Building the bypass channel 

in preparation for removal of 

Milltown Dam.

Unloading excavated bottom sediment from railcars.

Loading excavated bottom 

sediment into railcars.

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2008–1318

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

Water-Quality, Bed-Sediment, and Biological Data 

(October 2006 through September 2007) and 

Statistical Summaries of Long-Term Data for 

Streams in the Clark Fork Basin, Montana
Cover photographs:

 Left: Building the bypass channel for the Clark Fork at the Milltown Reservoir Superfund site near Bonner, Montana. 

 Photograph by Diana Hammer, U.S. Environmental Protection Agency, taken October 2, 2007.

 Top right: Loading excavated bottom sediment into railcars at the Milltown Reservoir Superfund site near Bonner, 

 Montana, for transport to the repository near Opportunity, Montana. Photograph by Diana Hammer, U.S. Environmental 

 Protection Agency, taken October 2, 2007.

 Bottom right: Unloading excavated bottom sediment from railcars at the Milltown Reservoir Superfund site near 

 Opportunity, Montana. Photograph by Kent A. Dodge, U.S. Geological Survey, taken April 18, 2008.
Water-Quality, Bed-Sediment, and 

Biological Data (October 2006 through 

September 2007) 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 2008–1318

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: 2008

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

U.S. Geological Survey

Box 25286, Denver Federal Center

Denver, CO 80225

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

1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

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

reproduce any copyrighted materials contained within this report.

Suggested citation:

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2008, Water-quality, bed-sediment, and biological data (October 2006 

through September 2007) and statistical summaries of long-term data for streams in the Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 2008–1318, 132 p.
iii

Contents

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

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

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

Water-Quality Data........................................................................................................................................6

Methods..................................................................................................................................................6

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

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

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

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

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

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

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

Methods................................................................................................................................................13

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

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

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

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

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

Figures

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

Tables

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

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

2. Properties and constituents measured onsite or analyzed in 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 ..........................................................................................................7

4. Water-quality data for the Clark Fork basin, Montana, October 2006 through 

September 2007...........................................................................................................................20

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

Lodge, Montana, October 2006 through September 2007....................................................45

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

Bridge, near Bonner, Montana, October 2006 through September 2007...........................49

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

near Bonner, Montana, October 2006 through September 2007.........................................53

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

Missoula, Montana, October 2006 through September 2007 ..............................................57

.....
iv

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

Anaconda, Montana, October through November, 2006 and March through 

September, 2007..........................................................................................................................61

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

Anaconda, Montana, October through November, 2006 and March through 

September, 2007..........................................................................................................................64

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

Creek near Anaconda, Montana, October through December, 2006 and 

April through September, 2007 .................................................................................................67

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

Anaconda, Montana, October through November, 2006 and March through 

September, 2007..........................................................................................................................70

13. Seasonal daily maximum, minimum, and mean turbidity at Clark Fork above 

Missoula, Montana, April through September, 2007.............................................................73

14. Analyses of field replicates for water samples, Clark Fork basin, Montana....................75

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

Montana .......................................................................................................................................78

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

Clark Fork basin, Montana ........................................................................................................79

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

blank samples..............................................................................................................................80

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

upper Clark Fork basin, Montana.............................................................................................80

19. Analyses of field blanks for water samples ...........................................................................81

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

August 2007..................................................................................................................................82

21. Recovery efficiency for analyses of standard reference materials for 

bed sediment...............................................................................................................................83

22. Analyses of procedural blanks for bed sediment..................................................................84

23. Analyses of biota, upper Clark Fork basin, Montana, August 2007....................................85

24. Recovery efficiency for analyses of standard reference material for biota ....................87

25. Analyses of procedural blanks for biota.................................................................................88

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

Clark Fork basin, Montana, March 1985 through September 2007.....................................89

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

upper Clark Fork basin, Montana, August 1986 through August 2007 .............................108

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

basin, Montana, August 1986 through August 2007............................................................113
v

Conversion Factors, Datum, Abbreviated Water-Quality 

Units, and Acronyms

Multiply By To obtain

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

)

cubic foot per second (ft3

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

gallon (gal) 3.785 liter (L)

gallon (gal) 3,785 milliliter (mL)

inch (in.) 25.4 millimeter (mm)

inch (in.) 25,400 micrometer (μm)

mile (mi) 1.609 kilometer (km)

ounce (oz) 28.35 gram (g)

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

square mile (mi2

) 2.59 square kilometer (km2)

ton 907.2 kilogram

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

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

°F = (1.8 x °C) + 32

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

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

1927 (NAD 27).

Water-year definition:

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

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

example, water year 2007 is the period from October 1, 2006, through September 30, 2007.
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

NTRU nephelometric turbidity ratio unit

NWQL USGS National Water Quality Laboratory, Denver, Colo.

RSD relative standard deviation

spp. species

SRM standard reference material

TFE tetraflouroethylene

USGS U.S. Geological Survey

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

(October 2006 through September 2007) and Statistical 

Summaries of Long-Term Data for Streams in the Clark 

Fork Basin, Montana

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

Abstract

Water, bed sediment, and biota were sampled in streams 

from Butte to 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 2006 through September 

2007. Bed-sediment and biological samples were collected 

once at 12 sites during August 2007.

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 2006 through September 2007.

Water-quality data include concentrations of selected major 

ions, trace elements, and suspended sediment. Turbidity was 

analyzed for samples collected at sites where seasonal daily 

values of turbidity were being determined. Nutrients also 

were analyzed in the supplemental water-quality samples. 

Daily values of suspended-sediment concentration and 

suspended-sediment discharge were determined for four sites, 

and seasonal daily values of turbidity were determined for 

five 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 the 1860s 

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

Moderate- and small-scale mining also occurred in the basins 

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

Tailings derived from past mineral processing commonly 

contain large quantities of trace elements such as arsenic, 

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

mixed with stream sediment, transported downstream, and 

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

Springs Ponds and Milltown Reservoir (Andrews, 1987). The 

widely dispersed tailings continue to be reeroded, transported, 

and redeposited along the stream channel and flood plain, 

especially during high flows. The occurrence of elevated traceelement concentrations in water and bed sediment can pose a 

potential risk to aquatic biota and human health (U.S. Environmental Protection Agency, 2004).

Concern about the potential toxicity of trace elements to 

aquatic biota and human health has resulted in a comprehensive effort by State, Federal, and private entities to characterize 
2 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

the aquatic resources in the upper Clark Fork basin to guide 

and monitor remedial cleanup activities. A long-term database 

was considered necessary to detect trends over time in order to 

evaluate the effectiveness of remediation. Water-quality data 

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

at selected sites in the upper Clark Fork basin since 1985 

(Lambing, 1987 through 1991; Lambing and others, 1994, 

1995; Dodge and others, 1996 through 2007). 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; 

table 1). Of the sites that bracket Milltown Reservoir, three 

also are part of the long-term monitoring network. The 

supplemental monitoring provides additional spatial 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 

2006 through September 2007. 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.

the upper basin and to provide reference comparisons to the 

main stem. The three smaller tributaries were sampled to gain 

better spatial resolution on sources of metals entering the 

Clark Fork in an area of historical metal-processing activities near Anaconda. In the long-term monitoring program, 

water-quality data were obtained periodically at 19 sites; 

daily suspended-sediment data were obtained at 4 sites and 

daily turbidity data were obtained by continuous turbidity 

monitors at 5 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 farther downstream in the basin. 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–day periods to generally 

coincide with traveltime along the Clark Fork main stem. The 

water-quality and streamflow data for each sampling episode 

can be used to calculate instantaneous constituent loads to 

identify the relative contributions of load from different source 

areas. Supplemental samples from the 6 sites were collected 

11 times. One sample was collected in October 2006 during 

a drawdown of Milltown Reservoir, and 10 were collected 

from April to June 2007 during the rising limb and peak of the 

annual hydrograph.

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 waterquality, bed-sediment, and biota samples; and quality-assurance data for water year 2007 are listed in tables 4 through 25 

at the back of the report. Statistical summaries of long-term 

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

between March 1985 and September 2007 are listed in tables 

26 through 28 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.

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 main stem 

(including Silver Bow Creek), three major tributaries (Blacktail Creek, Warm Springs Creek, and Blackfoot River), and 

three smaller tributaries (Mill Creek, Willow Creek, and Lost 

Creek). The sites, types of data collected, and period of record 

for each type of data are listed in table 1. Main-stem sampling 

sites were selected to divide the upper Clark Fork into reaches 

of relatively uniform length, with each reach encompassing 

either a major tributary or depositional environment (Warm 

Springs Ponds and Milltown Reservoir). Major tributaries 

were sampled to describe water-quality, bed-sediment, and 

biological characteristics of important hydrologic sources in 
Figure 1. Location of study area in the Clark Fork basin, Montana.

Mill Creek

Willow

Creek

Cr Silver

Bow

Opportunity

Missoula

Butte

Anaconda

Opportunity

Galen

Warm Springs

Deer Lodge

Garrison

Goldcreek

Drummond

Bonner

Turah

Clinton

Milltown

Reservoir

Clark

Bitterroot

River

Blackfoot

River

Fork

Rock

Creek

Flint

Little

Blackfoot

River

DIVIDE

Clark Fork

Warm Springs

 Ponds

Warm Springs Cr

Silver

Bow

Creek

Blacktail

Cr

CONTINENTAL

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

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

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

Station number 

(fig. 1) Station name Net- work Continuous- record streamflow Periodic water-quality1 Daily suspended sediment Daily turbidity (seasonal) Fine-grained bed sediment2 Bulk bed sediment 2,3 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

461903112440701 Clark Fork at Dempsey 

Creek diversion, near Racetrack

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

4 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 sediment 2,3 Biota2

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, 08/07

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, 08/07

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

06/88–01/96, 03/96–03/03, 08/03–P

04/07–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.

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

Sampling Locations and Types of Data 5
Table 2. Properties and constituents measured onsite or 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

pH Calcium Cadmium Cadmium

Specific conductance Magnesium Chromium Chromium

Temperature Nitrogen Copper Copper

Turbidity Phosphorous Iron Iron

Arsenic Lead Lead

Cadmium Manganese Manganese

Copper Nickel Nickel

Iron Zinc Zinc

Lead

Manganese

Zinc

Suspended sediment

6 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. Routine water-quality samples for the long-term 

monitoring program were collected at 19 sites in the upper 

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

to describe seasonal and hydrologic variability. Supplemental water-quality samples were collected 11 times at the 

3 sites bracketing Milltown Reservoir and at the 3 additional 

sites downstream from Missoula. At the 4 daily suspendedsediment sites, suspended-sediment samples were collected 

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

flow conditions. Continuous turbidity monitors were operated 

seasonally (October–November/December 2006 and March/

April–September 2007) at four sites near Anaconda and at 

Clark Fork above Missoula to determine daily values (table 1).

Methods

Water samples were collected from vertical transits 

throughout the entire stream depth at multiple locations across 

the stream by using depth- and width-integration methods 

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

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

provide a vertically and laterally discharge-weighted composite sample that is intended to be representative of the entire 

flow passing through the cross section of a stream. Sampling 

equipment consisted of depth-integrating suspended-sediment 

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

constructed of plastic or coated with a nonmetallic epoxy paint 

and equipped with nylon or tetraflouroethylene (TFE) 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). 

Daily mean streamflow was estimated during ice periods 

because backwater affected the stage-discharge relation. On 

July 1–3 at Clark Fork at Turah Bridge daily mean streamflow was estimated because of damage to the orifice line. 

Onsite measurements of pH, specific conductance, 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 past reports from this 

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

copper, iron, lead, manganese, and zinc) 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 waterquality 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 
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 .014 mg/L 20 --

Nitrogen, unfiltered recoverable .06 mg/L 20 25

Phosphorus, unfiltered recoverable .008 mg/L 20 25

Arsenic, filtered .12 μg/L 20 25

Arsenic, unfiltered recoverable .20 μg/L 20 25

Cadmium, filtered .04 μg/L 20 25

Cadmium, unfiltered recoverable .02 μg/L 20 25

Copper, filtered .4 μg/L 20 25

Copper, unfiltered recoverable 1.2 μg/L 20 25

Iron, filtered 6 μg/L 20 25

Iron, unfiltered recoverable 6 μg/L 20 25

Lead, filtered .12 μg/L 20 25

Lead, unfiltered recoverable .06 μg/L 20 25

Manganese, filtered .2 μg/L 20 25

Manganese, unfiltered recoverable .6 μg/L 20 25

Zinc, filtered .60 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 --

contract observers using the depth-integration method at a 

single vertical transit near midstream. The samples were 

analyzed for suspended-sediment concentration and were 

used to determine daily mean suspended-sediment concentrations according to methods described by Porterfield (1972).

Suspended-sediment discharge is determined according to the 

following equation (Porterfield, 1972):

Qs = Qw × Cs × k, (1)

where

Qs is suspended-sediment discharge, in tons per 

day;

Qw is streamflow, in cubic feet per second;

Cs is suspended-sediment concentration, in 

milligrams per liter; and

k is a units-conversion constant (0.0027) to 

convert instantaneous suspended-sediment 

discharge to an equivalent daily suspendedsediment discharge.

Turbidity data were obtained by continuous turbidity 

monitors [Yellow Springs Instrument (YSI, 6136 turbidity 

Water-Quality Data 7

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

sensor)] at four tributary sites in the upper Clark Fork basin 

near Anaconda and at Clark Fork above Missoula (table 1). 

The monitors near Anaconda were installed in May–June 

2006 to provide supporting information on runoff conditions 

in an area where remediation activities are being conducted. 

The monitor at Clark Fork above Missoula was installed in 

April 2007 to provide real-time turbidity information in an 

area where remediation activities related to the removal of 

Milltown Dam are being conducted. The monitors are operated 

seasonally, generally from early spring (after ice breakup) to 

early winter (before stream freeze-up). Turbidity values are 

recorded at 15-minute intervals and can be viewed in real-time 

on the USGS Web page at http://waterdata.usgs.gov/mt/nwis. 

Continuous recordings provide the minimum and maximum 

values for each day as well as a daily mean turbidity value 

based on the average of all values in a 24-hour period. Procedures for the operation of continuous turbidity monitors and 

for daily record computations are described by Wagner and 

others (2006).

Results

Water-quality data for samples collected periodically 

during water year 2007 are listed in table 4. Daily mean 

streamflow, daily mean suspended-sediment concentration, 

and daily suspended-sediment discharge for water year 2007 

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 five sites are listed 

in tables 9 through 13 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 in which 

standard reference water samples prepared by the USGS 

Branch of Quality Systems are routinely inserted into the 

sample line for each analytical method at a frequency proportional to the sample load (http://bqs.usgs.gov). The laboratory also participates in external evaluation studies and audits 

with the National Environmental Laboratory Accreditation 

Program, the U.S. Environmental Protection Agency, Environment Canada, and the USGS Branch of Quality Systems to 

assess analytical performance.

Replicate data can be obtained in different ways to 

provide an assessment of precision (reproducibility) of 

analytical results. Replicate samples are two or more samples 

considered to be essentially identical in composition. Replicate samples can be obtained in the field (field replicate) 

by either repeating the collection process to obtain two or 

more independent composite samples or by splitting a single 

composite sample into two or more subsamples. The individual replicate samples are then analyzed separately. Likewise, 

a single sample can be analyzed two or more times in the 

laboratory to obtain a measure of analytical precision (laboratory replicate).

Precision of analytical results for field replicates is 

affected by numerous sources of variability within the field 

and laboratory environments, including sample collection, 

sample processing, and sample analysis. To provide data 

on overall precision for samples exposed to all sources of 

variability, replicate stream samples for chemical analysis 

were obtained in the field by splitting a composite stream 

sample. 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 chemical analyses of aliquots from a single 

sample selected from the group of samples constituting each 

analytical run. A separate analysis of the sample was made 

at the beginning and end of each analytical run to provide 

information on the reproducibility of laboratory analytical 

results independent of possible variability caused by field 

sample collection and processing. Laboratory replicates are 
Water-Quality Data 9

not obtainable for suspended-sediment samples because the 

samples are consumed during the analysis.

Spiked samples are used to evaluate bias, which measures 

the ability of an analytical method to accurately quantify a 

known amount of analyte added to a sample. Because some 

constituents in stream water can potentially interfere with the 

analysis of a sample for a targeted analyte, it is important to 

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

and aliquots of stream samples were spiked in the laboratory 

with known amounts of the same trace elements for which 

water-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 

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 , (2)

where

S is the standard deviation of the difference in 

concentration between replicate analyses,

d is the difference in concentration between 

each pair of replicate analyses, and

k is the number of pairs of replicate analyses.

Precision also can be expressed as a relative standard 

deviation (RSD), in percent, which is computed from the 

standard deviation and the mean concentration for all the replicate analyses. Expressing precision relative to a mean concentration standardizes comparison of precision among individual 

constituents. The RSD is calculated according to the following 

equation (Taylor, 1987):

RSD = × S

x

100, (3)

where

RSD is the relative standard deviation,

S is the standard deviation, and

is the mean concentration for all replicate 

analyses.

Paired analyses of field replicates are listed in table 14. 

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 15. The 
10 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 15).

The precision estimated for each constituent on the basis 

of laboratory replicate analyses, which include only laboratory sources of variability, is listed in table 16. Statistics for 

the precision of analytical results for laboratory replicates 

are calculated by using unrounded values stored in laboratory data files. The data-quality objective used to indicate 

acceptable precision of results for laboratory replicates was 

a maximum RSD of 20 percent (table 3). Precision estimates 

for the laboratory replicates were within the 20-percent RSD

limit for all constituents (table 16), except filtered cadmium. 

The RSD for this constituent was 27 percent and is primarily 

a statistical artifact of comparing the results of one sample 

that was estimated (E0.02 μg/L) with one that was 0.06 μg/L. 

When analyzing metals near detection, a 100–percent variation can be expected (Gary Cottrell, U.S. Geological Survey, 

written commun., 2008). Because the reporting level for 

filtered cadmium is 0.04 μg/L, a +/- 0.04 μg/L difference can 

be expected; therefore, the spread of 0.02–0.06 μg/L is within 

expected laboratory analytical variation. When this replicate 

pair was excluded, the other seven replicate pairs had a RSD

for filtered cadmium of 7.1 percent; therefore, data quality 

objectives were met for precision on the basis of the laboratory 

replicate results for all constituents.

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, (4)

where

R is the spike recovery, in percent;

D is the difference between the spiked and 

unspiked sample concentrations; and

C is the concentration of material used to spike 

the sample.

If the spike recovery of a trace element was outside a 

range of 75 to 125 percent, the instrument was recalibrated 

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

improved to the extent possible. Recovery efficiency for 

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

is listed in tables 17 and 18, respectively. The mean spike 

recovery for deionized-water blank samples spiked with trace 

elements (table 17) ranged from 98.4 to 107 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 17) did not exceed a 

25-percent deviation from an expected 100-percent recovery. 

The mean spike recovery for spiked stream samples (table 18) 

ranged from 96.3 to 109 percent. The 95-percent confidence 

intervals for mean spike recoveries (table 18) did not exceed a 

25-percent deviation from an expected 100-percent recovery. 

No adjustments were made to analytical data on the basis of 

the mean spike recovery.

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

thereby indicating a consistent deviation in one direction. All 

laboratory-spiked deionized-water blank samples (table 17) 

had confidence intervals for percent recovery that included 

100 percent except for filtered cadmium (103–112 percent) 

and filtered zinc (102–113). All laboratory-spiked stream 

samples (table 18) also had confidence intervals for percent 

recovery that included 100 percent except for filtered cadmium 

(102–114 percent), filtered iron (103–111 percent), filtered 

lead (103–115 percent), and unfiltered recoverable lead 

(102–107 percent). Both the 95-percent confidence interval 

and mean spike recovery for these constituents indicate a 

persistent but minor, high bias. Because the mean spike recoveries for all constituents met data-quality objectives (less than 

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

the basis of spike recoveries.

Analytical results for field blanks are listed in table 19. 

A field blank with constituent concentrations equal to or less 

than the LRL for the analytical method indicates the entire 

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

than twice the LRL, the concentrations were noted during 

data review. Analytical results from the field blank for the 

next sample set were evaluated for a consistent trend that 

could indicate systematic contamination. Sporadic, infrequent 

exceedances of twice the LRL probably represented random 

contamination or instrument calibration error that was not 

persistent in the process and was not likely to cause positive 

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

concentrations for a particular constituent exceeded twice 

the LRL in field blanks from two consecutive field trips, 

blank samples were collected from individual components of 

the processing sequence and were submitted for analysis to 

identify the source of contamination.

Trace-element concentrations in field blanks (table 19) 

were almost always less than the LRL. Four detections 

exceeded twice the LRL in two separate samples. Three 

occurred on May 3, 2007, for filtered copper (3.6 μg/L), 

which was greater than the LRL of 0.4 μg/L; filtered lead 

(0.39 μg/L), which was greater than the LRL of 0.12 μg/L; 
Bed-Sediment Data 11

and filtered zinc (6.7 μg/L), which was greater than the LRL 

of 0.60. The fourth detection of more than twice the LRL 

occurred on June 27, 2007, for filtered zinc (2.8 μg/L). No 

adjustments were made to water-quality sample results on the 

basis of these four detections because no trends were indicated 

in blank samples for subsequent sampling trips.

Although random in occurrence, the relatively large 

magnitude of detectable concentrations (about 3–10 times 

the LRL) in blank samples was notable. Anomalous high 

concentrations for several filtered trace elements relative to 

the unfiltered concentrations, previous results for the site, 

and ambient flow conditions at the time of sampling were 

observed throughout the June–August 2007 period. Analytical reruns were requested for trace elements with questionable 

concentrations. The reruns produced more reasonable values 

in many cases, but were unable to resolve discrepancies in 

some samples. Where trace-element concentrations could not 

be considered reliable, they were deleted from the database 

and are indicated in table 4 by dashes (--). Almost all of the 

deleted trace-element concentrations are for filtered analyses 

and include 1 value for filtered arsenic, 8 values for filtered 

cadmium, 2 values for filtered copper, 1 value for filtered lead, 

and 2 values for filtered zinc; 1 value also was deleted for 

unfiltered recoverable iron.

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 in this report. 

Bed-sediment samples were collected once annually at 12 sites 

(fig. 1 and table 1) during low, stable flow conditions at about 

the same time of year (typically August) as previous samples 

to facilitate data comparisons among years. One site, Warm 

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

rather than once annually.

Methods

Fine-grained bed-sediment samples were collected in 

August 2007 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.

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 by using a hot, concentrated, nitric acid reflux 

according to methods described by Luoma and Bryan (1981). 

An additional aliquot was analyzed from one of the sieved 

replicate samples at each station. After a 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 by 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 2007 

are listed in table 20. 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, by 

using the following equation:

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

(dry weight of sample, in grams)(dilution ratio) . (5)

The reported solid-phase concentrations listed in table 20 

are the means of all analyses for replicate aliquots from each 

composite bed-sediment sample collected at the site. Because 

the conversion from liquid-phase to solid-phase concentration 

is dependent on both the dilution ratio and the dry weight of 

the sample, minimum reporting levels for some trace elements 

might differ among stations and among years.
12 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Quality Assurance

The protocols for field collection and processing of 

bed-sediment samples are designed to prevent contamination 

from metal sources. Nonmetallic sampling and processing 

equipment was acid-washed and rinsed with deionized water 

prior to the first sample collection. 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 betweensite cleaning. Bed-sediment samples were collected sequentially at sites along an increasing concentration gradient to 

minimize effects from potential site-to-site carryover contamination.

Quality assurance of analytical results for bed-sediment 

samples included laboratory instrument calibration with 

standard solutions and analysis of quality-control samples 

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

Axtmann, U.S. Geological Survey, written commun., 1994). 

Quality-control samples consisted of standard reference 

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

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

SRMs are commercially prepared materials that have 

certified concentrations of trace elements. Analyses of SRMs 

are used to indicate the ability of the method to accurately 

measure a known quantity of a constituent. Multiple analyses 

of 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 21. 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 21) illustrate analytical performance. 

For copper, iron, manganese, nickel, and zinc, mean SRM 

recoveries for the low-concentration standard (SRM 2709) 

ranged from 85.1 to 100.5 percent of the certified concentrations. Mean recoveries were lower for arsenic and chromium 

(72.7 and 74.5 percent, respectively) and higher for lead 

(119.4 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 80.7 to 95.7 percent of 

the certified concentrations. Chromium had a lower recovery 

(63.9 percent) for the high-concentration standard, possibly because of the strong binding nature of this element to 

sediment. The generally small range of variation (less than 

10 percent for all constituents) for the 95-percent confidence 

interval indicates good reproducibility of multiple analyses 

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

concentrations in bed-sediment samples on the basis of recovery efficiencies.

Procedural blanks for bed-sediment samples consisted of 

the same reagents used for sample digestion and reconstitution. Concentrated nitric acid used for sample digestion was 

heated and evaporated to dryness. After evaporation, 0.6N 

hydrochloric acid was added to reconstitute the dry residue. 

Procedural blanks, therefore, represent the same chemical 

matrix and exposure to analytical materials and handling as 

the reagents used to digest and reconstitute bed-sediment 

samples. Analytical results of procedural blanks for bed 

sediment (table 22) are reported as a liquid-phase concentration, in micrograms per milliliter, which is equivalent to parts 

per million. A procedural blank was prepared and analyzed 

concurrently with bed-sediment samples for each site. 

Concentrations of trace elements in all procedural blanks were 

less than the minimum reporting level; thus, no contamination 

bias was indicated and no adjustments to the data were necessary.

Biological Data

Biological data for the long-term monitoring program 

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

benthic insects. Insect samples were collected once annually 

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

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

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

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

once every 3 years rather than once annually.
Biological Data 13

Methods

Insect samples were collected using protocols described 

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

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

single riffle at each station was sampled repeatedly until an 

adequate number of individual insects was collected to provide 

sufficient mass for analysis. Targeted taxa for collection were 

the Order Trichoptera (caddisflies) and the Order Plecoptera 

(stoneflies).

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. During 1999–2007, samples were 

immediately frozen on dry ice in the field to reduce the possibility of metal loss through intracellular breakdown during 

depuration. A comparison of immediately frozen to depurated 

samples showed that although no substantial difference 

occurred for most metals, concentrations of copper were about 

20 percent lower in the depurated macroinvertebrate samples 

than in the samples that were immediately frozen. The data 

were not adjusted for this difference.

Insect samples were processed and analyzed at the 

USGS National Research Program Ecology and Contaminants 

Project laboratory in Menlo Park, Calif. Insects were thawed 

and rinsed with 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 2007 are listed in 

table 23. The variability in the number of composite samples 

among species and among sites reflects differences in insect 

abundance, with the number of composite samples increasing with the relative abundance of insects. Liquid-phase 

concentrations, in micrograms per milliliter, analyzed in the 

reconstituted samples were converted to solid-phase concentrations, in micrograms per gram, by using equation 4. As with 

minimum reporting levels for trace elements in bed sediment, 

minimum reporting levels for trace elements in insects may 

differ among sites as a result of varied sample weights. In 

general, the smaller the biological-sample weight (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 main-stem 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 24. 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 93.8 to 

106 percent for arsenic, cadmium, copper, iron, manganese, nickel and zinc. A lower mean recovery was measured 

for lead (91.0 percent), with 3 of the 12 analyses having 

concentrations less than or very near the minimum reporting level. A high mean recovery was measured for chromium 
14 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

(140 percent). With the exception of chromium and lead, 

both of which had low certified concentrations in the SRM 

(0.77 μg/g and 0.35 μg/g, respectively), the range of variation 

of the 95-percent confidence interval was within 10 percent, 

indicating reasonable recoveries in the SRM. No adjustments 

were made to the biota samples on the basis of trace element 

recovery efficiencies.

Procedural blanks for biota consisted of the same 

reagents used to digest and reconstitute tissue of aquatic 

insects and were analyzed undiluted. Analytical results of 

procedural blanks for biota (table 25) are reported as a liquidphase concentration, in micrograms per milliliter, which 

is equivalent to parts per million. A procedural blank was 

prepared and analyzed concurrently with biota samples for 

each site. Concentrations of trace elements in all procedural 

blanks were less than the minimum reporting level; therefore, 

no adjustments to the data were necessary.

Statistical Summaries of Data

Statistical summaries of long-term water-quality, 

bed-sediment, and biological data for the upper Clark Fork 

basin are listed in tables 26 through 28 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 26) are based on results of cross-section samples 

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

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

supplemental samples collected at selected sites. Inclusion 

of results for supplemental samples that targeted high-flow 

conditions or maintenance drawdowns of Milltown Reservoir 

would disproportionately skew the long-term statistics relative 

to the other sites in the network. Statistical summaries of finegrained bed-sediment (table 27) and biological data (table 28) 

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 27) 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 28) 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 varied 

minimum reporting levels. Where minimum reporting levels 

vary among years, differences in concentration with time are 

difficult to determine, especially when a large percentage of 

the samples have concentrations less than minimum reporting 

levels.

The presence or absence of insect species at a given site 

can vary among years and may result in different taxa being 

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

1986–89, statistics for stations sampled during those years are 

based on the results of all Hydropsyche species combined. At 

some sites, statistics for the Hydropsyche morosa group are 

based on the combined results for two or more species because 

these samples could not be clearly identified to the species 

level, but the individual insects had morosa characteristics.

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/.

Andrews, E.D., 1987, Longitudinal dispersion of trace metals 

in the Clark Fork River, Montana, in Averett, R.C., and 

McKnight, D.M., eds., Chemical Quality of water and the 

hydrologic cycle: Chelsea, Mich., Lewis Publishers, 

p 179–191.

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. 2736–2746.
References Cited 15

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

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

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

p. 2141–2154.

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

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

method detection levels and some considerations for 

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

Geological Survey National Water Quality Laboratory: U.S. 

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

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.

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 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.; 

available at http://pubs.usgs.gov/of/2005/1356/.

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. 

available at http://pubs.usgs.gov/of/2006/1266/.

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2007, Waterquality, 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.; available at http://pubs.usgs.gov/of/2007/1301/.

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., 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.usgs.gov/

of/2006/1242/.

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

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 OpenFile 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 wholewater digests using inductively coupled plasma-optical 

emission spectrometry and inductively coupled plasmamass 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. 1997–2004.

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

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

Water Quality Laboratory—In-bottle acid digestion of 

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

Report 96–225, 28 p.

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

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

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

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

Open-File Report 97–669, 84 p.

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

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

for the collection and processing of surface-water samples 

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

Report 94–539, 57 p.

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

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 WaterResources 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.
References Cited 17

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 Envi-

ronment, 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 Investigations 

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 Labora-

tory: U.S. Geological Survey Open-File Report 95–443, 

35 p.

