U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2010–1267

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

Water-Quality, Bed-Sediment, and Biological Data 

(October 2008 through September 2009) and 

Statistical Summaries of Long-Term Data for 

Streams in the Clark Fork Basin, Montana
Cover.  Artist’s rendition of the Clark Fork and Blackfoot River’s confluence near Bonner, Montana, after completion of the 

  Milltown Reservoir sediment remediation project.  Image provided by Diana Hammer, U.S. Environmental Protection  

  Agency, November 24, 2009.
Water-Quality, Bed-Sediment, and 

Biological Data (October 2008 through 

September 2009) and Statistical 

Summaries of Long-Term Data for Streams 

in the Clark Fork Basin, Montana

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

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

Open-File Report 2010–1267

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

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

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Suggested citation:

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2010, Water-quality, bed-sediment, and biological data (October 2008 

through September 2009) and statistical summaries of long-term data for streams in the Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 2010–1267, 137 p.
iii

Contents

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

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

Sampling Locations and Types of Data......................................................................................................2

Water-Quality Data........................................................................................................................................7

Methods..................................................................................................................................................7

Results ....................................................................................................................................................8

Quality Assurance.................................................................................................................................8

Bed-Sediment Data .....................................................................................................................................11

Methods................................................................................................................................................11

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

Quality Assurance...............................................................................................................................12

Biological Data.............................................................................................................................................12

Methods................................................................................................................................................12

Results ..................................................................................................................................................13

Quality Assurance...............................................................................................................................13

Statistical Summaries of Data ...................................................................................................................14

References Cited..........................................................................................................................................14

Data ...........................................................................................................................................................19

Figure

1. Map showing location of study area in the Clark Fork basin, Montana..............................3

Tables

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

Montana .........................................................................................................................................4

2. Properties and constituents measured onsite or analyzed in water, 

bed-sediment, and biota samples from the Clark Fork basin, Montana..............................6

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

Fork basin, Montana.....................................................................................................................6

4. Water-quality data for the Clark Fork basin, Montana, October 2008 through 

September 2009...........................................................................................................................20

5. Daily mean streamflow and suspended-sediment data for Clark Fork at 

Deer Lodge, Montana, October 2008 through September 2009 ..........................................55

6. Daily mean streamflow and suspended-sediment data for Clark Fork at 

Turah Bridge, near Bonner, Montana, October 2008 through September 2009 ...............59

7. Daily mean streamflow and suspended-sediment data for Blackfoot River 

near Bonner, Montana, October 2008 through September 2009.........................................63

8. Daily mean streamflow and suspended-sediment data for Clark Fork above 

Missoula, Montana, October 2008 through September 2009 ..............................................67

.....
iv

9. Seasonal daily maximum, minimum, and mean turbidity at Mill Creek near 

Anaconda, Montana, April through September 2009 ...........................................................71

10. Seasonal daily maximum, minimum, and mean turbidity at Willow Creek 

near Anaconda, Montana, June through September 2009..................................................73

11. Seasonal daily maximum, minimum, and mean turbidity at Warm Springs 

Creek near Anaconda, Montana, April through September 2009.......................................75

12. Seasonal daily maximum, minimum, and mean turbidity at Lost Creek near 

Anaconda, Montana, April through September 2009 ...........................................................77

13. Analyses of field replicates for water samples, Clark Fork basin, Montana....................79

14. Precision of analyses of field replicates for water samples, Clark Fork 

basin, Montana ...........................................................................................................................82

15. Precision of analyses of laboratory replicates for water samples, upper 

Clark Fork basin, Montana ........................................................................................................83

16. Recovery efficiency for analyses of laboratory-spiked deionized-water 

blank samples..............................................................................................................................83

17. Recovery efficiency for analyses of laboratory-spiked stream samples, 

upper Clark Fork basin, Montana.............................................................................................84

18. Analyses of field blanks for water samples ...........................................................................85

19. Bed-sediment data for the upper Clark Fork basin, Montana, August 2009.....................86

20. Recovery efficiency for analyses of standard reference materials for 

bed-sediment samples...............................................................................................................87

21. Analyses of procedural blanks for bed-sediment samples.................................................88

22. Biological data for the upper Clark Fork basin, Montana, August 2009 ............................89

23. Recovery efficiency for analyses of standard reference material for 

biota samples ..............................................................................................................................91

24. Analyses of procedural blanks for biota samples.................................................................92

25. Statistical summary of long-term water-quality data for the upper Clark 

Fork basin, Montana, March 1985 through September 2009...............................................93

26. Statistical summary of long-term bed-sediment data for the upper Clark 

Fork basin, Montana, August 1986 through August 2009 ...................................................113

27. Statistical summary of long-term biological data for the upper Clark Fork 

basin, Montana, August 1986 through August 2009............................................................118
v

Conversion Factors, Datum, Abbreviated Water-Quality 

Units, and Acronyms

Multiply By To obtain

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

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

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 (ppm) 1 microgram per gram (μg/g)

square mile (mi2) 2.59 square kilometer (km2)

ton 907.2 kilogram

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

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).

Water-year definition:

Water year is the 12-month period from October 1 through September 30 of the following 

calendar year. The water year is designated by the calendar year in which it ends. For example, 

water year 2009 is the period from October 1, 2008, through September 30, 2009.
vi

Abbreviated water-quality units used in this report:

μg/g microgram per gram

μg/L microgram per liter

μg/mL microgram per milliliter

μm micrometer

μS/cm microsiemen per centimeter at 25 degrees Celsius

mg/L milligram per liter

nm nanometer

ppm part per million

Acronyms used in the report:

FNU formazin nephelometric units

ICP–OES inductively coupled plasma–optical emission spectrometry

LRL laboratory reporting level

LT–MDL long-term method detection level

NTRU nephelometric turbidity ratio unit

NWQL USGS National Water Quality Laboratory, Denver, Colo.

RSD relative standard deviation

spp. species

SRM standard reference material

TFE tetrafluoroethylene

USGS U.S. Geological Survey

YSI Yellow Springs Instruments Company
Water-Quality, Bed-Sediment, and Biological Data 

(October 2008 through September 2009) and Statistical 

Summaries of Long-Term Data for Streams in the Clark 

Fork Basin, Montana

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

Abstract

Water, bed sediment, and biota were sampled in streams 

from Butte to near Missoula, Montana, as part of a long-term 

monitoring program in the upper Clark Fork basin; additional 

water samples were collected in the Clark Fork basin from 

sites near Missoula downstream to near the confluence of 

the Clark Fork and Flathead River as part of a supplemental 

sampling program. The sampling programs were conducted by 

the U.S. Geological Survey in cooperation with the U.S. Environmental Protection Agency to characterize aquatic resources 

in the Clark Fork basin of western Montana, with emphasis on 

trace elements associated with historic mining and smelting 

activities. Sampling sites were located on the Clark Fork and 

selected tributaries. Water samples were collected periodically 

at 24 sites from October 2008 through September 2009. Bedsediment and biota samples were collected once at 13 sites 

during August 2009. 

This report presents the analytical results and qualityassurance data for water-quality, bed-sediment, and biota 

samples collected at all long-term and supplemental monitoring sites from October 2008 through September 2009.

Water-quality data include concentrations of selected major 

ions, trace elements, and suspended sediment. Turbidity was 

analyzed for water samples collected at the four sites where 

seasonal daily values of turbidity were being determined as 

well as at Clark Fork above Missoula. Nutrients also were 

analyzed at all the supplemental water-quality sites, except for 

Clark Fork Bypass, near Bonner. Daily values of suspendedsediment concentration and suspended-sediment discharge 

were determined for four sites. Bed-sediment data include 

trace-element concentrations in the fine-grained fraction. 

Biological data include trace-element concentrations in wholebody tissue of aquatic benthic insects. Statistical summaries of 

long-term water-quality, bed-sediment, and biological data for 

sites in the upper Clark Fork basin are provided for the period 

of record since 1985.

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 near Missoula, six 

major tributaries enter: Blacktail Creek, Warm Springs Creek, 

Little Blackfoot River, Flint Creek, Rock Creek, and Blackfoot River. Principal surface-water uses in the 6,000‐mi2

 upper 

Clark Fork basin above Missoula include irrigation, stock 

watering, small-scale industry, 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 100 years but are now either discontinued 

or substantially smaller in scale.

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 the 1860s 

to the 1980s (U.S. Environmental Protection Agency, 2004). 

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, in the Warm Springs Ponds, 

and where the Milltown Reservoir was located (Andrews, 

1987). The widely dispersed tailings continue to be reeroded, 

transported, and redeposited along the stream channel and 

flood plain, especially during high flows. The occurrence 

of elevated trace-element concentrations in water and bedsediment can pose a potential risk to aquatic biota and human 

health (U.S. Environmental Protection Agency, 2004).

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 
2 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

characterize the aquatic resources in the upper Clark Fork 

basin to guide and monitor remedial cleanup activities. A 

long-term database 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 through 1991; 

Lambing and others, 1994, 1995; Dodge and others, 1996 

through 2009). Trace-element data for bed-sediment and biota 

(aquatic benthic insects) have been collected intermittently 

at selected sites since 1986 as part of studies on contamination of bed-sediment-quality and bioaccumulation of metals 

conducted by the USGS National Research Program (Axtmann 

and Luoma, 1991; Cain and others, 1992, 1995; Axtmann and 

others, 1997; Hornberger and others, 1997). 

In March 1993, an expanded long-term monitoring 

program for water, bed-sediment, and biota in the upper basin 

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

Environmental Protection Agency to systematically quantify 

the seasonal and annual variability in selected constituents. In 

April 2006, a supplemental water-quality sampling program 

was initiated at six sites for the part of the Clark Fork basin 

from near Milltown Reservoir to near the confluence of the 

Clark Fork and Flathead River (fig. 1 and table 1). In March 

2008, an additional site was added on the temporary bypass 

channel that is being used to redirect the Clark Fork around 

the cleanup area. Of the sites that bracket the former location 

of Milltown Reservoir, three also are part of the long-term 

monitoring network. The supplemental monitoring provides 

additional spatial coverage of constituent concentrations 

before and after the removal of Milltown Dam (at former 

Milltown Reservoir), which was breached on March 28, 2008. 

The purpose of this report is to present water-quality 

data for 24 sites and bed-sediment and biological data for 13 

sites in the Clark Fork basin collected from October 2008 

through September 2009. Quality-assurance data are presented 

for water-quality, bed-sediment, and biota samples. Statistical summaries also are provided for long-term water-quality, 

bed-sediment, and biological data collected since 1985.

Sampling Locations and Types of Data

Sampling sites for the long-term monitoring program 

in the upper Clark Fork basin from Butte to near Missoula 

(fig. 1) are located on the Clark Fork main stem (including 

Silver Bow Creek), three major tributaries (Blacktail Creek, 

Warm Springs 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 

type of data are listed in table 1. Main-stem 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 main 

stem. 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. In the long-term monitoring program, water-quality 

data were obtained periodically at 20 sites; daily suspendedsediment data were obtained at 4 sites and daily turbidity data 

were obtained by continuous turbidity monitors at 4 sites. 

Bed-sediment and biological data for 13 sites were obtained 

once annually. Continuous streamflow data were collected at 

19 sites in the long-term monitoring network.

Supplemental water samples were collected at seven sites 

from near the former Milltown Reservoir location to near the 

confluence of the Clark Fork and Flathead River (fig. 1). Of 

those sites, three (Clark Fork at Turah Bridge, near Bonner; 

Blackfoot River near Bonner; and Clark Fork above Missoula) 

bracket the former Milltown Reservoir and also are part of 

the long-term monitoring network. One additional site (Clark 

Fork Bypass, near Bonner) is located on the temporary bypass 

channel, within the Milltown Reservoir cleanup site, that 

diverts the Clark Fork around the cleanup work area. Three 

additional sites (Bitterroot River near Missoula, Clark Fork 

at St. Regis, and Flathead River at Perma) are farther downstream in the basin. The types of data collected and period of 

record for each type of data for the four additional sites that 

are not part of the long-term network also are listed in table 1 

and shown in figure 1. Supplemental water samples generally 

were collected during periods of high flow, which included the 

period when Milltown Dam was first breached, to characterize 

conditions when the potential for scour of bottom sediments 

from Milltown Reservoir was greatest. The sites were sampled 

in a downstream progression during 2-day periods that generally coincided with travel time of select water-quality constituents carried in solution along the Clark Fork main stem. The 

water-quality and streamflow data for each sampling episode 

can be used to calculate instantaneous constituent loads to 

identify the relative contributions of load from different source 

areas. Supplemental samples from the 7 sites were collected 

17–21 times. 

Properties measured onsite and constituents for which 

water, bed-sediment, and biota samples were analyzed are 

listed in table 2. Data-quality objectives for analyses of water 

samples are listed in table 3. Results of onsite measurements 

of properties; laboratory analyses of water-quality, bedsediment, and biota samples; and quality-assurance data for 

water year 2009 are listed in tables 4 through 24 at the back of 

the report. Statistical summaries of long-term water-quality, 

bed-sediment, and biological data collected between March 

1985 and September 2009 are listed in tables 25 through 27 at 

the back of the report.
Figure 1. Location of study area in the Clark Fork basin, Montana.

Mill Creek

Willow

Creek

Cr Silver

Bow

Opportunity

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

Little

Blackfoot

River

DIVIDE

Clark Fork

Warm Springs

 Ponds

Warm Springs Cr

Silver

Bow

Creek

Blacktail

Cr

CONTINENTAL

0 10 20 MILES

0 10 20 KILOMETERS

12340500

12340000

12334550

12331800

12324680

12324200

12323800

12323770 12323750

12323600

12323250

Streamflow site type

Water-quality, bed-sediment,

And biota site type

EXPLANATION

Site number

461903112440701 Miscellaneous site number

12324200

12323700

12323720

Lost Cr 12323850

46o

114o

113o

12323230

Racetrack

12323840

12323670

Mill

Creek

Willow

Creek

12323710

Creek

47o

A

A’

Helena

M O N T A N A

A

A’

Perma

115o

St. Regis

Thompson Falls

Clark

Fork

Clark

Fork

Flathead

River

47o

A

A’

 Continuous record

 Periodic measurement

 Periodic water quality

 Daily suspended sediment

 Daily turbidity

 Once-annual bed-sediment

 Once-annual biota

12323760

12352500

12354500

12388700

Plains

Dempsey

Creek 461903112440701

461559112443301

461415112450801

Study area

12334570 former

12324400

Base modified from U.S. Geological Survey, 

State base map, 1966, 1:1,000,000

North American Datum of 1927 (NAD 27) 

Sampling Locations and Types of Data 3
Table 1. Type and period of data collection at sampling sites in the Clark Fork basin, Montana.—Continued

[Abbreviations: LT, site is part of long-term monitoring network; S, site is part of supplemental monitoring network; P, present; D, discontinued. Symbol: --, no data]

Station number 

(fig. 1) Station name Network

Continuousrecord 

streamflow

Periodic 

water quality1

Daily 

suspended 

sediment

Daily 

turbidity 

(seasonal)

Fine-grained 

bed sediment2

B

se

12323230 Blacktail Creek at Harrison 

Avenue, at Butte

LT -- 03/93–08/95, 

12/96–08/03, 

12/04–P

-- -- -- 

12323250 Silver Bow Creek below 

Blacktail Creek, at Butte

LT 10/83–P 03/93–08/95, 

12/96–P

-- -- -- 

12323600 Silver Bow Creek at 

Opportunity

LT 07/88–P 03/93–08/95, 

12/96–P

03/93–09/95, 

D

-- 07/92–P 08/9

08/9

12323670 Mill Creek near Anaconda LT 10/04–P 12/04–P -- 06/06–P -- 12323700 Mill Creek at Opportunity LT 04/03–P 03/03–P -- -- -- 12323710 Willow Creek near 

Anaconda

LT 03/05–P 12/04–P -- 06/06–P -- 

12323720 Willow Creek at 

Opportunity

LT 04/03–P 03/03–P -- -- -- 

12323750 Silver Bow Creek at Warm 

Springs

LT 03/72–09/79, 

04/93–P

03/93–P 04/93–09/95, 

D

-- 07/92–P 

08/9

12323760 Warm Springs Creek near 

Anaconda

LT 10/97–P 10/05–P -- 05/06–P -- 

12323770 Warm Springs Creek at Warm 

Springs

LT 10/83–P 03/93–P -- -- 08/95, 08/97, 

08/99, 08/02, 

08/05, 08/08

08/908/9

12323800 Clark Fork near Galen LT 07/88–P 07/88–P -- -- 08/87, 08/91–P 08/912323840 Lost Creek near Anaconda LT 10/04–P 12/04–P -- 05/06–P -- 12323850 Lost Creek near Galen LT 04/03–P 03/03–P -- -- -- 461415112450801 Clark Fork below Lost Creek, 

near Galen

LT -- -- -- -- 08/96–P 08/9

461559112443301 Clark Fork at county bridge, 

near Racetrack

LT -- -- -- -- 08/96–P 08/9

461903112440701 Clark Fork at Dempsey Creek 

diversion, near Racetrack

LT -- -- -- -- 08/96–P 08/9

12324200 Clark Fork at Deer Lodge LT 10/78–P 03/85–P 03/85–08/86, 

04/87–03/03, 

08/03–P

-- 08/86–08/87, 

08/90–P

08/9
Table 1. Type and period of data collection at sampling sites in the Clark Fork basin, Montana.—Continued

[Abbreviations: LT, site is part of long-term monitoring network; S, site is part of supplemental monitoring network; P, present; D, discontinued. Symbol: --, no data]

Station number 

(fig. 1) Station name Network

Continuousrecord 

streamflow

Periodic 

water quality1

Daily 

suspended 

sediment

Daily 

turbidity 

(seasonal)

Fine-grained 

bed sediment2

B

se

12324400 Clark Fork above Little 

Blackfoot River, near Garrison

LT 02/09–P 03/09–P -- -- 08/09–P 

12324680 Clark Fork at Goldcreek LT 10/77-P 03/93–P -- -- 07/92–P 08/912331800 Clark Fork near Drummond LT 04/93–P 03/93–P -- -- 08/86, 08/87, 

08/91–P

08/9

12334550 Clark Fork at Turah Bridge, 

near Bonner

LT, S 03/85–P 03/85–P 03/85–03/03, 

08/03–P

-- 08/86, 08/91–P 08/9

12334570 Clark Fork Bypass, near 

Bonner

S -- 03/08–P -- -- -- 

12340000 Blackfoot River near Bonner LT, S 10/39–P 03/85–P 07/86–04/87, 

06/88–09/95, 

10/05–P

-- 08/86–08/87, 

08/91, 08/93–

96, 08/98–01, 

09/03, 08/06–P

08/9

08

0

12340500 Clark Fork above Missoula LT, S 03/29–P 07/86–P4 07/86–04/87, 

06/88–01/96, 03/96–03/03, 

08/03–P

04/07–

09/07

08/97–P 08/9

12352500 Bitterroot River near 

Missoula

S 07/1898–

11/1901, 

05/1903–

12/1904, 

07/89–P

05/97–P -- -- -- 

12354500 Clark Fork at St. Regis S 10/10–P 04/06–P -- -- -- 12388700 Flathead River at Perma S 10/83–P 10/70–09/73, 

10/96–09/03, 

04/06–P

-- -- -- 

1Onsite measurements of physical properties and laboratory analyses for selected major ions, trace elements, and suspended sediment. Prior to March 1993, laboratory analyse

and suspended sediment.

2Laboratory analyses for trace elements.3Bulk bed-sediment sampling was discontinued in 2005.4Prior to October 1989, water-quality data for Clark Fork above Missoula included only suspended-sediment data.
Table 2. Properties and constituents measured onsite or analyzed in water, bed-sediment, 

and biota samples from the Clark Fork basin, Montana.

Water Bed sediment Biota

Property Constituent Constituent Constituent

Streamflow Hardness (calculated) Arsenic Arsenic

pH Calcium Cadmium Cadmium

Specific conductance Magnesium Chromium Chromium

Temperature Nitrogen Copper Copper

Turbidity Phosphorous Iron Iron

Arsenic Lead Lead

Cadmium Manganese Manganese

Copper Nickel Nickel

Iron Zinc Zinc

Lead

Manganese

Zinc

Suspended sediment

Table 3. Data-quality objectives for analyses of water samples collected in the Clark Fork basin, Montana.

[Abbreviations: μg/L, microgram per liter; mg/L, milligram per liter; mm, millimeter. Symbol: --, not determined]

Constituent

Data-quality objectives

Detectability Precision Bias

Laboratory 

reporting 

level

Maximum relative standard 

deviation of replicate analyses 

(percent)

Maximum deviation of 

spike recovery 

(percent)

Calcium, filtered 0.02 mg/L 20 --

Magnesium, filtered .012 mg/L 20 --

Nitrogen, unfiltered recoverable .10 mg/L 20 25

Phosphorus, unfiltered recoverable .008 mg/L 20 25

Arsenic, filtered .06 μg/L 20 25

Arsenic, unfiltered recoverable .20 μg/L 20 25

Cadmium, filtered .02 μg/L 20 25

Cadmium, unfiltered recoverable .06 μg/L 20 25

Copper, filtered 1.0 μg/L 20 25

Copper, unfiltered recoverable 4.0 μg/L 20 25

Iron, filtered 4 μg/L 20 25

Iron, unfiltered recoverable 14 μg/L 20 25

Lead, filtered .06 μg/L 20 25

Lead, unfiltered recoverable .10 μg/L 20 25

Manganese, filtered .2 μg/L 20 25

Manganese, unfiltered recoverable .4 μg/L 20 25

Zinc, filtered 2.0 μg/L 20 25

Zinc, unfiltered recoverable 2.0 μg/L 20 25

Sediment, suspended, percent finer than 0.062 mm 1 percent 20 --

Sediment, suspended 1 mg/L 20 --

6 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Water-Quality Data 7

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. Routine water samples for the long-term 

monitoring program were collected at 20 sites in the upper 

Clark Fork basin 6–8 times per year on a schedule designed 

to describe seasonal and hydrologic variability. Supplemental 

water samples were collected 17–21 times at the 7 supplemental monitoring sites (which include 3 long-term monitoring 

sites) in the lower part of the basin. At the 4 daily suspendedsediment sites, suspended-sediment samples were collected 

by an observer 2–14 times per week, depending on season and 

flow conditions. Continuous turbidity monitors were operated 

seasonally (April/June–September 2009) at four sites near 

Anaconda to determine daily values (table 1).

Methods

Water samples were collected from vertical transits 

throughout the entire stream depth at multiple locations across 

the stream by 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 intended to be representative of the entire 

flow passing through the cross section of a stream. Sampling 

equipment consisted of depth-integrating suspended-sediment 

and water-quality samplers (Davis, 2005), which were 

constructed of plastic or coated with a nonmetallic epoxy paint 

and equipped with nylon or tetrafluoroethylene (TFE) nozzles.

Instantaneous streamflow at the time of water sampling 

was determined at all sites, either by direct measurement, from 

stage-discharge rating tables (Rantz and others, 1982), or by 

estimation from a nearby gage on the same channel. Daily 

mean streamflow during ice periods was estimated because 

backwater affected the stage-discharge relation. Onsite 

measurements of pH, specific conductance, and water temperature were made during collection of periodic water samples. 

Onsite sample processing, including filtration and preservation, was performed according to procedures described by 

Ward and Harr (1990), Horowitz and others (1994), and the 

USGS National Field Manual for the Collection of Water 

Quality Data (variously dated).

Composite 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 past reports from this 

project. Filtered (0.45-μm pore size) and unfiltered recoverable concentrations of the trace elements (arsenic, cadmium, 

copper, iron, lead, manganese, and zinc), filtered concentrations of calcium and magnesium, and unfiltered concentrations 

of nitrogen and phosphorous were determined by the USGS 

National Water Quality Laboratory (NWQL) in Denver, Colo. 

Concentrations of calcium and magnesium were determined 

to enable calculation of hardness. Concentrations of nitrogen 

and phosphorous were determined for the supplemental water 

samples, except for samples collected at Clark Fork Bypass, 

near Bonner. 

Filtered concentrations of arsenic, cadmium, copper, lead, 

manganese, and zinc were determined by inductively coupled 

plasma-mass spectrometry (Faires, 1993; Garbarino and 

others, 2006). Filtered concentrations of calcium, magnesium, 

and iron were determined by inductively coupled plasmaatomic emission 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). For cadmium, 

iron, lead, and manganese, the digested samples were analyzed 

by inductively coupled plasma-mass spectrometry by using 

the method described by Garbarino and Struzeski (1998). For 

arsenic, copper, and zinc, the digested samples were analyzed 

by inductively coupled plasma-mass spectrometry using the 

method described by Garbarino and others (2006). Unfiltered 

recoverable concentrations of nitrogen and phosphorous 

were determined from unfiltered samples that were digested 

with persulfate and then analyzed by colorimetry. Unfiltered 

recoverable nitrogen was analyzed using methods described 

by Patton and Kryskalla (2003), and unfiltered phosphorus 

was analyzed using methods described by U.S. Environmental 

Protection Agency (1993).

Water samples also were collected from multiple vertical 

transits for analysis of suspended sediment whenever periodic 

water 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 (hereinafter referred to as the Montana 

Sediment Laboratory) in Helena, Mont., according to methods 

described by Guy (1969) and Dodge and Lambing (2006).

Suspended-sediment samples for the four daily 

suspended-sediment sites (table 1) were collected by local 

contract observers using the depth-integration method at 

a single vertical transit 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).

Suspended-sediment discharge is determined according 

to the following equation (Porterfield, 1972):
8 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

, (1)

where

	 Qs is suspended-sediment discharge, in ton per 

day;

	 Qw is streamflow, in cubic feet per second;

	 Cs is suspended-sediment concentration, in 

milligram per liter; and

	 k is a units-conversion constant (0.0027) 

to convert instantaneous suspendedsediment discharge to an equivalent daily 

suspended-sediment discharge.

Turbidity data were obtained by continuous turbidity monitors [YSI Inc. (YSI, 6136 turbidity sensor)] at four 

tributary sites in the upper Clark Fork basin near Anaconda 

(table 1). The monitors were installed in May–June 2006 to 

provide supporting information on runoff conditions in an 

area where remediation activities are being conducted. They 

are operated seasonally, generally from early spring (after ice 

breakup) to early winter (before stream freeze-up). Turbidity 

values are recorded at 15-minute intervals and can be viewed 

in real-time on the USGS Web page at http://waterdata.usgs.

gov/mt/nwis. Continuous recordings provide the minimum 

and maximum values for each day as well as a daily mean 

turbidity value based on the average of all values in a 24-hour 

period. Procedures for the operation of continuous turbidity 

monitors and for daily record computations are described by 

Wagner and others (2006).

Results

Water-quality data for samples collected periodically 

during water year 2009 are listed in table 4. Daily mean 

streamflow, daily mean suspended-sediment concentration, 

and daily suspended-sediment discharge for water year 2009 

at the four daily suspended-sediment sites are listed in tables 

5 through 8 along with monthly summary statistics and annual 

totals for streamflow and suspended-sediment discharge. 

Daily maximum, minimum, and mean turbidity at four sites 

are listed in tables 9 through 12 along with monthly summary 

statistics.

Quality Assurance

Quality-assurance procedures used for the collection 

and field processing of water samples are described by Ward 

and Harr (1990), Horowitz and others (1994), Edwards and 

Glysson (1999), Lambing (2006), and the U.S. Geological 

Survey (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 Montana Sediment Laboratory are described by 

Dodge and Lambing (2006). Standard procedures used for the 

calibration, measurement, and quality assurance of turbidity 

monitors are described by Anderson (2004).

The quality of analytical results reported for water 

samples was evaluated by using 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 that provided 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 samples. Therefore, 

the total number of quality-control samples represented about 

15 percent of the total number of water samples.

In addition to the use of quality-control samples submitted from the field, internal quality-assurance practices are 

performed systematically by the NWQL to provide quality 

control of analytical procedures (Pritt and Raese, 1995; 

Maloney, 2005). These internal practices include analyses 

of quality-control samples such as calibration standard 

samples, standard reference water samples, replicate samples, 

deionized-water blank samples, or spiked samples at a proportion equivalent to at least 10 percent of the sample load. The 

NWQL participates in a blind-sample program in which 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 load (http://bqs.usgs.gov). The laboratory also 

participates in external evaluation studies and audits with the 

National Environmental Laboratory Accreditation Program, 

the U.S. Environmental Protection Agency, Environment 

Canada, 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 precision (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 

overall precision for samples exposed to both field and laboratory sources of variability, replicate stream samples for chemical analysis were obtained in the field by splitting a composite 

stream sample. Replicate stream samples for suspendedsediment 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.
Water-Quality Data 9

Precision of analytical results for laboratory replicates, 

which exclude field sources of variability, was determined by 

two independent chemical analyses of aliquots from a single 

sample selected from the group of samples constituting 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 

sample collection and processing. Laboratory replicates are 

not obtainable for suspended-sediment samples because the 

samples are consumed during the analysis.

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 sample for a targeted analyte, it is important to 

determine whether such effects are causing biased (consistently high or low) results. Deionized-water blank samples and 

aliquots of stream samples were spiked in the laboratory with 

known amounts of the same trace elements for which water 

samples were analyzed. 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 substantial bias to reported trace-element concentrations for stream samples.

Deionized-water blank samples were submitted for every 

field trip and 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 then are 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 stream samples to identify whether 

any detectable concentrations exist.

All water samples were handled in accordance with 

chain-of-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 qualitycontrol 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 dataquality objectives were used to evaluate whether sampling 

and analytical procedures were 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 (LRLs) 

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 LRLs. 

These values are reevaluated each year and, consequently, can 

change from year to year. The methods used to determine the 

LRLs 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 the LRL and that 

pass identification criteria are reported as estimated concentrations. 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 in concentrations between replicate analyses for several 

sets of samples. These replicate analyses may consist either 

of individual analyses of a pair of samples considered to be 

essentially identical (field replicates) or of multiple analyses of 

an individual sample (laboratory replicates). The differences in 

concentration between replicate analyses can be used to estimate a standard deviation according to the following equation 

(Taylor, 1987):

, (2)

where

	 S is the standard deviation of the difference in 

concentration between replicate analyses,

	 d is the difference in concentration between 

each pair of replicate analyses, and

	 k is the 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 is calculated according to the following 

equation (Taylor, 1987):
10 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

, (3)

where

	 RSD is the relative standard deviation;

	 S is the standard deviation; and

x is the mean concentration for all replicate 

analyses.

Paired analyses of field replicates are listed in table 13. 

The overall precision estimated for each constituent on the 

basis of analyses of field replicates, which include both field 

and laboratory sources of variability, is listed in table 14. 

The data-quality objective used to indicate acceptable precision of results for field replicates was a maximum RSD of 

20 percent (table 3). Precision estimates for the analytical 

results of field replicates were within the 20-percent RSD limit 

for all constituents, except unfiltered recoverable copper, lead, 

and manganese (table 14). The RSD for these constituents 

ranged from 22 to 46 percent and resulted from poor replicate 

comparison from a sample collected on May 19, 2009, at 

Clark Fork at Deer Lodge when suspended-sediment concentrations were relatively high. When this 1 replicate pair was 

excluded, the other 13 replicate pairs had a RSD for unfiltered 

recoverable copper of 5.1 percent, unfiltered recoverable 

lead of 12 percent, and unfiltered recoverable manganese of 

6.2 percent.

The precision estimated for each constituent on the basis 

of laboratory replicate analyses, which include only laboratory sources of variability, is listed in table 15. Statistics for 

the precision of analytical results for laboratory replicates are 

calculated by using unrounded values stored in laboratory data 

files. The data-quality objective used to indicate acceptable 

precision of results for laboratory replicates was a maximum 

RSD of 20 percent (table 3). Precision estimates for the laboratory replicates were within the 20-percent RSD limit for all 

constituents (table 15). No adjustments were made to analytical data on the basis of replicate analyses precision.

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 sample 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 4:

, (4)

where

	 R is the spike recovery, in percent;

	 D is the difference between the spiked and 

unspiked sample concentrations; and

	 C is the concentration of material used to spike 

the sample.

If the spike recovery of a trace element was outside a 

range of 75 to 125 percent, the instrument was recalibrated 

and the entire sample set and all spiked samples were reanalyzed for that particular trace element until recoveries were 

improved to the extent possible. Recovery efficiency for 

individual trace elements in laboratory-spiked deionizedwater blank samples and in laboratory-spiked stream samples 

is listed in tables 16 and 17, respectively. The mean spike 

recovery for deionized-water blank samples spiked with trace 

elements (table 16) ranged from 93.3 to 111 percent. The 

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

spike recovery for each constituent for which deionized-water 

blank samples were analyzed (table 16) did not exceed a 

25‐percent deviation from an expected 100-percent recovery, 

except for unfiltered recoverable iron (78.8–130 percent). The 

exceedance of this data quality objective resulted from using 

a low-concentration spiked solution (20 μg) on a constituent 

(unfiltered recoverable iron) with a high laboratory reporting level (+/- 14 μg/L). The mean spike recovery for spiked 

stream samples (table 17) ranged from 89.8 to 114 percent. 

The 95-percent confidence intervals for the mean spike recovery for each constituent for which streamwater samples were 

analyzed (table 17) did not exceed a 25-percent deviation from 

an expected 100-percent recovery. No adjustments were made 

to analytical data on the basis of the mean spike recovery.

High or low bias is indicated if the 95-percent confidence interval does not include 100-percent recovery, 

thereby indicating a consistent deviation in one direction. All laboratory-spiked deionized-water blank samples 

(table 16) had confidence intervals for percent recovery 

that included 100 percent except for unfiltered recoverable arsenic (94.9–99.1 percent), unfiltered recoverable 

copper (94.0–97.0), filtered manganese (103–106 percent), 

filtered zinc (104–118 percent), and unfiltered recoverable zinc (85.5–98.1 percent). All laboratory-spiked 

stream samples (table 17) also had confidence intervals 

for percent recovery that included 100 percent except for 

filtered cadmium (101–112 percent), unfiltered recoverable 

cadmium (89.5–99.8 percent), unfiltered recoverable copper 

(87.8–95.0 percent), filtered zinc (104–124 percent), and 

unfiltered recoverable zinc (80.4–99.2 percent). Because 

the mean spike recoveries for all constituents of laboratoryspiked stream samples met data-quality objectives (less than a 

25-percent deviation from 100-percent recovery), no adjustments were made to analytical results for stream samples on 

the basis of spike recoveries.

–
Bed-Sediment Data 11

Analytical results for field blanks are listed in table 18. 

A field blank with constituent concentrations equal to or less 

than the LRL for the analytical method indicates the entire 

process of sample collection, field processing, and laboratory analysis is presumably free of contamination. If detectable concentrations in field blanks were equal to or greater 

than twice the LRL, 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 

could indicate systematic contamination. Sporadic, infrequent 

exceedances of twice the LRL probably represented random 

contamination or instrument calibration error that was not 

persistent in the process and was not likely to cause positive 

bias in a long-term record of analytical results. However, if 

concentrations for a particular constituent 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 to identify the source of contamination.

Trace-element concentrations in field blanks (table 18) 

were almost always less than the LRL. Two detections 

exceeded the LRL in one sample for unfiltered recoverable 

lead (0.16 μg/L) and unfiltered recoverable zinc (2.7 μg/L), 

which had LRLs of 0.10 μg/L and 2.0 μg/L respectively. 

Because no trends were indicated in subsequent sampling 

trips, no adjustments were made to water-quality sample 

results on the basis of these two detections.

Bed-Sediment Data

Bed-sediment data for the long-term monitoring program 

in the upper Clark Fork basin consist of analyses of traceelement concentrations in the fine-grained (<0.063 mm) fraction of bed-sediment samples. Collection of bulk bed-sediment 

(fine-grained plus coarse-grained fractions) was discontinued 

in 2005; therefore, no bulk bed-sediment analytical results or 

statistical summaries are presented in this report. Bed-sediment samples are collected once annually at 13 sites (fig. 1 

and table 1) during low, stable flow conditions at about the 

same time of year (typically August) as previous samples 

to facilitate data comparisons among years. One site, Warm 

Springs Creek at Warm Springs, is sampled once every 3 years 

rather than once annually.

