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

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

2012 through September 2013) 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 2014–1244
Cover photographs. Center: Collecting aquatic insects for tissue analysis, Silver Bow Creek at Opportunity (12323600). 

Photograph by Michelle Hornberger, U.S. Geological Survey, taken August 2013.

Lower left: Identifying and collecting target taxa from rocks, Clark Fork near Drummond (12331800). 

Photograph by Michelle Hornberger, U.S. Geological Survey, taken August 2013.

Lower right: The net spinning caddisfly, Arctopsyche grandis. The retreat and net can be seen in the 

background. Photograph by Amy Kleckner, U.S. Geological Survey, taken August 2013.
Water-Quality, Bed-Sediment, and 

Biological Data (October 2012 through 

September 2013) 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 2014–1244

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 2012 

through September 2013) and statistical summaries of data for streams in the Clark Fork Basin, Montana: U.S. Geological Survey Open-File Report 2014–1244, 133 p., http://dx.doi.org/10.3133/ofr20141244.

ISSN 0196-1497 (print)

ISSN 2331-1258 (online)

ISBN 978-1-4113-3868-5
iii

Contents

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.............................................................................................................................7

4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through

September 2013...........................................................................................................................20

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

Montana (12324200), October 2012 through September 2013 .............................................46

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

Bridge, near Bonner, Montana (12334550), October 2012 through September 2013 .......50

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

Bonner, Montana (12340000), October 2012 through September 2013 ..............................54

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

Missoula, Montana (12340500), October 2012 through September 2013...........................58
iv

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

statistics at Mill Creek at Opportunity, Montana (12323700), April through

September 2013...........................................................................................................................62

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

statistics at Willow Creek at Opportunity, Montana (12323720), April through

September 2013...........................................................................................................................64

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

statistics at Willow Creek at Warm Springs Creek at Warm Springs, Montana

(12323770), April through September 2013..............................................................................66

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

statistics at Willow Creek at Lost Creek near Anaconda, Montana (12323840),

March through September 2013...............................................................................................68

13. Analyses of field replicates for water samples, Clark Fork Basin, Montana ...................71

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

Montana .......................................................................................................................................75

15. Precision of analyses of laboratory replicates for water samples, Clark Fork Basin,

Montana .......................................................................................................................................76

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

samples ........................................................................................................................................76

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

Basin, Montana...........................................................................................................................77

18. Analyses of field blanks for water samples ...........................................................................78

19. Bed-sediment data for the Clark Fork Basin, Montana, August 2013................................80

20. Recovery efficiency for analyses of standard reference materials for bed-sediment

samples ........................................................................................................................................81

21. Analyses of procedural blanks for bed-sediment samples.................................................82

22. Biological data for the Clark Fork Basin, Montana, August 2013 .......................................83

23. Recovery efficiency for analyses of standard reference material for 

biota samples ..............................................................................................................................85

24. Analyses of procedural blanks for biota samples.................................................................86

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

Montana, March 1985 through September 2013 ...................................................................87

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

Montana, August 1986 through August 2013........................................................................107

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

Montana, August 1986 through August 2013........................................................................112
v

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

inch (in.) 25,400 micrometer (μm)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 3,785 milliliter (mL) 

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

)

Flow rate

cubic foot per second (ft3

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

Mass

ounce (oz) 28.35 gram (g) 

parts per million 1 microgram per gram (μg/g)

ton 907.2 kilogram (kg) 

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

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

°F=(1.8×°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 2013 is the period from October 1, 2012, through September 30, 2013.
vi

Abbreviations

FNU formazin nephelometric units

ICP–AES inductively coupled plasma-atomic emission spectrometry

ICP–MS inductively coupled plasma-mass spectrometry

ICP–OES inductively coupled plasma-optical emission spectrometry

LRL laboratory reporting level

LT–MDL long-term method detection level

MRL minimum reporting level

NIST National Institute of Standards and Technology

NRP National Research Program

NTRU nephelometric turbidity ratio unit

NWQL National Water Quality Laboratory

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 2012 through September 2013) 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 led 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 2012 

through September 2013. Bed-sediment and biota samples 

were collected once at 13 sites during August 2013. 

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

samples collected at sites from October 2012 through September 2013. Water-quality data include concentrations of selected 

major ions, trace elements, and suspended sediment. Turbidity and dissolved organic carbon were 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, bed-sediment, and biological data for 

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

of record.

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 

6,000–square-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). 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 2014). 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 lead by the USGS National Research Program (NRP) 

(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 2012 through September 2013 

(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 

for the period of record.

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 Clark Fork 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, bedsediment, and biota samples; and quality-assurance data for 

water year 2013 are listed in tables 4 through 24 at the back of 

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

bed-sediment, and biological data collected between March 

1985 and September 2013 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 were 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 laboratory determination of 

concentrations of chemical and physical constituents 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 four daily suspended-sediment sites, suspendedsediment samples were collected by an observer 2–8 times per 

week, depending on season and flow conditions. Continuous 

turbidity monitors were operated seasonally (March/April to 

September 2013) at four sites near Warm Springs and 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.
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, 1:1,000,000, 

1966. North American Datum of 1927 

(NAD 27)

0 10 20 MILES

0 10 20 KILOMETERS

12340500

12340000

12334550

12331800

12324680

12324200

12323800

12323770 12323750

12323600

12323250

Streamflow site type

 Continuous record

 Periodic measurement

Water-quality, bed-sediment,

and biota site type

 Periodic water quality

 Daily suspended sediment

 Daily turbidity

 Once-annual bed sediment

 Once-annual biota

EXPLANATION

Site number

461903112440701 Miscellaneous site number

12324200

12323700

12323720

Lost Cr 12323850

46o

114o

113o

12323230

Racetrack

12323840

12323670

Mill

Creek

Willow

Creek

12323710

Creek

47o

Helena

M O N T A N A

12323760

Dempsey

Creek 461903112440701

461559112443301

461415112450801

Study area

former

12324400
4 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana 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 Continuous- record streamflow Periodic water quality1 Daily suspended sediment Daily turbidity (seasonal) Fine-grained bed sediment2 Biota2 12323230 Blacktail Creek at Harrison Avenue, at Butte -- 03/93–08/95, 12/96–08/03, 12/04–P -- -- -- -- 12323250 Silver Bow Creek below Blacktail Creek, at Butte 10/83–P 03/93–08/95, 12/96–P -- -- -- -- 12323600 Silver Bow Creek at Opportunity 07/88–P 03/93–08/95, 12/96–P 03/93–09/95, D -- 07/92–P 07/92, 08/94– 08/95, 08/97–P 12323670 Mill Creek near Anaconda 10/04–P 12/04–P -- 06/06–09/12, D -- -- 12323700 Mill Creek at Opportunity 04/03–P 03/03–P -- 04/13–P -- -- 12323710 Willow Creek near Anaconda 03/05–P 12/04–P -- 06/06–09/12, D -- -- 12323720 Willow Creek at Opportunity 04/03–P 03/03–P -- 04/13–P -- -- 12323750 Silver Bow Creek at Warm Springs 03/72–09/79, 04/93–P 03/93–P 04/93–09/95, D -- 07/92–P 07/92–P 12323760 Warm Springs Creek near Anaconda 10/97–P 10/05–P -- 05/06–09/12, D -- -- 12323770 Warm Springs Creek at Warm Springs 10/83–P 03/93–P -- 04/13–P 08/95, 08/97, 08/99, 08/02, 08/05, 08/08, 08/11 08/95, 08/97, 08/99, 08/02, 08/05, 08/08, 08/11 12323800 Clark Fork near Galen 07/88–P 07/88–P -- -- 08/87, 08/91–P 08/87, 08/91–P 12323840 Lost Creek near Anaconda 10/04–P 12/04–P -- 05/06–P -- -- 12323850 Lost Creek near Galen 04/03–P 03/03–P -- -- -- -- 461415112450801 Clark Fork below Lost Creek, near Galen -- -- -- -- 08/96–P 08/96–P 461559112443301 Clark Fork at county bridge, near Racetrack -- -- -- -- 08/96–P 08/96–P 461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack -- -- -- -- 08/96–P 08/96–P 12324200 Clark Fork at Deer Lodge 10/78–P 03/85–P 03/85–08/86, 04/87–03/03, 08/03–P -- 08/86–08/87, 08/90–P 08/86–08/87, 08/90–P 12324400 Clark Fork above Little Blackfoot River, near Garrison 02/09–P 03/09–P -- -- 08/09–P 08/09–P 12324680 Clark Fork at Goldcreek 10/77–P 03/93–P -- -- 07/92–P 07/92–P
Water-Quality Data 

5

Station number 

(fig. 1) Station name

Continuousrecord 

streamflow

Periodic 

water quality1

Daily suspended 

sediment

Daily turbidity 

(seasonal)

Fine-grained bed 

sediment2 Biota2

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

08/91–P

08/86, 08/91–P

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

08/03–P

-- 08/86, 08/91–P 08/86, 08/91–P

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

06/88–09/95,

10/05–P

-- 08/86–08/87, 

08/91, 08/93–08/96, 08/98–

08/01, 09/03,

08/06–P

08/86–08/87, 08/91, 08/93, 08/96, 08/98, 09/00, 09/03,

08/06–P

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 08/97–P 08/97–P

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

and suspended sediment.

2Laboratory analyses for trace elements.3Before 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 Potassium Copper Copper

Turbidity Sodium Iron Iron

Alkalinity Lead Lead

Chloride Manganese Manganese

Fluoride Nickel Nickel

Silica Zinc Zinc

Sulfate

Cadmium

Copper

Iron

Lead

Manganese

Zinc

Arsenic

Dissolved organic carbon

Suspended sediment

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 

were made during collection of periodic water samples. Onsite 

sample processing, including filtration and preservation, was 

completed 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. 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, magnesium, 

potassium, sodium, chloride, fluoride, silica, and sulfate were 

measured by the USGS National Water Quality Laboratory 

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

magnesium were used for 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). At select sites in the upper 

basin, filtered concentrations of potassium, sodium, alkalinity, 

chloride, fluoride, silica, sulfate, and dissolved organic carbon 

were measured by ICP–MS (Fishman, 1993; Fishman and 

Friedman, 1989; American Public Health Association, 1998). 

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).
Water-Quality Data 7

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). The turbidity sites are operated seasonally, generally from early spring (after ice breakup) 

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

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

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).

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 --

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 4.0 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 0.15 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

Arsenic, filtered 0.04 μg/L 20 25

Arsenic, unfiltered recoverable 0.28 μg/L 20 25

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

Sediment, suspended 1 mg/L 20 --
8 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Results

Water-quality data from samples collected periodically 

during water year 2013 are listed in table 4. Daily mean 

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

2013 at the four daily suspended-sediment sites are listed in 

tables 5 through 8 along with monthly summary statistics 

and annual totals for streamflow and suspended-sediment 

discharge. Daily maximum, minimum, and mean turbidity at 

four sites are listed in tables 9 through 12 along with monthly 

summary statistics.

Quality Assurance

Quality-assurance procedures used for the collection and 

field processing of water samples are described by Ward and 

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

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

internal sample handling and quality assurance are described 

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

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

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 crosssectional 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 
Water-Quality Data 9

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 constituent-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 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 environmental 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 

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 not detected. The 

LRL for organics is twice the LT-MDL. A thorough description of these laboratory definitions can be found at the USGS 

Branch of Quality Systems Website (https://bqs.usgs.gov/

ltmdl/definition.shtml). Estimated values are noted with a 

remark code of “E” for describing streamflow (for ice affected 

periods) and turbidity (for periods that exceed the manufacturers’ threshold for the sonde).

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. Standard deviation 

and RSD were not calculated for potassium, sodium, alkalinity, chloride, fluoride, silica, sulfate, and organic carbon 

because of the small sample set (only two replicate samples 

were collected for these constituents in water year 2013). 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 
10 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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.

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 92.4 to 105 percent with the 

smallest individual constituent recovery being copper, filtered, 

at 87.0 percent and the largest being iron, unfiltered recoverable, at 112 percent. The 95-percent confidence intervals 

(Taylor, 1987) for the mean spike recovery for each constituent for which deionized-water blank samples were analyzed 

(table 16) did not exceed a 25-percent deviation from an 

expected 100-percent recovery. The mean spike recovery for 

spiked stream samples (table 17) ranged from 84.1 to 102 percent with the smallest individual constituent recovery being 

zinc, unfiltered recoverable, at 79.5 percent and the largest 

being iron, filtered and unfiltered recoverable, at 110 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 copper (87.0–97.9 percent) and unfiltered 

zinc (91.7–98.7 percent). Confidence intervals for percent 

recovery include 100 percent for all laboratory-spiked stream 

samples (table 17) except for unfiltered arsenic (91.0–98.8 percent), filtered cadmium (90.4–99.3 percent), unfiltered cadmium (87.0–95.7 percent), filtered copper (86.0–95.8 percent), 

unfiltered copper (87.5–92.4 percent), filtered manganese 

(95.4–99.0 percent), and unfiltered zinc (79.5–88.7). Because 

the mean spike recoveries for all constituents of laboratoryspiked 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 most likely 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.

Constituent concentrations in field blanks (table 18) were 

almost always less than the LRL. One sample concentration 

of filtered copper (1.0 micrograms/liter [μg/L]) exceeded the 

LRL of 0.80 μg/L. Three sample concentrations of filtered iron 

(4.4, 5.2, and 5.9 μg/L) exceeded the LRL of 4.0 μg/L. Seven 

sample concentrations of filtered manganese (ranging from 

0.15 to 0.62 μg/L) exceeded the LRL of 0.15 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 
Bed-Sediment Data 11

(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 2013.

Methods

Fine-grained bed-sediment samples were collected in 

August 2013 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. Bedsediment samples were oven-dried at 60 degrees Celsius (°C) 

and ground into smaller particle sizes using an acid-washed, 

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 an 

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

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

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

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

The smallest concentration of a constituent that can be reliably 

reported for analyses of bed sediment is termed the minimum 

reporting level (MRL).

Results

Concentrations of trace elements measured in samples 

of fine-grained bed sediment collected during August 2013 

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/mL volumeof digested sample, in mL μg/g 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 stream water. Sampling equipment 

used at more than one site was rinsed thoroughly between 

sites with stream water. Separate sieves were used at each site 

and, therefore, did not require between-site cleaning. Bedsediment samples were collected sequentially at sites along an 

increasing concentration gradient (downstream to upstream 

sites) to minimize effects from potential site-to-site carryover 

contamination.

Quality assurance of analytical results for bed-sediment 

samples included laboratory instrument calibration with 

standard solutions and analysis of quality-control samples 

designed to identify the presence and magnitude of bias (Ellen 

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

Quality-control samples consisted of standard reference 

materials (SRMs), issued by the National Institute of Standards and Technology (NIST), and procedural blanks. Thirteen 

procedural blanks, 10 low-concentration SRMs, and 10 highconcentration 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 
12 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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. Metal 

recoveries of sediment digests were evaluated with NIST 

2709a San Joaquin soils and NIST 2711a Montana Soil II. 

In SRM 2709a, mean recoveries ranged from 51.6–86.6 percent of the certified concentrations and in SRM 2711a, mean 

recoveries ranged from 47.8–98.4 percent. The highest 

mean recoveries in SRM 2709a were iron (85.4 percent) and 

manganese (86.6 percent). Arsenic, cadmium, copper, and 

lead recoveries were low in SRM 2709a (51.6–70.8 percent), 

but these same elements performed up to 47 percent better in 

SRM 2711a (80.6–98.4 percent recoveries). Nickel and zinc 

recoveries were similar in both SRMs: nickel at 80.4 percent 

(SRM 2709a) and 79.3 percent (SRM 2711a), and zinc at 

80.2 percent (SRM 2709a) and 86.9 percent (SRM 2711a). 

Chromium recovery was poor for both SRM 2709a (58.1 percent) and SRM 2711a (47.8 percent). The small range of variation (3 percent) in the 95-percent confidence interval indicates 

good reproducibility of multiple analyses of SRM 2709a and 

SRM 2711a samples. No adjustments were made to traceelement 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 for all elements except iron indicating no contamination bias for these elements. Iron blanks 

were only slightly higher than the iron MRL (<0.021), thus 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 during water 

year 2013.

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. 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 
Statistical Summaries of Data 13

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 

inductively coupled plasma-optical emission spectrometry 

(ICP–OES) for arsenic, cadmium, chromium, copper, iron, 

lead, manganese, nickel, and zinc. The smallest concentration 

of a constituent that can be reliably reported for analyses of 

biota is termed the MRL.

Results

Concentrations of trace elements in whole-body tissue 

of aquatic insects collected during August 2013 are listed in 

table 22. The variability in the number of composite samples 

among species and among sites reflects differences in insect 

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

concentrations, in micrograms per milliliter, analyzed in the 

reconstituted samples were converted to solid-phase concentrations, in microgram per gram, 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.

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 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, issued 

by the NIST and 13 procedural blanks (1 at each site). Qualitycontrol 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 recoveries for arsenic, cadmium, 

copper, iron, manganese, nickel and zinc ranged from 91.7 to 

112 percent and were within 12 percent of the 95-percent confidence intervals for each metal. Higher mean recoveries were 

measured for chromium (167 percent) and lead (220 percent), 

due in part to the relatively low certified concentrations in the 

SRM (0.77 μg/g and 0.35 μg/g, respectively). 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. 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; 
14 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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.

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

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References Cited 15

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

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

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

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

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

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

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

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

2000 through September 2001) and statistical summaries of 

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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, 

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

2005–1356, 124 p. [Also available at http://pubs.usgs.gov/

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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.]

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 Dyke, J.L., 2014, Waterquality, 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. [Also 

available at http://pubs.usgs.gov/of/2014/1034.] 

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

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 plasma-mass 

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

92–634, 28 p.

Fishman, M.J., ed., 1993, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory—

Determination of inorganic and organic constituents in 

water and fluvial sediments: U.S. Geological Survey OpenFile Report 93–125, 217 p.

Fishman, M.J., and Friedman, L.C., 1989, Methods for 

determination of inorganic substances in water and fluvial 

sediments: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. A1, 545 p.

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

practices for the chemical and biological analyses of water 

and fluvial sediments: U.S. Geological Survey Techniques 

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

[Also available at http://pubs.usgs.gov/twri/twri5a6/.]

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

Laboratory—Determination of elements in whole-water 

digests using inductively coupled plasma-optical emission spectrometry and inductively coupled plasma-mass 

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

98–165, 101 p.

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

samples using collision/reaction cell inductively coupled 

plasma-mass spectrometry: U.S. Geological Survey Techniques and Methods, 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.

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.
References Cited 17

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://www2.epa.gov/

sites/production/files/documents/Pt2DecisionSummary.pdf.]

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/.]

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

and processing of surface-water and bed-material samples 

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

Open-File Report 90–140, 71 p.

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

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]

12323230—Blacktail Creek at Harrison Avenue, at Butte

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/13/2012 0955 6.5 7.5 315 4.0 131 38.1 8.75

03/12/2013 1220 6.7 7.8 310 4.0 120 34.5 8.12

04/08/2013 0930 13 7.6 246 2.0 93.5 26.8 6.43

05/20/2013 0920 9.2 7.6 278 7.0 107 30.0 7.67

06/03/2013 0900 15 7.6 250 8.0 95.1 26.6 6.97

06/17/2013 0945 10 7.6 267 10.5 104 29.5 7.42

07/15/2013 0830 2.3 7.6 365 9.0 149 42.0 10.7

08/12/2013 0840 2.7 7.6 369 9.0 153 42.9 11.1

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/13/2012 -- -- -- -- -- -- -- 0.025 0.022

03/12/2013 -- -- -- -- -- -- -- 0.026 0.017

04/08/2013 -- -- -- -- -- -- -- 0.019 0.025

05/20/2013 2.50 11.7 81.8 13.3 0.26 25.4 32.3 0.032 0.030

06/03/2013 2.43 10.1 74.8 10.7 0.24 23.9 28.9 0.025 0.036

06/17/2013 2.47 10.2 87.2 10.4 0.21 24.1 26.5 0.019 0.019

07/15/2013 3.05 14.1 122 14.7 0.30 25.4 34.1 0.019 <0.016

08/12/2013 3.01 14.2 124 15.7 0.29 25.4 35.4 0.022 0.018
Data 21

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]

12323230—Blacktail Creek at Harrison Avenue, at Butte

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)

11/13/2012 1.2 1.9 53.0 256 0.030 0.25 54.8 63.3

03/12/2013 1.6 2.2 90.9 248 0.049 0.19 48.6 54.2

04/08/2013 2.0 4.2 266 678 0.143 0.77 47.6 73.7

05/20/2013 2.0 3.6 166 500 0.083 0.48 53.5 82.2

06/03/2013 3.0 4.4 174 513 0.118 2.04 49.1 66.2

06/17/2013 2.0 2.6 218 523 0.087 0.36 49.2 57.2

07/15/2013 0.87 0.91 39.5 123 <0.025 0.08 50.5 52.6

08/12/2013 1.1 3.1 51.0 140 <0.025 0.15 56.8 58.2

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/13/2012 2.9 3.2 1.7 2.1 -- 87 3 0.05

03/12/2013 2.3 <3.0 1.7 2.1 -- 81 3 0.05

04/08/2013 3.1 5.5 2.7 3.8 -- 79 7 0.25

05/20/2013 2.1 <3.0 3.0 3.9 4.96 92 7 0.17

06/03/2013 2.7 4.1 3.4 4.3 4.62 86 5 0.20

06/17/2013 1.8 <3.0 4.2 5.4 3.85 97 3 0.08

07/15/2013 1.7 <3.0 1.7 2.1 1.40 94 1 0.01

08/12/2013 2.4 3.2 1.8 2.1 1.52 94 1 0.01
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 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]

12323250—Silver Bow Creek below Blacktail Creek, at Butte

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/13/2012 1125 19 7.5 571 5.0 191 49.7 16.1

03/12/2013 1345 19 7.6 539 6.0 166 45.7 12.6

04/08/2013 1045 26 7.6 444 3.0 144 40.1 10.6

05/20/2013 1055 24 7.6 476 9.0 149 41.5 11.1

06/03/2013 1035 33 7.7 444 10.0 144 39.8 10.8

06/17/2013 1125 20 7.6 470 14.0 146 40.6 10.9

07/15/2013 1000 13 7.6 550 15.0 159 44.9 11.3

08/12/2013 1015 16 7.6 544 15.0 158 45.4 10.8

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/13/2012 -- -- -- -- -- -- -- 0.069 0.081

03/12/2013 -- -- -- -- -- -- -- 0.063 0.136

04/08/2013 -- -- -- -- -- -- -- 0.050 0.088

05/20/2013 5.40 24.7 66.9 26.5 0.37 20.5 77.8 0.067 0.087

06/03/2013 4.96 22.2 102 24.2 0.41 21.8 69.5 0.057 0.122

06/17/2013 5.55 24.4 72.4 26.4 0.32 20.3 71.0 0.074 0.092

07/15/2013 6.96 30.5 72.4 32.3 0.43 17.6 83.7 0.064 0.078

08/12/2013 7.07 31.7 95.1 33.3 0.36 17.7 84.8 0.045 0.061
Data 23

12323250—Silver Bow Creek below Blacktail Creek, at Butte

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)

11/13/2012 3.8 8.8 32.0 127 0.219 0.79 59.6 73.4

03/12/2013 4.2 13.2 57.0 331 0.303 2.28 108 124

04/08/2013 3.8 11.3 135 398 0.265 1.70 89.0 98.5

05/20/2013 3.5 10.0 72.5 278 0.264 1.11 70.7 89.1

06/03/2013 4.1 11.4 112 393 0.247 1.71 86.6 109

06/17/2013 3.9 8.4 85.5 268 0.252 0.80 62.9 73.4

07/15/2013 3.6 11.0 39.6 108 0.313 0.80 36.5 44.5

08/12/2013 3.6 9.6 28.4 94.6 0.269 0.81 20.7 28.8

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/13/2012 31.4 35.0 2.8 3.0 -- 79 3 0.15

03/12/2013 33.3 41.7 2.9 3.4 -- 82 11 0.56

04/08/2013 20.8 30.6 3.2 4.2 -- 67 8 0.56

05/20/2013 21.3 28.1 3.7 4.6 7.12 86 5 0.32

06/03/2013 23.2 35.6 4.4 5.5 5.73 80 7 0.62

06/17/2013 27.6 31.4 4.5 5.0 5.94 92 4 0.22

07/15/2013 37.4 38.8 4.3 4.4 7.55 74 3 0.11

08/12/2013 31.4 32.4 4.2 4.1 5.76 79 3 0.13

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
24 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12323600—Silver Bow Creek at Opportunity

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/14/2012 0835 E34 7.9 526 4.5 196 58.3 12.2

03/13/2013 0955 44 8.0 514 2.0 178 51.4 12.0

04/09/2013 0840 49 8.0 469 -1.0 166 47.9 11.3

05/21/2013 0845 64 8.1 393 8.0 146 43.6 9.06

06/03/2013 1210 93 8.1 318 9.0 113 33.8 7.06

06/17/2013 1600 34 9.0 412 20.0 155 45.1 10.3

07/15/2013 1625 17 9.2 527 24.0 187 54.9 12.2

08/12/2013 1650 13 9.1 537 19.0 177 51.3 11.9

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/14/2012 0.403 0.417 12.2 21.3 16.6 366 0.165 2.48

03/13/2013 0.363 0.590 13.1 36.0 35.2 568 0.330 5.79

04/09/2013 0.225 0.325 8.7 17.0 44.0 285 0.194 1.65

05/21/2013 0.123 0.354 6.5 20.3 26.2 405 0.167 3.82

06/03/2013 0.095 0.402 8.5 30.1 44.9 793 0.325 6.39

06/17/2013 0.118 0.257 9.5 17.9 31.2 288 0.266 2.38

07/15/2013 0.229 0.364 15.2 24.1 25.5 249 0.340 2.78

08/12/2013 0.242 0.382 14.1 24.8 25.3 234 0.214 2.14

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/14/2012 114 141 112 124 6.2 6.7 55 10 0.92

03/13/2013 281 332 103 138 6.4 7.3 84 21 2.5

04/09/2013 240 247 79.9 99.0 5.6 6.5 85 9 1.2

05/21/2013 120 214 33.4 74.1 5.1 6.6 88 16 2.8

06/03/2013 80.5 166 32.4 83.3 5.3 6.8 65 36 9.0

06/17/2013 72.4 125 12.2 40.1 8.3 8.3 83 16 1.5

07/15/2013 48.6 120 17.2 50.3 10.7 11.7 89 11 0.50

08/12/2013 41.5 110 18.3 52.8 12.9 12.0 90 10 0.35

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 25

12323670—Mill Creek near Anaconda

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Turbidity,

unfiltered,

lab

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/13/2012 1310 12 7.9 187 1.0 E2.2 90.7 25.1 6.81

03/12/2013 1610 9.7 8.1 213 5.0 <2.0 95.0 25.8 7.42

04/08/2013 1340 19 7.9 150 2.0 -- 65.2 17.8 5.01

05/20/2013 1340 68 7.6 84 7.5 -- 37.3 10.6 2.66

06/03/2013 1415 96 7.6 82 7.0 -- 34.3 9.87 2.35

06/17/2013 1405 75 7.8 79 12.0 -- 33.6 9.74 2.26

07/15/2013 1235 30 8.0 115 13.0 -- 50.4 14.3 3.54

08/12/2013 1255 17 8.1 154 13.5 -- 69.6 19.0 5.38

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/13/2012 0.083 0.082 1.2 1.7 39.3 79.4 0.076 0.20

03/12/2013 0.071 0.087 1.1 1.8 25.5 79.4 0.075 0.35

04/08/2013 0.043 0.067 2.0 3.0 35.5 116 0.079 0.52

05/20/2013 0.043 0.067 2.1 3.1 32.5 155 0.078 0.57

06/03/2013 0.039 0.051 2.5 3.6 43.7 124 0.122 0.50

06/17/2013 0.031 0.039 1.9 2.5 29.5 110 0.084 0.34

07/15/2013 0.038 0.044 1.5 2.1 48.6 110 0.116 0.37

08/12/2013 0.045 0.067 2.7 2.4 61.3 103 0.135 0.36

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/13/2012 5.63 7.2 2.9 <3.0 14.8 13.7 86 1 0.03

03/12/2013 4.79 7.1 1.7 <3.0 16.1 15.7 71 1 0.03

04/08/2013 4.22 8.4 2.7 4.3 12.8 14.0 56 3 0.15

05/20/2013 3.73 12.3 1.8 3.0 8.4 9.7 43 5 0.92

06/03/2013 4.14 7.1 4.3 4.5 10.3 11.2 57 4 1.0

06/17/2013 4.00 7.5 2.3 3.0 9.1 9.7 71 4 0.81

07/15/2013 6.50 11.5 <1.4 <3.0 12.2 12.6 73 2 0.16

08/12/2013 6.48 10.1 1.9 <3.0 25.3 24.4 83 1 0.05

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
26 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12323700—Mill Creek at Opportunity

