Missoula

Butte

Deer Lodge

Clark

Fork

MONTANA

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2006-1266

In cooperation with the U.S. Environmental Protection Agency

Water-Quality, Bed-Sediment, and Biological Data 

(October 2004 through September 2005) and 

Statistical Summaries of Data for Streams in the 

Upper Clark Fork Basin, Montana
COVER PHOTOGRAPHS: Banner: Lost Creek near Galen, Mont. (12323850).

 Left: Gage house at Blackfoot River near Bonner, Mont. (12340000).

 Center: Gage house at Clark Fork near Drummond, Mont. (12331800).

 Lower: Gage house at Lost Creek near Galen, Mont. (12323850).

 Photographs by Kent A. Dodge, U.S. Geological Survey, taken in 

 the spring of 2006.
Water-Quality, Bed-Sediment, and 

Biological Data (October 2004 through 

September 2005) and Statistical 

Summaries of Data for Streams in the 

Upper Clark Fork Basin, Montana

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

Open-File Report 2006-1266

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2006

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Suggested citation:

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

through September 2005) and statistical summaries of data for streams in the upper Clark Fork basin, Montana: 

U.S. Geological Survey Open-File Report 2006-1266, 109 p.
iii

Contents

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

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

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

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

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

Results ....................................................................................................................................................7

Quality Assurance.................................................................................................................................7

Bed-Sediment Data .....................................................................................................................................10

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

Results ..................................................................................................................................................10

Quality Assurance...............................................................................................................................10

Biological Data.............................................................................................................................................11

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

Results ..................................................................................................................................................12

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

Statistical Summaries of Data ...................................................................................................................12

References Cited..........................................................................................................................................13

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

Figure

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

Tables

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

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

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

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

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

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

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

through September 2005............................................................................................................18

5–7. Daily mean streamflow and suspended-sediment data, October 2004 through 

September 2005, for:

5. Clark Fork at Deer Lodge, Montana................................................................................36

6. Clark Fork at Turah Bridge, near Bonner, Montana .....................................................40

7. Clark Fork above Missoula, Montana.............................................................................44

8. Analyses of field replicates for water samples, upper Clark Fork basin, Montana ........48

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

Montana .......................................................................................................................................51

.....
iv

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

Clark Fork basin, Montana ........................................................................................................52

11. Recovery efficiency for analyses of laboratory-spiked deionized-water blanks ............52

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

Clark Fork basin, Montana ........................................................................................................53

13. Analyses of field blanks for water samples ...........................................................................54

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

August 2005..................................................................................................................................55

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

sediment.......................................................................................................................................56

16. Analyses of procedural blanks for bed sediment..................................................................57

17. Analyses of biota, upper Clark Fork basin, Montana, August 2005....................................58

18. Recovery efficiency for analyses of standard reference material for biota ....................60

19. Analyses of procedural blanks for biota.................................................................................61

20. Statistical summary of water-quality data for the upper Clark Fork basin, 

Montana, March 1985 through September 2005 ...................................................................62

21. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork 

basin, Montana, August 1986 through August 2005..............................................................80

22. Statistical summary of biological data for the upper Clark Fork basin, Montana, 

August 1986 through August 2005............................................................................................86

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)

foot (ft) 0.3048 meter (m)

gallon (gal) 3.785 liter (L)

gallon (gal) 3,785 milliliter (mL)

inch (in.) 25.4 millimeter (mm)

inch (in.) 25,400 micrometer (μm)

mile (mi) 1.609 kilometer (km)

ounce (oz) 28.35 gram (g)

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

square mile (mi2

) 2.59 square kilometer (km2)

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

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 2005 is the period from October 1, 2004, through September 30, 2005.

Abbreviated water-quality units used in this report:

μg/g micrograms per gram

μg/L micrograms per liter

μg/mL micrograms per milliliter

μm micrometer

μS/cm microsiemens per centimeter at 25 degrees Celsius

mg/L milligrams per liter

ppm part per million

Acronyms used in this report:

ICAPES inductively coupled argon plasma-emission spectroscopy

LRL laboratory reporting level

LT-MDL long-term method detection level

NWQL USGS National Water Quality Laboratory, Denver, Colo.

RSD relative standard deviation

spp. species

SRM standard reference material

USGS U.S. Geological Survey
Water-Quality, Bed-Sediment, and Biological Data 

(October 2004 through September 2005) and Statistical 

Summaries of Data for Streams in the Upper Clark Fork 

Basin, Montana

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

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

six major tributaries enter: Blacktail Creek, Warm Springs 

Creek, Little Black­foot River, Flint Creek, Rock Creek, and 

Blackfoot River. Prin­cipal surface-water uses in the 6,000-mi2

Clark Fork basin above Missoula include irrigation, stock 

watering, light indus­try, hydroelectric power generation, and 

habitat for trout fisher­ies. Current land uses primarily are 

cattle production, logging, mining, residential development, 

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

years, but are now either discontin­ued or substantially smaller 

in scale.

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

Bow and Warm Springs Creeks from about 1870 to 1980. 

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

of most of the major tributaries to the upper Clark Fork. Tailings derived from past mineral processing commonly contain 

large quantities of trace elements such as arsenic, cadmium, 

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

stream sediment, transported downstream, and deposited in 

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

Ponds and Milltown Reservoir. The widely dispersed tailings 

continue to be re-eroded, transported, and redeposited along 

the stream channel and flood plain, especially during high 

flows. The occurrence of elevated trace-element concentrations in water and bed sediment can pose a potential risk to 

aquatic biota and human health.

Concern about the potential toxicity of trace elements to 

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

the aquatic resources in the upper Clark Fork basin to guide 

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

was considered necessary to detect trends over time in order to 

eval­uate the effectiveness of remediation. Water-quality data 

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

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

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

Abstract

Water, bed sediment, and biota were sampled in streams 

from Butte to below Missoula as part of a long-term monitoring program, conducted in cooperation with the U.S. Environmental Protection Agency, to characterize aquatic resources 

in the upper Clark Fork basin of western Montana. Sampling 

sites were located on the Clark Fork, six major tributaries, 

and three smaller tributaries. Water-quality samples were 

collected periodically at 18 sites during October 2004 through 

September 2005 (water year 2005). Bed-sediment and biological samples were collected once in August 2005. The primary 

constituents analyzed were trace elements associated with 

tailings from historical mining and smelting activities. This 

report summarizes the results of water-quality, bed-sediment, 

and biota samples col­lected in water year 2005 and provides 

statistical summaries of data collected since 1985.

Water-quality data for samples collected periodically 

from streams include concentrations of selected major ions, 

trace ele­ments, and suspended sediment. Daily values of 

suspended-sed­iment concentration and suspended-sediment 

discharge were determined for three sites. Bed-sediment data 

include trace-ele­ment concentrations in the fine-grained 

fraction. Bio­logical data include trace-element concentrations 

in whole-body tissue of aquatic benthic insects. Qualityassurance data are reported for analytical results of water, 

bed sediment, and biota. Statistical summaries of waterquality, bed-sediment, and biological data are provided for 

the period of record since 1985 for each site.

Introduction

The Clark Fork originates near Warm Springs in western 

Montana at the confluence of Silver Bow and Warm Springs 

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

1 U.S Geological Survey, Menlo Park, Calif.
Figure 1. Location of study area.

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 Creek

Silver

Bow

Creek

Blacktail

Cr

CONTINENTAL

47

Helena

Study area

M O N T A N A

Base modified from U.S. Geological 

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

1966. North American Datum of 1927 

(NAD 27)

0 10 20 MILES

0 10 20 KILOMETERS

12353000 12340500

12340000

12334550

12334510

12331800

12324680

12324590

12324200

12323800

12323770 12323750

12323600

12323250

461903112440701

461559112443301

461415112450801

STREAMFLOW SITE TYPE

 Continuous record

 Periodic measurement

WATER QUALITY, BED SEDIMENT, 

AND BIOTA SITE TYPE

 Periodic-water quality

 Daily suspended sediment

 Once-annual bed sediment

 Once-annual biota

EXPLANATION

SITE NUMBER

461903112440701 MISCELLANEOUS SITE NUMBER

12324200

12323700

12323720

Lost Cr 12323850

o

46o

114o

113o

12323230

Racetrack

12323840

12323670

Mill

Creek

Willow

Creek

12323710

Creek

2000, 2001, 2002, 2003, 2004, 2005). Trace-element data for 

bed sediment and biota (aquatic benthic insects) have been 

collected intermit­tently since 1986 at selected sites as part of 

studies on bed-sed­iment contamination and bioaccumulation 

of metals conducted by the USGS National Research Program 

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

Axtmann and oth­ers, 1997; Hornberger and others, 1997). 

In March 1993, an expanded sampling program for water, 

bed sediment, and biota was implemented by the USGS in 

cooperation with the U.S. Environmental Protection Agency 

to provide systematic, long-term monitoring to better quantify 

the seasonal and annual vari­ability in selected constituents.

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

for 18 sites and trace-element data for 13 bed-sediment and 

biological sites in the upper Clark Fork basin collected from 

October 2004 through September 2005 (water year 2005). 

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

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

collected since 1985.

Sampling Locations and Types of Data

Sampling sites in the upper Clark Fork basin from 

Butte to below Missoula (fig. 1) are located on the Clark 

Fork mainstem, six major tributaries (Blacktail Creek, Warm 

Springs Creek, Little Blackfoot River, Flint Creek, Rock 

Creek, and Blackfoot River), and three smaller tributaries 

(Mill Creek, Willow Creek, and Lost Creek). The sites, types 

of data collected, and period of record for each data type are 

listed in table 1. Mainstem sampling sites were selected to 

divide the upper Clark Fork into reaches of relatively uniform length, with each reach encompassing either a major 

tributary or depositional environment (Warm Springs Ponds 

   Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
and Milltown Reservoir). Major tributaries were sampled to 

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

and to provide reference comparisons to the mainstem. The 

three smaller tributaries were sampled to gain better spatial 

resolution on sources of metals entering the Clark Fork in an 

area of his­torical metal-processing activities near Anaconda. 

Water-qual­ity data were obtained periodically at 18 sites; daily 

suspended-sediment data were obtained at 3 of these sites. 

Trace-element data for 13 bed-sediment and 13 biological sites 

were obtained once-annually. Continuous streamflow data 

were collected at 20 sites.

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

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

samples are listed in table 3. Onsite measurements of properties, laboratory analyses of water, bed-sediment, and biota 

samples, and associated qual­ity-assurance data for water year 

2005 are listed in tables 4 through 19 at the back of the report. 

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

biological data collected between March 1985 and September 2005 are given in tables 20 through 22 at the back of the 

report.

Quality assurance of data was maintained through the 

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

procedures was verified with quality-control samples that were 

collected systematically to provide a measure of the accuracy, 

precision, and bias of the environmental data and to identify 

problems associated with sampling, processing, or analysis.

Water-Quality Data

Water-quality data consist of onsite measurements of 

selected stream properties and concentrations of chemical and 

physical constituents analyzed in periodically collected stream 

samples. At 17 sites on the Clark Fork mainstem and tributaries, samples were collected 8 times per year on a schedule 

designed to describe seasonal and hydrologic vari­ability. At 

Warm Springs Creek at Warm Springs, samples were collected 

6 times during the water year. At the three daily suspendedsediment sites, suspended-sediment samples were collected 2 

to 9 times per week during water year 2005 (table 1).

Methods

Water samples were collected from vertical transits 

throughout the entire stream depth at multiple locations 

across the stream using depth- and width-integration methods 

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

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

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

flow passing through the cross section of a stream. Sampling 

equipment consisted of depth-integrating suspended-sediment 

sam­plers (DH-48, DH-81, and D-74TM), which were either 

con­structed of plastic or coated with a non-metallic epoxy 

paint, and equipped with nylon or Teflon nozzles.

Instantaneous streamflow at the time of water sampling 

was determined at all sites, either by direct measurement or 

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

Onsite measurements of specific conductance, pH, and water 

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

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

(1994), and USGS (variously dated).

Water samples were analyzed for the constituents listed in 

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

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

(arsenic, cadmium, copper, iron, lead, manganese, and zinc) 

were ana­lyzed for filtered (0.45-μm pore size) and unfiltered 

recoverable concentrations by the USGS National Water 

Quality Labora­tory (NWQL) in Denver, Colo. Concentrations 

of calcium and magnesium also were determined in filtered 

samples to enable calculation of hardness. Filtered concentrations of arsenic, cadmium, copper, lead, manganese, and zinc 

were analyzed by inductively cou­pled plasma-mass spectrometry (Faires, 1993; Garbarino, 1999). Filtered concentrations 

of calcium, magnesium, and iron were analyzed by inductively 

coupled plasma-atomic emission spectrometry (Fishman, 

1993). Unfiltered recoverable concen­trations of trace elements 

were determined from unfiltered sam­ples that were first 

digested with dilute hydrochloric acid (Hoffman and others, 

1996) and then analyzed by inductively coupled plasma-mass 

spectrome­try (Garbarino and Struzeski, 1998). For part of 

water year 2005, unfiltered recoverable arsenic was analyzed 

by graphite furnace-atomic absorption spectrometry (Jones 

and Garbarino, 1999).

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

periodic water-quality samples were collected. These samples 

were analyzed for suspended-sediment concentration and the 

percentage of suspended-sediment mass finer than 0.062-mm 

diameter (silt size and smaller) by the USGS Montana Water 

Science Center sediment laboratory (herein referred to as 

Montana Sediment Laboratory) in Helena, Mont., according 

to methods described by Guy (1969) and Dodge and Lambing 

(2006).

Suspended-sediment samples for the three daily 

suspended sediment sites were collected by local contract 

observers using the depth-integration method at a single 

vertical near mid-stream. The samples were analyzed for 

suspended-sediment concentration and were used to determine 

daily mean sus­pended-sediment concentrations according to 

methods described by Porterfield (1972).

Water-Quality Data 
Table 1. Type and period of data collection at sampling sites in the upper Clark Fork basin, Montana.

[Abbreviation: P, present. Symbol: --, no data]

Station number 

(fig. 1) Station name Continuous-record streamflow Periodic water quality1 Daily suspended sediment Fine-grained bed sediment2 Bulk bed sediment2,3 Biota2

12323230 Blacktail Creek at Harrison 

Avenue, at Butte

-- 03/93-08/95, 

12/96-08/03, 12/04-P

-- -- -- --

12323250 Silver Bow Creek below Blacktail Creek, at Butte 10/83-P 03/93-08/95, 12/96-P -- -- -- --

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

12/96-P

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

08/97-08/04

07/92, 08/94, 

08/95, 08/97-P

12323670 Mill Creek near Anaconda 10/04-P 12/04-P -- -- -- --

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

12323710 Willow Creek near Anaconda 03/05-P 12/04-P -- -- -- --

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

12323750 Silver Bow Creek at Warm 

Springs

03/72-09/79, 

04/93-P

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

08/95-08/04

07/92-P

12323770 Warm Springs Creek at Warm 

Springs

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

08/99, 08/02, 08/05

08/95, 08/97, 

08/99, 08/02

08/95, 08/97, 

08/99, 08/02, 08/05

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

12323840 Lost Creek near Anaconda 10/04-P 12/04-P -- -- --12323850 Lost Creek near Galen 04/03-P 03/03-P -- -- -- --

461415112450801 Clark Fork below Lost Creek, 

near Galen

-- -- -- 08/96-P 08/96-08/04 08/96-P

461559112443301 Clark Fork at County Bridge, 

near Racetrack

-- -- -- 08/96-P 08/96-08/04 08/96-P

461903112440701 Clark Fork at Dempsey Creek 

diversion, near Racetrack

-- -- -- 08/96-P 08/96-08/04 08/96-P

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

04/87-03/03, 08/03-P

08/86, 08/87, 

08/90-P

08/93-08/04 08/86, 08/87, 

08/90-P

12324590 Little Blackfoot River near 

Garrison

10/72-P 03/85-08/04 -- 08/86, 08/87, 

08/94, 08/98, 08/01, 08/04

08/94, 08/98, 

08/01, 08/04

08/87, 08/94, 

08/98, 08/01, 08/04

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

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

(fig. 1) Station name Continuous-record streamflow Periodic water quality1 Daily suspended sediment Fine-grained bed sediment2 Bulk bed sediment2,3 Biota2

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

08/03-09/04

03/85-08/04 -- 08/86, 08/89, 

07/92-08/04

08/93-08/04 08/86, 

07/92-08/04

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

08/91-P

08/93-08/04 08/86, 08/91-P

12334510 Rock Creek near Clinton 10/72-P 03/85-08/04 -- 08/86, 08/87, 

08/89, 08/91-99, 08/01-P

08/93-99, 08/01-

08/04

08/87, 08/91-99, 

08/01-P

12334550 Clark Fork at Turah Bridge, near 

Bonner

03/85-P 03/85-P 03/85-03/03, 

08/03-P

08/86, 08/91-P 08/93-08/04 08/86, 08/91-P

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

06/88-09/95

08/86, 08/87, 

08/91, 08/93-96, 08/98-01, 09/03

08/93, 08/94, 

08/99-01, 09/03

08/86, 08/87, 

08/91, 08/93, 08/96, 08/98, 09/00, 09/03

12340500 Clark Fork above Missoula 03/29-P 07/86-P4 07/86-04/87, 

06/88-01/96, 03/96-03/03, 08/03-P

08/97-P 08/97-08/04 08/97-P

12353000 Clark Fork below Missoula5 10/29-P 03/85-09/95 -- 08/86, 08/90-

08/04

08/93-08/04 08/86, 

08/90-08/04

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

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

2Laboratory analyses of trace elements.3Bulk bed-sediment sampling was discontinued in 2005.4Prior to October 1989, water-quality data for Clark Fork above Missoula only included suspended-sediment data.5Bed sediment and biota sampled about 30 miles downstream from streamflow-gaging station to conform to previous sampling location.

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

Water-Quality Data   
Table 2. Properties measured onsite and constituents analyzed in samples of water, 

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

Water Bed Sediment Biota

Property Constituent Constituent Constituent

Streamflow Hardness (calculated) Arsenic Arsenic

Specific conductance Calcium Cadmium Cadmium

pH Magnesium Chromium Chromium

Temperature Arsenic Copper Copper

Cadmium Iron Iron

Copper Lead Lead

Iron Manganese Manganese

Lead Nickel Nickel

Manganese Zinc Zinc

Zinc

Suspended sediment

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

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

Constituent

Data-quality objectives

Detectability Precision Bias

Laboratory reporting 

level

Maximum relative standard 

deviation of laboratory 

replicate analyses, 

in percent

Maximum deviation 

of spike recovery, 

in percent

Calcium, filtered 0.02 mg/L 20 --

Magnesium, filtered .008 mg/L 20 --

Arsenic, filtered .2 μg/L 20 25

Arsenic, unfiltered recoverable1 .12–2 μg/L 20 25

Cadmium, filtered .04 μg/L 20 25

Cadmium, unfiltered recoverable .04 μg/L 20 25

Copper, filtered .4 μg/L 20 25

Copper, unfiltered recoverable .6 μg/L 20 25

Iron, filtered 6 μg/L 20 25

Iron, unfiltered recoverable 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 .2 μg/L 20 25

Zinc, filtered .6 μg/L 20 25

Zinc, unfiltered recoverable 2 μg/L 20 25

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

Sediment, suspended 1 mg/L -- --

1

The laboratory reporting level changed during water year 2005.

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

Water-quality data for samples collected periodically 

dur­ing water year 2005 are presented in table 4. Daily mean 

streamflow, daily mean suspended-sediment concentration, 

and daily suspended-sediment discharge for water year 2005 

at the three daily suspended-sediment stations are reported in 

tables 5 through 7, along with monthly summary statistics and 

annual totals for streamflow and sediment load.

Quality Assurance

Quality-assurance procedures used for the collection and 

field processing of water-quality samples are described by 

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

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

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

internal sample handling and quality assurance are described 

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

and Raese (1995). Quality-assurance procedures used by the 

Montana Sediment Laboratory are described by Dodge and 

Lambing (2006).

The quality of analytical results reported for waterquality samples was evaluated by quality-control samples that 

were submitted from the field and analyzed concurrently in 

the labo­ratory with routine samples. These quality-control 

samples consisted of replicates, spikes, and blanks which 

provide quan­titative information on the precision and bias of 

the overall field and laboratory process. Each type of qualitycontrol sample was submitted at a proportion equivalent to 

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

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

samples.

In addition to quality-control samples submitted from the 

field, internal quality-assurance practices at the NWQL are 

per­formed systematically to provide quality control of analytical procedures (Pritt and Raese, 1995). These internal 

practices include analyses of quality-control samples such as 

calibration standards, standard reference water samples, 

replicate samples, deionized-water blanks, or spiked samples 

at a proportion equivalent to at least 10 percent of the sample 

load. The NWQL participates in a blind-sample program 

where standard reference water samples prepared by the 

USGS Branch of Qual­ity Systems are routinely inserted into 

the sample line for each analytical method at a frequency 

proportional to the sample load. The laboratory also participates in external evaluation studies and audits with the 

National Environmental Laboratory Accreditation Program, 

U.S. Environmental Protection Agency, Environment Canada, 

and the USGS Branch of Quality Systems to assess analytical 

performance.

Replicate data can be obtained in different ways to provide an assessment of precision (reproducibility) of analytical 

results. Replicate samples are two or more samples considered 

to be essentially identical in composition. Replicate samples 

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

the collection process to obtain two or more independent 

com­posite samples, or by splitting a single composite sample 

into two or more subsamples. The individual replicate samples 

are then analyzed separately. Likewise, a single sample can 

be ana­lyzed two or more times in the laboratory to obtain a 

measure of analytical variability (laboratory replicate).

Precision of analytical results for field replicates is 

affected by numerous sources of variability within the field 

and laboratory environments, including sample collection, 

sample processing, and sample analysis. To provide data on 

precision for samples exposed to all sources of variability, 

replicate stream samples for chemical analysis were obtained 

in the field by splitting a composite stream sample, and 

replicate stream samples for suspended-sediment analysis 

were obtained in the field by concurrently collecting two 

independent cross-sec­tional samples. Analyses of these field 

replicates indicate the reproducibility of environmental data 

that are affected by the combined variability potentially 

introduced by field and labora­tory processes.

Analytical precision was evaluated with laboratory 

repli­cates, which exclude field sources of variability. Two 

indepen­dent analyses were made of an individual sample 

selected ran­domly in the laboratory from the group of samples 

comprising each analytical run. A separate analysis of the 

sample was made at the beginning and end of each analytical 

run to provide infor­mation on the reproducibility of laboratory 

analytical results independent of possible variability caused by 

field collection and processing of samples.

Spiked samples are used to evaluate bias, which measures 

the ability of an analytical method to accurately quantify a 

known amount of analyte added to a sample. Because some 

constituents in stream water can potentially interfere with 

the analysis of a targeted analyte, it is important to determine 

whether such effects are causing biased (consistently high or 

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

samples were spiked in the laboratory with known amounts of 

the same trace elements analyzed in water samples. Analyses 

of spiked blanks indicate if the spiking procedure and analytical method are within control for a water matrix that is 

presumably free of chemical interference. Analyses of spiked 

aliquots of stream samples indicate if the chemical matrix of 

the stream water interferes with the analytical measurement 

and whether these interferences could contribute significant 

bias to reported trace-element concentrations for stream 

samples.

Blank samples of deionized water were 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 are then subjected to the same processing (sample splitting, filtration, preserva­tion, transportation, 

and laboratory handling) as stream sam­ples. Blank samples are 

Water-Quality Data 
analyzed for the same constituents as those of stream samples 

to identify whether any detectable con­centrations exist.

All water samples were handled in accordance with 

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

data in a consistent manner. Data that did not meet the objectives were evaluated for acceptability. If necessary, additional 

quality-con­trol samples were submitted and corrective action 

was taken.

The NWQL uses a statistically based convention for 

estab­lishing minimum laboratory reporting levels for analytical results and for reporting low-concentration data (Childress 

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

NWQL on a continuing basis to determine long-term method 

detection levels (LT-MDLs) and laboratory reporting levels 

(LRLs). These values are reevaluated each year and, consequently, can change from year to year. The methods are 

designed to limit the possible occurrence of a false positive 

or false negative error to 1 percent or less. Accordingly, 

concentrations are reported as less than the LRL for samples 

in which the analyte was either not detected or did not pass 

identification criteria. Analytes that are detected at concentrations between the LT-MDL and LRL and that pass identification criteria are estimated. Estimated concentrations are noted 

with a remark code of “E.” These data need to be used with the 

understanding that their uncertainty is greater than that of data 

reported without the “E” remark code.

The precision of analytical results for a constituent 

can be determined by estimating a standard deviation of the 

differ­ences between replicate measurements for several sets 

of sam­ples. These replicate measurements may consist either 

of indi­vidual analyses of a pair of samples considered to be 

essentially identical (field replicates) or multiple analyses of 

an individual sample (laboratory replicates). The differences 

in concentra­tion between replicate analyses can be used to 

estimate a standard deviation according to the following 

equation (Taylor, 1987):

S = 3d2

2k

where

	 S is the standard deviation of the difference in 

concentration between replicate analyses,

	 d	 is the difference in concentration between 

each pair of replicate analyses, 

and

	 k	 is the number of pairs of replicate analyses.

Precision also can be expressed as a relative standard 

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

standard deviation and the mean concentration for all the 

replicate anal­yses. Expressing precision relative to a mean 

concentration standardizes comparison of precision among 

individual constit­uents. The RSD, in percent, is calculated 

according to the fol­lowing equation (Taylor, 1987):

× 100 x

S RSD =

where

RSD is the relative standard deviation,

S is the standard deviation, 

and

x is the mean of all replicate concentrations.

Paired analyses of field replicates are presented in table 8. 

The precision estimated for each constituent based on these 

paired results, which include both field and laboratory sources 

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

precision are not directly applicable to field replicates because 

of the inability to determine whether the variability results 

from field sample collection and processing, or laboratory 

handling and analysis. However, the precision for field replicate analy­ses is calculated to illustrate overall reproducibility 

of environ­mental data that incorporates both field and laboratory sources of variability. The data-quality objective used to 

indicate acceptable precision of results for field replicates was 

a maxi­mum relative standard deviation of 20 percent (table 3). 

Preci­sion estimates for field replicate analyses were within the 

20-percent relative standard deviation limit for all constituents 

(table 9).

Analytical precision for chemical constituents based on 

laboratory replicate analyses of individual samples, which 

includes only laboratory sources of variability, is reported in 

table 10. Statistics for analytical precision of laboratoryrepli­cate analyses are based on unrounded values stored in 

labora­tory data files. The data-quality objective for analytical 

preci­sion of laboratory-replicate analyses was a maximum 

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

estimates for laboratory-replicate analyses were less than the 

20-percent relative standard deviation limit for all constituents 

(table 10); thus, the data-quality objectives for precision were 

met.