Methods

Fine-grained bed-sediment samples were collected in 

August 2009 using protocols described by E.V. Axtmann 

(U.S. Geological Survey, written commun., 1994). Samples 

were collected from the surfaces of streambed deposits in lowvelocity areas near the edge of the stream by using an acidwashed polypropylene scoop. Whenever possible, samples 

were collected from both sides of the stream. 

Individual samples of 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 0.063-mm polyestermesh sieve using ambient stream water. The fraction of 

bed sediment in each composite sample that was finer 

than 0.063 mm was transferred to an acid-washed 500-mL 

polyethylene bottle and transported on ice to the laboratory.

Bed-sediment samples were processed and analyzed at 

the USGS National Research Program Ecology and Contaminants Project laboratory in Menlo Park, Calif. Bed-sediment 

samples were oven-dried at 60°C and ground into smaller 

particle sizes using an acid-washed ceramic mortar and pestle. 

Single aliquots of approximately 0.6 g of sediment from each 

of the three composite bed-sediment samples were digested 

by 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. After a 2-week digestion period, 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 pore-size filter by using a syringe and 

in-line disposable filter cartridge. The filtrate was diluted to 

a 1:10 ratio with 0.6N hydrochloric acid. These final solutions were analyzed for arsenic, cadmium, chromium, copper, 

iron, lead, manganese, nickel, and zinc by using inductively 

coupled plasma-optical emission spectrometry (ICP–OES).

The smallest concentration of a constituent that can be reliably 

reported for analyses of bed-sediment is termed the minimum 

reporting level.

Results

Concentrations of trace elements measured in samples of 

fine-grained bed-sediment collected during August 2009 are 

listed in table 19. Liquid-phase concentrations, in micrograms 

per milliliter (which is equivalent to parts per million; ppm), 

that were analyzed in the reconstituted aliquots of digested 

bed-sediment were converted to solid-phase concentrations, in 

micrograms per gram (μg/g), by using the following equation:

. (5)

The reported solid-phase concentrations listed in table 19 

are the means of all analyses for replicate aliquots from each 

composite bed-sediment 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.
12 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Quality Assurance

The protocols for field collection and processing of 

bed-sediment samples are designed to prevent contamination from metal sources. Nonmetallic sampling and processing equipment was acid-washed and rinsed with deionized 

water prior to the first sample collection. Polyester-mesh 

sieves were washed in a laboratory-grade detergent and rinsed 

with deionized water. All equipment received a final rinse 

onsite with stream water. Sampling equipment used at more 

than one site was rinsed between sites with 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 site-to-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). 

Quality-control samples consisted of standard reference 

materials (SRMs) and procedural blanks. Each type of qualitycontrol sample was analyzed in a proportion equivalent to 

about 10 percent of the total number of bed-sediment samples.

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 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 listed in table 20. 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 (table 20) illustrate analytical performance. For 

cadmium, chromium, copper, iron, manganese, nickel, and 

zinc, mean SRM recoveries for the low-concentration standard 

(SRM 2709) ranged from 89.6 to 106.1 percent of the certified concentrations. Mean recoveries were low for arsenic 

and lead (36.5 and 51.0 percent, respectively). The generally small range of variation (less than 11 percent for most 

constituents) for the 95-percent confidence interval indicates 

good reproducibility of multiple analyses of SRM 2709. The 

range of variation for the 95-percent confidence interval for 

chromium and copper were slightly higher (about 12 and 

14 percent, respectively). Mean SRM recoveries for cadmium, 

chromium, copper, iron, lead, manganese, and zinc for the 

high-concentration standard (SRM 2711) ranged from 96.4 

to 107.5 percent of the certified concentrations. Arsenic and 

nickel recoveries were slightly lower (86.5 and 84.9 percent, 

respectively). The generally small range of variation (less than 

11 percent for most constituents) for the 95-percent confidence 

interval indicates good reproducibility of multiple analyses 

of SRM 2711. No adjustments were made to trace-element 

concentrations in bed-sediment 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 reconstitute 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 bedsediment (table 21) are reported as a liquid-phase concentration, in micrograms per milliliter, 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 less than the minimum reporting level; thus, no contamination bias was indicated and no adjustments to the data 

were necessary.

Biological Data

Biological data for the long-term monitoring program 

in the upper Clark Fork basin consist of analyses of traceelement concentrations in the whole-body tissue of aquatic 

benthic insects. Insect samples are collected once annually 

at the same 13 sites and on the same dates as bed-sediment 

samples (fig. 1 and table 1), allowing for a direct comparison 

of biological data with bed-sediment data among the years. 

One site, Warm Springs Creek at Warm Springs, is sampled 

once every 3 years rather than once annually.

Methods

Insect samples were collected using protocols described 

in Hornberger and others (1997). Immature stages of benthic 

insects were collected with a large nylon-mesh kick net. 

A single riffle at each station was sampled repeatedly until 

an adequate number of individual insects was collected to 

provide sufficient mass for analysis. Targeted taxa for collection were the order Trichoptera (caddisflies) and the order 

Plecoptera (stoneflies).
Biological Data 13

Two caddisfly species of the genus Hydropsyche (Hydropsyche cockerelli and Hydropsyche occidentalis) were targeted 

for collection in this study because of their occurrence at most 

sites. Hydropsyche species (spp.) that could not be positively 

identified were categorized as Hydropsyche spp. or Hydropsyche morosa group (in previous reports). The caddisfly 

Arctopsyche grandis and the stonefly Claassenia sabulosa

were collected where available to represent additional insect 

taxa that are commonly distributed in the upper Clark Fork 

basin. In addition, specimens from the caddisfly group Brachycentrus spp. were collected in previous years 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 (depurate) for a period 

of 6 to 8 hours. Excess water was drained and insects were 

frozen for transport to the laboratory. During 1999–2008, 

samples were immediately frozen on dry ice in the field to 

reduce the possibility of metal loss through intracellular breakdown during depuration. A comparison of immediately frozen 

to depurated samples showed that although no substantial 

difference occurred for most metals, concentrations of copper 

were about 20 percent lower in the depurated samples than in 

the samples that were immediately frozen. The data were not 

adjusted for this difference.

Insect samples were processed and analyzed at the 

USGS National Research Program Ecology and Contaminants Project laboratory in Menlo Park, Calif. Insects were 

thawed and rinsed with ultrapure deionized water to remove 

particulate matter and then sorted to their lowest possible 

taxonomic level. If large numbers of specimens were 

collected at a site, similar-sized individuals were composited 

into replicate subsamples. Subsamples were placed in tared 

scintillation vials and oven-dried at 70°C. 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 pore-size filter, and analyzed 

undiluted by ICP–OES for arsenic, cadmium, chromium, 

copper, iron, lead, manganese, nickel, and zinc. The smallest 

concentration of a constituent that can be reliably reported for 

analyses of biota is termed the minimum reporting level.

Results

Concentrations of trace elements in whole-body tissue 

of aquatic insects collected during August 2009 are listed in 

table 22. 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, in micrograms per milliliter, analyzed in the 

reconstituted samples were converted to solid-phase concentrations, in micrograms per gram, by using equation 5. All 

tissue samples were analyzed undiluted (dilution ratio 1:1). 

As with minimum reporting levels for trace elements in 

bed-sediment, minimum reporting levels for trace elements 

in insects may differ among sites as a result of varied sample 

weights. In general, the smaller the biological-sample weight 

(primarily a function of insect abundance), the higher the 

minimum reporting level. Therefore, higher minimum reporting levels do not necessarily imply a higher trace-element 

concentration in tissue.

Quality Assurance

The protocols for field collection and processing of biota 

samples are designed to prevent contamination from metal 

sources. Nonmetallic nets, sampling equipment, and processing equipment were employed in all sample collection. Equipment was acid-washed and rinsed in ultrapure 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 

site-to-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 12 replicates of 

the tissue SRM (lobster hepatopancreas) and 13 procedural 

blanks (one at each station). Quality-control samples were 

analyzed in a proportion equivalent to about 20 percent of the 

total number of biota samples.

Recovery efficiency for trace-element analyses of the 

SRM for biota is listed in table 23. 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 95.1 to 

120 percent for all constituents. With the exception of chromium and lead, both of which had low certified concentrations 

in the SRM (0.77 μg/g and 0.35 μg/g, respectively), the range 

of variation of the 95-percent confidence interval was within 

10 percent, indicating reasonable recoveries in the SRM. No 

adjustments were made to the biota samples on the basis of 

trace-element 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 24) are reported as a liquidphase concentration, in micrograms per milliliter, 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 
14 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

blanks were less than the minimum reporting level; therefore, 

no adjustments to the data were necessary.

Statistical Summaries of Data

Statistical summaries of long-term water-quality, bedsediment, and biological data for the upper Clark Fork basin 

are listed in tables 25 through 27 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 long-term water-quality data 

(table 25) are based on results of cross-section samples 

collected periodically by the USGS for the long-term monitoring program in the upper Clark Fork basin during the period 

of record for each site. The summaries do not include data for 

supplemental samples collected at selected sites. Inclusion 

of results for supplemental samples that targeted high-flow 

conditions or maintenance drawdowns of Milltown Reservoir 

might disproportionately skew the long-term statistics relative 

to the other sites in the network. Statistical summaries of bedsediment (table 26) and biological data (table 27) 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. Sampling of bulk bed sediment 

has been discontinued; therefore, a statistical summary is not 

presented. Statistical summaries are not presented for discontinued sites.

Statistics for bed-sediment data (table 26) are based on 

the mean trace-element concentrations determined for each 

year from the mean of the 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 27) 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 number for other trace elements because 

sampling for arsenic began in September 2003. In addition, 

the number of samples analyzed for silver in bed sediment is 

smaller because analysis for this constituent was discontinued 

in 2004.

Differences in the number of composited biota 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 varied 

minimum reporting levels. Where minimum reporting levels 

vary among years, differences in concentration with 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.

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Data
20 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

12323230--Blacktail Creek at Harrison Avenue, at Butte

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/20/2008 0915 11 7.6 248 5.0 100 28.9 7.15

03/22/2009 1045 18 7.5 230 2.0 82 22.3 6.53

04/27/2009 0910 18 7.6 222 3.5 86 24.4 6.08

05/18/2009 0850 26 7.6 198 10.0 79 22.5 5.40

06/01/2009 0915 18 7.7 212 11.0 87 25.4 5.85

06/22/2009 0915 31 7.6 210 11.0 87 25.2 5.92

07/13/2009 0900 14 7.6 233 13.0 91 26.7 5.96

08/17/2009 0855 9.7 7.6 271 9.0 110 32.5 7.29

Date

Arsenic, 

filtered 

(μg/L)

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)

10/20/2008 3.0 3.3 0.02 <0.06 2.7 E3.2 117 382

03/22/2009 3.5 4.5 .03 E.04 3.9 6.4 311 835

04/27/2009 3.9 4.5 .04 <.06 2.9 4.3 334 626

05/18/2009 4.9 5.7 .04 <.06 4.2 6.6 271 690

06/01/2009 7.3 9.0 .03 <.06 3.7 6.6 362 887

06/22/2009 8.5 9.9 .04 <.06 5.2 8.1 480 1,110

07/13/2009 6.4 7.9 .03 E.04 3.2 4.1 382 819

08/17/2009 4.1 5.3 .04 E.03 2.2 E3.4 221 479

Date

Lead, 

filtered 

(μg/L)

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)

10/20/2008 0.09 0.36 23.0 30.2 2.3 2.8 87 3 0.09

03/22/2009 .19 .99 98.8 127 2.9 5.7 67 13 .63

04/27/2009 .19 .55 29.0 44.5 2.1 2.9 75 5 .24

05/18/2009 .19 .81 30.5 52.0 2.0 3.5 81 10 .70

06/01/2009 .21 .82 41.4 68.8 2.4 3.6 79 10 .49

06/22/2009 .22 .92 29.9 57.3 3.1 4.7 70 12 1.0

07/13/2009 .20 .67 23.3 47.4 2.8 4.0 79 7 .26

08/17/2009 .08 .25 25.6 29.6 E1.3 2.5 89 2 .05

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
Data 21

12323250--Silver Bow Creek below Blacktail Creek, at Butte

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/20/2008 1045 25 7.8 434 7.0 150 45.3 10.1

03/22/2009 1225 36 7.6 375 4.5 120 33.5 9.29

04/27/2009 1040 34 7.6 399 5.0 120 36.0 8.50

05/18/2009 1015 42 7.6 326 11.0 110 31.9 7.53

06/01/2009 1030 34 7.6 359 12.0 120 34.0 7.72

06/22/2009 1035 54 7.6 313 11.5 110 33.2 7.71

07/13/2009 1025 27 7.6 408 14.0 130 37.4 8.18

08/17/2009 1015 24 7.7 479 11.0 170 49.4 11.5

Date

Arsenic, 

filtered 

(μg/L)

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)

10/20/2008 3.6 3.9 0.10 0.14 5.9 9.5 49 300

03/22/2009 5.2 7.0 .10 .20 9.1 20.0 195 861

04/27/2009 3.9 4.9 .09 .10 7.4 12.7 175 483

05/18/2009 5.2 5.9 .06 .13 8.0 13.7 186 550

06/01/2009 6.2 8.1 .06 .09 8.0 14.1 181 598

06/22/2009 8.6 10.5 .19 .25 18.3 31.4 267 870

07/13/2009 6.3 7.5 .10 .19 15.2 16.8 149 468

08/17/2009 5.2 6.3 .10 .14 7.9 10.6 62 276

Date

Lead, 

filtered 

(μg/L)

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)

10/20/2008 0.17 1.61 68.8 90.7 28.5 36.8 85 5 0.34

03/22/2009 .41 4.64 118 162 31.7 50.8 82 18 1.7

04/27/2009 .23 1.35 71.0 105 26.8 32.9 80 6 .55

05/18/2009 .26 1.71 61.3 93.8 24.2 28.8 82 9 1.0

06/01/2009 .29 1.64 62.3 97.5 21.0 30.5 90 8 .73

06/22/2009 .34 3.32 68.2 115 59.4 81.4 87 13 1.9

07/13/2009 .33 1.88 73.6 112 32.8 42.9 88 6 .44

08/17/2009 .17 1.19 61.6 75.6 33.7 33.7 83 2 .13

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
22 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

12323600--Silver Bow Creek at Opportunity

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/20/2008 1650 44 8.9 443 10.0 160 47.7 10.1

03/23/2009 0955 97 7.9 317 1.0 100 28.2 7.05

04/27/2009 1710 89 8.3 329 6.0 120 34.7 7.17

05/18/2009 1635 173 8.5 265 15.0 100 30.7 5.67

06/02/2009 0715 222 7.9 248 6.5 99 31.1 5.25

06/22/2009 1605 173 8.5 296 8.0 110 33.2 6.58

07/13/2009 1640 88 8.9 349 16.5 120 37.1 7.18

08/17/2009 1635 45 8.9 444 18.0 170 49.9 10.6

Date

Arsenic, 

filtered 

(μg/L)

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)

10/20/2008 8.0 9.9 0.26 0.49 14.4 40.6 11 381

03/23/2009 13.7 21.2 .91 1.11 38.5 106 248 2,560

04/27/2009 7.8 11.3 .29 .55 18.3 51.0 72 814

05/18/2009 10.7 18.3 .21 .67 24.2 88.4 78 1,380

06/02/2009 8.3 12.4 .19 .45 22.7 46.1 72 800

06/22/2009 11.0 14.7 .21 .53 20.4 58.6 111 877

07/13/2009 11.4 15.1 .28 .73 30.8 87.8 35 762

08/17/2009 10.0 12.3 .26 .54 20.0 44.3 15 544

Date

Lead, 

filtered 

(μg/L)

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)

10/20/2008 0.29 8.96 49.7 115 35.5 99.0 84 13 1.5

03/23/2009 1.33 27.7 249 462 136 252 87 88 23

04/27/2009 .38 10.5 137 231 64.7 128 83 24 5.8

05/18/2009 .80 30.1 69.2 206 27.7 142 72 56 26

06/02/2009 .36 11.9 57.6 137 49.8 101 79 30 18

06/22/2009 .74 12.4 89.1 180 45.9 121 80 30 14

07/13/2009 .41 14.7 98.0 210 31.8 147 85 30 7.1

08/17/2009 .21 7.07 52.1 122 24.7 87.2 91 18 2.2

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
Data 23

12323670--Mill Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/20/2008 1310 15 <2.0 8.1 158 6.5 72 19.7 5.44

03/22/2009 1520 16 E2.0 8.1 175 4.0 70 18.7 5.79

04/27/2009 1315 38 E3.8 8.0 129 6.0 52 14.7 3.85

05/18/2009 1250 101 21 8.0 98 10.0 38 10.9 2.63

06/01/2009 1350 213 E4.2 7.8 63 6.5 24 7.00 1.60

06/22/2009 1315 136 E1.2 7.8 77 8.5 31 8.88 2.08

07/13/2009 1305 75 E2.0 8.0 95 12.0 39 11.4 2.50

08/17/2009 1135 25 E1.4 8.0 137 9.5 62 17.6 4.36

Date

Arsenic, 

filtered 

(μg/L)

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)

10/20/2008 13.9 13.4 0.05 E0.04 2.2 <4.0 51 105

03/22/2009 28.0 30.6 .11 .15 3.6 4.9 54 148

04/27/2009 24.5 24.8 .06 .09 3.4 4.6 56 207

05/18/2009 32.9 34.8 .07 .19 5.0 10.6 74 592

06/01/2009 15.3 17.7 .05 .12 5.1 7.1 35 353

06/22/2009 13.5 14.1 .04 E.04 2.2 E3.8 27 111

07/13/2009 16.3 17.5 .04 .10 2.1 E3.5 39 162

08/17/2009 15.9 17.5 .04 .07 1.7 E2.2 65 142

Date

Lead, 

filtered 

(μg/L)

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)

10/20/2008 0.19 0.32 5.6 8.3 2.1 E1.6 31 2 0.08

03/22/2009 .17 .62 11.0 16.3 4.0 4.8 69 2 .09

04/27/2009 .20 .68 4.0 12.7 2.0 3.5 71 4 .41

05/18/2009 .23 3.01 5.4 33.1 2.2 9.2 65 25 6.8

06/01/2009 .12 1.54 3.7 23.1 2.3 5.9 43 22 13

06/22/2009 .10 .47 3.9 8.6 E1.9 3.1 28 4 1.5

07/13/2009 .12 .62 6.8 13.7 E1.3 2.7 57 5 1.0

08/17/2009 .12 .44 7.9 13.3 E1.4 E1.5 61 2 .14

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
24 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

12323700--Mill Creek at Opportunity

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/20/2008 1520 5.0 7.9 182 8.0 80 22.3 5.94

03/23/2009 0820 12 8.0 194 1.5 79 21.2 6.31

04/27/2009 1550 17 8.0 141 7.0 57 16.0 4.15

05/18/2009 1515 46 7.9 106 14.0 41 11.8 2.92

06/01/2009 1650 158 7.7 68 7.0 26 7.36 1.74

06/22/2009 1505 83 7.8 84 9.5 35 10.3 2.27

07/13/2009 1535 47 8.0 105 15.0 42 12.2 2.70

08/17/2009 1500 8.0 8.0 156 13.0 70 20.0 4.78

Date

Arsenic, 

filtered 

(μg/L)

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)

10/20/2008 23.4 24.2 0.07 0.06 2.1 E3.2 56 96

03/23/2009 23.1 26.4 .06 .09 3.2 4.7 64 168

04/27/2009 26.9 28.2 .07 .08 4.1 5.6 56 200

05/18/2009 32.3 42.2 .08 .38 5.3 17.9 56 885

06/01/2009 20.4 28.1 .07 .25 5.3 18.4 38 939

06/22/2009 18.4 20.4 .06 .12 2.9 7.0 36 242

07/13/2009 20.6 23.9 .05 .17 2.5 7.0 49 317

08/17/2009 19.3 20.1 .04 .09 1.7 E2.3 68 134

Date

Lead, 

filtered 

(μg/L)

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)

10/20/2008 0.11 0.26 5.1 6.5 2.5 3.0 80 1 0.01

03/23/2009 .15 .60 3.2 9.3 2.5 4.3 58 3 .10

04/27/2009 .19 .78 3.6 11.7 2.5 3.8 76 5 .23

05/18/2009 .29 5.67 7.9 65.3 2.8 17.4 65 39 4.8

06/01/2009 .19 5.00 5.1 37.6 3.6 15.2 48 58 25

06/22/2009 .13 1.81 5.5 16.8 2.4 5.7 39 10 2.2

07/13/2009 .16 1.75 7.2 25.1 E1.7 5.7 56 12 1.5

08/17/2009 .14 .33 6.7 10.2 E1.5 E1.7 77 1 .02

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
Data 25

12323710--Willow Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/20/2008 1210 2.9 <2.0 7.9 122 4.5 45 15.2 1.83

03/22/2009 1415 3.2 E7.0 7.8 145 2.0 51 16.5 2.49

04/27/2009 1215 8.9 E12 7.7 116 3.5 42 13.9 1.79

05/18/2009 1150 65 39 7.6 81 6.5 27 9.09 1.16

06/01/2009 1235 75 E7.7 7.6 72 6.0 24 8.01 .95

06/22/2009 1215 16 E2.8 7.7 101 8.0 39 12.9 1.50

07/13/2009 1210 9.6 E6.0 7.7 112 11.0 41 13.7 1.59

08/17/2009 1320 3.8 E1.4 7.8 125 10.5 47 15.6 1.89

Date

Arsenic, 

filtered 

(μg/L)

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)

10/20/2008 10.7 9.8 0.03 <0.06 1.2 <4.0 54 100

03/22/2009 12.3 14.4 .03 E.05 1.5 E3.0 65 416

04/27/2009 17.6 19.2 .03 E.05 2.6 4.1 229 506

05/18/2009 19.8 25.4 .05 .33 4.2 15.3 126 2,380

06/01/2009 14.4 16.2 .04 .09 2.9 5.4 51 664

06/22/2009 13.8 14.1 .03 E.04 2.1 E3.4 46 150

07/13/2009 17.1 17.9 .04 .07 2.2 E3.1 58 236

08/17/2009 20.1 20.1 .04 .08 2.3 E2.7 79 149

Date

Lead, 

filtered 

(μg/L)

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)

10/20/2008 0.07 0.13 17.1 19.5 <2.0 <2.0 80 1 0.01

03/22/2009 .07 .81 22.3 34.8 E1.2 4.6 88 9 .08

04/27/2009 .27 1.13 10.8 24.6 E1.9 3.7 69 14 .34

05/18/2009 .31 7.96 11.4 99.9 2.5 17.8 46 195 34

06/01/2009 .16 2.00 6.0 24.7 E1.9 5.7 29 57 12

06/22/2009 .10 .40 12.2 18.2 E1.8 2.2 46 6 .26

07/13/2009 .12 .58 19.7 27.3 E1.5 2.5 87 8 .21

08/17/2009 .15 .32 20.5 26.0 E1.5 E1.6 82 3 .03

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
26 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

12323720--Willow Creek at Opportunity

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/20/2008 1615 6.2 8.7 288 10.5 130 36.8 8.34

03/23/2009 0900 8.7 7.7 341 2.0 130 37.2 9.98

04/27/2009 1630 12 7.9 226 7.0 93 27.9 5.67

05/18/2009 1550 44 7.8 164 17.0 65 20.1 3.52

06/01/2009 1730 60 7.7 156 10.0 66 20.3 3.77

06/22/2009 1535 39 7.9 279 13.0 120 36.4 7.99

07/13/2009 1615 18 8.3 248 16.0 100 30.9 6.29

08/17/2009 1605 17 8.3 290 16.0 130 38.5 8.01

Date

Arsenic, 

filtered 

(μg/L)

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)

10/20/2008 19.3 19.6 0.03 <0.06 2.7 E3.0 10 51

03/23/2009 68.3 70.3 .12 .20 10.9 15.8 179 322

04/27/2009 21.7 25.1 .03 .07 3.6 8.3 69 330

05/18/2009 53.7 60.0 .07 .36 12.9 40.4 114 1,130

06/01/2009 64.1 67.4 .07 .14 9.6 18.8 73 318

06/22/2009 86.5 87.4 .09 .16 9.3 15.9 100 297

07/13/2009 41.3 42.9 .04 .10 5.2 7.5 86 214

08/17/2009 38.0 38.5 .03 .06 3.4 4.5 21 94

Date

Lead, 

filtered 

(μg/L)

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)

10/20/2008 0.11 0.48 4.1 5.3 <2.0 E1.1 73 1 0.02

03/23/2009 .46 1.79 200 228 17.7 21.4 83 7 .16

04/27/2009 .22 2.02 31.5 53.4 3.4 9.9 91 8 .26

05/18/2009 .58 11.7 41.6 109 7.9 46.0 73 63 7.5

06/01/2009 .31 2.56 16.9 33.8 7.7 16.7 55 17 2.8

06/22/2009 .30 1.81 35.9 63.4 10.6 17.2 73 5 .53

07/13/2009 .36 1.03 10.4 16.0 2.5 5.1 96 2 .10

08/17/2009 .10 .58 6.5 11.8 E1.6 2.7 86 2 .09

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
Data 27

12323750--Silver Bow Creek at Warm Springs

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/21/2008 0925 47 8.4 555 5.5 230 67.8 15.2

03/23/2009 1040 101 8.9 515 3.5 190 53.9 13.9

04/28/2009 0850 195 8.2 523 6.0 210 61.2 12.9

05/19/2009 0810 252 8.6 352 11.0 140 42.5 8.24

06/02/2009 0850 481 8.8 282 8.5 120 36.7 6.04

06/23/2009 0730 303 8.9 309 9.0 130 39.6 7.04

07/14/2009 0810 118 9.2 305 12.0 120 37.9 7.19

08/18/2009 0800 65 9.6 391 13.5 170 51.8 10.8

Date

Arsenic, 

filtered 

(μg/L)

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)

10/21/2008 24.7 26.0 0.04 0.07 3.5 6.3 8 172

03/23/2009 19.2 21.2 .07 .12 5.5 8.8 36 204

04/28/2009 17.3 19.6 .04 .12 4.4 10.2 19 274

05/19/2009 32.0 41.9 .04 .43 6.8 29.0 43 1,200

06/02/2009 33.3 35.5 .05 .12 8.7 16.2 32 246

06/23/2009 28.6 29.4 .05 .07 6.8 11.7 26 184

07/14/2009 30.1 30.7 .03 .11 4.1 7.3 41 196

08/18/2009 46.5 45.1 .02 E.06 3.3 4.5 19 92

Date

Lead, 

filtered 

(μg/L)

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)

10/21/2008 0.09 1.47 50.8 84.8 3.5 8.7 69 3 0.38

03/23/2009 .16 1.47 63.2 92.3 4.3 11.6 79 4 1.1

04/28/2009 .14 1.95 166 210 6.0 19.4 90 5 2.6

05/19/2009 .23 8.76 65.7 185 3.1 36.8 82 47 32

06/02/2009 .19 1.79 50.4 84.7 4.0 16.7 76 8 10

06/23/2009 .14 1.24 35.4 59.1 4.4 10.9 64 5 4.1

07/14/2009 .16 .98 32.9 60.9 E1.9 6.5 81 4 1.3

08/18/2009 .09 .52 34.8 55.8 E1.6 3.7 90 1 .18

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
28 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

12323760--Warm Springs Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/20/2008 1440 92 <2.0 8.5 239 7.5 120 35.7 7.39

04/27/2009 1440 70 E1.4 8.7 251 6.0 130 37.5 7.86

05/18/2009 1410 134 E4.8 8.6 210 10.5 110 32.4 6.06

06/01/2009 1555 573 E6.7 8.0 125 6.5 59 18.5 2.96

07/13/2009 1430 215 E1.7 8.4 176 11.0 81 24.9 4.45

08/17/2009 1420 122 E1.1 8.4 223 10.5 110 33.1 6.13

Date

Arsenic, 

filtered 

(μg/L)

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)

10/20/2008 2.2 2.4 0.02 <0.06 E0.68 <4.0 E2 37

04/27/2009 2.0 2.1 E.02 <.06 E.86 <4.0 6 63

05/18/2009 2.1 3.0 .03 .07 1.6 8.1 10 375

06/01/2009 3.8 5.6 .03 .07 2.0 14.0 13 543

07/13/2009 3.0 3.2 E.02 E.04 2.2 E2.4 6 88

08/17/2009 1.9 2.5 .02 .06 E.63 <4.0 5 75

Date

Lead, 

filtered 

(μg/L)

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)

10/20/2008 0.08 0.16 0.7 2.1 <2.0 <2.0 80 3 0.75

04/27/2009 E.03 .16 .8 2.7 <2.0 <2.0 66 3 .57

05/18/2009 E.05 1.33 2.0 16.7 <2.0 7.2 62 21 7.6

06/01/2009 E.05 3.51 2.2 22.0 2.1 19.9 32 44 68

07/13/2009 <.06 .28 2.0 6.2 <2.0 3.5 61 5 2.9

08/17/2009 <.06 .27 1.2 4.8 <2.0 E1.8 57 4 1.3

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
Data 29

12323770--Warm Springs Creek at Warm Springs

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/21/2008 0850 73 8.1 286 5.0 140 43.0 8.39

04/28/2009 0800 64 8.1 296 3.0 150 44.1 8.62

05/19/2009 0745 157 8.0 214 8.0 100 32.3 5.76

06/02/2009 0800 362 7.9 157 5.5 73 23.0 3.75

07/14/2009 0740 174 8.0 201 9.5 91 28.3 4.87

08/18/2009 0725 103 8.2 263 10.0 130 39.3 7.01

Date

Arsenic, 

filtered 

(μg/L)

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)

10/21/2008 3.4 4.1 0.04 <0.06 1.8 7.0 15 116

04/28/2009 3.0 4.2 .03 E.05 1.8 14.0 9 190

05/19/2009 5.8 18.0 .04 .40 4.4 147 21 2,110

06/02/2009 7.2 11.2 .03 .12 5.6 33.4 17 525

07/14/2009 3.9 5.6 .02 .09 1.8 16.2 11 282

08/18/2009 3.6 5.2 .03 .08 2.7 11.0 11 198

Date

Lead, 

filtered 

(μg/L)

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)

10/21/2008 0.06 0.75 102 142 E1.5 3.5 62 5 0.99

04/28/2009 E.05 1.17 91.2 168 E1.6 4.6 73 8 1.4

05/19/2009 .10 13.8 78.8 528 E1.9 48.2 67 127 54

06/02/2009 .07 2.81 24.2 89.9 2.7 14.1 70 27 26

07/14/2009 E.03 1.43 44.0 83.5 E1.9 8.2 62 13 6.1

08/18/2009 E.04 1.10 66.1 94.5 E1.5 4.6 65 10 2.8

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
30 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

12323800--Clark Fork near Galen

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/21/2008 1100 136 8.3 406 5.0 180 54.2 11.3

03/23/2009 1215 162 8.6 451 4.0 180 52.8 12.6

04/28/2009 1015 252 8.2 467 5.0 200 59.6 12.0

05/19/2009 0930 415 8.3 303 11.0 130 39.3 7.44

06/02/2009 1020 875 8.4 228 9.0 98 30.9 5.11

06/23/2009 0855 615 8.6 236 9.0 100 32.4 5.74

07/14/2009 0935 295 8.6 248 12.0 110 32.4 5.90

08/18/2009 0915 175 8.8 327 12.0 150 46.3 8.59

Date

Arsenic, 

filtered 

(μg/L)

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)

10/21/2008 12.1 13.0 0.04 E0.04 3.0 7.0 13 132

03/23/2009 15.3 18.2 .07 .11 5.3 13.9 26 287

04/28/2009 13.4 16.5 .04 .14 4.2 15.4 14 368

05/19/2009 22.6 38.7 .04 .52 7.3 94.2 29 1,880

06/02/2009 22.2 26.2 .06 .16 8.8 33.9 24 522

06/23/2009 16.9 18.3 .04 .09 5.3 19.4 20 295

07/14/2009 14.7 15.8 .03 .09 3.4 14.2 21 246

08/18/2009 20.4 20.4 .03 .07 3.1 9.1 12 145

Date

Lead, 

filtered 

(μg/L)

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)

10/21/2008 0.07 1.03 71.2 104 3.2 6.4 74 4 1.5

03/23/2009 .13 1.93 65.0 123 3.3 13.1 67 12 5.2

04/28/2009 .10 2.49 117 190 5.3 19.8 55 13 8.8

05/19/2009 .18 18.4 70.7 389 2.6 64.6 67 97 109

06/02/2009 .14 3.79 33.7 109 5.5 26.2 53 26 61

06/23/2009 .09 2.12 30.7 74.8 2.6 13.9 40 15 25

07/14/2009 .08 1.43 37.2 78.7 E1.7 8.9 72 10 8.0

08/18/2009 .07 .98 38.6 77.2 E1.4 6.2 71 5 2.4

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
Data 31

12323840--Lost Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/20/2008 1350 6.4 <2.0 8.2 226 7.0 110 33.4 6.67

03/22/2009 1605 5.5 E1.5 8.2 209 4.0 99 28.8 6.47

04/27/2009 1355 8.2 E3.1 8.2 198 5.0 96 29.0 5.67

05/18/2009 1330 11 E11 8.2 164 11.0 78 23.9 4.39

06/01/2009 1445 54 E15 8.0 121 7.0 58 18.1 3.02

06/22/2009 1400 35 E2.2 8.0 155 8.0 74 23.2 3.94

07/13/2009 1345 14 E1.5 8.2 198 11.0 91 28.3 4.85

08/17/2009 1215 17 E1.5 8.2 211 8.0 100 32.4 5.78

Date

Arsenic, 

filtered 

(μg/L)

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)

10/20/2008 3.7 3.4 0.03 <0.06 1.4 <4.0 7 30

03/22/2009 3.2 3.5 .03 E.03 2.2 4.6 12 91

04/27/2009 2.1 2.4 .02 <.06 1.2 4.8 9 158

05/18/2009 3.0 4.6 .03 .09 2.7 16.7 14 526

06/01/2009 5.9 9.6 .03 .16 3.2 28.3 22 1,370

06/22/2009 5.5 5.9 .02 <.06 3.4 5.9 14 202

07/13/2009 5.4 5.3 E.02 E.05 1.9 4.5 10 110

08/17/2009 2.7 3.3 E.02 E.04 1.5 E3.8 9 110

Date

Lead, 

filtered 

(μg/L)

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)

10/20/2008 E0.05 0.16 0.7 1.5 2.2 <2.0 50 1 0.02

03/22/2009 E.03 .42 1.0 3.8 <2.0 2.2 75 5 .07

04/27/2009 E.05 .63 .9 5.9 <2.0 2.2 59 6 .13

05/18/2009 .06 2.60 2.0 21.0 E1.0 7.6 66 30 .89

06/01/2009 .09 6.82 2.5 40.9 E1.2 18.1 22 143 21

06/22/2009 E.04 .75 1.4 6.8 E1.2 3.3 26 19 1.8

07/13/2009 <.06 .46 2.0 5.3 <2.0 2.5 37 6 .23

08/17/2009 <.06 .45 1.2 4.5 E1.5 E1.5 43 5 .23

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
32 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

12323850--Lost Creek near Galen

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/21/2008 1020 45 8.2 629 5.0 320 94.6 20.6

03/23/2009 1135 56 8.2 618 3.5 290 83.1 19.2

04/28/2009 0940 43 8.2 629 3.0 300 85.2 20.5

05/19/2009 0900 19 8.2 644 12.0 310 89.2 20.7

06/02/2009 0940 11 8.2 578 9.0 270 80.1 17.3

06/23/2009 0810 11 8.1 691 9.0 340 97.2 23.0

07/14/2009 0910 2.6 8.0 674 12.0 280 72.9 23.2

08/18/2009 0850 27 8.1 618 12.0 300 88.1 20.2

Date

Arsenic, 

filtered 

(μg/L)

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)

