U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2014–1034

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

Water-Quality, Bed-Sediment, and Biological Data (October 

2011 through September 2012) and Statistical Summaries of 

Data for Streams in the Clark Fork Basin, Montana

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

Water-Quality, Bed-Sediment, and Biological Data (October 

2011 through September 2012) and Statistical Summaries of 

Data for Streams in the Clark Fork Basin, Montana

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2014–1034
Cover. Reconfigured channel of Silver Bow Creek near Opportunity, Montana, June 2013. Photograph by Kent A. Dodge, 

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

Biological Data (October 2011 through 

September 2012) 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 2014–1034

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2014, Water-quality, bed-sediment, and biological data (October 2011 

through September 2012) and statistical summaries of data for streams in the Clark Fork Basin, Montana: U.S. Geological Survey Open-File Report 2014–1034, 121 p., http://dx.doi.org/10.3133/ofr20141034.

ISSN 0196-1497 (print)

ISSN 2331-1258 (online)

ISBN 0-000-0000-0
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...............................................................................................................................13

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

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

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

Figure

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

Tables

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

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

2. Properties 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 2011 through

September 2012...........................................................................................................................18

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

Deer Lodge, Montana (12324200), October 2011 through September 2012.......................38

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

Bridge, near Bonner, Montana (12334550), October 2011 through September 2012 .......42

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

Bonner, Montana (12340000), October 2011 through September 2012 ..............................46

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

Missoula, Montana (12340500), October 2011 through September 2012...........................50

......
iv

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

statistics at Mill Creek near Anaconda (12323670), Montana, April through

September 2012...........................................................................................................................54

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

statistics at Willow Creek near Anaconda, Montana (12323710), April through

September 2012...........................................................................................................................56

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

statistics at Warm Springs Creek near Anaconda, Montana (12323760), April

through September 2012............................................................................................................58

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

statistics at Lost Creek near Anaconda, Montana (12323840), April through

September 2012...........................................................................................................................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 2012................................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 2012 .......................................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 2012 ..................................................................75

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

Montana, August 1986 through August 2012.........................................................................95

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

August 1986 through August 2012.........................................................................................100
v

Conversion Factors, Datum, Abbreviated Water-Quality 

Units, and Abbreviations

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 

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

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 2012 is the period from October 1, 2011, through September 30, 2012.
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

Abbreviations

FNU formazin nephelometric units

ICP–AES inductively coupled plasma–atomic emission spectrometry

ICP–MS inductively coupled plasma–mass spectrometry

LRL laboratory reporting level

LT–MDL long-term method detection level

MRL minimum reporting level

NTRU nephelometric turbidity ratio unit

NWQL USGS National Water Quality Laboratory, Denver, Colorado

PTFE polytetrafluoroethylene

RSD relative standard deviation

spp. species

SRM standard reference material

USGS U.S. Geological Survey

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

(October 2011 through September 2012) 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 of western Montana. 

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, 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 2011 

through September 2012. Bed-sediment and biota samples 

were collected once at 13 sites during August 2012. 

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

samples collected at sites from October 2011 through September 2012. 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 mean 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, bedsediment, 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 the town of 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 6,000square-mile (mi2

) upper Clark Fork Basin above Missoula include irrigation, stock watering, small-scale industry 

(Cannon and Johnson, 2004) , and habitat for trout fisheries. 

Primary current land uses 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 (2014) either discontinued or substantially reduced 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 took place in the 

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

Tailings produced during past mineral processing commonly 

contain large quantities of trace elements such as arsenic, cadmium, copper, lead, and zinc. Eroded tailings mix with stream 

sediment and get deposited farther downstream in stream 

channels, on flood plains, in the Warm Springs Ponds, and at 

the location of the former Milltown Reservoir (Milltown Dam 

was breached on March 28, 2008) (Andrews, 1987), especially 

during times of increased flow. 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, Tribal, 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, 

2012 through 2013). Trace-element data for bed sediment and 
2 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

biota (aquatic benthic insects) have been collected intermittently at selected sites since 1986 as part of studies on the 

contamination of bed-sediment 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 from samples collected at 20 sites and bed-sediment 

and biological data from samples collected at 13 sites in the 

Clark Fork Basin from October 2011 through September 2012 

(fig. 1). Quality-assurance data are presented for water-quality, 

bed-sediment, and biota samples collected during the same 

time period. Statistical summaries also are provided for waterquality, bed-sediment, and biological data collected at the sites 

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 approximate 

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, Montana. Water-quality samples were collected periodically at 20 sites. Daily suspended-sediment samples were 

collected at four sites, and daily turbidity data were measured 

by continuous turbidity monitors recording every 15 minutes 

at four sites. Bed-sediment and biological samples were collected once annually at 13 sites. Continuous streamflow data 

were collected at 19 sites.

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 2012 are listed in tables 4 through 24 at the 

back of the report. Statistical summaries of long-term waterquality, bed-sediment, and biological data collected between 

March 1985 and September 2012 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 described in the following sections, 

which were designed to provide environmentally representative data. Acceptable results 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. Water samples 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 

suspended-sediment sites, suspended-sediment samples were 

collected by an observer 2–11 times per week, depending 

on season and flow conditions. Continuous turbidity monitors were operated seasonally (April to September 2012) 

at four sites near Anaconda; turbidity data (recorded every 

15 minutes) were used to compute daily mean turbidity values 

(table 1).

Methods

Water samples were collected and composited 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 U.S. Geological Survey (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. Samplers consisted of isokinetic depthintegrating water-quality samplers (Davis, 2005) that were 

constructed of plastic or coated with a nonmetallic rubbercoating paint and equipped with nylon or polytetrafluoroethylene (PTFE) nozzles.

Instantaneous streamflow was determined at the time of 

water sampling either by direct measurement or from stagedischarge rating tables (Rantz and others, 1982). Daily mean 

streamflow values during ice periods were estimated because 

backwater affected the stage-discharge relation. Onsite measurements of pH, specific conductance, and water temperature 
Water-Quality Data 3

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

Mill Creek

Willow

Creek

Cr Silver

Bow

Opportunity

Missoula

Butte

Anaconda

Opportunity

Galen

Warm Springs

Deer Lodge

Garrison

Goldcreek

Drummond

Bonner

Turah

Clinton

Milltown

Reservoir

Clark

Bitterroot

River

Blackfoot

River

Fork

Rock

Creek

Flint

Little

Blackfoot

River

DIVIDE

Clark Fork

Warm Springs

 Ponds

Warm Springs Cr

Silver

Bow

Creek

Blacktail

Cr

CONTINENTAL

Base modified from 

U.S. Geological Survey State 

base map, 1966, 1:1,000,000

North American Datum of 

1927 (NAD 27) 

0 10 20 MILES

0 10 20 KILOMETERS

12340500 12340000

12334550

12331800

12324680

12324200

12323800

12323750 12323770

12323600

12323250

Streamflow site type

 Continuous record

 Periodic measurement

Water-quality, bed-sediment,

and biota site type

 Periodic water quality

 Daily suspended sediment

 Daily turbidity

 Once-annual bed-sediment

 Once-annual biota

EXPLANATION

Site number

461903112440701 Miscellaneous site number

12324200

12323700

12323720 Lost Cr 12323850

46°

114°

113°

12323230

Racetrack

12323840

12323670

Mill

Creek

Willow

Creek

12323710

Creek

47°

12323760

Dempsey

Creek 461903112440701

461559112443301

461415112450801

Helena

M O N T A N A

Study area

Former

12324400
Table 1. Type and period of data collection at sampling sites in the Clark Fork Basin, Montana.[--, no data; P, present; D, discontinued]

Station number 

(fig. 1) Station name

Continuousrecord 

streamflow

Periodic 

water quality1

Daily suspended 

sediment

Daily turbidity 

(seasonal)

Fine-gra

sedi

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 -- 07/9

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 -- 07/9

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, 

08/99, 08/05, 

08

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

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 -- -- -- -- 08/9

461559112443301 Clark Fork at county bridge, near Racetrack -- -- -- -- 08/9

461903112440701 Clark Fork at Dempsey Creek diversion, near 

Racetrack

-- -- -- -- 08/9

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–

08/9

12324400 Clark Fork above Little Blackfoot River, near 

Garrison

02/09–P 03/09–P -- -- 08/0

12324680 Clark Fork at Goldcreek 10/77–P 03/93–P -- -- 07/9
Station number 

(fig. 1) Station name

Continuousrecord 

streamflow

Periodic 

water quality1

Daily suspended 

sediment

Daily turbidity 

(seasonal)

Fine-gra

sedi

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

08/9

12334550 Clark Fork at Turah Bridge, near Bonner 03/85–P 03/85–P 03/85–03/03, 

08/03–P

-- 08

08/9

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

06/88–09/95,

10/05–P

-- 08/86–

08/91, 08/96, 

08/01, 

08/0

12340500 Clark Fork above Missoula 03/29–P 07/86–P3 07/86–04/87, 

06/88–01/96, 03/96–03/03, 

08/03–P

04/07–09/07 08/9

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

and suspended sediment.

2Laboratory analyses for trace elements.3Prior 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[--, no data; P, present; D, discontinued]
6 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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.

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

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 0.022 mg/L 20 --

Magnesium, filtered 0.011 mg/L 20 --

Arsenic, filtered 0.03 μg/L 20 25

Arsenic, unfiltered recoverable 0.28 μg/L 20 25

Cadmium, filtered 0.016 μg/L 20 25

Cadmium, unfiltered recoverable 0.016 μg/L 20 25

Copper, filtered 0.80 μg/L 20 25

Copper, unfiltered recoverable 0.70 μg/L 20 25

Iron, filtered 3.2 μg/L 20 25

Iron, unfiltered recoverable 4.6 μg/L 20 25

Lead, filtered 0.025 μg/L 20 25

Lead, unfiltered recoverable 0.04 μg/L 20 25

Manganese, filtered 0.13 μg/L 20 25

Manganese, unfiltered recoverable 0.4 μg/L 20 25

Zinc, filtered 1.4 μg/L 20 25

Zinc, unfiltered recoverable 3.0 μg/L 20 25

Sediment, suspended, percent finer 

than 0.062 mm

1 percent 20 --

Sediment, suspended 1 mg/L 20 --
Water-Quality Data 7

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 U.S. Geological Survey (variously dated).

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

recoverable” replaced the terms “dissolved” and “total recoverable,” respectively in 2003. Filtered [0.45-micrometer (μm) 

pore size] and unfiltered recoverable concentrations of trace 

elements (arsenic, cadmium, copper, iron, lead, manganese, 

and zinc) and filtered concentrations of calcium and magnesium were measured by the USGS National Water Quality 

Laboratory (NWQL) in Denver, Colorado. Concentrations 

of calcium and magnesium were used in the calculation of 

water hardness.

Filtered concentrations of arsenic, cadmium, copper, lead, 

manganese, and zinc were measured using inductively coupled 

plasma-mass spectrometry (ICP–MS) (Faires, 1993; Garbarino 

and others, 2006). Filtered concentrations of calcium, magnesium, and iron were measured using inductively coupled 

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

1993). Unfiltered recoverable concentrations of trace elements 

were measured in 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 as described by Garbarino and 

Struzeski (1998). For arsenic, copper, and zinc, the digested 

samples were analyzed by ICP–MS as described by Garbarino 

and others (2006). 

Water samples for analysis of suspended-sediment also 

were collected from multiple vertical transits when 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 WyomingMontana Water Science Center Sediment Laboratory (hereinafter referred to as the Wyoming-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 used to calculate 

daily mean suspended-sediment concentrations according to 

methods described by Porterfield (1972).

Suspended-sediment discharge is determined according 

to the following equation (Porterfield, 1972):

Q Q C k s w = × s × , (1)

where

Qs is suspended-sediment discharge, in tons per 

day;

Qw is streamflow, in cubic feet per second;

Cs is suspended-sediment concentration, in 

milligrams per liter; and

k is a units-conversion constant (0.0027) 

to convert instantaneous suspendedsediment discharge to an equivalent daily 

suspended-sediment discharge.

Turbidity data were measured using continuous turbidity 

monitors [Yellow Springs Instruments Company (YSI) 6136 

turbidity sensor] at four tributary sites in the upper Clark Fork 

Basin near Anaconda (table 1). 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 fall (before stream freezeup). 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 determination of the minimum and maximum 

value 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 from samples collected periodically 

during water year 2012 are listed in table 4. Daily mean 

streamflow, daily mean suspended-sediment concentration, and daily suspended-sediment discharge for water year 

2012 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 
8 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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

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

Wyoming-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 (2005).

The quality of analytical results reported for water 

samples was evaluated 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 qualitycontrol sample was submitted at a proportion equivalent to 

about 5 percent of the total number of water samples. Therefore, the total number of quality-control samples represented 

about 15 percent of the total number of water samples.

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

performed systematically by the NWQL to provide quality 

control of analytical procedures (D.L. Stevenson, U.S. Geological Survey, written commun., 2012). These internal 

practices include analyses of quality-control samples such 

as calibration standard samples, standard reference water 

samples, replicate samples, deionized-water blank samples, or 

spiked samples at a proportion equivalent to at least 10 percent 

of the sample load. The NWQL participates in a blind-sample 

program in which standard reference water samples prepared 

by the USGS Branch of Quality Systems are routinely inserted 

into the sample line for each analytical method at a frequency 

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

laboratory also participates in external evaluation studies and 

audits with the National Environmental Laboratory Accreditation Program, the U.S. Environmental Protection Agency, 

Environment Canada, and the USGS Branch of Quality Systems, to assess analytical performance.

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

results. Replicate samples are two or more samples considered 

to be essentially identical in composition. Replicate samples 

can be collected in the field (field replicate) either by 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 can be 

affected by numerous sources of variability within the field 

and laboratory environments, including sample collection, 

processing, and analysis. To provide data on overall precision 

for samples exposed to 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 suspended-sediment analysis 

were obtained in the field by collecting two independent 

cross-sectional samples. Analyses of field replicate samples 

indicate the reproducibility of environmental data that are 

affected by the combined potential variability introduced by 

field and laboratory processes.

Precision of analytical results for laboratory replicates, 

which exclude field sources of variability, was determined 

using 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 potentially can 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 being 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 could potentially bias analytical results. 

The 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 in the field 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 

(Driscoll and Hatcher, 2010). 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 quality-control 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 
Water-Quality Data 9

long-term monitoring program 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 data-quality 

objectives were used to evaluate whether sampling and analytical procedures produced environmentally representative 

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

quality-control samples were submitted and corrective action 

was taken.

The NWQL uses a statistically based convention for 

establishing minimum laboratory reporting levels (LRLs) for 

analytical results and for reporting low-concentration data 

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

by the NWQL on a continuing basis to determine long-term 

method detection levels (LT–MDLs) and LRLs. These values 

are reevaluated each year and, consequently, can change from 

year to year. The methods used to determine the LRLs are 

designed to limit the likelihood of a 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 = ∑ 22 , (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 for each constituent estimated from 

analyses of field replicates, which include 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 for each constituent estimated from 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 comparison of a sample and a spiked aliquot 

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

spike recovery of trace elements in water samples determined 

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

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 98.1 to 106 percent with the 

smallest individual constituent recovery being arsenic, filtered, 

at 90.4 percent and the largest being iron, unfiltered recoverable, at 117 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 25percent deviation from an 

expected 100-percent recovery. The mean spike recovery for 

spiked stream samples (table 17) ranged from 89.8 to 108 percent with the smallest individual constituent recovery being 

zinc, unfiltered recoverable, at 82.4 percent and the largest 

being iron, filtered, at 114 percent. The 95-percent confidence 

intervals for the mean spike recovery for each constituent for 

which stream water samples were analyzed (table 17) did not 

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

recovery. No adjustments were made to analytical data 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 or bias, either high or low. Confidence intervals for percent recovery include 100 percent for 

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

except for filtered iron (102–108 percent) and filtered manganese (101–110 percent). Confidence intervals for percent 

recovery include 100 percent for all laboratory-spiked stream 

samples (table 17) except for filtered arsenic (101–106 percent), filtered cadmium (104–110 percent), filtered copper 

(90.9–97.0 percent), filtered iron (102–114 percent), and 

unfiltered zinc (82.4–97.2). 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 collected as part of the subsequent sample set were evaluated for 

evidence of a consistent trend that could indicate systematic 

contamination. Sporadic, infrequent, nonconsecutive 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, additional 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. One sample concentration of filtered iron [4.2 micrograms per liter (μg/L)] exceeded 

the LRL of 3.2 μg/L. Seven sample concentrations of filtered 

manganese (ranging from 0.15 to 0.57 μg/L) exceeded the 

LRL of 0.13 μg/L. The systematic presence of filtered manganese has been documented and is currently (2014) being 

reviewed by the USGS Office of Water Quality. No adjustments were made to water-quality sample data pending the 

results of this review.

Bed-Sediment Data

Bed-sediment data for the long-term monitoring program 

in the Clark Fork Basin consist of trace-element concentrations in the fine-grained (less than 0.063 mm) fraction of bedsediment samples. 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 as previous samples 

(typically August), to facilitate data comparisons among years. 

Warm Springs Creek at Warm Springs is sampled once every 

3 years rather than once annually and was not sampled during 

water year 2012.

Methods

Fine-grained bed-sediment samples were collected in 

August 2012 using protocols described by Axtmann and 

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

streambed deposits in areas near the edge of the stream 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 collected in an acid-washed 500-milliliter (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, California. 

Bed-sediment samples were oven-dried at 60 °Celsius (C) 

and ground into smaller particle sizes using an acid-washed, 
Bed-Sediment Data 11

ceramic mortar and pestle. Single aliquots of approximately 

0.5–0.6 grams (g) of sediment from each of the three composite bed-sediment samples were digested using a hot, concentrated, nitric acid reflux according to methods described by 

Luoma and Bryan (1981). Laboratory replicates were analyzed 

by taking an aliquot from one of the three 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 were then filtered 

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

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

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

iron, lead, manganese, nickel, and zinc by using inductively 

coupled plasma-atomic emission spectrometry (ICP–AES).

The smallest concentration of a constituent that can be reliably 

reported for analyses of bed sediment is termed the minimum 

reporting level (MRL).

Results

Concentrations of trace elements measured in samples 

of fine-grained bed sediment collected during August 2012 

are listed in table 19. Liquid-phase concentrations, measured 

in microgram per milliliter (μg/mL), were analyzed in the 

reconstituted aliquots of digested bed sediment. Solid-phase 

concentrations, measured in microgram per gram (μg/g), were 

calculated using the following equation:

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

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

= . (5)

The reported solid-phase concentrations (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, MRLs for some trace elements might differ among 

stations and among years.

Quality Assurance

The USGS protocols for field collection and processing 

of bed-sediment samples are designed to prevent contamination from metal sources. Nonmetallic sampling and processing equipment (white plastic scoop, funnel-frame apparatus, 

and 500-mL sample bottles) were acid-washed and rinsed 

with deionized water before the collection of the first sample. 

Polyester-mesh sieves were washed in laboratory-grade detergent and rinsed with deionized water. All equipment received 

a final rinse onsite with native stream water. Sampling 

equipment used at more than one site was rinsed thoroughly 

between sites with native 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 (downstream 

to upstream sites) to minimize effects from potential site-tosite 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 (Ellen 

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

Quality-control samples consisted of standard reference 

materials (SRMs) and procedural blanks. Thirteen procedural 

blanks, 10 low-concentration SRMs, and 10 high-concentration SRMs were analyzed.

Standard reference materials 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. Two SRMs consisting of agricultural soils 

representing low and high concentrations of trace elements 

were analyzed to test recovery efficiency for a range of concentrations similar to those occurring in the bed sediment in 

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. In 

August 2012, the low-concentration standard (SRM 2709a) 

yielded better precision, that is, a lower range of variation. 

The high-concentration standard (SRM 2711a) generally had 

a better recovery accuracy (mean SRM recovery). For copper, 

iron, manganese, nickel, and zinc, mean SRM recoveries for 

the low-concentration standard (SRM sample 2709a) ranged 

from 82.1 to 95.2 percent of the certified concentrations. Mean 

recoveries were somewhat lower for arsenic (56.9 percent), 

chromium (77.5 percent), and lead (60.0 percent). Cadmium 

recovery was lowest at just 21.4 percent. The small range of 

variation (6–11 percent) in the 95-percent confidence interval 

indicates good reproducibility of multiple analyses of SRM 

sample 2709a. Mean recoveries of all elements for the highconcentration standard (SRM sample 2711a) ranged from 

78.4–100 percent. The range of variation for the 95-percent 

confidence interval in SRM sample 2711a recoveries (13.8–

20.4 percent) was higher than the range of variation for SRM 

sample 2709a. No adjustments were made to trace-element 
12 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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 

and analyzed concurrently with bed-sediment samples for each 

site. Concentrations of trace elements in all procedural blanks 

were less than the MRL indicating no contamination bias. No 

adjustments to the trace-element concentrations in bed sediment samples were made.

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 through the years. Warm Springs 

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

than once annually, and was not sampled this year.

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 were collected to provide sufficient mass for analysis. Targeted taxa for collection 

were the order Trichoptera (caddisflies) and the order Plecoptera (stoneflies).

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

for collection in this study 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). On the few occasions when Hydropsyche were not present, other caddisflies, 

including Brachycentrus spp. and Rhyacophila spp., were 

collected. The caddisfly Arctopsyche grandis and the stoneflies 

Claassenia sabulosa and Hesperoperla spp. were collected 

where available to represent additional insect taxa that are 

commonly distributed in the Clark Fork Basin.

Samples of each taxon were sorted by genus in the field 

and placed in acid-washed plastic containers. Samples were 

frozen in a small amount of ambient stream water on dry ice 

within 30 minutes of collection. Between 1986 and 1998, macroinvertebrate containers were kept on ice to allow the insects 

to evacuate their gut contents (depurate) for 6 to 8 hours. 

Excess water was drained and insects were frozen for transport to the laboratory. Since 1999, 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 indicated 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–AES 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 MRL.

Results

Concentrations of trace elements in whole-body tissue 

of aquatic insects collected during August 2012 are listed in 

table 22. The variability in the number of composite samples 

among species and among sites reflects differences in insect 

abundance, with the number of composite samples increasing 

with the relative abundance of insects. Liquid-phase concentrations, in μg/mL, analyzed in the reconstituted samples were 

converted to solid-phase concentrations, in μg/g, by using 

equation 5 (used earlier in this report to calculate solid-phase 

concentrations of trace elements in bed sediment). All tissue 

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

MRLs for trace elements in bed sediment, MRLs 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 MRL. Therefore, higher MRLs do not necessarily imply a 

higher trace-element concentration in tissue.
Statistical Summaries of Data 13

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 

before the first sample collection. Nets and equipment were 

thoroughly rinsed in ambient stream water at each main-stem 

site. New nets were used at each tributary site. Biota samples 

were collected sequentially at sites along an increasing 

concentration gradient, which was from downstream sites to 

upstream sites to minimize effects from potential site-to-site 

carryover contamination (Hornberger and others, 1997).

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 sample TORT-2 (lobster hepatopancreas) and 

13 procedural blanks (1 at each site). 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 sample TORT-2 for biota is listed in table 23. Dataquality objectives have not been established for analytical 

recovery in biota, but percent recoveries indicate analytical 

performance. Mean SRM sample TORT-2 recoveries ranged 

from 79.8 to 129 percent for all constituents. With the exception of chromium, lead and nickel, all of which had relatively 

low certified concentrations in the SRM sample TORT-2 

(0.77 μg/g, 0.35 μg/g and 2.5 μg/g, respectively), the range 

of variation of the 95-percent confidence interval was within 

13 percent, indicating reasonable recoveries in the SRM 

sample TORT-2. No adjustments were made to trace-element 

concentrations in biota samples on the basis of recovery 

efficiencies.

Procedural blanks for biota consisted of undiluted aliquots of the same reagents used to digest and reconstitute tissue of aquatic insects. Analytical results of procedural blanks 

for biota (table 24) are reported as a liquid-phase concentration, in microgram 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 MRL; 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 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 that targeted high-flow conditions or 

maintenance drawdowns of Milltown Reservoir, which might 

disproportionately skew the long-term statistics relative to 

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

results of samples collected once 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. 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. The 

number of samples for arsenic for bed sediment 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.

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. 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. Also, the number of samples for arsenic in biota samples is smaller than the 

number for other trace elements because sampling for arsenic 

began in September 2003. 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 MRLs. When MRLs 

vary among years, differences in concentration with time are 

difficult to determine, especially when a large percentage of 

the samples have concentrations less than MRLs.

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

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

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

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

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Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2005, 

Water-quality, bed-sediment, and biological data (October 2003 through September 2004) and statistical summaries of data for streams in the upper Clark Fork basin, 

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Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2006, 

Water-quality, bed-sediment, and biological data (October 2004 through September 2005) and statistical summaries of data for streams in the upper Clark Fork basin, 

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

2006–1266, 109 p. (Also available at http://pubs.usgs.gov/

of/2006/1266.)

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.)
References Cited 15

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.)

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 Dyke, J.L., 2012, Waterquality, 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. (Also 

available at http://pubs.usgs.gov/of/2011/1314.)

Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2013, Waterquality, bed-sediment, and biological data (October 2010 

through September 2011) and statistical summaries of data 

for streams in the Clark Fork basin, Montana: U.S. Geological Survey Open-File Report 2013–1017, 132 p. (Also 

available at http://pubs.usgs.gov/of/2013/1017.)

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.gov/of/2006/1242.)

Driscoll, A. and Hatcher, J., 2010, Chain of custody: 

U.S. Geological Survey National Water Quality Laboratory SOP QUAX0030.4, effective May 5, 2010, 17 p. (Also 

available at http://wwwnwql.cr.usgs.gov/USGS/htmls/

QUAX0030.4controlled.pdf.)

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 

Open-File Report 93–125, 217 p.

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

practices for the chemical and biological analyses of water 

and fluvial sediments: U.S. Geological Survey Techniques 

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

(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 wholewater digests using inductively coupled plasma-optical 

emission spectrometry and inductively coupled plasmamass spectrometry: U.S. Geological Survey Open-File 

Report 98–165, 101 p.

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, book 5, sec. B, chap. 1, 88 p.

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

analysis: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. C1, 58 p. (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.
16 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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

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

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

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

Open-File Report 97–669, 84 p.

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

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

for the collection and processing of surface-water samples 

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

Report 94–539, 57 p.

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

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

and selected tributaries from Deer Lodge to Milltown, 

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

Survey Open-File Report 87–110, 48 p.

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

September 1987) and statistical summaries (March 1985 

through September 1987) for the Clark Fork and selected 

tributaries from Deer Lodge to Missoula, Montana: 

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

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

through September 1988) and statistical summaries (March 

1985 through September 1988) for the Clark Fork and 

selected tributaries from Galen to Missoula, Montana: 

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

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

through September 1989) and statistical summaries (March 

1985 through September 1989) for the Clark Fork and 

selected tributaries from Galen to Missoula, Montana: 

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

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

of the upper Clark Fork basin from Galen to Missoula, 

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

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

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

Report 2006–1275, 39 p. (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.

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. (Also available at http://pubs.usgs.gov/of/1995/0443/.)

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

Paper 2175, v. 2, 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/.)

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

2006, Guidelines and standard procedures for continuous 

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

and Methods 1–D3, 51 p., 8 attachments (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 2011 through September 2012.

