WATER-QUALITY, BED-SEDIMENT, AND BIOLOGICAL 

DATA (OCTOBER 1995 THROUGH SEPTEMBER 1996) AND 

STATISTICAL SUMMARIES OF DATA FOR STREAMS IN 

THE UPPER CLARK FORK BASIN, MONTANA

By Kent A. Dodge, Michelle I. Hornberger, and Ellen V. Axtmann

U.S. GEOLOGICAL SURVEY 

Open-File Report 97-552

Prepared in cooperation with the

U.S. ENVIRONMENTAL PROTECTION AGENCY and the

CONFEDERATED SALISH AND KOOTENAI TRIBES

Helena, Montana 

September 1997
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

For additional information write to:

District Chief 

U.S. Geological Survey 

Federal Building, Drawer 10076 

Helena, Montana 59626-0076

Copies of this report may be purchased from:

U.S. Geological Survey 

Branch of Information Services 

Box 25286 

Denver, Colorado 80225-0286
CONTENTS

Page

Abstract...................................................................................................._^ 1

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

Sampling locations and types of data.................................................................................................................................... 3

Water-quality data................................................................................................................................................................. 4

Methods..................................................................................................................................................................... 4

Results........................................................................................................................................................................ 5

Quality assurance....................................................................................................................................................... 5

Bed-sediment data................................................................................................................................................................. 9

Methods..................................................................................................................................................................... 9

Results........................................................................................................................................................................ 10

Quality assurance....................................................................................................................................................... 10

Biological data....................................................................................................................................................................^ 11

Methods..................................................................................................................................^ 11

Results.....................................................................................................................^^ 12

Quality assurance....................................................................................................................................................... 12

Statistical summaries of data................................................................................................................................................. 13

References cited.................................................................................................................................................................... 13

Data....................................................................................................................................................................................... 15

ILLUSTRATION

Figure 1. Map showing location of study area............................................................................................................ 2

TABLES

Table 1. Type and period of data collection at sampling stations in the upper Clark Fork basin, Montana.................. 3

2. Properties and constituents analyzed in samples of water, bed sediment, and biota from the upper

Clark Fork basin, Montana.......................................................................................................................... 4

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

Montana....................................................................................................................................................... 7

4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996.......... 16

5.-7. Daily streamflow and suspended-sediment data, October 1995 through September 1996, for:

5. Clark Fork at Deer Lodge, Montana....................................................................................................... 28

6. Clark Fork at Turah Bridge, near Bonner, Montana............................................................................... 32

7. Clark Fork above Missoula, Montana.................................................................................................... 36

8. Chemical and suspended-sediment analyses of field replicates for water samples, upper Clark Fork

basin, Montana............................................................................................................................................ 40

9. Precision of chemical and suspended-sediment analyses of field replicates for water samples, upper

Clark Fork basin, Montana.......................................................................................................................... 41

10. Precision of chemical analyses of laboratory replicates for water samples, upper Clark Fork basin,

Montana....................................................................................................................................................... 42

11. Recovery efficiency for trace-element analyses of laboratory-spiked deionized-water blanks....................... 43

12. Recovery efficiency for trace-element analyses of laboratory-spiked stream samples, upper Clark

Fork basin, Montana.................................................................................................................................... 44

13. Chemical analyses of field blanks for water samples...................................................................................... 45

CONTENTS ill
TABLES-Continued

Page

Table 14. Trace-element analyses of fine-grained bed sediment, upper Clark Fork basin, Montana, August 1996........ 46

15. Trace-element analyses of bulk bed sediment, upper Clark Fork basin, Montana, August 1996.................... 47

16. Recovery efficiency for trace-element analyses of standard reference materials for bed sediment................. 48

17. Trace-element analyses of procedural blanks for bed sediment....................................................................... 49

18. Trace-element analyses of biota, upper Clark Fork basin, Montana, August 1996 ......................................... 50

19. Recovery efficiency for trace-element analyses of standard reference material for biota............................... 52

20. Trace-element analyses of procedural blanks for biota.................................................................................... 53

21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985

through September 1996.............................................................................................................................. 54

22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana,

August 1986 through August 1996.............................................................................................................. 66

23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, August 1993

through August 1996 ................................................................................................................................... 71

24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through

August 1996................................................................................................................................................. 76

CONVERSION FACTORS AND ABBREVIATED WATER-QUALITY UNITS

_________________Multiply______________By_____________To obtain______________

cubic foot per second (ft3/s) 0.028317 cubic meter per second

foot (ft) 0.3048 meter (m)

gallon (gal) 3.785 liter (L)

gallon (gal) 3,785 milliliter (ml)

inch (in.) 25.4 millimeter (mm)

inch (in.) 25,400 micrometer (f^m)

mile (mi) 1.609 kilometer

ounce (oz) 28.35 gram (g)

part per million 1 microgram per gram (ng/g)

square mile (mi2) 2.59 square kilometer 

___________ton per day (ton/d)______________907.2______________kilogram per day___________

Temperature can be converted from degrees Celsius (°C) to degrees Fahrenheit (°F) by the equation:

oF - 9/5 (OQ + 32

Abbreviated water-quality units used in this report:

Hg/g micrograms per gram

micrograms per liter

micrograms per milliliter 

j^S/cm microsiemens per centimeter at 25 degrees Celsius 

mg/L milligrams per liter

Water-year definition:

A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends.

iv Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Water-Quality, Bed-Sediment, and Biological Data 

(October 1995 through September 1996) and Statistical 

Summaries of Data for Streams in the Upper Clark Fork 

Basin, Montana

By Kent A. Dodge, Michelle I. Hornberger, and Ellen V. Axtmann

Abstract

Water, bed sediment, and biota were 

sampled in streams from Warm Springs to below 

Missoula as part of a program to characterize 

aquatic resources in the upper Clark Fork basin of 

western Montana. Sampling stations were located 

on the Clark Fork and major tributaries. Waterquality data were obtained periodically at 12 

stations during October 1995 through September 

1996 (water year 1996). Data for 14 bed-sediment 

and 13 biological stations were obtained in August 

1996. The primary constituents analyzed were 

trace elements associated with tailings from 

historical mining and smelting activities.

Water-quality data include concentrations of 

selected major ions, trace elements, and suspended 

sediment in stream samples collected periodically 

during water year 1996. Daily values of 

streamflow, suspended-sediment concentration, 

and suspended-sediment discharge are given for 

three stations. Bed-sediment data include traceelement concentrations in the fine-grained and 

bulk fractions. Biological data include traceelement concentrations in whole-body tissue of 

aquatic benthic insects. Quality-assurance data 

are reported for analytical results of water, bed 

sediment, and biota. Statistical summaries of 

water-quality, bed-sediment, and biological data 

are provided for the period of record at each 

station since 1985.

INTRODUCTION

The Clark Fork originates near Warm Springs in 

western Montana at the confluence of Silver Bow and 

Warm Springs Creeks (fig. 1). Along the 148-mi reach

of stream from Silver Bow Creek in Butte to the Clark 

Fork at Milltown Reservoir, 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-mi2 Clark 

Fork basin above Missoula include irrigation, stock 

watering, light industry, hydroelectric power 

generation, and habitat for trout fisheries. Current land 

uses primarily are cattle production, logging, mining, 

and recreation. Large-scale mining and smelting had 

been prevalent land uses in the upper basin for more 

than one hundred years, but are now largely 

discontinued.

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 1860 to 1980. Moderate- and small-scale 

mining also occurred in the basins of most of the major 

tributaries to the upper Clark Fork. Tailings derived 

from mineral processing commonly contain large 

quantities of trace elements such as cadmium, copper, 

lead, and zinc. Tailings have been eroded, mixed with 

stream sediment, and transported downstream since the 

late 1800's and redeposited in stream channels, on 

flood plains, and in the Warm Springs Ponds and 

Milltown Reservoir. The widely dispersed tailings 

continue to be eroded, transported, and redeposited 

along the stream channel and flood plain, especially 

during high flows. The occurrence of trace elements in 

elevated concentrations can pose a risk to aquatic biota 

and human health because they may accumulate to 

potentially toxic levels.

Concern about the potential toxicity of tailings to 

aquatic biota and human health has resulted in a 

comprehensive effort by State, Federal, and private 

entities to characterize the aquatic resources in the 

upper Clark Fork basin to guide and monitor remedial 

cleanup activities. A long-term data base was

Abstract
47 C

Base from U.S. Geological Survey State 

base map, 1=1,000,000 

1966

12340500 

12353000 V Mmom

46I903II244070I>! 

461559112443301°

EXPLANATION

12324200 STATION AND NUMBER

46I903II244070I MISCELLANEOUS SITE AND NUMBER 

Streamflow gaging 

A Continuous record 

APeriodic measurement 

Water quality, bed sediment, biota 

.57 Periodic water quality 

V-Daily suspended sediment 

VOnce- annual bed sediment 

"V Once-annual biota

10 20 MILES

10 20 KILOMETERS

Figure 1. Location of study area.

considered necessary to detect trends over time in order 

to evaluate the effectiveness of remediation. Waterquality data have been collected by the U.S. Geological 

Survey (USGS) at selected sites in the upper Clark 

Fork basin since 1985 (Lambing, 1987, 1988, 1989, 

1990, and 1991; Lambing and others, 1994, 1995; and 

Dodge and others, 1996). Trace-element data for bed 

sediment and biota (aquatic benthic insects) have been 

collected intermittently since 1986 at selected sites as 

part of studies on bed-sediment contamination and 

bioaccumulation of metals conducted by the USGS 

National Research Program (Axtmann and Luoma,

1991; Cain and others, 1992). In March 1993, an 

expanded sampling program for water, bed sediment, 

and biota was implemented in cooperation with the 

U.S. Environmental Protection Agency to provide 

systematic, long-term monitoring. In 1996, waterquality and daily sediment sampling in the expanded 

program was scaled back to a less extensive network 

and reduced sampling frequency. A portion of the 

sampling program daily suspended-sediment 

sampling at Clark Fork above Missoula~was resumed 

in March 1996 in cooperation with the Confederated 

Salish and Kootenai Tribes. Three bed sediment and

2 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
biological sampling sites were added in 1996 in the 

reach between Galen and Deer Lodge to improve the 

spatial resolution of accumulation characteristics. 

The purpose of this report is to present waterquality data for 12 stations and trace-element data for 

14 bed-sediment and 13 biological stations in the upper 

Clark Fork basin collected from October 1995 through 

September 1996 (water year 1996). Quality-assurance 

data are presented for water quality, bed sediment, and 

biota. Statistical summaries also are provided for 

water-quality, bed-sediment, and biological data 

collected since 1985.

SAMPLING LOCATIONS AND TYPES OF 

DATA

Sampling stations in the upper Clark Fork basin 

are located on both the Clark Fork mainstem and major

tributaries from Warm Springs to below Missoula (fig. 

1). Streamflow-gaging stations are operated at selected 

sampling stations, plus on Silver Bow Creek from 

Butte to Opportunity. Mainstem sampling sites were 

selected to divide the upper Clark Fork into reaches of 

relatively uniform length, with each reach 

encompassing either a major tributary or depositional 

environment (Warm Springs Ponds and Milltown 

Reservoir). Tributaries were sampled to describe 

water-quality characteristics for major hydrologic 

sources in the upper basin and to provide reference 

comparisons to the mainstem for bed sediment and 

biota. Water-quality data were obtained periodically at 

12 stations; daily suspended-sediment data were 

obtained at 3 of these stations. Data for 14 bedsediment and 13 biological stations were obtained 

once-annually (table 1).

Table 1. Type and period of data collection at sampling stations in the upper Clark Fork basin, Montana

[Abbreviation: P, present (1996). Symbol: --, no data]

Station 

number (fig-D

12323250

12323600

12323750

12323770

12323800

461415112450801

461559112443301

461903112440701

12324200

12324590

12324680

12331500

12331800

12334510

12334550

12340000

12340500

12353000

Station name

Silver Bow Creek below

Blacktail Creek, at Butte

Silver Bow Creek at

Opportunity

Silver Bow Creek at Warm

Springs

Warm Springs Creek at Warm

Springs

Clark Fork near Galen

Clark Fork below Lost Creek,

near Galen

Clark Fork near Racetrack

Clark Fork at Dempsey Creek

diversion, near Racetrack

Clark Fork at Deer Lodge

Little Blackfoot River near

Garrison

Clark Fork at Goldcreek

Flint Creek near Drummond

Clark Fork near Drummond

Rock Creek near Clinton

Clark Fork at Turah Bridge,

near Bonner

Blackfoot River near

Bonner

Clark Fork above Missoula

Clark Fork below Missoula3

Continuousrecord 

streamflow

10/83-P

07/88-P

03/72-09/79,

04/93-P

10/83-P

07/88-P

-

--

-

10/78-P

10/72-P

10/77-P

08/90-P

04/93-P

10/72-P

03/85-P

10/39-P

03/29-P

10/29-P

Periodic 

water quality1

03/93-08/95

03/93-08/95

03/93-P

03/93-P

07/88-P

-

--

-

03/85-P

03/85-P

. 03/93-P

03/85-P

03/93-P

03/85-P

03/85-P

03/85-P

07/86-P

03/85-08/95

Daily 

suspended 

sediment

-

03/93-09/95

04/93-09/95

-

-

-

-

-

03/85-08/86,

04/87-P

-

-

..

..

..

03/85-P

07/86-03/87,

06/88-09/95

07/86-03/87,

06/88-01/96

03/96-P

--

Fine-grained 

bed sediment2

-

07/92-P

07/92-P

08/95

08/87, 08/91 -P

08/96

08/96

08/96

08/86, 08/87,

08/90-P

08/86, 08/87, 08/94

07/92-P

08/86, 08/89,

07/92-P

08/86, 08/87,

08/9 1-P

08/86, 08/87,

08/89, 08/9 1-P

08/86, 08/9 1-P

08/86, 08/87,

08/91,08/93-P

..

08/86, 08/90-P

Bulk 

bed 

sediment2

-

08/93-08/95

08/93, 08/95-P

08/95

08/93-P

08/96

08/96

08/96

08/93-P

08/94

08/93-P

08/93-P

08/93-P

08/93-P

08/93-P

08/93-08/94

-

08/93-P

Biota2

-

07/92. 08/94-08/95

07/92-P

08/95

08/87, 08/9 1-P

08/96

08/96

08/96

08/86,08/87,08/90-P

08/87, 08/94

07/92-P

08/86, 07/92-P

08/86, 08/9 1-P

08/87, 08/9 1-P

08/86, 08/9 1-P

08/86,08/87,08/91,08/93,

08/96

08/86, 08/90-P

'Onsite measurements of physical properties and laboratory analyses of selected major ions, trace elements, and suspended sediment.

laboratory analyses of trace elements.

JBed sediment and biota sampled about 30 miles downstream from water-quality station to conform to previous sampling location.

SAMPLING LOCATIONS AND TYPES OF DATA
A list of properties and constituents analyzed in 

samples of water, bed sediment, and biota is given in 

table 2. Results of analyses for water, bed sediment, 

and biota for water year 1996 are listed in tables 4 

through 20 at the back of the report. Statistical 

summaries of water-quality, bed-sediment, and 

biological data collected since 1985 are given in tables 

21-24 at the back of the report.

Quality assurance of data was maintained through 

the use of documented procedures designed to provide 

environmentally representative data. Acceptable 

performance of the procedures was verified with 

quality-control samples that were collected 

systematically to provide a measure of the accuracy, 

precision, and bias of the environmental data and to 

identify problems associated with sampling, 

processing, or analysis.

WATER-QUALITY DATA

Water-quality data consist of measurements of 

physical properties and concentrations of chemical and 

physical constituents analyzed in stream samples. 

Samples were collected 4 to 6 times per year on a 

schedule designed to describe seasonal and hydrologic 

variability.

Methods

Cross-sectional water samples were collected 

from multiple verticals across the stream using depthand width-integration methods described by USGS 

(1977), Knapton (1985), and Edwards and Glysson

(1988). These methods provide a vertically and 

laterally discharge-weighted sample that is 

representative of the entire flow through the cross 

section of a stream. Sampling equipment consisted of 

standard USGS depth-integrating suspended-sediment 

samplers (DH-81 and D-74TM) which are either 

constructed of plastic or coated with a non-metallic 

epoxy paint, and equipped with nylon nozzles.

Onsite measurements of water temperature, 

specific conductance, and pH were made during 

collection of periodic water-quality samples. Onsite 

sample processing, including filtration and 

acidification, was performed according to procedures 

described by Horowitz and others (1994), Ward and 

Harr (1990), USGS (1977), and Knapton (1985). 

Instantaneous streamflow at the time of water sampling 

was determined at all stations, either by direct 

measurement or from stage-discharge rating tables 

(Rantz and others, 1982).

Water samples were analyzed for the constituents 

listed in table 2 by the USGS National Water Quality 

Laboratory (NWQL) in Arvada, Colo. The trace 

elements arsenic, cadmium, copper, iron, lead, 

manganese, and zinc were analyzed for both dissolved 

and total-recoverable concentrations. Analytical 

methods are described by Fishman and Friedman

(1989) and Fishman (1993).

Table 2. Properties and constituents analyzed in samples of water, bed 

sediment, and biota from the upper Clark Fork basin, Montana

Property

Streamflow

Specific conductance

pH

Temperature

Water

Constituent

Hardness

Calcium

Magnesium

Arsenic

Cadmium

Copper

Iron

Lead

Manganese

Zinc

Suspended sediment

Bed 

sediment

Constituent

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Biota

Constituent

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

4 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Cross-sectional water samples also were collected 

for analysis of suspended sediment whenever periodic 

water-quality samples were collected. These samples 

were analyzed for suspended-sediment concentration 

and the percentage of suspended sediment finer than 

0.062 mm diameter (silt size and smaller) by the USGS 

sediment laboratory in Helena, Mont., according to 

methods described by Guy (1969) and Lambing and 

Dodge (1993).

At the three daily suspended-sediment stations 

(table 1), suspended-sediment samples were collected 

2 to 7 times per week. These samples were collected 

by local contracted observers using the depthintegration method at a single vertical near mid-stream. 

The samples were analyzed for suspended-sediment 

concentration and were used to determine daily mean 

suspended-sediment concentrations according to 

methods described by Porterfield (1972).

Results

Water-quality data for samples collected 

periodically during October 1995 through September 

1996 (water year 1996) are presented in table 4. The 

types of data include instantaneous streamflow, onsite 

measurements of water-quality properties, and 

analytical results for chemical constituents and 

suspended sediment.

Daily streamflow and suspended-sediment data 

for water year 1996 at the three daily suspendedsediment stations are given in tables 5 through 7. 

Monthly descriptive statistics for each parameter are 

provided along with totals for the annual discharge of 

water and suspended sediment. The total suspendedsediment discharge for the Clark Fork above Missoula 

represents only a partial year due to temporary 

suspension of the daily sediment program.

Quality Assurance

Quality-assurance procedures used for the 

collection and field processing of water-quality 

samples are described by Horowitz and others (1994), 

Ward and Harr (1990), Edwards and Glysson (1988), 

Knapton and Nimick (1991), and Knapton (1985). 

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 (1992). Quality-assurance procedures used 

by the Montana District sediment laboratory are 

described by Lambing and Dodge (1993).

The quality of analytical results reported for 

water-quality samples was evaluated by 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 which provide 

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-quality samples. Therefore, the total number 

of quality-control samples represented about 15 

percent of the total number of water-quality samples.

In addition to quality-control samples submitted 

from the field, internal quality-assurance practices at 

the NWQL are performed systematically to provide 

quality control of analytical procedures (Pritt and 

Raese, 1992). These internal practices include 

analyses of quality-control samples such as calibration 

standards, standard reference water samples, replicate 

samples, deionized-water blanks, or spiked samples at 

a proportion equivalent to at least 10 percent of the 

sample load. The NWQL participates in a blindsample program where standard reference water 

samples prepared by the USGS Branch of Technical 

Development and Quality Systems are routinely 

inserted into the sample line for each analytical method 

at a frequency proportional to the sample load. The 

laboratory also participates in external evaluation 

studies twice-yearly with the U.S. Environmental 

Protection Agency, the Canadian Center for Inland 

Water, and the Branch of Technical Development and 

Quality Systems to assess analytical performance.

Replicate data can be obtained in different ways to 

provide an assessment of precision (reproducibility) of 

analytical results. Replicate samples are two or more 

samples considered to be essentially identical in 

composition. Replicate field samples can be obtained 

by either repeating the collection process to obtain two 

or more samples or by splitting a single sample into two 

or more subsamples which are then analyzed 

separately. Likewise, a single sample can be analyzed 

two or more times in the laboratory to obtain a measure 

of analytical variability. Precision of analytical results 

for field replicates is affected by numerous sources of 

variability within the field and laboratory 

environments, including sample collection, sample

WATER-QUALITY DATA
processing, and sample analysis. To provide data on 

precision for samples exposed to all sources of 

variability, replicate samples were obtained in the field 

by splitting a composite stream sample. Analyses of 

these field replicates indicate the reproducibility of 

environmental data that are affected by the combined 

variability potentially introduced by field and 

laboratory processes.

Analytical precision was evaluated by excluding 

field sources of variability. Replicate analyses were 

made of an individual sample selected randomly in the 

laboratory from the group of samples comprising each 

analytical run. A separate analysis of the sample was 

made at the beginning and end of each analytical run to 

provide information on laboratory analytical precision 

independent of possible effects on precision caused by 

field collection and processing of samples.

Spiked samples are used to evaluate the ability of 

an analytical method to accurately measure a known 

amount of analyte added to a sample. Because some 

constituents in stream water can potentially interfere 

with the analysis of a targeted analyte, it is important to 

determine whether such effects are causing inaccurate 

analyses. Deionized-water blanks and aliquots of 

stream samples were spiked in the laboratory with 

known amounts of the same trace elements analyzed in 

water samples. 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 significant bias to reported trace-element 

concentrations for stream samples.

Blank samples of deionized water were routinely 

analyzed to identify the presence and magnitude of 

contamination that potentially could bias analytical 

results. The particular type of blank sample routinely 

tested was a "field" blank. Field blanks are aliquots of 

deionized water that are certified as trace-element free 

and are processed through the sampling equipment 

used to collect stream samples. These blanks are then 

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 those of 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. All samples submitted from a 

sampling episode were stored and analyzed as a 

discrete sample group, independent of other samples 

submitted to the NWQL. Therefore, statistical 

descriptions of quality-control data generated for this 

program are directly applicable to the analytical results 

for stream samples reported herein.

Data-quality objectives (table 3) were established 

for water-quality data as part of the study plan for the 

expanded long-term monitoring program that was 

initiated in 1993. The objectives identify analytical 

requirements of detectability and serve as a guide for 

identifying questionable data by establishing limits for 

precision and bias of laboratory results. Comparisons 

of quality-control data to data-quality objectives are 

used to evaluate whether sampling and analytical 

procedures are producing environmentally 

representative data in a consistent manner. Data that 

did not meet the objectives were evaluated for 

acceptability, and corrective action was taken, when 

appropriate.

The precision of analytical results for a 

constituent can be determined by estimating a standard 

deviation of the differences between replicate 

measurements for several sets of samples. These 

replicate measurements may consist either of 

individual analyses of a pair of samples considered to 

be essentially identical (field replicates) or multiple 

analyses of an individual sample (laboratory 

replicates). The differences in concentration between 

replicate analyses can be used to estimate a standard 

deviation according to the following equation (Taylor, 

1987):

S =

2k

(1)

where

S = standard deviation of the difference in concentration between replicate analyses,

d = difference in concentration between each 

pair of replicate analyses, and

k = number of pairs of replicate analyses.