Rantz, S.E., and others, 1982, Measurement and computa-

tion of streamflow: U.S. Geological Survey Water-Supply 

Paper 2175, 2 v., 631 p.

Taylor, J.K., 1987, Quality assurance of chemical measure-

ments: Chelsea, Mich., Lewis Publishers, 328 p.

U.S. Environmental Protection Agency, 2004, Milltown 

Reservoir Sediments Operational Unit of the Milltown 

Reservoir/Clark Fork River Superfund Site—Record of 

Decision, Part 2: Decision Summary, 142 p., accessible at 

http://www.epa.gov/region8/superfund/sites/mt/milltown/

mrsrod.html

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 computa-

tion, 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.

Data
20 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 2006 through September 2007.

[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)

11/13/2006 0900 6.2 7.7 288 4.0 120 34.4 7.95

02/26/2007 0900 4.9 7.7 317 2.5 120 34.1 9.07

03/26/2007 0945 12 7.7 227 3.5 90 25.9 6.24

05/10/2007 0725 11 7.7 240 10.0 93 27.1 6.29

06/05/2007 0840 18 7.7 216 13.5 83 24.3 5.53

06/19/2007 0655 20 7.6 208 10.0 84 23.9 5.82

07/24/2007 0705 4.3 7.5 341 12.0 140 38.6 9.57

08/27/2007 1540 3.4 8.0 331 14.5 130 37.4 9.07

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)

11/13/2006 1.9 2.4 E0.03 0.03 1.5 3.1 137 388

02/26/2007 1.7 2.4 .04 .04 1.4 4.7 122 565

03/26/2007 3.7 4.7 .05 .03 2.9 4.8 378 675

05/10/2007 4.9 5.6 E.02 .03 3.6 4.9 214 481

06/05/2007 7.3 8.8 -- .03 4.4 6.0 297 673

06/19/2007 7.2 8.6 E.03 .04 4.2 6.0 289 631

07/24/2007 -- 4.4 -- .03 -- 2.2 82 235

08/27/2007 2.9 3.1 E.03 .03 1.2 1.8 25 220

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)

11/13/2006 E0.06 0.32 44.6 47.6 3.4 6 80 5 0.08

02/26/2007 E.06 .75 44.4 60.3 3.2 6 89 9 .12

03/26/2007 .30 .78 54.5 61.2 2.4 4 81 5 .16

05/10/2007 .14 .44 37.4 47.4 1.8 2.6 86 3 .09

06/05/2007 .17 .52 30.2 42.6 2.0 3.2 82 6 .29

06/19/2007 .19 .51 31.5 42.3 1.8 3.0 83 5 .27

07/24/2007 <.12 .17 54.5 59.6 -- 2.1 93 1 .01

08/27/2007 <.12 .57 27.8 32.5 .82 2.9 76 4 .04
Data 21

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

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/13/2006 1045 19 7.4 513 4.5 180 50.3 12.2

02/26/2007 1030 19 7.6 542 5.0 160 44.4 12.4

03/26/2007 1110 28 7.7 433 5.5 140 38.7 9.42

05/10/2007 0850 25 7.7 423 11.0 130 37.8 9.03

06/05/2007 0925 33 7.6 373 14.0 120 35.4 8.19

06/19/2007 0825 33 7.7 366 10.5 120 34.6 8.37

07/24/2007 0815 15 7.5 564 17.0 160 47.2 11.4

08/27/2007 1505 15 7.7 575 17.5 170 49.5 11.8

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/13/2006 3.6 4.5 0.12 0.22 8.9 18.7 35 347

02/26/2007 3.0 4.1 .16 .26 13.0 24.5 35 337

03/26/2007 3.7 4.9 .11 .14 12.2 19.3 148 453

05/10/2007 5.1 6.3 .12 .20 12.4 22.1 110 528

06/05/2007 6.8 8.3 .20 .21 12.7 19.7 161 600

06/19/2007 6.6 8.2 .08 .14 11.3 16.7 169 543

07/24/2007 4.8 5.5 .15 .15 9.5 13.3 29 120

08/27/2007 4.8 5.4 .07 .12 8.5 10.5 17 89

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)

11/13/2006 0.15 1.99 145 160 46.3 58 83 7 0.36

02/26/2007 .27 2.30 122 139 60.7 75 83 9 .46

03/26/2007 .26 1.52 109 118 36.0 47 89 6 .45

05/10/2007 .33 3.47 108 139 41.8 59.3 94 10 .68

06/05/2007 .35 2.53 86.3 114 36.0 45.5 88 8 .71

06/19/2007 .27 1.73 79.6 97.1 30.9 41.5 90 7 .62

07/24/2007 .24 .66 58.9 70.9 50.4 51.6 87 2 .08

08/27/2007 .18 .71 32.9 49.8 36.4 38.3 76 3 .12

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

11/14/2006 0800 34 8.3 499 0.5 180 54.7 11.5

02/26/2007 1505 32 8.3 522 1.5 170 49.1 12.1

03/27/2007 1120 59 8.3 414 5.0 140 42.3 9.04

05/09/2007 1105 59 8.5 391 11.0 150 44.1 8.65

06/05/2007 1425 80 8.3 361 14.5 130 39.4 7.70

06/19/2007 0935 81 8.3 352 11.0 130 37.9 7.99

07/24/2007 0935 25 8.5 528 19.5 190 55.3 11.8

08/28/2007 0720 15 8.1 619 10.0 220 63.4 14.1

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)

11/14/2006 8.0 10.6 0.55 0.96 18.9 65.4 20 552

02/26/2007 8.0 10.1 .77 .94 25.5 61.4 16 420

03/27/2007 9.1 13.8 .56 1.49 24.2 63.7 38 650

05/09/2007 9.5 12.4 .24 .60 18.6 59.5 39 618

06/05/2007 10.8 14.6 .22 .69 17.3 72.5 44 827

06/19/2007 11.3 15.2 .24 .65 21.8 68.7 71 757

07/24/2007 18.5 19.5 .27 .70 18.9 65.7 22 456

08/28/2007 13.1 12.2 -- .57 -- 31.1 14 --

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)

11/14/2006 0.25 10.7 216 268 214 274 92 16 1.5

02/26/2007 .27 8.60 264 334 194 251 74 13 1.1

03/27/2007 .37 14.2 260 284 142 217 79 17 2.7

05/09/2007 .33 13.1 126 223 49.4 136 86 20 3.2

06/05/2007 .58 16.9 115 223 47.5 139 84 23 5.0

06/19/2007 .70 14.9 104 169 67.2 142 85 21 4.6

07/24/2007 .51 12.9 87.4 182 35.8 120 81 16 1.1

08/28/2007 .36 5.66 121 165 -- 110 84 6 .24

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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 23

12323670--Mill Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/13/2006 1400 19 <2.0 8.3 144 2.5 68 18.9 5.03

02/26/2007 1200 9.1 2.6 8.3 191 1.0 85 22.5 6.99

03/26/2007 1350 21 <2.0 8.1 140 5.5 62 17.1 4.71

05/09/2007 1505 70 <2.0 8.0 97 12.0 38 11.0 2.65

06/04/2007 1650 122 <2.0 7.9 77 14.5 29 8.69 1.88

06/18/2007 1345 75 <2.0 7.8 91 10.0 37 10.7 2.50

07/23/2007 1320 21 <2.0 8.0 150 17.0 68 18.8 5.21

08/27/2007 1125 12 <2.0 8.3 186 11.5 83 22.4 6.62

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)

11/13/2006 11.7 12.6 <0.04 0.05 1.3 2.0 67 126

02/26/2007 9.5 10.2 E.03 .04 .79 1.4 36 89

03/26/2007 15.0 16.6 .05 .05 2.2 3.5 46 163

05/09/2007 17.8 19.1 E.03 .07 3.0 4.7 36 166

06/04/2007 17.0 18.5 -- .09 2.3 5.2 29 204

06/18/2007 17.2 18.8 .04 .07 1.8 3.4 35 124

07/23/2007 30.3 29.8 .07 .08 2.1 5.3 125 203

08/27/2007 23.6 23.6 E.03 .06 1.3 2.0 77 149

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/13/2006 E0.08 0.23 7.5 10.3 1.2 E2 64 2 0.10

02/26/2007 <.12 .19 6.9 8.8 1.0 E1 70 1 .02

03/26/2007 E.11 .56 5.5 10.8 .91 2 75 3 .17

05/09/2007 .16 .78 3.6 11.5 1.9 3.2 60 5 .95

06/04/2007 E.11 1.05 3.6 11.0 1.3 3.4 49 7 2.3

06/18/2007 E.07 .59 4.3 9.4 .97 2.4 64 4 .81

07/23/2007 .22 .72 7.1 15.6 .95 2.2 76 3 .17

08/27/2007 .14 .45 7.8 13.6 1.7 2.6 71 2 .06

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

11/13/2006 1630 12 8.1 164 2.5 73 20.6 5.36

02/26/2007 1340 E5.0 8.2 217 0.5 94 25.4 7.42

03/26/2007 1620 5.5 8.1 161 7.5 69 19.0 5.11

05/09/2007 1035 35 8.0 107 9.0 42 11.9 2.93

06/05/2007 1140 103 7.8 75 10.5 30 8.65 1.93

06/18/2007 1530 40 8.0 99 11.5 41 11.7 2.75

07/23/2007 1530 6.3 8.1 168 20.0 71 19.6 5.37

08/27/2007 1340 .83 8.0 199 15.0 84 23.4 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)

11/13/2006 20.6 21.0 0.06 0.11 1.9 2.8 74 129

02/26/2007 14.0 14.6 .05 .07 1.1 1.7 28 68

03/26/2007 17.9 19.8 E.02 .07 2.5 3.3 30 95

05/09/2007 22.9 25.0 .06 .12 4.0 6.6 34 212

06/05/2007 20.3 29.5 .13 .32 3.9 17.4 36 959

06/18/2007 23.1 25.2 .07 .12 2.6 6.3 42 233

07/23/2007 55.1 53.5 .07 .09 2.6 3.5 94 155

08/27/2007 26.4 27.8 .05 .07 1.6 2.2 42 115

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)

11/13/2006 0.12 0.26 5.6 8.0 4.2 5 71 2 0.06

02/26/2007 <.12 .13 2.2 3.5 2.4 2 86 1 E.01

03/26/2007 E.07 .26 4.1 5.8 2.2 3 67 2 .03

05/09/2007 .16 1.14 3.1 14.0 2.8 5.7 67 6 .57

06/05/2007 .12 4.54 5.1 49.2 3.4 15.9 47 49 14

06/18/2007 .16 1.12 4.8 13.6 2.1 5.1 60 8 .86

07/23/2007 .20 .42 5.7 9.3 1.3 E1.9 82 1 .02

08/27/2007 <.12 .30 9.3 12.5 1.6 2.2 75 2 <.01

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

11/13/2006 1230 2.2 <2.0 7.6 110 0.5 41 14.0 1.55

03/26/2007 1245 5.5 5.7 7.6 99 2.0 37 12.4 1.38

05/09/2007 1605 15 7.6 7.7 81 12.0 27 9.29 1.03

06/04/2007 1520 19 5.1 7.8 88 13.0 31 10.7 1.12

06/18/2007 1250 11 2.7 7.8 100 9.5 35 11.9 1.32

07/23/2007 1230 3.3 <2.0 7.8 109 15.5 39 13.3 1.44

08/27/2007 1045 1.9 <2.0 7.8 111 9.0 38 12.8 1.41

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)

11/13/2006 11.8 11.8 <0.04 0.04 1.3 1.9 82 136

03/26/2007 13.6 14.7 E.03 .04 2.3 3.2 86 302

05/09/2007 14.0 14.6 E.03 .08 2.2 4.3 64 573

06/04/2007 14.2 14.6 E.03 .06 1.9 3.5 63 344

06/18/2007 12.3 13.3 E.03 .04 1.3 2.4 69 206

07/23/2007 16.9 16.2 -- .04 1.2 1.5 54 111

08/27/2007 15.5 15.3 E.02 .02 .96 E1.0 51 106

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)

11/13/2006 E0.07 0.16 25.1 27.1 1.2 E1 88 2 0.01

03/26/2007 .16 .57 14.9 22.8 1.8 2 80 6 .09

05/09/2007 .17 1.36 11.2 31.6 1.2 4.5 49 31 1.3 

06/04/2007 .13 .83 10.6 20.0 .96 2.7 56 13 .67

06/18/2007 E.07 .38 14.7 21.4 .81 E1.7 80 5 .15

07/23/2007 E.07 .22 11.9 19.1 .75 E1.1 94 1 .01

08/27/2007 E.07 .21 13.2 18.1 .65 E1.3 74 2 .01

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

11/13/2006 1700 6.2 8.1 311 5.0 140 39.8 9.28

02/26/2007 1415 4.7 8.2 322 3.0 130 37.0 9.42

03/26/2007 1650 6.8 8.4 266 10.0 110 32.6 7.28

05/09/2007 1145 17 8.0 222 12.5 91 27.3 5.51

06/05/2007 1220 25 7.9 214 14.5 90 27.1 5.37

06/18/2007 1600 22 8.0 259 14.5 110 33.1 7.44

07/23/2007 1600 7.4 8.4 306 20.5 140 39.6 9.12

08/27/2007 1405 5.9 8.5 310 16.0 130 38.7 9.31

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)

11/13/2006 17.4 20.9 <0.04 0.15 1.3 13.5 18 482

02/26/2007 11.6 13.5 E.02 .07 1.1 6.0 29 231

03/26/2007 24.1 27.4 E.02 .07 3.0 6.6 43 242

05/09/2007 54.2 56.8 E.03 .13 9.1 19.4 70 400

06/05/2007 62.4 64.8 .07 .15 8.8 17.3 96 394

06/18/2007 46.6 48.0 .04 .09 5.0 9.0 49 204

07/23/2007 44.1 45.3 .04 .05 3.0 4.9 23 156

08/27/2007 22.0 21.5 E.02 .03 2.2 3.1 8 71

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)

11/13/2006 0.16 5.10 60.4 73.9 3.0 19 92 19 0.32

02/26/2007 .15 1.94 63.9 72.2 3.7 10 92 5 .06

03/26/2007 .23 1.63 48.9 56.0 2.7 7 86 7 .13

05/09/2007 .37 3.38 34.3 53.3 6.5 18.3 77 19 .87

06/05/2007 .40 2.72 27.5 44.3 6.0 15.5 77 13 .88

06/18/2007 .20 1.55 16.5 25.3 3.5 10.2 65 7 .42

07/23/2007 .12 1.12 10.7 23.5 .98 3.9 90 4 .08

08/27/2007 E.06 .64 6.4 11.7 .84 2.6 79 3 .05

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

11/14/2006 0920 64 8.4 530 1.0 230 66.3 15.2

02/26/2007 1550 54 8.6 605 3.0 240 69.1 16.6

03/27/2007 1220 50 8.5 557 7.0 240 69.5 15.2

05/09/2007 0930 150 8.3 451 13.5 180 51.5 11.9

06/05/2007 1535 249 9.2 333 13.5 130 38.0 8.54

06/19/2007 1010 155 9.2 460 13.0 190 56.0 11.9

07/24/2007 1030 33 9.0 503 20.0 210 61.5 13.7

08/28/2007 0815 25 8.6 598 12.5 250 73.0 16.5

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)

11/14/2006 12.4 16.8 0.04 0.27 1.7 14.6 12 427

02/26/2007 12.6 14.6 .11 .17 4.1 8.7 9 218

03/27/2007 10.1 13.0 E.03 .08 2.1 6.2 8 230

05/09/2007 20.7 23.4 E.03 .10 3.1 6.9 20 263

06/05/2007 26.7 30.1 .05 .16 5.2 12.6 24 449

06/19/2007 29.4 30.5 .04 .10 5.3 8.6 17 144

07/24/2007 36.4 37.1 .04 .06 3.0 4.5 8 101

08/28/2007 33.6 34.8 E.02 .03 2.0 2.4 E6 56

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)

11/14/2006 E0.09 3.24 96.1 147 3.6 29 96 7 1.2

02/26/2007 <.12 1.11 205 242 7.5 17 85 5 .73

03/27/2007 <.12 1.48 176 239 3.6 11 90 5 .68

05/09/2007 .13 1.33 180 224 3.6 10.9 87 7 2.8 

06/05/2007 .12 2.23 37.0 94.4 1.2 12.2 86 13 8.7 

06/19/2007 E.11 .75 98.4 127 3.0 6.3 86 4 1.7 

07/24/2007 <.12 .55 28.4 85.6 .98 3.1 76 3 .27

08/28/2007 <.12 .28 32.5 55.5 1.1 2.1 67 2 .14

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

11/13/2006 1545 65 <2.0 8.7 247 4.5 120 37.0 7.79

03/26/2007 1515 41 <2.0 8.7 264 8.0 130 38.6 8.47

05/09/2007 1310 145 <2.0 8.4 182 8.5 84 25.6 4.83

06/12/2007 1020 391 2.3 8.1 140 7.0 66 20.5 3.64

07/23/2007 1400 85 2.3 8.5 230 14.0 110 32.3 6.83

08/27/2007 1240 62 <2.0 8.5 255 10.5 120 36.3 7.84

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)

11/13/2006 1.9 2.0 <0.04 0.03 0.57 1.3 E6 45

03/26/2007 2.4 2.7 E.02 .02 .86 2.1 <6 75

05/09/2007 2.0 2.3 <.04 .04 1.1 3.3 7 125

06/12/2007 2.7 3.2 <.04 .05 1.4 4.7 13 237

07/23/2007 2.8 3.0 E.02 .07 .87 2.1 13 79

08/27/2007 2.6 2.6 E.02 .03 .62 E1.1 E5 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)

11/13/2006 <0.12 0.12 0.5 1.8 0.84 E1 67 2 0.35

03/26/2007 <.12 .26 .8 3.3 E.54 E2 71 4 .44

05/09/2007 <.12 .47 .9 5.1 1.2 2.7 57 6 2.3 

06/12/2007 <.12 .62 2.1 11.3 1.3 5.5 51 17 18

07/23/2007 <.12 .28 1.1 4.1 1.4 2.7 61 4 .92

08/27/2007 <.12 .23 .8 4.3 E.48 E1.6 67 3 .50

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

11/14/2006 0900 46 8.4 321 2.0 160 49.6 9.22

03/27/2007 1200 34 8.5 358 5.5 180 54.7 10.2

05/09/2007 0905 99 8.2 243 8.5 110 35.1 6.45

06/12/2007 1130 250 8.0 166 9.0 77 23.9 4.20

07/24/2007 1010 52 8.2 291 14.5 140 41.6 8.01

08/28/2007 0755 39 8.1 329 9.5 150 46.8 9.13

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/14/2006 3.3 3.7 <0.04 0.06 1.6 5.9 12 76

03/27/2007 4.2 4.5 <.04 .05 2.0 5.9 9 75

05/09/2007 4.1 6.1 E.03 .10 2.7 23.0 10 357

06/12/2007 5.1 7.2 E.02 .09 3.7 21.3 15 381

07/24/2007 5.6 5.7 .05 .05 1.8 4.7 11 63

08/28/2007 4.4 4.9 E.03 .05 1.8 6.2 11 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)

11/14/2006 <0.12 0.34 158 194 3.0 3 61 4 0.50

03/27/2007 <.12 .37 150 174 .90 3 68 4 .37

05/09/2007 <.12 2.09 72.9 201 1.2 8.9 65 20 5.3 

06/12/2007 <.12 1.88 44.9 113 5.1 9.1 68 20 14

07/24/2007 <.12 .31 78.7 108 .73 E1.7 71 3 .42

08/28/2007 <.12 .43 100 155 1.0 2.3 59 3 .32

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

11/14/2006 1045 101 8.6 447 2.0 200 60.0 13.1

02/27/2007 1120 81 8.5 514 1.0 210 62.0 14.1

03/27/2007 1340 87 8.4 480 6.0 210 63.1 13.2

05/08/2007 1315 225 8.4 377 12.0 150 46.1 9.56

06/05/2007 1720 492 8.8 243 13.0 99 29.8 6.07

06/19/2007 1125 341 8.9 338 12.0 140 41.9 8.59

07/24/2007 1155 79 8.6 383 18.0 170 50.1 10.3

08/28/2007 0935 60 8.4 435 11.0 200 58.2 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)

11/14/2006 8.2 11.2 E0.02 0.17 1.7 10.9 9 256

02/27/2007 8.7 10.8 .07 .17 3.3 19.2 E6 327

03/27/2007 7.5 9.7 E.02 .08 2.7 9.3 10 199

05/08/2007 14.4 16.8 E.03 .08 3.7 14.6 15 290

06/05/2007 17.1 23.6 E.02 .23 5.7 56.4 21 968

06/19/2007 17.4 18.8 E.03 .10 4.1 13.4 16 229

07/24/2007 16.2 17.0 .04 .05 3.1 5.8 7 64

08/28/2007 16.5 16.9 E.03 .06 2.7 10.3 7 300

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)

11/14/2006 <0.12 1.86 109 149 2.9 16 90 4 1.1

02/27/2007 <.12 2.07 178 273 5.3 21 72 12 2.6

03/27/2007 <.12 1.25 151 207 3.7 10 83 5 1.2

05/08/2007 E.07 1.83 95.9 174 3.0 13.0 74 11 6.7

06/05/2007 E.10 6.79 52.9 258 1.2 29.2 68 48 64

06/19/2007 E.07 1.30 66.5 113 1.2 8.5 75 8 7.4

07/24/2007 <.12 .41 34.4 67.8 1.4 2.7 77 2 .43

08/28/2007 <.12 1.13 37.6 110 1.3 9.9 78 2 .32

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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 31

12323840--Lost Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/13/2006 1500 5.7 <2.0 8.4 222 3.0 110 32.5 6.45

02/26/2007 1240 3.2 <2.0 8.4 218 1.5 100 30.0 6.54

03/26/2007 1420 4.1 <2.0 8.4 213 6.0 100 31.3 6.44

05/09/2007 1410 5.2 4.3 8.3 200 11.5 92 28.0 5.43

06/04/2007 1720 12 <2.0 8.2 187 15.0 86 26.8 4.72

06/18/2007 1425 9.6 <2.0 8.2 197 11.5 91 27.8 5.18

07/23/2007 1455 .37 <2.0 8.2 244 17.0 110 34.6 6.44

08/27/2007 1155 6.8 <2.0 8.3 232 10.5 110 32.8 6.69

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)

11/13/2006 3.5 3.7 <0.04 0.04 1.4 4.1 10 87

02/26/2007 2.8 2.6 E.03 .03 1.2 2.1 E4 30

03/26/2007 2.9 3.2 .05 .03 1.6 3.2 E6 60

05/09/2007 5.1 5.7 E.03 .07 2.6 7.6 14 199

06/04/2007 10.8 10.8 -- .06 3.3 8.3 11 192

06/18/2007 10.2 10.7 E.02 .05 2.6 6.0 8 116

07/23/2007 12.1 11.7 .06 .07 3.1 6.0 6 109

08/27/2007 4.1 4.4 <.04 .04 1.1 2.2 11 62

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)

11/13/2006 <0.12 0.37 1.0 3.1 2.2 3 65 3 0.05

02/26/2007 <.12 .13 .4 1.3 1.0 E1 62 1 .01

03/26/2007 <.12 .26 .9 2.6 1.3 E2 64 4 .04

05/09/2007 <.12 1.55 1.1 6.5 1.1 3.7 58 9 .13

06/04/2007 <.12 .75 1.3 5.8 1.3 3.9 51 12 .39

06/18/2007 <.12 .59 1.2 4.6 1.1 3.0 36 9 .23

07/23/2007 <.12 .54 1.5 7.0 1.2 3.0 54 1 <.01

08/27/2007 <.12 .28 .7 3.6 .62 E1.8 56 4 .07

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

11/14/2006 1015 42 8.4 628 2.0 310 91.8 20.7

02/27/2007 1050 40 8.3 615 0.0 290 84.6 19.1

03/27/2007 1315 42 8.3 641 6.0 320 94.8 20.8

05/08/2007 1245 32 8.5 608 13.5 290 82.5 19.3

06/05/2007 1640 2.4 8.2 673 16.5 260 69.9 21.8

06/19/2007 1055 9.4 8.4 700 12.5 320 93.1 21.8

07/24/2007 1135 1.7 8.3 604 19.5 220 56.0 19.1

08/28/2007 0910 2.0 8.2 629 10.0 240 61.7 20.7

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)

11/14/2006 11.5 12.1 E0.02 0.05 1.4 4.0 7 71

02/27/2007 8.1 9.6 E.03 .09 .99 9.5 E5 293

03/27/2007 13.0 14.2 E.02 .06 2.2 6.3 14 126

05/08/2007 15.3 15.9 E.03 .04 2.3 5.5 10 114

06/05/2007 18.8 21.3 -- .04 2.5 4.8 36 167

06/19/2007 11.3 11.5 <.04 .03 1.3 3.4 12 68

07/24/2007 9.5 10.0 .04 .04 1.7 2.9 8 47

08/28/2007 6.0 6.1 E.03 .03 1.3 1.6 8 23

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)

11/14/2006 <0.12 0.23 5.5 8.3 2.1 4 51 37 4.2

02/27/2007 <.12 1.06 13.5 29.0 2.8 8 67 30 3.2

03/27/2007 <.12 .44 21.7 26.1 2.2 5 70 6 .68

05/08/2007 <.12 .38 13.0 19.1 1.1 2.6 59 21 1.8 

06/05/2007 -- .18 39.4 42.8 .87 E1.5 56 29 .19

06/19/2007 <.12 .19 9.7 13.6 E.59 E1.4 38 12 .30

07/24/2007 <.12 .13 7.3 11.6 .71 <2.0 71 3 .01

08/28/2007 <.12 E.06 6.1 6.8 E.58 <2.0 67 5 .03

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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 33

12324200--Clark Fork at Deer Lodge

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/14/2006 1200 224 8.5 503 2.5 230 68.8 15.3

02/27/2007 1240 208 8.4 504 0.0 220 63.5 14.1

03/27/2007 1450 204 8.3 505 6.5 220 67.1 13.9

05/08/2007 1130 286 8.2 442 12.5 190 56.0 12.2

06/04/2007 1030 414 8.2 307 15.5 130 37.9 7.54

06/18/2007 1105 459 8.3 350 13.0 140 42.2 8.62

07/23/2007 1100 61 8.4 462 19.5 190 56.9 11.8

08/27/2007 0845 73 8.1 500 12.0 210 63.9 13.2

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)

11/14/2006 9.8 12.0 0.04 0.15 4.0 16.7 8 270

02/27/2007 8.1 10.5 .06 .17 3.8 24.7 E6 420

03/27/2007 9.8 13.5 .07 .15 5.2 29.9 11 459

05/08/2007 15.1 21.0 .05 .27 6.8 53.7 16 814

06/04/2007 16.8 21.0 .07 .18 7.7 41.9 16 628

06/18/2007 16.1 20.6 .10 .20 8.1 39.5 16 553

07/23/2007 17.5 17.2 -- .06 7.7 11.6 6 50

08/27/2007 13.5 13.9 .04 .05 6.3 10.7 7 57

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)

11/14/2006 <0.12 1.82 45.1 70.7 7.0 20 86 8 4.8

02/27/2007 <.12 2.80 72.0 117 7.2 29 76 19 11

03/27/2007 E.10 3.68 74.8 143 7.0 30 83 18 9.9

05/08/2007 E.11 6.83 29.0 183 6.1 45.0 76 34 26

06/04/2007 E.08 4.97 22.8 130 4.6 31.4 81 23 26

06/18/2007 E.10 4.69 32.6 119 5.0 28.9 71 23 29

07/23/2007 <.12 .47 16.9 31.7 3.5 6.4 75 2 .33

08/27/2007 <.12 .53 11.6 29.1 5.9 8.4 73 3 .59

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

11/14/2006 1400 390 8.9 433 3.0 200 60.4 13.0

02/27/2007 1415 317 8.8 460 0.0 200 57.7 13.1

03/27/2007 1600 501 8.6 374 5.5 170 51.0 10.5

05/08/2007 0930 725 8.3 347 10.0 150 43.2 9.36

06/06/2007 0720 1,730 8.1 268 12.0 110 32.5 7.01

06/19/2007 1305 944 8.5 327 14.5 140 40.6 8.53

07/24/2007 1325 202 8.6 384 20.0 160 49.1 10.3

08/28/2007 1055 140 8.5 436 14.5 190 54.5 12.1

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)

11/14/2006 9.1 9.9 0.04 0.09 3.6 12.5 E6 170

02/27/2007 7.5 8.7 .05 .11 3.5 16.5 E5 254

03/27/2007 7.2 9.1 <.04 .11 3.9 19.0 10 384

05/08/2007 9.8 13.8 E.03 .20 4.9 38.3 25 726

06/06/2007 11.9 20.8 .04 .32 10.0 79.4 30 1,580

06/19/2007 11.2 13.8 E.03 .12 6.0 24.5 14 404

07/24/2007 10.7 10.9 .04 .04 3.9 5.4 E3 34

08/28/2007 10.9 10.9 E.03 .04 4.2 5.9 E4 42

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)

11/14/2006 <0.12 1.20 15.3 46.8 2.2 12 89 7 7.4

02/27/2007 <.12 1.70 37.6 72.7 4.2 19 79 12 10

03/27/2007 E.06 2.73 24.7 73.9 2.7 19 85 16 22

05/08/2007 E.09 5.09 10.8 135 4.1 35.9 74 37 72

06/06/2007 .14 10.8 12.9 177 5.2 62.1 64 92 430

06/19/2007 E.06 2.76 17.9 71.5 2.7 20.0 78 16 41

07/24/2007 <.12 .16 5.8 17.6 1.1 2.3 70 1 .55

08/28/2007 <.12 .26 8.1 34.4 1.7 3.6 66 2 .76

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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 35

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)

11/14/2006 1500 573 8.7 459 5.0 220 62.7 14.8

02/27/2007 1525 460 8.4 478 3.0 210 59.4 14.5

03/28/2007 0850 720 8.3 401 5.5 180 53.5 12.1

05/08/2007 0815 1,030 8.2 356 11.5 150 44.0 10.8

06/07/2007 1140 3,160 8.2 293 9.0 120 34.8 8.26

06/19/2007 1425 1,410 8.3 352 15.5 150 44.7 10.1

07/24/2007 1440 298 8.6 463 21.0 210 57.5 15.2

08/28/2007 1215 232 8.4 573 16.5 250 71.4 18.0

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)