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323230—Blacktail Creek at Harrison Avenue, at Butte

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/07/2011 0945 8.9 7.6 304 1.0 129 36.8 8.94

03/19/2012 1000 17 7.5 279 1.0 107 29.7 7.97

04/09/2012 0915 24 7.6 265 2.0 108 30.6 7.67

05/14/2012 0905 12 7.6 273 8.0 115 33.0 7.90

06/04/2012 0855 18 7.6 232 10.0 94.3 26.8 6.67

06/18/2012 0840 10 7.6 265 10.0 108 31.1 7.47

07/16/2012 0900 21 7.6 253 13.0 101 28.8 7.03

08/13/2012 0830 4.5 7.6 322 11.0 132 37.9 9.17

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/07/2011 2.0 3.2 0.032 0.033 1.5 2.9 127 632

03/19/2012 3.9 4.7 0.040 0.031 3.0 4.6 371 726

04/09/2012 3.2 4.4 0.030 0.033 2.8 4.4 357 910

05/14/2012 3.6 4.4 0.026 0.037 2.3 2.9 304 704

06/04/2012 5.0 6.2 0.024 0.029 3.1 4.9 304 781

06/18/2012 4.7 6.0 0.025 0.034 2.3 3.5 285 710

07/16/2012 7.3 9.9 0.031 0.061 4.7 9.0 374 1,510

08/13/2012 2.9 3.3 0.037 <0.016 1.2 2.0 51.9 228

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2011 0.041 0.52 94.4 113 2.9 5.3 84 7 0.17

03/19/2012 0.223 0.66 120 131 3.5 4.7 75 6 0.28

04/09/2012 0.192 0.78 75.3 89.0 2.3 3.8 73 9 0.58

05/14/2012 0.134 0.47 70.5 82.8 2.1 <3.0 88 5 0.16

06/04/2012 0.194 0.78 55.5 87.4 1.5 3.3 89 7 0.34

06/18/2012 0.154 0.55 66.4 78.4 <1.4 <3.0 91 4 0.11

07/16/2012 0.243 1.85 92.0 178 2.4 9.2 85 22 1.2 

08/13/2012 0.043 0.23 36.6 44.1 1.6 <3.0 79 4 0.05
Data 19

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323250—Silver Bow Creek below Blacktail Creek, at Butte

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/07/2011 1115 21 7.8 526 4.0 184 52.2 13.0

03/19/2012 1140 33 7.7 435 2.5 145 40.5 10.7

04/09/2012 1055 40 7.7 413 4.0 148 41.8 10.5

05/14/2012 1030 27 7.7 445 10.5 154 44.7 10.4

06/04/2012 1030 33 7.9 385 12.0 135 38.8 9.28

06/18/2012 1000 24 7.8 458 12.0 155 44.7 10.6

07/16/2012 1045 30 7.6 387 15.0 127 36.8 8.61

08/13/2012 1005 16 7.5 579 16.0 203 59.7 13.0

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/07/2011 2.9 3.9 0.083 0.114 2.9 9.9 43.1 296

03/19/2012 3.9 5.0 0.074 0.130 4.6 13.7 231 645

04/09/2012 3.5 4.8 0.058 0.113 4.7 13.7 232 729

05/14/2012 3.8 4.4 0.060 0.091 3.5 9.1 118 388

06/04/2012 4.8 6.1 0.050 0.081 4.0 9.3 150 517

06/18/2012 4.4 5.2 0.051 0.103 3.3 10.8 108 447

07/16/2012 6.4 7.4 0.046 0.087 4.5 9.7 196 593

08/13/2012 3.9 4.2 0.053 0.084 3.1 11.0 28.1 105

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)

11/07/2011 0.181 1.50 105 110 30.7 37.5 73 6 0.34

03/19/2012 0.430 3.06 132 148 20.9 33.3 79 12 1.1

04/09/2012 0.268 2.06 95.8 111 19.6 30.3 84 11 1.2

05/14/2012 0.211 0.93 73.2 84.6 22.2 23.6 80 4 0.29

06/04/2012 0.232 1.40 57.4 87.1 13.8 20.5 83 6 0.53

06/18/2012 0.243 1.40 69.7 92.6 17.6 25.0 88 7 0.45

07/16/2012 0.319 1.93 51.5 73.5 16.6 23.9 95 7 0.57

08/13/2012 0.193 0.61 65.4 69.2 32.7 36.2 81 3 0.13
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 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323600—Silver Bow Creek at Opportunity

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/08/2011 0720 E52 8.1 497 0.0 195 57.5 12.4

03/19/2012 1630 64 8.2 485 4.5 165 46.3 12.0

04/10/2012 0740 81 7.9 428 5.0 159 46.3 10.5

05/15/2012 0800 76 8.3 379 10.0 149 45.4 8.75

06/05/2012 0730 83 8.0 331 11.5 127 38.4 7.61

06/19/2012 0740 59 8.0 420 8.5 154 46.1 9.38

07/17/2012 0750 95 8.0 446 15.5 160 47.1 10.4

08/14/2012 0745 21 8.2 592 13.5 217 64.0 13.8

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/08/2011 6.8 7.8 0.530 0.519 14.3 27.0 20.4 325

03/19/2012 6.6 9.3 0.408 0.629 17.5 45.2 116 1,110

04/10/2012 6.1 8.7 0.437 0.624 16.1 38.6 60.4 1,040

05/15/2012 7.4 8.2 0.227 0.370 11.3 23.6 33.5 494

06/05/2012 7.3 8.5 0.215 0.373 11.4 26.0 46.2 517

06/19/2012 8.7 8.9 0.247 0.370 11.2 23.6 44.7 398

07/17/2012 10.8 25.3 0.148 2.05 16.5 192 62.1 6,910

08/14/2012 11.7 11.5 0.394 0.532 16.6 25.8 21.9 196

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/08/2011 0.243 4.15 106 114 116 128 91 7 0.98

03/19/2012 0.628 9.44 159 225 75.5 131 69 40 6.9

04/10/2012 0.312 8.45 189 244 120 163 55 38 8.3

05/15/2012 0.235 4.22 102 146 38.7 76.5 71 22 4.5

06/05/2012 0.335 5.23 83.0 150 42.9 77.6 77 21 4.7

06/19/2012 0.354 4.51 89.4 124 56.4 79.2 84 12 1.9

07/17/2012 0.795 59.5 108 671 32.8 410 62 311 80

08/14/2012 0.184 1.81 59.2 111 55.1 87.9 94 8 0.45
Data 21

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323670—Mill Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/07/2011 1405 E13 <2.0 7.9 200 0.0 98.0 26.7 7.60

03/19/2012 1310 12 <2.0 8.0 199 3.0 95.2 25.4 7.70

04/09/2012 1330 20 <2.0 7.9 166 6.0 71.9 19.5 5.63

05/14/2012 1310 75 <2.0 7.8 97 10.0 43.4 12.2 3.11

06/04/2012 1300 212 E2.8 7.7 64 9.5 28.0 8.17 1.84

06/18/2012 1250 96 <2.0 7.7 76 9.0 33.5 9.66 2.28

07/16/2012 1320 41 E5.4 7.9 115 14.5 51.0 14.3 3.70

08/13/2012 1240 18 <2.0 8.2 169 15.0 79.1 21.6 6.12

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/07/2011 13.4 12.9 0.062 0.062 1.0 1.5 54.4 105

03/19/2012 14.5 15.0 0.073 0.071 1.4 2.4 49.7 101

04/09/2012 17.0 17.8 0.055 0.067 2.4 3.2 44.8 152

05/14/2012 12.8 13.1 0.035 0.063 2.3 3.2 35.5 138

06/04/2012 8.2 9.3 0.033 0.075 2.9 4.5 31.4 379

06/18/2012 7.8 7.8 0.031 0.046 1.7 2.8 29.6 134

07/16/2012 15.7 16.4 0.030 0.065 2.0 3.3 54.2 246

08/13/2012 21.6 21.9 0.036 0.044 1.5 2.1 64.0 134

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2011 0.071 0.24 10.7 12.3 2.3 <3.0 63 1 0.04

03/19/2012 0.075 0.40 7.96 10.0 2.1 <3.0 67 1 0.03

04/09/2012 0.126 0.52 6.76 9.1 1.9 <3.0 72 3 0.16

05/14/2012 0.106 0.50 4.18 8.1 1.7 <3.0 38 8 1.6

06/04/2012 0.092 0.99 4.49 17.5 2.0 4.4 44 18 10

06/18/2012 0.089 0.49 3.80 8.3 <1.4 3.8 32 7 1.8

07/16/2012 0.151 0.72 9.15 12.9 <1.4 <3.0 84 9 1.0

08/13/2012 0.187 0.37 5.90 10.7 <1.4 <3.0 81 2 0.10
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 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323700—Mill Creek at Opportunity

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/07/2011 1630 16 8.0 239 -1.0 112 31.0 8.44

03/19/2012 1510 E8.0 8.2 228 2.0 104 28.4 8.11

04/09/2012 1610 11 8.1 192 8.0 83.1 22.9 6.29

05/14/2012 1600 37 7.9 108 13.0 48.4 13.8 3.39

06/04/2012 1605 122 7.7 70 12.0 30.2 8.75 2.03

06/18/2012 1445 59 7.9 84 10.0 36.3 10.6 2.41

07/16/2012 1555 20 8.1 131 16.0 56.9 16.1 4.08

08/13/2012 1515 3.6 8.3 190 18.0 85.5 23.9 6.28

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered (μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/07/2011 16.1 16.4 0.090 0.091 1.4 2.0 58.6 130

03/19/2012 14.2 14.7 0.041 0.058 1.5 2.2 35.4 69.8

04/09/2012 16.2 17.1 0.055 0.077 2.4 3.4 42.5 136

05/14/2012 14.5 14.6 0.040 0.092 2.5 4.2 33.2 185

06/04/2012 10.7 12.1 0.040 0.141 2.9 8.0 33.3 536

06/18/2012 10.1 10.6 0.038 0.073 2.0 3.7 29.1 186

07/16/2012 19.1 19.5 0.046 0.085 2.1 3.5 44.0 200

08/13/2012 24.8 22.9 0.038 0.034 2.4 2.1 42.3 74.8

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2011 0.097 0.30 10.2 12.2 3.9 4.6 74 2 0.09

03/19/2012 0.066 0.19 3.68 4.2 2.1 <3.0 83 1 0.02

04/09/2012 0.121 0.44 5.40 7.8 2.1 3.1 68 3 0.09

05/14/2012 0.120 0.77 4.02 11.6 1.9 3.2 60 8 0.80

06/04/2012 0.132 2.25 3.75 23.9 1.7 6.3 51 29 9.6

06/18/2012 0.101 0.99 4.06 10.3 <1.4 3.5 60 7 1.1

07/16/2012 0.124 0.63 7.01 11.7 <1.4 3.7 91 6 0.32

08/13/2012 0.117 0.20 7.51 6.6 <1.4 <3.0 91 1 0.01
Data 23

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323710—Willow Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/07/2011 1255 E2.5 <2.0 7.6 138 0.0 54.7 17.7 2.53

04/09/2012 1225 2.9 E4.2 7.7 127 2.5 47.0 15.3 2.14

05/14/2012 1205 12 E3.2 7.6 85 7.0 32.2 10.7 1.32

06/04/2012 1205 22 E4.7 7.6 80 9.0 30.1 10.1 1.22

06/18/2012 1140 11 E2.4 7.8 93 8.0 35.6 11.9 1.43

07/16/2012 1220 5.4 E11 7.8 107 13.0 39.6 13.1 1.68

08/13/2012 1150 2.1 E2.8 7.7 112 13.0 42.7 14.2 1.74

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered (μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered (μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered

 (μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/07/2011 15.2 14.6 0.047 0.053 1.8 2.1 75.3 153

04/09/2012 14.7 15.5 0.031 0.042 2.4 2.8 89.2 317

05/14/2012 15.7 14.7 0.025 0.032 2.1 2.4 89.3 190

06/04/2012 15.3 14.5 0.025 0.039 2.5 3.0 120 289

06/18/2012 15.5 14.8 0.028 0.032 2.0 2.5 115 154

07/16/2012 22.7 24.2 0.053 0.091 2.4 4.0 64.0 407

08/13/2012 25.7 25.3 0.041 0.066 1.8 2.5 97.8 228

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2011 0.106 0.30 25.8 31.3 2.0 <3.0 63 3 0.02

04/09/2012 0.165 0.43 20.2 22.4 1.8 <3.0 69 3 0.02

05/14/2012 0.162 0.36 10.5 12.8 1.5 <3.0 74 3 0.10

06/04/2012 0.184 0.58 9.84 16.8 1.9 <3.0 83 4 0.24

06/18/2012 0.159 0.32 12.6 14.0 <1.4 <3.0 88 3 0.09

07/16/2012 0.210 1.14 15.2 26.7 <1.4 3.3 95 16 0.23

08/13/2012 0.235 0.54 17.3 24.8 <1.4 <3.0 87 4 0.02
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 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323720—Willow Creek at Opportunity

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/07/2011 1705 5.9 8.1 308 4.0 141 41.1 9.26

03/19/2012 1550 8.4 7.9 302 5.5 129 37.8 8.51

04/09/2012 1650 11 8.0 314 10.5 126 37.1 8.21

05/14/2012 1640 12 8.2 178 17.0 77.6 23.6 4.56

06/04/2012 1650 22 8.1 207 17.0 90.8 27.3 5.51

06/18/2012 1520 18 8.2 234 15.0 106 31.1 6.76

07/16/2012 1640 10 8.1 261 15.0 115 33.4 7.72

08/13/2012 1550 6.2 8.7 288 18.0 133 37.9 9.23

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/07/2011 11.9 12.5 0.041 0.047 2.1 4.2 21.3 119

03/19/2012 21.6 25.7 0.051 0.078 3.9 7.1 144 361

04/09/2012 30.1 34.0 0.052 0.085 5.3 8.4 90.1 308

05/14/2012 27.3 27.2 0.032 0.083 4.9 7.7 72.9 292

06/04/2012 48.1 43.5 0.044 0.085 6.2 10.2 78.4 367

06/18/2012 46.7 44.7 0.045 0.086 5.4 7.9 55.0 244

07/16/2012 28.9 27.3 0.031 0.051 3.5 4.9 41.5 142

08/13/2012 17.1 15.4 0.019 0.023 2.4 3.0 6.1 40.7

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2011 0.161 1.19 11.1 12.5 3.3 6.0 96 3 0.05

03/19/2012 0.365 1.37 83.2 91.9 5.6 9.2 92 7 0.16

04/09/2012 0.272 1.29 84.3 93.3 5.1 8.9 92 6 0.18

05/14/2012 0.398 1.60 34.5 47.2 3.0 7.1 92 8 0.26

06/04/2012 0.321 1.94 30.6 57.8 2.8 9.5 89 10 0.59

06/18/2012 0.259 1.21 25.3 35.7 5.2 9.1 95 5 0.24

07/16/2012 0.196 0.77 11.7 15.8 2.8 5.1 96 2 0.05

08/13/2012 0.073 0.36 5.49 7.8 <1.4 <3.0 85 1 0.02
Data 25

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323750—Silver Bow Creek at Warm Springs

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite (standard units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/08/2011 0835 64 8.4 526 1.0 236 68.6 15.6

03/20/2012 0805 132 8.5 487 0.0 202 58.6 13.4

04/10/2012 0905 118 8.8 466 6.0 195 56.5 13.0

05/15/2012 1010 125 9.4 331 12.5 136 38.5 9.62

06/05/2012 0945 246 9.2 272 10.5 108 31.3 7.16

06/19/2012 0900 118 9.2 326 8.5 137 39.8 9.03

07/17/2012 1010 59 9.2 370 17.0 165 47.5 11.2

08/14/2012 0915 40 9.3 469 16.0 204 59.0 13.8

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/08/2011 19.5 22.2 0.059 0.244 3.0 16.4 11.5 418

03/20/2012 10.6 14.7 0.095 0.316 3.7 21.9 25.5 521

04/10/2012 13.2 15.4 0.056 0.161 4.6 11.7 38.5 309

05/15/2012 21.8 22.4 0.033 0.088 5.0 7.8 38.7 223

06/05/2012 21.5 24.2 0.039 0.148 5.0 10.9 34.7 520

06/19/2012 23.5 23.3 0.033 0.082 4.4 7.0 52.6 235

07/17/2012 34.6 33.4 0.028 0.072 2.8 5.3 34.4 204

08/14/2012 37.0 34.4 0.026 0.051 2.6 4.4 7.0 87.8

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/08/2011 0.165 4.18 61.7 127 4.1 28.4 97 9 1.6

03/20/2012 0.179 5.63 175 257 5.2 34.7 84 12 4.3

04/10/2012 0.208 2.93 122 170 3.3 20.0 89 7 2.2

05/15/2012 0.221 1.31 41.6 77.5 1.9 7.7 82 6 2.0

06/05/2012 0.175 2.33 42.8 96.5 1.5 11.5 85 16 11

06/19/2012 0.262 1.20 67.2 97.8 2.2 7.8 95 4 1.3

07/17/2012 0.152 1.07 36.6 102 <1.4 5.7 80 6 0.96

08/14/2012 0.054 0.58 27.1 65.4 <1.4 3.6 73 3 0.32
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 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323760—Warm Springs Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/07/2011 1525 108 <2.0 8.5 278 3.0 145 42.8 9.34

04/09/2012 1500 71 <2.0 8.5 274 7.5 138 40.3 9.05

05/14/2012 1500 155 <2.0 8.5 187 10.0 98.8 30.2 5.70

06/04/2012 1445 344 <2.0 8.1 135 9.5 65.5 20.1 3.71

07/16/2012 1445 125 <2.0 8.3 220 12.0 107 31.9 6.59

08/13/2012 1415 81 <2.0 8.5 250 13.0 126 37.4 7.92

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, filtered (μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/07/2011 2.2 2.5 0.024 0.017 <0.80 1.2 3.6 31.1

04/09/2012 2.3 2.5 <0.016 <0.016 <0.80 1.3 7.9 49.2

05/14/2012 1.6 2.0 0.019 0.032 1.1 2.2 5.4 122

06/04/2012 1.7 1.8 0.021 0.046 1.3 4.0 5.7 166

07/16/2012 2.4 2.4 0.017 0.036 0.84 2.0 11.0 83.6

08/13/2012 2.5 2.3 0.022 0.016 -- 1.8 5.8 60.8

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2011 <0.025 0.11 1.24 1.8 <1.4 <3.0 63 1 0.29

04/09/2012 0.042 0.17 1.74 2.6 <1.4 <3.0 65 3 0.58

05/14/2012 0.032 0.37 1.81 5.4 <1.4 <3.0 53 9 3.8

06/04/2012 <0.025 0.47 1.97 9.2 <1.4 4.2 55 11 10

07/16/2012 <0.025 0.28 1.58 4.7 <1.4 <3.0 74 5 1.7

08/13/2012 0.029 0.17 1.13 2.9 <1.4 <3.0 78 3 0.66
Data 27

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323770—Warm Springs Creek at Warm Springs

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/08/2011 0805 99 8.2 320 1.5 167 49.8 10.2

04/10/2012 0840 69 8.2 352 5.0 182 53.9 11.6

05/15/2012 0945 128 8.1 222 8.0 114 35.2 6.36

06/05/2012 0850 277 7.9 150 8.0 72.2 22.3 4.02

07/17/2012 0940 75 8.2 264 12.0 129 39.2 7.46

08/14/2012 0850 40 8.2 309 12.0 154 46.7 9.07

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/08/2011 3.0 3.6 0.065 0.128 1.1 5.1 8.1 81.4

04/10/2012 3.8 4.1 0.055 0.096 2.0 6.5 18.9 109

05/15/2012 2.9 5.8 0.043 0.125 2.2 30.7 9.7 502

06/05/2012 3.9 10.7 0.037 0.230 3.9 58.3 19.4 1,380

07/17/2012 4.2 4.7 0.047 0.070 2.2 9.5 14.1 167

08/14/2012 4.7 4.7 0.029 0.046 2.1 5.1 9.1 51.7

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/08/2011 <0.025 0.40 57.2 62.6 1.9 <3.0 59 3 0.80

04/10/2012 0.064 0.52 82.5 102 <1.4 6.6 72 5 0.93

05/15/2012 0.042 2.83 46.6 116 1.4 9.8 63 31 11

06/05/2012 0.068 5.87 33.3 259 1.4 26.7 58 86 64

07/17/2012 0.048 0.83 51.8 74.7 2.2 3.9 75 7 1.4

08/14/2012 0.041 0.27 58.0 67.4 <1.4 <3.0 77 2 0.22
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 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323800—Clark Fork near Galen

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/08/2011 1000 160 8.3 416 1.0 197 58.1 12.6

03/20/2012 0940 181 8.2 438 0.0 186 54.4 12.3

04/10/2012 1025 189 8.5 433 6.0 196 57.6 12.6

05/15/2012 1145 262 9.0 282 11.5 124 36.5 7.94

06/05/2012 1115 523 8.6 210 11.0 89.8 26.9 5.51

06/19/2012 1015 339 8.6 236 8.5 105 31.4 6.37

07/17/2012 1145 143 8.6 321 15.5 146 43.6 9.02

08/14/2012 1050 71 8.7 394 15.0 183 54.1 11.7

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/08/2011 10.2 11.6 0.054 0.199 2.1 10.1 9.6 224

03/20/2012 7.3 10.7 0.079 0.162 3.1 18.7 19.8 431

04/10/2012 10.0 12.2 0.055 0.185 3.6 14.8 22.2 314

05/15/2012 12.9 13.8 0.037 0.109 4.2 17.4 20.0 334

06/05/2012 12.7 16.8 0.030 0.179 5.4 36.1 29.0 860

06/19/2012 10.7 11.2 0.028 0.076 3.3 13.0 21.1 248

07/17/2012 18.4 17.7 0.039 0.098 3.3 9.1 22.8 169

08/14/2012 20.2 19.2 0.036 0.052 3.9 9.0 10.4 94.2

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/08/2011 0.082 1.97 56.4 86.6 3.3 14.5 93 5 2.2

03/20/2012 0.127 4.11 127 178 5.2 18.7 78 13 6.4

04/10/2012 0.132 2.77 106 156 3.5 17.8 82 8 4.1

05/15/2012 0.119 2.17 41.5 87.0 1.4 11.1 70 14 9.9

06/05/2012 0.166 4.76 36.5 110 <1.4 23.4 66 59 83

06/19/2012 0.112 1.52 40.7 66.4 1.5 9.4 67 8 7.3

07/17/2012 0.107 1.05 39.8 73.5 2.1 5.9 75 5 1.9

08/14/2012 0.111 0.98 42.9 65.4 1.4 5.2 86 4 0.77
Data 29

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323840—Lost Creek near Anaconda

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

Turbidity, 

unfiltered, 

lab 

(NTRU)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water (°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/07/2011 1445 18 <2.0 8.1 226 0.0 116 34.9 7.14

03/19/2012 1405 8.5 <2.0 8.3 225 2.0 113 33.2 7.40

04/09/2012 1410 10 <2.0 8.1 226 5.5 111 32.8 7.00

05/14/2012 1355 4.9 <2.0 8.0 169 13.0 86.0 26.2 5.00

06/04/2012 1400 21 E3.3 8.0 148 11.0 71.4 21.9 4.04

06/18/2012 1350 16 <2.0 8.1 166 10.0 83.0 25.6 4.65

07/16/2012 1405 9.4 <2.0 8.1 216 12.0 102 31.0 5.91

08/13/2012 1330 13 <2.0 8.2 225 12.0 111 33.4 6.63

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/07/2011 2.2 2.8 0.033 0.027 1.0 4.5 6.7 159

03/19/2012 1.9 2.1 0.023 <0.016 1.0 1.8 10.3 32.5

04/09/2012 1.9 2.2 0.020 0.020 1.3 3.0 7.8 71.9

05/14/2012 4.5 4.2 0.026 0.035 2.9 4.7 11.7 79.8

06/04/2012 4.0 4.4 0.022 0.055 2.2 9.7 7.1 394

06/18/2012 4.5 4.5 0.019 0.034 1.8 4.6 10.5 102

07/16/2012 6.2 6.0 0.029 0.030 1.7 2.7 9.9 58.0

08/13/2012 3.1 3.3 0.021 0.024 0.92 2.6 8.5 96.3

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2011 <0.025 0.57 2.35 6.4 <1.4 <3.0 38 8 0.39

03/19/2012 <0.025 0.12 1.06 1.5 <1.4 <3.0 67 1 0.02

04/09/2012 0.034 0.28 2.06 2.5 <1.4 <3.0 74 7 0.19

05/14/2012 0.039 0.32 2.08 3.5 <1.4 <3.0 68 4 0.05

06/04/2012 0.028 1.45 1.43 10.7 1.5 5.6 40 21 1.2 

06/18/2012 0.031 0.42 1.45 4.1 <1.4 <3.0 40 7 0.30

07/16/2012 <0.025 0.21 1.98 3.4 1.4 <3.0 42 2 0.05

08/13/2012 <0.025 0.76 1.68 5.2 <1.4 <3.0 57 5 0.18
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 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12323850—Lost Creek near Galen

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/08/2011 0930 68 8.1 566 1.0 290 85.2 18.8

03/20/2012 0900 60 8.1 607 0.0 306 88.5 20.7

04/10/2012 0950 56 8.2 614 5.0 302 87.9 20.0

05/15/2012 1115 27 8.4 547 11.0 279 81.5 18.4

06/05/2012 1040 25 8.4 621 12.0 319 93.2 20.9

06/19/2012 0940 3.9 8.2 687 9.0 334 94.9 23.5

07/17/2012 1110 5.3 8.2 677 15.5 327 92.3 23.5

08/14/2012 1020 2.9 7.9 608 15.0 254 64.8 22.3

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/08/2011 13.1 13.6 0.036 0.038 1.2 3.6 11.6 97

03/20/2012 16.1 18.9 0.035 0.115 1.6 15.2 27.4 392

04/10/2012 12.5 14.2 0.025 0.082 1.6 8.8 19.4 250

05/15/2012 12.5 13.0 0.021 0.053 1.7 6.8 10.8 183

06/05/2012 12.9 13.4 0.019 0.027 1.7 3.8 6.9 101

06/19/2012 10.1 9.5 0.019 0.023 1.3 2.3 14.0 54.4

07/17/2012 16.6 15.7 0.021 0.028 1.9 3.1 15.5 59.7

08/14/2012 10.4 10.2 0.023 0.023 1.9 3.6 25.1 82.2

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/08/2011 0.032 0.34 12.1 10.9 2.5 4.3 51 9 1.7

03/20/2012 0.094 1.90 22.0 36.3 3.3 10.3 83 21 3.4

04/10/2012 0.074 1.14 19.4 28.0 2.9 6.6 80 15 2.3

05/15/2012 0.056 0.79 15.5 22.1 <1.4 4.3 79 11 0.80

06/05/2012 0.033 0.38 13.3 19.2 <1.4 <3.0 60 11 0.74

06/19/2012 0.029 0.13 23.7 22.7 <1.4 <3.0 22 18 0.19

07/17/2012 0.032 0.19 11.0 11.3 <1.4 <3.0 53 17 0.24

08/14/2012 0.074 0.21 17.8 16.3 <1.4 <3.0 88 10 0.08
Data 31

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12324200—Clark Fork at Deer Lodge

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/08/2011 1105 316 8.2 450 1.0 217 64.5 13.6

03/20/2012 1110 337 8.1 477 1.0 206 60.0 13.5

04/10/2012 1135 326 8.2 468 7.0 215 63.2 13.8

05/15/2012 1310 306 8.3 347 15.0 156 45.8 10.2

06/06/2012 0900 736 7.9 242 10.5 106 31.7 6.53

06/19/2012 1125 425 8.1 257 10.0 111 33.3 6.82

07/17/2012 1330 200 8.3 427 19.0 195 57.4 12.5

08/14/2012 1220 78 8.4 482 17.0 214 63.7 13.3

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/08/2011 9.8 12.4 0.077 0.182 3.6 31.1 9.9 401

03/20/2012 10.1 16.1 0.115 0.235 7.3 49.0 28.1 809

04/10/2012 10.3 14.8 0.080 0.207 7.6 35.4 20.6 607

05/15/2012 12.8 15.4 0.065 0.155 6.8 27.4 21.8 431

06/06/2012 14.1 43.2 0.074 0.784 12.9 220 34.3 4,290

06/19/2012 10.3 12.4 0.062 0.128 6.4 27.1 24.8 440

07/17/2012 19.8 20.4 0.073 0.151 8.1 26.8 25.7 374

08/14/2012 16.0 15.4 0.047 0.058 7.2 12.2 13.0 70

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/08/2011 0.075 3.19 46.0 76.8 7.4 24.6 83 15 13

03/20/2012 0.159 6.78 70.8 133 9.9 39.1 82 32 29

04/10/2012 0.140 4.63 48.8 116 10.7 31.2 82 22 19

05/15/2012 0.160 3.29 26.9 81.4 3.6 21.2 79 15 12

06/06/2012 0.301 32.8 30.0 364 8.0 164 50 218 433

06/19/2012 0.154 3.28 19.3 55.8 5.0 21.6 69 17 20

07/17/2012 0.169 2.91 31.6 87.4 4.1 20.8 80 16 8.6

08/14/2012 0.099 0.65 20.0 35.3 3.6 6.9 90 3 0.63
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 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, 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)