6 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

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

Montana

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

Data-quality objectives

Detectability

Constituent

Calcium, dissolved

Magnesium, dissolved

Arsenic, total recoverable

Arsenic, dissolved

Cadmium, total recoverable

Cadmium, dissolved

Copper, total recoverable

Copper, dissolved

Iron, total recoverable

Iron, dissolved

Lead, total recoverable

Lead, dissolved

Manganese, total recoverable

Manganese, dissolved

Zinc, total recoverable

Zinc, dissolved

Sediment, suspended

Sediment, suspended (percent finer than 0.062 mm)

Minimum 

reporting 

level, 

in units

0.1

.1

1

1

1

.1

1

1

10

3

1

.5

10

1

10

3

1

1

mg/L

mg/L

Mg/L

Mg/L

Mg/L

Mg/L

Mg/L

Mg/L

Mg/L

Mg/L

Mg/L

Mg/L

Mg/L

Mg/L

Mg/L

Mg/L

mg/L

percent

Precision

Maximum relative 

standard deviation 

of laboratory 

replicate analyses, 

in percent

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

20

-

-

Bias

Maximum 

deviation of 

spike recovery, 

in percent

-

--

25

25

25

25

25

25

25

25

25

25

25

25

25

25

-

~

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 

comparison of precision among individual 

constituents. The RSD, in percent, is calculated 

according to the following equation (Taylor, 1987):

RSD = -x 100 (2) Jc

where

RSD = relative standard deviation, 

S = standard deviation, and

jc = mean of all replicate concentrations.

Paired analyses of field replicates are presented in 

table 8. The precision estimated for each constituent 

based on these paired results, which include both field

and laboratory sources of variability, is reported in 

table 9. Statistics for precision of field-replicate 

analyses were based on the values reported in table 8, 

which are rounded to standard USGS reporting levels 

for the particular constituent and its analytical method 

(Timme, 1994).

Data-quality objectives for precision are not 

directly applicable to field replicates because of the 

inability to determine whether the variability results 

from field sample collection and processing, or 

laboratory handling and analysis. However, a 

statistical calculation of precision for the field 

replicates is provided in table 9 to illustrate overall 

reproducibility of environmental data that incorporates 

both field and laboratory sources of variability. 

Relative standard deviations estimated from 

differences in analytical results between field replicates 

were within 20 percent for all constituents, except 

dissolved lead. This exceedance was a mathematical

WATER-QUALITY DATA
artifact caused by the predominance of low 

concentrations at or below the minimum reporting 

level.

Analytical precision for chemical constituents 

based on replicate laboratory analyses of individual 

samples, which includes only laboratory sources of 

variability, is reported in table 10. Statistics for 

analytical precision of laboratory-replicate analyses 

are based on unrounded values stored in laboratory 

data files. Concentrations less than the minimum 

reporting level (censored values) were included in the 

calculations by arbitrarily substituting a value of onehalf the reporting level.

The data-quality objective for analytical precision 

is a maximum relative standard deviation of 20 percent 

for laboratory-replicate analyses. Precision estimates 

for laboratory-replicate analyses were within the 20- 

percent relative standard deviation limits for almost all 

constituents (table 10). However, laboratory-replicate 

analyses for dissolved cadmium and total-recoverable 

zinc did not meet objectives. The reason for 

exceedance of the 20-percent limit for dissolved 

cadmium was the imprecision of one pair of analyses at 

the analytical detection limit. The exceedance of the 

20-percent limit for total-recoverable zinc was due to 

poor precision for one pair of analyses. Excluding this 

one pair of replicate analyses results in a relative 

standard deviation of 1.4 percent. The large effects on 

the precision statistics by individual samples is partly a 

function of the small sample sizes imposed by the 

reduced sampling frequency. The precision data, 

therefore, indicate that reproducibility is random and

not an indication of systematic analytical procedure 

problems.

Analyses of an unspiked sample and a spiked 

aliquot of the same sample provide a measure of the 

recovery efficiency for the analytical method within the 

chemical matrix of the sample. Spike recovery, in 

percent, was calculated using equation 3 (see below).

The data-quality objective for acceptable spike 

recovery of trace elements in water samples was a 

maximum deviation of 25 percent from a theoretical 

100-percent recovery of added constituent. At the 

laboratory, a spiked deionized-water blank 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 according to equation 3. If the spike recovery 

for a trace element was outside a range of 75 to 125 

percent, the instrument was recalibrated and the entire 

sample set and spiked samples were reanalyzed for that 

particular trace element until recoveries were within 

acceptable limits. Results of recovery efficiency for 

individual trace elements in spiked deionized-water 

blanks and spiked stream samples are presented in 

tables 11 and 12, respectively.

The mean spike recovery for deionized-water 

samples spiked with trace elements ranged from 82.3 to 

104.1 percent. The mean spike recovery for spiked 

stream samples ranged from 88.4 to 105.9 percent. The 

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

mean of spike recovery for each constituent did not

Spike recovery in percent = spiked sample concentration unspiked sample concentration x 100

spike concentration

(3)

8 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
exceed a 25-percent deviation from an expected 100- 

percent recovery except for dissolved iron in spiked 

deionized-water blanks, and total-recoverable 

cadmium and iron in spiked stream water. The 

principal factor contributing to exceeding the 25 

percent deviation is the small number of sample sets (3) 

measured as a result of reduced sampling frequency. 

Because all mean spike recoveries were within the 25 

percent limit, spike recoveries for each trace element 

were considered to be within the limits of data-quality 

objectives and indicate acceptable analytical 

performance for stream samples. High or low bias is 

indicated if the confidence interval does not include 

100 percent. All laboratory-spiked stream samples 

(table 12) had confidence intervals for percent recovery 

that included 100 percent. Because of the small 

number of sample sets, and mean spike recoveries that 

met data-quality objectives, no adjustments were made 

to analytical results for stream samples on the basis of 

spike recoveries.

Analytical results for field blanks are presented in 

table 13. A field blank with constituent concentrations 

equal to or less than the minimum reporting level for 

the analytical method indicates that the entire process 

of sample collection, field processing, and laboratory 

analysis is presumably free of significant 

contamination. If detectable concentrations in field 

blanks were equal to or greater than twice the minimum 

reporting level (typical measurement precision at the 

detection level), the concentrations were noted during 

data review. Analytical results from the field blank for 

the next sample set is evaluated for a consistent trend 

that may indicate systematic contamination. Sporadic, 

infrequent exceedances of twice the minimum 

reporting level probably represent random 

contamination or instrument calibration error that is not 

persistent in the process and which is not likely to cause 

significant positive bias in analytical results. However, 

if concentrations for a particular constituent exceed 

twice the minimum reporting level in field blanks from 

two consecutive field trips, blank samples are collected 

from individual components of the processing 

sequence and are submitted for analysis in order to 

identify the source of contamination.

Constituent concentrations in field blanks were 

almost always less than the minimum reporting level. 

There was only one occurrence of a value equaling 

twice the minimum reporting level, and there were no 

occurrences of detectable concentrations for any trace

element in two consecutive blank samples. Therefore, 

the analytical results for field blanks indicate no 

systematic contamination that would bias the reported 

water-quality data for stream samples.

BED-SEDIMENT DATA

Bed-sediment data consist of analyses of solidphase concentrations of trace elements in the finegrained and bulk fractions. Bed-sediment samples are 

collected once-annually during low, stable flow 

conditions to facilitate data comparisons between 

years.

Methods

Bed-sediment samples were collected in August 

1996 using protocols described by E.V. Axtmann (U.S. 

Geological Survey, written cornmun., 1994). Samples 

were collected from the surfaces of streambed deposits 

in low-velocity areas near the edge of the stream using 

an acid-washed polypropylene scoop. Whenever 

possible, samples were collected from both sides of the 

stream. Three composite samples of fine-grained bed 

sediment and one composite sample of bulk bed 

sediment were collected at each site.

Individual samples of fine-grained bed sediment 

were collected by scooping material from the surfaces 

of three to five randomly selected deposits along pool 

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 

0.064-mm nylon-mesh sieve using ambient stream 

water. The fraction of bed sediment in each composite 

sample that was finer than 0.064 mm was transferred to 

an acid-washed 500-mL polyethylene bottle and 

transported to the laboratory on ice.

Individual samples of bulk bed sediment also were 

collected by scooping material from the surfaces of 

three to five randomly selected deposits. Because the 

streambed at most sampling locations is predominantly 

gravel and cobble, deposits were selected where 

cobbles and gravel could be excluded from the 

samples. Bulk bed-sediment samples are not sieved 

and generally are composed of particles smaller than 

about 10 mm in diameter. The individual unsieved 

samples were composited into an acid-washed

BED-SEDIMENT DATA
polyethylene bottle and transported to the laboratory on 

ice.

Bed-sediment samples were prepared for analysis 

at the USGS National Research Program laboratory in 

Boulder, Colo. Fine-grained and bulk bed-sediment 

samples were oven-dried at 60 °C and ground using an 

acid-washed ceramic mortar and pestle. Duplicate 

aliquots of approximately 0.6 g of sediment from each 

of the three composite fine-grained bed sediment 

samples were digested using a hot, concentrated nitric 

acid reflux according to methods described by Luoma 

and Bryan (1981). Triplicate aliquots were analyzed 

from the single composite sample of bulk bed 

sediment. After a digestion period of up to several 

weeks, the aliquots were evaporated to dryness on a hot 

plate. The dry residue was redissolved with 20 mL of 

0.6 N (normal) hydrochloric acid. The reconstituted 

aliquots then were filtered through a 0.45-fim filter 

using a syringe and in-line disposable filter cartridge. 

The filtrate was subsequently diluted to either a 1:5 or 

1:10 ratio with 0.6 N hydrochloric acid. These final 

solutions were assigned a sequential number and sent 

without station identification to the Geology 

Department at the University of Montana, Missoula, 

Mont., to be analyzed for cadmium, chromium, copper, 

iron, lead, manganese, nickel, and zinc using 

Inductively Coupled Argon Plasma Emission 

Spectroscopy (ICAPES). Silver was analyzed in 

undiluted digests by flame atomic absorption (AA) at 

the USGS National Research Program laboratory in 

Boulder, Colo.

Results

Solid-phase concentrations of trace elements 

measured in samples of fine-grained and bulk bed 

sediment collected during August 1996 are 

summarized in tables 14 and 15, respectively. Liquidphase concentrations, in |ig/mL, that were analyzed in 

the reconstituted aliquots of digested bed sediment 

were converted to solid-phase concentrations, in fig/g, 

using the following equation:

. _ }ig/mL x volume of digested sample, in mL f . 

dry weight of sample, in g x dilution ratio

The reported solid-phase concentrations in table 14 

and 15 are the means of all analyses of replicate 

aliquots from each composite sample collected at the

site. Because the conversion from liquid-phase to 

solid-phase concentration is dependent on both the 

dilution ratio and the dry weight of the sample, 

minimum reporting levels for some trace elements 

may differ between stations and among years.

Quality Assurance

The protocols for field collection and processing 

of bed-sediment samples are designed to prevent 

contamination from metal sources. Non-metallic 

sampling and processing equipment was acid-washed 

and rinsed with deionized water prior to the first sample 

collection. Nylon-mesh sieves were washed in a 

laboratory-grade detergent and rinsed with deionized 

water. All equipment was given a final rinse onsite 

with stream water. Sampling equipment that was 

reused at each site was rinsed between sites with 10- 

percent nitric acid, deionized water, and stream water. 

Separate sieves were used at each site and, therefore, 

did not require between-site cleaning.

Quality assurance of analytical results for bed 

sediment included laboratory instrument calibration 

with standard solutions and analysis of quality-control 

samples designed to identify the presence and 

magnitude of bias (E.V. Axtmann, written commun., 

1994). Quality-control samples consisted of standard 

reference materials and procedural blanks. Each type 

of sample was analyzed in a proportion equivalent to 

about 10 to 20 percent of the total number of bedsediment samples.

Standard reference materials (SRM) are 

commercially prepared materials that have certified 

concentrations of trace elements. Replicate analyses of 

standard reference materials are used to indicate the 

reproducibility of analytical results and the ability of 

the method to accurately measure a known quantity of 

a constituent. Recovery efficiency of trace-element 

analyses of standard reference materials for bed 

sediment is summarized in table 16. Two standard 

reference materials consisting of agricultural soils 

representing low and high concentrations of trace 

elements were analyzed to test recovery efficiency for 

a range of concentrations generally similar to those 

occurring in the 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

10 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
bound to the sediment. The percent recovery of trace 

elements in standard reference materials under such 

conditions serve to indicate which trace elements 

display strong sediment-binding characteristics and 

whether analytical recovery is consistent between 

multiple sets of analyses.

Although data-quality objectives have not been 

established for bed sediment, elements with mean 

recoveries outside a 25-percent deviation from 

complete recovery were chromium, copper, and silver 

for the low-concentration range (SRM 2709), and 

chromium for the high-concentration range (SRM 

2711). Mean recoveries were 100 percent or less for all 

elements, except cadmium and silver, indicating that 

the digestion during sample preparation does not 

release all of the element from the solid-phase matrix. 

The most notable recovery anomaly was 261 percent 

for silver in the low-range SRM. The reason for this 

high recovery is believed to be the result of analyzing 

concentrations near the detection limit, coupled with 

signal enhancement resulting from matrix interference. 

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, 0.6 N hydrochloric acid 

was added quantitatively to the dry residue to obtain 

the same dilution ratio as that used in the analysis of 

bed sediment. Procedural blanks, therefore, represent 

the same chemical matrix as the reagents used to digest 

and reconstitute bed-sediment samples. Analytical 

results for procedural blanks can indicate the presence 

and magnitude of potential contamination associated 

with sample handling and analysis in the laboratory 

environment. Results of trace-element analyses of 

procedural blanks for bed sediment are in table 17.

Analytical results of procedural blanks are 

reported as a liquid-phase concentration, in jag/mL, 

which is equivalent to parts per million. Determination 

of the significance of a detectable blank concentration 

is based on the magnitude of the equivalent solid-phase 

concentration, in jig/g, relative to the ambient 

concentration of the trace element in bed-sediment 

samples. Because sample weights of individual 

aliquots may vary, the relative significance of blank 

concentrations may differ among samples. If a

detectable blank concentration, after conversion to a 

solid-phase concentration, represents 10 percent or 

more of the ambient solid-phase concentration, then 

the blank concentration is subtracted to remove 

potential contamination bias. Almost all procedural 

blanks had concentrations less than analytical detection 

levels. No detectable concentrations were twice the 

detection level or greater than 10 percent of the 

ambient concentration. Therefore, no adjustments 

were made to trace-element concentrations in bedsediment samples on the basis of procedural blanks.

BIOLOGICAL DATA

Biological data consist of analyses of solid-phase 

concentrations of trace elements in the whole-body 

tissue of aquatic benthic insects. Insect samples are 

collected once-annually at the same stations where 

bed-sediment samples are collected (table 1). Biota 

samples are collected concurrently with bed-sediment 

samples to facilitate comparisons of results between 

years and between concentrations in bed sediment and 

biota.

Methods

Insect samples were collected using protocols 

described by M.I. Hornberger(U.S. Geological Survey, 

written commun., 1994). Immature stages of aquatic 

benthic insects were collected using a large nylonmesh kick net. A single riffle at each station was 

sampled repeatedly until an adequate number of 

individuals was collected to provide sufficient mass for 

analysis. Targeted taxa for collection were 

Hydropsyche spp., Family Trichoptera (caddisflies); 

Arctopsyche grandis, Family Trichoptera; and 

Claassenia sabulosa, Family Plecoptera (stoneflies). 

Samples of each taxon were stored separately, by 

genus, in acid-washed plastic containers. Containers 

were kept on ice in the field while the insects were 

allowed to evacuate the gut contents in ambient stream 

water for a period of six to eight hours. Excess water 

then was drained and insects were frozen for transport 

to the laboratory.

Insect samples were processed and analyzed at the 

USGS National Research Program laboratory in Menlo 

Park, Calif. Insects were thawed and rinsed with ultrapure deionized water to remove particulate matter, then

BIOLOGICAL DATA 11
sorted to their lowest possible taxonomic level. When 

large numbers of specimens were collected from a 

station, 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 0.6 N hydrochloric 

acid, filtered through a 0.45 -|nm filter, and analyzed 

undiluted by ICAPES for cadmium, chromium, copper, 

iron, lead, manganese, nickel, and zinc.

Results

Solid-phase concentrations of trace elements in 

whole-body tissue of aquatic insects collected during 

August 1996 are summarized in table 18. The 

variability in the number of composite samples 

between species and between sites reflects the 

difference in insect abundance, with number of 

composite samples increasing with abundance of 

insects. Liquid-phase concentrations analyzed in the 

reconstituted samples were converted to solid-phase 

concentrations using equation 4. As in bed sediment, 

minimum reporting levels may differ between sites as 

a result of variable sample weights. In general, the 

smaller the biological sample weight (a function of 

insect abundance), the higher the minimum reporting 

level. Therefore, higher minimum reporting levels do 

not necessarily imply a higher trace-element 

concentration in tissue.

Two genera of Hydropsyche were collected for 

this study: Hydropsyche occidentalis and 

Hydropsyche morosa group. Two species of 

Hydropsyche were identified within the morosa group 

(H. cockerelli and H. tana). Results of analyses are 

listed for the individual species within the morosa 

group where positive identification was possible. In 

some instances (as noted at the individual station), a 

sample was not positively identifiable as H. cockerelli 

although it could be identified as belonging to the 

morosa group. These samples are most likely H. 

cockerelli based on a distinct head pattern. However, 

the small size of the insect made it difficult to 

definitively determine the species. When positive 

identification of species was not possible, Hydropsyche 

spp. was used.

Quality Assurance

The protocols for field collection and processing 

of biota samples are designed to prevent contamination 

from metal sources. Non-metallic nets, sampling, and 

processing equipment were employed in all sample 

collection. Equipment was acid-washed and rinsed in 

ultra-pure deionized water prior to the first sample 

collection. Nets and equipment were thoroughly 

rinsed in ambient stream water at each new mainstem 

station. New nets and depuration chambers were used 

for the tributary stations. In addition, biota samples 

were collected concurrently with bed-sediment 

samples along an increasing concentration gradient to 

minimize effects from station-to-station carryover 

contamination.

Quality assurance of analytical results for biota 

samples included laboratory instrument calibration 

with standard solutions and analyses of quality-control 

samples designed to identify the presence and 

magnitude of bias (M.I. Hornberger, written commun., 

1994). Quality-control samples consisted of standard 

reference material and procedural blanks. Each type of 

sample was analyzed in a proportion equivalent to 

about 10 to 20 percent of the total number of biota 

samples.

Recovery efficiency for trace-element analyses of 

standard reference material for biota is summarized in 

table 19. The reference material tested was oyster 

tissue. Data-quality objectives have not been 

established for analytical recovery in biota, but mean 

recoveries were within 25 percent of complete 

recovery for all trace elements, with the exception of 

lead (mean recovery within 28 percent). A slightly low 

bias is indicated for iron and manganese (confidence 

interval does not include 100 percent). No 

adjustments were made to trace-element 

concentrations for insect samples on the basis of 

recovery efficiency.

Results of trace-element analyses of procedural 

blanks for biota are in table 20. Procedural blanks for 

biota consisted of the same reagents used to digest and 

reconstitute tissue of aquatic insects. The blanks were 

analyzed undiluted at a proportion of one blank per 

site. Analytical results for blanks indicated no 

significant contamination bias, although a blank 

correction for iron was applied to the Blackfoot River 

samples. The change of iron concentrations using this 

correction is very small (less than 15 |ng/g) and does

12 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
not significantly affect the iron concentrations in the 

samples. The adjusted values are reported in table 18. 

No other adjustments for procedural blanks were 

necessary because all blanks had concentrations that, 

when converted to solid-phase concentrations, were 

less than 10 percent of ambient solid-phase traceelement concentrations in insects.

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 identified clearly to 

the species, but had morosa characteristics.

STATISTICAL SUMMARIES OF DATA

Statistical summaries of water-quality, bedsediment, and biological data are provided in tables 21- 

24 for the period of record at each station since 1985. 

The summaries include the period of record, number of 

samples, maximum, minimum, mean, and median of 

concentrations.

Statistical summaries of water-quality data (table 

21) are based on results of samples collected 

periodically during the station's period of record. 

Statistical summaries of bed-sediment (table 22 and 

23) and biological data (table 24) are based on results 

of samples collected once-annually during the 

indicated years. Because not all stations were sampled 

for bed sediment and biota every year, these data do not 

represent a consecutive annual record.

Sample sizes and statistics for bed-sediment data 

are based on the annual mean concentrations 

determined from the combined results of composite 

samples for a given year. Therefore, sample sizes for 

bed sediment represent the number of years sampled. 

Sample sizes and statistics for biological data are based 

on individual analyses for each composite sample 

collected in individual years rather than the combined 

annual mean concentration. Biota sample sizes 

therefore reflect differences in species abundance 

between sites and between years. The statistics for 

biota describe the full range of trace-element 

concentrations measured among all available 

composite samples. 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 different taxa 

analyzed between years or in variable analytical 

detection limits. Where minimum reporting levels 

vary between years, statistical summaries are provided 

only as a general indication of the range of detection.

The presence or absence of insect species at a 

given site can vary between years and may result in 

different taxa being analyzed in the long-term period of 

record. Because Hydropsyche insects were not sorted

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Services Catalog: U.S. Geological Survey Open-File 

Report 94-304, 103 p.

U.S. Geological Survey, 1977, National handbook of 

recommended methods for water-data acquisition-- 

Chap. 5, Chemical and physical quality of water and 

sediment: Office of Water Data Coordination, 193 p.

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

collection and processing of surface-water and bedmaterial samples for physical and chemical analyses: 

U.S. Geological Survey Open-File Report 90-140,71 p.

14 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
DATA

DATA 15
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; ng/L, micrograms per liter; fiS/cm, microsiemens per centimeter at 25 °C; 

mg/L, milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than minimum reporting level; , no data]

12323750--SILVER BOW CREEK AT WARM SPRINGS, MONT.

Date

Feb 1996

08...

Mar

12...

Apr 

16...

May 

14...

Jun

05...

Jul

22...

Streamflow, Specific H =, Terrmer- Hardness, calcium Magne- 

 instan- conduct- P ' or;sllY icmper- ... uaicium, esium Time mown uonuun (standard aturp water luiai Hicsnlvert Slum,

"me taneous ance, onsite l ,fn itcY fd/" (mg/L as /~°^ dissolved 

(ft3/s) (^S/cm) urms' * ^' CaCO3) (mg/L) (mg/L)

0900 183 384 8.4 0.5 150 44 9.9

0715 147 461 8.7 2.0 190 57 11

0940 223 401 8.7 7.0 160 49 9.6

0810 284 348 8.3 9.0 140 42 8.3

1645 447 300 8.8 15.5 120 37 7.2

0945 103 365 8.9 16.0 150 44 10

Arsenic, 

total 

recoverable

(H9/L)

94

36

31

45

38

33

Date

Feb 1996

08...

Mar

12...

Apr 

16...

May 

14...

Jun

05...

Jul

22...

Arsenic, ^totlV"1 ' Cadmium, C?Qtafr' Copper, '""?: Iron, 

di o!'g/lL)ed recoverable di**ff recoverable ***${)* recoverable ^/L^

(fiQ/L) (fiQ/L) (}j,Cj/L)

60 <1 0.2 64 32 1,100 93

25 <1 .3 80 40 640 60

24 <1 <.l 39 17 450 31

33 <1 <.l 28 12 1,000 31

30 <1 <.l 22 12 510 21

27 <1 <.l 12 7 160 19

Lead, 

total 

recoverable (ng/L)

15

10

7

8

3

^

Date

Feb 1996

08...

Mar

12...

Apr 

16...

May 

14...

Jun

05...

Jul

22...

i OH n*£?~ Manga- f'nf.' Zinc, coHimont Sediment Sediment, 

dissolved total nese' recov- dissolved susrTnded discharae, suspended 

f /if M wILhio dissolved ^?,0 (ng/L) ffx?n suspended (percent finer than 

(ng/L) rec(°vg^ble (ng/L) Jabg {mg/L) (tbn/d) 0.062mm)

1.0 390 310 80 25 58 29

<.5 600 530 130 34 12 4.8

<.5 200 110 70 15 9 5.4

<.5 130 61 60 9 43 33

<.5 80 47 20 <3 26 31

<.5 90 54 <10 6 4 1.1

80

87

88

82

76

84

16 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued)

12323770--WARM SPRINGS CREEK AT WARM SPRINGS, MONT.

Date

Apr 1996

16...

May

14...

