U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2011–1314

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

Water-Quality, Bed-Sediment, and Biological Data 

(October 2009 through September 2010) and Statistical 

Summaries of Data for Streams in the Clark Fork Basin, 

Montana
Cover. Photograph of raindrops on water from http://www.dreamstime.com/royalty-free-stock-photos--image6515129. 

Used with permission.
Water-Quality, Bed-Sediment, and 

Biological Data (October 2009 through 

September 2010) and Statistical Summaries 

of Data for Streams in the Clark Fork Basin, 

Montana

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

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

Open-File Report 2011–1314

U.S. Department of the Interior

U.S. Geological Survey
ISBN 978-1-4113-3321-5

U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2012, Water-quality, bed-sediment, and biological data (October 2009 

through September 2010) and statistical summaries of data for streams in the Clark Fork basin, Montana: U.S. Geological Survey Open-File Report 2011–1314, 120 p.
iii

Contents

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

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

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

Water-Quality Data........................................................................................................................................2

Methods..................................................................................................................................................2

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

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

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

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

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

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

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

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

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

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

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

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

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

Figure

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

Tables

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

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

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

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

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

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

4. Water-quality data for the Clark Fork basin, Montana, October 2009 

through September 2010............................................................................................................18

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

at Deer Lodge, Montana, October 2009 through September 2010......................................38

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

at Turah Bridge, near Bonner, Montana, October 2009 through 

September 2010...........................................................................................................................42

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

River near Bonner, Montana, October 2009 through September 2010 ..............................46
iv

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

above Missoula, Montana, October 2009 through September 2010 ..................................50

9. Seasonal daily maximum, minimum, and mean turbidity, with monthly 

summary statistics at Mill Creek near Anaconda, Montana, April 

through September 2010............................................................................................................54

10. Seasonal daily maximum, minimum, and mean turbidity, with monthly 

summary statistics at Willow Creek near Anaconda, Montana, April 

through September 2010............................................................................................................56

11. Seasonal daily maximum, minimum, and mean turbidity, with monthly 

summary statistics at Warm Springs Creek near Anaconda, Montana, 

April through September 2010 ..................................................................................................58

12. Seasonal daily maximum, minimum, and mean turbidity, with monthly 

summary statistics at Lost Creek near Anaconda, Montana, April 

through September 2010............................................................................................................60

13. Analyses of field replicates for water samples, Clark Fork basin, Montana....................62

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

basin, Montana ...........................................................................................................................65

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

Clark Fork basin, Montana ........................................................................................................65

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

blank samples..............................................................................................................................66

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

Clark Fork basin, Montana ........................................................................................................66

18. Analyses of field blanks for water samples ...........................................................................67

19. Bed-sediment data for the Clark Fork basin, Montana, August 2010 ................................68

20. Recovery efficiency for analyses of standard reference materials for 

bed-sediment samples...............................................................................................................69

21. Analyses of procedural blanks for bed-sediment samples.................................................70

22. Biological data for the Clark Fork basin, Montana, August 2010........................................71

23. Recovery efficiency for analyses of standard reference material for 

biota samples ..............................................................................................................................73

24. Analyses of procedural blanks for biota samples.................................................................74

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

basin, Montana, March 1985 through September 2010........................................................75

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

basin, Montana, August 1986 through August 2010..............................................................95

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

basin, Montana, August 1986 through August 2010............................................................100
v

Conversion Factors, Datum, Abbreviated Water-Quality 

Units, and Acronyms

Inch/Pound to SI

Multiply By To obtain

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

)

cubic foot per second (ft3

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

gallon (gal) 3.785 liter (L)

gallon (gal) 3,785 milliliter (mL)

inch (in.) 25.4 millimeter (mm)

inch (in.) 25,400 micrometer (μm)

mile (mi) 1.609 kilometer (km)

ounce (oz) 28.35 gram (g)

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

square mile (mi2

) 2.59 square kilometer (km2)

ton 907.2 kilogram

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

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

°F = (1.8 x °C) + 32

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

(NGVD 29). 

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Water-year definition:

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

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

water year 2010 is the period from October 1, 2009, through September 30, 2010.
vi

Abbreviated water-quality units used in this report:

μg/g microgram per gram

μg/L microgram per liter

μg/mL microgram per milliliter

μm micrometer

μS/cm microsiemens per centimeter at 25 degrees Celsius

mg/L milligrams per liter

mm millimeter

ppm part per million

Acronyms used in the report:

FNU formazin nephelometric units

ICP–AES inductively coupled plasma–atomic emission spectrometry

ICP–MS inductively coupled plasma–mass spectrometry

ICP–OES inductively coupled plasma–optical emission spectrometry

LRL laboratory reporting level

LT–MDL long-term method detection level

NTRU nephelometric turbidity ratio unit

NWQL USGS National Water Quality Laboratory, Denver, Colo.

RSD relative standard deviation

spp. species

SRM standard reference material

TFE tetrafluoroethylene

USGS U.S. Geological Survey

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

(October 2009 through September 2010) and Statistical 

Summaries of Data for Streams in the Clark Fork Basin, 

Montana

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

Abstract

Water, bed sediment, and biota were sampled in streams 

from Butte to near Missoula, Montana, as part of a monitoring 

program in the upper Clark Fork basin. The sampling program 

was conducted by the U.S. Geological Survey in cooperation 

with the U.S. Environmental Protection Agency to characterize aquatic resources in the Clark Fork basin of western Montana, with emphasis on trace elements associated with historic 

mining and smelting activities. Sampling sites were located on 

the Clark Fork and selected tributaries. Water samples were 

collected periodically at 20 sites from October 2009 through 

September 2010. Bed-sediment and biota samples were collected once at 13 sites during August 2010. 

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

samples collected at sites from October 2009 through September 2010. Water-quality data include concentrations of 

selected major ions, trace elements, and suspended sediment. 

Turbidity was analyzed for water samples collected at the four 

sites where seasonal daily values of turbidity were being determined. Daily values of suspended-sediment concentration and 

suspended-sediment discharge were determined for four sites. 

Bed-sediment data include trace-element concentrations in the 

fine-grained fraction. Biological data include trace-element 

concentrations in whole-body tissue of aquatic benthic insects. 

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

biological data for sites in the upper Clark Fork basin are provided for the period of record since 1985.

Introduction

The Clark Fork originates near Warm Springs in western 

Montana at the confluence of Silver Bow and Warm Springs 

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

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

six major tributaries enter: Blacktail Creek, Warm Springs 

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

and Blackfoot River. Principal surface-water uses in the 

6,000-square-mile (mi2) upper Clark Fork basin above Missoula include irrigation, stock watering, small-scale industry, 

and habitat for trout fisheries. Current land uses primarily are 

cattle production, logging, mining, residential development, 

and recreation. Large-scale mining and smelting were prevalent land uses in the upper basin for more than 100 years but 

are now either discontinued or substantially smaller in scale.

Deposits of copper, gold, silver, and lead ores were 

extensively mined, milled, and smelted in the drainages of 

Silver Bow and Warm Springs Creeks from about the 1860s 

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

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

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

large quantities of trace elements such as arsenic, cadmium, 

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

with stream sediment; transported downstream; and deposited in stream channels, on flood plains, in the Warm Springs 

Ponds, and where the former Milltown Reservoir was located 

(Andrews, 1987). The widely dispersed tailings continue to 

be reeroded, transported, and redeposited along the stream 

channel and flood plain, especially during high flows. The 

occurrence of elevated trace-element concentrations in water 

and bed sediment can pose a potential risk to aquatic biota and 

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

Concern about the potential toxicity of trace elements to 

aquatic biota and human health has resulted in a comprehensive effort by State, Federal, and private entities to characterize the aquatic resources in the upper Clark Fork basin to 

guide and monitor remedial cleanup activities. A long-term 

database was considered necessary to detect trends over 

time in order to evaluate the effectiveness of remediation. 

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

basin since 1985 (Lambing, 1987 through 1991; Lambing 

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

2010). Trace-element data for bed sediment and biota (aquatic 
2 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

benthic insects) have been collected intermittently at selected 

sites since 1986 as part of studies on the contamination of bedsediment quality and bioaccumulation of metals conducted by 

the USGS National Research Program (Axtmann and Luoma, 

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

Hornberger and others, 1997). In March 1993, an expanded 

monitoring program for water, bed sediment, and biota in the 

upper basin was implemented by the USGS in cooperation 

with the U.S. Environmental Protection Agency to systematically quantify the seasonal and annual variability in selected 

constituents. 

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

for 20 sites and bed-sediment and biological data for 13 sites 

in the Clark Fork basin collected from October 2009 through 

September 2010. Quality-assurance data are presented for 

water-quality, bed-sediment, 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 for the monitoring program in the upper 

Clark Fork basin from Butte to near Missoula (fig. 1) are 

located on the Clark Fork main stem (including Silver Bow 

Creek), three major tributaries (Blacktail Creek, Warm Springs 

Creek, and Blackfoot River), and three smaller tributaries 

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

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

are listed in table 1. Main-stem sampling sites were selected to 

divide the upper Clark Fork into reaches of relatively uniform 

length, with each reach encompassing either a major tributary 

or depositional environment (Warm Springs Ponds and the 

former Milltown Reservoir). Major tributaries were sampled to 

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

and to provide reference comparisons to the main stem. The 

three smaller tributaries were sampled to gain better spatial 

resolution on sources of metals entering the Clark Fork in an 

area of historical metal-processing activities near Anaconda. 

Water-quality data were obtained periodically at 20 sites; daily 

suspended-sediment data were obtained at 4 sites; and daily 

turbidity data were obtained by continuous turbidity monitors 

at 4 sites. Bed-sediment and biological data for 13 sites were 

obtained once annually. Continuous streamflow data were collected at 19 sites in the long-term monitoring network.

Properties measured onsite and constituents for which 

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

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

samples are listed in table 3. Results of onsite measurements 

of stream properties; laboratory analyses of water-quality, 

bed-sediment, and biota samples; and quality-assurance data 

for water year 2010 are listed in tables 4 through 24 at the 

back of the report. Statistical summaries of water-quality, bedsediment, and biological data collected between March 1985 

and September 2010 are listed in tables 25 through 27 at the 

back of the report.

Quality assurance of data was maintained through the 

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

procedures was verified with quality-control samples that were 

collected systematically to provide a measure of the accuracy, 

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

problems associated with sampling, processing, or analysis.

Water-Quality Data

Water-quality data consist of onsite measurements of 

selected stream properties and concentrations of chemical 

and physical constituents analyzed in periodically collected 

stream samples. Routine water samples for the monitoring 

program were collected at 20 sites in the upper Clark Fork 

basin 6–8 times per year on a schedule designed to describe 

seasonal and hydrologic variability. At the 4 daily suspendedsediment sites, suspended-sediment samples were collected 

by an observer 2–9 times per week, depending on season and 

flow conditions. Continuous turbidity monitors were operated 

seasonally (April–September 2010) at four sites near Anaconda to determine daily values (table 1).

Methods

Water samples were collected from vertical transits 

throughout the entire stream depth at multiple locations across 

the stream by using depth- and width-integration methods 

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

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

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

flow passing through the cross section of a stream. Sampling 

equipment consisted of depth-integrating suspended-sediment 

and water-quality samplers (Davis, 2005), which were constructed of plastic or coated with a nonmetallic epoxy paint 

and equipped with nylon or tetrafluoroethylene (TFE) nozzles.

Instantaneous streamflow at the time of water sampling 

was determined at all sites, either by direct measurement 

or from stage-discharge rating tables (Rantz and others, 

1982). Daily mean streamflow during ice periods was estimated because backwater affected the stage-discharge relation. Onsite measurements of pH, specific conductance, and 

water temperature were made during collection of periodic 

water samples. Onsite sample processing, including filtration 

and preservation, was performed according to procedures 

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

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

Composite water samples were analyzed for the constituents listed in table 2. The terms “filtered” and “unfiltered 
Water-Quality Data 3

Mill Creek

Willow

Creek

Cr Silver

Bow

Opportunity

Missoula

Butte

Anaconda

Opportunity

Galen

Warm Springs

Deer Lodge

Garrison

Goldcreek

Drummond

Bonner

Turah

Clinton

Milltown

Reservoir

Clark

Bitterroot

River

Blackfoot

River

Fork

Rock

Creek

Flint

Little

Blackfoot

River

DIVIDE

Clark Fork

Warm Springs

 Ponds

Warm Springs Cr

Silver

Bow

Creek

Blacktail

Cr

CONTINENTAL

Base modified from 

U.S. Geological Survey, 1966,

1:1,000,000

North American Datum of 

1927 (NAD 27) 

0 10 20 MILES

0 10 20 KILOMETERS

12340500

12340000

12334550

12331800

12324680

12324200

12323800

12323770 12323750

12323600

12323250

Streamflow site type

Water-quality, bed-sediment, and 

biota site type

EXPLANATION

Site number

461903112440701 Miscellaneous site number

12324200

12323700

12323720

Lost Cr 12323850

46o

114o

113o

12323230

Racetrack

12323840

12323670

Mill

Creek

Willow

Creek

12323710

Creek

47o

Helena

M O N T A N A

12323760

Dempsey

Creek 461903112440701

461559112443301

461415112450801

Study area

former

12324400

 Continuous record

 Periodic measurement

 Periodic water quality

 Daily suspended sediment

 Daily turbidity

 Once-annual bed-sediment

 Once-annual biota

Figure 1. Location of study area in the Clark Fork basin, Montana.
Table 1. Type and period of data collection at sampling sites in the Clark Fork basin, Montana.

[Abbreviations: P, present; D, discontinued. Symbol: --, no data]

Station number 

(fig. 1) Station name

Continuousrecord 

streamflow

Periodic 

water quality1

Daily suspended 

sediment

Daily turbidity 

(seasonal)

Fine-grained 

bed sediment2

Bulk b

me

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, 

D

-- 07/92–P 08/93

08/97

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

12323710 Willow Creek near 

Anaconda

03/05–P 12/04–P -- 06/06–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, 

D

-- 07/92–P 08

08/95

12323760 Warm Springs Creek near 

Anaconda

10/97–P 10/05–P -- 05/06–P -- 

12323770 Warm Springs Creek at 

Warm Springs

10/83–P 03/93–P -- -- 08/95, 08/97, 

08/99, 08/02, 

08/05, 08/08

08/9508/99

12323800 Clark Fork near Galen 07/88–P 07/88–P -- -- 08/87, 

08/91–P

08/93

12323840 Lost Creek near Anaconda 10/04–P 12/04–P -- 05/06–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

461559112443301 Clark Fork at county bridge, 

near Racetrack

-- -- -- -- 08/96–P 08/96

461903112440701 Clark Fork at Dempsey 

Creek diversion, near Racetrack

-- -- -- -- 08/96–P 08/96
Station number 

(fig. 1) Station name

Continuousrecord 

streamflow

Periodic 

water quality1

Daily suspended 

sediment

Daily turbidity 

(seasonal)

Fine-grained 

bed sediment2

Bulk b

me

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

12324400 Clark Fork above Little 

Blackfoot River, near Garrison

02/09–P 03/09–P -- -- 08/09–P 

12324680 Clark Fork at Goldcreek 10/77–P 03/93–P -- -- 07/92–P 08/9312331800 Clark Fork near Drummond 04/93–P 03/93–P -- -- 08/86, 08/87, 

08/91–P

08/93

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

12340000 Blackfoot River near 

Bonner

10/39–P 03/85–P 07/86–04/87, 

06/88–09/95,

10/05–P

-- 08/86–08/87, 

08/91, 

08/93–96, 

08/98–01, 09/03,

08/06–P

08/93

08/9

09

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

04/07–09/07 08/97–P 08/97

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

and suspended sediment.

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

Table 1. Type and period of data collection at sampling sites in the Clark Fork basin, Montana.—Continued[Abbreviations: P, present; D, discontinued. Symbol: --, no data]
Table 2. Properties and constituents measured onsite or analyzed in water, bed-sediment, 

and biota samples from the Clark Fork basin, Montana.

Water Bed sediment Biota

Property Constituent Constituent Constituent

Streamflow Hardness (calculated) Arsenic Arsenic

pH Calcium Cadmium Cadmium

Specific conductance Magnesium Chromium Chromium

Temperature Arsenic Copper Copper

Turbidity 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 samples collected in the Clark Fork basin, Montana.

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

Constituent

Data-quality objectives

Detectability Precision Bias

Laboratory reporting 

level

Maximum relative standard 

deviation of replicate analyses 

(percent)

Maximum deviation of spike 

recovery (percent)

Calcium, filtered 0.04 mg/L 20 --

Magnesium, filtered .016 mg/L 20 --

Arsenic, filtered .04–.13 μg/L 20 25

Arsenic, unfiltered recoverable .18 μg/L 20 25

Cadmium, filtered .02–.06 μg/L 20 25

Cadmium, unfiltered recoverable .04 μg/L 20 25

Copper, filtered 1.0–3.0 μg/L 20 25

Copper, unfiltered recoverable 1.4 μg/L 20 25

Iron, filtered 6 μg/L 20 25

Iron, unfiltered recoverable 9 μg/L 20 25

Lead, filtered .03–.09 μg/L 20 25

Lead, unfiltered recoverable .06 μg/L 20 25

Manganese, filtered .3–.8 μg/L 20 25

Manganese, unfiltered recoverable .8 μg/L 20 25

Zinc, filtered 2.8–8.4 μg/L 20 25

Zinc, unfiltered recoverable 2.0 μg/L 20 25

Sediment, suspended, percent finer 

than 0.062 mm

1 percent 20 --

Sediment, suspended 1 mg/L 20 --

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

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

this project. Filtered [0.45-micrometer (μm) pore size] and 

unfiltered recoverable concentrations of the trace elements 

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

and filtered concentrations of calcium and magnesium were 

determined by the USGS National Water Quality Laboratory 

(NWQL) in Denver, Colo. Concentrations of calcium and 

magnesium were determined in order to enable the calculation 

of water hardness. 

Filtered concentrations of arsenic, cadmium, copper, lead, 

manganese, and zinc were determined by inductively coupled 

plasma-mass spectrometry (ICP–MS)(Faires, 1993; Garbarino and others, 2006). Filtered concentrations of calcium, 

magnesium, and iron were determined by inductively coupled 

plasma-atomic emission spectrometry (ICP–AES)(Fishman, 

1993). Unfiltered recoverable concentrations of trace elements were determined from unfiltered samples that were first 

digested with dilute hydrochloric acid (Hoffman and others, 

1996). For cadmium, iron, lead, and manganese, the digested 

samples were analyzed by ICP–MS by using the method 

described by Garbarino and Struzeski (1998). For arsenic, copper, and zinc, the digested samples were analyzed by ICP–MS 

using the method described by Garbarino and others (2006). 

Water samples also were collected from multiple vertical 

transits for analysis of suspended sediment whenever periodic 

water samples were collected. These samples were analyzed 

for suspended-sediment concentration and the percentage of 

suspended-sediment mass finer than 0.062-millimeter (mm) 

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

Science Center sediment laboratory (hereinafter referred to as 

the Montana Sediment Laboratory) in Helena, Mont., according to methods described by Guy (1969) and Dodge and 

Lambing (2006).

Suspended-sediment samples for the four daily 

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

contract observers using the depth-integration method at 

a single vertical transit near midstream. The samples were 

analyzed for suspended-sediment concentration and were used 

to determine daily mean suspended-sediment concentrations 

according to methods described by Porterfield (1972).

Suspended-sediment discharge is determined according 

to the following equation (Porterfield, 1972):

Q Q s w = × C k s × , (1)

where

Qs is suspended-sediment discharge, in tons per 

day;

Qw is streamflow, in cubic feet per second;

Cs is suspended-sediment concentration, in 

milligrams per liter; and

k is a units-conversion constant (0.0027) 

to convert instantaneous suspendedsediment discharge to an equivalent daily 

suspended-sediment discharge.

Turbidity data were obtained by continuous turbidity 

monitors (YSI 6136 turbidity sensor) at four tributary sites in 

the upper Clark Fork basin near Anaconda (table 1). The monitors were installed in May–June 2006 to provide supporting 

information on runoff conditions in an area where remediation 

activities are being conducted. They are operated seasonally, 

generally from early spring (after ice breakup) to early winter 

(before stream freeze-up). Turbidity values are recorded at 

15-minute intervals and can be viewed in real-time on the Web 

at http://waterdata.usgs.gov/mt/nwis/current/?type=quality. 

Continuous recordings enable the determination of the minimum and maximum values for each day as well as a daily 

mean turbidity, which is based on the average of all values 

in a 24-hour period. Procedures for the operation of continuous turbidity monitors and for daily record computations are 

described by Wagner and others (2006).

Results

Water-quality data for samples collected periodically during water year 2010 are listed in table 4. Daily mean streamflow, daily mean suspended-sediment concentration, and daily 

suspended-sediment discharge for water year 2010 at the four 

daily suspended-sediment sites are listed in tables 5 through 

8 along with monthly summary statistics and annual totals for 

streamflow and suspended-sediment discharge. Daily maximum, minimum, and mean turbidity at four sites are listed in 

tables 9 through 12 along with monthly summary statistics.

Quality Assurance

Quality-assurance procedures used for the collection and 

field processing of water samples are described by Ward and 

Harr (1990), Horowitz and others (1994), Edwards and Glysson (1999), Lambing (2006), and the U.S. Geological Survey 

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

internal sample handling and quality assurance are described 

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

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

Montana Sediment Laboratory are described by Dodge and 

Lambing (2006). Standard procedures used for the calibration, 

measurement, and quality assurance of turbidity monitors are 

described by Anderson (2004).

The quality of analytical results reported for water 

samples was evaluated by using quality-control samples that 

were submitted from the field and analyzed concurrently in the 

laboratory with routine samples. These quality-control samples 

consisted of replicates, spikes, and blanks that provided quantitative information on the precision and bias of the overall 

field and laboratory process. Each type of quality-control 

sample was submitted at a proportion equivalent to about 

5 percent of the total number of water samples. Therefore, 

the total number of quality-control samples represented about 

15 percent of the total number of water samples.
8 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

In addition to the use of quality-control samples submitted from the field, internal quality-assurance practices are performed systematically by the NWQL to provide quality control 

of analytical procedures (Pritt and Raese, 1995; Maloney, 

2005). These internal practices include analyses of qualitycontrol samples such as calibration standard samples, standard 

reference water samples, replicate samples, deionized-water 

blank samples, or spiked samples at a proportion equivalent to 

at least 10 percent of the sample load. The NWQL participates 

in a blind-sample program in which standard reference water 

samples prepared by the USGS Branch of Quality Systems 

are routinely inserted into the sample line for each analytical 

method at a frequency proportional to the sample load (http://

bqs.usgs.gov). The laboratory also participates in external 

evaluation studies and audits with the National Environmental 

Laboratory Accreditation Program, the U.S. Environmental 

Protection Agency, Environment Canada, and the USGS 

Branch of Quality Systems, in order 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 that are 

considered to be essentially identical in composition. Replicate 

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

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

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

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

obtain a measure of analytical precision (laboratory replicate).

Precision of analytical results for field replicates is 

affected by numerous sources of variability within the field 

and laboratory environments, including sample collection, 

sample processing, and sample analysis. To provide data on 

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

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

collecting two independent cross-sectional samples. Analyses 

of these field replicate samples indicate the reproducibility of 

environmental data that are affected by the combined variability potentially introduced by field and laboratory processes.

Precision of analytical results for laboratory replicates, 

which exclude field sources of variability, was determined by 

two independent chemical analyses of aliquots from a single 

sample selected from the group of samples constituting each 

analytical run. A separate analysis of the sample was made at 

the beginning and end of each analytical run to provide information on the reproducibility of laboratory analytical results 

independent of possible variability caused by field sample collection and processing. Laboratory replicates are not obtainable for suspended-sediment samples because the samples are 

consumed during the analysis.

Spiked samples are used to evaluate bias, which measures 

the ability of an analytical method to accurately quantify a 

known amount of analyte added to a sample. Because some 

constituents in stream water can potentially interfere with the 

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

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

aliquots of stream samples were spiked in the laboratory with 

known amounts of the same trace elements for which water 

samples were analyzed. Analyses of spiked blanks indicate if 

the spiking procedure and analytical method are within control 

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

if the chemical matrix of the stream water interferes with the 

analytical measurement and whether these interferences could 

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

Deionized-water blank samples were submitted for every 

field trip and analyzed to identify the presence and magnitude 

of contamination that potentially could bias analytical results. 

The particular type of blank sample routinely tested was a 

field blank. Field blanks are aliquots of deionized water that 

are certified as trace-element free and are processed through 

the sampling equipment used to collect stream samples. These 

blanks then are subjected to the same processing (sample 

splitting, filtration, preservation, transportation, and laboratory 

handling) as stream samples. Blank samples are analyzed for 

the same constituents as stream samples in order 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 the analytical requirements of detectability and serve as a guide for identifying questionable data 

by establishing acceptable limits for precision and bias of 

laboratory results. Comparisons of quality-control data to dataquality objectives were used to evaluate whether sampling 

and analytical procedures were producing environmentally 

representative data in a consistent manner. Data that did not 

meet the objectives were evaluated for acceptability. If necessary, additional quality-control samples were submitted and 

corrective action was taken.

The NWQL uses a statistically based convention for 

establishing minimum laboratory reporting levels (LRLs) 

for analytical results and for reporting low-concentration 

data (Childress and others, 1999). Quality-control data are 

collected by the NWQL on a continuing basis to determine 

long-term method detection levels (LT–MDLs) and LRLs. 
Water-Quality Data 9

These values are reevaluated each year and, consequently, can 

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

LRLs are designed to limit the possible occurrence of a false 

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

samples in which the analyte was either not detected or did 

not pass identification criteria. Analytes that are detected at 

concentrations between the LT–MDL and the LRL and that 

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

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

their uncertainty is greater than that of data reported without 

the “E” remark code.

The precision of analytical results for a constituent can be 

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

sets of samples. These replicate analyses may consist either 

of individual analyses of a pair of samples considered to be 

essentially identical (field replicates) or of multiple analyses of 

an individual sample (laboratory replicates). The differences in 

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

(Taylor, 1987):

S

d

k =

2

2 , (2)

where

S is the standard deviation of the difference in 

concentration between replicate analyses,

d is the difference in concentration between 

each pair of replicate analyses, and

k is the number of pairs of replicate analyses.

Precision also can be expressed as a relative standard 

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

standard deviation and the mean concentration for all the 

replicate analyses. Expressing precision relative to a mean 

concentration standardizes the comparison of precision among 

individual constituents. The RSD is calculated according to the 

following equation (Taylor, 1987):

RSD

S

x

= ×100 , (3)

where

RSD is the relative standard deviation;

S is the standard deviation; and

x

_

is the mean concentration for all replicate 

analyses.

Paired analyses of field replicates are listed in table 13. 

The overall precision estimated for each constituent on the 

basis of analyses of field replicates, which include both field 

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

data-quality objective used to indicate acceptable precision of 

results for field replicates was a maximum RSD of 20 percent 

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

replicates were within the 20-percent RSD limit for all constituents (table 14). 

The precision estimated for each constituent on the basis 

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

the precision of analytical results for laboratory replicates are 

calculated by using unrounded values stored in laboratory data 

files. The data-quality objective used to indicate acceptable 

precision of results for laboratory replicates was a maximum 

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

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

Recovery efficiency for analyses of constituents is determined by analyses of an unspiked sample and a spiked aliquot 

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

spike recovery of trace elements in water samples was a maximum deviation of 25 percent from a theoretical 100-percent 

recovery of added constituent (table 3). At the laboratory, a 

spiked deionized-water blank sample and a spiked aliquot of 

a stream sample were prepared and analyzed along with the 

original unspiked sample. The differences between the spiked 

and unspiked sample concentrations were determined and used 

to compute recovery, in percent, according to equation 4:

R

D

C

= ×100 , (4)

where

R is the spike recovery, in percent;

D is the difference between the spiked and 

unspiked sample concentrations; and

C is the concentration of material used to spike 

the sample.

If the spike recovery of a trace element was outside a 

range of 75 to 125 percent, the instrument was recalibrated 

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

improved to the extent possible. Recovery efficiency for 

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

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

recovery for deionized-water blank samples spiked with trace 

elements (table 16) ranged from 97.2 to 113 percent. The 

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

spike recovery for each constituent for which deionized-water 

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

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

except for filtered zinc (94.7–132 percent). The exceedance 

of this data-quality objective is an artifact of running the final 

filtered-zinc spike analysis after extensive instrument maintenance, which reduced a high zinc bias. Spikes before and 

after maintenance met data-quality objectives, but analytical 

results may not be comparable to each other due to the small 

number of sample sets. The mean spike recovery for spiked 

stream samples (table 17) ranged from 93.8 to 111 percent. 
10 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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

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

an expected 100-percent recovery, except for filtered cadmium 

(87.6 to 132 percent). The exceedance of this data quality 

objective resulted from one spike sample having a recovery 

of 136 percent. When this one spiked sample set is removed, 

filtered cadmium falls within the data-quality objective limit 

(91.4–121 percent) for the 95-percent confidence interval. No 

adjustments were made to analytical data on the basis of the 

mean spike recovery.

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

thereby indicating a consistent deviation in one direction. All 

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

had confidence intervals for percent recovery that included 

100 percent except for filtered iron (101–115 percent). All 

laboratory-spiked stream samples (table 17) also had confidence intervals for percent recovery that included 100 percent 

except for unfiltered recoverable iron (103–118 percent) and 

filtered zinc (101–118 percent). Because the mean spike recoveries for all constituents of laboratory-spiked stream samples 

met data-quality objectives (less than a 25-percent deviation 

from 100-percent recovery), no adjustments were made to 

analytical results for stream samples on the basis of spike 

recoveries.

Analytical results for field blanks are listed in table 18. 

A field blank with constituent concentrations equal to or less 

than the LRL for the analytical method indicates that the entire 

process of sample collection, field processing, and laboratory 

analysis is presumably free of contamination. If detectable 

concentrations of trace elements in field blanks were equal to 

or greater than twice the LRL, the concentrations were noted 

during data review. Analytical results from the field blank for 

the next sample set were evaluated for a consistent trend that 

could indicate systematic contamination. Sporadic, infrequent 

exceedances of twice the LRL probably represented random 

contamination or instrument calibration error that was not persistent in the process and was not likely to cause positive bias 

in a long-term record of analytical results. However, if concentrations for a particular constituent exceeded twice the LRL 

in field blanks from two consecutive field trips, blank samples 

were collected from individual components of the processing sequence and were submitted for analysis to identify the 

source of contamination.

Trace-element concentrations in field blanks (table 18) 

were almost always less than the LRL. Two detections 

exceeded the LRL for unfiltered recoverable zinc (3.3 and 

3.4 μg/L), which had a LRL of 2.0 μg/L. Because no trends 

were indicated in subsequent sampling trips, no adjustments 

were made to water-quality sample results on the basis of 

these two detections.

Bed-Sediment Data

Bed-sediment data for the long-term monitoring program 

in the Clark Fork basin consist of analyses of trace-element 

concentrations in the fine-grained (<0.063 mm) fraction of 

bed-sediment samples. Collection of bulk bed sediment (finegrained plus coarse-grained fractions) was discontinued in 

2005; therefore, no bulk bed sediment analytical results or statistical summaries are presented in this report. Bed-sediment 

samples are collected once annually at 13 sites (fig. 1 and 

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

time of year (typically August) as previous samples, in order 

to facilitate data comparisons among years. One site, Warm 

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

rather than once annually.