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Turbidity,

unfiltered,

lab

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/13/2012 1545 E5.0 7.8 220 1.0 -- 101 28.4 7.28

03/13/2013 0830 8.5 8.0 242 2.0 -- 106 29.5 7.83

04/08/2013 1655 12 8.0 176 3.0 <2.0 78.0 21.7 5.77

05/21/2013 0725 27 7.7 97 6.0 <2.0 39.4 11.0 2.89

06/04/2013 0745 38 7.7 93 6.5 E2.6 37.6 10.6 2.72

06/18/2013 0735 38 7.7 86 9.5 E2.3 36.8 10.6 2.49

07/15/2013 1510 8.0 8.0 132 17.0 <2.0 58.3 16.7 4.04

08/12/2013 1530 2.3 8.1 183 15.0 <2.0 79.2 21.9 5.97

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/13/2012 -- -- -- -- -- -- -- 0.088 0.080

03/13/2013 -- -- -- -- -- -- -- 0.067 0.061

04/08/2013 0.83 6.00 72.0 0.57 0.36 13.5 17.8 0.048 0.053

05/21/2013 0.55 3.25 41.4 0.30 0.37 11.6 7.30 0.053 0.079

06/04/2013 0.55 3.22 40.0 0.30 0.37 12.0 6.50 0.044 0.079

06/18/2013 0.48 2.29 38.2 0.22 0.31 9.47 5.01 0.048 0.087

07/15/2013 0.65 3.40 57.9 0.31 0.40 10.2 9.12 0.050 0.072

08/12/2013 0.82 4.98 79.5 0.48 0.37 11.4 15.2 0.035 0.039

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 27

12323700—Mill Creek at Opportunity

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)

11/13/2012 1.6 1.7 32.4 60.4 0.052 0.10 10.2 9.8

03/13/2013 1.2 2.0 20.9 49.8 0.045 0.11 2.56 2.9

04/08/2013 2.2 2.8 27.2 91.9 0.073 0.29 2.87 5.2

05/21/2013 2.4 4.1 31.1 164 0.084 0.73 3.60 10.4

06/04/2013 2.7 4.8 41.6 213 0.106 0.86 4.14 10.3

06/18/2013 2.4 4.3 29.0 197 0.092 0.90 3.92 12.0

07/15/2013 2.1 3.1 43.8 140 0.129 0.52 6.22 11.6

08/12/2013 1.7 2.3 40.8 62.3 0.086 0.18 4.73 5.2

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/13/2012 4.1 4.2 13.5 14.0 -- 63 1 0.01

03/13/2013 2.6 <3.0 13.1 12.6 -- 90 1 0.02

04/08/2013 1.8 <3.0 14.1 14.2 2.06 76 2 0.06

05/21/2013 2.5 4.1 11.5 13.0 2.66 66 5 0.36

06/04/2013 2.8 4.7 12.4 13.3 2.44 69 6 0.62

06/18/2013 2.1 3.9 12.0 13.2 2.04 53 5 0.51

07/15/2013 <1.4 <3.0 17.5 19.2 1.61 79 7 0.15

08/12/2013 <1.4 <3.0 23.6 23.1 1.33 88 1 0.01

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
28 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12323710—Willow Creek near Anaconda

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Turbidity,

unfiltered,

lab

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

03/12/2013 1510 E1.3 7.7 124 1.0 <2.0 44.9 14.9 1.86

04/08/2013 1240 4.1 7.6 109 0.5 -- 40.0 13.3 1.63

05/20/2013 1240 9.5 7.6 83 8.0 -- 28.3 9.49 1.13

06/03/2013 1320 16 7.7 81 7.0 -- 28.8 9.65 1.13

06/17/2013 1310 6.9 7.6 96 10.5 -- 35.7 12.0 1.40

07/15/2013 1140 2.6 7.8 108 12.0 -- 38.7 13.1 1.48

08/12/2013 1200 1.7 7.7 110 12.0 -- 39.8 13.3 1.62

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

03/12/2013 0.016 0.023 0.82 1.0 55.3 112 0.048 0.12

04/08/2013 <0.016 0.028 2.1 2.5 73.6 235 0.111 0.38

05/20/2013 0.019 0.038 1.8 2.7 67.1 251 0.141 0.61

06/03/2013 0.027 0.048 2.4 3.4 128 368 0.255 0.80

06/17/2013 0.028 0.041 1.9 2.1 65.7 209 0.166 0.42

07/15/2013 0.035 0.047 1.9 2.3 83.7 187 0.194 0.44

08/12/2013 0.034 0.060 2.3 2.9 107 207 0.260 0.53

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

03/12/2013 18.2 20.6 <1.4 <3.0 10.4 10.0 87 2 0.01

04/08/2013 13.0 19.9 1.9 3.1 12.1 13.0 88 2 0.02

05/20/2013 10.8 23.3 <1.4 <3.0 12.4 13.9 91 6 0.15

06/03/2013 11.2 21.0 2.7 4.2 13.3 14.0 90 7 0.30

06/17/2013 12.6 16.5 2.2 <3.0 14.6 14.6 97 4 0.07

07/15/2013 9.74 17.6 1.7 <3.0 19.5 20.6 92 3 0.02

08/12/2013 11.5 17.9 <1.4 <3.0 24.2 24.2 90 2 0.01

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 29

12323720—Willow Creek at Opportunity

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Turbidity,

unfiltered,

lab

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/14/2012 0800 5.1 7.7 299 2.5 -- 137 40.6 8.63

03/13/2013 0910 5.4 7.7 268 2.0 -- 110 32.3 7.24

04/09/2013 0800 6.5 7.7 273 0.0 E5.5 115 34.0 7.36

05/21/2013 0820 6.8 7.7 232 7.0 E4.0 98.1 28.2 6.70

06/04/2013 0845 14 7.6 199 8.0 E5.2 79.9 23.3 5.27

06/18/2013 0835 8.0 7.8 279 10.0 E3.4 123 35.7 8.14

07/15/2013 1600 6.5 8.7 282 24.0 <2.0 124 36.0 8.19

08/12/2013 1630 8.7 8.3 286 14.5 <2.0 128 36.6 9.01

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/14/2012 -- -- -- -- -- -- -- 0.030 0.060

03/13/2013 -- -- -- -- -- -- -- 0.043 0.056

04/09/2013 1.39 12.2 110 2.24 0.34 23.1 29.1 0.025 0.114

05/21/2013 1.40 9.28 94.5 1.56 0.35 22.5 22.3 0.041 0.066

06/04/2013 1.38 8.60 82.6 1.53 0.29 23.3 16.2 0.036 0.099

06/18/2013 1.45 8.92 120 2.00 0.43 22.2 21.0 0.032 0.055

07/15/2013 1.43 9.64 127 2.06 0.56 19.4 21.8 0.024 0.029

08/12/2013 1.29 9.39 125 2.15 0.49 18.4 24.0 0.018 0.024

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
30 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12323720—Willow Creek at Opportunity

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)

11/14/2012 1.7 4.2 23.1 161 0.139 1.17 65.2 76.3

03/13/2013 1.8 4.0 34.2 167 0.120 1.00 86.4 93.3

04/09/2013 2.1 11.5 38.6 421 0.198 4.14 68.8 104

05/21/2013 4.6 8.8 53.7 256 0.243 1.49 55.4 70.3

06/04/2013 6.2 11.3 83.7 335 0.323 1.91 37.0 51.3

06/18/2013 3.5 6.4 48.7 241 0.209 1.27 45.3 53.8

07/15/2013 2.7 3.7 20.5 111 0.125 0.71 12.8 18.8

08/12/2013 1.7 2.6 9.7 67.2 0.064 0.39 4.95 7.6

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/14/2012 5.0 7.9 11.2 11.4 -- 97 5 0.07

03/13/2013 6.0 7.8 11.2 12.3 -- 94 4 0.06

04/09/2013 4.8 17.5 12.2 15.1 2.63 95 11 0.19

05/21/2013 4.8 9.5 20.7 23.4 4.21 97 6 0.11

06/04/2013 7.8 14.1 30.9 32.6 5.59 95 10 0.38

06/18/2013 3.3 6.9 38.2 38.3 4.19 94 3 0.06

07/15/2013 <1.4 <3.0 24.1 24.9 2.28 97 3 0.05

08/12/2013 <1.4 3.7 14.0 13.7 1.60 93 1 0.02

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 31

12323750—Silver Bow Creek at Warm Springs

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/14/2012 1010 46 8.5 577 1.0 253 73.3 16.9

03/13/2013 1050 60 8.7 541 3.0 223 62.0 16.7

04/09/2013 1010 65 8.1 516 2.0 203 56.8 14.9

05/21/2013 1020 77 8.3 391 11.0 156 43.4 11.5

06/04/2013 1030 153 9.0 398 9.5 154 42.1 11.9

06/18/2013 1015 89 9.1 348 14.0 135 36.2 10.8

07/16/2013 0720 35 9.0 466 15.0 198 55.5 14.5

08/13/2013 0820 20 9.0 533 12.5 222 62.0 16.3

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/14/2012 0.032 0.066 2.7 4.0 9.9 131 0.128 0.89

03/13/2013 0.064 0.079 3.1 4.9 10.0 121 0.044 0.56

04/09/2013 0.025 0.286 1.6 15.3 15.4 481 0.104 4.57

05/21/2013 0.031 0.060 2.5 5.0 36.4 226 0.156 1.13

06/04/2013 0.055 0.083 4.2 6.7 36.7 189 0.161 0.86

06/18/2013 0.033 0.051 3.5 5.2 54.8 174 0.166 0.68

07/16/2013 0.026 0.037 3.0 3.2 24.3 120 0.107 0.50

08/13/2013 0.023 0.027 2.3 2.9 18.4 84.3 0.074 0.38

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/14/2012 53.0 88.5 2.7 5.5 23.2 22.9 81 3 0.37

03/13/2013 51.4 87.2 3.0 7.3 9.2 10.4 91 2 0.32

04/09/2013 208 259 3.3 30.6 8.4 13.0 90 8 1.4

05/21/2013 86.3 124 3.2 8.1 15.5 17.5 85 4 0.83

06/04/2013 38.7 62.2 2.8 9.1 18.2 19.7 94 2 0.83

06/18/2013 61.7 102 1.7 5.1 23.7 24.0 92 2 0.48

07/16/2013 84.2 149 <1.4 3.1 27.8 28.3 92 2 0.19

08/13/2013 60.6 88.0 <1.4 <3.0 30.9 30.1 77 1 0.05

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
32 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12323760—Warm Springs Creek near Anaconda

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Turbidity,

unfiltered,

lab

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/13/2012 1455 67 8.3 272 4.5 <2.0 141 42.2 8.74

04/08/2013 1535 62 8.5 271 3.5 -- 136 40.3 8.66

05/20/2013 1630 102 8.3 201 9.0 -- 97.1 28.8 6.14

06/03/2013 1545 125 8.4 188 9.0 -- 89.7 26.7 5.59

07/15/2013 1400 95 8.5 214 13.0 -- 101 30.2 6.25

08/12/2013 1425 66 8.6 247 12.0 -- 120 35.2 7.68

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/13/2012 0.021 0.016 <0.80 0.78 <4.0 26.5 0.038 0.09

04/08/2013 <0.016 0.016 <0.80 1.2 4.7 56.6 <0.025 0.17

05/20/2013 0.024 0.020 <0.80 3.3 7.8 76.3 <0.025 0.20

06/03/2013 <0.016 0.021 1.2 2.1 11.3 88.9 0.026 0.24

07/15/2013 0.021 0.024 0.96 1.6 6.7 63.2 <0.025 0.29

08/12/2013 0.021 0.025 1.0 1.7 6.1 41.9 <0.025 0.17

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/13/2012 1.27 1.3 <1.4 <3.0 1.9 1.7 71 1 0.18

04/08/2013 1.05 2.3 <1.4 <3.0 1.9 2.1 66 4 0.67

05/20/2013 1.16 3.7 <1.4 <3.0 1.8 2.0 75 4 1.1

06/03/2013 1.74 4.1 <1.4 <3.0 2.3 2.5 72 4 1.4

07/15/2013 1.08 3.7 <1.4 <3.0 2.0 2.3 74 4 1.0

08/12/2013 1.26 2.4 <1.4 <3.0 2.4 2.6 70 2 0.36

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 33

12323770—Warm Springs Creek at Warm Springs

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Turbidity,

unfiltered,

lab

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/14/2012 0940 48 8.2 348 2.0 -- 182 55.0 10.9

04/09/2013 1040 45 8.1 358 0.0 E2.5 185 54.8 11.7

05/21/2013 0955 65 8.1 280 8.0 E2.3 135 40.8 8.01

06/04/2013 0945 78 8.0 274 7.0 <2.0 130 39.4 7.72

06/18/2013 0925 90 8.0 226 10.0 E2.5 106 32.4 6.07

07/15/2013 1720 36 8.3 293 18.0 <2.0 138 42.6 7.64

08/13/2013 0740 10 8.1 382 11.0 <2.0 190 57.3 11.5

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/14/2012 -- -- -- -- -- -- -- 0.052 0.065

04/09/2013 1.54 4.34 141 1.56 0.43 11.5 47.6 0.033 0.072

05/21/2013 1.19 3.03 108 1.02 0.44 9.85 34.4 0.055 0.074

06/04/2013 1.09 2.90 105 1.03 0.43 10.0 33.5 0.038 0.062

06/18/2013 1.05 2.35 88.0 0.80 0.40 10.1 25.8 -- --

07/15/2013 1.37 3.31 113 1.15 0.52 9.90 36.1 0.037 0.040

08/13/2013 1.66 4.37 140 1.72 0.51 11.2 60.1 0.041 0.056

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
34 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12323770—Warm Springs Creek at Warm Springs

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)

11/14/2012 2.1 8.8 13.8 138 0.075 1.04 85.4 136

04/09/2013 1.6 11.2 6.6 213 <0.025 1.14 69.4 151

05/21/2013 2.3 10.9 8.0 181 0.029 0.98 86.8 144

06/04/2013 2.5 8.9 15.9 126 0.041 0.66 83.5 108

06/18/2013 -- -- 9.8 17.2 -- -- -- --

07/15/2013 2.8 4.9 11.6 54.9 0.044 3.42 58.5 78.9

08/13/2013 2.5 5.3 18.3 55.2 0.048 0.22 63.5 78.9

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/14/2012 3.0 4.3 3.9 4.2 -- 64 5 0.65

04/09/2013 <1.4 5.8 3.7 4.9 1.00 77 10 1.2

05/21/2013 <1.4 4.8 4.2 5.6 1.66 69 9 1.6

06/04/2013 3.5 3.6 4.3 4.8 1.84 77 5 1.1

06/18/2013 4.3 <3.0 -- -- 1.67 70 7 1.7

07/15/2013 <1.4 <3.0 6.2 6.6 1.24 85 2 0.19

08/13/2013 <1.4 <3.0 7.1 7.1 0.97 90 1 0.03

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 35

12323800—Clark Fork near Galen

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/14/2012 1130 95 8.3 473 2.0 221 64.5 14.5

03/13/2013 1200 105 8.4 480 4.0 210 59.6 14.8

04/09/2013 1210 E105 8.2 464 3.5 199 57.2 13.6

05/21/2013 1155 133 8.4 350 11.0 154 44.6 10.3

06/04/2013 1140 242 8.8 356 10.0 145 40.7 10.5

06/18/2013 1140 184 8.7 296 14.0 123 36.0 8.18

07/16/2013 0850 57 8.2 386 14.5 174 50.5 11.5

08/13/2013 0935 38 8.4 498 14.0 225 65.1 15.1

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/14/2012 0.041 0.082 2.8 9.3 9.4 184 0.069 1.17

03/13/2013 0.064 0.083 3.3 7.8 9.8 141 0.045 1.25

04/09/2013 0.042 0.228 3.0 20.6 12.1 471 0.130 3.91

05/21/2013 0.043 0.079 3.1 11.2 18.9 248 0.089 1.42

06/04/2013 0.042 0.101 4.1 11.9 26.9 245 0.125 1.46

06/18/2013 0.027 0.074 3.7 9.9 35.6 192 0.124 1.00

07/16/2013 0.020 0.065 1.4 6.9 15.5 96.2 0.042 0.63

08/13/2013 0.041 0.044 3.5 5.7 12.4 67.5 0.063 0.40

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/14/2012 56.5 107 3.2 7.8 13.3 13.7 80 6 1.5

03/13/2013 65.2 106 3.5 7.8 7.5 8.9 76 5 1.4

04/09/2013 130 216 6.4 28.5 7.0 10.9 87 13 3.7

05/21/2013 63.4 121 1.9 9.0 10.8 12.8 84 7 2.5

06/04/2013 41.6 81.6 3.6 12.6 14.0 15.4 72 8 5.2

06/18/2013 46.6 88.0 1.6 6.7 15.4 16.1 80 6 3.0

07/16/2013 13.1 77.3 1.5 4.9 12.5 15.8 89 2 0.31

08/13/2013 40.9 57.2 2.4 3.8 22.0 21.5 96 2 0.21

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
36 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12323840—Lost Creek near Anaconda

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Turbidity,

unfiltered,

lab

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/13/2012 1400 10 8.0 213 0.0 <2.0 109 33.2 6.40

03/12/2013 1700 6.2 8.2 222 3.0 <2.0 104 31.0 6.50

04/08/2013 1420 7.2 8.1 217 2.0 <2.0 107 32.0 6.62

05/20/2013 1500 2.6 8.0 183 11.0 <2.0 87.5 26.1 5.44

06/03/2013 1450 9.2 8.0 175 9.5 E2.3 81.9 24.8 4.89

06/17/2013 1450 9.9 8.1 192 12.0 <2.0 88.9 27.2 5.10

07/15/2013 1320 2.4 8.2 225 13.0 <2.0 106 32.6 5.92

08/12/2013 1335 9.6 8.2 224 11.5 <2.0 107 32.3 6.47

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/13/2012 -- -- -- -- -- -- -- 0.026 0.027

03/12/2013 -- -- -- -- -- -- -- 0.019 0.023

04/08/2013 1.30 2.92 103 0.73 0.47 11.3 10.8 <0.016 0.017

05/20/2013 1.18 2.66 86.1 0.69 0.43 11.3 8.34 0.028 0.029

06/03/2013 1.14 2.62 82.5 0.60 0.40 11.1 7.58 0.020 0.028

06/17/2013 1.14 2.63 91.8 0.57 0.37 10.9 7.33 0.020 0.022

07/15/2013 1.39 3.18 109 0.68 0.47 11.2 8.17 0.025 0.018

08/12/2013 1.26 2.67 109 0.64 0.42 11.3 8.80 0.020 0.023

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 37

12323840—Lost Creek near Anaconda

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)

11/13/2012 1.1 3.4 6.0 116 0.031 0.47 2.23 4.5

03/12/2013 0.98 4.4 5.1 115 <0.025 0.52 1.19 4.2

04/08/2013 1.2 3.1 4.6 70.5 0.045 0.29 1.68 3.2

05/20/2013 2.4 4.1 9.1 53.6 <0.025 0.22 1.48 3.1

06/03/2013 1.9 5.0 9.7 128 <0.025 0.51 1.32 4.9

06/17/2013 1.9 3.3 8.5 71.5 0.026 0.24 1.46 3.2

07/15/2013 1.6 2.1 8.7 27.3 <0.025 0.09 1.91 3.2

08/12/2013 1.2 3.2 5.7 98.3 0.027 0.36 1.64 5.3

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/13/2012 2.7 <3.0 2.1 2.1 -- 61 7 0.19

03/12/2013 <1.4 <3.0 2.1 2.4 -- 43 5 0.08

04/08/2013 <1.4 <3.0 2.0 2.1 1.09 51 3 0.06

05/20/2013 <1.4 <3.0 3.9 4.0 2.30 72 2 0.01

06/03/2013 1.5 <3.0 3.9 4.1 2.31 63 8 0.20

06/17/2013 <1.4 <3.0 5.1 5.1 1.95 47 3 0.08

07/15/2013 <1.4 <3.0 5.2 5.7 1.36 56 1 0.01

08/12/2013 <1.4 <3.0 3.4 3.5 0.91 52 5 0.13

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
38 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12323850—Lost Creek near Galen

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/14/2012 1055 60 8.2 589 2.0 296 87.6 18.8

03/13/2013 1125 49 8.1 588 4.0 292 84.8 19.5

04/09/2013 1135 E45 8.2 635 1.0 319 92.5 21.4

05/21/2013 1125 13 8.4 699 11.0 352 101 24.2

06/04/2013 1115 23 8.3 755 10.0 379 106 27.6

06/18/2013 1105 14 8.3 638 14.0 329 94.5 22.6

07/16/2013 0820 14 7.9 639 13.0 330 96.3 21.9

08/13/2013 0910 21 8.0 614 11.0 302 87.7 20.2

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/14/2012 0.025 0.039 1.2 3.4 6.8 89.4 0.046 0.35

03/13/2013 0.025 0.062 1.5 6.4 15.9 180 0.057 0.78

04/09/2013 0.018 0.073 0.99 8.3 13.0 280 0.053 1.19

05/21/2013 0.032 0.021 1.6 2.7 14.9 59.6 0.029 0.20

06/04/2013 0.020 0.030 1.8 3.1 17.7 49.1 0.030 0.34

06/18/2013 0.020 0.024 1.8 3.0 13.4 45.0 0.037 0.16

07/16/2013 0.026 0.020 2.3 2.3 14.2 49.6 0.106 0.18

08/13/2013 <0.016 <0.016 1.3 2.3 11.4 34.7 <0.025 0.15

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/14/2012 10.4 12.1 2.3 3.3 11.2 11.4 87 5 0.81

03/13/2013 20.0 28.6 3.0 5.2 11.5 12.1 86 8 1.1

04/09/2013 21.5 35.9 1.8 6.4 9.6 11.6 85 15 1.8

05/21/2013 19.2 21.9 3.1 3.4 11.3 12.0 46 25 0.88

06/04/2013 15.9 16.6 <1.4 <3.0 22.0 22.4 65 23 1.4

06/18/2013 13.2 21.8 <1.4 <3.0 16.4 15.9 73 9 0.34

07/16/2013 12.3 15.2 1.5 <3.0 13.5 12.3 76 25 0.95

08/13/2013 6.87 7.6 1.7 <3.0 11.8 11.4 86 10 0.57

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 39

12324200—Clark Fork at Deer Lodge

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/14/2012 1300 258 8.2 491 2.0 227 66.5 14.8

03/13/2013 1335 228 8.3 491 5.0 222 63.9 15.1

04/09/2013 1330 220 8.3 500 4.0 226 65.7 15.0

05/21/2013 1325 121 8.9 434 14.0 200 58.5 13.2

06/04/2013 1240 272 8.3 449 12.0 190 53.5 13.7

06/18/2013 1320 186 8.8 393 18.0 173 49.7 11.8

07/16/2013 1015 90 8.3 480 16.0 219 64.6 14.1

08/13/2013 1035 61 8.3 525 14.0 231 68.8 14.5

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/14/2012 0.036 0.125 4.0 24.2 5.5 405 0.061 2.80

03/13/2013 0.070 0.107 5.6 22.8 6.5 305 0.061 2.10

04/09/2013 0.054 0.147 4.8 25.1 12.3 405 0.065 3.28

05/21/2013 0.035 0.065 5.7 13.2 18.7 156 0.111 1.10

06/04/2013 0.060 0.191 7.3 37.2 24.3 575 0.183 4.46

06/18/2013 0.047 0.082 6.2 16.0 22.8 174 0.152 1.43

07/16/2013 0.049 0.077 3.4 12.5 14.5 116 0.083 0.96

08/13/2013 0.035 0.046 5.5 9.4 8.3 76.3 0.060 0.60

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/14/2012 29.7 87.3 6.4 22.0 10.2 12.0 87 18 13

03/13/2013 46.0 74.2 6.3 19.0 8.5 9.7 77 14 8.6

04/09/2013 61.2 114 5.1 22.4 9.2 12.2 87 15 8.9

05/21/2013 53.1 81.9 1.6 8.5 13.4 14.2 92 5 1.6

06/04/2013 28.1 102 6.6 32.6 15.9 20.2 80 23 17

06/18/2013 35.0 55.5 1.6 10.1 17.4 17.7 89 8 4.0

07/16/2013 50.2 59.2 2.5 8.8 14.7 17.4 96 3 0.73

08/13/2013 17.0 29.3 3.0 5.6 13.2 13.3 78 4 0.66

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
40 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12324400—Clark Fork above Little Blackfoot River, near Garrison

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/14/2012 1420 249 8.4 484 2.0 227 66.5 14.7

03/13/2013 1440 255 8.6 488 6.0 219 63.0 15.1

04/09/2013 1450 226 8.6 494 5.0 218 63.1 14.7

06/04/2013 1435 303 8.4 468 14.0 200 55.9 14.6

06/18/2013 1440 208 8.6 434 19.0 195 55.2 13.8

07/16/2013 1140 110 8.6 481 17.0 215 61.5 14.9

08/13/2013 1215 71 8.5 499 17.0 217 61.8 15.2

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/14/2012 0.035 0.143 4.2 26.9 23.0 460 0.113 3.26

03/13/2013 0.066 0.136 5.7 24.5 8.2 363 0.094 2.54

04/09/2013 0.058 0.139 6.0 25.5 9.2 383 0.068 3.02

06/04/2013 0.051 0.261 7.9 51.8 22.4 815 0.247 6.43

06/18/2013 0.045 0.118 7.3 20.9 13.5 215 0.135 2.02

07/16/2013 0.030 0.027 7.1 10.2 10.0 46.1 0.135 0.39

08/13/2013 0.024 0.034 6.2 10.0 9.2 66.9 0.113 0.57

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/14/2012 27.2 104 5.5 25.6 10.8 12.5 75 23 15

03/13/2013 46.8 84.5 3.8 21.4 9.3 10.9 75 18 12

04/09/2013 50.9 104 3.1 21.9 9.6 12.1 84 17 10

06/04/2013 30.6 138 4.8 44.5 17.1 21.5 81 37 30

06/18/2013 41.4 76.3 2.1 14.8 18.4 19.4 90 9 5.1

07/16/2013 12.3 19.7 4.9 <3.0 16.2 17.4 90 17 5.0

08/13/2013 19.9 36.6 2.3 4.6 16.1 15.2 81 4 0.77

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 41

12324680—Clark Fork at Goldcreek

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/14/2012 1525 370 8.4 441 2.5 211 62.1 13.6

03/13/2013 1545 366 8.8 437 6.5 196 56.8 13.2

04/09/2013 1535 383 8.5 419 6.0 190 55.0 12.8

05/21/2013 1515 396 8.6 297 15.0 131 38.1 8.72

06/04/2013 1600 892 8.2 321 13.5 142 40.3 10.0

06/19/2013 0810 431 8.1 360 13.0 161 46.6 10.8

07/16/2013 1240 276 8.8 369 18.0 174 50.1 11.9

08/13/2013 1310 137 8.7 415 18.0 194 56.5 12.7

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/14/2012 0.023 0.106 3.1 18.5 5.2 335 0.058 2.29

03/13/2013 0.043 0.090 4.9 15.2 8.9 240 0.079 1.53

04/09/2013 0.026 0.089 3.7 16.5 6.3 308 0.051 2.02

05/21/2013 0.022 0.078 3.4 11.0 19.7 353 0.083 1.50

06/04/2013 0.035 0.240 4.7 37.2 34.5 1,410 0.186 6.27

06/19/2013 0.030 0.062 4.3 11.2 19.8 171 0.085 1.11

07/16/2013 <0.016 0.021 4.2 5.6 8.6 31.8 0.038 0.14

08/13/2013 0.020 0.049 3.4 7.7 7.7 126 0.054 0.72

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/14/2012 13.9 79.5 2.8 17.6 8.5 9.1 88 16 16

03/13/2013 30.1 90.2 2.1 13.6 7.9 8.1 75 12 12

04/09/2013 26.4 69.4 1.8 15.5 7.5 9.1 83 14 14

05/21/2013 17.2 68.4 2.4 13.8 7.1 8.3 89 16 17

06/04/2013 18.9 176 3.4 44.5 9.1 14.1 73 74 178

06/19/2013 18.7 47.2 3.1 10.7 10.9 11.3 90 8 9.3

07/16/2013 5.48 9.3 <1.4 <3.0 10.6 10.8 91 5 3.7

08/13/2013 16.4 61.1 1.8 6.5 9.9 9.6 92 7 2.6

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
42 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12331800—Clark Fork near Drummond

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/15/2012 0820 582 8.2 472 3.0 227 65.1 15.6

