U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2007–1301

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

Water-Quality, Bed-Sediment, and Biological Data

(October 2005 through September 2006) and

Statistical Summaries of Long-Term Data for Streams in the

Clark Fork Basin, Montana
COVER PHOTOGRAPH: Clark Fork below Milltown Dam. Photograph by John Lambing, U.S. Geological Survey,

 taken in May 1989. 
Water-Quality, Bed-Sediment, and 

Biological Data (October 2005 through 

September 2006) 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 2007–1301

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

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Suggested citation:

Dodge K.A., Hornberger, M.I., and Dyke, J.L., 2007, Water-quality, bed-sediment, and biological data (October 2005 

through September 2006) and statistical summaries of long-term data for streams in the Clark Fork Basin, Montana: 

U.S. Geological Survey Open-File Report 2007–1301, 124 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...............................................................................................................................11

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

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

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

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

Statistical Summaries of Data ...................................................................................................................13

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

Data ...........................................................................................................................................................17

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 measured onsite and constituents analyzed in samples of water, 

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

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

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

4. Water-quality data for the Clark Fork basin, Montana, October 2005 through 

September 2006...........................................................................................................................18

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

Deer Lodge, Montana, October 2005 through September 2006 ..........................................43

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

Turah Bridge, near Bonner, Montana, October 2005 through September 2006 ...............47

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

near Bonner, Montana, October 2005 through September 2006.........................................51

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

above Missoula, Montana, October 2005 through September 2006 ..................................55
iv

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

Anaconda, Montana, June through September 2006...........................................................59

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

Anaconda, Montana, June through September 2006...........................................................61

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

near Anaconda, Montana, May through September 2006...................................................63

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

Anaconda, Montana, May through September 2006............................................................65

13. Analyses of field replicates for water samples, Clark Fork basin, Montana....................67

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

Montana .......................................................................................................................................70

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

basin, Montana ...........................................................................................................................71

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

samples ........................................................................................................................................72

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

upper Clark Fork basin, Montana.............................................................................................73

18. Analyses of field blanks for water samples ...........................................................................74

19. Analyses of fine-grained bed sediment, upper Clark Fork basin, Montana, 

August 2006..................................................................................................................................75

20. Recovery efficiency for analyses of standard reference materials for bed 

sediment.......................................................................................................................................76

21. Analyses of procedural blanks for bed sediment..................................................................77

22. Analyses of biota, upper Clark Fork basin, Montana, August 2006....................................78

23. Recovery efficiency for analyses of standard reference material for biota ....................80

24. Analyses of procedural blanks for biota.................................................................................81

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

basin, Montana, March 1985 through September 2006........................................................82

26. Statistical summary of long-term fine-grained bed-sediment data for the 

upper Clark Fork basin, Montana, August 1986 through August 2006. ............................101

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

Montana, August 1986 through August 2006........................................................................106
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 2006 is the period from October 1, 2005, through September 30, 2006.
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 microsiemens per centimeter at 25 degrees Celsius

mg/L milligrams per liter

nm nanometer

ppm part per million

Acronyms used in the report:

FNU formazin nephelometric units

ICAPES inductively coupled argon plasma-emission spectroscopy

LRL laboratory reporting level

LT–MDL long-term method detection level

NWQL USGS National Water Quality Laboratory, Denver, Colo.

NTRU nephelometric turbidity ratio unit

RSD relative standard deviation

spp. species

SRM standard reference material

USGS U.S. Geological Survey
Abstract

Water, bed sediment, and biota were sampled in streams 

from Butte to below Milltown Reservoir as part of a long-term 

monitoring program in the upper Clark Fork basin; additional 

water-quality samples were collected in the Clark Fork basin 

from sites near Milltown Reservoir downstream to near the 

confluence of the Clark Fork and Flathead River as part of 

a supplemental sampling program. The sampling programs 

were conducted 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-quality samples were collected 

periodically at 22 sites from October 2005 through September 

2006. Bed-sediment and biological samples were collected 

once at 12 sites during August 2006.

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 2005 through September 2006. Waterquality data include concentrations of selected major ions, 

trace ele­ments, and suspended sediment. Nutrients also were 

analyzed in the supplemental water-quality samples. Daily 

values of suspended-sed­iment concentration and suspendedsediment discharge were determined for four sites, and 

seasonal daily values of turbidity were determined for four 

sites. Bed-sediment data include trace-ele­ment concentrations in the fine-grained fraction. Bio­logical data include 

trace-element concentrations in whole-body tissue of aquatic 

benthic insects. Statistical summaries of long-term waterquality, 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 at Milltown Reservoir, 

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, light indus­try, hydroelectric power generation, 

and habitat for trout fisher­ies. Current land uses primarily are 

cattle production, logging, mining, residential development, 

and recreation. Large-scale mining and smelting were prevalent land uses in the upper basin for more than 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 1870 to 

1980. Mod­erate- and small-scale mining also occurred in the 

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

Tailings derived from past mineral processing commonly 

contain large quantities of trace elements such as arsenic, 

cadmium, copper, lead, and zinc. Tailings have been eroded, 

mixed with stream sediment, transported downstream, and 

deposited in stream channels, on flood plains, and in the Warm 

Springs Ponds and Milltown Reservoir. The widely dispersed 

tailings continue to be 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 bed sediment can pose a potential risk to 

aquatic biota and human health.

Concern about the potential toxicity of trace elements to 

aquatic biota and human health has resulted in a comprehensive effort by State, Federal, and private entities to characterize 

Water-Quality, Bed-Sediment, and Biological Data 

(October 2005 through September 2006) and Statistical 

Summaries of Long-Term Data for Streams in the Clark 

Fork Basin, Montana

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

1

U.S. Geological Survey, Menlo Park, Calif.
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, 1988, 1989, 1990, 1991; Lambing and others, 

1994, 1995; and Dodge and others, 1996, 1997, 1998, 1999, 

2000, 2001, 2002, 2003, 2004, 2005, 2006). 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 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 quality, 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). Of 

the sites that bracket Milltown Reservoir, three also are part of 

the long-term monitoring network. The supplemental monitoring provides additional special coverage of constituent concentrations prior to the planned removal of Milltown Dam.

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

for 22 sites and trace-element data for 12 bed-sediment and 

biological sites in the Clark Fork basin collected from October 

2005 through September 2006. Quality-assurance data are 

presented for water-quality, bed-sediment, and biota samples. 

Statistical summaries also are provided for long-term waterquality, 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 below Milltown 

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

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. Mainstem sampling sites were selected 

to divide the upper Clark Fork into reaches of relatively 

uniform length, with each reach encompassing either a major 

tributary or depositional environment (Warm Springs Ponds 

and Milltown Reservoir). Major tributaries were sampled to 

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

to provide reference comparisons to the mainstem. The three 

smaller tributaries were sampled to gain better spatial resolution on sources of metals entering the Clark Fork in an area 

of his­torical metal-processing activities near Anaconda. In 

the long-term monitoring program, water-quality data were 

obtained periodically at 19 sites; daily suspended-sediment 

data were obtained at 4 of the sites and daily turbidity data 

were obtained by continuous turbidity monitors at 4 of the 

sites. Trace-element data for 12 bed-sediment and 12 biological sites were obtained once annually. Continuous streamflow 

data were collected at 18 sites in the long-term monitoring 

network.

Supplemental water-quality samples were collected at 

six sites from near Milltown Reservoir 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 Milltown Reservoir and also are part of the long-term 

monitoring network; three additional sites (Bitterroot River 

near Missoula, Clark Fork at St. Regis, and Flathead River at 

Perma) are located farther downstream in the basin (fig. 1). 

The types of data collected and period of record for each 

type of data for the three additional sites that are not part of 

the long-term network also are listed in table 1 and shown in 

figure 1. Supplemental water-quality samples were collected 

during periods of either high flow or reservoir drawdown 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 2–3 day 

periods in an attempt to generally coincide with traveltime 

along the Clark Fork mainstem. 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 6 sites were collected 11 times from April 

to June 2006 during the rising limb and peak of the annual 

hydrograph and once in September during drawdown of 

Milltown Reservoir.

Properties measured onsite and constituents for which 

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

are listed in table 2. Data-quality objectives for analyses 

of water-quality samples are listed in table 3. Results of 

onsite measurements of properties; laboratory analyses of 

water-quality, bed-sediment, and biota samples; and qual­ityassurance data for water year 2006 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 2006 are listed 

in tables 25 through 27 at the back of the report.

Quality assurance of data was maintained through the 

use of documented procedures designed to provide environmentally representative data. Acceptable performance of the 

procedures was verified with quality-control samples that were 

collected systematically to provide a measure of the accuracy, 

precision, and bias of the environmental data and to identify 

problems associated with sampling, processing, or analysis.

   Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, 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

Base modified from U.S. Geological 

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

1966. North American Datum of 1927 

(NAD 27)

0 10 20 MILES

0 10 20 KILOMETERS

12340500

12340000

12334550

12331800

12324680

12324200

12323800

12323770 12323750

12323600

12323250

STREAMFLOW SITE TYPE

 Continuous record

 Periodic measurement

WATER-QUALITY, BED-SEDIMENT, 

AND BIOTA SITE TYPE

 Periodic water quality

 Daily suspended sediment

 Daily turbidity

 Once-annual bed sediment

 Once-annual biota

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’

12323760

12352500

12354500

12388700

Plains

Dempsey

Creek 461903112440701

461559112443301

461415112450801

Study area

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

Sampling Locations and Types of Data 
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 Net- work Continuous- record streamflow Periodic water-quality1 Daily suspended sediment Daily turbidity (seasonal) Fine-grained bed sediment2 Bulk bed sediment2,3 Biota2

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 08/93–08/95, 

08/97–08/04, D

07/92, 08/94–

08/95, 08/97–P

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 08/93, 08/95–

08/04, D

07/92–P

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

08/95, 08/97, 

08/99, 08/02, D

08/95, 08/97, 08/99, 08/02, 

08/05

12323800 Clark Fork near Galen LT 07/88–P 07/88–P -- -- 08/87, 08/91–P 08/93–08/04, D 08/87, 08/91–P

12323840 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 08/96–08/04, D 08/96–P

461559112443301 Clark Fork at county 

bridge, near Racetrack

LT -- -- -- -- 08/96–P 08/96–08/04, D 08/96–P

 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
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 Net- work Continuous- record streamflow Periodic water-quality1 Daily suspended sediment Daily turbidity (seasonal) Fine-grained bed sediment2 Bulk bed sediment2,3 Biota2

461903112440701 Clark Fork at Dempsey 

Creek diversion, near Racetrack

LT -- -- -- -- 08/96–P 08/96–08/04, D 08/96–P

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

08/93–08/04, D 08/86–08/87, 

08/90–P

12324680 Clark Fork at Goldcreek LT 10/77-P 03/93–P -- -- 07/92–P 08/93–08/04, D 07/92–P

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

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 08/93–08/04, D 08/86, 08/91–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

08/93, 08/94, 

08/99–01, 

09/03, D

08/86–08/87, 08/91, 08/93, 08/96, 08/98, 09/00, 09/03,

08/06

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

-- 08/97–P 08/97–08/04, D 08/97–P

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 analyses included only trace elements 

and suspended sediment, with the exception of Clark Fork below Missoula.

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 only included suspended-sediment data.

Sampling Locations and Types of Data   
Table 2. Properties measured onsite and constituents analyzed in samples of 

water, bed sediment, and biota from the Clark Fork basin, Montana.

Water quality Bed sediment Biota

Property Constituent Constituent Constituent

Streamflow Hardness (calculated) Arsenic Arsenic

Specific conductance Calcium Cadmium Cadmium

pH Magnesium Chromium Chromium

Temperature Nitrogen Copper Copper

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-quality samples collected in the Clark Fork basin, Montana.

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

Constituent

Data-quality objectives

Detectability Precision Bias

Laboratory 

reporting 

level

Maximum relative standard 

deviation of replicate analyses, 

in percent

Maximum deviation 

of spike recovery, 

in percent

Calcium, filtered 0.02 mg/L 20 --

Magnesium, filtered .008 mg/L 20 --

Nitrogen, unfiltered recoverable .06 mg/L 20 25

Phosphorus, unfiltered recoverable .004 mg/L 20 25

Arsenic, filtered .12 μg/L 20 25

Arsenic, unfiltered recoverable .12 μg/L 20 25

Cadmium, filtered .04 μg/L 20 25

Cadmium, unfiltered recoverable .04 μg/L 20 25

Copper, filtered .4 μg/L 20 25

Copper, unfiltered recoverable .6 μg/L 20 25

Iron, filtered 6 μg/L 20 25

Iron, unfiltered recoverable 6 μg/L 20 25

Lead, filtered .08 μg/L 20 25

Lead, unfiltered recoverable .06 μg/L 20 25

Manganese, filtered .2 μg/L 20 25

Manganese, unfiltered recoverable1 .2-.6 μg/L 20 25

Zinc, filtered .6 μg/L 20 25

Zinc, unfiltered recoverable 2 μg/L 20 25

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

Sediment, suspended 1 mg/L 20 --

1

The laboratory reporting level changed during water year 2006.

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

Water-quality data consist of onsite measurements of 

selected stream properties and concentrations of chemical 

and physical constituents analyzed in periodically collected 

stream samples. At 19 sites in the upper Clark Fork basin, 

samples for the long-term monitoring program were collected 

6–­­8 times per year on a schedule designed to describe seasonal and hydrologic vari­ability. At the 3 sites bracketing 

Milltown Reservoir and at the 3 additional sites downstream 

from Missoula, 12 supplemental water-quality samples were 

collected. At the 4 daily suspended-sediment sites, suspendedsediment samples were collected by an observer 2–11 times 

per week. Continuous turbidity monitors were operated 

seasonally (May/June–September) at four sites near Anaconda 

(table 1).

Methods

Water samples were collected from vertical transits 

throughout the entire stream depth at multiple locations 

across the stream using depth- and width-integration methods 

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

(1999), and the USGS National Field Manual for the Collection of Water-Quality Data (variously dated). These methods 

pro­vide a vertically and laterally discharge-weighted composite sample that is 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 non-metallic epoxy 

paint and equipped with nylon or Teflon nozzles.

Instantaneous streamflow at the time of water sampling 

was determined at all sites, either by direct measurement or 

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

Onsite measurements of specific conductance, pH, and water 

temperature were made during collection of periodic waterquality samples. Onsite sample processing, including filtration and preservation, was performed according to procedures 

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

(1994), and the USGS National Field Manual for the Collection of Water Quality Data (variously dated).

Water-quality samples were analyzed for the constituents 

listed in table 2. The terms “filtered” and “unfiltered recoverable” replace the terms “dissolved” and “total recoverable,” 

respec­tively, which were used in the past. Filtered (0.45-μm 

pore size) and unfiltered recoverable concentrations of the 

trace elements (arsenic, cadmium, copper, iron, lead, manganese, and zinc) were determined by the USGS National Water 

Quality Labora­tory (NWQL) in Denver, Colo. Filtered concentrations of calcium and magnesium also were determined to 

enable calculation of hardness. Concentrations of the nutrients 

total nitrogen and total phosphorous were determined for the 

supplemental water-quality samples.

Filtered concentrations of arsenic, cadmium, copper, lead, 

manganese, and zinc were determined by inductively cou­pled 

plasma-mass spectro­metry (Faires, 1993; Garbarino, 1999). 

Filtered concentrations of calcium, magnesium, and iron were 

determined by inductively coupled plasma-atomic 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) and then analyzed by inductively 

coupled plasma-mass spectrome­try (Garbarino and Struzeski, 

1998). Unfiltered recoverable concentrations of nitrogen and 

phosphorous were determined from unfiltered samples that 

were digested with alkaline persulfate and then analyzed by 

colorimetry (Patton and Kryskalla, 2003).

Water samples also were collected from multiple vertical transits for analysis of suspended sediment whenever 

periodic water-quality 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 near mid-stream. 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).

Turbidity data were obtained by continuous turbidity 

monitors at four tributary sites (table 1) in the upper Clark 

Fork basin near Anaconda. These monitors were installed in 

May–June 2006 to provide supporting information on runoff 

conditions in an area where remediation activities are being 

conducted. The monitors are operated seasonally, generally 

from early spring (after ice breakup) through September, 

although attempts are made to extend the period of operation 

as weather permits. The monitors record turbidity values at 

15–minute intervals, which can be viewed in near 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 for a 24–hour period. Procedures for the operation of continuous turbidity monitors and 

for daily record computations are described by Wagner and 

others (2006).

Water-Quality Data 
Results

Water-quality data for samples collected periodically 

dur­ing water year 2006 are listed in table 4. Daily mean 

streamflow, daily mean suspended-sediment concentration, 

and daily suspended-sediment discharge for water year 2006 

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 is 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-quality 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-quality 

samples was evaluated by the use of 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 qualitycontrol sample was submitted at a proportion equivalent to 

about 5 percent of the total number of water-quality samples. 

Therefore, the total number of quality-control samples represented about 15 percent of the total number of water-quality 

samples.

In addition to 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 where standard 

reference water samples prepared by the USGS Branch of 

Qual­ity Systems are routinely inserted into the sample line 

for each analytical method at a frequency proportional to 

the sample load. The laboratory also participates in external 

evaluation studies and audits with the National Environmental Laboratory Accreditation Program, 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 all sources of 

variability, replicate stream samples for chemical analysis 

were obtained in the field by splitting a composite stream 

sample, and replicate stream samples for suspended-sediment 

analysis were obtained in the field by concurrently collecting 

two independent cross-sec­tional samples. Analyses of these 

field replicates indicate the reproducibility of environmental 

data that are affected by the combined variability potentially 

introduced by field and labora­tory processes.

Precision of analytical results for laboratory repli­cates, 

which exclude field sources of variability, was determined by 

two indepen­dent analyses of a single sample selected from the 

group of samples comprising each analytical run. A separate 

analysis of the sample was made at the beginning and end of 

each analytical run to provide infor­mation on the reproducibility of laboratory analytical results independent of possible 

variability caused by field sample collection and processing.

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-quality samples were analyzed. Analyses of these 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 

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

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 

LT-MDL values are designed to limit the possible occurrence 

of a false positive or false negative error to 1 percent or less. 

Accordingly, concentrations are reported as less than the LRL 

for samples in which the analyte was either not detected or did 

not pass identification criteria. Analytes that are detected at 

concentrations between the LT–MDL and LRL and that pass 

identification criteria are 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):

S

d

k = ∑ 2

2

 , (1)

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, in percent, is calculated according to 

the fol­lowing equation (Taylor, 1987):

× 100

x

S RSD = , (2)

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. 

Data-quality objectives for precision are not directly applicable to field replicates because of the inability to determine 

whether the variability results from field sample collection and 

processing or laboratory handling and analysis. However, the 

precision of analytical results for field replicates is calculated 

to illustrate overall reproducibility of environ­mental data that 

incorporates both field and laboratory sources of variability. 

The data-quality objective used to indicate acceptable precision of results for field replicates was a maxi­mum 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 (table 14).

The precision estimated for each constituent on the 

basis of analyses of laboratory replicates, which include only 

laboratory sources of variability, is listed in table 15. Statistics 

for the precision of analytical results for laboratory repli­cates 

are based on 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); thus, the data-quality objectives for 

precision were met.

Water-Quality Data 
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 3:

R

D

C

= ×100 , (3)

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 94.9 to 106 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. 

The mean spike recovery for spiked stream samples (table 17) 

ranged from 91.2 to 108 percent. The 95-percent confidence 

intervals for the mean spike recovery for each constituent 

for which laboratory-spiked stream 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 based on 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 iron (101–112 percent). All laboratory-spiked stream 

samples (table 17) also had confidence intervals for percent 

recovery that included 100 percent except for unfiltered 

recoverable copper (91.0–98.6 percent), unfiltered recoverable iron (102–109 percent), and unfiltered recoverable zinc 

(87.8–94.6 percent). Both the 95-percent confidence interval (91.0–98.6) and mean spike recovery (94.8 percent) for 

unfiltered recoverable copper in laboratory-spiked stream 

samples indicate a persistent but minor, low bias. Similarly, 

the 95-percent confidence interval (87.8–94.6) and mean 

spike recovery (91.2 percent) for unfiltered recoverable zinc 

also showed a low bias. In contrast, the respective 95-percent 

confidence interval (93.8–104 and 90.1–100) and mean spike 

recovery (98.7 and 94.9 percent) for unfiltered recoverable 

copper and zinc in laboratory-spiked deionized-water blank 

sample showed no indication of bias. Thus, it appears that the 

minor bias in spiked stream samples is not necessarily caused 

by the analytical method but might be a result of analytical 

interference from the chemical matrix of the stream sample. 

For unfiltered recoverable iron in both the laboratory-spiked 

deionized-water blank sample and the laboratory-spiked 

stream sample, a slight high bias in the respective 95-percent 

confidence interval (101–112 and 102–109) and mean spike 

recovery (106 and 105 percent) was observed. Because the 

mean spike recoveries for all constituents met data-quality 

objectives (less than a 25-percent deviation from 100-percent 

recovery) for both laboratory-spiked deionized-water blank 

samples and laboratory-spiked stream samples, no adjustments 

were made to analytical results for stream samples on the basis 

of spike recoveries.

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 were 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. Three detections 

exceeded twice the LRL in two separate samples. Two 

occurred on May 24, 2006, for filtered copper (1.8 μg/L), 

which was greater than the LRL of 0.4 μg/L and filtered zinc 

(3.1 μg/L), which was greater than the LRL of 0.6 μg/L. The 

third occurred on June 13, 2006, for filtered zinc (1.3 μg/L). 

Because no trends were indicated in subsequent sampling 

trips, no adjustments were made to water-qual­ity sample 

results based on these three detections.

10 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
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 (<0.064 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. Bedsed­iment samples were collected once annually at 12 sites 

(fig. 1, 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 2006 using protocols described by E.V. Axtmann 

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

were collected from the surfaces of streambed deposits in 

low-velocity areas near the edge of the stream using an acidwashed polypropylene scoop. Whenever possible, samples 

were collected from both sides of the stream. Three composite 

samples of bed sediment were collected at each site.

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 0.064-mm nylonmesh sieve using ambient stream water. The fraction of 

bed sediment in each composite sample that was finer than 

0.064 mm was transferred to an acid-washed 500-mL polyethylene bottle and transported to the laboratory on ice.

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 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 digestion period of 

as much as 2 weeks, the aliquots were evaporated to dryness 

on a hot plate. The dry residue was reconstituted in 10 mL of 

0.6N (normal) hydrochloric acid. The reconstituted aliquots 

then were filtered through a 0.45-μm filter using a syringe and 

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

1:10 ratio with 0.6N hydro­chloric acid. These final solutions 

were analyzed for arsenic, cadmium, chromium, copper, iron, 

lead, manganese, nickel, and zinc using inductively coupled 

argon plasma-emission spectroscopy (ICAPES). The smallest 

concentration of a con­stituent that can be reliably reported for 

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 2006 

are listed in table 19. Liquid-phase concentrations, in μg/mL 

(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 μg/g, using 

the following equation:

μg/g = (μg/mL) (volume of digested sample, in mL)

(dry weight of sample, in grams)(dilution ratio)

 . (4)

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.

Quality Assurance

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

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

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

in a laboratory-grade detergent and rinsed with deionized 

water. All equipment received a final rinse onsite with stream 

water. 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 

Bed-Sediment Data 11
measure a known quantity of a constit­uent. Multiple analyses of the SRMs are made to derive a mean and 95-percent 

confidence interval for recovery. Recovery effi­ciency for 

trace-element analyses of SRMs for bed sediment is 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 

copper, iron, manganese, nickel, and zinc, mean SRM recoveries for the low-concentration standard (SRM 2709) ranged 

from 89.9 to 99.8 percent of the certified concentrations. Mean 

recoveries were lower for arsenic and chromium (73.5 and 

78.1 percent, respectively) and higher for lead (136.4 percent). 

Cadmium concentrations were near the minimum reporting 

level in SRM 2709 and were not reported. The lack of measurable recoveries for cadmium in the SRM likely is the result of 

analyzing concentrations very close to the liquid-phase detection limit (0.0005 μg/mL) coupled with signal enhancement 

resulting from matrix interference. The generally small range 

of variation (less than 5 percent for most constituents) for the 

95-percent confidence interval indicates good reproducibility 

of multiple analyses of SRM 2709. Mean SRM recoveries for 

arsenic, cadmium, copper, iron, lead, manganese, nickel, and 

zinc for the high-concentration standard (SRM 2711) ranged 

from 81.6 to 101.6 percent of the certified concentrations. 

Chro­mium had a lower recovery (66.1 percent) for the highconcentration standard, possibly because of the strong binding 

nature of this element to sediment. The generally small range 

of variation (less than 5 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 bedsediment samples. Analytical results of proce­dural blanks 

for bed sediment (table 21) are reported as a liquid-phase 

concentration, in μg/mL, which is equivalent to parts per 

million (ppm). 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 trace-element 

con­centrations in the whole-body tissue of aquatic benthic 

insects. Insect samples were collected once annually at the 

same 12 sites and on the same dates as bed-sediment samples 

(fig. 1, 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 using 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).

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 tana were collected in a few instances.

Hydropsyche species (spp.) that could not be positively 

iden­tified were considered to belong to the morosa group and 

are categorized as Hydropsyche spp. or Hydropsyche morosa

group (in previous reports). The caddisfly Arctopsyche grandis

and the stonefly Claasenia sabulosa were collected where 

available to represent additional insect taxa that are commonly 

distrib­uted in the upper Clark Fork basin. In addition, the 

caddisfly group Brachycentrus spp. was sometimes collected 

when tar­geted taxa were not available.

Samples of each taxon were sorted by genus in the field 

and placed in acid-washed plastic containers. Samples were 

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

amount of ambient stream water. Between 1986 and 1998, 

macroinvertebrate containers were kept on ice to allow the 

insects to evacuate their gut contents for a period of 6 to 

8 hours. Excess water was drained and insects were frozen 

for transport to the laboratory. To reduce the possibility of 

metal loss through intracellular breakdown during depuration, samples were immediately frozen on dry ice in the field 

between 1999 and 2006. A comparison of immediately frozen 

12 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
versus depurated samples showed that although no substantial difference occurred for most metals, concentrations of 

copper in the depurated macroinverte­brate samples were about 

20 percent lower 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 ultra-pure 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 filter, and analyzed undiluted by 

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

manganese, nickel, and zinc. The smallest concentration of a 

constituent that can be reliably reported for analyses of biota is 

termed the minimum reporting level.

Results

Concentrations of trace elements in whole-body tissue 

of aquatic insects collected during August 2006 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 μg/mL, analyzed in the reconstituted 

samples were converted to solid-phase concentrations, in μg/g, 

using equation 4. As with bed sedi­ment, minimum reporting 

levels may differ among sites as a result of variable sample 

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

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

reporting level. Therefore, higher mini­mum reporting levels do 

not necessarily imply a higher 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 ultra-pure deionized 

water prior to the first sample collection. Nets and equipment 

were thoroughly rinsed in ambient stream water at each new 

main­stem site. New nets were used for all tributary sites. Biota 

sam­ples were collected sequentially at sites along an increasing concentration gradient to minimize effects from potential 

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 12 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 99.5 to 110 percent 

of the certified concentrations for arsenic, cadmium, copper, 

iron, manganese, nickel, and zinc. A lower mean recovery 

was measured for lead (85.2 percent). A higher mean recovery was measured for chromium (173 percent), with 7 of the 

12 analyses having concentrations less than, or very near, the 

minimum reporting level. With the exception of chromium and 

lead, both of which had low certified concentrations (0.77 μg/g 

and 0.35 μg/g, respectively) in the SRM, the range in variation of the 95-percent confidence interval generally was 

within 10 percent, thereby indicating good reproducibility of 

multiple analyses of the SRM. No adjustments were made to 

trace-element concentrations in biota samples on the basis of 

recovery efficiencies.

Procedural blanks for biota consisted of the same 

reagents used to digest and reconstitute tissue of aquatic 

insects and were analyzed undiluted. Analytical results of 

procedural blanks for biota (table 24) are reported as a liquidphase concentration, in μg/mL, which is equivalent to ppm. A 

procedural blank was prepared and analyzed concurrently with 

biota sam­ples for each site. Concentrations of trace elements 

in most pro­cedural blanks were less than the minimum reporting level. In a few instances, concentrations exceeded the limit 

of detection; however, procedural-blank concentrations were 3 

to 4 orders of magnitude lower than those measured in tissue 

samples. 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 

Statistical Summaries of Data 13
of results for supplemental samples that targeted high-flow 

conditions or maintenance drawdowns of Milltown Reservoir 

would dispro­portionately skew the long-term statistics rel­ative 

to the other sites in the network. Statistical summaries of finegrained bed-sediment (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.

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 variable 

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.

References Cited

Anderson, C.W., 2004, Turbidity (version 2.0): U.S. Geological Survey Techniques of Water-Resources Investigations, 

book 9, chap. A6, section 6.7, 64 p; available at http://pubs.

water.usgs.gov/twri9A6/

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

of tributary inflows on the distribution of trace metals in 

fine-grained sediment and benthic insects of the Clark Fork 

River, Montana: Environmental Science and Technology, 

v. 31, no. 3, p. 750–758.

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

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

no. 6, p. 75–88.

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

of gut content in immature aquatic insects on assessments 

of environmental metal contamination: Canadian Journal of 

Fisheries and Aquatic Sciences, v. 52, no. 12, 

p. 2,736–2,746.

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

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

of Fisheries and Aquatic Sciences, v. 49, no. 10, 

p. 2,141–2,154.

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

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

method detection levels and some considerations for 

inter­pretations of water-quality data provided by the U.S. 

Geolog­ical Survey National Water Quality Laboratory: U.S. 

Geo­logical Survey Open-File Report 99–193, 19 p.

Davis, B.E., 2005, A guide to the proper selection and use of 

federally approved sediment and water-quality samplers: 

Federal Interagency Sedimentation Project, Vicksburg, 

Miss., U.S. Geological Survey Open-File Report 2005–

1087, 20 p.