10/21/2008 13.6 14.1 0.03 <0.06 2.0 E3.1 13 47

03/23/2009 20.2 22.2 .03 E.06 2.4 6.9 24 174

04/28/2009 10.9 11.9 .02 E.04 1.3 4.5 11 142

05/19/2009 16.3 17.2 .03 <.06 2.4 5.2 15 102

06/02/2009 13.5 14.1 E.02 <.06 1.7 E3.8 15 60

06/23/2009 19.6 19.8 .03 <.06 3.1 E3.8 24 64

07/14/2009 11.5 11.8 E.02 <.06 1.9 E3.1 20 56

08/18/2009 20.5 21.0 E.02 E.04 2.5 E3.9 13 60

Date

Lead, 

filtered 

(μg/L)

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)

10/21/2008 E0.04 0.15 7.5 9.1 E1.5 E1.7 40 8 0.97

03/23/2009 E.06 .64 21.0 33.1 E1.6 4.3 72 8 1.2

04/28/2009 E.05 .50 17.3 30.6 E1.3 2.9 46 19 2.2

05/19/2009 E.05 .40 33.6 46.5 E1.5 2.8 61 19 .97

06/02/2009 E.03 .19 13.1 18.0 E1.1 E1.5 59 5 .15

06/23/2009 E.03 .14 13.6 17.9 E1.5 E1.3 65 9 .27

07/14/2009 <.06 .11 17.8 18.9 E1.8 E1.3 64 3 .02

08/18/2009 E.03 .19 9.8 14.0 E1.6 E1.4 72 2 .15

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
Data 33

12324200--Clark Fork at Deer Lodge

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/21/2008 1200 291 8.2 442 5.5 200 57.9 12.3

03/24/2009 1025 306 8.2 479 2.5 190 56.7 12.9

04/28/2009 1120 386 8.1 479 5.0 200 58.5 12.8

05/19/2009 1045 526 8.0 354 14.0 150 45.6 9.03

06/02/2009 1155 1,130 8.1 245 9.5 100 31.8 5.53

06/23/2009 1025 996 8.1 266 10.0 110 34.9 6.54

07/14/2009 1030 425 8.0 330 13.5 140 41.2 7.82

08/18/2009 1020 250 8.3 416 13.5 190 56.4 11.7

Date

Arsenic, 

filtered 

(μg/L)

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)

10/21/2008 10.8 13.2 0.04 0.11 4.7 22.5 9 329

03/24/2009 12.2 19.1 .08 .24 7.6 53.1 20 915

04/28/2009 12.6 21.2 .07 .26 7.3 65.6 16 1,040

05/19/2009 17.8 -- .07 -- 12.1 101 21 3,220

06/02/2009 21.7 37.8 .12 .55 18.8 129 33 1,680

06/23/2009 17.2 24.4 .08 .24 12.0 65.6 27 922

07/14/2009 16.1 21.1 .06 .22 9.0 47.1 22 663

08/18/2009 19.4 21.2 .05 .13 6.8 24.2 10 334

Date

Lead, 

filtered 

(μg/L)

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)

10/21/2008 0.07 2.81 24.2 75.6 5.9 21.3 59 15 12

03/24/2009 .12 7.20 34.6 133 7.0 43.0 64 41 34

04/28/2009 .12 8.28 24.5 170 7.6 52.7 58 45 47

05/19/2009 .18 13.0 33.9 192 6.5 -- 58 142 202

06/02/2009 .32 17.1 29.9 207 19.2 109 57 84 256

06/23/2009 .19 8.43 21.9 110 9.4 49.2 49 51 137

07/14/2009 .14 5.51 20.1 101 5.9 33.9 71 29 33

08/18/2009 .09 3.09 21.8 75.5 6.9 18.8 77 13 8.8

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
34 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

12324400--Clark Fork above Little Blackfoot River, near Garrison

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

03/24/2009 1155 345 8.3 471 3.0 190 56.2 13.2

04/28/2009 1315 467 8.2 462 5.0 190 56.4 12.5

05/19/2009 1245 664 8.1 339 14.0 140 42.7 8.65

06/02/2009 1410 1,380 8.1 253 10.0 100 31.8 5.93

06/23/2009 1240 1,210 8.2 298 12.0 130 39.2 8.32

07/14/2009 1250 514 8.2 353 14.5 150 44.1 10.0

08/18/2009 1220 296 8.5 432 15.5 200 58.5 12.6

Date

Arsenic, 

filtered 

(μg/L)

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)

03/24/2009 12.9 19.9 0.08 0.38 9.1 59.4 18 1,090

04/28/2009 12.6 20.2 .06 .27 7.7 65.9 10 1,150

05/19/2009 16.5 39.1 .08 .75 11.7 197 15 3,190

06/02/2009 21.6 43.5 .11 .61 20.2 182 33 2,140

06/23/2009 18.4 27.7 .10 .34 15.7 87.6 28 1,180

07/14/2009 16.1 21.9 .07 .25 11.1 61.5 16 632

08/18/2009 19.8 21.6 .06 .17 14.1 27.4 7 364

Date

Lead, 

filtered 

(μg/L)

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)

03/24/2009 0.14 7.75 34.1 148 6.8 65.1 66 49 46

04/28/2009 .11 8.59 15.6 159 7.2 56.3 56 58 73

05/19/2009 .17 29.4 28.8 309 6.0 152 60 179 321

06/02/2009 .39 22.2 22.6 246 15.9 142 56 115 428

06/23/2009 .22 12.3 19.1 131 9.7 70.2 42 81 265

07/14/2009 .11 13.5 18.5 140 5.8 38.4 70 30 42

08/18/2009 .10 3.34 19.9 92.0 4.3 21.4 76 13 10

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
Data 35

12324680--Clark Fork at Goldcreek

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/21/2008 1400 483 8.5 397 6.0 180 52.9 11.3

03/25/2009 0955 575 8.2 383 3.0 160 45.9 10.4

04/28/2009 1430 1,040 8.2 334 4.5 140 42.4 9.39

05/19/2009 1415 1,640 8.1 237 12.5 100 29.8 6.23

06/02/2009 1520 2,300 8.1 221 10.0 94 28.8 5.40

06/23/2009 1505 1,610 8.3 280 13.5 120 36.2 7.37

07/14/2009 1345 823 8.3 333 14.0 140 42.8 8.10

08/18/2009 1315 519 8.5 368 16.0 170 50.6 10.3

Date

Arsenic, 

filtered 

(μg/L)

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)

10/21/2008 8.7 10.3 0.03 0.08 3.8 19.8 6 300

03/25/2009 8.3 11.8 .06 .15 6.7 31.4 33 734

04/28/2009 7.7 12.1 .04 .15 5.4 35.7 42 901

05/19/2009 9.5 22.6 .05 .43 7.8 89.2 59 3,020

06/02/2009 14.4 25.4 .07 .42 13.1 96.0 38 1,700

06/23/2009 13.8 20.4 .08 .24 13.8 66.1 24 1,020

07/14/2009 11.8 13.8 .05 .14 7.8 28.5 12 410

08/18/2009 12.8 14.1 .04 .10 5.1 14.3 6 249

Date

Lead, 

filtered 

(μg/L)

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)

10/21/2008 -- 2.44 10.2 81.0 2.4 17.4 84 11 14

03/25/2009 0.12 4.60 23.2 88.5 5.2 28.2 70 33 51

04/28/2009 .17 5.35 10.3 92.3 4.5 33.0 64 44 124

05/19/2009 .25 18.3 15.2 241 4.1 85.0 56 196 868

06/02/2009 .31 13.1 25.5 181 9.4 86.2 59 90 559

06/23/2009 .17 8.51 16.5 101 6.8 50.4 49 57 248

07/14/2009 .09 3.00 13.8 69.6 4.2 21.6 77 19 42

08/18/2009 .07 1.71 11.1 58.6 2.6 12.6 68 10 14

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
36 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

12331800--Clark Fork near Drummond

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/21/2008 1520 766 8.4 416 8.0 190 55.3 13.1

03/25/2009 0830 943 8.1 406 4.0 170 49.9 11.8

04/28/2009 1620 1,500 8.2 333 5.0 140 41.8 9.76

05/19/2009 1600 1,860 8.1 269 15.5 120 33.7 7.51

06/02/2009 1650 3,350 8.1 236 11.0 100 30.6 6.07

06/23/2009 1630 2,550 8.2 308 14.0 140 40.5 8.84

07/14/2009 1505 1,050 8.3 372 15.0 170 47.3 11.8

08/18/2009 1420 801 8.4 413 16.5 190 54.8 12.9

Date

Arsenic, 

filtered 

(μg/L)

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)

10/21/2008 8.4 10.1 0.03 0.08 3.4 13.7 8 323

03/25/2009 8.6 13.9 .06 .23 6.9 40.8 28 1,140

04/28/2009 7.1 13.6 .04 .22 5.1 38.3 41 1,180

05/19/2009 9.8 24.6 .05 .48 8.2 87.7 30 2,530

06/02/2009 15.2 25.4 .08 .43 14.3 83.3 36 1,640

06/23/2009 13.6 21.1 .09 .27 12.3 57.1 23 1,240

07/14/2009 11.6 13.1 .04 .13 5.3 15.9 8 321

08/18/2009 11.6 13.2 .04 .10 4.3 11.7 9 303

Date

Lead, 

filtered 

(μg/L)

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)

10/21/2008 0.07 2.88 9.5 81.2 3.1 17.9 82 13 27

03/25/2009 .15 6.95 17.6 134 5.8 49.0 66 59 150

04/28/2009 .21 8.17 8.5 152 4.6 49.1 55 70 284

05/19/2009 .22 20.9 15.2 323 4.3 113 60 179 899

06/02/2009 .35 12.9 20.9 202 9.4 89.8 60 95 859

06/23/2009 .20 10.1 17.0 152 5.9 63.4 50 76 523

07/14/2009 .08 2.77 14.4 74.8 3.2 18.9 81 17 48

08/18/2009 .06 2.44 11.4 69.4 2.6 14.8 67 17 37

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
Data 37

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12334550--Clark Fork at Turah Bridge, near Bonner

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Total 

nitrogen, 

unfiltered, 

(mg/L)

10/22/2008 0855 1,150 8.1 345 4.5 160 44.1 11.3 --

*03/02/2009 1000 970 8.3 353 3.0 170 47.8 12.3 0.25

*03/16/2009 1130 1,030 8.4 337 3.5 150 43.2 10.6 .24

03/24/2009 1420 1,670 8.2 287 5.0 120 32.8 8.76 --

*03/25/2009 1030 1,480 8.4 309 4.0 140 37.9 10.1 .54

*03/27/2009 0900 1,180 8.4 331 2.5 150 42.0 10.8 .36

*03/31/2009 0915 1,100 8.4 336 4.0 160 44.5 11.3 .25

*04/06/2009 1030 1,160 8.0 350 5.5 170 46.6 12.2 .27

*04/14/2009 1000 2,930 8.1 225 5.0 100 28.6 7.65 .78

*04/21/2009 1020 2,990 7.9 221 8.5 96 26.8 7.18 .63

*04/27/2009 1100 3,670 8.3 231 6.0 110 30.4 7.54 .47

04/29/2009 0800 3,120 8.1 251 4.5 110 30.6 7.79 --

*05/04/2009 1045 2,660 8.3 246 8.5 110 31.9 8.15 .32

*05/11/2009 1030 3,460 8.3 230 8.0 100 28.9 7.56 .27

*05/18/2009 0930 4,430 8.1 193 11.0 91 25.7 6.42 .39

05/20/2009 0745 7,560 7.9 143 10.0 63 17.9 4.45 --

*05/22/2009 0930 6,680 8.0 E152 9.0 69 19.8 4.82 .53

*05/26/2009 1130 7,310 8.0 150 10.5 68 19.7 4.63 .56

*05/31/2009 1100 7,380 7.9 143 12.0 64 18.7 4.29 .37

06/03/2009 0745 6,270 7.9 161 9.0 71 20.8 4.63 --

*06/04/2009 1200 5,480 8.0 170 12.0 76 22.2 5.04 .34

*06/08/2009 1000 5,330 8.1 187 9.5 84 24.2 5.59 .30

*06/15/2009 1030 3,210 8.2 205 13.0 96 27.6 6.42 .24

*06/23/2009 1000 4,370 8.2 218 10.0 100 29.6 6.98 .36

06/24/2009 0755 3,810 8.1 234 12.0 110 30.7 7.18 --

07/15/2009 0755 1,870 8.2 279 14.0 120 34.3 7.99 --

08/19/2009 0800 1,160 8.2 330 15.0 150 42.8 10.3 --
38 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12334550--Clark Fork at Turah Bridge, near Bonner—Continued

Date

Total 

phosphorous, 

unfiltered, 

(mg/L)

Arsenic, 

filtered 

(μg/L)

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)

10/22/2008 -- 5.8 6.7 0.03 E0.05 2.4 7.9 4 195

*03/02/2009 0.035 5.3 6.1 .06 .09 4.5 11.7 64 280

*03/16/2009 .032 4.7 6.1 .05 .08 2.9 11.2 8 274

03/24/2009 -- 6.7 11.7 .04 .26 7.7 40.0 48 1,370

*03/25/2009 .113 6.5 9.0 .05 .15 6.5 26.0 24 778

*03/27/2009 .134 5.4 7.3 .03 .10 3.7 14.5 13 424

*03/31/2009 .048 5.2 6.3 .03 .08 3.1 12.4 7 319

*04/06/2009 .141 5.6 6.7 .03 .07 3.8 11.6 10 267

*04/14/2009 .170 5.9 13.7 .02 .29 6.0 49.2 34 2,130

*04/21/2009 .121 5.3 10.0 .05 .24 5.0 38.5 26 1,550

*04/27/2009 .078 5.6 8.7 .03 .16 4.7 26.3 30 784

04/29/2009 -- 4.6 7.7 .03 .13 3.7 21.6 43 662

*05/04/2009 .056 4.8 7.3 .03 .12 3.3 19.8 21 582

*05/11/2009 .055 5.4 -- .03 -- 3.9 -- 28 --

*05/18/2009 .071 4.8 7.1 .03 .13 3.5 21.9 24 856

05/20/2009 -- 5.1 12.3 .04 .40 5.4 58.3 82 2,560

*05/22/2009 .119 6.7 11.2 .04 .26 7.2 45.4 32 1,520

*05/26/2009 .129 8.1 14.5 .05 .35 9.2 61.5 36 1,840

*05/31/2009 .091 8.1 11.8 .06 .25 7.6 41.6 28 1,210

06/03/2009 -- 8.3 12.4 .05 .23 8.0 41.1 41 1,020

*06/04/2009 .074 8.4 11.9 .05 .20 7.3 36.7 25 880

*06/08/2009 .070 8.5 10.8 .05 .17 7.7 33.4 26 798

*06/15/2009 .060 7.1 9.0 .04 .12 4.8 22.2 20 507

*06/23/2009 .088 8.5 12.6 .05 .17 7.9 37.0 29 970

06/24/2009 -- 8.4 11.6 .05 .13 7.7 28.6 26 638

07/15/2009 -- 6.7 7.6 .04 .10 3.7 9.7 10 206

08/19/2009 -- 8.1 9.1 .05 .09 3.1 10.3 6 271
Data 39

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12334550--Clark Fork at Turah Bridge, near Bonner—Continued

Date

Lead, 

filtered 

(μg/L)

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)

10/22/2008 E0.05 1.59 3.5 50.2 2.6 12.1 82 9 28

*03/02/2009 .47 2.12 14.3 47.6 6.8 18.1 89 15 39

*03/16/2009 .07 1.96 8.6 45.8 3.7 17.7 82 15 42

03/24/2009 .20 7.62 11.1 146 5.3 52.5 81 69 311

*03/25/2009 .24 4.61 9.5 91.6 6.5 33.8 82 39 156

*03/27/2009 .09 2.52 11.4 56.8 6.2 21.1 84 19 61

*03/31/2009 .06 2.04 11.1 48.3 5.7 21.6 83 14 42

*04/06/2009 .10 1.79 9.8 42.7 3.4 14.7 81 13 41

*04/14/2009 .15 10.8 7.4 207 4.8 72.2 74 99 783

*04/21/2009 .15 8.32 8.5 155 5.0 57.2 70 90 727

*04/27/2009 .16 5.21 8.3 96.7 6.3 48.2 73 46 456

04/29/2009 .16 3.89 6.2 80.2 4.8 26.9 74 33 278

*05/04/2009 .10 3.75 5.7 72.5 5.7 27.9 68 34 244

*05/11/2009 .12 -- 5.5 -- 3.4 -- 69 30 280

*05/18/2009 .11 4.58 7.6 83.9 2.8 32.8 55 59 706

05/20/2009 .25 13.5 13.4 249 5.1 94.8 54 211 4,310

*05/22/2009 .22 8.91 8.4 164 6.0 63.3 64 106 1,910

*05/26/2009 .22 11.2 15.0 199 8.8 90.1 65 136 2,680

*05/31/2009 .16 6.92 13.1 135 6.9 61.6 67 87 1,730

06/03/2009 .22 6.45 18.2 121 6.9 49.8 65 66 1,120

*06/04/2009 .15 5.47 21.7 105 6.4 44.7 66 59 873

*06/08/2009 .15 5.38 16.3 92.9 5.7 36.9 67 50 720

*06/15/2009 .09 3.26 10.8 63.3 3.9 26.4 64 33 286

*06/23/2009 .13 6.61 12.0 117 5.3 46.9 58 63 743

06/24/2009 .13 4.47 10.0 78.0 4.8 31.4 65 40 411

07/15/2009 .06 1.52 7.6 39.1 2.7 12.1 75 11 56

08/19/2009 .08 2.02 9.0 60.1 4.4 14.5 75 16 50

*Sample collected as part of a supplemental sampling program.
40 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12334570--Clark Fork Bypass, near Bonner

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

*03/02/2009 1230 E970 8.6 351 4.5 160 46.3 11.9

*03/16/2009 1315 E1,030 8.4 337 4.0 160 44.5 10.8

*03/25/2009 1300 E1,480 8.4 309 3.0 140 39.3 10.4

*03/27/2009 1130 E1,180 8.4 331 2.0 150 42.1 10.8

*03/31/2009 1140 E1,100 8.3 336 4.0 160 44.2 11.3

*04/06/2009 1200 E1,160 8.1 349 6.0 160 45.2 12.0

*04/14/2009 1230 E2,930 8.0 228 5.5 100 28.4 7.63

*04/21/2009 1210 E2,990 7.9 223 9.5 97 27.0 7.24

*04/27/2009 1230 E3,670 8.2 233 6.0 110 30.2 7.51

*05/04/2009 1230 E2,660 8.3 247 12.0 110 32.2 8.23

*05/11/2009 1200 E3,460 8.4 230 9.0 110 29.6 7.71

*05/18/2009 1215 E4,430 8.1 193 11.5 88 25.1 6.25

*05/22/2009 1130 E6,680 8.0 154 9.5 69 19.6 4.77

*05/26/2009 1345 E7,310 8.0 152 11.0 69 19.9 4.64

*05/31/2009 0900 E7,380 8.0 146 12.0 66 19.1 4.37

*06/04/2009 1435 E5,480 8.0 176 15.0 77 22.6 5.08

*06/08/2009 1130 E5,330 8.1 190 9.0 83 24.0 5.57

*06/15/2009 1230 E3,210 8.3 207 13.5 95 27.6 6.42

*06/23/2009 1400 E4,370 8.3 222 12.5 100 29.9 6.96

*07/15/2009 0950 E1,870 8.2 280 15.0 130 36.7 8.44

*08/19/2009 0945 E1,160 8.2 326 16.0 150 41.5 10.4

Date

Arsenic, 

filtered 

(μg/L)

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)

*03/02/2009 5.0 6.1 0.04 0.08 2.9 11.5 7 249

*03/16/2009 4.7 6.0 .04 .09 2.8 12.5 8 298

*03/25/2009 6.3 9.6 .04 .18 6.2 30.3 28 902

*03/27/2009 5.4 7.4 .04 .13 3.6 17.5 14 484

*03/31/2009 5.2 6.3 .03 .09 3.2 13.8 7 357

*04/06/2009 5.7 6.7 .03 .07 3.7 11.8 10 280

*04/14/2009 6.5 13.2 .05 .31 6.8 56.5 34 1,880

*04/21/2009 5.3 10.7 .06 .32 5.0 44.5 31 1,740

*04/27/2009 5.6 10.3 .05 .26 4.8 41.8 29 1,020

*05/04/2009 4.8 7.9 .03 .19 4.2 28.8 24 738

*05/11/2009 5.6 7.3 .03 .13 3.9 19.1 33 539

*05/18/2009 5.1 10.7 .03 .56 3.9 60.8 30 1,410

*05/22/2009 6.9 15.8 .06 .62 8.1 104 35 2,420

*05/26/2009 8.6 20.5 .07 1.09 10.5 164 37 3,050

*05/31/2009 8.2 14.1 .06 .48 8.4 66.5 30 1,750

*06/04/2009 8.6 14.8 .07 .41 7.9 66.4 26 1,340

*06/08/2009 8.5 13.0 .07 .29 7.4 49.9 27 1,090

*06/15/2009 7.5 9.5 .05 .19 5.3 27.9 19 686

*06/23/2009 8.8 13.4 .06 .24 8.2 44.0 24 1,160

*07/15/2009 7.6 7.8 .04 .09 4.4 12.3 16 220

*08/19/2009 7.7 9.0 .04 .10 3.5 11.1 6 261
Data 41

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12334570--Clark Fork Bypass, near Bonner—Continued

Date

Lead, 

filtered 

(μg/L)

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)

*03/02/2009 E0.06 1.86 8.7 43.7 2.8 16.5 80 13 E34

*03/16/2009 .07 2.06 9.8 46.6 4.4 19.4 71 18 E50

*03/25/2009 .13 5.32 12.8 95.0 6.9 39.5 55 65 E260

*03/27/2009 .09 2.77 14.0 57.2 6.1 23.9 67 25 E80

*03/31/2009 .07 2.05 13.4 50.2 6.4 23.5 68 19 E56

*04/06/2009 .10 1.76 11.4 42.3 3.6 15.2 62 17 E53

*04/14/2009 .19 10.9 14.2 214 6.5 83.4 61 128 E1,010

*04/21/2009 .18 9.30 12.2 171 8.3 74.9 54 126 E1,020

*04/27/2009 .17 7.70 12.2 121 10.3 70.8 47 86 E852

*05/04/2009 .15 4.76 8.1 82.9 6.9 40.0 49 55 E395

*05/11/2009 .12 3.47 15.1 69.7 3.9 27.4 55 38 E355

*05/18/2009 .15 9.46 17.4 247 3.7 149 52 93 E1,110

*05/22/2009 .24 17.2 18.5 232 8.2 150 44 214 E3,860

*05/26/2009 .27 17.4 21.8 533 10.0 229 51 227 E4,480

*05/31/2009 .18 10.6 16.4 192 9.4 120 46 157 E3,130

*06/04/2009 .17 9.84 26.5 159 9.6 115 34 183 E2,710

*06/08/2009 .17 7.83 22.5 127 7.7 75.1 36 110 E1,580

*06/15/2009 .10 4.40 16.0 83.8 5.2 45.1 30 70 E607

*06/23/2009 .12 7.19 18.3 163 6.8 76.0 43 87 E1,030

*07/15/2009 .11 1.33 18.7 47.8 4.4 16.7 41 20 E101

*08/19/2009 .06 1.87 12.4 57.9 3.3 15.9 58 18 E56

*Sample collected as part of a supplemental sampling program.
42 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12340000--Blackfoot River near Bonner

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Total 

nitrogen, 

unfiltered, 

(mg/L)

10/22/2008 1010 634 8.3 271 4.5 140 34.8 12.1 --

*03/02/2009 1400 654 8.6 251 3.0 130 33.9 11.2 0.20

*03/16/2009 1500 641 8.6 237 3.0 120 31.7 10.3 E.09

*03/25/2009 1430 1,350 8.5 221 4.0 100 25.8 9.30 .52

*03/27/2009 1245 1,140 8.4 218 2.0 110 27.2 9.84 .33

*03/31/2009 1400 1,100 8.5 222 3.5 110 28.6 9.83 .28

*04/06/2009 1400 1,100 8.3 238 6.5 120 29.8 10.7 .30

*04/14/2009 1440 3,420 8.2 182 5.0 89 22.7 7.90 .55

*04/21/2009 1410 4,410 8.0 168 10.0 82 20.9 7.10 .45

*04/27/2009 1430 4,950 8.2 170 6.5 86 22.4 7.38 .32

04/29/2009 1010 4,100 8.1 181 4.5 86 22.3 7.49 --

*05/04/2009 1400 3,220 8.4 243 8.0 93 23.7 8.23 .22

*05/11/2009 1400 4,070 8.4 181 8.5 93 23.9 8.04 .18

*05/18/2009 1415 5,380 8.2 169 11.0 89 23.4 7.40 .26

05/20/2009 0940 9,320 8.0 148 9.5 76 20.2 6.17 --

*05/22/2009 1330 8,170 8.1 166 E9.0 87 23.0 7.18 .30

*05/26/2009 1745 9,180 8.2 158 11.0 81 21.5 6.54 .21

*05/31/2009 1300 9,790 8.1 152 15.0 79 21.2 6.34 .23

06/03/2009 0940 7,590 8.1 165 10.0 82 22.1 6.53 --

*06/04/2009 1600 6,630 8.1 169 13.0 85 22.8 6.89 .17

*06/08/2009 1315 5,200 8.3 175 9.0 88 23.4 7.24 .13

*06/15/2009 1500 3,800 8.5 178 12.5 92 24.4 7.61 .12

*06/23/2009 1530 3,450 8.6 191 12.5 100 26.4 8.47 .10

07/15/2009 1130 1,570 8.4 236 15.5 120 30.0 11.0 --

08/19/2009 1110 816 8.5 261 17.0 130 33.9 11.8 --
Data 43

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12340000--Blackfoot River near Bonner—Continued

Date

Total 

phosphorous, 

unfiltered, 

(mg/L)

Arsenic, 

filtered 

(μg/L)

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)

10/22/2008 -- 1.0 1.1 <0.02 <0.06 <1.0 <4.0 E3 28

*03/02/2009 0.020 1.1 1.2 <.02 <.06 E.52 <4.0 14 77

*03/16/2009 .018 .96 1.1 <.02 <.06 <1.0 <4.0 15 83

*03/25/2009 .127 1.5 1.7 E.01 -- E.82 E2.0 34 460

*03/27/2009 .063 1.2 1.3 <.02 <.06 E.67 <4.0 24 282

*03/31/2009 .041 1.0 1.1 <.02 <.06 E.58 <4.0 17 232

*04/06/2009 .037 1.2 1.3 <.02 <.06 E.69 <4.0 18 230

*04/14/2009 .078 1.3 1.5 <.02 <.06 E.79 E2.2 36 714

*04/21/2009 .067 1.0 1.3 <.02 <.06 E.86 E2.5 33 742

*04/27/2009 .037 .97 1.3 <.02 <.06 E.88 <4.0 24 376

04/29/2009 -- .84 1.1 E.01 <.06 E.80 E2.3 34 340

*05/04/2009 .028 .90 1.0 E.01 <.06 E.79 <4.0 17 233

*05/11/2009 .027 .90 1.1 <.02 <.06 E.81 <4.0 20 263

*05/18/2009 .044 .85 1.3 <.02 <.06 E.73 E2.2 17 542

05/20/2009 -- .84 2.6 <.02 E.04 1.1 8.5 42 2,200

*05/22/2009 .067 .98 1.7 <.02 <.06 E.97 E3.8 15 1,030

*05/26/2009 .060 .96 1.6 <.02 <.06 E.73 E3.3 15 972

*05/31/2009 .060 .95 1.8 <.02 <.06 E.83 E3.6 20 1,020

06/03/2009 -- .95 1.4 E.01 <.06 E.93 E3.7 17 519

*06/04/2009 .030 .96 1.3 <.02 <.06 E.74 <4.0 18 408

*06/08/2009 .024 .89 1.0 <.02 <.06 E.65 <4.0 16 305

*06/15/2009 .021 .88 1.1 <.02 <.06 E.58 <4.0 9 200

*06/23/2009 .018 1.0 1.1 <.02 <.06 E.50 <4.0 10 155

07/15/2009 -- 1.1 1.1 <.02 <.06 E.59 <4.0 5 49

08/19/2009 -- 1.2 1.8 <.02 <.06 <1.0 <4.0 E3 29
44 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12340000--Blackfoot River near Bonner—Continued

Date

Lead, 

filtered 

(μg/L)

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)

10/22/2008 <0.06 <0.10 1.0 3.1 <2.0 <2.0 75 2 3.4

*03/02/2009 .07 E.09 2.4 6.8 <2.0 <2.0 82 2 3.5

*03/16/2009 <.06 .11 2.9 7.5 E1.9 E1.6 61 5 8.7

*03/25/2009 E.03 .47 12.2 37.5 2.8 4.0 87 20 73

*03/27/2009 <.06 .28 5.6 22.2 E1.1 E1.6 90 8 25

*03/31/2009 <.06 .26 3.5 14.9 4.6 4.8 90 7 21

*04/06/2009 <.06 .25 3.9 15.3 E1.2 E1.3 85 8 24

*04/14/2009 E.03 .69 4.7 56.9 3.1 3.5 87 42 388

*04/21/2009 E.04 .85 5.8 61.2 <2.0 3.7 81 57 679

*04/27/2009 E.03 .54 3.4 30.2 2.4 -- 86 28 374

04/29/2009 E.05 .44 2.7 25.9 <2.0 E1.7 88 20 221

*05/04/2009 E.03 .30 2.4 18.2 3.6 3.0 88 14 122

*05/11/2009 <.06 .38 2.0 18.2 <2.0 2.6 86 19 209

*05/18/2009 E.03 .76 3.6 39.6 2.0 3.4 78 62 901

05/20/2009 .07 3.61 3.3 150 E1.1 11.7 78 228 5,740

*05/22/2009 E.03 1.55 3.2 65.2 <2.0 5.8 82 95 2,100

*05/26/2009 <.06 1.40 3.8 62.1 <2.0 5.3 78 88 2,180

*05/31/2009 <.06 1.39 3.1 62.6 <2.0 5.2 75 99 2,620

06/03/2009 <.06 .76 3.2 36.5 E1.0 3.5 79 48 984

*06/04/2009 <.06 .59 4.1 28.4 E1.3 3.0 83 37 662

*06/08/2009 E.03 .51 3.4 22.2 2.6 4.2 83 26 365

*06/15/2009 <.06 .32 1.9 15.8 <2.0 2.1 83 16 164

*06/23/2009 <.06 .20 2.1 12.0 <2.0 E1.2 83 9 84

07/15/2009 <.06 .10 1.7 6.7 E1.1 <2.0 83 3 13

08/19/2009 <.06 E.06 1.3 4.6 <2.0 <2.0 72 2 4.4

*Sample collected as part of a supplemental sampling program.
Data 45

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12340500--Clark Fork above Missoula

Date Time

Streamflow, 

instantaneous 

(ft3/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/22/2008 1145 1,750 2.3 8.4 317 5.0 150 41.1 11.6

*03/02/2009 1530 1,650 -- 8.7 310 4.5 150 41.0 11.7

*03/16/2009 1630 1,720 -- 8.6 297 3.5 140 39.2 10.5

03/24/2009 1620 3,320 30 7.9 251 4.5 110 28.5 8.56

*03/25/2009 1630 2,880 -- 8.4 269 4.5 120 32.9 9.86

*03/27/2009 1600 2,350 -- 8.5 278 3.5 130 34.7 10.3

*03/31/2009 1600 2,240 -- 8.5 279 4.0 130 35.6 10.3

*04/06/2009 1530 2,270 -- 8.3 293 8.0 140 38.0 11.3

*04/14/2009 1630 6,520 -- 8.2 206 6.0 97 25.9 7.94

*04/21/2009 1610 7,620 -- 8.1 190 10.0 87 23.1 7.05

*04/27/2009 1600 8,350 -- 8.2 194 7.0 90 24.2 7.20

04/29/2009 1230 7,160 E14 8.0 210 4.5 96 25.7 7.76

*05/04/2009 1525 5,990 -- 8.2 244 8.0 100 28.2 8.28

*05/11/2009 1530 7,140 -- 8.4 201 9.5 100 26.8 8.04

*05/18/2009 1615 9,230 -- 8.3 176 12.5 89 24.3 6.95

05/20/2009 1120 15,400 100 8.0 148 9.5 71 19.4 5.44

*05/22/2009 1500 14,500 -- 8.1 161 10.0 79 21.4 6.08

*05/26/2009 1530 17,300 -- 8.1 155 11.0 74 20.5 5.61

*05/31/2009 1515 17,400 -- 8.1 148 12.5 73 20.2 5.42

06/03/2009 1110 14,000 27 8.0 165 10.0 77 21.6 5.68

*06/04/2009 1730 12,300 -- 8.1 172 13.0 82 22.6 6.07

*06/08/2009 1500 10,400 -- 8.2 182 10.0 85 23.4 6.34

*06/15/2009 1700 7,220 -- 8.3 192 14.0 94 25.9 7.05

*06/23/2009 1745 7,800 -- 8.3 208 13.5 100 28.6 7.71

06/24/2009 0940 7,120 E9.7 8.2 218 12.5 100 28.8 7.69

07/15/2009 1325 3,680 E2.8 8.3 261 16.0 130 33.7 10.2

08/19/2009 1300 2,070 E2.4 8.5 301 17.0 140 39.0 11.1
46 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

12340500--Clark Fork above Missoula—Continued

Date

Total 

nitrogen, 

unfiltered, 

(mg/L)

Total 

phosphorous, 

unfiltered, 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

10/22/2008 -- -- 4.2 4.7 0.03 E0.03 2.0 6.2

*03/02/2009 0.22 0.028 3.6 4.4 .02 E.05 2.2 7.8

*03/16/2009 .13 .032 3.4 4.5 .02 .07 2.9 10.6

03/24/2009 -- -- 4.5 7.7 .04 .18 5.6 31.1

*03/25/2009 .51 .115 4.2 6.1 .03 .13 3.9 21.4

*03/27/2009 .53 .118 4.4 14.2 .04 .50 3.5 79.7

*03/31/2009 .30 .051 3.9 5.9 .02 .12 2.4 20.7

*04/06/2009 .28 .032 3.7 4.5 E.02 E.06 2.7 9.6

*04/14/2009 .72 .128 3.5 7.9 .02 .19 3.5 33.9

*04/21/2009 .55 .104 2.5 6.3 E.02 .18 2.6 29.1

*04/27/2009 .37 .062 2.8 4.8 .04 .13 3.2 20.8

04/29/2009 -- -- 2.4 3.9 .02 E.06 2.6 14.8

*05/04/2009 .29 .045 2.9 4.0 .03 .09 2.5 13.1

*05/11/2009 .17 .041 2.9 3.8 E.02 E.06 2.2 9.1

*05/18/2009 .21 .081 2.8 5.6 E.02 .21 2.5 33.4

05/20/2009 -- -- 3.0 11.4 .03 .55 4.3 81.4

*05/22/2009 .42 .107 3.7 7.4 .02 .26 4.4 39.3

*05/26/2009 .35 .117 4.6 9.2 .04 .36 5.6 53.4

*05/31/2009 .19 .090 4.0 7.6 .03 .30 4.2 34.9

06/03/2009 -- -- 4.3 7.6 .04 .20 4.9 31.9

*06/04/2009 .24 .059 4.5 7.2 .04 .23 4.3 29.7

*06/08/2009 .21 .051 4.6 6.3 .04 .13 4.1 21.5

*06/15/2009 .20 .043 4.0 5.2 .02 .08 3.0 13.7

*06/23/2009 .27 .054 5.5 7.5 .04 .11 5.2 20.9

06/24/2009 -- -- 5.2 7.1 .04 .11 5.0 20.7

07/15/2009 -- -- 4.4 4.9 .02 .07 2.7 6.7

08/19/2009 -- -- 5.4 6.1 .02 .07 2.3 5.8

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]
Data 47

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12340500--Clark Fork above Missoula—Continued