Methods

Fine-grained bed-sediment samples were collected in 

August 2010 using protocols described by Axtmann and 

Luoma (1991). Samples were collected from the surfaces of 

streambed deposits in low-velocity areas near the edge of the 

stream by using an acid-washed polypropylene scoop. Whenever possible, samples were collected from both sides of the 

stream. 

Individual samples of bed sediment were collected by 

scooping material from the surfaces of three to five randomly 

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

to five individual samples were combined to form a single 

composite sample. This collection process was repeated three 

times to obtain three composite samples. Each composite sample was wet-sieved onsite through a 0.063-mm polyester-mesh 

sieve using ambient stream water. The fraction of bed sediment in each composite sample that was finer than 0.063 mm 

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

and transported to the laboratory on ice.

Bed-sediment samples were processed and analyzed at 

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

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

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

Single aliquots of approximately 0.6 grams (g) of sediment 

from each of the three composite bed-sediment samples 

were digested by using a hot, concentrated, nitric acid reflux 

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

An additional aliquot was analyzed from one of the sieved 

replicate samples at each station. After a 2-week digestion 

period, the aliquots were evaporated to dryness on a hot plate. 

The dry residue was reconstituted in 10 mL of 0.6N (normal) 

hydrochloric acid. The reconstituted aliquots then were filtered 

through a 0.45-μm pore-size filter by using a syringe and 

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

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

iron, lead, manganese, nickel, and zinc by using inductively 
Bed-Sediment Data 11

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

The smallest concentration of a constituent that can be reliably 

reported for analyses of bed sediment is termed the minimum 

reporting level.

Results

Concentrations of trace elements measured in samples of 

fine-grained bed sediment collected during August 2010 are 

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

per milliliter (μg/mL) (which is equivalent to parts per million; ppm), that were analyzed in the reconstituted aliquots of 

digested bed sediment were converted to solid-phase concentrations, in micrograms per gram (μg/g), by using the following equation:

μ

dry weight of sample, in grams = (μ g/mL volume of digested sample, in mL ) ( )

( ) ( ) g/g

dilution ratio

. (5)

The reported solid-phase concentrations listed in table 19 

are the means of all analyses for replicate aliquots from each 

composite bed-sediment sample collected at the site. Because 

the conversion from liquid-phase to solid-phase concentration 

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

the sample, minimum reporting levels for some trace elements 

might differ among stations and among years.

Quality Assurance

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

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

to the collection of the first sample. Polyester-mesh sieves 

were washed in a laboratory-grade detergent and rinsed with 

deionized water. All equipment received a final rinse onsite 

with stream water. Sampling equipment used at more than 

one site was rinsed between sites with stream water. Separate 

sieves were used at each site and, therefore, did not require 

between-site cleaning. Bed-sediment samples were collected 

sequentially at sites along an increasing concentration gradient to minimize effects from potential site-to-site carryover 

contamination.

Quality assurance of analytical results for bed-sediment 

samples included laboratory instrument calibration with 

standard solutions and analysis of quality-control samples 

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

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

Quality-control samples consisted of standard reference 

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

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

SRMs are commercially prepared materials that have 

certified concentrations of trace elements. Analyses of SRMs 

are used to indicate the ability of the method to accurately 

measure a known quantity of a constituent. Multiple analyses 

of SRMs are made to derive a mean and 95-percent confidence 

interval for recovery. Recovery efficiency for trace-element 

analyses of SRMs for bed sediment is listed in table 20. Three 

SRMs consisting of agricultural soils representing low and 

high concentrations of trace elements were analyzed to test 

recovery efficiency for a range of concentrations generally 

similar to those occurring in the bed sediment of streams in the 

upper Clark Fork basin. The digestion process used to analyze bed sediment samples is not a “total” digestion (does not 

liberate elements associated with crystalline lattices); therefore, 100-percent recovery may not be achieved for elements 

strongly bound to the sediment. The percent recovery of trace 

elements for SRM analyses that use less than a total digestion is useful to indicate which trace elements display strong 

sediment-binding characteristics in the SRM and whether 

analytical recovery is consistent between multiple sets of 

analyses.

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

trace elements (table 20) illustrate analytical performance. 

For cadmium, chromium, copper, iron, manganese, nickel, 

and zinc, mean SRM recoveries for the low-concentration 

standard (SRM 2709a) ranged from 81.4 to 103.0 percent of 

the certified concentrations. Mean recoveries were lower for 

arsenic and lead (66.8 and 67.4 percent, respectively). The 

generally small range of variation (less than 7 percent) for the 

95-percent confidence interval indicates good reproducibility 

of multiple analyses of SRM 2709a. Two high-concentration 

standards were used: SRM 2711 (seven of the samples) and 

SRM 2711a (3 of the samples). Mean SRM recoveries for cadmium, chromium, copper, iron, lead, manganese, and zinc for 

SRM 2711 ranged from 86.7 to 104.0 percent of the certified 

concentrations. Arsenic and nickel recoveries were slightly 

lower (82.4 and 82.7 percent, respectively). Mean recoveries 

for SRM 2711a were slightly higher than SRM 2711, ranging 

from 85.7 to 106.0. The generally small range of variation 

(less than 11 percent for most constituents) for the 95-percent 

confidence interval indicates good reproducibility of multiple 

analyses of SRM 2711 and SRM 2711a. No adjustments were 

made to trace-element concentrations in bed-sediment samples 

on the basis of recovery efficiencies.

Procedural blanks for bed-sediment samples consisted of 

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

heated and evaporated to dryness. After evaporation, 0.6N 

hydrochloric acid was added to reconstitute the dry residue. 

Procedural blanks, therefore, represent the same chemical 

matrix and exposure to analytical materials and handling as 

the reagents used to digest and reconstitute bed-sediment 

samples. Analytical results of procedural blanks for bed sediment (table 21) are reported as a liquid-phase concentration, 

in micrograms per milliliter. A procedural blank was prepared 
12 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

and analyzed concurrently with bed-sediment samples for each 

site. Concentrations of trace elements in all procedural blanks 

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

necessary.

Biological Data

Biological data for the long-term monitoring program 

in the Clark Fork basin consist of analyses of trace-element 

concentrations in the whole-body tissue of aquatic benthic 

insects. Insect samples are collected once annually at the same 

13 sites and on the same dates as bed-sediment samples (fig. 1 

and table 1), allowing for a direct comparison of biological 

data with bed-sediment data among the years. One site, Warm 

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

rather than once annually.

Methods

Insect samples were collected using protocols described 

in Hornberger and others (1997). Benthic insects at immature stages were collected with a large nylon-mesh kick net. 

A single riffle at each site was sampled repeatedly until an 

adequate number of individual insects was collected to provide 

sufficient mass for analysis. Targeted taxa for collection were 

the order Trichoptera (caddisflies) and the order Plecoptera 

(stoneflies).

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

for collection in this study because of their occurrence at most 

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

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

Arctopsyche grandis and the stonefly Claassenia sabulosa 

were collected where available to represent additional insect 

taxa that are commonly distributed in the Clark Fork basin. In 

addition, specimens from the caddisfly group Brachycentrus

spp. were collected in previous years when targeted taxa were 

not available.

Samples of each taxon were sorted by genus in the field 

and placed in acid-washed plastic containers. Samples were 

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

amount of ambient stream water. Between 1986 and 1998, 

macroinvertebrate containers were kept on ice to allow the 

insects to evacuate their gut contents (depurate) for a period of 

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

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

were immediately frozen on dry ice in the field to reduce the 

possibility of metal loss through intracellular breakdown during depuration. A comparison of immediately frozen to depurated samples showed that although no substantial difference 

occurred for most metals, concentrations of copper were about 

20 percent lower in the depurated samples than in the samples 

that were immediately frozen. The data were not adjusted for 

this difference.

Insect samples were processed and analyzed at the 

USGS National Research Program Ecology and Contaminants 

Project laboratory in Menlo Park, Calif. Insects were thawed 

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

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

similar-sized individuals were composited into replicate subsamples. Subsamples were placed in tared scintillation vials 

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

a final dry weight and digested by reflux using concentrated 

nitric acid (Cain and others, 1992). After digestion, insect 

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

residue was reconstituted in 0.6N hydrochloric acid, filtered 

through a 0.45-μm pore-size filter, and analyzed undiluted by 

ICP–OES for arsenic, cadmium, chromium, copper, iron, lead, 

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

constituent that can be reliably reported for analyses of biota is 

termed the minimum reporting level.

Results

Concentrations of trace elements in whole-body tissue 

of aquatic insects collected during August 2010 are listed in 

table 22. The variability in the number of composite samples 

among species and among sites reflects differences in insect 

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

concentrations, in micrograms per milliliter, analyzed in the 

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

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

with minimum reporting levels for trace elements in bed sediment, minimum reporting levels for trace elements in insects 

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

In general, the smaller the biological-sample weight (primarily a function of insect abundance), the higher the minimum 

reporting level. Therefore, higher minimum reporting levels 

do not necessarily imply a higher trace-element concentration 

in tissue.

Quality Assurance

The protocols for field collection and processing of biota 

samples are designed to prevent contamination from metal 

sources. Nonmetallic nets, sampling equipment, and processing equipment were used in all sample collection. Equipment 

was acid-washed and rinsed in ultrapure deionized water prior 

to the first sample collection. Nets and equipment were thoroughly rinsed in ambient stream water at each new main-stem 

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

were collected sequentially at sites along an increasing concentration gradient to minimize effects from potential site-tosite carryover contamination.
References Cited 13

Quality assurance of analytical results for biota samples 

included laboratory-instrument calibration with standard 

solutions and analyses of quality-control samples designed to 

quantify precision and to identify the presence and magnitude 

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

the tissue SRM (lobster hepatopancreas) and 13 procedural 

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

analyzed in a proportion equivalent to about 20 percent of the 

total number of biota samples.

Recovery efficiency for trace-element analyses of 

the SRM for biota is listed in table 23. Data-quality objectives have not been established for analytical recovery in 

biota, but percent recoveries are shown to illustrate analytical performance. Mean SRM recoveries ranged from 76.4 

to 125 percent for all constituents. With the exception of 

cadmium, chromium, and manganese, which had a slightly 

higher recovery variation of up to 25 percent, all values fell 

within 10 percent of the 95-percent confidence interval. These 

averages represent a reasonable range of recoveries; thus, no 

adjustments were made to biota samples on the basis of traceelement recovery efficiencies.

Procedural blanks for biota consisted of the same 

reagents used to digest and reconstitute tissue of aquatic 

insects and were analyzed undiluted. Analytical results of 

procedural blanks for biota (table 24) are reported as a liquidphase concentration, in micrograms per milliliter. A procedural 

blank was prepared and analyzed concurrently with biota 

samples for each site. Concentrations of trace elements in all 

procedural blanks were less than the minimum reporting level; 

therefore, no adjustments to the data were necessary.

Statistical Summaries of Data

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

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

site since 1985. The summaries include the period of record, 

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

median concentrations.

Statistical summaries of long-term water-quality data 

(table 25) are based on results of cross-section samples collected periodically by the USGS for the long-term monitoring 

program in the Clark Fork basin during the period of record 

for each site. The summaries do not include data for supplemental samples collected at selected sites. Inclusion of results 

for supplemental samples that targeted high-flow conditions or 

maintenance drawdowns of Milltown Reservoir might disproportionately skew the long-term statistics relative to the other 

sites in the network. Statistical summaries of bed-sediment 

(table 26) and biological data (table 27) are based on results 

of samples collected once annually during the indicated years. 

Because not all sites were sampled for bed sediment and biota 

every year, the data for some sites do not represent a consecutive annual record. Sampling of bulk bed sediment has been 

discontinued; therefore, a statistical summary is not presented. 

Statistical summaries are not presented for discontinued sites.

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

the mean trace-element concentrations determined for each 

year from the mean of the analyses of composite samples. 

Therefore, the number of samples for bed sediment represents 

the number of years that the constituent was analyzed. In 

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

individual analyses for each composite sample collected rather 

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

number of samples for arsenic for both bed sediment and biota 

is smaller than the number for other trace elements because 

sampling for arsenic began in September 2003. In addition, 

the number of samples analyzed for silver in bed sediment is 

smaller because analysis for this constituent was discontinued 

in 2004.

Differences in the number of composited biota samples 

among species reflect differences in species abundance, both 

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

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

individual composite samples were averaged. The abundance 

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

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

minimum reporting levels. Where minimum reporting levels 

vary among years, differences in concentration with time are 

difficult to determine, especially when a large percentage of 

the samples have concentrations less than minimum reporting 

levels.

The presence or absence of insect species at a given site 

can vary among years and may result in different taxa being 

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

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

based on the results of all Hydropsyche species combined. At 

some sites, statistics for the Hydropsyche morosa group are 

based on the combined results for two or more species because 

these samples could not be clearly identified to the species 

level, but the individual insects had morosa characteristics.

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

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1994 through September 1995) and statistical summaries 

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

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

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

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

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

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

2000 through September 2001) and statistical summaries 

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of/2005/1356.)

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

through September 2005) and statistical summaries of data 

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

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Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2007, 

Water-quality, bed-sediment, and biological data (October 2005 through September 2006) and statistical summaries of long-term data for streams in the Clark Fork 

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

2007–1301, 124 p. (Also available at http://pubs.usgs.gov/

of/2007/1301.)

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2008, 

Water-quality, bed-sediment, and biological data (October 2006 through September 2007) and statistical summaries of long-term data for streams in the Clark Fork 

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

2008–1318, 132 p. (Also available at http://pubs.usgs.gov/

of/2008/1318.)

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

through September 2008) and statistical summaries of 

long-term data for streams in the Clark Fork basin, Montana: U.S. Geological Survey Open-File Report 2009–1178, 

139 p. (Also available at http://pubs.usgs.gov/of/2009/1178.)
References Cited 15

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2010, 

Water-quality, bed-sediment, and biological data (October 2008 through September 2009) and statistical summaries of long-term data for streams in the Clark Fork 

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

2010–1267, 137 p. (Also available at http://pubs.usgs.gov/

of/2010/1267.)

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

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

2001 through September 2002) and statistical summaries 

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

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

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

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

2002 through September 2003) and statistical summaries 

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

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

107 p.

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

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

Report 2006–1242, 25 p. (Also available at http://pubs.usgs.

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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. (Also available at http://pubs.usgs.gov/twri/

twri3-c2/.)

Faires, L.M., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of metals in water by inductively coupled plasmamass spectrometry: U.S. Geological Survey Open-File 

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 OpenFile Report 93–125, 217 p.

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

practices for the chemical and biological analyses of water 

and fluvial sediments: U.S. Geological Survey Techniques 

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

(Also available at http://pubs.usgs.gov/twri/twri5a6/.)

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.

Garbarino, J.R., Kanagy, L.K., and Cree, M.E., 2006, Determination of elements in natural-water, biota, sediment, and soil 

samples using collision/reaction cell inductively coupled 

plasma-mass spectrometry: U.S. Geological Survey Techniques and Methods, 5–B1, 88 p. (Also available at http://

pubs.usgs.gov/tm/2006/tm5b1/.)

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. (Also 

available at http://pubs.usgs.gov/twri/twri5c1/.)

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

statistics for multiply censored water quality data: Water 

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

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

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

Water Quality Laboratory—In-bottle acid digestion of 

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

Report 96–225, 28 p.

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

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

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

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

Open-File Report 97–669, 84 p.

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

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

for the collection and processing of surface-water samples 

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

Report 94–539, 57 p.

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

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

and selected tributaries from Deer Lodge to Milltown, 

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

Survey Open-File Report 87–110, 48 p.

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

September 1987) and statistical summaries (March 1985 

through September 1987) for the Clark Fork and selected 

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

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

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

through September 1988) and statistical summaries (March 

1985 through September 1988) for the Clark Fork and 

selected tributaries from Galen to Missoula, Montana: 

U.S. Geological Survey Open-File Report 89–229, 51 p.
16 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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

through September 1989) and statistical summaries (March 

1985 through September 1989) for the Clark Fork and 

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

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

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

of the upper Clark Fork basin from Galen to Missoula, 

Montana, 1985–90: U.S. Geological Survey WaterResources Investigations Report 91–4139, 73 p.

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

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

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

gov/of/2006/1275/.)

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

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

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

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

Report 95–429, 104 p.

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

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

statistical summaries of water-quality data (March 1985 

through September 1993) for streams in the upper Clark 

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

Report 94–375, 85 p.

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

of the form of trace metals in oxidized estuarine sediments 

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

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

U.S. Geological Survey National Water Quality Laboratory: U.S. Geological Survey Open-File Report 2005–1263, 

version 1.3, November 9, 2005, chapters and appendixes 

[variously paged].

Porterfield, George, 1972, Computation of fluvial-sediment 

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

available at http://pubs.usgs.gov/twri/twri3-c3/.)

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. Environmental Protection Agency, 2004, Milltown Reservoir Sediments Operational Unit of the Milltown Reservoir/

Clark Fork River Superfund Site—Record of Decision, 

Part 2: Decision Summary: U.S. Environmental Protection Agency, 141 p. (Also available at http://www.epa.gov/

region8/superfund/mt/milltown/mrsrod.html.)

U.S. Geological Survey, variously dated, National field manual for the collection of water-quality data: U.S. Geological Survey Techniques of Water-Resources Investigations, 

book 9, chaps. A1–A9. (Also available at http://pubs.usgs.

gov/twri/.)

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2006, Guidelines and standard procedures for continuous 

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

and Methods 1–D3, 51 p., 8 attachments. (Also available at 

http://pubs.usgs.gov/tm/2006/tm1D3/.)

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and processing of surface-water and bed-material samples 

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

Open-File Report 90–140, 71 p.
Data
18 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.

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

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

level; --, no data]

12323230--Blacktail Creek at Harrison Avenue, at Butte

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/13/2009 0920 8.0 7.6 277 3.5 112 32.5 7.46

03/08/2010 1020 9.6 7.3 294 2.0 106 30.1 7.54

04/12/2010 0845 7.2 7.6 282 4.0 109 31.8 7.17

05/18/2010 0845 17 7.6 213 9.5 83 24.5 5.22

06/01/2010 0900 54 7.5 181 9.0 68 19.6 4.74

06/14/2010 0900 50 7.6 183 11.0 73 20.8 5.04

07/19/2010 0840 11 7.7 263 11.0 107 31.1 7.02

08/23/2010 0850 12 7.6 252 11.0 104 29.8 7.06

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/13/2009 2.2 3.2 0.05 E0.03 1.5 3.2 148 544

03/08/2010 3.8 4.4 .05 E.03 5.2 6.1 286 680

04/12/2010 2.6 3.1 E.04 E.02 E1.6 2.9 165 506

05/18/2010 4.5 5.7 .05 .04 3.4 5.7 276 694

06/01/2010 5.6 6.6 .05 E.03 5.0 8.3 174 676

06/14/2010 8.3 10.0 .04 E.04 5.0 8.0 250 673

07/19/2010 6.5 9.7 .03 .04 2.2 4.1 333 960

08/23/2010 5.0 6.8 .03 E.03 3.0 4.2 274 685

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/13/2009 0.07 0.67 33.4 47.7 3.9 4.2 83 14 0.30

03/08/2010 .15 .62 131 150 4.4 5.2 80 11 .29

04/12/2010 .09 .41 58.3 69.3 -- 3.0 93 4 .08

05/18/2010 .16 .76 39.4 62.0 7.7 35.0 87 8 .37

06/01/2010 .15 .87 26.0 47.3 5.4 13.7 68 14 2.0

06/14/2010 .15 .72 32.5 52.8 E2.5 4.6 59 12 1.6

07/19/2010 .16 .77 36.0 87.6 <2.8 3.6 88 9 .27

08/23/2010 .12 .53 32.2 49.0 E2.4 4.8 87 4 .13
Data 19

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

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

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/13/2009 1040 23 7.7 488 4.5 170 48.7 11.8

03/08/2010 1215 23 7.5 500 5.5 134 36.9 10.1

04/12/2010 1015 25 7.6 486 5.0 160 44.9 11.6

05/18/2010 1015 34 7.8 375 11.0 121 36.0 7.67

06/01/2010 1040 76 7.7 276 10.0 98 28.1 6.71

06/14/2010 1030 62 7.7 276 12.0 102 29.4 6.90

07/19/2010 0950 25 7.7 454 13.0 157 45.4 10.5

08/23/2010 1050 29 7.7 447 12.5 144 42.0 9.50

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/13/2009 3.3 4.8 0.10 0.16 5.4 14.0 38 421

03/08/2010 4.0 4.6 .10 .11 9.1 13.3 102 321

04/12/2010 3.1 3.9 .15 .15 7.2 15.3 44 340

05/18/2010 4.8 5.9 .07 .14 4.2 13.6 158 552

06/01/2010 6.5 8.9 .08 .19 7.1 21.0 129 946

06/14/2010 8.2 10.3 .07 .13 6.5 15.8 187 672

07/19/2010 5.7 8.5 .08 .21 7.0 17.4 96 524

08/23/2010 5.5 7.6 .07 .13 7.0 15.5 78 381

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/13/2009 0.21 2.96 72.4 113 36.0 48.4 91 10 0.62

03/08/2010 .33 1.35 112 128 37.4 39.5 80 8 .50

04/12/2010 .15 1.25 121 135 35.4 44.0 91 6 .41

05/18/2010 .23 1.99 71.8 100 21.6 34.8 81 8 .73

06/01/2010 .30 5.26 49.8 124 17.2 43.2 78 31 6.4

06/14/2010 .28 2.81 56.0 101 16.5 30.5 75 14 2.3

07/19/2010 .22 1.97 91.2 121 30.5 45.0 86 7 .47

08/23/2010 .27 2.04 54.8 75.6 34.4 45.6 93 7 .55
20 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323600--Silver Bow Creek at Opportunity

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/13/2009 1645 40 8.7 483 7.0 181 53.7 11.3

03/09/2010 0920 46 8.1 468 2.0 148 42.6 10.0

04/12/2010 1610 42 8.9 472 8.0 169 49.2 11.2

05/18/2010 1630 68 8.8 348 13.0 130 40.4 7.11

06/01/2010 1640 202 8.0 274 11.5 102 30.6 6.12

06/14/2010 1605 197 8.1 261 16.0 104 31.5 6.08

07/19/2010 1615 59 8.9 374 20.5 139 42.1 8.26

08/24/2010 1015 41 8.2 439 11.0 157 46.8 9.75

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/13/2009 6.4 9.1 0.24 0.52 12.0 52.5 20 683

03/09/2010 9.1 14.9 .52 .70 28.8 72.7 71 950

04/12/2010 7.4 9.6 .40 .59 17.7 48.6 11 611

05/18/2010 8.9 11.1 .19 .49 13.9 44.9 31 795

06/01/2010 9.6 35.6 .50 1.88 41.6 261 70 7,380

06/14/2010 10.5 20.7 .25 .86 -- 117 93 3,900

07/19/2010 11.7 14.2 .19 .44 16.3 40.6 23 559

08/24/2010 9.7 11.7 .36 .51 19.3 34.0 19 453

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/13/2009 0.31 9.20 75.7 170 45.6 122 91 21 2.3

03/09/2010 .56 13.1 218 292 126 181 88 29 3.6

04/12/2010 .24 9.09 234 282 50.8 145 91 20 2.3

05/18/2010 .22 9.79 96.3 189 25.2 101 85 32 5.9

06/01/2010 .84 78.7 148 548 102 440 72 286 156

06/14/2010 1.01 36.5 84.4 318 42.5 211 45 196 104

07/19/2010 .32 7.27 39.3 90.6 15.2 73.5 74 23 3.7

08/24/2010 .23 5.02 30.3 85.1 73.4 111 57 17 1.9
Data 21

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323670--Mill Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/13/2009 1310 15 <2.0 8.0 176 4.0 80 22.3 5.92

03/08/2010 1600 7.7 <2.0 8.3 213 6.0 90 24.2 7.10

04/12/2010 1240 8.1 <2.0 8.2 194 6.0 87 23.9 6.61

05/18/2010 1315 50 E4.6 7.7 101 10.0 44 12.7 2.88

06/01/2010 1320 103 E6.2 7.6 86 8.5 36 10.6 2.42

06/14/2010 1315 131 <2.0 7.9 77 10.0 30 8.75 2.07

07/19/2010 1220 68 <2.0 8.1 95 11.5 40 11.8 2.65

08/23/2010 1415 23 <2.0 7.9 143 14.0 62 17.3 4.43

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/13/2009 12.5 13.3 0.04 0.06 E0.88 E1.4 59 108

03/08/2010 17.4 17.2 .04 .05 1.0 1.5 21 78

04/12/2010 7.3 8.6 E.02 E.03 E.72 E1.3 21 97

05/18/2010 11.7 13.5 .05 .10 2.1 5.5 30 315

06/01/2010 13.1 14.6 .04 .07 3.3 5.7 39 272

06/14/2010 9.2 10.6 .04 .07 2.4 5.9 26 147

07/19/2010 9.3 10.6 .04 .06 1.4 2.6 25 120

08/23/2010 15.3 17.2 .04 .14 2.3 2.7 52 159

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/13/2009 0.06 0.22 7.4 10.9 <2.8 E1.7 80 1 0.04

03/08/2010 E.02 .15 11.9 14.2 <2.8 E1.1 70 2 .04

04/12/2010 E.02 .21 4.6 8.8 <2.8 E1.1 67 1 .02

05/18/2010 .07 1.42 4.7 26.5 <2.8 4.7 67 11 1.5

06/01/2010 .12 1.03 3.8 14.9 E1.6 4.2 57 12 3.3

06/14/2010 .09 .79 3.2 8.5 E1.8 3.1 42 6 2.1

07/19/2010 .09 .53 5.3 10.0 <2.8 2.3 53 5 .92

08/23/2010 .17 .57 6.5 14.8 E1.6 2.2 67 3 .19
22 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323700--Mill Creek at Opportunity

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/13/2009 1530 9.8 8.0 188 2.5 86 24.1 6.17

03/09/2010 0840 5.0 8.0 229 2.0 96 26.4 7.25

04/12/2010 1515 6.0 8.1 222 6.5 96 26.9 6.97

05/19/2010 0815 18 7.8 109 8.0 46 13.4 3.08

06/02/2010 0735 53 7.7 95 7.0 39 11.3 2.66

06/14/2010 1500 73 7.8 84 12.0 35 10.4 2.30

07/19/2010 1505 47 8.0 104 15.0 45 13.0 2.93

08/24/2010 0800 6.0 7.7 165 9.0 71 19.8 5.16

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/13/2009 14.9 15.5 0.05 0.11 1.5 2.6 61 129

03/09/2010 12.3 12.3 .05 E.04 1.2 1.5 19 59

04/12/2010 9.6 11.5 .05 .04 1.0 1.8 16 61

05/19/2010 15.1 23.2 .05 .30 2.6 12.0 36 726

06/02/2010 15.8 21.7 .06 .25 3.6 13.8 41 763

06/14/2010 12.8 15.5 .06 .11 2.9 7.5 29 323

07/19/2010 13.7 15.8 .05 .10 1.9 4.1 32 173

08/24/2010 16.9 18.6 .04 .07 1.7 2.3 58 117

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/13/2009 0.08 0.41 5.6 11.2 E2.1 3.8 62 1 0.03

03/09/2010 .03 .10 2.8 3.3 E2.1 E1.8 67 1 .01

04/12/2010 E.02 .11 2.7 3.7 <2.8 2.1 90 2 .03

05/19/2010 .12 4.12 6.5 64.1 E2.4 12.9 84 25 1.2

06/02/2010 .15 3.83 4.9 42.2 -- 13.0 67 31 4.4

06/14/2010 .10 1.52 3.6 16.6 E1.6 6.5 53 15 3.0

07/19/2010 .13 .90 5.4 13.5 E1.5 3.6 62 6 .76

08/24/2010 .13 .29 9.3 11.9 E2.0 2.5 89 1 .02
Data 23

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323710--Willow Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/13/2009 1210 2.6 <2.0 7.9 122 1.0 46 15.3 1.91

03/08/2010 1430 1.6 <2.0 7.6 132 1.0 47 15.5 2.08

04/12/2010 1145 2.0 <2.0 7.8 135 2.5 50 16.5 2.08

05/18/2010 1200 11 E4.7 7.5 88 8.0 32 10.8 1.14

06/01/2010 1210 32 E12 7.6 76 7.0 26 8.70 1.02

06/14/2010 1205 27 E5.0 7.8 86 7.5 33 11.3 1.23

07/19/2010 1120 7.6 E3.6 7.7 113 9.0 41 13.8 1.60

08/23/2010 1300 3.6 <2.0 7.6 123 10.0 45 14.9 1.82

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/13/2009 13.7 14.4 0.04 0.04 1.5 1.7 58 103

03/08/2010 10.6 10.9 E.02 <.04 E.93 E1.1 39 90

04/12/2010 10.3 10.7 -- <.04 E1.1 1.5 28 86

05/18/2010 13.4 14.0 .02 .05 1.9 3.8 46 257

06/01/2010 14.9 16.5 .04 .06 3.6 4.8 120 680

06/14/2010 13.8 13.4 .02 .04 2.1 3.2 152 293

07/19/2010 15.4 16.7 .03 .05 1.8 2.3 54 149

08/23/2010 19.5 21.2 .04 .07 1.9 2.6 75 169

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/13/2009 0.09 0.20 19.9 27.0 E1.8 3.5 88 1 0.01

03/08/2010 .03 .11 13.5 16.6 <2.8 <2.0 78 2 .01

04/12/2010 E.04 .13 10.9 14.0 <2.8 <2.0 90 1 .01

05/18/2010 .09 .61 7.2 23.5 <2.8 3.1 69 8 .24

06/01/2010 .24 1.29 6.2 23.9 E2.1 5.2 52 24 2.1

06/14/2010 .15 .53 6.9 14.2 E2.1 3.2 62 7 .51

07/19/2010 .15 .33 10.3 14.8 E1.5 E2.0 93 3 .06

08/23/2010 .21 .49 13.2 18.0 E1.5 E1.9 87 4 .04
24 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323720--Willow Creek at Opportunity

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/13/2009 1610 9.1 8.3 305 9.0 132 39.0 8.49

03/09/2010 1020 6.2 8.0 296 3.0 118 34.3 7.95

04/12/2010 1545 6.8 8.1 313 9.0 131 38.8 8.22

05/19/2010 0850 12 7.9 208 9.0 86 26.6 4.79

06/01/2010 1605 40 7.7 171 12.5 67 20.5 3.88

06/14/2010 1535 19 8.0 200 16.0 86 26.2 5.06

07/19/2010 1540 8.7 9.0 253 17.5 114 33.9 7.09

08/24/2010 0925 6.2 7.9 306 8.5 134 38.9 8.89

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/13/2009 17.1 16.7 0.02 0.07 1.9 3.2 11 112

03/09/2010 15.9 18.7 .04 .06 1.9 3.8 49 187

04/12/2010 15.6 18.1 E.03 .04 E2.3 4.6 14 205

05/19/2010 30.9 33.0 .04 .15 5.7 16.2 68 470

06/01/2010 36.8 44.4 .05 .31 8.5 29.6 87 937

06/14/2010 36.6 41.5 .05 .18 5.7 15.1 61 459

07/19/2010 26.3 28.5 E.02 .04 3.1 4.3 26 129

08/24/2010 17.5 18.6 .02 .05 2.4 4.2 12 105

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/13/2009 0.07 0.65 7.9 12.4 E1.8 5.0 91 2 0.05

