U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2015–1223

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

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

2013 through September 2014) and Statistical Summaries of 

Data for Streams in the Clark Fork Basin, Montana
Cover photograph. Blackfoot River near Bonner (12340000). Photograph by Kent A. Dodge, U.S. Geological Survey.
Water-Quality, Bed-Sediment, and 

Biological Data (October 2013 through 

September 2014) and Statistical Summaries 

of Data for Streams in the Clark Fork Basin, 

Montana

By Kent A. Dodge and Michelle I. Hornberger

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

Open-File Report 2015–1223

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

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Suggested citation:

Dodge, K.A., and Hornberger, M.I., 2015, Water-quality, bed-sediment, and biological data (October 2013 through September 2014) and statistical summaries of data for streams in the Clark Fork Basin, Montana: U.S. Geological Survey 

Open-File Report 2015–1223, 125 p., http://dx.doi.org/10.3133/ofr20151223.

ISSN 0196-1497 (print)

ISSN 2331-1258 (online)

ISBN 978-1-4113-4003-9
iii

Contents

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Figures

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

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 2013 through

September 2014...........................................................................................................................20

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

Lodge, Montana, October 2013 through September 2014....................................................40

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

Bridge, near Bonner, Montana, October 2013 through September 2014...........................44

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

Bonner, Montana, October 2013 through September 2014..................................................48

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

Missoula, Montana, October 2013 through September 2014 ..............................................52

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

statistics at Mill Creek at Opportunity, Montana, April through September 2014 ...........56

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

statistics at Willow Creek at Opportunity, Montana, April through September

2014 ...............................................................................................................................................58

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

statistics at Warm Springs Creek at Warm Springs, Montana, April through

September 2014...........................................................................................................................60

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

statistics at Lost Creek near Anacona, Montana, April through September 2014...........62

13. Analyses of field replicates for water samples, Clark Fork Basin, Montana ...................64

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

Montana ......................................................................................................................................68

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

Basin, Montana...........................................................................................................................69

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

samples ........................................................................................................................................70

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

Basin, Montana...........................................................................................................................70

18. Analyses of field blanks for water samples ...........................................................................71

19. Bed-sediment data for the Clark Fork Basin, Montana, August 2014................................72

20. Recovery efficiency for analyses of standard reference materials for

bed-sediment samples...............................................................................................................73

21. Analyses of procedural blanks for bed-sediment samples.................................................74

22. Biological data for the Clark Fork Basin, Montana, August 2014 .......................................75

23. Recovery efficiency for analyses of certified reference material for biota samples .....76

24. Analyses of procedural blanks for biota samples.................................................................77

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

Montana, March 1985 through September 2014 ...................................................................78

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

Montana, August 1986 through August 2014..........................................................................98
v

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

August 1986 through August 2014..........................................................................................103

Conversion Factors

Inch/Pound 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 microgram per gram (μg/g)

ton 907.2 kilogram (kg) 

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

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

°F=(1.8×°C)+32

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 of the following 

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

water year 2014 is the period from October 1, 2013, through September 30, 2014.
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 2013 through September 2014) and Statistical 

Summaries of Data for Streams in the Clark Fork Basin, 

Montana

By Kent A. Dodge and Michelle I. Hornberger

Abstract

Water, bed sediment, and biota were sampled in streams 

from Butte to near Missoula, Montana, as part of a monitoring program in the upper Clark Fork Basin of western Montana. The sampling program was led by the U.S. Geological 

Survey, in cooperation with the U.S. Environmental Protection Agency, to characterize aquatic resources in the Clark 

Fork Basin, with emphasis on trace elements associated with 

historic mining and smelting activities. Sampling sites were 

located on the Clark Fork and selected tributaries. Water samples were collected periodically at 20 sites from October 2013 

through September 2014. Bed-sediment and biota samples 

were collected once at 14 sites during August 2014.

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

samples collected at sites from October 2013 through September 2014. Water-quality data include concentrations of selected 

major ions, trace elements, and suspended sediment. At 12 

sites, dissolved organic carbon and turbidity samples were collected. In addition, nitrogen (nitrate plus nitrite) samples were 

collected at two sites. Daily values of mean suspended-sediment concentration and suspended-sediment discharge were 

determined for four 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 wholebody 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 (2015) 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 get deposited farther downstream in stream 

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

at the location of the former Milltown Reservoir whose dam 

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

1987). The occurrence of elevated trace-element concentrations in water and bed sediment can pose a potential risk to 

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

Concern about the potential toxicity of trace elements 

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

to characterize the aquatic resources in the upper Clark Fork 

Basin to guide and monitor remedial cleanup activities. 

A long-term database was considered necessary to detect 

trends over time to evaluate the effectiveness of remediation. 

Water-quality data have been collected by the U.S. Geological 

Survey (USGS) at selected sites in the upper Clark Fork Basin 

since 1985 (Lambing, 1987 through 1991; Lambing and others, 1994, 1995; Dodge and others, 1996 through 2010, 2012 

through 2013, 2014a, 2014b). Trace-element data for bed sediment and biota (aquatic benthic insects) have been collected 
2 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

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 14 sites in the 

Clark Fork Basin from October 2013 through September 2014 

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

bed-sediment, and biota samples collected during the same 

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

for the period of record.

Sampling Locations and Types of Data

Sampling sites for the monitoring program in the upper 

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

located on the Clark Fork main stem (including Silver Bow 

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

Creek, and Blackfoot River), and three smaller tributaries (Mill 

Creek, Willow Creek, and Lost Creek). The sites, types of data 

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

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

the upper Clark Fork into reaches of approximate uniform 

length, with each reach encompassing either a major tributary 

or depositional environment (Warm Springs Ponds and the 

former Milltown Reservoir). Major tributaries were sampled to 

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

Basin and to provide reference comparisons to the main stem. 

The three smaller tributaries were sampled to gain better spatial 

resolution on sources of metals entering the Clark Fork in an 

area of historical metal-processing activities near Anaconda, 

Montana. Water-quality samples were collected periodically at

20 sites. Daily suspended-sediment samples were collected at 

four sites, and daily turbidity data were measured by continuous turbidity monitors recording every 15 minutes at four sites. 

Bed-sediment and biological samples were collected annually 

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

Warm Springs) 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, bedsediment, and biota samples; and quality-assurance data for 

water year 2014 are listed in tables 4 through 24 at the back of 

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

bed-sediment, and biological data collected between March 

1985 and September 2014 are listed in tables 25 through 27 at 

the back of the report.

Quality assurance of data was maintained through the use

of documented procedures described in the following sections, 

which were designed to provide environmentally representative data. Acceptable results of the procedures were verified

with quality-control samples that were collected systematically 

to provide a measure of the accuracy, precision, and bias of the 

environmental data, and to identify problems associated with 

sampling, processing, or analysis.

Water-Quality Data

Water-quality data consist of onsite measurements of 

selected stream properties and laboratory determination 

of concentrations of chemical and physical constituents in 

periodically collected stream samples. Water samples were 

collected at 20 sites in the upper Clark Fork Basin 6–8 times 

per year on a schedule designed to describe seasonal and 

hydrologic variability. At the four daily suspended-sediment 

sites, suspended-sediment samples were collected by a contract observer 2–10 times per week, depending on season and 

flow conditions. Continuous turbidity monitors were operated seasonally (April to September 2014) at four sites near 

Warm Springs and Anaconda; turbidity data (recorded every 

15 minutes) were used to compute daily mean turbidity values 

(table 1).

Methods

Water samples were collected and composited from vertical transits throughout the entire stream depth at multiple locations across the stream by using depth- and width-integration 

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

Glysson (1999), and the U.S. Geological Survey (variously 

dated). These methods provide a vertically and laterally discharge-weighted composite sample that is intended to be representative of the entire flow passing through the cross section

of a stream. Samplers consisted of isokinetic 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.

Instantaneous streamflow was determined at the time of

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

streamflow values during ice periods were estimated because

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

were made during collection of periodic water samples. Onsite 

sample processing, including filtration and preservation, was

completed according to procedures described by Ward and 
Water-Quality Data 3

Mill Creek

Willow

Creek

Cr Silver

Bow

Opportunity

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

Warm Springs Cr

Silver

Bow

Creek

Blacktail

Cr

CONTINENTAL

Base modified from 

U.S. Geological Survey, 

State base map, 1966, 

1:100,000

North American Datum of 1927 

0 10 20 MILES

0 10 20 KILOMETERS

12340500

12340000

12334550

12331800

12324680

12324200

12323800

12323750 12323770

12323600

12323250

12323700

12323720

Lost Cr 12323850

46°

114°

113°

12323230

Racetrack

12323840

12323670

Mill

Creek

Willow

Creek

12323710

Creek

47°

Helena

M O N T A N A

Streamflow site type

 Continuous record

 Periodic measurement

Water-quality, bed-sediment, 

and biota site type

 Periodic water quality

 Daily suspended sediment

 Daily turbidity

 Once-annual bed sediment

 Once-annual biota

EXPLANATION

Site number

461903112440701 Miscellaneous site number

12324200

12323760

Dempsey

Creek 461903112440701

461559112443301

461415112450801

Study area

former

12324400

Warm Springs

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

Station number 

(fig. 1) Station name

Continuousrecord 

streamflow

Periodic 

water quality1

Daily suspended 

sediment

Daily turbidity 

(seasonal)

Fine-gra

bed sedi

12323230 Blacktail Creek at Harrison Avenue, at Butte -- 03/1993–08/1995, 12/1996–08/2003, 

12/2004–P

-- -- -- 

12323250 Silver Bow Creek below Blacktail 

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

-- 07/199

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

-- 07/199

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, 0

08/1999, 008/2005, 0

08/2011, 0

12323800 Clark Fork near Galen 07/1988–P 07/1988–P -- -- 08/198

08/199

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

-- -- -- -- 08/199

461559112443301 Clark Fork at county bridge, near 

Racetrack

-- -- -- -- 08/199

461903112440701 Clark Fork at Dempsey Creek 

diversion, near Racetrack

-- -- -- -- 08/199
Table 1. Type and period of data collection at sampling sites in the Clark Fork Basin, Montana.—Continued[--, no data; P, present; D, discontinued]

Station number 

(fig. 1) Station name

Continuousrecord 

streamflow

Periodic 

water quality1

Daily suspended 

sediment

Daily turbidity 

(seasonal)

Fine-gra

bed sedi

12324200 Clark Fork at Deer Lodge 10/1978–P 03/1985–P 03/1985–08/1986, 

04/1987–03/2003, 

08/2003–P

-- 08/1986–0

08/199

12324400 Clark Fork above Little Blackfoot 

River, near Garrison

02/2009–P 03/2009–P -- -- 08/200

12324680 Clark Fork at Goldcreek 10/1977–P 03/1993–P -- -- 07/19912331800 Clark Fork near Drummond 04/1993–P 03/1993–P -- -- 08/1986, 0

08/199

12334550 Clark Fork at Turah Bridge, near 

Bonner

03/1985–P 03/1985–P 03/1985–03/2003, 

08/2003–P

-- 08/198

08/199

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

06/1988–09/1995,

10/2005–P

-- 08/1986–0

08/199

08/1993–008/1998–0

09/200

08/200

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 08/199

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

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 nea

2Laboratory analyses of aquatic benthic insects for trace elements.3Before October 1989, water-quality data for Clark Fork above Missoula included only suspended-sediment data.
6 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Harr (1990), Horowitz and others (1994), and the U.S. Geological Survey (variously dated).

Composite water samples were analyzed for the constituents listed in table 2. Filtered (0.45-micrometer [μm] 

pore size) and unfiltered recoverable concentrations of trace

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

and zinc); 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 for the 

calculation of water hardness.

Filtered concentrations of arsenic, cadmium, copper, 

lead, manganese, and zinc were measured using inductively 

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

Garbarino and others, 2006). At select sites in the upper 

basin, filtered concentrations of potassium, sodium, alkalinity,

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

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

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

whereas nitrogen (nitrate plus nitrite) was measured using the 

enzymatic reduction, colorimetric reduction method (Patton 

and Kryskalla, 2011). Filtered concentrations of calcium, magnesium, and iron were measured using inductively coupled 

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

1993). Unfiltered recoverable concen­trations of trace elements

were measured in unfiltered sam­ples that were first digested

with dilute hydrochloric acid (Hoffman and others, 1996). For 

cadmium, iron, lead, and manganese, the digested samples 

were analyzed by ICP–MS as described by Garbarino and 

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

samples were analyzed by ICP–MS as described by Garbarino 

and others (2006). Selected unfiltered samples were measured

for turbidity by the NWQL using Standard Method 2130

(American Public Health Association and others, 1998).

Water samples for analysis of suspended sediment also 

were collected from multiple vertical transits when periodic 

water samples were collected. These samples were analyzed 

for suspended-sediment concentration and the percentage of 

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

diameter (silt size and smaller) by the USGS 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 four daily suspended-sediment sites (table 1) were collected by local contract observers using the depth-integration method at a single 

vertical transit near midstream. The samples were analyzed 

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
Water-Quality Data 7

for suspended-sediment concentration and used to calculate 

daily mean suspended-sediment concentrations according to 

methods described by Porterfield (1972).

Suspended-sediment discharge is determined according 

to the following equation (Porterfield, 1972):

sws ××= kCQQ , (1)

where

Qs is suspended-sediment discharge, in tons per 

day;

Qw is streamflow, in cubic feet per second;

Cs is suspended-sediment concentration, in 

milligrams per liter; and

k is a units-conversion constant (0.0027) 

to convert instantaneous suspendedsediment discharge to an equivalent daily 

suspended-sediment discharge.

Turbidity data were measured using continuous turbidity 

monitors (Yellow Springs Instruments Company [YSI] 6136 

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

Basin near Anaconda (table 1). The turbidity sites are operated seasonally, generally from early spring (after ice breakup) 

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

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

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 0.28 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 --
8 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

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

These values differ from the turbidity values resulting 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 value for each day as well as a daily 

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

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

described by Wagner and others (2006).

Results

Water-quality data from samples collected periodically 

during water year 2014 (October 1, 2013 through September 

30, 2014) are listed in table 4. Daily mean streamflow, daily

mean suspended-sediment concentration, and daily suspendedsediment discharge for water year 2014 at the four daily 

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

with monthly summary statistics and annual totals for streamflow and suspended-sediment discharge. Daily maximum,

minimum, and mean turbidity at four sites are listed in tables 9 

through 12 along with monthly summary statistics.

Quality Assurance

Quality-assurance procedures used for the collection and

field processing of water samples are described by Ward and

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

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

internal sample handling and quality assurance are described 

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

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

Wyoming-Montana Sediment Laboratory are described by 

Dodge and Lambing (2006). Standard procedures used for the 

calibration, measurement, and quality assurance of turbidity 

monitors are described by Anderson (2005).

The quality of analytical results reported for water 

samples was evaluated using quality-control samples that 

were submitted from the field and analyzed concurrently in

the laboratory with routine samples. These quality-control 

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

overall field and laboratory process. Each type of 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 (http://bqs.usgs.gov). The 

laboratory also participates in external evaluation studies and 

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

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

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

results. Replicate samples are two or more samples considered 

to be essentially identical in composition. Replicate samples 

can be collected in the field (field replicate) either by repeating the collection process to obtain two or more independent 

composite samples or by splitting a single composite sample 

into two or more subsamples. The individual replicate samples 

are then analyzed separately. Likewise, a single sample can 

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

measure of analytical precision (laboratory replicate).

Precision of analytical results for field replicates can be

affected by numerous sources of variability within the field

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

samples exposed to field and laboratory sources of variability,

replicate stream samples for chemical analysis were obtained 

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

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

reproducibility of environmental data that are affected by the 

combined potential variability introduced by field and laboratory processes.

Precision of analytical results for laboratory replicates, 

which exclude field sources of variability, was determined

using two independent chemical analyses of aliquots from a 

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

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

sample collection and processing. Laboratory replicates are 

not obtainable for suspended-sediment samples because the 

samples are consumed during the analysis.

Spiked samples are used to evaluate bias, which measures 

the ability of an analytical method to accurately quantify a 

known amount of analyte added to a sample. Because some 

constituents in stream water potentially can interfere with the 

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

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

and aliquots of stream samples were spiked in the laboratory 
Water-Quality Data 9

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 possible occurrence of a false positive or false negative error to 1 percent or 

less. Accordingly, concentrations are reported as less than the 

LRL for samples in which the analyte was not detected. The 

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

National Water Quality Laboratory 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):

k

d

S

2

2

∑ = , (2)

where

S is the standard deviation of the difference in 

concentration between replicate analyses,

d is the difference in concentration between 

each pair of replicate analyses, and

k is the number of pairs of replicate analyses.

Precision also can be expressed as a relative standard 

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

standard deviation and the mean concentration for all the 

replicate analyses. Expressing precision relative to a mean 

concentration standardizes the comparison of precision among 

individual constituents. The RSD is calculated according to 

the following equation (Taylor, 1987):

×= 100

x

S RSD , (3)

where

RSD is the relative standard deviation,

_S is the standard deviation, and

x is the mean concentration for all replicate 

analyses.

Paired analyses of field replicates are listed in table 13. The

overall precision for each constituent estimated from analyses 

of field replicates, which include field and laboratory sources of

variability, is listed in table 14. The data-quality objective used 

to indicate acceptable precision of results for field replicates was

a maximum RSD of 20 percent (table 3). Precision estimates

for the analytical results of field replicates within the 20-percent RSD limit for all constituents (table 14) except turbidity. 

This one exceedance of the data-quality objective resulted from 

a statistical artifact of calculating the difference between one 
10 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

replicate sample pair for which one value exceeds the LRL, and 

one that does not.

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

of variability, is listed in table 15. Statistics for the precision 

of analytical results for laboratory replicates are calculated 

by using unrounded values stored in labora­tory data files. The

data-quality objective used to indicate acceptable precision 

of results for laboratory replicates was a maximum RSD of 

20 percent (table 3). Precision estimates for the laboratory replicates were within the 20-percent RSD limit for all constituents (table 15). No adjustments were made to analytical data 

on the basis of replicate analyses precision.

Recov­ery efficiency for analyses of constituents is

determined by comparison of a sample and a spiked aliquot 

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

spike recovery of trace elements in water samples determined 

by NWQL was a maximum devia­tion of 25 percent from a

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

At the laboratory, a spiked deionized-water blank sample and a 

spiked aliquot of a stream sample were prepared and analyzed 

along with the original unspiked sample. The differences 

between the spiked and unspiked sample concentrations were 

determined and used to compute recovery, in percent, according to equation 4:

×= 100

C

D R , (4)

where

R is the spike recovery, in percent;

D is the difference between the spiked and 

unspiked sample concentrations; and

C is the concentration of material used to spike 

the sample.

If the spike recovery of a trace element was outside 

a range of 75 to 125 percent, the instrument was recalibrated and the entire sample set and all spiked samples were 

reanalyzed for that particular trace element until recoveries 

were improved to the extent possible. Recovery efficiency

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

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

recovery for deionized-water blank samples spiked with trace 

elements (table 16) ranged from 94.7 to 110 percent with 

the smallest individual constituent recovery being arsenic, 

filtered, at 87.6 percent and the largest being zinc, filtered,

at 117 percent. The 95-percent confidence intervals (Taylor, 1987) for the mean spike recovery for each constituent 

for which deionized-water blank samples were analyzed 

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

expected 100-percent recovery. The mean spike recovery for 

spiked stream samples (table 17) ranged from 88.9 to 103 

percent with the smallest individual constituent recovery 

being arsenic, filtered, at 82.7 percent and the largest being

cadmium, filtered, at 110 percent. The 95-percent confidence

intervals for the mean spike recovery for each constituent for 

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

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

recovery. No adjustments were made to analytical data on the 

basis of the mean spike recovery.

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

indicating a consistent deviation or bias, either high or low. 

Confidence intervals for percent recovery include 100 percent for all laboratory-spiked deionized-water blank samples 

(table 16) except for filtered zinc (103–117 percent). Confidence intervals for percent recovery include 100 percent for 

all laboratory-spiked stream samples (table 17) except for 

unfiltered cadmium (92.0–99.0 percent), unfiltered copper

(89.8–97.8 percent), and unfiltered zinc (83.1–94.6 percent).

Because the mean spike recoveries for all constituents of 

laboratory-spiked stream samples met data-quality objectives 

(less than a 25-percent deviation from 100-percent recovery), 

no adjustments were made to analytical results for stream 

samples on the basis of spike recoveries.

Analytical results for field blanks are listed in table 18.

A field blank with constituent concentrations 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 18) were

almost always less than the LRL. Two sample concentrations 

of filtered silica (0.069 and 0.023 milligrams per liter [mg/L])

exceeded the LRL of 0.018 mg/L. One sample concentration of unfiltered copper (1.5 micrograms per liter [μg/L])

exceeded the LRL of 0.80 μg/L. One sample concentration of 

unfiltered lead (0.06 μg/L) exceeded the LRL of 0.04 μg/L.

Three sample concentrations of filtered manganese (all three

were 0.41 μg/L) exceeded the LRL of 0.40 μg/L. The systematic presence of filtered manganese has been documented

and is currently (2015) being reviewed by the USGS Office

of Water Quality. No adjustments were made to water-quality

sample data pending the results of this review.
Bed-Sediment Data 11

Bed-Sediment Data

Bed-sediment data for the long-term monitoring program 

in the Clark Fork Basin consist of trace-element concentrations in the fine-grained (less than 0.063 mm) fraction of bedsediment samples. Bed-sediment samples are collected once 

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

conditions at about the same time of year as previous samples 

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

Warm Springs Creek at Warm Springs is sampled once every 

3 years rather than once annually and was sampled during 

water year 2014.

Methods

Fine-grained bed-sediment samples were collected in 

August 2014 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 polyestermesh sieve using ambient stream water. The fraction of bed 

sediment in each composite sample that was finer than 0.063

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

Bed-sediment samples were processed and analyzed at 

the USGS National Research Program Ecology and Contaminants Project Laboratory in Menlo Park, California. Bedsediment samples were oven-dried at 60 degrees Celsius (°C) 

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

ceramic mortar and pestle. Single aliquots of approximately 

0.5–0.6 grams (g) of sediment from each of the three composite 

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

nitric acid reflux according to methods described by Luoma

and Bryan (1981). Laboratory replicates were analyzed by 

taking an aliquot from one of the three sieved replicate samples 

at each station. After a 2-week digestion period, the aliquots 

were evaporated to dryness on a hot plate. The dry residue was 

reconstituted in 10 mL of 0.6N (normal) hydrochloric acid. 

The reconstituted aliquots were then filtered through a 0.45-

μm pore-size filter by using a syringe and an in-line disposable

filter cartridge. The filtrate was diluted to a 1:10 ratio with

0.6N hydro­chloric acid. These final solutions were analyzed for

arsenic, cadmium, chromium, copper, iron, lead, manganese, 

nickel, and zinc by using inductively coupled plasma-optical 

emission spectrometry (ICP–OES). The smallest concentration 

of a constituent that can be reliably reported for analyses of bed

sediment is termed the minimum reporting level (MRL).

Results

Concentrations of trace elements measured in samples of 

fine-grained bed sediment collected during August 2014 are

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

microgram per milliliter, were analyzed in the reconstituted 

aliquots of digested bed sediment. Solid-phase concentrations, 

measured in microgram per gram, were calculated using the 

following equation:

 . (5)

where

μg/g is micrograms per gram,

μg/mL is microgram per liter, and

mL is millimeter.

The reported solid-phase concentrations (table 19) are 

the means of all analyses for replicate aliquots from each 

composite bed-sediment sample collected at the site. Because 

the conversion from liquid-phase to solid-phase concentration 

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

sample, MRLs for some trace elements might differ among 

stations and among years.

Quality Assurance

The USGS protocols for field collection and processing

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

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

with deionized water before the collection of the first sample.

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

a final rinse onsite with stream water. Sampling equipment

used at more than one site was rinsed thoroughly between sites 

with stream water. Separate sieves were used at each site and, 

therefore, did not require between-site cleaning. Bed-sediment 

samples were collected sequentially at sites along a general 

increasing concentration gradient (downstream to upstream 

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

contamination.

Quality assurance of analytical results for bed-sediment

samples included laboratory instrument calibration with 

standard solutions and analysis of quality-control samples 

designed to identify the presence and magnitude of bias (Ellen 

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

Quality-control samples consisted of standard reference materials (SRMs), issued by the National Institute of Standards and 

Technology (NIST), and procedural blanks. Ten low-concentration SRMs, 10 high-concentration SRMs, and 14 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 

( ) ( )

( ) ( )

μg/mL volumeof digested sample, in mL μg/g dry weight of sample, in grams dilution ratio =
12 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

method to accurately measure a known quantity of a constituent. Multiple analyses of SRMs are made to derive a mean 

and 95-percent confidence interval for recovery. Recovery efficiency for trace-element analyses of SRMs for bed sediment is 

listed in table 20. Two SRMs, consisting of agricultural soils 

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 20) 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 38.7 to 

90.9 percent of the certified concentrations (table 20). The

mean recoveries were within 30 percent of the 95-percent 

confidence interval for arsenic, copper, manganese, nickel,

and zinc. Elements with relatively low certified concentrations (cadmium, 0.371 micrograms per gram [μg/g]) or with

a strong association with crystalline lattices (chromium, lead) 

had lower percent recoveries (between 40 and 65 percent). 

Mean recoveries in SRM 2711a ranged from 49.9 to 98.6 percent (table 20). The percent recoveries were within 20 percent 

of the 95-percent confidence interval for arsenic, cadmium,

copper, iron, lead, manganese, nickel, and zinc. Chromium 

had the lowest mean recovery (49.9 percent) 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 same reagents used for sample digestion and reconstitution. Concentrated nitric acid used for sample digestion 

was heated and evaporated to dryness. After evaporation, 

0.6N hydrochloric acid was added to reconstitute the dry

residue. Procedural blanks, therefore, represent the same

chemical matrix and exposure to analytical materials and

handling as the reagents used to digest and reconstitute bedsediment samples. Analytical results of procedural blanks for

bed sediment (table 21) are reported as a liquid-phase concentration, in microgram 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. 

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 annually, and was sampled during water year 2014.

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, 
Statistical Summaries of Data 13

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 2014 are listed in 

table 22. The variability in the number of composite samples 

among species and among sites reflects differences in insect

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

concentrations, in microgram per milliliter, analyzed in the 

reconstituted samples were converted to solid-phase concentrations, in microgram per gram, by using equation 5 (used 

earlier in this report to calculate solid-phase concentrations 

of trace elements in bed sediment). All tissue samples were 

analyzed undiluted (dilution ratio 1:1). As with MRLs for trace 

elements in bed sediment, MRLs for trace elements in insects 

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

general, the smaller the biological-sample weight (primarily a 

function of insect abundance), the higher the MRL; therefore, 

higher MRLs do not necessarily imply a higher trace-element 

concentration in tissue.

Quality Assurance

The 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 10 replicates

of the certified reference material (CRM) TORT-2 (lobster

hepatopancreas), 7 replicates of the CRM TORT-3 (also 

lobster hepatopancreas), and 14 procedural blanks (1 at each 

site). Both CRMs were purchased from the National Research 

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

version of the CRM standard. 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

CRM samples TORT-2 and TORT-3 are listed in table 23. 

Data-quality objectives have not been established for analytical recovery in biota, but percent recoveries indicate analytical 

performance. Mean CRM recoveries for TORT-2 ranged from 

76.4 to 139 percent for all constituents. The mean recoveries 

for arsenic, cadmium, copper, iron, lead, manganese, and zinc 

were within 20 percent of the certified value (based on the

95-percent confidence interval). Chromium had a higher percent recovery (139 percent), whereas nickel had a slightly low 

recovery (76.4 percent), due in part to the relatively low certified concentrations in the standard (0.77 μg/g and 2.5 μg/g,

respectively). Mean CRM recoveries for TORT-3 ranged from 

78.8 to 179 percent for all constituents. The mean recoveries were within 14 percent for arsenic, cadmium, chromium, 

copper, iron, manganese, nickel, and zinc. Mean recovery was 

high for lead (179 percent), likely due to the relatively low 

certified value 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 24) 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 25 through 27 for the period of record at each 

site. The summaries include the period of record; number 

of samples; and maximum, minimum, mean, and median 

concentrations.

Statistical summaries of water-quality data (table 25) are 

based on results of cross-section samples collected periodically by the USGS for the long-term monitoring program in 

the Clark Fork Basin during the period of record for each site. 

The summaries do not include data for supplemental samples 

collected at selected sites that targeted high-flow conditions or

maintenance drawdowns of Milltown Reservoir, which might 

disproportionately skew the long-term statistics relative to 

the other sites in the network. Statistical summaries of bedsediment (table 26) and biological data (table 27) are based on 
14 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

results of samples collected once during the indicated years. 

Because not all sites were sampled for bed sediment and biota 

every year, the data for some sites do not represent a consecutive annual record. Statistical summaries are not presented for 

discontinued sites.

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

the mean trace-element concentrations determined for each 

year from the mean of the analyses of composite samples; 

therefore, the number of samples for bed sediment represents 

the number of years that the constituent was analyzed. The 

number of samples for arsenic for bed sediment is smaller 

than the number for other trace elements because sampling for 

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

samples analyzed for silver in bed sediment is smaller because 

analysis for this constituent was discontinued in 2004.

In contrast, statistics for biological data (table 27) are 

based on individual analyses for each composite sample collected rather than on a single mean concentration for each 

year. Differences in the number of composited biota samples 

among species reflect differences in species abundance, both

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

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

individual composite samples were averaged. Also, the number of samples for arsenic in biota samples is smaller than the 

number for other trace elements because sampling for arsenic 

began in September 2003. The abundance of aquatic insects at 

a particular site in a given year limits the biomass of the sample, which in turn may result in varied MRLs. When MRLs 

vary among years, differences in concentration with time are 

difficult to determine, especially when a large percentage of

the samples have concentrations less than MRLs.

The presence or absence of insect species at a given site 

can vary among years and may result in different taxa being 

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

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

based on the results of all Hydropsyche species combined. At 

some sites, statistics for the Hydropsyche morosa group are 

based on the combined results for two or more species because 

these samples could not be clearly identified to the species

level, but the individual insects had morosa characteristics.

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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., 2009, 

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through September 2010) and statistical summaries of data 

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through September 2011) and statistical summaries of data 

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

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through September 2012) and statistical summaries of data 

for streams in the Clark Fork Basin, Montana: U.S. Geological Survey Open-File Report 2014–1034, 121 p. [Also 

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

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

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

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U.S. Geo­logical Survey National Water Quality Laboratory—Deter­mination of inorganic and organic constituents

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

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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 

and fluvial sediments: U.S. Geological Survey Techniques

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samples using collision/reaction cell inductively coupled 

plasma-mass spectrometry: U.S. Geological Survey Techniques and Methods, book 5, sec. B, chap. 1, 88 p.

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

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98–165, 101 p.

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

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Water Quality Laboratory—In-bottle acid digestion of

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

Report 96–225, 28 p.

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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 

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

Open-File Report 97–669, 84 p.

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

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

for the collection and processing of surface-water samples 

for the subsequent determination of inorganic constituents 

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

94–539, 57 p.

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

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

and selected tributaries from Deer Lodge to Milltown, 

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

Survey Open-File Report 87–110, 48 p.

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

September 1987) and statistical summaries (March 1985 

through September 1987) for the Clark Fork and selected 

tributaries from Deer Lodge to Missoula, Montana: 

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

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

through September 1988) and statistical summaries (March 

1985 through September 1988) for the Clark Fork and 

selected tributaries from Galen to Missoula, Montana: 

U.S. Geological Survey Open-File Report 89–229, 51 p.
References Cited 17

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

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

gov/of/2006/1275/.]

