1.0 33.1 33 24,500 39 1,120 17.2 17712324680 Clark Fork at Goldcreek 3 24 3.1 22.1 432 20,200 70 2,560 11.5 66912331500 Flint Creek near Drummond 3 102 1.6 17.4 44 22,300 143 5,140 10.2 56112331800 Clark Fork near Drummond 3 31 3.7 20.3 395 20,400 76 1,890 11.5 84912334510 Rock Creek near Clinton 3 6 <.1 16.4 7 15,500 12 361 8.7 3112334550 Clark Fork at Turah Bridge, near Bonner 3 22 2.3 17.8 250 16,700 57 1,570 10.3 64712340500 Clark Fork above Missoula 3 29 3.4 20.4 411 20,700 62 970 13.0 87212353000 Clark Fork below Missoula1 3 14 1.8 17.0 183 18,700 41 1,840 11.4 469

1Samples collected about 30 miles downstream from streamflow-gaging station to conform to previous sampling location.
TABLE 15 69

Table 15. Analyses of bulk bed sediment, upper Clark Fork basin, Montana, August 2004.[Bulk bed sediment is material less than about 10 millimeters in diameter. Reported concentrations are the mean of all analyses for replicate aliquots from each composite sample.

 Abbreviation: μg/g, micrograms per gram of dry sample weight. Symbol: <, less than minimum reporting level]

Site number

(fig. 1) Site name

Number 

of composite 

samples

Concentration, in μg/g

Arsenic Cad- mium Chro- mium Cop- per Iron Lead Manga- nese Nickel Zinc

12323600 Silver Bow Creek at Opportunity 1 60 5.4 11.3 615 18,300 138 1,620 6.1 1,72012323750 Silver Bow Creek at Warm Springs 1 15 1.3 8.1 27 8,060 13 711 5.8 125

12323800 Clark Fork near Galen 1 76 1.0 9.3 291 21,400 56 2,850 5.5 768461415112450801 Clark Fork below Lost Creek, near Galen 1 87 1.2 11.0 330 17,800 70 1,790 5.6 431

461559112443301 Clark Fork near Racetrack 1 46 1.0 9.4 296 15,800 52 2,040 5.0 520461903112440701 Clark Fork at Dempsey Creek diversion,

near Racetrack

1 18 .4 11.5 128 15,800 57 825 4.2 245

12324200 Clark Fork at Deer Lodge 1 37 2.7 19.3 523 21,500 81 873 9.8 67912324590 Little Blackfoot River near Garrison 1 12 .4 20.7 14 19,700 19 716 11.7 8212324680 Clark Fork at Goldcreek 1 16 .7 10.2 135 11,600 26 402 6.9 26012331500 Flint Creek near Drummond 1 30 .3 6.9 7 9,230 38 2,610 4.4 17012331800 Clark Fork near Drummond 1 16 1.7 13.0 195 14,000 41 615 8.0 47212334510 Rock Creek near Clinton 1 4 <.1 10.6 7 10,600 8 240 6.9 1712334550 Clark Fork at Turah Bridge, near Bonner 1 9 .9 11.7 114 11,600 28 510 7.6 32612340500 Clark Fork above Missoula 1 17 1.6 9.8 176 14,500 31 1,170 9.0 41612353000 Clark Fork below Missoula1 1 6 .3 13.2 36 18,700 9 601 12.0 124

1Samples collected about 30 miles downstream from streamflow-gaging station to conform to previous sampling location.
70 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 16. Recovery efficiency for analyses of standard reference materials for bed sediment.

[Abbreviations: μg/g, micrograms per gram of dry sample weight; SRM, standard reference material (agricultural

soils). Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to

final volume of solution after addition of 0.6N (normal) hydrochloric acid used for reconstituting dried residue]

Constituent Number of 

analyses

Dilution 

ratio

Certified 

concentration 

(μg/g)

Mean SRM 

recovery,

in percent

95-percent 

confidence interval 

for SRM recovery,

in percent

SRM sample 2709

Arsenic 9 1:10 17.7 63.0 60.8 - 65.1

Cadmium 9 1:10 .4 83.7 82.1 - 85.3

Chromium 9 1:10 130 66.7 63.6 - 69.8

Copper 9 1:10 35 71.2 64.3 - 78.1

Iron 9 1:10 35,000 92.4 91.0 - 93.9

Lead 9 1:10 19 98.6 95.0 - 102

Manganese 9 1:10 538 93.4 92.3 - 94.5

Nickel 9 1:10 88 83.7 82.2 - 85.2

Zinc 9 1:10 106 84.1 82.4 - 85.8

SRM sample 2711

Arsenic 9 1:10 105 83.5 82.1 - 84.9

Cadmium 9 1:10 41.7 95.9 94.4 - 97.4

Chromium 9 1:10 47 56.5 52.4 - 60.5

Copper 9 1:10 114 88.1 85.9 - 90.2

Iron 9 1:10 28,900 85.8 84.4 - 87.2

Lead 9 1:10 1,160 90.1 88.7 - 91.6

Manganese 9 1:10 638 83.3 82.4 - 84.1

Nickel 9 1:10 20.6 75.7 74.8 - 76.6

Zinc 9 1:10 350 92.5 91.7 - 93.4
TABLE 17 71

Table 17. Analyses of procedural blanks for bed sediment.[Abbreviation: μg/mL, micrograms per milliliter. Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to final volume of solution after addition

of 0.6N (normal) hydrochloric acid used for reconstituting dried residue. Symbol: <, less than minimum reporting level]

Site number

(fig. 1) Site name Dilution ratio

Trace element concentration, in μg/mL

Arsenic Cad- mium Chro- mium Cop- per Iron Lead Manga- nese Nickel Zinc

12323600 Silver Bow Creek at Opportunity 1:10 <0.01 <0.001 <0.004 <0.01 <0.02 <0.01 <0.002 <0.003 <0.0112323750 Silver Bow Creek at Warm Springs 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.01

12323800 Clark Fork near Galen 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.01

461415112450801 Clark Fork below Lost Creek, near Galen 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.01461559112443301 Clark Fork near Racetrack 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.01461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.0112324200 Clark Fork at Deer Lodge 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.0112324590 Little Blackfoot River near Garrison 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.0112324680 Clark Fork at Goldcreek 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.0112331500 Flint Creek near Drummond 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.01

12331800 Clark Fork near Drummond 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.0112334510 Rock Creek near Clinton 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.0112334550 Clark Fork at Turah Bridge, near Bonner 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.01

12340500 Clark Fork above Missoula 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.01

12353000 Clark Fork below Missoula 1:10 <.01 <.001 <.004 <.01 <.02 <.01 <.002 <.003 <.01
72 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 18. Analyses of biota, upper Clark Fork basin, Montana, August 2004.

[Analyses are for the whole-body tissue of aquatic insects. Composite samples are made by combining similar-sized insects of the same species into a sample of 

sufficient mass for analysis. Concentrations for biota samples composed of two or more composite samples are the means of all analyses. Abbreviations: μg/g, 

micrograms per gram of dry sample weight; spp., one or more similar species. Symbol: <, less than minimum reporting level]

Taxon

Number

of composite 

samples

Concentration, in μg/g

Arsenic Cadmium

ChromiumCopper

Iron Lead ManganeseNickel Zinc

12323600 Silver Bow Creek at Opportunity

Hydropsyche cockerelli 2 10.4 5.1 1.2 348 1,220 21.8 1,180 1.3 825

Hydropsyche spp. 1 10.7 4.6 1.1 312 1,050 21.8 1,180 .7 834

12323750 Silver Bow Creek at Warm Springs

Hydropsyche cockerelli 1 23.6 <.5 2.2 26.3 1,590 <5.0 3,890 <1.0 198

Hydropsyche occidentalis 1 31.0 .2 3.3 38.5 2,360 6.4 6,940 2.6 220

12323800 Clark Fork near Galen

Hydropsyche cockerelli 1 15.8 .9 1.8 123 1,460 7.3 2,500 1.8 212

Hydropsyche spp. 2 15.1 .8 2.3 80.9 1,260 6.9 4,580 1.6 223

461415112450801 Clark Fork below Lost Creek, near Galen

Hydropsyche cockerelli 2 11.6 1.5 1.1 125 1,050 7.3 1,300 .9 220

Hydropsyche occidentalis 1 15.6 <.5 1.2 97.3 1,420 8.0 3,870 <1.0 275

461559112443301 Clark Fork near Racetrack

Hydropsyche cockerelli 1 14.3 .8 1.2 84.3 871 5.5 2,020 .9 187

461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack

Hydropsyche cockerelli 2 9.4 1.0 1.0 90.2 738 3.8 1,950 .7 221

12324200 Clark Fork at Deer Lodge

Hydropsyche cockerelli 2 5.9 .7 1.1 76.2 578 3.9 1,050 .6 179

Hydropsyche occidentalis 1 6.6 .6 1.4 78.6 730 4.6 2,060 1.2 213

12324590 Little Blackfoot River near Garrison

Arctopsyche grandis 3 3.6 <.1 1.0 10.6 592 .6 970 1.2 148

Claassenia sabulosa 1 1.3 <.1 .5 37.2 201 <.4 149 .4 271

Hydropsyche spp. 1 3.7 <.2 1.8 11.1 1,000 <2.4 1,200 .9 151

12324680 Clark Fork at Goldcreek

Arctopsyche grandis 3 2.3 .9 .7 21.0 310 1.3 905 .3 191

Claassenia sabulosa 3 1.6 .2 .5 56.6 215 .6 260 .4 270

Hydropsyche cockerelli 2 4.3 .5 1.3 38.6 736 2.8 1,300 .8 187

Hydropsyche occidentalis 1 4.7 .4 1.8 41.1 975 4.3 2,120 .8 215
TABLE 18 73

12331500 Flint Creek near Drummond

Arctopsyche grandis 3 3.2 <.1 .9 11.4 708 4.5 1,460 .7 171

Hydropsyche cockerelli 1 6.4 <.2 1.7 11.6 1,610 10.1 2,480 .7 186

Hydropsyche occidentalis 1 6.1 <.3 2.1 11.5 1,430 10.2 3,330 <.5 166

12331800 Clark Fork near Drummond

Arctopsyche grandis 3 2.5 .6 .8 22.3 384 3.1 1,080 .5 195

Claassenia sabulosa 2 1.3 .1 .5 44.5 182 1.0 259 .2 278

Hydropsyche cockerelli 3 4.0 .4 1.2 38.9 875 5.7 1,360 .9 200

Hydropsyche occidentalis 1 4.5 .4 1.8 41.3 1,260 10.0 2,800 1.2 248

12334510 Rock Creek near Clinton

Arctopsyche grandis 2 2.4 <.1 .4 8.2 586 <.4 260 .9 130

Claassenia sabulosa 2 1.0 .1 .4 27.3 99 <.3 46 .2 174

Hydropsyche spp. 1 .7 <.5 <2.4 6.1 789 <4.9 377 <.9 112

12334550 Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 4 4.1 .5 .6 25.4 500 2.7 845 .8 199

Claassenia sabulosa 2 1.1 .1 .3 58.6 127 .5 132 .3 264

Hydropsyche cockerelli 2 5.0 .4 1.5 41.3 1,070 4.5 799 1.2 210

Hydropsyche occidentalis 2 4.1 .4 .7 36.7 1,010 4.7 1,040 1.2 230

12340500 Clark Fork above Missoula

Arctopsyche grandis 3 3.4 .2 1.2 36.1 884 4.9 1,100 1.0 184

Hydropsyche cockerelli 2 5.3 <.1 2.1 57.1 1,770 9.1 1,370 1.5 209

12353000 Clark Fork below Missoula1

Arctopsyche grandis 1 2.1 .4 .8 19.2 602 1.6 862 .6 158

Claassenia sabulosa 1 1.1 .3 .5 75.1 227 .3 275 .2 324

Hydropsyche cockerelli 3 2.8 .5 1.4 35.1 1,190 2.7 977 1.2 167

1

Samples collected about 30 miles downstream from streamflow-gaging station to conform to previous sampling location.

Table 18. Analyses of biota, upper Clark Fork basin, Montana, August 2004.—Continued

[Analyses are for the whole-body tissue of aquatic insects. Composite samples are made by combining similar-sized insects of the same species into a sample of 

sufficient mass for analysis. Concentrations for biota samples composed of two or more composite samples are the means of all analyses. Abbreviations: μg/g, 

micrograms per gram of dry sample weight; spp., one or more similar species. Symbol: <, less than minimum reporting level]

Taxon

Number

of composite 

samples

Concentration, in μg/g

Arsenic Cadmium

ChromiumCopper

Iron Lead ManganeseNickel Zinc
74 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

 

Table 19. Recovery efficiency for analyses of standard reference material

for biota.

[Abbreviations: μg/g, micrograms per gram of dry sample weight; μg/mL, micrograms per

milliliter; SRM, standard reference material (lobster hepatopancreas)]

Constituent Number of 

analyses 

Certified 

concentration

(μg/g)

Mean SRM 

recovery,

in percent

95-percent 

confidence 

interval for 

SRM recovery, 

in percent

SRM sample TORT-2

Arsenic 12 21.6 99.7 98.9 - 100

Cadmium 12 26.7 92.1 90.5 - 93.6

Chromium 12 .77 106 96.5 - 115

Copper 12 106 97.9 92.6 - 103

Iron 12 105 96.7 94.4 - 99.0

Lead 1

12 .35 70.4 33.4 - 107

Manganese 12 13.6 100 98.5 - 102

Nickel 12 2.5 82.5 79.6 - 85.3

Zinc 12 180 102 101 - 103

1

Lead concentrations in six analyses were less than the minimum reporting level (0.01 μg/mL).
Table 20 75

Table 20. Analyses of procedural blanks for biota.[Procedural blanks were not diluted prior to analyses. Abbreviation: μg/mL, micrograms per milliliter. Symbol: <, less than minimum reporting level]

Site number Site name Dilution ratio

Trace-element concentration, in μg/mL

Arsenic Cad- mium Chro- mium Cop- per Iron Lead Man- ganese Nickel Zinc

12323600 Silver Bow Creek at Opportunity 1:1 <0.008 <0.001 <0.005 <0.02 <0.005 <0.01 <0.002 <0.002 <0.01

12323750 Silver Bow Creek at Warm Springs 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.0112323800 Clark Fork near Galen 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01

461415112450801 Clark Fork below Lost Creek, near Galen 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01461559112443301 Clark Fork near Racetrack 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.0112324200 Clark Fork at Deer Lodge 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01

12324590 Little Blackfoot River near Garrison 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01

12324680 Clark Fork at Goldcreek 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01

12331500 Flint Creek near Drummond 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01

12331800 Clark Fork near Drummond 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01

12334510 Rock Creek near Clinton 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01

12334550 Clark Fork at Turah Bridge, near Bonner 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01

12340500 Clark Fork above Missoula 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.0112353000 Clark Fork below Missoula 1:1 <.008 <.001 <.005 <.02 <.005 <.01 <.002 <.002 <.01
76 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

 

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2004.