Jun

05...

Jul

22...

Streamflow, Specific ., _,,.. T ineton nsTnfjunt P"i onsite TemperTime £££» an'c^te (*"$«* *"W*<* 

(f&s) (nS/cm) unlts> (°)

1045 57 365 8.2 6.0

0915 113 267 8.2 7.0

1750 379 154 7.9 11.0

1045 67 269 8.2 12.0

Hardness, 

total 

(mg/L as 

CaC03)

180

130

73

130

dissolved 

(mg/L)

55

40

23

40

Magne- Arsenic, 

sium, total 

dissolved recoverable 

(mg/L) (ng/L)

11 6

7.3 1 2

3.8 23

7.4 6

Date

Apr 1996

16...

May

14...

Jun

05...

Jul

22...

A,~nn; n Cadmium, r>-^~.i..~ Copper, Arsenic, total Cadmium, total 

dissolved i dissolved / _/i\ recoverable / _/i\ recoverable

^9 (ng/L) ^9 (ng/L)

4 <1 <0.1 11

5 <1 <1 52

11 <1 <.l 85

5 <1 <.l 8

Copper, 

dissolved

(ng )

3

5

14

2

Iron, 

total 

recoverable

(H9/L)

110

820

1,200

100

, _ Lead,

lron ' total dissolved . , / _/ \ recoverable

(^g/L) (ng/L)

4 1

10 5

25 9

7 1

Date

Apr 1 996 

16... 

May 

14... 

Jun 

05... 

Jul 

22...

Lead, 

dissolved (ng/L)

<0.5

Manganese, 

total 

recoverable

280 

310 

280 

160

Manganese, 

dissolved

260 

140

57 

150

Zinc, 

total

(3/L)

<10 

20 

30 

<10

Zinc, 

dissolved

<3 

<3 

<3 

3

(mg/L)

6 

51 

69

5

Sediment 

discharge, 

suspended 

(ton/d)

0.92 

16 

71 

.90

Sediment, 

suspended 

(percent finer than 

0.062 mm)

85

75 

74 

87

TABLE 4 17
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued)

12323800--CLARK FORK NEAR GALEN, MONT.

Date

Feb 1996

08...

Mar

12...

Apr

16...

May

14...

Jun

05...

Jul

22...

-

1030

0830

1220

1030

1525

1145

Streamflow,

taneous

(ft3/s)

251

205

290

407

841

165

Specific

(nS/cm)

380

435

398

330

235

336

pH, onsite 

units)

8.2

8.4

8.5

8.1

8.6

8.6

""^S"

1.0

2.0

7.0

9.0

13.0

15.0

Hardness, 

CaC03)

160

180

170

140

100

150

Calcium, 

(mg/L)

46

54

52

42

31

44

Magne- 

(mg/L)

10

11

10

8.2

5.7

9.1

Arsenic,

78

32

26

37

36

25

Date

Feb 1996

08...

Mar

12...

Apr

16...

May

14...

Jun

05...

Jul

22...

Arsenic, 

dissolved

(l^g/L)

53

23

21

26

12

21

CaST' Cadmium, 

recovSLble difus°'vfd

(ng/L) ^9/ '

<1 0.2

<1 .2

<1 <. 1

<1 <- 1

<1 <.l

<1 <.l

Copper, 

total 

recoverable

(MO/L)

87

60

38

59

72

11

Copper,

(ng/U

32

32

14

10

14

7

Iron, 

total 

recoverable

(ug/L)

1,400

600

470

1,200

1,200

140

Iron, 

dissolved (ng/L)

81

48

22

20

21

10

Lead, 

total 

recoverable (ug/L)

13

9

6

9

8

1

Date

Feb 1996

08...

Mar

12...

Apr

16...

May

14...

Jun

05...

Jul

22...

Lead, 

dissolved (ug/L)

0.8

<.5

<.5

<.5

<.5

<.5

Manganese, 

total 

recoverable (ug/L)

400

490

220

250

230

90

Manganese, 

dissolved (ug/L)

260

380

120

70

43

58

Zinc, 

total

erable

100

100

60

70

50

<10

Zinc, 

dissolved

22

23

7

4

4

4

suspended

51

17

14

58

67

4

Sediment Sediment, 

discharge, suspended 

suspended (percent finer than 

(ton/d) 0.062 mm)

35

9.4

11

64

152

1.8

85

89

81

75

58

74

18 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued)

12324200-CLARK FORK AT DEER LODGE, MONT.

Date

Feb 1996

08...

Mar

12...

Apr 

16...

May 

14...

Jun

05...

Jul

22...

Time

1225

1015

1355

1220

1945

1315

Streamflow, instantaneous

(ft3/s)

992

437

444

558

1,010

172

Specific 

conductance, onsite

(nS/cm)

376

430

447

371

242

399

pH, onsite 

units)

8.0

8.2

8.2

8.3

8.1

8.6

Temperature, water

( C\

1.0

2.5

8.5

11.0

14.0

18.0

(mg/L as 

CaCO3)

140

190

200

160

100

180

Calcium, 

dissolved

41

56

59

48

32

52

Magnesium, 

dissolved 

(mg/L)

9.2

12

12

9.6

5.9

11

Arsenic, 

total 

recoverable (ng/L)

220

35

28

38

56

22

Date

Feb 1996

08...

Mar

12...

Apr

16...

May

14...

Jun

05...

Jul

22...

Arsenic, 

dissolved (ng/L)

36

20

17

20

20

20

°15!PI Cjdmlja 

recoverable / _/i\

(ng/L) ^9 '

5 0.2

<1 .1

<1 <.l

<1 .2

<1 <.l

<1 <.l

Copper, 

total 

recoverable (ng/L)

960

94

96

150

240

18

Copper, 

dissolved (ng/L)

85

23

14

14

27

10

Iron, 

total 

recoverable

(ng/M

1 9,000

1,300

1,100

2,100

3,100

130

Iron, 

dissolved (ng/L)

190

41

14

13

31

6

Lead, 

total 

recoverable (ng/L)

140

12

11

21

30

1

Date

Feb 1996

08...

Mar

12...

Apr

16...

May

14...

Jun

05...

Jul

22...

MangaLead, nese, 

dissolved total 

(ng/L) recoverable

1.3 1,900

<.5 220

<.5 180

<.5 240

<.5 260

<.5 60

Manganese,

130

70

31

36

45

33

Zinc, 

total

(ng/L)

1,100

100

80

130

130

<10

Zinc, 

dissolved

50

20

13

8

10

6

T3*

976

68

53

129

177

6

Sediment 

discharge, 

suspended 

(ton/d)

2,610

80

64

194

483

2.8

Sediment, 

suspended 

(percent finer than 

0.062 mm)

55

60

54

47

57

70

TABLE 4 19
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued)

12324590--LITTLE BLACKFOOT RIVER NEAR GARRISON, MONT.

Date

Apr 1996 

16... 

May 

14... 

Jun 

05... 

Jul 

22...

Time

1520 

1405 

0800 

1420

Streamflow, instantaneous 

(fP/s)

400 

459 

693 

81

Specific 

conductance, onsite

(uS/cm)

189 

191 

179 

269

pH, onsite 

(standard 

units)

7.9 

8.0 

8.0 

8.4

Temperature, water (dC)

6.0 

9.5 

9.5 

19.5

Hardness, 

total 

(mg/L as 

CaCO3)

88 

86 

82 

130

Calcium, 

dissolved 

(mg/L)

26

25 

24 

37

Magnesium, 

dissolved

(mg/L)

5.7 

5.8 

5.3 

8.3

Arsenic, 

total 

recoverable

(ug/L)

6

8

7 

7

Date

Apr 1996 

16...

May 

14...

Jun

05...

Jul

22...

Arsenic, 

dissolved

(ug/L)

4

4

5

6

Cadmium, Cadmium,

recoverable «"f-o{f

(ug/L) <"9/L>

<1 <0.1

<1 <.l

<1 <.l

<1 <.l

Copper, 

total 

recoverable

(ug/L)

4

4

6

<1

Copper, 

dissolved

(ug/L)

2

1

2

<1

Iron, 

total 

recoverable

(ug/L)

590

1,200

520

190

Iron, 

dissolved

89

34

44

8

Lead, 

total 

recoverable

(ug/L)

3

4

2

<1

Date

Apr 1996 

16... 

May 

14... 

Jun 

05... 

Jul 

22...

Lead, 

dissolved

(ug/L)

2.5 

.5 

<.5 

<.5

Manganese, 

total 

recoverable

(ug/L)

40 

70 

40 

40

Manganese, 

dissolved

(ug/L)

7 

10 

12 

16

Zinc, 

total 

recoverable

(ug/L)

<10 

20 

<10 

<10

Zinc, 

dissolved

(ug/L)

3 

<3 

4 

3

Sediment, 

suspended 

(mg/L)

27 

63 

29

2

Sediment 

discharge, 

suspended

(ton/d)

29

78 

54 

.44

Sediment, 

suspended 

(percent finer than 

0.062 mm)

69 

60

57 

79

20 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued)

12324680--CLARK FORK AT GOLDCREEK, MONT.

Date

Feb 1996

08...

Mar

13...

Apr

16...

May

17...

Jun

05...

Jul

22...

Time

1415

0915

1700

0845

1000

1530

Streamflow, 

instantaneous

1,560

1,020

1,020

1,810

2,060

372

Specific 

conductance, onsite

286

308

338

245

226

390

pH, onsite 

(standard 

units)

7.9

8.2

8.1

8.1

8.0

8.4

Temperature, water (6C)

0.5

2.0

8.0

8.0

11.0

20.0

Hardness, 

total 

(mg/L as 

CaCO3)

110

130

150

100

96

180

Calcium, 

dissolved

(mg/L)

32

40

45

31

29

53

Magnesium, 

dissolved

(mg/L)

7.5

8.5

9.4

6.3

5.7

11

Arsenic, 

total 

recoverable

31

20

18

48

26

17

Date

Feb 1996

08...

Mar

13...

Apr 

16...

May 

17...

Jun

05...

Jul

22...

Arsenic wuuiniuin, 

di^}ed recoverable

14 <1

10 <1

11 <1

13 <l

11 <1

15 <l

Cadmium, C°PPfr' 

dissolved «*«« / /i \ recoverable

<0.l 120

<.l 66

<.l 68

<.l 230

<.l 93

<.l 18

Copper,

36

15

10

15

13

8

Iron, 

total 

recoverable

(ng/D

3,200

1,500

1,000

4,900

1,900

200

dissolved

(uQ/L)

100

61

29

36

27

<3

Lead, 

total 

recoverable (ng/L)

16

9

9

36

14

2

Date

Feb 1996

08...

Mar

13...

Apr 

16...

May 

17...

Jun

05...

Jul

22...

MangaLead, nese, 

dissolved total 

(ng/L) recoverable

0.6 380

<.5 150

<.5 130

<.5 380

<.5 210

<.5 60

Manganese,

37

20

14

20

15

21

total'

170

70

60

240

90

10

Zinc, 

dissolved

26

10

8

9

4

7

Sediment, 

suspended

216

80

59

355

121

II

Sediment 

discharge, 

suspended

(ton/d)

910

220

162

1,730

673

II

Sediment, 

suspended 

(percent finer than 

0.062 mm)

43

69

64

52

56

77

TABLE 4 21
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued)

12331500--FLINT CREEK NEAR DRUMMOND, MONT.

Date

Feb 1996

11...

Mar

13...

Apr

17...

May

18...

Jun

05...

Jul

22...

St inas£n?W' cSc?- PH'°nsite TemPer' ""Stir1 Calcium 

Time ta^eous ance^Ste < ?"*«' ature water ^ dissolve

(ft3/s) (nS/cm) umis' ( u' CaCO3) img/u

1415 352 203 8.1 0.5 85 22

1100 186 253 8.3 3.0 120 31

0840 388 204 8.1 5.0 90 24

0700 547 149 8.0 7.5 66 18

1130 539 152 8.0 9.0 68 19

1645 102 335 8.6 19.0 160 44

Magne- Arsenic, 

'. slum, total 

dissolved recoverable

(mg/L) (Mg/L)

7.3 19

9.7 13

7.4 16

5.1 29

5.0 29

12 19

Date

Feb 1996

11...

Mar

13...

Apr

17...

May

18...

Jun

05...

Jul

22...

Arsenic, ^J^V"1 ' Cadmium, C°PPfr' Copper, |~"j Iron, Lead 

df£Lfd recoverable d*s°'vfd recoverable df°'vfd recoverable di?s_°^ed recoverable

^9 ' (ng/L) (W ' (ng/L) IM9/L' (ng/L)

10 <1 <0.1 15 6 1,500

7 <1 <.l 5 2 630

7 <! .1 12 5 1,300

6 <1 <.l 9 3 1,600

9 <1 <.l 9 5 1,200

12 <! <.! 4 1 420

^«"-' (jig/L)

200 14

77 6

160 12

86 26

48 22

8 7

Date

Feb 1996

11...

Mar

13...

Apr

17...

May

18...

Jun

05...

Jul

22...

Manga- Man«a Zinc, 7in_ 

Lead, nese, Mnaen.|a" total dissoPjed Sediment, 

dissolved total Hi«ni»oH recov- i, n/i 11 suspended 

(ng/L) recoverable f <?/ f arable (M9/L' (mg/L) 

(jig/L) (^/L> (jig/L)

2.1 220 32 40 7 82

.9 100 14 20 <3 32

.7 160 15 30 <3 70

.7 340 25 70 <3 121

.7 280 32 60 3 96

<.5 150 40 20 3 30

Sediment Sediment, 

discharge, suspended 

suspended (percent finer than 

(ton/d) 0.062 mm)

78 72

16 87

73 87

179 72

140 66

8.3 80

22 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued)

12331800--CLARK FORK NEAR DRUMMOND, MONT.

Date

Feb 1996

08...

Mar

13...

Apr

17...

May

17...

Jun

05...

Jul

23...

-°

1645

1250

1100

0700

1300

0915

Streamflow,

(ft5/s)

3,520

1,280

1,720

2,270

2,670

466

Specific

(nS/cm)

189

338

337

264

245

475

(standard 

units)

7.8

8.2

8.1

8.0

8.0

8.3

8 Ured$a er

0.5

4.5

7.0

9.0

13.0

17.0

Hardness, 

totdl

1ITIQ/L 3S

CaCO3)

74

150

150

120

110

220

Calcium, 

dissolved 

(mg/L)

21

44

44

35

33

63

Magne- 

(mg/L)

5.2

10

10

7.5

6.9

14

Arsenic,

(ng/L)

27

27

19

40

30

19

Date

Feb 1996

08...

Mar

13...

Apr

17...

May

17...

Jun

05...

Jul

23...

A ..,.,._:- Cadmium, Arsenic, tota)

/ _;i\ recoverable

11 <l

11 <1

10 <1

13 1

13 <1

15 <1

Cadmium, C°PPer'

"'fuaiT1 recoverable 

'W/L' (ng/L)

<0.1 120

<1 110

<1 66

<1 200

<1 92

<1 20

Copper, 

dissolved (ng/L)

16

17

9

13

13

6

Iron, 

totai 

recoverable (ng/L)

3,300

2,300

1,300

3,900

2,300

270

-a150

55

50

31

27

7

Lead, 

total 

recoverable (ng/L)

19

14

12

31

23

3

Date

Feb 1996

08...

Mar

13...

Apr

17...

May

17...

Jun

05...

Jul

23...

Lead, 

dissolved (ng/L)

0.9

<5

<5

<5

<5

<.5

Manganese, 

total 

recoverable (ng/L)

420

230

160

380

240

70

Manga39

16

17

15

23

17

Zinc, 

total 

recoverable (ng/L)

210

150

80

250

120

20

Zinc, 

dissolved

(|ag/L)

20

14

7

10

5

6

suspended

289

126

83

259

149

16

Sediment 

discharge, 

suspended 

(ton/d)

2,750

435

385

1,590

1,070

20

Sediment, 

suspended 

(percent finer than 

0.062 mm)

38

79

70

65

61

84

TABLE 4 23
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued)

12334510--ROCK CREEK NEAR CLINTON, MONT.

Date

Apr 1 996

17...

May 

16...

Jun

06...

Jul

25...

Time

1340

1440

0830

1030

Streamflow, instantaneous

(ft3/s)

1,220

3,060

3,550

558

Specific 

conductance, onsite

(|aS/cm)

86

58

58

127

pH, onsite 

units)

7.8

7.6

7.4

8.2

Temperature, water 

( C\

6.0

7.0

7.0

14.0

Hardness, 

total 

(mg/L as 

CaCO3 )

38

25

26

57

Calcium,

9.6

6.5

6.8

15

Magnesium, 

dissolved 

(mg/L)

3.3

2.1

2.1

4.7

Arsenic, 

total 

recoverable (Mg/L)

i

2

2

<1

Date

Apr 1996

17...

May

16...

Jun

06...

Jul

25...

Arsenic, total ' Cadmium, 

dissolved ,~,««,«LKI«, dissolved I a/L\ recoverable / _/ »

^9 ) (^g/L) IM9 )

<1 <1 <0.1

< 1 < 1 < 1

<1 <1 <.l

<1 <1 <.l

Copper, 

total 

recovera

5

27

4

<1

Copper,

(Mg/ )

<i

2

2

<1

Iron, 

totdl

TGCOVGrdbiG

(M9/L)

270

1,400

770

70

Iron,

(M9/ )

110

92

69

15

L&dd< 

totdl 

recovera

<l

2

1

<1

Date

Apr 1996 

17... 

May 

16... 

Jun 

06... 

Jul 

25...

Lead, 

dissolved (Mg/L)

<0.5

Manganese, 

total 

recoverable

10 

60 

30

Manganese, 

dissolved

(M9/L)

2 

3 

3 

3

(M9/L)

<10 

<10 

<10 

<10

7\fi(* 

«.n I**, Sediment dissolved ..n«,..,.»i,j«,i / /I * suspended (M9/M ^g^

<3 13 

<3 154 

<3 83

3 3

Sediment 

discharge, 

suspended 

(ton/d)

43 

1.270 

796 

4.5

Sediment, 

suspended 

(percent finer than 

0.062 mm)

65

42 

54 

65

24 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued) 

12334550--CLARK FORK ATTURAH BRIDGE, NEAR BONNER, MONT.

Date

Feb 1996

11...

Mar

13...

Apr 

17...

May 

16...

Jun

06...

Jul

23...

Streamflow, Specific _H nnc: t/. r~mn*r Hardness, /v,i/.i..,« Magne- :«»»..« ^nnAont P", onsite Temper- »_.»_i Calcium, .._. » £&, aSSe fc-g- aturf4atet °°s "sssy -SK-

(fe/s) (nS/cm) units) ( U) CaC03) (ma/L) (mg/L)

1100 3,600 240 7.9 0.5 100 29 7.3

1525 2,060 286 8.2 5.0 130 37 9.0

1605 3,610 235 8.1 8.0 100 29 7.3

1200 6.070 161 7.9 9.0 70 20 4.9

1045 7,300 147 7.9 10.5 66 19 4.4

1145 1,250 291 8.4 16.0 130 38 9.4

Arsenic, 

total 

recoverable

23

18

10

15

14

7

Date

Feb 1 996

11...

Mar

13...

Apr 

17...

May 

16...

Jun

06...

Jul

23...

Arsenic, Cad,±m' Cadmium, C°PPfr' Copper, Jr°nj Iron,

"MSB* recoverable dif^,vfd recoverable di?s°*ed recoverable «*s°*«* l^9 ' (^g/L) ^9"-; (ng/L) ws11-) (^g/L) ws11-)

13 <l <0.l 180 19 2,000 110

9 <1 <.l 56 15 1,400 48

5 <1 <.l 62 9 750 56

5 <l <.l 70 7 2,500 61

6 <l <.l 52 8 1,500 54

7 <l <.l 8 4 150 7

Lead, 

total 

recoverable

(HQ/L)

11

9

6

14

9

<l

Date

Feb 1996

II...

Mar

13...

Apr

17...

May 

16...

Jun

06...

Jul

23...

I MH MnaJlia" Manga- Jjff Zinc, oaHimont Sediment Sediment, 

Hie I^'H ^nfa.' "ese, rl°'ai dissolved ^'^HJH discharge, suspended 

f n.\6 £?ihi« dissolved 2»»- (^g/L) ^fP®?,^ suspended (percent finer than 

(HO/L) reCfJ5]3ble (HO/L) JjJJf (m9/L) (ton/d) 0.062mm)

0.6 230 17 110 22 100 972

<.5 140 12 80 12 74 412

<.5 90 13 40 7 48 468

<.5 220 13 120 5 188 3,080

<.5 140 15 80 7 128 2,520

<.5 30 9 10 6 8 27

61

79

62

54

55

76

TABLE 4 25
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued)

12340000--BLACKFOOT RIVER NEAR BONNER, MONT.

Date

Apr 1 9%

18...

May

16...

Jun

06...

Jul

25...

Time

1030

0800

1315

1310

Streamflow, instantaneous 

(ffts)

5,130

7,470

8,900

1,400

Specific 

conductance, onslte

(nS/cm)

174

159

158

233

pH, onsite 

(standard 

units)

8.0

8.0

8.1

8.6

Temperature, water 

?C)

4.5

7.5

13.5

17.5

Hardness, 

total 

(mg/L as 

CaC03)

88

80

79

120

Calcium, 

dissolved 

(mg/L)

23

21

21

30

Magnesium, 

dissolved 

(mg/L)

7.3

6.7

6.5

10

Arsenic, 

total 

recoverable

(ng/L)

2

2

2

1

Date

Apr 1996 

18... 

May 

16... 

Jun 

06... 

Jul 

25...

Arsenic, ^tt1"' Cadmium,

*T3S* recoverable dlfs°'ved 

mg/L) (ng/L) iw1"/

< 1 < 1 <0. 1

i <i <.i

Copper, 

total 

recoverable

29 

10 

6 

3

Copper, 

dissolved (ng/L)

4 

3 

3

Iron, 

total 

recoverable (ng/L)

400 

1,200 

1,200 

60

Iron, 

dissolved

65 

31 

30 

4

Lead, 

total 

recoverable (ng/L)

2 

2 

2

Date

Apr 19% 

18... 

May 

16... 

Jun 

06... 

Jul 

25...

Lead, 

dissolved (ng/L)

<0.5 

<.5 

<.5 

<.5

Manganese, 

total 

recoverable (ng/L)

30

70 

70 

10

Manganese, 

dissolved (ng/L)

2 

2 

4 

3

Zinc, 

total 

recoverable (ng/L)

<10 

<10 

<10 

<10

Zinc, 

dissolved (ng/L)

4 

<3 

<3 

<3

Sediment, 

suspended 

(mg/L)

30 

124 

130 

6

Sediment 

discharge, 

suspended 

(ton/d)

416 

2,500 

3,120 

23

Sediment, 

suspended 

(percent finer than 

0.062 mm)

75 

69 

66 

79

26 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 4. Water-quality data for the upper Clark Fork basin, Montana, October 1995 through September 1996 (Continued)

12340500--CLARK FORK ABOVE MISSOULA, MONT.

Date

Feb 1996

09...

Mar

14...

Apr

18...

May 

16...

Jun

06...

Jul

25...

Time

0930

0825

0830

0930

1515

1430

Streamflow, 

instantaneous

(ft3/s)

9,840

3,710

9,230

14,000

16,600

2,480

Specific 

conductance, onsite

(nS/cm)

183

245

198

163

154

261

units)

7.9

8.2

8.1

8.1

8.1

8.4

Temperature, water 

( C)

1.0

3.0

5.5

8.0

10.5

18.0

Hardness, 

total 

(mg/L as 

CaC03)

72

110

95

78

76

120

Calcium, 

dissolved 

(mg/L)

20

31

26

21

21

33

Magnesium, 

dissolved 

(mg/L)

5.3

8.7

7.4

6.1

5.7

9.9

Arsenic, 

total 

recoverable

69

10

5

7

7

4

Date

Feb 1996

09...

Mar

14...

Apr 

18...

May 

16...

Jun

06...

Jul

25...