11/14/2006 8.4 9.2 E0.02 0.08 2.9 9.7 E4 188

02/27/2007 7.4 8.5 .06 .12 3.3 14.3 E4 276

03/28/2007 6.9 10.0 E.03 .14 3.5 20.0 10 532

05/08/2007 9.7 14.6 .04 .22 4.8 38.2 11 913

06/07/2007 18.0 41.3 .07 1.02 16.0 170 54 4,450

06/19/2007 12.6 16.3 .05 .20 6.1 26.2 39 657

07/24/2007 11.5 11.6 E.03 .05 3.9 5.5 <6 26

08/28/2007 11.1 11.3 E.03 .07 3.1 5.9 <6 81

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)

11/14/2006 <0.12 1.32 11.0 44.4 2.6 12 79 12 19

02/27/2007 E.06 1.84 27.6 64.4 5.6 20 80 13 16

03/28/2007 E.07 3.80 18.0 91.3 4.0 30 74 27 52

05/08/2007 E.11 7.15 7.8 156 4.0 47.6 72 54 150

06/07/2007 .58 31.0 30.9 507 9.5 200 59 315 2,690

06/19/2007 .13 5.24 27.5 111 4.2 32.8 67 37 141

07/24/2007 <.12 .18 3.3 13.5 .95 2.9 71 7 5.6

08/28/2007 <.12 .67 11.7 53.6 2.1 7.4 82 9 5.6

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

*10/17/2006 1100 840 8.5 401 7.0 190 54.0 13.2 0.32

11/14/2006 1630 944 8.7 355 4.0 170 46.8 11.8 --

02/27/2007 1640 697 8.8 396 3.0 170 49.2 12.6 --

03/28/2007 1100 1,240 8.4 291 5.5 130 36.4 9.19 --

*04/09/2007 1130 1,080 8.1 322 8.0 140 40.2 10.3 .37

*04/23/2007 1030 1,240 8.3 331 9.5 150 42.6 11.1 .45

*05/03/2007 1100 2,700 8.1 168 8.0 76 21.4 5.46 .68

05/07/2007 1445 2,530 8.3 218 11.0 94 26.5 6.78 --

*05/14/2007 1100 3,340 8.1 166 10.0 72 20.4 5.11 .37

*05/22/2007 1100 3,360 8.0 174 7.0 75 21.4 5.33 .29

*05/31/2007 1230 3,360 8.2 222 13.0 98 27.6 6.92 .36

*06/06/2007 1100 3,670 8.2 197 11.5 85 24.4 5.95 .42

06/07/2007 1455 4,980 8.2 214 10.0 92 26.0 6.61 --

*06/12/2007 1030 5,390 8.0 219 12.5 96 27.2 6.87 .41

*06/19/2007 1230 3,390 8.3 249 13.0 110 31.1 7.70 .26

06/20/2007 0900 3,080 8.2 257 14.0 110 31.6 7.84 --

*06/26/2007 1030 2,180 8.4 278 12.0 130 36.0 9.34 .19

07/24/2007 1605 690 8.8 285 21.5 120 32.8 9.88 --

08/28/2007 1330 451 8.6 367 15.5 160 43.9 12.2 --

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)

*10/17/2006 0.041 6.7 7.9 <0.04 0.14 2.0 13.6 E5 296

11/14/2006 -- 5.6 6.0 E.02 .05 2.3 5.8 E5 114

02/27/2007 -- 5.6 6.2 .04 .08 2.6 9.0 11 145

03/28/2007 -- 4.4 5.8 .04 .09 2.9 12.3 13 327

*04/09/2007 .043 5.5 6.4 E.02 .08 3.3 12.6 10 287

*04/23/2007 .059 6.6 8.1 E.02 .12 7.8 18.4 13 472

*05/03/2007 .129 4.4 8.1 E.02 .24 3.6 30.7 26 1,340

05/07/2007 -- 5.2 7.3 E.03 .13 3.7 21.5 29 563

*05/14/2007 .059 4.7 6.8 E.02 .11 3.2 18.3 20 585

*05/22/2007 .051 4.2 5.9 E.02 .11 2.8 16.7 19 505

*05/31/2007 .066 7.4 10.3 E.02 .15 4.7 25.3 15 696

*06/06/2007 .076 6.8 10.5 E.02 .19 3.8 26.6 21 832

06/07/2007 -- 10.3 19.6 .04 .52 12.7 78.5 48 2,460

*06/12/2007 .092 9.5 13.2 E.02 .20 6.2 34.8 19 1,110

*06/19/2007 .046 7.7 9.0 E.02 .10 3.9 15.6 13 381

06/20/2007 -- 7.4 9.2 E.03 .10 3.5 15.5 40 399

*06/26/2007 .026 7.2 7.1 <.04 .05 3.2 6.9 12 142

07/24/2007 -- 5.6 5.7 E.02 .03 2.2 3.4 E4 44

08/28/2007 -- 6.0 6.2 <.04 .06 2.0 2.7 E3 42

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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 37

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)

*10/17/2006 <0.12 2.31 2.9 84.1 2.6 26 89 18 41

11/14/2006 E.07 .74 3.4 23.3 2.3 8 86 6 15

02/27/2007 <.12 1.03 6.3 30.3 1.9 11 85 7 13

03/28/2007 E.06 1.92 6.9 50.0 4.5 18 75 18 60

*04/09/2007 E.08 2.03 6.2 55.2 3.1 18.6 81 17 50

*04/23/2007 E.08 3.28 5.9 75.5 2.8 24.8 83 22 74

*05/03/2007 .18 6.50 11.0 151 4.0 52.5 62 92 671

05/07/2007 .12 3.74 7.2 79.1 2.9 27.8 69 35 239

*05/14/2007 E.07 3.57 6.3 74.6 3.1 26.0 59 45 406

*05/22/2007 E.06 2.74 5.5 70.0 3.0 21.3 63 32 290

*05/31/2007 <.12 4.38 7.4 90.3 3.3 32.4 73 41 372

*06/06/2007 <.12 5.38 6.2 118 3.5 48.5 64 55 545

06/07/2007 .37 14.9 17.7 283 6.8 113 65 157 2,110

*06/12/2007 E.07 6.08 9.5 130 4.8 47.5 61 74 1,080

*06/19/2007 <.12 2.38 12.4 60.1 3.9 21.2 71 21 192

06/20/2007 E.11 2.60 11.8 57.9 2.8 20.1 73 21 175

*06/26/2007 <.12 .77 9.3 20.1 2.7 8.9 73 5 29

07/24/2007 <.12 .19 3.6 13.0 1.4 3.3 73 4 7.5

08/28/2007 <.12 .30 4.3 16.5 .94 3.6 79 4 4.9

*Sample collected as part of a supplemental sampling program.

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

*10/17/2006 1230 517 8.5 266 7.0 140 35.4 12.3 0.17

11/15/2006 0830 1,260 8.4 202 3.0 100 27.2 8.71 --

03/28/2007 1310 2,550 8.4 177 5.0 88 22.9 7.52 --

*04/09/2007 1300 1,710 8.3 194 7.5 96 24.6 8.33 .19

*04/23/2007 1230 1,880 8.3 201 9.0 100 26.3 8.76 .20

*05/03/2007 1300 5,340 8.2 149 8.5 77 20.2 6.55 .43

05/07/2007 1330 4,140 8.3 180 9.5 88 22.8 7.45 --

*05/14/2007 1330 5,320 8.2 158 9.5 78 20.4 6.61 .20

*05/22/2007 1300 4,380 8.4 165 8.5 84 21.9 7.09 .17

*05/31/2007 1430 3,310 8.5 190 13.0 94 24.5 8.06 .16

*060/6/2007 1300 3,650 8.4 175 11.5 87 22.7 7.41 .15

*06/12/2007 1230 2,960 8.3 202 13.5 100 25.5 8.82 .13

06/12/2007 1450 2,950 8.5 204 15.0 99 25.5 8.69 --

*06/19/2007 1400 2,240 8.4 214 13.5 110 27.4 9.43 .13

*06/26/2007 1200 1,640 8.6 222 14.0 120 29.4 10.1 .13

07/25/2007 0725 680 8.3 256 18.5 120 29.4 11.2 --

08/28/2007 1445 461 8.6 265 16.0 130 31.9 12.3 --

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)

*10/17/2006 <0.008 1.1 1.3 <0.04 <0.02 0.50 1.2 7 30

11/15/2006 -- .79 .93 <.04 <.02 .46 E1.1 9 58

03/28/2007 -- .78 .93 <.04 E.01 .77 1.6 25 203

*04/09/2007 .019 .84 .90 <.04 <.02 .72 E.77 12 93

*04/23/2007 .022 .91 1.0 <.04 <.02 .77 E.79 12 141

*05/03/2007 .083 .74 1.4 <.04 .02 2.0 3.0 15 953

05/07/2007 -- .87 1.1 E.02 E.01 .71 2.0 14 407

*05/14/2007 .036 .89 1.2 <.04 <.02 .89 2.8 9 417

*05/22/2007 .023 .78 .98 <.04 E.01 .50 E1.1 8 293

*05/31/2007 .019 .84 1.0 <.04 <.02 E.37 1.4 7 196

*060/6/2007 .020 .82 1.0 <.04 E.01 <.40 E1.1 9 241

*06/12/2007 .019 1.0 1.1 <.04 E.01 <.40 E1.1 7 200

06/12/2007 -- .98 1.2 <.04 E.01 E.26 1.4 8 270

*06/19/2007 .015 .96 .99 <.04 E.01 <.40 1.3 9 137

*06/26/2007 .010 1.1 1.2 <.04 <.02 E.27 E.64 10 78

07/25/2007 -- 1.4 1.5 E.02 <.02 E.34 <1.2 <6 40

08/28/2007 -- 1.4 1.3 <.04 <.02 E.23 <1.2 E3 16

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

*10/17/2006 <0.12 <0.06 1.0 3.4 E0.42 <2 87 1 1.4

11/15/2006 <.12 E.06 1.0 5.0 .88 E1 87 4 14

03/28/2007 <.12 .23 2.6 18.2 .73 E2 81 12 83

*04/09/2007 <.12 .11 2.3 10.3 .76 <2.0 83 5 23

*04/23/2007 <.12 .16 2.6 16.2 1.2 E1.1 84 7 36

*05/03/2007 .17 1.30 3.0 70.2 2.5 5.1 83 84 1,210

05/07/2007 <.12 .59 2.5 31.3 .61 3.0 88 32 358

*05/14/2007 <.12 .61 2.2 29.9 2.0 2.8 83 40 575

*05/22/2007 <.12 .35 1.8 18.9 .92 E1.9 85 18 213

*05/31/2007 <.12 .26 2.0 15.1 E.39 E1.9 87 15 134

*060/6/2007 <.12 .35 1.3 18.6 <.60 2.1 86 19 187

*06/12/2007 <.12 .28 2.0 14.8 <.60 E2.0 91 13 104

06/12/2007 <.12 .32 2.5 16.0 <.60 2.1 91 14 112

*06/19/2007 <.12 .19 2.0 11.3 .65 E1.4 88 7 42

*06/26/2007 <.12 .11 2.0 7.7 .87 E1.0 84 5 22

07/25/2007 <.12 .07 1.1 7.0 E.44 <2.0 76 3 5.5

08/28/2007 <.12 <.06 1.6 3.4 <.60 <2.0 69 2 2.5

*Sample collected as part of a supplemental sampling program.

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

*10/17/2006 1400 1,350 -- 8.4 349 7.5 170 45.9 12.7

11/15/2006 1000 2,130 3.1 8.3 270 2.0 130 35.3 10.2

02/28/2007 0845 1,230 3.2 8.4 320 0.5 140 38.2 11.3

03/28/2007 1500 3,760 7.0 8.4 217 5.5 100 27.1 7.97

*04/09/2007 1500 2,800 -- 8.2 247 8.5 110 31.0 9.00

*04/23/2007 1430 3,010 -- 8.3 256 10.0 120 32.6 9.45

*05/03/2007 1530 8,560 38 8.1 158 9.0 78 21.0 6.20

05/07/2007 1130 6,540 17 8.2 198 9.5 89 23.9 7.07

*05/14/2007 1500 8,890 20 7.9 162 11.5 77 20.9 6.08

*05/22/2007 1430 7,580 12 8.3 170 9.0 81 22.0 6.38

*05/31/2007 1630 6,390 -- 8.3 206 15.0 98 26.6 7.60

*06/06/2007 1430 7,200 -- 8.1 188 12.0 88 24.1 6.71

06/08/2007 0815 8,370 21 8.2 215 10.0 98 26.6 7.56

*06/12/2007 1500 7,620 -- 8.2 216 14.5 99 26.9 7.74

*06/19/2007 1530 5,390 -- 8.2 234 14.5 110 29.4 8.41

06/20/2007 0720 4,440 4.9 8.2 240 13.5 110 29.7 8.48

*06/26/2007 1300 4,070 -- 8.4 247 15.0 120 32.4 9.78

07/25/2007 0840 1,320 2.4 8.3 272 20.0 120 31.2 10.5

08/29/2007 0745 873 2.3 8.4 318 15.0 150 38.5 12.2

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)

*10/17/2006 0.33 0.056 4.8 7.4 <0.04 0.27 3.0 27.9

11/15/2006 -- -- 3.2 3.6 <.04 .07 1.2 7.9

02/28/2007 -- -- 3.8 4.4 E.03 .13 1.8 12.8

03/28/2007 -- -- 2.3 3.3 E.02 .08 1.6 9.6

*04/09/2007 .27 .035 2.9 3.6 <.04 .06 1.7 8.4

*04/23/2007 .43 .062 3.6 6.1 <.04 .29 2.2 25.4

*05/03/2007 .60 .195 2.4 8.1 <.04 .25 2.0 30.4

05/07/2007 -- -- 2.7 4.8 .05 .13 2.3 20.0

*05/14/2007 .31 .063 2.6 4.9 <.04 .21 2.1 22.9

*05/22/2007 .23 .050 2.4 4.0 <.04 .09 1.8 15.4

*05/31/2007 .28 .059 4.5 7.0 <.04 .15 2.7 26.5

*06/06/2007 .31 .072 4.1 7.2 <.04 .20 2.3 29.5

06/08/2007 -- -- 8.1 16.7 E.03 .57 7.4 86.0

*06/12/2007 .38 .112 6.7 12.1 <.04 .46 4.3 58.9

*06/19/2007 .23 .043 5.2 7.0 <.04 .15 2.5 20.7

06/20/2007 -- -- 5.1 7.1 E.02 .21 2.6 23.2

*06/26/2007 .18 .031 4.5 5.4 <.04 .11 1.8 13.5

07/25/2007 -- -- 3.6 4.0 E.02 .09 1.9 13.9

08/29/2007 -- -- 4.1 4.6 <.04 .10 1.9 11.7

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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

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)

*10/17/2006 7 674 0.12 5.18 15.2 80.7 4.0 60

11/15/2006 14 223 <.12 1.09 10.7 24.4 3.0 15

02/28/2007 14 182 E.07 1.71 14.7 30.6 3.6 18

03/28/2007 22 618 <.12 1.98 8.1 44.7 1.7 22

*04/09/2007 14 294 <.12 1.91 9.8 37.7 1.9 15.0

*04/23/2007 15 788 E.07 4.39 14.8 69.8 2.2 54.4

*05/03/2007 32 2,050 E.07 6.53 11.1 143 2.9 52.8

05/07/2007 20 798 E.10 3.60 7.2 72.0 2.4 37.8

*05/14/2007 15 793 <.12 3.99 8.1 117 2.5 47.0

*05/22/2007 13 538 <.12 2.47 6.2 53.3 2.4 25.3

*05/31/2007 11 747 <.12 4.05 9.4 71.6 2.4 45.0

*06/06/2007 17 994 <.12 5.05 10.4 101 3.2 56.5

06/08/2007 39 2,550 .33 14.1 17.2 233 6.0 140

*06/12/2007 14 1,710 E.08 9.06 17.7 152 3.5 104

*06/19/2007 14 609 <.12 3.14 15.8 64.7 3.3 40.8

06/20/2007 17 682 E.07 6.07 17.6 80.9 2.9 45.5

*06/26/2007 16 361 E.06 1.69 15.4 39.0 2.6 23.1

07/25/2007 E5 182 E.08 1.73 9.5 33.0 2.0 16.9

08/29/2007 7 244 E.10 1.85 20.7 52.3 2.7 19.8

Date

Sediment, 

suspended 

(percent finer 

than 

0.062 mm)

Sediment,

 suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

*10/17/2006 70 47 171

11/15/2006 37 18 104

02/28/2007 65 10 33

03/28/2007 14 100 1,020

*04/09/2007 38 32 242

*04/23/2007 42 68 553

*05/03/2007 28 281 6,490

05/07/2007 56 70 1,240

*05/14/2007 34 126 3,020

*05/22/2007 47 51 1,040

*05/31/2007 49 62 1,070

*06/06/2007 39 93 1,810

06/08/2007 44 200 4,520

*06/12/2007 39 160 3,290

*06/19/2007 29 62 902

06/20/2007 43 50 599

*06/26/2007 29 40 440

07/25/2007 81 12 43

08/29/2007 76 14 33

*Sample collected as part of a supplemental sampling program.

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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]
42 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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)

10/18/2006 1530 657 8.2 178 8.5 78 22.9 5.08 0.18

04/10/2007 0830 2,860 7.7 68 7.0 28 8.41 1.81 .27

04/24/2007 0830 2,150 7.6 84 9.5 35 10.2 2.21 .21

05/04/2007 0730 7,800 7.6 44 6.5 18 5.45 1.15 .36

05/15/2007 0730 7,760 7.5 48 10.0 19 5.78 1.16 .21

05/23/2007 0700 6,600 7.5 59 8.0 25 7.29 1.53 .20

06/01/2007 0630 5,130 7.6 61 13.5 24 7.26 1.51 .17

06/07/2007 0700 6,990 7.5 56 9.5 23 6.68 1.44 .21

06/13/2007 0630 5,580 7.8 67 14.0 27 7.97 1.72 .15

06/20/2007 0700 3,480 7.6 81 15.0 33 9.69 2.12 .15

06/27/2007 0700 2,150 7.8 91 15.0 37 10.8 2.47 .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)

10/18/2006 E0.008 0.49 0.58 <0.04 <0.02 0.66 E1.0 23 63

04/10/2007 .025 .24 .31 <.04 E.01 .50 E.93 29 359

04/24/2007 .020 .27 .31 <.04 E.01 .61 E.83 30 196

05/04/2007 .050 .27 .39 <.04 E.01 .87 1.6 32 785

05/15/2007 .034 .27 .32 <.04 E.01 .66 1.3 28 442

05/23/2007 .024 .31 .34 <.04 <.02 .62 E.92 36 304

06/01/2007 .018 .26 .32 <.04 <.02 <.40 E.67 26 214

06/07/2007 .025 .28 .34 <.04 E.01 E.24 E.83 43 362

06/13/2007 .020 .33 .42 <.04 <.02 <.40 E.79 32 290

06/20/2007 .016 .35 .37 <.04 E.01 .47 E1.0 40 191

06/27/2007 .014 .36 .44 E.02 <.02 E.34 E.62 31 121

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)

10/18/2006 <0.12 <0.06 2.5 8.5 0.91 <2 80 1 1.8

04/10/2007 <.12 .30 4.5 20.4 .90 E1.6 52 21 162

04/24/2007 <.12 .16 5.1 14.0 .76 E1.1 73 9 52

05/04/2007 <.12 .70 3.8 33.5 1.3 3.3 36 96 2,020

05/15/2007 <.12 .42 4.4 17.8 1.6 2.9 32 68 1,420

05/23/2007 <.12 .25 6.9 15.6 .97 2.0 32 36 642

06/01/2007 <.12 .16 3.9 10.3 E.41 E1.2 48 16 222

06/07/2007 <.12 .28 5.2 15.8 .83 2.2 39 32 604

06/13/2007 <.12 .22 3.9 12.3 E.31 E1.4 39 20 301

06/20/2007 <.12 .15 4.3 11.2 .74 2.1 68 7 66

06/27/2007 <.12 .08 3.4 8.4 .98 E1.1 80 4 23

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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 43

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)

10/18/2006 1245 2,620 8.3 284 8.0 130 35.5 9.87 0.24

04/10/2007 1430 8,510 8.2 173 4.5 75 20.5 5.72 .28

04/24/2007 1545 8,080 8.3 187 7.0 83 22.9 6.34 .24

05/04/2007 1300 21,800 8.2 110 5.5 52 14.4 3.86 .63

05/15/2007 1430 21,800 7.9 116 9.0 52 14.3 3.85 .30

05/23/2007 1300 18,500 8.1 122 8.0 55 15.2 4.19 .21

06/01/2007 1300 14,800 8.1 150 11.5 65 18.0 4.95 .22

06/07/2007 1330 18,000 8.1 129 9.5 58 16.2 4.31 .25

06/13/2007 1330 15,800 7.9 156 12.5 68 18.8 5.16 .32

06/20/2007 1330 10,600 8.1 183 13.5 79 21.6 6.07 .19

06/27/2007 1300 7,210 8.4 188 14.0 86 23.3 6.70 .17

Date

Total 

phosphorous, 

unfiltered 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered, 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered, 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered, 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered, 

recoverable 

(μg/L)

10/18/2006 E0.008 2.8 2.8 <0.04 0.03 3.0 3.9 7 88

04/10/2007 .022 1.5 1.7 E.02 .03 1.5 4.5 13 179

04/24/2007 .029 2.0 2.1 E.02 .04 1.7 5.0 12 200

05/04/2007 .122 1.5 3.6 <.04 .19 1.7 25.8 21 1,720

05/15/2007 .078 1.4 2.6 E.02 .09 1.8 13.0 16 881

05/23/2007 .034 1.3 1.8 E.02 .05 1.5 6.3 17 392

06/01/2007 .030 2.4 3.2 <.04 .06 2.1 9.7 15 345

06/07/2007 .039 2.1 3.2 <.04 .10 2.0 12.6 18 585

06/13/2007 .048 3.7 5.3 <.04 .13 3.6 21.4 14 676

06/20/2007 .023 3.1 3.5 <.04 .07 2.0 8.1 14 262

06/27/2007 .013 2.9 2.9 <.04 .02 2.0 4.5 16 119

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)

10/18/2006 0.16 0.46 1.6 17.1 3.5 6 91 4 28

04/10/2007 E.07 .72 2.9 24.0 2.5 7.6 77 12 276

04/24/2007 E.08 .86 2.4 26.9 2.4 8.1 77 11 240

05/04/2007 E.07 5.27 2.6 126 2.3 50.8 60 151 8,890

05/15/2007 <.12 2.62 2.9 54.5 2.4 23.9 57 78 4,590

05/23/2007 <.12 1.10 3.4 30.5 2.6 10.6 62 34 1,700

06/01/2007 <.12 1.62 2.5 31.2 3.6 15.3 71 23 919

06/07/2007 <.12 2.23 1.8 49.5 2.0 21.0 58 49 2,380

06/13/2007 0.13 3.19 2.6 56.7 5.9 31.1 71 41 1,750

06/20/2007 E.06 1.17 4.2 26.3 3.6 13.7 80 14 401

06/27/2007 <.12 .46 2.6 13.2 1.6 5.0 83 5 97

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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]
44 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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)

10/18/2006 1000 5,640 8.4 179 11.5 90 25.5 6.49 0.15

04/10/2007 1230 14,700 8.0 172 6.5 89 25.3 6.28 .14

04/24/2007 1130 14,000 7.9 174 9.5 91 26.1 6.40 .13

05/04/2007 1100 16,300 8.4 173 9.0 91 25.8 6.39 .14

05/15/2007 1130 18,400 8.3 173 13.0 87 24.7 6.08 .14

05/23/2007 1030 25,400 8.4 173 13.0 88 25.1 6.16 .12

06/01/2007 1030 14,800 8.3 173 16.5 86 24.6 6.07 .12

06/07/2007 1100 32,600 8.2 171 16.0 87 25.0 6.03 .14

06/13/2007 1130 22,000 8.2 173 14.0 87 24.8 6.19 .11

06/20/2007 1100 19,200 8.3 172 16.5 87 24.5 6.27 .11

06/27/2007 1030 14,400 8.3 170 18.0 85 23.8 6.21 .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)

10/18/2006 <0.008 0.43 0.50 <0.04 <0.02 0.97 <1.2 <6 42

04/10/2007 E.005 .36 .39 <.04 <.02 .69 <1.2 <6 63

04/24/2007 E.007 .42 .44 <.04 <.02 .66 <1.2 E3 45

05/04/2007 E.008 .38 .38 <.04 <.02 .95 <1.2 E5 85

05/15/2007 .008 .46 .37 <.04 <.02 .46 <1.2 <6 72

05/23/2007 E.007 .38 .40 <.04 <.02 .69 E.62 <6 82

06/01/2007 E.005 .37 .43 <.04 <.02 <.40 <1.2 <6 50

06/07/2007 .011 .40 .47 <.04 E.01 <.40 <1.2 E3 186

06/13/2007 E.005 .38 .43 <.04 <.02 <.40 <1.2 E3 54

06/20/2007 E.005 .39 .43 <.04 E.01 E.22 <1.2 E4 70

06/27/2007 E.005 .42 .45 <.04 <.02 <.40 <1.2 <6 41

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)

10/18/2006 <.12 E0.03 0.5 3.8 0.64 <2 88 2 30

04/10/2007 <.12 .10 .9 4.6 .87 <2.0 84 5 198

04/24/2007 <.12 .07 .9 3.9 E.47 <2.0 82 3 113

05/04/2007 <.12 .13 .8 6.2 .89 <2.0 86 6 264

05/15/2007 <.12 .10 .9 5.6 .71 <2.0 75 7 348

05/23/2007 <.12 .09 .9 6.0 1.0 <2.0 76 7 480

06/01/2007 <.12 .07 .8 4.5 .67 <2.0 79 4 160

06/07/2007 <.12 .25 .6 10.9 E.36 E1.1 81 15 1,320

06/13/2007 <.12 .10 .8 4.2 <.60 <2.0 77 3 178

06/20/2007 <.12 .11 .7 4.8 .77 <2.0 83 4 207

06/27/2007 <.12 .06 .8 3.7 E.52 <2.0 84 3 117

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2006 through September 2007.—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 45

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2006 through 

September 2007.

[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

1 146 14 5.5 e180 19 9.2 e170 26 12

2 145 15 5.9 e190 17 8.7 e160 29 13

3 145 16 6.3 208 13 7.3 e160 27 12

4 140 17 6.4 227 11 6.7 e180 24 12

5 147 17 6.7 217 11 6.4 199 22 12

6 150 14 5.7 216 9 5.2 e200 19 10

7 158 10 4.3 228 7 4.3 e200 18 9.7

8 164 9 4.0 250 9 6.1 e210 21 12

9 165 9 4.0 263 13 9.2 e210 24 14

10 170 10 4.6 247 13 8.7 e210 25 14

11 173 10 4.7 250 12 8.1 231 25 16

12 176 10 4.8 242 10 6.5 232 25 16

13 178 11 5.3 239 9 5.8 237 24 15

14 186 11 5.5 226 8 4.9 249 24 16

15 187 10 5.0 218 11 6.5 261 24 17

16 200 10 5.4 217 19 11 e200 24 13

17 220 9 5.3 210 20 11 e160 24 10

18 212 8 4.6 200 20 11 e160 24 10

19 206 8 4.4 201 20 11 e170 22 10

20 230 7 4.3 209 20 11 e180 21 10

21 254 6 4.1 211 20 11 e180 19 9.2

22 236 6 3.8 220 23 14 e180 18 8.7

23 227 6 3.7 221 28 17 e180 17 8.3

24 223 7 4.2 203 30 16 e190 16 8.2

25 223 9 5.4 e190 28 14 203 16 8.8

26 216 10 5.8 e170 25 11 216 16 9.3

27 211 12 6.8 e180 22 11 223 15 9.0

28 205 14 7.7 e150 19 7.7 209 15 8.5

29 203 16 8.8 e160 18 7.8 e180 20 9.7

30 201 18 9.8 e160 21 9.1 e160 25 11

31 e170 19 8.7 -- -- -- e160 25 11

TOTAL 5,867 -- 171.5 6,303 -- 277.2 6,060 -- 355.4

MEAN 189 11 5.5 210 17 9.2 195 22 11

MAX 254 19 9.8 263 30 17 261 29 17

MIN 140 6 3.7 150 7 4.3 160 15 8.2
46 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)

JANUARY FEBRUARY MARCH

1 e180 24 12 e140 24 9.1 204 26 14

2 198 24 13 e150 24 9.7 190 27 14

3 223 23 14 e170 24 11 194 24 13

4 210 22 12 184 24 12 207 25 14

5 196 24 13 209 29 16 213 25 14

6 e170 26 12 227 50 31 228 32 20

7 e170 27 12 215 65 38 242 19 12

8 209 24 14 215 64 37 241 26 17

9 208 21 12 215 58 34 214 36 21

10 205 18 10 214 52 30 209 38 21

11 e130 15 5.3 209 46 26 215 22 13

12 e80 14 3.0 215 40 23 243 15 9.8

13 e100 16 4.3 210 36 20 270 13 9.5

14 e110 17 5.0 215 35 20 235 17 11

15 e110 17 5.0 214 35 20 208 18 10

16 e120 19 6.2 215 34 20 200 18 9.7

17 e130 20 7.0 212 32 18 200 18 9.7

18 e140 22 8.3 215 30 17 200 16 8.6

19 e150 24 9.7 210 28 16 200 19 10

20 154 25 10 207 26 15 201 17 9.2

21 e140 26 9.8 206 24 13 196 16 8.5

22 159 26 11 206 23 13 187 16 8.1

23 173 27 13 213 22 13 186 16 8.0

24 185 26 13 202 21 11 181 17 8.3

25 e200 24 13 205 21 12 183 20 9.9

26 e200 24 13 204 20 11 189 20 10

27 e160 24 10 198 20 11 200 19 10

28 e160 24 10 198 23 12 210 24 14

29 e160 24 10 -- -- -- 207 27 15

30 e160 24 10 -- -- -- 203 27 15

31 e160 24 10 -- -- -- 204 24 13

TOTAL 5,050 -- 310.6 5,693 -- 518.8 6,460 -- 380.3

MEAN 163 22 10 203 33 19 208 22 12

MAX 223 27 14 227 65 38 270 38 21

MIN 80 14 3.0 140 20 9.1 181 13 8.0

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2006 through 

September 2007.—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 47

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

1 203 22 12 250 34 23 405 20 22

2 208 25 14 273 43 32 390 21 22

3 214 28 16 441 217 258 394 50 53

4 204 23 13 495 153 204 417 31 35

5 205 21 12 403 63 69 528 125 178

6 205 23 13 352 43 41 798 200 431

7 226 25 15 312 38 32 974 142 373

8 221 21 13 293 36 28 747 48 97

9 216 22 13 303 40 33 651 98 172

10 209 26 15 309 45 38 623 98 165

11 209 28 16 349 46 43 791 68 145

12 223 28 17 382 55 57 800 60 130

13 226 25 15 400 49 53 649 41 72

14 216 21 12 406 42 46 590 36 57

15 209 17 9.6 367 31 31 546 31 46

16 206 17 9.5 314 26 22 477 28 36

17 199 17 9.1 317 28 24 471 26 33

18 271 64 47 311 25 21 454 20 25

19 341 110 101 312 27 23 408 15 17

20 314 57 48 324 24 21 348 12 11

21 247 28 19 389 44 46 349 12 11

22 226 21 13 540 84 122 336 8 7.3

23 221 22 13 562 84 127 319 6 5.2

24 211 19 11 430 32 37 293 16 13

25 205 17 9.4 410 28 31 270 18 13

26 213 18 10 373 22 22 233 13 8.2

27 209 17 9.6 341 19 17 223 6 3.6

28 202 15 8.2 464 42 53 209 6 3.4

29 202 17 9.3 570 49 75 195 2 1.1

30 222 22 13 482 34 44 196 2 1.1

31 -- -- -- 436 25 29 -- -- --

TOTAL 6,683 -- 535.7 11,910 -- 1,702 14,084 -- 2,186.9

MEAN 223 27 18 384 49 55 469 42 73

MAX 341 110 101 570 217 258 974 200 431

MIN 199 15 8.2 250 19 17 195 2 1.1

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2006 through 

September 2007.—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]
48 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)

JULY AUGUST SEPTEMBER

1 193 1 0.52 53 3 0.43 69 5 0.93

2 189 1 .51 51 3 .41 75 7 1.4

3 181 2 .98 54 3 .44 67 8 1.4

4 146 2 .79 56 3 .45 69 8 1.5

5 131 3 1.1 59 3 .48 84 9 2.0

6 120 4 1.3 63 3 .51 92 10 2.5

7 110 4 1.2 66 4 .71 84 10 2.3

8 113 5 1.5 65 6 1.1 77 10 2.1

9 105 5 1.4 63 7 1.2 79 10 2.1

10 94 6 1.5 64 6 1.0 81 9 2.0

11 91 7 1.7 67 5 .90 84 9 2.0

12 82 8 1.8 85 4 .92 82 8 1.8

13 71 8 1.5 76 3 .62 79 8 1.7

14 64 8 1.4 50 3 .41 85 8 1.8

15 63 7 1.2 57 4 .62 84 8 1.8

16 64 6 1.0 57 5 .77 83 9 2.0

17 67 6 1.1 62 6 1.0 81 9 2.0

18 83 5 1.1 71 6 1.2 86 10 2.3

19 87 5 1.2 76 7 1.4 86 8 1.9

20 69 4 .75 83 7 1.6 97 5 1.3

21 64 4 .69 87 8 1.9 108 4 1.2

22 64 3 .52 80 8 1.7 111 6 1.8

23 60 2 .32 73 9 1.8 141 6 2.3

24 58 1 .16 70 10 1.9 181 7 3.4

25 66 2 .36 75 10 2.0 189 8 4.1

26 81 6 1.3 73 6 1.2 181 8 3.9

27 76 6 1.2 72 3 .58 176 8 3.8

28 75 5 1.0 69 5 .93 173 7 3.3

29 71 5 .96 65 12 2.1 175 7 3.3

30 62 4 .67 61 9 1.5 180 6 2.9

31 60 4 .65 61 5 .82 -- -- --

TOTAL 2,860 -- 31.38 2,064 -- 32.6 3,239 -- 66.83

MEAN 92.3 4 1.0 66.6 6 1.1 108 8 2.2

MAX 193 8 1.8 87 12 2.1 189 10 4.1

MIN 58 1 .16 50 3 .41 67 4 .93

Total for water year 2007 (unrounded sum of daily values): streamflow–76,273 ft3/s (annual runoff–151,300 acre-ft); suspended-sediment 

discharge–6,569.21 tons.