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

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

1994 through September 1995) and statistical summaries 

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

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

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

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

1995 through September 1996) and statistical summaries 

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

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

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

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

1996 through September 1997) and statistical summaries 

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

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

Dodge, K.A., Hornberger, M.I., and Bouse, R.M., 1999, 

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

1997 through September 1998) and statistical summaries 

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

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

14  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Dodge, K.A., Hornberger, M.I., and David, C.P.C., 2000, 

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

1998 through September 1999) and statistical summaries 

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

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

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

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

1999 through September 2000) and statistical summaries 

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

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

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

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

2000 through September 2001) and statistical summaries 

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

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

Dodge, K.A., Hornberger, M.I., and Lavigne, I.R., 2003, 

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

2001 through September 2002) and statistical summaries 

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

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

Dodge, K.A., Hornberger, M.I., and Lavigne, I.R., 2004, 

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

2002 through September 2003) and statistical summaries 

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

U.S. Geological Survey Open-File Report 2004–1340, 

107 p.

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

through September 2004) and statistical summaries of data 

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

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

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2006, Waterquality, bed-sediment, and biological data (October 2004 

through September 2005) and statistical summaries of data 

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

Geological Survey Open-File Report 2006–1266, 109 p.

Dodge, K.A., and Lambing, J.H., 2006, Quality-assurance plan 

for the analysis of suspended sediment by the U.S. Geological Survey in Montana: U.S. Geological Survey Open-File 

Report 2006–1242, 25 p.; available at http://pubs.water.

usgs.gov/ofr2006–1242/

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

measurement of fluvial sediment: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

chap. C2, 89 p.; available at http://pubs.usgs.gov/twri/

Faires, L.M., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—

Determination of metals in water by inductively coupled 

plasma-mass spec­trometry: U.S. Geological Survey 

Open-File Report 92–634, 28 p.

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

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

Report 93–125, 217 p.

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

practices for the chemical and biological analyses of water 

and fluvial sediments: U.S. Geological Survey Techniques 

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

181 p.; available at http://pubs.usgs.gov/twri/

Garbarino, J.R., 1999, Methods of analysis by the U.S. Geolog­ical Survey National Water Quality Laboratory—

Determina­tion of dissolved arsenic, boron, lithium, selenium, strontium, thallium, and vanadium using inductively 

coupled plasma-mass spectrometry: U.S. Geological Survey 

Open-File Report 99–093, 31 p.

Garbarino, J.R., and Struzeski, T.M., 1998, Methods of analysis by the U.S. Geological Survey National Water Quality 

Lab­oratory—Determination of elements in whole-water 

digests using inductively coupled plasma-optical emission 

spec­trometry and inductively coupled plasma-mass spectrometry: U.S. Geological Survey Open-File Report 98–165, 

101 p.

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

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

at http://pubs.usgs.gov/twri/

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

statistics for multiply censored water quality data: Water 

Resources Research, v. 24, no. 12, p. 1,997–2,004.

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

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

Water Quality Laboratory—In-bottle acid digestion of 

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

Report 96–225, 28 p.

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

E.V., 1997, Spatial and temporal trends of trace metals in 

sur­face water, bed sediment, and biota of the upper Clark 

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

Open-File Report 97–669, 84 p.

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

and Rickert, D.A., 1994, U.S. Geological Survey protocol 

for the collection and processing of surface-water samples 

for the subsequent determination of inorganic constituents in filtered water: U.S. Geological Survey Open-File 

Report 94–539, 57 p.

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

References Cited 15
Lambing, J.H., 1987, Water-quality data for the Clark Fork 

and selected tributaries from Deer Lodge to Milltown, 

Montana, March 1985 through June 1986: U.S. Geological 

Survey Open-File Report 87–110, 48 p.

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

September 1987) and statistical summaries (March 1985 

through September 1987) for the Clark Fork and selected 

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

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

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

through September 1988) and statistical summaries (March 

1985 through September 1988) for the Clark Fork and 

selected tributaries from Galen to Missoula, Montana: U.S. 

Geologi­cal Survey Open-File Report 89–229, 51 p.

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

through September 1989) and statistical summaries (March 

1985 through September 1989) for the Clark Fork and 

selected tributaries from Galen to Missoula, Montana: U.S. 

Geologi­cal Survey Open-File Report 90–168, 68 p.

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

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

Investigations Report 91–4139, 73 p.

Lambing, J.H., comp., 2006, Quality-assurance plan for waterquality activities of the U.S. Geological Survey Montana 

Water Science Center: U.S. Geological Survey Open-File 

Report 2006–1275, 39 p.; available at http://pubs.usgs.

gov/of/2006/1275/

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

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

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

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

Report 95–429, 104 p.

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

D.A., 1994, Water-quality, bed-sediment, and biological data (October 1992 through September 1993) and 

statistical sum­maries of water-quality data (March 1985 

through September 1993) for streams in the upper Clark 

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

Report 94–375, 85 p.

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

of the form of trace metals in oxidized estuarine sediments 

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

Maloney. T.J., ed., 2005, Quality management system, U.S. 

Geological Survey National Water Quality Laboratory: 

U.S. Geological Survey Open-File Report 2005-1263, 

version 1.3, November 9, 2005, chapters and appendices 

[variously paged].

Patton, C.J., and Kryskalla, J.R., 2003, Methods of analysis by 

the U.S. Geological Survey National Water Quality Laboratory—Evaluation of alkaline persulfate digestion as an alternative to Kjeldahl digestion for determination of total and 

dissolved nitrogen and phosphorous in water: U.S. Geological Survey Water-Resources Investigation Report 03–4174, 

33 p.

Porterfield, George, 1972, Computation of fluvial-sediment 

dis­charge: U.S. Geological Survey Techniques of WaterResources Investigations, book 3, chap. C3, 66 p.; available 

at http://pubs.usgs.gov/twri/

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

quality control manual—National Water Quality Laboratory: U.S. Geological Survey Open-File Report 95–443, 

35 p.

Rantz, S.E., and others, 1982, Measurement and computation of streamflow: U.S. Geological Survey Water-Supply 

Paper 2175, 2 v., 631 p.

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

U.S. Geological Survey, variously dated, National field 

manual for the collection of water-quality data: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chaps. A1–A9; available at http://pubs.usgs.

gov/twri/

Wagner, R.J., Boulger, R.W., Oblinger, C.J., and Smith, B.A., 

2006, Guidelines and standard procedures for continuous 

water-quality monitors—Station operation, record computation, and data reporting: U.S. Geological Survey Techniques 

and Methods 1–D3, 51 p., 8 attachments; available at http://

pubs.usgs.gov/tm/2006/tm1D3/

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

and processing of surface-water and bed-material samples 

for physical and chemical analyses: U.S. Geological Survey 

Open-File Report 90–140, 71 p.

16 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Data
Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

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)

10/17/2005 0915 4.4 7.6 291 7.0 110 32.9 7.95

03/20/2006 0930 4.9 7.8 299 3.0 130 36.4 9.02

04/17/2006 1000 32 7.7 187 3.0 71 20.3 4.90

05/08/2006 0840 17 7.7 198 5.0 81 23.8 5.35

05/22/2006 0935 13 7.8 240 11.5 94 27.1 6.30

06/08/2006 1550 13 7.8 247 15.5 96 27.9 6.43

07/24/2006 0900 3.1 7.7 338 12.5 140 39.9 9.18

08/23/2006 0950 2.7 7.8 359 10.5 140 40.9 10.2

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)

10/17/2005 2.2 3.0 0.08 E0.04 2.3 4.4 121 426

03/20/2006 1.8 2.8 .06 .05 2.0 6.5 134 692

04/17/2006 5.1 6.4 .05 .06 7.6 10.4 313 806

05/08/2006 4.7 5.3 <.04 E.04 5.4 7.5 193 468

05/22/2006 8.7 10.3 E.04 .04 5.7 7.8 412 828

06/08/2006 8.2 11.4 E.03 .08 5.2 10.9 640 1,640

07/24/2006 2.9 3.5 .05 E.02 1.3 2.0 52 223

08/23/2006 2.1 2.5 E.03 .05 1.2 2.0 32 157

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)

10/17/2005 0.09 0.46 26.5 38.1 2.9 5 85 7 0.08

03/20/2006 .10 1.45 54.0 73.6 3.3 8 89 10 .13

04/17/2006 .37 1.07 24.9 33.5 5.5 6 69 10 .86

05/08/2006 .14 .55 27.7 31.7 2.2 3 83 5 .23

05/22/2006 .23 .72 44.5 52.2 2.9 4 95 4 .14

06/08/2006 .30 1.81 37.5 74.4 3.5 9 90 14 .49

07/24/2006 <.08 .14 52.8 52.7 2.2 2 73 3 .03

08/23/2006 <.08 .10 41.0 41.1 1.8 2 80 2 .01

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

10/17/2005 1010 17 7.7 445 13.0 140 39.7 10.5

03/20/2006 1100 19 7.6 532 4.5 160 46.0 11.1

04/17/2006 1140 54 7.7 326 4.5 110 30.7 7.37

05/08/2006 1000 36 7.7 363 7.0 120 35.0 7.88

05/22/2006 1055 27 7.8 408 13.5 140 39.3 9.15

06/08/2006 1720 34 7.7 414 18.0 140 41.1 9.35

07/24/2006 1020 15 7.6 520 17.0 160 45.3 11.2

08/23/2006 1120 15 7.7 577 16.0 180 51.8 13.1

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)

10/17/2005 4.2 4.9 0.13 0.16 7.7 14.1 35 248

03/20/2006 3.1 4.0 .09 .20 5.2 22.6 53 338

04/17/2006 6.0 7.9 .11 .23 14.4 22.5 219 685

05/08/2006 5.0 6.2 .15 .25 12.0 18.5 123 407

05/22/2006 7.6 9.7 .12 .23 13.4 20.4 194 615

06/08/2006 8.1 11.2 .13 .30 12.7 27.1 187 928

07/24/2006 5.2 5.7 .17 .21 13.9 18.7 24 144

08/23/2006 5.2 5.6 .11 .20 5.8 15.1 31 135

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)

10/17/2005 0.19 1.27 72.7 90.4 36.0 46 77 6 0.28

03/20/2006 .32 2.31 97.9 119 42.4 61 81 11 .56

04/17/2006 .46 3.19 82.7 104 40.2 48 81 12 1.7

05/08/2006 .22 1.34 91.5 94.6 45.8 56 84 7 .68

05/22/2006 .31 2.01 90.1 105 33.4 45 92 8 .58

06/08/2006 .44 4.99 86.7 117 68.8 61 88 15 1.4

07/24/2006 .23 .77 59.8 72.1 47.8 55 91 2 .08

08/23/2006 .17 .64 69.6 81.4 41.8 57 77 4 .16

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

Data 19
Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

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)

10/18/2005 0735 34 8.2 512 8.0 180 53.3 12.2

03/20/2006 1540 26 8.4 534 6.5 190 54.5 11.8

04/18/2006 0910 113 8.1 353 2.0 120 36.7 8.05

05/09/2006 0915 105 8.2 325 4.0 120 37.6 7.09

05/23/2006 0705 101 8.1 331 9.5 130 40.0 7.16

06/13/2006 1050 114 8.2 348 15.5 130 38.9 7.80

07/25/2006 0830 18 8.3 589 16.5 210 61.5 13.2

08/24/2006 0850 13 8.4 588 11.5 210 60.2 14.0

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)

10/18/2005 11.4 18.9 0.40 1.29 13.7 143 13 972

03/20/2006 11.4 14.9 .53 .87 25.2 78.4 21 628

04/18/2006 11.5 20.7 .85 1.52 57.1 141 152 1,380

05/09/2006 10.4 14.6 .34 .77 22.3 66.0 78 744

05/23/2006 10.3 14.7 .24 .72 15.7 70.8 61 881

06/13/2006 15.0 24.2 .46 1.30 38.9 146 139 1,420

07/25/2006 18.2 20.6 .22 .71 20.8 69.5 22 467

08/24/2006 16.6 19.0 .20 .70 19.3 70.8 28 434

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)

10/18/2005 0.44 30.0 210 346 148 320 92 26 2.4

03/20/2006 .37 14.6 304 340 138 221 84 15 1.1

04/18/2006 1.69 30.6 302 372 274 329 82 38 12

05/09/2006 .76 15.2 167 194 99.3 162 85 20 5.7

05/23/2006 .54 18.0 123 200 62.4 142 87 29 7.9

06/13/2006 2.22 33.4 170 275 98.3 245 84 38 12

07/25/2006 .57 12.4 153 210 42.1 139 81 14 .68

08/24/2006 .55 11.9 132 200 44.1 147 85 16 .56

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

10/17/2005 1325 13 E0.4 8.3 185 9.5 83 22.2 6.67

03/20/2006 1240 9.1 <2.0 8.5 203 3.0 98 25.9 8.01

04/17/2006 1425 42 5.5 8.1 129 5.0 49 13.7 3.66

05/08/2006 1230 63 2.8 8.1 106 6.0 44 12.5 3.06

05/22/2006 1325 165 2.5 7.9 65 8.0 27 7.87 1.71

06/09/2006 0845 136 <2.0 7.8 63 7.5 27 7.97 1.67

07/24/2006 1240 20 2.4 8.2 147 16.0 65 18.3 4.75

08/23/2006 1335 11 <2.0 8.4 180 15.5 79 21.5 6.09

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)

10/17/2005 15.4 16.6 E0.04 0.05 1.2 1.5 78 128

03/20/2006 10.6 12.0 E.04 .05 .86 1.6 30 125

04/17/2006 27.3 30.1 .05 .10 4.7 6.8 67 291

05/08/2006 22.5 23.0 <.04 .09 3.3 5.1 41 178

05/22/2006 12.3 13.7 E.03 .09 3.2 5.4 30 266

06/09/2006 8.6 9.9 E.03 .08 2.2 4.1 28 184

07/24/2006 23.0 24.2 .05 .08 1.8 3.1 78 173

08/23/2006 21.0 22.6 .04 .06 1.3 2.2 83 159

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)

10/17/2005 0.09 0.20 6.8 11.3 0.78 E1 74 2 0.07

03/20/2006 <.08 .28 6.7 13.8 .80 E1 68 2 .05

04/17/2006 .24 1.07 6.1 16.8 2.4 4 79 8 .91

05/08/2006 .10 1.05 4.3 10.9 1.5 4 53 9 1.5

05/22/2006 .09 1.12 3.6 15.4 1.8 4 39 12 5.3

06/09/2006 .08 .79 3.4 11.1 1.6 3 47 8 2.9

07/24/2006 .18 .63 7.9 14.9 1.0 E2 77 3 .16

08/23/2006 .12 .45 7.8 14.1 .73 E1 80 1 .03

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

Data 21
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)

10/17/2005 1550 4.0 8.1 211 11.0 91 25.1 6.89

03/20/2006 1410 1.9 8.1 223 4.5 100 28.0 7.83

04/18/2006 0745 22 8.0 145 1.0 58 16.2 4.34

05/08/2006 1525 24 8.1 120 10.5 49 13.9 3.39

05/22/2006 1510 120 7.8 70 9.5 28 8.30 1.87

06/09/2006 1215 113 7.8 69 9.5 28 8.10 1.77

07/24/2006 1505 3.5 8.2 165 20.0 72 20.4 5.11

08/23/2006 1600 1.5 8.2 199 17.5 86 23.9 6.29

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)

10/17/2005 23.9 25.3 0.07 0.09 1.9 2.5 90 140

03/20/2006 11.4 12.9 .05 .06 1.2 1.7 25 67

04/18/2006 26.8 31.1 .07 .12 4.9 7.1 63 246

05/08/2006 28.6 30.5 E.03 .11 3.9 6.1 38 199

05/22/2006 20.3 28.9 .07 .29 5.8 18.9 36 774

06/09/2006 16.2 19.7 .04 .14 3.5 8.1 33 332

07/24/2006 34.9 35.4 .05 .06 2.4 3.3 72 128

08/23/2006 32.2 34.1 E.03 .06 2.2 2.9 59 110

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)

10/17/2005 0.09 0.15 11.0 12.0 2.8 3 82 2 0.02

03/20/2006 <.08 .07 9.1 10.4 2.7 3 80 1 .01

04/18/2006 .20 .93 4.8 13.1 4.8 6 80 5 .30

05/08/2006 .09 .86 4.8 13.0 2.1 4 78 5 .32

05/22/2006 .17 4.88 4.7 29.1 3.9 14 41 39 13

06/09/2006 .13 1.79 3.2 15.8 2.9 7 43 18 5.5

07/24/2006 .18 .38 9.5 11.8 1.8 2 88 1 .01

08/23/2006 .10 .21 7.7 9.1 1.4 4 86 2 .01

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

22 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

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)

10/17/2005 1200 1.4 E0.8 7.7 115 6.0 41 13.7 1.63

04/17/2006 1315 15 12 7.6 93 3.5 33 11.2 1.25

05/08/2006 1135 18 5.8 7.7 73 4.5 26 8.85 .987

05/22/2006 1215 25 7.1 7.7 66 8.0 22 7.56 .777

06/09/2006 0735 10 2.5 7.8 92 7.5 34 11.8 1.18

07/24/2006 1145 3.0 2.1 7.6 109 15.0 39 13.3 1.40

08/23/2006 1235 1.3 2.1 7.7 111 13.0 39 13.2 1.48

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)

10/17/2005 16.5 17.7 0.04 0.04 1.6 2.1 74 145

04/17/2006 19.2 20.5 E.04 .06 3.9 5.0 154 474

05/08/2006 14.7 15.6 <.04 .04 2.6 3.7 67 337

05/22/2006 14.1 14.6 <.04 .08 2.3 4.1 43 401

06/09/2006 13.3 13.9 E.03 .05 2.0 2.8 52 168

07/24/2006 24.4 25.0 .05 .05 1.4 16.8 80 190

08/23/2006 24.9 25.9 E.02 E.04 1.3 1.9 116 226

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)

10/17/2005 0.11 0.20 10.2 22.4 1.2 E2 72 3 0.01

04/17/2006 .30 .94 13.4 27.3 2.6 4 78 12 .49

05/08/2006 .12 .67 8.1 15.2 1.9 3 72 8 .39

05/22/2006 .13 1.25 8.2 21.7 1.7 4 76 20 1.4

06/09/2006 .12 .41 14.8 19.9 1.9 E2 82 5 .14

07/24/2006 .15 .43 20.7 33.8 1.2 E2 91 4 .03

08/23/2006 .14 .37 34.5 45.2 1.7 E1 61 4 .01

Data 23
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)

10/17/2005 1620 5.9 8.6 312 13.0 150 41.1 10.3

03/20/2006 1445 4.5 8.2 324 9.5 150 42.8 10.4

04/18/2006 0820 9.1 7.9 247 1.5 100 29.7 6.42

05/08/2006 1600 16 8.2 116 10.0 67 20.5 3.73

05/22/2006 1540 30 8.0 167 14.0 70 21.4 4.14

06/09/2006 1245 25 8.1 304 13.5 140 40.6 9.25

07/24/2006 1540 5.6 8.5 324 17.0 150 42.4 10.5

08/23/2006 1620 5.1 8.2 331 16.5 150 41.0 10.5

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)

10/17/2005 19.9 20.7 E0.04 0.04 3.1 4.6 11 90

03/20/2006 12.1 13.5 E.03 .06 2.0 4.8 11 144

04/18/2006 34.0 38.3 .04 .12 7.9 14.0 88 339

05/08/2006 40.9 43.5 <.04 .10 9.3 16.3 60 282

05/22/2006 64.9 65.7 E.03 .15 12.2 21.7 65 371

06/09/2006 112 117 .07 .11 10.1 14.8 77 199

07/24/2006 33.3 33.4 E.03 E.04 3.5 4.4 8 44

08/23/2006 21.6 22.7 E.02 .06 2.3 5.4 12 108

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)

10/17/2005 0.10 0.99 8.7 11.6 1.1 4 86 3 0.05

03/20/2006 .08 1.26 51.3 63.8 3.3 7 90 6 .07

04/18/2006 .29 2.09 51.0 56.0 11.7 16 90 11 .27

05/08/2006 .24 2.15 19.2 30.7 5.8 13 95 21 .91

05/22/2006 .38 2.94 20.3 37.3 6.7 17 89 15 1.2

06/09/2006 .29 1.29 23.8 30.0 7.3 10 81 5 .34

07/24/2006 E.05 .34 4.4 7.6 1.2 2 91 1 .02

08/23/2006 .11 1.32 31.2 37.0 1.6 5 84 4 .06

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

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

10/18/2005 0855 51 8.1 584 9.0 240 67.1 17.1

03/20/2006 1625 39 8.8 618 5.0 270 75.7 18.6

04/18/2006 1020 163 8.4 514 6.5 210 60.0 13.7

05/09/2006 1020 145 9.0 432 9.5 180 54.1 11.0

05/23/2006 0825 232 8.4 297 10.0 110 33.9 6.85

06/13/2006 1155 169 8.5 307 15.5 120 35.7 7.37

07/25/2006 0925 38 9.4 482 19.5 210 62.4 13.1

08/24/2006 0945 25 9.3 535 15.0 230 66.7 14.7

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)

10/18/2005 15.3 17.9 0.04 0.06 3.5 4.5 9 165

03/20/2006 9.6 11.6 .06 .10 4.2 7.2 8 223

04/18/2006 13.8 17.7 E.03 .09 5.0 9.5 24 286

05/09/2006 24.4 26.6 <.04 .15 5.9 12.2 24 358

05/23/2006 30.8 34.5 <.04 .15 5.7 13.0 40 472

06/13/2006 29.1 33.0 E.02 .09 3.4 6.9 27 284

07/25/2006 37.5 38.5 E.02 .05 3.1 5.2 6 70

08/24/2006 32.9 35.5 E.02 .04 2.3 4.0 E4 36

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)

10/18/2005 <0.08 0.68 125 177 3.8 6 80 3 0.41

03/20/2006 <.08 1.08 170 224 4.7 11 89 4 .42

04/18/2006 .10 1.50 374 378 8.3 14 83 5 2.2

05/09/2006 E.07 1.85 255 312 4.1 20 82 8 3.1

05/23/2006 .10 2.05 362 446 3.3 14 75 19 12

06/13/2006 .10 1.21 149 179 2.6 7 82 7 3.2

07/25/2006 <.08 .39 23.8 53.5 1.1 4 65 3 .31

08/24/2006 <.08 .15 12.8 24.0 E.59 2 71 1 .07

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

Data 25
12323760—Warm Springs 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)

10/17/2005 1515 76 E0.6 8.6 254 9.5 130 37.4 8.00

04/17/2006 1605 52 <2.0 8.8 254 7.0 120 36.5 7.98

05/08/2006 1410 76 <2.0 8.6 222 8.0 110 33.4 6.60

06/09/2006 1100 268 <2.0 8.2 126 8.0 60 18.6 3.25

07/24/2006 1425 59 <2.0 8.6 242 16.0 110 34.2 6.96

08/23/2006 1435 60 <2.0 8.7 242 14.5 110 34.3 7.02

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)

10/17/2005 1.9 2.0 E0.03 E0.03 0.68 1.2 10 48

04/17/2006 2.5 2.8 E.02 E.03 1.3 2.4 7 77

05/08/2006 1.8 2.1 <.04 E.03 1.2 2.5 7 73

06/09/2006 1.8 2.3 E.02 .05 1.3 4.1 10 194

07/24/2006 2.5 2.7 <.04 E.03 1.4 2.4 E6 75

08/23/2006 2.2 2.3 <.04 E.02 .68 1.9 E6 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)

10/17/2005 <0.08 0.14 <0.2 2.4 E0.47 E1 80 3 0.62

04/17/2006 <.08 .24 .9 3.1 0.71 E2 76 3 .42

05/08/2006 <.08 .23 .7 3.1 E.40 E1 66 4 .82

06/09/2006 <.08 .55 1.1 9.1 1.3 4 51 13 9.4

07/24/2006 E.05 .24 1.2 4.2 1.2 E2 71 4 .64

08/23/2006 <.08 .24 .8 3.7 E.30 E1 68 4 .65

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

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

10/18/2005 0835 37 8.2 356 8.0 170 51.2 10.5

04/18/2006 1000 39 8.4 365 2.5 180 53.4 10.8

05/09/2006 1005 57 8.4 300 4.5 150 44.8 8.38

05/23/2006 0735 183 7.8 156 7.5 73 23.1 3.79

06/13/2006 1020 147 8.1 186 11.5 89 27.6 4.77

07/25/2006 0905 29 8.2 336 14.5 160 50.2 9.07

08/24/2006 0925 40 8.3 321 11.0 150 46.1 8.67

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)

10/18/2005 4.9 5.5 0.04 0.07 2.4 7.4 16 94

04/18/2006 4.0 4.6 E.04 .06 2.6 6.4 11 81

05/09/2006 3.5 4.1 <.04 .05 2.5 8.2 9 99

05/23/2006 3.6 6.2 <.04 .11 3.7 24.7 14 440

06/13/2006 4.2 5.5 E.03 .08 3.2 13.1 12 214

07/25/2006 6.2 6.6 E.02 .05 2.5 6.8 10 68

08/24/2006 4.2 12.8 E.02 .07 1.8 11.1 9 80

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)

10/18/2005 E0.05 0.50 176 222 1.5 3 72 6 0.60

04/18/2006 E.04 .40 164 190 1.9 3 71 4 .42

05/09/2006 <.08 .56 77.6 117 1.6 3 69 5 .77

05/23/2006 <.08 2.34 33.9 110 1.8 10 68 23 11

06/13/2006 E.07 1.13 75.2 119 1.4 5 64 11 4.4

07/25/2006 E.05 .38 124 156 1.1 3 77 2 .16

08/24/2006 <.08 .67 118 53.1 .83 10 67 3 .32

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

Data 27
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)

10/18/2005 1025 85 8.4 480 9.0 220 63.0 14.7

03/21/2006 1120 62 8.4 538 2.5 250 73.3 16.3

04/18/2006 1200 216 8.4 490 6.5 190 55.7 12.8

05/09/2006 1140 204 8.9 401 9.0 170 50.8 10.4

05/23/2006 0935 427 8.2 233 10.5 95 29.1 5.53

06/13/2006 1250 337 8.4 253 15.5 100 31.5 6.28

07/24/2006 1710 53 9.2 407 23.5 180 55.0 11.4

08/24/2006 0755 53 8.5 417 13.5 190 55.6 11.6

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)

10/18/2005 10.5 11.8 0.05 0.06 4.0 6.5 13 118

03/21/2006 6.4 7.9 .05 .10 3.8 9.1 7 184

04/18/2006 11.7 15.7 .04 .11 5.1 12.3 16 297

05/09/2006 18.9 21.0 <.04 .13 5.5 13.6 15 323

05/23/2006 19.5 23.4 <.04 .17 5.8 28.2 29 561

06/13/2006 18.2 21.2 E.02 .11 4.0 14.5 19 300

07/24/2006 24.9 26.1 E.02 .06 4.3 15.6 7 68

08/24/2006 16.8 17.2 E.02 .06 3.1 7.5 6 77

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)

10/18/2005 <0.08 0.51 99.7 130 2.6 5 82 3 0.69

03/21/2006 <.08 .99 169 232 4.8 11 78 4 .67

04/18/2006 .08 1.70 279 333 6.7 15 76 7 4.1

05/09/2006 E.06 1.75 174 251 3.0 17 81 7 3.9

05/23/2006 E.07 3.25 170 296 2.8 18 69 22 25

06/13/2006 E.06 1.66 72.6 135 1.7 10 73 10 9.1

07/24/2006 E.05 .47 29.9 62.8 1.2 4 80 3 .43

08/24/2006 <.08 .51 41.9 88.7 1.1 4 78 3 .43

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

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

10/17/2005 1410 2.7 E0.2 8.3 253 10.0 120 37.1 7.11

03/20/2006 1320 3.3 <2.0 8.3 216 2.5 110 32.6 6.82

04/17/2006 1505 4.5 <2.0 8.4 205 5.0 98 29.3 6.01

05/08/2006 1305 5.2 <2.0 8.3 187 7.5 92 28.0 5.41

05/22/2006 1400 9.1 6.6 8.1 136 9.5 62 19.1 3.58

06/09/2006 1020 14 2.6 8.1 168 9.0 79 24.6 4.36

07/24/2006 1325 9.6 3.9 8.3 224 13.5 110 32.6 6.14

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)

10/17/2005 8.7 9.0 0.05 0.04 2.0 2.9 E6 24

03/20/2006 2.4 2.5 E.03 E.03 1.3 2.8 E4 43

04/17/2006 2.9 3.3 E.03 .04 2.0 4.2 7 88

05/08/2006 3.0 3.2 <.04 E.04 1.8 4.1 8 98

05/22/2006 5.7 8.1 E.02 .13 4.1 24.1 16 574

06/09/2006 6.5 7.5 E.02 .07 2.8 9.0 13 266

07/24/2006 5.1 5.8 E.03 .07 1.9 9.9 9 311

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)

10/17/2005 <0.08 0.10 <0.2 1.9 1.1 E2 63 2 0.01

03/20/2006 <.08 .17 .6 1.7 1.0 E2 63 2 .02

04/17/2006 <.08 .38 1.4 3.4 1.0 E2 71 5 .06

05/08/2006 <.08 .40 1.1 3.6 .80 E2 60 6 .08

05/22/2006 .09 2.76 3.5 14.5 2.0 10 66 39 .96

06/09/2006 <.08 1.08 1.4 7.8 1.4 5 38 17 .64

07/24/2006 E.05 1.32 1.5 10.3 .77 4 47 19 .49

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

Data 29
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)

10/18/2005 1000 34 8.2 650 8.5 320 90.6 21.6

03/21/2006 1055 41 8.4 595 3.5 300 89.0 19.7

04/18/2006 1130 36 8.4 666 5.5 340 98.4 23.2

05/09/2006 1110 25 8.5 587 8.0 290 84.1 19.2

05/23/2006 0910 2.0 8.1 645 13.5 260 68.3 21.6

06/13/2006 1230 3.1 8.2 776 19.0 340 93.4 25.5

07/24/2006 1645 1.7 8.4 612 23.0 250 63.4 21.1

08/24/2006 0730 3.6 8.0 655 12.0 280 77.4 22.2

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)

10/18/2005 11.7 12.2 E0.03 E0.04 2.7 3.5 16 45

03/21/2006 10.1 11.3 E.02 .07 1.7 7.9 7 226

04/18/2006 14.5 17.7 E.02 .09 2.7 8.6 9 213

05/09/2006 11.9 12.7 <.04 .04 2.2 4.4 8 68

05/23/2006 23.1 23.2 <.04 E.04 2.9 5.6 30 107

06/13/2006 27.8 30.5 E.03 .04 2.8 6.3 22 77

07/24/2006 12.6 12.8 E.02 .05 1.9 4.7 9 82

08/24/2006 8.5 9.9 <.04 E.04 1.5 3.7 7 38

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)