03/09/2010 .15 .85 79.5 93.6 5.2 6.4 93 4 .07

04/12/2010 E.08 1.21 82.7 94.7 E2.9 8.7 88 5 .09

05/19/2010 .32 4.18 80.4 129 7.5 19.4 96 17 .55

06/01/2010 .44 7.88 41.6 87.4 12.0 43.9 92 40 4.3

06/14/2010 .41 3.28 28.8 52.7 4.3 17.4 95 17 .87

07/19/2010 .18 .72 3.3 7.6 <2.8 2.6 83 3 .07

08/24/2010 .07 .84 23.5 29.0 3.3 6.2 77 3 .05
Data 25

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323750--Silver Bow Creek at Warm Springs

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2009 0830 25 8.9 501 4.0 220 64.4 14.4

03/09/2010 1100 64 8.7 596 4.5 227 64.8 15.8

04/13/2010 0840 54 8.1 566 4.5 240 69.2 16.3

05/19/2010 1015 83 8.5 488 12.0 200 58.2 13.2

06/02/2010 0840 274 9.2 389 10.5 155 46.4 9.50

06/15/2010 0740 338 9.3 318 12.0 138 42.7 7.70

07/20/2010 0810 101 9.4 338 15.0 144 44.2 8.19

08/24/2010 1230 46 9.1 444 15.5 193 57.3 12.1

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/14/2009 30.5 31.8 0.03 0.07 2.2 4.1 11 100

03/09/2010 11.2 12.7 .10 .09 4.8 5.6 E6 134

04/13/2010 7.5 10.5 E.03 .09 E2.4 6.2 6 225

05/19/2010 15.0 18.1 .06 .07 2.6 5.4 14 218

06/02/2010 24.4 26.3 .08 .13 7.6 12.6 24 262

06/15/2010 25.2 25.9 .08 .12 9.2 14.3 24 186

07/20/2010 32.0 34.4 .04 .07 6.5 8.7 23 157

08/24/2010 36.8 39.1 E.02 E.03 2.8 3.6 17 83

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/14/2009 0.06 0.66 28.0 64.7 E1.6 5.2 68 2 0.14

03/09/2010 .03 .54 82.0 100 4.5 10.5 83 1 .17

04/13/2010 E.06 1.61 102 130 E6.0 12.6 85 2 .29

05/19/2010 .05 1.14 78.5 139 2.8 7.9 86 2 .45

06/02/2010 .12 1.62 46.1 86.3 E2.2 15.1 89 5 3.7

06/15/2010 .15 1.31 61.5 106 E2.5 12.7 87 4 3.7

07/20/2010 .12 .80 57.1 97.4 E1.5 6.4 93 2 .55

08/24/2010 .04 .38 50.2 77.6 <2.8 3.0 87 1 .12
26 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323760--Warm Springs Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/13/2009 1440 83 <2.0 8.4 257 5.0 125 37.5 7.56

04/12/2010 1420 49 <2.0 8.8 266 7.0 132 39.2 8.19

05/19/2010 0735 158 E18 8.1 188 5.5 93 29.1 5.00

06/01/2010 1515 174 E4.1 8.3 190 8.5 93 28.8 5.08

07/19/2010 1355 191 <2.0 8.5 183 11.0 88 27.0 4.87

08/23/2010 1655 123 <2.0 8.4 229 12.0 106 32.2 6.30

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/13/2009 2.1 2.5 0.02 E0.03 <1.0 1.9 E4 38

04/12/2010 1.9 2.3 .02 <.04 E.57 E1.3 E5 31

05/19/2010 1.9 5.1 .04 .14 1.3 28.0 15 1,000

06/01/2010 2.3 2.9 .03 E.03 1.2 4.2 8 186

07/19/2010 1.8 2.3 E.02 E.04 E.94 1.9 E3 70

08/23/2010 2.1 2.9 E.02 E.03 2.0 2.1 E5 87

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/13/2009 E0.02 0.19 0.70 2.1 E2.0 E1.2 83 1 0.22

04/12/2010 <.03 .10 .6 1.7 <2.8 <2.0 70 1 .13

05/19/2010 E.02 3.39 2.2 45.2 <2.8 20.1 65 65 28

06/01/2010 <.03 .48 1.3 9.3 <2.8 3.6 63 10 4.7

07/19/2010 <.03 .19 1.5 4.3 <2.8 3.0 71 4 2.1

08/23/2010 E.02 .30 1.0 5.1 <2.8 3.0 64 4 1.3
Data 27

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323770--Warm Springs Creek at Warm Springs

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2009 0805 71 8.1 301 5.0 150 46.0 8.61

04/13/2010 0735 48 8.2 331 4.0 172 50.6 11.0

05/19/2010 0945 119 8.0 224 8.0 111 34.5 5.91

06/02/2010 0810 165 8.0 211 7.0 101 31.5 5.46

07/20/2010 0735 151 8.0 210 9.5 99 30.8 5.42

08/24/2010 1130 92 8.3 260 9.0 125 38.2 7.20

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/14/2009 3.2 4.4 0.04 0.08 1.2 11.0 10 187

04/13/2010 3.3 3.7 E.04 .04 E1.5 6.4 10 98

05/19/2010 5.7 15.3 .05 .30 2.7 83.6 17 1,640

06/02/2010 3.6 7.5 .05 .12 2.5 33.2 14 685

07/20/2010 3.4 5.1 E.04 .06 <3.0 11.6 8 229

08/24/2010 3.3 4.7 .02 .04 1.5 6.9 8 154

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/14/2009 0.03 1.06 65.2 111 E1.5 4.9 64 8 1.5

04/13/2010 E.03 .49 61.4 77.6 -- 2.9 68 3 .39

05/19/2010 .07 9.58 52.7 266 <2.8 38.0 68 107 34

06/02/2010 .04 3.57 22.3 93.7 <2.8 14.9 65 40 18

07/20/2010 E.08 1.18 19.2 37.2 E5.0 5.9 72 12 4.9

08/24/2010 .03 .70 23.9 37.0 E1.5 4.0 76 5 1.2
28 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323800--Clark Fork near Galen

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2009 0945 125 8.5 399 5.0 189 56.6 11.5

03/09/2010 1220 118 8.7 477 4.0 198 57.3 13.3

04/13/2010 1025 103 8.2 460 4.0 210 61.1 13.9

05/19/2010 1145 199 8.3 334 11.0 148 45.4 8.48

06/02/2010 1015 423 8.9 324 10.0 135 40.8 8.01

06/15/2010 1005 610 9.0 248 11.0 111 34.5 6.06

07/20/2010 1005 258 8.9 263 13.0 116 35.8 6.54

08/24/2010 1500 129 8.9 333 14.0 147 44.3 8.80

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/14/2009 16.2 16.3 0.04 0.05 2.2 6.3 11 101

03/09/2010 8.1 9.2 .09 .08 4.3 8.4 7 153

04/13/2010 5.8 7.5 .07 .09 E2.4 11.3 7 219

05/19/2010 9.8 16.3 .05 .21 3.9 50.0 12 934

06/02/2010 16.6 22.5 .06 .21 6.3 44.3 18 751

06/15/2010 15.7 19.0 .09 .14 7.1 32.7 28 520

07/20/2010 15.3 18.1 .03 .07 4.1 12.8 10 201

08/24/2010 15.2 17.1 .03 .05 2.8 7.0 7 118

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/14/2009 0.05 0.72 48.5 80.3 E1.8 5.3 76 3 1.0

03/09/2010 .06 .79 62.1 91.4 3.1 7.5 75 4 1.3

04/13/2010 E.05 1.54 79.1 118 E4.5 16.1 76 5 1.4

05/19/2010 .06 6.17 57.8 229 E1.8 29.3 80 44 24

06/02/2010 .10 5.49 39.9 152 2.8 30.7 60 37 42

06/15/2010 .13 3.61 34.3 109 E1.8 22.1 62 25 41

07/20/2010 .06 1.24 27.2 62.1 <2.8 8.0 72 8 5.6

08/24/2010 .04 1.25 24.0 47.8 <2.8 4.5 79 2 .70
Data 29

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323840--Lost Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/13/2009 1345 10 <2.0 8.2 219 3.0 107 32.8 6.15

03/09/2010 0745 5.7 <2.0 8.1 212 2.0 93 27.6 5.78

04/12/2010 1330 4.3 <2.0 8.2 219 5.0 103 31.2 6.17

05/18/2010 1440 8.0 E5.4 7.8 161 10.0 77 23.8 4.22

06/01/2010 1410 16 E8.9 8.0 131 8.0 62 19.2 3.45

06/14/2010 1405 27 E2.8 8.0 139 9.0 68 21.2 3.57

07/19/2010 1305 10 <2.0 8.2 206 10.0 99 30.6 5.43

08/23/2010 1525 12 <2.0 8.2 212 10.5 101 31.0 5.77

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/13/2009 2.8 3.2 0.03 E0.03 E0.86 2.6 7 72

03/09/2010 1.9 2.1 .03 <.04 1.3 1.9 7 40

04/12/2010 1.8 2.2 E.01 <.04 E.95 2.5 E4 51

05/18/2010 2.2 3.1 E.02 .05 1.4 8.0 11 268

06/01/2010 2.6 3.7 .02 .07 2.4 11.8 21 268

06/14/2010 2.6 3.3 .03 .07 1.6 5.7 12 221

07/19/2010 3.2 3.8 E.01 E.02 1.1 2.3 6 64

08/23/2010 2.2 3.1 E.01 E.02 E.89 2.3 7 86

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/13/2009 E0.02 0.31 0.9 3.1 <2.8 E1.7 44 3 0.08

03/09/2010 E.02 .14 .4 1.6 <2.8 <2.0 62 2 .03

04/12/2010 <.03 .20 .6 2.0 <2.8 E1.2 77 2 .02

05/18/2010 E.03 1.22 1.2 12.5 <2.8 4.5 71 14 .30

06/01/2010 .06 1.93 1.5 16.2 <2.8 5.8 54 34 1.5

06/14/2010 .03 .79 1.1 7.4 <2.8 3.3 49 14 1.0

07/19/2010 E.02 .25 1.1 3.4 <2.8 2.2 62 4 .11

08/23/2010 E.02 .28 .8 4.1 <2.8 E1.5 58 3 .10
30 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12323850--Lost Creek near Galen

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2009 0920 71 8.1 576 5.5 283 83.5 18.1

03/09/2010 1150 55 8.3 571 4.0 254 73.2 17.3

04/13/2010 1000 47 8.2 606 3.5 291 83.6 20.0

05/19/2010 1115 9.4 8.3 728 11.0 358 104 24.1

06/02/2010 0940 6.0 8.2 799 10.0 382 107 28.0

06/15/2010 0930 5.3 8.0 689 12.0 313 86.2 23.8

07/20/2010 0935 5.0 8.1 647 13.0 293 80.6 22.2

08/24/2010 1425 13 8.5 619 14.0 306 89.5 20.1

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/14/2009 13.5 14.5 0.02 E0.04 1.4 3.6 10 80

03/09/2010 11.0 12.7 .05 .04 5.6 5.5 16 159

04/13/2010 9.4 11.1 E.02 .05 E1.0 6.1 7 192

05/19/2010 16.4 17.0 .04 E.02 1.4 3.4 20 121

06/02/2010 21.6 24.1 .04 E.03 1.8 3.7 35 117

06/15/2010 13.7 15.3 .05 E.02 1.5 3.2 32 112

07/20/2010 9.1 10.5 .02 E.02 1.5 2.6 7 37

08/24/2010 11.0 13.5 E.01 E.02 1.6 2.2 E5 37

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/14/2009 E0.02 0.33 5.0 9.7 <2.8 2.7 56 15 2.9

03/09/2010 .30 .55 16.6 27.5 E1.8 3.2 46 20 3.0

04/13/2010 E.03 .74 17.7 31.2 -- 4.8 82 11 1.4

05/19/2010 E.03 .34 46.2 52.1 E1.6 2.3 58 26 .66

06/02/2010 E.02 .16 41.5 45.6 <2.8 E1.8 32 79 1.3

06/15/2010 E.03 .16 38.5 44.8 E1.9 3.0 85 19 .27

07/20/2010 E.02 .21 6.7 9.1 <2.8 E1.0 49 7 .09

08/24/2010 E.02 .14 2.8 4.9 <2.8 E1.2 62 13 .46
Data 31

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12324200--Clark Fork at Deer Lodge

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2009 1055 306 8.2 463 5.0 211 62.5 13.4

03/09/2010 1400 250 8.5 477 4.0 200 58.5 13.2

04/13/2010 1225 212 8.2 507 4.0 228 66.5 15.0

05/19/2010 1325 193 8.4 411 14.0 190 56.8 11.6

06/02/2010 1210 520 8.1 359 12.0 142 42.5 8.70

06/15/2010 1145 736 8.2 280 13.0 121 37.2 6.85

07/20/2010 1215 272 8.4 322 16.0 138 42.5 7.84

08/25/2010 0755 159 8.1 430 12.5 192 58.0 11.5

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/14/2009 12.5 15.6 0.05 0.14 4.6 26.7 8 437

03/09/2010 8.8 10.8 .08 .10 5.6 19.4 7 322

04/13/2010 8.0 11.0 E.06 .12 4.5 20.5 7 350

05/19/2010 11.8 13.5 .07 .13 6.3 23.9 8 328

06/02/2010 15.5 33.2 .08 .51 10.1 142 15 2,420

06/15/2010 17.4 30.8 .09 .38 11.1 148 21 1,610

07/20/2010 17.3 19.8 .05 .11 7.7 19.6 8 207

08/25/2010 15.2 17.2 .06 .10 5.9 14.8 10 183

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/14/2009 0.04 3.60 20.7 77.9 6.0 26.0 72 18 15

03/09/2010 .05 1.99 48.4 76.6 4.9 16.6 63 14 9.5

04/13/2010 E.07 2.45 46.7 87.2 E7.8 20.5 81 14 8.0

05/19/2010 .06 2.80 34.6 84.8 3.6 19.7 84 14 7.3

06/02/2010 .14 25.9 24.7 275 5.7 109 46 156 219

06/15/2010 .19 31.8 20.2 232 4.6 75.4 31 128 254

07/20/2010 .10 1.95 29.7 54.5 3.8 13.7 79 8 5.9

08/25/2010 .09 1.47 29.1 52.1 6.6 13.9 91 5 2.1
32 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

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

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2009 1220 331 8.4 465 5.0 214 63.2 13.8

03/09/2010 1530 284 8.8 466 5.0 198 57.3 13.3

04/13/2010 1405 238 8.6 494 4.0 221 64.0 14.8

05/19/2010 1520 201 8.4 445 16.0 197 58.8 12.3

06/02/2010 1445 602 8.0 383 12.5 156 46.0 10.1

06/15/2010 1335 968 8.1 297 14.0 131 39.4 8.03

07/20/2010 1400 290 8.4 352 19.0 150 45.4 8.91

08/25/2010 0950 186 8.3 439 13.0 192 57.2 12.0

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/14/2009 12.4 15.9 0.04 0.22 4.3 35.5 E5 564

03/09/2010 10.1 12.4 .08 .16 6.6 29.7 6 459

04/13/2010 9.5 11.9 E.05 .14 5.0 24.4 E5 359

05/19/2010 13.7 15.7 .06 .16 7.1 32.2 7 408

06/02/2010 16.4 37.0 .08 .70 10.5 168 14 2,690

06/15/2010 17.7 31.2 .10 .45 12.9 124 23 1,780

07/20/2010 18.1 19.9 .08 .23 8.8 20.7 E6 180

08/25/2010 15.9 17.9 .06 .08 7.0 12.4 8 119

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/14/2009 0.04 5.38 16.3 118 5.0 36.0 58 28 25

03/09/2010 .06 3.25 41.7 85.8 2.9 25.3 59 25 19

04/13/2010 E.06 2.76 41.0 85.7 E4.8 21.6 80 15 9.6

05/19/2010 .07 3.55 45.3 129 3.0 28.9 78 21 11

06/02/2010 .18 23.6 23.6 304 6.4 145 63 146 237

06/15/2010 .24 15.7 17.0 196 6.7 98.6 53 107 280

07/20/2010 .09 1.69 29.7 54.3 4.2 16.5 70 7 5.5

08/25/2010 .08 .90 19.4 40.5 4.7 10.1 66 5 2.5
Data 33

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12324680--Clark Fork at Goldcreek

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2009 1310 489 8.5 413 5.5 193 57.8 11.9

03/10/2010 0820 460 8.3 422 1.0 177 51.6 11.7

04/13/2010 1520 422 8.4 422 4.0 194 56.3 13.0

05/19/2010 1625 675 8.3 274 14.0 120 36.2 7.08

06/02/2010 1620 1,420 8.1 282 12.0 117 34.8 7.33

06/15/2010 1555 1,820 8.1 255 13.0 114 34.4 6.87

07/20/2010 1455 513 8.4 329 18.5 141 42.6 8.34

08/25/2010 1255 317 8.4 394 16.0 181 55.1 10.6

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/14/2009 9.5 11.1 0.04 0.12 3.3 20.4 8 344

03/10/2010 7.4 9.2 .07 .11 5.2 18.9 15 348

04/13/2010 7.2 8.5 E.05 .09 3.9 16.3 E4 270

05/19/2010 7.7 11.4 .03 .17 4.3 23.4 20 1,080

06/02/2010 10.0 19.0 .05 .37 6.5 74.0 24 1,830

06/15/2010 11.7 19.7 .06 .28 9.6 77.1 28 1,350

07/20/2010 12.4 13.8 .06 .08 6.1 12.3 E5 139

08/25/2010 10.9 12.7 .03 .05 4.8 7.2 E6 75

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/14/2009 0.04 2.74 10.0 78.6 3.0 20.3 78 14 18

03/10/2010 .06 2.10 32.1 68.2 5.8 19.5 71 17 21

04/13/2010 E.04 1.76 21.9 59.2 E4.8 15.6 76 12 14

05/19/2010 .07 5.30 18.4 114 E2.2 29.0 78 59 108

06/02/2010 .17 11.2 10.9 196 4.1 72.7 49 132 506

06/15/2010 .21 9.82 11.3 127 8.0 62.3 48 94 462

07/20/2010 .06 .95 15.1 33.9 3.0 9.3 81 6 8.3

08/25/2010 .04 .47 9.4 22.9 E2.2 5.7 76 3 2.6
34 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12331800--Clark Fork near Drummond

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2009 1425 760 8.4 442 7.0 204 58.7 14.0

03/10/2010 0945 664 8.3 435 3.5 185 52.5 13.1

04/14/2010 0755 642 8.2 448 5.0 202 57.3 14.2

05/20/2010 0810 862 8.0 308 12.0 136 40.7 8.37

06/03/2010 0815 1,690 8.0 307 11.0 131 38.6 8.46

06/16/2010 0820 2,360 7.9 268 12.0 114 33.7 7.19

07/21/2010 0800 589 8.2 409 16.5 183 53.2 12.2

08/25/2010 1430 466 8.5 475 17.0 209 60.0 14.3

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/14/2009 8.7 10.8 0.03 0.12 2.5 15.1 E3 379

03/10/2010 8.1 9.8 .08 .13 11.8 22.4 16 472

04/14/2010 3.2 9.1 -- .10 -- 15.5 E3 310

05/20/2010 9.2 17.6 .03 .36 4.5 48.4 16 1,510

06/03/2010 10.7 25.9 .04 .61 6.8 123 23 3,050

06/16/2010 11.9 25.4 .08 .39 8.8 87.1 30 2,100

07/21/2010 12.9 13.1 E.06 .07 E4.8 9.9 E4 125

08/25/2010 10.9 13.3 .03 .05 3.8 6.3 E4 84

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/14/2009 0.04 3.32 10.0 84.0 3.1 21.1 81 18 37

03/10/2010 .49 3.00 23.6 79.8 10.0 25.4 74 24 43

04/14/2010 E.04 2.12 -- 71.0 <14.0 E6.4 80 16 28

05/20/2010 .15 13.6 9.8 242 4.4 74.0 91 78 182

06/03/2010 .22 21.9 9.0 354 4.9 141 58 197 899

06/16/2010 .28 16.8 8.0 242 6.3 108 54 147 937

07/21/2010 .28 .90 13.8 32.0 E4.9 9.9 87 5 8.0

08/25/2010 .05 .64 11.4 30.6 E2.3 5.9 82 4 5.0
Data 35

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12334550--Clark Fork at Turah Bridge, near Bonner

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2009 0805 984 8.2 368 6.0 167 47.8 11.6

03/10/2010 1145 838 8.4 370 3.0 155 43.6 11.3

04/14/2010 0945 819 8.3 365 5.5 168 47.1 12.3

05/20/2010 1025 2,150 8.0 186 10.0 81 23.3 5.41

06/03/2010 1015 3,090 7.9 218 10.5 96 27.6 6.50

06/16/2010 1115 4,500 7.9 198 12.0 85 24.6 5.73

07/21/2010 0945 1,230 8.2 293 15.5 128 37.0 8.58

08/26/2010 0835 810 8.1 358 13.5 159 44.9 11.3

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/15/2009 6.0 7.5 0.03 0.11 1.8 11.6 <6 284

03/10/2010 6.3 7.7 .06 .11 4.9 15.9 8 346

04/14/2010 5.4 6.2 -- .08 E2.7 10.6 E3 219

05/20/2010 3.8 6.2 E.02 .15 2.4 23.2 23 820

06/03/2010 6.5 13.0 .03 .33 4.2 57.1 23 1,520

06/16/2010 7.4 13.2 .04 .26 5.7 46.8 29 1,160

07/21/2010 7.3 7.8 E.04 .05 3.6 5.8 E4 90

08/26/2010 6.7 8.7 .03 .05 2.6 5.6 E3 99

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/15/2009 E0.03 2.36 4.0 62.8 3.3 18.6 89 14 37

03/10/2010 .06 2.20 9.6 60.2 3.9 20.7 88 17 38

04/14/2010 E.05 1.38 9.3 44.0 -- 15.0 83 12 27

05/20/2010 .06 4.12 8.6 99.5 E2.7 34.9 77 50 290

06/03/2010 .15 10.0 8.7 188 3.8 74.6 69 100 834

06/16/2010 .18 7.63 7.9 141 5.5 59.5 67 79 960

07/21/2010 .11 .50 20.4 18.8 E7.0 6.2 77 5 17

08/26/2010 .03 .58 5.0 23.6 E2.4 8.4 83 5 11
36 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12340000--Blackfoot River near Bonner

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2009 0950 553 8.3 282 5.5 146 37.7 12.5

04/14/2010 1200 729 8.4 229 5.5 113 28.5 10.2

05/20/2010 1300 4,140 8.0 140 10.0 69 18.6 5.37

06/03/2010 1250 3,980 8.1 169 10.5 -- -- --

07/21/2010 1155 990 8.6 235 18.0 120 30.8 10.4

08/26/2010 1120 589 8.4 263 15.0 128 32.1 11.6

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/15/2009 1.1 1.3 <0.02 <0.04 <1.0 1.9 <6 34

04/14/2010 .9 .95 -- <.04 -- E1.1 7 91

05/20/2010 .8 1.3 E.01 <.04 1.5 1.9 12 484

06/03/2010 -- 1.3 -- <.04 -- 1.9 -- 409

07/21/2010 .4 1.6 <.02 <.04 <1.0 E1.0 E5 28

08/26/2010 1.2 2.1 <.02 <.04 E.76 E1.0 <6 36

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/15/2009 <0.03 0.08 1.0 3.8 <2.8 <2.0 74 2 3.0

04/14/2010 -- .10 3.6 10.6 -- <2.0 84 5 9.8

05/20/2010 .03 .66 2.7 54.2 <2.8 3.9 82 41 458

06/03/2010 -- .55 -- 32.3 -- 2.7 85 31 333

07/21/2010 <.03 E.05 .5 3.9 <2.8 <2.0 76 2 5.3

08/26/2010 .04 .08 1.7 6.8 <2.8 E1.2 80 3 4.8
Data 37

Table 4. Water-quality data for the Clark Fork basin, Montana, October 2009 through September 2010.—Continued

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

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

level; --, no data]

12340500--Clark Fork above Missoula

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2009 1130 1,640 8.3 336 6.0 162 44.8 12.1

03/10/2010 1415 1,400 8.5 333 3.0 147 39.8 11.6

04/14/2010 1415 1,630 8.4 304 6.5 142 38.0 11.4

05/20/2010 1515 6,500 8.2 157 11.0 74 20.6 5.45

06/03/2010 1445 7,240 8.2 191 11.5 86 23.8 6.50

06/16/2010 1335 7,740 8.0 187 12.5 88 24.5 6.47

07/21/2010 1330 2,290 8.5 267 18.0 125 34.6 9.23

08/26/2010 1445 1,480 8.5 313 17.0 142 38.4 11.1

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

10/15/2009 4.6 5.3 0.03 0.08 1.6 8.6 E3 203

03/10/2010 4.6 5.5 .04 .08 3.8 11.3 10 247

04/14/2010 3.3 3.8 -- .04 E1.7 6.0 E4 152

05/20/2010 2.1 3.8 E.01 .11 2.3 16.7 17 842

06/03/2010 3.5 9.0 .02 .33 3.1 50.3 18 1,530

06/16/2010 4.6 8.1 .04 .17 3.9 31.1 18 797

07/21/2010 4.5 5.3 .03 .05 3.2 5.0 E3 71

08/26/2010 4.7 5.9 .02 .05 2.4 6.1 <6 135

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

10/15/2009 0.04 1.57 7.5 44.4 3.3 13.7 80 11 49

03/10/2010 .05 1.66 11.9 45.0 2.9 15.0 87 12 45

04/14/2010 -- .76 9.6 32.6 -- 8.6 79 10 44

05/20/2010 .06 5.03 7.3 90.7 E2.1 28.6 56 78 1,370

06/03/2010 .10 8.59 10.6 171 3.0 90.8 47 134 2,620

06/16/2010 .17 5.08 7.1 96.2 3.8 44.3 63 57 1,190

07/21/2010 .05 .48 6.3 15.6 E2.6 6.2 77 5 31

08/26/2010 .08 .81 8.8 22.3 E1.6 7.8 87 7 28
38 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2009 through 

September 2010.

[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

1 208 15 8.4 355 20 19 289 13 10

2 203 16 8.8 335 18 16 244 16 11

3 206 17 9.5 326 17 15 231 30 19

4 213 19 11 312 16 13 200 44 24

5 220 20 12 309 16 13 191 48 25

6 235 19 12 310 16 13 e150 49 20

7 246 17 11 309 16 13 e130 51 18

8 283 14 11 305 16 13 e120 52 17

9 275 10 7.4 299 16 13 e130 48 17

10 267 10 7.2 297 17 14 e140 40 15

11 278 10 7.5 300 16 13 e160 32 14

12 274 10 7.4 306 14 12 e170 27 12

13 291 12 9.4 291 12 9.4 e160 26 11

14 302 17 14 288 10 7.8 e170 26 12

15 302 19 15 280 10 7.6 e180 27 13

16 307 19 16 293 13 10 193 27 14

17 322 20 17 310 19 16 228 32 20

18 307 20 17 317 23 20 e240 43 28

19 309 21 18 305 20 16 254 54 37

20 370 32 32 313 16 14 282 60 46

21 345 14 13 310 12 10 294 58 46

22 333 11 9.9 285 11 8.5 e260 48 34

23 317 11 9.4 296 12 9.6 e240 42 27

24 315 12 10 293 13 10 e220 40 24

25 308 12 10 294 14 11 e220 40 24

26 306 12 9.9 299 15 12 e210 43 24

27 303 12 9.8 300 16 13 e210 62 35

28 303 12 9.8 295 16 13 e200 91 49

29 333 13 12 292 14 11 e200 108 58

30 377 19 19 291 13 10 e210 112 64

31 380 21 22 -- -- -- 217 112 66

TOTAL 9,038 -- 386.4 9,115 -- 375.9 6,343 -- 834

MEAN 292 16 12 304 15 13 205 48 27

MAX 380 32 32 355 23 20 294 112 66

MIN 203 10 7.2 280 10 7.6 120 13 10
Data 39

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

1 238 107 69 234 28 18 232 19 12

2 243 90 59 235 32 20 238 18 12

3 237 69 44 234 32 20 251 16 11

4 228 50 31 246 28 19 267 18 13

5 e210 37 21 237 25 16 257 40 28

6 e190 44 23 237 24 15 251 51 35

7 e180 62 30 238 24 15 250 31 21

8 e180 84 41 233 23 14 248 24 16

9 e190 94 48 224 23 14 250 21 14

10 e200 84 45 e225 23 14 245 25 17

11 215 62 36 228 22 14 236 18 11

12 232 43 27 227 21 13 241 18 12

13 259 31 22 234 20 13 244 18 12

14 256 29 20 232 20 13 239 21 14

15 248 29 19 233 20 13 243 26 17

16 253 29 20 235 24 15 247 28 19

17 254 29 20 235 29 18 251 24 16

18 251 31 21 234 32 20 253 22 15

19 248 37 25 231 32 20 248 20 13

20 242 44 29 222 32 19 245 18 12

21 238 47 30 203 31 17 245 20 13

22 235 46 29 219 31 18 255 16 11

23 251 45 30 229 30 19 246 17 11

24 235 43 27 232 27 17 240 32 21

25 256 42 29 224 24 15 241 28 18

26 241 36 23 221 23 14 248 35 23

27 239 30 19 225 22 13 242 35 23

28 235 25 16 229 21 13 238 57 37

29 246 22 15 -- -- -- 239 39 25

30 250 21 14 -- -- -- 256 70 48

31 235 24 15 -- -- -- 263 60 43

TOTAL 7,215 -- 897 6,436 -- 449 7,649 -- 593

MEAN 233 47 29 230 26 16 247 29 19

MAX 259 107 69 246 32 20 267 70 48

MIN 180 21 14 203 20 13 232 16 11

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2009 through 

September 2010.—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]
40 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 250 31 21 222 14 8.4 481 175 227

2 240 32 21 220 11 6.5 520 180 253

3 237 28 18 213 12 6.9 588 262 416

4 229 24 15 208 10 5.6 723 254 496

5 226 22 13 195 13 6.8 748 240 485

6 229 21 13 183 17 8.4 761 229 471

7 230 22 14 186 10 5.0 780 168 354

8 226 26 16 185 7 3.5 852 163 375

9 213 37 21 180 14 6.8 816 133 293

10 209 36 20 172 8 3.7 798 151 325

11 209 26 15 171 9 4.2 892 158 381

12 206 16 8.9 172 8 3.7 846 119 272

13 212 18 10 170 7 3.2 739 103 206

14 233 22 14 155 8 3.3 685 98 181

15 238 25 16 153 6 2.5 741 129 258

16 230 30 19 151 6 2.4 1,110 299 896

17 234 24 15 147 7 2.8 1,470 356 1,410

18 241 48 31 151 8 3.3 1,410 246 937

19 244 55 36 191 18 9.3 1,150 156 484

20 256 61 42 290 82 64 1,070 135 390

21 267 31 22 353 100 95 1,090 119 350

22 282 32 24 331 55 49 1,060 106 303

23 298 34 27 327 60 53 1,020 109 300

24 296 26 21 318 50 43 979 98 259

25 276 24 18 325 42 37 972 91 239

26 261 32 23 310 39 33 985 86 229

27 251 28 19 308 31 26 958 68 176

28 249 36 24 383 147 152 888 70 168

29 249 19 13 480 143 185 821 69 153

30 231 19 12 457 121 149 772 46 96

31 -- -- -- 432 134 156 -- -- --

TOTAL 7,252 -- 581.9 7,739 -- 1,138.3 26,725 -- 11,383

MEAN 242 30 19 250 39 37 891 154 379

MAX 298 61 42 480 147 185 1,470 356 1,410

MIN 206 16 8.9 147 6 2.4 481 46 96

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2009 through 

September 2010.—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)

JULY AUGUST SEPTEMBER

1 810 32 70 188 10 5.1 195 7 3.7

2 753 17 35 171 10 4.6 191 8 4.1

3 728 10 20 158 10 4.3 194 9 4.7

4 677 10 18 169 9 4.1 191 9 4.6

5 612 10 17 190 8 4.1 200 9 4.9

6 580 10 16 187 7 3.5 199 9 4.8

7 534 10 14 176 7 3.3 193 9 4.7

8 494 10 13 171 7 3.2 187 9 4.5

9 463 10 13 175 7 3.3 246 9 6

10 414 10 11 187 7 3.5 383 9 9.3

11 449 10 12 214 6 3.5 325 8 7

12 438 10 12 235 6 3.8 282 8 6.1

13 390 10 11 236 5 3.2 262 8 5.7

14 353 10 9.5 250 4 2.7 261 8 5.6

15 333 10 9.0 241 4 2.6 303 6 4.9

16 307 9 7.5 228 4 2.5 298 6 4.8

17 294 9 7.1 207 4 2.2 301 7 5.7

18 293 9 7.1 192 5 2.6 296 7 5.6

19 292 8 6.3 178 5 2.4 296 7 5.6

20 275 8 5.9 164 5 2.2 298 7 5.6

21 260 12 8.4 157 5 2.1 300 6 4.9

22 277 14 10 144 5 1.9 296 5 4

23 243 14 9.2 159 5 2.1 292 4 3.2

24 232 14 8.8 167 5 2.3 279 3 2.3

25 227 14 8.6 160 5 2.2 272 3 2.2

26 213 13 7.5 151 6 2.4 256 4 2.8

27 225 12 7.3 136 8 2.9 245 4 2.6

28 243 12 7.9 135 8 2.9 240 4 2.6

29 224 11 6.7 152 7 2.9 237 4 2.6

30 207 10 5.6 175 6 2.8 232 4 2.5

31 193 10 5.2 195 6 3.2 -- -- --

TOTAL 12,033 -- 399.6 5,648 -- 94.4 7,750 -- 137.6

MEAN 388 12 13 182 6 3.0 258 7 4.6

MAX 810 32 70 250 10 5.1 383 9 9.3

MIN 193 8 5.2 135 4 1.9 187 3 2.2 

Total for water year 2010 (unrounded sum of daily values): streamflow–112,943 ft3/s (annual runoff–224,000 acre-ft); suspended-sediment 

 discharge–17,270.1 tons.