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2006 through 

September 2007.—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 49

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2006 

through September 2007.

[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

1 621 15 25 692 5 9.3 e750 7 14

2 624 15 25 700 5 9.5 e769 6 12

3 634 14 24 794 5 11 729 7 14

4 642 15 26 820 7 15 714 8 15

5 653 16 28 862 10 23 767 8 17

6 674 16 29 871 11 26 761 7 14

7 703 16 30 903 12 29 762 7 14

8 687 15 28 1,140 19 58 775 6 13

9 701 14 26 1,290 26 91 e780 6 13

10 720 14 27 1,110 12 36 e800 6 13

11 734 13 26 1,030 10 28 843 7 16

12 735 13 26 990 9 24 843 9 20

13 730 12 24 949 8 20 849 10 23

14 730 11 22 940 7 18 858 10 23

15 747 11 22 901 6 15 888 8 19

16 773 15 31 895 6 14 e860 5 12

17 838 18 41 906 6 15 e720 4 7.8

18 832 18 40 865 6 14 e620 4 6.7

19 824 23 51 852 6 14 e600 3 4.9

20 902 28 68 850 6 14 e640 2 3.5

21 993 30 80 871 6 14 e660 2 3.6

22 985 26 69 900 6 15 e740 2 4.0

23 925 19 47 905 6 15 e720 2 3.9

24 887 14 34 880 6 14 e760 2 4.1

25 869 10 23 866 5 12 798 6 13

26 855 9 21 837 5 11 837 13 29

27 835 8 18 814 5 11 853 14 32

28 825 7 16 815 6 13 857 14 32

29 817 7 15 766 7 14 e740 5 10

30 812 6 13 e730 8 16 e640 3 5.2

31 772 6 13 -- -- -- e620 3 5.0

TOTAL 24,079 -- 968 26,744 -- 618.8 23,553 -- 416.7

MEAN 777 15 31 891 8 21 760 6 13

MAX 993 30 80 1,290 26 91 888 14 32

MIN 621 6 13 692 5 9.3 600 2 3.5
50 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)

JANUARY FEBRUARY MARCH

1 e600 3 4.9 e600 4 6.5 669 9 16

2 e700 12 23 e540 5 7.3 658 8 14

3 883 20 48 e520 6 8.4 640 7 12

4 897 14 34 590 7 11 677 10 18

5 828 10 22 664 8 14 762 13 27

6 735 8 16 747 14 28 867 29 68

7 672 8 15 848 24 55 1,060 68 195

8 731 13 26 833 21 47 1,150 97 301

9 768 12 25 880 16 38 1,140 84 259

10 e740 6 12 982 20 53 1,030 53 147

11 e560 3 4.5 951 18 46 1,030 48 133

12 e250 3 2.0 911 16 39 1,300 170 597

13 e177 2 .96 832 17 38 1,910 395 2,040

14 e211 2 1.1 781 17 36 1,610 130 565

15 e250 3 2.0 781 17 36 1,280 50 173

16 e280 3 2.3 861 41 95 1,120 33 100

17 e320 2 1.7 910 58 143 1,090 28 82

18 e410 2 2.2 886 46 110 1,130 30 92

19 e500 2 2.7 842 35 80 1,200 33 107

20 e620 4 6.7 793 24 51 1,190 29 93

21 e660 7 12 791 21 45 1,170 25 79

22 689 8 15 765 21 43 1,100 19 56

23 704 8 15 766 21 43 1,070 19 55

24 692 8 15 745 20 40 1,050 19 54

25 676 8 15 713 17 33 1,070 19 55

26 659 7 12 726 11 22 1,130 18 55

27 e620 6 10 701 8 15 1,180 20 64

28 e560 5 7.6 666 8 14 1,220 18 59

29 e540 3 4.4 -- -- -- 1,170 15 47

30 e540 3 4.4 -- -- -- 1,100 13 39

31 e580 3 4.7 -- -- -- 1,090 14 41

TOTAL 18,052 -- 367.16 21,625 -- 1,197.2 33,863 -- 5,643

MEAN 582 6 12 772 19 43 1,092 49 182

MAX 897 20 48 982 58 143 1,910 395 2,040

MIN 177 2 .96 520 4 6.5 640 7 12

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2006 

through September 2007.—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 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)

APRIL MAY JUNE

1 1,100 14 42 2,110 59 336 3,190 31 267

2 1,070 14 40 2,280 63 388 3,070 27 224

3 1,060 12 34 2,780 110 826 3,020 28 228

4 1,030 12 33 3,300 124 1,100 3,060 26 215

5 1,030 14 39 3,030 71 581 3,210 30 260

6 1,030 14 39 2,740 46 340 3,750 63 638

7 1,040 15 42 2,520 34 231 4,780 146 1,880

8 1,060 17 49 2,410 32 208 5,070 116 1,590

9 1,100 20 59 2,450 29 192 4,710 76 966

10 1,130 17 52 2,620 31 219 4,440 58 695

11 1,100 12 36 2,940 41 325 4,880 75 988

12 1,080 12 35 3,120 41 345 5,260 76 1,080

13 1,060 12 34 3,270 43 380 5,040 51 694

14 1,040 14 39 3,390 46 421 4,560 40 492

15 1,040 16 45 3,300 34 303 4,220 35 399

16 1,060 15 43 3,100 25 209 3,930 36 382

17 1,070 17 49 2,990 21 170 3,800 31 318

18 1,180 21 67 2,940 20 159 3,680 29 288

19 1,350 33 120 2,930 17 134 3,430 24 222

20 1,340 31 112 2,920 18 142 3,110 22 185

21 1,300 28 98 3,050 20 165 2,830 18 138

22 1,270 26 89 3,350 32 289 2,650 13 93

23 1,270 25 86 3,440 41 381 2,500 12 81

24 1,310 23 81 3,410 40 368 2,370 8 51

25 1,340 25 90 3,340 34 307 2,280 6 37

26 1,420 27 104 3,240 30 262 2,160 5 29

27 1,480 27 108 3,040 24 197 2,000 4 22

28 1,480 24 96 3,230 29 253 1,890 4 20

29 1,620 31 136 3,620 60 586 1,800 4 19

30 1,870 46 232 3,570 52 501 1,620 3 13

31 -- -- -- 3,380 42 383 -- -- --

TOTAL 36,330 -- 2,129 93,810 -- 10,701 102,310 -- 12,514

MEAN 1,211 20 71 3,026 42 345 3,410 37 417

MAX 1,870 46 232 3,620 124 1,100 5,260 146 1,880

MIN 1,030 12 33 2,110 17 134 1,620 3 13

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2006 

through September 2007.—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)

JULY AUGUST SEPTEMBER

1 e1,470 3 12 608 6 9.8 453 7 8.6

2 e1,320 3 11 592 6 9.6 442 7 8.4

3 e1,170 3 9.5 579 6 9.4 443 7 8.4

4 1,110 3 9.0 560 5 7.6 443 6 7.2

5 1,060 3 8.6 548 5 7.4 461 7 8.7

6 1,010 3 8.2 538 5 7.3 510 8 11

7 986 3 8.0 540 5 7.3 501 8 11

8 952 3 7.7 526 5 7.1 491 7 9.3

9 913 3 7.4 510 5 6.9 492 6 8.0

10 902 3 7.3 495 6 8.0 489 6 7.9

11 878 3 7.1 480 6 7.8 487 6 7.9

12 858 3 6.9 469 6 7.6 484 6 7.8

13 835 2 4.5 467 6 7.6 477 6 7.7

14 811 3 6.6 473 6 7.7 475 6 7.7

15 797 3 6.5 456 6 7.4 478 6 7.7

16 791 3 6.4 444 6 7.2 474 6 7.7

17 805 3 6.5 449 6 7.3 479 6 7.8

18 840 5 11 457 6 7.4 495 6 8.0

19 821 4 8.9 460 6 7.5 526 6 8.5

20 781 5 11 471 6 7.6 566 6 9.2

21 751 5 10 499 6 8.1 580 7 11

22 724 4 7.8 509 5 6.9 574 9 14

23 701 4 7.6 500 5 6.8 677 12 22

24 687 4 7.4 483 5 6.5 869 35 82

25 693 9 17 472 5 6.4 880 27 64

26 733 8 16 465 5 6.3 847 15 34

27 708 6 11 457 5 6.2 825 13 29

28 694 6 11 448 5 6.0 808 11 24

29 675 6 11 439 4 4.7 805 8 17

30 645 6 10 427 4 4.6 798 8 17

31 622 6 10 434 4 4.7 -- -- --

TOTAL 26,743 -- 282.9 15,255 -- 222.7 17,329 -- 482.5

MEAN 863 4 9.1 492 5 7.2 578 9 16

MAX 1,470 9 17 608 6 9.8 880 35 82

MIN 622 2 4.5 427 4 4.6 442 6 7.2

Total for water year 2007 (unrounded sum of daily values): streamflow–439,693 ft3/s (annual runoff–872,100 acre-ft); suspended-sediment 

discharge–35,542.96 tons.

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2006 

through September 2007.—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

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2006 through 

September 2007.

[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

1 472 2 2.5 e420 1 1.1 e700 3 5.7

2 472 1 1.3 e440 1 1.2 e730 3 5.9

3 472 1 1.3 e480 2 2.6 e740 3 6.0

4 472 1 1.3 534 2 2.9 e730 3 5.9

5 472 1 1.3 562 2 3.0 e730 3 5.9

6 472 1 1.3 600 4 6.5 e760 3 6.2

7 472 2 2.5 762 16 33 e710 3 5.8

8 472 2 2.5 2,480 50 335 e690 2 3.7

9 472 2 2.5 2,530 42 287 e680 2 3.7

10 472 2 2.5 2,130 14 81 e680 2 3.7

11 472 2 2.5 1,860 8 40 e720 2 3.9

12 472 2 2.5 1,640 8 35 756 3 6.1

13 467 1 1.3 1,470 5 20 755 4 8.2

14 467 2 2.5 1,390 4 15 762 3 6.2

15 468 2 2.5 1,250 4 14 773 3 6.3

16 493 2 2.7 1,190 3 9.6 762 3 6.2

17 520 2 2.8 1,140 3 9.2 e630 3 5.1

18 509 3 4.1 1,060 3 8.6 e450 3 3.6

19 512 4 5.5 1,010 3 8.2 e350 2 1.9

20 562 4 6.1 988 3 8.0 e360 2 1.9

21 567 4 6.1 1,020 3 8.3 e370 1 1.0

22 565 3 4.6 1,070 3 8.7 e400 1 1.1

23 555 3 4.5 1,050 3 8.5 e530 1 1.4

24 540 2 2.9 1,020 2 5.5 e580 2 3.1

25 529 2 2.9 1,010 2 5.5 e600 2 3.2

26 519 1 1.4 947 2 5.1 e670 1 1.8

27 510 2 2.8 921 2 5.0 686 1 1.9

28 504 2 2.7 e800 3 6.5 674 1 1.8

29 498 3 4.0 e600 3 4.9 e650 1 1.8

30 e490 2 2.6 e530 3 4.3 e560 1 1.5

31 e460 2 2.5 -- -- -- e430 1 1.2

TOTAL 15,399 -- 88.5 32,904 -- 983.2 19,618 -- 121.7

MEAN 497 2 2.9 1,097 7 33 633 2 3.9

MAX 567 4 6.1 2,530 50 335 773 4 8.2

MIN 460 1 1.3 420 1 1.1 350 1 1.0
54 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)

JANUARY FEBRUARY MARCH

1 e400 1 1.1 e500 2 2.7 549 3 4.4

2 e500 2 2.7 e480 2 2.6 527 3 4.3

3 e660 2 3.6 e430 3 3.5 526 3 4.3

4 e670 2 3.6 e410 3 3.3 548 3 4.4

5 665 2 3.6 e480 3 3.9 563 6 9.1

6 663 1 1.8 e520 3 4.2 602 11 18

7 659 1 1.8 e520 2 2.8 794 18 39

8 651 1 1.8 e550 3 4.5 1,060 22 63

9 646 1 1.7 e570 4 6.2 1,130 26 79

10 646 1 1.7 e580 4 6.3 1,030 23 64

11 e550 1 1.5 e620 4 6.7 1,040 23 65

12 e400 2 2.2 e600 4 6.5 1,240 33 110

13 e300 2 1.6 e560 4 6.0 1,710 45 208

14 e380 2 2.1 e540 4 5.8 1,690 32 146

15 e450 2 2.4 e550 6 8.9 1,480 16 64

16 e470 2 2.5 e600 7 11 1,430 14 54

17 e480 1 1.3 614 8 13 1,480 12 48

18 e500 2 2.7 625 7 12 1,670 13 59

19 e520 2 2.8 607 6 9.8 1,880 15 76

20 e570 2 3.1 612 6 9.9 2,010 15 81

21 e600 2 3.2 616 5 8.3 2,060 13 72

22 e660 2 3.6 592 5 8.0 2,030 10 55

23 e630 2 3.4 603 4 6.5 1,990 9 48

24 e600 2 3.2 592 4 6.4 1,980 10 53

25 e580 2 3.1 584 4 6.3 2,100 10 57

26 e540 2 2.9 580 3 4.7 2,350 12 76

27 e500 2 2.7 567 3 4.6 2,500 16 108

28 e480 2 2.6 558 3 4.5 2,550 15 103

29 e460 2 2.5 -- -- -- 2,440 11 72

30 e500 2 2.7 -- -- -- 2,310 9 56

31 e470 2 2.5 -- -- -- 2,200 8 48

TOTAL 16,800 -- 78.0 15,660 -- 178.9 47,469 -- 1,948.5

MEAN 542 2 2.5 559 4 6.4 1,531 15 63

MAX 670 2 3.6 625 8 13 2,550 45 208

MIN 300 1 1.1 410 2 2.6 526 3 4.3

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2006 through 

September 2007.—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 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)

APRIL MAY JUNE

1 2,120 8 46 3,980 63 677 3,290 14 124

2 2,060 7 39 4,340 68 797 3,350 16 145

3 2,000 5 27 5,190 86 1,210 3,440 19 176

4 1,910 5 26 5,610 93 1,410 3,460 19 177

5 1,850 5 25 5,140 71 985 3,520 19 181

6 1,770 6 29 4,570 47 580 3,640 20 197

7 1,700 6 28 4,160 34 382 3,730 22 222

8 1,670 6 27 3,990 34 366 3,590 22 213

9 1,710 6 28 4,140 34 380 3,340 22 198

10 1,800 7 34 4,580 40 495 3,160 19 162

11 1,810 6 29 4,990 44 593 3,110 18 151

12 1,770 6 29 5,220 47 662 2,960 17 136

13 1,720 6 28 5,400 49 714 2,770 15 112

14 1,680 7 32 5,320 42 603 2,630 13 92

15 1,700 8 37 4,890 35 462 2,480 11 74

16 1,760 8 38 4,530 31 379 2,330 10 63

17 1,800 12 58 4,430 27 323 2,310 10 62

18 1,960 13 69 4,550 26 319 2,370 9 58

19 2,110 15 85 4,750 28 359 2,240 8 48

20 2,060 12 67 4,750 29 372 2,080 8 45

21 1,990 12 64 4,600 25 310 1,980 8 43

22 1,930 10 52 4,390 21 249 1,900 7 36

23 1,890 10 51 4,080 22 242 1,830 8 40

24 1,950 10 53 3,770 18 183 1,760 7 33

25 2,100 13 74 3,630 17 167 1,700 5 23

26 2,290 16 99 3,490 17 160 1,630 5 22

27 2,440 18 119 3,310 17 152 1,550 8 33

28 2,600 22 154 3,360 15 136 1,480 5 20

29 3,030 32 262 3,450 16 149 1,390 5 19

30 3,590 48 465 3,400 16 147 1,340 5 18

31 -- -- -- 3,310 16 143 -- -- --

TOTAL 60,770 -- 2,174 135,320 -- 14,106 76,360 -- 2,923

MEAN 2,026 12 72 4,365 36 455 2,545 12 97

MAX 3,590 48 465 5,610 93 1,410 3,730 22 222

MIN 1,670 5 25 3,310 15 136 1,340 5 18

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2006 through 

September 2007.—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)

JULY AUGUST SEPTEMBER

1 1,300 5 18 e615 3 5.0 457 2 2.5

2 1,230 5 17 e600 3 4.9 452 2 2.4

3 1,210 6 20 e580 2 3.1 448 2 2.4

4 1,160 6 19 e570 2 3.1 443 2 2.4

5 1,110 6 18 e560 2 3.0 443 2 2.4

6 1,070 5 14 e550 2 3.0 449 2 2.4

7 1,040 5 14 e540 1 1.5 444 2 2.4

8 1,000 4 11 e530 1 1.4 439 2 2.4

9 974 3 7.9 e515 1 1.4 441 2 2.4

10 939 3 7.6 525 1 1.4 447 2 2.4

11 911 3 7.4 528 2 2.9 452 2 2.4

12 888 3 7.2 523 2 2.8 442 2 2.4

13 853 3 6.9 516 2 2.8 430 1 1.2

14 830 3 6.7 505 2 2.7 429 1 1.2

15 827 3 6.7 490 2 2.6 429 2 2.3

16 803 3 6.5 486 2 2.6 432 2 2.3

17 805 3 6.5 489 2 2.6 432 2 2.3

18 815 2 4.4 493 2 2.7 439 1 1.2

19 790 2 4.3 498 2 2.7 454 1 1.2

20 757 2 4.1 508 1 1.4 460 1 1.2

21 732 2 4.0 519 1 1.4 468 2 2.5

22 711 2 3.8 521 1 1.4 463 2 2.5

23 692 2 3.7 504 1 1.4 516 3 4.2

24 683 2 3.7 493 1 1.3 556 3 4.5

25 677 2 3.7 480 1 1.3 542 2 2.9

26 662 3 5.4 459 1 1.2 510 2 2.8

27 664 3 5.4 450 1 1.2 492 2 2.7

28 661 3 5.4 456 2 2.5 481 2 2.6

29 644 2 3.5 454 2 2.5 487 2 2.6

30 632 2 3.4 443 2 2.4 478 2 2.6

31 626 2 3.4 441 2 2.4 -- -- --

TOTAL 26,696 -- 252.6 15,841 -- 72.6 13,855 -- 71.7

MEAN 861 3 8.1 511 2 2.3 462 2 2.4

MAX 1,300 6 20 615 3 5.0 556 3 4.5

MIN 626 2 3.4 441 1 1.2 429 1 1.2

Total for water year 2007 (unrounded sum of daily values): streamflow–476,692 ft3/s (annual runoff–945,500 acre-ft); suspended-sediment 

discharge–22,998.7 tons.

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2006 through 

September 2007.—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

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2006 through 

September 2007.

[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 1,080 50 146 1,130 18 55 1,450 35 137

2 1,080 48 140 1,150 18 56 e1,500 23 93

3 1,090 47 138 1,280 22 76 e1,470 19 75

4 1,090 48 141 1,300 28 98 e1,450 15 59

5 1,110 58 174 1,360 36 132 e1,500 13 53

6 1,120 80 242 1,410 45 171 1,530 13 54

7 1,150 95 295 1,570 54 229 1,470 13 52

8 1,130 79 241 3,190 140 1,210 1,460 14 55

9 1,140 70 215 3,830 226 2,340 1,460 17 67

10 1,160 64 200 3,230 150 1,310 1,480 62 248

11 1,170 55 174 2,840 125 958 1,560 63 265

12 1,180 48 153 2,590 85 594 1,560 60 253

13 1,170 42 133 2,370 65 416 1,570 47 199

14 1,170 41 130 2,280 43 265 1,600 38 164

15 1,180 41 131 2,120 19 109 1,650 31 138

16 1,220 39 128 2,030 18 99 1,640 19 84

17 1,320 46 164 2,020 18 98 e1,400 8 30

18 1,320 59 210 1,890 17 87 e1,100 8 24

19 1,310 64 226 1,830 17 84 e950 13 33

20 1,430 71 274 1,790 17 82 e1,000 18 49

21 1,530 75 310 1,840 18 89 e1,030 26 72

22 1,540 73 304 1,900 17 87 e1,150 35 109

23 1,460 62 244 1,900 14 72 e1,270 44 151

24 1,400 53 200 1,860 11 55 e1,350 54 197

25 1,370 47 174 1,830 10 49 e1,400 72 272

26 1,340 44 159 1,760 10 48 e1,530 488 2,020

27 1,320 40 143 1,690 12 55 e1,600 552 2,380

28 1,290 36 125 1,620 14 61 e1,600 350 1,510

29 1,270 32 110 1,340 44 159 e1,450 378 1,480

30 1,270 28 96 1,260 228 776 e1,200 318 1,030

31 1,230 22 73 -- -- -- e1,050 240 680

TOTAL 38,640 -- 5,593 58,210 -- 9,920 43,430 -- 12,033

MEAN 1,246 53 180 1,940 51 331 1,401 100 388

MAX 1,540 95 310 3,830 228 2,340 1,650 552 2,380

MIN 1,080 22 73 1,130 10 48 950 8 24
58 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)

JANUARY FEBRUARY MARCH

1 e1,000 169 456 e1,100 7 21 1,180 13 41

2 e1,200 95 308 e1,030 7 19 1,160 13 41

3 e1,600 115 497 e950 7 18 1,130 13 40

4 e1,650 161 717 e1,000 11 30 1,180 13 41

5 1,590 147 631 e1,150 84 261 1,270 18 62

6 1,430 114 440 1,340 99 358 1,400 34 129

7 1,360 83 305 1,370 78 289 1,790 96 464

8 1,390 60 225 1,390 55 206 2,170 158 926

9 1,380 50 186 1,440 52 202 2,330 184 1,160

10 1,380 65 242 1,560 44 185 2,100 116 658

11 e1,100 104 309 1,560 32 135 2,060 80 445

12 e650 151 265 1,510 28 114 2,490 133 894

13 e450 198 241 1,390 28 105 3,860 515 5,370

14 e600 177 287 1,330 28 101 3,600 243 2,360

15 e700 103 195 1,340 28 101 2,940 102 810

16 e750 36 73 1,440 30 117 2,620 70 495

17 e800 5 11 1,540 57 237 2,600 65 456

18 e900 4 9.7 1,510 42 171 2,780 55 413

19 e1,030 4 11 1,460 41 162 3,110 76 638

20 e1,200 6 19 1,400 36 136 3,230 107 933

21 e1,270 9 31 1,390 26 98 3,290 99 879

22 e1,370 11 41 1,350 23 84 3,170 68 582

23 e1,350 17 62 1,350 22 80 3,080 55 457

24 e1,300 22 77 1,330 20 72 3,030 51 417

25 e1,270 24 82 1,280 16 55 3,130 61 516

26 e1,200 19 62 1,280 12 41 3,450 76 708

27 e1,130 14 43 1,260 9 31 3,650 106 1,040

28 e1,050 9 26 1,210 11 36 3,750 106 1,070

29 e1,000 7 19 -- -- -- 3,610 75 731

30 e1,030 7 19 -- -- -- 3,400 38 349

31 e1,050 7 20 -- -- -- 3,270 40 353

TOTAL 35,180 -- 5,909.7 37,260 -- 3465 81,830 -- 23,478

MEAN 1,135 64 191 1,331 33 124 2,640 93 757

MAX 1,650 198 717 1,560 99 358 3,860 515 5,370

MIN 450 4 9.7 950 7 18 1,130 13 40

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2006 through 

September 2007.—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 59

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 3,210 64 555 6,100 294 4,840 6,220 60 1,010

2 3,120 36 303 6,720 240 4,350 6,150 62 1,030

3 3,040 44 361 8,060 266 5,790 6,190 55 919

4 2,910 37 291 9,130 300 7,400 6,230 53 892

5 2,840 47 360 8,330 158 3,550 6,450 55 958

6 2,790 42 316 7,380 95 1,890 7,150 97 1,870

7 2,710 33 241 6,690 75 1,350 8,220 208 4,620

8 2,700 37 270 6,360 65 1,120 8,250 181 4,030

9 2,760 38 283 6,490 65 1,140 7,520 124 2,520

10 2,900 69 540 7,100 70 1,340 7,070 112 2,140

11 2,880 61 474 7,870 89 1,890 7,260 142 2,780

12 2,810 48 364 8,320 104 2,340 7,430 179 3,590

13 2,740 48 355 8,700 98 2,300 6,860 140 2,590

14 2,680 57 412 8,730 109 2,570 6,330 108 1,850

15 2,700 42 306 8,100 84 1,840 5,910 87 1,390

16 2,780 62 465 7,450 58 1,170 5,520 84 1,250

17 2,820 58 442 7,170 51 987 5,330 79 1,140

18 3,080 100 832 7,240 51 997 5,290 61 871

19 3,470 114 1,070 7,420 51 1,020 4,970 50 671

20 3,420 94 868 7,420 49 982 4,550 51 627

21 3,300 120 1,070 7,380 42 837 4,210 43 489

22 3,190 100 861 7,500 53 1,070 3,990 36 388

23 3,140 62 526 7,320 61 1,210 3,780 38 388

24 3,250 62 544 7,000 67 1,270 3,600 28 272

25 3,430 90 833 6,760 62 1,130 3,450 34 317

26 3,710 133 1,330 6,500 61 1,070 3,250 38 333

27 3,910 112 1,180 6,140 52 862 3,080 28 233

28 4,030 134 1,460 6,320 50 853 2,880 19 148

29 4,550 185 2,270 6,850 94 1,740 2,720 18 132

30 5,370 258 3,740 6,750 88 1,600 2,590 17 119

31 -- -- -- 6,430 71 1,230 -- -- --

TOTAL 96,240 -- 22,922 225,730 -- 61,738 162,450 -- 39,567

MEAN 3,208 80 764 7,282 99 1,990 5,415 76 1,320

MAX 5,370 258 3,740 9,130 300 7,400 8,250 208 4,620

MIN 2,680 33 241 6,100 42 837 2,590 17 119

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2006 through 

September 2007.—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]
60 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)

JULY AUGUST SEPTEMBER

1 2,490 16 108 1,170 12 38 881 15 36

2 2,350 14 89 1,140 12 37 870 15 35

3 2,310 12 75 1,130 12 37 859 14 32

4 2,230 10 60 1,100 12 36 858 14 32

5 2,150 8 46 1,070 12 35 865 13 30

6 2,070 8 45 1,070 12 35 915 12 30

7 2,010 8 43 1,060 12 34 912 10 25

8 1,950 8 42 1,040 12 34 895 9 22

9 1,900 8 41 1,020 12 33 897 9 22

10 1,860 8 40 993 12 32 900 10 24

11 1,810 8 39 979 13 34 902 10 24

12 1,770 10 48 972 13 34 894 11 27

13 1,700 10 46 959 14 36 876 12 28

14 1,640 10 44 957 14 36 873 11 26

15 1,610 10 43 932 14 35 873 10 24

16 1,580 11 47 911 14 34 869 10 23

17 1,590 11 47 916 14 35 876 9 21

18 1,620 11 48 927 14 35 892 9 22

19 1,590 11 47 934 14 35 932 9 23

20 1,510 11 45 962 14 36 974 11 29

21 1,450 11 43 992 15 40 1,010 12 33

22 1,400 11 42 1,010 15 41 996 13 35

23 1,370 11 41 986 15 40 1,140 19 58

24 1,340 12 43 955 14 36 1,370 38 141

25 1,330 12 43 930 14 35 1,410 33 126

26 1,360 14 51 903 15 37 1,350 21 77

27 1,330 16 57 881 15 36 1,290 18 63

28 1,310 18 64 876 15 35 1,270 16 55

29 1,270 19 65 870 15 35 1,270 14 48

30 1,220 16 53 852 15 35 1,250 14 47

31 1,190 13 42 851 15 34 -- -- --

TOTAL 52,310 -- 1,587 30,348 -- 1,105 30,169 -- 1,218

MEAN 1,687 11 51 979 14 36 1,006 14 41

MAX 2,490 19 108 1,170 15 41 1,410 38 141

MIN 1,190 8 39 851 12 32 858 9 21

Total for water year 2007 (unrounded sum of daily values): streamflow–891,797 ft3/s (annual runoff–1,769,000 acre-ft); suspended-sediment 

discharge–188,535.7 tons.