10/18/2005 <0.08 0.16 6.7 7.3 1.4 2 27 22 2.0

03/21/2006 <.08 .99 17.8 28.9 2.2 6 82 15 1.7

04/18/2006 <.08 .84 21.4 30.2 2.5 5 74 28 2.7

05/09/2006 <.08 .26 13.2 14.5 1.6 2 59 18 1.2

05/23/2006 <.08 .28 54.0 56.5 1.7 2 64 5 .03

06/13/2006 E.04 .20 21.1 25.6 1.2 2 54 19 .16

07/24/2006 E.05 .34 16.0 23.1 E.52 E2 66 13 .06

08/24/2006 <.08 .12 6.2 7.9 .84 E2 35 11 .11

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

30 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

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)

10/18/2005 1150 189 8.5 540 10.0 240 69.0 16.4

03/21/2006 1235 165 8.6 530 4.5 250 72.3 16.0

04/18/2006 1315 331 8.4 521 6.5 230 67.3 15.3

05/09/2006 1255 301 8.5 443 9.5 200 58.6 11.9

05/23/2006 1045 403 8.0 277 13.0 110 34.8 6.59

06/13/2006 1400 381 8.2 347 19.0 140 42.5 8.73

07/25/2006 0630 38 8.0 520 16.0 220 66.0 13.5

08/24/2006 1055 44 8.3 530 14.0 220 66.9 13.7

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)

10/18/2005 10.6 12.4 0.04 0.12 5.5 17.8 E3 231

03/21/2006 7.6 9.7 .06 .14 5.3 21.3 23 340

04/18/2006 12.5 19.2 .06 .26 8.3 42.1 10 741

05/09/2006 16.3 20.1 .04 .19 9.0 30.5 7 461

05/23/2006 20.6 31.7 .04 .42 11.1 92.1 26 1,450

06/13/2006 19.8 27.1 .06 .28 10.6 59.6 17 851

07/25/2006 16.7 24.4 .06 .10 8.6 15.3 E6 104

08/24/2006 12.4 -- .04 .06 6.5 -- E6 67

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)

10/18/2005 <0.08 1.65 27.0 74.5 4.0 18 60 23 12

03/21/2006 E.05 2.63 76.9 117 5.6 21 78 13 5.8

04/18/2006 E.08 5.50 69.0 192 8.6 37 68 28 25

05/09/2006 E.05 3.61 54.6 142 4.5 27 79 17 14

05/23/2006 .17 11.8 34.5 286 7.1 70 72 58 63

06/13/2006 .13 7.12 23.3 135 5.0 42 67 35 36

07/25/2006 E.07 .96 52.1 73.1 8.1 14 88 7 .72

08/24/2006 E.04 .33 30.9 162 4.9 -- 63 5 .59

Data  31
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)

10/18/2005 1310 355 8.6 453 11.0 210 60.3 13.9

03/21/2006 1350 295 8.8 460 5.0 220 64.1 14.0

04/18/2006 1430 854 8.4 367 6.5 160 47.5 10.7

05/09/2006 1430 747 8.6 320 10.0 140 42.0 8.38

05/23/2006 1250 1,010 8.3 256 13.5 110 32.8 6.56

06/13/2006 1535 1,060 8.3 310 19.0 130 39.5 8.19

07/25/2006 1105 132 8.5 416 19.5 180 53.4 11.7

08/24/2006 1305 115 8.7 431 18.0 180 52.7 12.2

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)

10/18/2005 8.3 9.5 E0.03 0.08 4.2 12.0 9 173

03/21/2006 6.8 7.8 .05 .09 4.4 11.5 E4 184

04/18/2006 7.5 11.9 .04 .19 5.8 30.2 29 835

05/09/2006 10.0 11.8 <.04 .16 5.0 19.2 11 411

05/23/2006 13.0 19.4 E.03 .27 7.5 56.3 22 1,100

06/13/2006 12.8 17.8 .04 .23 9.2 49.0 19 880

07/25/2006 10.7 11.2 E.02 .04 4.9 6.4 E4 34

08/24/2006 10.5 10.3 <.04 E.03 4.3 6.1 8 33

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)

10/18/2005 <0.08 1.26 10.7 65.2 1.9 12 88 7 6.7

03/21/2006 E.06 1.16 33.1 58.0 2.9 11 77 8 6.4

04/18/2006 .12 4.40 18.1 113 5.4 34 66 37 85

05/09/2006 <.08 2.27 14.1 80.5 1.9 19 77 17 34

05/23/2006 .14 7.54 12.8 160 4.5 49 75 47 128

06/13/2006 .13 5.69 12.8 103 7.6 39 65 38 109

07/25/2006 <.08 .29 13.2 26.2 1.6 4 81 3 1.1

08/24/2006 <.08 .14 4.1 20.4 .97 3 82 2 .62

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

32 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

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)

10/18/2005 1420 563 8.5 479 12.5 230 63.5 16.4

03/21/2006 1450 443 8.6 475 7.0 230 64.3 15.8

04/18/2006 1600 1,180 8.3 368 7.5 170 47.6 11.3

05/09/2006 1545 1,020 8.4 337 10.5 150 45.2 10.1

05/23/2006 1415 1,150 8.2 294 15.5 130 38.5 8.18

06/14/2006 0730 1,300 8.2 366 17.0 160 46.6 10.6

07/25/2006 1205 232 8.4 522 21.5 240 65.2 17.8

08/24/2006 1410 172 8.5 577 19.5 270 74.1 19.9

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)

10/18/2005 8.3 9.3 E0.04 0.08 3.8 8.8 9 176

03/21/2006 7.3 8.5 .04 .09 3.9 10.8 E4 233

04/18/2006 7.8 13.9 .05 .26 6.4 38.3 30 1,140

05/09/2006 8.9 11.6 <.04 .16 5.2 19.9 9 537

05/23/2006 13.7 19.3 E.04 .31 9.2 58.3 17 1,160

06/14/2006 13.3 20.6 .04 .33 8.8 52.5 15 1,120

07/25/2006 12.2 12.1 E.02 E.04 4.1 6.1 <6 27

08/24/2006 10.2 10.4 <.04 .05 3.3 5.3 <6 30

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)

10/18/2005 <0.08 1.35 7.9 61.4 2.1 12 76 11 17

03/21/2006 E.06 1.78 25.2 59.1 2.9 15 72 14 17

04/18/2006 .18 7.12 15.7 150 7.1 49 65 63 201

05/09/2006 E.04 3.54 12.4 78.2 3.0 25 70 27 74

05/23/2006 .14 8.35 10.7 170 4.8 58 78 55 171

06/14/2006 .13 8.80 8.6 184 5.0 59 74 53 186

07/25/2006 <.08 .21 7.0 15.2 1.5 3 58 8 5.0

08/24/2006 <.08 .22 6.8 19.3 2.2 4 67 7 3.3

Data  33
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)

10/18/2005 1535 824 8.7 394 12.0 180 49.3 13.7 --

03/21/2006 1610 660 8.7 389 6.5 180 52.0 13.3 --

*04/05/2006 1100 1,120 8.2 334 8.0 150 41.3 10.9 0.48

04/19/2006 0820 2,180 8.2 280 5.0 120 35.8 8.53 --

*04/19/2006 0945 2,150 8.2 277 6.0 120 35.6 8.61 .48

*05/02/2006 1130 2,970 8.1 201 7.5 93 26.9 6.35 .44

05/10/2006 0800 2,280 8.1 221 7.5 96 27.6 6.67 --

*05/16/2006 1100 2,680 8.3 180 12.0 82 23.6 5.55 .36

*05/19/2006 0930 4,090 7.9 139 17.0 61 17.3 4.33 .60

**05/24/2006 0750 3,560 7.9 149 10.5 66 18.8 4.62 .38

*05/31/2006 1130 2,240 8.1 213 11.0 93 26.7 6.50 .31

*06/05/2006 1130 2,250 8.4 214 11.5 94 26.8 6.67 .27

**06/13/2006 1100 2,710 8.2 250 15.0 110 30.8 7.64 .49

*06/19/2006 1100 1,740 8.3 268 13.0 120 33.1 8.43 .22

*06/26/2006 1100 1,230 8.4 292 17.0 130 37.6 9.35 .15

07/25/2006 1320 556 8.6 312 20.5 140 37.3 11.0 --

08/24/2006 1525 375 8.7 350 18.0 160 42.0 12.6 --

*09/26/2006 1200 590 8.3 414 12.0 190 54.0 13.6 .23

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)

10/18/2005 -- 6.3 6.7 E0.03 0.05 2.9 5.8 E4 112

03/21/2006 -- 5.4 6.1 E.03 .06 3.3 7.8 <6 157

*04/05/2006 0.087 4.7 7.5 E.02 .16 4.9 21.4 12 674

04/19/2006 -- 5.0 8.2 E.03 .17 4.3 24.1 33 708

*04/19/2006 .073 5.1 7.9 E.03 .14 6.0 21.8 15 664

*05/02/2006 .094 4.7 8.2 <.04 .16 5.6 21.2 22 796

05/10/2006 -- 4.5 5.5 <.04 .08 2.8 10.9 15 349

*05/16/2006 .066 4.3 5.6 <.04 .08 3.0 10.3 22 485

*05/19/2006 .116 4.3 6.6 E.03 .17 3.8 22.1 30 1,050

**05/24/2006 .072 4.9 6.8 <.04 .12 4.2 20.0 34 644

*05/31/2006 .047 5.8 6.6 E.03 .10 4.1 13.2 19 344

*06/05/2006 .049 5.1 6.1 E.02 .07 4.5 10.4 18 289

**06/13/2006 .090 9.2 12.9 E.03 .21 8.0 37.4 16 813

*06/19/2006 .030 6.2 4.1 E.02 .13 3.4 14.9 12 500

*06/26/2006 .023 5.8 6.0 E.02 .04 3.0 6.1 9 82

07/25/2006 -- 5.3 5.4 <.04 E.03 2.3 3.8 E3 42

08/24/2006 -- 5.2 5.2 <.04 E.03 1.8 3.1 E3 33

*09/26/2006 .019 6.7 7.1 <.04 .05 2.5 5.7 E3 96

.

*Sample collected as part of a supplemental sampling program.

.

**Supplemental sample collected in conjunction with routine sample for long-term monitoring program.

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

34  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons 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)

10/18/2005 E0.05 0.73 3.7 31.5 1.2 8 83 7 16

03/21/2006 E.05 1.03 8.0 34.3 2.0 11 77 10 18

*04/05/2006 .22 4.22 9.2 97.4 5.1 35 72 40 121

04/19/2006 .14 4.31 6.8 96.1 5.5 32 76 37 218

*04/19/2006 .20 4.20 6.8 87.3 9.5 30 77 33 192

*05/02/2006 .30 4.67 7.1 95.1 6.3 33 63 53 425

05/10/2006 <.08 1.87 6.6 43.3 2.9 15 72 18 111

*05/16/2006 <.08 1.85 6.2 50.6 2.4 16 63 36 260

*05/19/2006 .12 4.40 8.5 98.9 3.3 33 57 91 1,000

**05/24/2006 .08 2.99 7.9 68.7 3.4 24 63 41 394

*05/31/2006 E.07 1.80 9.7 46.0 3.0 16 69 19 115

*06/05/2006 .22 1.46 6.5 39.5 4.5 13 66 17 103

**06/13/2006 .15 6.06 7.8 105 7.5 43 78 42 307

*06/19/2006 E.06 2.25 8.4 36.1 3.0 29 71 11 52

*06/26/2006 E.05 .41 7.3 17.0 1.9 5 75 4 13

07/25/2006 <.08 .21 4.6 12.4 1.0 3 84 4 6.0

08/24/2006 <.08 .31 3.6 8.9 .97 3 76 3 3.0

*09/26/2006 .09 .63 3.2 27.6 2.3 9 85 6 9.6

.

*Sample collected as part of a supplemental sampling program.

.

**Supplemental sample collected in conjunction with routine sample for long-term monitoring program.

Data  35
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)

10/19/2005 0800 489 8.4 272 9.0 140 34.4 13.2 0.10

*04/05/2006 1400 1,760 8.4 202 5.0 99 25.7 8.42 .56

04/19/2006 1050 3,710 8.2 175 5.0 86 22.9 7.08 --

*04/19/2006 1230 3,680 8.5 174 8.5 87 23.0 7.18 .33

*05/02/2006 1330 4,670 8.6 158 7.5 83 22.0 6.88 .24

05/10/2006 0945 3,610 8.3 174 7.5 86 22.5 7.15 --

*05/16/2006 1300 5,020 8.2 156 11.5 81 21.7 6.58 .32

*05/19/2006 1530 8,170 8.2 142 11.0 67 17.9 5.37 .49

**05/24/2006 1020 7,040 8.1 146 10.5 72 19.1 5.85 .23

*05/31/2006 1400 4,210 8.4 175 11.0 87 22.9 7.29 .20

*06/05/2006 1330 4,550 8.4 163 12.0 80 20.7 6.76 .21

*06/13/2006 1300 4,160 8.4 185 14.5 87 22.5 7.46 .16

*06/19/2006 1300 3,110 8.4 185 13.5 89 23.0 7.68 .12

*06/26/2006 1230 2,030 8.2 208 18.0 110 27.4 8.86 .11

07/25/2006 1455 729 8.6 254 22.5 130 31.6 11.8 --

08/25/2006 0800 517 8.5 263 15.5 130 31.9 12.4 --

*09/26/2006 1330 511 8.5 270 20.0 130 33.3 12.1 .11

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)

10/19/2005 0.007 1.1 1.1 <0.04 <0.04 0.52 E0.5 6 35

*04/05/2006 .107 1.0 1.4 <.04 <.04 2.1 2.0 26 600

04/19/2006 -- .86 1.2 <.04 <.04 1.8 3.5 44 387

*04/19/2006 .050 .82 1.1 <.04 <.04 1.7 1.8 19 372

*05/02/2006 .055 .66 1.1 <.04 <.04 .95 1.7 16 375

05/10/2006 -- .72 .96 <.04 <.04 1.3 3.7 12 174

*05/16/2006 .053 .89 1.1 <.04 E.03 .76 1.9 14 525

*05/19/2006 .123 .81 2.2 <.04 <.04 2.1 5.2 13 1,670

**05/24/2006 .049 .78 1.2 <.04 <.04 1.2 4.3 18 626

*05/31/2006 .017 .85 1.1 <.04 <.04 -- 1.3 11 242

*06/05/2006 .019 .86 1.0 <.04 <.04 1.2 1.5 10 302

*06/13/2006 .028 .92 1.2 <.04 <.04 2.0 1.4 11 259

*06/19/2006 .017 .92 1.0 <.04 E.03 .64 1.2 10 131

*06/26/2006 .013 .98 1.2 <.04 <.04 .62 .8 11 72

07/25/2006 -- 1.2 1.4 <.04 <.04 .45 1.3 E4 36

08/25/2006 -- 1.3 1.3 <.04 <.04 E.38 .9 <6 27

*09/26/2006 .005 1.3 1.6 <.04 <.04 .85 E.5 E5 25

.

*Sample collected as part of a supplemental sampling program.

.

**Supplemental sample collected in conjunction with routine sample for long-term monitoring program.

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

36 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons 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)

10/19/2005 <0.08 0.06 1.0 4.2 E0.37 <2 84 2 2.6

*04/05/2006 .18 .68 6.8 39.1 3.3 3 79 39 185

04/19/2006 E.06 .48 3.9 28.2 1.3 3 88 22 220

*04/19/2006 E.07 .43 3.9 28.5 2.0 3 89 21 209

*05/02/2006 <.08 .46 2.8 28.8 1.1 3 83 25 315

05/10/2006 <.08 .27 2.2 15.0 1.0 2 83 13 127

*05/16/2006 <.08 .62 3.4 38.9 .64 3 78 48 651

*05/19/2006 .14 2.30 4.7 97.2 2.3 8 78 168 3,710

**05/24/2006 <.08 .85 2.4 37.3 .67 4 82 57 1,080

*05/31/2006 .29 .37 3.4 18.2 -- E2 86 18 205

*06/05/2006 E.07 .39 2.2 20.0 1.2 2 83 24 295

*06/13/2006 .09 .39 2.0 17.6 -- E2 86 19 213

*06/19/2006 <.08 .18 2.0 10.9 .67 E1 84 9 76

*06/26/2006 E.04 .12 1.9 8.4 .84 <2 80 5 27

07/25/2006 <.08 .06 2.3 8.0 E.46 <2 84 3 5.9

08/25/2006 <.08 E.04 .9 5.1 E.47 <2 69 2 2.8

*09/26/2006 E.07 E.04 1.2 2.8 1.9 <2 79 1 1.4

.

*Sample collected as part of a supplemental sampling program.

.

**Supplemental sample collected in conjunction with routine sample for long-term monitoring program.

Data  37
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)

10/19/2005 0945 1,290 8.5 8.4 348 10.0 170 44.2 13.4

03/22/2006 0800 1,180 3.5 8.5 331 5.0 160 43.6 12.4

*04/05/2006 1530 3,060 -- 8.4 257 7.0 120 32.4 9.05

04/19/2006 1250 5,710 14 8.2 214 5.5 99 27.4 7.52

*04/19/2006 1430 5,670 -- 8.4 211 6.5 99 27.4 7.54

*05/02/2006 1600 7,530 -- 8.4 176 8.5 86 23.7 6.45

05/10/2006 1045 5,670 6.9 8.3 194 8.0 91 24.7 7.08

*05/16/2006 1500 7,890 -- 8.1 169 13.0 83 22.7 6.39

*05/19/2006 1400 12,300 -- 8.1 144 12.5 68 18.4 5.29

**05/24/2006 1145 10,700 28 8.1 149 10.5 71 19.3 5.47

*05/31/2006 1530 6,270 -- 8.2 188 12.0 91 24.8 7.09

*06/05/2006 1500 6,920 -- 8.3 181 13.0 84 22.4 6.68

**06/13/2006 1430 6,900 18 8.3 213 16.5 99 26.9 7.72

*06/19/2006 1500 4,720 -- 8.4 215 14.5 98 26.3 7.85

*06/26/2006 1400 3,050 -- 8.3 238 19.0 110 30.2 8.74

07/25/2006 1615 1,320 3.8 8.6 278 22.0 130 33.7 11.3

08/25/2006 0910 873 3.4 8.5 298 17.0 140 36.3 12.3

*09/26/2006 1500 1,090 -- 8.4 352 12.0 160 42.1 12.7

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)

10/19/2005 -- -- 4.2 6.3 <0.04 0.24 2.2 24.6

03/22/2006 -- -- 3.7 4.0 <.04 .07 2.2 7.3

*04/05/2006 0.38 0.060 2.5 3.7 <.04 .07 2.5 8.3

04/19/2006 -- -- 2.4 3.7 <.04 .08 2.3 11.5

*04/19/2006 .42 .060 2.5 3.6 <.04 .07 2.5 9.7

*05/02/2006 .36 .063 2.4 4.0 <.04 .09 2.1 10.9

05/10/2006 -- -- 2.2 2.9 <.04 .05 1.8 6.5

*05/16/2006 .37 .061 2.1 3.0 -- .06 2.4 8.3

*05/19/2006 .53 .129 2.2 4.3 <.04 .12 2.1 17.8

**05/24/2006 .32 .066 2.2 3.2 <.04 .07 2.2 9.5

*05/31/2006 .22 .029 2.7 3.0 <.04 E.04 2.0 5.3

*06/05/2006 .26 .031 2.5 3.4 <.04 .08 1.9 10.0

**06/13/2006 .47 .102 4.7 8.6 <.04 .35 3.3 42.1

*06/19/2006 .21 .046 3.1 6.6 <.04 .08 1.8 9.9

*06/26/2006 .21 .033 3.2 4.0 <.04 .10 1.6 17.7

07/25/2006 -- -- 3.6 4.2 E.03 .11 2.0 14.6

08/25/2006 -- -- 3.0 3.3 <.04 .07 1.7 8.1

*09/26/2006 .30 .028 4.8 6.2 <.04 .15 2.0 17.7

.

*Sample collected as part of a supplemental sampling program.

.

**Supplemental sample collected in conjunction with routine sample for long-term monitoring program.

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

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

10/19/2005 8 585 E0.06 3.90 23.8 66.5 1.4 43

03/22/2006 9 189 E.05 .97 27.2 39.8 2.0 11

*04/05/2006 18 418 E.06 1.48 15.8 35.9 2.5 15

04/19/2006 42 555 .11 1.89 15.4 51.8 2.4 15

*04/19/2006 19 512 E.07 1.82 16.8 52.6 2.9 14

*05/02/2006 19 596 E.04 2.37 13.1 57.5 2.0 18

05/10/2006 14 295 <.08 1.11 11.0 29.8 1.3 9

*05/16/2006 16 555 E.06 1.73 10.3 46.8 4.0 14

*05/19/2006 24 1,460 E.07 3.73 11.7 109 1.7 28

**05/24/2006 24 699 E.04 1.85 8.1 51.1 1.5 14

*05/31/2006 14 267 E.04 .80 8.5 27.8 3.3 7

*06/05/2006 13 485 E.06 1.70 15.3 44.2 1.6 18

**06/13/2006 14 1,350 .12 6.89 17.0 99.2 2.6 91

*06/19/2006 12 216 .08 1.25 10.8 31.9 3.2 12

*06/26/2006 12 314 .10 1.60 11.3 28.7 2.0 19

07/25/2006 6 192 .08 1.98 12.8 27.3 1.2 21

08/25/2006 7 155 E.04 .97 9.9 24.0 2.8 12

*09/26/2006 10 436 .13 2.73 21.2 49.0 1.7 36

Date

Sediment, 

suspended 

(percent finer 

than 0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/19/2005 74 41 143

03/22/2006 83 9 29

*04/05/2006 53 30 248

04/19/2006 86 28 432

*04/19/2006 87 27 413

*05/02/2006 80 36 732

05/10/2006 85 16 245

*05/16/2006 76 40 852

*05/19/2006 74 139 4,620

**05/24/2006 79 56 1,620

*05/31/2006 88 15 254

*06/05/2006 72 38 710

**06/13/2006 39 117 2,180

*06/19/2006 40 47 599

*06/26/2006 61 26 214

07/25/2006 81 12 43

08/25/2006 85 11 26

*09/26/2006 78 27 79

.

*Sample collected as part of a supplemental sampling program.

.

**Supplemental sample collected in conjunction with routine sample for long-term monitoring program.

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

Data  39
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)

04/06/2006 0900 2,200 7.8 95 4.0 40 11.8 2.53 0.58

04/20/2006 0800 3,320 7.7 84 9.0 35 10.4 2.19 .32

05/03/2006 0745 5,930 7.8 58 7.0 24 7.17 1.46 .29

05/17/2006 0800 10,500 7.4 40 11.0 16 4.72 .954 .70

05/19/2006 1130 15,200 7.4 41 11.5 15 4.43 .980 .48

05/24/2006 1530 13,800 7.4 44 11.5 16 4.81 1.04 .28

06/01/2006 0800 6,260 7.6 62 12.0 25 7.44 1.57 .25

06/06/2006 0800 8,970 7.6 48 12.5 19 5.56 1.17 .21

06/14/2006 0700 8,450 7.5 48 15.0 19 5.57 1.19 .17

06/20/2006 0730 5,000 7.7 63 13.5 25 7.32 1.62 .16

06/27/2006 0730 3,290 7.7 70 18.0 28 8.11 1.76 .13

09/27/2006 0800 670 7.8 172 13.5 70 20.4 4.55 .18

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)

04/06/2006 0.099 0.26 0.63 <0.04 <0.04 1.2 1.9 28 1,020

04/20/2006 .036 .28 .44 <.04 <.04 .75 1.1 28 351

05/03/2006 .051 .27 .48 <.04 <.04 -- 1.3 34 553

05/17/2006 .121 .27 .62 <.04 E.03 1.4 4.0 60 2,010

05/19/2006 .088 .31 .51 <.04 E.03 1.1 3.2 71 1,460

05/24/2006 .047 .27 .42 <.04 <.04 2.9 2.1 47 741

06/01/2006 .019 .34 .43 <.04 <.04 .69 1.4 40 405

06/06/2006 .021 .29 .39 <.04 <.04 .78 1.4 39 567

06/14/2006 .025 .29 .38 <.04 <.04 1.3 1.1 45 355

06/20/2006 .021 .28 .40 <.04 <.04 .65 .9 43 238

06/27/2006 .015 .32 .36 <.04 <.04 .64 .9 35 133

09/27/2006 .011 .57 .55 E.03 <.04 .78 .7 30 73

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)

04/06/2006 E0.06 0.88 6.4 73.6 2.4 4 76 64 380

04/20/2006 <.08 .27 7.2 22.7 .79 E1 68 16 143

05/03/2006 .27 .49 4.8 27.9 -- 3 53 38 608

05/17/2006 E.06 1.89 6.7 75.3 2.1 8 43 226 6,410

05/19/2006 .10 1.57 7.4 52.3 .92 7 38 177 7,260

05/24/2006 .18 .74 6.4 23.3 4.4 3 47 80 2,980

06/01/2006 <.08 .36 8.6 19.0 E.60 E2 60 27 456

06/06/2006 E.04 .48 6.0 18.9 1.6 3 54 41 993

06/14/2006 .08 .32 5.0 14.2 1.4 3 53 29 662

06/20/2006 E.04 .21 7.1 13.3 1.0 E1 69 12 162

06/27/2006 E.04 .12 3.4 7.7 1.1 <2 80 5 44

09/27/2006 <.08 E.05 3.8 10.5 .70 <2 79 2 3.6

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

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

04/07/2006 0800 11,800 8.2 174 4.0 76 20.9 5.74 1.27

04/21/2006 0830 12,200 8.1 175 4.5 79 21.9 5.84 .38

05/04/2006 0800 18,000 8.4 133 4.0 61 17.2 4.33 .30

05/17/2006 1500 26,900 7.9 104 8.5 47 13.2 3.48 .62

05/20/2006 1030 38,000 8.0 95 8.0 43 12.1 3.05 .57

05/25/2006 1130 32,000 7.9 103 8.5 45 12.5 3.38 .29

06/01/2006 1500 18,100 8.0 144 10.5 62 17.1 4.64 .26

06/06/2006 1500 21,500 8.0 115 11.0 50 13.8 3.75 .24

06/14/2006 1430 20,800 8.0 131 12.0 57 15.7 4.34 .25

06/20/2006 1400 13,600 8.2 152 11.0 65 17.6 5.08 .18

06/27/2006 1400 8,900 8.6 166 15.5 75 20.7 5.79 .18

09/27/2006 1400 2,450 8.4 273 13.0 120 33.0 9.54 .20

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)

04/07/2006 0.226 1.5 3.8 <0.04 0.19 1.3 23.5 25 2,230

04/21/2006 .050 1.5 2.2 E.03 .05 2.2 6.7 14 399

05/04/2006 .049 1.2 2.0 <.04 .05 1.7 6.0 16 527

05/17/2006 .135 1.2 2.8 <.04 .12 1.4 13.8 20 1,860

05/20/2006 .166 1.3 3.0 <.04 .12 1.9 17.5 28 2,200

05/25/2006 .070 1.1 1.9 <.04 .06 1.6 6.9 21 892

06/01/2006 .029 1.4 1.8 <.04 E.04 1.6 4.2 19 385

06/06/2006 .027 1.2 1.7 <.04 .04 1.6 5.0 17 530

06/14/2006 .057 2.2 3.2 <.04 .10 2.5 13.2 17 648

06/20/2006 .023 1.7 1.9 <.04 E.04 1.3 4.5 18 243

06/27/2006 .011 1.8 1.9 <.04 E.02 1.4 2.4 13 76

09/27/2006 .011 2.3 2.9 <.04 E.03 1.5 3.5 8 68

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)

04/07/2006 E0.06 5.63 4.6 183 1.2 50 80 154 4,910

04/21/2006 E.08 1.13 4.1 36.4 3.3 9 76 23 758

05/04/2006 E.05 1.38 2.4 41.8 2.4 11 60 42 2,040

05/17/2006 <.08 4.18 3.5 100 1.4 28 50 188 13,700

05/20/2006 E.06 4.62 2.0 120 1.5 30 47 282 28,900

05/25/2006 E.06 1.70 3.2 46.4 1.5 11 58 103 8,900

06/01/2006 E.05 .83 6.0 28.1 1.8 6 81 27 1,320

06/06/2006 E.05 1.02 3.1 29.6 1.6 9 65 47 2,730

06/14/2006 .15 2.47 2.5 48.5 2.6 19 70 49 2,750

06/20/2006 E.07 .72 3.9 18.9 1.7 7 82 14 514

06/27/2006 E.06 .29 1.7 8.4 .90 3 83 4 96

09/27/2006 .08 .36 2.9 15.3 1.2 4 82 5 33

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons per day. Symbols: <, less than laboratory reporting 

level; --, no data]

Data  41
Table 4. Water-quality data for the Clark Fork basin, Montana, October 2005 through September 2006.—Continued

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

at 25°C; mg/L, milligrams per liter; mm, millimeters; NTRU, nephelometric turbidity ratio unit; ton/d, tons 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)

04/06/2006 1330 9,020 8.3 176 6.5 89 25.5 6.14 0.12

04/20/2006 1300 E15,300 8.3 178 8.0 94 27.1 6.29 .14

05/03/2006 1300 25,500 8.5 174 7.0 91 26.3 6.14 .14

05/17/2006 1200 27,900 8.2 173 12.5 91 26.3 6.16 .12

05/20/2006 0800 32,300 8.3 177 13.0 86 24.4 6.15 .11

05/25/2006 0845 35,800 8.4 179 14.0 88 25.0 6.23 .11

06/01/2006 1130 28,700 8.3 175 13.5 88 25.4 6.10 .13

06/06/2006 1200 25,200 8.3 173 15.5 85 24.2 6.02 .06

06/14/2006 1200 30,000 8.4 171 16.0 85 23.9 6.03 .10

06/20/2006 1100 44,300 8.3 167 13.0 83 23.6 5.87 .12

06/27/2006 1100 20,500 8.3 169 19.0 86 24.8 5.93 .10

09/27/2006 1130 6,180 8.2 176 16.0 85 23.9 6.13 .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)

04/06/2006 0.005 0.33 0.39 <0.04 <0.04 0.44 E0.4 <6 67

04/20/2006 .010 .38 .45 <.04 <.04 .86 E.5 <6 76

05/03/2006 .009 .36 .48 <.04 <.04 -- .8 <6 86

05/17/2006 .011 .36 .46 <.04 <.04 .72 .7 <6 121

05/20/2006 .011 .40 .46 <.04 <.04 .80 -- <6 138

05/25/2006 .010 .42 .53 <.04 <.04 .51 E.4 <6 116

06/01/2006 .007 .41 .46 <.04 <.04 .59 E.5 <6 70

06/06/2006 .004 .42 .40 <.04 <.04 .56 E.6 <6 67

06/14/2006 .007 .40 .53 <.04 <.04 .84 .9 <6 153

06/20/2006 .009 .35 .48 <.04 <.04 .54 E.6 <6 152

06/27/2006 .010 .38 .51 <.04 <.04 .87 E.5 <6 57

09/27/2006 .012 .47 .73 <.04 <.04 .68 E.5 <6 36

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)

04/06/2006 <0.08 0.19 1.2 5.3 0.73 <2 83 3 73

04/20/2006 <.08 .09 1.3 5.9 1.6 <2 85 5 E207

05/03/2006 -- .10 .8 5.9 -- <2 69 8 551

05/17/2006 <.08 .13 .9 7.1 <.60 <2 77 10 753

05/20/2006 E.05 .15 .7 7.8 1.4 <2 77 11 959

05/25/2006 <.08 .13 .7 6.8 E.53 <2 75 10 967

06/01/2006 <.08 .07 1.3 5.2 E.58 <2 79 5 387

06/06/2006 <.08 .09 1.2 4.8 .87 <2 80 5 340

06/14/2006 <.08 .20 1.0 8.2 .78 E1 89 11 891

06/20/2006 <.08 .19 .8 8.1 1.3 <2 78 12 1,440

06/27/2006 E.05 .09 .8 4.6 2.0 <2 81 4 221

09/27/2006 E.05 .06 .6 4.1 1.4 <2 85 2 33

42 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
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 19 9.1 205 12 6.6 237 24 15

2 194 17 8.9 216 12 7.0 231 24 15

3 204 17 9.4 228 12 7.4 224 31 19

4 225 17 10 233 12 7.5 237 64 41

5 223 17 10 230 11 6.8 208 106 60

6 215 16 9.3 229 10 6.2 e150 77 31

7 210 16 9.1 227 10 6.1 e100 42 11

8 208 16 9.0 242 10 6.5 e110 36 11

9 212 15 8.6 243 11 7.2 e120 35 11

10 211 15 8.5 234 12 7.6 e140 34 13

11 209 15 8.5 238 16 10 e150 33 13

12 202 15 8.2 236 14 8.9 e150 33 13

13 201 15 8.1 234 12 7.6 e150 32 13

14 196 15 7.9 239 10 6.5 e150 32 13

15 194 16 8.4 228 10 6.2 e170 32 15

16 190 17 8.7 233 10 6.3 e160 31 13

17 189 18 9.2 239 11 7.1 e140 31 12

18 189 19 9.7 238 11 7.1 e120 32 10

19 189 19 9.7 242 12 7.8 e110 37 11

20 188 18 9.1 239 12 7.7 e150 40 16

21 189 17 8.7 235 11 7.0 e170 42 19

22 193 17 8.9 231 10 6.2 e250 44 30

23 195 17 9.0 230 10 6.2 307 47 39

24 195 16 8.4 225 11 6.7 249 70 47

25 198 16 8.6 226 12 7.3 249 94 63

26 205 15 8.3 238 12 7.7 238 40 26

27 208 14 7.9 232 13 8.1 234 25 16

28 210 14 7.9 229 15 9.3 241 21 14

29 212 13 7.4 207 18 10 311 10 8.4

30 207 13 7.3 234 21 13 243 7 4.6

31 206 13 7.2 -- -- -- 238 12 7.7

TOTAL 6,245 -- 269.0 6,940 -- 225.6 5,937 -- 630.7

MEAN 201 16 8.7 231 12 7.5 192 39 20

MAX 225 19 10 243 21 13 311 106 63

MIN 178 13 7.2 205 10 6.1 100 7 4.6

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2005 through 

September 2006.