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 2009 through 

September 2010.—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]
42 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2009 

through September 2010.

[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

1 754 6 12 1,060 11 31 868 4 9.4

2 777 6 13 1,040 10 28 804 5 11

3 779 5 11 1,000 9 24 e620 6 10

4 793 5 11 986 7 19 e560 7 11

5 807 6 13 962 6 16 e580 7 11

6 865 8 19 970 6 16 e550 8 12

7 890 9 22 967 6 16 e450 8 9.7

8 926 10 25 953 6 15 e350 7 6.6

9 971 10 26 934 6 15 e370 7 7.0

10 950 9 23 913 6 15 e380 6 6.2

11 924 7 17 925 6 15 e420 6 6.8

12 897 6 15 935 6 15 e450 7 8.5

13 925 6 15 924 5 12 e500 16 22

14 972 10 26 856 5 12 e550 12 18

15 1,000 14 38 852 5 12 e600 11 18

16 1,010 12 33 849 5 11 e680 19 35

17 997 12 32 894 5 12 e700 18 34

18 1,000 12 32 915 4 9.9 e720 16 31

19 1,000 12 32 905 4 9.8 e700 14 26

20 1,070 18 52 876 4 9.5 e730 12 24

21 1,130 24 73 903 4 9.8 e750 9 18

22 1,080 20 58 884 4 9.5 e740 7 14

23 1,050 16 45 858 4 9.3 e700 6 11

24 1,050 12 34 874 4 9.4 e680 6 11

25 1,050 9 26 875 4 9.4 e650 6 11

26 1,030 7 19 875 4 9.4 e630 5 8.5

27 1,010 6 16 881 4 9.5 e600 5 8.1

28 1,010 6 16 880 4 9.5 e610 4 6.6

29 988 6 16 869 4 9.4 e640 4 6.9

30 992 6 16 861 4 9.3 e680 4 7.3

31 1,040 8 22 -- -- -- e700 4 7.6

TOTAL 29,737 -- 808 27,476 -- 407.7 18,962 -- 427.2

MEAN 959 10 26 916 5 14 612 8 14

MAX 1,130 24 73 1,060 11 31 868 19 35

MIN 754 5 11 849 4 9.3 350 4 6.2
Data 43

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e720 5 9.7 726 5 9.8 779 25 53

2 e740 7 14 715 5 9.7 785 28 59

3 e750 8 16 716 5 9.7 773 28 58

4 e740 6 12 702 4 7.6 836 33 74

5 e700 5 9.5 696 4 7.5 874 38 90

6 e650 5 8.8 718 5 9.7 847 31 71

7 e600 4 6.5 725 6 12 831 23 52

8 625 4 6.8 706 6 11 830 22 49

9 668 4 7.2 692 7 13 860 31 72

10 762 4 8.2 685 8 15 831 21 47

11 749 5 10 715 9 17 773 14 29

12 738 8 16 721 10 19 753 14 28

13 751 10 20 730 10 20 788 14 30

14 770 10 21 735 11 22 796 18 39

15 781 9 19 740 12 24 786 17 36

16 774 8 17 746 13 26 797 16 34

17 775 7 15 738 14 28 825 17 38

18 773 6 13 745 13 26 897 35 85

19 773 6 13 732 11 22 878 45 107

20 770 6 12 699 9 17 817 24 53

21 743 6 12 647 9 16 787 19 40

22 729 5 9.8 609 9 15 814 21 46

23 719 5 9.7 615 9 15 850 27 62

24 719 4 7.8 658 10 18 806 22 48

25 711 4 7.7 739 14 28 778 20 42

26 703 4 7.6 728 14 28 781 20 42

27 732 4 7.9 717 14 27 788 19 40

28 724 4 7.8 742 16 32 777 19 40

29 700 4 7.6 -- -- -- 795 22 47

30 691 4 7.5 -- -- -- 876 31 73

31 715 5 9.7 -- -- -- 919 33 82

TOTAL 22,495 -- 349.8 19,837 -- 505.0 25,327 -- 1,666

MEAN 726 6 11 708 9 18 817 24 54

MAX 781 10 21 746 16 32 919 45 107

MIN 600 4 6.5 609 4 7.5 753 14 28

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2009 

through September 2010.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]
44 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 864 21 49 1,330 24 86 2,560 61 422

2 823 19 42 1,280 22 76 2,900 92 720

3 802 18 39 1,240 22 74 3,230 115 1,000

4 792 15 32 1,230 19 63 3,990 194 2,090

5 767 15 31 1,200 19 62 4,400 178 2,110

6 767 15 31 1,140 15 46 4,580 142 1,760

7 761 15 31 1,110 14 42 4,560 107 1,320

8 761 14 29 1,080 13 38 5,010 143 1,930

9 762 10 21 1,060 13 37 4,860 94 1,230

10 736 11 22 1,040 15 42 4,650 70 879

11 728 13 26 1,020 14 39 4,540 61 748

12 736 12 24 1,010 13 35 4,770 84 1,080

13 761 14 29 1,000 13 35 4,370 66 779

14 812 14 31 976 13 34 4,000 47 508

15 833 19 43 997 13 35 3,860 49 511

16 873 23 54 1,090 13 38 4,510 86 1,050

17 903 24 59 1,210 18 59 5,340 160 2,310

18 970 29 76 1,410 24 91 5,840 173 2,730

19 1,030 33 92 1,750 35 165 5,810 141 2,210

20 1,120 37 112 2,180 60 353 5,580 107 1,610

21 1,300 72 253 2,330 60 377 5,430 86 1,260

22 1,590 98 421 2,220 48 288 5,330 67 964

23 1,810 113 552 2,070 38 212 4,870 62 815

24 1,780 87 418 1,960 32 169 4,600 53 658

25 1,670 59 266 1,970 32 170 4,440 46 551

26 1,550 43 180 1,890 33 168 4,320 45 525

27 1,450 42 164 1,840 33 164 4,140 40 447

28 1,460 35 138 2,020 36 196 3,840 40 415

29 1,460 30 118 2,450 80 529 3,530 37 353

30 1,380 25 93 2,580 100 697 3,460 37 346

31 -- -- -- 2,460 70 465 -- -- --

TOTAL 32,051 -- 3,476 48,143 -- 4,885 133,320 -- 33,331

MEAN 1,068 32 116 1,553 31 158 4,444 89 1,110

MAX 1,810 113 552 2,580 100 697 5,840 194 2,730

MIN 728 10 21 976 13 34 2,560 37 346

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2009 

through September 2010.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]
Data 45

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JULY AUGUST SEPTEMBER

1 3,390 34 311 1,060 5 14 836 5 11

2 3,280 30 266 1,030 5 14 862 6 14

3 3,020 27 220 990 5 13 844 5 11

4 2,820 25 190 944 5 13 827 5 11

5 2,650 22 157 914 5 12 828 5 11

6 2,460 21 139 918 5 12 844 5 11

7 2,300 18 112 931 5 13 854 5 12

8 2,190 15 89 929 6 15 846 5 11

9 2,010 12 65 914 6 15 867 6 14

10 1,890 12 61 951 6 15 1,120 23 70

11 1,820 13 64 977 7 18 1,210 23 75

12 1,800 10 49 1,030 9 25 1,140 16 49

13 1,720 8 37 1,090 11 32 1,070 12 35

14 1,610 8 35 1,140 11 34 1,040 11 31

15 1,560 8 34 1,090 12 35 1,020 10 28

16 1,520 7 29 1,040 11 31 1,060 9 26

17 1,430 6 23 1,000 9 24 1,070 8 23

18 1,360 5 18 940 7 18 1,090 9 26

19 1,300 6 21 909 6 15 1,070 9 26

20 1,260 5 17 878 6 14 1,060 9 26

21 1,220 4 13 837 6 14 1,080 8 23

22 1,200 4 13 811 6 13 1,070 8 23

23 1,190 4 13 812 6 13 1,050 7 20

24 1,140 4 12 822 6 13 1,030 6 17

25 1,100 4 12 820 6 13 1,010 6 16

26 1,070 4 12 800 5 11 996 6 16

27 1,070 3 8.7 778 4 8.4 977 6 16

28 1,120 4 12 753 4 8.1 959 6 16

29 1,140 4 12 751 4 8.1 947 6 15

30 1,070 4 12 786 3 6.4 931 6 15

31 1,030 4 11 811 4 8.8 -- -- --

TOTAL 53,740 -- 2,067.7 28,456 -- 498.8 29,608 -- 698

MEAN 1,734 11 67 918 6 16 987 8 23

MAX 3,390 34 311 1,140 12 35 1,210 23 75

MIN 1,030 3 8.7 751 3 6.4 827 5 11

Total for water year 2010 (unrounded sum of daily values): streamflow–469,152 ft3/s (annual runoff–930,600 acre-ft); suspended-sediment 

 discharge–49,120.2 tons.

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 2009 

through September 2010.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]
46 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2009 through 

September 2010.

[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

1 499 2 2.7 652 2 3.5 e450 2 2.4

2 502 2 2.7 652 2 3.5 e320 2 1.7

3 502 2 2.7 638 2 3.4 e300 3 2.4

4 506 2 2.7 623 2 3.4 e300 3 2.4

5 506 2 2.7 611 1 1.6 e320 3 2.6

6 507 2 2.7 612 1 1.7 e290 3 2.3

7 519 1 1.4 611 1 1.6 e220 3 1.8

8 529 1 1.4 600 2 3.2 e180 3 1.5

9 543 1 1.5 589 2 3.2 e200 2 1.1

10 521 1 1.4 581 2 3.1 e210 2 1.1

11 494 1 1.3 578 2 3.1 e220 2 1.2

12 493 1 1.3 583 2 3.1 e230 2 1.2

13 538 1 1.5 575 2 3.1 e240 2 1.3

14 544 1 1.5 555 2 3.0 e270 1 .73

15 552 1 1.5 546 2 2.9 e290 2 1.6

16 547 1 1.5 552 2 3.0 e320 2 1.7

17 541 2 2.9 543 2 2.9 e340 3 2.8

18 541 2 2.9 548 2 3.0 e340 3 2.8

19 550 3 4.5 529 2 2.9 e320 3 2.6

20 564 3 4.6 529 2 2.9 e340 3 2.8

21 571 2 3.1 538 2 2.9 e350 3 2.8

22 560 2 3.0 519 2 2.8 e350 2 1.9

23 550 2 3.0 525 2 2.8 e320 2 1.7

24 574 2 3.1 524 2 2.8 e300 2 1.6

25 575 2 3.1 527 2 2.8 e280 2 1.5

26 564 2 3.0 523 2 2.8 e260 2 1.4

27 573 2 3.1 523 2 2.8 e230 2 1.2

28 583 2 3.1 523 1 1.4 e230 2 1.2

29 586 2 3.2 520 1 1.4 e240 1 .65

30 589 2 3.2 517 1 1.4 e260 1 .70

31 614 2 3.3 -- -- -- e280 2 1.5

TOTAL 16,837 -- 79.6 16,946 -- 82.0 8,800 -- 54.18

MEAN 543 2 2.6 546 2 2.7 284 2 1.7

MAX 614 3 4.6 652 2 3.5 450 3 2.8

MIN 493 1 1.3 517 1 1.4 180 1 .65
Data 47

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2009 through 

September 2010.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e290 2 1.6 e300 2 1.6 421 3 3.4

2 e310 2 1.7 e320 2 1.7 422 3 3.4

3 e300 2 1.6 e330 2 1.8 424 5 5.7

4 e280 3 2.3 e340 1 .92 448 6 7.3

5 e250 3 2.0 e330 1 .89 467 6 7.6

6 e210 3 1.7 e350 2 1.9 484 5 6.5

7 e190 3 1.5 e360 2 1.9 492 5 6.6

8 e200 3 1.6 e380 3 3.1 500 5 6.8

9 e210 2 1.1 e400 3 3.2 532 5 7.2

10 e230 2 1.2 e420 3 3.4 518 4 5.6

11 e250 1 .68 437 3 3.5 482 3 3.9

12 e270 1 .73 430 3 3.5 467 3 3.8

13 e270 1 .73 430 3 3.5 479 4 5.2

14 e280 1 .76 425 3 3.4 513 5 6.9

15 e290 1 .78 428 3 3.5 525 6 8.5

16 e300 2 1.6 432 3 3.5 532 6 8.6

17 e300 4 3.2 423 3 3.4 549 5 7.4

18 e300 5 4.0 420 3 3.4 577 6 9.3

19 e290 3 2.3 410 3 3.3 578 6 9.4

20 e290 2 1.6 397 2 2.1 546 5 7.4

21 e280 2 1.5 376 2 2.0 533 4 5.8

22 e260 2 1.4 355 2 1.9 563 5 7.6

23 e260 2 1.4 e330 2 1.8 578 5 7.8

24 e260 2 1.4 e360 2 1.9 567 5 7.7

25 e270 2 1.5 e370 2 2.0 559 5 7.5

26 e270 2 1.5 e390 2 2.1 564 5 7.6

27 e290 2 1.6 407 2 2.2 568 5 7.7

28 e280 2 1.5 414 3 3.4 576 5 7.8

29 e280 2 1.5 -- -- -- 617 6 10

30 e270 2 1.5 -- -- -- 767 12 25

31 e290 2 1.6 -- -- -- 787 10 21

TOTAL 8,320 -- 49.08 10,764 -- 70.81 16,635 -- 246

MEAN 268 2 1.6 384 2 2.5 537 5 7.9

MAX 310 5 4.0 437 3 3.5 787 12 25

MIN 190 1 .68 300 1 .89 421 3 3.4
48 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2009 through 

September 2010.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 793 8 17 1,890 6 31 3,170 16 137

2 778 7 15 1,830 4 20 3,510 22 208

3 769 7 15 1,810 5 24 3,940 30 319

4 745 6 12 1,850 6 30 4,360 39 459

5 725 5 9.8 1,800 5 24 4,670 38 479

6 747 5 10 1,760 5 24 4,780 37 478

7 743 5 10 1,700 5 23 4,640 30 376

8 724 4 7.8 1,650 4 18 4,580 26 322

9 699 4 7.5 1,590 4 17 4,420 24 286

10 671 3 5.4 1,490 4 16 e4,250 22 252

11 653 4 7.1 1,450 4 16 e4,140 19 212

12 645 5 8.7 1,440 4 16 4,000 19 205

13 659 4 7.1 1,470 4 16 3,720 18 181

14 727 5 9.8 1,560 5 21 3,530 15 143

15 750 6 12 1,680 7 32 3,460 14 131

16 e750 6 12 1,900 9 46 3,570 14 135

17 e800 7 15 2,270 14 86 3,950 19 203

18 e850 8 18 2,840 25 192 4,290 27 313

19 947 9 23 3,540 36 344 4,200 30 340

20 1,080 11 32 4,050 42 459 4,040 26 284

21 1,380 22 82 4,000 34 367 4,200 29 329

22 1,950 34 179 3,650 30 296 4,180 24 271

23 2,560 41 283 3,300 24 214 4,020 22 239

24 2,740 28 207 3,030 16 131 3,820 17 175

25 2,560 15 104 2,840 12 92 3,640 13 128

26 2,320 11 69 2,680 12 87 3,440 12 111

27 2,120 8 46 2,580 10 70 3,250 10 88

28 2,080 8 45 2,930 16 127 3,030 10 82

29 2,060 6 33 3,200 16 138 2,830 10 76

30 1,950 5 26 3,170 17 146 2,860 13 100

31 -- -- -- 3,110 17 143 -- -- --

TOTAL 36,975 -- 1,328.2 74,060 -- 3,266 116,490 -- 7,062

MEAN 1,232 10 44 2,389 13 105 3,883 22 235

MAX 2,740 41 283 4,050 42 459 4,780 39 479

MIN 645 3 5.4 1,440 4 16 2,830 10 76
Data 49

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana, October 2009 through 

September 2010.—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 2,970 14 112 805 4 8.7 640 4 6.9

2 2,730 10 74 803 5 11 679 4 7.3

3 2,530 8 55 789 5 11 665 4 7.2

4 2,380 8 51 761 5 10 648 4 7.0

5 2,230 7 42 740 5 10 635 5 8.6

6 2,150 6 35 713 5 9.6 628 4 6.8

7 2,040 5 28 688 5 9.3 617 4 6.7

8 1,890 5 26 672 5 9.1 606 4 6.5

9 1,760 4 19 667 5 9.0 627 4 6.8

10 1,670 4 18 685 4 7.4 708 6 11

11 1,600 4 17 714 4 7.7 752 6 12

12 1,540 4 17 708 4 7.6 707 4 7.6

13 1,460 3 12 799 4 8.6 674 4 7.3

14 1,430 3 12 869 9 21 650 4 7.0

15 1,370 4 15 835 9 20 638 4 6.9

16 1,280 4 14 786 7 15 631 4 6.8

17 1,200 13 42 749 6 12 641 3 5.2

18 1,120 4 12 702 6 11 641 3 5.2

19 1,070 2 5.8 660 5 8.9 642 3 5.2

20 1,020 2 5.5 644 5 8.7 633 3 5.1

21 992 2 5.4 636 4 6.9 630 3 5.1

22 974 1 2.6 630 4 6.8 634 2 3.4

23 925 1 2.5 618 4 6.7 624 3 5.1

24 902 2 4.9 615 5 8.3 608 3 4.9

25 876 2 4.7 599 4 6.5 597 3 4.8

26 853 2 4.6 590 3 4.8 588 3 4.8

27 828 2 4.5 600 3 4.9 578 3 4.7

28 830 3 6.7 593 3 4.8 569 3 4.6

29 825 3 6.7 591 3 4.8 559 2 3.0

30 785 3 6.4 610 3 4.9 551 2 3.0

31 771 3 6.2 617 3 5.0 -- -- --

TOTAL 45,001 -- 667.5 21,488 -- 280.0 19,000 -- 186.5

MEAN 1,452 4 22 693 5 9.0 633 4 6.2

MAX 2,970 14 112 869 9 21 752 6 12

MIN 771 1 2.5 590 3 4.8 551 2 3.0

Total for water year 2010 (unrounded sum of daily values): streamflow–391,316 ft3/s (annual runoff–776,200 acre-ft); suspended-sediment 

 discharge–13,371.87 tons.
50 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2009 through 

September 2010.

[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 1,270 30 103 1,810 8 39 1,460 2 7.9

2 1,320 13 46 1,810 7 34 1,350 3 11

3 1,330 6 22 1,750 5 24 e950 22 56

4 1,350 6 22 1,720 5 23 e900 69 168

5 1,360 6 22 1,680 5 23 e930 58 146

6 1,410 7 27 1,670 5 23 e900 48 117

7 1,460 8 32 1,680 4 18 e850 40 92

8 1,510 9 37 1,650 4 18 e750 39 79

9 1,590 9 39 1,630 4 18 e600 40 65

10 1,590 8 34 1,590 4 17 e640 40 69

11 1,540 7 29 1,590 4 17 e700 38 72

12 1,480 7 28 1,610 4 17 e800 30 65

13 1,540 6 25 1,600 3 13 e900 20 49

14 1,600 7 30 1,500 3 12 e1,000 14 38

15 1,650 10 45 1,480 3 12 e1,000 13 35

16 1,660 10 45 1,460 3 12 e1,100 13 39

17 1,640 9 40 1,510 3 12 e1,200 12 39

18 1,640 9 40 1,540 3 12 e1,200 12 39

19 1,640 10 44 1,530 3 12 e1,300 12 42

20 1,720 12 56 1,480 3 12 e1,300 28 98

21 1,820 17 84 1,520 3 12 e1,400 54 204

22 1,770 15 72 1,500 3 12 e1,400 22 83

23 1,720 12 56 1,450 3 12 e1,400 7 26

24 1,730 10 47 1,470 3 12 1,400 5 19

25 1,730 8 37 1,470 3 12 e1,300 5 18

26 1,710 7 32 1,480 3 12 e1,200 5 16

27 1,680 6 27 1,480 3 12 e1,000 4 11

28 1,690 5 23 1,480 3 12 e950 8 21

29 1,680 4 18 1,470 2 7.9 e1,000 52 140

30 1,670 4 18 1,450 2 7.8 e1,000 46 124

31 1,740 5 23 -- -- -- e1,100 24 71

TOTAL 49,240 -- 1,203 47,060 -- 479.7 32,980 -- 2,059.9

MEAN 1,588 9 39 1,569 4 16 1,064 25 66

MAX 1,820 30 103 1,810 8 39 1,460 69 204

MIN 1,270 4 18 1,450 2 7.8 600 2 7.9
Data 51

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e1,200 11 36 1,190 5 16 1,250 11 37

2 e1,200 8 26 1,180 4 13 1,270 13 45

3 e1,200 7 23 1,180 4 13 1,250 16 54

4 e1,300 6 21 1,150 4 12 1,340 18 65

5 e1,300 4 14 1,120 3 9.1 1,420 21 81

6 e1,200 4 13 1,160 3 9.4 1,400 19 72

7 e900 5 12 1,190 4 13 1,390 15 56

8 e950 10 26 1,160 4 13 1,400 13 49

9 e1,000 23 62 1,140 4 12 1,460 17 67

10 e1,200 40 130 1,120 4 12 1,430 14 54

11 e1,200 57 185 1,160 5 16 1,320 8 29

12 e1,200 61 198 1,180 6 19 1,270 8 27

13 e1,300 54 190 1,200 6 19 1,320 9 32

14 e1,300 31 109 1,200 7 23 1,370 10 37

15 e1,300 12 42 1,210 7 23 1,360 11 40

16 1,300 6 21 1,220 8 26 1,390 11 41

17 1,300 4 14 1,200 8 26 1,420 13 50

18 1,290 4 14 1,210 8 26 1,530 30 124

19 1,280 5 17 1,190 8 26 1,540 29 121

20 1,280 7 24 1,140 8 25 1,440 15 58

21 1,230 8 27 1,050 7 20 1,380 12 45

22 1,190 7 22 945 7 18 1,420 13 50

23 1,190 6 19 979 8 21 1,500 18 73

24 1,180 4 13 1,070 8 23 1,440 15 58

25 1,170 3 9.5 1,210 9 29 1,400 11 42

26 1,160 3 9.4 1,190 9 29 1,400 11 42

27 1,210 3 9.8 1,160 9 28 1,410 12 46

28 1,180 3 9.6 1,200 10 32 1,400 12 45

29 1,160 3 9.4 -- -- -- 1,450 13 51

30 1,130 4 12 -- -- -- 1,700 21 96

31 1,180 4 13 -- -- -- 1,800 23 112

TOTAL 37,180 -- 1,330.7 32,304 -- 551.5 43,870 -- 1,799

MEAN 1,199 13 43 1,154 6 20 1,415 15 58

MAX 1,300 61 198 1,220 10 32 1,800 30 124

MIN 900 3 9.4 945 3 9.1 1,250 8 27

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2009 through 

September 2010.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]
52 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

APRIL MAY JUNE

1 1,740 16 75 3,360 11 100 5,740 46 713

2 1,680 12 54 3,250 10 88 6,430 85 1,480

3 1,640 13 58 3,160 12 102 7,170 135 2,610

4 1,610 11 48 3,190 10 86 8,390 238 5,390

5 1,550 10 42 3,120 9 76 9,060 225 5,500

6 1,570 9 38 3,000 8 65 9,420 163 4,150

7 1,560 9 38 2,920 7 55 9,180 123 3,050

8 1,540 8 33 2,820 6 46 9,530 114 2,930

9 1,520 7 29 2,750 8 59 9,120 111 2,730

10 1,460 6 24 2,630 10 71 8,700 67 1,570

11 1,430 8 31 2,550 9 62 8,390 57 1,290

12 1,430 8 31 2,540 8 55 8,460 66 1,510

13 1,480 8 32 2,540 8 55 7,780 53 1,110

14 1,610 9 39 2,570 9 62 7,200 39 758

15 1,650 13 58 2,690 9 65 6,970 38 715

16 1,720 14 65 2,990 11 89 7,640 56 1,160

17 1,780 16 77 3,480 17 160 8,940 114 2,750

18 1,910 21 108 4,290 29 336 10,100 140 3,820

19 2,080 24 135 5,360 54 781 10,000 104 2,810

20 2,290 29 179 6,330 76 1,300 9,530 91 2,340

21 2,760 57 425 6,440 68 1,180 9,440 77 1,960

22 3,640 87 855 5,950 48 771 9,290 62 1,560

23 4,540 92 1,130 5,430 34 498 8,760 47 1,110

24 4,760 68 874 5,040 24 327 8,220 40 888

25 4,460 41 494 4,830 20 261 7,850 38 805

26 4,070 27 297 4,600 20 248 7,520 34 690

27 3,760 22 223 4,430 19 227 7,140 32 617

28 3,690 19 189 4,900 22 291 6,650 28 503

29 3,700 17 170 5,650 41 625 6,170 25 416

30 3,510 14 133 5,800 60 940 6,140 27 448

31 -- -- -- 5,620 49 744 -- -- --

TOTAL 72,140 -- 5,984 124,230 -- 9,825 244,930 -- 57,383

MEAN 2,405 23 199 4,007 23 317 8,164 82 1,910

MAX 4,760 92 1,130 6,440 76 1,300 10,100 238 5,500

MIN 1,430 6 24 2,540 6 46 5,740 25 416

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2009 through 

September 2010.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]
Data 53

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JULY AUGUST SEPTEMBER

1 6,210 26 436 1,940 5 26 1,560 4 17

2 5,870 21 333 1,920 6 31 1,620 7 31

3 5,420 19 278 1,870 5 25 1,600 5 22

4 5,090 18 247 1,800 5 24 1,560 4 17

5 4,800 15 194 1,740 5 23 1,560 3 13

6 4,550 12 147 1,730 5 23 1,560 4 17

7 4,290 11 127 1,720 5 23 1,560 4 17

8 4,040 11 120 1,710 5 23 1,550 5 21

9 3,760 10 102 1,680 5 23 1,580 5 21

10 3,530 9 86 1,730 5 23 1,870 14 71

11 3,410 8 74 1,790 5 24 2,050 17 94

12 3,320 7 63 1,840 5 25 1,950 10 53

13 3,170 6 51 1,960 7 37 1,850 9 45

14 3,050 5 41 2,080 11 62 1,790 9 43

15 2,940 4 32 2,020 10 55 1,750 10 47

16 2,820 4 30 1,930 8 42 1,770 10 48

17 2,680 4 29 1,860 7 35 1,800 11 53

18 2,540 4 27 1,750 6 28 1,810 11 54

19 2,430 4 26 1,670 6 27 1,780 13 62

20 2,360 4 25 1,610 5 22 1,760 16 76

21 2,290 4 25 1,570 5 21 1,770 18 86

22 2,240 4 24 1,530 5 21 1,760 16 76

23 2,190 4 24 1,510 5 20 1,730 14 65

24 2,130 4 23 1,530 6 25 1,690 10 46

25 2,070 4 22 1,510 6 24 1,660 7 31

26 2,020 4 22 1,480 6 24 1,620 6 26

27 2,000 4 22 1,460 5 20 1,590 6 26

28 2,030 4 22 1,420 4 15 1,550 6 25

29 2,060 4 22 1,400 4 15 1,530 7 29

30 1,960 4 21 1,470 3 12 1,490 7 28

31 1,900 4 21 1,510 3 12 -- -- --

TOTAL 99,170 -- 2,716 52,740 -- 810 50,720 -- 1,260

MEAN 3,199 8 88 1,701 6 26 1,691 9 42

MAX 6,210 26 436 2,080 11 62 2,050 18 94

MIN 1,900 4 21 1,400 3 12 1,490 3 13

Total for water year 2010 (unrounded sum of daily values): streamflow–886,564 ft3/s (annual runoff–1,758,000 acre-ft); suspended-sediment 

 discharge–85,401.8 tons.

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 2009 through 

September 2010.—Continued

[Abbreviations: acre-ft, acre-feet; ft3/s, cubic feet per second; e, estimated; max, maximum; mg/L, milligrams per liter; min, minimum; ton/d, tons per day. 

Symbol: --, no data or value not computed]
54 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 9. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Mill Creek near Anaconda, 

Montana, April through September 2010.