Arsenic, 

dissolved

9

4

3

2

3

3

Cadmium, 

total 

recoverable

5

<1

<1

<1

<1

<1

Cadmium, 

dissolved

<0.1

<.l

<.l

<.l

<.l

<.l

Copper, 

total 

recoverable (ng/L)

400

37

18

28

37

6

Copper, 

dissolved

11

7

4

4

5

3

Iron, 

total 

recoverable (ng/L)

13,000

1,300

510

1,400

1,400

90

Iron, 

dissolved

200

88

62

37

40

7

Lead, 

total 

recoverable

78

5

3

5

6

<1

Date

Feb 1996

09...

Mar

14...

Apr

18...

May

16...

Jun

06...

Jul

25...

MangaLead, nese, 

dissolved total 

(jig/L) recoverable

1.2 1,100

<.5 100

<.5 50

<.5 110

<.5 110

<.5 30

Mangadissolved

230

17

10

8

16

19

Zinc, 

erable

1,100

70

20

40

50

<10

Zinc, 

dissolved

15

5

6

<3

<3

<3

Sediment, 

suspended 

(mg/L)

824

97

36

123

119

6

Sediment 

discharge, 

suspended 

(ton/d)

21,900

972

897

4,650

5,330

40

Sediment, 

suspended 

(percent finer than 

0.062 mm)

59

44

75

70

72

92

TABLE 4 27
Table 5. Daily streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 1995 through 

September 1996

[Abbreviations: ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day. Symbol: , no data]

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow

(ft3/s)

244

240

251

261

266

263

264

266

267

272

272

274

276

270

266

262

260

269

271

274

279

281

280

281

277

276

274

269

269

267

266

8,307

268

281

240

Suspended sediment

Mean 

concentration 

(mg/L)

October

8

10

12

12

12

10

10

10

10

10

11

11

13

15

15

15

14

13

13

12

12

11

12

12

12

13

13

12

12

12

12

...

12

15

8

Discharge 

(ton/d)

5.3

6.5

8.1

8.5

8.6

7.1

7.1

7.2

7.2

7.3

8.1

8.1

9.7

11

11

11

9.8

9.4

9.5

8.9

9.0

8.3

9.1

9.1

9.0

9.7

9.6

8.7

8.7

8.7

8.6

267.9

8.6

11

5.3

Mean 

streamflow 

(ff/s)

263

253

257

260

262

267

264

286

306

283

283

296

292

291

293

292

283

292

273

265

257

269

282

280

287

313

294

293

315

328

...

8,479

283

328

253

Suspended sediment

Mean 

concentration 

(mg/L)

1995

November

15

21

24

21

17

14

13

13

13

13

13

13

14

14

14

14

14

14

14

14

14

14

15

17

17

17

17

17

17

18

15

24

13

Discharge 

(ton/d)

11

14

17

15

12

10

9.3

10

11

9.9

9.9

10

11

11

11

11

11

11

10

10

9.7

10

11

13

13

14

13

13

14

16

351.8

12

17

9.3

Mean 

streamflow 

(f^/s)

364

383

350

336

271

259

259

204

185

207

297

341

329

298

289

287

275

220

210

210

200

200

187

180

169

180

183

186

175

179

191

7,604

245

383

169

Suspended sediment

Mean 

concentration 

(mg/L)

December

19

19

19

19

20

20

21

22

22

23

24

24

24

25

25

25

26

26

27

27

27

27

28

28

29

29

30

30

30

31

31

...

25

31

19

Discharge 

(ton/d)

19

20

18

17

15

14

15

12

11

13

19

22

21

20

20

19

19

15

15

15

15

15

14

14

13

14

15

15

14

15

16

499

16

22

11

28 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 5. Daily streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 1995 through 

September 1996 (Continued)

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow 

(tf/s)

197

204

225

208

190

200

220

233

222

227

222

221

223

225

241

257

252

204

192

225

228

220

210

190

180

160

140

130

130

120

120

6,216

201

257

120

Suspended sediment

Mean 

concentration 

(mg/L)

January

31

32

32

32

32

33

33

33

34

34

34

34

34

34

34

33

32

29

28

29

32

34

29

22

16

14

14

15

15

15

16

_

28

34

14

Discharge 

(ton/d)

16

18

19

18

16

18

20

21

20

21

20

20

20

21

22

23

22

16

15

18

20

20

16

11

7.8

6.0

5.3

5.3

5.3

4.9

5.2

490.8

16

23

4.9

Mean 

streamflow

(ft3/s)

115

120

130

130

150

250

533

936

1,020

587

457

429

447

452

432

374

343

330

324

317

312

295

273

264

207

200

190

190

195

...

...

10,002

345

1,020

115

Suspended sediment

Mean 

concentration 

(mg/L)

1996

February

17

18

20

21

22

85

359

835

555

131

100

100

92

83

75

67

60

57

57

58

63

59

57

55

52

52

50

48

49

._

--

114

835

17

Discharge 

(ton/d)

5.3

5.8

7.0

7.4

8.9

57

517

2,110

1,530

208

123

116

111

101

87

68

56

51

50

50

53

47

42

39

29

28

26

25

26

...

...

5,584.4

193

2,110

5.3

Mean 

streamflow

(tf/s)

210

229

230

235

233

244

289

326

336

380

488

416

399

394

393

326

307

311

302

301

301

298

292

259

269

292

284

274

276

275

281

9,450

305

488

210

Suspended sediment

Mean 

concentration 

(mg/L)

March

50

32

57

52

39

44

42

68

71

107

148

78

63

58

47

46

42

44

41

39

40

33

36

44

45

48

39

32

37

29

31

...

51

148

29

Discharge 

(ton/d)

28

20

35

33

25

29

33

60

64

110

195

88

68

62

50

40

35

37

33

32

33

27

28

31

33

38

30

24

28

22

24

1,395

45

195

20

TABLE 5 29
Table 5. Daily streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 1995 through 

September 1996 (Continued)

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow 

(ft3/s)

294

321

319

311

311

310

323

357

394

461

583

569

514

482

455

440

435

416

428

406

405

397

381

395

431

409

405

395

389

377

12,113

404

583

294

Suspended sediment

Mean 

concentration 

(mg/L)

April

51

51

40

34

30

39

43

59

99

166

244

150

83

61

57

57

46

43

38

35

36

34

39

46

47

38

32

34

29

31

_

60

244

29

Discharge 

(ton/d)

40

44

34

29

25

33

38

57

105

207

384

230

115

79

70

68

54

48

44

38

39

36

40

49

55

42

35

36

30

32

_.

2,136

71

384

25

Moan

streamflow 

(ft3/s)

1996

368

360

369

360

349

339

333

328

353

372

396

420

465

549

625

687

801

843

860

829

774

734

720

690

658

642

668

689

741

743

741

17,806

574

860

328

Suspended sediment

Mean 

concentration 

(mg/L)

May

29

24

20

20

25

19

15

19

21

21

36

33

54

120

170

196

257

195

153

124

92

71

58

63

57

54

60

70

71

61

57

73

257

15

Discharge 

(ton/d)

29

23

20

19

24

17

13

17

20

21

38

37

68

178

287

364

556

444

355

278

192

141

113

117

101

94

108

130

142

122

114

4,182

135

556

13

Mean 

streamflow 

(ft3/s)

753

738

757

831

933

972

943

944

1.010

1,080

1,130

1.100

1,030

992

977

959

956

923

848

713

655

674

661

575

602

576

549

533

496

467

24,377

813

1,130

467

Suspended sediment

Mean 

concentration 

(mg/L)

June

55

47

48

71

132

126

90

84

93

114

119

101

87

73

66

62

61

60

58

50

52

59

50

39

39

42

37

32

34

34

...

67

132

32

Discharge 

(ton/d)

112

94

98

159

333

331

229

214

254

332

363

300

242

196

174

161

157

150

133

96

92

107

89

61

63

65

55

46

46

43

4,795

160

363

43

30 Water-quality, bed-sediment, and bioiogicai data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 5. Daily streamflow and suspended-sediment data for Clark Fork at Deer Lodge, Montana, October 1995 through 

September 1996 (Continued)

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

NUN

Mean 

streamflow 

(tf/s)

440

447

451

426

409

372

335

310

300

303

276

265

267

254

225

220

224

212

207

202

198

169

171

162

132

113

99

89

81

85

82

7,526

243

451

81

Suspended sediment

Mean 

concentration 

(mg/L)

July

31

28

25

21

19

18

16

14

13

11

9

8

8

8

9

9

10

11

12

14

11

7

7

8

9

10

10

11

10

10

9

13

31

7

Discharge 

(ton/d)

37

34

30

24

21

18

14

12

11

9.0

6.7

5.7

5.8

5.5

5.5

5.3

6.0

6.3

6.7

7.6

5.9

3.2

3.2

3.5

3.2

3.1

2.7

2.6

2.2

2.3

2.0

305.0

9.8

37

2.0

Mean 

streamflow

(tf/s)

73

77

83

79

83

76

73

70

62

57

53

55

50

57

73

92

97

109

150

132

119

113

109

109

108

112

111

128

147

146

147

2,950

95

150

50

Suspended sediment

Mean 

concentration 

(mg/L)

1996

August

9

10

10

11

11

10

9

7

5

5

5

6

6

6

6

6

7

9

14

12

11

11

10

10

10

10

12

13

14

13

13

9

14

5

DiScharge 

(ton/d)

1.8

2.1

2.2

2.3

2.5

2.1

1.8

1.3

SA

.77

.72

8)

&\

91

1.2

1.5

1.8

2.6

5.7

4.3

3.5

3.4

2.9

2.9

2.9

3.0

3.6

4.5

5.6

5.1

5.2

80.75

2.6

5.7

.72

Mean 

streamflow

(tf/s)

141

140

140

140

137

147

148

144

138

140

137

129

126

128

145

184

179

176

182

185

183

180

180

177

186

189

189

194

194

192

4,850

162

194

126

Suspended sediment

Mean 

concentration 

(mg/L)

September

12

12

13

13

14

14

13

13

12

11

12

13

13

14

14

15

15

15

14

13

12

11

12

13

14

16

15

14

13

12

13

16

11

Discharge 

(ton/d)

4.6

4.5

4.9

4.9

5.2

5.6

5.2

5.)

4.5

4.2

4.4

4.5

4.4

4.8

5.5

7.5

7.2

7.1

6.9

6.5

5.9

5.3

5.8

6.2

7.0

8.2

7.7

7.3

6.8

6.2

...

173.9

5.8

8.2

4.2

TOTAL FOR WATER YEAR 1996: 

STREAMFLOW-119,680 ftVs 

SEDIMENT DISCHARGE-20,261.55 tons

TABLE 5 31
Table 6 . Daily streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 1995 

through September 1996

[Abbreviations: f^/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day. Symbol: , no data]

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow 

(ft3/s)

970

970

988

1,050

1,090

1,080

1,060

1,060

1,050

1,040

1,030

1,070

1,100

1,080

1,040

1,040

1,040

1,070

1,100

1,080

1,050

1,050

1,040

1,030

1,030

1,030

1,020

997

976

967

950

32,148

1,037

1,100

950

Suspended sediment

Mean 

concentration 

(mg/L)

October

11

11

11

11

11

11

11

11

11

11

11

12

13

12

12

12

11

11

11

10

10

10

9

9

8

8

8

7

7

6

5

_

10

13

5

Discharge 

(ton/d)

29

29

29

31

32

32

31

31

31

31

31

35

39

35

34

34

31

32

33

29

28

28

25

25

22

22

22

19

18

16

13

877

28

39

13

Mean 

streamflow

(ft3/!)

1995

898

869

845

865

931

946

947

952

1,020

1,070

1,030

1,100

1,130

1,090

1,090

1,100

1,080

1,060

1,050

1,010

958

991

1,010

1,020

1,090

1,260

1,270

1,230

1,250

1,710

31,872

1,062

1,710

845

Suspended sediment

Mean 

concentration 

(mg/L)

November

5

5

7

8

8

9

10

10

11

11

11

14

15

10

8

7

7

7

6

6

6

7

8

8

11

21

20

14

12

28

._

10

28

5

Discharge 

(ton/d)

12

12

16

19

20

23

26

26

30

32

31

42

46

29

24

21

20

20

17

16

16

19

22

22

32

71

69

46

40

129

--

948

32

129

12

Mean 

streamflow 

(tf/s)

2,380

2,430

2,050

1,850

1,610

1,320

1,260

1,200

900

1,000

1,300

1,600

1,890

1,560

1,390

1,330

1,270

1,150

950

1,000

1,060

1,000

850

750

700

670

650

650

700

800

950

38,220

1,233

2,430

650

Suspended sediment

Mean 

concentration 

(mg/L)

December

69

56

30

16

12

11

10

9

8

8

8

15

48

47

34

23

15

14

14

14

14

17

14

14

14

13

13

13

14

17

29

...

20

69

8

Discharge 

(ton/d)

443

367

166

80

52

39

34

29

19

22

28

65

245

198

128

83

51

43

36

38

40

46

32

28

26

24

23

23

26

37

74

2,545

82

443

19

32 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 6. Daily streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 1995 

through September 1996 (Continued)

Suspended sediment

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow 

(ft3/s)

1,040

936

943

1,020

850

800

900

966

934

954

915

882

875

907

994

1,100

1,000

800

700

800

850

850

800

800

750

750

700

600

500

450

400

25,766

831

1,100

400

Mean 

concentration 

(mg/L)

January

15

13

13

13

13

13

13

18

15

13

12

12

12

14

20

26

28

25

23

26

35

22

12

6

4

5

5

5

6

6

7

_

15

35

4

Discharge 

(ton/d)

42

33

33

36

30

28

32

47

38

33

30

29

28

34

54

77

76

54

43

56

80

50

26

13

8.1

10

9.4

8.1

8.1

7.3

7.6

1,060.6

34

80

7.3

Mean 

streamflow

(tf/s)

1996

400

400

450

500

600

800

2,000

5,000

8,000

9,010

3,720

2,670

2,370

2,280

2,190

1,930

1,800

1,780

1,950

1,880

1,730

1,760

1,610

1,460

1,370

1,150

941

917

935

...

...

61,603

2,124

9,010

400

Suspended sediment

Mean 

concentration 

(mg/L)

February

7

8

11

16

19

21

42

580

605

393

146

97

122

108

61

38

33

34

50

43

30

30

24

22

29

33

24

18

20

__

92

605

7

Discharge 

(ton/d)

7.6

8.6

13

22

31

45

227

7,830

13,100

9,560

1,470

699

781

665

361

198

160

163

263

218

140

143

104

87

107

102

61

45

50

...

36,661.2

1,260

13,100

7.6

Mean 

streamflow

(ft*/8)

1,050

1,160

1,180

1,160

1,120

994

1,030

1,100

1,210

1,460

2,210

2,420

2,080

1,880

1,780

1,740

1,640

1,540

1,480

1,450

1,470

1,480

1,480

1,320

1,170

1,230

1,350

1,270

1,250

1,230

1,220

44,154

1,424

2,420

994

Suspended sediment

Mean 

concentration 

(mg/L)

March

24

26

19

14

11

9

13

15

19

57

173

176

88

48

42

34

30

23

20

19

17

18

16

13

15

15

19

13

9

9

10

. 

33

176

9

Discharge 

(ton/d)

68

81

61

44

33

24

36

45

62

225

1,030

1,150

494

244

202

160

133

96

80

74

67

72

64

46

47

50

69

45

30

30

33

4,895

158

1,150

24

TABLE 6 33
Table 6. Daily streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 1995 

through September 1996 (Continued)

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow 

(ft3/s)

1,250

1,430

1,610

1,510

1,450

1,480

1,670

2,190

2,830

3,810

5,650

5,550

4,810

4,070

3,710

3,550

3,570

3,450

3,280

3,130

3,000

2,890

2,810

3,200

3,810

3,610

3,410

3,260

3,150

3,020

-

92,160

3,072

5,650

1,250

Suspended sediment

Mean 

concentration 

(mg/L)

April

9

18

38

27

17

17

32

102

190

325

390

226

124

79

61

50

46

43

34

32

28

25

27

46

74

43

30

24

21

18

_

73

390

9

Discharge 

(ton/d)

30

69

165

110

67

68

144

603

1,450

3,340

5,950

3,390

1,610

868

611

479

443

401

301

270

227

195

205

397

761

419

276

211

179

147

23,386

780

5,950

30

Mean 

streamflow 

(tf/s)

2,960

2,930

2,810

2,630

2,550

2,530

2,480

2,430

2,390

2,380

2,400

2,630

3,190

4,020

5,030

5,970

6,590

7,380

7,490

6,960

6,280

5,640

5,440

5,350

5,180

4,940

5,100

5,450

5,940

6,310

6,100

139,480

4,499

7,490

2,380

Suspended sediment

Mean 

concentration 

(mg/L)

1996

Mey

18

16

13

12

12

11

11

12

10

11

11

16

35

78

149

171

201

303

303

206

115

96

70

86

98

70

65

81

125

153

111

86

303

10

Discharge 

(ton/d)

144

127

99

85

83

75

74

79

65

71

71

114

301

847

2,020

2,760

3,580

6,040

6,130

3,870

1,950

1,460

1,030

1,240

1,370

934

895

1,190

2,000

2,610

1,830

43,144

1,390

6,130

65

Mean 

streamflow

(ftS/s)

5,730

5,450

5,600

6,240

7,140

7,440

6,920

6,810

7,620

8,190

7,770

7,150

6,260

5,760

5,540

5,510

5,450

5,290

4,870

4,200

3,830

4,120

4,100

3,730

3,780

3,610

3,410

3,230

3,060

2,860

160,670

5,356

8,190

2,860

Suspended sediment

Mean 

concentration 

(mg/L)

June

76

66

81

136

205

197

164

123

155

271

165

132

102

91

64

61

61

53

62

47

37

41

41

30

28

23

22

21

21

18

...

86

271

18

Discharge 

(ton/d)

1,180

971

1,220

2,290

3,950

3,960

3,060

2,260

3,190

5,990

3,460

2,550

1,720

1,420

957

907

898

757

815

533

383

456

454

302

286

224

203

183

174

139

44,892

1,500

5,990

139

34 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 6. Daily streamflow and suspended-sediment data for Clark Fork at Turah Bridge, near Bonner, Montana, October 1995 

through September 1996 (Continued)

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow 

(tf/s)

2,710

2,590

2,590

2,490

2,430

2,350

2,220

2,100

1,980

1,910

1,820

1,760

1,690

1,630

1,590

1,520

1,490

1,520

1,440

1,350

1,310

1,290

1,250

1,200

1,150

1,090

1,010

962

931

947

960

51,280

1,654

2,710

931

Suspended sediment

Mean 

concentration 

(mg/L)

July

16

16

17

17

17

16

15

14

13

12

11

9

8

8

8

8

9

12

13

12

12

11

8

7

8

8

9

9

10

10

10

_

11

17

7

Discharge 

(ton/d)

117

112

119

114

112

102

90

79

69

62

54

43

37

35

34

33

36

49

51

44

42

38

27

23

25

24

25

23

25

26

26

1,696

55

119

23

Moan

streamflow

(tf/s)

1996

921

919

914

890

907

892

877

839

802

770

727

699

673

668

661

656

651

643

680

714

710

697

680

662

633

620

627

678

754

780

743

23,087

745

921

620

Suspended sediment

Mean 

concentration 

(mg/L)

August

9

8

7

6

6

5

5

5

5

5

4

4

4

4

4

5

5

5

7

8

7

7

7

7

7

7

7

10

12

11

10

7

12

4

Discharge 

(ton/d)

22

20

17

14

15

12

12

11

11

10

7.9

7.5

7.3

7.2

7.1

8.9

8.8

8.7

13

15

13

13

13

13

12

12

12

18

24

23

20

408.4

13

24

7.1

Mean 

streamflow 

(frVs)

721

722

719

718

709

725

732

724

704

683

666

664

667

709

734

794

853

848

879

896

902

889

896

903

908

906

906

893

895

902

23,867

796

908

664

Suspended sediment

Mean 

concentration 

(mg/L)

September

9

9

8

8

8

7

7

7

7

9

11

13

15

15

14

13

13

13

13

13

12

12

11

9

8

9

10

11

12

12

...

...

11

15

7

Discharge 

(ton/d)

18

18

16

16

15

14

14

14

13

17

20

23

27

29

28

28

30

30

31

31

29

29

27

22

20

22

24

27

29

29

690

23

31

13

TOTAL FOR WATER YEAR 1996: 

STREAMFLOW- 724,307 ft^s 

SEDIMENT DISCHARGE-161,203.3 tons

TABLE 6 35
Table 7. Daily streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 1995 

through September 1996

[Abbreviations: ft3/s, cubic feet per second; mg/L, milligrams per liter; ton/d, tons per day. Symbol: , no data. Missing sediment data during JanuaryMarch due to suspension of daily sediment program]

Suspended sediment

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow 

(tf/s)

1,530

1,530

1,550

1,660

1,680

1,650

1,610

1,600

1,600

1,590

1,560

1,580

1,650

1,640

1,610

1,600

1,600

1,660

1,670

1,670

1,640

1,620

1,610

1,610

1,600

1,610

1,630

1,610

1,590

1,570

1,540

49,870

1,609

1,680

1,530

Mean 

concentration 

(mg/L)

October

4

4

4

4

4

5

5

5

5

5

5

5

4

5

5

5

5

5

4

4

4

4

4

4

4

4

4

4

3

3

3

_

4

5

3

Discharge 

(ton/d)

17

17

17

, 18

18

22

22

22

22

21

21

21

18

22

22

22

22

22

18

18

18

17

17

17

17

17

18

17

13

13

12

578

19

22

12

Mean 

streamflow 

(tf/s)

1995

1,460

1,310

1,380

1,330

1,520

1,550

1,480

1,510

1,600

1,680

1,690

1,720

1,830

1,790

1,830

1,860

1,820

1,790

1,770

1,730

1,630

1,680

1,740

1,740

1,970

2,490

2,550

2,550

2,580

3,840

55,420

1,847

3,840

1,310

Suspended sediment

Mean 

concentration 

(mg/L)

November

2

2

2

2

2

3

3

4

4

4

4

5

5

5

4

4

4

4

4

3

3

4

5

5

6

10

10

7

7

15

5

15

2

Discharge 

(ton/d)

7.9

7.1

7.5

7.2

8.2

13

12

16

17

18

18

23

25

24

20

20

20

19

19

14

13

18

23

23

32

67

69

48

49

156

813.9

27

156

7.1

Mean 

streamflow 

(ft3/s)

5,290

5,360

4,700

4,270

3,710

3,150

3,010

2,740

2,050

2,100

2,900

3,140

3,590

3,730

3,330

3,040

2,970

2,630

2,360

2,370

2,430

2,290

2,180

1,980

1,900

1,800

1,700

1,600

1,600

1,800

2,000

87,720

2,830

5,360

1,600

Suspended sediment

Mean 

concentration 

(mg/L)

December

38

31

19

14

12

9

7

6

6

7

9

13

17

36

25

14

7

7

7

9

10

10

10

10

10

10

10

10

10

10

10

13

38

6

Discharge 

(ton/d)

543

449

241

161

120

77

57

44

33

40

70

110

165

363

225

115

56

50

45

58

66

62

59

53

51

49

46

43

43

49

54

3,597

116

543

33

36 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 7. Daily streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 1995 

through September 1996 (Continued)

Suspended sediment

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow 

(ft3/s)

2,130

2,050

1,970

2,000

1,500

1,580

2,060

2,110

2,180

2,030

2,010

2,080

1,980

1,900

1,970

2,090

2,100

1,380

1,350

1,670

2,100

1,900

1,820

1,670

1,340

1,330

1,300

1,000

800

750

700

52,850

1,705

2,180

700

Mean 

concentration 

(mg/L)

January

10

10

10

10

10

10

10

10

10

10

11

12

12

10

10

10

12

8

5

9

12

...

...

...

--

-

-

...

...

...

...

_

...

...

Discharge

(ton/d)

58

55

53

54

40

43

56

57

59

55

60

67

64

51

53

56

68

30

18

41

68

...

...

...

...

...

...

...

...

...

...

...

Suspended sediment

Mean Mean _. 

stream- concen- .har"« 

flow tration 7,"*S? 