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Data  43
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

1 234 19 12 192 20 10 215 27 16

2 228 22 14 191 19 9.8 194 23 12

3 224 21 13 191 19 9.8 191 31 16

4 217 20 12 193 21 11 191 30 15

5 209 19 11 191 27 14 180 30 15

6 213 18 10 179 34 16 183 24 12

7 213 18 10 187 37 19 185 26 13

8 215 17 9.9 200 37 20 173 25 12

9 194 17 8.9 194 35 18 171 26 12

10 208 17 9.5 168 34 15 157 31 13

11 216 17 9.9 169 34 16 158 28 12

12 208 18 10 185 33 16 160 35 15

13 200 18 9.7 201 33 18 165 34 15

14 214 19 11 197 32 17 163 30 13

15 210 19 11 e150 31 13 173 37 17

16 192 20 10 e130 30 11 164 30 13

17 198 21 11 e80 28 6.0 167 28 13

18 207 22 12 e110 26 7.7 170 28 13

19 197 21 11 e130 25 8.8 168 27 12

20 186 21 11 e140 26 9.8 167 23 10

21 197 20 11 150 26 11 169 20 9.1

22 183 20 9.9 154 27 11 171 28 13

23 199 19 10 165 27 12 166 23 10

24 191 18 9.3 e170 28 13 169 23 10

25 190 18 9.2 e160 31 13 181 25 12

26 191 18 9.3 188 34 17 191 28 14

27 184 19 9.4 210 36 20 184 30 15

28 169 21 9.6 232 33 21 202 36 20

29 189 22 11 -- -- -- 224 26 16

30 197 22 12 -- -- -- 235 20 13

31 195 21 11 -- -- -- 217 18 11

TOTAL 6,268 -- 328.6 4,807 -- 383.9 5,604 -- 412.1

MEAN 202 19 11 172 29 14 181 27 13

MAX 234 22 14 232 37 21 235 37 20

MIN 169 17 8.9 80 19 6.0 157 18 9.1

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2005 through 

September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

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

1 187 20 10 348 30 28 248 23 15

2 205 22 12 348 26 24 232 23 14

3 226 20 12 336 21 19 252 27 18

4 208 51 29 321 22 19 299 27 22

5 230 145 90 316 17 15 297 17 14

6 446 328 395 316 18 15 278 17 13

7 465 133 167 312 17 14 240 27 17

8 368 58 58 310 14 12 307 168 139

9 352 49 47 297 15 12 433 214 250

10 333 43 39 289 18 14 547 132 195

11 321 37 32 287 18 14 578 51 80

12 309 39 33 276 18 13 440 36 43

13 314 38 32 270 17 12 385 34 35

14 317 44 38 270 19 14 362 29 28

15 332 41 37 277 22 16 318 23 20

16 338 39 36 304 28 23 287 15 12

17 351 37 35 355 49 47 247 10 6.7

18 333 28 25 412 80 89 224 9 5.4

19 317 24 21 441 92 110 214 9 5.2

20 302 22 18 495 116 155 225 8 4.9

21 297 25 20 518 116 162 209 8 4.5

22 303 30 25 455 78 96 195 8 4.2

23 325 28 25 406 56 61 179 7 3.4

24 326 23 20 385 48 50 158 7 3.0

25 317 22 19 334 41 37 145 7 2.7

26 317 22 19 328 37 33 143 8 3.1

27 309 22 18 335 28 25 135 7 2.6

28 303 21 17 349 29 27 150 5 2.0

29 305 20 16 361 28 27 144 4 1.6

30 325 26 23 318 24 21 164 6 2.7

31 -- -- -- 282 25 19 -- -- --

TOTAL 9,381 -- 1,368 10,651 -- 1,223 8,035 -- 967.0

MEAN 313 49 46 344 38 39 268 32 32

MAX 465 328 395 518 116 162 578 214 250

MIN 187 20 10 270 14 12 135 4 1.6

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2005 through 

September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Data  45
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

1 170 7 3.2 45 30 3.6 61 24 4.0

2 161 7 3.0 45 32 3.9 71 20 3.8

3 152 7 2.9 43 33 3.8 78 19 4.0

4 150 9 3.6 47 34 4.3 73 22 4.3

5 150 10 4.0 55 36 5.3 69 27 5.0

6 149 10 4.0 43 38 4.4 65 33 5.8

7 147 17 6.7 40 39 4.2 66 33 5.9

8 135 37 13 44 39 4.6 69 29 5.4

9 118 23 7.3 42 38 4.3 70 22 4.2

10 116 15 4.7 41 37 4.1 70 16 3.0

11 125 14 4.7 37 36 3.6 70 14 2.6

12 123 12 4.0 38 35 3.6 68 14 2.6

13 126 11 3.7 38 34 3.5 70 15 2.8

14 115 9 2.8 36 32 3.1 76 17 3.5

15 102 9 2.5 39 30 3.2 88 18 4.3

16 84 8 1.8 37 28 2.8 114 18 5.5

17 65 9 1.6 45 26 3.2 122 18 5.9

18 60 12 1.9 58 26 4.1 123 18 6.0

19 56 18 2.7 57 29 4.5 113 17 5.2

20 46 21 2.6 55 32 4.8 118 16 5.1

21 41 22 2.4 54 34 5.0 129 16 5.6

22 39 22 2.3 51 23 3.2 138 15 5.6

23 44 24 2.9 46 11 1.4 142 15 5.8

24 43 29 3.4 44 5 .59 139 16 6.0

25 37 12 1.2 46 16 2.0 139 16 6.0

26 35 9 .85 49 23 3.0 152 17 7.0

27 41 13 1.4 52 26 3.7 152 16 6.6

28 43 18 2.1 52 26 3.7 154 16 6.7

29 39 23 2.4 51 26 3.6 149 16 6.4

30 36 27 2.6 51 26 3.6 151 14 5.7

31 36 29 2.8 55 25 3.7 -- -- --

TOTAL 2,784 -- 105.05 1,436 -- 112.39 3,099 -- 150.3

MEAN 89.8 16 3.4 46.3 29 3.6 103 19 5.0

MAX 170 37 13 58 39 5.3 154 33 7.0

MIN 35 7 .85 36 5 .59 61 14 2.6

Total for water year 2006 (unrounded sum of daily values): streamflow–71,187 ft3

/s (annual runoff–141,200 acre-ft); suspended-sediment discharge–

6,175.64 tons.

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2005 through 

September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

46 Water-Quality, Bed-Sediment, 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 2005 

through September 2006.

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

OCTOBER NOVEMBER DECEMBER

1 795 12 26 847 8 18 696 4 7.5

2 835 14 32 856 9 21 e720 4 7.8

3 870 14 33 875 8 19 708 7 13

4 943 13 33 884 8 19 717 9 17

5 952 13 33 862 7 16 730 9 18

6 928 12 30 848 7 16 e670 9 16

7 913 11 27 849 7 16 e400 8 8.6

8 884 10 24 879 7 17 e210 8 4.5

9 873 8 19 858 7 16 e250 7 4.7

10 893 8 19 814 6 13 e350 7 6.6

11 882 8 19 841 7 16 e530 9 13

12 875 8 19 870 8 19 e570 11 17

13 860 8 19 866 8 19 e550 11 16

14 841 8 18 864 7 16 e600 10 16

15 836 8 18 854 7 16 e630 8 14

16 830 8 18 801 7 15 e600 6 9.7

17 819 8 18 838 6 14 e570 6 9.2

18 819 8 18 840 6 14 e530 5 7.2

19 806 7 15 822 6 13 e500 7 9.4

20 815 7 15 821 7 16 e470 9 11

21 811 7 15 795 7 15 e570 11 17

22 815 7 15 795 7 15 e650 21 37

23 820 7 15 777 7 15 e750 37 75

24 813 6 13 744 7 14 e1,100 34 101

25 805 6 13 715 7 14 e1,000 27 73

26 802 7 15 786 6 13 925 24 60

27 815 8 18 796 6 13 913 15 37

28 823 8 18 766 6 12 878 12 28

29 821 8 18 712 6 12 938 18 46

30 805 8 17 676 5 9.1 1,080 33 96

31 808 8 17 -- -- -- 1,010 20 55

TOTAL 26,207 -- 627 24,551 -- 461.1 20,815 -- 851.2

MEAN 845 9 20 818 7 15 671 13 27

MAX 952 14 33 884 9 21 1,100 37 101

MIN 795 6 13 676 5 9.1 210 4 4.5

Data  47
Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2005 

through September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 980 18 48 727 9 18 1,350 108 394

2 950 18 46 710 8 15 1,190 82 263

3 913 15 37 705 7 13 988 50 133

4 884 13 31 702 6 11 929 27 68

5 832 16 36 706 4 7.6 851 18 41

6 787 16 34 680 5 9.2 773 14 29

7 812 16 35 621 5 8.4 766 13 27

8 818 16 35 644 5 8.7 777 12 25

9 784 16 34 705 5 9.5 752 11 22

10 757 17 35 662 5 8.9 708 8 15

11 907 38 93 581 5 7.8 647 7 12

12 1,020 61 168 565 4 6.1 630 7 12

13 871 24 56 604 4 6.5 632 6 10

14 850 18 41 668 4 7.2 650 6 11

15 927 19 48 632 5 8.5 657 8 14

16 866 16 37 569 7 11 657 7 12

17 797 11 24 e350 8 7.6 646 8 14

18 800 10 22 e280 8 6.0 677 11 20

19 795 10 21 e230 8 5.0 700 11 21

20 754 10 20 e400 8 8.6 679 9 16

21 739 10 20 e470 7 8.9 660 10 18

22 732 8 16 e600 7 11 671 9 16

23 716 8 15 609 6 9.9 684 10 18

24 738 8 16 618 6 10 705 12 23

25 702 9 17 601 6 9.7 739 14 28

26 681 9 17 603 6 9.8 823 22 49

27 707 10 19 659 6 11 906 32 78

28 701 8 15 820 16 35 831 22 49

29 685 7 13 -- -- -- 873 22 52

30 701 8 15 -- -- -- 967 26 68

31 742 10 20 -- -- -- 1,010 31 85

TOTAL 24,948 -- 1,084 16,721 -- 288.9 24,528 -- 1,643

MEAN 805 15 35 597 6 10 791 20 53

MAX 1,020 61 168 820 16 35 1,350 108 394

MIN 681 7 13 230 4 5.0 630 6 10

48  Water-Quality, Bed-Sediment, 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 2005 

through September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 1,030 30 83 3,000 80 648 2,090 16 90

2 1,040 27 76 3,020 59 481 1,990 17 91

3 1,010 27 74 2,840 48 368 2,030 17 93

4 1,010 31 85 2,640 36 257 2,170 18 105

5 1,140 44 135 2,500 30 202 2,270 19 116

6 1,800 137 666 2,480 28 187 2,180 20 118

7 2,590 250 1,750 2,530 27 184 2,070 14 78

8 2,300 113 702 2,530 24 164 2,130 16 92

9 2,130 69 397 2,420 25 163 2,540 43 295

10 2,070 59 330 2,280 19 117 2,850 60 462

11 2,000 50 270 2,210 19 113 3,510 146 1,380

12 1,910 46 237 2,210 18 107 3,160 85 725

13 1,930 53 276 2,210 20 119 2,720 45 330

14 2,100 55 312 2,260 22 134 2,420 36 235

15 2,250 62 377 2,440 27 178 2,260 28 171

16 2,430 68 446 2,760 48 358 2,120 22 126

17 2,450 57 377 3,280 95 841 1,980 17 91

18 2,330 52 327 3,790 126 1,290 1,860 14 70

19 2,160 36 210 4,180 114 1,290 1,760 11 52

20 2,040 32 176 4,560 113 1,390 1,730 9 42

21 2,020 33 180 4,550 96 1,180 1,640 8 35

22 2,100 36 204 4,130 69 769 1,540 7 29

23 2,260 43 262 3,740 50 505 1,460 6 24

24 2,380 44 283 3,510 44 417 1,390 7 26

25 2,320 35 219 3,120 37 312 1,320 5 18

26 2,240 32 194 3,030 34 278 1,250 4 14

27 2,190 28 166 2,990 32 258 1,200 4 13

28 2,230 28 169 2,880 30 233 1,170 4 13

29 2,320 30 188 2,750 32 238 1,120 4 12

30 2,600 53 372 2,520 29 197 1,130 4 12

31 -- -- -- 2,260 18 110 -- -- --

TOTAL 60,380 -- 9,543 91,620 -- 13,088 59,060 -- 4,958

MEAN 2,013 55 318 2,955 47 422 1,969 24 165

MAX 2,600 250 1,750 4,560 126 1,390 3,510 146 1,380

MIN 1,010 27 74 2,210 18 107 1,120 4 12

Data  49
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 1,150 6 19 452 4 4.9 407 3 3.3

2 1,110 7 21 447 4 4.8 401 4 4.3

3 1,070 6 17 437 4 4.7 403 5 5.4

4 1,050 5 14 418 3 3.4 393 8 8.5

5 1,040 4 11 410 3 3.3 382 9 9.3

6 1,060 5 14 411 3 3.3 377 9 9.2

7 1,100 7 21 405 4 4.4 377 10 10

8 1,030 5 14 402 4 4.3 372 10 10

9 965 4 10 416 4 4.5 374 10 10

10 928 4 10 395 4 4.3 387 10 10

11 910 4 9.8 382 4 4.1 389 8 8.4

12 899 4 9.7 379 3 3.1 393 5 5.3

13 916 4 9.9 378 3 3.1 390 3 3.2

14 899 5 12 376 3 3.0 390 3 3.2

15 853 5 12 364 3 2.9 412 3 3.3

16 813 5 11 364 3 2.9 490 7 9.3

17 775 5 10 380 3 3.1 563 8 12

18 736 5 9.9 395 3 3.2 555 7 10

19 692 5 9.3 396 3 3.2 551 6 8.9

20 660 5 8.9 391 4 4.2 550 5 7.4

21 642 4 6.9 379 5 5.1 578 6 9.4

22 627 4 6.8 370 5 5.0 607 9 15

23 604 5 8.2 368 3 3.0 616 9 15

24 580 5 7.8 369 3 3.0 614 9 15

25 563 3 4.6 390 4 4.2 601 9 15

26 537 2 2.9 427 6 6.9 591 8 13

27 511 3 4.1 421 5 5.7 589 9 14

28 488 5 6.6 416 5 5.6 597 12 19

29 471 5 6.4 404 4 4.4 606 13 21

30 459 5 6.2 399 4 4.3 610 13 21

31 453 4 4.9 405 3 3.3 -- -- --

TOTAL 24,591 -- 318.9 12,346 -- 125.2 14,565 -- 308.4

MEAN 793 5 10 398 4 4.0 486 8 10

MAX 1,150 7 21 452 6 6.9 616 13 21

MIN 453 2 2.9 364 3 2.9 372 3 3.2

Total for water year 2006 (unrounded sum of daily values): streamflow–400,332 ft3

/s (annual runoff–794,100 acre-ft); suspended-sediment discharge–

33,296.7 tons.

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2005 

through September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

50 Water-Quality, Bed-Sediment, 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 2005 through 

September 2006.

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

OCTOBER NOVEMBER DECEMBER

1 509 2 2.7 557 2 3.0 418 4 4.5

2 514 2 2.8 584 2 3.2 443 4 4.8

3 518 2 2.8 574 1 1.5 455 3 3.7

4 538 2 2.9 549 1 1.5 412 2 2.2

5 532 2 2.9 528 1 1.4 e420 2 2.3

6 524 2 2.8 532 1 1.4 e440 2 2.4

7 521 2 2.8 527 1 1.4 e180 1 .49

8 516 2 2.8 552 1 1.5 e280 1 .76

9 511 2 2.8 547 1 1.5 e300 1 .81

10 514 2 2.8 529 1 1.4 e380 1 1.0

11 517 2 2.8 539 1 1.5 e400 2 2.2

12 516 2 2.8 549 1 1.5 e400 2 2.2

13 511 2 2.8 552 1 1.5 e420 2 2.3

14 510 2 2.8 576 1 1.6 e470 2 2.5

15 504 2 2.7 544 1 1.5 e430 2 2.3

16 500 1 1.4 536 1 1.4 e420 1 1.1

17 500 1 1.4 535 1 1.4 e400 1 1.1

18 494 1 1.3 520 1 1.4 e370 1 1.0

19 490 2 2.6 514 1 1.4 e358 1 .97

20 493 2 2.7 502 1 1.4 e329 1 .89

21 499 1 1.3 487 1 1.3 e321 1 .87

22 497 1 1.3 484 1 1.3 e373 1 1.0

23 493 2 2.7 480 1 1.3 e351 1 .95

24 488 3 4.0 464 1 1.3 e380 2 2.1

25 482 2 2.6 446 1 1.2 e373 3 3.0

26 478 2 2.6 473 1 1.3 e365 3 3.0

27 492 2 2.7 482 1 1.3 e402 3 3.3

28 498 2 2.7 466 1 1.3 e395 3 3.2

29 490 2 2.6 443 2 2.4 e432 4 4.7

30 487 1 1.3 468 2 2.5 e432 2 2.3

31 492 1 1.3 -- -- -- e458 2 2.5

TOTAL 15,628 -- 76.5 15,539 -- 47.6 12,007 -- 66.44

MEAN 504 2 2.5 518 1 1.6 387 2 2.1

MAX 538 3 4.0 584 2 3.2 470 4 4.8

MIN 478 1 1.3 443 1 1.2 180 1 .49

Data 51
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 e488 2 2.6 504 3 4.1 518 4 5.6

2 e512 2 2.8 503 3 4.1 576 2 3.1

3 e529 2 2.9 505 4 5.5 586 4 6.3

4 e537 2 2.9 499 4 5.4 586 7 11

5 e545 2 2.9 494 4 5.3 561 7 11

6 e545 1 1.5 481 4 5.2 541 6 8.8

7 e542 1 1.5 453 3 3.7 517 4 5.6

8 e538 1 1.5 465 3 3.8 513 4 5.5

9 e530 1 1.4 499 2 2.7 512 4 5.5

10 535 1 1.4 446 2 2.4 492 3 4.0

11 560 2 3.0 397 2 2.1 478 2 2.6

12 561 2 3.0 398 2 2.1 464 2 2.5

13 563 2 3.0 455 2 2.5 449 3 3.6

14 562 2 3.0 491 1 1.3 459 4 5.0

15 571 3 4.6 424 1 1.1 473 2 2.6

16 549 3 4.4 402 1 1.1 453 2 2.4

17 553 2 3.0 337 1 .91 461 3 3.7

18 555 2 3.0 279 1 .75 474 3 3.8

19 537 2 2.9 359 2 1.9 510 4 5.5

20 540 2 2.9 443 2 2.4 509 4 5.5

21 538 2 2.9 495 2 2.7 505 5 6.8

22 528 3 4.3 523 2 2.8 516 6 8.4

23 522 3 4.2 504 2 2.7 551 6 8.9

24 519 3 4.2 497 1 1.3 611 8 13

25 507 3 4.1 524 1 1.4 682 14 26

26 479 2 2.6 505 1 1.4 799 20 43

27 502 2 2.7 484 1 1.3 900 23 56

28 500 2 2.7 502 2 2.7 872 24 57

29 497 2 2.7 -- -- -- 908 22 54

30 497 2 2.7 -- -- -- 1,080 28 82

31 506 2 2.7 -- -- -- 1,160 32 100

TOTAL 16,447 -- 90.0 12,868 -- 74.66 18,716 -- 558.7

MEAN 531 2 2.9 460 2 2.7 604 8 18

MAX 571 3 4.6 524 4 5.5 1,160 32 100

MIN 479 1 1.4 279 1 .75 449 2 2.4

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2005 through 

September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

52 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
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 1,230 28 93 4,780 38 490 3,920 18 191

2 1,340 29 105 4,660 26 327 3,820 17 175

3 1,370 28 104 4,380 22 260 4,150 23 258

4 1,430 22 85 4,040 17 185 4,480 26 314

5 1,730 36 168 3,830 17 176 4,490 24 291

6 2,830 85 649 3,790 16 164 4,320 22 257

7 3,550 86 824 3,910 14 148 4,150 18 202

8 3,480 60 564 3,940 14 149 4,150 19 213

9 3,390 32 293 3,800 14 144 4,310 20 233

10 3,330 24 216 3,590 13 126 4,440 22 264

11 3,280 20 177 3,460 10 93 4,730 27 345

12 3,210 16 139 3,460 10 93 4,390 22 261

13 3,360 19 172 3,570 13 125 4,150 20 224

14 3,650 23 227 3,740 13 131 4,040 20 218

15 3,960 28 299 4,100 18 199 3,860 17 177

16 4,240 35 401 4,880 46 606 3,720 14 141

17 4,280 36 416 5,990 115 1,860 3,530 12 114

18 4,040 28 305 7,100 141 2,700 3,370 12 109

19 3,700 21 210 7,860 145 3,080 3,130 9 76

20 3,440 19 176 8,180 132 2,920 2,920 9 71

21 3,340 25 225 8,170 117 2,580 2,720 8 59

22 3,560 26 250 7,780 98 2,060 2,540 7 48

23 3,790 24 246 7,280 68 1,340 2,390 7 45

24 3,820 22 227 6,950 57 1,070 2,250 7 43

25 3,720 19 191 6,490 46 806 2,140 7 40

26 3,610 16 156 6,310 44 750 2,030 5 27

27 3,600 15 146 6,120 39 644 1,940 6 31

28 3,670 16 159 5,590 31 468 1,840 7 35

29 3,910 18 190 5,090 26 357 1,750 6 28

30 4,500 38 462 4,680 24 303 1,700 6 28

31 -- -- -- 4,220 19 216 -- -- --

TOTAL 98,360 -- 7,875 161,740 -- 24,570 101,370 -- 4,518

MEAN 3,279 30 262 5,217 45 793 3,379 15 151

MAX 4,500 86 824 8,180 145 3,080 4,730 27 345

MIN 1,230 15 85 3,460 10 93 1,700 5 27

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2005 through 

September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Data 53
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 1,630 6 26 651 3 5.3 511 2 2.8

2 1,540 6 25 633 3 5.1 511 2 2.8

3 1,460 6 24 623 3 5.0 510 2 2.8

4 1,410 5 19 606 3 4.9 506 3 4.1

5 1,340 5 18 596 3 4.8 500 3 4.0

6 1,350 5 18 586 3 4.7 488 3 4.0

7 1,400 6 23 577 3 4.7 481 3 3.9

8 1,310 5 18 571 3 4.6 475 3 3.8

9 1,250 5 17 562 3 4.6 469 3 3.8

10 1,180 5 16 557 3 4.5 465 3 3.8

11 1,140 5 15 551 2 3.0 458 2 2.5

12 1,090 5 15 537 2 2.9 462 2 2.5

13 1,080 5 15 535 2 2.9 468 2 2.5

14 1,050 4 11 533 2 2.9 466 2 2.5

15 987 5 13 523 2 2.8 476 2 2.6

16 946 5 13 541 2 2.9 526 2 2.8

17 912 5 12 574 2 3.1 539 2 2.9

18 881 5 12 589 2 3.2 536 2 2.9

19 855 5 12 585 2 3.2 518 2 2.8

20 837 4 9.0 566 2 3.1 522 2 2.8

21 811 4 8.8 547 2 3.0 525 2 2.8

22 783 4 8.5 529 2 2.9 525 2 2.8

23 767 5 10 517 2 2.8 521 2 2.8

24 754 5 10 513 2 2.8 520 2 2.8

25 732 4 7.9 525 2 2.8 511 2 2.8

26 714 2 3.9 558 2 3.0 503 2 2.7

27 704 3 5.7 547 2 3.0 498 2 2.7

28 688 5 9.3 530 2 2.9 488 3 4.0

29 674 4 7.3 514 2 2.8 482 3 3.9

30 666 4 7.2 504 2 2.7 475 3 3.8

31 661 4 7.1 514 2 2.8 -- -- --

TOTAL 31,602 -- 416.7 17,294 -- 109.7 14,935 -- 93.7

MEAN 1,019 5 13 558 2 3.5 498 2 3.1

MAX 1,630 6 26 651 3 5.3 539 3 4.1

MIN 661 2 3.9 504 2 2.7 458 2 2.5

Total for water year 2006 (unrounded sum of daily values): streamflow–516,506 ft3

/s (annual runoff–1,024,000 acre-ft); suspended-sediment discharge–

38,497.00 tons.

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2005 through 

September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

54  Water-Quality, Bed-Sediment, 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 2005 through 

September 2006.