Recov­ery efficiency for analyses of constituents is 

determined by analyses of an unspiked sample and a spiked (1)

(2)

 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
aliquot of the same sample. The data-quality objective for 

acceptable spike recov­ery of trace elements in water samples 

was a maximum devia­tion of 25 percent from a theoretical 

100-percent recovery of added constituent (table 3). At the 

laboratory, a spiked deion­ized-water blank and a spiked 

aliquot of a stream sample were prepared and analyzed along 

with the original unspiked sample. The differences between 

the spiked and unspiked sample con­centrations were determined and used to compute recovery, in percent, according to 

equation 3:

D

C

R = × 100

where

R is the spike recovery, in percent;

D is the difference between the spiked sample 

concentration and unspiked sample 

concentration;

and

C is the concentration of material used to spike 

the sample.

If the spike recovery for a trace element was outside a 

range of 75 to 125 percent, the instrument was recalibrated 

and the entire sample set and spiked samples were reanalyzed 

for that particular trace element until recoveries were 

improved to the extent possible. Results of recovery efficiency 

for individ­ual trace elements in spiked deionized-water blanks 

and spiked stream samples are presented in tables 11 and 12, 

respectively. The mean spike recovery for deionized-water 

samples spiked with trace elements (table 11) ranged from 

93.8 to 104 percent. The 95-percent confidence intervals 

(Taylor, 1987) for the mean spike recovery for each constituent analyzed in deionized-water samples (table 11) did not 

exceed a 25-percent devi­ation from an expected 100-percent 

recovery. The mean spike recovery for spiked stream samples 

(table 12) ranged from 88.3 to 104 percent. The 95-percent 

confidence intervals for the mean of spike recovery for each 

constituent analyzed in stream samples (table 12) did not 

exceed a 25-percent deviation from an expected 100-percent 

recovery, except for filtered cadmium (62.7-133), filtered copper (57.9-129), and filtered zinc (60.8-128). No adjustments 

were made to analytical data for filtered cadmium, copper, and 

zinc because the mean spike recoveries were 97.8, 93.6, and 

94.3 percent, respectively, which indicated that there was no 

systematic bias.

High or low bias is indicated if the confidence interval 

does not include 100 percent recovery, thereby indicating a 

con­sistent deviation in one direction. All laboratory-spiked 

deionized-water blank samples (table 11) had confidence 

intervals for percent recovery that included 100 percent, except 

filtered arsenic (95.5-99.3 percent). The 95-percent confidence 

intervals for percent recovery in all laboratory-spiked stream 

samples (table 12) included 100 percent, except unfiltered 

recoverable arsenic (101-108) and unfiltered recoverable 

manganese (78.3-98.3). Both the 95-percent confidence 

interval (101-108) and mean (104) percent recoveries for 

unfiltered recoverable arsenic in laboratory-spiked stream 

samples indicate a persistent, but very minor, high bias. In 

contrast, the 95-per­cent confidence interval (90.7-111) and 

mean (101) percent recoveries for unfiltered recoverable 

arsenic in laboratory-spiked deionized water blanks (table 11) 

indicate no bias. Thus, it appears that the minor bias in spiked 

stream samples is not necessarily caused by the analytical 

method, but might be a result of analytical interference from 

the chemical matrix of the stream samples. The same comparison is made for laboratory spiked stream samples for unfiltered recoverable manganese. Both the 95-percent confidence 

interval (78.3-98.3) and mean (88.3) percent recoveries for 

unfiltered recoverable manganese in laboratory-spiked stream 

sam­ples (table 12) indicate a persistent low bias of moderate magnitude. However, the 95-percent confidence interval 

(82.2-105) and mean (93.8) percent recoveries for laboratoryspiked deionized water (table 11) indicate no bias. Because 

the mean spike recoveries for all constituents met data-quality 

objectives, no adjustments were made to analytical results for 

stream samples on the basis of spike recoveries.

Analytical results for field blanks are presented in 

table 13. A field blank with constituent concentrations equal 

to or less than the LRL for the analytical method indicates 

that the entire process of sample collection, field processing, 

and laboratory analysis is presumably free of 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 

may indicate systematic contamination. Sporadic, infrequent 

exceedances of twice the LRL probably represent random 

contamination or instrument calibration error that is not persistent in the process and which is not likely to cause 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 in order 

to identify the source of contamination.

Trace-element concentrations in field blanks (table 13) 

were almost always less than the LRL. Two detections 

exceeded twice the LRL in two separate samples. One 

occurred on March 7 for filtered zinc (1.9 μg/L) which 

was greater than the LRL of 0.6 μg/L; several other blanks 

exceeded the LRL for filtered zinc but they did not exceed 

twice the LRL. The other occurred on June 2 for unfiltered 

recoverable iron (30 μg/L) which was greater than the LRL of 

6 μg/L. Since no trends were indicated in subsequent sampling 

trips, no adjustments were made to water-qual­ity sample 

results based on these two detections.

(3)

Bed-Sediment Data 
Bed-Sediment Data

Bed-sediment data consist of analyses of trace-element 

concentrations in the fine-grained fraction of bed-sediment 

samples. Collection of bulk bed sediment (fine-grained plus 

coarse-grained fractions) was discontinued in 2005; therefore, 

no analytical results or statistical summaries are presented. 

Bed-sed­iment samples were collected once-annually during 

low, stable flow conditions and the same season (typically 

August) as pre­vious samples to facilitate data comparisons 

among years.

Methods

Fine-grained bed-sediment samples were collected in 

August 2005 using protocols described by E.V. Axtmann 

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

were collected from the surfaces of streambed deposits in 

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

were collected from both sides of the stream. Three composite 

samples of bed sediment were collected at each site.

Individual samples of bed sediment were collected by 

scooping material from the surfaces of three to five randomly 

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

to five individual samples were combined to form a single 

composite sample. This collection process was repeated three 

times to obtain three composite samples. Each composite 

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

sieve using ambient stream water. The fraction of bed sediment in each composite sample that was finer than 0.064 mm 

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

and transported to the laboratory on ice.

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 using an acidwashed ceramic mortar and pestle. Single aliquots of approximately 0.6 g of sediment from each of the three composite 

bed-sediment samples were digested using a hot, concentrated, 

nitric acid reflux according to methods described by Luoma 

and Bryan (1981). An additional aliquot was analyzed from 

one of the sieved replicate samples at each station. After a 

digestion period of up to 2 weeks, the aliquots were evaporated to dryness on a hot plate. The dry residue was reconstituted in 10 mL of 0.6N (normal) hydrochloric acid. The 

reconstituted aliquots then were filtered through a 0.45-μm 

filter using a syringe and in-line disposable filter cartridge. 

The filtrate was diluted to a 1:10 ratio with 0.6N hydro­chloric 

acid. These final solutions were analyzed for arsenic, 

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

and zinc using inductively coupled argon plasma-emission 

spectroscopy (ICAPES). The smallest concentration of a 

con­stituent that can be reliably reported for analyses of bed 

sediment is termed the minimum reporting level.

Results

Concentrations of trace elements measured in samples 

of fine-grained bed sediment collected during August 2005 

are summarized in table 14. Liquid-phase concentrations, in 

μg/mL, that were analyzed in the reconstituted aliquots of 

digested bed sediment were converted to solid-phase concentrations, in μg/g, using the following equation:

μg/mL × volume of digested sample, in mL

dry weight of sample, in g × dilution ratio μg/g =

The reported solid-phase concentrations in table 14 

are the mean of all analyses for replicate aliquots from each 

composite bed-sediment sample collected at the site. Because 

the conversion from liquid-phase to solid-phase concentration 

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

the sample, mini­mum reporting levels for some trace elements 

might differ among stations and among years.

Quality Assurance

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

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

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

in a laboratory-grade detergent and rinsed with deionized 

water. All equipment received a final rinse onsite with stream 

water. Sampling equipment used at more than one site was 

rinsed between sites with stream water. Separate sieves were 

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

cleaning. Bed-sediment sam­ples were collected sequentially at 

sites along an increasing concentration gradient to minimize 

effects from potential site-to-site carryover contamination.

Quality assurance of analytical results for bed-sediment 

samples included laboratory instrument calibration with 

stan­dard solutions and analysis of quality-control samples 

designed to identify the presence and magnitude of bias 

(E.V. Axtmann, U.S. Geological Survey, written commun., 

1994). Quality-control samples consisted of standard reference 

materials 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.

Standard reference materials (SRMs) are commercially 

prepared materials that have certified concentrations of trace 

elements. Analyses of SRMs are used to indicate the ability 

of the method to accurately measure a known quantity of 

a constit­uent. Multiple analyses of the SRMs are made to 

derive a mean and 95-percent confidence interval for recovery. 

Recovery effi­ciency for trace-element analyses of SRMs for 

bed sediment is summarized in table 15. 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 

(4)

10 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
in the bed sediment of streams in the upper Clark Fork basin. 

The digestion process used to analyze bed-sediment samples 

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

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

not be achieved for ele­ments strongly bound to the sediment. 

The percent recovery of trace elements for SRM analyses that 

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

elements display strong sediment-binding characteristics in the 

SRM and whether ana­lytical recovery is consistent between 

multiple sets of analyses.

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

elements shown in table 15 illustrate analytical performance. 

Mean SRM recoveries for the low-concentration standard 

(SRM 2709) ranged from 82.2 to 89.1 percent of the certified 

concentrations for copper, iron, lead, manganese, and nickel. 

Mean recoveries were lower for arsenic, chromium, and zinc 

(65.4, 60.2, and 75.6 percent, respectively). Cadmium concentrations were near the minimum reporting level in SRM 2709 

and were not reported. The lack of measurable recoveries 

for cadmium in the SRM is likely the result of analyzing 

concentrations very close to the liquid-phase detection limit 

(0.0003 μg/mL) coupled with signal enhancement resulting 

from matrix interference. Percent recoveries for arsenic, 

cadmium, copper, iron, lead, manganese, and zinc in the 

high-concentration standard (SRM 2711) ranged from 80.6 

to 94.4 percent of the certified concentration. Chro­mium and 

nickel had lower recoveries (51.5 and 78.9 percent, respectively) for the high-concentration SRM, possibly due to the 

strong binding nature of these elements to sediment. The 

generally small range of variation (less than 10 percent for 

most constituents) for the 95-percent confidence interval 

indicates good reproducibility of multiple analyses of the 

SRMs. No adjustments were made to trace-element concentrations in 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 16) are reported as a liquid-phase concentration, in μg/mL, which is equivalent to parts per million. A 

procedural blank was prepared and analyzed con­currently with 

bed-sediment samples for each site. Concentra­tions of trace 

elements in all procedural blanks were below the minimum 

reporting level; thus, no contamination bias was indi­cated and 

no adjustments to the data were necessary.

Biological Data

Biological data consist of analyses of trace-element 

con­centrations in the whole-body tissue of aquatic benthic 

insects. Insect samples were collected once-annually at the 

same sites and dates as bed-sediment samples (table 1), 

allowing for a direct comparison of biological data with bedsediment data among the years.

Methods

Insect samples were collected using protocols described 

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

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

single riffle at each station was sampled repeatedly until 

an adequate number of individual insects were collected to 

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

Plecoptera (stoneflies).

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

for collection in this study due to their occurrence at most, but 

not all, sites. In a few instances, Hydropsyche tana were 

collected. Hydropsyche species (spp.) that could not be 

positively iden­tified were considered to belong to the morosa

group and are categorized as Hydropsyche spp. or Hydropsyche morosa group (in previous reports). The caddisfly 

Arctopsyche grandis and the stonefly Claasenia sabulosa were 

collected where available to represent additional insect taxa 

that are commonly distrib­uted in the upper Clark Fork basin. 

In addition, the caddisfly group Brachycentrus spp. was sometimes collected when tar­geted taxa were not available.

Samples of each taxon were sorted by genus in the field 

and placed in acid-washed plastic containers. Samples were 

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

amount of ambient stream water. Between 1986 and 1998, 

macroinvertebrate containers were kept on ice to allow the 

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

8 hours. Excess water was drained and insects were frozen for 

transport to the laboratory. In order to reduce the possibility of 

metal loss through intracellular breakdown during depuration, 

samples were frozen on dry ice in the field between 1999 and 

2005. A comparison of immediately frozen versus depurated 

samples showed that while no significant difference occurred 

for most metals, concentrations of copper in the depurated 

macroinverte­brate samples were about 20 percent lower than 

those which were immediately frozen. The data were not 

adjusted for this difference.

Insect samples were processed and analyzed at the USGS 

National Research Program, Ecology and Contaminants 

Project laboratory in Menlo Park, Calif. Insects were thawed 

Biological Data 11
and rinsed with ultra-pure deionized water to remove particulate matter and then sorted to their lowest pos­sible taxonomic 

level. If large numbers of specimens had been collected at a 

site, similar-sized individuals were composited into replicate 

subsamples. Subsamples were placed in tared scintillation 

vials and oven-dried at 70°C. Subsamples were weighed to 

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

insect samples were evaporated to dryness on a hot plate. 

The dry residue was reconstituted in 0.6N hydrochloric acid, 

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

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

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

constituent that can be reliably reported for analyses of biota is 

termed the minimum reporting level.

Results

Concentrations of trace elements in whole-body tissue 

of aquatic insects collected during August 2005 are summarized in table 17. 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. Liquidphase concentra­tions, in μg/mL, analyzed in the reconstituted 

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

using equation 4. As with bed sedi­ment, minimum reporting 

levels may differ among sites as a result of variable sample 

weights. In general, the smaller the biological sample weight 

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

reporting level. Therefore, higher mini­mum reporting levels do 

not necessarily imply a higher trace-element concentration in 

tissue.

Quality Assurance

The protocols for field collection and processing of 

biota samples are designed to prevent contamination from 

metal sources. Non-metallic nets, sampling equipment, and 

process­ing equipment were employed in all sample collection. 

Equipment was acid-washed and rinsed in ultra-pure deionized 

water prior to the first sample collection. Nets and equipment 

were thoroughly rinsed in ambient stream water at each new 

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

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

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 procedural blanks 

for 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 summarized in table 18. The reference material tested was lobster hepatopancreas. Data-quality objectives 

have not been established for analytical recovery in biota, but 

percent recoveries are shown to illustrate analytical performance. Mean SRM recoveries ranged from 92.6 to 100 percent 

of the certified concentrations for arsenic, cadmium, copper, 

iron, manganese, and zinc. Lower mean recoveries were 

measured for lead (84.7 percent) and nickel (84.8 percent). 

A higher mean recovery was measured for chromium 

(119 percent), with 2 of the 12 analyses having concentrations 

less than the minimum reporting level. With the exception of 

chromium and lead, both of which had low certified concentrations (0.77 μg/g and 0.35 μg/g, respectively) in the SRM, 

the range of variation generally was small (less than about 6 

percent) for the 95-percent confidence interval, thereby indicating good reproducibility of multiple analyses of the SRM. 

No adjustments were made to trace-element concentrations in 

biota samples on the basis of recovery efficiencies.

Procedural blanks for biota consisted of the same 

reagents used to digest and reconstitute tissue of aquatic 

insects and were analyzed undiluted. Analytical results of 

procedural blanks for biota (table 19) are reported as a liquidphase concentration, in μg/mL, which is equivalent to parts 

per million. A procedural blank was prepared and analyzed 

concurrently with biota sam­ples for each site. Concentrations 

of trace elements in all pro­cedural blanks were less than the 

minimum reporting level; thus, no contamination bias was 

indicated and no adjustments to the data were necessary.

Statistical Summaries of Data

Statistical summaries of water-quality, bed-sediment, 

and biological data are provided in tables 20 through 22 for 

the period of record at each site since 1985. The summaries 

include the period of record, number of samples, and maximum, minimum, mean, and median concentrations.

Statistical summaries of water-quality data (table 20) 

are based on results of cross-sectional samples collected 

periodically by the USGS during the period of record for each 

site. The summaries do not include data for supplemental 

single-vertical samples collected during several years by a 

contract observer at Clark Fork at Turah Bridge, near Bonner; 

Blackfoot River near Bonner; and Clark Fork above Missoula. 

Inclusion of results for supplemental samples that targeted 

high-flow conditions or maintenance drawdowns of 

Milltown Reservoir would dispro­portionately skew the longterm statistics at these three sites rel­ative to the other sites 

in the network. Statistical summaries of fine-grained bedsediment (table 21) and biological data (table 22) are based on 

results of samples collected once-annually during the indicated 

years. Because not all sites were sampled for bed sediment 

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

Statistics for bed-sediment data (table 21) are based on 

the mean trace-element concentrations determined for each 

year from the averaged results of analyses of composite 

samples. Therefore, the number of samples for bed sediment 

represents the number of years that the constituent was 

ana­lyzed. In contrast, statistics for biological data (table 22) 

are based on individual analyses for each composite sample 

col­lected, rather than on a single mean concentration for each 

year. Also, the number of samples for arsenic for both bed 

sediment and biota is smaller than the other trace elements 

because it was only recently (2003) included for analysis.

Differences in the number of biota composite samples 

among species reflect differences in species abundance, both 

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

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

individual composite samples were averaged. The abundance 

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

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

minimum reporting levels. Where minimum reporting levels 

vary among years, differences in concentration over time are 

difficult to determine, especially when a large percentage of 

the samples have concentrations less than minimum reporting 

lev­els.

The presence or absence of insect species at a given site 

can vary among years and may result in different taxa being 

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

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

based on the results of all Hydropsyche species combined. At 

some sites, statistics for the Hydropsyche morosa group are 

based on the combined results for two or more species because 

these samples could not be clearly identified to the species 

level, but the individual insects had morosa characteristics.

References Cited

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

of tributary inflows on the distribution of trace metals in 

fine-grained sediment and benthic insects of the Clark Fork 

River, Montana: Environmental Science and Technology, 

v. 31, no. 3, p. 750-758.

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

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

no. 6, p. 75-88.

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

of gut content in immature aquatic insects on assessments 

of environmental metal contamination: Canadian Journal of 

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

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

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

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

p. 2141-2154.

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

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

method detection levels and some considerations for 

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

Geolog­ical Survey National Water Quality Laboratory: U.S. 

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

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

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

1994 through September 1995) and statistical summaries 

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

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

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

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

1995 through September 1996) and statistical summaries 

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

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

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

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

1996 through September 1997) and statistical summaries 

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

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

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

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

1997 through September 1998) and statistical summaries 

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

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

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

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

1998 through September 1999) and statistical summaries 

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

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

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

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

1999 through September 2000) and statistical summaries 

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

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

References Cited 13
Dodge, K.A., Hornberger, M.I., and David, C.P.C., 2002, 

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

2000 through September 2001) and statistical summaries 

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

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

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

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

2001 through September 2002) and statistical summaries 

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

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

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

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

2002 through September 2003) and statistical summaries 

of data for streams in the upper Clark Fork basin, Montana: U.S. Geological Survey Open-File Report 2004-1340, 

107 p.

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

through September 2004) and statistical summaries of data 

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

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

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

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

Report 2006-1242, 25 p. [Available online at http://pubs.

water.usgs.gov/ofr2006-1242]

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

measurement of fluvial sediment: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

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

twri/]

Faires, L.M., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of metals in water by inductively coupled plasma-mass 

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

92-634, 28 p.

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

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

93-125, 217 p.

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

practices for the chemical and biological analyses of water 

and fluvial sediments: U.S. Geological Survey Techniques 

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

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

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

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

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

Lab­oratory—Determination of elements in whole-water 

digests using inductively coupled plasma-optical emission 

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

101 p.

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

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

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

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

statistics for multiply censored water quality data: Water 

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

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

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

Water Quality Laboratory—In-bottle acid digestion of 

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

Report 96-225, 28 p.

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

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

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

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

Open-File Report 97-669, 84 p.

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

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

for the collection and processing of surface-water samples 

for the subsequent determination of inorganic constituents 

in filtered water: U.S. Geological Survey Open-File Report 

94-539, 57 p.

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

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

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

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

14 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Knapton, J.R., and Nimick, D.A., 1991, Quality assurance for 

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

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

41 p.

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

and selected tributaries from Deer Lodge to Milltown, 

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

Survey Open-File Report 87-110, 48 p.

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

September 1987) and statistical summaries (March 1985 

through September 1987) for the Clark Fork and selected 

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

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

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

through September 1988) and statistical summaries (March 

1985 through September 1988) for the Clark Fork and 

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

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

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

through September 1989) and statistical summaries (March 

1985 through September 1989) for the Clark Fork and 

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

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

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

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

Investigations Report 91-4139, 73 p.

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

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

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

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

Report 95-429, 104 p.

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

D.A., 1994, Water-quality, bed-sediment, and biological 

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

September 1993) for streams in the upper Clark Fork basin, 

Montana: U.S. Geological Survey Open-File Report 94-375, 

85 p.

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

of the form of trace metals in oxidized estuarine sediments 

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

Porterfield, George, 1972, Computation of fluvial-sediment 

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

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

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

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

35 p.

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

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

2175, 2 v., 631 p.

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

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

for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chaps. A1-A9. [Available online at http://pubs.usgs.

gov/twri/]

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

and processing of surface-water and bed-material samples 

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

Open-File Report 90-140, 71 p.

References Cited 15
Data
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.

[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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]

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)

Arsenic, 

filtered 

(μg/L)

12/15/2004 0900 3.3 7.7 326 5.5 130 36.2 9.00 2.0

03/09/2005 0810 2.8 7.8 323 4.5 130 37.7 9.06 1.3

04/18/2005 0910 7.1 7.6 264 5.0 100 29.4 7.29 2.6

05/16/2005 0900 22 7.7 203 9.5 74 21.2 5.03 5.8

06/01/2005 1120 25 7.7 161 9.0 65 19.3 4.09 5.0

06/13/2005 1030 20 7.8 200 8.5 83 24.6 5.23 5.9

07/25/2005 1050 2.8 7.8 335 12.5 140 39.7 8.88 2.8

08/23/2005 0930 2.3 7.8 333 12.0 130 38.6 8.48 2.3

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron,

 filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/15/2004 2 0.07 0.07 8.9 8.0 49 1,030 2.80

03/09/2005 E1. E.03 E.04 .9 3.4 54 290 <.08

04/18/2005 4 .05 .07 3.4 7.2 201 690 .19

05/16/2005 7 .04 .05 8.5 12.4 179 540 .24

06/01/2005 7 .06 .07 7.5 14.2 143 810 .25

06/13/2005 6 E.04 .04 5.7 8.0 161 360 .12

07/25/2005 3.3 E.04 .04 2.5 3.7 41 200 E.07

08/23/2005 3.0 E.03 .05 1.7 4.1 43 300 <.08

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/15/2004 2.74 26.4 55 2.2 11 89 22 0.20

03/09/2005 .41 28.7 29 3.2 5 83 8 .06

04/18/2005 1.24 29.2 46 4.2 12 85 9 .17

05/16/2005 .92 19.0 28 3.9 7 54 13 .77

06/01/2005 2.67 23.1 51 6.2 18 71 24 1.6

06/13/2005 .62 14.2 23 3.2 4 71 7 .38

07/25/2005 .26 32.5 38 3.7 5 87 3 .02

08/23/2005 .61 35.4 47 2.2 5 83 9 .06

18  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
12323250—Silver Bow Creek below Blacktail Creek, at Butte

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered 

(μg/L)

12/15/2004 1005 16 7.5 554 6.5 160 44.9 12.1 2.9

03/09/2005 0935 16 7.6 564 6.5 170 47.7 12.0 2.3

04/18/2005 1030 21 7.6 475 7.0 140 39.4 8.90 3.6

05/16/2005 1025 38 7.6 370 11.0 110 32.4 7.92 5.7

06/01/2005 1240 67 7.6 238 9.0 79 23.4 5.02 6.9

06/13/2005 0955 34 7.8 361 9.5 130 38.1 8.44 6.2

07/25/2005 1215 16 7.9 545 15.0 190 53.2 13.1 5.6

08/23/2005 1045 15 7.9 552 16.5 180 50.9 12.7 5.7

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/15/2004 3 0.97 1.18 10.2 42.1 38 370 0.26

03/09/2005 3 1.18 1.54 9.1 61.9 37 570 .30

04/18/2005 4 .16 .26 11.3 21.8 268 290 .33

05/16/2005 9 .10 .22 12.1 22.5 126 460 .37

06/01/2005 19 .12 1.39 14.0 111 78 2,970 .68

06/13/2005 7 .09 .20 10.2 18.8 116 420 .26

07/25/2005 6.5 .12 .18 11.9 18.4 25 140 .27

08/23/2005 6.4 .10 .14 11.6 17.3 32 120 .27

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/15/2004 2.27 331 366 277 286 84 10 0.43

03/09/2005 2.73 498 509 284 323 83 9 .39

04/18/2005 1.68 113 129 54.0 68 88 5 .28

05/16/2005 2.41 70.8 102 27.8 47 86 10 1.0

06/01/2005 31.0 88.7 340 35.3 230 76 97 18

06/13/2005 2.27 58.1 98 27.2 38 86 9 .83

07/25/2005 1.11 61.3 88 26.7 38 77 5 .22

08/23/2005 1.09 48.4 70 31.9 43 81 4 .16

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]

Data 19
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)

Arsenic, 

filtered 

(μg/L)

12/15/2004 1635 21 8.4 565 3.0 200 59.9 13.2 11.0

03/08/2005 1330 26 8.8 558 7.5 200 57.4 12.7 12.5

04/18/2005 1505 37 9.0 492 6.0 180 52.8 11.1 12.4

05/17/2005 0710 165 7.9 316 6.5 110 34.6 6.44 10.3

06/01/2005 1720 119 8.2 319 8.5 120 38.7 6.60 9.5

06/13/2005 1210 95 8.6 332 10.5 130 39.5 7.32 10.8

07/26/2005 0735 27 8.2 493 11.0 180 52.5 11.3 16.6

08/24/2005 0720 17 8.1 597 10.5 230 66.5 14.9 13.7

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/15/2004 14 0.88 1.21 30.0 81.3 14 460 0.40

03/08/2005 17 .78 1.29 32.7 93.2 9 550 .30

04/18/2005 17 .39 .94 23.1 87.8 9 570 .23

05/17/2005 46 .57 4.09 41.0 554 83 4,730 1.49

06/01/2005 80 .49 3.87 36.2 472 62 9,190 .93

06/13/2005 16 .24 .79 24.0 93.0 63 640 .96

07/26/2005 19.2 .23 .78 18.5 79.6 23 450 .58

08/24/2005 18.3 2.72 3.85 60.0 206 13 440 .40

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/15/2004 12.7 359 391 256 315 83 11 0.62

03/08/2005 15.1 489 482 157 263 86 11 .77

04/18/2005 14.5 341 426 65.1 216 80 13 1.3

05/17/2005 125 352 829 203 791 66 202 90

06/01/2005 149 335 1,050 147 1,100 73 93 30

06/13/2005 17.6 159 213 77.2 159 89 18 4.6

07/26/2005 12.3 180 241 63.5 168 90 11 .80

08/24/2005 13.0 713 799 611 856 81 14 .64

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

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
12323670—Mill Creek near Anaconda

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)

Arsenic, 

filtered 

(μg/L)