[Abbreviations: ft3/s, cubic feet per second; oC, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25oC; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1

; --, indicates insufficient data greater than the

laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323230--BLACKTAIL CREEK AT HARRISON AVENUE, AT BUTTE, MONT.

Period of record for water-quality data: March 1993-August 1995, December 1996-August 2003

Streamflow, instantaneous (ft3/s) 83 156 1.9 14 7.9

pH, onsite (standard units) 83 8.4 7.3 7.8 7.8

Specific conductance, onsite (μS/cm) 83 412 116 267 271

Temperature, water (oC) 83 17.5 1.5 8.2 8.0

Hardness, filtered (mg/L as CaCO3) 83 150 38 105 110

Calcium, filtered (mg/L) 83 41.8 10.6 30 31

Magnesium, filtered (mg/L) 83 11.0 2.71 7.3 7.4

Arsenic, filtered (μg/L) 83 13 1 4 3

Arsenic, unfiltered (μg/L) 83 18 <2 2

5 4

Cadmium, filtered (μg/L) 83 .5 <.1 2

<.1 <.1

Cadmium, unfiltered (μg/L) 83 .11 <.04 2

<.1 <1

Copper, filtered (μg/L) 83 10 E.8 2

4 3

Copper, unfiltered (μg/L) 83 52 1.5 7 6

Iron, filtered (μg/L) 83 478 15 163 157

Iron, unfiltered (μg/L) 83 4,220 140 700 550

Lead, filtered (μg/L) 83 1 <.08 2

.2 <.5

Lead, unfiltered (μg/L) 83 47 <1 2

2 1

Manganese, filtered (μg/L) 83 144 17 44 39

Manganese, unfiltered (μg/L) 83 240 24 62 53

Zinc, filtered (μg/L) 83 11 <1 2

4 3

Zinc, unfiltered (μg/L) 83 130 <10 2

11 3

Sediment, suspended (percent finer than 0.062 mm) 83 97 50 83 84

Sediment, suspended concentration (mg/L) 83 139 2 15 7

Sediment, suspended discharge (ton/d) 83 59 .02 1.4 .14
TABLE 21 77

 

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323250--SILVER BOW CREEK BELOW BLACKTAIL CREEK, AT BUTTE, MONT.

Period of record for water-quality data: March 1993-August 1995, December 1996-September 2004

Streamflow, instantaneous (ft3/s) 91 134 13 28 23

pH, onsite (standard units) 91 8.1 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 91 691 226 479 485

Temperature, water (oC) 91 20.0 1.0 10.4 9.5

Hardness, filtered (mg/L as CaCO3) 91 220 66 152 160

Calcium, filtered (mg/L) 91 62.7 19.0 43.2 44.0

Magnesium, filtered (mg/L) 91 14.6 4.51 10.7 11.0

Arsenic, filtered (μg/L) 91 13 3.3 7 7

Arsenic, unfiltered (μg/L) 91 45 4 12 10

Cadmium, filtered (μg/L) 91 6.2 .09 1.5 1.2

Cadmium, unfiltered (μg/L) 91 6 .11 1.9 1.7

Copper, filtered (μg/L) 91 303 3.2 46 22

Copper, unfiltered (μg/L) 91 550 13.5 108 73

Iron, filtered (μg/L) 91 270 E10 2

81 61

Iron, unfiltered (μg/L) 91 7,400 90 1,030 650

Lead, filtered (μg/L) 91 2.4 <.5 2

.6 .17

Lead, unfiltered (μg/L) 91 250 .65 17 7

Manganese, filtered (μg/L) 91 1,700 21.4 458 392

Manganese, unfiltered (μg/L) 91 1,600 26 506 440

Zinc, filtered (μg/L) 91 2,200 34 477 328

Zinc, unfiltered (μg/L) 91 2,200 45 574 419

Sediment, suspended (percent finer than 0.062 mm) 90 98 42 84 86

Sediment, suspended concentration (mg/L) 90 405 2 27 12

Sediment, suspended discharge (ton/d) 90 70 .09 3.2 .86
78 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323600--SILVER BOW CREEK AT OPPORTUNITY, MONT.

Period of record for water-quality data: March 1993-August 1995, December 1996-September 2004

Streamflow, instantaneous (ft3/s) 94 361 13 73 51

pH, onsite (standard units) 93 9.5 7.2 8.4 8.4

Specific conductance, onsite (μS/cm) 93 633 202 411 400

Temperature, water (o

C) 93 22.5 0.0 9.5 9.5

Hardness, filtered (mg/L as CaCO3) 93 240 60 147 140

Calcium, filtered (mg/L) 93 71.6 18.5 43.6 43.0

Magnesium, filtered (mg/L) 93 15.0 3.42 9.4 9.0

Arsenic, filtered (μg/L) 93 34 1 11 10

Arsenic, unfiltered (μg/L) 93 235 11 29 18

Cadmium, filtered (μg/L) 93 41 .1 1.4 .9

Cadmium, unfiltered (μg/L) 93 49 .52 2

2.5 1.7

Copper, filtered (μg/L) 93 450 18.5 53.5 42.1

Copper, unfiltered (μg/L) 93 3,900 54.3 245 138

Iron, filtered (μg/L) 93 307 3 245 24

Iron, unfiltered (μg/L) 93 24,100 260 1,670 800

Lead, filtered (μg/L) 93 5.1 <.5 2

.8 .2

Lead, unfiltered (μg/L) 93 650 5.38 44 16

Manganese, filtered (μg/L) 93 9,300 68 530 421

Manganese, unfiltered (μg/L) 93 10,000 117 653 490

Zinc, filtered (μg/L) 93 13,000 27 372 202

Zinc, unfiltered (μg/L) 93 15,000 97 637 410

Sediment, suspended (percent finer than 0.062 mm) 94 95 37 78 82

Sediment, suspended concentration (mg/L) 94 801 5 54 17

Sediment, suspended discharge (ton/d) 94 781 .18 24 2.4
TABLE 21 79

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323700--MILL CREEK AT OPPORTUNITY, MONT.

Period of record for water-quality data: March 2003-September 2004

Streamflow, instantaneous (ft3/s) 16 261 1.8 35 7.1

pH, onsite (standard units) 16 8.2 7.8 8.0 8.0

Specific conductance, onsite (μS/cm) 16 221 59 148 152

Temperature, water (oC) 16 18.5 1.0 8.9 8.8

Hardness, filtered (mg/L as CaCO3) 16 100 24 63 66

Calcium, filtered (mg/L) 16 27.9 7.01 17.8 18.6

Magnesium, filtered (mg/L) 16 7.68 1.57 4.58 4.52

Arsenic, filtered (μg/L) 16 37.0 13.9 24.9 26.0

Arsenic, unfiltered (μg/L) 16 50 16 29 30

Cadmium, filtered (μg/L) 16 .10 .05 .07 .08

Cadmium, unfiltered (μg/L) 16 .85 .06 .17 .11

Copper, filtered (μg/L) 16 6.0 1.8 3.4 3.0

Copper, unfiltered (μg/L) 16 38.8 2.8 8.0 4.6

Iron, filtered (μg/L) 16 84 17 47 44

Iron, unfiltered (μg/L) 16 1,960 70 331 140

Lead, filtered (μg/L) 16 .32 .04 .16 .14

Lead, unfiltered (μg/L) 16 12.7 .14 1.82 .46

Manganese, filtered (μg/L) 16 15.7 3.6 8.0 7.2

Manganese, unfiltered (μg/L) 16 113 6 21 12

Zinc, filtered (μg/L) 16 8 2 4 3

Zinc, unfiltered (μg/L) 16 41 2 8 5

Sediment, suspended (percent finer than 0.062 mm) 16 90 49 77 80

Sediment, suspended concentration (mg/L) 16 107 1 14 2

Sediment, suspended discharge (ton/d) 16 55 <.01 2

5.7 .02
80 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323720--WILLOW CREEK AT OPPORTUNITY, MONT.

Period of record for water-quality data: March 2003-September 2004

Streamflow, instantaneous (ft3/s) 16 46 5.7 15 12

pH, onsite (standard units) 16 8.4 7.9 8.1 8.1

Specific conductance, onsite (μS/cm) 16 371 181 292 308

Temperature, water (o

C) 16 17.0 3.5 10.0 10.8

Hardness, filtered (mg/L as CaCO3) 16 170 73 128 130

Calcium, filtered (mg/L) 16 47.4 22.0 37.1 38.5

Magnesium, filtered (mg/L) 16 12.0 4.37 8.71 9.08

Arsenic, filtered (μg/L) 16 101 12.0 43.0 29.6

Arsenic, unfiltered (μg/L) 16 104 12 45 31

Cadmium, filtered (μg/L) 16 .09 E.03 .05 .05

Cadmium, unfiltered (μg/L) 16 .30 .03 .09 .07

Copper, filtered (μg/L) 16 14.1 2.0 5.5 4.4

Copper, unfiltered (μg/L) 16 36.9 2.8 10.6 8.6

Iron, filtered (μg/L) 16 87 7 35 32

Iron, unfiltered (μg/L) 16 840 30 212 135

Lead, filtered (μg/L) 16 .50 <.08 2

.18 .13

Lead, unfiltered (μg/L) 16 8.41 .27 1.83 1.28

Manganese, filtered (μg/L) 16 49.3 4.1 25.6 19.6

Manganese, unfiltered (μg/L) 16 70 5 34 28

Zinc, filtered (μg/L) 16 20 2 6 5

Zinc, unfiltered (μg/L) 16 41 2 12 8

Sediment, suspended (percent finer than 0.062 mm) 16 96 76 87 88

Sediment, suspended concentration (mg/L) 16 51 1 9 4

Sediment, suspended discharge (ton/d) 16 6.3 .02 .66 .15
TABLE 21 81

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323750--SILVER BOW CREEK AT WARM SPRINGS, MONT.

Period of record for water-quality data: March 1993-September 2004

Streamflow, instantaneous (ft3/s) 100 662 16 140 88

pH, onsite (standard units) 98 9.3 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 98 783 249 465 474

Temperature, water (oC) 99 25.0 .5 11.3 11.5

Hardness, filtered (mg/L as CaCO3) 98 310 97 193 190

Calcium, filtered (mg/L) 98 90.4 27.9 56 57

Magnesium, filtered (mg/L) 98 21.4 5.94 13 13

Arsenic, filtered (μg/L) 98 60 6.8 22.2 21.5

Arsenic, unfiltered (μg/L) 98 94 10 27 25

Cadmium, filtered (μg/L) 98 .31 <.1 2

.07 <.1

Cadmium, unfiltered (μg/L) 98 .56 <.1 2.12 <1

Copper, filtered (μg/L) 98 40 1.9 9.6 7.8

Copper, unfiltered (μg/L) 98 96.8 3.4 19.3 13.4

Iron, filtered (μg/L) 98 93 <5 2

17 14

Iron, unfiltered (μg/L) 98 3,000 70 362 280

Lead, filtered (μg/L) 98 1.0 <.08 2

.12 <.5

Lead, unfiltered (μg/L) 98 41.8 <1 2

2.7 1.4

Manganese, filtered (μg/L) 98 875 11.8 125 85

Manganese, unfiltered (μg/L) 98 899 55 192 155

Zinc, filtered (μg/L) 98 73 <1 210 6

Zinc, unfiltered (μg/L) 98 180 <10 239 26

Sediment, suspended (percent finer than 0.062 mm) 99 97 43 82 85

Sediment, suspended concentration (mg/L) 100 229 1 12 7

Sediment, suspended discharge (ton/d) 100 279 .11 8.0 1.6
82 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323770--WARM SPRINGS CREEK AT WARM SPRINGS, MONT.

Period of record for water-quality data: March 1993-September 2004

Streamflow, instantaneous (ft3/s) 72 420 2.8 95 54

pH, onsite (standard units) 71 8.7 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 71 795 139 301 311

Temperature, water (o

C) 72 20.0 .5 9.3 9.2

Hardness, filtered (mg/L as CaCO3) 71 420 40 146 150

Calcium, filtered (mg/L) 71 130 10.5 45 46

Magnesium, filtered (mg/L) 71 22.0 3.29 8.4 8.1

Arsenic, filtered (μg/L) 71 14 2 5 5

Arsenic, unfiltered (μg/L) 71 27 3 8 6

Cadmium, filtered (μg/L) 71 E.1 <.04 2.04 <.1

Cadmium, unfiltered (μg/L) 71 .36 <.1 2

.07 <1

Copper, filtered (μg/L) 71 16 1 4 3

Copper, unfiltered (μg/L) 71 96.7 2.3 19.6 8.6

Iron, filtered (μg/L) 71 30 <5 211 9

Iron, unfiltered (μg/L) 71 1,670 40 305 110

Lead, filtered (μg/L) 71 1.8 <.08 2

.1 <.5

Lead, unfiltered (μg/L) 71 14 <1 2

2 .4

Manganese, filtered (μg/L) 71 570 22.6 131 96.2

Manganese, unfiltered (μg/L) 71 1,400 57 219 183

Zinc, filtered (μg/L) 71 10 <1 2

2 .9

Zinc, unfiltered (μg/L) 71 60 <10 210 3

Sediment, suspended (percent finer than 0.062 mm) 72 88 55 73 74

Sediment, suspended concentration (mg/L) 72 100 2 18 8

Sediment, suspended discharge (ton/d) 72 87 .05 9.3 1.0
TABLE 21 83

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323800--CLARK FORK NEAR GALEN, MONT.