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

OCTOBER NOVEMBER DECEMBER

1 1,280 4 14 1,390 16 60 1,160 22 69

2 1,290 4 14 1,430 18 69 1,170 23 73

3 1,330 5 18 1,440 24 93 1,150 21 65

4 1,410 5 19 1,430 29 112 e1,100 20 59

5 1,530 6 25 1,390 28 105 e1,130 18 55

6 1,490 6 24 1,380 21 78 e1,100 17 50

7 1,480 7 28 1,370 18 67 e550 15 22

8 1,420 8 31 1,420 22 84 e500 14 19

9 1,390 9 34 1,410 16 61 e530 12 17

10 1,420 13 50 1,350 15 55 e800 11 24

11 1,390 19 71 1,370 14 52 e950 9 23

12 1,400 23 87 1,410 13 49 e1,000 7 19

13 1,380 26 97 1,420 13 50 e1,000 5 14

14 1,360 30 110 1,430 14 54 e1,100 5 15

15 1,350 34 124 1,420 17 65 e1,030 5 14

16 1,330 38 136 1,330 18 65 e1,030 5 14

17 1,310 41 145 1,360 17 62 e1,000 5 14

18 1,300 35 123 1,360 15 55 e900 5 12

19 1,290 38 132 1,330 13 47 e850 5 11

20 1,310 32 113 1,330 12 43 e900 8 19

21 1,300 25 88 1,300 10 35 e1,000 19 51

22 1,300 22 77 1,280 9 31 e1,100 34 101

23 1,310 20 71 1,270 10 34 e1,300 50 176

24 1,290 18 63 1,220 10 33 e1,500 39 158

25 1,280 16 55 1,160 10 31 e1,430 26 100

26 1,270 16 55 1,230 10 33 e1,450 42 164

27 1,290 19 66 1,310 10 35 e1,400 46 174

28 1,320 20 71 1,230 10 33 e1,350 57 208

29 1,310 19 67 1,170 10 32 e1,550 47 197

30 1,290 18 63 1,070 11 32 1,660 27 121

31 1,300 17 60 -- -- -- 1,600 17 73

TOTAL 41,720 -- 2,131 40,010 -- 1,655 34,290 -- 2,131

MEAN 1,346 19 69 1,334 15 55 1,106 21 69

MAX 1,530 41 145 1,440 29 112 1,660 57 208

MIN 1,270 4 14 1,070 9 31 500 5 11

Data 55
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 1,520 13 53 1,220 6 20 1,730 29 135

2 1,450 64 251 1,200 6 19 1,660 36 161

3 1,440 28 109 1,200 7 23 1,530 19 78

4 1,440 17 66 1,180 5 16 1,480 12 48

5 1,350 11 40 1,180 4 13 1,440 11 43

6 1,230 14 46 1,150 5 16 1,310 8 28

7 1,300 10 35 1,060 4 11 1,260 8 27

8 1,330 10 36 1,050 4 11 1,260 7 24

9 1,290 11 38 1,160 5 16 1,270 6 21

10 1,240 10 33 1,130 4 12 1,240 4 13

11 1,410 11 42 961 4 10 1,060 5 14

12 1,580 19 81 869 4 9.4 1,070 4 12

13 1,430 9 35 972 3 7.9 1,080 5 15

14 1,370 8 30 1,130 3 9.2 1,080 5 15

15 1,490 9 36 1,020 3 8.3 1,110 6 18

16 1,420 29 111 1,010 3 8.2 1,110 6 18

17 1,330 7 25 700 4 7.6 1,100 6 18

18 1,340 6 22 678 5 9.2 1,110 7 21

19 1,340 5 18 737 6 12 1,180 8 25

20 1,300 4 14 925 8 20 1,210 7 23

21 1,280 4 14 1,030 9 25 1,200 8 26

22 1,250 5 17 1,130 8 24 1,220 10 33

23 1,210 4 13 1,160 6 19 1,260 14 48

24 1,230 5 17 1,140 5 15 1,310 13 46

25 1,200 4 13 1,140 4 12 1,400 20 76

26 1,130 3 9.2 1,070 3 8.7 1,590 25 107

27 1,170 3 9.5 1,120 4 12 1,820 30 147

28 1,170 3 9.5 1,220 8 26 1,710 20 92

29 1,200 8 26 -- -- -- 1,750 18 85

30 1,140 4 12 -- -- -- 2,000 25 135

31 1,220 5 16 -- -- -- 2,170 26 152

TOTAL 40,800 -- 1,277.2 29,542 -- 400.5 42,720 -- 1,704

MEAN 1,316 11 41 1,055 5 14 1,378 13 55

MAX 1,580 64 251 1,220 9 26 2,170 36 161

MIN 1,130 3 9.2 678 3 7.6 1,060 4 12

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2005 through 

September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

56 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
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 2,170 25 146 7,700 47 977 6,040 16 261

2 2,200 21 125 7,550 40 815 5,800 16 251

3 2,410 30 195 7,150 36 695 6,110 22 363

4 2,370 22 141 6,590 28 498 6,640 33 592

5 2,880 30 233 6,200 23 385 6,730 37 672

6 4,560 65 800 6,060 20 327 6,470 32 559

7 6,110 90 1,480 6,200 21 352 6,170 40 666

8 5,800 68 1,060 6,280 22 373 6,210 66 1,110

9 5,470 49 724 6,070 20 328 6,800 126 2,310

10 5,330 40 576 5,680 17 261 7,260 163 3,200

11 5,210 34 478 5,470 16 236 8,230 216 4,800

12 5,020 32 434 5,430 15 220 7,700 170 3,530

13 5,130 31 429 5,560 16 240 6,940 108 2,020

14 5,600 34 514 5,750 16 248 6,510 89 1,560

15 6,090 40 658 6,270 20 339 6,140 83 1,380

16 6,550 48 849 7,380 39 777 5,840 73 1,150

17 6,650 48 862 9,140 79 1,950 5,480 58 858

18 6,260 40 676 10,800 123 3,590 5,170 57 796

19 5,750 29 450 12,000 139 4,500 4,790 50 647

20 5,320 26 373 12,600 121 4,120 4,550 36 442

21 5,160 25 348 12,700 116 3,980 4,250 35 402

22 5,430 23 337 12,000 92 2,980 3,920 40 423

23 5,870 30 475 11,200 68 2,060 3,670 39 386

24 6,060 31 507 10,700 55 1,590 3,440 38 353

25 5,890 24 382 9,750 48 1,260 3,250 37 325

26 5,720 22 340 9,400 43 1,090 3,070 27 224

27 5,640 24 365 9,280 39 977 2,910 24 189

28 5,690 20 307 8,610 30 697 2,790 26 196

29 6,030 26 423 7,900 27 576 2,650 28 200

30 6,880 33 613 7,290 26 512 2,620 34 241

31 -- -- -- 6,490 17 298 -- -- --

TOTAL 155,250 -- 15,300 251,200 -- 37,251 158,150 -- 30,106

MEAN 5,175 35 510 8,103 46 1,200 5,272 61 1,000

MAX 6,880 90 1,480 12,700 139 4,500 8,230 216 4,800

MIN 2,170 20 125 5,430 15 220 2,620 16 189

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2005 through 

September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Data 57
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 2,590 38 266 1,110 10 30 891 8 19

2 2,470 36 240 1,080 10 29 885 8 19

3 2,350 40 254 1,060 10 29 885 8 19

4 2,290 50 309 1,020 10 28 880 7 17

5 2,200 51 303 992 10 27 866 7 16

6 2,230 44 265 978 11 29 849 7 16

7 2,410 41 267 966 12 31 844 7 16

8 2,290 37 229 959 12 31 833 7 16

9 2,150 31 180 954 13 33 815 7 15

10 2,060 26 145 932 13 33 822 6 13

11 2,010 24 130 910 12 29 818 6 13

12 1,970 22 117 891 10 24 821 6 13

13 1,980 21 112 885 8 19 840 6 14

14 1,970 22 117 894 7 17 830 6 13

15 1,870 26 131 864 7 16 850 6 14

16 1,780 22 106 872 8 19 970 8 21

17 1,720 18 84 936 11 28 1,060 8 23

18 1,650 15 67 963 11 29 1,070 9 26

19 1,590 14 60 963 10 26 1,040 9 25

20 1,540 14 58 938 10 25 1,050 10 28

21 1,490 14 56 918 10 25 1,080 10 29

22 1,450 12 47 887 10 24 1,120 11 33

23 1,400 12 45 871 10 24 1,120 13 39

24 1,360 15 55 863 10 23 1,120 16 48

25 1,330 13 47 877 10 24 1,110 24 72

26 1,280 10 35 954 12 31 1,090 30 88

27 1,250 11 37 945 10 26 1,080 23 67

28 1,200 12 39 923 7 17 1,080 31 90

29 1,160 11 34 894 7 17 1,080 41 120

30 1,140 10 31 877 6 14 1,080 45 131

31 1,120 10 30 885 7 17 -- -- --

TOTAL 55,300 -- 3,896 29,061 -- 774 28,879 -- 1,073

MEAN 1,784 23 126 937 10 25 963 13 36

MAX 2,590 51 309 1,110 13 33 1,120 45 131

MIN 1,120 10 30 863 6 14 815 6 13

Total for water year 2006 (unrounded sum of daily values): streamflow–906,922 ft3

/s (annual runoff–1,799,000 acre-ft); suspended-sediment discharge–

97,698.7 tons.

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2005 through 

September 2006.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

58  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 9. Seasonal daily maximum, minimum, and mean turbidity at Mill Creek near Anaconda, Montana, June through September 2006.

[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

JUNE JULY AUGUST

1 -- -- -- 4.0 2.0 2.5 2.0 0.5 1.0

2 -- -- -- 5.0 1.5 2.0 2.5 .5 1.0

3 -- -- -- 4.5 1.5 2.5 1.5 1.0 1.0

4 -- -- -- 3.5 1.5 2.0 1.5 .5 1.0

5 -- -- -- 3.0 1.0 1.5 3.0 .5 1.0

6 -- -- -- 2.5 1.0 1.5 1.5 .5 1.0

7 -- -- -- 3.5 1.0 1.5 1.5 .5 1.0

8 -- -- -- 2.5 1.0 1.5 3.5 .5 1.0

9 -- -- -- 6.5 1.5 2.5 2.5 .5 1.0

10 -- -- -- 10 1.5 4.5 2.5 .5 1.0

11 -- -- -- -- -- -- 3.5 .5 1.0

12 -- -- -- -- -- -- 3.0 1.0 1.0

13 2.5 1.0 1.5 -- -- -- 2.5 1.0 1.0

14 2.5 1.0 1.0 -- -- -- 2.0 .5 1.0

15 1.5 1.0 1.0 -- -- -- 2.5 .5 1.0

16 2.0 1.0 1.0 5.5 1.0 2.0 2.5 .5 1.0

17 2.0 1.0 1.0 3.5 1.0 1.5 4.5 1.0 1.5

18 1.5 1.0 1.0 2.5 1.0 1.5 3.5 .5 1.0

19 3.5 1.0 1.5 3.5 1.0 1.5 2.0 .5 1.0

20 2.0 1.0 1.5 2.5 1.0 1.5 1.5 .5 1.0

21 6.5 1.5 2.5 2.5 1.0 1.5 2.0 .5 1.0

22 6.5 1.5 2.5 4.0 1.0 1.5 1.5 .5 1.0

23 -- -- -- 3.0 1.0 1.5 1.5 .5 1.0

24 3.0 1.0 1.5 3.0 1.0 1.5 2.5 .5 1.0

25 5.5 1.0 2.0 3.0 1.0 1.5 3.5 1.0 1.0

26 2.5 1.0 1.5 2.0 1.0 1.0 2.5 .5 1.0

27 3.5 1.5 2.0 3.0 .5 1.0 1.5 .5 1.0

28 4.5 1.0 1.5 2.5 .5 1.0 1.5 .5 1.0

29 7.5 1.0 2.0 2.0 .5 1.0 1.5 .5 1.0

30 5.5 2.0 3.5 1.5 .5 1.0 1.5 1.0 1.0

31 -- -- -- 1.5 .5 1.0 1.5 .5 1.0

MONTH1 7.5 1.0 1.7 10 .5 1.7 4.5 .5 1.0

Data 59
Day

Maximum Minimum Mean

SEPTEMBER

1 3.0 0.5 1.0

2 3.5 .5 1.0

3 1.5 .5 1.0

4 2.0 .5 1.0

5 2.5 .5 1.0

6 2.5 1.0 1.0

7 5.5 .5 1.5

8 3.5 .5 1.0

9 5.0 1.0 2.0

10 5.5 1.0 2.5

11 3.0 1.0 1.5

12 2.5 1.0 1.5

13 5.0 1.0 1.5

14 3.0 1.0 2.0

15 5.0 1.5 2.5

16 5.0 1.5 2.5

17 4.0 1.0 1.5

18 5.5 1.0 1.5

19 3.5 1.0 2.0

20 5.5 1.5 3.0

21 4.0 1.5 2.5

22 5.5 1.5 3.0

23 8.0 2.0 3.5

24 8.0 1.0 4.0

25 5.0 1.0 3.5

26 5.5 1.0 1.5

27 2.5 1.0 1.5

28 4.0 .5 1.5

29 1.5 .5 1.0

30 2.0 .5 1.0

31 -- -- --

MONTH1 8.0 .5 1.9

1

For months with missing daily values, the means are calculated using available values.

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

Table 9. Seasonal daily maximum, minimum, and 

mean turbidity at Mill Creek near Anaconda, Montana, 

June through September 2006.—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]
Table 10. Seasonal daily maximum, minimum, and mean turbidity at Willow Creek near Anaconda, Montana, June through September 

2006.

[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

JUNE JULY AUGUST

1 -- -- -- 10 5.0 6.5 4.0 1.5 2.0

2 -- -- -- 8.0 3.5 5.0 5.5 1.5 2.0

3 -- -- -- 6.5 3.0 4.0 4.5 1.5 2.0

4 -- -- -- 9.5 4.0 4.0 5.0 1.0 2.5

5 -- -- -- 9.5 3.0 4.5 6.0 1.5 2.5

6 -- -- -- 8.5 2.5 3.5 6.5 1.5 3.0

7 -- -- -- 5.5 2.0 3.0 5.5 1.5 2.5

8 -- -- -- 7.5 2.0 3.0 5.5 1.5 2.5

9 -- -- -- 4.5 2.0 2.5 6.5 2.0 3.5

10 -- -- -- 4.0 2.0 2.5 6.0 1.5 3.0

11 -- -- -- -- -- -- 7.0 1.5 3.0

12 -- -- -- 7.0 2.0 2.5 6.5 1.5 2.5

13 -- -- -- 4.5 1.5 2.5 6.0 2.0 3.0

14 -- -- -- 4.5 1.5 2.0 6.5 2.0 3.0

15 -- -- -- 2.5 1.5 2.0 7.0 2.0 3.0

16 5.0 2.0 2.5 4.0 1.5 2.0 7.0 2.0 3.5

17 5.5 1.5 2.5 5.0 1.5 2.0 5.5 1.5 3.0

18 -- -- -- 3.0 1.5 2.0 6.0 1.5 2.5

19 3.0 2.0 2.0 3.5 1.5 2.0 3.5 1.5 2.0

20 4.0 1.5 2.0 3.5 1.0 2.0 4.5 1.0 2.0

21 3.5 1.5 2.0 4.0 1.5 2.0 3.0 1.5 1.5

22 5.0 1.5 2.5 5.0 1.0 2.0 4.0 1.5 2.0

23 5.5 1.5 2.5 6.0 1.0 2.0 3.0 1.0 1.5

24 5.0 1.5 2.5 4.0 1.0 2.0 3.0 1.5 2.0

25 5.0 1.5 2.0 6.5 1.0 2.0 4.0 1.5 2.5

26 4.0 1.0 2.0 3.0 1.0 1.5 4.0 1.5 2.0

27 2.5 1.5 2.0 4.0 1.0 2.0 3.0 1.5 1.5

28 5.0 1.0 2.0 6.5 1.5 2.0 4.5 1.0 2.0

29 3.5 1.0 1.5 4.0 1.0 2.0 2.0 1.5 1.5

30 -- -- -- 5.0 1.0 2.0 3.0 1.0 1.5

31 -- -- -- 3.5 1.5 2.0 3.5 1.0 2.0

MONTH1 5.5 1.0 2.2 10 1.0 2.6 7.0 1.0 2.4

Data 61
Day

Maximum Minimum Mean

SEPTEMBER

1 6.0 1.5 2.0

2 6.0 1.0 2.0

3 4.5 1.0 1.5

4 4.0 1.0 2.0

5 3.5 1.0 2.0

6 -- -- --

7 2.0 1.0 1.5

8 3.5 1.0 1.5

9 3.5 1.0 2.0

10 4.5 1.0 1.5

11 2.5 1.0 2.0

12 -- -- --

13 -- -- --

14 9.0 1.5 3.0

15 9.0 1.5 3.5

16 5.5 1.5 3.0

17 4.0 1.5 2.5

18 2.5 1.0 1.5

19 3.5 1.5 2.0

20 4.5 1.5 2.0

21 7.0 2.5 3.5

22 -- -- --

23 -- -- --

24 -- -- --

25 -- -- --

26 2.0 1.5 1.5

27 4.5 1.5 2.0

28 3.5 1.5 2.0

29 4.0 1.5 1.5

30 4.0 1.5 2.0

31 -- -- --

MONTH1 9.0 1.0 2.1

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 2006.—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]

62 Water-Quality, Bed-Sediment, 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, May through 

September 2006.

[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

MAY JUNE JULY

1 -- -- -- 14 2.0 3.0 3.0 2.0 2.5

2 -- -- -- 3.0 2.0 2.5 3.0 2.0 2.5

3 -- -- -- 5.0 3.0 4.0 34 2.0 3.5

4 -- -- -- 6.0 2.0 3.5 4.0 2.0 2.5

5 3.0 2.0 2.5 4.0 2.0 2.5 4.0 2.0 2.5

6 3.0 2.0 2.5 3.0 2.0 2.5 6.0 2.0 3.0

7 5.0 2.0 3.0 5.0 2.0 2.5 3.0 2.0 2.5

8 3.0 2.0 2.5 24 5.0 8.5 3.0 2.0 2.5

9 5.0 2.0 2.5 25 3.0 4.5 4.0 2.0 2.5

10 3.0 2.0 2.0 27 3.0 5.0 16 2.0 3.0

11 3.0 2.0 2.0 4.0 2.0 3.0 5.0 2.0 2.5

12 3.0 2.0 2.5 3.0 2.0 2.5 3.0 2.0 2.5

13 4.0 2.0 3.0 3.0 2.0 2.5 3.0 2.0 2.5

14 6.0 3.0 4.0 3.0 2.0 2.5 3.0 2.0 2.5

15 14 5.0 9.5 3.0 2.0 2.5 6.0 2.0 2.5

16 18 7.0 12 2.0 1.0 2.0 6.0 2.0 2.5

17 26 8.0 15 2.0 1.0 2.0 3.0 1.0 2.5

18 26 8.0 16 3.0 2.0 2.0 3.0 2.0 2.0

19 19 8.0 12 3.0 2.0 2.0 3.0 1.0 2.5

20 22 10 14 2.0 1.0 2.0 3.0 2.0 2.0

21 25 6.0 11 3.0 2.0 2.0 3.0 2.0 2.0

22 7.0 4.0 5.0 3.0 2.0 2.5 3.0 2.0 2.0

23 6.0 3.0 4.5 14 2.0 8.0 3.0 2.0 2.0

24 6.0 3.0 4.5 13 1.0 10 3.0 2.0 2.0

25 4.0 3.0 3.5 3.0 1.0 2.0 4.0 2.0 2.0

26 5.0 3.0 3.5 3.0 1.0 2.0 5.0 2.0 3.0

27 5.0 3.0 3.5 2.0 1.0 2.0 6.0 2.0 2.5

28 22 3.0 4.0 3.0 2.0 2.0 3.0 2.0 2.5

29 6.0 3.0 3.0 21 2.0 3.5 3.0 2.0 2.5

30 4.0 2.0 2.5 18 2.0 4.0 3.0 2.0 2.5

31 14 2.0 3.0 -- -- -- 3.0 2.0 2.5

MONTH1 26 2.0 5.7 27 1.0 3.3 34 1.0 2.5

Data 63
Day

Maximum Minimum Mean Maximum Minimum Mean

AUGUST SEPTEMBER

1 3.0 2.0 2.0 4.0 2.0 2.0

2 3.0 2.0 2.0 4.0 2.0 2.0

3 3.0 2.0 2.0 3.0 2.0 2.0

4 4.0 1.0 2.0 3.0 1.0 2.0

5 3.0 1.0 2.0 2.0 1.0 2.0

6 7.5 2.0 2.0 2.0 2.0 2.0

7 7.0 2.0 3.0 3.0 1.0 2.0

8 3.0 2.0 2.0 3.0 2.0 2.0

9 3.0 2.0 2.0 4.0 1.0 2.0

10 3.0 1.0 2.0 2.0 2.0 2.0

11 4.0 2.0 2.0 3.0 1.0 2.0

12 3.0 2.0 2.0 3.0 1.0 2.0

13 4.0 2.0 2.0 2.0 2.0 2.0

14 3.0 2.0 2.0 3.0 2.0 2.0

15 4.0 2.0 2.0 15 2.0 3.5

16 46 2.0 4.0 5.0 2.0 3.0

17 23 2.0 4.5 3.0 2.0 2.5

18 3.0 2.0 2.5 3.0 2.0 2.0

19 3.0 2.0 2.0 2.0 2.0 2.0

20 3.0 2.0 2.0 3.0 2.0 2.0

21 3.0 2.0 2.5 9.5 2.0 2.0

22 3.0 2.0 2.0 2.0 2.0 2.0

23 3.0 2.0 2.0 2.0 2.0 2.0

24 3.0 2.0 2.0 3.0 2.0 2.0

25 6.0 2.0 3.0 5.0 1.0 2.0

26 5.0 2.0 2.5 3.0 1.0 2.0

27 3.0 2.0 2.0 2.0 1.0 2.0

28 3.0 2.0 2.0 2.0 2.0 2.0

29 3.0 2.0 2.0 3.0 2.0 2.0

30 3.0 2.0 2.0 3.0 2.0 2.0

31 4.0 2.0 2.0 -- -- --

MONTH1 46 1.0 2.3 15 1.0 2.1

1

For months with missing daily values, the means are calculated using available values.

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

near Anaconda, Montana, May through September 2006.—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]

64  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 12. Seasonal daily maximum, minimum, and mean turbidity at Lost Creek near Anaconda, Montana, May through September 

2006.

[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

MAY JUNE JULY

1 -- -- -- 7.5 2.0 2.5 4.0 2.0 2.5

2 -- -- -- 12 2.0 3.5 3.0 1.5 2.0

3 -- -- -- 6.0 2.0 3.0 4.5 1.5 2.0

4 -- -- -- 7.5 2.0 3.0 3.5 1.0 2.0

5 -- -- -- 10 2.0 3.5 2.5 1.0 1.5

6 -- -- -- 11 2.0 3.5 3.5 1.0 1.5

7 -- -- -- 12 2.0 3.0 2.0 1.0 1.0

8 -- -- -- 24 5.0 11 3.0 1.0 1.0

9 -- -- -- 7.5 3.5 4.5 1.5 1.0 1.0

10 -- -- -- 57 4.0 21 7.0 1.0 2.0

11 -- -- -- 13 5.0 8.0 -- -- --

12 -- -- -- 13 4.0 5.0 3.0 1.0 1.5

13 -- -- -- 7.0 3.5 4.5 2.5 1.0 1.0

14 -- -- -- 7.0 2.5 3.5 2.5 1.0 1.0

15 -- -- -- 5.5 2.0 2.5 2.0 1.0 1.0

16 -- -- -- 4.5 1.5 2.5 1.5 .5 1.0

17 -- -- -- 6.5 2.0 3.0 1.0 .5 1.0

18 -- -- -- 5.0 2.0 2.5 1.0 .5 1.0

19 -- -- -- 6.5 1.5 2.5 2.0 .5 1.0

20 -- -- -- 5.5 1.5 2.5 1.5 .5 1.0

21 -- -- -- 3.0 1.5 2.0 1.5 .5 1.0

22 -- -- -- 3.0 1.5 2.0 4.0 .5 1.0

23 -- -- -- 3.5 1.5 2.0 23 1.5 6.5

24 12 3.0 5.0 3.0 1.5 2.0 6.0 3.0 4.0

25 8.5 2.5 4.5 5.0 1.5 2.0 4.0 2.0 3.0

26 9.0 3.0 5.0 8.0 1.5 2.5 5.5 2.5 3.0

27 6.5 2.5 4.0 11 1.5 3.0 3.0 2.0 2.5

28 13 2.5 5.0 4.5 1.5 2.0 4.0 2.0 2.5

29 7.5 2.5 3.5 30 1.0 2.0 3.5 2.0 2.5

30 9.5 2.0 3.5 61 3.5 11 6.0 2.0 2.5

31 8.5 2.0 3.0 -- -- -- 3.5 1.5 2.5

MONTH1 13 2.0 4.2 61 1.0 4.2 23 .5 1.9

Data 65
Day

Maximum Minimum Mean Maximum Minimum Mean

AUGUST SEPTEMBER

1 3.0 2.0 2.5 -- -- --

2 3.5 1.5 2.5 -- -- --

3 5.0 2.0 2.5 -- -- --

4 5.5 1.5 2.5 -- -- --

5 2.0 1.0 1.5 -- -- --

6 2.0 1.0 1.0 -- -- --

7 2.0 .5 1.0 -- -- --

8 1.0 .5 .5 1.5 1.0 1.0

9 1.5 .5 1.0 -- -- --

10 1.0 .5 .5 -- -- --

11 1.5 .5 .5 -- -- --

12 1.5 .5 .5 -- -- --

13 -- -- -- -- -- --

14 2.0 .5 1.0 1.0 1.0 1.0

15 -- -- -- 1.5 1.0 1.0

16 -- -- -- 3.0 1.0 1.5

17 -- -- -- 1.0 1.0 1.0

18 -- -- -- 1.0 1.0 1.0

19 -- -- -- 1.0 1.0 1.0

20 -- -- -- 1.0 1.0 1.0

21 -- -- -- 1.5 1.0 1.0

22 -- -- -- 1.0 1.0 1.0

23 -- -- -- 1.5 1.0 1.0

24 -- -- -- -- -- --

25 -- -- -- -- -- --

26 1.0 .5 1.0 1.0 1.0 1.0

27 1.0 .5 1.0 1.0 1.0 1.0

28 -- -- -- 1.0 .5 .5

29 -- -- -- -- -- --

30 -- -- -- -- -- --

31 -- -- -- -- -- --

MONTH1 5.5 .5 1.3 3.0 .5 1.0

1

For months with missing daily values, the means are calculated using available values.

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

Anaconda, Montana, May through September 2006.—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]

66 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.

[Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams 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)

Arsenic,

 filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

12323600 Silver Bow Creek at 

Opportunity

03/20/2006 1540 190 54.5 11.8 -- -- 11.4 14.9

03/20/2006 1545 180 54.3 11.9 -- -- 11.0 14.6

12323670 Mill Creek near 

Anaconda

06/09/2006 0845 27 7.97 1.67 -- -- 8.6 9.9

06/09/2006 0850 27 8.10 1.70 -- -- 8.8 9.8

12323700 Mill Creek at 

Opportunity

07/24/2006 1505 72 20.4 5.11 -- -- 34.9 35.4

07/24/2006 1510 72 20.3 5.10 -- -- 35.2 35.3

12323750 Silver Bow Creek at Warm 

Springs

04/18/2006 1020 210 60.0 13.7 -- -- 13.8 17.7

04/18/2006 1025 210 60.3 13.8 -- -- 14.3 18.2

12323760 Warm Springs Creek near 

Anaconda

08/23/2006 1435 110 34.3 7.02 -- -- 2.2 2.3

08/23/2006 1440 120 35.3 7.24 -- -- 2.2 2.0

12324200 Clark Fork at 

Deer Lodge 

05/09/2006 1255 200 58.6 11.9 -- -- 16.3 20.1

05/09/2006 1300 200 58.5 11.9 -- -- 16.4 19.3

12334550 Clark Fork at Turah 

Bridge, near Bonner

05/24/2006 0750 66 18.8 4.62 0.38 0.072 4.9 6.8

05/24/2006 0800 65 18.5 4.55 -- -- 4.8 6.6

12340000 Blackfoot River near 

Bonner

05/02/2006 1330 83 22.0 6.88 .24 .055 .66 1.1

05/02/2006 1335 81 21.6 6.65 .24 .042 .72 1.0

12340500 Clark Fork above 

Missoula 

10/19/2005 0945 170 44.2 13.4 -- -- 4.2 6.3

10/19/2005 0950 170 44.8 13.7 -- -- 4.3 6.3

05/16/2006 1500 83 22.7 6.39 .37 .061 2.1 3.0

05/16/2006 1510 84 23.0 6.47 .34 .060 2.1 3.1

12354500 Clark Fork at St. Regis 06/01/2006 1500 62 17.1 4.64 .26 .029 1.4 1.8

06/01/2006 1505 61 16.7 4.58 .26 .025 1.4 1.8

09/27/2006 1400 120 33.0 9.54 .20 .011 2.3 2.9

09/27/2006 1405 120 32.1 9.28 .18 .011 2.3 2.6

12388700 Flathead River at Perma 06/20/2006 1100 83 23.6 5.87 .12 .009 .35 .48

06/20/2006 1105 83 23.5 5.99 .13 .008 .36 .47

Data 67
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)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12323600 Silver Bow Creek at 

Opportunity

03/20/2006 1540 0.53 0.87 25.2 78.4 21 628 0.37

03/20/2006 1545 .55 .86 25.6 76.8 21 623 .40

12323670 Mill Creek near 

Anaconda

06/09/2006 0845 E.03 .08 2.2 4.1 28 184 .08

06/09/2006 0850 E.03 .07 2.4 7.0 29 188 .08

12323700 Mill Creek at 

Opportunity

07/24/2006 1505 .05 .06 2.4 3.3 72 128 .18

07/24/2006 1510 .05 .08 2.4 3.2 73 128 .19

12323750 Silver Bow Creek at Warm 

Springs

04/18/2006 1020 E.03 .09 5.0 9.5 24 286 .10

04/18/2006 1025 .04 .11 5.0 8.9 24 287 .11

12323760 Warm Springs Creek near 

Anaconda

08/23/2006 1435 <.04 E.02 .68 1.9 E6 75 <.08

08/23/2006 1440 <.04 E.03 .76 2.0 E6 74 <.08

12324200 Clark Fork at 

Deer Lodge 

05/09/2006 1255 .04 .19 9.0 30.5 7 461 E.05

05/09/2006 1300 .05 .17 8.9 29.9 10 447 <.08

12334550 Clark Fork at Turah 

Bridge, near Bonner

05/24/2006 0750 <.04 .12 4.2 20.0 34 644 .08

05/24/2006 0800 <.04 .12 4.1 20.3 33 650 .08

12340000 Blackfoot River near 

Bonner

05/02/2006 1330 <.04 <.04 .95 1.7 16 375 <.08

05/02/2006 1335 <.04 <.04 .76 1.6 14 360 <.08

12340500 Clark Fork above 

Missoula 

10/19/2005 0945 <.04 .24 2.2 24.6 8 585 E.06

10/19/2005 0950 <.04 .19 2.1 25.1 9 597 E.07

05/16/2006 1500 -- .06 2.4 8.3 16 555 E.06

05/16/2006 1510 -- .07 2.0 8.8 17 575 <.08

12354500 Clark Fork at St. Regis 06/01/2006 1500 <.04 E.04 1.6 4.2 19 385 E.05

06/01/2006 1505 <.04 E.03 1.5 4.3 18 399 <.08

09/27/2006 1400 <.04 E.03 1.5 3.5 8 68 .08

09/27/2006 1405 <.04 E.04 1.7 2.5 9 67 .09

12388700 Flathead River at Perma 06/20/2006 1100 <.04 <.04 .54 E.6 <6 152 <.08

06/20/2006 1105 <.04 <.04 E.37 E.6 <6 149 <.08

Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.—Continued[Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbols: <, less than laboratory reporting level; --, no data]

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

Sediment 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

12323600 Silver Bow Creek at 

Opportunity

03/20/2006 1540 14.6 304 340 138 221 84 15

03/20/2006 1545 14.3 296 329 139 219 84 16

12323670 Mill Creek near 

Anaconda

06/09/2006 0845 .79 3.4 11.1 1.6 3 47 8

06/09/2006 0850 .75 3.4 11.1 1.6 3 48 7

12323700 Mill Creek at 

Opportunity

07/24/2006 1505 .38 9.5 11.8 1.8 2 88 1

07/24/2006 1510 .35 9.7 11.6 1.4 E2 89 1

12323750 Silver Bow Creek at Warm 

Springs

04/18/2006 1020 1.50 374 378 8.3 14 83 5

04/18/2006 1025 1.44 361 367 7.7 14 82 5

12323760 Warm Springs Creek near 

Anaconda

08/23/2006 1435 .24 .8 3.7 E.30 E1 68 4

08/23/2006 1440 .24 .7 3.7 E.48 E2 69 5

12324200 Clark Fork at 

Deer Lodge 

05/09/2006 1255 3.61 54.6 142 4.5 27 79 17

05/09/2006 1300 3.31 54.1 141 4.4 27 76 16

12334550 Clark Fork at Turah 

Bridge, near Bonner

05/24/2006 0750 2.99 7.9 68.7 3.4 24 63 41

05/24/2006 0800 3.08 8.1 68.7 3.7 24 63 41

12340000 Blackfoot River near 

Bonner

05/02/2006 1330 .46 2.8 28.8 1.1 3 83 25

05/02/2006 1335 .45 2.8 28.6 .7 2 83 25

12340500 Clark Fork above 

Missoula 

10/19/2005 0945 3.90 23.8 66.5 1.4 43 74 41

10/19/2005 0950 3.94 24.5 60.7 1.5 42 79 37

05/16/2006 1500 1.73 10.3 46.8 4.0 14 76 40

05/16/2006 1510 1.60 10.2 47.3 3.0 15 77 40

12354500 Clark Fork at St. Regis 06/01/2006 1500 .83 6.0 28.1 1.8 6 81 27

06/01/2006 1505 .83 6.1 28.6 1.4 6 79 27

09/27/2006 1400 .36 2.9 15.3 1.2 4 82 5

09/27/2006 1405 .32 2.9 15.9 1.2 4 82 5

12388700 Flathead River at Perma 06/20/2006 1100 .19 .8 8.1 1.3 <2 78 12

06/20/2006 1105 .19 .7 8.3 .62 <2 78 13

Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.—Continued[Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbols: <, less than laboratory reporting level; --, no data]

Data 69
Table 14. Precision of analyses of field replicates for water samples, Clark Fork basin, Montana.