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

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

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

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

Report 95–429, 104 p.

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

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

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

September 1993) for streams in the upper Clark Fork 

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

94–375, 85 p.

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

of the form of trace metals in oxidized estuarine sediments 

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

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[Also available at http://pubs.usgs.gov/tm/05b08/].

Porterfield, George, 1972, Computation of fluvial-sediment

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

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Paper 2175, v.2, 631 p.

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

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

Clark Fork River Superfund Site—Record of decision,

part 2—Decision summary: U.S. Environmental Protection

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

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

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Open-File Report 90–140, 71 p.

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

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.

[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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/04/2013 0940 6.7 7.6 308 4.0 -- 125 35.9 8.67

03/24/2014 1015 6.5 7.7 312 2.5 <2.0 120 34.2 8.51

04/21/2014 0920 21 7.5 216 4.0 E3.0 78.6 22.7 5.30

05/12/2014 1120 32 7.5 199 3.0 E6.5 71.9 20.8 4.84

05/27/2014 0900 35 7.6 190 11.5 E3.4 74.0 21.2 5.10

06/09/2014 0900 15 7.6 217 10.0 E5.6 87.4 24.8 6.17

07/14/2014 0850 6 7.6 303 12.0 E2.0 121 34.6 8.53

08/11/2014 0850 4 7.6 338 10.0 <2.0 143 40.7 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 

(mg/L)

Nitrate 

plus nitrite, 

filtered 

(mg/L)

Cadmium, 

filtered 

(μg/L)

11/04/2013 2.57 12.5 84.7 14.2 0.22 25.9 40.2 -- <0.030

03/24/2014 3.59 12.5 96.5 14.8 0.21 24.6 32.8 1.18 <0.030

04/21/2014 2.98 9.86 60.9 11.9 0.19 19.7 23.7 0.29 0.034

05/12/2014 2.35 10.2 54.5 9.76 0.18 22.1 25.0 0.20 0.042

05/27/2014 2.48 8.05 63.4 6.16 0.19 23.2 19.0 0.16 0.031

06/09/2014 2.20 8.08 75.1 7.77 0.20 22.9 18.9 0.35 0.035

07/14/2014 2.66 11.6 101 12.3 0.27 27.0 27.3 1.08 <0.030

08/11/2014 2.81 13.5 113 13.7 0.25 24.9 31.7 1.22 <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)

11/04/2013 <0.030 1.3 2.2 80.5 258 0.055 0.27 41.7 48.0

03/24/2014 <0.030 1.7 3.1 159 410 0.070 0.42 78.3 87.8

04/21/2014 0.034 4.8 9.0 409 738 0.349 0.74 37.5 46.1

05/12/2014 <0.030 6.2 11.3 279 813 0.232 1.08 29.5 43.7

05/27/2014 0.037 6.0 7.8 270 609 0.180 0.64 36.2 49.9

06/09/2014 0.040 3.4 5.9 398 1,080 0.191 0.83 50.4 94.0

07/14/2014 <0.030 1.6 2.5 168 416 0.076 0.29 50.1 57.8

08/11/2014 <0.030 1.2 1.6 52.1 178 <0.040 0.13 40.9 43.9

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/04/2013 3.2 3.6 1.5 1.9 2.37 87 3 0.05

03/24/2014 3.0 4.5 2.1 2.6 3.39 85 3 0.05

04/21/2014 2.9 3.7 4.6 4.7 7.58 84 6 0.34

05/12/2014 2.8 6.5 3.5 4.5 8.18 93 10 0.86

05/27/2014 2.4 4.3 5.6 7.5 9.52 88 5 0.47

06/09/2014 2.1 4.3 4.8 7.3 7.64 93 9 0.36

07/14/2014 <2.0 2.3 4.1 4.9 3.27 96 2 0.03

08/11/2014 <2.0 2.1 2.1 2.5 1.80 93 1 0.01
Data 21

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/04/2013 1135 19 7.8 515 11.0 -- 172 48.2 12.5

03/24/2014 1145 19 7.6 522 5.0 E2.6 160 43.6 12.4

04/21/2014 1045 38 7.6 395 6.0 E4.4 132 35.0 10.7

05/12/2014 1310 51 7.8 333 7.0 E5.0 112 32.2 7.59

05/27/2014 1040 50 7.7 321 12.5 E5.3 105 30.1 7.21

06/09/2014 1025 31 8.0 400 12.0 E3.6 130 36.9 9.09

07/14/2014 1025 19 7.7 525 16.0 <2.0 162 45.6 11.6

08/11/2014 1040 17 7.6 533 16.0 E2.4 171 48.2 12.4

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)

11/04/2013 5.70 28.7 104 30.3 0.34 21.8 86.6 -- 0.069

03/24/2014 6.69 26.9 119 33.8 0.35 21.3 79.2 0.97 0.086

04/21/2014 4.70 19.1 88.6 25.9 0.28 19.6 58.0 0.52 0.058

05/12/2014 3.64 17.6 75.3 18.7 0.27 20.9 53.7 0.44 0.064

05/27/2014 3.96 16.6 82.9 15.7 0.26 21.8 46.0 0.34 0.048

06/09/2014 4.56 19.5 96.1 21.3 0.29 19.1 59.1 0.53 0.054

07/14/2014 6.07 27.6 80.5 31.3 0.40 20.8 85.2 1.03 0.065

08/11/2014 7.62 32.0 78.0 33.9 0.36 19.5 90.4 4.40 0.065

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)

11/04/2013 0.092 3.3 9.3 34.4 162 0.202 1.18 77.6 90.5

03/24/2014 0.121 5.4 12.3 102 270 0.283 1.36 130 139

04/21/2014 0.105 5.4 11.6 264 605 0.375 2.04 66.9 84.8

05/12/2014 0.103 6.7 14.2 197 624 0.285 2.07 60.1 78.2

05/27/2014 0.126 6.5 21.1 201 701 0.409 3.52 56.4 94.7

06/09/2014 0.106 4.6 12.7 207 679 0.292 2.10 67.2 90.7

07/14/2014 0.094 4.4 11.0 44.2 154 0.197 1.14 30.9 43.2

08/11/2014 0.099 4.2 12.2 36.6 100 0.277 0.96 33.2 38.3

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/04/2013 32.7 36.5 2.7 3.2 5.73 88 5 0.26

03/24/2014 40.3 44.9 3.3 3.6 7.49 80 4 0.21

04/21/2014 20.6 30.3 4.6 5.3 8.12 57 10 1.0

05/12/2014 15.1 24.9 4.2 5.1 8.35 66 11 1.5

05/27/2014 15.5 29.6 5.5 8.1 9.97 76 12 1.6

06/09/2014 17.5 27.7 4.5 6.6 8.91 83 8 0.67

07/14/2014 31.8 37.4 4.3 5.0 6.89 73 2 0.10

08/11/2014 42.3 47.5 3.9 4.3 7.66 74 3 0.14
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 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/05/2013 1135 31 8.2 545 -0.5 -- 194 57.2 12.4

03/24/2014 1325 49 8.0 526 5.0 E4.0 223 67.2 13.4

04/21/2014 1220 70 8.3 354 7.0 E5.7 124 37.4 7.48

05/12/2014 1445 130 8.3 308 8.5 E6.8 110 33.6 6.41

05/27/2014 1220 179 8.5 248 9.5 E7.5 99.8 31.0 5.45

06/09/2014 1215 99 8.6 296 12.0 E3.2 118 35.9 6.96

07/14/2014 1205 37 8.6 439 17.5 E2.5 165 49.0 10.3

08/11/2014 1230 22 9.0 499 19.0 E5.4 185 54.2 12.0

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 -- -- -- -- -- -- -- 0.218 0.304

03/24/2014 1.79 5.06 104 38.2 0.61 10.7 92.9 0.404 0.531

04/21/2014 3.70 17.9 79.1 19.3 0.37 18.4 59.4 0.174 0.325

05/12/2014 3.14 16.6 74.1 14.1 0.27 21.0 50.9 0.135 0.244

05/27/2014 2.26 9.67 71.6 7.65 0.16 17.7 37.0 0.086 0.278

06/09/2014 2.53 12.3 83.3 11.6 0.21 17.6 43.1 0.082 0.177

07/14/2014 4.29 22.6 101 27.2 0.40 23.4 73.1 0.187 0.230

08/11/2014 5.46 30.2 105 35.1 0.45 13.5 89.8 0.224 0.321

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 6.6 16.5 15.4 285 0.133 2.47 109 140

03/24/2014 15.5 29.8 14.7 384 0.231 2.86 226 249

04/21/2014 12.8 27.6 102 728 0.421 4.36 95.0 150

05/12/2014 10.2 21.3 100 618 0.341 3.52 71.3 117

05/27/2014 10.8 27.0 88.8 842 0.332 5.75 57.5 120

06/09/2014 7.4 14.9 53.6 385 0.247 3.26 66.4 103

07/14/2014 10.7 16.1 31.3 176 0.234 1.48 47.8 73.8

08/11/2014 11.9 18.8 20.1 199 0.191 1.67 27.5 88.4

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)

11/05/2013 61.9 81.7 4.4 5.5 -- 86 9 0.75

03/24/2014 116 131 6.7 7.1 4.45 71 11 1.5

04/21/2014 43.5 76.5 7.1 7.6 6.33 53 25 4.7

05/12/2014 30.9 57.9 7.0 8.2 8.18 64 22 7.7

05/27/2014 19.0 53.5 6.6 9.2 8.35 40 53 26

06/09/2014 16.1 36.8 5.5 7.3 6.67 68 13 3.5

07/14/2014 20.9 32.7 9.8 10.0 4.20 88 5 0.50

08/11/2014 16.6 42.3 9.4 9.9 4.33 85 8 0.48
Data 23

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/04/2013 1530 17 8.1 146 1.5 -- 65.7 18.0 5.04

03/25/2014 0800 11 7.8 192 1.0 <2.0 84.3 22.6 6.74

04/21/2014 1545 45 8.0 127 9.5 E2.6 51.1 14.3 3.74

05/12/2014 1820 73 7.8 113 9.5 E2.5 44.3 12.6 3.10

05/27/2014 1550 251 7.7 69 9.0 E4.8 27.1 7.90 1.79

06/09/2014 1550 157 7.7 74 11.0 <2.0 31.9 9.31 2.09

07/14/2014 1520 60 7.9 97 13.0 <2.0 45.6 13.1 3.15

08/11/2014 1540 24 8.1 145 17.0 <2.0 69.1 19.3 5.10

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/04/2013 -- -- -- -- -- -- -- 0.043 0.058

03/25/2014 0.82 6.04 85.1 0.54 0.34 13.2 13.9 0.065 0.095

04/21/2014 0.74 5.50 54.4 0.46 0.34 14.6 8.89 0.052 0.080

05/12/2014 0.73 5.66 48.9 0.41 0.28 15.5 7.07 0.052 0.072

05/27/2014 0.55 2.62 30.8 0.27 0.29 11.3 3.38 0.037 0.157

06/09/2014 0.47 2.14 34.1 0.18 0.30 9.83 3.12 0.032 0.056

07/14/2014 0.48 2.18 45.4 0.17 0.35 9.27 3.67 0.033 0.051

08/11/2014 0.65 3.07 68.7 0.24 0.33 11.0 5.37 0.035 0.049

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

11/04/2013 1.1 1.3 34.0 64.9 0.048 0.15 4.34 6.2

03/25/2014 1.6 2.8 40.3 120 0.074 0.41 8.40 12.9

04/21/2014 3.4 5.2 52.6 206 0.135 0.64 4.69 12.2

05/12/2014 3.6 5.3 43.1 201 0.135 0.75 4.43 10.5

05/27/2014 3.4 7.6 42.9 730 0.133 2.19 6.64 35.0

06/09/2014 2.1 3.5 30.0 164 0.081 0.54 4.12 10.9

07/14/2014 1.6 2.8 46.3 132 0.086 0.47 7.02 12.3

08/11/2014 1.5 2.1 71.3 143 0.095 0.36 6.90 14.7

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)

11/04/2013 2.0 <2.0 9.9 11.2 -- 14 6 0.28

03/25/2014 2.9 3.4 25.0 26.5 1.65 42 3 0.09

04/21/2014 <2.0 3.3 26.7 25.5 3.48 77 5 0.61

05/12/2014 2.4 3.6 26.7 26.9 3.46 43 6 1.2

05/27/2014 <2.0 8.2 10.1 14.5 3.45 31 42 28

06/09/2014 <2.0 2.4 8.1 10.5 2.56 52 8 3.4

07/14/2014 <2.0 2.7 9.3 10.3 1.53 45 4 0.65

08/11/2014 <2.0 <2.0 12.3 13.6 1.35 60 3 0.19
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 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/05/2013 0910 9.2 7.8 178 0.0 <2.0 81.3 22.6 6.05

03/25/2014 0900 9.8 8.0 226 1.0 <2.0 95.4 26.2 7.31

04/21/2014 1650 20 8.0 142 10.0 E2.6 57.5 16.3 4.07

05/12/2014 1920 35 7.9 122 10.0 E2.9 47.9 13.7 3.30

05/27/2014 1700 136 7.7 74 10.5 E7.2 29.3 8.49 1.97

06/09/2014 1705 81 7.8 80 12.0 <2.0 33.8 9.82 2.24

07/14/2014 1620 41 7.9 106 14.5 <2.0 48.2 13.8 3.33

08/11/2014 1630 9.2 8.1 161 18.0 <2.0 75.2 21.1 5.48

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 0.78 5.08 72.4 0.56 0.36 13.0 16.7 0.067 0.080

03/25/2014 1.02 8.15 88.2 0.82 0.36 12.8 27.7 0.054 0.072

04/21/2014 0.79 5.70 57.2 0.55 0.35 14.3 13.0 0.056 0.083

05/12/2014 0.71 5.90 50.4 0.45 0.29 14.9 9.68 0.062 0.101

05/27/2014 0.58 2.95 31.9 0.24 0.30 11.6 4.41 0.049 0.249

06/09/2014 0.51 2.33 35.8 0.21 0.30 10.2 4.19 0.048 0.097

07/14/2014 0.57 2.58 47.2 0.21 0.33 9.59 5.66 0.042 0.078

08/11/2014 0.80 4.19 71.2 0.34 0.34 11.7 10.2 0.056 0.063

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 1.2 1.6 53.2 84.1 0.048 0.14 9.73 9.7

03/25/2014 1.8 3.4 31.4 105 0.066 0.26 3.58 5.3

04/21/2014 3.6 5.3 40.4 207 0.121 0.68 3.33 10.7

05/12/2014 3.3 6.0 36.6 247 0.117 1.03 4.09 16.3

05/27/2014 3.9 12.3 46.8 924 0.210 3.80 6.22 40.5

06/09/2014 2.6 4.8 30.5 256 0.108 1.00 4.32 14.7

07/14/2014 2.0 3.7 57.8 184 0.124 0.68 6.33 16.6

08/11/2014 2.3 3.0 88.3 159 0.144 0.44 5.82 12.7

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)

11/05/2013 4.8 5.0 11.3 12.2 2.10 90 1 0.02

03/25/2014 2.6 3.6 22.9 23.2 1.73 67 1 0.03

04/21/2014 2.6 3.9 25.5 24.8 2.98 76 6 0.32

05/12/2014 <2.0 4.7 25.8 26.5 3.31 56 9 0.85

05/27/2014 2.3 12.4 13.5 21.0 4.10 47 48 18

06/09/2014 2.0 4.2 11.9 15.3 2.51 67 10 2.2

07/14/2014 <2.0 3.2 17.7 19.4 1.58 65 4 0.44

08/11/2014 <2.0 2.6 24.4 25.6 1.85 79 4 0.10
Data 25

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/04/2013 1350 1.2 7.6 119 1.0 -- 32.1 10.6 1.38

03/24/2014 1540 2.6 7.6 139 1.5 <2.0 51.0 16.6 2.33

04/21/2014 1420 12 7.7 104 6.0 E9.3 37.4 12.4 1.53

05/12/2014 1700 26 7.6 86 8.0 E6.1 30.1 10.1 1.21

05/27/2014 1430 47 7.6 65 8.5 E6.0 21.5 7.22 0.84

06/09/2014 1425 16 7.7 84 10.0 E2.4 31.0 10.5 1.17

07/14/2014 1410 4.7 7.7 104 12.0 <2.0 39.2 13.2 1.54

08/11/2014 1425 2.6 7.8 108 16.0 <2.0 40.4 13.6 1.58

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab (mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/04/2013 -- -- -- -- -- -- -- <0.030 0.031

03/24/2014 1.06 7.94 53.5 0.83 0.07 22.9 15.7 <0.030 0.032

04/21/2014 0.92 6.10 38.6 0.69 0.07 24.9 10.7 <0.030 0.046

05/12/2014 0.94 5.99 32.3 0.55 0.07 24.9 8.36 0.034 0.052

05/27/2014 0.70 4.58 26.3 0.34 0.06 21.7 5.10 0.037 0.068

06/09/2014 0.73 4.39 35.3 0.34 0.06 20.9 6.00 <0.030 0.047

07/14/2014 0.91 5.39 45.7 0.30 0.07 23.7 6.18 0.034 0.056

08/11/2014 1.08 6.47 47.8 0.33 0.07 24.7 5.89 0.033 0.059

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

11/04/2013 1.0 1.6 57.2 150 0.072 0.19 11.2 17.6

03/24/2014 1.3 1.8 72.0 176 0.064 0.23 16.2 22.6

04/21/2014 2.9 4.1 134 541 0.276 0.76 13.6 27.0

05/12/2014 3.4 4.7 152 372 0.242 0.64 7.69 15.8

05/27/2014 2.8 5.1 70.2 334 0.207 1.01 6.94 19.0

06/09/2014 2.5 2.8 59.7 174 0.165 0.56 10.7 17.0

07/14/2014 1.9 2.9 89.1 182 0.189 0.47 12.1 23.9

08/11/2014 3.0 2.7 133 218 0.278 0.54 8.61 17.0

Date

Zinc, 

filtered

 (μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/04/2013 2.1 <2.0 7.7 12.6 -- 90 1 <0.01

03/24/2014 <2.0 <2.0 13.2 14.2 3.57 77 1 0.01

04/21/2014 <2.0 3.9 18.6 19.4 6.77 89 9 0.29

05/12/2014 <2.0 3.3 17.6 17.0 7.03 86 5 0.35

05/27/2014 <2.0 4.7 11.9 14.5 5.23 70 15 1.9

06/09/2014 3.0 2.1 12.0 14.2 4.79 97 3 0.13

07/14/2014 <2.0 <2.0 18.7 20.6 4.38 90 4 0.05

08/11/2014 <2.0 2.1 22.7 24.5 4.25 76 3 0.02
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 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/05/2013 1020 5.1 8.1 286 2.5 E5.8 129 37.4 8.75

03/24/2014 1420 7.7 8.2 317 8.0 <2.0 134 38.6 9.21

04/21/2014 1300 15 8.0 186 8.0 E4.7 72.4 22.2 4.11

05/12/2014 1530 30 7.9 143 11.0 E5.2 54.9 17.1 2.99

05/27/2014 1310 45 7.8 131 11.0 E3.8 54.2 16.5 3.15

06/09/2014 1310 30 8.0 197 14.0 E2.4 87.8 26.1 5.53

07/14/2014 1250 9.9 8.0 241 14.0 <2.0 109 31.6 7.22

08/11/2014 1310 7.1 8.3 270 16.0 <2.0 122 35.2 8.23

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 1.40 10.7 117 2.05 0.43 22.1 25.5 <0.030 0.074

03/24/2014 1.74 12.0 124 3.28 0.42 20.9 36.5 <0.030 0.060

04/21/2014 1.26 8.65 68.8 1.54 0.19 23.4 21.8 0.040 0.101

05/12/2014 1.07 7.56 53.3 1.12 0.15 23.5 15.0 0.036 0.091

05/27/2014 0.94 6.12 54.9 0.79 0.18 23.5 9.21 0.047 --

06/09/2014 1.20 6.76 89.9 0.99 0.34 22.5 10.5 0.038 0.069

07/14/2014 1.24 8.19 106 1.63 0.41 22.0 16.1 0.036 0.053

08/11/2014 1.30 9.09 117 2.14 0.46 20.2 20.0 0.033 0.036

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 0.87 7.1 10.8 346 0.075 2.58 47.6 63.0

03/24/2014 2.4 6.1 24.5 142 0.150 1.32 53.7 60.1

04/21/2014 5.7 11.1 63.1 368 0.266 1.93 29.4 46.8

05/12/2014 6.5 13.5 77.4 348 0.306 2.03 18.5 29.5

05/27/2014 8.5 -- 80.8 -- 0.296 -- 15.9 --

06/09/2014 5.3 8.2 53.1 193 0.197 1.13 19.4 27.6

07/14/2014 3.0 4.9 38.5 151 0.186 0.84 18.2 23.7

08/11/2014 2.9 3.1 79.7 111 0.442 0.62 7.98 9.9

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/05/2013 2.8 11.0 9.3 11.6 1.75 99 13 0.18

03/24/2014 4.4 8.0 17.7 19.1 2.46 97 3 0.06

04/21/2014 5.2 11.9 22.6 22.9 5.97 91 12 0.49

05/12/2014 5.1 11.2 23.2 24.3 6.85 90 11 0.89

05/27/2014 7.8 -- 31.7 35.0 6.83 81 11 1.3

06/09/2014 5.3 8.8 44.5 51.7 6.46 90 5 0.41

07/14/2014 3.1 5.0 25.3 27.5 3.80 95 3 0.08

08/11/2014 2.5 3.2 17.1 17.2 2.41 95 6 0.12
Data 27

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/05/2013 1350 67 8.6 524 2.0 -- 196 54.0 15.0

03/25/2014 1045 72 8.8 496 3.5 E5.1 206 59.9 13.7

04/22/2014 1035 153 8.3 441 9.0 E11 173 50.7 11.3

05/13/2014 1200 210 8.5 388 9.0 E2.1 150 45.4 8.84

05/28/2014 1030 307 8.8 267 10.0 E3.8 103 30.7 6.49

06/10/2014 1030 186 8.9 241 10.5 E2.4 101 29.8 6.40

07/15/2014 1020 93 9.1 289 15.5 E3.3 125 36.2 8.42

08/12/2014 1110 50 9.4 376 17.0 E2.9 169 48.5 11.6

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 -- -- -- -- -- -- -- 0.045 0.102

03/25/2014 4.73 19.4 104 21.6 0.70 11.1 115 0.055 0.123

04/22/2014 4.45 20.0 97.1 19.6 0.66 10.5 93.7 0.033 0.567

05/13/2014 3.70 17.9 92.4 15.9 0.49 12.4 74.1 0.054 0.082

05/28/2014 2.41 11.9 69.2 8.75 0.42 11.4 47.5 0.050 0.119

06/10/2014 1.77 8.61 69.8 6.05 0.41 10.1 39.2 0.046 0.087

07/15/2014 1.72 9.30 78.9 5.98 0.50 12.7 57.2 <0.030 0.073

08/12/2014 2.31 14.4 95.7 9.88 0.64 15.8 83.0 <0.030 0.036

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 2.0 5.0 16.5 168 0.088 0.96 63.1 107

03/25/2014 6.4 15.0 37.6 372 0.360 4.58 122 153

04/22/2014 2.3 32.8 14.5 839 0.098 6.39 135 332

05/13/2014 4.1 7.7 27.5 187 0.167 1.06 65.4 83.5

05/28/2014 6.9 11.1 45.1 296 0.184 1.50 52.4 93.8

06/10/2014 5.2 8.0 34.0 216 0.128 1.05 43.9 66.9

07/15/2014 3.5 6.5 48.3 222 0.159 1.05 66.5 111

08/12/2014 2.1 2.8 27.7 88.0 0.110 0.37 42.8 68.3

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/05/2013 2.9 7.3 13.5 16.9 -- 98 15 2.7

03/25/2014 5.8 21.7 13.0 15.0 5.91 97 7 1.4

04/22/2014 2.8 69.8 12.2 16.9 4.89 95 21 8.7

05/13/2014 4.2 12.7 15.1 16.9 4.86 83 3 1.7

05/28/2014 3.3 12.6 18.2 22.3 5.56 90 8 6.6

06/10/2014 <2.0 7.4 18.9 24.4 4.69 85 5 2.5

07/15/2014 <2.0 5.4 23.8 26.8 4.54 87 6 1.5

08/12/2014 <2.0 2.3 32.7 33.9 5.33 83 1 0.14
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 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/05/2013 0755 59 8.2 268 0.5 -- 132 38.8 8.66

04/22/2014 0855 60 8.4 272 6.0 <2.0 131 39.1 8.14

05/13/2014 0930 90 8.4 254 4.5 <2.0 127 38.4 7.53

05/28/2014 0900 382 7.9 136 4.5 E5.6 62.9 19.8 3.25

07/15/2014 0830 172 8.2 183 10.5 <2.0 92.1 28.0 5.42

08/12/2014 0830 93 8.3 238 10.0 <2.0 120 35.9 7.38

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 -- -- -- -- -- -- -- <0.030 <0.030

04/22/2014 1.34 3.44 126 1.53 0.39 9.70 15.9 <0.030 <0.030

05/13/2014 1.25 3.25 118 1.26 0.37 9.92 13.5 <0.030 <0.030

05/28/2014 0.80 1.54 60.3 0.49 0.30 8.25 7.98 <0.030 0.073

07/15/2014 0.94 1.93 83.2 0.75 0.39 9.59 10.0 <0.030 <0.030

08/12/2014 1.17 2.83 111 1.06 0.39 10.7 11.9 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)

11/05/2013 <0.80 <0.80 <4.0 19.1 <0.040 0.08 0.77 0.9

04/22/2014 <0.80 2.4 5.1 93.4 <0.040 0.32 0.75 4.2

05/13/2014 0.83 4.4 7.1 77.0 <0.040 0.26 0.83 3.6

05/28/2014 1.4 8.8 15.2 525 <0.040 1.58 2.38 20.5

07/15/2014 0.88 2.9 7.0 92.3 <0.040 0.33 1.31 5.8

08/12/2014 1.6 2.0 8.8 72.7 <0.040 0.24 0.80 4.1

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)

11/05/2013 <2.0 <2.0 1.7 1.8 -- 64 1 0.16

04/22/2014 <2.0 2.8 2.7 2.7 1.31 80 6 0.97

05/13/2014 <2.0 3.3 2.3 2.6 1.77 68 3 0.73

05/28/2014 <2.0 9.6 1.3 2.7 2.92 55 32 33

07/15/2014 <2.0 3.7 1.8 2.1 1.28 63 5 2.3

08/12/2014 <2.0 2.4 2.1 2.3 0.83 59 3 0.75
Data 29

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/05/2013 1250 32 8.3 379 1.0 <2.0 193 58.1 11.5

03/25/2014 1005 24 8.1 443 2.0 <2.0 203 59.2 13.5

04/22/2014 1120 33 8.3 405 8.0 <2.0 203 61.4 12.0

05/13/2014 1040 56 8.3 356 6.0 <2.0 177 53.3 10.7

05/28/2014 1115 239 7.9 180 7.0 E11 85.5 27.0 4.36

06/10/2014 0910 207 8.0 167 7.0 E2.4 82.3 25.8 4.36

07/15/2014 0935 109 8.0 228 12.5 E4.3 112 34.2 6.40

08/12/2014 0940 50 8.2 304 12.0 <2.0 154 46.9 8.92

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 1.50 4.31 139 1.57 0.48 11.9 55.1 0.050 0.052

03/25/2014 4.66 19.2 149 2.11 0.50 11.1 84.4 0.055 0.069

04/22/2014 1.56 4.64 145 2.21 0.48 10.6 64.9 0.054 0.062

05/13/2014 1.56 4.33 132 1.74 0.45 9.86 51.0 0.061 0.057

05/28/2014 0.93 1.84 69.5 0.64 0.34 8.91 19.5 0.034 0.204

06/10/2014 0.83 1.78 66.8 0.60 0.34 9.05 16.3 0.041 0.082

07/15/2014 1.25 2.39 91.7 1.07 0.41 10.0 22.7 0.043 0.088

08/12/2014 1.35 3.30 124 1.37 0.42 10.8 32.7 0.031 0.038

Date

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 1.4 3.9 15.0 52.8 <0.040 0.20 163 182

03/25/2014 2.4 5.1 33.8 58.2 <0.040 0.21 218 233

04/22/2014 2.9 7.2 10.9 93.4 <0.040 0.37 123 175

05/13/2014 3.4 6.9 11.4 88.0 <0.040 0.41 88.3 131

05/28/2014 4.5 50.3 21.1 1,280 0.083 5.96 44.5 233

06/10/2014 3.2 14.2 15.6 308 0.045 1.57 37.6 78.6

07/15/2014 3.6 15.6 19.8 312 0.087 1.87 35.7 71.7

08/12/2014 2.3 5.7 18.3 76.5 0.049 0.37 28.9 46.6

Date

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Organic 

carbon, 

filtered 

(mg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/05/2013 2.1 2.5 3.7 4.2 0.89 63 2 0.17

03/25/2014 2.1 2.9 6.9 7.1 1.45 82 1 0.06

04/22/2014 <2.0 3.1 7.1 7.0 1.53 67 4 0.36

05/13/2014 <2.0 2.9 5.3 5.9 1.84 64 3 0.45

05/28/2014 <2.0 23.7 5.2 11.8 3.27 60 65 42

06/10/2014 2.2 7.4 3.9 5.9 2.29 68 14 7.8

07/15/2014 <2.0 8.2 6.9 8.5 2.14 79 13 3.8

08/12/2014 <2.0 3.0 6.1 7.0 1.25 84 2 0.27
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 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/05/2013 1530 111 8.8 481 2.0 194 55.1 13.7

03/25/2014 1230 85 8.6 494 4.0 208 61.3 13.5

04/22/2014 1245 181 8.6 432 10.0 178 52.5 11.4

05/13/2014 1340 265 8.8 374 10.0 155 47.1 9.04

05/28/2014 1330 535 8.5 227 11.5 93.2 28.4 5.43

06/10/2014 1230 390 8.5 206 12.0 91.3 27.7 5.37

07/15/2014 1220 197 8.7 262 16.0 119 35.4 7.36

08/12/2014 1235 87 8.9 346 17.0 164 48.5 10.5

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 0.044 0.103 2.8 10.3 7.5 199 0.052 1.16

03/25/2014 0.060 0.120 5.3 14.3 26.0 299 0.229 3.35

04/22/2014 0.037 0.223 3.3 17.5 8.7 447 0.075 2.97

05/13/2014 0.065 0.096 4.8 11.1 21.7 231 0.143 1.50

05/28/2014 0.045 0.195 6.3 42.2 27.7 855 0.157 5.13

06/10/2014 0.040 0.097 4.6 14.6 19.9 291 0.086 1.54

07/15/2014 0.037 0.071 4.3 11.6 26.5 223 0.113 1.29

08/12/2014 0.035 0.044 3.9 6.2 43.0 97.3 0.225 0.59

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

 filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/05/2013 64.8 96.4 2.7 8.2 10.4 12.7 94 5 1.5

