U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2005 – 5033

Version 1.2

Status of and Changes in Water Quality 

Monitored for the Idaho Statewide 

Surface-Water-Quality Network, 

1989 – 2002

Prepared in cooperation with Idaho Department of Environmental Quality
Note: The changes listed below were made to this report on July 7, 2005 (Version 1.1):

 Page 2: figure 1, line added to explanation

 Page 12: first paragraph under pH, Lapwai River changed to Lapwai Creek

 Page 13: first paragraph under NITROGEN, Clearwater River changed to Lapwai Creek

The change listed below was made to this report on October 25, 2005 (Version 1.2):

Page 66: Table 10, column heading DO > Idaho criteria changed to DO < Idaho criteria 
Status of and Changes in Water 

Quality Monitored for the Idaho 

Statewide Surface-WaterQuality Network, 1989 – 2002

By Mark A. Hardy, D.J. Parliman, and Ivalou O’Dell

Prepared in cooperation with Idaho Department of Environmental Quality

Scientific Investigations Report 2005 – 5033

U.S. Department of the Interior

U.S. Geological Survey

Version 1.2
ii

U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2005

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Hardy, M.A., Parliman, D.J., and O’Dell, Ivalou., 2005, Status of and Changes in Water Quality Monitored for the 

Idaho Statewide Surface-Water-Quality Network, 1989 – 2002: U.S. Geological Survey Scientific Investigations 

Report 2005 – 5033, 66 p. plus 3 apps.
iii

Contents iii

CONTENTS

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

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Network design and evolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Environmental setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Land use, land cover, and stream-quality effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Hydrologic conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Site selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Sample collection and analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Data verification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Status of and changes in water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Sediment and turbidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Dissolved solids, specific conductance, and hardness . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Dissolved oxygen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

pH. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Reference sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Trace elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Fish tissue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Organic compounds in fish tissue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Fecal coliform bacteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Selected references. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Appendix A. Selected water-quality data collected at sites in the Idaho statewide 

surface-water-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . A – 1

Appendix B. Concentrations of selected trace elements in tissue of fish collected 

at selected sites in the Idaho statewide surface-water-quality monitoring 

network, 1996 – 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B – 1

Appendix C. Concentrations of organochlorine compounds and lipids in wholebody fish collected at selected sites in the Idaho statewide surface-waterquality monitoring network, 1996 – 99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C – 1
iv

iv Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002

FIGURES (explanation for various boxplots is on page v)

1. Locations of sampling sites and nutrient ecoregions in the Idaho statewide 

surface-water-quality monitoring network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Stream discharges at times samples were collected for selected sites in the 

Idaho statewide surface-water-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . 27

3A. Summer maximum daily water temperatures at all sites in the Idaho statewide 

surface-water-quality monitoring network, 1996 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3B. Summer minimum daily water temperatures at all sites in the Idaho statewide 

surface-water-quality monitoring network, 1996 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

3C. Summer mean daily water temperatures at all sites in the Idaho statewide 

surface-water-quality monitoring network, 1996 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4. Sites in the Idaho statewide surface-water-quality monitoring network 

where water temperature exceeded criteria, 1996 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . 34

5. Suspended-sediment concentrations at all sites in the Idaho statewide 

surface-water-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

6. Suspended-sediment concentrations in relation to time at selected sites in 

the Idaho statewide surface-water-quality monitoring network. . . . . . . . . . . . . . . . . . . . 8

7. Turbidity in relation to suspended-sediment concentrations at all sites in the 

Idaho statewide surface-water-quality monitoring network, 1989 –2002. . . . . . . . . . . . . 9

8. Turbidity in relation to suspended-sediment concentrations at selected sites in 

the Idaho statewide surface-water-quality monitoring network, 1989 – 2002 . . . . . . . . . 36

9. Turbidity at all sites in the Idaho statewide surface-water-quality monitoring 

network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

10. Sites in the Idaho statewide surface-water-quality monitoring network where 

turbidity exceeded 25 nephelometric turbidity units (NTU), 1989 – 2002 . . . . . . . . . . . . . 38

11. Specific conductance at all sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

12. Ratios of total dissolved-solids concentrations to specific conductance at all 

sites in the Idaho statewide surface-water-quality monitoring network, 

1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

13. Hardness concentrations at all sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

14. Hardness in relation to specific conductance at all sites in the Idaho statewide 

surface-water-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

15. Dissolved-oxygen concentrations and saturations at all sites in the Idaho 

statewide surface-water-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . 42

16. Dissolved-oxygen concentrations and saturations in relation to time at 

selected sites in the Idaho statewide suface-water-quality monitoring network, 

1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

17. pH at all sites in the Idaho statewide surface-water-quality monitoring network, 

1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

 18. pH in relation to time at selected sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
v

Contents v

19. Total nitrogen concentrations at all sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

20. Inorganic nitrogen concentrations at all sites in the Idaho statewide surfacewater-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

 21. Total nitrogen concentrations in relation to time at selected sites in the Idaho 

statewide surface-water-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . 49

22. Total phosphorus concentrations at all sites in the Idaho statewide surfacewater-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

23. Total phosphorus concentrations in relation to time at selected sites in the 

Idaho statewide surface-water-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . 51

24. Total phosphorus and total nitrogen concentrations at proposed reference 

sites and combined nutrient ecoregion sites in the Idaho statewide surfacewater-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

25. Sites in the Idaho statewide surface-water-quality monitoring network where

 concentrations of trace elements in water exceeded criteria, 1989 – 95 . . . . . . . . . . . . 53

26. Concentrations of selected trace elements in livers of fish collected at selected 

sites in the Idaho statewide surface-water-quality monitoring network, 

1996 – 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

27. Sites in the Idaho statewide surface-water-quality monitoring network where 

concentrations of selected trace elements were enriched in fish tissue, 

1996 – 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

28. Ratios of selected organic compounds to lipids in whole fish collected at 

selected sites in the Idaho statewide surface-water-quality monitoring 

network, 1996 – 98 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

29. Fecal coliform populations at all sites in the Idaho statewide surfacewater-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

3rd Quartile plus

 1.5 times the IQR

1st Quartile minus

 1.5 times the IQR

Interquartile range

(IQR)

Outlier—3rd Quartile plus

 between 1.5 and 3 times

 the IQR

3rd Quartile

Median

1st Quartile

�����������

Outlier—1st Quartile minus

 between 1.5 and 3 times

 the IQR

398 Number of samples

For figures 3, 5, 9, 11, 12, 13,

15, 17, 19, 20, 22, and 29
vi

vi Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002

TABLES

 1. Basin and site characteristics for sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

 2. Types of data and periods of data collection for sites in the Idaho statewide 

surface-water-quality monitoring network and for other programs. . . . . . . . . . . . . . . . . 64

3. Sampling site changes made to the Idaho statewide surface-water-quality 

monitoring network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4. Total nitrogen and phosphorus concentrations at proposed reference sites 

in the Idaho statewide surface-water-quality monitoring network in relation

to nutrient criteria recommended for, and background concentrations 

modeled for, two nutrient ecoregions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5. Idaho criteria for selected dissolved trace elements in water . . . . . . . . . . . . . . . . . . . . . 15

 6. Sites in the Idaho statewide surface-water-quality monitoring network 

where concentrations of selected trace elements exceeded Idaho criteria, 

1989 – 95 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

7. Sites in the Idaho statewide surface-water-quality monitoring network where 

fish tissue was analyzed for selected trace elements, 1996 – 2000. . . . . . . . . . . . . . . . . . 16

8. Sites in the Idaho statewide surface-water-quality monitoring network where 

concentrations of selected trace elements exceeded criteria for water or were 

enriched in fish tissue, 1989 –2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

9. Concentrations of selected organic compounds and ratios of concentrations 

to lipid content in whole-body samples of fish from sites in the Idaho statewide 

surface-water-quality monitoring network, 1996 –99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

 10. Major network and water-quality issues for sites in the Idaho statewide 

surface-water-quality monitoring network, 1989 – 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
vii

Contents vii

Conversion Factors, Datum, and Other Abbreviated Units

Multiply By To obtain

centimeter (cm) 0.3937 inch (in.)

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

kilometer (km) 0.6214 mile (mi)

meter (m) 3.281 foot (ft) 

square kilometer (km2) 0.3861 square mile (mi2)

square meter (m2) 10.76 square foot (ft2) 

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

°F = (1.8 × °C) + 32

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD of 1929). Elevation above sea level, as used in this report, refers to distance above the 

vertical datum.

Other abbreviated units:

micrograms per gram (μg/g)

micrograms per liter (μg/L)

microsiemens per centimeter (μS/cm)

milligrams per liter (mg/L)

milliliters (mL)
[This page intentionally left blank]
Dissolved-solids and hardness concentrations were 

strongly correlated. This is probably because the limestones 

present in some basins are more soluble than the igneous rocks 

that predominate in others. Low hardness in streams of northern Idaho, where watersheds are underlain by resistant igneous 

rocks, enhances the toxicity of some trace elements to aquatic 

life in these streams.

Only a few measurements of dissolved-oxygen concentrations at six sites were less than 6.0 milligrams per liter, the 

Idaho minimum criterion for protection of aquatic organisms. 

High supersaturations of dissolved oxygen at four sites suggest excessive photosynthetic activity by algal communities. 

Nighttime monitoring would help determine whether dissolvedoxygen concentrations at these sites might fall below the Idaho 

criterion. Data from four sites suggest that dissolved-oxygen 

concentrations may have decreased over time.

The pH at 15 sites sometimes fell outside the range specified (6.5 – 9.0) for the protection of aquatic organisms in Idaho 

streams. Values exceeded 9.0 at 10 sites, probably because of 

excessive algal photosynthetic activity in waters where carbonate rocks are present. Values were sometimes less than 6.5 at 

five sites in areas of mountain bedrock geology where pH is 

likely to be naturally low. Mining activities also may contribute to low pH at some of these sites.

Inorganic nitrogen and total phosphorus concentrations 

commonly exceeded those considered sufficient for supporting excess algal production (0.3 and 0.1 milligrams per liter, 

respectively). Data from a few sites suggest that nitrogen 

and(or) phosphorus concentrations might be changing over 

time. Low concentrations of nitrogen and phosphorus at six 

sites, most representing forested basins, might make them 

ABSTRACT

The Idaho statewide surface-water-quality monitoring 

network consists of 56 sites that have been monitored from 

1989 through 2002 to provide data to document status and 

changes in the quality of Idaho streams. Sampling at 33 sites 

has covered a wide range of flows and seasons that describe 

water-quality variations representing both natural conditions 

and human influences. Targeting additional high- or low-flow 

sampling would better describe conditions at 20 sites during 

hydrologic extremes. At the three spring site types, sampling 

covered the range of flow conditions from 1989 through 

2002 well. However, high flows at these sites since 1989 

were lower than historical high flows as a result of declining 

ground-water levels in the Snake River Plain.

Summertime stream temperatures at 45 sites commonly 

exceeded 19 and 22 degrees Celsius, the Idaho maximum 

daily mean and daily maximum criteria, respectively, for the 

protection of coldwater aquatic life. Criteria exceedances in 

stream basins with minimal development suggest that such 

high temperatures may occur naturally in many Idaho streams.

Suspended-sediment concentrations were generally 

higher in southern Idaho than in central and northern Idaho, 

and network data suggest that the turbidity criteria are most 

likely to be exceeded at sites in southern Idaho and other sections of the Columbia Plateaus geomorphic province. This 

is probably because this province has more fine-grained soils 

that are subject to erosion and disturbance by land uses than 

the Northern Rocky Mountains province of northern and central Idaho has. Although erodable soils are likely a cause of 

elevated turbidities, suspended-sediment concentrations were 

not strongly correlated with turbidities.

Status of and Changes in Water Quality 

Monitored for the Idaho Statewide 

Surface-Water-Quality Network, 

1989 – 2002

By Mark A. Hardy, D.J. Parliman, and Ivalou O’Dell
2 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

Figure 1. Locations of sampling sites and nutrient ecoregions in the Idaho statewide surface-water-quality monitoring 

network (Rotation of sampling sites shown represents status in 2002 or status when site was dropped from network.)

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For additional site information

see table 1 
Introduction 3

good candidates as reference sites that represent naturally 

occurring nutrient concentrations.

Trace elements examined for this report were cadmium, 

copper, lead, mercury, selenium, and zinc. In water, many traceelement concentrations were below the minimum analytical 

reporting levels. Concentrations of cadmium, copper, lead, 

and zinc generally were highest in mined and other mineralrich basins in northern Idaho. Concentrations of mercury were 

highest in southern Idaho. Data showed that concentrations of 

one or more of these elements at 33 sites sometimes exceeded 

Idaho criteria for protection of aquatic organisms. Selenium 

concentrations were not high at any of the sites.

Concentrations of these elements in fish tissue were highest in some of the same areas where concentrations were high in 

water. However, there were 22 instances where trace-element

concentrations in water exceeded criteria but concentrations 

in fish tissue did not. These inconsistencies may require that 

the scope of trace-element monitoring be reassessed to meet 

network objectives. Mercury concentrations in several fishtissue samples were greater than 0.3 micrograms per gram, 

the maximum concentration for edible fish tissue that the U.S. 

Environmental Protection Agency recommends for protection 

of human health.

Organic compounds detected in fish tissue included 

PCBs (in northern and southeastern Idaho) and the pesticides 

dieldrin, nonachlor, and DDT and its metabolites (in southern 

and central Idaho). The common presence of PCBs, DDT, 

and DDT metabolites reflects the wide-scale use of PCBs and 

DDT before they were banned more than 30 years ago and 

their persistence in the environment.

Populations of fecal coliform bacteria exceeded the current

Idaho primary- or secondary-contact criteria for Escherichia 

coli (E. coli) (406 and 526 colonies per 100 milliliters, respectively) at 22 sites representing a wide range of site types. The 

number of samples in which populations exceeded criteria 

were greatest at agricultural site types on the Boise River and 

Lapwai Creek, where populations in more than 25 percent of 

the samples exceeded both criteria. Replacing fecal coliform 

analyses with E. coli analyses would provide data that would 

directly address current criteria.

INTRODUCTION

The Idaho statewide surface-water-quality monitoring 

network was implemented in 1989 by the U.S. Geological 

Survey (USGS), in cooperation with the Idaho Department 

of Environmental Quality (IDEQ), in response to Idaho’s 

antidegradation policy as required by the Clean Water Act 

(CWA). The program objective was to provide resource managers with data to document status and changes over time in 

surface-water quality through a network that was coordinated 

with and supplemented by data from other State and Federal 

agencies. Many of the data are used in biennial reports on 

the status of Idaho water quality published by the IDEQ. The 

data also are used for establishing total maximum daily loads 

(TMDLs). As programs are implemented to meet TMDLs, the 

network data will continue to be important for verifying the 

effectiveness of these programs and tracking overall trends in 

Idaho’s surface-water quality.

Purpose and Scope

The purpose of this report is to describe the status of and 

changes in selected chemical and physical data collected for 

the Idaho statewide surface-water-quality monitoring network 

from 1989 through 2002. Data addressed in the report include 

those constituents related to water-quality issues that are currently priorities to IDEQ (Don Essig, oral commun., 2004). 

All data collected at each site, including additional data 

collected for other USGS projects, were evaluated.

Network Design and Evolution

The network consists of 56 stream sites on the Bear, 

Clearwater, Kootenai, Pend Oreille, Salmon, Snake, and 

Spokane Rivers and their major tributaries (figure 1 and 

table 1). Whenever possible, all sites are located at existing 

USGS gaging stations where continuous stream discharge data 

are available. From 1989 through 1995, water samples were 

collected and analyzed for temperature, suspended sediment, 

turbidity, specific conductance, dissolved oxygen, pH, major 

ions, nutrients, trace elements, and fecal bacteria. Bimonthly 

samples were collected each year at 5 sites (annual sites), every 

other year at 19 sites (biennial sites) and every third year at 

32 sites (triennial sites). This sampling rotation occasionally

was changed to meet evolving needs for data. As a result, 

about 25 sites representing annual, biennial, and triennial sites 

were sampled each year.

The network was changed in 1996 to include continuous temperature monitoring during summer months, habitat 

evaluation, and sampling of aquatic biological communities. 

Biological communities were chosen because they reflect 

the time-integrated effects of water quality better than water 

samples do through community structure and accumulation 

of chemicals in tissues. Evaluation of biological communities also provided more direct measures of biotic integrity and 

associated beneficial uses (such as coldwater biota populations, fish spawning, and recreation), which were needed for 

water-quality reporting required under sections 305(b) and 

303(d) of the CWA. Additional information on biological 

aspects of the network is provided in a report by Maret and 

others (2001). To make these changes without increasing program costs, analyses of trace elements in water were dropped 

and major-ion analyses were reduced to one set of samples 

during base-flow conditions in September. The frequency of 

water-sample collection was changed from bimonthly throughout the year, to monthly during April through September, the 

period when beneficial uses are most likely to be stressed by 

poor water quality. Sites in figure 1 were classified as annual, 
4 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

biennial, or triennial by their sample collection frequency in 

2002 or by their status at the time they were dropped from the 

network.

Some network sites also were sampled as part of other 

USGS projects. Where possible, sampling was coordinated 

at these sites to avoid duplication of efforts and allow better 

coverage for other network sites. However, higher intensity 

sampling for selected constituents for some projects resulted 

in more data for some sites than for others.

The types and periods of data collection for the network 

are summarized in table 2. Some sampling sites were added, 

dropped, or replaced for various reasons and are summarized 

in table 3. Chemical, physical, and hydrologic data collected for this program are stored in the USGS National Water 

Information System (NWIS). This database can be accessed 

at http://www.usgs.gov. Much of the biological data collected 

for this program can be accessed at http://id.water.usgs.gov/

public/wq/index.html.

Environmental Setting

Idaho is a large State that spans 7 degrees of latitude, 

from 42°N at its southern border with Nevada to 49°N at 

its northern border with Canada. Its varied geography covers 

11 ecoregions (McGrath and others, 2002). Major river basins 

are the Bear, Clearwater, Kootenai, Pend Oreille, Salmon, 

Snake, and Spokane and their tributaries. Most of the sampling sites in this study are located in the Snake River Basin/

High Desert and Central Basin and Range ecoregions.

Elevations in Idaho range from about 225 m above sea 

level where the Snake River leaves Idaho to 3,859 m at Borah 

Peak in east-central Idaho. Sampling site elevations in the network range from about 300 m to just over 2,000 m. Precipitation varies widely with topography; average rainfall is about 

56 cm a year. The climate of Idaho is primarily arid during 

summer. Precipitation is primarily winter snowfall, and peak 

flows in streams generally result from spring snowmelt (Maret 

and others, 2001).

Idaho includes parts of four geomorphic provinces (Ross 

and Savage, 1967). The Northern Rocky Mountains province 

covers most of the northern and central parts of the State and 

is characterized by steep, high mountains and deep valleys. 

Granitic rocks of the Idaho batholith primarily underlie and 

outcrop in the southern and central parts of this province, and 

sedimentary and metamorphosed sedimentary rocks primarily 

underlie the northern part. Rich mineral deposits have supported an extensive mining industry in this province.

The Middle Rocky Mountains province occupies the 

southeastern edge of Idaho along the Wyoming border. The 

northern part of this province includes the Yellowstone 

Plateau, which is dominated by volcanic rocks and is charTable 3. Sampling site changes made to the Idaho statewide surface-water-quality monitoring network

[Locations of sites shown on figure 1; No., number; WA, Washington; USGS, U.S. Geological Survey]

Site

No. Site name Action Comments

8 Snake River at Heise

Replacement

1997

Replaced Snake River at Lorenzo (site 9). New site better represents low impacted 

water quality and was originally part of a national program with historical waterquality data.

12 Willow Creek near Ririe Dropped 1996 Site represented water quality in upstream reservoir.

22 Rock Creek at Daydream Ranch

Replacement

1996

Replaced Rock Creek near Twin Falls. Gage discontinued at old site. New site was 

part of an existing national program with several years of water-chemistry and 

biological data.

25 Camas Creek at Red Road Dropped 1997 Intermittent flow owing to location in the basin. The gage was discontinued in 1992.

26 Beaver Creek at Spencer Dropped 1997 Intermittent flow owing to location in the basin. The gage was discontinued in 1993.

27 Big Lost River near Chilly

Replacement

1999

Replaced Big Lost River below Mackay, which represented water quality in upstream 

reservoir. New site was part of an existing national program with additional chemical and biological data.

28 Big Wood River near Bellevue

Replacement

1999

Site moved about 1.6 kilometers upstream because of gage-operation problems at old 

location. Data from both locations combined for analysis.

34 Boise River below Diversion Dam Dropped 1999 Site represented water quality in upstream reservoir.

40 North Fork Payette River at Cascade Dropped 1998 Site represented water quality in upstream reservoir.

49 Snake River near Anatone, WA Dropped 1998 Site operation transferred to Washington District of USGS.

54 Salmon River near White Bird Added 2000

Site was part of a national program. Site represents all of the flow from the Salmon 

River and has considerable historical data.

56

St. Joe River at Red Ives Ranger 

Station Added 2001

Site was part of a national program as a reference site with considerable chemical and 

biological data. The location in the upper basin makes it a candidate as a reference 

site.
Introduction 5

acterized by high mountains and deep, narrow canyons. The 

southern part is characterized by mountains of complexly 

folded sedimentary rocks and wide valleys. Carbonate deposits and rich phosphate deposits are present in the central and 

southern parts of this province, and phosphate mining is a 

major industry.

The Basin and Range province is located in southeastern 

Idaho between the Utah State line and the Snake River Plain 

and is characterized by mountains separated by open valleys 

and basins. The mountains are sedimentary rocks that are 

sometimes metamorphosed, and valleys are filled with alluvial 

material. Carbonate deposits and limestone quarries are common throughout this province.