Date

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

10/22/2008 7 140 0.07 1.27 11.0 39.5 2.4 8.7

*03/02/2009 13 192 E.05 1.24 9.0 32.1 E1.3 10.8

*03/16/2009 12 270 E.05 1.62 8.6 35.6 4.1 16.3

03/24/2009 106 1,300 .26 5.67 19.2 117 4.9 40.3

*03/25/2009 26 742 .10 3.31 12.4 71.3 5.1 28.5

*03/27/2009 16 1,800 .10 12.7 77.5 198 8.3 114

*03/31/2009 12 448 .07 3.23 12.3 45.1 8.1 36.9

*04/06/2009 14 285 .07 1.43 11.6 35.7 2.7 13.3

*04/14/2009 41 1,660 .13 6.44 9.4 138 8.0 55.2

*04/21/2009 35 1,530 .09 6.14 9.2 122 5.9 49.8

*04/27/2009 27 748 .11 3.52 8.8 68.9 -- 29.9

04/29/2009 41 501 .15 2.96 5.9 50.2 2.9 17.0

*05/04/2009 19 441 .07 2.30 6.3 48.4 6.0 19.6

*05/11/2009 16 365 .07 1.65 5.8 35.5 2.2 12.8

*05/18/2009 23 1,070 .11 5.90 11.2 93.0 2.5 47.0

05/20/2009 64 3,650 .22 15.8 14.7 300 4.5 139

*05/22/2009 22 1,580 .11 7.51 11.4 131 3.8 61.2

*05/26/2009 24 1,940 .14 9.36 14.2 164 6.0 96.8

*05/31/2009 19 1,420 .07 6.31 9.7 124 3.4 61.4

06/03/2009 28 970 .15 4.66 13.8 104 5.4 57.7

*06/04/2009 19 863 .10 4.55 16.0 90.7 5.6 51.4

*06/08/2009 20 659 .10 3.36 13.3 70.1 5.7 32.7

*06/15/2009 16 390 .07 2.08 9.5 43.6 2.8 20.0

*06/23/2009 20 573 .10 3.36 11.6 71.3 3.8 30.5

06/24/2009 17 480 .12 3.12 9.4 58.2 3.8 26.5

07/15/2009 8 138 E.05 .78 8.5 28.9 E1.7 8.1

08/19/2009 6 140 E.04 .88 9.3 33.9 E1.6 7.7
48 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, 

October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; 

lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter 

at 25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric 

turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; --, no data]

12340500--Clark Fork above Missoula—Continued

Date

Sediment, 

suspended 

(percent finer 

than 0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/22/2008 82 7 33

*03/02/2009 82 13 58

*03/16/2009 75 16 74

03/24/2009 76 71 636

*03/25/2009 75 38 295

*03/27/2009 77 94 596

*03/31/2009 68 25 151

*04/06/2009 73 14 86

*04/14/2009 58 108 1,900

*04/21/2009 52 126 2,590

*04/27/2009 64 56 1,260

04/29/2009 64 36 696

*05/04/2009 68 29 469

*05/11/2009 65 33 636

*05/18/2009 50 111 2,770

05/20/2009 46 422 17,500

*05/22/2009 49 183 7,160

*05/26/2009 59 171 7,990

*05/31/2009 55 152 7,140

06/03/2009 64 83 3,140

*06/04/2009 59 82 2,720

*06/08/2009 61 56 1,570

*06/15/2009 56 34 663

*06/23/2009 59 40 842

06/24/2009 51 26 500

07/15/2009 68 7 70

08/19/2009 73 9 50

*Sample collected as part of a supplemental sampling program.
Data 49

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12352500--Bitterroot River near Missoula

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Total 

nitrogen, 

unfiltered, 

(mg/L)

03/03/2009 0800 1,000 7.8 135 3.5 59 16.9 3.99 0.19

03/17/2009 0830 1,020 7.6 129 2.0 59 17.1 3.90 .14

03/26/2009 0830 1,300 8.1 110 3.5 45 13.1 3.10 .18

04/01/2009 0830 1,210 7.7 114 4.0 49 14.3 3.25 .17

04/07/2009 0745 1,180 7.9 127 6.5 54 15.5 3.69 .23

04/15/2009 0830 2,700 7.8 88 5.0 36 10.6 2.41 .30

04/22/2009 0800 4,540 7.5 68 9.5 27 7.95 1.74 .52

04/28/2009 0800 3,870 7.7 73 7.0 30 8.72 1.91 .21

05/05/2009 0800 3,490 7.8 76 8.0 32 9.47 2.07 .16

05/12/2009 0730 4,560 7.7 71 9.5 29 8.41 1.92 .17

05/19/2009 0730 9,260 7.5 47 10.5 18 5.49 1.15 .41

05/27/2009 0745 15,900 7.5 49 11.0 19 5.57 1.19 .20

06/01/2009 0800 17,800 7.3 43 10.5 17 5.03 1.10 .22

06/05/2009 0800 12,200 7.4 48 11.0 19 5.59 1.22 .21

06/09/2009 0800 9,260 7.6 60 10.0 23 6.75 1.50 .19

06/16/2009 0830 9,310 7.6 49 14.0 19 5.62 1.24 .21

06/24/2009 0800 6,720 7.7 64 12.0 27 7.73 1.75 .15

Date

Total 

phosphorous, 

unfiltered, 

(mg/L)

Arsenic, 

filtered 

(μg/L)

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)

03/03/2009 0.015 0.34 0.41 <0.02 <0.06 E0.52 <4.0 28 129

03/17/2009 .013 .31 .37 <.02 <.06 E.67 <4.0 29 116

03/26/2009 .018 .30 .34 <.02 <.06 E.57 <4.0 36 159

04/01/2009 .013 .30 .33 <.02 <.06 <1.0 <4.0 34 140

04/07/2009 .017 .33 .41 <.02 <.06 <1.0 <4.0 32 157

04/15/2009 .030 .26 .40 <.02 <.06 <1.0 <4.0 43 456

04/22/2009 .069 .49 .66 E.01 <.06 E.70 E2.4 62 1,650

04/28/2009 .026 .31 .41 E.02 <.06 E.77 <4.0 73 346

05/05/2009 .022 .31 .32 <.02 E.04 E.66 <4.0 52 338

05/12/2009 .024 .28 .38 <.02 <.06 E.75 <4.0 48 286

05/19/2009 .124 .31 .83 <.02 <.06 E.87 E3.9 74 2,310

05/27/2009 .037 .31 .51 <.02 <.06 1.9 E2.2 52 785

06/01/2009 .059 .34 .47 <.02 <.06 1.0 E2.0 66 780

06/05/2009 .028 .31 .39 <.02 <.06 E.82 <4.0 55 490

06/09/2009 .027 .34 .44 <.02 <.06 E.90 <4.0 56 543

06/16/2009 .039 .28 .37 <.02 <.06 E.76 <4.0 57 572

06/24/2009 .023 .34 .50 <.02 <.06 E.78 <4.0 59 283
50 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12352500--Bitterroot River near Missoula—Continued

Date

Lead, 

filtered 

(μg/L)

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)

03/03/2009 E0.04 0.12 9.1 19.2 <2.0 <2.0 75 6 16

03/17/2009 <.06 .19 8.4 17.5 E1.0 4.3 74 5 14

03/26/2009 E.03 .15 7.3 16.7 E1.9 <2.0 77 6 21

04/01/2009 <.06 E.09 7.9 16.2 3.1 9.0 71 5 16

04/07/2009 <.06 .11 7.5 23.1 E1.0 E1.4 72 7 22

04/15/2009 E.04 .35 4.5 25.1 5.4 6.7 76 21 153

04/22/2009 .07 1.32 3.9 72.6 8.5 5.8 60 98 1,200

04/28/2009 .09 .40 6.0 18.5 6.5 -- 76 15 157

05/05/2009 E.05 .36 4.0 17.3 3.3 2.8 72 17 160

05/12/2009 E.04 .31 3.3 12.6 <2.0 2.0 56 19 234

05/19/2009 .10 2.37 5.1 98.7 <2.0 9.9 44 233 5,830

05/27/2009 .08 .93 3.8 26.2 E1.4 3.6 35 99 4,250

06/01/2009 .09 .88 4.7 27.2 <2.0 3.8 37 93 4,470

06/05/2009 .07 .54 7.1 21.2 E1.2 2.3 41 60 1,980

06/09/2009 E.06 .60 10.4 26.9 E1.1 3.0 54 41 1,030

06/16/2009 E.05 .58 5.7 22.9 E1.5 2.7 57 46 1,160

06/24/2009 E.05 .26 6.5 15.7 E1.1 E1.8 58 17 308
Data 51

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12354500--Clark Fork at St. Regis

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Total 

nitrogen, 

unfiltered, 

(mg/L)

03/03/2009 1400 3,610 8.3 251 5.0 110 31.1 8.71 0.22

03/17/2009 1415 3,650 8.3 234 6.0 110 30.1 8.25 .14

03/26/2009 1530 5,670 8.3 209 5.5 91 24.7 7.21 .51

04/01/2009 1615 4,780 8.3 221 5.0 100 27.9 7.89 .28

04/07/2009 1330 4,760 8.3 230 7.5 110 28.7 8.28 .23

04/15/2009 1500 11,700 8.1 163 5.0 73 19.9 5.77 .60

04/22/2009 1455 16,700 7.9 147 7.5 64 17.3 5.00 .57

04/28/2009 1330 15,200 8.1 159 4.5 73 19.8 5.68 .38

05/05/2009 1250 12,000 8.2 166 6.0 75 20.5 5.79 .26

05/12/2009 1330 15,200 8.3 154 6.0 72 19.5 5.68 .19

05/19/2009 1330 25,200 8.1 121 6.5 56 15.7 4.20 .47

05/27/2009 1430 40,500 8.0 106 9.0 47 13.3 3.47 .28

06/01/2009 1430 42,600 7.9 100 11.0 46 12.9 3.39 .27

06/05/2009 1430 30,600 7.9 115 10.0 51 14.4 3.73 .23

06/09/2009 1300 24,800 8.0 127 9.0 57 16.1 4.16 .21

06/16/2009 1430 20,200 8.1 121 12.0 55 15.6 4.00 .20

06/24/2009 1330 17,700 8.1 142 12.5 67 18.5 4.97 .17

Date

Total 

phosphorous, 

unfiltered, 

(mg/L)

Arsenic, 

filtered 

(μg/L)

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)

03/03/2009 0.023 2.0 2.3 0.03 E0.04 1.8 E3.8 15 110

03/17/2009 .016 1.8 2.0 E.01 <.06 1.5 E3.2 13 110

03/26/2009 .104 2.9 4.0 E.01 .08 3.9 13.2 24 562

04/01/2009 .039 3.0 3.6 <.02 E.04 2.3 8.9 9 267

04/07/2009 .026 2.2 2.6 E.02 <.06 1.9 5.5 12 210

04/15/2009 .100 2.6 5.5 E.01 .18 3.2 27.2 27 1,250

04/22/2009 .104 1.9 4.6 .02 .18 2.3 26.5 32 1,640

04/28/2009 .052 2.1 3.0 .03 .08 2.7 13.0 21 596

05/05/2009 .033 1.7 2.2 E.02 E.05 1.7 8.2 18 367

05/12/2009 .029 1.7 2.1 .03 E.05 2.2 6.1 23 325

05/19/2009 .086 1.5 3.7 E.01 .13 2.2 20.7 22 1,700

05/27/2009 .100 2.5 4.6 .02 .15 3.9 25.0 29 1,760

06/01/2009 .097 2.3 4.0 .02 .13 3.5 17.8 26 1,530

06/05/2009 .051 2.3 3.7 .02 .09 3.1 14.3 27 879

06/09/2009 .047 2.4 3.4 .03 .07 2.7 11.9 25 701

06/16/2009 .048 1.9 2.5 E.02 E.05 2.0 8.7 20 570

06/24/2009 .035 2.6 3.1 E.02 <.06 2.9 7.9 25 405
52 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12354500--Clark Fork at St. Regis—Continued

Date

Lead, 

filtered 

(μg/L)

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)

03/03/2009 E0.05 0.52 8.6 25.1 E1.4 5.8 83 6 58

03/17/2009 E.05 .44 6.9 25.0 2.8 14.9 78 7 69

03/26/2009 .11 2.33 6.2 61.8 3.2 18.8 87 29 444

04/01/2009 .07 2.31 6.7 34.0 2.7 11.3 87 11 142

04/07/2009 E.06 .86 5.9 31.7 E1.7 8.0 83 10 129

04/15/2009 .21 5.18 3.4 124 5.1 38.9 79 71 2,240

04/22/2009 .12 5.97 5.1 135 3.1 47.5 65 132 5,950

04/28/2009 .09 2.36 3.5 56.0 4.9 20.1 76 40 1,640

05/05/2009 .09 1.38 2.7 34.2 3.0 15.3 79 20 648

05/12/2009 .10 1.09 2.7 26.2 2.1 9.8 62 30 1,230

05/19/2009 .10 4.94 2.6 102 E1.9 37.2 43 203 13,800

05/27/2009 .13 5.22 4.2 105 2.7 45.6 41 222 24,300

06/01/2009 .09 4.03 4.0 90.8 2.3 33.6 50 170 19,600

06/05/2009 .10 2.64 6.0 60.1 3.2 23.9 63 86 7,110

06/09/2009 .08 2.25 7.7 53.4 3.8 20.3 65 60 4,020

06/16/2009 .06 1.60 2.8 38.1 E1.5 12.8 67 52 2,840

06/24/2009 .07 1.34 3.6 30.7 2.1 10.5 68 29 1,390
Data 53

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12388700--Flathead River at Perma

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Total 

nitrogen, 

unfiltered, 

(mg/L)

03/03/2009 1100 8,690 8.3 175 2.5 89 25.1 6.43 0.10

03/17/2009 1200 6,690 8.1 180 3.0 94 26.7 6.69 .11

03/26/2009 1200 6,780 8.4 174 5.0 88 24.5 6.54 .17

04/01/2009 1300 6,560 8.3 178 5.0 94 26.3 6.74 .31

04/07/2009 1100 6,460 8.3 176 7.5 88 24.8 6.45 .12

04/15/2009 1230 6,760 8.3 179 8.5 87 24.4 6.30 .14

04/22/2009 1210 7,500 8.2 179 13.0 88 24.7 6.42 .13

04/28/2009 1130 11,900 8.3 174 7.0 93 26.6 6.44 .12

05/05/2009 1600 12,000 8.4 175 13.0 91 25.8 6.47 E.08

05/12/2009 1100 13,800 8.4 172 8.5 92 26.2 6.48 E.09

05/19/2009 1100 13,800 8.2 172 11.5 89 25.5 6.07 .15

05/27/2009 1130 15,900 8.3 170 14.0 90 25.9 6.20 E.09

06/01/2009 1130 17,100 8.3 169 17.0 87 25.1 5.99 .12

06/05/2009 1200 22,000 8.3 177 15.0 90 25.9 6.06 .12

06/09/2009 1100 22,000 8.4 178 13.0 88 25.3 6.02 E.09

06/16/2009 1200 21,400 8.3 170 17.0 90 25.8 6.07 E.10

06/24/2009 1115 24,200 8.4 170 15.5 92 26.5 6.26 E.09

Date

Total 

phosphorous, 

unfiltered, 

(mg/L)

Arsenic, 

filtered 

(μg/L)

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)

03/03/2009 E0.004 0.37 0.47 E0.01 <0.06 <1.0 <4.0 <4 33

03/17/2009 E.006 .39 .45 <.02 <.06 <1.0 <4.0 7 78

03/26/2009 .008 .40 .45 <.02 <.06 E.77 <4.0 6 57

04/01/2009 <.008 .39 .41 <.02 <.06 E.98 <4.0 <4 61

04/07/2009 E.007 .38 .40 <.02 <.06 E.78 <4.0 E3 46

04/15/2009 E.006 .39 .44 <.02 <.06 <1.0 <4.0 <4 72

04/22/2009 .009 .46 .45 <.02 <.06 <1.0 <4.0 10 92

04/28/2009 .011 .48 .49 <.02 <.06 <1.0 <4.0 E4 142

05/05/2009 E.007 .42 .44 <.02 <.06 <1.0 <4.0 E3 89

05/12/2009 E.004 .42 .44 <.02 <.06 <1.0 <4.0 E3 68

05/19/2009 .008 .43 .44 <.02 <.06 <1.0 <4.0 E3 99

05/27/2009 E.007 .43 .45 <.02 <.06 E.81 <4.0 E3 109

06/01/2009 .013 .48 .50 <.02 <.06 <1.0 <4.0 E3 164

06/05/2009 .008 .42 .50 <.02 <.06 <1.0 <4.0 <4 119

06/09/2009 E.008 .43 .40 <.02 <.06 E.71 <4.0 E2 102

06/16/2009 .008 .43 .45 <.02 <.06 <1.0 <4.0 <4 118

06/24/2009 .009 .39 .37 <.02 <.06 <1.0 <4.0 <4 87
54 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2008 through September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; lab, laboratory; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 

25°C; mg/L, milligram per liter; mm, millimeter; NTRU, nephelometric turbidity ratio unit; ton/d, ton per day. Symbols: <, less than laboratory reporting level; 

--, no data]

12388700--Flathead River at Perma—Continued

Date

Lead, 

filtered 

(μg/L)

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)

03/03/2009 <0.06 <0.10 1.1 3.1 <2.0 <2.0 68 1 23

03/17/2009 <.06 .10 1.2 4.3 E1.5 4.5 91 3 54

03/26/2009 .06 E.09 1.4 3.7 <2.0 <2.0 85 2 37

04/01/2009 <.06 E.08 1.2 3.6 2.8 2.4 90 2 35

04/07/2009 E.03 <.10 1.4 3.9 <2.0 <2.0 81 2 35

04/15/2009 <.06 E.07 1.2 5.1 E1.2 E1.2 86 4 73

04/22/2009 <.06 .17 1.7 7.6 <2.0 <2.0 88 6 122

04/28/2009 <.06 .20 1.0 9.0 -- -- 89 10 321

05/05/2009 <.06 .14 1.0 5.8 3.0 3.0 84 5 162

05/12/2009 <.06 .13 .9 4.6 <2.0 E1.1 79 8 298

05/19/2009 <.06 .14 1.1 7.0 E1.3 <2.0 81 6 224

05/27/2009 <.06 .15 1.3 7.9 <2.0 E1.0 89 9 386

06/01/2009 <.06 .24 1.4 11.3 <2.0 E1.1 92 13 600

06/05/2009 <.06 .16 1.0 8.5 E1.2 <2.0 78 11 653

06/09/2009 <.06 .16 .8 7.4 <2.0 <2.0 75 8 475

06/16/2009 <.06 .17 .9 8.2 <2.0 <2.0 80 8 462

06/24/2009 <.06 .12 .7 5.9 E1.0 <2.0 75 5 327
Data 55

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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

1 178 6 2.9 268 13 9.4 289 20 16

2 180 7 3.4 277 14 10 290 22 17

3 183 8 4.0 288 13 10 285 22 17

4 209 10 5.6 287 13 10 254 21 14

5 220 12 7.1 293 13 10 251 18 12

6 218 13 7.7 297 12 9.6 290 15 12

7 212 14 8.0 305 12 9.9 289 14 11

8 220 15 8.9 323 12 10 283 14 11

9 230 15 9.3 318 11 9.4 270 15 11

10 247 14 9.3 309 11 9.2 269 16 12

11 251 13 8.8 296 10 8.0 264 16 11

12 255 13 9.0 287 10 7.7 239 14 9.0

13 268 13 9.4 339 14 13 237 11 7.0

14 279 13 9.8 360 20 19 e90 8 1.9

15 272 13 9.5 323 18 16 e80 8 1.7

16 278 13 9.8 318 17 15 e80 9 1.9

17 273 13 9.6 303 16 13 e100 10 2.7

18 278 13 9.8 298 15 12 e130 12 4.2

19 277 14 10 291 15 12 e150 14 5.7

20 277 14 10 286 14 11 e140 15 5.7

21 288 13 10 290 13 10 e130 17 6.0

22 283 13 9.9 280 13 9.8 e140 19 7.2

23 276 13 9.7 269 13 9.4 e150 20 8.1

24 279 13 9.8 252 13 8.8 e160 19 8.2

25 285 13 10 256 12 8.3 e160 19 8.2

26 280 13 9.8 262 12 8.5 e170 18 8.3

27 273 13 9.6 256 12 8.3 e170 17 7.8

28 268 13 9.4 261 13 9.2 188 17 8.6

29 266 13 9.3 275 15 11 209 19 11

30 268 13 9.4 284 18 14 e220 23 14

31 275 13 9.7 -- -- -- 249 24 16

TOTAL 7,846 -- 268.5 8,751 -- 321.5 6,226 -- 287.2

MEAN 253 13 8.7 292 14 11 201 16 9.3

MAX 288 15 10.0 360 20 19 290 24 17

MIN 178 6 2.9 252 10 7.7 80 8 1.7
56 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

JANUARY FEBRUARY MARCH

1 261 23 16 e230 38 24 253 25 17

2 285 18 14 237 38 24 259 25 17

3 e250 14 9.4 241 38 25 280 18 14

4 e220 11 6.5 e240 38 25 265 42 30

5 e200 11 5.9 e240 38 25 254 26 18

6 236 10 6.4 238 38 24 247 32 21

7 296 16 13 237 44 28 242 28 18

8 431 47 55 233 53 33 251 30 20

9 385 47 49 237 57 36 230 34 21

10 316 42 36 235 50 32 224 30 18

11 303 52 43 225 39 24 220 28 17

12 302 69 56 231 29 18 228 28 17

13 309 74 62 225 23 14 225 30 18

14 285 64 49 221 23 14 230 30 19

15 283 51 39 229 27 17 235 28 18

16 280 41 31 230 31 19 245 25 17

17 272 38 28 228 32 20 239 39 25

18 265 43 31 228 30 18 238 38 24

19 270 51 37 227 29 18 245 52 34

20 281 55 42 229 27 17 271 80 59

21 280 47 36 226 25 15 295 67 53

22 270 34 25 227 25 15 325 55 48

23 e250 22 15 241 28 18 324 42 37

24 e200 14 7.6 264 32 23 303 45 37

25 e170 17 7.8 260 35 25 270 35 26

26 e150 25 10 249 35 24 232 27 17

27 e160 33 14 245 30 20 237 37 24

28 e200 37 20 231 27 17 243 28 18

29 217 38 22 -- -- -- 247 25 17

30 234 38 24 -- -- -- 214 43 25

31 257 38 26 -- -- -- 243 42 28

TOTAL 8,118 -- 836.6 6,584 -- 612 7,814 -- 772

MEAN 262 36 27 235 34 22 252 36 25

MAX 431 74 62 264 57 36 325 80 59

MIN 150 10 5.9 221 23 14 214 18 14
Data 57

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

APRIL MAY JUNE

1 229 40 25 305 37 30 1,140 98 302

2 235 36 23 307 45 37 1,130 85 259

3 253 28 19 310 38 32 1,010 74 202

4 265 35 25 343 47 44 863 71 165

5 273 45 33 337 46 42 844 84 191

6 302 63 51 352 46 44 967 78 204

7 313 54 46 378 68 69 1,040 60 168

8 321 49 42 402 49 53 905 55 134

9 324 47 41 410 36 40 822 53 118

10 305 45 37 384 41 43 731 48 95

11 300 56 45 373 44 44 651 48 84

12 297 93 75 394 47 50 598 54 87

13 306 77 64 433 51 60 573 50 77

14 348 74 70 410 49 54 564 46 70

15 350 36 34 407 42 46 642 67 116

16 317 28 24 402 38 41 783 82 173

17 245 30 20 407 42 46 852 64 147

18 245 38 25 438 63 75 973 58 152

19 257 62 43 530 185 265 958 73 189

20 277 104 78 683 190 350 927 61 153

21 309 102 85 719 156 303 997 42 113

22 377 95 97 694 250 468 1,020 47 129

23 453 110 135 678 310 567 975 49 129

24 457 84 104 762 141 290 792 41 88

25 458 62 77 997 250 673 711 41 79

26 423 62 71 1,050 225 638 718 36 70

27 387 42 44 1,010 139 379 655 34 60

28 386 39 41 993 116 311 585 32 51

29 384 27 28 1,010 106 289 532 28 40

30 310 33 28 1,050 108 306 473 27 34

31 -- -- -- 1,090 109 321 -- -- --

TOTAL 9,706 -- 1,530 18,058 -- 6,010 24,431 -- 3,879

MEAN 324 57 51 583 100 194 814 56 129

MAX 458 110 135 1,090 310 673 1,140 98 302

MIN 229 27 19 305 36 30 473 27 34
58 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

JULY AUGUST SEPTEMBER

1 457 23 28 204 12 6.6 198 4 2.1

2 428 21 24 189 12 6.1 185 4 2.0

3 429 19 22 166 10 4.5 181 4 2.0

4 409 18 20 152 9 3.7 168 5 2.3

5 391 16 17 142 8 3.1 145 5 2.0

6 378 15 15 157 7 3.0 148 5 2.0

7 374 17 17 206 8 4.4 146 5 2.0

8 349 18 17 247 11 7.3 152 5 2.1

9 363 19 19 231 8 5.0 151 5 2.0

10 346 18 17 217 6 3.5 144 5 1.9

11 323 18 16 208 5 2.8 150 5 2.0

12 305 18 15 195 5 2.6 151 5 2.0

13 358 26 25 187 7 3.5 150 5 2.0

14 417 28 32 199 8 4.3 149 6 2.4

15 395 16 17 230 9 5.6 143 6 2.3

16 354 13 12 237 10 6.4 143 6 2.3

17 332 12 11 250 14 9.4 143 7 2.7

18 314 11 9.3 249 10 6.7 145 7 2.7

19 296 10 8.0 220 3 1.8 142 7 2.7

20 276 9 6.7 199 4 2.1 179 7 3.4

21 262 8 5.7 185 5 2.5 158 7 3.0

22 246 8 5.3 177 8 3.8 140 8 3.0

23 234 8 5.1 170 10 4.6 139 8 3.0

24 218 10 5.9 183 9 4.4 136 8 2.9

25 212 13 7.4 179 8 3.9 142 9 3.5

26 214 17 9.8 175 7 3.3 162 9 3.9

27 251 19 13 170 6 2.8 157 9 3.8

28 253 16 11 163 6 2.6 163 9 4.0

29 250 12 8.1 157 5 2.1 164 9 4.0

30 230 12 7.5 157 4 1.7 211 12 6.8

31 207 12 6.7 164 4 1.8 -- -- --

TOTAL 9,871 -- 433.5 5,965 -- 125.9 4,685 -- 82.8

MEAN 318 15 14 192 8 4.1 156 7 2.8

MAX 457 28 32 250 14 9.4 211 12 6.8

MIN 207 8 5.1 142 3 1.7 136 4 1.9 

Total for water year 2009 (unrounded sum of daily values): streamflow–118,055 ft3/s (annual runoff–234,200 acre-ft); suspended-sediment 

discharge–15,159 tons.
Data 59

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2008 

through September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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

1 866 7 16 1,070 7 20 1,220 7 23

2 870 8 19 1,090 7 21 1,240 7 23

3 881 8 19 1,190 8 26 1,240 7 23

4 896 9 22 1,250 11 37 1,150 6 19

5 942 10 25 1,210 9 29 1,040 4 11

6 957 9 23 1,180 7 22 1,150 6 19

7 959 8 21 1,160 7 22 1,210 7 23

8 960 8 21 1,270 12 41 1,200 7 23

9 968 7 18 1,320 15 53 1,170 6 19

10 990 6 16 1,300 16 56 1,150 5 16

11 1,000 6 16 1,270 16 55 1,150 5 16

12 1,020 6 17 1,260 18 61 1,100 5 15

13 1,030 6 17 1,590 27 116 1,070 4 12

14 1,050 7 20 1,970 45 239 e600 4 6.5

15 1,080 7 20 1,710 22 102 e350 3 2.8

16 1,080 8 23 1,610 16 70 e300 2 1.6

17 1,080 8 23 1,550 10 42 e350 2 1.9

18 1,080 9 26 1,490 9 36 e450 2 2.4

19 1,100 9 27 1,440 9 35 e550 2 3.0

20 1,110 9 27 1,400 8 30 e620 1 1.7

21 1,150 9 28 1,390 8 30 e660 1 1.8

22 1,150 9 28 1,350 7 26 e720 1 1.9

23 1,120 9 27 1,290 6 21 e760 2 4.1

24 1,110 9 27 1,240 6 20 e780 4 8.4

25 1,110 8 24 1,160 5 16 e820 8 18

26 1,100 8 24 1,210 6 20 e860 10 23

27 1,090 8 24 1,190 6 19 e900 12 29

28 1,080 8 23 1,140 6 18 e960 13 34

29 1,070 7 20 1,200 7 23 e980 12 32

30 1,070 7 20 1,210 7 23 e960 10 26

31 1,070 7 20 -- -- -- e920 9 22

TOTAL 32,039 -- 681 39,710 -- 1,329 27,630 -- 462.1

MEAN 1,034 8 22 1,324 11 44 891 6 15

MAX 1,150 10 28 1,970 45 239 1,240 13 34

MIN 866 6 16 1,070 5 16 300 1 1.6
60 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2008 

through September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

JANUARY FEBRUARY MARCH

1 e940 8 20 890 4 9.6 918 10 25

2 e960 8 21 874 4 9.4 980 15 40

3 e900 6 15 918 4 9.9 1,080 19 55

4 e820 7 15 901 3 7.3 1,200 28 91

5 e750 7 14 897 3 7.3 1,100 25 74

6 e850 8 18 920 3 7.5 1,030 16 44

7 991 9 24 929 3 7.5 966 11 29

8 1,090 13 38 910 3 7.4 961 10 26

9 1,430 46 178 907 3 7.3 934 10 25

10 1,440 33 128 913 3 7.4 861 10 23

11 1,280 15 52 884 3 7.2 873 10 24

12 1,210 13 42 878 4 9.5 882 10 24

13 1,200 13 42 862 4 9.3 884 9 21

14 1,200 16 52 837 4 9.0 922 10 25

15 1,210 20 65 829 4 9.0 946 14 36

16 1,190 20 64 846 4 9.1 1,040 18 51

17 1,110 16 48 885 5 12 997 14 38

18 1,030 12 33 906 8 20 960 12 31

19 973 7 18 912 14 34 972 12 31

20 942 4 10 934 20 50 1,130 40 122

21 961 3 7.8 917 26 64 1,450 114 446

22 969 4 10 893 30 72 1,710 137 633

23 992 4 11 923 34 85 2,080 190 1,070

24 945 4 10 1,080 46 134 1,690 85 388

25 920 4 9.9 1,300 101 355 1,470 41 163

26 803 3 6.5 1,170 46 145 1,320 28 100

27 629 4 6.8 1,030 20 56 1,190 21 67

28 734 6 12 928 14 35 1,180 22 70

29 811 6 13 -- -- -- 1,230 24 80

30 853 5 12 -- -- -- 1,200 17 55

31 899 5 12 -- -- -- 1,130 15 46

TOTAL 31,032 -- 1,008 26,073 -- 1,195.7 35,286 -- 3,953

MEAN 1,001 11 33 931 15 43 1,138 32 128

MAX 1,440 46 178 1,300 101 355 2,080 190 1,070

MIN 629 3 6.5 829 3 7.2 861 9 21
Data 61

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2008 

through September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

APRIL MAY JUNE

1 1,140 16 49 2,580 30 209 7,390 88 1,760

2 1,120 18 54 2,430 27 177 6,930 77 1,440

3 1,130 17 52 2,430 26 171 6,290 66 1,120

4 1,140 14 43 2,820 35 266 5,670 60 919

5 1,160 16 50 3,130 45 380 5,360 52 753

6 1,190 15 48 3,470 48 450 5,400 53 773

7 1,320 33 118 3,730 52 524 5,560 53 796

8 1,580 57 243 3,700 43 430 5,170 50 698

9 1,850 96 480 3,520 34 323 4,830 48 626

10 2,130 101 581 3,400 32 294 4,370 43 507

11 2,270 84 515 3,390 30 275 3,840 39 404

12 2,670 113 815 3,600 33 321 3,400 35 321

13 3,100 129 1,080 3,850 38 395 3,120 28 236

14 2,980 96 772 3,680 36 358 3,030 27 221

15 2,380 62 398 3,580 30 290 3,270 35 309

16 2,040 44 242 3,510 30 284 3,750 49 496

17 1,880 36 183 3,700 36 360 3,810 47 483

18 1,880 44 223 4,640 70 877 3,840 43 446

19 2,070 59 330 6,630 192 3,440 3,710 40 401

20 2,320 77 482 7,660 231 4,780 3,550 33 316

21 3,020 99 807 7,430 181 3,630 3,490 31 292

22 4,010 147 1,590 6,840 108 1,990 3,940 51 543

23 5,160 193 2,690 6,510 86 1,510 4,280 58 670

24 5,380 137 1,990 6,880 86 1,600 3,640 37 364

25 4,710 77 979 7,900 170 3,630 3,100 29 243

26 4,190 57 645 7,720 136 2,830 2,800 26 197

27 3,740 46 465 7,060 101 1,930 2,660 23 165

28 3,350 39 353 6,640 78 1,400 2,420 22 144

29 3,080 33 274 7,010 83 1,570 2,180 21 124

30 2,810 31 235 7,330 97 1,920 2,030 18 99

31 -- -- -- 7,330 89 1,760 -- -- --

TOTAL 76,800 -- 16,786 154,100 -- 38,374 122,830 -- 15,866

MEAN 2,560 66 560 4,971 75 1,240 4,094 43 529

MAX 5,380 193 2,690 7,900 231 4,780 7,390 88 1,760

MIN 1,120 14 43 2,430 26 171 2,030 18 99
62 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2008 

through September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

JULY AUGUST SEPTEMBER

1 1,930 16 83 1,150 9 28 874 8 19

2 1,860 14 70 1,110 9 27 867 8 19

3 1,750 12 57 1,060 8 23 845 7 16

4 1,700 10 46 1,020 8 22 822 6 13

5 1,640 9 40 985 8 21 811 6 13

6 1,650 8 36 998 8 22 806 5 11

7 1,670 8 36 1,230 13 43 795 5 11

8 1,720 8 37 1,670 69 311 786 5 11

9 1,720 9 42 1,480 30 120 782 4 8.4

10 1,680 8 36 1,320 20 71 782 4 8.4

11 1,600 7 30 1,220 17 56 778 5 11

12 1,530 7 29 1,140 15 46 769 6 12

13 1,580 7 30 1,100 13 39 773 6 13

14 1,780 8 38 1,120 12 36 775 6 13

15 1,850 11 55 1,160 12 38 764 7 14

16 1,710 10 46 1,190 12 39 750 7 14

17 1,580 8 34 1,210 13 42 739 7 14

18 1,500 8 32 1,190 16 51 736 7 14

19 1,440 8 31 1,140 16 49 737 6 12

20 1,380 7 26 1,090 14 41 740 6 12

21 1,320 6 21 1,040 13 37 752 6 12

22 1,260 6 20 990 12 32 771 6 12

23 1,210 6 20 969 11 29 763 6 12

24 1,160 6 19 952 10 26 757 6 12

25 1,120 6 18 943 9 23 745 6 12

26 1,100 6 18 919 8 20 738 5 10

27 1,220 10 33 900 7 17 742 6 12

28 1,470 19 75 877 6 14 742 6 12

29 1,400 14 53 855 6 14 753 6 12

30 1,310 10 35 845 7 16 770 6 12

31 1,220 8 26 853 8 18 -- -- --

TOTAL 47,060 -- 1,172 33,726 -- 1,371 23,264 -- 376.8

MEAN 1,518 9 38 1,088 14 44 775 6 13

MAX 1,930 19 83 1,670 69 311 874 8 19

MIN 1,100 6 18 845 6 14 736 4 8.4

Total for water year 2009 (unrounded sum of daily values): streamflow–649,550 ft3/s (annual runoff–1,288,000 acre-ft); suspended-sediment 

discharge–82,574.6 tons.
Data 63

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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