03/25/2014 126 162 5.2 17.0 11.6 13.6 90 6 1.4

04/22/2014 93.6 220 2.9 30.6 11.8 13.9 88 11 5.4

05/13/2014 56.3 93.7 4.0 13.3 14.3 15.4 79 5 3.6

05/28/2014 41.5 163 2.3 24.9 12.6 20.8 68 42 61

06/10/2014 34.4 76.7 <2.0 9.9 11.6 15.6 68 11 12

07/15/2014 42.0 85.0 <2.0 7.1 14.6 15.7 87 7 3.7

08/12/2014 38.0 60.1 2.2 3.9 18.0 19.1 47 6 1.4
Data 31

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/04/2013 1630 5.7 8.2 237 2.5 <2.0 119 35.2 7.47

03/24/2014 1710 5.5 8.2 237 4.0 <2.0 112 33.0 7.21

04/22/2014 0745 8.3 8.1 223 6.0 <2.0 110 32.2 7.14

05/13/2014 0840 5.8 7.8 202 4.0 <2.0 96.2 29.4 5.52

05/28/2014 0740 35 7.8 130 5.0 E9.4 61.0 18.9 3.35

06/10/2014 0740 31 7.8 149 6.0 E2.0 71.7 22.2 3.93

07/15/2014 0740 13 8.0 206 10.0 <2.0 103 31.6 5.92

08/12/2014 0735 15 8.0 223 10.0 <2.0 112 34.1 6.54

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/04/2013 1.37 3.62 110 0.92 0.47 12.3 13.3 0.037 0.037

03/24/2014 1.46 3.63 110 1.05 0.49 11.3 13.8 <0.030 0.040

04/22/2014 1.30 3.01 102 0.96 0.45 10.9 11.9 <0.030 0.049

05/13/2014 1.25 2.86 92.8 0.83 0.39 10.9 10.2 0.031 0.047

05/28/2014 0.95 1.87 59.5 0.51 0.28 9.69 5.93 <0.030 0.123

06/10/2014 0.88 1.91 69.8 0.54 0.29 9.65 5.89 <0.030 0.044

07/15/2014 1.25 2.77 99.3 0.71 0.38 11.1 6.99 <0.030 0.031

08/12/2014 1.30 2.77 108 0.70 0.39 11.5 8.04 <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)

11/04/2013 1.5 2.7 5.8 42.6 <0.040 0.18 1.83 2.1

03/24/2014 1.3 5.2 6.6 115 <0.040 0.55 0.82 4.1

04/22/2014 1.6 6.3 7.1 218 <0.040 0.81 1.04 6.7

05/13/2014 1.4 6.8 5.7 146 <0.040 0.56 0.90 5.1

05/28/2014 2.6 20.7 24.1 994 0.064 3.51 2.22 25.3

06/10/2014 2.0 8.9 14.0 284 <0.040 1.06 1.38 8.0

07/15/2014 1.7 3.6 14.5 109 <0.040 0.35 2.24 6.1

08/12/2014 2.6 4.4 12.1 160 <0.040 0.64 1.43 7.7

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)

11/04/2013 2.0 <2.0 3.0 3.4 1.05 88 1 0.02

03/24/2014 <2.0 2.5 3.4 3.9 0.90 76 4 0.06

04/22/2014 <2.0 3.5 3.0 3.8 1.43 68 13 0.29

05/13/2014 <2.0 3.3 2.7 3.1 2.09 63 6 0.09

05/28/2014 <2.0 11.5 3.1 6.1 3.84 41 65 6.1

06/10/2014 <2.0 3.5 3.3 4.6 2.79 31 16 1.3

07/15/2014 <2.0 2.1 5.2 5.5 1.81 51 4 0.14

08/12/2014 <2.0 2.4 3.6 3.9 1.18 62 8 0.32
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 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/05/2013 1450 39 8.3 605 1.5 -- 285 83.8 18.5

03/25/2014 1145 46 8.2 625 4.0 E5.4 317 92.0 21.1

04/22/2014 1210 44 8.3 604 10.0 <2.0 302 88.1 19.8

05/13/2014 1300 E46 8.4 597 10.0 E2.3 305 89.6 19.8

05/28/2014 1225 32 8.5 568 13.0 <2.0 294 85.1 19.8

06/10/2014 1130 16 8.3 596 13.0 <2.0 299 85.4 20.9

07/15/2014 1125 5.3 8.2 624 17.0 <2.0 292 81.0 21.8

08/12/2014 1205 1.9 8.0 637 17.0 <2.0 282 74.3 23.4

Date

Potassium, 

filtered 

(mg/L)

Sodium, 

filtered 

(mg/L)

Alkalinity, 

filtered, 

lab 

(mg/L)

Chloride, 

filtered 

(mg/L)

Fluoride, 

filtered 

(mg/L)

Silica, 

filtered 

(mg/L)

Sulfate, 

filtered 

(μg/L)

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

11/05/2013 -- -- -- -- -- -- -- <0.030 <0.030

03/25/2014 2.43 12.8 188 4.82 0.48 16.2 146 <0.030 0.072

04/22/2014 2.09 11.6 182 4.83 0.48 14.0 140 <0.030 0.039

05/13/2014 2.07 11.5 178 4.70 0.44 11.7 135 0.032 0.051

05/28/2014 2.05 10.1 166 3.90 0.49 14.0 138 <0.030 0.031

06/10/2014 2.30 11.1 176 3.94 0.54 14.2 142 <0.030 <0.090

07/15/2014 3.04 21.4 196 5.62 0.67 17.6 134 <0.030 <0.030

08/12/2014 3.68 31.5 213 5.61 0.77 19.6 122 0.031 <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)

11/05/2013 <0.80 1.5 4.0 26.2 <0.040 0.16 2.34 2.7

03/25/2014 0.92 9.4 11.6 290 0.057 1.50 28.8 41.9

04/22/2014 1.3 3.5 11.0 88.0 <0.040 0.37 15.6 19.9

05/13/2014 1.4 5.2 11.0 141 <0.040 0.63 17.3 24.7

05/28/2014 3.0 5.0 16.5 94.8 0.042 0.32 15.3 20.5

06/10/2014 1.9 3.5 14.2 59.1 <0.040 0.21 10.8 14.0

07/15/2014 1.4 3.0 13.9 62.0 <0.040 0.19 15.2 20.3

08/12/2014 1.8 3.4 29.6 87.9 0.075 0.27 36.9 43.1

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)

11/05/2013 <2.0 <2.0 7.4 8.7 -- 79 12 1.3

03/25/2014 <2.0 6.4 12.4 13.6 1.48 94 14 1.7

04/22/2014 <2.0 3.0 12.6 12.3 1.62 46 15 1.8

05/13/2014 <2.0 3.4 10.3 11.5 1.71 54 15 1.9

05/28/2014 <2.0 <2.0 16.4 19.2 3.09 70 5 0.43

06/10/2014 <2.0 <6.0 15.3 18.1 2.82 79 15 0.65

07/15/2014 <2.0 <2.0 15.1 15.1 2.25 61 14 0.20

08/12/2014 <2.0 2.0 13.0 13.6 3.25 70 10 0.05
Data 33

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/06/2013 0810 212 8.1 511 1.0 225 65.5 15.0

03/25/2014 1355 250 8.2 521 6.0 228 66.5 14.9

04/22/2014 1425 282 8.4 487 10.5 206 60.5 13.4

05/13/2014 1520 353 8.8 417 12.0 185 54.7 11.7

05/28/2014 1535 691 8.1 256 14.0 107 32.2 6.38

06/10/2014 1435 419 8.3 275 15.0 122 36.5 7.49

07/15/2014 1405 208 8.7 342 20.0 154 46.1 9.52

08/12/2014 1405 112 8.6 430 19.5 195 58.3 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)

11/06/2013 0.041 0.097 4.7 13.6 6.2 230 <0.040 1.62

03/25/2014 0.064 0.377 6.1 50.2 18.3 790 0.169 6.90

04/22/2014 0.063 0.216 6.2 37.1 8.3 588 0.083 4.95

05/13/2014 0.056 0.152 7.6 27.8 14.4 444 0.126 3.39

05/28/2014 0.067 0.507 12.5 201 33.4 2,640 0.363 20.7

06/10/2014 0.065 0.215 8.9 62.6 20.2 787 0.195 6.58

07/15/2014 0.059 0.074 7.4 15.1 22.2 140 0.199 1.24

08/12/2014 0.048 0.060 7.0 11.8 13.6 82.6 0.121 0.78

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

 filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/06/2013 29.9 54.2 8.2 16.4 7.7 9.9 90 8 4.6

03/25/2014 66.1 131 8.1 40.1 11.7 16.9 82 30 20

04/22/2014 33.1 124 4.2 34.9 12.5 16.6 79 24 18

05/13/2014 24.0 76.1 3.4 24.4 13.8 16.6 73 18 17

05/28/2014 23.8 232 6.6 108 12.9 33.7 47 137 256

06/10/2014 19.7 101 4.4 37.1 14.4 22.5 66 34 38

07/15/2014 33.4 47.1 3.5 8.6 17.7 19.8 87 4 2.2

08/12/2014 14.6 34.8 2.7 6.5 16.8 17.7 90 2 0.60
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 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/06/2013 0955 233 8.2 520 1.5 225 65.5 14.9

03/25/2014 1525 233 8.2 527 6.5 228 66.3 15.0

04/22/2014 1550 306 8.5 482 10.0 209 61.1 13.7

05/13/2014 1700 374 8.9 420 13.0 185 54.4 12.1

05/28/2014 1710 826 8.0 270 15.0 113 33.7 6.92

06/10/2014 1615 461 8.4 324 17.0 144 42.2 9.29

07/15/2014 1620 228 8.8 380 21.0 172 50.5 11.3

08/12/2014 1520 115 8.5 451 21.0 201 58.4 13.3

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/06/2013 0.032 0.120 2.8 17.7 5.5 278 <0.040 2.14

03/25/2014 0.062 0.283 6.2 58.9 15.1 919 0.172 7.94

04/22/2014 0.052 0.230 6.2 46.4 5.8 738 0.104 5.96

05/13/2014 0.053 0.155 7.4 34.6 11.2 541 0.110 4.17

05/28/2014 0.071 0.644 14.1 167 36.0 2,750 0.478 23.2

06/10/2014 0.069 0.248 10.1 54.7 19.1 797 0.216 6.82

07/15/2014 0.066 0.076 8.9 16.6 20.9 127 0.208 1.21

08/12/2014 0.042 0.047 7.2 11.1 9.5 58.4 0.076 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)

11/06/2013 34.8 78.1 6.1 19.5 7.8 10.5 82 16 10

03/25/2014 65.1 149 9.2 51.7 12.2 17.9 81 37 23

04/22/2014 35.8 136 3.2 42.3 13.2 16.7 71 36 30

05/13/2014 21.0 82.4 2.6 28.7 15.2 18.6 76 21 21

05/28/2014 22.3 252 7.8 130 14.3 35.1 70 125 279

06/10/2014 20.3 102 5.0 40.9 15.2 22.2 72 32 40

07/15/2014 31.0 45.7 3.2 8.8 19.6 19.8 88 3 1.8

08/12/2014 14.8 29.6 2.3 5.4 17.3 17.8 92 1 0.31
Data 35

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/06/2013 1105 345 8.3 449 3.0 190 55.6 12.4

03/25/2014 1645 446 8.3 456 7.0 196 57.4 12.9

04/23/2014 0800 1,100 8.0 306 5.0 128 38.3 7.87

05/14/2014 0805 992 8.1 302 8.0 130 39.2 7.85

05/29/2014 0820 1,840 8.0 216 10.0 98.5 29.6 5.96

06/11/2014 0840 908 8.2 293 12.0 133 39.8 8.23

07/15/2014 1525 457 8.4 357 20.0 164 48.5 10.3

08/12/2014 1620 204 8.5 395 19.5 175 51.3 11.5

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/06/2013 0.036 0.081 2.1 12.1 4.5 206 <0.040 1.47

03/25/2014 0.050 0.190 4.5 38.4 11.4 607 0.115 5.01

04/23/2014 0.034 0.379 4.3 74.9 57.7 2,670 0.183 15.6

05/14/2014 0.039 0.108 4.7 18.6 26.4 569 0.113 2.62

05/29/2014 0.040 0.280 9.5 69.2 46.2 1,460 0.309 9.63

06/11/2014 0.047 0.137 6.5 31.1 20.6 518 0.138 3.59

07/15/2014 0.049 0.062 5.6 10.9 15.3 168 0.109 0.89

08/12/2014 0.041 0.042 5.3 7.2 26.6 67.8 0.156 0.40

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

 filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/06/2013 18.0 57.5 5.8 13.0 5.9 7.5 87 9 8.4

03/25/2014 41.1 96.2 6.1 32.7 9.2 12.6 86 22 26

04/23/2014 14.7 253 4.1 81.5 7.1 16.6 70 128 380

05/14/2014 13.3 55.8 3.4 18.5 8.3 9.8 74 23 62

05/29/2014 11.1 133 6.5 55.0 8.5 17.4 66 73 363

06/11/2014 12.8 66.3 6.1 23.9 10.0 14.3 83 18 44

07/15/2014 19.9 40.3 2.6 7.7 12.5 12.6 85 6 7.4

08/12/2014 15.8 28.8 3.4 4.2 11.5 11.6 65 2 1.1
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 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/06/2013 1315 514 8.3 469 5.0 213 60.9 14.9

03/26/2014 0830 695 8.1 468 6.0 210 60.3 14.5

04/23/2014 0945 1,280 8.1 331 6.5 146 41.6 10.2

05/14/2014 1000 1,250 8.2 327 9.5 142 42.1 9.04

05/29/2014 0955 2,130 8.0 243 12.0 109 32.6 6.75

06/11/2014 1040 1,110 8.2 342 14.0 156 45.2 10.4

07/16/2014 0755 637 8.2 420 17.5 197 57.0 13.3

08/13/2014 0815 324 8.1 516 17.0 244 69.0 17.4

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)

11/06/2013 <0.030 0.067 1.9 8.0 <4.0 176 <0.040 1.31

03/26/2014 0.054 0.163 3.9 29.7 12.0 567 0.121 4.43

04/23/2014 0.040 0.252 4.0 41.8 26.9 1,480 0.141 8.14

05/14/2014 0.046 0.145 7.8 26.9 20.2 697 0.137 3.80

05/29/2014 0.050 0.370 9.7 79.1 48.4 1,960 0.364 12.8

06/11/2014 0.058 0.145 6.7 27.3 15.6 461 0.130 3.20

07/16/2014 0.046 0.061 5.2 9.8 11.8 181 0.113 1.04

08/13/2014 0.035 0.049 3.5 5.7 6.6 62.3 0.048 0.43

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

 filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/06/2013 13.0 42.4 4.0 11.7 6.4 7.7 78 11 15

03/26/2014 33.0 89.7 7.5 30.6 8.9 11.8 80 25 47

04/23/2014 12.5 160 4.4 58.3 7.7 12.5 64 80 276

05/14/2014 15.3 78.7 4.2 29.8 8.5 11.5 68 33 111

05/29/2014 10.2 192 6.7 86.8 9.0 19.1 58 117 673

06/11/2014 14.6 64.9 5.0 22.8 10.0 13.8 69 21 63

07/16/2014 15.6 41.9 3.8 9.2 12.8 13.3 87 7 12

08/13/2014 11.9 32.0 3.4 5.7 11.5 11.9 87 2 1.7
Data 37

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/07/2013 1110 796 8.3 385 4.5 169 47.6 12.2

03/26/2014 1040 1,150 8.2 378 6.0 169 47.2 12.3

04/23/2014 1140 2,580 8.1 232 7.0 97.4 27.8 6.77

05/14/2014 1200 2,970 8.1 214 9.0 83.6 22.9 6.42

05/29/2014 1140 6,030 7.9 140 10.0 60.1 17.3 4.11

06/11/2014 1230 3,250 8.1 181 13.0 81.2 23.0 5.77

07/16/2014 0945 1,400 8.2 285 16.0 131 37.2 9.27

08/13/2014 0950 665 8.3 324 16.0 154 43.0 11.4

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)

11/07/2013 <0.030 0.047 1.3 6.0 <4.0 134 <0.040 0.87

03/26/2014 0.037 0.104 2.7 16.0 11.7 356 0.078 2.54

04/23/2014 <0.030 0.139 2.9 23.1 37.6 973 0.108 4.24

05/14/2014 0.032 0.093 3.2 13.5 37.3 448 0.114 2.09

05/29/2014 0.036 0.214 5.5 37.3 47.1 1,290 0.189 5.86

06/11/2014 0.033 0.071 3.2 11.0 23.2 396 0.083 1.67

07/16/2014 0.031 0.040 3.0 8.2 14.3 107 <0.040 0.52

08/13/2014 <0.030 0.045 2.0 4.1 6.6 70.9 <0.040 0.42

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2013 4.09 25.0 3.7 9.6 4.5 5.8 85 7 15

03/26/2014 15.9 53.3 5.2 21.0 6.1 7.4 79 16 50

04/23/2014 7.03 87.3 3.0 38.3 4.5 6.8 60 56 390

05/14/2014 7.04 42.3 3.3 17.7 4.5 5.8 68 23 184

05/29/2014 9.64 107 5.2 52.5 4.2 8.7 47 106 1,730

06/11/2014 9.24 37.1 2.9 14.2 4.0 5.9 57 25 219

07/16/2014 6.41 19.4 2.3 5.2 6.6 6.7 64 6 23

08/13/2014 5.79 20.8 <2.0 5.2 5.6 5.8 88 3 5.4
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 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

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)

11/07/2013 0940 515 8.2 269 3.0 130 32.9 11.6

04/23/2014 1420 3,650 8.2 158 6.0 73.3 19.4 6.02

05/14/2014 1430 4,760 8.2 171 9.0 76.2 19.2 6.83

05/29/2014 1410 10,000 8.1 151 11.0 74.1 20.0 5.87

07/16/2014 1200 1,810 8.4 214 17.5 108 27.8 9.45

08/13/2014 1155 815 8.5 256 17.5 135 33.7 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)

11/07/2013 <0.030 <0.030 <0.80 <0.80 <4.0 30.6 <0.040 <0.04

04/23/2014 <0.030 <0.030 <0.80 1.7 44.1 543 <0.040 0.50

05/14/2014 <0.030 <0.030 <0.80 2.3 23.4 262 <0.040 0.33

05/29/2014 <0.030 <0.030 0.88 2.9 30.2 823 <0.040 0.94

07/16/2014 <0.030 <0.030 <0.80 <0.80 9.1 80.9 <0.040 0.09

08/13/2014 <0.030 <0.030 1.2 <0.80 4.9 38.6 <0.040 0.05

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

 filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent finer 

than 0.062 

mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2013 1.52 2.6 <2.0 <2.0 0.90 1.1 75 2 2.8

04/23/2014 3.65 43.6 <2.0 2.6 0.80 1.1 84 33 325

05/14/2014 2.54 17.7 <2.0 2.2 0.78 1.1 86 17 218

05/29/2014 3.53 44.8 <2.0 4.6 0.79 1.7 76 73 1,970

07/16/2014 1.45 7.4 <2.0 <2.0 1.1 1.2 89 5 24

08/13/2014 1.60 5.4 <2.0 <2.0 1.2 1.2 90 2 4.4
Data 39

Table 4. Water-quality data for the Clark Fork Basin, Montana, October 2013 through September 2014.—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; --, no data; <, less than laboratory reporting level; E, estimated; μg/L, microgram per 

liter; mm, millimeter; ton/d, ton per day]

12340500—Clark Fork above Missoula

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)

11/07/2013 0750 1,280 8.3 341 3.5 154 42.0 12.0

03/26/2014 1330 1,880 8.4 322 6.0 147 39.8 11.5

04/23/2014 1620 6,310 8.1 189 7.0 83.4 23.0 6.31

05/14/2014 1610 7,650 8.2 188 10.0 85.9 23.6 6.54

05/29/2014 1550 16,600 8.0 148 11.0 70.7 19.6 5.30

06/11/2014 1430 9,340 8.2 168 13.0 81.5 21.9 6.54

07/16/2014 1345 3,290 8.4 244 18.0 117 31.5 9.30

08/13/2014 1345 1,500 8.5 282 18.0 141 37.3 11.7

Date

Cadmium, 

filtered 

(μg/L)

Cadmium, 

unfiltered 

recoverable 

(μg/L)

Copper, 

filtered 

(μg/L)

Copper, 

unfiltered 

recoverable 

(μg/L)

Iron, 

filtered 

(μg/L)

Iron, 

unfiltered 

recoverable 

(μg/L)

Lead, 

filtered 

(μg/L)

Lead, 

unfiltered 

recoverable 

(μg/L)

11/07/2013 <0.030 0.035 1.0 3.7 4.5 172 <0.040 0.55

03/26/2014 <0.030 0.066 1.8 8.8 13.0 259 0.057 1.60

04/23/2014 <0.030 0.067 1.8 11.6 49.0 770 0.088 2.36

05/14/2014 <0.030 0.040 1.9 9.7 27.5 333 0.060 1.00

05/29/2014 <0.030 0.096 2.9 14.8 38.5 1,010 0.105 2.79

06/11/2014 <0.030 0.046 1.7 4.8 20.7 290 0.041 0.71

07/16/2014 <0.030 <0.030 1.5 2.8 9.9 76.7 <0.040 0.23

08/13/2014 <0.030 <0.030 1.5 2.0 5.2 40.9 <0.040 0.16

Date

Manganese, 

filtered 

(μg/L)

Manganese, 

unfiltered 

recoverable 

(μg/L)

Zinc, 

 filtered 

(μg/L)

Zinc, 

unfiltered 

recoverable 

(μg/L)

Arsenic, 

filtered 

(μg/L)

Arsenic, 

unfiltered 

recoverable 

(μg/L)

Sediment, 

suspended 

(percent 

finer than 

0.062 mm)

Sediment, 

suspended 

(mg/L)

Sediment 

discharge, 

suspended 

(ton/d)

11/07/2013 5.68 19.5 2.8 6.2 3.0 3.8 95 4 14

03/26/2014 13.5 36.4 2.9 11.8 4.1 5.1 84 11 56

04/23/2014 6.72 65.4 <2.0 18.0 2.5 3.7 67 50 852

05/14/2014 5.88 28.1 <2.0 8.9 2.5 3.0 79 18 372

05/29/2014 8.01 68.2 2.3 21.9 2.1 4.2 66 85 3,810

06/11/2014 6.54 24.3 <2.0 6.2 2.1 2.9 76 19 479

07/16/2014 5.41 14.6 <2.0 2.5 3.6 4.0 82 4 36

08/13/2014 5.59 14.0 <2.0 2.3 3.1 3.4 82 2 8.1
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 Deer Lodge, Montana (12324200), October 2013 

through September 2014.

[ft3/s, cubic foot 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

1 181 10 4.9 218 19 11 227 39 24

2 191 10 5.1 223 20 12 233 40 25

3 196 10 5.1 225 17 10 187 41 21

4 202 10 5.2 216 13 7.8 145 42 16

5 202 9 5.2 209 10 5.8 e120 40 13

6 201 9 5.1 216 13 7.6 e120 37 12

7 202 9 5.0 227 22 13 e110 34 10

8 201 9 4.9 235 21 14 e110 32 9.4

9 202 9 4.9 228 19 12 e120 33 11

10 208 9 5.0 222 20 12 e130 36 13

11 209 9 4.9 227 20 12 e150 39 16

12 213 9 5.0 223 19 12 187 40 20

13 220 9 5.1 226 19 11 164 27 12

14 219 8 5.0 222 18 11 164 21 9.4

15 218 8 4.9 225 19 12 171 24 11

16 213 8 4.7 225 21 13 184 27 14

17 223 8 4.8 218 22 13 e170 28 13

18 218 8 4.9 215 24 14 e170 28 13

19 214 9 5.1 214 26 15 e170 28 13

20 208 9 5.3 223 28 17 e170 28 13

21 205 10 5.5 201 30 16 190 29 15

22 204 10 5.6 197 32 17 191 30 15

23 204 10 5.8 203 35 19 196 31 16

24 201 11 5.8 208 38 21 207 32 18

25 201 11 6.0 197 41 22 e180 31 15

26 206 12 6.9 205 43 24 192 31 16

27 212 14 8.1 211 43 24 203 30 16

28 205 16 8.8 217 41 24 198 29 16

29 200 18 9.5 215 40 23 204 29 16

30 208 18 10 222 38 23 195 28 15

31 216 19 11 -- -- -- 198 28 15

Total1 6,403 -- 183.1 6,513 -- 448.2 5,356 -- 461.8

Mean 207 11 5.9 217 26 15 173 32 15

Max 223 19 11 235 43 24 233 42 25

Min 181 8 4.7 197 10 5.8 110 21 9.4
Data 41

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana (12324200), October 2013 

through September 2014.—Continued

[ft3/s, cubic foot 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

1 195 27 14 e160 20 8.7 e90 131 32

2 192 27 14 e150 22 9.0 e130 131 46

3 198 27 15 e130 24 8.6 207 131 73

4 197 28 15 e120 26 8.6 254 128 88

5 184 28 14 e105 28 8.0 244 107 70

6 168 28 13 e100 30 8.0 581 536 841

7 190 28 14 e150 42 17 490 284 376

8 195 27 14 e180 51 25 405 141 154

9 204 27 15 e180 42 21 409 260 287

10 199 28 15 e180 30 15 551 263 391

11 197 29 15 e160 25 11 591 136 218

12 201 29 16 e150 33 13 513 76 105

13 196 30 16 177 52 25 419 55 63

14 196 28 15 186 63 32 368 47 47

15 198 25 13 184 71 35 345 43 40

16 197 22 12 198 74 40 333 48 43

17 193 20 10 209 75 43 338 48 44

18 192 19 10 199 71 38 320 45 39

19 192 19 10 191 66 34 314 42 36

20 187 20 10 196 60 32 306 39 32

21 183 20 9.8 185 55 28 287 32 25

22 188 20 9.9 190 58 30 271 33 24

23 183 19 9.4 182 71 35 263 32 23

24 182 19 9.1 164 100 44 254 34 23

25 186 18 9.1 e160 125 54 246 31 21

26 182 17 8.5 e150 133 54 252 29 20

27 176 17 7.9 e150 132 54 255 30 21

28 166 16 7.1 e140 132 50 253 32 22

29 186 15 7.7 -- -- -- 264 31 22

30 e180 16 8.0 -- -- -- 275 34 25

31 e170 18 8.4 -- -- -- 271 28 20

Total1 5,853 -- 364.9 4,626 -- 780.9 10,099 -- 3,271

Mean 189 23 12 165 61 28 326 98 106

Max 204 30 16 209 133 54 591 536 841

Min 166 15 7.1 100 20 8.0 90 28 20
42 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana (12324200), October 2013 

through September 2014.—Continued

[ft3/s, cubic foot 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)

April May June

1 274 21 16 334 32 29 585 67 107

2 269 18 13 337 38 35 538 70 101

3 263 18 13 361 42 41 509 60 82

4 262 17 12 399 54 58 507 53 73

5 259 18 13 420 56 63 510 41 57

6 260 24 17 423 58 67 501 33 44

7 264 61 43 401 38 41 475 35 44

8 269 74 54 394 32 34 438 34 40

9 327 58 51 384 30 31 416 27 30

10 367 66 66 380 27 27 408 26 28

11 361 43 42 391 21 22 399 26 28

12 346 32 30 370 18 18 348 23 22

13 327 35 31 348 17 16 354 42 40

14 313 30 25 365 16 15 398 34 36

15 295 25 20 354 17 16 388 22 24

16 258 18 13 360 34 33 382 33 34

17 250 15 10 419 74 84 450 71 86

18 259 16 11 458 123 152 469 23 30

19 263 16 11 530 70 100 443 64 77

20 269 20 14 536 57 82 439 53 63

21 270 21 15 525 86 122 495 113 151

22 288 34 26 541 152 223 515 63 88

23 339 29 27 582 187 294 519 46 64

24 324 22 19 621 175 294 494 34 45

25 310 70 58 669 180 324 524 33 47

26 406 61 67 668 154 278 626 28 48

27 396 48 52 682 140 258 725 21 41

28 353 31 30 698 137 258 741 19 38

29 325 25 22 668 98 177 683 19 34

30 329 29 25 665 101 182 602 15 24

31 -- -- -- 616 76 127 -- -- --

Total1 9,095 -- 846 14,899 -- 3,501 14,881 -- 1,626

Mean 303 33 28 481 75 113 496 41 54

Max 406 74 67 698 187 324 741 113 151

Min 250 15 10 334 16 15 348 15 22
Data 43

Table 5. Daily mean streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana (12324200), October 2013 

through September 2014.—Continued

[ft3/s, cubic foot 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)

July August September

1 532 13 18 120 3 0.97 262 6 4.4

2 473 16 20 120 3 1.0 252 6 4.1

3 426 22 25 124 3 1.2 236 6 3.8

4 456 20 24 121 4 1.2 222 6 3.6

5 449 9 11 118 4 1.3 225 6 3.6

6 417 7 7.4 123 5 1.5 223 6 3.6

7 376 4 4.1 130 5 1.9 219 6 3.5

8 344 4 3.9 124 7 2.2 214 6 3.5

9 316 7 6.0 126 10 3.3 198 6 3.2

10 281 5 3.9 122 9 2.8 221 6 3.3

11 255 4 2.5 115 4 1.3 246 5 3.4

12 229 4 2.3 113 4 1.2 258 5 3.2

13 214 3 1.6 130 85 30 252 4 2.8

14 196 2 1.1 160 82 35 249 5 3.1

15 207 3 1.6 176 34 16 241 7 4.3

16 257 3 2.4 217 14 8.2 257 9 6.0

17 234 3 1.6 190 8 3.9 242 11 6.9

18 204 2 1.1 173 9 4.0 239 10 6.7

19 193 2 1.0 158 9 3.9 213 10 5.6

20 176 1 0.63 152 11 4.5 200 9 4.8

21 169 2 0.80 162 24 11 196 8 4.3

22 166 3 1.3 182 61 30 194 8 4.0

23 172 9 4.1 284 114 88 194 7 3.7

24 170 5 2.3 441 28 33 190 7 3.4

25 160 3 1.4 413 13 15 186 6 3.1

26 154 2 0.95 378 12 12 190 6 3.1

27 154 2 0.84 348 11 9.9 212 6 3.4

28 143 3 1.0 319 9 8.2 225 6 3.7

29 138 3 1.1 289 8 6.5 227 7 4.0

30 128 3 1.0 272 7 5.3 237 7 4.4

31 123 3 1.0 267 7 5.0 -- -- --

Total1 7,912 -- 154.92 6,167 -- 349.27 6,720 -- 120.5

Mean 255 6 5.0 199 20 11 224 7 4.0

Max 532 22 25 441 114 88 262 11 6.9

Min 123 1 0.63 113 3 0.97 186 4 2.8

1

Total for water year 2014 (unrounded sum of daily values): streamflow=98,524 ft3/s (annual runoff=195,400 acre-feet); suspended-sediment 

discharge=12,107.59 tons.
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 Clark Fork at Turah Bridge, near Bonner, Montana (12334550), 

October 2013 through September 2014.