(ftS/s) (mg/L) (ton/d)

1996

February

750

800

900

1,100

1,400

1,720

2,140

4,600

9,800

12,900

6,510

4,550

3,990

3,840

3,630

3,390

3,260

3,250

3,700

3,790

3,480

3,430

3,230

2,920

2,690

2,220

1,850

1,830

1,830

...

99,500

3,431

12,900

750

Suspended sediment

Mean 

streamflow

2,090

2,240

2,200

2,090

1,960

1,710

1,850

1,900

2,000

2,250

3,010

3,630

3,520

3,380

3,300

3,350

3,230

3,010

2,900

2,900

3,020

3,000

2,960

2,400

2,140

2,560

2,480

2,380

2,410

2,290

2,320

80,480

2,596

3,630

1,710

Mean 

concentration 

(mg/L)

March

...

...

...

...

...

...

...

...

...

...

...

120

128

102

98

92

70

78

87

65

47

18

19

23

19

14

17

14

13

...

-

...

...

Discharge 

(ton/d)

...

-

...

...

...

...

...

...

...

...

...

...

1,100

1,140

923

855

748

548

611

709

526

376

117

110

159

127

90

111

87

81

...

...

TABLE 7 37
Table 7. Daily streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 1995 

through September 1996 (Continued)

Suspended sediment

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow

(ft3/s)

2,310

2,790

3,160

3,120

3,090

3,210

3,680

4,940

6,700

9,370

13,200

13,400

12,100

10,800

9,830

9,310

9,280

9,200

8,760

8,320

7,970

7,570

7,320

8,400

10,000

9,910

9,330

8,730

8,260

7,890

231,950

7,732

13,400

2,310

Mean 

concentration 

(mg/L)

April

12

15

20

25

26

30

57

135

205

250

292

200

105

64

47

39

37

32

27

25

24

26

39

57

85

54

36

28

21

18

...

_

68

292

12

Discharge 

(ton/d)

75

113

171

211

217

260

566

1,800

3,710

6,320

10,400

7,240

3,430

1,870

1,250

980

927

795

639

562

516

531

771

1,290

2,300

1,440

907

660

468

383

50,802

1,690

10,400

75

Mean 

streamflow

(tf/s)

1996

7,690

7,540

7,200

6,820

6,510

6,210

6,060

5,910

5,760

5,670

5,630

6,060

7,360

9,680

12,200

13,800

14,700

16,000

16,900

16,100

14,800

13,800

13,300

13,000

12,700

12,600

13,100

14,100

14,900

15,200

14,600

335,900

10,840

16,900

5,630

Suspended sediment

Mean 

concentration 

(mg/L)

May

19

15

13

13

14

15

13

14

14

11

10

12

24

46

105

125

145

200

215

145

95

72

56

53

55

54

61

76

91

95

80

63

215

10

Discharge 

(ton/d)

394

305

253

239

246

252

213

223

218

168

152

196

477

1,200

3,460

4,660

5,760

8,640

9,810

6,300

3,800

2,680

2,010

1,860

1,890

1,840

2,160

2,890

3,660

3,900

3,150

73,006

2,360

9,810

152

Mean 

streamflow 

(ftts)

13,800

13,200

13,400

14,600

16,300

16,700

15,900

16,000

17,500

18,300

17,700

16,400

15,000

14,000

13,500

13,300

13,700

13,400

12,300

10,500

9,460

9,670

10,100

9,420

9,420

9,060

8,800

8,600

8,090

7,530

385,650

12,850

18,300

7,530

Suspended sediment

Mean 

concentration 

(mg/L)

June

64

55

55

70

131

140

108

96

128

176

150

102

74

63

54

50

52

48

39

34

26

26

31

22

20

17

16

15

18

14

_.

63

176

14

Discharge 

(ton/d)

2,380

1,960

1,990

2,760

5,770

6,310

4,640

4,150

6,050

8,700

7,170

4,520

3,000

2,380

1,970

1,800

1,920

1,740

1,300

964

664

679

845

560

509

416

380

348

393

285

76,553

2,550

8,700

285

38 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 7. Daily streamflow and suspended-sediment data for Clark Fork above Missoula, Montana, October 1995 

through September 1996 (Continued)

Suspended sediment

Day

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MEAN

MAX

MIN

Mean 

streamflow 

(ft3/s)

7,120

6,950

6,850

6,630

6,350

6,100

5,900

5,600

4,800

4,580

4,400

4,200

3,960

3,780

3,650

3,530

3,380

3,380

3,250

3,080

2,970

2,870

2,810

2,620

2,550

2,460

2,340

2,270

2,200

2,220

2,270

125,070

4,035

7,120

2,200

Mean 

concentration 

(mg/L)

July

12

13

11

9

9

9

9

9

9

9

9

8

8

7

7

7

6

6

6

6

5

5

6

6

5

6

6

6

6

6

5

_

7

13

5

Discharge 

(ton/d)

231

244

203

161

154

148

143

136

117

111

107

91

86

71

69

67

55

55

53

50

40

39

46

42

34

40

38

37

36

36

31

2,771

89

244

31

Mean 

streamflow 

(tf/s)

1996

2,190

2,170

2,180

2,160

2,180

2,160

2,120

2,030

1,920

1,850

1,780

1,720

1,630

1,640

1,630

1,590

1,580

1,550

1,570

1,640

1,590

1,560

1,520

1,480

1,440

1,380

1,420

1,450

1,510

1,570

1,490

53,700

1,732

2,190

1,380

Suspended sediment

Mean 

concentration 

(mg/L)

August

5

5

5

5

5

5

5

5

4

4

4

4

3

3

3

3

2

3

3

3

4

4

4

3

3

3

4

4

5

4

4

_

4

5

2

Discharge 

(ton/d)

30

29

29

29

29

29

29

27

21

20

19

19

13

13

13

13

8.5

13

13

13

17

17

16

12

12

11

15

16

20

17

16

578.5

19

30

8.5

Mean 

streamflow 

(ft8/*)

1,440

1,420

1,420

1,410

1,420

1,430

1,450

1,450

1,420

1,390

1,350

1,330

1,360

1,450

1,460

1,550

1,630

1,620

1,630

1,640

1,630

1,610

1,610

1,600

1,630

1,630

1,620

1,610

1,600

1,590

45,400

1,513

1,640

1,330

Suspended sediment

Mean 

concentration 

(mg/L)

September

3

3

4

4

4

4

4

4

4

4

5

6

7

6

6

5

5

5

5

5

5

5

5

5

5

4

4

4

4

4

5

7

3

Discharge 

(ton/d)

12

12

15

15

15

15

16

16

15

15

18

22

26

23

24

21

22

22

22

22

22

22

22

22

22

18

17

17

17

17

564

19

26

12

TOTAL FOR WATER YEAR 1996:

STREAMFLOW- 1,603,510 ft3/s

SEDIMENT DISCHARGE (partial year)- 218,787.4 tons

TABLE 7 39
Table 8. Chemical and suspended-sediment analyses of field replicates for water samples, upper Clark Fork basin, Montana

[Abbreviations: |ag/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbols: <, less than minimum reporting level; --, no data]

Station 

number

12324590

12324680

12334550

Station name

Little Blackfoot River near Garrison

Clark Fork at Goldcreek

Clark Fork at Turah Bridge, near Bonner

Hard- Ca|- Magne'

Date Time ness nessioiai total clum> djg slum> djg

Caco \ solved solved 

3; (mg/L) (mg/L)

05-14-96 1405 86 25 5.8

05-14-96 1410 86 25 5.7

04-16-96 > 1700 150 45 9.4

04-16-96 1705 150 45 9.3

02-11-96 1100 100 29 7.3

02-11-96 1105 100 28 7.2

Arsenic, 

total recoverable

8

8

18

18

23

22

Station 

number

12324590

12324680

12334550

Date

05-14-96

05-14-96

04-16-96

04-16-96

02-11-96

02-11-96

Arsenic, Ca? m' C 

dis- total . 

solved . .

(^g/L) JJu

4 <1

5 <1

11 <1

10 <1

13 <1

13 <1

dis- dis- _,. . ' . 

solved . . recov- M solved , . recov- dissolved i«»«v.w ^,^^,,,^

(ug/L) , .. . (i^g/L) / . (ug/L) * * (ng/L)

<0.1 4 1 1,200 34

<.l 4 1 1,100 33

<.l 68 10 1,000 29

<.l 73 11 1,000 31

<.l 180 19 2,000 110

<.l 180 19 1,900 95

Lead, 

total 

recoverable

4

4

9

10

11

11

Station 

number

12324590

12324680

12334550

Date

05-14-96

05-14-96

04-16-96

04-16-96

02-11-96

02-11-96

MangaLead, nese, 

dissolved total 

(ng/L) recoverable

0.5 70

<.5 70

<.5 130

<.5 130

.6 230

.8 210

Manganese, '""7 Zinc, Sediment,

dl*so^ recoverable d '^s^ "SOS?* (ng/L) / ... (ng/L) (mg/L)

10 20 <3 63

10 10 <3 66

14 60 8 59

15 70 8 56

17 110 22 98

17 110 18 102

Sediment, 

suspended, 

diameter, 

percent 

finer than 

0.062 mm

60

58

64

66

61

--

40 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 9. Precision of chemical and suspended-sediment analyses of field replicates for water 

samples, upper Clark Fork basin, Montana

[Abbreviations: ug/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter. Symbol, , insufficient 

data for statistical calculation]

Constituent and reporting unit

Calcium, dissolved, mg/L

Magnesium, dissolved, mg/L

Arsenic, total recoverable, (ig/L

Arsenic, dissolved, M.g/L

Cadmium, total recoverable, |^g/L

Cadmium, dissolved, M.g/L

Copper, total recoverable, |^g/L

Copper, dissolved, M.g/L

Iron, total recoverable, p.g/L

Iron, dissolved, |ug/L

Lead, total recoverable, |ug/L

Lead, dissolved, |^g/L

Manganese, total recoverable, \igl~L

Manganese, dissolved, |^g/L

Zinc, total recoverable, H-g/L

Zinc, dissolved, |u,g/L

Sediment, suspended, mg/L

Sediment, suspended, percent finer than 0.062 mm

Number of 

replicate pairs

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3

2

Standard 

deviation, 

in units (+/-)

0.41

.07

.41

.58

.0

.0

2.0

.41

58

6.2

.41

.13

8.2

.41

5.8

1.6

2.4

--

Relative 

standard 

deviation, 

in percent (+/-)

1.2

1.0

2.5

6.2

.0

.0

2.4

4.0

4.2

11

5.0

30

5.8

3.0

9.1

17

3.2

--

TABLE 9 41
Table 10. Precision of chemical analyses of laboratory replicates for water samples, upper Clark 

Fork basin, Montana

[Abbreviations: ug/L, micrograms per liter; mg/L, milligrams per liter]

Constituent and reporting unit

Calcium, dissolved, mg/L

Magnesium, dissolved, mg/L

Arsenic, total recoverable, ng/L

Arsenic, dissolved, ng/L

Cadmium, total recoverable, ng/L

Cadmium, dissolved, ng/L

Copper, total recoverable, ng/L

Copper, dissolved, ng/L

Iron, total recoverable, ng/L

Iron, dissolved, ng/L

Lead, total recoverable, ng/L

Lead, dissolved, ng/L

Manganese, total recoverable, ng/L

Manganese, dissolved, ng/L

Zinc, total recoverable, ng/L

Zinc, dissolved, ng/L

Number of 

replicate pairs

6

6

6

6

6

6

6

6

6

6

6

6

6

6

6

6

Standard 

deviation, 

in units (+/-)

0.33

.05

.33

.37

.0

.02

3.2

.70

277

.95

.29

.01

2.5

.26

28

.81

Relative 

standard 

deviation, 

in percent (+/-)

1.0

.6

1.3

2.8

.0

36

3.9

4.5

15

1.8

2.6

3.2

1.7

.9

27

8.4

Within limits 

of dataquality 

objective

Yes

Yes

Yes

Yes

Yes

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

No

Yes

42 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 11. Recovery efficiency for trace-element analyses of laboratory-spiked deionized-water blanks

[Abbreviation: ng/L, micrograms per liter]

Constituent and reporting unit Number of 

samples

95-percent 

confidence 

interval for 

spike recovery, 

in percent

Mean spike 

recovery, 

in percent

Within limits 

of dataquality 

objective

Arsenic, total recoverable, 

Arsenic, dissolved, ng/L 

Cadmium, total recoverable, 

Cadmium, dissolved, ng/L 

Copper, total recoverable, 

Copper, dissolved, \ig/L 

Iron, total recoverable, 

Iron, dissolved, ng/L 

Lead, total recoverable, 

Lead, dissolved, ng/L 

Manganese, total recoverable, 

Manganese, dissolved, 

Zinc, total recoverable, 

Zinc, dissolved, \ig/L

101-107

77.1-102

79.7-84.9

92.2-98.4

93.5-106

91.4-107

76.0-104

70.9-111

80.2-115

93.3-108

77.9-100

91.6-101

82.8-92.8

84.3-108

104.1

89.7

82.3

95.3

99.6

99.2

89.8

90.8

97.4

100.5

89.2

96.5

87.8

96.1

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes

TABLE 11 43
Table 12. Recovery efficiency for trace-element analyses of laboratory-spiked stream samples, upper Clark Fork basin, 

Montana

[Abbreviation: |^g/L, micrograms per liter]

Constituent and reporting unit Number of samples

95-percent 

confidence interval 

for spike recovery,

in percent

Mean spike 

recovery, 

in percent

Within limits of

data-quality

objective

Arsenic, total recoverable, (ig/L 

Arsenic, dissolved, ng/L 

Cadmium, total recoverable, (ig/L 

Cadmium, dissolved, (ig/L 

Copper, total recoverable, (ig/L 

Copper, dissolved, ng/L 

Iron, total recoverable, 

Iron, dissolved, (ig/L 

Lead, total recoverable, 

Lead, dissolved, jig/L 

Manganese, total recoverable, ng/L 

Manganese, dissolved, jig/L 

Zinc, total recoverable, (ig/L 

Zinc, dissolved,

96.0-110 

94.4-117 

57.8-119 

91.5-109 

92.3-108 

91.9-110 

73.3-114 

88.5-114 

98.4-113 

90.4-120 

79.1-102 

92.9-106 

74.8-124 

90.2-116

102.8

105.9

88.4

100.2

100.3

101.1

93.8

101.5

105.6

105.1

90.3

99.5

99.3

103.2

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes

44 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 13. Chemical analyses of field blanks for water samples

[Abbreviations: °C, degrees Celsius; ng/L, micrograms per liter; ^S/cm, microsiemens per centimeter at 25 °C; mg/L, milligrams per liter. 

Symbol: <, less than minimum reporting level]

Date

Feb 1996

08..

Mar

12...

Apr

17...

May

16...

Jun

05...

Jul

25...

Time

2000

1400

1730

1830

2130

1000

Specific 

conductance, 

onsite 

(uS/cm)

4

2

3

3

2

2

PH, 

units)

5.6

5.6

5.8

5.6

5.4

6.4

Calcium, 

dissolved 

(mg/L)

<0.02

<.02

<02

<.02

<.02

<.02

Magne- 

(mg/L)

O.OI

<01

<OI

<OI

<01

<01

Arsenic, 

total Arsenic, 

recov- dissolved 

erable (ug/L) 

(ug/L)

<i <i

<i <i

<i <i

<i <i

<i <i

<i <i

Casm' ssss c?r"

recoverable , ° . recoverable

(ug/L) ^g/L) (ug/L)

<1 <0.1 2

<1 <.l <1

<1 <.l <1

<1 <.l <1

<1 <1 <1

<1 <.l <1

C°PP"- lotai 

0316 d'jg/L)ed recoverable

Feb 1996 

08.. <1 <IO

Mar

12... <1 <IO

Apr

17... <1 <10

May

16... <1 <10

Jun

05... <1 <10

Jul

25... <1 <10

Iron, .®? ' .' Lead, 

l&alL) recoverable fSn/n

<3 <1 <0.5

<3 <1 <.5

<3 <1 <.5

<3 <1 <.5

<3 <1 <.5

<3 <1 <5

Manga- _. 

nese, Manganese, ^' Zinc, 

total dissolved recoverable ***<>*"* 

recoverable (ug/L) /,,fl/n ^g/L> (ug/L) ins"-j

<10 <1 <10 <3

<10 <1 <10 <3

<10 <1 <10 <3

<10 <1 <10 <3

<10 <1 <10 <3

<10 <1 <10 3

TABLE 13 45
Table 14. Trace-element analyses of fine-grained bed sediment, upper Clark Fork basin, Montana, August 1996

[Fine-grained sediment is material less than 0.064 millimeter in diameter. Concentrations are the mean of all analyses for replicate aliquots from each 

composite sample. Abbreviation: ug/g, micrograms per gram of dry sample weight. Symbol: <, less than]

Station number

(fig.D

12323600

12323750

12323800

461415112450801

461559112443301

461903112440701

12324200

12324680

12331500

12331800

12334510

12334550

12340000

12353000

Numbei

01 * of corn- Station name .. posite

sample!

Silver Bow Creek at Opportunity

Silver Bow Creek at Warm Springs

Clark Fork near Galen

Clark Fork below Lost Creek, 

near Galen

Clark Fork near Racetrack

Clark Fork at Dempsey Creek 

diversion, near Racetrack

Clark Fork at Deer Lodge

Clark Fork at Goldcreek

Flint Creek near Drummond

Clark Fork near Drummond

Rock Creek near Clinton

Clark Fork at Turah Bridge, 

near Bonner

Blackfoot River near Bonner

Clark Fork below Missoula 1

3

3

3

3

3

3

3

3

3

3

3

3

2

3

f

Cadi mium

42.0

6.7

7.8

9.0

8.5

8.1

7.6

5.8

3.1

5.2

<1.5

3.5

<1.5

1.9

Concentration

Chromium

23.2

24.8

29.9

32.9

30.1

28.9

36.5

34.5

27.9

35.4

27.9

34.7

24.7

27.6

Copper

4,670

344

1,140

1,730

1,370

1,280

1,210

766

64

609

10

356

19

136

Iron

38,400

20,800

28,400

30,800

29,000

28,200

29,400

24,300

25,600

23,800

19,100

21,700

18,400

19,500

Lead

834

73

143

197

155

152

155

88

174

83

<13

49

<13

12

, in j^g/g

Manganese

3,940

1,470

4,320

5,900

2,390

3,910

2,480

2,290

4,780

1,340

554

749

542

1,260

Nickel

21.4

14.6

19.7

19.9

18.4

16.9

19.0

17.2

14.9

16.8

13.0

16.2

13.3

13.3

Silver

17.2

2.1

4.8

6.8

6.1

6.2

6.0

4.2

6.6

4.0

.8

2.6

.7

1.4

Zinc

10,800

845

1,370

1,680

1,550

1,570

1,460

1,180

777

1,200

45

917

61

436

'Samples collected about 30 miles downstream from water-quality station to conform to previous sampling location.

46 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 15. Trace-element analyses of bulk bed sediment, upper Clark Fork basin, Montana, August 1996

[Bulk bed sediment collected in this study generally is material smaller than about 10 millimeters in diameter. Concentrations are the mean of all analyses for 

replicate aliquots for each composite sample. Abbreviation: ug/g, micrograms per gram of dry sample weight. Symbol: <, less than]

Station number

(«g. 1)

12323750

12323800

461415112450801

461559112443301

461903112440701

12324200

12324680

12331500

12331800

12334510

12334550

12353000

Station name

Silver Bow Creek at Warm Springs

Clark Fork near Galen

Clark Fork below Lost Creek, 

near Galen

Clark Fork near Racetrack

Clark Fork at Dempsey Creek 

diversion, near Racetrack

Clark Fork at Deer Lodge

Clark Fork at Goldcreek

Flint Creek near Drummond

Clark Fork near Drummond

Rock Creek near Clinton

Clark Fork at Turah Bridge, 

near Bonner

Clark Fork below Missoula 1

Number 

of composite 

samples

1

1

1

1

1

1

1

1

1

1

1

1

Concentration

Cadmium

1.7

2.6

2.5

3.4

3.9

2.1

5.2

1.5

3.9

<1.5

2.9

<1.5

Chromium

11.8

23.0

12.0

16.4

17.3

19.6

29.5

13.9

26.9

14.3

23.8

12.6

Copper

86

408

455

594

651

370

747

30

491

7

336

58

Iron

11,200

31,300

16,000

18,200

20,100

20,200

22,900

14,300

20,600

11,100

17,900

11,300

Lead

21

64

72

87

89

67

75

84

58

<13

49

<13

, in ng/g

Manganese

884

1,880

1,740

1,500

1,860

653

2,600

2,190

1,430

258

1,320

444

Nickel

9.2

9.9

7.7

9.9

10.0

10.1

15.9

6.8

13.9

8.2

14.0

7.1

Silver

1.0

1.9

2.1

2.6

2.8

1.7

3.6

5.3

2.8

.4

2.0

.6

Zinc

238

653

632

743

804

529

1,020

336

939

21

769

163

Samples collected about 30 miles downstream from water-quality station to conform to previous sampling location.

TABLE 15 47
Table 16. Recovery efficiency for trace-element analyses of standard reference materials for bed sediment

[Abbreviations: ng/g, micrograms per gram of dry sample weight; SRM, standard reference material. Symbol: , recovery could not be determined because 

all analyses were less than the analytical detection limit of 1.5 ng/g for cadmium and 12.5 ng/g for lead]

Constituent

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Number of 

measurements

5

5

5

5

5

5

5

5

5

7

7

7

7

7

7

7

7

7

Dilution ratio

1:5

1:5

1:5

1:5

1:5

1:5

1:5

1:1

1:5

1:10

1:10

1:10

1:10

1:10

1:10

1:10

1:1

1:10

Certified 

concentration

SRM sample 2709

0.4

130

35

35,000

19

538

88

.4

106

SRM sample 2711

41.7

47.0

114

28,900

1,160

638

20.6

4.6

350

Mean SRM 

recovery (percent)

-

70.6

63.0

83.6

-

83.9

89.3

261

87.4

106

73.9

90.4

85.7

100

83.1

92.6

96.8

92.8

95-percent confidence 

interval for SRM 

recovery 

(percent)

--

62.2-79.0

55.2-70.8

81.5-85.7

-

82.6-85.2

87.9-90.7

220-302

84.0-90.8

105-107

67.0-80.8

87.2-93.6

83.4-88.0

98.8-101

81.7-84.5

91.4-93.8

91.0-103

89.9-95.7

48 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 17. Trace-element analyses of procedural blanks for bed sediment

[Abbreviation: ug/mL, micrograms per milliliter. 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 0.6 N hydrochloric acid used for reconstituting dried residue. Symbols: <, less than; --, no data]

Sample 

identification

A

A

B

B

C

C

D

D

E

E

F

F

G

G

H

H

I

I

Dilution 

ratio

1:1

1:5

1:1

1:5

1:1

1:5

1:1

1:5

1:1

1:5

1:1

1:5

1:1

1:5

1:1

1:5

1:1

1:5

Trace-element concentration, in ug/mL

Cadmium

O.009

_

<.009

_

<.009

_

<.009

_

<.009

_

<.009

_

<.009

_

<.009

_

<.009

Chromium

O.009

_

<.009

_

<.009

_

<.009

_

<.009

_

<.009

_

<.009

_

<.009

_

<.009

Copper

<0.006

_

<.006

_

<.006

_

<.006

_

<.006

_

<.006

_

<.006

_

<.006

_

<.006

Iron

0.015

_

<.015

_

<.015

_

<.015

_

<.015

_

<.015

_

<.015

_

.028

_

.019

Lead

<0.08

_

<.08

_

<.08

__

<.08

_

<.08

_

<.08

_

<.08

_

<.08

_

<.08

Manganese

~

<0.006

_

<.006

_

<.006

_

<.006

_

<.006

_

<.006

_

<.006

_

<.006

_

<.006

Nickel Silver

<0.01

<0.009

<.01

<.009

<.01

<.009

<.01

<.009

<.01

<.009

<.01

<.009

<.01

<.009

<.01

<.009

<.01

<.009

Zinc

0.006

_

<.006

_

.008

_

<.006

_

.010

_

.007

_

.008

_

<.006

_

<.006

TABLE 17 49
Table 18. Trace-element analyses of biota, upper Clark Fork basin, Montana, August 1996

[Analyses are of whole-body tissue of aquatic insects. Composite samples made by combining similar-sized insects of the same species into a 

sample of sufficient mass for analysis. Concentrations for biota samples composed of two or more composite samples are the means of all 

analyses. Abbreviations: ng/g, micrograms per gram of dry sample weight. Symbol: <, less than minimum reporting level]

Number of

Taxon Will

posite 

samples

CadmiumChromiumCopper

Concentration, in |ig/g

Iron Lead Manganese

Nickel Zinc

12323750 Silver Bow Creek at Warm Springs

Hydropsyche cockerelli

Hydropsyche spp.

