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

Water-Quality, Bed-Sediment, and Biological Data 

(October 2014 through September 2015) and 

Statistical Summaries of Data for Streams in the 

Clark Fork Basin, Montana

Open-File Report 2016–1201

U.S. Department of the Interior

U.S. Geological Survey
Cover. Photograph of the Clark Fork River near Missoula, Montana, by Michael Williams taken on 

September 1, 2016. Michael Williams Photography, Missoula, Montana. Used with permission.
Water-Quality, Bed-Sediment, and 

Biological Data (October 2014 through 

September 2015) and Statistical Summaries 

of Data for Streams in the Clark Fork Basin, 

Montana

By Kent A. Dodge, Michelle I. Hornberger, and Matthew A. Turner

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

Open-File Report 2016–1201

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, Director

U.S. Geological Survey, Reston, Virginia: 2017

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Suggested citation:

Dodge, K.A., Hornberger, M.I., and Turner, M.A., 2017, Water-quality, bed-sediment, and biological data (October 2014 

through September 2015) and statistical summaries of data for streams in the Clark Fork Basin, Montana: U.S. Geological Survey Open-File Report 2016–1201, 122 p., https://doi.org/10.3133/ofr20161201.

ISSN 0196-1497 (print)

ISSN 2331-1258 (online)
iii

Contents

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

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

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

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

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

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

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

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

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

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

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

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

Methods................................................................................................................................................13

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

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

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

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

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

Figure

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

Tables

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

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

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

and biota samples from the Clark Fork Basin, Montana ........................................................6

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

Basin, Montana .............................................................................................................................7

 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through 

September 2015 ...........................................................................................................................20

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

Bridge, near Bonner, Montana (12334550), October 2014 through September 2015 .......40

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

Bonner, Montana (12340000), October 2014 through September 2015 ..............................44

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

Missoula, Montana (12340500), October 2014 through September 2015 ...........................48

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

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

September 2015 ...........................................................................................................................52
iv

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

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

September 2015...........................................................................................................................54

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

statistics at Warm Springs Creek at Warm Springs, Montana (12323770), March

through September 2015............................................................................................................56

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

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

September 2015...........................................................................................................................58

12. Analyses of field replicates for water samples, Clark Fork Basin, Montana ...................60

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

Montana .......................................................................................................................................63

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

Montana .......................................................................................................................................64

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

samples ........................................................................................................................................65

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

Basin, Montana...........................................................................................................................66

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

18. Bed-sediment data for the Clark Fork Basin, Montana, August 2015................................68

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

samples ........................................................................................................................................69

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

21. Biological data for the Clark Fork Basin, Montana, August 2015 .......................................71

22. Recovery efficiency for analyses of standard reference material for biota samples ....73

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

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

Montana, March 1985 through September 2015 ...................................................................75

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

Montana, August 1986 through August 2015..........................................................................95

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

August 1986 through August 2015..........................................................................................100
v

Conversion Factors

U.S. customary units to International System of Units

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 micrograms per gram (μg/g)

parts per million 1 micrograms per milliliter (μg/mL)

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

Datum

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

Supplemental Information

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Water year is the 12-month period from October 1 through September 30 and is designated by 

the calendar year in which it ends. For example, water year 2015 is the period from October 1, 

2014, through September 30, 2015.
vi

Abbreviations

CRM certified reference material

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 2014 through September 2015) and Statistical 

Summaries of Data for Streams in the Clark Fork Basin, 

Montana

By Kent A. Dodge, Michelle I. Hornberger, and Matthew A. Turner

Abstract

Water, bed sediment, and biota were sampled in selected 

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 2014 through September 2015. Bed-sediment and biota 

samples were collected once at 13 sites during August 2015. 

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

samples collected at sites from October 2014 through September 2015. Water-quality data include concentrations of 

selected major ions, trace elements, and suspended sediment. 

At 12 sites, samples for analysis of dissolved organic carbon 

and turbidity were collected. In addition, samples for analysis 

of nitrogen (nitrate plus nitrite) were collected at two sites. 

Daily values of mean suspended-sediment concentration and 

suspended-sediment discharge were determined for three sites. 

Seasonal daily values of turbidity were determined for four 

sites. Bed-sediment data include trace-element concentrations 

in the fine-grained fraction. Biological data include trace-element concentrations in 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 (2016) 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 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 are deposited farther downstream in stream channels, on flood plains, in the Warm Springs Ponds, and at the 

location of the former Milltown Reservoir (fig.1) whose dam 

(Milltown Dam) was breached on March 28, 2008 (Andrews, 

1987). The presence 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. The 

development of a long-term database was considered necessary to detect trends over time 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 
2 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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

Helena

M O N T A N A

Study area

Missoula

Butte

Anaconda

Opportunity

Galen

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

WarmSprings Cr

Silver

Bow

Creek

Blacktail

Cr

CONTINENTAL

12340500 12340000

12334550

12331800

12324680

12324200

12323800

12323750 12323770

12323600

12323250

Streamflow site type

 Continuous record

 Periodic measurement

Water-quality, bed-sediment,

and biota site type

 Periodic water quality

 Daily suspended sediment

 Daily turbidity

 Once-annual bed sediment

 Once-annual biota

EXPLANATION

12323700

12323720

Lost Cr 12323850

12323230

12323670

Mill

Creek

Willow

Creek

12323710

Creek

47°

12323760

Dempsey

Creek 461903112440701

461559112443301

461415112450801

Mill Creek

Willow

Creek

Cr Silver

Bow

Opportunity

Base modified from 

U.S. Geological Survey, 

State base map, 1966

1:1,000,000

North American Datum of 1927

Site number

461903112440701 Miscellaneous site number

12324200

12323840

12324400

0 10 20 MILES

0 10 20 KILOMETERS

46°

114°

113°

Racetrack

former

Warm Springs
Water-Quality Data 3

1991; Lambing and others, 1994, 1995; Dodge and others, 

1996 through 2010, 2012, 2013, 2014a, 2014b; Dodge and 

Hornberger, 2015). Trace-element data for bed sediment and 

biota (aquatic benthic insects) have been collected intermittently at selected sites since 1986 as part of studies on 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 2014 through September 2015 

(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 three sites, and daily turbidity 

values were computed using data measured by continuous 

turbidity monitors recording every 15 minutes at four sites. 

Bed-sediment and biological samples were collected annually 

at 13 sites, with one additional site (Warm Springs Creek at 

Warm Springs [12323770]) sampled every third year. Continuous streamflow data were collected at 19 sites.

Properties measured onsite and constituents for which 

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

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

samples are listed in table 3. Results of onsite measurements 

of stream properties; laboratory analyses of water-quality, 

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

for water year 2015 (October 1, 2014 through September 30, 

2015) are listed in tables 4 through 23 at the back of the 

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

and September 2015 are listed in tables 24 through 26 at the 

back of the report.

Quality assurance of data was maintained through the use 

of documented procedures described in the following sections. 

These quality-assurance data 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 three daily suspended-sediment 

sites, suspended-sediment samples were collected by a contract observer 2–7 times per week, depending on season and 

flow conditions. Continuous turbidity monitors were operated seasonally (March to September 2015) 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). The use of these methods provides 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 

depth-integrating water-quality samplers (Davis, 2005) that 

were constructed of plastic or coated with a nonmetallic 

rubber-coating paint and equipped with polytetrafluoroethylene (PTFE) nozzles.
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] Site number (fig. 1) Site 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 -- 03/1993–08/1995, 12/1996–08/2003, 12/2004–P -- -- -- -- 12323250 Silver Bow Creek below Black- tail Creek, at Butte 10/1983–P 03/1993–08/1995, 12/1996–P -- -- -- -- 12323600 Silver Bow Creek at Opportunity 07/1988–P 03/1993–08/1995, 12/1996–P 03/1993–09/1995, D -- 07/1992–P 07/1992, 08/1994– 08/1995, 08/1997–P 12323670 Mill Creek near Anaconda 10/2004–P 12/2004–P -- 06/2006–09/2012, D -- -- 12323700 Mill Creek at Opportunity 04/2003–P 03/2003–P -- 04/2013–P -- -- 12323710 Willow Creek near Anaconda 03/2005–P 12/2004–P -- 06/2006–09/2012, D -- -- 12323720 Willow Creek at Opportunity 04/2003–P 03/2003–P -- 04/2013–P -- -- 12323750 Silver Bow Creek at Warm Springs 03/1972– 09/1979, 04/1993–P 03/1993–P 04/1993–09/1995, D -- 07/1992–P 07/1992–P 12323760 Warm Springs Creek near Anaconda 10/1997–P 10/2005–P -- 05/2006–09/2012, D -- -- 12323770 Warm Springs Creek at Warm Springs 10/1983–P 03/1993–P -- 04/2013–P 08/1995, 08/1997, 08/1999, 08/2002, 08/2005, 08/2008, 08/2011, 08/2014 08/1995, 08/1997, 08/1999, 08/2002, 08/2005, 08/2008, 08/2011, 08/2014 12323800 Clark Fork near Galen 07/1988–P 07/1988–P -- -- 08/1987, 08/1991–P 08/1987, 08/1991–P 12323840 Lost Creek near Anaconda 10/2004–P 12/2004–P -- 05/2006–P -- -- 12323850 Lost Creek near Galen 04/2003–P 03/2003–P -- -- -- -- 461415112450801 Clark Fork below Lost Creek, near Galen -- -- -- -- 08/1996–P 08/1996–P 461559112443301 Clark Fork at county bridge, near Racetrack -- -- -- -- 08/1996–P 08/1996–P 461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack -- -- -- -- 08/1996–P 08/1996–P 12324200 Clark Fork at Deer Lodge 10/1978–P 03/1985–P 03/1985–08/1986, 04/1987–03/2003, 08/2003–2014 -- 08/1986–08/1987, 08/1990–P 08/1986–08/1987, 08/1990–P

12324400 Clark Fork above Little Blackfoot River, near Garrison 02/2009–P 03/2009–P -- -- 08/2009–P 08/2009–P
Water-Quality Data 

5

Site number (fig. 1) Site name

Continuousrecord 

streamflow

Periodic 

water quality1

Daily suspended 

sediment

Daily turbidity 

(seasonal)

Fine-grained bed 

sediment2 Biota2

12324680 Clark Fork at Goldcreek 10/1977–P 03/1993–P -- -- 07/1992–P 07/1992–P

12331800 Clark Fork near Drummond 04/1993–P 03/1993–P -- -- 08/1986, 08/1987, 

08/1991–P

08/1986, 08/1991–P

12334550 Clark Fork at Turah Bridge, near 

Bonner

03/1985–P 03/1985–P 03/1985–03/2003, 

08/2003–P

-- 08/1986, 08/1991–P 08/1986, 08/1991–P

12340000 Blackfoot River near Bonner 10/1939–P 03/1985–P 07/1986–04/1987, 

06/1988–09/1995,

10/2005–P

-- 08/1986–08/1987, 

08/1991, 08/1993–08/1996, 08/1998–

08/2001, 09/2003,

08/2006–P

08/1986–08/1987, 08/1991, 08/1993, 08/1996, 08/1998, 09/2000, 09/2003,08/2006–P

12340500 Clark Fork above Missoula 03/1929–P 07/1986–P3 07/1986–04/1987, 

06/1988–01/1996, 03/1996–03/2003, 

08/2003–P

04/2007–09/2007 08/1997–P 08/1997–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. In 2012, dissolved organic carbon and turbidity analyses were included at select sites. In 2013, nutrient sample analyses were included for two sites (12323230 and 12323250) near Butte, Montana.

2Laboratory analyses of fine-grained bed sediment and aquatic benthic insects 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

Nitrate plus nitrite

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 labeled as 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).

Composited 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); filtered concentrations of calcium, magnesium, 

potassium, sodium, chloride, fluoride, silica, sulfate, nitrogen (nitrate plus nitrite), and organic carbon; and unfiltered 

turbidity (selected sites) were measured by the USGS National 

Water Quality Laboratory (NWQL) in Denver, Colorado. Concentrations of calcium and magnesium were used to calculate 

water hardness. 

Concentrations of arsenic, cadmium, copper, lead, 

manganese, and zinc in filtered samples were measured using 

inductively coupled plasma-mass spectrometry (ICP–MS) 

(Faires, 1993; Garbarino and others, 2006). Concentrations 

of calcium, magnesium, and iron in filtered samples were 

measured using inductively coupled plasma-atomic emission 

spectrometry (ICP–AES) (Fishman, 1993). Concentrations 

of potassium, sodium, alkalinity, chloride, fluoride, silica, 

sulfate, nitrogen (nitrate plus nitrite), and dissolved organic 

carbon were measured in filtered samples collected at select 

sites in the upper Clark Fork Basin. Potassium was measured 

by Standard Method 3120 (American Public Health Association, 1998); sodium and silica were analyzed by ICP–AES 

(Fishman, 1993); alkalinity was measured by electrometric 

titration (Fishman, 1993); chloride, fluoride, and sulfate were 

measured by ion chromatography (Fishman and Friedman, 

1989); nitrogen (nitrate plus nitrite) was measured by colorimetric enzymatic reduction (Patton and Kryskalla, 2011); and 

dissolved organic carbon was measured by persulfate oxidation and infrared spectrometry (Brenton and Arnett, 1993). 

Recoverable concentrations of trace elements were measured 

in unfiltered samples that were first digested with dilute 
Water-Quality Data 7

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

[lab, laboratory; NTRU, nephelometric turbidity ratio unit; --, not determined; mg/L, milligram per liter; μg/L, microgram 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)

Turbidity, unfiltered, lab, NTRU 2.0 units 20 --

Calcium, filtered 0.022 mg/L 20 --

Magnesium, filtered 0.011 mg/L 20 --

Potassium, filtered 0.03 mg/L 20 --

Sodium, filtered 0.06 mg/L 20 --

Alkalinity, filtered, lab 4.6 mg/L 20 --

Chloride, filtered 0.02 mg/L 20 --

Fluoride, filtered 0.01 mg/L 20 --

Silica, filtered 0.018 mg/L 20 --

Sulfate, filtered 0.02 mg/L 20 --

Nitrate plus nitrite, filtered 0.01 mg/L 20 --

Cadmium, filtered 0.030 μg/L 20 25

Cadmium, unfiltered recoverable 0.030 μg/L 20 25

Copper, filtered 0.80 μg/L 20 25

Copper, unfiltered recoverable 0.80 μg/L 20 25

Iron, filtered 4.0 μg/L 20 25

Iron, unfiltered recoverable 4.6 μg/L 20 25

Lead, filtered 0.040 μg/L 20 25

Lead, unfiltered recoverable 0.04 μg/L 20 25

Manganese, filtered 0.40 μg/L 20 25

Manganese, unfiltered recoverable 0.4 μg/L 20 25

Zinc, filtered 2.0 μg/L 20 25

Zinc, unfiltered recoverable 2.0 μg/L 20 25

Arsenic, filtered 0.01 μg/L 20 25

Arsenic, unfiltered recoverable 0.20 μg/L 20 25

Organic carbon, filtered 0.23 mg/L 20 --

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

Sediment, suspended 1 mg/L 20 --

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). Turbidity was measured by the NWQL using Standard 

Method 2130 (American Public Health Association, 1998) in 

selected unfiltered samples.

Water samples for analysis of suspended sediment also 

were collected from multiple vertical transits when periodic 

water samples were collected. Water 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 Wyoming-Montana Water Science Center Sediment Laboratory (hereinafter 

referred to as the “Wyoming-Montana Sediment Laboratory”) 

in Helena, Mont., according to methods described by Guy 

(1969) and Dodge and Lambing (2006).

Suspended-sediment samples for the three daily 

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

contract observers using the depth-integration method at a 

single vertical transit near midstream as described by Guy 

(1969). The samples were analyzed for suspended-sediment 

concentration, which was used to calculate daily mean 
8 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

suspended-sediment concentrations according to methods 

described by Porterfield (1972).

Suspended-sediment discharge was 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 was measured using 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. These 

values differ from the turbidity values reported from laboratory analyses of the discrete water-quality samples because 

of differences in instrumentation and sampling procedures. 

Continuous recordings enable determination of the minimum 

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

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

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

described by Wagner and others (2006).

Results

Water-quality data from samples collected periodically 

during water year 2015 (October 1, 2014 through September 30, 2015) are listed in table 4. In water year 2015, there 

were two water-quality samples with missing constituents 

because the constituents did not pass review and could not 

be resolved by reruns. Daily mean streamflow, daily mean 

suspended-sediment concentration, and daily suspendedsediment discharge for water year 2015 at the three daily 

suspended-sediment sites are listed in tables 5 through 7 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 8 

through 11 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 quality-control 

sample was submitted at a proportion equivalent to about 

5 percent of the total number of water samples; therefore, the 

total number of quality-control samples represented about 

15 percent of the total number of water samples. 

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. 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).
Water-Quality Data 9

Precision of analytical results for field replicates can be 

affected by numerous sources of variability within the field 

and laboratory environments, including sample collection, processing, and analysis. To provide data on overall precision for 

samples exposed to field and laboratory sources of variability, 

replicate stream samples for chemical analysis were obtained 

in the field by splitting a composite stream sample. Replicate stream samples for suspended-sediment analysis were 

obtained in the field by collecting two independent cross-sectional samples. Analyses of field replicate samples indicate the 

reproducibility of environmental data that are affected by the 

combined potential variability introduced by field and laboratory processes.

Precision of analytical results for laboratory replicates, 

which exclude field sources of variability, was determined 

using two independent chemical analyses of aliquots from a 

single sample selected from the group of samples constituting each analytical run. A separate analysis of the sample was 

made at the beginning and end of each analytical run to provide information on the reproducibility of laboratory analytical results independent of possible variability caused by field 

sample collection and processing. Laboratory replicates are 

not obtainable for suspended-sediment samples because the 

samples are consumed during the analysis.

Spiked samples are used to evaluate bias, which measures 

the ability of an analytical method to accurately quantify a 

known amount of analyte added to a sample. Because some 

constituents in stream water potentially can interfere with the 

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

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

and aliquots of stream samples were spiked in the laboratory 

with known amounts of the same trace elements for which 

water samples were being analyzed. Analyses of spiked blanks 

indicate if the spiking procedure and analytical method are 

within control for a water matrix that is presumably free of 

chemical interference. Analyses of spiked aliquots of stream 

samples indicate if the chemical matrix of the stream water 

interferes with the analytical measurement and whether these 

interferences could contribute substantial bias to reported 

trace-element concentrations for stream samples.

Deionized-water blank samples were submitted for every 

field trip and analyzed to identify the presence and magnitude 

of contamination that could potentially bias analytical results. 

The type of blank sample routinely tested was a field blank. 

Field blanks are aliquots of deionized water that are certified 

as 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 qualitycontrol 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 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 NWQL Web site (http://

wwwnwql.cr.usgs.gov/qas/Reporting_Limits/Website/Abbreviations_Definitions.pdf). 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):
10 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

S

d

k = ∑ 2

2 , (2)

where

S is the standard deviation of the difference in 

concentration between replicate analyses,

d is the difference in concentration between 

each pair of replicate analyses, and

k is the number of pairs of replicate analyses.

Precision also can be expressed as a relative standard 

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

standard deviation and the mean concentration for all of 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 12. 

The overall precision for each constituent estimated from 

analyses of field replicates, which include field and laboratory 

sources of variability, is listed in table 13. The data-quality 

objective used to indicate acceptable precision of results for 

field replicates was a maximum RSD of 20 percent (table 3). 

Precision estimates for the analytical results of field replicates 

were within the 20-percent RSD limit for all constituents 

except turbidity (table 13). This one exceedance of the dataquality objective resulted from a statistical artifact of calculating the difference between one estimated replicate sample pair 

and one replicate sample pair that is less than the LRL.

The precision for each constituent estimated from laboratory replicate analyses, which include only laboratory sources 

of variability, is listed in table 14. Statistics for the precision 

of analytical results for laboratory replicates are calculated 

by using unrounded values stored in laboratory data files. The 

data-quality objective used to indicate acceptable precision 

of results for laboratory replicates was a maximum RSD of 

20 percent (table 3). Precision estimates for the laboratory replicates were within the 20-percent RSD limit for all constituents (table 14). 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 15 and 16, respectively. The mean spike 

recovery for deionized-water blank samples spiked with trace 

elements (table 15) ranged from 91.9 to 115 percent with the 

smallest individual constituent recovery being manganese, 

filtered, at 64.7 percent and the largest being zinc, unfiltered recoverable, at 129 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 15) did not exceed a 25-percent deviation from 

an expected 100-percent recovery except for copper, unfiltered 

recoverable (126 percent); manganese, filtered (64.7 percent); 

and zinc, unfiltered recoverable (129 percent). The mean 

spike recovery for spiked stream samples (table 16) ranged 

from 94.2 to 110 percent with the smallest individual constituent recovery being iron, filtered, at 80.7 percent and the 

largest being iron, unfiltered recoverable, at 127 percent. The 

95-percent confidence intervals for the mean spike recovery 

for each constituent for which stream water samples were 

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

an expected 100-percent recovery except for iron, unfiltered 

recoverable (127 percent). 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 15) 

except for zinc, unfiltered recoverable (101–129 percent). 

Confidence intervals for percent recovery include 100 percent 

for all laboratory-spiked stream samples (table 16) except 

for lead, filtered (102–106 percent) and manganese, filtered 

(101–105 percent). No adjustments were made to analytical 

results for stream samples on the basis of spike recoveries.
Bed-Sediment Data 11

Analytical results for field blanks are listed in table 17. A 

field blank with constituent concentrations less than or equal 

to 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 greater 

than or equal to 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 17) 

almost always were less than the LRL. Two sample concentrations of filtered silica (0.072 and 0.042 milligrams per 

liter [mg/L]) exceeded the LRL of 0.018 mg/L. One sample 

concentration of iron, unfiltered recoverable (7.5 micrograms 

per liter [μg/L]) exceeded the LRL of 4.6 μg/L. Two blank 

samples (05/12/2015 and 08/11/2015) inadvertently were not 

analyzed for major constituents. 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 were collected once 

annually at 13 sites (fig. 1 and table 1) during low, stable flow 

conditions at about the same time of year as previous samples 

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

Warm Springs Creek at Warm Springs is sampled once every 

3 years rather than once annually and was not sampled during 

water year 2015.

Methods

Fine-grained bed-sediment samples were collected in 

August 2015 using protocols described by Axtmann and 

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

streambed deposits in areas near the edge of the stream using 

an acid-washed polypropylene scoop. Whenever possible, 

samples were collected from both sides of the stream. 

Individual samples of bed sediment were collected by 

scooping material from the surfaces of three to five randomly 

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

to five individual samples were combined to form a single 

composite sample. This collection process was repeated three 

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

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

was collected in an acid-washed 500-milliliter (mL) polyethylene bottle and transported to the laboratory on ice.

Bed-sediment samples were processed and analyzed 

at the USGS National Research Program Ecology and Contaminants Project Laboratory in Menlo Park, California. 

Bed-sediment samples were oven-dried at 60 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 site. 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 2015 are 

listed in table 18. Liquid-phase concentrations, measured in 

micrograms per milliliter, were analyzed in the reconstituted 

aliquots of digested bed sediment. Solid-phase concentrations, 

measured in micrograms per gram, were calculated using the 

following equation:

( ) ( )

( ) ( )

μg/mL volumeof digested sample, in mL μg/g dry weight of sample, in grams dilution ratio = . (5)

where

μg/g is micrograms per gram,

μg/mL is micrograms per milliliter, and

mL is milliliters.

The reported solid-phase concentrations (table 18) 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 the dilution ratio and the dry weight of the 
12 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

sample, MRLs for some trace elements might differ among 

sites 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. Bed-sediment 

samples were collected sequentially at sites along a general 

increasing concentration gradient (that is, downstream sites 

have lower metal concentrations in bed sediments compared 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. Ten low-concentration SRMs, 10 high-concentration SRMs, and 13 procedural 

blanks 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 19. Two SRMs, consisting of agricultural soils 

and representing low and high concentrations of trace elements, were analyzed to test recovery efficiency for a range of 

concentrations similar to those discovered 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 19) illustrate analytical performance. Metal 

recoveries of sediment digests were evaluated with NIST 

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

Mean recoveries in SRM 2709a ranged from 46.7 to 88.0 percent of the certified concentrations (table 19). The mean 

recoveries were within 18 percent of the SRM (based on the 

95-percent confidence interval) for copper, iron, manganese, 

nickel, and zinc. The lowest percent recoveries (between 46.7 

and 65.9 percent) were observed in trace elements with the 

lowest certified concentrations (cadmium, 0.371 micrograms 

per gram [μg/g]) or with a strong association with crystalline 

lattices (arsenic, chromium, and lead). Mean recoveries in 

SRM 2711a ranged from 56.9 to 97.4 percent (table 19). The 

percent recoveries were within 14 percent of the SRM (based 

on the 95-percent confidence interval) for arsenic, cadmium, 

copper, iron, lead, nickel, zinc, and 20 percent for manganese. 

The lowest mean recovery (56.9 percent) was observed in 

chromium analysis due to the strong binding nature of the 

crystalline lattice. No adjustments were made to trace-element 

concentrations in bed-sediment samples on the basis of recovery efficiencies. 

Procedural blanks for bed-sediment samples consisted 

of the analysis 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. Analytical results of procedural blanks for bed 

sediment (table 20) 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 

for one nickel value (0.003 micrograms per milliliter [μg/mL]) 

in the procedural blank analyzed with the sample collected 

from the Clark Fork at Goldcreek site. No adjustments were 

made to analytical data on the basis of procedural blanks.

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 2015.
Biological Data 13

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 matter and then sorted to their lowest possible taxonomic 

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

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

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

a final dry weight and digested by reflux using concentrated 

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

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

residue was reconstituted in 0.6N hydrochloric acid, filtered 

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

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

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

constituent that can be reliably reported for analyses of biota is 

termed the MRL.

Results

Concentrations of trace elements in whole-body tissue 

of aquatic insects collected during August 2015 are listed in 

table 21. The variability in the number of composite samples 

among species and among sites reflects differences in insect 

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

concentrations, in micrograms per milliliter, analyzed in the 

reconstituted samples were converted to solid-phase concentrations, in micrograms per gram, by using equation 5 (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 USGS 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 certified reference material (CRM) TORT-3 (lobster hepatopancreas) purchased from the National Research Council 

Canada. TORT-3 is the replacement for the preceding version 

of the CRM standard TORT-2 (also lobster hepatopancreas) 

reported in an earlier report (Dodge and Hornberger, 2015). 

Quality-control samples were analyzed in a proportion equivalent to about 20 percent of the total number of biota samples.

Recovery efficiencies for trace-element analyses of the 

TORT-3 CRM are listed in table 22. Data-quality objectives 

have not been established for analytical recovery in biota, 

but percent recoveries indicate analytical performance. Mean 

CRM recoveries for TORT-3 ranged from 79.6 to 170 percent for all constituents. The mean recoveries were within 

20 percent (based on the 95-percent confidence interval) for 

arsenic, cadmium, chromium, copper, iron, manganese, nickel, 
14 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

and zinc. Mean recovery was the highest for lead analysis 

(170 percent), likely because of the low certified concentration 

in the standard (0.225 μg/g). 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 23) are reported as a liquid-phase concentration, in micrograms per milliliter. A procedural blank was prepared and analyzed concurrently with biota samples for each 

site. Concentrations of trace elements in all procedural blanks 

were less than the 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 24 through 26 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 24) 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 bed-sediment (table 25) and biological data (table 26) are 

based on results of samples collected once each year 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 25) are based on 

the mean trace-element concentrations determined for each 

year from the mean of the analyses of composite samples; 

therefore, the number of samples for bed sediment represents 

the number of years that the constituent was analyzed. The 

number of samples for arsenic for bed sediment is smaller 

than the number for other trace elements because sampling for 

arsenic began in September 2003. In addition, the number of 

samples analyzed for silver in bed sediment is smaller because 

analysis for this constituent was discontinued in 2004.

In contrast, statistics for biological data (table 26) 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 among sites and among years. As a result, 

the statistics for biota describe a wider range of variation in 

trace-element 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 sites 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 clearly be identified to the species 

level, but the individual insects had morosa characteristics.

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of/2007/1301.]
16 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

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

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

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through September 2011) and statistical summaries of data 

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Dodge, K.A., Hornberger, M.I., and Dyke, J.L., 2014b, Waterquality, bed-sediment, and biological data (October 2012 

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

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

2001 through September 2002) and statistical summaries of 

data for streams in the upper Clark Fork Basin, Montana: 

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

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

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measurement of fluvial sediment: U.S. Geological Survey 

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92–634, 28 p.

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in water and fluvial sediments: U.S. Geological Survey 

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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.

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practices for the chemical and biological analyses of water 

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plasma-mass spectrometry: U.S. Geological Survey Techniques and Methods, book 5, sec. B, chap. 1, 88 p.
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Garbarino, J.R., and Struzeski, T.M., 1998, Methods of analysis by the U.S. Geological Survey National Water Quality 

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98–165, 101 p.

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

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

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

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

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94–539, 57 p.

Jones, B.E., 1987, Quality control manual of the U.S. Geological Survey’s National Water Quality Laboratory: U.S. 

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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 

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

September 1987) and statistical summaries (March 1985 

through September 1987) for the Clark Fork and selected 

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

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

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

through September 1988) and statistical summaries (March 

1985 through September 1988) for the Clark Fork and 

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

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

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

through September 1989) and statistical summaries (March 

1985 through September 1989) for the Clark Fork and 

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

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

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

of the upper Clark Fork Basin from Galen to Missoula, 

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

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

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

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

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

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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 2014 through September 2015.