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2006 through 

September 2007.—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 61

Table 9. Seasonal daily maximum, minimum, and mean turbidity at Mill Creek near Anaconda, Montana, October through November, 

2006 and March through September, 2007.

[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

OCTOBER NOVEMBER MARCH

1 2.0 0.5 1.0 3.0 1.0 1.5 -- -- --

2 1.5 .5 1.0 3.0 1.0 1.5 -- -- --

3 1.5 .5 1.0 2.5 1.0 1.5 -- -- --

4 2.0 1.0 1.0 3.0 1.0 1.5 -- -- --

5 2.0 1.0 1.5 2.5 1.0 1.5 -- -- --

6 2.0 1.0 1.5 3.0 1.0 1.5 -- -- --

7 3.0 1.5 2.0 12 1.5 4.5 -- -- --

8 3.0 1.0 1.5 12 2.0 4.0 -- -- --

9 2.0 1.0 1.0 3.5 1.5 2.0 -- -- --

10 2.0 1.0 1.0 4.0 1.5 2.5 -- -- --

11 3.5 1.0 1.0 4.5 1.5 2.5 -- -- --

12 2.5 .5 1.0 3.5 2.0 3.0 -- -- --

13 1.5 1.0 1.0 5.0 3.0 4.0 -- -- --

14 1.5 1.0 1.0 7.0 4.0 5.0 -- -- 2.5

15 2.0 1.0 1.5 6.0 2.5 4.5 4.0 1.5 3.0

16 3.0 1.5 2.0 5.0 3.0 4.0 5.0 2.0 2.5

17 4.5 1.0 2.0 5.5 3.0 4.0 5.5 2.0 3.0

18 3.5 1.0 1.0 6.0 3.5 4.0 6.0 2.5 4.0

19 2.0 1.0 1.0 7.0 3.5 5.0 6.5 2.0 3.5

20 5.5 1.0 2.5 9.0 3.0 5.0 6.0 2.0 3.5

21 2.0 1.0 1.5 -- -- -- 4.5 2.0 3.5

22 1.5 1.0 1.0 -- -- -- 5.0 2.0 3.0

23 1.5 1.0 1.0 -- -- -- 8.0 1.5 3.0

24 1.5 .5 1.0 -- -- -- 8.5 1.5 3.0

25 1.5 .5 1.0 -- -- -- 9.0 1.5 3.5

26 1.5 .5 1.0 -- -- -- 4.5 2.0 2.5

27 1.0 .5 .5 -- -- -- 6.0 2.0 3.0

28 1.5 .5 1.0 -- -- -- 5.5 1.5 2.0

29 3.5 .5 1.0 -- -- -- 6.5 1.5 2.5

30 3.5 1.0 1.5 -- -- -- 7.5 1.0 2.0

31 3.5 1.0 2.0 -- -- -- 6.5 1.5 2.5

MONTH1 5.5 .5 1.3 12 1.0 3.2 9.0 1.0 2.9
62 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 5.5 1.5 2.0 18 7.5 11 -- -- 2.0

2 7.5 1.5 2.5 14 7.0 9.5 -- -- 2.5

3 6.0 1.5 3.0 24 5.5 11 -- -- 3.0

4 6.5 1.5 3.0 8.5 3.5 5.5 -- -- 3.0

5 7.0 1.5 3.0 7.5 3.0 4.5 8.0 2.5 5.0

6 6.0 1.5 3.5 7.0 3.0 4.0 5.5 2.5 4.0

7 7.0 2.0 3.5 6.0 3.0 4.0 4.5 1.5 3.5

8 -- -- -- 5.5 2.0 4.0 4.5 1.5 3.5

9 -- -- 2.5 6.0 2.5 4.0 6.5 1.5 4.5

10 4.0 2.0 3.0 8.0 3.5 4.5 10 3.5 5.5

11 8.0 1.5 4.0 8.0 4.0 5.5 14 4.0 7.5

12 8.5 2.0 5.5 10 4.0 6.5 8.0 2.5 4.5

13 4.5 1.5 2.5 9.5 4.0 6.0 -- -- --

14 -- -- -- 6.0 3.5 4.0 10 1.0 4.5

15 -- -- -- 4.5 3.0 3.5 -- -- --

16 -- -- -- 4.0 1.0 2.5 -- -- --

17 8.5 3.5 6.0 2.5 .5 1.5 12 1.0 5.0

18 9.5 4.5 7.0 -- -- 2.0 -- -- --

19 10 3.5 7.0 -- -- 1.5 7.0 1.5 2.5

20 10 3.0 6.5 4.0 1.0 2.0 3.5 1.5 2.5

21 9.5 4.0 6.0 4.0 1.0 2.0 3.5 2.0 2.5

22 10 4.0 6.5 2.0 1.0 1.5 3.0 2.0 2.5

23 10 4.5 7.5 -- -- 1.5 -- -- 2.5

24 10 5.0 8.0 2.5 1.0 1.5 -- -- 2.0

25 11 5.0 8.5 3.0 1.0 1.5 -- -- 2.0

26 10 5.5 8.0 -- -- 1.5 -- -- 2.0

27 10 5.0 8.0 -- -- 1.5 3.0 1.5 2.0

28 17 7.0 9.5 -- -- 2.0 3.5 2.0 2.5

29 20 8.5 13 2.5 1.5 2.0 3.0 1.5 2.0

30 18 7.0 11 -- -- 2.0 -- -- 2.0

31 -- -- -- -- -- 2.0 -- -- --

MONTH1 20 1.5 5.8 24 .5 3.7 14 1.0 3.3

Table 9. Seasonal daily maximum, minimum, and mean turbidity at Mill Creek near Anaconda, Montana, October through November, 

2006 and March through September, 2007.—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]
Data 63

Table 9. Seasonal daily maximum, minimum, and mean turbidity at Mill Creek near Anaconda, Montana, October through November, 

2006 and March through September, 2007.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbol: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 3.0 1.5 2.0 -- -- 2.0 7.0 2.0 4.5

2 2.5 1.5 2.0 3.5 1.0 2.0 -- -- --

3 -- -- 2.0 3.5 1.0 2.0 -- -- --

4 2.5 1.5 2.0 4.0 1.0 2.0 -- -- --

5 3.0 1.0 2.0 3.0 1.0 2.0 -- -- --

6 3.0 1.0 2.0 3.0 1.0 2.0 -- -- --

7 3.0 1.0 2.0 3.0 1.0 2.0 -- -- 2.5

8 -- -- 2.0 -- -- 2.0 3.5 2.5 2.5

9 2.5 1.0 1.5 3.5 1.5 2.5 3.0 2.0 2.5

10 2.5 1.0 1.5 4.0 2.5 3.0 2.5 1.5 2.0

11 -- -- 1.5 4.0 2.5 3.0 2.5 1.5 2.0

12 2.5 1.0 1.5 3.5 2.0 2.5 2.5 1.5 2.0

13 2.5 1.0 1.5 3.5 2.5 3.0 3.0 2.0 2.0

14 3.5 1.0 2.0 3.5 2.5 3.0 4.0 2.0 2.5

15 -- -- 2.0 3.0 2.0 2.5 4.0 2.0 2.5

16 4.0 1.0 1.5 3.0 2.0 2.5 5.5 2.0 3.0

17 6.0 1.0 2.0 3.0 2.0 2.0 4.0 2.0 2.5

18 9.5 1.5 3.5 2.5 1.5 2.0 3.0 2.0 2.5

19 3.0 1.0 1.5 3.0 2.0 2.0 3.5 2.5 3.0

20 2.5 1.0 1.5 2.5 1.5 2.0 3.5 3.0 3.0

21 3.5 1.0 1.5 3.0 1.5 2.0 4.5 3.0 3.5

22 3.5 1.0 1.5 3.5 1.5 2.0 6.5 3.5 4.0

23 3.5 1.0 1.5 2.5 1.5 2.0 8.0 4.5 6.0

24 3.5 1.0 2.0 2.5 1.5 2.0 5.5 1.5 3.0

25 4.0 1.5 2.5 2.5 1.5 1.5 3.0 1.5 2.0

26 3.5 .5 1.5 2.0 1.5 1.5 2.0 1.5 1.5

27 2.0 1.0 1.5 2.5 1.5 2.0 2.5 1.5 1.5

28 3.0 1.0 1.5 3.0 1.5 2.0 2.0 1.5 1.5

29 3.5 1.0 1.5 4.0 1.5 2.5 2.5 1.5 2.0

30 3.5 1.0 2.0 -- -- 2.5 2.5 1.5 2.0

31 4.0 1.0 2.0 -- -- 2.0 -- -- --

MONTH1 9.5 .5 1.8 4.0 1.0 2.2 8.0 1.5 2.6

1

For months with missing daily values, the means are calculated using available values.
64 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 10. Seasonal daily maximum, minimum, and mean turbidity at Willow Creek near Anaconda, Montana, October through 

November, 2006 and March through September, 2007.

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

OCTOBER NOVEMBER MARCH

1 2.5 1.5 1.5 7.0 1.5 4.0 -- -- --

2 2.5 1.0 1.5 6.0 2.0 3.5 -- -- --

3 3.0 1.0 1.5 6.0 1.5 3.5 -- -- --

4 3.5 1.5 2.0 7.0 1.5 3.5 -- -- --

5 3.0 1.0 1.5 6.5 2.0 3.5 -- -- --

6 8.5 1.5 3.0 5.5 2.0 2.5 -- -- --

7 3.5 1.5 2.0 -- -- 4.5 -- -- --

8 2.5 1.5 2.0 -- -- -- -- -- --

9 3.5 1.5 2.0 -- -- -- -- -- --

10 3.0 1.5 2.0 -- -- -- -- -- --

11 2.5 2.0 2.0 -- -- -- -- -- --

12 3.0 1.5 2.0 -- -- -- -- -- --

13 2.5 1.5 2.0 -- -- -- -- -- --

14 3.0 1.5 2.0 2.0 1.0 1.5 -- -- 4.5

15 3.0 1.5 2.0 2.5 1.0 1.5 10 4.0 5.5

16 5.0 2.0 2.5 3.0 1.0 2.0 5.0 3.5 4.0

17 5.0 1.5 3.0 3.5 1.0 1.5 13 3.5 5.0

18 5.0 1.5 2.5 4.0 1.0 2.0 9.5 5.0 6.0

19 5.5 1.5 2.5 4.0 1.0 1.5 -- -- --

20 -- -- -- 3.5 1.0 1.5 -- -- --

21 -- -- -- -- -- -- -- -- --

22 -- -- -- -- -- -- -- -- --

23 -- -- -- -- -- -- -- -- --

24 -- -- 2.0 -- -- -- -- -- --

25 3.5 1.0 1.5 -- -- -- -- -- --

26 3.5 1.0 1.5 -- -- -- -- -- --

27 5.0 1.5 2.0 -- -- -- -- -- --

28 4.0 1.5 2.0 -- -- -- -- -- --

29 5.0 1.5 3.0 -- -- -- -- -- --

30 5.5 1.5 3.0 -- -- -- -- -- --

31 5.5 1.5 3.0 -- -- -- -- -- --

MONTH1 8.5 1.0 2.1 7.0 1.0 2.6 13 3.5 5.0
Data 65

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 -- -- -- -- -- -- 11 6.5 8.5

2 -- -- -- -- -- -- 12 6.0 8.0

3 -- -- -- -- -- -- 13 6.0 7.5

4 7.5 3.0 4.0 -- -- -- 11 6.0 7.0

5 4.5 3.0 3.0 17 12 14 10 5.0 6.5

6 4.0 2.5 3.0 17 12 13 10 4.5 6.0

7 6.5 3.0 3.0 18 12 13 10 4.5 5.5

8 7.0 2.5 3.5 14 12 12 10 4.5 6.0

9 6.5 3.0 4.0 24 12 15 7.0 4.0 5.0

10 7.0 3.5 4.0 -- -- -- 8.5 3.5 5.5

11 8.5 3.5 5.5 -- -- -- 9.0 3.5 5.0

12 10 3.5 6.0 -- -- -- 7.5 3.5 4.5

13 -- -- -- -- -- -- 7.0 3.5 4.5

14 -- -- -- -- -- -- 7.0 3.5 4.5

15 11 4.5 7.0 -- -- -- 5.5 3.5 4.5

16 17 3.5 6.0 -- -- -- 6.5 3.5 4.5

17 18 6.5 10 7.5 3.5 4.5 7.0 3.5 4.5

18 11 6.5 10 7.5 3.5 4.5 6.5 3.5 4.0

19 11 4.5 7.0 5.5 3.5 4.0 6.0 3.0 4.0

20 11 4.5 6.5 7.5 3.5 4.5 8.0 3.0 4.5

21 14 4.5 6.5 8.0 4.0 5.5 7.5 3.0 4.0

22 19 6.0 11 6.0 4.0 4.5 7.0 3.0 4.0

23 19 7.0 12 8.5 3.5 4.5 5.5 2.5 3.5

24 38 1.5 17 11 5.0 6.5 5.5 2.5 3.5

25 -- -- -- 16 8.0 9.5 8.5 2.5 3.5

26 -- -- -- 12 8.5 9.5 5.0 2.5 3.0

27 -- -- -- 18 8.5 10 5.0 2.0 3.0

28 -- -- -- 40 10 17 4.5 2.0 3.0

29 -- -- -- -- -- -- 6.0 2.0 3.0

30 -- -- -- -- -- -- 5.0 2.0 3.0

31 -- -- -- -- -- -- -- -- --

MONTH1 38 1.5 6.8 40 3.5 8.9 13 2.0 4.8

Table 10. Seasonal daily maximum, minimum, and mean turbidity at Willow Creek near Anaconda, Montana, October through 

November, 2006 and March through September, 2007.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]
66 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 4.0 2.0 2.5 2.5 <0.5 0.5 3.0 1.0 1.5

2 5.0 2.0 3.0 1.5 <.5 .5 2.0 1.0 1.5

3 4.5 2.5 3.0 2.0 <.5 .5 2.0 1.0 1.5

4 4.0 2.0 3.0 1.0 <.5 .5 2.0 1.5 1.5

5 4.0 2.0 2.5 2.0 <.5 .5 2.5 1.5 1.5

6 4.0 2.0 2.5 2.0 <.5 .5 3.0 1.5 2.0

7 4.0 2.0 2.5 3.0 <.5 .5 3.5 .5 1.5

8 4.5 1.5 2.0 3.0 <.5 .5 3.0 1.0 1.5

9 5.5 1.5 2.0 3.0 .5 1.5 4.5 1.0 2.5

10 3.0 1.0 2.0 7.0 2.0 3.5 8.5 1.5 4.5

11 3.0 1.0 1.5 6.0 2.0 3.5 9.0 1.0 4.5

12 2.5 1.0 1.5 5.5 1.5 3.0 7.5 .5 3.0

13 2.0 1.0 1.5 3.0 1.5 2.0 2.0 .5 1.0

14 3.5 1.0 1.5 4.0 1.5 2.0 2.0 .5 1.0

15 2.5 1.0 1.5 3.5 1.5 2.0 2.0 .5 1.0

16 3.5 1.0 1.5 4.5 1.5 2.5 2.0 .5 1.0

17 5.0 1.0 1.5 4.0 1.5 2.5 1.5 .5 1.0

18 27 1.0 5.0 4.0 1.5 2.0 1.5 1.0 1.0

19 3.0 .5 1.0 4.5 1.5 2.5 3.0 1.0 1.5

20 3.0 .5 1.0 20 2.0 4.0 2.0 1.0 1.0

21 2.5 <.5 1.0 4.5 1.5 2.5 2.0 .5 1.0

22 2.0 <.5 1.0 3.0 1.5 2.0 11 1.0 1.5

23 2.0 .5 1.0 3.5 1.5 2.0 100 2.0 10

24 2.0 .5 1.0 4.0 1.5 2.0 9.0 2.0 4.5

25 2.0 <.5 1.0 3.0 1.5 2.0 4.5 1.5 2.5

26 1.5 <.5 .5 3.5 1.5 2.0 3.5 1.5 2.0

27 2.0 <.5 .5 3.5 1.5 2.0 4.5 1.5 2.0

28 2.0 <.5 .5 3.0 1.5 2.0 4.0 1.5 2.0

29 1.5 <.5 .5 4.0 1.5 2.0 4.0 1.5 2.0

30 1.0 <.5 .5 3.5 1.5 2.0 4.0 1.0 2.0

31 1.5 <.5 .5 3.5 1.5 1.5 -- -- --

MONTH1 27 <.5 1.6 20 <.5 1.8 100 .5 2.2

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, October through 

November, 2006 and March through September, 2007.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]
Data 67

Table 11. Seasonal daily maximum, minimum, and mean turbidity at Warm Springs Creek near Anaconda, Montana, October through 

December, 2006 and April through September, 2007.

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

OCTOBER NOVEMBER DECEMBER

1 3.0 2.0 2.0 4.0 2.0 3.0 5.0 3.0 3.0

2 3.0 2.0 2.0 3.0 2.0 2.5 4.0 3.0 3.0

3 2.0 2.0 2.0 43 2.0 5.5 3.0 2.0 2.5

4 5.5 2.0 2.0 3.0 2.0 2.5 4.0 3.0 3.0

5 3.0 2.0 2.0 6.0 2.0 2.5 4.0 3.0 3.0

6 6.5 2.0 2.0 4.0 2.0 2.5 4.0 3.0 3.0

7 3.5 2.0 2.0 5.0 2.0 3.0 5.0 3.0 3.0

8 2.5 1.5 2.0 8.0 3.0 5.0 3.0 3.0 3.0

9 2.5 1.5 2.0 4.0 2.0 3.0 4.0 3.0 3.0

10 2.5 1.5 2.0 3.0 2.0 3.0 4.0 3.0 3.0

11 3.5 1.5 1.5 5.0 2.0 2.5 4.0 3.0 3.0

12 2.5 1.5 2.0 3.0 2.0 2.5 -- -- 3.0

13 2.5 1.5 1.5 5.0 2.0 2.5 -- -- --

14 2.5 1.5 1.5 4.0 2.0 3.0 -- -- --

15 1.5 1.5 1.5 4.0 2.0 3.0 -- -- --

16 4.0 1.5 2.0 3.0 2.0 2.5 -- -- --

17 3.0 1.5 2.0 3.0 2.0 2.0 -- -- --

18 2.5 1.5 1.5 3.0 2.0 2.0 -- -- --

19 2.5 1.5 1.5 3.0 2.0 2.0 -- -- --

20 39 1.5 6.0 3.0 2.0 2.0 -- -- --

21 3.5 1.5 2.0 7.0 2.0 2.5 -- -- --

22 2.0 1.5 2.0 5.0 2.0 3.0 -- -- --

23 2.0 1.5 2.0 3.0 2.0 3.0 -- -- --

24 2.5 2.0 2.0 3.0 2.0 3.0 -- -- --

25 3.0 2.0 2.0 3.0 2.0 3.0 -- -- --

26 3.0 2.0 2.0 3.0 3.0 3.0 -- -- --

27 3.0 2.0 2.0 4.0 3.0 3.0 -- -- --

28 2.0 2.0 2.0 5.0 2.0 2.5 -- -- --

29 3.0 2.0 2.0 4.0 2.0 2.5 -- -- --

30 3.0 2.0 2.0 11 2.0 3.0 -- -- --

31 5.0 2.0 3.0 -- -- -- -- -- --

MONTH1 39 1.5 2.1 43 2.0 2.8 5.0 2.0 3.0
68 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 -- -- -- 21 6.0 10 6.5 3.0 3.5

2 -- -- -- 16 7.0 10 4.5 3.0 3.5

3 -- -- -- 55 7.0 16 5.5 3.0 4.0

4 4.0 3.0 3.0 12 4.0 5.5 22 2.5 5.0

5 4.0 2.0 3.0 6.0 3.0 4.0 29 7.0 14

6 4.0 3.0 3.0 4.0 3.0 3.5 14 6.0 8.5

7 4.0 3.0 3.0 5.0 3.0 3.0 7.0 4.0 5.0

8 4.0 3.0 3.0 4.0 3.0 3.0 6.0 3.0 3.5

9 4.0 3.0 3.5 5.0 3.0 3.5 5.0 3.0 3.5

10 4.0 3.0 3.0 7.5 3.0 4.5 10 3.0 5.0

11 4.0 3.0 3.0 10 5.0 7.0 24 8.5 13

12 4.0 2.0 3.0 10 5.0 7.5 39 4.0 7.5

13 4.0 3.0 3.0 15 5.0 9.0 9.5 3.0 4.5

14 4.0 3.0 3.0 7.5 4.0 5.5 8.5 3.0 4.0

15 4.0 3.0 3.0 6.5 3.0 4.0 4.5 3.0 3.5

16 4.0 3.0 3.0 5.0 3.0 3.5 5.5 3.0 3.5

17 14 2.0 3.5 5.0 3.0 4.0 7.5 3.5 5.0

18 16 4.0 7.5 5.0 3.0 4.0 14 4.5 8.5

19 5.0 3.0 3.5 11 4.0 5.5 43 7.5 20

20 7.0 3.0 4.0 10 4.0 5.5 33 5.5 11

21 28 3.0 7.0 18 5.0 7.0 47 6.5 12

22 9.0 3.0 3.5 7.0 3.0 4.0 25 7.0 14

23 5.0 2.0 3.5 11 3.0 3.5 33 2.5 7.5

24 7.0 3.0 3.5 7.5 3.0 3.5 4.5 2.5 2.5

25 5.0 3.0 3.5 7.5 2.0 3.5 12 2.5 3.0

26 5.0 3.0 3.5 4.0 2.0 2.5 3.5 2.5 2.5

27 5.0 3.0 3.5 8.5 2.0 3.5 2.5 2.5 2.5

28 5.0 3.0 4.0 8.5 3.0 5.0 4.5 2.5 2.5

29 9.0 4.0 6.0 4.0 2.0 3.0 3.5 1.0 2.5

30 23 7.0 13 5.5 2.0 2.5 3.5 1.0 2.0

31 -- -- -- 3.0 2.0 2.5 -- -- --

MONTH1 28 2.0 4.0 55 2.0 5.1 47 1.0 6.2

Table 11. Seasonal daily maximum, minimum, and mean turbidity at Warm Springs Creek near Anaconda, Montana, October through 

December, 2006 and April through September, 2007.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]
Data 69

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 3.5 1.0 2.0 3.0 2.0 2.5 -- -- 2.5

2 -- -- 2.5 3.0 2.0 2.5 -- -- --

3 5.0 2.0 3.5 3.0 2.0 2.5 -- -- --

4 4.0 2.0 3.0 3.0 2.0 2.5 -- -- 2.5

5 4.0 2.0 3.0 8.5 3.0 3.5 7.5 1.5 3.0

6 4.0 2.0 3.0 4.5 2.5 3.5 2.5 1.5 2.0

7 4.0 2.0 3.0 5.5 3.5 4.0 2.0 .5 1.0

8 5.0 2.0 3.0 6.5 4.5 5.5 .5 .5 .5

9 4.0 2.0 3.0 6.5 2.0 3.5 .5 .5 .5

10 4.0 2.0 3.0 2.5 2.0 2.0 .5 .5 .5

11 4.0 2.0 3.0 2.5 2.0 2.0 .5 .5 .5

12 4.0 2.0 3.0 2.5 2.0 2.0 .5 .5 .5

13 3.0 2.0 2.5 3.5 2.0 2.0 .5 .5 .5

14 4.0 2.0 2.5 2.5 2.0 2.0 1.5 <.5 .5

15 6.0 2.0 3.0 2.5 2.0 2.0 1.0 <.5 .5

16 4.0 2.0 2.5 7.0 2.0 2.0 1.5 <.5 .5

17 59 2.0 7.0 2.5 2.0 2.0 1.0 .5 .5

18 35 2.0 5.0 11 2.0 2.5 1.5 .5 .5

19 5.0 2.0 2.5 5.5 2.0 2.0 1.5 .5 1.0

20 5.0 2.0 2.5 2.5 2.0 2.0 1.0 <.5 .5

21 5.0 2.0 2.5 2.5 2.0 2.0 1.0 <.5 .5

22 4.0 2.0 2.5 2.5 2.0 2.0 1.0 .5 .5

23 4.0 2.0 2.5 3.5 1.5 2.0 37 1.0 5.0

24 4.5 2.0 2.5 2.5 1.5 2.0 2.0 .5 1.0

25 8.5 3.0 3.5 2.5 1.5 1.5 1.5 .5 1.0

26 4.0 2.0 2.5 2.5 1.5 1.5 1.5 .5 .5

27 4.0 2.0 3.0 2.5 1.5 1.5 2.5 .5 1.0

28 4.0 2.0 2.5 1.5 1.5 1.5 1.0 .5 1.0

29 4.5 2.0 2.5 1.5 1.5 1.5 1.5 .5 1.0

30 4.5 2.0 2.5 2.5 1.5 1.5 1.0 .5 1.0

31 3.0 2.0 2.5 -- -- 3.0 -- -- --

MONTH1 59 1.0 3.0 11 1.5 2.3 37 <.5 1.1

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, October through 

December, 2006 and April through September, 2007.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]
70 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, October through November, 

2006 and March through September, 2007.