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbol: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 -- -- -- 8.0 4.0 5.5 9.0 3.5 5.0

2 -- -- -- 7.5 4.5 5.5 7.0 3.0 4.5

3 -- -- -- 9.0 5.0 6.5 18 6.5 10

4 -- -- -- 9.0 5.0 6.0 16 6.0 9.0

5 -- -- -- 8.0 4.5 6.0 10 4.5 6.5

6 -- -- -- 11 5.0 6.5 6.5 2.5 4.0

7 -- -- -- -- -- 7.0 9.5 5.0 6.5

8 -- -- -- -- -- -- 8.5 3.0 4.5

9 -- -- -- -- -- -- 5.0 2.0 3.0

10 -- -- -- -- -- -- 3.5 1.5 2.5

11 -- -- -- -- -- -- 3.5 1.5 2.0

12 -- -- -- -- -- -- 3.0 1.5 2.0

13 -- -- -- -- -- -- 4.5 1.0 2.0

14 -- -- -- -- -- -- 5.0 1.5 2.5

15 -- -- -- -- -- -- 12 4.5 6.5

16 -- -- -- -- -- -- 29 10 20

17 -- -- -- -- -- -- 18 8.5 11

18 -- -- -- -- -- -- 13 6.5 7.5

19 -- -- -- -- -- 7.0 8.0 5.5 6.5

20 -- -- -- 9.5 3.5 5.0 7.0 5.0 6.0

21 -- -- -- 5.0 2.0 3.0 6.5 4.5 5.0

22 -- -- -- 6.5 1.5 2.5 7.5 4.0 4.5

23 16 5.0 7.5 5.0 1.5 2.5 5.5 3.5 4.0

24 9.5 4.0 5.5 5.0 2.0 3.0 6.0 3.0 4.0

25 6.0 4.0 5.0 4.0 1.5 2.0 6.0 3.5 4.5

26 5.5 3.5 4.5 4.5 1.5 2.0 5.5 3.0 4.0

27 7.0 3.5 4.5 7.5 1.5 2.5 5.5 3.0 4.0

28 7.0 4.0 5.0 12 3.0 7.0 4.5 2.5 3.5

29 8.0 4.5 5.5 7.0 3.5 5.0 8.0 2.5 4.0

30 8.0 4.5 5.5 5.5 3.5 4.5 11 3.5 6.0

31 -- -- -- 8.5 3.0 4.5 -- -- --

MONTH1 16 3.5 5.4 12 1.5 4.7 29 1.0 5.5
Data 55

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 5.5 3.0 4.0 4.0 1.0 1.5 -- -- --

2 4.5 3.0 3.5 4.0 .5 1.5 -- -- 1.5

3 6.0 3.0 3.5 5.5 .5 1.5 4.5 1.0 2.0

4 5.5 3.0 3.5 3.0 1.0 1.5 4.5 1.0 2.0

5 4.0 2.5 3.0 26 .5 5.5 4.5 2.0 2.5

6 3.5 2.5 3.0 12 1.5 3.5 4.5 2.0 3.0

7 5.0 2.0 3.0 3.0 .5 1.5 6.5 2.5 3.0

8 3.5 2.0 2.5 2.5 1.0 1.5 5.5 2.5 3.0

9 6.0 1.5 2.5 3.0 1.0 1.5 28 3.5 9.5

10 5.5 2.0 2.5 3.5 1.0 2.0 5.0 1.5 2.5

11 3.5 1.5 2.0 3.5 1.0 2.0 4.0 1.5 2.0

12 3.0 1.5 2.0 2.5 1.0 1.5 5.5 1.5 2.5

13 4.0 1.5 2.0 3.5 1.0 1.5 5.5 2.0 2.5

14 4.5 1.5 2.0 4.0 .5 1.5 7.5 2.0 3.0

15 4.5 1.0 2.0 3.5 .5 1.5 8.0 2.5 3.5

16 3.5 1.5 2.0 3.5 .5 1.5 6.5 2.5 3.0

17 3.5 1.0 2.0 3.5 .5 1.5 4.5 2.5 3.5

18 3.0 1.0 1.5 4.0 .5 1.5 5.5 2.5 3.5

19 3.5 1.0 2.0 5.5 1.0 2.0 5.0 2.5 3.0

20 3.0 1.0 2.0 6.5 1.5 2.5 6.0 2.5 3.5

21 3.5 1.0 2.0 4.5 1.5 2.5 5.0 2.5 3.5

22 3.0 1.0 1.5 5.0 2.0 2.5 5.0 3.0 3.5

23 3.0 1.0 1.5 7.5 2.0 3.0 4.5 2.5 3.5

24 3.5 1.0 1.5 7.0 2.5 4.0 6.5 3.0 4.0

25 4.0 1.0 2.0 7.5 3.5 5.0 4.5 3.5 4.0

26 3.5 1.0 1.5 6.0 2.5 3.5 7.5 3.5 4.0

27 3.0 1.0 1.5 4.0 2.0 3.0 7.5 4.0 5.0

28 2.5 1.0 1.5 6.0 2.5 3.0 -- -- --

29 3.0 1.0 1.5 -- -- 3.5 -- -- --

30 3.5 1.0 2.0 -- -- -- -- -- --

31 4.0 1.0 2.0 -- -- -- -- -- --

MONTH1 6.0 1.0 2.2 26 .5 2.4 28 1.0 3.3

1

For months with missing daily values, the means are calculated using available values.

Table 9. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Mill Creek near Anaconda, 

Montana, April through September 2010.—Continued

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbol: --, no data]
56 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 10. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Willow Creek near Anaconda, 

Montana, April through September 2010.

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 -- -- -- 9.0 7.0 8.0 29 15 20

2 -- -- -- 8.0 6.5 7.0 32 13 17

3 -- -- -- 8.0 6.5 7.0 -- -- 17

4 -- -- -- 7.0 6.0 6.5 -- -- --

5 -- -- -- 8.5 6.0 6.5 25 12 14

6 -- -- -- 8.0 6.0 6.5 31 12 15

7 -- -- -- 8.5 5.5 6.0 36 11 17

8 -- -- -- 6.5 5.5 6.0 26 10 15

9 -- -- -- 6.5 5.0 5.5 17 9.0 11

10 -- -- -- 8.0 5.0 5.5 12 8.5 9.5

11 -- -- -- 8.0 5.0 5.5 10 8.0 8.5

12 -- -- -- 6.5 5.0 5.5 10 8.0 8.5

13 -- -- -- 7.0 5.5 6.0 10 7.0 8.5

14 -- -- -- 7.5 5.5 6.5 11 7.5 9.0

15 -- -- -- 8.0 5.5 6.5 12 9.0 10

16 -- -- -- 9.5 6.0 7.0 37 9.5 18

17 -- -- -- 10 6.5 8.0 34 18 24

18 -- -- -- 11 7.0 8.5 30 20 23

19 -- -- -- 13 8.0 9.5 23 17 19

20 -- -- -- 12 8.0 9.5 24 14 17

21 -- -- -- 11 7.5 9.0 18 13 14

22 -- -- -- 9.0 7.0 7.5 17 12 13

23 25 15 18 9.5 6.5 7.5 14 11 12

24 17 13 14 13 6.5 9.0 13 10 11

25 15 11 12 11 7.0 8.5 12 10 11

26 12 10 11 12 9.5 10 12 9.0 10

27 12 9.5 10 -- -- 15 11 8.5 9.0

28 12 8.5 9.0 -- -- -- 14 8.0 9.5

29 10 8.0 8.5 -- -- -- -- -- 9.5

30 9.5 7.5 8.0 41 21 28 -- -- 9.5

31 -- -- -- 42 18 25 -- -- --

MONTH1 25 7.5 11 42 5.0 8.8 37 7.0 13
Data 57

Table 10. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Willow Creek near Anaconda, 

Montana, April through September 2010.—Continued

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 -- -- 8.5 7.0 2.0 3.0 4.5 2.5 3.0

2 -- -- 8.0 7.5 1.5 3.5 5.0 2.0 3.0

3 -- -- 8.0 5.0 1.5 2.5 4.0 2.5 3.0

4 -- -- 6.5 5.5 2.0 2.5 7.0 2.5 3.0

5 -- -- -- -- -- 5.5 4.0 2.0 3.0

6 8.0 6.0 6.5 -- -- -- 4.0 2.0 2.5

7 7.5 5.5 6.5 -- -- -- 6.0 2.0 3.0

8 7.0 5.5 6.0 -- -- -- 7.0 3.0 4.0

9 -- -- -- -- -- -- 79 3.5 20

10 -- -- -- -- -- 8.5 26 4.5 8.5

11 -- -- -- 18 6.5 11 7.0 3.5 5.0

12 -- -- -- 8.0 5.5 6.5 7.0 3.5 4.0

13 -- -- -- -- -- 6.5 6.0 3.0 4.0

14 -- -- -- 8.0 4.5 5.5 6.0 3.5 4.5

15 -- -- -- 7.5 4.5 5.5 40 4.5 14

16 -- -- -- 6.0 4.0 5.0 7.5 4.0 5.5

17 -- -- -- 6.0 4.0 4.5 6.0 4.0 4.5

18 -- -- -- 6.0 4.0 4.5 6.0 3.5 4.5

19 -- -- 3.0 9.0 3.5 4.5 6.5 3.5 4.0

20 8.0 1.5 3.5 9.0 3.5 5.0 5.5 3.0 4.0

21 8.5 2.0 3.5 7.5 3.5 4.0 6.0 3.0 4.0

22 9.0 1.5 3.5 4.5 3.5 4.0 5.0 3.0 3.5

23 5.5 2.0 3.0 7.0 3.5 4.5 5.5 2.5 4.0

24 4.5 2.0 2.5 6.5 3.0 4.0 6.0 3.0 4.0

25 4.5 2.0 2.5 7.0 3.0 4.0 6.5 3.0 4.5

26 6.0 2.0 2.5 8.0 3.0 4.0 8.0 3.0 4.5

27 6.5 2.0 3.0 6.0 3.0 4.0 -- -- 5.0

28 4.0 2.0 2.5 5.5 3.0 3.5 10 3.5 5.5

29 5.0 2.0 2.5 5.0 3.0 3.5 10 2.5 4.5

30 4.5 2.0 2.5 7.0 3.0 4.0 -- -- 3.0

31 6.0 1.5 3.0 4.5 2.5 3.5 -- -- --

MONTH1 9.0 1.5 4.4 18 1.5 4.7 79 2.0 5.0

1

For months with missing daily values, the means are calculated using available values.
58 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 11. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Warm Springs Creek near 

Anaconda, Montana, April through September 2010.

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 -- -- -- 3.5 2.0 3.0 14 5.0 7.5

2 -- -- -- 4.5 2.0 2.5 -- -- --

3 -- -- -- 29 2.0 4.0 -- -- --

4 -- -- -- 4.5 2.0 3.0 -- -- --

5 -- -- -- -- -- -- -- -- --

6 -- -- -- -- -- -- -- -- --

7 -- -- -- -- -- -- -- -- --

8 -- -- -- 3.0 2.0 2.5 -- -- 11

9 -- -- -- 4.0 2.5 3.0 11 6.0 8.5

10 -- -- -- 3.5 2.0 2.5 8.5 5.5 6.5

11 -- -- -- 18 3.0 5.5 6.5 4.5 5.5

12 -- -- -- 9.0 3.0 4.0 6.5 4.0 5.0

13 -- -- -- 4.5 2.5 3.5 5.5 3.5 4.5

14 -- -- -- 4.5 2.0 3.0 8.0 4.0 5.0

15 -- -- -- 4.5 2.5 3.0 22 8.0 13

16 -- -- -- 5.5 2.5 3.5 -- -- --

17 -- -- -- 8.0 3.5 5.0 -- -- --

18 -- -- -- 14 6.5 10 -- -- 7.5

19 -- -- -- -- -- -- 10 5.5 6.5

20 -- -- -- -- -- -- 8.0 5.0 6.0

21 -- -- -- -- -- 5.0 9.0 5.5 6.5

22 -- -- 5.5 7.5 3.0 4.5 10 5.0 6.0

23 8.0 3.5 4.5 5.0 3.0 3.5 9.5 4.5 5.5

24 6.5 3.0 4.0 39 3.5 7.0 23 5.5 7.5

25 4.5 2.5 3.5 5.5 3.0 3.5 9.5 5.5 7.5

26 6.5 2.5 3.5 4.0 2.5 3.0 9.5 5.5 7.0

27 15 2.5 3.5 36 3.0 5.0 15 5.5 7.0

28 8.5 3.0 4.0 47 5.5 11 8.0 5.0 6.0

29 4.0 2.5 3.0 6.5 4.0 5.0 12 5.5 7.0

30 3.5 2.5 3.0 5.5 3.5 4.0 15 7.0 10

31 -- -- -- 9.5 3.5 4.5 -- -- --

MONTH1 15 2.5 3.8 47 2.0 4.4 23 3.5 7.1
Data 59

Table 11. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Warm Springs Creek near 

Anaconda, Montana, April through September 2010.—Continued

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 9.5 5.5 7.0 4.0 3.0 3.5 7.0 3.0 3.5

2 12 5.0 6.0 7.5 3.0 4.0 6.0 3.0 3.5

3 6.5 4.5 5.5 13 5.5 6.5 4.0 2.5 3.0

4 5.5 4.5 5.0 8.0 3.5 6.0 3.5 2.5 3.0

5 6.0 4.0 4.5 69 3.0 8.5 4.5 2.5 3.0

6 6.0 4.0 4.5 -- -- 6.0 3.5 2.5 3.0

7 6.0 3.5 4.5 -- -- -- 4.0 2.5 3.0

8 5.5 4.0 4.0 -- -- 4.0 4.5 2.5 3.5

9 7.0 3.5 4.0 6.5 3.0 4.0 34 2.5 9.5

10 7.0 3.5 4.5 7.0 3.0 3.5 8.5 3.5 5.5

11 6.0 3.5 4.0 8.0 3.0 4.5 4.5 3.5 4.0

12 5.5 3.5 4.0 4.5 3.0 3.5 5.0 3.0 3.5

13 -- -- 4.0 9.0 3.0 4.0 5.5 3.0 3.5

14 -- -- 3.5 4.0 3.0 3.5 13 3.0 4.5

15 6.0 3.0 3.5 4.5 3.0 3.5 10 2.5 6.5

16 6.5 3.5 4.5 4.0 3.0 3.5 5.5 3.0 3.5

17 8.5 3.0 6.0 5.0 3.0 3.5 6.0 3.0 3.5

18 8.5 3.0 3.5 6.0 3.0 3.5 5.0 3.0 3.5

19 6.0 3.0 3.5 7.0 3.0 4.0 5.0 3.0 3.5

20 -- -- 4.5 5.0 3.0 3.5 5.0 3.0 3.0

21 -- -- -- 4.5 3.0 3.0 3.5 3.0 3.0

22 -- -- 4.0 36 2.5 4.5 3.5 3.0 3.0

23 -- -- 5.0 5.5 3.0 4.0 5.0 3.0 3.0

24 -- -- -- 6.5 3.0 3.5 5.5 3.0 3.0

25 -- -- -- 5.5 3.0 3.5 7.0 3.0 4.5

26 8.0 3.0 3.5 4.5 2.5 3.0 8.5 3.0 5.0

27 7.0 3.0 3.5 -- -- 3.0 -- -- 7.0

28 4.0 3.0 3.5 -- -- 3.5 -- -- 7.0

29 4.0 3.0 3.5 9.0 3.0 3.5 8.5 3.5 5.5

30 4.5 3.0 3.5 7.5 3.0 3.5 19 3.5 7.0

31 5.0 3.0 3.5 5.5 3.0 3.5 -- -- --

MONTH1 12 3.0 4.3 69 2.5 4.0 34 2.5 4.2

1

For months with missing daily values, the means are calculated using available values.
60 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 12. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Lost Creek near Anaconda, 

Montana, April through September 2010.

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE

1 -- -- -- 5.0 3.0 3.5 29 10 17

2 -- -- -- 8.5 3.0 4.0 26 13 18

3 -- -- -- 7.0 3.5 5.0 47 25 34

4 -- -- -- 7.0 3.0 4.0 35 14 22

5 -- -- -- 7.0 3.0 4.0 38 17 23

6 -- -- -- 4.0 2.5 3.5 23 11 15

7 -- -- -- 4.5 3.0 3.5 21 11 14

8 -- -- -- 5.0 3.0 3.5 21 10 14

9 -- -- -- 4.5 3.0 3.5 15 8.0 10

10 -- -- -- 5.0 3.0 3.5 14 7.5 9.0

11 -- -- -- 7.5 3.0 4.5 9.5 7.0 8.0

12 -- -- -- 6.0 3.0 4.0 8.5 6.0 7.5

13 -- -- -- 8.0 3.0 5.0 9.0 6.0 7.0

14 -- -- -- 7.5 3.5 4.5 9.5 5.0 7.0

15 -- -- -- 8.5 4.0 5.5 18 8.0 11

16 -- -- -- 8.5 4.5 6.0 64 13 29

17 -- -- -- 11 5.0 7.5 31 12 18

18 -- -- -- 24 7.5 13 14 9.5 12

19 -- -- -- 31 14 21 15 9.0 11

20 -- -- -- 28 9.0 15 12 7.0 9.0

21 -- -- -- 12 6.5 8.5 16 6.5 8.5

22 -- -- 7.5 12 5.5 8.0 14 6.0 8.0

23 10 4.5 6.5 26 5.5 8.0 13 6.0 8.0

24 8.5 4.0 5.0 9.0 5.5 7.0 10 5.5 7.5

25 8.5 3.5 4.5 10 4.5 6.0 9.5 5.0 6.5

26 6.0 3.5 4.0 11 4.0 5.5 10 5.0 6.5

27 8.5 3.0 4.0 24 4.5 9.0 11 5.0 6.5

28 6.0 3.5 4.5 26 9.0 16 7.5 5.0 6.0

29 5.0 3.0 3.5 13 7.0 9.0 9.0 4.5 6.0

30 4.5 3.0 3.5 8.5 6.0 7.0 9.5 4.0 6.0

31 -- -- -- 14 5.5 7.0 -- -- --

MONTH1 10 3.0 4.8 31 2.5 6.9 64 4.0 12
Data 61

Table 12. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Lost Creek near Anaconda, 

Montana, April through September 2010.—Continued

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 +/- 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). Symbols: <, less than; --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 9.5 4.0 5.5 3.0 1.5 2.0 3.0 2.0 2.0

2 7.0 4.0 4.5 3.0 1.5 2.0 9.5 2.0 2.5

3 6.0 3.5 4.5 5.0 2.0 2.5 4.0 1.5 2.5

4 7.5 3.5 4.5 5.0 2.0 2.5 2.5 1.5 2.0

5 5.5 3.5 4.0 4.5 1.5 2.5 2.5 1.5 2.0

6 5.5 3.0 4.0 3.5 1.5 2.0 2.0 1.5 2.0

7 8.0 3.0 4.0 3.0 1.5 2.0 2.0 1.0 1.5

8 8.0 3.0 4.5 28 1.5 3.5 1.5 1.0 1.0

9 5.0 3.0 3.5 6.5 2.5 3.5 41 1.0 7.5

10 5.0 2.5 3.5 5.5 2.0 3.0 2.5 1.5 2.0

11 5.0 2.5 3.5 6.5 2.0 3.0 2.0 1.5 1.5

12 4.0 2.5 3.0 3.5 2.0 2.5 2.0 1.5 1.5

13 4.0 2.0 3.0 4.0 2.5 3.0 2.0 1.5 1.5

14 4.0 2.0 2.5 4.5 2.0 2.5 2.5 1.5 1.5

15 4.0 2.0 2.5 4.0 2.0 2.5 2.0 1.5 1.5

16 5.0 2.0 2.5 3.5 2.0 2.5 3.5 1.5 2.0

17 4.0 2.0 2.5 4.0 2.0 2.5 3.5 1.5 2.5

18 3.0 1.5 2.5 4.0 2.0 2.5 2.0 1.5 1.5

19 5.0 2.0 2.5 5.0 2.0 2.5 1.5 1.5 1.5

20 4.5 2.0 2.5 5.0 2.0 2.5 2.0 1.5 1.5

21 3.5 2.0 2.5 6.0 2.0 3.0 1.5 1.0 1.0

22 3.5 2.0 2.5 3.5 2.0 2.5 1.5 1.0 1.0

23 3.5 2.0 2.5 5.0 2.0 3.0 1.5 1.0 1.0

24 3.5 2.0 2.5 5.0 2.0 3.0 1.5 1.0 1.0

25 3.5 2.0 2.5 4.0 2.0 2.5 2.0 1.0 1.0

26 3.5 1.5 2.5 9.5 2.0 3.0 2.0 1.0 1.5

27 3.5 2.0 2.5 4.0 2.0 2.5 1.5 1.0 1.0

28 2.5 1.5 2.0 2.5 1.5 2.0 1.5 1.0 1.0

29 2.5 1.5 2.0 3.0 1.5 2.0 1.5 1.0 1.0

30 3.0 1.5 2.0 4.0 1.5 2.0 1.0 .5 1.0

31 2.5 1.5 2.0 2.5 2.0 2.0 -- -- --

MONTH1 9.5 1.5 3.1 28 1.5 2.5 41 .5 1.7

1

For months with missing daily values, the means are calculated using available values.
Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.[Abbreviations: E, estimated; μg/L, 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)

Ar

unf

reco

(μ

12323700 Mill Creek at Opportunity 08/24/2010 0800 70.6 19.8 5.16 16.9 18

08/24/2010 0805 71.6 20.0 5.25 17.3 18

12323750 Silver Bow Creek at Warm Springs 07/20/2010 0810 144 44.2 8.19 32.0 34

07/20/2010 0815 147 45.2 8.29 32.5 34

12323840 Lost Creek near Anaconda 04/12/2010 1330 103 31.2 6.17 1.8 2

04/12/2010 1335 105 31.8 6.26 1.8 2

12324200 Clark Fork at Deer Lodge 05/19/2010 1325 190 56.8 11.6 11.8 13

05/19/2010 1330 189 56.8 11.4 12.0 13

12324400 Clark Fork above Little Blackfoot, 

near Garrison

03/09/2010 1530 198 57.3 13.3 10.1 12

03/09/2010 1535 195 56.7 13.1 9.9 12

12324680 Clark Fork at Goldcreek 10/14/2009 1310 193 57.8 11.9 9.5 11

10/14/2009 1315 191 57.0 11.8 9.5 10

12334550 Clark Fork at Turah Bridge, near 

Bonner

06/03/2010 1015 95.8 27.6 6.50 6.5 13

06/03/2010 1020 96.2 27.8 6.52 6.6 12

12340500 Clark Fork above Missoula 06/16/2010 1335 87.8 24.5 6.47 4.6 8

06/16/2010 1340 86.9 24.3 6.39 4.7 8
Site number 

(fig. 1) Site name Date Time

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered (μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

12323700 Mill Creek at Opportunity 08/24/2010 0800 0.07 1.7 2.3 58 117 

08/24/2010 0805 .07 1.7 2.4 59 119 

12323750 Silver Bow Creek at Warm Springs 07/20/2010 0810 .07 6.5 8.7 23 157 

07/20/2010 0815 .07 6.5 8.6 24 152 

12323840 Lost Creek near Anaconda 04/12/2010 1330 <.04 E.95 2.5 E4 51 

04/12/2010 1335 <.04 E.96 2.6 E4 53 

12324200 Clark Fork at Deer Lodge 05/19/2010 1325 .13 6.3 23.9 8 328 

05/19/2010 1330 .12 6.3 23.7 7 336 

12324400 Clark Fork above Little Blackfoot, 

near Garrison

03/09/2010 1530 .16 6.6 29.7 6 459 

03/09/2010 1535 .14 7.1 28.7 7 467 

12324680 Clark Fork at Goldcreek 10/14/2009 1310 .12 3.3 20.4 8 344 

10/14/2009 1315 .12 3.3 20.4 E4 330 

12334550 Clark Fork at Turah Bridge, near 

Bonner

06/03/2010 1015 .33 4.2 57.1 23 1,520 06/03/2010 1020 .32 4.3 55.1 24 1,490 

12340500 Clark Fork above Missoula 06/16/2010 1335 .17 3.9 31.1 18 797 

06/16/2010 1340 .18 4.0 32.3 20 824 

Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.—Continued[Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbol: <, less than laboratory reporting level]
Table 13. Analyses of field replicates for water samples, Clark Fork basin, Montana.—Continued[Abbreviations: E, estimated; μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbol: <, less than laboratory reporting level]

Site number 

(fig. 1) Site name Date Time

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sedi

 susp

(percent 

0.062 

12323700 Mill Creek at Opportunity 08/24/2010 0800 9.3 11.9 E2.0 2.5 8

08/24/2010 0805 9.7 12.0 E2.2 2.5 8

12323750 Silver Bow Creek at Warm Springs 07/20/2010 0810 57.1 97.4 E1.5 6.4 9

07/20/2010 0815 58.2 96.6 E1.4 6.1 8

12323840 Lost Creek near Anaconda 04/12/2010 1330 .6 2.0 <2.8 E1.2 7

04/12/2010 1335 .7 2.1 <2.8 E1.2 7

12324200 Clark Fork at Deer Lodge 05/19/2010 1325 34.6 84.8 3.6 19.7 8

05/19/2010 1330 34.6 88.5 3.7 19.4 8

12324400 Clark Fork above Little Blackfoot, 

near Garrison

03/09/2010 1530 41.7 85.8 2.9 25.3 5

03/09/2010 1535 41.3 83.6 3.1 24.4 6

12324680 Clark Fork at Goldcreek 10/14/2009 1310 10.0 78.6 3.0 20.3 7

10/14/2009 1315 10.1 76.4 4.0 19.7 8

12334550 Clark Fork at Turah Bridge, near 

Bonner

06/03/2010 1015 8.7 188 3.8 74.6 6

06/03/2010 1020 8.7 187 4.2 72.2 6

12340500 Clark Fork above Missoula 06/16/2010 1335 7.1 96.2 3.8 44.3 6

06/16/2010 1340 7.2 90.5 4.1 45.0 6
Data 65

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

[Abbreviations: μg/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter]

Constituent and reporting unit Number of 

replicate pairs

Standard 

deviation1

 (listed units)

Relative standard 

deviation 

(percent)

Within limits2

of data-quality 

objective

Calcium, filtered, mg/L 8 0.39 0.99 Yes

Magnesium, filtered, mg/L 8 .09 1.0 Yes

Arsenic, filtered, μg/L 8 .18 1.5 Yes

Arsenic, unfiltered recoverable, μg/L 8 .19 1.3 Yes

Cadmium, filtered, μg/L 8 .01 11 Yes

Cadmium, unfiltered recoverable, μg/L 8 .01 5.0 Yes

Copper, filtered, μg/L 8 .13 3.1 Yes

Copper, unfiltered recoverable, μg/L 8 .64 2.9 Yes

Iron, filtered, μg/L 8 1.2 6.7 Yes

Iron, unfiltered recoverable, μg/L 8 11 2.4 Yes

Lead, filtered, μg/L 8 .01 12 Yes

Lead, unfiltered recoverable, μg/L 8 .08 2.4 Yes

Manganese, filtered, μg/L 8 .31 1.5 Yes

Manganese, unfiltered recoverable, μg/L 8 1.9 2.4 Yes

Zinc, filtered, μg/L 8 .29 10 Yes

Zinc, unfiltered recoverable, μg/L 8 .69 2.9 Yes

Sediment, suspended, percent finer than 0.062 mm 8 .18 1.5 Yes

Sediment, suspended, mg/L 8 .19 1.3 Yes

1

Standard deviation is calculated using one-half the laboratory reporting level for censored values (less than the laboratory reporting level).

2

Data-quality objective for an acceptable level of precision is a maximum relative standard deviation of 20 percent for field replicate analyses (table 3).

Table 15. Precision of analyses of laboratory replicates for water samples, Clark Fork basin, Montana.

[Abbreviations: μg/L, micrograms per liter; mg/L, milligrams per liter]

Constituent and reporting unit Number of 

replicate pairs

Standard deviation1

, 

in listed units

Relative standard 

deviation, 

in percent

Within limits2

of data-quality 

objective

Calcium, filtered, mg/L 8 0.53 1.3 Yes

Magnesium, filtered, mg/L 8 .16 1.9 Yes

Arsenic, filtered, μg/L 8 .20 1.7 Yes

Arsenic, unfiltered recoverable, μg/L 8 .20 1.4 Yes

Cadmium, filtered, μg/L 8 .01 16 Yes

Cadmium, unfiltered recoverable, μg/L 8 .02 15 Yes

Copper, filtered, μg/L 8 .23 5.3 Yes

Copper, unfiltered recoverable, μg/L 8 .19 .89 Yes

Iron, filtered, μg/L 8 .45 2.3 Yes

Iron, unfiltered recoverable, μg/L 8 2.4 .51 Yes

Lead, filtered, μg/L 8 .00 2.3 Yes

Lead, unfiltered recoverable, μg/L 8 .06 1.9 Yes

Manganese, filtered, μg/L 8 1.1 5.2 Yes

Manganese, unfiltered recoverable, μg/L 8 .56 .70 Yes

Zinc, filtered, μg/L 8 .24 7.1 Yes

Zinc, unfiltered recoverable, μg/L 8 .22 .94 Yes

1

Standard deviation is calculated using laboratory reporting level for censored values.

2

Data-quality objective for an acceptable level of precision is a maximum relative standard deviation of 20 percent for laboratory replicate analyses (table 3).
66 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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

[Abbreviation: μg/L, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent confidence 

interval for spike recovery, 

in percent

Mean spike recovery, 

in percent

Within limits1

of data-quality 

objective

Arsenic, filtered, μg/L 5 96.7–113 105 Yes

Arsenic, unfiltered recoverable, μg/L 5 89.7–114 102 Yes

Cadmium, filtered, μg/L 5 94.9–117 106 Yes

Cadmium, unfiltered recoverable, μg/L 5 88.4–112 100 Yes

Copper, filtered, μg/L 5 84.9–109 97.2 Yes

Copper, unfiltered recoverable, μg/L 5 84.0–113 98.6 Yes

Iron, filtered, μg/L 5 101–115 108 Yes

Iron, unfiltered recoverable, μg/L 5 95.8–108 102 Yes

Lead, filtered, μg/L 5 91.5–113 102 Yes

Lead, unfiltered recoverable, μg/L 5 91.0–113 102 Yes

Manganese, filtered, μg/L 5 95.2–111 103 Yes

Manganese, unfiltered recoverable, μg/L 5 97.2–112 105 Yes

Zinc, filtered, μg/L 5 94.7–132 113 No2

Zinc, unfiltered recoverable, μg/L 5 89.6–113 101 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

2

Exceedance of data-quality objective is an artifact of running the final filtered-zinc spike analysis after extensive instrument maintenance, which reduced a 

high zinc bias. Spikes before and after the maintenance met data-quality objectives, but analytical results may not be comparable to each other due to the small 

number of sample sets.

Table 17. Recovery efficiency for analyses of laboratory-spiked stream samples, Clark Fork basin, Montana.