11/08/2011 1255 360 8.5 449 1.0 218 64.6 13.7

03/20/2012 1245 335 8.2 476 2.0 215 62.6 14.3

04/10/2012 1305 353 8.2 469 8.0 210 61.4 13.8

05/15/2012 1435 267 8.6 364 17.0 164 47.8 10.8

06/06/2012 1040 994 8.0 282 11.0 122 34.7 8.62

06/19/2012 1330 519 8.3 301 12.0 131 37.9 8.88

07/17/2012 1450 189 8.5 449 21.0 205 60.0 13.4

08/14/2012 1330 99 8.5 474 19.0 206 59.6 14.0

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/08/2011 9.8 11.4 0.071 0.144 4.0 18.7 9.2 294

03/20/2012 10.9 16.1 0.111 0.246 8.1 45.6 23.2 787

04/10/2012 10.5 15.7 0.079 0.290 6.5 53.3 38.1 826

05/15/2012 15.0 14.7 0.063 0.115 8.8 24.1 16.3 335

06/06/2012 16.2 41.4 0.082 0.835 16.6 222 39.3 3,860

06/19/2012 11.5 13.7 0.059 0.151 7.9 32.9 17.6 468

07/17/2012 21.9 20.9 0.070 0.087 10.9 17.2 17.6 114

08/14/2012 17.9 17.4 0.039 0.061 7.7 14.4 9.8 111

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/08/2011 0.075 2.22 37.0 69.8 7.7 20.5 82 11 11

03/20/2012 0.155 5.74 64.6 129 8.7 40.5 80 33 30

04/10/2012 0.148 6.43 48.1 136 6.9 43.3 81 33 31

05/15/2012 0.168 2.60 24.1 56.7 2.8 16.8 76 13 9.4

06/06/2012 0.422 32.3 42.4 344 8.8 181 64 205 550

06/19/2012 0.151 3.74 20.3 60.1 4.4 25.2 68 20 28

07/17/2012 0.126 1.05 13.5 39.8 2.6 9.0 79 5 2.6

08/14/2012 0.096 1.02 21.6 59.8 1.9 8.0 79 7 1.9
Data 33

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12324680—Clark Fork at Goldcreek

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temperature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/08/2011 1400 501 8.7 413 2.0 201 59.5 12.6

03/20/2012 1405 542 8.2 426 2.5 193 56.4 12.7

04/10/2012 1405 704 8.3 377 8.0 169 49.7 11.0

05/15/2012 1530 677 8.5 295 16.0 131 38.8 8.30

06/06/2012 1220 1,730 8.1 257 10.5 117 34.2 7.75

06/19/2012 1500 958 8.4 282 12.0 126 37.0 8.16

07/17/2012 1555 362 8.7 392 21.0 183 54.1 11.7

08/14/2012 1430 179 8.7 417 20.0 194 57.0 12.7

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/08/2011 7.9 9.3 0.027 0.074 2.8 11.5 8.5 200

03/20/2012 8.7 11.8 0.081 0.159 6.2 29.4 21.4 586

04/10/2012 7.2 10.2 0.048 0.150 4.5 27.8 18.9 640

05/15/2012 8.5 9.7 0.033 0.096 4.7 13.2 18.8 358

06/06/2012 11.2 26.1 0.059 0.530 11.0 133 37.5 2,940

06/19/2012 8.4 9.2 0.043 0.098 5.3 18.7 18.3 361

07/17/2012 13.8 12.3 0.043 0.045 6.3 9.2 10.5 74.2

08/14/2012 12.3 11.5 0.029 0.026 5.4 6.7 4.6 49.9

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/08/2011 0.04 1.37 28.0 48.1 2.6 13.4 90 7 9.5

03/20/2012 0.126 3.79 45.1 102 6.1 27.1 82 23 34

04/10/2012 0.112 4.21 26.6 87.1 4.0 25.7 78 26 49

05/15/2012 0.110 1.69 15.5 38.7 2.0 11.4 78 15 27

06/06/2012 0.314 19.9 20.2 244 5.6 113 56 176 822

06/19/2012 0.127 2.19 13.4 40.4 2.9 15.2 68 16 41

07/17/2012 0.061 0.40 8.59 20.9 <1.4 4.3 81 5 4.9

08/14/2012 0.049 0.31 10.3 26.2 <1.4 3.4 85 4 1.9
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 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, no data]

12331800—Clark Fork near Drummond

Date Time

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Temper- ature, 

water 

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/09/2011 0810 771 8.2 440 2.0 212 61.4 14.3

03/21/2012 0820 791 8.1 444 4.0 206 59.1 14.3

04/11/2012 0830 973 8.2 400 9.0 181 52.0 12.3

05/16/2012 0755 826 8.1 347 14.0 164 47.5 11.1

06/06/2012 1400 2,020 8.1 278 11.5 128 37.2 8.42

06/20/2012 0845 1,130 8.2 334 11.5 154 44.2 10.7

07/18/2012 0810 549 8.1 461 18.0 211 59.7 15.2

08/15/2012 0810 278 8.0 555 18.0 265 74.9 19.0

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/09/2011 7.6 9.0 0.042 0.067 2.3 8.7 67.9 196

03/21/2012 8.0 10.8 0.075 0.137 4.8 24.2 16.8 542

04/11/2012 7.6 10.8 0.049 0.190 4.2 28.8 19.8 774

05/16/2012 9.6 10.8 0.044 0.121 5.1 18.8 9.3 406

06/06/2012 11.1 24.0 0.052 0.442 8.8 97.3 29.7 2,530

06/20/2012 8.8 10.1 0.047 0.118 5.2 18.9 15.8 419

07/18/2012 12.5 11.4 0.029 0.113 5.7 9.1 22.1 55.6

08/15/2012 11.8 11.7 0.027 0.074 2.9 8.3 3.6 158

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/09/2011 0.039 1.47 19.2 49.5 3.9 12.5 86 8 17

03/21/2012 0.111 3.58 37.7 92.3 6.1 27.1 79 25 53

04/11/2012 0.126 4.71 24.2 106 5.2 35.1 76 38 100

05/16/2012 0.107 2.58 14.2 54.8 3.7 20.7 82 18 40

06/06/2012 0.349 19.8 17.2 277 5.2 106 66 146 796

06/20/2012 0.117 2.83 14.7 52.3 3.8 21.4 68 21 64

07/18/2012 0.050 0.73 6.31 16.2 2.4 6.3 78 3 4.4

08/15/2012 0.052 1.12 22.6 134 2.9 12.7 79 17 13
Data 35

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, 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)

11/09/2011 0945 1,130 8.3 369 2.0 180 51.3 12.6

03/21/2012 1025 1,240 8.2 360 3.5 160 44.9 11.5

04/11/2012 1015 1,740 8.2 305 8.0 136 38.7 9.56

05/16/2012 1010 3,130 8.0 160 11.0 72.5 20.3 5.29

06/07/2012 0735 4,820 7.9 185 8.5 85.8 24.3 6.09

06/20/2012 1040 2,800 8.2 215 10.5 97.7 27.6 7.01

07/18/2012 1000 1,120 8.2 284 17.0 126 34.8 9.59

08/15/2012 0940 555 8.1 330 15.5 155 42.6 11.8

Date

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

11/09/2011 6.0 6.2 0.057 0.056 4.2 5.7 74.2 122

03/21/2012 6.1 7.5 0.069 0.093 3.8 13.8 20.4 351

04/11/2012 5.0 6.6 0.026 0.113 3.2 16.6 22.2 489

05/16/2012 3.2 3.9 0.021 0.069 2.2 8.8 27.7 423

06/07/2012 6.3 11.4 0.034 0.263 5.9 49.7 30.7 1,340

06/20/2012 4.6 5.1 0.024 0.072 3.1 10.0 17.9 254

07/18/2012 5.7 5.3 0.019 0.046 2.7 3.8 12.6 47.7

08/15/2012 5.7 5.7 0.020 0.032 2.1 4.3 8.7 85.7

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/09/2011 0.553 0.80 20.1 27.4 7.7 9.5 88 5 15

03/21/2012 0.098 2.02 17.1 55.8 4.9 17.9 82 16 54

04/11/2012 0.100 2.76 11.3 63.0 3.3 22.7 77 23 108

05/16/2012 0.065 1.67 6.28 41.2 2.8 13.3 52 29 245

06/07/2012 0.230 8.75 6.81 142 4.5 58.1 63 87 1,130

06/20/2012 0.067 1.45 7.10 30.3 2.3 12.6 70 13 98

07/18/2012 <0.025 0.20 4.68 9.5 1.5 3.8 73 3 9.1

08/15/2012 0.033 0.44 6.08 33.6 1.9 6.6 88 7 10
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 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, 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)

11/09/2011 1145 718 8.4 272 3.0 146 37.5 12.7

04/11/2012 1230 2,310 8.3 199 8.0 97.8 25.3 8.44

05/16/2012 1220 6,250 8.0 157 12.5 80.1 20.9 6.74

06/07/2012 0945 7,030 8.0 156 8.5 81.4 21.4 6.82

07/18/2012 1215 1,350 8.5 230 19.0 118 29.7 10.8

08/15/2012 1200 704 8.5 261 16.0 137 33.9 12.6

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)

11/09/2011 1.0 1.4 <0.016 <0.016 <0.80 <0.70 3.3 34.5

04/11/2012 0.97 1.0 <0.016 <0.016 1.1 1.1 54.6 283

05/16/2012 0.81 1.2 <0.016 <0.016 0.81 1.8 18.3 592

06/07/2012 0.78 2.0 <0.016 <0.016 <.80 2.5 20.2 836

07/18/2012 1.2 1.1 <0.016 <0.016 <.80 <.70 7.8 42.6

08/15/2012 1.3 1.2 <0.016 <0.016 <.80 <.70 6.0 30.4

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/09/2011 <0.025 <0.04 1.41 3.0 <1.4 <3.0 76 1 1.9

04/11/2012 0.042 0.26 5.42 21.9 <1.4 <3.0 88 13 81

05/16/2012 0.032 0.66 2.67 33.4 3.2 <3.0 75 52 878

06/07/2012 0.025 0.90 2.35 44.6 <1.4 3.2 75 65 1,230

07/18/2012 <0.025 0.05 2.30 6.1 <1.4 <3.0 87 2 7.3

08/15/2012 <0.025 <0.04 1.68 6.1 <1.4 <3.0 87 2 3.8
Data 37

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2011 through September 2012.—Continued

[mg/L, milligrams per liter; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; lab, laboratory; NTRU, nephelometric turbidity ratio 

unit; E, estimated; --, 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)

11/09/2011 1330 1,900 8.5 327 3.0 163 44.9 12.5

03/21/2012 1315 E2,300 8.2 308 3.0 144 38.9 11.3

04/11/2012 1430 4,150 8.3 243 9.5 114 30.8 8.88

05/16/2012 1400 9,830 8.1 160 12.0 78.8 21.1 6.32

06/07/2012 1120 11,600 8.0 168 9.0 80.8 21.9 6.37

06/20/2012 1255 7,360 8.2 189 11.5 89.3 24.0 7.12

07/18/2012 1350 2,520 8.5 255 19.5 121 31.2 10.3

08/15/2012 1345 1,340 8.5 284 17.0 141 36.7 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)

11/09/2011 3.8 4.4 0.026 0.029 1.3 3.5 5.4 85.2

03/21/2012 3.9 4.6 0.034 0.051 2.5 7.6 45.6 320

04/11/2012 2.8 3.6 0.019 0.060 1.9 8.0 39.6 408

05/16/2012 1.7 2.4 <0.016 0.040 1.6 4.8 23.6 520

06/07/2012 2.9 5.4 0.018 0.097 3.0 19.3 26.1 954

06/20/2012 2.3 2.6 0.017 0.027 1.7 4.8 16.9 215

07/18/2012 3.3 2.9 <0.016 0.023 1.7 2.1 9.2 47.3

08/15/2012 3.4 3.5 <0.016 <0.016 1.2 1.9 6.9 42.1

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/09/2011 0.031 0.45 8.30 19.9 1.8 5.5 83 3 15

03/21/2012 0.103 1.15 15.3 43.1 3.1 10.6 85 15 93

04/11/2012 0.073 1.35 8.69 41.3 1.4 11.0 75 20 224

05/16/2012 0.093 1.26 6.08 34.3 2.2 7.4 71 46 1,220

06/07/2012 0.108 3.71 5.15 81.7 2.3 24.2 67 78 2,440

06/20/2012 0.051 0.83 5.71 20.6 1.5 6.1 76 12 238

07/18/2012 <0.025 0.13 5.53 10.9 1.6 <3.0 83 2 14

08/15/2012 0.030 0.16 6.81 17.5 <1.4 <3.0 89 3 11
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 (12324200), October 2011 

through September 2012.

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; --, no data or value not computed; max, maximum; min, minimum; acre-ft, acre-feet]

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

1 198 5 2.7 320 21 18 304 16 13

2 206 7 4.1 314 22 19 307 17 14

3 209 9 5.0 322 24 21 309 17 14

4 218 9 5.6 316 26 22 306 17 14

5 261 10 7.0 325 39 34 262 17 12

6 264 10 7.4 315 27 23 265 16 12

7 267 11 7.8 305 18 15 286 16 12

8 271 11 8.0 317 16 13 295 17 13

9 275 11 8.5 317 17 15 287 18 14

10 278 13 9.6 315 18 15 294 19 15

11 283 14 10 321 18 16 286 20 15

12 282 12 9.5 331 18 16 284 24 18

13 288 11 8.4 329 18 16 271 29 22

14 292 10 8.1 318 18 15 277 38 28

15 316 10 8.8 319 17 15 273 50 37

16 349 13 12 298 17 14 275 53 40

17 355 15 15 328 18 16 284 53 40

18 339 15 14 334 19 17 286 52 40

19 334 14 13 307 18 15 295 51 41

20 333 13 12 314 18 16 289 46 36

21 327 12 11 336 19 18 291 40 31

22 329 11 10 342 19 18 277 33 25

23 319 10 8.9 350 19 18 274 27 20

24 325 11 9.4 348 18 17 300 27 22

25 325 12 10 333 18 16 305 27 23

26 342 13 12 317 18 15 288 28 22

27 343 14 13 326 17 15 283 29 22

28 331 15 13 330 17 15 282 28 21

29 330 16 14 324 16 14 304 26 22

30 326 18 16 324 16 14 301 25 20

31 327 19 17 -- -- -- 307 23 19

TOTAL 9,242 -- 310.8 9,695 -- 511 8,947 -- 697

MEAN 298 12 10 323 19 17 289 29 22

MAX 355 19 17 350 39 34 309 53 41

MIN 198 5 207 298 16 13 262 16 12
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

1 280 23 17 260 17 12 253 21 14

2 301 23 18 269 17 12 269 23 17

3 300 22 18 265 17 12 261 26 18

4 294 22 17 254 16 11 269 29 21

5 294 22 17 252 16 11 302 32 26

6 286 21 16 262 16 11 305 32 27

7 267 21 15 261 16 11 267 23 17

8 280 20 15 240 17 11 269 22 16

9 289 21 17 262 19 13 283 21 16

10 282 24 18 257 17 12 298 19 16

11 269 28 20 259 16 11 304 18 15

12 255 32 22 259 14 10 303 16 13

13 273 33 24 258 14 9.8 302 17 13

14 294 33 26 259 14 10 294 17 14

15 290 33 26 250 15 10 290 21 17

16 264 33 23 246 15 10 323 37 33

17 217 27 16 262 16 11 362 46 45

18 248 21 14 255 16 11 387 58 61

19 299 19 15 248 16 11 361 38 37

20 293 18 14 248 17 11 344 39 36

21 289 19 15 257 17 12 333 43 38

22 295 19 15 293 28 23 410 58 65

23 272 20 15 325 32 28 395 49 52

24 256 21 14 283 18 14 378 46 47

25 274 22 16 277 16 12 363 45 44

26 271 23 17 265 17 12 372 44 44

27 257 24 17 265 17 12 377 43 44

28 247 25 16 254 18 12 367 42 42

29 274 23 17 264 19 13 359 40 39

30 279 20 15 -- -- -- 365 38 38

31 267 18 13 -- -- -- 377 37 38

TOTAL 8,556 -- 538 7,609 -- 358.8 10,142 -- 963

MEAN 276 24 17 262 17 12 327 34 31

MAX 301 33 26 325 32 28 410 58 65

MIN 217 18 13 240 14 9.8 253 16 13

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana (12324200), October 2011 

through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; --, no data or value not computed; max, maximum; min, minimum; acre-ft, acre-feet]
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

1 404 41 45 502 54 74 330 13 12

2 393 44 46 436 39 46 393 32 35

3 381 35 36 419 31 35 587 156 258

4 370 31 31 409 23 26 618 135 227

5 349 30 28 424 25 29 633 195 341

6 337 26 23 386 21 21 781 169 349

7 339 27 25 350 22 21 759 79 163

8 335 30 27 320 22 19 651 57 100

9 331 28 25 307 22 18 647 41 72

10 327 26 23 311 17 14 584 31 49

11 332 28 25 317 16 14 550 29 44

12 374 35 35 306 15 12 464 27 33

13 387 35 37 304 17 14 478 34 44

14 366 30 30 299 17 14 532 40 57

15 350 27 25 307 16 14 489 27 36

16 351 24 23 347 29 28 457 21 26

17 336 23 21 404 47 52 431 19 22

18 332 21 19 430 42 49 431 20 23

19 331 26 23 375 26 27 429 17 20

20 324 34 29 336 18 16 388 14 15

21 319 37 32 304 15 13 348 12 11

22 342 53 49 347 26 25 307 11 9.3

23 364 74 72 442 50 60 282 10 7.7

24 397 37 39 384 27 29 285 7 5.6

25 434 36 42 356 15 14 269 8 5.9

26 481 106 141 349 13 12 252 7 5.1

27 622 242 409 381 17 18 226 6 3.5

28 627 139 237 427 22 25 199 5 2.7

29 572 77 119 406 18 20 181 4 2.1

30 532 60 86 357 13 13 168 4 1.9

31 -- -- -- 334 12 11 -- -- --

TOTAL 11,739 -- 1,802 11,376 -- 783 13,149 -- 1,980.8

MEAN 391 49 60 367 24 25 438 41 66

MAX 627 242 409 502 54 74 781 195 349

MIN 319 21 19 299 12 11 168 4 1.9

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana (12324200), October 2011 

through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; --, no data or value not computed; max, maximum; min, minimum; acre-ft, acre-feet]
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

1 167 7 3.2 93 4 1.1 98 12 3.2

2 181 7 3.3 85 5 1.1 97 13 3.5

3 172 6 2.8 84 5 1.1 96 14 3.6

4 169 5 2.4 81 5 1.1 91 14 3.4

5 161 6 2.5 85 5 1.1 84 11 2.4

6 154 6 2.6 83 5 1.1 86 9 2.1

7 146 7 2.7 88 5 1.2 93 10 2.4

8 142 7 2.8 85 5 1.2 100 10 2.7

9 138 8 2.9 83 5 1.2 95 11 2.8

10 133 8 2.7 86 6 1.3 94 12 3.0

11 131 7 2.5 90 6 1.4 95 13 3.3

12 132 7 2.3 85 5 1.2 98 14 3.6

13 123 6 2.0 81 4 0.90 99 13 3.6

14 125 7 2.4 78 3 0.70 101 13 3.5

15 172 16 7.3 80 5 1.0 99 12 3.2

16 181 15 7.2 90 7 1.7 98 11 3.0

17 195 17 8.8 91 8 1.9 100 11 2.9

18 183 16 8.0 85 8 1.8 98 10 2.7

19 167 12 5.4 84 8 1.7 99 10 2.6

20 151 9 3.7 88 8 1.8 103 9 2.5

21 142 7 2.8 82 8 1.7 108 9 2.6

22 130 7 2.5 88 8 1.9 108 9 2.6

23 114 6 2.0 91 8 2.0 113 9 2.7

24 98 6 1.5 86 8 1.8 113 9 2.8

25 96 5 1.3 85 7 1.6 114 10 3.0

26 94 4 1.1 94 10 2.6 122 10 3.4

27 98 4 1.1 95 11 2.7 119 11 3.6

28 118 4 1.3 88 10 2.4 127 12 4.1

29 117 4 1.3 87 10 2.3 127 12 4.1

30 101 4 1.1 89 10 2.4 122 12 3.9

31 95 4 1.1 95 11 2.8 -- -- --

TOTAL 4,326 -- 94.6 2,685 -- 49.8 3,097 -- 92.8

MEAN 140 8 3.1 86.6 7 1.6 103 11 3.1

MAX 195 17 8.8 95 11 2.8 127 14 4.1

MIN 94 4 1.1 78 3 0.70 84 9 2.1

Total for water year 2012 (unrounded sum of daily values): streamflow–100,563 ft3/s (annual runoff–199,500 acre-ft); suspended-sediment discharge–8,181.6 tons.

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana (12324200), October 2011 

through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; --, no data or value not computed; max, maximum; min, minimum; acre-ft, acre-feet]
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 (12334550), 

October 2011 through September 2012.

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]

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

1 839 7 16 1,200 9 29 1,070 6 18

2 860 7 16 1,180 8 26 979 6 16

3 870 7 16 1,130 7 23 993 6 16

4 906 8 19 1,160 7 21 988 8 23

5 984 12 31 1,180 6 19 e895 22 59

6 1,070 18 53 1,170 6 18 e905 11 28

7 1,080 16 46 1,110 5 16 e950 8 20

8 1,090 13 37 1,090 5 15 e975 8 21

9 1,070 11 32 1,130 6 17 926 8 20

10 1,050 10 29 1,120 6 18 e920 8 19

11 1,100 11 34 1,110 6 18 e900 7 17

12 1,130 13 40 1,140 7 22 e860 7 16

13 1,130 14 43 1,150 8 25 e840 6 14

14 1,150 14 44 1,160 8 24 880 6 15

15 1,220 14 47 1,140 7 22 955 6 17

16 1,270 15 53 1,070 6 18 968 7 18

17 1,310 16 56 1,030 6 17 988 7 19

18 1,300 14 49 1,130 7 20 969 7 18

19 1,270 12 40 e1,080 7 22 1,000 7 19

20 1,240 10 34 e1,010 8 23 962 7 18

21 1,250 10 34 e1,080 9 26 990 7 19

22 1,230 10 34 1,100 10 30 950 7 19

23 1,240 11 37 1,160 11 34 e830 8 18

24 1,260 12 40 1,160 12 37 e840 11 25

25 1,290 12 40 1,160 12 38 e990 17 43

26 1,270 10 34 1,120 11 34 e1,030 19 52

27 1,240 9 30 1,040 10 29 e990 16 45

28 1,230 8 25 1,130 9 28 e990 15 39

29 1,220 7 23 1,120 8 24 e1,000 14 38

30 1,220 8 25 1,100 7 21 e980 14 37

31 1,210 9 28 -- -- -- e960 14 37

TOTAL 35,599 -- 1,085 33,660 -- 714 29,473 -- 783

MEAN 1,148 11 35 1,122 8 24 951 10 25

MAX 1,310 18 56 1,200 12 38 1,070 22 59

MIN 839 7 16 1,010 5 15 830 6 14
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 e950 15 38 995 17 46 876 8 19

2 956 14 36 933 13 33 863 8 19

3 1,010 13 35 914 10 24 890 8 20

4 1,010 12 32 862 7 16 957 13 35

5 977 11 29 815 6 13 1,580 136 608

6 972 11 28 810 6 13 1,800 139 684

7 938 10 26 871 7 16 1,330 69 257

8 899 10 24 832 6 14 1,090 20 60

9 923 10 25 836 5 12 1,040 15 41

10 935 10 25 894 7 16 1,220 21 69

11 922 7 18 880 6 15 1,450 54 213

12 e810 4 10 866 5 12 1,520 49 202

13 e815 3 6.6 861 5 12 1,400 38 143

14 e850 3 6.7 857 5 11 1,320 27 98

15 e890 3 7.1 848 5 10 1,250 22 74

16 e850 3 8.0 813 4 9.4 1,400 32 126

17 e780 4 8.5 825 4 9.0 1,680 54 247

18 e770 4 8.4 853 4 9.8 1,580 36 153

19 e780 4 8.4 836 4 10 1,490 26 105

20 e785 4 8.5 822 5 11 1,320 21 75

21 e920 6 14 831 5 12 1,240 18 60

22 971 11 30 986 24 73 1,270 24 84

23 924 11 27 2,070 245 1,430 1,480 32 128

24 868 9 22 1,340 81 304 1,580 34 145

25 858 8 19 1,120 23 71 1,510 35 141

26 946 7 19 1,030 18 50 1,540 33 137

27 904 7 17 952 15 37 1,620 32 138

28 841 7 16 892 11 27 1,650 34 151

29 866 7 17 858 8 20 1,660 31 139

30 1,170 20 64 -- -- -- 1,640 34 150

31 1,220 23 76 -- -- -- 1,880 54 276

TOTAL 28,310 -- 709.2 27,302 -- 2,336.2 43,126 -- 4,797

MEAN 913 9 23 941 19 81 1,391 37 155

MAX 1,220 23 76 2,070 245 1,430 1,880 139 684

MIN 770 3 6.6 810 4 9.0 863 8 19

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana (12334550), 

October 2011 through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]
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 2,250 91 556 4,010 53 573 2,720 14 103

2 2,270 84 516 3,640 44 434 2,920 19 153

3 2,060 47 260 3,310 37 329 3,310 34 310

4 1,970 38 200 3,110 32 270 3,620 50 492

5 1,920 33 170 3,010 30 245 3,880 58 617

6 1,870 28 140 2,880 29 228 4,710 87 1,110

7 1,820 25 121 2,670 26 186 4,660 81 1,020

8 1,750 22 105 2,550 23 159 3,960 53 575

9 1,700 22 101 2,550 23 158 3,660 37 364

10 1,690 22 99 2,720 32 239 3,540 29 280

11 1,750 26 125 2,820 25 189 3,420 25 234

12 2,070 46 260 2,750 19 143 3,240 24 212

13 2,460 79 526 2,700 18 130 3,240 23 198

14 2,480 75 506 2,730 19 137 3,590 34 331

15 2,420 56 369 2,900 24 187 3,350 26 238

16 2,350 46 292 3,230 36 315 3,110 20 169

17 2,260 37 226 3,690 62 620 3,020 18 146

18 2,220 38 226 3,760 49 494 2,980 17 134

19 2,200 33 197 3,470 32 298 2,920 15 118

20 2,180 35 208 3,120 21 175 2,750 14 101

21 2,280 44 273 2,920 16 129 2,520 13 89

22 2,620 83 592 3,150 22 187 2,350 12 78

23 3,010 145 1,190 3,810 48 494 2,250 10 60

24 3,600 204 2,000 3,380 28 259 2,160 8 47

25 4,580 227 2,790 2,990 20 159 2,070 7 40

26 5,580 196 2,960 2,750 14 106 1,980 7 36

27 7,490 239 4,860 2,720 13 97 1,890 6 30

28 7,440 170 3,470 2,800 15 115 1,770 5 24

29 5,620 95 1,450 2,910 23 178 1,660 5 22

30 4,560 67 824 2,810 16 123 1,560 5 20

31 -- -- -- 2,720 14 103 -- -- --

TOTAL 88,470 -- 25,612 94,580 -- 7,459 88,810 -- 7,351

MEAN 2,949 78 854 3,051 28 241 2,960 25 245

MAX 7,490 239 4,860 4,010 62 620 4,710 87 1,110

MIN 1,690 22 99 2,550 13 97 1,560 5 20

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana (12334550), 

October 2011 through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]
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 1,490 4 17 747 4 8.2 527 5 6.7

2 1,440 5 19 726 4 7.8 523 4 5.7

3 1,410 4 17 699 4 7.6 520 4 5.3

4 1,350 4 14 675 4 7.3 510 3 4.8

5 1,290 3 12 650 4 7.1 511 3 4.5

6 1,240 3 10 632 4 7.2 528 3 4.4

7 1,200 3 9.7 619 4 7.5 534 4 5.1

8 1,180 3 9.5 610 5 7.8 533 4 5.8

9 1,170 3 9.5 604 5 8.2 536 5 6.6

10 1,160 3 9.4 592 6 9.2 542 5 7.3

11 1,130 3 9.1 584 7 10 539 5 7.3

12 1,080 3 8.5 579 7 11 539 5 7.3

13 1,050 2 7.0 572 8 12 548 5 7.4

14 1,040 2 5.8 556 7 11 555 5 7.4

15 1,050 2 5.7 550 7 10 562 5 7.1

16 1,070 2 5.8 556 7 11 557 4 6.7

17 1,120 4 12 557 7 10 545 4 6.2

18 1,120 5 14 553 7 10 542 4 5.9

19 1,080 3 7.5 544 6 9.5 539 4 6.2

20 1,050 3 8.4 539 6 9.1 545 5 6.7

21 1,020 3 8.3 541 6 8.6 550 5 7.1

22 978 3 8.0 565 5 8.0 550 5 7.3

23 940 3 8.9 568 5 6.9 548 5 7.0

24 906 4 9.2 561 4 5.7 554 4 6.7

25 872 3 6.8 555 3 4.8 564 4 6.4

26 850 2 5.2 555 4 6.0 569 4 6.3

27 840 3 7.1 565 5 7.7 570 5 7.0

28 842 4 9.5 569 6 9.4 576 5 7.9

29 831 5 12 558 7 10 576 6 8.7

30 800 6 12 538 6 8.9 580 6 9.2

31 770 5 10 530 5 7.8 -- -- --

TOTAL 33,369 -- 307.9 18,249 -- 265.3 16,372 -- 198

MEAN 1,076 3 9.9 589 5 8.6 546 4 6.6

MAX 1,490 6 19 747 8 12 580 6 9.2

MIN 770 2 5.2 530 3 4.8 510 3 4.4

Total for water year 2012 (unrounded sum of daily values): streamflow–537,320 ft3/s (annual runoff–1,066,000 acre-ft); suspended-sediment 

discharge–51,617.6 tons. 