[ft3/s, cubic foot 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

1 910 27 65 806 10 21 780 8 17

2 875 26 61 810 9 21 839 8 19

3 846 25 57 823 9 20 792 9 18

4 849 24 55 818 9 20 681 9 16

5 846 23 53 794 9 18 e390 9 9.5

6 841 22 51 781 8 17 e280 9 7.0

7 841 22 49 806 8 18 e250 10 6.5

8 836 21 47 837 8 18 e255 10 6.8

9 844 20 45 848 8 19 e270 10 7.5

10 845 19 43 826 8 19 e310 11 9.1

11 845 18 41 813 9 19 e380 11 12

12 849 17 39 811 9 19 e440 13 15

13 849 16 37 805 9 19 e520 15 21

14 849 15 35 806 9 19 e590 19 30

15 851 15 34 799 9 19 e620 23 39

16 850 14 33 805 8 18 e640 28 49

17 840 14 31 802 8 17 e660 31 55

18 843 13 30 778 7 16 e690 28 52

19 841 13 29 770 7 15 700 22 41

20 834 12 28 778 7 14 e650 14 24

21 820 12 27 760 6 13 649 8 14

22 807 12 26 668 6 11 651 10 17

23 802 12 25 678 6 11 683 12 22

24 795 11 24 675 6 12 699 11 20

25 793 11 24 676 7 12 673 9 17

26 787 11 23 680 7 13 645 9 15

27 783 11 23 691 7 13 661 8 15

28 783 11 22 699 7 14 679 9 16

29 780 10 22 673 8 14 677 9 17

30 745 10 21 744 8 16 658 10 18

31 792 10 21 -- -- -- 686 11 20

Total1 25,671 -- 1,121 23,060 -- 495 18,098 -- 645.4

Mean 828 16 36 769 8 16 584 13 21

Max 910 27 65 848 10 21 839 31 55

Min 745 10 21 668 6 11 250 8 6.5
Data 45

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

October 2013 through September 2014.—Continued

[ft3/s, cubic foot 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

1 696 10 19 e470 5 6.4 e480 4 5.8

2 679 10 18 e480 4 5.8 e400 5 4.9

3 703 10 19 e460 4 4.9 e400 6 6.3

4 699 10 18 e470 3 4.4 e500 8 11

5 e580 9 13 e440 3 3.9 768 13 27

6 e460 7 9.0 e320 4 3.2 991 69 185

7 e500 7 9.0 e300 4 3.6 2,120 269 1,540

8 540 7 11 e390 7 7.3 2,310 333 2,080

9 672 9 16 e420 13 14 2,040 164 902

10 687 10 18 e460 20 25 3,190 553 4,770

11 682 10 18 e480 29 37 3,820 354 3,650

12 708 9 18 e510 38 53 2,770 180 1,350

13 697 9 17 e560 49 74 2,140 90 520

14 733 10 20 e590 56 89 1,930 61 320

15 733 11 22 e600 47 76 1,750 47 222

16 707 12 22 e630 25 43 1,690 44 202

17 668 11 20 e650 13 23 1,840 60 299

18 657 10 18 672 12 22 1,720 53 244

19 638 9 16 687 12 22 1,490 29 117

20 655 9 16 670 10 18 1,410 25 96

21 624 9 15 648 8 14 1,330 23 82

22 621 9 15 630 6 11 1,240 20 68

23 650 9 15 620 7 12 1,190 18 59

24 624 8 14 e600 9 14 1,160 18 56

25 604 8 13 e540 9 14 1,140 18 54

26 611 8 13 e490 8 11 1,170 17 53

27 596 7 12 e480 7 8.9 1,240 21 71

28 e540 7 10 e480 5 7.0 1,220 18 60

29 e520 7 9.4 -- -- -- 1,280 18 62

30 e620 6 11 -- -- -- 1,460 26 103

31 e540 6 8.5 -- -- -- 1,400 23 87

Total1 19,644 -- 472.9 14,747 -- 627.4 47,589 -- 17,307

Mean 634 9 15 527 15 22 1,535 83 558

Max 733 12 22 687 56 89 3,820 553 4,770

Min 460 6 8.5 300 3 3.2 400 4 4.9
46 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

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

October 2013 through September 2014.—Continued

[ft3/s, cubic foot 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)

April May June

1 1,330 16 59 2,380 37 235 5,070 67 916

2 1,310 15 53 2,680 64 466 4,840 64 832

3 1,300 14 49 3,370 136 1,240 4,670 63 798

4 1,300 14 51 4,320 185 2,160 4,520 58 707

5 1,340 15 56 4,830 199 2,600 4,390 51 605

6 1,340 15 53 4,690 135 1,700 4,260 54 623

7 1,390 17 65 4,380 96 1,130 4,030 43 473

8 1,630 36 158 3,970 67 723 3,720 41 407

9 2,150 112 651 3,750 56 570 3,490 33 310

10 2,520 149 1,010 3,690 49 484 3,410 34 314

11 2,380 84 541 3,630 41 401 3,280 28 251

12 2,390 68 437 3,380 34 306 3,090 26 220

13 2,310 58 360 3,140 31 261 3,000 25 206

14 2,060 37 207 2,960 25 203 2,980 23 185

15 1,960 32 169 3,000 27 222 2,870 22 169

16 1,900 26 136 3,330 37 331 2,730 20 148

17 1,800 20 99 3,880 61 643 2,890 26 201

18 1,840 23 114 4,680 117 1,470 3,060 30 245

19 1,950 25 131 5,230 137 1,930 3,000 24 191

20 1,960 28 146 4,980 99 1,340 2,880 21 166

21 2,070 28 157 4,780 72 924 2,720 19 139

22 2,260 45 272 4,870 69 907 2,750 18 134

23 2,580 67 467 5,240 111 1,560 2,750 18 134

24 2,670 79 568 5,800 194 3,040 2,680 18 127

25 2,550 51 353 6,140 206 3,410 2,670 18 129

26 2,650 59 423 6,090 167 2,750 3,000 44 353

27 2,880 97 752 6,180 137 2,290 3,490 69 647

28 2,670 61 439 6,210 127 2,120 3,500 52 487

29 2,490 43 291 6,110 110 1,810 3,370 42 383

30 2,360 37 238 5,810 95 1,490 3,000 30 241

31 -- -- -- 5,280 77 1,090 -- -- --

Total1 61,340 -- 8,505 138,780 -- 39,806 102,110 -- 10,741

Mean 2,045 46 284 4,477 97 1,280 3,404 36 358

Max 2,880 149 1,010 6,210 206 3,410 5,070 69 916

Min 1,300 14 49 2,380 25 203 2,670 18 127
Data 47

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

October 2013 through September 2014.—Continued

[ft3/s, cubic foot 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)

July August September

1 2,670 22 156 831 4 9.0 1,030 10 28

2 2,440 19 124 813 4 8.8 1,000 9 25

3 2,270 14 89 797 4 8.6 972 8 22

4 2,180 12 72 786 4 8.5 948 8 20

5 2,140 12 69 797 4 8.7 920 7 18

6 2,060 11 59 782 4 9.1 909 7 17

7 1,930 11 59 718 5 8.8 892 7 17

8 1,790 9 45 696 5 9.0 884 7 17

9 1,680 8 35 710 5 9.6 877 7 16

10 1,600 6 28 694 5 9.4 860 7 16

11 1,510 6 25 667 5 9.0 881 6 15

12 1,420 6 25 659 5 8.4 913 6 15

13 1,360 7 26 664 4 7.5 942 6 16

14 1,310 7 25 712 5 9.1 947 7 17

15 1,330 7 25 819 6 13 931 7 18

16 1,380 7 27 856 8 17 909 8 19

17 1,390 8 29 846 8 18 895 8 19

18 1,310 7 24 823 7 16 880 7 18

19 1,240 6 20 777 6 12 860 7 16

20 1,180 6 19 749 5 11 848 6 15

21 1,120 6 18 770 9 19 822 6 13

22 1,090 6 18 879 19 46 802 6 13

23 1,110 6 17 1,000 45 122 786 6 13

24 1,110 5 14 1,360 47 173 769 6 12

25 1,080 4 12 1,420 40 155 748 6 12

26 1,040 4 11 1,320 33 117 734 6 12

27 985 4 11 1,230 26 87 744 7 14

28 949 4 10 1,190 20 65 788 7 16

29 921 4 9.9 1,140 16 49 820 8 18

30 891 4 9.6 1,110 14 41 858 9 20

31 856 4 9.2 1,080 12 34 -- -- --

Total1 45,342 -- 1,120.7 27,695 -- 1,118.5 26,169 -- 507

Mean 1,463 8 36 893 12 36 872 7 17

Max 2,670 22 156 1,420 47 173 1,030 10 28

Min 856 4 9.2 659 4 7.5 734 6 12

1

Total for water year 2014 (unrounded sum of daily values): streamflow=550,245 ft3/s (annual runoff=1,091,000 acre-feet); suspended-sediment discharge=82,466.9 tons.
48 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2013 

through September 2014.

[ft3/s, cubic foot 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

1 592 3 4.8 511 2 2.8 569 6 9.2

2 592 3 4.8 508 2 2.7 593 6 9.6

3 581 3 4.7 516 2 2.8 563 5 7.6

4 569 3 4.6 512 2 2.8 e350 3 2.8

5 565 3 4.6 512 2 2.8 e310 2 1.7

6 561 3 4.5 515 2 2.8 e280 1 0.76

7 570 3 4.6 519 2 2.8 e260 1 0.70

8 584 3 4.7 535 2 2.9 e250 1 0.68

9 595 3 4.8 536 2 2.9 e240 1 0.65

10 597 3 4.8 544 2 2.9 e250 1 0.68

11 597 3 4.8 552 2 3.0 e300 1 0.81

12 592 3 4.8 549 2 3.0 e440 2 2.4

13 589 3 4.8 544 2 2.9 e510 4 5.5

14 587 3 4.8 536 2 2.9 e480 4 5.2

15 582 3 4.7 532 2 2.9 e480 4 5.2

16 576 3 4.7 542 2 2.9 e480 5 6.5

17 570 3 4.6 540 2 2.9 e480 5 6.5

18 557 2 3.0 535 2 2.9 e490 5 6.6

19 547 2 3.0 539 2 2.9 e500 5 6.8

20 538 2 2.9 553 2 3.0 e440 4 4.8

21 530 2 2.9 514 2 2.8 e440 3 3.6

22 527 2 2.8 e460 2 2.5 e450 2 2.4

23 526 2 2.8 e350 2 1.9 e500 2 2.7

24 525 2 2.8 e420 2 2.3 e500 2 2.7

25 524 2 2.8 e500 3 4.0 e470 1 1.3

26 526 2 2.8 e520 4 5.6 e480 4 5.2

27 524 2 2.8 e510 4 5.5 e470 6 7.6

28 521 2 2.8 e520 4 5.6 e460 6 7.5

29 513 2 2.8 e500 4 5.4 e460 4 5.0

30 507 2 2.7 e570 5 7.7 e460 3 3.7

31 514 2 2.8 -- -- -- e500 2 2.7

Total1 17,278 -- 119.8 15,494 -- 100.8 13,455 -- 129.08

Mean 557 3 3.9 516 2 3.4 434 3 4.2

Max 597 3 4.8 570 5 7.7 593 6 9.6

Min 507 2 2.7 350 2 1.9 240 1 0.65
Data 49

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2013 

through September 2014.—Continued

[ft3/s, cubic foot 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 2 2.8 e400 2 2.2 e450 2 2.4

2 492 2 2.7 e380 2 2.1 e500 2 2.7

3 506 2 2.7 e350 2 1.9 e650 2 3.5

4 488 2 2.6 e300 2 1.6 666 2 3.6

5 e400 1 1.1 e240 2 1.3 669 2 3.6

6 e300 1 0.81 e230 2 1.2 657 4 7.1

7 e380 1 1.0 e240 2 1.3 712 6 12

8 e460 1 1.2 e260 2 1.4 722 6 12

9 e480 2 2.6 e320 2 1.7 776 9 19

10 e500 3 4.0 e370 2 2.0 1,070 19 55

11 483 3 3.9 e420 2 2.3 1,490 29 117

12 480 2 2.6 e450 2 2.4 1,590 26 112

13 479 2 2.6 e510 2 2.8 1,410 21 80

14 569 2 3.1 e540 1 1.5 1,250 25 84

15 546 2 2.9 e560 1 1.5 1,130 32 98

16 493 2 2.7 e580 2 3.1 1,080 28 82

17 e500 3 4.0 e600 2 3.2 1,170 24 76

18 e460 3 3.7 e600 1 1.6 1,160 26 81

19 e440 4 4.8 e610 1 1.6 981 27 72

20 e440 3 3.6 e480 1 1.3 897 19 46

21 e430 1 1.2 e480 1 1.3 829 13 29

22 e440 1 1.2 e460 1 1.2 768 10 21

23 e450 1 1.2 e440 3 3.6 747 7 14

24 e450 2 2.4 e410 6 6.6 743 6 12

25 e420 2 2.3 e370 7 7.0 738 6 12

26 e400 2 2.2 e400 6 6.5 745 9 18

27 e400 1 1.1 e460 4 5.0 794 14 30

28 e370 1 1.0 e460 3 3.7 798 13 28

29 e420 1 1.1 -- -- -- 932 15 38

30 e420 2 2.3 -- -- -- 1,090 17 50

31 e410 2 2.2 -- -- -- 1,080 16 47

Total1 14,016 -- 73.61 11,920 -- 72.9 28,294 -- 1,267.9

Mean 452 2 2.4 426 2 2.6 913 14 41

Max 569 4 4.8 610 7 7.0 1,590 32 117

Min 300 1 0.81 230 1 1.2 450 2 2.4
50 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2013 

through September 2014.—Continued

[ft3/s, cubic foot 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)

April May June

1 1,040 16 45 3,890 20 210 7,930 40 856

2 1,040 16 45 4,600 33 410 7,710 35 729

3 1,040 16 45 6,060 85 1,390 7,550 35 713

4 1,090 14 41 7,310 94 1,860 7,490 32 647

5 1,120 13 39 8,060 93 2,020 7,350 29 576

6 1,180 14 45 7,740 64 1,340 7,170 30 581

7 1,330 19 68 7,170 49 949 6,750 29 529

8 1,530 25 103 6,580 41 728 6,290 26 442

9 1,930 36 188 6,150 33 548 6,010 24 389

10 2,290 37 229 5,830 28 441 5,950 21 337

11 2,420 30 196 5,540 24 359 5,820 20 314

12 2,580 25 174 5,160 20 279 5,470 22 325

13 2,620 18 127 4,830 17 222 5,360 19 275

14 2,540 16 110 4,720 16 204 5,370 17 246

15 2,460 16 106 4,870 15 197 5,050 15 205

16 2,390 14 90 5,670 22 337 4,670 15 189

17 2,320 12 75 6,740 42 764 4,640 13 163

18 2,360 12 76 7,830 68 1,440 4,600 12 149

19 2,450 12 79 8,060 61 1,330 4,660 13 164

20 2,560 12 83 7,950 55 1,180 4,600 12 149

21 2,730 15 111 7,900 50 1,070 4,360 11 129

22 3,090 23 192 8,220 51 1,130 4,260 10 115

23 3,590 36 349 8,930 62 1,490 4,330 16 187

24 3,890 44 462 10,000 102 2,750 4,290 14 162

25 3,870 41 428 10,400 110 3,090 4,260 19 219

26 4,000 35 378 10,500 103 2,920 4,360 14 165

27 4,180 37 418 10,600 102 2,920 4,520 16 195

28 4,120 37 412 10,200 75 2,070 4,400 15 178

29 3,910 27 285 9,900 66 1,760 4,180 12 135

30 3,760 22 223 9,250 56 1,400 3,900 10 105

31 -- -- -- 8,410 46 1,040 -- -- --

Total1 75,430 -- 5,222 229,070 -- 37,848 163,300 -- 9,568

Mean 2,514 23 174 7,389 55 1,220 5,443 20 319

Max 4,180 44 462 10,600 110 3,090 7,930 40 856

Min 1,040 12 39 3,890 15 197 3,900 10 105
Data 51

Table 7. Daily mean streamflow and suspended-sediment data for Blackfoot River near Bonner, Montana (12340000), October 2013 

through September 2014.—Continued

[ft3/s, cubic foot 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)

July August September

1 3,610 10 97 975 2 5.3 738 1 2.0

2 3,350 9 81 984 3 8.0 741 1 2.0

3 3,200 9 78 985 4 11 721 2 3.9

4 3,130 8 68 961 5 13 706 2 3.8

5 2,990 8 65 976 6 16 693 2 3.7

6 2,810 7 53 993 6 16 686 2 3.7

7 2,630 6 43 950 6 15 682 2 3.7

8 2,480 6 40 905 6 15 671 2 3.6

9 2,330 6 38 905 5 12 659 2 3.6

10 2,200 5 30 889 4 9.6 656 2 3.5

11 2,090 4 23 855 3 6.9 665 2 3.6

12 1,990 4 21 831 2 4.5 669 2 3.6

13 1,880 4 20 815 2 4.4 672 2 3.6

14 1,780 4 19 823 2 4.4 677 2 3.7

15 1,740 4 19 850 2 4.6 670 3 5.4

16 1,810 4 20 848 2 4.6 665 3 5.4

17 1,730 3 14 831 2 4.5 659 3 5.3

18 1,600 2 8.6 807 2 4.4 644 3 5.2

19 1,520 2 8.2 777 2 4.2 625 2 3.4

20 1,440 2 7.8 764 2 4.1 617 2 3.3

21 1,380 2 7.5 765 2 4.1 613 2 3.3

22 1,330 2 7.2 782 2 4.2 605 2 3.3

23 1,290 4 14 829 2 4.5 591 2 3.2

24 1,290 3 10 871 2 4.7 588 3 4.8

25 1,240 2 6.7 886 2 4.8 591 3 4.8

26 1,200 2 6.5 857 2 4.6 589 3 4.8

27 1,140 2 6.2 821 2 4.4 582 3 4.7

28 1,090 2 5.9 790 2 4.3 586 4 6.3

29 1,060 2 5.7 764 2 4.1 590 4 6.4

30 1,030 2 5.6 749 2 4.0 604 4 6.5

31 999 2 5.4 744 1 2.0 -- -- --

Total1 59,359 -- 834.3 26,582 -- 213.2 19,455 -- 124.1

Mean 1,915 4 27 857 3 6.9 648 2 4.1

Max 3,610 10 97 993 6 16 741 4 6.5

Min 999 2 5.4 744 1 2.0 582 1 2.0

1

Total for water year 2014 (unrounded sum of daily values): streamflow=673,653 ft3/s (annual runoff=1,336,00 acre-feet); suspended-sediment discharge=55,573.69 tons.
52 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2013 

through September 2014.

[ft3/s, cubic foot 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 1,460 13 51 1,280 4 14 1,360 21 77

2 1,440 13 51 1,280 4 14 1,460 26 102

3 1,390 12 45 1,300 4 14 1,350 22 80

4 1,380 11 41 1,300 4 14 e1,050 17 48

5 1,370 10 37 1,270 5 17 e750 13 26

6 1,360 10 37 1,260 5 17 e550 10 15

7 1,370 10 37 1,290 5 17 e530 8 11

8 1,380 10 37 1,330 5 18 e500 7 9.4

9 1,400 10 38 1,350 5 18 e510 6 8.3

10 1,400 11 42 1,340 5 18 e550 7 10

11 1,410 11 42 1,330 5 18 e680 10 18

12 1,400 11 42 1,320 5 18 e980 13 34

13 1,400 11 42 1,310 5 18 e1,030 16 44

14 1,400 12 45 1,310 5 18 e1,070 20 58

15 1,400 12 45 1,330 5 18 e1,100 23 68

16 1,390 11 41 1,370 6 22 e1,120 26 79

17 1,370 10 37 1,370 6 22 e1,140 29 89

18 1,360 10 37 1,340 7 25 e1,170 29 92

19 1,350 9 33 1,330 7 25 e1,200 26 84

20 1,330 8 29 1,360 8 29 e1,080 19 55

21 1,310 7 25 1,320 8 29 e1,100 10 30

22 1,290 6 21 1,120 9 27 e1,100 7 21

23 1,280 6 21 1,020 10 28 1,180 6 19

24 1,280 6 21 1,090 11 32 1,200 5 16

25 1,280 5 17 1,170 12 38 1,140 4 12

26 1,270 5 17 1,200 12 39 1,110 5 15

27 1,270 5 17 1,200 13 42 1,120 6 18

28 1,260 4 14 1,190 14 45 1,140 5 15

29 1,260 4 14 1,170 15 47 1,140 4 12

30 1,210 4 13 1,310 17 60 1,110 4 12

31 1,260 4 14 -- -- -- 1,170 5 16

Total1 41,730 -- 1,003 38,160 -- 761 31,690 -- 1,193.7

Mean 1,346 9 32 1,272 8 25 1,022 13 39

Max 1,460 13 51 1,370 17 60 1,460 29 102

Min 1,210 4 13 1,020 4 14 500 4 8.3
Data 53

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2013 

through September 2014.—Continued

[ft3/s, cubic foot 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 1,190 6 19 938 4 10 e910 3 7.4

2 1,160 6 19 864 4 9.3 e924 3 7.5

3 1,210 6 20 e1,030 5 14 e1,050 3 8.5

4 1,200 6 19 e891 8 19 e1,170 7 22

5 1,070 5 14 e741 10 20 e1,380 17 63

6 e760 3 6.2 e672 6 11 e1,560 31 131

7 e880 3 7.1 e695 3 5.6 2,660 156 1,120

8 e1,000 3 8.1 e780 2 4.2 3,030 200 1,640

9 e1,100 5 15 e886 2 4.8 2,850 115 885

10 1,180 6 19 e986 3 8.0 4,210 250 2,840

11 1,170 6 19 e1,080 4 12 5,610 221 3,350

12 1,200 5 16 e1,170 5 16 4,660 114 1,430

13 1,190 5 16 e1,290 6 21 3,740 57 576

14 1,320 7 25 e1,410 9 34 3,330 43 387

15 1,310 7 25 e1,470 12 48 3,000 38 308

16 1,220 6 20 e1,510 18 73 2,870 33 256

17 1,150 5 16 e1,540 19 79 3,080 37 308

18 1,120 5 15 1,390 14 53 3,000 31 251

19 1,080 4 12 1,170 10 32 2,560 27 187

20 1,090 4 12 1,130 8 24 2,360 22 140

21 1,050 4 11 1,100 6 18 2,210 18 107

22 1,060 4 11 1,070 4 12 2,040 15 83

23 1,100 4 12 1,050 5 14 1,960 12 64

24 1,070 4 12 996 6 16 1,910 12 62

25 1,030 4 11 923 7 17 1,880 12 61

26 1,010 4 11 895 6 14 1,900 11 56

27 986 4 11 948 5 13 2,040 15 83

28 905 4 9.8 e940 4 10 2,030 13 71

29 938 4 10 -- -- -- 2,210 14 84

30 1,060 7 20 -- -- -- 2,600 17 119

31 954 6 15 -- -- -- 2,580 18 125

Total1 33,763 -- 456.2 29,565 -- 611.9 77,314 -- 14,832.4

Mean 1,089 5 15 1,056 7 22 2,494 50 478

Max 1,320 7 25 1,540 19 79 5,610 250 3,350

Min 760 3 6.2 672 2 4.2 910 3 7.4
54 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2013 

through September 2014.—Continued

[ft3/s, cubic foot 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)

April May June

1 2,440 16 105 6,250 23 388 13,400 48 1,740

2 2,400 14 91 7,200 41 797 12,900 44 1,530

3 2,400 12 78 9,370 106 2,680 12,500 42 1,420

4 2,440 12 79 11,400 142 4,370 12,300 40 1,330

5 2,500 12 81 12,800 143 4,940 12,100 38 1,240

6 2,570 13 90 12,500 93 3,140 11,800 36 1,150

7 2,740 17 126 11,600 68 2,130 11,100 31 929

8 3,180 26 223 10,600 51 1,460 10,300 27 751

9 4,110 62 688 9,890 41 1,090 9,770 27 712

10 4,980 83 1,120 9,490 34 871 9,600 24 622

11 5,010 57 771 9,190 30 744 9,350 20 505

12 5,110 47 648 8,570 24 555 8,810 19 452

13 5,140 37 513 7,970 22 473 8,550 18 416

14 4,760 24 308 7,640 19 392 8,560 18 416

15 4,550 21 258 7,780 19 399 8,150 16 352

16 4,440 18 216 8,870 28 671 7,590 15 307

17 4,250 14 161 10,500 52 1,470 7,670 15 311

18 4,260 14 161 12,400 92 3,080 7,870 16 340

19 4,470 16 193 13,300 102 3,660 7,880 16 340

20 4,580 16 198 13,000 83 2,910 7,720 16 334

21 4,850 19 249 12,800 61 2,110 7,270 14 275

22 5,360 27 391 13,200 60 2,140 7,180 14 271

23 6,180 44 734 14,300 80 3,090 7,250 14 274

24 6,690 53 957 16,100 134 5,820 7,150 13 251

25 6,560 44 779 17,000 139 6,380 7,070 12 229

26 6,610 43 767 17,000 121 5,550 7,510 18 365

27 7,100 57 1,090 17,100 103 4,760 8,200 30 664

28 7,000 46 869 16,800 89 4,040 8,140 26 571

29 6,570 32 568 16,500 82 3,650 7,810 23 485

30 6,240 26 438 15,700 70 2,970 7,140 18 347

31 -- -- -- 14,200 55 2,110 -- -- --

Total1 139,490 -- 12,950 371,020 -- 78,840 272,640 -- 18,929

Mean 4,650 31 432 11,970 71 2,540 9,088 24 631

Max 7,100 83 1,120 17,100 143 6,380 13,400 48 1,740

Min 2,400 12 78 6,250 19 388 7,070 12 229
Data 55

Table 8. Daily mean streamflow and suspended-sediment data for Clark Fork above Missoula, Montana (12340500), October 2013 

through September 2014.—Continued

[ft3/s, cubic foot 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)

July August September

1 6,500 14 246 1,850 2 10 1,770 5 24

2 5,980 12 194 1,830 2 9.9 1,730 4 19

3 5,630 10 152 1,820 2 9.8 1,690 4 18

4 5,450 10 147 1,790 2 9.7 1,640 3 13

5 5,300 9 129 1,800 2 9.7 1,610 3 13

6 5,020 8 108 1,810 2 9.8 1,580 3 13

7 4,720 8 102 1,720 2 9.3 1,560 4 17

8 4,410 7 83 1,640 2 8.9 1,540 4 17

9 4,150 6 67 1,640 2 8.9 1,520 4 16

10 3,940 5 53 1,610 2 8.7 1,500 4 16

11 3,730 4 40 1,560 2 8.4 1,520 4 16

12 3,530 4 38 1,520 2 8.2 1,560 4 17

13 3,360 4 36 1,500 2 8.1 1,590 4 17

14 3,190 4 34 1,550 2 8.4 1,610 4 17

15 3,160 4 34 1,680 3 14 1,590 4 17

16 3,270 4 35 1,710 3 14 1,560 4 17

17 3,230 4 35 1,700 3 14 1,530 4 17

18 3,020 3 24 1,650 3 13 1,510 4 16

19 2,860 3 23 1,570 2 8.5 1,460 4 16

20 2,720 3 22 1,510 2 8.2 1,440 4 16

21 2,590 3 21 1,530 2 8.3 1,410 4 15

22 2,510 2 14 1,640 16 71 1,380 4 15

23 2,480 2 13 1,800 22 107 1,350 4 15

24 2,480 2 13 2,190 19 112 1,320 3 11

25 2,400 2 13 2,320 18 113 1,310 3 11

26 2,310 2 12 2,200 14 83 1,290 3 10

27 2,200 2 12 2,070 11 61 1,280 3 10

28 2,110 2 11 2,000 7 38 1,330 3 11

29 2,040 3 17 1,910 6 31 1,360 4 15

30 1,980 2 11 1,850 6 30 1,420 5 19

31 1,910 2 10 1,820 5 25 -- -- --

Total1 108,180 -- 1,749 54,790 -- 878.8 44,960 -- 464

Mean 3,490 5 56 1,767 5 28 1,499 4 15

Max 6,500 14 246 2,320 22 113 1,770 5 24

Min 1,910 2 10 1,500 2 8.1 1,280 3 10

1

Total for water year 2014 (unrounded sum of daily values): streamflow=1,243,302 ft3/s (annual runoff=2,466,000 acre-feet); suspended-sediment discharge=132,669.0 tons.
56 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 9. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Mill Creek at Opportunity, Montana

(12323700), April through September 2014.

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 ± 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

April May June

1 -- -- -- 9.5 5.5 6.5 11 6.0 7.5

2 -- -- -- 18 7.5 10 9.0 5.5 7.0

3 3.5 2.5 3.0 27 15 21 10 6.0 7.5

4 3.5 2.5 3.0 30 16 21 12 8.0 9.5

5 4.0 3.0 3.0 30 17 22 12 5.5 7.0

6 4.0 3.0 3.5 24 11 15 12 5.5 8.0

7 7.0 3.0 4.0 14 9.5 11 12 7.5 8.5

8 11 4.5 6.5 14 9.0 11 9.0 7.0 8.0

9 15 7.0 9.5 13 7.0 8.5 9.0 7.0 8.0

10 14 7.5 10 10 7.5 8.5 10 7.5 8.5

11 10 6.0 8.0 10 7.0 8.0 8.5 7.0 7.5

12 10 6.0 8.0 9.0 7.0 7.5 9.0 7.0 7.5

13 7.5 5.5 6.5 9.0 6.0 7.0 9.5 7.5 8.0

14 7.5 5.0 6.0 8.5 6.0 7.0 9.0 7.0 7.5

15 7.0 4.5 5.5 10 6.5 7.5 8.0 6.5 7.0

16 6.5 4.5 5.0 12 8.0 9.5 8.0 6.0 6.5

17 6.5 3.5 4.5 23 12 14 8.5 6.0 7.0

18 6.0 4.0 5.0 43 17 24 7.5 5.5 6.5

19 6.5 4.0 5.0 22 13 16 7.5 5.0 6.0

20 6.0 4.0 5.0 15 9.0 12 9.5 6.5 7.5

21 7.5 4.5 6.0 13 8.0 10 11 7.0 8.5

22 21 5.5 9.0 30 11 15 8.5 6.5 7.5

23 25 7.0 12 64 21 32 8.0 6.0 6.5

24 9.0 6.0 7.5 -- -- -- 8.0 6.5 7.0

25 17 6.0 8.5 -- -- -- 16 7.5 10

26 24 6.5 10 -- -- -- 9.5 6.5 8.0

27 8.5 6.0 7.0 -- -- -- 8.0 5.0 6.0

28 7.5 5.5 6.5 -- -- -- 5.5 4.0 5.0

29 8.0 5.0 6.0 -- -- -- 5.5 4.0 4.5

30 7.5 5.0 6.0 -- -- -- 5.5 4.0 4.5

31 -- -- -- 10 6.5 8.0 -- -- --

Month1 25 2.5 6.4 64 5.5 13 16 4.0 7.3
Data 57

Table 9. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Mill Creek at Opportunity, Montana 

(12323700), April through September 2014.—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 5.0 3.5 4.0 5.0 3.5 4.0

2 6.5 3.0 4.5 5.0 3.0 4.0 5.0 3.5 4.0

3 6.0 3.5 4.5 5.0 3.0 4.0 4.5 3.0 3.5

4 5.5 4.0 4.5 4.5 3.0 4.0 4.5 3.5 4.0

5 6.0 4.0 5.0 6.0 4.0 4.5 4.5 3.0 3.5

6 6.5 4.0 5.0 5.0 3.5 4.5 4.5 2.5 3.5

7 6.0 4.0 5.0 5.0 3.5 4.0 4.0 3.0 3.5

8 6.5 4.5 5.0 4.5 3.5 4.0 4.0 3.0 3.5

9 6.0 4.0 5.0 4.5 3.0 4.0 4.0 3.5 3.5

10 9.0 4.0 5.5 4.5 3.0 3.5 4.5 3.0 3.5

11 -- -- -- 4.5 3.0 3.5 4.0 3.0 3.5

12 -- -- -- 4.5 3.0 3.5 4.5 3.0 3.5

13 -- -- -- 11 3.0 4.5 4.0 3.0 3.5

14 -- -- -- 12 4.0 7.0 4.5 3.0 3.5

15 -- -- -- 19 3.0 5.0 3.5 2.5 3.0

16 -- -- -- 5.0 3.0 4.0 3.5 2.5 3.0

17 -- -- -- 4.5 3.0 3.5 3.5 2.0 3.0

18 6.5 5.0 5.5 4.5 2.0 3.5 3.5 2.0 2.5

19 6.5 3.0 4.5 20 3.0 4.0 3.0 2.0 2.5

20 5.5 3.5 4.5 5.0 3.0 4.0 3.0 2.0 2.5

21 5.5 3.0 4.5 5.5 4.0 4.5 3.0 2.0 2.5

22 5.5 3.5 4.5 10 4.5 5.5 3.0 2.0 2.5

23 5.5 3.5 4.5 32 10 20 2.5 2.0 2.0

24 6.0 4.0 4.5 17 6.5 9.0 2.5 1.5 2.0

25 5.5 3.5 4.5 8.5 5.0 6.5 3.5 2.0 2.5

26 5.0 3.0 4.0 7.0 4.5 5.5 2.5 2.0 2.0

27 4.5 2.5 3.5 6.0 4.0 5.0 4.5 2.0 2.5

28 5.0 3.0 4.0 6.0 4.0 5.0 4.0 3.0 3.5

29 5.5 3.5 4.5 5.5 4.0 4.5 3.5 2.5 3.0

30 4.5 3.0 4.0 5.5 4.0 4.5 4.0 2.5 3.5

31 5.0 3.5 4.0 5.0 3.5 4.0 -- -- --

Month1 9.0 2.5 4.6 32 2.0 5.1 5.0 1.5 3.1

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 10. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Willow Creek at Opportunity, 

Montana (12323720), April through September 2014.