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

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 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2014 0845 13 7.5 234 6.0 <2.0 92.7 25.8 6.85

03/23/2015 0925 15 7.5 231 3.0 E3.5 90.4 25.8 6.31

04/20/2015 0900 12 7.6 245 4.0 E2.7 102 29.7 6.78

05/11/2015 0905 13 7.7 234 6.0 E3.7 96.5 27.9 6.53

05/26/2015 0915 25 7.7 195 11.0 E6.5 81.0 23.2 5.59

06/08/2015 0915 20 7.7 213 13.0 E7.5 88.3 25.2 6.16

07/13/2015 1015 5.7 7.7 295 12.0 E2.6 126 36.0 8.76

08/10/2015 0845 4.6 7.6 317 10.0 <2.0 129 36.9 8.84

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 

(mg/L)

Nitrate plus 

nitrite, 

filtered 

(mg/L)

Cadmium, 

filtered 

(μg/L)

10/14/2014 2.74 9.60 78.4 8.25 0.19 21.6 24.2 0.53 <0.030

03/23/2015 2.55 9.45 74.1 10.6 0.18 21.1 22.3 0.52 0.033

04/20/2015 2.39 10.8 78.0 11.9 0.19 23.9 23.4 0.61 <0.030

05/11/2015 2.34 9.81 77.5 10.8 0.18 22.6 21.3 0.50 0.045

05/26/2015 2.66 8.99 66.7 7.43 0.21 24.9 16.2 0.23 <0.030

06/08/2015 2.53 8.84 76.7 6.87 0.19 26.1 14.7 0.28 0.037

07/13/2015 2.73 11.9 101 11.9 0.23 24.4 25.6 1.05 0.049

08/10/2015 2.62 12.2 105 13.1 0.23 26.2 30.4 1.24 <0.030

Date

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)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/14/2014 <0.030 1.8 2.6 165 387 0.092 0.30 28.0 33.2

03/23/2015 <0.030 2.9 4.2 356 781 0.232 0.64 45.1 57.3

04/20/2015 <0.030 2.6 3.6 224 512 0.136 0.38 43.1 52.0

05/11/2015 <0.030 3.2 4.1 233 652 0.167 0.55 43.2 53.0

05/26/2015 <0.030 5.5 8.2 348 866 0.297 0.99 36.4 57.4

06/08/2015 0.037 4.8 7.2 739 1,370 0.531 1.32 60.6 91.7

07/13/2015 <0.030 1.9 2.2 122 420 0.139 0.56 49.1 54.8

08/10/2015 <0.030 1.2 2.3 51.9 372 0.050 0.38 44.4 54.8

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)

10/14/2014 2.1 2.4 2.5 3.1 3.43 95 2 0.07

03/23/2015 2.1 3.4 2.7 3.6 5.22 86 4 0.16

04/20/2015 <2.0 2.9 2.3 2.7 4.29 92 3 0.10

05/11/2015 <2.0 2.3 2.9 3.6 4.88 93 4 0.14

05/26/2015 <2.0 3.8 5.2 6.6 8.13 74 9 0.61

06/08/2015 2.3 4.9 7.7 9.8 7.71 93 12 0.65

07/13/2015 <2.0 2.1 3.8 4.6 3.37 91 4 0.06

08/10/2015 <2.0 3.6 2.7 3.4 2.14 85 4 0.05
Data 21

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

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 temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2014 1035 29 7.7 445 8.0 E2.4 148 41.1 11.1

03/23/2015 1120 30 7.8 406 4.5 E3.0 141 39.8 10.2

04/20/2015 1020 27 7.7 441 6.5 E2.0 148 41.7 10.5

05/11/2015 1040 27 7.8 401 8.0 E4.5 132 38.0 8.91

05/26/2015 1105 44 7.8 348 13.0 E6.4 116 33.2 7.99

06/08/2015 1050 37 7.9 389 15.0 E8.6 126 36.3 8.62

07/13/2015 1140 19 7.8 514 16.0 E3.0 165 46.7 11.8

08/10/2015 1015 18 7.7 562 14.0 <2.0 169 47.7 12.2

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)

Nitrate plus 

nitrite, 

filtered 

(mg/L)

Cadmium, 

filtered 

(μg/L)

10/14/2014 5.50 26.2 101 25.7 0.31 20.5 72.7 1.61 0.057

03/23/2015 4.26 19.8 92.6 24.1 0.28 20.5 65.0 0.82 0.082

04/20/2015 4.98 23.4 77.3 26.6 0.29 22.6 65.2 0.80 0.062

05/11/2015 4.50 20.8 98.7 24.5 0.28 20.8 57.0 0.61 0.052

05/26/2015 4.48 18.2 89.9 18.5 0.29 22.9 45.0 0.44 0.043

06/08/2015 4.74 20.1 69.7 19.7 0.28 23.2 48.6 0.39 0.045

07/13/2015 6.25 28.5 80.4 31.5 0.33 19.7 77.0 0.65 0.049

08/10/2015 6.64 31.6 99.9 34.4 0.35 21.7 82.0 0.71 0.070

Date

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)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/14/2014 0.084 2.6 8.9 63.4 335 0.142 1.80 43.5 66.4

03/23/2015 0.073 7.4 8.0 392 484 0.720 1.11 67.8 76.2

04/20/2015 0.063 5.0 8.5 127 322 0.256 0.81 61.9 74.3

05/11/2015 0.081 4.0 10.2 154 535 0.240 1.67 61.0 77.2

05/26/2015 0.113 6.9 18.6 217 896 0.580 5.87 49.1 86.2

06/08/2015 0.091 6.0 12.5 353 959 0.806 2.90 65.8 89.7

07/13/2015 0.072 3.3 8.2 60.2 157 0.206 0.88 50.7 62.9

08/10/2015 0.078 3.8 11.0 41.1 123 0.196 0.75 51.9 62.3

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)

10/14/2014 31.0 41.1 2.8 3.6 4.93 82 7 0.55

03/23/2015 28.1 30.5 3.4 3.7 5.94 79 4 0.32

04/20/2015 30.8 37.4 2.9 3.1 6.09 87 6 0.44

05/11/2015 24.9 36.4 3.2 4.2 6.06 81 7 0.51

05/26/2015 18.8 42.7 4.9 7.1 8.66 85 19 2.3

06/08/2015 15.1 30.3 6.6 8.2 8.58 90 15 1.5

07/13/2015 13.1 26.1 4.1 4.4 7.21 80 4 0.21

08/10/2015 33.6 43.3 3.7 3.9 7.68 81 3 0.15
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 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323600—Silver Bow Creek at Opportunity

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2014 1215 43 8.4 452 8.5 E3.3 162 46.9 10.9

03/23/2015 1315 69 8.5 384 5.0 E4.4 148 44.5 8.83

04/20/2015 1200 70 8.8 397 8.0 E3.4 146 44.1 8.83

05/11/2015 1230 78 9.2 372 9.0 E3.7 142 43.0 8.42

05/27/2015 1340 143 8.3 274 12.0 E12 111 33.9 6.37

06/08/2015 1220 88 8.6 332 16.0 E5.7 131 39.9 7.67

07/13/2015 1310 25 9.2 497 20.0 E2.5 193 57.2 12.2

08/10/2015 1140 21 8.7 535 17.0 E3.6 191 56.2 12.3

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)

10/14/2014 4.82 25.9 100 26.9 0.47 21.5 78.4 0.255 0.276

03/23/2015 3.92 20.1 87.1 23.0 0.31 20.3 61.0 0.204 0.276

04/20/2015 3.74 20.9 89.3 25.8 0.34 18.6 62.4 0.157 0.249

05/11/2015 3.35 17.2 91.5 20.7 0.31 14.0 60.4 0.130 0.238

05/27/2015 3.17 12.6 75.8 10.7 0.25 20.2 37.2 0.192 0.313

06/08/2015 3.08 15.9 90.0 14.7 0.25 21.3 44.1 0.106 0.239

07/13/2015 5.47 29.0 105 39.0 0.43 12.2 83.6 0.165 0.228

08/10/2015 5.06 27.9 109 41.4 0.47 20.7 88.0 0.162 0.271

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/14/2014 12.4 18.7 154 289 0.975 1.92 60.9 91.4

03/23/2015 9.5 17.0 48.7 427 0.190 1.76 106 139

04/20/2015 9.9 16.8 39.5 323 0.168 1.31 123 174

05/11/2015 8.4 13.6 36.0 275 0.129 1.30 110 137

05/27/2015 18.5 28.5 397 841 4.22 6.79 82.3 139

06/08/2015 9.4 18.7 65.0 458 0.284 2.48 58.8 102

07/13/2015 11.8 15.9 20.9 114 0.132 0.67 35.0 62.8

08/10/2015 9.5 16.2 13.7 257 0.138 1.67 36.2 130

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)

10/14/2014 61.6 69.9 5.1 5.7 3.06 92 8 0.93

03/23/2015 46.3 69.6 4.9 6.0 5.55 77 11 2.0

04/20/2015 29.8 63.6 5.2 5.8 4.70 86 12 2.3

05/11/2015 18.1 44.6 4.8 5.5 5.33 85 8 1.7

05/27/2015 42.9 72.0 8.1 9.0 7.69 44 48 19

06/08/2015 14.8 42.8 7.3 8.4 6.40 87 12 2.9

07/13/2015 11.7 26.8 8.2 8.8 5.10 86 5 0.34

08/10/2015 17.3 44.9 8.2 8.8 3.89 90 8 0.45
Data 23

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323670—Mill Creek near Anaconda

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2014 1620 19 8.0 158 9.0 <2.0 71.4 19.5 5.49

03/23/2015 1635 41 7.8 128 5.0 E3.1 53.3 14.8 3.98

04/20/2015 1505 35 7.9 140 10.0 E2.0 62.8 17.7 4.50

05/11/2015 1605 64 7.9 104 9.5 E2.1 44.2 12.6 3.09

05/26/2015 1705 125 7.9 86 11.0 E3.5 36.4 10.5 2.45

06/08/2015 1535 147 7.8 75 14.0 E2.6 32.7 9.72 2.04

07/13/2015 1455 39 8.1 125 15.0 <2.0 58.1 16.4 4.16

08/10/2015 1430 22 8.2 159 15.0 <2.0 74.8 20.7 5.63

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)

10/14/2014 0.73 4.26 73.6 0.41 0.36 12.1 7.47 0.046 0.044

03/23/2015 0.73 5.47 56.3 0.40 0.32 14.7 8.12 0.050 0.052

04/20/2015 0.75 5.52 62.2 0.36 0.29 15.3 7.79 0.041 0.047

05/11/2015 0.57 3.64 46.5 0.26 0.29 13.6 5.17 0.035 0.058

05/26/2015 0.57 3.45 38.0 0.21 0.30 12.5 4.29 0.052 0.087

06/08/2015 0.51 2.57 33.0 0.16 0.29 9.88 3.20 0.040 0.061

07/13/2015 0.60 3.32 58.6 0.21 0.31 10.3 4.99 <0.030 0.048

08/10/2015 0.65 3.87 75.3 0.26 0.34 12.1 6.48 0.031 0.043

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/14/2014 1.8 1.8 60.9 107 0.065 0.20 6.43 9.8

03/23/2015 3.7 4.0 94.4 218 0.193 0.52 4.23 9.6

04/20/2015 2.4 3.1 40.6 144 0.091 0.41 4.85 10.2

05/11/2015 2.2 3.2 42.1 157 0.095 0.59 3.95 10.4

05/26/2015 3.5 4.9 117 306 0.364 1.12 8.29 16.3

06/08/2015 2.2 3.4 41.5 174 0.112 0.60 3.98 10.1

07/13/2015 2.4 2.5 69.4 167 0.125 0.45 7.22 13.3

08/10/2015 1.4 2.0 77.6 138 0.122 0.31 6.92 11.5

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)

10/14/2014 <2.0 <2.0 11.5 12.8 1.29 78 1 0.05

03/23/2015 2.3 3.1 16.0 17.9 2.80 96 2 0.22

04/20/2015 <2.0 2.5 16.4 16.9 2.16 85 3 0.28

05/11/2015 <2.0 4.0 13.9 14.4 2.35 66 3 0.52

05/26/2015 2.3 3.8 15.3 16.9 2.58 52 11 3.7

06/08/2015 <2.0 3.1 10.9 12.1 2.27 61 8 3.2

07/13/2015 <2.0 <2.0 16.4 18.3 2.03 65 3 0.32

08/10/2015 <2.0 <2.0 18.8 19.4 1.39 75 1 0.06
24 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323700—Mill Creek at Opportunity

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2014 1715 11 8.0 181 9.5 <2.0 80.1 22.2 6.01

03/23/2015 1745 34 8.0 142 5.0 E2.9 58.8 16.4 4.33

04/20/2015 1600 24 8.2 157 11.0 E2.1 67.9 19.0 4.99

05/11/2015 1705 38 8.0 114 9.0 E2.6 47.8 13.7 3.33

05/27/2015 0750 69 7.8 89 8.0 E5.0 39.0 11.2 2.64

06/08/2015 1630 85 7.9 80 15.0 E3.4 35.1 10.4 2.21

07/13/2015 1640 15 8.2 136 17.0 <2.0 63.8 18.0 4.56

08/10/2015 1535 3.6 8.1 176 17.0 <2.0 78.8 22.1 5.73

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)

10/14/2014 0.90 5.42 77.0 0.55 0.37 12.5 14.3 0.064 0.070

03/23/2015 0.72 5.89 59.5 0.50 0.32 14.2 12.0 0.054 0.078

04/20/2015 0.80 6.33 65.7 0.46 0.31 15.5 12.2 0.052 0.066

05/11/2015 0.60 4.06 49.1 0.31 0.29 13.8 7.55 0.067 0.082

05/27/2015 0.56 3.57 38.4 0.24 0.30 11.9 5.45 0.043 0.177

06/08/2015 0.57 2.75 34.5 0.18 0.30 10.2 4.11 0.047 0.103

07/13/2015 0.76 3.99 60.4 0.29 0.31 10.3 8.00 0.048 0.076

08/10/2015 0.78 4.98 77.4 0.41 0.36 12.1 11.8 0.057 0.052

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/14/2014 1.4 2.1 83.0 145 0.109 0.26 5.58 8.3

03/23/2015 3.0 4.5 77.9 238 0.164 0.69 3.05 10.5

04/20/2015 2.5 3.5 41.0 163 0.102 0.53 4.48 11.3

05/11/2015 2.4 3.8 46.7 195 0.151 0.79 4.25 13.8

05/27/2015 3.2 8.5 108 606 0.153 2.41 4.30 31.8

06/08/2015 3.1 5.5 66.2 300 0.274 1.29 4.93 17.5

07/13/2015 2.7 3.6 66.9 172 0.178 0.59 5.03 11.8

08/10/2015 2.2 2.8 68.0 115 0.142 0.29 6.40 8.6

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)

10/14/2014 2.7 3.1 18.6 21.3 1.76 64 1 0.03

03/23/2015 2.6 5.0 16.8 19.5 2.89 79 4 0.37

04/20/2015 <2.0 3.6 18.7 18.5 2.13 84 4 0.26

05/11/2015 <2.0 3.7 16.8 17.9 2.25 71 5 0.51

05/27/2015 2.2 8.5 15.1 19.8 2.79 61 19 3.5

06/08/2015 <2.0 5.5 14.0 16.1 2.30 56 14 3.2

07/13/2015 <2.0 2.9 23.7 25.9 2.45 86 2 0.08

08/10/2015 <2.0 <2.0 29.7 30.2 1.70 83 1 0.01
Data 25

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323710—Willow Creek near Anaconda

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2014 1415 2.1 7.8 124 8.0 <2.0 46.0 15.2 1.97

03/23/2015 1520 11 7.6 95 4.0 E12 38.0 12.7 1.54

04/20/2015 1335 10 7.7 98 6.0 E5.9 38.4 12.8 1.54

05/11/2015 1440 20 7.7 81 7.0 E4.9 30.1 10.1 1.21

05/26/2015 1445 26 7.7 86 10.5 E6.6 32.3 10.8 1.29

06/08/2015 1420 14 7.9 100 13.0 E5.5 38.9 13.1 1.47

07/14/2015 0750 3.8 7.7 113 11.0 E2.4 45.4 15.2 1.81

08/10/2015 1330 1.9 7.9 115 15.0 <2.0 42.9 14.4 1.68

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)

10/14/2014 1.13 7.48 53.3 0.72 0.07 24.8 8.44 0.035 0.043

03/23/2015 0.95 6.22 37.1 0.57 0.06 26.9 8.83 <0.030 0.047

04/20/2015 0.84 6.25 38.9 0.48 0.07 24.9 8.21 <0.030 <0.030

05/11/2015 0.84 5.08 33.4 0.38 0.06 26.0 5.98 <0.030 0.048

05/26/2015 0.87 5.03 34.7 0.37 E0.06 24.0 6.29 <0.030 0.052

06/08/2015 0.95 5.68 41.4 0.33 0.06 24.4 6.45 <0.030 0.047

07/14/2015 1.05 6.61 50.5 0.33 0.07 24.8 6.36 <0.030 0.037

08/10/2015 1.05 6.71 50.3 0.38 0.08 26.1 6.54 <0.030 0.045

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/14/2014 1.6 2.0 117 174 0.152 0.26 9.28 13.3

03/23/2015 3.2 3.9 226 759 0.390 0.94 9.82 24.1

04/20/2015 2.5 2.5 101 336 0.193 0.46 9.28 18.7

05/11/2015 2.2 2.9 121 282 0.200 0.67 7.58 17.6

05/26/2015 3.0 3.7 129 416 0.266 0.78 7.86 17.6

06/08/2015 2.2 2.7 84.2 253 0.220 0.58 10.8 14.7

07/14/2015 1.9 2.5 95.4 204 0.236 0.51 7.96 15.0

08/10/2015 2.2 2.8 106 231 0.215 0.49 7.79 13.6

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)

10/14/2014 <2.0 <2.0 15.8 17.4 3.63 92 1 0.01

03/23/2015 2.2 4.1 16.7 17.9 7.07 96 4 0.12

04/20/2015 <2.0 2.7 15.0 14.4 4.44 96 4 0.11

05/11/2015 <2.0 2.1 12.5 12.9 4.20 85 6 0.32

05/26/2015 <2.0 2.5 13.4 14.4 5.02 81 10 0.70

06/08/2015 <2.0 2.4 14.5 15.2 4.69 79 6 0.23

07/14/2015 <2.0 <2.0 19.5 20.6 4.24 94 3 0.03

08/10/2015 <2.0 <2.0 22.2 23.1 3.44 95 2 0.01
26 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323720—Willow Creek at Opportunity

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/14/2014 1255 6.5 8.2 275 10.0 <2.0 117 33.8 7.97

03/23/2015 1405 14 8.1 191 5.0 E7.2 79.8 24.1 4.79

04/20/2015 1240 11 8.0 200 9.0 E3.8 83.8 25.2 5.07

05/11/2015 1320 21 7.9 181 10.0 E3.1 75.6 22.7 4.62

05/26/2015 1315 34 7.9 191 13.5 E5.2 84.7 25.9 4.86

06/08/2015 1305 32 8.1 248 17.5 E4.2 115 34.1 7.26

07/13/2015 1350 7.7 8.6 278 17.0 <2.0 130 37.7 8.69

08/10/2015 1225 5.4 8.2 298 14.0 <2.0 134 38.7 9.06

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)

10/14/2014 1.48 10.9 117 2.40 0.44 21.5 23.3 <0.030 0.032

03/23/2015 1.34 8.98 75.2 1.65 0.20 24.4 18.0 0.034 0.076

04/20/2015 1.25 9.29 79.3 1.64 0.21 24.8 18.1 <0.030 0.050

05/11/2015 1.15 8.00 76.4 1.29 0.22 24.6 13.4 0.046 0.064

05/26/2015 1.50 9.00 81.5 1.29 0.25 25.8 12.4 0.053 0.137

06/08/2015 2.28 8.80 111 1.45 0.43 27.8 11.6 0.074 0.117

07/13/2015 1.45 9.53 124 2.01 0.44 19.8 18.7 <0.030 0.031

08/10/2015 1.39 9.22 131 2.35 0.49 20.4 21.7 <0.030 0.032

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/14/2014 1.4 3.4 25.3 139 0.172 0.97 13.8 18.7

03/23/2015 3.7 7.8 113 472 0.324 1.93 31.4 50.3

04/20/2015 4.0 7.2 59.0 264 0.238 1.34 30.6 45.0

05/11/2015 6.5 9.5 69.9 244 0.268 1.49 20.5 28.1

05/26/2015 8.7 15.3 100 381 0.378 2.44 22.9 41.8

06/08/2015 9.4 13.4 130 283 0.588 1.83 28.9 40.2

07/13/2015 2.3 2.8 28.7 105 0.166 0.55 4.15 7.2

08/10/2015 2.4 3.3 14.7 77.7 0.108 0.62 10.6 14.6

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)

10/14/2014 <2.0 4.0 12.1 14.3 2.30 89 2 0.04

03/23/2015 3.2 9.0 16.6 20.3 5.53 97 9 0.34

04/20/2015 2.7 8.0 19.4 20.3 4.02 96 6 0.18

05/11/2015 5.6 10.2 34.1 35.6 5.77 80 6 0.34

05/26/2015 6.5 15.0 48.4 53.1 7.67 86 12 1.1

06/08/2015 5.3 11.1 105 107 9.75 87 8 0.69

07/13/2015 <2.0 <2.0 23.9 26.3 3.04 92 2 0.04

08/10/2015 2.5 4.4 15.8 16.9 2.15 83 1 0.01
Data 27

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323750—Silver Bow Creek at Warm Springs

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2014 1030 67 8.7 477 8.5 <2.0 188 51.3 14.6

03/24/2015 0945 107 8.4 425 3.0 E4.7 182 53.0 12.0

04/21/2015 1025 99 8.4 447 8.0 E2.6 185 54.3 12.1

05/12/2015 1130 95 8.6 345 10.0 E3.0 136 39.5 9.12

05/27/2015 0955 219 8.7 354 11.5 E2.4 147 43.6 9.22

06/09/2015 0845 169 8.4 299 14.0 E3.5 122 36.0 7.82

07/14/2015 1050 48 9.3 380 16.0 E2.0 171 48.3 12.2

08/11/2015 1020 35 9.3 464 15.5 <2.0 205 58.6 14.3

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)

10/15/2014 4.36 20.4 100 18.6 0.75 9.44 110 0.040 0.053

03/24/2015 3.69 18.5 94.6 17.9 0.64 12.1 89.6 0.039 0.105

04/21/2015 3.81 19.1 98.9 18.9 0.59 11.1 94.1 0.033 0.062

05/12/2015 2.54 13.1 82.1 11.9 0.53 11.9 68.8 0.036 0.081

05/27/2015 3.41 16.9 86.3 15.1 0.52 10.8 65.0 0.053 0.114

06/09/2015 2.46 11.8 81.4 9.15 0.45 13.5 48.1 0.051 0.089

07/14/2015 2.34 14.3 93.3 10.8 0.63 13.7 84.5 <0.030 0.032

08/11/2015 2.73 16.6 103 13.9 0.77 15.6 114 <0.030 0.074

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/15/2014 2.0 4.1 26.0 105 0.122 0.61 36.7 66.8

03/24/2015 2.6 8.0 30.0 314 0.154 1.76 144 199

04/21/2015 2.3 6.6 29.9 252 0.185 1.42 128 158

05/12/2015 3.5 6.7 38.0 274 0.189 1.49 63.7 88.2

05/27/2015 5.7 9.5 40.5 275 0.196 1.45 60.4 87.6

06/09/2015 5.7 8.4 63.0 226 0.250 1.01 76.9 93.3

07/14/2015 2.4 2.8 25.7 99.8 0.087 0.38 48.7 88.2

08/11/2015 3.3 3.7 16.7 61.1 0.077 0.37 41.3 60.1

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)

10/15/2014 <2.0 5.5 16.1 18.7 3.96 91 2 0.36

03/24/2015 3.9 14.1 9.7 12.8 4.24 96 7 2.0

04/21/2015 3.3 13.3 10.5 12.7 3.80 96 6 1.6

05/12/2015 2.8 9.8 16.4 18.1 3.98 91 6 1.5

05/27/2015 3.7 13.2 17.9 21.1 5.00 80 6 3.5

06/09/2015 3.1 8.1 28.5 30.9 5.09 84 5 2.3

07/14/2015 <2.0 2.6 28.5 30.1 4.31 77 1 0.13

08/11/2015 <2.0 <2.0 29.7 30.7 4.36 88 1 0.09
28 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323760—Warm Springs Creek near Anaconda

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2014 0840 86 8.4 260 6.0 <2.0 131 38.8 8.34

04/21/2015 0845 78 8.4 254 5.0 <2.0 135 40.7 8.14

05/12/2015 0910 135 8.2 199 5.0 <2.0 98.2 29.8 5.78

05/27/2015 1520 238 8.2 148 8.0 E2.6 76.8 24.0 4.11

07/14/2015 0900 96 8.3 235 9.0 <2.0 123 36.5 7.70

08/11/2015 0820 68 8.4 258 9.5 <2.0 130 38.6 8.17

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)

10/15/2014 1.33 3.27 121 1.33 0.42 10.9 14.0 0.030 <0.030

04/21/2015 1.27 3.07 120 1.15 0.36 10.4 13.0 <0.030 <0.030

05/12/2015 0.94 2.08 91.6 0.75 0.31 9.29 10.4 <0.030 <0.030

05/27/2015 0.85 1.90 65.6 0.57 0.31 9.17 8.75 <0.030 0.033

07/14/2015 1.15 2.77 110 0.98 0.37 9.70 12.0 <0.030 <0.030

08/11/2015 1.23 3.09 120 1.19 0.41 10.9 13.9 <0.030 <0.030

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/15/2014 <0.80 1.1 <4.0 41.4 <0.040 0.12 0.58 2.1

04/21/2015 0.83 1.5 5.5 59.2 <0.040 0.19 0.55 2.7

05/12/2015 0.93 1.6 7.8 69.8 <0.040 0.23 0.70 3.4

05/27/2015 1.7 3.5 37 188 0.099 0.71 2.70 8.6

07/14/2015 0.95 1.9 9.1 73.7 <0.040 0.25 0.82 4.0

08/11/2015 <0.80 1.8 4.3 49.2 <0.040 0.19 0.50 2.7

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)

10/15/2014 <2.0 <2.0 1.9 2.1 0.84 68 2 0.46

04/21/2015 <2.0 6.2 1.7 1.8 1.18 71 3 0.63

05/12/2015 <2.0 3.0 1.4 1.5 1.40 72 4 1.5

05/27/2015 <2.0 6.2 1.5 1.9 2.06 62 9 5.8

07/14/2015 <2.0 2.6 2.8 3.0 1.07 84 3 0.78

08/11/2015 <2.0 <2.0 2.1 2.1 0.85 70 2 0.37
Data 29

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323770—Warm Springs Creek at Warm Springs

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2014 0950 37 8.2 385 7.0 <2.0 190 56.8 11.6

03/24/2015 0910 42 8.1 353 2.5 <2.0 187 56.3 11.2

04/21/2015 0945 49 8.2 338 6.0 <2.0 173 51.7 10.6

05/12/2015 1020 89 8.2 247 7.0 E2.3 121 36.9 7.01

05/27/2015 0900 156 8.0 190 9.0 E3.6 95.3 29.6 5.22

06/09/2015 0945 151 8.0 177 10.5 E4.7 87.2 27.0 4.79

07/14/2015 1010 26 8.3 316 12.0 <2.0 163 49.5 9.62

08/11/2015 0935 19 8.2 331 11.5 <2.0 167 50.0 10.1

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)

10/15/2014 1.67 4.56 144 1.91 0.47 11.5 55.8 0.048 0.042

03/24/2015 1.42 4.15 138 1.70 0.40 11.4 44.7 0.054 0.043

04/21/2015 1.39 3.92 134 1.53 0.40 10.9 40.1 0.041 0.038

05/12/2015 1.07 2.56 103 0.98 0.34 9.70 23.2 0.036 0.048

05/27/2015 0.97 2.29 77.3 0.74 0.33 9.26 17.7 0.032 0.089

06/09/2015 0.91 2.09 71.4 0.61 0.36 9.52 15.3 0.063 0.071

07/14/2015 1.46 3.93 127 1.52 0.40 10.0 35.4 0.031 <0.030

08/11/2015 1.43 3.81 135 1.54 0.43 11.0 35.9 0.044 0.050

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/15/2014 3.4 5.3 36.8 65.5 0.113 0.29 46.6 59.1

03/24/2015 2.0 6.6 5.0 93.6 <0.040 0.40 48.6 84.2

04/21/2015 2.5 7.0 10.7 90.6 <0.040 0.42 41.5 77.4

05/12/2015 2.4 9.5 11.8 161 0.042 0.89 24.7 53.8

05/27/2015 2.8 22.2 7.3 391 0.042 2.16 22.6 73.9

06/09/2015 3.8 15.0 23.9 252 0.127 1.50 24.6 56.8

07/14/2015 2.8 5.3 19.2 67.1 0.069 0.34 33.0 40.4

08/11/2015 2.9 5.4 19.3 64.5 0.082 0.28 25.5 40.4

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)

10/15/2014 2.1 2.6 6.3 7.4 1.22 89 2 0.20

03/24/2015 <2.0 3.1 4.0 4.6 1.23 95 2 0.23

04/21/2015 <2.0 3.8 4.7 5.3 1.49 72 4 0.53

05/12/2015 <2.0 5.3 4.1 5.2 1.50 70 7 1.7

05/27/2015 <2.0 8.9 4.3 6.9 1.92 57 20 8.4

06/09/2015 <2.0 7.5 5.1 6.6 1.99 53 15 6.1

07/14/2015 <2.0 <2.0 7.7 8.5 1.36 90 2 0.14

08/11/2015 <2.0 <2.0 7.1 8.0 1.16 89 2 0.10
30 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323800—Clark Fork near Galen

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2014 1210 111 8.7 445 8.5 189 53.2 13.7

03/24/2015 1135 157 8.3 398 4.0 164 48.0 10.6

04/21/2015 1155 152 8.3 414 10.0 177 51.9 11.6

05/12/2015 1320 192 8.5 299 11.0 125 37.3 7.85

05/27/2015 1215 416 8.5 286 12.0 127 38.5 7.43

06/09/2015 1110 373 8.4 246 15.0 108 32.4 6.55

07/14/2015 1230 99 8.9 359 17.0 165 47.7 11.1

08/11/2015 1205 51 8.8 424 18.0 189 54.6 12.9

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)

10/15/2014 0.044 0.037 2.9 4.8 12.4 75.9 0.069 0.44

03/24/2015 0.045 0.111 2.7 12.9 21.5 355 0.099 2.04

04/21/2015 0.035 0.091 3.1 10.4 18.3 265 0.123 1.80

05/12/2015 0.043 0.082 4.1 11.9 27.9 265 0.133 1.57

05/27/2015 0.048 0.126 5.4 20.9 33.1 414 0.170 2.69

06/09/2015 0.040 0.098 5.1 16.0 31.8 271 0.126 1.38

07/14/2015 <0.030 0.034 3.8 6.2 16.9 76.0 0.082 0.45

08/11/2015 <0.030 0.041 3.8 6.5 13.3 80.6 0.069 0.51

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)

10/15/2014 23.7 40.9 2.2 3.6 12.6 13.8 87 2 0.60

03/24/2015 88.8 158 3.4 19.4 8.4 11.5 84 12 5.1

04/21/2015 76.5 125 3.1 10.6 9.1 11.0 87 7 2.9

05/12/2015 40.1 85.0 3.3 10.1 10.9 12.5 70 9 4.7

05/27/2015 37.2 90.5 3.2 16.2 13.1 16.5 65 16 18

06/09/2015 39.5 71.3 <2.0 10.7 18.9 21.8 76 9 9.1

07/14/2015 31.5 50.9 <2.0 2.8 20.5 21.9 76 2 0.53

08/11/2015 36.4 57.5 <2.0 4.0 21.4 22.4 75 2 0.28
Data 31

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323840—Lost Creek near Anaconda

Date Time

(hhmm)

Streamflow, 

instantaneous (ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2014 0750 9.4 8.2 239 6.5 <2.0 115 34.5 7.04

03/24/2015 0800 8.1 8.1 217 2.0 <2.0 110 33.0 6.82

04/21/2015 0745 10 7.9 203 5.0 E2.4 103 31.2 5.96

05/12/2015 0745 11 7.8 170 5.5 E4.8 83.4 25.2 4.96

05/26/2015 1605 12 7.9 176 12.0 E3.1 85.6 26.7 4.60

06/09/2015 0745 20 8.0 172 8.5 E2.9 85.6 26.7 4.62

07/13/2015 1540 4.4 8.2 234 12.5 <2.0 117 35.6 6.69

08/11/2015 0735 9.4 8.1 227 10.0 <2.0 115 34.8 6.74

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)

10/15/2014 1.46 3.47 114 0.95 0.45 12.0 10.1 <0.030 <0.030

03/24/2015 1.32 3.10 101 0.93 0.41 12.2 11.0 -- --

04/21/2015 1.20 2.81 94.2 0.75 0.40 11.6 9.44 <0.030 <0.030

05/12/2015 1.01 2.30 79.3 0.60 0.32 10.9 7.22 <0.030 0.065

05/26/2015 1.16 2.78 77.2 2.13 0.31 10.9 7.43 <0.030 0.067

06/09/2015 1.04 2.68 80.5 0.52 0.31 11.2 6.48 <0.030 0.040

07/13/2015 1.39 3.68 118 0.82 0.39 11.3 7.93 0.034 0.040

08/11/2015 1.30 3.06 111 0.73 0.40 12.2 8.48 <0.030 0.039

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/15/2014 1.7 4.3 11.5 110 <0.040 0.44 1.38 5.7