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana (12334550), 

October 2011 through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]
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 (12340000), October 2011 

through September 2012.

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]

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

1 682 4 7.2 766 3 6.1 674 2 3.7

2 688 4 7.4 759 3 5.6 653 2 3.1

3 681 4 7.4 738 2 4.9 636 2 2.6

4 688 4 7.4 735 2 4.4 e620 1 2.1

5 712 4 7.7 741 2 4.1 606 1 1.7

6 730 4 7.9 730 2 3.9 e630 1 1.7

7 744 4 8.0 708 2 3.8 e645 1 1.7

8 748 4 8.0 715 2 3.9 e620 1 1.7

9 742 4 7.6 715 2 3.9 e640 1 1.8

10 732 4 7.1 708 2 3.8 e585 1 2.0

11 737 3 6.7 700 2 3.8 e585 1 2.3

12 746 3 6.4 712 2 3.8 e655 2 2.9

13 739 3 6.1 721 2 4.0 e665 2 3.6

14 731 3 6.5 731 2 4.4 e680 2 4.5

15 764 4 7.3 738 2 5.0 e665 3 5.4

16 783 4 8.0 686 3 5.1 e650 3 6.2

17 783 4 8.4 718 3 5.7 639 4 6.7

18 764 4 8.2 751 3 6.1 611 4 6.2

19 754 4 8.1 707 3 5.7 615 4 5.8

20 746 4 8.1 666 3 5.4 597 3 5.3

21 744 4 8.1 700 3 5.7 608 3 5.0

22 741 4 8.5 712 3 6.3 589 3 4.8

23 757 5 9.2 727 4 6.9 547 3 4.4

24 798 5 10 717 4 7.3 562 4 5.4

25 816 5 11 743 4 7.9 e590 5 7.8

26 795 4 9.6 708 4 7.1 e600 5 8.4

27 767 4 8.2 697 3 6.6 612 5 9.1

28 755 3 7.0 706 3 6.2 e630 6 9.5

29 749 3 6.1 702 3 5.7 e620 6 9.7

30 744 3 6.0 696 3 4.8 e600 5 8.8

31 758 3 6.1 -- -- -- e575 5 7.4

TOTAL 23,118 -- 239.3 21,553 -- 157.9 19,204 -- 151.3

MEAN 746 4 7.7 718 3 5.3 619 3 4.9

MAX 816 5 11 766 4 7.9 680 6 9.7

MIN 681 3 6.0 666 2 3.8 547 1 1.7
Data 47

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JANUARY FEBRUARY MARCH

1 e565 4 6.4 626 3 5.2 631 7 12

2 e605 4 6.3 604 3 5.7 604 4 6.9

3 e630 4 6.7 599 4 6.4 600 3 4.9

4 e610 4 6.7 584 4 7.0 621 5 7.9

5 e640 4 6.7 533 5 7.1 710 13 24

6 613 4 6.3 535 5 7.2 936 21 53

7 577 4 5.6 578 5 7.8 1,000 24 65

8 587 3 5.4 532 5 7.2 853 20 47

9 587 3 5.1 557 5 7.5 759 17 35

10 586 3 4.7 556 5 7.2 749 16 33

11 566 3 4.1 538 5 6.6 893 18 43

12 506 2 3.2 533 4 6.1 1,040 27 77

13 479 2 2.6 528 4 5.7 1,030 30 83

14 e555 2 2.6 521 4 5.3 958 24 63

15 e550 2 2.2 507 4 4.8 908 20 50

16 e530 1 1.8 505 3 4.5 1,000 24 65

17 e545 1 1.7 515 3 4.2 1,220 32 104

18 e530 1 2.1 503 3 4.1 1,250 30 102

19 526 2 2.6 506 3 4.1 1,150 19 61

20 559 2 3.3 504 3 4.1 1,010 14 37

21 600 3 4.2 513 4 4.9 962 12 30

22 e605 3 5.0 603 6 10 946 11 29

23 e600 4 5.9 723 9 19 1,010 14 39

24 e565 4 6.7 876 16 38 1,110 19 57

25 e605 5 7.4 805 15 32 1,180 23 73

26 e600 5 7.4 722 12 24 1,290 24 83

27 602 4 6.5 678 10 18 1,370 25 94

28 585 3 5.5 619 8 14 1,500 29 117

29 612 3 5.0 612 7 12 1,590 27 117

30 634 3 5.1 -- -- -- 1,730 30 139

31 632 3 5.1 -- -- -- 2,220 49 294

TOTAL 17,986 -- 149.9 17,015 -- 289.7 32,830 -- 2,045.7

MEAN 580 3 4.8 587 6 10 1,059 20 66

MAX 640 5 7.4 876 16 38 2,220 49 294

MIN 479 1 1.7 503 3 4.1 600 3 4.9

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2011 

through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]
48 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 2,690 58 421 7,380 47 948 3,660 12 115

2 2,820 41 313 6,540 38 678 3,900 13 135

3 2,750 28 210 5,820 29 461 4,500 20 245

4 2,670 22 161 5,310 27 383 4,830 24 311

5 2,600 17 122 4,970 24 323 5,420 36 500

6 2,530 16 110 4,640 22 275 6,840 80 1,510

7 2,460 15 99 4,270 20 233 6,940 69 1,290

8 2,350 14 87 4,100 20 224 6,080 44 722

9 2,240 12 74 4,240 22 253 5,460 29 428

10 2,190 12 72 e4,920 28 359 5,080 22 300

11 2,320 13 84 5,010 29 396 4,740 20 254

12 2,850 23 177 4,830 24 310 4,360 19 220

13 3,560 39 380 4,760 21 269 4,300 17 203

14 3,800 38 388 4,940 24 325 4,640 19 244

15 3,860 34 351 5,430 33 493 4,670 18 231

16 3,830 30 306 6,110 50 840 4,550 16 197

17 3,690 24 238 7,150 77 1,490 4,480 15 187

18 3,620 24 234 7,410 68 1,360 4,710 17 216

19 3,610 21 204 6,860 48 898 4,670 17 216

20 3,610 21 203 6,170 36 601 4,300 13 155

21 4,010 26 285 5,750 27 425 3,940 12 129

22 4,610 42 530 5,990 31 503 3,730 12 119

23 5,440 62 920 6,500 39 692 3,740 12 117

24 6,860 110 2,070 6,050 30 498 3,930 14 144

25 8,820 165 3,960 5,400 24 362 4,030 13 144

26 10,100 139 3,760 4,810 19 248 3,960 14 145

27 11,700 182 5,790 4,460 17 202 3,760 12 119

28 11,300 132 4,060 4,310 14 167 3,380 10 90

29 9,680 87 2,290 4,110 14 154 3,050 8 68

30 8,240 62 1,390 3,890 13 138 2,850 8 62

31 -- -- -- 3,680 13 126 -- -- --

TOTAL 140,810 -- 29,289 165,810 -- 14,634 134,500 -- 8,816

MEAN 4,694 50 976 5,349 30 472 4,483 21 294

MAX 11,700 182 5,790 7,410 77 1,490 6,940 80 1,510

MIN 2,190 12 72 3,680 13 126 2,850 8 62

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2011 

through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]
Data 49

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment Mean 

streamflow 

(ft3/s)

Suspended sediment

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

Mean concentration 

(mg/L)

Discharge 

(ton/d)

JULY AUGUST SEPTEMBER

1 2,730 8 59 875 3 7.0 614 4 6.6

2 2,610 8 57 853 3 6.3 609 4 6.5

3 2,460 9 57 843 2 5.7 607 4 6.1

4 2,320 9 54 833 2 5.1 603 3 5.7

5 2,200 7 40 823 2 4.5 603 3 5.3

6 2,070 5 29 804 2 4.3 593 3 4.8

7 e1,960 4 24 790 2 4.3 591 3 4.8

8 1,880 4 20 783 2 4.2 587 3 4.8

9 1,800 3 17 786 2 4.3 593 3 4.8

10 1,720 3 15 791 2 4.8 591 3 4.8

11 1,660 4 16 786 3 5.3 582 3 4.7

12 1,600 4 17 763 3 5.7 579 3 4.7

13 1,510 3 14 739 3 5.8 573 3 4.6

14 1,470 3 12 715 2 4.8 578 3 4.6

15 1,430 2 9.5 707 2 4.1 579 3 4.2

16 1,430 2 7.9 706 3 4.9 575 2 3.8

17 1,390 2 8.3 702 3 5.6 568 2 3.4

18 1,340 3 12 690 3 5.6 563 2 3.1

19 1,300 3 11 684 3 5.5 557 2 3.4

20 1,260 3 10 679 3 5.5 551 3 3.8

21 1,260 3 10 686 3 5.5 548 3 4.1

22 1,210 3 9.8 693 3 5.2 547 3 4.4

23 1,170 3 9.5 677 3 4.6 544 3 4.4

24 1,110 3 8.7 659 2 4.0 539 3 4.4

25 1,070 2 7.1 660 2 3.7 533 3 4.3

26 1,020 2 5.8 656 2 4.4 535 3 4.3

27 1,000 3 6.9 644 3 5.2 534 3 4.3

28 989 3 7.9 644 4 6.2 535 3 4.3

29 983 3 8.0 637 4 6.8 544 3 4.4

30 929 3 7.5 625 4 6.7 541 3 4.3

31 899 3 7.3 615 4 6.6 -- -- --

TOTAL 47,780 -- 578.2 22,548 -- 162.2 17,096 -- 137.7

MEAN 1,541 4 19 727 3 5.2 570 3 4.6

MAX 2,730 9 59 875 4 7.0 614 4 6.6

MIN 899 2 5.8 615 2 3.7 533 2 3.1

Total for water year 2012 (unrounded sum of daily values): streamflow–660,250 ft3/s (annual runoff–1,310,000 acre-ft); suspended-sediment 

discharge–56,650.9 tons.

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2011 

through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]
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 (12340500), October 2011 

through September 2012.

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]

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 1,670 5 23 2,010 5 26 1,810 12 61

2 1,690 5 23 1,990 4 22 1,700 15 68

3 1,690 6 25 1,930 4 21 1,680 17 77

4 1,730 7 30 1,940 5 24 1,680 29 134

5 1,830 9 43 1,960 5 26 1,560 31 129

6 1,930 11 56 1,950 4 24 1,550 27 112

7 1,970 9 49 1,880 4 20 1,610 25 107

8 1,980 8 43 1,850 3 17 1,600 22 97

9 1,950 7 39 1,890 3 16 1,560 20 86

10 1,930 7 37 1,870 3 15 1,490 20 81

11 1,970 8 40 1,860 3 16 1,480 23 90

12 2,000 8 43 1,890 4 18 1,530 28 116

13 2,000 8 43 1,920 4 20 1,540 32 135

14 1,980 8 43 1,940 4 20 1,590 28 119

15 2,040 9 51 1,930 3 18 1,660 21 95

16 2,100 10 57 1,820 3 15 1,650 15 65

17 2,140 10 58 1,790 3 15 1,680 8 38

18 2,110 10 54 1,890 4 19 1,630 6 28

19 2,080 9 49 1,800 4 22 1,670 6 25

20 2,040 8 44 1,660 5 23 1,620 5 21

21 2,050 8 44 1,740 6 28 1,660 4 19

22 2,020 8 44 1,850 7 34 1,530 4 16

23 2,040 8 44 1,920 8 40 1,360 4 15

24 2,090 8 45 1,920 9 45 1,350 5 19

25 2,140 8 45 1,950 9 47 1,620 13 56

26 2,110 7 38 1,890 9 45 1,690 13 58

27 2,060 6 31 1,790 8 41 1,630 11 50

28 2,040 4 24 1,880 8 42 e1,650 11 49

29 2,010 4 22 1,870 8 41 e1,650 11 49

30 2,010 4 23 1,850 9 45 e1,630 11 47

31 2,010 5 25 -- -- -- e1,620 10 45

TOTAL 61,410 -- 1,235 56,430 -- 805 49,680 -- 2,107

MEAN 1,981 7 40 1,881 5 27 1,603 16 68

MAX 2,140 11 58 2,010 9 47 1,810 32 135

MIN 1,670 4 22 1,660 3 15 1,350 4 15
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 e1,600 10 43 1,680 13 57 1,570 11 45

2 1,650 9 40 1,610 9 38 1,540 10 40

3 1,680 8 37 1,580 7 30 1,560 8 34

4 1,720 7 33 1,480 6 22 1,630 21 96

5 1,680 6 28 1,380 4 16 2,260 92 576

6 1,660 6 25 1,380 4 16 2,710 81 603

7 1,600 5 22 1,520 5 20 2,420 56 375

8 1,570 5 21 1,430 5 19 2,030 20 112

9 1,580 5 21 1,470 5 20 1,880 16 79

10 1,600 5 22 1,530 5 22 1,990 16 89

11 1,570 5 23 1,500 5 19 2,340 35 227

12 1,360 6 21 1,480 4 16 2,580 42 291

13 1,270 6 20 1,470 4 16 2,490 34 230

14 1,430 4 16 1,470 4 15 2,340 28 175

15 1,550 3 12 1,450 4 14 2,220 23 137

16 1,470 2 7.6 1,410 3 13 2,400 28 181

17 1,480 1 4.4 1,430 3 12 2,950 44 352

18 1,380 1 3.7 1,440 3 13 2,900 38 296

19 1,350 1 4.1 1,430 3 14 2,740 24 182

20 1,500 3 13 1,420 4 14 2,430 19 124

21 1,650 6 27 1,430 5 19 e2,300 17 103

22 1,650 8 35 1,630 30 140 e2,260 17 107

23 1,590 7 30 2,750 199 1,540 2,500 20 138

24 1,460 6 24 2,270 62 382 2,740 24 180

25 1,480 5 20 1,990 25 137 2,730 28 206

26 1,640 4 19 1,830 19 94 2,860 30 228

27 1,570 4 17 1,710 14 67 3,030 32 261

28 1,470 4 16 1,600 10 43 3,190 37 322

29 1,540 4 18 1,540 6 27 3,320 38 339

30 1,820 13 67 -- -- -- 3,430 38 355

31 1,900 18 90 -- -- -- 4,140 73 828

TOTAL 48,470 -- 779.8 46,310 -- 2,855 77,480 -- 7,311

MEAN 1,564 6 25 1,597 16 98 2,499 32 236

MAX 1,900 18 90 2,750 199 1,540 4,140 92 828

MIN 1,270 1 3.7 1,380 3 12 1,540 8 34

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2011 

through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]
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 5,090 103 1,410 11,800 56 1,800 6,670 12 207

2 5,320 88 1,260 10,700 41 1,200 7,060 14 276

3 5,000 73 982 9,560 32 838 8,000 24 515

4 4,800 43 557 8,820 28 675 8,710 33 765

5 4,670 33 415 8,370 27 605 9,400 40 1,020

6 4,540 26 323 7,960 24 519 11,300 83 2,570

7 4,420 23 279 7,380 22 443 11,500 76 2,360

8 4,200 20 231 7,070 22 415 10,300 48 1,340

9 4,040 21 224 7,170 21 399 9,370 31 777

10 3,970 23 249 7,910 24 512 8,920 25 598

11 4,130 22 250 8,240 24 531 8,470 23 526

12 4,990 40 546 8,000 21 447 7,930 19 408

13 6,250 94 1,600 7,850 20 424 7,780 18 372

14 6,610 75 1,330 8,050 22 488 8,540 24 544

15 6,600 56 1,000 8,640 29 677 8,380 20 445

16 6,470 50 875 9,680 44 1,170 8,000 18 380

17 6,200 37 622 11,000 72 2,170 7,820 15 322

18 6,050 32 519 11,400 65 1,990 7,960 15 322

19 6,010 27 444 10,600 45 1,290 7,920 15 314

20 5,980 28 446 9,570 30 786 7,400 13 257

21 6,470 34 607 8,940 24 574 6,800 13 237

22 7,430 61 1,230 9,350 26 650 6,360 12 213

23 8,630 97 2,290 10,500 41 1,150 6,210 10 175

24 10,500 169 4,830 9,750 30 783 6,300 11 188

25 13,100 245 8,660 8,680 19 453 6,320 12 200

26 14,900 194 7,780 7,860 16 336 6,150 11 181

27 17,400 250 11,800 7,470 14 279 5,850 10 154

28 17,600 185 8,870 7,390 16 324 5,310 8 117

29 15,200 109 4,510 7,320 15 298 4,840 8 105

30 13,100 70 2,470 7,020 14 262 4,520 8 95

31 -- -- -- 6,720 12 219 -- -- --

TOTAL 229,670 -- 66,609 270,770 -- 22,707 230,090 -- 15,983

MEAN 7,656 78 2,220 8,735 29 732 7,670 22 533

MAX 17,600 250 11,800 11,800 72 2,170 11,500 83 2,570

MIN 3,970 20 224 6,720 12 219 4,520 8 95

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2011 

through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]
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 4,300 7 80 1,710 3 14 1,210 4 14

2 4,130 6 68 1,660 3 15 1,190 4 13

3 3,940 6 64 1,630 3 15 1,180 4 13

4 3,740 6 60 1,600 4 16 1,170 4 13

5 3,570 5 53 1,570 4 17 1,170 4 13

6 3,380 5 46 1,530 4 16 1,170 4 13

7 3,230 5 39 1,500 4 14 1,180 4 13

8 3,110 4 34 1,480 3 13 1,170 4 13

9 3,030 4 33 1,480 3 12 1,170 4 13

10 2,930 4 31 1,470 3 13 1,170 4 13

11 2,860 3 27 1,450 4 14 1,160 4 13

12 2,760 3 23 1,420 4 14 1,160 4 12

13 2,640 3 21 1,390 4 15 1,160 4 13

14 2,580 3 21 1,350 3 13 1,170 4 13

15 2,540 3 21 1,340 3 11 1,180 4 13

16 2,560 3 21 1,340 4 13 1,170 4 13

17 2,560 4 24 1,340 4 14 1,150 4 12

18 2,520 4 27 1,330 4 13 1,150 4 12

19 2,440 2 13 1,300 3 12 1,140 4 12

20 2,360 2 13 1,290 3 11 1,140 4 12

21 2,340 2 16 1,300 3 11 1,140 4 12

22 2,260 3 18 1,320 3 11 1,140 4 12

23 2,170 3 18 1,320 3 11 1,130 4 12

24 2,090 3 16 1,290 3 10 1,130 4 12

25 2,020 2 13 1,290 3 11 1,130 4 12

26 1,940 2 11 1,270 3 12 1,140 4 12

27 1,910 3 13 1,270 4 14 1,140 4 12

28 1,900 3 16 1,270 5 16 1,150 4 12

29 1,890 4 18 1,260 5 17 1,150 4 12

30 1,810 4 19 1,230 5 16 1,150 4 12

31 1,750 3 16 1,210 4 15 -- -- --

TOTAL 83,260 -- 893 43,210 -- 419 34,760 -- 376

MEAN 2,686 4 29 1,394 4 14 1,159 4 13

MAX 4,300 7 80 1,710 5 17 1,210 4 14

MIN 1,750 2 11 1,210 3 10 1,130 4 12

Total for water year 2012 (unrounded sum of daily values): streamflow–1,231,540 ft3/s (annual runoff–2,443,000 acre-ft); suspendedsediment discharge–122,079.8 tons. 

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2011 

through September 2012.—Continued

[ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum; 

acre-ft, acre-feet]
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 

(12323670), Montana, April through September 2012.

[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); --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE 

1 -- -- -- 5.5 4.5 5.0 7.0 4.0 5.0 

2 -- -- -- 5.5 4.0 4.5 22 5.0 9.0 

3 7.5 5.0 6.0 5.5 4.0 4.5 26 5.5 11 

4 7.0 5.0 5.5 5.0 4.0 4.5 9.5 5.0 7.0 

5 6.5 4.5 5.5 4.5 3.5 4.0 18 6.0 10 

6 5.5 4.5 5.0 4.5 3.5 4.0 -- -- -- 

7 5.5 4.0 5.0 4.5 3.0 4.0 -- -- -- 

8 5.0 4.0 4.5 4.5 3.0 3.5 -- -- -- 

9 5.5 3.5 4.0 5.0 2.5 3.5 5.0 3.5 4.0 

10 5.0 3.5 4.5 5.0 2.5 4.0 4.5 3.5 4.0 

11 8.0 4.0 5.0 4.5 2.5 4.0 4.5 3.5 3.5 

12 8.0 5.5 6.5 4.5 2.0 3.5 4.5 3.0 3.5 

13 8.5 5.0 6.5 5.0 3.0 4.0 6.0 3.0 4.0 

14 7.0 4.5 5.5 6.5 2.5 4.0 4.5 3.0 3.5 

15 6.5 5.0 5.5 7.0 3.5 5.0 4.0 3.0 3.0 

16 6.5 5.0 5.5 9.5 4.0 6.0 5.0 2.5 3.0 

17 6.0 4.5 5.0 10 4.5 6.5 4.0 2.0 3.0 

18 6.0 5.0 5.5 5.5 3.5 4.5 4.5 2.0 3.0 

19 6.5 4.5 5.0 5.0 3.5 4.0 4.0 2.0 3.0 

20 8.0 3.5 5.0 4.5 3.5 4.0 4.5 2.5 3.5 

21 18 5.5 7.5 5.5 3.5 4.0 5.5 3.5 4.5 

22 -- -- -- 12 5.0 8.0 -- -- -- 

23 -- -- -- 6.5 3.5 4.5 -- -- -- 

24 28 8.5 14 4.5 3.0 3.5 -- -- -- 

25 17 7.0 10 4.5 3.0 3.5 13 3.5 6.5 

26 33 9.5 17 4.0 3.0 3.5 -- -- -- 

27 24 8.0 12 4.0 3.0 3.5 9.5 1.5 4.0 

28 9.0 6.0 7.0 4.5 3.5 3.5 2.5 1.0 1.5 

29 8.0 5.5 6.0 5.0 3.5 4.0 3.5 1.5 2.5 

30 6.5 5.0 5.5 5.0 3.5 4.0 3.5 2.0 2.5 

31 -- -- -- 5.0 3.5 4.0 -- -- -- 

MONTH1 33 3.5 6.7 12 2.0 4.3 26 1.0 4.5 
Data 55

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 3.5 2.0 2.5 2.5 1.0 1.5 4.0 3.0 3.5

2 3.5 2.0 2.5 2.0 1.0 1.5 4.0 3.0 3.5

3 3.5 2.0 2.5 2.5 1.0 1.5 -- -- --

4 3.0 2.0 2.5 2.5 1.0 2.0 -- -- --

5 4.0 2.0 2.5 3.0 0.5 2.0 -- -- --

6 3.0 1.5 2.0 -- -- -- -- -- --

7 3.0 1.5 2.0 -- -- -- -- -- --

8 3.0 1.5 2.0 2.5 1.0 1.5 -- -- --

9 3.5 1.5 2.0 3.0 1.0 2.0 -- -- --

10 3.0 2.0 2.5 4.0 1.0 2.5 -- -- --

11 3.5 2.0 2.5 -- -- -- -- -- --

12 3.0 1.5 2.0 -- -- -- -- -- --

13 3.5 1.5 2.5 -- -- -- -- -- --

14 6.0 0.5 2.5 2.5 1.0 1.5 -- -- --

15 -- -- -- 2.5 1.5 2.0 -- -- --

16 -- -- -- 3.0 1.0 2.0 -- -- --

17 -- -- -- 2.5 1.0 1.5 -- -- --

18 4.5 3.0 3.5 3.0 1.0 2.0 -- -- --

19 5.0 3.0 3.5 2.5 1.5 2.0 -- -- --

20 4.5 2.5 3.0 3.0 1.5 2.0 -- -- --

21 4.0 2.5 3.0 3.5 2.0 2.5 3.5 2.5 3.0

22 3.5 2.5 3.0 3.5 2.0 2.5 3.5 2.5 3.0

23 3.5 2.5 3.0 3.0 1.5 2.0 4.0 2.5 3.0

24 4.0 2.0 3.0 3.0 1.5 2.0 4.0 2.5 3.0

25 4.0 2.5 3.0 2.5 1.5 2.0 3.5 2.0 2.5

26 3.5 2.0 3.0 3.0 2.0 2.5 3.5 1.5 2.0

27 62 2.5 13 3.0 2.0 2.0 2.0 1.5 1.5

28 12 3.0 5.5 2.5 1.5 2.0 2.5 1.5 2.0

29 3.5 2.0 2.5 2.5 1.5 2.0 2.5 1.5 2.0

30 3.0 2.0 2.5 2.5 1.5 2.0 2.5 1.5 2.0

31 2.5 1.5 2.0 4.0 2.0 3.0 -- -- --

MONTH1 62 .5 3.1 4.0 0.5 2.0 4.0 1.5 2.6

Table 9. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Mill Creek near Anaconda 

(12323670), Montana, April through September 2012.—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); --, no data]

1

For months with missing daily values, the means are calculated using available values.
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 (12323710), April through September 2012.