Period of record for water-quality data: July 1988-September 2004

Streamflow, instantaneous (ft3/s) 141 1,050 14 207 124

pH, onsite (standard units) 128 9.0 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 129 720 197 427 442

Temperature, water (oC) 140 22.5 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3) 127 370 81 186 190

Calcium, filtered (mg/L) 127 110 24.2 55 57

Magnesium, filtered (mg/L) 127 22.0 5.08 12 12

Arsenic, filtered (μg/L) 127 53 4 15 13

Arsenic, unfiltered (μg/L) 127 78 3 20 17

Cadmium, filtered (μg/L) 127 1 <.1 2

.07 <.1

Cadmium, unfiltered (μg/L) 127 3 <.1 2.2 <1

Copper, filtered (μg/L) 127 50 2.3 9 7

Copper, unfiltered (μg/L) 126 240 4.8 31 17

Iron, filtered (μg/L) 127 110 <3 2

16 10

Iron, unfiltered (μg/L) 127 9,200 60 525 270

Lead, filtered (μg/L) 127 3 <.08 2

.2 <.6

Lead, unfiltered (μg/L) 127 31.0 <1 2

4 2

Manganese, filtered (μg/L) 127 460 25.2 114 82

Manganese, unfiltered (μg/L) 127 1,400 47 246 183

Zinc, filtered (μg/L) 127 110 <1 212 6

Zinc, unfiltered (μg/L) 127 360 <10 245 30

Sediment, suspended (percent finer than 0.062 mm) 140 97 41 78 78

Sediment, suspended concentration (mg/L) 141 338 2 19 8

Sediment, suspended discharge (ton/d) 141 459 .12 22 2.3
84 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323850--LOST CREEK NEAR GALEN, MONT.

Period of record for water-quality data: March 2003-September 2004

Streamflow, instantaneous (ft3/s) 16 59 1.3 18 9.0

pH, onsite (standard units) 16 8.7 8.4 8.5 8.5

Specific conductance, onsite (μS/cm) 16 861 540 630 624

Temperature, water (o

C) 16 26.5 4.5 14.2 13.8

Hardness, filtered (mg/L as CaCO3) 16 420 200 288 290

Calcium, filtered (mg/L) 16 117 48.5 79.3 79.3

Magnesium, filtered (mg/L) 16 32.3 18.0 21.6 21.0

Arsenic, filtered (μg/L) 16 41.8 6.6 13.4 11.1

Arsenic, unfiltered (μg/L) 16 43 6 14 12

Cadmium, filtered (μg/L) 16 .05 <.04 2.03 .03

Cadmium, unfiltered (μg/L) 16 .11 E.02 .04 .04

Copper, filtered (μg/L) 16 6.7 1.5 3.3 2.9

Copper, unfiltered (μg/L) 16 22.5 3.9 7.3 5.2

Iron, filtered (μg/L) 16 18 <6 28 6

Iron, unfiltered (μg/L) 16 280 10 104 70

Lead, filtered (μg/L) 16 .33 <.08 2

.08 <.08

Lead, unfiltered (μg/L) 16 1.30 E.04 .41 .22

Manganese, filtered (μg/L) 16 23.6 1.9 9.6 8.6

Manganese, unfiltered (μg/L) 16 33 2 13 12

Zinc, filtered (μg/L) 16 2 <1 2

1 1

Zinc, unfiltered (μg/L) 16 9 <2 23 2

Sediment, suspended (percent finer than 0.062 mm) 16 86 18 54 55

Sediment, suspended concentration (mg/L) 16 34 2 15 15

Sediment, suspended discharge (ton/d) 16 3.8 .01 .87 .23
TABLE 21 85

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324200--CLARK FORK AT DEER LODGE, MONT.

Period of record for water-quality data: March 1985-September 2004

Streamflow, instantaneous (ft3/s) 193 1,920 23 290 217

pH, onsite (standard units) 141 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 176 642 234 485 506

Temperature, water (oC) 192 23.0 0.0 9.9 10.0

Hardness, filtered (mg/L as CaCO3) 133 270 95 205 220

Calcium, filtered (mg/L) 133 81.0 28.2 60 64

Magnesium, filtered (mg/L) 133 18 5.9 13 14

Arsenic, filtered (μg/L) 143 39 6 14 13

Arsenic, unfiltered (μg/L) 143 215 8 25 17

Cadmium, filtered (μg/L) 143 2 <.1 2

.08 <1

Cadmium, unfiltered (μg/L) 143 5 <.1 2.5 <1

Copper, filtered (μg/L) 143 120 3.2 12 9

Copper, unfiltered (μg/L) 142 1,500 8.2 90 39

Iron, filtered (μg/L) 143 190 <3 2

15 9

Iron, unfiltered (μg/L) 143 29,000 30 1,690 590

Lead, filtered (μg/L) 143 6 <.08 2

.4 <1

Lead, unfiltered (μg/L) 143 200 <1 2

12 5

Manganese, filtered (μg/L) 143 400 1 43 34

Manganese, unfiltered (μg/L) 143 4,600 12 266 156

Zinc, filtered (μg/L) 143 230 <10 213 10

Zinc, unfiltered (μg/L) 143 1,700 4 99 50

Sediment, suspended (percent finer than 0.062 mm) 184 99 40 71 72

Sediment, suspended concentration (mg/L) 193 2,250 2 76 23

Sediment, suspended discharge (ton/d) 193 8,690 .29 168 12
86 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324590--LITTLE BLACKFOOT RIVER NEAR GARRISON, MONT.

Period of record for water-quality data: March 1985-September 2004

Streamflow, instantaneous (ft3/s) 110 2,080 15 274 169

pH, onsite (standard units) 97 8.7 7.0 8.1 8.1

Specific conductance, onsite (μS/cm) 98 347 120 233 231

Temperature, water (o

C) 109 23.0 0.0 8.8 9.0

Hardness, filtered (mg/L as CaCO3) 92 170 51 107 105

Calcium, filtered (mg/L) 92 49.3 14.0 31 31

Magnesium, filtered (mg/L) 92 11.9 3.30 7.2 7.1

Arsenic, filtered (μg/L) 97 7 3 5 5

Arsenic, unfiltered (μg/L) 97 17 4 6 6

Cadmium, filtered (μg/L) 97 .2 <.04 -- <.1

Cadmium, unfiltered (μg/L) 97 2 <.04 2

.1 <1

Copper, filtered (μg/L) 97 7 <1 2

2 1

Copper, unfiltered (μg/L) 96 45 <1 2

4 2

Iron, filtered (μg/L) 97 120 <3 233 21

Iron, unfiltered (μg/L) 97 25,000 20 1,030 220

Lead, filtered (μg/L) 96 6 <.08 2

.3 <1

Lead, unfiltered (μg/L) 97 25 <1 2

2 <5

Manganese, filtered (μg/L) 97 45.2 1.0 9 8

Manganese, unfiltered (μg/L) 97 1,100 <10 2

65 28

Zinc, filtered (μg/L) 97 24 <.6 2

3 .8

Zinc, unfiltered (μg/L) 97 140 <1 211 <40

Sediment, suspended (percent finer than 0.062 mm) 110 97 32 76 80

Sediment, suspended concentration (mg/L) 110 1,410 1 47 8

Sediment, suspended discharge (ton/d) 110 7,920 .08 126 3.8
TABLE 21 87

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324680--CLARK FORK AT GOLDCREEK, MONT.

Period of record for water-quality data: March 1993-September 2004

Streamflow, instantaneous (ft3/s) 99 3,920 87 739 513

pH, onsite (standard units) 98 8.8 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 98 510 206 373 394

Temperature, water (oC) 99 23.0 0.0 9.9 10.0

Hardness, filtered (mg/L as CaCO3) 98 230 86 164 170

Calcium, filtered (mg/L) 98 68.0 25.9 48 51

Magnesium, filtered (mg/L) 98 15.0 5.15 11 11

Arsenic, filtered (μg/L) 98 20 5.8 10 10

Arsenic, unfiltered (μg/L) 98 75 7 15 13

Cadmium, filtered (μg/L) 98 .2 <.04 2

.04 <.1

Cadmium, unfiltered (μg/L) 98 2 <.1 2.2 <1

Copper, filtered (μg/L) 97 36 2.1 7 6

Copper, unfiltered (μg/L) 97 440 5.2 44 25

Iron, filtered (μg/L) 98 100 <3 2

19 12

Iron, unfiltered (μg/L) 98 12,000 30 936 470

Lead, filtered (μg/L) 97 .8 <.08 2

.1 <.5

Lead, unfiltered (μg/L) 97 73 <1 2

6 3

Manganese, filtered (μg/L) 98 57.3 4.0 20 18

Manganese, unfiltered (μg/L) 98 1,100 10 133 90

Zinc, filtered (μg/L) 98 26 <1 26 4

Zinc, unfiltered (μg/L) 98 510 2 50 30

Sediment, suspended (percent finer than 0.062 mm) 99 94 43 76 78

Sediment, suspended concentration (mg/L) 99 752 2 54 23

Sediment, suspended discharge (ton/d) 99 7,960 .94 241 33
88 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12331500--FLINT CREEK NEAR DRUMMOND, MONT.

Period of record for water-quality data: March 1985-September 2004

Streamflow, instantaneous (ft3/s) 139 892 2.8 175 114

pH, onsite (standard units) 125 8.8 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 128 529 134 310 306

Temperature, water (o

C) 137 21.0 0.0 9.0 9.5

Hardness, filtered (mg/L as CaCO3) 118 260 59 146 140

Calcium, filtered (mg/L) 118 73.0 16.4 40 39

Magnesium, filtered (mg/L) 118 20 4.3 11 12

Arsenic, filtered (μg/L) 125 20 5 9 9

Arsenic, unfiltered (μg/L) 125 57 7 17 13

Cadmium, filtered (μg/L) 125 .1 <.04 -- <.1

Cadmium, unfiltered (μg/L) 125 3 <.04 2

.2 <1

Copper, filtered (μg/L) 125 7 <1 2

2 1

Copper, unfiltered (μg/L) 124 32 1 6 4

Iron, filtered (μg/L) 125 240 <3 237 19

Iron, unfiltered (μg/L) 125 7,200 60 842 420

Lead, filtered (μg/L) 125 7 <.5 2

.6 <1

Lead, unfiltered (μg/L) 125 87 <1 2

11 6

Manganese, filtered (μg/L) 125 139 14 43 37

Manganese, unfiltered (μg/L) 125 1,600 50 203 130

Zinc, filtered (μg/L) 125 27 <1 2

5 2

Zinc, unfiltered (μg/L) 125 290 <10 236 20

Sediment, suspended (percent finer than 0.062 mm) 139 98 28 80 84

Sediment, suspended concentration (mg/L) 139 556 3 48 26

Sediment, suspended discharge (ton/d) 139 904 .02 42 7.3
TABLE 21 89

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12331800--CLARK FORK NEAR DRUMMOND, MONT.

Period of record for water-quality data: March 1993-September 2004

Streamflow, instantaneous (ft3/s) 99 3,860 149 1,040 758

pH, onsite (standard units) 98 8.5 7.8 8.3 8.3

Specific conductance, onsite (μS/cm) 98 630 189 412 430

Temperature, water (oC) 99 22.5 .5 10.8 11.0

Hardness, filtered (mg/L as CaCO3) 98 300 74 186 190

Calcium, filtered (mg/L) 98 83 21 53 55

Magnesium, filtered (mg/L) 98 22 5.2 13 13

Arsenic, filtered (μg/L) 98 20 6.6 11 10

Arsenic, unfiltered (μg/L) 98 62 8 17 13

Cadmium, filtered (μg/L) 98 .2 <.04 2

<.1 <.1

Cadmium, unfiltered (μg/L) 98 2 <.1 2.2 <1

Copper, filtered (μg/L) 96 21 1 7 5

Copper, unfiltered (μg/L) 96 360 4.6 46 22

Iron, filtered (μg/L) 98 150 <3 2

19 8

Iron, unfiltered (μg/L) 97 8,800 20 1,070 460

Lead, filtered (μg/L) 94 1.2 <.08 2

.2 <.5

Lead, unfiltered (μg/L) 94 56 <1 2

8 4

Manganese, filtered (μg/L) 98 60.7 4.5 17 15

Manganese, unfiltered (μg/L) 98 880 8 156 98

Zinc, filtered (μg/L) 98 21 <3 27 5

Zinc, unfiltered (μg/L) 98 490 3 68 39

Sediment, suspended (percent finer than 0.062 mm) 99 92 38 74 75

Sediment, suspended concentration (mg/L) 99 530 2 69 26

Sediment, suspended discharge (ton/d) 99 4,720 1.7 351 53
90 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12334510--ROCK CREEK NEAR CLINTON, MONT.

Period of record for water-quality data: March 1985-September 2004

Streamflow, instantaneous (ft3/s) 109 5,060 113 945 521

pH, onsite (standard units) 99 8.8 6.9 8.0 8.0

Specific conductance, onsite (μS/cm) 100 160 53 108 104

Temperature, water (o

C) 109 18.0 0.0 8.4 8.5

Hardness, filtered (mg/L as CaCO3) 91 90 22 50 50

Calcium, filtered (mg/L) 91 23.0 5.92 13 13

Magnesium, filtered (mg/L) 91 8.00 1.86 4.3 4.3

Arsenic, filtered (μg/L) 97 1 <1 2

.6 <1

Arsenic, unfiltered (μg/L) 97 5 <1 2

.9 <2

Cadmium, filtered (μg/L) 97 1 <.04 2.03 <.1

Cadmium, unfiltered (μg/L) 97 3 <.04 2

.1 <1

Copper, filtered (μg/L) 96 6 <1 2

1 <1

Copper, unfiltered (μg/L) 95 41 <.6 2

3 1

Iron, filtered (μg/L) 97 163 5 233 23

Iron, unfiltered (μg/L) 97 2,100 20 284 120

Lead, filtered (μg/L) 95 5 <.08 2

.4 <.6

Lead, unfiltered (μg/L) 95 19 <.06 2

1 <1

Manganese, filtered (μg/L) 97 8 <1 2

2 2

Manganese, unfiltered (μg/L) 97 90 <10 2

15 7

Zinc, filtered (μg/L) 97 15 <.6 2

2 <3

Zinc, unfiltered (μg/L) 97 60 <1 25 <10

Sediment, suspended (percent finer than 0.062 mm) 109 95 35 70 72

Sediment, suspended concentration (mg/L) 109 223 1 20 5

Sediment, suspended discharge (ton/d) 109 3,050 .31 134 8.9
TABLE 21 91

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12334550--CLARK FORK AT TURAH BRIDGE, NEAR BONNER, MONT.