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 ± 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

April May June

1 -- -- -- -- -- -- 9.0 4.5 5.5

2 -- -- -- -- -- -- 8.0 4.5 5.5

3 5.5 3.5 4.5 25 17 21 6.0 4.0 4.5

4 5.0 4.0 4.5 -- -- -- 6.0 4.0 4.5

5 5.0 4.0 4.0 -- -- -- 7.5 4.0 5.0

6 5.0 4.0 4.0 -- -- -- 5.5 4.0 4.5

7 8.5 4.0 6.5 -- -- -- 5.0 3.5 4.0

8 8.0 6.0 6.5 -- -- -- 5.0 3.5 4.0

9 10 6.5 8.5 -- -- -- 6.0 3.0 4.5

10 14 8.5 11 -- -- -- 7.0 3.5 5.0

11 -- -- -- -- -- -- 6.5 4.0 5.0

12 -- -- -- -- -- -- 6.0 3.5 4.5

13 24 13 16 12 7.5 7.5 6.5 3.5 4.0

14 -- -- -- 8.0 7.5 7.5 5.0 3.0 3.5

15 -- -- -- -- -- -- 6.0 2.5 3.5

16 -- -- -- 12 7.5 9.0 5.0 2.5 3.0

17 -- -- -- 13 7.5 11 14 3.0 6.5

18 -- -- -- 15 8.5 10 4.5 2.5 3.0

19 -- -- -- 14 9.0 11 4.0 2.0 2.5

20 -- -- -- 12 8.0 9.0 -- -- --

21 -- -- -- 9.0 7.5 8.0 -- -- --

22 -- -- -- 11 7.5 8.5 -- -- --

23 -- -- -- 10 8.0 9.0 -- -- --

24 -- -- -- 10 8.5 9.5 -- -- --

25 -- -- -- 10 8.0 9.0 -- -- --

26 -- -- -- 8.5 7.0 7.5 -- -- --

27 -- -- -- 8.0 6.5 7.0 -- -- --

28 -- -- -- 7.5 5.5 6.5 -- -- --

29 -- -- -- 8.5 5.5 6.5 -- -- --

30 -- -- -- 9.5 5.0 6.5 -- -- --

31 -- -- -- 6.5 4.5 5.5 -- -- --

Month1 24 3.5 7.3 25 4.5 8.9 14 2.0 4.3
Data 59

Table 10. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Willow Creek at Opportunity, 

Montana (12323720), April through September 2014.—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 -- -- -- 6.5 3.0 4.5 4.0 2.5 3.0

2 -- -- -- 4.5 2.5 3.5 5.0 2.5 3.5

3 5.0 2.5 3.5 5.0 3.0 4.0 4.5 2.5 3.0

4 4.0 2.0 3.0 5.0 3.0 4.0 4.0 2.5 3.0

5 4.0 1.5 3.0 5.0 3.0 3.5 3.5 2.5 3.0

6 5.0 2.0 3.0 4.5 2.5 3.5 4.0 2.5 3.0

7 5.0 2.0 3.5 4.0 2.5 3.5 4.0 2.5 3.0

8 6.5 2.5 3.5 4.5 2.5 3.5 4.5 2.5 3.5

9 8.0 2.5 5.0 4.0 2.5 3.0 4.0 2.5 3.0

10 7.5 3.0 4.5 3.5 2.0 3.0 3.5 2.5 3.0

11 7.0 2.5 4.5 4.0 2.0 2.5 4.0 2.5 3.0

12 6.0 3.0 4.0 3.5 2.0 3.0 3.5 2.0 3.0

13 10 3.5 5.0 4.0 2.5 3.0 3.5 2.5 3.0

14 10 3.5 6.0 5.0 3.5 4.0 3.5 2.5 3.0

15 8.0 4.5 6.0 16 3.0 6.5 3.5 2.5 3.0

16 7.5 3.5 5.0 13 3.0 6.0 3.5 2.5 2.5

17 7.0 3.0 4.5 5.0 2.5 3.5 3.5 2.0 2.5

18 6.0 2.5 4.0 4.0 2.5 3.0 3.5 2.0 2.5

19 5.0 2.0 3.5 4.0 2.5 3.0 4.0 2.5 3.0

20 4.5 2.0 3.0 4.0 2.5 3.0 3.5 2.5 3.0

21 6.5 2.5 3.5 4.0 2.5 3.0 3.5 2.5 3.0

22 4.5 2.0 3.5 5.0 2.5 3.5 4.0 2.5 3.0

23 7.5 3.0 4.5 9.5 4.0 7.0 3.5 2.5 3.0

24 5.5 3.0 4.0 11 4.0 6.5 4.5 2.5 3.0

25 4.5 2.5 3.5 5.5 2.5 3.5 4.5 2.5 3.0

26 4.5 2.0 3.5 5.5 2.5 4.0 4.0 2.5 3.5

27 5.0 2.5 3.5 5.0 2.5 3.5 4.5 3.0 3.5

28 5.0 3.0 3.5 4.5 2.5 3.5 4.5 3.0 3.5

29 4.5 2.5 3.5 4.5 2.5 3.5 4.5 2.5 3.5

30 6.0 3.0 4.0 4.5 3.0 3.5 5.0 3.0 4.0

31 5.0 3.0 4.0 4.5 3.0 3.5 -- -- --

Month1 10 1.5 4.0 16 2.0 3.8 5.0 2.0 3.1

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 11. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Warm Springs Creek at Warm 

Springs, Montana (12323770), April through September 2014.

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 ± 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

April May June

1 -- -- -- 3.0 1.5 2.0 7.5 5.5 6.5

2 2.0 1.0 1.5 3.5 1.5 2.5 7.5 4.5 5.5

3 2.0 1.0 1.5 5.5 2.5 4.0 6.5 4.5 5.5

4 2.0 1.0 1.0 6.0 3.5 4.5 8.0 5.0 6.5

5 2.0 1.0 1.0 6.5 3.0 4.5 7.0 4.5 5.5

6 1.5 1.0 1.0 4.5 2.5 3.0 7.0 5.0 6.0

7 2.5 1.0 1.5 3.5 2.0 2.5 6.5 4.0 5.0

8 2.5 1.0 1.5 3.5 1.5 2.5 5.0 3.5 4.0

9 3.0 1.5 2.5 3.5 2.0 2.5 5.0 3.5 4.0

10 3.5 1.5 2.5 4.5 2.0 3.0 6.5 4.0 5.0

11 2.5 1.0 2.0 4.5 2.0 3.0 7.0 3.5 5.0

12 2.5 1.0 2.0 3.0 1.5 2.5 4.5 3.0 3.5

13 2.5 1.5 2.0 3.0 1.5 2.0 8.5 3.5 4.5

14 2.5 1.0 1.5 2.5 1.0 2.0 5.0 3.0 4.0

15 2.0 1.0 1.5 3.0 1.5 2.0 6.5 3.5 4.5

16 2.5 1.0 1.5 6.0 2.0 4.5 8.0 5.5 7.0

17 2.5 1.0 1.5 13 5.0 9.5 9.0 6.0 7.5

18 2.5 1.5 1.5 27 10 20 8.0 6.0 7.0

19 2.5 1.0 1.5 20 7.5 11 8.5 6.5 7.5

20 2.5 1.0 1.5 8.5 5.5 6.5 10 7.0 7.5

21 2.0 1.0 1.5 18 6.0 7.5 8.5 5.0 6.0

22 4.0 1.5 2.5 18 7.5 12 7.5 5.5 6.5

23 4.5 2.0 3.0 33 11 22 8.5 6.5 7.5

24 3.0 1.0 2.0 42 15 28 9.5 6.5 7.5

25 5.0 1.0 2.0 24 12 19 10 6.0 7.5

26 10 2.5 5.0 25 12 18 10 4.0 5.5

27 3.5 1.5 2.5 32 14 23 10 4.5 6.0

28 3.0 1.5 2.0 23 16 19 -- -- --

29 3.0 1.5 2.0 24 13 19 -- -- --

30 3.0 1.5 2.0 15 9.0 12 -- -- --

31 -- -- -- 12 7.0 8.5 -- -- --

Month1 10 1.0 1.9 42 1.0 9.1 10 3.0 5.9
Data 61

Table 11. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Warm Springs Creek at Warm 

Springs, Montana (12323770), April through September 2014.—Continued

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 ± 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

July August September

1 -- -- -- 2.5 0.5 1.5 -- -- --

2 -- -- -- -- -- -- 3.0 1.5 2.0

3 7.5 3.0 4.0 -- -- -- 4.0 1.5 2.5

4 4.5 2.0 3.0 -- -- -- 4.0 1.5 2.0

5 4.0 2.5 3.5 -- -- -- -- -- --

6 4.0 2.0 3.0 -- -- -- -- -- --

7 3.5 2.0 2.5 -- -- -- -- -- --

8 3.5 1.5 2.5 -- -- -- -- -- --

9 4.0 2.0 2.5 -- -- -- -- -- --

10 3.5 1.5 2.5 -- -- -- -- -- --

11 4.5 2.0 3.0 -- -- -- 3.5 2.0 2.5

12 3.0 1.5 2.5 -- -- -- 4.5 1.0 2.0

13 3.5 1.0 2.0 3.5 1.5 2.0 4.0 2.0 2.5

14 3.0 1.5 2.5 5.0 2.0 3.0 4.0 2.0 2.5

15 -- -- -- 3.5 1.5 2.5 -- -- --

16 4.0 2.0 3.0 4.5 1.5 2.5 3.5 2.0 2.5

17 3.0 1.0 2.0 3.0 2.0 2.5 -- -- --

18 3.0 1.5 2.0 -- -- -- 1.5 1.0 1.5

19 3.0 1.0 2.0 -- -- -- -- -- --

20 3.0 1.0 2.0 -- -- -- -- -- --

21 2.5 1.0 1.5 16 4.5 11 -- -- --

22 3.0 1.0 2.0 18 10 13 -- -- --

23 9.0 1.5 3.0 -- -- -- -- -- --

24 3.0 1.0 2.0 -- -- -- -- -- --

25 3.5 0.5 2.0 -- -- -- -- -- --

26 3.0 0.5 1.5 -- -- -- -- -- --

27 2.5 0.5 1.5 -- -- -- -- -- --

28 3.0 0.5 1.5 -- -- -- -- -- --

29 2.5 1.0 1.5 3.5 1.5 2.5 -- -- --

30 2.5 0.5 1.5 -- -- -- -- -- --

31 2.0 0.5 1.0 4.5 2.0 2.5 -- -- --

Month1 9.0 0.5 2.3 18 0.5 4.3 4.5 1.0 2.2

1

For months with missing daily values, the means are calculated using available values.
62 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 12. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Lost Creek near Anacona, 

Montana (12323840), April through September 2014.

[Turbidity values are based on near-infrared monochrome light emitted at wavelengths of 780 to 900 nanometers with a detection angle of 90 ± 2.5 degrees to 

incident beam, reported in formazin nephelometric units (FNU). --, no data]

Day

Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean

April May June

1 -- -- -- -- -- -- 10 6.0 7.0

2 -- -- -- 14 5.0 6.5 8.5 5.5 7.0

3 3.5 2.0 2.5 18 8.5 12 10 6.0 7.5

4 3.5 2.0 2.5 23 9.0 14 12 6.5 8.5

5 3.5 2.0 2.5 -- -- -- 13 6.5 8.5

6 5.5 2.5 3.5 12 6.0 9.0 13 7.0 9.0

7 13 2.5 5.0 9.0 5.0 6.0 10 5.5 7.0

8 36 3.0 9.0 -- -- -- 9.5 4.5 6.0

9 34 5.5 13 7.0 4.0 5.0 7.0 4.5 5.5

10 20 4.5 8.0 7.0 4.0 5.0 -- -- --

11 -- -- -- 7.0 4.0 4.5 -- -- --

12 16 4.5 7.5 6.0 3.5 4.5 -- -- --

13 -- -- -- 8.0 3.5 5.0 8.5 5.5 7.0

14 18 3.0 5.5 8.0 4.0 5.0 11 3.5 5.5

15 6.0 3.5 4.5 14 4.5 6.0 5.0 3.0 4.0

16 5.0 2.5 3.5 13 7.0 9.5 5.0 3.5 4.0

17 11 3.0 5.5 34 10 18 7.5 3.5 5.0

18 9.0 3.5 5.0 61 19 33 6.0 3.0 4.0

19 6.0 3.0 4.5 26 11 15 6.5 3.5 5.0

20 6.5 3.0 4.5 15 8.0 10 24 3.0 6.0

21 18 3.5 6.0 18 8.0 10 7.0 3.5 4.5

22 13 4.5 7.5 26 10 15 9.0 3.5 5.0

23 36 4.0 8.0 50 13 20 7.5 3.5 5.0

24 18 6.0 8.5 77 24 42 6.0 3.5 4.5

25 53 4.5 9.5 -- -- -- 6.5 3.5 4.5

26 62 7.0 17 33 15 21 7.0 3.5 4.5

27 24 5.0 7.5 49 15 23 5.0 3.0 4.0

28 8.5 4.0 5.5 22 12 16 5.0 3.0 4.0

29 9.5 4.0 7.0 25 11 16 4.5 3.0 3.5

30 22 4.5 9.5 15 9.0 11 4.0 3.0 3.5

31 -- -- -- 11 7.0 8.5 -- -- --

Month1 62 2.0 6.6 77 3.5 13 24 3.0 5.5
Data 63

Table 12. Seasonal daily maximum, minimum, and mean turbidity, with monthly summary statistics at Lost Creek near Anacona, 

Montana (12323840), April through September 2014.—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 5.0 3.0 3.5 2.0 1.5 1.5 4.0 2.0 3.0

2 7.0 2.5 3.5 4.5 1.5 2.0 5.0 2.5 3.0

3 7.0 2.5 3.5 2.5 1.5 2.0 5.5 2.5 3.0

4 4.0 2.5 3.0 72 1.5 6.5 4.5 2.0 3.0

5 5.5 2.5 3.5 10 3.5 5.5 4.5 2.0 3.0

6 4.5 2.5 3.5 6.0 3.0 4.0 4.5 2.0 3.0

7 4.5 2.5 3.0 5.5 3.0 4.0 5.0 2.5 3.5

8 4.0 2.5 3.0 7.0 3.0 4.0 5.0 2.0 3.5

9 4.0 2.5 3.0 4.5 2.5 3.5 4.5 2.0 3.0

10 6.0 2.0 3.0 4.5 2.5 3.5 5.0 2.5 3.5

11 3.5 2.0 2.5 4.0 2.5 3.5 3.5 1.5 2.5

12 6.0 2.0 2.5 4.5 2.5 3.5 3.5 2.0 2.5

13 4.5 2.0 2.5 24 2.5 4.5 3.5 2.0 2.5

14 4.5 2.0 3.0 27 3.0 6.0 3.5 2.0 3.0

15 5.0 2.0 3.0 5.0 2.5 3.5 4.0 2.0 3.0

16 3.5 2.0 2.5 6.0 2.5 3.5 4.5 2.0 3.0

17 -- -- -- 4.5 2.5 3.0 3.0 1.5 2.5

18 -- -- -- 4.0 2.5 3.5 3.5 1.5 2.0

19 -- -- -- 4.5 2.5 3.5 3.0 1.5 2.0

20 -- -- -- 4.5 2.5 3.5 2.5 1.5 2.0

21 -- -- -- 7.0 3.0 4.0 3.0 1.5 2.0

22 -- -- -- 14 3.0 5.0 3.0 1.5 2.0

23 -- -- -- 32 8.5 16 2.5 1.5 2.0

24 -- -- -- 11 3.5 5.5 2.5 1.5 1.5

25 -- -- -- 5.5 3.0 4.0 2.0 1.0 1.5

26 -- -- -- 5.0 2.5 3.5 9.5 1.0 2.0

27 -- -- -- 4.5 2.5 3.5 3.5 1.5 2.5

28 -- -- -- 4.5 2.5 3.5 3.5 1.0 2.0

29 2.5 1.5 2.0 4.5 2.5 3.5 2.5 1.0 2.0

30 3.0 1.5 2.0 6.5 2.5 3.5 4.5 1.5 2.0

31 2.5 1.5 2.0 4.5 2.5 3.0 -- -- --

Month1 7.0 1.5 2.9 72 1.5 4.2 9.5 1.0 2.5

1

For months with missing daily values, the means are calculated using available values.
Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana. [hh, hour; mm, minute; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millime

reporting level; --, no data; 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) 

12323700 Mill Creek at Opportunity 8/11/2014 1630 <2.0 75.2 21.1 5.48 0.80 

8/11/2014 1635 <2.0 74.4 20.9 5.42 0.78 

12323750 Silver Bow Creek at Warm Springs 7/15/2014 1020 E3.3 125 36.2 8.42 1.72 

7/15/2014 1025 E2.8 127 36.6 8.53 1.67 

12323840 Lost Creek near Anaconda 4/22/2014 0745 <2.0 110 32.2 7.14 1.30 

4/22/2014 0750 E2.3 110 32.6 7.02 1.35 

12324200 Clark Fork at Deer Lodge 5/13/2014 1520 -- 185 54.7 11.7 -- 

5/13/2014 1525 -- 184 54.3 11.7 -- 

12324400 Clark Fork above Little Black- foot, near Garrison 3/25/2014 1525 -- 228 66.3 15.0 -- 

3/25/2014 1530 -- 232 68.0 15.2 -- 

12324680 Clark Fork at Goldcreek 11/6/2013 1105 -- 190 55.6 12.4 -- 

11/6/2013 1110 -- 200 58.3 13.1 -- 

12334550 Clark Fork at Turah Bridge, near Bonner 5/29/2014 1140 -- 60.1 17.3 4.11 -- 

5/29/2014 1145 -- 60.3 17.4 4.11 -- 

12340500 Clark Fork above Missoula 6/11/2014 1430 -- 81.5 21.9 6.54 -- 

6/11/2014 1435 -- 80.0 21.6 6.31 -- 
Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana.—Continued[hh, hour; mm, minute; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millime

ing level; --, no data; E, estimated]

Site 

number 

(fig. 1)

Site name Date Time (hhmm) Chloride, filtered (mg/L) Flouride, filtered (mg/L) Silica, filtered (mg/l) Sulfate, filtered (mg/L) Cadmium, filtered (μg/L) Cadmium, unfiltered recoverable (μg/L) 

12323700 Mill Creek at Opportunity 8/11/2014 1630 0.34 0.34 11.7 10.2 0.056 0.063 

8/11/2014 1635 0.34 0.34 11.8 10.2 0.065 0.072 

12323750 Silver Bow Creek at Warm 

Springs

7/15/2014 1020 5.98 0.50 12.7 57.2 <0.030 0.073 

7/15/2014 1025 5.98 0.50 12.7 57.2 0.031 0.075 

12323840 Lost Creek near Anaconda 4/22/2014 0745 0.96 0.45 10.9 11.9 <0.030 0.049 

4/22/2014 0750 0.96 0.45 10.9 11.9 -- -- 

12324200 Clark Fork at Deer Lodge 5/13/2014 1520 -- -- -- -- 0.056 0.152 

5/13/2014 1525 -- -- -- -- 0.067 0.150 

12324400 Clark Fork above Little Blackfoot, near Garrison 3/25/2014 1525 -- -- -- -- 0.062 0.283 

3/25/2014 1530 -- -- -- -- 0.067 0.284 

12324680 Clark Fork at Goldcreek 11/6/2013 1105 -- -- -- -- 0.036 0.081 

11/6/2013 1110 -- -- -- -- 0.033 0.093 

12334550 Clark Fork at Turah Bridge, near 

Bonner

5/29/2014 1140 -- -- -- -- 0.036 0.214 

5/29/2014 1145 -- -- -- -- 0.031 0.197 

12340500 Clark Fork above Missoula 6/11/2014 1430 -- -- -- -- <0.030 0.046 

6/11/2014 1435 -- -- -- -- <0.030 0.043 
Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana.—Continued [hh, hour; mm, minute; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millime

ing level; --, no data; E, estimated] Site number (fig. 1) Site name Date Time (hhmm) Iron, filtered (μg/L) Iron, unfiltered recoverable (μg/L) Lead, filtered (μg/L) Lead, unfiltered recoverable (μg/L) Manganese, filtered (μg/L) Manganese, unfiltered recoverable (μg/L) 

12323700 Mill Creek at Opportunity 8/11/2014 1630 88.3 159 0.144 0.44 5.82 12.7 

8/11/2014 1635 89.0 158 0.167 0.43 5.97 13.3 

12323750 Silver Bow Creek at Warm Springs 7/15/2014 1020 48.3 222 0.159 1.05 66.5 111 

7/15/2014 1025 48.8 223 0.169 1.05 66.9 110 

12323840 Lost Creek near Anaconda 4/22/2014 0745 7.1 218 <0.040 0.81 1.04 6.7 

4/22/2014 0750 7.1 -- <0.040 -- 1.03 -- 

12324200 Clark Fork at Deer Lodge 5/13/2014 1520 14.4 444 0.126 3.39 24.0 76.1 

5/13/2014 1525 13.7 460 0.125 3.48 23.8 75.1 

12324400 Clark Fork above Little Black- foot, near Garrison 3/25/2014 1525 15.1 919 0.172 7.94 65.1 149 

3/25/2014 1530 16.0 931 0.169 8.29 65.0 149 

12324680 Clark Fork at Goldcreek 11/6/2013 1105 4.5 206 <0.040 1.47 18.0 57.5 

11/6/2013 1110 5.0 218 <0.040 1.49 19.2 57.6 

12334550 Clark Fork at Turah Bridge, near Bonner 5/29/2014 1140 47.1 1,290 0.189 5.86 9.64 107 

5/29/2014 1145 48.4 1,270 0.188 5.89 9.54 102 

12340500 Clark Fork above Missoula 6/11/2014 1430 20.7 290 0.041 0.71 6.54 24.3 

6/11/2014 1435 16.3 318 <0.040 0.80 6.41 25.7 
Table 13. Analyses of field replicates for water samples, Clark Fork Basin, Montana.—Continued[hh, hour; mm, minute; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligram per liter; CaCO3, calcium carbonate; μg/L, microgram per liter; mm, millime

ing level; --, no data; E, estimated]

Site 

number 

(fig. 1)

Site name Date Time (hhmm) Arsenic, filtered (μg/L) Arsenic, unfiltered recoverable (μg/L) Organic carbon, filtered (mg/L) Sediment suspe

(percent finer 

0.062 mm) 

12323700 Mill Creek at Opportunity 8/11/2014 1630 24.4 25.6 1.85 79 

8/11/2014 1635 24.7 26.1 1.59 80 

12323750 Silver Bow Creek at Warm 

Springs

7/15/2014 1020 23.8 26.8 4.54 87 

7/15/2014 1025 24.0 25.7 4.12 86 

12323840 Lost Creek near Anaconda 4/22/2014 0745 3.0 3.8 1.43 68 

4/22/2014 0750 -- -- 1.49 67 

12324200 Clark Fork at Deer Lodge 5/13/2014 1520 13.8 16.6 -- 73 

5/13/2014 1525 13.7 16.6 -- 76 

12324400 Clark Fork above Little Blackfoot, near Garrison 3/25/2014 1525 12.2 17.9 -- 81 

3/25/2014 1530 12.1 18.4 -- 82 

12324680 Clark Fork at Goldcreek 11/6/2013 1105 5.9 7.5 -- 87 

11/6/2013 1110 6.2 7.4 -- 76 

12334550 Clark Fork at Turah Bridge, near 

Bonner

5/29/2014 1140 4.2 8.7 -- 47 

5/29/2014 1145 4.2 8.4 -- 49 

12340500 Clark Fork above Missoula 6/11/2014 1430 2.1 2.9 -- 76 

6/11/2014 1435 2.1 3.1 -- 75 
68 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 14. 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 3 0.57 30 Yes3

Calcium, filtered, mg/L 8 0.82 2.1 Yes

Magnesium, filtered, mg/L 8 0.20 2.2 Yes

Potassium, filtered, mg/L 3 0.03 2.4 Yes

Sodium, filtered, mg/L 3 0.09 1.7 Yes

Alkalinity, filtered, lab, mg/L 3 0.04 0.05 Yes

Chloride, filtered, mg/L 3 0.00 0.00 Yes

Fluoride, filtered, mg/L 3 0.00 0.00 Yes

Silica, filtered, mg/L 3 0.04 0.35 Yes

Sulfate, filtered, mg/L 3 0.00 0.00 Yes

Cadmium, filtered, μg/L 7 0.01 15 Yes

Cadmium, unfiltered recoverable, μg/L 7 0.01 4.7 Yes

Copper, filtered, μg/L 8 0.24 6.6 Yes

Copper, unfiltered recoverable, μg/L 7 0.93 4.3 Yes

Iron, filtered, μg/L 8 1.2 3.9 Yes

Iron, unfiltered recoverable, μg/L 7 11 2.2 Yes

Lead, filtered, μg/L 8 0.01 7.5 Yes

Lead, unfiltered recoverable, μg/L 7 0.10 3.3 Yes

Manganese, filtered, μg/L 8 0.33 1.3 Yes

Manganese, unfiltered recoverable, μg/L 7 1.4 1.9 Yes

Zinc, filtered, μg/L 7 0.5 14 Yes

Zinc, unfiltered recoverable, μg/L 7 1.7 7.7 Yes

Arsenic, filtered, μg/L 7 0.13 1.1 Yes

Arsenic, unfiltered recoverable, μg/L 7 0.36 2.4 Yes

Organic carbon, filtered, mg/L 3 0.20 8.1 Yes

Sediment, suspended, percent finer than 0.062 mm 8 3 4.0 Yes

Sediment, suspended, mg/L 8 0.66 2.5 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 

exceeds the laboratory reporting level, and one does not. 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.
Data 69

Table 15. 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 

(listed units)

Relative standard deviation 

(percent)

Within limits1

 of 

data-quality objective

Calcium, filtered, mg/L 7 0.45 1.1 Yes

Magnesium, filtered, mg/L 7 0.05 0.49 Yes

Cadmium, filtered, μg/L 7 0.00 6.3 Yes

Cadmium, unfiltered recoverable, μg/L 7 0.00 1.8 Yes

Copper, filtered, μg/L 7 0.18 4.3 Yes

Copper, unfiltered recoverable, μg/L 7 1.1 5.4 Yes

Iron, filtered, μg/L 7 3.6 9.9 Yes

Iron, unfiltered recoverable, μg/L 7 9.9 1.9 Yes

Lead, filtered, μg/L 7 0.00 0.75 Yes

Lead, unfiltered recoverable, μg/L 7 0.05 1.7 Yes

Manganese, filtered, μg/L 7 0.15 0.56 Yes

Manganese, unfiltered recoverable, μg/L 7 1.4 1.9 Yes

Zinc, filtered, μg/L 7 0.21 1.4 Yes

Zinc, unfiltered recoverable, μg/L 7 1.1 3.7 Yes

Arsenic, filtered, μg/L 7 0.08 0.65 Yes

Arsenic, unfiltered recoverable, μg/L 7 0.48 3.1 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).
70 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

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

[μg/L, 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 95.1–104 99.4 Yes

Cadmium, unfiltered recoverable, μg/L 5 99.0–104 101 Yes

Copper, filtered, μg/L 5 91.0–105 98.1 Yes

Copper, unfiltered recoverable, μg/L 5 98.8–102 100 Yes

Iron, filtered, μg/L 5 95.8–111 103 Yes

Iron, unfiltered recoverable, μg/L 5 99.7–106 103 Yes

Lead, filtered, μg/L 5 100–104 102 Yes

Lead, unfiltered recoverable, μg/L 5 100–107 103 Yes

Manganese, filtered, μg/L 5 91.6–107 99.2 Yes

Manganese, unfiltered recoverable, μg/L 5 97.7–103 100 Yes

Zinc, filtered, μg/L 5 103–117 110 Yes

Zinc, unfiltered recoverable, μg/L 5 97.1–104 101 Yes

Arsenic, filtered, μg/L 5 87.6–102 94.7 Yes

Arsenic, unfiltered recoverable, μg/L 5 99.0–105 102 Yes

1

The data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).

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

[μg/L, 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 95.6–110 103 Yes

Cadmium, unfiltered recoverable, μg/L 5 92.0–99.0 95.5 Yes

Copper, filtered, μg/L 5 90.1–103 96.6 Yes

Copper, unfiltered recoverable, μg/L 5 89.8–97.8 93.8 Yes

Iron, filtered, μg/L 5 92.7–103 97.6 Yes

Iron, unfiltered recoverable, μg/L 5 92.7–109 101 Yes

Lead, filtered, μg/L 5 96.7–103 100 Yes

Lead, unfiltered recoverable, μg/L 5 94.9–104 99.7 Yes

Manganese, filtered, μg/L 5 90.4–104 97.1 Yes

Manganese, unfiltered recoverable, μg/L 5 89.3–100 94.8 Yes

Zinc, filtered, μg/L 5 94.2–108 101 Yes

Zinc, unfiltered recoverable, μg/L 5 83.1–94.6 88.9 Yes

Arsenic, filtered, μg/L 5 82.7–102 92.4 Yes

Arsenic, unfiltered recoverable, μg/L 5 93.5–102 97.7 Yes

1

The data-quality objective for acceptable bias is a maximum deviation of 25 percent from a theoretical 100-percent recovery (table 3).
Data 71

Table 18. Analyses of field blanks for water samples.