4

I

0.7

1.2

1.0

<1.5

42.2

40.7

768

767

4.9

<10.2

876

804

0.8

2.0

174

162

12323800 Clark Fork near Galen

Hydropsyche cockerelli

Hydropsyche occidentalis

Hydropsyche tana

1

4

1

1.4

1.3

1.5

<1.3

1.4

1.4

74.7

96.4

92.9

1,130

1,350

1,340

<7.9

7.8

9.0

1,400

2,330

2,160

1.0

1.8

2.1

136

197

206

461415112450801 Clark Fork below Lost Creek, near Galen

Hydropsyche cockerelli

Hydropsyche occidentalis

Hydropsyche spp.

3

3

1

2.4

1.5

1.8

2.0

1.7

2.4

137

124

121

1,730

1,470

1,340

13.4

11.5

20.5

1,700

2.150

1,950

1.7

1.5

2.8

229

237

225

461559112443301 Clark Fork near Racetrack

Hydropsyche cockerelli

Hydropsyche occidentalis

Hydropsyche spp.

2

2

1

1.2

1.4

1.0

1.1

1.5

.7

84.4

100

82.9

1,030

1,310

1,140

7.7

10.1

5.7

963

2,610

910

1.0

1.2

1.1

163

229

151

461903112440701 Clark Fork at Demosev Creek diversion, near Racetrack

Arctopsyche grandis

Hydropsyche cockerelli

Hydropsyche occidentalis

Hydropsyche spp.

1

1

2

1

1.7

.9

1.5

1.6

<2.4

1.0

1.2

1.4

30.8

87.6

121

104

340

831

1,140

1,070

<14.5

6.8

9.9

10.5

510

697

2,220

1,150

1.0

1.9

1.2

1.6

87

162

236

191

12324200 Clark Fork at Deer Lodge

Arctopsyche grandis

Hydropsyche cockerelli

Hydropsyche occidentalis

1

1

4

2.4

1.3

1.5

<1.3

1.7

1.9

39.1

105

154

676

1,210

1,580

<7.8

13.9

14.8

727

672

1,890

<1.3

1.4

1.4

178

185

257

12324680 Clark Fork at Goldcreek

Arctopsyche grandis

Claassenia sabulosa

Hydropsyche cockerelli

Hydropsyche occidentalis

Arctopsyche grandis

Hydropsyche cockerelli

Hydropsyche occidentalis

Arctopsyche grandis

Claassenia sabulosa

Hydropsyche cockerelli

Hydropsyche occidentalis

5

3

3

1

5

2

1

4

4

3

1

2.6

2.1

2.5

1.7

12331500

.5

.6

.7

12331800

1.6

1.9

1.7

<1.0

1.0

.4

1.9

1.4

60.0

50.0

114

81.3

695

140

1,460

1,040

3.9

1.2

9.4

8.6

817

87

921

1,140

.8

.2

1.3

1.1

175

245

214

177

Flint Creek near Drummond

2.0

2.0

1.6

18.8

18.6

17.6

1,930

2,100

1,870

11.8

15.4

24.9

1,750

1,210

2,050

2.1

2.3

2.4

226

181

188

Clark Fork near Drummond

1.0

.5

1.7

<1.0

49.7

65.9

77.6

53.1

713

126

1,360

972

4.6

.8

8.4

<7.3

726

138

903

843

.7

.1

1.2

.8

181

243

202

157

50 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 18. Trace-element analyses of biota, upper Clark Fork basin, Montana, August 1996 (Continued)

Taxon

Number of 

composite 

samples

Concentration, in ng/g

Cad- Chromium mium

Copper

Iron Lead Manga- ... , , nese Nickel Zinc

12334510 Rock Creek near Clinton

Arctopsyche grandis

Claassenia sabulosa

Hydropsyche spp. 

Arctopsyche grandis

Claassenia sabulosa

Hydropsyche cockerelli

Hydropsyche occidentalis

3

2

.4 1.1

.3 .4

9.9

27.6

621 <2.9

110 <1.3

1 <.5 1.1 15.0 837 <3.1 

12334550 Clark Fork at Turah Bridse. near Bonner

5

3

3

1

1.7 1.7

2.4 .5

1.2 2.0

1.3 1.0

40.2

45.3

50.8

44.9

1,030 3.6

106 <.8

1,390 5.7

977 <5.5

326 1.1

47.0 .3

299 .8 

613 1.0

62.1 .1

572 1.1

596 1.8

154

215

135 

199

255

192

158

12340000 Blackfoot River near Bonner

Hydropsyche occidentalis

Hydropsyche spp.

2

1

.4 1.1

.6 1.6

13.2

13.9

1,190 1.8

1,120 2.9

521 1.6

525 2.8

124

132

12353000 Clark Fork below Missoula 1

Arctopsyche grandis

Claassenia sabulosa

Hydropsyche cockerelli

Hydropsyche spp.

3

3

3

1

.3 1.1

.9 .4

.4 1.6

.5 .8

13.1

56.1

24.5

20.8

659 1.1

136 <.7

1,210 2.1

894 1.1

641 .6

114 .2

715 1.1

756 1.1

134

215

134

124

'Samples collected about 30 miles downstream from water-quality station to conform to previous sampling location.

TABLE 18 51
Table 19. Recovery efficiency for trace-element analyses of standard reference material for biota

[Abbreviations: SRM, standard reference material; ng/g, micrograms per gram of dry sample weight]

Constituent Number of 

measurements

Certified concentration Mean SRM recovery 

(percent)

95-percent confidence

interval for SRM

recovery

(percent)

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

12

12

12

12

12

12

12

12

SRM sample 1566 a

4.15

1.43

66.3

539

.37

12.3

2.25

830

103

84.3

97.7

93.2

128

94.5

96.5

99.4

98.3-108

64.3-104

91.9-104

88.2-98.2

97.0-159

89.6-99.4

81.5-112

95.0-104

52 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 20. Trace-element analyses of procedural blanks for biota

[Procedural blanks were not diluted prior to analysis. Abbreviation: )ig/mL, micrograms per milliliter. Symbol: <, less than]

Trace-element concentration, in |ig/mL

Station 

number

Station 

name

Dilution 

ratio Cadmium Copper Iron Lead Nickel Zinc

12323750

12323800

461415112450801

461559112443301

461903112440701

12324200

12324680

12331500

12331800

12334510

12334550

12340000

12353000

Silver Bow Creek at Warm Springs 1 : 1

Clark Fork near Galen 1 : 1

Clark Fork below Lost Creek, near Galen 1 : 1

Clark Fork near Racetrack 1 : 1

Clark Fork at Dempsey Creek diversion, 1 : 1 

near Racetrack

Clark Fork at Deer Lodge 1 : 1

Clark Fork at Goldcreek 1 : 1

Flint Creek near Drummond 1 : 1

Clark Fork near Drummond 1 : 1

Rock Creek near Clinton 1 : 1

Clark Fork at Turah Bridge, near Bonner 1 : 1

Blackfoot near Bonner 1 : 1

Clark Fork below Missoula 1 : 1

<0.003

<.003

<.003

<.003

<.003

<003

<.003

<.003

<.003

<003

<.003

<.003

<.003

<0.004

<.004

<.004

<.004

.010

<.004

<.004

.010

<.004

<.004

<.004

<.004

<.004

<0.004

<.002

.006

<.002

<.002

<.002

.010

<.002

.006

<.002

<.002

<.002

.030

0.05

<.01

.05

.02

.05

.05

.05

.02

.05

.04

.02

.38

.10

<0.02

<.02

<.02

<.02

<.02

.04

<.02

.06

<.02

<.02

<.02

.04

<.02

0.01 <0.01 <0.01

.01 <.01 <.01

.01 <.01 <.01

.01 <.01 <.01

.12 <.01 <.01

<,01 <.01 <.01

<.01 <.01 <.01

<.01 <.01 <.01

<.01 <.01 <.01

.01 <.01 .07

.01 <.0l <.01

.01 <.01 <.01

<.01 <.01 <.01

TABLE 20 53
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996

[Abbreviations: ft3/s, cubic feet per second; °C, degrees Celsius; (ig/L, micrograms per liter; (iS/cm, microsiemens per centimeter at 25 °C: mg/L, 

milligrams per liter; mm, millimeter; ton/d, tons per day. Symbols: <, less than minimum reporting level 1 ; --, indicates insufficient data 

greater than minimum reporting level to compute statistic]

Property or constituent and reporting unit

12323750-SILVER

Number of 

samples Maximum Minimum Mean Median

BOW CREEK AT WARM SPRINGS. MONT.

Period of record for water-quality data:

Streamflow, instantaneous (ft3/s) 36

Specific conductance, onsite ()aS/cm)

Temperature, water (°C)

pH, onsite (standard units)

Hardness, total (mg/L as CaCO3 )

Calcium, dissolved (mg/L)

Magnesium, dissolved (mg/L)

Arsenic, total recoverable (jag/L)

Arsenic, dissolved ()Jg/L)

Cadmium, total recoverable ()ag/L)

Cadmium, dissolved ()ag/L)

Copper, total recoverable ()ag/L)

Copper, dissolved (jag/L)

Iron, total recoverable (jag/L)

Iron, dissolved ()ag/L) 

Lead, total recoverable ()ag/L)

Lead, dissolved (jag/L)

Manganese, total recoverable (jag/L)

Manganese, dissolved (jag/L) 

Zinc, total recoverable ()ag/L) 

Zinc, dissolved (^ig/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

34

35

34

34

34

34

34

34

34

34

34

34

34

34 

34

34

34

34

34 

34

36

36

35

March

452

614

22.0

9.3

260

78

19

94

60

<1

.3

80

40

3,000

93

15

1.0

600

530 

180

73

229

279

97

1993-September 1996

24

281

.5

8.0

120

36

6.7

12

8

<1

<-l

10

7

130

3

<.5

80

34 

<3

2

.26

63

161

446

11.3

8.7

187

55

12

26

21

-

2 .1

30

15

494

18

23

--

231

151 

268 

2 15

17

13

82

134

448

12.0

8.8

190

55

12

21

19

<1

<.l

24

12

395

14

2

<.5

195

110 

60 

10

7

2.0

82

54 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12323770- WARM SPRINGS CREEK AT WARM SPRINGS. MONT.

Period of record for water quality data:

Streamflow, instantaneous (ft3/s) 22

Specific conductance, onsite (^S/cm)

Temperature, water (°C)

pH, onsite (standard units)

Hardness, total (mg/L as CaCO3)

Calcium, dissolved (mg/L)

Magnesium, dissolved (mg/L)

Arsenic, total recoverable (ng/L)

Arsenic, dissolved (ng/L)

Cadmium, total recoverable (ng/L)

Cadmium, dissolved (ng/L)

Copper, total recoverable (ng/L)

Copper, dissolved (ng/L)

Iron, total recoverable (ng/L)

Iron, dissolved (ng/L) 

Lead, total recoverable (ng/L)

Lead, dissolved (ng/L)

Manganese, total recoverable (ng/L)

Manganese, dissolved (ng/L) 

Zinc, total recoverable (ng/L) 

Zinc, dissolved (ng/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

21

22

21

21

21

21

21

21

21

21

21

21

21

21 

21

21

21

21 

21 

21

22

22

22

March

379

795

16.0

8.6

420

130

22

23

14

<1

<.l

88

16

1,400

30 

14

1.8

1,400

570 

60 

10

90

71

88

1993-September 1996

2.8

154

.5

7.4

73

23

3.8

3

3

<1

<.l

4

1

40

4 

<1

<5

120

57 

<10 

<3

3

.14

57

106

327

8.3

8.2

162

50

9.3

9

5

-

--

26

4

411

12

23

--

339

189

2 17 

23

25

12

77

84

269

8.8

8.2

130

40

7.4

6

4

<1

<.l

10

3

140

9 

1

<.5

280

120 

10

<3

12

1.4

77

TABLE 21 55
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean

77

65

76

64

63

63

63

63

63

63

63

1,050

720

22.5

9.0

370

110

22

78

53

3

1

14

220

.0

7.5

96

29

5.7

3

4

205

444

9.5

8.4

196

58

12

20

14

2 .4

Median

12323800-CLARK FORK NEAR GALEN. MONT. 

Period of record for water-quality data: July 1988-September 1996

Streamflow, instantaneous (ft3/s) 

Specific conductance, onsite 

Temperature, water (°C) 

pH, onsite (standard units) 

Hardness, total (mg/L as CaCO3 ) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Arsenic, total recoverable (ng/L) 

Arsenic, dissolved (ng/L) 

Cadmium, total recoverable (ng/L) 

Cadmium, dissolved (ng/L)

126

445

9.2

8.4

200

59

12

15

12

Copper, total recoverable (ng/L)

Copper, dissolved (ng/L)

Iron, total recoverable (|J.g/L)

Iron, dissolved (ng/L)

Lead, total recoverable (ng/L)

Lead, dissolved (ng/L)

Manganese, total recoverable (ng/L)

Manganese, dissolved (^ig/L)

Zinc, total recoverable (^ig/L)

Zinc, dissolved (ng/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

62

63

63

63

63

63

63

63

63

63

77

77

76

240

50

9,200

110

28

3

1,400

380

360

110

338

459

97

8

3

90

3

<1

<.5

80

33

10

3

2

.12

58

42

12

728

19

25

2.4

320

136

69

18

24

28

79

30

10

350

11

2

<5

270

110

50

12

9

2.3

79

56 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit

12324200-CL

Number of 

samples Maximum

,ARK FORK AT DEER LODGE.

Period of record for water-quality data

Streamflow, instantaneous (ft3/s) 129

Specific conductance, onsite (|iS/cm)

Temperature, water (°C)

pH, onsite (standard units)

Hardness, total (mg/L as CaCO3 )

Calcium, dissolved (mg/L)

Magnesium, dissolved (mg/L)

Arsenic, total recoverable (|ig/L)

Arsenic, dissolved (|ig/L) 

Cadmium, total recoverable (|ig/L)

Cadmium, dissolved (|ig/L)

Copper, total recoverable (|ig/L)

Copper, dissolved (ng/L)

Iron, total recoverable (|ig/L) 

Iron, dissolved (|ig/L) 

Lead, total recoverable (|ig/L) 

Lead, dissolved (|ig/L)

Manganese, total recoverable (|ig/L)

Manganese, dissolved (|ig/L)

Zinc, total recoverable (|ig/L)

Zinc, dissolved (|ig/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

112

128

77

69

69

69

79

79 

79

79

78

79

Minimum

. MONT.

: March 1985-September 1996

1,920 23

642

23.0

8.7

270

81

18

215

39

5

2

1,500

120

79 29,000 

79 190 

79 200 

79 6

79

79

79

79

129

129

120

4,600

400

1,700

230

2,250

8,690

99

242

.0

7.4

100

32

5.9

8

7

<.l

11

4

60 2 

<3

30

1

10

3

2

.29

40

Mean

286

503

9.3

8.2

212

63

13

28

14

2 .7

2 -l

123

14

,510 

2 18 

2 16

2 .7

368

48

144

18

95

224

71

Median

213

524

10.0

8.2

230

66

14

18

13

<1

52

10

790 

10 

6

210

34

70

13

24

12

72

TABLE 21 57
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit

12324590--LITTLE BL

Number of 

samples Maximum Minimum Mean Median

ACKFOOT RIVER NEAR GARRISON. MONT.

Period of record for water-quality data:

Streamflow, instantaneous (ft /s)

Specific conductance, onsite (|aS/cm)

Temperature, water (°C)

pH, onsite (standard units)

Hardness, total (mg/L as CaCO3 )

Calcium, dissolved (mg/L)

Magnesium, dissolved (mg/L)

Arsenic, total recoverable (|ag/L)

Arsenic, dissolved (ng/L)

Cadmium, total recoverable (|ag/L)

Cadmium, dissolved (f^g/L)

Copper, total recoverable (ng/L)

Copper, dissolved (f^g/L)

Iron, total recoverable (|ag/L)

Iron, dissolved (|ag/L)

Lead, total recoverable (f^g/L)

Lead, dissolved (f^g/L)

Manganese, total recoverable (|ag/L)

Manganese, dissolved (f^g/L)

Zinc, total recoverable (f^g/L)

Zinc, dissolved (|ag/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

66

54

65

53

48

48

48

53

53

53

53

52

53

53

53

53

52

53

53

53

53

66

66

66

March 1985-September 1996

2,080

300

22

8.5

140

43

9.4

17

7

2

1

45

7

25,000

120

25

6

1,100

30

140

24

1,410

7,920

95

21

120

.0

7.0

51

14

3.3

4

3

<1

<.l

<1

<1

20 1,

<3

<1

<.5

<10

1

<10

<3

1

.08

49

305

219

7.4

8.0

100

29

6.8

7

5

2 .4

-

26

22

590

237

24

2 .6

292

8

2 18

24

64

190

75

184

215

7.0

8.0

99

28

7.0

6

5

<1

<1

3

2

330

26

1

<1

30

7

10

3

10

5.6

79

58 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit

12324680-CL

Number of 

samples Maximum Minimum Mean Median

ARK FORK AT GOLDCREEK MONT.

Period of record for water-quality data

Streamflow, instantaneous (ft3/s) 35

Specific conductance, onsite (nS/cm)

Temperature, water (°C)

pH, onsite (standard units)

Hardness, total (mg/L as CaCC^)

Calcium, dissolved (mg/L)

Magnesium, dissolved (mg/L)

Arsenic, total recoverable (ng/L)

Arsenic, dissolved (ng/L)

Cadmium, total recoverable (ng/L)

Cadmium, dissolved (ng/L)

Copper, total recoverable (ng/L)

Copper, dissolved (ng/L)

Iron, total recoverable (|J.g/L) 

Iron, dissolved (ng/L) 

Lead, total recoverable (ng/L)

Lead, dissolved (ng/L)

Manganese, total recoverable (ng/L)

Manganese, dissolved (ng/L)

Zinc, total recoverable (ng/L) 

Zinc, dissolved (ng/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

34

35

34

34

34

34

34

34

34

34

33

33

34 

34 

33

33

34

34

34 

34

35

35

35

: March

3,920

496

20.0

8.7

230

68

15

75

18

2

<.l

440

36

12,000 

100

73

.6

1,100

43

510

26

752

7,960

93

1993-September 1996

87

226

.0

7.9

96

29

5.7

8

6

<1

<.l

8

3

847

365

8.9

8.3

160

47

10

18

10

~

--

62

9

60 1,400 

<3 223 

<1 29

<.5

30

11

10

<3

2

.94

43

-

181

21

77 

29

79

407

75

605

378

8.0

8.2

165

50

10

14

10

<1

<.l

40

7

680 

16

5

<5

130

20

55 

8

28

47

78

TABLE 21 59
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12331500-FLINT CREEK NEAR DRUMMOND. MONT.

Period of record for water-quality data:

Streamflow, instantaneous (fr /s) 84

Specific conductance, onsite (|aS/cm)

Temperature, water (°C)

pH, onsite (standard units)

Hardness, total (mg/L as CaCC^)

Calcium, dissolved (mg/L)

Magnesium, dissolved (mg/L)

Arsenic, total recoverable (|ag/L)

Arsenic, dissolved (|ag/L) 

Cadmium, total recoverable (|ag/L)

Cadmium, dissolved (|ag/L)

Copper, total recoverable (ng/L) 

Copper, dissolved (ng/L)

Iron, total recoverable (|ag/L)

Iron, dissolved (|ag/L) 

Lead, total recoverable (|ag/L) 

Lead, dissolved (ng/L)

Manganese, total recoverable (|ag/L)

Manganese, dissolved (|ag/L) 

Zinc, total recoverable (|ag/L) 

Zinc, dissolved (|ag/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

73

82

70

63

63

63

70

70 

70

70

69

70

70

70 

70 

70

70

70 

70 

70

84

84

84

March

892

507

21.0

8.8

260

73

20

57

20 

3

.1

32 

7

7,200

240 

87

7

1,600

120 

290

27

556

904

98

1985-September 1996

4.2

135

.0

7.5

60

17

4.3

7

5 

<1

<.l

1 

<1

70 1

4 

<1 

<.5

50

14 

<10 

<3

3

.03

28

185

298

8.6

8.2

142

38

11

19

9

2 .3

-

8

22

,140

43 

2 14 

2 1

251

43 

249

27

58

52

81

120

299

9.0

8.3

140

38

11

15

9 

<1

<1

7 

2

610

28 

9 

<5

160

38 

30 

4

31

9.4

84

60 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit

12331800-CL

Number of 

samples

ARK FORK NEAR

Period of record for water-quality data:

Streamflow, instantaneous (ft3/s) 35

Specific conductance, onsite ((aS/cm)

Temperature, water (°C)

pH, onsite (standard units)

Hardness, total (mg/L as CaCO3 )

Calcium, dissolved (mg/L)

Magnesium, dissolved (mg/L)

Arsenic, total recoverable (ng/L)

Arsenic, dissolved (|ag/L)

Cadmium, total recoverable (|ag/L)

Cadmium, dissolved (ng/L)

Copper, total recoverable (ng/L)

Copper, dissolved (|ag/L)

Iron, total recoverable (|ag/L) 

Iron, dissolved (|ag/L) 

Lead, total recoverable (ng/L) 

Lead, dissolved (|ag/L)

Manganese, total recoverable (|ag/L)

Manganese, dissolved (|ag/L) 

Zinc, total recoverable (ng/L)

Zinc, dissolved (ng/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

34

35

34

34

34

34

34

34

34

34

32

32

34 

34 

30 

30

34

34 

34

34

35

35

35

Maximum Minimum Mean Median

DRUMMOND. MONT.

March

3,520

630

21.0

8.5

300

83

22

62

19

2

.2

360

21

8,800 

150 

56 

1.2

880

50 

490

21

530

4,720

91

1993-September 1996

149 1

189

.5

7.8

74

21

5.2

8

7

<1

<.l

5

1

50 1 

<3 

<1

<.5

20

8 

<10

3

2

1.9

38

,180

391

9.7

8.2

176

51

12

20

11

-

~

63

8

,520 

226 

2 13

2 .4

209

18 

298

9

93

493

73

942

416

9.0

8.2

185

54

12

16

11

<1

<.l

36

6

870 

12 

6

<.5

135

15 

50

8

42

103

73

TABLE 21 61
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit Number of 

samples Maximum Minimum Mean Median

12334510-ROCK CREEK NEAR CLINTON. MONT.