03/24/2015 -- -- -- -- -- -- -- --

04/21/2015 1.4 5.5 10.1 192 <0.040 0.69 0.99 7.1

05/12/2015 1.9 14.0 13.0 344 0.066 1.84 2.07 11.8

05/26/2015 3.0 13.8 8.1 485 0.044 2.23 1.40 50.1

06/09/2015 2.0 5.7 25.6 204 0.043 0.72 2.12 6.8

07/13/2015 2.0 2.6 9.3 40.4 <0.040 0.21 1.52 3.3

08/11/2015 1.4 5.5 15.7 165 <0.040 0.68 1.98 8.5

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)

10/15/2014 <2.0 2.1 3.2 3.9 1.25 54 5 0.13

03/24/2015 -- -- -- -- 1.44 64 4 0.09

04/21/2015 <2.0 3.2 2.5 3.2 1.53 63 11 0.30

05/12/2015 <2.0 5.8 2.8 4.0 2.06 72 18 0.53

05/26/2015 2.3 15.2 4.8 4.5 2.46 51 24 0.78

06/09/2015 <2.0 4.4 5.0 5.6 2.20 34 17 0.92

07/13/2015 <2.0 <2.0 6.8 6.4 1.78 59 1 0.01

08/11/2015 <2.0 2.6 5.0 5.9 1.34 68 6 0.15
32 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12323850—Lost Creek near Galen

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Turbidity, 

unfiltered, 

lab 

(NTRU)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2014 1130 45 8.2 580 8.0 <2.0 281 80.4 19.6

03/24/2015 1045 53 8.2 579 3.0 E4.4 271 78.8 18.1

04/21/2015 1120 46 8.2 581 9.5 E3.1 295 85.4 19.8

05/12/2015 1235 16 8.4 604 11.5 E2.1 301 85.5 21.2

05/27/2015 1105 16 8.3 774 13.0 <2.0 401 114 28.0

06/09/2015 1025 13 8.2 674 16.5 <2.0 347 100 23.4

07/14/2015 1210 8.8 8.2 669 15.0 <2.0 343 97.6 24.2

08/11/2015 1130 2.3 8.0 610 15.0 <2.0 248 63.5 21.8

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)

10/15/2014 2.40 11.5 186 4.71 0.50 15.2 117 <0.030 <0.030

03/24/2015 2.09 11.2 181 4.57 0.47 14.3 121 0.041 0.070

04/21/2015 2.25 12.9 182 4.31 0.45 15.7 117 <0.030 0.044

05/12/2015 2.17 12.9 185 4.34 0.47 15.1 123 <0.030 0.030

05/27/2015 3.57 18.5 218 5.33 0.67 19.9 200 <0.030 <0.030

06/09/2015 2.55 15.7 194 4.42 0.56 16.8 161 <0.030 <0.030

07/14/2015 2.63 19.6 193 4.93 0.54 17.6 165 <0.030 <0.030

08/11/2015 3.18 29.2 224 5.09 0.78 19.2 95.3 <0.030 <0.030

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

10/15/2014 1.1 3.0 13.7 83.9 <0.040 0.29 8.08 11.0

03/24/2015 2.7 7.8 84.5 253 0.320 1.11 21.6 31.6

04/21/2015 1.7 6.8 16.1 200 0.079 0.83 17.0 24.4

05/12/2015 1.9 4.1 21.2 137 0.090 0.59 20.5 26.8

05/27/2015 2.5 4.3 27.8 97.5 0.066 0.32 26.7 30.8

06/09/2015 2.0 3.7 26.2 79.7 0.059 0.21 25.3 25.8

07/14/2015 1.6 2.8 26.1 84.5 0.045 0.22 14.9 17.2

08/11/2015 2.8 3.6 35.3 91.3 0.053 0.15 26.2 27.3

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)

10/15/2014 <2.0 2.4 10.7 12.3 1.69 77 13 1.6

03/24/2015 2.6 6.4 9.6 11.4 1.73 87 12 1.7

04/21/2015 <2.0 4.9 10.2 11.5 1.52 39 25 3.1

05/12/2015 <2.0 3.3 12.2 12.8 1.81 53 26 1.1

05/27/2015 <2.0 <2.0 28.3 30.1 4.33 52 26 1.1

06/09/2015 <2.0 <2.0 20.8 21.9 2.78 78 28 0.98

07/14/2015 <2.0 <2.0 14.0 15.4 2.16 69 29 0.69

08/11/2015 <2.0 <2.0 11.0 12.1 2.61 72 12 0.07
Data 33

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12324200—Clark Fork at Deer Lodge

Date Time

(hhmm)

Streamflow, 

instantaneous (ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2014 1330 228 8.6 493 9.0 220 62.7 15.5

03/24/2015 1305 286 8.3 438 4.0 203 59.1 13.3

04/21/2015 1325 245 8.3 465 11.5 212 62.2 13.7

05/12/2015 1500 212 8.6 379 13.0 171 49.8 11.2

05/27/2015 1505 483 8.2 341 14.5 154 46.1 9.57

06/09/2015 1255 414 8.2 290 18.5 130 39.0 7.94

07/14/2015 1425 93 8.6 427 19.0 200 59.1 12.7

08/11/2015 1340 61 8.5 492 20.0 211 62.5 13.4

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)

10/15/2014 0.062 0.086 5.6 14.8 19.9 205 0.164 1.59

03/24/2015 0.068 0.184 5.4 38.2 14.2 634 0.126 5.15

04/21/2015 0.076 0.141 6.5 28.5 17.3 449 0.152 3.12

05/12/2015 0.064 0.112 7.0 21.2 21.9 305 0.143 2.36

05/27/2015 0.071 0.356 10.6 98.6 28.2 1,640 0.304 13.4

06/09/2015 0.069 0.239 10.9 57.9 25.1 824 0.243 7.08

07/14/2015 0.046 0.053 6.9 12.4 8.1 96.6 0.103 0.88

08/11/2015 0.047 0.048 7.3 10.2 13.7 63.0 0.114 0.55

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)

10/15/2014 24.4 47.9 3.4 11.8 12.3 13.8 86 7 4.3

03/24/2015 31.7 106 6.7 33.2 8.7 14.0 76 25 19

04/21/2015 30.9 89.5 5.9 24.0 10.8 13.8 83 16 11

05/12/2015 28.4 60.3 3.6 16.7 12.7 15.3 83 9 5.2

05/27/2015 19.4 142 5.4 74.4 14.9 27.1 61 68 89

06/09/2015 18.6 83.1 5.1 42.2 17.3 24.1 64 35 39

07/14/2015 17.4 28.1 2.7 7.4 15.7 16.8 92 2 0.50

08/11/2015 11.7 22.9 3.1 5.0 14.1 14.6 82 4 0.66
34 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

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 

temperature, 

onsite (°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2014 1500 260 8.5 502 10.0 222 63.6 15.5

03/24/2015 1435 306 8.5 443 5.0 202 58.8 13.3

04/21/2015 1450 274 8.4 473 13.0 209 61.0 13.8

05/12/2015 1645 213 8.6 392 15.0 171 49.3 11.6

05/28/2015 1320 564 8.1 357 14.0 163 48.2 10.3

06/09/2015 1435 473 8.2 321 20.0 143 42.5 8.93

07/14/2015 1610 122 8.7 430 22.0 189 54.1 13.1

08/11/2015 1510 69 8.5 483 21.5 206 58.8 14.4

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)

10/15/2014 0.051 0.096 4.7 19.4 5.6 249 0.100 2.21

03/24/2015 0.066 0.195 6.8 46.5 36.3 809 0.326 5.71

04/21/2015 0.072 0.162 8.2 36.1 13.3 541 0.171 4.00

05/12/2015 0.064 0.131 7.9 28.4 21.7 407 0.188 3.16

05/28/2015 0.072 0.472 11.6 127 27.2 2,150 0.351 17.0

06/09/2015 0.084 0.340 14.4 89.2 64.4 1,260 0.715 9.97

07/14/2015 0.050 0.040 8.1 10.8 60.2 -- 0.086 0.43

08/11/2015 <0.030 0.035 9.2 11.3 7.0 40.7 0.057 0.33

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)

10/15/2014 24.0 79.8 3.5 15.9 12.2 15.1 86 9 6.3

03/24/2015 30.8 112 6.2 38.7 9.5 15.4 76 31 26

04/21/2015 22.4 92.2 4.2 29.3 11.8 15.2 83 21 16

05/12/2015 28.8 71.3 3.3 22.1 13.8 16.3 86 18 10

05/28/2015 15.7 190 6.5 104 15.8 30.5 59 97 148

06/09/2015 23.3 126 6.7 67.2 18.7 29.0 61 51 65

07/14/2015 8.56 13.4 <2.0 4.9 17.2 18.5 89 3 0.99

08/11/2015 12.0 24.3 <2.0 3.2 16.1 16.4 73 5 0.93
Data 35

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12324680—Clark Fork at Goldcreek

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/15/2014 1600 396 8.6 447 10.0 200 57.6 13.6

03/25/2015 0820 650 8.1 346 3.5 151 44.6 9.53

04/21/2015 1550 507 8.7 369 12.0 165 47.9 11.1

05/13/2015 0820 431 8.2 326 9.5 140 41.5 8.79

05/28/2015 1200 822 8.2 317 13.0 145 43.4 8.89

06/10/2015 1125 868 8.2 288 17.0 129 38.4 7.94

07/14/2015 1705 337 9.1 362 22.0 171 49.5 11.5

08/11/2015 1610 129 8.7 401 22.0 180 52.1 12.1

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)

10/15/2014 0.047 0.067 4.0 12.7 11.7 185 0.111 1.37

03/25/2015 0.044 0.138 3.7 25.9 39.7 632 0.139 3.55

04/21/2015 0.038 0.084 5.6 20.3 15.2 358 0.123 2.19

05/13/2015 0.041 0.096 5.2 18.5 17.4 376 0.104 2.43

05/28/2015 0.050 0.353 11.0 93.4 74.8 1,350 0.677 11.1

06/10/2015 0.053 0.198 9.8 50.1 42.8 799 0.377 5.90

07/14/2015 <0.030 0.031 5.7 7.2 6.0 46.2 0.041 0.27

08/11/2015 <0.030 0.048 5.0 8.3 59.3 79.6 <0.040 0.51

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)

10/15/2014 13.4 63.2 2.5 10.9 9.4 10.7 89 7 7.5

03/25/2015 12.8 71.4 5.0 24.7 5.6 9.2 80 23 40

04/21/2015 11.2 55.6 2.1 16.2 8.2 9.9 82 15 21

05/13/2015 16.5 56.6 3.9 17.5 8.7 10.3 87 14 16

05/28/2015 14.4 132 6.3 65.7 12.2 21.0 71 56 124

06/10/2015 12.1 83.8 4.4 38.9 13.0 17.6 68 35 82

07/14/2015 5.58 14.3 <2.0 2.9 11.5 11.6 94 4 3.6

08/11/2015 11.6 46.1 <2.0 4.9 10.7 11.0 90 5 1.7
36 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12331800—Clark Fork near Drummond

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/16/2014 0750 582 8.1 474 8.5 215 60.4 15.5

03/25/2015 0930 864 8.2 373 5.0 170 47.9 12.2

04/22/2015 0800 641 8.2 400 10.5 177 50.2 12.6

05/13/2015 0930 514 8.2 398 12.0 178 50.8 12.4

05/28/2015 1030 1,170 8.1 371 14.0 172 50.4 11.2

06/10/2015 1010 938 8.1 353 17.0 158 46.1 10.5

07/15/2015 0720 378 7.9 460 17.5 215 59.8 15.9

08/12/2015 0750 222 8.0 560 18.0 258 72.0 18.9

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)

10/16/2014 0.042 0.069 3.0 9.6 12.8 195 0.118 1.43

03/25/2015 0.042 0.127 3.9 21.4 27.9 614 0.145 3.48

04/22/2015 0.032 0.128 4.8 23.2 14.3 494 0.159 3.27

05/13/2015 0.039 0.078 5.4 12.0 17.1 188 0.126 1.36

05/28/2015 0.045 0.385 9.2 83.3 33.2 1,750 0.307 11.5

06/10/2015 0.053 0.247 8.3 51.8 18.2 1,100 0.235 6.83

07/15/2015 <0.030 <0.030 5.3 7.3 5.2 39.8 <0.040 0.25

08/12/2015 0.044 0.050 3.4 6.3 7.9 61.8 0.074 0.50

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)

10/16/2014 13.0 65.3 3.8 12.1 8.3 10.1 87 9 14

03/25/2015 13.0 70.6 4.5 24.8 6.3 9.5 71 27 63

04/22/2015 17.1 81.2 4.1 26.9 8.5 11.0 91 22 38

05/13/2015 23.2 45.9 4.4 12.6 9.8 10.7 92 6 8.3

05/28/2015 24.9 188 5.5 81.6 12.7 20.1 84 76 240

06/10/2015 11.7 116 4.5 51.2 13.3 18.1 58 56 142

07/15/2015 6.14 14.8 2.5 4.6 10.4 10.7 82 4 4.1

08/12/2015 22.4 56.1 2.7 5.7 11.0 11.1 42 18 11
Data 37

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

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 

temperature, 

onsite (°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/16/2014 1000 973 8.2 374 8.5 172 47.4 12.9

03/25/2015 1110 1,730 8.2 256 4.5 110 31.1 7.85

04/22/2015 0950 1,610 8.1 247 9.0 111 31.1 8.01

05/13/2015 1120 1,750 8.3 196 10.0 85.1 23.8 6.25

05/28/2015 0840 2,470 8.0 213 12.0 100 29.1 6.73

06/10/2015 0800 1,910 8.1 244 16.0 110 31.7 7.53

07/15/2015 0905 812 8.1 290 16.0 133 35.5 10.8

08/12/2015 0905 468 8.1 341 16.0 155 42.1 12.1

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)

10/16/2014 <0.030 0.043 2.2 6.4 6.8 146 <0.040 0.87

03/25/2015 0.034 0.077 2.6 12.0 41.2 405 0.107 1.85

04/22/2015 <0.030 0.054 3.0 9.3 22.0 295 0.088 1.26

05/13/2015 <0.030 <0.030 2.0 4.1 22.1 162 0.056 0.45

05/28/2015 0.083 0.200 17.9 37.8 359 1,020 2.79 6.16

06/10/2015 <0.030 0.150 4.3 27.9 22.8 619 0.171 3.94

07/15/2015 <0.030 <0.030 2.7 5.0 6.0 86.8 <0.040 0.39

08/12/2015 <0.030 0.041 2.0 5.2 5.3 127 0.042 0.56

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)

10/16/2014 3.90 35.3 3.3 9.3 5.5 6.3 86 7 18

03/25/2015 4.74 44.7 3.3 16.8 3.6 5.2 67 19 89

04/22/2015 5.66 32.2 2.3 12.7 4.1 5.4 77 14 61

05/13/2015 4.41 14.6 <2.0 4.9 3.5 3.9 79 7 33

05/28/2015 48.6 102 17.4 44.6 7.3 9.9 77 41 273

06/10/2015 10.3 74.2 5.1 30.7 7.4 9.6 74 32 165

07/15/2015 3.05 15.3 <2.0 4.9 4.8 5.5 85 5 11

08/12/2015 5.43 27.5 <2.0 8.2 5.2 6.0 84 9 11
38 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 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12340000—Blackfoot River near Bonner

Date Time

(hhmm)

Streamflow, 

instantaneous 

(ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/16/2014 1235 579 8.4 277 9.0 142 35.4 13.1

04/22/2015 1205 2,440 8.3 184 10.0 93.2 24.4 7.84

05/13/2015 1340 2,500 8.2 186 10.0 89.9 23.2 7.75

05/28/2015 1605 3,350 8.3 179 12.0 95.9 25.4 7.86

07/15/2015 1050 711 8.4 250 16.0 132 32.9 12.2

08/12/2015 1045 472 8.4 256 17.0 133 32.2 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)

10/16/2014 <0.030 <0.030 <0.80 <0.80 4.3 33.6 <0.040 <0.04

04/22/2015 <0.030 <0.030 <0.80 0.90 13.0 144 <0.040 0.15

05/13/2015 <0.030 <0.030 <0.80 <0.80 12.2 95.4 <0.040 0.11

05/28/2015 <0.030 <0.030 0.96 1.3 104 286 0.167 0.39

07/15/2015 <0.030 <0.030 <0.80 <0.80 10.0 38.6 <0.040 0.05

08/12/2015 <0.030 <0.030 <0.80 <0.80 4.4 30.6 <0.040 0.06

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)

10/16/2014 1.41 4.6 <2.0 <2.0 1.0 1.1 84 2 3.1

04/22/2015 2.00 12.4 <2.0 <2.0 0.80 0.89 86 7 46

05/13/2015 1.86 9.3 <2.0 <2.0 0.79 0.82 78 6 40

05/28/2015 9.82 22.5 <2.0 <2.0 0.96 1.1 87 20 181

07/15/2015 1.34 5.6 <2.0 <2.0 1.2 1.3 80 2 3.8

08/12/2015 1.86 6.4 <2.0 <2.0 1.2 1.4 89 2 2.5
Data 39

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2014 through September 2015.—Continued

[hh, hour; mm, minute; ft3/s, cubic foot per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric 

turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; <, less than laboratory reporting level; E, estimated; μg/L, microgram per liter; 

mm, millimeters; ton/d, ton per day; --, no data]

12340500—Clark Fork above Missoula

Date Time

(hhmm)

Streamflow, 

instan-taneous (ft3

/s)

pH, onsite 

(standard 

units)

Specific 

conductance, onsite 

(μS/cm)

Water 

temperature, 

onsite (°C)

Hardness, 

filtered 

(mg/L as 

CaCO3

)

Calcium, 

filtered 

(mg/L)

Magnesium, 

filtered 

(mg/L)

10/16/2014 1420 1,520 8.5 330 9.0 157 41.7 12.9

03/25/2015 1345 5,140 8.2 202 5.0 96.5 25.7 7.85

04/22/2015 1350 4,120 8.4 210 10.5 99.8 27.0 7.87

05/13/2015 1520 4,260 8.4 189 11.0 89.6 23.9 7.27

05/28/2015 1740 6,080 8.3 193 13.0 95.2 26.1 7.27

06/10/2015 1400 4,690 8.4 213 18.0 105 28.7 8.02

07/15/2015 1310 1,530 8.6 265 17.5 129 33.2 11.2

08/12/2015 1240 965 8.4 292 18.5 143 36.8 12.3

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)

10/16/2014 <0.030 <0.030 1.4 3.6 4.9 85.3 <0.040 0.44

03/25/2015 <0.030 0.032 1.3 4.7 36.3 303 0.066 0.77

04/22/2015 <0.030 <0.030 1.7 4.2 11.7 195 0.042 0.59

05/13/2015 <0.030 <0.030 1.6 2.4 57.5 122 0.139 0.30

05/28/2015 <0.030 0.058 3.0 8.6 32.0 266 0.194 1.11

06/10/2015 <0.030 0.100 2.2 10.8 10.2 330 0.071 1.51

07/15/2015 <0.030 <0.030 1.9 2.8 4.8 45.5 <0.040 0.17

08/12/2015 <0.030 <0.030 1.6 2.8 6.1 73.6 <0.040 0.30

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)

10/16/2014 5.63 22.9 2.3 5.1 3.9 4.7 89 4 16

03/25/2015 4.28 25.9 <2.0 7.7 1.9 2.5 77 13 180

04/22/2015 4.56 21.9 <2.0 6.5 2.2 2.6 71 11 122

05/13/2015 7.56 13.5 <2.0 3.1 2.0 1.9 82 7 81

05/28/2015 6.58 8.8 2.1 3.9 3.3 5.8 82 27 443

06/10/2015 5.37 39.4 <2.0 13.1 3.7 4.8 82 19 241

07/15/2015 3.48 11.1 <2.0 3.5 3.1 3.3 88 2 8.3

08/12/2015 7.04 21.6 <2.0 4.3 3.3 3.6 89 5 13
40 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 Turah Bridge, near Bonner, Montana (12334550), 

October 2014 through September 2015.

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton 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

1 926 9 23 1,050 8 23 e1,020 14 39

2 956 8 21 1,100 11 33 e1,000 7 19

3 951 8 21 1,120 11 33 e1,030 10 28

4 940 8 20 1,080 10 29 e1,060 16 46

5 948 8 20 1,070 9 26 e1,090 20 59

6 932 8 20 1,080 9 26 1,100 19 56

7 920 8 20 1,100 9 27 1,070 16 46

8 914 8 20 1,110 8 24 1,050 14 40

9 916 8 20 1,120 8 24 1,030 12 33

10 912 8 20 e1,120 11 33 1,020 12 33

11 926 8 20 e1,080 10 29 1,030 13 36

12 985 8 21 e950 8 21 1,050 13 37

13 1,000 8 22 e710 6 12 1,070 14 40

14 990 8 21 e650 3 5.3 1,090 15 44

15 969 8 21 e670 2 3.6 1,060 14 40

16 961 8 21 e670 2 3.6 936 11 28

17 937 6 15 e680 2 3.7 947 10 26

18 933 6 15 e690 3 5.6 1,000 10 27

19 932 6 15 e710 5 9.6 1,010 10 27

20 922 7 17 e760 8 16 1,020 10 28

21 943 8 20 e860 10 23 1,030 11 31

22 1,040 11 31 e950 13 33 1,070 11 32

23 1,090 13 38 e1,010 16 44 1,030 11 31

24 1,080 12 35 1,030 18 50 1,010 10 27

25 1,120 13 39 1,030 21 58 1,050 9 26

26 1,110 11 33 1,070 25 72 1,010 9 25

27 1,090 10 29 1,050 28 79 e950 8 21

28 1,060 8 23 e1,150 45 140 931 6 15

29 1,070 8 23 e1,100 59 175 e905 5 12

30 1,080 8 23 e1,050 38 108 e635 3 5.1

31 1,050 8 23 -- -- -- e410 2 2.2

Total1 30,603 -- 710 28,820 -- 1,169.4 30,714 -- 959.3

Mean 987 9 23 961 14 39 991 11 31

Max 1,120 13 39 1,150 59 175 1,100 20 59

Min 912 6 15 650 2 3.6 410 2 2.2
Data 41

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana (12334550), 

October 2014 through September 2015.—Continued

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton 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 e510 3 4.1 1,120 17 51 1,050 10 28

2 e690 7 13 1,110 17 51 1,030 10 28

3 e815 12 26 1,120 16 48 1,040 10 28

4 e890 18 43 1,100 16 48 966 10 26

5 e910 23 57 1,080 16 47 1,010 10 27

6 e980 23 61 1,080 17 50 1,040 10 28

7 e950 17 44 1,310 23 81 1,050 10 28

8 e900 10 24 2,000 94 508 1,050 10 28

9 e900 6 15 1,970 99 527 1,060 8 23

10 e950 7 18 2,180 107 630 1,060 9 26

11 994 12 32 2,040 71 391 1,060 10 29

12 1,060 18 52 1,840 51 253 1,060 9 26

13 1,050 18 51 1,740 36 169 1,080 9 26

14 951 15 39 1,680 26 118 1,100 10 30

15 894 13 31 1,640 21 93 1,190 17 55

16 860 11 26 1,590 20 86 1,510 40 163

17 979 11 29 1,510 20 82 1,740 50 235

18 996 14 38 1,420 19 73 1,810 46 225

19 1,100 27 80 1,410 17 65 1,850 46 230

20 1,140 38 117 1,390 15 56 1,780 36 173

21 1,020 21 58 1,370 15 55 1,760 32 152

22 907 16 39 1,220 14 46 1,760 30 143

23 945 21 54 1,020 13 36 1,750 27 128

24 1,030 36 100 1,070 15 43 1,750 22 104

25 1,440 111 432 1,210 18 59 1,720 20 93

26 1,600 89 384 1,210 15 49 1,680 22 100

27 1,550 71 297 1,140 12 37 1,640 23 102

28 1,450 56 219 1,100 10 30 1,700 23 106

29 1,330 44 158 -- -- -- 1,790 27 130

30 1,240 32 107 -- -- -- 1,770 25 119

31 1,170 23 73 -- -- -- 1,820 31 152

Total1 32,201 -- 2,721.1 39,670 -- 3,782 43,676 -- 2,791

Mean 1,039 27 88 1,417 30 135 1,409 21 90

Max 1,600 111 432 2,180 107 630 1,850 50 235

Min 510 3 4.1 1,020 10 30 966 8 23
42 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

April May June

1 1,950 40 211 1,900 18 92 2,610 51 359

2 1,980 34 182 1,870 15 76 2,700 59 430

3 1,920 26 135 1,900 15 77 2,830 72 550

4 1,870 26 131 1,930 15 78 2,740 65 481

5 1,830 23 114 1,970 16 85 2,560 56 387

6 1,790 20 97 2,020 17 93 2,410 43 280

7 1,740 17 80 2,000 17 92 2,240 37 224

8 1,680 17 77 1,890 11 56 2,080 36 202

9 1,640 16 71 1,790 8 39 1,970 34 181

10 1,600 17 73 1,730 8 37 1,940 33 173

11 1,590 16 69 1,690 8 37 1,900 34 174

12 1,570 14 59 1,670 7 32 1,760 27 128

13 1,530 14 58 1,750 8 38 1,630 22 97

14 1,500 15 61 1,800 9 44 1,510 16 65

15 1,510 15 61 1,810 9 44 1,390 13 49

16 1,470 16 64 2,050 15 83 1,300 12 42

17 1,410 16 61 2,390 36 232 1,230 10 33

18 1,410 17 65 2,570 44 305 1,200 8 26

19 1,460 20 79 2,400 36 233 1,160 8 25

20 1,500 14 57 2,280 25 154 1,120 7 21

21 1,550 14 59 2,190 21 124 1,080 5 15

22 1,630 17 75 2,160 18 105 1,050 5 14

23 1,760 23 109 2,180 18 106 1,010 4 11

24 1,880 25 127 2,200 20 119 973 3 7.9

25 1,900 24 123 2,230 20 120 915 3 7.4

26 1,890 24 122 2,240 21 127 871 3 7.1

27 1,830 20 99 2,280 25 154 831 3 6.7

28 1,770 17 81 2,490 43 289 799 2 4.3

29 1,770 16 76 2,620 52 368 773 2 4.2

30 1,850 18 90 2,590 49 343 799 3 6.5

31 -- -- -- 2,590 47 329 -- -- --

Total1 50,780 -- 2,766 65,180 -- 4,111 47,381 -- 4,011

Mean 1,693 20 92 2,103 22 133 1,579 23 134

Max 1,980 40 211 2,620 52 368 2,830 72 550

Min 1,410 14 57 1,670 7 32 773 2 4.2

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana (12334550), 

October 2014 through September 2015.—Continued

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum]
Data 43

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

July August September

1 800 2 4.3 605 16 26 378 10 10

2 765 2 4.1 577 13 20 378 10 10

3 747 2 4.0 554 11 16 389 10 11

4 730 2 3.9 534 10 14 401 11 12

5 711 2 3.8 531 9 13 467 14 18

6 723 3 5.9 531 9 13 586 29 46

7 716 3 5.8 512 9 12 609 29 48

8 715 4 7.7 497 10 13 594 22 35

9 705 4 7.6 490 10 13 583 18 28

10 699 4 7.5 489 10 13 570 17 26

11 762 5 10 476 10 13 559 15 23

12 817 7 15 457 11 14 534 15 22

13 821 7 16 449 12 15 504 14 19

14 810 7 15 433 12 14 499 13 18

15 795 7 15 440 12 14 523 13 18

16 760 7 14 430 12 14 562 12 18

17 722 8 16 436 12 14 610 12 20

18 701 8 15 434 11 13 642 14 24

19 687 8 15 427 10 12 659 24 43

20 657 8 14 414 9 10 677 22 40

21 619 8 13 392 9 9.5 661 18 32

22 583 8 13 387 9 9.4 636 17 29

23 580 8 13 387 9 9.4 609 15 25

24 625 10 17 387 10 10 606 14 23

25 617 10 17 390 10 11 602 13 21

26 609 11 18 384 10 10 583 12 19

27 631 12 20 382 11 11 572 11 17

28 746 19 38 376 12 12 570 9 14

29 756 18 37 373 12 12 581 9 14

30 707 15 29 385 11 11 607 9 15

31 651 14 25 389 10 11 -- -- --

Total1 21,967 -- 439.6 13,948 -- 402.3 16,751 -- 698

Mean 709 8 14 450 11 13 558 15 23

Max 821 19 38 605 16 26 677 29 48

Min 580 2 3.8 373 9 9.4 378 9 10

1

Total for water year 2015 (unrounded sum of daily values): streamflow=421,691 ft3/s (annual runoff=836,400 acre-feet); suspended-sediment 

discharge=24,560.8 tons.

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana (12334550), 

October 2014 through September 2015.—Continued

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum]
44 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 Blackfoot River near Bonner, Montana (12340000), October 2014 

through September 2015.