[hh, hour; mm, minute; μS/cm, microsiemen per centimeter at 25 degrees Celsius; lab, laboratory; NTRU, nephelometric turbidity ratio unit; mg/L, milligram 

per liter; --, no data; <, less than laboratory reporting level; 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)

11/4/2013 1345 5.5 2 -- <0.022 <0.011 -- -- -- --

1

3/19/2014 0800 5.5 2 <2.0 <0.022 <0.011 <0.03 <0.06 <4.6 <0.02

4/23/2014 1615 5.5 2 -- <0.022 <0.011 -- -- -- --

5/13/2014 0835 5.4 2 <2.0 <0.022 <0.011 <0.03 <0.06 <4.6 <0.02

5/28/2014 1530 5.2 2 -- <0.022 <0.011 -- -- -- --

6/11/2014 1035 5.6 2 -- <0.022 <0.011 -- -- -- --

7/15/2014 1215 5.4 2 -- <0.022 <0.011 -- -- -- --

8/12/2014 1105 5.5 2 <2.0 <0.022 <0.011 <0.03 <0.06 <4.6 <0.02

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)

11/4/2013 -- -- -- -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

1

3/19/2014 <0.01 0.069 <0.02 <0.01 <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

4/23/2014 -- -- -- -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

5/13/2014 <0.01 0.023 <0.02 -- <0.030 <0.030 <0.80 1.5 <4.0 <4.6

5/28/2014 -- -- -- -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

6/11/2014 -- -- -- -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

7/15/2014 -- -- -- -- <0.030 <0.030 <0.80 <0.80 <4.0 <4.6

8/12/2014 <0.01 <0.018 <0.02 -- <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)

11/4/2013 <0.040 <0.04 0.41 <0.4 <2.0 <2.0 <0.10 <0.28 --

1

3/19/2014 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.28 <0.23

4/23/2014 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.28 --

5/13/2014 <0.040 <0.04 0.41 <0.4 <2.0 <2.0 <0.10 <0.28 <0.23

5/28/2014 <0.040 <0.04 0.41 <0.4 <2.0 <2.0 <0.10 <0.28 --

6/11/2014 <0.040 0.06 <0.40 <0.4 <2.0 <2.0 <0.10 <0.28 --

7/15/2014 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.28 --

8/12/2014 <0.040 <0.04 <0.40 <0.4 <2.0 <2.0 <0.10 <0.28 <0.23

1

Annual office equipment blank collected before any equipment was used in the field.
Table 19. Bed-sediment data for the Clark Fork Basin, Montana, August 2014. [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 m

ses from each composite sample. μg/g, microgram per gram of dry sample weight; <, less than laboratory reporting level] Site number (fig. 1) Site name Number of composite samples Concentration (μg/g) Arsenic Cadmium Chromium Copper Iron Lead Mangan

12323600 Silver Bow Creek at Opportunity 3 37.8 10.0 19.6 699 28,200 113 3,4712323750 Silver Bow Creek at Warm Springs 3 132 7.0 23.5 333 27,600 91.5 7,32

12323770 Warm Springs Creek at Warm Springs 3 64.5 2.8 24.1 767 22,100 75.8 4,69

12323800 Clark Fork near Galen 3 143 5.0 21.5 1,060 28,600 126 5,49

461415112450801 Clark Fork below Lost Creek, near Galen 3 163 5.5 19.4 1,470 28,800 161 4,88461559112443301 Clark Fork at county bridge, near Racetrack 3 121 5.3 19.2 1,350 28,800 134 3,48461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 3 109 5.2 19.0 1,200 31,400 151 3,8212324200 Clark Fork at Deer Lodge 3 98.9 5.0 23.1 1,210 30,000 145 2,0612324400 Clark Fork above Little Blackfoot River, near Garrison 3 86.4 5.0 22.5 1,200 26,500 132 3,41

12324680 Clark Fork at Goldcreek 3 51.5 3.2 23.6 687 24,100 94.8 1,45

12331800 Clark Fork near Drummond 3 51.1 3.9 20.1 638 44,000 102 1,81

12334550 Clark Fork at Turah Bridge, near Bonner 3 26.0 2.1 19.2 322 20,800 58.3 1,06

12340000 Blackfoot River near Bonner 3 4.7 <0.11 15.3 21.9 18,400 11.7 38

12340500 Clark Fork above Missoula 3 18.4 1.0 17.2 167 19,300 34.4 65
Data 73

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

[Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to final volume of solution after addition of

0.6N (normal) hydrochloric acid used for reconstituting dried residue. μg/g, 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 69.8 69.0–70.7

Cadmium 10 1:10 0.371 38.7 35.7–41.6

Chromium 10 1:10 130 63.9 62.3–65.6

Copper 10 1:10 33.9 79.9 77.5–82.4

Iron 10 1:10 33,600 90.9 89.0–92.8

Lead 10 1:10 17.3 56.6 55.5–57.7

Manganese 10 1:10 529 89.4 87.8–91.1

Nickel 10 1:10 85 83.5 82.7–84.2

Zinc 10 1:10 103 84.8 84.0–85.7

SRM sample 2711a

Arsenic 10 1:10 107 87.1 86.1–88.2

Cadmium 10 1:10 54.1 98.6 97.6–99.7

Chromium 10 1:10 52.3 49.9 48.0–51.7

Copper 10 1:10 140 98.0 95.5–100

Iron 10 1:10 28,200 85.7 83.8–87.7

Lead 10 1:10 1,400 91.0 89.9–92.1

Manganese 10 1:10 675 81.1 79.4–82.8

Nickel 10 1:10 21.7 82.9 81.7–84.0

Zinc 10 1:10 414 88.3 87.1–89.4
Table 21. Analyses of procedural blanks for bed-sediment samples. [Dilution ratio is the proportion of initial volume of concentrated nitric acid used as a digesting reagent to final volume of solution after addition of 0.6N (normal) hydrochloric aresidue. μg/mL, 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 Mangan

12323600 Silver Bow Creek at Opportunity 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

12323750 Silver Bow Creek at Warm Springs 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

12323770 Warm Springs Creek at Warm Springs 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

12323800 Clark Fork near Galen 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

461415112450801 Clark Fork below Lost Creek, near Galen 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

461559112443301 Clark Fork at county bridge, near Racetrack 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

461903112440701 Clark Fork at Dempsey Creek diversion, near Racetrack 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

12324200 Clark Fork at Deer Lodge 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

12324400 Clark Fork above Little Blackfoot River, near Garrison 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

12324680 Clark Fork at Goldcreek 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

12331800 Clark Fork near Drummond 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

12334550 Clark Fork at Turah Bridge, near Bonner 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

12340000 Blackfoot River near Bonner 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0

12340500 Clark Fork above Missoula 1:10 <0.002 <0.001 <0.003 <0.002 <0.10 <0.004 <0.0
Data 75

Table 22. Biological data for the Clark Fork Basin, Montana, August 2014.

[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 Manganese Nickel Zinc

12323600—Silver Bow Creek at Opportunity

Hydropsyche cockerelli 2 4.7 3.8 4.1 87.7 2,420 12.5 827 2.1 445

12323750—Silver Bow Creek at Warm Springs

Hydropsyche cockerelli 2 9.0 0.5 1.4 28.7 826 3.0 719 0.8 171

12323770—Warm Springs Creek at Warm Springs

Arctopsyche grandis 1 7.6 2.5 5.0 102 1,490 7.7 1,550 4.0 216

Hesperoperla pacifica 1 2.9 2.6 0.9 55.9 375 1.4 270 1.1 427

Hydropsyche occidentalis 1 9.8 1.4 3.1 116 1,520 7.0 1,440 3.5 171

12323800—Clark Fork near Galen

Hydropsyche cockerelli 2 13.5 2.3 4.2 120 2,390 11.1 1,720 2.7 229

461415112450801—Clark Fork below Lost Creek, near Galen

Hydropsyche cockerelli 3 15.4 2.4 2.4 167 2,000 15.0 1,540 2.8 263

461559112443301—Clark Fork at county bridge, near Racetrack

Arctopsyche grandis 1 5.2 2.4 3.3 81.0 889 9.1 1,430 1.9 243

Hydropsyche cockerelli 2 14.3 2.7 2.5 124 1,660 11.8 1,640 1.9 247

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack

Arctopsyche grandis 2 6.4 3.8 0.9 69.1 542 6.8 1,280 1.1 283

Claassenia sabulosa 1 2.6 0.9 0.5 59.0 216 1.4 98.4 0.7 255

Hydropsyche cockerelli 2 13.6 1.7 3.1 100 2,150 12.0 1,420 2.1 247

Hydropsyche occidentalis 1 16.1 1.4 3.8 107 1,880 16.2 1,410 2.0 280

12324200—Clark Fork at Deer Lodge

Arctopsyche grandis 1 6.3 3.3 2.0 78.5 1,320 12.5 1,580 1.7 265

Hydropsyche cockerelli 2 9.2 3.5 2.1 98.0 1,260 13.2 1,570 1.2 218

Hydropsyche occidentalis 1 9.0 1.9 2.0 87.7 1,160 12.4 1,760 1.5 232

12324400—Clark Fork above Little Blackfoot River, near Garrison

Arctopsyche grandis 2 4.8 3.6 1.2 59.5 552 5.4 1,110 1.0 232

Claassenia sabulosa 2 2.7 1.1 0.6 71.3 282 2.1 210 1.0 264

Hydropsyche cockerelli 1 9.5 3.4 2.5 129 1,380 14.3 1,880 1.5 242

12324680—Clark Fork at Goldcreek

Arctopsyche grandis 3 4.5 2.5 1.0 40.2 526 3.9 1,240 0.9 198

Claassenia sabulosa 2 1.7 0.8 0.7 59.3 290 1.5 144 0.7 235

12331800—Clark Fork near Drummond

Arctopsyche grandis 3 2.6 1.5 0.9 24.8 460 4.3 914 0.7 191

Claassenia sabulosa 2 1.7 0.8 0.6 49.0 251 1.3 121 0.8 305

Hydropsyche cockerelli 1 5.0 2.1 2.7 61.8 1,320 10.3 1,380 1.5 226

Hydropsyche occidentalis 1 4.5 2.9 3.0 65.0 1,320 10.4 1,670 1.5 267
76 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 22. Biological data for the Clark Fork Basin, Montana, August 2014.—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]

Taxon

Number of 

composite 

samples

Concentration (μg/g)

Arsenic Cadmium Chromium Copper Iron Lead Manganese Nickel Zinc

12334550—Clark Fork at Turah Bridge, near Bonner

Arctopsyche grandis 2 4.1 1.7 2.0 39.0 1,060 5.8 966 1.4 246

Claassenia sabulosa 2 2.5 2.0 0.6 72.8 176 0.7 99.4 0.4 386

Hydropsyche cockerelli 2 5.0 1.5 2.3 60.1 1,440 6.9 927 1.9 224

Hydropsyche occidentalis 1 4.2 1.1 2.7 50.7 1,410 7.1 1,070 1.6 227

12340000—Blackfoot River near Bonner

Arctopsyche grandis 2 2.8 0.4 2.3 17.0 1,010 1.2 407 2.0 151

Hydropsyche cockerelli 1 2.9 0.3 5.7 17.5 2,140 2.6 409 2.6 132

Hydropsyche occidentalis 1 2.2 0.4 3.2 16.7 1,600 1.8 457 1.7 162

12340500—Clark Fork above Missoula

Arctopsyche grandis 2 2.2 1.5 1.2 20.0 576 1.9 697 0.8 196

Claassenia sabulosa 2 1.0 1.2 0.6 45.2 216 0.5 108 0.6 279

Hydropsyche cockerelli 2 3.0 1.0 2.5 38.4 1,310 3.9 874 1.4 190

Table 23. Recovery efficiency for analyses of certified reference material for biota samples.

[CRM, certified reference material (lobster hepatopancreas); μg/g, microgram per gram of dry sample weight]

Constituent Number of 

analyses

Certified 

concentration 

(μg/g)

Mean CRM 

recovery

(percent)

95-percent confidence 

interval for CRM recovery

(percent)

CRM sample TORT-2

Arsenic 10 21.6 97.6 96.9–98.3

Cadmium 10 26.7 90.7 89.6–91.8

Chromium 10 0.77 139 80.7–197

Copper 10 106 81.6 80.6–82.7

Iron 10 105 106 98.8–113

Lead 10 0.35 114 96.8–130

Manganese 10 13.6 88.3 86.8–89.9

Nickel 10 2.5 76.4 74.3–78.5

Zinc 10 180 89.6 87.0–92.3

CRM sample TORT-3

Arsenic 7 59.5 109 107–110

Cadmium 7 42.3 86.1 84.0–88.1

Chromium 7 1.95 87.3 82.8–91.9

Copper 7 497 86.1 84.9–87.2

Iron 7 179 89.4 86.3–92.5

Lead 7 0.225 179 165–193

Manganese 7 15.6 84.8 82.8–86.8

Nickel 7 5.3 78.8 76.9–80.8

Zinc 7 136 89.1 86.7–91.5
Table 24. 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

12323600 Silver Bow Creek at Opportunity 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

12323750 Silver Bow Creek at Warm Springs 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

12323770 Warm Springs Creek at Warm Springs 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

12323800 Clark Fork near Galen 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

461415112450801 Clark Fork below Lost Creek, near Galen 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

461559112443301 Clark Fork at county bridge, near Racetrack 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

461903112440701 Clark Fork at Dempsey Creek diversion, 

near Racetrack

1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

12324200 Clark Fork at Deer Lodge 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

12324400 Clark Fork above Little Blackfoot River, 

near Garrison

1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

12324680 Clark Fork at Goldcreek 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

12331800 Clark Fork near Drummond 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

12334550 Clark Fork at Turah Bridge, near Bonner 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

12340000 Blackfoot River near Bonner 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0

12340500 Clark Fork above Missoula 1:1 <0.003 <0.001 <0.005 <0.003 <0.4 <0.009 <0.0
78 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through September 2014.

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 163 156 1.9 16 9.2

pH, onsite (standard units) 163 8.4 7.3 7.7 7.7

Specific conductance, onsite (μS/cm) 163 412 116 263 264

Temperature, water (°C) 163 17.5 1.0 7.9 8.0

Turbidity, unfiltered, lab (NTRU) 7 6.5 <2.0 23.2 3.0

Hardness, filtered (mg/L as CaCO3) 163 153 37.7 104 106

Calcium, filtered (mg/L) 163 42.9 10.6 29.7 30.0

Magnesium, filtered (mg/L) 163 11.1 2.71 7.23 7.29

Potassium, filtered (mg/L) 41 6.40 2.00 2.78 2.57

Sodium, filtered (mg/L) 41 18.0 6.40 10.6 10.7

Alkalinity, filtered, lab (mg/L) 13 124 54.5 87.6 84.7

Chloride, filtered (mg/L) 41 18.0 2.80 8.22 7.50

Fluoride, filtered (mg/L) 41 0.60 0.18 0.30 0.30

Silica, filtered (mg/L) 41 32.0 14.0 24.4 24.6

Sulfate, filtered (mg/L) 41 40.2 15.0 26.9 27.3

Nitrate plus nitrite, filtered (mg/L) 7 1.2 0.16 0.64 0.35

Cadmium, filtered (μg/L) 161 0.50 <0.03 20.04 0.02

Cadmium, unfiltered recoverable (μg/L) 163 0.11 <0.01 20.04 <1

Copper, filtered (μg/L) 162 10.0 <1.0 23.5 3.0

Copper, unfiltered recoverable (μg/L) 163 52.0 0.91 6.3 5.0

Iron, filtered (μg/L) 163 640 15.2 192 174

Iron, unfiltered recoverable (μg/L) 163 4,220 123 659 590

Lead, filtered (μg/L) 163 2.80 <0.02 20.18 0.05

Lead, unfiltered recoverable (μg/L) 163 47.0 <1.00 21.60 0.64

Manganese, filtered (μg/L) 163 144 14.2 44.4 39.0

Manganese, unfiltered recoverable (μg/L) 163 240 23.5 61.6 52.7

Zinc, filtered (μg/L) 161 11 <1.0 23.3 2.6

Zinc, unfiltered recoverable (μg/L) 163 130 <3.0 27.7 4.0

Arsenic, filtered (μg/L) 162 13.0 1.0 4.0 3.4

Arsenic, unfiltered recoverable (μg/L) 163 18.0 1.0 25.4 4.5

Organic carbon, filtered (mg/L) 13 9.52 1.40 4.62 3.85

Sediment, suspended (percent finer than 0.062 mm) 163 97 50 82 84

Sediment, suspended concentration (mg/L) 163 139 1 11 7

Sediment, suspended discharge (ton/d) 163 59 0.01 0.96 0.17
Data 79

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3

/s) 171 202 13 31 25

pH, onsite (standard units) 171 8.2 7.2 7.6 7.6

Specific conductance, onsite (μS/cm) 171 691 209 459 468

Temperature, water (°C) 171 20.0 1.0 10.2 10.0

Turbidity, unflitered, lab (NTRU) 7 5.3 <2.0 2

3.6 3.6

Hardness, filtered (mg/L as CaCO3

) 171 217 66.0 147 150

Calcium, filtered (mg/L) 171 62.7 19.0 41.8 42.4

Magnesium, filtered (mg/L) 171 16.1 4.51 10.4 10.7

Potassium, filtered (mg/L) 41 35.0 3.64 7.95 5.80

Sodium, filtered (mg/L) 41 66.0 12.0 25.2 25.0

Alkalinity, filtered, lab (mg/L) 13 119 66.9 87.2 82.9

Chloride, filtered (mg/L) 40 88.0 6.70 23.4 21.0

Fluoride, filtered (mg/L) 40 0.80 0.26 0.43 0.40

Silica, filtered (mg/L) 40 28.0 17.0 22.2 22.0

Sulfate, filtered (mg/L) 40 96.0 35.0 72.4 75.5

Nitrate plus nitrite, filtered (mg/L) 7 4.40 0.34 1.18 0.53

Cadmium, filtered (μg/L) 171 6.2 0.04 0.83 0.20

Cadmium, unfiltered recoverable (μg/L) 171 6.0 0.06 1.12 0.30

Copper, filtered (μg/L) 171 303 2.9 28.4 12.1

Copper, unfiltered recoverable (μg/L) 171 550 8.4 65.6 22.6

Iron, filtered (μg/L) 171 292 9.6 97.3 78.5

Iron, unfiltered recoverable (μg/L) 171 7,400 85.4 777 546

Lead, filtered (μg/L) 171 2.4 <0.5 2

0.42 0.24

Lead, unfiltered recoverable (μg/L) 171 250 0.61 10.1 2.41

Manganese, filtered (μg/L) 171 1,700 20.7 283 145

Manganese, unfiltered recoverable (μg/L) 171 1,600 25.9 322 165

Zinc, filtered (μg/L) 171 2,200 5.3 271 81.5

Zinc, unfiltered recoverable (μg/L) 171 2,200 20.5 329 106

Arsenic, filtered (μg/L) 171 13.4 2.3 6.0 5.6

Arsenic, unfiltered recoverable (μg/L) 171 45.0 3.0 9.5 8.0

Organic carbon, filtered (mg/L) 13 9.97 5.73 7.32 7.49

Sediment, suspended (percent finer than 0.062 mm) 170 98 42 83 85

Sediment, suspended concentration (mg/L) 170 405 2 19 9

Sediment, suspended discharge (ton/d) 170 70 0.08 2.2 0.62
80 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 171 648 13 79 52

pH, onsite (standard units) 173 9.5 7.2 8.4 8.3

Specific conductance, onsite (μS/cm) 173 633 202 414 407

Temperature, water (°C) 173 24.0 -1.0 9.4 9.5

Turbidity, unfiltered, lab (NTRU) 7 7.5 2.5 5.0 5.4

Hardness, filtered (mg/L as CaCO3) 173 240 60.2 149 148

Calcium, filtered (mg/L) 173 71.6 18.5 44.1 44.0

Magnesium, filtered (mg/L) 173 15.0 3.42 9.44 9.34

Potassium, filtered (mg/L) 44 16.0 1.79 4.69 4.20

Sodium, filtered (mg/L) 44 33.5 5.06 17.5 16.8

Alkalinity, filtered, lab (mg/L) 15 110 71.6 91.8 93.6

Chloride, filtered (mg/L) 43 38.2 3.20 14.2 12.0

Fluoride, filtered (mg/L) 43 0.80 0.16 0.40 0.40

Silica, filtered (mg/L) 43 28.0 9.56 20.2 21.0

Sulfate, filtered (mg/L) 43 190 32.0 65.8 62.0

Cadmium, filtered (μg/L) 172 41.0 <0.1 20.94 0.50

Cadmium, unfiltered recoverable (μg/L) 173 49.0 0.18 21.70 1.00

Copper, filtered (μg/L) 171 450 6.5 38.6 30.0

Copper, unfiltered recoverable (μg/L) 173 3,900 14.9 167 92.0

Iron, filtered (μg/L) 173 307 <3 248.7 28.1

Iron, unfiltered recoverable (μg/L) 172 24,100 176 1,430 748

Lead, filtered (μg/L) 173 5.1 <0.5 20.64 0.32

Lead, unfiltered recoverable (μg/L) 173 650 1.48 31.3 13.8

Manganese, filtered (μg/L) 173 9,300 27.5 354 264

Manganese, unfiltered recoverable (μg/L) 173 10,000 69.8 466 342

Zinc, filtered (μg/L) 172 13,000 11.2 241 116

Zinc, unfiltered recoverable (μg/L) 173 15,000 32.7 425 249

Arsenic, filtered (μg/L) 173 34.0 1.0 10.5 10.0

Arsenic, unfiltered recoverable (μg/L) 173 235 5.5 22.5 16.0

Organic carbon, filtered (mg/L) 12 8.35 3.70 5.62 5.16

Sediment, suspended (percent finer than 0.062 mm) 174 95 37 78 82

Sediment, suspended concentration (mg/L) 174 801 5 47 19

Sediment, suspended discharge (ton/d) 171 781 0.18 21 2.7
Data 81

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 79 309 7.4 64 33

pH, onsite (standard units) 80 8.6 7.5 8.0 8.0

Specific conductance, onsite (μS/cm) 80 213 56 131 129

Temperature, water (°C) 80 17.0 0.0 8.3 8.2

Turbidity, unfiltered, lab, (NTRU) 73 21 <2.0 22.4 <2.0

Hardness, filtered (mg/L as CaCO3) 80 98.0 23.7 57.1 54.2

Calcium, filtered (mg/L) 80 26.7 7.00 15.8 15.0

Magnesium, filtered (mg/L) 80 8.01 1.45 4.27 3.96

Potassium, filtered (mg/L) 7 0.82 0.47 0.63 0.65

Sodium, filtered (mg/L) 7 6.04 2.14 3.89 3.07

Alkalinity, filtered, lab (mg/L) 7 85.1 30.8 52.5 48.9

Chloride, filtered (mg/L) 7 0.54 0.17 0.32 0.27

Fluoride, filtered (mg/L) 7 0.35 0.28 0.32 0.33

Silica, filtered (mg/L) 7 15.5 9.27 12.1 11.3

Sulfate, filtered (mg/L) 7 13.9 3.12 6.49 5.37

Cadmium, filtered (μg/L) 79 0.11 0.02 20.05 0.04

Cadmium, unfiltered recoverable (μg/L) 80 0.19 0.03 0.08 0.07

Copper, filtered (μg/L) 80 5.1 0.72 2.2 2.0

Copper, unfiltered recoverable (μg/L) 80 10.6 1.3 3.7 3.1

Iron, filtered (μg/L) 80 125 21.2 45.5 40.8

Iron, unfiltered recoverable (μg/L) 80 730 64.9 191 148

Lead, filtered (μg/L) 80 0.24 0.02 20.12 0.10

Lead, unfiltered recoverable (μg/L) 80 3.12 0.15 0.72 0.54

Manganese, filtered (μg/L) 80 12.0 3.1 5.8 5.6

Manganese, unfiltered recoverable (μg/L) 80 36.6 6.2 13.3 11.5

Zinc, filtered (μg/L) 80 4.3 <1.4 21.7 1.5

Zinc, unfiltered recoverable (μg/L) 80 9.2 <2.0 23.0 2.6

Arsenic, filtered (μg/L) 80 32.9 7.3 16.2 14.6

Arsenic, unfiltered recoverable (μg/L) 80 34.8 7.8 17.4 15.4

Organic carbon, filtered (mg/L) 7 3.48 1.35 2.50 2.56

Sediment, suspended (percent finer than 0.062 mm) 80 86 14 61 64

Sediment, suspended concentration (mg/L) 80 42 1 6 4

Sediment, suspended discharge (ton/d) 79 28 0.02 2.1 0.36
82 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 94 261 0.43 38 12

pH, onsite (standard units) 96 8.3 7.5 7.9 8.0

Specific conductance, onsite (μS/cm) 96 242 59 147 148

Temperature, water (°C) 96 20.0 -1.0 9.1 9.2

Turbidity, unfiltered, lab (NTRU) 14 7.2 <2.0 21.8 <2.0

Hardness, filtered (mg/L as CaCO3) 96 112 24.0 63.1 62.5

Calcium, filtered (mg/L) 96 31.0 7.01 17.7 17.4

Magnesium, filtered (mg/L) 96 8.44 1.56 4.59 4.54

Potassium, filtered (mg/L) 14 1.02 0.48 0.69 0.68

Sodium, filtered (mg/L) 14 8.15 2.29 4.29 3.80

Alkalinity, filtered, lab (mg/L) 14 88.2 31.9 56.0 53.8

Chloride, filtered (mg/L) 14 0.82 0.21 0.40 0.32

Fluoride, filtered (mg/L) 14 0.40 0.29 0.34 0.36

Silica, filtered (mg/L) 14 14.9 9.47 11.9 11.6

Sulfate, filtered (mg/L) 14 27.7 4.19 10.9 9.40

Cadmium, filtered (μg/L) 96 0.13 0.02 0.06 0.06

Cadmium, unfiltered recoverable (μg/L) 96 0.86 0.03 0.13 0.09

Copper, filtered (μg/L) 96 6.1 1.0 2.8 2.4

Copper, unfiltered recoverable (μg/L) 96 38.8 1.5 6.1 3.9

Iron, filtered (μg/L) 96 93.8 15.9 45.7 41.2

Iron, unfiltered recoverable (μg/L) 96 1,960 44.3 284 150

Lead, filtered (μg/L) 96 0.35 <0.08 20.13 0.12

Lead, unfiltered recoverable (μg/L) 96 12.7 0.07 1.34 0.47

Manganese, filtered (μg/L) 96 32.8 2.1 6.8 5.1

Manganese, unfiltered recoverable (μg/L) 96 113 2.9 17.5 12.0

Zinc, filtered (μg/L) 95 7.7 <1.4 22.8 2.6

Zinc, unfiltered recoverable (μg/L) 96 41 <2.4 26.0 4.1

Arsenic, filtered (μg/L) 96 55.1 9.0 21.0 19.2

Arsenic, unfiltered recoverable (μg/L) 96 53.5 10.0 23.6 22.0

Organic carbon, filtered (mg/L) 14 4.10 1.33 2.31 2.08

Sediment, suspended (percent finer than 0.062 mm) 96 91 26 69 71

Sediment, suspended concentration (mg/L) 96 107 1 12 4

Sediment, suspended discharge (ton/d) 94 55 <0.01 2

3.3 0.10
Data 83

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 71 114 1.0 15 7.6

pH, onsite (standard units) 73 8.2 7.5 7.7 7.7

Specific conductance, onsite (μS/cm) 73 151 65 103 108

Temperature, water (°C) 73 16.0 0.0 7.2 7.5

Turbidity, unfiltered, lab (NTRU) 66 39 <2.0 25.2 2.8

Hardness, filtered (mg/L as CaCO3) 73 56.3 22.5 37.4 38.5

Calcium, filtered (mg/L) 73 18.3 7.22 12.5 13.0

Magnesium, filtered (mg/L) 73 2.60 0.78 1.50 1.47

Potassium, filtered (mg/L) 7 1.08 0.70 0.91 0.92

Sodium, filtered (mg/L) 7 7.94 4.39 5.84 5.99

Alkalinity, filtered, lab (mg/L) 7 53.5 26.3 39.9 38.6

Chloride, filtered (mg/L) 7 0.83 0.30 0.48 0.34

Fluoride, filtered (mg/L) 7 0.07 0.06 0.07 0.07

Silica, filtered (mg/L) 7 24.9 20.9 23.4 23.7

Sulfate, filtered (mg/L) 7 15.7 5.10 8.3 6.18

Cadmium, filtered (μg/L) 71 0.05 <0.02 20.03 0.03

Cadmium, unfiltered recoverable (μg/L) 73 0.33 <0.04 20.06 0.05

Copper, filtered (μg/L) 73 4.2 0.82 2.1 2.1

Copper, unfiltered recoverable (μg/L) 73 16.8 1.0 3.7 3.0

Iron, filtered (μg/L) 73 277 28 85.9 72.0

Iron, unfiltered recoverable (μg/L) 73 2,380 85.7 349 218

Lead, filtered (μg/L) 73 0.37 0.03 20.16 0.15

Lead, unfiltered recoverable (μg/L) 73 7.96 0.10 0.85 0.49

Manganese, filtered (μg/L) 73 34.5 6.0 14.1 12.6

Manganese, unfiltered recoverable (μg/L) 73 99.9 12.8 25.8 22.6

Zinc, filtered (μg/L) 73 3.3 0.65 21.7 1.5

Zinc, unfiltered recoverable (μg/L) 73 17.8 <2.0 23.1 2.0

Arsenic, filtered (μg/L) 73 25.7 7.7 15.9 14.9

Arsenic, unfiltered recoverable (μg/L) 73 27.0 9.8 16.9 15.4

Organic carbon, filtered (mg/L) 7 7.03 3.57 5.15 4.79

Sediment, suspended (percent finer than 0.062 mm) 73 97 25 76 80

Sediment, suspended concentration (mg/L) 73 195 1 15 4

Sediment, suspended discharge (ton/d) 71 50 <0.01 2

2.1 0.09
84 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 96 116 4.5 17 8.9