03/14/2013 1105 586 8.2 457 6.0 211 59.6 15.1

04/10/2013 0805 565 8.1 447 7.0 207 58.6 14.8

05/22/2013 0745 398 8.0 403 13.5 184 51.8 13.3

06/05/2013 0815 1,020 8.1 367 12.0 160 44.8 11.8

06/19/2013 0920 557 8.1 437 14.5 199 56.3 14.2

07/16/2013 1345 315 8.5 453 20.0 212 58.0 16.3

08/13/2013 1415 248 8.4 538 20.0 247 68.9 18.3

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/15/2012 0.029 0.102 2.5 14.7 <4.0 346 0.052 2.55

03/14/2013 0.039 0.113 4.1 18.7 12.2 393 0.089 2.82

04/10/2013 0.029 0.130 3.7 19.9 9.6 464 0.071 3.58

05/22/2013 0.038 0.087 4.2 12.0 12.4 233 0.090 1.56

06/05/2013 0.023 0.311 4.7 48.4 26.8 1,390 0.204 8.47

06/19/2013 0.024 0.064 4.5 11.5 11.6 168 0.091 1.16

07/16/2013 0.021 0.026 4.5 5.4 8.6 24.8 0.046 0.17

08/13/2013 0.024 0.037 2.8 5.4 28.4 103 0.129 0.61

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/15/2012 11.3 86.0 5.2 20.0 8.0 8.6 83 19 30

03/14/2013 25.3 81.9 3.5 22.5 7.9 8.9 79 27 43

04/10/2013 19.9 97.0 3.4 26.2 7.5 9.8 87 25 38

05/22/2013 19.5 70.2 4.6 15.7 8.7 9.1 93 11 12

06/05/2013 15.2 175 4.4 62.0 10.0 14.3 78 78 215

06/19/2013 18.3 42.9 3.4 11.1 11.2 11.8 87 8 12

07/16/2013 4.24 9.9 <1.4 <3.0 10.9 11.0 85 4 3.4

08/13/2013 11.5 37.1 2.2 5.8 11.2 10.8 86 6 4.0

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 43

12334550—Clark Fork at Turah Bridge, near Bonner

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/15/2012 0955 886 8.2 385 3.0 186 52.8 13.1

03/14/2013 0940 837 8.1 379 5.0 174 48.0 13.1

04/10/2013 1000 1,230 8.1 294 5.0 132 36.3 10.0

05/22/2013 0940 1,740 8.0 178 10.0 184 52.0 13.1

06/05/2013 0955 2,130 8.0 250 11.0 110 30.7 7.99

06/19/2013 1130 1,310 8.2 281 13.0 123 34.7 8.87

07/17/2013 0730 804 7.9 307 17.0 137 36.6 11.2

08/14/2013 1040 490 8.3 339 15.5 149 39.8 12.0

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/15/2012 0.018 0.071 1.8 9.2 <4.0 217 0.038 1.57

03/14/2013 0.022 0.078 2.7 11.2 6.4 248 0.059 1.70

04/10/2013 <0.016 0.073 2.1 11.4 22.2 336 0.070 1.99

05/22/2013 0.018 0.032 1.6 3.8 15.3 148 0.042 0.50

06/05/2013 0.017 0.200 2.8 27.8 23.9 757 0.169 5.18

06/19/2013 <0.016 0.059 2.2 6.6 43.1 145 0.148 0.85

07/17/2013 0.019 0.025 2.7 4.7 6.0 79.4 0.032 0.39

08/14/2013 <0.016 0.038 1.6 4.4 20.4 120 0.034 0.59

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/15/2012 5.26 54.3 3.7 14.2 5.7 6.2 91 11 26

03/14/2013 11.2 57.3 3.1 16.3 5.5 5.9 82 17 38

04/10/2013 6.87 50.8 2.3 16.6 4.4 5.3 81 18 60

05/22/2013 4.56 16.6 4.2 8.4 2.7 3.0 67 9 42

06/05/2013 6.89 110 4.0 37.6 5.9 8.4 88 38 219

06/19/2013 6.88 27.1 2.1 10.4 5.8 5.6 87 7 25

07/17/2013 4.93 16.0 2.5 5.2 4.6 4.8 86 6 13

08/14/2013 5.53 23.5 1.7 6.9 5.6 5.6 84 9 12

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
44 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

12340000—Blackfoot River near Bonner

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/15/2012 1220 711 8.3 255 3.5 135 34.3 11.9

04/10/2013 1215 2,350 8.1 156 5.0 75.8 19.8 6.39

05/22/2013 1150 5,220 8.1 149 10.0 74.7 19.3 6.47

06/05/2013 1155 4,230 8.2 173 11.0 84.6 21.6 7.44

07/17/2013 0845 965 8.3 234 17.0 124 31.2 11.2

08/14/2013 0915 634 8.4 251 15.5 122 29.5 11.8

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/15/2012 <0.016 <0.016 <0.80 <0.70 <4.0 45.0 <0.025 0.04

04/10/2013 <0.016 <0.016 <0.80 <0.70 32.1 158 <0.025 0.13

05/22/2013 <0.016 <0.016 <0.80 1.1 15.0 270 <0.025 0.31

06/05/2013 <0.016 <0.016 <0.80 0.83 36.2 191 0.068 0.22

07/17/2013 <0.016 <0.016 <0.80 <0.70 7.4 29.0 <0.025 --

08/14/2013 <0.016 <0.016 <0.80 <0.70 20.9 24.6 0.031 <0.04

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/15/2012 2.36 4.8 <1.4 <3.0 0.95 1.0 83 3 5.8

04/10/2013 3.44 15.4 <1.4 <3.0 0.70 0.68 79 9 57

05/22/2013 1.85 19.5 1.7 <3.0 0.67 0.88 82 23 324

06/05/2013 3.05 13.1 <1.4 <3.0 0.77 0.92 87 14 160

07/17/2013 1.62 4.6 <1.4 <3.0 1.0 1.1 83 2 5.2

08/14/2013 5.17 5.1 <1.4 <3.0 1.2 1.1 87 2 3.4

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
Data 45

12340500—Clark Fork above Missoula

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, 

onsite 

(standard 

units)

Specific 

conductance, 

onsite 

(μS/cm)

Water 

temperture, 

onsite

(°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

11/15/2012 1405 1,640 8.4 326 3.5 160 43.9 12.3

03/14/2013 0815 1,540 8.1 316 4.5 144 38.5 11.7

04/10/2013 1405 3,660 8.1 204 5.5 93.3 25.4 7.25

05/22/2013 1405 7,200 8.1 157 10.5 73.7 19.3 6.22

06/05/2013 1340 6,520 8.3 198 12.5 92.4 24.5 7.58

06/19/2013 1345 4,060 8.2 216 13.5 101 27.1 8.08

07/17/2013 1020 1,720 8.4 263 18.0 128 33.0 11.0

08/14/2013 0755 1,090 8.2 286 16.0 128 32.5 11.3

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/15/2012 0.018 0.036 1.3 4.6 <4.0 124 0.089 0.74

03/14/2013 0.019 0.044 2.1 6.6 12.6 210 0.041 1.04

04/10/2013 <0.016 0.026 1.0 3.9 27.3 219 0.037 0.71

05/22/2013 <0.016 <0.016 1.1 2.3 17.1 250 <0.025 0.43

06/05/2013 <0.016 0.065 2.1 8.4 17.4 329 0.087 1.56

06/19/2013 <0.016 0.020 1.4 2.5 14.6 118 0.036 0.34

07/17/2013 <0.016 <0.016 1.5 1.9 5.4 48.6 <0.025 0.14

08/14/2013 <0.016 0.029 1.0 3.3 6.2 100 <0.025 0.45

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/15/2012 6.42 31.1 2.4 6.9 3.7 3.8 91 6 27

03/14/2013 15.1 43.2 2.5 11.0 3.4 3.6 88 13 54

04/10/2013 5.59 28.2 <1.4 6.3 1.8 2.3 80 13 128

05/22/2013 4.53 19.8 3.4 6.6 1.2 1.4 83 20 389

06/05/2013 5.34 41.6 2.4 11.9 2.5 3.5 88 19 334

06/19/2013 4.49 14.8 <1.4 <9.0 2.4 2.2 85 7 77

07/17/2013 5.15 10.1 1.5 <3.0 2.6 2.7 87 3 14

08/14/2013 6.11 26.9 <1.4 5.7 3.3 3.3 81 7 21

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2012 through September 2013.—Continued

[hh, hours; mm, minutes; 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; lab, laboratory; μg/L, micrograms per liter; --, no data; <, less than laboratory reporting level; mm, millimeters; ton/d, tons per day; E, estimated; NTRU, nephelometric turbidity ratio unit]
46 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 2012 

through September 2013.

[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]

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

1 111 11 3.3 236 17 11 255 12 8.3

2 115 10 3.1 242 19 12 263 11 7.8

3 131 10 3.5 234 21 13 274 12 8.9

4 148 10 4.0 239 23 15 270 13 9.5

5 154 10 4.2 232 21 13 264 14 10

6 155 10 4.2 237 20 13 261 16 11

7 157 10 4.2 232 18 11 251 15 10

8 162 10 4.4 e220 17 10 237 14 9.0

9 180 10 4.9 e200 18 9.7 e190 13 6.7

10 186 10 5.0 e210 19 11 e200 12 6.5

11 183 10 4.9 e220 19 11 e220 14 8.3

12 182 10 4.9 e230 20 12 243 18 12

13 182 10 4.9 250 19 13 240 22 14

14 183 12 5.9 260 18 13 e200 24 13

15 185 10 5.0 258 18 13 e210 22 12

16 193 11 5.7 265 18 13 e220 19 11

17 214 13 7.5 286 16 12 e210 17 9.6

18 206 12 6.7 286 15 12 e190 15 7.7

19 218 13 7.7 280 13 9.8 e170 15 6.9

20 221 14 8.4 279 12 9.0 e160 17 7.3

21 216 14 8.2 287 12 9.3 e160 18 7.8

22 219 14 8.3 285 12 9.2 e180 20 9.7

23 233 14 8.8 257 13 9.0 e190 23 12

24 235 13 8.2 253 13 8.9 211 26 15

25 233 12 7.5 248 14 9.4 212 28 16

26 233 12 7.5 232 14 8.8 210 31 18

27 236 12 7.6 e200 15 8.1 217 31 18

28 237 12 7.7 e210 15 8.5 218 30 18

29 233 13 8.2 241 15 9.8 e210 29 16

30 230 14 8.7 247 14 9.3 e200 28 15

31 231 15 9.4 -- -- -- e190 28 14

Total1 6,002 -- 192.5 7,356 -- 326.8 6,726 -- 349

Mean 194 12 6.2 245 17 11 217 20 11

Max 237 15 9.4 287 23 15 274 31 18

Min 111 10 3.1 200 12 8.1 160 11 6.5
Data 47

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana (12324200), October 2012 

through September 2013.—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]

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

January February March

1 e180 29 14 230 35 22 220 19 11

2 e170 29 13 229 34 21 235 19 12

3 e160 30 13 226 32 20 240 18 12

4 e160 32 14 230 31 19 227 17 10

5 e180 34 17 227 29 18 209 17 9.6

6 e190 37 19 224 25 15 224 17 10

7 e200 39 21 217 21 12 234 16 10

8 215 37 21 219 19 11 237 16 10

9 221 33 20 219 19 11 231 16 10

10 224 30 18 221 21 13 232 15 9.4

11 e180 28 14 207 22 12 236 15 9.6

12 e150 27 11 e200 23 12 224 14 8.5

13 e160 28 12 e210 23 13 229 14 8.7

14 e170 28 13 217 22 13 237 14 9.0

15 e170 29 13 216 21 12 240 16 10

16 e180 31 15 219 20 12 238 18 12

17 e200 33 18 226 19 12 239 19 12

18 e220 36 21 220 18 11 231 19 12

19 e210 38 22 215 17 9.9 229 20 12

20 e200 37 20 e210 16 9.1 233 20 13

21 e190 33 17 211 16 9.1 231 20 12

22 e180 30 15 e210 18 10 215 20 12

23 e190 28 14 219 19 11 207 19 11

24 222 29 17 210 20 11 e190 20 10

25 226 33 20 215 20 12 210 23 13

26 232 37 23 215 20 12 221 22 13

27 232 41 26 211 20 11 219 19 11

28 e210 41 23 214 20 12 216 15 8.7

29 e210 39 22 -- -- -- 218 17 10

30 224 38 23 -- -- -- 224 20 12

31 226 36 22 -- -- -- 221 15 9.0

Total1 6,082 -- 551 6,087 -- 366.1 6,997 -- 332.5

Mean 196 33 18 217 22 13 226 18 11

Max 232 41 26 230 35 22 240 23 13

Min 150 27 11 200 16 9.1 190 14 8.5
48 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 2012 

through September 2013.—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]

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

1 221 16 9.5 177 9 4.3 303 32 26

2 221 16 9.5 167 9 4.1 275 20 15

3 219 14 8.3 158 8 3.4 290 21 16

4 221 17 10 156 9 3.8 278 23 17

5 226 16 9.8 155 10 4.2 256 16 11

6 225 15 9.1 153 8 3.3 225 13 7.9

7 e220 16 9.5 144 9 3.5 228 11 6.8

8 e220 19 11 137 11 4.1 228 13 8.0

9 222 17 10 133 8 2.9 231 12 7.5

10 223 14 8.4 132 6 2.1 212 11 6.3

11 220 14 8.3 136 7 2.6 188 10 5.1

12 213 12 6.9 136 7 2.6 210 13 7.4

13 213 15 8.6 142 13 5.0 221 19 11

14 207 13 7.3 167 25 11 271 26 19

15 205 14 7.7 183 15 7.4 258 19 13

16 198 14 7.5 149 7 2.8 228 16 9.8

17 196 15 7.9 132 9 3.2 199 18 9.7

18 197 13 6.9 142 9 3.5 190 9 4.6

19 202 12 6.5 144 9 3.5 186 6 3.0

20 203 12 6.6 138 10 3.7 190 8 4.1

21 201 9 4.9 123 10 3.3 185 8 4.0

22 198 11 5.9 116 116 36 182 8 3.9

23 197 12 6.4 202 138 75 187 6 3.0

24 193 10 5.2 310 50 42 181 6 2.9

25 192 11 5.7 250 17 11 193 9 4.7

26 183 11 5.4 203 28 15 187 11 5.6

27 179 12 5.8 224 41 25 187 13 6.6

28 179 12 5.8 278 60 45 185 7 3.5

29 171 11 5.1 336 63 57 176 10 4.8

30 176 10 4.8 349 47 44 173 8 3.7

31 -- -- -- 344 35 33 -- -- --

Total1 6,141 -- 224.3 5,716 -- 467.3 6,503 -- 250.9

Mean 205 13 7.5 184 26 15 217 13 8.4

Max 226 19 11 349 138 75 303 32 26

Min 171 9 4.8 116 6 2.1 173 6 2.9
Data 49

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana (12324200), October 2012 

through September 2013.—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]

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

1 168 5 2.3 63 17 2.9 72 21 4.1

2 158 4 1.7 86 19 4.4 75 20 4.0

3 150 4 1.6 97 18 4.7 77 20 4.2

4 155 5 2.1 85 16 3.7 79 19 4.1

5 148 6 2.4 76 14 2.9 87 18 4.2

6 144 5 1.9 65 13 2.3 100 17 4.6

7 142 5 1.9 58 13 2.0 107 19 5.5

8 133 6 2.2 55 12 1.8 100 16 4.3

9 131 6 2.1 57 12 1.8 102 15 4.1

10 121 7 2.3 64 11 1.9 102 16 4.4

11 119 7 2.2 66 9 1.6 96 13 3.4

12 120 7 2.3 65 6 1.1 97 13 3.4

13 113 14 4.3 65 3 0.53 97 13 3.4

14 108 12 3.5 71 6 1.2 99 12 3.2

15 103 4 1.1 71 4 0.77 102 12 3.3

16 91 4 0.98 66 5 0.89 100 12 3.2

17 92 7 1.7 63 5 0.85 100 13 3.5

18 110 17 5.0 66 5 0.89 112 14 4.2

19 97 14 3.7 63 5 0.85 117 16 5.1

20 88 12 2.9 57 6 0.92 116 14 4.4

21 83 10 2.2 56 6 0.91 111 11 3.3

22 80 9 1.9 61 13 2.1 108 9 2.6

23 73 9 1.8 59 9 1.4 123 10 3.3

24 67 8 1.4 62 11 1.8 131 9 3.2

25 66 7 1.2 57 8 1.2 148 9 3.6

26 64 8 1.4 58 10 1.6 160 10 4.3

27 60 11 1.8 61 8 1.3 160 10 4.3

28 56 14 2.1 57 6 0.92 162 10 4.4

29 58 16 2.5 70 16 3.0 160 10 4.3

30 56 16 2.4 73 22 4.3 172 10 4.6

31 60 17 2.8 72 21 4.1 -- -- --

Total1 3,214 -- 69.68 2,045 -- 60.63 3,372 -- 118.5

Mean 104 9 2.2 66 11 2.0 112 14 4.0

Max 168 17 5.0 97 22 4.7 172 21 5.5

Min 56 4 0.98 55 3 0.53 72 9 2.6

1

Total for water year 2013 (unrounded sum of daily values): streamflow=66,241 ft3/s (annual runoff=131,400 acre-feet); suspended-sediment discharge=3,309.21 tons.
50 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 2012 through September 2013.

[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]

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

1 584 6 9.5 945 14 36 921 10 25

2 590 6 9.6 948 14 36 998 13 35

3 614 6 9.9 939 15 38 1,130 21 64

4 634 6 10 919 16 40 1,080 16 47

5 679 7 13 898 16 39 1,040 12 34

6 712 9 17 884 14 33 1,070 14 40

7 738 12 24 882 12 29 1,040 11 31

8 753 12 24 887 11 26 992 7 19

9 759 13 27 897 10 24 847 6 14

10 776 13 27 886 9 22 817 6 13

11 789 13 28 794 9 19 860 7 16

12 793 14 30 e750 9 18 926 11 28

13 801 15 32 858 10 23 925 10 25

14 808 17 37 891 12 29 833 8 18

15 814 19 42 894 12 29 793 6 13

16 900 23 56 884 12 29 819 6 13

17 980 25 66 878 13 31 841 6 14

18 964 20 52 904 13 32 834 5 11

19 922 15 37 915 13 32 751 4 8.1

20 913 13 32 906 14 34 704 4 7.6

21 916 13 32 1,020 22 61 e730 4 7.9

22 910 12 29 1,110 32 96 775 4 8.4

23 919 12 30 1,010 20 55 795 4 8.6

24 927 12 30 944 13 33 805 5 11

25 921 12 30 954 13 33 780 5 11

26 917 12 30 922 10 25 782 5 11

27 915 12 30 792 9 19 796 5 11

28 943 12 31 e750 8 16 828 5 11

29 955 12 31 878 8 19 763 5 10

30 961 14 36 913 9 22 699 5 9.4

31 966 14 37 -- -- -- 750 5 10

Total1 25,773 -- 929 27,052 -- 978 26,724 -- 585

Mean 831 13 30 902 13 33 862 8 19

Max 980 25 66 1,110 32 96 1,130 21 64

Min 584 6 9.5 750 8 16 699 4 7.6
Data 51

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana (12334550), 

October 2012 through September 2013.—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]

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 e700 5 9.5 807 6 13 745 8 16

2 e650 4 7.0 820 8 18 783 10 21

3 e600 4 6.5 789 8 17 832 17 38

4 e550 3 4.5 790 7 15 873 19 45

5 e600 3 4.9 822 8 18 797 12 26

6 e650 3 5.3 816 9 20 770 10 21

7 735 4 7.9 795 9 19 804 11 24

8 799 6 13 768 10 21 798 11 24

9 827 6 13 790 11 23 790 10 21

10 850 5 11 778 10 21 783 9 19

11 e750 3 6.1 729 9 18 790 9 19

12 e650 2 3.5 742 8 16 805 11 24

13 e550 2 3.0 760 8 16 807 15 33

14 e550 2 3.0 790 9 19 861 18 42

15 e600 2 3.2 769 10 21 929 23 58

16 e650 2 3.5 771 11 23 991 29 78

17 e700 2 3.8 792 12 26 1,010 23 63

18 e700 3 5.7 788 11 23 960 17 44

19 e750 4 8.1 766 9 19 916 15 37

20 e770 4 8.3 770 7 15 896 14 34

21 e770 4 8.3 756 6 12 922 16 40

22 e750 4 8.1 737 6 12 920 15 37

23 755 4 8.2 761 5 10 865 11 26

24 792 4 8.6 754 5 10 828 10 22

25 804 6 13 734 5 9.9 819 11 24

26 808 4 8.7 731 6 12 823 13 29

27 813 3 6.6 726 7 14 848 16 37

28 779 2 4.2 726 7 14 861 18 42

29 769 2 4.2 -- -- -- 889 19 46

30 780 3 6.3 -- -- -- 928 20 50

31 782 4 8.4 -- -- -- 970 22 58

Total1 22,233 -- 215.4 21,577 -- 474.9 26,613 -- 1,098

Mean 717 4 6.9 771 8 17 858 15 35

Max 850 6 13 822 12 26 1,010 29 78

Min 550 2 3.0 726 5 9.9 745 8 16
52 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 2012 through September 2013.—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]

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

April May June

1 1,020 24 66 1,210 14 46 2,100 34 193

2 1,080 27 79 1,150 12 37 1,930 24 125

3 1,150 33 102 1,100 12 36 2,070 32 179

4 1,220 35 115 1,100 12 36 2,150 31 180

5 1,310 36 127 1,110 12 36 2,080 37 208

6 1,410 41 156 1,150 12 37 1,870 30 151

7 1,430 34 131 1,290 18 63 1,760 25 119

8 1,400 28 106 1,510 31 126 1,690 23 105

9 1,310 19 67 1,710 36 166 1,640 25 111

10 1,230 19 63 1,840 35 174 1,560 22 93

11 1,210 19 62 2,000 36 194 1,470 19 75

12 1,180 18 57 2,190 38 225 1,400 16 60

13 1,150 19 59 2,470 48 320 1,470 17 67

14 1,140 15 46 2,770 56 419 1,710 23 106

15 1,100 14 42 2,700 40 292 1,670 20 90

16 1,050 12 34 2,420 25 163 1,500 15 61

17 1,000 9 24 2,240 19 115 1,390 12 45

18 991 11 29 2,130 16 92 1,300 9 32

19 982 12 32 2,050 15 83 1,310 8 28

20 988 13 35 1,900 13 67 1,440 11 43

21 987 12 32 1,780 12 58 1,490 13 52

22 989 11 29 1,810 13 64 1,440 10 39

23 959 9 23 1,900 14 72 1,390 6 23

24 942 12 31 1,970 19 101 1,390 6 23

25 934 10 25 1,960 26 138 1,420 7 27

26 935 8 20 1,850 22 110 1,440 6 23

27 963 12 31 1,840 20 99 1,390 4 15

28 1,050 12 34 2,000 26 140 1,310 4 14

29 1,200 17 55 2,250 41 249 1,220 3 9.9

30 1,260 18 61 2,280 45 277 1,160 4 13

31 -- -- -- 2,240 42 254 -- -- --

Total1 33,570 -- 1,773 57,920 -- 4,289 47,160 -- 2,309.9

Mean 1,119 19 59 1,868 25 138 1,572 17 77

Max 1,430 41 156 2,770 56 419 2,150 37 208

Min 934 8 20 1,100 12 36 1,160 3 9.9
Data 53

Table 6. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana (12334550), 

October 2012 through September 2013.—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]

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 1,120 6 18 507 10 14 387 4 4.2

2 1,080 5 15 545 12 18 383 4 4.1

3 1,020 3 8.3 566 15 23 388 4 4.2

4 983 2 5.3 539 14 20 401 4 4.3

5 964 2 5.2 514 13 18 421 5 5.7

6 956 2 5.2 497 13 17 484 8 10

7 921 2 5.0 480 13 17 523 8 11

8 897 2 4.8 460 13 16 511 7 9.7

9 872 2 4.7 458 13 16 504 6 8.2

10 843 2 4.6 517 14 20 494 6 8.0

11 825 2 4.5 530 14 20 484 6 7.8

12 820 2 4.4 500 14 19 469 6 7.6

13 832 3 6.7 492 14 19 452 6 7.3

14 813 4 8.8 480 11 14 451 6 7.3

15 781 5 11 456 9 11 459 6 7.4

16 781 6 13 443 8 9.6 457 6 7.4

17 793 7 15 433 8 9.4 462 8 10

18 805 7 15 421 7 8.0 485 10 13

19 789 8 17 417 7 7.9 501 11 15

20 744 8 16 410 6 6.6 506 10 14

21 707 9 17 398 6 6.4 506 10 14

22 684 10 18 385 6 6.2 514 10 14

23 666 9 16 381 6 6.2 528 11 16

24 637 9 15 379 6 6.1 554 13 19

25 612 10 17 381 6 6.2 622 19 32

26 587 11 17 383 6 6.2 676 25 46

27 558 10 15 384 6 6.2 717 25 48

28 527 9 13 388 6 6.3 708 24 46

29 516 8 11 398 6 6.4 716 23 44

30 503 8 11 403 6 6.5 801 25 54

31 494 9 12 392 5 5.3 -- -- --

Total1 24,130 -- 349.5 13,937 -- 371.5 15,564 -- 499.2

Mean 778 6 11 450 9 12 519 11 17

Max 1,120 11 18 566 15 23 801 25 54

Min 494 2 4.4 379 5 5.3 383 4 4.1

1

Total for water year 2013 (unrounded sum of daily values): streamflow=342,253 ft3/s (annual runoff=678,900 acre-feet); suspended-sediment discharge=13,872.4 tons.
54 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 2012 

through September 2013.