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton 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

1 612 3 5.0 593 2 3.2 585 8 13

2 606 2 3.3 621 2 3.4 619 6 10

3 599 2 3.2 645 2 3.5 632 4 6.8

4 597 2 3.2 648 3 5.2 679 4 7.3

5 591 2 3.2 653 3 5.3 734 3 5.9

6 586 2 3.2 655 2 3.5 725 3 5.9

7 580 2 3.1 668 2 3.6 705 3 5.7

8 571 2 3.1 664 2 3.6 665 2 3.6

9 563 2 3.0 685 2 3.7 656 2 3.5

10 562 2 3.0 e700 2 3.8 662 2 3.6

11 566 2 3.1 e640 3 5.2 657 2 3.5

12 595 4 6.4 e500 3 4.0 654 2 3.5

13 592 2 3.2 e420 3 3.4 662 2 3.6

14 585 2 3.2 e400 3 3.2 669 2 3.6

15 575 2 3.1 e410 2 2.2 656 2 3.5

16 579 2 3.1 e430 2 2.3 594 2 3.2

17 573 2 3.1 e470 2 2.5 638 2 3.4

18 573 2 3.1 e500 2 2.7 643 2 3.5

19 570 2 3.1 e560 3 4.5 639 2 3.5

20 565 2 3.1 e600 3 4.9 627 2 3.4

21 576 2 3.1 e650 4 7.0 647 1 1.7

22 605 2 3.3 e700 4 7.6 646 1 1.7

23 611 2 3.3 e680 4 7.3 632 1 1.7

24 607 2 3.3 e670 4 7.2 632 1 1.7

25 597 2 3.2 e670 4 7.2 648 1 1.7

26 596 2 3.2 e680 4 7.3 630 1 1.7

27 589 2 3.2 691 4 7.5 e603 1 1.6

28 585 2 3.2 712 5 9.6 e580 1 1.6

29 590 2 3.2 e743 6 12 e500 2 2.7

30 592 2 3.2 e672 7 13 e350 2 1.9

31 592 2 3.2 -- -- -- e340 2 1.8

Total1 18,180 -- 103.2 18,330 -- 159.4 19,309 -- 119.8

Mean 586 2 3.3 611 3 5.3 623 2 3.9

Max 612 4 6.4 743 7 13 734 8 13

Min 562 2 3.0 400 2 2.2 340 1 1.6
Data 45

Table 6. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2014 

through September 2015.—Continued

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton 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 e380 1 1.0 763 4 8.2 990 4 11

2 e450 1 1.2 763 4 8.2 994 4 11

3 e500 1 1.4 774 4 8.4 945 3 7.7

4 e550 2 3.0 771 4 8.3 906 3 7.3

5 e600 2 3.2 759 5 10 935 3 7.6

6 e700 2 3.8 746 5 10 926 4 10

7 e700 2 3.8 795 6 13 938 4 10

8 e670 1 1.8 1,170 16 51 944 6 15

9 e680 1 1.8 1,520 34 140 969 6 16

10 e700 1 1.9 1,640 37 164 990 7 19

11 e740 2 4.0 1,650 31 138 1,010 8 22

12 761 2 4.1 1,560 23 97 1,020 9 25

13 e700 2 3.8 1,540 18 75 1,110 9 27

14 e620 2 3.3 1,570 15 64 1,190 11 35

15 e600 1 1.6 1,620 13 57 1,580 24 102

16 e660 1 1.8 1,600 12 52 2,900 71 556

17 e680 1 1.8 1,530 10 41 3,480 49 460

18 695 2 3.8 1,480 9 36 3,580 30 290

19 704 3 5.7 1,450 9 35 3,580 25 242

20 688 4 7.4 1,430 8 31 3,500 21 198

21 e650 4 7.0 1,410 8 30 3,450 18 168

22 e600 4 6.5 1,260 7 24 3,430 16 148

23 e640 3 5.2 1,150 7 22 3,420 14 129

24 682 4 7.4 1,190 6 19 3,340 13 117

25 747 5 10 1,210 6 20 3,190 12 103

26 862 4 9.3 1,160 5 16 3,030 11 90

27 986 6 16 1,100 5 15 2,940 11 87

28 895 5 12 1,050 4 11 3,030 13 106

29 843 6 14 -- -- -- 3,210 14 121

30 804 5 11 -- -- -- 3,280 14 124

31 780 4 8.4 -- -- -- 3,400 14 129

Total1 21,267 -- 167.0 34,661 -- 1,204.1 68,207 -- 3,393.6

Mean 686 3 5.4 1,238 11 43 2,200 15 109

Max 986 6 16 1,650 37 164 3,580 71 556

Min 380 1 1.0 746 4 8.2 906 3 7.3
46 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

April May June

1 3,560 16 154 2,840 8 61 3,460 32 299

2 3,560 15 144 2,900 9 70 3,740 37 374

3 3,410 13 120 3,000 10 81 3,910 46 486

4 3,230 13 113 3,060 11 91 3,610 40 390

5 3,050 11 91 3,150 13 111 3,290 30 266

6 2,880 9 70 3,320 14 125 3,050 22 181

7 2,720 9 66 3,320 15 134 2,900 18 141

8 2,540 8 55 3,150 12 102 2,780 17 128

9 2,320 8 50 2,950 10 80 2,670 15 108

10 2,190 8 47 2,780 8 60 2,640 15 107

11 2,160 8 47 2,660 7 50 2,520 15 102

12 2,150 6 35 2,570 6 42 2,290 14 87

13 2,110 7 40 2,510 6 41 2,100 12 68

14 2,070 6 34 2,480 6 40 1,950 9 47

15 2,040 5 28 2,490 6 40 1,820 8 39

16 1,990 5 27 2,560 6 41 1,700 8 37

17 1,990 6 32 2,650 6 43 1,590 7 30

18 2,050 8 44 2,680 6 43 1,500 6 24

19 2,130 7 40 2,640 7 50 1,420 6 23

20 2,180 8 47 2,520 6 41 1,350 4 15

21 2,260 8 49 2,450 6 40 1,310 4 14

22 2,430 8 52 2,490 6 40 1,260 4 14

23 2,660 10 72 2,620 8 57 1,210 4 13

24 2,820 12 91 2,840 11 84 1,160 4 13

25 2,830 10 76 3,020 13 106 1,120 3 9.1

26 2,780 10 75 3,070 15 124 1,090 3 8.8

27 2,700 8 58 3,180 18 155 1,040 2 5.6

28 2,580 6 42 3,300 21 187 1,010 4 11

29 2,570 6 42 3,310 24 214 979 3 7.9

30 2,720 7 51 3,290 27 240 963 3 7.8

31 -- -- -- 3,390 29 265 -- -- --

Total1 76,680 -- 1,892 89,190 -- 2,858 61,432 -- 3,056.2

Mean 2,556 9 63 2,877 11 92 2,048 13 102

Max 3,560 16 154 3,390 29 265 3,910 46 486

Min 1,990 5 27 2,450 6 40 963 2 5.6

Table 6. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2014 

through September 2015.—Continued

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum]
Data 47

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

July August September

1 925 4 10 582 2 3.1 423 2 2.3

2 898 3 7.3 566 2 3.1 409 2 2.2

3 875 3 7.1 549 2 3.0 407 2 2.2

4 849 4 9.2 537 3 4.3 424 3 3.4

5 825 4 8.9 527 3 4.3 464 4 5.0

6 816 3 6.6 532 4 5.7 544 3 4.4

7 817 2 4.4 524 5 7.1 552 4 6.0

8 795 2 4.3 511 6 8.3 517 3 4.2

9 769 2 4.2 498 6 8.1 492 3 4.0

10 744 2 4.0 490 5 6.6 474 3 3.8

11 730 2 3.9 484 3 3.9 456 4 4.9

12 764 7 14 472 2 2.5 446 4 4.8

13 754 6 12 471 3 3.8 437 4 4.7

14 734 3 5.9 456 3 3.7 431 3 3.5

15 711 2 3.8 467 4 5.0 442 3 3.6

16 699 2 3.8 463 5 6.3 448 2 2.4

17 684 2 3.7 456 6 7.4 451 2 2.4

18 670 3 5.4 452 4 4.9 454 3 3.7

19 656 3 5.3 446 2 2.4 446 3 3.6

20 647 3 5.2 448 2 2.4 440 4 4.8

21 631 3 5.1 433 2 2.3 429 4 4.6

22 611 3 4.9 435 2 2.3 425 4 4.6

23 598 3 4.8 428 2 2.3 419 3 3.4

24 596 3 4.8 437 2 2.4 411 3 3.3

25 590 2 3.2 434 2 2.3 409 3 3.3

26 587 2 3.2 424 2 2.3 405 3 3.3

27 605 2 3.3 419 2 2.3 401 3 3.2

28 651 5 8.8 411 2 2.2 407 3 3.3

29 672 3 5.4 416 2 2.2 410 3 3.3

30 644 4 7.0 421 2 2.3 410 3 3.3

31 606 3 4.9 424 2 2.3 -- -- --

Total1 22,153 -- 184.4 14,613 -- 121.1 13,283 -- 111.5

Mean 715 3 5.9 471 3 3.9 443 3 3.7

Max 925 7 14 582 6 8.3 552 4 6.0

Min 587 2 3.2 411 2 2.2 401 2 2.2

1

Total for water year 2015 (unrounded sum of daily values): streamflow=457,305 ft3/s (annual runoff=907,100 acre-feet); suspended-sediment 

discharge=13,370.3 tons.

Table 6. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2014 

through September 2015.—Continued

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum]
48 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2014 

through September 2015.

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton 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 1,480 4 16 1,610 5 22 e1,600 19 82

2 1,520 4 16 1,700 5 23 e1,550 13 54

3 1,510 4 16 1,740 6 28 e1,600 13 56

4 1,500 4 16 1,710 6 28 e1,700 12 55

5 1,500 4 16 1,710 6 28 e1,800 13 63

6 1,480 4 16 1,720 5 23 1,810 14 68

7 1,460 4 16 1,740 5 23 1,760 9 43

8 1,450 4 16 1,750 5 24 1,700 6 28

9 1,450 4 16 1,790 5 24 1,660 6 27

10 1,440 4 16 e1,800 5 24 1,650 6 27

11 1,460 4 16 e1,700 6 28 1,650 6 27

12 1,550 4 17 e1,400 7 26 1,670 6 27

13 1,570 4 17 e1,100 9 27 1,700 6 28

14 1,550 4 17 e1,000 12 32 1,740 6 28

15 1,520 4 16 e1,000 15 40 1,700 6 28

16 1,510 4 16 e1,050 18 51 1,520 5 21

17 1,480 3 12 e1,100 21 62 1,530 4 17

18 1,470 3 12 e1,150 22 68 1,610 4 17

19 1,470 3 12 e1,200 17 55 1,620 4 17

20 1,460 3 12 e1,300 11 39 1,620 4 17

21 1,490 4 16 e1,450 6 23 1,650 5 22

22 1,600 6 26 e1,600 5 22 1,690 5 23

23 1,670 7 32 e1,650 6 27 1,640 5 22

24 1,660 8 36 e1,700 8 37 1,610 5 22

25 1,680 8 36 1,690 9 41 1,680 5 23

26 1,680 7 32 1,740 10 47 1,620 5 22

27 1,660 7 31 1,710 10 46 1,550 5 21

28 1,620 6 26 1,890 23 117 1,530 4 17

29 1,630 6 26 e1,850 40 200 e1,300 3 11

30 1,640 6 27 e1,750 30 142 e900 3 7.3

31 1,620 5 22 -- -- -- e800 13 28

Total1 47,780 -- 617 46,300 -- 1,377 49,160 -- 948.3

Mean 1,541 5 20 1,543 11 46 1,586 7 31

Max 1,680 8 36 1,890 40 200 1,810 19 82

Min 1,440 3 12 1,000 5 22 800 3 7.3
Data 49

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2014 

through September 2015.—Continued

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton 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 e900 45 109 1,890 9 46 2,110 6 34

2 e1,100 91 270 1,870 9 45 2,060 6 33

3 e1,250 138 466 1,890 9 46 2,040 5 28

4 e1,400 185 699 1,870 8 40 1,900 5 26

5 e1,600 233 1,010 1,830 8 40 1,970 4 21

6 e1,500 245 992 1,820 9 44 2,010 5 27

7 e1,400 189 714 2,050 12 66 2,020 6 33

8 e1,400 98 370 3,210 38 329 2,040 6 33

9 e1,500 30 122 3,690 53 528 2,060 6 33

10 e1,600 8 35 4,040 56 611 2,090 6 34

11 e1,700 9 41 3,990 44 474 2,110 6 34

12 e1,800 11 53 3,650 30 296 2,130 7 40

13 e1,750 11 52 3,510 24 227 2,220 8 48

14 1,660 10 45 3,450 19 177 2,330 9 57

15 1,500 9 36 3,460 19 177 2,780 16 120

16 1,520 7 29 3,390 16 146 4,410 56 667

17 1,580 5 21 3,220 13 113 5,400 51 744

18 1,620 6 26 3,060 12 99 5,600 37 559

19 1,720 7 33 3,000 11 89 5,660 32 489

20 1,790 9 43 2,960 10 80 5,530 27 403

21 1,650 10 45 2,910 10 79 5,430 22 323

22 1,490 10 40 2,620 9 64 5,410 19 278

23 1,540 10 42 2,230 9 54 5,400 18 262

24 1,670 12 54 2,290 8 49 5,320 16 230

25 2,150 40 232 2,500 8 54 5,150 14 195

26 2,480 50 335 2,460 7 46 4,930 14 186

27 2,600 48 337 2,330 7 44 4,790 14 181

28 2,440 31 204 2,220 6 36 4,910 16 212

29 2,230 23 138 -- -- -- 5,210 17 239

30 2,060 17 95 -- -- -- 5,270 17 242

31 1,960 12 64 -- -- -- 5,410 18 263

Total1 52,560 -- 6,752 77,410 -- 4,099 115,700 -- 6,074

Mean 1,695 52 218 2,765 17 146 3,732 16 196

Max 2,600 245 1,010 4,040 56 611 5,660 56 744

Min 900 5 21 1,820 6 36 1,900 4 21
50 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

April May June

1 5,720 20 309 4,800 12 156 6,310 32 545

2 5,800 19 298 4,840 11 144 6,670 37 666

3 5,610 15 227 4,950 11 147 7,010 50 946

4 5,370 14 203 5,050 12 164 6,620 44 786

5 5,160 12 167 5,160 12 167 6,090 34 559

6 4,930 12 160 5,380 15 218 5,630 26 395

7 4,720 10 127 5,390 16 233 5,290 22 314

8 4,470 10 121 5,120 12 166 5,000 22 297

9 4,200 10 113 4,800 10 130 4,750 20 256

10 3,980 10 107 4,550 8 98 4,670 18 227

11 3,920 10 106 4,380 8 95 4,530 18 220

12 3,900 8 84 4,260 7 81 4,160 16 180

13 3,790 9 92 4,260 7 81 3,820 13 134

14 3,710 9 90 4,280 8 92 3,530 10 95

15 3,680 8 79 4,290 8 93 3,260 9 79

16 3,580 8 77 4,590 10 124 3,050 8 66

17 3,510 8 76 5,050 17 232 2,850 7 54

18 3,540 8 76 5,330 23 331 2,720 6 44

19 3,650 8 79 5,110 19 262 2,600 6 42

20 3,760 8 81 4,880 13 171 2,480 4 27

21 3,880 10 105 4,700 10 127 2,390 5 32

22 4,120 10 111 4,720 10 127 2,310 4 25

23 4,490 14 170 4,880 12 158 2,210 3 18

24 4,790 16 207 5,130 12 166 2,140 3 17

25 4,840 14 183 5,370 13 188 2,040 3 17

26 4,780 13 168 5,450 15 221 1,960 2 11

27 4,630 12 150 5,590 17 257 1,880 2 10

28 4,430 9 108 5,990 28 453 1,810 3 15

29 4,400 10 119 6,160 30 499 1,740 2 9.4

30 4,610 11 137 6,130 29 480 1,740 2 9.4

31 -- -- -- 6,240 30 505 -- -- --

Total1 131,970 -- 4,130 156,830 -- 6,366 111,260 -- 6,095.8

Mean 4,399 11 138 5,059 14 205 3,709 14 203

Max 5,800 20 309 6,240 30 505 7,010 50 946

Min 3,510 8 76 4,260 7 81 1,740 2 9.4

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2014 

through September 2015.—Continued

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum]
Data 51

Day

Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment Mean 

streamflow 

(ft3

/s)

Suspended sediment

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

Mean 

concentration 

(mg/L)

Discharge 

(ton/d)

July August September

1 1,720 2 9.3 1,230 5 17 830 3 6.7

2 1,670 2 9.0 1,180 4 13 814 3 6.6

3 1,620 2 8.7 1,140 4 12 815 3 6.6

4 1,590 2 8.6 1,110 4 12 842 3 6.8

5 1,540 2 8.3 1,090 4 12 935 4 10

6 1,530 2 8.3 1,100 4 12 1,140 8 25

7 1,540 2 8.3 1,070 4 12 1,190 10 32

8 1,520 3 12 1,040 5 14 1,140 9 28

9 1,490 3 12 1,020 5 14 1,110 7 21

10 1,440 4 16 1,010 5 14 1,080 6 17

11 1,500 5 20 993 4 11 1,050 6 17

12 1,580 3 13 962 4 10 1,010 6 16

13 1,580 2 8.5 950 4 10 972 6 16

14 1,560 2 8.4 920 4 9.9 954 6 15

15 1,520 2 8.2 932 4 10 990 6 16

16 1,470 1 4.0 923 4 10 1,030 6 17

17 1,420 1 3.8 922 4 10 1,080 6 17

18 1,390 1 3.8 915 3 7.4 1,120 8 24

19 1,360 2 7.3 905 3 7.3 1,130 10 31

20 1,330 3 11 892 2 4.8 1,140 10 31

21 1,280 3 10 856 2 4.6 1,120 10 30

22 1,220 3 9.9 847 2 4.6 1,090 9 26

23 1,200 3 9.7 840 3 6.8 1,060 8 23

24 1,240 4 13 845 3 6.8 1,040 7 20

25 1,240 4 13 848 3 6.9 1,030 6 17

26 1,220 5 16 834 3 6.8 1,010 5 14

27 1,260 5 17 823 3 6.7 994 5 13

28 1,420 7 27 809 3 6.6 999 4 11

29 1,480 8 32 811 3 6.6 1,010 4 11

30 1,410 7 27 825 3 6.7 1,040 4 11

31 1,310 6 21 837 3 6.8 -- -- --

Total1 44,650 -- 384.1 29,479 -- 292.3 30,765 -- 535.7

Mean 1,440 3 12 951 4 9.4 1,026 6 18

Max 1,720 8 32 1,230 5 17 1,190 10 32

Min 1,200 1 3.8 809 2 4.6 814 3 6.6

1

Total for water year 2015 (unrounded sum of daily values): streamflow=893,864 ft3/s (annual runoff=1,773,000 acre-feet); suspended-sediment 

discharge=37,671.2 tons.

Table 7. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2014 

through September 2015.—Continued

[ft3/s, cubic feet per second; mg/L, milligram per liter; ton/d, ton per day; e, estimated; --, no data or value not computed; max, maximum; min, minimum]
52 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 8. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Mill Creek at Opportunity, Montana 

(12323700), March through September 2015.

[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 Maximum Minimum Mean

March April May June

1 -- -- -- 7.0 5.0 5.5 7.0 4.0 5.5 23 9.5 15

2 -- -- -- 6.0 4.5 5.0 6.0 4.0 5.0 14 7.5 10

3 -- -- -- 6.0 4.5 5.0 7.5 4.0 5.5 9.5 6.0 7.5

4 -- -- -- 5.5 4.0 4.5 8.0 5.0 6.0 8.5 6.0 7.0

5 -- -- -- 5.0 4.0 4.5 14 5.5 8.5 9.0 5.0 6.5

6 -- -- -- 5.0 3.5 4.0 16 6.5 9.5 9.5 4.5 6.0

7 -- -- -- 5.5 4.0 4.5 8.5 4.5 6.5 -- -- --

8 -- -- -- 5.0 3.5 4.0 80 5.0 12 -- -- --

9 -- -- -- 5.0 3.5 4.0 9.5 4.0 6.5 -- -- --

10 -- -- -- 5.5 3.5 4.0 8.0 3.5 5.0 -- -- --

11 -- -- -- 4.5 3.5 3.5 7.0 3.5 4.5 5.5 4.0 4.5

12 -- -- -- 4.5 3.0 3.5 7.5 3.0 4.5 5.5 3.5 4.0

13 -- -- -- 4.5 3.0 3.5 11 4.0 7.0 5.0 3.0 3.5

14 -- -- -- 4.5 3.0 3.5 7.0 4.0 5.5 4.5 2.5 3.5

15 -- -- -- 4.0 3.0 3.5 14 4.0 6.0 4.5 2.5 3.5

16 -- -- -- 4.0 2.0 3.0 43 11 23 4.5 2.5 3.5

17 -- -- -- 4.5 2.0 3.5 35 11 18 4.5 2.5 3.0

18 -- -- -- 4.0 3.0 3.5 14 8.5 10 4.0 2.0 3.0

19 -- -- -- 4.5 2.0 3.5 11 7.5 9.0 5.0 2.0 3.0

20 -- -- -- 4.5 2.0 3.5 10 6.5 8.0 4.0 2.0 2.5

21 -- -- -- 5.0 2.5 3.5 9.5 5.5 7.0 12 2.0 3.0

22 -- -- -- 6.5 3.5 4.5 8.5 5.5 6.5 12 3.5 5.5

23 -- -- -- 6.5 4.0 5.0 9.5 5.5 7.0 5.5 3.0 4.0

24 -- -- -- 9.5 5.0 6.0 8.5 6.0 7.0 5.0 2.5 3.5

25 -- -- -- 8.0 4.0 5.5 8.5 5.5 6.5 5.0 2.5 3.5

26 -- -- -- 5.0 3.5 4.5 11 6.5 8.0 5.0 2.0 3.0

27 -- -- -- 5.5 3.0 4.0 12 6.5 8.5 7.5 2.5 3.5

28 -- -- -- 5.5 3.0 4.5 21 7.5 11 5.0 2.0 3.0

29 -- -- -- 6.5 3.5 4.5 25 8.0 13 6.5 1.5 3.0

30 -- -- -- 6.5 4.0 5.0 13 7.5 10 6.5 2.0 3.5

31 6.5 4.5 5.5 -- -- -- 12 6.5 9.0 -- -- --

Month1 6.5 4.5 5.5 9.5 2.0 4.2 80 3.0 8.4 23 1.5 4.7
Data 53

Table 8. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Mill Creek at Opportunity, Montana 

(12323700), March through September 2015.—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 2.0 2.5 2.5 1.5 2.0 2.0 1.0 1.5

2 4.0 1.5 2.5 2.5 1.5 2.0 1.5 1.0 1.0

3 3.5 1.0 2.0 4.0 1.5 2.0 1.5 1.0 1.0

4 3.5 1.0 2.0 2.0 1.5 1.5 3.0 1.5 1.5

5 4.0 1.0 2.0 2.5 1.5 1.5 5.5 2.0 3.0

6 3.0 1.5 2.0 2.0 1.5 1.5 2.0 1.0 1.5

7 3.0 1.0 2.0 3.5 1.5 1.5 2.0 1.0 1.5

8 3.5 1.0 2.0 2.5 1.5 1.5 2.0 1.0 1.5

9 3.0 1.5 2.0 2.0 1.0 1.5 1.5 1.5 1.5

10 3.5 2.0 2.5 6.0 1.5 2.0 2.0 1.5 1.5

11 -- -- -- 2.5 1.5 2.0 2.5 1.5 1.5

12 -- -- -- 2.0 1.5 1.5 2.5 1.5 1.5

13 3.0 1.5 2.5 2.0 1.5 1.5 2.0 1.5 1.5

14 3.0 1.5 2.0 2.0 1.5 1.5 2.5 1.5 1.5

15 3.0 1.0 1.5 -- -- -- 3.5 2.0 2.5

16 2.5 1.0 1.5 -- -- -- -- -- --

17 2.0 1.0 1.5 -- -- -- 3.5 2.0 2.5

18 2.5 1.0 1.5 -- -- -- 3.5 2.0 2.5

19 2.0 1.0 1.5 -- -- -- -- -- --

20 2.0 1.0 1.5 -- -- -- -- -- --

21 2.0 1.0 1.5 2.0 1.5 2.0 2.5 1.5 2.0

22 3.0 1.0 1.5 2.0 1.5 1.5 -- -- --

23 3.5 1.5 2.0 2.0 1.5 1.5 -- -- --

24 2.5 1.5 2.0 2.0 1.0 1.5 2.0 1.5 2.0

25 3.0 1.5 2.0 2.0 1.0 1.5 2.5 2.0 2.0

26 5.0 1.5 2.0 3.5 1.0 1.5 -- -- --

27 4.0 2.0 3.0 2.5 1.0 1.5 -- -- --

28 4.0 2.0 3.0 2.0 1.0 1.5 -- -- --

29 3.5 2.0 2.5 2.0 1.0 1.5 -- -- --

30 3.0 2.0 2.5 2.0 1.0 1.5 -- -- --

31 3.0 2.0 2.5 1.5 1.0 1.5 -- -- --

Month1 5.0 1.0 2.1 6.0 1.0 1.6 5.5 1.0 1.8

1

For months with missing daily values, the means are calculated using available values.
54 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 9. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Willow Creek at Opportunity, 

Montana (12323720), March through September 2015.

[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 Maximum Minimum Mean

March April May June

1 -- -- -- 12 9.5 11 9.0 6.0 7.0 7.5 5.0 6.5

2 -- -- -- 13 9.5 11 8.5 6.5 7.0 8.0 5.0 6.0

3 -- -- -- 15 9.0 11 8.0 6.0 7.0 7.0 4.5 5.5

4 -- -- -- 12 9.0 10 9.0 7.0 8.0 7.5 5.0 5.5

5 -- -- -- 10 7.5 9.0 9.5 6.0 7.5 7.0 4.5 6.0

6 -- -- -- 10 7.0 8.0 -- -- -- 7.5 5.0 6.0

7 -- -- -- 10 6.0 7.5 -- -- -- 7.5 4.5 6.0

8 -- -- -- 7.5 6.0 6.5 -- -- -- 8.5 4.5 5.5

9 -- -- -- 7.0 5.5 6.5 9.0 5.5 7.0 8.0 4.5 6.0

10 -- -- -- 7.0 5.5 6.0 7.5 5.0 6.5 7.5 4.5 5.0

11 -- -- -- 7.0 5.0 6.0 8.5 6.0 7.0 -- -- --

12 -- -- -- 7.0 5.0 6.0 9.5 4.5 6.0 7.0 4.0 5.0

13 -- -- -- 6.5 5.0 5.5 11 6.5 8.0 6.5 3.5 5.0

14 -- -- -- 7.0 5.0 6.0 9.0 4.5 6.5 6.5 3.5 4.5

15 -- -- -- 6.5 5.0 5.5 11 5.5 7.5 6.0 3.5 4.5

16 -- -- -- 8.0 4.5 6.0 22 7.5 14 7.5 3.0 5.0

17 -- -- -- 8.0 6.0 6.5 22 12 15 7.0 3.0 4.5

18 -- -- -- 7.5 5.5 6.0 17 14 15 6.0 3.0 4.0

19 -- -- -- 7.5 4.5 6.0 17 12 14 5.5 3.0 4.0

20 -- -- -- 7.5 5.0 6.0 13 11 11 4.5 2.5 3.5

21 -- -- -- 6.5 4.5 5.5 12 9.5 10 4.5 2.5 3.0

22 -- -- -- 9.5 5.0 6.0 13 8.5 10 4.0 2.0 3.0

23 -- -- -- 11 5.0 7.0 11 8.5 9.5 4.0 2.0 3.0

24 -- -- -- 9.5 4.5 6.5 11 7.5 9.0 4.5 2.5 3.0

25 -- -- -- 10 5.5 7.0 10 7.5 8.5 4.0 2.5 3.0

26 -- -- -- 11 6.0 7.5 9.0 7.0 8.0 4.5 2.5 3.0

27 -- -- -- 9.5 6.0 7.5 8.5 6.5 7.5 4.5 2.0 3.0

28 -- -- -- 9.0 7.0 7.5 9.0 6.5 7.0 4.0 2.0 2.5

29 -- -- -- 8.5 6.5 7.5 8.5 5.5 7.0 3.5 2.0 3.0

30 -- -- -- 11 6.5 8.0 8.5 5.0 6.0 3.5 2.0 2.5

31 13 9.5 11 -- -- -- 8.0 5.5 6.5 -- -- --

Month1 13 9.5 11 15 4.5 7.2 22 4.5 8.7 8.5 2.0 4.4
Data 55

Table 9. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Willow Creek at Opportunity, 

Montana (12323720), March through September 2015.—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 3.0 1.5 2.0 -- -- -- 3.5 2.5 3.0

2 2.5 1.5 2.0 -- -- -- -- -- --

3 3.0 1.5 2.0 -- -- -- -- -- --

4 3.5 1.5 2.0 -- -- -- 3.0 2.0 2.0

5 2.5 1.5 2.0 -- -- -- 4.5 2.5 3.0

6 2.5 1.5 2.0 -- -- -- 5.0 2.5 3.5

7 3.0 2.0 2.0 -- -- -- 3.5 2.0 2.5

8 3.5 1.5 2.5 -- -- -- 3.0 2.0 2.5

9 4.5 2.0 3.0 -- -- -- 3.5 2.0 2.5

10 3.0 2.0 2.5 -- -- -- 4.0 2.0 2.5

11 3.0 1.5 2.5 -- -- -- 3.5 2.0 2.5

12 3.5 2.0 2.5 -- -- -- 3.5 2.0 2.5

13 3.0 2.0 2.5 -- -- -- 3.0 2.0 2.5

14 3.0 2.0 2.5 -- -- -- 3.5 2.5 2.5

15 3.0 2.0 2.5 -- -- -- 3.5 2.0 2.5

16 3.0 2.0 2.5 -- -- -- 4.5 3.0 3.5

17 3.0 1.5 2.5 -- -- -- 4.5 2.5 3.5

18 2.5 1.5 2.0 -- -- -- 4.0 2.5 3.5

19 2.5 1.5 2.0 -- -- -- 3.5 2.5 3.0

20 2.5 1.5 2.0 -- -- -- 3.5 2.0 2.5

21 2.5 2.0 2.0 4.0 2.5 3.0 3.5 2.0 2.5

22 3.0 2.0 2.5 3.5 2.5 2.5 3.0 2.0 2.5

23 3.0 2.0 2.5 4.0 2.5 2.5 2.5 2.0 2.0

24 3.5 2.5 2.5 4.0 2.5 2.5 3.5 1.5 2.0

25 3.5 2.0 2.5 4.0 2.5 3.0 3.5 2.0 2.0

26 3.0 1.5 2.0 4.0 2.5 3.0 3.5 2.0 2.0

27 3.5 2.0 2.5 3.5 2.5 2.5 3.5 2.0 2.5

28 6.0 2.5 3.5 3.0 2.0 2.5 3.0 2.0 2.5

29 4.0 2.0 3.0 3.0 2.5 2.5 3.0 2.0 2.5

30 4.0 2.0 3.0 3.5 2.5 3.0 3.5 2.0 2.5

31 -- -- -- 3.5 2.5 3.0 -- -- --

Month1 6.0 1.5 2.4 4.0 2.0 2.7 5.0 1.5 2.6

1

For months with missing daily values, the means are calculated using available values.
56 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 10. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Warm Springs Creek at Warm 

Springs, Montana (12323770), March through September 2015.

