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

Water-Quality, Bed-Sediment, and Biological Data 

(October 2007 through September 2008) and 

Statistical Summaries of Long-Term Data for 

Streams in the Clark Fork Basin, Montana

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2009–1178 “The forces of man and nature combined... 

to allow the Clark Fork and Blackfoot rivers 

to flow freely for the first time in a century.” 

—John Cramer, Missoulian
Cover.

Photograph: Soon after workers breached Milltown Dam, the Clark Fork River carved a new channel through the clean fill by 

the northern end of the radial gate and spillway at the Milltown Reservoir Superfund site near Bonner, Montana. Photograph 

by Kurt Wilson, Missoulian, taken March 28, 2008.

Text: From John Cramer, “Into the Breach—Clark Fork and Blackfoot Rivers Punch Through Milltown Dam,” Missoulian, 

March 29, 2008.
Water-Quality, Bed-Sediment, and 

Biological Data (October 2007 through 

September 2008) 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 2009–1178

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

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

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2009, Water-quality, bed-sediment, and biological data (October 2007 

through September 2008) and statistical summaries of long-term data for streams in the Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 2009–1178, 139 p.
iii

Contents

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Figures

1. Map showing location of study area in the Clark Fork basin, Montana..............................2

Tables

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

basin, Montana .............................................................................................................................4

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

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

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

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

4. Water-quality data for the Clark Fork basin, Montana, October 2007 

through September 2008............................................................................................................20

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

at Deer Lodge, Montana, October 2007 through September 2008......................................54

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

at Turah Bridge, near Bonner, Montana, October 2007 through 

September 2008...........................................................................................................................58

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

River near Bonner, Montana, October 2007 through September 2008 ..............................62
iv

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

above Missoula, Montana, October 2007 through September 2008 ..................................66

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

near Anaconda, Montana, October 2007 and March through 

September 2008...........................................................................................................................70

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

Creek near Anaconda, Montana, October 2007 and April through 

September 2008...........................................................................................................................73

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

Creek near Anaconda, Montana, October 2007 and March through 

September 2008...........................................................................................................................76

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

near Anaconda, Montana, October 2007 and March through 

September 2008...........................................................................................................................79

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

Montana .......................................................................................................................................82

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

Fork basin, Montana...................................................................................................................85

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

upper Clark Fork basin, Montana.............................................................................................86

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

blank samples..............................................................................................................................86

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

upper Clark Fork basin, Montana.............................................................................................87

18. Analyses of field blanks for water samples ...........................................................................88

19. Bed-sediment data for the upper Clark Fork basin, Montana, August 2008.....................89

20. Recovery efficiency for analyses of standard reference materials for 

bed-sediment samples...............................................................................................................90

21. Analyses of procedural blanks for bed-sediment samples.................................................91

22. Biological data for the upper Clark Fork basin, Montana, August 2008 ............................92

23. Recovery efficiency for analyses of standard reference material for 

biota samples ..............................................................................................................................94

24. Analyses of procedural blanks for biota samples.................................................................95

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

Clark Fork basin, Montana, March 1985 through September 2008.....................................96

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

Clark Fork basin, Montana, August 1986 through August 2008.........................................115

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

Fork basin, Montana, August 1986 through August 2008 ...................................................120
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 2008 is the period from October 1, 2007, through September 30, 2008.
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 this report:

FNU formazin nephelometric units

ICP–OES inductively coupled plasma–optical emission spectrometry

LRL laboratory reporting level

LT–MDL long-term method detection level

NTRU nephelometric turbidity ratio unit

NWQL USGS National Water Quality Laboratory, Denver, Colo.

RSD relative standard deviation

spp. species

SRM standard reference material

TFE tetraflouroethylene

USGS U.S. Geological Survey

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

(October 2007 through September 2008) and Statistical 

Summaries of Long-Term Data for Streams in the Clark 

Fork Basin, Montana

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

Abstract

Water, bed sediment, and biota were sampled in streams 

from Butte to near Missoula as part of a long-term monitoring program in the upper Clark Fork basin; additional water 

samples were collected in the Clark Fork basin from sites 

near Missoula downstream to near the confluence of the Clark 

Fork and Flathead River as part of a supplemental sampling 

program. The sampling programs were conducted in cooperation with the U.S. Environmental Protection Agency to 

characterize aquatic resources in the Clark Fork basin of 

western Montana, with emphasis on trace elements associated 

with historic mining and smelting activities. Sampling sites 

were located on the Clark Fork and selected tributaries. Water 

samples were collected periodically at 23 sites from October 

2007 through September 2008. Bed-sediment and biota 

samples were collected once at 13 sites during August 2008. 

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 2007 through September 2008.

Water-quality data include concentrations of selected major 

ions, trace elements, and suspended sediment. Turbidity was 

analyzed for water samples collected at sites where seasonal 

daily values of turbidity were being determined and at Clark 

Fork above Missoula. Nutrients also were analyzed at all 

the supplemental water-quality sites, except for Clark Fork 

Bypass, near Bonner. Daily values of suspended-sediment 

concentration and suspended-sediment discharge were determined for four sites, and seasonal daily values of turbidity 

were determined for four sites. Bed-sediment data include 

trace-element concentrations in the fine-grained fraction. 

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

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

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

of record since 1985.

Introduction

The Clark Fork originates near Warm Springs in western 

Montana at the confluence of Silver Bow and Warm Springs 

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

Bow Creek in Butte to the Clark Fork near Missoula, six 

major tributaries enter: Blacktail Creek, Warm Springs Creek, 

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

 upper 

Clark Fork basin above Missoula include irrigation, stock 

watering, small-scale industry, 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, in the Warm Springs Ponds, 

and where the Milltown Reservoir was located (Andrews, 

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

transported, and redeposited along the stream channel and 

flood plain, especially during high flows. The occurrence of 

elevated trace-element concentrations in water and 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 
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, 1966, 1:1,000,000

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

12334570 former

2 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana
Sampling Locations and Types of Data 3

characterize the aquatic resources in the upper Clark Fork 

basin to guide and monitor remedial cleanup activities. A 

long-term database was considered necessary to detect trends 

over time in order to evaluate the effectiveness of remediation. 

Water-quality data have been collected by the U.S. Geological Survey (USGS) at selected sites in the upper Clark Fork 

basin since 1985 (Lambing, 1987 through 1991; Lambing 

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

2008). 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 bedsediment-quality and bioaccumulation of metals conducted by 

the USGS National Research Program (Axtmann and Luoma, 

1991; Cain and others, 1992, 1995; Axtmann and others, 1997; 

Hornberger and others, 1997).

In March 1993, an expanded long-term monitoring 

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

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

Environmental Protection Agency to systematically quantify 

the seasonal and annual variability in selected constituents. In 

April 2006, a supplemental water-quality sampling program 

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

from near Milltown Reservoir to near the confluence of the 

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

2008, an additional site was added on the temporary bypass 

channel that is being used to redirect the Clark Fork around 

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

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

monitoring network. The supplemental monitoring provides 

additional spatial coverage of constituent concentrations 

before and after the removal of Milltown Dam, which was 

breached on March 28, 2008.

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

for 23 sites and bed-sediment and biological data for 13 sites 

in the Clark Fork basin collected from October 2007 through 

September 2008. Quality-assurance data are presented for 

water-quality, bed-sediment, and biota samples. Statistical 

summaries also are provided for long-term water-quality, bedsediment, and biological data collected since 1985.

Sampling Locations and Types of Data

Sampling sites for the long-term monitoring program 

in the upper Clark Fork basin from Butte to near Missoula 

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

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

Warm Springs Creek, and Blackfoot River), and three smaller 

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

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

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

were selected to divide the upper Clark Fork into reaches of 

relatively uniform length, with each reach encompassing either 

a major tributary or depositional environment (Warm Springs 

Ponds and Milltown Reservoir). Major tributaries were 

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

upper basin and to provide reference comparisons to the main 

stem. The three smaller tributaries were sampled to gain better 

spatial resolution on sources of metals entering the Clark 

Fork in an area of historical metal-processing activities near 

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

data were obtained periodically at 19 sites; daily suspendedsediment data were obtained at 4 sites and daily turbidity data 

were obtained by continuous turbidity monitors at 4 sites. 

Bed-sediment and biological data for 13 sites were obtained 

once annually. Continuous streamflow data were collected at 

18 sites in the long-term monitoring network.

Supplemental water samples were collected at seven sites 

from near the former Milltown Reservoir location to near the 

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

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

Blackfoot River near Bonner; and Clark Fork above Missoula) 

bracket the former Milltown Reservoir and also are part of 

the long-term monitoring network; one additional site (Clark 

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

channel, within the Milltown Reservoir cleanup site, that 

diverts the Clark Fork around the cleanup work area; and three 

additional sites (Bitterroot River near Missoula, Clark Fork 

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

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

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

and shown in figure 1. Supplemental water samples generally 

were collected during periods of high flow, which included the 

period when Milltown Dam was first breached, to characterize conditions when the potential for scour of bottom sediments from Milltown Reservoir was greatest. The sites were 

sampled in a downstream progression during 2-day periods 

that generally coincided with 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 

7 sites were collected 15–17 times. One sample was collected 

on March 28, the day Milltown Dam was first breached.

Properties measured onsite and constituents for which 

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

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

samples are listed in table 3. Results of onsite measurements 

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

water year 2008 are listed in tables 4 through 24 at the back of 

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

bed-sediment, and biological data collected between March 

1985 and September 2008 are listed in tables 25 through 27 at 

the back of the report.

Quality assurance of data was maintained through the 

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

procedures was verified with quality-control samples that were 
Table 1. Type and period of data collection at sampling sites in the Clark Fork basin, Montana.—Continued

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

Station number 

(fig. 1) Station name Network

Continuousrecord 

streamflow

Periodic 

water quality1

Daily 

suspended 

sediment

Daily turbidity 

(seasonal)

Fine-grained 

bed sediment2

Bulk bed 

sediment2,3 Biota2

12323230 Blacktail Creek at 

Harrison Avenue, at Butte

LT -- 03/93–08/95, 

12/96–08/03, 12/04–P

-- -- -- -- --

12323250 Silver Bow Creek 

below Blacktail Creek, at Butte

LT 10/83–P 03/93–08/95, 

12/96–P

-- -- -- -- --

12323600 Silver Bow Creek at 

Opportunity

LT 07/88–P 03/93–08/95, 

12/96–P

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

08/97–08/04, D

07/92, 

08/94–08/95, 08/97–P

12323670 Mill Creek near 

Anaconda

LT 10/04–P 12/04–P -- 06/06–P -- -- --

12323700 Mill Creek at 

Opportunity

LT 04/03–P 03/03–P -- -- -- -- --

12323710 Willow Creek near 

Anaconda

LT 03/05–P 12/04–P -- 06/06–P -- -- --

12323720 Willow Creek at 

Opportunity

LT 04/03–P 03/03–P -- -- -- -- --

12323750 Silver Bow Creek at 

Warm Springs

LT 03/72–09/79, 

04/93–P

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

08/04, D

07/92–P

12323760 Warm Springs Creek 

near Anaconda

LT 10/97–P 10/05–P -- 05/06–P -- -- --

12323770 Warm Springs Creek at 

Warm Springs

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

08/99, 08/02, 08/05, 08/08

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

08/95, 08/97, 08/99, 08/02, 08/05, 08/08

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–P12323840 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, and 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 Network

Continuousrecord 

streamflow

Periodic 

water quality1

Daily 

suspended 

sediment

Daily turbidity 

(seasonal)

Fine-grained 

bed sediment2

Bulk bed 

sediment2,3 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

12334570 Clark Fork Bypass, 

near Bonner

S -- 03/08–P -- -- -- -- --

12340000 Blackfoot River near 

Bonner

LT, S 10/39–P 03/85–P 07/86–04/87, 

06/88–09/95,10/05–P

-- 08/86–08/87, 

08/91, 08/93–96, 08/98–01, 09/03,08/06–P

08/93, 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–P

12340500 Clark Fork above 

Missoula

LT, S 03/29–P 07/86–P4 07/86–04/87, 

06/88–01/96, 03/96–03/03, 08/03–P

04/07–09/07 08/97–P 08/97–08/04, 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 water, bedsediment, and biota samples from the Clark Fork basin, Montana.

Water Bed sediment Biota

Property Constituent Constituent Constituent

Streamflow Hardness (calculated) Arsenic Arsenic

pH Calcium Cadmium Cadmium

Specific conductance Magnesium Chromium Chromium

Temperature Nitrogen Copper Copper

Turbidity Phosphorous Iron Iron

Arsenic Lead Lead

Cadmium Manganese Manganese

Copper Nickel Nickel

Iron Zinc Zinc

Lead

Manganese

Zinc

Suspended sediment

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

collected systematically to provide a measure of the accuracy, 

precision, and bias of the environmental data, and to identify 

problems associated with sampling, processing, or analysis.

Water-Quality Data

Water-quality data consist of onsite measurements of 

selected stream properties and concentrations of chemical 

and physical constituents analyzed in periodically collected 

stream samples. Routine water samples for the long-term 

monitoring program were collected at 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 samples were collected 15–17 times at the 7 supplemental monitoring sites (which include 3 long-term monitoring 

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

by an observer 1–14 times per week, depending on season and 

flow conditions. Continuous turbidity monitors were operated 

seasonally (October 2007 and March/April–September 2008) 

at four sites near Anaconda to determine daily values (table 1).

Methods

Water samples were collected from vertical transits 

throughout the entire stream depth at multiple locations 

across the stream by using depth- and width-integration 

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

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

the Collection of Water-Quality Data (variously dated). 

These methods provide a vertically and laterally dischargeweighted 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, from 

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

estimation from a nearby gage on the same channel. Daily 

mean streamflow during ice periods was estimated because 

backwater affected the stage-discharge relation. Onsite 

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

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

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

USGS National Field Manual for the Collection of Water 

Quality Data (variously dated).

Composited water samples were analyzed for the constituents listed in table 2. The terms “filtered” and “unfiltered 

recoverable” replace the terms “dissolved” and “total recoverable,” respectively, which were used in past reports from this 

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

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

of nitrogen and phosphorous were determined by the USGS 

National Water Quality Laboratory (NWQL) in Denver, Colo. 
Table 3. Data-quality objectives for analyses of water 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 

(percent)

Maximum deviation of 

spike recovery 

(percent)

Calcium, filtered 0.04 mg/L 20 --

Magnesium, filtered .02 mg/L 20 --

Nitrogen, unfiltered recoverable .06 mg/L 20 25

Phosphorus, unfiltered recoverable .008 mg/L 20 25

Arsenic, filtered .06 μg/L 20 25

Arsenic, unfiltered recoverable .60 μg/L 20 25

Cadmium, filtered .04 μg/L 20 25

Cadmium, unfiltered recoverable .01 μg/L 20 25

Copper, filtered 1.0 μg/L 20 25

Copper, unfiltered recoverable 1.2 μg/L 20 25

Iron, filtered 8 μg/L 20 25

Iron, unfiltered recoverable 6 μg/L 20 25

Lead, filtered .08 μg/L 20 25

Lead, unfiltered recoverable .06 μg/L 20 25

Manganese, filtered .2 μg/L 20 25

Manganese, unfiltered recoverable .8 μg/L 20 25

Zinc, filtered 1.8 μg/L 20 25

Zinc, unfiltered recoverable 2.0 μg/L 20 25

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

Sediment, suspended 1 mg/L 20 --

Water-Quality Data 7

Concentrations of calcium and magnesium were determined 

to enable calculation of hardness, while concentrations of 

nitrogen and phosphorous were determined for the supplemental water samples, except for samples collected at Clark Fork 

Bypass, near Bonner. 

Filtered concentrations of arsenic, cadmium, copper, lead, 

manganese, and zinc were determined by inductively coupled 

plasma-mass spectrometry (Faires, 1993; Garbarino and 

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

and iron were determined by inductively coupled plasmaatomic emission spectrometry (Fishman, 1993). Unfiltered 

recoverable concentrations of trace elements were determined 

from unfiltered samples that were first digested with dilute 

hydrochloric acid (Hoffman and others, 1996). For cadmium, 

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

by inductively coupled plasma-mass spectrometry by using 

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

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

by inductively coupled plasma-mass spectrometry by using the 

method described by Garbarino and others (2006). Unfiltered 

recoverable concentrations of nitrogen and phosphorous were 

determined from unfiltered samples that were digested with 

persulfate and then analyzed by colorimetry. Unfiltered recoverable nitrogen was analyzed by using methods described by 

Patton and Kryskalla (2003), and unfiltered phosphorus was 

analyzed by using methods described by U.S. Environmental 

Protection Agency (1993).

Water samples also were collected from multiple vertical 

transits for analysis of suspended sediment whenever periodic 

water samples were collected. These samples were analyzed 

for suspended-sediment concentration and the percentage of 

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

size and smaller) by the USGS Montana Water Science Center 

sediment laboratory (hereinafter referred to as the Montana 

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

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

Suspended-sediment samples for the four daily 

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

contract observers using the depth-integration method at 

a single vertical transit near midstream. The samples were 
8 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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):

Q Q C k s w = × s × , (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 suspendedsediment discharge to an equivalent daily 

suspended-sediment discharge.

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

tributary sites in the upper Clark Fork basin near Anaconda 

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

provide supporting information on runoff conditions in an 

area where remediation activities are being conducted. They 

are operated seasonally, generally from early spring (after ice 

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

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

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

gov/mt/nwis. Continuous recordings provide the minimum 

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

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

period. Procedures for the operation of continuous turbidity 

monitors and for daily record computations are described by 

Wagner and others (2006).

Results

Water-quality data for samples collected periodically 

during water year 2008 are listed in table 4. Daily mean 

streamflow, daily mean suspended-sediment concentration, 

and daily suspended-sediment discharge for water year 2008 

at the four daily suspended-sediment sites are listed in tables 5 

through 8 along with monthly summary statistics and annual 

totals for streamflow and suspended-sediment discharge. 

Daily maximum, minimum, and mean turbidity at four sites 

are listed in tables 9 through 12 along with monthly summary 

statistics.

Quality Assurance

Quality-assurance procedures used for the collection 

and field processing of water samples are described by Ward 

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

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

Survey (variously dated). Standard procedures used by the 

NWQL for internal sample handling and quality assurance are 

described by Friedman and Erdmann (1982), Jones (1987), 

and Pritt and Raese (1995). Quality-assurance procedures used 

by the Montana Sediment Laboratory are described by Dodge 

and Lambing (2006). Standard procedures used for the calibration, measurement, and quality assurance of turbidity monitors 

are described by Anderson (2004).

The quality of analytical results reported for water 

samples was evaluated by 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 samples. Therefore, the total number of quality-control samples represented 

about 15 percent of the total number of water samples.

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

performed systematically by the NWQL to provide quality 

control of analytical procedures (Pritt and Raese, 1995; 

Maloney, 2005). These internal practices include analyses of quality-control samples such as calibration standard 

samples, standard reference water samples, replicate samples, 

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

NWQL participates in a blind-sample program in which standard reference water samples prepared by the USGS Branch 

of Quality Systems are routinely inserted into the sample 

line for each analytical method at a frequency proportional 

to the sample load (http://bqs.usgs.gov). The laboratory also 

participates in external evaluation studies and audits with the 

National Environmental Laboratory Accreditation Program, 

the U.S. Environmental Protection Agency, Environment 

Canada, and the USGS Branch of Quality Systems to assess 

analytical performance.

Replicate data can be obtained in different ways to 

provide an assessment of precision (reproducibility) of 

analytical results. Replicate samples are two or more samples 

considered to be essentially identical in composition. Replicate 

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

repeating the collection process to obtain two or more independent composite samples or by splitting a single composite 

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

sample can be analyzed two or more times in the laboratory to 

obtain a measure of analytical precision (laboratory replicate).

Precision of analytical results for field replicates is 

affected by numerous sources of variability within the field 

and laboratory environments, including sample collection, 

sample processing, and sample analysis. To provide data on 

overall precision for samples exposed to both field and laboratory sources of variability, replicate stream samples for chemical analysis were obtained in the field by splitting a composite 
Water-Quality Data 9

stream sample. Replicate stream samples for suspendedsediment analysis were obtained in the field by concurrently 

collecting two independent cross-sectional samples. Analyses 

of these field replicates indicate the reproducibility of environmental data that are affected by the combined variability 

potentially introduced by field and laboratory processes.

Precision of analytical results for laboratory replicates, 

which exclude field sources of variability, was determined by 

two independent chemical analyses of aliquots from a single 

sample selected from the group of samples constituting each 

analytical run. A separate analysis of the sample was made 

at the beginning and end of each analytical run to provide 

information on the reproducibility of laboratory analytical 

results independent of possible variability caused by field 

sample collection and processing. Laboratory replicates are 

not obtainable for suspended-sediment samples because the 

samples are consumed during the analysis.

Spiked samples are used to evaluate bias, which measures 

the ability of an analytical method to accurately quantify a 

known amount of analyte added to a sample. Because some 

constituents in stream water can potentially interfere with the 

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

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

aliquots of stream samples were spiked in the laboratory with 

known amounts of the same trace elements for which water 

samples were analyzed. Analyses of spiked blanks indicate if 

the spiking procedure and analytical method are within control 

for a water matrix that is presumably free of chemical interference. Analyses of spiked aliquots of stream samples indicate 

if the chemical matrix of the stream water interferes with the 

analytical measurement and whether these interferences could 

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

Deionized-water blank samples were submitted for every 

field trip and analyzed to identify the presence and magnitude 

of contamination that potentially could bias analytical results. 

The particular type of blank sample routinely tested was a 

field blank. Field blanks are aliquots of deionized water that 

are certified as trace-element free and are processed through 

the sampling equipment used to collect stream samples. These 

blanks then are subjected to the same processing (sample 

splitting, filtration, preservation, transportation, and laboratory 

handling) as stream samples. Blank samples are analyzed for 

the same constituents as stream samples to identify whether 

any detectable concentrations exist.

All water samples were handled in accordance with 

chain-of-custody procedures that provide documentation of 

sample identity, shipment, receipt, and laboratory handling. 

All routine and quality-control samples submitted from a 

sampling episode were stored in a secure area of the NWQL 

and analyzed as a discrete sample group, independent of other 

samples submitted to the NWQL. Therefore, the qualitycontrol data apply solely to the analytical results for stream 

samples reported herein and provide a direct measure of data 

quality for this monitoring program.

Data-quality objectives (table 3) were established for 

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

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

objectives identify analytical requirements of detectability and 

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

results. Comparisons of quality-control data to 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 

LRLs are designed to limit the possible occurrence of a false 

positive or false negative error to 1 percent or less. Accordingly, concentrations are reported as less than the LRL for 

samples in which the analyte was either not detected or did 

not pass identification criteria. Analytes that are detected at 

concentrations between the LT–MDL and the LRL and that 

pass identification criteria are reported as estimated concentrations. Estimated concentrations are noted with a remark code 

of “E.” These data need to be used with the understanding that 

their uncertainty is greater than that of data reported without 

the “E” remark code.

The precision of analytical results for a constituent can be 

determined by estimating a standard deviation of the differences in concentrations between replicate analyses for several 

sets of samples. These replicate analyses may consist either 

of individual analyses of a pair of samples considered to be 

essentially identical (field replicates) or of multiple analyses of 

an individual sample (laboratory replicates). The differences in 

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

(Taylor, 1987):

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

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 

x is the mean concentration for all replicate 

analyses.

Paired analyses of field replicates are listed in table 13. 

The overall precision estimated for each constituent on the 

basis of analyses of field replicates, which include both field 

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

data-quality objective used to indicate acceptable precision of 

results for field replicates was a maximum RSD of 20 percent 

(table 3). Precision estimates for the analytical results of 

field replicates were within the 20-percent RSD limit for all 

constituents, except unfiltered recoverable iron (table 14). The 

RSD for this constituent was 30 percent and resulted from 

poor replicate comparison from a sample collected on May 5, 

2008, at Clark Fork above Missoula when suspended-sediment 

concentrations were relatively high. When this 1 replicate 

pair was excluded, the other 11 replicate pairs had a RSD for 

unfiltered recoverable iron of 6.6 percent.

The precision estimated for each constituent on the basis 

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

the precision of analytical results for laboratory replicates are 

calculated by using unrounded values stored in laboratory data 

files. The data-quality objective used to indicate acceptable 

precision of results for laboratory replicates was a maximum 

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

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

Recovery efficiency for analyses of constituents is 

determined by analyses of an unspiked sample and a spiked 

aliquot of the same sample. The data-quality objective for 

acceptable spike recovery of trace elements in water samples 

was a maximum deviation of 25 percent from a theoretical 100-percent recovery of added constituent (table 3). At 

the laboratory, a spiked deionized-water blank sample and a 

spiked aliquot of a stream sample were prepared and analyzed 

along with the original unspiked sample. The differences 

between the spiked and unspiked sample concentrations were 

determined and used to compute recovery, in percent, according to equation 4:

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 16 and 17, respectively. The mean spike 

recovery for deionized-water blank samples spiked with trace 

elements (table 16) ranged from 97.9 to 105 percent. The 

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

spike recovery for each constituent for which deionized-water 

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

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

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

ranged from 92.8 to 106 percent. The 95-percent confidence 

intervals for mean spike recoveries (table 17) did not exceed a 

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

No adjustments were made to analytical data on the basis of 

the mean spike recovery.

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

thereby indicating a consistent deviation in one direction. All 

laboratory-spiked deionized-water blank samples (table 16) 

had confidence intervals for percent recovery that included 

100 percent. All laboratory-spiked stream samples (table 17) 

also had confidence intervals for percent recovery that 

included 100 percent except for unfiltered recoverable copper 

(86.4–99.1 percent) and unfiltered recoverable zinc (93.1–

98.2 percent). Both the 95-percent confidence interval and 

mean spike recovery for these constituents indicate a persistent 

but minor, low 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 18. 

A field blank with constituent concentrations equal to or less 

than the LRL for the analytical method indicates the entire 

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

than twice the LRL, the concentrations were noted during 

data review. Analytical results from the field blank for the 

next sample set were evaluated for a consistent trend that 

could indicate systematic contamination. Sporadic, infrequent 

exceedances of twice the LRL probably represented random 

contamination or instrument calibration error that was not 
Bed-Sediment Data 11

persistent in the process and was not likely to cause positive 

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

concentrations for a particular constituent exceeded twice the 

LRL in field blanks from two consecutive field trips, blank 

samples were collected from individual components of the 

processing sequence and were submitted for analysis to identify the source of contamination.

Trace-element concentrations in field blanks (table 18) 

were almost always less than the LRL. Two detections 

exceeded the LRL in two separate samples for filtered zinc, 

which had a LRL of 1.8 μg/L. One occurred on May 28, 2008 

(4.0 μg/L), and one occurred on June 11, 2008 (3.6 μg/L). 

Because no trends were indicated in subsequent sampling 

trips, no adjustments were made to water-quality sample 

results on the basis of these two detections.

Bed-Sediment Data

Bed-sediment data for the long-term monitoring program 

in the upper Clark Fork basin consist of analyses of traceelement concentrations in the fine-grained (<0.064 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. Bedsediment samples were collected once annually at 13 sites 

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

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

to facilitate data comparisons among years. One site, Warm 

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

rather than once annually.

Methods

Fine-grained bed-sediment samples were collected in 

August 2008 using protocols described by E.V. Axtmann (U.S. 

Geological Survey, written commun., 1994). Samples were 

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

were collected from both sides of the stream.

Individual samples of bed sediment were collected by 

scooping material from the surfaces of three to five randomly 

selected deposits along pool or low-velocity areas. The three 

to five individual samples were combined to form a single 

composite sample. This collection process was repeated three 

times to obtain three composite samples. Each composite 

sample was wet-sieved onsite through a 0.064-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 2-week digestion period, the aliquots 

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

was reconstituted in 10 mL of 0.6N (normal) hydrochloric 

acid. The reconstituted aliquots then were filtered through 

a 0.45-μm pore-size filter by using a syringe and in-line 

disposable filter cartridge. The filtrate was diluted to a 1:10 

ratio with 0.6N hydrochloric acid. These final solutions were 

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

manganese, nickel, and zinc by using inductively coupled 

plasma-optical emission spectrometry (ICP–OES). The smallest concentration of a constituent that can be reliably reported 

for analyses of bed sediment is termed the minimum reporting 

level.

Results

Concentrations of trace elements measured in samples of 

fine-grained bed sediment collected during August 2008 are 

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

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

that were analyzed in the reconstituted aliquots of digested 

bed sediment were converted to solid-phase concentrations, in 

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

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 19 

are the means of all analyses for replicate aliquots from each 

composite bed-sediment sample collected at the site. Because 

the conversion from liquid-phase to solid-phase concentration 

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

the sample, minimum reporting levels for some trace elements 

might differ among stations and among years.

Quality Assurance

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

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

water. All equipment received a final rinse onsite with stream 

water. Sampling equipment used at more than one site was 

rinsed between sites with stream water. Separate sieves were 

used at each site and, therefore, did not require between-site 

cleaning. Bed-sediment samples were collected sequentially at 

sites along an increasing concentration gradient to minimize 

effects from potential site-to-site carryover contamination.

Quality assurance of analytical results for bed-sediment 

samples included laboratory instrument calibration with 

standard solutions and analysis of quality-control samples 

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

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

Quality-control samples consisted of standard reference 

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

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

SRMs are commercially prepared materials that have 

certified concentrations of trace elements. Analyses of SRMs 

are used to indicate the ability of the method to accurately 

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

confidence interval for recovery. Recovery efficiency for 

trace-element analyses of SRMs for bed sediment is listed 

in table 20. Two SRMs consisting of agricultural soils 

representing low and high concentrations of trace elements 

were analyzed to test recovery efficiency for a range of 

concentrations generally similar to those occurring in the 

bed sediment of streams in the upper Clark Fork basin. The 

digestion process used to analyze bed-sediment samples is 

not a “total” digestion (does not liberate elements associated 

with crystalline lattices); therefore, 100-percent recovery may 

not be achieved for elements strongly bound to the sediment. 

The percent recovery of trace elements for SRM analyses that 

use less than a total digestion is useful to indicate which trace 

elements display strong sediment-binding characteristics in the 

SRM and whether analytical recovery is consistent between 

multiple sets of analyses.

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

trace elements (table 20) illustrate analytical performance. 

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

from 94.9 to 106.4 percent of the certified concentrations. 

Mean recoveries were low for chromium and copper (81.1 

and 78.5 percent, respectively), even lower for arsenic and 

lead (63.0 and 55.4 percent, respectively), and higher for 

cadmium (134.0 percent). 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. The range of variation for the 95-percent confidence interval for copper was 

slightly higher (about 12 percent). Mean SRM recoveries for 

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

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

from 87.1 to 104.4 percent of the certified concentrations. 

Chromium again had a lower recovery (71.7 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 11 percent for most constituents) for the 95-percent confidence interval indicates good 

reproducibility of multiple analyses of SRM 2711. The range 

of variation for the 95-percent confidence interval for chromium was higher (about 16 percent). 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 21) are reported as a liquid-phase concentration, in micrograms per milliliter, which is equivalent to parts 

per million. A procedural blank was prepared and analyzed 

concurrently with bed-sediment samples for each site. 

Concentrations of trace elements in all procedural blanks were 

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

necessary.

Biological Data

Biological data for the long-term monitoring program 

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

benthic insects. Insect samples were collected once annually 

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

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

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

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

once every 3 years rather than once annually.

Methods

Insect samples were collected using protocols described 

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

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

single riffle at each station was sampled repeatedly until an 

adequate number of individual insects was collected to provide 

sufficient mass for analysis. Targeted taxa for collection were 

the order Trichoptera (caddisflies) and the order Plecoptera 

(stoneflies).

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 
Biological Data 13

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 Claassenia sabulosa were collected where 

available to represent additional insect taxa that are commonly 

distributed in the upper Clark Fork basin. In addition, specimens from the caddisfly group Brachycentrus spp. 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 1999–2008, samples were 

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

depuration. A comparison of immediately frozen to depurated samples showed that although no substantial difference 

occurred for most metals, concentrations of copper were about 

20 percent lower in the depurated samples than in the samples 

that were immediately frozen. The data were not adjusted for 

this difference.

Insect samples were processed and analyzed at the 

USGS National Research Program Ecology and Contaminants 

Project laboratory in Menlo Park, Calif. Insects were thawed 

and rinsed with ultrapure deionized water to remove particulate matter and then sorted to their lowest possible taxonomic 

level. If large numbers of specimens were collected at a site, 

similar-sized individuals were composited into replicate 

subsamples. Subsamples were placed in tared scintillation 

vials and ovendried at 70°C. Subsamples were weighed to 

obtain a final dry weight and digested by reflux using concentrated nitric acid (Cain and others, 1992). After digestion, 

insect samples were evaporated to dryness on a hot plate. 

The dry residue was reconstituted in 0.6N hydrochloric acid, 

filtered through a 0.45-μm pore-sized filter, and analyzed 

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

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

concentration of a constituent that can be reliably reported for 

analyses of biota is termed the minimum reporting level.