Period of record for water-quality data: March 1985-September 2004

Streamflow, instantaneous (ft3/s) 196 9,560 296 1,860 1,120

pH, onsite (standard units) 142 8.8 7.4 8.2 8.3

Specific conductance, onsite (μS/cm) 171 483 139 304 316

Temperature, water (oC) 195 22.0 0.0 9.4 9.5

Hardness, filtered (mg/L as CaCO3) 132 210 54 132 130

Calcium, filtered (mg/L) 132 59.0 14.9 37 38

Magnesium, filtered (mg/L) 132 14.0 3.94 9.5 9.4

Arsenic, filtered (μg/L) 141 17 2.7 6 5

Arsenic, unfiltered (μg/L) 141 110 3 10 7

Cadmium, filtered (μg/L) 141 .11 <.04 2

.03 <.1

Cadmium, unfiltered (μg/L) 141 4 <.1 2.3 <1

Copper, filtered (μg/L) 140 25 E1.1 5 4

Copper, unfiltered (μg/L) 139 500 3 39 18

Iron, filtered (μg/L) 141 190 <3 2

25 14

Iron, unfiltered (μg/L) 141 19,000 40 1,160 390

Lead, filtered (μg/L) 137 7 <.08 2

.4 <1

Lead, unfiltered (μg/L) 137 100 <1 2

8 3

Manganese, filtered (μg/L) 141 37.4 1.0 8 7

Manganese, unfiltered (μg/L) 141 2,000 10 136 70

Zinc, filtered (μg/L) 140 39 <3 27 4

Zinc, unfiltered (μg/L) 141 1,100 <10 268 30

Sediment, suspended (percent finer than 0.062 mm) 185 98 27 73 75

Sediment, suspended concentration (mg/L) 196 1,370 2 61 19

Sediment, suspended discharge (ton/d) 196 34,700 3.5 677 61
92 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12340000--BLACKFOOT RIVER NEAR BONNER, MONT.

Period of record for water-quality data: March 1985-September 2004

Streamflow, instantaneous (ft3/s) 140 13,400 344 2,680 1,310

pH, onsite (standard units) 100 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 117 294 131 207 205

Temperature, water (o

C) 140 21.0 0.0 9.2 9.8

Hardness, filtered (mg/L as CaCO3) 93 140 55 102 97

Calcium, filtered (mg/L) 93 37 14 26 25

Magnesium, filtered (mg/L) 93 13 4.9 9.0 8.6

Arsenic, filtered (μg/L) 100 2 <1 2

.9 1

Arsenic, unfiltered (μg/L) 100 4 <1 2

1 1

Cadmium, filtered (μg/L) 100 1 <.04 -- <.1

Cadmium, unfiltered (μg/L) 100 2 <.04 2

.1 <1

Copper, filtered (μg/L) 98 7 <1 2

2 1

Copper, unfiltered (μg/L) 97 34 <1 2

6 3

Iron, filtered (μg/L) 100 100 <3 218 10

Iron, unfiltered (μg/L) 100 3,600 10 477 210

Lead, filtered (μg/L) 96 8 <.08 2

.5 <1

Lead, unfiltered (μg/L) 96 25 <.06 2

3 <5

Manganese, filtered (μg/L) 100 11 <1 2

2 2

Manganese, unfiltered (μg/L) 100 180 <10 2

32 20

Zinc, filtered (μg/L) 100 15 <1 2

3 <10

Zinc, unfiltered (μg/L) 100 60 <1 27 <10

Sediment, suspended (percent finer than 0.062 mm) 138 98 42 80 82

Sediment, suspended concentration (mg/L) 140 271 1 31 9

Sediment, suspended discharge (ton/d) 140 7,670 1.1 551 31
TABLE 21 93

Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2004.—Continued 

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12340500--CLARK FORK ABOVE MISSOULA, MONT.

Period of record for water-quality data: July 1986-September 2004

Streamflow, instantaneous (ft3/s) 162 21,600 720 4,430 2,400

pH, onsite (standard units) 119 8.7 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 139 399 142 253 261

Temperature, water (oC) 159 21.0 0.0 9.3 9.0

Hardness, filtered (mg/L as CaCO3) 119 170 61 117 120

Calcium, filtered (mg/L) 119 46 14 31 32

Magnesium, filtered (mg/L) 119 13.0 5.28 9.2 9.2

Arsenic, filtered (μg/L) 119 9 1 3 3

Arsenic, unfiltered (μg/L) 119 69 1 5 4

Cadmium, filtered (μg/L) 119 .2 <.04 2

.03 <.1

Cadmium, unfiltered (μg/L) 119 5 <.1 2.1 <1

Copper, filtered (μg/L) 118 12.6 .7 3 2

Copper, unfiltered (μg/L) 117 400 2 17 8

Iron, filtered (μg/L) 119 200 <3 2

22 15

Iron, unfiltered (μg/L) 119 13,000 40 613 230

Lead, filtered (μg/L) 114 1.2 <.08 2

.2 <.6

Lead, unfiltered (μg/L) 114 78 <1 2

3 1

Manganese, filtered (μg/L) 119 230 6.2 18 14

Manganese, unfiltered (μg/L) 119 1,100 10 65 40

Zinc, filtered (μg/L) 119 16 <1 24 2

Zinc, unfiltered (μg/L) 119 1,100 <10 232 13

Sediment, suspended (percent finer than 0.062 mm) 157 99 44 87 90

Sediment, suspended concentration (mg/L) 162 824 2 38 12

Sediment, suspended discharge (ton/d) 162 21,900 5.8 968 74

1Differing less-than (<) values for an individual constituent are the result of changes in the laboratory reporting level during the period of record.

2Value is estimated by using a log-probability regression to predict the values of data less than the laboratory reporting level (Helsel and Cohn, 1988).
94 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 

1986 through August 2004. 

[Fine-grained bed sediment is material less than 0.064 millimeter in diameter. Reported concentrations are in micrograms per gram

dry weight. Number of samples represents the number of years that the constituent was analyzed, with each year represented by a

single mean concentration of composite samples. Arsenic data were not collected at some sites. Values are reported using U.S.

Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data to compute

statistic or element not analyzed]

Constituent Number of 

samples Maximum Minimum Mean Median

12323600--SILVER BOW CREEK AT OPPORTUNITY, MONT.

Period of record for fine-grained bed-sediment data: 1992-2004

Arsenic 2 186 163 174 --

Cadmium 13 43.9 23.7 33.9 34.7

Chromium 11 32.4 16.8 25.3 24.8

Copper 13 9,020 3,390 5,040 4,670

Iron 13 41,200 28,200 35,900 37,400

Lead 13 1,030 381 740 797

Manganese 13 9,220 1,690 3,750 2,770

Nickel 12 21.4 12.7 15.6 15.4

Silver 12 20.0 8.3 15.5 15.8

Zinc 13 13,400 5,620 8,580 8,010

12323750--SILVER BOW CREEK AT WARM SPRINGS, MONT.

Period of record for fine-grained bed-sediment data: 1992-2004

Arsenic 2 178 103 140 --

Cadmium 13 12.2 4.2 7.8 7.4

Chromium 11 34.1 12.3 20.4 19.5

Copper 13 769 169 365 286

Iron 13 31,700 15,400 21,800 20,800

Lead 13 100 49 72 73

Manganese 13 17,700 1,470 8,270 8,150

Nickel 12 19.1 9.2 14.9 15.0

Silver 12 4.4 .3 11.9 1

1.8

Zinc 13 2,220 620 1,060 845

12323770--WARM SPRINGS CREEK AT WARM SPRINGS, MONT.

Period of record for fine-grained bed-sediment data: 1995,1997,1999, 2002

Arsenic 0 -- -- -- --

Cadmium 4 5.8 1.3 3.4 3.2

Chromium 4 33.4 27.5 30.8 31.1

Copper 4 892 779 850 864

Iron 4 22,400 16,800 20,400 21,200

Lead 4 86 67 81 85

Manganese 4 11,000 2,020 6,950 7,410

Nickel 4 21.9 17.6 19.2 18.6

Silver 4 5.1 3.1 3.8 3.5

Zinc 4 421 372 391 385
TABLE 22 95

Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 

1986 through August 2004.—Continued

Constituent Number of 

samples Maximum Minimum Mean Median

12323800--CLARK FORK NEAR GALEN, MONT.

Period of record for fine-grained bed-sediment data: 1987,1991-2004

Arsenic 2 119 111 115 --

Cadmium 15 20.1 4.0 9.7 9.3

Chromium 11 33.9 19.1 26.3 26.4

Copper 15 2,300 838 1,250 1,140

Iron 15 39,800 22,600 28,000 27,000

Lead 15 235 92 142 136

Manganese 15 15,600 2,780 9,040 8,540

Nickel 12 23.2 13.9 18.3 18.3

Silver 14 7.3 <3.2 14.4 1

4.5

Zinc 15 3,560 999 1,650 1,230

461415112450801--CLARK FORK BELOW LOST CREEK, NEAR GALEN, MONT.

Period of record for fine-grained bed-sediment data: 1996-2004

Arsenic 2 204 92 148 --

Cadmium 9 10.5 5.8 8.0 8.1

Chromium 8 34.5 20.5 28.4 29.7

Copper 9 2,050 1,150 1,530 1,440

Iron 9 32,800 24,400 29,900 30,800

Lead 9 218 127 180 182

Manganese 9 9,670 3,540 5,550 5,570

Nickel 9 19.9 11.7 16.5 16.5

Silver 8 7.8 4.2 6.5 6.7

Zinc 9 1,680 1,120 1,390 1,450

461559112443301--CLARK FORK NEAR RACETRACK, MONT.

Period of record for fine-grained bed-sediment data: 1996-2004

Arsenic 2 101 56 79 --

Cadmium 9 8.7 5.0 7.1 7.5

Chromium 8 33.3 19.0 25.7 27.1

Copper 9 1,610 933 1,200 1,240

Iron 9 31,700 21,200 26,600 28,100

Lead 9 186 103 146 143

Manganese 9 6,310 2,100 3,520 3,130

Nickel 9 18.4 10.3 14.2 15.6

Silver 8 6.1 <3.3 15.0 15.4

Zinc 9 1,550 999 1,220 1,170
96 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

461903112440701--CLARK FORK AT DEMPSEY CREEK DIVERSION, NEAR RACETRACK, MONT.

Period of record for fine-grained bed-sediment data: 1996-2004

Arsenic 2 80 58 69 --

Cadmium 9 10.3 4.3 6.9 6.9

Chromium 8 34.1 16.0 25.2 26.0

Copper 9 1,550 721 1,030 1,030

Iron 9 33,700 20,600 26,400 25,300

Lead 9 155 92 130 130

Manganese 9 8,370 1,810 3,880 2,680

Nickel 9 16.9 8.7 13.0 12.9

Silver 8 6.2 2.7 4.9 5.0

Zinc 9 1,570 900 1,140 1,070

12324200--CLARK FORK AT DEER LODGE, MONT.

Period of record for fine-grained bed-sediment data: 1986, 1987, 1990-2004

Arsenic 2 77 49 63 --

Cadmium 17 10.0 3.8 6.7 6.3

Chromium 11 43.9 19.5 30.9 32.5

Copper 17 4,180 683 1,340 1,070

Iron 17 35,300 21,100 27,500 26,800

Lead 17 242 103 152 150

Manganese 17 6,020 1,460 2,830 2,440

Nickel 12 21.1 11.5 15.7 15.2

Silver 16 7.9 2.4 4.7 4.5

Zinc 17 1,730 846 1,260 1,260

12324590--LITTLE BLACKFOOT RIVER NEAR GARRISON, MONT.

Period of record for fine-grained bed-sediment data: 1986, 1987, 1994, 1998, 2001, 2004

Arsenic 1 -- -- 12 --

Cadmium 6 2.3 .2 1.1 .9

Chromium 4 54.4 22.1 40.6 43.0

Copper 6 85 33 52 40

Iron 6 30,700 16,100 24,300 24,400

Lead 6 53 36 40 38

Manganese 6 2,700 905 1,370 1,080

Nickel 4 21.9 13.6 17.6 17.4

Silver 5 .9 <.5 1

.6 1<1.5

Zinc 6 204 161 176 174

Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 

1986 through August 2004.—Continued

Constituent Number of 

samples Maximum Minimum Mean Median
TABLE 22 97

12324680--CLARK FORK AT GOLDCREEK, MONT.

Period of record for fine-grained bed-sediment data: 1992-2004

Arsenic 2 32 24 28 --

Cadmium 13 8.1 3.1 5.2 5.5

Chromium 11 48.9 22.1 32.7 31.9

Copper 13 1,080 393 704 748

Iron 13 30,600 19,500 23,900 24,300

Lead 13 152 61 99 105

Manganese 13 2,610 1,160 1,900 1,840

Nickel 12 18.6 10.9 14.9 15.5

Silver 12 4.8 2.3 3.3 3.2

Zinc 13 1,320 590 995 1,090

12331500--FLINT CREEK NEAR DRUMMOND, MONT.