The Columbia Plateaus province includes the Snake 

River Plain and Owyhee uplands in southern Idaho and 

extends northward along the west-central edge of the State 

along the Oregon and Washington borders. The eastern part of 

this province is primarily basalt flows covered with thin loess 

in places. The porous basalts account for significant subsurface drainage, some of which resurfaces as major springs on 

the north side of the Snake River. In the southwestern part 

of the province, basalts of the Snake River Plain become 

interbedded with lacustrine and fluvial sediments, and the silty 

soils support the most intensely developed agricultural lands 

in Idaho. The Owyhee uplands consist of a variety of volcanic 

rocks that are covered by volcanic ash and loess deposits in 

places. River canyons are cut deeply into the volcanic rocks. 

North of the Snake River Plain, topography becomes rugged 

and dominated by igneous and sedimentary rocks that include 

numerous limestone deposits. Lacustrine and alluvial sediments here are subject to frequent landslides as a result of the 

steep mountain slopes. The northernmost part of this province 

consists of the Palouse Hills, which are large dunes of thick 

loess over basalt flows.

LAND USE, LAND COVER, AND STREAMQUALITY EFFECTS

Rangeland and forested land dominate the Idaho landscape. Of the 56 network sites, 33 of them are located in 

drainage basins that consist of more than 80 percent combined 

rangeland and forested land cover, and 46 of them are located 

in basins that consist of more than 70 percent combined rangeland and forested land cover (table 1). Although Idaho has 

a small population of just over 1 million, it ranks fifth in the 

Nation in amount of irrigated cropland, according to the 1997 

Census of Agriculture (U.S. Department of Agriculture, Farm 

and Ranch Irrigation Survey, Census of Agriculture, table 4, 

accessed July 29, 2004 at http://www.nass.usda.gov/census/

census97/fris/fris.htm). Agricultural land composes at least 

10 percent of the land cover in half of the network basins. 

In the central part of the State, much of the land is roadless 

national forest and wilderness, and water use is minimal.

The southern basins are primarily in semiarid, high desert 

plains and contain the greatest population densities. The 

population of Ada and Canyon Counties (including the Boise 

metropolitan area) constitutes more than a third of the population in the State. The basins toward the north are primarily 

forested and sparsely populated; logging, mining, and grazing 

are the predominant land uses. The State’s landscape makes it 

a popular destination for sports enthusiasts and tourists. More 

than 60 percent of the land is federally owned and available 

for recreational activities such as hiking, fishing, hunting, and 

whitewater rafting (Maret and others, 2001).

The site types used by Maret and others (2001) were 

assigned to all network sites on the basis of land use and land 

cover (table 1). Generally, irrigated agriculture and rowcrop 

production composed more than 10 percent of the land use 

in basins represented by agricultural site types; rangeland 

composed more than 40 percent of the land use in basins represented by rangeland site types; and forested land composed 

more than 60 percent of the land use in basins represented 

by forested site types. Large-river sites included streams 

larger than sixth order. Three sites were assigned to a spring 

category because of their small size and proximity to spring 

sources.

Nonpoint-source pollution and water diversions are the 

predominant influences on surface-water quality in the State 

(Idaho Department of Health and Welfare, 1998). Pollutants 

of greatest concern that have been associated with habitat 

degradation of streams are nutrients, suspended sediment, 

bacteria, organic waste, and elevated water temperature. 

Beneficial uses of streams most impaired by pollutants are 

coldwater aquatic life, salmonid spawning, and water-contact 

recreation (Idaho Department of Health and Welfare, 1998). 

Water diversions often result in large streamflow reductions in 

many streams. In addition, water transfer from one river basin 

to irrigate crops in another is common practice in most of 

southern Idaho. The ecological consequences of this practice 

include changes in streamflow, introduction of exotic species, 

alteration of habitat, and changes in water quality (Meador, 

1992). Most rivers in Idaho are designated as supporting 

coldwater aquatic life (Grafe and others, 2002), and waterquality standards require conditions supporting maintenance 

and propagation of coldwater-adapted fish and other aquatic 

life in these waters.

HYDROLOGIC CONDITIONS

Streamflow is a major factor that can affect water quality, 

and sampling at a wide range of flows usually is desirable for 

monitoring programs. Because samples for monitoring programs often are collected at predetermined time intervals and 

high-flow events are difficult to predict and often short lived, it 

is not unusual to miss flow extremes that might cause unique 

water-quality conditions. To determine how well the network 

samples represented the range of long-term streamflow conditions at sites, the flows measured when samples were collected 

from 1989 through 2002 were compared to flow frequencies 

representing all recorded historical flows for each site. Dis-
6 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

charge records for 10 selected network streams are shown in 

figure 2.

Generally, sampling at network sites represented a wide 

range of flow conditions without targeting specific flow events. 

Sampling at 33 sites covered conditions ranging from low 

flows that were exceeded more than 98 percent of the time to 

high flows that were exceeded less than 2 percent of the time. 

Sites 54, 56, and 57 are examples of the sites having this desirable sample distribution.

Sample distributions at 10 sites missed some of the lowest flows (sites 18, 26, 39, and 40) or were somewhat biased 

toward high flows (sites 1, 2, 10, 12, 25, and 38). These sites 

might benefit from targeting low flows for sample collection to 

better describe water quality during such conditions. Sites 2, 

25, and 39 are examples of sites having poor coverage of lowest flows or high-flow bias.

Sample distributions at 12 sites missed some of the highest flows (sites 24 and 29) or were somewhat biased toward 

low flows (sites 14, 15, 19, 21, 23, 28, 32, 44, 46, and 53). All 

spring site types (sites 21, 23, and 29) were biased toward low 

flows, probably as a result of declining ground-water levels in 

the Snake River Plain. For example, since the beginning of the 

monitoring network in 1989, flows exceeding 6 m3/s (200 ft3/s; 

a flow historically exceeded less than 42 percent of time) have 

not occurred at Blue Lakes Spring (site 21). However, during 

the recent period of the network, sample distributions at the 

spring site types covered flow conditions well and represented 

some of the highest flows that have occurred since 1989. All 

of these sites except the three spring site types might benefit from targeting high flows for sample collection to better 

describe water quality during such conditions. Sites 15, 21, 

and 24 are examples of sites having poor coverage of high 

flows or low-flow bias.

Although samples collected at site 13 (Blackfoot River) 

were not biased toward low or high flows, neither lowest nor 

highest flows were well represented (figure 2). This might be 

a result of different regulation of releases from the Blackfoot 

Reservoir since 1989 than during earlier times. This site might 

benefit from targeting low and high flows for sample collection to better describe water quality during such conditions.

METHODS

Site Selection

The network originally was built around, but did not 

include, seven sites that composed the USGS National Stream 

Accounting Network (NASQAN) in 1989. These sites were 

located either near the outflow of major hydrologic units or 

where broad, temporal patterns in water quality related to upstream land and water uses could be detected. A wide range 

of water-quality constituents were monitored — nutrients, 

major ions, trace elements, bacteria, and sediment. Since 

the end of the NASQAN program, only three of these sites 

(sites 8, 36, and 54) have continued to be sampled as part of 

the network or other projects.

Fifty-six sites were chosen for the network. Only sites 

that were part of the existing USGS streamflow-gaging network were chosen, so that continuous flow information would 

be available for interpreting data. Water-quality constituents 

analyzed for the monitoring network were the same as those 

analyzed for the NASQAN program. Annual, biennial, and 

triennial sampling rotations were assigned to sites on the 

basis of spatial distribution, upstream land and water uses, 

and point sources. Annual sites were located in basins where 

water quality has been managed on a long-term basis. Biennial sites were located in basins where land and water uses 

were expected to change slowly. Triennial sites were located 

in basins where future development proposals could affect 

water quality. To provide flexibility, sampling rotations can be 

changed to accommodate available funding or unanticipated 

changes in land or water use.

Sample Collection and Analyses

Water samples for analyses of chemical constituents and 

suspended sediment were collected and processed using depthintegrating samplers, the equal-width-increment method, and 

a modified clean-sampling procedure described by Wilde 

and others (May 1999 and September 1999). At the time of 

sample collections, temperature, pH, dissolved oxygen, and 

specific conductance were measured instream at the center 

of flow using calibrated electrometric meters. All analyses 

designated as “dissolved” were filtered through 0.45-μm capsule filters that are certified by the manufacturer and verified 

by USGS to be free of contamination. Suspended sediment 

was analyzed according to methods described by Guy (1969). 

These analyses were performed at the USGS Boise District 

Sediment Laboratory from 1989 through 1993 and at the USGS

Sediment Laboratory in Vancouver, Washington, starting in 

1994. Chemical constituents in water were analyzed at the 

USGS National Water Quality Laboratory (NWQL) using the 

methods of Fishman (1993). Because samples from many 

network sites contained very low nutrient concentrations, lowlevel analytical techniques (Fishman, 1993) were adopted in 

1999.

Samples for analyses of fecal coliform bacteria were 

collected using sterilized bottles at the center of flow. Samples were analyzed using the membrane filtration methods 

described by Myers and Wilde (July 1997).

Fish were collected from a representative reach using 

electrofishing techniques described by Meador and others 

(1993). Whole-body fish-tissue and fish-liver composite 

samples were analyzed at the NWQL for organic compounds 

and trace elements using methods described by Leiker and 

others (1995) and Hoffman (1996), respectively.

Hourly water-temperature data were collected by 

deploying calibrated, self-logging microthermistors from 

April through September 1996 through 2002. The thermis-
Status of and Changes in Water Quality 7

tors were deployed in deep parts of stream channels to ensure 

that they would remain submerged during summer low flows. 

In most cases, daily minimum, mean, and maximum values 

were stored in the USGS Automated Data-Processing System 

(ADAPS). However, the earliest daily mean values were not 

stored for sites 1, 36, and 49.

Data Verification

Temperature, pH, dissolved oxygen, and specific conductance were measured at the center of flow where the stream 

appeared to be well mixed. Measurements were made periodically at 10 equally spaced locations in the stream cross section 

to ensure that measurements at the center of flow represented 

the entire stream cross section.

Quality-control procedures used by the NWQL consisted 

of verifying condition of reagents and equipment, managing 

samples, participating in internal and external performanceevaluation studies, conducting internal and external audits, 

verifying data, performing chemical-logic checks, and following protocols for continuously monitoring quality-control 

data. These procedures are summarized in reports by Pritt and 

Raese (1995) and Friedman and Erdmann (1982).

STATUS OF AND CHANGES IN WATER 

QUALITY

Water Temperature

Temperature criteria for Idaho streams vary according 

to designated uses that have been adopted in Idaho Water 

Quality rules (http://www2.state.id.us/adm/adminrules/rules/

idapa58/0102.pdf). Data in this report were compared with 

criteria recommended for protection of coldwater aquatic 

life and seasonal coldwater aquatic life. Other Idaho stream 

criteria, such as those for protection of fish during spawning 

and rearing periods, were not considered because the effective 

locations and timing of the criteria vary, depending on presence and activities of specific communities to be protected.

Nearly 80 percent of network sites sometimes had temperatures exceeding criteria for coldwater aquatic life (daily 

mean and maximum temperatures not to exceed 19° and 22°C, 

respectively) (figure 3 and figure 4). At nearly 65 percent 

of sites, even the daily minimum temperatures sometimes 

exceeded both of these criteria. Because 12 of the 16 forested 

network sites had temperatures that exceed criteria, it is likely 

that such high temperatures in many streams occur naturally. 

The only sites where temperature did not exceed criteria were 

located in basin headwaters in mountainous and foothill terrain 

(sites 12, 26, 27, 44, 46, 47, and 56); downstream from large 

reservoirs (sites 8 and 34); and at springs discharging to the 

Snake River (sites 21 and 23).

In the Snake River, temperature exceeded coldwater 

criteria most frequently at middle and lower Snake River sites 

(sites 19, 20, 32, and 37). Temperature criteria exceedances 

at the lowest Snake River site (site 49) were less frequent than 

at upstream sites and may be a result of discharges from large, 

upstream reservoirs in Hells Canyon.

Temperatures in the North Fork Payette River downstream from Cascade Reservoir (site 40) and the Bruneau 

River (site 31) exceeded criteria most frequently among all 

the sites. Water-temperature variations at site 40 were small 

compared with those at most other sites, and although only 

25 percent of the measurements exceeded the maximum 

daily criterion (22°C), more than 75 percent of measurements 

exceeded the daily mean criterion (19°C). At site 31, where 

discharge from hot springs may affect the stream, more than 

75 percent of both maximum and mean daily temperatures 

exceeded criteria.

Although the effects of discharges from thermal springs 

on stream temperatures might not be readily apparent during 

periods when streams are naturally warm, the effects might be 

detected during cooler periods. For this reason, year-round 

collection of temperature data might benefit the network.

Sediment and Turbidity

Sediment has been identified as a pollutant of concern in more than 90 percent of Idaho streams identified as 

impaired, and is considered the State’s most extensive waterquality problem (Rowe and others, 2003). Most sediment in 

streams is fragmentary material that originates primarily from 

weathering of rocks. Sources to streams can be natural, such 

as resuspension of streambed materials during high flows 

or streambank collapse, or human-caused, such as erosion 

of soils that have been disturbed by construction, livestock 

grazing, crop cultivation, and other land uses. Certain contaminants such as trace elements and pesticides sometimes 

preferentially partition onto sediment; thus, their distribution 

throughout the watershed is controlled primarily by sediment 

transport, and their availability to biota is most significant 

in zones of sediment deposits. Movement and deposition of 

uncontaminated sediment also affects biota and the beneficial uses of streams by scouring, reducing light penetration, 

accumulating in low-velocity reaches where bottom-dwelling 

organisms may suffocate, reducing reservoir storage capacities, interfering with irrigation pumps, and esthetically degrading recreational waters.

Measurements made at network sites to address sediment 

transported in water were suspended-sediment concentrations 

(SSC) and turbidity, an optical, qualitative measure of water 

clarity. The only numeric, sediment-related criterion for Idaho 

streams is based on turbidity (http://www2.state.id.us/adm/

adminrules/rules/idapa58/0102.pdf). Note that SSC measurements cannot routinely be interchanged with the commonly 

used measurements of total suspended solids because of 

differences in sampling and analytical techniques (Gray and 
8 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

others, 2000). Turbidity can be measured by several different 

methods and technologies, and these variables can result in 

turbidity data that are not comparable between or within sites, 

even if the data are collected with calibrated instruments and 

reported in the same measurement units (Gray and Glysson, 

2003). In addition, other factors besides the amount of sediment in suspension (such as water color and phytoplankton) 

can significantly affect turbidity measurements.

SSCs were measured at the 56 network sites from 1989 

through 2002 (figure 1 and table 2). SSCs throughout the 

network ranged from less than 1 to 1,930 mg/L. Concentration distributions varied widely throughout the network, 

which suggests that normal conditions might be different 

for individual streams or groups of streams. The data for 

each site are summarized in figure 5.

At most sites in northern and central Idaho, at least 

75 percent of SSCs were less than 40 milligrams per liter 

(mg/L), and few concentrations exceeded 50 mg/L. These 

low concentrations probably are due to the resistant granitic 

rocks and coarse soils that develop from such rocks in the 

Northern Rocky Mountains province. Concentrations less 

than 40 mg/L were also common in southern Idaho. Some 

of the consistently lowest concentrations were measured in 

the middle Snake River upstream from Twin Falls (where 

reservoirs probably reduce the load of sediment in suspension) 

and near headwater springs.

Higher SSCs were measured at more sites in the Columbia Plateaus province of southern Idaho than in northern or 

central Idaho. In southeastern Idaho, at least 25 percent of 

the concentrations exceeded 80 mg/L at sites in the Portneuf 

River Basin (sites 15, 16, and 17); Bear River (site 53); Blackfoot River (site 13); and Rock Creek (site 22). In southwestern Idaho, at least 25 percent of the concentrations exceeded 

65 mg/L in the lower Snake River (sites 37 and 43), Boise 

River (sites 33 and 36), South Fork Payette River (site 38), and 

Weiser River (site 42). Natural basin characteristics, presence 

of loess and other fine-grained soils, and land use probably 

contribute to these high concentrations. Most of these sites are 

agricultural site types or Snake River sites located at or downstream from large areas of irrigated rowcrop agriculture.

Sediment concentrations usually were highest during 

some of the highest stream discharges. However, correlations 

between sediments and stream discharge were not particularly 

strong (all r2 less than 0.6).

Data from only two sites suggest patterns in SSCs over 

time. Data from the Pahsimeroi River (site 44) suggest that 

concentrations have decreased in the latter years of the network, whereas data from Camas Creek (site 25) suggest 

that concentrations have increased (figure 6). However, the 

increase in Camas Creek is due to high concentrations in 1997, 

the last year of data collection in an extreme high-flow year 

when SSCs may have been elevated naturally.

Correlations between SSCs and turbidity were generally 

poor (figure 7). Considering the variety of factors that can 

affect turbidity measurements, this is not surprising. Correlations between turbidity and suspended sediment for two sites 

representing the range of relations from poor (site 42) to relatively good (site 16) are shown in figure 8. As a result of poor 

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Figure 6. Suspended-sediment concentrations in relation to time at selected sites in the Idaho statewide surface-waterquality monitoring network (Locations of sites shown on figure 1)
Status of and Changes in Water Quality 9

correlations, the utility of turbidity as a surrogate measure 

of SSC needs to be determined on a site-by-site basis.

Idaho water-quality criteria require that turbidity shall 

not exceed background concentrations by more than 

50 nephelometric turbidity units (NTU) instantaneously 

or more than 25 NTU for more than 10 consecutive days 

(http://www2.state.id.us/adm/adminrules/rules/idapa58/0102.pdf). 

Because background concentrations are not known and only 

instantaneous measurements were made, exceedances of 

criteria could not be determined. However, background concentrations of turbidity are likely to be low (minimums never 

exceeded 3 NTU and the 25th percentile for any individual site 

never exceeded 8 NTU; figure 9). Network sites where turbidity exceeded 25 NTU (figure 10) indicate locations where 

the potential to exceed Idaho turbidity criteria may be greatest. 

Although turbidity exceeded 25 NTU at a variety of site types, 

nearly all the sites where turbidity exceeded 50 NTU are agricultural site types.

Dissolved Solids, Specific Conductance, and 

Hardness

Specific conductance (SC) is the ability of water to conduct electrical current, and it increases as the concentrations 

of ions dissolved in water increase. As a result, SC frequently 

is used to estimate concentrations of dissolved solids in water.

Geology and land use primarily control SC in streams, and 

values generally vary inversely with flow as a result of 

dilution from runoff.

SC at network sites ranged from 10 to 1,330 μS/cm, 

indicating a wide range of dissolved-solids concentrations 

across Idaho (figure 11). SC was commonly less than 

100 μS/cm at sites in northern Idaho and mountainous areas 

of central Idaho associated with argillites, quartzites, and granitic rocks (sites 3, 4, 6, 7, 33, 34, 38, 39, 40, 47, 51, 52, and 

56). Most of these are forested site types.

SC was commonly 100 to 400 μS/cm at 24 sites distributed widely across the network (sites 1, 2, 5, 10, 11, 13, 14, 

25, 27, 28, 29, 30, 31, 35, 41, 42, 43, 44, 45, 48, 49, 50, 54, 

and 55). These sites were located where the streams came into 

contact with various sedimentary and volcanic rocks, alluvial 

deposits, urban and suburban areas, and agricultural activities.

SC commonly exceeded 400 μS/cm in the middle and 

upper Snake River (sites 8, 18, 19, 20, 32, 37, and 57); its 

tributaries and springs (sites 12, 15, 16, 17, 21, 22, 23, 24, 26, 

and 36); the Lemhi River (site 46); and Bear River (site 53).

These sites are in areas likely to be affected by irrigated 

agriculture and(or) urban effluents.

The ratios of dissolved-solids concentration to SC 

(figure 12) ranged from 0.34 to 1.16, and most were within 

the 0.55 to 0.75 range that Hem (1992) reported for most 

waters. The median ratio for each site can be multiplied by 

SC measurements to yield reasonable estimates of dissolvedsolids concentrations. Estimates will be better for sites having 

small ratio variations than for those having wide variations.

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Figure 7. Turbidity in relation to suspended-sediment concentrations at all sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002
10 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

Ratios were largest and most variable at selected forested, 

rangeland, and agricultural site types. SC at many of these 

sites (sites 3, 4, 6, 7, 33, 38, 39, 40, 47, 51, 52, and 56), most 

being forested site types, was typically less than 100 μS/cm.

In such dilute waters, small variations and bias in laboratory 

analyses and SC measurements combined with rounding of 

analytical reports can significantly affect the variation and 

accuracy of ratios. At sites 11, 25, 31, 42, 48, and 50, SCs 

typically exceeded 100 μS/cm, and ratios of dissolved solids 

to SC commonly exceeded 0.70 and varied widely. The large 

ratios at these sites are probably the result of different dominant dissolved ions than those at sites where ratios are small.

Generally, SC at most sites was inversely correlated 

with stream discharge, and correlations at 14 sites (sites 6, 8, 

15, 27, 28, 33, 41, 42, 45, 47, 48, 54, 56, and 57) were fairly 

strong (r2 greater than 0.7). In contrast, correlations at other 

sites were poor (r2 from 0.7 to less than 0.1). Data for Silver 

Creek (site 29) suggest a weak positive correlation with stream 

discharge (r2 = 0.33). The variations in SC/stream-discharge 

correlations did not seem to be associated with any particular 

geology or land cover.

Hardness is a property of water caused by content of 

dissolved alkaline-earth cations and is expressed as equivalent 

weight of calcium carbonate (CaCO3). Because calcium and 

magnesium ions are the most common alkaline-earth cations 

in natural waters, hardness values are calculated from concentrations of these ions. Toxicity of many trace elements to 

aquatic organisms often is inversely related to hardness. As a 

result, this information is important for determining potential 

effects of trace elements on beneficial uses of streams, particularly in areas where mining and other activities contribute 

trace elements to streams. The relative contributions of calcium and magnesium to hardness also may affect toxicities of 

trace elements (Welsh and others, 2000) but are not currently 

considered in Idaho water-quality criteria.