Results

Concentrations of trace elements in whole-body tissue 

of aquatic insects collected during August 2008 are listed in 

table 22. The variability in the number of composite samples 

among species and among sites reflects differences in insect 

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

concentrations, in micrograms per milliliter, analyzed in the 

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

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

As with minimum reporting levels for trace elements in bed 

sediment, minimum reporting levels for trace elements in 

insects may differ among sites as a result of varied sample 

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

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

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

concentration in tissue.

Quality Assurance

The protocols for field collection and processing of biota 

samples are designed to prevent contamination from metal 

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

prior to the first sample collection. Nets and equipment were 

thoroughly rinsed in ambient stream water at each new mainstem site. New nets were used for all tributary sites. Biota 

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

site-to-site carryover contamination.

Quality assurance of analytical results for biota samples 

included laboratory-instrument calibration with standard 

solutions and analyses of quality-control samples designed to 

quantify precision and to identify the presence and magnitude 

of bias. Quality-control samples consisted of 12 replicates of 

the tissue SRM (lobster hepatopancreas) and 13 procedural 

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

analyzed in a proportion equivalent to about 20 percent of the 

total number of biota samples.

Recovery efficiency for trace-element analyses of the 

SRM for biota is listed in table 23. Data-quality objectives 

have not been established for analytical recovery in biota, but 

percent recoveries are shown to illustrate analytical performance. Mean SRM recoveries ranged from 97.7 to 107 percent 

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

zinc. Higher mean recoveries were measured for chromium 

(169 percent) and lead (139 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 24) are reported as a liquidphase concentration, in micrograms per milliliter, which 

is equivalent to parts per million. A procedural blank was 

prepared and analyzed concurrently with biota samples for 

each site. Concentrations of trace elements in all procedural 

blanks were less than the minimum reporting level; therefore, 

no adjustments to the data were necessary.
14 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Statistical Summaries of Data

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

are listed in tables 25 through 27 for the period of record at 

each site since 1985. The summaries include the period of 

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

and median concentrations.

Statistical summaries of long-term water-quality data 

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

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

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

supplemental samples collected at selected sites. Inclusion 

of results for supplemental samples that targeted high-flow 

conditions or maintenance drawdowns of Milltown Reservoir 

might disproportionately skew the long-term statistics relative 

to the other sites in the network. Statistical summaries of bedsediment (table 26) and biological data (table 27) are based on 

results of samples collected once annually during the indicated 

years. Because not all sites were sampled for bed sediment 

and biota every year, the data for some sites do not represent 

a consecutive annual record. Sampling of bulk bed sediment 

has been discontinued; therefore, a statistical summary is not 

presented. Statistical summaries are not presented for discontinued sites.

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

the mean trace-element concentrations determined for each 

year from the mean of the analyses of composite samples. 

Therefore, the number of samples for bed sediment represents 

the number of years that the constituent was analyzed. In 

contrast, statistics for biological data (table 27) are based on 

individual analyses for each composite sample collected rather 

than on a single mean concentration for each year. Also, the 

number of samples for arsenic for both bed sediment and biota 

is smaller than the number for other trace elements because 

sampling for arsenic began in September 2003.

Differences in the number of composited biota samples 

among species reflect differences in species abundance, both 

within and between sites and among years. As a result, the 

statistics for biota describe a wider range of variation in traceelement concentrations than would be evident if results from 

individual composite samples were averaged. The abundance 

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

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

minimum reporting levels. Where minimum reporting levels 

vary among years, differences in concentration with time are 

difficult to determine, especially when a large percentage of 

the samples have concentrations less than minimum reporting 

levels.

The presence or absence of insect species at a given site 

can vary among years and may result in different taxa being 

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

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

based on the results of all Hydropsyche species combined. At 

some sites, statistics for the Hydropsyche morosa group are 

based on the combined results for two or more species because 

these samples could not be clearly identified to the species 

level, but the individual insects had morosa characteristics.

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

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

1999 through September 2000) and statistical summaries 

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

2000 through September 2001) and statistical summaries 

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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 

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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 

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

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

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

107 p.

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measurement of fluvial sediment: U.S. Geological Survey 

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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 plasmamass spectrometry: U.S. Geological Survey Open-File 

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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/twri5a6/.
16 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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 

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samples using collision/reaction cell inductively coupled 

plasma-mass spectrometry: U.S. Geological Survey Techniques and Methods, book 5, sec. B, chap. 1, 88 p.

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

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

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

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Report 96–225, 28 p.

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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 

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

September 1987) and statistical summaries (March 1985 

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through September 1988) and statistical summaries (March 

1985 through September 1988) for the Clark Fork and 

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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 

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

statistical summaries of water-quality data (March 1985 

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quality control manual—National Water Quality Labora-

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35 p.

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2175, 2 v., 631 p.

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

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voir Sediments Operational Unit of the Milltown Reservoir/

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

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.

[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)

11/06/2007 0730 6.4 7.6 287 3.5 110 32.2 7.83

03/04/2008 0720 4.8 7.6 319 2.0 120 33.3 8.77

04/07/2008 0850 5.4 7.6 304 2.5 110 32.0 7.99

05/05/2008 0855 19 7.7 212 5.5 83 23.4 5.89

06/03/2008 0720 48 7.6 181 9.5 68 19.2 4.76

06/18/2008 0715 45 7.6 181 12.0 70 20.0 4.83

07/07/2008 0825 17 7.8 230 13.0 91 26.2 6.33

08/18/2008 0900 4.4 7.7 331 10.5 130 36.0 8.90

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)

11/06/2007 1.9 2.8 E0.02 0.03 1.4 4.2 93 484

03/04/2008 1.6 1.9 E.02 .02 1.3 1.7 135 288

04/07/2008 1.7 2.3 E.02 .03 1.2 2.3 121 422

05/05/2008 5.3 6.7 <.04 .03 7.0 15.7 420 813

06/03/2008 6.8 8.0 E.03 .03 6.7 11.1 193 600

06/18/2008 8.6 10.0 E.03 .04 6.7 9.2 229 630

07/07/2008 7.7 10.4 <.04 .03 3.4 5.0 317 747

08/18/2008 2.7 3.5 <.04 <.01 1.2 1.7 48 226

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/06/2007 E0.05 0.55 32.5 45.1 2.6 4.4 88 4 0.07

03/04/2008 E.04 .21 46.8 51.4 3.0 3.3 80 2 .03

04/07/2008 E.04 .40 59.1 66.1 2.4 3.5 88 5 .07

05/05/2008 .24 .82 29.3 61.1 3.5 4.0 79 7 .36

06/03/2008 .18 1.01 21.2 35.9 3.1 5.3 63 12 1.6

06/18/2008 .17 .72 31.2 46.1 3.7 4.8 69 10 1.2

07/07/2008 .12 .57 23.8 47.1 1.9 3.5 87 6 .28

08/18/2008 .11 .14 36.9 46.4 2.8 2.5 91 2 .02
Data 21

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/06/2007 0855 22 7.5 516 6.5 150 43.7 10.4

03/03/2008 1525 19 7.7 575 5.5 170 45.1 13.9

04/07/2008 1125 21 7.7 535 6.0 160 44.7 11.5

05/05/2008 1010 37 7.6 378 7.0 120 35.3 8.87

06/02/2008 1535 67 7.8 272 13.0 94 27.0 6.53

06/17/2008 1525 73 7.7 277 16.5 95 27.3 6.58

07/07/2008 0945 35 7.7 410 14.0 140 39.0 9.19

08/18/2008 1020 15 7.7 588 16.0 170 50.8 11.7

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/06/2007 3.2 4.2 0.11 0.15 8.6 35.1 29 257

03/03/2008 3.0 4.1 .10 .15 11.7 18.1 28 376

04/07/2008 3.0 4.3 .10 .14 9.8 19.8 30 399

05/05/2008 4.8 6.2 .05 .11 10.9 21.3 216 605

06/02/2008 7.8 9.2 .06 .13 9.2 16.6 145 657

06/17/2008 9.3 10.8 .06 .10 8.4 14.8 142 530

07/07/2008 6.8 9.2 .10 .13 14.0 22.1 115 548

08/18/2008 4.5 5.1 .08 .09 8.5 11.7 24 125

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)

11/06/2007 0.27 1.53 76.5 104 51.2 56.1 86 5 0.30

03/03/2008 .16 2.10 113 136 37.8 46.4 88 10 .51

04/07/2008 .16 2.00 118 136 37.7 49.8 90 12 .68

05/05/2008 .27 1.69 78.3 109 24.0 31.9 83 9 .90

06/02/2008 .31 2.85 47.2 90.6 16.0 29.1 70 14 2.5

06/17/2008 .30 2.15 55.4 86.6 18.3 31.1 72 10 2.0

07/07/2008 .25 2.05 95.4 127 29.7 42.3 90 8 .76

08/18/2008 .23 1.03 31.9 52.4 37.5 42.9 88 2 .08
22 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12323600--Silver Bow Creek at Opportunity

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/05/2007 1415 33 9.0 503 6.5 170 50.5 11.0

03/03/2008 1410 E27 8.2 544 0.0 180 49.3 12.9

04/08/2008 0745 32 8.0 535 1.0 170 48.5 11.4

05/06/2008 0805 82 7.9 331 6.0 110 34.0 7.25

06/02/2008 1410 209 8.1 261 12.0 98 29.8 5.59

06/18/2008 0920 211 8.2 252 11.0 91 27.1 5.57

07/07/2008 1730 71 9.3 350 20.5 130 38.2 8.00

08/19/2008 0740 16 8.1 572 14.5 200 57.4 12.8

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)

11/05/2007 7.6 9.5 0.33 0.55 19.5 55.6 14 380

03/03/2008 7.6 14.0 .64 1.21 28.6 106 21 1,150

04/08/2008 8.3 10.3 .76 .97 26.0 50.6 26 414

05/06/2008 8.3 13.1 .30 .68 18.8 64.9 76 853

06/02/2008 10.1 17.4 .34 .79 31.7 94.7 83 1,360

06/18/2008 15.0 18.1 .30 .56 30.4 65.2 134 753

07/07/2008 12.7 15.9 .17 .38 19.7 45.4 38 469

08/19/2008 13.1 15.2 .44 .65 22.3 46.3 18 240

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)

11/05/2007 0.28 7.51 80.7 121 53.6 119 85 8 0.71

03/03/2008 .27 24.1 288 418 173 268 78 36 E2.6

04/08/2008 .28 7.18 344 387 206 249 88 12 1.0

05/06/2008 .51 16.3 138 224 96.0 168 85 30 6.6

06/02/2008 .96 23.9 77.8 183 75.7 162 64 37 21

06/18/2008 1.02 12.2 74.1 120 80.2 126 77 21 12

07/07/2008 .30 7.36 56.6 110 11.2 69.7 85 12 2.3

08/19/2008 .33 5.69 70.7 126 67.3 110 85 7 .30
Data 23

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/05/2007 1040 12 <2.0 8.2 184 3.5 83 22.4 6.56

03/04/2008 0920 E8.5 <2.0 8.1 196 0.0 87 23.2 7.08

04/07/2008 1315 8.8 <2.0 8.2 203 4.5 88 23.4 7.11

05/05/2008 1355 38 3.8 8.0 129 9.5 50 14.0 3.73

06/02/2008 1100 161 2.4 7.8 80 7.5 30 8.55 2.07

06/17/2008 1215 134 E1.4 7.9 87 10.0 33 9.57 2.30

07/07/2008 1415 90 2.5 7.9 83 12.5 35 10.1 2.31

08/18/2008 1355 18 E1.4 8.3 156 16.0 70 19.1 5.33

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)

11/05/2007 15.2 16.3 0.04 0.05 1.2 1.8 54 105

03/04/2008 10.4 12.2 E.03 .06 E.98 1.8 21 120

04/07/2008 12.6 14.2 .05 .06 E.98 1.4 23 99

05/05/2008 26.5 29.9 E.03 .10 4.0 6.9 52 255

06/02/2008 18.6 20.3 .04 .08 3.6 5.9 40 236

06/17/2008 19.8 20.8 .05 .07 3.1 4.6 29 163

07/07/2008 12.8 15.3 E.03 .05 1.7 2.9 31 171

08/18/2008 17.7 20.7 E.02 .09 1.4 2.5 67 168

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)

11/05/2007 0.08 0.21 6.0 8.5 E1.5 E1.8 80 1 0.03

03/04/2008 <.08 .44 6.5 13.5 E.91 2.6 71 2 E.05

04/07/2008 E.04 .34 7.0 11.3 E.94 E1.5 76 2 .05

05/05/2008 .13 1.09 5.0 16.9 E1.5 3.8 79 6 .62

06/02/2008 .13 1.08 3.6 12.1 2.4 4.3 57 8 3.5

06/17/2008 .10 .73 3.9 10.3 1.9 3.7 36 6 2.2

07/07/2008 .08 .59 5.4 11.4 E1.1 2.6 69 6 1.5

08/18/2008 .14 .52 6.0 15.5 E1.3 E1.8 66 3 .15
24 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/05/2007 1250 1.5 7.9 206 5.0 89 24.6 6.66

03/03/2008 1300 E4.0 8.0 230 0.0 97 26.4 7.44

04/07/2008 1530 2.5 8.0 223 6.0 95 26.0 7.26

05/05/2008 1615 6.0 7.9 150 12.5 60 16.8 4.51

06/02/2008 1320 97 7.9 86 10.0 33 9.27 2.29

06/17/2008 1355 62 8.0 95 13.0 38 10.8 2.57

07/07/2008 1630 64 7.9 90 15.0 37 10.7 2.45

08/18/2008 1625 1.7 8.1 178 19.5 75 20.9 5.58

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)

11/05/2007 17.7 18.6 0.08 0.09 2.1 2.5 49 82

03/03/2008 12.8 15.0 .06 .09 1.3 1.8 42 114

04/07/2008 14.4 16.1 .05 .04 1.5 1.5 16 44

05/05/2008 28.3 31.3 .05 .09 4.2 5.6 32 126

06/02/2008 27.2 31.3 .07 .17 5.2 9.8 40 324

06/17/2008 28.4 30.3 .07 .14 4.0 7.0 33 210

07/07/2008 23.7 29.0 .06 .12 2.7 5.9 45 223

08/18/2008 28.6 31.0 .04 .05 2.4 2.8 61 108

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/05/2007 0.10 0.20 8.1 7.8 4.9 4.7 89 1 <0.01

03/03/2008 <.08 .21 28.5 32.3 4.3 5.4 46 1 E.01

04/07/2008 <.08 .08 3.8 4.2 2.2 2.5 57 1 .01

05/05/2008 .09 .46 4.5 8.2 2.7 4.0 32 5 .08

06/02/2008 .16 1.84 3.8 17.8 3.7 8.3 43 14 3.7

06/17/2008 .13 1.26 4.3 15.7 3.0 6.4 51 7 1.2

07/07/2008 .14 1.16 7.1 16.6 2.2 5.2 59 8 1.4

08/18/2008 .12 .23 6.9 10.3 E1.7 E2.0 71 1 <.01
Data 25

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12323710--Willow Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/05/2007 0940 1.6 <2.0 7.8 119 0.5 43 14.4 1.68

05/05/2008 1305 13 13 7.6 104 6.0 38 12.5 1.57

06/02/2008 0950 62 7.1 7.6 75 6.0 25 8.33 1.02

06/17/2008 1115 28 5.3 7.8 89 7.5 32 10.6 1.21

07/07/2008 1325 7.7 7.4 8.0 108 12.0 39 13.0 1.53

08/18/2008 1305 2.9 E1.5 7.9 112 13.0 38 12.9 1.47

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)

11/05/2007 9.9 10.3 E0.02 0.03 E0.90 3.1 49 98

05/05/2008 19.2 21.7 <.04 .10 3.2 5.7 277 712

06/02/2008 15.1 16.6 E.04 .08 2.9 5.2 132 657

06/17/2008 14.9 15.4 E.03 .05 2.4 3.4 85 352

07/07/2008 14.2 17.6 .04 .09 1.7 3.4 43 448

08/18/2008 14.0 15.4 <.04 .02 E.98 1.5 54 123

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)

11/05/2007 E0.05 0.10 19.4 24.3 2.0 E1.4 88 1 <0.01

05/05/2008 .21 1.82 13.8 46.3 2.0 5.7 77 26 .91

06/02/2008 .18 1.76 6.2 23.8 2.5 5.8 25 61 10

06/17/2008 .17 .95 9.8 18.3 2.6 4.0 31 22 1.7 

07/07/2008 .09 1.11 17.4 29.0 E1.1 3.6 92 25 .52

08/18/2008 E.05 .19 12.5 18.9 E1.3 <2.0 87 2 .02
26 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/05/2007 1345 5.9 8.9 292 8.5 130 36.4 8.62

03/03/2008 1330 4.7 8.2 326 4.0 140 38.9 9.61

04/07/2008 1610 4.5 8.0 326 9.0 140 38.7 9.39

05/05/2008 1645 14 8.0 214 13.0 83 24.9 5.11

06/02/2008 1345 70 7.9 213 14.0 88 25.7 5.70

06/17/2008 1420 44 8.0 227 17.0 98 28.9 6.18

07/07/2008 1705 17 8.1 270 19.5 120 33.9 7.77

08/18/2008 1650 6.8 8.6 314 19.0 140 40.0 9.42

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)

11/05/2007 14.2 16.7 <0.04 0.03 1.4 3.4 E7 108

03/03/2008 12.2 14.0 E.03 .06 1.9 4.3 37 169

04/07/2008 10.9 15.1 E.03 .10 1.2 8.5 15 362

05/05/2008 33.6 40.5 <.04 .13 6.1 16.8 74 508

06/02/2008 98.5 104 .06 .16 11.3 22.6 65 468

06/17/2008 80.2 80.6 .07 .14 7.7 15.2 54 321

07/07/2008 67.1 76.6 .05 .08 5.9 9.3 53 194

08/18/2008 29.0 31.6 <.04 .02 2.9 4.6 8 90

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)

11/05/2007 E0.07 0.88 12.9 17.2 <1.8 3.6 95 2 0.03

03/03/2008 .16 1.30 50.8 57.3 3.2 6.5 89 5 .06

04/07/2008 .13 3.67 82.2 98.6 2.7 13.2 92 13 .16

05/05/2008 .30 3.93 48.5 77.7 4.0 17.7 89 19 .72

06/02/2008 .31 4.17 15.6 35.9 9.5 23.2 55 29 5.5

06/17/2008 .27 2.54 17.7 30.6 7.6 16.5 59 16 1.9

07/07/2008 .19 1.08 17.4 27.8 4.8 8.9 84 4 .18

08/18/2008 E.07 .83 5.1 13.6 E1.2 2.9 90 3 .06
Data 27

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/05/2007 1525 59 8.8 643 6.0 260 75.3 17.4

03/03/2008 1100 47 8.6 644 2.0 260 73.5 17.9

04/08/2008 0850 46 8.9 545 2.0 210 57.3 16.2

05/06/2008 0900 99 9.2 519 10.5 200 58.3 14.1

06/03/2008 1035 351 8.6 368 10.0 140 43.0 8.23

06/18/2008 1000 355 9.4 346 13.0 140 45.2 7.46

07/08/2008 0750 130 8.2 323 12.5 130 40.4 7.67

08/19/2008 0835 37 8.9 485 17.0 210 61.4 13.3

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/05/2007 18.5 20.9 0.06 0.09 2.8 4.5 <8 138

03/03/2008 12.6 15.7 .11 .17 4.8 7.7 10 258

04/08/2008 11.6 14.1 .09 .12 3.4 6.4 9 229

05/06/2008 19.2 23.3 <.04 .08 3.4 7.9 20 288

06/03/2008 40.1 42.2 E.03 .12 5.0 12 25 264

06/18/2008 34.9 36.5 .07 .16 10.6 16.6 22 217

07/08/2008 35.5 39.7 E.03 .08 3.0 6.7 38 235

08/19/2008 45.2 49.5 <.04 .05 2.6 4.4 8 122

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)

11/05/2007 0.20 0.54 64.0 125 2.8 5.1 61 3 0.48

03/03/2008 <.08 1.02 148 220 6.1 13.6 81 5 .63

04/08/2008 .09 1.37 87.8 163 3.9 13.0 86 6 .75

05/06/2008 .09 1.79 238 373 E1.6 11.6 76 6 1.6

06/03/2008 .12 1.94 160 191 3.4 15.4 89 6 5.7

06/18/2008 .17 2.03 61.3 99.0 3.5 19.8 86 5 4.8

07/08/2008 .13 1.24 185 234 2.6 7.6 89 6 2.1

08/19/2008 .09 .78 52.1 110 E1.4 5.0 74 3 .30
28 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

12323760--Warm Springs Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/05/2007 1220 61 <2.0 8.6 259 5.5 120 35.7 7.85

04/07/2008 1450 43 <2.0 8.6 271 6.0 130 37.1 8.57

05/05/2008 1440 59 <2.0 8.7 251 10.5 120 35.7 7.86

06/03/2008 0915 268 2.3 8.3 140 5.0 65 20.0 3.52

07/07/2008 1535 239 5.5 8.3 161 11.5 75 23.0 4.23

08/18/2008 1510 79 E1.1 8.5 241 14.0 120 36.2 7.71

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)

11/05/2007 2.0 2.1 <0.04 0.02 <1.0 1.6 <8 28

04/07/2008 2.0 2.3 E.02 .02 E.59 1.2 <8 54

05/05/2008 2.2 2.5 <.04 .02 E.88 2.2 E6 86

06/03/2008 1.9 2.5 E.03 .04 1.4 3.5 11 192

07/07/2008 2.3 2.9 E.02 .03 1.2 2.7 8 118

08/18/2008 2.3 2.6 <.04 E.01 E.75 1.6 E6 66

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)

11/05/2007 <0.08 0.08 0.5 1.2 <1.8 <2.0 69 1 0.16

04/07/2008 <.08 .23 .7 2.1 <1.8 E1.0 67 3 .35

05/05/2008 <.08 .28 .9 3.7 <1.8 E1.5 61 4 .64

06/03/2008 .11 .52 1.9 9.6 2.8 4.7 53 12 8.7

07/07/2008 <.08 .29 2.9 7.1 E1.2 3.8 65 6 3.9

08/18/2008 <.08 .26 1.1 4.7 <1.8 E1.7 56 6 1.3
Data 29

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/05/2007 1510 40 8.5 332 5.5 160 47.5 9.33

04/08/2008 0830 30 8.2 365 2.0 170 50.9 10.7

05/06/2008 0840 45 8.1 318 7.0 150 45.4 9.13

06/03/2008 1005 201 8.1 166 5.5 73 22.9 3.95

07/08/2008 0720 183 8.0 190 10.0 88 27.1 4.92

08/19/2008 0815 38 8.2 308 13.0 140 43.0 8.49

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)

11/05/2007 3.7 4.2 E0.03 0.03 1.6 4.5 E6 54

04/08/2008 3.4 4.1 .04 .04 1.7 4.9 E6 72

05/06/2008 4.0 5.2 <.04 .05 2.1 10.3 8 149

06/03/2008 3.4 5.2 E.03 .06 3.0 16.4 12 291

07/08/2008 4.5 6.1 E.03 .06 2.2 12.8 16 224

08/19/2008 5.3 6.1 <.04 .04 2.1 6.1 12 87

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)

11/05/2007 <0.08 0.21 103 125 E1.1 E1.2 43 1 0.11

04/08/2008 <.08 .37 146 170 E1.5 2.6 48 13 1.1

05/06/2008 <.08 .88 83.3 174 E1.0 4.1 70 6 .73

06/03/2008 E.05 1.66 38.7 97.6 E1.5 7.6 62 16 8.7 

07/08/2008 <.08 1.06 47.4 78.9 1.9 6.0 73 10 4.9 

08/19/2008 E.06 .48 72.0 123 E1.2 2.8 70 3 .31
30 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/06/2007 1205 93 8.6 511 4.0 220 65.5 14.4

03/03/2008 1000 77 8.4 526 0.0 220 65.1 14.9

04/08/2008 1030 83 8.5 486 3.0 200 55.5 14.0

05/06/2008 1015 170 8.9 461 10.0 190 55.4 12.8

06/03/2008 1210 590 8.4 307 10.0 120 37.4 6.91

06/18/2008 1135 595 9.1 279 12.5 120 37.5 6.25

07/10/2008 0825 258 8.1 257 13.0 110 34.6 6.50

08/19/2008 0950 56 8.6 397 15.5 180 53.1 11.0

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)

11/06/2007 11.1 12.5 0.04 0.05 2.5 4.1 E4 80

03/03/2008 8.7 10.8 .07 .13 3.7 10.7 E7 194

04/08/2008 8.5 10.4 .06 .10 3.1 7.7 E7 198

05/06/2008 14.8 18.2 E.02 .10 3.4 13.1 15 338

06/03/2008 26.9 30.9 E.03 .16 5.8 26.9 17 486

06/18/2008 23.3 25.9 .04 .15 8.2 26.3 15 421

07/10/2008 17.4 20.5 E.04 .09 3.3 13.3 23 258

08/19/2008 23.9 26.7 <.04 .06 3.3 10.0 E7 148

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)

11/06/2007 <0.08 0.36 59.4 96 E1.7 3.7 67 1 0.25

03/03/2008 <.08 1.09 130 194 5.2 11.9 66 4 .83

04/08/2008 E.04 1.18 107 170 2.6 10.6 80 6 1.3

05/06/2008 E.06 2.02 158 304 E1.3 12.8 68 12 5.5

06/03/2008 .09 3.40 98.9 197 3.3 22.4 65 20 32

06/18/2008 .10 3.04 42.0 127 1.9 22.2 55 20 32

07/10/2008 E.07 1.67 82.2 143 2.4 9.9 73 9 6.3

08/19/2008 E.06 1.19 54.9 129 E1.3 7.3 82 4 .60
Data 31

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/05/2007 1120 4.3 <2.0 8.3 242 4.5 120 35.0 7.22

03/03/2008 1150 1.8 E1.7 8.3 226 1.0 110 31.4 6.67

04/07/2008 1400 3.5 <2.0 8.2 221 4.0 100 30.3 6.44

05/05/2008 1515 5.7 E1.3 8.2 212 9.5 100 30.2 6.25

06/02/2008 1135 13 5.4 8.1 153 9.0 69 21.1 3.95

06/17/2008 1300 28 3.9 8.1 159 10.5 72 22.4 3.98

07/07/2008 1450 14 2.5 8.2 188 12.0 86 26.6 4.84

08/18/2008 1430 8.7 E1.2 8.3 225 13.0 110 31.9 6.32

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)

11/05/2007 3.9 3.9 E0.03 0.02 1.1 2.1 E6 38

03/03/2008 2.7 3.2 E.02 .03 1.2 3.7 <8 92

04/07/2008 2.4 2.8 E.02 .04 1.2 4.3 E7 68

05/05/2008 2.9 3.3 <.04 .03 1.5 4.4 9 131

06/02/2008 5.0 6.5 E.03 .07 3.0 12.2 14 399

06/17/2008 7.3 8.3 E.03 .07 3.2 11.5 15 425

07/07/2008 7.1 7.8 E.03 .03 1.9 3.8 11 91

08/18/2008 3.4 3.6 <.04 E.01 1.1 2.5 E5 65

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)

11/05/2007 <0.08 0.15 0.7 1.5 E1.3 E1.8 67 1 0.01

03/03/2008 <.08 .42 .5 3.2 <1.8 2.2 69 4 .02

04/07/2008 <.08 .33 .9 2.4 <1.8 E1.8 76 3 .03

05/05/2008 <.08 .51 1.0 4.6 <1.8 2.1 62 3 .05

06/02/2008 E.06 1.61 2.0 12.1 E1.5 6.3 61 19 .67

06/17/2008 E.05 1.67 1.8 13.2 E1.5 6.3 50 27 2.0

07/07/2008 <.08 .32 2.0 4.6 E1.1 2.4 48 4 .15

08/18/2008 <.08 .33 1.0 4.6 E.92 E1.4 47 3 .07
32 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/06/2007 1135 48 8.3 590 3.5 280 81.0 17.8

03/03/2008 0930 41 8.2 622 0.0 290 84.5 19.3

04/08/2008 1000 41 8.2 618 2.5 290 83.5 19.1

05/06/2008 0950 15 8.2 654 9.0 310 91.3 21.0

06/03/2008 1135 6.7 8.4 772 11.0 360 101 25.4

06/18/2008 1100 7.4 8.4 672 13.0 300 87.9 20.5

07/10/2008 0805 2.0 8.0 634 14.0 260 66.4 21.8

08/19/2008 0930 2.4 8.1 658 14.5 280 74.3 23.2

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)

11/06/2007 10.2 10.7 <0.04 0.02 1.3 2.5 E5 45

03/03/2008 8.4 9.7 <.04 .05 1.2 3.7 E8 134

04/08/2008 9.5 11.5 E.03 .05 1.1 4.4 E6 154

05/06/2008 12.7 14.5 <.04 .03 1.5 4.4 11 118

06/03/2008 16.6 17.2 E.02 .02 2.1 3.3 16 81

06/18/2008 14.2 15.0 <.04 .02 1.8 2.8 11 62

07/10/2008 11.2 12.1 E.03 .02 1.9 3.0 12 55

08/19/2008 14.8 15.6 E.02 .01 2.1 3.1 10 40

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)

Sediment 

discharge, 

suspended 

(ton/d)

11/06/2007 <0.08 0.14 3.4 4.8 E1.7 E2.0 64 17 2.2

03/03/2008 <.08 .48 14.4 23.5 2.4 4.0 75 4 .44

04/08/2008 <.08 .65 20.6 29.4 1.8 3.7 36 31 3.4 

05/06/2008 <.08 .42 29.9 40.5 E1.4 2.6 23 19 .77

06/03/2008 <.08 .14 21.2 25.2 <1.8 E1.2 28 46 .83

06/18/2008 <.08 .13 14.9 19.8 <1.8 <2.0 44 22 .44

07/10/2008 .08 .18 16.8 23.5 E1.2 E1.1 75 25 .14

08/19/2008 <.08 .12 7.0 10.7 E1.0 <2.0 77 2 .01
Data 33

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12324200--Clark Fork at Deer Lodge

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/06/2007 1305 220 8.6 534 4.0 240 70.1 15.0

03/04/2008 1045 196 8.3 525 2.0 230 66.4 14.8

04/08/2008 1145 182 8.3 518 5.0 220 63.2 14.4

05/06/2008 1115 232 8.2 498 10.0 210 61.3 13.9

06/04/2008 0910 669 8.1 348 11.0 140 42.3 8.28

06/18/2008 1250 647 8.7 309 14.5 130 39.3 7.21

07/10/2008 0930 337 8.2 309 15.0 130 40.0 7.70

08/19/2008 1100 67 8.4 476 17.0 200 60.4 12.7

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)

11/06/2007 9.5 11.8 E0.03 0.10 3.8 14.1 E4 180

03/04/2008 8.5 12.9 .06 .21 4.4 31.9 E7 548

04/08/2008 8.9 11.6 .07 .14 4.9 20.0 E4 325

05/06/2008 14.6 19.1 .05 .17 6.0 31.9 9 499

06/04/2008 25.8 42.0 .07 .50 14.2 130 20 1,940

06/18/2008 23.9 31.4 .05 .30 11.4 70.1 17 1,040

07/10/2008 17.4 21.6 .06 .14 6.9 29.2 16 410

08/19/2008 17.6 19.2 E.03 .02 6.9 11.0 E4 54

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)

Sediment 

discharge, 

suspended 

(ton/d)

11/06/2007 <0.08 1.60 31.3 68.4 4.5 14.5 73 5 3.0

03/04/2008 E.04 4.52 51.8 136 8.3 32.2 76 21 11

04/08/2008 E.05 2.75 74.8 129 5.8 21.1 72 18 8.8

05/06/2008 E.07 4.36 66.8 186 4.1 28.1 77 21 13

06/04/2008 .18 42.9 27.4 328 10.6 95.0 37 135 244

06/18/2008 .16 9.07 23.9 160 4.0 54.6 56 49 86

07/10/2008 E.08 3.30 37.2 93.7 5.6 24.3 71 15 14

08/19/2008 E.05 .55 4.0 21.5 3.5 6.1 68 1 .18
34 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/06/2007 1420 355 8.5 472 5.0 210 61.8 13.0

03/04/2008 1240 299 8.5 469 2.5 200 59.0 13.4

04/08/2008 1330 295 8.4 463 6.5 200 57.0 13.0

05/08/2008 0805 661 8.1 365 7.0 150 44.9 10.2

06/04/2008 1115 1,670 8.1 262 10.0 110 31.8 6.44

06/17/2008 0915 2,050 8.2 246 12.5 100 30.5 6.32

07/08/2008 1640 854 8.5 292 19.0 120 37.3 7.67

08/19/2008 1240 188 8.6 391 19.0 170 50.0 10.8

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/06/2007 7.8 9.2 E0.03 0.06 3.2 8.7 <8 118