12/15/2004 1330 10 8.3 179 3.0 82 21.7 6.75 9.8

03/08/2005 0940 7.4 8.6 195 3.5 92 24.4 7.58 8.7

04/18/2005 1155 14 8.2 161 4.0 72 19.3 5.71 11.3

05/16/2005 1315 113 7.7 86 8.0 33 9.40 2.25 19.1

06/01/2005 1410 153 8.0 67 6.0 28 8.29 1.83 11.7

06/22/2005 1145 165 7.8 56 9.5 24 7.12 1.45 7.3

07/25/2005 1440 27 8.2 129 13.0 58 16.6 4.08 23.4

08/23/2005 1305 12 8.5 169 15.0 78 21.8 5.60 21.3

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/15/2004 10 0.08 0.05 1.0 1.3 41 90 0.17

03/08/2005 9 .11 .05 1.1 1.9 27 90 E.05

04/18/2005 13 .04 .06 1.6 2.8 42 130 .10

05/16/2005 25 .05 .18 4.5 10.3 62 620 .24

06/01/2005 15 .04 .08 3.8 5.7 35 170 .11

06/22/2005 10 .04 .15 2.4 7.2 26 590 .08

07/25/2005 25.5 .05 .08 2.6 4.3 80 170 .22

08/23/2005 23.8 .04 .07 1.7 2.9 89 180 .16

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/15/2004 0.27 6.4 7 1.2 E1 81 1 0.03

03/08/2005 .31 7.0 9 1.1 E1 75 2 .04

04/18/2005 .54 5.8 13 1.3 E2 78 2 .08

05/16/2005 3.12 5.9 37 2.1 8 64 29 8.8

06/01/2005 .83 3.6 11 2.4 4 51 6 2.5

06/22/2005 2.35 5.1 36 1.6 7 57 29 13

07/25/2005 .59 8.9 17 1.2 3 79 2 .15

08/23/2005 .57 6.8 18 .8 E2 75 3 .10

Data 21

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/15/2004 1515 2.0 8.0 200 2.0 86 23.6 6.66 18.6

03/08/2005 1150 .48 8.1 214 5.0 94 25.8 7.12 9.0

04/18/2005 1340 .43 7.8 222 6.5 98 27.0 7.38 10.2

05/16/2005 1600 68 7.8 95 9.0 36 10.1 2.56 27.0

06/01/2005 1555 117 7.9 72 7.0 31 8.91 2.04 18.2

06/22/2005 1405 117 7.9 61 13.0 25 7.36 1.56 14.7

07/25/2005 1615 5.5 8.2 147 16.5 65 18.6 4.56 36.6

08/23/2005 1500 1.1 8.1 190 18.5 83 23.9 5.74 25.8

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/15/2004 20 0.08 0.10 1.7 2.2 57 100 0.14

03/08/2005 10 .07 .07 1.2 2.2 64 120 <.08

04/18/2005 12 .05 .07 1.5 2.5 70 130 E.06

05/16/2005 46 .08 .63 6.1 27.8 64 1,510 .31

06/01/2005 24 .07 .29 4.7 9.9 40 490 .15

06/22/2005 21 .06 .25 3.5 12.4 31 710 .14

07/25/2005 40.0 .06 .08 3.2 4.5 90 140 .23

08/23/2005 27.9 .05 .06 2.1 3.0 75 120 E.07

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/15/2004 0.17 14.1 13 5.2 5 77 2 0.01

03/08/2005 .08 32.8 27 3.9 4 67 1 <.01

04/18/2005 .15 27.1 30 3.8 4 80 1 <.01

05/16/2005 9.55 7.5 79 4.5 28 65 81 15

06/01/2005 2.22 4.0 24 3.8 12 26 29 9.2

06/22/2005 3.86 4.1 37 2.8 12 44 45 14

07/25/2005 .40 11.1 14 2.8 3 77 1 .01

08/23/2005 .15 15.5 19 1.7 2 90 1 <.01

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

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
12323710—Willow Creek near Anaconda

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)

Arsenic, 

filtered 

(μg/L)

12/15/2004 1145 1.0 7.9 113 0.5 40 13.4 1.65 12.8

03/09/2005 1125 1.0 8.2 114 2.0 41 13.7 1.61 9.9

04/21/2005 0750 1.9 7.7 114 0.5 42 13.9 1.69 11.1

05/16/2005 1200 39 7.5 66 6.0 23 7.74 .877 16.6

06/02/2005 0745 26 7.8 80 5.0 31 10.6 1.04 12.2

06/22/2005 1015 13 7.8 95 10.0 37 12.8 1.22 12.9

07/25/2005 1340 3.3 7.9 102 11.0 38 13.0 1.30 19.8

08/23/2005 1210 1.9 7.6 108 13.0 40 13.6 1.41 24.3

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/15/2004 13 E0.03 E0.03 1.2 1.5 43 110 0.11

03/09/2005 10 E.02 E.03 1.0 1.7 36 90 E.05

04/21/2005 13 E.03 .06 1.9 2.9 55 190 E.07

05/16/2005 21 .04 .19 4.2 10.5 125 1,260 .37

06/02/2005 14 E.03 .06 3.1 4.1 68 270 .15

06/22/2005 14 .05 .04 2.1 2.8 45 130 .12

07/25/2005 20.7 E.03 .06 2.4 3.0 66 170 .16

08/23/2005 27.0 E.04 .07 1.8 3.4 90 290 .18

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/15/2004 0.25 17.8 20 1.7 E1 86 4 0.01

03/09/2005 .20 13.1 15 1.1 E1 77 3 .01

04/21/2005 .48 18.2 29 1.5 2 92 4 .02

05/16/2005 4.08 11.5 49 2.5 10 44 93 9.8

06/02/2005 .75 11.4 19 2.5 3 46 13 .91

06/22/2005 .35 16.4 19 1.9 2 76 5 .18

07/25/2005 .47 20.0 30 3.3 E2 89 4 .04

08/23/2005 .84 23.0 49 1.4 3 94 9 .05

Data 23

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/15/2004 1540 6.2 8.2 305 5.5 130 37.0 9.31 13.3

03/08/2005 1225 4.5 8.3 298 8.5 130 36.5 8.72 11.5

04/18/2005 1410 5.6 8.3 340 6.0 150 42.0 10.5 18.8

05/16/2005 1635 47 7.7 210 12.0 80 23.4 5.18 68.9

06/01/2005 1625 53 8.0 272 10.0 120 34.8 7.57 117

06/22/2005 1435 23 8.3 348 20.5 170 47.3 12.3 164

07/25/2005 1650 6.5 8.5 318 16.0 160 44.3 10.9 22.2

08/23/2005 1525 5.4 8.4 312 16.5 140 39.8 9.00 17.0

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/15/2004 14 E0.02 0.05 2.1 6.4 26 140 .18

03/08/2005 13 E.03 .05 1.9 4.7 20 120 .09

04/18/2005 21 E.03 .07 2.8 7.7 20 180 .10

05/16/2005 84 .06 .52 13.0 48.8 111 1,420 .52

06/01/2005 133 .11 .28 21.4 37.0 91 520 .47

06/22/2005 164 .06 .12 11.0 17.0 41 220 .24

07/25/2005 22.5 E.02 E.04 2.9 4.0 8 50 E.06

08/23/2005 18.1 E.03 .04 3.0 4.6 9 60 E.06

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/15/2004 1.18 20.1 21 2.9 5 89 5 0.08

03/08/2005 .98 33.0 30 2.3 5 86 4 .05

04/18/2005 1.62 45.7 56 4.2 9 95 4 .06

05/16/2005 14.4 47.7 104 16.7 68 75 84 11

06/01/2005 5.09 25.8 49 17.9 35 70 27 3.9

06/22/2005 1.97 17.0 29 4.6 10 86 10 .62

07/25/2005 .47 5.9 8 1.7 2 96 2 .04

08/23/2005 .64 5.8 10 1.9 3 81 2 .03

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

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/16/2004 0830 39 8.7 638 2.0 270 74.7 19.7 15.8

03/08/2005 1435 37 8.9 631 7.0 270 78.1 18.9 11.1

04/18/2005 1615 34 8.6 685 7.0 310 87.6 21.1 9.8

05/17/2005 0840 270 8.8 442 8.0 170 45.5 13.3 36.9

06/02/2005 0930 249 9.1 356 8.0 150 41.6 10.1 29.2

06/23/2005 1250 183 9.0 407 12.0 180 52.1 10.9 26.2

07/26/2005 0835 42 8.6 512 13.5 240 68.5 15.7 27.0

08/24/2005 0820 30 8.8 590 13.5 260 76.3 17.8 31.1

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/16/2004 17 0.16 0.19 6.6 10.1 E5 110 E0.08

03/08/2005 13 .08 .15 4.7 10.2 E6 190 <.08

04/18/2005 13 E.03 .08 2.7 7.8 E4 250 E.05

05/17/2005 49 E.03 .37 6.6 28.8 72 1,000 .25

06/02/2005 34 .04 .12 6.6 13.4 37 240 .12

06/23/2005 28 .07 .14 7.7 11.4 22 200 .11

07/26/2005 28.6 E.03 .06 3.3 5.1 16 140 E.07

08/24/2005 32.5 E.04 .07 2.9 4.4 6 120 <.08

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/16/2004 0.35 78.0 80 6.5 10 79 4 0.42

03/08/2005 .58 168 189 4.6 12 87 4 .40

04/18/2005 1.09 195 245 4.7 12 82 3 .28

05/17/2005 6.72 175 304 4.3 38 89 37 27

06/02/2005 1.18 207 265 3.4 14 87 5 3.4

06/23/2005 1.06 192 222 6.6 13 88 4 2.0

07/26/2005 .58 62.8 135 3.5 5 75 3 .34

08/24/2005 .55 55.0 127 3.7 5 72 3 .24

Data 25

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/16/2004 0815 22 8.3 424 0.0 210 64.3 12.4 4.5

04/18/2005 1550 22 8.5 430 5.5 220 67.9 12.8 6.3

05/17/2005 0745 94 8.1 281 7.0 130 40.2 7.68 8.2

06/02/2005 0855 177 8.0 176 5.5 84 26.3 4.30 6.1

07/26/2005 0810 50 8.2 295 10.0 150 47.0 7.81 6.9

08/24/2005 0800 39 8.3 338 10.5 170 52.2 8.99 6.5

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/16/2004 5 0.05 0.08 2.1 7.2 9 70 <0.08

04/18/2005 7 .04 .08 3.0 6.6 7 60 <.08

05/17/2005 22 .04 .41 5.1 108 20 1,700 .10

06/02/2005 11 E.03 .17 5.0 45.5 23 670 .09

07/26/2005 7.6 E.03 .07 2.9 8.2 18 90 E.06

08/24/2005 7.2 E.04 .07 2.6 8.7 16 100 E.05

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/16/2004 0.36 394 435 3.0 3 73 9 0.53

04/18/2005 .23 219 242 1.1 2 73 2 .12

05/17/2005 10.3 160 1,270 2.0 39 60 106 27

06/02/2005 3.90 65.3 298 7.6 17 63 37 18

07/26/2005 .51 217 249 1.5 3 74 4 .54

08/24/2005 .55 177 255 1.4 3 67 4 .42

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

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/16/2004 1005 65 9.0 569 1.0 250 72.3 17.0 11.4

03/08/2005 1550 54 8.7 593 8.0 280 81.7 17.6 9.1

04/19/2005 0745 59 8.2 592 5.0 280 82.3 18.1 7.3

05/17/2005 0955 383 8.6 401 9.0 160 44.5 12.1 29.6

06/02/2005 1050 427 8.8 289 8.5 120 35.3 6.90 20.4

06/22/2005 1615 566 8.6 218 16.5 93 28.7 5.29 21.0

07/26/2005 0950 77 8.4 390 13.0 190 58.0 11.7 15.2

08/23/2005 1700 70 9.0 440 18.0 220 63.9 13.5 20.1

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/16/2004 12 0.12 0.17 4.9 9.3 7 90 <0.08

03/08/2005 11 .07 .13 4.8 12.2 E4 180 <.08

04/19/2005 10 .06 .12 4.8 8.2 11 210 E.04

05/17/2005 50 E.03 .64 6.8 89.3 63 2,030 .22

06/02/2005 27 .04 .18 6.8 31.3 29 520 .10

06/22/2005 28 E.03 .22 7.8 53.3 18 780 .12

07/26/2005 16.1 E.04 .06 4.0 8.1 13 100 E.06

08/23/2005 21.5 E.03 .07 4.0 9.0 7 120 E.05

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/16/2004 0.36 158 152 5.3 9 96 2 0.35

03/08/2005 .82 176 208 4.4 12 79 6 .87

04/19/2005 .98 204 274 7.2 12 84 4 .64

05/17/2005 14.3 177 785 3.2 80 67 94 97

06/02/2005 2.94 116 307 2.8 20 71 20 23

06/22/2005 4.95 52.5 251 2.4 24 70 35 53

07/26/2005 .57 91.3 152 2.3 5 85 4 .83

08/23/2005 .80 41.1 139 1.2 6 76 4 .76

Data 27

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
12323840—Lost Creek near Anaconda

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)

Arsenic, 

filtered 

(μg/L)

12/15/2004 1430 4.5 8.4 221 3.0 100 30.8 6.69 2.7

03/08/2005 1100 2.8 8.6 221 4.5 110 31.4 6.79 2.5

04/18/2005 1250 4.0 8.4 211 4.5 100 30.3 6.46 2.8

05/16/2005 1400 8.3 7.4 163 8.5 50 15.7 2.71 156

06/01/2005 1500 15 8.2 170 7.0 84 26.0 4.60 8.0

06/22/2005 1310 17 8.2 176 13.0 87 27.2 4.48 10.2

07/25/2005 1520 .97 8.4 227 13.0 110 35.7 6.16 9.3

08/23/2005 1400 4.0 8.3 224 14.5 110 33.9 6.11 5.6

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/15/2004 3 E0.02 E0.02 1.2 1.7 <6 30 <0.08

03/08/2005 2 .05 E.03 1.5 4.5 <6 60 <.08

04/18/2005 3 E.03 E.04 1.5 3.6 E4 60 <.08

05/16/2005 3,860 .90 147 90.5 29,100 25 99,700 .18

06/01/2005 11 .04 .11 4.5 18.9 15 640 E.06

06/22/2005 10 .04 .07 3.4 8.2 11 210 E.04

07/25/2005 8.9 .04 .04 3.3 4.4 8 20 <.08

08/23/2005 6.2 .05 .08 3.6 8.9 <6 160 E.05

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/15/2004 0.13 0.5 1 1.2 3 83 3 0.04

03/08/2005 .38 .8 2 1.0 3 87 11 .08

04/18/2005 .35 .9 3 1.1 E2 66 2 .02

05/16/2005 1,290 42.4 8,830 30.0 7,780 97 58,900 1,320

06/01/2005 2.80 2.0 18 1.8 11 30 53 2.1

06/22/2005 .95 2.3 8 1.7 4 41 16 .73

07/25/2005 .18 1.9 3 1.2 2 73 1 <.01

08/23/2005 .70 1.2 6 1.3 4 80 8 .09

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

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/16/2004 0935 43 8.7 618 1.5 310 89.0 20.3 8.7

03/08/2005 1520 37 8.7 627 9.5 320 95.5 20.9 13.7

04/19/2005 0720 42 8.3 702 4.0 380 109 25.5 15.9

05/17/2005 0925 20 8.2 934 8.5 450 122 35.7 36.9

06/02/2005 1020 11 8.4 705 8.5 340 97.0 24.6 12.6

06/22/2005 1545 11 8.5 663 22.0 330 93.6 24.4 15.7

07/26/2005 0930 2.4 8.0 668 13.0 310 85.2 24.0 24.6

08/23/2005 1630 5.6 8.3 680 18.0 330 92.9 24.4 23.6

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/16/2004 8 E0.02 0.04 1.7 4.0 E5 80 <0.08

03/08/2005 14 E.03 .04 2.6 7.4 E5 80 <.08

04/19/2005 15 .04 .09 2.9 10.1 10 160 E.04

05/17/2005 37 E.03 .06 5.4 18.7 61 110 E.06

06/02/2005 14 E.02 .06 2.6 6.3 14 50 E.05

06/22/2005 15 E.02 E.03 3.0 4.4 7 40 <.08

07/26/2005 24.7 .04 .08 3.2 6.3 25 80 .11

08/23/2005 23.4 E.04 .07 3.5 6.1 17 80 .10

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/16/2004 0.25 6.1 8 2.4 4 29 29 3.4

03/08/2005 .33 13.5 14 2.3 3 63 10 1.0

04/19/2005 .63 15.7 24 3.8 7 65 15 1.7

05/17/2005 .38 39.5 45 2.8 8 67 7 .38

06/02/2005 .12 8.3 10 1.3 2 49 11 .33

06/22/2005 .19 3.8 6 1.2 E1 36 17 .50

07/26/2005 .45 28.3 32 3.6 3 76 6 .04

08/23/2005 .39 11.3 17 1.7 2 72 5 .08

Data 29

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/16/2004 1105 186 8.4 541 1.0 240 71.5 16.0 9.1

03/08/2005 1705 146 8.7 565 8.0 270 78.6 17.2 10.2

04/18/2005 1735 152 8.6 605 7.0 280 82.0 18.7 11.5

05/17/2005 1110 436 8.1 438 10.0 180 51.6 13.2 18.2

06/02/2005 1200 552 8.2 353 9.5 150 44.3 10.2 20.8

06/23/2005 0715 698 8.1 259 15.0 110 35.0 6.53 19.3

07/26/2005 1055 88 8.5 484 14.5 210 64.0 13.2 16.2

08/24/2005 0935 90 8.1 524 12.0 240 70.6 14.7 14.2

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/16/2004 11 0.06 0.15 4.4 20.0 6 290 E0.04

03/08/2005 12 .06 .13 6.0 22.9 7 300 E.06

04/18/2005 13 .05 .14 5.4 18.8 E4 250 E.06

05/17/2005 78 E.04 2.06 10.6 468 41 6,960 .40

06/02/2005 39 .06 .52 12.7 97.6 35 1,690 .20

06/23/2005 31 .07 .43 11.4 96.8 23 1,740 .19

07/26/2005 17.1 .06 .06 8.6 11.8 7 40 E.07

08/24/2005 15.9 .06 .07 8.4 14.2 6 70 E.04

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/16/2004 2.13 47.0 74 8.4 23 78 17 8.5

03/08/2005 2.46 66.5 95 4.2 20 79 14 5.5

04/18/2005 1.95 51.2 88 5.1 19 84 10 4.1

05/17/2005 61.7 97.9 1,010 9.3 359 67 387 456

06/02/2005 14.1 35.6 339 8.1 87 58 83 124

06/23/2005 14.2 18.3 255 7.4 72 37 114 215

07/26/2005 .37 13.0 18 5.1 7 82 1 .24

08/24/2005 .69 21.6 47 10.8 13 79 3 .73

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

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/16/2004 1255 322 8.8 458 1.0 210 60.1 13.3 7.2

03/09/2005 1410 312 8.8 442 8.0 210 61.0 13.3 7.9

04/19/2005 0915 365 8.4 446 4.5 210 60.7 13.6 7.5

05/17/2005 1315 1,460 8.2 280 10.0 110 31.9 7.34 9.6

06/02/2005 1400 1,880 8.1 286 8.5 130 36.7 8.19 11.1

06/23/2005 1015 1,500 8.2 253 14.5 120 35.7 6.83 12.4

07/26/2005 1225 248 8.5 392 16.5 190 55.4 11.5 10.5

08/24/2005 1055 221 8.4 431 13.5 200 58.3 12.3 10.9

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/16/2004 8 E0.03 0.10 3.1 14.1 E4 200 <0.08

03/09/2005 10 .05 .12 4.9 21.4 7 390 E.06

04/19/2005 8 E.03 .14 3.7 17.5 19 330 E.05

05/17/2005 24 E.03 .60 6.3 99.5 60 2,690 .33

06/02/2005 22 .05 .43 9.3 74.7 48 2,110 .25

06/23/2005 18 .07 .29 9.1 62.7 21 940 .19

07/26/2005 11.1 E.03 .05 4.5 6.1 7 50 <.08

08/24/2005 11.1 E.03 .04 5.0 7.6 E5 70 <.08

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/16/2004 1.52 16.8 54 3.4 16 85 10 8.7

03/09/2005 2.38 27.0 71 2.7 21 78 19 16

04/19/2005 2.08 19.5 68 4.5 21 82 14 14

05/17/2005 16.6 23.7 314 4.5 104 74 148 583

06/02/2005 12.2 17.4 257 6.7 89 44 143 726

06/23/2005 7.79 12.3 138 5.1 44 61 52 211

07/26/2005 .18 10.0 20 1.8 3 72 2 1.3

08/24/2005 .33 7.7 32 2.3 5 74 4 2.4

Data  31

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/20/2004 0930 451 8.5 487 3.0 220 63.4 15.7 7.5

03/09/2005 1515 447 8.6 473 10.0 230 65.5 15.6 8.6

04/18/2005 1020 469 8.4 477 7.5 230 66.2 16.2 9.3

05/17/2005 1515 1,810 8.2 289 11.0 120 34.7 8.44 9.5

06/02/2005 1630 2,210 8.2 312 9.5 140 39.6 10.1 12.2

06/23/2005 1150 2,030 8.2 289 16.0 130 39.7 8.16 12.9

07/26/2005 1340 323 8.5 495 18.5 240 67.5 16.7 11.5

08/24/2005 1210 270 8.4 536 15.5 260 72.8 18.1 11.6

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/20/2004 8 0.30 0.10 2.6 12.3 12 220 E0.05

03/09/2005 10 .05 .17 4.9 24.5 E5 470 E.07

04/18/2005 11 E.03 .17 3.8 24.7 E6 510 E.07

05/17/2005 24 E.03 .55 6.4 77.7 51 2,280 .40

06/02/2005 30 .07 .82 12.8 146 37 3,320 .29

06/23/2005 18 .07 .28 8.6 48.3 14 880 .18

07/26/2005 12.7 E.04 .04 4.3 6.1 <6 40 E.04

08/24/2005 11.7 E.03 E.04 4.2 6.3 7 50 <.08

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/20/2004 1.78 11.5 53 5.0 17 74 14 17

03/09/2005 3.45 20.1 78 3.7 31 78 27 33

04/18/2005 4.11 17.8 98 4.0 35 85 26 33

05/17/2005 17.8 23.7 295 4.9 104 80 132 645

06/02/2005 23.0 18.1 403 9.0 201 61 222 1,320

06/23/2005 7.48 14.0 137 5.4 45 69 49 269

07/26/2005 .30 11.7 21 2.9 5 77 5 4.4

08/24/2005 .45 7.3 30 2.6 6 72 8 5.8

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

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/20/2004 1055 702 8.6 390 2.0 170 48.6 12.7 5.0

03/09/2005 1630 702 8.7 383 8.5 180 50.2 12.9 5.8

04/20/2005 1530 900 8.5 343 7.0 160 43.9 11.8 5.2

05/17/2005 1710 3,340 8.1 186 11.5 77 21.4 5.63 4.7

06/03/2005 1045 4,310 8.1 214 9.0 95 27.3 6.57 7.4

06/29/2005 1020 3,130 8.3 263 13.0 120 35.7 8.01 8.7

07/26/2005 1505 746 8.8 312 18.5 150 40.1 11.0 5.9

08/24/2005 1320 520 8.6 360 14.5 170 48.4 12.9 5.9

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/20/2004 5 0.10 0.06 2.0 6.6 <6 120 <0.08

03/09/2005 6 E.03 .10 3.6 14.6 E3 280 E.04

04/20/2005 6 <.04 .10 2.4 12.2 6 290 E.05

05/17/2005 10 E.02 .42 3.6 48.1 47 1,700 .23

06/03/2005 16 E.04 .40 6.9 62.8 46 1,700 .24

06/29/2005 11 .05 .16 5.7 25.9 22 550 .12

07/26/2005 6.1 <.04 E.03 2.4 3.7 E4 30 <.08

08/24/2005 6.0 <.04 E.03 2.5 4.6 <6 70 <.08

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/20/2004 0.86 3.0 24 3.1 10 88 7 13

03/09/2005 2.07 7.3 51 2.3 21 82 17 32

04/20/2005 2.10 5.4 49 2.2 20 81 15 36

05/17/2005 10.3 12.1 221 3.6 81 65 123 1,110

06/03/2005 10.9 7.5 221 5.9 93 68 110 1,280

06/29/2005 4.01 8.2 79 4.6 30 66 35 296

07/26/2005 .18 4.4 11 1.3 3 82 2 4.0

08/24/2005 .35 3.9 19 1.6 5 75 5 7.0

Data  33

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
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)

Arsenic, 

filtered 

(μg/L)

12/20/2004 1215 641 8.4 240 2.0 120 30.2 11.0 0.9

04/20/2005 1415 1,570 8.4 185 6.5 91 23.2 7.99 .8

05/18/2005 0930 5,250 8.2 161 9.0 77 20.2 6.51 .8

06/03/2005 0845 4,070 8.3 172 9.0 89 23.6 7.28 .8

07/27/2005 0745 772 8.4 247 15.0 130 32.6 12.3 1.2

08/24/2005 1455 E540 8.6 257 16.0 140 33.6 12.7 1.4

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/20/2004 <2 E0.02 <0.04 E0.4 E0.3 <6 30 <0.08

04/20/2005 <2 <.04 <.04 .9 1.2 12 100 <.08

05/18/2005 <2 <.04 E.03 1.1 4.8 24 750 E.05

06/03/2005 <2 E.02 <.04 .9 2.7 29 400 0.09

07/27/2005 1.1 <.04 <.04 .6 1.2 E5 50 <.08

08/24/2005 1.5 <.04 <.04 .6 0.7 E4 30 <.08

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/20/2004 <0.06 0.8 2 <0.6 <2 73 2 3.5

04/20/2005 .13 1.9 12 .9 <2 81 6 25

05/18/2005 1.34 2.1 54 1.1 6 87 66 936

06/03/2005 .62 1.7 33 .6 4 89 33 363

07/27/2005 .10 1.6 9 .7 E1 82 4 8.3

08/24/2005 E.04 1.5 6 .6 <2 81 2 E2.9

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

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
12340500—Clark Fork above 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)

Arsenic, 

filtered 

(μg/L)

12/20/2004 1350 1,290 8.6 323 3.0 150 40.5 12.2 3.2

03/10/2005 0750 1,280 8.4 312 7.0 150 40.3 11.8 3.6

04/20/2005 1030 2,360 8.4 248 7.0 120 31.2 9.30 2.5

05/18/2005 0715 9,110 8.1 170 9.5 77 20.7 6.11 2.7

06/03/2005 0645 7,960 8.2 193 9.0 91 25.1 6.79 4.0

06/29/2005 1235 5,180 8.3 243 13.5 120 32.9 8.39 5.4

07/27/2005 0900 1,430 8.5 276 18.0 140 37.0 11.6 3.8

08/24/2005 1630 959 8.5 306 16.0 150 39.4 12.3 3.7

Date

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium 

filtered 

(μg/L)

Cadmium 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

12/20/2004 3 E0.03 0.04 1.4 3.3 <6 70 <0.08

03/10/2005 3 <.04 .05 2.1 6.5 7 120 E.05

04/20/2005 2 <.04 .06 1.4 5.5 13 150 E.05

05/18/2005 6 <.04 .22 2.3 26.2 43 1,260 .16

06/03/2005 7 E.03 .21 4.2 31.9 32 930 .17

06/29/2005 6 E.03 .10 4.3 14.8 16 330 .09

07/27/2005 4.0 <.04 .06 2.4 6.1 9 80 E.05

08/24/2005 3.9 <.04 E.03 1.8 4.2 7 80 E.04

Date

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended, 

percent 

finer than 

0.062 mm

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

12/20/2004 0.43 7.5 12 2.3 6 86 5 17

03/10/2005 .73 30.3 34 6.3 9 90 7 24

04/20/2005 .83 14.1 25 1.5 9 92 9 57

05/18/2005 5.91 8.8 121 2.4 44 90 89 2,190

06/03/2005 5.32 8.0 122 3.9 48 90 55 1,180

06/29/2005 2.23 13.6 49 3.8 19 89 18 252

07/27/2005 .52 13.8 25 1.3 8 92 5 19

08/24/2005 .46 14.1 30 1.2 5 84 5 13

Data  35

Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 2004 through September 2005.—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, millimeters; ton/d, tons per day. Symbol: <, less than laboratory reporting level]
Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2004 through 

September 2005.