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

OCTOBER NOVEMBER MARCH

1 2.0 0.5 1.0 2.5 1.0 1.5 -- -- --

2 2.5 .5 1.0 3.5 1.0 1.5 -- -- --

3 5.0 .5 1.0 3.0 1.5 2.0 -- -- --

4 1.0 .5 1.0 3.0 1.5 1.5 -- -- --

5 8.0 .5 1.5 3.0 1.0 1.5 -- -- --

6 5.0 1.0 1.5 3.0 1.0 1.5 -- -- --

7 1.5 .5 1.0 4.5 1.5 2.5 -- -- --

8 1.5 .5 1.0 15 2.0 6.0 -- -- --

9 2.5 1.0 1.0 3.0 1.5 2.0 -- -- --

10 12 1.0 2.0 3.5 1.5 1.5 -- -- --

11 3.5 1.0 2.0 3.0 1.5 1.5 -- -- --

12 3.0 1.0 1.5 3.5 1.5 1.5 -- -- --

13 2.5 1.0 1.0 3.0 1.5 1.5 -- -- --

14 3.0 1.0 1.0 3.5 1.5 2.0 -- -- --

15 3.5 1.0 1.0 5.5 1.5 2.5 -- -- --

16 9.0 1.0 2.0 4.5 1.5 2.0 -- -- --

17 3.0 1.0 1.0 4.0 1.5 2.0 -- -- --

18 3.0 1.0 1.0 3.5 1.5 2.0 -- -- --

19 19 1.0 2.5 4.0 1.5 2.0 -- -- --

20 19 1.5 4.0 4.5 1.5 2.0 -- -- --

21 8.0 1.0 2.0 -- -- -- -- -- --

22 2.5 1.0 1.0 -- -- -- 2.5 1.0 1.5

23 -- -- -- -- -- -- 2.0 1.0 1.5

24 -- -- -- -- -- -- 3.0 1.0 1.5

25 5.5 1.0 1.5 -- -- -- 2.5 1.0 1.5

26 5.0 1.0 1.5 -- -- -- 2.5 1.0 2.0

27 4.0 1.0 1.5 -- -- -- 4.5 1.5 2.5

28 3.0 1.0 1.5 -- -- -- 3.0 1.0 2.0

29 4.0 1.0 1.5 -- -- -- 7.0 1.5 2.5

30 2.5 1.0 1.5 -- -- -- 4.5 1.5 2.0

31 2.5 1.0 1.5 -- -- -- 3.5 1.0 1.5

MONTH1 19 .5 1.5 15 1.0 2.0 7.0 1.0 1.9
Data 71

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 2.5 1.0 1.5 26 6.0 10 9.5 3.5 4.5

2 3.0 1.0 1.5 28 7.0 14 9.0 3.0 4.5

3 4.5 1.0 2.0 49 8.0 21 8.5 3.5 5.0

4 3.5 1.0 2.0 32 3.0 7.0 8.5 3.5 5.0

5 3.0 1.0 1.5 3.5 2.0 2.5 16 6.0 9.0

6 2.5 1.0 1.5 5.5 2.0 3.0 16 7.0 11

7 2.5 1.0 1.5 8.0 1.5 2.5 7.5 4.0 5.5

8 2.5 1.0 1.5 5.5 1.0 2.5 8.0 3.5 5.0

9 2.5 1.0 1.5 32 1.5 6.5 6.5 3.0 4.0

10 2.5 1.0 1.5 15 3.5 7.0 20 3.0 5.5

11 2.5 1.0 1.5 9.5 3.0 5.5 10 3.5 6.0

12 3.5 1.5 2.0 16 2.5 6.0 8.5 3.5 4.5

13 3.0 1.5 2.0 8.5 3.5 5.0 6.5 3.0 4.0

14 2.5 1.0 2.0 8.0 3.0 5.0 6.0 3.0 4.0

15 3.5 2.0 2.5 6.0 2.0 3.5 7.0 3.0 4.0

16 3.5 1.5 2.5 7.0 3.0 4.0 7.5 3.0 4.0

17 3.5 1.5 2.0 6.0 3.0 4.0 9.0 3.0 3.5

18 9.5 3.0 6.5 16 3.0 5.5 10 2.5 4.0

19 18 3.0 6.5 12 4.5 6.5 8.5 3.0 4.0

20 8.5 2.0 3.5 8.0 4.0 5.5 7.5 3.0 4.0

21 5.5 2.0 3.0 22 5.5 9.5 9.5 3.0 4.0

22 4.0 1.5 2.5 11 5.5 7.0 -- -- --

23 9.0 2.0 3.0 8.0 3.5 4.5 -- -- --

24 5.0 2.5 3.0 28 3.5 5.5 -- -- --

25 18 2.5 3.5 19 3.5 5.5 -- -- --

26 4.0 2.0 2.5 6.5 3.0 4.0 -- -- --

27 11 2.0 3.0 12 3.5 5.0 10 1.0 2.0

28 23 3.0 5.5 67 5.0 15 3.0 .5 1.5

29 24 4.0 7.5 7.0 4.0 5.0 3.0 .5 1.5

30 18 5.0 11 10 3.5 5.0 6.5 1.0 2.0

31 -- -- -- 8.5 3.5 5.0 -- -- --

MONTH1 24 1.0 3.0 67 1.0 6.4 20 .5 4.5

Table 12. Seasonal daily maximum, minimum, and mean turbidity at Lost Creek near Anaconda, Montana, October through November, 

2006 and March through September, 2007.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data
72 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 5.0 <0.5 1.5 2.5 0.5 1.0 4.0 2.5 3.0

2 5.0 .5 2.0 1.5 .5 1.0 4.0 2.0 3.0

3 8.5 .5 2.0 21 .5 2.0 11 2.0 3.0

4 3.5 1.0 2.0 3.0 1.0 1.5 5.0 2.0 2.5

5 2.5 .5 1.5 7.0 .5 1.5 5.5 2.5 3.0

6 2.5 .5 1.5 4.0 1.5 2.0 5.0 2.0 2.5

7 6.0 1.0 1.5 3.0 1.5 2.0 3.0 1.5 2.0

8 2.0 .5 1.5 2.0 1.0 1.5 3.5 1.5 2.0

9 2.0 .5 1.5 20 1.0 2.0 3.5 1.5 2.0

10 2.5 .5 1.5 4.5 2.0 3.0 -- -- 2.0

11 5.5 .5 1.5 64 2.5 8.5 -- -- --

12 5.5 .5 1.5 7.0 3.5 5.0 -- -- --

13 4.5 .5 1.5 4.5 3.0 3.5 -- -- --

14 6.0 1.0 2.0 4.0 2.5 3.0 3.0 1.5 2.5

15 2.5 1.0 1.5 4.5 2.5 3.0 -- -- 2.0

16 1.5 1.0 1.5 4.5 2.5 3.0 -- -- --

17 8.5 1.0 2.0 4.5 2.5 3.5 -- -- 2.5

18 48 .5 4.5 4.5 2.5 3.5 -- -- 2.5

19 2.5 1.0 1.5 4.0 2.5 3.0 -- -- 2.0

20 2.5 .5 1.5 4.0 2.5 3.0 -- -- --

21 3.0 1.0 2.0 4.0 2.5 3.0 -- -- --

22 6.5 1.0 2.0 12 2.5 3.5 -- -- --

23 7.0 .5 1.5 4.0 2.5 3.0 -- -- 6.0

24 7.0 1.0 2.5 7.5 2.5 3.0 3.0 2.0 2.5

25 4.0 .5 1.0 4.0 2.5 3.0 2.5 2.0 2.5

26 4.0 .5 1.5 4.5 2.5 3.0 -- -- 2.0

27 2.0 .5 1.0 4.5 2.5 3.0 -- -- --

28 2.0 <.5 1.0 4.0 2.5 3.0 -- -- --

29 6.0 .5 1.0 4.0 2.5 3.0 3.0 2.5 2.5

30 2.0 .5 1.0 4.0 2.5 3.0 4.5 2.5 3.0

31 1.5 <.5 0.5 6.5 2.5 3.0 -- -- --

MONTH1 48 <.5 1.6 64 .5 2.9 11 1.5 2.6

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, October through November, 

2006 and March through September, 2007.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data
Data 73

Table 13. Seasonal daily maximum, minimum, and mean turbidity at Clark Fork above Missoula, Montana, April through September, 

2007.

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbol: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 -- -- -- 37 25 30 17 12 15

2 -- -- -- 34 25 29 17 12 14

3 -- -- -- 52 28 37 17 12 14

4 -- -- -- 55 39 44 17 12 14

5 -- -- -- 41 26 34 19 12 15

6 -- -- -- 28 19 22 27 16 19

7 -- -- -- 21 16 18 46 26 36

8 -- -- -- 18 14 16 47 26 36

9 -- -- -- 17 13 15 31 22 27

10 -- -- -- 20 13 16 26 18 22

11 -- -- -- 24 17 19 30 19 23

12 -- -- -- 24 18 20 32 23 28

13 -- -- -- 24 18 21 34 21 25

14 -- -- -- 24 18 21 35 16 20

15 -- -- -- 23 15 18 23 14 18

16 -- -- -- 17 12 14 18 12 16

17 -- -- -- 14 11 12 18 12 14

18 -- -- -- 14 10 12 15 9.0 11

19 -- -- -- 14 11 13 -- -- 9.5

20 -- -- -- 15 11 12 -- -- --

21 -- -- -- 14 11 12 -- -- --

22 -- -- -- 15 11 12 -- -- 8.5

23 -- -- -- 17 12 14 11 7.5 8.5

24 -- -- -- 18 13 15 10 6.0 7.5

25 -- -- 7.5 16 11 13 8.5 5.5 7.0

26 11 6.5 8.5 15 11 13 8.5 5.0 6.5

27 13 8.5 10 15 10 12 8.0 5.0 6.0

28 13 9.0 11 18 9.5 12 8.5 5.5 6.0

29 26 11 16 25 15 19 10 5.0 6.5

30 38 21 26 24 16 18 9.5 5.0 6.0

31 -- -- -- 20 13 16 -- -- --

MONTH1 38 6.5 13 55 9.5 19 47 5.0 16
74 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 9.5 4.5 6.0 -- -- -- -- -- --

2 10 4.0 6.5 -- -- -- -- -- --

3 -- -- 5.5 7.5 3.0 4.5 -- -- --

4 9.0 3.5 4.5 7.5 3.0 4.5 -- -- 2.5

5 8.5 4.0 5.5 7.5 3.0 4.5 6.0 2.0 3.0

6 -- -- -- -- -- -- 5.5 2.5 3.5

7 -- -- -- -- -- -- 9.5 2.5 4.5

8 -- -- -- -- -- -- -- -- 6.0

9 -- -- -- 7.0 3.5 5.0 8.5 2.5 4.0

10 -- -- -- 7.0 3.5 5.0 12 1.5 5.0

11 -- -- -- 7.0 3.0 4.5 -- -- --

12 -- -- -- 8.5 3.0 5.0 -- -- 3.5

13 -- -- -- 9.0 3.0 5.0 8.0 2.5 4.0

14 -- -- 3.0 7.5 2.5 4.0 5.5 2.5 3.5

15 4.0 2.0 3.0 7.0 3.5 5.0 9.0 3.0 4.5

16 5.0 1.5 2.5 7.0 3.0 4.5 9.0 2.5 4.0

17 5.0 2.0 2.5 7.0 3.5 5.0 7.0 2.5 4.0

18 6.5 1.5 3.5 7.0 3.5 5.5 7.0 3.0 4.0

19 8.5 1.5 3.5 7.0 4.0 5.5 9.0 3.0 6.0

20 3.0 1.5 2.0 7.0 3.5 5.0 -- -- 5.5

21 3.0 1.0 2.0 8.5 3.5 5.0 6.5 3.5 4.5

22 7.0 1.0 2.0 12 4.0 7.0 10 3.0 5.5

23 3.0 1.0 2.0 8.0 4.0 5.5 11 4.5 6.5

24 7.0 1.0 2.0 -- -- 8.0 16 7.0 9.0

25 4.0 1.5 2.5 -- -- -- 17 5.5 9.5

26 5.5 2.5 3.5 -- -- -- 12 4.5 6.5

27 8.0 3.0 4.5 -- -- -- 8.5 3.5 5.5

28 6.0 2.5 4.0 -- -- -- 7.5 3.0 4.5

29 6.5 2.5 4.0 -- -- -- 7.0 3.0 4.5

30 6.5 2.5 4.0 -- -- -- 5.0 2.5 3.5

31 -- -- -- -- -- -- -- -- --

MONTH1 10 1.0 3.4 12 2.5 5.2 17 1.5 4.9

1

For months with missing daily values, the means are calculated using available values.

Table 13. Seasonal daily maximum, minimum, and mean turbidity at Clark Fork above Missoula, Montana, April through September, 

2007.—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]
Data 75

Table 14. 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

02/26/2007 1505 170 49.1 12.1 -- -- 8.0 10.1

02/26/2007 1510 170 49.1 12.2 -- -- 8.1 10.0

12323670 Mill Creek near Anaconda 06/18/2007 1345 37 10.7 2.50 -- -- 17.2 18.8

06/18/2007 1350 38 10.8 2.55 -- -- 18.0 18.1

12323700 Mill Creek at Opportunity 07/23/2007 1530 71 19.6 5.37 -- -- 55.1 53.5

07/23/2007 1535 69 19.4 5.05 -- -- 52.2 54.3

12323750 Silver Bow Creek at Warm 

Springs

03/27/2007 1220 240 69.5 15.2 -- -- 10.1 13.0

03/27/2007 1225 240 70.0 15.4 -- -- 10.1 13.2

12323760 Warm Springs Creek near 

Anaconda

08/27/2007 1240 120 36.3 7.84 -- -- 2.6 2.6

08/27/2007 1245 120 36.4 7.89 -- -- 2.7 2.6

12324200 Clark Fork at Deer Lodge 05/08/2007 1130 190 56.0 12.2 -- -- 15.1 21.0

05/08/2007 1135 190 54.9 12.4 -- -- 15.3 21.4

12334550 Clark Fork at Turah Bridge, 

near Bonner

06/07/2007 1455 92 26.0 6.61 -- -- 10.3 19.6

06/07/2007 1500 89 25.2 6.39 -- -- 10.2 19.6

12340000 Blackfoot River near Bonner 05/31/2007 1430 94 24.5 8.06 0.16 0.019 .84 1.0

05/31/2007 1435 93 24.2 7.94 .15 .017 .89 1.1

12340500 Clark Fork above Missoula 11/15/2006 1000 130 35.3 10.2 -- -- 3.2 3.6

11/15/2006 1005 130 36.4 10.4 -- -- 3.4 3.8

05/14/2007 1500 77 20.9 6.08 .31 .063 2.6 4.9

05/14/2007 1505 77 20.9 6.07 .30 .064 2.7 5.0

12352500 Bitterroot River near 

Missoula

06/20/2007 0700 33 9.69 2.12 .15 .016 .35 .37

06/20/2007 0705 33 9.66 2.10 .17 .016 .36 .42

12354500 Clark Fork at St. Regis 06/07/2007 1330 58 16.2 4.31 .25 .039 2.1 3.2

06/07/2007 1340 57 15.9 4.15 .24 .042 2.1 3.2
76 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana 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 02/26/2007 1505 0.77 0.94 25.5 61.4 16 420 0.27 02/26/2007 1510 .78 .93 25.7 59.2 17 422 .29 12323670 Mill Creek near Anaconda 06/18/2007 1345 .04 .07 1.8 3.4 35 124 E.07 06/18/2007 1350 .04 .06 1.9 4.1 37 131 E.08 12323700 Mill Creek at Opportunity 07/23/2007 1530 .07 .09 2.6 3.5 94 155 .20 07/23/2007 1535 .08 .08 2.5 3.7 89 156 .20 12323750 Silver Bow Creek at Warm Springs 03/27/2007 1220 E.03 .08 2.1 6.2 8 230 <.12 03/27/2007 1225 E.02 .08 2.1 5.8 7 233 E.06 12323760 Warm Springs Creek near Anaconda 08/27/2007 1240 E.02 .03 .62 E1.1 E5 67 <.12 08/27/2007 1245 <.04 .03 .69 1.2 E5 64 <.12 12324200 Clark Fork at Deer Lodge 05/08/2007 1130 .05 .27 6.8 53.7 16 814 E.11 05/08/2007 1135 .06 .27 6.8 53.7 13 827 .12 12334550 Clark Fork at Turah Bridge, near Bonner 06/07/2007 1455 .04 .52 12.7 78.5 48 2,460 .37 06/07/2007 1500 .05 .46 8.8 76.9 47 2,410 .35 12340000 Blackfoot River near Bonner 05/31/2007 1430 <.04 <.02 E.37 1.4 7 196 <.12 05/31/2007 1435 <.04 <.02 E.35 1.3 6 198 <.12 12340500 Clark Fork above Missoula 11/15/2006 1000 <.04 .07 1.2 7.9 14 223 <.12 11/15/2006 1005 <.04 .07 1.2 7.6 13 239 <.12 05/14/2007 1500 <.04 .21 2.1 22.9 15 793 <.12 05/14/2007 1505 E.02 .19 2.5 25.4 15 820 E.07

12352500 Bitterroot River near 

Missoula

06/20/2007 0700 <.04 E.01 .47 E1.0 40 191 <.12

06/20/2007 0705 <.04 E.01 .45 E1.1 40 204 <.12

12354500 Clark Fork at St. Regis 06/07/2007 1330 <.04 .10 2.0 12.6 18 585 <.12

06/07/2007 1340 <.04 .08 2.1 13.4 18 613 <.12

Table 14. 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 77

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

02/26/2007 1505 8.60 264 334 194 251 74 13

02/26/2007 1510 8.61 268 322 195 244 71 11

12323670 Mill Creek near Anaconda 06/18/2007 1345 .59 4.3 9.4 .97 2 64 4

06/18/2007 1350 .58 4.5 9.8 .91 2 62 3

12323700 Mill Creek at Opportunity 07/23/2007 1530 .42 5.7 9.3 1.3 E2 82 1

07/23/2007 1535 .41 5.5 9.1 1.2 2 85 1

12323750 Silver Bow Creek at Warm 

Springs

03/27/2007 1220 1.48 176 239 3.6 11 90 5

03/27/2007 1225 1.53 172 240 4.1 11 89 6

12323760 Warm Springs Creek near 

Anaconda

08/27/2007 1240 .23 .8 4.3 E.48 E2 67 3

08/27/2007 1245 .25 .8 3.8 <.60 E2 69 3

12324200 Clark Fork at Deer Lodge 05/08/2007 1130 6.83 29.0 183 6.1 45 76 34

05/08/2007 1135 7.23 28.9 178 6.3 45 76 34

12334550 Clark Fork at Turah Bridge, 

near Bonner

06/07/2007 1455 14.9 17.7 283 6.8 113 65 157

06/07/2007 1500 14.7 17.0 274 6.7 104 66 154

12340000 Blackfoot River near Bonner 05/31/2007 1430 .26 2.0 15.1 E.39 E2 87 15

05/31/2007 1435 .27 2.0 15.4 E.30 E2 87 15

12340500 Clark Fork above Missoula 11/15/2006 1000 1.09 10.7 24.4 3.0 15 37 18

11/15/2006 1005 1.08 10.8 25.8 3.3 15 40 17

05/14/2007 1500 3.99 8.1 117 2.5 47 34 126

05/14/2007 1505 3.96 8.3 84.2 3.0 44 39 110

12352500 Bitterroot River near 

Missoula

06/20/2007 0700 .15 4.3 11.2 .74 2 68 7

06/20/2007 0705 .15 4.4 11.3 E.32 E1 72 7

12354500 Clark Fork at St. Regis 06/07/2007 1330 2.23 1.8 49.5 2.0 21 58 49

06/07/2007 1340 2.31 1.8 49.2 2.0 21 60 48

Table 14. 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]
78 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 15. 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 12 0.38 1.2 Yes

Magnesium, filtered, mg/L 12 .12 1.5 Yes

Total nitrogen, unfiltered, mg/L 4 .01 4.3 Yes

Total phosphorous, unfiltered, mg/L 4 .00 3.8 Yes

Arsenic, filtered, μg/L 12 .62 5.9 Yes

Arsenic, unfiltered recoverable, μg/L 12 .24 1.9 Yes

Cadmium, filtered, μg/L 12 .00 4.8 Yes

Cadmium, unfiltered recoverable, μg/L 12 .01 7.2 Yes

Copper, filtered, μg/L 12 .80 17 Yes

Copper, unfiltered recoverable, μg/L 12 .79 3.8 Yes

Iron, filtered, μg/L 12 1.3 5.2 Yes

Iron, unfiltered recoverable, μg/L 12 14 2.7 Yes

Lead, filtered, μg/L 12 .01 5.6 Yes

Lead, unfiltered recoverable, μg/L 12 .09 2.7 Yes

Manganese, filtered, μg/L 12 1.2 2.7 Yes

Manganese, unfiltered recoverable, μg/L 12 7.4 7.1 Yes

Zinc, filtered, μg/L 12 .28 1.5 Yes

Zinc, unfiltered recoverable, μg/L 12 2.4 5.8 Yes

Sediment, suspended, percent finer than 0.062 mm 12 1.8 2.7 Yes

Sediment, suspended, mg/L 12 3.4 9.6 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).
Data 79

Table 16. 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 0.21 0.62 Yes

Magnesium, filtered, mg/L 8 .08 .89 Yes

Arsenic, filtered, μg/L 8 .44 3.3 Yes

Arsenic, unfiltered recoverable, μg/L 8 .32 2.1 Yes

Cadmium, filtered, μg/L 8 .01 27 Yes3

Cadmium, unfiltered recoverable, μg/L 8 .01 7.6 Yes

Copper, filtered, μg/L 8 .02 .84 Yes

Copper, unfiltered recoverable, μg/L 8 .49 4.4 Yes

Iron, filtered, μg/L 8 .90 4.0 Yes

Iron, unfiltered recoverable, μg/L 8 7.1 2.4 Yes

Lead, filtered, μg/L 8 .01 7.2 Yes

Lead, unfiltered recoverable, μg/L 8 .05 2.9 Yes

Manganese, filtered, μg/L 8 2.0 6.8 Yes

Manganese, unfiltered recoverable, μg/L 8 3.3 4.8 Yes

Zinc, filtered, μg/L 8 .14 6.1 Yes

Zinc, unfiltered recoverable, μg/L 8 .79 6.2 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).

3

Exceedance of data-quality objective resulted from a statistical artifact of calculating the difference between one replicate sample pair for which one value 

was estimated and one was near the laboratory reporting level. Because analytical variation, in percent, can be large at very low concentrations, the precision 

estimate may not be representative of analytical performance at detectable concentrations. When this one replicate pair was excluded, the other seven replicate 

pairs had an acceptable relative standard deviation for filtered cadmium of 7.1 percent.
80 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 17. 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 5 96.6–114 105 Yes

Arsenic, unfiltered recoverable, μg/L 5 95.2–109 102 Yes

Cadmium, filtered, μg/L 5 103–112 107 Yes

Cadmium, unfiltered recoverable, μg/L 5 94.4–111 103 Yes

Copper, filtered, μg/L 5 99.2–111 105 Yes

Copper, unfiltered recoverable, μg/L 5 86.9–110 98.4 Yes

Iron, filtered, μg/L 5 92.1–108 99.9 Yes

Iron, unfiltered recoverable, μg/L 5 98.5–110 104 Yes

Lead, filtered, μg/L 5 93.9–105 99.6 Yes

Lead, unfiltered recoverable, μg/L 5 100–106 103 Yes

Manganese, filtered, μg/L 5 99.9–114 107 Yes

Manganese, unfiltered recoverable, μg/L 5 97.0–116 107 Yes

Zinc, filtered, μg/L 5 102–113 107 Yes

Zinc, unfiltered recoverable, μg/L 5 96.5–110 103 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

Table 18. 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 5 100–113 106 Yes

Arsenic, unfiltered recoverable, μg/L 5 98.2–106 102 Yes

Cadmium, filtered, μg/L 5 102–114 108 Yes

Cadmium, unfiltered recoverable, μg/L 5 92.2–104 98.0 Yes

Copper, filtered, μg/L 5 89.8–110 100 Yes

Copper, unfiltered recoverable, μg/L 5 91.8–101 96.3 Yes

Iron, filtered, μg/L 5 103–111 107 Yes

Iron, unfiltered recoverable, μg/L 5 94.7–112 103 Yes

Lead, filtered, μg/L 5 103–115 109 Yes

Lead, unfiltered recoverable, μg/L 5 102–107 104 Yes

Manganese, filtered, μg/L 5 100–113 106 Yes

Manganese, unfiltered recoverable, μg/L 5 96.1–106 101 Yes

Zinc, filtered, μg/L 5 95.7–113 104 Yes

Zinc, unfiltered recoverable, μg/L 5 89.2–107 98.0 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).
Data 81

Table 19. 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)

10/17/2006 1410 5.8 2 <0.02 <0.014 <0.06 <0.008 <0.12 <0.20 <0.04 <0.02

11/13/2006 1300 5.5 2 <.02 <.014 -- -- <.12 <.20 <.04 <.02

02/23/2007 1000 5.7 2 <.02 <.014 -- -- <.12 <.20 <.04 <.02

03/28/2007 1630 5.6 2 <.02 <.014 -- -- <.12 <.20 <.04 <.02

05/03/2007 1110 5.5 2 <.02 .014 <.06 <.008 <.12 <.20 <.04 <.02

05/09/2007 1300 5.6 2 <.02 <.014 -- -- <.12 <.20 <.04 <.02

06/01/2007 0640 6.0 2 <.02 <.014 <.06 <.008 <.12 <.20 <.04 <.02

06/04/2007 1330 5.7 2 <.02 <.014 -- -- <.12 <.20 <.04 <.02

06/13/2007 1140 5.8 -- <.02 <.014 <.06 <.008 <.12 <.20 <.04 <.02

06/19/2007 1700 5.5 2 <.02 <.014 -- -- <.12 <.20 <.04 <.02

06/27/2007 1240 6.1 2 <.02 <.014 <.06 <.008 <.12 <.20 <.04 <.02

07/24/2007 1800 5.4 2 <.02 <.014 -- -- <.12 <.20 <.04 <.02

08/28/2007 1700 5.7 2 <.02 <.014 -- -- <.12 <.20 <.04 <.02

Date Time

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)

10/17/2006 1410 <0.40 <1.2 <6 <6 <0.12 <0.06 <0.2 <0.6 <0.60 <2

11/13/2006 1300 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 <.60 <2

02/23/2007 1000 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 <.60 <2

03/28/2007 1630 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 <.60 <2

05/03/2007 1110 3.6 <1.2 <6 <6 .39 <.06 <.2 <.6 6.7 <2

05/09/2007 1300 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 <.60 <2

06/01/2007 0640 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 <.60 <2

06/04/2007 1330 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 <.60 <2

06/13/2007 1140 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 <.60 <2

06/19/2007 1700 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 <.60 <2

06/27/2007 1240 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 2.8 <2

07/24/2007 1800 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 <.60 <2

08/28/2007 1700 <.40 <1.2 <6 <6 <.12 <.06 <.2 <.6 <.60 <2
82 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana Table 20. Analyses of fine-grained bed sediment, upper Clark Fork basin, Montana, August 2007. [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 

3 123 25.0 25.9 3,030 34,100 464 2,900 14.0 5,590

12323750 Silver Bow Creek at Warm 

Springs

3 108 5.4 24.6 294 25,100 75 7,190 15.6 672

12323800 Clark Fork near Galen 3 87 5.3 26.4 956 26,100 116 17,200 20.0 1,040

461415112450801 Clark Fork below Lost Creek, 

near Galen 

3 109 6.2 27.1 1,540 31,100 170 7,900 15.1 1,430

461559112443301 Clark Fork at county bridge, 

near Racetrack 

3 79 6.0 24.1 1,320 25,900 142 2,890 13.0 1,240

461903112440701 Clark Fork at Demspey Creek 

diversion, near Racetrack 

3 87 5.2 24.0 1,120 27,100 132 7,570 12.7 1,160

12324200 Clark Fork at Deer Lodge 3 63 4.7 26.4 986 25,200 128 3,600 13.0 1,140

12324680 Clark Fork at Goldcreek 3 36 3.0 24.2 476 19,700 73 1,380 10.2 673

12331800 Clark Fork near Drummond 3 31 2.7 18.5 303 25,900 59 2,700 9.3 673

12334550 Clark Fork at Turah Bridge, 

near Bonner 

3 25 2.1 17.9 248 15,900 50 1,600 10.6 626

12340000 Blackfoot River near Bonner 3 3 .2 21.1 22 19,500 19 545 11.7 72

12340500 Clark Fork above Missoula 3 40 3.9 26.2 501 21,700 67 1,120 13.0 992
Data 83

Table 21. 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 2:8 17.7 72.7 70.6–74.7

Cadmium 10 2:8 .4 -- --

Chromium 10 2:8 130 74.5 73.1–76.0

Copper 10 2:8 35 100.5 97.5–104

Iron 10 2:8 35,000 92.0 90.9–93.2

Lead 10 2:8 19 119.4 118–121

Manganese 10 2:8 538 94.1 92.5–95.6

Nickel 10 2:8 88 85.1 84.3–86.0

Zinc 10 2:8 106 91.4 89.0–93.7

SRM sample 2711

Arsenic 10 1:10 105 84.8 80.4–89.1

Cadmium 10 1:10 41.7 95.4 90.8–99.9

Chromium 10 1:10 47 63.9 59.2–68.7

Copper 10 1:10 114 94.1 89.8–98.4 

Iron 10 1:10 28,900 87.3 84.0–90.7

Lead 10 1:10 1,160 95.7 91.1–100

Manganese 10 1:10 638 80.7 77.7–83.7 

Nickel 10 1:10 20.6 84.3 80.1–88.6

Zinc 10 1:10 350 94.5 90.9–98.1
84 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana Table 22. 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 0.6N (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 <0.007 <0.006 <0.1 <0.02 <0.01 <0.002 <0.01 12323750 Silver Bow Creek at Warm Springs 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01 12323800 Clark Fork near Galen 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01 461415112450801 Clark Fork below Lost Creek, near Galen 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01 461559112443301 Clark Fork at county bridge, near Racetrack 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01 461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01 12324200 Clark Fork at Deer Lodge 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01 12324680 Clark Fork at Goldcreek 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01 12331800 Clark Fork near Drummond 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01 12334550 Clark Fork at Turah Bridge, near Bonner 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01 12340000 Blackfoot River near Bonner 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01 12340500 Clark Fork above Missoula 1:10 <.005 <.001 <.007 <.006 <.1 <.02 <.01 <.002 <.01
Data 85

Table 23. Analyses of biota, upper Clark Fork basin, Montana, August 2007.

[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]

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 11.7 6.3 2.6 452 2,140 39.3 1,420 2.5 872

Hydropsyche spp. 1 10.7 5.9 3.7 480 2,220 43.5 1,200 2.7 876

12323750 Silver Bow Creek at Warm Springs

Hydropsyche cockerelli 1 15.6 0.4 0.9 32.8 1,050 4.6 1,790 1.4 145

12323800 Clark Fork near Galen

Claassenia sabulosa 1 2.0 0.2 1.5 54.7 242 1.0 323 0.5 237

Hydropsyche occidentalis 3 14.3 1.3 2.2 97.0 1,700 9.5 4,690 2.2 233

461415112450801 Clark Fork below Lost Creek, near Galen

Hydropsyche cockerelli 1 10.0 1.5 1.3 108 1,030 8.2 1,790 1.3 216

Hydropsyche occidentalis 4 14.8 1.8 2.4 128 2,190 13.8 3,820 2.0 286

461559112443301 Clark Fork at county bridge, near Racetrack

Hydropsyche occidentalis 2 14.4 1.8 2.8 127 2,650 12.8 2,930 1.9 287

461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack

Hydropsyche occidentalis 3 16.0 1.9 2.8 144 2,050 13.4 4,320 1.9 377

12324200 Clark Fork at Deer Lodge

Hydropsyche occidentalis 2 10.0 1.8 1.9 157 1,360 12.9 2,430 1.6 326

12324680 Clark Fork at Goldcreek

Arctopsyche grandis 2 3.1 1.3 0.6 29.6 265 1.6 953 0.5 179

Claassenia sabulosa 2 1.8 .6 .3 60.8 144 .7 211 .4 286

Hydropsyche cockerelli 2 5.1 1.0 1.1 57.1 657 3.2 1,280 1.0 185

Hydropsyche occidentalis 1 5.1 1.0 1.1 53.9 733 3.8 1,620 1.0 214
86 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 4.2 0.6 0.9 34.2 464 3.7 952 0.8 179

Claassenia sabulosa 3 1.4 .3 .7 74.0 224 1.6 510 .4 306

Hydropsyche cockerelli 1 5.3 .6 1.8 53.7 854 5.4 1,060 1.2 175

Hydropsyche occidentalis 2 5.2 .6 1.4 58.1 1,050 6.3 1,210 1.2 197

12334550 Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 2 4.0 0.7 1.2 34.3 722 3.7 716 1.1 183

Claassenia sabulosa 2 1.1 .5 .8 82.7 190 1.1 212 .3 287

Hydropsyche cockerelli 2 4.7 .7 1.9 50.5 1,120 5.2 774 1.3 197

Hydropsyche occidentalis 1 4.0 .6 1.6 44.7 1,010 4.9 902 1.2 211

12340000 Blackfoot River near Bonner

Arctopsyche grandis 1 4.6 0.2 6.9 16.2 808 2.0 607 3.7 150

Claassenia sabulosa 1 3.0 .2 5.2 32.7 211 .8 133 1.1 292

Hydropsyche cockerelli 1 3.1 .2 3.8 15.5 1,640 2.0 637 4.5 142

Hydropsyche occidentalis 1 3.8 .3 5.8 17.5 1,830 1.9 713 4.9 157

12340500 Clark Fork above Missoula

Arctopsyche grandis 2 4.1 0.8 1.3 44.7 846 4.8 1,110 1.1 211

Claassenia sabulosa 2 1.7 .4 .9 58.5 266 1.5 216 .4 337

Hydropsyche cockerelli 2 6.0 1.1 1.9 78.3 1,940 10.5 1,510 1.5 253

Table 23. Analyses of biota, upper Clark Fork basin, Montana, August 2007.—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.]
Data 87

Table 24. 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 97.0 96.1–97.8

Cadmium 12 26.7 96.2 93.8–98.6

Chromium 12 .77 140 129–151

Copper 12 106 102 101–103

Iron 12 105 104 103–104

Lead 1

12 .35 91.0 87.9–94.0

Manganese 12 13.6 101 100–103

Nickel 12 2.5 93.8 90.7–97.0

Zinc 12 180 106 106–107

1

Lead concentrations in three analyses were less than the liquid-phase minimum reporting level (0.003 μg/mL) and were 

not used to calculate SRM recovery.
88 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana Table 25. 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 Oppor- tunity 1:1 <0.004 <0.001 <0.01 <0.001 <0.05 <0.003 <0.001 <0.001 <0.003 12323750 Silver Bow Creek at Warm Springs 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003 12323800 Clark Fork near Galen 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003 461415112450801 Clark Fork below Lost Creek, near Galen 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003 461559112443301 Clark Fork at county bridge, near Racetrack 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003 461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003 12324200 Clark Fork at Deer Lodge 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003 12324680 Clark Fork at Goldcreek 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003 12331800 Clark Fork near Drummond 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003 12334550 Clark Fork at Turah Bridge, near Bonner 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003 12340000 Blackfoot River near Bonner 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003 12340500 Clark Fork above Missoula 1:1 <.004 <.001 <.01 <.001 <.05 <.003 <.001 <.001 <.003
Data 89

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.