03/04/2008 7.4 10.3 .04 .16 4.1 25.1 <8 425

04/08/2008 7.5 9.4 .06 .11 4.9 14.8 E5 246

05/08/2008 9.1 14.3 <.04 .23 4.3 42.9 20 976

06/04/2008 13.6 20.3 E.03 .27 7.4 59.9 25 1,240

06/17/2008 12.3 17.2 .04 .22 7.6 45.5 34 1,090

07/08/2008 12.9 15.6 .04 .11 6.0 21.4 12 371

08/19/2008 11.6 12.5 <.04 .03 5.0 7.2 <8 79

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)

11/06/2007 <0.08 0.84 14.4 49.9 2.8 9.5 83 4 3.8

03/04/2008 <.08 3.29 24.2 99.8 5.3 24.6 81 17 14

04/08/2008 E.04 1.88 39.3 85.8 3.1 16.2 83 11 8.8

05/08/2008 .09 6.13 17.0 172 3.5 41.9 79 45 80

06/04/2008 .17 8.30 10.3 172 5.6 53.5 49 86 388

06/17/2008 .26 7.10 11.8 127 6.1 42.8 57 62 343

07/08/2008 E.07 2.51 21.1 63.3 2.4 17.3 74 15 35

08/19/2008 <.08 .39 8.4 34.1 E1.4 4.3 65 4 2.0
Data 35

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12331800--Clark Fork near Drummond

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/06/2007 1530 568 8.5 475 6.0 220 62.5 15.0

03/04/2008 1345 465 8.5 480 4.0 210 59.6 14.9

04/09/2008 0915 465 8.3 479 6.0 200 57.7 14.4

05/08/2008 0910 867 8.1 363 8.5 160 44.7 11.1

06/04/2008 1305 2,210 8.1 280 11.0 120 33.9 7.50

06/17/2008 0740 2,740 8.1 274 13.5 120 34.5 7.71

07/09/2008 1455 1,130 8.4 357 19.0 160 45.1 10.4

08/19/2008 1340 270 8.5 499 19.5 210 59.8 15.5

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)

11/06/2007 7.8 8.1 E0.02 0.03 2.6 6.3 <8 115

03/04/2008 7.3 9.6 E.04 .13 3.6 16.7 <8 376

04/09/2008 7.7 9.8 E.04 .13 3.8 15.2 <8 333

05/08/2008 9.0 17.3 <.04 .25 4.0 37.4 28 1,200

06/04/2008 13.2 20.5 .05 .30 8.3 55.8 27 1,280

06/17/2008 13.8 19.8 .05 .29 9.1 52.0 29 1,260

07/09/2008 13.5 16.9 .07 .14 7.1 23.1 E8 431

08/19/2008 11.2 12.1 E.03 .02 4.3 5.7 <8 74

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)

11/06/2007 <0.08 0.83 9.8 36.9 2.4 6.9 77 4 6.1

03/04/2008 <.08 3.08 23.5 88.8 4.3 20.9 80 19 24

04/09/2008 E.05 2.73 26.2 87.5 4.1 21.9 72 23 29

05/08/2008 .15 10.5 11.9 219 3.8 56.4 81 64 150

06/04/2008 .21 10.2 11.5 191 6.9 66.3 66 78 465

06/17/2008 .26 9.29 13.3 168 7.5 66.2 65 72 533

07/09/2008 .23 3.61 26.9 83.8 4.0 24.4 71 19 58

08/19/2008 <.08 .32 6.2 21.6 2.3 4.3 68 3 2.2
36 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12334550--Clark Fork at Turah Bridge, near Bonner

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)

11/07/2007 0800 818 8.3 393 4.5 180 51.2 13.1 --

03/04/2008 1455 703 8.8 390 4.0 170 48.1 12.6 --

*03/10/2008 1045 753 8.3 394 3.5 190 53.3 13.3 0.27

*03/24/2008 0930 738 8.1 401 4.5 180 52.1 13.3 .29

*03/28/2008 0800 731 8.3 394 1.5 180 52.0 13.1 .19

*03/31/2008 1000 683 8.5 383 3.0 190 54.4 13.5 .24

*04/08/2008 1015 697 8.2 379 5.0 170 48.1 12.8 .27

04/09/2008 1020 697 8.3 394 5.0 170 47.1 12.4 --

*04/16/2008 1130 1,470 8.2 242 5.5 100 29.3 7.61 1.31

*04/22/2008 1020 1,170 8.2 310 3.5 140 38.9 10.3 .37

*04/29/2008 1000 1,510 8.2 301 9.0 130 36.8 9.52 .50

*05/05/2008 1100 1,780 8.4 239 6.5 110 30.0 7.88 .41

05/08/2008 1100 2,450 8.0 208 7.5 89 24.9 6.58 --

*05/12/2008 1020 2,230 8.1 216 6.5 97 27.0 7.09 .33

*05/19/2008 1030 4,620 7.9 136 11.0 59 16.6 4.31 .98

*05/23/2008 1030 5,180 8.1 139 6.5 62 17.5 4.42 .50

*05/27/2008 1100 5,270 8.1 167 9.0 74 21.1 5.25 .53

*06/02/2008 1030 5,150 8.1 165 10.0 70 19.9 4.94 .40

06/04/2008 1515 5,270 8.0 170 10.0 71 20.3 4.96 --

*06/10/2008 1015 4,980 8.2 200 9.0 85 24.2 5.90 .31

06/16/2008 1045 5,270 8.1 191 11.5 80 22.8 5.60 --

*06/24/2008 1000 4,950 8.1 177 9.0 78 22.2 5.35 .30

07/09/2008 0730 2,340 8.2 250 15.5 110 31.4 7.66 --

08/19/2008 1455 616 8.7 318 18.5 140 38.1 10.8 --
Data 37

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12334550--Clark Fork at Turah Bridge, near Bonner—Continued

Date

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)

11/07/2007 -- 5.4 6.0 <0.04 0.04 1.8 4.8 <8 87

03/04/2008 -- 5.5 6.5 E.02 .07 3.1 8.1 <8 154

*03/10/2008 0.033 5.3 6.6 E.02 .08 3.2 9.4 8 201

*03/24/2008 .035 5.8 6.8 E.02 .07 3.4 9.4 10 210

*03/28/2008 .013 5.6 6.2 E.03 .07 3.1 8.5 9 174

*03/31/2008 .027 5.4 6.2 E.03 .06 4.6 8.1 E8 159

*04/08/2008 .030 5.6 6.3 E.03 .09 3.4 8.2 10 189

04/09/2008 -- 5.3 6.7 E.04 .09 2.9 8.7 <8 194

*04/16/2008 .224 7.5 19.1 E.03 .41 4.3 46.5 33 2,120

*04/22/2008 .042 4.6 6.6 E.03 .09 2.6 11.1 15 382

*04/29/2008 .059 5.8 8.8 E.03 .17 3.6 21.6 20 748

*05/05/2008 .048 4.7 6.6 <.04 .10 2.7 12.8 28 506

05/08/2008 -- 4.1 7.3 <.04 .14 2.3 18.9 53 840

*05/12/2008 .040 4.3 6.1 <.04 .07 2.2 10.5 22 392

*05/19/2008 .204 3.8 9.9 <.04 .22 3.1 37.2 49 1,880

*05/23/2008 .108 4.8 8.5 E.02 .23 4.0 30.6 45 999

*05/27/2008 .111 6.5 11.1 E.03 .21 6.2 35.5 46 1,190

*06/02/2008 .073 6.1 9.1 E.04 .14 4.7 24.0 32 778

06/04/2008 -- 6.3 9.9 E.04 .17 5.4 32.5 37 927

*06/10/2008 .089 8.1 11.3 .05 .16 6.5 27.9 27 868

06/16/2008 -- 7.4 10.2 .04 .17 5.9 25.4 37 733

*06/24/2008 .062 8.2 10.3 E.04 .11 5.8 20.1 26 626

07/09/2008 -- 7.8 9.6 .04 .10 4.0 13.4 16 346

08/19/2008 -- 5.4 6.0 <.04 <.01 2.2 3.2 <8 40
38 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12334550--Clark Fork at Turah Bridge, near Bonner—Continued

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2007 <0.08 0.56 2.9 20.9 3.6 8.1 85 4 8.8

03/04/2008 <.08 1.22 7.4 39.5 E1.7 10.8 84 9 17

*03/10/2008 E.08 1.62 9.9 53.4 3.5 14.4 88 14 28

*03/24/2008 .12 1.57 10.7 58.5 4.3 16.3 82 14 28

*03/28/2008 .09 1.38 9.0 47.2 4.1 14.2 86 9 18

*03/31/2008 .20 1.28 10.2 46.8 4.7 13.8 88 10 18

*04/08/2008 .14 1.53 9.3 49.8 3.6 14.2 86 11 21

04/09/2008 .12 1.59 10.1 52.0 8.8 14.7 88 10 19

*04/16/2008 .23 16.9 8.2 338 5.0 87.0 90 122 484

*04/22/2008 .10 2.69 7.4 64.1 5.8 18.3 83 16 51

*04/29/2008 .15 5.19 9.4 109 4.1 36.6 74 44 179

*05/05/2008 .11 3.12 6.8 68.8 2.7 22.1 74 28 135

05/08/2008 .12 4.86 8.7 110 2.6 34.8 74 50 331

*05/12/2008 E.07 2.35 5.7 58.2 2.5 17.4 73 21 126

*05/19/2008 .12 7.71 10.9 184 2.9 52.5 63 151 1,880

*05/23/2008 .21 6.19 7.1 129 4.9 41.7 65 69 965

*05/27/2008 .24 6.22 9.0 150 10.5 50.4 68 79 1,120

*06/02/2008 .15 4.01 9.6 103 5.1 35.5 64 58 806

06/04/2008 .18 5.42 9.9 108 5.1 39.9 62 64 911

*06/10/2008 .15 4.77 11.4 103 7.3 39.2 65 57 766

06/16/2008 .19 4.26 12.5 85.2 6.0 37.5 63 50 711

*06/24/2008 .14 3.30 15.4 73.2 4.9 26.4 72 34 454

07/09/2008 .15 2.56 15.6 57.5 3.1 17.4 65 21 133

08/19/2008 <.08 .17 3.6 12.3 E.98 2.9 64 3 5.0

*Sample collected as part of a supplemental sampling program.
Data 39

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

12334570--Clark Fork Bypass, near Bonner

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

*03/24/2008 1100 E738 8.0 398 -- 190 52.9 13.3

*03/28/2008 0930 E731 8.5 390 2.0 190 52.8 13.2

*03/31/2008 1230 E683 8.4 382 -- 190 52.4 13.3

*04/08/2008 1200 E697 8.4 377 6.0 170 47.3 12.6

*04/16/2008 1300 E1,470 8.0 246 5.0 100 29.4 7.56

*04/22/2008 1210 E1,170 8.1 310 4.0 140 39.0 10.3

*04/29/2008 1200 E1,510 8.1 300 10.5 130 36.6 9.63

*05/05/2008 1230 E1,780 8.2 239 -- 110 30.2 7.85

*05/12/2008 1140 E2,230 8.2 219 6.5 99 27.6 7.19

*05/19/2008 1230 E4,620 7.8 140 11.5 61 17.1 4.36

*05/23/2008 1200 E5,180 7.9 143 7.0 64 18.0 4.54

*05/27/2008 1300 E5,270 8.0 170 9.5 76 21.7 5.35

*06/02/2008 1200 E5,150 8.0 168 10.0 72 20.6 5.05

*06/10/2008 1210 E4,980 8.3 202 7.0 87 24.8 6.02

*06/16/2008 1315 E5,270 8.1 192 13.0 81 23.1 5.67

*06/24/2008 1130 E4,950 8.0 180 4.0 80 23.0 5.53

*07/09/2008 0915 E2,340 8.2 251 15.0 110 30.9 7.64

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

*03/24/2008 5.8 9.0 E0.04 0.16 3.3 19.4 10 640

*03/28/2008 5.6 6.6 E.03 .07 3.4 10.6 12 234

*03/31/2008 5.5 7.9 E.02 .24 3.1 19.4 9 505

*04/08/2008 5.6 6.9 E.03 .10 3.0 10.2 11 228

*04/16/2008 7.7 40.2 .04 2.81 5.4 155 32 4,550

*04/22/2008 4.8 9.2 E.04 .29 2.6 46.5 17 1,020

*04/29/2008 5.9 11.8 E.04 .36 3.7 50.8 20 1,270

*05/05/2008 4.8 9.1 E.02 .39 3.0 37.3 19 849

*05/12/2008 4.5 12.2 <.04 .58 2.6 66.5 27 1,430

*05/19/2008 5.4 98.5 .18 10.8 12.2 1,120 79 24,800

*05/23/2008 5.4 33.2 .06 1.70 8.9 289 57 4,940

*05/27/2008 6.8 20.3 .06 .91 7.6 124 49 2,690

*06/02/2008 6.3 14.4 .04 .57 5.6 70.6 44 2,690

*06/10/2008 7.9 15.5 .04 .45 6.9 58.1 24 1,990

*06/16/2008 7.6 12.2 .05 .31 6.6 38.4 39 1,120

*06/24/2008 8.2 12.7 .04 .27 5.9 42.8 25 1,360

*07/09/2008 7.8 10.2 E.04 .11 4.1 17.8 16 399
40 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

12334570--Clark Fork Bypass, near Bonner—Continued

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

*03/24/2008 0.10 3.51 16.3 84.6 5.1 48.4 35 74 E147

*03/28/2008 .11 1.74 17.9 57.6 5.7 20.7 64 16 E32

*03/31/2008 .11 3.25 16.9 76.2 4.2 47.0 29 51 E94

*04/08/2008 .11 1.83 13.7 54.1 4.1 19.7 36 31 E58

*04/16/2008 .26 35.8 19.8 641 11.7 436 27 518 E2,060

*04/22/2008 .12 7.94 11.8 107 5.2 109 22 132 E417

*04/29/2008 .14 9.32 14.1 157 5.2 92.1 26 188 E766

*05/05/2008 .13 7.20 10.9 96.1 3.9 89.3 34 82 E394

*05/12/2008 .09 11.0 17.6 127 4.1 118 28 144 E867

*05/19/2008 .54 183 49.0 2,240 44.5 3,290 9 3,780 E47,200

*05/23/2008 .31 36.5 34.0 422 18.9 476 27 669 E9,360

*05/27/2008 .28 18.4 22.1 325 15.7 223 29 366 E5,210

*06/02/2008 .14 12.5 15.7 204 7.1 168 21 241 E3,350

*06/10/2008 .12 9.74 16.8 168 7.4 130 23 203 E2,730

*06/16/2008 .19 6.45 18.3 140 6.9 80.1 35 116 E1,650

*06/24/2008 .14 6.96 21.1 117 6.0 80.0 22 178 E2,380

*07/09/2008 .08 2.54 20.1 66.7 3.7 25.0 49 33 E208

*Sample collected as part of a supplemental sampling program.
Data 41

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12340000--Blackfoot River near Bonner

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)

11/07/2008 0930 472 8.4 278 3.5 140 35.9 12.4 --

*03/10/2008 1230 450 8.2 258 3.0 140 35.5 12.3 0.15

*03/24/2008 1330 494 8.3 263 4.5 140 35.1 12.0 .20

*03/28/2008 1530 467 8.7 263 4.5 130 34.5 11.7 .16

*03/31/2008 1100 450 8.3 256 3.5 140 35.1 12.1 .14

*04/08/2008 1400 478 8.4 257 6.0 130 32.1 11.7 .17

04/09/2008 1135 500 8.4 268 5.0 130 31.7 11.5 --

*04/16/2008 1445 1,030 8.4 218 6.5 110 27.5 9.28 .40

*04/22/2008 1340 1,160 8.4 200 5.5 99 25.6 8.55 .24

*04/29/2008 1330 1,490 8.5 181 10.0 88 22.9 7.62 .35

*05/05/2008 1400 2,800 8.3 155 9.0 77 20.0 6.57 .36

05/08/2008 1325 4,070 8.0 150 8.0 73 18.9 6.16 --

*05/12/2008 1350 3,700 8.4 152 7.0 78 20.1 6.64 .24

*05/19/2008 1430 9,410 8.1 129 10.0 65 17.6 5.15 .89

*05/23/2008 1330 8,210 8.2 144 7.5 73 19.3 6.05 .27

*05/27/2008 1400 8,040 8.2 165 8.5 83 21.7 7.05 .40

*06/02/2008 1330 7,700 8.2 158 10.0 77 20.2 6.45 .23

06/05/2008 0745 6,710 8.2 167 9.0 78 20.5 6.47 --

*06/10/2008 1530 5,030 8.5 180 8.0 88 22.9 7.43 .20

06/16/2008 1500 5,150 8.3 175 12.5 84 21.9 7.13 --

*06/24/2008 1330 5,480 8.2 162 11.0 80 21.2 6.69 .16

07/09/2008 1120 2,640 8.4 198 15.5 96 25.0 8.24 --

08/19/2008 1620 667 8.7 258 19.0 130 31.5 11.8 --
42 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12340000--Blackfoot River near Bonner—Continued

Date

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)

11/07/2008 -- 1.0 1.2 <0.04 <0.01 <1.0 <1.2 E5 25

*03/10/2008 0.011 .95 1.1 <.04 <.01 E.69 <1.2 10 63

*03/24/2008 .015 1.2 1.4 <.04 <.01 E.81 <1.2 14 100

*03/28/2008 .011 1.2 1.4 <.04 <.01 E.86 <1.2 10 71

*03/31/2008 .010 1.1 1.3 <.04 <.01 E.59 E1.1 10 62

*04/08/2008 .013 1.2 1.1 <.04 <.01 E.80 <1.2 10 73

04/09/2008 -- 1.1 1.2 <.04 <.01 <1.0 <1.2 E7 81

*04/16/2008 .048 1.2 1.6 <.04 <.01 E.72 E.85 20 328

*04/22/2008 .021 .83 .93 <.04 <.01 <1.0 <1.2 12 157

*04/29/2008 .023 .88 1.1 <.04 <.01 E.71 E.82 23 244

*05/05/2008 .035 .66 1.0 <.04 <.01 E.63 E.95 24 327

05/08/2008 -- .67 1.1 <.04 E.01 1.1 3.2 40 414

*05/12/2008 .018 .70 .84 <.04 <.01 E.61 E.90 21 202

*05/19/2008 .247 .86 3.4 <.04 .05 1.1 9.5 38 3,240

*05/23/2008 .060 .73 1.4 <.04 .04 E.79 3.4 20 841

*05/27/2008 .099 1.1 2.5 <.04 .03 1.6 5.8 36 1,580

*06/02/2008 .042 .89 1.5 <.04 E.01 E.87 2.7 12 735

06/05/2008 -- .83 1.4 <.04 .02 1.3 3.4 17 497

*06/10/2008 .049 .96 1.5 <.04 <.01 E.80 2.0 15 586

06/16/2008 -- .91 1.2 <.04 E.01 1.2 3.8 13 366

*06/24/2008 .024 .86 1.1 <.04 <.01 E.55 E1.1 9 326

07/09/2008 -- .96 1.1 <.04 E.01 E.75 2.0 E7 126

08/19/2008 -- 1.2 1.3 <.04 <.01 E.52 <1.2 <8 24
Data 43

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12340000--Blackfoot River near Bonner—Continued

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2008 <0.08 <0.06 0.8 2.0 <1.8 E1.0 78 1 1.3

*03/10/2008 E.04 .06 2.5 5.7 <1.8 <2.0 88 3 3.6

*03/24/2008 E.06 .11 2.7 6.2 -- <2.0 85 3 4.0

*03/28/2008 E.06 E.05 2.3 5.1 <1.8 <2.0 86 2 2.5

*03/31/2008 <.08 .06 2.7 5.4 <1.8 <2.0 84 3 3.6

*04/08/2008 E.04 .07 2.8 6.5 <1.8 <2.0 79 3 3.9

04/09/2008 <.08 .06 3.1 7.3 <1.8 <2.0 82 5 6.8

*04/16/2008 .08 .37 3.3 29.3 E.95 E1.6 85 19 53

*04/22/2008 <.08 .15 2.3 14.5 <1.8 <2.0 86 7 22

*04/29/2008 <.08 .23 3.1 25.0 <1.8 E1.4 83 15 60

*05/05/2008 <.08 .34 3.2 40.1 2.0 E2.0 73 23 174

05/08/2008 <.08 .50 3.3 48.1 <1.8 2.7 79 33 363

*05/12/2008 <.08 .26 2.3 22.8 E1.0 E1.5 81 13 130

*05/19/2008 E.06 4.67 5.0 217 <1.8 15.8 79 302 7,670

*05/23/2008 <.08 1.19 2.4 56.5 E.91 5.3 80 77 1,710

*05/27/2008 .10 2.78 4.0 97.1 3.9 10.9 89 128 2,780

*06/02/2008 <.08 .98 2.7 48.4 <1.8 4.7 82 69 1,430

06/05/2008 <.08 .80 2.4 34.0 E.97 4.9 81 47 851

*06/10/2008 <.08 .80 5.9 34.7 E1.2 3.5 89 28 380

06/16/2008 E.05 .92 2.6 23.5 2.2 3.7 83 33 459

*06/24/2008 <.08 .37 2.3 20.4 E1.2 2.1 79 26 385

07/09/2008 <.08 .34 1.8 12.6 E.95 E1.8 83 8 57

08/19/2008 <.08 <.06 1.5 5.2 <1.8 <2.0 74 1 1.8

*Sample collected as part of a supplemental sampling program.
44 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/07/2007 1100 1,270 E1.9 8.4 347 4.0 160 44.6 12.4

03/05/2008 0910 1,160 E1.6 8.3 333 1.5 130 36.1 9.00

*03/10/2008 1400 1,170 -- 8.2 342 5.0 170 45.9 12.9

*03/24/2008 1530 1,180 -- 8.4 340 7.0 170 45.2 12.7

*03/28/2008 1350 1,560 -- 8.4 343 3.0 160 43.9 12.5

*03/31/2008 1500 1,100 -- 8.2 328 4.5 160 44.5 12.5

*04/08/2008 1600 1,160 -- 8.2 328 7.5 150 41.0 12.2

04/09/2008 1400 1,170 14 8.3 339 6.5 150 39.9 11.8

*04/16/2008 1600 2,510 -- 8.3 234 6.0 110 29.1 8.31

*04/22/2008 1510 2,350 -- 8.3 257 5.0 120 32.5 9.18

*04/29/2008 1530 3,170 -- 8.3 239 11.0 110 29.7 8.42

*05/05/2008 1515 4,640 -- 8.3 186 13.0 89 24.0 7.05

05/08/2008 1530 6,580 66 8.0 172 9.0 78 21.0 6.26

*05/12/2008 1500 6,090 -- 8.3 176 8.0 86 23.0 6.86

*05/19/2008 1530 14,800 -- 8.0 133 11.5 63 17.4 4.86

*05/23/2008 1515 14,400 -- 8.2 145 8.0 70 18.8 5.46

*05/27/2008 1600 14,100 -- 8.1 167 10.0 76 20.4 5.99

*06/02/2008 1445 13,300 -- 8.2 162 11.0 75 20.3 5.83

06/05/2008 0945 12,900 25 8.1 172 9.0 75 20.6 5.81

*06/10/2008 1700 10,500 -- 8.3 192 9.0 88 24.1 6.75

06/16/2008 1630 10,800 17 8.2 183 13.5 83 22.6 6.35

*06/24/2008 1530 10,500 -- 8.3 170 17.0 79 21.8 6.06

07/09/2008 1240 4,970 2.9 8.3 225 17.0 100 28.1 7.92

08/19/2008 1740 1,270 E1.2 8.8 279 20.0 130 33.6 10.9
Data 45

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

12340500--Clark Fork above Missoula—Continued

11/07/2007 -- -- 3.9 4.9 <0.04 0.07 1.4 8.5

03/05/2008 -- -- 3.7 4.7 E.03 .07 2.2 9.5

*03/10/2008 0.23 0.028 3.8 4.9 <.04 .07 2.3 8.9

*03/24/2008 .26 .036 6.3 9.2 E.03 .07 7.0 11.1

*03/28/2008 .19 .011 4.0 9.3 <.04 .34 1.8 37.8

*03/31/2008 .39 .103 6.4 19.7 E.04 1.67 4.2 303

*04/08/2008 .34 .078 5.9 11.5 E.03 .69 3.6 126

04/09/2008 -- -- 5.6 10.4 E.03 .54 3.5 102

*04/16/2008 1.00 .195 6.0 20.8 E.03 1.17 4.9 182

*04/22/2008 .39 .089 4.1 9.9 E.02 .59 2.5 104

*04/29/2008 .58 .153 5.0 16.4 E.03 1.11 4.1 205

*05/05/2008 .59 .270 5.2 22.5 E.03 1.72 4.5 349

05/08/2008 -- -- 4.6 26.9 <.04 1.93 5.0 386

*05/12/2008 .35 .132 3.5 10.1 <.04 .51 2.4 95.8

*05/19/2008 1.19 .543 3.6 26.0 <.04 2.05 5.2 308

*05/23/2008 .45 .206 2.8 13.0 <.04 .74 3.9 107

*05/27/2008 .45 .131 3.3 9.2 E.03 .37 4.1 66.6

*06/02/2008 .35 .076 3.2 6.1 E.03 .19 3.0 29.9

06/05/2008 -- -- 3.8 9.0 E.03 .29 4.0 46.0

*06/10/2008 .26 .080 4.7 7.7 E.03 .20 3.9 29.5

06/16/2008 -- -- 4.6 8.9 E.04 .31 4.7 38.4

*06/24/2008 .24 .063 4.7 7.2 <.04 .14 3.4 24.9

07/09/2008 -- -- 4.4 5.7 E.03 .07 2.7 10.3

08/19/2008 -- -- 3.6 4.0 <.04 <.01 1.5 2.5
46 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

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)

11/07/2007 E7 155 E0.04 1.15 18.0 37.8 3.1 15.7

03/05/2008 <8 185 E.05 1.79 19.3 45.4 4.0 13.8

*03/10/2008 12 210 E.06 1.42 18.9 46.8 3.8 14.8

*03/24/2008 13 565 .45 1.87 20.2 56.4 7.4 19.9

*03/28/2008 14 2,150 E.07 7.35 32.3 153 3.1 94.9

*03/31/2008 26 2,200 .64 42.5 33.6 180 6.4 404

*04/08/2008 17 1,370 .40 20.5 20.6 98.0 3.6 170

04/09/2008 8 923 .26 15.8 19.0 78.1 4.2 130

*04/16/2008 30 2,750 .33 32.0 20.9 280 5.5 258

*04/22/2008 16 1,500 .21 16.1 13.4 98.7 3.4 143

*04/29/2008 25 3,180 .41 30.6 17.3 200 7.3 289

*05/05/2008 36 6,490 .87 53.5 14.6 274 4.2 444

05/08/2008 74 5,980 -- 54.0 21.0 314 4.7 495

*05/12/2008 33 2,200 .31 14.9 12.6 116 2.4 134

*05/19/2008 71 9,620 .45 45.6 30.2 589 6.8 541

*05/23/2008 37 3,150 .18 15.5 14.5 200 5.9 184

*05/27/2008 40 2,070 .17 9.45 12.8 168 5.5 100

*06/02/2008 25 1,300 .12 5.06 9.5 97.1 5.5 55.6

06/05/2008 34 1,500 .20 7.62 11.7 131 5.2 81.4

*06/10/2008 18 943 .08 5.02 10.9 89.4 5.0 50.1

06/16/2008 27 999 .19 5.66 12.4 95.1 4.8 67.4

*06/24/2008 18 808 .11 3.95 13.7 69.5 3.9 42.0

07/09/2008 10 296 .08 1.55 13.8 39.8 2.6 14.8

08/19/2008 <8 51 <.08 .18 9.2 20.0 <1.8 3.3
Data 47

Table 4. Water-quality data for the Clark Fork basin, Montana, 

October 2007 through September 2008.—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]

12340500--Clark Fork above Missoula—Continued

Date

Sediment, 

suspended 

(percent finer 

than 0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2007 67 7 24

03/05/2008 74 9 28

*03/10/2008 73 13 41

*03/24/2008 84 27 86

*03/28/2008 80 180 758

*03/31/2008 84 127 377

*04/08/2008 84 87 272

04/09/2008 82 58 183

*04/16/2008 55 247 1,670

*04/22/2008 39 147 933

*04/29/2008 36 325 2,780

*05/05/2008 25 557 6,980

05/08/2008 19 950 16,900

*05/12/2008 20 333 5,480

*05/19/2008 36 1,060 42,400

*05/23/2008 37 334 13,000

*05/27/2008 48 272 10,400

*06/02/2008 47 146 5,240

06/05/2008 47 150 5,220

*06/10/2008 53 80 2,270

06/16/2008 54 89 2,600

*06/24/2008 54 68 1,930

07/09/2008 69 20 268

08/19/2008 75 3 10

*Sample collected as part of a supplemental sampling program.
48 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

12352500--Bitterroot River near Missoula

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Total 

nitrogen, 

unfiltered, 

(mg/L)

03/10/2008 1600 833 8.2 147 8.0 65 18.9 4.45 0.27

03/25/2008 0800 889 7.6 146 4.0 61 17.9 3.98 .27

04/01/2008 0730 833 7.8 141 3.5 63 18.7 4.09 .25

04/09/2008 0730 786 7.9 144 5.0 60 17.6 4.03 .25

04/17/2008 0715 1,920 7.7 91 6.0 35 10.5 2.25 .44

04/23/2008 0705 1,700 7.4 100 6.5 40 11.8 2.52 .26

04/30/2008 0715 2,580 7.8 87 9.5 35 10.2 2.20 .61

05/06/2008 0730 3,560 7.6 72 9.0 28 8.21 1.81 .43

05/13/2008 0720 4,040 7.9 72 8.0 27 7.97 1.81 .24

05/20/2008 0730 17,200 7.2 43 11.0 15 4.42 1.06 .60

05/24/2008 0745 12,400 7.5 55 7.0 21 6.13 1.40 .29

05/28/2008 0800 9,830 7.5 54 11.0 21 6.11 1.32 .25

06/03/2008 0745 12,600 7.4 46 9.5 18 5.25 1.15 .21

06/11/2008 0730 8,540 7.7 60 8.0 23 6.79 1.50 .16

06/25/2008 0730 12,000 7.5 55 13.5 20 5.80 1.29 .20

Date

Total 

phosphorous, 

unfiltered, 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

03/10/2008 0.019 0.36 E0.45 <0.04 <0.01 E0.71 <1.2 35 124

03/25/2008 .023 .36 E.45 <.04 <.01 -- <1.2 32 184

04/01/2008 .017 .33 E.43 <.04 <.01 E.96 E.70 31 133

04/09/2008 .018 .36 E.46 <.04 E.01 E.53 <1.2 36 148

04/17/2008 .050 .29 E.54 <.04 .02 E.71 1.4 37 565

04/23/2008 .023 .31 E.40 <.04 <.01 E.55 E.81 28 286

04/30/2008 .055 .31 E.57 <.04 E.01 E.62 1.6 44 794

05/06/2008 .051 .28 E.59 <.04 E.01 E.58 1.6 50 848

05/13/2008 .024 .29 E.40 <.04 <.01 E.61 E.94 38 308

05/20/2008 .143 .35 .70 <.04 .02 1.5 4.7 132 1,960

05/24/2008 .046 .31 E.47 E.03 .02 1.2 2.7 82 635

05/28/2008 .035 .30 E.43 <.04 <.01 1.0 1.6 66 522

06/03/2008 .029 .31 E.55 <.04 <.01 E.91 1.8 57 693

06/11/2008 .032 .35 E.48 <.04 <.01 E.89 E1.2 55 435

06/25/2008 .030 .32 E.42 <.04 E.01 E.73 E1.1 53 486
Data 49

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

12352500--Bitterroot River near Missoula—Continued

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

03/10/2008 E0.04 0.12 1.4 20.6 <1.8 <2.0 78 5 11

03/25/2008 .13 .20 9.1 28.1 -- <2.0 80 9 22

04/01/2008 E.07 .07 8.8 22.3 E1.0 <2.0 80 6 13

04/09/2008 <.08 .12 9.2 26.1 <1.8 <2.0 81 7 15

04/17/2008 E.06 .51 4.2 44.9 E1.2 2.8 76 31 161

04/23/2008 <.08 .25 5.7 25.0 <1.8 E1.5 73 12 55

04/30/2008 E.04 .65 4.3 62.8 <1.8 3.6 59 61 425

05/06/2008 <.08 .77 3.3 60.7 <1.8 4.2 61 48 461

05/13/2008 <.08 .30 4.4 19.6 <1.8 2.2 56 15 164

05/20/2008 .16 1.89 8.3 69.5 2.2 8.7 30 257 11,900

05/24/2008 .14 .73 6.2 25.5 2.4 3.8 46 68 2,280

05/28/2008 E.07 .51 5.9 22.1 E1.2 2.8 34 68 1,800

06/03/2008 E.06 .74 5.7 25.0 <1.8 5.1 38 81 2,750

06/11/2008 E.05 .38 7.2 19.1 1.9 E2.0 63 27 623

06/25/2008 E.05 .43 6.1 18.4 E.95 2.1 39 59 1,900
50 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