The distribution of hardness concentrations across Idaho 

(figure 13) was similar to the distribution of SC. Concentrations generally exceeded 100 mg/L as CaCO3

 at sites in or 

downstream from basins or ground-water recharge zones 

where limestone and other carbonate rock deposits were present (Ross and Savage, 1967). These sites were: all sites on 

the Snake River (sites 8, 14, 18, 19, 20, 32, 37, 43, 49, 55, and 

57); all spring site types (sites 21, 23, and 29); selected tributaries to the Snake River (sites 10, 12, 13, 15, 16, 17, 22, 24, 

26, 30, and 36); the Wood River (site 28); the upper Salmon 

River drainage (sites 44, 45, and 46); Lapwai Creek (site 50); 

and Bear River (site 53). Concentrations were generally highest (most exceeding 200 mg/L as CaCO3

) at sites in the Twin 

Falls area (sites 20, 21, 22, 24, and 57); the Portneuf River 

drainage (sites 15, 16, and 17); the Bear River (site 53); and 

Beaver Creek (site 26).

Concentrations were generally less than 100 mg/L as 

CaCO3 at sites in areas without deposits of carbonate rocks 

(Ross and Savage, 1967). These sites were: most sites at and 

north of Potlach (sites 2, 3, 4, 5, 6, 7, 52, and 56); the South 

Fork Clearwater River (site 51); the lower Salmon River 

Figure 14. Hardness in relation to specific conductance at all sites in the Idaho statewide surface-water-quality monitoring 

network, 1989 – 2002

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Status of and Changes in Water Quality 11

drainage (sites 48 and 54); the Weiser River (site 42); the 

Payette River drainage (sites 38, 39, 40, and 41); the Boise 

River upstream from Parma (sites 33, 34, and 35); Johnson 

Creek (site 47); the Bruneau River (site 31); Henrys Fork (site 

11); Camas Creek (site 25); and the Big Lost River (site 27). 

Hardness concentrations were lowest (commonly less than 25 

mg/L as CaCO3) in the northern and central mountains of Idaho 

at sites on the Priest River (site 3); Spokane River and tributaries (sites 4, 6, 7, and 56); Palouse River (site 52); South Fork 

Clearwater River (site 51); and North Fork Payette River 

(sites 39 and 40). Many of these areas are rich in trace 

elements, and low hardness values provide minimal offset 

to the toxicity of these elements.

Hardness concentrations generally were directly correlated with SC (figure 14), possibly allowing hardness values 

to be reasonably estimated from a simple field measurement 

when laboratory analyses are not available. Similar correlations could be developed for individual sites to provide sitespecific estimates of hardness for evaluations of trace-element 

toxicities.

The ratio of calcium and magnesium that contributes to 

hardness has been reported to significantly affect toxicities of 

some trace elements to aquatic organisms (Welch and others, 

2000). Low ratios favor high trace-element toxicities. Molar 

ratios of calcium : magnesium across the network ranged from 

0.56 to 9.73, and median ratios at all sites except one exceeded 

1.3. Ratios were lowest at the Bear River (site 53), where 

values ranged from 0.56 to 1.36 and the median value was 1.0. 

Although these low ratios suggest that the current adjustments 

made to criteria may underestimate the true trace-element 

toxicities, hardness concentrations at this site were some of the 

highest in the network.

Dissolved Oxygen

Nearly all stream fauna depend on adequate dissolved 

oxygen (DO) in water, though different organisms have different minimum requirements. Fish, particularly salmon species, 

require some of the highest concentrations, and Idaho waterquality criteria are generally designed to accommodate these 

fish.

Major factors and processes affect DO in water:

• Atmospheric pressure. The amount of DO that water 

can hold is directly related to barometric pressure. As 

a result, the maximum DO concentration that water 

can hold (saturation) is lower at high elevations (where 

pressure is low) than at low elevations.

• Stream turbulence. Turbulence in stream riffles 

enhances the contact of stream water with the atmosphere, improving the diffusion of oxygen and other 

gasses between water and air. If DO concentrations 

are below saturation, oxygen will move into the water. 

If concentrations exceed saturation (supersaturation), 

oxygen will move out. Water spilling from high-head 

dams is an extreme form of turbulence that frequently 

results in supersaturation of oxygen and other gasses 

in streams that can persist for significant distances 

downstream.

• Photosynthesis by aquatic plants. Attached and 

suspended algae and other plants photosynthesize during daylight at a rate exceeding their respiration rate, 

which results in increased DO concentrations. Water 

enriched in nutrients can support abnormally large 

populations of aquatic plants that can, in turn, cause 

significant supersaturations of DO during daylight.

• Respiration by aquatic organisms. Plants and animals in streams deplete DO from water as they respire. 

Discharges of sewage and other types of organic pollution to streams can result in large populations of organisms that decompose the organic materials. Respiration by these large populations can significantly reduce 

DO in streams. Large populations of aquatic plants 

that cause supersaturations of DO during daylight can 

cause significant oxygen depletions at night as they 

continue to respire in the absence of photosynthesis.

• Water temperature. DO concentrations are inversely 

related to water temperature. Cold water accommodates higher concentrations than warm water accommodates. In addition, warm water increases metabolic 

rates of organisms, including those that decompose 

organic matter, and results in faster depletion of DO.

• Dissolved solids. Although the solubility of oxygen 

is inversely related to dissolved-solids concentrations, 

this factor is not significant for fresh water where 

dissolved-solids concentrations are small.

In Idaho, the DO criterion (Idaho Department of Environmental Quality, http://www2.state.id.us/adm/adminrules/rules/

idapa58/0102.pdf) for protection of coldwater aquatic organisms 

is a minimum of 6.0 mg/L for most streams. There can be 

additional criteria. For example, segments of streams supporting salmon spawning must maintain at least the greater of 

6.0 mg/L or 90 percent saturation during spawning seasons.

All saturation data in this report were based on onsite 

measurements of atmospheric pressure and water temperature 

made at the time that DO measurements were made. The DO 

data from network sites are presented in figure 15.

DO concentrations less than 6 mg/L are not common, but 

such concentrations were measured one time at the Kootenai 

River (site 1), South Fork Coeur d’Alene River (site 5), and 

North Fork Payette River (site 40); two times at Clark Fork 

River (site 2) and Snake River at Milner (site 19); and three 

times at Silver Creek (site 29). Because all of these concentrations were less than 70 percent of saturated conditions, it 

is likely that decomposition of organic loads contributed to 

the low DO concentrations measured in these streams. Most 

of these measurements were made from May through early 
12 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

September, when warm temperatures may have contributed 

to low DO concentrations. However, the measurement on the 

Kootenai River was made in early April at cold temperatures 

with no ice cover on the river and would have supported DO 

concentrations nearly 3.7 times higher.

Because measurements at sites in this network always are 

made during daylight, the lowest DO concentrations probably 

were not measured. Sites where large supersaturations of DO 

were measured may have large phytoplankton and periphyton 

communities that could have depleted DO by respiration at 

night. All measurements of DO that exceeded 170 percent 

saturation were made during the summers of 1991, 1993, and 

1994 in eastern Idaho at the Blackfoot River (site 13), Marsh 

Creek (site 16), the Portneuf River (site 17), and the Snake 

River near Shelley (site 55). These sites probably would be 

good candidates for more intensive DO monitoring, such as 

diel measurements (measurements made throughout a 24-hour 

period) during warm periods, to determine whether minimum 

concentrations are met throughout the day.

During the summer, temperatures of many Idaho streams 

can exceed 25°C. At such high temperatures, even saturated 

DO concentrations may be near the 6 mg/L criterion. Only 

small amounts of natural or human-caused organic loading 

might result in concentrations that fall below the criterion 

under these summer conditions.

Data suggest decreasing concentrations and saturation 

of DO over time at the Snake River at Milner (site 19), Silver 

Creek (site 29), Lapwai Creek (site 50), and the Bear River 

(site 53) (figure 16). All these sites are agricultural site types 

or large-river and spring site types where agricultural land 

composes more than 20 percent of the land cover. Although 

specific causes of DO reduction are not known, it is likely 

that land-use changes and(or) population growth in each 

basin might be major factors. All these sites were sampled on 

only 2- or 3-year cycles, and more frequently collected data 

probably will be necessary to verify whether the patterns are 

real and to determine when continued DO reductions might 

significantly affect the aquatic communities.

pH

Most network pH values (figure 17) were within the 

6.5 – 9.0 range specified to protect aquatic organisms in 

Idaho streams (Idaho Department of Environmental Quality, 

http://www2.state.id.us/adm/adminrules/rules/idapa58/0102.pdf). 

pH values in at least one sample equaled or exceeded 9.0 at 

sites on the Snake River (sites 19, 32, 37, 43, 55, and 57); 

Camas Creek (site 25); the Lemhi River (site 46); the Blackfoot River (site 13); the Malad River (site 30); the Boise 

River (site 36); North Fork Payette River (site 40); and the 

Lapwai Creek (site 50). Sites where pH values were consistently higher than at other sites were on the lower Snake River 

(sites 32, 37, and 43), where 90 percent of pH measurements 

equaled or exceeded 8.4. Except for the Lemhi River site, all 

of these are agricultural site types or large-river and rangeland 

site types where agricultural land composes at least 16.2 percent of the land cover. Although the Lemhi River is a rangeland site type and agricultural land composes only 8.6 percent 

of the land cover, agriculture is concentrated in the alluvial 

river bottom and uses an extensive system of diversions and 

returns of river water (Donato, 1998).

All these sites are located in basins where carbonate 

deposits are common (Ross and Savage, 1967). The high 

pH values are probably a result of the combination of highcarbonate water and photosynthetic activity by large algal 

communities. DO concentrations as high as 118 to 212 percent of saturated conditions are additional evidence that algal 

communities are highly active at all of these sites. In addition 

to adequate nutrient concentrations, physical conditions such 

as velocity of streamflow, light penetration, warm temperature, 

and depth of water can enhance photosynthesis of phytoplankton and periphyton that favor high pH.

pH values in at least one sample were less than 6.5 at 

sites on the North Fork Coeur d’Alene River (site 4), South 

Fork Coeur d’Alene River (site 5), Palouse River (site 52), 

North Fork Payette River (site 39), and Boise River below 

Diversion Dam (site 34). Values of pH were consistently 

lower on the Spokane River (site 7) and sites 4, 5, 39, and 52 

than at other sites. These sites are not located in basins with 

significant amounts of limestone or other carbonate deposits (Ross and Savage, 1967). Specific conductance at all of 

these sites except site 5 was generally less than 100 μS/cm, 

which suggests that water in these streams is naturally poorly 

buffered against pH reduction. The South Fork Coeur d’Alene 

River has been affected by extensive mining activities for 

many years, but it is not known if these activities might have 

caused any of the low pH measurements made at site 5.

Data suggest decreasing pH over time at the Snake 

River at Milner (site 19), Big Wood River (site 28), Silver 

Creek (site 29), and the Snake River near Anatone (site 49) 

(figure 18). At two of these sites (19 and 29), the decreases 

in pH are accompanied by possible decreasing concentrations 

of DO, total phosphorus, and(or) nitrogen, which suggests that 

primary production by algal communities may be decreasing 

at these sites.

Nutrients

Phosphorus and nitrogen are two major nutrients essential 

to aquatic plant growth, and high concentrations in water can 

cause excessive amounts of plant growth that can seriously 

limit beneficial uses of streams. High concentrations commonly are caused by sewage disposal, urban runoff, agricultural activities, and some industrial activities. Adequate 

amounts of both of these nutrients must be present to support 

nuisance plant growth. If one is present in high concentrations while concentrations of the other are too low to support 

growth, the low-concentration nutrient is called the “limiting” 

nutrient. Dissolved inorganic forms of nitrogen (ammonia, 

nitrite, and nitrate) and phosphorus (orthophosphate) are the 
Status of and Changes in Water Quality 13

most readily usable forms for most plants. However, organic 

and suspended forms are naturally cycled into dissolved inorganic forms, so total nutrient concentrations are of ultimate 

concern.

Ammonia is a form of nitrogen that can be toxic to 

aquatic organisms. It can enter natural water systems from 

several sources, including discharge of industrial wastes 

and sewage effluents, runoff from agricultural fields where 

commercial fertilizers and animal manure are applied, and 

degradation of nitrogenous organic matter carried in streams. 

Laboratory analyses of total dissolved ammonia measure 

both ammonium ions (NH4

+

) and un-ionized ammonia (NH3). 

The latter is the more toxic form, and concentrations vary as 

temperature, pH, and concentrations of dissolved ammonia 

vary. High pH and temperature favor higher proportions of 

NH3.

NITROGEN

Total nitrogen concentrations ranged from less than 

0.001 to 7.3 mg/L and commonly exceeded 0.5 mg/L 

across the network (figure 19). Concentrations equaled or 

exceeded 0.99 mg/L in more than 25 percent of the samples 

from sites on the middle and lower Snake River (sites 20, 

32, 37, 43, 49, and 57); spring site types on the Snake River 

Plain (sites 21, 23, and 29); the Portneuf River drainage 

(sites 15, 16, and 17); Rock Creek (site 22); Salmon Falls 

Creek (site 24); the Boise River at Parma (site 36); the Bear 

River (site 53); and the Lapwai Creek (site 50). Nearly 

all these sites are agricultural site types or large-river or 

spring site types in areas of significant agricultural land use. 

Concentrations were generally highest at springs and stream 

sites near Twin Falls (sites 21, 22, and 24) and the Boise 

River (site 36), exceeding 2.0 mg/L in more than 50 percent 

of the samples.

At almost half of the network sites, inorganic nitrogen concentrations in more than 25 percent of the samples 

exceeded 0.3 mg/L (figure 20), a concentration considered 

critical for supporting algal production when adequate phosphorus is present (Mackenthun, 1969). These sites were: 

all sites listed in the previous paragraph, the Snake River at 

Milner (site 19), the Teton River (site 10), the Malad River 

(site 30), the Boise River at Glenwood Bridge (site 35), 

the Payette River (site 41), Willow Creek (site 12), the 

Pahsimeroi River (site 44), and the South Fork Coeur d’Alene 

River (site 5).

Dissolved ammonia concentrations were generally well 

below 0.07 mg/L at most sites. Exceptions were sites 5, 12, 

16, 22, 53, and 57. Calculations presented in the Idaho Administrative Code (Idaho Department of Environmental Quality, 

http://www2.state.id.us/adm/adminrules/rules/idapa58/0102.pdf) 

were performed on all ammonia data to determine if concentrations exceeded Idaho criteria. No concentrations exceeded 

Idaho’s acute or chronic toxicity criteria for aquatic biota at 

ambient temperatures and pH.

Depending on sources of nitrogen and activities of 

biological communities, the forms of nitrogen can be quite 

variable at sites, sometimes over short periods of time. Nonetheless, some forms of nitrogen were prevalent at some sites 

(figure 19). At about 50 percent of the network sites, organic 

and(or) particulate forms composed more than half of the 

nitrogen in more than 75 percent of the samples. Many of 

these samples were from sites where nitrogen concentrations 

were low and from sites in the upper Snake River Basin. At 

about 25 percent of the network sites, inorganic forms composed more than half of the nitrogen in more than 75 percent 

of the samples. These samples were from spring site types, 

tributaries, and large-river sites in the middle and upper Snake 

River Basin. No consistently prevalent form of nitrogen was 

associated with any individual site type or area of Idaho.

Data suggest possible patterns in total nitrogen over time 

at several sites (figure 21). Data from agricultural site types 

(sites 10, 16, and 17) and two sites associated with irrigated 

agriculture in the middle Snake River and tributaries (sites 19 

and 24), Silver Creek (site 29), and Bear River (site 53) suggest

decreasing concentrations. Data from Rock Creek (site 22), 

also an agricultural site type, suggest increasing concentrations 

in total nitrogen.

Few sites suggest correlations (r2 greater than 0.75) 

between stream discharge and nitrogen concentrations. 

Although sites 39 and 52 showed a correlation, only one 

measurement at each site was made during a relatively high 

flow; more data during high flows would be needed to support 

a high-confidence correlation.

There were no strong correlations between SSCs and 

nitrogen or between turbidity and nitrogen at any network 

sites.

PHOSPHORUS

Concentrations of total phosphorus ranged from less than 

0.001 to 1.3 mg/L. Concentrations exceeding 0.1 mg/L are 

considered able to support nuisance levels of algal production 

in flowing waters (Mackenthun, 1969; U.S. Environmental 

Protection Agency, 1986). Phosphorus in more than 25 percent of the samples from sites 16, 17, 19, 20, 22, 30, 35, 36, 

37, 42, 43, 50, 53, and 57 equaled or exceeded this concentration (figure 22). All of these sites are agricultural site types, 

Snake River sites in areas of significant agricultural land use, 

or sites downstream from Boise. Concentrations were consistently highest at the Boise River near Parma (site 36), where 

total phosphorus exceeded 0.2 mg/L in more than 75 percent 

of the samples and exceeded 0.4 mg/L in more than 25 percent 

of the samples. In contrast, some of the lowest total phosphorus concentrations were from the three spring sites (sites 21, 

23, and 29), also located in areas of significant agricultural 

land use. This may reflect the fact that phosphorus is not 

readily transported in ground water due to sorption and 

precipitation reactions.

Depending on sources of phosphorus and activities of 

biological communities, the forms of phosphorus can be 
14 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

quite variable at sites, sometimes over short periods of time. 

Nonetheless, some forms of phosphorus were prevalent 

at some network sites (figure 22). At about 13 percent of 

the sites, organic and(or) particulate forms composed more 

than half of the phosphorus in more than 75 percent of the 

samples. These samples were from the South Fork Coeur 

d’Alene River (site 5); Palouse River (site 52); the middle to 

lower Snake River (sites 32, 37, and 43); Blackfoot River (13); 

and Bear River (site 53). At about 23 percent of the sites, 

orthophosphate composed more than half of the phosphorus 

in more than 75 percent of the samples. These samples were 

from the lowest Snake River site (site 49); Lapwai Creek 

(site 50); Boise River (sites 35 and 36); spring site types in 

south-central Idaho (sites 21, 23, and 29); upper reaches of the 

Salmon River Basin (sites 44 and 46); Kootenai River (site 1); 

Johnson Creek (site 47); Beaver Creek (site 26); and Willow 

Creek (site 12). No consistently prevalent form of phosphorus 

was apparent at any individual site type or area of Idaho.

Data suggest a possible decreasing total phosphorus 

concentration over time at the Snake River near Kimberly 

(site 20) and possible increasing concentrations at Salmon 

Falls Creek (site 24) and Bear River (site 53) (figure 23). All 

these sites are affected by agricultural activities, and trends 

might reflect changes in the amount of agricultural land use or 

land-management practices employed.

Only site 50 showed a correlation (r2 greater than 

0.75) between stream discharge and total phosphorus concentrations. Although site 50 showed a correlation, only one 

measurement was made during high flow; more data during 

high flows would be needed to support a high-confidence 

correlation. Donato (2004) examined the relation between 

phosphorus and stream discharge at sites 34, 35, and 36 in 

greater detail to estimate phosphorus loads transported in the 

lower Boise River.

Five sites (sites 4, 31, 49, 50, and 54) showed correlations 

(r2 greater than 0.75) between SSCs and phosphorus concentrations.

REFERENCE SITES

Some network sites may be good indicators of naturally 

occurring (background) nutrient concentrations that may be 

useful for assessing nutrient impacts on other streams. Total 

nitrogen concentrations at 15 sites (sites 1, 2, 3, 4, 6, 7, 27, 38, 

39, 45, 47, 48, 51, 54, and 56) and total phosphorus concentrations at 21 sites (sites 1, 2, 3, 4, 6, 7, 8, 10, 21, 23, 27, 29, 33, 

38, 39, 47, 48, 51, 54, 55, and 56) were less than or similar to 

those summarized by Clark and others (2000) for relatively 

undeveloped basins in the United States. Most of the Idaho 

sites where nutrient concentrations were low are forested site 

types.

Seven of these sites were chosen as “reference” sites on 

the basis of low concentrations of both nitrogen and phosphorus, minimal land development, and location. Three of the 

sites are on the North Fork Coeur d’Alene and St. Joe River 

(sites 4, 6, and 56) in northern Idaho, where median nitrogen 

and phosphorus concentrations were less than 0.14 and 

0.01 mg/L, respectively. Two sites are on the South Fork 

Payette River and Johnson Creek (sites 38 and 47) in central 

Idaho, where median nitrogen and phosphorus concentrations 

were 0.19 and 0.01 mg/L, respectively. The site on the Big 

Lost River (site 27) in central Idaho represents a rangeland site 

type where median nitrogen and phosphorus concentrations 

were less than 0.25 and 0.01 mg/L, respectively. The site on 

the Salmon River near White Bird (site 54) in north-central 

Idaho is unique because it is a large-river site type where 

median nitrogen and phosphorus concentrations were less than 

0.25 and 0.02 mg/L, respectively.