[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]

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

1 531 4 5.7 668 4 7.2 754 4 8.1

2 528 4 5.7 670 5 9.0 823 5 11

3 542 4 5.9 698 6 11 905 7 17

4 540 4 5.8 719 6 12 902 7 17

5 547 3 4.4 728 7 14 902 7 17

6 550 3 4.5 726 7 14 914 7 17

7 552 2 3.0 727 6 12 899 6 15

8 552 2 3.0 730 6 12 874 5 12

9 550 2 3.0 744 6 12 771 4 8.3

10 545 2 2.9 713 5 9.6 813 4 8.8

11 546 2 2.9 680 5 9.2 817 4 8.8

12 544 2 2.9 689 4 7.4 811 4 8.8

13 544 3 4.4 704 4 7.6 795 4 8.6

14 549 3 4.4 706 3 5.7 738 4 8.0

15 557 4 6.0 710 3 5.8 712 3 5.8

16 613 4 6.6 700 4 7.6 738 3 6.0

17 627 6 10 687 4 7.4 752 3 6.1

18 625 7 12 689 4 7.4 757 3 6.1

19 602 7 11 680 6 11 e700 3 5.7

20 600 6 9.7 676 7 13 e550 4 5.9

21 597 5 8.1 779 9 19 e580 4 6.3

22 597 4 6.4 871 12 28 e650 4 7.0

23 606 2 3.3 822 12 27 741 3 6.0

24 603 1 1.6 783 9 19 709 3 5.7

25 605 1 1.6 775 6 13 659 2 3.6

26 597 2 3.2 741 5 10 655 2 3.5

27 607 2 3.3 681 4 7.4 703 2 3.8

28 633 2 3.4 721 4 7.8 e750 2 4.0

29 671 3 5.4 709 4 7.7 e700 2 3.8

30 695 3 5.6 717 4 7.7 e650 2 3.5

31 682 4 7.4 -- -- -- e600 2 3.2

Total1 18,137 -- 163.1 21,643 -- 341.5 23,324 -- 251.4

Mean 585 3 5.3 721 6 11 752 4 8.1

Max 695 7 12 871 12 28 914 7 17

Min 528 1 1.6 668 3 5.7 550 2 3.2
Data 55

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2012 

through September 2013.—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]

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

January February March

1 e600 2 3.2 660 6 11 560 3 4.5

2 e550 2 3.0 646 6 10 603 5 8.1

3 e450 2 2.4 659 7 12 649 6 11

4 e400 2 2.2 633 7 12 673 6 11

5 e450 3 3.6 629 8 14 627 7 12

6 e600 4 6.5 617 7 12 627 7 12

7 e650 5 8.8 605 6 9.8 623 6 10

8 e700 5 9.5 595 4 6.4 613 5 8.3

9 699 6 11 592 3 4.8 610 5 8.2

10 685 5 9.2 579 3 4.7 612 5 8.3

11 648 5 8.7 558 3 4.5 620 5 8.4

12 e500 4 5.4 580 4 6.3 628 6 10

13 e400 4 4.3 581 4 6.3 646 7 12

14 e350 3 2.8 586 4 6.3 701 10 19

15 e380 3 3.1 582 4 6.3 770 14 29

16 e400 3 3.2 582 4 6.3 859 18 42

17 e400 2 2.2 590 4 6.4 887 17 41

18 e450 2 2.4 587 3 4.8 868 11 26

19 e520 2 2.8 582 3 4.7 856 10 23

20 e550 2 3.0 579 3 4.7 863 10 23

21 e500 2 2.7 569 2 3.1 899 10 24

22 e480 3 3.9 568 2 3.1 891 9 22

23 e470 4 5.1 570 3 4.6 871 8 19

24 e550 5 7.4 561 3 4.5 840 7 16

25 e700 6 11 555 4 6.0 827 8 18

26 e680 5 9.2 553 4 6.0 824 8 18

27 e660 5 8.9 545 3 4.4 824 8 18

28 e650 4 7.0 546 3 4.4 833 8 18

29 650 3 5.3 -- -- -- 867 9 21

30 650 4 7.0 -- -- -- 919 10 25

31 654 5 8.8 -- -- -- 996 11 30

Total1 17,026 -- 173.6 16,489 -- 189.4 23,486 -- 555.8

Mean 549 4 5.6 589 4 6.8 758 8 18

Max 700 6 11 660 8 14 996 18 42

Min 350 2 2.2 545 2 3.1 560 3 4.5
56 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 2012 

through September 2013.—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]

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

April May June

1 1,110 15 45 2,650 13 93 4,590 14 174

2 1,280 21 73 2,530 11 75 4,310 14 163

3 1,480 23 92 2,420 10 65 4,260 13 150

4 1,710 25 115 2,360 9 57 4,350 15 176

5 1,950 26 137 2,350 10 63 4,210 14 159

6 2,280 28 172 2,530 11 75 4,080 13 143

7 2,540 33 226 3,020 18 147 4,220 14 160

8 2,590 22 154 3,830 33 341 4,480 16 194

9 2,460 13 86 4,740 45 576 4,540 17 208

10 2,320 10 63 5,760 55 855 4,420 15 179

11 2,190 9 53 6,490 62 1,090 4,150 14 157

12 2,060 8 44 7,000 64 1,210 3,940 13 138

13 1,960 8 42 8,050 85 1,850 3,860 13 135

14 1,890 7 36 9,680 180 4,700 3,880 14 147

15 1,780 7 34 9,290 126 3,160 3,560 14 135

16 1,670 5 23 7,950 79 1,700 3,140 11 93

17 1,580 4 17 6,770 51 932 2,870 9 70

18 1,500 6 24 5,960 36 579 2,730 9 66

19 1,450 4 16 5,500 30 446 2,690 8 58

20 1,430 4 15 5,180 26 364 2,830 9 69

21 1,450 4 16 5,030 25 340 2,970 13 104

22 1,500 4 16 5,210 24 338 2,730 9 66

23 1,490 3 12 5,810 29 455 2,550 7 48

24 1,490 4 16 e5700 28 431 2,410 6 39

25 1,480 4 16 5,210 22 309 2,380 7 45

26 1,480 4 16 4,700 18 228 2,380 8 51

27 1,590 6 26 4,490 19 230 2,290 8 49

28 1,940 9 47 4,580 16 198 2,110 7 40

29 2,410 17 111 4,860 19 249 2,000 6 32

30 2,630 20 142 4,900 17 225 1,930 6 31

31 -- -- -- 4,930 17 226 -- -- --

Total1 54,690 -- 1,885 159,480 -- 21,607 100,860 -- 3,279

Mean 1,823 12 63 5,145 38 697 3,362 11 109

Max 2,630 33 226 9,680 180 4,700 4,590 17 208

Min 1,110 3 12 2,350 9 57 1,930 6 31
Data 57

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2012 

through September 2013.—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]

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 1,820 6 29 689 2 3.7 478 2 2.6

2 1,720 5 23 736 2 4.0 475 2 2.6

3 1,620 5 22 755 2 4.1 479 2 2.6

4 1,530 5 21 741 2 4.0 493 2 2.7

5 1,460 4 16 704 2 3.8 499 2 2.7

6 1,410 4 15 669 2 3.6 517 2 2.8

7 1,360 3 11 652 2 3.5 515 2 2.8

8 1,300 3 11 641 2 3.5 519 2 2.8

9 1,290 3 10 639 2 3.5 540 2 2.9

10 1,240 3 10 643 2 3.5 530 2 2.9

11 1,200 3 9.7 640 2 3.5 512 2 2.8

12 1,160 2 6.3 644 2 3.5 494 2 2.7

13 1,140 2 6.2 648 2 3.5 483 2 2.6

14 1,090 2 5.9 629 2 3.4 476 2 2.6

15 1,060 2 5.7 604 2 3.3 484 2 2.6

16 1,010 2 5.5 586 1 1.6 486 2 2.6

17 967 2 5.2 575 1 1.6 491 2 2.7

18 952 1 2.6 567 1 1.5 499 2 2.7

19 924 2 5.0 550 2 3.0 513 2 2.8

20 900 3 7.3 538 2 2.9 511 3 4.1

21 868 3 7.0 527 2 2.8 515 3 4.2

22 841 3 6.8 524 2 2.8 516 3 4.2

23 827 3 6.7 522 2 2.8 521 3 4.2

24 802 2 4.3 514 2 2.8 526 3 4.3

25 780 2 4.2 524 2 2.8 552 3 4.5

26 762 2 4.1 517 2 2.8 560 3 4.5

27 744 3 6.0 506 2 2.7 550 3 4.5

28 730 4 7.9 507 2 2.7 550 3 4.5

29 713 2 3.9 503 2 2.7 559 3 4.5

30 703 2 3.8 502 2 2.7 584 3 4.7

31 693 2 3.7 488 2 2.6 -- -- --

Total1 33,616 -- 285.8 18,484 -- 95.2 15,427 -- 99.7

Mean 1,084 3 9.2 596 2 3.1 514 2 3.3

Max 1,820 6 29 755 2 4.1 584 3 4.7

Min 693 1 2.6 488 1 1.5 475 2 2.6

1

Total for water year 2013 (unrounded sum of daily values): streamflow=502,662 ft3/s (annual runoff=997,000 acre-feet); suspended-sediment discharge=28,926.5 tons.
58 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 2012 

through September 2013.

[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]

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 1,150 4 12 1,620 8 35 1,730 6 28

2 1,150 3 9.3 1,620 8 35 1,860 7 35

3 1,190 3 9.6 1,630 8 35 2,080 8 45

4 1,200 2 6.5 1,640 9 40 2,050 8 44

5 1,240 3 10 1,640 9 40 2,020 8 44

6 1,280 4 14 1,630 8 35 2,050 9 50

7 1,300 5 18 1,630 7 31 2,020 7 38

8 1,320 6 21 1,630 7 31 1,960 5 26

9 1,320 6 21 1,660 6 27 1,730 4 19

10 1,330 7 25 1,630 6 26 1,680 4 18

11 1,340 7 25 1,520 5 21 1,760 5 24

12 1,340 7 25 1,510 5 20 1,810 6 29

13 1,350 7 26 1,570 6 25 1,790 5 24

14 1,360 8 29 1,630 7 31 1,660 5 22

15 1,370 10 37 1,630 7 31 1,580 4 17

16 1,490 11 44 1,620 6 26 1,620 3 13

17 1,580 10 43 1,600 6 26 1,650 4 18

18 1,570 9 38 1,620 6 26 1,640 3 13

19 1,510 8 33 1,620 6 26 1,510 3 12

20 1,500 7 28 1,610 6 26 e1,300 2 7.0

21 1,500 7 28 1,810 11 54 e1,350 2 7.3

22 1,500 7 28 2,010 11 60 e1,500 3 12

23 1,510 6 24 1,890 7 36 1,590 7 30

24 1,520 6 25 1,770 7 33 1,570 8 34

25 1,520 6 25 1,770 7 33 1,480 6 24

26 1,510 6 24 1,720 5 23 e1,400 3 11

27 1,520 6 25 1,550 4 17 e1,500 4 16

28 1,580 6 26 1,520 4 16 1,590 6 26

29 1,630 7 31 1,620 4 17 1,500 2 8.1

30 1,660 9 40 1,680 5 23 1,400 2 7.6

31 1,650 8 36 -- -- -- e1,400 3 11

Total1 43,990 -- 786.4 49,600 -- 905 51,780 -- 713

Mean 1,419 6 25 1,653 7 30 1,670 5 23

Max 1,660 11 44 2,010 11 60 2,080 9 50

Min 1,150 2 6.5 1,510 4 16 1,300 2 7.0
Data 59

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2012 

through September 2013.—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]

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 e1,350 1 3.6 1,490 4 16 1,320 6 21

2 e1,300 1 3.5 1,490 4 16 1,390 7 26

3 e1,100 2 5.9 1,450 5 20 1,480 8 32

4 e1,000 3 8.1 1,450 5 20 1,560 12 51

5 e1,100 4 12 1,490 5 20 1,460 9 35

6 e1,300 4 14 1,470 6 24 1,420 8 31

7 e1,450 4 16 1,450 6 23 1,450 8 31

8 1,540 5 21 1,410 6 23 1,440 8 31

9 1,540 5 21 1,420 6 23 1,420 8 31

10 1,570 5 21 1,400 6 23 1,420 8 31

11 1,470 5 20 1,340 6 22 1,440 8 31

12 e1,250 4 14 1,350 6 22 1,460 8 32

13 e1,000 4 11 1,370 6 22 1,470 9 36

14 e950 4 10 1,410 6 23 1,560 12 51

15 e1,100 5 15 1,390 6 23 1,690 16 73

16 e1,150 5 16 1,390 6 23 1,870 22 111

17 e1,150 6 19 1,410 6 23 1,940 18 94

18 e1,200 6 19 1,410 6 23 1,880 14 71

19 e1,350 5 18 1,380 6 22 1,820 12 59

20 e1,400 5 19 1,390 6 23 1,800 11 53

21 e1,350 5 18 1,360 6 22 1,850 13 65

22 e1,300 5 18 1,350 6 22 1,850 10 50

23 e1,300 5 18 1,370 5 18 1,780 9 43

24 e1,450 6 23 1,360 4 15 1,700 9 41

25 1,510 6 24 1,330 4 14 1,680 8 36

26 1,490 5 20 1,320 4 14 1,680 8 36

27 1,470 4 16 1,300 5 18 1,700 9 41

28 1,420 4 15 1,300 5 18 1,710 11 51

29 1,410 3 11 -- -- -- 1,770 11 53

30 1,420 3 12 -- -- -- 1,860 12 60

31 1,440 4 16 -- -- -- 1,980 15 80

Total1 40,830 -- 478.1 39,050 -- 575 50,850 -- 1,487

Mean 1,317 4 15 1,395 5 21 1,640 11 48

Max 1,570 6 24 1,490 6 24 1,980 22 111

Min 950 1 3.5 1,300 4 14 1,320 6 21
60 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 2012 

through September 2013.—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]

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 2,130 19 109 3,960 14 150 6,910 20 373

2 2,370 23 147 3,770 12 122 6,430 16 278

3 2,630 26 185 3,600 10 97 6,480 16 280

4 2,960 30 240 3,540 10 96 6,680 18 325

5 3,280 29 257 3,530 10 95 6,500 19 333

6 3,740 32 323 3,730 12 121 6,150 18 299

7 4,080 34 375 4,370 18 212 6,140 16 265

8 4,120 22 245 5,460 34 501 6,330 16 273

9 3,890 14 147 6,660 47 845 6,360 16 275

10 3,640 14 138 7,760 53 1,110 6,160 17 283

11 3,490 14 132 8,630 60 1,400 5,810 15 235

12 3,320 12 108 9,240 63 1,570 5,520 12 179

13 3,180 12 103 10,400 84 2,360 5,470 15 222

14 3,090 10 83 12,300 155 5,150 5,730 15 232

15 2,950 9 72 12,000 142 4,600 5,420 14 205

16 2,790 8 60 10,500 70 1,980 4,820 12 156

17 2,630 6 43 9,140 46 1,140 4,410 11 131

18 2,540 6 41 8,170 33 728 4,160 10 112

19 2,480 8 54 7,630 24 494 4,090 9 99

20 2,450 8 53 7,200 21 408 4,340 9 105

21 2,470 6 40 6,910 20 373 4,540 10 123

22 2,530 5 34 7,110 20 384 4,270 8 92

23 2,500 6 40 7,800 23 484 4,020 6 65

24 2,470 7 47 7,890 24 511 3,840 6 62

25 2,450 8 53 7,400 22 440 3,820 7 72

26 2,450 8 53 6,780 19 348 3,830 7 72

27 2,560 11 76 6,500 16 281 3,690 7 70

28 2,960 14 112 6,730 17 309 3,420 5 46

29 3,620 18 176 7,260 24 470 3,210 5 43

30 3,970 20 214 7,350 26 516 3,060 5 41

31 -- -- -- 7,380 24 478 -- -- --

Total1 89,740 -- 3,760 220,700 -- 27,773 151,610 -- 5,346

Mean 2,991 15 125 7,119 37 896 5,054 12 178

Max 4,120 34 375 12,300 155 5,150 6,910 20 373

Min 2,130 5 34 3,530 10 95 3,060 5 41
Data 61

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2012 

through September 2013.—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]

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 2,910 6 47 1,150 9 28 828 6 13

2 2,770 7 52 1,230 7 23 817 6 13

3 2,610 5 35 1,280 10 35 829 6 13

4 2,460 4 27 1,250 8 27 854 6 14

5 2,370 4 26 1,180 7 22 871 6 14

6 2,290 4 25 1,130 7 21 938 7 18

7 2,230 3 18 1,100 6 18 989 9 24

8 2,140 3 17 1,060 6 17 981 7 19

9 2,110 3 17 1,050 5 14 998 9 24

10 2,030 3 16 1,120 8 24 981 6 16

11 1,970 5 27 1,130 7 21 953 5 13

12 1,920 6 31 1,100 7 21 921 5 12

13 1,920 4 21 1,100 7 21 895 4 9.7

14 1,870 4 20 1,070 7 20 878 4 9.5

15 1,800 4 19 1,030 7 19 894 4 9.7

16 1,750 4 19 993 8 21 896 5 12

17 1,720 4 19 970 8 21 903 5 12

18 1,700 3 14 947 7 18 933 6 15

19 1,670 3 14 925 7 17 961 6 16

20 1,610 4 17 907 7 17 967 5 13

21 1,540 6 25 885 7 17 969 5 13

22 1,490 8 32 871 6 14 976 5 13

23 1,450 8 31 865 6 14 997 6 16

24 1,390 8 30 857 6 14 1,030 7 19

25 1,340 7 25 864 6 14 1,120 10 30

26 1,300 6 21 869 6 14 1,190 12 39

27 1,250 5 17 854 6 14 1,220 13 43

28 1,210 5 16 853 6 14 1,220 12 40

29 1,180 6 19 865 6 14 1,230 11 37

30 1,160 7 22 870 6 14 1,330 12 43

31 1,140 8 25 843 6 14 -- -- --

Total1 56,300 -- 744 31,218 -- 582 29,569 -- 582.9

Mean 1,816 5 24 1,007 7 19 986 7 19

Max 2,910 8 52 1,280 10 35 1,330 13 43

Min 1,140 3 14 843 5 14 817 4 9.5

1

Total for water year 2013 (unrounded sum of daily values): streamflow=855,237 ft3/s (annual runoff=1,696,000 acre-feet); suspended-sediment discharge=43,732.4 tons.
62 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 at Opportunity, Montana 

(12323700), April through September 2013.

[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 -- -- -- 2.5 1.0 1.5 6.0 3.5 4.5

2 -- -- -- 3.5 1.5 2.0 6.0 3.0 4.0

3 -- -- -- 2.5 1.5 2.0 5.0 3.0 3.5

4 -- -- -- 3.5 1.5 2.0 5.0 3.0 4.0

5 -- -- -- 3.5 0.5 2.0 5.0 2.5 3.5

6 -- -- -- 3.0 1.5 2.0 5.5 2.5 3.5

7 -- -- -- 5.5 2.5 4.0 7.0 3.5 5.0

8 -- -- -- 14 5.0 9.5 18 6.0 10

9 -- -- -- 14 9.5 12 9.0 4.0 6.0

10 -- -- -- 16 7.0 11 7.0 3.5 4.5

11 -- -- -- 20 8.5 13 8.0 4.0 5.0

12 -- -- -- 24 12 17 8.5 4.0 6.0

13 -- -- -- -- -- -- 8.0 4.5 6.5

14 -- -- -- -- -- -- 8.0 3.5 6.0

15 -- -- -- -- -- -- 7.5 4.0 6.0

16 -- -- -- -- -- -- 8.5 3.5 6.0

17 -- -- -- -- -- -- 8.5 4.0 6.5

18 3.0 2.0 2.5 -- -- -- 10 4.5 7.5

19 2.5 1.5 2.0 -- -- -- 13 5.0 8.0

20 2.5 1.5 2.0 -- -- -- 12 5.0 8.0

21 -- -- -- 4.5 3.0 3.5 10 4.5 6.5

22 -- -- -- 7.0 2.0 3.5 8.0 4.0 5.5

23 -- -- -- 14 4.5 7.5 8.0 4.5 5.5

24 -- -- -- 7.0 3.0 4.5 7.5 3.0 5.5

25 -- -- -- 5.5 2.5 3.5 8.0 1.5 4.0

26 2.0 1.0 1.5 9.5 2.0 3.5 2.5 1.0 1.5

27 2.0 0.5 1.0 9.5 3.0 4.5 3.0 1.0 2.0

28 2.0 0.5 1.0 14 3.5 9.5 -- -- --

29 2.5 1.0 1.5 13 6.5 8.5 -- -- --

30 2.5 1.0 1.5 9.0 5.0 6.0 -- -- --

31 -- -- -- 6.5 4.5 5.5 -- -- --

Month1 3.0 0.5 1.6 24 0.5 6.0 18 1.0 5.4
Data 63

Table 9. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Mill Creek at Opportunity, Montana 

(12323700), April through September 2013.—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]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

July August September

1 -- -- -- 2.0 0.5 1.5 1.0 0.5 1.0

2 -- -- -- 2.0 0.5 1.5 1.5 <0.5 1.0

3 -- -- -- 2.5 1.0 1.0 2.0 0.5 1.5

4 -- -- -- 2.0 0.5 1.0 1.5 1.0 1.0

5 -- -- -- 1.5 0.5 1.0 -- -- --

6 -- -- -- 1.5 <0.5 1.0 -- -- --

7 -- -- -- 1.5 0.5 1.0 -- -- --

8 -- -- -- 2.0 0.5 1.0 -- -- --

9 -- -- -- 2.0 0.5 1.0 -- -- --

10 -- -- -- 1.5 0.5 1.0 -- -- --

11 -- -- -- 1.5 0.5 1.0 -- -- --

12 2.0 1.5 2.0 2.0 0.5 1.0 -- -- --

13 2.5 1.0 1.5 2.0 0.5 1.0 -- -- --

14 2.5 0.5 1.0 2.0 0.5 1.0 1.0 0.5 0.5

15 2.5 1.0 1.5 1.5 0.5 1.0 1.5 0.5 1.0

16 2.0 0.5 1.0 2.0 0.5 1.0 1.5 0.5 1.0

17 2.0 0.5 1.0 2.0 0.5 1.0 1.5 0.5 1.0

18 2.0 0.5 1.0 2.0 1.0 1.0 2.0 0.5 1.0

19 1.5 0.5 0.5 2.0 0.5 1.0 1.0 <0.5 0.5

20 1.5 <0.5 0.5 2.0 1.0 1.5 1.0 <0.5 0.5

21 1.0 <0.5 0.5 1.5 0.5 1.0 1.0 <0.5 0.5

22 1.5 <0.5 0.5 1.5 1.0 1.0 1.0 <0.5 0.5

23 1.0 <0.5 0.5 1.5 1.0 1.0 0.5 0.5 0.5

24 1.0 <0.5 0.5 1.5 1.0 1.0 2.5 <0.5 0.5

25 1.0 <0.5 0.5 1.5 1.0 1.0 4.0 0.5 1.0

26 1.0 <0.5 0.5 1.5 1.0 1.0 16 3.5 6.5

27 1.0 0.5 0.5 2.0 1.5 1.5 6.5 4.0 5.0

28 1.5 <0.5 0.5 1.5 1.0 1.5 7.5 5.0 5.5

29 1.0 0.5 0.5 2.0 1.5 1.5 8.5 4.0 5.0

30 1.5 <0.5 0.5 2.0 1.0 1.5 -- -- --

31 2.0 0.5 1.0 2.0 0.5 1.5 -- -- --

Month1 2.5 0.5 0.8 2.5 0.5 1.1 16 0.5 1.8

1

For months with missing daily values, the means are calculated using available values.
64 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 at Opportunity, 

Montana (12323720), April through September 2013.

[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 -- -- -- 9.0 5.0 6.0 18 10 13

2 -- -- -- 11 4.5 6.5 19 10 13

3 -- -- -- 7.0 5.0 6.0 56 16 30

4 -- -- -- 7.0 5.0 6.0 110 20 47

5 -- -- -- 7.5 4.5 6.0 22 10 16

6 -- -- -- 8.0 4.5 6.0 24 11 17

7 -- -- -- 8.0 4.0 5.5 22 12 16

8 -- -- -- 7.0 5.0 6.0 65 16 40

9 -- -- -- 8.0 5.0 6.5 -- -- --

10 -- -- -- 9.0 5.5 7.0 15 6.5 9.0

11 -- -- -- 9.0 4.0 6.0 14 5.0 9.0

12 -- -- -- 7.5 4.5 5.5 16 6.5 11

13 -- -- -- 6.5 4.5 5.0 14 6.5 9.0

14 -- -- -- 7.5 3.5 5.5 -- -- --

15 -- -- -- 5.5 4.0 5.0 7.0 2.5 4.5

16 -- -- -- 9.0 4.5 6.0 6.5 2.5 4.5

17 -- -- -- 10 4.5 6.0 7.0 2.5 5.0

18 16 4.5 7.0 6.5 4.5 5.5 7.0 3.0 4.0

19 8.5 5.0 6.5 6.5 4.5 5.5 6.5 3.0 4.5

20 8.0 5.0 6.0 -- -- -- 5.0 3.0 4.0

21 9.0 5.0 6.5 8.5 4.5 6.5 6.0 2.5 4.0

22 16 4.5 8.0 11 4.5 6.5 5.0 2.5 3.5

23 19 4.5 7.0 39 10 23 5.0 2.0 3.5

24 13 5.0 6.5 34 11 17 6.5 2.5 3.5

25 -- -- -- 22 12 16 6.5 2.5 4.0

26 8.0 5.0 7.0 31 19 24 4.0 2.0 2.5

27 9.5 5.5 7.0 190 23 87 4.0 2.0 2.5

28 8.5 5.5 6.5 -- -- -- 4.5 2.0 3.0

29 9.0 6.5 8.0 -- -- -- -- -- --

30 10 6.5 7.5 20 12 15 -- -- --

31 -- -- -- 15 9.0 11 -- -- --

Month1 19 4.5 7.0 190 3.5 11 110 2.0 11
Data 65

Table 10. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Willow Creek at Opportunity, 

Montana (12323720), April through September 2013.—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]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

July August September

1 -- -- -- -- -- -- -- -- --

2 -- -- -- -- -- -- -- -- --

3 -- -- -- -- -- -- -- -- --

4 -- -- -- -- -- -- -- -- --

5 -- -- -- -- -- -- -- -- --

6 -- -- -- -- -- -- -- -- --

7 -- -- -- -- -- -- -- -- --

8 -- -- -- -- -- -- -- -- --

9 -- -- -- -- -- -- -- -- --

10 -- -- -- -- -- -- -- -- --

11 -- -- -- -- -- -- -- -- --

12 2.5 1.5 2.0 -- -- -- -- -- --

13 2.5 1.5 2.0 -- -- -- -- -- --

14 2.5 1.5 2.0 -- -- -- -- -- --

15 3.0 1.5 2.0 -- -- -- -- -- --

16 3.0 1.5 2.0 -- -- -- -- -- --

17 3.0 2.0 2.0 -- -- -- 3.5 2.0 2.5

18 3.5 2.0 2.5 -- -- -- 8.0 2.0 3.5

19 3.5 1.5 2.5 -- -- -- 6.5 1.5 3.0

20 3.0 1.5 2.0 2.0 1.0 1.5 5.0 2.0 2.5

21 3.0 1.5 2.0 2.0 1.0 1.5 7.0 2.0 3.0

22 2.5 1.5 2.0 3.0 1.5 2.0 4.5 2.0 3.0

23 2.5 2.0 2.0 2.5 1.0 2.0 4.5 2.5 3.0

24 3.0 2.0 2.0 3.0 1.5 2.0 5.0 2.5 3.0

25 3.0 2.0 2.0 3.5 1.5 2.5 4.0 2.5 3.0

26 3.0 2.0 2.5 3.5 1.5 2.5 6.0 3.5 4.0

27 3.0 2.0 2.5 4.0 2.0 2.5 8.0 3.5 5.5

28 3.0 2.0 2.5 4.0 2.5 3.0 8.0 3.0 4.5

29 3.5 2.0 2.5 -- -- -- 11 3.0 5.0

30 3.0 2.5 2.5 -- -- -- 7.5 4.0 5.5

31 -- -- -- -- -- -- -- -- --

Month1 3.5 1.5 2.2 4.0 1.0 2.2 11 1.5 3.6

1

For months with missing daily values, the means are calculated using available values.
66 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 Willow Creek at Warm Springs 

Creek at Warm Springs, Montana (12323770), April through September 2013.

[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 -- -- -- 6.5 2.0 3.5 4.5 3.0 3.5

2 -- -- -- 4.5 2.0 3.0 5.0 3.0 4.0

3 -- -- -- 3.0 1.5 2.0 6.5 3.5 4.5

4 -- -- -- 3.0 1.5 2.0 5.0 3.0 4.0

5 -- -- -- 3.0 1.0 2.0 5.0 3.0 3.5

6 -- -- -- 3.0 1.5 2.0 5.0 3.0 4.0

7 -- -- -- 4.5 1.5 2.5 8.0 4.0 5.5

8 -- -- -- 3.0 1.0 2.0 16 4.0 10

9 -- -- -- 3.0 1.5 2.0 8.0 4.0 5.5

10 -- -- -- 4.5 2.0 2.5 7.5 3.5 5.0

11 4.5 2.5 3.5 5.0 2.0 3.0 6.5 3.5 4.5

12 3.5 2.5 3.0 4.0 2.0 3.0 7.5 3.5 5.0

13 3.5 2.5 3.0 32 3.5 16 14 4.0 7.5

14 4.0 2.5 3.0 47 9.0 32 11 4.5 7.5

15 4.0 3.0 3.5 -- -- -- 11 5.5 7.0

16 5.0 3.5 4.0 -- -- -- 7.5 4.5 6.0

17 6.5 3.5 4.5 -- -- -- -- -- --

18 5.0 3.5 4.0 -- -- -- 7.0 4.0 5.5

19 4.5 3.0 3.5 -- -- -- 7.0 4.0 5.5

20 4.5 3.0 3.5 -- -- -- 6.5 3.0 4.5

21 4.5 3.0 3.5 4.5 3.5 4.0 5.5 3.0 4.0

22 5.0 3.0 3.5 6.0 4.0 5.0 5.0 3.0 4.0

23 4.5 2.5 3.5 20 6.0 11 5.0 2.5 3.5

24 4.0 2.5 3.0 10 4.0 6.0 4.5 2.0 3.0

25 3.5 2.5 3.0 5.5 3.5 4.5 4.0 3.0 3.5

26 3.5 2.0 2.5 5.5 3.0 4.0 4.0 2.5 3.0

27 3.0 1.5 2.0 9.0 3.5 5.0 4.5 2.0 3.0

28 3.0 2.0 2.5 16 4.5 9.5 5.0 2.5 3.5

29 4.0 2.0 2.5 11 5.5 8.0 4.5 2.5 3.5

30 6.0 2.0 3.5 8.0 5.0 6.5 5.5 2.5 4.0

31 -- -- -- 6.0 3.5 4.5 -- -- --

Month1 6.5 1.5 3.2 47 1.0 5.8 16 2.0 4.7
Data 67

Table 11. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Warm Springs Creek at Warm 

Springs, Montana (12323770), April through September 2013.—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]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

July August September

1 4.5 1.5 3.0 1.0 0.5 0.5 3.5 2.0 2.5

2 4.0 2.0 3.0 2.0 0.5 1.0 3.0 2.0 2.5

3 4.0 2.0 3.0 -- -- -- 6.5 2.0 2.5

4 3.5 2.0 2.5 -- -- -- 6.0 1.5 2.5

5 3.5 2.0 3.0 -- -- -- 3.5 1.5 2.0

6 4.0 2.0 3.0 -- -- -- 5.5 1.5 2.5

7 4.0 2.0 2.5 -- -- -- 3.0 1.0 2.0

8 3.5 2.0 2.5 -- -- -- 2.5 1.0 1.5

9 3.5 1.5 2.5 -- -- -- 2.5 1.0 1.5

10 3.0 1.5 2.0 -- -- -- 2.5 1.0 1.5

11 3.0 1.5 2.0 -- -- -- 2.0 1.0 1.5

12 3.5 1.5 2.0 -- -- -- 2.5 1.0 1.5

13 3.0 1.5 2.0 -- -- -- 2.0 0.5 1.0

14 3.0 1.5 2.0 -- -- -- 2.0 0.5 1.5

15 3.5 1.5 2.0 -- -- -- 2.0 0.5 1.0

16 3.0 1.5 2.0 -- -- -- 1.5 0.5 1.0

17 6.0 1.5 2.5 -- -- -- 2.5 0.5 1.5

18 7.0 1.5 3.0 -- -- -- 3.0 1.5 2.0

19 2.5 1.0 1.5 -- -- -- 2.5 1.0 1.5

20 2.5 1.0 1.5 3.5 2.0 2.5 2.0 1.0 1.5

21 2.5 1.0 1.5 3.5 2.0 2.5 2.0 1.0 1.0

22 2.0 0.5 1.0 3.0 2.5 2.5 2.0 1.0 1.0

23 1.5 0.5 1.0 3.5 2.5 3.0 2.0 1.0 1.5

24 1.0 0.5 1.0 3.5 2.0 3.0 3.5 1.0 1.5

25 1.0 0.5 0.5 3.5 2.5 2.5 3.5 1.0 2.0

26 1.0 0.5 1.0 3.0 2.0 2.5 5.0 1.5 2.5

27 1.0 0.5 0.5 3.0 2.0 2.5 3.0 1.0 2.0

28 1.0 0.5 0.5 4.0 2.0 3.0 2.5 1.0 1.5

29 1.0 0.5 0.5 4.0 2.5 3.0 3.0 1.5 2.0

30 1.0 0.5 0.5 3.5 2.5 2.5 4.5 1.5 2.5

31 0.5 0.5 0.5 3.5 2.5 2.5 -- -- --

Month1 7.0 0.5 1.8 4.0 0.5 2.4 6.5 0.5 1.8

1

For months with missing daily values, the means are calculated using available values.
68 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 Willow Creek at Lost Creek near 

Anaconda, Montana (12323840), March through September 2013.