Period of record for fine-grained bed-sediment data: 1986, 1989, 1992-2004

Arsenic 2 113 102 108 --

Cadmium 15 7.0 <.2 1

3.3 13.1

Chromium 11 29.2 17.5 24.3 24.3

Copper 15 73 44 59 59

Iron 15 28,100 19,800 23,300 23,200

Lead 15 240 126 171 168

Manganese 15 5,720 2,370 4,010 4,180

Nickel 12 14.9 10.2 12.2 11.7

Silver 13 7.8 5.0 6.4 6.4

Zinc 15 777 503 630 644

12331800--CLARK FORK NEAR DRUMMOND, MONT.

Period of record for fine-grained bed-sediment data: 1986, 1987, 1991-2004

Arsenic 2 33 31 32 --

Cadmium 16 7.7 2.6 4.8 4.8

Chromium 11 35.4 17.0 29.2 31.6

Copper 16 747 321 504 495

Iron 16 27,000 16,500 21,700 21,800

Lead 16 135 68 93 93

Manganese 16 3,090 1,150 1,860 1,810

Nickel 12 16.8 10.8 14.0 14.5

Silver 15 4.7 <3.2 13.0 12.9

Zinc 16 1,230 761 1,010 1,010

Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 

1986 through August 2004.—Continued

Constituent Number of 

samples Maximum Minimum Mean Median
98 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

12334510--ROCK CREEK NEAR CLINTON, MONT.

Period of record for fine-grained bed-sediment data: 1986, 1987, 1989, 1991-1999, 2001-2004

Arsenic 2 6 5 6 --

Cadmium 16 3.7 <.1 1.8 1<.8

Chromium 10 27.9 16.4 21.6 20.9

Copper 16 16 3 11 12

Iron 16 21,400 13,100 17,500 17,400

Lead 16 16 <3 9 10

Manganese 16 724 126 381 372

Nickel 11 14.8 8.7 11.8 11.6

Silver 14 1.9 <.3 1

.5 1<.6

Zinc 16 58 23 43 46

12334550--CLARK FORK AT TURAH BRIDGE, NEAR BONNER, MONT.

Period of record for fine-grained bed-sediment data: 1986, 1991-2004

Arsenic 2 22 19 21 --

Cadmium 15 7.3 2.3 4.1 3.9

Chromium 11 34.7 15.3 25.3 27.7

Copper 15 635 211 367 323

Iron 15 24,400 12,600 18,800 17,300

Lead 15 115 47 72 66

Manganese 15 2,270 671 1,230 1,130

Nickel 12 19.1 8.7 13.0 11.8

Silver 14 3.9 <1.9 12.1 11.9

Zinc 15 1,160 586 859 842

12340000--BLACKFOOT RIVER NEAR BONNER, MONT.

Period of record for fine-grained bed-sediment data: 1986, 1987, 1991, 1993-1996, 1998-2001, 2003

Arsenic 1 -- -- 2 --

Cadmium 12 2.0 <.2 1

.7 1<1.0

Chromium 8 25.8 15.1 20.5 21.8

Copper 12 27 11 20 21

Iron 12 20,200 12,400 16,800 16,800

Lead 12 20 <13 113 112

Manganese 12 683 298 531 538

Nickel 9 14.3 9.4 11.9 12.5

Silver 12 1.0 <.3 1

.5 1<.6

Zinc 12 73 35 58 61

Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 

1986 through August 2004.—Continued

Constituent Number of 

samples Maximum Minimum Mean Median
TABLE 22 99

12340500--CLARK FORK ABOVE MISSOULA, MONT.

Period of record for fine-grained bed-sediment data: 1997-2004

Arsenic 2 29 23 26 --

Cadmium 8 5.8 1.5 3.5 3.6

Chromium 7 30.6 19.0 25.7 28.5

Copper 8 543 166 337 304

Iron 8 24,300 18,100 20,600 20,500

Lead 8 78 37 56 57

Manganese 8 1,420 477 1,030 1,060

Nickel 8 15.8 11.8 13.5 13.1

Silver 7 2.9 .8 12.0 1

2.1

Zinc 8 1,090 438 724 706

12353000--CLARK FORK BELOW MISSOULA, MONT.2

Period of record for fine-grained bed-sediment data: 1986, 1990-2004

Arsenic 2 14 6 10 --

Cadmium 16 6.0 1.1 2.3 1.9

Chromium 11 27.6 12.3 21.4 21.5

Copper 16 293 69 150 140

Iron 16 21,100 13,100 18,100 18,600

Lead 16 58 12 36 36

Manganese 16 2,530 446 1,360 1,270

Nickel 12 14.1 8.4 12.0 12.5

Silver 15 3.0 .4 11.3 1

1.2

Zinc 16 675 239 396 395

1Value determined by substituting one-half of the minimum reporting level for censored (<) values when both uncensored and censored values were used to determine the mean and (or) median. When all data were less than the minimum reporting level, the median 

was determined by ranking the censored values by order of magnitude.

2Samples collected about 30 miles downstream from streamflow-gaging station to conform to previous sampling location.

Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 

1986 through August 2004.—Continued

Constituent Number of 

samples Maximum Minimum Mean Median
100 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, August

1993 through August 2004. 

[Bulk bed sediment is material smaller than about 10 millimeters in diameter. Reported concentrations are in micrograms per gram

dry weight. Number of samples represents the number of years that the constituent was analyzed, with each year represented

by a single mean concentration of composite samples. Arsenic data were not collected at some sites. Values are reported using U.S.

Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data to compute

 statistic or element not analyzed]

Constituent Number of 

samples Maximum Minimum Mean Median

12323600--SILVER BOW CREEK AT OPPORTUNITY, MONT.

Period of record for bulk bed-sediment data: 1993-1995, 1997-2004

Arsenic 2 148 60 104 --

Cadmium 11 30.2 4.2 12.9 8.5

Chromium 10 18.1 9.6 13.3 12.4

Copper 11 3,800 615 1,490 976

Iron 11 29,300 18,300 23,000 20,800

Lead 11 398 138 275 263

Manganese 11 5,480 504 1,850 1,620

Nickel 11 12.7 6.0 7.9 6.8

Silver 10 8.0 3.2 5.1 4.4

Zinc 11 5,930 1,720 3,170 2,270

12323750--SILVER BOW CREEK AT WARM SPRINGS, MONT.

Period of record for bulk bed-sediment data: 1993, 1995-2004

Arsenic 2 36 15 26 --

Cadmium 11 3.4 <.9 11.3 1

1.3

Chromium 10 11.8 5.2 8.6 9.2

Copper 11 111 9 46 32

Iron 11 13,200 6,100 9,580 9,600

Lead 11 33 <10 115 1

12

Manganese 11 2,100 209 974 830

Nickel 11 10.3 4.8 6.4 5.5

Silver 10 1.3 <.3 1

.7 1.8

Zinc 11 303 93 157 131

12323770--WARM SPRINGS CREEK AT WARM SPRINGS, MONT.

Period of record for bulk bed-sediment data: 1995, 1997, 1999, 2002

Arsenic 0 -- -- -- --

Cadmium 4 1.5 <.8 1

.8 1.7

Chromium 4 12.0 7.4 10.2 10.7

Copper 4 238 127 193 204

Iron 4 12,700 8,010 10,200 9,960

Lead 4 38 18 29 29

Manganese 4 4,240 1,220 2,640 2,540

Nickel 4 8.5 5.7 7.2 7.4

Silver 4 1.3 <.8 1

.9 11.0

Zinc 4 275 146 183 155
TABLE 23 101

Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, August

1993 through August 2004.—Continued

Constituent Number of 

samples Maximum Minimum Mean Median

12323800--CLARK FORK NEAR GALEN, MONT.

Period of record for bulk bed-sediment data: 1993-2004

Arsenic 2 97 76 86 --

Cadmium 12 8.2 <.9 14.0 1

4.0

Chromium 11 23.7 4.2 14.9 15.0

Copper 12 902 223 483 475

Iron 12 31,300 9,930 20,000 20,000

Lead 12 158 41 80 79

Manganese 12 9,490 899 3,400 2,380

Nickel 12 15.2 4.9 8.6 8.0

Silver 11 5.2 .7 12.1 1<3.2

Zinc 12 1,280 417 711 665

461415112450801--CLARK FORK BELOW LOST CREEK, NEAR GALEN, MONT.

Period of record for bulk bed-sediment data: 1996-2004

Arsenic 2 87 82 85 --

Cadmium 9 5.2 <.9 12.6 1

2.5

Chromium 8 17.5 6.8 11.6 11.5

Copper 9 763 238 417 398

Iron 9 21,000 12,300 16,700 17,300

Lead 9 104 41 70 71

Manganese 9 3,720 1,260 1,750 1,440

Nickel 9 8.4 4.2 6.4 6.7

Silver 8 2.8 .8 11.7 1

1.6

Zinc 9 787 339 516 522

461559112443301--CLARK FORK NEAR RACETRACK, MONT.

Period of record for bulk bed-sediment data: 1996-2004

Arsenic 2 90 46 68 --

Cadmium 9 10.5 <.9 13.8 1

2.7

Chromium 8 19.7 9.4 14.3 13.7

Copper 9 757 296 500 475

Iron 9 25,900 15,700 18,700 18,200

Lead 9 101 52 77 78

Manganese 9 4,170 759 1,720 1,500

Nickel 9 9.9 5.0 7.5 7.3

Silver 8 3.3 1.4 1

2.4 12.6

Zinc 9 997 472 661 626
102 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

461903112440701--CLARK FORK AT DEMPSEY CREEK DIVERSION, NEAR RACETRACK, MONT.

Period of record for bulk bed-sediment data: 1996-2004

Arsenic 2 82 18 50 --

Cadmium 9 9.2 .4 3.9 3.0

Chromium 8 21.1 11.5 16.5 16.8

Copper 9 1,000 128 506 577

Iron 9 25,400 15,800 20,900 20,900

Lead 9 115 47 78 88

Manganese 9 4,930 825 1,900 1,630

Nickel 9 12.8 4.2 8.1 7.9

Silver 8 4.4 <.8 12.4 1

2.5

Zinc 9 1,240 245 612 604

12324200--CLARK FORK AT DEER LODGE, MONT.

Period of record for bulk bed-sediment data: 1993-2004

Arsenic 2 84 37 60 --

Cadmium 12 8.3 1.0 1

3.5 12.5

Chromium 11 29.2 12.1 19.1 19.6

Copper 12 906 281 525 445

Iron 12 25,000 13,200 20,000 20,900

Lead 12 122 45 81 82

Manganese 12 3,560 607 1,380 1,040

Nickel 12 12.3 7.7 10.1 10.1

Silver 11 3.9 <.7 12.0 1<3.2

Zinc 12 1,060 456 666 609

12324590--LITTLE BLACKFOOT RIVER NEAR GARRISON, MONT.

Period of record for bulk bed-sediment data: 1994, 1998, 2001, 2004

Arsenic 1 -- -- 12 --

Cadmium 4 <1.5 .4 1

.6 1.6

Chromium 4 33.2 14.7 25.2 26.4

Copper 4 20 12 16 16

Iron 4 21,000 15,600 18,400 18,500

Lead 4 19 12 16 16

Manganese 4 716 308 444 377

Nickel 4 15.2 8.6 11.8 11.7

Silver 3 <1.6 <.7 -- 1

<1.5

Zinc 4 86 65 76 77

Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, August

1993 through August 2004.—Continued

Constituent Number of 

samples Maximum Minimum Mean Median
TABLE 23 103

12324680--CLARK FORK AT GOLDCREEK, MONT.

Period of record for bulk bed-sediment data: 1993-2004

Arsenic 2 16 15 16 --

Cadmium 12 7.6 .7 13.1 1

2.8

Chromium 11 33.2 10.2 21.0 21.1

Copper 12 858 135 395 280

Iron 12 24,900 11,600 17,900 18,100

Lead 12 92 26 59 55

Manganese 12 2,930 377 1,160 840

Nickel 12 15.9 6.9 11.0 10.4

Silver 11 3.7 <.7 11.8 1

1.5

Zinc 12 1,020 260 616 586

12331500--FLINT CREEK NEAR DRUMMOND, MONT.

Period of record for bulk bed-sediment data: 1993-2004

Arsenic 2 80 30 55 --

Cadmium 12 3.8 <.2 11.8 1

1.6

Chromium 11 13.9 4.9 9.5 10.7

Copper 12 40 7 23 22

Iron 12 15,700 8,630 12,700 13,400

Lead 12 120 38 76 80

Manganese 12 3,200 1,150 2,250 2,350

Nickel 12 8.0 4.4 5.8 5.9

Silver 11 5.8 2.5 4.3 4.3

Zinc 12 429 170 275 279

12331800--CLARK FORK NEAR DRUMMOND, MONT.

Period of record for bulk bed-sediment data: 1993-2004

Arsenic 2 31 16 24 --

Cadmium 12 5.1 <1.6 12.6 1

2.1

Chromium 11 29.5 6.9 17.9 16.9

Copper 12 605 114 259 210

Iron 12 21,800 12,100 15,900 15,500

Lead 12 78 31 48 46

Manganese 12 3,280 409 1,140 964

Nickel 12 14.2 7.7 10.1 9.8

Silver 11 3.5 .5 11.7 1<3.2

Zinc 12 939 381 576 506

Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, August

1993 through August 2004.—Continued

Constituent Number of 

samples Maximum Minimum Mean Median
104 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

12334510--ROCK CREEK NEAR CLINTON, MONT.

Period of record for bulk bed-sediment data: 1993-1999, 2001-2004

Arsenic 2 4 1 2 --

Cadmium 11 3.0 <.1 1

.7 1.5

Chromium 10 22.6 6.4 10.5 8.9

Copper 11 10 .6 15 1

5

Iron 11 14,800 5,290 8,560 7,410

Lead 11 12 1 15 1

5

Manganese 11 265 60 157 145

Nickel 11 10.2 3.6 5.8 5.1

Silver 10 <1.6 .1 1

.4 1.4

Zinc 11 37 .3 17 17

12334550--CLARK FORK AT TURAH BRIDGE, NEAR BONNER, MONT.