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; milligrams per liter; min, minimum; mg/L, 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

1 126 11 3.7 154 15 6.2 e140 20 7.6

2 132 10 3.6 160 20 8.6 e160 19 8.2

3 135 10 3.6 168 21 9.5 171 18 8.3

4 132 10 3.6 168 19 8.6 172 17 7.9

5 133 10 3.6 165 16 7.1 175 16 7.6

6 132 10 3.6 172 13 6.0 179 15 7.2

7 130 11 3.9 168 11 5.0 178 15 7.2

8 132 11 3.9 164 11 4.9 177 14 6.7

9 130 12 4.2 168 12 5.4 178 14 6.7

10 136 12 4.4 170 13 6.0 183 16 7.9

11 152 14 5.7 170 14 6.4 195 19 10

12 163 17 7.5 168 14 6.4 196 20 11

13 164 18 8.0 165 14 6.2 183 20 9.9

14 171 18 8.3 166 15 6.7 189 19 9.7

15 169 15 6.8 168 15 6.8 189 18 9.2

16 165 13 5.8 177 18 8.6 185 17 8.5

17 160 12 5.2 173 21 9.8 185 16 8.0

18 166 12 5.4 173 22 10 183 17 8.4

19 163 12 5.3 175 22 10 187 18 9.1

20 168 12 5.4 180 21 10 187 19 9.6

21 175 16 7.6 169 20 9.1 171 20 9.2

22 169 14 6.4 172 20 9.3 e160 20 8.6

23 165 13 5.8 192 20 10 e130 21 7.4

24 162 12 5.2 200 23 12 e160 21 9.1

25 158 11 4.7 214 26 15 174 22 10

26 154 11 4.6 222 26 16 e180 24 12

27 156 12 5.1 202 26 14 e180 28 14

28 163 12 5.3 e190 24 12 e170 30 14

29 168 13 5.9 e170 22 10 e170 27 12

30 164 13 5.8 e150 20 8.1 176 23 11

31 158 13 5.5 --- --- --- e150 20 8.1

Total 4,751 --- 163.4 5,253 --- 263.7 5,413 --- 284.1

Mean 153 13 5.3 175 18 8.8 175 19 9.2

Max 175 18 8.3 222 26 16 196 30 14

Min 126 10 3.6 150 11 4.9 130 14 6.7

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

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

January February March

1 e140 17 6.4 171 31 14 158 16 6.8

2 e140 17 6.4 172 29 13 156 16 6.7

3 e140 19 7.2 172 28 13 155 15 6.3

4 e130 24 8.4 175 26 12 149 15 6.0

5 e120 23 7.5 171 25 12 150 15 6.1

6 e110 20 5.9 157 25 11 151 15 6.1

7 e130 17 6.0 159 24 10 149 15 6.0

8 e150 16 6.5 161 24 10 146 14 5.5

9 e150 16 6.5 151 23 9.4 146 13 5.1

10 e150 16 6.5 154 22 9.1 145 12 4.7

11 e150 16 6.5 156 21 8.8 142 12 4.6

12 e160 16 6.9 164 20 8.9 143 18 6.9

13 e150 16 6.5 164 20 8.9 143 23 8.9

14 e140 16 6.0 158 20 8.5 143 24 9.3

15 e130 16 5.6 150 22 8.9 144 26 10

16 e150 16 6.5 143 23 8.9 145 28 11

17 160 19 8.2 151 23 9.4 146 28 11

18 193 44 23 157 23 9.7 143 28 11

19 250 116 78 161 23 10 143 25 9.7

20 223 73 44 163 23 10 148 20 8.0

21 205 72 40 159 23 9.9 147 18 7.1

22 192 56 29 153 23 9.5 143 18 6.9

23 191 50 26 152 22 9.0 140 18 6.8

24 185 39 19 153 20 8.3 132 18 6.4

25 178 31 15 157 19 8.1 146 19 7.5

26 173 30 14 153 18 7.4 144 19 7.4

27 172 30 14 154 17 7.1 147 20 7.9

28 172 32 15 154 16 6.7 152 20 8.2

29 174 31 15 --- --- --- 157 19 8.1

30 173 31 14 --- --- --- 150 17 6.9

31 171 31 14 --- --- --- 143 14 5.4

Total 5,052 --- 473.5 4,445 --- 271.5 4,546 --- 228.3

Mean 163 31 15 159 23 9.7 147 19 7.4

Max 250 116 78 175 31 14 158 28 11

Min 110 16 5.6 143 16 6.7 132 12 4.6

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2004 through 

September 2005.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: ---, no data or value not computed]

Data  37
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

1 141 12 4.6 133 14 5.0 403 63 69

2 141 10 3.8 125 12 4.0 522 90 127

3 139 14 5.3 126 9 3.1 518 65 91

4 140 18 6.8 124 12 4.0 511 72 99

5 141 19 7.2 120 12 3.9 484 77 101

6 142 18 6.9 121 22 7.2 533 83 119

7 144 16 6.2 120 22 7.1 577 85 132

8 146 14 5.5 123 51 17 490 33 44

9 148 15 6.0 165 60 27 453 19 23

10 140 14 5.3 249 61 41 412 17 19

11 134 12 4.3 322 61 53 370 22 22

12 131 12 4.2 278 62 47 388 34 36

13 129 14 4.9 237 44 28 418 28 32

14 147 16 6.4 214 39 23 363 15 15

15 153 23 9.5 231 44 27 398 37 40

16 150 19 7.7 270 90 66 448 92 111

17 146 19 7.5 438 330 390 598 205 331

18 150 15 6.1 438 155 183 785 120 254

19 158 16 6.8 435 137 161 690 69 129

20 155 20 8.4 539 210 306 572 82 127

21 150 20 8.1 550 145 215 585 98 155

22 146 17 6.7 520 86 121 656 101 179

23 143 20 7.7 507 85 116 711 102 196

24 142 21 8.1 504 78 106 615 58 96

25 141 20 7.6 448 56 68 512 38 53

26 142 16 6.1 373 42 42 480 35 45

27 144 14 5.4 320 46 40 541 40 58

28 146 20 7.9 313 40 34 571 30 46

29 144 18 7.0 323 34 30 558 25 38

30 142 14 5.4 323 35 31 529 20 29

31 --- --- --- 302 27 22 --- --- ---

Total 4,315 --- 193.4 9,291 --- 2,228.3 15,691 --- 2,816

Mean 144 17 6.4 300 68 72 523 62 94

Max 158 23 9.5 550 330 390 785 205 331

Min 129 10 3.8 120 9 3.1 363 15 15

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

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2004 through 

September 2005.—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

1 485 14 18 96 10 2.6 109 29 8.5

2 462 12 15 103 10 2.8 111 28 8.4

3 436 10 12 97 16 4.2 108 24 7.0

4 404 8 8.7 93 19 4.8 102 20 5.5

5 372 7 7.0 82 19 4.2 100 20 5.4

6 319 6 5.2 77 18 3.7 103 22 6.1

7 294 5 4.0 75 17 3.4 102 24 6.6

8 292 4 3.2 73 16 3.2 106 26 7.4

9 268 3 2.2 88 14 3.3 91 26 6.4

10 243 3 2.0 90 12 2.9 108 26 7.6

11 241 3 2.0 85 8 1.8 128 25 8.6

12 213 3 1.7 94 8 2.0 127 24 8.2

13 187 3 1.5 88 6 1.4 133 24 8.6

14 175 5 2.4 91 6 1.5 130 23 8.1

15 166 13 5.8 91 6 1.5 127 23 7.9

16 145 21 8.2 86 5 1.2 124 22 7.4

17 130 22 7.7 84 5 1.1 149 21 8.4

18 125 19 6.4 86 6 1.4 166 20 9.0

19 116 15 4.7 88 8 1.9 165 19 8.5

20 101 10 2.7 88 9 2.1 162 19 8.3

21 95 10 2.6 90 8 1.9 157 18 7.6

22 94 11 2.8 85 6 1.4 155 18 7.5

23 93 12 3.0 96 4 1.0 151 18 7.3

24 91 10 2.5 94 3 .76 174 18 8.5

25 91 6 1.5 94 7 1.8 187 18 9.1

26 98 2 .53 87 14 3.3 179 18 8.7

27 92 12 3.0 85 21 4.8 170 20 9.2

28 83 28 6.3 89 25 6.0 165 20 8.9

29 82 23 5.1 91 26 6.4 168 20 9.1

30 82 17 3.8 100 27 7.3 166 20 9.0

31 85 12 2.8 112 29 8.8 --- --- ---

Total 6,160 --- 154.33 2,778 --- 94.46 4,123 --- 236.8

Mean 199 11 5.0 90 13 3.0 137 22 7.9

Max 485 28 18 112 29 8.8 187 29 9.2

Min 82 2 .53 73 3 .76 91 18 5.4

Total for water year 2005 (unrounded sum of the daily values): streamflow, 71,818 ft3/s (142,500 acre-ft); sediment load, 7,407.79 tons.

Data  39

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2004 through 

September 2005.—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]
Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2004 

through September 2005.

[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

1 863 8 19 771 6 12 628 5 8.5

2 851 7 16 753 5 10 683 5 9.2

3 841 6 14 777 4 8.4 701 6 11

4 827 6 13 790 3 6.4 690 6 11

5 820 6 13 762 3 6.2 681 6 11

6 828 6 13 766 3 6.2 684 6 11

7 826 6 13 775 4 8.4 698 6 11

8 822 6 13 770 4 8.3 703 6 11

9 823 6 13 761 4 8.2 713 6 12

10 813 6 13 756 4 8.2 699 6 11

11 799 6 13 756 4 8.2 717 5 9.7

12 807 5 11 747 4 8.1 740 5 10

13 815 5 11 732 4 7.9 717 5 9.7

14 831 6 13 723 4 7.8 668 5 9.0

15 840 8 18 716 4 7.7 725 5 9.8

16 852 9 21 725 4 7.8 707 4 7.6

17 845 8 18 737 4 8.0 687 4 7.4

18 850 8 18 730 4 7.9 684 4 7.4

19 855 8 18 719 4 7.8 686 5 9.3

20 842 7 16 724 4 7.8 697 7 13

21 851 7 16 690 4 7.5 672 7 13

22 858 6 14 654 4 7.1 665 6 11

23 845 6 14 698 4 7.5 e600 6 9.7

24 831 5 11 746 5 10 e500 5 6.8

25 818 5 11 772 6 13 e570 5 7.7

26 798 4 8.6 779 7 15 652 5 8.8

27 793 5 11 744 6 12 633 5 8.5

28 789 6 13 664 6 11 e560 5 7.6

29 787 6 13 674 5 9.1 e500 7 9.4

30 788 6 13 606 5 8.2 e700 11 21

31 781 5 11 --- --- --- 670 14 25

Total 25,589 --- 432.6 22,017 --- 261.7 20,630 --- 328.1

Mean 825 6 14 734 4 8.7 665 6 11

Max 863 9 21 790 7 15 740 14 25

Min 781 4 8.6 606 3 6.2 500 4 6.8

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

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

January February March

1 591 14 22 707 10 19 607 9 15

2 e400 10 11 705 9 17 625 12 20

3 e320 6 5.2 689 10 19 629 10 17

4 e270 4 2.9 690 12 22 634 13 22

5 e220 4 2.4 696 13 24 636 14 24

6 e230 4 2.5 674 13 24 648 14 24

7 e280 4 3.0 619 13 22 669 16 29

8 e400 4 4.3 634 12 21 690 18 34

9 e420 4 4.5 639 12 21 708 19 36

10 e420 4 4.5 588 12 19 719 20 39

11 e440 4 4.8 587 12 19 708 21 40

12 e480 4 5.2 607 11 18 707 22 42

13 e540 4 5.8 646 11 19 707 19 36

14 e560 5 7.6 637 10 17 666 17 31

15 e500 5 6.8 609 10 16 660 14 25

16 e400 5 5.4 572 10 15 655 14 25

17 e460 6 7.5 528 10 14 666 14 25

18 e550 13 19 527 9 13 656 12 21

19 e750 30 61 552 8 12 629 12 20

20 926 35 88 593 8 13 641 15 26

21 968 42 110 635 8 14 658 16 28

22 892 21 51 602 7 11 658 16 28

23 850 13 30 584 7 11 650 12 21

24 819 10 22 590 7 11 618 9 15

25 778 9 19 601 6 9.7 604 9 15

26 759 8 16 609 6 9.9 622 11 18

27 746 8 16 604 6 9.8 615 14 23

28 746 8 16 600 7 11 663 18 32

29 744 10 20 --- --- --- 735 23 46

30 740 10 20 --- --- --- 741 21 42

31 722 10 19 --- --- --- 700 14 26

Total 17,921 --- 612.4 17,324 --- 451.4 20,524 --- 845

Mean 578 10 20 619 10 16 662 15 27

Max 968 42 110 707 13 24 741 23 46

Min 220 4 2.4 527 6 9.7 604 9 15

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2004 

through September 2005.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: ---, no data or value not computed]

Data 41
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

1 666 13 23 1,080 17 50 2,740 34 252

2 667 15 27 1,020 16 44 3,690 86 857

3 682 16 29 968 13 34 4,340 139 1,630

4 702 16 30 951 13 33 4,710 193 2,450

5 691 13 24 970 12 31 4,970 165 2,210

6 675 13 24 1,030 12 33 4,810 112 1,450

7 676 15 27 1,140 16 49 4,690 91 1,150

8 737 20 40 1,260 22 75 4,450 69 829

9 797 24 52 1,430 32 124 4,100 51 565

10 793 19 41 1,800 57 277 3,830 39 403

11 762 16 33 2,630 131 930 3,490 36 339

12 734 16 32 3,160 165 1,410 3,560 35 336

13 720 16 31 2,760 70 522 3,970 51 547

14 782 16 34 2,480 48 321 3,660 39 385

15 783 15 32 2,400 38 246 3,340 30 271

16 760 16 33 2,540 47 322 3,460 36 336

17 797 23 49 3,100 95 795 3,660 42 415

18 836 24 54 3,760 125 1,270 4,290 84 973

19 871 22 52 3,810 108 1,110 4,180 65 734

20 888 18 43 4,600 136 1,690 3,700 42 420

21 896 17 41 4,540 98 1,200 3,410 36 331

22 883 18 43 4,520 101 1,230 3,290 30 266

23 892 20 48 4,400 67 796 3,260 30 264

24 948 26 67 4,060 55 603 3,090 26 217

25 1,010 28 76 3,710 45 451 2,790 25 188

26 1,090 33 97 3,350 40 362 2,680 23 166

27 1,200 42 136 3,020 32 261 2,710 21 154

28 1,230 29 96 2,790 29 218 3,000 25 202

29 1,160 22 69 2,670 27 195 3,090 32 267

30 1,110 20 60 2,620 27 191 2,920 25 197

31 --- --- --- 2,530 23 157 --- --- ---

Total 25,438 --- 1,443 81,099 --- 15,030 109,880 --- 18,804

Mean 848 20 48 2,616 55 485 3,663 57 627

Max 1,230 42 136 4,600 165 1,690 4,970 193 2,450

Min 666 13 23 951 12 31 2,680 21 154

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

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2004 

through September 2005.—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 2,690 18 131 631 4 6.8 517 4 5.6

2 2,410 15 98 664 8 14 519 4 5.6

3 2,220 14 84 660 9 16 515 4 5.6

4 2,080 12 67 630 8 14 513 3 4.2

5 1,950 11 58 599 8 13 512 3 4.1

6 1,830 8 40 574 7 11 507 3 4.1

7 1,700 7 32 544 7 10 506 3 4.1

8 1,600 7 30 536 7 10 501 3 4.1

9 1,530 7 29 547 7 10 499 3 4.0

10 1,490 6 24 549 7 10 538 3 4.4

11 1,450 6 23 545 7 10 564 3 4.6

12 1,410 5 19 537 6 8.7 584 4 6.3

13 1,330 4 14 542 6 8.8 597 4 6.4

14 1,240 4 13 542 6 8.8 612 4 6.6

15 1,170 4 13 543 6 8.8 621 4 6.7

16 1,120 3 9.1 534 5 7.2 610 4 6.6

17 1,050 3 8.5 519 5 7.0 712 10 19

18 1,010 3 8.2 533 5 7.2 837 20 45

19 960 3 7.8 537 5 7.2 835 16 36

20 902 2 4.9 533 5 7.2 796 12 26

21 855 2 4.6 517 5 7.0 757 9 18

22 819 2 4.4 505 5 6.8 736 9 18

23 801 2 4.3 518 5 7.0 758 9 18

24 778 2 4.2 519 5 7.0 788 10 21

25 750 2 4.0 523 5 7.1 856 12 28

26 739 2 4.0 526 5 7.1 859 11 26

27 727 2 3.9 514 5 6.9 839 8 18

28 720 3 5.8 506 4 5.5 820 7 15

29 698 3 5.7 500 4 5.4 801 7 15

30 646 3 5.2 498 4 5.4 794 7 15

31 625 4 6.8 506 4 5.5 --- --- ---

Total 39,300 --- 766.4 16,931 --- 266.4 19,903 --- 401.0

Mean 1,268 5 25 546 6 8.6 663 7 13

Max 2,690 18 131 664 9 16 859 20 45

Min 625 2 3.9 498 4 5.4 499 3 4.0

Total for water year 2005 (unrounded sum of daily values): streamflow, 416,556 ft3/s (826,200 acre-ft); sediment load, 39,642 tons.

Data 43

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2004 

through September 2005.—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]
Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2004 through 

September 2005.

[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 1,510 6 24 1,370 5 18 1,190 3 9.6

2 1,470 7 28 1,330 4 14 1,250 3 10

3 1,460 7 28 1,370 3 11 1,250 3 10

4 1,440 6 23 1,350 3 11 1,220 3 9.9

5 1,420 5 19 1,370 3 11 1,210 2 6.5

6 1,420 5 19 1,360 3 11 1,200 2 6.5

7 1,430 5 19 1,330 3 11 1,210 2 6.5

8 1,430 6 23 1,370 3 11 1,230 2 6.6

9 1,390 5 19 1,350 3 11 1,230 3 10

10 1,390 5 19 1,350 3 11 1,230 3 10

11 1,370 4 15 1,360 2 7.3 1,280 4 14

12 1,360 4 15 1,350 2 7.3 1,340 3 11

13 1,360 5 18 1,330 2 7.2 1,340 2 7.2

14 1,360 5 18 1,310 2 7.1 1,270 2 6.9

15 1,360 6 22 1,300 2 7.0 1,350 2 7.3

16 1,370 6 22 1,290 2 7.0 1,330 2 7.2

17 1,410 6 23 1,310 3 11 1,310 2 7.1

18 1,450 6 23 1,300 3 11 1,290 2 7.0

19 1,460 5 20 1,270 3 10 1,300 2 7.0

20 1,450 5 20 1,290 2 7.0 1,290 4 14

21 1,450 5 20 1,260 2 6.8 1,280 4 14

22 1,480 4 16 1,170 2 6.3 1,290 3 10

23 1,460 4 16 1,230 3 10 e1,100 2 5.9

24 1,450 4 16 1,300 3 11 e900 2 4.9

25 1,460 3 12 1,390 3 11 e1,100 3 8.9

26 1,410 3 11 1,440 4 16 1,300 3 11

27 1,400 3 11 1,400 4 15 1,210 3 9.8

28 1,390 3 11 1,260 3 10 e1,000 3 8.1

29 1,380 3 11 1,220 3 9.9 e900 3 7.3

30 1,380 3 11 1,140 3 9.2 e1,100 3 8.9

31 1,370 4 15 --- --- --- e1,200 3 9.7

Total 43,940 --- 567 39,470 --- 307.1 37,700 --- 272.8

Mean 1,417 5 18 1,316 3 10 1,216 3 8.8

Max 1,510 7 28 1,440 5 18 1,350 4 14

Min 1,360 3 11 1,140 2 6.3 900 2 4.9

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

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

January February March

1 e950 3 7.7 1,450 6 23 1,100 5 15

2 e700 3 5.7 1,470 6 24 1,140 6 18

3 e630 3 5.1 1,420 6 23 1,130 4 12

4 e530 3 4.3 1,380 5 19 1,130 5 15

5 e500 3 4.0 1,390 5 19 1,150 5 16

6 e550 3 4.5 1,370 4 15 1,160 6 19

7 e630 3 5.1 1,260 4 14 1,170 6 19

8 e800 3 6.5 1,230 4 13 1,200 6 19

9 e830 4 9.0 1,270 3 10 1,240 6 20

10 e850 4 9.2 1,220 4 13 1,320 9 32

11 e900 4 9.7 1,190 4 13 1,290 6 21

12 e950 4 10 1,220 5 16 1,340 6 22

13 e1,050 3 8.5 1,210 5 16 1,390 6 23

14 e1,000 3 8.1 1,230 5 17 1,340 9 33

15 e830 3 6.7 1,200 6 19 1,330 8 29

16 e700 3 5.7 1,120 7 21 1,320 7 25

17 e800 3 6.5 1,030 8 22 1,360 7 26

18 e1,000 5 14 1,030 7 19 1,350 9 33

19 e1,250 6 20 1,110 6 18 1,320 7 25

20 e1,500 12 49 1,130 5 15 1,310 7 25

21 e1,900 10 51 1,180 4 13 1,330 7 25

22 e2,100 9 51 1,120 3 9.1 1,350 6 22

23 e2,000 7 38 1,100 2 5.9 1,320 7 25

24 1,920 6 31 1,100 2 5.9 1,280 4 14

25 1,740 4 19 1,100 2 5.9 1,240 6 20

26 1,690 4 18 1,110 3 9.0 1,260 6 20

27 1,660 4 18 1,110 3 9.0 1,260 6 20

28 1,650 5 22 1,090 4 12 1,420 8 31

29 1,630 5 22 --- --- --- 1,600 10 43

30 1,610 5 22 --- --- --- 1,650 9 40

31 1,530 8 33 --- --- --- 1,600 10 43

Total 36,380 --- 524.3 33,840 --- 418.8 40,400 --- 750

Mean 1,174 5 17 1,209 5 15 1,303 7 24

Max 2,100 12 51 1,470 8 24 1,650 10 43

Min 500 3 4.0 1,030 2 5.9 1,100 4 12

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2004 through 

September 2005.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: ---, no data or value not computed]

Data 45
Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

April May June

1 1,560 10 42 3,450 10 93 5,700 18 277

2 1,560 8 34 3,210 10 87 7,130 30 578

3 1,600 9 39 3,040 9 74 8,140 58 1,270

4 1,660 8 36 2,970 8 64 8,800 81 1,920

5 1,670 8 36 3,000 9 73 9,050 90 2,200

6 1,660 8 36 3,240 8 70 8,980 68 1,650

7 1,680 8 36 3,840 12 124 8,890 60 1,440

8 1,830 8 40 4,530 20 245 8,330 52 1,170

9 2,010 12 65 5,090 27 371 7,620 34 700

10 2,080 10 56 5,690 32 492 6,940 26 487

11 2,080 11 62 6,630 48 859 6,380 25 431

12 2,080 9 51 7,600 116 2,380 6,310 20 341

13 2,070 8 45 7,410 114 2,280 6,780 28 513

14 2,240 8 48 6,740 65 1,180 6,320 28 478

15 2,280 9 55 6,660 55 989 5,970 22 355

16 2,110 10 57 7,060 50 953 5,950 23 369

17 2,200 8 48 8,330 66 1,480 6,130 23 381

18 2,310 10 62 9,070 80 1,960 7,050 54 1,030

19 2,360 9 57 8,680 64 1,500 7,040 44 836

20 2,370 8 51 9,170 71 1,760 6,240 30 505

21 2,380 8 51 8,900 58 1,390 5,820 23 361

22 2,320 10 63 8,580 57 1,320 5,600 20 302

23 2,290 10 62 8,200 53 1,170 5,460 19 280

24 2,610 10 70 7,800 46 969 5,170 15 209

25 2,980 9 72 7,150 36 695 4,790 17 220

26 3,450 13 121 6,600 31 552 4,670 16 202

27 3,930 21 223 6,070 26 426 4,670 14 177

28 4,000 14 151 5,790 22 344 5,020 16 217

29 3,840 13 135 5,680 18 276 5,170 18 251

30 3,630 12 118 5,640 18 274 4,970 16 215

31 --- --- --- 5,540 18 269 --- --- ---

Total 70,840 --- 2,022 191,360 --- 24,719 195,090 --- 19,365

Mean 2,361 10 67 6,173 41 797 6,503 33 646

Max 4,000 21 223 9,170 116 2,380 9,050 90 2,200

Min 1,560 8 34 2,970 8 64 4,670 14 177

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

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2004 through 

September 2005.—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 4,630 13 163 1,230 7 23 923 3 7.5

2 4,250 9 103 1,220 6 20 940 3 7.6

3 3,990 8 86 1,220 6 20 936 3 7.6

4 3,700 8 80 1,120 5 15 930 3 7.5

5 3,510 8 76 1,100 4 12 899 3 7.3

6 3,280 8 71 1,090 4 12 895 2 4.8

7 3,050 8 66 1,060 4 11 905 3 7.3

8 2,820 8 61 1,060 5 14 911 3 7.4

9 2,730 9 66 1,030 4 11 908 3 7.4

10 2,590 8 56 1,050 4 11 960 3 7.8

11 2,580 7 49 1,030 4 11 1,010 4 11

12 2,510 6 41 1,010 5 14 1,050 4 11

13 2,410 5 33 1,020 5 14 1,050 5 14

14 2,250 5 30 1,040 5 14 1,070 5 14

15 2,220 5 30 1,040 5 14 1,080 4 12

16 2,070 5 28 1,010 4 11 1,050 6 17

17 2,020 5 27 990 5 13 1,170 4 13

18 1,970 5 27 986 4 11 1,330 6 22

19 1,910 5 26 1,030 4 11 1,350 5 18

20 1,810 5 24 1,020 3 8.3 1,310 5 18

21 1,690 5 23 1,000 3 8.1 1,210 5 16

22 1,660 5 22 971 3 7.9 1,190 5 16

23 1,590 5 21 984 3 8.0 1,220 6 20

24 1,520 5 21 977 4 11 1,240 5 17

25 1,470 5 20 960 4 10 1,320 5 18

26 1,450 5 20 973 3 7.9 1,340 5 18

27 1,430 6 23 962 3 7.8 1,330 5 18

28 1,430 4 15 945 2 5.1 1,300 5 18

29 1,380 4 15 921 2 5.0 1,280 5 17

30 1,310 4 14 911 2 4.9 1,280 5 17

31 1,260 6 20 907 2 4.9 --- --- ---

Total 72,490 --- 1,357 31,867 --- 350.9 33,387 --- 397.2

Mean 2,338 6 44 1,028 4 11 1,113 4 13

Max 4,630 13 163 1,230 7 23 1,350 6 22

Min 1,260 4 14 907 2 4.9 895 2 4.8

Total for water year 2005 (unrounded sum of daily values): streamflow, 826,764 ft3/s (1,640,000 acre-ft); sediment load, 51,051.1 tons.