12354500--Clark Fork at St. Regis

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Total 

nitrogen, 

unfiltered, 

(mg/L)

03/11/2008 1000 2,830 8.3 265 5.5 120 32.8 9.15 0.31

03/25/2008 1400 3,000 8.3 246 5.5 110 31.4 8.40 .27

04/01/2008 1330 2,850 8.1 254 4.5 120 33.1 8.79 .32

04/09/2008 1400 2,810 8.0 262 7.0 110 30.2 8.39 .30

04/17/2008 1400 5,980 8.2 195 7.0 82 22.7 6.11 .87

04/23/2008 1250 5,670 8.0 200 6.0 83 22.9 6.31 .38

04/30/2008 1315 7,580 8.3 192 4.5 81 22.2 6.11 .45

05/06/2008 1230 11,400 8.0 152 5.0 66 18.2 5.00 .52

05/13/2008 1315 13,800 8.2 141 5.0 64 17.7 4.82 .44

05/20/2008 1300 42,300 7.9 88 5.5 40 11.3 2.78 .88

05/24/2008 1230 36,000 8.0 110 6.0 50 13.8 3.69 .39

05/28/2008 1300 31,600 8.0 127 7.0 59 16.4 4.46 .41

06/03/2008 1230 34,500 8.1 114 7.0 49 13.7 3.67 .30

06/11/2008 1315 24,800 8.2 141 5.5 61 17.0 4.59 .21

06/25/2008 1215 29,300 8.0 113 10.5 50 13.9 3.71 .22

Date

Total 

phosphorous, 

unfiltered, 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

03/11/2008 0.020 1.9 2.3 <0.04 0.03 2.4 3.1 13 113

03/25/2008 .020 2.4 2.8 <.04 .02 5.2 3.9 13 122

04/01/2008 .025 4.9 7.2 E.02 .20 4.8 47.8 16 368

04/09/2008 .030 3.5 4.5 <.04 .12 5.2 24.4 13 233

04/17/2008 .116 5.1 11.8 E.03 .74 4.7 127 27 1,540

04/23/2008 .049 2.6 4.4 <.04 .24 2.9 42.4 15 554

04/30/2008 .046 2.9 5.1 <.04 .27 3.5 52.4 25 753

05/06/2008 .073 3.3 7.7 <.04 .54 4.2 106 24 1,280

05/13/2008 .051 2.7 5.2 <.04 .27 3.2 48.9 31 763

05/20/2008 .265 2.5 9.2 <.04 .65 4.9 106 64 4,420

05/24/2008 .099 1.9 4.8 E.04 .28 3.8 36.1 41 1,560

05/28/2008 .100 2.3 5.2 E.02 .20 3.7 30.6 30 1,610

06/03/2008 .076 1.8 3.6 E.03 .13 2.7 18.6 26 1,340

06/11/2008 .058 2.6 4.2 E.02 .13 3.0 16.5 24 809

06/25/2008 .057 2.3 3.2 <.04 .08 2.6 11.4 28 807
Data 51

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—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]

12354500--Clark Fork at St. Regis—Continued

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

03/11/2008 0.08 0.51 10.4 38.3 3.6 6.5 86 8 61

03/25/2008 .34 .52 6.9 30.6 3.8 6.4 88 7 57

04/01/2008 .37 6.48 8.4 41.2 5.5 51.3 95 15 115

04/09/2008 .26 3.36 6.5 38.8 3.7 25.7 91 12 91

04/17/2008 .35 19.2 4.0 162 4.6 167 92 98 1,580

04/23/2008 .17 6.29 4.4 55.8 3.6 54.7 90 28 429

04/30/2008 .24 7.81 4.3 74.7 3.4 65.8 86 50 1,020

05/06/2008 .29 15.4 3.7 110 3.8 134 81 85 2,630

05/13/2008 .23 7.15 3.4 60.0 4.3 65.2 76 49 1,830

05/20/2008 .31 17.1 4.1 254 4.2 173 54 464 53,000

05/24/2008 .16 5.70 4.9 95.7 4.3 58.8 60 156 15,200

05/28/2008 .13 5.26 4.3 102 3.5 54.1 56 172 14,700

06/03/2008 .09 3.50 4.3 79.0 2.7 36.1 44 170 15,800

06/11/2008 .11 2.82 5.9 60.1 3.7 28.0 65 68 4,550

06/25/2008 .09 2.03 4.0 48.1 3.2 19.9 49 91 7,190
52 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12388700--Flathead River at Perma

Date Time

Streamflow, 

instantaneous 

(ft3/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Total 

nitrogen, 

unfiltered, 

(mg/L)

03/11/2008 1200 7,430 7.9 178 5.5 97 27.5 6.93 0.12

03/25/2008 1130 6,210 7.9 183 5.0 93 26.6 6.43 .10

04/01/2008 1030 6,020 7.9 175 4.5 95 27.2 6.57 .11

04/09/2008 1100 5,840 8.0 177 6.5 88 25.0 6.29 .12

04/17/2008 1200 E5,750 8.3 177 9.0 88 25.1 6.26 .12

04/23/2008 1030 E6,710 8.0 182 6.5 90 25.5 6.35 .11

04/30/2008 1100 E7,900 8.2 180 8.0 91 26.1 6.40 .12

05/06/2008 1030 9,450 8.2 175 10.5 89 25.5 6.26 .13

05/13/2008 1030 13,800 8.5 172 9.5 90 25.7 6.35 .14

05/20/2008 1100 18,900 8.2 170 13.0 86 24.4 6.03 .14

05/24/2008 1030 29,800 8.3 173 9.5 90 25.6 6.36 .13

05/28/2008 1000 37,800 8.3 174 10.0 86 24.6 6.08 .14

06/03/2008 1030 40,400 8.2 171 11.0 85 24.2 5.98 .11

06/11/2008 1100 36,900 8.4 171 8.5 84 23.8 5.87 .11

06/25/2008 1030 37,400 8.4 169 15.5 86 24.5 6.01 .12

Date

Total 

phosphorous, 

unfiltered, 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

03/11/2008 E0.005 0.35 E0.43 <0.04 <0.01 <1.0 <1.2 E8 36

03/25/2008 E.004 .38 E.46 <.04 <.01 1.1 <1.2 <8 39

04/01/2008 E.006 .39 E.46 <.04 <.01 <1.0 E.60 <8 30

04/09/2008 E.005 .41 E.39 <.04 <.01 E.74 <1.2 <8 37

04/17/2008 E.007 .40 E.52 <.04 <.01 E.88 <1.2 <8 46

04/23/2008 E.006 .35 E.41 <.04 <.01 <1.0 <1.2 <8 82

04/30/2008 E.005 .39 E.42 <.04 <.01 <1.0 <1.2 E4 76

05/06/2008 E.006 .43 E.45 <.04 E.01 <1.0 5.4 <8 74

05/13/2008 E.007 .39 E.45 <.04 <.01 <1.0 <1.2 <8 98

05/20/2008 .011 .41 E.49 <.04 <.01 <1.0 <1.2 E5 178

05/24/2008 .017 .40 E.57 <.04 <.01 <1.0 1.8 <8 253

05/28/2008 .014 .41 E.54 <.04 <.01 E.61 11.9 <8 199

06/03/2008 .010 .42 E.53 <.04 <.01 <1.0 <1.2 <8 136

06/11/2008 .010 .39 E.57 E.03 <.01 E.58 E.62 E5 143

06/25/2008 E.007 .38 E.43 <.04 <.01 <1.0 <1.2 <8 109
Data 53

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2007 through September 2008.—Continued

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

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

level; --, no data]

12388700--Flathead River at Perma—Continued

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered

 (μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

03/11/2008 <0.08 0.06 1.4 3.4 <1.8 <2.0 70 1 20

03/25/2008 E.06 <.06 1.3 3.4 <1.8 <2.0 80 3 50

04/01/2008 <.08 <.06 1.2 3.2 <1.8 <2.0 85 2 33

04/09/2008 <.08 E.04 1.2 3.8 <1.8 <2.0 82 2 32

04/17/2008 E.05 .10 1.4 5.0 2.4 <2.0 77 4 E62

04/23/2008 <.08 .11 1.1 5.3 <1.8 <2.0 87 4 E72

04/30/2008 <.08 .09 1.2 5.6 1.9 <2.0 85 5 E107

05/06/2008 <.08 .13 1.1 5.9 <1.8 <2.0 76 4 102

05/13/2008 <.08 .12 .9 6.8 <1.8 <2.0 74 8 298

05/20/2008 <.08 .22 1.2 11.0 <1.8 E1.3 85 14 714

05/24/2008 <.08 .31 .8 14.3 <1.8 E1.6 76 24 1,930

05/28/2008 <.08 .21 .8 10.2 2.3 E1.3 71 16 1,630

06/03/2008 <.08 .15 .7 7.9 <1.8 E1.3 74 10 1,090

06/11/2008 E.04 .18 .7 7.8 -- E1.1 79 11 1,100

06/25/2008 <.08 .11 .8 5.9 <1.8 <2.0 78 9 909
54 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2007 through 

September 2008.

[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

1 184 7 3.5 230 12 7.5 216 19 11

2 183 8 4.0 222 11 6.6 213 15 8.6

3 181 10 4.9 221 10 6.0 217 13 7.6

4 186 11 5.5 228 9 5.5 262 12 8.5

5 204 12 6.6 223 7 4.2 272 12 8.8

6 223 13 7.8 222 6 3.6 255 12 8.3

7 224 14 8.5 223 6 3.6 239 11 7.1

8 237 14 9.0 220 9 5.3 224 11 6.7

9 223 14 8.4 221 13 7.8 213 12 6.9

10 217 11 6.4 228 15 9.2 203 12 6.6

11 217 8 4.7 231 16 10 e200 12 6.5

12 212 7 4.0 234 16 10 202 12 6.5

13 205 6 3.3 236 15 9.6 223 14 8.4

14 203 8 4.4 229 16 9.9 216 17 9.9

15 211 10 5.7 232 20 13 212 18 10

16 215 11 6.4 212 24 14 204 18 9.9

17 228 11 6.8 215 29 17 206 17 9.5

18 231 10 6.2 221 30 18 203 16 8.8

19 229 10 6.2 242 29 19 209 16 9.0

20 235 10 6.3 239 28 18 216 15 8.7

21 231 9 5.6 217 25 15 218 18 11

22 242 9 5.9 e210 20 11 208 28 16

23 234 8 5.1 e205 16 8.9 216 34 20

24 239 7 4.5 206 13 7.2 220 32 19

25 226 8 4.9 210 12 6.8 210 26 15

26 213 9 5.2 221 15 9.0 186 22 11

27 218 10 5.9 216 20 12 e170 19 8.7

28 229 12 7.4 204 24 13 e170 20 9.2

29 236 12 7.6 205 26 14 e180 21 10

30 237 12 7.7 212 24 14 e180 22 11

31 231 12 7.5 -- -- -- e170 23 11

TOTAL 6,784 -- 185.9 6,635 -- 308.7 6,533 -- 309.2

MEAN 219 10 6.0 221 17 10 211 18 10

MAX 242 14 9.0 242 30 19 272 34 20

MIN 181 6 3.3 204 6 3.6 170 11 6.5
Data 55

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2007 through 

September 2008.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e160 24 10 185 32 16 206 26 14

2 e170 26 12 e190 31 16 197 30 16

3 e180 28 14 e190 30 15 194 30 16

4 e190 29 15 182 29 14 196 25 13

5 210 30 17 182 28 14 193 32 17

6 214 30 17 e180 28 14 193 25 13

7 201 28 15 e180 30 15 197 24 13

8 186 26 13 182 32 16 200 28 15

9 182 23 11 188 35 18 202 26 14

10 209 20 11 203 37 20 207 28 16

11 204 18 9.9 208 39 22 214 25 14

12 204 15 8.3 200 41 22 212 22 13

13 205 17 9.4 203 43 24 211 26 15

14 221 24 14 193 40 21 212 33 19

15 204 30 17 191 34 18 213 32 18

16 203 35 19 193 28 15 207 26 15

17 207 36 20 193 26 14 206 24 13

18 197 34 18 190 25 13 208 18 10

19 197 34 18 188 25 13 212 18 10

20 e150 33 13 190 25 13 213 17 9.8

21 e100 32 8.6 188 25 13 210 18 10

22 e110 28 8.3 189 24 12 203 16 8.8

23 e130 24 8.4 187 24 12 202 17 9.3

24 e150 22 8.9 187 23 12 212 14 8.0

25 e170 22 10 191 23 12 202 16 8.7

26 e190 21 11 191 23 12 197 17 9.0

27 e220 21 12 190 24 12 199 15 8.1

28 e210 20 11 193 24 13 189 21 11

29 e200 21 11 201 24 13 197 31 16

30 200 26 14 -- -- -- 190 14 7.2

31 e200 30 16 -- -- -- 194 14 7.3

TOTAL 5,774 -- 400.8 5,528 -- 444 6,288 -- 387.2

MEAN 186 26 13 191 29 15 203 23 12

MAX 221 36 20 208 43 24 214 33 19

MIN 100 15 8.3 180 23 12 189 14 7.2
56 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2007 through 

September 2008.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 189 13 6.6 237 17 11 579 76 119

2 185 14 7.0 218 22 13 648 98 171

3 187 13 6.6 213 25 14 658 101 179

4 191 14 7.2 224 54 33 766 222 459

5 194 17 8.9 227 35 21 957 205 530

6 189 18 9.2 232 22 14 828 99 221

7 184 20 9.9 262 17 12 777 85 178

8 182 19 9.3 305 20 16 733 67 133

9 182 14 6.9 289 15 12 703 62 118

10 185 22 11 276 12 8.9 733 62 123

11 186 17 8.5 269 19 14 757 48 98

12 186 15 7.5 256 18 12 748 46 93

13 195 17 9.0 244 21 14 670 46 83

14 206 22 12 237 17 11 631 50 85

15 208 22 12 237 12 7.7 614 59 98

16 195 16 8.4 220 13 7.7 630 51 87

17 190 16 8.2 234 17 11 608 52 85

18 224 22 13 277 67 50 645 50 87

19 237 36 23 369 177 176 668 58 105

20 235 37 23 455 208 256 688 58 108

21 240 32 21 529 134 191 691 62 116

22 240 27 17 530 82 117 729 66 130

23 246 41 27 513 125 173 874 92 217

24 266 47 34 493 88 117 895 72 174

25 285 31 24 559 112 169 733 51 101

26 277 25 19 544 108 159 699 42 79

27 252 26 18 551 96 143 639 39 67

28 243 22 14 552 95 142 577 39 61

29 243 20 13 557 76 114 562 34 52

30 253 18 12 560 71 107 571 37 57

31 -- -- -- 568 76 117 -- -- --

TOTAL 6,475 -- 406.2 11,237 -- 2,263.3 21,011 -- 4,214

MEAN 216 22 14 362 60 73 700 71 140

MAX 285 47 34 568 208 256 957 222 530

MIN 182 13 6.6 213 12 7.7 562 34 52
Data 57

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2007 through 

September 2008.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JULY AUGUST SEPTEMBER

1 614 37 61 80 1 0.22 215 47 27

2 653 35 62 77 1 .21 264 92 66

3 628 28 47 80 1 .22 220 38 23

4 543 21 31 83 2 .45 194 15 7.9

5 630 32 54 74 2 .40 177 10 4.8

6 569 32 49 67 2 .36 183 7 3.5

7 479 27 35 64 2 .35 191 7 3.6

8 419 22 25 69 3 .56 190 6 3.1

9 371 18 18 76 4 .82 186 6 3.0

10 337 13 12 73 4 .79 182 6 2.9

11 294 10 7.9 72 3 .58 196 6 3.2

12 271 9 6.6 66 2 .36 209 6 3.4

13 242 8 5.2 65 2 .35 204 6 3.3

14 217 7 4.1 69 2 .37 199 6 3.2

15 204 5 2.8 67 3 .54 194 6 3.1

16 203 4 2.2 68 4 .73 186 8 4.0

17 194 3 1.6 70 4 .76 179 11 5.3

18 183 4 2.0 70 3 .57 165 12 5.3

19 182 5 2.5 71 2 .38 164 13 5.8

20 169 6 2.7 82 3 .66 164 13 5.8

21 162 6 2.6 95 13 3.3 168 13 5.9

22 155 6 2.5 126 22 7.5 179 13 6.3

23 184 6 3.0 136 17 6.2 176 13 6.2

24 166 6 2.7 138 10 3.7 177 12 5.7

25 149 5 2.0 147 8 3.2 172 12 5.6

26 142 5 1.9 125 9 3.0 161 12 5.2

27 131 5 1.8 110 9 2.7 159 11 4.7

28 118 5 1.6 109 10 2.9 155 10 4.2

29 109 4 1.2 118 10 3.2 156 8 3.4

30 101 3 .82 127 10 3.4 170 7 3.2

31 86 1 .23 120 10 3.2 -- -- --

TOTAL 8,905 -- 451.95 2,794 -- 51.98 5,535 -- 237.6

MEAN 287 12 15 90.1 6 1.7 184 14 7.9

MAX 653 37 62 147 22 7.5 264 92 66

MIN 86 1 .23 64 1 .21 155 6 2.9 

Total for water year 2008 (unrounded sum of daily values): streamflow–93,499 ft3/s (annual runoff–185,500 acre-ft); suspended-sediment 

discharge–9,660.83 tons.
58 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2007 

through September 2008.

[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

1 798 6 13 852 5 12 e720 4 7.8

2 829 8 18 845 6 14 e700 4 7.6

3 845 10 23 829 6 13 759 4 8.2

4 841 10 23 829 6 13 912 11 27

5 840 10 23 829 6 13 1,050 21 60

6 872 11 26 821 4 8.9 1,050 22 62

7 881 12 29 816 3 6.6 944 15 38

8 873 12 28 816 4 8.8 850 10 23

9 873 11 26 815 6 13 816 9 20

10 872 11 26 813 6 13 822 8 18

11 888 10 24 818 6 13 826 7 16

12 890 10 24 818 6 13 804 6 13

13 869 10 23 821 6 13 758 5 10

14 852 10 23 830 6 13 758 4 8.2

15 840 10 23 792 6 13 744 5 10

16 838 10 23 811 6 13 744 7 14

17 863 10 23 816 7 15 734 9 18

18 880 9 21 846 8 18 744 9 18

19 905 8 20 932 11 28 778 8 17

20 952 10 26 928 9 23 804 7 15

21 965 8 21 865 6 14 772 6 13

22 931 8 20 742 5 10 691 6 11

23 917 8 20 e650 6 11 702 6 11

24 909 8 20 e550 6 8.9 781 8 17

25 909 8 20 e600 6 9.7 765 7 14

26 905 7 17 e650 5 8.8 714 5 9.6

27 886 7 17 703 5 9.5 691 5 9.3

28 869 6 14 830 4 9.0 708 6 11

29 867 6 14 809 3 6.6 704 6 11

30 870 5 12 764 4 8.3 700 6 11

31 864 5 12 -- -- -- 690 8 15

TOTAL 27,193 -- 652 23,840 -- 373.1 24,235 -- 543.7

MEAN 877 9 21 795 6 12 782 8 18

MAX 965 12 29 932 11 28 1,050 22 62

MIN 798 5 12 550 3 6.6 690 4 7.6
Data 59

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2007 

through September 2008.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e620 11 18 652 4 7.0 734 16 32

2 e550 9 13 617 4 6.7 748 12 24

3 e600 7 11 613 4 6.6 715 11 21

4 742 6 12 643 4 6.9 711 10 19

5 809 6 13 644 4 7.0 724 7 14

6 733 5 9.9 649 3 5.3 701 7 13

7 732 5 9.9 651 4 7.0 700 10 19

8 774 4 8.4 651 4 7.0 704 10 19

9 766 4 8.3 649 4 7.0 723 13 25

10 766 8 17 677 4 7.3 753 16 33

11 757 13 27 713 4 7.7 776 14 29

12 739 18 36 717 5 9.7 813 15 33

13 735 19 38 736 7 14 816 17 37

14 684 15 28 724 5 9.8 810 16 35

15 691 8 15 704 5 9.5 809 15 33

16 641 4 6.9 716 5 9.7 800 13 28

17 530 3 4.3 723 6 12 786 12 25

18 612 3 5.0 696 6 11 781 15 32

19 673 4 7.3 667 6 11 795 17 36

20 681 4 7.4 668 6 11 803 15 33

21 e550 4 5.9 678 6 11 798 13 28

22 e350 4 3.8 688 5 9.3 779 12 25

23 e400 5 5.4 698 6 11 744 16 32

24 e400 5 5.4 706 7 13 764 15 31

25 e450 5 6.1 716 9 17 793 12 26

26 e500 6 8.1 710 10 19 776 12 25

27 e600 6 9.7 704 11 21 771 14 29

28 e650 6 11 712 14 27 734 13 26

29 e620 7 12 724 17 33 722 9 18

30 e630 6 10 -- -- -- 720 10 19

31 651 4 7.0 -- -- -- 697 10 19

TOTAL 19,636 -- 379.8 19,846 -- 334.5 23,500 -- 818

MEAN 633 7 12 684 6 12 758 13 26

MAX 809 19 38 736 17 33 816 17 37

MIN 350 3 3.8 613 3 5.3 697 7 13
60 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2007 

through September 2008.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 718 10 19 1,750 41 194 5,070 55 753

2 686 8 15 1,600 28 121 5,270 60 854

3 681 7 13 1,550 24 100 5,430 86 1,260

4 696 11 21 1,630 25 110 5,270 70 996

5 731 12 24 1,780 31 149 5,710 123 1,900

6 726 11 22 2,020 48 262 5,610 126 1,910

7 708 10 19 2,300 60 373 5,450 93 1,370

8 714 11 21 2,470 57 380 5,200 68 955

9 714 11 21 2,490 52 350 5,080 60 823

10 723 12 23 2,350 39 247 4,960 58 777

11 729 13 26 2,240 32 194 5,220 58 817

12 736 17 34 2,210 24 143 5,240 60 849

13 811 20 44 2,130 23 132 5,340 73 1,050

14 1,010 57 155 2,110 20 114 5,320 64 919

15 1,510 174 709 2,280 23 142 5,280 54 770

16 1,490 135 543 2,630 47 334 5,290 59 843

17 1,210 44 144 3,130 77 651 5,320 76 1,090

18 1,170 37 117 3,730 104 1,050 5,420 48 702

19 1,310 42 149 4,750 160 2,050 5,380 46 668

20 1,330 31 111 5,500 168 2,490 5,180 42 587

21 1,170 19 60 5,770 145 2,270 5,020 37 501

22 1,140 19 58 5,680 106 1,630 5,130 36 499

23 1,130 25 76 5,210 69 971 5,170 39 544

24 1,160 24 75 4,940 62 827 4,980 37 498

25 1,160 20 63 5,100 76 1,050 4,580 38 470

26 1,150 18 56 5,480 103 1,520 4,120 33 367

27 1,120 18 54 5,300 79 1,130 3,850 31 322

28 1,200 22 71 5,070 62 849 3,590 31 300

29 1,510 41 167 5,050 61 832 3,400 29 266

30 1,800 59 287 5,070 62 849 3,280 30 266

31 -- -- -- 5,120 60 829 -- -- --

TOTAL 30,943 -- 3,197 108,440 -- 22,343 149,160 -- 23,926

MEAN 1,031 31 107 3,498 63 721 4,972 57 798

MAX 1,800 174 709 5,770 168 2,490 5,710 126 1,910

MIN 681 7 13 1,550 20 100 3,280 29 266
Data 61

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2007 

through September 2008.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JULY AUGUST SEPTEMBER

1 3,280 28 248 932 4 10 1,010 19 52

2 3,730 42 423 881 4 9.5 1,350 36 131

3 3,850 46 478 868 4 9.4 1,250 15 51

4 3,350 36 326 857 3 6.9 1,150 12 37

5 3,150 33 281 842 3 6.8 1,090 11 32

6 3,110 32 269 809 3 6.6 1,060 11 31

7 2,770 26 194 784 3 6.4 1,060 10 29

8 2,470 23 153 766 3 6.2 1,050 10 28

9 2,230 20 120 756 3 6.1 1,040 10 28

10 2,070 17 95 764 3 6.2 1,030 10 28

11 1,900 13 67 751 3 6.1 1,050 9 26

12 1,800 10 49 709 3 5.7 1,050 9 26

13 1,700 8 37 689 3 5.6 1,080 9 26

14 1,600 8 35 662 3 5.4 994 9 24

15 1,540 7 29 647 3 5.2 968 9 24

16 1,540 6 25 634 4 6.8 961 8 21

17 1,520 6 25 622 4 6.7 958 8 21

18 1,490 5 20 613 3 5.0 935 8 20

19 1,450 5 20 604 3 4.9 914 8 20

20 1,410 5 19 645 3 5.2 895 9 22

21 1,350 5 18 756 4 8.2 925 9 22

22 1,310 5 18 849 6 14 963 9 23

23 1,360 5 18 856 8 18 977 9 24

24 1,370 5 18 799 6 13 956 9 23

25 1,290 4 14 762 6 12 949 9 23

26 1,180 4 13 757 6 12 937 9 23

27 1,120 4 12 762 6 12 915 9 22

28 1,070 4 12 755 6 12 895 8 19

29 1,040 4 11 742 6 12 879 7 17

30 1,020 4 11 719 7 14 868 7 16

31 977 4 11 772 8 17 -- -- --

TOTAL 59,047 -- 3,069 23,364 -- 274.9 30,159 -- 889

MEAN 1,905 14 99 754 4 8.9 1,005 10 30

MAX 3,850 46 478 932 8 18 1,350 36 131

MIN 977 4 11 604 3 4.9 868 7 16

Total for water year 2008 (unrounded sum of daily values): streamflow–93,499 ft3/s (annual runoff–185,500 acre-ft); suspended-sediment 

discharge–9,660.83 tons.
62 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2007 through 

September 2008.

[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

1 478 2 2.6 473 1 1.3 e440 2 2.4

2 483 2 2.6 472 1 1.3 e430 2 2.3

3 483 2 2.6 469 2 2.5 e550 2 3.0

4 477 2 2.6 472 2 2.5 e620 3 5.0

5 478 2 2.6 469 2 2.5 e600 3 4.9

6 485 3 3.9 471 1 1.3 e570 3 4.6

7 480 3 3.9 469 1 1.3 e530 3 4.3

8 478 3 3.9 467 2 2.5 e500 3 4.0

9 473 3 3.8 467 4 5.0 e480 2 2.6

10 472 3 3.8 467 2 2.5 e460 3 3.7

11 478 3 3.9 467 1 1.3 e450 3 3.6

12 489 3 4.0 467 1 1.3 e460 4 5.0

13 492 3 4.0 480 1 1.3 e480 4 5.2

14 480 3 3.9 489 1 1.3 e470 4 5.1

15 473 3 3.8 501 2 2.7 e450 4 4.9

16 472 2 2.5 514 2 2.8 e440 3 3.6

17 477 2 2.6 538 3 4.4 e430 2 2.3

18 480 2 2.6 574 3 4.6 e450 2 2.4

19 504 2 2.7 602 3 4.9 e470 2 2.5

20 512 2 2.8 593 3 4.8 e450 2 2.4

21 507 2 2.7 534 3 4.3 e420 2 2.3

22 498 2 2.7 486 2 2.6 e430 2 2.3

23 493 2 2.7 e450 1 1.2 e450 2 2.4

24 487 2 2.6 e400 1 1.1 e460 2 2.5

25 484 2 2.6 e420 1 1.1 e430 2 2.3

26 480 2 2.6 e450 1 1.2 e420 2 2.3

27 478 2 2.6 e470 1 1.3 e410 2 2.2

28 480 1 1.3 e500 2 2.7 e400 3 3.2

29 477 1 1.3 e480 2 2.6 e410 4 4.4

30 478 1 1.3 e460 2 2.5 e420 3 3.4

31 474 1 1.3 -- -- -- e430 2 2.3

TOTAL 14,980 -- 88.8 14,571 -- 72.7 14,410 -- 103.4

MEAN 483 2 2.9 486 2 2.4 465 3 3.3

MAX 512 3 4.0 602 4 5.0 620 4 5.2

MIN 472 1 1.3 400 1 1.1 400 2 2.2
Data 63

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2007 through 

September 2008.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e400 1 1.1 e390 1 1.1 453 3 3.7

2 e370 1 1.0 e390 1 1.1 450 3 3.6

3 e350 1 .95 e380 1 1.0 442 3 3.6

4 e450 2 2.4 e380 1 1.0 448 2 2.4

5 e500 2 2.7 e380 2 2.1 444 3 3.6

6 e480 2 2.6 e390 2 2.1 444 3 3.6

7 e450 2 2.4 e400 2 2.2 444 4 4.8

8 e430 2 2.3 e410 2 2.2 439 3 3.6

9 e420 2 2.3 e420 2 2.3 440 2 2.4

10 e420 1 1.1 e440 2 2.4 450 3 3.6

11 e450 2 2.4 e470 3 3.8 466 4 5.0

12 e480 5 6.5 e500 2 2.7 475 4 5.1

13 e470 7 8.9 e480 2 2.6 479 4 5.2

14 e450 4 4.9 e460 2 2.5 489 5 6.6

15 e430 2 2.3 e450 3 3.6 495 6 8.0

16 e400 1 1.1 e440 2 2.4 496 4 5.4

17 e370 1 1.0 e420 1 1.1 490 3 4.0

18 e380 1 1.0 e400 1 1.1 488 5 6.6

19 e400 1 1.1 e390 1 1.1 500 6 8.1

20 e350 1 .95 e380 1 1.0 514 5 6.9

21 e280 1 .76 e390 2 2.1 517 4 5.6

22 e250 1 .68 e400 2 2.2 497 3 4.0

23 e270 1 .73 e400 2 2.2 482 3 3.9

24 e280 1 .76 e410 2 2.2 492 3 4.0

25 e300 1 .81 425 2 2.3 494 3 4.0

26 e330 1 .89 417 1 1.1 493 3 4.0

27 e400 1 1.1 418 2 2.3 495 3 4.0

28 e450 1 1.2 429 3 3.5 477 2 2.6

29 e420 1 1.1 445 2 2.4 478 3 3.9

30 e400 1 1.1 -- -- -- 460 3 3.7

31 e400 1 1.1 -- -- -- 459 3 3.7

TOTAL 12,230 -- 59.23 12,104 -- 59.7 14,690 -- 139.2

MEAN 395 2 1.9 417 2 2.1 474 3 4.5

MAX 500 7 8.9 500 3 3.8 517 6 8.1

MIN 250 1 .68 380 1 1.0 439 2 2.4
64 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2007 through 

September 2008.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 452 3 3.7 2,130 27 155 7,390 69 1,380

2 444 4 4.8 2,080 17 95 7,600 68 1,400

3 440 4 4.8 2,130 15 86 7,610 68 1,400

4 447 4 4.8 2,370 16 102 7,200 55 1,070

5 464 4 5.0 2,740 23 170 6,620 45 804

6 469 3 3.8 3,230 32 279 6,240 40 674

7 469 4 5.1 3,740 35 353 5,940 38 609

8 480 3 3.9 4,040 33 360 5,570 34 511

9 504 4 5.4 4,090 29 320 5,210 31 436

10 534 5 7.2 3,960 22 235 5,010 28 379

11 553 5 7.5 3,810 20 206 4,920 26 345

12 575 6 9.3 3,690 14 139 4,790 24 310

13 653 10 18 3,520 14 133 4,650 26 326

14 790 16 34 3,510 12 114 4,590 26 322

15 968 25 65 3,670 12 119 4,760 28 360

16 1,020 21 58 4,300 20 232 5,040 32 435

17 1,010 19 52 5,390 66 960 5,270 33 470

18 1,050 20 57 6,810 116 2,110 5,530 37 552

19 1,160 14 44 8,810 228 5,420 5,630 38 578

20 1,230 13 43 9,790 202 5,340 5,550 35 524

21 1,200 10 32 10,100 171 4,660 5,400 30 437

22 1,170 9 28 9,490 126 3,230 5,470 30 443

23 1,150 10 31 8,330 82 1,840 5,650 32 488

24 1,140 9 28 7,700 75 1,560 5,440 29 426

25 1,110 10 30 7,740 93 1,940 5,120 24 332

26 1,100 7 21 7,820 108 2,280 4,790 21 272

27 1,100 7 21 7,950 127 2,730 4,500 19 231

28 1,190 9 29 7,860 120 2,550 4,240 17 195

29 1,490 15 60 7,560 84 1,710 4,030 16 174

30 1,910 28 144 7,250 67 1,310 3,910 15 158

31 -- -- -- 7,210 64 1,250 -- -- --

TOTAL 26,272 -- 860.3 172,820 -- 41,988 163,670 -- 16,041

MEAN 876 10 29 5,575 67 1,350 5,456 34 535

MAX 1,910 28 144 10,100 228 5,420 7,610 69 1,400

MIN 440 3 3.7 2,080 12 86 3,910 15 158
Data 65

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2007 through 

September 2008.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JULY AUGUST SEPTEMBER

1 3,840 16 166 959 3 7.8 876 6 14

2 4,060 25 274 937 3 7.6 989 6 16

3 4,010 26 282 925 3 7.5 963 5 13

4 3,660 22 217 912 4 9.8 891 5 12

5 3,420 19 175 882 4 9.5 851 5 11

6 3,220 17 148 853 3 6.9 834 4 9.0

7 3,010 16 130 820 3 6.6 829 3 6.7

8 2,800 14 106 796 3 6.4 818 3 6.6

9 2,650 9 64 800 3 6.5 801 2 4.3

10 2,490 6 40 823 3 6.7 787 2 4.2

11 2,350 6 38 812 3 6.6 801 2 4.3

12 2,200 6 36 787 2 4.2 785 2 4.2

13 2,060 6 33 764 2 4.1 759 3 6.1

14 1,940 6 31 748 2 4.0 740 2 4.0

15 1,800 6 29 737 3 6.0 727 2 3.9

16 1,720 5 23 715 3 5.8 714 2 3.9

17 1,630 5 22 694 3 5.6 705 2 3.8

18 1,530 5 21 676 2 3.7 691 2 3.7

19 1,470 5 20 667 2 3.6 674 2 3.6

20 1,410 4 15 684 2 3.7 662 3 5.4

21 1,350 4 15 758 2 4.1 660 3 5.3

22 1,280 4 14 812 2 4.4 695 3 5.6

23 1,280 4 14 804 2 4.3 725 4 7.8

24 1,250 4 14 768 3 6.2 703 3 5.7

25 1,190 4 13 727 3 5.9 689 3 5.6

26 1,150 4 12 716 3 5.8 676 2 3.7

27 1,110 3 9.0 709 3 5.7 660 2 3.6

28 1,060 3 8.6 708 3 5.7 656 2 3.5

29 1,040 3 8.4 709 3 5.7 652 3 5.3

30 1,010 3 8.2 703 3 5.7 649 3 5.3

31 983 3 8.0 737 2 4.0 -- -- --

TOTAL 63,973 -- 1,994.2 24,142 -- 180.1 22,662 -- 191.1

MEAN 2,064 8 64 779 3 5.8 755 3 6.4

MAX 4,060 26 282 959 4 9.8 989 6 16

MIN 983 3 8.0 667 2 3.6 649 2 3.5

Total for water year 2008 (unrounded sum of daily values): streamflow–556,524 ft3/s (annual runoff–1,104,000 acre-ft); suspended-sediment 

discharge–61,777.73 tons.
66 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2007 through 

September 2008.