[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

March April May

1 -- -- -- 3.5 2.0 2.5 3.5 1.5 2.0

2 -- -- -- 4.0 2.0 2.5 3.0 1.5 2.0

3 -- -- -- 3.0 2.0 2.5 3.0 1.5 2.0

4 -- -- -- 3.5 2.0 2.5 4.0 1.5 2.5

5 -- -- -- 5.5 2.0 3.0 5.5 1.5 3.0

6 -- -- -- 3.5 2.0 2.5 11 2.0 4.0

7 -- -- -- 3.0 2.0 2.5 17 2.0 3.5

8 -- -- -- -- -- -- 6.0 1.5 3.0

9 -- -- -- 20 2.0 5.5 4.5 1.5 2.5

10 -- -- -- 4.0 2.0 2.5 5.5 1.5 2.5

11 -- -- -- 3.5 2.0 2.5 8.0 2.0 4.0

12 -- -- -- 2.5 1.5 2.0 12 1.5 3.5

13 -- -- -- 3.5 2.0 2.5 8.5 2.0 4.0

14 -- -- -- 3.0 1.5 2.0 15 2.5 6.0

15 -- -- -- 4.5 1.5 2.5 5.0 2.0 3.0

16 -- -- -- 7.5 1.5 3.0 4.0 1.5 2.5

17 -- -- -- 10 1.5 4.0 8.0 1.5 3.0

18 -- -- -- 10 2.0 4.0 6.0 1.5 2.5

19 -- -- -- 3.0 1.5 2.0 4.5 1.5 2.0

20 -- -- -- 3.0 1.5 2.0 4.5 1.5 2.5

21 -- -- -- 2.5 1.5 2.0 2.5 1.0 1.5

22 -- -- -- 6.0 1.5 2.5 16 1.5 2.5

23 -- -- -- 5.5 1.5 2.5 35 7.0 11

24 -- -- -- 3.0 1.5 2.0 8.0 3.5 5.5

25 -- -- -- 3.0 1.5 2.0 5.0 2.0 3.0

26 -- -- -- 3.5 1.5 2.5 47 2.0 5.0

27 -- -- -- 9.0 2.5 3.5 14 4.5 7.5

28 -- -- -- 4.5 2.0 3.0 91 9.5 25

29 3.5 2.0 2.5 4.5 2.0 3.0 15 7.5 11

30 3.5 1.5 2.5 15 1.5 3.0 12 4.5 6.5

31 3.5 2.0 2.5 -- -- -- 6.5 3.5 4.5

Month1 3.5 1.5 2.5 20 1.5 2.7 91 1.0 4.6
Data 69

Table 12. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Lost Creek near Anaconda, 

Montana (12323840), March through September 2013.—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]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

June July August

1 8.0 3.0 4.0 1.5 0.5 1.0 9.5 0.5 1.5

2 7.0 3.0 4.0 1.5 0.5 1.0 3.5 0.5 1.0

3 9.0 3.0 4.0 1.5 0.5 1.0 1.5 0.5 0.5

4 6.5 2.5 3.5 2.0 0.5 1.0 1.5 0.5 0.5

5 5.5 2.0 3.5 1.5 0.5 1.0 1.0 <0.5 0.5

6 5.0 2.5 3.5 1.5 0.5 1.0 68 <0.5 4.0

7 7.5 2.5 4.0 2.0 0.5 1.0 24 3.5 6.5

8 5.5 2.5 4.0 17 0.5 1.5 27 2.5 4.5

9 11 3.5 4.5 1.5 0.5 1.0 5.0 2.5 3.0

10 7.5 2.0 4.0 1.0 0.5 0.5 4.5 2.0 2.5

11 27 2.5 6.0 1.0 0.5 0.5 4.5 2.0 2.5

12 5.5 2.5 3.5 1.5 0.5 1.0 3.0 1.5 2.0

13 9.0 3.5 5.0 2.0 0.5 1.0 4.0 1.5 2.5

14 6.0 2.0 3.0 2.0 0.5 1.0 2.5 1.5 2.0

15 3.0 1.5 2.0 2.5 0.5 1.0 2.5 1.5 2.0

16 2.5 1.5 1.5 3.5 0.5 1.0 3.0 1.5 2.0

17 3.0 1.5 2.0 40 0.5 2.5 2.5 1.5 2.0

18 4.5 1.0 1.5 40 2.5 6.0 3.0 1.5 2.0

19 3.0 1.0 1.5 3.0 1.0 2.0 3.0 1.5 2.0

20 2.5 1.0 1.5 2.0 1.0 1.5 2.5 1.5 2.0

21 1.5 1.0 1.0 5.5 1.0 2.0 4.0 1.5 2.0

22 2.0 1.0 1.5 2.5 1.5 1.5 6.5 1.5 2.0

23 2.0 1.0 1.5 2.0 1.0 1.5 2.0 1.0 1.5

24 7.5 1.0 1.5 2.0 1.0 1.5 2.0 1.0 1.0

25 4.0 1.0 1.5 2.0 1.0 1.0 210 1.0 14

26 1.5 1.0 1.0 1.5 1.0 1.0 52 1.5 4.0

27 2.5 1.0 1.0 2.0 0.5 1.0 3.0 1.0 1.5

28 2.0 1.0 1.0 1.5 1.0 1.0 1.5 1.0 1.0

29 1.5 0.5 1.0 1.5 0.5 1.0 2.5 1.0 1.0

30 1.5 0.5 1.0 1.5 0.5 1.0 2.0 1.0 1.0

31 -- -- -- 1.5 0.5 1.0 2.0 0.5 1.0

Month1 27 0.5 2.6 40 0.5 1.3 210 <0.5 2.4
70 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), March through September 2013.—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]

Day

Maximum Minimum Mean

September

1 1.5 0.5 1.0

2 2.0 0.5 1.0

3 1.5 0.5 1.0

4 1.5 0.5 0.5

5 15 0.5 1.0

6 160 8.5 29

7 10 4.5 7.0

8 6.5 3.5 4.5

9 5.0 3.0 3.5

10 3.5 2.5 3.0

11 4.0 2.5 3.0

12 3.0 2.5 2.5

13 4.5 2.5 2.5

14 3.0 2.5 2.5

15 7.0 2.5 3.0

16 3.5 2.5 3.0

17 3.0 2.0 2.5

18 2.5 1.0 1.5

19 1.0 1.0 1.0

20 3.5 1.0 1.5

21 2.0 1.0 1.5

22 1.5 1.0 1.5

23 1.5 1.0 1.0

24 4.5 1.0 1.5

25 5.0 1.0 1.5

26 10 1.5 3.5

27 2.0 1.5 1.5

28 4.5 1.5 2.0

29 31 2.0 5.5

30 9.5 2.0 3.0

31 -- -- --

Month1 160 0.5 3.2

1

For months with missing daily values, the means are calculated using 

available values.
Data 71

Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana.[hh, hour; mm, minute; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligrams per liter; CaCO3, calcium carbonate; μg/L, micrograms per liter; mm, millimeter; <, less than laboratory 

reporting level; --, no data]

Site 

number 

(fig. 1)

Site name Date Time, hhmm

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3)

Calcium, 

filtered 

(mg/L)

Magnesium 

filtered 

(mg/L)

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered

(mg/L)

Alkalinity,

filtered, 

lab

(mg/L)

12323700 Mill Creek at Opportunity 08/12/2013 1530 <2.0 79.2 21.9 5.97 0.82 4.98 79.5

08/12/2013 1535 <2.0 80.7 22.4 6.05 0.81 4.80 79.4

12323750 Silver Bow Creek at Warm Springs 07/16/2013 0720 -- 198 55.5 14.5 -- -- --

07/16/2013 0725 -- 204 57.3 14.7 -- -- --

12323840 Lost Creek near Anaconda 04/08/2013 1420 <2.0 107 32.0 6.62 1.30 2.92 103

04/08/2013 1425 <2.0 108 32.4 6.67 1.28 2.85 103

12324200 Clark Fork at Deer Lodge 05/21/2013 1325 -- 200 58.5 13.2 -- -- --

05/21/2013 1330 -- 199 58.1 13.2 -- -- --

12324400 Clark Fork above Little Blackfoot, near Garrison 03/13/2013 1440 -- 219 63.0 15.1 -- -- --

03/13/2013 1445 -- 222 63.9 15.1 -- -- --

12324680 Clark Fork at Goldcreek 11/14/2012 1525 -- 211 62.1 13.6 -- -- --

11/14/2012 1530 -- 216 64.3 13.6 -- -- --

12334550 Clark Fork at Turah Bridge, near Bonner 06/05/2013 0955 -- 110 30.7 7.99 -- -- --

06/05/2013 1000 -- 107 29.8 7.85 -- -- --

12340500 Clark Fork above Missoula 06/19/2013 1345 -- 101 27.1 8.08 -- -- --

06/19/2013 1350 -- 101 27.0 8.10 -- -- --
72 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana.—Continued [hh, hour; mm, minute; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligrams per liter; CaCO3, calcium carbonate; μg/L, micrograms per liter; mm, millimeter; <, less than laboratory reporting level; --, no data] Site number (fig. 1) Site name Date Time, hhmm Chloride, filtered (mg/L) Flouride, filtered (mg/L) Silica, filtered (mg/l) Sulfate, filtered (mg/L) Cadmium, filtered (μg/L) Cadmium, unfiltered recoverable (μg/L) Copper, filtered (μg/L) Copper, unfiltered recoverable (μg/L) 12323700 Mill Creek at Opportunity 08/12/2013 1530 0.48 0.37 11.4 15.2 0.035 0.039 1.7 2.3 08/12/2013 1535 0.48 0.37 11.2 15.3 0.032 0.035 1.6 2.2 12323750 Silver Bow Creek at Warm Springs 07/16/2013 0720 -- -- -- -- 0.026 0.037 3.0 3.2 07/16/2013 0725 -- -- -- -- 0.029 0.036 2.4 3.1 12323840 Lost Creek near Anaconda 04/08/2013 1420 0.73 0.47 11.3 10.8 <0.016 0.017 1.2 3.1 04/08/2013 1425 0.73 0.47 11.3 10.8 <0.016 0.019 <0.80 2.8 12324200 Clark Fork at Deer Lodge 05/21/2013 1325 -- -- -- -- 0.035 0.065 5.7 13.2 05/21/2013 1330 -- -- -- -- 0.035 0.073 5.7 13.0 12324400 Clark Fork above Little Blackfoot, near Garrison 03/13/2013 1440 -- -- -- -- 0.066 0.136 5.7 24.5 03/13/2013 1445 -- -- -- -- 0.057 0.156 5.5 28.8 12324680 Clark Fork at Goldcreek 11/14/2012 1525 -- -- -- -- 0.023 0.106 3.1 18.5 11/14/2012 1530 -- -- -- -- 0.026 0.097 3.1 18.7 12334550 Clark Fork at Turah Bridge, near Bonner 06/05/2013 0955 -- -- -- -- 0.017 0.200 2.8 27.8 06/05/2013 1000 -- -- -- -- 0.018 0.195 3.0 29.7 12340500 Clark Fork above Missoula 06/19/2013 1345 -- -- -- -- <0.016 0.020 1.4 2.5 06/19/2013 1350 -- -- -- -- <0.016 0.022 1.1 2.6
Data 73

Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana.—Continued[hh, hour; mm, minute; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligrams per liter; CaCO3, calcium carbonate; μg/L, micrograms per liter; mm, millimeter; <, less than laboratory 

reporting level; --, no data]

Site 

number 

(fig. 1)

Site name Date Time, hhmm 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)

12323700 Mill Creek at Opportunity 08/12/2013 1530 40.8 62.3 0.086 0.18 4.73 5.2

08/12/2013 1535 39.4 61.3 0.085 0.18 5.04 5.2

12323750 Silver Bow Creek at Warm Springs 07/16/2013 0720 24.3 120 0.107 0.50 84.2 149

07/16/2013 0725 34.1 118 0.124 0.50 87.7 151

12323840 Lost Creek near Anaconda 04/08/2013 1420 4.6 70.5 0.045 0.29 1.68 3.2

04/08/2013 1425 5.3 88.4 <0.025 0.34 1.78 4.0

12324200 Clark Fork at Deer Lodge 05/21/2013 1325 18.7 156 0.111 1.10 53.1 81.9

05/21/2013 1330 17.9 157 0.110 1.11 53.6 81.0

12324400 Clark Fork above Little Blackfoot, near Garrison 03/13/2013 1440 8.2 363 0.094 2.54 46.8 84.5

03/13/2013 1445 12.7 379 0.098 2.60 46.9 85.5

12324680 Clark Fork at Goldcreek 11/14/2012 1525 5.2 335 0.058 2.29 13.9 79.5

11/14/2012 1530 <4.0 329 0.046 2.27 15.2 78.5

12334550 Clark Fork at Turah Bridge, near Bonner 06/05/2013 0955 23.9 757 0.169 5.18 6.89 110

06/05/2013 1000 22.9 747 0.165 4.96 7.33 110

12340500 Clark Fork above Missoula 06/19/2013 1345 14.6 118 0.036 0.34 4.49 14.8

06/19/2013 1350 14.6 130 0.049 0.34 4.42 18.7
74 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana.—Continued [hh, hour; mm, minute; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligrams per liter; CaCO3, calcium carbonate; μg/L, micrograms per liter; mm, millimeter; <, less than laboratory reporting level; --, no data] Site number (fig. 1) Site name Date Time, hhmm Zinc, filtered (μg/L) Zinc, unfiltered recoverable (μg/L) Arsenic, filtered (μg/L) Arsenic, unfiltered recoverable (μg/L) Organic carbon, filtered (mg/L) Sediment suspended (percent finer than 0.062 mm) Sediment, suspended (mg/L) 12323700 Mill Creek at Opportunity 08/12/2013 1530 <1.4 <3.0 23.6 23.1 1.33 88 1 08/12/2013 1535 <1.4 <3.0 22.9 22.7 1.31 83 1 12323750 Silver Bow Creek at Warm Springs 07/16/2013 0720 <1.4 3.1 27.8 28.3 -- 92 2 07/16/2013 0725 1.6 3.1 26.8 28.2 -- 95 2 12323840 Lost Creek near Anaconda 04/08/2013 1420 <1.4 <3.0 2.0 2.1 1.09 51 3 04/08/2013 1425 <1.4 <3.0 1.9 2.2 1.15 58 3 12324200 Clark Fork at Deer Lodge 05/21/2013 1325 1.6 8.5 13.4 14.2 -- 92 5 05/21/2013 1330 <1.4 8.5 13.2 14.2 -- 90 7 12324400 Clark Fork above Little Blackfoot, near Garrison 03/13/2013 1440 3.8 21.4 9.3 10.9 -- 75 18 03/13/2013 1445 3.6 22.3 9.2 12.3 -- 69 20 12324680 Clark Fork at Goldcreek 11/14/2012 1525 2.8 17.6 8.5 9.1 -- 88 16 11/14/2012 1530 2.8 18.1 8.7 9.5 -- 86 16 12334550 Clark Fork at Turah Bridge, near Bonner 06/05/2013 0955 4.0 37.6 5.9 8.4 -- 88 38 06/05/2013 1000 4.6 38.1 5.9 8.9 -- 87 37 12340500 Clark Fork above Missoula 06/19/2013 1345 <1.4 <9.0 2.4 2.2 -- 85 7 06/19/2013 1350 <1.4 3.6 2.4 2.4 -- 85 7
Data 75

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 0.80 1.8 Yes

Magnesium, filtered, mg/L 8 0.07 0.62 Yes

Arsenic, filtered, μg/L 8 0.32 2.7 Yes

Arsenic, unfiltered recoverable, μg/L 8 0.40 3.2 Yes

Cadmium, filtered, μg/L 8 0.00 9.7 Yes

Cadmium, unfiltered recoverable, μg/L 8 0.01 7.8 Yes

Copper, filtered, μg/L 8 0.27 9.2 Yes

Copper, unfiltered recoverable, μg/L 8 1.2 9.6 Yes

Iron, filtered, μg/L 8 2.9 16 Yes

Iron, unfiltered recoverable, μg/L 8 7.3 2.9 Yes

Lead, filtered, μg/L 8 0.01 12 Yes

Lead, unfiltered recoverable, μg/L 8 0.06 3.8 Yes

Manganese, filtered, μg/L 8 0.95 3.5 Yes

Manganese, unfiltered recoverable, μg/L 8 1.2 1.8 Yes

Zinc, filtered, μg/L 8 0.36 19 Yes

Zinc, unfiltered recoverable, μg/L 8 0.36 3.0 Yes

Sediment, suspended, percent finer than 0.062 mm 8 2.8 3.4 Yes

Sediment, suspended, mg/L 8 0.75 6.6 Yes

1

Standard deviation is calculated using one-half of the laboratory reporting level for censored values (less than the laboratory reporting level).

2

The data-quality objective for an acceptable level of precision is a maximum relative standard deviation of 20 percent for field replicate analyses (table 3).
76 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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 deviation

 (listed units)

Relative 

standard deviation 

(percent)

Within limits1

of data-quality 

objective

Calcium, filtered, mg/L 8 0.32 0.72 Yes

Magnesium, filtered, mg/L 8 0.17 1.6 Yes

Arsenic, filtered, μg/L 8 0.05 0.42 Yes

Arsenic, unfiltered recoverable, μg/L 8 0.43 3.5 Yes

Cadmium, filtered, μg/L 8 0.00 7.4 Yes

Cadmium, unfiltered recoverable, μg/L 8 0.02 19 Yes

Copper, filtered, μg/L 8 0.08 2.7 Yes

Copper, unfiltered recoverable, μg/L 8 0.68 5.5 Yes

Iron, filtered, μg/L 8 1.5 8.6 Yes

Iron, unfiltered recoverable, μg/L 8 2.2 0.88 Yes

Lead, filtered, μg/L 8 0.00 2.7 Yes

Lead, unfiltered recoverable, μg/L 8 0.03 2.0 Yes

Manganese, filtered, μg/L 8 0.34 1.2 Yes

Manganese, unfiltered recoverable, μg/L 8 0.68 1.0 Yes

Zinc, filtered, μg/L 8 0.11 5.3 Yes

Zinc, unfiltered recoverable, μg/L 8 0.32 2.6 Yes

1

The data-quality objective for an acceptable level of precision is a maximum relative standard deviation of 20 percent for laboratory replicate analyses 

(table 3).

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, 

in percent

Mean spike 

recovery, 

in percent

Within limits1

of data-quality 

objective

Arsenic, filtered, μg/L 5 93.1–103 98.0 Yes

Arsenic, unfiltered recoverable, μg/L 5 96.0–103 99.3 Yes

Cadmium, filtered, μg/L 5 92.4–100 96.3 Yes

Cadmium, unfiltered recoverable, μg/L 5 92.9–100 96.6 Yes

Copper, filtered, μg/L 5 87.0–97.9 92.4 Yes

Copper, unfiltered recoverable, μg/L 5 92.6–100 96.3 Yes

Iron, filtered, μg/L 5 95.5–111 103 Yes

Iron, unfiltered recoverable, μg/L 5 98.2–112 105 Yes

Lead, filtered, μg/L 5 92.3–103 97.5 Yes

Lead, unfiltered recoverable, μg/L 5 97.1–103 99.9 Yes

Manganese, filtered, μg/L 5 92.3–104 98.1 Yes

Manganese, unfiltered recoverable, μg/L 5 94.8–102 98.5 Yes

Zinc, filtered, μg/L 5 90.9–106 98.6 Yes

Zinc, unfiltered recoverable, μg/L 5 91.7–98.7 95.2 Yes

1

The data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).
Data 77

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, 

in percent

Mean spike 

recovery, 

in percent

Within limits1

of data-quality 

objective

Arsenic, filtered, μg/L 5 91.2–108 99.5 Yes

Arsenic, unfiltered recoverable, μg/L 5 91.0–98.8 94.9 Yes

Cadmium, filtered, μg/L 5 90.4–99.3 94.8 Yes

Cadmium, unfiltered recoverable, μg/L 5 87.0–95.7 91.3 Yes

Copper, filtered, μg/L 5 86.0–95.8 90.9 Yes

Copper, unfiltered recoverable, μg/L 5 87.5–92.4 90.0 Yes

Iron, filtered, μg/L 5 94.8–110 102 Yes

Iron, unfiltered recoverable, μg/L 5 92.6–110 101 Yes

Lead, filtered, μg/L 5 92.8–108 101 Yes

Lead, unfiltered recoverable, μg/L 5 92.3–101 96.7 Yes

Manganese, filtered, μg/L 5 95.4–99.0 97.2 Yes

Manganese, unfiltered recoverable, μg/L 5 84.9–101 93.0 Yes

Zinc, filtered, μg/L 5 92.0–107 99.5 Yes

Zinc, unfiltered recoverable, μg/L 5 79.5–88.7 84.1 Yes

1

The data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).
78 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana Table 18. Analyses of field blanks for water samples. [hh, hours; mm, minutes; μS/cm, microsiemens per centimeter at 25 degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligrams per liter; <, less than laboratory reporting level; --, no data; μg/L, micrograms per liter] Date Time, hhmm pH, onsite (standard units) Specific conductance, onsite (μS/cm) Turbidity, unfiltered, lab (NTRU) Calcium, filtered (mg/L) Magnesium, filtered (mg/L) Potassium, filtered (mg/L) Sodium, filtered (mg/L) Chloride, filtered (mg/L) 11/13/2012 1305 5.4 2 <2.0 <0.022 <0.011 -- -- --

103/11/2013 0800 5.6 2 -- <0.022 <0.011 -- -- --

04/10/2013 1400 5.6 2 -- <0.022 <0.011 -- -- --

05/20/2013 1455 5.3 2 <2.0 <0.022 <0.011 <0.03 <0.06 <0.06

06/04/2013 1235 5.4 2 -- <0.022 <0.011 -- -- --

06/19/2013 0915 5.6 2 -- <0.022 <0.011 -- -- --

07/16/2013 0845 5.5 2 -- <0.022 <0.011 -- -- --

08/13/2013 0815 5.5 2 -- <0.022 <0.011 -- -- --

Date Time, hhmm Fluoride, filtered (mg/L) Silica, filtered (mg/L) Sulfate, filtered (mg/L) Cadmium, filtered (μg/L) Cadmium, unfiltered recoverable (μg/L) Copper, filtered (μg/L) Copper, unfiltered recoverable (μg/L) Iron, filtered (μg/L) Iron, unfiltered recoverable (μg/L)

11/13/2012 1305 -- -- -- <0.016 <0.016 <0.80 <0.70 <4.0 <4.6

103/11/2013 0800 -- -- -- <0.016 <0.016 <0.80 <0.70 <4.0 <4.6

04/10/2013 1400 -- -- -- <0.016 <0.016 <0.80 <0.70 <4.0 <4.6

05/20/2013 1455 <0.01 <0.018 <0.09 <0.016 <0.016 <0.80 <0.70 5.2 <4.6

06/04/2013 1235 -- -- -- <0.016 <0.016 <0.80 <0.70 5.9 <4.6

06/19/2013 0915 -- -- -- <0.016 <0.016 <0.80 <0.70 4.4 <4.6

07/16/2013 0845 -- -- -- <0.016 <0.016 1.0 <0.70 <4.0 <4.6

08/13/2013 0815 -- -- -- <0.016 <0.016 <0.80 <0.70 <4.0 <4.6
Data 79

Table 18. Analyses of field blanks for water samples.—Continued[hh, hours; mm, minutes; μS/cm, microsiemens per centimeter at 25 degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligrams per liter; <, less than laboratory reporting level; --, no data; μg/L, micrograms per liter]

Date Time, hhmm 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) Arsenic, filtered (μg/L) Arsenic, unfiltered recoverable (μg/L) Organic carbon, filtered (mg/L)

11/13/2012 1305 <0.025 <0.04 0.33 <0.4 <1.4 <3.0 <0.04 <0.28 --

103/11/2013 0800 <0.025 <0.04 <0.15 <0.4 <1.4 <3.0 <0.04 <0.28 --

04/10/2013 1400 <0.025 <0.04 0.24 <0.4 <1.4 <3.0 <0.04 <0.28 --

05/20/2013 1455 <0.025 <0.04 0.28 <0.4 <1.4 <3.0 <0.04 <0.28 <0.2306/04/2013 1235 <0.025 <0.04 0.62 <0.4 <1.4 <3.0 <0.04 <0.28 --

06/19/2013 0915 <0.025 <0.04 0.34 <0.4 <1.4 <3.0 <0.04 <0.28 --

07/16/2013 0845 <0.025 <0.04 0.54 <0.4 <1.4 <3.0 <0.04 <0.28 --

08/13/2013 0815 <0.025 <0.04 0.15 <0.4 <1.4 <3.0 <0.04 <0.28 --

1Annual office equipment blank collected before any equipment was used in the field.
80 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana Table 19. Bed-sediment data for the Clark Fork Basin, Montana, August 2013. [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 mean of all replicate aliquot analyses from each composite sample. μg/g, micrograms per gram of dry sample weight; <, less than laboratory reporting level] Site number (fig. 1) Site name Number of composite samples Concentration (μg/g) Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc 12323600 Silver Bow Creek at Opportunity 3 51 14.8 25.9 882 30,200 137 3,910 14.8 2,270 12323750 Silver Bow Creek at Warm Springs 3 136 5.0 15.3 255 26,300 59 6,470 12.8 676 12323800 Clark Fork near Galen 3 156 5.5 22.8 1,250 32,300 106 4,280 15.5 939 461415112450801 Clark Fork below Lost Creek, near Galen 

3 108 5.2 22.0 1,540 29,600 145 2,910 12.1 1,050

461559112443301 Clark Fork at county bridge, near 

Racetrack 

3 69 4.6 22.8 978 26,300 109 2,250 12.3 911

461903112440701 Clark Fork at Dempsey Creek 

diversion, near Racetrack 

3 103 7.2 18.9 1,350 25,400 106 3,520 11.8 1,090

12324200 Clark Fork at Deer Lodge 3 76 3.7 27.7 981 28,500 105 1,920 14.8 869

12324400 Clark Fork above Little Blackfoot 

River, near Garrison

3 57 4.1 19.9 773 20,400 92 2,660 10.6 850

12324680 Clark Fork at Goldcreek 3 25 3.4 20.2 480 17,500 54 1,580 9.3 566

12331800 Clark Fork near Drummond 3 17 2.0 9.2 183 14,800 27 912 4.8 380

12334550 Clark Fork at Turah Bridge, near 

Bonner 

3 17 1.5 20.8 213 15,500 37 591 9.5 448

12340000 Blackfoot River near Bonner 3 4 <0.15 14.5 18 15,900 10 634 10.4 55

12340500 Clark Fork above Missoula 3 13 1.3 13.2 141 14,700 28 1,420 9.8 376
Data 81

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; μg/g, micrograms per gram of dry sample weight; SRM, standard reference material (agricultural 

soils)]

Constituent Number of analyses Dilution 

ratio

Certified 

concentration 

(μg/g)

Mean SRM 

recovery

(percent)

95-percent 

confidence interval 

for SRM recovery 

(percent)

SRM sample 2709a

Arsenic 10 1:10 10.5 60.0 58.5–61.6

Cadmium 10 1:10 0.371 51.6 49.6–53.6

Chromium 10 1:10 130 58.1 56.7–59.5

Copper 10 1:10 33.9 70.8 68.5–73.1

Iron 10 1:10 33,600 85.4 84.1–86.8

Lead 10 1:10 17.3 56.5 55.7–57.3

Manganese 10 1:10 529 86.6 85.3–88.0

Nickel 10 1:10 85 80.4 79.6–81.3

Zinc 10 1:10 103 80.2 79.3–81.0

SRM sample 2711a

Arsenic 10 1:10 107 80.6 79.3–81.9

Cadmium 10 1:10 54.1 98.4 96.6–100

Chromium 10 1:10 52.3 47.8 46.5–49.1

Copper 10 1:10 140 95.7 93.0–98.4

Iron 10 1:10 28,200 80.7 78.9–82.5

Lead 10 1:10 1,400 94.3 92.5–96.0

Manganese 10 1:10 675 79.4 77.4–81.4

Nickel 10 1:10 21.7 79.3 78.1–80.5

Zinc 10 1:10 414 86.9 85.3–88.4
82 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana Table 21. Analyses of procedural blanks for bed-sediment samples. [Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to final volume of solution after addition of 0.6N (normal) hydrochloric acid used for reconstituting dried residue. 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 Manganese Nickel Zinc 12323600 Silver Bow Creek at Opportunity 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 12323750 Silver Bow Creek at Warm Springs 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 12323800 Clark Fork near Galen 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 461415112450801 Clark Fork below Lost Creek, near Galen 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 461559112443301 Clark Fork at county bridge, near Racetrack 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 12324200 Clark Fork at Deer Lodge 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 12324400 Clark Fork above Little Blackfoot River, near Garrison 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 12324680 Clark Fork at Goldcreek 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 12331800 Clark Fork near Drummond 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 12334550 Clark Fork at Turah Bridge, near Bonner 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 12340000 Blackfoot River near Bonner 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01 12340500 Clark Fork above Missoula 1:10 <0.002 <0.001 <0.003 <0.002 <0.117 <0.004 <0.003 <0.001 <0.01
Data 83

Table 22. Biological data for the Clark Fork Basin, Montana, August 2013.