[Abbreviation: μg/L, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent confidence 

interval for spike recovery, 

in percent

Mean spike recovery, 

in percent

Within limits1

of data-quality 

objective

Arsenic, filtered, μg/L 5 96.0–116 106 Yes

Arsenic, unfiltered recoverable, μg/L 5 90.1–113 102 Yes

Cadmium, filtered, μg/L 5 87.6–132 110 No2

Cadmium, unfiltered recoverable, μg/L 5 87.1–109 98.2 Yes

Copper, filtered, μg/L 5 83.6–104 93.8 Yes

Copper, unfiltered recoverable, μg/L 5 84.4–108 96.5 Yes

Iron, filtered, μg/L 5 91.7–119 105 Yes

Iron, unfiltered recoverable, μg/L 5 103–118 111 Yes

Lead, filtered, μg/L 5 87.7–115 101 Yes

Lead, unfiltered recoverable, μg/L 5 91.5–116 104 Yes

Manganese, filtered, μg/L 5 93.3–114 104 Yes

Manganese, unfiltered recoverable, μg/L 5 86.4–111 98.7 Yes

Zinc, filtered, μg/L 5 101–118 109 Yes

Zinc, unfiltered recoverable, μg/L 5 81.3–107 94.0 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

2

Exceedance of data-quality objective resulted from one spike sample having a percent recovery of 136 percent. When this one spiked sample set is removed, 

filtered cadmium falls within the data-quality objective limit (91.4–121) for the 95-percent confidence interval.
Table 18. Analyses of field blanks for water samples.[Abbreviations: E, estimated; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter. Symbol: <, less than laboratory 

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)

C

u

re

10/13/2009 2100 5.7 2 <0.04 <0.016 <0.04 <0.18 <0.02 03/04/2010 1055 5.5 2 <.04 <.016 <.04 <.18 <.02 04/14/2010 1355 5.8 2 <.04 <.016 <.13 <.18 <.06 05/18/2010 1535 5.8 2 <.04 <.016 <.04 <.18 <.02 06/02/2010 1315 5.6 2 <.04 <.016 <.04 <.18 <.02 06/16/2010 0915 5.6 2 <.04 <.016 <.04 <.18 <.02 07/20/2010 1105 5.9 2 <.04 <.016 <.09 E.09 <.04 

08/24/2010 1320 5.6 2 <.04 <.016 <.04 <.18 <.02 

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) 

10/13/2009 <1.0 <1.4 <6 <9 <0.03 <0.06 <0.3 <0.8 

03/04/2010 <1.0 <1.4 <6 <9 <.03 <.06 <.3 <.8 

04/14/2010 <3.0 <1.4 <6 <9 <.09 <.06 <.8 <.8 

05/18/2010 <1.0 <1.4 <6 <9 <.03 <.06 <.3 <.8 

06/02/2010 <1.0 <1.4 <6 <9 <.03 <.06 <.3 <.8 

06/16/2010 <1.0 <1.4 <6 <9 <.03 <.06 <.3 <.8 

07/20/2010 <2.0 <1.4 <6 <9 <.06 <.06 <.5 <.8 

08/24/2010 <1.0 <1.4 <6 <9 <.03 <.06 <.3 <.8 
Table 19. Bed-sediment data for the Clark Fork basin, Montana, August 2010. [Trace-element concentrations in bed sediment were determined for the fine-grained fraction (material less than 0.063 millimeter in diameter). Reported concentrations are the maliquots from each composite sample. Abbreviation: μg/g, micrograms per gram of dry sample weight] Site number (fig. 1) Site name Number of composite samples Concentration (μg/g) Arsenic Cadmium Chromium Copper Iron Lead Mang

12323600 Silver Bow Creek at Opportunity 3 34 6.8 50.7 837 33,200 181 1,

12323750 Silver Bow Creek at Warm Springs 3 159 7.5 46.8 466 32,500 83 8,2

12323800 Clark Fork near Galen 3 74 3.9 40.0 1,120 25,400 104 1,

461415112450801 Clark Fork below Lost Creek, near Galen 3 102 4.9 38.6 1,450 25,600 131 2,4

461559112443301 Clark Fork at county bridge, near Racetrack 3 118 6.6 44.8 1,810 30,800 175 1,

461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 3 73 4.7 36.3 1,300 26,100 137 1,3

12324200 Clark Fork at Deer Lodge 3 70 3.5 42.9 1,060 26,500 126 1,0

12324400 Clark Fork above Little Blackfoot River, near Garrison 3 81 4.8 45.5 1,290 27,300 145 1,5

12324680 Clark Fork at Goldcreek 3 61 3.7 45.6 967 26,300 115 1,2

12331800 Clark Fork near Drummond 3 55 3.3 40.2 630 41,500 95 2,0

12334550 Clark Fork at Turah Bridge, near Bonner 3 36 2.5 41.9 435 23,500 70 1,2

12340000 Blackfoot River near Bonner 3 3 .05 25.3 18 16,300 10 3

12340500 Clark Fork above Missoula 3 28 2.1 32.5 353 19,500 50 9
Data 69

Table 20. Recovery efficiency for analyses of standard reference materials for bed-sediment samples.

[Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to final volume of solution after 

addition of 0.6N (normal) hydrochloric acid used for reconstituting dried residue. Abbreviations: μg/g, micrograms per gram of dry sample 

weight; SRM, standard reference material (agricultural soils)]

Constituent Number of 

analyses

Dilution 

ratio

Certified 

concentration 

(μg/g)

Mean SRM 

recovery

(percent)

95-percent 

confidence interval 

for SRM recovery 

(percent)

SRM sample 2709a

Arsenic 10 1:10 10.5 66.8 64.9–68.7

Cadmium 10 1:10 .4 81.4 78.0–84.8

Chromium 10 1:10 130 83.0 80.0–85.2

Copper 10 1:10 34 93.0 89.6–96.4

Iron 10 1:10 33,600 95.0 92.8–97.1

Lead 10 1:10 17 67.4 66.0–68.7

Manganese 10 1:10 529 97.5 95.3–99.7

Nickel 10 1:10 85 90.0 88.4–91.6

Zinc 10 1:10 103 103.0 101–105

SRM sample 2711 (2711a)1

Arsenic 10 1:10 105 (107) 82.4 (85.8) 79.8–87.1

Cadmium 10 1:10 41.7 (54.1) 95.4 (98.1) 92.5–99.9

Chromium 10 1:10 47 (52) 87.2 (85.7) 81.8–91.7

Copper 10 1:10 114 (1,410) 104.0 (106.0) 99.3–110

Iron 10 1:10 28,900 (28,200) 87.2 (89.0) 84.0–91.5

Lead 10 1:10 1,160 (1,400) 91.5 (93.0) 88.8–95.2

Manganese 10 1:10 638 (675) 86.7 (86.0) 82.8–90.2

Nickel 10 1:10 20.6 (21.7) 82.7 (89.2) 80.3–89.0

Zinc 10 1:10 350 (414) 97.5 (100.0) 94.5–102

1

SRM 2711 was used for seven samples and SRM 2711a was used for three samples.
Table 21. Analyses of procedural blanks for bed-sediment samples. [Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to final volume of solution after addition of 0.6N (normal) hydrochloric aresidue. Abbreviation: μg/mL, micrograms per milliliter. Symbol: <, less than minimum reporting level for liquid-phase concentration, in μg/mL] Site number (fig. 1) Site name Dilution ratio Trace-element concentration (μg/mL) Arsenic Cadmium Chromium Copper Iron Lead Mangane

12323600 Silver Bow Creek at Opportunity 1:10 <0.004 <0.0002 <0.01 <0.006 <0.06 <0.004 <0.006 

12323750 Silver Bow Creek at Warm Springs 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

12323800 Clark Fork near Galen 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

461415112450801 Clark Fork below Lost Creek, near Galen 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

461559112443301 Clark Fork at county bridge, near Racetrack 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

12324200 Clark Fork at Deer Lodge 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

12324400 Clark Fork above Little Blackfoot River, near Garrison 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

12324680 Clark Fork at Goldcreek 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

12331800 Clark Fork near Drummond 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

12334550 Clark Fork at Turah Bridge, near Bonner 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

12340000 Blackfoot River near Bonner 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 

12340500 Clark Fork above Missoula 1:10 <.004 <.0002 <.01 <.006 <.06 <.004 <.006 
Data 71

Table 22. Biological data for the Clark Fork basin, Montana, August 2010.

[Analyses are for the whole-body tissue of aquatic insects. Composite samples were made by combining similar-sized insects of the same species into a sample 

of sufficient mass for analysis. Concentrations for biota samples composed of two or more composite samples are the means of all analyses. Abbreviations: μg/g, 

micrograms per gram of dry sample weight; spp., species. Symbol: <, less than minimum reporting level for solid-phase concentration, in μg/g]

Taxon

Number of 

composite 

samples

Concentration (μg/g)

Arsenic Cadmium Chromium Copper Iron Lead ManganeseNickel Zinc

12323600--Silver Bow Creek at Opportunity

Hydropsyche cockerelli 1 11.2 7.4 4.9 232 4,960 35.8 788 3.2 741

Hydropsyche spp. 2 6.9 2.5 2.1 111 2,310 19.7 720 1.3 434

12323750--Silver Bow Creek at Warm Springs

Hydropsyche cockerelli 1 9.7 0.7 0.8 34.4 784 2.9 908 1.1 221

Hydropsyche occidentalis 1 15.6 1.0 .9 40.9 1,460 5.9 1,690 1.5 210

12323800--Clark Fork near Galen

Hydropsyche occidentalis 1 9.1 1.3 2.4 84.3 1,490 7.3 991 1.8 189

Hydropsyche spp. 2 5.6 .7 1.2 56.0 938 3.9 687 1.0 138

461415112450801--Clark Fork below Lost Creek, near Galen

Hydropsyche spp. 2 7.2 1.0 1.2 79.5 977 6.1 790 1.1 165

461559112443301--Clark Fork at county bridge, near Racetrack

Hydropsyche occidentalis 1 11.3 2.2 1.7 129 1,590 12.4 1,330 1.8 261

Hydropsyche spp. 2 7.1 1.2 1.0 78.4 907 6.4 984 .8 165

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Hydropsyche occidentalis 2 12.6 1.9 1.6 129 1,890 16.9 1,430 1.4 294

Hydropsyche spp. 2 6.5 1.0 .9 66.2 889 7.6 756 .6 166

12324200--Clark Fork at Deer Lodge

Arctopsyche grandis 1 5.8 4.7 <7.7 77.3 1,090 11.2 946 1.2 369

Hydropsyche occidentalis 2 9.4 2.1 1.7 125 1,740 13.4 945 1.3 231

Hydropsyche spp. 1 6.0 1.6 .8 91.0 1,070 9.0 837 .9 196

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

Arctopsyche grandis 1 5.5 4.9 <2.2 83.6 826 8.1 940 0.8 282

Hydropsyche occidentalis 2 7.9 2.5 1.9 99.8 1,300 11.3 1,220 1.0 232

12324680--Clark Fork at Goldcreek

Arctopsyche grandis 3 5.5 3.1 1.3 68.4 884 6.2 937 <0.2 252

Claassenia sabulosa 3 1.9 1.8 <1.9 58.6 205 1.6 132 .2 311

Hydropsyche cockerelli 1 8.8 4.2 <18.2 158 2,300 17.6 1,390 3.5 359

Hydropsyche occidentalis 2 6.3 1.8 1.3 81.1 1,190 8.1 1,100 .8 199

Hydropsyche spp. 2 5.8 1.8 1.6 78.6 1,130 8.6 1,150 .8 203
72 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Taxon

Number of 

composite 

samples

Concentration (μg/g)

Arsenic Cadmium Chromium Copper Iron Lead ManganeseNickel Zinc

12331800--Clark Fork near Drummond

Arctopsyche grandis 4 3.9 2.5 1.1 41.7 844 5.9 881 <0.2 257

Claassenia sabulosa 2 1.6 1.3 .6 67.6 214 1.4 206 .2 268

Hydropsyche cockerelli 1 6.3 4.5 1.3 107 2,080 15.0 1,200 1.7 322

Hydropsyche occidentalis 2 5.6 1.9 1.6 71.4 1,380 10.1 1,420 1.0 232

12334550--Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 3 3.7 2.0 1.7 34.5 782 4.5 618 0.7 229

Claassenia sabulosa 2 1.3 1.6 .6 59.1 125 .5 108 .2 208

Hydropsyche cockerelli 2 4.3 1.8 1.6 56.3 1,170 6.5 679 1.0 200

Hydropsyche occidentalis 2 4.0 1.5 1.6 48.4 1,150 5.9 755 1.0 205

12340000--Blackfoot River near Bonner

Arctopsyche grandis 1 4.4 0.4 1.2 15.3 757 0.8 422 1.3 144

Claassenia sabulosa 1 1.5 .2 .6 36.6 138 .1 59 <.1 192

Hydropsyche cockerelli 1 4.2 .6 3.8 14.8 1,550 1.9 428 <.3 162

Hydropsyche occidentalis 1 3.2 .4 1.8 17.0 1,010 1.1 445 1.1 143

12340500--Clark Fork above Missoula

Arctopsyche grandis 3 5.3 2.2 1.6 70.4 1,670 6.3 723 1.8 251

Claassenia sabulosa 2 1.4 1.4 <.6 76.3 150 .5 112 .3 261

Hydropsyche cockerelli 1 6.6 2.0 2.3 78.1 2,160 7.7 764 1.8 266

Hydropsyche occidentalis 1 5.5 1.5 1.5 64.7 1,640 6.9 980 1.4 229

Table 22. Biological data for the Clark Fork basin, Montana, August 2010.—Continued

[Analyses are for the whole-body tissue of aquatic insects. Composite samples were made by combining similar-sized insects of the same species into a sample 

of sufficient mass for analysis. Concentrations for biota samples composed of two or more composite samples are the means of all analyses. Abbreviations: μg/g, 

micrograms per gram of dry sample weight; spp., species. Symbol: <, less than minimum reporting level for solid-phase concentration, in μg/g]
Data 73

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

samples.

[Abbreviations: μg/g, micrograms per gram of dry sample weight; SRM, standard reference material (lobster 

hepatopancreas)]

Constituent Number of 

analyses

Certified 

concentration 

(μg/g)

Mean 

SRM recovery

(percent)

95-percent confidence 

interval for SRM recovery

(percent)

SRM sample TORT-2

Arsenic 12 21.6 93.3 92.6–93.9

Cadmium 12 26.7 76.4 74.2–78.6

Chromium 12 .77 125 107–144

Copper 12 106 92.7 92.2–93.2

Iron 12 105 91.0 89.6–93.4

Lead 12 .35 98.1 93.2–103

Manganese 12 13.6 89.6 86.8–92.4

Nickel 12 2.5 94.2 71.7–76.6

Zinc 12 180 91.4 88.8–93.9
Table 24. Analyses of procedural blanks for biota samples. [Procedural blanks were not diluted prior to analyses. Abbreviation: μg/mL, micrograms per milliliter. Symbol: <, less than minimum reporting level for liquid-phase concentrat

Site number (fig. 1) Site name Dilution ratio Trace-element concentration (μg/mL) Arsenic Cadmium Chromium Copper Iron Lead Manganes

12323600 Silver Bow Creek at Opportunity 1:1 <0.003 <0.001 <0.02 <0.005 <0.10 <0.002 <0.008 

12323750 Silver Bow Creek at Warm Springs 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

12323800 Clark Fork near Galen 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

461415112450801 Clark Fork below Lost Creek, near Galen 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

461559112443301 Clark Fork at county bridge, near Racetrack 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

12324200 Clark Fork at Deer Lodge 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

12324400 Clark Fork above Little Blackfoot River, near Garrison 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

12324680 Clark Fork at Goldcreek 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

12331800 Clark Fork near Drummond 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

12334550 Clark Fork at Turah Bridge, near Bonner 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

12340000 Blackfoot River near Bonner 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 

12340500 Clark Fork above Missoula 1:1 <.003 <.001 <.02 <.005 <.10 <.002 <.008 
Data 75

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]

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 2010

Streamflow, instantaneous (ft3

/s) 131 156 1.9 14 8.5

pH, onsite (standard units) 131 8.4 7.3 7.8 7.7

Specific conductance, onsite (μS/cm) 131 412 116 263 262

Temperature, water (°C) 131 17.5 1.5 8.2 8.5

Hardness, filtered (mg/L as CaCO3

) 131 150 38 103 110

Calcium, filtered (mg/L) 131 41.8 10.6 29.6 30.1

Magnesium, filtered (mg/L) 131 11.0 2.71 7.16 7.17

Arsenic, filtered (μg/L) 130 13 1 4.0 3.2

Arsenic, unfiltered recoverable (μg/L) 131 18 1 2

5.4 4.5

Cadmium, filtered (μg/L) 129 .5 <.04 2

.05 <1

Cadmium, unfiltered recoverable (μg/L) 131 .11 <.01 2

.04 <1

Copper, filtered (μg/L) 130 10.0 <1.0 2

3.7 3.2

Copper, unfiltered recoverable (μg/L) 131 52.0 1.5 6.7 5.5

Iron, filtered (μg/L) 131 640 15 181 165

Iron, unfiltered recoverable (μg/L) 131 4,220 139 663 570

Lead, filtered (μg/L) 131 2.80 <.08 2

.20 <1.00

Lead, unfiltered recoverable (μg/L) 131 47.0 <1.00 2

1.83 .67

Manganese, filtered (μg/L) 131 144 14.2 41.4 37.4

Manganese, unfiltered recoverable (μg/L) 131 240 23.5 58.3 50.6

Zinc, filtered (μg/L) 129 11 <1.0 2

3.6 2.8

Zinc, unfiltered recoverable (μg/L) 131 130 <10 2

8.7 4

Sediment, suspended (percent finer than 0.062 mm) 131 97 50 82 83

Sediment, suspended concentration (mg/L) 131 139 1 12 7

Sediment, suspended discharge (ton/d) 131 59 .01 1.0 .16
76 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, 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 2010

Streamflow, instantaneous (ft3

/s) 139 134 13 29 24

pH, onsite (standard units) 139 8.1 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 139 691 226 464 475

Temperature, water (°C) 139 20.0 1.0 10.4 10.0

Hardness, filtered (mg/L as CaCO3

) 139 220 66 148 150

Calcium, filtered (mg/L) 139 62.7 19.0 42.1 43.2

Magnesium, filtered (mg/L) 139 14.6 4.51 10.3 10.7

Arsenic, filtered (μg/L) 139 13 2.3 6.3 6.0

Arsenic, unfiltered recoverable (μg/L) 139 45 3 10.4 9.0

Cadmium, filtered (μg/L) 139 6.2 .05 1.01 .70

Cadmium, unfiltered recoverable (μg/L) 139 6.0 .09 1.35 1.00

Copper, filtered (μg/L) 139 303 3.2 33.9 13.9

Copper, unfiltered recoverable (μg/L) 139 550 9.5 78.0 29.9

Iron, filtered (μg/L) 139 270 10 90.0 74.0

Iron, unfiltered recoverable (μg/L) 139 7,400 85 846 552

Lead, filtered (μg/L) 139 2.4 <.5 2

.46 .23

Lead, unfiltered recoverable (μg/L) 139 250 .64 12.0 3.10

Manganese, filtered (μg/L) 139 1,700 21.4 332 246

Manganese, unfiltered recoverable (μg/L) 139 1,600 25.9 374 298

Zinc, filtered (μg/L) 139 2,200 16.0 328 217

Zinc, unfiltered recoverable (μg/L) 139 2,200 28.8 397 247

Sediment, suspended (percent finer than 0.062 mm) 138 98 42 84 86

Sediment, suspended concentration (mg/L) 138 405 2 21 10

Sediment, suspended discharge (ton/d) 138 70 .08 2.5 .68

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]
Data 77

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 2010

Streamflow, instantaneous (ft3

/s) 142 361 13 74 51

pH, onsite (standard units) 141 9.5 7.2 8.4 8.3

Specific conductance, onsite (μS/cm) 141 633 202 414 400

Temperature, water (°C) 141 22.5 0.0 9.5 9.5

Hardness, filtered (mg/L as CaCO3

) 141 240 60 148 140

Calcium, filtered (mg/L) 141 71.6 18.5 43.9 43.0

Magnesium, filtered (mg/L) 141 15.0 3.42 9.37 9.01

Arsenic, filtered (μg/L) 141 34 1 11.0 10.3

Arsenic, unfiltered recoverable (μg/L) 141 235 9.1 25.0 17.0

Cadmium, filtered (μg/L) 140 41.0 <.1 2

1.09 .67

Cadmium, unfiltered recoverable (μg/L) 141 49.0 .38 2

1.97 1.20

Copper, filtered (μg/L) 139 450 12 44.1 33.6

Copper, unfiltered recoverable (μg/L) 141 3,900 31.1 195 101

Iron, filtered (μg/L) 141 307 <3 2

47 26

Iron, unfiltered recoverable (μg/L) 140 24,100 240 1,520 780

Lead, filtered (μg/L) 141 5.1 <.5 2

.70 .32

Lead, unfiltered recoverable (μg/L) 141 650 5.02 36.1 14.9

Manganese, filtered (μg/L) 141 9,300 30.3 411 330

Manganese, unfiltered recoverable (μg/L) 141 10,000 85.1 528 420

Zinc, filtered (μg/L) 140 13,000 11.2 282 144

Zinc, unfiltered recoverable (μg/L) 141 15,000 69.7 496 274

Sediment, suspended (percent finer than 0.062 mm) 142 95 37 79 83

Sediment, suspended concentration (mg/L) 142 801 5 48 18

Sediment, suspended discharge (ton/d) 142 781 .18 20 2.6

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]
78 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, 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 2010

Streamflow, instantaneous (ft3

/s) 48 213 7.4 58 26

pH, onsite (standard units) 48 8.6 7.6 8.1 8.0

Specific conductance, onsite (μS/cm) 48 213 56 132 133

Temperature, water (°C) 48 17.0 0.0 8.4 8.2

Hardness, filtered (mg/L as CaCO3

) 48 98 24 57 60

Calcium, filtered (mg/L) 48 25.9 7.00 15.8 16.8

Magnesium, filtered (mg/L) 48 8.01 1.45 4.28 4.22

Arsenic, filtered (μg/L) 48 32.9 7.3 16.4 15.3

Arsenic, unfiltered recoverable (μg/L) 48 34.8 8.6 17.9 16.9

Cadmium, filtered (μg/L) 47 .11 .02 2

.04 .04

Cadmium, unfiltered recoverable (μg/L) 48 .19 .03 .08 .07

Copper, filtered (μg/L) 48 5.1 .72 2.3 2.1

Copper, unfiltered recoverable (μg/L) 48 10.6 1.3 3.9 3.5

Iron, filtered (μg/L) 48 125 21 47 40

Iron, unfiltered recoverable (μg/L) 48 619 78 192 162

Lead, filtered (μg/L) 48 .24 <.08 2

.12 .11

Lead, unfiltered recoverable (μg/L) 48 3.12 .15 .76 .59

Manganese, filtered (μg/L) 48 11.9 3.2 5.9 5.8

Manganese, unfiltered recoverable (μg/L) 48 36.6 7.4 14.3 12.6

Zinc, filtered (μg/L) 48 4.0 .73 2

1.5 1.3

Zinc, unfiltered recoverable (μg/L) 48 9.2 1.0 3.0 2.6

Sediment, suspended (percent finer than 0.062 mm) 48 81 28 64 67

Sediment, suspended concentration (mg/L) 48 29 1 6 3

Sediment, suspended discharge (ton/d) 48 13 .02 1.7 .18

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]
Data 79

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 2010

Streamflow, instantaneous (ft3

/s) 64 261 0.43 35 9.7

pH, onsite (standard units) 64 8.2 7.7 8.0 8.0

Specific conductance, onsite (μS/cm) 64 230 59 148 153

Temperature, water (°C) 64 20.0 0.0 9.4 9.0

Hardness, filtered (mg/L as CaCO3

) 64 100 24 63 67

Calcium, filtered (mg/L) 64 28.0 7.01 17.6 18.8

Magnesium, filtered (mg/L) 64 7.83 1.56 4.56 4.67

Arsenic, filtered (μg/L) 64 55.1 9.0 22.4 20.6

Arsenic, unfiltered recoverable (μg/L) 64 53.5 10 25.7 24.6

Cadmium, filtered (μg/L) 64 .13 .02 .06 .06

Cadmium, unfiltered recoverable (μg/L) 64 .85 .04 .14 .10

Copper, filtered (μg/L) 64 6.1 1.0 3.0 2.6

Copper, unfiltered recoverable (μg/L) 64 38.8 1.5 6.8 4.4

Iron, filtered (μg/L) 64 94 16 48 43

Iron, unfiltered recoverable (μg/L) 64 1,960 44 299 145

Lead, filtered (μg/L) 64 .32 <.08 2

.14 .13

Lead, unfiltered recoverable (μg/L) 64 12.7 .07 1.50 .44

Manganese, filtered (μg/L) 64 32.8 2.2 7.7 5.6

Manganese, unfiltered recoverable (μg/L) 64 113 3.3 19.8 13.0

Zinc, filtered (μg/L) 63 7.7 1.3 3.0 2.8

Zinc, unfiltered recoverable (μg/L) 64 41 1.7 6.7 4.8

Sediment, suspended (percent finer than 0.062 mm) 64 90 26 69 74

Sediment, suspended concentration (mg/L) 64 107 1 12 2

Sediment, suspended discharge (ton/d) 64 55 <.01 2

3.3 .04

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]
80 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, 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 2010

Streamflow, instantaneous (ft3

/s) 44 75 1.0 14 7.6

pH, onsite (standard units) 44 8.2 7.5 7.7 7.7

Specific conductance, onsite (μS/cm) 44 145 66 102 108

Temperature, water (°C) 44 15.5 .5 7.0 7.2

Hardness, filtered (mg/L as CaCO3

) 44 52 22 37 38

Calcium, filtered (mg/L) 44 16.5 7.56 12.4 13.0

Magnesium, filtered (mg/L) 44 2.49 .78 1.44 1.42

Arsenic, filtered (μg/L) 44 24.9 9.9 15.2 14.2

Arsenic, unfiltered recoverable (μg/L) 44 27.0 9.8 16.3 15.4

Cadmium, filtered (μg/L) 42 .05 <.04 2

.03 .03

Cadmium, unfiltered recoverable (μg/L) 44 .33 .02 2

.06 .05

Copper, filtered (μg/L) 44 4.2 .90 2.0 1.9

Copper, unfiltered recoverable (μg/L) 44 16.8 1.0 3.8 3.2

Iron, filtered (μg/L) 44 277 28 80 64

Iron, unfiltered recoverable (μg/L) 44 2,380 86 342 216

Lead, filtered (μg/L) 44 .37 .03 2

.14 .12

Lead, unfiltered recoverable (μg/L) 44 7.96 .10 .87 .48

Manganese, filtered (μg/L) 44 34.5 6.0 14.3 13.2

Manganese, unfiltered recoverable (μg/L) 44 99.9 14.0 26.4 23.2

Zinc, filtered (μg/L) 44 3.3 .65 2

1.7 1.5

Zinc, unfiltered recoverable (μg/L) 44 17.8 <2.0 2

3.2 2.0

Sediment, suspended (percent finer than 0.062 mm) 44 94 25 73 78

Sediment, suspended concentration (mg/L) 44 195 1 17 6

Sediment, suspended discharge (ton/d) 44 34 <.01 2

1.8 .12

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]
Data 81

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 2010

Streamflow, instantaneous (ft3

/s) 64 70 4.5 17 9.1

pH, onsite (standard units) 64 9.0 7.7 8.1 8.1

Specific conductance, onsite (μS/cm) 64 371 116 276 297

Temperature, water (°C) 64 20.5 1.5 11.3 11.8

Hardness, filtered (mg/L as CaCO3

) 64 170 65 120 130

Calcium, filtered (mg/L) 64 47.4 20.1 34.8 36.9

Magnesium, filtered (mg/L) 64 12.3 3.52 7.98 8.56

Arsenic, filtered (μg/L) 64 164 10.9 41.8 32.0

Arsenic, unfiltered recoverable (μg/L) 64 164 12 44.6 33.2

Cadmium, filtered (μg/L) 64 .12 <.04 2

.04 .04

Cadmium, unfiltered recoverable (μg/L) 64 .52 .02 .11 .07

Copper, filtered (μg/L) 64 21.4 1.1 5.6 3.6

Copper, unfiltered recoverable (μg/L) 64 48.8 2.8 11.7 8.0

Iron, filtered (μg/L) 64 179 7 44 36

Iron, unfiltered recoverable (μg/L) 64 1,420 27 272 204

Lead, filtered (μg/L) 64 .58 .04 2

.21 .18

Lead, unfiltered recoverable (μg/L) 64 14.4 .27 2.28 1.49

Manganese, filtered (μg/L) 64 200 3.3 31.8 23.6

Manganese, unfiltered recoverable (μg/L) 64 228 4.7 44.8 34.8

Zinc, filtered (μg/L) 64 19.8 .84 5.3 3.9

Zinc, unfiltered recoverable (μg/L) 64 68 1.1 12.6 9.4

Sediment, suspended (percent finer than 0.062 mm) 64 96 55 85 88

Sediment, suspended concentration (mg/L) 64 84 1 11 5

Sediment, suspended discharge (ton/d) 64 11 .02 .91 .14

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

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

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323750--Silver Bow Creek at Warm Springs

Period of record for water-quality data: March 1993–September 2010

Streamflow, instantaneous (ft3

/s) 148 662 16 137 88

pH, onsite (standard units) 146 9.6 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 146 783 249 468 478

Temperature, water (°C) 147 25.0 .5 10.8 10.5

Hardness, filtered (mg/L as CaCO3

) 146 310 97 194 200

Calcium, filtered (mg/L) 146 90.4 27.9 56.6 57.6

Magnesium, filtered (mg/L) 146 21.4 5.94 12.9 13.0

Arsenic, filtered (μg/L) 146 60 6.8 23.1 23.4

Arsenic, unfiltered recoverable (μg/L) 146 94 10 27.0 26.4

Cadmium, filtered (μg/L) 146 .31 <.04 2

.06 .03

Cadmium, unfiltered recoverable (μg/L) 146 .56 <.1 2

.12 .05

Copper, filtered (μg/L) 146 40.0 1.7 7.9 6.1

Copper, unfiltered recoverable (μg/L) 146 96.8 2.4 15.9 11.4

Iron, filtered (μg/L) 146 93 <5 2

18 15

Iron, unfiltered recoverable (μg/L) 146 3,000 36 324 244

Lead, filtered (μg/L) 146 1.0 <.08 2

.12 <1.0

Lead, unfiltered recoverable (μg/L) 146 41.8 <1 2

2.30 1.24

Manganese, filtered (μg/L) 146 875 11.8 121 81.5

Manganese, unfiltered recoverable (μg/L) 146 899 24.0 182 146

Zinc, filtered (μg/L) 146 73 <1.0 2

7.6 4.0

Zinc, unfiltered recoverable (μg/L) 146 180 2.0 2

30.9 18.7

Sediment, suspended (percent finer than 0.062 mm) 147 97 43 82 85

Sediment, suspended concentration (mg/L) 148 229 1 10 6

Sediment, suspended discharge (ton/d) 148 279 .07 6.4 1.3

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]
Data 83

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323760--Warm Springs Creek near Anaconda

Period of record for water-quality data: October 2005–September 2010

Streamflow, instantaneous (ft3

/s) 30 573 41 137 84

pH, onsite (standard units) 30 8.8 8.0 8.5 8.5

Specific conductance, onsite (μS/cm) 30 271 125 217 234

Temperature, water (°C) 30 16.0 4.5 9.0 8.2

Hardness, filtered (mg/L as CaCO3

) 30 130 58 105 110

Calcium, filtered (mg/L) 30 39.2 18.5 31.6 33.8

Magnesium, filtered (mg/L) 30 8.57 2.96 6.36 6.90

Arsenic, filtered (μg/L) 30 3.8 1.8 2.2 2.1

Arsenic, unfiltered recoverable (μg/L) 30 5.6 2.0 2.7 2.5

Cadmium, filtered (μg/L) 30 .04 <.04 2

.02 .02

Cadmium, unfiltered recoverable (μg/L) 30 .14 <.04 2

.04 .03

Copper, filtered (μg/L) 30 2.2 <1.0 2

1.1 .88

Copper, unfiltered recoverable (μg/L) 30 28.0 1.1 2

3.7 2.1

Iron, filtered (μg/L) 30 15 <6 2

7 6

Iron, unfiltered recoverable (μg/L) 30 1,000 28 144 75

Lead, filtered (μg/L) 30 .11 <.03 2

.04 <.08

Lead, unfiltered recoverable (μg/L) 30 3.51 .08 .52 .26

Manganese, filtered (μg/L) 30 2.9 <.2 2

1.2 1.0

Manganese, unfiltered recoverable (μg/L) 30 45.2 1.2 6.9 4.2

Zinc, filtered (μg/L) 30 2.8 <1.8 21.0 .30

Zinc, unfiltered recoverable (μg/L) 30 20.1 <2 2

3.6 2.0

Sediment, suspended (percent finer than 0.062 mm) 30 83 32 64 66

Sediment, suspended concentration (mg/L) 30 65 1 9 4

Sediment, suspended discharge (ton/d) 30 68 .13 5.6 .87

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

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

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323770--Warm Springs Creek at Warm Springs