Data 47

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2004 through 

September 2005.—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]
Table 8. Analyses of field replicates for water samples, upper Clark Fork basin, Montana.

[Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbol: <, less than laboratory reporting level]

Site 

number 

(fig. 1)

Site name Date Time

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium 

filtered 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

12340500 Clark Fork above Missoula 12/20/04 1350 150 40.5 12.2 3.2 3

12/20/04 1355 150 39.8 11.8 3.1 3

12323600 Silver Bow Creek at 

Opportunity 

03/08/05 1330 200 57.4 12.7 12.5 17

03/08/05 1335 200 57.8 12.6 12.6 17

12323750 Silver Bow Creek at Warm 

Springs 

04/18/05 1615 310 87.6 21.1 9.8 13

04/18/05 1620 310 88.8 21.1 9.9 13

12324200 Clark Fork at Deer Lodge 05/17/05 1110 180 51.6 13.2 18.2 78

05/17/05 1115 180 51.5 13.4 18.6 76

12334550 Clark Fork at Turah Bridge, 

near Bonner

06/03/05 1045 95 27.3 6.57 7.4 16

06/03/05 1050 96 27.5 6.59 7.6 16

12323670 Mill Creek near Anaconda 06/22/05 1145 24 7.12 1.45 7.3 10

06/22/05 1150 24 7.15 1.44 7.3 10

12323700 Mill Creek at Opportunity 07/25/05 1615 65 18.6 4.56 36.6 40

07/25/05 1620 67 19.0 4.66 37.2 38

12323840 Lost Creek near Anaconda 08/23/05 1400 110 33.9 6.11 5.6 6.2

08/23/05 1405 110 34.3 6.15 5.6 6.6

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

number Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

12340500 12/20/04 E0.03 0.04 1.4 3.3 <6 70 <0.08 0.43

12/20/04 E.03 E.03 1.4 3.5 <6 80 <.08 .43

12323600 03/08/05 .78 1.29 32.7 93.2 9 550 .30 15.1

03/08/05 .85 1.25 32.5 94.9 9 560 .30 15.0

12323750 04/18/05 E.03 .08 2.7 7.8 E4 250 E.05 1.09

04/18/05 E.03 .09 2.8 7.5 E5 250 E.05 1.13

12324200 05/17/05 E.04 2.06 10.6 468 41 6,960 .40 61.7

05/17/05 E.04 2.05 11.2 478 44 6,910 .43 62.0

12334550 06/03/05 E.04 .40 6.9 62.8 46 1,700 .24 10.9

06/03/05 E.04 .41 7.2 63.8 44 1,680 .25 11.1

12323670 06/22/05 .04 .15 2.4 7.2 26 590 .08 2.35

06/22/05 .04 .17 2.4 7.8 29 580 .09 2.38

12323700 07/25/05 .06 .08 3.2 4.5 90 140 .23 .40

07/25/05 .07 .09 3.1 4.5 96 130 .23 .40

12323840 08/23/05 .05 .08 3.6 8.9 <6 160 E.05 .70

08/23/05 .05 .07 3.8 9.3 7 150 E.05 .72

Data 49

Table 8. Analyses of field replicates for water samples, upper Clark Fork basin, Montana.—Continued

[Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbol: <, less than laboratory reporting level]
Site 

number Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment 

suspended, 

percent 

finer than

 0.062 mm

Sediment, 

suspended 

(mg/L)

12340500 12/20/04 7.5 12 2.3 6 86 5

12/20/04 7.4 12 2.0 6 86 4

12323600 03/08/05 489 482 157 263 86 11

03/08/05 498 497 160 271 82 12

12323750 04/18/05 195 245 4.7 12 82 3

04/18/05 197 246 4.0 11 91 3

12324200 05/17/05 97.9 1,010 9.3 359 67 387

05/17/05 104 995 9.6 366 66 399

12334550 06/03/05 7.5 221 5.9 93 68 110

06/03/05 7.9 224 6.9 95 66 114

12323670 06/22/05 5.1 36 1.6 7 57 29

06/22/05 5.1 38 1.7 7 55 30

12323700 07/25/05 11.1 14 2.8 3 77 1

07/25/05 11.4 14 2.1 3 82 1

12323840 08/23/05 1.2 6 1.3 4 80 8

08/23/05 1.3 6 1.4 3 86 11

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

Table 8. Analyses of field replicates for water samples, upper Clark Fork basin, Montana.—Continued

[Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbol: <, less than laboratory reporting level]
Table 9. Precision of analyses of field replicates for water samples, upper Clark Fork basin, Montana.

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

Constituent and reporting unit Number of replicate 

pairs

Standard deviation1

, 

in listed units

Relative standard 

deviation, 

in percent

Calcium, filtered, mg/L 8 0.39 0.97

Magnesium, filtered, mg/L 8 .12 1.2

Arsenic, filtered, μg/L 8 .19 1.5

Arsenic, unfiltered recoverable, μg/L 8 .71 3.1

Cadmium, filtered, μg/L 8 .02 13

Cadmium, unfiltered recoverable, μg/L 8 .01 2.4

Copper, filtered, μg/L 8 .19 2.3

Copper, unfiltered recoverable, μg/L 8 2.6 3.1

Iron, filtered, μg/L 8 2.2 7.5

Iron, unfiltered recoverable, μg/L 8 15 1.1

Lead, filtered, μg/L 8 .01 4.7

Lead, unfiltered recoverable, μg/L 8 .09 .81

Manganese, filtered, μg/L 8 2.8 2.7

Manganese, unfiltered recoverable, μg/L 8 5.4 2.1

Zinc, filtered, μg/L 8 .84 3.6

Zinc, unfiltered recoverable, μg/L 8 2.7 2.9

Sediment, suspended, percent finer than 0.062 mm 8 3.2 4.2

Sediment, suspended, mg/L 8 3.3 4.7

1

Standard deviation was calculated using the laboratory reporting level for censored values.

Data 51
Table 10. Precision of analyses of laboratory replicates for water samples, upper Clark Fork basin, Montana.

[Abbreviations: μg/L, micrograms per liter; mg/L, milligrams per liter]

Constituent and reporting unit Number of replicate 

pairs

Standard deviation1

, 

in listed units

Relative standard 

deviation, 

in percent

Within limits of 

data-quality 

objective2

Calcium, filtered, mg/L 8 0.88 2.3 Yes

Magnesium, filtered, mg/L 8 .10 1.1 Yes

Arsenic, filtered, μg/L 8 .12 2.5 Yes

Arsenic, unfiltered recoverable, μg/L 7 .52 7.2 Yes

Cadmium, filtered, μg/L 8 .00 11 Yes

Cadmium, unfiltered recoverable, μg/L 8 .00 4.6 Yes

Copper, filtered, μg/L 8 .08 2.0 Yes

Copper, unfiltered recoverable, μg/L 8 .14 .67 Yes

Iron, filtered, μg/L 8 3.0 9.6 Yes

Iron, unfiltered recoverable, μg/L 8 13 2.3 Yes

Lead, filtered, μg/L 8 .02 4.7 Yes

Lead, unfiltered recoverable, μg/L 8 .05 1.9 Yes

Manganese, filtered, μg/L 8 2.8 6.6 Yes

Manganese, unfiltered recoverable, μg/L 8 7.5 3.8 Yes

Zinc, filtered, μg/L 8 .30 7.4 Yes

Zinc, unfiltered recoverable, μg/L 8 .22 1.7 Yes

1

Standard deviation was calculated using the laboratory reporting level for censored values.

2

Data-quality objective for an acceptable level of precision is a maximum relative deviation of 20 percent for laboratory replicate analyses (table 3).

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

[Abbreviation: μg/L, micrograms per liter]

Constituent and reporting unit Number of samples

95–percent 

confidence interval 

for spike recovery, 

in percent

Mean spike 

recovery, 

in percent

Within limits

of data–quality 

objective1

Arsenic, filtered, μg/L 5 95.5–99.3 97.4 Yes

Arsenic, unfiltered recoverable, μg/L 5 90.7–111 101 Yes

Cadmium, filtered, μg/L 5 97.3–106 102 Yes

Cadmium, unfiltered recoverable, μg/L 5 88.1–107 97.5 Yes

Copper, filtered, μg/L 5 97.4–107 102 Yes

Copper, unfiltered recoverable, μg/L 5 88.4–107 97.6 Yes

Iron, filtered, μg/L 5 95.2–105 100 Yes

Iron, unfiltered recoverable, μg/L 5 90.5–105 97.6 Yes

Lead, filtered, μg/L 5 95.5–106 101 Yes

Lead, unfiltered recoverable, μg/L 5 99.4–108 104 Yes

Manganese, filtered, μg/L 5 86.4–117 102 Yes

Manganese, unfiltered recoverable, μg/L 5 82.2–105 93.8 Yes

Zinc, filtered, μg/L 5 88.3–116 102 Yes

Zinc, unfiltered recoverable, μg/L 5 83.5–109 96.1 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

52 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Table 12. Recovery efficiency for analyses of laboratory-spiked stream samples, upper Clark Fork basin, Montana.

[Abbreviation: μg/L, micrograms per liter]

Constituent and reporting unit Number of samples

95–percent 

confidence interval 

for spike recovery, 

in percent

Mean spike 

recovery, 

in percent

Within limits of 

data–quality 

objective1

Arsenic, filtered, μg/L 5 98.3–107 103 Yes

Arsenic, unfiltered recoverable, μg/L 5 101–108 104 Yes

Cadmium, filtered, μg/L 5 62.7–133 97.8 Yes

Cadmium, unfiltered recoverable, μg/L 5 88.5–108 98.2 Yes

Copper, filtered, μg/L 5 57.9–129 93.6 Yes

Copper, unfiltered recoverable, μg/L 5 84.8–101 93.0 Yes

Iron, filtered, μg/L 5 95.6–103 99.3 Yes

Iron, unfiltered recoverable, μg/L 5 95.9–108 102 Yes

Lead, filtered, μg/L 5 96.1–109 102 Yes

Lead, unfiltered recoverable, μg/L 5 99.7–106 103 Yes

Manganese, filtered, μg/L 5 87.3–108 97.5 Yes

Manganese, unfiltered recoverable, μg/L 5 78.3–98.3 88.3 Yes

Zinc, filtered, μg/L 5 60.8–128 94.3 Yes

Zinc, unfiltered recoverable, μg/L 5 80.8–102 91.6 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

Data 53
Table 13. Analyses of field blanks for water samples.

[Abbreviations; °C, degrees Celsius; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per liter. 

Symbol: <, less than laboratory reporting level]

Date Time

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

12/15/2004 1130 5.5 2 <0.02 <0.008 <0.2 <2 <0.04 <0.04

03/07/2005 1200 5.5 2 <.02 <.008 <.2 <2 .06 <.04

04/20/2005 1000 5.6 2 <.02 <.008 <.2 <2 <.04 <.04

05/16/2005 1500 5.6 2 .02 <.008 <.2 <2 <.04 <.04

06/02/2005 1500 5.5 1 <.02 <.008 <.2 <2 <.04 <.04

06/23/2005 0600 5.7 2 <.02 <.008 <.2 <2 <.04 <.04

07/26/2005 0600 5.7 2 <.02 <.008 <.2 <.12 <.04 <.04

08/24/2005 0600 5.7 1 <.02 <.008 <.2 <.12 <.04 <.04

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(ug/L)

12/15/2004 <0.4 <0.6 <6 <6 <0.08 <0.06 <0.2 <0.2 <0.6 <2

03/07/2005 .5 .7 <6 <6 <.08 <.06 <.2 <.2 1.9 <2

04/20/2005 <.4 <.6 <6 <6 <.08 <.06 <.2 <.2 .7 <2

05/16/2005 <.4 <.6 <6 <6 <.08 <.06 <.2 <.2 <.6 <2

06/02/2005 <.4 <.6 <6 30 <.08 <.06 <.2 <.2 <.6 <2

06/23/2005 <.4 <.6 <6 <6 <.08 <.06 <.2 <.2 .9 <2

07/26/2005 <.4 <.6 <6 <6 <.08 .06 <.2 <.2 .7 <2

08/24/2005 <.4 <.6 <6 <6 <.08 .06 <.2 <.2 .9 <2

54 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Table 14. Analyses of fine-grained bed sediment, upper Clark Fork basin, Montana, August 2005.

[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. Symbol: <, less than minimum reporting level for solid-phase concentration, in μg/g]

Site number 

(fig. 1) Site name

Number of composite 

samples

Concentration, in μg/g 

Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12323600 Silver Bow Creek at 

Opportunity

3 165 34.6 19.7 3,570 32,400 538 3,170 12.4 6,880

12323750 Silver Bow Creek at 

Warm Springs

3 141 6.4 <15.7 229 27,300 53 11,300 12.6 728

12323770 Warm Springs Creek at 

Warm Springs

3 66 4.5 29.0 991 22,000 82 12,100 19.2 414

12323800 Clark Fork near Galen 3 107 6.4 25.2 1,020 25,200 102 17,300 16.2 1,020

461415112450801 Clark Fork below Lost 

Creek, near Galen

3 107 6.3 24.2 1,350 27,500 141 6,560 13.4 1,220

461559112443301 Clark Fork at County 

Bridge, near Racetrack

3 86 6.4 19.2 1,100 23,500 119 5,050 11.6 1,090

461903112440701 Clark Fork at Demspey 

Creek diversion, near Racetrack

3 71 5.7 20.4 967 24,300 117 5,680 12.4 1,080

12324200 Clark Fork at Deer Lodge 3 72 4.7 23.6 875 26,100 123 1,110 11.7 951

12324680 Clark Fork at Goldcreek 3 39 4.0 25.2 548 22,300 79 1,770 12.6 759

12331800 Clark Fork near 

Drummond

3 34 3.2 21.9 352 18,500 64 2,410 10.4 742

12334510 Rock Creek near Clinton 3 <6 .7 16.1 12 14,200 10 253 8.7 24

12334550 Clark Fork at Turah 

Bridge, near Bonner

3 30 3.1 17.2 307 17,300 54 1,330 11.2 686

12340500 Clark Fork above 

Missoula

3 17 2.6 20.3 259 18,200 46 515 10.9 590

Data 55
Table 15. Recovery efficiency for analyses of standard reference materials for bed sediment.

[Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to final volume of solution after 

addition of 0.6N (normal) hydrochloric acid used for reconstituting dried residue. Abbreviations: μg/g, micrograms per gram of dry sample 

weight; SRM,standard reference material (agricultural soils). Symbol: --, recovery could not be determined because all analyses were less 

than the minimum reporting level]

Constituent Number of 

analyses

Dilution 

ratio

Certified 

concentration 

(μg/g)

Mean SRM recovery, 

in percent

95–percent 

confidence interval 

for SRM recovery, 

in percent

SRM sample 2709

Arsenic 10 1:10 17.7 65.4 61.7–69.1

Cadmium 10 1:10 .4 -- --

Chromium 10 1:10 130 60.2 58.1–62.4

Copper 10 1:10 35 83.6 77.5–89.7

Iron 10 1:10 35,000 85.0 83.5–86.4

Lead 10 1:10 19 86.1 82.9–89.3

Manganese 10 1:10 538 89.1 87.7–90.6

Nickel 10 1:10 88 82.2 80.3–84.0

Zinc 10 1:10 106 75.6 72.9–78.3

SRM sample 2711

Arsenic 10 1:10 105 83.4 81.2–85.7

Cadmium 10 1:10 41.7 94.4 92.2–96.6

Chromium 10 1:10 47 51.5 49.1–53.9

Copper 10 1:10 114 93.7 92.1–95.3

Iron 10 1:10 28,900 80.7 79.3–82.1

Lead 10 1:10 1,160 88.9 86.9–90.9

Manganese 10 1:10 638 80.6 79.4–81.7

Nickel 10 1:10 20.6 78.9 76.6–81.2

Zinc 10 1:10 350 88.1 86.7–89.4

56  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Table 16. Analyses of procedural blanks for bed sediment.

[Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to final volume of solution after addition of 0.6 N (normal) hydrochloric acid used for reconstituting dried residue. Abbreviation: μg/mL, micrograms per milliliter. Symbol: <, less than minimum reporting level for liquid-phase concentration, in μg/mL]

Site number 

(fig. 1) Site Name Dilution ratio Trace element concentration, in μg/mL Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12323600 Silver Bow Creek at 

Opportunity

1:10 <0.009 <0.0003 <0.01 <0.002 <0.02 <0.004 <0.0004 <0.001 <0.003

12323750 Silver Bow Creek at Warm 

Springs

1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

12323770 Warm Springs Creek at 

Warm Springs

1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

12323800 Clark Fork near Galen 1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

461415112450801 Clark Fork below Lost Creek, 

near Galen

1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

461559112443301 Clark Fork at County Bridge, 

near Racetrack

1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

461903112440701 Clark Fork at Demspey 

Creek diversion, near Racetrack

1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

12324200 Clark Fork at Deer Lodge 1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

12324680 Clark Fork at Goldcreek 1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

12331800 Clark Fork near Drummond 1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

12334510 Rock Creek near Clinton 1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

12334550 Clark Fork at Turah Bridge, 

near Bonner

1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

12340500 Clark Fork above Missoula 1:10 <.009 <.0003 <.01 <.002 <.02 <.004 <.0004 <.001 <.003

Data 57
Table 17. Analyses of biota, upper Clark Fork basin, Montana, August 2005.

[Analyses are for the whole-body tissue of aquatic insects. Composite samples are made by combining similar-sized insects of the same species into a sample of 

sufficient mass for analysis. Concentrations for biota samples composed of two or more composite samples are the means of all analyses. Abbreviations: μg/g, 

micrograms per gram of dry sample weight; spp., species. Symbol: <, less than minimum reporting level for solid-phase concentration, in μg/g]

Taxon

Number 

of composite 

samples

Concentration, in μg/g

Arsenic Cadmium

Chromium Copper Iron Lead Manganese

Nickel Zinc

12323600—Silver Bow Creek at Opportunity

Hydropsyche cockerelli 1 13.1 4.9 1.4 382 2,110 45.0 847 2.0 789

Hydropsyche spp. 1 15.1 6.1 <9.7 418 2,550 51.4 1,040 2.5 909

12323750—Silver Bow Creek at Warm Springs

Hydropsyche cockerelli 3 10.4 .4 <2.6 19.7 833 1.7 1,440 0.6 147

Hydropsyche occidentalis 2 10.8 .4 <5.4 24.4 959 2.1 1,770 .9 144

12323770—Warm Springs Creek at Warm Springs

Arctopsyche grandis 2 9.6 3.4 <0.3 130 1,080 5.2 3,180 2.5 197

Hydropsyche occidentalis 2 13.2 1.2 .3 130 1,660 7.4 3,130 2.1 151

12323800—Clark Fork near Galen

Hydropsyche cockerelli 1 13.2 1.6 1.5 133 1,520 8.5 2,960 1.9 191

Hydropsyche occidentalis 1 12.5 1.3 1.7 92.4 1,450 8.4 3,940 1.5 198

461415112450801—Clark Fork below Lost Creek, near Galen

Hydropsyche cockerelli 2 9.5 1.8 1.1 124 1,150 7.1 1,700 1.1 195

461559112443301—Clark Fork at County Bridge, near Racetrack

Hydropsyche cockerelli 3 11.5 1.5 1.0 118 993 7.3 1,930 1.0 192

461903112440701—Clark Fork at Dempsey Creek Diversion, near Racetrack

Hydropsyche cockerelli 1 8.0 1.7 1.3 106 1,180 6.3 1,480 1.0 188

Hydropsyche occidentalis 1 10.2 1.2 1.5 90.7 1,270 7.0 2,320 1.4 211

12324200—Clark Fork at Deer Lodge

Hydropsyche cockerelli 1 7.3 2.0 <4.6 133 844 9.3 979 0.9 185

Hydropsyche occidentalis 2 9.3 1.8 1.4 145 1,240 13.6 2,080 1.4 309

12324680—Clark Fork at Goldcreek

Arctopsyche grandis 4 2.5 1.6 <1.6 29.2 245 1.5 640 0.4 163

Claassenia sabulosa 2 1.6 .7 <1.2 55.7 179 .7 130 .3 264

Hydropsyche cockerelli 2 4.7 1.5 2.5 60.4 759 3.5 1,100 0.8 181

Hydropsyche occidentalis 1 5.3 1.5 <2.6 57.6 1,250 4.6 1,320 1.0 203

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

Number 

of composite 

samples

Concentration, in μg/g

Arsenic Cadmium

Chromium Copper Iron Lead Manganese

Nickel Zinc

12331800—Clark Fork near Drummond

Arctopsyche grandis 3 4.1 0.8 1.1 26.2 343 2.4 577 0.5 153

Claassenia sabulosa 2 1.2 1.0 .7 55.2 119 .6 142 .2 272

Hydropsyche cockerelli 1 5.7 1.0 <2.7 60.5 1,040 5.6 795 1.1 175

Hydropsyche occidentalis 2 6.0 1.0 2.2 55.4 1,130 6.1 1,040 1.0 202

12334510—Rock Creek near Clinton

Arctopsyche grandis 2 1.6 0.2 <0.9 9.8 640 <0.4 258 1.0 127

Claassenia sabulosa 1 1.0 .1 <.3 37.7 96 <.2 50 .3 213

12334550—Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 3 3.7 1.3 <2.2 27.0 483 3.0 680 0.7 192

Claassenia sabulosa 3 1.5 .9 .6 67.8 237 .7 144 .2 255

Hydropsyche cockerelli 2 4.0 1.0 1.0 39.1 948 5.5 751 1.0 180

Hydropsyche occidentalis 3 4.7 1.1 1.4 43.5 1,180 6.2 1,080 1.2 238

12340500—Clark Fork above Missoula

Arctopsyche grandis 3 2.4 0.9 <1.7 27.4 572 2.9 1,160 0.9 173

Claassenia sabulosa 1 1.9 1.0 <2.9 43.6 226 .6 153 .4 271

Hydropsyche cockerelli 2 4.2 1.1 <2.1 53.8 1,730 7.0 1,670 1.7 213

Hydropsyche occidentalis 1 3.9 1.2 <4.4 58.6 1,710 7.4 2,460 1.8 251

Table 17. Analyses of biota, upper Clark Fork basin, Montana, August 2005.—Continued

[Analyses are for the whole-body tissue of aquatic insects. Composite samples are made by combining similar-sized insects of the same species into a sample of 

sufficient mass for analysis. Concentrations for biota samples composed of two or more composite samples are the means of all analyses. Abbreviations: μg/g, 

micrograms per gram of dry sample weight; spp., species. Symbol: <, less than minimum reporting level for solid-phase concentration, in μg/g]

Data 59
Table 18. Recovery efficiency for analyses of standard reference material for biota.

[Abbreviations: μg/g, micrograms per gram of dry sample weight; μg/mL, micrograms per milliliter; 

SRM, standard reference material (lobster hepatopancreas)]

Constituent Number of 

analyses

Certified 

concentration 

(μg/g)

Mean SRM 

recovery, 

in percent

95–percent confidence 

interval for SRM recovery, 

in percent

SRM sample TORT–2

Arsenic 12 21.6 97.7 96.9–98.6

Cadmium 12 26.7 92.6 91.4–93.8

Chromium 1

12 .77 119 101–136

Copper 12 106 96.7 95.9–97.6

Iron 12 105 100 97.4–103

Lead 12 .35 84.7 74.6–94.8

Manganese 12 13.6 95.4 94.0–96.8

Nickel 12 2.5 84.8 82.7–86.9

Zinc 12 180 99.7 98.8–101

1

Chromium concentrations in two analyses were less than the liquid-phase minimum reporting level 

(0.03 μg/mL) and omitted from the calculation of SRM recovery.

60 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Table 19. Analyses of procedural blanks for biota.