[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] 

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 7.1 3.5 4.0 129 3,410 22.9 1,370 3.9 657

Hydropsyche spp. 1 6.3 4.0 4.1 151 3,630 26.3 1,790 4.1 805

12323750—Silver Bow Creek at Warm Springs

Claassenia sabulosa 1 5.0 0.5 0.6 66.4 300 1.5 922 0.6 340

Hydropsyche cockerelli 1 15.3 0.4 1.9 33.7 1,470 5.5 1,080 1.8 178

Hydropsyche occidentalis 1 14.8 0.4 2.0 29.6 1,490 6.0 1,260 1.8 197

12323800—Clark Fork near Galen

Hydropsyche cockerelli 2 19.8 1.9 2.7 142 2,270 14.7 2,400 3.0 277

Hydropsyche occidentalis 2 17.4 1.3 2.4 125 2,040 12.9 2,590 2.6 261

461415112450801—Clark Fork below Lost Creek, near Galen

Hydropsyche cockerelli 2 24.8 1.7 2.7 180 2,520 20.1 2,160 2.4 289

461559112443301—Clark Fork at county bridge, near Racetrack

Hydropsyche cockerelli 2 12.9 2.0 2.1 84.9 1,700 10.2 2,070 1.6 237

Hydropsyche occidentalis 1 12.8 1.4 2.2 89.3 1,470 11.1 2,540 1.9 281

461903112440701–Clark Fork at Dempsey Creek diversion, near Racetrack

Arctopsyche grandis 1 8.1 2.5 1.4 72.4 840 5.9 1,360 1.2 256

Claassenia sabulosa 1 3.8 1.5 1.2 87.2 485 3.4 1,260 1.0 394

Hydropsyche cockerelli 2 14.4 1.7 2.0 119 1,640 10.9 1,960 1.6 265

Hydropsyche occidentalis 1 11.3 1.5 1.6 106 1,290 8.2 1,800 1.4 250

12324200—Clark Fork at Deer Lodge

Arctopsyche grandis 1 7.3 2.6 1.9 88.6 1,000 8.9 1,440 1.7 257

Hydropsyche cockerelli 3 12.3 2.0 2.8 147 2,000 15.7 1,440 2.3 249

Hydropsyche occidentalis 2 11.1 1.3 2.8 131 1,930 14.1 1,500 2.3 259

12324400—Clark Fork above Little Blackfoot River, near Garrison

Arctopsyche grandis 2 3.6 1.3 1.0 44.2 431 4.5 720 0.7 233

Hydropsyche cockerelli 1 7.8 0.9 2.0 81.5 1,050 10.1 1,270 1.4 216

Hydropsyche occidentalis 1 6.4 1.3 2.3 85.7 1,220 8.8 1,220 1.9 290
84 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

12324680—Clark Fork at Goldcreek

Arctopsyche grandis 3 2.4 1.7 0.8 30.0 481 2.1 729 0.6 235

Claassenia sabulosa 1 1.0 0.5 0.6 60.0 170 0.9 192 0.6 327

Hydropsyche occidentalis 1 8.2 1.3 2.3 68.3 1,530 8.9 2,900 2.4 328

12331800—Clark Fork near Drummond

Arctopsyche grandis 2 2.0 1.4 0.9 25.7 305 3.1 690 0.6 268

Claassenia sabulosa 2 1.2 0.6 0.7 70.6 222 1.4 201 0.5 371

Hydropsyche cockerelli 1 4.8 0.6 1.7 41.9 899 7.4 1,320 1.2 221

Hydropsyche occidentalis 1 6.1 0.9 2.6 58.2 1,280 9.1 1,520 1.7 272

12334550—Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 2 3.5 0.9 1.5 26.0 546 3.8 790 1.1 228

Hydropsyche cockerelli 2 4.4 0.5 1.6 30.3 891 5.4 764 1.3 200

Hydropsyche occidentalis 1 7.3 1.0 3.4 65.5 1,930 10.3 1,260 2.9 371

12340000—Blackfoot River near Bonner

Arctopsyche grandis 2 2.2 0.3 1.5 17.9 823 1.2 343 1.4 169

Hydropsyche cockerelli 1 2.7 0.2 2.0 17.0 1,380 1.6 417 1.5 163

Hydropsyche occidentalis 2 2.0 0.2 1.9 19.0 1,320 1.7 481 1.6 185

12340500—Clark Fork above Missoula

Arctopsyche grandis 3 3.4 1.0 1.2 23.7 618 2.6 1,070 1.1 209

Claassenia sabulosa 2 1.2 0.6 0.7 52.9 293 0.9 189 0.5 339

Hydropsyche cockerelli 3 4.0 0.7 2.1 28.1 1,300 5.1 1,140 1.9 222

Hydropsyche occidentalis 1 4.2 0.7 2.4 30.8 1,460 5.8 1,360 2.0 250

Table 22. Biological data for the Clark Fork Basin, Montana, August 2013.—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] 
Data 85

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 21.6 110 108–112

Cadmium 12 26.7 98.9 95.1–103

Chromium 12 0.77 167 157–176

Copper 12 106 92.9 90.9–94.9

Iron 12 105 112 108–117

Lead 12 0.35 220 202–238

Manganese 12 13.6 96.8 94.0–99.6

Nickel 12 2.5 91.7 88.1–95.4

Zinc 12 180 104 99.2–108
86 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana 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 Manganese Nickel Zinc 12323600 Silver Bow Creek at Opportunity 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 12323750 Silver Bow Creek at Warm Springs 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 12323800 Clark Fork near Galen 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 461415112450801 Clark Fork below Lost Creek, near Galen 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 461559112443301 Clark Fork at county bridge, near Racetrack 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 12324200 Clark Fork at Deer Lodge 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 12324400 Clark Fork above Little Blackfoot River, near Garrison 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 12324680 Clark Fork at Goldcreek 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 12331800 Clark Fork near Drummond 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 12334550 Clark Fork at Turah Bridge, near Bonner 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 12340000 Blackfoot River near Bonner 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005 12340500 Clark Fork above Missoula 1:10 <0.003 <0.0004 <0.005 <0.002 <0.4 <0.005 <0.006 <0.002 <0.005
Data 87

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 2013.

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]

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 2013

Streamflow, instantaneous (ft3/s) 155 156 1.9 16 9.2

pH, onsite (standard units) 155 8.4 7.3 7.7 7.7

Specific conductance, onsite (μS/cm) 155 412 116 263 264

Temperature, water (oC) 155 17.5 1.0 8.0 8.0

Hardness, filtered (mg/L as CaCO3) 155 153 37.7 104 106

Calcium, filtered (mg/L) 155 42.9 10.6 29.7 30.0

Magnesium, filtered (mg/L) 155 11.1 2.71 7.24 7.29

Potassium, filtered (mg/L) 33 6.40 2.00 2.80 2.50

Sodium, filtered (mg/L) 33 18.0 6.40 10.6 10.7

Alkalinity, filtered, lab (mg/L) 5 124 74.8 98.0 87.2

Chloride, filtered (mg/L) 33 18.0 2.80 7.47 6.50

Fluoride, filtered (mg/L) 33 0.60 0.20 0.32 0.30

Silica, filtered (mg/L) 33 32.0 14.0 24.5 25.0

Sulfate, filtered (mg/L) 33 36.0 15.0 26.9 28.0

Cadmium, filtered (μg/L) 153 0.50 <0.04 2

0.04 0.02

Cadmium, unfiltered recoverable (μg/L) 155 0.11 <0.01 2

0.04 <1

Copper, filtered (μg/L) 154 10.0 <1.0 2

3.5 3.0

Copper, unfiltered recoverable (μg/L) 155 52.0 0.91 6.4 5.0

Iron, filtered (μg/L) 155 640 15 190 174

Iron, unfiltered recoverable (μg/L) 155 4,220 123 664 590

Lead, filtered (μg/L) 155 2.80 <0.02 2

0.18 0.04

Lead, unfiltered recoverable (μg/L) 155 47.0 <1.00 2

1.66 0.66

Manganese, filtered (μg/L) 155 144 14.2 44.4 38.8

Manganese, unfiltered recoverable (μg/L) 155 240 23.5 61.8 52.7

Zinc, filtered (μg/L) 153 11 <1.0 2

3.4 2.6

Zinc, unfiltered recoverable (μg/L) 155 130 <3.0 2

7.9 4.0

Arsenic, filtered (μg/L) 154 13.0 1.0 4.1 3.4

Arsenic, unfiltered recoverable (μg/L) 155 18.0 1.0 2

5.4 4.5

Organic carbon, filtered (mg/L) 5 4.96 1.40 3.27 3.85

Sediment, suspended (percent finer than 0.062 mm) 155 97 50 82 83

Sediment, suspended concentration (mg/L) 155 139 1 12 7

Sediment, suspended discharge (ton/d) 155 59 0.01 0.99 0.17
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

12323250—Silver Bow Creek below Blacktail Creek, at Butte

Period of record for water-quality data: March 1993–August 1995, December 1996–September 2013

Streamflow, instantaneous (ft3/s) 163 202 13 31 25

pH, onsite (standard units) 163 8.2 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 163 691 209 460 468

Temperature, water (oC) 163 20.0 1.0 10.2 10.0

Hardness, filtered (mg/L as CaCO3) 163 217 66.0 147 150

Calcium, filtered (mg/L) 163 62.7 19.0 41.9 42.4

Magnesium, filtered (mg/L) 163 16.1 4.51 10.4 10.7

Potassium, filtered (mg/L) 33 35.0 4.00 8.58 5.90

Sodium, filtered (mg/L) 33 66.0 12.0 25.6 25.0

Alkalinity, filtered, lab (mg/L) 5 102 66.9 81.8 72.4

Chloride, filtered (mg/L) 32 88.0 6.70 22.7 20.5

Fluoride, filtered (mg/L) 32 0.80 0.30 0.46 0.40

Silica, filtered (mg/L) 32 28.0 17.0 22.6 23.0

Sulfate, filtered (mg/L) 32 96.0 35.0 73.1 75.5

Cadmium, filtered (μg/L) 163 6.2 0.04 0.87 0.22

Cadmium, unfiltered recoverable (μg/L) 163 6.0 0.06 1.17 0.40

Copper, filtered (μg/L) 163 303 2.9 29.5 12.2

Copper, unfiltered recoverable (μg/L) 163 550 8.4 68.2 23.6

Iron, filtered (μg/L) 163 292 9.6 95.4 77.6

Iron, unfiltered recoverable (μg/L) 163 7,400 85 795 546

Lead, filtered (μg/L) 163 2.4 <0.5 2

0.43 0.24

Lead, unfiltered recoverable (μg/L) 163 250 0.61 10.5 2.69

Manganese, filtered (μg/L) 163 1,700 20.7 293 153

Manganese, unfiltered recoverable (μg/L) 163 1,600 25.9 333 188

Zinc, filtered (μg/L) 163 2,200 5.3 283 89.7

Zinc, unfiltered recoverable (μg/L) 163 2,200 20.5 343 128

Arsenic, filtered (μg/L) 163 13.4 2.3 6.0 6.0

Arsenic, unfiltered recoverable (μg/L) 163 45.0 3.0 9.8 8.3

Organic carbon, filtered (mg/L) 5 7.55 5.73 6.42 5.94

Sediment, suspended (percent finer than 0.062 mm) 162 98 42 83 85

Sediment, suspended concentration (mg/L) 162 405 2 20 9

Sediment, suspended discharge (ton/d) 162 70 0.08 2.3 0.62

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
Data 89

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 2013

Streamflow, instantaneous (ft3/s) 163 648 13 79 52

pH, onsite (standard units) 165 9.5 7.2 8.4 8.3

Specific conductance, onsite (μS/cm) 165 633 202 415 407

Temperature, water (oC) 165 24.0 -1.0 9.4 9.5

Hardness, filtered (mg/L as CaCO3) 165 240 60.2 149 148

Calcium, filtered (mg/L) 165 71.6 18.5 44.0 44.0

Magnesium, filtered (mg/L) 165 15.0 3.42 9.44 9.34

Potassium, filtered (mg/L) 37 16.0 2.85 4.95 4.20

Sodium, filtered (mg/L) 37 33.5 8.10 17.7 17.0

Alkalinity, filtered, lab (mg/L) 8 110 76.2 94.9 94.1

Chloride, filtered (mg/L) 36 36.0 3.20 12.7 11.5

Fluoride, filtered (mg/L) 36 0.80 0.20 0.42 0.40

Silica, filtered (mg/L) 36 28.0 9.56 20.7 21.0

Sulfate, filtered (mg/L) 36 190 32.0 66.2 62.2

Cadmium, filtered (μg/L) 164 41.0 <0.1 2

0.97 0.51

Cadmium, unfiltered recoverable (μg/L) 165 49.0 0.26 2

1.77 1.00

Copper, filtered (μg/L) 163 450 6.5 40.0 30.4

Copper, unfiltered recoverable (μg/L) 165 3,900 17 174 94.7

Iron, filtered (μg/L) 165 307 <3 2

48.5 27.5

Iron, unfiltered recoverable (μg/L) 164 24,100 196 1,470 764

Lead, filtered (μg/L) 165 5.1 <0.5 2

0.66 0.32

Lead, unfiltered recoverable (μg/L) 165 650 1.65 32.7 14.5

Manganese, filtered (μg/L) 165 9,300 30.3 367 279

Manganese, unfiltered recoverable (μg/L) 165 10,000 69.8 482 359

Zinc, filtered (μg/L) 164 13,000 11.2 250 124

Zinc, unfiltered recoverable (μg/L) 165 15,000 40.1 443 251

Arsenic, filtered (μg/L) 165 34.0 1.0 10.6 10.0

Arsenic, unfiltered recoverable (μg/L) 165 235 6.5 23.2 16.0

Organic carbon, filtered (mg/L) 5 6.05 3.70 4.99 5.19

Sediment, suspended (percent finer than 0.062 mm) 166 95 37 78 83

Sediment, suspended concentration (mg/L) 166 801 5 49 20

Sediment, suspended discharge (ton/d) 163 781 0.18 21 2.7

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
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

12323670—Mill Creek near Anaconda

Period of record for water-quality data: December 2004–September 2013

Streamflow, instantaneous (ft3/s) 71 309 7.4 62 30

pH, onsite (standard units) 72 8.6 7.5 8.0 8.0

Specific conductance, onsite (μS/cm) 72 213 56 132 132

Temperature, water (oC) 72 17.0 0.0 8.2 8.0

Turbidity, unfiltered, lab, (NTRU) 66 21 <2.0 2

2.5 <2.0

Hardness, filtered (mg/L as CaCO3) 72 98.0 23.7 57.6 57.1

Calcium, filtered (mg/L) 72 26.7 7.00 16.0 16.0

Magnesium, filtered (mg/L) 72 8.01 1.45 4.32 4.18

Cadmium, filtered (μg/L) 71 0.11 0.02 2

0.05 0.04

Cadmium, unfiltered recoverable (μg/L) 72 0.19 0.03 0.08 0.07

Copper, filtered (μg/L) 72 5.1 0.72 2.2 2.0

Copper, unfiltered recoverable (μg/L) 72 10.6 1.3 3.7 3.1

Iron, filtered (μg/L) 72 125 21.2 45.6 40.2

Iron, unfiltered recoverable (μg/L) 72 619 77.8 188 148

Lead, filtered (μg/L) 72 0.24 0.02 2

0.12 0.11

Lead, unfiltered recoverable (μg/L) 72 3.12 0.15 0.72 0.55

Manganese, filtered (μg/L) 72 12.0 3.1 5.8 5.6

Manganese, unfiltered recoverable (μg/L) 72 36.6 7.1 13.2 11.4

Zinc, filtered (μg/L) 72 4.3 <1.4 2

1.7 1.5

Zinc, unfiltered recoverable (μg/L) 72 9.2 1.0 2

3.0 2.4

Arsenic, filtered (μg/L) 72 32.9 7.3 16.2 14.9

Arsenic, unfiltered recoverable (μg/L) 72 34.8 7.8 17.4 15.6

Sediment, suspended (percent finer than 0.062 mm) 72 86 28 63 67

Sediment, suspended concentration (mg/L) 72 29 1 6 3

Sediment, suspended discharge (ton/d) 71 13 0.02 1.9 0.19

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
Data 91

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 2013

Streamflow, instantaneous (ft3/s) 86 261 0.43 37 12

pH, onsite (standard units) 88 8.3 7.5 8.0 8.0

Specific conductance, onsite (μS/cm) 88 242 59 148 152

Temperature, water (oC) 88 20.0 -0.1 9.1 9.0

Turbidity, unfiltered, lab (NTRU) 6 2.6 <2.0 2

1.5 <2.0

Hardness, filtered (mg/L as CaCO3) 88 112 24.0 63.5 65.0

Calcium, filtered (mg/L) 88 31.0 7.01 17.8 18.2

Magnesium, filtered (mg/L) 88 8.44 1.56 4.63 4.67

Potassium, filtered (mg/L) 6 0.83 0.48 0.65 0.60

Sodium, filtered (mg/L) 6 6.00 2.29 3.86 3.32

Alkalinity, filtered, lab (mg/L) 6 79.5 38.2 54.8 49.6

Chloride, filtered (mg/L) 6 0.57 0.22 0.36 0.30

Fluoride, filtered (mg/L) 6 0.40 0.31 0.36 0.37

Silica, filtered (mg/L) 6 13.5 9.47 11.4 11.5

Sulfate, filtered (mg/L) 6 17.8 5.01 10.2 8.21

Cadmium, filtered (μg/L) 88 0.13 0.02 0.06 0.06

Cadmium, unfiltered recoverable (μg/L) 88 0.86 0.03 0.13 0.09

Copper, filtered (μg/L) 88 6.1 1.0 2.8 2.4

Copper, unfiltered recoverable (μg/L) 88 38.8 1.5 6.2 3.9

Iron, filtered (μg/L) 88 93.8 15.9 45.5 41.2

Iron, unfiltered recoverable (μg/L) 88 1,960 44.3 285 140

Lead, filtered (μg/L) 88 0.35 <0.08 2

0.13 0.12

Lead, unfiltered recoverable (μg/L) 88 12.7 0.07 1.37 0.45

Manganese, filtered (μg/L) 88 32.8 2.1 6.9 5.1

Manganese, unfiltered recoverable (μg/L) 88 113 2.9 17.6 12.0

Zinc, filtered (μg/L) 87 7.7 <1.4 2

2.8 2.7

Zinc, unfiltered recoverable (μg/L) 88 41 <2.4 2

6.1 4.1

Arsenic, filtered (μg/L) 88 55.1 9.0 21.1 19.2

Arsenic, unfiltered recoverable (μg/L) 88 53.5 10.0 23.9 22.0

Organic carbon, filtered (mg/L) 6 2.66 1.33 2.02 2.05

Sediment, suspended (percent finer than 0.062 mm) 88 91 26 69 72

Sediment, suspended concentration (mg/L) 88 107 1 12 2

Sediment, suspended discharge (ton/d) 86 55 <0.01 2

3.4 0.09

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
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

12323710—Willow Creek near Anaconda

Period of record for water-quality data: December 2004–September 2013

Streamflow, instantaneous (ft3/s) 63 114 1.0 15 7.6

pH, onsite (standard units) 65 8.2 7.5 7.7 7.7

Specific conductance, onsite (μS/cm) 65 151 66 103 108

Temperature, water (oC) 65 15.5 0.0 7.1 7.0

Turbidity, unfiltered, lab (NTRU) 59 39 <2.0 2

5.4 2.8

Hardness, filtered (mg/L as CaCO3) 65 56.3 22.1 37.6 38.7

Calcium, filtered (mg/L) 65 18.3 7.56 12.6 13.0

Magnesium, filtered (mg/L) 65 2.60 0.78 1.51 1.47

Cadmium, filtered (μg/L) 63 0.05 <0.02 2

0.03 0.03

Cadmium, unfiltered recoverable (μg/L) 65 0.33 <0.04 2

0.06 0.05

Copper, filtered (μg/L) 65 4.2 0.82 2.1 2.0

Copper, unfiltered recoverable (μg/L) 65 16.8 1.0 3.7 3.0

Iron, filtered (μg/L) 65 277 28 84.7 68.6

Iron, unfiltered recoverable (μg/L) 65 2,380 85.7 358 226

Lead, filtered (μg/L) 65 0.37 0.03 2

0.15 0.15

Lead, unfiltered recoverable (μg/L) 65 7.96 0.10 0.89 0.49

Manganese, filtered (μg/L) 65 34.5 6.0 14.5 13.1

Manganese, unfiltered recoverable (μg/L) 65 99.9 12.8 26.5 23.3

Zinc, filtered (μg/L) 65 3.3 0.65 2

1.7 1.6

Zinc, unfiltered recoverable (μg/L) 65 17.8 <2.0 2

3.2 2.0

Arsenic, filtered (μg/L) 65 25.7 9.9 15.9 14.9

Arsenic, unfiltered recoverable (μg/L) 65 27.0 9.8 16.9 15.4

Sediment, suspended (percent finer than 0.062 mm) 65 97 25 75 80

Sediment, suspended concentration (mg/L) 65 195 1 16 5

Sediment, suspended discharge (ton/d) 63 50 <0.01 2

2.3 0.09

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
Data 93

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 2013

Streamflow, instantaneous (ft3/s) 88 116 4.5 17 8.7

pH, onsite (standard units) 88 9.0 7.6 8.1 8.1

Specific conductance, onsite (μS/cm) 88 371 116 269 289

Temperature, water (oC) 88 24.0 0.0 11.1 11.0

Turbidity, unfiltered, lab (NTRU) 6 5.5 <2.0 2

3.4 3.7

Hardness, filtered (mg/L as CaCO3) 88 169 58.5 117 124

Calcium, filtered (mg/L) 88 47.4 18.1 34.0 36.4

Magnesium, filtered (mg/L) 88 12.3 3.24 7.73 8.16

Potassium, filtered (mg/L) 6 1.45 1.29 1.39 1.40

Sodium, filtered (mg/L) 6 12.2 8.60 9.67 9.34

Alkalinity, filtered, lab (mg/L) 6 127 82.6 110 115

Chloride, filtered (mg/L) 6 2.24 1.53 1.92 2.03

Fluoride, filtered (mg/L) 6 0.56 0.29 0.41 0.39

Silica, filtered (mg/L) 6 23.3 18.4 21.5 22.4

Sulfate, filtered (mg/L) 6 29.1 16.2 22.4 22.0

Cadmium, filtered (μg/L) 88 0.12 <0.04 2

0.04 0.04

Cadmium, unfiltered recoverable (μg/L) 88 0.52 0.02 0.10 0.07

Copper, filtered (μg/L) 88 21.4 1.1 5.2 3.5

Copper, unfiltered recoverable (μg/L) 88 48.8 2.6 11.0 7.7

Iron, filtered (μg/L) 88 274 6.1 50.2 42.3

Iron, unfiltered recoverable (μg/L) 88 1,670 27 289 220

Lead, filtered (μg/L) 88 0.89 0.04 2

0.22 0.19

Lead, unfiltered recoverable (μg/L) 88 14.4 0.27 2.26 1.46

Manganese, filtered (μg/L) 88 200 3.3 33.8 25.7

Manganese, unfiltered recoverable (μg/L) 88 228 4.7 47.2 37.2

Zinc, filtered (μg/L) 88 19.8 <1.4 2

5.0 4.0

Zinc, unfiltered recoverable (μg/L) 88 68 1.1 12.2 9.0

Arsenic, filtered (μg/L) 88 164 10.9 38.1 28.1

Arsenic, unfiltered recoverable (μg/L) 88 164 11.4 40.5 28.0

Organic carbon, filtered (mg/L) 6 5.59 1.60 3.42 3.41

Sediment, suspended (percent finer than 0.062 mm) 88 97 54 86 89

Sediment, suspended concentration (mg/L) 88 87 1 11 5

Sediment, suspended discharge (ton/d) 88 11 0.02 0.94 0.16

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
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

12323750—Silver Bow Creek at Warm Springs

Period of record for water-quality data: March 1993–September 2013

Streamflow, instantaneous (ft3/s) 172 1,030 16 140 88

pH, onsite (standard units) 170 9.6 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 170 783 182 462 474