[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); --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE 

1 -- -- -- 11 9.5 10 11 9.0 10 

2 13 10 11 10 9.0 9.5 11 9.0 9.5 

3 12 9.0 10 10 9.0 9.0 10 8.0 9.0 

4 12 9.0 9.5 10 8.0 9.0 9.0 7.5 8.5 

5 10 8.5 9.0 9.5 8.0 8.5 11 7.0 8.0 

6 10 7.5 9.0 -- -- -- 9.5 7.0 8.0 

7 14 8.0 9.5 -- -- -- 8.0 6.5 7.0 

8 9.5 7.5 8.5 -- -- -- 7.5 6.0 6.5 

9 9.5 7.0 8.0 8.5 7.0 7.5 7.0 5.5 6.5 

10 9.5 7.0 7.5 7.5 6.5 7.0 7.0 5.5 6.0 

11 13 7.5 9.0 8.0 6.5 7.0 6.5 5.0 5.5 

12 16 11 13 8.0 6.5 7.0 6.5 5.0 5.5 

13 16 12 13 7.0 6.0 6.5 6.5 5.0 5.5 

14 14 11 12 7.0 6.0 6.5 6.5 4.5 5.5 

15 13 11 12 7.0 5.5 6.0 7.0 4.5 5.0 

16 12 10 11 7.5 5.5 6.0 6.0 4.5 5.0 

17 19 11 12 7.0 6.0 6.5 6.5 4.5 5.0 

18 13 10 11 8.5 6.0 6.5 6.5 4.0 5.0 

19 12 10 11 7.5 6.0 6.5 6.0 4.0 4.5 

20 18 9.5 11 7.0 5.5 6.0 5.5 4.0 4.5 

21 21 11 14 7.0 5.0 6.0 6.5 4.0 4.5 

22 22 13 16 7.5 5.0 5.5 6.5 4.0 5.0 

23 32 14 20 6.0 5.0 5.5 6.0 4.0 4.5 

24 26 18 21 6.0 5.0 5.5 6.0 4.0 4.5 

25 22 16 18 6.5 5.0 5.5 6.5 4.0 5.0 

26 55 15 25 7.0 5.0 5.5 -- -- -- 

27 34 16 20 6.5 5.5 5.5 -- -- -- 

28 17 13 14 7.0 5.0 5.5 -- -- -- 

29 13 11 12 9.0 5.5 6.5 -- -- -- 

30 11 9.0 10 10 8.0 9.0 5.5 4.0 4.5 

31 -- -- -- 11 9.0 9.5 -- -- -- 

MONTH1 55 7.0 13 11 5.0 6.9 11 4.0 6.1 
Data 57

Day 

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 5.5 4.0 4.5 9.0 5.0 6.0 6.0 5.0 5.5

2 6.0 4.0 4.5 10 5.0 6.5 8.5 5.0 6.0

3 5.5 4.0 4.5 9.5 5.0 6.5 7.0 4.5 5.0

4 5.5 3.5 4.5 9.0 4.5 6.0 8.0 4.5 5.0

5 6.5 3.5 4.5 10 5.5 7.5 6.5 5.0 5.5

6 5.5 3.5 4.0 20 5.5 9.0 6.0 5.0 5.5

7 5.5 3.5 4.0 10 5.5 7.5 6.0 4.5 5.0

8 5.0 4.0 4.5 10 5.0 7.5 6.0 4.5 5.0

9 5.5 4.0 4.5 11 5.0 7.5 8.0 4.5 5.0

10 6.0 3.5 4.5 9.0 5.0 6.0 6.0 4.5 5.0

11 6.5 3.5 4.5 10 4.5 6.0 10 5.0 6.5

12 5.5 3.5 4.5 8.0 4.5 5.5 12 4.5 7.0

13 5.5 4.0 4.5 9.0 4.5 6.0 17 5.0 7.0

14 10 4.0 5.0 8.5 4.5 5.5 -- -- --

15 1,280 8.5 200 8.5 5.0 6.0 -- -- --

16 26 11 15 12 5.0 6.5 -- -- --

17 14 7.5 10 12 5.5 7.5 -- -- --

18 13 6.5 8.5 9.5 5.0 8.0 -- -- --

19 13 6.0 8.0 14 6.0 8.5 -- -- --

20 10 6.0 7.5 22 5.0 10 -- -- --

21 10 5.5 6.5 9.5 3.5 5.5 4.0 3.0 3.0

22 8.5 5.0 6.5 41 5.5 16 4.0 3.0 3.5

23 9.5 5.0 6.0 13 5.5 9.0 3.5 3.0 3.0

24 9.0 4.5 6.0 9.5 5.0 6.0 3.5 3.0 3.0

25 8.0 4.5 5.5 12 5.5 7.0 3.5 3.0 3.0

26 8.0 4.0 5.5 12 5.5 7.0 3.5 2.5 3.0

27 12 4.5 6.5 28 5.5 10 3.5 2.5 3.0

28 9.5 4.0 5.5 8.5 5.0 6.0 3.0 2.5 3.0

29 8.0 4.5 5.5 8.5 5.0 6.0 3.0 2.5 2.5

30 7.5 4.5 5.5 6.5 4.5 5.0 3.0 2.5 2.5

31 8.5 4.5 6.0 7.0 5.0 5.5 -- -- --

MONTH1 1,280 3.5 12 41 3.5 7.2 17.0 2.5 4.5

Table 10. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Willow Creek near Anaconda, 

Montana (12323710), April through September 2012.—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); --, no data]

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 (12323760), April through September 2012.

[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); --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

APRIL MAY JUNE 

1 -- -- -- -- -- -- 7.5 5.0 5.5 

2 4.5 3.5 4.0 -- -- -- 59 5.5 9.5 

3 11 3.5 4.5 -- -- -- 28 6.0 12 

4 5.0 3.5 4.0 11 3.5 4.0 10 4.5 6.5 

5 -- -- -- 5.5 2.5 3.5 39 7.5 15 

6 -- -- -- 4.0 3.0 3.5 24 6.0 9.0 

7 -- -- -- 4.0 3.0 3.5 7.0 5.0 5.5 

8 -- -- -- 4.0 3.0 3.5 6.5 4.5 5.5 

9 -- -- -- 4.0 3.5 4.0 8.0 4.0 5.0 

10 4.5 3.5 4.0 5.5 3.5 4.5 6.5 4.5 5.0 

11 5.0 3.5 4.0 5.5 3.5 4.0 6.0 4.0 4.5 

12 -- -- -- 4.5 3.5 4.0 5.5 4.0 4.5 

13 -- -- -- 7.5 3.5 4.5 10 4.5 6.5 

14 5.0 3.5 4.0 6.5 4.5 5.0 8.0 4.5 5.5 

15 10 4.5 6.5 -- -- -- 6.0 4.5 5.0 

16 10 3.5 8.0 -- -- -- 6.0 4.5 5.0 

17 4.0 3.0 3.5 -- -- -- 6.5 4.0 5.0 

18 4.5 3.5 3.5 7.5 5.0 6.0 5.5 4.5 5.0 

19 4.5 3.0 3.5 7.5 4.5 5.5 7.0 4.0 4.5 

20 4.5 3.5 4.0 6.5 4.5 5.5 6.0 4.0 4.5 

21 5.0 4.0 4.5 7.5 4.5 5.5 8.0 4.0 5.0 

22 6.0 4.5 5.0 15 6.0 10 8.5 4.0 5.0 

23 8.0 4.5 5.5 11 5.5 7.0 8.5 4.5 6.0 

24 -- -- -- 7.0 5.0 5.5 10 4.5 6.5 

25 18 5.0 9.5 13 5.0 6.0 13 5.0 7.5 

26 73 8.0 26 6.5 4.5 5.5 21 4.0 7.5 

27 27 6.5 14 6.5 4.5 5.0 8.5 4.0 5.0 

28 11 5.0 6.0 6.0 4.5 5.0 15 4.0 5.0 

29 6.5 4.5 5.5 6.0 4.0 5.0 12 4.0 5.0 

30 5.5 4.5 5.5 5.5 4.0 5.0 5.5 3.5 4.0 

31 -- -- -- 6.5 4.0 4.5 -- -- -- 

MONTH1 73 3.0 6.4 15 2.5 5.0 59 3.5 6.2 
Data 59

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 21 3.5 4.5 3.5 3.0 3.5 3.0 2.5 2.5

2 21 4.0 6.0 3.5 3.0 3.5 3.0 2.5 2.5

3 13 3.5 5.5 3.5 3.0 3.0 3.0 2.5 3.0

4 6.5 4.0 4.5 3.5 3.0 3.0 3.0 2.5 3.0

5 9.5 3.5 4.5 3.5 3.0 3.0 3.0 2.5 3.0

6 7.0 3.5 4.5 3.5 3.0 3.5 3.5 2.5 3.0

7 8.5 4.0 5.5 4.0 3.0 3.5 3.5 2.5 3.0

8 17 4.0 8.0 4.0 3.0 3.5 3.0 2.0 3.0

9 18 3.0 8.0 5.0 3.0 3.5 3.5 2.5 3.0

10 7.0 2.5 3.0 4.0 3.0 3.5 3.5 2.5 3.0

11 8.5 2.5 3.5 4.0 3.0 3.5 3.0 2.5 3.0

12 4.0 2.5 3.0 3.5 3.0 3.5 3.0 2.5 2.5

13 4.0 2.5 3.0 4.0 3.0 3.5 3.0 2.5 2.5

14 81 2.5 7.0 3.5 3.0 3.5 3.0 2.5 2.5

15 18 3.0 4.5 3.5 3.0 3.5 3.5 2.0 2.5

16 6.0 3.0 3.5 3.5 3.0 3.5 3.0 2.5 2.5

17 26 3.0 5.0 4.0 3.0 3.5 3.0 2.5 2.5

18 7.0 3.5 4.5 3.5 3.0 3.5 3.0 2.5 2.5

19 5.0 3.5 4.0 4.0 3.0 3.5 3.0 2.5 2.5

20 5.0 3.0 3.5 8.0 3.0 3.5 3.0 2.5 2.5

21 8.5 3.0 3.5 3.5 2.5 3.0 3.0 2.5 2.5

22 5.0 3.0 3.5 6.0 3.0 3.5 3.0 2.5 2.5

23 5.5 3.0 3.5 3.5 2.5 3.0 3.0 2.5 2.5

24 6.5 3.0 4.0 3.5 2.5 3.0 3.0 2.5 2.5

25 4.5 3.0 4.0 3.5 2.5 3.0 3.0 2.5 2.5

26 4.5 3.0 3.5 3.5 2.5 3.0 3.0 2.5 2.5

27 6.5 3.0 3.5 3.5 2.5 3.0 3.0 2.0 2.5

28 4.5 3.0 3.5 3.5 2.5 3.0 3.0 2.5 2.5

29 5.0 3.0 3.5 3.5 2.5 3.0 3.0 2.0 2.5

30 3.5 3.0 3.5 3.0 2.5 2.5 2.5 2.0 2.5

31 5.0 3.0 3.5 3.0 2.5 2.5 -- -- --

MONTH1 81 2.5 4.4 8.0 2.5 3.3 3.5 2.0 2.6

1

For months with missing daily values, the means are calculated using available values.

Table 11. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Warm Springs Creek near 

Anaconda, Montana (12323760), April through September 2012.—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); --, no data]
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 (12323840), April through September 2012.

[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); --, no data; <, less than]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean 

APRIL MAY JUNE 

1 -- -- -- 7.5 4.0 5.5 20 20 17 

2 120 2.0 14 8.0 4.0 5.0 40 20 21 

3 6.0 3.0 4.0 20 3.0 5.0 85 30 34 

4 8.5 3.0 4.5 9.0 3.0 5.0 70 30 41 

5 6.5 2.0 3.5 7.0 3.0 4.0 66 30 48 

6 4.5 2.0 3.0 4.0 2.0 3.5 -- -- -- 

7 20 2.0 5.0 6.0 2.0 3.5 -- -- -- 

8 5.0 2.0 3.0 10 2.0 4.5 -- -- -- 

9 4.0 2.0 3.0 6.0 2.0 4.0 9.0 4.0 5.5 

10 5.0 2.0 3.0 5.5 2.0 3.5 7.5 4.0 4.5 

11 5.0 2.0 3.5 6.5 2.0 3.0 6.5 3.0 4.5 

12 6.5 3.0 4.5 5.0 2.0 2.5 6.0 3.0 4.0 

13 5.0 2.0 3.5 5.5 2.0 3.0 25 4.0 7.0 

14 4.5 2.0 3.0 9.5 2.0 4.0 6.0 3.0 4.0 

15 4.5 2.0 3.0 9.0 2.0 4.5 5.0 2.0 3.5 

16 4.5 2.0 3.0 16 4.0 6.5 5.5 2.0 3.5 

17 4.0 2.0 2.5 20 5.0 9.0 5.5 3.0 3.5 

18 5.5 2.0 3.0 8.0 4.0 5.0 5.5 3.0 3.5 

19 4.0 2.0 3.0 5.5 3.0 4.0 4.5 2.0 3.0 

20 6.0 2.0 3.0 7.0 2.0 3.5 4.0 2.0 3.0 

21 7.0 4.0 5.0 8.5 3.0 4.5 4.5 2.0 3.0 

22 11 4.0 6.5 18 6.0 10 4.0 2.0 3.0 

23 12 5.0 8.0 19 10 14 6.0 2.0 3.0 

24 18 6.0 10 16 10 13 4.5 2.0 3.0 

25 27 7.0 14 15 10 12 7.5 2.0 3.5 

26 55 10 21 20 10 14 4.0 2.0 2.5 

27 30 9.0 18 16 10 13 3.5 2.0 2.5 

28 11 7.0 8.5 16 10 12 5.0 2.0 2.5 

29 9.0 6.0 7.0 21 10 14 3.0 2.0 2.5 

30 7.5 4.0 5.5 20 10 15 3.5 2.0 2.0 

31 -- -- -- 17 10 14 -- -- -- 

MONTH1 120 2.0 6.2 21 2.0 7.2 85 2.0 8.8 
Data 61

Day Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

JULY AUGUST SEPTEMBER

1 4.0 2.0 2.5 1.5 0.5 1.0 1.5 0.5 0.5

2 2.5 1.0 2.0 2.0 1.0 1.0 1.0 0.5 0.5

3 3.0 2.0 2.0 4.5 1.0 1.5 1.0 0.5 0.5

4 3.0 2.0 2.0 4.5 1.0 1.5 1.5 0.5 0.5

5 5.0 2.0 2.0 5.5 1.0 1.5 1.5 0.5 0.5

6 3.5 2.0 2.0 2.5 1.0 1.5 1.0 <0.5 0.5

7 2.5 2.0 1.5 2.0 0.5 1.0 1.5 0.5 0.5

8 2.5 1.0 1.5 2.0 1.0 1.0 1.0 0.5 0.5

9 2.5 2.0 1.5 39 1.0 4.0 1.5 0.5 0.5

10 3.5 2.0 2.0 7.0 2.0 3.5 1.5 0.5 1.0

11 3.0 1.0 1.5 3.5 2.0 2.0 1.5 0.5 1.0

12 3.0 2.0 1.5 2.5 2.0 2.0 1.5 0.5 1.0

13 3.0 1.0 1.5 3.0 2.0 2.0 1.5 0.5 1.0

14 5.5 1.0 1.5 2.5 2.0 2.0 1.5 0.5 1.0

15 7.5 2.0 3.0 2.5 2.0 2.0 1.0 0.5 0.5

16 5.0 2.0 2.0 2.0 2.0 1.5 1.5 0.5 0.5

17 2.5 1.0 1.5 3.0 2.0 1.5 1.0 0.5 0.5

18 2.0 1.0 1.5 2.5 2.0 1.5 1.0 0.5 0.5

19 2.5 2.0 1.5 4.5 2.0 1.5 16 0.5 1.5

20 1.5 1.0 1.5 2.5 1.0 1.5 4.0 0.5 1.0

21 1.5 1.0 1.5 3.5 1.0 1.5 1.0 0.5 0.5

22 1.5 1.0 1.5 2.5 0.5 1.0 0.5 0.5 0.5

23 2.0 1.0 1.5 2.0 0.5 1.0 1.0 0.5 0.5

24 1.5 1.0 1.0 1.5 0.5 1.0 1.0 0.5 0.5

25 2.0 1.0 1.5 1.5 0.5 1.0 5.0 0.5 1.0

26 1.5 1.0 1.0 1.5 0.5 0.5 0.5 0.5 0.5

27 1.5 1.0 1.0 1.5 0.5 0.5 1.0 0.5 0.5

28 1.5 1.0 1.0 1.5 0.5 0.5 1.0 0.5 0.5

29 2.0 1.0 1.0 1.5 0.5 0.5 1.0 0.5 0.5

30 1.5 1.0 1.0 1.0 0.5 0.5 1.0 0.5 0.5

31 1.5 1.0 1.0 1.5 0.5 0.5 -- -- --

MONTH1 7.5 1.0 1.6 39 0.5 1.4 16 0.5 0.7

1

For months with missing daily values, the means are calculated using available values.

Table 12. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Lost Creek near Anaconda, 

Montana (12323840), April through September 2012.—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); --, no data; <, less than]
Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana.[mg/L, milligrams per liter; μg/L, micrograms per liter; CaCO3, calcium carbonate; mm, millimeter; <, 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)

12323700 Mill Creek at Opportunity 08/13/2012 1515 85.5 23.9 6.28 24.8 

08/13/2012 1520 86.6 24.1 6.39 24.6 

12323750 Silver Bow Creek at Warm Springs 07/17/2012 1010 165 47.5 11.2 34.6 

07/17/2012 1015 167 48.2 11.2 34.7 

12323840 Lost Creek near Anaconda 04/09/2012 1410 111 32.8 7.00 1.9 

04/09/2012 1415 112 33.3 7.05 1.9 

12324200 Clark Fork at Deer Lodge 05/15/2012 1310 156 45.8 10.2 12.8 

05/15/2012 1315 161 47.6 10.3 13.3 

12324400 Clark Fork above Little Blackfoot, near Garrison 03/20/2012 1245 215 62.6 14.3 10.9 

03/20/2012 1250 212 61.8 14.1 11.0 

12324680 Clark Fork at Goldcreek 11/08/2011 1400 201 59.5 12.6 7.9 

11/08/2011 1405 200 59.2 12.7 8.0 

12334550 Clark Fork at Turah Bridge, near Bonner 06/07/2012 0735 85.8 24.3 6.09 6.3 

06/07/2012 0740 82.7 23.6 5.80 6.3 

12340500 Clark Fork above Missoula 06/20/2012 1255 89.3 24.0 7.12 2.3 

06/20/2012 1300 104 28.9 7.76 2.4 
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 

recoverab

(μg/L)

12323700 Mill Creek at Opportunity 08/13/2012 1515 0.034 2.4 2.1 42.3 74.8 

08/13/2012 1520 0.038 2.0 2.2 44.6 70.3 

12323750 Silver Bow Creek at Warm Springs 07/17/2012 1010 0.072 2.8 5.3 34.4 204 

07/17/2012 1015 0.069 2.9 5.4 32.4 209 

12323840 Lost Creek near Anaconda 04/09/2012 1410 0.020 1.3 3.0 7.8 71.9 

04/09/2012 1415 0.025 1.2 3.2 7.9 86.1 

12324200 Clark Fork at Deer Lodge 05/15/2012 1310 0.155 6.8 27.4 21.8 431 

05/15/2012 1315 0.144 7.1 25.6 21.4 428 

12324400 Clark Fork above Little Blackfoot, near Garrison 03/20/2012 1245 0.246 8.1 45.6 23.2 787 

03/20/2012 1250 0.228 8.0 43.2 19.7 761 

12324680 Clark Fork at Goldcreek 11/08/2011 1400 0.074 2.8 11.5 8.5 200 

11/08/2011 1405 0.075 2.8 11.3 4.4 193 

12334550 Clark Fork at Turah Bridge, near Bonner 06/07/2012 0735 0.263 5.9 49.7 30.7 1,340 

06/07/2012 0740 0.294 5.9 52.7 34.1 1,410 

12340500 Clark Fork above Missoula 06/20/2012 1255 0.027 1.7 4.8 16.9 215 

06/20/2012 1300 0.029 1.6 4.4 14.4 203 

Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana.—Continued[mg/L, milligrams per liter; μg/L, micrograms per liter; CaCO3, calcium carbonate; mm, millimeter; <, 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) 

12323700 Mill Creek at Opportunity 08/13/2012 1515 7.51 6.6 <1.4 <3.0 

08/13/2012 1520 7.25 6.7 <1.4 <3.0 

12323750 Silver Bow Creek at Warm Springs 07/17/2012 1010 36.6 102 <1.4 5.7 

07/17/2012 1015 37.4 102 <1.4 6.7 

12323840 Lost Creek near Anaconda 04/09/2012 1410 2.06 2.5 <1.4 <3.0 

04/09/2012 1415 2.06 3.2 <1.4 <3.0 

12324200 Clark Fork at Deer Lodge 05/15/2012 1310 26.9 81.4 3.6 21.2 

05/15/2012 1315 29.6 66.4 3.8 18.7 

12324400 Clark Fork above Little Blackfoot, near Garrison 03/20/2012 1245 64.6 129 8.7 40.5 

03/20/2012 1250 63.8 125 8.7 38.2 

12324680 Clark Fork at Goldcreek 11/08/2011 1400 28.0 48.1 2.6 13.4 

11/08/2011 1405 26.4 46.7 2.6 11.6 

12334550 Clark Fork at Turah Bridge, near Bonner 06/07/2012 0735 6.81 142 4.5 58.1 

06/07/2012 0740 7.39 159 4.6 69.8 

12340500 Clark Fork above Missoula 06/20/2012 1255 5.71 20.6 1.5 6.1 

06/20/2012 1300 6.62 19.9 <1.4 5.5 

Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana.—Continued[mg/L, milligrams per liter; μg/L, micrograms per liter; CaCO3, calcium carbonate; mm, millimeter; <, less than laboratory reporting level]
Data 65

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

[mg/L, milligrams per liter; μg/L, micrograms 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 1.4 3.3 Yes

Magnesium, filtered, mg/L 8 0.19 2.0 Yes

Arsenic, filtered, μg/L 8 0.14 1.1 Yes

Arsenic, unfiltered recoverable, μg/L 8 0.27 1.9 Yes

Cadmium, filtered, μg/L 8 0.00 2.8 Yes

Cadmium, unfiltered recoverable, μg/L 8 0.01 8.5 Yes

Copper, filtered, μg/L 8 0.13 3.4 Yes

Copper, unfiltered recoverable, μg/L 8 1.1 5.7 Yes

Iron, filtered, μg/L 8 1.9 8.2 Yes

Iron, unfiltered recoverable, μg/L 8 19 4.6 Yes

Lead, filtered, μg/L 8 0.01 6.3 Yes

Lead, unfiltered recoverable, μg/L 8 0.14 5.2 Yes

Manganese, filtered, μg/L 8 0.88 3.9 Yes

Manganese, unfiltered recoverable, μg/L 8 5.8 8.7 Yes

Zinc, filtered, μg/L 8 0.21 7.3 Yes

Zinc, unfiltered recoverable, μg/L 8 3.1 16 Yes

Sediment, suspended, percent finer than 0.062 mm 8 2.8 3.5 Yes

Sediment, suspended, mg/L 8 0.66 3.2 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.

[mg/L, milligrams per liter; μg/L, micrograms per liter]

Constituent and reporting unit Number of 

replicate pairs

Standard deviation1 

 (listed units)

Relative standard 

deviation 

(percent)

Within limits1

 of 

data-quality 

objective

Calcium, filtered, mg/L 8 0.54 1.3 Yes

Magnesium, filtered, mg/L 8 0.10 1.0 Yes

Arsenic, filtered, μg/L 8 0.15 1.2 Yes

Arsenic, unfiltered recoverable, μg/L 8 0.36 2.5 Yes

Cadmium, filtered, μg/L 8 0.00 5.9 Yes

Cadmium, unfiltered recoverable, μg/L 8 0.01 9.3 Yes

Copper, filtered, μg/L 8 0.13 3.3 Yes

Copper, unfiltered recoverable, μg/L 8 0.59 3.2 Yes

Iron, filtered, μg/L 8 2.0 8.5 Yes

Iron, unfiltered recoverable, μg/L 8 1.5 0.36 Yes

Lead, filtered, μg/L 8 0.00 2.2 Yes

Lead, unfiltered recoverable, μg/L 8 0.02 0.67 Yes

Manganese, filtered, μg/L 8 0.25 1.1 Yes

Manganese, unfiltered recoverable, μg/L 8 0.90 1.4 Yes

Zinc, filtered, μg/L 8 0.17 5.7 Yes

Zinc, unfiltered recoverable, μg/L 8 0.29 1.5 Yes

1

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.

[μg/L, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent confidence interval 

for spike recovery 

(percent)

Mean spike recovery 

(percent)

Within limits1

of data-quality 

objective

Arsenic, filtered, μg/L 5 90.4–106 98.1 Yes

Arsenic, unfiltered recoverable, μg/L 5 94.3–108 101 Yes

Cadmium, filtered, μg/L 5 93.2–112 102 Yes

Cadmium, unfiltered recoverable, μg/L 5 95.1–108 101 Yes

Copper, filtered, μg/L 5 93.1–104 98.4 Yes

Copper, unfiltered recoverable, μg/L 5 92.5–107 100 Yes

Iron, filtered, μg/L 5 102–108 105 Yes

Iron, unfiltered recoverable, μg/L 5 96.2–117 106 Yes

Lead, filtered, μg/L 5 96.8–106 102 Yes

Lead, unfiltered recoverable, μg/L 5 98.4–107 103 Yes

Manganese, filtered, μg/L 5 101–110 105 Yes

Manganese, unfiltered recoverable, μg/L 5 95.4–106 101 Yes

Zinc, filtered, μg/L 5 96.5–109 103 Yes

Zinc, unfiltered recoverable, μg/L 5 94.9–106 100 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

Table 17. Recovery efficiency for analyses of laboratory-spiked stream samples, Clark Fork Basin, Montana.

[μg/L, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent confidence interval 

for spike recovery

(percent)

Mean spike recovery 

(percent)

Within limits1

of data-quality 

objective

Arsenic, filtered, μg/L 5 101–106 104 Yes

Arsenic, unfiltered recoverable, μg/L 5 91.8–103 97.5 Yes

Cadmium, filtered, μg/L 5 104–110 107 Yes

Cadmium, unfiltered recoverable, μg/L 5 91.9–106 98.8 Yes

Copper, filtered, μg/L 5 90.9–97.0 94.0 Yes

Copper, unfiltered recoverable, μg/L 5 87.2–101 93.9 Yes

Iron, filtered, μg/L 5 102–114 108 Yes

Iron, unfiltered recoverable, μg/L 5 98.6–102 100 Yes

Lead, filtered, μg/L 5 97.9–107 102 Yes

Lead, unfiltered recoverable, μg/L 5 96.3–105 101 Yes

Manganese, filtered, μg/L 5 97.7–104 101 Yes

Manganese, unfiltered recoverable, μg/L 5 88.0–103 95.5 Yes

Zinc, filtered, μg/L 5 95.2–109 102 Yes

Zinc, unfiltered recoverable, μg/L 5 82.4–97.2 89.8 Yes

1

Data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).
Table 18. Analyses of field blanks for water samples.[mg/L, milligrams per liter; μg/L, micrograms per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; <, less than laboratory reporting level]

Date Time

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered recoverable (μg/L)

Cadmium, 

filtered 

(μg/L)

Ca

un

rec

11/07/2011 1250 5.4 2 <0.022 <0.011 <0.03 <0.28 <0.016 <

03/15/2012 0900 5.6 2 <0.022 <0.011 <0.03 <0.28 <0.016 <

04/11/2012 1425 5.5 2 <0.022 <0.011 <0.03 <0.28 <0.016 <

05/14/2012 1350 5.5 2 <0.022 <0.011 <0.03 <0.28 <0.016 <

06/06/2012 0855 5.6 1 <0.022 <0.011 <0.03 <0.28 <0.016 <

06/20/2012 0800 5.6 2 <0.022 <0.011 <0.03 <0.28 <0.016 <

07/17/2012 1140 5.6 2 <0.022 <0.011 <0.03 <0.28 <0.016 <

08/14/2012 0900 5.6 2 <0.022 <0.011 <0.03 <0.28 <0.016 <

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)

f

11/07/2011 <0.80 <0.70 <3.2 <4.6 <0.025 <0.04 0.51 <0.4 

03/15/2012 <0.80 <0.70 <3.2 <4.6 <0.025 <0.04 <0.13 <0.4 04/11/2012 <0.80 <0.70 <3.2 <4.6 <0.025 <0.04 0.43 <0.4 

05/14/2012 <0.80 <0.70 <3.2 <4.6 <0.025 <0.04 0.46 <0.4 

06/06/2012 <0.80 <0.70 <3.2 <4.6 <0.025 <0.04 0.15 <0.4 

06/20/2012 <0.80 <0.70 4.2 <4.6 <0.025 <0.04 0.57 <0.4 

07/17/2012 <0.80 <0.70 <3.2 <4.6 <0.025 <0.04 0.57 <0.4 

08/14/2012 <0.80 <0.70 <3.2 <4.6 <0.025 <0.04 0.38 <0.4 
Table 19. Bed-sediment data for the Clark Fork Basin, Montana, August 2012. [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 mses from each composite sample. 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 Mangan

12323600 Silver Bow Creek at Opportunity 3 36 5.9 48.0 522 32,900 121 1,57

12323750 Silver Bow Creek at Warm Springs 3 90 7.0 40.9 302 26,400 63 4,38

12323800 Clark Fork near Galen 3 99 5.3 43.8 1,150 27,700 106 3,44

461415112450801 Clark Fork below Lost Creek, near Galen 3 90 5.5 38.0 1,330 25,600 123 4,07

461559112443301 Clark Fork at county bridge, near Racetrack 3 90 5.0 43.2 1,270 26,800 125 3,06

461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 3 66 5.0 39.2 1,020 27,600 109 3,06

12324200 Clark Fork at Deer Lodge 3 70 4.9 40.8 1,100 26,100 112 1,83

12324400 Clark Fork above Little Blackfoot River, near Garrison 3 50 4.5 39.0 855 23,500 102 3,56

12324680 Clark Fork at Goldcreek 3 34 2.5 27.7 388 16,300 52 1,86

12331800 Clark Fork near Drummond 3 19 2.0 16.9 220 15,900 29 1,35

12334550 Clark Fork at Turah Bridge, near Bonner 3 19 1.2 30.7 219 16,400 41 89

12340000 Blackfoot River near Bonner 3 4 0.04 25.4 18 15,900 10 69

12340500 Clark Fork above Missoula 3 12 1.0 30.2 129 17,900 25 85
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. SRM, standard reference material (agricultural soils); 

μg/g, micrograms per gram of dry sample weight]

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 56.9 54.0–59.8

Cadmium 10 1:10 0.371 21.4 18.1–24.7

Chromium 10 1:10 130 77.5 73.6–81.3

Copper 10 1:10 33.9 82.1 77.1–87.1

Iron 10 1:10 33,600 85.0 80.7–89.3

Lead 10 1:10 17.3 60.0 56.5–63.5

Manganese 10 1:10 529 84.9 80.1–89.8

Nickel 10 1:10 85 82.3 78.4–86.2

Zinc 10 1:10 103 95.2 89.8–101

SRM sample 2711a

Arsenic 10 1:10 107 78.4 70.1–86.7

Cadmium 10 1:10 54.1 90.8 80.7–101

Chromium 10 1:10 52 86.1 78.2–94.1

Copper 10 1:10 1,410 100 90.9–110

Iron 10 1:10 28,200 84.4 77.5–91.3

Lead 10 1:10 1,400 87.1 78.3–95.9

Manganese 10 1:10 675 79.7 72.6–86.8

Nickel 10 1:10 21.7 83.4 74.5–92.4

Zinc 10 1:10 414 94.0 83.6–104
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. μg/mL, micrograms per milliliter; <, 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 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.0012323750 Silver Bow Creek at Warm Springs 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.0012323800 Clark Fork near Galen 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.00461415112450801 Clark Fork below Lost Creek, near Galen 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.00461559112443301 Clark Fork at county bridge, near Racetrack 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.00461903112440701 Clark Fork at Dempsey Creek diver- sion, near Racetrack 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.0012324200 Clark Fork at Deer Lodge 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.0012324400 Clark Fork above Little Blackfoot River, near Garrison 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.0012324680 Clark Fork at Goldcreek 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.0012331800 Clark Fork near Drummond 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.00

12334550 Clark Fork at Turah Bridge, near Bonner 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.0012340000 Blackfoot River near Bonner 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.0012340500 Clark Fork above Missoula 1:10 <0.004 <0.0003 <0.003 <0.003 <0.03 <0.003 <0.00
Data 71

Table 22. Biological data for the Clark Fork Basin, Montana, August 2012.