1 647 2 3.5 596 1 1.6 850 1 2.3

2 642 2 3.5 603 1 1.6 874 1 2.4

3 635 3 5.1 634 1 1.7 912 1 2.5

4 645 3 5.2 646 1 1.7 842 1 2.3

5 650 3 5.3 652 1 1.8 805 1 2.2

6 642 3 5.2 636 1 1.7 857 1 2.3

7 635 3 5.1 641 1 1.7 830 1 2.2

8 632 2 3.4 675 1 1.8 833 1 2.2

9 628 2 3.4 681 1 1.8 818 1 2.2

10 622 2 3.4 670 1 1.8 806 1 2.2

11 620 2 3.3 658 1 1.8 799 1 2.2

12 624 2 3.4 696 3 5.6 758 1 2.0

13 626 1 1.7 1,170 22 69 e700 1 1.9

14 625 1 1.7 1,590 21 90 e450 1 1.2

15 626 2 3.4 1,510 10 41 e330 1 .89

16 621 2 3.4 1,440 7 27 e300 1 .81

17 614 2 3.3 1,360 6 22 e320 1 .86

18 611 2 3.3 1,290 5 17 e500 1 1.4

19 618 2 3.3 1,220 4 13 e550 1 1.5

20 616 2 3.3 1,160 3 9.4 e500 1 1.4

21 629 2 3.4 1,120 2 6.0 e550 1 1.5

22 633 2 3.4 1,080 2 5.8 e550 1 1.5

23 627 2 3.4 1,030 1 2.8 e600 1 1.6

24 617 2 3.3 978 1 2.6 e600 2 3.2

25 615 2 3.3 928 1 2.5 e600 2 3.2

26 609 2 3.3 921 1 2.5 e650 2 3.5

27 603 2 3.3 897 2 4.8 e650 2 3.5

28 602 1 1.6 866 2 4.7 e700 2 3.8

29 602 1 1.6 871 2 4.7 e720 2 3.9

30 602 1 1.6 861 2 4.6 e700 2 3.8

31 598 1 1.6 -- -- -- e700 2 3.8

TOTAL 19,316 -- 103 28,080 -- 354 20,654 -- 70.26

MEAN 623 2 3.3 936 4 12 666 1 2.3

MAX 650 3 5.3 1,590 22 90 912 2 3.9

MIN 598 1 1.6 596 1 1.6 300 1 .81
64 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

JANUARY FEBRUARY MARCH

1 e700 2 3.8 e740 3 6.0 597 2 3.2

2 e700 1 1.9 e740 3 6.0 607 2 3.3

3 e650 1 1.8 e720 3 5.8 617 3 5.0

4 e600 1 1.6 e700 3 5.7 641 4 6.9

5 e650 1 1.8 e680 3 5.5 708 5 9.6

6 e750 1 2.0 e700 3 5.7 703 4 7.6

7 e900 2 4.9 e650 3 5.3 644 3 5.2

8 1,140 4 12 e620 4 6.7 650 2 3.5

9 1,280 5 17 e620 4 6.7 592 2 3.2

10 1,150 4 12 e600 4 6.5 549 1 1.5

11 1,070 4 12 e600 4 6.5 516 1 1.4

12 1,010 4 11 e590 3 4.8 562 2 3.0

13 981 4 11 e580 3 4.7 601 2 3.2

14 953 3 7.7 e570 3 4.6 617 3 5.0

15 937 3 7.6 e580 3 4.7 616 4 6.7

16 905 2 4.9 581 3 4.7 635 6 10

17 893 2 4.8 586 3 4.7 648 2 3.5

18 e880 2 4.8 587 3 4.8 668 3 5.4

19 e850 2 4.6 591 4 6.4 705 6 11

20 e820 3 6.6 583 5 7.9 824 11 24

21 e800 3 6.5 573 6 9.3 1,120 25 76

22 e850 2 4.6 567 6 9.2 1,610 68 296

23 e800 2 4.3 577 6 9.3 1,880 94 477

24 e750 2 4.0 599 6 9.7 1,600 50 216

25 e700 2 3.8 631 6 10 1,360 23 84

26 e600 2 3.2 662 6 11 1,220 14 46

27 e550 1 1.5 643 4 6.9 1,150 9 28

28 e600 1 1.6 590 3 4.8 1,170 14 44

29 e700 1 1.9 -- -- -- 1,230 14 46

30 e760 2 4.1 -- -- -- 1,160 9 28

31 e780 3 6.3 -- -- -- 1,110 7 21

TOTAL 25,709 -- 175.6 17,460 -- 183.9 27,310 -- 1,484.2

MEAN 829 2 5.7 624 4 6.6 881 13 48

MAX 1,280 5 17 740 6 11 1,880 94 477

MIN 550 1 1.5 567 3 4.6 516 1 1.4
Data 65

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

APRIL MAY JUNE

1 1,090 8 24 3,450 15 140 9,610 82 2,130

2 1,070 10 29 3,250 15 132 8,650 63 1,470

3 1,070 10 29 3,140 15 127 7,490 48 971

4 1,080 7 20 3,200 15 130 6,650 39 700

5 1,090 9 26 3,430 19 176 6,260 35 592

6 1,100 9 27 3,860 24 250 6,130 37 612

7 1,230 13 43 4,090 25 276 5,800 30 470

8 1,460 21 83 4,150 24 269 5,230 26 367

9 1,660 30 134 4,070 25 275 4,780 24 310

10 1,900 36 185 4,020 22 239 4,290 22 255

11 2,150 40 232 4,040 20 218 3,910 17 179

12 2,570 51 354 4,160 20 225 3,640 16 157

13 3,060 54 446 4,200 20 227 3,480 15 141

14 3,430 50 463 4,150 21 235 3,540 14 134

15 3,530 43 410 4,110 22 244 3,750 16 162

16 3,360 45 408 4,080 20 220 3,930 19 202

17 3,130 24 203 4,220 20 228 3,950 18 192

18 3,040 23 189 5,090 41 563 3,860 15 156

19 3,170 23 197 7,120 135 2,600 3,710 14 140

20 3,530 26 248 9,150 192 4,740 3,560 12 115

21 4,300 51 592 8,780 131 3,110 3,450 11 102

22 5,590 96 1,450 8,110 98 2,150 3,450 12 112

23 6,980 116 2,190 7,630 74 1,520 3,480 12 113

24 7,020 93 1,760 8,080 80 1,750 3,190 10 86

25 6,330 58 991 9,240 112 2,790 3,000 11 89

26 5,630 39 593 9,200 93 2,310 2,900 11 86

27 5,010 30 406 9,210 83 2,060 2,770 9 67

28 4,480 26 314 9,300 80 2,010 2,630 10 71

29 4,080 20 220 9,410 78 1,980 2,520 10 68

30 3,740 17 172 9,430 85 2,160 2,430 8 52

31 -- -- -- 9,590 89 2,300 -- -- --

TOTAL 96,880 -- 12,438 184,960 -- 35,654 132,040 -- 10,301

MEAN 3,229 36 415 5,966 55 1,150 4,401 22 343

MAX 7,020 116 2,190 9,590 192 4,740 9,610 82 2,130

MIN 1,070 7 20 3,140 15 127 2,430 8 52
66 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

JULY AUGUST SEPTEMBER

1 2,330 8 50 987 4 11 624 2 3.4

2 2,210 8 48 941 4 10 620 2 3.3

3 2,110 8 46 895 4 9.7 597 2 3.2

4 2,010 8 43 855 3 6.9 578 1 1.6

5 1,940 8 42 824 3 6.7 568 1 1.5

6 1,850 8 40 830 3 6.7 591 1 1.6

7 1,830 8 40 968 4 10 602 2 3.3

8 1,800 7 34 1,060 4 11 597 2 3.2

9 1,760 6 29 1,020 4 11 595 2 3.2

10 1,670 6 27 974 5 13 592 2 3.2

11 1,570 6 25 946 4 10 580 2 3.1

12 1,500 6 24 918 3 7.4 571 2 3.1

13 1,470 6 24 894 2 4.8 565 2 3.1

14 1,550 6 25 901 2 4.9 551 2 3.0

15 1,570 5 21 914 2 4.9 539 2 2.9

16 1,480 3 12 887 2 4.8 532 2 2.9

17 1,390 4 15 875 2 4.7 525 2 2.8

18 1,310 4 14 850 2 4.6 521 2 2.8

19 1,250 3 10 824 2 4.4 521 2 2.8

20 1,190 4 13 776 2 4.2 513 2 2.8

21 1,110 4 12 740 2 4.0 511 2 2.8

22 1,060 3 8.6 724 2 3.9 517 2 2.8

23 1,030 3 8.3 709 3 5.7 515 2 2.8

24 1,010 3 8.2 698 3 5.7 509 2 2.7

25 997 3 8.1 679 3 5.5 501 3 4.1

26 967 3 7.8 661 3 5.4 497 3 4.0

27 1,080 5 15 651 2 3.5 494 3 4.0

28 1,180 8 25 635 2 3.4 494 3 4.0

29 1,120 5 15 622 2 3.4 495 3 4.0

30 1,090 4 12 621 2 3.4 497 2 2.7

31 1,020 4 11 618 2 3.3 -- -- --

TOTAL 45,454 -- 713 25,497 -- 197.9 16,412 -- 90.7

MEAN 1,466 5 23 822 3 6.4 547 2 3.0

MAX 2,330 8 50 1,060 5 13 624 3 4.1

MIN 967 3 7.8 618 2 3.3 494 1 1.5

Total for water year 2009 (unrounded sum of daily values): streamflow–639,772 ft3/s (annual runoff–1,269,000 acre-ft); suspended-sediment 

discharge–61,765.56 tons.
Data 67

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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 1,500 4 16 1,680 4 18 2,100 6 34

2 1,500 4 16 1,710 5 23 2,140 5 29

3 1,500 5 20 1,820 7 34 2,190 5 30

4 1,530 6 25 1,890 8 41 2,050 4 22

5 1,580 6 26 1,870 8 40 1,870 4 20

6 1,590 6 26 1,830 8 40 2,010 3 16

7 1,590 5 21 1,810 8 39 2,060 3 17

8 1,580 4 17 1,950 11 58 2,060 3 17

9 1,590 4 17 2,010 12 65 2,020 3 16

10 1,610 4 17 1,990 12 64 1,980 3 16

11 1,630 4 18 1,950 12 63 1,980 4 21

12 1,650 4 18 1,960 12 64 1,910 5 26

13 1,660 4 18 2,670 30 216 1,850 6 30

14 1,680 4 18 3,600 49 476 e1,200 5 16

15 1,710 4 18 3,290 23 204 e700 4 7.6

16 1,710 5 23 3,100 14 117 e620 3 5.0

17 1,710 6 28 2,950 12 96 e750 2 4.0

18 1,700 6 28 2,810 10 76 e1,000 2 5.4

19 1,730 6 28 2,690 8 58 e1,200 5 16

20 1,740 6 28 2,590 7 49 e1,200 10 32

21 1,780 6 29 2,530 6 41 e1,250 17 57

22 1,780 6 29 2,470 6 40 e1,300 25 88

23 1,760 6 29 2,360 5 32 e1,400 33 125

24 1,740 5 23 2,270 4 25 e1,500 40 162

25 1,720 4 19 2,120 4 23 e1,550 42 176

26 1,720 4 19 2,150 3 17 e1,600 38 164

27 1,700 4 18 2,130 3 17 e1,650 30 134

28 1,690 4 18 2,040 3 17 e1,700 23 106

29 1,700 4 18 2,090 4 23 e1,750 22 104

30 1,690 4 18 2,100 5 28 e1,700 30 138

31 1,680 4 18 -- -- -- e1,700 28 129

TOTAL 51,450 -- 664 68,430 -- 2,104 49,990 -- 1,763

MEAN 1,160 5 21 2,281 10 70 1,613 13 57

MAX 1,780 6 29 3,600 49 476 2,190 42 176

MIN 1,500 4 16 1,680 3 17 620 2 4.0
68 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

JANUARY FEBRUARY MARCH

1 e1,700 24 110 e1750 6 28 1,520 8 33

2 e1,750 21 99 e1700 6 28 1,600 12 52

3 e1,700 21 96 e1650 6 27 1,700 14 64

4 e1,550 23 96 e1600 6 26 1,880 22 112

5 e1,600 24 104 1,600 6 26 1,850 18 90

6 e1,800 24 117 1,590 6 26 1,780 13 62

7 e2,000 33 178 1,580 6 26 1,640 8 35

8 e2,300 60 373 1,520 6 25 1,630 8 35

9 e2,800 96 726 1,530 6 25 1,560 9 38

10 e2,750 93 691 1,510 6 24 1,420 8 31

11 e2,600 119 835 1,480 5 20 1,370 8 30

12 e2,350 56 355 1,470 5 20 1,390 8 30

13 e2,300 24 149 1,430 4 15 1,460 9 35

14 e2,250 21 128 1,390 4 15 1,510 9 37

15 2,250 19 115 1,390 4 15 1,550 10 42

16 2,190 16 95 1,410 5 19 1,680 14 64

17 2,030 13 71 1,450 5 20 1,650 12 53

18 1,920 12 62 1,490 5 20 1,610 11 48

19 1,760 10 48 1,500 8 32 1,650 9 40

20 1,590 8 34 1,520 11 45 1,900 15 77

21 1,580 7 30 1,490 12 48 2,520 78 531

22 e1,800 6 29 1,450 13 51 3,290 118 1,050

23 e1,850 8 40 1,490 14 56 4,070 146 1,600

24 e1,750 22 104 1,670 22 99 3,460 87 813

25 e1,700 40 184 1,960 59 312 2,900 43 337

26 e1,500 27 109 1,880 36 183 2,600 26 183

27 e1,200 9 29 1,710 16 74 2,350 29 184

28 e1,400 4 15 1,540 10 42 2,340 21 133

29 e1,600 3 13 -- -- -- 2,470 22 147

30 e1,700 3 14 -- -- -- 2,400 39 253

31 e1,800 5 24 -- -- -- 2,240 30 181

TOTAL 59,070 -- 5,073 43,750 -- 1,347 62,990 --. 6,420

MEAN 1,905 27 164 1,562 11 48 2,032 28 207

MAX 2,800 119 835 1,960 59 312 4,070 146 1,600

MIN 1,200 3 13 1,390 4 15 1,370 8 30
Data 69

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

APRIL MAY JUNE

1 2,250 17 103 6,140 28 464 17,300 116 5,420

2 2,190 15 89 5,800 26 407 16,000 95 4,100

3 2,200 14 83 5,670 29 444 14,000 82 3,100

4 2,230 15 90 5,930 30 480 12,400 81 2,710

5 2,250 15 91 6,400 39 674 11,700 82 2,590

6 2,270 16 98 7,060 47 896 11,500 76 2,360

7 2,520 22 150 7,490 53 1,070 11,400 62 1,910

8 3,070 51 423 7,570 46 940 10,500 53 1,500

9 3,610 81 790 7,330 40 792 9,690 54 1,410

10 4,240 103 1,180 7,170 32 619 8,750 45 1,060

11 4,550 102 1,250 7,140 32 617 7,830 37 782

12 5,230 130 1,840 7,380 35 697 7,160 30 580

13 6,060 140 2,290 7,650 37 764 6,770 26 475

14 6,490 127 2,230 7,510 35 710 6,740 26 473

15 6,240 74 1,250 7,380 30 598 7,100 32 613

16 5,760 38 591 7,300 29 572 7,680 43 892

17 5,310 39 559 7,470 33 666 7,860 46 976

18 5,150 40 556 8,720 85 2,000 7,800 40 842

19 5,490 50 741 11,800 274 8,730 7,640 37 763

20 6,070 62 1,020 15,300 394 16,300 7,370 29 577

21 7,360 115 2,290 15,800 255 10,900 7,210 26 506

22 9,250 230 5,740 14,600 170 6,700 7,470 42 847

23 11,200 300 9,070 13,700 121 4,480 7,900 51 1,090

24 11,500 205 6,370 14,300 129 4,980 7,080 29 554

25 10,300 113 3,140 16,800 205 9,300 6,400 23 397

26 9,340 76 1,920 17,300 185 8,640 6,000 23 373

27 8,490 60 1,380 16,900 141 6,430 5,750 18 279

28 7,740 46 961 16,800 134 6,080 5,400 18 262

29 7,160 37 715 16,800 124 5,620 5,080 16 219

30 6,630 30 537 17,100 126 5,820 4,830 14 183

31 -- -- -- 17,300 130 6,070 -- -- --

TOTAL 172,150 -- 47,547 331,610 -- 113,460 260,310 -- 37,843

MEAN 5,738 79 1,580 10,700 99 3,660 8,677 45 1,260

MAX 11,500 300 9,070 17,300 394 16,300 17,300 116 5,420

MIN 2,190 14 83 5,670 26 407 4,830 14 183
70 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2008 through 

September 2009.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligram per liter; min, minimum; ton/d, ton 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)

JULY AUGUST SEPTEMBER

1 4,620 12 150 2,270 7 43 1,500 7 28

2 4,420 11 131 2,170 7 41 1,490 6 24

3 4,180 11 124 2,050 7 39 1,440 6 23

4 4,000 10 108 1,940 7 37 1,390 6 23

5 3,870 9 94 1,860 8 40 1,360 5 18

6 3,770 8 81 1,870 9 45 1,370 5 18

7 3,750 8 81 2,240 12 73 1,370 5 18

8 3,760 7 71 2,880 57 443 1,350 4 15

9 3,750 7 71 2,680 23 166 1,330 4 14

10 3,620 6 59 2,440 17 112 1,330 4 14

11 3,450 6 56 2,290 11 68 1,320 4 14

12 3,280 6 53 2,160 8 47 1,300 5 18

13 3,270 7 62 2,090 8 45 1,290 5 17

14 3,540 10 96 2,090 8 45 1,280 5 17

15 3,650 7 69 2,150 8 46 1,260 6 20

16 3,450 5 47 2,180 8 47 1,240 6 20

17 3,210 5 43 2,190 8 47 1,210 6 20

18 3,030 5 41 2,140 9 52 1,200 6 19

19 2,900 5 39 2,070 9 50 1,200 6 19

20 2,780 5 38 1,950 8 42 1,190 5 16

21 2,650 4 29 1,860 8 40 1,210 5 16

22 2,530 5 34 1,770 7 33 1,240 5 17

23 2,430 5 33 1,720 7 33 1,240 5 17

24 2,360 5 32 1,690 7 32 1,220 5 16

25 2,300 4 25 1,660 6 27 1,190 6 19

26 2,240 4 24 1,600 6 26 1,180 6 19

27 2,440 6 40 1,560 6 25 1,170 5 16

28 2,850 13 100 1,520 5 21 1,180 5 16

29 2,730 13 96 1,470 5 20 1,190 5 16

30 2,600 12 84 1,450 6 23 1,210 5 16

31 2,410 8 52 1,460 6 24 -- -- --

TOTAL 99,840 -- 2,063 61,470 -- 1,832 38,450 -- 543

MEAN 3,221 7 67 1,983 10 59 1,282 5 18

MAX 4,620 13 150 2,880 57 443 1,500 7 28

MIN 2,240 4 24 1,450 5 20 1,170 4 14

Total for water year 2009 (unrounded sum of daily values): streamflow–1,299,510 ft3/s (annual runoff–2,578,000 acre-ft); suspended-sediment 

discharge–220,659 tons.
Data 71

Table 9. Seasonal daily maximum, minimum, and mean turbidity at Mill Creek near Anaconda, Montana, April through 

September 2009.

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbol: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 -- -- -- 6.5 3.5 4.0 14 5.5 8.5

2 -- -- -- 6.5 3.5 4.5 8.5 4.5 5.5

3 -- -- -- 10 3.5 5.0 6.0 4.0 4.5

4 -- -- -- 9.5 4.0 6.0 5.0 3.5 4.0

5 -- -- -- 9.5 5.0 6.5 5.5 3.0 4.0

6 -- -- -- 8.5 5.5 7.0 8.5 3.5 5.0

7 -- -- -- 8.5 6.5 7.0 4.5 2.5 3.5

8 -- -- -- 10 5.5 6.5 7.0 2.5 3.5

9 -- -- -- 7.5 5.0 6.0 4.5 2.5 3.0

10 -- -- -- 8.0 5.0 6.0 5.5 2.5 3.0

11 -- -- -- 8.5 5.0 6.0 5.5 2.5 3.0

12 -- -- -- 8.5 6.0 7.0 5.0 2.5 3.0

13 8.5 5.5 6.5 6.5 5.0 5.5 4.0 2.5 3.0

14 7.0 4.5 5.5 8.0 4.5 5.5 4.5 3.0 3.5

15 6.0 4.0 4.5 7.0 4.5 5.0 5.0 3.0 3.5

16 5.0 3.5 4.0 9.0 4.5 6.0 5.5 3.0 4.0

17 4.5 3.5 4.0 26 6.0 9.5 5.5 3.5 4.5

18 6.0 3.0 4.0 30 11 16 5.5 3.0 4.0

19 7.0 3.5 4.5 30 15 21 4.0 2.5 3.0

20 21 4.0 8.5 31 10 17 4.0 3.0 3.5

21 29 7.5 14 12 7.0 8.5 4.5 2.5 3.5

22 29 9.5 17 8.0 5.5 6.0 5.0 2.5 3.5

23 26 8.5 12 8.0 4.5 5.5 7.0 2.5 3.5

24 9.5 6.5 7.5 31 6.5 14 3.5 2.5 3.0

25 8.0 5.5 6.5 31 12 17 4.5 2.5 3.0

26 6.5 4.5 5.5 20 7.0 13 5.0 2.5 3.5

27 6.0 4.0 4.5 16 5.5 9.5 6.0 2.5 3.0

28 5.0 4.0 4.0 22 5.0 12 4.0 2.5 3.0

29 5.0 4.0 4.0 11 5.0 7.5 4.5 2.5 3.0

30 4.5 3.5 4.0 20 6.5 10 5.0 2.5 3.0

31 -- -- -- 24 9.0 15 -- -- --

MONTH1 29 3.0 6.7 31 3.5 8.9 14 2.5 3.7
72 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 9. Seasonal daily maximum, minimum, and mean turbidity at Mill Creek near Anaconda, Montana, April through 

September 2009.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbol: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 11 2.5 5.0 5.5 2.0 3.0 3.5 2.0 3.0

2 7.5 2.5 4.5 4.5 2.0 3.0 4.0 2.0 3.0

3 8.5 2.5 4.5 5.0 2.0 3.0 4.0 2.0 3.0

4 8.0 2.5 3.5 4.0 2.0 3.0 4.0 2.0 3.0

5 6.0 2.5 3.5 4.5 2.5 3.0 4.5 2.5 3.0

6 6.5 2.0 3.5 4.5 2.5 3.0 5.0 2.0 3.0

7 7.5 2.0 3.5 9.0 3.0 5.0 4.0 2.0 3.0

8 5.5 2.0 3.0 4.0 2.5 3.5 4.0 2.0 3.0

9 7.0 2.0 3.5 4.5 2.5 3.0 4.5 2.5 3.0

10 6.0 1.5 3.0 4.0 2.5 3.0 4.5 2.5 3.0

11 5.5 1.5 2.5 4.0 2.5 3.0 4.5 2.5 3.0

12 4.5 1.5 2.5 4.0 2.0 3.0 4.0 2.5 3.0

13 5.5 2.0 3.0 3.5 2.0 2.5 -- -- --

14 3.5 1.5 2.0 3.5 2.5 3.0 -- -- --

15 4.5 1.5 2.5 4.0 2.5 3.0 -- -- --

16 6.0 1.5 3.0 4.5 2.5 3.0 4.5 2.5 3.5

17 6.5 2.0 4.0 4.0 2.0 2.5 4.5 2.0 3.0

18 7.0 1.5 4.0 3.5 2.0 2.5 3.5 2.0 3.0

19 6.0 1.0 3.0 3.5 2.0 2.5 4.0 2.0 3.0

20 4.5 1.5 2.0 4.0 2.0 2.5 4.5 2.5 3.0

21 6.5 1.5 3.0 3.5 2.0 2.5 4.5 2.0 3.0

22 5.5 1.5 3.5 4.0 2.0 2.5 4.0 2.0 2.5

23 4.5 1.5 2.5 19 2.0 4.0 3.5 2.5 2.5

24 4.0 1.5 2.5 6.0 2.5 3.5 4.0 2.0 2.5

25 4.5 2.5 3.0 4.0 2.0 3.0 3.5 2.5 3.0

26 4.5 2.5 3.0 4.0 2.0 3.0 3.5 2.0 2.5

27 5.0 2.5 3.5 4.0 2.0 3.0 3.5 2.0 2.5

28 5.0 2.5 3.5 4.0 2.0 3.0 3.0 2.0 2.5

29 5.0 2.5 3.5 4.0 2.0 2.5 4.0 2.0 2.5

30 6.0 2.5 3.5 4.0 2.0 3.0 -- -- 3.0

31 5.5 2.5 3.5 5.5 2.5 3.5 -- -- --

MONTH1 11 1.0 3.3 19 2.0 3.0 5.0 2.0 2.9

1

For months with missing daily values, the means are calculated using available values.
Data 73

Table 10. Seasonal daily maximum, minimum, and mean turbidity at Willow Creek near Anaconda, Montana, June through 

September 2009.

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JUNE JULY AUGUST

1 -- -- -- 8.5 4.0 5.0 6.5 4.0 5.0

2 -- -- -- 6.5 4.0 4.5 9.0 4.0 5.0

3 -- -- -- 6.0 3.5 4.5 7.5 4.0 4.5

4 -- -- -- 7.5 3.0 3.5 9.5 4.0 5.0

5 -- -- -- 13 3.0 5.5 6.5 4.0 4.5

6 -- -- -- 16 4.0 7.5 6.0 4.0 4.5

7 -- -- -- 10 5.5 7.5 37 4.5 14

8 -- -- -- 9.0 4.5 6.0 7.0 4.5 5.5

9 -- -- -- 5.5 3.5 4.5 6.0 4.0 4.5

10 -- -- -- 5.5 3.5 4.5 5.5 3.5 4.5

11 8.5 6.5 8.0 6.0 4.0 4.5 5.5 3.5 4.5

12 9.5 6.0 7.5 12 4.0 4.5 6.5 3.5 4.0

13 8.5 6.0 7.0 110 5.0 17 8.0 3.5 4.0

14 9.0 6.0 6.5 7.5 4.0 5.0 5.5 4.0 4.5

15 9.5 6.0 7.0 6.5 4.0 5.0 8.0 3.0 4.5

16 9.5 5.5 6.5 7.5 4.0 4.5 9.0 2.5 4.5

17 8.5 5.5 6.5 9.5 3.5 4.5 4.0 2.5 3.0

18 9.0 5.5 6.0 8.5 4.0 4.5 5.0 3.0 3.5

19 7.0 5.0 6.0 6.5 4.0 4.5 5.0 3.0 3.5

20 9.0 5.5 6.5 7.5 4.0 5.0 8.0 3.5 4.5

21 9.0 5.0 6.0 7.0 4.0 5.0 8.0 4.0 5.0

22 10 5.0 6.5 9.0 4.5 5.5 5.5 4.0 4.5

23 10 5.0 6.5 8.0 5.0 6.0 6.5 4.0 5.0

24 8.0 5.0 6.0 7.0 4.5 5.5 8.5 3.5 4.5

25 9.5 5.0 6.5 6.5 4.0 4.5 -- -- --

26 9.0 4.5 6.0 8.5 4.0 5.0 -- -- --

27 8.0 4.5 5.5 8.5 4.0 5.0 -- -- --

28 7.0 4.0 5.0 5.5 4.0 4.5 -- -- --

29 7.0 4.0 5.0 7.0 3.5 4.5 -- -- --

30 9.5 4.0 5.0 5.0 4.0 4.5 -- -- --

31 -- -- -- 5.5 4.0 4.5 -- -- --

MONTH1 10 4.0 6.3 110 3.0 5.4 37 2.5 4.9
74 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Day

Maximum Minimum Mean

SEPTEMBER

1 -- -- --

2 -- -- --

3 4.0 2.5 3.0

4 4.0 3.0 3.0

5 5.5 3.0 3.5

6 3.5 3.0 3.0

7 4.0 3.0 3.0

8 4.5 3.0 3.0

9 4.0 3.0 3.5

10 5.0 3.0 3.5

11 5.5 3.0 3.5

12 5.0 3.0 3.5

13 4.5 3.0 3.5

14 4.5 3.0 3.5

15 5.5 3.0 3.5

16 8.0 3.0 3.5

17 7.0 3.0 3.5

18 5.5 3.0 3.5

19 9.0 3.0 3.5

20 7.5 3.0 4.0

21 8.5 3.0 4.5

22 7.0 3.0 4.0

23 4.5 3.0 3.5

24 8.5 3.5 4.0

25 6.0 3.0 3.5

26 5.0 3.0 3.5

27 4.0 2.5 3.0

28 3.5 2.5 2.5

29 4.0 2.5 2.5

30 9.0 2.5 4.0

31 -- -- --

MONTH1 9.0 2.5 3.4

1

For months with missing daily values, the means are calculated using available values.

Table 10. Seasonal daily maximum, minimum, and mean turbidity at Willow Creek 

near Anaconda, Montana, June through September 2009.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 

900 nanometers with a detection angle of 90 +/- 2.5 degrees to incident beam, reported in formazin 

nephelometric units (FNU). Symbols: --, no data]
Data 75

Table 11. Seasonal daily maximum, minimum, and mean turbidity at Warm Springs Creek near Anaconda, Montana, April through 

September 2009.

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 -- -- -- -- -- -- -- -- --

2 -- -- -- -- -- -- -- -- --

3 -- -- -- 21 3.5 4.5 -- -- --

4 -- -- -- 21 3.5 5.5 -- -- --

5 -- -- -- 7.0 3.5 4.5 -- -- --

6 -- -- -- 5.5 3.0 4.0 -- -- --

7 -- -- -- 4.5 3.5 4.0 -- -- --

8 -- -- -- 6.0 3.0 3.5 -- -- --

9 -- -- -- 4.0 3.0 3.5 -- -- --

10 -- -- -- 6.0 3.0 3.5 -- -- --

11 -- -- -- 5.0 3.0 3.5 -- -- --

12 -- -- -- 9.0 3.5 4.5 4.5 3.0 4.0

13 -- -- -- 6.0 3.0 4.0 5.5 3.0 4.0

14 5.0 4.0 4.0 8.5 3.0 4.0 9.0 3.5 4.5

15 9.0 4.0 4.5 14 3.5 5.0 8.5 4.5 6.0

16 9.5 4.0 5.5 8.0 3.5 5.0 7.5 4.5 6.0

17 5.0 3.5 4.0 11 3.5 5.0 7.5 5.0 6.0

18 5.5 3.0 4.0 -- -- -- 7.5 4.5 6.0

19 6.0 3.5 4.0 -- -- -- 7.0 4.0 4.5

20 7.0 4.0 5.0 37 13 22 6.0 4.0 4.5

21 -- -- -- 22 6.0 8.5 6.0 3.5 4.0

22 -- -- -- 9.5 5.0 6.0 7.0 3.5 4.5

23 -- -- -- 10 5.0 7.0 5.5 3.5 4.0

24 -- -- -- 36 9.0 21 4.5 3.0 3.5

25 -- -- -- 32 11 15 4.5 3.0 3.5

26 -- -- -- 16 7.0 10 6.0 3.0 4.0

27 -- -- -- 10 6.5 8.0 5.0 3.0 3.5

28 -- -- -- 12 7.0 9.5 4.5 3.0 3.5

29 -- -- -- 21 10 14 4.0 2.5 3.0

30 -- -- -- -- -- -- 4.0 2.5 3.0

31 -- -- -- -- -- -- -- -- --

MONTH1 9.5 3.0 4.4 37 3.0 7.4 9.0 2.5 4.3
76 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 11. Seasonal daily maximum, minimum, and mean turbidity at Warm Springs Creek near Anaconda, Montana, April through 

September 2009.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 4.5 2.5 3.0 7.0 4.0 4.5 5.5 4.0 4.5

2 7.0 3.0 3.5 8.0 4.0 5.0 6.5 4.0 5.0

3 5.0 2.5 3.0 9.5 4.0 4.5 6.0 4.0 5.0

4 3.5 2.5 3.0 11 3.5 5.0 5.5 4.0 4.5

5 4.0 2.5 3.0 18 4.0 7.0 7.0 4.5 5.0

6 3.5 2.5 3.0 18 5.0 10 6.0 4.0 4.5

7 4.5 2.5 3.0 21 5.5 11 5.0 4.0 4.5

8 4.5 2.5 3.0 9.5 4.5 6.5 5.0 4.0 4.5

9 3.5 2.5 3.0 6.0 4.0 5.0 6.0 4.0 4.5

10 3.5 2.5 3.0 6.5 4.0 4.5 5.0 4.0 4.5

11 5.0 2.5 3.0 5.0 4.0 4.5 5.0 4.0 4.5

12 32 2.5 3.5 9.5 4.0 5.0 5.0 4.0 4.5

13 16 3.0 4.0 6.5 4.0 4.5 5.0 4.0 4.5

14 4.0 2.5 3.0 5.5 4.0 5.0 5.0 4.0 4.5

15 4.0 2.5 3.5 10 4.0 5.0 5.5 4.0 4.5

16 4.5 3.0 3.5 8.0 4.5 5.0 5.0 3.5 4.0

17 6.0 2.5 3.5 9.0 4.0 5.0 4.5 4.0 4.5

18 4.0 2.0 2.5 30 6.0 9.0 5.5 3.5 4.0

19 3.5 2.5 3.0 8.5 4.0 6.0 4.5 4.0 4.5

20 3.0 2.0 2.5 9.5 4.0 7.0 5.0 4.0 4.5

21 3.5 2.0 2.5 9.0 3.5 5.0 5.0 4.0 4.5

22 5.5 2.0 2.5 5.5 4.0 4.5 5.5 4.0 4.5

23 4.0 2.0 2.5 7.5 4.0 5.0 5.5 4.0 4.5

24 7.0 1.5 3.5 7.0 4.0 5.5 5.0 4.0 4.5

25 9.5 3.5 5.0 6.5 4.5 5.5 8.5 4.5 5.5

26 9.5 4.0 5.5 5.5 4.0 4.5 6.5 4.5 5.0

27 24 4.5 8.0 5.0 4.0 4.5 9.0 5.0 6.0

28 76 4.0 7.5 5.5 4.0 4.5 9.0 4.5 5.5

29 6.5 4.0 5.0 5.0 4.0 4.5 8.5 3.5 4.5

30 5.0 4.0 4.5 5.5 4.0 4.5 9.0 4.5 5.5

31 5.0 4.0 4.5 12 4.5 5.5 -- -- --

MONTH1 76 1.5 3.7 30 3.5 5.6 9.0 3.5 4.7

1

For months with missing daily values, the means are calculated using available values.
Data 77

Table 12. Seasonal daily maximum, minimum, and mean turbidity at Lost Creek near Anaconda, Montana, April through 

September 2009.