The U.S. Environmental Protection Agency (USEPA) 

recommends two methods for determining background nutrient concentrations (U.S. Environmental Protection Agency, 

2000a). One method uses the 25th percentile of all data from 

a nutrient ecoregion. The other uses the 75th percentile of all 

data from a selected reference site. Comparisons between 

nutrient concentrations at the reference sites and background 

concentrations calculated from network data for two nutrient 

ecoregions, the Western Forested Mountains and the Xeric 

West (figure 1), using USEPA’s 25th percentile method are 

Table 4. Total nitrogen and phosphorus concentrations at proposed reference sites in the Idaho 

statewide surface-water-quality monitoring network in relation to nutrient criteria recommended for, and 

background concentrations modeled for, two nutrient ecoregions

[mg/L, milligrams per liter; USEPA, U.S. Environmental Protection Agency]

Constituent

Ecoregion II - 

Western Forested Mountains

Ecoregion III - 

Xeric West

Idaho 

network 

data

USEPA 

criteria 

(2000b)

Modeled by

Smith and others

(2003)

Idaho 

network 

data

USEPA 

criteria 

(2000c)

Modeled by

Smith and others

(2003)

Total nitrogen (mg/L) 0.12 0.12 0.21 0.4 0.38 0.11

Total phosphorus (mg/L) 0.008 0.01 0.02 0.023 0.021 0.03
Status of and Changes in Water Quality 15

Table 5. Idaho criteria for selected dissolved trace elements in water

[Hardness concentrations in milligrams per liter as calcium carbonate; trace-element concentrations in micrograms per liter; CMC, criterion

maximum concentration; CCC, criterion continuous concentration; criteria from Idaho Department of Environmental Quality, http://www2.state.

id.us/adm/adminrules/rules/ idapa58/0102.pdf; HCwater+orgs, human consumption of water and organisms; HCorgs, human consumption of organisms only]

Hardness

Cadmium Copper Lead Selenium Zinc Mercury

CMC CCC CMC CCC CMC CCC CMC CCC CMC CCC CMC CCC HCwater+orgs HCorgs

25 0.78 0.35 4.6 3.4 11 0.43 18 5 35 32 2.1 0.012 0.14 0.15

50 1.7 0.6 8.9 6.3 27 1 18 5 64 58 2.1 0.012 0.14 0.15

100 3.7 1 17 11 65 2.5 18 5 114 105 2.1 0.012 0.14 0.15

200 8.1 1.8 33 21 156 6 18 5 206 188 2.1 0.012 0.14 0.15

shown in figure 24. On the basis of USEPA assumptions, 

the 75th percentile of all data from the reference sites will 

be similar to the 25th percentile of all data from the nutrient 

ecoregion. The background concentrations calculated using 

Idaho network data compared well with USEPA criteria (U.S. 

Environmental Protection Agency, 2000b and 2000c) (table 4).

In contrast, for both the network calculations and USEPA criteria, total phosphorus concentrations were lower than concentrations modeled by Smith and others (2003) in both nutrient 

ecoregions, and total nitrogen concentrations were lower than 

modeled concentrations in the Western Forested Mountains 

ecoregion but were higher in the Xeric West ecoregion.

For the Xeric West site (site 27), nearly all total nitrogen 

concentrations were lower than the 25th percentile of all nutrient ecoregion concentrations. Slightly fewer than 75 percent 

of total phosphorus concentrations at this site were lower than 

the 25th percentile of all nutrient ecoregion concentrations.

For the northern Idaho sites in the Western Forested 

Mountains nutrient ecoregion, about 75 percent of total nitrogen concentrations at sites 4 and 56 and about 50 percent at 

site 6 were lower than the 25th percentile of all nutrient 

ecoregion concentrations. About 50 percent of total phosphorus concentrations at all three sites were lower than the 25th

percentile of all nutrient ecoregion concentrations. This suggests that sites 4 and 56 might be the best choices as reference 

sites in northern Idaho.

For the central Idaho streams (sites 38 and 47) and largeriver site (site 54) in the Western Forested Mountains nutrient 

ecoregion, fewer than 25 percent of both total nitrogen and 

phosphorus concentrations were lower than the 25th percentile 

of all nutrient ecoregion concentrations. If the concentrations 

at these sites are not a result of low-level contamination, they 

might be better estimates of background nutrient concentrations specifically for central Idaho and large-river site types.

Small analytical variations can affect these background 

concentrations. For several sites in figure 24, the difference 

between the 75th percentile concentration and the background 

concentration is less than one analytical detection limit. 

These calculated background concentrations may not represent historical background concentrations. For example, 

atmospheric nutrient contributions to streams may be higher 

than in the past (Smith and others, 2003), or instream contributions from anadromous fish may be lower (Thomas and 

others, 2003).

Trace Elements

Trace-element concentrations in water at network sites 

were measured from 1989 through 1995 and, in fish tissue, 

from 1996 through 2002. Variations in trace-element sources, 

water chemistry, and flow conditions can affect solubility and 

amounts of trace elements delivered to streams. As a result, 

trace-element concentrations in water can be variable, and 

more frequent sampling than done for this network would 

be required to adequately characterize all streams. Because 

aquatic organisms and bottom sediments are continuously 

exposed to the stream water, accumulations of trace elements 

in organism tissues and on sediments can sometimes help to 

better define where impacts of trace elements are the greatest.

Trace elements analyzed for network sites were aluminum, arsenic, barium, beryllium, cadmium, chromium, cobalt, 

copper, iron, lead, lithium, manganese, mercury, molybdenum, 

nickel, selenium, silver, strontium, vanadium, and zinc. However, only those constituents related to water-quality issues 

that are currently priorities to IDEQ — cadmium, copper, lead, 

mercury, selenium, and zinc — are addressed in this report 

(Don Essig, oral commun., 2004).

WATER

Many of the trace elements were not routinely detected 

at many sites (appendix A). In general, concentrations of dissolved cadmium, copper, lead, and zinc were highest at sites 

in northern Idaho, although some copper and zinc concentrations were elevated at Snake River sites and spring site types 

in southern Idaho. Mercury concentrations were highest at 

sites in southern Idaho. Selenium concentrations had a narrow 

range and were not high at any site.
16 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

Idaho criteria for trace elements consider concentration,

duration, and frequency of exposure (http://www2.state.id.us/

adm/adminrules/rules/idapa58/0102.pdf). Criteria maximum 

concentrations (CMC) are not to exceed 1-hour average 

concentrations more than once in 3 years. Criteria continuous 

concentrations (CCC) are not to exceed 4-day average concentrations more than once in 3 years. To determine whether 

trace-element concentrations in network streams could pose 

a risk of toxicity to some aquatic organisms, network data 

were compared with Idaho water-quality criteria concentrations without considering duration or frequency of occurrence. 

For cadmium, copper, lead, and zinc, the criteria were based 

on hardness values of 25, 50, 100, or 200 mg/L as CaCO3

(table 5), whichever value was below and closest to the lowest 

hardness value measured at each site. The lowest hardness 

value assigned was 25 mg/L as CaCO3, as required by Idaho 

water-quality criteria (http://www2.state.id.us/adm/adminrules/

rules/idapa58/0102.pdf).

Concentrations of all the trace elements except selenium 

exceeded criteria at some network sites. The most common 

areas where concentrations exceeded criteria were northern 

Idaho; the Snake River and tributaries upstream from American Falls Reservoir; and the Salmon, Weiser, Payette, and 

Boise Rivers. The naturally mineral-rich geology and(or) 

mining activities in these basins may contribute to the high 

trace-element concentrations. In addition, the extremely low 

hardness concentrations in many northern Idaho streams result 

in higher sensitivity of some aquatic organisms to selected 

trace elements and corresponding lower criteria values. At 

several of these northern Idaho sites, particularly those in the 

Coeur d’Alene River Basin, some trace-element concentrations in more than 25 percent of the samples exceeded Idaho 

criteria. Sites where one or more concentrations exceeded 

Idaho criteria are summarized in table 6 and figure 25.

Concentrations of cadmium, copper, and lead exceeded 

criteria at the spring site types (sites 21, 23, and 29). It is not 

known whether the presence of these trace elements reflects 

land-use activities or the geology of the aquifers that support 

the springs.

Although mercury was detected in only 25 of 536 samples analyzed, concentrations at 18 of the 25 sites exceeded 

CCCs and human-consumption criteria. These criteria were 

below or nearly the same as analytical reporting levels. As a 

result, only concentrations that were reported above the minimum reporting level are known to exceed these criteria. It is 

probable that lower laboratory reporting levels would show a 

greater frequency of criteria exceedances. In addition to natural geology, mining, and other land-use activities, atmospheric 

deposition also might contribute to mercury in these streams.

FISH TISSUE

Since the network was changed in 1996, tissue samples 

from trout, catfish, and(or) suckers have been collected and 

analyzed for trace elements at only 15 of the 56 network sites. 

More than one sample was collected at some sites, and liver 

was the most common tissue analyzed. Fourteen liver samples 

from fish at 10 of the 15 sites, additional fillet samples from 

fish at 4 of the 10 sites, and whole-body samples from fish at 

the remaining 5 sites were analyzed. Sites where fish were 

collected and types of tissue analyzed are shown in table 7.

Probability plots of selected trace-element concentrations in fish-liver samples were used to identify sites where 

concentrations were enriched (Helsel and Hirsch, 1991; Hardy, 

1984). Concentrations that plotted on or near a straight line 

were considered to be from a single statistical population having background concentrations. Concentrations that plotted 

above those on the background line were considered enriched 

concentrations that belonged to a different statistical population. Plots of the six trace elements examined for this report 

are shown in figure 26. On the basis of these plots, cadmium, 

copper, lead, and zinc concentrations that exceeded 5, 75, 2, 

and 200 μg/g, respectively, appeared to be enriched. Both 

background and enriched concentrations of trace elements 

were identified in trout and sucker tissues, which suggests that 

combining data from different fish species might not seriously 

bias comparisons.

Sites where samples of fish livers contained enriched 

trace-element concentrations are shown in figure 27. Sites 

where any fillet or whole-body samples contained enriched 

concentrations also are identified on this figure. Enriched 

concentrations of cadmium, lead, and(or) zinc were most common in northern Idaho in the Spokane River Basin (sites 4, 5, 

6, and 7). Zinc also was enriched in whole-body samples of 

Sites in the Idaho statewide surface-water-quality 

monitoring network where fish tissue was analyzed for selected 

trace elements, 1996 – 2000

[Locations of sites shown on figure 1]

Site No. Liver Fillet Whole body

3 X

4 X X

5 X X

6 X X

7 X

11 X

14 X

17 X

22 X

33 X

36 X

37 X X

54 X

56 X

57 X

Table 7.
Status of and Changes in Water Quality 17

fish from the Portneuf River (site 17). These trace elements 

typically were not enriched in samples of fish fillets, except 

for those of fish collected from the South Fork Coeur d’Alene 

River (site 5).

Mercury concentrations in several fish-liver samples 

exceeded 0.3 μg/g, the maximum concentration for edible fish 

tissue recommended by USEPA (U.S. Environmental Protection Agency, 2002), and probability plots (figure 26) suggest 

that background concentrations of mercury may exceed this 

criterion. Because mercury preferentially concentrates in 

muscle tissue (Goldstein and others, 1996), such high concentrations in livers suggest that concentrations in edible 

tissues might be at least as high. However, sites 4, 5, and 6 

are examples of sites where concentrations in fish fillets were 

lower than those in livers. High mercury concentrations in fillets of fish from the Snake River at Nyssa (0.9 μg/g at site 37) 

and in whole-body fish from the Snake River near Blackfoot 

(1.0 μg/g at site 14) further suggest that mercury concentrations exceeding edible-tissue criteria might not be unusual in 

Idaho. Additional study of fillet samples from fish collected 

across Idaho is needed to verify that background mercury concentrations might exceed the edible fish tissue criteria.

A comparison between trace-element concentrations 

in fish tissue and concentrations in water (table 8) indicates 

seven sites where concentrations were enriched in fish tissue 

but did not exceed maximum criteria for water. This is not 

surprising, given that trace-element concentrations in water 

can be quite variable and difficult to represent by routine 

monitoring. However, there were 22 sites where concentrations may have exceeded criteria for water but were not 

enriched in fish tissue. This inconsistency suggests that 

fish-tissue data were not a good indicator of enrichment for 

streams where concentrations of dissolved trace elements 

were sometimes high. Part of the problem might be that the 

water and tissue data were collected during different years. In 

addition, fish are mobile and are likely to have been exposed 

to a wider range of environments than the one where they were 

collected. This presents a dilemma for water-quality monitoring. If the purpose of the data is to address impacts to fish 

or consumers of fish, direct analyses of fish-tissue samples 

are probably most appropriate. If the purpose of the data is 

to identify streams that may be subject to impacts from trace 

elements, a less mobile media (such as a selected size fraction 

of bottom sediments or low-mobility aquatic insects) might be 

most appropriate.

Organic Compounds in Fish Tissue

Many synthetic organic compounds that have significant 

implications for the environment have low solubility in water. 

As a result, they often preferentially partition into organisms 

and other organic material in streams. Analyses of wholeTable 8. Sites in the Idaho statewide surface-water-quality monitoring network where concentrations of selected trace elements 

exceeded criteria for water or were enriched in fish tissue, 1989-2000

[Locations of sites shown on figure 1; CMC, criterion maximum concentration; CCC, criterion continuous concentration; criteria from Idaho Department 

of Environmental Quality, http://www2.state.id.us/adm/adminrules/rules/idapa58/0102.pdf; #, trace element enriched in fillet or whole-body samples]

Site 

No.

Cadmium Copper Lead Mercury Zinc

CMC or CCC

exceeded

Enriched

in fish

CMC or CCC

exceeded

Enriched

in fish

CMC or CCC

exceeded

Enriched

in fish

CMC or CCC

exceeded

Enriched

in fish

CMC or CCC

exceeded

Enriched

in fish

3 X X X

4 X X X X X X X

5 X X X X X X X X X

6 X X X X

7 X X X X X

11 X X

14 # X X # X

17 # #

22 X

33 X X

36 X X

37 #

54 X X X X

56 X X

57
18 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

body fish for content of 28 organic compounds began in 1996 

to help define where fauna are accumulating these contaminants. So far, only 15 sites have been sampled. Compounds 

analyzed were:

Only four compounds or groups of compounds were 

detected above analytical reporting limits: PCBs and the pesticides dieldrin, nonachlor, and DDT and its metabolites (DDD 

and DDE). One or more of these compounds were detected 

in fish from all 15 sites sampled, and the greatest number of 

compounds was detected in fish from the Boise River (site 36). 

The most commonly detected compounds were PCBs, DDT, 

and DDT metabolites.

Many of the organic compounds analyzed preferentially 

accumulate in fatty tissues. For comparisons among sites, data 

were normalized by calculating the ratios of compound and 

lipid concentrations (table 9). Concentrations of DDT and 

metabolites were added and evaluated as “total DDT.” These 

data are summarized in figure 28.

Ratios of PCBs to lipids were highest in samples from 

the Priest River (site 3); the Spokane River Basin (sites 4, 5, 

and 7); and the Portneuf River (site 17). High ratios at these 

sites may be the result of industrial and urban activities in 

those basins. Ratios of pesticides to lipids were highest in 

samples from the Salmon River (site 54); the Snake River 

(sites 14, 37, and 57); Henrys Fork (site 11); the Boise River 

(sites 33 and 36); Rock Creek (site 22); and the Portneuf River 

(site 17). High ratios at these sites may be the result of urban 

and agricultural activities in those basins. The wide-scale 

presence of DDT and its metabolites and PCBs reflects both 

the persistence and wide-scale use of these compounds before 

being banned from use in the United States in the 1970s. Use 

of nonachlor and dieldrin have been banned since the 1980s.

Fecal Coliform Bacteria

At the beginning of network monitoring, fecal coliform 

bacteria (FC) routinely were monitored as indicators of water 

contamination by humans and other warmblooded animals. 

Analysis for this organism was adopted by the network and 

has continued for the sake of consistency. In addition, a relatively simple procedure and limited equipment were required 

for onsite analyses of FC that were needed to accommodate 

remote network sites. However, current Idaho microbiological 

water-quality requirements have replaced FC with Escherichia 

coli (E. coli) criteria. Although E. coli is part of the FC group 

of bacteria, E. coli is more strongly correlated with swimmers’ gastrointestinal illness than FC is (Dufour, 1984). In 

the future, if the network can accommodate the necessary 

equipment and procedures, replacing FC with E. coli analyses 

(with a period of replicate E. coli and FC analyses) would be a 

benefit for monitoring statewide water quality.

E. coli and FC populations are often strongly correlated. 

Studies in Ohio report E. coli : FC ratios from 0.72 to 0.89 (Francy

and others, 1993). Problems with agar selectivity that, for 

example, allows nonfecal coliform bacteria to grow could 

result in ratios higher than 1 (Dufour, 1984). Because E. coli

and FC are frequently correlated, FC data for this study were 

compared with Idaho single-sample criteria for E. coli (526 

and 406 colonies/100 mL for secondary- and primarycontact recreation, respectively (http://www2.state.id.us/adm/

adminrules/rules/idapa58/0102.pdf), as a conservative indicator 

of network sites where bacterial problems may exist and may 

warrant further investigation.

FC populations ranged from 0 to 4,770 colonies/100 mL 

and sometimes exceeded E. coli criteria at agricultural site 

types and agriculture-affected large-river site types in the

Portneuf River Basin (sites 15, 16, and 17); Blackfoot River 

(site 13); Bear River (site 53); Bruneau River (site 31); 

Payette River (site 41); Weiser River (site 42); Lapwai Creek 

(site 50); Palouse River (site 52); and lower Snake River (sites 

37 and 43) (figure 29). FC populations also exceeded E. coli

criteria at rangeland site types in the upper Snake River Basin 

(sites 25 and 26) and upper Salmon River Basin (sites 44 and 

46); agricultural and rangeland site types in tributaries to the 

middle Snake River (sites 22, 24, and 30); and agricultural, 

rangeland, and forested site types in the lower Boise River 

(sites 34, 35, and 36). The number of samples that exceeded 

criteria was greatest at the Boise River near Parma (site 36) 

and Lapwai Creek (site 50). Populations in more than 25 percent of the samples from these sites exceeded both primaryand secondary-contact criteria.

Aldrin cis-Chlordane

trans-Chlordane DCPA

o,p’-DDD p,p’-DDD

o,p’-DDE p,p’-DDE

o,p’-DDT p,p’-DDT

Dieldrin Endrin

alpha-HCH beta-HCH

delta-HCH Heptachlor

Heptachlor epoxide Hexachlorobenzene

Lindane o,p’-Methoxychlor

p,p’-Methoxychlor Mirex

cis-Nonachlor trans-Nonachlor

Oxychlordane PCBs

Pentachloroanisole Toxaphene
Summary and Conclusions 19

Table 9. Concentrations of selected organic compounds and ratios of concentrations to lipid content in whole-body samples of 

fish from sites in the Idaho statewide surface-water-quality monitoring network, 1996 – 99

[Locations of sites shown on figure 1; concentrations in micrograms per kilogram; %, percent]

Site 

No.

Lipids 

%

Dieldrin

Dieldrin: 

Lipid o,p’DDD o,p’DDE p,p’DDD p,p’DDE p,p’DDT

Total 

DDT

Total 

DDT: 

Lipid PCBs

PCBs:

Lipid

Nonachlor

Nonachlor:

Lipid

3 3.4 11 11 3.2 60 17.6

4 9.4 150 16.0

5 7.1 14 14 2.0 310 43.7

5 11 9 9 0.8 200 18.2

6 3.9 10 10 2.6

7 3 11 11 3.7 270 90.0

11 13 16 290 17 323 24.8 50 3.8

14 16 17 250 13 280 17.5 60 3.8

17 4.2 47 13 60 14.3 240 57.1 6 1.43

22 5.3 16 650 38 704 132.8 50 9.4

22 9.2 5 0.54 8 68 6 82 8.9 60 6.5

33 3 5 79 14 98 32.7

36 22 14 0.64 6 52 770 60 888 40.4 100 4.5 13 0.59

37 10 5 0.50 9 24 510 50 593 59.3

54 5.5 5 0.91 33 6 39 7.1

56 8.9

56 5.8 5 5 0.9

57 6.4 17 470 11 498 77.8 5 0.78

Although FC populations sometimes were highest when 

suspended-sediment concentrations were highest, correlations 

of FC with both suspended sediment and stream discharge 

were generally poor. Data suggest no obvious patterns in FC 

populations over time.

SUMMARY AND CONCLUSIONS

The Idaho statewide surface-water-quality network was 

implemented in 1989 by the U.S. Geological Survey, in cooperation with the Idaho Department of Environmental Quality, 

to provide water-quality managers with data to document 

status and changes in the quality of Idaho streams. The 56-site 

network covers forested, rangeland, agricultural, spring, and 

large-river site types across the State. This report summarizes 

selected data collected at network sites from 1989 through 

2002. Some of the major issues addressed in the report are 

summarized in table 10.

Although sampling was not designed to represent the full 

range of flow conditions at sites, sampling at 33 sites covered 

the range of flows well. The network might benefit from additional high- or low-flow sampling at 20 sites. At the 3 spring 

site types, high flows during the period of network operation 

were lower than historical high flows. This was probably a 

result of declining ground-water levels in the Snake River 

Plain.

Summertime stream temperatures commonly exceeded 

Idaho criteria for the protection of coldwater aquatic life (daily 

mean and daily maximum temperatures of 19 and 22 degrees 

Celsius, respectively). Only temperatures at sites near headwaters, sites immediately downstream from large reservoirs, 

and spring site types did not exceed these criteria. Criteria 

exceedances in stream basins with minimal development suggest that such high temperatures may occur naturally in many 

Idaho streams.

Suspended-sediment concentrations were generally 

higher in southern Idaho than in central and northern Idaho. 

Although correlations between suspended-sediment concentrations and stream discharge were not particularly strong, 

most of the highest concentrations occurred during the highest 

flows. Idaho’s only sediment-related numeric criteria are 

based on turbidity, which was not strongly correlated with 

suspended sediment at most network sites. Network data indicated that the turbidity criterion is most likely to be exceeded 

at sites in southern Idaho and other sections of the Columbia 

Plateaus geomorphic province where loess and other fine-
20 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

grained soils are subject to erosion and disturbance by land 

uses.

Specific conductance values ranging from 10 to 

1,320 microsiemens per centimeter indicated a wide range 

of dissolved solids across the network. At most sites, specific 

conductance was inversely correlated with stream discharge. 