[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. All tissues were 

analyzed undiluted (dilution ratio 1:1). μg/g, micrograms per gram of dry sample weight; spp., species; <, 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 Manganese Nickel Zinc

12323600–Silver Bow Creek at Opportunity

Hydropsyche cockerelli 3 6.0 3.7 3.6 120 2,750 17.3 611 2.6 559

12323750–Silver Bow Creek at Warm Springs

Hydropsyche cockerelli 2 11.5 0.5 1.2 38.3 1,100 5.2 902 1.1 201

12323800–Clark Fork near Galen

Hydropsyche occidentalis 3 13.6 1.2 2.8 143 2,160 12.1 1,630 2.0 204

461415112450801–Clark Fork below Lost Creek, near Galen

Hydropsyche cockerelli 3 18.3 2.2 3.8 224 2,890 21.9 1,720 2.4 278

461559112443301--Clark Fork at county bridge, near Racetrack

Arctopsyche grandis 1 13.0 1.2 1.9 101 1,410 13.2 2,480 1.4 260

Hydropsyche cockerelli 2 18.0 2.1 2.9 165 2,460 18.6 1,700 1.9 275

Hydropsyche occidentalis 2 11.9 1.3 1.8 101 1,450 11.1 1,750 1.1 217

Hydropsyche spp. 1 5.7 2.4 0.9 68.1 787 6.8 1,170 1.0 229

461903112440701–Clark Fork at Dempsey Creek diversion, near Racetrack

Arctopsyche grandis 1 17.5 3.6 3.4 196 2,800 17.6 2,060 2.5 380

Claassenia sabulosa 1 1.6 0.9 0.2 58.6 173 0.9 372 0.2 168

Hydropsyche cockerelli 1 13.3 1.5 2.4 149 1,890 14.4 1,570 1.7 285

Hydropsyche occidentalis 2 10.0 1.0 1.7 108 1,470 8.6 1,210 1.0 200

12324200–Clark Fork at Deer Lodge

Arctopsyche grandis 3 11.4 3.6 2.2 144 1,730 13.3 1,420 1.5 294

Hydropsyche cockerelli 1 17.1 2.3 4.3 241 3,160 24.9 1,410 2.2 335

Hydropsyche occidentalis 1 8.9 1.1 1.9 121 1,500 11.2 937 1.0 214

12324400–Clark Fork above Little Blackfoot River, near Garrison

Arctopsyche grandis 3 7.7 4.0 1.7 132 1,260 10.6 1,870 1.6 296

Hydropsyche occidentalis 2 8.3 2.0 1.6 145 1,210 11.4 2,070 1.5 251

12324680–Clark Fork at Goldcreek

Arctopsyche grandis 3 7.5 1.8 1.4 64.5 886 4.9 1,130 1.3 222

Claassenia sabulosa 2 0.5 0.6 0.2 60.5 165 0.7 177 0.3 211

Hydropsyche cockerelli 1 7.3 1.4 1.8 73.6 1,210 6.0 1,000 1.3 180

Hydropsyche occidentalis 2 4.9 0.9 1.3 54.6 882 4.8 822 1.0 178
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 Manganese Nickel Zinc

12331800–Clark Fork near Drummond

Arctopsyche grandis 3 5.9 1.0 0.5 33.9 390 3.1 619 0.6 209

Claassenia sabulosa 2 0.7 0.7 0.2 54.4 130 0.6 102 0.2 274

Hydropsyche cockerelli 2 7.2 0.9 1.2 47.1 779 5.2 749 0.8 168

Hydropsyche occidentalis 1 4.3 0.5 0.6 41.0 444 3.3 477 0.6 153

12334550–Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 2 4.3 1.7 0.7 23.8 491 3.4 584 0.8 238

Claassenia sabulosa 2 0.2 0.7 0.2 44.8 133 0.5 117 0.2 218

Hydropsyche cockerelli 2 4.6 1.2 1.2 32.8 799 3.9 563 0.8 189

Hydropsyche occidentalis 2 3.2 1.0 1.0 32.0 690 3.2 478 0.7 181

12340000–Blackfoot River near Bonner

Arctopsyche grandis 1 2.1 0.2 0.7 10.3 409 0.8 302 1.0 106

Claassenia sabulosa 1 <1.0 0.2 <0.8 44.1 143 0.4 61 0.4 399

Hydropsyche cockerelli 1 2.1 0.3 1.6 16.1 1,120 1.5 468 1.4 165

Hydropsyche occidentalis 2 1.6 0.2 1.4 15.6 983 1.2 443 1.2 154

12340500–Clark Fork above Missoula

Arctopsyche grandis 3 1.5 1.2 0.5 15.9 351 1.4 726 0.4 196

Claassenia sabulosa 3 0.2 0.8 0.1 42.0 97 0.3 112 0.2 223

Hydropsyche cockerelli 1 2.4 0.8 1.0 24.4 830 2.5 786 0.9 177

Hydropsyche occidentalis 2 2.3 0.7 0.9 25.5 784 2.3 755 0.8 188

Table 22. Biological data for the Clark Fork Basin, Montana, August 2012.—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. All tissues were 

analyzed undiluted (dilution ratio 1:1). μg/g, micrograms per gram of dry sample weight; spp., species; <, 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.

[SRM, standard reference material (lobster hepatopancreas); μg/g, micrograms per gram of dry sample weight]

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 96.7 95.6–97.9

Cadmium 12 26.7 89.0 87.1–90.9

Chromium 12 0.77 95.6 70.4–121

Copper 12 106 88.8 87.9–89.8

Iron 12 105 95.0 93.3–97.5

Lead 12 0.35 129 115–143

Manganese 12 13.6 91.3 89.6–93.0

Nickel 12 2.5 79.8 76.0–83.5

Zinc 12 180 102 98.3–106
Table 24. Analyses of procedural blanks for biota samples. [Procedural blanks were not diluted prior to analyses. μg/mL, micrograms per milliliter; <, 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 Mang

12323600 Silver Bow Creek at Opportunity 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

12323750 Silver Bow Creek at Warm Springs 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

12323800 Clark Fork near Galen 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

461415112450801 Clark Fork below Lost Creek, near Galen 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

461559112443301 Clark Fork at county bridge, near Racetrack 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

12324200 Clark Fork at Deer Lodge 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

12324400 Clark Fork above Little Blackfoot River, near Garrison 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

12324680 Clark Fork at Goldcreek 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

12331800 Clark Fork near Drummond 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

12334550 Clark Fork at Turah Bridge, near Bonner 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

12340000 Blackfoot River near Bonner 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0

12340500 Clark Fork above Missoula 1:1 <0.003 <0.002 <0.002 <0.001 <0.03 <0.002 <0
Data 75

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]

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 2012

Streamflow, instantaneous (ft3

/s) 147 156 1.9 16 9.3

pH, onsite (standard units) 147 8.4 7.3 7.7 7.7

Specific conductance, onsite (μS/cm) 147 412 116 261 262

Temperature, water (°C) 147 17.5 1.0 8.0 8.5

Hardness, filtered (mg/L as CaCO3

) 147 146 37.7 103 106

Calcium, filtered (mg/L) 147 41.8 10.6 29.5 30.0

Magnesium, filtered (mg/L) 147 11.0 2.71 7.17 7.20

Arsenic, filtered (μg/L) 146 13.0 1.0 4.2 3.6

Arsenic, unfiltered recoverable (μg/L) 147 18.0 1.0 2

5.5 4.7

Cadmium, filtered (μg/L) 145 0.50 <0.04 2

0.05 0.02

Cadmium, unfiltered recoverable (μg/L) 147 0.11 <0.01 2

0.04 <1

Copper, filtered (μg/L) 146 10.0 <1.0 2

3.6 3.1

Copper, unfiltered recoverable (μg/L) 147 52.0 1.5 6.6 5.0

Iron, filtered (μg/L) 147 640 15 193 175

Iron, unfiltered recoverable (μg/L) 147 4,220 139 679 600

Lead, filtered (μg/L) 147 2.80 <0.08 2

0.20 0.04

Lead, unfiltered recoverable (μg/L) 147 47.0 <1.00 2

1.72 0.67

Manganese, filtered (μg/L) 147 144 14.2 44.0 37.8

Manganese, unfiltered recoverable (μg/L) 147 240 23.5 61.7 52.0

Zinc, filtered (μg/L) 145 11 <1.0 2

3.4 2.7

Zinc, unfiltered recoverable (μg/L) 147 130 <3.0 2

8.3 4.0

Sediment, suspended (percent finer than 0.062 mm) 147 97 50 82 83

Sediment, suspended concentration (mg/L) 147 139 1 12 7

Sediment, suspended discharge (ton/d) 147 59 0.01 1.0 0.18
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 2012

Streamflow, instantaneous (ft3

/s) 155 202 13 31 25

pH, onsite (standard units) 155 8.2 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 155 691 209 458 465

Temperature, water (°C) 155 20.0 1.0 10.3 10.0

Hardness, filtered (mg/L as CaCO3

) 155 217 66.0 147 150

Calcium, filtered (mg/L) 155 62.7 19.0 41.9 42.4

Magnesium, filtered (mg/L) 155 14.6 4.51 10.3 10.5

Arsenic, filtered (μg/L) 155 13.4 2.3 6.2 6.0

Arsenic, unfiltered recoverable (μg/L) 155 45.0 3.0 10.0 8.9

Cadmium, filtered (μg/L) 155 6.2 0.04 0.91 0.25

Cadmium, unfiltered recoverable (μg/L) 155 6.0 0.08 1.23 0.70

Copper, filtered (μg/L) 155 303 2.9 30.9 12.7

Copper, unfiltered recoverable (μg/L) 155 550 8.9 71.2 25.5

Iron, filtered (μg/L) 155 292 9.6 96.7 78.5

Iron, unfiltered recoverable (μg/L) 155 7,400 85 823 552

Lead, filtered (μg/L) 155 2.4 <0.5 2

0.44 0.24

Lead, unfiltered recoverable (μg/L) 155 250 0.61 11.0 2.85

Manganese, filtered (μg/L) 155 1,700 21.4 305 178

Manganese, unfiltered recoverable (μg/L) 155 1,600 25.9 347 212

Zinc, filtered (μg/L) 155 2,200 5.3 296 118

Zinc, unfiltered recoverable (μg/L) 155 2,200 20.5 359 186

Sediment, suspended (percent finer than 0.062 mm) 154 98 42 84 85

Sediment, suspended concentration (mg/L) 154 405 2 20 10

Sediment, suspended discharge (ton/d) 154 70 0.08 2.4 0.68

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 156 648 13 80 54

pH, onsite (standard units) 157 9.5 7.2 8.4 8.3

Specific conductance, onsite (μS/cm) 157 633 202 412 403

Temperature, water (°C) 157 22.5 0.0 9.4 9.5

Hardness, filtered (mg/L as CaCO3

) 157 240 60.2 148 146

Calcium, filtered (mg/L) 157 71.6 18.5 43.8 43.8

Magnesium, filtered (mg/L) 157 15.0 3.42 9.38 9.04

Arsenic, filtered (μg/L) 157 34.0 1.0 10.8 10.1

Arsenic, unfiltered recoverable (μg/L) 157 235 7.8 23.9 16.0

Cadmium, filtered (μg/L) 156 41.0 <0.1 2

1.01 0.56

Cadmium, unfiltered recoverable (μg/L) 157 49.0 0.34 2

1.84 1.10

Copper, filtered (μg/L) 155 450 11.2 41.5 31.5

Copper, unfiltered recoverable (μg/L) 157 3,900 23.6 181 97

Iron, filtered (μg/L) 157 307 <3 2

49.4 27.5

Iron, unfiltered recoverable (μg/L) 156 24,100 196 1,530 780

Lead, filtered (μg/L) 157 5.1 <0.5 2

0.68 0.33

Lead, unfiltered recoverable (μg/L) 157 650 1.81 34.2 14.7

Manganese, filtered (μg/L) 157 9,300 30.3 379 282

Manganese, unfiltered recoverable (μg/L) 157 10,000 69.8 497 387

Zinc, filtered (μg/L) 156 13,000 11.2 261 130

Zinc, unfiltered recoverable (μg/L) 157 15,000 52.6 461 260

Sediment, suspended (percent finer than 0.062 mm) 158 95 37 78 82

Sediment, suspended concentration (mg/L) 158 801 5 50 20

Sediment, suspended discharge (ton/d) 156 781 0.18 22 3.0

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 63 309 7.4 65 33

pH, onsite (standard units) 64 8.6 7.5 8.0 8.0

Specific conductance, onsite (μS/cm) 64 213 56 132 132

Temperature, water (°C) 64 17.0 0.0 8.3 8.0

Hardness, filtered (mg/L as CaCO3

) 64 98.0 23.7 57.4 57.1

Calcium, filtered (mg/L) 64 26.7 7.00 15.9 16.0

Magnesium, filtered (mg/L) 64 8.01 1.45 4.31 4.18

Arsenic, filtered (μg/L) 64 32.9 7.3 16.5 15.2

Arsenic, unfiltered recoverable (μg/L) 64 34.8 7.8 17.8 16.5

Cadmium, filtered (μg/L) 63 0.11 0.02 2

0.04 0.04

Cadmium, unfiltered recoverable (μg/L) 64 0.19 0.03 0.08 0.07

Copper, filtered (μg/L) 64 5.1 0.72 2.2 2.0

Copper, unfiltered recoverable (μg/L) 64 10.6 1.3 3.9 3.2

Iron, filtered (μg/L) 64 125 21 46.3 40.8

Iron, unfiltered recoverable (μg/L) 64 619 77.8 198 159

Lead, filtered (μg/L) 64 0.24 0.02 2

0.12 0.11

Lead, unfiltered recoverable (μg/L) 64 3.12 0.15 0.76 0.58

Manganese, filtered (μg/L) 64 12.0 3.1 5.9 5.7

Manganese, unfiltered recoverable (μg/L) 64 36.6 7.4 13.8 12.2

Zinc, filtered (μg/L) 64 4.0 <1.4 2

1.6 1.4

Zinc, unfiltered recoverable (μg/L) 64 9.2 1.0 2

3.0 2.4

Sediment, suspended (percent finer than 0.062 mm) 64 84 28 63 66

Sediment, suspended concentration (mg/L) 64 29 1 6 4

Sediment, suspended discharge (ton/d) 63 13 0.02 2.1 0.36

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 79 261 0.43 39 12

pH, onsite (standard units) 80 8.3 7.5 8.0 8.0

Specific conductance, onsite (μS/cm) 80 239 59 148 152

Temperature, water (°C) 80 20.0 -1.0 9.2 9.0

Hardness, filtered (mg/L as CaCO3

) 80 112 24.0 63.1 65.0

Calcium, filtered (mg/L) 80 31.0 7.01 17.7 18.2

Magnesium, filtered (mg/L) 80 8.44 1.56 4.60 4.67

Arsenic, filtered (μg/L) 80 55.1 9.0 21.8 20.3

Arsenic, unfiltered recoverable (μg/L) 80 53.5 10.0 24.7 23.0

Cadmium, filtered (μg/L) 80 0.13 0.02 0.06 0.06

Cadmium, unfiltered recoverable (μg/L) 80 0.86 0.03 0.14 0.10

Copper, filtered (μg/L) 80 6.1 1.0 2.9 2.5

Copper, unfiltered recoverable (μg/L) 80 38.8 1.5 6.5 4.1

Iron, filtered (μg/L) 80 94 15.9 46.7 42.2

Iron, unfiltered recoverable (μg/L) 80 1,960 44 301 145

Lead, filtered (μg/L) 80 0.35 <0.08 2

0.14 0.13

Lead, unfiltered recoverable (μg/L) 80 12.7 0.07 1.46 0.45

Manganese, filtered (μg/L) 80 32.8 2.1 7.1 5.4

Manganese, unfiltered recoverable (μg/L) 80 113 3.2 18.6 12.4

Zinc, filtered (μg/L) 79 7.7 <1.4 2

2.9 2.8

Zinc, unfiltered recoverable (μg/L) 80 41 1.7 6.5 4.5

Sediment, suspended (percent finer than 0.062 mm) 80 91 26 69 72

Sediment, suspended concentration (mg/L) 80 107 1 12 2

Sediment, suspended discharge (ton/d) 79 55 <0.01 2

3.6 0.09

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 57 114 1.0 16 7.7

pH, onsite (standard units) 58 8.2 7.5 7.7 7.7

Specific conductance, onsite (μS/cm) 58 151 66 104 108

Temperature, water (°C) 58 15.5 0.0 7.0 7.0

Hardness, filtered (mg/L as CaCO3

) 58 56.3 22.1 37.7 38.6

Calcium, filtered (mg/L) 58 18.3 7.56 12.6 13.0

Magnesium, filtered (mg/L) 58 2.60 0.78 1.51 1.46

Arsenic, filtered (μg/L) 58 25.7 9.9 16.0 15.0

Arsenic, unfiltered recoverable (μg/L) 58 27.0 9.8 17.0 15.4

Cadmium, filtered (μg/L) 56 0.05 <0.04 2

0.03 0.03

Cadmium, unfiltered recoverable (μg/L) 58 0.33 <0.04 2

0.06 0.05

Copper, filtered (μg/L) 58 4.2 0.90 2.1 2.0

Copper, unfiltered recoverable (μg/L) 58 16.8 1.0 3.9 3.1

Iron, filtered (μg/L) 58 277 28 84.9 68.2

Iron, unfiltered recoverable (μg/L) 58 2,380 85.7 375 227

Lead, filtered (μg/L) 58 0.37 0.03 2

0.15 0.15

Lead, unfiltered recoverable (μg/L) 58 7.96 0.10 0.94 0.49

Manganese, filtered (μg/L) 58 34.5 6.0 14.8 13.3

Manganese, unfiltered recoverable (μg/L) 58 99.9 12.8 27.3 24.0

Zinc, filtered (μg/L) 58 3.3 0.65 2

1.7 1.6

Zinc, unfiltered recoverable (μg/L) 58 17.8 <2.0 2

3.3 2.0

Sediment, suspended (percent finer than 0.062 mm) 58 95 25 73 78

Sediment, suspended concentration (mg/L) 58 195 1 18 5

Sediment, suspended discharge (ton/d) 57 50 <0.01 2

2.5 0.10

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 80 116 4.5 18 9.4

pH, onsite (standard units) 80 9.0 7.7 8.1 8.1

Specific conductance, onsite (μS/cm) 80 371 116 270 289

Temperature, water (°C) 80 20.5 1.5 11.3 11.5

Hardness, filtered (mg/L as CaCO3

) 80 169 58.5 117 126

Calcium, filtered (mg/L) 80 47.4 18.1 34.1 36.4

Magnesium, filtered (mg/L) 80 12.3 3.24 7.75 8.22

Arsenic, filtered (μg/L) 80 164 10.9 39.9 29.6

Arsenic, unfiltered recoverable (μg/L) 80 164 12.0 42.4 32.3

Cadmium, filtered (μg/L) 80 0.12 <0.04 2

0.04 0.04

Cadmium, unfiltered recoverable (μg/L) 80 0.52 0.02 0.11 0.08

Copper, filtered (μg/L) 80 21.4 1.1 5.4 3.6

Copper, unfiltered recoverable (μg/L) 80 48.8 2.8 11.4 7.8

Iron, filtered (μg/L) 80 274 6.1 51.3 44.5

Iron, unfiltered recoverable (μg/L) 80 1,670 27 296 220

Lead, filtered (μg/L) 80 0.89 0.04 2

0.23 0.19

Lead, unfiltered recoverable (μg/L) 80 14.4 0.27 2.33 1.53

Manganese, filtered (μg/L) 80 200 3.3 32.5 24.8

Manganese, unfiltered recoverable (μg/L) 80 228 4.7 46.0 36.4

Zinc, filtered (μg/L) 80 19.8 <1.4 2

5.1 3.8

Zinc, unfiltered recoverable (μg/L) 80 68 1.1 12.6 9.2

Sediment, suspended (percent finer than 0.062 mm) 80 97 54 85 88

Sediment, suspended concentration (mg/L) 80 87 1 12 6

Sediment, suspended discharge (ton/d) 80 11 0.02 1.0 0.16

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 164 1,030 16 143 92

pH, onsite (standard units) 162 9.6 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 162 783 182 461 474

Temperature, water (°C) 163 25.0 0.0 10.5 10.5

Hardness, filtered (mg/L as CaCO3

) 162 314 74.9 191 195

Calcium, filtered (mg/L) 162 90.4 22.5 55.8 57.3

Magnesium, filtered (mg/L) 162 21.4 4.52 12.7 13.0

Arsenic, filtered (μg/L) 162 60.0 6.8 23.1 23.0

Arsenic, unfiltered recoverable (μg/L) 162 94.0 10.0 26.7 26.0

Cadmium, filtered (μg/L) 162 0.31 <0.04 2

0.06 0.03

Cadmium, unfiltered recoverable (μg/L) 162 0.56 <0.1 2

0.12 0.06

Copper, filtered (μg/L) 162 40.0 1.7 7.8 5.5

Copper, unfiltered recoverable (μg/L) 162 96.8 2.4 15.6 11.1

Iron, filtered (μg/L) 162 93 <5 2

19.0 15.1

Iron, unfiltered recoverable (μg/L) 162 3,000 35.8 321 247

Lead, filtered (μg/L) 162 1.0 <0.08 2

0.13 <1.0

Lead, unfiltered recoverable (μg/L) 162 41.8 <1.00 2

2.31 1.27

Manganese, filtered (μg/L) 162 875 11.8 116 77.6

Manganese, unfiltered recoverable (μg/L) 162 899 24.0 175 138

Zinc, filtered (μg/L) 162 73 <1.0 2

7.1 3.8

Zinc, unfiltered recoverable (μg/L) 162 180 2.0 2

29.4 17.5

Sediment, suspended (percent finer than 0.062 mm) 163 98 43 82 85

Sediment, suspended concentration (mg/L) 164 229 1 10 6

Sediment, suspended discharge (ton/d) 164 279 0.07 6.2 1.5

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 42 573 41 148 100

pH, onsite (standard units) 42 8.8 7.8 8.5 8.5

Specific conductance, onsite (μS/cm) 42 278 125 218 230

Temperature, water (°C) 42 16.0 3.0 9.0 8.8

Hardness, filtered (mg/L as CaCO3

) 42 145 58.5 106 110

Calcium, filtered (mg/L) 42 42.8 18.5 31.9 33.2

Magnesium, filtered (mg/L) 42 9.34 2.96 6.48 6.72

Arsenic, filtered (μg/L) 42 3.9 1.6 2.3 2.2

Arsenic, unfiltered recoverable (μg/L) 42 5.6 1.8 2.8 2.5

Cadmium, filtered (μg/L) 42 0.05 <0.02 2

0.02 0.02

Cadmium, unfiltered recoverable (μg/L) 42 0.14 <0.02 2

0.04 0.03

Copper, filtered (μg/L) 41 6.4 <0.80 2

1.2 0.88

Copper, unfiltered recoverable (μg/L) 42 28.0 1.1 2

3.6 2.1

Iron, filtered (μg/L) 42 22.4 <6 2

7.5 5.8

Iron, unfiltered recoverable (μg/L) 42 1,000 27 133 76.0

Lead, filtered (μg/L) 42 0.11 <0.01 2

0.03 <0.12

Lead, unfiltered recoverable (μg/L) 42 3.51 0.07 0.46 0.26

Manganese, filtered (μg/L) 42 2.9 <0.1 2

1.3 1.1

Manganese, unfiltered recoverable (μg/L) 42 45.2 1.2 6.4 4.2

Zinc, filtered (μg/L) 42 5.6 <1.4 21.1 <2.8

Zinc, unfiltered recoverable (μg/L) 42 20.1 <2.0 2

3.4 1.7

Sediment, suspended (percent finer than 0.062 mm) 42 83 32 64 65

Sediment, suspended concentration (mg/L) 42 65 1 8 4

Sediment, suspended discharge (ton/d) 42 68 0.13 5.0 1.3

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 121 420 2.8 100 57

pH, onsite (standard units) 120 8.7 7.4 8.3 8.2

Specific conductance, onsite (μS/cm) 120 795 139 290 296

Temperature, water (°C) 121 20.0 0.0 8.5 8.0

Hardness, filtered (mg/L as CaCO3

) 120 415 39.8 141 144

Calcium, filtered (mg/L) 120 130 10.5 43.0 43.7

Magnesium, filtered (mg/L) 120 22.0 3.29 8.13 8.06

Arsenic, filtered (μg/L) 120 14.0 2.0 5.0 4.4

Arsenic, unfiltered recoverable (μg/L) 120 27.0 3.0 7.3 5.8

Cadmium, filtered (μg/L) 120 0.10 <0.04 2

0.04 0.02

Cadmium, unfiltered recoverable (μg/L) 120 0.41 <0.05 2

0.08 0.03

Copper, filtered (μg/L) 120 16.0 1.0 3.2 2.7

Copper, unfiltered recoverable (μg/L) 120 147 2.3 19.6 9.0

Iron, filtered (μg/L) 120 30 <5 2

11.5 10.0

Iron, unfiltered recoverable (μg/L) 120 2,110 39 315 121

Lead, filtered (μg/L) 120 1.8 <0.025 2

0.07 <0.6

Lead, unfiltered recoverable (μg/L) 120 14.0 <1.00 2

1.92 0.56

Manganese, filtered (μg/L) 120 570 18.8 113 82.9

Manganese, unfiltered recoverable (μg/L) 120 1,400 37.0 198 156

Zinc, filtered (μg/L) 119 10 <1.0 2

2.0 1.4

Zinc, unfiltered recoverable (μg/L) 120 60 <2.4 2

9.2 3.0

Sediment, suspended (percent finer than 0.062 mm) 121 88 43 70 71

Sediment, suspended concentration (mg/L) 121 127 1 18 8

Sediment, suspended discharge (ton/d) 121 87 0.05 8.7 1.1

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 205 1,380 14 226 143

pH, onsite (standard units) 192 9.2 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 193 720 182 410 417