[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 Maximum Minimum Mean

March April May June

1 -- -- -- 4.5 3.0 3.5 8.0 3.5 4.5 12 7.5 9.5

2 -- -- -- 4.0 2.0 3.0 9.0 6.0 7.5 -- -- --

3 -- -- -- 4.0 2.0 3.0 9.0 6.0 7.5 -- -- --

4 -- -- -- 3.5 2.0 3.0 10 6.5 8.0 -- -- --

5 -- -- -- 3.5 2.0 2.5 15 6.5 11 -- -- --

6 -- -- -- 4.0 2.0 2.5 15 8.5 12 -- -- --

7 -- -- -- 4.5 2.0 2.5 9.5 5.5 7.5 -- -- --

8 -- -- -- 4.5 2.0 2.5 8.0 4.5 5.5 -- -- --

9 -- -- -- 4.5 2.0 2.5 6.5 3.5 4.5 -- -- --

10 -- -- -- 3.5 1.5 2.5 6.0 3.5 4.5 -- -- --

11 -- -- -- 3.5 2.0 2.5 6.0 3.5 4.5 -- -- --

12 -- -- -- 3.5 1.5 2.5 5.5 3.0 4.0 13 4.0 5.0

13 -- -- -- 3.0 2.0 2.0 7.5 4.5 5.5 6.5 3.5 4.5

14 -- -- -- 3.0 2.0 2.5 8.0 5.0 6.0 5.0 3.0 4.0

15 -- -- -- 2.5 1.5 2.0 9.0 6.5 8.0 5.0 3.0 4.0

16 -- -- -- 2.5 2.0 2.0 17 9.0 13 5.5 3.5 4.0

17 -- -- -- 5.5 2.0 3.0 16 7.5 11 5.0 3.0 4.0

18 -- -- -- 3.5 2.0 2.5 8.5 5.0 6.5 4.5 3.0 3.5

19 -- -- -- 3.0 2.0 2.5 7.0 4.5 5.5 4.5 3.0 3.5

20 -- -- -- 3.5 2.0 2.5 6.0 4.0 5.0 5.5 3.0 4.0

21 -- -- -- 3.5 2.0 2.5 6.5 4.0 5.0 4.5 2.5 3.5

22 -- -- -- 4.0 2.5 3.0 8.5 5.5 6.5 4.5 2.5 3.5

23 -- -- -- 5.0 3.0 3.5 8.0 5.5 6.5 4.0 2.5 3.0

24 -- -- -- 6.5 3.5 4.5 9.5 6.0 7.5 4.0 2.0 3.0

25 -- -- -- 6.0 3.0 4.5 8.0 5.5 6.5 6.0 2.0 3.0

26 -- -- -- 4.5 3.0 3.5 9.5 6.5 8.0 5.0 2.0 3.0

27 -- -- -- 5.0 2.5 3.0 8.5 6.0 7.5 -- -- --

28 -- -- -- 4.0 2.5 3.0 23 7.0 11 5.5 1.5 2.5

29 -- -- -- 4.5 2.5 3.0 11 6.0 8.0 190 1.5 6.5

30 -- -- -- 5.5 3.0 3.5 11 6.0 7.0 240 3.0 21

31 4.5 2.0 3.0 -- -- -- 8.5 6.0 7.0 -- -- --

Month1 4.5 2.0 3.0 6.5 1.5 2.8 23 3.0 7.2 240 1.5 5.0
Data 57

Table 10. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Warm Springs Creek at Warm 

Springs, Montana (12323770), March through September 2015.—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 2 3 2.0 0.5 1.0 3.0 0.5 1.0

2 -- -- -- 2.0 0.5 1.0 2.0 0.5 1.0

3 4.0 1.5 2.5 4.0 0.5 1.5 2.0 0.5 1.0

4 3.5 1.0 2.0 1.5 0.5 1.0 9.0 1.0 2.5

5 3.5 1.0 2.0 1.0 0.5 0.5 15 3.0 6.5

6 2.5 1.0 1.5 1.5 0.5 1.0 4.5 1.0 2.0

7 3.0 1.0 1.5 1.5 0.5 1.0 2.5 0.5 1.0

8 -- -- -- 1.5 0.5 1.0 3.0 1.0 1.0

9 1.5 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0

10 1.5 0.5 1.0 1.5 0.5 1.0 1.5 0.5 1.0

11 2.0 1.0 1.5 1.5 0.5 1.0 2.5 0.5 1.0

12 2.0 0.5 1.0 2.5 0.5 1.0 1.5 0.5 1.0

13 2.0 0.5 1.0 1.5 0.5 1.0 1.5 0.5 1.0

14 2.5 0.5 1.0 1.5 0.5 1.0 2.5 1.0 1.0

15 2.0 0.5 1.0 2.0 0.5 1.0 4.5 1.5 2.5

16 1.5 0.5 1.0 2.5 0.5 1.0 2.5 1.0 1.5

17 2.0 0.5 1.0 3.0 0.5 1.0 2.0 1.0 1.5

18 2.0 0.5 1.0 2.0 0.5 1.0 2.0 1.0 1.0

19 1.5 0.5 1.0 1.5 0.5 1.0 2.0 0.5 1.0

20 1.5 0.5 1.0 1.5 0.5 1.0 2.0 0.5 1.0

21 1.0 0.5 0.5 2.0 0.5 1.0 2.0 0.5 1.0

22 3.0 0.5 1.0 1.5 0.5 1.0 2.0 0.5 1.0

23 4.5 1.0 2.0 1.5 0.5 1.0 2.5 1.0 1.5

24 6.0 1.0 2.5 1.5 0.5 1.0 3.5 1.0 2.0

25 8.5 0.5 4.0 1.5 0.5 1.0 3.5 1.0 2.0

26 11 1.0 4.0 1.5 0.5 1.0 3.5 1.0 2.0

27 -- -- -- 1.5 0.5 1.0 3.5 1.0 2.0

28 -- -- -- 2.5 0.5 1.0 3.5 1.0 2.0

29 -- -- -- 1.5 0.5 1.0 2.5 1.0 1.5

30 1.5 0.5 0.5 1.5 0.5 1.0 -- -- --

31 2.0 0.5 1.0 2.0 0.5 1.0 -- -- --

Month1 11 0.5 1.6 4.0 0.5 1.0 15 0.5 1.6

1

For months with missing daily values, the means are calculated using available values.
58 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 11. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Lost Creek near Anaconda, 

Montana (12323840), March through September 2015.

[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 Maximum Minimum Mean

March April May June

1 -- -- -- 8.5 6.0 7.0 -- -- -- 18 10 13

2 -- -- -- 7.5 5.0 6.0 -- -- -- 25 12 17

3 -- -- -- 7.0 4.5 5.5 -- -- -- 14 9.0 11

4 -- -- -- 6.0 4.5 5.0 -- -- -- 12 8.0 9.5

5 -- -- -- 8.0 4.5 5.0 -- -- -- 10 7.0 8.5

6 -- -- -- 6.0 4.5 5.0 -- -- -- 10 7.0 8.0

7 -- -- -- 7.0 4.5 5.0 -- -- -- 9.5 6.5 7.5

8 -- -- -- 5.0 4.5 4.5 -- -- -- 9.0 6.0 7.0

9 -- -- -- 18 4.5 6.0 8.5 6.0 7.0 8.5 6.0 7.0

10 -- -- -- 7.0 5.0 5.5 8.0 5.5 6.5 9.5 6.0 7.0

11 -- -- -- 7.0 4.5 5.5 7.5 5.0 6.0 7.5 5.5 6.0

12 -- -- -- 6.0 4.5 5.5 9.0 5.0 6.0 6.5 5.0 5.5

13 -- -- -- 6.5 4.5 5.5 12 5.5 7.0 6.0 4.5 5.0

14 -- -- -- 6.5 5.0 5.5 8.5 5.0 6.5 7.0 4.5 5.5

15 -- -- -- 9.5 5.0 6.0 10 5.5 7.0 6.5 4.5 5.5

16 -- -- -- 8.0 4.5 5.5 20 8.0 13 7.0 4.5 5.5

17 -- -- -- 6.5 5.0 5.5 21 6.5 10 6.0 4.5 5.0

18 -- -- -- 6.5 5.0 5.5 8.0 5.5 6.5 6.0 4.5 5.0

19 -- -- -- 7.0 5.0 5.5 19 5.5 7.0 5.5 4.0 5.0

20 -- -- -- 7.0 5.0 5.5 11 6.0 7.5 6.5 4.0 5.0

21 -- -- -- 8.0 5.5 7.0 9.5 5.5 7.5 6.0 3.5 4.5

22 -- -- -- -- -- -- 11 5.0 7.0 5.5 3.5 4.0

23 -- -- -- -- -- -- 10 6.0 7.0 5.5 3.5 4.0

24 -- -- -- -- -- -- 11 7.0 8.5 6.5 4.0 5.0

25 -- -- -- -- -- -- 30 7.0 9.5 6.0 4.0 5.0

26 -- -- -- -- -- -- 29 8.5 12 7.0 4.0 5.0

27 -- -- -- -- -- -- 18 9.0 11 7.0 3.5 5.0

28 -- -- -- -- -- -- 18 10 13 6.0 3.5 4.5

29 -- -- -- -- -- -- 16 9.0 12 12 4.0 6.5

30 -- -- -- -- -- -- 21 11 14 6.5 4.5 5.5

31 7.5 5.0 6.0 -- -- -- 31 10 15 -- -- --

Month1 7.5 5.0 6.0 18 4.5 5.6 31 5.0 9.0 25 3.5 6.6
Data 59

Table 11. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Lost Creek near Anaconda, 

Montana (12323840), March through September 2015.—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 5.5 4.0 4.5 7.5 5.0 6.0 3.5 2.0 3.0

2 5.0 4.0 4.5 8.0 5.0 6.0 3.5 2.5 3.0

3 -- -- -- 8.0 5.0 6.0 3.0 2.5 3.0

4 7.0 4.5 5.5 8.0 5.0 6.0 5.5 2.5 3.5

5 6.5 4.0 4.5 7.5 5.0 6.0 9.0 3.5 5.5

6 5.5 4.0 4.5 8.0 5.0 6.0 3.5 2.5 3.0

7 5.5 4.0 4.5 7.5 5.0 6.0 16 2.5 4.0

8 7.0 4.0 5.0 6.5 4.5 5.5 5.0 3.0 4.0

9 5.0 4.0 4.5 6.5 4.5 5.5 3.5 3.0 3.0

10 5.5 4.0 4.0 9.5 5.0 6.5 3.5 2.5 3.0

11 7.5 4.0 4.5 7.5 4.5 6.0 3.5 2.5 3.0

12 5.0 3.5 4.0 8.5 4.5 6.0 3.5 2.5 3.0

13 6.0 3.5 4.0 7.5 4.5 5.5 3.0 2.5 2.5

14 7.5 4.0 4.5 7.5 5.0 6.0 3.5 2.5 3.0

15 4.5 4.0 4.0 7.5 4.5 5.5 10 2.5 3.5

16 4.5 4.0 4.0 7.5 3.5 5.0 10 2.5 3.5

17 4.5 4.0 4.0 4.5 3.5 4.0 3.0 2.5 3.0

18 5.0 4.0 4.5 5.5 3.5 4.0 3.5 2.5 2.5

19 5.0 3.5 4.0 4.5 3.0 3.5 2.5 2.0 2.5

20 4.5 3.5 4.0 4.0 3.0 3.5 3.5 2.0 2.5

21 8.0 2.5 4.0 4.0 3.0 3.5 2.5 2.0 2.5

22 5.0 2.5 3.0 4.0 3.0 3.5 3.0 2.0 2.5

23 4.5 2.5 3.0 4.0 3.0 3.5 3.0 2.0 2.0

24 4.5 2.5 3.5 4.0 2.5 3.0 2.5 2.0 2.0

25 4.0 2.0 2.5 3.5 3.0 3.0 2.5 2.0 2.0

26 3.0 2.0 2.0 3.5 2.5 3.0 3.0 2.0 2.0

27 5.0 2.0 4.0 3.5 2.5 2.5 2.5 2.0 2.0

28 4.5 1.5 3.0 2.5 2.0 2.5 2.5 2.0 2.5

29 26 1.5 6.0 4.0 2.0 2.5 2.5 2.0 2.5

30 26 5.5 9.0 3.0 2.5 2.5 3.0 2.5 2.5

31 9.5 5.5 7.0 3.0 2.0 2.5 -- -- --

Month1 26 1.5 4.3 9.5 2.0 4.5 16 2.0 2.9

1

For months with missing daily values, the means are calculated using available values.
60 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana Table 12. Analyses of field replicates for water samples, Clark Fork Basin, Montana. [hh, hours; mm, minutes; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; --, no data; <, less than laboratory reporting level; E, estimated] 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)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/l)

12324680 Clark Fork at 

Goldcreek

10/15/2014 1600 -- 200 57.6 13.6 -- -- -- -- -- --

10/15/2014 1605 -- 205 59.8 13.6 -- -- -- -- -- --

12323250 Silver Bow Creek 

below Blacktail Creek, at Butte

03/23/2015 1120 E3.0 141 39.8 10.2 4.26 19.8 92.6 24.1 0.28 20.5

03/23/2015 1125 E2.5 140 39.7 10.0 4.26 19.8 92.5 24.1 0.29 20.4

12324400 Clark Fork above 

Little Blackfoot River, near Garrison

03/24/2015 1435 -- 202 58.8 13.3 -- -- -- -- -- --

03/24/2015 1440 -- 202 59.1 13.2 -- -- -- -- -- --

12323840 Lost Creek near 

Anaconda

04/21/2015 0745 E2.4 103 31.2 5.96 1.20 2.81 94.2 0.75 0.40 11.6

04/21/2015 0750 E2.5 103 31.4 5.99 1.20 2.83 94.3 0.75 0.39 11.6

12324200 Clark Fork at Deer 

Lodge

05/12/2015 1500 -- 171 49.8 11.2 -- -- -- -- -- --

05/12/2015 1505 -- 170 49.4 11.3 -- -- -- -- -- --

12334550 Clark Fork at Turah 

Bridge, near Bonner

05/28/2015 0840 -- 100 29.1 6.73 -- -- -- -- -- --

05/28/2015 0845 -- 94.1 27.1 6.39 -- -- -- -- -- --

12340500 Clark Fork above 

Missoula

06/10/2015 1400 -- 105 28.7 8.02 -- -- -- -- -- --

06/10/2015 1405 -- 108 30.0 7.94 -- -- -- -- -- --

12323750 Silver Bow Creek 

at Warm Springs

07/14/2015 1050 E2.0 171 48.3 12.2 2.34 14.3 93.3 10.8 0.63 13.7

07/14/2015 1055 <2.0 173 49.4 12.1 2.37 14.6 93.2 10.8 0.63 13.5

12323700 Mill Creek at 

Opportunity

08/10/2015 1535 <2.0 78.8 22.1 5.73 0.78 4.98 77.4 0.41 0.36 12.1

08/10/2015 1540 <2.0 78.6 22.2 5.66 0.74 4.70 77.3 0.41 0.36 11.9
Data 61

Site 

number 

(fig. 1)

Site name Date Time (hhmm) Sulfate, filtered (mg/L) Nitrate plus nitrite, 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) Lead, filtered (μg/L) Lead, unfiltered recoverable (μg/L)

12324680 Clark Fork at Goldcreek 10/15/2014 1600 -- -- 0.047 0.067 4.0 12.7 11.7 185 0.111 1.37

10/15/2014 1605 -- -- 0.050 0.074 3.9 13.2 12.3 181 0.111 1.39

12323250 Silver Bow Creek below 

Blacktail Creek, at Butte

03/23/2015 1120 65.0 0.82 0.082 0.073 7.4 8.0 392 484 0.720 1.1103/23/2015 1125 65.0 0.82 0.073 0.076 6.5 9.7 389 476 0.719 1.14

12324400 Clark Fork above 

Little Blackfoot River, 

near Garrison

03/24/2015 1435 -- -- 0.066 0.195 6.8 46.5 36.3 809 0.326 5.71

03/24/2015 1440 -- -- 0.070 0.199 6.9 43.1 37.8 791 0.350 5.61

12323840 Lost Creek near 

Anaconda

04/21/2015 0745 9.44 -- <0.030 <0.030 1.4 5.5 10.1 192 <0.040 0.69

04/21/2015 0750 9.45 -- <0.030 <0.030 1.4 5.6 9.5 186 <0.040 0.73

12324200 Clark Fork at Deer 

Lodge

05/12/2015 1500 -- -- 0.064 0.112 7.0 21.2 21.9 305 0.143 2.36

05/12/2015 1505 -- -- 0.062 0.104 6.7 22.2 23.5 305 0.145 2.52

12334550 Clark Fork at Turah 

Bridge, near Bonner

05/28/2015 0840 -- -- 0.083 0.200 17.9 37.8 359 1,020 2.79 6.16

05/28/2015 0845 -- -- 0.094 0.182 17.5 36.3 339 905 2.74 5.56

12340500 Clark Fork above 

Missoula

06/10/2015 1400 -- -- <0.030 0.100 2.2 10.8 10.2 330 0.071 1.51

06/10/2015 1405 -- -- <0.030 0.058 2.1 11.0 12.0 342 0.069 1.55

12323750 Silver Bow Creek at 

Warm Springs

07/14/2015 1050 84.5 -- <0.030 0.032 2.4 2.8 25.7 99.8 0.087 0.38

07/14/2015 1055 84.6 -- <0.030 0.031 2.4 3.3 25.0 98.1 0.085 0.39

12323700 Mill Creek at 

Opportunity

08/10/2015 1535 11.8 -- 0.057 0.052 2.2 2.8 68.0 115 0.142 0.29

08/10/2015 1540 11.8 -- 0.049 0.070 2.4 3.1 65.1 114 0.162 0.31

Table 12. Analyses of field replicates for water samples, Clark Fork Basin, Montana.—Continued[hh, hours; mm, minutes; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; --, no data; <, less than 

laboratory reporting level; E, estimated]
62 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana Site number (fig. 1) Site name Date Time (hhmm) 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) Sediment, suspended (percent finer than 0.062 mm) Sediment, suspended (mg/L) 12324680 Clark Fork at Goldcreek 10/15/2014 1600 13.4 63.2 2.5 10.9 9.4 10.7 -- 89 7 10/15/2014 1605 13.9 62.0 2.5 10.6 9.4 11.3 -- 87 6 12323250 Silver Bow Creek below Blacktail Creek, at Butte 03/23/2015 1120 67.8 76.2 28.1 30.5 3.4 3.7 5.94 79 4 03/23/2015 1125 67.5 73.8 28.6 30.2 3.3 3.5 5.92 81 4 12324400 Clark Fork above Little Blackfoot River, near Garrison 03/24/2015 1435 30.8 112 6.2 38.7 9.5 15.4 -- 76 31 03/24/2015 1440 31.4 111 5.9 36.9 9.6 14.8 -- 72 33 12323840 Lost Creek near Anaconda 04/21/2015 0745 0.99 7.1 <2.0 3.2 2.5 3.2 1.53 63 11 04/21/2015 0750 0.99 7.0 <2.0 5.0 2.6 3.0 1.51 62 11 12324200 Clark Fork at Deer Lodge 05/12/2015 1500 28.4 60.3 3.6 16.7 12.7 15.3 -- 83 9 05/12/2015 1505 27.9 57.7 3.0 18.4 13.1 14.8 -- 82 9 12334550 Clark Fork at Turah Bridge, near Bonner 05/28/2015 0840 48.6 102 17.4 44.6 7.3 9.9 -- 77 41 05/28/2015 0845 46.9 99.1 16.9 39.6 7.4 9.2 -- 76 42 12340500 Clark Fork above Missoula 06/10/2015 1400 5.37 39.4 <2.0 13.1 3.7 4.8 -- 82 19 06/10/2015 1405 5.45 39.7 <2.0 12.2 3.7 4.9 -- 82 19 12323750 Silver Bow Creek at Warm Springs 07/14/2015 1050 48.7 88.2 <2.0 2.6 28.5 30.1 4.31 77 1 07/14/2015 1055 49.3 90.8 <2.0 2.2 29.1 31.1 4.30 83 1 12323700 Mill Creek at Opportunity 08/10/2015 1535 6.40 8.6 <2.0 <2.0 29.7 30.2 1.70 83 1 08/10/2015 1540 6.17 8.4 <2.0 2.0 28.8 30.6 1.81 91 1 Table 12. Analyses of field replicates for water samples, Clark Fork Basin, Montana.—Continued [hh, hours; mm, minutes; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; --, no data; <, less than laboratory reporting level; E, estimated]
Data 63

Table 13. Precision of analyses of field replicates for water samples, Clark Fork Basin, Montana.

[lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligram per liter; μg/L, microgram 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

Turbidity, unfiltered, lab, NTRU 4 0.40 21 Yes3

Calcium, filtered, mg/L 9 0.82 2.0 Yes

Magnesium, filtered, mg/L 9 0.10 1.1 Yes

Potassium, filtered, mg/L 4 0.02 0.82 Yes

Sodium, filtered, mg/L 4 0.15 1.4 Yes

Alkalinity, filtered, lab, mg/L 4 0.07 0.08 Yes

Chloride, filtered, mg/L 4 0.00 0.00 Yes

Fluoride, filtered, mg/L 4 0.00 1.2 Yes

Silica, filtered, mg/L 4 0.11 0.74 Yes

Sulfate, filtered, mg/L 4 0.04 0.08 Yes

Cadmium, filtered, μg/L 9 0.00 8.2 Yes

Cadmium, unfiltered recoverable, μg/L 9 0.01 13 Yes

Copper, filtered, μg/L 9 0.25 4.5 Yes

Copper, unfiltered recoverable, μg/L 9 1.0 6.1 Yes

Iron, filtered, μg/L 9 4.9 4.7 Yes

Iron, unfiltered recoverable, μg/L 9 28 7.2 Yes

Lead, filtered, μg/L 9 0.01 2.8 Yes

Lead, unfiltered recoverable, μg/L 9 0.15 6.9 Yes

Manganese, filtered, μg/L 9 0.49 1.8 Yes

Manganese, unfiltered recoverable, μg/L 9 1.3 2.1 Yes

Zinc, filtered, μg/L 9 0.23 3.4 Yes

Zinc, unfiltered recoverable, μg/L 9 1.4 8.1 Yes

Arsenic, filtered, μg/L 9 0.28 2.3 Yes

Arsenic, unfiltered recoverable, μg/L 9 0.39 2.8 Yes

Organic carbon, filtered, mg/L 4 0.04 1.2 Yes

Sediment, suspended, percent finer than 0.062 mm 9 2.7 3.4 Yes

Sediment, suspended, mg/L 9 0.58 4.2 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).

3

Exceedence of data-quality objective resulted from a statistical artifact of calculating the difference between one replicate sample pair for which one value 

is estimated and one is less than the laboratory reporting level. Because analytical variation, in percent, can be large at very low concentrations, the precision 

estimated may not be representative of analytical performance at detectable concentrations.
64 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 14. Precision of analyses of laboratory replicates for water samples, Clark Fork Basin, Montana.

[mg/L, milligram per liter; μg/L, microgram per liter]

Constituent and reporting unit Number of 

replicate pairs

Standard deviation, 

in listed units

Relative standard 

deviation 

(percent)

Within limits1

 of 

data-quality 

objective

Calcium, filtered, mg/L 7 2.4 6.1 Yes

Magnesium, filtered, mg/L 7 0.56 3.9 Yes

Cadmium, filtered, μg/L 7 0.00 5.4 Yes

Cadmium, unfiltered recoverable, μg/L 7 0.00 4.4 Yes

Copper, filtered, μg/L 7 0.09 1.5 Yes

Copper, unfiltered recoverable, μg/L 7 0.20 1.1 Yes

Iron, filtered, μg/L 7 2.5 3.4 Yes

Iron, unfiltered recoverable, μg/L 7 1.0 0.27 Yes

Lead, filtered, μg/L 7 0.01 2.0 Yes

Lead, unfiltered recoverable, μg/L 7 0.02 0.69 Yes

Manganese, filtered, μg/L 7 0.13 0.53 Yes

Manganese, unfiltered recoverable, μg/L 7 0.52 0.88 Yes

Zinc, filtered, μg/L 7 0.08 1.7 Yes

Zinc, unfiltered recoverable, μg/L 7 0.23 1.4 Yes

Arsenic, filtered, μg/L 7 0.24 1.8 Yes

Arsenic, unfiltered recoverable, μg/L 7 0.31 2.0 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).
Data 65

Table 15. Recovery efficiency for analyses of laboratory-spiked deionized-water blank samples.

[μg/L, microgram per liter]

Constituent and reporting unit Number of 

samples

95-percent confidence 

interval for spike recovery 

(percent)

Mean spike recovery 

(percent)

Within limits1

 of 

data-quality 

objective

Cadmium, filtered, μg/L 5 96.1–102 99.0 Yes

Cadmium, unfiltered recoverable, μg/L 5 99.9–109 104 Yes

Copper, filtered, μg/L 5 94.2–107 100 Yes

Copper, unfiltered recoverable, μg/L 5 95.7–126 111 No2

Iron, filtered, μg/L 5 96.1–104 100 Yes

Iron, unfiltered recoverable, μg/L 5 83.3–113 98.2 Yes

Lead, filtered, μg/L 5 96.1–104 100 Yes

Lead, unfiltered recoverable, μg/L 5 88.0–111 99.6 Yes

Manganese, filtered, μg/L 5 64.7–119 91.9 No3

Manganese, unfiltered recoverable, μg/L 5 96.1–121 108 Yes

Zinc, filtered, μg/L 5 97.0–109 103 Yes

Zinc, unfiltered recoverable, μg/L 5 101–129 115 No4

Arsenic, filtered, μg/L 5 98.2–103 100 Yes

Arsenic, unfiltered recoverable, μg/L 5 91.8–108 99.9 Yes

1

The data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

2

Exceedance of data-quality objective resulted from two samples having a recovery of 123 percent. 

3

Exceedance of data-quality objective resulted from one sample having a recovery of 52.9 percent. When data from this one spiked-sample set are removed 

from the 95-percent confidence interval calculation, filtered manganese meets the data-quality objective limit (97.9–105 percent).

4

Exceedance of data-quality objective resulted from two samples having a recovery of 127 percent.
66 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 16. Recovery efficiency for analyses of laboratory-spiked stream samples, Clark Fork Basin, Montana.

[μg/L, microgram per liter]

Constituent and reporting unit Number of 

samples

95-percent confidence 

interval for spike recovery 

(percent)

Mean spike recovery 

(percent)

Within limits1

 of 

data-quality objective

Cadmium, filtered, μg/L 5 98.5–104 101 Yes

Cadmium, unfiltered recoverable, μg/L 5 95.4–116 106 Yes

Copper, filtered, μg/L 5 93.1–100 96.7 Yes

Copper, unfiltered recoverable, μg/L 5 92.6–103 97.7 Yes

Iron, filtered, μg/L 5 80.7–120 100 Yes

Iron, unfiltered recoverable, μg/L 5 93.1–127 110 No2

Lead, filtered, μg/L 5 102–106 104 Yes

Lead, unfiltered recoverable, μg/L 5 96.4–115 106 Yes

Manganese, filtered, μg/L 5 101–105 103 Yes

Manganese, unfiltered recoverable, μg/L 5 94.0–105 99.7 Yes

Zinc, filtered, μg/L 5 87.0–101 94.2 Yes

Zinc, unfiltered recoverable, μg/L 5 90.2–107 98.6 Yes

Arsenic, filtered, μg/L 5 97.6–104 101 Yes

Arsenic, unfiltered recoverable, μg/L 5 86.7–121 104 Yes

1

The data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

2

Exceedance of data-quality objective resulted from one sample having a recovery of 135 percent. When data from this one spiked-sample set are removed 

from the 95-percent confidence interval calculation, unfiltered recoverable iron meets the data-quality objective limit (101–107 percent).
Data 67

Table 17. Analyses of field blanks for water samples.

[hh, hours; mm, minutes; μS/cm, microsiemen per centimeter at 25 degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligram 

per liter; <, less than laboratory reporting level; --, no data; μg/L, microgram 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)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

10/14/2014 1410 5.5 2 <2.0 <0.022 <0.011 <0.03 <0.06 <4.6 <0.02

1

03/19/2015 1200 5.6 2 <2.0 <0.022 <0.011 <0.03 <0.06 <4.6 <0.02

04/22/2015 1345 5.4 2 -- <0.022 <0.011 -- -- -- --

05/12/2015 0740 5.3 2 <2.0 <0.022 <0.011 --2 --2 --2 --2

05/27/2015 1500 5.4 2 -- <0.022 <0.011 -- -- -- --

06/10/2015 1005 5.5 2 -- <0.022 <0.011 -- -- -- --

07/14/2015 1225 5.5 2 -- <0.022 <0.011 -- -- -- --

08/11/2015 1015 5.4 2 <2.0 <0.022 <0.011 --2 --2 --2 --2

Date

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(mg/L)

Nitrate 

plus nitrite, 

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)

10/14/2014 <0.01 0.072 <0.02 -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

1

03/19/2015 <0.01 0.042 <0.02 <0.01 <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

04/22/2015 -- -- -- -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

05/12/2015 --2 --2 --2 -- <0.030 <0.030 <0.80 <0.80 <4.0 7.5

05/27/2015 -- -- -- -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

06/10/2015 -- -- -- -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

07/14/2015 -- -- -- -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

08/11/2015 --2 --2 --2 -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

Date

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

10/14/2014 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.20 <0.23

1

03/19/2015 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.20 <0.23

04/22/2015 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.20 --

05/12/2015 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.20 <0.23

05/27/2015 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.20 --

06/10/2015 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.20 --

07/14/2015 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.20 --

08/11/2015 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.20 <0.23

1

Annual office equipment blank collected before any equipment was used in the field.

2

Laboratory analysis for this constituent inadvertently not requested.
68 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana Table 18. Bed-sediment data for the Clark Fork Basin, Montana, August 2015. [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 analy- ses from each composite sample. μg/g, microgram per gram of dry sample weight] Site number (fig. 1) Site name Number of composite samples Concentration (μg/g) Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc 12323600 Silver Bow Creek at Opportunity 

3 27.3 12.0 21.3 574 28,400 112 3,760 14.8 1,740

12323750 Silver Bow Creek at 

Warm Springs

3 98.3 5.5 15.1 264 21,300 76.4 7,610 13.5 674

12323800 Clark Fork near Galen 3 129 5.0 20.6 1,060 26,600 136 6,180 16.9 930

461415112450801 Clark Fork below Lost 

Creek, near Galen 

3 143 5.4 17.2 1,490 25,900 175 4,340 12.8 1,160

461559112443301 Clark Fork at county 

bridge, near 

Racetrack 

3 104 5.2 14.4 1,060 23,800 137 3,540 11.4 990

461903112440701 Clark Fork at Dempsey 

Creek diversion, near Racetrack 

3 79.0 4.2 15.7 996 24,400 135 1,590 10.3 951

12324200 Clark Fork at Deer 

Lodge

3 72.6 4.1 22.2 1,000 23,800 131 1,430 12.0 987

12324400 Clark Fork above 

Little Blackfoot River, near Garrison

3 49.4 4.3 15.0 666 16,800 93.6 2,670 9.2 780

12324680 Clark Fork at 

Goldcreek 

3 28.6 2.0 9.9 281 11,500 45.4 2,730 7.6 427

12331800 Clark Fork near 

Drummond 

3 32.2 2.9 14.3 437 16,000 66.9 1,490 9.5 638

12334550 Clark Fork at Turah 

Bridge, near Bonner 

3 18.0 1.4 13.6 229 13,400 41.9 383 9.1 451

12340000 Blackfoot River near 

Bonner 

3 5.3 0.05 13.3 17.3 15,000 11.1 345 10.4 59.3

12340500 Clark Fork above 

Missoula 

3 15.7 1.3 12.8 163 13,800 31.6 903 9.8 394
Data 69

Table 19. 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, microgram 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 58.5 57.6–59.3

Cadmium 10 1:10 0.371 46.7 44.9–48.6

Chromium 10 1:10 130 65.9 64.6–67.2

Copper 10 1:10 33.9 85.2 84.7–85.6

Iron 10 1:10 33,600 88.0 87.5–88.4

Lead 10 1:10 17.3 56.3 55.4–57.3

Manganese 10 1:10 529 83.5 83.0–84.0

Nickel 10 1:10 85 81.3 80.8–81.8

Zinc 10 1:10 103 85.3 84.9–85.8

SRM sample 2711a

Arsenic 10 1:10 107 89.0 87.6–90.3

Cadmium 10 1:10 54.1 97.4 96.7–98.0

Chromium 10 1:10 52.3 56.9 54.9–58.9

Copper 10 1:10 140 94.1 93.0–95.3

Iron 10 1:10 28,200 85.1 84.4–85.8

Lead 10 1:10 1,400 93.2 92.2–94.2

Manganese 10 1:10 675 79.4 78.5–80.4

Nickel 10 1:10 21.7 85.5 84.4–86.6

Zinc 10 1:10 414 92.3 91.2–93.3
70 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana Table 20. 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, microgram per milliliter; <, less than minimum reporting level for liquid-phase concentration, in μg/mL] Site number (fig. 1) Site name Dilution ratio Concentration (μg/mL) Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc 12323600 Silver Bow Creek at Opportunity 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 12323750 Silver Bow Creek at Warm Springs 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 12323800 Clark Fork near Galen 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 461415112450801 Clark Fork below Lost Creek, near Galen 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 461559112443301 Clark Fork at county bridge, near Racetrack 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 12324200 Clark Fork at Deer Lodge 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 12324400 Clark Fork above Little Blackfoot River, near Garrison 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 12324680 Clark Fork at Goldcreek 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 0.003 <0.01 12331800 Clark Fork near Drummond 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 12334550 Clark Fork at Turah Bridge, near Bonner 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 12340000 Blackfoot River near Bonner 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01 12340500 Clark Fork above Missoula 1:10 <0.002 <0.001 <0.02 <0.005 <0.06 <0.004 <0.007 <0.001 <0.01
Data 71

Table 21. Biological data for the Clark Fork Basin, Montana, August 2015.