Period of record for water-quality data

Streamflow, instantaneous (ft3/s)

Specific conductance, onsite ((j.S/cm)

Temperature, water (°C)

pH, onsite (standard units)

Hardness, total (mg/L as CaCO3 )

Calcium, dissolved (mg/L)

Magnesium, dissolved (mg/L)

Arsenic, total recoverable (jig/L)

Arsenic, dissolved (ng/L)

Cadmium, total recoverable (ng/L)

Cadmium, dissolved (f^g/L)

Copper, total recoverable (ng/L)

Copper, dissolved (jig/L)

Iron, total recoverable (jig/L)

Iron, dissolved (jig/L)

Lead, total recoverable (ng/L)

Lead, dissolved (ng/L)

Manganese, total recoverable (f^g/L)

Manganese, dissolved (ng/L)

Zinc, total recoverable (ng/L)

Zinc, dissolved (jig/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

65

56

65

55

47

47

47

53

53

53

53

51

52

53

53

51

51

53

53

53

53

65

65

65

: March

3,550

155

18

8.6

90

23

8.0

2

1

3

1

41

6

2,100

110

19

5

90

8

60

15

157

1,280

95

1985-September 1996

113

55

.0

6.9

25

6.5

2.1

<1

<1

<1

<.l

<1

<1

20

5

<1

<.5

<10

<1

<10

<3

1

.31

35

914

105

7.9

7.9

50

13

4.3

2 .9

2 1

2 .4

--

25

2 1

365

36

23

2 .7

2 19

22

2 10

23

21

116

70

548

98

8.0

7.9

50

13

4.3

<1

<1

<1

<1

3

1

200

34

1

<1

10

2

<10

<3

6

9.8

72

62 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit Number of 

samples Maximum

12334550-CLARK FORK AT TURAH BRIDGE. NEAR

Period of record for water-quality data

Streamflow, instantaneous (ft3/s)

Specific conductance, onsite (^S/cm)

Temperature, water (°C)

pH, onsite (standard units)

Hardness, total (mg/L as CaCO3 )

Calcium, dissolved (mg/L)

Magnesium, dissolved (mg/L)

Arsenic, total recoverable (ng/L)

Arsenic, dissolved (ng/L)

Cadmium, total recoverable (ng/L)

Cadmium, dissolved (ng/L)

Copper, total recoverable (ng/L)

Copper, dissolved (ng/L)

Iron, total recoverable (ng/L)

Iron, dissolved (^g/L)

Lead, total recoverable (ng/L)

Lead, dissolved (ng/L)

Manganese, total recoverable (ng/L)

Manganese, dissolved (ng/L)

Zinc, total recoverable (ng/L)

Zinc, dissolved (ng/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

132

107

131

78

68

68

68

77

77

77

77

75

76

77

77

73

73

77

77

77

77

132

132

121

Minimum

BONNER.

: Marcvh 1985-September

9,370

483

22.0

8.7

210

59

14

110

17

4

1

500

25

19,000

190

100

7

2,000

31

1,100

39

1,370

34,700

98

296

147

.0

7.4

66

19

4.4

5

4

<1

<.l

3

2

60

<3

<1

<.5

10

1

<10

<3

2

3.5

27

Mean

MONT.

1996

1,760

315

9.0

8.1

138

39

10

12

6

2 .5

-

53

6

1,590

227

2 12

2 .6

183

8

293

29

69

771

72

Median

1,010

332

9.5

8.2

140

39

10

8

5

<1

<1

24

5

550

16

6

<1

90

7

40

7

23

64

72

TABLE 21 63
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit Number of 

samples

12340000-BLACKFOOT RIVER

Period of record for water-quality data

Streamflow, instantaneous (ft3/s)

Specific conductance, onsite (|uS/cm)

Temperature, water (°C)

pH, onsite (standard units)

Hardness, total (mg/L as CaCO3)

Calcium, dissolved (mg/L)

Magnesium, dissolved (mg/L)

Arsenic, total recoverable (|ug/L)

Arsenic, dissolved (|ug/L)

Cadmium, total recoverable (|ug/L)

Cadmium, dissolved (|ug/L)

Copper, total recoverable (|ug/L)

Copper, dissolved (|ug/L)

Iron, total recoverable (^ig/L)

Iron, dissolved (|ug/L)

Lead, total recoverable (|ug/L)

Lead, dissolved (i^g/L)

Manganese, total recoverable ((^g/L)

Manganese, dissolved (|ug/L)

Zinc, total recoverable (^ig/L)

Zinc, dissolved ((^g/L)

Sediment, suspended concentration (mg/L)

Sediment, suspended discharge (ton/d)

Sediment, suspended (percent finer than 0.062 mm)

96

73

96

56

49

49

49

56

56

56

56

53

54

56

56

52

52

56

56

56

56

96

96

94

Maximum Minimum Mean Median

NEAR BONNER. MONT.

: March

10,300

294

20.5

8.7

140

37

13

4

2

2

1

34

7

3,600

100

25

8

180

11

60

15

271

7,540

98

1985-September 1996

344 2

131

.0

7.5

55

14

4.9

<1

<1

<1

<.l

<1

<1

20

<3

<1

<.5

<10

<1

<10

<3

1

1.1

42

,560

205

8.7

8.2

101

26

9.0

2 1

2 .9

2 .5

--

28

22

619

221

25

2 1

239

23

2 12

24

32

537

78

1,230

203

8.5

8.2

95

24

8.4

1

<1

<1

<1

6

2

250

14

2

<1

20

2

<10

<3

8

26

80

64 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 21. Statistical summary of water-quality data for the upper Clark Fork basin, Montana, March 1985 

through September 1996 (Continued)

Property or constituent and reporting unit . Maximum Minimum Mean Median

12340SOQ-CLARK FORK ABOVE MISSOULA. MONT. 

Period of record for water-quality data: July 1986-September 1996

Streamflow, instantaneous (ft3/s) 98 16,600 720 4,150 2,210

Specific conductance, onsite OS/cm) 75 399 145 260 270

Temperature, water (°C) 95 19.5 .0 9.0 8.5

pH, onsite (standard units) 55 8.6 7.9 8.2 8.3

Hardness, total (mg/L as CaCO3 ) 55 170 61 120 120

Calcium, dissolved (mg/L) 55 46 14 32 32

Magnesium, dissolved (mg/L) 55 13 5.3 9.4 9.5

Arsenic, total recoverable (ng/L) 55 69 2 6 4

Arsenic, dissolved (ng/L) 55 9 1 3 3

Cadmium, total recoverable (ng/L) 55 5 <1 ~ <1

Cadmium, dissolved (ng/L) 55 .1 <.l -- <.l

Copper, total recoverable (ng/L) 53 400 2 21 8

Copper, dissolved (ug/L) 54 11 1 3 2

Iron, total recoverable (ng/L) 55 13,000 60 785 270

Iron, dissolved (ug/L) 55 200 <3 224 16

Lead, total recoverable (ug/L) 50 78 <1 25 2

Lead, dissolved (ug/L) 50 1 <.5 2 .6 <.5

Manganese, total recoverable (ug/L) 55 1,100 10 79 50

Manganese, dissolved (ug/L) 55 230 7 19 15

Zinc, total recoverable (ug/L) 55 1,100 <10 244 20

Zinc, dissolved (ug/L) 55 16 <3 2 5 4

Sediment, suspended concentration (mg/L) 98 824 2 40 10

Sediment, suspended discharge (ton/d) 98 21,900 6.1 977 58

Sediment, suspended (percent finer than 0.062 mm) 93 99 44 86 90

'Multiple minimum reporting levels during the period of record may result in varying values identified with a less-than (<) symbol.

2Value is estimated by using a log-probability regression to predict the values of data less than the minimum reporting level (Helsel and Cohn, 1988).

TABLE 21 65
Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, 

August 1986 through August 1996

[Fine-grained bed sediment is material less than 0.064 millimeter in diameter. Concentrations are in micrograms per gram dry 

weight. Symbols: <, less than minimum reporting level; , indicates either too few samples or insufficient data greater 

than the minimum reporting level to compute statistic. 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. Values for single samples are 

arbitrarily listed in the "Mean" column]

- ... . Number of Constituent samp|es

Maximum

Minimum Mean Median

12323600-SILVER BOW CREEK AT OPPORTUNITY. MONT.

Period of record for fine-grained bed-sediment data:

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

5

4

5

5

5

5

4

5

5

42.0

30.1

6,280

41,200

1,030

3,940

21.4

19.6

10,800

27.1

23.2

4,560

34,400

752

1,680

14.5

13.7

6,850

1992-96

34.7

26.3

5,020

38,200

870

2,740

17.0

16.5

8,750

36.7

25.9

4,670

38,400

834

2,460

16.2

17.2

8,680

12323750-SILVER BOW CREEK AT WARM SPRINGS. MONT.

Period of record for fine-grained bed-sediment data:

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

5

4

5

5

5

5

4

5

5

12.2

24.8

769

26,000

99

17,700

16.5

2.1

2,220

6.0

12.8

259

19,500

58

1,470

14.4

.3

620

1992-96

8.7

19.3

525

21,500

77

8,620

15.3

1.1

1,430

8.2

19.8

536

20,800

74

8,150

15.2

1.0

1,450

12323770- WARM SPRINGS CREEK AT WARM SPRINGS. MONT.

Period of record for fine-grained bed-sediment data

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

1

1

1

1

1

1

1

1

1

--

~

~

-

--

--

--

-

-

~

~

--

-

--

:1995

3.9

33.4

892

21,900

85

8,790

21.9

3.2

421

--

-

~

-

-

~

--

66 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, 

August 1986 through August 1996 (Continued)

- ... . Number of Maxi- Constituent . samples mum

Minimum Mean Median

12323800-CLARK FORK NEAR GALEN. MONT.

Period of record for fine-grained bed-sediment data: 1987,

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

7

4

7

7

7

7

4

7

7

20.1

30.9

2,300

39,800

235

15,600

23.2

5.5

3,560

7.5

22.1

1,140

22,600

116

4,320

17.7

2.8

1,370

46 14151 12450801 -CLARK FORK BELOW LOST CREEK. NEAR

1991-96

12.3

26.6

1,410

29,100

156

10,100

20.6

3.9

2,240

GALEN. MONT

11.9

26.6

1,230

28,400

143

12,200

20.8

3.7

2,330

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Period of record for fine-grained bed-sediment data: 1996

1 - - 9.0

1 - - 32.9

1 -- -- 1,730

1 - -- 30,800

1 -- -- 197

1 - -- 5,900

1 - -- 19.9

1 - - 6.8

1 -- -- 1,680

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

461559112443301-CLARK FORK NEAR RACETRACK. MONT. 

Period of record for fine-grained bed-sediment data: 1996

1 -- - 8.5 

1 - - 30.1 

1 -- - 1,370 

1 -- -- 29,000 

1 - - 155 

1 -- - 2,390 

1 -- -- 18.4 

1 - - 6.1 

1 - - 1,550

461903112440701-CLARK FORK AT DEMPSEY CREEK DIVERSION. NEAR RACETRACK. MONT. 

Period of record for fine-grained bed-sediment data: 1996

Cadmium 1 - - 8.1 

Chromium 1 - - 28.9 

Copper 1 - - 1,280 

Iron 1 - - 28,200 

Lead 1 - - 152 

Manganese 1 - - 3,910 

Nickel 1 -- -- 16.9 

Silver 1 - - 6.2 

Zinc 1 -- - 1,570

TABLE 22 67
Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, 

August 1986 through August 1996 (Continued)

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

« ... . Number of Maxi- ... . .. Constituent samp,es mum Minimum Mean

12324200-CLARK FORK AT DEER LODGE. MONT.

Period of record for fine-grained bed-sediment data: 1986-87, 1990-96

9 9.0 5.1 7.2

4 36.5 19.5 30.0

9 4,180 837 1,620

9 31,700 22,600 27,600

9 242 121 166

9 6,020 1,460 2,790

4 19.0 15.0 16.5

9 7.9 2.4 4.7

9 1,730 977 1,400

12324590-LITTLE BLACKFOOT RIVER NEAR GARRISON. MONT.

Period of record for fine-grained bed-sediment data: 1986-87, 1994

3 .9 .2 .6

1 -- -- 22.1

3 85 38 54

3 26,400 16,100 22,100

3 53 37 43

3 2,700 907 1,550

1 - - 13.6

3 .9 <.5 '.5

3 180 161 170

12324680-CLARK FORK AT GOLDCREEK. MONT.

Period of record for fine-grained bed-sediment data: 1992-96

5 6.2 5.4 5.8

4 37.8 31.6 34.0

5 1,030 653 802

5 27,500 20,500 24,500

5 152 88 112

5 2,610 1,180 2,050

4 17.2 15.0 16.4

5 4.2 2.3 3.2

5 1,320 1,120 1,200

12331500-FLINT CREEK NEAR DRUMMOND. MONT.

Period of record for fine-grained bed-sediment data: 1986, 1989, 1992-96

7 4.5 <1.0 '2.7

4 27.9 21.1 24.8

7 73 55 62

7 28,100 21,100 24,100

7 240 151 187

7 5,510 2,710 3,990

4 14.9 11.7 13.2

6 7.8 5.0 6.3

7 777 610 684

Median

7.6

31.9

1,210

28,400

159

2,440

16.0

4.6

1,460

.7

--

40

23,800

40

1,040

.3

170

5.8

33.2

766

24,300

107

2,290

16.7

3.2

1,180

3.1

25.2

63

23,600

181

3,910

13.0

6.4

674

68 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, 

August 1986 through August 1996 (Continued)

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

_ ... . Number of Maxi- ... . Constituent . Minimum Mean samples mum

12331800-CLARK FORK NEAR DRUMMOND. MONT.

Period of record for fine-grained bed-sediment data: 1986-87, 1991-96

8 5.4 4.1 4.8

4 35.4 17.0 29.1

8 614 469 557

8 26,100 16,500 22,100

8 135 83 102

8 2,780 1,220 1,900

4 16.8 14.0 15.6

8 4.0 2.1 3.0

8 1,230 1,030 1,130

1233451 0-ROCK CREEK NEAR CLINTON. MONT.

Period of record for fine-grained bed-sediment data: 1986-87, 89, 1991-96

9 <1.5 <.3 --'

4 27.9 16.5 22.5

9 15 3 12

9 21,400 13,100 17,800

9 16 <3 '8

9 598 126 338

4 13.7 10.8 12.6

8 .8 <.3 '.3

9 58 36 48

12334550-CLARK FORK AT TURAH BRIDGE. NEAR BONNER. MONT.

Period of record for fine-grained bed-sediment data: 1986, 1991-96

7 5.2 3.1 3.7

4 34.7 15.3 24.0

7 561 300 382

7 23,200 15,100 18,900

7 115 49 75

7 1,670 671 1,080

4 16.2 11.6 13.9

7 2.9 1.3 2.1

7 1,160 775 911

12340000-BLACKFOOT RIVER NEAR BONNER. MONT.

Period of record for fine-grained bed-sediment data: 1986-87, 1991, 1993-96

7 <1.5 <.3 -- 1

4 24.7 15.1 19.3

7 25 16 21

7 19,100 12,400 16,300

7 20 <13 '12

7 672 298 497

4 13.3 11.7 12.6

7 .7 <.3 '.3

7 73 54 63

Median

4.8

32.0

565

23,500

100

1,910

15.8

3.0

1,130

'<.8

22.8

13

18,000

9

278

12.8

<.5

48

3.5

23.0

323

17,300

70

1,130

14.0

2.1

880

'<.8

18.6

21

15,800

11

497

12.6

<5

61

TABLE 22 69
Table 22. Statistical summary of fine-grained bed-sediment data for the upper Clark Fork basin, Montana, 

August 1986 through August 1996 (Continued)

Constituent Number of Maxisamples mum

Minimum Mean Median

12353000-CLARK FORK BELOW MISSOULA. MONT.2

Period of record for fine-grained bed-sediment data: 1986, 1990-96

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

8

4

8

8

8

8

4

8

8

2.6

27.6

293

21,100

58

2,530

14.1

2.1

675

1.1

18.8

98

14,500

12

752

13.3

.4

319

1.7

23.4

162

18,700

39

1,500

13.5

1.2

433

1.8

23.6

137

19,500

36

1,300

13.4

1.2

422

'Value determined by arbitrarily substituting one-half of the detection level for censored (<) values, when both 

uncensored and censored values are used in determining the mean. When all data are below the detection level, the 

median is determined by ranking the censored values in order of detection level. No mean is reported when all values 

are below the detection level. 

2Samples collected about 30 miles downstream from water-quality station to conform to previous sampling location.

70 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, 

August 1993 through August 1996

[Bulk bed sediment is material smaller than about 10 mm in diameter. Concentrations are in micrograms per gram dry weight. 

Symbols: <, less than minimum reporting level; --, indicates either too few samples or insufficient data greater than the minimum 

reporting level to compute statistic. 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. Values for single samples are arbitrarily 

listed in the "Mean" column]

° * "SSL01 Maximum

Minimum Mean Median

12323600-SILVER BOW CREEK AT OPPORTUNITY. MONT.

Period of record for bulk bed-sediment data: 1993-95

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

3

3

3

3

3

3

3

3

3

12.7

14.9

1,550

27,200

300

1,670

8.9

4.8

3,420

6.7

9.6

831

18,600

221

671

6.0

3.4

2,050

9.3

12.4

1,120

21,800

256

1,030

7.2

4.0

2,580

8.5

12.7

976

19,700

248

745

6.8

3.9

2,270

12323750-SILVER BOW CREEK AT WARM SPRINGS. MONT.

Period of record for bulk bed-sediment data: 1993, 1995-96

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

3

3

3

3

3

3

3

3

3

1.7

11.8

111

12,300

33

884

9.2

1.0

303

<1.1

9.9

42

9,160

11

543

5.5

<.3

137

'1.2

10.6

80

10,900

22

752

7.6

'.5

226

1.2

10.1

86

11,200

21

830

8.1

<.5

238

12327700-WARM SPRINGS CREEK AT WARM SPRINGS. MONT.

Period of record for bulk bed-sediment data: 1995

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

1

1

--

--

--

~

--

--

~

-

-

-

--

--

--

-

~

1.0

9.7

205

8,980

34

2,650

7.8

.9

148

--

--

-

--

--

--

-

TABLE 23 71
Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, 

August 1993 through August 1996 (Continued)

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Silver

Zinc

- ... . Number of Maxi- ... . ., Constituent . , Minimum Mean samples mum

1232380Q--CLARK FORK NEAR GALEN. MONT.

Period of record for bulk bed-sediment data: 1993-96

4 6.0 1.5 3.5

4 23.0 4.2 15.1

4 685 223 464 

4 31,300 9,930 22,400

4 87 41 68

4 5,410 1,280 2,530 

4 12.5 4.9 9.0

4 1.9 .7 1.4

4 1,280 498 782 

4614151 12450801 -CLARK FORK BELOW LOST CREEK. NEAR GALEN. MONT

Median

3.3

16.6

475 

24,200

72

1,710 

9.4

1.6

674

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Period of record for bulk bed-sediment data: 1996

1 - - 2.5

12.0 

455 

16,000 

72

1,740 

7.7 

2.1 

632

461559112443301-C1.ARK FORK NEAR RACETRACK. MONT.

Period of record for bulk bed-sediment data: 1996

1

3.4

16.4

594

,200

87

,500

9.9

2.6

743

461903112440701-CLARK FORK AT DEMPSEY CREEK DIVERSION. NEAR RACETRACK. MONT.

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Period of record for bulk bed-sediment data: 1996

1 - - 3.9

1 - - 17.3

1 - - 651

1 -- - 20,100

1 . -- - 89

1 -- - 1,860

1 -- -- 10.0

1 -- -- 2.8

1 - -- 804

72 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, 

August 1993 through August 1996 (Continued)

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

_ ... . Number of Maxi- ... . Constituent samp|es mum Mm.mum Mean

12324200-CLARK FORK AT DEER LODGE. MONT.

Period of record for bulk bed-sediment data: 1993-96

4 3.1 2.0 2.4

4 19.6 12.1 15.3

4 449 281 371

4 20,200 13,200 16,700

4 85 45 68

4 2,060 653 1,190

4 10.2 7.7 9.1

4 1.7 <.7 '1.3

4 619 456 551

12324590-LITTLE BLACKFOOT RIVER NEAR GARRISON. MONT.

Period of record for bulk bed-sediment data: 1994

1 - -- <1.2

1 - - 14.7

1 - -- 19

1 - -- 15,600

1 - -- 12

1 - - 420

1 - - 8.6

1 -- - <.7

1 - -- 73

12324680-CLARK FORK AT GOLDCREEK. MONT.

Period of record for bulk bed-sediment data: 1993-96

4 5.2 2.3 3.3

4 29.5 17.6 22.7

4 747 282 468

4 22,900 15,500 19,200

4 75 46 66

4 2,600 649 1,300

4 15.9 9.1 12.4

4 3.6 <.7 '1.8

4 1,020 549 735

12331500-FLINT CREEK NEAR DRUMMOND. MONT.

Period of record for bulk bed-sediment data: 1993-96

4 3.2 .3 1.7

4 13.9 4.9 10.0

4 40 19 28

4 15,000 8,630 12,800

4 120 51 84

4 3,200 1,150 2,250

4 8.0 5.8 6.6

4 5.3 3.3 4.4

4 429 190 310

Median

2.2

14.7

376

16,800

70

1,020

9.2

1.5

564

-

--

~

--

-

2.9

21.8

420

19,100

72

970

12.2

1.6

686

1.6

10.6

28

13,900

82

2,320

6.4

4.5

310

TABLE 23 73
Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, 

August 1993 through August 1996 (Continued)

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Silver

Zinc

« ... . Number of Maxi- ... . .. Constituent . Minimum Mean samples mum

12331800-CLARK FORK NEAR DRUMMOND. MONT.

Period of record for bulk bed-sediment data: 1993-96

4 3.9 1.5 2.2

4 26.9 13.8 20.2

4 491 173 294

4 20,600 14,100 16,800

4 61 35 50

4 1,430 711 1,040

4 13.9 9.0 11.0

4 2.8 .5 1.6

4 939 434 623

12334510-ROCK CREEK NEAR CLINTON. MONT.

Period of record for bulk bed-sediment data: 1993-96

4 <1.5 <.8 - 1

4 14.3 6.6 10.2

4 746

4 11,100 6,380 9,070

4 <13 5 '5

4 258 91 172

4 8.2 4.9 6.2

4 .4 .1 '.2

4 29 16 22

12334550-CLARK FORK AT TURAH BRIDGE. NEAR BONNER. MONT.

Period of record for bulk bed-sediment data: 1993-96

4 2.9 <.5 'l.4

4 23.8 6.9 13.8

4 336 75 179

4 17,900 9,530 12,800

4 49 21 34

4 1,320 234 613

4 14.0 6.4 9.0

4 2.0 <.3 '.7

4 769 281 476

12340000-BLACKFOOT RIVER NEAR BONNER. MONT.

Period of record for bulk bed-sediment data: 1993-94

2 <1.2 <.8 -- 1

2 17.7 6.7 12.2

2 19 14 16

2 16,600 10,300 13,400

2 10 8 9

2 305 179 242

2 9.8 7.6 8.7

2 <.7 <.5 - 1

2 58 33 46

Median

1.8

20.0

256

16,200

51

1,020

10.6

1.4

559

'<1.2

9.8

6

9,400

5

170

6.0

'<.5

20

1.2

12.3

152

11,900

34

450

7.8

'.3

428

-

--

--

--

--

--

-

74 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 23. Statistical summary of bulk bed-sediment data for the upper Clark Fork basin, Montana, 

August 1993 through August 1996 (Continued)

Constituent Number of 

samples

Maximum Minimum Mean Median

12353000-CLARK FORK BELOW MISSOULA. MONT.2

Period of record for bulk bed-sediment data: 1993-96

Cadmium

Chromium

Copper 

Iron 

Lead

Manganese 

Nickel 

Silver

Zinc

4

4

4 

4 

4

4 

4 

4

4

<1.5

12.6

77 

11,300 

19

444

7.1 

.6

172

.5

4.4

22 

6,160 8 

<13

223 

3.5 

<3

88

'.6

7.8

46 

:,640 

'11

350 

5.6 

] .4

131

'.6

7.0

43 

8,550 

9

366

5.8 

'.4

132

'Value determined by arbitrarily substituting one-half of the detection level for censored (<) values, when both 

uncensored and censored values are used in determining the mean and/or median. When all data are below the detection 

level, the median is determined by ranking the censored values in order of detection level. No mean is reported when all 

values are below the detection level.

2Samples collected about 30 miles downstream from water-quality station to conform to previous sampling location.

TABLE 23 75
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996

[Concentrations are in micrograms per gram dry weight. Symbols: <, less than minimum reporting level; , indicates either 

too few samples or insufficient data greater than the minimum reporting level to compute statistic, or element not analyzed. 

Number of composite samples represents the total of all individual composite samples collected for every year that the constituent 

was analyzed. Values for single samples are arbitrarily listed in the "Mean" column. 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]

Number of 

Constituent composite " Minimum 

samples mum

Mean Median

12323600-SILVER BOW CREEK AT OPPORTUNITY. MONT.