[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 1,250 14 47 1,300 9 32 e1,100 14 42

2 1,270 14 48 1,290 9 31 e1,000 44 119

3 1,310 14 50 1,270 9 31 e1,200 114 369

4 1,310 14 50 1,270 11 38 1,490 158 636

5 1,300 14 49 1,260 11 37 1,710 151 697

6 1,340 16 58 1,260 10 34 1,660 112 502

7 1,370 18 67 1,250 9 30 1,480 68 272

8 1,340 16 58 1,250 21 71 1,330 29 104

9 1,330 15 54 1,250 29 98 1,180 8 25

10 1,330 14 50 1,240 27 90 e1,150 10 31

11 1,350 13 47 1,250 26 88 e1,150 13 40

12 1,370 12 44 1,250 24 81 e1,100 16 48

13 1,350 12 44 1,260 21 71 e1,200 19 62

14 1,320 12 43 1,290 20 70 1,290 22 77

15 1,300 12 42 1,250 20 68 1,250 22 74

16 1,290 12 42 1,280 19 66 1,200 20 65

17 1,320 12 43 1,320 18 64 1,160 17 53

18 1,340 13 47 1,380 18 67 1,170 15 47

19 1,370 14 52 1,490 17 68 1,220 13 43

20 1,430 15 58 1,490 16 64 1,280 11 38

21 1,460 15 59 1,390 16 60 1,210 10 33

22 1,410 15 57 1,170 16 51 1,050 9 26

23 1,380 15 56 e1,000 18 49 1,080 10 29

24 1,370 15 55 e900 24 58 1,230 10 33

25 1,370 15 55 948 28 72 1,210 10 33

26 1,360 13 48 1,080 29 85 1,130 9 27

27 1,350 12 44 1,130 32 98 1,100 8 24

28 1,320 10 36 1,300 46 161 1,050 8 23

29 1,320 8 29 e1,250 63 213 1,080 7 20

30 1,320 8 29 e1,200 33 107 1,090 7 21

31 1,320 8 29 -- -- -- 1,110 10 30

TOTAL 41,570 -- 1,490 37,268 -- 2,153 37,660 -- 3,643

MEAN 1,341 13 48 1,242 22 72 1,215 31 118

MAX 1,460 18 67 1,490 63 213 1,710 158 697

MIN 1,250 8 29 900 9 30 1,000 7 20
Data 67

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2007 through 

September 2008.

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e1,050 10 28 e1,000 171 462 1,150 16 50

2 e900 10 24 e1,000 205 554 1,170 14 44

3 e800 10 22 e1,000 237 640 1,140 11 34

4 e1,200 10 32 e1,000 271 732 1,130 10 31

5 1,480 10 40 e1,000 305 824 1,140 10 31

6 1,300 10 35 e1,050 337 955 1,120 11 33

7 1,140 8 25 e1,050 369 1,050 1,120 10 30

8 1,070 4 12 e1,050 400 1,130 1,120 10 30

9 1,100 2 5.9 e1,050 388 1,100 1,130 11 34

10 1,090 2 5.9 e1,100 183 544 1,170 13 41

11 1,200 6 19 e1,150 47 146 1,200 15 49

12 1,290 23 80 e1,200 24 78 1,250 18 61

13 1,270 41 141 1,200 19 62 1,270 19 65

14 1,170 28 88 1,170 14 44 1,270 20 69

15 1,120 23 70 1,130 10 31 1,280 16 55

16 1,020 67 185 1,150 11 34 1,270 18 62

17 874 26 61 1,150 13 40 1,250 16 54

18 980 56 148 1,100 12 36 1,200 15 49

19 1,110 70 210 1,050 11 31 1,230 16 53

20 e1,000 31 84 1,030 10 28 1,280 18 62

21 e700 6 11 1,050 9 26 1,290 17 59

22 e600 4 6.5 1,060 9 26 1,250 13 44

23 e650 4 7.0 1,080 9 26 1,190 15 48

24 e700 3 5.7 1,100 9 27 1,210 21 69

25 e800 3 6.5 1,120 9 27 1,250 35 118

26 e900 6 15 1,100 10 30 1,230 30 100

27 e1,100 22 65 1,100 12 36 1,230 11 37

28 e1,200 65 211 1,110 14 42 1,310 220 778

29 e1,100 104 309 1,140 14 43 1,190 572 1,840

30 e1,050 126 357 -- -- -- 1,160 260 814

31 e1,000 148 400 -- -- -- 1,130 140 427

TOTAL 31,964 -- 2,709.5 31,490 -- 8,804 37,330 -- 5,271

MEAN 1,031 30 87 1,086 108 304 1,204 52 170

MAX 1,480 148 400 1,200 400 1,130 1,310 572 1,840

MIN 600 2 5.7 1,000 9 26 1,120 10 30
68 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2007 through 

September 2008.

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 1,140 115 354 3,910 637 6,720 12,900 144 5,020

2 1,110 100 300 3,710 511 5,120 13,300 148 5,350

3 1,090 85 250 3,690 358 3,570 13,500 145 5,360

4 1,110 83 249 3,970 435 4,660 13,000 126 4,460

5 1,160 83 260 4,510 560 6,820 13,000 147 5,200

6 1,170 78 246 5,190 588 8,240 12,800 160 5,570

7 1,150 65 202 5,980 660 10,700 12,200 127 4,220

8 1,160 81 254 6,520 704 12,400 11,400 136 4,190

9 1,180 61 194 6,670 560 10,100 10,800 98 2,860

10 1,220 62 204 6,480 424 7,420 10,500 81 2,300

11 1,250 65 219 6,220 336 5,640 10,600 81 2,320

12 1,270 66 226 6,080 272 4,470 10,500 76 2,150

13 1,400 100 378 5,820 224 3,520 10,600 86 2,460

14 1,710 216 997 5,760 255 3,970 10,400 72 2,020

15 2,440 317 2,090 6,050 288 4,700 10,400 62 1,740

16 2,610 314 2,210 6,920 504 9,420 10,700 74 2,140

17 2,250 216 1,310 8,460 760 17,400 10,900 92 2,710

18 2,210 167 996 10,400 785 22,000 11,100 95 2,870

19 2,480 202 1,350 13,800 955 35,600 11,200 92 2,810

20 2,630 294 2,090 16,200 1,060 46,400 10,900 74 2,200

21 2,410 188 1,220 16,800 685 31,100 10,600 63 1,800

22 2,320 142 889 16,400 408 18,200 10,600 60 1,720

23 2,270 185 1,130 14,600 345 13,700 10,900 75 2,210

24 2,270 167 1,020 13,600 312 11,500 10,600 65 1,860

25 2,250 159 966 13,600 262 9,620 9,880 46 1,230

26 2,220 156 935 14,100 317 12,200 9,180 46 1,140

27 2,180 184 1,080 14,100 258 9,820 8,570 48 1,110

28 2,330 196 1,230 13,700 230 8,570 8,080 43 938

29 2,970 329 2,640 13,300 190 6,820 7,650 48 991

30 3,720 630 6,330 12,900 164 5,760 7,380 45 897

31 -- -- -- 12,800 161 5,610 -- -- --

TOTAL 56,680 -- 31,819 292,240 -- 361,770 324,140 -- 81,846

MEAN 1,889 170 1,060 9,427 458 11,700 10,800 88 2,730

MAX 3,720 630 6,330 16,800 1,060 46,400 13,500 160 5,570

MIN 1,090 61 194 3,690 161 3,520 7,380 43 897
Data 69

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2007 through 

September 2008.

[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)

JULY AUGUST SEPTEMBER

1 7,270 39 766 1,900 5 26 1,830 12 59

2 7,860 88 1,870 1,830 4 20 2,350 28 178

3 8,090 66 1,440 1,790 4 19 2,240 10 60

4 7,170 38 736 1,770 4 19 2,060 8 44

5 6,660 28 503 1,730 4 19 1,940 8 42

6 6,460 30 523 1,670 3 14 1,900 7 36

7 5,920 32 511 1,610 3 13 1,880 7 36

8 5,400 29 423 1,560 3 13 1,860 7 35

9 4,990 21 283 1,540 3 12 1,820 6 29

10 4,650 19 239 1,570 3 13 1,800 6 29

11 4,310 19 221 1,550 4 17 1,830 6 30

12 4,030 16 174 1,480 4 16 1,810 6 29

13 3,810 13 134 1,440 4 16 1,770 6 29

14 3,590 12 116 1,410 4 15 1,740 6 28

15 3,370 12 109 1,380 4 15 1,710 6 28

16 3,250 11 97 1,350 4 15 1,680 6 27

17 3,150 10 85 1,320 4 14 1,670 6 27

18 2,990 8 65 1,290 4 14 1,630 6 26

19 2,860 7 54 1,260 3 10 1,590 6 26

20 2,760 7 52 1,320 3 11 1,560 7 29

21 2,640 7 50 1,510 4 16 1,580 7 30

22 2,520 6 41 1,660 6 27 1,660 7 31

23 2,570 6 42 1,670 7 32 1,710 7 32

24 2,580 6 42 1,580 5 21 1,670 7 32

25 2,430 7 46 1,490 4 16 1,650 6 27

26 2,300 6 37 1,480 4 16 1,610 6 26

27 2,210 5 30 1,470 4 16 1,580 6 26

28 2,120 5 29 1,460 4 16 1,550 5 21

29 2,060 5 28 1,450 4 16 1,540 5 21

30 2,020 5 27 1,420 5 19 1,510 5 20

31 1,960 5 26 1,500 5 20 -- -- --

TOTAL 124,000 -- 8,799 47,460 -- 526 52,730 -- 1,093

MEAN 4,000 18 284 1,531 4 17 1,758 7 36

MAX 8,090 88 1,870 1,900 7 32 2,350 28 178

MIN 1,960 5 26 1,260 3 10 1,510 5 20

Total for water year 2008 (unrounded sum of daily values): streamflow–1,114,532 ft3/s (annual runoff–2,211,000 acre-ft); 

suspended-sediment discharge–509,923.5 tons.
70 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 9. Seasonal daily maximum, minimum, and mean turbidity at Mill Creek near Anaconda, Montana, October 2007 and March 

through September 2008.

[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 MARCH APRIL

1 2.5 1.0 1.5 -- -- -- 4.0 2.5 3.0

2 1.5 1.0 1.5 -- -- -- 7.0 2.5 4.0

3 2.0 1.5 1.5 -- -- -- 7.0 4.0 5.0

4 2.0 1.0 1.5 -- -- -- 6.5 4.5 5.0

5 2.5 1.5 2.0 -- -- -- 7.0 4.0 5.0

6 3.0 1.5 2.0 -- -- -- 8.5 4.0 4.5

7 2.5 1.5 2.0 -- -- -- 9.0 4.5 6.0

8 2.5 1.5 2.0 -- -- -- 9.0 5.5 6.5

9 2.5 1.5 2.0 -- -- -- 7.5 4.5 5.0

10 2.5 1.0 1.5 -- -- -- 11 5.0 6.0

11 2.0 1.0 1.5 -- -- -- 15 6.5 9.5

12 -- -- 2.0 -- -- -- 18 3.5 10

13 -- -- -- -- -- -- 15 4.0 7.0

14 -- -- -- -- -- -- 20 5.5 11

15 -- -- -- -- -- -- 14 8.0 10

16 -- -- -- -- -- -- 8.5 6.0 7.5

17 -- -- -- -- -- -- 8.0 4.5 6.0

18 -- -- -- -- -- -- 11 5.5 7.5

19 -- -- -- -- -- 5.0 11 6.5 7.5

20 -- -- -- 5.0 4.5 4.5 14 3.5 7.0

21 -- -- -- 5.5 4.0 4.5 10 4.0 5.5

22 -- -- -- 6.5 3.5 4.5 8.0 4.5 5.5

23 -- -- -- 6.5 3.0 4.0 9.0 5.0 6.5

24 -- -- -- 4.0 3.0 3.0 12 4.5 5.0

25 -- -- -- 4.0 2.5 3.0 6.0 4.0 5.0

26 -- -- -- 4.0 2.5 3.0 5.0 4.0 4.5

27 -- -- -- 4.5 2.0 3.0 8.0 4.5 5.0

28 -- -- -- 6.0 2.5 3.0 24 6.5 10

29 -- -- -- 5.0 3.0 3.5 29 10 16

30 -- -- -- 5.0 3.0 3.5 24 8.0 11

31 -- -- -- 7.0 2.5 3.0 -- -- --

MONTH1 3.0 1.0 1.8 7.0 2.0 3.7 29 2.5 6.9
Data 71

Table 9. Seasonal daily maximum, minimum, and mean turbidity at Mill Creek near Anaconda, Montana, October 2007 and March 

through September 2008.—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

MAY JUNE JULY

1 17 8.5 12 7.5 5.5 6.0 -- -- --

2 20 4.0 11 8.0 5.0 6.0 -- -- --

3 7.5 4.0 5.0 7.5 5.0 5.5 -- -- --

4 7.5 4.0 5.0 11 5.5 7.0 -- -- --

5 14 4.5 7.5 6.5 5.0 5.5 -- -- --

6 14 6.5 9.5 7.0 5.0 5.5 -- -- --

7 13 7.5 9.5 6.0 5.0 5.5 -- -- --

8 10 6.0 7.5 7.0 5.0 5.5 -- -- --

9 8.5 6.0 7.0 8.0 4.5 5.5 -- -- --

10 10 5.5 7.5 6.5 5.5 6.0 -- -- --

11 13 5.5 8.5 7.5 6.0 6.5 -- -- --

12 10 6.0 8.0 7.0 5.5 6.0 -- -- --

13 10 4.5 7.0 6.5 5.0 6.0 -- -- --

14 16 7.0 10 8.0 5.0 6.0 -- -- --

15 20 7.5 12 6.5 5.0 5.5 -- -- --

16 30 9.5 18 7.5 4.5 5.5 8.5 2.5 4.5

17 30 12 21 6.5 4.5 5.5 6.5 2.5 4.0

18 29 14 19 8.0 4.5 5.5 8.0 2.0 3.5

19 30 16 21 6.5 4.5 5.5 4.0 1.5 2.5

20 30 16 22 8.0 5.5 6.5 3.5 1.5 2.0

21 18 10 13 13 5.5 7.0 3.0 1.5 2.0

22 11 8.0 9.5 19 10 13 4.5 2.0 3.0

23 11 7.5 8.5 21 8.0 12 3.5 1.5 2.0

24 14 7.0 8.5 11 6.5 7.5 4.5 1.5 2.0

25 10 7.0 7.5 8.5 5.5 6.5 3.0 1.5 2.0

26 9.0 7.0 7.5 8.5 5.0 6.0 3.5 2.0 2.5

27 9.0 6.5 7.5 8.0 5.0 5.5 3.5 2.0 2.5

28 9.5 6.5 7.0 6.5 5.0 5.5 5.0 1.5 2.5

29 8.0 6.0 6.5 9.0 5.5 6.5 3.0 1.0 2.0

30 8.0 5.5 6.5 -- -- -- 3.5 1.5 2.0

31 7.5 5.5 6.0 -- -- -- 3.5 1.5 2.0

MONTH1 30 4.0 10 21 4.5 6.4 8.5 1.0 2.6
72 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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

Anaconda, Montana, October 2007 and March through September 2008.—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

AUGUST SEPTEMBER

1 3.5 1.5 2.5 18 4.5 7.0

2 3.5 1.5 2.0 8.0 4.0 5.0

3 4.0 2.0 2.5 6.5 3.5 4.5

4 3.5 2.0 2.5 6.5 5.0 5.5

5 5.5 2.0 2.5 6.0 4.0 5.0

6 4.0 2.0 2.5 5.5 3.5 4.5

7 4.5 2.0 3.0 5.0 3.0 4.0

8 4.5 2.0 2.5 6.0 3.0 4.0

9 3.5 1.5 2.5 4.5 3.0 3.5

10 3.0 2.0 2.5 6.0 3.5 4.0

11 3.0 2.0 2.5 5.5 3.5 4.5

12 3.5 2.0 2.5 7.0 3.0 4.0

13 3.5 2.0 2.5 4.5 3.0 3.5

14 5.5 2.5 3.0 4.5 2.5 3.5

15 5.5 2.5 3.5 6.0 3.0 3.5

16 4.5 2.5 3.5 4.5 3.0 3.5

17 5.0 3.0 4.0 7.0 3.0 4.0

18 5.5 3.5 4.5 4.5 3.0 3.5

19 8.5 4.0 5.5 4.5 2.5 3.5

20 7.0 3.5 5.0 -- -- --

21 7.0 3.5 4.5 -- -- --

22 4.5 3.0 3.5 -- -- --

23 4.5 3.5 3.5 -- -- --

24 6.0 3.5 4.5 -- -- --

25 6.0 4.0 4.5 -- -- --

26 5.5 3.0 4.0 -- -- --

27 4.5 2.5 3.0 -- -- --

28 5.0 2.5 3.5 -- -- --

29 8.5 3.0 4.0 -- -- --

30 5.0 3.0 4.0 -- -- --

31 13 3.0 4.5 -- -- --

MONTH1 13 1.5 3.4 18 2.5 4.2

1

For months with missing daily values, the means are calculated using available values.
Data 73

Table 10. Seasonal daily maximum, minimum, and mean turbidity at Willow Creek near Anaconda, Montana, October 2007 and April 

through September 2008.

[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 APRIL MAY

1 4.0 1.0 2.0 -- -- -- 33 18 22

2 3.5 1.5 2.0 -- -- -- 28 16 19

3 7.0 1.5 2.5 -- -- -- 31 17 20

4 5.0 1.5 2.0 -- -- -- -- -- --

5 7.0 1.5 2.0 -- -- -- -- -- --

6 6.0 1.5 2.0 -- -- -- -- -- --

7 5.0 1.0 2.0 -- -- -- -- -- --

8 5.5 1.5 2.0 -- -- -- -- -- --

9 4.0 1.0 2.0 -- -- -- -- -- --

10 3.5 1.0 1.5 -- -- -- -- -- --

11 4.0 1.0 1.5 -- -- -- -- -- --

12 -- -- -- -- -- -- -- -- --

13 -- -- -- -- -- -- -- -- --

14 -- -- -- -- -- -- -- -- --

15 -- -- -- -- -- -- -- -- --

16 -- -- -- 21 10 12 -- -- --

17 -- -- -- 12 9.0 10 -- -- --

18 -- -- -- 17 8.0 11 -- -- --

19 -- -- -- 19 10 12 -- -- --

20 -- -- -- 26 10 14 43 9.0 19

21 -- -- -- 33 8.5 15 39 9.5 21

22 -- -- -- 31 8.5 14 58 22 39

23 -- -- -- 13 9.0 10 -- -- --

24 -- -- -- 15 8.5 10 -- -- --

25 -- -- -- 10 7.5 8.5 -- -- --

26 -- -- -- 12 8.0 9.5 -- -- --

27 -- -- -- 13 8.0 9.0 -- -- --

28 -- -- -- 38 9.5 16 -- -- --

29 -- -- -- -- -- -- -- -- --

30 -- -- -- -- -- -- -- -- --

31 -- -- -- -- -- -- -- -- --

MONTH1 7.0 1.0 2.0 38 7.5 12 58 9.0 23
74 Water-Quality, Bed-Sediment, and 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 2007 and April 

through September 2008.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JUNE JULY AUGUST

1 -- -- -- 5.0 3.0 3.5 7.0 3.5 4.0

2 -- -- -- 5.0 3.0 3.5 9.0 3.5 5.0

3 -- -- -- 9.0 3.0 4.0 11 4.5 5.5

4 -- -- -- -- -- -- 16 4.0 5.5

5 -- -- -- -- -- -- 12 4.5 6.0

6 -- -- -- -- -- -- -- -- --

7 -- -- -- -- -- -- -- -- --

8 -- -- -- 14 9.0 11 -- -- --

9 -- -- -- 13 8.0 10 -- -- --

10 12 8.0 9.0 14 6.5 8.5 -- -- --

11 14 7.5 9.0 9.5 6.0 7.5 -- -- --

12 11 7.0 8.0 11 5.5 7.0 -- -- --

13 52 7.5 16 8.0 5.5 6.5 -- -- --

14 16 8.5 10 8.5 5.0 5.5 -- -- --

15 12 7.5 8.5 7.5 4.0 5.5 -- -- --

16 10 6.5 8.0 7.0 4.0 5.0 -- -- --

17 12 6.5 7.5 9.5 4.0 4.5 -- -- --

18 8.0 5.5 6.5 7.0 3.5 4.5 -- -- --

19 7.5 5.0 6.0 6.0 3.5 4.0 -- -- --

20 9.0 5.0 6.0 8.0 3.0 4.0 -- -- --

21 8.5 4.5 5.5 7.5 3.0 4.0 -- -- --

22 6.0 4.5 5.0 88 3.0 9.0 -- -- --

23 8.0 4.0 5.0 73 4.0 9.0 -- -- --

24 6.5 4.0 4.5 9.0 3.5 5.0 -- -- --

25 6.0 3.5 4.5 9.0 4.5 5.5 -- -- --

26 6.5 3.5 4.5 -- -- -- 4.0 1.5 2.5

27 6.0 3.5 4.5 -- -- -- 4.0 2.0 2.5

28 7.5 3.5 4.5 -- -- -- 4.0 2.0 2.5

29 6.0 3.5 4.0 -- -- -- 4.0 1.5 2.5

30 5.5 3.0 4.0 8.0 3.5 4.5 4.0 1.5 2.5

31 -- -- -- 8.0 3.0 4.5 -- -- --

MONTH1 52 3.0 6.7 88 3.0 5.9 16 1.5 3.8
Data 75

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

Creek near Anaconda, Montana, October 2007 and April through September 

2008.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths 

of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to incident beam, 

reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean

SEPTEMBER

1 -- -- --

2 -- -- --

3 -- -- --

4 -- -- --

5 4.0 1.5 2.0

6 2.5 1.5 2.0

7 3.5 1.5 2.0

8 2.5 1.5 2.0

9 3.0 1.5 2.0

10 3.0 2.0 2.0

11 2.5 1.5 2.0

12 2.5 1.5 2.0

13 2.0 1.5 1.5

14 2.5 1.5 2.0

15 3.0 1.5 2.0

16 3.0 2.0 2.5

17 3.0 2.0 2.5

18 2.5 1.5 2.0

19 2.5 1.5 2.0

20 2.5 1.5 2.0

21 2.0 1.5 2.0

22 2.0 1.5 1.5

23 2.0 1.5 1.5

24 2.0 1.5 1.5

25 2.0 1.5 1.5

26 2.5 1.5 2.0

27 2.5 1.5 2.0

28 2.5 1.5 1.5

29 5.0 1.5 2.0

30 6.0 1.5 2.0

31 -- -- --

MONTH1 6.0 1.5 1.9

1

For months with missing daily values, the means are calculated using available values.
76 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 11. Seasonal daily maximum, minimum, and mean turbidity at Warm Springs Creek near Anaconda, Montana, October 2007 and 

March through September 2008.

[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 MARCH APRIL

1 1.0 0.5 1.0 -- -- -- 2.0 0.5 1.5

2 -- -- -- -- -- -- 3.5 1.0 1.5

3 -- -- -- -- -- -- 2.0 1.0 1.5

4 -- -- -- -- -- -- 4.0 .5 1.5

5 3.0 .5 .5 -- -- -- 2.5 .5 1.5

6 -- -- -- -- -- -- 2.5 1.0 1.5

7 -- -- -- -- -- -- 2.0 .5 1.0

8 -- -- -- -- -- -- 2.0 .5 1.0

9 -- -- -- -- -- -- 3.0 1.0 2.0

10 4.0 .5 1.5 -- -- -- 6.0 2.0 3.0

11 3.0 .5 .5 -- -- -- 5.0 2.5 3.5

12 -- -- .5 -- -- -- -- -- 3.0

13 -- -- -- -- -- -- -- -- --

14 -- -- -- -- -- -- -- -- --

15 -- -- -- -- -- -- -- -- 3.0

16 -- -- -- -- -- -- 6.0 2.5 4.0

17 -- -- -- -- -- -- 5.5 2.0 3.5

18 -- -- -- -- -- -- -- -- --

19 -- -- -- -- -- -- -- -- --

20 -- -- -- 3.5 1.0 2.0 -- -- 2.5

21 -- -- -- 1.5 .5 1.0 7.5 1.0 4.0

22 -- -- -- 2.5 1.0 1.0 6.0 1.0 2.0

23 -- -- -- 3.0 .5 1.5 -- -- --

24 -- -- -- 4.0 1.0 1.5 6.0 1.5 3.5

25 -- -- -- 2.5 .5 1.0 6.0 1.0 2.5

26 -- -- -- 2.0 .5 1.0 6.5 .5 2.5

27 -- -- -- 2.5 1.0 1.0 -- -- --

28 -- -- -- -- -- 2.0 -- -- --

29 -- -- -- -- -- 1.5 8.0 2.0 4.0

30 -- -- -- -- -- 2.5 -- -- --

31 -- -- -- -- -- 1.5 -- -- --

MONTH1 4.0 .5 .8 4.0 .5 1.5 8.0 .5 2.5
Data 77

Table 11. Seasonal daily maximum, minimum, and mean turbidity at Warm Springs Creek near Anaconda, Montana, October 2007 and 

March through September 2008.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

MAY JUNE JULY

1 -- -- -- 6.0 3.5 4.5 3.5 2.0 2.5

2 -- -- -- 7.5 4.0 5.5 4.0 2.0 2.5

3 -- -- -- 5.5 2.5 3.5 3.0 1.5 2.0

4 -- -- 2.0 17 3.0 5.0 4.5 1.5 2.0

5 5.0 1.0 2.5 4.5 2.0 3.0 3.0 1.5 2.0

6 -- -- 3.0 3.5 2.0 3.0 4.5 1.5 2.0

7 -- -- -- 3.0 2.0 2.5 6.5 1.5 2.0

8 -- -- -- 2.5 1.5 2.0 2.5 1.0 1.5

9 -- -- -- 4.5 1.5 2.0 2.5 1.0 1.5

10 -- -- -- 3.5 1.5 2.0 2.5 1.0 1.5

11 -- -- 2.0 4.5 2.0 2.5 3.0 1.0 1.5

12 4.5 1.5 2.0 4.0 1.5 2.0 2.0 .5 1.5

13 3.0 1.0 2.0 4.0 1.5 2.0 2.0 .5 1.0

14 4.0 1.5 2.0 3.5 1.5 2.5 2.0 .5 1.0

15 7.5 1.5 3.0 3.5 1.5 2.5 2.0 .5 1.0

16 16 4.5 8.0 4.0 2.0 3.0 1.5 .5 1.0

17 22 5.5 12 9.5 4.0 6.0 2.0 .5 1.0

18 57 10 28 15 5.0 8.5 2.5 .5 1.5

19 64 14 34 11 5.0 7.5 2.5 1.5 2.0

20 35 11 19 8.5 4.0 6.0 3.5 1.5 2.0

21 24 7.5 14 15 5.0 8.0 3.0 1.5 2.0

22 9.5 4.5 6.5 26 12 18 36 1.5 3.0

23 9.5 4.0 5.0 29 7.0 17 5.5 1.5 2.5

24 6.5 3.0 4.0 10 5.0 7.0 3.5 1.5 2.0

25 6.0 2.5 4.0 14 3.5 7.0 2.5 1.5 2.0

26 3.5 2.5 3.0 5.5 3.0 4.0 3.0 1.5 2.0

27 4.0 2.0 3.0 5.0 2.5 3.5 3.0 1.5 2.0

28 4.0 2.0 2.5 5.0 2.0 3.0 4.5 1.5 2.0

29 4.0 2.0 2.5 4.0 2.0 3.0 5.0 1.5 2.0

30 5.0 2.5 3.5 4.5 2.0 3.0 3.5 1.5 2.0

31 4.5 2.5 3.5 -- -- -- 3.0 1.5 2.0

MONTH1 6.4 1.0 7.1 29 1.5 5.0 36 .5 1.8
78 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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

Creek near Anaconda, Montana, October 2007 and March through September 2008.

—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 

900 nanometers with a detection angle of 90 +/- 2.5 degrees to incident beam, reported in formazin 

nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean

AUGUST SEPTEMBER

1 4.5 1.5 2.0 12 2.0 5.0

2 4.0 1.5 2.0 4.5 1.0 2.0

3 3.0 1.5 2.0 4.0 .5 1.5

4 5.5 1.0 2.0 2.5 .5 1.0

5 2.5 1.5 2.0 2.0 .5 1.0

6 2.5 1.5 2.0 1.0 .5 .5

7 4.0 1.5 2.0 1.5 .5 1.0

8 2.5 1.5 2.0 1.0 <.5 .5

9 2.5 1.5 2.0 1.5 <.5 .5

10 3.5 1.0 2.0 3.0 .5 .5

11 2.5 1.0 1.5 1.0 .5 .5

12 2.0 1.0 1.5 1.0 <.5 .5

13 2.0 1.0 1.5 1.0 <.5 .5

14 2.0 1.0 1.5 1.0 .5 .5

15 2.0 1.0 1.5 1.0 .5 .5

16 2.5 1.0 1.5 1.0 <.5 .5

17 2.0 1.0 1.5 1.0 <.5 .5

18 3.0 1.0 1.5 1.0 <.5 .5

19 7.5 1.0 2.0 1.0 <.5 .5

20 8.0 1.5 2.5 1.0 <.5 .5

21 5.0 1.5 2.5 1.5 <.5 .5

22 4.0 1.5 2.5 2.0 <.5 .5

23 2.5 1.5 1.5 1.5 <.5 .5

24 3.0 1.0 1.5 .5 <.5 .5

25 2.0 1.0 1.5 .5 <.5 .5

26 2.0 1.0 1.5 .5 <.5 .5

27 2.5 .5 1.0 1.0 <.5 .5

28 1.0 .5 .5 .5 <.5 .5

29 1.5 <.5 .5 .5 <.5 .5

30 1.5 .5 .5 .5 <.5 .5

31 16 .5 3.0 -- -- --

MONTH1 16 <.5 1.7 12 <.5 .8

1

For months with missing daily values, the means are calculated using available values.
Data 79

Table 12. Seasonal daily maximum, minimum, and mean turbidity at Lost Creek near Anaconda, Montana, October 2007 and March 

through September 2008.