[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, microgram per gram of dry sample weight]

Taxon

Number of 

composite 

samples

Concentration (μg/g)

Arsenic Cadmium Chromium Copper Iron Lead ManganeseNickel Zinc

12323600—Silver Bow Creek at Opportunity

Hydropsyche cockerelli 3 5.8 2.4 3.8 92.5 2,840 14.1 1,490 3.4 539

12323750—Silver Bow Creek at Warm Springs

Hydropsyche cockerelli 3 11.8 0.3 1.1 30.6 821 2.9 1,260 1.4 165

12323800—Clark Fork near Galen

Hydropsyche cockerelli 3 14.2 1.5 2.7 105 1,540 11.2 2,180 2.4 227

Hydropsyche occidentalis 1 13.7 1.3 3.3 104 1,460 10.9 2,560 2.7 251

461415112450801—Clark Fork below Lost Creek, near Galen

Hydropsyche cockerelli 2 18.0 1.7 2.5 185 2,130 18.0 1,650 2.3 254

Hydropsyche occidentalis 1 16.9 1.6 6.5 186 1,980 20.4 1,750 3.2 330

461559112443301—Clark Fork at county bridge, near Racetrack

Hydropsyche cockerelli 1 14.7 1.6 2.4 124 1,670 11.3 1,400 1.7 232

Hydropsyche occidentalis 1 12.2 1.2 1.8 104 1,510 10.6 1,560 1.7 233

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack

Arctopsyche grandis 3 5.1 1.0 0.9 35.3 387 2.2 758 0.6 160

Claassenia sabulosa 3 1.6 0.5 0.5 55.6 120 0.7 199 0.2 270

Hydropsyche cockerelli 1 8.1 1.5 1.1 71.3 873 4.7 1,190 0.9 172

Hydropsyche occidentalis 1 8.5 1.1 0.3 76.6 764 4.4 1,270 1.2 189

12324200—Clark Fork at Deer Lodge

Hydropsyche cockerelli 3 10.6 3.2 3.4 144 2,090 15.2 1,530 2.5 251

Hydropsyche occidentalis 1 9.6 2.1 1.6 138 1,470 13.3 1,490 2.1 256

12324400—Clark Fork above Little Blackfoot River, near Garrison

Arctopsyche grandis 2 3.9 1.0 1.2 44.2 265 2.9 585 0.5 193

Hydropsyche cockerelli 1 8.8 0.9 1.9 101 746 8.7 1,110 1.8 211

Hydropsyche occidentalis 2 8.7 1.0 2.2 108 920 10.3 1,390 1.6 228

12324680—Clark Fork at Goldcreek

Arctopsyche grandis 3 4.1 1.2 1.1 37.3 323 2.3 672 0.6 164

Claassenia sabulosa 3 1.3 0.7 0.8 58.7 167 0.9 235 0.4 259

Hydropsyche cockerelli 1 7.6 1.1 2.3 79.6 1,050 6.8 927 1.9 201

Hydropsyche occidentalis 1 6.6 1.1 2.5 76.4 1,070 6.0 1,180 1.5 198
72 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Taxon

Number of 

composite 

samples

Concentration (μg/g)

Arsenic Cadmium Chromium Copper Iron Lead ManganeseNickel Zinc

12331800—Clark Fork near Drummond

Arctopsyche grandis 3 6.2 0.6 1.9 49.8 979 5.5 985 1.3 171

Claassenia sabulosa 3 1.6 0.4 0.6 56.5 130 0.6 171 0.4 271

Hydropsyche cockerelli 1 6.4 0.8 2.4 52.8 770 5.6 976 1.3 173

Hydropsyche occidentalis 1 6.4 0.8 2.7 60.9 1,160 7.2 1,310 1.6 208

12334550—Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 2 3.2 0.7 1.0 18.1 372 2.6 464 0.6 163

Claassenia sabulosa 2 0.6 0.6 1.2 49.0 96 0.5 71 0.4 247

Hydropsyche cockerelli 2 4.2 0.6 1.9 30.1 826 4.6 516 1.1 166

Hydropsyche occidentalis 1 4.4 0.7 2.2 34.4 1,070 5.1 598 1.4 189

12340000—Blackfoot River near Bonner

Arctopsyche grandis 2 2.7 0.2 1.9 12.5 765 0.9 412 1.2 148

Claassenia sabulosa 2 0.6 0.1 0.8 38.2 111 0.1 70 0.3 211

Hydropsyche cockerelli 1 3.2 0.3 3.6 14.2 1,400 1.8 516 1.7 147

Hydropsyche occidentalis 1 3.0 0.2 2.5 15.1 1,350 1.6 616 1.5 163

12340500—Clark Fork above Missoula

Arctopsyche grandis 4 3.5 0.7 1.3 27.7 544 2.3 794 1.1 170

Claassenia sabulosa 2 0.9 0.6 0.7 37.7 119 0.5 137 0.4 292

Hydropsyche cockerelli 3 4.3 0.6 1.9 34.9 1,020 4.1 783 1.5 186

Table 21. Biological data for the Clark Fork Basin, Montana, August 2015.—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, microgram per gram of dry sample weight]
Data 73

Table 22. Recovery efficiency for analyses of standard reference material for biota samples.

[μg/g, microgram per gram of dry sample weight; CRM, certified reference material (lobster hepatopancreas)]

Constituent Number of 

analyses

Certified 

concentration 

(μg/g)

Mean CRM 

recovery

(percent)

95-percent confidence 

interval for CRM recovery

(percent)

CRM sample TORT-3

Arsenic 12 59.5 108 108–109

Cadmium 12 42.3 79.6 78.7–80.4

Chromium 12 1.95 121 105–137

Copper 12 497 83.8 83.0–84.6

Iron 12 179 88.6 87.6–89.6

Lead 12 0.225 170 166–175

Manganese 12 15.6 84.7 83.6–85.8

Nickel 12 5.3 82.6 79.2–86.0

Zinc 12 136 89.4 88.8–90.0
74 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana Table 23. Analyses of procedural blanks for biota samples. [Procedural blanks were not diluted prior to analyses. μg/mL, microgram per milliliter; <, less than minimum reporting level for liquid-phase concentration, in μg/mL] Site number (fig. 1) Site name Dilution ratio Concentration (μg/mL) Arsenic Cadmium Chromium Copper Iron Lead Manga- nese Nickel Zinc 12323600 Silver Bow Creek at Opportunity 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 12323750 Silver Bow Creek at Warm Springs 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 12323800 Clark Fork near Galen 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 461415112450801 Clark Fork below Lost Creek, near Galen 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 461559112443301 Clark Fork at county bridge, near Racetrack 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 12324200 Clark Fork at Deer Lodge 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 12324400 Clark Fork above Little Blackfoot River, near Garrison 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 12324680 Clark Fork at Goldcreek 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 12331800 Clark Fork near Drummond 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 12334550 Clark Fork at Turah Bridge, near Bonner 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 12340000 Blackfoot River near Bonner 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01 12340500 Clark Fork above Missoula 1:1 <0.003 <0.001 <0.01 <0.005 <0.02 <0.005 <0.001 <0.001 <0.01
Data 75

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 2015.

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323230—Blacktail Creek at Harrison Avenue, at Butte

Period of record for water-quality data: March 1993–August 1995, December 1996–August 2003, December 2004–September 2015

Streamflow, instantaneous (ft3

/s) 171 156 1.9 16 9.3

pH, onsite (standard units) 171 8.4 7.3 7.7 7.7

Specific conductance, onsite (μS/cm) 171 412 116 262 262

Temperature, water (°C) 171 17.5 1.0 7.9 8.0

Turbidity, unfiltered, lab (NTRU) 15 7.5 <2.0 2

3.5 3.0

Hardness, filtered (mg/L as CaCO3

) 171 153 37.7 104 105

Calcium, filtered (mg/L) 171 42.9 10.6 29.7 29.8

Magnesium, filtered (mg/L) 171 11.1 2.71 7.22 7.20

Potassium, filtered (mg/L) 49 6.40 2.00 2.75 2.57

Sodium, filtered (mg/L) 49 18.0 6.40 10.6 10.2

Alkalinity, filtered, lab (mg/L) 21 124 54.5 85.5 78.4

Chloride, filtered (mg/L) 49 18.0 2.80 8.53 8.00

Fluoride, filtered (mg/L) 49 0.60 0.18 0.28 0.30

Silica, filtered (mg/L) 49 32.0 14.0 24.3 24.4

Sulfate, filtered (mg/L) 49 40.2 14.7 26.2 26.0

Nitrate plus nitrite, filtered (mg/L) 15 1.2 0.16 0.63 0.52

Cadmium, filtered (μg/L) 169 0.50 <0.03 2

0.04 0.02

Cadmium, unfiltered recoverable (μg/L) 171 0.11 <0.01 2

0.04 <1

Copper, filtered (μg/L) 170 10.0 <1.0 2

3.5 3.0

Copper, unfiltered recoverable (μg/L) 171 52.0 0.91 6.2 4.9

Iron, filtered (μg/L) 171 739 15.2 196 174

Iron, unfiltered recoverable (μg/L) 171 4,220 123 659 590

Lead, filtered (μg/L) 171 2.80 <0.02 2

0.18 0.06

Lead, unfiltered recoverable (μg/L) 171 47.0 <1.00 2

1.565 0.62

Manganese, filtered (μg/L) 171 144 14.2 44.4 39.5

Manganese, unfiltered recoverable (μg/L) 171 240 23.5 61.4 52.7

Zinc, filtered (μg/L) 169 11 <1.0 2

3.2 2.4

Zinc, unfiltered recoverable (μg/L) 171 130 <3.0 2

7.5 4.0

Arsenic, filtered (μg/L) 170 13.0 1.0 4.0 3.4

Arsenic, unfiltered recoverable (μg/L) 171 18.0 1.0 2

5.3 4.5

Organic carbon, filtered (mg/L) 21 9.52 1.40 4.73 4.29

Sediment, suspended (percent finer than 

0.062 mm)

171 97 50 83 85

Sediment, suspended concentration (mg/L) 171 139 1 11 7

Sediment, suspended discharge (ton/d) 171 59 0.01 0.92 0.17
76 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323250—Silver Bow Creek below Blacktail Creek, at Butte

Period of record for water-quality data: March 1993–August 1995, December 1996–September 2015

Streamflow, instantaneous (ft3

/s) 179 202 13 31 25

pH, onsite (standard units) 179 8.2 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 179 691 209 458 465

Temperature, water (°C) 179 20.0 1.0 10.3 10.0

Turbidity, unflitered, lab (NTRU) 15 8.6 <2.0 2

3.7 3.0

Hardness, filtered (mg/L as CaCO3

) 179 217 66.0 147 150

Calcium, filtered (mg/L) 179 62.7 19.0 41.8 42.2

Magnesium, filtered (mg/L) 179 16.1 4.51 10.4 10.7

Potassium, filtered (mg/L) 49 35.0 3.64 7.50 5.70

Sodium, filtered (mg/L) 49 66.0 12.0 24.9 24.7

Alkalinity, filtered, lab (mg/L) 21 119 66.9 87.7 88.6

Chloride, filtered (mg/L) 48 88.0 6.70 23.8 21.2

Fluoride, filtered (mg/L) 48 0.80 0.26 0.41 0.40

Silica, filtered (mg/L) 48 28.0 17.0 22.1 22.0

Sulfate, filtered (mg/L) 48 96.0 35.0 71.1 73.8

Nitrate plus nitrite, filtered (mg/L) 15 4.40 0.34 0.95 0.65

Cadmium, filtered (μg/L) 179 6.2 0.04 0.79 0.16

Cadmium, unfiltered recoverable (μg/L) 179 6.0 0.06 1.07 0.26

Copper, filtered (μg/L) 179 303 2.6 27.3 11.7

Copper, unfiltered recoverable (μg/L) 179 550 8.0 63.2 22.1

Iron, filtered (μg/L) 179 392 9.6 101 79.8

Iron, unfiltered recoverable (μg/L) 179 7,400 85.4 763 535

Lead, filtered (μg/L) 179 2.4 <0.5 2

0.42 0.24

Lead, unfiltered recoverable (μg/L) 179 250 0.61 9.75 2.31

Manganese, filtered (μg/L) 179 1,700 20.7 273 132

Manganese, unfiltered recoverable (μg/L) 179 1,600 25.9 311 160

Zinc, filtered (μg/L) 179 2,200 5.3 260 65.6

Zinc, unfiltered recoverable (μg/L) 179 2,200 20.5 316 88.0

Arsenic, filtered (μg/L) 179 13.4 2.3 5.9 5.5

Arsenic, unfiltered recoverable (μg/L) 179 45.0 3.0 9.3 8.0

Organic carbon, filtered (mg/L) 21 9.97 4.93 7.16 7.21

Sediment, suspended (percent finer than 

0.062 mm)

178 98 42 83 85

Sediment, suspended concentration (mg/L) 178 405 2 18 9

Sediment, suspended discharge (ton/d) 178 70 0.08 2.2 0.61

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
Data 77

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323600—Silver Bow Creek at Opportunity

Period of record for water-quality data: March 1993–August 1995, December 1996–September 2015

Streamflow, instantaneous (ft3

/s) 179 648 13 78 52

pH, onsite (standard units) 181 9.5 7.2 8.4 8.3

Specific conductance, onsite (μS/cm) 181 633 202 414 403

Temperature, water (°C) 181 24.0 -1.0 9.5 9.5

Turbidity, unfiltered, lab (NTRU) 15 12 2.5 4.9 4.0

Hardness, filtered (mg/L as CaCO3

) 181 240 60.2 149 148

Calcium, filtered (mg/L) 181 71.6 18.5 44.2 44.0

Magnesium, filtered (mg/L) 181 15.0 3.42 9.44 9.10

Potassium, filtered (mg/L) 52 16.0 1.79 4.60 4.10

Sodium, filtered (mg/L) 52 33.5 5.06 18.1 17.1

Alkalinity, filtered, lab (mg/L) 23 110 71.6 92.4 91.5

Chloride, filtered (mg/L) 51 41.4 3.20 15.9 12.0

Fluoride, filtered (mg/L) 51 0.80 0.16 0.40 0.40

Silica, filtered (mg/L) 51 28.0 9.56 19.9 21.0

Sulfate, filtered (mg/L) 51 190 32.0 65.6 62.0

Cadmium, filtered (μg/L) 180 41.0 <0.1 2

0.90 0.47

Cadmium, unfiltered recoverable (μg/L) 181 49.0 0.18 2

1.64 1.00

Copper, filtered (μg/L) 179 450 6.5 37.4 28.8

Copper, unfiltered recoverable (μg/L) 181 3,900 13.6 160 87.2

Iron, filtered (μg/L) 181 397 <3 2

50.8 30.0

Iron, unfiltered recoverable (μg/L) 180 24,100 114 1,380 730

Lead, filtered (μg/L) 181 5.1 <0.5 2

0.64 0.31

Lead, unfiltered recoverable (μg/L) 181 650 0.67 30.0 13.0

Manganese, filtered (μg/L) 181 9,300 27.5 342 259

Manganese, unfiltered recoverable (μg/L) 181 10,000 62.8 450 340

Zinc, filtered (μg/L) 180 13,000 11.2 231 110

Zinc, unfiltered recoverable (μg/L) 181 15,000 26.8 409 237

Arsenic, filtered (μg/L) 181 34.0 1.0 10.3 9.7

Arsenic, unfiltered recoverable (μg/L) 181 235 5.5 21.8 16.0

Organic carbon, filtered (mg/L) 20 8.35 3.06 5.46 5.16

Sediment, suspended (percent finer than 

0.062 mm)

182 95 37 78 83

Sediment, suspended concentration (mg/L) 182 801 5 46 18

Sediment, suspended discharge (ton/d) 179 781 0.18 20 2.6

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
78 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323670—Mill Creek near Anaconda

Period of record for water-quality data: December 2004–September 2015

Streamflow, instantaneous (ft3

/s) 87 309 7.4 64 38

pH, onsite (standard units) 88 8.6 7.5 8.0 8.0

Specific conductance, onsite (μS/cm) 88 213 56 130 129

Temperature, water (°C) 88 17.0 0.0 8.5 9.0

Turbidity, unfiltered, lab, (NTRU) 81 21 <2.0 2

2.4 <2.0

Hardness, filtered (mg/L as CaCO3

) 88 98.0 23.7 56.8 54.6

Calcium, filtered (mg/L) 88 26.7 7.00 15.8 15.0

Magnesium, filtered (mg/L) 88 8.01 1.45 4.24 4.03

Potassium, filtered (mg/L) 15 0.82 0.47 0.64 0.65

Sodium, filtered (mg/L) 15 6.04 2.14 3.95 3.64

Alkalinity, filtered, lab (mg/L) 15 85.1 30.8 54.1 54.4

Chloride, filtered (mg/L) 15 0.54 0.16 0.30 0.26

Fluoride, filtered (mg/L) 15 0.36 0.28 0.32 0.31

Silica, filtered (mg/L) 15 15.5 9.27 12.3 12.1

Sulfate, filtered (mg/L) 15 13.9 3.12 6.19 5.37

Cadmium, filtered (μg/L) 87 0.11 0.02 2

0.04 0.04

Cadmium, unfiltered recoverable (μg/L) 88 0.19 0.03 0.07 0.07

Copper, filtered (μg/L) 88 5.1 0.72 2.2 2.1

Copper, unfiltered recoverable (μg/L) 88 10.6 1.3 3.7 3.1

Iron, filtered (μg/L) 88 125 21.2 47.6 41.8

Iron, unfiltered recoverable (μg/L) 88 730 64.9 190 150

Lead, filtered (μg/L) 88 0.36 0.02 2

0.12 0.11

Lead, unfiltered recoverable (μg/L) 88 3.12 0.15 0.70 0.54

Manganese, filtered (μg/L) 88 12.0 3.1 5.8 5.6

Manganese, unfiltered recoverable (μg/L) 88 36.6 6.2 13.2 11.4

Zinc, filtered (μg/L) 88 4.3 <1.4 2

1.7 1.4

Zinc, unfiltered recoverable (μg/L) 88 9.2 <2.0 2

3.0 2.6

Arsenic, filtered (μg/L) 88 32.9 7.3 16.1 14.9

Arsenic, unfiltered recoverable (μg/L) 88 34.8 7.8 17.3 15.6

Organic carbon, filtered (mg/L) 15 3.48 1.29 2.29 2.27

Sediment, suspended (percent finer than 

0.062 mm)

88 96 14 62 66

Sediment, suspended concentration (mg/L) 88 42 1 6 3

Sediment, suspended discharge (ton/d) 87 28 0.02 2.0 0.32

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
Data 79

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323700—Mill Creek at Opportunity

Period of record for water-quality data: March 2003–September 2015

Streamflow, instantaneous (ft3

/s) 102 261 0.43 38 14

pH, onsite (standard units) 104 8.3 7.5 8.0 8.0

Specific conductance, onsite (μS/cm) 104 242 59 146 146

Temperature, water (°C) 104 20.0 -1.0 9.3 9.5

Turbidity, unfiltered, lab (NTRU) 22 7.2 <2.0 2

2.1 <2.0

Hardness, filtered (mg/L as CaCO3

) 104 112 24.0 62.8 62.2

Calcium, filtered (mg/L) 104 31.0 7.01 17.6 17.4

Magnesium, filtered (mg/L) 104 8.44 1.56 4.56 4.54

Potassium, filtered (mg/L) 22 1.02 0.48 0.70 0.72

Sodium, filtered (mg/L) 22 8.15 2.29 4.41 4.12

Alkalinity, filtered, lab (mg/L) 22 88.2 31.9 56.6 57.6

Chloride, filtered (mg/L) 22 0.82 0.18 0.39 0.32

Fluoride, filtered (mg/L) 22 0.40 0.29 0.34 0.34

Silica, filtered (mg/L) 22 15.5 9.47 12.1 12.0

Sulfate, filtered (mg/L) 22 27.7 4.11 10.4 9.40

Cadmium, filtered (μg/L) 104 0.13 0.02 0.06 0.06

Cadmium, unfiltered recoverable (μg/L) 104 0.86 0.03 0.13 0.09

Copper, filtered (μg/L) 104 6.1 1.0 2.8 2.4

Copper, unfiltered recoverable (μg/L) 104 38.8 1.5 6.0 3.8

Iron, filtered (μg/L) 104 108 15.9 47.6 42.2

Iron, unfiltered recoverable (μg/L) 104 1,960 44.3 280 157

Lead, filtered (μg/L) 104 0.35 <0.08 2

0.13 0.12

Lead, unfiltered recoverable (μg/L) 104 12.7 0.07 1.30 0.52

Manganese, filtered (μg/L) 104 32.8 2.1 6.6 5.0

Manganese, unfiltered recoverable (μg/L) 104 113 2.9 17.2 12.0

Zinc, filtered (μg/L) 103 7.7 <1.4 2

2.7 2.5

Zinc, unfiltered recoverable (μg/L) 104 41 <2.0 2

5.9 4.0

Arsenic, filtered (μg/L) 104 55.1 9.0 20.8 18.6

Arsenic, unfiltered recoverable (μg/L) 104 53.5 10.0 23.5 21.5

Organic carbon, filtered (mg/L) 22 4.10 1.33 2.30 2.19

Sediment, suspended (percent finer than 

0.062 mm)

104 91 26 69 71

Sediment, suspended concentration (mg/L) 104 107 1 11 4

Sediment, suspended discharge (ton/d) 102 55 <0.01 2

3.1 0.12

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
80 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323710—Willow Creek near Anaconda

Period of record for water-quality data: December 2004–September 2015

Streamflow, instantaneous (ft3

/s) 79 114 1.0 15 7.7

pH, onsite (standard units) 81 8.2 7.5 7.7 7.7

Specific conductance, onsite (μS/cm) 81 151 65 103 107

Temperature, water (°C) 81 16.0 0.0 7.4 7.5

Turbidity, unfiltered, lab (NTRU) 74 39 <2.0 2

5.2 2.8

Hardness, filtered (mg/L as CaCO3

) 81 56.3 21.5 37.5 38.5

Calcium, filtered (mg/L) 81 18.3 7.22 12.5 13.0

Magnesium, filtered (mg/L) 81 2.60 0.78 1.51 1.48

Potassium, filtered (mg/L) 15 1.13 0.70 0.94 0.94

Sodium, filtered (mg/L) 15 7.94 4.39 6.00 6.10

Alkalinity, filtered, lab (mg/L) 15 53.5 26.3 41.3 38.9

Chloride, filtered (mg/L) 15 0.83 0.30 0.46 0.38

Fluoride, filtered (mg/L) 15 0.08 0.06 0.07 0.07

Silica, filtered (mg/L) 15 26.9 20.9 24.4 24.8

Sulfate, filtered (mg/L) 15 15.7 5.10 7.7 6.45

Cadmium, filtered (μg/L) 79 0.05 <0.02 2

0.03 0.03

Cadmium, unfiltered recoverable (μg/L) 81 0.33 <0.03 2

0.06 0.05

Copper, filtered (μg/L) 81 4.2 0.82 2.2 2.1

Copper, unfiltered recoverable (μg/L) 81 16.8 1.0 3.6 2.9

Iron, filtered (μg/L) 81 277 28 89.6 75.3

Iron, unfiltered recoverable (μg/L) 81 2,380 85.7 347 228

Lead, filtered (μg/L) 81 0.39 0.03 2

0.16 0.16

Lead, unfiltered recoverable (μg/L) 81 7.96 0.10 0.83 0.50

Manganese, filtered (μg/L) 81 34.5 6.0 13.6 12.1

Manganese, unfiltered recoverable (μg/L) 81 99.9 12.8 24.9 21.7

Zinc, filtered (μg/L) 81 3.3 0.65 2

1.7 1.5

Zinc, unfiltered recoverable (μg/L) 81 17.8 <2.0 2

3.0 2.0

Arsenic, filtered (μg/L) 81 25.7 7.7 15.9 14.9

Arsenic, unfiltered recoverable (μg/L) 81 27.0 9.8 16.9 15.4

Organic carbon, filtered (mg/L) 15 7.07 3.44 4.85 4.44

Sediment, suspended (percent finer than 

0.062 mm)

81 97 25 77 82

Sediment, suspended concentration (mg/L) 81 195 1 14 4

Sediment, suspended discharge (ton/d) 79 50 <0.01 2

1.9 0.10

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
Data 81

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323720—Willow Creek at Opportunity

Period of record for water-quality data: March 2003–September 2015

Streamflow, instantaneous (ft3

/s) 104 116 4.5 17 9.1

pH, onsite (standard units) 104 9.0 7.6 8.1 8.1

Specific conductance, onsite (μS/cm) 104 371 116 263 280

Temperature, water (°C) 104 24.0 0.0 11.1 11.0

Turbidity, unfiltered, lab (NTRU) 22 7.2 <2.0 2

3.7 3.4

Hardness, filtered (mg/L as CaCO3

) 104 169 54.2 114 122

Calcium, filtered (mg/L) 104 47.4 16.5 33.3 35.8

Magnesium, filtered (mg/L) 104 12.3 2.99 7.52 8.00

Potassium, filtered (mg/L) 22 2.28 0.94 1.38 1.38

Sodium, filtered (mg/L) 22 12.2 6.12 9.13 9.04

Alkalinity, filtered, lab (mg/L) 22 127 53.3 99.3 108

Chloride, filtered (mg/L) 22 3.28 0.79 1.78 1.64

Fluoride, filtered (mg/L) 22 0.56 0.15 0.35 0.38

Silica, filtered (mg/L) 22 27.8 18.4 22.6 22.5

Sulfate, filtered (mg/L) 22 36.5 9.21 19.4 19.4

Cadmium, filtered (μg/L) 104 0.12 <0.03 2

0.04 0.04

Cadmium, unfiltered recoverable (μg/L) 103 0.52 0.02 0.10 0.07

Copper, filtered (μg/L) 104 21.4 0.87 5.1 3.5

Copper, unfiltered recoverable (μg/L) 103 48.8 2.6 10.5 7.7

Iron, filtered (μg/L) 104 274 6.1 51.8 46.3

Iron, unfiltered recoverable (μg/L) 103 1,670 27.4 282 221

Lead, filtered (μg/L) 104 0.89 0.04 2

0.23 0.20

Lead, unfiltered recoverable (μg/L) 103 14.4 0.27 2.14 1.43

Manganese, filtered (μg/L) 104 200 3.3 32.2 24.8

Manganese, unfiltered recoverable (μg/L) 103 228 4.7 45.2 37.1

Zinc, filtered (μg/L) 104 19.8 <1.4 2

4.9 4.0

Zinc, unfiltered recoverable (μg/L) 103 68 1.2 11.6 9.0

Arsenic, filtered (μg/L) 104 164 9.3 36.7 25.7

Arsenic, unfiltered recoverable (μg/L) 104 164 11.4 39.1 27.2

Organic carbon, filtered (mg/L) 22 9.75 1.60 4.42 4.10

Sediment, suspended (percent finer than 

0.062 mm)

104 99 54 86 90

Sediment, suspended concentration (mg/L) 104 87 1 10 6

Sediment, suspended discharge (ton/d) 104 11 0.01 0.85 0.16

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
82 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323750—Silver Bow Creek at Warm Springs

Period of record for water-quality data: March 1993–September 2015

Streamflow, instantaneous (ft3

/s) 188 1,030 16 138 89

pH, onsite (standard units) 186 9.6 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 186 783 182 455 465

Temperature, water (°C) 187 25.0 0.0 10.4 10.0

Turbidity, unfiltered, lab (NTRU) 15 11 <2.0 2

3.4 2.9

Hardness, filtered (mg/L as CaCO3

) 186 314 74.9 189 192

Calcium, filtered (mg/L) 186 90.4 22.5 54.9 55.8

Magnesium, filtered (mg/L) 186 21.4 4.52 12.6 13.0

Potassium, filtered (mg/L) 46 8.30 1.72 4.00 3.90

Sodium, filtered (mg/L) 46 23.0 8.20 15.9 16.8

Alkalinity, filtered, lab (mg/L) 18 104 69.2 89.0 92.8

Chloride, filtered (mg/L) 46 21.6 1.30 9.91 9.54

Fluoride, filtered (mg/L) 46 1.20 0.41 0.68 0.68

Silica, filtered (mg/L) 46 20.0 6.30 12.4 12.0

Sulfate, filtered (mg/L) 46 210 39.2 105 97.0

Cadmium, filtered (μg/L) 186 0.31 <0.03 2

0.06 0.03

Cadmium, unfiltered recoverable (μg/L) 186 0.57 <0.10 2

0.12 0.07

Copper, filtered (μg/L) 186 40.0 1.6 7.1 5.1

Copper, unfiltered recoverable (μg/L) 186 96.8 2.4 14.6 10.2

Iron, filtered (μg/L) 186 93 <5 2

20.5 16.8

Iron, unfiltered recoverable (μg/L) 186 3,000 35.8 309 235

Lead, filtered (μg/L) 186 1.0 <0.08 2

0.13 0.05

Lead, unfiltered recoverable (μg/L) 186 41.8 <1.00 2

2.20 1.23

Manganese, filtered (μg/L) 186 875 11.8 111 74.0

Manganese, unfiltered recoverable (μg/L) 186 899 24.0 168 130

Zinc, filtered (μg/L) 186 73 <1.0 2

6.5 3.5

Zinc, unfiltered recoverable (μg/L) 186 180 2.0 2

27.1 14.1

Arsenic, filtered (μg/L) 186 60.0 6.8 22.6 22.1

Arsenic, unfiltered recoverable (μg/L) 186 94.0 10.0 26.1 24.7

Organic carbon, filtered (mg/L) 15 5.91 3.80 4.70 4.69

Sediment, suspended (percent finer than 

0.062 mm)

187 98 43 83 86

Sediment, suspended concentration (mg/L) 188 229 1 9 6

Sediment, suspended discharge (ton/d) 188 279 0.05 5.7 1.4

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
Data 83

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323760—Warm Springs Creek near Anaconda