pH, onsite (standard units) 96 9.0 7.6 8.1 8.1

Specific conductance, onsite (μS/cm) 96 371 116 265 285

Temperature, water (°C) 96 24.0 0.0 11.0 11.0

Turbidity, unfiltered, lab (NTRU) 14 5.8 <2.0 23.6 3.4

Hardness, filtered (mg/L as CaCO3) 96 169 54.2 115 124

Calcium, filtered (mg/L) 96 47.4 16.5 33.5 36.1

Magnesium, filtered (mg/L) 96 12.3 2.99 7.60 8.13

Potassium, filtered (mg/L) 14 1.74 0.94 1.32 1.34

Sodium, filtered (mg/L) 14 12.2 6.12 9.08 9.00

Alkalinity, filtered, lab (mg/L) 14 127 53.3 99.3 108

Chloride, filtered (mg/L) 14 3.28 0.79 1.79 1.82

Fluoride, filtered (mg/L) 14 0.56 0.15 0.36 0.38

Silica, filtered (mg/L) 14 23.5 18.4 21.9 22.4

Sulfate, filtered (mg/L) 14 36.5 9.21 20.6 21.4

Cadmium, filtered (μg/L) 96 0.12 <0.03 20.04 0.04

Cadmium, unfiltered recoverable (μg/L) 95 0.52 0.02 0.10 0.07

Copper, filtered (μg/L) 96 21.4 0.87 5.1 3.5

Copper, unfiltered recoverable (μg/L) 95 48.8 2.6 10.7 7.7

Iron, filtered (μg/L) 96 274 6.1 50.5 44.5

Iron, unfiltered recoverable (μg/L) 95 1,670 27 285 218

Lead, filtered (μg/L) 96 0.89 0.04 20.23 0.20

Lead, unfiltered recoverable (μg/L) 95 14.4 0.27 2.20 1.43

Manganese, filtered (μg/L) 96 200 3.3 33.2 25.4

Manganese, unfiltered recoverable (μg/L) 95 228 4.7 46.5 37.1

Zinc, filtered (μg/L) 96 19.8 <1.4 25.0 4.0

Zinc, unfiltered recoverable (μg/L) 95 68 1.2 11.9 9.0

Arsenic, filtered (μg/L) 96 164 9.3 36.9 26.2

Arsenic, unfiltered recoverable (μg/L) 96 164 11.4 39.3 27.4

Organic carbon, filtered (mg/L) 14 6.85 1.60 4.07 4.00

Sediment, suspended (percent finer than 0.062 mm) 96 99 54 86 90

Sediment, suspended concentration (mg/L) 96 87 1 11 6

Sediment, suspended discharge (ton/d) 96 11 0.02 0.90 0.16
Data 85

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 180 1,030 16 140 88

pH, onsite (standard units) 178 9.6 8.0 8.8 8.8

Specific conductance, onsite (μS/cm) 178 783 182 458 470

Temperature, water (°C) 179 25.0 0.0 10.4 10.0

Turbidity, unfiltered, lab (NTRU) 7 11 2.1 4.4 3.3

Hardness, filtered (mg/L as CaCO3) 178 314 74.9 190 194

Calcium, filtered (mg/L) 178 90.4 22.5 55.2 56.6

Magnesium, filtered (mg/L) 178 21.4 4.52 12.6 13.0

Potassium, filtered (mg/L) 38 8.30 1.72 4.18 4.20

Sodium, filtered (mg/L) 38 23.0 8.20 15.8 16.5

Alkalinity, filtered, lab (mg/L) 10 104 69.2 86.2 85.6

Chloride, filtered (mg/L) 38 21.6 1.30 8.94 8.60

Fluoride, filtered (mg/L) 38 1.20 0.41 0.69 0.70

Silica, filtered (mg/L) 38 20.0 6.30 12.4 12.0

Sulfate, filtered (mg/L) 38 210 39.2 109 110

Cadmium, filtered (μg/L) 178 0.31 <0.03 20.06 0.03

Cadmium, unfiltered recoverable (μg/L) 178 0.57 <0.1 20.12 0.07

Copper, filtered (μg/L) 178 40.0 1.6 7.3 5.2

Copper, unfiltered recoverable (μg/L) 178 96.8 2.4 14.9 10.6

Iron, filtered (μg/L) 178 93 <5 219.9 16.2

Iron, unfiltered recoverable (μg/L) 178 3,000 35.8 314 235

Lead, filtered (μg/L) 178 1.0 <0.08 20.13 0.04

Lead, unfiltered recoverable (μg/L) 178 41.8 <1.00 22.25 1.23

Manganese, filtered (μg/L) 178 875 11.8 112 75.5

Manganese, unfiltered recoverable (μg/L) 178 899 24.0 171 130

Zinc, filtered (μg/L) 178 73 <1.0 26.7 3.5

Zinc, unfiltered recoverable (μg/L) 178 180 2.0 228.0 15.2

Arsenic, filtered (μg/L) 178 60.0 6.8 22.7 22.6

Arsenic, unfiltered recoverable (μg/L) 178 94.0 10.0 26.2 25.0

Organic carbon, filtered (mg/L) 7 5.91 4.54 5.11 4.89

Sediment, suspended (percent finer than 0.062 mm) 179 98 43 83 85

Sediment, suspended concentration (mg/L) 180 229 1 9 6

Sediment, suspended discharge (ton/d) 180 279 0.05 5.9 1.4
86 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 54 573 41 140 92

pH, onsite (standard units) 54 8.8 7.8 8.4 8.4

Specific conductance, onsite (μS/cm) 54 278 125 221 234

Temperature, water (°C) 54 16.0 0.5 8.6 8.8

Turbidity, unfiltered, lab (NTRU) 48 18 <2.0 22.1 <2.0

Hardness, filtered (mg/L as CaCO3) 54 145 58.5 108 112

Calcium, filtered (mg/L) 54 42.8 18.5 32.2 33.8

Magnesium, filtered (mg/L) 54 9.34 2.96 6.59 6.90

Potassium, filtered (mg/L) 5 1.34 0.80 1.10 1.17

Sodium, filtered (mg/L) 5 3.44 1.54 2.60 2.83

Alkalinity, filtered, lab (mg/L) 5 126 60.3 99.7 111

Chloride, filtered (mg/L) 5 1.53 0.49 1.02 1.06

Fluoride, filtered (mg/L) 5 0.39 0.30 0.37 0.39

Silica, filtered (mg/L) 5 10.7 8.25 9.63 9.70

Sulfate, filtered (mg/L) 5 15.9 7.98 11.9 11.9

Cadmium, filtered (μg/L) 54 0.04 <0.02 20.02 0.02

Cadmium, unfiltered recoverable (μg/L) 54 0.14 <0.02 20.03 0.02

Copper, filtered (μg/L) 53 6.4 <0.80 21.1 0.88

Copper, unfiltered recoverable (μg/L) 54 28.0 <0.80 23.4 2.1

Iron, filtered (μg/L) 54 22.4 <4 27.4 6.1

Iron, unfiltered recoverable (μg/L) 54 1,000 19.1 126 75.8

Lead, filtered (μg/L) 54 0.11 <0.02 20.03 <0.08

Lead, unfiltered recoverable (μg/L) 54 3.51 0.07 0.43 0.26

Manganese, filtered (μg/L) 54 2.8 0.13 21.2 1.1

Manganese, unfiltered recoverable (μg/L) 54 45.2 0.90 6.0 4.1

Zinc, filtered (μg/L) 54 5.6 <1.4 21.0 <2.0

Zinc, unfiltered recoverable (μg/L) 54 20.1 <2.0 23.2 1.6

Arsenic, filtered (μg/L) 54 3.9 1.3 2.2 2.2

Arsenic, unfiltered recoverable (μg/L) 54 5.6 1.7 2.7 2.5

Organic carbon, filtered (mg/L) 5 2.92 0.83 1.62 1.31

Sediment, suspended (percent finer than 0.062 mm) 54 83 32 65 66

Sediment, suspended concentration (mg/L) 54 65 1 8 4

Sediment, suspended discharge (ton/d) 54 68 0.13 4.7 0.98
Data 87

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 136 420 2.8 97 57

pH, onsite (standard units) 135 8.7 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 135 795 139 292 296

Temperature, water (°C) 136 20.0 0.0 8.4 8.0

Turbidity, unfiltered, lab (NTRU) 14 11 <2.0 22.1 <2.0

Hardness, filtered (mg/L as CaCO3) 135 415 39.8 142 145

Calcium, filtered (mg/L) 135 130 10.5 43.3 43.8

Magnesium, filtered (mg/L) 135 22.0 3.29 8.23 8.10

Potassium, filtered (mg/L) 33 4.70 0.83 1.56 1.35

Sodium, filtered (mg/L) 33 19.2 1.78 3.93 3.30

Alkalinity, filtered, lab (mg/L) 16 149 66.8 115 118

Chloride, filtered (mg/L) 33 3.60 0.50 1.28 1.03

Fluoride, filtered (mg/L) 33 0.60 0.30 0.42 0.40

Silica, filtered (mg/L) 33 13.0 8.40 10.3 10.0

Sulfate, filtered (mg/L) 33 270 16.3 53.8 36.1

Cadmium, filtered (μg/L) 134 0.10 <0.04 20.04 0.02

Cadmium, unfiltered recoverable (μg/L) 134 0.41 <0.05 20.08 0.04

Copper, filtered (μg/L) 134 16.0 1.0 3.2 2.7

Copper, unfiltered recoverable (μg/L) 134 147 2.3 18.8 8.8

Iron, filtered (μg/L) 135 33.8 <5.0 211.9 10.5

Iron, unfiltered recoverable (μg/L) 135 2,110 17.2 302 120

Lead, filtered (μg/L) 134 1.8 <0.025 20.07 <0.60

Lead, unfiltered recoverable (μg/L) 134 14.0 <1.00 21.85 0.66

Manganese, filtered (μg/L) 134 570 18.8 110 82.9

Manganese, unfiltered recoverable (μg/L) 134 1,400 37.1 191 150

Zinc, filtered (μg/L) 134 10 <1.0 22.0 1.2

Zinc, unfiltered recoverable (μg/L) 135 60 <2.4 28.7 3.0

Arsenic, filtered (μg/L) 134 14.0 2.0 5.0 4.4

Arsenic, unfiltered recoverable (μg/L) 134 27.0 3.0 7.2 5.9

Organic carbon, filtered (mg/L) 14 3.27 0.89 1.65 1.60

Sediment, suspended (percent finer than 0.062 mm) 136 90 43 71 70

Sediment, suspended concentration (mg/L) 136 127 1 17 8

Sediment, suspended discharge (ton/d) 136 87 0.03 8.2 1.0
88 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 220 1,380 14 223 140

pH, onsite (standard units) 208 9.2 7.5 8.5 8.6

Specific conductance, onsite (μS/cm) 209 720 182 408 417

Temperature, water (°C) 220 23.5 0.0 9.8 10.0

Hardness, filtered (mg/L as CaCO3) 207 365 76.4 178 184

Calcium, filtered (mg/L) 207 110 23.2 52.7 54.2

Magnesium, filtered (mg/L) 207 22.0 4.44 11.3 11.7

Potassium, filtered (mg/L) 32 5.90 2.00 3.51 3.30

Sodium, filtered (mg/L) 32 19.0 3.60 12.0 12.5

Alkalinity, filtered, lab (mg/L) 3 117 84.4 96.3 87.4

Chloride, filtered (mg/L) 32 11.0 2.00 6.50 6.22

Fluoride, filtered (mg/L) 32 1.10 0.40 0.60 0.60

Silica, filtered (mg/L) 32 17.0 8.10 11.7 11.8

Sulfate, filtered (mg/L) 32 220 34.0 97.2 98.5

Cadmium, filtered (μg/L) 207 1.0 <0.04 20.06 0.03

Cadmium, unfiltered recoverable (μg/L) 207 3.0 <0.1 20.18 0.06

Copper, filtered (μg/L) 207 50.0 1.4 7.4 5.4

Copper, unfiltered recoverable (μg/L) 206 240 4.1 25.9 14.7

Iron, filtered (μg/L) 207 110 <3.0 216.2 12.1

Iron, unfiltered recoverable (μg/L) 207 9,200 56.2 456 260

Lead, filtered (μg/L) 207 3.00 <0.08 20.14 <1.00

Lead, unfiltered recoverable (μg/L) 207 31.0 <1.00 23.30 1.75

Manganese, filtered (μg/L) 207 460 13.1 99.9 72.6

Manganese, unfiltered recoverable (μg/L) 207 1,400 47.3 209 162

Zinc, filtered (μg/L) 207 110 <1.0 28.2 3.7

Zinc, unfiltered recoverable (μg/L) 207 360 2.7 234.3 20.0

Arsenic, filtered (μg/L) 207 53.0 4.0 15.0 14.0

Arsenic, unfiltered recoverable (μg/L) 207 78.0 3.0 18.9 16.9

Sediment, suspended (percent finer than 0.062 mm) 220 97 32 76 78

Sediment, suspended concentration (mg/L) 221 338 1 17 8

Sediment, suspended discharge (ton/d) 220 459 0.12 20 2.8
Data 89

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 79 73 0.37 12 8.7

pH, onsite (standard units) 79 8.6 7.4 8.1 8.2

Specific conductance, onsite (μS/cm) 79 253 121 198 211

Temperature, water (°C) 79 17.0 0.0 7.8 8.0

Turbidity, unfiltered, lab (NTRU) 79 24,200 <2.0 2309 <2.0

Hardness, filtered (mg/L as CaCO3) 79 122 50.4 94.9 101

Calcium, filtered (mg/L) 79 37.1 15.7 28.8 30.3

Magnesium, filtered (mg/L) 79 7.47 2.71 5.61 5.92

Potassium, filtered (mg/L) 14 1.46 0.88 1.23 1.26

Sodium, filtered (mg/L) 14 3.63 1.87 2.79 2.77

Alkalinity, filtered, lab (mg/L) 14 110 59.5 95.2 101.0

Chloride, filtered (mg/L) 14 1.05 0.51 0.72 0.70

Fluoride, filtered (mg/L) 14 0.49 0.28 0.41 0.41

Silica, filtered (mg/L) 14 12.3 9.65 11.0 11.2

Sulfate, filtered (mg/L) 14 13.8 5.89 9.08 8.26

Cadmium, filtered (μg/L) 78 0.90 <0.02 20.04 0.02

Cadmium, unfiltered recoverable (μg/L) 79 147 <0.02 21.9 0.04

Copper, filtered (μg/L) 79 90.5 0.80 3.0 1.6

Copper, unfiltered recoverable (μg/L) 79 29,100 1.3 375 4.4

Iron, filtered (μg/L) 79 26.5 <6.0 29.8 8.7

Iron, unfiltered recoverable (μg/L) 79 99,700 22.3 1,450 110

Lead, filtered (μg/L) 79 0.18 <0.02 20.04 <0.12

Lead, unfiltered recoverable (μg/L) 79 1,290 0.08 17.1 0.46

Manganese, filtered (μg/L) 79 42.4 <0.2 21.9 1.4

Manganese, unfiltered recoverable (μg/L) 79 8,830 1.2 118 4.6

Zinc, filtered (μg/L) 78 30.0 <1.4 21.6 <2.8

Zinc, unfiltered recoverable (μg/L) 78 7,780 <2 2103 2.2

Arsenic, filtered (μg/L) 79 156 1.8 6.0 3.3

Arsenic, unfiltered recoverable (μg/L) 79 3,860 2.0 53.5 3.9

Organic carbon, filtered (mg/L) 14 3.84 0.90 1.79 1.62

Sediment, suspended (percent finer than 0.062 mm) 79 97 22 57 58

Sediment, suspended concentration (mg/L) 79 58,900 1 758 6

Sediment, suspended discharge (ton/d) 79 1,320 <0.01 2

18 0.13
90 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 94 71 1.3 24 18

pH, onsite (standard units) 96 8.7 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 96 934 540 640 628

Temperature, water (°C) 96 26.5 0.0 10.2 10.0

Turbidity, unfiltered, lab (NTRU) 7 5.4 <2.0 21.8 <2.0

Hardness, filtered (mg/L as CaCO3) 96 451 203 303 300

Calcium, filtered (mg/L) 96 122 48.5 85.9 86.6

Magnesium, filtered (mg/L) 96 35.7 17.3 21.5 20.9

Potassium, filtered (mg/L) 7 3.68 2.05 2.52 2.30

Sodium, filtered (mg/L) 7 31.5 10.1 15.7 11.6

Alkalinity, filtered, lab (mg/L) 7 213 166 186 182

Chloride, filtered (mg/L) 7 5.62 3.90 4.77 4.82

Fluoride, filtered (mg/L) 7 0.77 0.44 0.55 0.49

Silica, filtered (mg/L) 7 19.6 11.7 15.3 14.2

Sulfate, filtered (mg/L) 7 146 122 137 138

Cadmium, filtered (μg/L) 95 0.05 <0.02 20.03 0.02

Cadmium, unfiltered recoverable (μg/L) 96 0.12 <0.02 20.04 0.04

Copper, filtered (μg/L) 96 6.7 0.80 2.2 1.8

Copper, unfiltered recoverable (μg/L) 96 22.5 1.5 5.2 4.2

Iron, filtered (μg/L) 96 61.1 4.0 213.3 11.2

Iron, unfiltered recoverable (μg/L) 96 392 14 104 80.0

Lead, filtered (μg/L) 95 0.33 <0.025 20.05 0.02

Lead, unfiltered recoverable (μg/L) 96 1.90 0.04 0.39 0.28

Manganese, filtered (μg/L) 96 54.0 1.91 15.6 14.3

Manganese, unfiltered recoverable (μg/L) 96 56.5 2.20 20.7 19.2

Zinc, filtered (μg/L) 95 3.8 <1.0 21.5 1.2

Zinc, unfiltered recoverable (μg/L) 96 10.3 <2.0 22.9 2.0

Arsenic, filtered (μg/L) 96 41.8 6.0 14.1 12.6

Arsenic, unfiltered recoverable (μg/L) 96 43.0 6.0 14.9 13.6

Organic carbon, filtered (mg/L) 7 3.25 1.48 2.32 2.25

Sediment, suspended (percent finer than 0.062 mm) 96 94 18 61 64

Sediment, suspended concentration (mg/L) 96 79 2 16 14

Sediment, suspended discharge (ton/d) 94 4.2 0.01 1.0 0.67
Data 91

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 273 2,000 23 307 229

pH, onsite (standard units) 221 8.9 7.4 8.3 8.3

Specific conductance, onsite (μS/cm) 256 642 228 467 491

Temperature, water (°C) 272 23.0 0.0 10.0 10.0

Hardness, filtered (mg/L as CaCO3) 213 282 94.9 198 207

Calcium, filtered (mg/L) 213 82.0 28.2 58.4 60.9

Magnesium, filtered (mg/L) 213 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) 222 2.0 <0.10 20.08 0.03

Cadmium, unfiltered recoverable (μg/L) 222 5.0 <0.10 20.38 0.10

Copper, filtered (μg/L) 223 120 3.2 10.4 8.0

Copper, unfiltered recoverable (μg/L) 221 1,500 8.2 76.0 35.0

Iron, filtered (μg/L) 223 190 <3 215.2 9.6

Iron, unfiltered recoverable (μg/L) 223 29,000 27.2 1,360 499

Lead, filtered (μg/L) 223 6.00 <0.04 20.29 <5.00

Lead, unfiltered recoverable (μg/L) 223 200 0.33 210.0 4.36

Manganese, filtered (μg/L) 223 400 1.0 40.7 33.0

Manganese, unfiltered recoverable (μg/L) 223 4,600 11.9 217 129

Zinc, filtered (μg/L) 223 230 <10.0 211.0 7.4

Zinc, unfiltered recoverable (μg/L) 221 1,700 4.0 78.4 37.1

Arsenic, filtered (μg/L) 223 39.0 6.0 14.4 13.4

Arsenic, unfiltered recoverable (μg/L) 222 215 4.8 23.3 17.2

Sediment, suspended (percent finer than 0.062 mm) 264 99 31 72 73

Sediment, suspended concentration (mg/L) 273 2,250 1 65 22

Sediment, suspended discharge (ton/d) 273 8,690 0.18 136 12
92 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 46 2,310 71 472 318

pH, onsite (standard units) 46 8.9 7.9 8.4 8.4

Specific conductance, onsite (μS/cm) 46 527 249 412 447

Temperature, water (°C) 46 21.0 1.0 11.4 12.2

Hardness, filtered (mg/L as CaCO3) 46 228 104 181 196

Calcium, filtered (mg/L) 46 66.5 31.8 529 56.8

Magnesium, filtered (mg/L) 46 15.2 5.93 11.8 12.9

Cadmium, filtered (μg/L) 46 0.23 0.02 0.07 0.07

Cadmium, unfiltered recoverable (μg/L) 46 0.84 0.03 0.27 0.22

Copper, filtered (μg/L) 46 40.6 2.8 9.5 7.8

Copper, unfiltered recoverable (μg/L) 46 222 10.0 60.0 33.7

Iron, filtered (μg/L) 46 43.2 4.5 16.3 13.8

Iron, unfiltered recoverable (μg/L) 46 3,860 46.1 901 552

Lead, filtered (μg/L) 46 0.48 0.04 0.16 0.12

Lead, unfiltered recoverable (μg/L) 46 32.3 0.39 7.8 4.16

Manganese, filtered (μg/L) 46 65.1 12.3 29.9 27.6

Manganese, unfiltered recoverable (μg/L) 46 344 19.7 123 103

Zinc, filtered (μg/L) 46 37.1 1.9 6.2 5.2

Zinc, unfiltered recoverable (μg/L) 46 181 3.0 49.0 28.8

Arsenic, filtered (μg/L) 46 36.7 7.8 15.3 15.6

Arsenic, unfiltered recoverable (μg/L) 46 46.0 10.5 21.5 18.2

Sediment, suspended (percent finer than 0.062 mm) 46 92 42 72 75

Sediment, suspended concentration (mg/L) 46 205 1 45 26

Sediment, suspended discharge (ton/d) 46 550 0.31 90 24
Data 93

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 179 4,450 87 777 513

pH, onsite (standard units) 178 8.9 7.9 8.4 8.3

Specific conductance, onsite (μS/cm) 178 510 206 366 378

Temperature, water (°C) 179 23.0 0.0 10.2 10.5

Hardness, filtered (mg/L as CaCO3) 178 232 85.8 161 169

Calcium, filtered (mg/L) 178 68.0 25.9 47.6 49.8

Magnesium, filtered (mg/L) 178 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) 178 0.2 <0.02 20.04 0.02

Cadmium, unfiltered recoverable (μg/L) 178 2.0 <0.10 20.17 0.08

Copper, filtered (μg/L) 177 36.0 2.1 6.5 5.3

Copper, unfiltered recoverable (μg/L) 177 440 5.2 38.5 22.9

Iron, filtered (μg/L) 178 100 <3 219.3 12.7

Iron, unfiltered recoverable (μg/L) 178 12,000 27.3 832 420

Lead, filtered (μg/L) 176 0.6 <0.04 20.11 <1.00

Lead, unfiltered recoverable (μg/L) 177 73.0 0.14 25.40 2.79

Manganese, filtered (μg/L) 178 57.3 4.0 18.9 17.0

Manganese, unfiltered recoverable (μg/L) 178 1,100 9.3 115 81.7

Zinc, filtered (μg/L) 178 26 <1.0 25.3 3.7

Zinc, unfiltered recoverable (μg/L) 178 510 2 41.1 27.6

Arsenic, filtered (μg/L) 178 22.5 5.8 10.0 9.8

Arsenic, unfiltered recoverable (μg/L) 178 75.0 7.0 14.5 12.0

Sediment, suspended (percent finer than 0.062 mm) 179 94 43 75 78

Sediment, suspended concentration (mg/L) 179 752 1 47 20

Sediment, suspended discharge (ton/d) 179 7,960 0.55 198 27
94 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 179 5,540 149 1,060 771

pH, onsite (standard units) 178 8.7 7.8 8.3 8.3

Specific conductance, onsite (μS/cm) 178 630 189 406 419

Temperature, water (°C) 179 22.5 0.5 11.0 11.0

Hardness, filtered (mg/L as CaCO3) 178 298 73.9 183 190

Calcium, filtered (mg/L) 178 83.0 21.0 52.5 54.6

Magnesium, filtered (mg/L) 178 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) 177 0.30 <0.03 20.05 0.03

Cadmium, unfiltered recoverable (μg/L) 178 2.0 <0.10 20.22 0.08

Copper, filtered (μg/L) 175 21.0 1.0 6.3 4.9

Copper, unfiltered recoverable (μg/L) 176 360 4.6 40.7 22.0

Iron, filtered (μg/L) 178 150 <3 218.7 9.7

Iron, unfiltered recoverable (μg/L) 177 8,800 19.7 954 461

Lead, filtered (μg/L) 174 1.2 <0.04 20.16 0.04

Lead, unfiltered recoverable (μg/L) 174 56.0 <1.00 27.22 3.45

Manganese, filtered (μg/L) 177 60.7 3.3 16.6 14.9

Manganese, unfiltered recoverable (μg/L) 178 880 8.0 138 89.8

Zinc, filtered (μg/L) 178 21.0 <1.4 25.7 4.3

Zinc, unfiltered recoverable (μg/L) 178 490 2.9 55.6 30.0

Arsenic, filtered (μg/L) 178 23.9 3.2 10.5 10.0

Arsenic, unfiltered recoverable (μg/L) 178 62 7.7 15.7 13.0

Sediment, suspended (percent finer than 0.062 mm) 179 93 38 74 75

Sediment, suspended concentration (mg/L) 179 530 2 60 25

Sediment, suspended discharge (ton/d) 179 4,720 1.7 303 48
Data 95

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 276 10,600 296 1,970 1,170

pH, onsite (standard units) 222 8.8 7.4 8.2 8.2

Specific conductance, onsite (μS/cm) 251 483 139 298 311

Temperature, water (°C) 275 22.0 0.0 9.6 10.0

Hardness, filtered (mg/L as CaCO3) 212 205 53.6 130 133

Calcium, filtered (mg/L) 212 59.0 14.9 36.8 37.2

Magnesium, filtered (mg/L) 212 14.0 3.95 9.39 9.48

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 20.027 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) 220 0.10 <0.02 20.03 <1

Cadmium, unfiltered recoverable (μg/L) 221 4.00 <0.01 20.23 0.03

Copper, filtered (μg/L) 220 25.0 1.1 4.6 3.6

Copper, unfiltered recoverable (μg/L) 219 500 2.7 31.5 14.6

Iron, filtered (μg/L) 221 190 <3 223.5 14.0

Iron, unfiltered recoverable (μg/L) 221 19,000 32.6 936 360

Lead, filtered (μg/L) 217 7.00 <0.02 20.26 <1.00

Lead, unfiltered recoverable (μg/L) 217 100 <1.00 26.34 2.40

Manganese, filtered (μg/L) 221 37.4 <1.0 28.4 7.0

Manganese, unfiltered recoverable (μg/L) 221 2,000 8.9 112 57.9

Zinc, filtered (μg/L) 219 39 <2.0 2

5.6 3.9

Zinc, unfiltered recoverable (μg/L) 221 1,100 2.9 253.4 26.2

Arsenic, filtered (μg/L) 221 17.0 2.7 6.0 5.6

Arsenic, unfiltered recoverable (μg/L) 221 110 3.0 9.4 7.0

Sediment, suspended (percent finer than 0.062 mm) 265 98 27 74 75

Sediment, suspended concentration (mg/L) 276 1,370 2 53 18

Sediment, suspended discharge (ton/d) 276 34,700 3.0 602 60
96 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 202 13,400 344 2,810 1,380

pH, onsite (standard units) 162 8.7 7.5 8.3 8.3

Specific conductance, onsite (μS/cm) 179 294 131 208 204

Temperature, water (°C) 202 22.5 0.0 9.6 9.5

Turbidity, unfiltered, lab (NTRU) 7 30 <2.0 27.2 2.0

Hardness, filtered (mg/L as CaCO3) 154 146 55.1 104 98.6

Calcium, filtered (mg/L) 154 37.7 14.0 26.5 25.4

Magnesium, filtered (mg/L) 154 13.2 4.90 9.13 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 20.010 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) 160 1.00 <0.02 20.02 <0.10

Cadmium, unfiltered recoverable (μg/L) 162 2.00 <0.01 20.09 <1.00

Copper, filtered (μg/L) 158 7.0 <0.80 21.3 0.70

Copper, unfiltered recoverable (μg/L) 159 34.0 <0.70 24.2 1.9

Iron, filtered (μg/L) 161 100 <3 217.5 10.2

Iron, unfiltered recoverable (μg/L) 162 3,600 13.9 400 185

Lead, filtered (μg/L) 156 8.00 <0.02 20.27 <0.50

Lead, unfiltered recoverable (μg/L) 157 25.0 <0.04 22.00 0.09

Manganese, filtered (μg/L) 161 11.0 <1.0 22.4 2.0

Manganese, unfiltered recoverable (μg/L) 162 180 <10.0 227.5 16.0

Zinc, filtered (μg/L) 160 15.0 <0.60 21.9 <3.0

Zinc, unfiltered recoverable (μg/L) 162 60.0 <1.0 24.9 <10.0

Arsenic, filtered (μg/L) 161 2.0 <1.0 20.96 0.95

Arsenic, unfiltered recoverable (μg/L) 162 4.0 <1.0 21.3 1.0

Sediment, suspended (percent finer than 0.062 mm) 200 98 42 80 82

Sediment, suspended concentration (mg/L) 202 271 1 28 8

Sediment, suspended discharge (ton/d) 202 7,670 1.1 512 31
Data 97

Table 25. Statistical summary of long-term water-quality data for the Clark Fork Basin, Montana, March 1985 through 

September 2014.—Continued

[ft3/s, cubic foot 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; --, no data]

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 2014

Streamflow, instantaneous (ft3/s) 241 22,900 720 4,660 2,480

pH, onsite (standard units) 199 8.8 7.9 8.3 8.3

Specific conductance, onsite (μS/cm) 219 399 142 251 260

Temperature, water (°C) 239 22.0 0.0 9.7 9.5

Turbidity, unfiltered, lab (NTRU) 40 100 <2.0 213 4.9

Hardness, filtered (mg/L as CaCO3) 199 168 60.5 116 117

Calcium, filtered (mg/L) 199 46.0 14.0 31.3 31.5

Magnesium, filtered (mg/L) 199 13.4 5.28 9.19 9.20

Potassium, filtered (mg/L) 28 4.50 0.90 1.72 1.50

Sodium, filtered (mg/L) 28 7.80 2.40 5.29 5.35

Chloride, filtered (mg/L) 28 4.20 0.90 1.92 1.80

Fluoride, filtered (mg/L) 28 0.30 <0.10 20.19 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) 198 0.20 <0.02 20.03 <0.10

Cadmium, unfiltered recoverable (μg/L) 199 5.0 <0.01 20.14 <1.0

Copper, filtered (μg/L) 198 12.6 0.7 2.7 2.0

Copper, unfiltered recoverable (μg/L) 197 400 1.9 18.3 8.1

Iron, filtered (μg/L) 199 200 <3 221.5 15.0

Iron, unfiltered recoverable (μg/L) 199 13,000 40.9 604 250

Lead, filtered (μg/L) 192 1.20 <0.02 20.13 <1.00

Lead, unfiltered recoverable (μg/L) 194 78.0 <1.00 23.24 1.50

Manganese, filtered (μg/L) 199 230 4.5 15.1 13.0

Manganese, unfiltered recoverable (μg/L) 199 1,100 10.0 62.6 40.0

Zinc, filtered (μg/L) 198 16.0 <1.0 23.4 2.3

Zinc, unfiltered recoverable (μg/L) 199 1,100 <3.0 232.2 13.0

Arsenic, filtered (μg/L) 199 9.0 1.0 3.4 3.2

Arsenic, unfiltered recoverable (μg/L) 199 69.0 1.0 5.3 4.0

Sediment, suspended (percent finer than 0.062 mm) 237 99 14 82 87

Sediment, suspended concentration (mg/L) 242 950 2 42 12

Sediment, suspended discharge (ton/d) 241 21,900 5.8 1,080 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.
98 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2014.