[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 MARCH APRIL

1 3.0 2.5 2.5 -- -- -- 19 3.0 6.5

2 3.0 2.0 2.5 -- -- -- 37 3.0 8.5

3 2.5 2.0 2.5 -- -- -- 22 3.5 5.5

4 3.0 2.0 2.5 -- -- -- 7.0 3.5 4.0

5 3.0 2.0 2.5 -- -- -- 4.0 3.0 3.5

6 2.5 2.5 2.5 -- -- -- 8.0 3.5 4.0

7 3.0 2.0 2.5 -- -- -- 5.5 3.0 3.5

8 2.5 2.0 2.5 -- -- -- 7.0 3.0 3.5

9 2.5 2.0 2.0 -- -- -- 5.5 3.0 3.5

10 2.5 2.0 2.0 -- -- -- 5.0 3.0 3.5

11 2.5 2.0 2.0 -- -- -- 5.0 3.0 3.5

12 -- -- 2.5 -- -- -- 9.5 3.0 4.5

13 -- -- -- -- -- -- 16 3.0 6.0

14 -- -- -- -- -- -- 11 3.0 6.0

15 -- -- -- -- -- -- 10 3.5 5.0

16 -- -- -- -- -- -- 7.0 3.0 4.0

17 -- -- -- -- -- -- 6.0 2.5 3.5

18 -- -- -- -- -- -- 5.0 3.0 3.5

19 -- -- -- -- -- 3.5 36 3.0 7.0

20 -- -- -- 6.0 3.0 3.5 54 4.5 25

21 -- -- -- 5.0 3.0 3.5 24 3.0 7.0

22 -- -- -- 22 3.0 5.0 21 3.0 6.0

23 -- -- -- 10 3.5 5.0 6.5 3.0 4.5

24 -- -- -- 6.0 3.0 4.0 21 3.5 6.0

25 -- -- -- 7.0 3.0 4.0 5.0 3.0 3.5

26 -- -- -- 8.5 3.5 4.0 9.0 3.0 3.5

27 -- -- -- 6.5 3.0 4.0 10 3.0 4.0

28 -- -- -- 18 3.0 6.0 6.5 2.5 4.0

29 -- -- -- 17 3.5 5.5 8.0 3.5 5.0

30 -- -- -- 21 3.0 5.0 10 4.0 5.5

31 -- -- -- 7.0 3.0 4.0 -- -- --

MONTH1 3.0 2.0 2.4 22 3.0 4.4 54 2.5 5.4
80 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 12. Seasonal daily maximum, minimum, and mean turbidity at Lost Creek near Anaconda, Montana, October 2007 and March 

through September 2008.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

MAY JUNE JULY

1 6.5 3.0 4.0 12 6.0 9.0 9.0 3.5 4.5

2 5.0 3.0 4.0 15 6.0 9.5 8.0 3.5 5.0

3 4.5 3.0 3.5 13 5.5 8.0 8.0 3.0 4.5

4 10 3.5 5.0 27 7.0 12 32 3.0 6.0

5 5.5 3.0 4.0 11 5.0 7.0 8.5 3.0 4.0

6 8.5 4.0 5.0 9.5 5.0 6.5 4.5 2.5 3.5

7 13 5.0 8.0 7.0 4.5 5.5 4.5 2.5 3.0

8 11 3.5 5.5 8.5 3.5 5.5 5.0 2.0 3.0

9 8.0 3.5 5.0 9.0 4.5 5.5 4.0 2.0 2.5

10 5.0 3.0 4.0 8.0 4.5 5.5 3.5 2.0 2.5

11 5.0 3.0 4.0 9.0 4.5 6.0 3.0 2.0 2.5

12 5.0 3.0 4.0 8.0 4.0 5.5 3.0 1.5 2.5

13 4.5 3.0 3.5 9.0 4.0 5.5 5.0 1.5 2.5

14 4.5 3.0 4.0 12 5.0 7.5 4.5 1.5 2.5

15 7.0 4.0 5.0 18 6.5 11 3.0 1.5 2.5

16 12 4.5 7.5 17 7.5 11 4.5 1.5 2.5

17 23 5.5 11 16 8.0 11 4.0 1.0 2.0

18 37 7.5 11 17 8.5 12 4.0 1.5 2.0

19 52 11 28 14 8.0 11 4.0 2.0 2.5

20 50 11 21 15 7.0 10 5.0 2.5 3.0

21 23 14 18 19 7.0 11 3.5 2.0 2.5

22 15 8.0 10 19 9.5 13 6.0 2.5 3.0

23 21 6.5 8.5 19 8.5 12 4.0 2.0 2.5

24 9.5 4.5 7.0 11 6.5 8.5 3.5 2.0 2.5

25 30 5.5 8.5 9.5 5.5 7.0 4.0 2.0 2.5

26 11 4.5 6.5 8.0 4.5 6.5 5.0 1.5 2.5

27 6.5 4.0 5.0 9.0 4.5 6.0 3.5 1.5 2.0

28 7.5 4.0 5.0 6.5 4.0 5.0 3.5 1.5 2.0

29 6.0 4.0 5.0 6.5 4.0 5.0 2.5 1.5 2.0

30 12 4.5 6.5 6.0 4.0 4.5 3.5 1.5 2.0

31 10 4.5 6.0 -- -- -- 3.0 1.5 2.0

MONTH1 52 3.0 7.5 27 3.5 8.1 32 1.0 2.9
Data 81

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

Anaconda, Montana, October 2007 and March through September 2008.—Continued

[Turbidity values are based on near infrared monochrome light emitted at wavelengths of 780 to 900 

nanometers with a detection angle of 90 +/- 2.5 degrees to incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean

AUGUST SEPTEMBER

1 4.5 1.5 2.0 99 3.5 11

2 43 2.5 6.5 5.5 2.0 3.0

3 5.0 3.0 3.5 4.0 2.0 2.5

4 4.5 2.5 3.5 4.0 2.5 2.5

5 4.5 2.5 3.0 3.5 2.5 2.5

6 5.5 2.5 3.0 96 2.5 13

7 5.0 2.5 3.0 8.0 4.0 5.0

8 5.5 2.5 3.5 4.0 3.0 3.5

9 6.0 2.5 3.5 5.5 3.0 3.5

10 5.0 2.5 3.0 4.0 3.0 3.0

11 4.5 2.5 3.0 4.0 3.0 3.0

12 6.5 2.5 3.0 3.5 2.5 3.0

13 4.5 2.5 3.0 4.0 2.5 3.0

14 5.5 2.5 3.0 8.0 2.5 3.0

15 4.5 2.5 3.5 3.5 2.0 2.5

16 4.0 2.5 3.5 3.5 2.0 2.5

17 6.0 3.0 3.5 3.5 2.0 2.5

18 4.0 2.5 3.0 3.5 2.0 2.5

19 10 3.0 3.5 5.5 2.0 2.5

20 -- -- 10 3.0 2.0 2.5

21 17 4.5 6.5 3.0 2.0 2.5

22 9.5 3.5 5.0 3.5 2.5 2.5

23 6.0 3.5 4.5 3.5 2.5 3.0

24 5.0 3.0 4.0 4.0 2.0 2.5

25 5.0 1.5 3.0 3.0 2.0 2.5

26 4.0 2.0 2.5 3.0 2.0 2.5

27 3.5 2.0 2.5 3.0 2.0 2.5

28 3.0 2.0 2.5 3.5 2.0 2.5

29 3.0 1.5 2.5 5.0 2.0 3.0

30 5.5 1.5 2.0 5.5 2.5 3.0

31 4.0 2.0 2.5 -- -- --

MONTH1 43 1.5 3.6 99 2.0 3.4

1

For months with missing daily values, the means are calculated using available values.
82 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana. [Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbols: <, less than laboratory reporting level; --, no data] Site number (fig. 1) Site name Date Time Hardness, filtered (mg/L as CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Total 

nitrogen, 

unfiltered 

(mg/L)

Total 

phosphorous, 

unfiltered 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

12323600 Silver Bow at Opportunity 03/03/2008 1410 180 49.3 12.9 -- -- 7.6 14.0

03/03/2008 1415 170 48.7 12.8 -- -- 7.5 13.8

12323670 Mill Creek near Anaconda 06/17/2008 1215 33 9.6 2.30 -- -- 19.8 20.8

06/17/2008 1220 35 10.2 2.34 -- -- 19.7 20.5

12323700 Mill Creek at Opportunity 07/07/2008 1630 37 10.7 2.45 -- -- 23.7 29.0

07/07/2008 1635 38 10.9 2.51 -- -- 24.0 28.4

12323750 Silver Bow Creek at Warm Springs 04/08/2008 0850 210 57.3 16.2 -- -- 11.6 14.1

04/08/2008 0855 210 56.1 15.9 -- -- 11.8 14.4

12323760 Warm Springs Creek near Anaconda 08/18/2008 1510 120 36.2 7.71 -- -- 2.3 2.6

08/18/2008 1515 120 34.7 7.35 -- -- 2.3 2.6

12324200 Clark Fork at Deer Lodge 05/06/2008 1115 210 61.3 13.9 -- -- 14.6 19.1

05/06/2008 1120 210 62.0 14.1 -- -- 14.5 19.7

12334550 Clark Fork at Turah Bridge, near 

Bonner

05/23/2008 1030 62 17.5 4.42 0.50 0.108 4.8 8.505/23/2008 1035 62 17.4 4.45 .49 .101 4.7 8.306/04/2008 1515 71 20.3 4.96 -- -- 6.3 9.906/04/2008 1520 71 20.2 4.93 -- -- 6.4 10.4

12340000 Blackfoot River near Bonner 06/24/2008 1330 80 21.2 6.69 .16 .024 .86 1.1

06/24/2008 1335 81 21.2 6.72 .15 .025 .85 1.1

12340500 Clark Fork above Missoula 11/07/2007 1100 160 44.6 12.4 -- -- 3.9 4.9

11/07/2007 1105 160 44.0 12.7 -- -- 3.9 4.605/05/2008 1515 89 24.0 7.05 .59 .270 5.2 22.505/05/2008 1525 87 23.4 6.87 .56 .370 5.1 20.1

12354500 Clark Fork at St. Regis 05/20/2008 1300 40 11.3 2.78 .88 .265 2.5 9.2

05/20/2008 1305 40 11.4 2.80 .84 .260 2.5 9.2
Data 83

Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.—Continued[Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbols: <, less than laboratory reporting level; --, no data]

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 at Opportunity 03/03/2008 1410 0.64 1.21 28.6 106 21 1,150 0.27

03/03/2008 1415 .67 1.15 28.9 112 22 1,160 .28

12323670 Mill Creek near Anaconda 06/17/2008 1215 .05 .07 3.1 4.6 29 163 .10

06/17/2008 1220 .05 .08 3.1 4.7 30 168 .10

12323700 Mill Creek at Opportunity 07/07/2008 1630 .06 .12 2.7 5.9 45 223 .14

07/07/2008 1635 .06 .12 3.9 5.8 45 215 .14

12323750 Silver Bow Creek at Warm Springs 04/08/2008 0850 .09 .12 3.4 6.4 9 229 .09

04/08/2008 0855 .07 .13 3.6 6.4 9 232 E.07

12323760 Warm Springs Creek near Anaconda 08/18/2008 1510 <.04 E.01 E.75 1.6 E6 66 <.08

08/18/2008 1515 <.04 E.01 1.2 1.7 E5 74 E.06

12324200 Clark Fork at Deer Lodge 05/06/2008 1115 .05 .17 6.0 31.9 9 499 E.07

05/06/2008 1120 .05 .17 5.9 32.4 10 509 E.07

12334550 Clark Fork at Turah Bridge, near 

Bonner

05/23/2008 1030 E.02 .23 4.0 30.6 45 999 .2105/23/2008 1035 E.02 .19 3.9 29.5 46 970 .20

06/04/2008 1515 E.04 .17 5.4 32.5 37 927 .18

06/04/2008 1520 E.04 .17 5.5 32.2 38 914 .18

12340000 Blackfoot River near Bonner 06/24/2008 1330 <.04 <.01 E.55 E1.1 9 326 <.08

06/24/2008 1335 <.04 <.01 E.58 E1.0 9 293 <.08

12340500 Clark Fork above Missoula 11/07/2007 1100 <.04 .07 1.4 8.5 E7 155 E.04

11/07/2007 1105 <.04 .07 1.4 6.9 E6 153 E.04

05/05/2008 1515 E.03 1.72 4.5 349 36 6,490 .87

05/05/2008 1525 E.03 1.58 5.1 326 44 4,720 1.05

12354500 Clark Fork at St. Regis 05/20/2008 1300 <.04 .65 4.9 106 64 4,420 .31

05/20/2008 1305 <.04 .67 4.8 104 62 4,170 .29
84 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.—Continued [Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbols: <, less than laboratory reporting level; --, no data] 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 at Opportunity 03/03/2008 1410 24.1 288 418 173 268 78 36 03/03/2008 1415 24.2 287 416 175 275 77 36 12323670 Mill Creek near Anaconda 06/17/2008 1215 .73 3.9 10.3 1.9 4 36 6 06/17/2008 1220 .75 3.8 10.7 2.0 5 42 5 12323700 Mill Creek at Opportunity 07/07/2008 1630 1.16 7.1 16.6 2.2 5 59 8 07/07/2008 1635 1.32 7.2 17.5 2.9 6 62 7 12323750 Silver Bow Creek at Warm Springs 04/08/2008 0850 1.37 87.8 163 3.9 13 86 6 04/08/2008 0855 1.40 86.7 182 2.6 12 87 5 12323760 Warm Springs Creek near Anaconda 08/18/2008 1510 .26 1.1 4.7 <1.8 E2 56 6 08/18/2008 1515 .32 1.1 4.7 <1.8 2 21 23 12324200 Clark Fork at Deer Lodge 05/06/2008 1115 4.36 66.8 186 4.1 28 77 21 05/06/2008 1120 4.20 68.0 187 4.0 28 76 22 12334550 Clark Fork at Turah Bridge, near Bonner 05/23/2008 1030 6.19 7.1 129 4.9 42 65 69 05/23/2008 1035 5.21 7.0 134 3.7 42 66 69 06/04/2008 1515 5.42 9.9 108 5.1 40 62 64 06/04/2008 1520 5.16 9.8 105 5.1 39 64 62 12340000 Blackfoot River near Bonner 06/24/2008 1330 .37 2.3 20.4 E1.2 2 79 26 06/24/2008 1335 .35 2.3 19.1 E1.1 E2 74 30 12340500 Clark Fork above Missoula 11/07/2007 1100 1.15 18.0 37.8 3.1 16 67 7 11/07/2007 1105 .99 18.7 36.5 3.2 14 66 8

05/05/2008 1515 53.5 14.6 274 4.2 444 25 55705/05/2008 1525 49.1 13.9 228 5.1 402 24 583

12354500 Clark Fork at St. Regis 05/20/2008 1300 17.1 4.1 254 4.2 173 54 464

05/20/2008 1305 17.3 4.0 249 4.1 169 51 475
Data 85

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

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

Constituent and reporting unit

Number of 

replicate 

pairs

Standard 

deviation1

 (listed units)

Relative standard 

deviation 

(percent)

Within limits2

of data-quality 

objective

Calcium, filtered, mg/L 12 0.49 1.6 Yes

Magnesium, filtered, mg/L 12 .13 1.7 Yes

Total nitrogen, unfiltered, mg/L 4 .02 3.5 Yes

Total phosphorous, unfiltered, mg/L 4 .04 20 Yes

Arsenic, filtered, μg/L 12 .09 1.0 Yes

Arsenic, unfiltered recoverable, μg/L 12 .54 4.2 Yes

Cadmium, filtered, μg/L 12 .01 8.3 Yes

Cadmium, unfiltered recoverable, μg/L 12 .03 8.8 Yes

Copper, filtered, μg/L 12 .30 5.4 Yes

Copper, unfiltered recoverable, μg/L 12 4.9 8.7 Yes

Iron, filtered, μg/L 12 1.8 6.6 Yes

Iron, unfiltered recoverable, μg/L 12 365 30 No3

Lead, filtered, μg/L 12 .04 18 Yes

Lead, unfiltered recoverable, μg/L 12 .92 9.8 Yes

Manganese, filtered, μg/L 12 .44 1.0 Yes

Manganese, unfiltered recoverable, μg/L 12 10 7.7 Yes

Zinc, filtered, μg/L 12 .59 3.4 Yes

Zinc, unfiltered recoverable, μg/L 12 8.7 10 Yes

Sediment, suspended, percent finer than 0.062 mm 12 7.4 12 Yes

Sediment, suspended, mg/L 12 6.8 6.3 Yes

1

Standard deviation is calculated using one-half the laboratory reporting level for censored values (less than the laboratory reporting level).

2

Data-quality objective for an acceptable level of precision is a maximum relative deviation of 20 percent for field replicate analyses (table 3).

3

Exceedance of data-quality objective resulted from a poor comparison between one replicate sample pair collected on May 5, 2008, at Clark Fork above Missoula when suspended-sediment concentrations were relatively high. When this one replicate pair was excluded, the other 11 replicate pairs had an acceptable 

relative standard deviation for unfiltered recoverable iron of 6.6 percent.
86 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

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

[Abbreviations: μg/L, micrograms per liter; mg/L, milligrams per liter]

Constituent and reporting unit

Number of 

replicate 

pairs

Standard 

deviation1

(listed units)

Relative standard 

deviation 

(percent)

Within limits2

of data-quality 

objective

Calcium, filtered, mg/L 8 0.23 0.65 Yes

Magnesium, filtered, mg/L 8 .06 .70 Yes

Arsenic, filtered, μg/L 8 .12 1.1 Yes

Arsenic, unfiltered recoverable, μg/L 8 .17 1.2 Yes

Cadmium, filtered, μg/L 8 .01 3.9 Yes

Cadmium, unfiltered recoverable, μg/L 8 .01 5.9 Yes

Copper, filtered, μg/L 8 .21 3.2 Yes

Copper, unfiltered recoverable, μg/L 8 .89 3.5 Yes

Iron, filtered, μg/L 8 .79 3.9 Yes

Iron, unfiltered recoverable, μg/L 8 3.8 .94 Yes

Lead, filtered, μg/L 8 .01 9.7 Yes

Lead, unfiltered recoverable, μg/L 8 .15 3.2 Yes

Manganese, filtered, μg/L 8 .78 1.3 Yes

Manganese, unfiltered recoverable, μg/L 8 1.7 1.5 Yes

Zinc, filtered, μg/L 8 .16 .66 Yes

Zinc, unfiltered recoverable, μg/L 8 5.0 11 Yes

1

Standard deviation is calculated using laboratory reporting level for censored values.

2

Data-quality objective for an acceptable level of precision is a maximum relative deviation of 20 percent for laboratory replicate analyses (table 3).

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

[Abbreviation: μg/L, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent confidence 

interval for spike recovery 

(percent)

Mean spike 

recovery 

(percent)

Within limits1

of data-quality 

objective

Arsenic, filtered, μg/L 5 89.2–117 103 Yes

Arsenic, unfiltered recoverable, μg/L 5 93.9–110 102 Yes

Cadmium, filtered, μg/L 5 88.2–116 102 Yes

Cadmium, unfiltered recoverable, μg/L 5 91.9–110 101 Yes

Copper, filtered, μg/L 5 88.0–121 105 Yes

Copper, unfiltered recoverable, μg/L 5 87.2–109 97.9 Yes

Iron, filtered, μg/L 5 95.9–110 103 Yes

Iron, unfiltered recoverable, μg/L 5 96.5–106 101 Yes

Lead, filtered, μg/L 5 89.0–112 101 Yes

Lead, unfiltered recoverable, μg/L 5 98.0–105 101 Yes

Manganese, filtered, μg/L 5 92.9–111 102 Yes

Manganese, unfiltered recoverable, μg/L 5 92.5–112 102 Yes

Zinc, filtered, μg/L 5 87.9–112 99.8 Yes

Zinc, unfiltered recoverable, μg/L 5 96.0–111 103 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).
Data 87

Table 17. Recovery efficiency for analyses of laboratory-spiked stream samples, upper Clark Fork basin, Montana.

[Abbreviation: μg/L, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent confidence 

interval for spike recovery 

(percent)

Mean spike 

recovery 

(percent)

Within limits1

of data-quality 

objective

Arsenic, filtered, μg/L 5 90.2–110 100 Yes

Arsenic, unfiltered recoverable, μg/L 5 98.5–104 101 Yes

Cadmium, filtered, μg/L 5 91.0–112 101 Yes

Cadmium, unfiltered recoverable, μg/L 5 93.6–100 97.0 Yes

Copper, filtered, μg/L 5 92.0–106 98.9 Yes

Copper, unfiltered recoverable, μg/L 5 86.4–99.1 92.8 Yes

Iron, filtered, μg/L 5 94.1–117 105 Yes

Iron, unfiltered recoverable, μg/L 5 92.0–107 99.4 Yes

Lead, filtered, μg/L 5 91.3–109 100 Yes

Lead, unfiltered recoverable, μg/L 5 99.5–106 103 Yes

Manganese, filtered, μg/L 5 90.3–108 98.9 Yes

Manganese, unfiltered recoverable, μg/L 5 92.5–104 98.4 Yes

Zinc, filtered, μg/L 5 88.1–124 106 Yes

Zinc, unfiltered recoverable, μg/L 5 93.1–98.2 95.7 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).
88 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana Table 18. Analyses of field blanks for water samples. [Abbreviations: E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; 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) 11/20/2007 2000 5.6 2 <0.04 <0.020 -- -- <0.06 <0.60 <0.04 <0.01 02/28/2008 1200 5.6 2 <.04 <.020 -- -- <.06 <.60 <.04 <.01 03/25/2008 1340 6.0 3 <.04 <.020 <0.06 <0.008 <.06 <.60 <.04 <.01 04/09/2008 1145 5.5 2 <.04 <.020 -- -- <.06 <.60 <.04 <.01 04/17/2008 1100 7.0 3 <.04 <.020 <.06 <.008 <.06 <.60 <.04 <.01 05/08/2008 1500 5.2 2 E.02 <.020 -- -- <.06 <.60 <.04 <.01 05/12/2008 1150 6.0 2 <.04 <.020 <.06 <.008 <.06 <.60 <.04 <.01 05/28/2008 0700 6.7 2 E.04 <.020 <.06 <.008 <.06 <.60 <.04 <.01 06/04/2008 0600 5.6 2 <.04 <.020 -- -- <.06 <.60 <.04 <.01 06/11/2008 0740 6.5 1 E.03 <.020 <.06 <.008 <.06 <.60 <.04 <.01 06/17/2008 2000 5.5 2 <.04 <.020 -- -- <.06 <.60 <.04 <.01 07/08/2008 1330 5.5 1 <.04 <.020 -- -- <.06 <.60 <.04 <.01 08/19/2008 1930 5.5 2 <.04 <.020 -- -- <.06 <.60 <.04 <.01 Date Copper, filtered (μg/L) Copper, unfiltered recoverable (μg/L) Iron, filtered (μg/L) Iron, unfiltered recoverable (μg/L) Lead, filtered (μg/L) Lead, unfiltered recoverable (μg/L) Manganese, filtered (μg/L) Manganese, unfiltered recoverable (μg/L) Zinc, filtered (μg/L) Zinc, unfiltered recoverable (ug/L) 11/20/2007 <1.0 <1.2 <8 <6 <0.08 <0.06 <0.2 <0.8 <1.8 <2.0 02/28/2008 <1.0 <1.2 <8 <6 <.08 <.06 <.2 <.8 <1.8 <2.0 03/25/2008 <1.0 <1.2 <8 <6 <.08 <.06 <.2 <.8 <1.8 <2.0 04/09/2008 <1.0 <1.2 <8 <6 <.08 <.06 <.2 <.8 <1.8 <2.0 04/17/2008 <1.0 <1.2 <8 <6 <.08 <.06 <.2 <.8 <1.8 <2.0 05/08/2008 <1.0 <1.2 <8 <6 <.08 <.06 <.2 <.8 <1.8 <2.0 05/12/2008 <1.0 <1.2 <8 <6 <.08 <.06 <.2 <.8 <1.8 E1.1 05/28/2008 <1.0 <1.2 <8 6 <.08 <.06 <.2 <.8 4.0 <2.0 06/04/2008 <1.0 <1.2 <8 E6 <.08 <.06 <.2 <.8 <1.8 <2.0

06/11/2008 <1.0 <1.2 <8 <6 <.08 <.06 <.2 <.8 3.6 <2.006/17/2008 <1.0 <1.2 <8 <6 <.08 <.06 <.2 <.8 <1.8 <2.007/08/2008 <1.0 <1.2 <8 <6 <.08 <.06 <.2 <.8 <1.8 <2.008/19/2008 <1.0 <1.2 <8 <6 <.08 <.06 <.2 <.8 <1.8 <2.0
Data 89

Table 19. Bed-sediment data for the upper Clark Fork basin, Montana, August 2008.[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 (μg/g)

Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12323600 Silver Bow Creek at Opportunity 3 153 26.0 38.6 2,930 45,300 503 3,530 14.8 5,01012323750 Silver Bow Creek at Warm 

Springs

3 67 5.8 33.2 367 28,100 78 3,920 14.4 688

12323770 Warm Springs Creek at Warm 

Springs

3 52 3.3 39.3 1,060 26,600 79 7,780 25.5 453

12323800 Clark Fork near Galen 3 114 6.1 35.7 1,170 30,100 116 12,100 22.7 1,090461415112450801 Clark Fork below Lost Creek, 

near Galen 

3 123 6.8 33.5 1,730 32,600 152 5,980 18.5 1,360

461559112443301 Clark Fork at county bridge, near 

Racetrack 

3 90 6.3 32.2 1,540 31,300 143 3,330 14.5 1,250

461903112440701 Clark Fork at Demspey Creek 

diversion, near Racetrack 

3 91 6.9 32.9 1,580 31,500 152 3,330 15.3 1,370

12324200 Clark Fork at Deer Lodge 3 69 4.5 27.2 1,090 24,100 127 2,730 12.5 1,05012324680 Clark Fork at Goldcreek 3 44 3.5 36.4 675 26,600 93 2,170 15.4 86912331800 Clark Fork near Drummond 3 45 4.5 31.3 460 39,200 81 4,820 13.9 1,00012334550 Clark Fork at Turah Bridge, near 

Bonner 

3 32 2.7 32.8 346 24,600 65 1,580 6.9 759

12340000 Blackfoot River near Bonner 3 6 .4 28.5 22 23,000 13 746 6.0 8212340500 Clark Fork above Missoula 3 54 2.8 33.0 475 27,000 57 2,250 7.6 839
90 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 20. Recovery efficiency for analyses of standard reference materials for bed-sediment samples.

[Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to final volume of solution 

after addition of 0.6N (normal) hydrochloric acid used for reconstituting dried residue. Abbreviations: μg/g, micrograms per gram 

of dry sample weight; SRM, standard reference material (agricultural soils)]

Constituent Number of 

analyses

Dilution 

ratio

Certified 

concentration 

(μg/g)

Mean SRM recovery

(percent)

95-percent 

confidence interval 

for SRM recovery 

(percent)

SRM sample 2709

Arsenic 10 1:10 17.7 63.0 60.7–65.3

Cadmium 10 1:10 .4 134.0 132–136

Chromium 10 1:10 130 81.1 76.7–85.6

Copper 10 1:10 35 78.5 72.2–84.7

Iron 10 1:10 35,000 103.2 100–106

Lead 10 1:10 19 55.4 52.9–57.8

Manganese 10 1:10 538 106.4 104–109

Nickel 10 1:10 88 94.9 93.4–96.5

Zinc 10 1:10 106 100.3 98.4–102

SRM sample 2711

Arsenic 10 1:10 105 93.2 89.4–97.0

Cadmium 10 1:10 41.7 104.4 99.3–109

Chromium 10 1:10 47 71.7 63.6–79.7

Copper 10 1:10 114 104.1 100–108

Iron 10 1:10 28,900 94.6 89.3–100

Lead 10 1:10 1,160 102.1 97.1–107

Manganese 10 1:10 638 95.0 89.6–100

Nickel 10 1:10 20.6 87.1 83.8–90.4

Zinc 10 1:10 350 101.7 97.7–106
Data 91

Table 21. Analyses of procedural blanks for bed-sediment samples.[Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to final volume of solution after addition of 0.6N (normal) hydrochloric 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 (μg/mL) Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12323600 Silver Bow Creek at 

Opportunity 

1:10 <0.004 <0.0002 <0.02 <0.02 <0.02 <0.002 <0.004 <0.0009 <0.005

12323750 Silver Bow Creek at Warm 

Springs

1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.005

12323770 Warm Springs Creek at 

Warm Springs

1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.005

12323800 Clark Fork near Galen 1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.005461415112450801 Clark Fork below Lost 

Creek, near Galen 

1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.005

461559112443301 Clark Fork at county bridge, 

near Racetrack 

1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.005

461903112440701 Clark Fork at Dempsey 

Creek diversion, near Racetrack 

1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.005

12324200 Clark Fork at Deer Lodge 1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.00512324680 Clark Fork at Goldcreek 1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.00512331800 Clark Fork near Drummond 1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.00512334550 Clark Fork at Turah Bridge, 

near Bonner 

1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.005

12340000 Blackfoot River near Bonner 1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.00512340500 Clark Fork above Missoula 1:10 <.004 <.0002 <.02 <.02 <.02 <.002 <.004 <.0009 <.005
92 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 22. Biological data for the upper Clark Fork basin, Montana, August 2008.—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 bioaccumulation 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 (μg/g)

Arsenic Cadmium Chromium Copper Iron Lead ManganeseNickel Zinc

12323600--Silver Bow Creek at Opportunity

Hydropsyche cockerelli 2 16.5 6.9 4.1 506 4,180 66.2 1,170 3.0 1,010

Hydropsyche spp. 1 13.0 4.7 3.0 333 3,250 237 1,060 2.4 809

12323750--Silver Bow Creek at Warm Springs

Hydropsyche cockerelli 3 8.5 0.4 1.4 26.6 656 3.5 930 0.6 162

12323770--Warm Springs Creek at Warm Springs

Arctopsyche grandis 1 9.6 3.0 2.8 126 1,350 7.2 2,480 3.5 267

Hydropsyche occidentalis 1 13.3 1.3 8.6 165 2,360 12.6 2,880 4.5 204

12323800--Clark Fork near Galen

Hydropsyche cockerelli 2 13.8 1.6 2.6 127 1,740 10.1 2,030 2.0 246

Hydropsyche occidentalis 1 12.8 1.2 2.0 79.0 1,390 9.0 2,630 1.6 201

461415112450801--Clark Fork below Lost Creek, near Galen

Hydropsyche cockerelli 1 17.5 1.8 3.0 225 2,000 17.5 1,750 2.2 288

461559112443301--Clark Fork at county bridge, near Racetrack

Hydropsyche cockerelli 2 17.8 1.9 2.6 154 2,480 15.9 2,190 1.9 297

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Hydropsyche cockerelli 2 10.3 1.9 1.6 99.9 1,050 10.5 1,350 1.0 230

Hydropsyche occidentalis 1 13.1 2.4 2.9 113 1,510 13.5 2,730 1.3 278

12324200--Clark Fork at Deer Lodge

Hydropsyche cockerelli 1 8.3 3.5 2.3 114 1,240 12.2 1,050 1.1 247

Hydropsyche occidentalis 2 8.5 3.1 2.1 114 1,130 12.1 1,550 1.1 263
Data 93

Table 22. Biological data for the upper Clark Fork basin, Montana, August 2008.—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 bioaccumulation 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 (μg/g)

Arsenic Cadmium Chromium Copper Iron Lead ManganeseNickel Zinc

12324680--Clark Fork at Goldcreek

Arctopsyche grandis 3 4.0 1.6 0.9 36.8 710 2.8 820 0.8 185

Claassenia sabulosa 2 .9 .8 .6 62.8 139 .7 162 .2 231

Hydropsyche cockerelli 2 7.2 2.2 1.7 95.1 1,190 7.1 1,440 1.4 234

Hydropsyche occidentalis 1 6.7 2.3 1.7 92.2 1,270 8.1 1,700 1.5 258

12331800--Clark Fork near Drummond

Arctopsyche grandis 3 3.4 1.3 0.7 28.9 472 4.5 857 0.6 207

Claassenia sabulosa 2 1.1 1.5 .5 75.5 144 .9 172 .2 239

Hydropsyche cockerelli 2 6.3 1.4 1.7 62.3 1,240 9.6 1,400 1.2 224

Hydropsyche occidentalis 1 6.4 1.5 3.0 65.9 1,360 10.7 1,680 1.3 277

12334550--Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 3 4.7 1.5 1.9 35.4 860 3.9 717 1.1 218

Claassenia sabulosa 2 .7 1.2 .9 66.6 89.7 .4 80.3 .2 224

Hydropsyche cockerelli 2 5.1 1.0 2.9 55.3 1,450 5.7 683 1.4 201

Hydropsyche occidentalis 2 4.3 .9 2.6 48.3 1,480 5.6 862 1.4 217

12340000--Blackfoot River near Bonner

Arctopsyche grandis 1 2.2 0.4 4.1 13.7 664 1.0 633 1.0 156

Claassenia sabulosa 2 .5 .2 1.0 45.3 223 .3 111 .3 234

Hydropsyche cockerelli 1 2.4 .3 3.6 16.2 1,990 2.1 814 1.8 140

Hydropsyche occidentalis 1 1.9 .3 3.0 16.5 1,630 2.0 798 1.5 163

12340500--Clark Fork above Missoula

Arctopsyche grandis 2 3.9 1.4 2.1 57.6 1,290 4.5 890 1.4 243

Claassenia sabulosa 2 1.3 1.1 .7 55.3 191 .8 201 .4 288

Hydropsyche cockerelli 2 6.9 1.1 3.7 79.7 2,380 7.2 1,380 2.0 251

Hydropsyche occidentalis 1 6.5 1.1 3.3 71.2 2,540 7.7 1,740 1.9 278
94 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 23. Recovery efficiency for analyses of standard reference material for biota samples.