Period of record for bulk bed-sediment data: 1993-2004

Arsenic 2 18 9 14 --

Cadmium 12 5.5 .4 1

2.3 12.1

Chromium 11 23.8 6.9 15.0 15.5

Copper 12 336 75 186 184

Iron 12 19,100 9,270 13,300 13,000

Lead 12 67 21 38 37

Manganese 12 2,620 234 829 576

Nickel 12 14.0 6.4 9.1 8.6

Silver 11 2.9 <.3 11.3 1

1.2

Zinc 12 769 271 469 493

12340000--BLACKFOOT RIVER NEAR BONNER, MONT.

Period of record for bulk bed-sediment data: 1993, 1994, 1999-2001, 2003

Arsenic 1 -- -- <.5 --

Cadmium 6 2.5 <.2 1

.9 1<1.5

Chromium 5 19.2 6.7 13.0 12.5

Copper 6 19 6 14 15

Iron 6 17,000 10,300 13,800 13,800

Lead 6 11 5 9 9

Manganese 6 650 179 340 316

Nickel 6 9.8 7.5 8.8 9.0

Silver 6 <1.9 <.4 1

.5 1<1.1

Zinc 6 58 23 38 35

Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, August

1993 through August 2004.—Continued

Constituent Number of 

samples Maximum Minimum Mean Median
TABLE 23 105

12340500--CLARK FORK ABOVE MISSOULA, MONT.

Period of record for bulk bed-sediment data: 1997-2004

Arsenic 2 17 4 10 --

Cadmium 8 5.2 <.8 11.9 1

1.2

Chromium 7 31.5 9.7 15.9 15.0

Copper 8 633 43 166 106

Iron 8 21,500 11,100 15,200 15,300

Lead 8 84 7 30 24

Manganese 8 1,170 228 647 570

Nickel 8 14.4 8.1 9.9 9.1

Silver 7 3.4 <.4 11.2 1<1.7

Zinc 8 1,210 145 409 315

12353000--CLARK FORK BELOW MISSOULA, MONT.2

Period of record for bulk bed-sediment data: 1993-2004

Arsenic 2 6 1 4 --

Cadmium 12 3.0 <.2 1

.9 1<1.2

Chromium 11 13.2 4.4 8.2 7.4

Copper 12 77 9 38 31

Iron 12 18,700 5,830 9,730 8,840

Lead 12 23 5 110 1

8

Manganese 12 601 150 360 366

Nickel 12 12.0 3.5 5.9 5.2

Silver 11 <1.9 <.3 1

.5 1.4

Zinc 12 183 39 111 111

1Value determined by arbitrarily substituting one-half of the minimum reporting level for censored (<) values when both uncensored 

and censored values were used in determining the mean and (or) median. When all data were less than the minimum reporting level, 

the median was determined by ranking the censored values in order of magnitude.

2Samples collected about 30 miles downstream from streamflow-gaging station to conform to previous sampling location.

Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, August

1993 through August 2004.—Continued

Constituent Number of 

samples Maximum Minimum Mean Median
106 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite

samples collected for every year that the constituent was analyzed. Values for single samples are arbitrarily listed in the “Mean” column.

Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled

during those years are based on the results of all Hydropsyche species combined. At some sites, statistics for the Hydropsyche morosa

group are based on the combined results for two or more species. Insects collected during 1986-98 were depurated prior to analysis;

depuration was discontinued in 1999. Arsenic data were not collected at some sites. Values are reported using U.S. Geological Survey

rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; --, indicates either

too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median

12323600--SILVER BOW CREEK AT OPPORTUNITY, MONT.

Period of record for biological data: 1992, 1994, 1995, 1997-2004

Brachycentrus spp.

Arsenic 0 -- -- -- --

Cadmium 5 12.5 5.8 10.1 11.6

Chromium 5 5.9 .7 2.1 .9

Copper 5 846 235 587 592

Iron 5 1,190 335 617 469

Lead 5 21.5 7.4 13.7 13.8

Manganese 5 817 231 515 503

Nickel 5 2.1 <.1 11.3 1

1.6

Zinc 5 995 629 803 815

Hydropsyche cockerelli

Arsenic 3 20.4 9.5 13.6 10.9

Cadmium 9 9.7 4.1 5.9 5.2

Chromium 9 8.0 1.0 3.1 1.9

Copper 9 1,090 269 458 373

Iron 9 2,660 689 1,310 1,070

Lead 9 47.2 19.0 25.7 21.0

Manganese 9 3,030 180 986 718

Nickel 9 3.6 .7 2.0 1.6

Zinc 9 1,590 749 967 871

Hydropsyche spp.

Arsenic 4 23.1 10.7 17.8 18.7

Cadmium 9 10.9 4.6 7.1 5.7

Chromium 9 4.7 .6 2.1 1.5

Copper 9 930 312 617 472

Iron 9 2,290 1,050 1,780 1,880

Lead 9 50.8 21.8 37.5 36.5

Manganese 9 1,340 712 1,090 1,070

Nickel 9 2.5 .7 2.1 2.4

Zinc 9 1,290 834 1,090 1,090

Hydropsyche tana

Arsenic 0 -- -- -- --

Cadmium 6 9.2 4.8 6.8 6.9

Chromium 6 11.5 .9 4.5 1.8

Copper 6 456 10.5 236 298

Iron 6 1,520 875 1,100 1,050

Lead 6 21.0 15.6 18.6 18.3

Manganese 6 969 307 634 675

Nickel 6 1.8 .7 1.4 1.6

Zinc 6 1,070 760 961 1,020
TABLE 24 107

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median

12323750--SILVER BOW CREEK AT WARM SPRINGS, MONT.

Period of record for biological data: 1992-2004

Hydropsyche cockerelli

Arsenic 3 23.6 17.4 19.8 18.2

Cadmium 29 2.1 .2 .7 .6

Chromium 29 4.3 .4 1.0 .8

Copper 29 97.0 22.4 40.5 37.8

Iron 29 1,590 351 764 754

Lead 29 5.7 .3 3.0 2.8

Manganese 29 3,890 491 1,290 928

Nickel 29 1.8 .3 .9 .8

Zinc 29 276 115 179 169

Hydropsyche occidentalis

Arsenic 3 31.0 25.6 27.8 26.8

Cadmium 18 1.6 .2 .6 .4

Chromium 18 6.8 .3 1.7 1.0

Copper 18 48.9 11.0 33.2 32.0

Iron 18 2,960 372 1,220 989

Lead 18 8.2 <1.7 1

4.1 13.7

Manganese 18 6,940 1,200 2,650 2,210

Nickel 18 2.7 .7 1.6 1.5

Zinc 18 220 141 182 182

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 4 2.3 .4 1.1 .9

Chromium 4 1.4 .5 1.0 1.2

Copper 4 47.6 34.9 40.9 40.6

Iron 4 773 561 680 693

Lead 4 5.1 1.9 3.9 4.7

Manganese 4 1,100 443 725 678

Nickel 4 1.9 <.4 1.8 1.5

Zinc 4 285 141 195 177

12323770--WARM SPRINGS CREEK AT WARM SPRINGS, MONT.

Period of record for biological data: 1995, 1997, 1999, 2002

Arctopsyche grandis

Arsenic 0 -- -- -- --

Cadmium 4 3.0 1.9 2.4 2.2

Chromium 4 2.9 .8 1.7 1.6

Copper 4 102 78.3 93.7 97.2

Iron 4 1,040 684 839 815

Lead 4 5.6 3.0 14.3 1

4.3

Manganese 4 3,560 1,340 2,250 2,040

Nickel 4 2.3 1.8 12.1 1

2.2

Zinc 4 222 181 196 190
108 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

12323770--WARM SPRINGS CREEK AT WARM SPRINGS, MONT.—Continued

Period of record for biological data: 1995, 1997, 1999, 2002

Hydropsyche occidentalis

Arsenic 0 -- -- -- --

Cadmium 2 .8 .7 .8 --

Chromium 2 3.2 3.2 3.2 --

Copper 2 183 181 182 --

Iron 2 2,070 1,950 2,010 --

Lead 2 8.2 6.7 7.4 --

Manganese 2 2,480 2,400 2,440 --

Nickel 2 3.3 3.0 3.2 --

Zinc 2 172 166 169 --

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 2 1.1 .6 .9 --

Chromium 2 1.6 1.4 1.5 --

Copper 2 95.9 94.8 95.3 --

Iron 2 1,220 1,150 1,190 --

Lead 2 5.9 5.2 5.6 --

Manganese 2 3,390 956 2,170 --

Nickel 2 2.0 1.8 1.9 --

Zinc 2 129 125 127 --

12323800--CLARK FORK NEAR GALEN, MONT.

Period of record for biological data: 1987, 1991-2004

Hydropsyche cockerelli

Arsenic 2 15.8 13.6 14.7 --

Cadmium 27 2.7 .7 1.5 1.5

Chromium 27 4.4 .8 1.8 1.6

Copper 27 181 48.7 98.9 97.5

Iron 27 2,460 816 1,390 1,340

Lead 27 11.7 1.2 7.5 7.6

Manganese 27 3,620 1,070 2,250 2,290

Nickel 27 3.1 .9 1.6 1.4

Zinc 27 299 136 211 211

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 5 3.2 2.4 2.5 2.4

Chromium 5 4.6 1.8 2.6 2.2

Copper 5 185 156 173 175

Iron 5 1,890 1,360 1,510 1,430

Lead 5 12.4 7.1 8.5 7.9

Manganese 5 3,960 2,360 3,500 3,860

Nickel 5 3.6 1.9 2.3 2.1

Zinc 5 349 292 309 303

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
TABLE 24 109

12323800--CLARK FORK NEAR GALEN, MONT.—Continued

Period of record for biological data: 1987, 1991-2004

Hydropsyche occidentalis

Arsenic 3 16.5 15.9 16.1 16.1

Cadmium 35 1.7 .6 1.1 1.0

Chromium 35 6.6 .4 2.0 1.5

Copper 35 121 49.2 82.0 80.8

Iron 35 1,920 642 1,260 1,200

Lead 35 13.5 1.6 7.0 6.5

Manganese 35 6,170 1,220 2,560 2,240

Nickel 35 3.5 .8 1.6 1.5

Zinc 35 286 168 199 191

Hydropsyche tana

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 1.5 --

Chromium 1 -- -- 1.4 --

Copper 1 -- -- 92.9 --

Iron 1 -- -- 1,340 --

Lead 1 -- -- 9.0 --

Manganese 1 -- -- 2,160 --

Nickel 1 -- -- 2.1 --

Zinc 1 -- -- 206 --

Hydropsyche spp.

Arsenic 2 15.7 14.5 15.1 --

Cadmium 6 3.5 .8 2.3 2.8

Chromium 2 2.4 2.2 2.3 --

Copper 6 154 78.4 126 143

Iron 6 1,540 1,190 1,360 1,360

Lead 6 13.5 5.9 10.4 10.9

Manganese 2 4,760 4,400 4,580 --

Nickel 2 1.8 1.5 1.6 --

Zinc 6 329 218 280 291

461415112450801--CLARK FORK BELOW LOST CREEK, NEAR GALEN, MONT.

Period of record for biological data: 1996-2004

Claassenia sabulosa

Arsenic 1 -- -- 1.5 --

Cadmium 2 .4 .3 .4 --

Chromium 2 1.9 .4 1.2 --

Copper 2 70.1 67.1 68.6 --

Iron 2 209 189 199 --

Lead 2 1.2 .7 1.0 --

Manganese 2 238 90.4 164 --

Nickel 2 .2 <.2 1.1 --

Zinc 2 245 208 226 --

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
110 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

461415112450801--CLARK FORK BELOW LOST CREEK, NEAR GALEN, MONT.—Continued

Period of record for biological data: 1996-2004

Hydropsyche cockerelli

Arsenic 5 11.8 11.2 11.6 11.6

Cadmium 16 2.8 1.1 1.8 1.6

Chromium 16 2.7 .8 1.9 2.0

Copper 16 147 48.8 106 97.8

Iron 16 2,570 691 1,290 1,130

Lead 16 15.2 4.5 9.9 9.0

Manganese 16 3,160 1,230 1,810 1,630

Nickel 16 1.9 .9 1.2 1.1

Zinc 16 321 151 215 223

Hydropsyche occidentalis

Arsenic 3 15.6 12.7 13.7 12.9

Cadmium 17 1.8 .9 1.3 1.3

Chromium 17 3.3 1.2 2.0 1.8

Copper 17 157 52.1 103 107

Iron 17 1,920 963 1,380 1,360

Lead 17 12.4 6.6 9.5 9.5

Manganese 17 3,870 1,220 2,250 2,150

Nickel 17 1.7 .9 1.3 1.4

Zinc 17 283 174 227 236

Hydropsyche spp.

Arsenic 1 -- -- 12.0 --

Cadmium 5 1.8 1.2 1.5 1.4

Chromium 5 2.4 .9 1.5 1.5

Copper 5 122 45.1 91.8 103

Iron 5 1,410 533 1,110 1,200

Lead 5 20.5 4.1 10.0 8.7

Manganese 5 1,980 799 1,440 1,230

Nickel 5 2.8 1.0 1.6 1.4

Zinc 5 225 143 179 179

461559112443301--CLARK FORK NEAR RACETRACK, MONT.

Period of record for biological data: 1996-2004

Claassenia sabulosa

Arsenic 0 -- -- -- --

Cadmium 1 -- -- .4 --

Chromium 1 -- -- .3 --

Copper 1 -- -- 40.3 --

Iron 1 -- -- 113 --

Lead 1 -- -- .8 --

Manganese 1 -- -- 172 --

Nickel 1 -- -- .2 --

Zinc 1 -- -- 213 --

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
TABLE 24 111

461559112443301--CLARK FORK NEAR RACETRACK, MONT.—Continued

Period of record for biological data: 1996-2004

Hydropsyche cockerelli

Arsenic 3 14.3 11.5 12.5 11.7

Cadmium 14 1.9 .8 1.4 1.3

Chromium 14 2.7 .6 1.6 1.3

Copper 14 109 50.0 78.6 78.4

Iron 14 1,370 657 949 926

Lead 14 10.5 3.7 6.6 6.1

Manganese 14 2,020 646 1,430 1,550

Nickel 14 1.4 .7 1.0 .9

Zinc 14 199 139 173 172

Hydropsyche occidentalis

Arsenic 2 14.3 13.7 14.0 --

Cadmium 15 2.2 .7 1.4 1.4

Chromium 15 3.7 1.1 2.1 2.0

Copper 15 160 59.5 107 107

Iron 15 1,880 1,030 1,510 1,520

Lead 15 11.7 4.3 9.6 10.1

Manganese 15 3,770 1,090 2,070 2,050

Nickel 15 1.9 1.1 1.3 1.3

Zinc 15 255 181 225 220

Hydropsyche spp.