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 -- -- -- 6.5 3.0 4.0 48 15 27

2 -- -- -- 7.0 3.0 4.0 22 12 15

3 -- -- -- 8.0 3.5 4.5 14 9.0 11

4 -- -- -- 8.5 4.0 5.5 17 8.5 10

5 -- -- -- 8.0 4.0 5.0 12 6.5 9.0

6 -- -- -- 7.0 3.0 4.5 18 7.0 10

7 -- -- -- 5.0 2.5 3.5 10 5.0 7.0

8 -- -- -- 4.5 2.5 3.5 10 5.0 6.5

9 -- -- -- 5.5 2.5 3.5 10 5.0 6.0

10 -- -- -- 6.0 2.5 3.5 10 4.5 6.5

11 -- -- -- 6.5 3.0 4.0 7.5 3.5 5.0

12 -- -- -- 8.5 4.5 6.0 7.0 3.0 4.5

13 -- -- -- 6.5 3.5 5.0 8.5 2.5 4.0

14 6.0 2.5 3.5 7.0 3.5 5.0 14 2.5 5.0

15 6.0 2.5 3.0 9.0 3.5 6.0 34 5.0 12

16 6.5 2.5 3.5 10 4.0 6.0 9.0 3.5 5.5

17 8.5 2.5 4.0 10 4.5 6.0 30 3.5 5.5

18 9.0 3.5 5.5 38 7.0 15 9.5 3.0 5.0

19 6.5 3.0 4.5 45 20 31 9.0 2.5 4.5

20 9.0 3.0 4.5 45 13 24 8.0 3.0 4.5

21 17 5.5 8.0 20 8.0 11 8.5 2.0 4.0

22 19 7.5 11 12 5.5 7.5 10 2.5 4.5

23 22 7.0 13 9.5 4.5 6.5 9.0 2.5 3.5

24 8.5 5.0 6.0 41 8.0 17 8.5 2.0 3.5

25 7.5 3.5 5.0 39 12 19 7.5 2.0 3.5

26 8.5 3.5 5.0 18 7.5 11 6.0 1.5 3.0

27 7.0 3.5 4.5 25 7.5 12 6.5 1.5 2.5

28 5.0 3.5 4.0 32 9.5 17 8.0 1.5 3.0

29 19 3.5 5.5 49 12 23 5.5 1.5 2.5

30 7.0 3.5 4.0 59 16 29 6.0 1.5 2.5

31 -- -- -- 52 14 24 -- -- --

MONTH1 22 2.5 5.6 59 2.5 11 48 1.5 6.5
78 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 12. Seasonal daily maximum, minimum, and mean turbidity at Lost Creek near Anaconda, Montana, April through 

September 2009.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 5.5 1.5 2.5 3.5 1.0 1.5 2.0 0.5 1.0

2 8.0 1.5 3.0 2.0 .5 1.0 2.0 .5 1.0

3 5.5 1.5 2.0 8.0 .5 1.5 2.0 .5 1.0

4 4.5 1.0 2.5 4.5 1.5 2.5 2.0 .5 1.0

5 6.0 1.0 2.5 4.0 1.0 2.0 1.5 .5 1.0

6 5.5 1.5 2.5 61 1.5 5.5 6.0 .5 1.5

7 6.5 1.5 2.5 31 7.0 13 2.0 .5 1.0

8 7.5 1.0 2.5 7.0 3.0 4.0 1.5 .5 1.0

9 5.0 .5 2.0 38 2.5 6.0 1.0 <.5 .5

10 5.5 1.0 2.0 5.0 2.5 3.5 1.0 <.5 .5

11 5.5 .5 2.0 4.0 2.5 3.0 2.0 <.5 .5

12 5.5 1.0 2.0 3.5 2.0 2.5 1.0 <.5 .5

13 5.5 1.0 2.5 6.0 2.0 3.0 1.0 <.5 .5

14 3.5 1.0 1.5 4.0 2.0 3.0 -- -- --

15 4.0 1.0 2.0 5.5 2.0 3.0 -- -- --

16 7.0 1.0 2.0 3.5 1.5 2.0 -- -- --

17 4.5 1.0 2.0 3.5 1.5 2.0 3.0 <.5 2.0

18 5.5 1.0 2.0 3.0 1.5 2.0 3.0 <.5 2.0

19 5.0 .5 2.0 4.5 1.5 2.0 3.5 <.5 2.0

20 4.0 .5 1.5 4.0 1.5 2.5 3.0 .5 1.0

21 3.0 .5 1.5 5.0 1.5 2.5 2.0 <.5 .5

22 4.0 .5 1.5 5.5 1.5 2.0 5.5 <.5 1.0

23 5.5 .5 1.5 5.0 1.5 2.5 1.5 <.5 .5

24 3.0 .5 1.0 3.0 1.0 2.0 4.5 .5 1.5

25 5.5 .5 1.5 3.5 1.0 2.0 4.5 1.0 2.5

26 58 .5 7.0 2.5 1.0 1.5 4.5 1.0 3.0

27 8.0 2.0 3.5 3.0 1.0 1.5 5.0 1.0 2.5

28 3.0 1.5 2.0 3.0 1.0 1.5 2.0 .5 1.5

29 3.0 1.0 1.5 14 1.5 2.5 4.5 .5 2.0

30 2.5 1.0 1.5 4.0 1.0 1.5 -- -- --

31 3.0 .5 1.5 8.5 1.0 2.0 -- -- --

MONTH1 58 .5 2.2 61 .5 2.8 6.0 .5 1.3

1

For months with missing daily values, the means are calculated using available values.
Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.[Abbreviations: E, estimated; μg/L, microgram per liter; mg/L, milligram per liter; mm, millimeter. Symbols: <, less than laboratory reporting level; --, no data]

Site 

number 

(fig. 1)

Site name Date Time

Hardness, 

filtered 

(mg/L as CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium 

filtered 

(mg/L)

Total nitrogen, 

unfiltered 

(mg/L)

Total 

phosphorous, 

unfiltered 

(mg/L)

12323700 Mill Creek at Opportunity 08/17/2009

08/17/2009

15001505

7071

20.020.5

4.784.89

----

----

12323750 Silver Bow Creek at Warm Springs 07/14/2009

07/14/2009

08100815

120120

37.937.7

7.197.18

----

----

12323840 Lost Creek near Anaconda 04/27/2009

04/27/2009

13551400

9698

29.030.1

5.675.62

----

----

12324200 Clark Fork at Deer Lodge 05/19/2009

05/19/2009

10451050

150150

45.645.6

9.039.06

----

----

12324400 Clark Fork above Little Blackfoot, near Garrison 03/24/2009

03/24/2009

1155

1200

190200

56.258.4

13.213.4

----

----

12324680 Clark Fork at Goldcreek 10/21/2008

10/21/2008

14001405

180180

52.954.2

11.311.4

----

----

12334550 Clark Fork at Turah Bridge, near Bonner 05/18/2009

05/18/2009

09300940

9190

25.725.5

6.426.34

0.39

.33

0.071

.073

06/03/200906/03/2009

07450750

7171

20.820.9

4.634.64

----

----

12334570 Clark Fork Bypass near Bonner 06/15/2009

06/15/2009

12301235

9596

27.627.7

6.426.42

----

----

12340000 Blackfoot River near Bonner 05/31/2009

05/31/2009

13001310

7980

21.221.3

6.346.40

.23.23

.060.062

12340500 Clark Fork above Missoula 04/27/2009

04/27/2009

16001605

9098

24.227.2

7.207.40

.37.38

.062.065

06/23/200906/23/2009

17451755

100100

28.628.1

7.717.53

.27.22

.054.059

06/24/200906/24/2009

09400945

100

110

28.829.2

7.697.87

----

----

12352500 Bitterroot River near Missoula 06/09/2009

06/09/2009

08000805

2323

6.756.73

1.501.50

.19.19

.027.029

12354500 Clark Fork at St. Regis 05/27/2009

05/27/2009

14301440

4749

13.313.7

3.473.51

.28.32

.100.105
Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.—Continued [Abbreviations: E, estimated; μg/L, microgram per liter; mg/L, milligram per liter; mm, millimeter. Symbols: <, less than laboratory reporting level; --, no data] Site number (fig. 1) Site name Date Time Cadmium, filtered (μg/L) Cadmium, unfiltered recoverable (μg/L) Copper, filtered (μg/L) Copper, unfiltered recoverable (μg/L) Iron, filtered (μg/L) 

r

12323700 Mill Creek at Opportunity 08/17/2009 08/17/2009 1500 1505 0.04 <.02 0.09 E.06 1.7 1.1 E2.3 E2.3 6870 12323750 Silver Bow Creek at Warm Springs 07/14/2009 07/14/2009 0810 0815 .03 .02 .11 .08 4.1 4.4 7.3 7.5 4141 12323840 Lost Creek near Anaconda 04/27/2009 04/27/2009 1355 1400 .02 .02 <.06 <.06 1.2 1.5 4.8 E3.9 97 12324200 Clark Fork at Deer Lodge 05/19/2009 05/19/2009 1045 1050 .07 .08 --.57 12.1 13.9 101 161 2122 12324400 Clark Fork above Little Blackfoot, near Garrison 03/24/2009 03/24/2009 1155 1200 .08 .09 .38 .28 9.1 9.4 59.4 58.5 1819 12324680 Clark Fork at Goldcreek 10/21/2008 10/21/2008 1400 1405 .03 .04 .08 .10 3.8 3.6 19.8 16.5 6E4 12334550 Clark Fork at Turah Bridge, near Bonner 05/18/2009 05/18/2009 0930 0940 .03 .03 .13 -- 3.5 3.7 21.9-- 2424 

06/03/2009 06/03/2009 0745 0750 .05 .05 .23 .21 8.0 8.0 41.1 40.2 4142 

12334570 Clark Fork Bypass near Bonner 06/15/2009 06/15/2009 1230 1235 .05 .05 .19 .18 5.3 5.7 27.9 30.4 1921 12340000 Blackfoot River near Bonner 05/31/2009 05/31/2009 1300 1310 <.02 <.02 <.06 <.06 E.83 E.74 E3.6 E3.2 2014 12340500 Clark Fork above Missoula 04/27/2009 04/27/2009 1600 1605 .04 .02 .13 .13 3.2 2.7 20.8 21.2 2722 

06/23/2009 06/23/2009 1745 1755 .04 .04 .11 .12 5.2 5.1 20.9 23.2 2019 06/24/200906/24/2009

09400945

.04.04

.11.15

5.05.2

20.721.6

1718

12352500 Bitterroot River near Missoula 06/09/2009

06/09/2009

08000805

<.02<.02

<.06<.06

E.90

1.1

<4.0<4.0

5657

12354500 Clark Fork at St. Regis 05/27/2009

05/27/2009

14301440

.02

E.02

.15.16

3.93.8

25.025.6

2929
Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.—Continued[Abbreviations: E, estimated; μg/L, microgram per liter; mg/L, milligram per liter; mm, millimeter. Symbols: <, less than laboratory reporting level; --, no data]

Site 

number 

(fig. 1)

Site name Date Time

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

t

12323700 Mill Creek at Opportunity 08/17/2009

08/17/2009

15001505

0.33

.33

6.72.6

10.210.4

E1.5

<2.0

E1.7E1.9

12323750 Silver Bow Creek at Warm Springs 07/14/2009

07/14/2009

08100815

.98

1.00

32.933.1

60.962.0

E1.9

2.6

6.56.7

12323840 Lost Creek near Anaconda 04/27/2009

04/27/2009

13551400

.63.50

.9.9

5.94.8

<2.0<2.0

2.2

E1.9

12324200 Clark Fork at Deer Lodge 05/19/2009

05/19/2009

10451050

13.023.2

33.936.1

192284

6.57.2

--

119

12324400 Clark Fork above Little Blackfoot, near Garrison 03/24/2009

03/24/2009

1155

1200

7.757.76

34.134.4

148136

6.86.8

65.150.7

12324680 Clark Fork at Goldcreek 10/21/2008

10/21/2008

14001405

2.442.45

10.2

9.8

81.081.5

2.42.7

17.417.5

12334550 Clark Fork at Turah Bridge, near Bonner 05/18/2009

05/18/2009

09300940

4.58

--

7.67.5

83.9

--

2.82.8

32.8

--

06/03/200906/03/2009

07450750

6.456.33

18.218.3

121

111

6.96.8

49.849.0

12334570 Clark Fork Bypass near Bonner 06/15/2009

06/15/2009

12301235

4.404.80

16.016.0

83.884.8

5.25.5

45.146.2

12340000 Blackfoot River near Bonner 05/31/2009

05/31/2009

13001310

1.391.35

3.13.2

62.659.8

<2.0<2.0

5.24.8

12340500 Clark Fork above Missoula 04/27/2009

04/27/2009

16001605

3.523.67

8.88.8

68.970.6

--

4.9

29.931.6

06/23/200906/23/2009

17451755

3.363.39

11.611.6

71.372.0

3.83.2

30.535.5

06/24/200906/24/2009

09400945

3.123.50

9.49.2

58.257.2

3.83.6

26.528.3

12352500 Bitterroot River near Missoula 06/09/2009

06/09/2009

08000805

.60.61

10.410.6

26.927.2

E1.1E1.4

3.03.2

12354500 Clark Fork at St. Regis 05/27/2009

05/27/2009

14301440

5.227.04

4.24.2

105120

2.73.5

45.646.0
82 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 14. Precision of analyses of field replicates for water samples, Clark Fork basin, Montana.

[Abbreviations: μg/L, microgram per liter; mg/L, milligram per liter; mm, millimeter]

Constituent and reporting unit Number of 

replicate pairs

Standard 

deviation1

 (listed units)

Relative standard 

deviation 

(percent)

Within limits2

of data-quality 

objective

Calcium, filtered, mg/L 15 0.77 2.6 Yes

Magnesium, filtered, mg/L 15 .08 1.1 Yes

Total nitrogen, unfiltered, mg/L 6 .03 9.0 Yes

Total phosphorous, unfiltered, mg/L 6 .00 3.8 Yes

Arsenic, filtered, μg/L 15 .55 6.3 Yes

Arsenic, unfiltered recoverable, μg/L 13 .28 2.8 Yes

Cadmium, filtered, μg/L 15 .01 21 Yes3

Cadmium, unfiltered recoverable, μg/L 13 .02 19 Yes

Copper, filtered, μg/L 15 .39 8.4 Yes

Copper, unfiltered recoverable, μg/L 14 11 41 No4

Iron, filtered, μg/L 15 1.7 6.0 Yes

Iron, unfiltered recoverable, μg/L 14 120 15 Yes

Lead, filtered, μg/L 14 .02 14 Yes

Lead, unfiltered recoverable, μg/L 14 2.0 46 No4

Manganese, filtered, μg/L 15 .86 6.2 Yes

Manganese, unfiltered recoverable, μg/L 14 18 22 No4

Zinc, filtered, μg/L 14 .30 8.8 Yes

Zinc, unfiltered recoverable, μg/L 13 3.0 12 Yes

Sediment, suspended, percent finer than 0.062 mm 15 2.7 4.3 Yes

Sediment, suspended, mg/L 15 3.4 5.7 Yes

1

Standard deviation is calculated using one-half the laboratory reporting level for censored values (less than the laboratory reporting level).

2

Data-quality objective for an acceptable level of precision is a maximum relative deviation of 20 percent for field replicate analyses (table 3).

3

Exceedance of data-quality objective resulted from a statistical artifact of calculating the difference between one replicate sample pair for which one value 

was twice the laboratory reporting level and one was censored. Because analytical variation, in percent, can be large at very low concentrations, the precision 

estimate may not be representative of analytical performance at detectable concentrations. When this one replicate pair was excluded, the other 14 replicate pairs 

had an acceptable relative standard deviation for filtered cadmium of 14 percent.

4

Exceedance of data-quality objective resulted from a poor comparison between one replicate pair collected on May 19, 2009, at Clark Fork at Deer Lodge 

during high-flow conditions. When this one replicate pair was excluded, the other thirteen replicate pairs had an acceptable relative standard deviation for unfiltered copper of 5.1 percent, unfiltered lead of 12 percent, and unfiltered manganese of 6.2 percent.
Data 83

Table 15. Precision of analyses of laboratory replicates for water samples, upper Clark Fork basin, Montana.

[Abbreviations: μg/L, microgram per liter; mg/L, milligram per liter]

Constituent and reporting unit

Number of 

replicate 

pairs

Standard 

deviation1

(listed units)

Relative standard 

deviation, 

(percent)

Within limits2

of data-quality 

objective

Calcium, filtered, mg/L 8 0.51 1.4 Yes

Magnesium, filtered, mg/L 8 .12 1.5 Yes

Arsenic, filtered, μg/L 8 .53 3.9 Yes

Arsenic, unfiltered recoverable, μg/L 8 .46 2.6 Yes

Cadmium, filtered, μg/L 8 .01 16 Yes

Cadmium, unfiltered recoverable, μg/L 8 .02 11 Yes

Copper, filtered, μg/L 8 .20 3.5 Yes

Copper, unfiltered recoverable, μg/L 8 1.4 3.6 Yes

Iron, filtered, μg/L 8 .48 1.7 Yes

Iron, unfiltered recoverable, μg/L 8 7.3 .99 Yes

Lead, filtered, μg/L 8 .01 11 Yes

Lead, unfiltered recoverable, μg/L 8 .08 1.5 Yes

Manganese, filtered, μg/L 8 .14 .74 Yes

Manganese, unfiltered recoverable, μg/L 8 .44 .47 Yes

Zinc, filtered, μg/L 8 .26 6.1 Yes

Zinc, unfiltered recoverable, μg/L 8 1.5 4.3 Yes

1

Standard deviation is calculated using laboratory reporting level for censored values.

2

Data-quality objective for an acceptable level of precision is a maximum relative deviation of 20 percent for laboratory replicate analyses (table 3).

Table 16. Recovery efficiency for analyses of laboratory-spiked deionized-water blank samples.

[Abbreviation: μg/L, microgram per liter]

Constituent and reporting unit Number of 

samples

95-percent confidence 

interval for spike recovery 

(percent)

Mean spike 

recovery 

(percent)

Within limits1 of 

data-quality 

objective

Arsenic, filtered, μg/L 5 92.3–110 101 Yes

Arsenic, unfiltered recoverable, μg/L 5 94.9–99.1 97.0 Yes

Cadmium, filtered, μg/L 5 97.4–107 102 Yes

Cadmium, unfiltered recoverable, μg/L 5 93.6–101 97.2 Yes

Copper, filtered, μg/L 5 92.0–113 102 Yes

Copper, unfiltered recoverable, μg/L 5 94.0–97.0 96.0 Yes

Iron, filtered, μg/L 5 91.4–112 102 Yes

Iron, unfiltered recoverable, μg/L 5 78.8–130 104 No2

Lead, filtered, μg/L 5 96.0–107 102 Yes

Lead, unfiltered recoverable, μg/L 5 96.1–101 98.4 Yes

Manganese, filtered, μg/L 5 103–106 105 Yes

Manganese, unfiltered recoverable, μg/L 5 94.6–105 99.7 Yes

Zinc, filtered, μg/L 5 104–118 111 Yes

Zinc, unfiltered recoverable, μg/L 5 88.5–98.1 93.3 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

2

Exceedance of data quality objective resulted from using a low-concentration spiked solution (20 μg) on a constituent (iron, unfiltered recoverable) with a 

high laboratory reporting level (+/- 14 μg/L).
84 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 17. Recovery efficiency for analyses of laboratory-spiked stream samples, upper Clark Fork basin, Montana.

[Abbreviation: μg/L, microgram per liter]

Constituent and reporting unit Number of 

samples

95-percent confidence 

interval for spike recovery 

(percent)

Mean spike recovery 

(percent)

Within limits1 of 

data-quality objective

Arsenic, filtered, μg/L 5 97.7–114 106 Yes

Arsenic, unfiltered recoverable, μg/L 5 89.6–111 100 Yes

Cadmium, filtered, μg/L 5 101–112 106 Yes

Cadmium, unfiltered recoverable, μg/L 5 89.5–99.8 94.7 Yes

Copper, filtered, μg/L 5 91.2–101 96.2 Yes

Copper, unfiltered recoverable, μg/L 5 87.8–95.0 91.4 Yes

Iron, filtered, μg/L 5 89.7–124 107 Yes

Iron, unfiltered recoverable, μg/L 5 86.9–118 102 Yes

Lead, filtered, μg/L 5 97.0–103 100 Yes

Lead, unfiltered recoverable, μg/L 5 98.8–101 100 Yes

Manganese, filtered, μg/L 5 88.0–106 97.0 Yes

Manganese, unfiltered recoverable, μg/L 5 81.7–104 92.8 Yes

Zinc, filtered, μg/L 5 104–124 114 Yes

Zinc, unfiltered recoverable, μg/L 5 80.4–99.2 89.8 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).
Table 18. Analyses of field blanks for water samples.[Abbreviations: E, estimated; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25 degrees Celsius; mg/L, milligram per liter. Symbols: <, less than laboratory re

Date Time

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Total 

nitrogen, 

unfiltered, 

(mg/L)

Total 

phosphorous, 

unfiltered, 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

10/20/2008 1830 5.4 2 E0.01 <0.012 -- -- <0.06 <0.20 03/02/2009 1100 5.6 2 E.01 <.012 <0.10 <0.008 <.06 <.20 03/20/2009 1400 5.5 2 E.01 <.012 -- -- <.06 <.20 03/26/2009 1500 6.0 2 E.01 <.012 <.10 <.008 <.06 <.20 04/15/2009 0840 6.1 1 <.02 <.012 <.10 <.008 <.06 <.20 04/29/2009 1200 5.5 2 <.02 <.012 -- -- <.06 <.20 05/11/2009 1535 5.5 3 E.02 <.012 <.10 <.008 <.06 <.20 05/18/2009 2100 5.6 2 E.01 <.012 -- -- <.06 <.20 06/02/2009 2100 5.4 2 E.01 <.012 -- -- <.06 <.20 06/23/2009 1900 5.6 2 E.02 <.012 -- -- <.06 <.20 07/14/2009 1025 5.7 2 E.01 <.012 -- -- <.06 <.20 08/17/2009 2200 5.6 2 E.01 <.012 -- -- <.06 <.20 

Date

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)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

10/20/2008 <1.0 <4.0 <4 <14 <0.06 <0.10 <0.2 <0.4 <2.0 03/02/2009 <1.0 <4.0 <4 <14 <.06 <.10 <.2 <.4 <2.0 03/20/2009 <1.0 <4.0 <4 <14 <.06 <.10 <.2 <.4 <2.0 03/26/2009 <1.0 <4.0 <4 <14 <.06 <.10 <.2 <.4 <2.0 04/15/2009 <1.0 <4.0 <4 <14 <.06 <.10 <.2 <.4 <2.0 04/29/2009 <1.0 <4.0 <4 <14 <.06 <.10 <.2 <.4 <2.0 05/11/2009 <1.0 <4.0 <4 <14 <.06 .16 <.2 E.3 <2.0 05/18/2009 <1.0 <4.0 <4 <14 <.06 <.10 <.2 <.4 <2.0 06/02/2009 <1.0 <4.0 <4 E13 <.06 <.10 <.2 <.4 <2.0 06/23/2009 <1.0 <4.0 <4 <14 <.06 <.10 <.2 <.4 <2.0 07/14/2009 <1.0 <4.0 <4 <14 <.06 <.10 <.2 <.4 <2.0 08/17/2009 <1.0 <4.0 <4 <14 <.06 <.10 <.2 <.4 <2.0 
Table 19. Bed-sediment data for the upper Clark Fork basin, Montana, August 2009. [Trace-element concentrations in bed sediment were determined for the fine-grained fraction (material less than 0.063 millimeter in diameter). Reported concentrations are the maliquots from each composite sample. Abbreviation: μg/g, microgram per gram of dry sample weight. Symbol: <, less than laboratory reporting level] Site number (fig. 1) Site name Number of composite samples Concentration (μg/g) Arsenic Cadmium Chromium Copper Iron Lead Manga

12323600 Silver Bow Creek at Opportunity 3 59 7.5 50.0 1,040 32,700 267 1,73

12323750 Silver Bow Creek at Warm Springs 3 87 5.2 41.4 306 27,000 70 3,6412323800 Clark Fork near Galen 3 86 4.2 44.6 1,080 29,200 106 4,90

461415112450801 Clark Fork below Lost Creek, near Galen 3 95 5.2 42.4 1,410 29,600 136 3,47461559112443301 Clark Fork at county bridge, near Racetrack 3 96 5.9 45.2 1,480 31,700 148 2,72

461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 3 100 5.0 39.2 1,330 30,400 137 3,08

12324200 Clark Fork at Deer Lodge 3 102 4.7 50.7 1,270 33,400 142 2,6812324400 Clark Fork above Little Blackfoot River, near Garrison 3 83 5.5 52.8 1,270 32,400 140 2,95

12324680 Clark Fork at Goldcreek 3 61 4.2 55.3 958 32,100 124 1,8612331800 Clark Fork near Drummond 3 66 3.1 41.9 443 43,700 92 1,80

12334550 Clark Fork at Turah Bridge, near Bonner 3 43 2.8 42.5 363 25,900 74 2,34

12340000 Blackfoot River near Bonner 3 <.2 .1 35.2 21 20,800 10 6612340500 Clark Fork above Missoula 3 33 2.8 40.7 421 24,900 65 1,41
Data 87

Table 20. Recovery efficiency for analyses of standard reference materials for bed-sediment samples.

[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. Abbreviations: μg/g, microgram per gram of dry sample weight; SRM, standard reference material (agricultural soils)]

Constituent Number of 

analyses

Dilution 

ratio

Certified 

concentration 

(μg/g)

Mean SRM 

recovery

(percent)

95-percent 

confidence interval 

for SRM recovery 

(percent)

SRM sample 2709

Arsenic 10 1:10 17.7 36.5 35.8–37.2

Cadmium 10 1:10 .4 91.7 88.3–95.1

Chromium 10 1:10 130 90.5 84.6–96.4

Copper 10 1:10 35 89.6 82.5–96.6

Iron 10 1:10 35,000 103.5 98.3–109

Lead 10 1:10 19 51.0 49.8–52.2

Manganese 10 1:10 538 106.1 101–111

Nickel 10 1:10 88 91.5 88.5–94.4

Zinc 10 1:10 106 99.6 95.8–104

SRM sample 2711

Arsenic 10 1:10 105 86.5 83.5–89.5

Cadmium 10 1:10 41.7 99.6 96.2–103

Chromium 10 1:10 47 100.3 94.9–106

Copper 10 1:10 114 107.5 104–111

Iron 10 1:10 28,900 98.3 94.5–102

Lead 10 1:10 1,160 98.1 95.0–101

Manganese 10 1:10 638 96.4 92.9–99.8

Nickel 10 1:10 20.6 84.9 82.0–87.8

Zinc 10 1:10 350 98.7 95.2–102
Table 21. Analyses of procedural blanks for bed-sediment samples. [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 residue. Abbreviation: μg/mL, microgram per milliliter. Symbol: <, less than minimum reporting level for liquid-phase concentration, in μg/mL] Site number (fig. 1) Site name Dilution ratio Trace-element concentration (μg/mL) Arsenic Cadmium Chromium Copper Iron Lead Manganese 

12323600 Silver Bow Creek at Opportunity 1:10 <0.002 <0.0002 <0.04 <0.03 <0.04 <0.002 <0.009 12323750 Silver Bow Creek at Warm Springs 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 12323800 Clark Fork near Galen 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 461415112450801 Clark Fork below Lost Creek, near Galen 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 461559112443301 Clark Fork at county bridge, near Racetrack 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 12324200 Clark Fork at Deer Lodge 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 12324400 Clark Fork above Little Blackfoot River, near Garrison 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 12324680 Clark Fork at Goldcreek 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 12331800 Clark Fork near Drummond 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 12334550 Clark Fork at Turah Bridge, near Bonner 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 12340000 Blackfoot River near Bonner 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 12340500 Clark Fork above Missoula 1:10 <.002 <.0002 <.04 <.03 <.04 <.002 <.009 
Data 89

Table 22. Biological data for the upper Clark Fork basin, Montana, August 2009.—Continued

[Analyses are for the whole-body tissue of aquatic insects. Composite samples were 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, microgram per gram of dry sample weight; spp., species. Symbol: <, less than minimum reporting level for solid-phase concentration, in μg/g]

Taxon

Number of 

composite 

samples

Concentration (μg/g)

Arsenic Cadmium Chromium Copper Iron Lead ManganeseNickel Zinc

12323600--Silver Bow Creek at Opportunity

Hydropsyche cockerelli 2 25.9 4.4 4.3 358 5,160 55.9 1,180 3.2 786

Hydropsyche spp. 1 9.8 3.0 3.5 223 2,230 27.2 1,080 2.1 607

12323750--Silver Bow Creek at Warm Springs

Claassenia sabulosa 1 1.8 1.1 2.8 47.6 151 0.6 98.1 0.5 400

Hydropsyche cockerelli 2 9.3 .4 1.0 24.4 851 2.9 738 .8 169

Hydropsyche occidentalis 1 18.0 .6 2.0 33.2 1,380 5.1 1,750 1.3 191

Hydropsyche spp. 1 14.0 .5 2.5 35.9 1,100 4.2 1,190 1.0 159

12323800--Clark Fork near Galen

Hydropsyche occidentalis 3 16.7 1.3 2.1 144 2,440 11.9 1,860 3.2 225

Hydropsyche spp. 1 14.2 1.3 1.9 126 2,110 10.6 1,520 2.7 197

461415112450801--Clark Fork below Lost Creek, near Galen

Hydropsyche occidentalis 1 20.9 1.5 2.5 208 2,760 17.3 1,820 3.0 277

Hydropsyche spp. 1 14.5 1.3 .9 153 1,810 13.2 1,380 2.3 228

461559112443301--Clark Fork at county bridge, near Racetrack

Hydropsyche occidentalis 2 15.5 2.0 2.8 161 2,060 15.4 1,680 2.3 269

Hydropsyche spp. 1 12.8 1.6 3.9 144 1,610 13.4 1,400 2.0 228

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Arctopsyche grandis 1 11.8 7.1 12.9 151 1,500 12.4 1,190 2.3 489

Claassenia sabulosa 1 3.1 2.4 1.7 73.4 297 1.9 115 .4 330

Hydropsyche cockerelli 1 18.0 2.0 3.7 247 3,010 21.9 1,120 2.5 279

Hydropsyche occidentalis 2 16.5 1.6 2.0 186 2,300 17.7 1,650 2.0 260

12324200--Clark Fork at Deer Lodge

Arctopsyche grandis 1 8.3 3.1 4.7 90.5 844 9.5 1,010 1.1 315

Hydropsyche occidentalis 3 12.1 2.0 2.0 149 1,890 15.8 1,350 1.6 235

12324400--Clark Fork above Little Blackfoot River, near Garrison

Arctopsyche grandis 1 6.0 3.2 1.9 65.7 694 6.6 990 0.7 253

Hydropsyche cockerelli 1 11.1 4.0 3.4 158 2,150 18.8 1,500 1.7 284

Hydropsyche occidentalis 2 12.9 2.5 1.3 141 1,940 17.6 1,580 1.7 265
90 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 22. Biological data for the upper Clark Fork basin, Montana, August 2009.—Continued

[Analyses are for the whole-body tissue of aquatic insects. Composite samples were 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, microgram per gram of dry sample weight; spp., species. Symbol: <, less than minimum reporting level for solid-phase concentration, in μg/g]

Taxon

Number of 

composite 

samples

Concentration (μg/g)

Arsenic Cadmium Chromium Copper Iron Lead ManganeseNickel Zinc

12324680--Clark Fork at Goldcreek

Arctopsyche grandis 3 6.1 2.7 1.4 66.4 1,140 6.2 1,060 1.1 244

Claassenia sabulosa 3 1.3 1.5 .4 65.8 183 .8 138 .3 254

Hydropsyche cockerelli 1 9.8 2.4 3.3 133 2,240 13.7 1,200 1.9 248

Hydropsyche occidentalis 2 7.8 1.7 2.9 98.9 1,790 10.3 1,330 1.6 222

12331800--Clark Fork near Drummond

Arctopsyche grandis 3 5.0 1.9 2.3 39.6 1,070 7.7 924 0.8 246

Claassenia sabulosa 2 1.1 1.4 .5 57.9 248 1.1 122 .3 276

Hydropsyche cockerelli 2 6.9 1.2 1.5 62.4 1,770 12.9 999 1.3 209

Hydropsyche occidentalis 1 6.0 1.3 3.2 54.7 1,660 12.0 1,110 1.3 222

12334550--Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 3 5.3 1.6 1.2 39.7 1,130 6.1 727 1.1 214

Claassenia sabulosa 2 1.1 2.3 .4 78.3 268 1.1 176 .3 234

Hydropsyche cockerelli 2 5.8 1.2 2.2 59.2 1,730 8.8 814 1.6 202

Hydropsyche occidentalis 2 5.6 1.5 3.5 59.1 1,720 9.7 1,040 1.6 234

12340000--Blackfoot River near Bonner

Arctopsyche grandis 1 1.6 0.3 0.5 13.2 761 0.9 528 1.3 156

Claassenia sabulosa 2 .5 .2 <1.6 44.7 180 .2 114 .3 236

Hydropsyche cockerelli 1 3.1 .3 2.4 14.3 2,390 2.3 615 2.5 148

Hydropsyche occidentalis 2 2.2 .3 2.2 17.4 2,010 1.8 686 2.0 150

12340500--Clark Fork above Missoula

Arctopsyche grandis 3 6.1 2.0 2.8 67.5 1,780 7.6 833 1.7 246

Claassenia sabulosa 1 .5 1.5 <2.9 52.0 189 .7 57.8 .3 295

Hydropsyche cockerelli 2 8.7 1.4 3.4 99.3 2,810 11.6 939 2.4 258

Hydropsyche occidentalis 1 7.4 1.4 3.0 80.7 2,470 11.4 1,180 2.1 271
Data 91

Table 23. Recovery efficiency for analyses of standard reference material for biota samples.