Period of record for water-quality data: March 1993–September 2010

Streamflow, instantaneous (ft3

/s) 109 420 2.8 95 56

pH, onsite (standard units) 108 8.7 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 108 795 139 294 298

Temperature, water (°C) 109 20.0 0.0 8.7 8.5

Hardness, filtered (mg/L as CaCO3

) 108 420 40 142 150

Calcium, filtered (mg/L) 108 130 10.5 43.4 44.4

Magnesium, filtered (mg/L) 108 22.0 3.29 8.18 8.24

Arsenic, filtered (μg/L) 108 14 2 5.1 4.4

Arsenic, unfiltered recoverable (μg/L) 108 27 3 7.4 6.0

Cadmium, filtered (μg/L) 108 .1 <.04 2

.04 <.1

Cadmium, unfiltered recoverable (μg/L) 108 .41 <.06 2

.08 .03

Copper, filtered (μg/L) 108 16.0 1.0 3.3 2.9

Copper, unfiltered recoverable (μg/L) 108 147 2.3 20.0 8.8

Iron, filtered (μg/L) 108 30 <5 2

11 10

Iron, unfiltered recoverable (μg/L) 108 2,110 39 313 118

Lead, filtered (μg/L) 108 1.8 <.08 2

.08 <.5

Lead, unfiltered recoverable (μg/L) 108 14.0 <1.0 2

1.96 .55

Manganese, filtered (μg/L) 108 570 19.2 121 92.6

Manganese, unfiltered recoverable (μg/L) 108 1,400 37.0 210 170

Zinc, filtered (μg/L) 107 10 <1.0 2

2.1 1.4

Zinc, unfiltered recoverable (μg/L) 108 60 <10 2

9.4 3.0

Sediment, suspended (percent finer than 0.062 mm) 109 88 43 71 71

Sediment, suspended concentration (mg/L) 109 127 1 18 8

Sediment, suspended discharge (ton/d) 109 87 .05 8.5 1.0

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]
Data 85

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 2010

Streamflow, instantaneous (ft3

/s) 189 1,050 14 215 129

pH, onsite (standard units) 176 9.2 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 177 720 197 417 427

Temperature, water (°C) 188 23.5 0.0 9.9 10.0

Hardness, filtered (mg/L as CaCO3

) 175 370 81 182 190

Calcium, filtered (mg/L) 175 110 24.2 53.8 55.4

Magnesium, filtered (mg/L) 175 22.0 5.08 11.5 12.0

Arsenic, filtered (μg/L) 175 53 4 15.2 14.7

Arsenic, unfiltered recoverable (μg/L) 175 78 3 19.5 17.0

Cadmium, filtered (μg/L) 175 1.0 <.04 2

.06 <1

Cadmium, unfiltered recoverable (μg/L) 175 3 <.1 2

.19 <1

Copper, filtered (μg/L) 175 50 1.7 7.9 6.0

Copper, unfiltered recoverable (μg/L) 174 240 4.1 27.7 15.5

Iron, filtered (μg/L) 175 110 <3 2

16 11

Iron, unfiltered recoverable (μg/L) 175 9,200 56 481 270

Lead, filtered (μg/L) 175 3 <.08 2

.15 <1

Lead, unfiltered recoverable (μg/L) 175 31.0 <1.0 2

3.44 1.83

Manganese, filtered (μg/L) 175 460 24.0 108 81.0

Manganese, unfiltered recoverable (μg/L) 175 1,400 47.3 227 177

Zinc, filtered (μg/L) 175 110 <1.0 2

9.2 4.6

Zinc, unfiltered recoverable (μg/L) 175 360 <10 2

37.2 20.0

Sediment, suspended (percent finer than 0.062 mm) 188 97 40 77 78

Sediment, suspended concentration (mg/L) 189 338 1 18 8

Sediment, suspended discharge (ton/d) 189 459 .12 20 2.4

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

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

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323840--Lost Creek near Anaconda

Period of record for water-quality data: December 2004–September 2010

Streamflow, instantaneous (ft3

/s) 47 54 0.37 10 8

pH, onsite (standard units) 47 8.6 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 47 253 121 198 211

Temperature, water (°C) 47 17.0 1.0 8.1 8.5

Hardness, filtered (mg/L as CaCO3

) 47 120 50 94 99

Calcium, filtered (mg/L) 47 37.1 15.7 28.5 30.0

Magnesium, filtered (mg/L) 47 7.22 2.71 5.50 5.78

Arsenic, filtered (μg/L) 47 156 1.8 7.8 3.4

Arsenic, unfiltered recoverable (μg/L) 47 3,860 2 87.2 3.7

Cadmium, filtered (μg/L) 46 .90 <.04 2

.05 .03

Cadmium, unfiltered recoverable (μg/L) 47 147 .01 3.2 .04

Copper, filtered (μg/L) 47 90.5 .86 3.9 1.8

Copper, unfiltered recoverable (μg/L) 47 29,100 1.7 626 4.4

Iron, filtered (μg/L) 47 25 <6 2

10 9

Iron, unfiltered recoverable (μg/L) 47 99,700 22 2,300 98

Lead, filtered (μg/L) 47 .18 <.03 2

.04 <.12

Lead, unfiltered recoverable (μg/L) 47 1,290 .10 28.3 .42

Manganese, filtered (μg/L) 47 42.4 <.2 2

2.1 1.1

Manganese, unfiltered recoverable (μg/L) 47 8,830 1.2 194 4.6

Zinc, filtered (μg/L) 47 30.0 <1.8 2

1.9 1.1

Zinc, unfiltered recoverable (μg/L) 47 7,780 1.0 169 2.4

Sediment, suspended (percent finer than 0.062 mm) 47 97 22 58 61

Sediment, suspended concentration (mg/L) 47 58,900 1 1,270 5

Sediment, suspended discharge (ton/d) 47 1,320 <.01 2

29 .09

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]
Data 87

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 2010

Streamflow, instantaneous (ft3

/s) 64 71 1.3 21 13

pH, onsite (standard units) 64 8.7 8.0 8.3 8.3

Specific conductance, onsite (μS/cm) 64 934 540 648 631

Temperature, water (°C) 64 26.5 0.0 10.8 10.5

Hardness, filtered (mg/L as CaCO3

) 64 450 200 301 300

Calcium, filtered (mg/L) 64 122 48.5 84.7 85.2

Magnesium, filtered (mg/L) 64 35.7 17.3 21.7 21.0

Arsenic, filtered (μg/L) 64 41.8 6 14.2 12.6

Arsenic, unfiltered recoverable (μg/L) 64 43 6 15.0 14.0

Cadmium, filtered (μg/L) 63 .05 <.04 2

.03 .02

Cadmium, unfiltered recoverable (μg/L) 64 .11 .01 2

.04 .04

Copper, filtered (μg/L) 64 6.7 .99 2.4 2.4

Copper, unfiltered recoverable (μg/L) 64 22.5 1.6 5.5 4.4

Iron, filtered (μg/L) 64 61 <6 2

13 10

Iron, unfiltered recoverable (μg/L) 64 293 14 99 77

Lead, filtered (μg/L) 63 .33 <.06 2

.06 <.12

Lead, unfiltered recoverable (μg/L) 64 1.30 .04 .35 .24

Manganese, filtered (μg/L) 64 54.0 1.9 15.4 13.5

Manganese, unfiltered recoverable (μg/L) 64 56.5 2.2 20.5 18.0

Zinc, filtered (μg/L) 63 3.8 <1.0 2

1.5 1.3

Zinc, unfiltered recoverable (μg/L) 64 9 <2 2

2.8 2.0

Sediment, suspended (percent finer than 0.062 mm) 64 86 18 57 60

Sediment, suspended concentration (mg/L) 64 79 2 16 15

Sediment, suspended discharge (ton/d) 64 4.2 .01 1.0 .44

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

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

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]

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 2010

Streamflow, instantaneous (ft3

/s) 241 1,920 23 297 224

pH, onsite (standard units) 189 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 224 642 234 474 500

Temperature, water (°C) 240 23.0 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3

) 181 280 95 200 210

Calcium, filtered (mg/L) 181 82.0 28.2 59.2 62.0

Magnesium, filtered (mg/L) 181 18.7 5.53 12.7 13.3

Arsenic, filtered (μg/L) 191 39 6.0 14.4 13.5

Arsenic, unfiltered recoverable (μg/L) 190 215 4.8 23.9 17.6

Cadmium, filtered (μg/L) 190 2 <.1 2

.08 <1

Cadmium, unfiltered recoverable (μg/L) 190 5 <.1 2

.40 .06

Copper, filtered (μg/L) 191 120 3.2 10.8 8.0

Copper, unfiltered recoverable (μg/L) 189 1,500 8.2 80.7 37.0

Iron, filtered (μg/L) 191 190 <3 2

15 9

Iron, unfiltered recoverable (μg/L) 191 29,000 27 1,470 510

Lead, filtered (μg/L) 191 6 <.08 2

.31 <1

Lead, unfiltered recoverable (μg/L) 191 200 .33 2

10.7 4.60

Manganese, filtered (μg/L) 191 400 1.0 41.7 33.4

Manganese, unfiltered recoverable (μg/L) 191 4,600 11.9 236 133

Zinc, filtered (μg/L) 191 230 <10 2

11.7 8.0

Zinc, unfiltered recoverable (μg/L) 189 1,700 4 85.4 40.0

Sediment, suspended (percent finer than 0.062 mm) 232 99 31 71 72

Sediment, suspended concentration (mg/L) 241 2,250 1 69 22

Sediment, suspended discharge (ton/d) 241 8,690 .18 146 12
Data 89

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

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

Period of record for water-quality data: March 2009–September 2010

Streamflow, instantaneous (ft3

/s) 15 1,380 186 532 345

pH, onsite (standard units) 15 8.8 8 8.3 8.3

Specific conductance, onsite (μS/cm) 15 494 253 397 432

Temperature, water (°C) 15 19.0 3.0 10.8 12.5

Hardness, filtered (mg/L as CaCO3

) 15 220 100 172 190

Calcium, filtered (mg/L) 15 64.0 31.8 50.7 56.2

Magnesium, filtered (mg/L) 15 14.8 5.93 11.0 12.0

Arsenic, filtered (μg/L) 15 21.6 9.5 15.4 16.1

Arsenic, unfiltered recoverable (μg/L) 15 43.5 11.9 23.7 20.2

Cadmium, filtered (μg/L) 15 .11 .04 .07 .08

Cadmium, unfiltered recoverable (μg/L) 15 .75 .08 .33 .25

Copper, filtered (μg/L) 15 20.2 4.3 10.1 9.1

Copper, unfiltered recoverable (μg/L) 15 197 12.4 75.2 59.4

Iron, filtered (μg/L) 15 33 5 13 10

Iron, unfiltered recoverable (μg/L) 15 3,190 119 1,090 632

Lead, filtered (μg/L) 15 .39 .04 .14 .11

Lead, unfiltered recoverable (μg/L) 15 29.4 .90 10.3 7.75

Manganese, filtered (μg/L) 15 45.3 15.6 26.2 22.6

Manganese, unfiltered recoverable (μg/L) 15 309 40.5 149 131

Zinc, filtered (μg/L) 15 15.9 2.9 6.2 5.8

Zinc, unfiltered recoverable (μg/L) 15 152 10.1 61.8 38.4

Sediment, suspended (percent finer than 0.062 mm) 15 80 42 64 63

Sediment, suspended concentration (mg/L) 15 179 5 59 30

Sediment, suspended discharge (ton/d) 15 428 2.5 118 42
90 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]

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 2010

Streamflow, instantaneous (ft3

/s) 147 3,920 87 752 513

pH, onsite (standard units) 146 8.9 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 146 510 206 369 384

Temperature, water (°C) 147 23.0 0.0 10.1 10.0

Hardness, filtered (mg/L as CaCO3

) 146 230 86 162 170

Calcium, filtered (mg/L) 146 68.0 25.9 47.8 50.1

Magnesium, filtered (mg/L) 146 15.0 5.15 10.4 10.7

Arsenic, filtered (μg/L) 146 20 5.8 10.1 10.0

Arsenic, unfiltered recoverable (μg/L) 146 75 7 14.8 12.0

Cadmium, filtered (μg/L) 146 .2 <.04 2

.04 <.1

Cadmium, unfiltered recoverable (μg/L) 146 2 <.1 2

.17 .05

Copper, filtered (μg/L) 145 36.0 2.1 6.6 5.4

Copper, unfiltered recoverable (μg/L) 145 440 5.2 39.8 23.2

Iron, filtered (μg/L) 146 100 <3 2

18 12

Iron, unfiltered recoverable (μg/L) 146 12,000 27 850 422

Lead, filtered (μg/L) 144 .6 <.08 2

.11 <.6

Lead, unfiltered recoverable (μg/L) 145 73.0 .14 2

5.56 2.81

Manganese, filtered (μg/L) 146 57.3 4.0 18.7 16.9

Manganese, unfiltered recoverable (μg/L) 146 1,100 10.5 121 86.4

Zinc, filtered (μg/L) 146 26 <1.0 2

5.5 4.0

Zinc, unfiltered recoverable (μg/L) 146 510 2 43.5 30.0

Sediment, suspended (percent finer than 0.062 mm) 147 94 43 75 78

Sediment, suspended concentration (mg/L) 147 752 1 48 21

Sediment, suspended discharge (ton/d) 147 7,960 .55 206 33
Data 91

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]

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 2010

Streamflow, instantaneous (ft3

/s) 147 3,860 149 1,050 766

pH, onsite (standard units) 146 8.7 7.8 8.3 8.3

Specific conductance, onsite (μS/cm) 146 630 189 408 420

Temperature, water (°C) 147 22.5 .5 11.0 11.0

Hardness, filtered (mg/L as CaCO3

) 146 300 74 183 190

Calcium, filtered (mg/L) 146 83.0 21.0 52.6 54.6

Magnesium, filtered (mg/L) 146 22.0 5.2 12.6 13.0

Arsenic, filtered (μg/L) 146 20 3.2 10.5 10.0

Arsenic, unfiltered recoverable (μg/L) 146 62 8 16.2 13.0

Cadmium, filtered (μg/L) 145 .30 <.04 2

.05 <.1

Cadmium, unfiltered recoverable (μg/L) 146 2.0 <.1 2

.23 .06

Copper, filtered (μg/L) 143 21.0 1.0 6.4 5.0

Copper, unfiltered recoverable (μg/L) 144 360 4.6 42.9 22.2

Iron, filtered (μg/L) 146 150 <3 2

18 9

Iron, unfiltered recoverable (μg/L) 145 8,800 20 1,000 468

Lead, filtered (μg/L) 142 1.2 <.08 2

.17 <1.0

Lead, unfiltered recoverable (μg/L) 142 56.0 <1.00 2

7.75 3.50

Manganese, filtered (μg/L) 145 60.7 3.3 16.4 14.0

Manganese, unfiltered recoverable (μg/L) 146 880 8.0 146 93.6

Zinc, filtered (μg/L) 146 21 <3 2

5.9 4.3

Zinc, unfiltered recoverable (μg/L) 146 490 2.9 60.0 31.0

Sediment, suspended (percent finer than 0.062 mm) 147 92 38 73 74

Sediment, suspended concentration (mg/L) 147 530 2 63 26

Sediment, suspended discharge (ton/d) 147 4,720 1.7 320 49
92 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]

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 2010

Streamflow, instantaneous (ft3

/s) 244 9,560 296 1,910 1,150

pH, onsite (standard units) 190 8.8 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 219 483 139 300 313

Temperature, water (°C) 243 22.0 0.0 9.5 10.0

Hardness, filtered (mg/L as CaCO3

) 180 200 54 131 130

Calcium, filtered (mg/L) 180 59.0 14.9 36.9 37.2

Magnesium, filtered (mg/L) 180 14.0 3.94 9.40 9.39

Arsenic, filtered (μg/L) 189 17 2.7 6.1 5.5

Arsenic, unfiltered recoverable (μg/L) 189 110 3 9.8 7.0

Cadmium, filtered (μg/L) 188 .10 <.04 2

.03 <.1

Cadmium, unfiltered recoverable (μg/L) 189 4 <.01 2

.25 <1

Copper, filtered (μg/L) 188 25 1.1 4.8 3.8

Copper, unfiltered recoverable (μg/L) 187 500 2.7 33.9 15.9

Iron, filtered (μg/L) 189 190 <3 2

23 13

Iron, unfiltered recoverable (μg/L) 189 19,000 33 1,000 370

Lead, filtered (μg/L) 185 7 <.08 2

.28 <1

Lead, unfiltered recoverable (μg/L) 185 100 <1.00 2

6.94 3.00

Manganese, filtered (μg/L) 189 37.4 <1.0 2

8.2 7.0

Manganese, unfiltered recoverable (μg/L) 189 2,000 8.9 121 60.2

Zinc, filtered (μg/L) 187 39 <3 2

5.9 4.0

Zinc, unfiltered recoverable (μg/L) 189 1,100 <10 2

58 29

Sediment, suspended (percent finer than 0.062 mm) 233 98 27 74 75

Sediment, suspended concentration (mg/L) 244 1,370 2 56 18

Sediment, suspended discharge (ton/d) 244 34,700 3.0 615 60
Data 93

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]

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 2010

Streamflow, instantaneous (ft3

/s) 177 13,400 344 2,660 1,310

pH, onsite (standard units) 137 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 154 294 131 209 205

Temperature, water (°C) 177 22.5 0.0 9.5 9.5

Hardness, filtered (mg/L as CaCO3

) 129 150 55 104 100

Calcium, filtered (mg/L) 129 37.7 14.0 26.5 26.0

Magnesium, filtered (mg/L) 129 13.2 4.90 9.16 8.69

Arsenic, filtered (μg/L) 136 2 <1 2

.96 .96

Arsenic, unfiltered recoverable (μg/L) 137 4 <1 2

1.2 1

Cadmium, filtered (μg/L) 135 1 <.02 2

.02 <.1

Cadmium, unfiltered recoverable (μg/L) 137 2 <.01 2

.10 <1

Copper, filtered (μg/L) 133 7.0 <1.0 2

1.4 .8

Copper, unfiltered recoverable (μg/L) 134 34 <1.0 2

4.7 2.0

Iron, filtered (μg/L) 136 100 <3 2

17 10

Iron, unfiltered recoverable (μg/L) 137 3,600 14 417 180

Lead, filtered (μg/L) 131 8 <.03 2

.35 <.6

Lead, unfiltered recoverable (μg/L) 133 25.0 <.06 2

2.30 .08

Manganese, filtered (μg/L) 136 11.0 <1 2

2.3 2.0

Manganese, unfiltered recoverable (μg/L) 137 180 <10 2

28.9 18.2

Zinc, filtered (μg/L) 135 15 <.60 2

2.1 <10

Zinc, unfiltered recoverable (μg/L) 137 60 <1 2

5.5 <10

Sediment, suspended (percent finer than 0.062 mm) 175 98 42 80 82

Sediment, suspended concentration (mg/L) 177 271 1 29 8

Sediment, suspended discharge (ton/d) 177 7,670 1.1 509 30
94 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork basin, Montana, March 1985 through 

September 2010.—Continued

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; 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

]

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 2010

Streamflow, instantaneous (ft3

/s) 210 21,600 720 4,450 2,400

pH, onsite (standard units) 167 8.8 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 187 399 142 253 261

Temperature, water (°C) 207 22.0 0.0 9.6 9.5

Hardness, filtered (mg/L as CaCO3

) 167 170 60 117 120

Calcium, filtered (mg/L) 167 46.0 14.0 31.5 32.0

Magnesium, filtered (mg/L) 167 13.4 5.28 9.22 9.20

Arsenic, filtered (μg/L) 167 9 1 3.5 3.0

Arsenic, unfiltered recoverable (μg/L) 167 69 1 5.5 4

Cadmium, filtered (μg/L) 166 .2 <.04 2

.03 <.1

Cadmium, unfiltered recoverable (μg/L) 167 5.0 <.01 2

.17 <1

Copper, filtered (μg/L) 166 12.6 .7 2.8 2.2

Copper, unfiltered recoverable (μg/L) 165 400 2.0 20.0 8.5

Iron, filtered (μg/L) 167 200 <3 2

21 14

Iron, unfiltered recoverable (μg/L) 167 13,000 43 640 244

Lead, filtered (μg/L) 160 1.2 <.08 2

.15 <1

Lead, unfiltered recoverable (μg/L) 162 78.0 <1.00 2

3.58 1.60

Manganese, filtered (μg/L) 167 230 5.9 16.4 14.0

Manganese, unfiltered recoverable (μg/L) 167 1,100 10 66.8 40

Zinc, filtered (μg/L) 166 16 <1.0 2

3.7 2.4

Zinc, unfiltered recoverable (μg/L) 167 1,100 <10 2

34.6 15

Sediment, suspended (percent finer than 0.062 mm) 205 99 14 83 89

Sediment, suspended concentration (mg/L) 210 950 2 44 12

Sediment, suspended discharge (ton/d) 210 21,900 5.8 1,080 82

1

Differing less-than (<) values for an individual constituent are the result of changes in the laboratory reporting level during the period of record.

2

Value for the mean is estimated by using a log-probability regression to predict the values of data less than the laboratory reporting level (Helsel 

and Cohn, 1988). Minimum values that are not censored are a result of changes in the laboratory reporting level during the period of record.
Data 95

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork basin, Montana, August 1986 through August 2010.

[Reported concentrations are in micrograms per gram dry weight (μg/g). Number of samples represents the number of years that the constituent was analyzed, 

with each year represented by a single mean concentration of composite samples. Arsenic was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]

Constituent Number of samples Maximum Minimum Mean Median

12323600--Silver Bow Creek at Opportunity

Period of record for bed-sediment data: 1992–2010

Arsenic 8 186 34 125 138

Cadmium 19 43.9 6.8 29.7 29.3

Chromium 17 50.7 16.8 28.7 25.9

Copper 19 9,020 837 4,180 4,510

Iron 19 45,300 28,200 35,600 34,400

Lead 19 1,030 181 634 581

Manganese 19 9,220 1,160 3,350 2,770

Nickel 18 21.4 12.0 14.9 14.6

Silver 12 20.0 8.3 15.5 15.8

Zinc 19 13,400 1,610 7,250 6,990

12323750--Silver Bow Creek at Warm Springs

Period of record for bed-sediment data: 1992–2010

Arsenic 8 177 67 118 106

Cadmium 19 12.2 4.2 7.2 6.6

Chromium 17 46.8 <15.7 1

23.3 122.9

Copper 19 769 169 352 294

Iron 19 32,500 15,400 23,400 22,100

Lead 19 100 49 72 73

Manganese 19 17,700 1,470 7,940 8,150

Nickel 18 20.0 9.2 15.0 15.0

Silver 12 4.4 .3 1

1.9 11.8

Zinc 19 2,220 554 945 728

12323770--Warm Springs Creek at Warm Springs

Period of record for bed-sediment data: 1995, 1997, 1999, 2002, 2005, 2008

Arsenic 2 66 52 59 --

Cadmium 6 5.8 1.3 3.6 3.6

Chromium 6 39.3 27.5 31.9 31.1

Copper 6 1,060 779 908 886

Iron 6 26,600 16,800 21,700 21,900

Lead 6 86 67 81 83

Manganese 6 12,100 2,020 7,950 8,280

Nickel 6 25.5 17.6 20.2 19.4

Silver 4 5.1 3.1 3.8 3.5

Zinc 6 453 372 405 405
96 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, 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, 1991–2010

Arsenic 8 119 73 99 101

Cadmium 21 20.1 3.9 8.4 7.5

Chromium 17 44.6 19.1 28.9 27.0

Copper 21 2,300 838 1,200 1,110

Iron 21 39,800 22,600 27,700 27,000

Lead 21 235 92 133 129

Manganese 21 17,300 1,870 9,520 11,000

Nickel 18 23.2 13.9 18.7 18.6

Silver 14 7.3 <3.2 1

4.4 14.5

Zinc 21 3,560 721 1,450 1,150

461415112450801--Clark Fork below Lost Creek, near Galen

Period of record for bed-sediment data: 1996–2010

Arsenic 8 204 92 118 108

Cadmium 15 10.0 4.9 7.1 6.8

Chromium 14 42.4 20.5 29.8 29.7

Copper 15 2,050 1,150 1,500 1,440

Iron 15 32,800 24,400 29,400 30,300

Lead 15 218 127 166 168

Manganese 15 9,820 2,460 5,740 5,750

Nickel 15 19.9 11.7 16.2 16.5

Silver 8 7.8 4.2 6.5 6.7

Zinc 15 1,680 930 1,310 1,300

461559112443301--Clark Fork at county bridge, near Racetrack

Period of record for bed-sediment data: 1996–2010

Arsenic 8 118 56 86 88

Cadmium 15 8.7 5.0 6.7 6.4

Chromium 14 45.2 19.0 28.5 28.4

Copper 15 1,810 933 1,280 1,310

Iron 15 31,700 21,200 27,400 28,100

Lead 15 186 103 145 143

Manganese 15 6,310 1,840 3,390 3,130

Nickel 15 18.4 10.3 14.4 14.8

Silver 8 6.1 <3.3 1

5.0 15.4

Zinc 15 1,550 999 1,210 1,180

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Reported concentrations are in micrograms per gram dry weight (μg/g). Number of samples represents the number of years that the constituent was analyzed, 

with each year represented by a single mean concentration of composite samples. Arsenic was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]
Data 97

Constituent Number of samples Maximum Minimum Mean Median

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for bed-sediment data: 1996–2010

Arsenic 8 100 58 78 76

Cadmium 15 10.3 4.3 6.4 5.9

Chromium 14 39.2 16.0 26.9 26.0

Copper 15 1,580 721 1,100 1,090

Iron 15 33,700 20,600 26,800 26,100

Lead 15 155 92 130 132

Manganese 15 8,370 1,330 4,020 3,330

Nickel 15 16.9 8.7 13.0 12.7

Silver 8 6.2 2.7 4.9 5.0

Zinc 15 1,570 900 1,140 1,080

12324200--Clark Fork at Deer Lodge

Period of record for bed-sediment data: 1986–87, 1990–2010

Arsenic 8 102 49 70 69

Cadmium 23 10.0 3.5 6.1 5.5

Chromium 17 50.7 19.5 31.5 28.4

Copper 23 4,180 683 1,260 1,060

Iron 23 35,300 21,100 27,200 26,100

Lead 23 242 103 146 142

Manganese 23 6,020 1,070 2,700 2,460

Nickel 18 21.1 11.5 14.9 13.9

Silver 16 7.9 2.4 4.7 4.5

Zinc 23 1,730 844 1,200 1,140

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

Period of record for bed-sediment data: 2009-2010

Arsenic 2 83 81 82 --

Cadmium 2 5.5 4.8 5.1 --

Chromium 2 52.8 45.5 49.2 --

Copper 2 1,290 1,270 1,280 --

Iron 2 32,400 27,300 29,900 --

Lead 2 145 140 143 --

Manganese 2 2,950 1,560 2,260 --

Nickel 2 17.2 13.9 15.5 --

Silver 0 -- -- -- --

Zinc 2 1,240 1,100 1,170 --

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Reported concentrations are in micrograms per gram dry weight (μg/g). Number of samples represents the number of years that the constituent was analyzed, 

with each year represented by a single mean concentration of composite samples. Arsenic was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]
98 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of samples Maximum Minimum Mean Median

12324680--Clark Fork at Goldcreek

Period of record for bed-sediment data: 1992–2010

Arsenic 8 61 23 40 37

Cadmium 19 8.1 2.6 4.7 4.2

Chromium 17 55.3 21.3 33.4 31.9

Copper 19 1,080 338 690 729

Iron 19 32,100 15,500 23,900 24,300

Lead 19 152 52 96 93

Manganese 19 2,610 1,160 1,850 1,840

Nickel 18 18.6 9.0 14.3 14.7

Silver 12 4.8 2.3 3.3 3.2

Zinc 19 1,320 584 932 985

12331800--Clark Fork near Drummond

Period of record for bed-sediment data: 1986–87, 1991–2010

Arsenic 8 66 31 41 33

Cadmium 22 7.7 2.6 4.4 4.3

Chromium 17 41.9 17.0 29.4 31.3

Copper 22 747 303 484 470

Iron 22 43,700 16,500 24,400 23,200

Lead 22 135 59 89 89

Manganese 22 4,820 1,150 2,140 1,900

Nickel 18 16.8 9.3 13.5 13.8

Silver 15 4.7 <3.2 1

3.0 12.9

Zinc 22 1,230 673 960 955

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for bed-sediment data: 1986, 1991–2010

Arsenic 8 43 19 29 27

Cadmium 21 7.3 1.9 3.6 3.5

Chromium 17 42.5 15.3 26.6 27.7

Copper 21 635 211 354 323

Iron 21 25,900 12,600 19,300 17,300

Lead 21 115 47 68 65

Manganese 21 2,340 671 1,320 1,260

Nickel 18 19.1 6.9 12.5 11.6

Silver 14 3.9 <1.9 1

2.1 11.9

Zinc 21 1,160 584 812 786

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Reported concentrations are in micrograms per gram dry weight (μg/g). Number of samples represents the number of years that the constituent was analyzed, 

with each year represented by a single mean concentration of composite samples. Arsenic was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]
Data 99

Constituent Number of samples Maximum Minimum Mean Median

12340000--Blackfoot River near Bonner

Period of record for bed-sediment data: 1986–87, 1991, 1993–96, 1998–2001, 2003, 2006–10

Arsenic 6 6 <0.2 1

3 13

Cadmium 17 2.0 .05 1

.5 1.4

Chromium 13 35.2 15.1 22.9 23.6

Copper 17 27 11 20 21

Iron 17 23,000 12,400 17,700 18,100

Lead 17 20 <13 1

13 113

Manganese 17 746 298 528 542

Nickel 14 14.3 6.0 11.4 11.8

Silver 12 <1.9 <.3 1

.5 1<.6

Zinc 17 82 35 61 63

12340500--Clark Fork above Missoula

Period of record for bed-sediment data: 1997–2010

Arsenic 8 54 17 35 31

Cadmium 14 5.8 1.5 3.3 3.1

Chromium 13 40.7 19.0 27.6 28.5

Copper 14 551 166 375 382

Iron 14 27,000 18,100 21,200 20,600

Lead 14 78 37 57 58

Manganese 14 2,250 477 1,110 1,070

Nickel 14 15.8 7.6 12.8 13.0

Silver 7 2.9 .8 1

2.0 12.1

Zinc 14 1,090 438 761 777

1

Value determined by substituting one-half of the minimum reporting level for censored (<) values when both uncensored and censored values were used to 

determine the mean and (or) median.