Arsenic 1 -- -- 11.9 --

Cadmium 3 2.4 1.0 1.6 1.5

Chromium 3 1.7 .7 1.2 1.1

Copper 3 113 82.9 93.7 85.2

Iron 3 1,290 1,140 1,210 1,200

Lead 3 9.6 5.7 7.5 7.4

Manganese 3 1,600 910 1,210 1,130

Nickel 3 1.4 1.1 1.3 1.3

Zinc 3 208 151 180 181

461903112440701--CLARK FORK AT DEMPSEY CREEK DIVERSION, NEAR RACETRACK, MONT.

Period of record for biological data: 1996-2004

Arctopsyche grandis

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 1.7 --

Chromium 1 -- -- <2.4 --

Copper 1 -- -- 30.8 --

Iron 1 -- -- 340 --

Lead 1 -- -- <14.5 --

Manganese 1 -- -- 510 --

Nickel 1 -- -- 1.0 --

Zinc 1 -- -- 87 --

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
112 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

461903112440701--CLARK FORK AT DEMPSEY CREEK DIVERSION, NEAR RACETRACK, MONT.—Continued

Period of record for biological data: 1996-2004

Hydropsyche cockerelli

Arsenic 3 18.8 9.2 12.6 9.7

Cadmium 12 1.6 .7 1.2 1.3

Chromium 12 4.0 .4 1.3 1.0

Copper 12 190 60.7 91.1 78.1

Iron 12 2,310 552 934 794

Lead 12 17.7 3.5 6.5 4.7

Manganese 12 2,070 487 1,170 1,160

Nickel 12 1.9 .5 1.0 .7

Zinc 12 275 162 193 180

Hydropsyche occidentalis

Arsenic 1 -- -- 24.0 --

Cadmium 18 1.8 .7 1.2 1.1

Chromium 18 6.2 .8 2.1 1.8

Copper 18 238 74.9 103 88.3

Iron 18 3,390 940 1,520 1,500

Lead 18 21.8 6.1 11.6 11.4

Manganese 18 3,990 826 2,420 2,280

Nickel 18 2.4 1.2 1.5 1.4

Zinc 18 355 222 252 236

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 2 1.7 1.6 1.6 --

Chromium 2 2.1 1.4 1.8 --

Copper 2 140 104 122 --

Iron 2 1,610 1,070 1,340 --

Lead 2 13.2 10.5 11.8 --

Manganese 2 1,150 638 892 --

Nickel 2 1.6 1.6 1.6 --

Zinc 2 212 191 202 --

12324200--CLARK FORK AT DEER LODGE, MONT.

Period of record for biological data: 1986, 1987, 1990-2004

Arctopsyche grandis

Arsenic 0 -- -- -- --

Cadmium 2 2.4 <4.2 12.2 --

Chromium 2 1.0 <1.3 1

.8 --

Copper 2 69.1 34.9 52.0 --

Iron 2 676 537 606 --

Lead 2 <7.8 3.8 1

3.8 --

Manganese 2 727 380 554 --

Nickel 2 <1.7 <1.3 1-- --

Zinc 2 178 140 159 --

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
TABLE 24 113

12324200--CLARK FORK AT DEER LODGE, MONT.—Continued

Period of record for biological data: 1986, 1987, 1990-2004

Hydropsyche cockerelli

Arsenic 3 10.1 5.8 7.3 6.1

Cadmium 26 2.3 .6 1.3 1.3

Chromium 26 3.2 .4 1.6 1.6

Copper 26 136 54.7 93.1 92.5

Iron 26 3,340 490 1,100 1,040

Lead 26 18.2 3.8 9.2 8.9

Manganese 26 1,490 396 838 747

Nickel 26 2.4 .3 1.1 1.0

Zinc 26 391 132 186 184

Hydropsyche occidentalis

Arsenic 3 12.4 6.6 10.1 11.3

Cadmium 40 2.7 .6 1.3 1.2

Chromium 40 3.6 .6 1.9 1.9

Copper 40 162 49.4 112 110

Iron 40 2,060 557 1,400 1,420

Lead 40 18.6 3.5 10.9 10.8

Manganese 40 2,850 649 1,680 1,720

Nickel 40 12.9 1.0 1.8 1.4

Zinc 40 329 166 237 230

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 3 2.6 2.0 2.4 2.5

Chromium 0 -- -- -- --

Copper 3 222 175 191 177

Iron 3 2,220 1,850 2,010 1,950

Lead 3 16.7 15.0 16.1 16.7

Manganese 0 -- -- -- --

Nickel 0 -- -- -- --

Zinc 3 298 197 257 276

12324590--LITTLE BLACKFOOT RIVER NEAR GARRISON, MONT.

Period of record for biological data: 1987, 1994, 1998, 2001, 2004

Arctopsyche grandis

Arsenic 3 4.2 3.2 3.6 3.3

Cadmium 18 .7 .2 .4 .4

Chromium 18 1.6 .6 .9 .8

Copper 18 14.2 9.0 11.9 11.9

Iron 18 716 177 419 414

Lead 18 1.3 .5 .8 .8

Manganese 18 1,140 318 733 719

Nickel 18 1.4 .4 .8 .8

Zinc 18 214 113 162 160

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
114 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

12324590--LITTLE BLACKFOOT RIVER NEAR GARRISON, MONT.—Continued

Period of record for biological data: 1987, 1994, 1998, 2001, 2004

Claassenia sabulosa

Arsenic 1 -- -- 1.3 --

Cadmium 8 .5 .1 .2 .2

Chromium 8 .9 .3 .6 .7

Copper 8 37.2 20.0 30.4 30.9

Iron 8 319 98.4 178 178

Lead 8 <.8 <.1 1

.4 1.3

Manganese 8 149 46.7 75.9 62.1

Nickel 8 .7 .4 .5 .5

Zinc 8 271 172 211 206

Hydropsyche cockerelli

Arsenic 0 -- -- -- --

Cadmium 1 -- -- .6 --

Chromium 1 -- -- 1.6 --

Copper 1 -- -- 28.4 --

Iron 1 -- -- 478 --

Lead 1 -- -- 3.6 --

Manganese 1 -- -- 399 --

Nickel 1 -- -- 1.2 --

Zinc 1 -- -- 123 --

Hydropsyche occidentalis

Arsenic 0 -- -- -- --

Cadmium 2 <.7 .3 1.3 --

Chromium 2 2.3 1.3 1.8 --

Copper 2 15.2 15.1 15.2 --

Iron 2 1,340 426 883 --

Lead 2 2.3 <3.7 12.1 --

Manganese 2 554 434 494 --

Nickel 2 1.1 .8 .9 --

Zinc 2 137 110 124 --

Hydropsyche spp.

Arsenic 1 -- -- 3.7 --

Cadmium 1 -- -- <.2 --

Chromium 1 -- -- 1.8 --

Copper 1 -- -- 11.1 --

Iron 1 -- -- 1,000 --

Lead 1 -- -- <2.4 --

Manganese 1 -- -- 1,200 --

Nickel 1 -- -- .9 --

Zinc 1 -- -- 151 --

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
TABLE 24 115

12324680--CLARK FORK AT GOLDCREEK, MONT.

Period of record for biological data: 1992-2004

Arctopsyche grandis

Arsenic 9 6.4 2.2 4.8 5.9

Cadmium 38 6.6 .6 2.1 1.9

Chromium 38 3.3 .4 1.4 1.1

Copper 38 129 19.9 45.8 39.7

Iron 38 2,360 275 732 586

Lead 38 10.9 1.1 3.8 3.5

Manganese 38 1,580 592 855 812

Nickel 38 1.8 .2 .8 .7

Zinc 38 326 149 203 186

Claassenia sabulosa

Arsenic 6 1.6 .7 1.2 1.2

Cadmium 26 3.5 .1 1.1 .7

Chromium 26 1.6 .2 .6 .5

Copper 26 81.7 33.0 56.7 56.3

Iron 26 567 63.0 194 190

Lead 26 1.8 .4 .9 1.0

Manganese 26 320 50.6 139 108

Nickel 26 .7 .1 .3 .3

Zinc 26 351 166 263 260

Hydropsyche cockerelli

Arsenic 6 6.1 4.1 5.4 5.8

Cadmium 25 2.6 .5 1.3 1.2

Chromium 25 4.7 .5 2.1 2.0

Copper 25 188 17.1 70.7 55.5

Iron 25 3,250 522 1,180 954

Lead 25 16.2 2.4 6.9 5.4

Manganese 25 1,670 538 897 902

Nickel 25 2.3 .3 1.2 1.2

Zinc 25 249 106 183 186

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 4 1.7 1.1 1.4 1.4

Chromium 4 1.4 1.3 1.4 1.4

Copper 4 72.9 43.8 60.5 62.7

Iron 4 1,320 612 1,050 1,130

Lead 4 6.9 2.4 4.6 4.6

Manganese 4 1,030 538 804 822

Nickel 4 1.4 .9 1.2 1.2

Zinc 4 190 137 167 170

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
116 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

12324680--CLARK FORK AT GOLDCREEK, MONT.—Continued

Period of record for biological data: 1992-2004

Hydropsyche occidentalis

Arsenic 2 5.8 4.7 5.3 --

Cadmium 17 1.7 .4 1.2 1.3

Chromium 17 3.9 .4 1.6 1.7

Copper 17 156 26.4 63.1 58.3

Iron 17 2,720 466 1,130 1,040

Lead 17 15.7 2.9 7.1 6.0

Manganese 17 2,210 530 1,200 1,030

Nickel 17 2.5 .8 1.2 1.1

Zinc 17 277 97 194 192

12331500--FLINT CREEK NEAR DRUMMOND, MONT.

Period of record for biological data: 1986, 1992-2004

Arctopsyche grandis

Arsenic 6 9.0 2.8 5.6 5.4

Cadmium 45 .8 .1 .3 .3

Chromium 45 7.1 .3 2.0 1.7

Copper 45 22.2 8.9 14.9 15.2

Iron 45 2,460 412 1,320 1,300

Lead 45 17.5 3.7 8.6 7.8

Manganese 45 3,160 424 1,560 1,440

Nickel 45 2.7 .3 1.3 1.3

Zinc 45 275 93.3 197 192

Hydropsyche cockerelli

Arsenic 3 17.1 6.4 13.5 16.8

Cadmium 14 .9 .1 .4 .3

Chromium 14 9.1 .9 2.8 1.9

Copper 14 28.3 9.5 17.8 18.1

Iron 14 4,400 996 2,390 2,100

Lead 14 28.4 3.1 15.1 16.2

Manganese 14 3,020 401 1,650 1,330

Nickel 14 4.0 .7 2.1 2.2

Zinc 14 224 85.3 178 185

Hydropsyche occidentalis

Arsenic 1 -- -- 6.1 --

Cadmium 8 1.1 .2 .6 .6

Chromium 8 17.6 .7 4.2 2.1

Copper 8 27.3 11.5 19.3 18.0

Iron 8 2,990 912 1,840 1,780

Lead 8 29.8 5.8 18.2 19.3

Manganese 8 4,790 1,400 2,410 1,910

Nickel 8 6.9 .8 3.0 2.4

Zinc 8 243 128 183 185

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
TABLE 24 117

12331500--FLINT CREEK NEAR DRUMMOND, MONT.—Continued

Period of record for biological data: 1986, 1992-2004

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- <.3 --

Chromium 1 -- -- 1.4 --

Copper 1 -- -- 12.5 --

Iron 1 -- -- 1,440 --

Lead 1 -- -- 4.5 --

Manganese 1 -- -- 1,320 --

Nickel 1 -- -- 1.3 --

Zinc 1 -- -- 130 --

Hydropsyche tana

Arsenic 0 -- -- -- --

Cadmium 2 <1.2 <.1 1-- --

Chromium 2 10.3 .6 5.4 --

Copper 2 16.0 5.4 10.7 --

Iron 2 1,320 729 1,020 --

Lead 2 15.3 5.0 10.2 --

Manganese 2 1,400 1,180 1,290 --

Nickel 2 3.1 .5 1.8 --

Zinc 2 139 107 123 --

12331800--CLARK FORK NEAR DRUMMOND, MONT.

Period of record for biological data: 1986, 1991-2004

Arctopsyche grandis

Arsenic 6 3.6 2.4 2.9 2.9

Cadmium 38 3.8 .4 1.4 1.2

Chromium 38 2.5 .2 1.0 1.0

Copper 38 89.2 16.9 32.9 28.0

Iron 38 1,660 240 586 529

Lead 38 11.8 2.1 4.5 3.9

Manganese 38 2,010 462 860 737

Nickel 38 1.9 .2 .7 .6

Zinc 38 308 140 191 188

Claassenia sabulosa

Arsenic 4 1.3 .7 1.0 1.0

Cadmium 40 2.8 .1 1.1 1.0

Chromium 40 3.3 .1 .7 .5

Copper 40 165 18.0 63.9 53.8

Iron 40 387 45.4 160 135

Lead 40 2.9 .2 .9 .8

Manganese 40 410 33.1 162 140

Nickel 40 1.1 .1 .3 .2

Zinc 40 567 103 273 253

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
118 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

12331800--CLARK FORK NEAR DRUMMOND, MONT.—Continued

Period of record for biological data: 1986, 1991-2004

Hydropsyche cockerelli

Arsenic 5 4.5 3.9 4.2 4.1

Cadmium 34 2.3 .3 1.1 .8

Chromium 34 3.5 .4 1.6 1.5

Copper 34 156 30.0 58.0 47.7

Iron 34 2,500 506 1,150 940

Lead 34 15.0 5.1 8.3 7.5

Manganese 34 1,680 549 982 914

Nickel 34 2.0 .5 1.1 1.0

Zinc 34 248 134 192 187

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 6 1.3 1.1 1.2 1.2

Chromium 6 2.8 1.9 2.3 2.2

Copper 6 57.4 50.2 55.2 55.8

Iron 6 1,730 1,370 1,570 1,600

Lead 6 10.8 7.0 8.9 9.0

Manganese 6 1,940 1,260 1,610 1,610

Nickel 6 1.7 1.3 1.5 1.5

Zinc 6 250 227 239 240

Hydropsyche occidentalis

Arsenic 3 4.5 4.3 4.4 4.3

Cadmium 19 2.0 .4 1.0 1.0

Chromium 19 8.1 .4 2.3 2.2

Copper 19 118 13.3 53.9 53.1

Iron 19 2,060 424 1,270 1,190

Lead 19 14.0 2.9 9.0 9.1

Manganese 19 2,920 619 1,550 1,220

Nickel 19 2.4 .5 1.4 1.3

Zinc 19 293 157 222 223

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 2.6 --

Chromium 0 -- -- -- --

Copper 1 -- -- 85.0 --

Iron 1 -- -- 913 --

Lead 1 -- -- 9.1 --

Manganese 0 -- -- -- --

Nickel 0 -- -- -- --

Zinc 1 -- -- 260 --

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
TABLE 24 119

12334510--ROCK CREEK NEAR CLINTON, MONT.