Temperature, water (°C) 204 23.5 0.0 9.8 10.0

Hardness, filtered (mg/L as CaCO3

) 191 365 76.4 179 186

Calcium, filtered (mg/L) 191 110 23.2 53.0 55.0

Magnesium, filtered (mg/L) 191 22.0 4.44 11.3 11.7

Arsenic, filtered (μg/L) 191 53.0 4.0 15.1 14.4

Arsenic, unfiltered recoverable (μg/L) 191 78.0 3.0 19.2 17.0

Cadmium, filtered (μg/L) 191 1.0 <0.04 2

0.06 0.02

Cadmium, unfiltered recoverable (μg/L) 191 3.0 <0.1 2

0.18 0.06

Copper, filtered (μg/L) 191 50.0 1.7 7.7 5.8

Copper, unfiltered recoverable (μg/L) 190 240 4.1 27.0 15.4

Iron, filtered (μg/L) 191 110 <3 2

15.9 12.0

Iron, unfiltered recoverable (μg/L) 191 9,200 56 471 270

Lead, filtered (μg/L) 191 3.00 <0.08 2

0.15 <1.00

Lead, unfiltered recoverable (μg/L) 191 31.0 <1.00 2

3.38 1.90

Manganese, filtered (μg/L) 191 460 24.0 103 74.2

Manganese, unfiltered recoverable (μg/L) 191 1,400 47.3 216 170

Zinc, filtered (μg/L) 191 110 <1.0 2

8.6 4.0

Zinc, unfiltered recoverable (μg/L) 191 360 <10.0 2

35.5 20.0

Sediment, suspended (percent finer than 0.062 mm) 204 97 32 76 77

Sediment, suspended concentration (mg/L) 205 338 1 18 8

Sediment, suspended discharge (ton/d) 205 459 0.12 21 2.9

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 63 73 0.37 13 8.7

pH, onsite (standard units) 63 8.6 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 63 253 121 197 211

Temperature, water (°C) 63 17.0 0.0 8.0 8.0

Hardness, filtered (mg/L as CaCO3

) 63 122 50.4 94.0 98.8

Calcium, filtered (mg/L) 63 37.1 15.7 28.5 30.0

Magnesium, filtered (mg/L) 63 7.40 2.71 5.53 5.87

Arsenic, filtered (μg/L) 63 156 1.8 6.7 3.2

Arsenic, unfiltered recoverable (μg/L) 63 3,860 2.0 66.1 3.8

Cadmium, filtered (μg/L) 62 0.90 <0.02 2

0.04 0.02

Cadmium, unfiltered recoverable (μg/L) 63 147 0.01 2

2.4 0.04

Copper, filtered (μg/L) 63 90.5 0.80 3.4 1.7

Copper, unfiltered recoverable (μg/L) 63 29,100 1.3 468 4.5

Iron, filtered (μg/L) 63 27 <6 2

10.0 8.8

Iron, unfiltered recoverable (μg/L) 63 99,700 22 1,780 109

Lead, filtered (μg/L) 63 0.18 <0.02 2

0.04 0.02

Lead, unfiltered recoverable (μg/L) 63 1,290 0.08 21.3 0.45

Manganese, filtered (μg/L) 63 42.4 <0.2 2

2.0 1.2

Manganese, unfiltered recoverable (μg/L) 63 8,830 1.2 147 4.6

Zinc, filtered (μg/L) 62 30.0 <1.4 2

1.7 1.0

Zinc, unfiltered recoverable (μg/L) 62 7,780 <2 2

129 2.2

Sediment, suspended (percent finer than 0.062 mm) 63 97 22 57 58

Sediment, suspended concentration (mg/L) 63 58,900 1 948 6

Sediment, suspended discharge (ton/d) 63 1,320 <0.01 2

22 0.13

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
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 2012

Streamflow, instantaneous (ft3

/s) 80 71 1.3 24 18

pH, onsite (standard units) 80 8.7 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 80 934 540 642 629

Temperature, water (°C) 80 26.5 0.0 10.3 9.8

Hardness, filtered (mg/L as CaCO3

) 80 451 203 301 299

Calcium, filtered (mg/L) 80 122 48.5 85.2 85.6

Magnesium, filtered (mg/L) 80 35.7 17.3 21.5 20.8

Arsenic, filtered (μg/L) 80 41.8 6.0 14.3 12.6

Arsenic, unfiltered recoverable (μg/L) 80 43.0 6.0 15.1 13.8

Cadmium, filtered (μg/L) 79 0.05 <0.04 2

0.03 0.02

Cadmium, unfiltered recoverable (μg/L) 80 0.12 0.01 2

0.04 0.04

Copper, filtered (μg/L) 80 6.7 0.99 2.3 2.0

Copper, unfiltered recoverable (μg/L) 80 22.5 1.6 5.4 4.4

Iron, filtered (μg/L) 80 61.1 <6 2

13.2 10.4

Iron, unfiltered recoverable (μg/L) 80 392 14 105 80.0

Lead, filtered (μg/L) 79 0.33 <0.06 2

0.05 0.02

Lead, unfiltered recoverable (μg/L) 80 1.90 0.04 0.38 0.27

Manganese, filtered (μg/L) 80 54.0 1.9 15.5 13.9

Manganese, unfiltered recoverable (μg/L) 80 56.5 2.2 20.5 19.0

Zinc, filtered (μg/L) 79 3.8 <1.0 2

1.5 1.2

Zinc, unfiltered recoverable (μg/L) 80 10.3 <2 2

3.0 2.0

Sediment, suspended (percent finer than 0.062 mm) 80 88 18 58 60

Sediment, suspended concentration (mg/L) 80 79 2 16 15

Sediment, suspended discharge (ton/d) 80 4.2 0.01 1.0 0.60

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
88 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

12324200--Clark Fork at Deer Lodge

Period of record for water-quality data: March 1985–September 2012

Streamflow, instantaneous (ft3

/s) 257 2,000 23 311 229

pH, onsite (standard units) 205 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 240 642 228 468 495

Temperature, water (°C) 256 23.0 0.0 9.9 10.0

Hardness, filtered (mg/L as CaCO3

) 197 282 94.9 198 208

Calcium, filtered (mg/L) 197 82.0 28.2 58.5 61.0

Magnesium, filtered (mg/L) 197 18.7 5.53 12.6 13.2

Arsenic, filtered (μg/L) 207 39.0 6.0 14.5 13.5

Arsenic, unfiltered recoverable (μg/L) 206 215 4.8 23.8 17.2

Cadmium, filtered (μg/L) 206 2.0 <0.10 2

0.08 <1.0

Cadmium, unfiltered recoverable (μg/L) 206 5.0 <0.10 2

0.40 0.10

Copper, filtered (μg/L) 207 120 3.2 10.8 8.0

Copper, unfiltered recoverable (μg/L) 205 1,500 8.2 79.2 36.0

Iron, filtered (μg/L) 207 190 <3 2

15.1 9.4

Iron, unfiltered recoverable (μg/L) 207 29,000 27 1,430 514

Lead, filtered (μg/L) 207 6.00 <0.08 2

0.30 <1.00

Lead, unfiltered recoverable (μg/L) 207 200 0.33 2

10.5 4.63

Manganese, filtered (μg/L) 207 400 1.0 41.2 33.0

Manganese, unfiltered recoverable (μg/L) 207 4,600 11.9 227 130

Zinc, filtered (μg/L) 207 230 <10.0 2

11.5 8.0

Zinc, unfiltered recoverable (μg/L) 205 1,700 4 82.5 40.0

Sediment, suspended (percent finer than 0.062 mm) 248 99 31 71 72

Sediment, suspended concentration (mg/L) 257 2,250 1 68 22

Sediment, suspended discharge (ton/d) 257 8,690 0.18 143 12

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
Data 89

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 2012

Streamflow, instantaneous (ft3

/s) 31 2,310 99 565 353

pH, onsite (standard units) 31 8.8 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 31 494 249 395 432

Temperature, water (°C) 31 21.0 1.0 10.9 12.0

Hardness, filtered (mg/L as CaCO3

) 31 221 104 173 192

Calcium, filtered (mg/L) 31 64.6 31.8 50.8 56.2

Magnesium, filtered (mg/L) 31 14.8 5.93 11.1 12.0

Arsenic, filtered (μg/L) 31 36.7 9.2 15.8 16.1

Arsenic, unfiltered recoverable (μg/L) 31 46.0 11.4 23.3 19.9

Cadmium, filtered (μg/L) 31 0.23 0.04 0.08 0.08

Cadmium, unfiltered recoverable (μg/L) 31 0.84 0.06 0.31 0.23

Copper, filtered (μg/L) 31 40.6 4.0 10.7 8.8

Copper, unfiltered recoverable (μg/L) 31 222 12.4 70.4 45.6

Iron, filtered (μg/L) 31 43.2 4.5 17.1 15.0

Iron, unfiltered recoverable (μg/L) 31 3,860 111 1,060 632

Lead, filtered (μg/L) 31 0.42 0.04 0.16 0.13

Lead, unfiltered recoverable (μg/L) 31 32.3 0.90 9.4 5.74

Manganese, filtered (μg/L) 31 64.6 13.5 29.0 24.1

Manganese, unfiltered recoverable (μg/L) 31 344 39.8 135 118

Zinc, filtered (μg/L) 31 37.1 1.9 7.1 6.0

Zinc, unfiltered recoverable (μg/L) 31 181 8.0 57.8 38.4

Sediment, suspended (percent finer than 0.062 mm) 31 85 42 68 70

Sediment, suspended concentration (mg/L) 31 205 5 54 30

Sediment, suspended discharge (ton/d) 31 550 1.9 118 28

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
90 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

12324680--Clark Fork at Goldcreek

Period of record for water-quality data: March 1993–September 2012

Streamflow, instantaneous (ft3

/s) 163 4,450 87 794 529

pH, onsite (standard units) 162 8.9 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 162 510 206 366 380

Temperature, water (°C) 163 23.0 0.0 10.1 10.5

Hardness, filtered (mg/L as CaCO3

) 162 232 85.8 161 169

Calcium, filtered (mg/L) 162 68.0 25.9 47.5 49.8

Magnesium, filtered (mg/L) 162 15.0 5.15 10.3 10.6

Arsenic, filtered (μg/L) 162 22.5 5.8 10.1 10.0

Arsenic, unfiltered recoverable (μg/L) 162 75.0 7.0 14.8 12.0

Cadmium, filtered (μg/L) 162 0.2 <0.04 2

0.04 <0.10

Cadmium, unfiltered recoverable (μg/L) 162 2 <0.10 2

0.18 0.07

Copper, filtered (μg/L) 161 36.0 2.1 6.7 5.4

Copper, unfiltered recoverable (μg/L) 161 440 5.2 40.0 23.4

Iron, filtered (μg/L) 162 100 <3 2

19.3 12.0

Iron, unfiltered recoverable (μg/L) 162 12,000 27 858 426

Lead, filtered (μg/L) 160 0.6 <0.08 2

0.12 <1.00

Lead, unfiltered recoverable (μg/L) 161 73.0 0.14 2

5.57 3.00

Manganese, filtered (μg/L) 162 57.3 4.0 19.0 17.0

Manganese, unfiltered recoverable (μg/L) 162 1,100 10.5 118 86.4

Zinc, filtered (μg/L) 162 26 <1.0 2

5.5 4.0

Zinc, unfiltered recoverable (μg/L) 162 510 2 42.9 30.0

Sediment, suspended (percent finer than 0.062 mm) 163 94 43 74 78

Sediment, suspended concentration (mg/L) 163 752 1 49 21

Sediment, suspended discharge (ton/d) 163 7,960 0.55 211 33

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
Data 91

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 2012

Streamflow, instantaneous (ft3

/s) 163 5,540 149 1,090 799

pH, onsite (standard units) 162 8.7 7.8 8.3 8.3

Specific conductance, onsite (μS/cm) 162 630 189 405 417

Temperature, water (°C) 163 22.5 0.5 10.9 11.0

Hardness, filtered (mg/L as CaCO3

) 162 298 73.9 182 189

Calcium, filtered (mg/L) 162 83.0 21.0 52.3 54.3

Magnesium, filtered (mg/L) 162 22.0 5.2 12.5 12.8

Arsenic, filtered (μg/L) 162 23.9 3.2 10.6 10.0

Arsenic, unfiltered recoverable (μg/L) 162 62 8 16.1 13.0

Cadmium, filtered (μg/L) 161 0.30 <0.04 2

0.05 0.02

Cadmium, unfiltered recoverable (μg/L) 162 2.0 <0.10 2

0.23 0.08

Copper, filtered (μg/L) 159 21.0 1.0 6.5 5.0

Copper, unfiltered recoverable (μg/L) 160 360 4.6 42.5 22.7

Iron, filtered (μg/L) 162 150 <3 2

19.0 9.2

Iron, unfiltered recoverable (μg/L) 161 8,800 19.7 995 472

Lead, filtered (μg/L) 158 1.2 <0.08 2

0.17 <1.0

Lead, unfiltered recoverable (μg/L) 158 56.0 <1.00 2

7.60 3.54

Manganese, filtered (μg/L) 161 60.7 3.3 16.7 14.9

Manganese, unfiltered recoverable (μg/L) 162 880 8.0 144 94.2

Zinc, filtered (μg/L) 162 21.0 <3 2

5.9 4.3

Zinc, unfiltered recoverable (μg/L) 162 490 2.9 58.5 30.5

Sediment, suspended (percent finer than 0.062 mm) 163 92 38 73 74

Sediment, suspended concentration (mg/L) 163 530 2 62 26

Sediment, suspended discharge (ton/d) 163 4,720 1.7 323 53

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
92 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

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for water-quality data: March 1985–September 2012

Streamflow, instantaneous (ft3

/s) 260 10,600 296 1,980 1,160

pH, onsite (standard units) 206 8.8 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 235 483 139 298 312

Temperature, water (°C) 259 22.0 0.0 9.5 10.0

Hardness, filtered (mg/L as CaCO3

) 196 205 53.6 130 132

Calcium, filtered (mg/L) 196 59.0 14.9 36.7 37.2

Magnesium, filtered (mg/L) 196 14.0 3.94 9.36 9.40

Arsenic, filtered (μg/L) 205 17.0 2.7 6.1 5.6

Arsenic, unfiltered recoverable (μg/L) 205 110 3.0 9.7 7.0

Cadmium, filtered (μg/L) 204 0.10 <0.04 2

0.04 <1

Cadmium, unfiltered recoverable (μg/L) 205 4.00 <0.01 2

0.24 0.03

Copper, filtered (μg/L) 204 25.0 1.1 4.8 3.8

Copper, unfiltered recoverable (μg/L) 203 500 2.7 33.0 16.0

Iron, filtered (μg/L) 205 190 <3 2

23.7 14.0

Iron, unfiltered recoverable (μg/L) 205 19,000 32.6 980 380

Lead, filtered (μg/L) 201 7.00 <0.02 2

0.27 <1.00

Lead, unfiltered recoverable (μg/L) 201 100 <1.00 2

6.69 2.76

Manganese, filtered (μg/L) 205 37.4 <1.0 2

8.4 7.0

Manganese, unfiltered recoverable (μg/L) 205 2,000 8.9 117 60.1

Zinc, filtered (μg/L) 203 39 <3.0 2

5.7 4.0

Zinc, unfiltered recoverable (μg/L) 205 1,100 2.9 2

56.2 30.0

Sediment, suspended (percent finer than 0.062 mm) 249 98 27 73 75

Sediment, suspended concentration (mg/L) 260 1,370 2 55 18

Sediment, suspended discharge (ton/d) 260 34,700 3.0 627 61

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
Data 93

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 2012

Streamflow, instantaneous (ft3

/s) 190 13,400 344 2,800 1,360

pH, onsite (standard units) 150 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 167 294 131 208 204

Temperature, water (°C) 190 22.5 0.0 9.6 9.5

Hardness, filtered (mg/L as CaCO3

) 142 146 55.1 104 98.6

Calcium, filtered (mg/L) 142 37.7 14.0 26.5 25.4

Magnesium, filtered (mg/L) 142 13.2 4.90 9.15 8.66

Arsenic, filtered (μg/L) 149 2.0 <1.0 2

0.97 0.97

Arsenic, unfiltered recoverable (μg/L) 150 4.0 <1.0 2

1.3 1.0

Cadmium, filtered (μg/L) 148 1.00 <0.02 2

0.02 <0.10

Cadmium, unfiltered recoverable (μg/L) 150 2.00 <0.01 2

0.09 <1.00

Copper, filtered (μg/L) 146 7.0 <0.80 2

1.3 0.77

Copper, unfiltered recoverable (μg/L) 147 34.0 <0.70 2

4.5 2.0

Iron, filtered (μg/L) 149 100 <3 2

17.4 10.0

Iron, unfiltered recoverable (μg/L) 150 3,600 13.9 415 195

Lead, filtered (μg/L) 144 8.00 <0.01 2

0.31 <0.60

Lead, unfiltered recoverable (μg/L) 146 25.0 <0.04 2

2.13 0.08

Manganese, filtered (μg/L) 149 11.0 <1.0 2

2.4 2.0

Manganese, unfiltered recoverable (μg/L) 150 180 <10.0 2

28.5 18.6

Zinc, filtered (μg/L) 148 15.0 <0.60 2

2.0 <3.0

Zinc, unfiltered recoverable (μg/L) 150 60.0 <1.0 2

5.2 <10.0

Sediment, suspended (percent finer than 0.062 mm) 188 98 42 80 82

Sediment, suspended concentration (mg/L) 190 271 1 29 8

Sediment, suspended discharge (ton/d) 190 7,670 1.1 528 31

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
94 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

12340500--Clark Fork above Missoula

Period of record for water-quality data: July 1986–September 2012

Streamflow, instantaneous (ft3

/s) 225 22,900 720 4,660 2,470

pH, onsite (standard units) 183 8.8 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 203 399 142 252 261

Temperature, water (°C) 223 22.0 0.0 9.6 9.5

Hardness, filtered (mg/L as CaCO3

) 183 168 60.5 116 118

Calcium, filtered (mg/L) 183 46.0 14.0 31.4 31.6

Magnesium, filtered (mg/L) 183 13.4 5.28 9.20 9.20

Arsenic, filtered (μg/L) 183 9.0 1.0 3.5 3.2

Arsenic, unfiltered recoverable (μg/L) 183 69.0 1.0 5.4 4.0

Cadmium, filtered (μg/L) 182 0.20 <0.02 2

0.03 <0.10

Cadmium, unfiltered recoverable (μg/L) 183 5.0 <0.01 2

0.16 <1.0

Copper, filtered (μg/L) 182 12.6 0.7 2.8 2.2

Copper, unfiltered recoverable (μg/L) 181 400 1.9 19.5 8.5

Iron, filtered (μg/L) 183 200 <3 2

21.9 15.1

Iron, unfiltered recoverable (μg/L) 183 13,000 42.1 633 260

Lead, filtered (μg/L) 176 1.20 <0.02 2

0.14 <1.00

Lead, unfiltered recoverable (μg/L) 178 78.0 <1.00 2

3.45 1.57

Manganese, filtered (μg/L) 183 230 5.2 15.8 13.6

Manganese, unfiltered recoverable (μg/L) 183 1,100 10.0 65.4 40.0

Zinc, filtered (μg/L) 182 16.0 <1.0 2

3.5 2.3

Zinc, unfiltered recoverable (μg/L) 183 1,100 <3.0 2

33.2 15

Sediment, suspended (percent finer than 0.062 mm) 221 99 14 82 88

Sediment, suspended concentration (mg/L) 226 950 2 44 12

Sediment, suspended discharge (ton/d) 225 21,900 5.8 1,120 97

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 when the mean indicates that a censored value was used in the mean calculation, are a result of changes in the 

laboratory reporting level during the period of record.

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2012.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; <, less than laboratory reporting level1; mm, millimeter; ton/d, tons per day]
Data 95

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.

[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. <, 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: 1992–2012

Arsenic 10 186 34 111 121

Cadmium 21 43.9 5.9 27.5 27.1

Chromium 19 50.7 16.8 30.5 27.6

Copper 21 9,020 522 3,860 4,220

Iron 21 45,300 28,200 35,400 34,300

Lead 21 1,030 121 593 563

Manganese 21 9,220 1,160 3,190 2,590

Nickel 20 21.4 12.0 14.9 14.6

Silver 12 20.0 8.3 15.5 15.8

Zinc 21 13,400 1,490 6,720 6,880

12323750--Silver Bow Creek at Warm Springs

Period of record for bed-sediment data: 1992–2012

Arsenic 10 177 67 110 100

Cadmium 21 12.2 4.2 7.1 6.6

Chromium 19 46.8 <15.7 1

24.8 123.6

Copper 21 769 169 347 296

Iron 21 32,500 15,400 23,600 22,100

Lead 21 100 49 71 70

Manganese 21 17,700 1,470 7,510 7,230

Nickel 20 20.0 9.2 14.9 14.7

Silver 12 4.4 0.3 1

1.9 11.8

Zinc 21 2,220 554 915 726

12323770--Warm Springs Creek at Warm Springs

Period of record for bed-sediment data: 1995, 1997, 1999, 2002, 2005, 2008, 2011

Arsenic 3 66 34 51 52

Cadmium 7 5.8 1.2 3.2 3.3

Chromium 7 39.3 27.5 32.1 31.5

Copper 7 1,060 496 849 881

Iron 7 26,600 16,800 21,400 21,900

Lead 7 86 42 75 82

Manganese 7 12,100 555 6,890 7,780

Nickel 7 25.5 14.5 19.4 19.2

Silver 4 5.1 3.1 3.8 3.5

Zinc 7 453 237 381 396
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, 1991–2012

Arsenic 10 119 73 99 97

Cadmium 23 20.1 3.8 8.1 7.1

Chromium 19 44.6 19.1 30.2 29.5

Copper 23 2,300 838 1,190 1,110

Iron 23 39,800 22,600 27,700 27,000

Lead 23 235 92 131 128

Manganese 23 17,300 1,530 8,910 8,540

Nickel 20 23.2 13.9 18.8 18.6

Silver 14 7.3 <3.2 1

4.4 14.5

Zinc 23 3,560 721 1,390 1,130

461415112450801--Clark Fork below Lost Creek, near Galen

Period of record for bed-sediment data: 1996–2012

Arsenic 10 204 90 116 108

Cadmium 17 10.0 4.8 6.9 6.5

Chromium 16 42.4 20.5 30.9 31.9

Copper 17 2,050 1,150 1,490 1,440

Iron 17 32,800 24,400 29,100 29,600

Lead 17 218 123 163 167

Manganese 17 9,820 1,430 5,390 5,570

Nickel 17 19.9 11.7 16.1 16.4

Silver 8 7.8 4.2 6.5 6.7

Zinc 17 1,680 930 1,280 1,280

461559112443301--Clark Fork at county bridge, near Racetrack

Period of record for bed-sediment data: 1996–2012

Arsenic 10 132 56 91 90

Cadmium 17 8.7 5.0 6.5 6.3

Chromium 16 45.2 19.0 30.1 29.6

Copper 17 1,810 933 1,290 1,310

Iron 17 31,700 21,200 27,400 28,100

Lead 17 186 103 144 143

Manganese 17 6,310 1,600 3,270 3,060

Nickel 17 18.4 10.3 14.5 14.8

Silver 8 6.1 <3.3 1

5.0 15.4

Zinc 17 1,550 999 1,190 1,170

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. <, 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: 1996–2012

Arsenic 10 100 58 78 76

Cadmium 17 10.3 4.1 6.2 5.7

Chromium 16 39.2 16.0 28.4 27.6

Copper 17 1,580 721 1,100 1,090

Iron 17 33,700 20,600 27,000 27,100

Lead 17 155 92 129 132

Manganese 17 8,370 1,200 3,800 3,080

Nickel 17 16.9 8.7 12.9 12.7

Silver 8 6.2 2.7 4.9 5.0

Zinc 17 1,570 900 1,120 1,080

12324200--Clark Fork at Deer Lodge

Period of record for bed-sediment data: 1986–87, 1990–2012

Arsenic 10 102 49 73 70

Cadmium 25 10.0 3.5 6.0 5.1

Chromium 19 50.7 19.5 32.7 32.5

Copper 25 4,180 683 1,250 1,070

Iron 25 35,300 21,100 27,300 26,100

Lead 25 242 103 144 142

Manganese 25 6,020 1,070 2,610 2,440

Nickel 20 21.1 11.5 14.8 13.9

Silver 16 7.9 2.4 4.7 4.5

Zinc 25 1,730 844 1,180 1,140

12324400--Clark Fork above Little Blackfoot River, near Garrison

Period of record for bed-sediment data: 2009-2012

Arsenic 4 91 50 76 82

Cadmium 4 5.5 4.2 4.7 4.6

Chromium 4 52.8 39.0 46.0 46.0

Copper 4 1,290 855 1,170 1,270

Iron 4 32,400 23,500 28,100 28,200

Lead 4 145 102 133 142

Manganese 4 3,560 1,150 2,300 2,260

Nickel 4 17.2 12.5 14.6 14.4

Silver 0 -- -- -- --

Zinc 4 1,240 977 1,100 1,100

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. <, 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: 1992–2012

Arsenic 10 62 23 42 37

Cadmium 21 8.1 2.5 4.5 4.0

Chromium 19 55.3 21.3 33.8 31.9

Copper 21 1,080 338 683 729

Iron 21 32,100 15,500 23,700 24,300

Lead 21 152 52 95 93

Manganese 21 2,610 977 1,810 1,840

Nickel 20 18.6 9.0 14.0 14.3

Silver 12 4.8 2.3 3.3 3.2

Zinc 21 1,320 531 910 904

12331800--Clark Fork near Drummond

Period of record for bed-sediment data: 1986–87, 1991–2012

Arsenic 10 66 19 38 33

Cadmium 24 7.7 1.7 4.2 4.2

Chromium 19 41.9 16.9 29.1 31.3

Copper 24 747 220 470 464

Iron 24 43,700 15,900 24,500 23,200

Lead 24 135 29 86 84

Manganese 24 4,820 832 2,050 1,890

Nickel 20 16.8 5.9 13.0 13.6

Silver 15 4.7 <3.2 1

3.0 12.9

Zinc 24 1,230 478 927 948

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for bed-sediment data: 1986, 1991–2012

Arsenic 10 43 19 28 27

Cadmium 23 7.3 1.2 3.4 3.4

Chromium 19 42.5 15.3 27.4 29.0

Copper 23 635 211 351 323

Iron 23 25,900 12,600 19,400 17,300

Lead 23 115 41 67 65

Manganese 23 2,340 671 1,290 1,240

Nickel 20 19.1 6.9 12.4 11.6

Silver 14 3.9 <1.9 1

2.1 11.9

Zinc 23 1,160 489 794 786

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. <, 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, 2006–12

Arsenic 8 6 <0.2 1

3 13

Cadmium 19 2.0 0.04 1

0.5 10.3

Chromium 15 35.2 15.1 23.1 23.7

Copper 19 27 11 20 21

Iron 19 23,000 12,400 17,600 18,100

Lead 19 20 <13 1

13 112

Manganese 19 746 298 539 544

Nickel 16 14.3 6.0 11.2 11.7

Silver 12 <1.9 <0.3 1

0.5 1<0.6

Zinc 19 82 35 61 61

12340500--Clark Fork above Missoula

Period of record for bed-sediment data: 1997–2012

Arsenic 10 54 12 32 30

Cadmium 16 5.8 1.0 3.0 2.8

Chromium 15 40.7 19.0 27.9 29.5

Copper 16 551 129 354 340

Iron 16 27,000 17,900 20,900 20,500

Lead 16 78 25 54 55

Manganese 16 2,250 477 1,070 1,000

Nickel 16 15.8 7.6 12.7 12.8

Silver 7 2.9 0.8 1

2.0 12.1

Zinc 16 1,090 346 716 706

1

Value determined by substituting one-half of the minimum reporting level for censored (<) values when both uncensored and censored values were used to 

determine the mean and (or) median.

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. <, 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 2012.