[Procedural blanks were not diluted prior to analyses. Abbreviation: μg/mL, micrograms per milliliter. Symbol: <, less than minimum reporting level for liquid-phase concentration, in μg/mL]

Site number 

(fig. 1) Site name Dilution ratio Trace-element concentration, in μg/mL Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12323600 Silver Bow Creek at 

Opportunity

1:1 <0.006 <0.002 <0.03 <0.01 <0.06 <0.01 <0.01 <0.002 <0.01

12323750 Silver Bow Creek at Warm 

Springs

1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

12323770 Warm Springs Creek at Warm 

Springs

1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

12323800 Clark Fork near Galen 1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

461415112450801 Clark Fork below Lost Creek, 

near Galen

1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

461559112443301 Clark Fork at County Bridge, 

near Racetrack

1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

461903112440701 Clark Fork at Dempsey Creek 

Diversion, near Racetrack

1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

12324200 Clark Fork at Deer Lodge 1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

12324680 Clark Fork at Goldcreek 1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

12331800 Clark Fork near Drummond 1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

12334510 Rock Creek near Clinton 1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

12334550 Clark Fork at Turah Bridge, 

near Bonner

1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

12340500 Clark Fork above Missoula 1:1 <.006 <.002 <.03 <.01 <.06 <.01 <.01 <.002 <.01

Data  61
Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

[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 2005

Streamflow, instantaneous (ft3/s) 91 156 1.9 14 7.6

pH, onsite (standard units) 91 8.4 7.3 7.8 7.8

Specific conductance, onsite (μS/cm) 91 412 116 267 271

Temperature, water (°C) 91 17.5 1.5 8.2 8.0

Hardness, filtered (mg/L as CaCO3

) 91 150 38 105 110

Calcium, filtered (mg/L) 91 41.8 10.6 30.0 30.9

Magnesium, filtered (mg/L) 91 11.0 2.71 7.3 7.4

Arsenic, filtered (μg/L) 91 13 1 3.8 3.0

Arsenic, unfiltered (μg/L) 91 18 1 2

5 4

Cadmium, filtered (μg/L) 91 .5 <.1 2

.06 <.1

Cadmium, unfiltered (μg/L) 91 .11 <.04 2

.05 <1

Copper, filtered (μg/L) 91 10 .8 2

3.8 3.2

Copper, unfiltered (μg/L) 91 52 1.5 7.2 5.7

Iron, filtered (μg/L) 91 478 15 157 150

Iron, unfiltered (μg/L) 91 4,220 140 685 550

Lead, filtered (μg/L) 91 2.8 <.08 2

.22 <.6

Lead, unfiltered (μg/L) 91 47 <1 2

2.31 .92

Manganese, filtered (μg/L) 91 144 14.2 42.0 37.9

Manganese, unfiltered (μg/L) 91 240 23 60 51

Zinc, filtered (μg/L) 91 11 <1 2

3.9 2.8

Zinc, unfiltered (μg/L) 91 130 <10 2

10 4

Sediment, suspended (percent finer than 0.062 mm) 91 97 50 82 83

Sediment, suspended concentration (mg/L) 91 139 2 14 8

Sediment, suspended discharge (ton/d) 91 59 .02 1.3 .16

62 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323250—Silver Bow Creek below Blacktail Creek, at Butte

Period of record for water-quality data: March 1993-August 1995, December 1996-September 2005

Streamflow, instantaneous (ft3/s) 99 134 13 28 23

pH, onsite (standard units) 99 8.1 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 99 691 226 477 485

Temperature, water (°C) 99 20.0 1.0 10.4 9.5

Hardness, filtered (mg/L as CaCO3

) 99 220 66 151 160

Calcium, filtered (mg/L) 99 62.7 19.0 43.1 44.0

Magnesium, filtered (mg/L) 99 14.6 4.51 10.6 11.0

Arsenic, filtered (μg/L) 99 13 2.3 6.7 6.5

Arsenic, unfiltered (μg/L) 99 45 3 12 10

Cadmium, filtered (μg/L) 99 6.2 .09 1.37 1.10

Cadmium, unfiltered (μg/L) 99 6 .11 1.83 1.60

Copper, filtered (μg/L) 99 303 3.2 43.6 19.7

Copper, unfiltered (μg/L) 99 550 13.5 102 62

Iron, filtered (μg/L) 99 270 10 2

82 61

Iron, unfiltered (μg/L) 99 7,400 90 1,000 640

Lead, filtered (μg/L) 99 2.4 <.5 2

.54 .20

Lead, unfiltered (μg/L) 99 250 .65 16.0 5.80

Manganese, filtered (μg/L) 99 1,700 21.4 433 386

Manganese, unfiltered (μg/L) 99 1,600 26 482 432

Zinc, filtered (μg/L) 99 2,200 26.7 445 320

Zinc, unfiltered (μg/L) 99 2,200 38 538 380

Sediment, suspended (percent finer than 0.062 mm) 98 98 42 84 86

Sediment, suspended concentration (mg/L) 98 405 2 27 11

Sediment, suspended discharge (ton/d) 98 70 .09 3.2 .82

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the 

laboratory reporting level to compute statistic]

Data  63
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 2005

Streamflow, instantaneous (ft3/s) 102 361 13 72 50

pH, onsite (standard units) 101 9.5 7.2 8.4 8.4

Specific conductance, onsite (μS/cm) 101 633 202 415 403

Temperature, water (°C) 101 22.5 0.0 9.4 9.5

Hardness, filtered (mg/L as CaCO3

) 101 240 60 149 150

Calcium, filtered (mg/L) 101 71.6 18.5 44.1 43.1

Magnesium, filtered (mg/L) 101 15.0 3.42 9.44 9.04

Arsenic, filtered (μg/L) 101 34 1 11.0 10.0

Arsenic, unfiltered (μg/L) 101 235 11 29 18

Cadmium, filtered (μg/L) 101 41 .1 1.36 .90

Cadmium, unfiltered (μg/L) 101 49 .52 2

2.44 1.60

Copper, filtered (μg/L) 101 450 18.5 51.9 40.2

Copper, unfiltered (μg/L) 101 3,900 54.3 242 132

Iron, filtered (μg/L) 101 307 3 2

44 23

Iron, unfiltered (μg/L) 101 24,100 260 1,700 780

Lead, filtered (μg/L) 101 5.1 <.5 2

.76 .27

Lead, unfiltered (μg/L) 101 650 5.38 43.9 15.5

Manganese, filtered (μg/L) 101 9,300 68 517 418

Manganese, unfiltered (μg/L) 101 10,000 117 646 488

Zinc, filtered (μg/L) 101 13,000 27 359 200

Zinc, unfiltered (μg/L) 101 15,000 97 625 405

Sediment, suspended (percent finer than 0.062 mm) 102 95 37 78 82

Sediment, suspended concentration (mg/L) 102 801 5 54 17

Sediment, suspended discharge (ton/d) 102 781 .18 23 2.3

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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]

64 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323670—Mill Creek near Anaconda

Period of record for water-quality data: December 2004-September 2005

Streamflow, instantaneous (ft3

/s) 8 165 7.4 63 20

pH, onsite (standard units) 8 8.6 7.7 8.2 8.2

Specific conductance, onsite (μS/cm) 8 195 56 130 145

Temperature, water (°C) 8 15.0 3.0 7.8 7.0

Hardness, filtered (mg/L as CaCO3

) 8 92 24 58 65

Calcium, filtered (mg/L) 8 24.4 7.12 16.1 18.0

Magnesium, filtered (mg/L) 8 7.58 1.45 4.41 4.84

Arsenic, filtered (μg/L) 8 23.4 7.3 14.1 11.5

Arsenic, unfiltered (μg/L) 8 26 9 16 14

Cadmium, filtered (μg/L) 8 .11 .04 .06 .04

Cadmium, unfiltered (μg/L) 8 .18 .05 .09 .08

Copper, filtered (μg/L) 8 4.5 1.0 2.3 2.0

Copper, unfiltered (μg/L) 8 10.3 1.3 4.6 3.6

Iron, filtered (μg/L) 8 89 26 50 42

Iron, unfiltered (μg/L) 8 620 90 255 170

Lead, filtered (μg/L) 8 .24 .05 .14 .14

Lead, unfiltered (μg/L) 8 3.12 .27 1.07 .58

Manganese, filtered (μg/L) 8 8.9 3.6 6.2 6.2

Manganese, unfiltered (μg/L) 8 37 7 18 15

Zinc, filtered (μg/L) 8 2.4 .8 1.5 1.2

Zinc, unfiltered (μg/L) 8 8 1 4 2

Sediment, suspended (percent finer than 0.062 mm) 8 81 51 70 75

Sediment, suspended concentration (mg/L) 8 29 1 9 2

Sediment, suspended discharge (ton/d) 8 13 .03 3.1 .12

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the 

laboratory reporting level to compute statistic]

Data  65
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 2005

Streamflow, instantaneous (ft3/s) 24 261 0.43 37 5.0

pH, onsite (standard units) 24 8.2 7.8 8.0 8.0

Specific conductance, onsite (μS/cm) 24 222 59 149 157

Temperature, water (°C) 24 18.5 1.0 9.2 8.8

Hardness, filtered (mg/L as CaCO3

) 24 100 24 64 69

Calcium, filtered (mg/L) 24 27.9 7.01 17.9 19.3

Magnesium, filtered (mg/L) 24 7.68 1.56 4.62 4.84

Arsenic, filtered (μg/L) 24 37.0 9.0 23.3 21.8

Arsenic, unfiltered (μg/L) 24 50 10 28 26

Cadmium, filtered (μg/L) 24 .10 .05 .07 .07

Cadmium, unfiltered (μg/L) 24 .85 .06 .18 .10

Copper, filtered (μg/L) 24 6.1 1.2 3.2 3.0

Copper, unfiltered (μg/L) 24 38.8 2.2 8.0 4.4

Iron, filtered (μg/L) 24 90 17 52 49

Iron, unfiltered (μg/L) 24 1,960 70 359 135

Lead, filtered (μg/L) 24 .32 .04 .16 .14

Lead, unfiltered (μg/L) 24 12.7 .08 1.90 .42

Manganese, filtered (μg/L) 24 32.8 3.6 10.2 7.6

Manganese, unfiltered (μg/L) 24 113 6 24 14

Zinc, filtered (μg/L) 24 7.7 1.7 3.7 3.6

Zinc, unfiltered (μg/L) 24 41 2 9 5

Sediment, suspended (percent finer than 0.062 mm) 24 90 26 73 79

Sediment, suspended concentration (mg/L) 24 107 1 16 2

Sediment, suspended discharge (ton/d) 24 55 <.01 2

5.4 .02

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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]

66  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323710—Willow Creek near Anaconda

Period of record for water-quality data: December 2004-September 2005

Streamflow, instantaneous (ft3

/s) 8 39 1.0 11 2.6

pH, onsite (standard units) 8 8.2 7.5 7.8 7.8

Specific conductance, onsite (μS/cm) 8 114 66 99 105

Temperature, water (°C) 8 13.0 .5 6.0 5.5

Hardness, filtered (mg/L as CaCO3

) 8 42 23 36 39

Calcium, filtered (mg/L) 8 13.9 7.74 12.3 13.2

Magnesium, filtered (mg/L) 8 1.69 .88 1.35 1.36

Arsenic, filtered (μg/L) 8 24.3 9.9 15.0 12.8

Arsenic, unfiltered (μg/L) 8 27 10 17 14

Cadmium, filtered (μg/L) 8 .05 .02 .03 .03

Cadmium, unfiltered (μg/L) 8 .19 .03 .07 .06

Copper, filtered (μg/L) 8 4.2 1.0 2.2 2.0

Copper, unfiltered (μg/L) 8 10.5 1.5 3.7 3.0

Iron, filtered (μg/L) 8 125 36 66 60

Iron, unfiltered (μg/L) 8 1,260 90 314 180

Lead, filtered (μg/L) 8 .37 .05 .15 .14

Lead, unfiltered (μg/L) 8 4.08 .20 .93 .48

Manganese, filtered (μg/L) 8 23.0 11.4 16.4 17.1

Manganese, unfiltered (μg/L) 8 49 15 29 24

Zinc, filtered (μg/L) 8 3.3 1.1 2.0 1.8

Zinc, unfiltered (μg/L) 8 10 1 3 2

Sediment, suspended (percent finer than 0.062 mm) 8 94 44 76 82

Sediment, suspended concentration (mg/L) 8 93 3 17 4

Sediment, suspended discharge (ton/d) 8 9.8 .01 1.4 .04

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the 

laboratory reporting level to compute statistic]

Data  67
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 2005

Streamflow, instantaneous (ft3/s) 24 53 4.5 16 9.0

pH, onsite (standard units) 24 8.5 7.7 8.1 8.1

Specific conductance, onsite (μS/cm) 24 371 181 295 308

Temperature, water (°C) 24 20.5 3.5 10.6 10.8

Hardness, filtered (mg/L as CaCO3

) 24 170 73 130 130

Calcium, filtered (mg/L) 24 47.4 22.0 37.5 38.5

Magnesium, filtered (mg/L) 24 12.3 4.37 8.87 9.08

Arsenic, filtered (μg/L) 24 164 11.5 46.7 25.2

Arsenic, unfiltered (μg/L) 24 164 12 50 25

Cadmium, filtered (μg/L) 24 .11 .02 .05 .05

Cadmium, unfiltered (μg/L) 24 .52 .03 .11 .07

Copper, filtered (μg/L) 24 21.4 1.9 6.1 3.6

Copper, unfiltered (μg/L) 24 48.8 2.8 12.5 7.8

Iron, filtered (μg/L) 24 111 7 37 28

Iron, unfiltered (μg/L) 24 1,420 30 255 140

Lead, filtered (μg/L) 24 .52 .04 2

.19 .16

Lead, unfiltered (μg/L) 24 14.4 .27 2.32 1.30

Manganese, filtered (μg/L) 24 49.3 4.1 25.4 20.2

Manganese, unfiltered (μg/L) 24 104 5.0 35 30

Zinc, filtered (μg/L) 24 20 1.7 6.0 4.4

Zinc, unfiltered (μg/L) 24 68 2 14 8

Sediment, suspended (percent finer than 0.062 mm) 24 96 70 86 86

Sediment, suspended concentration (mg/L) 24 84 1 12 4

Sediment, suspended discharge (ton/d) 24 11 .02 1.1 .11

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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]

68  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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 2005

Streamflow, instantaneous (ft3/s) 108 662 16 138 88

pH, onsite (standard units) 106 9.3 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 106 783 249 470 476

Temperature, water (°C) 107 25.0 .5 11.1 11.0

Hardness, filtered (mg/L as CaCO3

) 106 310 97 196 195

Calcium, filtered (mg/L) 106 90.4 27.9 56.8 57.6

Magnesium, filtered (mg/L) 106 21.4 5.94 13.1 13.0

Arsenic, filtered (μg/L) 106 60 6.8 22.2 22.1

Arsenic, unfiltered (μg/L) 106 94 10 27 26

Cadmium, filtered (μg/L) 106 .31 <.1 2

.07 <.1

Cadmium, unfiltered (μg/L) 106 .56 <.1 2

.13 <1

Copper, filtered (μg/L) 106 40 1.9 9.2 7.4

Copper, unfiltered (μg/L) 106 96.8 3.4 18.7 13.0

Iron, filtered (μg/L) 106 93 <5 2

18 14

Iron, unfiltered (μg/L) 106 3,000 70 356 270

Lead, filtered (μg/L) 106 1.0 <.08 2

.12 <.5

Lead, unfiltered (μg/L) 106 41.8 <1 2

2.64 1.24

Manganese, filtered (μg/L) 106 875 11.8 126 90

Manganese, unfiltered (μg/L) 106 899 55 193 160

Zinc, filtered (μg/L) 106 73 <1 2

9.3 5.9

Zinc, unfiltered (μg/L) 106 180 <10 2

37 24

Sediment, suspended (percent finer than 0.062 mm) 107 97 43 82 85

Sediment, suspended concentration (mg/L) 108 229 1 12 6

Sediment, suspended discharge (ton/d) 108 279 .11 7.8 1.6

Data  69
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 2005

Streamflow, instantaneous (ft3/s) 78 420 2.8 93 52

pH, onsite (standard units) 77 8.7 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 77 795 139 303 311

Temperature, water (°C) 78 20.0 0.0 9.1 9.0

Hardness, filtered (mg/L as CaCO3

) 77 420 40 147 150

Calcium, filtered (mg/L) 77 130 10.5 45.0 46.1

Magnesium, filtered (mg/L) 77 22.0 3.29 8.46 8.10

Arsenic, filtered (μg/L) 77 14 2 5.4 4.9

Arsenic, unfiltered (μg/L) 77 27 3 8 6

Cadmium, filtered (μg/L) 77 .1 <.04 2

.04 <.1

Cadmium, unfiltered (μg/L) 77 .41 <.1 2

.08 <1

Copper, filtered (μg/L) 77 16 1 3.7 3.0

Copper, unfiltered (μg/L) 77 108 2.3 20.5 8.6

Iron, filtered (μg/L) 77 30 <5 2

11 9

Iron, unfiltered (μg/L) 77 1,700 40 317 110

Lead, filtered (μg/L) 77 1.8 <.08 2

.10 <.5

Lead, unfiltered (μg/L) 77 14 <1 2

2.05 .43

Manganese, filtered (μg/L) 77 570 22.6 137 110

Manganese, unfiltered (μg/L) 77 1,400 57 237 190

Zinc, filtered (μg/L) 77 10 <1 2

2.2 1.1

Zinc, unfiltered (μg/L) 77 60 <10 2

10 3

Sediment, suspended (percent finer than 0.062 mm) 78 88 55 73 74

Sediment, suspended concentration (mg/L) 78 106 2 19 8

Sediment, suspended discharge (ton/d) 78 87 .05 9.2 1.0

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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]

70 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
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 2005

Streamflow, instantaneous (ft3/s) 149 1,050 14 208 124

pH, onsite (standard units) 136 9.0 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 137 720 197 427 440

Temperature, water (°C) 148 22.5 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3

) 135 370 81 187 190

Calcium, filtered (mg/L) 135 110 24.2 55.2 57.5

Magnesium, filtered (mg/L) 135 22.0 5.08 11.9 12.1

Arsenic, filtered (μg/L) 135 53 4 15.2 13.3

Arsenic, unfiltered (μg/L) 135 78 3 20 17

Cadmium, filtered (μg/L) 135 1 <.1 2

.07 <1

Cadmium, unfiltered (μg/L) 135 3 <.1 2

.21 <1

Copper, filtered (μg/L) 135 50 2.3 9.0 7.0

Copper, unfiltered (μg/L) 134 240 4.8 30.4 17.0

Iron, filtered (μg/L) 135 110 <3 2

16 11

Iron, unfiltered (μg/L) 135 9,200 60 523 270

Lead, filtered (μg/L) 135 3 <.08 2

.18 <1

Lead, unfiltered (μg/L) 135 31.0 <1 2

3.76 2.00

Manganese, filtered (μg/L) 135 460 25.2 115 82.7

Manganese, unfiltered (μg/L) 135 1,400 47 248 193

Zinc, filtered (μg/L) 135 110 <1 2

11.2 6.0

Zinc, unfiltered (μg/L) 135 360 <10 2

44 29

Sediment, suspended (percent finer than 0.062 mm) 148 97 41 78 78

Sediment, suspended concentration (mg/L) 149 338 2 19 8

Sediment, suspended discharge (ton/d) 149 459 .12 22 2.3

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the 

laboratory reporting level to compute statistic]

Data  71
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 2005

Streamflow, instantaneous (ft3

/s) 8 17 .97 7.1 4.2

pH, onsite (standard units) 8 8.6 7.4 8.2 8.4

Specific conductance, onsite (μS/cm) 8 227 163 202 216

Temperature, water (°C) 8 14.5 3.0 8.5 7.8

Hardness, filtered (mg/L as CaCO3

) 8 110 50 94 100

Calcium, filtered (mg/L) 8 35.7 15.7 28.9 30.6

Magnesium, filtered (mg/L) 8 6.79 2.71 5.50 6.14

Arsenic, filtered (μg/L) 8 156 2.5 24.6 6.8

Arsenic, unfiltered (μg/L) 8 3,860 2 488 8

Cadmium, filtered (μg/L) 8 .90 .02 .15 .04

Cadmium, unfiltered (μg/L) 8 147 .02 18.4 .06

Copper, filtered (μg/L) 8 90.5 1.2 13.7 3.4

Copper, unfiltered (μg/L) 8 29,100 1.7 3,640 6.4

Iron, filtered (μg/L) 8 25 <6 2

9 4

Iron, unfiltered (μg/L) 8 99,700 20 12,600 110

Lead, filtered (μg/L) 8 .18 <.08 -- <.08

Lead, unfiltered (μg/L) 8 1,290 .13 162 .54

Manganese, filtered (μg/L) 8 42.4 .5 6.5 1.6

Manganese, unfiltered (μg/L) 8 8,830 1 1,110 4

Zinc, filtered (μg/L) 8 30.0 1.0 4.9 1.2

Zinc, unfiltered (μg/L) 8 7,780 2 976 4

Sediment, suspended (percent finer than 0.062 mm) 8 97 30 70 76

Sediment, suspended concentration (mg/L) 8 58,900 1 7,370 10

Sediment, suspended discharge (ton/d) 8 1,320 <.1 2

165 .08

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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]

72 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
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 2005

Streamflow, instantaneous (ft3/s) 24 59 1.3 19 12

pH, onsite (standard units) 24 8.7 8.0 8.5 8.5

Specific conductance, onsite (μS/cm) 24 934 540 653 630

Temperature, water (°C) 24 26.5 1.5 13.0 12.2

Hardness, filtered (mg/L as CaCO3

) 24 450 200 307 300

Calcium, filtered (mg/L) 24 122 48.5 85.6 86.6

Magnesium, filtered (mg/L) 24 35.7 18.0 22.7 21.2

Arsenic, filtered (μg/L) 24 41.8 6.6 15.2 12.9

Arsenic, unfiltered (μg/L) 24 43 6 15 14

Cadmium, filtered (μg/L) 24 .05 <.04 2

.03 .03

Cadmium, unfiltered (μg/L) 24 .11 .02 .05 .04

Copper, filtered (μg/L) 24 6.7 1.5 3.2 2.9

Copper, unfiltered (μg/L) 24 22.5 3.9 7.5 6.2

Iron, filtered (μg/L) 24 61 <6 2

11 7

Iron, unfiltered (μg/L) 24 280 10 98 75

Lead, filtered (μg/L) 24 .33 <.08 2

.08 <.08

Lead, unfiltered (μg/L) 24 1.30 .04 .39 .31

Manganese, filtered (μg/L) 24 39.5 1.9 11.6 9.4

Manganese, unfiltered (μg/L) 24 45 2 15 13

Zinc, filtered (μg/L) 24 3.8 <1 2

1.6 1.2

Zinc, unfiltered (μg/L) 24 9 <2 2

3 3

Sediment, suspended (percent finer than 0.062 mm) 24 86 18 55 60

Sediment, suspended concentration (mg/L) 24 34 2 14 14

Sediment, suspended discharge (ton/d) 24 3.8 .01 .89 .32

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the 

laboratory reporting level to compute statistic]

Data  73
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 2005

Streamflow, instantaneous (ft3/s) 201 1,920 23 290 215

pH, onsite (standard units) 149 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 184 642 234 485 506

Temperature, water (°C) 200 23.0 0.0 9.9 10.0

Hardness, filtered (mg/L as CaCO3

) 141 280 95 205 220

Calcium, filtered (mg/L) 141 82.0 28.2 60.5 64.0

Magnesium, filtered (mg/L) 141 19 5.9 13.1 13.8

Arsenic, filtered (μg/L) 151 39 6 14.4 13.0

Arsenic, unfiltered (μg/L) 151 215 8 25 17

Cadmium, filtered (μg/L) 151 2 <.1 2

.08 <1

Cadmium, unfiltered (μg/L) 151 5 <.1 2

.45 <1

Copper, filtered (μg/L) 151 120 3.2 11.6 9.0

Copper, unfiltered (μg/L) 150 1,500 8.2 89.8 38.2

Iron, filtered (μg/L) 151 190 <3 2

15 9

Iron, unfiltered (μg/L) 151 29,000 30 1,670 580

Lead, filtered (μg/L) 151 6 <.08 2

.38 <1

Lead, unfiltered (μg/L) 151 200 <1 2

11.7 4.08

Manganese, filtered (μg/L) 151 400 1 43.1 33.9

Manganese, unfiltered (μg/L) 151 4,600 12 264 150

Zinc, filtered (μg/L) 151 230 <10 2

13.1 9.0

Zinc, unfiltered (μg/L) 151 1,700 4 98 50

Sediment, suspended (percent finer than 0.062 mm) 192 99 37 71 72

Sediment, suspended concentration (mg/L) 201 2,250 1 76 22

Sediment, suspended discharge (ton/d) 201 8,690 .24 165 11

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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]

74 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
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 2005

Streamflow, instantaneous (ft3/s) 107 3,920 87 743 507

pH, onsite (standard units) 106 8.8 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 106 510 206 373 394

Temperature, water (°C) 106 23.0 0.0 9.8 10.0

Hardness, filtered (mg/L as CaCO3

) 106 230 86 164 170

Calcium, filtered (mg/L) 106 68.0 25.9 48.4 51.2

Magnesium, filtered (mg/L) 106 15.0 5.15 10.5 11.0

Arsenic, filtered (μg/L) 106 20 5.8 10.1 10.0

Arsenic, unfiltered (μg/L) 106 75 7 15 12

Cadmium, filtered (μg/L) 106 .2 <.04 2

.04 <.1

Cadmium, unfiltered (μg/L) 106 2 <.1 2

.18 <1

Copper, filtered (μg/L) 105 36 2.1 6.9 5.6

Copper, unfiltered (μg/L) 105 440 5.2 43.1 25.0

Iron, filtered (μg/L) 106 100 <3 2

19 12

Iron, unfiltered (μg/L) 106 12,000 30 929 460

Lead, filtered (μg/L) 105 .8 <.08 2

.11 <.5

Lead, unfiltered (μg/L) 105 73 <1 2

6.04 3.00

Manganese, filtered (μg/L) 106 57.3 4.0 19.6 17.8

Manganese, unfiltered (μg/L) 106 1,100 10 132 90

Zinc, filtered (μg/L) 106 26 <1 2

6.2 4.0

Zinc, unfiltered (μg/L) 106 510 2 49 30

Sediment, suspended (percent finer than 0.062 mm) 107 94 43 76 78

Sediment, suspended concentration (mg/L) 107 752 2 54 22

Sediment, suspended discharge (ton/d) 107 7,960 .94 238 33

Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25°C; mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than laboratory reporting level1; --, indicates insufficient data greater than the 

laboratory reporting level to compute statistic]

Data  75
Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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 2005

Streamflow, instantaneous (ft3/s) 107 3,860 149 1,030 755

pH, onsite (standard units) 106 8.6 7.8 8.3 8.3

Specific conductance, onsite (μS/cm) 106 630 189 412 433

Temperature, water (°C) 107 22.5 .5 10.8 11.0

Hardness, filtered (mg/L as CaCO3

) 106 300 74 186 195

Calcium, filtered (mg/L) 106 83 21 53.4 55.2

Magnesium, filtered (mg/L) 106 22 5.2 12.8 13.1

Arsenic, filtered (μg/L) 106 20 6.6 10.6 10.0

Arsenic, unfiltered (μg/L) 106 62 8 17 13

Cadmium, filtered (μg/L) 106 .30 <.04 2

<.05 <.1

Cadmium, unfiltered (μg/L) 106 2 <.1 2

.23 <1

Copper, filtered (μg/L) 104 21 1 6.6 5.0

Copper, unfiltered (μg/L) 104 360 4.6 46.2 23.0

Iron, filtered (μg/L) 106 150 <3 2

19 8

Iron, unfiltered (μg/L) 105 8,800 20 1,060 470

Lead, filtered (μg/L) 102 1.2 <.08 2

.17 <.60

Lead, unfiltered (μg/L) 102 56 <1 2

8.32 3.50

Manganese, filtered (μg/L) 106 60.7 4.5 17.1 15.0

Manganese, unfiltered (μg/L) 106 880 8 155 97.5

Zinc, filtered (μg/L) 106 21 <3 2

6.6 4.7

Zinc, unfiltered (μg/L) 106 490 3 67 36

Sediment, suspended (percent finer than 0.062 mm) 107 92 38 74 75

Sediment, suspended concentration (mg/L) 107 530 2 68 26

Sediment, suspended discharge (ton/d) 107 4,720 1.7 346 49

76  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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 2005

Streamflow, instantaneous (ft3/s) 204 9,560 296 1,860 1,110

pH, onsite (standard units) 150 8.8 7.4 8.2 8.3

Specific conductance, onsite (μS/cm) 179 483 139 304 316

Temperature, water (°C) 203 22.0 0.0 9.4 9.5

Hardness, filtered (mg/L as CaCO3

) 140 210 54 132 135

Calcium, filtered (mg/L) 140 59.0 14.9 37.3 38.2

Magnesium, filtered (mg/L) 140 14.0 3.94 9.49 9.50

Arsenic, filtered (μg/L) 149 17 2.7 6.0 5.2

Arsenic, unfiltered (μg/L) 149 110 3 10 7

Cadmium, filtered (μg/L) 149 .11 <.04 2

.03 <.1

Cadmium, unfiltered (μg/L) 149 4 <.1 2

.28 <1

Copper, filtered (μg/L) 148 25 E1.1 5.0 4.0

Copper, unfiltered (μg/L) 147 500 3 37.9 17.6

Iron, filtered (μg/L) 149 190 <3 2

24 13

Iron, unfiltered (μg/L) 149 19,000 30 1,120 390

Lead, filtered (μg/L) 145 7 <.08 2

.34 <1

Lead, unfiltered (μg/L) 145 100 <1 2

7.93 3.00

Manganese, filtered (μg/L) 149 37.4 1.0 8.2 7.0

Manganese, unfiltered (μg/L) 149 2,000 10 134 70

Zinc, filtered (μg/L) 148 39 <3 2

6.5 4.2

Zinc, unfiltered (μg/L) 149 1,100 <10 2

66 30

Sediment, suspended (percent finer than 0.062 mm) 193 98 27 73 75

Sediment, suspended concentration (mg/L) 204 1,370 2 60 18

Sediment, suspended discharge (ton/d) 204 34,700 3.5 664 60

Data  77
Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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 2005

Streamflow, instantaneous (ft3/s) 146 13,400 344 2,650 1,310

pH, onsite (standard units) 106 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 123 294 131 207 205

Temperature, water (°C) 146 21.0 0.0 9.2 9.5

Hardness, filtered (mg/L as CaCO3

) 99 140 55 102 97

Calcium, filtered (mg/L) 99 37 14 26.3 24.8

Magnesium, filtered (mg/L) 99 13 4.9 9.08 8.63

Arsenic, filtered (μg/L) 106 2 <1 2

1.0 1.0

Arsenic, unfiltered (μg/L) 106 4 <1 2

1 1

Cadmium, filtered (μg/L) 106 1 <.04 -- <.1

Cadmium, unfiltered (μg/L) 106 2 <.04 2

.14 <1

Copper, filtered (μg/L) 104 7 <1 2

1.5 .9

Copper, unfiltered (μg/L) 103 34 <1 2

5.6 2.6

Iron, filtered (μg/L) 106 100 <3 2

18 10

Iron, unfiltered (μg/L) 106 3,600 10 463 205

Lead, filtered (μg/L) 102 8 <.08 2

.46 <1

Lead, unfiltered (μg/L) 102 25 <.06 2

2.86 <5

Manganese, filtered (μg/L) 106 11 <1 2

2.4 2.0

Manganese, unfiltered (μg/L) 106 180 <10 2

31 20

Zinc, filtered (μg/L) 106 15 <.6 2

2.4 <10

Zinc, unfiltered (μg/L) 106 60 <1 2

6.4 <10

Sediment, suspended (percent finer than 0.062 mm) 144 98 42 80 82

Sediment, suspended concentration (mg/L) 146 271 1 30 8

Sediment, suspended discharge (ton/d) 146 7,670 1.1 538 30

78  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Table 20. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 through September 2005.