Values were generally lowest in northern Idaho and the mountainous areas of central Idaho and highest in southern Idaho 

in rivers affected by agricultural and urban land uses. Water 

hardness was closely correlated with specific conductance 

across the network. Hardness concentrations less than 25 milligrams per liter (mg/L) as calcium carbonate were common 

in streams in northern and central Idaho. Such low hardness 

concentrations enhance the toxicities of some trace elements 

to aquatic organisms in these streams. Hardness concentrations exceeded 100 mg/L as calcium carbonate in basins where 

carbonate rocks are present, primarily in southern Idaho.

Only a few measurements of dissolved-oxygen (DO) 

concentrations at six sites were less than 6.0 mg/L, the Idaho 

criterion for protection of aquatic organisms. Highly supersaturated DO concentrations at another four sites suggest excessive photosynthetic activity by large algal communities. These 

sites might benefit from nighttime monitoring to determine 

whether DO concentrations might fall below the criterion as 

these large communities respire in the absence of photosynthesis. Data from four sites suggest that DO concentrations may 

have decreased over time.

The pH at 15 sites sometimes fell outside the range Idaho 

has adopted for protection of aquatic organisms (6.5 – 9.0).

Values exceeded 9.0 at 10 sites and are likely a result of photosynthetic activity by large algal communities in water where 

pH was elevated owing to contact with carbonate minerals. 

Values were less than 6.5 at five sites and are likely to be naturally low as a result of low concentrations of carbonate and 

other dissolved solids. One of these sites receives drainage 

from areas of extensive mining activities that may contribute 

acidic discharges.

Nutrient concentrations commonly exceeded those considered necessary for supporting algal production. At nearly 

half of the network sites, inorganic nitrogen concentrations 

in more than 25 percent of the samples exceeded 0.3 mg/L, 

a level considered necessary for supporting algal production. Total nitrogen concentrations exceeding 1 mg/L were 

not unusual. Data from eight sites suggest that total nitrogen 

concentrations might be changing over time. Total phosphorus concentrations in 25 percent or more of the samples 

at one-fourth of network sites exceeded 0.1 mg/L, a concentration considered sufficient for supporting nuisance algal 

growth. Data from three sites suggest increasing or decreasing 

phosphorus concentrations over time. Low concentrations of 

nitrogen and phosphorus at six sites might make them good 

candidates as reference sites that represent naturally occurring 

nutrient concentrations. The sites represent forested site types 

in mountainous areas of northern and central Idaho, a rangeland site type in south-central Idaho, and a large-river site type 

in north-central Idaho.

Trace elements in water were monitored from 1989 through

1995 and, in fish tissue, from 1996 through 2002. Of the

20 trace elements monitored, only cadmium, copper, lead, 

mercury, selenium, and zinc were addressed in this report. 

In water, many of these trace elements were not routinely 

detected. Concentrations of cadmium, copper, lead, and zinc 

generally were highest in mined and other mineral-rich basins 

in northern Idaho. Concentrations of mercury were highest 

in southern Idaho. Data showed that concentrations of one or 

more of these elements at 33 sites sometimes exceeded Idaho 

criteria for the protection of aquatic organisms. Selenium concentrations were not particularly high at any network sites.

Fish-tissue samples have not yet been collected at all 

network sites. At the 15 sites sampled, liver was the most 

common tissue analyzed, but fillet and whole-body tissue 

samples were analyzed for selected sites. Similar to the results 

from water analyses, cadmium, copper, lead, and zinc were 

enriched in tissue of fish collected at sites in mined and other 

mineral-rich basins in northern Idaho, and mercury concentrations were highest in fish collected from sites in southern 

Idaho. Although these data did not demonstrate mercury to be 

enriched in livers of fish from any of the sites sampled, several 

concentrations were greater than 0.3 micrograms per gram, the 

maximum concentration for edible fish tissue recommended 

for the protection of human health.

The water and fish-tissue data seemed to give inconsistent 

information about impacts from trace elements. Trace-element

concentrations in water at 22 sites exceeded criteria but were 

not enriched in fish tissue. Collection of water and tissue data 

in different years and the mobility of fish might contribute 

to this problem. If fish mobility is a significant contributor, 

the scope of the network might have to be reassessed to meet 

network objectives. Although fish tissue is appropriate for 

assessing direct impacts of trace elements on fish and consumers of fish, another less mobile media might be better for 

identifying specific streams that may be subject to significant 

trace-element impacts.

Twenty-eight synthetic organic compounds were analyzed in samples of whole-body fish from the same 15 sites 

where samples of fish tissue were analyzed for trace elements. 

Compounds detected in these samples were PCBs (in northern and southeastern Idaho) and the pesticides DDT and its 

metabolites, dieldrin, and nonachlor (in southern and central 

Idaho). PCB residues might be a result of past urban and 

industrial activities, and the pesticide residues might be more 

closely related to urban and agricultural activities. The common presence of PCBs, DDT, and DDT metabolites reflects 

the wide-scale use of these compounds before they were 

banned more than 30 years ago and their persistence in the 

environment. Additional sampling will help to better assess 

the distribution of these compounds in fish across Idaho. As 

observed for trace elements, a less mobile media might be 

better for identifying stream reaches significantly affected by 

these compounds.

Populations of fecal coliform bacteria ranged from 0 to 

4,770 colonies per 100 milliliters. Because fecal coliform 
Selected References 21

and Escherichia coli (E. coli) are closely related, fecal coliform 

populations were compared with the current Idaho criteria 

for E. coli to identify sites where E. coli criteria might be 

exceeded. Fecal coliform populations exceeded Idaho primary- or secondary-contact criteria for E. coli (406 and 526 

colonies per 100 milliliters, respectively) at 22 sites representing a wide range of site types. Populations exceeded criteria 

most frequently at agricultural site types on the Boise River 

and Lapwai Creek, where populations in more than 25 percent of the samples exceeded both criteria. Replacing fecal 

coliform analyses with E. coli analyses, allowing an overlap 

period when both are analyzed, would benefit the network.

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their relation to temperature variables of least-disturbed 

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Selected References 23

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2000, Relative importance of calcium and magnesium 

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p. 1624 – 1631.

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May 1999, Processing of water samples: U.S. Geological 

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chap. A4, [variously paged].
[This page intentionally left blank]
Figures 2 – 5, 8 – 13, and 15 – 29 (explanation for various boxplots on next page)

2. Stream discharges at times samples were collected for selected sites in the 

Idaho statewide surface-water-quality monitoring network, 1989 – 2002

3A. Summer maximum daily water temperatures at all sites in the Idaho statewide 

surface-water-quality monitoring network, 1996 – 2002

3B. Summer minimum daily water temperatures at all sites in the Idaho statewide 

surface-water-quality monitoring network, 1996 – 2002

3C. Summer mean daily water temperatures at all sites in the Idaho statewide 

surface-water-quality monitoring network, 1996 – 2002

4. Sites in the Idaho statewide surface-water-quality monitoring network, where 

water temperature exceeded criteria 1996 – 2002

5. Suspended-sediment concentrations at all sites in the Idaho statewide surfacewater-quality monitoring network, 1996 — 2002

8. Turbidity in relation to suspended-sediment concentrations at selected sites in 

the Idaho statewide surface-water-quality monitoring network, 1989 – 2002

9. Turbidity at sites in the Idaho statewide surface-water-quality monitoring 

network, 1989 – 2002 

10. Sites in the Idaho statewide surface-water-quality monitoring network where 

turbidity exceeded 25 nephelometric turbidity units (NTU), 1989 – 2002

11. Specific conductance at all sites in the Idaho statewide surface-water-quality

monitoring network, 1989 – 2002

12. Ratios of total dissolved-solids concentrations to specific conductance at all 

sites in the Idaho statewide surface-water-quality monitoring network, 

1989 – 2002

13. Hardness concentrations at all sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

15. Dissolved-oxygen concentrations and saturations at all sited in the Idaho 

statewide surface-water-quality monitoring network, 1989 – 2002

16. Dissolved-oxygen concentrations and saturations in relation to time at selected 

sites in the Idaho statewide suface-water-quality monitoring network, 1989 – 2002

17. pH at all sites in the Idaho statewide surface-water-quality monitoring network, 

1989 – 2002 (Criteria from Idaho Department of Environmental Quality

 18. pH in relation to time at selected sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002

19. Total nitrogen concentrations at all sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002 

20. Inorganic nitrogen concentrations at all sites in the Idaho statewide surfacewater-quality monitoring network, 1989 – 2002
 21. Total nitrogen concentrations in relation to time at selected sites in the Idaho 

statewide surface-water-quality monitoring network, 1989 – 2002 

22. Total phosphorus concentrations at all sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002

23. Total phosphorus concentrations in relation to time at selected sites in the Idaho 

statewide surface-water-quality monitoring network, 1989 – 2002

24. Total phosphorus and total nitrogen concentrations at proposed reference and 

combined nutrient ecoregion sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

25. Sites in the Idaho statewide surface-water-quality monitoring network where 

concentrations of trace elements in water exceeded criteria, 1989 – 95

26. Concentrations of selected trace elements in livers of fish collected at sites in 

the Idaho statewide surface-water-quality monitoring network, 1996 – 2000

27. Sites in the Idaho statewide surface-water-quality monitoring network where 

concentrations of selected trace elements were enriched in tissue of fish, 

1996 – 2000

28. Ratios of selected organic compounds to lipids in whole fish collected at 

selected sites in the Idaho statewide surface-water-quality monitoring network, 

1996 – 98

29. Fecal coliform populations at all sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002

3rd Quartile plus

 1.5 times the IQR

1st Quartile minus

 1.5 times the IQR

Interquartile range

(IQR)

Outlier—3rd Quartile plus

 between 1.5 and 3 times

 the IQR

3rd Quartile

Median

1st Quartile

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Outlier—1st Quartile minus

 between 1.5 and 3 times

 the IQR

398 Number of samples

For figures 3, 5, 9, 11, 12, 13,

15, 17, 19, 20, 22, and 29
Figure 2 27

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Figure 2. Stream discharges at times samples were collected for selected sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002 (Locations of sites shown on figure 1)
28 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

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Figure 2. Stream discharges at times samples were collected for selected sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002 — Continued (Locations of sites shown on figure 1)
Figure 2 29

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Figure 2. Stream discharges at times samples were collected for selected sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002 — Continued (Locations of sites shown on figure 1)
30 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

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Figure 2. Stream discharges at times samples were collected for selected sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002 — Continued (Locations of sites shown on figure 1)
Figure 3 31

Figure 3A. Summer maximum daily water temperatures at all sites in the Idaho statewide surface-water-quality monitoring 

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network, 1996 – 2002. (Locations of sites shown on figure 1; temperature criteria from Idaho Department of Environmental 

Quality, http://www2.state.id.us/adm/adminrules/idapa58/0102.pdf)
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34 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

Figure 4. Sites in the Idaho statewide surface-water-quality monitoring network where water temperature 

exceeded criteria1996 – 2002. (Temperature criteria from Idaho Department of Environmental Quality, 

http://www2.state.id.us/adm/adminrules/idapa58/0102.pdf)

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Figure 5. Suspended-sediment concentrations at all sites in the Idaho statewide surface-water-quality monitoring network, 

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Figure 9. Turbidity at sites in the Idaho statewide surface-water-quality monitoring network, 1989 – 2002 (Locations of sites

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38 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

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Figure 10. Sites in the Idaho statewide surface-water-quality monitoring network where turbidity exceeded 25 nephelometric

turbidity units (NTU), 1989–2002

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Figure 11. Specific conductance at all sites in the Idaho statewide surface-water-quality monitoring network, 1989 – 2002 

(Locations of sites shown on figure 1)
40 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

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Figure 12. Ratios of total dissolved-solids concentrations to specific conductance at all sites in the Idaho statewide surfacewater-quality monitoring network, 1989 – 2002 (Locations of sites shown on figure 1) 
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42 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

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Figure 15. Dissolved-oxygen concentrations and saturations at all sited in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002 (Locations of sites shown on figure 1; Idaho minimum criterion from Idaho Department of 

Environmental Quality, http://www2.state.isd.us/adm/adminrules/rules/idapa58/0102.pdf)
Figure 15 43

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Figure 15. Dissolved-oxygen concentrations and saturations at all sited in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002 — Continued (Locations of sites shown on figure 1; Idaho minimum criterion from Idaho 

Department of Environmental Quality, http://www2.state.isd.us/adm/adminrules/rules/idapa58/0102.pdf)
44 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

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Figure 16. Dissolved-oxygen concentrations and saturations in relation to time at selected sites in the Idaho statewide 

suface-water-quality monitoring network, 1989 – 2002 (Locations of sites shown on figure 1)
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Figure 17. pH at all sites in the Idaho statewide surface-water-quality monitoring network, 1989 – 2002 (Locations of sites 

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46 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

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Figure 18. pH in relation to time at selected sites in the Idaho statewide surface-water-quality monitoring network, 1989 – 2002 

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Figure 19 47

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Figure 19. Total nitrogen concentrations at all sites in the Idaho statewide surface-water-quality monitoring network, 

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48 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

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Figure 20. Inorganic nitrogen concentrations at all sites in the Idaho statewide surface-water-quality monitoring network, 

1989 – 2002 (Locations of sites shown on figure 1; concentrations that plot at 0.007 could be less than or equal to that value)
Figure 21 49

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Figure 21. Total nitrogen concentrations in relation to time at selected sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002 (Locations of sites shown on figure 1)
50 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

Figure 22. Total phosphorus concentrations at all sites in the Idaho statewide surface-water-quality monitoring network, 

1989 – 2002 (Locations of sites shown on figure 1; concentrations that plot at 0.01 or 0.0001 could be less than or equal to 

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Figure 23. Total phosphorus concentrations in relation to time at selected sites in the Idaho statewide surface-water-quality 

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Figure 24. Total phosphorus and total nitrogen concentrations at proposed reference and combined nutrient ecoregion sites 

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Figure 25. Sites in the Idaho statewide surface-water-quality monitoring network where concentrations of trace elements in 

water exceeded criteria, 1989 – 95 (CCC and CMC criteria from Idaho Department of Environmental Quality, 

http://www2.state.id.us/adm/adminrules/rules/idapa58/0102.pdf)
54 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

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Figure 25. Sites in the Idaho statewide surface-water-quality monitoring network where concentrations of trace elements in 

water exceeded criteria, 1989 – 95 — Continued (CCC and CMC criteria from Idaho Department of Environmental Quality, 

http://www2.state.id.us/adm/adminrules/rules/idapa58/0102.pdf)
Figure 25 55

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Figure 25. Sites in the Idaho statewide surface-water-quality monitoring network where concentrations of

trace elements in water exceeded criteria, 1989-95 -- Continued (CCC and CMC criteria from Idaho Department

of Environmental Quality, 
56 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

Figure 26. Concentrations of selected trace elements in livers of fish collected at selected sites in the Idaho statewide 

surface-water-quality monitoring network, 1996 – 2000 (Locations of sites shown on figure 1)

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Figure 27. Sites in the Idaho statewide surface-water-quality monitoring network where concentrations of 

selected trace elements were enriched in fish tissue, 1996 – 2000

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58 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002 

Figure 28. Ratios of selected organic compounds to lipids in whole fish collected at selected sites in the Idaho statewie 

surface-water-quality monitoring network, 1996 – 98

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Figure 29. Fecal coliform populations at all sites in the Idaho statewide surface-water-quality monitoring network, 1989 – 2002 

(Locations of sites shown on figure 1)
[This page intentionally left blank]
Tables 1 – 2, 6, 10

 1. Basin and site characteristics for sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

 2. Types of data and periods of data collection for sites in the Idaho statewide surfacewater-quality monitoring network and for other programs

 6. Sites in the Idaho statewide surface-water-quality monitoring network where 

concentrations of selected trace elements exceeded Idaho criteria, 1989 – 95

 10. Major network and water-quality issues for sites in the Idaho statewide surface-waterquality monitoring network, 1989 – 2002
[This page intentionally left blank]
1 Kootenai R. at Porthill 48°59'47"/116°30'22" F 518 5 2.08 12,409 0.4 3 

2 Clark Fork R. below Cabinet Gorge Dam 48°05'30"/116°07'00" F 628 6 4.48 55,614 0.6 6.4 3 Priest R. near Priest R. 48°12'31"/116°54'49" F 637 5 0.61 2,460 0.6 0.8 4 North Fork Coeur d'Alene R. at Enaville 47°34'21"/116°15'11" F 640 5 0.36 2,325 0 0.2 5 South Fork Coeur d'Alene R. near Pinehurst 47°33'06"/116°14'13" F 667 5 16.11 738 2.6 0.1 6 St. Joe R. at Calder 47°16'29"/116°11'17" F 662 5 0.12 2,679 0 0 7 Spokane R. near Post Falls 47°42'11"/116°58'37" F 625 6 0.09 10,162 0.4 0 8 Snake R. near Heise 43°36'45"/111°39'33" F 1,528 6 1.28 14,841 0.3 5.9 

10 Teton R. near St. Anthony 43°55'38"/111°36'55" A 1,515 5 1.78 2,294 0.2 39.5 11 Henrys Fork near Rexburg 43°49'34"/111°54'15" A 1,465 6 4.33 8,337 0.4 25.9 12 Willow Creek near Ririe 43°35'02"/111°44'44" R 1,509 6 0.46 1,661 0 21.4 13 Blackfoot R. near Blackfoot 43°07'50"/112°28'35" A 1,347 6 1.33 2,851 0.1 13.7 14 Snake R. near Blackfoot 43°07'31"/112°31'06" LR 1,341 7 5.47 31,555 0.6 19.1 15 Portneuf R. at Topaz 42°37'30"/112°05'20" A 1,499 5 1.03 1,520 0.2 33.6 16 Marsh Cr. near McCammon 42°37'48"/112°13'29" A 1,405 5 1.86 885 1 52.1 17 Portneuf R. at Pocatello 42°52'20"/112°28'05" A 1,347 6 8.53 3,292 1.3 36.2 18 Snake R. near Minidoka 42°40'23"/113°29'58" LR 1,259 7 5.26 48,830 0.7 23 19 Snake R. at Milner 42°31'41"/114°01'04" LR 1,238 7 5.1 57,826 0.7 22.9 20 Snake R. near Kimberly 42°35'28"/114°21'28" LR 1,025 7 5.07 59,097 0.7 23.4 21 Blue Lakes Spring 42°36'53"/114°28'06" S 1,006 1 0 3 0 0 22 Rock Creek at Daydream Ranch 42°33'47"/114°29'42" A 1,106 5 11.36 623 1.8 22.8 23 Box Canyon Springs 42°42'29"/114°48'35" S 920 1 0 3 0 0 24 Salmon Falls Creek near Hagerman 42°41'47"/114°51'15" R 881 6 0.23 5,362 0 5.1 25 Camas Creek at Red Road 44°17'20"/111°53'31" R 1,457 4 0 660 0 17.5 26 Beaver Creek at Spencer 44°21'20"/112°10'45" R 1,783 4 0.03 328 0.2 0 27 Big Lost R. near Chilly 43°59'54"/114°01'12" R 2,018 5 0.4 1,141 0 0.2 28 Big Wood R. near Bellevue 43°19'40"/114°20'25" R 1,469 5 5.73 2,128 0.9 5.1 29 Silver Creek near Picabo 43°19'22"/114°06'29" S 1,478 4 1.21 152 0.1 35.6 30 Malad R. near Gooding 42°53'12"/114°48'08" A 1,019 5 2.52 8,607 0.4 14.2 31 Bruneau R. near Hot Spring 42°46'16"/115°43'10" R 792 6 0.1 6,766 0 0.4 32 Snake R. near Murphy 43°17'31"/116°25'12" LR 692 7 4.29 129,052 0.6 19.8 33 Boise R. near Twin Springs 43°39'33"/115°43'34" F 992 6 0.01 2,148 0 0 34 Boise R. below Diversion Dam 43°32'23"/116°05'37" F 838 6 0.23 6,970 0 0.5 35 Boise R. at Glenwood Bridge 43°39'37"/116°16'41" R 792 6 8.41 7,463 0.7 0.7 36 Boise R. near Parma 43°46'54"/116°58'17" A 669 6 26.23 10,141 2.5 12.5 37 Snake R. at Nyssa, Oregon 43°52'34"/116°58'53" LR 661 7 5.02 171,363 0.6 16.5 38 South Fork Payette R. at Lowman 44°05'07"/115°37'16" F 1,155 5 0.16 1,157 0.1 0 39 North Fork Payette R. at McCall 44°54'27"/116°07'04" F 1,514 4 4.07 379 1.9 0.2 40 North Fork Payette R. at Cascade 44°31'30"/116°02'45" A 1,439 6 2.93 1,601 0.8 11.9 41 Payette R. near Payette 44°02'33"/116°55'27" A 652 6 3.15 8,536 0.5 9.4 42 Weiser R. near Weiser 44°16'03"/116°46'16" A 672 6 0.95 3,800 0.2 11.8 43 Snake R. at Weiser 44°14'44"/116°58'48" LR 636 7 4.98 184,995 0.6 16.2 44 Pahsimeroi R. at Ellis 44°41'34"/114°02'51" R 1,413 5 0.05 2,151 0 7.5 45 Salmon R. at Salmon 45°11'00"/113°53'40" R 1,192 6 0.61 12,982 0.3 4.8 46 Lemhi R. near Lemhi 44°56'24"/113°38'16" R 1,512 5 0.25 2,349 0.1 8.6 47 Johnson Creek at Yellow Pine 44°57'44"/115°29'58" F 1,419 4 0 555 0 0 48 Little Salmon R. at Riggins 45°24'47"/116°19'29" F 536 5 1.04 1,491 0.2 4.8 49 Snake R. near Anatone, Wash. 46°05'50"/116°58'36" LR 246 8 3.83 258,802 0.5 13.8 50 Lapwai Creek near Lapwai 46°25'36"/116°48'15" A 264 5 4.09 682 0.4 48.9 51 South Fork Clearwater R. at Stites 46°05'12"/115°58'32" F 400 5 2.19 3,016 0.3 19 52 Palouse R. near Potlatch 46°54'55"/116°57'00" A 748 4 3.02 822 0.4 23.6 53 Bear R. at Idaho-Utah State Line 42°00'47"/111°55'14" A 1,845 6 3.59 5,139 0.6 29.5 54 Salmon River near White Bird 45°45'01"/116°19'26" LR 430 7 0.36 35,095 0.1 2.2 55 Snake River near Shelley 43°24'48"/112°08'03" A 1,402 6 5.57 25,356 0.6 18.4 56 St. Joe River at Red Ives Ranger Station 47°03'22"/115°21'08" F 1,131 4 0 275 0 0 57 Snake R. near Buhl 42°39'58"/114°42'41" LR 900 7 4.67 76,104 0.7 21.3 

[No., number; fig., figure; m, meters; km2, square kilometers; %, pecent; R., river; Site type: F, forested; A, agricultural; R, rangeland; LR, large river; S, spring; Site type from Maret and others, 2

Site No. (fig. 