[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. spp., one or more similar species; <, 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, 1997–2012

Brachycentrus spp.

Arsenic 0 -- -- -- --

Cadmium 5 12.5 5.8 10.1 11.6

Chromium 5 5.9 0.7 2.1 0.9

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 <0.1 1

1.3 11.6

Zinc 5 995 629 803 815

Hydropsyche cockerelli

Arsenic 17 33.3 5.4 14.0 12.3

Cadmium 23 9.7 3.1 5.5 5.0

Chromium 23 25.5 1.0 4.3 3.1

Copper 23 1,090 115 386 373

Iron 23 6,150 689 2,660 2,330

Lead 23 74.3 16.6 37.3 38.5

Manganese 23 3,030 180 997 847

Nickel 23 3.6 0.7 2.5 2.5

Zinc 23 1,590 540 873 801

Hydropsyche spp.

Arsenic 13 23.1 6.1 12.6 10.7

Cadmium 18 11.0 2.0 5.5 5.1

Chromium 18 4.7 0.6 2.5 2.9

Copper 18 930 80.7 443 385

Iron 18 3,250 1,050 2,180 2,170

Lead 18 237 19.3 46.5 36.5

Manganese 18 1,340 612 1,000 1,040

Nickel 18 2.7 0.7 2.0 2.3

Zinc 18 1,290 388 879 893

Hydropsyche tana

Arsenic 0 -- -- -- --

Cadmium 6 9.2 4.8 6.8 6.9

Chromium 6 11.5 0.9 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 0.7 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: 1992–2012

Claassenia sabulosa

Arsenic 1 -- -- 1.8 --

Cadmium 1 -- -- 1.1 --

Chromium 1 -- -- 2.8 --

Copper 1 -- -- 47.6 --

Iron 1 -- -- 151 --

Lead 1 -- -- 0.6 --

Manganese 1 -- -- 98.1 --

Nickel 1 -- -- 0.5 --

Zinc 1 -- -- 400 --

Hydropsyche cockerelli

Arsenic 17 23.6 7.9 12.8 10.7

Cadmium 43 2.1 0.2 0.6 0.5

Chromium 43 4.3 0.4 1.1 0.8

Copper 43 97.0 16.7 36.9 31.1

Iron 43 1,650 351 823 762

Lead 43 6.0 0.3 3.2 2.9

Manganese 43 3,890 491 1,250 971

Nickel 43 1.8 0.3 0.9 0.8

Zinc 43 276 115 176 169

Hydropsyche occidentalis

Arsenic 8 31.0 10.5 19.1 16.8

Cadmium 23 1.6 0.2 .6 0.4

Chromium 23 6.8 0.3 1.7 1.0

Copper 23 48.9 11.0 33.4 32.8

Iron 23 2,960 372 1,230 998

Lead 23 8.2 <1.7 14.1 13.8

Manganese 23 6,940 996 2,420 1,940

Nickel 23 2.7 0.7 1.5 1.4

Zinc 23 220 140 180 181

Hydropsyche spp.

Arsenic 1 -- -- 14.0 --

Cadmium 5 2.3 0.4 1.0 0.6

Chromium 5 2.5 0.5 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 <0.4 1

1.0 10.8

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 2012.—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. spp., one or more similar species; <, 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, 2011

Arctopsyche grandis

Arsenic 4 9.8 7.9 9.2 9.5

Cadmium 8 3.6 0.4 2.5 2.7

Chromium 8 4.2 0.8 2.3 2.4

Copper 8 133 53.2 102 100

Iron 8 1,350 684 970 969

Lead 8 7.2 3.0 1

5.2 15.2

Manganese 8 3,560 738 2,320 2,380

Nickel 8 3.5 1.1 1

2.3 12.3

Zinc 8 267 181 205 196

Hesperoperla spp.

Arsenic 1 -- -- 1.2 --

Cadmium 1 -- -- 1.0 --

Chromium 1 -- -- 2.0 --

Copper 1 -- -- 64.9 --

Iron 1 -- -- 456 --

Lead 1 -- -- 1.9 --

Manganese 1 -- -- 202 --

Nickel 1 -- -- 0.6 --

Zinc 1 -- -- 573 --

Hydropsyche occidentalis

Arsenic 3 13.6 12.7 13.2 13.3

Cadmium 5 1.3 0.7 1.0 1.2

Chromium 5 8.6 0.3 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 0.8 --

Chromium 2 1.6 1.4 1.5 --

Copper 2 95.9 94.8 95.4 --

Iron 2 1,220 1,150 1,180 --

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 2012.—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. spp., one or more similar species; <, 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, 1991–2012

Claassenia sabulosa

Arsenic 1 -- -- 2.0 --

Cadmium 1 -- -- 0.2 --

Chromium 1 -- -- 1.5 --

Copper 1 -- -- 54.7 --

Iron 1 -- -- 242 --

Lead 1 -- -- 1.0 --

Manganese 1 -- -- 323 --

Nickel 1 -- -- 0.5 --

Zinc 1 -- -- 237 --

Hydropsyche cockerelli

Arsenic 9 16.9 13.2 14.4 14.0

Cadmium 34 2.7 0.7 1.5 1.5

Chromium 34 9.6 0.8 2.2 1.7

Copper 34 181 48.7 105 104

Iron 34 2,660 816 1,470 1,430

Lead 34 17.1 1.2 8.3 7.9

Manganese 34 3,620 1,070 2,290 2,250

Nickel 34 6.5 0.9 1.8 1.6

Zinc 34 363 136 214 208

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 5 3.2 2.4 2.5 2.4

Chromium 5 4.6 1.8 2.6 2.2

Copper 5 185 156 173 175

Iron 5 1,890 1,360 1,510 1,430

Lead 5 12.4 7.1 8.5 7.9

Manganese 5 3,960 2,360 3,500 3,860

Nickel 5 3.6 1.9 2.3 2.1

Zinc 5 349 292 309 303

Hydropsyche occidentalis

Arsenic 18 17.0 9.1 13.9 14.3

Cadmium 50 1.6 0.6 1.1 1.2

Chromium 50 6.6 0.4 2.1 1.8

Copper 50 151 49.2 93.4 89.8

Iron 50 2,590 642 1,490 1,400

Lead 50 13.5 1.6 8.0 8.0

Manganese 50 6,170 653 2,480 2,030

Nickel 50 3.5 0.8 1.8 1.6

Zinc 50 286 168 204 200

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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, 1991–2012

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 0.7 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 0.9 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 2012.—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. spp., one or more similar species; <, 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: 1996–2012

Claassenia sabulosa

Arsenic 1 -- -- 1.5 --

Cadmium 2 0.4 0.3 0.4 --

Chromium 2 1.9 0.4 1.2 --

Copper 2 70.1 67.1 68.6 --

Iron 2 209 189 199 --

Lead 2 1.2 0.7 1.0 --

Manganese 2 238 90.4 164 --

Nickel 2 0.2 <0.2 1

0.2 --

Zinc 2 245 208 226 --

Hydropsyche cockerelli

Arsenic 14 27.8 8.8 15.2 11.8

Cadmium 22 2.8 1.1 1.8 1.8

Chromium 22 4.0 0.8 2.2 2.2

Copper 22 338 48.8 145 119

Iron 22 4,080 691 1,700 1,240

Lead 22 28.6 4.5 12.9 10.2

Manganese 22 3,160 1,230 1,830 1,720

Nickel 22 2.8 0.9 1.5 1.3

Zinc 22 339 151 234 231

Hydropsyche occidentalis

Arsenic 9 20.9 12.7 15.8 15.0

Cadmium 23 1.9 0.9 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 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 0.9 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 0.9 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 2012.—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. spp., one or more similar species; <, 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

461415112450801--Clark Fork below Lost Creek, near Galen—Continued

Period of record for biological data: 1996–2012

Rhyacophila spp.

Arsenic 2 5.2 3.5 4.4 --

Cadmium 2 4.3 3.9 4.1 --

Chromium 2 1.1 1.0 1.0 --

Copper 2 93.1 73.7 83.4 --

Iron 2 346 324 335 --

Lead 2 5.9 4.8 5.4 --

Manganese 2 320 192 256 --

Nickel 2 0.3 0.3 0.3 --

Zinc 2 411 301 356 --

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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

461559112443301--Clark Fork at county bridge, near Racetrack

Period of record for biological data: 1996–2012

Arctopsyche grandis

Arsenic 1 -- -- 13.0 --

Cadmium 1 -- -- 1.2 --

Chromium 1 -- -- 1.9 --

Copper 1 -- -- 101 --

Iron 1 -- -- 1,410 --

Lead 1 -- -- 13.2 --

Manganese 1 -- -- 2,480 --

Nickel 1 -- -- 1.4 --

Zinc 1 -- -- 260 --

Claassenia sabulosa

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.4 --

Chromium 1 -- -- 0.3 --

Copper 1 -- -- 40.3 --

Iron 1 -- -- 113 --

Lead 1 -- -- 0.8 --

Manganese 1 -- -- 172 --

Nickel 1 -- -- 0.2 --

Zinc 1 -- -- 213 --

Hydropsyche cockerelli

Arsenic 12 20.2 11.1 14.7 14.9

Cadmium 23 2.1 0.8 1.5 1.5

Chromium 23 3.0 0.6 1.8 1.4

Copper 23 198 50.0 108 99.5

Iron 23 3,330 657 1,370 1020

Lead 23 18.7 3.7 9.6 7.7

Manganese 23 2,360 646 1,630 1,830

Nickel 23 2.0 0.7 1.2 1.1

Zinc 23 302 139 200 187

Hydropsyche occidentalis

Arsenic 14 16.8 9.2 13.1 12.8

Cadmium 27 2.3 0.7 1.4 1.4

Chromium 27 3.7 1.1 2.2 2.0

Copper 27 164 59.5 117 124

Iron 27 3,690 1,030 1,680 1,590

Lead 27 15.7 4.3 10.9 10.7

Manganese 27 3,770 660 1,970 1,810

Nickel 27 2.3 1.1 1.5 1.3

Zinc 27 361 181 232 224

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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

461559112443301--Clark Fork at county bridge, near Racetrack—Continued

Period of record for biological data: 1996–2012

Hydropsyche spp.

Arsenic 6 12.8 5.7 9.6 9.8

Cadmium 8 2.4 1.0 1.6 1.5

Chromium 8 3.9 0.7 1.6 1.0

Copper 8 144 68.1 97 84.0

Iron 8 1,880 787 1,220 1,170

Lead 8 15.0 5.7 8.8 7.1

Manganese 8 2,370 886 1,320 1,150

Nickel 8 2.0 0.7 1.3 1.2

Zinc 8 229 151 193 194

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for biological data: 1996–2012

Arctopsyche grandis

Arsenic 2 17.5 11.8 14.6 --

Cadmium 3 7.1 1.7 4.1 3.6

Chromium 3 12.9 <2.4 1

17.4 118.1

Copper 3 196 30.8 126 151

Iron 3 2,800 340 1,550 1,500

Lead 3 17.6 <14.5 1

12.4 112.4

Manganese 3 2,060 510 1,260 1,190

Nickel 3 2.5 1.0 1.9 2.3

Zinc 3 489 86.8 319 380

Claassenia sabulosa

Arsenic 2 3.1 1.6 2.4 --

Cadmium 2 2.4 0.9 1.6 --

Chromium 2 1.7 0.2 0.9 --

Copper 2 73.4 58.6 66.0 --

Iron 2 297 173 235 --

Lead 2 1.9 0.9 1.4 --

Manganese 2 372 115 244 --

Nickel 2 0.4 0.2 0.3 --

Zinc 2 330 168 249 --

Hydropsyche cockerelli

Arsenic 10 18.8 8.0 13.0 11.8

Cadmium 19 2.0 0.7 1.3 1.3

Chromium 19 4.0 0.5 1.6 1.3

Copper 19 247 60.7 115 92.0

Iron 19 3,010 552 1,230 971

Lead 19 21.9 3.5 9.0 7.9

Manganese 19 2,650 487 1,380 1,230

Nickel 19 2.5 0.5 1.2 1.0

Zinc 19 285 162 212 192

Hydropsyche occidentalis

Arsenic 17 24.0 9.8 15.0 15.8

Cadmium 34 2.4 0.7 1.3 1.3

Chromium 34 6.2 0.8 2.2 1.9

Copper 34 345 74.9 129 111

Iron 34 3,390 940 1,760 1,550

Lead 34 21.8 6.1 12.7 11.6

Manganese 34 4,460 826 2,340 2,220

Nickel 34 2.4 1.0 1.6 1.5

Zinc 34 386 197 262 241

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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

461903112440701--Clark Fork at Dempsey Creek diversion, near Racetrack—Continued

Period of record for biological data: 1996–2012

Hydropsyche spp.

Arsenic 2 6.5 6.4 6.4 --

Cadmium 4 1.7 0.9 1.3 1.3

Chromium 4 2.1 0.8 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 0.6 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 2012.—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. spp., one or more similar species; <, 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

12324200--Clark Fork at Deer Lodge

Period of record for biological data: 1986–87, 1990–2012

Arctopsyche grandis

Arsenic 5 13.3 5.8 9.7 10.1

Cadmium 7 4.7 <4.2 1

3.5 13.4

Chromium 7 4.7 1.0 1

2.4 12.0

Copper 7 183 34.9 101 90.5

Iron 7 2,320 537 1,190 1,090

Lead 7 17.4 3.8 1

10.7 111.2

Manganese 7 1,620 380 1,050 1,010

Nickel 7 1.9 <1.3 1

1.3 11.2

Zinc 7 370 140 269 279

Hydropsyche cockerelli

Arsenic 7 17.1 5.8 9.4 8.3

Cadmium 30 3.5 0.6 1.5 1.3

Chromium 30 4.3 0.4 1.7 1.7

Copper 30 241 54.7 103 100

Iron 30 3,340 490 1,190 1,050

Lead 30 24.9 3.8 10.0 9.1

Manganese 30 1,570 396 899 859

Nickel 30 2.4 0.3 1.2 1.0

Zinc 30 391 132 195 188

Hydropsyche occidentalis

Arsenic 19 21.1 6.6 11.5 10.6

Cadmium 56 3.4 0.6 1.4 1.3

Chromium 56 3.7 0.6 2.0 1.9

Copper 56 222 49.4 124 119

Iron 56 3,240 558 1,510 1,490

Lead 56 20.1 3.5 11.9 11.7

Manganese 56 2,850 649 1,610 1,660

Nickel 56 12.9 1.0 1.7 1.4

Zinc 56 346 166 245 237

Hydropsyche spp.

Arsenic 1 -- -- 6.0 --

Cadmium 4 2.6 1.6 2.2 2.3

Chromium 1 -- -- 0.8 --

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 -- -- 0.9 --

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 2012.—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. spp., one or more similar species; <, 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

12324400--Clark Fork above Little Blackfoot River, near Garrison

Period of record for biological data: 2009–12

Arctopsyche grandis

Arsenic 6 16.6 5.5 8.5 7.4

Cadmium 6 4.9 3.2 3.9 3.8

Chromium 6 4.6 <2.2 1

2.3 11.9

Copper 6 209 65.7 126 128

Iron 6 2,580 694 1,310 1,200

Lead 6 18.0 6.6 10.8 10.1

Manganese 6 1,940 940 1,420 1,370

Nickel 6 2.2 0.7 1.4 1.6

Zinc 6 378 253 300 291

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 8 14.7 7.8 10.5 9.9

Cadmium 8 2.5 1.3 2.1 2.2

Chromium 8 3.6 0.7 2.1 1.9

Copper 8 182 98.2 138 143

Iron 8 2,390 1,190 1,710 1,600

Lead 8 17.9 11.1 14.0 12.9

Manganese 8 2,100 975 1,490 1,410

Nickel 8 1.9 1.0 1.5 1.5

Zinc 8 299 223 256 253

Hydropsyche spp.

Arsenic 1 -- -- 13.6 --

Cadmium 1 -- -- 1.7 --

Chromium 1 -- -- 4.3 --

Copper 1 -- -- 187 --

Iron 1 -- -- 2,570 --

Lead 1 -- -- 18.5 --

Manganese 1 -- -- 919 --

Nickel 1 -- -- 1.8 --

Zinc 1 -- -- 296 --

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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

12324680--Clark Fork at Goldcreek

Period of record for biological data: 1992–2012

Arctopsyche grandis

Arsenic 34 17.0 1.8 5.3 5.1

Cadmium 63 6.6 0.6 2.0 1.8

Chromium 63 5.3 0.1 1.4 1.1

Copper 63 232 19.9 52.8 39.9

Iron 63 3,070 195 788 610

Lead 63 16.9 1.0 4.2 3.5

Manganese 63 1,580 436 883 871

Nickel 63 3.1 0.2 0.8 0.7

Zinc 63 326 146 206 189

Claassenia sabulosa

Arsenic 25 2.5 0.4 1.4 1.5

Cadmium 45 3.5 0.1 1.0 0.7

Chromium 45 1.6 0.2 0.6 0.5

Copper 45 84.9 33.0 59.4 58.3

Iron 45 640 63.0 200 171

Lead 45 2.8 0.4 1.0 0.8

Manganese 45 320 50.6 152 142

Nickel 45 0.7 0.1 0.3 0.3

Zinc 45 364 166 264 258

Hydropsyche cockerelli

Arsenic 17 9.8 4.1 6.0 5.7

Cadmium 36 4.2 0.5 1.5 1.3

Chromium 36 4.7 0.5 2.0 1.9

Copper 36 188 17.1 73.6 58.5

Iron 36 3,250 522 1,160 942

Lead 36 17.6 2.4 6.7 5.3

Manganese 36 1,710 538 1,000 981

Nickel 36 3.5 0.3 1.2 1.1

Zinc 36 359 106 192 185

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 0.9 1.2 1.2

Zinc 4 190 137 167 170

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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

12324680--Clark Fork at Goldcreek—Continued

Period of record for biological data: 1992–2012

Hydropsyche occidentalis

Arsenic 14 11.5 4.4 6.7 5.9

Cadmium 29 2.3 0.4 1.3 1.3

Chromium 29 3.9 0.4 1.8 1.7

Copper 29 170 26.4 72.8 62.4

Iron 29 2,720 466 1,230 1,120

Lead 29 15.7 2.9 7.4 6.0

Manganese 29 2,210 530 1,200 1,140

Nickel 29 2.5 0.8 1.2 1.0

Zinc 29 276 97.0 200 203

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 1,160 --

Nickel 2 0.8 0.8 0.8 --

Zinc 2 210 196 203 --

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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

12331800--Clark Fork near Drummond

Period of record for biological data: 1986, 1991–2012

Arctopsyche grandis

Arsenic 26 8.2 2.3 4.3 4.0

Cadmium 58 3.8 0.4 1.5 1.2

Chromium 58 4.2 0.2 1.1 1.0

Copper 58 103 16.9 35.5 30.0

Iron 58 1,720 193 630 529

Lead 58 11.8 1.6 4.8 4.0

Manganese 58 2,010 456 838 747

Nickel 58 1.9 0.2 0.7 0.6

Zinc 58 314 140 201 190

Claassenia sabulosa

Arsenic 21 1.9 0.6 1.2 1.2

Cadmium 57 2.8 0.1 1.1 1.0

Chromium 57 3.3 0.2 0.7 0.6

Copper 57 165 18.0 64.9 61.3

Iron 57 449 45.4 175 146

Lead 57 2.9 0.2 1.0 0.8

Manganese 57 748 33.1 183 147

Nickel 57 1.1 0.1 1

0.3 10.2

Zinc 57 567 103 276 265

Hydropsyche cockerelli

Arsenic 15 7.2 3.9 5.6 5.7

Cadmium 44 4.5 0.3 1.2 .9

Chromium 44 3.5 0.4 1.6 1.4

Copper 44 156 30.0 59.0 51.7

Iron 44 2,500 506 1,170 976

Lead 44 15.0 4.7 8.4 7.5

Manganese 44 1,680 549 994 926

Nickel 44 2.0 0.5 1.1 1.1

Zinc 44 322 134 195 187

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 6 1.3 1.1 1.2 1.2

Chromium 6 2.8 1.9 2.3 2.2

Copper 6 57.4 50.2 55.2 55.8

Iron 6 1,730 1,370 1,570 1,600

Lead 6 10.8 7.0 8.9 9.0

Manganese 6 1,940 1,260 1,610 1,610

Nickel 6 1.7 1.3 1.5 1.5

Zinc 6 250 227 239 240

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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

12331800--Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991–2012

Hydropsyche occidentalis

Arsenic 16 7.7 4.3 5.6 5.4

Cadmium 32 2.0 0.4 1.0 1.0

Chromium 32 8.1 0.4 2.2 2.1

Copper 32 118 13.3 58.0 55.5

Iron 32 2,060 424 1,230 1,190

Lead 32 14.0 3.0 8.6 8.7

Manganese 32 2,920 477 1,400 1,210

Nickel 32 2.4 0.5 1.3 1.2

Zinc 32 293 153 219 221

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 2.6 --

Chromium 0 -- -- -- --

Copper 1 -- -- 85.0 --

Iron 1 -- -- 913 --

Lead 1 -- -- 9.1 --

Manganese 0 -- -- -- --

Nickel 0 -- -- -- --

Zinc 1 -- -- 260 --

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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 2012.—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. spp., one or more similar species; <, less than minimum 

reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

12334550--Clark Fork at Turah Bridge, near Bonner

Period of record for biological data: 1986, 1991–2012

Arctopsyche grandis

Arsenic 29 7.2 3.1 4.5 4.5

Cadmium 71 2.7 0.4 1.2 1.1

Chromium 71 4.1 0.5 1.6 1.5

Copper 71 125 17.6 38.0 32.0

Iron 71 2,870 372 929 790

Lead 71 13.2 1.6 4.4 3.7

Manganese 71 902 324 648 660

Nickel 71 2.6 0.4 1.1 0.9

Zinc 71 282 111 202 198

Claassenia sabulosa

Arsenic 21 1.9 0.2 1.1 1.0

Cadmium 47 2.5 0.1 1.0 0.8

Chromium 47 2.0 0.2 0.7 0.6

Copper 47 95.1 37.5 59.6 56.8

Iron 47 378 58.6 134 114

Lead 47 1.6 0.2 0.7 0.6

Manganese 47 229 37.2 103 90.2

Nickel 47 0.6 0.04 0.2 0.2

Zinc 47 342 144 230 235

Hydropsyche cockerelli

Arsenic 21 9.8 3.7 4.9 4.8

Cadmium 49 2.2 0.3 0.9 0.7

Chromium 49 14.2 0.2 2.2 1.6

Copper 49 126 26.4 49.8 44.2

Iron 49 3,180 566 1,240 1,140

Lead 49 19.7 2.2 5.6 5.1

Manganese 49 848 426 643 658

Nickel 49 2.7 0.6 1.3 1.2

Zinc 49 332 119 190 194

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 --
118 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 2012.—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. spp., one or more similar species; <, less than minimum 

reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]

Constituent Number of 

composite samples Maximum Minimum Mean Median

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

Period of record for biological data: 1986, 1991–2012

Hydropsyche occidentalis

Arsenic 18 7.3 2.9 4.6 4.2

Cadmium 38 1.8 0.3 1.0 0.9

Chromium 38 5.0 0.6 1.9 1.7

Copper 38 102 27.4 49.5 45.1

Iron 38 2,590 472 1,260 1,150

Lead 38 14.2 2.8 6.4 5.6

Manganese 38 1,600 454 846 791

Nickel 38 3.2 0.6 1.2 1.2

Zinc 38 416 145 212 220

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 --
Data 119

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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, 2006–12

Arctopsyche grandis

Arsenic 8 4.6 1.6 2.7 2.2

Cadmium 18 0.5 0.1 0.3 0.2

Chromium 13 6.9 0.5 2.2 1.3

Copper 18 18.0 9.9 13.0 12.4

Iron 18 1,880 108 720 757

Lead 18 2.3 0.5 1.1 0.9

Manganese 13 633 286 471 476

Nickel 13 3.7 0.7 1.4 1.2

Zinc 18 156 106 139 138

Claassenia sabulosa

Arsenic 11 3.0 0.1 1.0 0.7

Cadmium 22 0.2 0.1 0.1 0.2

Chromium 17 5.2 0.3 1.0 0.7

Copper 22 88.5 19.0 43.8 44.0

Iron 22 317 46.2 147 140

Lead 22 0.8 0.1 0.3 0.2

Manganese 17 133 26.3 80.3 73.4

Nickel 17 1.1 0.1 0.3 0.3

Zinc 22 399 117 230 207

Hydropsyche cockerelli

Arsenic 6 4.2 2.1 3.0 3.1

Cadmium 6 0.6 <.1 1

0.4 10.3

Chromium 6 3.8 1.6 3.0 3.0

Copper 6 16.2 5.6 13.8 15.2

Iron 6 2,390 1,120 1,780 1,800

Lead 6 2.3 1.5 2.0 2.0

Manganese 6 814 428 613 626

Nickel 6 4.6 1.4 2.4 1.9

Zinc 6 165 140 149 145

Hydropsyche occidentalis

Arsenic 12 3.8 1.2 2.2 2.0

Cadmium 24 0.5 0.1 0.2 0.2

Chromium 24 5.8 0.8 2.1 1.9

Copper 24 20.6 12.0 15.6 15.3

Iron 24 2,090 927 1,480 1,490

Lead 24 2.0 0.8 1.4 1.5

Manganese 24 798 414 522 460

Nickel 24 4.9 0.9 1.6 1.4

Zinc 24 163 116 140 143
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

12340000--Blackfoot River near Bonner—Continued

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006–12

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 2012.—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. spp., one or more similar species; <, less than minimum 

reporting level; --, indicates either too few samples (less than three) or insufficient data to compute statistic, or element not analyzed]
Data 121

Constituent Number of 

composite samples Maximum Minimum Mean Median

12340500--Clark Fork above Missoula

Period of record for biological data: 1997–2012

Arctopsyche grandis

Arsenic 26 7.2 1.2 3.8 3.8

Cadmium 45 2.3 0.1 1.0 0.8

Chromium 45 4.2 0.4 1.7 1.6

Copper 45 81.2 13.7 39.7 35.8

Iron 45 2,340 302 1,050 908

Lead 45 8.8 1.1 4.2 4.1

Manganese 45 1,410 476 898 872

Nickel 45 2.1 0.3 1.2 1.0

Zinc 45 272 133 200 198

Claassenia sabulosa

Arsenic 18 1.9 0.1 1.2 1.2

Cadmium 27 2.0 0.2 0.8 0.6

Chromium 27 1.4 0.1 0.7 0.8

Copper 27 81.1 25.8 52.5 51.0

Iron 27 402 82.0 220 227

Lead 27 3.1 0.2 1.0 0.8

Manganese 27 683 57.8 196 146

Nickel 27 0.5 0.2 1

0.3 10.3

Zinc 27 363 191 268 271

Hydropsyche cockerelli

Arsenic 17 8.9 2.4 6.3 6.6

Cadmium 26 2.0 0.4 1.0 1.0

Chromium 26 6.0 1.0 3.0 3.2

Copper 26 99.7 24.4 66.8 69.2

Iron 26 3,590 830 2,120 2,120

Lead 26 12.1 2.5 7.8 7.4

Manganese 26 1,910 764 1,230 1,210

Nickel 26 2.4 0.9 1.8 1.8

Zinc 26 266 156 221 223

Hydropsyche occidentalis

Arsenic 11 7.4 2.2 5.2 5.8

Cadmium 17 1.5 0.4 0.8 0.7

Chromium 17 5.5 0.7 2.9 3.0

Copper 17 80.7 25.3 55.2 59.3

Iron 17 2,540 690 1,930 2,110

Lead 17 11.4 2.1 6.8 6.9

Manganese 17 2,470 717 1,510 1,590

Nickel 17 2.4 0.7 1.8 1.8

Zinc 17 278 183 227 229 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.

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through 

August 2012.—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. spp., one or more similar species; <, 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: 

Rolla Publishing Service Center

For more information concerning this publication, contact: 

Director, Wyoming-Montana Water Science Center 

U.S. Geological Survey 

3162 Bozeman Ave. 

Helena, MT 59601 

(406) 457–5900

Or visit the Wyoming-Montana Water Science Center Web site at: 

http://wy-mt.water.usgs.gov/

ISSN 0196-1497 (print)

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20141034

ISSN 0196-1497 (print) 

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20141034

Dodge and others—Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana—OFR 2014–1034