Period of record for biological data: 1992, 94-95

Hydropsyche cockeretti

Cadmium

Chromium

Copper 

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

5

5

5 

5

5

5 

5

5

6

6

6 

6

6

6 

6

6.3

8.0

462 

1,180

21.7

718 

2.1

898

Hydropsyche tana

9.2

11.5

456 

1,520

21.0

969 

1.8

4.1

1.0

269 

689

19.0

180

.7

749

4.8

.9

10.5 

857

15.6

307

.7

4.9

3.7

365 

931

20.3

460 

1.4

818

6.8

4.5

236 

1,100

18.6

634 

1.4

6 1,070 760 961 

12323750-SILVER BOW CREEK AT WARM SPRINGS. MONT.

Period of record for biological data: 1992-96

4.7

3.1

333 

953

20.1

434 

1.6

805

6.9

1.8

298 

1,050

18.3

675 

1.6

1,020

Hydropsyche cockeretti

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

14

14

14 

14

14

14 

14

14

2.1

1.3

96.9 

1,240

5.7

2,450 

1.8

276

.5

.5

25.1 

553

.3

528 

.7

118

1.0

.8

52.2 

798

3.5

1,140 

1.0

190

.8

.9

45.0 

761

3.5

914 

.8

191

Hydropsyche occidentalls

Cadmium

Chromium

Copper 

Iron 

Lead

Manganese 

Nickel

Zinc

3

3

3 

3 

3

3 

3

3

1.1

.9

46.5 

1,040 

<3.6

2,250 

1.5

202

.4

.3

38.6

372 

<2.3

1,780

.7

149

.8

.6

41.5 

803 

'1.6

2,060 

1.0

184

.9

.7

39.4 

998

1.7

2,140 

.9

201

76 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Number of M .

Constituent composite 

. mum Minimum

samples

Mean Median

12323750-SILVER BOW CREEK AT WARM SPRINGS. MONT.-Cnntinued

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1992-95

Hvdropsvche spp.

2 2.3 1.2

2 1.4 <1.5

2 47.6 40.7

2 767 619

2 5.1 <10.2

2 1,100 804

2 2.0 <4

2 284 162

12323770-WARM SPRINGS CREEK AT WARM SPRINGS

Period of record for biological data: 1995

Arctopsyche grandis

1

1

1

\

1

1

1

1

12323800-CLARK FORK NEAR GALEN. MONT.

Period of record for biological data: 1987, 1991-96

Hvdropsvche cockerelli

11 2.7 1.3

11 3.3 .8

11 181 74.7

11 1,500 901

11 9.3 1.2

11 2,950 1,400

11 3.1 1.0

11 299 136

Hvdropsvche morosa group

5 3.2 2.4

5 4.6 1.8

5 185 156

5 1,890 1,360

5 12.4 7.1

5 3,960 2,360

5 3.6 1.9

5 349 292

1.8

'1.1

44.1

692

'5.1

951

'1.1

223

. MONT.

2.4

1.9

98.8

684

5.6

2,280

2.3

222

1.7

1.3

103

1,180

5.9

2,060

1.6

220

2.5

2.6

173

1,510

8.5

3,500

2.3

309

--

«

--

--

-

--

--

--

--

--

1.7

1.2

98.7

1,620

7.5

2,120

1.4

227

2.4

2.2

175

1,430

7.9

3,860

2.1

303

TABLE 24 77
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Number of M . 

Constituent composite Xl~ Minimum 

samples mum

Mean Median

12323800-CLARK FORK NEAR GALEN. MONT.-Continued

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1987, 1991-96

Hydropsyche occidentalis

16 1.6 1.0

16 6.6 .7

16 101 66.7

16 1,400 642

16 9.1 1.6

16 4,070 1,980

16 3.5 1.1

16 278 170

Hydropsyche tana

1

1

1

1

1

1

1

1

Hvdropsvche spp.

4 3.5 2.6

0

4 154 135

4 1,540 1,190

4 13.5 10.5

0

0

4 329 279

461415112450801-CLARK FORK BELOW LOST CREEK. NEAR GAI

Period of record for biological data: 1996

Hydropsyche cockerelli

3 2.8 2.2

3 2.1 1.8

3 147 121

3 1,900 1,560

3 14.8 12.1

3 1,850 1,590

3 2.0 1.6

3 235 221

1.2

1.7

80.7

1,080

5.7

2,780

1.7

207

1.5

1.4

92.9

1,340

9.0

2,160

2.1

206

3.0

--

148

1,400

12.2

--

--

308

,EN. MONT.

2.4

2.0

137

1,730

13.4

1,700

1.7

229

1.2

1.5

78.2

1,110

5.8

2,500

1.7

201

-

~

-

-

-

-

-

--

3.0

-

152

1,450

12.4

-

-

313

2.2

2.0

144

1,730

13.3

1,670

1.7

231

78 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Number of Maxj

Constituent composite Minimum 

, mum samples

46141 51 12450801 -CLARK FORK BELOW LOST CREEK. NEAR GALEN.

Period of record for biological data: 1996

Hydropsyche occidentalis

3 1.6 1.4

3 1.8 1.7

3 132 121

3 1,540 1,360

3 12.4 10.7

3 2,190 2,100

3 1.5 1.4

3 245 230

Hydropsyche spp.

1

1

1

1

1

1

1

1

Mean

MONT.-Continued

1.5

1.7

124

1,470 1

11.5

.2,150 2

1.5

237

1.8

2.4

121

1,340

20.5

1,950

2.8

225

Median

1.5

1.7

121

,510

11.5

,170

1.5

237

-

--

--

--

--

--

--

--

461559112443301-CLARK FORK NEAR RACETRACK. MONT.

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1996

Hydropsyche cockerelli

2 1.3 1.1

2 1.4 .7

2 98.2 70.6

2 1,200 862

2 8.7 6.7

2 1,050 878

2 1.0 1.0

2 186 139

Hydropsyche occidentalis

2 1.5 1.4

2 1.5 1.5

2 107 93.5

2 1,320 1,300

2 10.1 10.1

2 2,640 2,580

2 1.3 1.2

2 230 229

1.2

1.1

84.4

1,030

7.7

963

1.0

163

1.4

1.5

100

1,310

10.1

2,610

1.2

229

--

-

--

--

--

--

--

--

--

--

--

~

-

--

--

~

TABLE 24 79
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Constituent

Number of 

composite 

samples

Maximum

Minimum Mean Median

461559112443301-CLARK FORK NEAR RACETRACK. MONT. -Continued 

Period of record for biological data: 1996

Hvdroosvche SDD.

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

1.0

.7

82.9

1,140

5.7

910

1.1

151

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

461903112440701-CLARK FORK AT DEMPSEY CREEK DIVERSION. NEAR RACETRACK. MONT. 

Period of record for biological data: 1996

Arctopsyche grandis

1

1

1

1

1

1

1

1

Hydropsyche cockerelli

1

1

1

1

1

1

1

1

Hvdropsvche occidentalis

1.5

1.3

125

1,180

10.1

2,280

1.2

240

1.4

1.2

117

1,100

9.7

2,170

1.2

232

1.7 

<2.4 

30.8 

340 

<14.5 

510

1.0 

87

.9

1.0

87.6

831

6.8

697

1.9

162

1.5

1.2

121

1,140

9.9

2,220

1.2

236

80 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Constituent

Number of Maxj

composite Minimum Mean 

. mum samples

Median

461903112440701-CLARK FORK AT DEMPSEY CREEK DIVERSION. NEAR RACETRACK. MONT.-Continued

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1996

Hydropsyche spp.

1 -- -- 1.6

1 -- - 1.4

1 -- -- 104

1 - -- 1,070

1 -- -- 10.5

1 - -- 1,150

1 - -- 1.6

1 -- -- 191

12324200-CLARK FORK AT DEER LODGE. MONT.

Period of record for biological data: 1986-87, 1990-96

Arctopsyche grandis

1 - - 2.4

1 - -- <1.3

1 - -- 39.1

1 - - 676

1 -- -- <7.8

1 -- -- 727

1 - - <1.3

1 -- - 178

Hydropsyche cockerelli

16 2.3 .8 1.4

16 3.2 .4 1.7

16 136 54.7 96.5

16 3,340 490 1,170

16 18.2 4.3 9.4

16 1,030 499 705

16 2.4 .3 1.2

16 391 132 188

Hydropsyche occidentalis

19 2.7 .8 1.4

19 2.3 .6 1.8

19 160 49 114

19 1,640 557 1,370

19 16.2 6.3 11.3

19 2,840 1,130 1,840

19 12.9 1.1 2.2

19 299 196 243

~

-

--

--

--

--

--

--

--

--

--

--

--

--

--

1.3

1.8

101

1,050

8.9

686

1.3

184

1.3

1.9

112

1,420

10.9

1,830

1.5

238

TABLE 24 81
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Number of M .

Constituent composite Minimum 

. mum samples

Mean Median

12324200-CLARK FORK AT DEER LODGE. MONT.-Continued

Cadmium

Chromium

Copper 

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper 

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper 

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

Period of record for biological data: 1986-87, 1990-96

Hvdropsvche spp.

3 2.0 1.2

0

3 222 103 

3 2,220 1,110 1

3 15.0 5.6

0 

0

1.6

~

145 

,520

8.8

3 203 185 195 

12324590-LITTLE BLACKFOOT RIVER NEAR GARRISON. MONT.

Period of record for biological data: 1987, 1994

Arctopsyche grandis

9 A .2

9 .8 .6

9 14.0 9.1 

9 325 177

9 1.3 .5

9 596 318 

9 .6 .4

9 179 113

Claassenia sabulosa

4 .3 .1

4 .8 .7

4 34.0 20.0 

4 200 98

4 <.7 <.4

4 62.1 46.7 

4 .7 .5

4 233 191

Hydropsyche cockerelli

1

1

1 

1

1

1 

1

1

.3

.7

11.5

242

.8

471 

.5

146

.2

.8

27.9 

138

--'

53.4 

.6

206

.6

1.6

28.4 

478

3.6

399 

1.2

123

1.6

-

Ill 

1.240

5.7

~

197

.3

.8

11.8 

230

.8

492

.5

145

.2

.8

28.8 

127

<6

51.3 

.5

201

--

-

~

--

82 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Number of Maxj

Constituent composite Minimum 

. mum samples

Mean Median

12324590-LITTLE BLACKFOOT RIVER NEAR GARRISON. MONT.-Continued

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1987, 1994

Hydropsyche occidentalis

1

1

1

1

1

1

1

1

12324680-CLARK FORK AT GOLDCREEK. MONT.

Period of record for biological data: 1992-96

Arctopsyche grandis

10 6.6 1.4

10 2.3 .8

10 61.1 28.8

10 737 339

10 4.5 2.3

10 1,100 592

10 1.0 .2

10 309 165

Claassenia sabulosa

10 2.5 .6

10 1.6 .3

10 66.6 33.0

10 230 63.0

10 1.6 .5

10 179 65.1

10 .7 .2

10 296 166

Hydropsyche cockerelli

9 2.6 .6

9 4.2 .7

9 122 33.5

9 1,510 589

9 10.1 4.5

9 954 538

9 1.5 .6

9 218 137

<.7

1.3

15.1

426

<3.7

434

.8

110

2.7

1.1

46.0

553

3.4

862

.7

196

1.4

.7

52.0

151

1.0

104

.3

239

1.9

2.0

74.4

896

6.7

711

1.2

185

-

-

--

--

-

--

--

2.5

1.0

48.2

564

3.6

851

.8

184

1.1

.6

50.0

151

1.0

91.4

.3

258

2.0

1.9

66.6

631

6.0

596

1.2

200

TABLE 24 83
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Number of .. . _ ... . .. Maxi- ... . Constituent composite Minimum

samples mum

Mean Median

12324680-CLARK FORK AT GOLDCREEK. MONT.-Continued

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1992-96

Hydropsyche morosa group

4 1.7 1.1

4 1.4 1.3

4 72.9 43.8

4 1,320 612

4 6.9 2.4

4 1,030 538

4 1.4 .9

4 190 137

Hydropsyche occidentalis

8 1.7 .7

8 1.7 .4

8 81.3 26.4

8 1,180 466

8 8.6 2.9

8 1,800 530

8 1.2 .8

8 207 97

1.4

1.4

60.5

1,050

4.6

804

1.2

167

1.2

1.0

46.6

786

5.5

1,140

1.0

168

1.4

1.4

62.7

1,130

4.6

822

1.2

170

1.3

1.1

45.4

752

5.5

1,050

1.0

174

12331500-FLINT CREEK NEAR DRUMMOND. MONT.

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1986, 1992-96

Arctopsyche grandis

27 .8 .2

27 4.7 .6

27 21.7 9.8

27 2,460 606

27 17.5 3.7

27 2,480 848

27 2.7 .6

27 275 151

Hydropsyche cockerelli

6 .1 .2

6 2.2 1.0

6 28.3 9.5

6 2,180 996

6 17.9 3.1

6 1,440 401

6 2.3 .9

6 193 85

.4

2.0

15.7

1,430

9.5

1,600

1.4

204

.4

1.4

18.4

1,510

9.6

1,040

1.8

149

.4

1.9

15.3

1,410

9.3

1,390

1.3

199

.4

1.1

18.6

1,360

9.1

1,130

1.9

159

84 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Number of Maxj

Constituent composite Minimum , mum samples

Mean Median

12331500-FLINT CREEK NEAR DRUMMOND. MONT.-Continued

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1986, 1992-96

Hydropsyche occidentalis

5 1.0 .2

5 17.6 .7

5 26.4 15.1

5 2,550 912

5 29.2 5.8

5 2,690 1,400

5 6.9 .8

5 243 128

Hydropsyche tana

2 <1.2 <.l

2 10.3 .6

2 16.0 5.4

2 1,320 729

2 15.3 5.0

2 1,400 1,180

2 3.1 .5

2 139 107

.6

5.1

19.6

1,790

18.3

1,870

3.4

182

__i

5.4

10.7

1,020

10.2

1,290

1.8

123

.7

1.6

18.4

1,870

24.0

1,750

3.5

188

-

~

--

--

-

--

--

--

12331800--CLARK FORK NEAR DRUMMOND. MONT.

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1986, 1991-96

Arctopsyche grandis

17 1.8 .7

17 1.1 .2

17 55.3 18.2

17 931 240

17 11.8 2.1

17 2,010 462

17 1.9 .2

17 308 142

Claassenia sabulosa

24 2.2 .3

24 3.3 .3

24 130 18.0

24 290 76.0

24 2.2 .2

24 270 45.9

24 1.1 .1

24 469 140

1.3

.8

32.1

548

4.5

871

.6

190

1.2

.8

46.9

137

.8

134

.3

262

1.3

.9

28.2

547

3.9

669

.6

183

1.3

.6

52.6

110

.8

144

.2

240

TABLE 24 85
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Number of 

Constituent composite 

samples

Maxi- ... . mum Mmimum Mean Median

12331800-CLARK FORK NEAR DRUMMOND. MONT.-Continued

Period of record for biological data: 1986, 1991-96

Hydropsyche cockerelli

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

11

11

11

11

11

11

11

11

1.7 .7

1.8 .4

85.6 37.9

1,450 506

9.2 5.1

929 549

1.2 .5

209 164

1.4

1.4

57.9

904

6.9

760

.9

183

1.5

1.5

55.9

817

6.7

743

1.1

184

Hydropsyche morosa group

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

6

6

6

6

6

6

6

6

1.3 1.1

2.8 1.9

57.4 50.2

1,730 1,380

10.8 7.0

1,940 1,260

1.7 1.3

250 227

1.2

2.3

55.2

1,570

8.9

1,610

1.5

239

1.2

2.2

55.8

1,600

9.0

1,620

1.5

240

Hydropsyche occidentalis

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

9

9

9

9

9

9

9

9

1.5 .7

8.1 .4

57.2 13.3

1,800 424

12.5 2.9

2,920 619

2.4 .5

283 157

1.0

2.6

47.2

1,070

7.2

1,580

1.4

219

1.1

2.0

51.1

972

7.3

1,200

1.7

221

Hydropsyche spp.

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

1

0

1

1

1

0

0

1

--

--

--

--

..

--

..

.-

2.6

-

85.0

940

9.1

--

-

260

--

-

--

--

--

--

--

86 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Constituent

Number of 

composite 

samples

Maximum

Minimum Mean Median

12334510-ROCK CREEK NEAR CLINTON. MONT.

Period of record for biological data: 1987, 1991-96

Arctopsyche grandis

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

25

25

25 

25

25

25 

25

25

.4

2.9

12.3 

799

<2.9

364 

1.6

189

.06

.5

4.7 

191

.1

113

.2

84

.2

1.1

8.2 

442

.4

223 

.7

125

.1

1.0

7.6 

421

.3

216 

.6

121

Claassenia sabulosa

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

13

13

13

13

13

13 

13

13

.3

1.8

40.7 

118

1.0

51.2 

.9

242

.05

.4

18.1 

49.8

.1

15.7 

.1

164

.2

.8

29.2 

85.7

.3

31.4 

.3

203

.1

.6

28.5 

83.8

.3

30.3

.3

211

Hydropsyche cockerelli

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

3

3

3 

3

3

3 

3

3

<.2

1.0

13.1 

609

<1.1

258 

.9

99

<.2

.9

6.0 

485

<1.1

192 

.4

82

-- 1

.9

8.6 

530

--'

219 

.6

89

<.2

.9

6.6

497

<1.1

208 

.4

86

Hydropsyche occidentalis

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

4

4

4 

4

4

4 

4

4

<1.0

2.4

17.6

752

6.0

268

1.7

144

<.3

.9

9.6 

520

1.2

169 

.6

99

-- 1

1.6

12.0 

642

3.0

228 

1.2

121

<.3

.9

10.2 

648

1.2

215 

.9

117

TABLE 24 87
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Number of Maxj 

Constituent composite Minimum 

samples mum

Mean Median

12334510-ROCK CREEK NEAR CLINTON. MONT.-Continued

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

Period of record for biological data: 1987, 1991-96

Hvdropsvche spp.

1

1

1

1

1

1 

1

<.5

l.l

15.0

837

<3.1

299 

.8

--

--

~

--

1 - -- 135 

12334550-CLARK FORK AT TURAH BRIDGE. NEAR BONNER. MONT.

Period of record for biological data: 1986, 1991-96

Arctopsyche grandis

20 1.9 .6

20 2.6 .6

20 48.6 20.1 

20 1,380 420

20 5.0 2.1

20 825 351 

20 1.4 .4

20 240 152

Claassenia sabulosa

17 2.5 .3

17 2.0 .4

17 76.5 38.3 

17 181 58.6

17 1.0 .2

17 117 42.0 

17 .6 .1

17 283 144

Hydropsyche cockerelli

15 1.4 .6

15 8.0 1.0

15 63.6 26.4 

15 1,580 688

15 6.3 2.2

15 788 426 

15 2.6 .6

15 224 148

1.1

1.4

28.9 

719

3.1

556

.8

185

1.1

.8

54.5 

98.9

.6

71.8

.2

218

.8

2.0

39.7 

1,030

4.1

550 

1.1

180

.9

1.4

26.3 

685

2.9

534

.7

176

.8

.6

53.4 

97.9

.6

64.3 

.1

230

.7

1.6

40.2 

1,030

4.3

537 

1.0

180

88 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Number of .. . 

Constituent composite " Minimum

samples mum

Mean Median

12334550-CLARK FORK AT TURAH BRIDGE. NEAR BONNER. MONT.-Continued

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1986, 1991-96

Hydropsyche morosa group

1

1

1

1

1

1

1

1

Hydropsyche occidentalis

10 1.3 .3

10 2.4 .6

10 44.9 34.1

10 1,130 472

10 8.2 3.0

10 1,510 454

10 1.8 .6

10 231 145

1.1

4.6

26.8

986

6.6

1,320

1.7

231

.7

1.5

38.3

871

5.0

775

.9

182

~

--

--

-

--

-

--

.7

1.5

38.2

898

4.6

656

.8

175

12340000-BLACKFOOT RIVER NEAR BONNER. MONT.

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1986-87, 1991, 1993,

Arctopsyche grandis

6 .3 <.l

0

6 17.9 12.1

6 483 108

6 2.1 <.6

0

0

6 366 123

Claassenia sabulosa

9 .6 .1

0

9 51.0 32.0

9 199 68.0

9 .6 <.3

0

0

9 233 184

1996

'.2

-

14.3

327

'1.1

--

--

223

.4

--

43.0

116

'.3

--

--

203

'.2

--

13.1

431

'<1.9

--

--

136

.5

--

44.0

113

<.5

--

--

197

TABLE 24 89
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Number of M .

Constituent composite " Minimum , mum samples

12340000-BLACKFOOT RIVER NEAR BONNER. MONT.-

Period of record for biological data: 1986-87, 1991, 1993,

Hydropsyche occidentalis

9 .5 .1

9 2.1 .8

9 20.6 13.0

9 1,530 1,060

9 1.9 1.1

9 527 414

9 1.8 .9

9 150 123

Hvdropsvche spp.

1

1

1

1

1

1

1

1

Mean

Continued

1996

.2

1.5

14.9

1,270

1.3

463

1.2

138

.6

1.6

13.9

1,120

2.9

525

2.8

132

Median

.2

1.5

14.5

1,260

1.6

452

1.2

144

--

--

--

--

--

--

--

--

ms^onn-rLARK FORK BELOW MISSOULA. MONT.2

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Nickel

Zinc

Period of record for biological data: 1986, 1990-96

Arctopsyche grandis

9 .9 .3

9 2.7 .5

9 22.0 9.4

9 813 343

9 1.9 .9

9 1,090 511

9 1.0 .4

9 169 106

Claassenia sabulosa

25 1.0 .2

25 1.2 .05

25 61.5 31.1

25 152 66.6

25 1.3 .1

25 168 48.9

25 .3 .1

25 286 146

.4

1.1

14.8

510

1.3

723

.7

137

.5

.5

46.1

94.4

.4

98.5

.2

201

.4

1.0

16.0

497

1.3

668

.6

137

.4

.5

46.5

87.3

.3

93.0

.2

200

90 Water-quality, bed-sediment, and biological data (October 1995 through September 1996) and statistical summaries of data for 

streams in the Upper Clark Fork Basin, Montana
Table 24. Statistical summary of biological data for the upper Clark Fork basin, Montana, August 1986 through 

August 1996 (Continued)

Number of 

Constituent composite 

samples

Maxi- ... . _ Minimum 

mum

12353000-CLARK FORK BELOW MISSOULA. MONT.2-

Mean

Continued

Median

Period of record for biological data: 1986, 1990-96

Hydropsyche cockerelli

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

21

21

21 

21

21

21 

21

21

.7 .2

3.4 .8

39.3 12.4 

1,590 645

3.6 1.2

1,180 353 

1.5 .5

172 77.4

.5

1.9

27.5 

1,150

2.1

726 

1.2

144

.6

1.9

27.5 

1,200

1.9

664 

1.1

158

Hydropsyche occidentalis

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

8

8

8 

8

8

8 

8

8

.9 .2

3.5 .2

30.5 18.9 

1,420 482

3.5 .7

1,460 667

2.2 .5

193 116

.4

1.4

23.4 

806

1.8

949 

1.0

141

.2

1.2

20.7 

731

1.8

956

.8

131

Hydropsyche spp.

Cadmium

Chromium

Copper 

Iron

Lead

Manganese 

Nickel

Zinc

1

1

1 

1

1

1 

1

1

..

..

~

..

~

--

.5

.8

20.8 

894

1.1

756 

1.1

124

-

-

~

--

~

--

'Values determined by arbitrarily substituting one-half of the detection level for censored (<) values, when both 

uncensored and censored values are used in determining the mean. When all data are below the detection level, the 

median is determined by ranking the censored values in order of detection level. No mean is reported when all values 

are below the detection level.

2Samples collected about 30 miles downstream from water-quality station to conform to previous sampling location.

*U.S. GOVERNMENT PRINTING OFFICE: 1997-576-687/65078

TABLE 24 91