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Reported concentrations are in micrograms per gram dry weight (μg/g). Number of samples represents the number of years that the constituent was analyzed, 

with each year represented by a single mean concentration of composite samples. Arsenic was not analyzed until 2003; therefore, the number of samples is 

smaller than that for the other trace elements. Values are reported using U.S. Geological Survey rounding standards. Symbols: <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute statistic]
100 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323600--Silver Bow Creek at Opportunity

Period of record for biological data: 1992, 1994–95, 1997–2010

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 13 33.3 9.5 15.2 13.1

Cadmium 19 9.7 3.1 5.6 5.2

Chromium 19 8.0 1.0 3.3 3.0

Copper 19 1,090 232 420 373

Iron 19 5,890 689 2,460 2,110

Lead 19 68.3 19.0 38.5 39.5

Manganese 19 3,030 180 1,030 1,100

Nickel 19 3.6 .7 2.4 2.5

Zinc 19 1,590 619 891 805

Hydropsyche spp.

Arsenic 11 23.1 6.1 13.3 11.8

Cadmium 16 11.0 2.0 5.8 5.3

Chromium 16 4.7 .6 2.4 2.6

Copper 16 930 80.7 472 436

Iron 16 3,250 1,050 2,090 2,120

Lead 16 237 19.3 48.9 38.2

Manganese 16 1,340 612 1,040 1,050

Nickel 16 2.7 .7 2.1 2.4

Zinc 16 1,290 388 917 988

Hydropsyche tana

Arsenic 0 -- -- -- --

Cadmium 6 9.2 4.8 6.8 6.9

Chromium 6 11.5 .9 4.5 1.8

Copper 6 456 10.5 236 298

Iron 6 1,520 875 1,100 1,050

Lead 6 21.0 15.6 18.6 18.3

Manganese 6 969 307 634 675

Nickel 6 1.8 .7 1.4 1.6

Zinc 6 1,070 760 961 1,020
Data 101

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323750--Silver Bow Creek at Warm Springs

Period of record for biological data: 1992–2010

Claassenia sabulosa

Arsenic 1 -- -- 1.8 --

Cadmium 1 -- -- 1.1 --

Chromium 1 -- -- 2.8 --

Copper 1 -- -- 47.6 --

Iron 1 -- -- 151 --

Lead 1 -- -- .6 --

Manganese 1 -- -- 98.1 --

Nickel 1 -- -- .5 --

Zinc 1 -- -- 400 --

Hydropsyche cockerelli

Arsenic 14 23.6 7.9 12.6 10.3

Cadmium 40 2.1 .2 .6 .5

Chromium 40 4.3 .4 1.1 .8

Copper 40 97.0 16.7 36.6 29.9

Iron 40 1,590 351 788 761

Lead 40 5.7 .3 3.0 2.9

Manganese 40 3,890 491 1,280 992

Nickel 40 1.8 .3 .9 .8

Zinc 40 276 115 175 167

Hydropsyche occidentalis

Arsenic 7 31.0 10.5 19.8 18.0

Cadmium 22 1.6 .2 .6 .4

Chromium 22 6.8 .3 1.6 1.0

Copper 22 48.9 11.0 32.8 32.0

Iron 22 2,960 372 1,210 989

Lead 22 8.2 <1.7 1

4.0 13.7

Manganese 22 6,940 1,200 2,490 2,040

Nickel 22 2.7 .7 1.5 1.5

Zinc 22 220 140 180 182

Hydropsyche spp.

Arsenic 1 -- -- 14.0 --

Cadmium 5 2.3 0.4 1.0 0.6

Chromium 5 2.5 .5 1.4 1.3

Copper 5 47.6 34.9 39.9 40.4

Iron 5 1,100 561 763 767

Lead 5 5.1 1.9 4.0 4.5

Manganese 5 1,190 443 817 804

Nickel 5 1.9 <.4 1

1.0 1.8

Zinc 5 284 141 188 162

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
102 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323770--Warm Springs Creek at Warm Springs

Period of record for biological data: 1995, 1997, 1999, 2002, 2005, 2008

Arctopsyche grandis

Arsenic 3 9.8 9.5 9.6 9.6

Cadmium 7 3.6 1.9 2.8 3.0

Chromium 7 2.9 .8 2.0 1.8

Copper 7 133 78.3 109 102

Iron 7 1,350 684 980 1040

Lead 7 7.2 3.0 1

5.2 15.3

Manganese 7 3,560 1,340 2,540 2,480

Nickel 7 3.5 1.8 1

2.5 12.3

Zinc 7 267 181 206 197

Hydropsyche occidentalis

Arsenic 3 13.6 12.7 13.2 13.3

Cadmium 5 1.3 .7 1.0 1.2

Chromium 5 8.6 .3 3.8 3.2

Copper 5 183 125 158 165

Iron 5 2,360 1,590 1,940 1,950

Lead 5 12.6 6.7 8.5 7.7

Manganese 5 3,190 2,400 2,800 2,880

Nickel 5 4.5 2.0 3.0 3.0

Zinc 5 204 148 169 166

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 2 1.1 0.6 0.9 --

Chromium 2 1.6 1.4 1.5 --

Copper 2 95.9 94.8 95.3 --

Iron 2 1,220 1,150 1,190 --

Lead 2 5.9 5.2 5.6 --

Manganese 2 3,390 956 2,170 --

Nickel 2 2.0 1.8 1.9 --

Zinc 2 129 125 127 --

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
Data 103

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen

Period of record for biological data: 1987, 1991–2010

Claassenia sabulosa

Arsenic 1 -- -- 2.0 --

Cadmium 1 -- -- .2 --

Chromium 1 -- -- 1.5 --

Copper 1 -- -- 54.7 --

Iron 1 -- -- 242 --

Lead 1 -- -- 1.0 --

Manganese 1 -- -- 323 --

Nickel 1 -- -- .5 --

Zinc 1 -- -- 237 --

Hydropsyche cockerelli

Arsenic 8 15.8 13.2 14.1 13.8

Cadmium 33 2.7 .7 1.5 1.5

Chromium 33 4.4 .8 1.9 1.7

Copper 33 181 48.7 105 102

Iron 33 2,660 816 1,470 1,400

Lead 33 11.8 1.2 8.1 7.8

Manganese 33 3,620 1,070 2,250 2,200

Nickel 33 6.5 .9 1.8 1.6

Zinc 33 299 136 210 205

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 5 3.2 2.4 2.5 2.4

Chromium 5 4.6 1.8 2.6 2.2

Copper 5 185 156 173 175

Iron 5 1,890 1,360 1,510 1,430

Lead 5 12.4 7.1 8.5 7.9

Manganese 5 3,960 2,360 3,500 3,860

Nickel 5 3.6 1.9 2.3 2.1

Zinc 5 349 292 309 303

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
104 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of 

composite samples Maximum Minimum Mean Median

12323800--Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991–2010

Hydropsyche occidentalis

Arsenic 12 17.0 9.1 14.7 15.4

Cadmium 44 1.7 .6 1.1 1.2

Chromium 44 6.6 .4 2.0 1.7

Copper 44 151 49.2 87.5 83.9

Iron 44 2,590 642 1,390 1,320

Lead 44 13.5 1.6 7.6 7.3

Manganese 44 6,170 992 2,660 2,260

Nickel 44 3.5 .8 1.7 1.6

Zinc 44 286 168 203 198

Hydropsyche tana

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 1.5 --

Chromium 1 -- -- 1.4 --

Copper 1 -- -- 92.9 --

Iron 1 -- -- 1,340 --

Lead 1 -- -- 9.0 --

Manganese 1 -- -- 2,160 --

Nickel 1 -- -- 2.1 --

Zinc 1 -- -- 206 --

Hydropsyche spp.

Arsenic 5 15.7 5.5 11.1 14.2

Cadmium 9 3.5 .7 1.8 1.3

Chromium 5 2.4 1.1 1.8 1.9

Copper 9 154 55.3 110 126

Iron 9 2,110 914 1,350 1,300

Lead 9 13.5 3.8 9.0 10.5

Manganese 5 4,760 668 2,410 1,520

Nickel 5 2.7 .9 1.6 1.5

Zinc 9 329 132 239 228

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
Data 105

Constituent Number of 

composite samples Maximum Minimum Mean Median

461415112450801--Clark Fork below Lost Creek, near Galen

Period of record for biological data: 1996–2010

Claassenia sabulosa

Arsenic 1 -- -- 1.5 --

Cadmium 2 0.4 0.3 .4 --

Chromium 2 1.9 .4 1.2 --

Copper 2 70.1 67.1 68.6 --

Iron 2 209 189 199 --

Lead 2 1.2 .7 1.0 --

Manganese 2 238 90.4 164 --

Nickel 2 .2 <.2 1

.1 --

Zinc 2 245 208 226 --

Hydropsyche cockerelli

Arsenic 11 27.8 8.8 14.3 11.6

Cadmium 22 2.8 1.1 1.8 1.6

Chromium 22 3.6 .8 2.0 2.0

Copper 22 338 48.8 134 113

Iron 22 4,080 691 1,530 1,180

Lead 22 28.6 4.5 11.6 9.0

Manganese 22 3,160 1,230 1,850 1,720

Nickel 22 2.8 .9 1.4 1.2

Zinc 22 339 151 228 223

Hydropsyche occidentalis

Arsenic 9 20.9 12.7 15.8 15.0

Cadmium 23 1.9 .9 1.4 1.4

Chromium 23 3.6 1.2 2.1 2.0

Copper 23 219 52.1 117 119

Iron 23 2,830 963 1,650 1,510

Lead 23 19.4 6.6 11.0 10.7

Manganese 23 4,150 1,220 2,540 2,190

Nickel 23 3.0 .9 1.6 1.5

Zinc 23 308 174 243 245

Hydropsyche spp.

Arsenic 4 14.5 7.0 10.2 9.7

Cadmium 8 1.8 1.0 1.3 1.3

Chromium 8 2.4 .9 1.4 1.2

Copper 8 153 45.1 96.4 93.0

Iron 8 1,810 533 1,160 1,130

Lead 8 20.5 4.1 9.5 8.0

Manganese 8 1,980 775 1,270 1,230

Nickel 8 2.8 .9 1.6 1.4

Zinc 8 228 143 182 173

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
106 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of 

composite samples Maximum Minimum Mean Median

461559112443301--Clark Fork at county bridge, near Racetrack

Period of record for biological data: 1996–2010

Claassenia sabulosa

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.4 --

Chromium 1 -- -- .3 --

Copper 1 -- -- 40.3 --

Iron 1 -- -- 113 --

Lead 1 -- -- .8 --

Manganese 1 -- -- 172 --

Nickel 1 -- -- .2 --

Zinc 1 -- -- 213 --

Hydropsyche cockerelli

Arsenic 10 20.2 11.1 14.1 13.1

Cadmium 21 2.0 .8 1.5 1.5

Chromium 21 2.8 .6 1.7 1.4

Copper 21 198 50.0 102 98.2

Iron 21 3,330 657 1,270 992

Lead 21 17.2 3.7 8.7 7.5

Manganese 21 2,360 646 1,630 1,900

Nickel 21 2.0 .7 1.2 1.0

Zinc 21 302 139 193 186

Hydropsyche occidentalis

Arsenic 9 16.8 11.3 14.3 14.9

Cadmium 22 2.3 .7 1.5 1.5

Chromium 22 3.7 1.1 2.2 2.1

Copper 22 164 59.5 117 132

Iron 22 3,690 1,030 1,730 1,610

Lead 22 15.7 4.3 11.0 10.9

Manganese 22 3,770 1,090 2,160 2,070

Nickel 22 2.3 1.1 1.5 1.4

Zinc 22 361 181 238 235

Hydropsyche spp.

Arsenic 5 12.8 6.5 10.3 11.9

Cadmium 7 2.4 1.0 1.5 1.5

Chromium 7 3.9 .7 1.7 1.1

Copper 7 144 74.0 101 85.2

Iron 7 1,880 847 1,280 1,200

Lead 7 15.0 5.7 9.1 7.4

Manganese 7 2,370 886 1,340 1,130

Nickel 7 2.0 .7 1.3 1.3

Zinc 7 228 151 188 181

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
Data 107

Constituent Number of 

composite samples Maximum Minimum Mean Median

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for biological data: 1996–2010

Arctopsyche grandis

Arsenic 1 -- -- 11.8 --

Cadmium 2 7.1 1.7 4.4 --

Chromium 2 12.9 <2.4 1

7.0 --

Copper 2 151 30.8 91.0 --

Iron 2 1,500 340 922 --

Lead 2 12.4 <14.5 1

9.8 --

Manganese 2 1,190 510 852 --

Nickel 2 2.3 1.0 1.7 --

Zinc 2 489 86.8 288 --

Claassenia sabulosa

Arsenic 1 -- -- 3.1 --

Cadmium 1 -- -- 2.4 --

Chromium 1 -- -- 1.7 --

Copper 1 -- -- 73.4 --

Iron 1 -- -- 297 --

Lead 1 -- -- 1.9 --

Manganese 1 -- -- 115 --

Nickel 1 -- -- .4 --

Zinc 1 -- -- 330 --

Hydropsyche cockerelli

Arsenic 9 18.8 8.0 13.0 10.4

Cadmium 18 2.0 .7 1.3 1.3

Chromium 18 4.0 .5 1.6 1.3

Copper 18 247 60.7 113 90.2

Iron 18 3,010 552 1,200 923

Lead 18 21.9 3.5 8.7 7.3

Manganese 18 2,650 487 1,370 1,230

Nickel 18 2.5 .5 1.2 1.0

Zinc 18 279 162 208 190

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
108 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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: 1996–2010

Hydropsyche occidentalis

Arsenic 12 24.0 10.2 14.8 15.3

Cadmium 29 2.4 .7 1.4 1.3

Chromium 29 6.2 .8 2.1 1.8

Copper 29 238 74.9 117 95.5

Iron 29 3,390 940 1,640 1,520

Lead 29 21.8 6.1 12.4 11.5

Manganese 29 4,460 826 2,570 2,320

Nickel 29 2.4 1.1 1.6 1.5

Zinc 29 386 211 267 249

Hydropsyche spp.

Arsenic 2 6.5 6.4 6.4 --

Cadmium 4 1.7 .9 1.3 1.3

Chromium 4 2.1 .8 1.4 1.2

Copper 4 140 65.5 94.1 85.4

Iron 4 1,610 875 1,120 987

Lead 4 13.2 7.3 9.7 9.1

Manganese 4 1,150 638 824 756

Nickel 4 1.6 .6 1.1 1.1

Zinc 4 212 162 184 180

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
Data 109

Constituent Number of 

composite samples Maximum Minimum Mean Median

12324200--Clark Fork at Deer Lodge

Period of record for biological data: 1986–87, 1990–2010

Arctopsyche grandis

Arsenic 2 8.3 5.8 7.1 --

Cadmium 4 4.7 <4.2 1

3.4 13.1

Chromium 4 4.7 1.0 1

2.8 12.8

Copper 4 90.5 34.9 68.0 73.2

Iron 4 1,090 537 788 760

Lead 4 11.2 3.8 1

8.2 1<9.5

Manganese 4 1,010 380 766 837

Nickel 4 1.2 <1.3 1

1.1 11.1

Zinc 4 369 140 250 2

46

Hydropsyche cockerelli

Arsenic 6 11.4 5.8 8.2 7.8

Cadmium 29 3.5 .6 1.4 1.3

Chromium 29 3.2 .4 1.6 1.7

Copper 29 180 54.7 98.2 98.2

Iron 29 3,340 490 1,120 1,040

Lead 29 18.1 3.8 9.5 8.9

Manganese 29 1,570 396 879 815

Nickel 29 2.4 .3 1.1 1.0

Zinc 29 391 132 190 185

Hydropsyche occidentalis

Arsenic 15 12.7 6.6 10.2 9.7

Cadmium 52 3.4 .6 1.5 1.3

Chromium 52 3.6 .6 1.9 1.9

Copper 52 180 49.4 119 114

Iron 52 2,060 558 1,430 1,430

Lead 52 18.6 3.5 11.6 11.5

Manganese 52 2,850 649 1,680 1,700

Nickel 52 12.9 1.0 1.7 1.4

Zinc 52 346 166 244 236

Hydropsyche spp.

Arsenic 1 -- -- 6.0 --

Cadmium 4 2.6 1.6 2.2 2.3

Chromium 1 -- -- .8 --

Copper 4 222 91 166 176

Iron 4 2,220 1,070 1,770 1,900

Lead 4 16.7 9.0 14.4 15.9

Manganese 1 -- -- 837 --

Nickel 1 -- -- .9 --

Zinc 4 298 196 242 237

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
110 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of 

composite samples Maximum Minimum Mean Median

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

Period of record for biological data: 2009-10

Arctopsyche grandis

Arsenic 2 6.0 5.5 5.8 --

Cadmium 2 4.9 3.2 4.1 --

Chromium 2 1.9 <2.2 1

1.5 --

Copper 2 83.6 65.7 74.6 --

Iron 2 826 694 760 --

Lead 2 8.1 6.6 7.4 --

Manganese 2 990 940 965 --

Nickel 2 .8 .7 .8 --

Zinc 2 282 253 267 --

Hydropsyche cockerelli

Arsenic 1 -- -- 11.1 --

Cadmium 1 -- -- 4.0 --

Chromium 1 -- -- 3.4 --

Copper 1 -- -- 158 --

Iron 1 -- -- 2,150 --

Lead 1 -- -- 18.8 --

Manganese 1 -- -- 1,500 --

Nickel 1 -- -- 1.7 --

Zinc 1 -- -- 284 --

Hydropsyche occidentalis

Arsenic 4 14.7 7.9 10.4 9.5

Cadmium 4 2.5 2.4 2.5 2.5

Chromium 4 2.1 .7 1.6 1.8

Copper 4 144 98.2 120 120

Iron 4 2,000 1,290 1,620 1,600

Lead 4 17.9 11.1 14.5 14.5

Manganese 4 1,610 1,190 1,400 1,410

Nickel 4 1.7 1.0 1.3 1.3

Zinc 4 266 223 248 253

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
Data 111

Constituent Number of 

composite samples Maximum Minimum Mean Median

12324680--Clark Fork at Goldcreek

Period of record for biological data: 1992–2010

Arctopsyche grandis

Arsenic 28 6.9 1.8 4.2 3.6

Cadmium 57 6.6 .6 2.0 1.8

Chromium 57 3.3 .1 1.2 1.0

Copper 57 129 19.9 44.3 38.4

Iron 57 2,360 195 675 516

Lead 57 10.9 1.0 3.6 3.3

Manganese 57 1,580 436 862 861

Nickel 57 1.8 .2 .7 .6

Zinc 57 326 146 200 184

Claassenia sabulosa

Arsenic 21 2.5 0.4 1.4 1.5

Cadmium 41 3.5 .1 1.1 .7

Chromium 41 1.6 .2 .5 .5

Copper 41 81.7 33.0 58.6 58.1

Iron 41 567 63.0 185 165

Lead 41 2.3 .4 .9 .8

Manganese 41 320 50.6 152 129

Nickel 41 .7 .1 .3 .3

Zinc 41 364 166 266 258

Hydropsyche cockerelli

Arsenic 16 9.8 4.1 5.9 5.6

Cadmium 35 4.2 .5 1.5 1.3

Chromium 35 4.7 .5 2.0 1.9

Copper 35 188 17.1 73.6 58.4

Iron 35 3,250 522 1,160 930

Lead 35 17.6 2.4 6.7 5.3

Manganese 35 1,710 538 1,000 963

Nickel 35 3.5 .3 1.2 1.0

Zinc 35 359 106 193 186

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
112 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, 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: 1992–2010

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 10 8.1 4.7 6.1 5.9

Cadmium 25 2.3 .4 1.3 1.5

Chromium 25 3.9 .4 1.7 1.7

Copper 25 156 26.4 67.3 61.4

Iron 25 2,720 466 1,170 1,120

Lead 25 15.7 2.9 7.1 6.0

Manganese 25 2,210 530 1,260 1,280

Nickel 25 2.5 .8 1.2 1.0

Zinc 25 277 97.0 201 203

Hydropsyche spp.

Arsenic 2 5.9 5.7 5.8 --

Cadmium 2 1.8 1.7 1.8 --

Chromium 2 1.6 1.6 1.6 --

Copper 2 83.5 73.6 78.6 --

Iron 2 1,150 1,110 1,130 --

Lead 2 9.2 8.0 8.6 --

Manganese 2 1,180 1,130 1,150 --

Nickel 2 .8 .8 .8 --

Zinc 2 210 196 203 --

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
Data 113

Constituent Number of 

composite samples Maximum Minimum Mean Median

12331800--Clark Fork near Drummond

Period of record for biological data: 1986, 1991–2010

Arctopsyche grandis

Arsenic 21 5.3 2.3 3.7 3.8

Cadmium 53 3.8 .4 1.4 1.3

Chromium 53 3.3 .2 1.0 1.0

Copper 53 89.2 16.9 33.1 29.1

Iron 53 1,660 193 603 535

Lead 53 11.8 1.6 4.6 4.1

Manganese 53 2,010 456 844 754

Nickel 53 1.9 .2 .6 .6

Zinc 53 308 140 197 189

Claassenia sabulosa

Arsenic 17 1.8 0.7 1.2 1.2

Cadmium 53 2.8 .1 1.0 1.0

Chromium 53 3.3 .1 .7 .6

Copper 53 165 18.0 65.0 60.6

Iron 53 387 45.4 166 146

Lead 53 2.9 .2 1.0 .9

Manganese 53 748 33.1 188 150

Nickel 53 1.1 .1 1

.3 1.2

Zinc 53 567 103 274 261

Hydropsyche cockerelli

Arsenic 13 7.1 3.9 5.4 5.3

Cadmium 42 4.5 .3 1.2 1.0

Chromium 42 3.5 .4 1.6 1.5

Copper 42 156 30.0 59.5 52.6

Iron 42 2,500 506 1,190 987

Lead 42 15.0 4.7 8.5 7.7

Manganese 42 1,680 549 1,010 934

Nickel 42 2.0 .5 1.1 1.1

Zinc 42 322 134 197 190

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
114 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, 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, 1991–2010

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 6 1.3 1.1 1.2 1.2

Chromium 6 2.8 1.9 2.3 2.2

Copper 6 57.4 50.2 55.2 55.8

Iron 6 1,730 1,370 1,570 1,600

Lead 6 10.8 7.0 8.9 9.0

Manganese 6 1,940 1,260 1,610 1,610

Nickel 6 1.7 1.3 1.5 1.5

Zinc 6 250 227 239 240

Hydropsyche occidentalis

Arsenic 13 6.9 4.3 5.4 5.4

Cadmium 29 2.0 .4 1.1 1.0

Chromium 29 8.1 .4 2.2 2.1

Copper 29 118 13.3 56.1 55.2

Iron 29 2,060 424 1,230 1,180

Lead 29 14.0 2.9 8.6 8.7

Manganese 29 2,920 619 1,470 1,230

Nickel 29 2.4 .5 1.3 1.2

Zinc 29 293 157 222 222

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 --

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
Data 115

Constituent Number of 

composite samples Maximum Minimum Mean Median

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for biological data: 1986, 1991–2010

Arctopsyche grandis

Arsenic 25 6.1 3.1 4.4 4.4

Cadmium 67 2.7 .3 1.2 .9

Chromium 67 4.1 .5 1.6 1.4

Copper 67 125 20.1 37.1 32.0

Iron 67 2,870 372 910 790

Lead 67 13.2 1.6 4.3 3.7

Manganese 67 902 324 645 660

Nickel 67 2.6 .4 1.1 .9

Zinc 67 276 111 199 198

Claassenia sabulosa

Arsenic 17 1.9 0.5 1.1 1.2

Cadmium 43 2.5 .1 1.0 .8

Chromium 43 2.0 .2 .7 .6

Copper 43 95.1 37.5 60.1 56.7

Iron 43 340 58.6 127 114

Lead 43 1.6 .2 .6 .6

Manganese 43 229 37.2 99.0 89.4

Nickel 43 .6 .04 .2 .2

Zinc 43 342 144 230 235

Hydropsyche cockerelli

Arsenic 18 6.0 3.7 4.7 4.9

Cadmium 46 1.8 .3 .9 .7

Chromium 46 8.0 .2 2.0 1.7

Copper 46 118 26.4 48.9 44.3

Iron 46 2,530 566 1,220 1,160

Lead 46 12.1 2.2 5.4 5.1

Manganese 46 831 426 642 659

Nickel 46 2.6 .6 1.3 1.2

Zinc 46 228 119 187 194

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
116 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, 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, 1991–2010

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 2 1.3 1.1 1.2 --

Chromium 2 4.6 2.4 3.5 --

Copper 2 84.1 26.8 55.4 --

Iron 2 1,800 986 1,390 --

Lead 2 6.6 <7.8 1

5.2 --

Manganese 2 1,320 537 928 --

Nickel 2 1.7 1.3 1.5 --

Zinc 2 231 171 201 --

Hydropsyche occidentalis

Arsenic 14 5.9 3.6 4.4 4.2

Cadmium 34 1.8 .3 .9 .9

Chromium 34 5.0 .6 1.9 1.7

Copper 34 102 27.4 48.2 45.1

Iron 34 2,310 472 1,230 1,150

Lead 34 14.2 3.0 6.4 5.6

Manganese 34 1,600 454 863 791

Nickel 34 3.2 .6 1.2 1.2

Zinc 34 416 145 213 220

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 --

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
Data 117

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12340000--Blackfoot River near Bonner

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006-10

Arctopsyche grandis

Arsenic 6 4.6 1.6 3.0 2.5

Cadmium 16 .4 .1 .3 .2

Chromium 11 6.9 .5 2.0 1.3

Copper 16 16.2 9.9 12.8 12.4

Iron 16 1,230 108 664 757

Lead 16 2.3 .5 1.1 .9

Manganese 11 633 286 472 476

Nickel 11 3.7 .7 1.3 1.2

Zinc 16 156 123 140 138

Claassenia sabulosa

Arsenic 8 3.0 0.3 1.3 1.4

Cadmium 19 .2 .1 .1 .1

Chromium 14 5.2 .3 1.0 .7

Copper 19 88.5 19.0 43.2 41.0

Iron 19 265 46.2 138 135

Lead 19 .8 .1 .3 .2

Manganese 14 133 26.3 82.2 83.8

Nickel 14 1.1 .1 .3 .3

Zinc 19 328 117 221 197

Hydropsyche cockerelli

Arsenic 5 4.2 2.4 3.2 3.1

Cadmium 5 .6 <.1 1

.4 1.4

Chromium 5 3.8 2.4 3.2 3.6

Copper 5 16.2 5.6 13.3 14.8

Iron 5 2,390 1,550 1,910 1,970

Lead 5 2.3 1.9 2.1 2.1

Manganese 5 814 428 642 637

Nickel 5 4.6 1.8 2.7 2.2

Zinc 5 162 140 146 142
118 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of 

composite samples Maximum Minimum Mean Median

12340000--Blackfoot River near Bonner—Continued

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006-10

Hydropsyche occidentalis

Arsenic 7 3.8 1.9 2.7 2.4

Cadmium 19 .5 .1 .2 .2

Chromium 19 5.8 .8 2.2 1.9

Copper 19 20.6 12.0 15.3 14.7

Iron 19 2,090 1,010 1,490 1,500

Lead 19 2.0 .8 1.5 1.6

Manganese 19 798 414 543 510

Nickel 19 4.9 .9 1.6 1.4

Zinc 19 163 116 141 144

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.6 --

Chromium 1 -- -- 1.6 --

Copper 1 -- -- 13.9 --

Iron 1 -- -- 1,140 --

Lead 1 -- -- 2.9 --

Manganese 1 -- -- 525 --

Nickel 1 -- -- 2.8 --

Zinc 1 -- -- 132 --

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
Data 119

Constituent Number of 

composite samples Maximum Minimum Mean Median

12340500--Clark Fork above Missoula

Period of record for biological data: 1997–2010

Arctopsyche grandis

Arsenic 22 7.2 2.1 4.1 4.0

Cadmium 41 2.3 .1 .9 .7

Chromium 41 4.2 .6 1.7 1.6

Copper 41 81.2 19.5 40.9 36.8

Iron 41 2,340 476 1,080 990

Lead 41 8.9 1.2 4.4 4.1

Manganese 41 1,410 476 914 910

Nickel 41 2.1 .5 1.2 1.1

Zinc 41 272 133 200 198

Claassenia sabulosa

Arsenic 13 1.9 0.5 1.4 1.5

Cadmium 22 2.0 .2 .8 .5

Chromium 22 1.4 .3 .8 .8

Copper 22 81.1 33.0 54.0 51.2

Iron 22 402 95.3 234 233

Lead 22 3.1 .4 1.1 1.0

Manganese 22 683 57.8 213 165

Nickel 22 .5 <.3 1

.4 1.4

Zinc 22 363 191 279 272

Hydropsyche cockerelli

Arsenic 16 8.9 3.7 6.5 6.6

Cadmium 25 2.0 .4 1.0 1.0

Chromium 25 6.0 1.8 3.1 3.3

Copper 25 99.7 29.9 68.5 75.9

Iron 25 3,590 1,400 2,170 2,160

Lead 25 12.1 4.2 8.1 7.6

Manganese 25 1,910 764 1,250 1,220

Nickel 25 2.4 1.4 1.9 1.9

Zinc 25 266 156 223 226

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
120 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, 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: 1997–2010

Hydropsyche occidentalis

Arsenic 7 7.4 3.9 6.0 6.2

Cadmium 13 1.5 .4 .9 .7

Chromium 13 5.5 1.5 3.2 3.0

Copper 13 80.7 30.3 58.1 59.5

Iron 13 2,540 1,450 2,060 2,210

Lead 13 11.4 4.0 7.6 7.4

Manganese 13 2,470 939 1,750 1,730

Nickel 13 2.4 1.4 1.9 1.9

Zinc 13 278 192 238 232

1

Values determined by substituting one-half of the minimum reporting level for censored (<) values when both uncensored and censored values were used 

in determining the mean and median. When all data were less than the minimum reporting level, the median was determined by ranking the censored values in 

order of detection.

Table 27. Statistical summary of long-term biological data for the Clark Fork basin, Montana, August 1986 through 

August 2010.—Continued

[Concentrations are in micrograms per gram dry weight (μg/g). Number of composite samples represents the total of all individual composite samples collected 

for every year that the constituent was analyzed. Values for a single sample are arbitrarily listed in the “Mean” column. Because Hydropsyche insects were not 

sorted to the species level during 1986–89, Hydropsyche species statistics for stations sampled during those years are based on the results of all Hydropsyche

species combined. At some sites, statistics of Hydropsyche morosa group are based on the combined results of two or more species. Insects collected during 

1986–98 were depurated prior to analysis; depuration was discontinued in 1999. Arsenic was not analyzed until 2003; therefore, the number of samples may be 

small or zero for some taxa. Values are reported using U.S. Geological Survey rounding standards. Abbreviation: spp., one or more similar species. Symbols: <, 

less than minimum reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Publishing support provided by the: 

Denver and Rolla Publishing Service Centers

For more information concerning this publication, contact: 

Director, Montana Water Science Center 

U.S. Geological Survey 

3162 Bozeman Ave. 

Helena, MT 59601 

(406) 457–5900

Or visit the Montana Water Science Center Web site at: 

http://mt.water.usgs.gov/

Dodge and others—Water-Quality, Bed-Sediment, and Biological Data (October 2009 through September 2010) and Statistical Summaries of Data for Streams 

in the Clark Fork Basin, Montana—OFR 2011–1314

Printed on recycled paper