[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 2007

Streamflow, instantaneous (ft3

/s) 107 156 1.9 13 7.6

pH, onsite (standard units) 107 8.4 7.3 7.8 7.8

Specific conductance, onsite (μS/cm) 107 412 116 267 271

Temperature, water (°C) 107 17.5 1.5 8.3 8.0

Hardness, filtered (mg/L as CaCO3

) 107 150 38 106 110

Calcium, filtered (mg/L) 107 41.8 10.6 30.2 30.9

Magnesium, filtered (mg/L) 107 11.0 2.71 7.30 7.37

Arsenic, filtered (μg/L) 106 13 1 3.9 3.0

Arsenic, unfiltered (μg/L) 107 18 E1 2

5.3 4

Cadmium, filtered (μg/L) 105 .5 <.04 2

.05 <.1

Cadmium, unfiltered (μg/L) 107 .11 <.04 2

.04 <1

Copper, filtered (μg/L) 106 10.0 <1.0 2

3.7 3.2

Copper, unfiltered (μg/L) 107 52.0 1.5 6.9 5.6

Iron, filtered (μg/L) 107 640 15 166 150

Iron, unfiltered (μg/L) 107 4,220 139 667 550

Lead, filtered (μg/L) 107 2.80 <.08 2

.21 <.6

Lead, unfiltered (μg/L) 107 47.0 <1.00 2

2.07 .72

Manganese, filtered (μg/L) 107 144 14.2 41.6 37.9

Manganese, unfiltered (μg/L) 107 240 23.5 58.1 50.6

Zinc, filtered (μg/L) 106 11 <1.0 2

3.7 2.8

Zinc, unfiltered (μg/L) 107 130 <10 2

9.4 4

Sediment, suspended (percent finer than 0.062 mm) 107 97 50 82 83

Sediment, suspended concentration (mg/L) 107 139 1 13 7

Sediment, suspended discharge (ton/d) 107 59 .01 1.2 .14
90 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 2007

Streamflow, instantaneous (ft3

/s) 115 134 13 28 23

pH, onsite (standard units) 115 8.1 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 115 691 226 475 482

Temperature, water (°C) 115 20.0 1.0 10.5 9.5

Hardness, filtered (mg/L as CaCO3

) 115 220 66 151 150

Calcium, filtered (mg/L) 115 62.7 19.0 42.9 44.0

Magnesium, filtered (mg/L) 115 14.6 4.51 10.6 11.0

Arsenic, filtered (μg/L) 115 13 2.3 6.5 6.3

Arsenic, unfiltered (μg/L) 115 45 3 11.2 10.0

Cadmium, filtered (μg/L) 115 6.2 .07 1.20 .90

Cadmium, unfiltered (μg/L) 115 6.0 .11 1.61 1.30

Copper, filtered (μg/L) 115 303 3.2 39.1 15.3

Copper, unfiltered (μg/L) 115 550 10.5 90.6 40.7

Iron, filtered (μg/L) 115 270 10 2

84.2 61

Iron, unfiltered (μg/L) 115 7,400 85 918 600

Lead, filtered (μg/L) 115 2.4 <.5 2

.50 .22

Lead, unfiltered (μg/L) 115 250 .64 14.1 4.00

Manganese, filtered (μg/L) 115 1,700 21.4 385 348

Manganese, unfiltered (μg/L) 115 1,600 25.9 429 370

Zinc, filtered (μg/L) 115 2,200 26.7 390 277

Zinc, unfiltered (μg/L) 115 2,200 38 471 334

Sediment, suspended (percent finer than 0.062 mm) 114 98 42 84 86

Sediment, suspended concentration (mg/L) 114 405 2 24 11

Sediment, suspended discharge (ton/d) 114 70 .08 2.8 .68

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
Data 91

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 2007

Streamflow, instantaneous (ft3

/s) 118 361 13 70 50

pH, onsite (standard units) 117 9.5 7.2 8.4 8.4

Specific conductance, onsite (μS/cm) 117 633 202 420 403

Temperature, water (°C) 117 22.5 0.0 9.3 9.5

Hardness, filtered (mg/L as CaCO3

) 117 240 60 151 150

Calcium, filtered (mg/L) 117 71.6 18.5 44.6 43.8

Magnesium, filtered (mg/L) 117 15.0 3.42 9.55 9.04

Arsenic, filtered (μg/L) 117 34 1 11.2 10.3

Arsenic, unfiltered (μg/L) 117 235 10.1 27.1 18.0

Cadmium, filtered (μg/L) 116 41.0 <.1 2

1.24 .80

Cadmium, unfiltered (μg/L) 117 49.0 .52 2

2.23 1.40

Copper, filtered (μg/L) 116 450 13.7 48.3 37.6

Copper, unfiltered (μg/L) 117 3,900 31.1 220 121

Iron, filtered (μg/L) 117 307 3 2

45 24

Iron, unfiltered (μg/L) 116 24,100 255 1,580 780

Lead, filtered (μg/L) 117 5.1 <.5 2

.75 .31

Lead, unfiltered (μg/L) 117 650 5.38 40.2 15.1

Manganese, filtered (μg/L) 117 9,300 67.6 470 379

Manganese, unfiltered (μg/L) 117 10,000 117 591 467

Zinc, filtered (μg/L) 116 13,000 26.6 326 179

Zinc, unfiltered (μg/L) 117 15,000 97 566 360

Sediment, suspended (percent finer than 0.062 mm) 118 95 37 79 83

Sediment, suspended concentration (mg/L) 118 801 5 49 17

Sediment, suspended discharge (ton/d) 118 781 .18 20 2.4

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
92 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 2007

Streamflow, instantaneous (ft3

/s) 24 165 7.4 55 21

pH, onsite (standard units) 24 8.6 7.7 8.1 8.2

Specific conductance, onsite (μS/cm) 24 203 56 133 142

Temperature, water (°C) 24 17.0 1.0 8.6 8.0

Hardness, filtered (mg/L as CaCO3

) 24 98 24 59 64

Calcium, filtered (mg/L) 24 25.9 7.12 16.2 17.7

Magnesium, filtered (mg/L) 24 8.01 1.45 4.44 4.73

Arsenic, filtered (μg/L) 24 30.3 7.3 16.5 16.2

Arsenic, unfiltered (μg/L) 24 30.1 9 18.0 17.6

Cadmium, filtered (μg/L) 24 .11 <.04 2

.04 .04

Cadmium, unfiltered (μg/L) 24 .18 .04 .08 .07

Copper, filtered (μg/L) 24 4.7 .79 2.2 2.0

Copper, unfiltered (μg/L) 24 10.3 1.3 3.9 3.4

Iron, filtered (μg/L) 24 125 26 54 42

Iron, unfiltered (μg/L) 24 619 89 199 167

Lead, filtered (μg/L) 24 .24 <.08 2

.13 .11

Lead, unfiltered (μg/L) 24 3.12 .19 .78 .59

Manganese, filtered (μg/L) 24 8.9 3.4 5.9 6.2

Manganese, unfiltered (μg/L) 24 36.6 7.4 14.5 12.0

Zinc, filtered (μg/L) 24 2.4 .73 1.3 1.2

Zinc, unfiltered (μg/L) 24 8 1 2.8 2.3

Sediment, suspended (percent finer than 0.062 mm) 24 81 39 67 70

Sediment, suspended concentration (mg/L) 24 29 1 6 3

Sediment, suspended discharge (ton/d) 24 13 .02 1.7 .16

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
Data 93

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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 2007

Streamflow, instantaneous (ft3

/s) 40 261 0.43 34 5.9

pH, onsite (standard units) 40 8.2 7.8 8.0 8.0

Specific conductance, onsite (μS/cm) 40 223 59 149 162

Temperature, water (°C) 40 20.0 .5 9.5 9.2

Hardness, filtered (mg/L as CaCO3

) 40 100 24 64 70

Calcium, filtered (mg/L) 40 28.0 7.01 17.9 19.3

Magnesium, filtered (mg/L) 40 7.83 1.56 4.64 5.11

Arsenic, filtered (μg/L) 40 55.1 9.0 23.8 23.0

Arsenic, unfiltered (μg/L) 40 53.5 10 27.4 26.6

Cadmium, filtered (μg/L) 40 .13 .02 .07 .07

Cadmium, unfiltered (μg/L) 40 .85 .06 .16 .10

Copper, filtered (μg/L) 40 6.1 1.1 3.1 2.8

Copper, unfiltered (μg/L) 40 38.8 1.7 7.2 4.2

Iron, filtered (μg/L) 40 94 17 51 44

Iron, unfiltered (μg/L) 40 1,960 67 314 138

Lead, filtered (μg/L) 40 .32 <.08 2

.14 .14

Lead, unfiltered (μg/L) 40 12.7 .07 1.58 .42

Manganese, filtered (μg/L) 40 32.8 2.2 8.5 6.7

Manganese, unfiltered (μg/L) 40 113 3.5 20.2 13.0

Zinc, filtered (μg/L) 40 7.7 1.3 3.3 3.1

Zinc, unfiltered (μg/L) 40 41 1.9 7.2 5

Sediment, suspended (percent finer than 0.062 mm) 40 90 26 72 78

Sediment, suspended concentration (mg/L) 40 107 1 13 2

Sediment, suspended discharge (ton/d) 40 55 <.01 2

4.1 .02
94 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 2007

Streamflow, instantaneous (ft3

/s) 22 39 1.0 9.9 4.4

pH, onsite (standard units) 22 8.2 7.5 7.7 7.7

Specific conductance, onsite (μS/cm) 22 115 66 98 101

Temperature, water (°C) 22 15.5 .5 7.6 7.8

Hardness, filtered (mg/L as CaCO3

) 22 42 22 35 38

Calcium, filtered (mg/L) 22 14.0 7.56 11.9 12.8

Magnesium, filtered (mg/L) 22 1.69 .78 1.31 1.40

Arsenic, filtered (μg/L) 22 24.9 9.9 15.7 14.2

Arsenic, unfiltered (μg/L) 22 27.0 10 16.7 14.6

Cadmium, filtered (μg/L) 22 .05 <.04 2

.03 .03

Cadmium, unfiltered (μg/L) 22 .19 .02 .06 .05

Copper, filtered (μg/L) 22 4.2 .96 2.0 1.9

Copper, unfiltered (μg/L) 22 16.8 1.0 3.8 3.0

Iron, filtered (μg/L) 22 154 36 72 67

Iron, unfiltered (μg/L) 22 1,260 93 283 198

Lead, filtered (μg/L) 22 .37 .05 .14 .12

Lead, unfiltered (μg/L) 22 4.08 .16 .70 .45

Manganese, filtered (μg/L) 22 34.5 8.1 15.6 14.0

Manganese, unfiltered (μg/L) 22 49.1 15.1 26.2 22.0

Zinc, filtered (μg/L) 22 3.3 .65 1.6 1.6

Zinc, unfiltered (μg/L) 22 10 1 2.6 2

Sediment, suspended (percent finer than 0.062 mm) 22 94 44 75 78

Sediment, suspended concentration (mg/L) 22 93 1 11 5

Sediment, suspended discharge (ton/d) 22 9.8 .01 .72 .07

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
Data 95

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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 2007

Streamflow, instantaneous (ft3

/s) 40 53 4.5 15 7.8

pH, onsite (standard units) 40 8.6 7.7 8.2 8.1

Specific conductance, onsite (μS/cm) 40 371 116 285 308

Temperature, water (°C) 40 20.5 1.5 11.2 11.8

Hardness, filtered (mg/L as CaCO3

) 40 170 67 126 130

Calcium, filtered (mg/L) 40 47.4 20.5 36.3 38.5

Magnesium, filtered (mg/L) 40 12.3 3.73 8.52 9.12

Arsenic, filtered (μg/L) 40 164 11.5 43.6 29.6

Arsenic, unfiltered (μg/L) 40 164 12 46.1 30.4

Cadmium, filtered (μg/L) 40 .11 <.04 2

.04 .04

Cadmium, unfiltered (μg/L) 40 .52 .03 .10 .07

Copper, filtered (μg/L) 40 21.4 1.1 5.7 3.3

Copper, unfiltered (μg/L) 40 48.8 2.8 11.6 7.8

Iron, filtered (μg/L) 40 111 7 39 29

Iron, unfiltered (μg/L) 40 1,420 27 246 190

Lead, filtered (μg/L) 40 .52 .04 2

.20 .17

Lead, unfiltered (μg/L) 40 14.4 .27 2.15 1.49

Manganese, filtered (μg/L) 40 63.9 4.1 27.2 22.0

Manganese, unfiltered (μg/L) 40 104 4.7 37.0 30.6

Zinc, filtered (μg/L) 40 19.8 .84 5.3 3.9

Zinc, unfiltered (μg/L) 40 68 2 12.2 9.5

Sediment, suspended (percent finer than 0.062 mm) 40 96 65 86 86

Sediment, suspended concentration (mg/L) 40 84 1 11 5

Sediment, suspended discharge (ton/d) 40 11 .02 .80 .13
96 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 2007

Streamflow, instantaneous (ft3

/s) 124 662 16 133 87

pH, onsite (standard units) 122 9.4 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 122 783 249 473 478

Temperature, water (°C) 123 25.0 .5 11.1 11.0

Hardness, filtered (mg/L as CaCO3

) 122 310 97 197 200

Calcium, filtered (mg/L) 122 90.4 27.9 57.1 58.8

Magnesium, filtered (mg/L) 122 21.4 5.94 13.1 13.2

Arsenic, filtered (μg/L) 122 60 6.8 22.4 22.6

Arsenic, unfiltered (μg/L) 122 94 10 26.6 26.3

Cadmium, filtered (μg/L) 122 .31 <.04 2

.06 .02

Cadmium, unfiltered (μg/L) 122 .56 <.1 2

.12 <1

Copper, filtered (μg/L) 122 40.0 1.7 8.5 6.6

Copper, unfiltered (μg/L) 122 96.8 2.4 17.3 12.2

Iron, filtered (μg/L) 122 93 <5 2

17 14

Iron, unfiltered (μg/L) 122 3,000 36 341 262

Lead, filtered (μg/L) 122 1.0 <.08 2

.11 <.5

Lead, unfiltered (μg/L) 122 41.8 <1 2

2.45 1.23

Manganese, filtered (μg/L) 122 875 11.8 129 96.3

Manganese, unfiltered (μg/L) 122 899 24.0 192 160

Zinc, filtered (μg/L) 122 73 <1.0 2

8.5 4.4

Zinc, unfiltered (μg/L) 122 180 <10 2

33.7 20

Sediment, suspended (percent finer than 0.062 mm) 123 97 43 82 85

Sediment, suspended concentration (mg/L) 124 229 1 11 6

Sediment, suspended discharge (ton/d) 124 279 .07 7.1 1.5

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
Data 97

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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 2007

Streamflow, instantaneous (ft3

/s) 12 391 41 115 70

pH, onsite (standard units) 12 8.8 8.1 8.5 8.6

Specific conductance, onsite (μS/cm) 12 264 126 222 242

Temperature, water (°C) 12 16.0 4.5 9.6 8.2

Hardness, filtered (mg/L as CaCO3

) 12 130 60 106 110

Calcium, filtered (mg/L) 12 38.6 18.6 32.1 34.2

Magnesium, filtered (mg/L) 12 8.47 3.25 6.60 6.99

Arsenic, filtered (μg/L) 12 2.8 1.8 2.3 2.3

Arsenic, unfiltered (μg/L) 12 3.2 2.0 2.5 2.4

Cadmium, filtered (μg/L) 12 .03 <.04 2

.02 <.04

Cadmium, unfiltered (μg/L) 12 .07 .02 .04 .03

Copper, filtered (μg/L) 12 1.4 .57 1.0 .98

Copper, unfiltered (μg/L) 12 4.7 1.1 2.4 2.2

Iron, filtered (μg/L) 12 13 <6 8 7

Iron, unfiltered (μg/L) 12 237 45 98 75

Lead, filtered (μg/L) 12 .05 <.08 -- <.12

Lead, unfiltered (μg/L) 12 .62 .12 .30 .24

Manganese, filtered (μg/L) 12 2.1 <.2 2

.9 .8

Manganese, unfiltered (μg/L) 12 11.3 1.8 4.6 3.9

Zinc, filtered (μg/L) 12 1.4 .30 .84 .77

Zinc, unfiltered (μg/L) 12 5.5 1 2.2 2

Sediment, suspended (percent finer than 0.062 mm) 12 80 51 66 67

Sediment, suspended concentration (mg/L) 12 17 2 6 4

Sediment, suspended discharge (ton/d) 12 18 .35 2.9 .64
98 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 2007

Streamflow, instantaneous (ft3

/s) 91 420 2.8 91 50

pH, onsite (standard units) 90 8.7 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 90 795 139 301 312

Temperature, water (°C) 91 20.0 0.0 9.0 9.0

Hardness, filtered (mg/L as CaCO3

) 90 420 40 146 150

Calcium, filtered (mg/L) 90 130 10.5 44.5 46.1

Magnesium, filtered (mg/L) 90 22.0 3.29 8.38 8.46

Arsenic, filtered (μg/L) 90 14 2 5.2 4.8

Arsenic, unfiltered (μg/L) 90 27 3 7.6 6

Cadmium, filtered (μg/L) 90 .1 <.04 2

.04 <.1

Cadmium, unfiltered (μg/L) 90 .41 <.1 2

.08 <1.0

Copper, filtered (μg/L) 90 16.0 1.0 3.5 3.0

Copper, unfiltered (μg/L) 90 108 2.3 19.1 8.2

Iron, filtered (μg/L) 90 30 <5 2

11 10

Iron, unfiltered (μg/L) 90 1,700 39 295 110

Lead, filtered (μg/L) 90 1.8 <.08 2

.09 <.5

Lead, unfiltered (μg/L) 90 14.0 <1.0 2

1.89 .43

Manganese, filtered (μg/L) 90 570 22.6 132 105

Manganese, unfiltered (μg/L) 90 1,400 53.1 224 186

Zinc, filtered (μg/L) 90 10 <1.0 2

2.2 1.1

Zinc, unfiltered (μg/L) 90 60 <10 2

9.2 3

Sediment, suspended (percent finer than 0.062 mm) 91 88 55 72 72

Sediment, suspended concentration (mg/L) 91 106 2 17 7

Sediment, suspended discharge (ton/d) 91 87 .05 8.3 .92

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
Data 99

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 2007

Streamflow, instantaneous (ft3

/s) 165 1,050 14 205 123

pH, onsite (standard units) 152 9.2 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 153 720 197 425 435

Temperature, water (°C) 164 23.5 0.0 10.1 10.0

Hardness, filtered (mg/L as CaCO3

) 151 370 81 186 190

Calcium, filtered (mg/L) 151 110 24.2 54.9 57.0

Magnesium, filtered (mg/L) 151 22.0 5.08 11.8 12.0

Arsenic, filtered (μg/L) 151 53 4 15.1 14.0

Arsenic, unfiltered (μg/L) 151 78 3 19.6 17.0

Cadmium, filtered (μg/L) 151 1.0 <.04 2

.06 <1

Cadmium, unfiltered (μg/L) 151 3 <.1 2

.20 <1

Copper, filtered (μg/L) 151 50 1.7 8.4 6.5

Copper, unfiltered (μg/L) 150 240 4.8 28.8 16.0

Iron, filtered (μg/L) 151 110 <3 2

16 11

Iron, unfiltered (μg/L) 151 9,200 56 498 270

Lead, filtered (μg/L) 151 3 <.08 2

.16 <1

Lead, unfiltered (μg/L) 151 31.0 <1.0 2

3.54 1.86

Manganese, filtered (μg/L) 151 460 25.2 115 88.9

Manganese, unfiltered (μg/L) 151 1,400 47.3 241 183

Zinc, filtered (μg/L) 151 110 <1.0 2

10.2 5.3

Zinc, unfiltered (μg/L) 151 360 <10 2

40.5 20.0

Sediment, suspended (percent finer than 0.062 mm) 164 97 41 78 78

Sediment, suspended concentration (mg/L) 165 338 2 18 7

Sediment, suspended discharge (ton/d) 165 459 .12 21 2.3

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
100 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 2007

Streamflow, instantaneous (ft3

/s) 23 17 0.37 6.6 5.2

pH, onsite (standard units) 23 8.6 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 23 253 136 205 213

Temperature, water (°C) 23 17.0 1.5 8.7 9.0

Hardness, filtered (mg/L as CaCO3

) 23 120 50 97 100

Calcium, filtered (mg/L) 23 37.1 15.7 29.5 30.3

Magnesium, filtered (mg/L) 23 7.11 2.71 5.71 6.14

Arsenic, filtered (μg/L) 23 156 2.4 12.3 5.1

Arsenic, unfiltered (μg/L) 23 3,860 2 174 5.8

Cadmium, filtered (μg/L) 23 .90 <.04 2

.07 .03

Cadmium, unfiltered (μg/L) 23 147 .02 6.4 .04

Copper, filtered (μg/L) 23 90.5 1.1 6.2 2.0

Copper, unfiltered (μg/L) 23 29,100 1.7 1,270 4.5

Iron, filtered (μg/L) 23 25 <6 2

9 8

Iron, unfiltered (μg/L) 23 99,700 22 4,480 98

Lead, filtered (μg/L) 23 .18 <.08 2

.06 <.12

Lead, unfiltered (μg/L) 23 1,290 .10 56.8 .40

Manganese, filtered (μg/L) 23 42.4 .2 3.0 1.2

Manganese, unfiltered (μg/L) 23 8,830 1.2 389 3.6

Zinc, filtered (μg/L) 23 30.0 .62 2.5 1.2

Zinc, unfiltered (μg/L) 23 7,780 1.0 342 3.0

Sediment, suspended (percent finer than 0.062 mm) 23 97 30 61 63

Sediment, suspended concentration (mg/L) 23 58,900 1 2,570 6

Sediment, suspended discharge (ton/d) 23 1,320 <.1 2

58 .08

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
Data 101

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 2007

Streamflow, instantaneous (ft3

/s) 40 59 1.3 19 12

pH, onsite (standard units) 40 8.7 8.0 8.4 8.4

Specific conductance, onsite (μS/cm) 40 934 540 649 631

Temperature, water (°C) 40 26.5 0.0 12.1 11.8

Hardness, filtered (mg/L as CaCO3

) 40 450 200 300 300

Calcium, filtered (mg/L) 40 122 48.5 83.8 85.6

Magnesium, filtered (mg/L) 40 35.7 18.0 22.1 21.2

Arsenic, filtered (μg/L) 40 41.8 6 14.5 12.2

Arsenic, unfiltered (μg/L) 40 43 6 15.0 12.8

Cadmium, filtered (μg/L) 40 .05 <.04 2

.03 .03

Cadmium, unfiltered (μg/L) 40 .11 .02 .05 .04

Copper, filtered (μg/L) 40 6.7 .99 2.7 2.6

Copper, unfiltered (μg/L) 40 22.5 1.6 6.6 5.6

Iron, filtered (μg/L) 40 61 <6 2

12 8

Iron, unfiltered (μg/L) 40 293 14 103 76.5

Lead, filtered (μg/L) 40 .33 <.08 2

.07 <.08

Lead, unfiltered (μg/L) 40 1.30 .04 .38 .27

Manganese, filtered (μg/L) 40 54.0 1.9 13.8 11.1

Manganese, unfiltered (μg/L) 40 56.5 2.2 18.0 13.8

Zinc, filtered (μg/L) 40 3.8 <1.0 2

1.5 1.2

Zinc, unfiltered (μg/L) 40 9 <2 2

3.2 2.0

Sediment, suspended (percent finer than 0.062 mm) 40 86 18 57 60

Sediment, suspended concentration (mg/L) 40 37 2 15 14

Sediment, suspended discharge (ton/d) 40 4.2 .01 .99 .32

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
102 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 2007

Streamflow, instantaneous (ft3

/s) 217 1,920 23 286 215

pH, onsite (standard units) 165 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 200 642 234 482 504

Temperature, water (°C) 216 23.0 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3

) 157 280 95 204 220

Calcium, filtered (mg/L) 157 82.0 28.2 60.3 63.9

Magnesium, filtered (mg/L) 157 18.7 5.9 13.0 13.7

Arsenic, filtered (μg/L) 167 39 6.0 14.3 13.0

Arsenic, unfiltered (μg/L) 166 215 8 24.4 17.0

Cadmium, filtered (μg/L) 166 2 <.1 2

.08 <1

Cadmium, unfiltered (μg/L) 167 5 <.1 2

.43 <1

Copper, filtered (μg/L) 167 120 3.2 11.2 8.6

Copper, unfiltered (μg/L) 165 1,500 8.2 84.8 38.0

Iron, filtered (μg/L) 167 190 <3 2

15 9

Iron, unfiltered (μg/L) 167 29,000 27 1,560 514

Lead, filtered (μg/L) 167 6 <.08 2

.34 <1

Lead, unfiltered (μg/L) 167 200 <1.00 2

11.0 4.69

Manganese, filtered (μg/L) 167 400 1 43.0 33.9

Manganese, unfiltered (μg/L) 167 4,600 11.9 251 140

Zinc, filtered (μg/L) 167 230 <10 2

12.4 8.9

Zinc, unfiltered (μg/L) 166 1,700 4 91.8 40

Sediment, suspended (percent finer than 0.062 mm) 208 99 37 72 73

Sediment, suspended concentration (mg/L) 217 2,250 1 72 22

Sediment, suspended discharge (ton/d) 217 8,690 .24 154 11

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
Data 103

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 2007

Streamflow, instantaneous (ft3

/s) 123 3,920 87 724 505

pH, onsite (standard units) 122 8.9 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 122 510 206 374 392

Temperature, water (°C) 123 23.0 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3

) 122 230 86 165 170

Calcium, filtered (mg/L) 122 68.0 25.9 48.5 51.0

Magnesium, filtered (mg/L) 122 15.0 5.15 10.5 11.0

Arsenic, filtered (μg/L) 122 20 5.8 10.0 10.0

Arsenic, unfiltered (μg/L) 122 75 7 14.9 12

Cadmium, filtered (μg/L) 122 .2 <.04 2

.04 <.1

Cadmium, unfiltered (μg/L) 122 2.0 <.1 2

.17 <1

Copper, filtered (μg/L) 121 36.0 2.1 6.7 5.4

Copper, unfiltered (μg/L) 121 440 5.2 40.7 23.0

Iron, filtered (μg/L) 122 100 <3 2

18 11

Iron, unfiltered (μg/L) 122 12,000 27 867 423

Lead, filtered (μg/L) 121 .6 <.08 2

.10 <.5

Lead, unfiltered (μg/L) 121 73.0 <1.00 2

5.66 2.80

Manganese, filtered (μg/L) 122 57.3 4.0 19.1 17.4

Manganese, unfiltered (μg/L) 122 1,100 10.5 125 85.2

Zinc, filtered (μg/L) 122 26 <1.0 2

5.8 3.7

Zinc, unfiltered (μg/L) 122 510 2 45.6 30

Sediment, suspended (percent finer than 0.062 mm) 123 94 43 76 78

Sediment, suspended concentration (mg/L) 123 752 2 49 21

Sediment, suspended discharge (ton/d) 123 7,960 .62 215 27

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
104 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 2007

Streamflow, instantaneous (ft3

/s) 123 3,860 149 1,010 749

pH, onsite (standard units) 122 8.7 7.8 8.3 8.3

Specific conductance, onsite (μS/cm) 122 630 189 414 433

Temperature, water (°C) 123 22.5 .5 11.0 11.0

Hardness, filtered (mg/L as CaCO3

) 122 300 74 187 195

Calcium, filtered (mg/L) 122 83.0 21.0 53.5 55.2

Magnesium, filtered (mg/L) 122 22.0 5.2 12.8 13.1

Arsenic, filtered (μg/L) 122 20 6.6 10.6 10.0

Arsenic, unfiltered (μg/L) 122 62 8 16.4 13.0

Cadmium, filtered (μg/L) 122 .30 <.04 2

.05 <.1

Cadmium, unfiltered (μg/L) 122 2.0 <.1 2

.23 <1

Copper, filtered (μg/L) 120 21.0 1.0 6.5 5.0

Copper, unfiltered (μg/L) 120 360 4.6 44.1 22.0

Iron, filtered (μg/L) 122 150 <3 2

18 9

Iron, unfiltered (μg/L) 121 8,800 20 1,020 468

Lead, filtered (μg/L) 118 1.2 <.08 2

.16 <.60

Lead, unfiltered (μg/L) 118 56.0 <1.00 2

7.88 3.50

Manganese, filtered (μg/L) 122 60.7 4.5 16.8 15.0

Manganese, unfiltered (μg/L) 122 880 8.0 149 96.0

Zinc, filtered (μg/L) 122 21 <3 2

6.1 4.2

Zinc, unfiltered (μg/L) 122 490 2.9 63.0 31.9

Sediment, suspended (percent finer than 0.062 mm) 123 92 38 74 74

Sediment, suspended concentration (mg/L) 123 530 2 65 26

Sediment, suspended discharge (ton/d) 123 4,720 1.7 332 49

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
Data 105

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 2007

Streamflow, instantaneous (ft3

/s) 220 9,560 296 1,850 1,110

pH, onsite (standard units) 166 8.8 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 195 483 139 303 315