1) Site name Latitude/Longitude

Site

type Elevation (m) Stream order Urban land (%) 

Table 1. Basin and site characteristics for sites in the Idaho statewide surface-water-quality monitoring network, 1989-2002

Population 

(people/km2

)

Agricutural land 

(%) Ra

Basin area 

(km2

)
 Site No. 

(fig. 1) Site name

USGS site 

ID

Site 

type Sediment Onsite measurements Major ions Nutrients 

Trace 

elements Sediment

1 Kootenai R. at Porthill 12322000 F 1989, 1992, 1995, 1998, 2001 1989, 1992, 1998, 2001 1992, 1995, 1998, 2001 1992, 1995, 1998, 2001 1992, 19952 Clark Fork R. below Cabinet Gorge Dam 12391950 F 90-02 96-02 90-01 90-99, 02 90-94

3 Priest R. near Priest R. 12395000 F 90, 92, 94, 96, 98, 00, 02 89, 90, 92, 94, 96, 98, 02 90, 92, 94, 96, 98, 00 89, 90, 92, 94, 96, 98, 00, 02 90, 92, 944 North Fork Coeur d'Alene R. at Enaville 12413000 F 90, 93, 96, 98, 00, 01 89, 90, 93, 96, 98, 00, 01 90, 93, 96, 98-01 90, 93, 96, 98, 00, 01 90, 93 1999, 2002 

5 South Fork Coeur d'Alene R. near Pinehurst 12413470 F 89, 90-02 89-94, 96-02 90-02 89, 90-02 99, 02 

6 St. Joe R. at Calder 12414500 F 89, 90, 93, 96, 98-01 89, 90, 93, 96, 98, 99-01 90, 93, 96, 98-01 89, 90, 93, 96, 98-01 90, 93 99 

7 Spokane R. near Post Falls 12419000 F 89, 90-02 89-93, 96-02 90-02 89, 90-02 90-95 99 

8 Snake R. near Heise 13037500 F 89, 96, 99, 02 89, 96, 99, 02 89, 96, 99 89, 96, 99, 02 89-92 94, 95 

10 Teton R. near St. Anthony 13055000 A 90, 96, 99, 01 89, 90, 96, 99, 01 90, 93, 96, 99, 01 90, 96, 99, 01 90, 93 93-95 11 Henrys Fork near Rexburg 13056500 A 89, 90, 92, 96, 98, 00, 02 89, 90, 92, 96, 98, 00, 02 90, 92, 96, 98, 00 89, 90, 96, 98, 00, 02 90, 92, 94 93-95 

12 Willow Creek near Ririe 13058000 R 93, 96, 99 89, 90, 92, 93, 96 90, 93, 96, 99 90, 93, 96, 99 90, 93

13 Blackfoot R. near Blackfoot 13068500 A 89, 90-02 89-97, 99-02 90-97, 99-01 89-97, 99-02 90-95 94 

14 Snake R. near Blackfoot 13069500 LR 89, 90, 92, 96, 98, 00, 02 89, 90, 92, 96, 98, 00-02 90, 92, 96, 98, 00, 01 89, 90, 92, 96, 98, 00-02 90, 92, 94 93-95 15 Portneuf R. at Topaz 13073000 A 96, 98, 00, 02 89, 96, 98, 00, 02 96, 98, 00 96, 98, 00, 02 93-95 16 Marsh Creek near McCammon 13075000 A 91, 93, 95, 96, 98, 00 89, 91, 93, 95, 96, 98, 00 91, 93, 95, 96, 98, 00 91, 93, 95, 96, 98, 00 91, 93, 9517 Portneuf R. at Pocatello 13075500 A 91, 93, 95, 96, 98, 00, 02 89, 91, 93, 95, 96, 98, 00, 02 91, 93, 95, 96, 98, 00 89, 91, 93, 95, 96, 98, 00, 02 91, 93, 95 18 Snake R. near Minidoka 13081500 LR 89, 90, 92, 96, 98, 00, 02 89, 90, 92, 96, 98, 00, 02 90, 92, 96, 98, 00 90, 92, 96, 98, 00, 02 90, 92, 94 93-95 

19 Snake R. at Milner 13087995 LR 91, 93, 95, 96, 99 89, 91, 93, 97, 99, 01 91, 93, 95, 97, 99, 01 91, 93, 95, 97, 99, 01 91, 93 95 94, 95 

20 Snake R. near Kimberly 13090000 LR 91, 93, 95, 97, 99 89, 91, 93, 95, 97, 99, 01 91, 93, 95, 97, 99, 01 91, 93, 95, 97, 99, 01 91, 93, 95 94, 95 

21 Blue Lakes Spring 13091000 S 91 89, 91-94, 96 90, 96 91, 94, 96 91, 94 

22 Rock Creek at Daydream Ranch 13092747 A 96 00 00 97 93-02 23 Box Canyon Springs 13095500 S 91, 02 89-94, 97, 99, 02 89, 91-94, 97, 99, 01 91-94, 97, 99, 02 91, 94 

24 Salmon Falls Creek near Hagerman 13108150 R 90, 92, 94, 96, 98, 00, 02 89, 90, 92, 94, 96, 98, 00, 02 90, 92, 94, 96, 98, 00 89, 90, 92, 94, 96, 98, 00, 02 90, 92, 94 94, 95 25 Camas Creek at Red Road 13108900 R 92, 95, 97 89, 91, 94, 97 91, 94, 97 91, 94, 97 91, 94

26 Beaver Creek at Spencer 13113000 R 95, 97 89, 92, 95, 97 92, 95, 97 92, 95, 97 92, 95

27 Big Lost R. near Chilly 13120500 R 96, 99, 02 89, 96, 99, 02 96, 99 96, 99, 02 93-95 

28 Big Wood R. near Bellevue 113140800 R 90, 92, 94, 96, 97, 99, 01 89, 90, 92, 94, 96, 97, 99, 01 90, 92, 94, 96, 97, 00, 01 90, 92, 94, 93, 96-97, 99, 01 90, 92, 93, 94

29 Silver Creek near Picabo 13150430 S 90, 93, 96, 97, 99, 01 89, 90, 93, 96, 97, 99, 01 90, 93, 96, 97, 99, 01 90, 92, 94, 93, 96-97, 99, 01 90, 93 

30 Malad R. near Gooding 13152500 A 89, 90, 93, 96, 97, 00 89, 90, 93, 96, 97, 01 89, 90, 96, 97, 00 89, 90, 96, 97, 00 90, 93 93-95 31 Bruneau R. near Hot Spring 13168500 R 91, 94, 97, 00 89, 91, 94, 97, 00 91, 94, 97, 00 91, 94, 97, 00 91, 9432 Snake R. near Murphy 13172500 LR 91, 94, 97, 00 89, 91, 94, 97, 00 91, 94, 97, 00 91, 94, 97, 00 91, 9433 Boise R. near Twin Springs 13185000 F 91, 94, 96, 97, 00 89, 91, 94, 97, 00 91, 94, 97, 99, 00 91, 94, 97, 00 91, 94

34 Boise R. below Diversion Dam 13203510 F 91, 94, 97, 99 89, 91, 94, 95, 97, 99 91, 94, 99 91, 94, 95, 97, 99 91, 94 93-02 

35 Boise R. at Glenwood Bridge 13206000 R 90-01 89-01 90-01 90-01 90-95 94-02 36 Boise R. near Parma 13213000 A 89, 96, 97, 99 89, 96, 97, 99 89, 97, 99 89, 96, 97, 99 89 93-02 

37 Snake R. at Nyssa, Oregon 13213100 LR 90, 93, 96, 97, 00 89, 90, 93, 96, 97, 00 90, 93, 96, 97, 00 90, 93, 96, 97, 00 90, 93

38 South Fork Payette R. at Lowman 13235000 F 92, 95, 98, 01 89,92, 95, 98, 01 92, 95, 98, 01 92, 95, 98, 01 92, 9539 North Fork Payette R. at McCall 13239000 F 92, 95, 98, 02 89,92, 95, 98, 02 92, 95, 98 92, 95, 98, 02 92, 95 94, 98, 02 

40 North Fork Payette R. at Cascade 13245000 A 90, 92, 94, 96, 98, 89, 90, 92, 94, 96, 98 90, 92, 94, 96, 98 90, 92, 94, 96, 98 90, 92, 9441 Payette R. near Payette 13251000 A 90, 93, 96, 97, 99, 02 89, 90, 93, 96, 97, 99, 02 90, 93, 96, 97, 99 90, 93, 96, 97, 99, 02 90, 9342 Weiser R. near Weiser 13266000 A 90, 93, 96, 97, 00 89, 90, 93, 96, 97, 00 90, 93, 96, 97, 00 90, 93, 96, 97, 99 90, 93

43 Snake R. near Weiser 13269000 LR 90, 93, 96, 99, 02 89, 90, 93, 96, 99, 02 90, 93, 96, 99 90, 93, 96, 99, 02 90, 93

44 Pahsimeroi R. at Ellis 13302005 R 92, 95, 98, 01 89, 92, 95, 98, 01 92, 95, 98, 01 92, 95, 98, 01 92, 9545 Salmon R. at Salmon 13302500 R 92, 95, 98, 01 89, 92, 95, 98, 01 92, 95, 98, 01 92, 95, 98, 01 92, 9546 Lemhi R. near Lemhi 13305000 R 92, 95, 98, 01 89, 92, 95, 98, 01 92, 95, 98, 01 92, 95, 98, 01 92, 9547 Johnson Creek at Yellow Pine 13313000 F 92, 95, 98, 01 89, 92, 95, 98, 01 92, 95, 98, 01 92, 95, 98, 01 92, 9548 Little Salmon R. at Riggins 13316500 F 92, 95, 98, 01 89, 92, 95, 98, 01 92, 95, 98, 01 92, 95, 98, 01 92, 9549 Snake R. near Anatone, Wash. 13334300 LR 91, 94, 97 89, 91, 94, 97 91, 94, 97 91, 94, 97 91-94

50 Lapwai Creek near Lapwai 13342450 A 91, 93, 95, 97, 98, 00, 02 89, 91, 93, 95, 97, 98, 00, 02 91, 93, 95, 97, 98, 00 91, 93, 95, 97, 98, 00, 02 91, 93, 95

51 South Fork Clearwater R. at Stites 13338500 F 90, 93, 96, 98, 01 89, 90, 93, 96, 98, 01 90, 93, 96, 98, 01 90, 93, 96, 98, 01 90, 93

52 Palouse R. near Potlatch 13345000 A 89, 91, 93, 95, 97, 98, 00, 02 89, 91, 93, 95, 97, 98, 00, 02 91, 93, 95, 97, 98, 00 89, 91, 93, 95, 97, 98, 00, 02 91, 93, 95

53 Bear R. at Idaho-Utah State line 10092700 A 91, 94, 96, 99, 02 91, 94, 96, 99, 02 91, 94, 96, 99 91, 94, 96, 99, 02 91, 94

54 Salmon R. near White Bird 13317000 LR 89, 00-02 89, 94, 00-02 89, 94, 00, 01 89, 94, 00-02 89, 94

55 Snake R. near Shelley 13060000 A 91, 93, 95, 02 89, 91, 93, 95, 00-02 91, 93, 95, 01 91, 93, 95, 01, 02 91, 93, 95 94 56 St. Joe R. at Red Ives Ranger Station 12413875 F 00-02 00-02 01 01, 02

57 Snake R. near Buhl 13094000 LR 91, 97-02 89, 91, 97-02 91, 97-01 91, 97-02 91, 93, 95 93-97 

Types 

Table 2. Types of data and periods of data collection for sites in the Idaho statewide surface-water-quality monitoring network and for sites in other programs

Types of data and periods of data collection, Idaho statewide network

1Also under site ID 13141000. Site moved about 1.6 kilometers upstream because of gage-operation problems at old location. Data from both locations combined for analysis.

[USGS, U.S. Geological Survey; ID, identification; periods of data collection by fiscal year from January 1, 1989 (partial 1989) through December 31, 2002 (partial 2002); R., river; Site types: F, forested; A, agricultural; R, rangelandothers, 2001]
Table 6 65

Table 6. Sites in the Idaho statewide surface-water-quality monitoring network where concentrations of selected trace elements 

exceeded Idaho criteria, 1989 – 95

[Where appropriate, criteria are based on lowest hardness measured at each site; locations of sites shown on figure 1; CCC, criterion continuous concentration; 

criteria from Idaho Department of Environmental Quality, http://www2.state.id.us/adm/adminrules/rules/idapa58/0102.pdf; CMC, criterion maximum concentration; HC water+orgs, human consumption of water and organisms; HCorgs, human consumption of organisms only; X, fewer than 25 percent of measurements; 

<, greater than; %, percent]

Site No 

Cadmium Copper Lead Zinc Mercury

CMC CCC CMC CCC CMC CCC CMC CCC CMC CCC HCwater+orgs HCorgs

 1 X X X X

 2 X >25% X X X >25% X X X

 3 X X X X X X

 4 >25% >25% X >25% X X X X X

 5 100% 100% X X X 100% 100% 100% X X X

 6 X X X X X

 7 >25% >25% X X X >50% >75% >75%

 8 X X X X X

 10 X

 11 X X X X X

 12 X X X

 13 X X X X

 14 X X X X X X

 16 X X X

 21 X

 23 X X

 25 X X

 29 X X X

 33 X

 36 X X X X

 39 X X X

 40 X X X X

 41 X

 42 X X X X

 43 X

 46 X X

 48 X X X

 49 X

 51 100% X X X

 52 X >25% >75%

 54 X X X X

 55 X X X X

 56 >25% >25% >50%
66 Status of and Changes in Water Quality, Idaho Statewide Surface-Water-Quality Network, 1989 – 2002

Table 10. Major network and water-quality issues for sites in the Idaho statewide surface-water-quality monitoring network, 

1989 – 2002 

[Locations of sites shown on figure 1; No., number; fig., figure; >, greater than; <, less than; NTU, nephelometric turbidity units; DO, dissolved oxygen; 

%, percent; N, nitrogen; P, phosphorus; mg/L, milligrams per liter; TE, trace elements; FC, fecal coliform bacteria; E. coli, Escherichia coliform bacteria; 

criteria from Idaho Department of Environmental Quality, http://www2.state.id.us/adm/adminrules/rules/idapa58/0102.pdf]

Site 

No.

Sampling 

a wider 

range of 

flows is 

desirable

Water

temperatures

>

Idaho 

criteria

Turbidity 

> 50 NTU

DO <

Idaho 

criteria

DO

saturation

> 170%

pH

< 6.5

pH 

> 9.0

More than

25%

inorganic 

N >

0.3 mg/L

More

than

25%

total 

P >

0.1 mg/L

Candidate

for

nutrient 

reference 

site

TE

in 

water

> Idaho 

criteria

TE

enriched 

in fish

Organic

compounds

detected

FC >

Idaho 

E. coli

criteria

1 x x x x

2 x x x x

3 x x x

4 x x x x x x

5 x x x x x x

6 x x x x

7 x x x x

8 x

10 x x x x

11 x x x

12 x x x

13 x x x x x x x

14 x x x x x

15 x x x x x

16 x x x x x x x

17 x x x x x x x x

18 x x

19 x x x x x

20 x x x

21 x x

22 x x x x x x

23 x x

24 x x x x

25 x x x x x

26 x x

27 x x

28 x x x

29 x x x x

30 x x x x x

31 x x

32 x x x x

33 x x x

34 x x

35 x x x x

36 x x x x x x x

37 x x x x x x x x

38 x x x

39 x x x x

40 x x x x x

41 x x x x x

42 x x x x x

43 x x x x x x x

44 x x x

45 x

46 x x x x

47 x

48 x x

49 x x x

50 x x x x x x

51 x x

52 x x x x x

53 x x x x x x

54 x x x x x

55 x x x x

56 x x x

57 x x x x x
Appendix A. Selected water-quality data collected at sites in the 

Idaho statewide surface-water-quality monitoring network, 1989-

2002

 1. Maximum water temperature

 2. Minimum water temperature

 3. Mean water temperature

 4. Suspended sediment

 5. Turbidity

 6. Specific conductance

 7. Hardness

 8. Calcium-magnesium ratio

 9. Dissolved oxygen

 10. Dissolved oxygen, percent saturation

 11. pH

 12. Inorganic nitrogen

 13. Total nitrogen

 14. Total phosphorus

 15. Dissolved cadmium

 16. Dissolved copper

 17. Dissolved lead

 18. Dissolved mercury

 19. Dissolved selenium

 20. Dissolved zinc

 21. Fecal coliform bacteria
[This page intentionally left blank]
10 25 50 75 90

1 1,730 -3.9 20.6 3.6 5.4 9.1 14.8 17.5

2 591 2.4 22.0 3.8 7.8 13.2 17.6 20.0

3 371 0.9 25.3 2.0 5.4 14.6 19.2 22.3

4 596 6.0 21.9 9.5 12.4 15.7 18.4 19.6

5 1,076 2.0 22.5 4.1 5.4 9.1 14.9 19.3

6 444 5.8 24.5 8.4 10.4 15.8 19.5 21.7

7 1,099 1.8 27.1 3.6 5.9 15.5 21.2 23.6

8 275 6.8 16.9 10.7 11.7 13.1 14.4 16.3

10 398 6.8 21.0 10.9 13.3 15.3 17.8 19.5

11 598 0.8 25.6 9.6 13.2 17.3 20.2 22.2

12 35 11.2 16.0 11.6 11.9 12.3 13.1 14.6

13 712 0.0 34.1 0.1 12.1 19.6 23.2 25.9

14 580 6.2 36.7 12.4 14.6 17.2 20.2 21.8

15 770 2.3 24.9 8.0 13.5 18.5 21.5 23.0

16 430 9.5 24.4 14.8 17.0 19.7 21.5 22.5

17 754 0.1 27.8 1.9 11.6 17.8 21.6 23.6

18 450 1.9 23.6 7.5 14.4 18.2 21.3 22.6

19 224 9.8 28.0 15.1 18.5 21.8 23.1 24.8

20 277 11.9 24.0 16.7 18.0 19.9 21.1 22.2

21 249 15.7 17.8 15.8 16.0 16.2 16.5 16.7

22 396 11.5 22.9 14.6 17.0 18.5 20.1 21.1

23 277 14.3 15.4 14.5 14.7 14.8 14.9 15.0

24 664 5.1 27.9 8.4 13.7 18.4 21.7 23.7

25 129 8.7 22.9 14.1 16.9 19.0 20.5 21.4

26 130 8.7 21.4 12.5 14.9 16.7 18.0 19.4

27 577 0.0 20.0 0.1 5.6 11.9 14.9 16.8

28 322 8.7 22.9 13.1 15.0 18.2 20.3 21.6

29 366 2.9 28.2 9.6 15.5 20.1 24.2 26.0

30 422 9.6 22.7 14.2 16.2 18.4 20.2 21.2

31 127 18.8 31.6 22.5 24.8 26.8 29.4 30.7

32 272 9.7 36.0 14.5 18.0 21.0 23.2 25.0

33 146 9.6 24.1 13.1 16.4 19.2 20.8 22.3

34 375 2.4 18.4 5.6 8.8 11.5 15.3 17.4

35 936 1.6 22.0 5.5 7.7 12.1 17.9 19.4

36 712 0.3 25.1 5.3 7.4 13.4 19.9 22.6

37 320 13.2 26.9 17.5 19.3 22.3 24.0 25.5

38 249 7.0 22.7 11.5 13.8 16.3 19.0 20.7

39 469 1.4 25.2 2.2 4.1 11.9 20.8 23.7

40 85 17.2 23.5 18.4 20.1 21.1 22.5 22.8

41 578 1.2 28.4 3.5 11.0 18.6 23.1 25.0

42 348 9.3 29.0 14.6 17.5 23.2 24.9 26.0

43 481 0.4 29.3 2.0 7.1 15.8 22.2 25.2

44 428 5.4 20.1 10.6 13.0 14.4 16.3 17.8

45 268 10.1 23.1 12.1 14.8 16.2 19.0 20.9

46 356 2.2 19.3 8.4 11.1 14.2 16.6 17.7

47 270 4.1 19.0 8.0 11.1 14.0 16.1 17.4

48 326 7.6 23.4 11.3 14.7 17.6 19.3 20.2

49 2,073 1.0 25.5 4.0 6.5 11.5 18.5 22.5

50 647 2.8 29.1 6.0 12.0 18.7 23.0 25.7

51 390 6.6 28.0 10.4 14.4 20.6 24.0 25.9

52 610 0.0 29.3 1.1 7.0 16.3 21.6 25.4

53 314 0.1 25.3 0.2 3.4 13.4 19.7 23.2

54 703 0.1 26.0 2.5 9.1 12.8 19.6 22.5

55 326 6.3 24.3 12.0 14.2 17.5 20.7 21.8

56 459 0.0 22.0 0.0 0.2 7.4 14.9 17.5

57 1,215 3.9 23.2 9.2 14.5 17.8 19.9 21.1

Percentiles

Appendix A-1. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality monitoring 

network, 1989 – 2002

Site No.