[Abbreviations: μg/g, microgram per gram of dry sample weight; SRM, standard reference material (lobster 

hepatopancreas)]

Constituent Number of 

analyses

Certified 

concentration 

(μg/g)

Mean 

SRM recovery

(percent)

95-percent confidence 

interval for SRM recovery

(percent)

SRM sample TORT-2

Arsenic 12 21.6 99.4 98.7–100

Cadmium 12 26.7 96.0 94.6–96.5

Chromium 12 .77 120 92.2–148

Copper 12 106 103 102–103

Iron 12 105 102 99.2–105

Lead 12 .35 116 106–127

Manganese 12 13.6 102 100–104

Nickel 12 2.5 95.1 93.9–96.3

Zinc 12 180 105 104–106
Table 24. Analyses of procedural blanks for biota samples. [Procedural blanks were not diluted prior to analyses. Abbreviation: μg/mL, microgram per milliliter. Symbol: <, less than minimum reporting level for liquid-phase concentrati

Site number (fig. 1) Site name Dilution ratio Trace-element concentration (μg/mL) Arsenic Cadmium Chromium Copper Iron Lead Mangane

12323600 Silver Bow Creek at Opportunity 1:1 <0.001 <0.0003 <0.023 <0.034 <0.06 <0.006 <0.001 12323750 Silver Bow Creek at Warm Springs 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 12323800 Clark Fork near Galen 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 461415112450801 Clark Fork below Lost Creek, near Galen 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 461559112443301 Clark Fork at county bridge, near Racetrack 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 12324200 Clark Fork at Deer Lodge 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 12324400 Clark Fork above Little Black- foot River, near Garrison 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 12324680 Clark Fork at Goldcreek 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 12331800 Clark Fork near Drummond 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 12334550 Clark Fork at Turah Bridge, near Bonner 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 12340000 Blackfoot River near Bonner 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 12340500 Clark Fork above Missoula 1:1 <.001 <.0003 <.023 <.034 <.06 <.006 <.001 
Data 93

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323230--Blacktail Creek at Harrison Avenue, at Butte

Period of record for water-quality data: March 1993–August 1995, December 1996–August 2003, December 2004–September 2009

Streamflow, instantaneous (ft3/s) 123 156 1.9 14 8.4

pH, onsite (standard units) 123 8.4 7.3 7.8 7.8

Specific conductance, onsite (μS/cm) 123 412 116 264 262

Temperature, water (°C) 123 17.5 1.5 8.2 8.5

Hardness, filtered (mg/L as CaCO3) 123 150 38 104 110

Calcium, filtered (mg/L) 123 41.8 10.6 29.7 30.4

Magnesium, filtered (mg/L) 123 11.0 2.71 7.21 7.29

Arsenic, filtered (μg/L) 122 13 1 4.0 3.0

Arsenic, unfiltered recoverable (μg/L) 123 18 1 25.4 4.4

Cadmium, filtered (μg/L) 121 .5 <.04 2.05 <.1

Cadmium, unfiltered recoverable (μg/L) 123 .11 <.01 2

.04 <1

Copper, filtered (μg/L) 122 10.0 <1.0 23.7 3.2

Copper, unfiltered recoverable (μg/L) 123 52.0 1.5 6.8 5.5

Iron, filtered (μg/L) 123 640 15 178 160

Iron, unfiltered recoverable (μg/L) 123 4,220 139 662 555

Lead, filtered (μg/L) 123 2.80 <.08 2.20 <1.00

Lead, unfiltered recoverable (μg/L) 123 47.0 <1.00 21.89 .67

Manganese, filtered (μg/L) 123 144 14.2 40.9 37.5

Manganese, unfiltered recoverable (μg/L) 123 240 23.5 57.5 50.1

Zinc, filtered (μg/L) 122 11 <1.0 23.5 2.8

Zinc, unfiltered recoverable (μg/L) 123 130 <10 28.7 4

Sediment, suspended (percent finer than 0.062 mm) 123 97 50 82 83

Sediment, suspended concentration (mg/L) 123 139 1 12 7

Sediment, suspended discharge (ton/d) 123 59 .01 1.1 .16
94 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323250--Silver Bow Creek below Blacktail Creek, at Butte

Period of record for water-quality data: March 1993–August 1995, December 1996–September 2009

Streamflow, instantaneous (ft3/s) 131 134 13 29 24

pH, onsite (standard units) 131 8.1 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 131 691 226 467 478

Temperature, water (°C) 131 20.0 1.0 10.4 9.5

Hardness, filtered (mg/L as CaCO3) 131 220 66 148 150

Calcium, filtered (mg/L) 131 62.7 19.0 42.3 43.5

Magnesium, filtered (mg/L) 131 14.6 4.51 10.4 10.8

Arsenic, filtered (μg/L) 131 13 2.3 6.3 6.0

Arsenic, unfiltered recoverable (μg/L) 131 45 3 10.6 9.0

Cadmium, filtered (μg/L) 131 6.2 .05 1.06 .80

Cadmium, unfiltered recoverable (μg/L) 131 6.0 .09 1.43 1.10

Copper, filtered (μg/L) 131 303 3.2 35.5 14.1

Copper, unfiltered recoverable (μg/L) 131 550 9.5 81.8 32.3

Iron, filtered (μg/L) 131 270 10 89.2 65.0

Iron, unfiltered recoverable (μg/L) 131 7,400 85 866 573

Lead, filtered (μg/L) 131 2.4 <.5 2.47 .23

Lead, unfiltered recoverable (μg/L) 131 250 .64 12.6 3.32

Manganese, filtered (μg/L) 131 1,700 21.4 347 270

Manganese, unfiltered recoverable (μg/L) 131 1,600 25.9 390 326

Zinc, filtered (μg/L) 131 2,200 16.0 346 240

Zinc, unfiltered recoverable (μg/L) 131 2,200 28.8 418 265

Sediment, suspended (percent finer than 0.062 mm) 130 98 42 84 86

Sediment, suspended concentration (mg/L) 130 405 2 22 10

Sediment, suspended discharge (ton/d) 130 70 .08 2.6 .68
Data 95

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323600--Silver Bow Creek at Opportunity

Period of record for water-quality data: March 1993–August 1995, December 1996–September 2009

Streamflow, instantaneous (ft3/s) 134 361 13 74 51

pH, onsite (standard units) 133 9.5 7.2 8.4 8.3

Specific conductance, onsite (μS/cm) 133 633 202 415 400

Temperature, water (°C) 133 22.5 0.0 9.4 9.5

Hardness, filtered (mg/L as CaCO3) 133 240 60 149 140

Calcium, filtered (mg/L) 133 71.6 18.5 44.0 43.0

Magnesium, filtered (mg/L) 133 15.0 3.42 9.41 9.01

Arsenic, filtered (μg/L) 133 34 1 11.1 10.3

Arsenic, unfiltered recoverable (μg/L) 133 235 9.5 25.6 17.0

Cadmium, filtered (μg/L) 132 41.0 <.1 21.14 .70

Cadmium, unfiltered recoverable (μg/L) 133 49.0 .38 22.04 1.29

Copper, filtered (μg/L) 132 450 13.7 45.3 35.0

Copper, unfiltered recoverable (μg/L) 133 3,900 31.1 201 102

Iron, filtered (μg/L) 133 307 <3 247 26

Iron, unfiltered recoverable (μg/L) 132 24,100 240 1,490 780

Lead, filtered (μg/L) 133 5.1 <.5 2.72 .33

Lead, unfiltered recoverable (μg/L) 133 650 5.38 37.0 15.0

Manganese, filtered (μg/L) 133 9,300 49.7 428 343

Manganese, unfiltered recoverable (μg/L) 133 10,000 110 545 430

Zinc, filtered (μg/L) 132 13,000 11.2 296 152

Zinc, unfiltered recoverable (μg/L) 133 15,000 69.7 516 301

Sediment, suspended (percent finer than 0.062 mm) 134 95 37 79 83

Sediment, suspended concentration (mg/L) 134 801 5 47 18

Sediment, suspended discharge (ton/d) 134 781 .18 19 2.4
96 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323670--Mill Creek near Anaconda

Period of record for water-quality data: December 2004–September 2009

Streamflow, instantaneous (ft3/s) 40 213 7.4 60 26

pH, onsite (standard units) 40 8.6 7.7 8.1 8.1

Specific conductance, onsite (μS/cm) 40 203 56 131 133

Temperature, water (°C) 40 17.0 0.0 8.3 8.0

Hardness, filtered (mg/L as CaCO3) 40 98 24 57 60

Calcium, filtered (mg/L) 40 25.9 7.00 15.7 16.8

Magnesium, filtered (mg/L) 40 8.01 1.45 4.28 4.22

Arsenic, filtered (μg/L) 40 32.9 7.3 17.2 16.1

Arsenic, unfiltered recoverable (μg/L) 40 34.8 9.0 18.8 17.6

Cadmium, filtered (μg/L) 39 .11 <.04 2.05 .04

Cadmium, unfiltered recoverable (μg/L) 40 .19 .04 .08 .07

Copper, filtered (μg/L) 40 5.1 .79 2.4 2.2

Copper, unfiltered recoverable (μg/L) 40 10.6 1.3 4.1 3.6

Iron, filtered (μg/L) 40 125 21 50 42

Iron, unfiltered recoverable (μg/L) 40 619 89 198 164

Lead, filtered (μg/L) 40 .24 <.08 2.13 .11

Lead, unfiltered recoverable (μg/L) 40 3.12 .19 .79 .59

Manganese, filtered (μg/L) 40 11 3.4 5.9 6.0

Manganese, unfiltered recoverable (μg/L) 40 36.6 7.4 14.4 12.6

Zinc, filtered (μg/L) 40 4.0 .73 1.5 1.4

Zinc, unfiltered recoverable (μg/L) 40 9.2 1.0 3.0 2.6

Sediment, suspended (percent finer than 0.062 mm) 40 81 28 64 68

Sediment, suspended concentration (mg/L) 40 29 1 6 3

Sediment, suspended discharge (ton/d) 40 13 .02 1.8 .17
Data 97

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323700--Mill Creek at Opportunity

Period of record for water-quality data: March 2003–September 2009

Streamflow, instantaneous (ft3/s) 56 261 0.43 36 8.8

pH, onsite (standard units) 56 8.2 7.7 8.0 8.0

Specific conductance, onsite (μS/cm) 56 230 59 147 153

Temperature, water (°C) 56 20.0 0.0 9.6 9.5

Hardness, filtered (mg/L as CaCO3) 56 100 24 63 67

Calcium, filtered (mg/L) 56 28.0 7.01 17.5 18.8

Magnesium, filtered (mg/L) 56 7.83 1.56 4.56 4.67

Arsenic, filtered (μg/L) 56 55.1 9.0 23.6 23.0

Arsenic, unfiltered recoverable (μg/L) 56 53.5 10 27.0 27.1

Cadmium, filtered (μg/L) 56 .13 .02 .06 .07

Cadmium, unfiltered recoverable (μg/L) 56 .85 .04 .15 .10

Copper, filtered (μg/L) 56 6.1 1.1 3.1 2.8

Copper, unfiltered recoverable (μg/L) 56 38.8 1.5 7.0 4.6

Iron, filtered (μg/L) 56 94 16 50 45

Iron, unfiltered recoverable (μg/L) 56 1,960 44 300 145

Lead, filtered (μg/L) 56 .32 <.08 2.14 .14

Lead, unfiltered recoverable (μg/L) 56 12.7 .07 1.51 .44

Manganese, filtered (μg/L) 56 32.8 2.2 8.0 6.0

Manganese, unfiltered recoverable (μg/L) 56 113 3.5 19.7 13.0

Zinc, filtered (μg/L) 56 7.7 1.3 3.1 2.8

Zinc, unfiltered recoverable (μg/L) 56 41 1.7 6.9 5.0

Sediment, suspended (percent finer than 0.062 mm) 56 90 26 68 76

Sediment, suspended concentration (mg/L) 56 107 1 12 2

Sediment, suspended discharge (ton/d) 56 55 <.01 23.6 .04
98 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323710--Willow Creek near Anaconda

Period of record for water-quality data: December 2004–September 2009

Streamflow, instantaneous (ft3/s) 36 75 1.0 14 8.3

pH, onsite (standard units) 36 8.2 7.5 7.7 7.7

Specific conductance, onsite (μS/cm) 36 145 66 101 106

Temperature, water (°C) 36 15.5 .5 7.3 7.0

Hardness, filtered (mg/L as CaCO3) 36 51 22 36 38

Calcium, filtered (mg/L) 36 16.5 7.56 12.2 12.9

Magnesium, filtered (mg/L) 36 2.49 .78 1.40 1.41

Arsenic, filtered (μg/L) 36 24.9 9.9 15.5 14.3

Arsenic, unfiltered recoverable (μg/L) 36 27.0 9.8 16.7 15.4

Cadmium, filtered (μg/L) 35 .05 <.04 2.03 .03

Cadmium, unfiltered recoverable (μg/L) 36 .33 .02 .07 .05

Copper, filtered (μg/L) 36 4.2 .90 2.1 2.0

Copper, unfiltered recoverable (μg/L) 36 16.8 1.0 4.1 3.3

Iron, filtered (μg/L) 36 277 36 81 66

Iron, unfiltered recoverable (μg/L) 36 2,380 93 367 231

Lead, filtered (μg/L) 36 .37 .05 .14 .12

Lead, unfiltered recoverable (μg/L) 36 7.96 .10 .96 .52

Manganese, filtered (μg/L) 36 34.5 6.0 15.1 13.6

Manganese, unfiltered recoverable (μg/L) 36 99.9 15.1 28.1 24.0

Zinc, filtered (μg/L) 36 3.3 .65 1.7 1.7

Zinc, unfiltered recoverable (μg/L) 36 17.8 <2.0 23.3 2.0

Sediment, suspended (percent finer than 0.062 mm) 36 94 25 72 78

Sediment, suspended concentration (mg/L) 36 195 1 19 6

Sediment, suspended discharge (ton/d) 36 34 <.01 22.1 .14
Data 99

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323720--Willow Creek at Opportunity

Period of record for water-quality data: March 2003–September 2009

Streamflow, instantaneous (ft3/s) 56 70 4.5 17 9.4

pH, onsite (standard units) 56 8.9 7.7 8.1 8.1

Specific conductance, onsite (μS/cm) 56 371 116 278 301

Temperature, water (°C) 56 20.5 1.5 11.5 12.0

Hardness, filtered (mg/L as CaCO3) 56 170 65 122 130

Calcium, filtered (mg/L) 56 47.4 20.1 35.2 37.0

Magnesium, filtered (mg/L) 56 12.3 3.52 8.15 9.00

Arsenic, filtered (μg/L) 56 164 10.9 44.3 33.4

Arsenic, unfiltered recoverable (μg/L) 56 164 12 47.1 36.6

Cadmium, filtered (μg/L) 56 .12 <.04 2.05 .04

Cadmium, unfiltered recoverable (μg/L) 56 .52 .02 .10 .07

Copper, filtered (μg/L) 56 21.4 1.1 5.8 3.9

Copper, unfiltered recoverable (μg/L) 56 48.8 2.8 11.9 8.4

Iron, filtered (μg/L) 56 179 7 45 36

Iron, unfiltered recoverable (μg/L) 56 1,420 27 265 208

Lead, filtered (μg/L) 56 .58 .04 2.21 .19

Lead, unfiltered recoverable (μg/L) 56 14.4 .27 2.26 1.58

Manganese, filtered (μg/L) 56 200 4.1 30.1 20.2

Manganese, unfiltered recoverable (μg/L) 56 228 4.7 42.1 32.2

Zinc, filtered (μg/L) 56 19.8 .84 5.3 3.9

Zinc, unfiltered recoverable (μg/L) 56 68 1.1 12.5 10.0

Sediment, suspended (percent finer than 0.062 mm) 56 96 55 84 86

Sediment, suspended concentration (mg/L) 56 84 1 11 5

Sediment, suspended discharge (ton/d) 56 11 .02 .93 .16
100 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323750--Silver Bow Creek at Warm Springs

Period of record for water-quality data: March 1993–September 2009

Streamflow, instantaneous (ft3/s) 140 662 16 137 88

pH, onsite (standard units) 138 9.6 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 138 783 249 469 478

Temperature, water (°C) 139 25.0 .5 10.8 10.5

Hardness, filtered (mg/L as CaCO3) 138 310 97 195 200

Calcium, filtered (mg/L) 138 90.4 27.9 56.6 57.6

Magnesium, filtered (mg/L) 138 21.4 5.94 12.9 13.0

Arsenic, filtered (μg/L) 138 60 6.8 23.1 23.0

Arsenic, unfiltered recoverable (μg/L) 138 94 10 27.1 26.8

Cadmium, filtered (μg/L) 138 .31 <.04 2.06 .03

Cadmium, unfiltered recoverable (μg/L) 138 .56 <.1 2.12 .04

Copper, filtered (μg/L) 138 40.0 1.7 8.1 6.2

Copper, unfiltered recoverable (μg/L) 138 96.8 2.4 16.4 11.6

Iron, filtered (μg/L) 138 93 <5 218 15

Iron, unfiltered recoverable (μg/L) 138 3,000 36 332 252

Lead, filtered (μg/L) 138 1.0 <.08 2.12 <.6

Lead, unfiltered recoverable (μg/L) 138 41.8 <1 22.38 1.24

Manganese, filtered (μg/L) 138 875 11.8 125 90.4

Manganese, unfiltered recoverable (μg/L) 138 899 24.0 187 160

Zinc, filtered (μg/L) 138 73 <1.0 27.9 4.0

Zinc, unfiltered recoverable (μg/L) 138 180 <10 231.2 18

Sediment, suspended (percent finer than 0.062 mm) 139 97 43 82 84

Sediment, suspended concentration (mg/L) 140 229 1 11 6

Sediment, suspended discharge (ton/d) 140 279 .07 6.7 1.5
Data 101

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323760--Warm Springs Creek near Anaconda

Period of record for water-quality data: October 2005–September 2009

Streamflow, instantaneous (ft3/s) 24 573 41 139 78

pH, onsite (standard units) 24 8.8 8.0 8.5 8.6

Specific conductance, onsite (μS/cm) 24 271 125 217 240

Temperature, water (°C) 24 16.0 4.5 9.2 8.2

Hardness, filtered (mg/L as CaCO3) 24 130 59 105 110

Calcium, filtered (mg/L) 24 38.6 18.5 31.4 34.2

Magnesium, filtered (mg/L) 24 8.57 2.96 6.41 6.99

Arsenic, filtered (μg/L) 24 3.8 1.8 2.3 2.2

Arsenic, unfiltered recoverable (μg/L) 24 5.6 2.0 2.7 2.5

Cadmium, filtered (μg/L) 24 .03 <.04 2.02 .02

Cadmium, unfiltered recoverable (μg/L) 24 .07 <.06 2.04 .03

Copper, filtered (μg/L) 24 2.2 .57 21.1 .94

Copper, unfiltered recoverable (μg/L) 24 14.0 1.1 23.0 2.1

Iron, filtered (μg/L) 24 13 <6 27 6

Iron, unfiltered recoverable (μg/L) 24 543 28 121 75

Lead, filtered (μg/L) 24 .11 <.06 2.05 <.08

Lead, unfiltered recoverable (μg/L) 24 3.51 .08 .46 .26

Manganese, filtered (μg/L) 24 2.9 <.2 21.2 .9

Manganese, unfiltered recoverable (μg/L) 24 22.0 1.2 5.8 4.2

Zinc, filtered (μg/L) 24 2.8 <1.8 2.99 .47

Zinc, unfiltered recoverable (μg/L) 24 19.9 <2 23.1 1.8

Sediment, suspended (percent finer than 0.062 mm) 24 80 32 63 66

Sediment, suspended concentration (mg/L) 24 44 1 7 4

Sediment, suspended discharge (ton/d) 24 68 .16 5.5 .78
102 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323770--Warm Springs Creek at Warm Springs

Period of record for water-quality data: March 1993–September 2009

Streamflow, instantaneous (ft3/s) 103 420 2.8 95 53

pH, onsite (standard units) 102 8.7 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 102 795 139 296 304

Temperature, water (°C) 103 20.0 0.0 8.8 8.5

Hardness, filtered (mg/L as CaCO3) 102 420 40 143 150

Calcium, filtered (mg/L) 102 130 10.5 43.7 45.0

Magnesium, filtered (mg/L) 102 22.0 3.29 8.23 8.38

Arsenic, filtered (μg/L) 102 14 2 5.1 4.6

Arsenic, unfiltered recoverable (μg/L) 102 27 3 7.5 6.0

Cadmium, filtered (μg/L) 102 .1 <.04 2.03 <.1

Cadmium, unfiltered recoverable (μg/L) 102 .41 <.06 2.08 <1.0

Copper, filtered (μg/L) 102 16.0 1.0 3.4 3.0

Copper, unfiltered recoverable (μg/L) 102 147 2.3 19.7 8.6

Iron, filtered (μg/L) 102 30 <5 211 10

Iron, unfiltered recoverable (μg/L) 102 2,110 39 302 112

Lead, filtered (μg/L) 102 1.8 <.08 2.08 <.5

Lead, unfiltered recoverable (μg/L) 102 14.0 <1.0 21.92 .50

Manganese, filtered (μg/L) 102 570 22.6 125 95.7

Manganese, unfiltered recoverable (μg/L) 102 1,400 53.1 216 170

Zinc, filtered (μg/L) 102 10 <1.0 22.1 1.2

Zinc, unfiltered recoverable (μg/L) 102 60 <10 29.2 3.0

Sediment, suspended (percent finer than 0.062 mm) 103 88 43 71 71

Sediment, suspended concentration (mg/L) 103 127 1 18 8

Sediment, suspended discharge (ton/d) 103 87 .05 8.4 .99
Data 103

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen

Period of record for water-quality data: July 1988–September 2009

Streamflow, instantaneous (ft3/s) 181 1,050 14 214 129

pH, onsite (standard units) 168 9.2 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 169 720 197 420 430

Temperature, water (°C) 180 23.5 0.0 9.9 10.0

Hardness, filtered (mg/L as CaCO3) 167 370 81 183 190

Calcium, filtered (mg/L) 167 110 24.2 54.1 55.5

Magnesium, filtered (mg/L) 167 22.0 5.08 11.6 12.0

Arsenic, filtered (μg/L) 167 53 4 15.3 14.4

Arsenic, unfiltered recoverable (μg/L) 167 78 3 19.7 17.0

Cadmium, filtered (μg/L) 167 1.0 <.04 2.06 <1

Cadmium, unfiltered recoverable (μg/L) 167 3 <.1 2.19 <1

Copper, filtered (μg/L) 167 50 1.7 8.1 6.0

Copper, unfiltered recoverable (μg/L) 166 240 4.1 28.0 15.6

Iron, filtered (μg/L) 167 110 <3 216 12

Iron, unfiltered recoverable (μg/L) 167 9,200 56 486 270

Lead, filtered (μg/L) 167 3 <.08 2.15 <1

Lead, unfiltered recoverable (μg/L) 167 31.0 <1.0 23.48 1.86

Manganese, filtered (μg/L) 167 460 25.2 111 82.2

Manganese, unfiltered recoverable (μg/L) 167 1,400 47.3 233 180

Zinc, filtered (μg/L) 167 110 <1.0 29.5 5.0

Zinc, unfiltered recoverable (μg/L) 167 360 <10 238.2 20.0

Sediment, suspended (percent finer than 0.062 mm) 180 97 40 77 78

Sediment, suspended concentration (mg/L) 181 338 1 18 8

Sediment, suspended discharge (ton/d) 181 459 .12 21 2.4
104 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323840--Lost Creek near Anaconda

Period of record for water-quality data: December 2004–September 2009

Streamflow, instantaneous (ft3/s) 39 54 0.37 9.8 6.4

pH, onsite (standard units) 39 8.6 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 39 253 121 201 211

Temperature, water (°C) 39 17.0 1.0 8.3 8.5

Hardness, filtered (mg/L as CaCO3) 39 120 50 95 100

Calcium, filtered (mg/L) 39 37.1 15.7 28.8 30.0

Magnesium, filtered (mg/L) 39 7.22 2.71 5.58 6.11

Arsenic, filtered (μg/L) 39 156 2.1 9.0 4.1

Arsenic, unfiltered recoverable (μg/L) 39 3,860 2 104 4.6

Cadmium, filtered (μg/L) 38 .90 <.04 2.05 .03

Cadmium, unfiltered recoverable (μg/L) 39 147 .01 3.8 .04

Copper, filtered (μg/L) 39 90.5 1.1 4.5 1.9

Copper, unfiltered recoverable (μg/L) 39 29,100 1.7 753 4.5

Iron, filtered (μg/L) 39 25 <6 210 9

Iron, unfiltered recoverable (μg/L) 39 99,700 22 2,740 109

Lead, filtered (μg/L) 39 .18 <.06 2.06 <.12

Lead, unfiltered recoverable (μg/L) 39 1,290 .10 33.9 .45

Manganese, filtered (μg/L) 39 42.4 <.2 22.3 1.2

Manganese, unfiltered recoverable (μg/L) 39 8,830 1.2 233 4.6

Zinc, filtered (μg/L) 39 30.0 <1.8 22.0 1.1

Zinc, unfiltered recoverable (μg/L) 39 7,780 1.0 203 2.5

Sediment, suspended (percent finer than 0.062 mm) 39 97 22 58 61

Sediment, suspended concentration (mg/L) 39 58,900 1 1,520 5

Sediment, suspended discharge (ton/d) 39 1,320 <.01 235 .08
Data 105

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323850--Lost Creek near Galen

Period of record for water-quality data: March 2003–September 2009

Streamflow, instantaneous (ft3/s) 56 59 1.3 21 14

pH, onsite (standard units) 56 8.7 8.0 8.3 8.4

Specific conductance, onsite (μS/cm) 56 934 540 648 631

Temperature, water (°C) 56 26.5 0.0 11.0 10.5

Hardness, filtered (mg/L as CaCO3) 56 450 200 300 300

Calcium, filtered (mg/L) 56 122 48.5 84.2 85.2

Magnesium, filtered (mg/L) 56 35.7 17.3 21.7 21.0

Arsenic, filtered (μg/L) 56 41.8 6 14.3 12.6

Arsenic, unfiltered recoverable (μg/L) 56 43 6 15.0 14.0

Cadmium, filtered (μg/L) 55 .05 <.04 2.03 .02

Cadmium, unfiltered recoverable (μg/L) 56 .11 .01 2.04 .04

Copper, filtered (μg/L) 56 6.7 .99 2.5 2.5

Copper, unfiltered recoverable (μg/L) 56 22.5 1.6 5.8 4.4

Iron, filtered (μg/L) 56 61 <6 212 10

Iron, unfiltered recoverable (μg/L) 56 293 14 98 74

Lead, filtered (μg/L) 55 .33 <.06 2.06 <.08

Lead, unfiltered recoverable (μg/L) 56 1.30 .04 .35 .24

Manganese, filtered (μg/L) 56 54.0 1.9 14.5 13.4

Manganese, unfiltered recoverable (μg/L) 56 56.5 2.2 19.4 17.6

Zinc, filtered (μg/L) 56 3.8 <1.0 21.5 1.3

Zinc, unfiltered recoverable (μg/L) 56 9 <2 22.9 2.0

Sediment, suspended (percent finer than 0.062 mm) 56 86 18 56 60

Sediment, suspended concentration (mg/L) 56 46 2 15 14

Sediment, suspended discharge (ton/d) 56 4.2 .01 .96 .37
106 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324200--Clark Fork at Deer Lodge

Period of record for water-quality data: March 1985–September 2009

Streamflow, instantaneous (ft3/s) 233 1,920 23 296 220

pH, onsite (standard units) 181 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 216 642 234 477 500

Temperature, water (°C) 232 23.0 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3) 173 280 95 202 210

Calcium, filtered (mg/L) 173 82.0 28.2 59.5 62.0

Magnesium, filtered (mg/L) 173 18.7 5.53 12.8 13.5

Arsenic, filtered (μg/L) 183 39 6.0 14.5 13.5

Arsenic, unfiltered recoverable (μg/L) 182 215 4.8 24.1 18.0

Cadmium, filtered (μg/L) 182 2 <.1 2.08 <1

Cadmium, unfiltered recoverable (μg/L) 182 5 <.1 2.41 .05

Copper, filtered (μg/L) 183 120 3.2 11.0 8.3

Copper, unfiltered recoverable (μg/L) 181 1,500 8.2 81.9 38.0

Iron, filtered (μg/L) 183 190 <3 215 9

Iron, unfiltered recoverable (μg/L) 183 29,000 27 1,500 520

Lead, filtered (μg/L) 183 6 <.08 2.32 <1

Lead, unfiltered recoverable (μg/L) 183 200 .33 210.8 4.70

Manganese, filtered (μg/L) 183 400 1.0 42.1 33.5

Manganese, unfiltered recoverable (μg/L) 183 4,600 11.9 241 136

Zinc, filtered (μg/L) 183 230 <10 212.0 8.1

Zinc, unfiltered recoverable (μg/L) 181 1,700 4 87.5 40.0

Sediment, suspended (percent finer than 0.062 mm) 224 99 37 71 72

Sediment, suspended concentration (mg/L) 223 2,250 1 70 22

Sediment, suspended discharge (ton/d) 223 8,690 .18 149 12
Data 107

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324400--Clark Fork above Little Blackfoot River, near Garrison

Period of record for water-quality data: March 2009–September 2009

Streamflow, instantaneous (ft3/s) 7 1,380 296 697 514

pH, onsite (standard units) 7 8.5 8.1 8.2 8.2

Specific conductance, onsite (μS/cm) 7 471 253 373 353

Temperature, water (°C) 7 15.5 3.0 10.6 12.0

Hardness, filtered (mg/L as CaCO3) 7 200 100 157 150

Calcium, filtered (mg/L) 7 58.5 31.8 47.0 44.1

Magnesium, filtered (mg/L) 7 13.2 5.93 10.2 10.0

Arsenic, filtered (μg/L) 7 21.6 12.6 16.8 16.5

Arsenic, unfiltered recoverable (μg/L) 7 43.5 19.9 27.7 21.9

Cadmium, filtered (μg/L) 7 .11 .06 .08 .08

Cadmium, unfiltered recoverable (μg/L) 7 .75 .17 .40 .34

Copper, filtered (μg/L) 7 20.2 7.7 12.8 11.7

Copper, unfiltered recoverable (μg/L) 7 197 27.4 97.3 65.9

Iron, filtered (μg/L) 7 33 7 18 16

Iron, unfiltered recoverable (μg/L) 7 3,190 364 1,390 1,150

Lead, filtered (μg/L) 7 .39 .10 .18 .14

Lead, unfiltered recoverable (μg/L) 7 29.4 3.34 13.9 12.3

Manganese, filtered (μg/L) 7 34.1 15.6 22.7 19.9

Manganese, unfiltered recoverable (μg/L) 7 309 92.0 175 148

Zinc, filtered (μg/L) 7 15.9 4.3 8.0 6.8

Zinc, unfiltered recoverable (μg/L) 7 152 21.4 77.9 65.1

Sediment, suspended (percent finer than 0.062 mm) 7 76 42 61 60

Sediment, suspended concentration (mg/L) 7 179 13 75 58

Sediment, suspended discharge (ton/d) 7 428 10 169 73
108 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324680--Clark Fork at Goldcreek

Period of record for water-quality data: March 1993–September 2009

Streamflow, instantaneous (ft3/s) 139 3,920 87 751 513

pH, onsite (standard units) 138 8.9 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 138 510 206 370 384

Temperature, water (°C) 139 23.0 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3) 138 230 86 162 170

Calcium, filtered (mg/L) 138 68.0 25.9 47.9 50.1

Magnesium, filtered (mg/L) 138 15.0 5.15 10.4 10.8

Arsenic, filtered (μg/L) 138 20 5.8 10.1 10.0

Arsenic, unfiltered recoverable (μg/L) 138 75 7 14.9 12.0

Cadmium, filtered (μg/L) 138 .2 <.04 2.04 <.1

Cadmium, unfiltered recoverable (μg/L) 138 2 <.1 2.18 .04

Copper, filtered (μg/L) 137 36.0 2.1 6.7 5.4

Copper, unfiltered recoverable (μg/L) 137 440 5.2 40.3 24.5

Iron, filtered (μg/L) 138 100 <3 219 12

Iron, unfiltered recoverable (μg/L) 138 12,000 27 859 426

Lead, filtered (μg/L) 136 .6 <.08 2.11 <.5

Lead, unfiltered recoverable (μg/L) 137 73.0 .14 25.63 3.00

Manganese, filtered (μg/L) 138 57.3 4.0 18.9 17.0

Manganese, unfiltered recoverable (μg/L) 138 1,100 10.5 123 87.7

Zinc, filtered (μg/L) 138 26 <1.0 25.6 4.0

Zinc, unfiltered recoverable (μg/L) 138 510 2 44.3 30.0

Sediment, suspended (percent finer than 0.062 mm) 139 94 43 75 78

Sediment, suspended concentration (mg/L) 139 752 1 49 21

Sediment, suspended discharge (ton/d) 139 7,960 .55 210 33
Data 109

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12331800--Clark Fork near Drummond

Period of record for water-quality data: March 1993–September 2009

Streamflow, instantaneous (ft3/s) 139 3,860 149 1,050 768

pH, onsite (standard units) 138 8.7 7.8 8.3 8.3

Specific conductance, onsite (μS/cm) 138 630 189 409 420

Temperature, water (°C) 139 22.5 .5 11.0 11.0

Hardness, filtered (mg/L as CaCO3) 138 300 74 184 190

Calcium, filtered (mg/L) 138 83.0 21.0 52.8 54.8

Magnesium, filtered (mg/L) 138 22.0 5.2 12.6 13.0

Arsenic, filtered (μg/L) 138 20 6.6 10.6 10.0

Arsenic, unfiltered recoverable (μg/L) 138 62 8 16.3 13.0

Cadmium, filtered (μg/L) 138 .30 <.04 2.05 <.1

Cadmium, unfiltered recoverable (μg/L) 138 2.0 <.1 2.23 .04

Copper, filtered (μg/L) 136 21.0 1.0 6.5 5.0

Copper, unfiltered recoverable (μg/L) 136 360 4.6 43.0 22.5

Iron, filtered (μg/L) 138 150 <3 218 9

Iron, unfiltered recoverable (μg/L) 137 8,800 20 999 468

Lead, filtered (μg/L) 134 1.2 <.08 2.16 <1.0

Lead, unfiltered recoverable (μg/L) 134 56.0 <1.00 27.75 3.54

Manganese, filtered (μg/L) 138 60.7 3.3 16.6 14.6

Manganese, unfiltered recoverable (μg/L) 138 880 8.0 147 96.0

Zinc, filtered (μg/L) 138 21 <3 26.0 4.2

Zinc, unfiltered recoverable (μg/L) 138 490 2.9 60.6 31.9

Sediment, suspended (percent finer than 0.062 mm) 139 92 38 73 74

Sediment, suspended concentration (mg/L) 139 530 2 63 26

Sediment, suspended discharge (ton/d) 139 4,720 1.7 323 52
110 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for water-quality data: March 1985–September 2009

Streamflow, instantaneous (ft3/s) 236 9,560 296 1,910 1,150

pH, onsite (standard units) 182 8.8 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 211 483 139 301 313

Temperature, water (°C) 235 22.0 0.0 9.5 9.5

Hardness, filtered (mg/L as CaCO3) 172 200 54 131 130

Calcium, filtered (mg/L) 172 59.0 14.9 36.9 37.2

Magnesium, filtered (mg/L) 172 14.0 3.94 9.42 9.39

Arsenic, filtered (μg/L) 181 17 2.7 6.1 5.4

Arsenic, unfiltered recoverable (μg/L) 181 110 3 9.8 7.0

Cadmium, filtered (μg/L) 181 .10 <.04 2.03 <.1

Cadmium, unfiltered recoverable (μg/L) 181 4 <.01 2.26 <1

Copper, filtered (μg/L) 180 25 1.1 4.8 3.9

Copper, unfiltered recoverable (μg/L) 179 500 2.7 34.4 16.0

Iron, filtered (μg/L) 181 190 <3 224 13

Iron, unfiltered recoverable (μg/L) 181 19,000 33 1,020 380

Lead, filtered (μg/L) 177 7 <.08 2.30 <1

Lead, unfiltered recoverable (μg/L) 177 100 <1.00 27.09 3.00

Manganese, filtered (μg/L) 181 37.4 <1.0 28.2 7.0

Manganese, unfiltered recoverable (μg/L) 181 2,000 8.9 123 60.1

Zinc, filtered (μg/L) 180 39 <3 26.0 4.0

Zinc, unfiltered recoverable (μg/L) 181 1,100 <10 259 30

Sediment, suspended (percent finer than 0.062 mm) 225 98 27 73 75

Sediment, suspended concentration (mg/L) 236 1,370 2 57 18

Sediment, suspended discharge (ton/d) 236 34,700 3.0 626 60
Data 111

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12340000--Blackfoot River near Bonner

Period of record for water-quality data: March 1985–September 2009

Streamflow, instantaneous (ft3/s) 171 13,400 344 2,690 1,330

pH, onsite (standard units) 131 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 148 294 131 208 204

Temperature, water (°C) 171 22.5 0.0 9.5 9.5

Hardness, filtered (mg/L as CaCO3) 124 140 55 103 98

Calcium, filtered (mg/L) 124 37.0 14.0 26.4 25.2

Magnesium, filtered (mg/L) 124 13.2 4.90 9.12 8.66

Arsenic, filtered (μg/L) 131 2 <1 2.97 .98

Arsenic, unfiltered recoverable (μg/L) 131 4 <1 21.2 1

Cadmium, filtered (μg/L) 131 1 <.02 2.03 <.1

Cadmium, unfiltered recoverable (μg/L) 131 2 <.01 2.10 <1

Copper, filtered (μg/L) 129 7.0 <1.0 21.4 .8

Copper, unfiltered recoverable (μg/L) 128 34 <1.0 24.9 2.2

Iron, filtered (μg/L) 131 100 <3 217 10

Iron, unfiltered recoverable (μg/L) 131 3,600 14 428 190

Lead, filtered (μg/L) 127 8 <.06 2.39 <.6

Lead, unfiltered recoverable (μg/L) 127 25.0 <.06 22.39 .07

Manganese, filtered (μg/L) 131 11.0 <1 22.4 2.0

Manganese, unfiltered recoverable (μg/L) 131 180 <10 229.3 18.6

Zinc, filtered (μg/L) 131 15 <.60 22.1 <20

Zinc, unfiltered recoverable (μg/L) 131 60 <1 25.6 <10

Sediment, suspended (percent finer than 0.062 mm) 169 98 42 80 82

Sediment, suspended concentration (mg/L) 171 271 1 29 8

Sediment, suspended discharge (ton/d) 171 7,670 1.1 522 30
112 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2009.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; μg/L, microgram per liter; μS/cm, microsiemen per centimeter at 25°C; mg/L, milligram per 

liter; mm, millimeter; ton/d, ton per day. Symbols: <, less than laboratory reporting level1]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12340500--Clark Fork above Missoula

Period of record for water-quality data: July 1986–September 2009

Streamflow, instantaneous (ft3/s) 202 21,600 720 4,480 2,430

pH, onsite (standard units) 159 8.8 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 179 399 142 253 261

Temperature, water (°C) 199 22.0 0.0 9.5 9.5

Hardness, filtered (mg/L as CaCO3) 159 170 60 117 120

Calcium, filtered (mg/L) 159 46.0 14.0 31.4 31.7

Magnesium, filtered (mg/L) 159 13.4 5.28 9.22 9.20

Arsenic, filtered (μg/L) 159 9 1 3.4 3.0

Arsenic, unfiltered recoverable (μg/L) 159 69 1 5.5 4

Cadmium, filtered (μg/L) 159 .2 <.04 2.03 <.1

Cadmium, unfiltered recoverable (μg/L) 159 5.0 <.01 2.17 <1

Copper, filtered (μg/L) 158 12.6 .7 2.9 2.2

Copper, unfiltered recoverable (μg/L) 157 400 2.0 20.1 8.5

Iron, filtered (μg/L) 159 200 <3 222 15

Iron, unfiltered recoverable (μg/L) 159 13,000 43 647 244

Lead, filtered (μg/L) 153 1.2 <.08 2.16 <1

Lead, unfiltered recoverable (μg/L) 154 78.0 <1.00 23.61 1.60

Manganese, filtered (μg/L) 159 230 5.9 16.8 14.1

Manganese, unfiltered recoverable (μg/L) 159 1,100 10 66.9 40

Zinc, filtered (μg/L) 159 16 <1.0 23.7 2.3

Zinc, unfiltered recoverable (μg/L) 159 1,100 <10 235.0 15

Sediment, suspended (percent finer than 0.062 mm) 197 99 14 83 89

Sediment, suspended concentration (mg/L) 202 950 2 44 12

Sediment, suspended discharge (ton/d) 202 21,900 5.8 1,090 84

1

Differing less-than (<) values for an individual constituent are the result of changes in the laboratory reporting level during the period of record.