—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 2005

Streamflow, instantaneous (ft3/s) 170 21,600 720 4,400 2,380

pH, onsite (standard units) 127 8.7 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 147 399 142 254 261

Temperature, water (°C) 167 21.0 0.0 9.4 9.0

Hardness, filtered (mg/L as CaCO3

) 127 170 61 117 120

Calcium, filtered (mg/L) 127 46 14 31.5 32.0

Magnesium, filtered (mg/L) 127 13.0 5.28 9.26 9.20

Arsenic, filtered (μg/L) 127 9 1 3.3 3.0

Arsenic, unfiltered (μg/L) 127 69 1 5 4

Cadmium, filtered (μg/L) 127 .2 <.04 2

.03 <.1

Cadmium, unfiltered (μg/L) 127 5 <.1 2

.14 <1

Copper, filtered (μg/L) 126 12.6 .7 2.8 2.0

Copper, unfiltered (μg/L) 125 400 2 16.4 8.0

Iron, filtered (μg/L) 127 200 <3 2

22 15

Iron, unfiltered (μg/L) 127 13,000 40 598 230

Lead, filtered (μg/L) 122 1.2 <.08 2

.17 <1

Lead, unfiltered (μg/L) 122 78 <1 2

3.12 1.17

Manganese, filtered (μg/L) 127 230 6.2 17.6 14.2

Manganese, unfiltered (μg/L) 127 1,100 10 65 40

Zinc, filtered (μg/L) 127 16 <1 2

3.8 2.1

Zinc, unfiltered (μg/L) 127 1,100 <10 2

31 12

Sediment, suspended (percent finer than 0.062 mm) 165 99 44 87 90

Sediment, suspended concentration (mg/L) 170 824 2 37 12

Sediment, suspended discharge (ton/d) 170 21,900 5.8 945 68

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  79
Table 21. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2005.

[For water year 2005, bulk bed (fine-grained plus coarse-grained) sediment was not collected as in previous years. Bed-sediment data consist of only the 

fine-grained fraction (material less than 0.064 millimeter in diameter). Reported concentrations are in micrograms per gram dry weight. Number of 

samples represents the number of years that the constituent was analyzed, with each year represented by a single mean concentration of composite 

samples. Values for a single sample are arbitrarily listed in the “Mean” column. Values are reported using U.S. Geological Survey rounding standards. 

Symbols: <, less than the minimum reporting level; --, indicates insufficient data to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12323600—Silver Bow Creek at Opportunity

Period of record for bed-sediment data: 1992-2005

Arsenic 3 186 163 171 165

Cadmium 14 43.9 23.7 34.0 34.6

Chromium 12 32.4 16.8 24.8 24.5

Copper 14 9,020 3,390 4,940 4,620

Iron 14 41,200 28,200 35,600 36,000

Lead 14 1,030 381 726 792

Manganese 14 9,220 1,680 3,710 2,970

Nickel 13 21.4 12.4 15.4 15.3

Silver 12 20.0 8.3 15.5 15.8

Zinc 14 13,400 5,620 8,460 7,820

12323750—Silver Bow Creek at Warm Springs

Period of record for bed-sediment data: 1992-2005

Arsenic 3 177 103 141 141

Cadmium 14 12.2 4.2 7.7 7.1

Chromium 12 34.1 <15.7 19.4 18.5

Copper 14 769 169 355 279

Iron 14 31,700 15,400 22,200 20,800

Lead 14 100 49 71 71

Manganese 14 17,700 1,470 8,490 8,370

Nickel 13 19.1 9.2 14.8 14.6

Silver 12 4.4 .3 1

1.9 11.8

Zinc 14 2,220 620 1,040 828

12323770—Warm Springs Creek at Warm Springs

Period of record for bed-sediment data: 1995, 1997, 1999, 2002, 2005

Arsenic 1 -- -- 66 --

Cadmium 5 5.8 1.3 3.6 3.9

Chromium 5 33.4 27.5 30.4 30.8

Copper 5 991 779 878 881

Iron 5 22,400 16,800 20,700 21,900

Lead 5 86 67 81 85

Manganese 5 12,100 2,020 7,980 8,790

Nickel 5 21.9 17.6 19.2 19.2

Silver 4 5.1 3.1 3.8 3.5

Zinc 5 421 372 395 396

80 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of samples Maximum Minimum Mean Median

12323800—Clark Fork near Galen

Period of record for bed-sediment data: 1987, 1991-2005

Arsenic 3 119 107 112 111

Cadmium 16 20.1 4.0 9.5 8.5

Chromium 12 33.9 19.1 26.2 26.1

Copper 16 2,300 838 1,230 1,130

Iron 16 39,800 22,600 27,800 26,900

Lead 16 235 92 139 134

Manganese 16 17,300 2,780 9,560 10,200

Nickel 13 23.2 13.9 18.2 18.2

Silver 14 7.3 <3.2 1

4.4 14.5

Zinc 16 3,560 999 1,610 1,200

461415112450801—Clark Fork below Lost Creek, near Galen

Period of record for bed-sediment data: 1996-2005

Arsenic 3 204 92 134 107

Cadmium 10 10.5 5.8 7.8 7.7

Chromium 9 34.5 20.5 27.9 27.5

Copper 10 2,050 1,150 1,510 1,430

Iron 10 32,800 24,400 29,600 30,500

Lead 10 218 127 176 178

Manganese 10 9,670 3,540 5,650 5,660

Nickel 10 19.9 11.7 16.2 164.0

Silver 8 7.8 4.2 6.5 6.7

Zinc 10 1,680 1,120 1,380 1,380

461559112443301—Clark Fork at County Bridge, near Racetrack

Period of record for bed-sediment data: 1996-2005

Arsenic 3 101 56 81 86.00

Cadmium 10 8.7 5.0 7.0 7.0

Chromium 9 33.3 19.0 25.0 24.9

Copper 10 1,610 933 1,190 1,170

Iron 10 31,700 21,200 26,300 26,400

Lead 10 186 103 143 138

Manganese 10 6,310 2,100 3,670 3,560

Nickel 10 18.4 10.3 14.0 14.1

Silver 8 6.1 <3.3 1

5.0 15.4

Zinc 10 1,550 999 1,210 1,150

Table 21. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2005.—Continued

[For water year 2005, bulk bed (fine-grained plus coarse-grained) sediment was not collected as in previous years. Bed-sediment data consist of only the 

fine-grained fraction (material less than 0.064 millimeter in diameter). Reported concentrations are in micrograms per gram dry weight. Number of 

samples represents the number of years that the constituent was analyzed, with each year represented by a single mean concentration of composite 

samples. Values for a single sample are arbitrarily listed in the “Mean” column. Values are reported using U.S. Geological Survey rounding standards. 

Symbols: <, less than the minimum reporting level; --, indicates insufficient data to compute statistic]

Data  81
Constituent Number of samples Maximum Minimum Mean Median

461903112440701—Clark Fork at Dempsey Creek Diversion, near Racetrack

Period of record for bed-sediment data: 1996-2005

Arsenic 3 80 58 70 71

Cadmium 10 10.3 4.3 6.8 6.4

Chromium 9 34.1 16.0 24.7 25.6

Copper 10 1,550 721 1,020 996

Iron 10 33,700 20,600 26,100 25,200

Lead 10 155 92 129 126

Manganese 10 8,370 1,810 4,060 3,290

Nickel 10 16.9 8.7 13.0 12.7

Silver 8 6.2 2.7 4.9 5.0

Zinc 10 1,570 900 1,130 1,080

12324200—Clark Fork at Deer Lodge

Period of record for bed-sediment data: 1986-1987, 1990-2005

Arsenic 3 77 49 66 72

Cadmium 18 10.0 3.8 6.6 6.2

Chromium 12 43.9 19.5 30.3 30.4

Copper 18 4,180 683 1,320 1,060

Iron 18 35,300 21,100 27,400 26,400

Lead 18 242 103 150 149

Manganese 18 6,020 1,110 2,730 2,420

Nickel 13 21.1 11.5 15.4 15.0

Silver 16 7.9 2.4 4.7 4.5

Zinc 18 1,730 846 1,240 1,260

12324590—Little Blackfoot River near Garrison

Period of record for bed-sediment data: 1986-1987, 1994, 1998, 2001, 2004

Arsenic 1 -- -- 12 --

Cadmium 6 2.3 0.2 1.1 0.9

Chromium 4 54.4 22.1 40.6 43.0

Copper 6 85 33 52 40

Iron 6 30,700 16,100 24,300 24,400

Lead 6 53 36 40 38

Manganese 6 2,700 905 1,370 1,080

Nickel 4 21.9 13.6 17.6 17.4

Silver 5 .9 <.5 1

.6 1<1.5

Zinc 6 204 161 176 173

Table 21. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2005.—Continued

[For water year 2005, bulk bed (fine-grained plus coarse-grained) sediment was not collected as in previous years. Bed-sediment data consist of only the 

fine-grained fraction (material less than 0.064 millimeter in diameter). Reported concentrations are in micrograms per gram dry weight. Number of 

samples represents the number of years that the constituent was analyzed, with each year represented by a single mean concentration of composite 

samples. Values for a single sample are arbitrarily listed in the “Mean” column. Values are reported using U.S. Geological Survey rounding standards. 

Symbols: <, less than the minimum reporting level; --, indicates insufficient data to compute statistic]

82 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of samples Maximum Minimum Mean Median

12324680—Clark Fork at Goldcreek

Period of record for bed-sediment data: 1992-2005

Arsenic 3 39 24 32 32

Cadmium 14 8.1 3.1 5.1 5.4

Chromium 12 48.9 22.1 32.1 31.8

Copper 14 1,080 393 693 738

Iron 14 30,600 19,500 23,800 24,000

Lead 14 152 61 98 99

Manganese 14 2,610 1,160 1,890 1,810

Nickel 13 18.6 10.9 14.7 15.0

Silver 12 4.8 2.3 3.3 3.2

Zinc 14 1,320 590 978 1,080

12331800—Clark Fork near Drummond

Period of record for bed-sediment data: 1986-1987, 1991-2005

Arsenic 3 34 31 32 33

Cadmium 17 7.7 2.6 4.7 4.8

Chromium 12 35.4 17.0 28.6 30.8

Copper 17 747 321 495 491

Iron 17 27,000 16,500 21,500 20,400

Lead 17 135 64 91 93

Manganese 17 3,090 1,150 1,900 1,880

Nickel 13 16.8 10.4 13.7 14.0

Silver 15 4.7 <3.2 1

3.0 12.9

Zinc 17 1,230 742 991 1,000

12334510—Rock Creek near Clinton

Period of record for bed-sediment data: 1986-1987, 1989, 1991-1999, 2001-2005

Arsenic 3 6 <6 15 15

Cadmium 17 3.7 <.1 1

.8 1<.8

Chromium 11 27.9 16.1 21.1 20.5

Copper 17 16 3 11 12

Iron 17 21,400 13,100 17,300 17,200

Lead 17 16 <3 9 10

Manganese 17 724 126 373 361

Nickel 12 14.8 8.7 11.5 11.4

Silver 14 1.9 <.3 1

.5 1<.6

Zinc 17 58 23 42 45

Table 21. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2005.—Continued

[For water year 2005, bulk bed (fine-grained plus coarse-grained) sediment was not collected as in previous years. Bed-sediment data consist of only the 

fine-grained fraction (material less than 0.064 millimeter in diameter). Reported concentrations are in micrograms per gram dry weight. Number of 

samples represents the number of years that the constituent was analyzed, with each year represented by a single mean concentration of composite 

samples. Values for a single sample are arbitrarily listed in the “Mean” column. Values are reported using U.S. Geological Survey rounding standards. 

Symbols: <, less than the minimum reporting level; --, indicates insufficient data to compute statistic]

Data  83
Constituent Number of samples Maximum Minimum Mean Median

12334550—Clark Fork at Turah Bridge, near Bonner

Period of record for bed-sediment data: 1986, 1991-2005

Arsenic 3 30 19 24 22

Cadmium 16 7.3 2.3 4.0 3.9

Chromium 12 34.7 15.3 24.6 27.2

Copper 16 635 211 363 322

Iron 16 24,400 12,600 18,700 17,300

Lead 16 115 47 71 65

Manganese 16 2,270 671 1,230 1,200

Nickel 13 19.1 8.7 12.9 11.6

Silver 14 3.9 <1.9 1

2.1 11.9

Zinc 16 1,160 586 848 816

12340000—Blackfoot River near Bonner

Period of record for bed-sediment data: 1986-1987, 1991, 1993-1996, 1998-2001, 2003

Arsenic 1 -- -- 2 --

Cadmium 12 2.0 <0.2 1

.7 1<1.0

Chromium 8 25.8 15.1 20.5 21.8

Copper 12 27 11 20 21

Iron 12 20,200 12,400 16,800 16,800

Lead 12 20 <13 1

13 112

Manganese 12 683 298 531 538

Nickel 9 14.3 9.4 11.9 12.5

Silver 12 <1.9 <.3 1

.5 1<.6

Zinc 12 73 35 58 61

12340500—Clark Fork above Missoula

Period of record for bed-sediment data: 1997-2005

Arsenic 3 29 17 23 23

Cadmium 9 5.8 1.5 3.4 3.4

Chromium 8 30.6 19.0 25.0 24.6

Copper 9 543 166 328 282

Iron 9 24,300 18,100 20,300 20,400

Lead 9 78 37 55 54

Manganese 9 1,420 477 977 970

Nickel 9 15.8 10.9 13.2 13.0

Silver 7 2.9 .8 1

2.0 12.1

Zinc 9 1,090 438 709 696

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

Table 21. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2005.—Continued

[For water year 2005, bulk bed (fine-grained plus coarse-grained) sediment was not collected as in previous years. Bed-sediment data consist of only the 

fine-grained fraction (material less than 0.064 millimeter in diameter). Reported concentrations are in micrograms per gram dry weight. Number of 

samples represents the number of years that the constituent was analyzed, with each year represented by a single mean concentration of composite 

samples. Values for a single sample are arbitrarily listed in the “Mean” column. Values are reported using U.S. Geological Survey rounding standards. 

Symbols: <, less than the minimum reporting level; --, indicates insufficient data to compute statistic]
Constituent Number of samples Maximum Minimum Mean Median

12353000—Clark Fork below Missoula2

Period of record for bed-sediment data: 1986, 1990-2004

Arsenic 2 14 6 -- --

Cadmium 16 6.0 1.1 2.3 1.9

Chromium 11 27.6 12.3 21.4 21.5

Copper 16 293 69 150 140

Iron 16 21,100 13,100 18,100 18,600

Lead 16 58 12 36 36

Manganese 16 2,530 446 1,360 1,270

Nickel 12 14.1 8.4 12.0 12.5

Silver 15 3.0 .4 1

1.3 11.2

Zinc 16 675 239 396 395

1

Value was determined by substituting one-half of the minimum reporting level for censored (<) values when both uncensored and censored values 

were used to determine the mean and (or) median. When all data were less than the minimum reporting level, the median was determined by ranking the 

censored values by order of magnitude.

2

Samples were collected about 30 miles downstream from streamflow-gaging station to conform to previous sampling location.

Data  85

Table 21. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, August 1986 through 

August 2005.—Continued

[For water year 2005, bulk bed (fine-grained plus coarse-grained) sediment was not collected as in previous years. Bed-sediment data consist of only the 

fine-grained fraction (material less than 0.064 millimeter in diameter). Reported concentrations are in micrograms per gram dry weight. Number of 

samples represents the number of years that the constituent was analyzed, with each year represented by a single mean concentration of composite 

samples. Values for a single sample are arbitrarily listed in the “Mean” column. Values are reported using U.S. Geological Survey rounding standards. 

Symbols: <, less than the minimum reporting level; --, indicates insufficient data to compute statistic]
Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323600—Silver Bow Creek at Opportunity

Period of record for biological data: 1992, 1994-95, 1997-2005

Brachycentrus spp.

Arsenic 0 -- -- -- --

Cadmium 5 12.5 5.8 10.1 11.6

Chromium 5 5.9 .7 2.1 .9

Copper 5 846 235 587 592

Iron 5 1,190 335 617 469

Lead 5 21.5 7.4 13.7 13.8

Manganese 5 817 231 515 503

Nickel 5 2.1 <.1 1

1.3 11.6

Zinc 5 995 629 803 815

Hydropsyche cockerelli

Arsenic 4 20.4 9.5 13.5 12.0

Cadmium 10 9.7 4.1 5.8 5.1

Chromium 10 8.0 1.0 2.9 1.9

Copper 10 1,090 269 451 378

Iron 10 2,660 689 1,390 1,120

Lead 10 47.2 19.0 27.6 21.3

Manganese 10 3,030 180 972 782

Nickel 10 3.6 .7 2.0 1.8

Zinc 10 1,590 749 949 838

Hydropsyche spp.

Arsenic 5 23.1 10.7 17.2 18.4

Cadmium 10 10.9 4.6 7.0 5.9

Chromium 10 4.7 .6 2.1 1.5

Copper 10 930 312 597 471

Iron 10 2,550 1,050 1,860 1,990

Lead 10 51.4 21.8 38.9 38.2

Manganese 10 1,340 712 1,080 1,060

Nickel 10 2.5 .7 2.2 2.4

Zinc 10 1,290 834 1,070 1,090

86  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323600—Silver Bow Creek at Opportunity—Continued

Period of record for biological data: 1992, 1994-95, 1997-2005

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: 1992-2005

Hydropsyche cockerelli

Arsenic 6 23.6 7.9 15.1 15.4

Cadmium 32 2.1 .2 .7 .5

Chromium 32 4.3 .4 1.0 .8

Copper 32 97.0 16.7 38.5 30.5

Iron 32 1,590 351 770 761

Lead 32 5.7 .3 2.9 2.6

Manganese 32 3,890 491 1,310 1,160

Nickel 32 1.8 .3 .9 .8

Zinc 32 276 115 176 167

Hydropsyche occidentalils

Arsenic 5 31.0 10.5 21.0 25.6

Cadmium 20 1.6 .2 .6 .4

Chromium 20 6.8 .3 1.7 1.0

Copper 20 48.9 11.0 32.4 30.8

Iron 20 2,960 372 1,190 971

Lead 20 8.2 <1.7 1

3.8 13.5

Manganese 20 6,940 1,200 2,560 2,150

Nickel 20 2.7 .7 1.5 1.5

Zinc 20 220 140 178 179

Data  87
Constituent Number of 

composite samples Maximum Minimum Mean Median

12323750—Silver Bow Creek at Warm Springs—Continued

Period of record for biological data: 1992-2005

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 4 2.3 0.4 1.1 0.9

Chromium 4 1.4 .5 1.0 1.2

Copper 4 47.6 34.9 40.9 40.6

Iron 4 773 561 680 693

Lead 4 5.1 1.9 3.9 4.7

Manganese 4 1,100 443 725 678

Nickel 4 1.9 <.4 1

.8 1.5

Zinc 4 285 141 195 177

12323770—Warm Springs Creek at Warm Springs

Period of record for biological data: 1995, 1997, 1999, 2002, 2005

Arctopsyche grandis

Arsenic 2 9.8 9.5 -- --

Cadmium 6 3.6 1.9 2.7 2.7

Chromium 6 2.9 .8 1.7 1.6

Copper 6 133 78.3 106 100

Iron 6 1,100 684 918 957

Lead 6 5.6 3.0 1

4.7 15.2

Manganese 6 3,560 1,340 2,560 2,710

Nickel 6 2.8 1.8 1

2.3 12.3

Zinc 6 222 181 196 196

Hydropsyche occidentalis

Arsenic 2 13.6 12.7 -- --

Cadmium 4 1.2 .7 1.0 1.0

Chromium 4 3.2 .3 2.2 3.2

Copper 4 183 125 156 158

Iron 4 2,070 1,590 1,840 1,840

Lead 4 8.2 6.7 7.4 7.4

Manganese 4 3,190 2,400 2,790 2,770

Nickel 4 3.3 2.0 2.6 2.6

Zinc 4 172 148 160 160

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

88  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of 

composite samples Maximum Minimum Mean Median

12323770—Warm Springs Creek at Warm Springs—Continued

Period of record for biological data: 1995, 1997, 1999, 2002, 2005

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 2 1.1 0.6 -- --

Chromium 2 1.6 1.4 -- --

Copper 2 95.9 94.8 -- --

Iron 2 1,220 1,150 -- --

Lead 2 5.9 5.2 -- --

Manganese 2 3,390 956 -- --

Nickel 2 2.0 1.8 -- --

Zinc 2 129 125 -- --

12323800—Clark Fork near Galen

Period of record for biological data: 1987, 1991-2005

Hydropsyche cockerelli

Arsenic 3 15.8 13.2 14.2 13.6

Cadmium 28 2.7 .7 1.5 1.5

Chromium 28 4.4 .8 1.8 1.6

Copper 28 181 48.7 100 98.1

Iron 28 2,460 816 1,390 1,350

Lead 28 11.7 1.2 7.6 7.6

Manganese 28 3,620 1,070 2,280 2,320

Nickel 28 3.1 .9 1.6 1.5

Zinc 28 299 136 210 208

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 5 3.2 2.4 2.5 2.4

Chromium 5 4.6 1.8 2.6 2.2

Copper 5 185 156 173 175

Iron 5 1,890 1,360 1,510 1,430

Lead 5 12.4 7.1 8.5 7.9

Manganese 5 3,960 2,360 3,500 3,860

Nickel 5 3.6 1.9 2.3 2.1

Zinc 5 349 292 309 303

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data  89
Constituent Number of 

composite samples Maximum Minimum Mean Median

12323800—Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991-2005

Hydropsyche occidentalis

Arsenic 4 16.5 12.5 15.2 16.0

Cadmium 36 1.7 .6 1.1 1.1

Chromium 36 6.6 .4 2.0 1.5

Copper 36 121 49.2 82.3 81.6

Iron 36 1,920 642 1,270 1,220

Lead 36 13.5 1.6 7.0 6.6

Manganese 36 6,170 1,220 2,600 2,260

Nickel 36 3.5 .8 1.6 1.5

Zinc 36 286 168 199 193

Hydropsyche tana

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 1.5 --

Chromium 1 -- -- 1.4 --

Copper 1 -- -- 92.9 --

Iron 1 -- -- 1,340 --

Lead 1 -- -- 9.0 --

Manganese 1 -- -- 2,160 --

Nickel 1 -- -- 2.1 --

Zinc 1 -- -- 206 --

Hydropsyche spp.