[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: 1992–2014

Arsenic 12 186 34 100 96

Cadmium 23 43.9 5.9 26.1 26.5

Chromium 21 50.7 16.8 29.9 25.9

Copper 23 9,020 522 3,590 3,700

Iron 23 45,300 28,200 35,000 34,100

Lead 23 1,030 121 553 538

Manganese 23 9,220 1,160 3,140 2,590

Nickel 22 21.4 12.0 14.9 14.6

Silver 12 20.0 8.3 15.5 15.8

Zinc 23 13,400 1,490 6,310 6,850

12323750—Silver Bow Creek at Warm Springs

Period of record for bed-sediment data: 1992–2014

Arsenic 12 177 67 114 106

Cadmium 23 12.2 4.2 7.0 6.5

Chromium 21 46.8 <15.7 1

24.3 123.5

Copper 23 769 169 342 296

Iron 23 32,500 15,400 23,900 23,800

Lead 23 100 49 71 70

Manganese 23 17,700 1,470 7,460 7,230

Nickel 22 20.0 9.2 14.9 14.7

Silver 12 4.4 0.3 1

1.9 11.8

Zinc 23 2,220 554 891 688

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 3.3

Chromium 8 39.3 24.1 31.0 31.5

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 19.4 19.2

Silver 4 5.1 3.1 3.8 3.5

Zinc 8 453 237 379 385
Data 99

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

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

12323800—Clark Fork near Galen

Period of record for bed-sediment data: 1987, 1991–2014

Arsenic 12 156 73 107 103

Cadmium 25 20.1 3.8 8.0 6.0

Chromium 21 44.6 19.1 29.8 27.0

Copper 25 2,300 838 1,190 1,110

Iron 25 39,800 22,600 27,900 27,400

Lead 25 235 92 129 126

Manganese 25 17,300 1,530 8,590 8,470

Nickel 22 23.2 13.9 18.6 18.3

Silver 14 7.3 <3.2 1

4.4 14.5

Zinc 25 3,560 721 1,350 1,120

461415112450801—Clark Fork below Lost Creek, near Galen

Period of record for bed-sediment data: 1996–2014

Arsenic 12 204 90 119 109

Cadmium 19 10.5 4.8 6.8 6.4

Chromium 19 42.4 19.4 30.8 30.0

Copper 19 2,050 1,150 1,490 1,450

Iron 19 32,800 24,400 29,100 29,600

Lead 19 218 123 162 161

Manganese 19 9,820 1,430 5,230 5,000

Nickel 19 19.9 11.7 15.9 16.3

Silver 8 7.8 4.2 6.5 6.7

Zinc 19 1,680 930 1,250 1,220

461559112443301—Clark Fork at county bridge, near Racetrack

Period of record for bed-sediment data: 1996–2014

Arsenic 12 132 56 92 90

Cadmium 19 8.7 4.6 6.4 6.0

Chromium 19 45.2 19.0 29.1 28.4

Copper 19 1,810 933 1,280 1,310

Iron 19 31,700 21,200 27,400 28,100

Lead 19 186 103 142 143

Manganese 19 6,310 1,600 3,210 3,060

Nickel 19 18.4 10.3 14.4 14.7

Silver 8 6.1 <3.3 1

5.0 15.4

Zinc 19 1,550 911 1,160 1,130
100 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

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

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for bed-sediment data: 1996–2014

Arsenic 12 109 58 83 83

Cadmium 19 10.3 4.1 6.2 5.7

Chromium 19 39.9 16.0 27.4 26.0

Copper 19 1,580 721 1,120 1,100

Iron 19 33,700 20,600 27,200 27,100

Lead 19 155 92 129 132

Manganese 19 8,370 1,200 3,790 3,210

Nickel 19 16.9 8.7 12.9 12.7

Silver 8 6.2 2.7 4.9 5.0

Zinc 19 1,570 900 1,120 1,080

12324200—Clark Fork at Deer Lodge

Period of record for bed-sediment data: 1986–87, 1990–2014

Arsenic 12 102 49 75 71

Cadmium 27 10.0 3.5 5.9 5.0

Chromium 21 50.7 19.5 32.5 28.4

Copper 27 4,180 683 1,240 1,070

Iron 27 35,300 21,100 27,400 26,500

Lead 27 242 103 143 142

Manganese 27 6,020 1,070 2,570 2,410

Nickel 22 21.1 11.5 14.9 14.5

Silver 16 7.9 2.4 4.7 4.5

Zinc 27 1,730 844 1,160 1,050

12324400—Clark Fork above Little Blackfoot River, near Garrison

Period of record for bed-sediment data: 2009-2014

Arsenic 6 91 50 75 82

Cadmium 6 5.5 4.1 4.7 4.6

Chromium 6 52.8 19.9 37.7 42.3

Copper 6 1,290 773 1,110 1,230

Iron 6 32,400 20,400 26,500 26,900

Lead 6 145 92 126 136

Manganese 6 3,560 1,150 2,550 2,800

Nickel 6 17.2 10.6 13.8 14.0

Silver 0 -- -- -- --

Zinc 6 1,240 850 1,060 1,100
Data 101

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

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

12324680—Clark Fork at Goldcreek

Period of record for bed-sediment data: 1992–2014

Arsenic 12 62 23 41 37

Cadmium 23 8.1 2.5 4.4 4.0

Chromium 21 55.3 20.2 32.6 31.6

Copper 23 1,080 338 674 687

Iron 23 32,100 15,500 23,400 24,000

Lead 23 152 52 93 94

Manganese 23 2,610 977 1,780 1,770

Nickel 22 18.6 9.0 13.8 14.1

Silver 12 4.8 2.3 3.2 3.2

Zinc 23 1,320 531 888 880

12331800—Clark Fork near Drummond

Period of record for bed-sediment data: 1986–87, 1991–2014

Arsenic 12 66 17 38 33

Cadmium 26 7.7 1.7 4.1 4.1

Chromium 21 41.9 9.2 27.7 30.1

Copper 26 747 183 465 464

Iron 26 44,000 14,800 24,900 23,200

Lead 26 135 27 84 84

Manganese 26 4,820 832 2,010 1,840

Nickel 22 16.8 4.8 12.8 13.6

Silver 15 4.7 <3.2 1

3.0 12.9

Zinc 26 1,230 380 908 947

12334550—Clark Fork at Turah Bridge, near Bonner

Period of record for bed-sediment data: 1986, 1991–2014

Arsenic 12 43 17 27 25

Cadmium 25 7.3 1.2 3.3 3.4

Chromium 21 42.5 15.3 26.7 27.7

Copper 25 635 211 344 322

Iron 25 25,900 12,600 19,300 17,300

Lead 25 115 37 66 63

Manganese 25 2,340 591 1,250 1,230

Nickel 22 19.1 6.9 12.3 11.6

Silver 14 3.9 <1.9 1

2.1 11.9

Zinc 25 1,160 448 773 775
102 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 26. Statistical summary of long-term bed-sediment data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

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, 2006–14

Arsenic 10 6 <0.2 1

3 14

Cadmium 21 2.0 0.04 1

0.5 10.3

Chromium 17 35.2 14.5 22.2 23.6

Copper 21 27 11 20 21

Iron 21 23,000 12,400 17,600 18,100

Lead 21 20 <13 1

13 112

Manganese 21 746 298 536 544

Nickel 18 14.3 6.0 11.2 11.4

Silver 12 <1.9 <0.3 1

0.5 1<0.6

Zinc 21 82 35 60 61

12340500—Clark Fork above Missoula

Period of record for bed-sediment data: 1997–2014

Arsenic 12 54 12 29 29

Cadmium 18 5.8 1.0 2.8 2.7

Chromium 17 40.7 13.2 26.4 28.5

Copper 18 551 129 332 304

Iron 18 27,000 14,700 20,500 20,400

Lead 18 78 25 52 52

Manganese 18 2,250 477 1,070 996

Nickel 18 15.8 7.6 12.5 12.5

Silver 7 2.9 0.8 1

2.0 12.1

Zinc 18 1,090 346 676 664

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.
Data 103

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.

[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, 1997–2014

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 22 33.3 4.3 12.2 11.0

Cadmium 28 9.7 3.0 5.2 4.7

Chromium 28 25.5 1.0 4.3 3.7

Copper 28 1,090 78.6 337 342

Iron 28 6,150 689 2,720 2,420

Lead 28 74.3 11.9 34.0 25.0

Manganese 28 3,030 180 1,030 997

Nickel 28 4.3 0.7 2.6 2.5

Zinc 28 1,590 432 819 768

Hydropsyche spp.

Arsenic 14 23.1 6.1 12.1 10.7

Cadmium 19 11.0 2.0 5.4 5.0

Chromium 19 4.7 0.6 2.6 3.0

Copper 19 930 80.7 428 352

Iron 19 3,630 1,050 2,260 2,210

Lead 19 237 19.3 45.5 36.5

Manganese 19 1,790 612 1,040 1,040

Nickel 19 4.1 0.7 2.2 2.3

Zinc 19 1,290 388 875 876

Hydropsyche tana

Arsenic 0 -- -- -- --

Cadmium 6 9.2 4.8 6.8 6.9

Chromium 6 11.5 0.9 4.5 1.8

Copper 6 456 10.5 236 298

Iron 6 1,520 875 1,100 1,050

Lead 6 21.0 15.6 18.6 18.3

Manganese 6 969 307 634 675

Nickel 6 1.8 0.7 1.4 1.6

Zinc 6 1,070 760 961 1,020
104 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12323750—Silver Bow Creek at Warm Springs

Period of record for biological data: 1992–2014

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 20 23.6 7.9 12.5 10.6

Cadmium 46 2.1 0.2 0.6 0.5

Chromium 46 4.3 0.4 1.1 0.9

Copper 46 97.0 16.7 36.5 30.5

Iron 46 1,650 351 837 780

Lead 46 6.0 0.3 3.2 3.0

Manganese 46 3,890 491 1,230 954

Nickel 46 1.8 0.3 0.9 0.8

Zinc 46 276 115 176 169

Hydropsyche occidentalis

Arsenic 9 31.0 10.5 18.6 15.6

Cadmium 24 1.6 0.2 0.6 0.4

Chromium 24 6.8 0.3 1.7 1.0

Copper 24 48.9 11.0 33.2 32.0

Iron 24 2,960 372 1,240 1,000

Lead 24 8.2 <1.7 1

4.2 13.8

Manganese 24 6,940 996 2,380 1,890

Nickel 24 2.7 0.7 1.5 1.5

Zinc 24 220 140 181 182

Hydropsyche spp.

Arsenic 1 -- -- 14.0 --

Cadmium 5 2.3 0.4 1.0 0.6

Chromium 5 2.5 0.5 1.4 1.3

Copper 5 47.6 34.9 39.9 40.4

Iron 5 1,100 561 763 767

Lead 5 5.1 1.9 4.0 4.5

Manganese 5 1,190 443 817 804

Nickel 5 1.9 <0.4 1

1.0 10.8

Zinc 5 284 141 188 162
Data 105

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

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

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

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12323800—Clark Fork near Galen

Period of record for biological data: 1987, 1991–2014

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 13 20.5 13.2 15.1 14.0

Cadmium 38 2.7 0.7 1.5 1.5

Chromium 38 9.6 0.8 2.3 1.9

Copper 38 181 48.7 108 116

Iron 38 2,660 816 1,560 1,510

Lead 38 17.1 1.2 8.8 8.5

Manganese 38 3,620 1,070 2,260 2,250

Nickel 38 6.5 0.9 1.9 1.7

Zinc 38 363 136 218 213

Hydropsyche morosa group

Arsenic 0 -- -- -- --

Cadmium 5 3.2 2.4 2.5 2.4

Chromium 5 4.6 1.8 2.6 2.2

Copper 5 185 156 173 175

Iron 5 1,890 1,360 1,510 1,430

Lead 5 12.4 7.1 8.5 7.9

Manganese 5 3,960 2,360 3,500 3,860

Nickel 5 3.6 1.9 2.3 2.1

Zinc 5 349 292 309 303

Hydropsyche occidentalis

Arsenic 20 17.7 9.1 14.3 14.6

Cadmium 52 1.6 0.6 1.1 1.2

Chromium 52 6.6 0.4 2.1 1.9

Copper 52 151 49.2 94.6 91.6

Iron 52 2,590 642 1,510 1,420

Lead 52 13.5 1.6 8.2 8.1

Manganese 52 6,170 653 2,480 2,080

Nickel 52 3.5 0.8 1.8 1.7

Zinc 52 286 168 206 200
Data 107

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12323800—Clark Fork near Galen—Continued

Period of record for biological data: 1987, 1991–2014

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

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

461415112450801—Clark Fork below Lost Creek, near Galen

Period of record for biological data: 1996–2014

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 19 27.8 8.8 16.3 15.6

Cadmium 30 2.8 1.1 1.9 1.8

Chromium 30 4.0 0.8 2.3 2.4

Copper 30 338 48.8 149 131

Iron 30 4,080 691 1,790 1,640

Lead 30 28.6 4.5 13.6 12.1

Manganese 30 3,160 1,230 1,820 1,720

Nickel 30 2.8 0.9 1.7 1.4

Zinc 30 339 151 241 237

Hydropsyche occidentalis

Arsenic 9 20.9 12.7 15.8 15.0

Cadmium 23 1.9 0.9 1.4 1.4

Chromium 23 3.6 1.2 2.1 2.0

Copper 23 219 52.1 117 119

Iron 23 2,830 963 1,650 1,510

Lead 23 19.4 6.6 11.0 10.7

Manganese 23 4,150 1,220 2,540 2,190

Nickel 23 3.0 0.9 1.6 1.5

Zinc 23 308 174 243 245

Hydropsyche spp.

Arsenic 4 14.5 7.0 10.2 9.7

Cadmium 8 1.8 1.0 1.3 1.3

Chromium 8 2.4 0.9 1.4 1.2

Copper 8 153 45.1 96.4 93.0

Iron 8 1,810 533 1,160 1,130

Lead 8 20.5 4.1 9.5 8.0

Manganese 8 1,980 775 1,270 1,230

Nickel 8 2.8 0.9 1.6 1.4

Zinc 8 228 143 182 173
Data 109

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

461415112450801—Clark Fork below Lost Creek, near Galen

Period of record for biological data: 1996–2014—Continued

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

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

461559112443301—Clark Fork at county bridge, near Racetrack

Period of record for biological data: 1996–2014

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 --

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 16 20.2 11.1 14.4 14.0

Cadmium 27 2.7 0.8 1.6 1.5

Chromium 27 3.0 0.6 1.9 2.1

Copper 27 198 50.0 107 99.5

Iron 27 3,330 657 1,420 1,150

Lead 27 18.7 3.7 9.8 8.6

Manganese 27 2,360 646 1,670 1,830

Nickel 27 2.0 0.7 1.3 1.2

Zinc 27 302 139 207 192
Data 111

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

461559112443301—Clark Fork at county bridge, near Racetrack—Continued

Period of record for biological data: 1996–2014

Hydropsyche occidentalis

Arsenic 15 16.8 9.2 13.1 12.8

Cadmium 28 2.3 0.7 1.4 1.4

Chromium 28 3.7 1.1 2.2 2.0

Copper 28 164 59.5 116 122

Iron 28 3,690 1,030 1,670 1,580

Lead 28 15.7 4.3 10.9 10.9

Manganese 28 3,770 660 1,990 1,910

Nickel 28 2.3 1.1 1.5 1.3

Zinc 28 361 181 234 227

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

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack

Period of record for biological data: 1996–2014

Arctopsyche grandis

Arsenic 5 17.5 6.2 10.0 8.1

Cadmium 6 7.1 1.7 3.8 3.6

Chromium 6 12.9 0.9 1

3.9 11.4

Copper 6 196 30.8 98.1 75.3

Iron 6 2,800 340 1,090 693

Lead 6 17.6 5.7 1

9.9 17.9

Manganese 6 2,060 510 1,280 1,270

Nickel 6 2.5 1.0 1.5 1.1

Zinc 6 489 87 296 283

Claassenia sabulosa

Arsenic 4 3.8 1.6 2.8 2.9

Cadmium 4 2.4 0.9 1.4 1.2

Chromium 4 1.7 0.2 0.9 0.8

Copper 4 87.2 58.6 69.6 66.2

Iron 4 485 173 293 257

Lead 4 3.4 0.9 1.9 1.6

Manganese 4 1,260 98 461 243

Nickel 4 1.0 0.2 0.6 0.6

Zinc 4 394 168 287 292

Hydropsyche cockerelli

Arsenic 14 18.8 8.0 13.3 13.4

Cadmium 23 2.1 0.7 1.4 1.4

Chromium 23 4.6 0.5 1.8 1.5

Copper 23 247 60.7 114 95.1

Iron 23 3,010 552 1,350 1,130

Lead 23 21.9 3.5 9.4 8.9

Manganese 23 2,650 487 1,430 1,350

Nickel 23 2.5 0.5 1.3 1.0

Zinc 23 285 162 220 227
Data 113

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

461903112440701—Clark Fork at Dempsey Creek diversion, near Racetrack—Continued

Period of record for biological data: 1996–2014

Hydropsyche occidentalis

Arsenic 19 24.0 9.8 14.8 15.8

Cadmium 36 2.4 0.7 1.3 1.3

Chromium 36 6.2 0.8 2.2 1.9

Copper 36 345 74.9 128 108

Iron 36 3,390 940 1,750 1,550

Lead 36 21.8 6.1 12.6 11.6

Manganese 36 4,460 826 2,300 2,160

Nickel 36 2.4 1.0 1.6 1.5

Zinc 36 386 197 262 245

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

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12324200—Clark Fork at Deer Lodge

Period of record for biological data: 1986–87, 1990–2014

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 12 17.1 5.8 10.1 9.8

Cadmium 35 3.6 0.6 1.6 1.7

Chromium 35 4.3 0.4 1.8 1.9

Copper 35 241 54.7 106 102

Iron 35 3,340 490 1,260 1,110

Lead 35 24.9 3.8 10.7 10.6

Manganese 35 1,580 396 992 1,020

Nickel 35 2.4 0.3 1.3 1.1

Zinc 35 391 132 201 194

Hydropsyche occidentalis

Arsenic 22 21.1 6.6 11.3 10.2

Cadmium 59 3.4 0.6 1.4 1.3

Chromium 59 3.7 0.6 2.0 1.9

Copper 59 222 49.4 123 121

Iron 59 3,240 558 1,520 1,490

Lead 59 20.1 3.5 12.0 11.8

Manganese 59 2,850 649 1,610 1,680

Nickel 59 12.9 1.0 1.7 1.4

Zinc 59 346 166 246 237

Hydropsyche spp.

Arsenic 1 -- -- 6.0 --

Cadmium 4 2.6 1.6 2.2 2.3

Chromium 1 -- -- 0.8 --

Copper 4 222 91 166 176

Iron 4 2,220 1,070 1,770 1,900

Lead 4 16.7 9.0 14.4 15.9

Manganese 1 -- -- 837 --

Nickel 1 -- -- 0.9 --

Zinc 4 298 196 242 237
Data 115

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12324400—Clark Fork above Little Blackfoot River, near Garrison

Period of record for biological data: 2009–14

Arctopsyche grandis

Arsenic 10 16.6 3.2 6.8 5.8

Cadmium 10 4.9 1.2 3.3 3.6

Chromium 10 4.6 0.9 1

1.8 11.5

Copper 10 209 42.0 96.3 74.7

Iron 10 2,580 410 986 760

Lead 10 18.0 4.2 8.4 7.4

Manganese 10 1,940 659 1,210 1,030

Nickel 10 2.2 0.7 1.2 1.0

Zinc 10 378 227 273 267

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 --

Hydropsyche cockerelli

Arsenic 3 11.1 7.8 9.5 9.5

Cadmium 3 4.0 0.9 2.8 3.4

Chromium 3 3.4 2.0 2.6 2.5

Copper 3 158 81.5 123 129

Iron 3 2,150 1,050 1,520 1,380

Lead 3 18.8 10.1 14.4 14.3

Manganese 3 1,870 1,270 1,550 1,500

Nickel 3 1.7 1.4 1.5 1.5

Zinc 3 284 216 247 242
116 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12324400—Clark Fork above Little Blackfoot River, near Garrison—Continued

Period of record for biological data: 2009–14

Hydropsyche occidentalis

Arsenic 9 14.7 6.4 10.1 8.8

Cadmium 9 2.5 1.3 2.0 2.0

Chromium 9 3.6 0.7 2.1 2.0

Copper 9 182 85.7 132 142

Iron 9 2,390 1,190 1,650 1,300

Lead 9 17.9 8.8 13.4 11.5

Manganese 9 2,100 975 1,460 1,260

Nickel 9 1.9 1.0 1.5 1.5

Zinc 9 299 223 260 254

Hydropsyche spp.

Arsenic 1 -- -- 13.6 --

Cadmium 1 -- -- 1.7 --

Chromium 1 -- -- 4.3 --

Copper 1 -- -- 187 --

Iron 1 -- -- 2,570 --

Lead 1 -- -- 18.5 --

Manganese 1 -- -- 919 --

Nickel 1 -- -- 1.8 --

Zinc 1 -- -- 296 --
Data 117

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12324680—Clark Fork at Goldcreek

Period of record for biological data: 1992–2014

Arctopsyche grandis

Arsenic 40 17.0 1.8 5.1 4.7

Cadmium 69 6.6 0.6 2.0 1.8

Chromium 69 5.3 0.1 1.4 1.1

Copper 69 232 19.9 52.0 39.3

Iron 69 3,070 195 778 570

Lead 69 16.9 1.0 4.1 3.5

Manganese 69 1,580 436 883 871

Nickel 69 3.1 0.2 0.8 0.7

Zinc 69 326 146 206 190

Claassenia sabulosa

Arsenic 28 2.5 0.4 1.4 1.5

Cadmium 48 3.5 0.1 1.0 0.7

Chromium 48 1.6 0.2 0.6 0.5

Copper 48 84.9 33.0 59.4 58.8

Iron 48 640 63.0 203 170

Lead 48 2.8 0.4 1.0 0.8

Manganese 48 320 50.6 153 143

Nickel 48 0.7 0.1 0.3 0.3

Zinc 48 364 166 264 260

Hydropsyche cockerelli

Arsenic 17 9.8 4.1 6.0 5.7

Cadmium 36 4.2 0.5 1.5 1.3

Chromium 36 4.7 0.5 2.0 1.9

Copper 36 188 17.1 73.6 58.5

Iron 36 3,250 522 1,160 942

Lead 36 17.6 2.4 6.7 5.3

Manganese 36 1,710 538 1,000 981

Nickel 36 3.5 0.3 1.2 1.1

Zinc 36 359 106 192 185
118 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12324680—Clark Fork at Goldcreek—Continued

Period of record for biological data: 1992–2014

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 15 11.5 4.4 6.8 6.0

Cadmium 30 2.3 0.4 1.3 1.3

Chromium 30 3.9 0.4 1.8 1.7

Copper 30 170 26.4 72.6 62.5

Iron 30 2,720 466 1,240 1,140

Lead 30 15.7 2.9 7.4 6.0

Manganese 30 2,900 530 1,250 1,140

Nickel 30 2.5 0.8 1.3 1.1

Zinc 30 328 97.0 205 203

Hydropsyche spp.

Arsenic 2 5.9 5.7 5.8 --

Cadmium 2 1.8 1.7 1.8 --

Chromium 2 1.6 1.6 1.6 --

Copper 2 83.5 73.6 78.6 --

Iron 2 1,150 1,110 1,130 --

Lead 2 9.2 8.0 8.6 --

Manganese 2 1,180 1,130 1,160 --

Nickel 2 0.8 0.8 0.8 --

Zinc 2 210 196 203 --
Data 119

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12331800—Clark Fork near Drummond

Period of record for biological data: 1986, 1991–2014

Arctopsyche grandis

Arsenic 31 8.2 1.8 4.0 3.8

Cadmium 63 3.8 0.4 1.5 1.3

Chromium 63 4.2 0.2 1.1 1.0

Copper 63 103 16.9 34.7 29.1

Iron 63 1,720 193 612 504

Lead 63 11.8 1.6 4.7 4.1

Manganese 63 2,010 456 837 754

Nickel 63 1.9 0.2 0.7 0.6

Zinc 63 314 140 203 194

Claassenia sabulosa

Arsenic 25 1.9 0.6 1.3 1.2

Cadmium 61 2.8 0.1 1.0 0.9

Chromium 61 3.3 0.2 0.7 0.6

Copper 61 165 18.0 64.6 60.6

Iron 61 449 45.4 179 149

Lead 61 2.9 0.2 1.0 0.9

Manganese 61 748 33.1 182 144

Nickel 61 1.1 0.1 1

0.3 10.2

Zinc 61 567 103 280 269

Hydropsyche cockerelli

Arsenic 17 7.2 3.9 5.5 5.3

Cadmium 46 4.5 0.3 1.2 0.9

Chromium 46 3.5 0.4 1.6 1.5

Copper 46 156 30.0 58.6 51.7

Iron 46 2,500 506 1,170 976

Lead 46 15.0 4.7 8.4 7.5

Manganese 46 1,680 549 1,010 934

Nickel 46 2.0 0.5 1.1 1.1

Zinc 46 322 134 197 190
120 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12331800—Clark Fork near Drummond—Continued

Period of record for biological data: 1986, 1991–2014

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 18 7.7 4.3 5.5 5.4

Cadmium 34 2.8 0.4 1.1 1.0

Chromium 34 8.1 0.4 2.2 2.1

Copper 34 118 13.3 58.2 56.0

Iron 34 2,060 424 1,240 1,230

Lead 34 14.0 3.0 8.6 9.1

Manganese 34 2,920 477 1,410 1,220

Nickel 34 2.4 0.5 1.3 1.2

Zinc 34 293 153 222 222

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 --
Data 121

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12334550—Clark Fork at Turah Bridge, near Bonner

Period of record for biological data: 1986, 1991–2014

Arctopsyche grandis

Arsenic 33 7.2 3.1 4.4 4.3

Cadmium 75 2.7 0.4 1.2 1.1

Chromium 75 4.1 0.5 1.6 1.5

Copper 75 125 17.6 37.7 32.0

Iron 75 2,870 372 922 790

Lead 75 13.2 1.6 4.4 3.8

Manganese 75 1,050 324 660 668

Nickel 75 2.6 0.4 1.1 0.9

Zinc 75 282 111 204 203

Claassenia sabulosa

Arsenic 23 3.1 0.2 1.2 1.1

Cadmium 49 2.5 0.05 1.1 0.9

Chromium 49 2.0 0.2 0.7 0.6

Copper 49 97.8 37.5 60.2 56.8

Iron 49 378 58.6 135 115

Lead 49 1.6 0.2 0.7 0.6

Manganese 49 229 37.2 103 90.2

Nickel 49 0.6 0.04 0.2 0.2

Zinc 49 429 144 236 243

Hydropsyche cockerelli

Arsenic 25 9.8 3.7 4.9 4.8

Cadmium 53 2.2 0.3 0.9 0.7

Chromium 53 14.2 0.2 2.2 1.7

Copper 53 126 26.4 49.4 44.2

Iron 53 3,180 566 1,240 1,140

Lead 53 19.7 2.2 5.7 5.2

Manganese 53 957 426 658 665

Nickel 53 2.7 0.6 1.3 1.3

Zinc 53 332 119 192 195
122 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12334550—Clark Fork at Turah Bridge, near Bonner—Continued

Period of record for biological data: 1986, 1991–2014

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 20 7.3 2.9 4.7 4.2

Cadmium 40 1.8 0.3 1.0 0.9

Chromium 40 5.0 0.6 2.0 1.7

Copper 40 102 27.4 49.9 45.8

Iron 40 2,590 472 1,280 1,170

Lead 40 14.2 2.8 6.5 5.7

Manganese 40 1,600 454 862 821

Nickel 40 3.2 0.6 1.3 1.2

Zinc 40 416 145 217 222

Hydropsyche spp.

Arsenic 0 -- -- -- --

Cadmium 1 -- -- 1.3 --

Chromium 1 -- -- 2.4 --

Copper 1 -- -- 84.1 --

Iron 1 -- -- 1,800 --

Lead 1 -- -- <7.8 --

Manganese 1 -- -- 537 --

Nickel 1 -- -- 1.3 --

Zinc 1 -- -- 171 --
Data 123

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12340000—Blackfoot River near Bonner

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006–14

Arctopsyche grandis

Arsenic 12 4.6 1.6 2.6 2.2

Cadmium 22 0.5 0.1 0.3 0.3

Chromium 17 6.9 0.5 2.1 1.5

Copper 22 19.3 9.9 13.8 13.0

Iron 22 1,880 108 758 769

Lead 22 2.3 0.5 1.1 0.9

Manganese 17 633 286 448 422

Nickel 17 3.7 0.7 1.4 1.2

Zinc 22 170 106 143 143

Claassenia sabulosa

Arsenic 11 3.0 0.1 1.0 0.7

Cadmium 22 0.2 0.1 0.1 0.2

Chromium 17 5.2 0.3 1.0 0.7

Copper 22 88.5 19.0 43.8 44.0

Iron 22 317 46.2 147 140

Lead 22 0.8 0.1 0.3 0.2

Manganese 17 133 26.3 80.3 73.4

Nickel 17 1.1 0.1 0.3 0.3

Zinc 22 399 117 230 207

Hydropsyche cockerelli

Arsenic 8 4.2 2.1 3.0 3.0

Cadmium 8 0.6 <0.1 1

0.3 10.3

Chromium 8 5.7 1.6 3.2 3.0

Copper 8 17.5 5.6 14.6 15.8

Iron 8 2,390 1,120 1,770 1,800

Lead 8 2.6 1.5 2.0 2.0

Manganese 8 814 409 563 541

Nickel 8 4.6 1.4 2.3 1.9

Zinc 8 165 132 149 145
124 Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

12340000—Blackfoot River near Bonner—Continued

Period of record for biological data: 1986–87, 1991, 1993, 1996, 1998, 2000, 2003, 2006–14

Hydropsyche occidentalis

Arsenic 15 3.8 1.2 2.2 2.1

Cadmium 27 0.5 0.1 0.2 0.2

Chromium 27 5.8 0.8 2.2 1.9

Copper 27 20.9 12.0 16.0 16.0

Iron 27 2,090 927 1,480 1,490

Lead 27 2.0 0.8 1.5 1.6

Manganese 27 798 412 516 457

Nickel 27 4.9 0.9 1.6 1.4

Zinc 27 202 116 144 145

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 --
Data 125

Table 27. Statistical summary of long-term biological data for the Clark Fork Basin, Montana, August 1986 through August 2014.—

Continued

[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

Period of record for biological data: 1997–2014

Arctopsyche grandis

Arsenic 31 7.2 1.2 3.7 3.6

Cadmium 50 2.3 0.1 1.0 0.8

Chromium 50 4.2 0.4 1.6 1.5

Copper 50 81.2 13.7 37.9 34.3

Iron 50 2,340 302 1,010 881

Lead 50 8.8 1.1 4.0 3.8

Manganese 50 1,410 476 900 868

Nickel 50 2.1 0.3 1.1 1.0

Zinc 50 272 133 200 200

Claassenia sabulosa

Arsenic 22 1.9 0.1 1.2 1.2

Cadmium 31 2.0 0.2 0.8 0.7

Chromium 31 1.4 0.1 0.7 0.7

Copper 31 81.1 25.8 52.0 51.0

Iron 31 424 82.0 224 227

Lead 31 3.1 0.2 0.9 0.8

Manganese 31 683 57.8 189 142

Nickel 31 0.7 0.2 1

0.4 10.4

Zinc 31 379 191 274 271

Hydropsyche cockerelli

Arsenic 22 8.9 2.4 5.7 5.9

Cadmium 31 2.0 0.4 0.9 1.0

Chromium 31 6.0 1.0 2.9 2.7

Copper 31 99.7 24.4 61.2 58.1

Iron 31 3,590 830 1,990 2,040

Lead 31 12.1 2.5 7.3 6.8

Manganese 31 1,910 764 1,200 1,170

Nickel 31 2.4 0.9 1.8 1.8

Zinc 31 266 156 219 220

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/
9 781411 340039

ISBN 978-1-4113-4003-9

Dodge and Hornberger—Water-Quality, Bed-Sediment, and Biological Data and Statistical Summaries of Data, Clark Fork Basin, Montana—OFR 2015–1223

ISSN 0196-1497 (print)

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20151223