MAXIMUM WATER TEMPERATURE (degrees Celsius)

Minimum Maximum

No. of

obs.

Appendix A-1
10 25 50 75 90

1 1730 -3.9 19.7 3.1 5.1 9.8 14.6 17.2

2 591 1.4 20.6 2.0 6.7 12.7 16.3 18.7

3 371 0.1 22.0 5.0 9.4 12.9 115.3 16.9

4 596 4.7 18.5 3.0 4.7 8.7 13.1 15.0

5 1,076 0.4 16.5 2.8 4.4 7.6 12.6 15.3

6 444 4.2 20.2 3.8 6.7 13.6 18.5 21.5

7 1,099 1.4 25.9 3.4 6.9 13.0 18.6 21.8

8 275 4.0 14.3 8.3 10.5 12.6 14.1 15.8

10 398 5.1 18.1 8.2 11.2 13.9 16.7 18.5

11 598 0.7 22.0 8.2 10.9 14.7 17.6 19.1

12 35 9.6 14.5 0.0 8.4 14.1 17.1 18.6

13 712 0.0 22.8 5.2 10.9 14.6 17.4 18.9

14 580 5.3 20.8 7.8 11.5 15.0 17.7 19.0

15 770 0.1 21.9 7.8 12.0 15.4 17.5 18.7

16 430 6.1 19.9 4.5 11.2 15.3 17.5 19.3

17 754 0.0 23.3 3.5 10.7 16.0 19.1 20.7

18 450 0.8 22.8 10.9 14.4 18.2 20.5 21.6

19 224 9.0 23.8 14.9 16.6 19.0 20.4 21.0

20 277 10.8 21.3 15.3 15.5 15.6 18.9 20.5

21 249 15.2 15.7 12.9 14.6 15.4 15.6 16.4

22 396 9.7 18.2 13.0 14.1 14.5 15.3 16.4

23 277 14.0 14.5 8.2 12.6 14.3 16.5 18.8

24 664 4.0 21.9 7.1 11.0 14.7 17.0 19.1

25 129 6.0 18.2 9.5 11.5 13.1 14.5 15.8

26 130 6.1 15.7 0.0 2.3 7.1 10.1 12.4

27 577 0.0 14.1 0.0 4.3 8.5 10.9 13.2

28 322 5.6 15.5 8.4 10.6 13.5 17.9 21.5

29 366 0.2 24.2 9.3 12.6 15.5 17.7 20.9

30 422 5.5 20.1 10.7 13.1 15.6 17.6 21.8

31 126 15.3 26.3 13.1 17.2 20.5 21.9 23.5

32 272 6.0 24.0 10.6 14.4 17.2 20.7 22.1

33 146 7.3 20.1 5.6 8.6 12.8 15.2 16.7

34 375 1.8 17.0 3.5 5.9 9.5 14.1 15.7

35 936 0.0 18.9 3.7 5.7 9.8 14.8 17.8

36 712 -0.1 21.2 4.8 8.9 15.4 19.4 20.9

37 320 11.2 24.3 9.1 12.4 15.8 20.4 22.2

38 249 3.1 17.7 1.6 5.4 11.2 15.8 19.7

39 469 0.6 23.2 1.2 3.7 14.1 19.2 21.3

40 85 15.8 22.3 2.3 8.7 15.8 19.8 21.1

41 578 0.0 24.5 3.5 10.9 16.1 19.4 20.8

42 348 7.3 23.7 1.9 9.8 16.1 19.6 21.5

43 481 0.3 26.6 2.3 8.1 11.0 14.2 20.8

44 428 1.8 14.2 7.9 9.6 11.9 14.8 16.3

45 268 6.9 19.3 6.3 8.8 11.8 15.2 16.4

46 356 0.1 13.6 4.5 7.1 10.0 11.6 12.4

47 270 1.4 14.7 6.3 8.8 11.5 13.6 14.8

48 326 4.3 17.2 4.0 6.5 11.5 16.0 21.0

49 2,070 0.5 24.0 3.5 6.0 11.5 16.0 20.5

50 647 0.4 20.1 4.9 9.1 13.3 16.1 18.5

51 390 4.0 21.6 1.1 8.7 14.6 18.4 20.4

52 610 0.0 25.8 0.1 3.9 12.4 18.2 21.0

53 314 0.0 23.1 1.7 7.4 12.1 19.0 21.7

54 703 0.1 26.0 3.5 10.0 14.5 18.7 21.6

55 326 3.7 20.1 0.0 2.9 9.6 14.2 17.8

56 459 0.0 14.2 2.1 8.0 13.8 17.4 19.0

57 1,214 3.2 21.2 8.4 12.9 16.0 18.1 19.2

Appendix A-2. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality monitoring 

network, 1989 – 2002

MINIMUM WATER TEMPERATURE (degrees Celsius)

Site No.

Percentiles

Minimum Maximum

No. of

obs.

Appendix A-2
10 25 50 75 90

1 1,730 2.0 20.0 3.8 5.3 8.9 14.4 17.1

2 591 1.9 21.3 2.9 7.6 13.0 17.2 19.4

3 371 0.4 23.5 1.6 4.9 13.4 17.5 20.6

4 596 5.3 20.1 8.5 11.2 14.2 16.7 17.9

5 1,076 1.2 19.0 3.2 4.7 7.3 12.5 16.1

6 444 4.7 21.7 7.1 9.2 14.2 17.8 19.7

7 1,099 1.6 26.3 3.5 5.8 15.0 20.6 22.7

8 275 5.8 15.3 9.4 10.8 12.7 14.0 14.8

10 398 5.9 19.3 9.5 12.1 14.1 16.5 17.9

11 598 0.8 23.6 8.8 12.2 16.1 19.0 20.6

12 35 10.4 14.6 10.5 10.6 11.0 12.4 14.2

13 712 0.0 27.5 0.0 9.8 16.9 19.9 21.6

14 580 5.7 24.2 11.4 13.6 16.0 18.9 20.3

15 770 1.0 22.2 6.6 12.1 16.8 19.7 20.8

16 430 8.4 21.7 13.1 15.2 17.6 19.3 20.1

17 754 0.0 25.5 1.0 10.4 16.4 19.9 21.8

18 450 1.2 23.2 7.2 13.7 17.7 20.7 22.1

19 224 9.5 25.5 14.7 17.4 20.6 21.8 22.8

20 277 11.4 22.1 16.1 17.5 19.4 20.7 21.1

21 249 15.4 16.1 15.5 15.6 15.7 15.9 16.0

22 396 10.8 20.4 13.5 15.5 16.8 17.9 18.6

23 277 14.1 14.7 14.3 14.4 14.5 14.6 14.6

24 664 4.5 24.4 7.6 12.0 16.7 19.5 21.4

25 129 7.4 20.2 11.4 14.6 16.5 18.2 18.9

26 130 7.3 17.4 11.1 13.1 14.5 15.6 16.6

27 577 0.0 16.6 0.0 3.1 8.9 11.9 13.4

28 322 7.1 18.1 10.7 12.2 14.5 16.4 17.2

29 366 1.7 25.9 8.7 14.4 18.6 22.2 24.1

30 422 7.9 21.0 12.2 14.1 16.5 18.2 19.1

31 127 17.5 28.0 19.6 22.4 23.7 26.1 27.0

32 272 8.6 25.2 12.5 17.0 19.8 22.1 24.0

33 146 9.0 22.3 11.6 14.8 17.4 18.9 20.1

34 375 2.2 17.4 5.3 8.0 10.9 14.5 16.4

35 936 0.9 20.2 4.5 6.5 10.4 15.9 17.4

36 488 0.0 22.5 5.1 8.0 14.8 19.0 20.8

37 320 12.5 25.5 16.3 18.1 21.1 22.7 24.3

38 249 5.2 19.7 9.3 11.7 14.2 16.2 17.6

39 469 1.1 24.0 1.5 3.5 11.0 19.4 22.0

40 85 16.9 23.1 17.6 19.5 20.7 21.6 22.2

41 578 0.8 26.4 2.8 9.5 16.7 21.1 22.8

42 348 8.3 26.4 12.8 15.9 20.8 22.1 23.2

43 481 0.3 28.0 1.5 6.6 14.3 20.8 23.6

44 428 3.9 16.6 8.8 11.4 12.5 13.5 14.9

45 268 8.8 21.1 11.8 14.0 15.9 17.3 19.3

46 356 1.1 16.1 6.7 9.2 11.9 14.1 15.0

47 270 3.2 16.7 6.3 9.4 12.3 14.0 14.8

48 326 6.4 19.2 9.3 12.7 15.4 16.7 17.6

49 1,066 2.5 23.5 4.0 6.0 11.5 18.0 21.5

50 647 1.8 23.8 5.0 10.1 15.6 18.5 20.7

51 390 5.7 24.8 9.1 13.0 18.2 20.8 22.7

52 610 0.0 27.3 0.6 5.8 15.0 20.0 23.6

53 314 0.0 24.1 0.1 2.2 12.1 17.8 21.6

54 703 0.1 23.7 2.0 8.5 12.2 18.8 21.6

55 326 5.2 21.7 10.6 13.0 16.1 19.0 19.8

56 459 0.0 17.2 0.0 0.0 5.1 11.9 13.9

57 1,215 3.6 22.2 8.7 13.7 17.0 19.0 20.1

Appendix A-3. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality

monitoring network, 1989 – 2002

MEAN WATER TEMPERATURE (degrees Celsius)

Site No.

Percentiles

Minimum Maximum

No. of

obs.

Appendix A-3
10 25 50 75 90

1 23 1 25 1 2 3 6 9

2 51 1 94 1 2 5 14 21

3 29 1 49 2 3 7 13 19

4 112 < 1 220 1 1 2 7 32

5 281 < 1 302 2 3 5 10 27

6 37 < 1 15 < 1 1 2 3 6

7 79 1 8 1 1 2 2 4

8 52 1 75 3 4 8 15 31

10 70 1 57 2 4 8 15 27

11 66 3 219 6 8 14 26 42

12 16 1 19 2 2 4 8 10

13 63 3 1,930 5 13 38 80 248

14 97 < 1 94 4 8 14 25 40

15 55 5 1,750 19 30 55 82 144

16 30 7 851 12 17 47 127 191

17 32 13 445 16 24 59 159 301

18 63 1 32 3 5 7 10 14

19 47 1 274 7 12 17 28 36

20 42 3 231 6 12 18 25 41

21 1 1 1 1 1 1 1 1

22 115 3 648 10 21 52 101 161

23 1 2 2 2 2 2 2 2

24 38 4 103 10 18 33 52 72

25 12 4 89 4 7 12 26 49

26 17 4 48 4 7 12 22 40

27 47 1 198 1 2 5 41 114

28 33 1 359 1 3 5 12 207

29 32 < 1 76 1 3 5 12 28

30 59 2 162 7 12 21 36 54

31 20 1 164 2 4 21 31 100

32 20 6 81 9 12 16 23 74

33 77 1 958 3 5 17 65 258

34 78 < 1 41 < 1 2 3 6 9

35 114 < 1 120 < 1 3 5 11 27

36 112 < 1 245 < 1 17 39 62 92

37 27 14 211 22 35 48 61 82

38 75 1 692 3 6 13 78 131

39 23 < 1 2 < 1 1 1 1 2

40 24 1 5 1 1 3 4 5

41 31 6 118 13 19 25 39 56

42 27 2 486 4 13 18 65 138

43 24 4 437 22 37 50 65 94

44 20 3 29 3 5 9 14 20

45 19 2 149 3 9 13 29 44

46 20 7 113 8 9 13 15 29

47 73 < 1 36 < 1 2 3 9 13

48 21 2 63 2 3 5 10 24

49 10 2 427 5 6 11 24 130

50 28 3 1,420 6 11 18 27 47

51 26 1 410 2 3 7 14 37

52 30 1 121 6 7 12 19 45

53 24 7 198 15 28 62 102 135

54 46 1 189 2 3 5 13 37

55 51 < 1 41 2 3 5 11 14

56 19 1 17 1 1 2 3 6

57 97 5 283 13 17 29 48 68

Appendix A-4. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality

monitoring network, 1989 – 2002

SUSPENDED SEDIMENT, milligrams per liter (mg/L)

Site No.

Percentiles

Minimum Maximum

No. of

obs.

Appendix A-4
10 25 50 75 90

1 9 0.5 24 0.9 1.0 1.5 2.0 6.7

2 42 0.2 15 0.4 0.5 0.9 2.0 5.5

3 25 0.5 11 0.6 1.0 1.5 2.2 3.4

4 30 0.2 18 0.2 0.3 0.4 1.0 1.9

5 47 0.3 48 0.5 0.6 1.1 1.8 4.4

6 28 0.2 17 0.3 0.3 0.5 1.0 1.5

7 44 0.2 15 0.3 0.4 0.7 1.7 2.2

8 47 0.2 14 0.5 0.8 1.2 2.2 8.4

10 20 0.3 28 0.5 0.8 1.5 4.6 6.4

11 28 0.5 14 0.8 1.3 2.0 3.1 4.9

12 19 0.4 10 0.6 1.1 1.4 2.2 2.6

13 47 0.6 84 1.4 2.4 6.5 22.5 46.4

14 34 0.3 19 0.5 1.0 2.2 3.5 5.6

15 17 1.4 71 1.8 2.0 3.8 17.0 29.8

16 29 0.5 170 2.0 3.0 6.1 25.0 36.8

17 29 1.5 97 2.3 2.8 20.0 32.0 40.8

18 28 0.6 16 1.1 1.6 2.3 3.6 6.9

19 23 2.5 15 3.0 3.7 4.5 6.4 9.8

20 23 1.2 28 2.3 3.1 4.3 7.4 13.9

21 14 < 0.1 17 0.1 0.1 0.2 0.3 0.4

22 7 3 31 5.6 7.9 12.0 25.5 28.0

23 19 < 0.1 8 < 0.1 0.1 0.2 0.5 1.4

24 29 0.4 25 1.1 2.7 5.9 8.5 15.0

25 13 1.7 44 1.8 2.5 4.3 9.7 13.8

26 14 0.7 8.3 0.8 1.6 2.0 3.8 5.5

27 9 0.3 55 0.5 0.5 1.3 9.5 23.8

28 29 0.1 120 0.3 0.4 0.6 1.6 10.8

29 25 0.2 10 0.3 0.4 0.5 1.6 3.6

30 25 1.3 28 2.6 3.0 4.8 10.0 16.4

31 20 0.2 33 0.4 0.8 1.8 15.0 22.6

32 20 1 14 1.1 1.9 2.7 5.0 5.7

33 20 0.2 42 0.3 0.5 0.9 2.5 18.6

34 13 0.4 11 0.8 1.0 1.2 2.1 9.7

35 52 0.4 13 0.6 1.1 1.8 3.0 5.1

36 44 0.8 37 3.1 4.0 8.1 19.3 28.7

37 25 2 61 4.2 6.0 10.0 16.0 23.6

38 14 0.2 5.8 0.3 0.6 1.1 2.1 3.4

39 20 0.2 0.7 0.2 0.3 0.3 0.5 0.6

40 24 0.3 4 0.4 0.6 1.1 1.7 2.1

41 28 1.5 58 1.8 3.6 4.6 10.0 12.0

42 26 0.9 85 2.1 3.2 19.0 36.0 42.5

43 20 1.6 77 3.5 5.8 8.8 17.0 18.0

44 13 0.4 5.3 0.5 0.9 2.0 3.7 4.4

45 13 0.6 28 0.9 1.4 2.4 3.7 5.0

46 13 1.1 20 1.5 2.2 2.3 3.5 6.2

47 14 0.2 1.3 0.2 0.3 0.4 0.5 1.2

48 14 0.4 4.3 0.5 0.6 1.5 2.7 3.9

49 11 0.5 46 0.5 1.0 2.0 6.7 28.0

50 24 0.6 140 1.1 1.6 3.0 15.5 21.7

51 17 0.2 13 0.3 1.1 1.9 7.5 11.4

52 23 0.4 52 1.8 2.6 4.8 14.5 29.0

53 20 1.1 75 1.9 2.9 6.1 16.0 26.5

54 37 0.2 6.1 0.3 0.6 1.0 1.8 3.7

55 24 0.5 15 0.6 1.0 1.9 3.6 6.7

56 0

57 33 1.9 28 4.0 5.0 6.0 10.0 15.8

Appendix A-5. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality monitoring 

network, 1989 – 2002

TURBIDITY, nephelometric turbidity units (NTU)

Site No.

Percentiles

Minimum Maximum

No. of

obs.

Appendix A-5
10 25 50 75 90

1 62 95 256 129.1 180 205.5 227 240.8

2 176 108 243 140.5 152 173 183.25 193.5

3 126 40 126 44.5 47 54 65 77

4 147 10 79 32 38 45 51 54

5 177 40 451 73 105 175 258 314

6 109 30 75 37 44 53 60 64

7 172 39 71 45 48 52 55 59.9

8 112 254 640 306 336.25 399.5 501 529.7

10 104 93 1,200 137 172 192 201 209.7

11 122 125 362 197.1 220 265.5 320.75 338

12 73 357 557 413.2 425 456 477 533.8

13 137 195 521 301.6 329 343 362 395.4

14 102 277 768 325.6 348 384.5 485.75 604.5

15 114 295 965 606.6 669.5 804 870 887.7

16 89 537 958 703.8 776 829 870 898

17 87 263 800 517.2 556.5 677 748.5 770

18 110 112 594 408.5 429 461 492.75 521.4

19 99 303 660 359.2 415.5 456 511 574

20 60 352 688 387 429 513.5 603.75 655

21 75 594 668 608.6 620 632 643.5 650.6

22 145 249 821 367.2 513 680 725 777.6

23 94 378 607 392.3 406 414.5 420 426

24 69 607 964 670.6 704 759 853 879.4

25 44 91 182 125.8 140.25 153.5 168.25 173

26 60 147 508 321.7 383 416.5 442.5 451.2

27 101 94 233 121 160 190 204 210

28 90 160 407 240.3 295.25 334 352.75 365.2

29 96 103 506 265.5 339.75 395.5 438 461.5

30 82 281 464 333 360.25 381.5 391 404

31 78 73 420 106.4 159 189.5 239.75 272.5

32 76 185 814 419.5 447.75 486 521 542

33 136 <1 106 37 47 56.5 81.25 93

34 103 51 121 61.2 70 79 92 102

35 142 52 274 73.1 82 102.5 138 157

36 124 128 640 165.4 316.75 449 515.75 558.1

37 66 205 627 372 451.25 509 560.75 586.5

38 115 36 108 46 52 66 88.5 96

39 131 16 25 18 19 20 21 22

40 81 31 67 33 36 38 41 44

41 68 50 384 68.7 98 156 190.5 254

42 74 64 258 74.6 87.25 128.5 150 174.4

43 73 95 543 127.6 229 349 440 510.4

44 78 233 553 327.7 341 371 395.75 413.6

45 68 111 352 147.7 169.75 234 266.25 298.9

46 79 222 567 302.2 364.5 413 462 511.6

47 130 29 105 33.9 40 52 82.75 95

48 54 46 170 55.3 71.25 122 139.75 147.8

49 31 114 441 156 214 310 378 413

50 75 103 370 139.8 176.5 233 281 307.2

51 61 25 119 34 43 55 64 76

52 77 16 104 36 50 66 75 84.4

53 27 541 1,330 603 757 883 994.5 1084

54 70 51 194 63.8 95.5 150 170 182

55 116 120 462 286 300.75 323.5 344 364.5

56 20 27 53 28.8 32.5 42.5 49.5 52.1

57 127 383 726 450.2 517 590 654.5 687.4

Appendix A-6. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality monitoring 

network, 1989 – 2002

SPECIFIC CONDUCTANCE, microsiemens per centimeter (μS/cm)

Site No.

Percentiles

Minimum Maximum

No. of

obs.

Appendix A-6
10 25 50 75 90

1 6 64 120 78 96 110 110 110

2 38 64 97 71 77 90 93 96

3 12 20 33 21 23 24 27 32

4 89 10 25 13 16 19 22 23

5 102 17 190 27 39 64 96 120

6 26 14 32 18 22 23 26 30

7 85 16 29 17 19 21 22 23

8 44 120 270 140 160 200 223 240

10 53 67 180 87 110 130 160 180

11 45 34 95 52 61 67 71 75

12 10 190 210 190 190 195 200 210

13 29 120 340 148 160 190 260 280

14 47 81 170 130 140 150 155 160

15 37 230 410 270 290 360 380 390

16 15 250 350 304 320 340 340 350

17 15 170 340 206 275 300 305 320

18 42 150 210 161 180 190 200 210

19 15 140 230 154 175 180 200 220

20 15 150 240 174 190 210 215 230

21 16 220 240 220 220 230 240 240

22 98 91 340 137 213 270 290 310

23 19 150 170 158 160 160 160 170

24 15 240 330 260 265 280 300 312

25 9 57 82 64 69 73 77 80

26 9 180 230 188 210 210 230 230

27 36 44 110 52 68 91 95 98

28 15 160 190 160 160 170 175 180

29 12 190 210 190 190 190 200 209

30 40 71 210 119 148 170 180 200

31 10 25 59 29 41 47 48 51

32 10 170 210 170 190 190 200 210

33 10 18 34 21 28 34 34 34

34 10 22 39 23 29 34 35 39

35 29 25 55 28 31 39 45 52

36 36 52 170 97 130 150 160 170

37 11 110 210 130 165 180 190 190

38 10 21 39 21 35 37 39 39

39 9 6 7 6 7 7 7 7

40 14 10 14 11 11 12 13 14

41 13 19 81 29 36 51 63 72

42 11 24 73 32 39 51 58 59

43 10 78 190 83 101 155 180 190

44 10 160 200 160 170 180 188 191

45 10 42 140 63 100 115 128 131

46 10 130 240 148 180 200 225 231

47 10 12 44 12 35 39 42 43

48 10 18 74 23 36 55 61 70

49 7 89 150 102 110 120 140 150

50 11 54 150 54 64 110 120 130

51 10 11 22 15 16 20 21 21

52 10 14 33 16 20 24 27 31

53 10 300 390 300 313 330 330 354

54 33 23 80 28.6 43 63 69 73.8

55 13 69 160 101.2 130 130 140 158

56 13 13 24 14 16 18 22 22.8

57 48 170 260 197 210 220 240 250

Appendix A-7. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality monitoring 

network, 1989 – 2002

HARDNESS, milligrams per liter (mg/L) as calcium carbonate

Site No.