Temperature, water (°C) 219 22.0 0.0 9.6 9.5

Hardness, filtered (mg/L as CaCO3

) 156 210 54 132 130

Calcium, filtered (mg/L) 156 59.0 14.9 37.2 37.8

Magnesium, filtered (mg/L) 156 14.0 3.94 9.51 9.50

Arsenic, filtered (μg/L) 165 17 2.7 6.0 5.2

Arsenic, unfiltered (μg/L) 165 110 3 9.9 7.0

Cadmium, filtered (μg/L) 165 .10 <.04 2

.03 <.1

Cadmium, unfiltered (μg/L) 165 4 <.1 2

.27 <1

Copper, filtered (μg/L) 164 25 E1.1 4.9 4.0

Copper, unfiltered (μg/L) 163 500 3.0 35.7 16.0

Iron, filtered (μg/L) 165 190 <3 2

23 13

Iron, unfiltered (μg/L) 165 19,000 33 1,060 380

Lead, filtered (μg/L) 161 7 <.08 2

.31 <1

Lead, unfiltered (μg/L) 161 100 <1.00 2

7.41 3.00

Manganese, filtered (μg/L) 165 37.4 1.0 8.1 6.8

Manganese, unfiltered (μg/L) 165 2,000 8.9 127 60

Zinc, filtered (μg/L) 164 39 <3 2

6.1 4.0

Zinc, unfiltered (μg/L) 165 1,100 <10 2

62 30

Sediment, suspended (percent finer than 0.062 mm) 209 98 27 73 75

Sediment, suspended concentration (mg/L) 220 1,370 2 58 18

Sediment, suspended discharge (ton/d) 220 34,700 3.0 632 60

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
106 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 2007

Streamflow, instantaneous (ft3

/s) 158 13,400 344 2,630 1,310

pH, onsite (standard units) 118 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 135 294 131 208 205

Temperature, water (°C) 158 22.5 0.0 9.4 9.5

Hardness, filtered (mg/L as CaCO3

) 111 140 55 103 99

Calcium, filtered (mg/L) 111 37.0 14.0 26.4 25.5

Magnesium, filtered (mg/L) 111 13.2 4.90 9.12 8.68

Arsenic, filtered (μg/L) 118 2 <1 2

.96 .98

Arsenic, unfiltered (μg/L) 118 4 <1 2

1.2 1

Cadmium, filtered (μg/L) 118 1 <.04 2

.04 <.1

Cadmium, unfiltered (μg/L) 118 2 <.04 2

.12 <1

Copper, filtered (μg/L) 116 7.0 <1.0 2

1.4 .8

Copper, unfiltered (μg/L) 115 34 <1.0 2

5.2 2.2

Iron, filtered (μg/L) 118 100 <3 2

17 10

Iron, unfiltered (μg/L) 118 3,600 10 435 195

Lead, filtered (μg/L) 114 8 <.08 2

.43 <.6

Lead, unfiltered (μg/L) 114 25.0 <.06 2

2.59 .06

Manganese, filtered (μg/L) 118 11.0 <1 2

2.4 2.0

Manganese, unfiltered (μg/L) 118 180 <10 2

29.5 18.6

Zinc, filtered (μg/L) 118 15 <.60 2

2.2 <20

Zinc, unfiltered (μg/L) 118 60 <1 2

5.9 <10

Sediment, suspended (percent finer than 0.062 mm) 156 98 42 80 82

Sediment, suspended concentration (mg/L) 158 271 1 29 8

Sediment, suspended discharge (ton/d) 158 7,670 1.1 510 30

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
Data 107

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 2007

Streamflow, instantaneous (ft3

/s) 186 21,600 720 4,350 2,380

pH, onsite (standard units) 143 8.7 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 163 399 142 254 261

Temperature, water (°C) 183 22.0 0.0 9.5 9.5

Hardness, filtered (mg/L as CaCO3

) 143 170 61 117 120

Calcium, filtered (mg/L) 143 46.0 14.0 31.6 32.0

Magnesium, filtered (mg/L) 143 13.4 5.28 9.29 9.20

Arsenic, filtered (μg/L) 143 9 1 3.4 3.0

Arsenic, unfiltered (μg/L) 143 69 E1 5.2 4

Cadmium, filtered (μg/L) 143 .2 <.04 2

.03 <.1

Cadmium, unfiltered (μg/L) 143 5.0 <.1 2

.15 <1

Copper, filtered (μg/L) 142 12.6 E.7 2.8 2.0

Copper, unfiltered (μg/L) 141 400 2.0 16.7 8.0

Iron, filtered (μg/L) 143 200 <3 2

21 15

Iron, unfiltered (μg/L) 143 13,000 43 598 234

Lead, filtered (μg/L) 138 1.2 <.08 2

.16 <1

Lead, unfiltered (μg/L) 138 78.0 <1.00 2

3.14 1.50

Manganese, filtered (μg/L) 143 230 6.2 17.2 14.2

Manganese, unfiltered (μg/L) 143 1,100 10 64.0 40

Zinc, filtered (μg/L) 143 16 <1.0 2

3.7 2.1

Zinc, unfiltered (μg/L) 143 1,100 <10 2

31.1 15

Sediment, suspended (percent finer than 0.062 mm) 181 99 14 85 89

Sediment, suspended concentration (mg/L) 186 824 2 38 12

Sediment, suspended discharge (ton/d) 186 21,900 5.8 930 81

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).

Table 26. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 

2007.—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]
108 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 

through August 2007.

[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. Arsenic was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. 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: 1992–2007

Arsenic 5 186 119 151 163

Cadmium 16 43.9 22.8 32.7 32.3

Chromium 14 32.4 16.8 24.9 25.1

Copper 16 9,020 2,480 4,660 4,560

Iron 16 41,200 28,200 35,300 34,500

Lead 16 1,030 381 694 770

Manganese 16 9,220 1,680 3,580 2,840

Nickel 15 21.4 12.0 15.1 14.9

Silver 12 20.0 8.3 15.5 15.8

Zinc 16 13,400 4,950 8,060 7,380

12323750--Silver Bow Creek at Warm Springs

Period of record for bed-sediment data: 1992–2007

Arsenic 5 177 97 126 108

Cadmium 16 12.2 4.2 7.4 6.7

Chromium 14 34.1 <15.7 1

19.6 118.7

Copper 16 769 169 346 282

Iron 16 31,700 15,400 22,300 21,300

Lead 16 100 49 71 71

Manganese 16 17,700 1,470 8,440 8,370

Nickel 15 19.1 9.2 14.7 14.6

Silver 12 4.4 .3 1

1.9 11.8

Zinc 16 2,220 620 994 770

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 109

Constituent Number of samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen

Period of record for bed-sediment data: 1987, 1991–2007

Arsenic 5 119 87 104 107

Cadmium 18 20.1 4.0 9.0 7.7

Chromium 14 33.9 19.1 26.4 26.4

Copper 18 2,300 838 1,210 1,110

Iron 18 39,800 22,600 27,700 26,900

Lead 18 235 92 137 132

Manganese 18 17,300 2,780 10,100 11,400

Nickel 15 23.2 13.9 18.2 18.2

Silver 14 7.3 <3.2 1

4.4 14.5

Zinc 18 3,560 999 1,550 1,160

461415112450801--Clark Fork below Lost Creek, near Galen

Period of record for bed-sediment data: 1996–2007

Arsenic 5 204 92 125 109

Cadmium 12 10.5 5.2 7.5 7.0

Chromium 11 34.5 20.5 27.6 27.1

Copper 12 2,050 1,150 1,490 1,430

Iron 12 32,800 24,400 29,400 30,500

Lead 12 218 127 172 172

Manganese 12 9,820 3,540 6,190 5,820

Nickel 12 19.9 11.7 15.8 15.7

Silver 8 7.8 4.2 6.5 6.7

Zinc 12 1,680 1,120 1,360 1,360

461559112443301--Clark Fork at county bridge, near Racetrack

Period of record for bed-sediment data: 1996–2007

Arsenic 5 101 56 77 79

Cadmium 12 8.7 5.0 6.8 6.4

Chromium 11 33.3 19.0 25.2 24.9

Copper 12 1,610 933 1,200 1,180

Iron 12 31,700 21,200 26,400 27,000

Lead 12 186 103 142 138

Manganese 12 6,310 2,100 3,580 3,260

Nickel 12 18.4 10.3 14.0 13.9

Silver 8 6.1 <3.3 1

5.0 15.4

Zinc 12 1,550 999 1,200 1,150

Table 27. Statistical summary of long-term fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 

through August 2007.—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. Arsenic was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. 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]
110 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Constituent Number of samples Maximum Minimum Mean Median

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for bed-sediment data: 1996–2007

Arsenic 5 87 58 72 71

Cadmium 12 10.3 4.3 6.6 5.9

Chromium 11 34.1 16.0 24.4 24.0

Copper 12 1,550 721 1,030 1,010

Iron 12 33,700 20,600 26,100 25,200

Lead 12 155 92 127 126

Manganese 12 8,370 1,810 4,380 3,950

Nickel 12 16.9 8.7 12.8 12.5

Silver 8 6.2 2.7 4.9 5.0

Zinc 12 1,570 900 1,140 1,120

12324200--Clark Fork at Deer Lodge

Period of record for bed-sediment data: 1986–87, 1990–2007

Arsenic 5 77 49 64 63

Cadmium 20 10.0 3.8 6.4 5.8

Chromium 14 43.9 19.5 29.6 28.3

Copper 20 4,180 683 1,280 1,020

Iron 20 35,300 21,100 27,100 26,100

Lead 20 242 103 148 147

Manganese 20 6,020 1,110 2,790 2,450

Nickel 15 21.1 11.5 15.0 13.6

Silver 16 7.9 2.4 4.7 4.5

Zinc 20 1,730 846 1,230 1,240

12324680--Clark Fork at Goldcreek

Period of record for bed-sediment data: 1992–2007

Arsenic 5 39 23 31 32

Cadmium 16 8.1 2.6 4.8 5.1

Chromium 14 48.9 21.3 30.7 30.5

Copper 16 1,080 338 657 691

Iron 16 30,600 15,500 23,000 23,000

Lead 16 152 52 93 90

Manganese 16 2,610 1,160 1,860 1,810

Nickel 15 18.6 9.0 14.0 14.1

Silver 12 4.8 2.3 3.3 3.2

Zinc 16 1,320 584 934 1,080

Table 27. Statistical summary of long-term fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 

through August 2007.—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. Arsenic was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. 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]
Data 111

Table 27. Statistical summary of long-term fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 

through August 2007.—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. Arsenic was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. 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, 1991–2007

Arsenic 5 34 31 32 31

Cadmium 19 7.7 2.6 4.6 4.3

Chromium 14 35.4 17.0 27.6 28.6

Copper 19 747 303 480 470

Iron 19 27,000 16,500 21,600 20,400

Lead 19 135 59 89 85

Manganese 19 3,520 1,150 2,020 1,890

Nickel 15 16.8 9.3 13.4 13.4

Silver 15 4.7 <3.2 1

3.0 12.9

Zinc 19 1,230 673 967 948

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for bed-sediment data: 1986, 1991–2007

Arsenic 5 30 19 23 22

Cadmium 18 7.3 1.9 3.8 3.7

Chromium 14 34.7 15.3 23.9 24.2

Copper 18 635 211 350 320

Iron 18 24,400 12,600 18,400 17,200

Lead 18 115 47 68 63

Manganese 18 2,270 671 1,250 1,250

Nickel 15 19.1 8.7 12.6 11.5

Silver 14 3.9 <1.9 1

2.1 11.9

Zinc 18 1,160 584 821 788

12340000--Blackfoot River near Bonner

Period of record for bed-sediment data: 1986–87, 1991, 1993–96, 1998–2001, 2003, 2006, 2007

Arsenic 3 4 2 3 3

Cadmium 14 2.0 <.2 1

.6 1.4

Chromium 10 25.8 15.1 20.9 21.8

Copper 14 27 11 20 21

Iron 14 20,200 12,400 17,200 17,900

Lead 14 20 <13 1

14 113

Manganese 14 683 298 515 538

Nickel 11 14.3 9.4 11.9 11.8

Silver 12 <1.9 <.3 1

.5 1<.6

Zinc 14 73 35 59 62
112 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Constituent Number of samples Maximum Minimum Mean Median

12340500--Clark Fork above Missoula

Period of record for bed-sediment data: 1997–2007

Arsenic 5 52 17 32 29

Cadmium 11 5.8 1.5 3.5 3.5

Chromium 10 30.6 19.0 25.2 26.0

Copper 11 551 166 364 326

Iron 11 24,300 18,100 20,400 20,500

Lead 11 78 37 57 60

Manganese 11 1,420 477 994 1,020

Nickel 11 15.8 10.9 13.1 13.0

Silver 7 2.9 .8 1

2.0 12.1

Zinc 11 1,090 438 758 716

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.

Table 27. Statistical summary of long-term fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 

through August 2007.—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. Arsenic was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. 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]
Data 113

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323600--Silver Bow Creek at Opportunity

Period of record for biological data: 1992, 1994–95, 1997–2007

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 8 20.4 9.6 12.7 11.7

Cadmium 14 9.7 3.1 5.5 5.1

Chromium 14 8.0 1.0 2.8 2.4

Copper 14 1,090 269 431 378

Iron 14 2,880 689 1,650 1,690

Lead 14 56.7 19.0 32.3 31.0

Manganese 14 3,030 180 1,010 818

Nickel 14 3.6 .7 2.0 2.0

Zinc 14 1,590 619 899 835

Hydropsyche spp.

Arsenic 7 23.1 10.7 16.1 16.8

Cadmium 12 11.0 4.2 6.7 5.8

Chromium 12 4.6 .6 2.2 2.2

Copper 12 930 312 564 471

Iron 12 2,630 1,050 1,950 2,110

Lead 12 51.4 21.8 39.9 40.2

Manganese 12 1,340 712 1,090 1,060

Nickel 12 2.7 .7 2.2 2.4

Zinc 12 1,290 784 1,030 1,080
114 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323600--Silver Bow Creek at Opportunity—Continued

Period of record for biological data: 1992, 1994–95, 1997–2007

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: 1992–2007

Hydropsyche cockerelli

Arsenic 8 23.6 7.9 15.4 16.3

Cadmium 34 2.1 .2 .7 .5

Chromium 34 4.3 .4 1.0 .8

Copper 34 97.0 16.7 38.3 32.0

Iron 34 1,590 351 796 762

Lead 34 5.7 .3 3.0 2.7

Manganese 34 3,890 491 1,350 1,230

Nickel 34 1.8 .3 .9 .8

Zinc 34 276 115 175 167

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 115

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323750--Silver Bow Creek at Warm Springs—Continued

Period of record for biological data: 1992–2007

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 1

2.3 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
116 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323770--Warm Springs Creek at Warm Springs—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, 1991–2007

Claassenia sabulosa

Arsenic 1 -- -- 2.0 --

Cadmium 1 -- -- .2 --

Chromium 1 -- -- 1.5 --

Copper 1 -- -- 54.7 --

Iron 1 -- -- 242 --

Lead 1 -- -- 1.0 --

Manganese 1 -- -- 323 --

Nickel 1 -- -- .5 --

Zinc 1 -- -- 237 --

Hydropsyche cockerelli

Arsenic 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
Data 117

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991–2007

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

Hydropsyche occidentalis

Arsenic 7 16.4 12.5 14.8 14.9

Cadmium 39 1.6 .6 1.1 1.1

Chromium 39 6.6 .4 2.0 1.6

Copper 39 121 49.2 83.4 83.3

Iron 39 1,920 642 1,300 1,250

Lead 39 13.5 1.6 7.2 6.7

Manganese 39 6,170 1,220 2,760 2,290

Nickel 39 3.5 .8 1.6 1.6

Zinc 39 286 168 202 197

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

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991–2007

Hydropsyche spp.

Arsenic 2 15.7 14.5 15.1 --

Cadmium 6 3.5 .8 2.3 2.8

Chromium 2 2.4 2.2 2.3 --

Copper 6 154 78.4 126 143

Iron 6 1,540 1,190 1,360 1,360

Lead 6 13.5 5.9 10.4 10.9

Manganese 2 4,760 4,400 4,580 --

Nickel 2 1.8 1.5 1.6 --

Zinc 6 329 218 280 291

461415112450801--Clark Fork below Lost Creek, near Galen

Period of record for biological data: 1996–2007

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 10 27.8 8.8 14.0 11.5

Cadmium 21 2.8 1.1 1.8 1.6

Chromium 21 3.6 .8 1.9 2.0

Copper 21 338 48.8 129 108

Iron 21 4,080 691 1,510 1,170

Lead 21 28.6 4.5 11.3 9.0

Manganese 21 3,160 1,230 1,850 1,720

Nickel 21 2.8 .8 1.4 1.2

Zinc 21 339 151 225 221
Data 119

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

461415112450801--Clark Fork below Lost Creek, near Galen—Continued

Period of record for biological data: 1996–2007

Hydropsyche occidentalis

Arsenic 8 20.8 12.7 15.5 14.6

Cadmium 22 1.9 .9 1.4 1.4

Chromium 22 3.6 1.2 2.1 2.0

Copper 22 219 52.1 113 118

Iron 22 2,830 963 1,600 1,500

Lead 22 19.4 6.6 10.7 10.6

Manganese 22 4,150 1,220 2,570 2,240

Nickel 22 2.5 .9 1.5 1.5

Zinc 22 308 174 242 242

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: 1996–2007

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

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

461559112443301--Clark Fork at county bridge, near Racetrack—Continued

Period of record for biological data: 1996–2007

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

Hydropsyche occidentalis

Arsenic 6 16.8 11.6 14.4 14.6

Cadmium 19 2.3 .7 1.4 1.4

Chromium 19 3.6 1.1 2.2 2.0

Copper 19 160 59.5 112 124

Iron 19 3,690 1,030 1,700 1,600

Lead 19 14.7 4.3 10.5 10.3

Manganese 19 3,770 1,090 2,260 2,130

Nickel 19 2.3 1.1 1.4 1.3

Zinc 19 361 181 233 229

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
Data 121

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for biological data: 1996–2007

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 --

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 7 24.0 10.2 15.2 15.8

Cadmium 24 1.9 .7 1.2 1.2

Chromium 24 6.2 .8 2.1 1.8

Copper 24 238 74.9 110 91.2

Iron 24 3,390 940 1,570 1,500

Lead 24 21.8 6.1 11.6 11.4

Manganese 24 4,460 826 2,730 2,370

Nickel 24 2.4 1.2 1.6 1.5

Zinc 24 386 211 265 239
122 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack—Continued

Period of record for biological data: 1996–2007

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 2 1.7 1.6 1.6 --

Chromium 2 2.1 1.4 1.8 --

Copper 2 140 104 122 --

Iron 2 1,610 1,070 1,340 --

Lead 2 13.2 10.5 11.8 --

Manganese 2 1,150 638 892 --

Nickel 2 1.6 1.6 1.6 --

Zinc 2 212 191 202 --

12324200--Clark Fork at Deer Lodge

Period of record for biological data: 1986–87, 1990–2007

Arctopsyche grandis

Arsenic 0 -- -- -- --

Cadmium 2 2.4 <4.2 1

2.2 --

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
Data 123

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324200--Clark Fork at Deer Lodge—Continued

Period of record for biological data: 1986–87, 1990–2007

Hydropsyche occidentalis

Arsenic 8 12.4 6.6 10.1 10.0

Cadmium 45 2.7 .6 1.3 1.3

Chromium 45 3.6 .6 1.9 1.9

Copper 45 180 49.4 117 112

Iron 45 2,060 557 1,400 1,420

Lead 45 18.6 3.5 11.2 10.9

Manganese 45 2,850 649 1,750 1,740

Nickel 45 12.9 1.0 1.7 1.4

Zinc 45 346 166 245 237

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 3 2.6 2.0 2.4 2.5

Chromium 0 -- -- -- --

Copper 3 222 175 191 177

Iron 3 2,220 1,850 2,010 1,950

Lead 3 16.7 15.0 16.1 16.7

Manganese 0 -- -- -- --

Nickel 0 -- -- -- --

Zinc 3 298 197 257 276

12324680--Clark Fork at Goldcreek

Period of record for biological data: 1992–2007

Arctopsyche grandis

Arsenic 19 6.4 1.8 3.7 2.7

Cadmium 48 6.6 .6 1.9 1.6

Chromium 48 3.3 .1 1.2 1.0

Copper 48 129 19.9 41.9 31.8

Iron 48 2,360 195 630 474

Lead 48 10.9 1.0 3.3 3.3

Manganese 48 1,580 436 848 831

Nickel 48 1.8 .2 .7 .6

Zinc 48 326 146 195 179
124 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324680--Clark Fork at Goldcreek—Continued

Period of record for biological data: 1992–2007

Claassenia sabulosa

Arsenic 13 2.1 0.7 1.4 1.4

Cadmium 33 3.5 .1 1.0 .7

Chromium 33 1.6 .2 .6 .5

Copper 33 81.7 33.0 57.6 57.1

Iron 33 567 63.0 186 158

Lead 33 1.8 .4 .9 .8

Manganese 33 320 50.6 154 123

Nickel 33 .7 .1 .3 .3

Zinc 33 351 166 265 261

Hydropsyche cockerelli

Arsenic 12 6.1 4.1 5.1 4.8

Cadmium 31 2.6 .5 1.3 1.2

Chromium 31 4.7 .5 2.0 1.9

Copper 31 188 17.1 67.6 56.6

Iron 31 3,250 522 1,080 810

Lead 31 16.2 2.4 6.1 5.1

Manganese 31 1,670 538 957 953

Nickel 31 2.3 .3 1.1 1.0

Zinc 31 249 106 183 184

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
Data 125

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324680--Clark Fork at Goldcreek—Continued

Period of record for biological data: 1992–2007

Hydropsyche occidentalis

Arsenic 5 5.8 4.7 5.2 5.1

Cadmium 20 1.8 .4 1.2 1.2

Chromium 20 3.9 .4 1.6 1.6

Copper 20 156 26.4 61.6 56.6

Iron 20 2,720 466 1,100 1,040

Lead 20 15.7 2.9 6.7 5.7

Manganese 20 2,210 530 1,250 1,210

Nickel 20 2.5 .8 1.2 1.0

Zinc 20 277 97 196 202

12331800--Clark Fork near Drummond

Period of record for biological data: 1986, 1991–2007

Arctopsyche grandis

Arsenic 11 4.4 2.3 3.3 3.3

Cadmium 43 3.8 .4 1.3 1.1

Chromium 43 2.5 .2 1.0 1.0

Copper 43 89.2 16.9 32.1 27.4

Iron 43 1,660 193 557 482

Lead 43 11.8 1.6 4.3 3.9

Manganese 43 2,010 456 833 733

Nickel 43 1.9 .2 .6 .6

Zinc 43 308 140 187 183

Claassenia sabulosa

Arsenic 11 1.8 0.7 1.2 1.2

Cadmium 47 2.8 .1 1.0 .8

Chromium 47 3.3 .2 .7 .6

Copper 47 165 18.0 64.7 60.0

Iron 47 387 45.4 162 141

Lead 47 2.9 .2 1.0 .8

Manganese 47 748 33.1 191 153

Nickel 47 1.1 .1 1

.3 1.2

Zinc 47 567 103 275 261
126 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12331800--Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991–2007

Hydropsyche cockerelli

Arsenic 8 5.7 3.9 4.6 4.5

Cadmium 37 2.3 .3 1.1 .8

Chromium 37 3.5 .4 1.6 1.6

Copper 37 156 30.0 58.0 50.7

Iron 37 2,500 506 1,130 912

Lead 37 15.0 4.8 8.0 6.7

Manganese 37 1,680 549 979 915

Nickel 37 2.0 .5 1.1 1.0

Zinc 37 248 134 191 184

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 9 6.9 4.3 5.1 5.1

Cadmium 25 2.0 .4 1.0 1.0

Chromium 25 8.1 .4 2.2 2.0

Copper 25 118 13.3 54.6 55.1

Iron 25 2,060 424 1,200 1,180

Lead 25 14.0 3.0 8.3 7.5

Manganese 25 2,920 619 1,480 1,220

Nickel 25 2.4 .5 1.3 1.2

Zinc 25 293 157 219 207
Data 127

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12331800--Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991–2007

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 --

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for biological data: 1986, 1991–2007

Arctopsyche grandis

Arsenic 16 5.0 3.1 4.3 4.4

Cadmium 58 2.7 .4 1.1 .8

Chromium 58 4.1 .5 1.6 1.4

Copper 58 125 20.1 37.2 30.4

Iron 58 2,870 372 908 789

Lead 58 13.2 1.6 4.2 3.4

Manganese 58 902 324 638 651

Nickel 58 2.6 .4 1.1 .9

Zinc 58 276 111 196 196

Claassenia sabulosa

Arsenic 11 1.9 0.8 1.2 1.1

Cadmium 37 2.5 .1 .9 .8

Chromium 37 2.0 .2 .7 .6

Copper 37 95.1 37.5 58.9 54.4

Iron 37 340 58.6 121 107

Lead 37 1.6 .2 .6 .6

Manganese 37 229 37.2 95.4 79.4

Nickel 37 .6 .1 .2 .2

Zinc 37 342 144 231 235
128 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12334550--Clark Fork at Turah Bridge, near Bonner—Continued

Period of record for biological data: 1986, 1991–2007

Hydropsyche cockerelli

Arsenic 12 5.1 3.7 4.5 4.7

Cadmium 40 1.8 .3 .8 .7

Chromium 40 8.0 .2 1.9 1.6

Copper 40 118 26.4 47.6 42.7

Iron 40 2,530 566 1,180 1,100

Lead 40 12.1 2.2 5.2 4.9

Manganese 40 805 426 629 651

Nickel 40 2.6 .6 1.2 1.2

Zinc 40 228 119 185 184

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 8 5.9 3.6 4.3 4.1

Cadmium 28 1.8 .3 .8 .8

Chromium 28 3.2 .6 1.7 1.6

Copper 28 102 27.4 47.4 42.8

Iron 28 2,310 472 1,180 1,130

Lead 28 14.2 3.0 6.2 5.4

Manganese 28 1,600 454 858 763

Nickel 28 3.2 .6 1.2 1.1

Zinc 28 416 145 211 220
Data 129

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12334550--Clark Fork at Turah Bridge, near Bonner—Continued

Period of record for biological data: 1986, 1991–2007

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 1.3 --

Chromium 1 -- -- 2.4 --

Copper 1 -- -- 84.1 --

Iron 1 -- -- 1,800 --

Lead 1 -- -- <7.8 --

Manganese 1 -- -- 537 --

Nickel 1 -- -- 1.3 --

Zinc 1 -- -- 171 --

12340000--Blackfoot River near Bonner

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006, 2007

Arctopsyche grandis

Arsenic 3 4.6 2.2 3.2 2.8

Cadmium 13 .4 .1 .2 .2

Chromium 8 6.9 .8 2.1 1.3

Copper 13 16.2 9.9 12.5 12.0

Iron 13 1,230 108 648 697

Lead 13 2.3 .5 1.1 .9

Manganese 8 607 286 451 437

Nickel 8 3.7 .7 1.3 1.1

Zinc 13 150 123 137 137

Claassenia sabulosa

Arsenic 3 3.0 1.4 2.0 1.7

Cadmium 14 .2 .1 .1 .1

Chromium 9 5.2 .3 1.1 .7

Copper 14 88.5 19.0 43.1 42.5

Iron 14 211 46.2 119 114

Lead 14 .8 .1 .4 .5

Manganese 9 133 26.3 71.4 60.0

Nickel 9 1.1 .1 .3 .3

Zinc 14 328 117 219 197
130 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12340000--Blackfoot River near Bonner—Continued

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006, 2007

Hydropsyche cockerelli

Arsenic 2 3.1 3.0 3.1 --

Cadmium 2 .2 <.1 1

.2 --

Chromium 2 3.8 2.4 3.1 --

Copper 2 15.5 5.6 10.6 --

Iron 2 1,970 1,640 1,800 --

Lead 2 2.3 2.0 2.1 --

Manganese 2 716 637 677 --

Nickel 2 4.6 1.9 3.2 --

Zinc 2 142 140 141 --

Hydropsyche occidentalis

Arsenic 3 3.8 2.4 3.2 3.2

Cadmium 15 .5 .1 .2 .2

Chromium 15 5.8 .8 2.2 1.9

Copper 15 20.6 12.0 14.8 14.5

Iron 15 1,930 1,060 1,440 1,470

Lead 15 1.9 .8 1.4 1.4

Manganese 15 762 414 514 474

Nickel 15 4.9 .9 1.6 1.4

Zinc 15 157 116 138 142

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.6 --

Chromium 1 -- -- 1.6 --

Copper 1 -- -- 13.9 --

Iron 1 -- -- 1,140 --

Lead 1 -- -- 2.9 --

Manganese 1 -- -- 525 --

Nickel 1 -- -- 2.8 --

Zinc 1 -- -- 132 --
Data 131

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12340500--Clark Fork above Missoula

Period of record for biological data: 1997–2007

Arctopsyche grandis

Arsenic 14 4.5 2.1 3.4 3.5

Cadmium 33 1.8 .1 .7 .6

Chromium 33 3.4 .6 1.6 1.4

Copper 33 77.6 19.5 34.8 33.8

Iron 33 2,340 476 949 869

Lead 33 6.8 1.2 3.9 3.8

Manganese 33 1,410 476 940 929

Nickel 33 2.0 .5 1.1 1.0

Zinc 33 260 133 188 185

Claassenia sabulosa

Arsenic 8 1.9 0.7 1.5 1.6

Cadmium 17 2.0 .2 .6 .4

Chromium 17 1.4 .3 .8 .8

Copper 17 71.7 33.0 51.3 47.3

Iron 17 402 95.3 251 246

Lead 17 3.1 .5 1.2 1.1

Manganese 17 683 75.2 235 190

Nickel 17 .5 <.3 1

.4 1.4

Zinc 17 363 191 279 271

Hydropsyche cockerelli

Arsenic 11 8.0 3.6 6.1 6.4

Cadmium 20 1.3 .4 .8 .9

Chromium 20 6.0 1.8 3.1 3.2

Copper 20 97.9 29.9 63.8 58.9

Iron 20 3,590 1,400 2,100 2,050

Lead 20 11.8 4.2 7.8 7.4

Manganese 20 1,910 781 1,290 1,230

Nickel 20 2.4 1.4 1.8 1.7

Zinc 20 266 156 214 214
132 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 28. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 through August 

2007.—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 was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12340500--Clark Fork above Missoula—Continued

Period of record for biological data: 1997–2007

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.

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For more information concerning this publication, contact:

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3162 Bozeman Ave.

Helena, MT 59601

(406) 457–5900

Or visit the Montana Water Science Center Web site at:

http://mt.water.usgs.gov

Dodge and others—Water-Quality, Bed-Sediment, and Biological Data (October 2006 through September 2007)

 and Statistical Summaries of Long-Term Data for Streams in the Clark Fork Basin, Montana

Open-File Report 2008–1318

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