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

Constituent and reporting unit

Number of 

replicate 

pairs

Standard 

deviation1, 

in listed units

Relative standard 

deviation, 

in percent

Within limits2

of data-quality 

objective

Calcium, filtered, mg/L 13 0.33 1.0 Yes

Magnesium, filtered, mg/L 13 .11 1.4 Yes

Total nitrogen, unfiltered, mg/L 5 .01 5.1 Yes

Total phosphorous, unfiltered, mg/L 5 .00 14 Yes

Arsenic, filtered, μg/L 13 .15 1.9 Yes

Arsenic, unfiltered recoverable, μg/L 13 .22 2.3 Yes

Cadmium, filtered, μg/L 12 .00 7.1 Yes

Cadmium, unfiltered recoverable, μg/L 13 .01 9.2 Yes

Copper, filtered, μg/L 13 .14 3.2 Yes

Copper, unfiltered recoverable, μg/L 13 .72 4.9 Yes

Iron, filtered, μg/L 13 .88 4.3 Yes

Iron, unfiltered recoverable, μg/L 13 6.9 2.0 Yes

Lead, filtered, μg/L 13 .01 8.9 Yes

Lead, unfiltered recoverable, μg/L 13 .09 3.8 Yes

Manganese, filtered, μg/L 13 3.0 4.9 Yes

Manganese, unfiltered recoverable, μg/L 13 3.3 3.7 Yes

Zinc, filtered, μg/L 13 .36 2.8 Yes

Zinc, unfiltered recoverable, μg/L 13 .55 2.0 Yes

Sediment, suspended, percent finer than 0.062 mm 13 1.3 1.7 Yes

Sediment, suspended, mg/L 13 .90 4.9 Yes

1

Standard deviation is calculated using one-half the 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 field replicate analyses (table 3).

70 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 15. Precision of analyses of laboratory replicates for water samples, upper Clark Fork basin, Montana.

[Abbreviations: μg/L, micrograms per liter; mg/L, milligrams per liter]

Constituent and reporting unit Number of 

replicate pairs

Standard 

deviation1, 

in listed units

Relative standard 

deviation, 

in percent

Within limits2

of data-quality 

objective

Calcium, filtered, mg/L 8 0.33 0.88 Yes

Magnesium, filtered, mg/L 8 .07 .81 Yes

Arsenic, filtered, μg/L 8 .09 .72 Yes

Arsenic, unfiltered recoverable, μg/L 8 .20 1.5 Yes

Cadmium, filtered, μg/L 8 .00 5.1 Yes

Cadmium, unfiltered recoverable, μg/L 8 .01 3.9 Yes

Copper, filtered, μg/L 8 .10 1.6 Yes

Copper, unfiltered recoverable, μg/L 8 .41 1.9 Yes

Iron, filtered, μg/L 8 1.1 4.4 Yes

Iron, unfiltered recoverable, μg/L 8 2.2 .58 Yes

Lead, filtered, μg/L 8 .01 5.3 Yes

Lead, unfiltered recoverable, μg/L 8 .05 1.5 Yes

Manganese, filtered, μg/L 8 6.2 6.4 Yes

Manganese, unfiltered recoverable, μg/L 8 3.1 2.5 Yes

Zinc, filtered, μg/L 8 .47 2.4 Yes

Zinc, unfiltered recoverable, μg/L 8 .40 .97 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).

Data  71
Table 16. Recovery efficiency for analyses of laboratory-spiked deionized-water blank samples.

[Abbreviation: μg/L, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent 

confidence interval for 

spike recovery, 

in percent

Mean spike recovery, 

in percent

Within limits1

of data-quality 

objective

Arsenic, filtered, μg/L 4 89.2–101 95.2 Yes

Arsenic, unfiltered recoverable, μg/L 3 94.7–102 98.5 Yes

Cadmium, filtered, μg/L 5 92.6–107 100 Yes

Cadmium, unfiltered recoverable, μg/L 5 94.1–104 98.9 Yes

Copper, filtered, μg/L 5 97.7–107 102 Yes

Copper, unfiltered recoverable, μg/L 5 93.8–104 98.7 Yes

Iron, filtered, μg/L 5 95.4–111 103 Yes

Iron, unfiltered recoverable, μg/L 5 101–112 106 Yes

Lead, filtered, μg/L 5 89.3–109 99 Yes

Lead, unfiltered recoverable, μg/L 5 91.2–105 98 Yes

Manganese, filtered, μg/L 5 95.3–115 105 Yes

Manganese, unfiltered recoverable, μg/L 5 90.7–103 97 Yes

Zinc, filtered, μg/L 5 95.4–115 105 Yes

Zinc, unfiltered recoverable, μg/L 5 90.1–100 94.9 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

72 Water-Quality, Bed-Sediment, 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, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent 

confidence interval for 

spike recovery, 

in percent

Mean spike recovery, 

in percent

Within limits1

of data-quality 

objective

Arsenic, filtered, μg/L 5 89.0–104 96.5 Yes

Arsenic, unfiltered recoverable, μg/L 5 94.9–103 99.1 Yes

Cadmium, filtered, μg/L 5 99.0–108 104 Yes

Cadmium, unfiltered recoverable, μg/L 5 94.7–104 99.6 Yes

Copper, filtered, μg/L 5 96.7–104 101 Yes

Copper, unfiltered recoverable, μg/L 5 91.0–98.6 94.8 Yes

Iron, filtered, μg/L 5 93.6–110 102 Yes

Iron, unfiltered recoverable, μg/L 5 102–109 105 Yes

Lead, filtered, μg/L 5 94.2–111 102 Yes

Lead, unfiltered recoverable, μg/L 5 92.9–106 100 Yes

Manganese, filtered, μg/L 5 97.9–113 106 Yes

Manganese, unfiltered recoverable, μg/L 5 88.2–102 94.9 Yes

Zinc, filtered, μg/L 5 93.3–123 108 Yes

Zinc, unfiltered recoverable, μg/L 5 87.8–94.6 91.2 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

Data  73
Table 18. Analyses of field blanks for water samples.

[Abbreviations: μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per liter. Symbols: <, less than laboratory reporting level; --, no data]

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)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

10/17/2005 1145 5.6 2 <0.02 <0.008 -- -- <0.12 <0.12 <0.04 <0.04

03/16/2006 1000 5.6 2 <.02 <.008 -- -- <.12 <.12 <.04 <.0404/05/2006 1110 6.8 3 <.02 <.008 <0.06 <0.004 <.12 <.12 <.04 <.0404/19/2006 1200 5.7 3 <.02 <.008 -- -- <.12 <.12 <.04 <.0405/08/2006 1400 5.8 2 <.02 <.008 -- -- <.12 <.12 <.04 <.0405/22/2006 2000 5.7 2 <.02 <.008 -- -- <.12 <.12 <.04 <.0405/24/2006 1600 5.7 2 .02 <.008 <.06 <.004 <.12 <.12 <.04 <.04

06/06/2006 1130 5.6 2 <.02 <.008 <.06 <.004 <.12 <.12 <.04 <.04

06/13/2006 1630 5.8 1 <.02 <.008 -- -- <.12 <.12 <.04 <.0406/14/2006 1420 6.2 2 <.02 <.008 <.06 <.004 <.12 <.12 <.04 <.0407/25/2006 0600 5.7 2 .02 <.008 -- -- <.12 <.12 <.04 <.0408/24/2006 0600 5.7 2 .02 <.008 -- -- <.12 <.12 <.04 <.04

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)

Zinc, 

unfiltered 

recoverable 

(ug/L)

10/17/2005 <0.4 <0.6 <6 <6 0.08 <0.06 <0.2 <0.2 <0.6 <2

03/16/2006 <.4 <.6 <6 <6 <.08 <.06 <.2 <.2 .7 <2

04/05/2006 .5 <.6 <6 <6 <.08 <.06 <.2 <.6 <.6 <2

04/19/2006 <.4 <.6 <6 <6 <.08 <.06 <.2 <.6 <.6 <2

05/08/2006 <.4 <.6 <6 <6 <.08 <.06 <.2 <.6 <.6 <2

05/22/2006 <.4 <.6 <6 <6 <.08 <.06 <.2 <.6 <.6 <2

05/24/2006 1.8 <.6 <6 <6 .12 <.06 <.2 <.6 3.1 <2

06/06/2006 <.4 <.6 <6 <6 <.08 <.06 <.2 <.6 <.6 <2

06/13/2006 <.4 <.6 <6 <6 <.08 <.06 <.2 <.6 1.3 <2

06/14/2006 <.4 <.6 <6 <6 <.08 <.06 <.2 <.6 <.6 <2

07/25/2006 <.4 <.6 <6 <6 <.08 <.06 <.2 <.6 <.6 <2

08/24/2006 .6 <.6 <6 <6 <.08 <.06 <.2 <.6 <.6 <2

74  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 19. Analyses of fine-grained bed sediment, upper Clark Fork basin, Montana, August 2006.

[Trace-element concentrations in bed sediment were determined for the fine-grained fraction (material less than 0.064 millimeter in diameter). Reported concentrations are the mean of all analyses for replicate aliquots from each composite sample. Abbreviation: μg/g, micrograms per gram of dry sample weight]

Site number 

(fig. 1) Site name

Number of composite 

samples

Concentration, in μg/g 

Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12323600 Silver Bow Creek at Opportunity 3 119 22.8 25.5 2,480 31,700 470 2,420 12.0 4,950

12323750 Silver Bow Creek at Warm Springs 3 97 4.9 17.8 278 22,100 65 8,960 12.5 666

12323800 Clark Fork near Galen 3 95 5.6 29.5 1,090 27,400 117 11,000 17.5 1,090

461415112450801 Clark Fork below Lost Creek, near Galen 3 111 5.2 24.6 1,280 25,500 134 9,820 13.3 1,160

461559112443301 Clark Fork at county bridge, near 

Racetrack 

3 61 5.9 27.6 1,120 28,100 135 3,400 14.8 1,100

461903112440701 Clark Fork at Demspey Creek diversion, 

near Racetrack 

3 63 6.0 22.7 992 25,000 102 4,420 11.0 1,250

12324200 Clark Fork at Deer Lodge 3 60 4.4 24.5 930 22,800 121 2,960 11.6 1,050

12324680 Clark Fork at Goldcreek 3 23 2.6 21.3 338 15,500 52 1,990 9.0 584

12331800 Clark Fork near Drummond 3 31 3.8 25.2 390 19,500 79 3,520 13.4 848

12334550 Clark Fork at Turah Bridge, near Bonner 3 21 1.9 21.8 237 15,900 47 1,240 10.3 584

12340000 Blackfoot River near Bonner 3 4 .3 23.6 22 19,000 20 303 11.8 63

12340500 Clark Fork above Missoula 3 52 3.5 25.9 551 20,500 66 1,020 12.4 960

Data  75
Table 20. Recovery efficiency for analyses of standard reference materials for bed sediment.

[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, micrograms 

per gram of dry sample weight; SRM, standard reference material (agricultural soils). Symbol: --, recovery could not be determined because all analyses were less than the minimum reporting level]

Constituent Number of 

analyses Dilution ratio

Certified 

concentration 

(μg/g)

Mean SRM 

recovery, 

in percent

95-percent 

confidence interval 

for SRM recovery, 

in percent

SRM sample 2709

Arsenic 10 1:10 17.7 73.5 70.9–76.1

Cadmium 10 1:10 .4 -- --

Chromium 10 1:10 130 78.1 76.8–79.4

Copper 10 1:10 35 99.8 98.3–101

Iron 10 1:10 35,000 90.4 88.6–92.1

Lead 10 1:10 19 136.4 134–139

Manganese 10 1:10 538 91.7 90.0–93.5

Nickel 10 1:10 88 89.9 88.8–91.0

Zinc 10 1:10 106 92.4 91.0–93.8

SRM sample 2711

Arsenic 10 1:10 105 87.7 85.6–89.7

Cadmium 10 1:10 41.7 95.4 93.6–97.3

Chromium 10 1:10 47 66.1 62.6–69.6

Copper 10 1:10 114 101.6 98.9–104

Iron 10 1:10 28,900 83.5 81.6–85.3

Lead 10 1:10 1,160 94.7 93.0–96.5

Manganese 10 1:10 638 81.6 80.1–83.1

Nickel 10 1:10 20.6 84.8 83.3–86.3

Zinc 10 1:10 350 92.9 91.3–94.6

76 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 21. Analyses of procedural blanks for bed sediment.

[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 0.6 N (normal) hydrochloric acid used for reconstituting dried residue. Abbreviation: μg/mL, micrograms 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, in μg/mL Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12323600 Silver Bow Creek at 

Opportunity 

1:10 <0.005 <0.001 <0.006 <0.006 <0.1 <0.02 <0.01 <0.002 <0.01

12323750 Silver Bow Creek at 

Warm Springs

1:10 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

12323800 Clark Fork near Galen 1:10 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

461415112450801 Clark Fork below Lost Creek, 

near Galen 

1:10 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

461559112443301 Clark Fork at county bridge, 

near Racetrack 

1:10 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

461903112440701 Clark Fork at Dempsey Creek 

diversion, near Racetrack 

1:10 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

12324200 Clark Fork at Deer Lodge 1:10 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

12324680 Clark Fork at Goldcreek 1:10 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

12331800 Clark Fork near Drummond 1:20 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

12334550 Clark Fork at Turah Bridge, 

near Bonner 

1:10 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

12340000 Blackfoot River near 

Bonner

1:10 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

12340500 Clark Fork above Missoula 1:10 <.005 <.001 <.006 <.006 <.1 <.02 <.01 <.002 <.01

Data  77
Table 22. Analyses of biota, upper Clark Fork basin, Montana, August 2006.

[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, micrograms 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, in μg/g

Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12323600—Silver Bow Creek at Opportunity

Hydropsyche cockerelli 2 12.3 3.3 2.6 307 2,500 48.5 764 1.9 678

Hydropsyche spp. 1 <1.3 4.2 <2.9 324 2,630 45.9 1,030 2.3 784

12323750—Silver Bow Creek at Warm Springs

Hydropsyche cockerelli 1 16.9 0.5 1.0 37.2 1,380 4.2 2,360 1.8 191

12323800—Clark Fork near Galen

Hydropsyche cockerelli 3 14.1 0.9 2.7 132 2,040 11.1 2,200 3.3 187

461415112450801—Clark Fork below Lost Creek, near Galen

Hydropsyche cockerelli 2 26.6 1.6 3.6 330 3,850 27.5 2,370 2.7 335

Hydropsyche occidentalis 1 20.8 1.4 3.6 219 2,830 19.4 2,980 2.5 308

461559112443301—Clark Fork at county bridge, near Racetrack

Hydropsyche cockerelli 2 16.4 1.5 2.4 190 2,680 16.8 1,970 2.0 237

Hydropsyche occidentalis 2 15.0 1.3 2.5 138 2,180 14.7 3,020 1.6 245

Hydropsyche spp. 1 12.7 1.5 2.5 124 1,880 15.0 2,370 1.9 220

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack

Hydropsyche cockerelli 2 16.2 1.3 2.8 192 2,030 14.2 2,620 1.9 256

Hydropsyche occidentalis 2 12.3 1.1 1.7 137 1,480 10.6 3,390 1.4 244

12324200—Clark Fork at Deer Lodge

Hydropsyche cockerelli 1 11.4 1.9 1.9 180 1,860 14.4 1,570 1.5 240

Hydropsyche occidentalis 1 11.7 1.7 2.1 180 1,830 14.7 2,160 1.6 280

12324680—Clark Fork at Goldcreek

Arctopsyche grandis 4 2.6 1.0 0.6 23.6 228 1.1 933 0.4 156

Claassenia sabulosa 3 1.4 .6 .6 65.2 149 .5 267 .4 265

Hydropsyche cockerelli 2 4.5 1.1 1.2 46.3 576 2.8 1,240 .8 179

Hydropsyche occidentalis 1 5.0 1.1 .8 47.8 690 5.2 1,680 1.0 210

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

Number of 

composite 

samples

Concentration, in μg/g

Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12331800—Clark Fork near Drummond

Arctopsyche grandis 1 2.3 0.8 0.7 19.3 193 1.6 531 0.2 158

Claassenia sabulosa 2 1.5 .4 .8 76.7 147 .8 278 .3 276

Hydropsyche cockerelli 1 4.9 .8 1.6 56.9 740 4.8 975 1.0 183

Hydropsyche occidentalis 2 5.3 .8 1.7 56.5 775 5.6 1,500 1.0 222

12334550—Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 3 4.7 0.7 2.0 41.0 913 3.8 629 1.3 200

Claassenia sabulosa 2 1.3 .7 1.3 66.4 141 .6 138 .3 288

Hydropsyche cockerelli 3 5.0 .6 2.5 54.2 1,230 4.8 670 1.4 195

Hydropsyche occidentalis 1 4.5 .6 2.2 49.4 1,320 4.4 830 1.4 207

12340000—Blackfoot River near Bonner

Arctopsyche grandis 1 2.2 <0.1 1.6 14.9 907 0.9 578 1.2 145

Claassenia sabulosa 2 1.6 .2 .9 36.7 177 .2 84 .3 242

Hydropsyche cockerelli 1 3.1 <.1 2.5 5.6 1,960 2.3 716 1.9 140

Hydropsyche occidentalis 1 2.4 <.1 3.2 17.1 1,410 1.7 762 1.8 153

12340500—Clark Fork above Missoula

Arctopsyche grandis 3 3.2 0.5 1.7 37.2 838 4.7 737 0.8 187

Claassenia sabulosa 3 1.6 .4 1.1 57.8 265 1.1 181 .4 279

Hydropsyche cockerelli 3 7.6 .8 3.5 89.5 2,370 10.7 1,200 2.1 256

Hydropsyche occidentalis 1 6.2 .7 3.0 69.2 1,960 11.1 1,600 1.7 258

Table 22. Analyses of biota, upper Clark Fork basin, Montana, August 2006.—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, micrograms per gram of dry sample weight; spp., species. Symbol: <, less than minimum reporting level for solid-phase concentration, in μg/g]

Data  79
Table 23. Recovery efficiency for analyses of standard reference material for biota.

[Abbreviations: μg/g, micrograms per gram of dry sample weight; μg/mL, micrograms per milliliter; SRM, standard 

reference material (lobster hepatopancreas)]

Constituent Number of 

analyses

Certified 

concentration 

(μg/g)

Mean SRM 

recovery, 

in percent

95-percent confidence 

interval for SRM recovery, 

in percent

SRM sample TORT-2

Arsenic 12 21.6 101 99.5–102

Cadmium 12 26.7 104 102–106

Chromium 1

12 .77 173 164–182

Copper 12 106 109 108–110

Iron 12 105 110 107–113

Lead 12 .35 85.2 76.2–94.2

Manganese 12 13.6 102 101–103

Nickel 12 2.5 99.5 97.3–102

Zinc 12 180 106 105–108

1

Chromium concentrations in seven analyses were less than the liquid-phase minimum reporting level (0.01 μg/mL) 

and were not used to calculate SRM recovery.

80 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 24. Analyses of procedural blanks for biota.

[Procedural blanks were not diluted prior to analyses. Abbreviation: μg/mL, micrograms per milliliter. Symbol: <, less than minimum reporting level for liquid-phase concentration, in μg/mL]

Site number 

(fig. 1) Site name Dilution ratio Trace-element concentration, in μg/mL Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12323600 Silver Bow Creek at 

Opportunity

1:1 <0.004 <0.0003 <0.01 <0.002 0.02 <0.001 <0.001 <0.01 <0.01

12323750 Silver Bow Creek at Warm 

Springs

1:1 <.004 <.0003 <.01 <.002 <.01 <.001 <.001 <.01 <.01

12323800 Clark Fork near Galen 1:1 <.004 <.0003 <.01 <.002 .03 <.001 <.001 <.01 <.01

461415112450801 Clark Fork below Lost Creek, 

near Galen

1:1 <.004 <.0003 <.01 <.002 .03 .005 <.001 <.01 <.01

461559112443301 Clark Fork at county bridge, 

near Racetrack

1:1 <.004 <.0003 <.01 <.002 .04 .006 <.001 <.01 <.01

461903112440701 Clark Fork at Dempsey Creek 

diversion, near Racetrack

1:1 <.004 <.0003 <.01 <.002 .14 .004 <.001 <.01 <.01

12324200 Clark Fork at Deer Lodge 1:1 <.004 <.0003 <.01 <.002 .02 <.001 <.001 <.01 <.01

12324680 Clark Fork at Goldcreek 1:1 <.004 <.0003 <.01 <.002 <.01 <.001 <.001 <.01 <.01

12331800 Clark Fork near Drummond 1:1 <.004 <.0003 <.01 <.002 <.01 <.001 <.001 <.01 <.01

12334550 Clark Fork at Turah Bridge, 

near Bonner

1:1 <.004 <.0003 <.01 <.002 <.01 <.001 <.001 <.01 <.01

12340000 Blackfoot River near 

Bonner

1:1 <.004 <.0003 <.01 <.002 <.01 <.001 <.001 <.01 <.01

12340500 Clark Fork above Missoula 1:1 <.004 <.0003 <.01 <.002 <.01 <.001 <.001 <.01 <.01

Data  81
Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323230—Blacktail Creek at Harrison Avenue, at Butte

Period of record for water-quality data: March 1993–August 1995, December 1996–August 2003, December 2004–September 2006

Streamflow, instantaneous (ft3/s) 99 156 1.9 13 7.6

pH, onsite (standard units) 99 8.4 7.3 7.8 7.8

Specific conductance, onsite (μS/cm) 99 412 116 267 271

Temperature, water (°C) 99 17.5 1.5 8.2 8.0

Hardness, filtered (mg/L as CaCO3) 99 150 38 105 110

Calcium, filtered (mg/L) 99 41.8 10.6 30.1 30.9

Magnesium, filtered (mg/L) 99 11.0 2.71 7.3 7.4

Arsenic, filtered (μg/L) 99 13 1 3.8 3.0

Arsenic, unfiltered (μg/L) 99 18 1 2

5 4

Cadmium, filtered (μg/L) 99 .5 <.04 2

.06 <.1

Cadmium, unfiltered (μg/L) 99 .11 <.04 2

.05 <1

Copper, filtered (μg/L) 99 10 .8 2

3.8 3.2

Copper, unfiltered (μg/L) 99 52 1.5 7.2 5.9

Iron, filtered (μg/L) 99 640 15 164 150

Iron, unfiltered (μg/L) 99 4,220 139 682 550

Lead, filtered (μg/L) 99 2.8 <.08 2

.21 <.6

Lead, unfiltered (μg/L) 99 47 <1 2

2.18 .90

Manganese, filtered (μg/L) 99 144 14.2 41.7 37.9

Manganese, unfiltered (μg/L) 99 240 23 59 51

Zinc, filtered (μg/L) 99 11 <1 2

3.8 2.9

Zinc, unfiltered (μg/L) 99 130 <10 2

10 4

Sediment, suspended (percent finer than 0.062 mm) 99 97 50 82 83

Sediment, suspended concentration (mg/L) 99 139 2 14 7

Sediment, suspended discharge (ton/d) 99 59 .01 1.2 .14

82 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323250—Silver Bow Creek below Blacktail Creek, at Butte 

Period of record for water-quality data: March 1993–August 1995, December 1996–September 2006

Streamflow, instantaneous (ft3/s) 107 134 13 28 23

pH, onsite (standard units) 107 8.1 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 107 691 226 475 482

Temperature, water (°C) 107 20.0 1.0 10.5 9.5

Hardness, filtered (mg/L as CaCO3

) 107 220 66 151 150

Calcium, filtered (mg/L) 107 62.7 19.0 42.9 44.0

Magnesium, filtered (mg/L) 107 14.6 4.51 10.6 11.0

Arsenic, filtered (μg/L) 107 13 2.3 6.6 6.4

Arsenic, unfiltered (μg/L) 107 45 3 12 10

Cadmium, filtered (μg/L) 107 6.2 .09 1.28 1.00

Cadmium, unfiltered (μg/L) 107 6 .11 1.71 1.40

Copper, filtered (μg/L) 107 303 3.2 41.2 16.0

Copper, unfiltered (μg/L) 107 550 13.5 96 51

Iron, filtered (μg/L) 107 270 10 2

84 61

Iron, unfiltered (μg/L) 107 7,400 85 958 640

Lead, filtered (μg/L) 107 2.4 <.5 2

.52 .22

Lead, unfiltered (μg/L) 107 250 .64 15.0 4.80

Manganese, filtered (μg/L) 107 1,700 21.4 407 358

Manganese, unfiltered (μg/L) 107 1,600 26 453 409

Zinc, filtered (μg/L) 107 2,200 26.7 416 303

Zinc, unfiltered (μg/L) 107 2,200 38 502 352

Sediment, suspended (percent finer than 0.062 mm) 106 98 42 84 86

Sediment, suspended concentration (mg/L) 106 405 2 25 11

Sediment, suspended discharge (ton/d) 106 70 .08 3.0 .74

Data  83
Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323600—Silver Bow Creek at Opportunity 

Period of record for water-quality data: March 1993–August 1995, December 1996–September 2006

Streamflow, instantaneous (ft3/s) 110 361 13 72 50

pH, onsite (standard units) 109 9.5 7.2 8.4 8.4

Specific conductance, onsite (μS/cm) 109 633 202 418 403

Temperature, water (°C) 109 22.5 0.0 9.3 9.5

Hardness, filtered (mg/L as CaCO3) 109 240 60 150 150

Calcium, filtered (mg/L) 109 71.6 18.5 44.4 43.1

Magnesium, filtered (mg/L) 109 15.0 3.42 9.49 9.04

Arsenic, filtered (μg/L) 109 34 1 11.2 10.3

Arsenic, unfiltered (μg/L) 109 235 11 28 18

Cadmium, filtered (μg/L) 109 41 .1 1.30 .84

Cadmium, unfiltered (μg/L) 109 49 .52 2

2.33 1.49

Copper, filtered (μg/L) 109 450 13.7 50.0 38.9

Copper, unfiltered (μg/L) 109 3,900 54.3 232 130

Iron, filtered (μg/L) 109 307 3 2

45 24

Iron, unfiltered (μg/L) 109 24,100 255 1,640 782

Lead, filtered (μg/L) 109 5.1 <.5 2.77 .30

Lead, unfiltered (μg/L) 109 650 5.38 42.2 15.5

Manganese, filtered (μg/L) 109 9,300 68 493 395

Manganese, unfiltered (μg/L) 109 10,000 117 618 480

Zinc, filtered (μg/L) 109 13,000 27 341 183

Zinc, unfiltered (μg/L) 109 15,000 97 595 392

Sediment, suspended (percent finer than 0.062 mm) 110 95 37 79 82

Sediment, suspended concentration (mg/L) 110 801 5 51 17

Sediment, suspended discharge (ton/d) 110 781 .18 22 2.4

84  Water-Quality, Bed-Sediment, 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 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323670—Mill Creek near Anaconda 

Period of record for water-quality data: December 2004–September 2006

Streamflow, instantaneous (ft3/s) 16 165 7.4 60 24

pH, onsite (standard units) 16 8.6 7.7 8.2 8.2

Specific conductance, onsite (μS/cm) 16 203 56 132 138

Temperature, water (°C) 16 16.0 3.0 8.3 7.8

Hardness, filtered (mg/L as CaCO3) 16 98 24 59 62

Calcium, filtered (mg/L) 16 25.9 7.12 16.2 17.4

Magnesium, filtered (mg/L) 16 8.01 1.45 4.43 4.42

Arsenic, filtered (μg/L) 16 27.3 7.3 15.8 13.8

Arsenic, unfiltered (μg/L) 16 30 9 18 16

Cadmium, filtered (μg/L) 16 .11 <.04 2

.05 .04

Cadmium, unfiltered (μg/L) 16 .18 .05 .08 .08

Copper, filtered (μg/L) 16 4.7 0.9 2.3 2.0

Copper, unfiltered (μg/L) 16 10.3 1.3 4.1 3.6

Iron, filtered (μg/L) 16 89 26 52 42

Iron, unfiltered (μg/L) 16 620 90 222 171

Lead, filtered (μg/L) 16 .24 <.08 2

.13 .10

Lead, unfiltered (μg/L) 16 3.12 .20 .89 .61

Manganese, filtered (μg/L) 16 8.9 3.4 6.0 6.2

Manganese, unfiltered (μg/L) 16 37 7 16 14

Zinc, filtered (μg/L) 16 2.4 .7 1.4 1.2

Zinc, unfiltered (μg/L) 16 8 1 3 2

Sediment, suspended (percent finer than 0.062 mm) 16 81 39 67 74

Sediment, suspended concentration (mg/L) 16 29 1 7 3

Sediment, suspended discharge (ton/d) 16 13 .03 2.2 .16

Data  85
Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323700—Mill Creek at Opportunity 