[Abbreviations: μg/g, micrograms per gram of dry sample weight; SRM, standard reference material (lobster hepatopancreas)]

Constituent Number of 

analyses

Certified 

concentration 

(μg/g)

Mean 

SRM recovery

(percent)

95-percent confidence interval 

for SRM recovery

(percent)

SRM sample TORT-2

Arsenic 12 21.6 98.4 97.5–99.4

Cadmium 12 26.7 100 99.2–102

Chromium 12 .77 169 133–205

Copper 12 106 100 98.9–102

Iron 12 105 98.6 96.1–101

Lead 12 .35 139 132–145

Manganese 12 13.6 99.3 97.5–101

Nickel 12 2.5 97.7 92.9–102

Zinc 12 180 107 106–108
Data 95

Table 24. Analyses of procedural blanks for biota samples.[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 (μg/mL) Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12323600 Silver Bow Creek at Opportunity 1:1 <0.001 <0.001 <0.01 <0.008 <0.05 <0.001 <0.001 <0.001 <0.0312323750 Silver Bow Creek at Warm 

Springs

1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.03

12323770 Warm Springs Creek at Warm 

Springs

1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.03

12323800 Clark Fork near Galen 1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.03461415112450801 Clark Fork below Lost Creek, near 

Galen

1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.03

461559112443301 Clark Fork at county bridge, near 

Racetrack

1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.03

461903112440701 Clark Fork at Dempsey Creek 

diversion, near Racetrack

1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.03

12324200 Clark Fork at Deer Lodge 1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.0312324680 Clark Fork at Goldcreek 1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.0312331800 Clark Fork near Drummond 1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.0312334550 Clark Fork at Turah Bridge, near 

Bonner

1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.03

12340000 Blackfoot River near Bonner 1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.0312340500 Clark Fork above Missoula 1:1 <.001 <.001 <.01 <.008 <.05 <.001 <.001 <.001 <.03
96 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.

[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 2008

Streamflow, instantaneous (ft3/s) 115 156 1.9 14 7.6

pH, onsite (standard units) 115 8.4 7.3 7.8 7.8

Specific conductance, onsite (μS/cm) 115 412 116 266 271

Temperature, water (°C) 115 17.5 1.5 8.2 8.0

Hardness, filtered (mg/L as CaCO3) 115 150 38 105 110

Calcium, filtered (mg/L) 115 41.8 10.6 30.0 30.9

Magnesium, filtered (mg/L) 115 11.0 2.71 7.27 7.37

Arsenic, filtered (μg/L) 114 13 1 3.9 3.0

Arsenic, unfiltered (μg/L) 115 18 E1 25.3 4

Cadmium, filtered (μg/L) 113 .5 <.04 2.05 <.1

Cadmium, unfiltered (μg/L) 115 .11 <.01 2.04 <1

Copper, filtered (μg/L) 114 10.0 <1.0 23.7 3.2

Copper, unfiltered (μg/L) 115 52.0 1.5 6.9 5.5

Iron, filtered (μg/L) 115 640 15 168 150

Iron, unfiltered (μg/L) 115 4,220 139 658 550

Lead, filtered (μg/L) 115 2.80 <.08 2.20 <1.00

Lead, unfiltered (μg/L) 115 47.0 <1.00 21.96 .62

Manganese, filtered (μg/L) 115 144 14.2 41.2 37.6

Manganese, unfiltered (μg/L) 115 240 23.5 57.6 50.1

Zinc, filtered (μg/L) 114 11 <1.0 23.6 2.8

Zinc, unfiltered (μg/L) 115 130 <10 29.0 4

Sediment, suspended (percent finer than 0.062 mm) 115 97 50 82 83

Sediment, suspended concentration (mg/L) 115 139 1 13 7

Sediment, suspended discharge (ton/d) 115 59 .01 1.1 .14
Data 97

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

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

Period of record for water-quality data: March 1993–August 1995, December 1996–September 2008

Streamflow, instantaneous (ft3/s) 123 134 13 28 23

pH, onsite (standard units) 123 8.1 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 123 691 226 473 482

Temperature, water (°C) 123 20.0 1.0 10.5 9.5

Hardness, filtered (mg/L as CaCO3) 123 220 66 150 150

Calcium, filtered (mg/L) 123 62.7 19.0 42.6 44.0

Magnesium, filtered (mg/L) 123 14.6 4.51 10.5 11.0

Arsenic, filtered (μg/L) 123 13 2.3 6.4 6.2

Arsenic, unfiltered (μg/L) 123 45 3 10.9 9.2

Cadmium, filtered (μg/L) 123 6.2 .05 1.12 .87

Cadmium, unfiltered (μg/L) 123 6.0 .09 1.51 1.20

Copper, filtered (μg/L) 123 303 3.2 37.2 14.3

Copper, unfiltered (μg/L) 123 550 10.5 86.0 36.0

Iron, filtered (μg/L) 123 270 10 84.7 61

Iron, unfiltered (μg/L) 123 7,400 85 887 583

Lead, filtered (μg/L) 123 2.4 <.5 2.48 .23

Lead, unfiltered (μg/L) 123 250 .64 13.3 3.88

Manganese, filtered (μg/L) 123 1,700 21.4 365 297

Manganese, unfiltered (μg/L) 123 1,600 25.9 408 352

Zinc, filtered (μg/L) 123 2,200 16.0 367 248

Zinc, unfiltered (μg/L) 123 2,200 29.1 443 292

Sediment, suspended (percent finer than 0.062 mm) 122 98 42 84 86

Sediment, suspended concentration (mg/L) 122 405 2 23 10

Sediment, suspended discharge (ton/d) 122 70 .08 2.7 .68
98 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323600--Silver Bow Creek at Opportunity

Period of record for water-quality data: March 1993–August 1995, December 1996–September 2008

Streamflow, instantaneous (ft3/s) 126 361 13 71 50

pH, onsite (standard units) 125 9.5 7.2 8.4 8.3

Specific conductance, onsite (μS/cm) 125 633 202 420 403

Temperature, water (°C) 125 22.5 0.0 9.3 9.5

Hardness, filtered (mg/L as CaCO3) 125 240 60 150 150

Calcium, filtered (mg/L) 125 71.6 18.5 44.5 43.8

Magnesium, filtered (mg/L) 125 15.0 3.42 9.54 9.04

Arsenic, filtered (μg/L) 125 34 1 11.1 10.3

Arsenic, unfiltered (μg/L) 125 235 9.5 26.3 17.0

Cadmium, filtered (μg/L) 124 41.0 <.1 21.19 .76

Cadmium, unfiltered (μg/L) 125 49.0 .38 22.13 1.30

Copper, filtered (μg/L) 124 450 13.7 46.7 36.0

Copper, unfiltered (μg/L) 125 3,900 31.1 210 107

Iron, filtered (μg/L) 125 307 <3 245 25

Iron, unfiltered (μg/L) 124 24,100 240 1,520 775

Lead, filtered (μg/L) 125 5.1 <.5 2.73 .31

Lead, unfiltered (μg/L) 125 650 5.38 38.4 15.0

Manganese, filtered (μg/L) 125 9,300 56.6 449 352

Manganese, unfiltered (μg/L) 125 10,000 110 567 446

Zinc, filtered (μg/L) 124 13,000 11.2 312 172

Zinc, unfiltered (μg/L) 125 15,000 69.7 540 324

Sediment, suspended (percent finer than 0.062 mm) 126 95 37 79 83

Sediment, suspended concentration (mg/L) 126 801 5 47 17

Sediment, suspended discharge (ton/d) 126 781 .18 19 2.4
Data 99

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323670--Mill Creek near Anaconda

Period of record for water-quality data: December 2004–September 2008

Streamflow, instantaneous (ft3/s) 32 165 7.4 56 21

pH, onsite (standard units) 32 8.6 7.7 8.1 8.1

Specific conductance, onsite (μS/cm) 32 203 56 135 142

Temperature, water (°C) 32 17.0 0.0 8.4 8.0

Hardness, filtered (mg/L as CaCO3) 32 98 24 59 64

Calcium, filtered (mg/L) 32 25.9 7.12 16.2 17.7

Magnesium, filtered (mg/L) 32 8.01 1.45 4.47 4.73

Arsenic, filtered (μg/L) 32 30.3 7.3 16.5 16.2

Arsenic, unfiltered (μg/L) 32 30.1 9 18.2 17.6

Cadmium, filtered (μg/L) 31 .11 <.04 2.04 .04

Cadmium, unfiltered (μg/L) 32 .18 .04 .08 .07

Copper, filtered (μg/L) 32 4.7 .79 2.2 1.8

Copper, unfiltered (μg/L) 32 10.3 1.3 3.8 3.2

Iron, filtered (μg/L) 32 125 21 50 41

Iron, unfiltered (μg/L) 32 619 89 190 167

Lead, filtered (μg/L) 32 .24 <.08 2.12 .10

Lead, unfiltered (μg/L) 32 3.12 .19 .74 .59

Manganese, filtered (μg/L) 32 8.9 3.4 5.8 6.0

Manganese, unfiltered (μg/L) 32 36.6 7.4 14.0 11.8

Zinc, filtered (μg/L) 32 2.4 .73 1.4 1.2

Zinc, unfiltered (μg/L) 32 8 1 2.8 2.5

Sediment, suspended (percent finer than 0.062 mm) 32 81 36 67 70

Sediment, suspended concentration (mg/L) 32 29 1 6 3

Sediment, suspended discharge (ton/d) 32 13 .02 1.5 .16
100 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—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 2008

Streamflow, instantaneous (ft3/s) 48 261 0.43 34 5.8

pH, onsite (standard units) 48 8.2 7.8 8.0 8.0

Specific conductance, onsite (μS/cm) 48 230 59 150 162

Temperature, water (°C) 48 20.0 0.0 9.6 9.5

Hardness, filtered (mg/L as CaCO3) 48 100 24 64 70

Calcium, filtered (mg/L) 48 28.0 7.01 17.9 19.3

Magnesium, filtered (mg/L) 48 7.83 1.56 4.67 5.11

Arsenic, filtered (μg/L) 48 55.1 9.0 23.6 23.0

Arsenic, unfiltered (μg/L) 48 53.5 10 27.1 27.8

Cadmium, filtered (μg/L) 48 .13 .02 .06 .07

Cadmium, unfiltered (μg/L) 48 .85 .04 .15 .10

Copper, filtered (μg/L) 48 6.1 1.1 3.1 2.7

Copper, unfiltered (μg/L) 48 38.8 1.5 6.8 4.2

Iron, filtered (μg/L) 48 94 16 49 43

Iron, unfiltered (μg/L) 48 1,960 44 287 135

Lead, filtered (μg/L) 48 .32 <.08 2.14 .13

Lead, unfiltered (μg/L) 48 12.7 .07 1.43 .42

Manganese, filtered (μg/L) 48 32.8 2.2 8.5 6.6

Manganese, unfiltered (μg/L) 48 113 3.5 19.2 13.0

Zinc, filtered (μg/L) 48 7.7 1.3 3.2 3.0

Zinc, unfiltered (μg/L) 48 41 1.9 6.8 5

Sediment, suspended (percent finer than 0.062 mm) 48 90 26 69 77

Sediment, suspended concentration (mg/L) 48 107 1 12 2

Sediment, suspended discharge (ton/d) 48 55 <.01 23.5 .02
Data 101

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323710--Willow Creek near Anaconda

Period of record for water-quality data: December 2004–September 2008

Streamflow, instantaneous (ft3/s) 28 62 1.0 12 6.6

pH, onsite (standard units) 28 8.2 7.5 7.8 7.8

Specific conductance, onsite (μS/cm) 28 119 66 98 103

Temperature, water (°C) 28 15.5 .5 7.6 7.5

Hardness, filtered (mg/L as CaCO3) 28 43 22 35 38

Calcium, filtered (mg/L) 28 14.4 7.56 11.9 12.8

Magnesium, filtered (mg/L) 28 1.69 .78 1.33 1.39

Arsenic, filtered (μg/L) 28 24.9 9.9 15.4 14.2

Arsenic, unfiltered (μg/L) 28 27.0 10 16.6 15.4

Cadmium, filtered (μg/L) 27 .05 <.04 2.03 .03

Cadmium, unfiltered (μg/L) 28 .19 .02 .06 .05

Copper, filtered (μg/L) 28 4.2 .90 2.0 1.9

Copper, unfiltered (μg/L) 28 16.8 1.0 3.8 3.2

Iron, filtered (μg/L) 28 277 36 79 67

Iron, unfiltered (μg/L) 28 1,260 93 308 216

Lead, filtered (μg/L) 28 .37 .05 .14 .12

Lead, unfiltered (μg/L) 28 4.08 .10 .76 .48

Manganese, filtered (μg/L) 28 34.5 6.2 15.1 13.6

Manganese, unfiltered (μg/L) 28 49.1 15.1 26.3 22.6

Zinc, filtered (μg/L) 28 3.3 .65 1.7 1.7

Zinc, unfiltered (μg/L) 28 10 1 2.8 2

Sediment, suspended (percent finer than 0.062 mm) 28 94 25 73 78

Sediment, suspended concentration (mg/L) 28 93 1 14 5

Sediment, suspended discharge (ton/d) 28 10 <.01 21.0 .12
102 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—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 2008

Streamflow, instantaneous (ft3/s) 48 70 4.5 16 7.8

pH, onsite (standard units) 48 8.9 7.7 8.2 8.1

Specific conductance, onsite (μS/cm) 48 371 116 283 306

Temperature, water (°C) 48 20.5 1.5 11.5 12.0

Hardness, filtered (mg/L as CaCO3) 48 170 67 125 130

Calcium, filtered (mg/L) 48 47.4 20.5 35.9 38.2

Magnesium, filtered (mg/L) 48 12.3 3.73 8.39 9.08

Arsenic, filtered (μg/L) 48 164 10.9 43.5 31.0

Arsenic, unfiltered (μg/L) 48 164 12 46.3 32.5

Cadmium, filtered (μg/L) 48 .11 <.04 2.04 .04

Cadmium, unfiltered (μg/L) 48 .52 .02 .10 .07

Copper, filtered (μg/L) 48 21.4 1.1 5.6 3.3

Copper, unfiltered (μg/L) 48 48.8 2.8 11.5 8.2

Iron, filtered (μg/L) 48 111 7 39 32

Iron, unfiltered (μg/L) 48 1,420 27 251 196

Lead, filtered (μg/L) 48 .52 E.04 2.20 .17

Lead, unfiltered (μg/L) 48 14.4 .27 2.18 1.49

Manganese, filtered (μg/L) 48 82.2 4.1 27.9 20.2

Manganese, unfiltered (μg/L) 48 104 4.7 38.3 30.6

Zinc, filtered (μg/L) 48 19.8 .84 5.1 3.9

Zinc, unfiltered (μg/L) 48 68 2 12.1 9.5

Sediment, suspended (percent finer than 0.062 mm) 48 96 55 85 88

Sediment, suspended concentration (mg/L) 48 84 1 11 5

Sediment, suspended discharge (ton/d) 48 11 .02 .85 .14
Data 103

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323750--Silver Bow Creek at Warm Springs

Period of record for water-quality data: March 1993–September 2008

Streamflow, instantaneous (ft3/s) 132 662 16 134 87

pH, onsite (standard units) 130 9.4 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 130 783 249 473 481

Temperature, water (°C) 131 25.0 .5 10.9 11.0

Hardness, filtered (mg/L as CaCO3) 130 310 97 196 200

Calcium, filtered (mg/L) 130 90.4 27.9 57.1 58.4

Magnesium, filtered (mg/L) 130 21.4 5.94 13.1 13.3

Arsenic, filtered (μg/L) 130 60 6.8 22.7 22.6

Arsenic, unfiltered (μg/L) 130 94 10 26.8 26.3

Cadmium, filtered (μg/L) 130 .31 <.04 2.06 .02

Cadmium, unfiltered (μg/L) 130 .56 <.1 2.12 <1

Copper, filtered (μg/L) 130 40.0 1.7 8.3 6.4

Copper, unfiltered (μg/L) 130 96.8 2.4 16.7 12.0

Iron, filtered (μg/L) 130 93 <5 217 14

Iron, unfiltered (μg/L) 130 3,000 36 333 258

Lead, filtered (μg/L) 130 1.0 <.08 2.11 <.6

Lead, unfiltered (μg/L) 130 41.8 <1 22.38 1.24

Manganese, filtered (μg/L) 130 875 11.8 128 96.3

Manganese, unfiltered (μg/L) 130 899 24.0 192 162

Zinc, filtered (μg/L) 130 73 <1.0 28.1 4.1

Zinc, unfiltered (μg/L) 130 180 <10 232.3 20

Sediment, suspended (percent finer than 0.062 mm) 131 97 43 82 85

Sediment, suspended concentration (mg/L) 132 229 1 11 6

Sediment, suspended discharge (ton/d) 132 279 .07 6.8 1.5
104 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—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 2008

Streamflow, instantaneous (ft3/s) 18 391 41 118 70

pH, onsite (standard units) 18 8.8 8.1 8.5 8.6

Specific conductance, onsite (μS/cm) 18 271 126 221 242

Temperature, water (°C) 18 16.0 4.5 9.3 8.2

Hardness, filtered (mg/L as CaCO3) 18 130 60 106 115

Calcium, filtered (mg/L) 18 38.6 18.6 31.8 35.0

Magnesium, filtered (mg/L) 18 8.57 3.25 6.61 7.36

Arsenic, filtered (μg/L) 18 2.8 1.8 2.2 2.2

Arsenic, unfiltered (μg/L) 18 3.2 2.0 2.5 2.5

Cadmium, filtered (μg/L) 18 .03 <.04 2.02 <.04

Cadmium, unfiltered (μg/L) 18 .07 .01 .03 .03

Copper, filtered (μg/L) 18 1.4 <1.0 2.98 .87

Copper, unfiltered (μg/L) 18 4.7 1.1 2.3 2.2

Iron, filtered (μg/L) 18 13 <6 28 6

Iron, unfiltered (μg/L) 18 237 28 95 75

Lead, filtered (μg/L) 18 .11 <.08 -- <.08

Lead, unfiltered (μg/L) 18 .62 .08 .29 .25

Manganese, filtered (μg/L) 18 2.9 <.2 21.1 .9

Manganese, unfiltered (μg/L) 18 11.3 1.2 4.7 3.9

Zinc, filtered (μg/L) 18 2.8 <1.8 2.97 .54

Zinc, unfiltered (μg/L) 18 5.5 <2 22.2 2

Sediment, suspended (percent finer than 0.062 mm) 18 80 51 64 66

Sediment, suspended concentration (mg/L) 18 17 1 6 4

Sediment, suspended discharge (ton/d) 18 18 .016 2.8 .64
Data 105

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323770--Warm Springs Creek at Warm Springs

Period of record for water-quality data: March 1993–September 2008

Streamflow, instantaneous (ft3/s) 97 420 2.8 91 48

pH, onsite (standard units) 96 8.7 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 96 795 139 299 312

Temperature, water (°C) 97 20.0 0.0 8.9 9.0

Hardness, filtered (mg/L as CaCO3) 96 420 40 145 150

Calcium, filtered (mg/L) 96 130 10.5 44.2 46.0

Magnesium, filtered (mg/L) 96 22.0 3.29 8.34 8.51

Arsenic, filtered (μg/L) 96 14 2 5.2 4.6

Arsenic, unfiltered (μg/L) 96 27 3 7.4 6

Cadmium, filtered (μg/L) 96 E.1 <.04 2.03 <.1

Cadmium, unfiltered (μg/L) 96 .41 <.1 2.07 <1.0

Copper, filtered (μg/L) 96 16.0 1.0 3.4 3.0

Copper, unfiltered (μg/L) 96 108 2.3 18.5 8.2

Iron, filtered (μg/L) 96 30 <5 211 10

Iron, unfiltered (μg/L) 96 1,700 39 285 110

Lead, filtered (μg/L) 96 1.8 <.08 2.09 <.5

Lead, unfiltered (μg/L) 96 14.0 <1.0 21.82 .43

Manganese, filtered (μg/L) 96 570 22.6 129 98.5

Manganese, unfiltered (μg/L) 96 1,400 53.1 218 174

Zinc, filtered (μg/L) 96 10 <1.0 22.1 1.1

Zinc, unfiltered (μg/L) 96 60 <10 28.9 3

Sediment, suspended (percent finer than 0.062 mm) 97 88 43 71 71

Sediment, suspended concentration (mg/L) 97 106 1 17 7

Sediment, suspended discharge (ton/d) 97 87 .05 8.0 .92
106 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen

Period of record for water-quality data: July 1988–September 2008

Streamflow, instantaneous (ft3/s) 173 1,050 14 207 123

pH, onsite (standard units) 160 9.2 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 161 720 197 424 435

Temperature, water (°C) 172 23.5 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3) 159 370 81 185 190

Calcium, filtered (mg/L) 159 110 24.2 54.6 55.8

Magnesium, filtered (mg/L) 159 22.0 5.08 11.8 12.0

Arsenic, filtered (μg/L) 159 53 4 15.2 14.0

Arsenic, unfiltered (μg/L) 159 78 3 19.6 17.0

Cadmium, filtered (μg/L) 159 1.0 <.04 2.06 <1

Cadmium, unfiltered (μg/L) 159 3 <.1 2.19 <1

Copper, filtered (μg/L) 159 50 1.7 8.2 6.2

Copper, unfiltered (μg/L) 158 240 4.1 28.1 15.8

Iron, filtered (μg/L) 159 110 <3 215 11

Iron, unfiltered (μg/L) 159 9,200 56 487 270

Lead, filtered (μg/L) 159 3 <.08 2.15 <1

Lead, unfiltered (μg/L) 159 31.0 <1.0 23.45 1.83

Manganese, filtered (μg/L) 159 460 25.2 113 88.9

Manganese, unfiltered (μg/L) 159 1,400 47.3 237 180

Zinc, filtered (μg/L) 159 110 <1.0 29.8 5.0

Zinc, unfiltered (μg/L) 159 360 <10 239.1 20.0

Sediment, suspended (percent finer than 0.062 mm) 172 97 41 77 78

Sediment, suspended concentration (mg/L) 173 338 1 18 7

Sediment, suspended discharge (ton/d) 173 459 .12 20 2.3
Data 107

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323840--Lost Creek near Anaconda

Period of record for water-quality data: December 2004–September 2008

Streamflow, instantaneous (ft3/s) 31 28 0.37 7.4 5.2

pH, onsite (standard units) 31 8.6 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 31 253 136 205 213

Temperature, water (°C) 31 17.0 1.0 8.5 9.0

Hardness, filtered (mg/L as CaCO3) 31 120 50 96 100

Calcium, filtered (mg/L) 31 37.1 15.7 29.3 30.3

Magnesium, filtered (mg/L) 31 7.22 2.71 5.71 6.16

Arsenic, filtered (μg/L) 31 156 2.4 10.2 5.0

Arsenic, unfiltered (μg/L) 31 3,860 2 130 5.7

Cadmium, filtered (μg/L) 30 .90 <.04 2.06 .03

Cadmium, unfiltered (μg/L) 31 147 .01 4.8 .04

Copper, filtered (μg/L) 31 90.5 1.1 5.0 1.9

Copper, unfiltered (μg/L) 31 29,100 1.7 945 4.4

Iron, filtered (μg/L) 31 25 <6 29 8

Iron, unfiltered (μg/L) 31 99,700 22 3,370 92

Lead, filtered (μg/L) 31 .18 <.08 2.06 <.12

Lead, unfiltered (μg/L) 31 1,290 .10 42.3 .40

Manganese, filtered (μg/L) 31 42.4 <.2 22.6 1.1

Manganese, unfiltered (μg/L) 31 8,830 1.2 290 4.6

Zinc, filtered (μg/L) 31 30.0 <1.8 22.2 1.1

Zinc, unfiltered (μg/L) 31 7,780 1.0 254 3.0

Sediment, suspended (percent finer than 0.062 mm) 31 97 30 61 62

Sediment, suspended concentration (mg/L) 31 58,900 1 1,910 4

Sediment, suspended discharge (ton/d) 31 1,320 <.01 243 .07
108 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323850--Lost Creek near Galen

Period of record for water-quality data: March 2003–September 2008

Streamflow, instantaneous (ft3/s) 48 59 1.3 20 12

pH, onsite (standard units) 48 8.7 8.0 8.4 8.4

Specific conductance, onsite (μS/cm) 48 934 540 650 634

Temperature, water (°C) 48 26.5 0.0 11.5 11.2

Hardness, filtered (mg/L as CaCO3) 48 450 200 299 300

Calcium, filtered (mg/L) 48 122 48.5 83.8 84.9

Magnesium, filtered (mg/L) 48 35.7 17.8 21.9 21.1

Arsenic, filtered (μg/L) 48 41.8 6 14.1 12.2

Arsenic, unfiltered (μg/L) 48 43 6 14.7 12.8

Cadmium, filtered (μg/L) 47 .05 <.04 2.03 .02

Cadmium, unfiltered (μg/L) 48 .11 .01 .05 .04

Copper, filtered (μg/L) 48 6.7 .99 2.6 2.6

Copper, unfiltered (μg/L) 48 22.5 1.6 6.0 4.5

Iron, filtered (μg/L) 48 61 <6 212 8

Iron, unfiltered (μg/L) 48 293 14 100 76.5

Lead, filtered (μg/L) 47 .33 <.08 2.06 <.08

Lead, unfiltered (μg/L) 48 1.30 .04 .36 .26

Manganese, filtered (μg/L) 48 54.0 1.9 14.2 13.1

Manganese, unfiltered (μg/L) 48 56.5 2.2 18.7 14.8

Zinc, filtered (μg/L) 48 3.8 <1.0 21.5 1.2

Zinc, unfiltered (μg/L) 48 9 <2 23.0 2.0

Sediment, suspended (percent finer than 0.062 mm) 48 86 18 56 60

Sediment, suspended concentration (mg/L) 48 46 2 16 16

Sediment, suspended discharge (ton/d) 48 4.2 .01 1.0 .37
Data 109

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324200--Clark Fork at Deer Lodge

Period of record for water-quality data: March 1985–September 2008

Streamflow, instantaneous (ft3/s) 225 1,920 23 287 217

pH, onsite (standard units) 173 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 208 642 234 481 504

Temperature, water (°C) 224 23.0 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3) 165 280 95 204 220

Calcium, filtered (mg/L) 165 82.0 28.2 60.1 63.8

Magnesium, filtered (mg/L) 165 18.7 5.9 13.0 13.7

Arsenic, filtered (μg/L) 175 39 6.0 14.4 13.0

Arsenic, unfiltered (μg/L) 175 215 4.8 24.2 17.1

Cadmium, filtered (μg/L) 174 2 <.1 2.08 <1

Cadmium, unfiltered (μg/L) 175 5 <.1 2.42 <1

Copper, filtered (μg/L) 175 120 3.2 11.0 8.3

Copper, unfiltered (μg/L) 173 1,500 8.2 82.8 37.0

Iron, filtered (μg/L) 175 190 <3 214 9

Iron, unfiltered (μg/L) 175 29,000 27 1,520 510

Lead, filtered (μg/L) 175 6 <.08 2.33 <1

Lead, unfiltered (μg/L) 175 200 .33 210.9 4.60

Manganese, filtered (μg/L) 175 400 1.0 42.9 33.9

Manganese, unfiltered (μg/L) 175 4,600 11.9 246 140

Zinc, filtered (μg/L) 175 230 <10 212.1 8.3

Zinc, unfiltered (μg/L) 174 1,700 4 89.2 40

Sediment, suspended (percent finer than 0.062 mm) 216 99 37 71 73

Sediment, suspended concentration (mg/L) 225 2,250 1 71 22

Sediment, suspended discharge (ton/d) 225 8,690 .18 151 11
110 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324680--Clark Fork at Goldcreek

Period of record for water-quality data: March 1993–September 2008

Streamflow, instantaneous (ft3/s) 131 3,920 87 728 505

pH, onsite (standard units) 130 8.9 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 130 510 206 374 392

Temperature, water (°C) 131 23.0 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3) 130 230 86 164 170

Calcium, filtered (mg/L) 130 68.0 25.9 48.4 51.0

Magnesium, filtered (mg/L) 130 15.0 5.15 10.5 11.0

Arsenic, filtered (μg/L) 130 20 5.8 10.0 10.0

Arsenic, unfiltered (μg/L) 130 75 7 14.8 12

Cadmium, filtered (μg/L) 130 .2 <.04 2.04 <.1

Cadmium, unfiltered (μg/L) 130 2.0 <.1 2.17 .03

Copper, filtered (μg/L) 129 36.0 2.1 6.6 5.4

Copper, unfiltered (μg/L) 129 440 5.2 39.9 23.0

Iron, filtered (μg/L) 130 100 <3 218 11

Iron, unfiltered (μg/L) 130 12,000 27 848 422

Lead, filtered (μg/L) 129 .6 <.08 2.10 <.5

Lead, unfiltered (μg/L) 129 73.0 .14 25.54 2.80

Manganese, filtered (μg/L) 130 57.3 4.0 19.1 17.2

Manganese, unfiltered (μg/L) 130 1,100 10.5 123 86.4

Zinc, filtered (μg/L) 130 26 <1.0 25.6 3.5

Zinc, unfiltered (μg/L) 130 510 2 44.5 30

Sediment, suspended (percent finer than 0.062 mm) 131 94 43 75 78

Sediment, suspended concentration (mg/L) 131 752 1 48 21

Sediment, suspended discharge (ton/d) 131 7,960 .55 208 27
Data 111

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12331800--Clark Fork near Drummond

Period of record for water-quality data: March 1993–September 2008

Streamflow, instantaneous (ft3/s) 131 3,860 149 1,020 749

pH, onsite (standard units) 130 8.7 7.8 8.3 8.3

Specific conductance, onsite (μS/cm) 130 630 189 413 433

Temperature, water (°C) 131 22.5 .5 11.0 11.0

Hardness, filtered (mg/L as CaCO3) 130 300 74 186 195

Calcium, filtered (mg/L) 130 83.0 21.0 53.3 55.2

Magnesium, filtered (mg/L) 130 22.0 5.2 12.8 13.1

Arsenic, filtered (μg/L) 130 20 6.6 10.6 10.0

Arsenic, unfiltered (μg/L) 130 62 8 16.2 13.0

Cadmium, filtered (μg/L) 130 .30 <.04 2.05 <.1

Cadmium, unfiltered (μg/L) 130 2.0 <.1 2.22 .04

Copper, filtered (μg/L) 128 21.0 1.0 6.4 5.0

Copper, unfiltered (μg/L) 128 360 4.6 43.0 22.0

Iron, filtered (μg/L) 130 150 <3 218 8

Iron, unfiltered (μg/L) 129 8,800 20 994 457

Lead, filtered (μg/L) 126 1.2 <.08 2.16 <.60

Lead, unfiltered (μg/L) 126 56.0 <1.00 27.71 3.50

Manganese, filtered (μg/L) 130 60.7 3.3 16.7 14.6

Manganese, unfiltered (μg/L) 130 880 8.0 147 93.6

Zinc, filtered (μg/L) 130 21 <3 26.0 4.2

Zinc, unfiltered (μg/L) 130 490 2.9 61.2 31.0

Sediment, suspended (percent finer than 0.062 mm) 131 92 38 74 74

Sediment, suspended concentration (mg/L) 131 530 2 63 26

Sediment, suspended discharge (ton/d) 131 4,720 1.7 321 49
112 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for water-quality data: March 1985–September 2008

Streamflow, instantaneous (ft3/s) 228 9,560 296 1,860 1,110

pH, onsite (standard units) 174 8.8 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 203 483 139 302 315

Temperature, water (°C) 227 22.0 0.0 9.6 9.5

Hardness, filtered (mg/L as CaCO3) 164 200 54 132 130

Calcium, filtered (mg/L) 164 59.0 14.9 37.2 37.8

Magnesium, filtered (mg/L) 164 14.0 3.94 9.50 9.50

Arsenic, filtered (μg/L) 173 17 2.7 6.0 5.4

Arsenic, unfiltered (μg/L) 173 110 3 9.8 7.0

Cadmium, filtered (μg/L) 173 .10 <.04 2.03 <.1

Cadmium, unfiltered (μg/L) 173 4 <.01 2.26 <1

Copper, filtered (μg/L) 172 25 E1.1 4.8 3.9

Copper, unfiltered (μg/L) 171 500 2.7 34.7 15.5

Iron, filtered (μg/L) 173 190 <3 223 13

Iron, unfiltered (μg/L) 173 19,000 33 1,030 370

Lead, filtered (μg/L) 169 7 <.08 2.30 <1

Lead, unfiltered (μg/L) 169 100 <1.00 27.18 3.00

Manganese, filtered (μg/L) 173 37.4 <1.0 28.1 7.0

Manganese, unfiltered (μg/L) 173 2,000 8.9 123 60

Zinc, filtered (μg/L) 172 39 <3 26.0 4.0

Zinc, unfiltered (μg/L) 173 1,100 <10 260 30

Sediment, suspended (percent finer than 0.062 mm) 217 98 27 73 75

Sediment, suspended concentration (mg/L) 228 1,370 2 57 18

Sediment, suspended discharge (ton/d) 228 34,700 3.0 620 60
Data 113

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12340000--Blackfoot River near Bonner

Period of record for water-quality data: March 1985–September 2008

Streamflow, instantaneous (ft3/s) 165 13,400 344 2,640 1,310

pH, onsite (standard units) 125 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 142 294 131 208 204

Temperature, water (°C) 165 22.5 0.0 9.4 9.5

Hardness, filtered (mg/L as CaCO3) 118 140 55 103 98

Calcium, filtered (mg/L) 118 37.0 14.0 26.4 25.2

Magnesium, filtered (mg/L) 118 13.2 4.90 9.12 8.66

Arsenic, filtered (μg/L) 125 2 <1 2.97 .98

Arsenic, unfiltered (μg/L) 125 4 <1 21.2 1

Cadmium, filtered (μg/L) 125 1 <.04 -- <.1

Cadmium, unfiltered (μg/L) 125 2 <.01 2.10 <1

Copper, filtered (μg/L) 123 7.0 <1.0 21.4 .8

Copper, unfiltered (μg/L) 122 34 <1.0 25.0 2.2

Iron, filtered (μg/L) 125 100 <3 217 10

Iron, unfiltered (μg/L) 125 3,600 14 423 190

Lead, filtered (μg/L) 121 8 <.08 2.41 <.6

Lead, unfiltered (μg/L) 121 25.0 <.06 22.47 .06

Manganese, filtered (μg/L) 125 11.0 <1 22.4 2.0

Manganese, unfiltered (μg/L) 125 180 <10 228.9 18.6

Zinc, filtered (μg/L) 125 15 <.60 22.2 <20

Zinc, unfiltered (μg/L) 125 60 <1 25.8 <10

Sediment, suspended (percent finer than 0.062 mm) 163 98 42 80 82

Sediment, suspended concentration (mg/L) 165 271 1 28 8

Sediment, suspended discharge (ton/d) 165 7,670 1.1 499 30
114 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the upper Clark Fork basin, Montana, March 1985 through 

September 2008.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the laboratory reporting level to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12340500--Clark Fork above Missoula

Period of record for water-quality data: July 1986–September 2008

Streamflow, instantaneous (ft3/s) 194 21,600 720 4,380 2,380

pH, onsite (standard units) 151 8.8 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 171 399 142 254 261

Temperature, water (°C) 191 22.0 0.0 9.5 9.0

Hardness, filtered (mg/L as CaCO3) 151 170 60 117 120

Calcium, filtered (mg/L) 151 46.0 14.0 31.5 32.0

Magnesium, filtered (mg/L) 151 13.4 5.28 9.26 9.20

Arsenic, filtered (μg/L) 151 9 1 3.4 3.0

Arsenic, unfiltered (μg/L) 151 69 E1 5.4 4

Cadmium, filtered (μg/L) 151 .2 <.04 2.03 <.1

Cadmium, unfiltered (μg/L) 151 5.0 <.01 2.17 <1

Copper, filtered (μg/L) 150 12.6 E.7 2.8 2.0

Copper, unfiltered (μg/L) 149 400 2.0 19.9 8.1

Iron, filtered (μg/L) 151 200 <3 221 14

Iron, unfiltered (μg/L) 151 13,000 43 633 234

Lead, filtered (μg/L) 145 1.2 <.08 2.15 <1

Lead, unfiltered (μg/L) 146 78.0 <1.00 23.56 1.55

Manganese, filtered (μg/L) 151 230 6.2 17.1 14.2

Manganese, unfiltered (μg/L) 151 1,100 10 65.7 40

Zinc, filtered (μg/L) 151 16 <1.0 23.7 2.3

Zinc, unfiltered (μg/L) 151 1,100 <10 234.8 15

Sediment, suspended (percent finer than 0.062 mm) 189 99 14 84 89

Sediment, suspended concentration (mg/L) 194 950 2 43 12

Sediment, suspended discharge (ton/d) 194 21,900 5.8 1,020 82

1

Differing less-than (<) values for an individual constituent are the result of changes in the laboratory reporting level during the period of record.