Period of record for water-quality data: October 2005–September 2015

Streamflow, instantaneous (ft3

/s) 60 573 41 138 92

pH, onsite (standard units) 60 8.8 7.8 8.4 8.4

Specific conductance, onsite (μS/cm) 60 278 125 221 236

Temperature, water (°C) 60 16.0 0.5 8.4 8.5

Turbidity, unfiltered, lab (NTRU) 54 18 <2.0 2

2.0 <2.0

Hardness, filtered (mg/L as CaCO3

) 60 145 58.5 108 114

Calcium, filtered (mg/L) 60 42.8 18.5 32.5 34.2

Magnesium, filtered (mg/L) 60 9.34 2.96 6.63 6.99

Potassium, filtered (mg/L) 11 1.34 0.80 1.12 1.17

Sodium, filtered (mg/L) 11 3.44 1.54 2.65 2.83

Alkalinity, filtered, lab (mg/L) 11 126 60.3 102 111

Chloride, filtered (mg/L) 11 1.53 0.49 1.00 1.06

Fluoride, filtered (mg/L) 11 0.42 0.30 0.36 0.37

Silica, filtered (mg/L) 11 10.9 8.25 9.86 9.70

Sulfate, filtered (mg/L) 11 15.9 7.98 11.9 12.0

Cadmium, filtered (μg/L) 60 0.04 <0.02 2

0.02 0.02

Cadmium, unfiltered recoverable (μg/L) 60 0.14 <0.02 2

0.03 0.02

Copper, filtered (μg/L) 59 6.4 <0.80 2

1.1 0.88

Copper, unfiltered recoverable (μg/L) 60 28.0 <0.80 2

3.2 2.0

Iron, filtered (μg/L) 60 37.0 <4 2

7.8 6.1

Iron, unfiltered recoverable (μg/L) 60 1,000 19.1 122 74.8

Lead, filtered (μg/L) 60 0.11 <0.02 2

0.03 <0.08

Lead, unfiltered recoverable (μg/L) 60 3.51 0.07 0.42 0.24

Manganese, filtered (μg/L) 60 2.8 0.13 2

1.2 1.1

Manganese, unfiltered recoverable (μg/L) 60 45.2 0.90 5.8 4.0

Zinc, filtered (μg/L) 60 5.6 <1.4 2

1.0 <2.0

Zinc, unfiltered recoverable (μg/L) 60 20.1 <2.0 2

3.2 1.7

Arsenic, filtered (μg/L) 60 3.9 1.3 2.2 2.1

Arsenic, unfiltered recoverable (μg/L) 60 5.6 1.5 2.6 2.5

Organic carbon, filtered (mg/L) 11 2.92 0.83 1.41 1.28

Sediment, suspended (percent finer than 

0.062 mm)

60 84 32 66 66

Sediment, suspended concentration (mg/L) 60 65 1 7 4

Sediment, suspended discharge (ton/d) 60 68 0.13 4.4 0.94

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
84 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323770—Warm Springs Creek at Warm Springs

Period of record for water-quality data: March 1993–September 2015

Streamflow, instantaneous (ft3

/s) 144 420 2.8 96 57

pH, onsite (standard units) 143 8.7 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 143 795 139 292 299

Temperature, water (°C) 144 20.0 0.0 8.4 8.0

Turbidity, unfiltered, lab (NTRU) 22 11 <2.0 2

2.1 <2.0

Hardness, filtered (mg/L as CaCO3

) 143 415 39.8 142 146

Calcium, filtered (mg/L) 143 130 10.5 43.4 44.1

Magnesium, filtered (mg/L) 143 22.0 3.29 8.26 8.38

Potassium, filtered (mg/L) 41 4.70 0.83 1.51 1.37

Sodium, filtered (mg/L) 41 19.2 1.78 3.83 3.31

Alkalinity, filtered, lab (mg/L) 24 149 66.8 116 126

Chloride, filtered (mg/L) 41 3.60 0.50 1.29 1.07

Fluoride, filtered (mg/L) 41 0.60 0.30 0.42 0.40

Silica, filtered (mg/L) 41 13.0 8.40 10.3 10.0

Sulfate, filtered (mg/L) 41 270 15.3 49.8 35.9

Cadmium, filtered (μg/L) 142 0.10 <0.04 2

0.04 0.03

Cadmium, unfiltered recoverable (μg/L) 142 0.41 <0.03 2

0.08 0.04

Copper, filtered (μg/L) 142 16.0 1.0 3.2 2.7

Copper, unfiltered recoverable (μg/L) 142 147 2.3 18.2 8.8

Iron, filtered (μg/L) 143 36.8 <5.0 2

12.3 10.7

Iron, unfiltered recoverable (μg/L) 143 2,110 17.2 294 119

Lead, filtered (μg/L) 142 1.8 <0.025 2

0.07 <1.0

Lead, unfiltered recoverable (μg/L) 142 14.0 <1.00 2

1.79 0.56

Manganese, filtered (μg/L) 142 570 18.8 106 78.2

Manganese, unfiltered recoverable (μg/L) 142 1,400 37.1 184 139

Zinc, filtered (μg/L) 142 10 <1.0 2

2.0 1.1

Zinc, unfiltered recoverable (μg/L) 143 60 <2.0 2

8.5 3.1

Arsenic, filtered (μg/L) 142 14.0 2.0 5.0 4.4

Arsenic, unfiltered recoverable (μg/L) 142 27.0 3.0 7.2 6.0

Organic carbon, filtered (mg/L) 22 3.27 0.89 1.59 1.50

Sediment, suspended (percent finer than 

0.062 mm)

144 95 43 71 71

Sediment, suspended concentration (mg/L) 144 127 1 17 7

Sediment, suspended discharge (ton/d) 144 87 0.03 7.9 1.0

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
Data 85

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323800—Clark Fork near Galen

Period of record for water-quality data: July 1988–September 2015

Streamflow, instantaneous (ft3

/s) 228 1,380 14 222 143

pH, onsite (standard units) 216 9.2 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 217 720 182 406 414

Temperature, water (°C) 228 23.5 0.0 9.8 10.0

Hardness, filtered (mg/L as CaCO3

) 215 365 76.4 177 183

Calcium, filtered (mg/L) 215 110 23.2 52.4 54.0

Magnesium, filtered (mg/L) 215 22.0 4.44 11.3 11.6

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 6.47 6.22

Fluoride, filtered (mg/L) 32 1.10 0.40 0.62 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) 215 1.0 <0.03 2

0.06 0.03

Cadmium, unfiltered recoverable (μg/L) 215 3.0 <0.1 2

0.17 0.06

Copper, filtered (μg/L) 215 50.0 1.4 7.2 5.3

Copper, unfiltered recoverable (μg/L) 214 240 4.1 25.4 14.6

Iron, filtered (μg/L) 215 110 <3.0 2

16.4 12.4

Iron, unfiltered recoverable (μg/L) 215 9,200 56.2 447 260

Lead, filtered (μg/L) 215 3.00 <0.08 2

0.14 <1.00

Lead, unfiltered recoverable (μg/L) 215 31.0 <1.00 2

3.18 1.72

Manganese, filtered (μg/L) 215 460 13.1 98.0 71.0

Manganese, unfiltered recoverable (μg/L) 215 1,400 40.9 204 156

Zinc, filtered (μg/L) 215 110 <1.0 2

7.9 3.5

Zinc, unfiltered recoverable (μg/L) 215 360 2.7 2

33.4 20.0

Arsenic, filtered (μg/L) 215 53.0 4.0 14.9 14.0

Arsenic, unfiltered recoverable (μg/L) 215 78.0 3.0 18.8 16.8

Sediment, suspended (percent finer than 

0.062 mm)

228 97 32 76 77

Sediment, suspended concentration (mg/L) 229 338 1 17 8

Sediment, suspended discharge (ton/d) 228 459 0.12 19 2.9

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
86 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323840—Lost Creek near Anaconda

Period of record for water-quality data: December 2004–September 2015

Streamflow, instantaneous (ft3

/s) 87 73 0.37 12 9.2

pH, onsite (standard units) 87 8.6 7.4 8.1 8.2

Specific conductance, onsite (μS/cm) 87 253 121 199 211

Temperature, water (°C) 87 17.0 0.0 7.8 8.0

Turbidity, unfiltered, lab (NTRU) 87 24,200 <2.0 2

280 <2.0

Hardness, filtered (mg/L as CaCO3

) 87 122 50.4 95.6 102

Calcium, filtered (mg/L) 87 37.1 15.7 29.0 30.3

Magnesium, filtered (mg/L) 87 7.47 2.71 5.64 5.92

Potassium, filtered (mg/L) 22 1.46 0.88 1.23 1.26

Sodium, filtered (mg/L) 22 3.68 1.87 2.86 2.80

Alkalinity, filtered, lab (mg/L) 22 118 59.5 95.8 100

Chloride, filtered (mg/L) 22 2.13 0.51 0.80 0.72

Fluoride, filtered (mg/L) 22 0.49 0.28 0.40 0.40

Silica, filtered (mg/L) 22 12.3 9.65 11.2 11.2

Sulfate, filtered (mg/L) 22 13.8 5.89 8.87 8.26

Cadmium, filtered (μg/L) 85 0.90 <0.02 2

0.04 0.02

Cadmium, unfiltered recoverable (μg/L) 86 147 <0.02 2

1.8 0.04

Copper, filtered (μg/L) 86 90.5 0.80 2.9 1.7

Copper, unfiltered recoverable (μg/L) 86 29,100 1.3 345 4.5

Iron, filtered (μg/L) 86 26.5 <6.0 2

10.2 9.0

Iron, unfiltered recoverable (μg/L) 86 99,700 22.3 1,350 112

Lead, filtered (μg/L) 86 0.18 <0.02 2

0.04 <0.12

Lead, unfiltered recoverable (μg/L) 86 1,290 0.08 15.8 0.48

Manganese, filtered (μg/L) 86 42.4 <0.2 2

1.9 1.4

Manganese, unfiltered recoverable (μg/L) 86 8,830 1.2 110 4.8

Zinc, filtered (μg/L) 85 30.0 <1.4 2

1.6 <2.8

Zinc, unfiltered recoverable (μg/L) 85 7,780 <2 2

95.0 2.2

Arsenic, filtered (μg/L) 86 156 1.8 5.9 3.4

Arsenic, unfiltered recoverable (μg/L) 86 3,860 2.0 49.5 3.9

Organic carbon, filtered (mg/L) 22 3.84 0.90 1.78 1.66

Sediment, suspended (percent finer than 

0.062 mm)

87 97 22 57 59

Sediment, suspended concentration (mg/L) 87 58,900 1 689 6

Sediment, suspended discharge (ton/d) 87 1,320 <0.01 2

16 0.13

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
Data 87

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323850—Lost Creek near Galen

Period of record for water-quality data: March 2003–September 2015

Streamflow, instantaneous (ft3

/s) 102 71 1.3 24 18

pH, onsite (standard units) 104 8.7 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 104 934 540 639 627

Temperature, water (°C) 104 26.5 0.0 10.3 10.0

Turbidity, unfiltered, lab (NTRU) 15 5.4 <2.0 2

1.7 <2.0

Hardness, filtered (mg/L as CaCO3

) 104 451 203 304 300

Calcium, filtered (mg/L) 104 122 48.5 86.1 86.1

Magnesium, filtered (mg/L) 104 35.7 17.3 21.5 20.9

Potassium, filtered (mg/L) 15 3.68 2.05 2.57 2.40

Sodium, filtered (mg/L) 15 31.5 10.1 16.1 12.9

Alkalinity, filtered, lab (mg/L) 15 224 166 191 186

Chloride, filtered (mg/L) 15 5.62 3.90 4.74 4.71

Fluoride, filtered (mg/L) 15 0.78 0.44 0.55 0.50

Silica, filtered (mg/L) 15 19.9 11.7 16.1 15.7

Sulfate, filtered (mg/L) 15 200 95.3 137 135

Cadmium, filtered (μg/L) 103 0.05 <0.02 2

0.03 0.02

Cadmium, unfiltered recoverable (μg/L) 104 0.12 <0.02 2

0.04 0.03

Copper, filtered (μg/L) 104 6.7 0.80 2.1 1.9

Copper, unfiltered recoverable (μg/L) 104 22.5 1.5 5.2 4.1

Iron, filtered (μg/L) 104 84.5 4.0 2

14.7 11.6

Iron, unfiltered recoverable (μg/L) 104 392 14.0 106 82.0

Lead, filtered (μg/L) 103 0.33 <0.025 2

0.05 0.03

Lead, unfiltered recoverable (μg/L) 104 1.90 0.04 0.40 0.28

Manganese, filtered (μg/L) 104 54.0 1.91 16.0 14.9

Manganese, unfiltered recoverable (μg/L) 104 56.5 2.20 21.0 19.8

Zinc, filtered (μg/L) 103 3.8 <1.0 2

1.5 1.1

Zinc, unfiltered recoverable (μg/L) 104 10.3 <2.0 2

2.9 2.0

Arsenic, filtered (μg/L) 104 41.8 6.0 14.1 12.6

Arsenic, unfiltered recoverable (μg/L) 104 43.0 6.0 15.0 13.4

Organic carbon, filtered (mg/L) 15 4.33 1.48 2.32 2.16

Sediment, suspended (percent finer than 

0.062 mm)

104 94 18 61 64

Sediment, suspended concentration (mg/L) 104 79 2 16 15

Sediment, suspended discharge (ton/d) 102 4.2 0.01 1.0 0.71

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
88 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324200—Clark Fork at Deer Lodge

Period of record for water-quality data: March 1985–September 2015

Streamflow, instantaneous (ft3

/s) 281 2,000 23 306 229

pH, onsite (standard units) 229 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 264 642 228 465 490

Temperature, water (°C) 280 23.0 0.0 10.1 10.5

Hardness, filtered (mg/L as CaCO3

) 221 282 94.9 197 206

Calcium, filtered (mg/L) 221 82.0 28.2 58.3 60.7

Magnesium, filtered (mg/L) 221 18.7 5.53 12.6 13.2

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) 230 2.0 <0.10 2

0.08 0.04

Cadmium, unfiltered recoverable (μg/L) 230 5.0 <0.10 2

0.36 0.10

Copper, filtered (μg/L) 231 120 3.2 10.3 7.8

Copper, unfiltered recoverable (μg/L) 229 1,500 8.2 74.7 34.0

Iron, filtered (μg/L) 231 190 <3 2

15.3 10.0

Iron, unfiltered recoverable (μg/L) 231 29,000 27.2 1,340 494

Lead, filtered (μg/L) 231 6.00 <0.04 2

0.29 <5.00

Lead, unfiltered recoverable (μg/L) 231 200 0.33 2

9.84 4.08

Manganese, filtered (μg/L) 231 400 1.0 40.1 31.7

Manganese, unfiltered recoverable (μg/L) 231 4,600 11.9 212 124

Zinc, filtered (μg/L) 231 230 <10.0 2

10.8 7.0

Zinc, unfiltered recoverable (μg/L) 229 1,700 4.0 76.6 35.8

Arsenic, filtered (μg/L) 231 39.0 6.0 14.4 13.4

Arsenic, unfiltered recoverable (μg/L) 230 215 4.8 23.1 17.0

Sediment, suspended (percent finer than 

0.062 mm)

272 99 31 72 73

Sediment, suspended concentration (mg/L) 281 2,250 1 64 21

Sediment, suspended discharge (ton/d) 281 8,690 0.18 133 12

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
Data 89

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324400—Clark Fork above Little Blackfoot River, near Garrison

Period of record for water-quality data: March 2009–September 2015

Streamflow, instantaneous (ft3

/s) 54 2,310 69 444 306

pH, onsite (standard units) 54 8.9 7.9 8.4 8.4

Specific conductance, onsite (μS/cm) 54 527 249 414 444

Temperature, water (°C) 54 22.0 1.0 11.9 13.0

Hardness, filtered (mg/L as CaCO3

) 54 228 104 182 196

Calcium, filtered (mg/L) 54 66.5 31.8 53.2 56.8

Magnesium, filtered (mg/L) 54 15.5 5.93 12.0 13.2

Cadmium, filtered (μg/L) 54 0.23 0.02 0.07 0.07

Cadmium, unfiltered recoverable (μg/L) 54 0.84 0.03 0.26 0.18

Copper, filtered (μg/L) 54 40.6 2.8 9.4 7.9

Copper, unfiltered recoverable (μg/L) 54 222 10.0 57.9 33.8

Iron, filtered (μg/L) 54 64.4 4.5 18.2 14.6

Iron, unfiltered recoverable (μg/L) 53 3,860 40.7 885 541

Lead, filtered (μg/L) 54 0.72 0.04 0.17 0.13

Lead, unfiltered recoverable (μg/L) 54 32.3 0.33 7.5 4.08

Manganese, filtered (μg/L) 54 65.1 8.56 28.5 24.0

Manganese, unfiltered recoverable (μg/L) 54 344 13.4 117 100

Zinc, filtered (μg/L) 54 37.1 1.9 5.9 5.0

Zinc, unfiltered recoverable (μg/L) 54 181 3.0 47.0 28.8

Arsenic, filtered (μg/L) 54 36.7 7.8 15.1 15.5

Arsenic, unfiltered recoverable (μg/L) 54 46.0 10.5 21.2 17.9

Sediment, suspended (percent finer than 

0.062 mm)

54 92 42 73 75

Sediment, suspended concentration (mg/L) 54 205 1 43 24

Sediment, suspended discharge (ton/d) 54 550 0.31 82 22

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
90 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12324680—Clark Fork at Goldcreek

Period of record for water-quality data: March 1993–September 2015

Streamflow, instantaneous (ft3

/s) 187 4,450 87 766 513

pH, onsite (standard units) 186 9.1 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 186 510 206 366 376

Temperature, water (°C) 187 23.0 0.0 10.3 10.5

Hardness, filtered (mg/L as CaCO3

) 186 232 85.8 161 169

Calcium, filtered (mg/L) 186 68.0 25.9 47.5 49.4

Magnesium, filtered (mg/L) 186 15.0 5.15 10.3 10.7

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) 186 0.2 <0.02 2

0.04 0.02

Cadmium, unfiltered recoverable (μg/L) 186 2.0 <0.10 2

0.17 0.08

Copper, filtered (μg/L) 185 36.0 2.1 6.5 5.3

Copper, unfiltered recoverable (μg/L) 185 440 5.2 38.2 21.5

Iron, filtered (μg/L) 186 100 <3 2

19.9 12.9

Iron, unfiltered recoverable (μg/L) 186 12,000 27.3 817 416

Lead, filtered (μg/L) 184 0.68 <0.04 2

0.12 <1.00

Lead, unfiltered recoverable (μg/L) 185 73.0 0.14 2

5.29 2.76

Manganese, filtered (μg/L) 186 57.3 4.0 18.6 16.4

Manganese, unfiltered recoverable (μg/L) 186 1,100 9.3 113 80.8

Zinc, filtered (μg/L) 186 26 <1.0 2

5.2 3.7

Zinc, unfiltered recoverable (μg/L) 186 510 2 40.3 26.7

Arsenic, filtered (μg/L) 186 22.5 5.6 10.0 9.8

Arsenic, unfiltered recoverable (μg/L) 186 75.0 7.0 14.5 12.0

Sediment, suspended (percent finer than 

0.062 mm)

187 94 43 75 78

Sediment, suspended concentration (mg/L) 187 752 1 46 19

Sediment, suspended discharge (ton/d) 187 7,960 0.55 192 27

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
Data 91

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12331800—Clark Fork near Drummond

Period of record for water-quality data: March 1993–September 2015

Streamflow, instantaneous (ft3

/s) 187 5,540 149 1,050 768

pH, onsite (standard units) 186 8.7 7.8 8.3 8.2

Specific conductance, onsite (μS/cm) 186 630 189 407 418

Temperature, water (°C) 187 22.5 0.5 11.0 11.0

Hardness, filtered (mg/L as CaCO3

) 186 298 73.9 183 190

Calcium, filtered (mg/L) 186 83.0 21.0 52.6 54.4

Magnesium, filtered (mg/L) 186 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) 185 0.30 <0.03 2

0.05 0.03

Cadmium, unfiltered recoverable (μg/L) 186 2.0 <0.03 2

0.22 0.08

Copper, filtered (μg/L) 183 21.0 1.0 6.3 4.9

Copper, unfiltered recoverable (μg/L) 184 360 4.6 40.1 21.8

Iron, filtered (μg/L) 186 150 <3 2

18.7 10.0

Iron, unfiltered recoverable (μg/L) 185 8,800 19.7 937 461

Lead, filtered (μg/L) 182 1.2 <0.04 2

0.16 0.05

Lead, unfiltered recoverable (μg/L) 182 56.0 0.17 2

7.08 3.45

Manganese, filtered (μg/L) 185 60.7 3.3 16.6 14.9

Manganese, unfiltered recoverable (μg/L) 186 880 8.0 136 88.4

Zinc, filtered (μg/L) 186 21.0 <1.4 2

5.6 4.3

Zinc, unfiltered recoverable (μg/L) 186 490 2.9 54.4 30.0

Arsenic, filtered (μg/L) 186 23.9 3.2 10.5 10.0

Arsenic, unfiltered recoverable (μg/L) 186 62 7.7 15.6 12.8

Sediment, suspended (percent finer than 

0.062 mm)

187 93 38 74 75

Sediment, suspended concentration (mg/L) 187 530 2 58 25

Sediment, suspended discharge (ton/d) 187 4,720 1.7 293 47

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
92 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12334550—Clark Fork at Turah Bridge, near Bonner

Period of record for water-quality data: March 1985–September 2015

Streamflow, instantaneous (ft3

/s) 284 10,600 296 1,960 1,190

pH, onsite (standard units) 230 8.8 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 259 483 139 297 310

Temperature, water (°C) 283 22.0 0.0 9.6 10.0

Hardness, filtered (mg/L as CaCO3

) 220 205 53.6 130 132

Calcium, filtered (mg/L) 220 59.0 14.9 36.7 37.0

Magnesium, filtered (mg/L) 220 14.0 3.95 9.38 9.40

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) 4 155 52.5 108 111

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

Nitrate plus nitrite, filtered (mg/L) 8 0.069 <0.013 2

0.027 0.012

Phosphorus, unfiltered (mg/L) 10 0.240 0.014 0.080 0.068

Total nitrogen, unfiltered (mg/L) 2 0.49 0.38 0.44 --

Cadmium, filtered (μg/L) 228 0.10 <0.02 2

0.03 <1

Cadmium, unfiltered recoverable (μg/L) 229 4.00 <0.01 2

0.22 0.03

Copper, filtered (μg/L) 228 25.0 1.1 4.6 3.4

Copper, unfiltered recoverable (μg/L) 227 500 2.7 30.9 14.0

Iron, filtered (μg/L) 229 359 <3 2

24.8 14.3

Iron, unfiltered recoverable (μg/L) 229 19,000 32.6 915 356

Lead, filtered (μg/L) 225 7.00 <.02 2

0.26 <1.00

Lead, unfiltered recoverable (μg/L) 225 100 <1.00 2

6.18 2.33

Manganese, filtered (μg/L) 229 48.6 <1.0 2

8.4 7.0

Manganese, unfiltered recoverable (μg/L) 229 2,000 8.9 110 57.3

Zinc, filtered (μg/L) 227 39 <2.0 2

5.5 3.9

Zinc, unfiltered recoverable (μg/L) 229 1,100 2.9 2

52.1 22.7

Arsenic, filtered (μg/L) 229 17.0 2.7 6.0 5.5

Arsenic, unfiltered recoverable (μg/L) 229 110 3.0 9.3 7.0

Sediment, suspended (percent finer than 

0.062 mm)

273 98 27 74 76

Sediment, suspended concentration (mg/L) 284 1,370 2 52 18

Sediment, suspended discharge (ton/d) 284 34,700 3.0 587 60

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
Data 93

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12340000—Blackfoot River near Bonner

Period of record for water-quality data: March 1985–September 2015

Streamflow, instantaneous (ft3

/s) 208 13,400 344 2,780 1,380

pH, onsite (standard units) 168 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 185 294 131 209 204

Temperature, water (°C) 208 22.5 0.0 9.7 10.0

Turbidity, unfiltered, lab (NTRU) 7 30 <2.0 2

7.2 2.0

Hardness, filtered (mg/L as CaCO3

) 160 146 55.1 104 98.6

Calcium, filtered (mg/L) 160 37.7 14.0 26.5 25.4

Magnesium, filtered (mg/L) 160 13.2 4.90 9.17 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

Nitrate plus nitrite, filtered (mg/L) 30 0.040 <0.005 2

0.010 0.005

Phosphorus, unfiltered (mg/L) 31 0.167 0.003 0.027 0.015

Total nitrogen, unfiltered (mg/L) 14 0.33 0.08 0.15 0.14

Cadmium, filtered (μg/L) 166 1.00 <0.02 2

0.02 <0.10

Cadmium, unfiltered recoverable (μg/L) 168 2.00 <0.01 2

0.08 <1.00

Copper, filtered (μg/L) 164 7.0 <0.80 2

1.2 0.70

Copper, unfiltered recoverable (μg/L) 165 34.0 <0.70 2

4.1 1.7

Iron, filtered (μg/L) 167 104 <3 2

17.8 10.2

Iron, unfiltered recoverable (μg/L) 168 3,600 13.9 389 172

Lead, filtered (μg/L) 162 8.00 <0.02 2

0.26 <0.50

Lead, unfiltered recoverable (μg/L) 163 25.0 <0.04 2

1.93 0.09

Manganese, filtered (μg/L) 167 11.0 <1.0 2

2.4 2.0

Manganese, unfiltered recoverable (μg/L) 168 180 <10.0 2

26.9 15.0

Zinc, filtered (μg/L) 166 15.0 <0.60 2

1.8 <3.0

Zinc, unfiltered recoverable (μg/L) 168 60.0 <1.0 2

4.7 <10.0

Arsenic, filtered (μg/L) 167 2.0 <1.0 2

0.97 0.96

Arsenic, unfiltered recoverable (μg/L) 168 4.0 <1.0 2

1.3 1.0

Sediment, suspended (percent finer than 

0.062 mm)

206 98 42 80 82

Sediment, suspended concentration (mg/L) 208 271 1 28 8

Sediment, suspended discharge (ton/d) 208 7,670 1.1 499 31

Table 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
94 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12340500—Clark Fork above Missoula

Period of record for water-quality data: July 1986–September 2015

Streamflow, instantaneous (ft3

/s) 249 22,900 720 4,630 2,520

pH, onsite (standard units) 207 8.8 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 227 399 142 251 259

Temperature, water (°C) 247 22.0 0.0 9.8 9.5

Turbidity, unfiltered, lab (NTRU) 40 100 <2.0 2

13 4.9

Hardness, filtered (mg/L as CaCO3

) 207 168 60.5 116 117

Calcium, filtered (mg/L) 207 46.0 14.0 31.3 31.2

Magnesium, filtered (mg/L) 207 13.4 5.28 9.19 9.15

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

Phosphorus, unfiltered (mg/L) 2 0.102 0.066 0.084 --

Total nitrogen, unfiltered (mg/L) 2 0.470 0.320 0.395 --

Cadmium, filtered (μg/L) 206 0.20 <0.02 2

0.03 <0.10

Cadmium, unfiltered recoverable (μg/L) 207 5.0 <0.01 2

0.14 <1.0

Copper, filtered (μg/L) 206 12.6 0.7 2.7 2.0

Copper, unfiltered recoverable (μg/L) 205 400 1.9 17.8 8.0

Iron, filtered (μg/L) 207 200 <3 2

21.5 14.9

Iron, unfiltered recoverable (μg/L) 207 13,000 40.9 588 247

Lead, filtered (μg/L) 200 1.20 <0.02 2

0.12 <1.00

Lead, unfiltered recoverable (μg/L) 202 78.0 <1.00 2

3.14 1.29

Manganese, filtered (μg/L) 207 230 3.5 14.8 12.9

Manganese, unfiltered recoverable (μg/L) 207 1,100 8.8 61.0 40.0

Zinc, filtered (μg/L) 206 16.0 <1.0 2

3.3 2.3

Zinc, unfiltered recoverable (μg/L) 207 1,100 <3.0 2

30.2 12.0

Arsenic, filtered (μg/L) 207 9.0 1.0 3.4 3.2

Arsenic, unfiltered recoverable (μg/L) 207 69.0 1.0 5.2 4.0

Sediment, suspended (percent finer than 

0.062 mm)

245 99 14 82 87

Sediment, suspended concentration (mg/L) 250 950 2 41 12

Sediment, suspended discharge (ton/d) 249 21,900 5.8 1,050 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 24. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 

2015.—Continued

[ft3/s, cubic feet per second; μS/cm, microsiemen per centimeter at 25 °C; °C, degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; 

<, less than laboratory reporting level1; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millimeter; ton/d, ton per day; 

--, indicates either too few samples (less than three) or insufficient data to compute statistic]
Data 95

Table 25. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2015.