Temperature, water (oC) 171 25.0 0.0 10.4 10.5

Hardness, filtered (mg/L as CaCO3) 170 314 74.9 192 196

Calcium, filtered (mg/L) 170 90.4 22.5 55.7 57.2

Magnesium, filtered (mg/L) 170 21.4 4.52 12.7 13.0

Potassium, filtered (mg/L) 31 8.30 2.60 4.44 4.30

Sodium, filtered (mg/L) 31 23.0 8.20 16.0 17.0

Alkalinity, filtered, lab (mg/L) 3 99.7 77.4 85.0 77.9

Chloride, filtered (mg/L) 31 15.0 1.30 8.13 7.60

Fluoride, filtered (mg/L) 31 1.20 0.50 0.72 0.70

Silica, filtered (mg/L) 31 20.0 6.3 12.5 12.0

Sulfate, filtered (mg/L) 31 210 44.0 117 120

Cadmium, filtered (μg/L) 170 0.31 <0.04 2

0.06 0.03

Cadmium, unfiltered recoverable (μg/L) 170 0.56 <0.1 2

0.12 0.06

Copper, filtered (μg/L) 170 40.0 1.6 7.4 5.2

Copper, unfiltered recoverable (μg/L) 170 96.8 2.4 15.1 10.7

Iron, filtered (μg/L) 170 93 <5 2

19.3 15.4

Iron, unfiltered recoverable (μg/L) 170 3,000 35.8 315 236

Lead, filtered (μg/L) 170 1.0 <0.08 2

0.13 <1.0

Lead, unfiltered recoverable (μg/L) 170 41.8 <1.00 2

2.26 1.24

Manganese, filtered (μg/L) 170 875 11.8 114 76.8

Manganese, unfiltered recoverable (μg/L) 170 899 24.0 173 135

Zinc, filtered (μg/L) 170 73 <1.0 2

6.9 3.6

Zinc, unfiltered recoverable (μg/L) 170 180 2.0 2

28.5 16.4

Arsenic, filtered (μg/L) 170 60.0 6.8 22.9 23.0

Arsenic, unfiltered recoverable (μg/L) 170 94.0 10.0 26.5 25.4

Sediment, suspended (percent finer than 0.062 mm) 171 98 43 83 85

Sediment, suspended concentration (mg/L) 172 229 1 9 5

Sediment, suspended discharge (ton/d) 172 279 0.05 6.0 1.3

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
Data 95

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 2013

Streamflow, instantaneous (ft3/s) 48 573 41 140 94

pH, onsite (standard units) 48 8.8 7.8 8.5 8.5

Specific conductance, onsite (μS/cm) 48 278 125 220 230

Temperature, water (oC) 48 16.0 3.0 8.9 9.0

Turbidity, unfiltered, lab (NTRU) 43 18 <2.0 2

2.1 <2.0

Hardness, filtered (mg/L as CaCO3) 48 145 58.5 107 110

Calcium, filtered (mg/L) 48 42.8 18.5 32.2 33.2

Magnesium, filtered (mg/L) 48 9.34 2.96 6.57 6.72

Cadmium, filtered (μg/L) 48 0.05 <0.02 2

0.02 0.02

Cadmium, unfiltered recoverable (μg/L) 48 0.14 <0.02 2

0.04 0.03

Copper, filtered (μg/L) 47 6.4 <0.80 2

1.1 0.88

Copper, unfiltered recoverable (μg/L) 48 28.0 1.1 2

3.4 2.1

Iron, filtered (μg/L) 48 22.4 <4 2

7.4 5.8

Iron, unfiltered recoverable (μg/L) 48 1,000 26.5 124 75.0

Lead, filtered (μg/L) 48 0.11 <0.01 2

0.03 <0.08

Lead, unfiltered recoverable (μg/L) 48 3.51 0.07 0.43 0.24

Manganese, filtered (μg/L) 48 2.9 <0.1 2

1.3 1.1

Manganese, unfiltered recoverable (μg/L) 48 45.2 1.2 6.0 4.1

Zinc, filtered (μg/L) 48 5.6 <1.4 2

1.0 <2.0

Zinc, unfiltered recoverable (μg/L) 48 20.1 <2.0 2

3.1 1.2

Arsenic, filtered (μg/L) 48 3.9 1.6 2.3 2.2

Arsenic, unfiltered recoverable (μg/L) 48 5.6 1.7 2.7 2.5

Sediment, suspended (percent finer than 0.062 mm) 48 83 32 65 66

Sediment, suspended concentration (mg/L) 48 65 1 8 4

Sediment, suspended discharge (ton/d) 48 68 0.13 4.5 1.0

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
96 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 2013

Streamflow, instantaneous (ft3/s) 128 420 2.8 97 57

pH, onsite (standard units) 127 8.7 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 127 795 139 291 295

Temperature, water (oC) 128 20.0 0.0 8.5 8.0

Turbidity, unfiltered, lab (NTRU) 6 2.5 <2.0 2 1.7 1.6

Hardness, filtered (mg/L as CaCO3) 127 415 39.8 141 142

Calcium, filtered (mg/L) 127 130 10.5 43.1 43.6

Magnesium, filtered (mg/L) 127 22.0 3.29 8.18 8.02

Potassium, filtered (mg/L) 25 4.70 0.90 1.51 1.30

Sodium, filtered (mg/L) 25 7.40 1.80 3.52 3.03

Alkalinity, filtered, lab (mg/L) 8 141 88.0 116 110

Chloride, filtered (mg/L) 25 3.60 0.50 1.24 1.00

Fluoride, filtered (mg/L) 25 0.60 0.30 0.42 0.40

Silica, filtered (mg/L) 25 13.0 8.40 10.4 10.0

Sulfate, filtered (mg/L) 25 270 20.0 57.1 36.1

Cadmium, filtered (μg/L) 126 0.10 <0.04 2

0.04 0.02

Cadmium, unfiltered recoverable (μg/L) 126 0.41 <0.05 2

0.08 0.04

Copper, filtered (μg/L) 126 16.0 1.0 3.2 2.6

Copper, unfiltered recoverable (μg/L) 126 147 2.3 19.1 8.9

Iron, filtered (μg/L) 127 30 <5.0 2

11.5 10.1

Iron, unfiltered recoverable (μg/L) 127 2,110 17.2 304 122

Lead, filtered (μg/L) 126 1.8 <0.025 2

0.07 <0.60

Lead, unfiltered recoverable (μg/L) 126 14.0 <1.00 2

1.89 0.67

Manganese, filtered (μg/L) 126 570 18.8 111 82.9

Manganese, unfiltered recoverable (μg/L) 126 1,400 37.0 194 150

Zinc, filtered (μg/L) 126 10 <1.0 2

2.0 1.4

Zinc, unfiltered recoverable (μg/L) 127 60 <2.4 2

8.8 3.0

Arsenic, filtered (μg/L) 126 14.0 2.0 5.0 4.3

Arsenic, unfiltered recoverable (μg/L) 126 27.0 3.0 7.2 5.8

Organic carbon, filtered (mg/L) 6 1.84 0.97 1.40 1.45

Sediment, suspended (percent finer than 0.062 mm) 128 90 43 71 71

Sediment, suspended concentration (mg/L) 128 127 1 18 8

Sediment, suspended discharge (ton/d) 128 87 0.03 8.3 1.1

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
Data 97

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 2013

Streamflow, instantaneous (ft3/s) 212 1,380 14 223 137

pH, onsite (standard units) 200 9.2 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 201 720 182 410 417

Temperature, water (oC) 212 23.5 0.0 9.7 10.0

Hardness, filtered (mg/L as CaCO3) 199 365 76.4 179 186

Calcium, filtered (mg/L) 199 110 23.2 53.0 55.0

Magnesium, filtered (mg/L) 199 22.0 4.44 11.4 11.7

Potassium, filtered (mg/L) 32 5.90 2.00 3.51 3.30

Sodium, filtered (mg/L) 32 19.0 3.60 12.0 12.5

Alkalinity, filtered, lab (mg/L) 3 117 84.4 96.3 87.4

Chloride, filtered (mg/L) 32 11.0 2.00 6.50 6.20

Fluoride, filtered (mg/L) 32 1.10 0.40 0.60 0.60

Silica, filtered (mg/L) 32 17.0 8.10 11.7 11.8

Sulfate, filtered (mg/L) 32 220 34.0 97.2 98.5

Cadmium, filtered (μg/L) 199 1.0 <0.04 2

0.06 0.02

Cadmium, unfiltered recoverable (μg/L) 199 3.0 <0.1 2

0.18 0.06

Copper, filtered (μg/L) 199 50.0 1.4 7.5 5.6

Copper, unfiltered recoverable (μg/L) 198 240 4.1 26.3 14.9

Iron, filtered (μg/L) 199 110 <3.0 2

15.9 12.0

Iron, unfiltered recoverable (μg/L) 199 9,200 56 461 260

Lead, filtered (μg/L) 199 3.00 <0.08 2

0.14 <1.00

Lead, unfiltered recoverable (μg/L) 199 31.0 <1.00 2

3.30 1.80

Manganese, filtered (μg/L) 199 460 13.1 101 74.0

Manganese, unfiltered recoverable (μg/L) 199 1,400 47.3 212 163

Zinc, filtered (μg/L) 199 110 <1.0 2

8.4 4.0

Zinc, unfiltered recoverable (μg/L) 199 360 <10.0 2

34.4 20.0

Arsenic, filtered (μg/L) 199 53.0 4.0 15.0 14.0

Arsenic, unfiltered recoverable (μg/L) 199 78.0 3.0 19.0 17.0

Sediment, suspended (percent finer than 0.062 mm) 212 97 32 76 77

Sediment, suspended concentration (mg/L) 213 338 1 17 8

Sediment, suspended discharge (ton/d) 212 459 0.12 20 2.8

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
98 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 2013

Streamflow, instantaneous (ft3/s) 71 73 0.37 12 8.7

pH, onsite (standard units) 71 8.6 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 71 253 121 198 211

Temperature, water (oC) 71 17.0 0.0 8.0 8.5

Turbidity, unfiltered, lab (NTRU) 71 24,200 <2.0 2

343 <2.0

Hardness, filtered (mg/L as CaCO3) 71 122 50.4 94.6 101

Calcium, filtered (mg/L) 71 37.1 15.7 28.7 30.2

Magnesium, filtered (mg/L) 71 7.40 2.71 5.58 5.91

Potassium, filtered (mg/L) 6 1.39 1.14 1.24 1.22

Sodium, filtered (mg/L) 6 3.18 2.62 2.78 2.66

Alkalinity, filtered, lab (mg/L) 6 109 82.5 96.9 97.4

Chloride, filtered (mg/L) 6 0.73 0.57 0.65 0.66

Fluoride, filtered (mg/L) 6 0.47 0.37 0.43 0.42

Silica, filtered (mg/L) 6 11.3 10.9 11.2 11.2

Sulfate, filtered (mg/L) 6 10.8 7.33 8.50 8.26

Cadmium, filtered (μg/L) 70 0.90 <0.02 2

0.04 0.02

Cadmium, unfiltered recoverable (μg/L) 71 147 0.01 2

2.1 0.03

Copper, filtered (μg/L) 71 90.5 0.80 3.1 1.6

Copper, unfiltered recoverable (μg/L) 71 29,100 1.3 416 4.4

Iron, filtered (μg/L) 71 26.5 <6.0 2

9.6 8.7

Iron, unfiltered recoverable (μg/L) 71 99,700 22 1,590 102

Lead, filtered (μg/L) 71 0.18 <0.02 2

0.04 0.02

Lead, unfiltered recoverable (μg/L) 71 1,290 0.08 19.0 0.42

Manganese, filtered (μg/L) 71 42.4 <0.2 2

1.9 1.3

Manganese, unfiltered recoverable (μg/L) 71 8,830 1.2 131 4.5

Zinc, filtered (μg/L) 70 30.0 <1.4 2

1.7 0.8

Zinc, unfiltered recoverable (μg/L) 70 7,780 <2 2

114 2.0

Arsenic, filtered (μg/L) 71 156 1.8 6.3 3.4

Arsenic, unfiltered recoverable (μg/L) 71 3,860 2.0 59.0 3.8

Organic carbon, filtered (mg/L) 6 2.31 0.91 1.65 1.66

Sediment, suspended (percent finer than 0.062 mm) 71 97 22 57 58

Sediment, suspended concentration (mg/L) 71 58,900 1 841 5

Sediment, suspended discharge (ton/d) 71 1,320 <0.01 2

19 0.11

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
Data 99

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 2013

Streamflow, instantaneous (ft3/s) 87 71 1.3 24 18

pH, onsite (standard units) 88 8.7 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 88 934 540 643 629

Temperature, water (oC) 88 26.5 0.0 10.1 10.0

Hardness, filtered (mg/L as CaCO3) 88 451 203 303 302

Calcium, filtered (mg/L) 88 122 48.5 86.0 87.4

Magnesium, filtered (mg/L) 88 35.7 17.3 21.6 20.9

Cadmium, filtered (μg/L) 87 0.05 <0.02 2

0.03 0.02

Cadmium, unfiltered recoverable (μg/L) 88 0.12 <0.02 2

0.04 0.04

Copper, filtered (μg/L) 88 6.7 0.99 2.2 1.9

Copper, unfiltered recoverable (μg/L) 88 22.5 1.6 5.3 4.3

Iron, filtered (μg/L) 88 61.1 <6 2

13.2 11.0

Iron, unfiltered recoverable (μg/L) 88 392 14 104 79.0

Lead, filtered (μg/L) 87 0.33 <0.025 2

0.05 0.02

Lead, unfiltered recoverable (μg/L) 88 1.90 0.04 0.38 0.27

Manganese, filtered (μg/L) 88 54.0 1.9 15.4 13.9

Manganese, unfiltered recoverable (μg/L) 88 56.5 2.2 20.5 19.0

Zinc, filtered (μg/L) 87 3.8 <1.0 2

1.6 1.3

Zinc, unfiltered recoverable (μg/L) 88 10.3 <2.0 2

3.0 2.0

Arsenic, filtered (μg/L) 88 41.8 6.0 14.2 12.6

Arsenic, unfiltered recoverable (μg/L) 88 43.0 6.0 15.0 13.4

Sediment, suspended (percent finer than 0.062 mm) 88 88 18 60 62

Sediment, suspended concentration (mg/L) 88 79 2 16 15

Sediment, suspended discharge (ton/d) 87 4.2 0.01 1.0 0.68

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
100 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 2013

Streamflow, instantaneous (ft3/s) 265 2,000 23 307 228

pH, onsite (standard units) 213 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 248 642 228 469 494

Temperature, water (oC) 264 23.0 0.0 9.9 10.0

Hardness, filtered (mg/L as CaCO3) 205 282 94.9 198 208

Calcium, filtered (mg/L) 205 82.0 28.2 58.6 61.0

Magnesium, filtered (mg/L) 205 18.7 5.53 12.6 13.3

Potassium, filtered (mg/L) 31 6.30 2.40 3.62 3.60

Sodium, filtered (mg/L) 31 25.0 8.60 14.9 14.0

Alkalinity, filtered, lab (mg/L) 3 142 105 119 109

Chloride, filtered (mg/L) 31 12.0 1.20 7.00 7.10

Fluoride, filtered (mg/L) 31 0.70 0.10 0.61 0.60

Silica, filtered (mg/L) 31 34.0 11.0 16.6 16.0

Sulfate, filtered (mg/L) 31 140 44.0 96.2 98.0

Cadmium, filtered (μg/L) 214 2.0 <0.10 2

0.08 <1.0

Cadmium, unfiltered recoverable (μg/L) 214 5.0 <0.10 2

0.38 0.10

Copper, filtered (μg/L) 215 120 3.2 10.6 8.0

Copper, unfiltered recoverable (μg/L) 213 1,500 8.2 77.0 35.0

Iron, filtered (μg/L) 215 190 <3 2

15.1 9.4

Iron, unfiltered recoverable (μg/L) 215 29,000 27 1,390 499

Lead, filtered (μg/L) 215 6.00 <0.08 2

0.30 <5.00

Lead, unfiltered recoverable (μg/L) 215 200 0.33 2

10.2 4.36

Manganese, filtered (μg/L) 215 400 1.0 41.1 33.4

Manganese, unfiltered recoverable (μg/L) 215 4,600 11.9 221 130

Zinc, filtered (μg/L) 215 230 <10.0 2

11.2 7.5

Zinc, unfiltered recoverable (μg/L) 213 1,700 4.0 80.0 38.2

Arsenic, filtered (μg/L) 215 39.0 6.0 14.4 13.4

Arsenic, unfiltered recoverable (μg/L) 214 215 4.8 23.4 17.2

Sediment, suspended (percent finer than 0.062 mm) 256 99 31 72 73

Sediment, suspended concentration (mg/L) 265 2,250 1 66 22

Sediment, suspended discharge (ton/d) 265 8,690 0.18 139 12

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
Data 101

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 2013

Streamflow, instantaneous (ft3/s) 38 2,310 71 498 326

pH, onsite (standard units) 38 8.8 7.9 8.3 8.4

Specific conductance, onsite (μS/cm) 38 499 249 410 447

Temperature, water (oC) 38 21.0 1.0 11.0 12.0

Hardness, filtered (mg/L as CaCO3) 38 227 104 180 196

Calcium, filtered (mg/L) 38 66.5 31.8 52.7 56.8

Magnesium, filtered (mg/L) 38 15.2 5.93 11.8 12.9

Cadmium, filtered (μg/L) 38 .23 0.02 0.07 0.07

Cadmium, unfiltered recoverable (μg/L) 38 .84 0.03 0.28 0.22

Copper, filtered (μg/L) 38 40.6 4.0 9.9 7.9

Copper, unfiltered recoverable (μg/L) 38 222 10.0 61.9 32.6

Iron, filtered (μg/L) 38 43.2 4.5 16.5 13.8

Iron, unfiltered recoverable (μg/L) 38 3,860 46.1 928 516

Lead, filtered (μg/L) 38 .42 0.04 0.15 0.12

Lead, unfiltered recoverable (μg/L) 38 32.3 0.39 8.1 3.95

Manganese, filtered (μg/L) 38 64.6 12.3 29.7 27.6

Manganese, unfiltered recoverable (μg/L) 38 344 19.7 125 104

Zinc, filtered (μg/L) 38 37.1 1.9 6.5 5.4

Zinc, unfiltered recoverable (μg/L) 38 181 3.0 50.7 28.8

Arsenic, filtered (μg/L) 38 36.7 9.2 15.5 16.1

Arsenic, unfiltered recoverable (μg/L) 38 46.0 10.9 21.9 18.6

Sediment, suspended (percent finer than 0.062 mm) 38 90 42 71 74

Sediment, suspended concentration (mg/L) 38 205 4 47 26

Sediment, suspended discharge (ton/d) 38 550 0.77 99 26

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
102 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 2013

Streamflow, instantaneous (ft3/s) 171 4,450 87 776 513

pH, onsite (standard units) 170 8.9 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 170 510 206 367 380

Temperature, water (oC) 171 23.0 0.0 10.2 10.5

Hardness, filtered (mg/L as CaCO3) 170 232 85.8 162 169

Calcium, filtered (mg/L) 170 68.0 25.9 47.7 50.0

Magnesium, filtered (mg/L) 170 15.0 5.15 10.4 10.8

Potassium, filtered (mg/L) 28 6.90 2.00 3.11 3.00

Sodium, filtered (mg/L) 28 19.0 6.90 11.5 12.0

Chloride, filtered (mg/L) 28 7.20 2.50 4.73 4.40

Fluoride, filtered (mg/L) 28 0.60 0.10 0.43 0.40

Silica, filtered (mg/L) 28 25.0 14.0 18.3 18.0

Sulfate, filtered (mg/L) 28 88.0 31.0 59.5 55.5

Cadmium, filtered (μg/L) 170 0.2 <0.02 2

0.04 0.02

Cadmium, unfiltered recoverable (μg/L) 170 2 <0.10 2

0.17 0.07

Copper, filtered (μg/L) 169 36.0 2.1 6.6 5.3

Copper, unfiltered recoverable (μg/L) 169 440 5.2 38.8 22.9

Iron, filtered (μg/L) 170 100 <3 2

19.0 12.0

Iron, unfiltered recoverable (μg/L) 170 12,000 27 835 416

Lead, filtered (μg/L) 168 0.6 <0.08 2

0.11 <1.00

Lead, unfiltered recoverable (μg/L) 169 73.0 0.14 2

5.40 2.79

Manganese, filtered (μg/L) 170 57.3 4.0 18.9 17.0

Manganese, unfiltered recoverable (μg/L) 170 1,100 9.3 116 82.9

Zinc, filtered (μg/L) 170 26 <1.0 2

5.3 3.5

Zinc, unfiltered recoverable (μg/L) 170 510 2 41.6 28.6

Arsenic, filtered (μg/L) 170 22.5 5.8 10.1 10.0

Arsenic, unfiltered recoverable (μg/L) 170 75.0 7.0 14.6 12.0

Sediment, suspended (percent finer than 0.062 mm) 171 94 43 75 78

Sediment, suspended concentration (mg/L) 171 752 1 47 20

Sediment, suspended discharge (ton/d) 171 7,960 0.55 202 27

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
Data 103

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 2013

Streamflow, instantaneous (ft3/s) 171 5,540 149 1,070 771

pH, onsite (standard units) 170 8.7 7.8 8.3 8.3

Specific conductance, onsite (μS/cm) 170 630 189 407 419

Temperature, water (oC) 171 22.5 0.5 11.0 11.0

Hardness, filtered (mg/L as CaCO3) 170 298 73.9 183 190

Calcium, filtered (mg/L) 170 83.0 21.0 52.6 54.6

Magnesium, filtered (mg/L) 170 22.0 5.2 12.6 13.0

Potassium, filtered (mg/L) 28 10.0 2.10 3.67 3.40

Sodium, filtered (mg/L) 28 20.0 5.60 11.5 12.0

Chloride, filtered (mg/L) 28 7.80 2.70 4.83 4.65

Fluoride, filtered (mg/L) 28 0.50 0.20 0.39 0.40

Silica, filtered (mg/L) 28 24.0 10.0 18.7 18.5

Sulfate, filtered (mg/L) 28 130 25.0 64.8 64.5

Cadmium, filtered (μg/L) 169 0.30 <0.04 2

0.05 0.02

Cadmium, unfiltered recoverable (μg/L) 170 2.0 <0.10 2

0.22 0.08

Copper, filtered (μg/L) 167 21.0 1.0 6.3 4.9

Copper, unfiltered recoverable (μg/L) 168 360 4.6 41.3 21.8

Iron, filtered (μg/L) 170 150 <3 2

18.8 9.6

Iron, unfiltered recoverable (μg/L) 169 8,800 19.7 966 457

Lead, filtered (μg/L) 166 1.2 <0.08 2

0.16 0.04

Lead, unfiltered recoverable (μg/L) 166 56.0 <1.00 2

7.36 3.45

Manganese, filtered (μg/L) 169 60.7 3.3 16.6 15.0

Manganese, unfiltered recoverable (μg/L) 170 880 8.0 140 90.6

Zinc, filtered (μg/L) 170 21.0 1.4 2

5.7 4.3

Zinc, unfiltered recoverable (μg/L) 170 490 2.9 56.7 30.0

Arsenic, filtered (μg/L) 170 23.9 3.2 10.5 10.0

Arsenic, unfiltered recoverable (μg/L) 170 62 8 15.9 13.0

Sediment, suspended (percent finer than 0.062 mm) 171 93 38 74 75

Sediment, suspended concentration (mg/L) 171 530 2 61 25

Sediment, suspended discharge (ton/d) 171 4,720 1.7 310 48

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
104 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 2013

Streamflow, instantaneous (ft3/s) 268 10,600 296 1,960 1,160

pH, onsite (standard units) 214 8.8 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 243 483 139 299 312

Temperature, water (oC) 267 22.0 0.0 9.5 10.0

Hardness, filtered (mg/L as CaCO3) 204 205 53.6 131 134

Calcium, filtered (mg/L) 204 59.0 14.9 36.9 37.2

Magnesium, filtered (mg/L) 204 14.0 3.94 9.43 9.58

Potassium, filtered (mg/L) 32 5.70 1.51 2.45 2.45

Sodium, filtered (mg/L) 32 12.0 3.34 7.95 8.45

Alkalinity, filtered, lab (mg/L) 5 155 52.5 110 120

Chloride, filtered (mg/L) 32 5.60 1.50 3.13 2.95

Fluoride, filtered (mg/L) 32 0.40 0.17 0.29 0.30

Silica, filtered (mg/L) 32 19.0 12.0 14.9 15.0

Sulfate, filtered (mg/L) 32 68.0 12.6 41.8 41.0

Cadmium, filtered (μg/L) 212 0.10 <0.02 2

0.03 <1

Cadmium, unfiltered recoverable (μg/L) 213 4.00 <0.01 2

0.24 0.03

Copper, filtered (μg/L) 212 25.0 1.1 4.7 3.7

Copper, unfiltered recoverable (μg/L) 211 500 2.7 32.1 14.6

Iron, filtered (μg/L) 213 190 <3 2

23.5 14.0

Iron, unfiltered recoverable (μg/L) 213 19,000 32.6 953 360

Lead, filtered (μg/L) 209 7.00 <.02 2

0.27 <1.00

Lead, unfiltered recoverable (μg/L) 209 100 <1.00 2

6.49 2.56

Manganese, filtered (μg/L) 213 37.4 <1.0 2

8.4 7.0

Manganese, unfiltered recoverable (μg/L) 213 2,000 8.9 115 58.7

Zinc, filtered (μg/L) 211 39 <3.0 2

5.7 4.0

Zinc, unfiltered recoverable (μg/L) 213 1,100 2.9 2

54.6 27.0

Arsenic, filtered (μg/L) 213 17.0 2.7 6.1 5.6

Arsenic, unfiltered recoverable (μg/L) 213 110 3.0 9.5 7.0

Sediment, suspended (percent finer than 0.062 mm) 257 98 27 74 76

Sediment, suspended concentration (mg/L) 268 1,370 2 54 18

Sediment, suspended discharge (ton/d) 268 34,700 3.0 610 60

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
Data 105

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 2013

Streamflow, instantaneous (ft3/s) 196 13,400 344 2,790 1,360

pH, onsite (standard units) 156 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 173 294 131 208 204

Temperature, water (oC) 196 22.5 0.0 9.6 9.5

Turbidity, unfiltered, lab (NTRU) 7 30 <2.0 2

7.2 2.0

Hardness, filtered (mg/L as CaCO3) 148 146 55.1 104 98.6

Calcium, filtered (mg/L) 148 37.7 14.0 26.5 25.4

Magnesium, filtered (mg/L) 148 13.2 4.90 9.15 8.66

Potassium, filtered (mg/L) 26 2.80 0.48 0.87 0.80

Sodium, filtered (mg/L) 26 3.41 1.17 2.46 2.50

Alkalinity, filtered, lab (mg/L) 9 148 71.5 117 131

Chloride, filtered (mg/L) 26 1.60 0.23 0.64 0.58

Fluoride, filtered (mg/L) 26 0.10 <0.10 2

0.10 <0.10

Silica, filtered (mg/L) 26 12.0 6.80 8.64 8.10

Sulfate, filtered (mg/L) 26 6.60 1.10 4.58 4.80

Cadmium, filtered (μg/L) 154 1.00 <0.02 2

0.02 <0.10

Cadmium, unfiltered recoverable (μg/L) 156 2.00 <0.01 2

0.09 <1.00

Copper, filtered (μg/L) 152 7.0 <0.80 2

1.3 0.71

Copper, unfiltered recoverable (μg/L) 153 34.0 <0.70 2

4.3 1.9

Iron, filtered (μg/L) 155 100 <3 2

17.5 10.2

Iron, unfiltered recoverable (μg/L) 156 3,600 13.9 404 185

Lead, filtered (μg/L) 150 8.00 <0.01 2

0.29 <0.60

Lead, unfiltered recoverable (μg/L) 151 25.0 <0.04 2

2.06 0.08

Manganese, filtered (μg/L) 155 11.0 <1.0 2

2.4 2.0

Manganese, unfiltered recoverable (μg/L) 156 180 <10.0 2

27.8 16.0

Zinc, filtered (μg/L) 154 15.0 <0.60 2

1.9 <3.0

Zinc, unfiltered recoverable (μg/L) 156 60.0 <1.0 2

5.0 <10.0

Arsenic, filtered (μg/L) 155 2.0 <1.0 2

0.96 0.96

Arsenic, unfiltered recoverable (μg/L) 156 4.0 <1.0 2

1.3 1.0

Sediment, suspended (percent finer than 0.062 mm) 194 98 42 80 82

Sediment, suspended concentration (mg/L) 196 271 1 28 8

Sediment, suspended discharge (ton/d) 196 7,670 1.1 515 31

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
106 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 2013

Streamflow, instantaneous (ft3/s) 233 22,900 720 4,620 2,470

pH, onsite (standard units) 191 8.8 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 211 399 142 252 261

Temperature, water (oC) 231 22.0 0.0 9.6 9.5

Turbidity, unfiltered, lab (NTRU) 40 100 <2.0 2

13 4.9

Hardness, filtered (mg/L as CaCO3) 191 168 60.5 116 118

Calcium, filtered (mg/L) 191 46.0 14.0 31.4 31.6

Magnesium, filtered (mg/L) 191 13.4 5.28 9.20 9.20

Potassium, filtered (mg/L) 28 4.50 0.90 1.72 1.50

Sodium, filtered (mg/L) 28 7.80 2.40 5.29 5.35

Chloride, filtered (mg/L) 28 4.20 0.90 1.92 1.80

Fluoride, filtered (mg/L) 28 0.30 <0.10 2

0.19 0.20

Silica, filtered (mg/L) 28 16.0 9.40 11.8 11.0

Sulfate, filtered (mg/L) 28 43.0 9.30 23.3 23.0

Cadmium, filtered (μg/L) 190 .20 <0.02 2

0.03 <0.10

Cadmium, unfiltered recoverable (μg/L) 191 5.0 <0.01 2

0.15 <1.0

Copper, filtered (μg/L) 190 12.6 0.7 2.8 2.1

Copper, unfiltered recoverable (μg/L) 189 400 1.9 18.8 8.1

Iron, filtered (μg/L) 191 200 <3 2

21.6 15.0

Iron, unfiltered recoverable (μg/L) 191 13,000 42.1 614 247

Lead, filtered (μg/L) 184 1.20 <0.02 2

0.13 <1.00

Lead, unfiltered recoverable (μg/L) 186 78.0 <1.00 2

3.33 1.50

Manganese, filtered (μg/L) 191 230 4.5 15.5 13.2

Manganese, unfiltered recoverable (μg/L) 191 1,100 10.0 63.8 40.0

Zinc, filtered (μg/L) 190 16.0 <1.0 2

3.4 2.3

Zinc, unfiltered recoverable (μg/L) 191 1,100 <3.0 2

32.1 13.8

Arsenic, filtered (μg/L) 191 9.0 1.0 3.4 3.2

Arsenic, unfiltered recoverable (μg/L) 191 69.0 1.0 5.3 4.0

Sediment, suspended (percent finer than 0.062 mm) 229 99 14 83 88

Sediment, suspended concentration (mg/L) 234 950 2 43 12

Sediment, suspended discharge (ton/d) 233 21,900 5.8 1,090 85

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 

2013.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 oC; oC, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; lab, laboratory; μg/L, micrograms per liter; <, less than laboratory reporting level1

; mm, millimeter; ton/d, tons per day; NTRU, nephelometric turbidity ratio unit]
Data 107

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2013.