2

Value for the mean is estimated by using a log-probability regression to predict the values of data less than the laboratory reporting level (Helsel and Cohn, 

1988).
Data 115

Table 26. Statistical summary of long-term bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through August 

2008.—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 are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12323600--Silver Bow Creek at Opportunity

Period of record for bed-sediment data: 1992–2008

Arsenic 6 186 119 152 158

Cadmium 17 43.9 22.8 32.3 30.1

Chromium 15 38.6 16.8 25.8 25.5

Copper 17 9,020 2,480 4,560 4,560

Iron 17 45,300 28,200 35,900 34,600

Lead 17 1,030 381 682 752

Manganese 17 9,220 1,680 3,580 2,900

Nickel 16 21.4 12.0 15.0 14.8

Silver 12 20.0 8.3 15.5 15.8

Zinc 17 13,400 4,950 7,880 7,130

12323750--Silver Bow Creek at Warm Springs

Period of record for bed-sediment data: 1992–2008

Arsenic 6 177 67 116 106

Cadmium 17 12.2 4.2 7.3 6.6

Chromium 15 34.1 <15.7 120.5 119.5

Copper 17 769 169 348 286

Iron 17 31,700 15,400 22,700 21,700

Lead 17 100 49 71 73

Manganese 17 17,700 1,470 8,170 8,150

Nickel 16 19.1 9.2 14.7 14.6

Silver 12 4.4 .3 11.9 11.8

Zinc 17 2,220 620 976 728

12323770--Warm Springs Creek at Warm Springs

Period of record for bed-sediment data: 1995, 1997, 1999, 2002, 2005, 2008

Arsenic 2 66 52 59 --

Cadmium 6 5.8 1.3 3.6 3.6

Chromium 6 39.3 27.5 31.9 31.1

Copper 6 1,060 779 908 887

Iron 6 26,600 16,800 21,700 21,900

Lead 6 86 67 81 83

Manganese 6 12,100 2,020 7,950 8,280

Nickel 6 25.5 17.6 20.2 19.4

Silver 4 5.1 3.1 3.8 3.5

Zinc 6 453 372 405 405
116 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 26. Statistical summary of long-term bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through August 

2008.—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 are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen

Period of record for bed-sediment data: 1987, 1991–2008

Arsenic 6 119 87 106 109

Cadmium 19 20.1 4.0 8.9 7.6

Chromium 15 35.7 19.1 27.1 26.4

Copper 19 2,300 838 1,210 1,110

Iron 19 39,800 22,600 27,800 27,000

Lead 19 235 92 136 131

Manganese 19 17,300 2,780 10,200 11,900

Nickel 16 23.2 13.9 18.5 18.3

Silver 14 7.3 <3.2 14.4 14.5

Zinc 19 3,560 999 1,520 1,160

461415112450801--Clark Fork below Lost Creek, near Galen

Period of record for bed-sediment data: 1996–2008

Arsenic 6 204 92 124 110

Cadmium 13 10.5 5.2 7.4 6.8

Chromium 12 34.5 20.5 28.0 27.3

Copper 13 2,050 1,150 1,510 1,440

Iron 13 32,800 24,400 29,600 30,800

Lead 13 218 127 171 170

Manganese 13 9,820 3,540 6,170 5,890

Nickel 13 19.9 11.7 16.0 16.3

Silver 8 7.8 4.2 6.5 6.7

Zinc 13 1,680 1,120 1,360 1,360

461559112443301--Clark Fork at county bridge, near Racetrack

Period of record for bed-sediment data: 1996–2008

Arsenic 6 101 56 79 83

Cadmium 13 8.7 5.0 6.8 6.4

Chromium 12 33.3 19.0 25.7 26.3

Copper 13 1,610 933 1,220 1,240

Iron 13 31,700 21,200 26,800 28,100

Lead 13 186 103 142 142

Manganese 13 6,310 2,100 3,570 3,330

Nickel 13 18.4 10.3 14.0 14.5

Silver 8 6.1 <3.3 15.0 15.4

Zinc 13 1,550 999 1,210 1,170
Data 117

Table 26. Statistical summary of long-term bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through August 

2008.—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 are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for bed-sediment data: 1996–2008

Arsenic 6 91 58 75 75

Cadmium 13 10.3 4.3 6.6 6.0

Chromium 12 34.1 16.0 25.1 24.8

Copper 13 1,580 721 1,070 1,030

Iron 13 33,700 20,600 26,500 25,300

Lead 13 155 92 129 130

Manganese 13 8,370 1,810 4,300 3,910

Nickel 13 16.9 8.7 13.0 12.7

Silver 8 6.2 2.7 4.9 5.0

Zinc 13 1,570 900 1,160 1,160

12324200--Clark Fork at Deer Lodge

Period of record for bed-sediment data: 1986–87, 1990–2008

Arsenic 6 77 49 65 66

Cadmium 21 10.0 3.8 6.3 5.6

Chromium 15 43.9 19.5 29.4 28.2

Copper 21 4,180 683 1,270 1,040

Iron 21 35,300 21,100 26,900 26,100

Lead 21 242 103 147 146

Manganese 21 6,020 1,110 2,780 2,460

Nickel 16 21.1 11.5 14.8 13.3

Silver 16 7.9 2.4 4.7 4.5

Zinc 21 1,730 846 1,220 1,230

12324680--Clark Fork at Goldcreek

Period of record for bed-sediment data: 1992–2008

Arsenic 6 44 23 33 34

Cadmium 17 8.1 2.6 4.8 4.9

Chromium 15 48.9 21.3 31.1 31.6

Copper 17 1,080 338 658 675

Iron 17 30,600 15,500 23,200 23,700

Lead 17 152 52 93 93

Manganese 17 2,610 1,160 1,880 1,840

Nickel 16 18.6 9.0 14.1 14.5

Silver 12 4.8 2.3 3.3 3.2

Zinc 17 1,320 584 930 1,070
118 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 26. Statistical summary of long-term bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through August 

2008.—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 are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12331800--Clark Fork near Drummond

Period of record for bed-sediment data: 1986–87, 1991–2008

Arsenic 6 45 31 34 32

Cadmium 20 7.7 2.6 4.6 4.4

Chromium 15 35.4 17.0 27.9 30.1

Copper 20 747 303 479 470

Iron 20 39,200 16,500 22,500 21,800

Lead 20 135 59 89 84

Manganese 20 4,820 1,150 2,160 1,900

Nickel 16 16.8 9.3 13.4 13.7

Silver 15 4.7 <3.2 13.0 12.9

Zinc 20 1,230 673 968 975

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for bed-sediment data: 1986, 1991–2008

Arsenic 6 32 19 25 23

Cadmium 19 7.3 1.9 3.7 3.6

Chromium 15 34.7 15.3 24.5 26.7

Copper 19 635 211 350 322

Iron 19 24,600 12,600 18,700 17,300

Lead 19 115 47 68 63

Manganese 19 2,270 671 1,270 1,260

Nickel 16 19.1 6.9 12.2 11.4

Silver 14 3.9 <1.9 12.1 11.9

Zinc 19 1,160 584 818 786

12340000--Blackfoot River near Bonner

Period of record for bed-sediment data: 1986–87, 1991, 1993–96, 1998–2001, 2003, 2006–08

Arsenic 4 6 2 4 3

Cadmium 15 2.0 <.2 1.6 1.4

Chromium 11 28.5 15.1 21.6 22.0

Copper 15 27 11 20 21

Iron 15 23,000 12,400 17,600 18,100

Lead 15 20 <13 113 113

Manganese 15 746 298 531 542

Nickel 12 14.3 6.0 11.4 11.8

Silver 12 <1.9 <.3 1.5 1<.6

Zinc 15 82 35 61 63
Data 119

Table 26. Statistical summary of long-term bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through August 

2008.—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 are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12340500--Clark Fork above Missoula

Period of record for bed-sediment data: 1997–2008

Arsenic 6 54 17 36 34

Cadmium 12 5.8 1.5 3.4 3.5

Chromium 11 33.0 19.0 25.9 26.2

Copper 12 551 166 373 368

Iron 12 27,000 18,100 21,000 20,600

Lead 12 78 37 57 58

Manganese 12 2,250 477 1,100 1,070

Nickel 12 15.8 7.6 12.6 12.8

Silver 7 2.9 .8 12.0 12.1

Zinc 12 1,090 438 764 777

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

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323600--Silver Bow Creek at Opportunity

Period of record for biological data: 1992, 1994–95, 1997–2008

Brachycentrus spp.

Arsenic 0 -- -- -- --

Cadmium 5 12.5 5.8 10.1 11.6

Chromium 5 5.9 .7 2.1 .9

Copper 5 846 235 587 592

Iron 5 1,190 335 617 469

Lead 5 21.5 7.4 13.7 13.8

Manganese 5 817 231 515 503

Nickel 5 2.1 <.1 11.3 11.6

Zinc 5 995 629 803 815

Hydropsyche cockerelli

Arsenic 10 20.4 9.5 13.5 12.7

Cadmium 16 9.7 3.1 5.7 5.4

Chromium 16 8.0 1.0 3.0 2.6

Copper 16 1,090 269 440 410

Iron 16 4,950 689 1,970 1,890

Lead 16 68.3 19.0 36.5 39.0

Manganese 16 3,030 180 1,030 975

Nickel 16 3.6 .7 2.2 2.1

Zinc 16 1,590 619 913 868

Hydropsyche spp.

Arsenic 8 23.1 10.7 15.7 15.1

Cadmium 13 11.0 4.2 6.6 5.7

Chromium 13 4.7 .6 2.3 2.8

Copper 13 930 312 547 469

Iron 13 3,250 1,050 2,050 2,110

Lead 13 237 21.8 55.0 40.4

Manganese 13 1,340 712 1,090 1,060

Nickel 13 2.7 .7 2.2 2.4

Zinc 13 1,290 784 1,020 1,080
Data 121

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323600--Silver Bow Creek at Opportunity—Continued

Period of record for biological data: 1992, 1994–95, 1997–2008

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: 1992–2008

Hydropsyche cockerelli

Arsenic 11 23.6 7.9 13.5 13.3

Cadmium 37 2.1 .2 .6 .5

Chromium 37 4.3 .4 1.1 .8

Copper 37 97.0 16.7 37.4 29.9

Iron 37 1,590 351 785 761

Lead 37 5.7 .3 3.0 2.9

Manganese 37 3,890 491 1,320 1,110

Nickel 37 1.8 .3 .9 .8

Zinc 37 276 115 174 167

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 13.8 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
122 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323750--Silver Bow Creek at Warm Springs—Continued

Period of record for biological data: 1992–2008

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, 2008

Arctopsyche grandis

Arsenic 3 9.8 9.5 9.6 9.6

Cadmium 7 3.6 1.9 2.8 3.0

Chromium 7 2.9 .8 2.0 1.8

Copper 7 133 78.3 109 102

Iron 7 1,350 684 980 1,040

Lead 7 7.2 3.0 15.2 15.3

Manganese 7 3,560 1,340 2,540 2,480

Nickel 7 3.5 1.8 12.5 12.3

Zinc 7 267 181 206 197

Hydropsyche occidentalis

Arsenic 3 13.6 12.7 13.2 13.3

Cadmium 5 1.3 .7 1.0 1.2

Chromium 5 8.6 .3 3.8 3.2

Copper 5 183 125 158 165

Iron 5 2,360 1,590 1,940 1,950

Lead 5 12.6 6.7 8.5 7.7

Manganese 5 3,190 2,400 2,800 2,880

Nickel 5 4.5 2.0 3.0 3.0

Zinc 5 204 148 169 166
Data 123

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323770--Warm Springs Creek at Warm Springs—Continued

Period of record for biological data: 1995, 1997, 1999, 2002, 2005, 2008

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, 1991–2008

Claassenia sabulosa

Arsenic 1 -- -- 2.0 --

Cadmium 1 -- -- .2 --

Chromium 1 -- -- 1.5 --

Copper 1 -- -- 54.7 --

Iron 1 -- -- 242 --

Lead 1 -- -- 1.0 --

Manganese 1 -- -- 323 --

Nickel 1 -- -- .5 --

Zinc 1 -- -- 237 --

Hydropsyche cockerelli

Arsenic 8 15.8 13.2 14.1 13.8

Cadmium 33 2.7 .7 1.5 1.5

Chromium 33 4.4 .8 1.9 1.7

Copper 33 181 48.7 105 102

Iron 33 2,660 816 1,470 1,400

Lead 33 11.8 1.2 8.1 7.8

Manganese 33 3,620 1,070 2,250 2,200

Nickel 33 6.5 .9 1.8 1.6

Zinc 33 299 136 210 205
124 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991–2008

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 8 16.5 12.5 14.6 14.8

Cadmium 40 1.7 .6 1.1 1.1

Chromium 40 6.6 .4 2.0 1.6

Copper 40 121 49.2 83.3 82.8

Iron 40 1,920 642 1,300 1,270

Lead 40 13.5 1.6 7.3 6.9

Manganese 40 6,170 1,220 2,760 2,310

Nickel 40 3.5 .8 1.6 1.6

Zinc 40 286 168 202 197

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 --
Data 125

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991–2008

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: 1996–2008

Claassenia sabulosa

Arsenic 1 -- -- 1.5 --

Cadmium 2 0.4 0.3 .4 --

Chromium 2 1.9 .4 1.2 --

Copper 2 70.1 67.1 68.6 --

Iron 2 209 189 199 --

Lead 2 1.2 .7 1.0 --

Manganese 2 238 90.4 164 --

Nickel 2 .2 <.2 1.1 --

Zinc 2 245 208 226 --

Hydropsyche cockerelli

Arsenic 11 27.8 8.8 14.3 11.6

Cadmium 22 2.8 1.1 1.8 1.6

Chromium 22 3.6 .8 2.0 2.0

Copper 22 338 48.8 134 113

Iron 22 4,080 691 1,530 1,180

Lead 22 28.6 4.5 11.6 9.0

Manganese 22 3,160 1,230 1,850 1,720

Nickel 22 2.8 .9 1.4 1.2

Zinc 22 339 151 228 223
126 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

461415112450801--Clark Fork below Lost Creek, near Galen—Continued

Period of record for biological data: 1996–2008

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: 1996–2008

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 --
Data 127

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

461559112443301--Clark Fork at county bridge, near Racetrack—Continued

Period of record for biological data: 1996–2008

Hydropsyche cockerelli

Arsenic 10 20.2 11.1 14.1 13.1

Cadmium 21 2.0 .8 1.5 1.5

Chromium 21 2.8 .6 1.7 1.4

Copper 21 198 50.0 102 98.2

Iron 21 3,330 657 1,270 992

Lead 21 17.2 3.7 8.7 7.5

Manganese 21 2,360 646 1,630 1,900

Nickel 21 2.0 .7 1.2 1.0

Zinc 21 302 139 193 186

Hydropsyche occidentalis

Arsenic 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 12.3 --

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

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for biological data: 1996–2008

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 8 18.8 8.0 12.3 10.3

Cadmium 17 2.0 .7 1.3 1.3

Chromium 17 4.0 .5 1.5 1.3

Copper 17 198 60.7 105 88.5

Iron 17 2,310 552 1,090 875

Lead 17 17.7 3.5 7.9 6.8

Manganese 17 2,650 487 1,380 1,230

Nickel 17 2.1 .5 1.1 1.0

Zinc 17 275 162 204 188

Hydropsyche occidentalis

Arsenic 8 24.0 10.2 15.0 14.4

Cadmium 25 2.4 .7 1.3 1.2

Chromium 25 6.2 .8 2.1 1.9

Copper 25 238 74.9 110 91.4

Iron 25 3,390 940 1,570 1,500

Lead 25 21.8 6.1 11.7 11.4

Manganese 25 4,460 826 2,730 2,420

Nickel 25 2.4 1.2 1.5 1.5

Zinc 25 386 211 266 240
Data 129

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack—Continued

Period of record for biological data: 1996–2008

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, 1990–2008

Arctopsyche grandis

Arsenic 0 -- -- -- --

Cadmium 2 2.4 <4.2 12.2 --

Chromium 2 1.0 <1.3 1.8 --

Copper 2 69.1 34.9 52.0 --

Iron 2 676 537 606 --

Lead 2 <7.8 3.8 13.8 --

Manganese 2 727 380 554 --

Nickel 2 <1.7 <1.3 1-- --

Zinc 2 178 140 159 --

Hydropsyche cockerelli

Arsenic 6 11.4 5.8 8.2 7.8

Cadmium 29 3.5 .6 1.4 1.3

Chromium 29 3.2 .4 1.6 1.7

Copper 29 180 54.7 98.2 98.2

Iron 29 3,340 490 1,120 1,040

Lead 29 18.1 3.8 9.5 8.9

Manganese 29 1,570 396 879 815

Nickel 29 2.4 .3 1.1 1.0

Zinc 29 391 132 190 185
130 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12324200--Clark Fork at Deer Lodge—Continued

Period of record for biological data: 1986–87, 1990–2008

Hydropsyche occidentalis

Arsenic 10 12.4 6.6 9.8 9.4

Cadmium 47 3.4 .6 1.4 1.3

Chromium 47 3.6 .6 1.9 1.9

Copper 47 180 49.4 117 112

Iron 47 2,060 557 1,390 1,420

Lead 47 18.6 3.5 11.2 11.2

Manganese 47 2,850 649 1,740 1,730

Nickel 47 12.9 1.0 1.7 1.4

Zinc 47 346 166 246 238

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: 1992–2008

Arctopsyche grandis

Arsenic 22 6.4 1.8 3.7 3.1

Cadmium 51 6.6 .6 1.9 1.6

Chromium 51 3.3 .1 1.2 1.0

Copper 51 129 19.9 41.6 32.0

Iron 51 2,360 195 635 482

Lead 51 10.9 1.0 3.3 3.0

Manganese 51 1,580 436 846 842

Nickel 51 1.8 .2 .7 .6

Zinc 51 326 146 194 180
Data 131

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12324680--Clark Fork at Goldcreek—Continued

Period of record for biological data: 1992–2008

Claassenia sabulosa

Arsenic 15 2.1 0.4 1.3 1.4

Cadmium 35 3.5 .1 1.0 .7

Chromium 35 1.6 .2 .6 .5

Copper 35 81.7 33.0 57.9 57.1

Iron 35 567 63.0 184 158

Lead 35 1.8 .4 .9 .8

Manganese 35 320 50.6 155 142

Nickel 35 .7 .1 .3 .3

Zinc 35 351 166 263 258

Hydropsyche cockerelli

Arsenic 14 8.2 4.1 5.4 5.3

Cadmium 33 2.6 .5 1.3 1.2

Chromium 33 4.7 .5 2.0 1.9

Copper 33 188 17.1 69.2 57.6

Iron 33 3,250 522 1,090 813

Lead 33 16.2 2.4 6.2 5.2

Manganese 33 1,710 538 986 954

Nickel 33 2.3 .3 1.2 1.0

Zinc 33 269 106 186 184

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

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12324680--Clark Fork at Goldcreek—Continued

Period of record for biological data: 1992–2008

Hydropsyche occidentalis

Arsenic 6 6.7 4.7 5.4 5.2

Cadmium 21 2.3 .4 1.3 1.3

Chromium 21 3.9 .4 1.6 1.7

Copper 21 156 26.4 63.0 57.6

Iron 21 2,720 466 1,100 1,040

Lead 21 15.7 2.9 6.7 5.7

Manganese 21 2,210 530 1,270 1,280

Nickel 21 2.5 .8 1.2 1.0

Zinc 21 277 97.0 199 203

12331800--Clark Fork near Drummond

Period of record for biological data: 1986, 1991–2008

Arctopsyche grandis

Arsenic 14 4.4 2.3 3.3 3.4

Cadmium 46 3.8 .4 1.3 1.1

Chromium 46 2.5 .2 .9 1.0

Copper 46 89.2 16.9 31.9 27.6

Iron 46 1,660 193 552 493

Lead 46 11.8 1.6 4.3 3.9

Manganese 46 2,010 456 835 733

Nickel 46 1.9 .2 .6 .6

Zinc 46 308 140 188 183

Claassenia sabulosa

Arsenic 13 1.8 0.7 1.2 1.2

Cadmium 49 2.8 .1 1.0 .9

Chromium 49 3.3 .2 .7 .6

Copper 49 165 18.0 65.2 60.6

Iron 49 387 45.4 161 141

Lead 49 2.9 .2 1.0 .8

Manganese 49 748 33.1 190 153

Nickel 49 1.1 .1 1.3 1.2

Zinc 49 567 103 274 261
Data 133

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12331800--Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991–2008

Hydropsyche cockerelli

Arsenic 10 6.4 3.9 5.0 4.7

Cadmium 39 2.3 .3 1.1 .8

Chromium 39 3.5 .4 1.6 1.6

Copper 39 156 30.0 58.2 51.1

Iron 39 2,500 506 1,140 969

Lead 39 15.0 4.8 8.1 7.4

Manganese 39 1,680 549 1,000 924

Nickel 39 2.0 .5 1.1 1.1

Zinc 39 248 134 193 186

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 10 6.9 4.3 5.2 5.1

Cadmium 26 2.0 .4 1.0 1.0

Chromium 26 8.1 .4 2.2 2.1

Copper 26 118 13.3 55.0 55.1

Iron 26 2,060 424 1,200 1,180

Lead 26 14.0 3.0 8.4 8.0

Manganese 26 2,920 619 1,490 1,220

Nickel 26 2.4 .5 1.3 1.2

Zinc 26 293 157 221 214
134 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12331800--Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991–2008

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, 1991–2008

Arctopsyche grandis

Arsenic 19 5.1 3.1 4.4 4.4

Cadmium 61 2.7 .4 1.1 .8

Chromium 61 4.1 .5 1.6 1.5

Copper 61 125 20.1 37.1 31.5

Iron 61 2,870 372 906 790

Lead 61 13.2 1.6 4.2 3.4

Manganese 61 902 324 642 660

Nickel 61 2.6 .4 1.1 .9

Zinc 61 276 111 197 196

Claassenia sabulosa

Arsenic 13 1.9 0.5 1.1 1.1

Cadmium 39 2.5 .1 .9 .8

Chromium 39 2.0 .2 .7 .6

Copper 39 95.1 37.5 59.3 55.0

Iron 39 340 58.6 120 107

Lead 39 1.6 .2 .6 .6

Manganese 39 229 37.2 94.6 79.4

Nickel 39 .6 .04 .2 .2

Zinc 39 342 144 230 235
Data 135

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12334550--Clark Fork at Turah Bridge, near Bonner—Continued

Period of record for biological data: 1986, 1991–2008

Hydropsyche cockerelli

Arsenic 14 5.2 3.7 4.6 4.8

Cadmium 42 1.8 .3 .8 .7

Chromium 42 8.0 .2 2.0 1.6

Copper 42 118 26.4 48.0 43.9

Iron 42 2,530 566 1,200 1,100

Lead 42 12.1 2.2 5.2 5.0

Manganese 42 805 426 632 656

Nickel 42 2.6 .6 1.2 1.2

Zinc 42 228 119 186 191

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 2 1.3 1.1 1.2 --

Chromium 2 4.6 2.4 3.5 --

Copper 2 84.1 26.8 55.4 --

Iron 2 1,800 986 1,390 --

Lead 2 6.6 <7.8 15.2 --

Manganese 2 1,320 537 928 --

Nickel 2 1.7 1.3 1.5 --

Zinc 2 231 171 201 --

Hydropsyche occidentalis

Arsenic 10 5.9 3.6 4.3 4.2

Cadmium 30 1.8 .3 .8 .8

Chromium 30 3.2 .6 1.8 1.6

Copper 30 102 27.4 47.5 43.9

Iron 30 2,310 472 1,200 1,130

Lead 30 14.2 3.0 6.2 5.6

Manganese 30 1,600 454 858 769

Nickel 30 3.2 .6 1.2 1.2

Zinc 30 416 145 212 220
136 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12334550--Clark Fork at Turah Bridge, near Bonner—Continued

Period of record for biological data: 1986, 1991–2008

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, 2006–08

Arctopsyche grandis

Arsenic 4 4.6 2.2 2.9 2.5

Cadmium 14 .4 .1 .2 .2

Chromium 9 6.9 .8 2.3 1.4

Copper 14 16.2 9.9 12.6 12.2

Iron 14 1,230 108 649 664

Lead 14 2.3 .5 1.1 .9

Manganese 9 633 286 472 476

Nickel 9 3.7 .7 1.3 1.0

Zinc 14 156 123 138 138

Claassenia sabulosa

Arsenic 5 3.0 0.3 1.4 1.4

Cadmium 16 .2 .1 .1 .1

Chromium 11 5.2 .3 1.1 .7

Copper 16 88.5 19.0 43.4 42.5

Iron 16 265 46.2 132 120

Lead 16 .8 .1 .4 .3

Manganese 11 133 26.3 78.6 72.2

Nickel 11 1.1 .1 .3 .3

Zinc 16 328 117 221 203
Data 137

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12340000--Blackfoot River near Bonner—Continued

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006–08

Hydropsyche cockerelli

Arsenic 3 3.1 2.4 2.9 3.0

Cadmium 3 .4 <.1 1.3 1.3

Chromium 3 3.8 2.4 3.3 3.6

Copper 3 16.2 5.6 12.4 15.5

Iron 3 1,990 1,640 1,860 1,960

Lead 3 2.3 2.0 2.1 2.1

Manganese 3 814 637 723 716

Nickel 3 4.6 1.8 2.8 1.9

Zinc 3 142 140 141 140

Hydropsyche occidentalis

Arsenic 4 3.8 1.9 2.8 2.8

Cadmium 16 .5 .1 .2 .2

Chromium 16 5.8 .8 2.2 1.9

Copper 16 20.6 12.0 14.9 14.6

Iron 16 1,930 1,060 1,450 1,480

Lead 16 2.0 .8 1.4 1.6

Manganese 16 798 414 532 492

Nickel 16 4.9 .9 1.6 1.4

Zinc 16 163 116 139 143

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

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12340500--Clark Fork above Missoula

Period of record for biological data: 1997–2008

Arctopsyche grandis

Arsenic 16 4.7 2.1 3.5 3.5

Cadmium 35 1.8 .1 .7 .6

Chromium 35 3.4 .6 1.6 1.5

Copper 35 77.6 19.5 36.1 34.9

Iron 35 2,340 476 968 892

Lead 35 6.8 1.2 4.0 3.8

Manganese 35 1,410 476 938 929

Nickel 35 2.0 .5 1.1 1.0

Zinc 35 260 133 191 192

Claassenia sabulosa

Arsenic 10 1.9 0.7 1.4 1.5

Cadmium 19 2.0 .2 .7 .4

Chromium 19 1.4 .3 .8 .8

Copper 19 71.7 33.0 51.7 47.3

Iron 19 402 95.3 245 246

Lead 19 3.1 .5 1.2 1.1

Manganese 19 683 75.2 232 190

Nickel 19 .5 <.3 1.4 1.4

Zinc 19 363 191 280 271

Hydropsyche cockerelli

Arsenic 13 8.0 3.6 6.2 6.5

Cadmium 22 1.3 .4 .9 1.0

Chromium 22 6.0 1.8 3.1 3.2

Copper 22 97.9 29.9 65.2 61.1

Iron 22 3,590 1,400 2,110 2,060

Lead 22 11.8 4.2 7.7 7.4

Manganese 22 1,910 781 1,300 1,280

Nickel 22 2.4 1.4 1.8 1.8

Zinc 22 266 156 218 219
Data 139

Table 27. Statistical summary of long-term biological data for the upper Clark Fork basin, Montana, August 1986 

through August 2008.—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 arbitrarily listed in the 

“Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986–89, Hydropsyche species statistics for 

stations sampled during those years are based on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 1986–98 were depurated 

prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may 

be small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more 

similar species. Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient 

data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12340500--Clark Fork above Missoula—Continued

Period of record for biological data: 1997–2008

Hydropsyche occidentalis

Arsenic 5 6.5 3.9 5.8 6.2

Cadmium 11 1.2 .4 .8 .7

Chromium 11 5.5 2.0 3.4 3.1

Copper 11 76.5 30.3 55.4 58.6

Iron 11 2,540 1,450 2,060 2,210

Lead 11 11.1 4.0 7.3 7.4

Manganese 11 2,460 939 1,870 1,930

Nickel 11 2.4 1.6 2.0 2.0

Zinc 11 278 192 236 232

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:

Director, USGS Montana Water Science Center

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 2007 through September 2008) and Statistical Summaries of Long-Term Data

for Streams in the Clark Fork Basin, Montana—Open-File Report 2009–1178

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