Arsenic 2 15.7 14.5 -- --

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 -- --

Nickel 2 1.8 1.5 -- --

Zinc 6 329 218 280 291

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

90 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of 

composite samples Maximum Minimum Mean Median

461415112450801—Clark Fork below Lost Creek, near Galen

Period of record for biological data: 1996-2005

Claassenia sabulosa

Arsenic 1 -- -- 1.5 --

Cadmium 2 0.4 0.3 -- --

Chromium 2 1.9 .4 -- --

Copper 2 70.1 67.1 -- --

Iron 2 209 189 -- --

Lead 2 1.2 .7 -- --

Manganese 2 238 90.4 -- --

Nickel 2 .2 <.2 -- --

Zinc 2 245 208 -- --

Hydropsyche cockerelli

Arsenic 7 11.8 8.8 11.0 11.4

Cadmium 18 2.8 1.1 1.8 1.7

Chromium 18 2.7 .8 1.8 1.9

Copper 18 147 48.8 108 102

Iron 18 2,570 691 1,280 1,130

Lead 18 15.2 4.5 9.6 8.9

Manganese 18 3,160 1,230 1,800 1,670

Nickel 18 1.9 .9 1.2 1.1

Zinc 18 321 151 213 219

Hydropsyche occidentalis

Arsenic 3 15.6 12.7 13.7 12.9

Cadmium 17 1.8 .9 1.3 1.3

Chromium 17 3.3 1.2 2.0 1.8

Copper 17 157 52.1 103 107

Iron 17 1,920 963 1,380 1,360

Lead 17 12.4 6.6 9.5 9.5

Manganese 17 3,870 1,220 2,250 2,150

Nickel 17 1.7 .9 1.3 1.4

Zinc 17 283 174 227 236

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data  91
Constituent Number of 

composite samples Maximum Minimum Mean Median

461415112450801—Clark Fork below Lost Creek, near Galen—Continued

Period of record for biological data: 1996-2005

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: 1996-2005

Claassenia sabulosa

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.4 --

Chromium 1 -- -- .3 --

Copper 1 -- -- 40.3 --

Iron 1 -- -- 113 --

Lead 1 -- -- .8 --

Manganese 1 -- -- 172 --

Nickel 1 -- -- .2 --

Zinc 1 -- -- 213 --

Hydropsyche cockerelli

Arsenic 6 14.3 11.1 12.0 11.6

Cadmium 17 1.9 .8 1.4 1.4

Chromium 17 2.7 .6 1.5 1.1

Copper 17 121 50.0 85.5 84.3

Iron 17 1,370 657 957 981

Lead 17 10.5 3.7 6.8 6.9

Manganese 17 2,020 646 1,520 1,690

Nickel 17 1.4 .7 1.0 1.0

Zinc 17 199 139 176 176

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

92 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of 

composite samples Maximum Minimum Mean Median

461559112443301—Clark Fork at County Bridge, near Racetrack—Continued

Period of record for biological data: 1996-2005

Hydropsyche occidentalis

Arsenic 2 14.3 13.7 -- --

Cadmium 15 2.2 .7 1.4 1.4

Chromium 15 3.7 1.1 2.1 2.0

Copper 15 160 59.5 107 107

Iron 15 1,880 1,030 1,510 1,520

Lead 15 11.7 4.3 9.6 10.1

Manganese 15 3,770 1,090 2,070 2,050

Nickel 15 1.9 1.1 1.3 1.3

Zinc 15 255 181 225 220

Hydropsyche spp.

Arsenic 1 -- -- 11.9 --

Cadmium 3 2.4 1.0 1.6 1.5

Chromium 3 1.7 .7 1.2 1.1

Copper 3 113 82.9 93.7 85.2

Iron 3 1,290 1,140 1,210 1,200

Lead 3 9.6 5.7 7.5 7.4

Manganese 3 1,600 910 1,210 1,130

Nickel 3 1.4 1.1 1.3 1.3

Zinc 3 208 151 180 181

461903112440701—Clark Fork at Dempsey Creek Diversion, near Racetrack

Period of record for biological data: 1996-2005

Arctopsyche grandis

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 1.7 --

Chromium 1 -- -- <2.4 --

Copper 1 -- -- 30.8 --

Iron 1 -- -- 340 --

Lead 1 -- -- <14.5 --

Manganese 1 -- -- 510 --

Nickel 1 -- -- 1.0 --

Zinc 1 -- -- 87 --

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data  93
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: 1996-2005

Hydropsyche cockerelli

Arsenic 4 18.8 8.0 11.4 9.4

Cadmium 13 1.7 .7 1.2 1.3

Chromium 13 4.0 .4 1.3 1.0

Copper 13 190 60.7 92.3 78.8

Iron 13 2,310 552 953 831

Lead 13 17.7 3.5 6.5 5.0

Manganese 13 2,070 487 1,200 1,190

Nickel 13 1.9 .5 1.0 .7

Zinc 13 275 162 192 180

Hydropsyche occidentalis

Arsenic 2 24.0 10.2 -- --

Cadmium 19 1.8 .7 1.2 1.2

Chromium 19 6.2 .8 2.0 1.8

Copper 19 238 74.9 102 89.0

Iron 19 3,390 940 1,510 1,500

Lead 19 21.8 6.1 11.4 11.4

Manganese 19 3,990 826 2,410 2,290

Nickel 19 2.4 1.2 1.5 1.4

Zinc 19 355 211 250 236

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 2 1.7 1.6 -- --

Chromium 2 2.1 1.4 -- --

Copper 2 140 104 -- --

Iron 2 1,610 1,070 -- --

Lead 2 13.2 10.5 -- --

Manganese 2 1,150 638 -- --

Nickel 2 1.6 1.6 -- --

Zinc 2 212 191 -- --

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

94 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of 

composite samples Maximum Minimum Mean Median

12324200—Clark Fork at Deer Lodge

Period of record for biological data: 1986-87, 1990-2005

Arctopsyche grandis

Arsenic 0 -- -- -- --

Cadmium 2 2.4 <4.2 -- --

Chromium 2 1.0 <1.3 -- --

Copper 2 69.1 34.9 -- --

Iron 2 676 537 -- --

Lead 2 3.8 <7.8 -- --

Manganese 2 727 380 -- --

Nickel 2 <1.7 <1.3 -- --

Zinc 2 178 140 -- --

Hydropsyche cockerelli

Arsenic 4 10.1 5.8 7.3 6.7

Cadmium 27 2.3 .6 1.3 1.3

Chromium 27 3.2 .4 1.6 1.6

Copper 27 136 54.7 94.6 97.7

Iron 27 3,340 490 1,090 1,040

Lead 27 18.1 3.8 9.2 8.9

Manganese 27 1,490 396 844 759

Nickel 27 2.4 .3 1.1 1.0

Zinc 27 391 132 186 185

Hydropsyche occidentalis

Arsenic 5 12.4 6.6 9.8 9.4

Cadmium 42 2.7 .6 1.3 1.3

Chromium 42 3.6 .6 1.9 1.9

Copper 42 162 49.4 114 111

Iron 42 2,060 557 1,390 1,420

Lead 42 18.6 3.5 11.0 10.8

Manganese 42 2,850 649 1,700 1,730

Nickel 42 12.9 1.0 1.7 1.4

Zinc 42 329 166 240 233

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data  95
Constituent Number of 

composite samples Maximum Minimum Mean Median

12324200—Clark Fork at Deer Lodge—Continued

Period of record for biological data: 1986-87, 1990-2005

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 3 2.6 2.0 2.4 2.5

Chromium 0 -- -- -- --

Copper 3 222 175 191 177

Iron 3 2,220 1,850 2,010 1,950

Lead 3 16.7 15.0 16.1 16.7

Manganese 0 -- -- -- --

Nickel 0 -- -- -- --

Zinc 3 298 197 257 276

12324590—Little Blackfoot River near Garrison

Period of record for biological data: 1987, 1994, 1998, 2001, 2004

Arctopsyche grandis

Arsenic 3 4.2 3.2 3.6 3.3

Cadmium 18 .7 .2 .4 .4

Chromium 18 1.6 .6 .9 .8

Copper 18 14.2 9.0 11.9 11.9

Iron 18 716 177 419 414

Lead 18 1.3 .5 .8 .8

Manganese 18 1,140 318 733 719

Nickel 18 1.4 .4 .8 .8

Zinc 18 214 113 162 160

Claassenia sabulosa

Arsenic 1 -- -- 1.3 --

Cadmium 8 0.5 0.1 .2 0.2

Chromium 8 .9 .3 .6 .7

Copper 8 37.2 20.0 30.4 30.9

Iron 8 319 98.4 178 178

Lead 8 <.8 <.1 1

.4 1.3

Manganese 8 149 46.7 75.9 62.1

Nickel 8 .7 .4 .5 .5

Zinc 8 271 172 211 206

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

96  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of 

composite samples Maximum Minimum Mean Median

12324590—Little Blackfoot River near Garrison—Continued

Period of record for biological data: 1987, 1994, 1998, 2001, 2004

Hydropsyche cockerelli

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.6 --

Chromium 1 -- -- 1.6 --

Copper 1 -- -- 28.4 --

Iron 1 -- -- 478 --

Lead 1 -- -- 3.6 --

Manganese 1 -- -- 399 --

Nickel 1 -- -- 1.2 --

Zinc 1 -- -- 123 --

Hydropsyche occidentalis

Arsenic 0 -- -- -- --

Cadmium 2 0.3 <0.7 -- --

Chromium 2 2.3 1.3 -- --

Copper 2 15.2 15.1 -- --

Iron 2 1,340 426 -- --

Lead 2 2.3 <3.7 -- --

Manganese 2 554 434 -- --

Nickel 2 1.1 .8 -- --

Zinc 2 137 110 -- --

Hydropsyche spp.

Arsenic 1 -- -- 3.7 --

Cadmium 1 -- -- <.2 --

Chromium 1 -- -- 1.8 --

Copper 1 -- -- 11.1 --

Iron 1 -- -- 1,000 --

Lead 1 -- -- <2.4 --

Manganese 1 -- -- 1,200 --

Nickel 1 -- -- .9 --

Zinc 1 -- -- 151 --

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data  97
Constituent Number of 

composite samples Maximum Minimum Mean Median

12324680—Clark Fork at Goldcreek

Period of record for biological data: 1992-2005

Arctopsyche grandis

Arsenic 13 6.4 1.8 4.1 3.3

Cadmium 42 6.6 .6 2.0 1.8

Chromium 42 3.3 .4 1.4 1.1

Copper 42 129 19.9 44.3 37.5

Iron 42 2,360 195 686 517

Lead 42 10.9 1.1 3.6 3.4

Manganese 42 1,580 436 835 789

Nickel 42 1.8 .2 .7 .6

Zinc 42 326 149 199 183

Claassenia sabulosa

Arsenic 8 2.1 0.7 1.3 1.2

Cadmium 28 3.5 .1 1.0 .7

Chromium 28 1.6 .2 .6 .5

Copper 28 81.7 33.0 56.6 56.3

Iron 28 567 63.0 193 189

Lead 28 1.8 .4 .9 .9

Manganese 28 320 50.6 138 113

Nickel 28 .7 .1 .3 .3

Zinc 28 351 166 263 260

Hydropsyche cockerelli

Arsenic 8 6.1 4.1 5.2 5.4

Cadmium 27 2.6 .5 1.3 1.3

Chromium 27 4.7 .5 2.2 2.0

Copper 27 188 17.1 69.9 58.4

Iron 27 3,250 522 1,150 930

Lead 27 16.2 2.4 6.6 5.3

Manganese 27 1,670 538 913 906

Nickel 27 2.3 .3 1.2 1.0

Zinc 27 249 106 183 184

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

98  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of 

composite samples Maximum Minimum Mean Median

12324680—Clark Fork at Goldcreek—Continued

Period of record for biological data: 1992-2005

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 4 1.7 1.1 1.4 1.4

Chromium 4 1.4 1.3 1.4 1.4

Copper 4 72.9 43.8 60.5 62.7

Iron 4 1,320 612 1,050 1,130

Lead 4 6.9 2.4 4.6 4.6

Manganese 4 1,030 538 804 822

Nickel 4 1.4 .9 1.2 1.2

Zinc 4 190 137 167 170

Hydropsyche occidentalis

Arsenic 3 5.8 4.7 5.3 5.3

Cadmium 18 1.7 .4 1.2 1.3

Chromium 18 3.9 .4 1.6 1.7

Copper 18 156 26.4 62.8 58.0

Iron 18 2,720 466 1,140 1,070

Lead 18 15.7 2.9 6.9 5.8

Manganese 18 2,210 530 1,210 1,080

Nickel 18 2.5 .8 1.2 1.0

Zinc 18 277 97 195 196

12331800—Clark Fork near Drummond

Period of record for biological data: 1986, 1991-2005

Arctopsyche grandis

Arsenic 9 4.4 2.4 3.3 3.3

Cadmium 41 3.8 .4 1.3 1.1

Chromium 41 2.5 .2 1.0 1.0

Copper 41 89.2 16.9 32.4 27.4

Iron 41 1,660 240 568 511

Lead 41 11.8 2.1 4.4 3.9

Manganese 41 2,010 456 838 733

Nickel 41 1.9 .2 .7 .6

Zinc 41 308 140 188 183

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data  99
Constituent Number of 

composite samples Maximum Minimum Mean Median

12331800—Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991-2005

Claassenia sabulosa

Arsenic 6 1.3 0.7 1.1 1.2

Cadmium 42 2.8 .1 1.1 1.0

Chromium 42 3.3 .1 .7 .6

Copper 42 165 18.0 63.5 53.8

Iron 42 387 45.4 158 135

Lead 42 2.9 .2 .9 .8

Manganese 42 410 33.1 161 140

Nickel 42 1.1 .1 .3 .2

Zinc 42 567 103 273 256

Hydropsyche cockerelli

Arsenic 6 5.7 3.9 4.5 4.3

Cadmium 35 2.3 .3 1.1 .8

Chromium 35 3.5 .4 1.6 1.5

Copper 35 156 30.0 58.1 50.3

Iron 35 2,500 506 1,150 969

Lead 35 15.0 5.1 8.2 7.4

Manganese 35 1,680 549 977 913

Nickel 35 2.0 .5 1.1 1.0

Zinc 35 248 134 192 186

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

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

100 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of 

composite samples Maximum Minimum Mean Median

12331800—Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991-2005

Hydropsyche occidentalis

Arsenic 5 6.9 4.3 5.0 4.6

Cadmium 21 2.0 .4 1.0 1.0

Chromium 21 8.1 .4 2.3 2.2

Copper 21 118 13.3 54.1 55.0

Iron 21 2,060 424 1,250 1,180

Lead 21 14.0 2.9 8.7 8.7

Manganese 21 2,920 619 1,500 1,200

Nickel 21 2.4 .5 1.4 1.2

Zinc 21 293 157 220 221

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 2.6 --

Chromium 0 -- -- -- --

Copper 1 -- -- 85.0 --

Iron 1 -- -- 913 --

Lead 1 -- -- 9.1 --

Manganese 0 -- -- -- --

Nickel 0 -- -- -- --

Zinc 1 -- -- 260 --

12334510—Rock Creek near Clinton

Period of record for biological data: 1987; 1991-1999; 2001-2005

Arctopsyche grandis

Arsenic 8 2.5 1.5 2.0 2.0

Cadmium 46 .4 <.1 1

.2 1.2

Chromium 46 2.9 .4 1.1 1.0

Copper 46 15.7 4.7 8.6 8.5

Iron 46 1,090 191 585 531

Lead 46 1.1 <.1 1

.4 1.4

Manganese 46 454 113 251 245

Nickel 46 1.8 .2 .9 .9

Zinc 46 189 83.9 127 130

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data 101
Constituent Number of 

composite samples Maximum Minimum Mean Median

12334510—Rock Creek near Clinton—Continued

Period of record for biological data: 1987; 1991-1999; 2001-2005

Claassenia sabulosa

Arsenic 4 1.1 1.0 1.0 1.0

Cadmium 23 .3 <.1 1

.2 1.1

Chromium 23 1.8 .1 .6 .5

Copper 23 40.7 18.1 28.7 28.5

Iron 23 129 49.8 93.8 102

Lead 23 1.0 .1 .4 .3

Manganese 23 76.3 15.7 36.6 34.8

Nickel 23 .9 .1 .3 .3

Zinc 23 264 139 194 190

Hydropsyche cockerelli

Arsenic 1 -- -- 2.4 --

Cadmium 4 0.3 <0.2 1

.2 1<0.2

Chromium 4 1.0 .3 .8 .9

Copper 4 13.1 6.0 8.5 7.4

Iron 4 825 485 604 553

Lead 4 <1.1 .4 1

.5 1<1.1

Manganese 4 266 192 231 233

Nickel 4 1.0 .4 .6 .6

Zinc 4 99 82 91 91

Hydropsyche occidentalis

Arsenic 1 -- -- 2.2 --

Cadmium 5 0.4 <0.3 1

.2 10.1

Chromium 5 2.4 .9 1.6 1.6

Copper 5 17.6 5.1 10.6 10.2

Iron 5 973 520 709 652

Lead 5 6.0 1.2 3.0 1.8

Manganese 5 295 169 242 262

Nickel 5 1.7 .6 1.2 1.4

Zinc 5 144 99 116 117

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

102 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of 

composite samples Maximum Minimum Mean Median

12334510—Rock Creek near Clinton—Continued

Period of record for biological data: 1987; 1991-1999; 2001-2005

Hydropsyche spp.

Arsenic 1 -- -- 0.7 --

Cadmium 4 0.3 <0.5 1

.2 10.2

Chromium 4 2.1 1.1 1.6 1.7

Copper 4 16.2 6.1 12.2 13.3

Iron 4 1,140 789 949 932

Lead 4 <4.9 <1.8 1

-- 1<2.9

Manganese 4 462 299 394 407

Nickel 4 1.3 .8 1.1 1.1

Zinc 4 135 112 123 121

12334550—Clark Fork at Turah Bridge, near Bonner

Period of record for biological data: 1986; 1991-2005

Arctopsyche grandis

Arsenic 11 5.0 3.1 4.2 4.2

Cadmium 53 2.7 .3 1.2 .8

Chromium 53 4.1 .5 1.6 1.4

Copper 53 125 20.1 37.1 29.2

Iron 53 2,870 372 915 712

Lead 53 13.2 1.6 4.2 3.2

Manganese 53 902 324 636 643

Nickel 53 2.7 .4 1.1 .9

Zinc 53 276 111 196 196

Claassenia sabulosa

Arsenic 7 1.9 0.8 1.2 1.1

Cadmium 33 2.5 .1 1.0 .8

Chromium 33 2.0 .2 .7 .6

Copper 33 87.6 37.5 57.0 53.4

Iron 33 340 58.6 116 105

Lead 33 1.6 .2 .6 .6

Manganese 33 215 37.2 85.7 74.5

Nickel 33 .6 .1 .2 .2

Zinc 33 284 144 224 230

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data 103
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; 1991-2005

Hydropsyche cockerelli

Arsenic 7 5.1 3.7 4.2 4.0

Cadmium 35 1.8 .3 .8 .7

Chromium 35 8.0 .2 1.8 1.6

Copper 35 118 26.4 46.9 41.8

Iron 35 2,530 566 1,180 1,060

Lead 35 12.1 2.2 5.2 4.9

Manganese 35 805 426 617 589

Nickel 35 2.6 .6 1.2 1.2

Zinc 35 228 119 183 180

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 2 1.3 1.1 -- --

Chromium 2 4.6 2.4 -- --

Copper 2 84.1 26.8 -- --

Iron 2 1,800 986 -- --

Lead 2 6.6 <7.8 -- --

Manganese 2 1,320 537 -- --

Nickel 2 1.7 1.3 -- --

Zinc 2 231 171 -- --

Hydropsyche occidentalis

Arsenic 6 5.9 3.6 4.3 4.1

Cadmium 26 1.8 .3 .9 .8

Chromium 26 3.2 .6 1.7 1.5

Copper 26 102 27.4 47.4 42.2

Iron 26 2,310 472 1,180 1,130

Lead 26 14.2 3.0 6.4 5.7

Manganese 26 1,600 454 857 744

Nickel 26 3.2 .6 1.2 1.1

Zinc 26 416 145 211 222

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

104 Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
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; 1991-2005

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, 1987, 1991, 1993, 1996, 1998, 2000, 2003

Arctopsyche grandis

Arsenic 1 -- -- 2.8 --

Cadmium 11 0.4 <0.1 1

.2 10.2

Chromium 6 1.8 .8 1.2 1.2

Copper 11 13.4 9.9 12.0 12.0

Iron 11 1,230 108 606 617

Lead 11 2.3 .5 1.0 .6

Manganese 6 517 286 404 393

Nickel 6 1.2 .7 .9 .9

Zinc 11 143 123 135 136

Claassenia sabulosa

Arsenic 0 -- -- -- --

Cadmium 11 0.2 0.1 0.1 0.1

Chromium 6 .9 .3 .5 .5

Copper 11 88.5 19.0 45.2 44.0

Iron 11 158 46.2 100 99.0

Lead 11 .6 .4 .5 .6

Manganese 6 127 26.3 57.1 44.7

Nickel 6 .3 .1 .2 .2

Zinc 11 329 117 209 194

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data 105
Constituent Number of 

composite samples Maximum Minimum Mean Median

12340000—Blackfoot River near Bonner—Continued

Period of record for biological data: 1986, 1987, 1991, 1993, 1996, 1998, 2000, 2003

Hydropsyche occidentalis

Arsenic 1 -- -- 3.2 --

Cadmium 13 .5 0.1 .2 0.2

Chromium 13 2.7 .8 1.8 1.7

Copper 13 20.6 12.0 14.4 14.4

Iron 13 1,930 1,060 1,410 1,470

Lead 13 1.9 .8 1.3 1.3

Manganese 13 577 414 480 466

Nickel 13 1.8 .9 1.3 1.2

Zinc 13 150 116 135 130

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.6 --

Chromium 1 -- -- 1.6 --

Copper 1 -- -- 13.9 --

Iron 1 -- -- 1,140 --

Lead 1 -- -- 2.9 --

Manganese 1 -- -- 525 --

Nickel 1 -- -- 2.8 --

Zinc 1 -- -- 132 --

12340500—Clark Fork above Missoula

Period of record for biological data: 1997-2005

Arctopsyche grandis

Arsenic 9 4.5 2.1 3.3 3.5

Cadmium 28 1.8 .1 .7 .6

Chromium 28 3.4 .6 1.6 1.4

Copper 28 77.6 19.5 33.8 29.1

Iron 28 2,340 476 968 894

Lead 28 6.8 1.2 3.8 3.3

Manganese 28 1,410 476 950 937

Nickel 28 2.0 .5 1.1 1.0

Zinc 28 260 133 186 183

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

106  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of 

composite samples Maximum Minimum Mean Median

12340500—Clark Fork above Missoula—Continued

Period of record for biological data: 1997-2005

Claassenia sabulosa

Arsenic 3 1.9 0.7 1.2 1.1

Cadmium 12 2.0 .2 .7 .4

Chromium 12 1.1 .3 .7 .7

Copper 12 71.7 33.0 48.5 44.8

Iron 12 402 95.3 245 241

Lead 12 3.1 .5 1.2 1.1

Manganese 12 683 75.2 252 212

Nickel 12 <.4 <.3 1

.4 1.4

Zinc 12 363 191 269 261

Hydropsyche cockerelli

Arsenic 6 6.5 3.6 5.3 5.3

Cadmium 15 1.3 .4 .8 1.0

Chromium 15 6.0 1.8 3.1 3.1

Copper 15 96.1 29.9 56.7 56.3

Iron 15 3,590 1,400 2,050 1,900

Lead 15 10.0 4.2 6.8 6.3

Manganese 15 1,910 781 1,270 1,250

Nickel 15 2.4 1.4 1.8 1.7

Zinc 15 237 156 201 207

Hydropsyche occidentalis

Arsenic 3 6.2 3.9 5.4 6.2

Cadmium 9 1.2 .4 .7 .7

Chromium 9 5.5 2.1 3.4 3.0

Copper 9 76.5 30.3 52.2 56.0

Iron 9 2,400 1,450 2,020 2,210

Lead 9 10.2 4.0 6.8 7.1

Manganese 9 2,460 939 1,910 1,970

Nickel 9 2.4 1.6 2.0 2.1

Zinc 9 257 192 229 230

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data 107
Constituent Number of 

composite samples Maximum Minimum Mean Median

12353000—Clark Fork below Missoula2

Period of record for biological data: 1986; 1990-2004

Arctopsyche grandis

Arsenic 4 2.6 2.1 2.4 2.4

Cadmium 29 1.5 .2 .6 .6

Chromium 29 2.7 .5 1.3 1.4

Copper 29 38.0 9.4 21.1 19.2

Iron 29 1,590 343 797 682

Lead 29 3.9 .9 1.9 1.7

Manganese 29 1,090 511 707 692

Nickel 29 1.6 .4 .9 .9

Zinc 29 217 106 152 148

Claassenia sabulosa

Arsenic 3 1.1 0.8 0.9 0.8

Cadmium 42 1.3 .1 .5 .4

Chromium 42 1.2 .05 .5 .5

Copper 42 75.1 31.1 48.8 47.0

Iron 42 239 66.6 114 108

Lead 42 1.3 .1 .4 .3

Manganese 42 275 48.9 107 99

Nickel 42 .3 .1 .2 .2

Zinc 42 324 146 218 211

Hydropsyche cockerelli

Arsenic 8 2.9 2.2 2.5 2.4

Cadmium 46 1.1 .2 .5 .5

Chromium 46 3.4 .3 1.7 1.7

Copper 46 54.1 12.4 30.4 29.5

Iron 46 2,220 584 1,290 1,270

Lead 46 6.6 1.2 2.5 2.4

Manganese 46 1,210 353 768 690

Nickel 46 1.9 .5 1.2 1.3

Zinc 46 187 77 144 151

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

108  Water-Quality, Bed-Sediment, Biological Data, and Statistical Summaries, Upper Clark Fork Basin, Montana
Constituent Number of 

composite samples Maximum Minimum Mean Median

12353000—Clark Fork below Missoula2—Continued

Period of record for biological data: 1986; 1990-2004

Hydropsyche occidentalis

Arsenic 1 -- -- 2.5 --

Cadmium 17 1.1 0.1 .4 0.3

Chromium 17 3.5 .1 1.4 1.5

Copper 17 38.2 13.5 23.8 20.9

Iron 17 1,420 482 941 907

Lead 17 4.2 .7 2.1 1.9

Manganese 17 1,460 491 841 812

Nickel 17 2.2 .5 1.0 .9

Zinc 17 193 112 143 144

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.5 --

Chromium 1 -- -- .8 --

Copper 1 -- -- 20.8 --

Iron 1 -- -- 894 --

Lead 1 -- -- 1.1 --

Manganese 1 -- -- 756 --

Nickel 1 -- -- 1.1 --

Zinc 1 -- -- 124 --

1

Values were determined by substituting one-half of the minimum reporting level for censored (<) values when both uncensored and censored 

values were used in determining the mean and median. When all data were less than the minimum reporting level, the median was determined by 

ranking the censored values in order of detection. No mean is reported when all values were below the minimum reporting level.

2

Samples were collected about 30 miles downstream from streamflow-gaging station to conform to previous sampling location.

Table 22. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through August 2005.

—Continued

[Concentrations are in micrograms per gram dry weight. Number of composite samples represents the total of all individual composite samples 

collected for every year that the constituent was analyzed. Values for a single sample are arbitraily listed in the “Mean” column. Because Hydropsyche insects were not sorted to the species level during 1986-89, Hydropsyche species statistics for stations sampled during those years are based 

on the results of all Hydropsyche species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of 

two or more species. Insects collected during 1986-98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic data were 

not collected at some sites. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or 

element not analyzed]

Data 109
For additional information contact:

Director, Montana Water Science Center

U.S. Geological Survey

3162 Bozeman Avenue

Helena, Montana 59601

Telephone: 1-406-457-5900

World Wide Web: http://mt.water.usgs.gov/
Printed on recycled paper

Dodge and others— Water-Quality, Bed-Sediment, and Biological Data (October 2004 through September 2005)

 and Statistical Summaries of Data for Streams in the Upper Clark Fork Basin, Montana

Open-File Report 2006-1266