[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: 1992–2013

Arsenic 11 186 34 106 119

Cadmium 22 43.9 5.9 26.9 26.8

Chromium 20 50.7 16.8 30.2 26.8

Copper 22 9,020 522 3,720 3,960

Iron 22 45,300 28,200 35,100 34,200

Lead 22 1,030 121 572 551

Manganese 22 9,220 1,160 3,220 2,680

Nickel 21 21.4 12.0 14.9 14.8

Silver 12 20.0 8.3 15.5 15.8

Zinc 22 13,400 1,490 6,520 6,870

12323750—Silver Bow Creek at Warm Springs

Period of record for bed-sediment data: 1992–2013

Arsenic 11 177 67 112 103

Cadmium 22 12.2 4.2 7.0 6.5

Chromium 20 46.8 <15.7 1

24.3 123.2

Copper 22 769 169 343 295

Iron 22 32,500 15,400 23,700 23,000

Lead 22 100 49 70 69

Manganese 22 17,700 1,470 7,460 7,210

Nickel 21 20.0 9.2 14.8 14.6

Silver 12 4.4 0.3 1

1.9 11.8

Zinc 22 2,220 554 904 707

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
108 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, 1991–2013

Arsenic 11 156 73 104 99

Cadmium 24 20.1 3.8 8.0 6.8

Chromium 20 44.6 19.1 29.8 28.3

Copper 24 2,300 838 1,190 1,120

Iron 24 39,800 22,600 27,900 27,200

Lead 24 235 92 129 122

Manganese 24 17,300 1,530 8,720 8,510

Nickel 21 23.2 13.9 18.6 18.3

Silver 14 7.3 <3.2 1

4.4 14.5

Zinc 24 3,560 721 1,370 1,120

461415112450801—Clark Fork below Lost Creek, near Galen

Period of record for bed-sediment data: 1996–2013

Arsenic 11 204 90 115 108

Cadmium 18 10.5 4.8 6.8 6.4

Chromium 18 42.4 20.5 30.4 31.8

Copper 18 2,050 1,150 1,490 1,440

Iron 18 32,800 24,400 29,100 29,600

Lead 18 218 123 162 160

Manganese 18 9,820 1,430 5,250 5,280

Nickel 18 19.9 11.7 15.9 16.3

Silver 8 7.8 4.2 6.5 6.7

Zinc 18 1,680 930 1,260 1,250

461559112443301—Clark Fork at county bridge, near Racetrack

Period of record for bed-sediment data: 1996–2013

Arsenic 11 132 56 89 90

Cadmium 18 8.7 4.6 6.4 6.1

Chromium 18 45.2 19.0 30.1 29.2

Copper 18 1,810 933 1,270 1,290

Iron 18 31,700 21,200 27,400 28,100

Lead 18 186 103 142 143

Manganese 18 6,310 1,600 3,210 2,990

Nickel 18 18.4 10.3 14.4 14.7

Silver 8 6.1 <3.3 1

5.0 15.4

Zinc 18 1,550 911 1,170 1,150

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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 109

Constituent Number of samples Maximum Minimum Mean Median

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for bed-sediment data: 1996–2013

Arsenic 11 103 58 80 80

Cadmium 18 10.3 4.1 6.2 5.8

Chromium 18 39.2 16.0 28.5 27.6

Copper 18 1,580 721 1,120 1,100

Iron 18 33,700 20,600 26,900 26,600

Lead 18 155 92 128 131

Manganese 18 8,370 1,200 3,790 3,210

Nickel 18 16.9 8.7 12.9 12.5

Silver 8 6.2 2.7 4.9 5.0

Zinc 18 1,570 900 1,120 1,080

12324200—Clark Fork at Deer Lodge

Period of record for bed-sediment data: 1986–87, 1990–2013

Arsenic 11 102 49 73 70

Cadmium 26 10.0 3.5 5.9 5.1

Chromium 20 50.7 19.5 32.5 30.4

Copper 26 4,180 683 1,240 1,070

Iron 26 35,300 21,100 27,400 26,300

Lead 26 242 103 143 140

Manganese 26 6,020 1,070 2,590 2,420

Nickel 21 21.1 11.5 14.8 14.3

Silver 16 7.9 2.4 4.7 4.5

Zinc 26 1,730 844 1,170 1,090

12324400—Clark Fork above Little Blackfoot River, near Garrison

Period of record for bed-sediment data: 2009-2013

Arsenic 5 91 50 72 81

Cadmium 5 5.5 4.1 4.6 4.5

Chromium 5 52.8 19.9 40.7 45.5

Copper 5 1,290 773 1,090 1,260

Iron 5 32,400 20,400 26,500 27,300

Lead 5 145 92 125 140

Manganese 5 3,560 1,150 2,370 2,660

Nickel 5 17.2 10.6 13.8 13.9

Silver 0 -- -- -- --

Zinc 5 1,240 850 1,050 1,100

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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]
110 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: 1992–2013

Arsenic 11 62 23 40 36

Cadmium 22 8.1 2.5 4.4 4.0

Chromium 20 55.3 20.2 33.1 31.8

Copper 22 1,080 338 674 702

Iron 22 32,100 15,500 23,400 24,000

Lead 22 152 52 93 93

Manganese 22 2,610 977 1,800 1,810

Nickel 21 18.6 9.0 13.8 14.1

Silver 12 4.8 2.3 3.2 3.2

Zinc 22 1,320 531 895 892

12331800—Clark Fork near Drummond

Period of record for bed-sediment data: 1986–87, 1991–2013

Arsenic 11 66 17 37 33

Cadmium 25 7.7 1.7 4.1 4.2

Chromium 20 41.9 9.2 28.1 30.7

Copper 25 747 183 458 460

Iron 25 43,700 14,800 24,100 23,200

Lead 25 135 27 84 83

Manganese 25 4,820 832 2,010 1,880

Nickel 21 16.8 4.8 12.7 13.4

Silver 15 4.7 <3.2 1

3.0 12.9

Zinc 25 1,230 380 905 947

12334550—Clark Fork at Turah Bridge, near Bonner

Period of record for bed-sediment data: 1986, 1991–2013

Arsenic 11 43 17 27 25

Cadmium 24 7.3 1.2 3.4 3.4

Chromium 20 42.5 15.3 27.0 28.4

Copper 24 635 211 345 322

Iron 24 25,900 12,600 19,200 17,300

Lead 24 115 37 66 64

Manganese 24 2,340 591 1,260 1,240

Nickel 21 19.1 6.9 12.3 11.5

Silver 14 3.9 <1.9 1

2.1 11.9

Zinc 24 1,160 448 779 781

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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 111

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, 2006–13

Arsenic 9 6 <0.2 1

3 14

Cadmium 20 2.0 0.04 1

0.5 10.3

Chromium 16 35.2 14.5 22.6 23.7

Copper 20 27 11 20 21

Iron 20 23,000 12,400 17,500 17,900

Lead 20 20 <13 1

13 111

Manganese 20 746 298 544 544

Nickel 17 14.3 6.0 11.2 11.7

Silver 12 <1.9 <0.3 1

0.5 1<0.6

Zinc 20 82 35 60 61

12340500—Clark Fork above Missoula

Period of record for bed-sediment data: 1997–2013

Arsenic 11 54 12 30 29

Cadmium 17 5.8 1.0 2.9 2.8

Chromium 16 40.7 13.2 27.0 29.0

Copper 17 551 129 342 326

Iron 17 27,000 14,700 20,600 20,400

Lead 17 78 25 53 54

Manganese 17 2,250 477 1,090 1,020

Nickel 17 15.8 7.6 12.5 12.7

Silver 7 2.9 0.8 1

2.0 12.1

Zinc 17 1,090 346 696 696

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 median.

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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]
112 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 2013.

[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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323600—Silver Bow Creek at Opportunity

Period of record for biological data: 1992, 1994–95, 1997–2013

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 11.3 11.6

Zinc 5 995 629 803 815

Hydropsyche cockerelli

Arsenic 20 33.3 5.4 12.9 11.1

Cadmium 26 9.7 3.0 5.3 4.8

Chromium 26 25.5 1.0 4.3 3.7

Copper 26 1,090 115 356 351

Iron 26 6,150 689 2,750 2,430

Lead 26 74.3 16.6 35.7 31.1

Manganese 26 3,030 180 1,040 1,120

Nickel 26 4.3 0.7 2.6 2.6

Zinc 26 1,590 540 848 780

Hydropsyche spp.

Arsenic 14 23.1 6.1 12.1 10.7

Cadmium 19 11.0 2.0 5.4 5.0

Chromium 19 4.7 0.6 2.6 3.0

Copper 19 930 80.7 428 352

Iron 19 3,630 1,050 2,260 2,210

Lead 19 237 19.3 45.5 36.5

Manganese 19 1,790 612 1,040 1,040

Nickel 19 4.1 0.7 2.2 2.3

Zinc 19 1,290 388 875 876

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 113

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323750—Silver Bow Creek at Warm Springs

Period of record for biological data: 1992–2013

Claassenia sabulosa

Arsenic 2 5.0 1.8 3.4 --

Cadmium 2 1.1 0.5 0.8 --

Chromium 2 2.8 0.6 1.7 --

Copper 2 66.4 47.6 57.0 --

Iron 2 300 151 226 --

Lead 2 1.5 0.6 1.0 --

Manganese 2 922 98 510 --

Nickel 2 0.6 0.5 0.6 --

Zinc 2 400 340 370 --

Hydropsyche cockerelli

Arsenic 18 23.6 7.9 12.9 11.5

Cadmium 44 2.1 0.2 0.6 0.5

Chromium 44 4.3 0.4 1.1 0.9

Copper 44 97.0 16.7 36.9 32.0

Iron 44 1,650 351 837 773

Lead 44 6.0 0.3 3.2 3.0

Manganese 44 3,890 491 1,250 992

Nickel 44 1.8 0.3 0.9 0.8

Zinc 44 276 115 176 169

Hydropsyche occidentalis

Arsenic 9 31.0 10.5 18.6 15.6

Cadmium 24 1.6 0.2 0.6 0.4

Chromium 24 6.8 0.3 1.7 1.0

Copper 24 48.9 11.0 33.2 32.0

Iron 24 2,960 372 1,240 1,000

Lead 24 8.2 <1.7 1

4.2 13.8

Manganese 24 6,940 996 2,380 1,890

Nickel 24 2.7 0.7 1.5 1.5

Zinc 24 220 140 181 182

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
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

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
Data 115

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323800—Clark Fork near Galen

Period of record for biological data: 1987, 1991–2013

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 11 20.5 13.2 15.4 14.2

Cadmium 36 2.7 0.7 1.5 1.5

Chromium 36 9.6 0.8 2.2 1.8

Copper 36 181 48.7 107 111

Iron 36 2,660 816 1,520 1,480

Lead 36 17.1 1.2 8.7 8.4

Manganese 36 3,620 1,070 2,290 2,320

Nickel 36 6.5 0.9 1.9 1.6

Zinc 36 363 136 218 212

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 20 17.7 9.1 14.3 14.6

Cadmium 52 1.6 0.6 1.1 1.2

Chromium 52 6.6 0.4 2.1 1.9

Copper 52 151 49.2 94.6 91.6

Iron 52 2,590 642 1,510 1,420

Lead 52 13.5 1.6 8.2 8.1

Manganese 52 6,170 653 2,480 2,080

Nickel 52 3.5 0.8 1.8 1.7

Zinc 52 286 168 206 200

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
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

12323800—Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991–2013

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
Data 117

Constituent Number of composite 

samples Maximum Minimum Mean Median

461415112450801—Clark Fork below Lost Creek, near Galen

Period of record for biological data: 1996–2013

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 .7 1.0 --

Manganese 2 238 90.4 164 --

Nickel 2 0.2 <0.2 10.2 --

Zinc 2 245 208 226 --

Hydropsyche cockerelli

Arsenic 16 27.8 8.8 16.4 14.6

Cadmium 27 2.8 1.1 1.8 1.7

Chromium 27 4.0 0.8 2.2 2.5

Copper 27 338 48.8 147 121

Iron 27 4,080 691 1,760 1,290

Lead 27 28.6 4.5 13.4 11.3

Manganese 27 3,160 1,230 1,860 1,750

Nickel 27 2.8 0.9 1.6 1.4

Zinc 27 339 151 238 234

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
118 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of composite 

samples Maximum Minimum Mean Median

461415112450801—Clark Fork below Lost Creek, near Galen—Continued

Period of record for biological data: 1996–2013

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
Data 119

Constituent Number of composite 

samples Maximum Minimum Mean Median

461559112443301—Clark Fork at county bridge, near Racetrack

Period of record for biological data: 1996–2013

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 14 20.2 11.1 14.5 13.7

Cadmium 25 2.2 0.8 1.6 1.5

Chromium 25 3.0 0.6 1.8 2.0

Copper 25 198 50.0 106 98.2

Iron 25 3,330 657 1,400 1,080

Lead 25 18.7 3.7 9.6 8.2

Manganese 25 2,360 646 1,670 1,900

Nickel 25 2.0 0.7 1.3 1.1

Zinc 25 302 139 203 188

Hydropsyche occidentalis

Arsenic 15 16.8 9.2 13.1 12.8

Cadmium 28 2.3 0.7 1.4 1.4

Chromium 28 3.7 1.1 2.2 2.0

Copper 28 164 59.5 116 122

Iron 28 3,690 1,030 1,670 1,580

Lead 28 15.7 4.3 10.9 10.9

Manganese 28 3,770 660 1,990 1,910

Nickel 28 2.3 1.1 1.5 1.3

Zinc 28 361 181 234 227

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
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

461559112443301—Clark Fork at county bridge, near Racetrack—Continued

Period of record for biological data: 1996–2013

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
Data 121

Constituent Number of composite 

samples Maximum Minimum Mean Median

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for biological data: 1996–2013

Arctopsyche grandis

Arsenic 3 17.5 8.1 12.5 11.8

Cadmium 4 7.1 1.7 3.7 3.1

Chromium 4 12.9 1.4 1

5.9 13.4

Copper 4 196 30.8 113 112

Iron 4 2,800 340 1,370 1,170

Lead 4 17.6 5.9 1

12.0 112.4

Manganese 4 2,060 510 1,280 1,270

Nickel 4 2.5 1.0 1.7 1.7

Zinc 4 489 87 303 318

Claassenia sabulosa

Arsenic 3 3.8 1.6 2.8 3.1

Cadmium 3 2.4 0.9 1.6 1.5

Chromium 3 1.7 0.2 1.0 1.2

Copper 3 87.2 58.6 73.1 73.4

Iron 3 485 173 318 297

Lead 3 3.4 0.9 2.1 1.9

Manganese 3 1,260 115 582 372

Nickel 3 1.0 0.2 0.5 0.4

Zinc 3 394 168 297 330

Hydropsyche cockerelli

Arsenic 12 18.8 8.0 13.2 13.4

Cadmium 21 2.0 0.7 1.4 1.4

Chromium 21 4.0 0.5 1.7 1.5

Copper 21 247 60.7 115 95.1

Iron 21 3,010 552 1,270 979

Lead 21 21.9 3.5 9.2 8.4

Manganese 21 2,650 487 1,430 1,350

Nickel 21 2.5 0.5 1.2 1.0

Zinc 21 285 162 217 214

Hydropsyche occidentalis

Arsenic 18 24.0 9.8 14.8 15.3

Cadmium 35 2.4 0.7 1.3 1.3

Chromium 35 6.2 0.8 2.1 1.9

Copper 35 345 74.9 128 110

Iron 35 3,390 940 1,750 1,550

Lead 35 21.8 6.1 12.5 11.5

Manganese 35 4,460 826 2,320 2,170

Nickel 35 2.4 1.0 1.6 1.5

Zinc 35 386 197 262 241

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
122 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: 1996–2013

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
Data 123

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324200—Clark Fork at Deer Lodge

Period of record for biological data: 1986–87, 1990–2013

Arctopsyche grandis

Arsenic 6 13.3 5.8 9.3 9.2

Cadmium 8 4.7 2.6 1

3.5 13.4

Chromium 8 4.7 1.0 1

2.4 11.9

Copper 8 183 34.9 99.1 89.6

Iron 8 2,320 537 1,170 1,050

Lead 8 17.4 3.8 1

10.5 111.2

Manganese 8 1,620 380 1,100 1,170

Nickel 8 1.9 <1.3 1

1.4 11.2

Zinc 8 370 140 268 274

Hydropsyche cockerelli

Arsenic 10 17.1 5.8 10.3 10.7

Cadmium 33 3.5 0.6 1.5 1.5

Chromium 33 4.3 0.4 1.8 1.8

Copper 33 241 54.7 107 104

Iron 33 3,340 490 1,260 1,060

Lead 33 24.9 3.8 10.6 9.9

Manganese 33 1,570 396 953 994

Nickel 33 2.4 0.3 1.3 1.1

Zinc 33 391 132 200 192

Hydropsyche occidentalis

Arsenic 21 21.1 6.6 11.4 10.6

Cadmium 58 3.4 0.6 1.4 1.3

Chromium 58 3.7 0.6 2.0 1.9

Copper 58 222 49.4 124 121

Iron 58 3,240 558 1,530 1,490

Lead 58 20.1 3.5 12.0 11.8

Manganese 58 2,850 649 1,610 1,660

Nickel 58 12.9 1.0 1.7 1.4

Zinc 58 346 166 246 237

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
124 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 8 16.6 3.2 7.3 6.6

Cadmium 8 4.9 1.2 3.2 3.5

Chromium 8 4.6 0.9 1

1.9 11.7

Copper 8 209 42.0 106 103

Iron 8 2,580 410 1,090 974

Lead 8 18.0 4.2 9.2 8.5

Manganese 8 1,940 659 1,240 981

Nickel 8 2.2 0.7 1.3 1.2

Zinc 8 378 228 283 285

Hydropsyche cockerelli

Arsenic 2 11.1 7.8 9.5 --

Cadmium 2 4.0 0.9 2.5 --

Chromium 2 3.4 2.0 2.7 --

Copper 2 158 81.5 120 --

Iron 2 2,150 1,050 1,600 --

Lead 2 18.8 10.1 14.4 --

Manganese 2 1,500 1,270 1,380 --

Nickel 2 1.7 1.4 1.5 --

Zinc 2 284 216 250 --

Hydropsyche occidentalis

Arsenic 9 14.7 6.4 10.1 8.8

Cadmium 9 2.5 1.3 2.0 2.0

Chromium 9 3.6 0.7 2.1 2.0

Copper 9 182 85.7 132 142

Iron 9 2,390 1,190 1,650 1,300

Lead 9 17.9 8.8 13.4 11.5

Manganese 9 2,100 975 1,460 1,260

Nickel 9 1.9 1.0 1.5 1.5

Zinc 9 299 223 260 254

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
Data 125

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324680—Clark Fork at Goldcreek

Period of record for biological data: 1992–2013

Arctopsyche grandis

Arsenic 37 17.0 1.8 5.1 4.7

Cadmium 66 6.6 0.6 2.0 1.8

Chromium 66 5.3 0.1 1.4 1.1

Copper 66 232 19.9 51.7 39.3

Iron 66 3,070 195 774 586

Lead 66 16.9 1.0 4.1 3.4

Manganese 66 1,580 436 876 870

Nickel 66 3.1 0.2 0.8 0.7

Zinc 66 326 146 207 192

Claassenia sabulosa

Arsenic 26 2.5 0.4 1.4 1.4

Cadmium 46 3.5 0.1 1.0 0.7

Chromium 46 1.6 0.2 0.6 0.5

Copper 46 84.9 33.0 59.4 58.8

Iron 46 640 63.0 199 170

Lead 46 2.8 0.4 1.0 0.8

Manganese 46 320 50.6 153 143

Nickel 46 0.7 0.1 0.3 0.3

Zinc 46 364 166 265 260

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
126 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: 1992–2013

Hydropsyche occidentalis

Arsenic 15 11.5 4.4 6.8 6.0

Cadmium 30 2.3 0.4 1.3 1.3

Chromium 30 3.9 0.4 1.8 1.7

Copper 30 170 26.4 72.6 62.5

Iron 30 2,720 466 1,240 1,140

Lead 30 15.7 2.9 7.4 6.0

Manganese 30 2,900 530 1,250 1,140

Nickel 30 2.5 0.8 1.3 1.1

Zinc 30 328 97.0 205 203

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
Data 127

Constituent Number of composite 

samples Maximum Minimum Mean Median

12331800—Clark Fork near Drummond

Period of record for biological data: 1986, 1991–2013

Arctopsyche grandis

Arsenic 28 8.2 1.8 4.1 4.0

Cadmium 60 3.8 0.4 1.5 1.3

Chromium 60 4.2 0.2 1.1 1.0

Copper 60 103 16.9 35.2 29.6

Iron 60 1,720 193 620 516

Lead 60 11.8 1.6 4.7 3.9

Manganese 60 2,010 456 833 737

Nickel 60 1.9 0.2 0.7 0.6

Zinc 60 314 140 203 192

Claassenia sabulosa

Arsenic 23 1.9 0.6 1.2 1.2

Cadmium 59 2.8 0.1 1.0 1.0

Chromium 59 3.3 0.2 0.7 0.6

Copper 59 165 18.0 65.1 61.3

Iron 59 449 45.4 176 148

Lead 59 2.9 0.2 1.0 0.9

Manganese 59 748 33.1 184 147

Nickel 59 1.1 0.1 1

0.3 10.2

Zinc 59 567 103 280 268

Hydropsyche cockerelli

Arsenic 16 7.2 3.9 5.6 5.5

Cadmium 45 4.5 0.3 1.2 0.9

Chromium 45 3.5 0.4 1.6 1.5

Copper 45 156 30.0 58.6 51.1

Iron 45 2,500 506 1,160 969

Lead 45 15.0 4.7 8.4 7.4

Manganese 45 1,680 549 1,000 929

Nickel 45 2.0 0.5 1.1 1.1

Zinc 45 322 134 196 187

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
128 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, 1991–2013

Hydropsyche occidentalis

Arsenic 17 7.7 4.3 5.6 5.4

Cadmium 33 2.0 0.4 1.0 1.0

Chromium 33 8.1 0.4 2.2 2.1

Copper 33 118 13.3 58.0 55.8

Iron 33 2,060 424 1,230 1,190

Lead 33 14.0 3.0 8.6 8.9

Manganese 33 2,920 477 1,400 1,220

Nickel 33 2.4 0.5 1.3 1.2

Zinc 33 293 153 221 222

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 2.6 --

Chromium 0 -- -- -- --

Copper 1 -- -- 85.0 --

Iron 1 -- -- 913 --

Lead 1 -- -- 9.1 --

Manganese 0 -- -- -- --

Nickel 0 -- -- -- --

Zinc 1 -- -- 260 --

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
Data 129

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12334550—Clark Fork at Turah Bridge, near Bonner

Period of record for biological data: 1986, 1991–2013

Arctopsyche grandis

Arsenic 31 7.2 3.1 4.5 4.4

Cadmium 73 2.7 0.4 1.2 1.0

Chromium 73 4.1 0.5 1.6 1.5

Copper 73 125 17.6 37.6 31.7

Iron 73 2,870 372 919 790

Lead 73 13.2 1.6 4.4 3.7

Manganese 73 902 324 652 662

Nickel 73 2.6 0.4 1.1 0.9

Zinc 73 282 111 203 201

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 23 9.8 3.7 4.9 4.7

Cadmium 51 2.2 0.3 0.9 0.7

Chromium 51 14.2 0.2 2.2 1.6

Copper 51 126 26.4 49.0 44.0

Iron 51 3,180 566 1,230 1,110

Lead 51 19.7 2.2 5.6 5.2

Manganese 51 848 426 648 661

Nickel 51 2.7 0.6 1.3 1.2

Zinc 51 332 119 190 194

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 --
130 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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]

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, 1991–2013

Hydropsyche occidentalis

Arsenic 19 7.3 2.9 4.7 4.2

Cadmium 39 1.8 0.3 1.0 0.9

Chromium 39 5.0 0.6 2.0 1.7

Copper 39 102 27.4 49.9 45.3

Iron 39 2,590 472 1,280 1,160

Lead 39 14.2 2.8 6.5 5.7

Manganese 39 1,600 454 857 813

Nickel 39 3.2 0.6 1.3 1.2

Zinc 39 416 145 216 221

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 131

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]

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, 2006–13

Arctopsyche grandis

Arsenic 10 4.6 1.6 2.6 2.2

Cadmium 20 0.5 0.1 0.3 0.2

Chromium 15 6.9 0.5 2.1 1.3

Copper 20 19.3 9.9 13.5 12.7

Iron 20 1,880 108 731 761

Lead 20 2.3 0.5 1.1 0.9

Manganese 15 633 286 454 422

Nickel 15 3.7 0.7 1.4 1.2

Zinc 20 170 106 142 141

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 7 4.2 2.1 3.0 3.0

Cadmium 7 0.6 <0.1 1

0.3 10.3

Chromium 7 3.8 1.6 2.8 2.4

Copper 7 17.0 5.6 14.2 15.5

Iron 7 2,390 1,120 1,720 1,640

Lead 7 2.3 1.5 2.0 2.0

Manganese 7 814 417 585 615

Nickel 7 4.6 1.4 2.3 1.9

Zinc 7 165 140 151 148

Hydropsyche occidentalis

Arsenic 14 3.8 1.2 2.2 2.0

Cadmium 26 0.5 0.1 0.2 0.2

Chromium 26 5.8 0.8 2.1 1.9

Copper 26 20.9 12.0 15.9 15.8

Iron 26 2,090 927 1,470 1,480

Lead 26 2.0 0.8 1.5 1.5

Manganese 26 798 412 518 460

Nickel 26 4.9 0.9 1.6 1.4

Zinc 26 202 116 143 144
132 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, 2006–13

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 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]
Data 133

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2013.—

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; --, indicates either too few 

samples (less than three) or insufficient data to compute statistic, or element not analyzed; <, less than minimum reporting level]

Constituent Number of composite 

samples Maximum Minimum Mean Median

12340500—Clark Fork above Missoula

Period of record for biological data: 1997–2013

Arctopsyche grandis

Arsenic 29 7.2 1.2 3.8 3.6

Cadmium 48 2.3 0.1 1.0 0.8

Chromium 48 4.2 0.4 1.6 1.5

Copper 48 81.2 13.7 38.7 35.0

Iron 48 2,340 302 1,020 894

Lead 48 8.8 1.1 4.1 3.9

Manganese 48 1,410 476 909 890

Nickel 48 2.1 0.3 1.2 1.1

Zinc 48 272 133 200 200

Claassenia sabulosa

Arsenic 20 1.9 0.1 1.2 1.2

Cadmium 29 2.0 0.2 0.7 0.6

Chromium 29 1.4 0.1 0.7 0.8

Copper 29 81.1 25.8 52.5 51.0

Iron 29 424 82.0 225 227

Lead 29 3.1 0.2 1.0 0.8

Manganese 29 683 57.8 195 146

Nickel 29 0.6 0.2 1

0.3 10.3

Zinc 29 379 191 273 271

Hydropsyche cockerelli

Arsenic 20 8.9 2.4 6.0 6.4

Cadmium 29 2.0 0.4 0.9 1.0

Chromium 29 6.0 1.0 2.9 3.1

Copper 29 99.7 24.4 62.8 59.7

Iron 29 3,590 830 2,030 2,060

Lead 29 12.1 2.5 7.5 7.2

Manganese 29 1,910 764 1,220 1,180

Nickel 29 2.4 0.9 1.8 1.8

Zinc 29 266 156 221 222

Hydropsyche occidentalis

Arsenic 12 7.4 2.2 5.1 5.6

Cadmium 18 1.5 0.4 0.8 0.7

Chromium 18 5.5 0.7 2.9 3.0

Copper 18 80.7 25.3 53.9 58.9

Iron 18 2,540 690 1,900 2,060

Lead 18 11.4 2.1 6.8 6.6

Manganese 18 2,470 717 1,510 1,560

Nickel 18 2.4 0.7 1.8 1.8

Zinc 18 278 183 229 230 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. 
Publishing support provided by: 

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/ofr20141244

Dodge and others—Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana—OFR 2014–1244