[Reported concentrations are in microgram 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. <, 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: 1992–2015

Arsenic 13 186 27 95 73

Cadmium 24 43.9 5.9 25.5 26.3

Chromium 22 50.7 16.8 29.5 25.9

Copper 24 9,020 522 3,460 3,640

Iron 24 45,300 28,200 34,700 33,700

Lead 24 1,030 112 535 520

Manganese 24 9,220 1,160 3,170 2,680

Nickel 23 21.4 12.0 14.9 14.8

Silver 12 20.0 8.3 15.5 15.8

Zinc 24 13,400 1,490 6,120 6,760

12323750—Silver Bow Creek at Warm Springs

Period of record for bed-sediment data: 1992–2015

Arsenic 13 177 67 113 103

Cadmium 24 12.2 4.2 6.9 6.5

Chromium 22 46.8 <15.7 1

23.9 123.2

Copper 24 769 169 339 295

Iron 24 32,500 15,400 23,800 23,000

Lead 24 100 49 71 72

Manganese 24 17,700 1,470 7,460 7,280

Nickel 23 20.0 9.2 14.9 14.6

Silver 12 4.4 0.3 1

1.9 11.8

Zinc 24 2,220 554 883 687

12323770—Warm Springs Creek at Warm Springs

Period of record for bed-sediment data: 1995, 1997, 1999, 2002, 2005, 2008, 2011, 2014

Arsenic 4 66 34 54 58

Cadmium 8 5.8 1.2 3.2 3.1

Chromium 8 39.3 24.1 31.1 31.1

Copper 8 1,060 496 839 864

Iron 8 26,600 16,800 21,500 21,900

Lead 8 86 42 75 81

Manganese 8 12,100 555 6,620 6,900

Nickel 8 25.5 14.5 19.6 19.2

Silver 4 5.1 3.1 3.8 3.5

Zinc 8 453 237 379 385
96 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of samples Maximum Minimum Mean Median

12323800—Clark Fork near Galen

Period of record for bed-sediment data: 1987, 1991–2015

Arsenic 13 156 73 109 107

Cadmium 26 20.1 3.8 7.7 6.4

Chromium 22 44.6 19.1 29.0 26.7

Copper 26 2,300 838 1,180 1,110

Iron 26 39,800 22,600 27,900 27,200

Lead 26 235 92 130 127

Manganese 26 17,300 1,530 8,500 7,400

Nickel 23 23.2 13.9 18.6 18.3

Silver 14 7.3 <3.2 1

4.4 14.5

Zinc 26 3,560 721 1,340 1,110

461415112450801—Clark Fork below Lost Creek, near Galen

Period of record for bed-sediment data: 1996–2015

Arsenic 13 204 90 121 109

Cadmium 20 10.5 4.8 6.6 6.2

Chromium 19 42.4 17.2 29.1 27.5

Copper 20 2,050 1,150 1,490 1,460

Iron 20 32,800 24,400 29,000 29,200

Lead 20 218 123 162 164

Manganese 20 9,820 1,430 5,190 4,940

Nickel 20 19.9 11.7 15.8 16.2

Silver 8 7.8 4.2 6.5 6.7

Zinc 20 1,680 930 1,250 1,190

461559112443301—Clark Fork at county bridge, near Racetrack

Period of record for bed-sediment data: 1996–2015

Arsenic 13 132 56 93 90

Cadmium 20 8.7 4.6 6.3 5.9

Chromium 19 45.2 14.4 28.3 27.6

Copper 20 1,810 933 1,270 1,290

Iron 20 31,700 21,200 27,300 28,100

Lead 20 186 103 141 139

Manganese 20 6,310 1,600 3,240 3,090

Nickel 20 18.4 10.3 14.2 14.5

Silver 8 6.1 <3.3 1

5.0 15.4

Zinc 20 1,550 911 1,160 1,130

Table 25. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute 

statistic]
Data 97

Constituent Number of samples Maximum Minimum Mean Median

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for bed-sediment data: 1996–2015

Arsenic 13 109 58 82 80

Cadmium 20 10.3 4.1 6.1 5.5

Chromium 19 39.2 15.7 26.7 25.6

Copper 20 1,580 721 1,120 1,100

Iron 20 33,700 20,600 27,000 26,600

Lead 20 155 92 130 133

Manganese 20 8,370 1,200 3,680 3,200

Nickel 20 16.9 8.7 12.8 12.5

Silver 8 6.2 2.7 4.9 5.0

Zinc 20 1,570 900 1,110 1,080

12324200—Clark Fork at Deer Lodge

Period of record for bed-sediment data: 1986–87, 1990–2015

Arsenic 13 102 49 75 72

Cadmium 28 10.0 3.5 5.8 5.0

Chromium 22 50.7 19.5 32.0 28.3

Copper 28 4,180 683 1,230 1,070

Iron 28 35,300 21,100 27,300 26,300

Lead 28 242 103 142 140

Manganese 28 6,020 1,070 2,520 2,360

Nickel 23 21.1 11.5 14.7 14.3

Silver 16 7.9 2.4 4.7 4.5

Zinc 28 1,730 844 1,160 1,050

12324400—Clark Fork above Little Blackfoot River, near Garrison

Period of record for bed-sediment data: 2009-2015

Arsenic 7 91 49 71 81

Cadmium 7 5.5 4.1 4.6 4.5

Chromium 7 52.8 15.0 34.5 39.0

Copper 7 1,290 666 1,040 1,200

Iron 7 32,400 16,800 25,100 26,500

Lead 7 145 92 121 132

Manganese 7 3,560 1,150 2,570 2,670

Nickel 7 17.2 9.2 13.2 13.9

Silver 0 -- -- -- --

Zinc 7 1,240 780 1,020 1,100

Table 25. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute 

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

Constituent Number of samples Maximum Minimum Mean Median

12324680—Clark Fork at Goldcreek

Period of record for bed-sediment data: 1992–2015

Arsenic 13 62 23 40 36

Cadmium 24 8.1 2.0 4.3 3.9

Chromium 22 55.3 9.9 31.6 30.5

Copper 24 1,080 281 658 681

Iron 24 32,100 11,500 22,900 23,900

Lead 24 152 45 91 93

Manganese 24 2,730 977 1,820 1,810

Nickel 23 18.6 7.6 13.5 14.1

Silver 12 4.8 2.3 3.2 3.2

Zinc 24 1,320 427 870 874

12331800—Clark Fork near Drummond

Period of record for bed-sediment data: 1986–87, 1991–2015

Arsenic 13 66 17 37 33

Cadmium 27 7.7 1.7 4.1 4.1

Chromium 22 41.9 9.2 27.1 28.6

Copper 27 747 183 464 460

Iron 27 44,000 14,800 24,600 23,200

Lead 27 135 27 84 83

Manganese 27 4,820 832 1,980 1,810

Nickel 23 16.8 4.8 12.6 13.4

Silver 15 4.7 <3.2 1

3.0 12.9

Zinc 27 1,230 380 898 947

12334550—Clark Fork at Turah Bridge, near Bonner

Period of record for bed-sediment data: 1986, 1991–2015

Arsenic 13 43 17 26 25

Cadmium 26 7.3 1.2 3.2 3.2

Chromium 22 42.5 13.6 26.1 27.2

Copper 26 635 211 340 322

Iron 26 25,900 12,600 19,100 17,300

Lead 26 115 37 65 63

Manganese 26 2,340 383 1,220 1,180

Nickel 23 19.1 6.9 12.2 11.5

Silver 14 3.9 <1.9 1

2.1 11.9

Zinc 26 1,160 448 760 767

Table 25. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute 

statistic]
Data 99

Table 25. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. <, less than the minimum reporting level; --, indicates insufficient data (less than three samples) to compute 

statistic]

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, 2006–15

Arsenic 11 6 <0.2 1

4 14

Cadmium 22 2.0 0.04 1

0.4 10.2

Chromium 18 35.2 13.3 21.7 22.8

Copper 22 27 11 20 21

Iron 22 23,000 12,400 17,500 17,900

Lead 22 20 <13 1

13 111

Manganese 22 746 298 527 543

Nickel 19 14.3 6.0 11.1 11.1

Silver 12 1.0 <0.3 1

0.5 10.3

Zinc 22 82 35 60 60

12340500—Clark Fork above Missoula

Period of record for bed-sediment data: 1997–2015

Arsenic 13 54 12 28 28

Cadmium 19 5.8 1.0 2.7 2.6

Chromium 18 40.7 12.8 25.6 27.3

Copper 19 551 129 323 282

Iron 19 27,000 13,800 20,100 20,400

Lead 19 78 25 50 50

Manganese 19 2,250 477 1,060 970

Nickel 19 15.8 7.6 12.3 12.4

Silver 7 2.9 0.8 1

2.0 12.1

Zinc 19 1,090 346 662 631

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

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.

[Reported concentrations are in microgram 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. 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, 1997–2015

Brachycentrus spp.

Arsenic 0 -- -- -- --

Cadmium 5 12.5 5.8 10.1 11.6

Chromium 5 5.9 0.7 2.1 0.9

Copper 5 846 235 587 592

Iron 5 1,190 335 617 469

Lead 5 21.5 7.4 13.7 13.8

Manganese 5 817 231 515 503

Nickel 5 2.1 <0.1 1

1.3 11.6

Zinc 5 995 629 803 815

Hydropsyche cockerelli

Arsenic 25 33.3 4.3 11.4 10.5

Cadmium 31 9.7 2.4 4.9 4.4

Chromium 31 25.5 1.0 4.2 3.8

Copper 31 1,090 78.6 313 333

Iron 31 6,150 689 2,740 2,500

Lead 31 74.3 11.9 32.1 21.7

Manganese 31 3,030 180 1,070 1,140

Nickel 31 4.3 0.7 2.7 2.7

Zinc 31 1,590 432 792 762

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
Data 101

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323600—Silver Bow Creek at Opportunity—Continued

Period of record for biological data: 1992, 1994–95, 1997–2015

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

12323750—Silver Bow Creek at Warm Springs

Period of record for biological data: 1992–2015

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 23 23.6 7.9 12.4 11.7

Cadmium 49 2.1 0.2 0.6 0.5

Chromium 49 4.3 0.4 1.1 0.9

Copper 49 97.0 16.7 36.1 31.1

Iron 49 1,650 351 836 799

Lead 49 6.0 0.3 3.2 2.9

Manganese 49 3,890 491 1,230 1,010

Nickel 49 1.8 0.3 1.0 0.9

Zinc 49 276 115 175 168

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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]
102 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323750—Silver Bow Creek at Warm Springs—Continued

Period of record for biological data: 1992–2015

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

12323770—Warm Springs Creek at Warm Springs

Period of record for biological data: 1995, 1997, 1999, 2002, 2005, 2008, 2011, 2014

Arctopsyche grandis

Arsenic 5 9.8 7.6 8.9 9.5

Cadmium 9 3.6 0.4 2.5 2.5

Chromium 9 5.0 0.8 2.7 2.8

Copper 9 132 53.2 102 102

Iron 9 1,490 684 1,030 1,040

Lead 9 7.7 3.0 1

5.6 15.3

Manganese 9 3,560 738 2,230 2,280

Nickel 9 4.0 1.1 1

2.5 12.3

Zinc 9 267 181 206 197

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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 103

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323770—Warm Springs Creek at Warm Springs—Continued

Period of record for biological data: 1995, 1997, 1999, 2002, 2005, 2008, 2011, 2014

Hesperoperla spp.

Arsenic 2 2.9 1.2 2.0 --

Cadmium 2 2.6 1.0 1.8 --

Chromium 2 2.0 0.9 1.4 --

Copper 2 64.9 55.9 60.4 --

Iron 2 456 375 416 --

Lead 2 1.9 1.4 1.6 --

Manganese 2 270 202 236 --

Nickel 2 1.1 0.6 0.8 --

Zinc 2 573 427 500 --

Hydropsyche occidentalis

Arsenic 4 13.6 9.8 12.4 13.0

Cadmium 6 1.4 0.7 1.1 1.2

Chromium 6 8.6 0.3 3.7 3.2

Copper 6 183 116 151 150

Iron 6 2,360 1,520 1,870 1,840

Lead 6 12.6 6.7 8.2 7.4

Manganese 6 3,190 1,440 2,580 2,680

Nickel 6 4.5 2.0 3.1 3.2

Zinc 6 204 148 169 168

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 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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]
104 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323800—Clark Fork near Galen

Period of record for biological data: 1987, 1991–2015

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 16 20.5 13.2 14.9 14.1

Cadmium 41 2.7 0.7 1.5 1.5

Chromium 41 9.6 0.8 2.3 2.1

Copper 41 181 48.7 108 107

Iron 41 2,660 816 1,560 1,510

Lead 41 17.1 1.2 9.0 8.8

Manganese 41 3,620 1,070 2,260 2,200

Nickel 41 6.5 0.9 2.0 1.8

Zinc 41 363 136 219 216

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 5 3.2 2.4 2.5 2.4

Chromium 5 4.6 1.8 2.6 2.2

Copper 5 185 156 173 175

Iron 5 1,890 1,360 1,510 1,430

Lead 5 12.4 7.1 8.5 7.9

Manganese 5 3,960 2,360 3,500 3,860

Nickel 5 3.6 1.9 2.3 2.1

Zinc 5 349 292 309 303

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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 105

Constituent Number of composite 

samples Maximum Minimum Mean Median

12323800—Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991–2015

Hydropsyche occidentalis

Arsenic 21 17.7 9.1 14.2 14.6

Cadmium 53 1.6 0.6 1.1 1.2

Chromium 53 6.6 0.4 2.1 2.0

Copper 53 151 49.2 94.8 92.4

Iron 53 2,590 642 1,510 1,450

Lead 53 13.5 1.6 8.2 8.3

Manganese 53 6,170 653 2,480 2,110

Nickel 53 3.5 0.8 1.8 1.8

Zinc 53 286 168 207 201

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 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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]
106 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of composite 

samples Maximum Minimum Mean Median

461415112450801—Clark Fork below Lost Creek, near Galen

Period of record for biological data: 1996–2015

Claassenia sabulosa

Arsenic 1 -- -- 1.5 --

Cadmium 2 0.4 0.3 0.4 --

Chromium 2 1.9 0.4 1.2 --

Copper 2 70.1 67.1 68.6 --

Iron 2 209 189 199 --

Lead 2 1.2 0.7 1.0 --

Manganese 2 238 90.4 164 --

Nickel 2 0.2 <0.2 1

0.2 --

Zinc 2 245 208 226 --

Hydropsyche cockerelli

Arsenic 21 27.8 8.8 16.4 16.6

Cadmium 32 2.8 1.1 1.9 1.7

Chromium 32 4.0 0.8 2.3 2.4

Copper 32 338 48.8 152 137

Iron 32 4,080 691 1,810 1,780

Lead 32 28.6 4.5 13.9 13.3

Manganese 32 3,160 1,230 1,810 1,700

Nickel 32 2.8 0.9 1.7 1.6

Zinc 32 339 151 242 243

Hydropsyche occidentalis

Arsenic 10 20.9 12.7 15.9 15.3

Cadmium 24 1.9 0.9 1.4 1.4

Chromium 24 6.5 1.2 2.3 2.0

Copper 24 219 52.1 120 120

Iron 24 2,830 963 1,660 1,520

Lead 24 20.4 6.6 11.4 10.8

Manganese 24 4,150 1,220 2,500 2,180

Nickel 24 3.2 0.9 1.6 1.5

Zinc 24 330 174 247 247

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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 107

Constituent Number of composite 

samples Maximum Minimum Mean Median

461415112450801—Clark Fork below Lost Creek, near Galen—Continued

Period of record for biological data: 1996–2015

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

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 --

461559112443301—Clark Fork at county bridge, near Racetrack

Period of record for biological data: 1996–2015

Arctopsyche grandis

Arsenic 2 13.0 5.2 9.1 --

Cadmium 2 2.4 1.2 1.8 --

Chromium 2 3.3 1.9 2.6 --

Copper 2 101 81.0 91.0 --

Iron 2 1,410 889 1,150 --

Lead 2 13.2 9.1 11.2 --

Manganese 2 2,480 1,430 1,960 --

Nickel 2 1.9 1.4 1.6 --

Zinc 2 260 243 252 --

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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]
108 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of composite 

samples Maximum Minimum Mean Median

461559112443301—Clark Fork at county bridge, near Racetrack—Continued

Period of record for biological data: 1996–2015

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 17 20.2 11.1 14.4 14.3

Cadmium 28 2.7 0.8 1.6 1.5

Chromium 28 3.0 0.6 1.9 2.1

Copper 28 198 50.0 108 100

Iron 28 3,330 657 1,420 1,160

Lead 28 18.7 3.7 9.8 8.7

Manganese 28 2,360 646 1,660 1,780

Nickel 28 2.0 0.7 1.3 1.3

Zinc 28 302 139 208 193

Hydropsyche occidentalis

Arsenic 16 16.8 9.2 13.0 12.5

Cadmium 29 2.3 0.7 1.4 1.3

Chromium 29 3.7 1.1 2.1 2.0

Copper 29 164 59.5 115 122

Iron 29 3,690 1,030 1,670 1,580

Lead 29 15.7 4.3 10.9 10.9

Manganese 29 3,770 660 1,980 1,760

Nickel 29 2.3 1.1 1.5 1.4

Zinc 29 361 181 234 227

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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 109

Constituent Number of composite 

samples Maximum Minimum Mean Median

461559112443301—Clark Fork at county bridge, near Racetrack—Continued

Period of record for biological data: 1996–2015

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

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for biological data: 1996–2015

Arctopsyche grandis

Arsenic 8 17.5 4.4 8.2 6.4

Cadmium 9 7.1 0.9 2.9 2.5

Chromium 9 12.9 0.7 1

2.8 11.1

Copper 9 196 30.8 77.2 60.0

Iron 9 2,800 340 859 538

Lead 9 17.6 2.1 1

7.0 15.8

Manganese 9 2,060 510 1,110 1,160

Nickel 9 2.5 0.5 1.2 1.0

Zinc 9 489 87 251 256

Claassenia sabulosa

Arsenic 7 3.8 1.2 2.3 2.1

Cadmium 7 2.4 0.4 1.0 0.9

Chromium 7 1.7 0.2 0.7 0.5

Copper 7 87.2 47.5 63.6 59.0

Iron 7 485 94 219 173

Lead 7 3.4 0.4 1.4 1.1

Manganese 7 1,260 98 349 228

Nickel 7 1.0 0.2 0.4 0.3

Zinc 7 394 168 280 255

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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]
110 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of composite 

samples Maximum Minimum Mean Median

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack—Continued

Period of record for biological data: 1996–2015

Hydropsyche cockerelli

Arsenic 15 18.8 8.0 12.9 13.3

Cadmium 24 2.1 0.7 1.4 1.5

Chromium 24 4.6 0.5 1.8 1.5

Copper 24 247 60.7 112 93.5

Iron 24 3,010 552 1,330 1,060

Lead 24 21.9 3.5 9.2 8.7

Manganese 24 2,650 487 1,420 1,290

Nickel 24 2.5 0.5 1.3 1.0

Zinc 24 285 162 218 221

Hydropsyche occidentalis

Arsenic 20 24.0 8.5 14.5 15.3

Cadmium 37 2.4 0.7 1.3 1.3

Chromium 37 6.2 0.3 2.1 1.9

Copper 37 345 74.9 126 107

Iron 37 3,390 764 1,730 1,550

Lead 37 21.8 4.4 12.4 11.5

Manganese 37 4,460 826 2,270 2,160

Nickel 37 2.4 1.0 1.6 1.5

Zinc 37 386 189 260 241

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 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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 111

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324200—Clark Fork at Deer Lodge

Period of record for biological data: 1986–87, 1990–2015

Arctopsyche grandis

Arsenic 7 13.3 5.8 8.8 8.3

Cadmium 9 4.7 2.6 1

3.5 13.4

Chromium 9 4.7 1.0 1

2.3 12.0

Copper 9 183 34.9 96.8 88.6

Iron 9 2,320 537 1,180 1,090

Lead 9 17.4 3.8 1

10.7 111.2

Manganese 9 1,620 380 1,150 1,320

Nickel 9 1.9 <1.3 1

1.4 11.3

Zinc 9 370 140 268 269

Hydropsyche cockerelli

Arsenic 15 17.1 5.8 10.2 10.1

Cadmium 38 3.6 0.6 1.7 1.7

Chromium 38 4.3 0.4 1.9 2.0

Copper 38 241 54.7 109 104

Iron 38 3,340 490 1,330 1,220

Lead 38 24.9 3.8 11.1 11.4

Manganese 38 1,580 396 1,040 1,030

Nickel 38 3.3 0.3 1.4 1.1

Zinc 38 391 132 205 195

Hydropsyche occidentalis

Arsenic 23 21.1 6.6 11.2 9.7

Cadmium 60 3.4 0.6 1.5 1.3

Chromium 60 3.7 0.6 2.0 1.9

Copper 60 222 49.4 124 121

Iron 60 3,240 558 1,520 1,490

Lead 60 20.1 3.5 12.0 11.9

Manganese 60 2,850 649 1,610 1,660

Nickel 60 12.9 1.0 1.7 1.4

Zinc 60 346 166 246 237

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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]
112 Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324200—Clark Fork at Deer Lodge—Continued

Period of record for biological data: 1986–87, 1990–2015

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

12324400—Clark Fork above Little Blackfoot River, near Garrison

Period of record for biological data: 2009–15

Arctopsyche grandis

Arsenic 12 16.6 3.2 6.3 5.4

Cadmium 12 4.9 0.9 2.9 3.3

Chromium 12 4.6 0.9 1

1.7 11.3

Copper 12 209 42.0 87.6 64.6

Iron 12 2,580 259 865 634

Lead 12 18.0 2.8 7.5 6.1

Manganese 12 1,940 578 1,110 981

Nickel 12 2.2 0.5 1.1 0.9

Zinc 12 378 185 260 246

Claassenia sabulosa

Arsenic 2 2.9 2.4 2.6 --

Cadmium 2 1.3 1.0 1.2 --

Chromium 2 0.6 0.6 0.6 --

Copper 2 73.1 69.4 71.2 --

Iron 2 284 281 282 --

Lead 2 2.1 2.1 2.1 --

Manganese 2 226 193 210 --

Nickel 2 0.8 0.6 0.7 --

Zinc 2 297 231 264 --

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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 113

Constituent Number of composite 

samples Maximum Minimum Mean Median

12324400—Clark Fork above Little Blackfoot River, near Garrison—Continued

Period of record for biological data: 2009–15

Hydropsyche cockerelli

Arsenic 4 11.1 7.8 9.3 9.2

Cadmium 4 4.0 0.9 2.3 2.2

Chromium 4 3.4 1.9 2.4 2.3

Copper 4 158 81.5 117 115

Iron 4 2,150 746 1,330 1,210

Lead 4 18.8 8.7 13.0 12.2

Manganese 4 1,870 1,110 1,440 1,380

Nickel 4 1.8 1.4 1.6 1.6

Zinc 4 284 212 238 229

Hydropsyche occidentalis

Arsenic 11 14.7 6.4 9.8 8.8

Cadmium 11 2.5 1.0 1.8 1.9

Chromium 11 3.6 0.7 2.1 2.0

Copper 11 182 85.7 128 138

Iron 11 2,390 913 1,520 1,290

Lead 11 17.9 8.8 12.8 11.5

Manganese 11 2,100 975 1,450 1,320

Nickel 11 1.9 1.0 1.5 1.5

Zinc 11 299 223 254 252

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 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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

12324680—Clark Fork at Goldcreek

Period of record for biological data: 1992–2015

Arctopsyche grandis

Arsenic 43 17.0 1.8 5.0 4.1

Cadmium 72 6.6 0.6 1.9 1.8

Chromium 72 5.3 0.1 1.4 1.1

Copper 72 232 19.9 51.4 38.7

Iron 72 3,070 195 758 518

Lead 72 16.9 1.0 4.0 3.4

Manganese 72 1,580 436 874 870

Nickel 72 3.1 0.2 0.8 0.7

Zinc 72 326 146 204 189

Claassenia sabulosa

Arsenic 31 2.5 0.4 1.4 1.4

Cadmium 51 3.5 0.1 1.0 0.7

Chromium 51 1.6 0.2 0.6 0.5

Copper 51 84.9 33.0 59.3 58.3

Iron 51 640 63.0 201 170

Lead 51 2.8 0.4 1.0 0.8

Manganese 51 320 50.6 157 149

Nickel 51 0.7 0.1 0.3 0.3

Zinc 51 364 166 264 258

Hydropsyche cockerelli

Arsenic 18 9.8 4.1 6.0 5.8

Cadmium 37 4.2 0.5 1.4 1.3

Chromium 37 4.7 0.5 2.0 1.9

Copper 37 188 17.1 73.7 58.6

Iron 37 3,250 522 1,160 954

Lead 37 17.6 2.4 6.7 5.4

Manganese 37 1,710 538 1,000 963

Nickel 37 3.5 0.3 1.3 1.2

Zinc 37 359 106 193 186

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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

12324680—Clark Fork at Goldcreek—Continued

Period of record for biological data: 1992–2015

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

Hydropsyche occidentalis

Arsenic 16 11.5 4.4 6.8 6.3

Cadmium 31 2.3 0.4 1.3 1.3

Chromium 31 3.9 0.4 1.8 1.7

Copper 31 170 26.4 72.7 62.6

Iron 31 2,720 466 1,230 1,120

Lead 31 15.7 2.9 7.4 6.0

Manganese 31 2,900 530 1,250 1,140

Nickel 31 2.5 0.8 1.3 1.1

Zinc 31 328 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 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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

12331800—Clark Fork near Drummond

Period of record for biological data: 1986, 1991–2015

Arctopsyche grandis

Arsenic 34 9.9 1.8 4.2 4.0

Cadmium 66 3.8 0.4 1.4 1.2

Chromium 66 4.2 0.2 1.1 1.0

Copper 66 103 16.9 35.4 28.7

Iron 66 2,400 193 629 498

Lead 66 12.4 1.6 4.7 4.0

Manganese 66 2,010 456 844 747

Nickel 66 2.6 0.2 0.7 0.6

Zinc 66 314 137 201 192

Claassenia sabulosa

Arsenic 28 1.9 0.6 1.3 1.3

Cadmium 64 2.8 0.1 1.0 0.8

Chromium 64 3.3 0.2 0.7 0.6

Copper 64 165 18.0 64.2 60.3

Iron 64 449 45.4 177 147

Lead 64 2.9 0.2 1.0 0.9

Manganese 64 748 33.1 181 146

Nickel 64 1.1 0.1 1

0.3 10.3

Zinc 64 567 103 280 269

Hydropsyche cockerelli

Arsenic 18 7.2 3.9 5.6 5.5

Cadmium 47 4.5 0.3 1.2 0.9

Chromium 47 3.5 0.4 1.6 1.6

Copper 47 156 30.0 58.5 52.3

Iron 47 2,500 506 1,160 969

Lead 47 15.0 4.7 8.3 7.4

Manganese 47 1,680 549 1,010 939

Nickel 47 2.0 0.5 1.2 1.1

Zinc 47 322 134 196 187

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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

12331800—Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991–2015

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 6 1.3 1.1 1.2 1.2

Chromium 6 2.8 1.9 2.3 2.2

Copper 6 57.4 50.2 55.2 55.8

Iron 6 1,730 1,370 1,570 1,600

Lead 6 10.8 7.0 8.9 9.0

Manganese 6 1,940 1,260 1,610 1,610

Nickel 6 1.7 1.3 1.5 1.5

Zinc 6 250 227 239 240

Hydropsyche occidentalis

Arsenic 19 7.7 4.3 5.6 5.4

Cadmium 35 2.8 0.4 1.1 1.0

Chromium 35 8.1 0.4 2.2 2.2

Copper 35 118 13.3 58.3 56.3

Iron 35 2,060 424 1,240 1,190

Lead 35 14.0 3.0 8.6 8.9

Manganese 35 2,920 477 1,410 1,230

Nickel 35 2.4 0.5 1.3 1.2

Zinc 35 293 153 222 222

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 2.6 --

Chromium 0 -- -- -- --

Copper 1 -- -- 85.0 --

Iron 1 -- -- 913 --

Lead 1 -- -- 9.1 --

Manganese 0 -- -- -- --

Nickel 0 -- -- -- --

Zinc 1 -- -- 260 --

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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

12334550—Clark Fork at Turah Bridge, near Bonner

Period of record for biological data: 1986, 1991–2015

Arctopsyche grandis

Arsenic 35 7.2 2.8 4.4 4.3

Cadmium 77 2.7 0.4 1.2 1.2

Chromium 77 4.1 0.5 1.6 1.5

Copper 77 125 15.9 37.2 32.2

Iron 77 2,870 321 908 793

Lead 77 13.2 1.6 4.4 3.9

Manganese 77 1,050 324 655 676

Nickel 77 2.6 0.4 1.1 1.0

Zinc 77 282 111 203 204

Claassenia sabulosa

Arsenic 25 3.1 0.2 1.1 1.0

Cadmium 51 2.5 0.05 1.1 0.8

Chromium 51 2.0 0.2 0.7 0.6

Copper 51 97.8 37.5 59.8 55.0

Iron 51 378 58.6 134 114

Lead 51 1.6 0.2 0.7 0.6

Manganese 51 229 37.2 102 90.2

Nickel 51 0.6 0.04 0.2 0.2

Zinc 51 429 144 237 243

Hydropsyche cockerelli

Arsenic 27 9.8 3.7 4.8 4.7

Cadmium 55 2.2 0.3 0.9 0.7

Chromium 55 14.2 0.2 2.2 1.7

Copper 55 126 26.4 48.7 44.0

Iron 55 3,180 566 1,220 1,110

Lead 55 19.7 2.2 5.6 5.2

Manganese 55 957 426 653 661

Nickel 55 2.7 0.6 1.3 1.2

Zinc 55 332 119 191 194

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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

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

Period of record for biological data: 1986, 1991–2015

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 2 1.3 1.1 1.2 --

Chromium 2 4.6 2.4 3.5 --

Copper 2 84.1 26.8 55.4 --

Iron 2 1,800 986 1,390 --

Lead 2 6.6 <7.8 1

5.2 --

Manganese 2 1,320 537 928 --

Nickel 2 1.7 1.3 1.5 --

Zinc 2 231 171 201 --

Hydropsyche occidentalis

Arsenic 21 7.3 2.9 4.7 4.2

Cadmium 41 1.8 0.3 1.0 0.9

Chromium 41 5.0 0.6 2.0 1.8

Copper 41 102 27.4 49.6 45.3

Iron 41 2,590 472 1,270 1,160

Lead 41 14.2 2.8 6.5 5.7

Manganese 41 1,600 454 855 813

Nickel 41 3.2 0.6 1.3 1.2

Zinc 41 416 145 216 221

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 --

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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

12340000—Blackfoot River near Bonner

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006–15

Arctopsyche grandis

Arsenic 14 4.6 1.6 2.7 2.4

Cadmium 24 0.5 0.1 0.3 0.3

Chromium 19 6.9 0.5 2.1 1.5

Copper 24 19.3 9.9 13.7 12.8

Iron 24 1,880 108 758 769

Lead 24 2.3 0.5 1.1 0.9

Manganese 19 633 286 444 422

Nickel 19 3.7 0.7 1.4 1.2

Zinc 24 170 106 143 144

Claassenia sabulosa

Arsenic 13 3.0 0.1 1.0 0.7

Cadmium 24 0.2 0.1 0.1 0.2

Chromium 19 5.2 0.3 1.0 0.7

Copper 24 88.5 19.0 43.3 44.0

Iron 24 317 46.2 144 137

Lead 24 0.8 0.1 0.3 0.2

Manganese 19 133 26.3 79.3 73.4

Nickel 19 1.1 0.1 0.3 0.3

Zinc 24 399 117 229 207

Hydropsyche cockerelli

Arsenic 9 4.2 2.1 3.0 3.0

Cadmium 9 0.6 <0.1 1

0.3 10.3

Chromium 9 5.7 1.6 3.2 3.6

Copper 9 17.5 5.6 14.6 15.5

Iron 9 2,390 1,120 1,730 1,640

Lead 9 2.6 1.5 2.0 2.0

Manganese 9 814 409 558 516

Nickel 9 4.6 1.4 2.2 1.9

Zinc 9 165 132 149 147

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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

12340000—Blackfoot River near Bonner—Continued

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006–15

Hydropsyche occidentalis

Arsenic 16 3.8 1.2 2.2 2.1

Cadmium 28 0.5 0.1 0.2 0.2

Chromium 28 5.8 0.8 2.2 1.9

Copper 28 20.9 12.0 15.9 15.8

Iron 28 2,090 927 1,470 1,480

Lead 28 2.0 0.8 1.5 1.6

Manganese 28 798 412 520 461

Nickel 28 4.9 0.9 1.6 1.4

Zinc 28 202 116 145 145

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 0.6 --

Chromium 1 -- -- 1.6 --

Copper 1 -- -- 13.9 --

Iron 1 -- -- 1,140 --

Lead 1 -- -- 2.9 --

Manganese 1 -- -- 525 --

Nickel 1 -- -- 2.8 --

Zinc 1 -- -- 132 --

12340500—Clark Fork above Missoula

Period of record for biological data: 1997–2015

Arctopsyche grandis

Arsenic 35 7.2 1.2 3.6 3.5

Cadmium 54 2.3 0.1 1.0 0.8

Chromium 54 4.2 0.4 1.6 1.4

Copper 54 81.2 13.7 37.2 31.1

Iron 54 2,340 302 972 839

Lead 54 8.8 1.1 3.9 3.6

Manganese 54 1,410 476 892 868

Nickel 54 2.1 0.3 1.1 1.1

Zinc 54 272 133 198 197

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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

Table 26. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2015.—

Continued

[Reported concentrations are in microgram 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. 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—Continued

Period of record for biological data: 1997–2015

Claassenia sabulosa

Arsenic 24 1.9 0.1 1.2 1.2

Cadmium 33 2.0 0.2 0.8 0.7

Chromium 33 1.4 0.1 0.7 0.7

Copper 33 81.1 25.8 51.2 48.6

Iron 33 424 82.0 218 226

Lead 33 3.1 0.2 0.9 0.8

Manganese 33 683 57.8 186 142

Nickel 33 0.7 0.2 1

0.4 10.4

Zinc 33 379 191 275 271

Hydropsyche cockerelli

Arsenic 25 8.9 2.4 5.5 5.4

Cadmium 34 2.0 0.4 0.9 0.9

Chromium 34 6.0 1.0 2.8 2.4

Copper 34 99.7 24.4 58.9 57.1

Iron 34 3,590 830 1,900 1,860

Lead 34 12.1 2.5 7.0 6.3

Manganese 34 1,910 764 1,160 1,170

Nickel 34 2.4 0.9 1.8 1.7

Zinc 34 266 156 216 218

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/
Dodge and others—Water-Quality, Bed-Sediment, and Biological Data, and Statistical Summaries of Data, Clark Fork Basin, Montana—OFR 2016–1201

ISSN 0196-1497 (print)

ISSN 2331-1258 (online)

https://doi.org/10.3133/ofr20161201