2

Value for the mean is estimated by using a log-probability regression to predict the values of data less than the laboratory reporting level (Helsel 

and Cohn, 1988).
Data 113

Table 26. Statistical summary of long-term bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Reported concentrations are in microgram per gram dry weight (μg/g). 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 was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12323600--Silver Bow Creek at Opportunity

Period of record for bed-sediment data: 1992–2009

Arsenic 7 186 59 138 153

Cadmium 18 43.9 7.5 30.9 29.7

Chromium 16 50.0 16.8 27.3 25.7

Copper 18 9,020 1,040 4,370 4,530

Iron 18 45,300 28,200 35,700 34,500

Lead 18 1,030 267 659 667

Manganese 18 9,220 1,680 3,470 2,840

Nickel 17 21.4 12.0 14.9 14.8

Silver 12 20.0 8.3 15.5 15.8

Zinc 18 13,400 2,130 7,560 7,060

12323750--Silver Bow Creek at Warm Springs

Period of record for bed-sediment data: 1992–2009

Arsenic 7 177 67 112 103

Cadmium 18 12.2 4.2 7.2 6.5

Chromium 16 41.4 <15.7 121.8 121.2

Copper 18 769 169 345 290

Iron 18 31,700 15,400 22,900 21,900

Lead 18 100 49 71 72

Manganese 18 17,700 1,470 7,920 7,690

Nickel 17 19.1 9.2 14.7 14.6

Silver 12 4.4 .3 11.9 11.8

Zinc 18 2,220 554 952 727

12323770--Warm Springs Creek at Warm Springs

Period of record for bed-sediment data: 1995, 1997, 1999, 2002, 2005, 2008

Arsenic 2 66 52 59 --

Cadmium 6 5.8 1.3 3.6 3.6

Chromium 6 39.3 27.5 31.9 31.1

Copper 6 1,060 779 908 886

Iron 6 26,600 16,800 21,700 21,900

Lead 6 86 67 81 83

Manganese 6 12,100 2,020 7,950 8,280

Nickel 6 25.5 17.6 20.2 19.4

Silver 4 5.1 3.1 3.8 3.5

Zinc 6 453 372 405 405
114 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 26. Statistical summary of long-term bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Reported concentrations are in microgram per gram dry weight (μg/g). 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 was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen

Period of record for bed-sediment data: 1987, 1991–2009

Arsenic 7 119 86 103 107

Cadmium 20 20.1 4.0 8.6 7.5

Chromium 16 44.6 19.1 28.2 26.7

Copper 20 2,300 838 1,200 1,110

Iron 20 39,800 22,600 27,900 27,200

Lead 20 235 92 134 130

Manganese 20 17,300 2,780 9,910 11,400

Nickel 17 23.2 13.9 18.7 18.3

Silver 14 7.3 <3.2 14.4 14.5

Zinc 20 3,560 819 1,490 1,150

461415112450801--Clark Fork below Lost Creek, near Galen

Period of record for bed-sediment data: 1996–2009

Arsenic 7 204 92 120 109

Cadmium 14 10.5 5.2 7.2 6.8

Chromium 13 42.4 20.5 29.2 27.5

Copper 14 2,050 1,150 1,500 1,430

Iron 14 32,800 24,400 29,600 30,500

Lead 14 218 127 168 169

Manganese 14 9,820 3,470 5,980 5,820

Nickel 14 19.9 11.7 16.1 16.4

Silver 8 7.8 4.2 6.5 6.7

Zinc 14 1,680 1,060 1,340 1,330

461559112443301--Clark Fork at county bridge, near Racetrack

Period of record for bed-sediment data: 1996–2009

Arsenic 7 101 56 81 86

Cadmium 14 8.7 5.0 6.7 6.4

Chromium 13 45.2 19.0 27.2 27.6

Copper 14 1,610 933 1,240 1,280

Iron 14 31,700 21,200 27,100 28,100

Lead 14 186 103 143 143

Manganese 14 6,310 2,100 3,510 3,230

Nickel 14 18.4 10.3 14.2 14.7

Silver 8 6.1 <3.3 15.0 15.4

Zinc 14 1,550 999 1,210 1,180
Data 115

Table 26. Statistical summary of long-term bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Reported concentrations are in microgram per gram dry weight (μg/g). 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 was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for bed-sediment data: 1996–2009

Arsenic 7 100 58 79 80

Cadmium 14 10.3 4.3 6.5 5.9

Chromium 13 39.2 16.0 26.2 25.6

Copper 14 1,580 721 1,090 1,060

Iron 14 33,700 20,600 26,800 26,200

Lead 14 155 92 129 131

Manganese 14 8,370 1,810 4,220 3,620

Nickel 14 16.9 8.7 13.1 12.8

Silver 8 6.2 2.7 4.9 5.0

Zinc 14 1,570 900 1,150 1,120

12324200--Clark Fork at Deer Lodge

Period of record for bed-sediment data: 1986–87, 1990–2009

Arsenic 7 102 49 70 69

Cadmium 22 10.0 3.8 6.2 5.5

Chromium 16 50.7 19.5 30.8 28.3

Copper 22 4,180 683 1,270 1,060

Iron 22 35,300 21,100 27,200 26,100

Lead 22 242 103 146 144

Manganese 22 6,020 1,110 2,780 2,470

Nickel 17 21.1 11.5 14.9 13.6

Silver 16 7.9 2.4 4.7 4.5

Zinc 22 1,730 846 1,210 1,190

12324400--Clark Fork above Little Blackfoot River, near Garrison

Period of record for bed-sediment data: 2009

Arsenic 1 -- -- 83 --

Cadmium 1 -- -- 5.5 --

Chromium 1 -- -- 52.8 --

Copper 1 -- -- 1,270 --

Iron 1 -- -- 32,400 --

Lead 1 -- -- 140 --

Manganese 1 -- -- 2,950 --

Nickel 1 -- -- 17.2 --

Silver 0 -- -- -- --

Zinc 1 -- -- 1,240 --
116 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 26. Statistical summary of long-term bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Reported concentrations are in microgram per gram dry weight (μg/g). 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 was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12324680--Clark Fork at Goldcreek

Period of record for bed-sediment data: 1992–2009

Arsenic 7 61 23 37 36

Cadmium 18 8.1 2.6 4.7 4.6

Chromium 16 55.3 21.3 32.6 31.8

Copper 18 1,080 338 675 702

Iron 18 32,100 15,500 23,700 24,000

Lead 18 152 52 95 93

Manganese 18 2,610 1,160 1,880 1,840

Nickel 17 18.6 9.0 14.3 15.0

Silver 12 4.8 2.3 3.3 3.2

Zinc 18 1,320 584 933 1,030

12331800--Clark Fork near Drummond

Period of record for bed-sediment data: 1986–87, 1991–2009

Arsenic 7 66 31 39 33

Cadmium 21 7.7 2.6 4.5 4.3

Chromium 16 41.9 17.0 28.7 30.7

Copper 21 747 303 477 469

Iron 21 43,700 16,500 23,500 23,200

Lead 21 135 59 89 85

Manganese 21 4,820 1,150 2,150 1,890

Nickel 17 16.8 9.3 13.4 13.7

Silver 15 4.7 <3.2 13.0 12.9

Zinc 21 1,230 673 960 948

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for bed-sediment data: 1986, 1991–2009

Arsenic 7 43 19 27 25

Cadmium 20 7.3 1.9 3.7 3.6

Chromium 16 42.5 15.3 25.6 27.2

Copper 20 635 211 350 322

Iron 20 25,900 12,600 19,100 17,300

Lead 20 115 47 68 64

Manganese 20 2,340 671 1,320 1,300

Nickel 17 19.1 6.9 12.4 11.5

Silver 14 3.9 <1.9 12.1 11.9

Zinc 20 1,160 584 813 786
Data 117

Table 26. Statistical summary of long-term bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Reported concentrations are in microgram per gram dry weight (μg/g). 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 was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12340000--Blackfoot River near Bonner

Period of record for bed-sediment data: 1986–87, 1991, 1993–96, 1998–2001, 2003, 2006–09

Arsenic 5 6 <0.2 13 13

Cadmium 16 2.0 <.2 1.6 1.4

Chromium 12 35.2 15.1 22.7 22.8

Copper 16 27 11 20 21

Iron 16 23,000 12,400 17,800 18,200

Lead 16 20 <13 113 113

Manganese 16 746 298 539 543

Nickel 13 14.3 6.0 11.5 11.8

Silver 12 <1.9 <.3 1.5 1<.6

Zinc 16 82 35 62 63

12340500--Clark Fork above Missoula

Period of record for bed-sediment data: 1997–2009

Arsenic 7 54 17 35 33

Cadmium 13 5.8 1.5 3.4 3.4

Chromium 12 40.7 19.0 27.2 27.3

Copper 13 551 166 377 411

Iron 13 27,000 18,100 21,300 20,700

Lead 13 78 37 57 60

Manganese 13 2,250 477 1,120 1,120

Nickel 13 15.8 7.6 12.8 13.0

Silver 7 2.9 .8 12.0 12.1

Zinc 13 1,090 438 771 839

1

Value 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.
118 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

Period of record for biological data: 1992, 1994–95, 1997–2009

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 11.6

Zinc 5 995 629 803 815

Hydropsyche cockerelli

Arsenic 12 33.3 9.5 15.6 13.6

Cadmium 18 9.7 3.1 5.5 5.1

Chromium 18 8.0 1.0 3.2 2.8

Copper 18 1,090 269 431 378

Iron 18 5,890 689 2,320 2,030

Lead 18 68.3 19.0 38.7 39.8

Manganese 18 3,030 180 1,040 1,120

Nickel 18 3.6 .7 2.3 2.3

Zinc 18 1,590 619 899 835

Hydropsyche spp.

Arsenic 9 23.1 9.8 15.0 14.1

Cadmium 14 11.0 3.0 6.3 5.5

Chromium 14 4.7 .6 2.4 2.9

Copper 14 930 223 523 462

Iron 14 3,250 1,050 2,060 2,120

Lead 14 237 21.8 53.0 40.1

Manganese 14 1,340 712 1,090 1,070

Nickel 14 2.7 .7 2.2 2.4

Zinc 14 1,290 607 986 1,070

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
Data 119

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12323750--Silver Bow Creek at Warm Springs

Period of record for biological data: 1992–2009

Claassenia sabulosa

Arsenic 1 -- -- 1.8 --

Cadmium 1 -- -- 1.1 --

Chromium 1 -- -- 2.8 --

Copper 1 -- -- 47.6 --

Iron 1 -- -- 151 --

Lead 1 -- -- .6 --

Manganese 1 -- -- 98.1 --

Nickel 1 -- -- .5 --

Zinc 1 -- -- 400 --

Hydropsyche cockerelli

Arsenic 13 23.6 7.9 12.9 10.4

Cadmium 39 2.1 .2 .6 .5

Chromium 39 4.3 .4 1.1 .8

Copper 39 97.0 16.7 36.7 29.9

Iron 39 1,590 351 788 761

Lead 39 5.7 .3 3.0 2.9

Manganese 39 3,890 491 1,290 1,010

Nickel 39 1.8 .3 .9 .8

Zinc 39 276 115 174 167

Hydropsyche occidentalis

Arsenic 6 31.0 10.5 20.5 21.8

Cadmium 21 1.6 .2 .6 .4

Chromium 21 6.8 .3 1.7 1.0

Copper 21 48.9 11.0 32.4 31.2

Iron 21 2,960 372 1,200 980

Lead 21 8.2 <1.7 13.9 13.6

Manganese 21 6,940 1,200 2,530 2,140

Nickel 21 2.7 .7 1.5 1.4

Zinc 21 220 140 179 181

Hydropsyche spp.

Arsenic 1 -- -- 14.0 --

Cadmium 5 2.3 0.4 1.0 0.6

Chromium 5 2.5 .5 1.4 1.3

Copper 5 47.6 34.9 39.9 40.4

Iron 5 1,100 561 763 767

Lead 5 5.1 1.9 4.0 4.5

Manganese 5 1,190 443 817 804

Nickel 5 1.9 <.4 11.0 1.8

Zinc 5 284 141 188 162
120 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12323770--Warm Springs Creek at Warm Springs

Period of record for biological data: 1995, 1997, 1999, 2002, 2005, 2008

Arctopsyche grandis

Arsenic 3 9.8 9.5 9.6 9.6

Cadmium 7 3.6 1.9 2.8 3.0

Chromium 7 2.9 .8 2.0 1.8

Copper 7 133 78.3 109 102

Iron 7 1,350 684 980 1,040

Lead 7 7.2 3.0 15.2 15.3

Manganese 7 3,560 1,340 2,540 2,480

Nickel 7 3.5 1.8 12.5 12.3

Zinc 7 267 181 206 197

Hydropsyche occidentalis

Arsenic 3 13.6 12.7 13.2 13.3

Cadmium 5 1.3 .7 1.0 1.2

Chromium 5 8.6 .3 3.8 3.2

Copper 5 183 125 158 165

Iron 5 2,360 1,590 1,940 1,950

Lead 5 12.6 6.7 8.5 7.7

Manganese 5 3,190 2,400 2,800 2,880

Nickel 5 4.5 2.0 3.0 3.0

Zinc 5 204 148 169 166

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 2 1.1 0.6 0.9 --

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 --
Data 121

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12323800--Clark Fork near Galen

Period of record for biological data: 1987, 1991–2009

Claassenia sabulosa

Arsenic 1 -- -- 2.0 --

Cadmium 1 -- -- .2 --

Chromium 1 -- -- 1.5 --

Copper 1 -- -- 54.7 --

Iron 1 -- -- 242 --

Lead 1 -- -- 1.0 --

Manganese 1 -- -- 323 --

Nickel 1 -- -- .5 --

Zinc 1 -- -- 237 --

Hydropsyche cockerelli

Arsenic 8 15.8 13.2 14.1 13.8

Cadmium 33 2.7 .7 1.5 1.5

Chromium 33 4.4 .8 1.9 1.7

Copper 33 181 48.7 105 102

Iron 33 2,660 816 1,470 1,400

Lead 33 11.8 1.2 8.1 7.8

Manganese 33 3,620 1,070 2,250 2,200

Nickel 33 6.5 .9 1.8 1.6

Zinc 33 299 136 210 205

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
122 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12323800--Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991–2009

Hydropsyche occidentalis

Arsenic 11 17.0 12.5 15.2 15.9

Cadmium 43 1.7 .6 1.1 1.2

Chromium 43 6.6 .4 2.0 1.7

Copper 43 151 49.2 87.5 83.8

Iron 43 2,590 642 1,380 1,300

Lead 43 13.5 1.6 7.6 7.3

Manganese 43 6,170 1,220 2,700 2,280

Nickel 43 3.5 .8 1.7 1.6

Zinc 43 286 168 203 198

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 3 15.7 14.2 14.8 14.5

Cadmium 7 3.5 .8 2.1 2.6

Chromium 3 2.4 1.9 2.2 2.2

Copper 7 154 78.4 126 135

Iron 7 2,110 1,190 1,460 1,430

Lead 7 13.5 5.9 10.4 10.6

Manganese 3 4,760 1,520 3,560 4,400

Nickel 3 2.7 1.5 2.0 1.8

Zinc 7 329 197 268 279
Data 123

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

461415112450801--Clark Fork below Lost Creek, near Galen

Period of record for biological data: 1996–2009

Claassenia sabulosa

Arsenic 1 -- -- 1.5 --

Cadmium 2 0.4 0.3 .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 --

Hydropsyche cockerelli

Arsenic 11 27.8 8.8 14.3 11.6

Cadmium 22 2.8 1.1 1.8 1.6

Chromium 22 3.6 .8 2.0 2.0

Copper 22 338 48.8 134 113

Iron 22 4,080 691 1,530 1,180

Lead 22 28.6 4.5 11.6 9.0

Manganese 22 3,160 1,230 1,850 1,720

Nickel 22 2.8 .9 1.4 1.2

Zinc 22 339 151 228 223

Hydropsyche occidentalis

Arsenic 9 20.9 12.7 15.8 15.0

Cadmium 23 1.9 .9 1.4 1.4

Chromium 23 3.6 1.2 2.1 2.0

Copper 23 219 52.1 117 119

Iron 23 2,830 963 1,650 1,510

Lead 23 19.4 6.6 11.0 10.7

Manganese 23 4,150 1,220 2,540 2,190

Nickel 23 3.0 .9 1.6 1.5

Zinc 23 308 174 243 245

Hydropsyche spp.

Arsenic 2 14.5 12.0 13.2 --

Cadmium 6 1.8 1.2 1.4 1.4

Chromium 6 2.4 .9 1.4 1.3

Copper 6 153 45.1 102 112

Iron 6 1,810 533 1,220 1,270

Lead 6 20.5 4.1 10.6 9.2

Manganese 6 1,980 799 1,430 1,310

Nickel 6 2.8 1.0 1.8 1.4

Zinc 6 228 143 187 183
124 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

461559112443301--Clark Fork at county bridge, near Racetrack

Period of record for biological data: 1996–2009

Claassenia sabulosa

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.4 --

Chromium 1 -- -- .3 --

Copper 1 -- -- 40.3 --

Iron 1 -- -- 113 --

Lead 1 -- -- .8 --

Manganese 1 -- -- 172 --

Nickel 1 -- -- .2 --

Zinc 1 -- -- 213 --

Hydropsyche cockerelli

Arsenic 10 20.2 11.1 14.1 13.1

Cadmium 21 2.0 .8 1.5 1.5

Chromium 21 2.8 .6 1.7 1.4

Copper 21 198 50.0 102 98.2

Iron 21 3,330 657 1,270 992

Lead 21 17.2 3.7 8.7 7.5

Manganese 21 2,360 646 1,630 1,900

Nickel 21 2.0 .7 1.2 1.0

Zinc 21 302 139 193 186

Hydropsyche occidentalis

Arsenic 8 16.8 11.6 14.7 14.9

Cadmium 21 2.3 .7 1.5 1.4

Chromium 21 3.6 1.1 2.2 2.2

Copper 21 164 59.5 117 134

Iron 21 3,690 1,030 1,730 1,620

Lead 21 15.7 4.3 11.0 10.7

Manganese 21 3,770 1,090 2,200 2,100

Nickel 21 2.3 1.1 1.5 1.3

Zinc 21 361 181 237 230

Hydropsyche spp.

Arsenic 3 12.8 11.9 12.5 12.7

Cadmium 5 2.4 1.0 1.6 1.5

Chromium 5 3.9 .7 2.0 1.7

Copper 5 144 82.9 110 113

Iron 5 1,880 1,140 1,430 1,290

Lead 5 15.0 5.7 10.2 9.6

Manganese 5 2,370 910 1,480 1,400

Nickel 5 2.0 1.1 1.5 1.4

Zinc 5 228 151 197 208
Data 125

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for biological data: 1996–2009

Arctopsyche grandis

Arsenic 1 -- -- 11.8 --

Cadmium 2 7.1 1.7 4.4 --

Chromium 2 12.9 <2.4 17.0 --

Copper 2 151 30.8 91.0 --

Iron 2 1,500 340 922 --

Lead 2 12.4 <14.5 19.8 --

Manganese 2 1,190 510 852 --

Nickel 2 2.3 1.0 1.7 --

Zinc 2 489 86.8 288 --

Claassenia sabulosa

Arsenic 1 -- -- 3.1 --

Cadmium 1 -- -- 2.4 --

Chromium 1 -- -- 1.7 --

Copper 1 -- -- 73.4 --

Iron 1 -- -- 297 --

Lead 1 -- -- 1.9 --

Manganese 1 -- -- 115 --

Nickel 1 -- -- .4 --

Zinc 1 -- -- 330 --

Hydropsyche cockerelli

Arsenic 9 18.8 8.0 13.0 10.4

Cadmium 18 2.0 .7 1.3 1.3

Chromium 18 4.0 .5 1.6 1.3

Copper 18 247 60.7 113 90.2

Iron 18 3,010 552 1,200 923

Lead 18 21.9 3.5 8.7 7.3

Manganese 18 2,650 487 1,370 1,230

Nickel 18 2.5 .5 1.2 1.0

Zinc 18 279 162 208 190
126 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack—Continued

Period of record for biological data: 1996–2009

Hydropsyche occidentalis

Arsenic 10 24.0 10.2 15.3 15.9

Cadmium 27 2.4 .7 1.3 1.2

Chromium 27 6.2 .8 2.1 1.9

Copper 27 238 74.9 116 92.5

Iron 27 3,390 940 1,620 1,510

Lead 27 27.0 6.1 12.1 11.4

Manganese 27 4,460 826 2,650 2,320

Nickel 27 2.4 1.2 1.6 1.5

Zinc 27 386 211 265 249

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 --
Data 127

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12324200--Clark Fork at Deer Lodge

Period of record for biological data: 1986–87, 1990–2009

Arctopsyche grandis

Arsenic 1 -- -- 8.3 --

Cadmium 3 3.1 <4.2 12.5 12.4

Chromium 3 4.7 <1.3 12.1 11.0

Copper 3 90.5 34.9 64.8 69.1

Iron 3 844 537 686 676

Lead 3 9.5 3.8 15.7 1<7.8

Manganese 3 1,010 380 706 727

Nickel 3 1.1 <1.3 1.9 1<1.7

Zinc 3 315 140 211 178.0

Hydropsyche cockerelli

Arsenic 6 11.4 5.8 8.2 7.8

Cadmium 29 3.5 .6 1.4 1.3

Chromium 29 3.2 .4 1.6 1.7

Copper 29 180 54.7 98.2 98.2

Iron 29 3,340 490 1,120 1,040

Lead 29 18.1 3.8 9.5 8.9

Manganese 29 1,570 396 879 815

Nickel 29 2.4 .3 1.1 1.0

Zinc 29 391 132 190 185

Hydropsyche occidentalis

Arsenic 13 12.7 6.6 10.3 10.6

Cadmium 50 3.4 .6 1.4 1.3

Chromium 50 3.6 .6 1.9 1.9

Copper 50 180 49.4 119 113

Iron 50 2,060 557 1,420 1,420

Lead 50 18.6 3.5 11.5 11.4

Manganese 50 2,850 649 1,710 1,720

Nickel 50 12.9 1.0 1.7 1.4

Zinc 50 346 166 245 237

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
128 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12324400--Clark Fork above Little Blackfoot River, near Garrison

Period of record for biological data: 2009

Arctopsyche grandis

Arsenic 1 -- -- 6.0 --

Cadmium 1 -- -- 3.2 --

Chromium 1 -- -- 1.9 --

Copper 1 -- -- 65.7 --

Iron 1 -- -- 694 --

Lead 1 -- -- 6.6 --

Manganese 1 -- -- 990 --

Nickel 1 -- -- .7 --

Zinc 1 -- -- 253 --

Hydropsyche cockerelli

Arsenic 1 -- -- 11.1 --

Cadmium 1 -- -- 4.0 --

Chromium 1 -- -- 3.4 --

Copper 1 -- -- 158 --

Iron 1 -- -- 2,150 --

Lead 1 -- -- 18.8 --

Manganese 1 -- -- 1,500 --

Nickel 1 -- -- 1.7 --

Zinc 1 -- -- 284 --

Hydropsyche occidentalis

Arsenic 2 14.7 11.1 12.9 --

Cadmium 2 2.5 2.5 2.5 --

Chromium 2 2.0 .7 1.3 --

Copper 2 144 138 141 --

Iron 2 2,000 1,890 1,940 --

Lead 2 17.9 17.4 17.6 --

Manganese 2 1,610 1,560 1,580 --

Nickel 2 1.7 1.6 1.7 --

Zinc 2 265 264 265 --
Data 129

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12324680--Clark Fork at Goldcreek

Period of record for biological data: 1992–2009

Arctopsyche grandis

Arsenic 25 6.9 1.8 4.0 3.3

Cadmium 54 6.6 .6 1.9 1.7

Chromium 54 3.3 .1 1.2 1.0

Copper 54 129 19.9 43.0 33.0

Iron 54 2,360 195 663 488

Lead 54 10.9 1.0 3.4 3.3

Manganese 54 1,580 436 858 860

Nickel 54 1.8 .2 .7 .6

Zinc 54 326 146 197 181

Claassenia sabulosa

Arsenic 18 2.1 0.4 1.3 1.4

Cadmium 38 3.5 .1 1.0 .7

Chromium 38 1.6 .2 .5 .5

Copper 38 81.7 33.0 58.6 58.0

Iron 38 567 63.0 183 161

Lead 38 1.8 .4 .9 .8

Manganese 38 320 50.6 153 132

Nickel 38 .7 .1 .3 .3

Zinc 38 351 166 262 258

Hydropsyche cockerelli

Arsenic 15 9.8 4.1 5.7 5.6

Cadmium 34 2.6 .5 1.4 1.2

Chromium 34 4.7 .5 2.0 1.9

Copper 34 188 17.1 71.1 58.0

Iron 34 3,250 522 1,120 872

Lead 34 16.2 2.4 6.4 5.3

Manganese 34 1,710 538 993 959

Nickel 34 2.3 .3 1.2 1.0

Zinc 34 269 106 188 185
130 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12324680--Clark Fork at Goldcreek—Continued

Period of record for biological data: 1992–2009

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

Hydropsyche occidentalis

Arsenic 8 8.1 4.7 6.0 5.6

Cadmium 23 2.3 .4 1.3 1.3

Chromium 23 3.9 .4 1.7 1.7

Copper 23 156 26.4 66.1 58.3

Iron 23 2,720 466 1,160 1,100

Lead 23 15.7 2.9 7.0 6.0

Manganese 23 2,210 530 1,280 1,290

Nickel 23 2.5 .8 1.2 1.1

Zinc 23 277 97.0 201 204
Data 131

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12331800--Clark Fork near Drummond

Period of record for biological data: 1986, 1991–2009

Arctopsyche grandis

Arsenic 17 5.3 2.3 3.6 3.6

Cadmium 49 3.8 .4 1.3 1.1

Chromium 49 3.3 .2 1.0 1.0

Copper 49 89.2 16.9 32.4 28.1

Iron 49 1,660 193 584 511

Lead 49 11.8 1.6 4.5 3.9

Manganese 49 2,010 456 841 740

Nickel 49 1.9 .2 .7 .6

Zinc 49 308 140 192 186

Claassenia sabulosa

Arsenic 15 1.8 0.7 1.2 1.2

Cadmium 51 2.8 .1 1.0 1.0

Chromium 51 3.3 .1 .7 .6

Copper 51 165 18.0 64.9 60.6

Iron 51 387 45.4 164 145

Lead 51 2.9 .2 1.0 .9

Manganese 51 748 33.1 187 150

Nickel 51 1.1 .1 1.3 1.2

Zinc 51 567 103 274 261

Hydropsyche cockerelli

Arsenic 12 7.1 3.9 5.3 5.1

Cadmium 41 2.3 .3 1.1 .9

Chromium 41 3.5 .4 1.6 1.6

Copper 41 156 30.0 58.4 52.3

Iron 41 2,500 506 1,170 984

Lead 41 15.0 4.7 8.4 7.7

Manganese 41 1,680 549 1,000 929

Nickel 41 2.0 .5 1.1 1.1

Zinc 41 248 134 194 187
132 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12331800--Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991–2009

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 11 6.9 4.3 5.3 5.1

Cadmium 27 2.0 .4 1.0 1.0

Chromium 27 8.1 .4 2.3 2.1

Copper 27 118 13.3 55.0 55.1

Iron 27 2,060 424 1,220 1,180

Lead 27 14.0 2.9 8.5 8.4

Manganese 27 2,920 619 1,470 1,220

Nickel 27 2.4 .5 1.3 1.2

Zinc 27 293 157 221 221

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 --
Data 133

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for biological data: 1986, 1991–2009

Arctopsyche grandis

Arsenic 22 6.1 3.1 4.5 4.5

Cadmium 64 2.7 .4 1.2 .9

Chromium 64 4.1 .5 1.6 1.4

Copper 64 125 20.1 37.2 31.9

Iron 64 2,870 372 916 792

Lead 64 13.2 1.6 4.3 3.7

Manganese 64 902 324 646 661

Nickel 64 2.6 .4 1.1 .9

Zinc 64 276 111 198 197

Claassenia sabulosa

Arsenic 15 1.9 0.5 1.1 1.1

Cadmium 41 2.5 .1 1.0 .8

Chromium 41 2.0 .2 .7 .6

Copper 41 95.1 37.5 60.2 56.7

Iron 41 340 58.6 127 112

Lead 41 1.6 .2 .7 .6

Manganese 41 229 37.2 98.5 80.4

Nickel 41 .6 .04 .2 .2

Zinc 41 342 144 231 235

Hydropsyche cockerelli

Arsenic 16 6.0 3.7 4.7 4.9

Cadmium 44 1.8 .3 .8 .7

Chromium 44 8.0 .2 2.0 1.7

Copper 44 118 26.4 48.5 44.1

Iron 44 2,530 566 1,220 1,120

Lead 44 12.1 2.2 5.4 5.0

Manganese 44 831 426 640 657

Nickel 44 2.6 .6 1.3 1.3

Zinc 44 228 119 186 193
134 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12334550--Clark Fork at Turah Bridge, near Bonner—Continued

Period of record for biological data: 1986, 1991–2009

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 12 5.9 3.6 4.5 4.3

Cadmium 32 1.8 .3 .9 .9

Chromium 32 5.0 .6 1.9 1.7

Copper 32 102 27.4 48.2 44.8

Iron 32 2,310 472 1,230 1,150

Lead 32 14.2 3.0 6.4 5.6

Manganese 32 1,600 454 869 800

Nickel 32 3.2 .6 1.3 1.2

Zinc 32 416 145 213 222

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 --
Data 135

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12340000--Blackfoot River near Bonner

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006–09

Arctopsyche grandis

Arsenic 5 4.6 1.6 2.7 2.2

Cadmium 15 .4 .1 .2 .2

Chromium 10 6.9 .5 2.1 1.3

Copper 15 16.2 9.9 12.6 12.4

Iron 15 1,230 108 657 713

Lead 15 2.3 .5 1.1 .9

Manganese 10 633 286 477 496

Nickel 10 3.7 .7 1.3 1.1

Zinc 15 156 123 140 138

Claassenia sabulosa

Arsenic 7 3.0 0.3 1.3 1.1

Cadmium 18 .2 .1 .1 .1

Chromium 13 5.2 .3 1.0 .7

Copper 18 88.5 19.0 43.5 42.5

Iron 18 265 46.2 138 131

Lead 18 .8 .1 .4 .3

Manganese 13 133 26.3 84.0 95.5

Nickel 13 1.1 .1 .3 .3

Zinc 18 328 117 223 203

Hydropsyche cockerelli

Arsenic 4 3.1 2.4 2.9 3.1

Cadmium 4 .4 <.1 1.3 1.3

Chromium 4 3.8 2.4 3.1 3.0

Copper 4 16.2 5.6 12.9 14.9

Iron 4 2,390 1,640 2,000 1,980

Lead 4 2.3 2.0 2.2 2.2

Manganese 4 814 615 696 677

Nickel 4 4.6 1.8 2.7 2.2

Zinc 4 148 140 143 141
136 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12340000--Blackfoot River near Bonner—Continued

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006–09

Hydropsyche occidentalis

Arsenic 6 3.8 1.9 2.6 2.4

Cadmium 18 .5 .1 .2 .2

Chromium 18 5.8 .8 2.2 1.9

Copper 18 20.6 12.0 15.2 14.7

Iron 18 2,080 1,060 1,520 1,500

Lead 18 2.0 .8 1.5 1.6

Manganese 18 798 414 549 512

Nickel 18 4.9 .9 1.6 1.4

Zinc 18 163 116 140 144

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.6 --

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 --
Data 137

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2009.—Continued

[Concentrations are in microgram per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample 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 of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. 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

12340500--Clark Fork above Missoula

Period of record for biological data: 1997–2009

Arctopsyche grandis

Arsenic 19 7.2 2.1 3.9 3.6

Cadmium 38 2.2 .1 .8 .6

Chromium 38 4.2 .6 1.7 1.6

Copper 38 81.0 19.5 38.6 35.5

Iron 38 2,340 476 1,030 902

Lead 38 8.9 1.2 4.2 4.0

Manganese 38 1,410 476 929 919

Nickel 38 2.1 .5 1.2 1.0

Zinc 38 272 133 195 195

Claassenia sabulosa

Arsenic 11 1.9 0.5 1.4 1.5

Cadmium 20 2.0 .2 .7 .4

Chromium 20 1.4 .3 .8 .8

Copper 20 71.7 33.0 51.7 49.1

Iron 20 402 95.3 242 241

Lead 20 3.1 .5 1.2 1.1

Manganese 20 683 57.8 223 180

Nickel 20 .5 <.3 1.4 1.4

Zinc 20 363 191 280 272

Hydropsyche cockerelli

Arsenic 15 8.9 3.6 6.5 6.6

Cadmium 24 1.4 .4 .9 1.0

Chromium 24 6.0 1.8 3.2 3.3

Copper 24 99.7 29.9 68.1 69.2

Iron 24 3,590 1,400 2,170 2,120

Lead 24 12.1 4.2 8.1 7.4

Manganese 24 1,910 781 1,260 1,240

Nickel 24 2.4 1.4 1.9 1.9

Zinc 24 266 156 221 223

Hydropsyche occidentalis

Arsenic 6 7.4 3.9 6.1 6.2

Cadmium 12 1.4 .4 .8 .7

Chromium 12 5.5 2.1 3.3 3.0

Copper 12 80.7 30.3 57.6 59.0

Iron 12 2,540 1,450 2,100 2,220

Lead 12 11.4 4.0 7.6 7.5

Manganese 12 2,460 939 1,810 1,830

Nickel 12 2.4 1.6 2.0 2.0

Zinc 12 278 192 239 242

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.
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For more information concerning this publication, contact:

Director, Montana Water Science Center

U.S. Geological Survey

3162 Bozeman Ave.

Helena, MT 59601

(406) 457–5900

Or visit the Montana Water Science Center Web site at:

http://mt.water.usgs.gov/

Dodge and others—Water-Quality, Bed-Sediment, and Biological Data (October 2008 through September 2009) and Statistical Summaries of Long-Term Data 

for Streams in the Clark Fork Basin, Montana—Open-File Report 2010–1267

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