Period of record for water-quality data: March 2003–September 2006

Streamflow, instantaneous (ft3/s) 32 261 0.43 37 5

pH, onsite (standard units) 32 8.2 7.8 8.0 8.0

Specific conductance, onsite (μS/cm) 32 223 59 149 156

Temperature, water (°C) 32 20 1.0 9.5 9.2

Hardness, filtered (mg/L as CaCO3) 32 100 24 64 68

Calcium, filtered (mg/L) 32 28.0 7.01 17.9 19.3

Magnesium, filtered (mg/L) 32 7.83 1.56 4.64 4.84

Arsenic, filtered (μg/L) 32 37.0 9.0 23.5 23.4

Arsenic, unfiltered (μg/L) 32 50 10 28 28

Cadmium, filtered (μg/L) 32 .10 .03 .07 .07

Cadmium, unfiltered (μg/L) 32 .85 .06 .16 .10

Copper, filtered (μg/L) 32 6.1 1.2 3.2 3.0

Copper, unfiltered (μg/L) 32 38.8 1.7 7.6 4.4

Iron, filtered (μg/L) 32 90 17 52 49

Iron, unfiltered (μg/L) 32 1,960 67 331 138

Lead, filtered (μg/L) 32 .32 <.08 2

.15 .14

Lead, unfiltered (μg/L) 32 12.7 .07 1.72 .42

Manganese, filtered (μg/L) 32 32.8 3.2 9.4 7.6

Manganese, unfiltered (μg/L) 32 113 6 22 13

Zinc, filtered (μg/L) 32 7.7 1.4 3.5 3.2

Zinc, unfiltered (μg/L) 32 41 2 8 5

Sediment, suspended (percent finer than 0.062 mm) 32 90 26 73 80

Sediment, suspended concentration (mg/L) 32 107 1 14 2

Sediment, suspended discharge (ton/d) 32 55 <.01 2

4.6 .02

86 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323710—Willow Creek near Anaconda 

Period of record for water-quality data: December 2004–September 2006

Streamflow, instantaneous (ft3/s) 15 39 1.0 11 3.3

pH, onsite (standard units) 15 8.2 7.5 7.7 7.7

Specific conductance, onsite (μS/cm) 15 115 66 97 102

Temperature, water (°C) 15 15.0 .5 7.0 6.0

Hardness, filtered (mg/L as CaCO3) 15 42 22 35 38

Calcium, filtered (mg/L) 15 13.9 7.56 11.9 13.0

Magnesium, filtered (mg/L) 15 1.69 .78 1.30 1.30

Arsenic, filtered (μg/L) 15 24.9 9.9 16.4 14.7

Arsenic, unfiltered (μg/L) 15 27 10 18 16

Cadmium, filtered (μg/L) 15 .05 <.04 2

.03 .03

Cadmium, unfiltered (μg/L) 15 .19 .03 .06 .05

Copper, filtered (μg/L) 15 4.2 1.0 2.2 2.0

Copper, unfiltered (μg/L) 15 16.8 1.5 4.4 3.0

Iron, filtered (μg/L) 15 154 36 74 67

Iron, unfiltered (μg/L) 15 1,260 90 297 190

Lead, filtered (μg/L) 15 .37 .05 .15 .13

Lead, unfiltered (μg/L) 15 4.08 .20 .78 .47

Manganese, filtered (μg/L) 15 34.5 8.1 16.1 14.8

Manganese, unfiltered (μg/L) 15 49 15 28 22

Zinc, filtered (μg/L) 15 3.3 1.1 1.9 1.7

Zinc, unfiltered (μg/L) 15 10 1 3 2

Sediment, suspended (percent finer than 0.062 mm) 15 94 44 76 77

Sediment, suspended concentration (mg/L) 15 93 3 13 5

Sediment, suspended discharge (ton/d) 15 9.8 .01 .90 .05

Data  87
Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323720—Willow Creek at Opportunity 

Period of record for water-quality data: March 2003–September 2006

Streamflow, instantaneous (ft3/s) 32 53 4.5 15 8.7

pH, onsite (standard units) 32 8.6 7.7 8.1 8.1

Specific conductance, onsite (μS/cm) 32 371 116 288 308

Temperature, water (°C) 32 20.5 1.5 10.9 11.5

Hardness, filtered (mg/L as CaCO3) 32 170 67 128 135

Calcium, filtered (mg/L) 32 47.4 20.5 36.8 38.8

Magnesium, filtered (mg/L) 32 12.3 3.73 8.69 9.18

Arsenic, filtered (μg/L) 32 164 11.5 45.6 29.6

Arsenic, unfiltered (μg/L) 32 164 12 48 30

Cadmium, filtered (μg/L) 32 .11 .02 .05 .04

Cadmium, unfiltered (μg/L) 32 .52 .03 .10 .07

Copper, filtered (μg/L) 32 21.4 1.9 6.1 3.8

Copper, unfiltered (μg/L) 32 48.8 2.8 12.1 7.8

Iron, filtered (μg/L) 32 111 7 38 28

Iron, unfiltered (μg/L) 32 1,420 27 239 142

Lead, filtered (μg/L) 32 .52 .04 2

.19 .16

Lead, unfiltered (μg/L) 32 14.4 .27 2.13 1.30

Manganese, filtered (μg/L) 32 51.3 4.1 25.6 20.2

Manganese, unfiltered (μg/L) 32 104 4.7 35 30

Zinc, filtered (μg/L) 32 20 1.1 5.7 4.4

Zinc, unfiltered (μg/L) 32 68 2 12 8

Sediment, suspended (percent finer than 0.062 mm) 32 96 70 87 88

Sediment, suspended concentration (mg/L) 32 84 1 11 5

Sediment, suspended discharge (ton/d) 32 11 .02 .91 .10

88  Water-Quality, Bed-Sediment, 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 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323750—Silver Bow Creek at Warm Springs 

Period of record for water-quality data: March 1993–September 2006

Streamflow, instantaneous (ft3/s) 116 662 16 136 88

pH, onsite (standard units) 114 9.4 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 114 783 249 470 476

Temperature, water (°C) 115 25.0 .5 11.1 11.0

Hardness, filtered (mg/L as CaCO3) 114 310 97 196 200

Calcium, filtered (mg/L) 114 90.4 27.9 56.8 58.3

Magnesium, filtered (mg/L) 114 21.4 5.94 13.1 13.0

Arsenic, filtered (μg/L) 114 60 6.8 22.4 22.6

Arsenic, unfiltered (μg/L) 114 94 10 27 26

Cadmium, filtered (μg/L) 114 .31 <.04 2

.07 <.1

Cadmium, unfiltered (μg/L) 114 .56 <.1 2

.12 <1

Copper, filtered (μg/L) 114 40 1.9 8.9 7

Copper, unfiltered (μg/L) 114 96.8 3.4 17.9 12.6

Iron, filtered (μg/L) 114 93 <5 2

18 14

Iron, unfiltered (μg/L) 114 3,000 36 348 270

Lead, filtered (μg/L) 114 1.0 <.08 2.11 <.5

Lead, unfiltered (μg/L) 114 41.8 <1 2

2.53 1.23

Manganese, filtered (μg/L) 114 875 11.8 130 96

Manganese, unfiltered (μg/L) 114 899 24 195 165

Zinc, filtered (μg/L) 114 73 <1 2

8.9 4.7

Zinc, unfiltered (μg/L) 114 180 <10 2

35 20

Sediment, suspended (percent finer than 0.062 mm) 115 97 43 82 84

Sediment, suspended concentration (mg/L) 116 229 1 11 6

Sediment, suspended discharge (ton/d) 116 279 .07 7.4 1.6

Data  89
Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323760—Warm Springs Creek near Anaconda 

Period of record for water-quality data: October 2005–September 2006

Streamflow, instantaneous (ft3

/s) 6 268 52 98 68

pH, onsite (standard units) 6 8.8 8.2 8.6 8.6

Specific conductance, onsite (μS/cm) 6 254 126 223 242

Temperature, water (°C) 6 16.0 7.0 10.5 8.8

Hardness, filtered (mg/L as CaCO3) 6 130 60 107 110

Calcium, filtered (mg/L) 6 37.4 18.6 32.4 34.2

Magnesium, filtered (mg/L) 6 8.00 3.25 6.64 6.99

Arsenic, filtered (μg/L) 6 2.5 1.8 2.1 2.0

Arsenic, unfiltered (μg/L) 6 2.8 2.0 2.4 2.3

Cadmium, filtered (μg/L) 6 .03 <.04 -- <.04

Cadmium, unfiltered (μg/L) 6 .05 .02 .03 .03

Copper, filtered (μg/L) 6 1.4 .68 1.1 1.2

Copper, unfiltered (μg/L) 6 4.1 1.2 2.4 2.4

Iron, filtered (μg/L) 6 10 6 8 7

Iron, unfiltered (μg/L) 6 194 48 90 75

Lead, filtered (μg/L) 6 .05 <.08 -- <.08

Lead, unfiltered (μg/L) 6 .55 .14 .27 .24

Manganese, filtered (μg/L) 6 1.2 <.2 2

.9 .8

Manganese, unfiltered (μg/L) 6 9.1 2.4 4.3 3.4

Zinc, filtered (μg/L) 6 1.3 .3 .7 .6

Zinc, unfiltered (μg/L) 6 4 1 2 2

Sediment, suspended (percent finer than 0.062 mm) 6 80 51 69 70

Sediment, suspended concentration (mg/L) 6 13 3 5 4

Sediment, suspended discharge (ton/d) 6 9.4 .42 2.1 .64

90 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323770—Warm Springs Creek at Warm Springs 

Period of record for water-quality data: March 1993–September 2006

Streamflow, instantaneous (ft3/s) 85 420 2.8 91 50

pH, onsite (standard units) 84 8.7 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 84 795 139 302 312

Temperature, water (°C) 85 20.0 0.0 9.1 9.0

Hardness, filtered (mg/L as CaCO3) 84 420 40 146 150

Calcium, filtered (mg/L) 84 130 10.5 44.7 46.1

Magnesium, filtered (mg/L) 84 22.0 3.29 8.42 8.46

Arsenic, filtered (μg/L) 84 14 2 5.3 4.9

Arsenic, unfiltered (μg/L) 84 27 3 8 6

Cadmium, filtered (μg/L) 84 .1 <.04 2

.04 <.1

Cadmium, unfiltered (μg/L) 84 .41 <.1 2

.08 <1

Copper, filtered (μg/L) 84 16 1 3.6 3.0

Copper, unfiltered (μg/L) 84 108 2.3 19.7 8.4

Iron, filtered (μg/L) 84 30 <5 2

11 10

Iron, unfiltered (μg/L) 84 1,700 39 303 110

Lead, filtered (μg/L) 84 1.8 <.08 2.09 <.5

Lead, unfiltered (μg/L) 84 14 <1 2

1.96 .43

Manganese, filtered (μg/L) 84 570 22.6 134 110

Manganese, unfiltered (μg/L) 84 1,400 53 229 190

Zinc, filtered (μg/L) 84 10 <1 2

2.2 1.1

Zinc, unfiltered (μg/L) 84 60 <10 2

10 3

Sediment, suspended (percent finer than 0.062 mm) 85 88 55 72 72

Sediment, suspended concentration (mg/L) 85 106 2 18 8

Sediment, suspended discharge (ton/d) 85 87 .05 8.7 .92

Data  91
Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323800—Clark Fork near Galen 

Period of record for water-quality data: July 1988–September 2006

Streamflow, instantaneous (ft3/s) 157 1,050 14 206 124

pH, onsite (standard units) 144 9.2 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 145 720 197 426 438

Temperature, water (°C) 156 23.5 0.0 10.1 10.0

Hardness, filtered (mg/L as CaCO3) 143 370 81 186 190

Calcium, filtered (mg/L) 143 110 24.2 55.0 57.0

Magnesium, filtered (mg/L) 143 22.0 5.08 11.9 12.0

Arsenic, filtered (μg/L) 143 53 4 15.2 14.0

Arsenic, unfiltered (μg/L) 143 78 3 20 17

Cadmium, filtered (μg/L) 143 1 <.04 2

.06 <1

Cadmium, unfiltered (μg/L) 143 3 <.1 2

.20 <1

Copper, filtered (μg/L) 143 50 2.3 8.7 6.8

Copper, unfiltered (μg/L) 142 240 4.8 29.5 16.6

Iron, filtered (μg/L) 143 110 <3 2

16 11

Iron, unfiltered (μg/L) 143 9,200 56 508 270

Lead, filtered (μg/L) 143 3 <.08 2.17 <1

Lead, unfiltered (μg/L) 143 31.0 <1 2

3.63 1.90

Manganese, filtered (μg/L) 143 460 25.2 116 88.9

Manganese, unfiltered (μg/L) 143 1,400 47 245 193

Zinc, filtered (μg/L) 143 110 <1 2

10.7 5.7

Zinc, unfiltered (μg/L) 143 360 <10 2

42 20

Sediment, suspended (percent finer than 0.062 mm) 156 97 41 78 78

Sediment, suspended concentration (mg/L) 157 338 2 19 7

Sediment, suspended discharge (ton/d) 157 459 .12 21 2.3

92 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323840—Lost Creek near Anaconda 

Period of record for water-quality data: December 2004–September 2006

Streamflow, instantaneous (ft3/s) 15 17 0.97 7.0 4.5

pH, onsite (standard units) 15 8.6 7.4 8.2 8.3

Specific conductance, onsite (μS/cm) 15 253 136 200 211

Temperature, water (°C) 15 14.5 2.5 8.3 8.5

Hardness, filtered (mg/L as CaCO3) 15 120 50 95 100

Calcium, filtered (mg/L) 15 37.1 15.7 29.0 30.3

Magnesium, filtered (mg/L) 15 7.11 2.71 5.56 6.11

Arsenic, filtered (μg/L) 15 156 2.4 15.4 5.6

Arsenic, unfiltered (μg/L) 15 3,860 2 263 6

Cadmium, filtered (μg/L) 15 .90 <.04 2

.09 .03

Cadmium, unfiltered (μg/L) 15 147 .02 9.9 .04

Copper, filtered (μg/L) 15 90.5 1.2 8.4 2.0

Copper, unfiltered (μg/L) 15 29,100 1.7 1,950 4.5

Iron, filtered (μg/L) 15 25 <6 2

9 8

Iron, unfiltered (μg/L) 15 99,700 20 6,820 98

Lead, filtered (μg/L) 15 .18 <.08 2.06 <.08

Lead, unfiltered (μg/L) 15 1,290 .10 87 .40

Manganese, filtered (μg/L) 15 42.4 <.2 2

4.1 1.4

Manganese, unfiltered (μg/L) 15 8,830 1 594 4

Zinc, filtered (μg/L) 15 30.0 .8 3.2 1.2

Zinc, unfiltered (μg/L) 15 7,780 2 522 3

Sediment, suspended (percent finer than 0.062 mm) 15 97 30 64 66

Sediment, suspended concentration (mg/L) 15 58,900 1 3,940 8

Sediment, suspended discharge (ton/d) 15 1,320 <.1 2

88 .08

Data  93
Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323850—Lost Creek near Galen 

Period of record for water-quality data: March 2003–September 2006

Streamflow, instantaneous (ft3/s) 32 59 1.3 19 12

pH, onsite (standard units) 32 8.7 8.0 8.4 8.4

Specific conductance, onsite (μS/cm) 32 934 540 652 636

Temperature, water (°C) 32 26.5 1.5 12.7 11.8

Hardness, filtered (mg/L as CaCO3) 32 450 200 305 300

Calcium, filtered (mg/L) 32 122 48.5 84.9 86.6

Magnesium, filtered (mg/L) 32 35.7 18.0 22.5 21.4

Arsenic, filtered (μg/L) 32 41.8 6.6 15.2 12.6

Arsenic, unfiltered (μg/L) 32 43 6 16 13

Cadmium, filtered (μg/L) 32 .05 <.04 2

.03 .02

Cadmium, unfiltered (μg/L) 32 .11 .02 .05 .04

Copper, filtered (μg/L) 32 6.7 1.5 3 2.8

Copper, unfiltered (μg/L) 32 22.5 3.5 7 6

Iron, filtered (μg/L) 32 61 <6 2

12 8

Iron, unfiltered (μg/L) 32 280 10 100 76

Lead, filtered (μg/L) 32 .33 <.08 2.07 <.08

Lead, unfiltered (μg/L) 32 1.30 .04 .39 .29

Manganese, filtered (μg/L) 32 54.0 1.9 13.6 11.1

Manganese, unfiltered (μg/L) 32 56 2 18 14

Zinc, filtered (μg/L) 32 3.8 <1 2

1.6 1.2

Zinc, unfiltered (μg/L) 32 9 <2 2

3 2

Sediment, suspended (percent finer than 0.062 mm) 32 86 18 56 60

Sediment, suspended concentration (mg/L) 32 34 2 15 14

Sediment, suspended discharge (ton/d) 32 3.8 .01 .91 .32

94  Water-Quality, Bed-Sediment, 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 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324200—Clark Fork at Deer Lodge 

Period of record for water-quality data: March 1985–September 2006

Streamflow, instantaneous (ft3/s) 209 1,920 23 288 215

pH, onsite (standard units) 157 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 192 642 234 484 506

Temperature, water (°C) 208 23.0 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3) 149 280 95 205 220

Calcium, filtered (mg/L) 149 82.0 28.2 60.5 64.0

Magnesium, filtered (mg/L) 149 19 5.9 13.1 13.7

Arsenic, filtered (μg/L) 159 39 6 14.4 13.0

Arsenic, unfiltered (μg/L) 158 215 8 25 17

Cadmium, filtered (μg/L) 159 2 <.1 2

.08 <1

Cadmium, unfiltered (μg/L) 159 5 <.1 2

.44 <1

Copper, filtered (μg/L) 159 120 3.2 11.4 9.0

Copper, unfiltered (μg/L) 157 1,500 8.2 87.6 38.1

Iron, filtered (μg/L) 159 190 <3 2

15 9

Iron, unfiltered (μg/L) 159 29,000 30 1,620 520

Lead, filtered (μg/L) 159 6 <.08 2.36 <1

Lead, unfiltered (μg/L) 159 200 <1 2

11.3 4.00

Manganese, filtered (μg/L) 159 400 1 43.3 34.0

Manganese, unfiltered (μg/L) 159 4,600 12 259 147

Zinc, filtered (μg/L) 159 230 <10 2

12.8 9.0

Zinc, unfiltered (μg/L) 158 1,700 4 95 43

Sediment, suspended (percent finer than 0.062 mm) 200 99 37 71 72

Sediment, suspended concentration (mg/L) 209 2,250 1 74 22

Sediment, suspended discharge (ton/d) 209 8,690 .24 160 12

Data  95
Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324680—Clark Fork at Goldcreek 

Period of record for water-quality data: March 1993–September 2006

Streamflow, instantaneous (ft3/s) 115 3,920 87 731 507

pH, onsite (standard units) 114 8.8 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 114 510 206 374 394

Temperature, water (°C) 115 23.0 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3) 114 230 86 165 170

Calcium, filtered (mg/L) 114 68.0 25.9 48.5 51.2

Magnesium, filtered (mg/L) 114 15.0 5.15 10.5 11.0

Arsenic, filtered (μg/L) 114 20 5.8 10.0 10.0

Arsenic, unfiltered (μg/L) 114 75 7 15 12

Cadmium, filtered (μg/L) 114 .2 <.04 2

.04 <.1

Cadmium, unfiltered (μg/L) 114 2 <.1 2

.18 <1

Copper, filtered (μg/L) 113 36 2.1 6.8 5.6

Copper, unfiltered (μg/L) 113 440 5.2 41.8 23.2

Iron, filtered (μg/L) 114 100 <3 2

19 12

Iron, unfiltered (μg/L) 114 12,000 27 896 447

Lead, filtered (μg/L) 113 .8 <.08 2.11 <.5

Lead, unfiltered (μg/L) 113 73 <1 2

5.81 3.00

Manganese, filtered (μg/L) 114 57.3 4.0 19.3 17.4

Manganese, unfiltered (μg/L) 114 1,100 10 128 90

Zinc, filtered (μg/L) 114 26 <1 2

6.0 4.0

Zinc, unfiltered (μg/L) 114 510 2 47 30

Sediment, suspended (percent finer than 0.062 mm) 115 94 43 76 78

Sediment, suspended concentration (mg/L) 115 752 2 51 22

Sediment, suspended discharge (ton/d) 115 7,960 .62 224 33

96 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12331800—Clark Fork near Drummond 

Period of record for water-quality data: March 1993–September 2006

Streamflow, instantaneous (ft3/s) 115 3,860 149 1,010 755

pH, onsite (standard units) 114 8.6 7.8 8.3 8.3

Specific conductance, onsite (μS/cm) 114 630 189 413 433

Temperature, water (°C) 115 22.5 .5 11.0 11.0

Hardness, filtered (mg/L as CaCO3) 114 300 74 187 195

Calcium, filtered (mg/L) 114 83 21 53.6 55.2

Magnesium, filtered (mg/L) 114 22 5.2 12.8 13.1

Arsenic, filtered (μg/L) 114 20 6.6 10.6 10.0

Arsenic, unfiltered (μg/L) 114 62 8 16 13

Cadmium, filtered (μg/L) 114 .30 <.04 2

.05 <.1

Cadmium, unfiltered (μg/L) 114 2 <.1 2

.23 <1

Copper, filtered (μg/L) 112 21 1 6.5 5.0

Copper, unfiltered (μg/L) 112 360 4.6 44.7 22.5

Iron, filtered (μg/L) 114 150 <3 2

19 9

Iron, unfiltered (μg/L) 113 8,800 20 1,030 468

Lead, filtered (μg/L) 110 1.2 <.08 2.16 <.60

Lead, unfiltered (μg/L) 110 56 <1 2

8.00 3.50

Manganese, filtered (μg/L) 114 60.7 4.5 16.7 15.0

Manganese, unfiltered (μg/L) 114 880 8 150 96.3

Zinc, filtered (μg/L) 114 21 <3 2

6.3 4.6

Zinc, unfiltered (μg/L) 114 490 3 64 34

Sediment, suspended (percent finer than 0.062 mm) 115 92 38 74 74

Sediment, suspended concentration (mg/L) 115 530 2 65 26

Sediment, suspended discharge (ton/d) 115 4,720 1.7 328 49

Data  97
Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12334550—Clark Fork at Turah Bridge, near Bonner 

Period of record for water-quality data: March 1985–September 2006

Streamflow, instantaneous (ft3/s) 212 9,560 296 1,850 1,110

pH, onsite (standard units) 158 8.8 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 187 483 139 303 315

Temperature, water (°C) 211 22.0 0.0 9.5 9.5

Hardness, filtered (mg/L as CaCO3) 148 210 54 132 135

Calcium, filtered (mg/L) 148 59.0 14.9 37.3 38.0

Magnesium, filtered (mg/L) 148 14.0 3.94 9.51 9.50

Arsenic, filtered (μg/L) 157 17 2.7 6.0 5.2

Arsenic, unfiltered (μg/L) 157 110 3 10 7

Cadmium, filtered (μg/L) 157 .11 <.04 2

.03 <.1

Cadmium, unfiltered (μg/L) 157 4 <.1 2

.27 <1

Copper, filtered (μg/L) 156 25 E1.1 4.9 4.0

Copper, unfiltered (μg/L) 155 500 3 36.6 16.4

Iron, filtered (μg/L) 157 190 <3 2

24 13

Iron, unfiltered (μg/L) 157 19,000 30 1,090 389

Lead, filtered (μg/L) 153 7 <.08 2.32 <1

Lead, unfiltered (μg/L) 153 100 <1 2

7.63 3.00

Manganese, filtered (μg/L) 157 37.4 1.0 8.1 6.8

Manganese, unfiltered (μg/L) 157 2,000 9 129 69

Zinc, filtered (μg/L) 156 39 <3 2

6.3 4.0

Zinc, unfiltered (μg/L) 157 1,100 <10 2

64 30

Sediment, suspended (percent finer than 0.062 mm) 201 98 27 73 76

Sediment, suspended concentration (mg/L) 212 1,370 2 59 18

Sediment, suspended discharge (ton/d) 212 34,700 3.0 644 60

98  Water-Quality, Bed-Sediment, 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 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12340000—Blackfoot River near Bonner 

Period of record for water-quality data: March 1985–September 2006

Streamflow, instantaneous (ft3/s) 152 13,400 344 2,650 1,310

pH, onsite (standard units) 112 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 129 294 131 208 205

Temperature, water (°C) 152 22.5 0.0 9.3 9.5

Hardness, filtered (mg/L as CaCO3) 105 140 55 103 97

Calcium, filtered (mg/L) 105 37 14 26.3 24.8

Magnesium, filtered (mg/L) 105 13.2 4.9 9.11 8.63

Arsenic, filtered (μg/L) 112 2 <1 2

1.0 1.0

Arsenic, unfiltered (μg/L) 112 4 <1 2

1 1

Cadmium, filtered (μg/L) 112 1 <.04 -- <.1

Cadmium, unfiltered (μg/L) 112 2 <.04 2.14 <1

Copper, filtered (μg/L) 110 7 <1 2

1.5 .9

Copper, unfiltered (μg/L) 109 34 <1 25.4 2.6

Iron, filtered (μg/L) 112 100 <3 218 10

Iron, unfiltered (μg/L) 112 3,600 10 450 195

Lead, filtered (μg/L) 108 8 <.08 2.45 <.6

Lead, unfiltered (μg/L) 108 25 <.06 2

2.72 <.05

Manganese, filtered (μg/L) 112 11 <1 2

2.4 2.0

Manganese, unfiltered (μg/L) 112 180 <10 230 20

Zinc, filtered (μg/L) 112 15 <.6 22.3 <10

Zinc, unfiltered (μg/L) 112 60 <1 2

6.2 <10

Sediment, suspended (percent finer than 0.062 mm) 150 98 42 80 82

Sediment, suspended concentration (mg/L) 152 271 1 30 8

Sediment, suspended discharge (ton/d) 152 7,670 1.1 526 30

Data  99
Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2006.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12340500—Clark Fork above Missoula 

Period of record for water-quality data: July 1986–September 2006

Streamflow, instantaneous (ft3/s) 178 21,600 720 4,390 2,380

pH, onsite (standard units) 135 8.7 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 155 399 142 254 261

Temperature, water (°C) 175 22.0 0.0 9.5 9.0

Hardness, filtered (mg/L as CaCO3) 135 170 61 117 120

Calcium, filtered (mg/L) 135 46 14 31.6 32.0

Magnesium, filtered (mg/L) 135 13.4 5.28 9.28 9.20

Arsenic, filtered (μg/L) 135 9 1 3.3 3.0

Arsenic, unfiltered (μg/L) 135 69 1 5 4

Cadmium, filtered (μg/L) 135 .2 <.04 2

.03 <.1

Cadmium, unfiltered (μg/L) 135 5 <.1 2

.14 <1

Copper, filtered (μg/L) 134 12.6 .7 2.8 2.0

Copper, unfiltered (μg/L) 133 400 2 16.3 8.0

Iron, filtered (μg/L) 135 200 <3 2

22 15

Iron, unfiltered (μg/L) 135 13,000 40 592 230

Lead, filtered (μg/L) 130 1.2 <.08 2.16 <1

Lead, unfiltered (μg/L) 130 78 <1 2

3.08 1.26

Manganese, filtered (μg/L) 135 230 6.2 17.4 14.2

Manganese, unfiltered (μg/L) 135 1,100 10 64 40

Zinc, filtered (μg/L) 135 16 <1 2

3.7 2

Zinc, unfiltered (μg/L) 135 1,100 <10 2

31 13

Sediment, suspended (percent finer than 0.062 mm) 173 99 39 87 90

Sediment, suspended concentration (mg/L) 178 824 2 37 12

Sediment, suspended discharge (ton/d) 178 21,900 5.8 929 74

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).

100 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 26. Statistical summary of long-term fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 

through August 2006.—Continued

[Reported concentrations are in micrograms 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. Values for a single sample are arbitrarily listed in the “Mean” column. 

Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data to 

compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12323600—Silver Bow Creek at Opportunity 

Period of record for bed-sediment data: 1992–2006

Arsenic 4 186 119 158 164

Cadmium 15 43.9 22.8 33.2 34.6

Chromium 13 32.4 16.8 24.8 24.8

Copper 15 9,020 2,480 4,770 4,570

Iron 15 41,200 28,200 35,400 34,600

Lead 15 1,030 381 709 788

Manganese 15 9,220 1,680 3,620 2,770

Nickel 14 21.4 12.0 15.1 15.1

Silver 12 20.0 8.3 15.5 15.8

Zinc 15 13,400 4,950 8,220 7,630

12323750—Silver Bow Creek at Warm Springs 

Period of record for bed-sediment data: 1992–2006

Arsenic 4 177 97 130 122

Cadmium 15 12.2 4.2 7.5 6.7

Chromium 13 34.1 <15.7 19.2 17.8

Copper 15 769 169 350 278

Iron 15 31,700 15,400 22,200 20,800

Lead 15 100 49 70 68

Manganese 15 17,700 1,470 8,520 8,590

Nickel 14 19.1 9.2 14.6 14.6

Silver 12 4.4 .3 1

1.9 11.8

Zinc 15 2,220 620 1,020 812

12323770—Warm Springs Creek at Warm Springs 

Period of record for bed-sediment data: 1995, 1997, 1999, 2002, 2005

Arsenic 1 -- -- 66 --

Cadmium 5 5.8 1.3 3.6 3.9

Chromium 5 33.4 27.5 30.4 30.8

Copper 5 991 779 878 881

Iron 5 22,400 16,800 20,700 21,900

Lead 5 86 67 81 85

Manganese 5 12,100 2,020 7,980 8,790

Nickel 5 21.9 17.6 19.2 19.2

Silver 4 5.1 3.1 3.8 3.5

Zinc 5 421 372 395 396

Data 101
Table 26. Statistical summary of long-term fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 

through August 2006.—Continued

[Reported concentrations are in micrograms 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. Values for a single sample are arbitrarily listed in the “Mean” column. 

Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data to 

compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12323800—Clark Fork near Galen 

Period of record for bed-sediment data: 1987, 1991–2006

Arsenic 4 119 95 108 109

Cadmium 17 20.1 4.0 9.2 7.8

Chromium 13 33.9 19.1 26.4 26.4

Copper 17 2,300 838 1,220 1,110

Iron 17 39,800 22,600 27,800 27,000

Lead 17 235 92 138 133

Manganese 17 17,300 2,780 9,640 11,000

Nickel 14 23.2 13.9 18.1 18.0

Silver 14 7.3 <3.2 1

4.4 14.5

Zinc 17 3,560 999 1,580 1,170

461415112450801—Clark Fork below Lost Creek, near Galen 

Period of record for bed-sediment data: 1996–2006

Arsenic 4 204 92 129 109

Cadmium 11 10.5 5.2 7.6 7.3

Chromium 10 34.5 20.5 27.6 26.6

Copper 11 2,050 1,150 1,490 1,420

Iron 11 32,800 24,400 29,300 30,300

Lead 11 218 127 173 174

Manganese 11 9,820 3,540 6,030 5,750

Nickel 11 19.9 11.7 15.9 16.3

Silver 8 7.8 4.2 6.5 6.7

Zinc 11 1,680 1,120 1,360 1,300

461559112443301—Clark Fork at county bridge, near Racetrack 

Period of record for bed-sediment data: 1996–2006

Arsenic 4 101 56 76 73

Cadmium 11 8.7 5.0 6.9 6.4

Chromium 10 33.3 19.0 25.3 26.3

Copper 11 1,610 933 1,190 1,120

Iron 11 31,700 21,200 26,500 28,100

Lead 11 186 103 142 135

Manganese 11 6,310 2,100 3,650 3,400

Nickel 11 18.4 10.3 14.1 14.8

Silver 8 6.1 <3.3 1

5.0 15.4

Zinc 11 1,550 999 1,200 1,130

102 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 26. Statistical summary of long-term fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 

through August 2006.—Continued

[Reported concentrations are in micrograms 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. Values for a single sample are arbitrarily listed in the “Mean” column. 

Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data 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: 1996–2006

Arsenic 4 80 58 68 67

Cadmium 11 10.3 4.3 6.7 6.0

Chromium 10 34.1 16.0 24.5 24.1

Copper 11 1,550 721 1,020 992

Iron 11 33,700 20,600 26,000 25,200

Lead 11 155 92 127 121

Manganese 11 8,370 1,810 4,090 3,910

Nickel 11 16.9 8.7 12.8 12.4

Silver 8 6.2 2.7 4.9 5.0

Zinc 11 1,570 900 1,140 1,080

12324200—Clark Fork at Deer Lodge 

Period of record for bed-sediment data: 1986–87, 1990–2006

Arsenic 4 77 49 65 66

Cadmium 19 10.0 3.8 6.5 6.0

Chromium 13 43.9 19.5 29.9 28.4

Copper 19 4,180 683 1,300 1,040

Iron 19 35,300 21,100 27,200 26,100

Lead 19 242 103 149 148

Manganese 19 6,020 1,110 2,740 2,440

Nickel 14 21.1 11.5 15.1 14.3

Silver 16 7.9 2.4 4.7 4.5

Zinc 19 1,730 846 1,230 1,260

12324680—Clark Fork at Goldcreek 

Period of record for bed-sediment data: 1992–2006

Arsenic 4 39 23 30 28

Cadmium 15 8.1 2.6 5.0 5.4

Chromium 13 48.9 21.3 31.2 31.6

Copper 15 1,080 338 669 729

Iron 15 30,600 15,500 23,300 23,700

Lead 15 152 52 94 93

Manganese 15 2,610 1,160 1,900 1,840

Nickel 14 18.6 9.0 14.3 14.5

Silver 12 4.8 2.3 3.3 3.2

Zinc 15 1,320 584 951 1,080

Data 103
Table 26. Statistical summary of long-term fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 

through August 2006.—Continued

[Reported concentrations are in micrograms 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. Values for a single sample are arbitrarily listed in the “Mean” column. 

Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data to 

compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12331800—Clark Fork near Drummond 

Period of record for bed-sediment data: 1986–87, 1991–2006

Arsenic 4 34 31 32 32

Cadmium 18 7.7 2.6 4.7 4.6

Chromium 13 35.4 17.0 28.3 30.1

Copper 18 747 321 490 480

Iron 18 27,000 16,500 21,400 20,300

Lead 18 135 64 91 89

Manganese 18 3,520 1,150 1,990 1,890

Nickel 14 16.8 10.4 13.7 13.7

Silver 15 4.7 <3.2 1

3.0 12.9

Zinc 18 1,230 742 983 975

12334550—Clark Fork at Turah Bridge, near Bonner 

Period of record for bed-sediment data: 1986, 1991–2006

Arsenic 4 30 19 23 22

Cadmium 17 7.3 1.9 3.9 3.9

Chromium 13 34.7 15.3 24.4 26.7

Copper 17 635 211 356 322

Iron 17 24,400 12,600 18,500 17,300

Lead 17 115 47 69 63

Manganese 17 2,270 671 1,230 1,240

Nickel 14 19.1 8.7 12.7 11.6

Silver 14 3.9 <1.9 1

2.1 11.9

Zinc 17 1,160 584 832 789

12340000—Blackfoot River near Bonner 

Period of record for bed-sediment data: 1986–87, 1991, 1993–96, 1998–2001, 2003, 2006

Arsenic 2 4 2 -- --

Cadmium 13 2.0 <.2 10.6 1<0.8

Chromium 9 25.8 15.1 20.9 22.0

Copper 13 27 11 20 21

Iron 13 20,200 12,400 17,000 17,800

Lead 13 20 <13 1

13 113

Manganese 13 683 298 513 535

Nickel 10 14.3 9.4 11.9 12.2

Silver 12 <1.9 <.3 1

.5 1<.6

Zinc 13 73 35 59 61

104  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Table 26. Statistical summary of long-term fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 

through August 2006.—Continued

[Reported concentrations are in micrograms 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. Values for a single sample are arbitrarily listed in the “Mean” column. 

Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data to 

compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12340500—Clark Fork above Missoula 

Period of record for bed-sediment data: 1997–2006

Arsenic 4 52 17 30 26

Cadmium 10 5.8 1.5 3.4 3.5

Chromium 9 30.6 19.0 25.1 25.9

Copper 10 551 166 351 304

Iron 10 24,300 18,100 20,300 20,500

Lead 10 78 37 56 57

Manganese 10 1,420 477 981 996

Nickel 10 15.8 10.9 13.1 12.8

Silver 7 2.9 .8 1

2.0 12.1

Zinc 10 1,090 438 734 706

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.

Data 105
Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323600—Silver Bow Creek at Opportunity 

Period of record for biological data: 1992, 1994–95, 1997–2006

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 1

1.3 11.6

Zinc 5 995 629 803 815

Hydropsyche cockerelli

Arsenic 6 20.4 9.5 13.1 12.0

Cadmium 12 9.7 3.1 5.4 5.0

Chromium 12 8.0 1.0 2.9 1.9

Copper 12 1,090 269 427 365

Iron 12 2,880 689 1,570 1,360

Lead 12 56.7 19.0 31.1 22.7

Manganese 12 3,030 180 937 764

Nickel 12 3.6 .7 2.0 1.9

Zinc 12 1,590 619 904 797

Hydropsyche spp.

Arsenic 6 23.1 10.7 17.2 18.4

Cadmium 11 11.0 4.2 6.8 5.7

Chromium 11 4.7 .6 2.1 1.5

Copper 11 930 312 572 469

Iron 11 2,630 1,050 1,930 2,100

Lead 11 51.4 21.8 39.6 39.9

Manganese 11 1,340 712 1,080 1,040

Nickel 11 2.5 .7 2.2 2.4

Zinc 11 1,290 784 1,050 1,090

106 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323600—Silver Bow Creek at Opportunity—Continued

Period of record for biological data: 1992, 1994–95, 1997–2006

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

12323750—Silver Bow Creek at Warm Springs 

Period of record for biological data: 1992–2006

Hydropsyche cockerelli

Arsenic 7 23.6 7.9 15.4 16.9

Cadmium 33 2.1 .2 .7 .5

Chromium 33 4.3 .4 1.0 .8

Copper 33 97.0 16.7 38.5 31.1

Iron 33 1,590 351 789 762

Lead 33 5.7 .3 2.9 2.6

Manganese 33 3,890 491 1,340 1,220

Nickel 33 1.8 .3 .9 .8

Zinc 33 276 115 176 168

Hydropsyche occidentalis

Arsenic 5 31.0 10.5 21.0 25.6

Cadmium 20 1.6 .2 .6 .4

Chromium 20 6.8 .3 1.7 1.0

Copper 20 48.9 11.0 32.4 30.8

Iron 20 2,960 372 1,190 971

Lead 20 8.2 <1.7 1

3.8 13.5

Manganese 20 6,940 1,200 2,560 2,150

Nickel 20 2.7 .7 1.5 1.5

Zinc 20 220 140 178 179

Data 107
Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323750—Silver Bow Creek at Warm Springs—Continued

Period of record for biological data: 1992–2006

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 4 2.3 0.4 1.1 0.9

Chromium 4 1.4 .5 1.0 1.2

Copper 4 47.6 34.9 40.9 40.6

Iron 4 773 561 680 693

Lead 4 5.1 1.9 3.9 4.7

Manganese 4 1,100 443 725 678

Nickel 4 1.9 <.4 1

.8 1.5

Zinc 4 285 141 195 177

12323770—Warm Springs Creek at Warm Springs 

Period of record for biological data: 1995, 1997, 1999, 2002, 2005

Arctopsyche grandis

Arsenic 2 9.8 9.5 9.6 --

Cadmium 6 3.6 1.9 2.7 2.7

Chromium 6 2.9 .8 1.7 1.6

Copper 6 133 78.3 106 100

Iron 6 1,100 684 918 957

Lead 6 5.6 3.0 1

4.7 15.2

Manganese 6 3,560 1,340 2,560 2,710

Nickel 6 2.8 1.8 12.3 12.3

Zinc 6 222 181 196 196

Hydropsyche occidentalis

Arsenic 2 13.6 12.7 13.2 --

Cadmium 4 1.2 .7 1.0 1.0

Chromium 4 3.2 .3 2.2 3.2

Copper 4 183 125 156 158

Iron 4 2,070 1,590 1,840 1,840

Lead 4 8.2 6.7 7.4 7.4

Manganese 4 3,190 2,400 2,790 2,770

Nickel 4 3.3 2.0 2.6 2.6

Zinc 4 172 148 160 160

108  Water-Quality, Bed-Sediment, 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 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323770—Warm Springs Creek at Warm Springs—Continued

Period of record for biological data: 1995, 1997, 1999, 2002, 2005

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 --

12323800—Clark Fork near Galen 

Period of record for biological data: 1987, 1991–2006

Hydropsyche cockerelli

Arsenic 6 15.8 13.2 14.2 13.8

Cadmium 31 2.7 .7 1.4 1.5

Chromium 31 4.4 .8 1.9 1.6

Copper 31 181 48.7 103 98.9

Iron 31 2,660 816 1,450 1,350

Lead 31 11.8 1.2 7.9 7.7

Manganese 31 3,620 1,070 2,270 2,290

Nickel 31 6.5 .9 1.8 1.6

Zinc 31 299 136 208 204

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

Data 109
Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323800—Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991–2006

Hydropsyche occidentalis

Arsenic 4 16.5 12.5 15.2 16.0

Cadmium 36 1.7 .6 1.1 1.1

Chromium 36 6.6 .4 2.0 1.5

Copper 36 121 49.2 82.3 81.6

Iron 36 1,920 642 1,270 1,220

Lead 36 13.5 1.6 7.0 6.6

Manganese 36 6,170 1,220 2,600 2,260

Nickel 36 3.5 .8 1.6 1.5

Zinc 36 286 168 199 193

Hydropsyche tana

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 1.5 --

Chromium 1 -- -- 1.4 --

Copper 1 -- -- 92.9 --

Iron 1 -- -- 1,340 --

Lead 1 -- -- 9.0 --

Manganese 1 -- -- 2,160 --

Nickel 1 -- -- 2.1 --

Zinc 1 -- -- 206 --

Hydropsyche spp.

Arsenic 2 15.7 14.5 15.1 --

Cadmium 6 3.5 .8 2.3 2.8

Chromium 2 2.4 2.2 2.3 --

Copper 6 154 78.4 126 143

Iron 6 1,540 1,190 1,360 1,360

Lead 6 13.5 5.9 10.4 10.9

Manganese 2 4,760 4,400 4,580 --

Nickel 2 1.8 1.5 1.6 --

Zinc 6 329 218 280 291

110 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

461415112450801—Clark Fork below Lost Creek, near Galen 

Period of record for biological data: 1996–2006

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 9 27.8 8.8 14.5 11.6

Cadmium 20 2.8 1.1 1.8 1.6

Chromium 20 3.6 .8 2.0 2.0

Copper 20 338 48.8 130 112

Iron 20 4,080 691 1,540 1,180

Lead 20 28.6 4.5 11.5 9.0

Manganese 20 3,160 1,230 1,860 1,700

Nickel 20 2.8 .9 1.3 1.1

Zinc 20 339 151 225 223

Hydropsyche occidentalis

Arsenic 4 20.8 12.7 15.5 14.3

Cadmium 18 1.8 .9 1.3 1.4

Chromium 18 3.6 1.2 2.0 1.9

Copper 18 219 52.1 110 110

Iron 18 2,830 963 1,460 1,390

Lead 18 19.4 6.6 10.0 9.6

Manganese 18 3,870 1,220 2,290 2,160

Nickel 18 2.5 .9 1.4 1.4

Zinc 18 308 174 232 236

Data 111
Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

461415112450801—Clark Fork below Lost Creek, near Galen—Continued

Period of record for biological data: 1996–2006

Hydropsyche spp.

Arsenic 1 -- -- 12.0 --

Cadmium 5 1.8 1.2 1.5 1.4

Chromium 5 2.4 .9 1.5 1.5

Copper 5 122 45.1 91.8 103

Iron 5 1,410 533 1,110 1,200

Lead 5 20.5 4.1 10.0 8.7

Manganese 5 1,980 799 1,440 1,230

Nickel 5 2.8 1.0 1.6 1.4

Zinc 5 225 143 179 179

461559112443301—Clark Fork at county bridge, near Racetrack 

Period of record for biological data: 1996–2006

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 8 16.5 11.1 13.1 11.9

Cadmium 19 1.9 .8 1.4 1.5

Chromium 19 2.7 .6 1.6 1.2

Copper 19 198 50.0 96.5 91.4

Iron 19 2,720 657 1,140 981

Lead 19 17.2 3.7 7.9 7.2

Manganese 19 2,020 646 1,570 1,830

Nickel 19 2.0 .7 1.1 1.0

Zinc 19 240 139 182 179

112 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

461559112443301—Clark Fork at county bridge, near Racetrack—Continued

Period of record for biological data: 1996–2006

Hydropsyche occidentalis

Arsenic 4 15.0 13.7 14.5 14.6

Cadmium 17 2.2 .7 1.4 1.3

Chromium 17 3.7 1.1 2.1 2.0

Copper 17 160 59.5 110 124

Iron 17 2,370 1,030 1,590 1,580

Lead 17 14.7 4.3 10.2 10.1

Manganese 17 3,770 1,090 2,180 2,100

Nickel 17 1.9 1.1 1.4 1.3

Zinc 17 255 181 227 229

Hydropsyche spp.

Arsenic 2 12.7 11.9 -- --

Cadmium 4 2.4 1.0 1.6 1.5

Chromium 4 2.5 .7 1.5 1.4

Copper 4 124 82.9 101 99.2

Iron 4 1,880 1,140 1,380 1,240

Lead 4 15.0 5.7 9.4 8.5

Manganese 4 2,370 910 1,500 1,360

Nickel 4 1.9 1.1 1.4 1.3

Zinc 4 220 151 190 194

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack 

Period of record for biological data: 1996–2006

Arctopsyche grandis

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 1.7 --

Chromium 1 -- -- <2.4 --

Copper 1 -- -- 30.8 --

Iron 1 -- -- 340 --

Lead 1 -- -- <14.5 --

Manganese 1 -- -- 510 --

Nickel 1 -- -- 1.0 --

Zinc 1 -- -- 87 --

Data 113
Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack—Continued

Period of record for biological data: 1996–2006

Hydropsyche cockerelli

Arsenic 6 18.8 8.0 13.0 12.8

Cadmium 15 1.7 .7 1.2 1.3

Chromium 15 4.0 .5 1.5 1.0

Copper 15 198 60.7 106 87.6

Iron 15 2,310 552 1,100 851

Lead 15 17.7 3.5 7.5 6.3

Manganese 15 2,650 487 1,380 1,230

Nickel 15 2.1 .5 1.1 .9

Zinc 15 275 162 201 182

Hydropsyche occidentalis

Arsenic 4 24.0 10.2 14.7 12.3

Cadmium 21 1.8 .7 1.2 1.1

Chromium 21 6.2 .8 2.0 1.8

Copper 21 238 74.9 106 90.7

Iron 21 3,390 940 1,500 1,500

Lead 21 21.8 6.1 11.3 11.2

Manganese 21 3,990 826 2,500 2,320

Nickel 21 2.4 1.2 1.5 1.4

Zinc 21 355 211 249 237

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 --

114  Water-Quality, Bed-Sediment, 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 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324200—Clark Fork at Deer Lodge 

Period of record for biological data: 1986–87, 1990–2006

Arctopsyche grandis

Arsenic 0 -- -- -- --

Cadmium 2 2.4 <4.2 12.2 --

Chromium 2 1.0 <1.3 1

.8 --

Copper 2 69.1 34.9 52.0 --

Iron 2 676 537 606 --

Lead 2 <7.8 3.8 1

3.8 --

Manganese 2 727 380 554 --

Nickel 2 <1.7 <1.3 1

-- --

Zinc 2 178 140 159 --

Hydropsyche cockerelli

Arsenic 5 11.4 5.8 8.1 7.3

Cadmium 28 2.3 .6 1.4 1.3

Chromium 28 3.2 .4 1.6 1.6

Copper 28 180 54.7 97.6 98.0

Iron 28 3,340 490 1,120 1,040

Lead 28 18.1 3.8 9.4 8.9

Manganese 28 1,570 396 873 772

Nickel 28 2.4 .3 1.1 1.0

Zinc 28 391 132 188 185

Hydropsyche occidentalis

Arsenic 6 12.4 6.6 10.1 10.4

Cadmium 43 2.7 .6 1.3 1.3

Chromium 43 3.6 .6 1.9 1.9

Copper 43 180 49.4 116 112

Iron 43 2,060 557 1,400 1,420

Lead 43 18.6 3.5 11.1 10.8

Manganese 43 2,850 649 1,710 1,730

Nickel 43 12.9 1.0 1.7 1.4

Zinc 43 329 166 241 236

Data 115
Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324200—Clark Fork at Deer Lodge—Continued

Period of record for biological data: 1986–87, 1990–2006

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

12324680—Clark Fork at Goldcreek 

Period of record for biological data: 1992–2006

Arctopsyche grandis

Arsenic 17 6.4 1.8 3.8 2.7

Cadmium 46 6.6 .6 1.9 1.7

Chromium 46 3.3 .1 1.3 1.0

Copper 46 129 19.9 42.5 32.3

Iron 46 2,360 195 646 479

Lead 46 10.9 1.0 3.4 3.3

Manganese 46 1,580 436 843 812

Nickel 46 1.8 .2 .7 .6

Zinc 46 326 146 196 179

Claassenia sabulosa

Arsenic 11 2.1 0.7 1.3 1.4

Cadmium 31 3.5 .1 1.0 .7

Chromium 31 1.6 .2 .6 .5

Copper 31 81.7 33.0 57.4 57.1

Iron 31 567 63.0 189 171

Lead 31 1.8 .4 .9 .8

Manganese 31 320 50.6 151 119

Nickel 31 .7 .1 .3 .3

Zinc 31 351 166 264 261

116 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324680—Clark Fork at Goldcreek—Continued

Period of record for biological data: 1992–2006

Hydropsyche cockerelli

Arsenic 10 6.1 4.1 5.1 4.8

Cadmium 29 2.6 .5 1.3 1.2

Chromium 29 4.7 .5 2.1 1.9

Copper 29 188 17.1 68.3 55.5

Iron 29 3,250 522 1,110 813

Lead 29 16.2 2.4 6.3 5.2

Manganese 29 1,670 538 935 937

Nickel 29 2.3 .3 1.2 1.0

Zinc 29 249 106 183 184

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 4 5.8 4.7 5.2 5.2

Cadmium 19 1.7 .4 1.2 1.3

Chromium 19 3.9 .4 1.6 1.7

Copper 19 156 26.4 62.0 57.6

Iron 19 2,720 466 1,110 1,040

Lead 19 15.7 2.9 6.8 5.7

Manganese 19 2,210 530 1,230 1,140

Nickel 19 2.5 .8 1.2 1.0

Zinc 19 277 97 196 201

Data 117
Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12331800—Clark Fork near Drummond 

Period of record for biological data: 1986, 1991–2006

Arctopsyche grandis

Arsenic 10 4.4 2.3 3.2 3.2

Cadmium 42 3.8 .4 1.3 1.1

Chromium 42 2.5 .2 1.0 1.0

Copper 42 89.2 16.9 32.1 26.7

Iron 42 1,660 193 560 496

Lead 42 11.8 1.6 4.3 3.9

Manganese 42 2,010 456 831 721

Nickel 42 1.9 .2 .6 .6

Zinc 42 308 140 187 183

Claassenia sabulosa

Arsenic 8 1.5 0.7 1.2 1.2

Cadmium 44 2.8 .1 1.1 1.0

Chromium 44 3.3 .1 .7 .6

Copper 44 165 18.0 64.1 55.9

Iron 44 387 45.4 157 135

Lead 44 2.9 .2 .9 .8

Manganese 44 410 33.1 167 146

Nickel 44 1.1 .1 1

.3 1.2

Zinc 44 567 103 273 256

Hydropsyche cockerelli

Arsenic 7 5.7 3.9 4.5 4.4

Cadmium 36 2.3 .3 1.1 .8

Chromium 36 3.5 .4 1.6 1.5

Copper 36 156 30.0 58.1 50.5

Iron 36 2,500 506 1,140 940

Lead 36 15.0 4.8 8.1 7.0

Manganese 36 1,680 549 977 914

Nickel 36 2.0 .5 1.1 1.0

Zinc 36 248 134 192 185

118  Water-Quality, Bed-Sediment, 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 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12331800—Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991–2006

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 7 6.9 4.3 5.1 5.1

Cadmium 23 2.0 .4 1.0 1.0

Chromium 23 8.1 .4 2.3 2.1

Copper 23 118 13.3 54.3 55.1

Iron 23 2,060 424 1,210 1,180

Lead 23 14.0 2.9 8.5 8.4

Manganese 23 2,920 619 1,500 1,220

Nickel 23 2.4 .5 1.3 1.2

Zinc 23 293 157 220 221

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 119
Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12334550—Clark Fork at Turah Bridge, near Bonner 

Period of record for biological data: 1986, 1991–2006

Arctopsyche grandis

Arsenic 14 5.0 3.1 4.3 4.4

Cadmium 56 2.7 .4 1.1 .8

Chromium 56 4.1 .5 1.6 1.4

Copper 56 125 20.1 37.3 29.4

Iron 56 2,870 372 915 789

Lead 56 13.2 1.6 4.2 3.4

Manganese 56 902 324 635 641

Nickel 56 2.7 .4 1.1 .9

Zinc 56 276 111 196 196

Claassenia sabulosa

Arsenic 9 1.9 0.8 1.2 1.1

Cadmium 35 2.5 .1 1.0 .8

Chromium 35 2.0 .2 .7 .6

Copper 35 87.6 37.5 57.5 53.4

Iron 35 340 58.6 117 107

Lead 35 1.6 .2 .6 .6

Manganese 35 215 37.2 88.7 74.6

Nickel 35 .6 .1 .2 .2

Zinc 35 342 144 228 234

Hydropsyche cockerelli

Arsenic 10 5.1 3.7 4.4 4.5

Cadmium 38 1.8 .3 .8 .7

Chromium 38 8.0 .2 1.9 1.6

Copper 38 118 26.4 47.5 42.4

Iron 38 2,530 566 1,190 1,090

Lead 38 12.1 2.2 5.2 4.9

Manganese 38 805 426 621 624

Nickel 38 2.6 .6 1.2 1.2

Zinc 38 228 119 184 184

120 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12334550—Clark Fork at Turah Bridge, near Bonner—Continued

Period of record for biological data: 1986, 1991–2006

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 1

5.2 --

Manganese 2 1,320 537 928 --

Nickel 2 1.7 1.3 1.5 --

Zinc 2 231 171 201 --

Hydropsyche occidentalis

Arsenic 7 5.9 3.6 4.3 4.1

Cadmium 27 1.8 .3 .8 .8

Chromium 27 3.2 .6 1.7 1.6

Copper 27 102 27.4 47.5 42.5

Iron 27 2,310 472 1,190 1,130

Lead 27 14.2 3.0 6.3 5.6

Manganese 27 1,600 454 856 758

Nickel 27 3.2 .6 1.2 1.1

Zinc 27 416 145 211 222

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 121
Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12340000—Blackfoot River near Bonner 

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006

Arctopsyche grandis

Arsenic 2 2.8 2.2 -- --

Cadmium 12 .4 .1 0.2 0.2

Chromium 7 1.8 .8 1.3 1.2

Copper 12 14.9 9.9 12.2 12.0

Iron 12 1,230 108 633 625

Lead 12 2.3 .5 1.0 .8

Manganese 7 578 286 429 398

Nickel 7 1.2 .7 1.0 1.0

Zinc 12 145 123 136 137

Claassenia sabulosa

Arsenic 2 1.7 1.4 -- --

Cadmium 13 .2 .1 0.1 0.1

Chromium 8 1.0 .3 .6 .6

Copper 13 88.5 19.0 43.9 44.0

Iron 13 194 46.2 112 113

Lead 13 .6 .1 .4 .4

Manganese 8 127 26.3 63.8 52.6

Nickel 8 .4 .1 .2 .2

Zinc 13 329 117 214 197

Hydropsyche cockerelli

Arsenic 1 -- -- 3.0 --

Cadmium 1 -- -- <.1 --

Chromium 1 -- -- 2.4 --

Copper 1 -- -- 5.6 --

Iron 1 -- -- 1,960 --

Lead 1 -- -- 2.3 --

Manganese 1 -- -- 716 --

Nickel 1 -- -- 1.9 --

Zinc 1 -- -- 140 --

122 Water-Quality, Bed-Sediment, 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 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12340000—Blackfoot River near Bonner—Continued

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006

Hydropsyche occidentalis

Arsenic 2 3.2 2.4 -- --

Cadmium 14 .5 .1 0.2 0.2

Chromium 14 3.2 .8 1.9 1.9

Copper 14 20.6 12.0 14.6 14.4

Iron 14 1,930 1,060 1,410 1,440

Lead 14 1.9 .8 1.4 1.3

Manganese 14 762 414 500 470

Nickel 14 1.8 .9 1.3 1.3

Zinc 14 153 116 136 136

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 --

12340500—Clark Fork above Missoula 

Period of record for biological data: 1997–2006

Arctopsyche grandis

Arsenic 12 4.5 2.1 3.3 3.3

Cadmium 31 1.8 .1 .7 .6

Chromium 31 3.4 .6 1.6 1.5

Copper 31 77.6 19.5 34.1 30.2

Iron 31 2,340 476 955 892

Lead 31 6.8 1.2 3.9 3.8

Manganese 31 1,410 476 930 924

Nickel 31 2.0 .5 1.1 1.0

Zinc 31 260 133 186 184

Data 123
Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 2006.—Continued

[Concentrations are in micrograms 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 arbitraily 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 data were not collected at some sites. Values are 

reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, less than minimum reporting level; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12340500—Clark Fork above Missoula—Continued

Period of record for biological data: 1997–2006

Claassenia sabulosa

Arsenic 6 1.9 0.7 1.4 1.5

Cadmium 15 2.0 .2 .6 .4

Chromium 15 1.4 .3 .8 .7

Copper 15 71.7 33.0 50.4 46.8

Iron 15 402 95.3 249 246

Lead 15 3.1 .5 1.2 1.1

Manganese 15 683 75.2 238 190

Nickel 15 .5 <.3 1

.4 1.4

Zinc 15 363 191 271 271

Hydropsyche cockerelli

Arsenic 9 8.0 3.6 6.1 6.4

Cadmium 18 1.3 .4 .8 .8

Chromium 18 6.0 1.8 3.2 3.2

Copper 18 97.9 29.9 62.2 58.0

Iron 18 3,590 1,400 2,100 2,060

Lead 18 11.8 4.2 7.5 6.6

Manganese 18 1,910 781 1,260 1,210

Nickel 18 2.4 1.4 1.8 1.8

Zinc 18 266 156 210 210

Hydropsyche occidentalis

Arsenic 4 6.2 3.9 5.6 6.2

Cadmium 10 1.2 .4 .7 .7

Chromium 10 5.5 2.1 3.3 3.0

Copper 10 76.5 30.3 53.9 57.3

Iron 10 2,400 1,450 2,010 2,110

Lead 10 11.1 4.0 7.3 7.2

Manganese 10 2,460 939 1,880 1,950

Nickel 10 2.4 1.6 2.0 2.0

Zinc 10 258 192 232 231

1

Values determined by substituting one-half of the minimum reporting level for censored (<) values when both uncensored and censored values were used in 

determining the mean and median. When all data were less than the minimum reporting level, the median was determined by ranking the censored values in 

order of detection. No mean is reported when all values were below the minimum reporting level.

124  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Prepared by the Helena Publishing Service Center

For additional information contact:

Director, Montana Water Science Center

U.S. Geological Survey

3162 Bozeman Avenue

Helena, Montana 59601

(406) 457-5900

http://mt.water.usgs.gov/
Dodge and others—Water-Quality, Bed-Sediment, and Biological Data, and Statitical Summaries, Clark Fork Basin, Montana—Open-File Report 2007–1301

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