Period of record for biological data: 1987, 1991-99, 2001-04

Arctopsyche grandis

Arsenic 6 2.5 1.9 2.2 2.1

Cadmium 44 .4 <.1 1.2 1.2

Chromium 44 2.9 .4 1.1 1.0

Copper 44 15.7 4.7 8.6 8.4

Iron 44 1,090 191 582 527

Lead 44 1.1 <.1 1

.4 1.4

Manganese 44 454 113 250 239

Nickel 44 1.8 .2 .9 .9

Zinc 44 189 83.9 127 130

Claassenia sabulosa

Arsenic 3 1.1 1.0 1.0 1.1

Cadmium 22 .3 <.1 1.2 1.1

Chromium 22 1.8 .1 .6 .5

Copper 22 40.7 18.1 28.3 27.9

Iron 22 129 49.8 93.7 102

Lead 22 1.0 .1 .4 .3

Manganese 22 76.3 15.7 36.0 34.6

Nickel 22 .9 .1 .3 .3

Zinc 22 264 139 193 187

Hydropsyche cockerelli

Arsenic 1 -- -- 2.4 --

Cadmium 4 .3 <.2 1.2 1

<.2

Chromium 4 1.0 .3 .8 .9

Copper 4 13.1 6.0 8.5 7.4

Iron 4 825 485 604 553

Lead 4 <1.1 .4 1.5 1<1.1

Manganese 4 266 192 231 233

Nickel 4 1.0 .4 .6 .6

Zinc 4 98.8 82.2 90.8 91.0

Hydropsyche occidentalis

Arsenic 1 -- -- 2.2 --

Cadmium 5 .4 <.3 1

.2 1.1

Chromium 5 2.4 .9 1.6 1.6

Copper 5 17.6 5.1 10.6 10.2

Iron 5 973 520 709 652

Lead 5 6.0 1.2 3.0 1.8

Manganese 5 295 169 242 262

Nickel 5 1.7 .6 1.2 1.4

Zinc 5 144 99.2 116 117

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
120 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

12334510--ROCK CREEK NEAR CLINTON, MONT.—Continued

Period of record for biological data: 1987, 1991-99, 2001-04

Hydropsyche spp.

Arsenic 1 -- -- .7 --

Cadmium 4 .3 <.5 1.2 1.2

Chromium 4 2.1 1.1 1.6 1.7

Copper 4 16.2 6.1 12.2 13.3

Iron 4 1,140 789 949 932

Lead 4 <4.9 <1.8 1

-- 1<2.9

Manganese 4 462 299 394 407

Nickel 4 1.3 .8 1.1 1.1

Zinc 4 135 112 123 121

12334550--CLARK FORK AT TURAH BRIDGE, NEAR BONNER, MONT.

Period of record for biological data: 1986, 1991-2004

Arctopsyche grandis

Arsenic 8 5.0 4.0 4.4 4.4

Cadmium 50 2.7 .3 1.1 .8

Chromium 50 4.1 .5 1.6 1.4

Copper 50 125 20.1 37.7 29.3

Iron 50 2,870 372 941 789

Lead 50 13.2 1.6 4.3 3.5

Manganese 50 902 324 633 637

Nickel 50 2.7 .4 1.1 .9

Zinc 50 276 111 197 196

Claassenia sabulosa

Arsenic 4 1.2 .8 1.0 .9

Cadmium 30 2.5 .1 1.0 .7

Chromium 30 2.0 .2 .7 .6

Copper 30 79.2 37.5 55.9 52.5

Iron 30 181 58.6 104 101

Lead 30 1.6 .2 .6 .6

Manganese 30 174 37.2 79.9 69.7

Nickel 30 .6 .1 .2 .2

Zinc 30 283 144 221 226

Hydropsyche cockerelli

Arsenic 5 5.1 3.7 4.3 4.1

Cadmium 33 1.8 .3 .8 .7

Chromium 33 8.0 .2 1.9 1.6

Copper 33 118 26.4 47.3 42.3

Iron 33 2,530 566 1,200 1,080

Lead 33 12.1 2.2 5.2 4.9

Manganese 33 805 426 608 581

Nickel 33 2.6 .6 1.2 1.2

Zinc 33 228 119 183 182

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
TABLE 24 121

12334550--CLARK FORK AT TURAH BRIDGE, NEAR BONNER, MONT.—Continued

Period of record for biological data: 1986, 1991-2004

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 2 1.3 1.1 1.2 --

Chromium 2 4.6 2.4 3.5 --

Copper 2 84.1 26.8 55.4 --

Iron 2 1,800 986 1,390 --

Lead 2 6.6 <7.8 15.2 --

Manganese 2 1,320 537 928 --

Nickel 2 1.7 1.3 1.5 --

Zinc 2 231 171 201 --

Hydropsyche occidentalis

Arsenic 3 4.1 3.6 3.9 4.0

Cadmium 23 1.8 .3 .8 .8

Chromium 23 3.2 .6 1.8 1.6

Copper 23 102 27.4 47.9 41.8

Iron 23 2,310 472 1,180 1,050

Lead 23 14.2 3.0 6.4 5.4

Manganese 23 1,600 454 828 728

Nickel 23 3.2 .6 1.2 1.1

Zinc 23 416 145 208 200

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 1.3 --

Chromium 1 -- -- 2.4 --

Copper 1 -- -- 84.1 --

Iron 1 -- -- 1,800 --

Lead 1 -- -- <7.8 --

Manganese 1 -- -- 537 --

Nickel 1 -- -- 1.3 --

Zinc 1 -- -- 171 --

12340000--BLACKFOOT RIVER NEAR BONNER, MONT.

Period of record for biological data: 1986, 1987, 1991, 1993,1996, 1998, 2000, 2003

Arctopsyche grandis

Arsenic 1 -- -- 2.8 --

Cadmium 11 .4 <.1 1.2 1.2

Chromium 6 1.8 .8 1.2 1.2

Copper 11 13.4 9.9 12.0 12.0

Iron 11 1,230 108 606 617

Lead 11 2.3 .5 1.0 .6

Manganese 6 517 286 404 393

Nickel 6 1.2 .7 .9 .9

Zinc 11 143 123 135 136

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
122 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

12340000--BLACKFOOT RIVER NEAR BONNER, MONT.—Continued

Period of record for biological data: 1986, 1987, 1991, 1993, 1996, 1998, 2000, 2003

Claassenia sabulosa

Arsenic 0 -- -- -- --

Cadmium 11 .2 .1 .1 .1

Chromium 6 .9 .3 .5 .5

Copper 11 88.5 19.0 45.2 44.0

Iron 11 158 46.2 100 99.0

Lead 11 .6 .4 .5 .6

Manganese 6 127 26.3 57.1 44.7

Nickel 6 .3 .1 .2 .2

Zinc 11 329 117 209 194

Hydropsyche occidentalis

Arsenic 1 -- -- 3.2 --

Cadmium 13 .5 .1 .2 .2

Chromium 13 2.7 .8 1.8 1.7

Copper 13 20.6 12.0 14.4 14.4

Iron 13 1,930 1,060 1,410 1,470

Lead 13 1.9 .8 1.3 1.3

Manganese 13 577 414 480 466

Nickel 13 1.8 .9 1.3 1.2

Zinc 13 150 116 135 130

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- .6 --

Chromium 1 -- -- 1.6 --

Copper 1 -- -- 13.9 --

Iron 1 -- -- 1,140 --

Lead 1 -- -- 2.9 --

Manganese 1 -- -- 525 --

Nickel 1 -- -- 2.8 --

Zinc 1 -- -- 132 --

12340500--CLARK FORK ABOVE MISSOULA, MONT.

Period of record for biological data: 1997-2004

Arctopsyche grandis

Arsenic 6 4.5 3.1 3.8 3.8

Cadmium 25 1.8 .1 .7 .6

Chromium 25 3.4 .6 1.6 1.4

Copper 25 77.6 19.5 34.6 30.2

Iron 25 2,340 476 1,020 908

Lead 25 6.8 1.2 3.9 3.8

Manganese 25 1,410 476 926 924

Nickel 25 2.0 .5 1.1 1.0

Zinc 25 260 133 188 192

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
TABLE 24 123

12340500--CLARK FORK ABOVE MISSOULA, MONT.—Continued

Period of record for biological data: 1997-2004

Claassenia sabulosa

Arsenic 2 1.1 .7 .9 --

Cadmium 11 2.0 .2 .7 .4

Chromium 11 1.1 .3 .7 .7

Copper 11 71.7 33.0 48.9 46.0

Iron 11 402 95.3 247 246

Lead 11 3.1 .5 1.3 1.2

Manganese 11 683 75.2 261 270

Nickel 11 <.4 <.3 1.4 1.4

Zinc 11 363 191 268 250

Hydropsyche cockerelli

Arsenic 4 6.5 5.2 5.9 5.9

Cadmium 13 1.3 .4 .8 .8

Chromium 13 6.0 1.8 3.1 3.1

Copper 13 96.1 29.9 57.2 56.3

Iron 13 3,590 1,400 2,100 2,040

Lead 13 10.0 4.2 6.7 6.0

Manganese 13 1,890 781 1,210 1,170

Nickel 13 2.4 1.4 1.8 1.6

Zinc 13 237 156 199 207

Hydropsyche occidentalis

Arsenic 2 6.2 6.1 6.2 --

Cadmium 8 1.1 .4 .7 .6

Chromium 8 5.5 2.1 3.4 3.0

Copper 8 76.5 30.3 51.4 52.9

Iron 8 2,400 1,450 2,060 2,220

Lead 8 10.2 4.0 6.8 6.6

Manganese 8 2,450 939 1,840 1,950

Nickel 8 2.4 1.6 2.0 2.2

Zinc 8 257 192 227 230

12353000--CLARK FORK BELOW MISSOULA, MONT.2

Period of record for biological data: 1986, 1990-2004

Arctopsyche grandis

Arsenic 4 2.6 2.1 2.4 2.4

Cadmium 29 1.5 .2 .6 .6

Chromium 29 2.7 .5 1.3 1.4

Copper 29 38.0 9.4 21.1 19.2

Iron 29 1,590 343 797 682

Lead 29 3.9 .9 1.9 1.7

Manganese 29 1,090 511 707 692

Nickel 29 1.6 .4 .9 .9

Zinc 29 217 106 152 148

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median
124 Water-Quality, Bed-Sediment, and Biological Data (October 2003 through September 2004) and Statistical Summaries of Data for Streams 

in the Upper Clark Fork Basin, Montana 

12353000--CLARK FORK BELOW MISSOULA, MONT.2

—Continued

Period of record for biological data: 1986, 1990-2004

Claassenia sabulosa

Arsenic 3 1.1 .8 .9 .8

Cadmium 42 1.3 .1 .5 .4

Chromium 42 1.2 <.1 .5 .5

Copper 42 75.1 31.1 48.8 47.0

Iron 42 239 66.6 114 108

Lead 42 1.3 .1 .4 .3

Manganese 42 275 48.9 107 99

Nickel 42 .3 .1 .2 .2

Zinc 42 324 146 218 211

Hydropsyche cockerelli

Arsenic 8 2.9 2.2 2.5 2.4

Cadmium 46 1.1 .2 .5 .5

Chromium 46 3.4 .3 1.7 1.7

Copper 46 54.1 12.4 30.4 29.5

Iron 46 2,220 584 1,290 1,270

Lead 46 6.6 1.2 2.5 2.4

Manganese 46 1,210 353 768 690

Nickel 46 1.9 .5 1.2 1.3

Zinc 46 187 77.4 144 151

Hydropsyche occidentalis

Arsenic 1 -- -- 2.5 --

Cadmium 17 1.1 .1 .4 .3

Chromium 17 3.5 .1 1.4 1.5

Copper 17 38.2 13.5 23.8 20.9

Iron 17 1,420 482 941 907

Lead 17 4.2 .7 2.1 1.9

Manganese 17 1,460 491 841 812

Nickel 17 2.2 .5 1.0 .9

Zinc 17 193 112 143 144

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- .5 --

Chromium 1 -- -- .8 --

Copper 1 -- -- 20.8 --

Iron 1 -- -- 894 --

Lead 1 -- -- 1.1 --

Manganese 1 -- -- 756 --

Nickel 1 -- -- 1.1 --

Zinc 1 -- -- 124 --

1

Values determined by substituting one-half of the minimum reporting level for censored (<) values when both uncensored and

censored values were used in determining the mean and median. When all data were less than the minimum reporting level, the median 

was determined by ranking the censored values in order of detection. No mean is reported when all values were below the

minimum reporting level.

2

Samples collected about 30 miles downstream from streamflow-gaging station to conform to previous sampling location.

Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 2004.—Continued

Constituent

Number of

 composite 

samples

Maximum Minimum Mean Median