No. of PERCENTILES

obs. Maximum Minimum

Appendix A-7
10 25 50 75 90

1 6 2.12 2.37 2.14 2.17 2.24 2.34 2.37

2 38 2.09 2.53 2.19 2.25 2.3 2.35 2.41

3 12 2.09 2.86 2.1 2.22 2.34 2.5 2.74

4 89 1.45 1.94 1.5 1.53 1.56 1.61 1.65

5 102 1.4 2.86 1.73 1.8 1.93 2.06 2.25

6 26 2.58 3.17 2.67 2.71 2.77 2.87 2.94

7 85 1.75 2.55 1.89 1.94 2.02 2.08 2.15

8 44 2.12 2.79 2.29 2.38 2.47 2.54 2.63

10 53 1.64 2.55 1.91 2.04 2.1 2.24 2.44

11 45 1.81 2.46 1.99 2.02 2.1 2.19 2.34

12 10 1.69 2.52 1.72 1.85 1.93 2.01 2.36

13 29 1.27 2.63 1.46 1.65 1.85 1.97 2.25

14 47 2.14 2.73 2.21 2.25 2.31 2.4 2.57

15 37 1.16 2.06 1.64 1.42 1.49 1.63 1.75

16 15 1.2 1.76 1.22 1.29 1.37 1.42 1.49

17 15 1.07 2.1 1.19 1.29 1.32 1.53 1.69

18 42 1.5 2.12 1.6 1.68 1.82 1.86 1.95

19 15 0.98 2.04 1.48 1.64 1.78 1.86 1.95

20 15 1.23 2.01 1.28 1.43 1.6 1.71 1.74

21 16 1.65 1.85 1.68 1.73 1.76 1.76 1.8

22 98 0.64 2.26 1.53 1.59 1.66 1.79 2.01

23 19 1.32 1.59 1.32 1.33 1.39 1.4 1.47

24 15 1.52 1.8 1.59 1.65 1.72 1.74 1.77

25 9 2.31 2.7 2.32 2.45 2.52 2.62 2.65

26 9 2.52 2.94 2.54 2.61 2.68 2.89 2.91

27 36 2.52 3.27 2.68 2.74 2.82 2.9 3.03

28 15 2.98 3.4 3.02 3.05 3.12 3.19 3.28

29 12 2.03 2.66 2.31 2.4 2.47 2.53 2.61

30 40 1.35 2.61 1.57 1.69 1.94 2.26 2.38

31 10 3.41 4.33 3.62 3.75 3.93 4.15 4.28

32 10 1.3 1.62 1.32 1.4 1.42 1.45 1.56

33 10 6.88 8.46 6.94 7.15 7.58 7.88 8.38

34 10 4.9 6.07 5.06 5.16 5.37 5.59 5.65

35 29 4.12 5.63 4.33 4.55 4.89 5.2 5.52

36 36 2.05 3.24 2.15 2.17 2.23 2.35 2.62

37 11 1.31 1.82 1.32 1.41 1.52 1.58 1.76

38 10 8.05 9.73 8.17 8.29 8.56 8.74 9.1

39 9 3.71 5.13 3.93 3.98 4.04 4.06 4.35

40 14 2.71 3.5 2.96 3 3.13 3.3 3.39

41 13 2.64 3.96 2.47 2.55 2.84 3.18 3.68

42 11 1.39 1.6 1.41 1.45 1.46 1.49 1.58

43 10 0.65 1.78 1.31 1.41 1.49 1.62 1.67

44 10 1.74 1.99 1.79 1.82 1.83 1.86 1.91

45 10 2.33 3.29 2.46 2.5 2.58 2.68 3.28

46 10 1.3 1.85 1.54 1.67 1.71 1.78 1.82

47 10 3.58 5.26 3.62 3.66 3.88 4.22 4.53

48 10 2.4 3.81 2.76 2.91 3.33 3.52 3.62

49 7 1.35 1.81 1.48 1.58 1.71 1.74 1.78

50 11 1.6 1.9 1.68 1.72 1.76 1.84 1.89

51 10 1.93 2.38 2.05 2.09 2.23 2.27 2.32

52 10 1.92 2.33 2.07 2.16 2.22 2.29 2.32

53 10 0.56 1.36 0.68 0.87 1 1.16 1.24

54 33 1.97 4.58 2.45 2.54 2.82 3.11 3.36

55 13 2.26 2.7 2.3 2.36 2.37 2.43 2.58

56 13 2.72 2.95 2.73 2.79 2.86 2.88 2.93

57 48 1.4 1.83 1.44 1.46 1.56 1.63 1.69

Appendix A-8. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality monitoring 

network, 1989 – 2002

Calcium-Magnesium ratio

Site No.

Percentiles

Minimum Maximum

No. of

obs.

Appendix A-8
10 25 50 75 90

1 21 3.2 12.6 8.0 9.0 9.8 11.0 11.5

2 55 5.4 14.5 7.7 8.7 10.6 11.8 12.8

3 34 7.7 13.4 8.6 9.4 10.5 11.4 12.2

4 67 7.0 14.5 8.5 9.7 10.8 11.8 12.4

5 97 5.1 14.0 8.8 10.1 11.0 11.9 12.4

6 40 7.6 14.6 8.4 9.4 11.1 12.2 12.5

7 86 6.3 15.1 7.9 8.7 10.4 12.1 13.1

8 58 8.2 13.8 8.4 9.3 10.5 11.4 12.8

10 73 7.9 13.4 9.0 9.4 10.0 11.0 12.1

11 72 6.4 14.3 7.1 7.9 8.8 10.0 11.2

12 25 8.4 12.9 9.4 9.7 10.3 11.0 11.6

13 74 6.0 17.3 8.5 9.3 10.6 12.1 12.9

14 101 6.7 14.1 8.0 8.7 9.6 10.6 12.4

15 58 6.4 12.4 7.7 8.3 9.1 10.5 11.0

16 36 6.5 16.6 8.0 8.5 9.4 11.0 11.8

17 40 7.4 13.5 8.0 8.8 10.0 10.9 12.2

18 68 6.3 14.3 7.7 8.3 9.2 11.0 12.0

19 51 3.2 14.7 7.8 8.5 10.0 11.3 12.4

20 47 7.4 13.9 8.0 8.5 9.3 11.3 12.7

21 27 7.6 13.1 8.4 8.7 9.0 9.5 9.9

22 141 6.9 15.3 7.9 8.4 9.2 10.2 11.1

23 40 6.7 10.8 8.6 9.0 9.3 9.6 10.2

24 43 6.3 13.6 7.9 9.0 10.0 11.1 12.1

25 18 7.1 15.4 7.5 9.1 9.8 11.6 12.2

26 18 7.3 12.2 7.9 9.0 9.8 11.2 11.5

27 48 7.6 11.9 9.3 9.5 10.1 10.7 11.6

28 39 6.7 11.8 7.8 8.6 9.9 10.6 11.2

29 36 5.3 13.7 6.2 7.2 8.9 10.8 12.1

30 64 6.4 15.6 7.9 8.9 9.7 11.1 12.8

31 23 6.7 13.0 8.1 8.8 9.6 10.8 11.8

32 22 7.7 14.2 8.6 9.3 10.3 12.0 12.4

33 25 8.4 14.6 8.9 9.6 10.8 12.0 12.9

34 75 8.7 14.6 9.3 10.4 11.6 12.4 13.4

35 110 8.4 15.8 10.0 10.4 11.4 12.5 13.7

36 100 6.4 17.3 8.3 9.1 10.2 11.7 13.7

37 28 8.2 13.7 9.4 10.0 10.9 11.6 12.3

38 24 7.6 14.9 8.9 9.8 10.4 11.7 12.7

39 26 7.4 11.7 7.6 7.9 9.9 10.5 10.9

40 30 5.4 11.6 6.7 7.8 8.6 9.3 9.8

41 35 7.4 13.9 8.5 9.1 10.4 11.1 12.0

42 28 7.8 14.5 8.6 9.1 10.3 11.2 11.7

43 26 8.5 13.9 9.8 10.2 11.0 11.7 12.7

44 23 8.3 12.3 8.6 9.2 10.1 11.3 11.8

45 23 8.2 15.0 8.6 9.1 9.4 10.5 12.7

46 23 8.5 12.9 9.0 9.9 10.6 11.5 12.0

47 24 8.6 12.4 9.2 10.0 10.5 11.5 12.2

48 24 9.1 12.8 9.4 9.8 10.8 11.9 12.4

49 14 8.3 13.9 8.6 9.9 11.3 12.4 13.3

50 31 7.1 14.0 8.4 9.7 10.6 11.4 12.4

51 28 8.6 14.7 9.2 9.8 11.0 12.1 13.3

52 32 6.1 13.4 7.7 8.6 10.0 11.6 12.6

53 27 6.6 13.8 7.5 7.9 8.4 9.8 11.9

54 47 6.9 14.5 8.6 9.6 10.8 12.4 13.7

55 54 7.6 17.8 9.3 9.7 10.8 12.3 13.5

56 20 7.3 13.3 7.9 9.0 10.9 12.4 12.7

57 100 6.8 14.0 7.9 8.4 9.3 10.4 11.9

Appendix A-9. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality monitoring 

network, 1989 – 2002

DISSOLVED OXYGEN, milligrams per liter (mg/L)

Site No.

No. of

obs.

Percentiles

Minimum Maximum

Appendix A-9
10 25 50 75 90

1 20 27 129 84.2 97.75 100 104 110.7

2 55 58 139 91 95 101 106 116.2

3 34 87 140 96.3 98 101.5 105.75 111.1

4 66 71 155 87.5 94 98 101.75 109.5

5 97 58 150 89.8 97 101 106 114.4

6 40 10 157 88.8 94 100 104 114.7

7 85 77 132 93 97 103 110 117.2

8 58 87 130 95 100.25 104.5 110 119

10 73 94 152 98.2 103 108 116 121

11 72 83 129 88.1 92 95 100 106.8

12 25 85 139 91.4 102 106 110 119.2

13 74 88 190 97.3 104 114 126.75 143.4

14 101 87 139 93 97 106 116 128

15 58 85 151 92.7 99 105.5 115.5 120.9

16 36 78 193 82.5 89.75 102 121.25 143

17 40 86 175 94.9 98 106 114.75 141.6

18 68 75 146 90.7 96 102.5 109 116.3

19 51 44 154 95 101 107 109.5 119

20 46 82 148 97.5 101.5 107 112.75 119

21 27 85 149 96 99 102 106 112.4

22 140 72 168 87 92 97 101 105.1

23 39 91 117 94.8 98.5 102 105.5 112

24 43 79 166 91.4 97 105 118 134.4

25 18 66 163 91.4 96 104.5 114.25 129.2

26 18 92 141 92.7 98.25 100 106 108.9

27 48 98 120 100.7 102 105 107.25 111.3

28 39 73 126 87 92 102 108 113

29 35 36 152 67.2 78 92 107 130.2

30 63 80 159 94 98 104 111 121.4

31 23 83 141 101.2 104.5 112 120 122.8

32 22 96 129 102.2 106.5 111.5 116.75 121.6

33 25 97 122 98.4 102 105 110 115

34 74 94 145 100.3 103.25 107 113.75 120

35 109 92 152 101 106 116 123 130

36 100 77 165 90 95 101 113.25 129.3

37 28 92 154 99 106.5 114.5 130.25 142.6

38 24 96 125 99.3 100 103.5 106.5 116.1

39 26 91 117 94 96.25 102.5 110 113

40 30 61 118 69 81.25 95 102.5 111.3

41 35 90 132 94 99 106 112.5 119.8

42 28 81 130 95.7 101.75 104 112 123.2

43 26 94 166 97 103.25 116 128.75 141

44 23 86 136 94 97 102 107.5 131.4

45 23 93 129 94.2 96.5 101 110.5 116.8

46 23 92 126 95.6 101 105 111.5 117.8

47 24 95 141 99 100 102 104 108.5

48 24 96 116 100.3 101.75 103 106 106.7

49 14 97 120 97.3 99.25 102 110.25 112.4

50 31 82 136 95 99.5 104 113 119

51 28 97 134 98 105.75 108 112.25 115.9

52 32 71 164 84.2 97 100 107 115

53 27 81 114 90 92.5 96 103.5 109.4

54 47 71 133 95.6 99 103 107 114.8

55 54 89 212 102.3 108.25 119.5 136 148.7

56 20 80 129 81.9 85 100 103 110

57 98 74 128 89.7 93 99 102.75 108

Appendix A-10. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

DISSOLVED OXYGEN, percent saturation

Site No.

No. of

obs.

Percentiles

Minimum Maximum

Appendix A-10
10 25 50 75 90

1 21 7.5 8.5 7.6 7.7 8.1 8.3 8.3

2 72 7.4 8.6 7.6 7.8 8.0 8.2 8.3

3 34 6.8 8.3 7.2 7.2 7.5 7.7 7.8

4 101 6.3 7.9 6.8 7.1 7.3 7.5 7.6

5 126 6.1 7.8 6.9 7.0 7.2 7.3 7.5

6 63 6.6 8.4 7.0 7.3 7.5 7.7 7.9

7 110 6.7 8.0 7.0 7.1 7.3 7.5 7.7

8 59 7.4 8.7 7.9 8.1 8.3 8.4 8.5

10 73 7.7 8.8 8.2 8.3 8.4 8.6 8.7

11 73 7.3 8.8 7.7 8.0 8.1 8.2 8.3

12 25 7.9 8.6 8.0 8.1 8.3 8.4 8.5

13 74 8.0 9.2 8.2 8.3 8.6 8.7 8.9

14 101 7.5 8.8 8.0 8.2 8.4 8.5 8.7

15 58 7.8 8.5 8.0 8.1 8.2 8.3 8.4

16 36 7.6 8.8 8.0 8.1 8.2 8.3 8.4

17 40 8.1 8.8 8.3 8.4 8.5 8.6 8.7

18 68 7.5 8.9 8.2 8.4 8.5 8.6 8.7

19 53 7.2 9.1 8.1 8.4 8.6 8.7 8.8

20 46 7.5 8.8 8.2 8.3 8.5 8.5 8.6

21 43 7.6 8.3 7.8 7.9 8.0 8.1 8.2

22 144 7.3 8.6 7.8 8.0 8.2 8.3 8.4

23 68 7.2 8.9 7.8 8.0 8.1 8.2 8.5

24 44 7.9 8.8 8.0 8.3 8.5 8.5 8.6

25 18 6.5 9.4 7.3 7.7 7.9 8.2 8.7

26 18 8.0 8.8 8.2 8.3 8.4 8.5 8.6

27 48 7.6 8.6 7.9 8.1 8.2 8.3 8.4

28 40 7.4 8.4 7.8 8.0 8.1 8.3 8.3

29 36 7.1 8.8 7.7 8.0 8.1 8.4 8.5

30 64 7.5 9.2 8.1 8.3 8.5 8.7 8.8

31 24 7.0 8.8 7.8 8.0 8.2 8.4 8.7

32 24 8.2 9.1 8.5 8.5 8.5 8.7 8.8

33 25 6.8 8.4 7.3 7.6 7.9 8.0 8.1

34 76 5.1 8.5 7.1 7.4 7.7 7.8 8.1

35 109 7.0 8.9 7.4 7.7 8.0 8.3 8.6

36 99 7.3 9.1 7.7 7.9 8.1 8.4 8.5

37 30 8.1 9.2 8.4 8.5 8.6 8.7 8.9

38 23 7.2 8.6 7.4 7.7 7.8 8.2 8.4

39 48 6.1 8.0 6.7 6.9 7.1 7.3 7.6

40 30 6.6 9.2 7.0 7.2 7.4 7.6 8.0

41 34 6.8 8.6 7.3 7.6 8.0 8.2 8.3

42 30 6.6 8.8 7.2 7.8 8.2 8.5 8.7

43 27 8.1 9.1 8.5 8.6 8.7 8.8 8.9

44 24 7.5 8.8 7.9 8.0 8.2 8.4 8.6

45 24 7.0 8.7 7.5 8.0 8.2 8.5 8.6

46 24 7.5 9.1 7.9 8.3 8.5 8.6 8.6

47 22 6.9 8.4 7.3 7.5 7.7 7.9 8.2

48 23 7.3 8.9 7.4 7.7 8.0 8.3 8.9

49 15 7.3 8.6 7.8 8.0 8.3 8.4 8.5

50 32 7.5 9.0 7.8 8.1 8.3 8.5 8.8

51 28 6.5 8.9 7.1 7.4 7.9 8.3 8.6

52 34 6.4 8.2 6.9 7.2 7.3 7.5 7.7

53 27 7.9 8.7 8.1 8.2 8.3 8.4 8.5

54 49 7.2 8.6 7.7 7.8 8.1 8.2 8.3

55 55 7.8 9.0 8.2 8.3 8.4 8.6 8.8

56 20 6.7 8.1 7.2 7.3 7.6 7.8 7.9

57 100 7.8 9.7 8.1 8.2 8.4 8.4 8.5

Appendix A-11. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

pH (units)

Site No.

No. of

obs.

Percentiles

Minimum Maximum

Appendix A-11
10 25 50 75 90

1 18 0.02 0.19 0.03 0.05 0.10 0.13 0.15

2 61 0.01 0.26 0.02 0.04 0.06 0.10 0.12

3 31 < 0.007 0.13 < 0.007 0.03 0.07 0.09 0.09

4 84 < 0.007 0.13 < 0.007 0.01 0.02 0.05 0.07

5 112 < 0.007 0.81 0.07 0.11 0.21 0.44 0.61

6 54 < 0.007 0.12 < 0.007 0.01 0.02 0.06 0.10

7 99 < 0.007 0.31 0.03 0.05 0.08 0.11 0.16

8 58 0.06 0.42 0.08 0.10 0.14 0.20 0.23

10 66 0.08 1.03 0.16 0.22 0.33 0.58 0.72

11 60 0.04 0.47 0.09 0.13 0.18 0.27 0.35

12 18 0.07 1.13 0.09 0.13 0.18 0.36 1.12

13 64 < 0.007 1.03 0.02 0.06 0.08 0.21 0.49

14 89 0.03 0.63 0.06 0.08 0.12 0.23 0.32

15 55 0.23 1.26 0.38 0.45 0.62 0.87 1.07

16 36 0.13 1.77 0.35 0.47 0.57 0.89 1.60

17 39 < 0.007 1.47 0.05 0.10 0.47 0.79 1.02

18 59 < 0.007 1.85 0.06 0.07 0.12 0.24 0.47

19 53 0.01 1.89 0.07 0.09 0.16 0.32 1.27

20 45 0.17 2.61 0.18 0.24 0.52 1.42 1.91

21 33 1.71 2.12 1.85 1.92 2.01 2.02 2.09

22 118 0.06 5.62 0.81 1.10 1.75 2.28 2.77

23 47 0.75 1.23 0.87 0.92 0.98 1.05 1.13

24 34 1.62 4.05 1.91 2.17 2.38 2.61 3.81

25 18 0.06 0.25 0.06 0.06 0.09 0.18 0.20

26 18 0.06 0.18 0.06 0.06 0.07 0.08 0.17

27 47 0.03 0.12 0.06 0.06 0.06 0.07 0.09

28 35 0.02 0.80 0.03 0.07 0.13 0.20 0.35

29 30 0.07 0.88 0.43 0.57 0.64 0.75 0.85

30 53 < 0.007 1.93 0.06 0.07 0.09 0.31 1.12

31 24 0.02 0.38 0.07 0.09 0.14 0.17 0.27

32 24 0.41 1.82 0.53 0.57 0.81 1.01 1.52

33 24 < 0.007 0.26 0.02 0.06 0.08 0.10 0.18

34 72 0.06 0.32 0.08 0.10 0.12 0.15 0.20

35 98 0.09 3.25 0.19 0.22 0.30 0.56 0.91

36 94 0.44 4.68 0.77 1.36 1.83 3.41 4.16

37 25 0.26 1.93 0.39 0.52 0.79 1.05 1.44

38 23 < 0.007 0.12 0.02 0.06 0.07 0.10 0.11

39 89 < 0.007 0.25 < 0.007 0.02 0.05 0.10 0.14

40 25 0.06 0.27 0.08 0.09 0.10 0.14 0.21

41 30 0.06 0.78 0.10 0.12 0.25 0.46 0.67

42 25 0.02 1.45 0.06 0.07 0.11 0.14 0.28

43 22 0.14 1.71 0.21 0.39 0.60 0.98 1.46

44 24 0.06 0.48 0.14 0.15 0.25 0.38 0.42

45 24 0.01 0.15 0.01 0.05 0.07 0.09 0.11

46 24 0.01 0.38 0.04 0.06 0.10 0.17 0.22

47 23 < 0.007 0.12 < 0.009 0.04 0.07 0.08 0.10

48 23 0.02 0.46 0.05 0.06 0.10 0.13 0.15

49 15 0.15 1.33 0.24 0.38 0.53 0.81 1.09

50 32 0.21 5.83 0.44 0.68 1.00 1.60 2.44

51 22 < 0.007 0.56 < 0.009 0.06 0.07 0.12 0.15

52 31 < 0.007 2.63 0.02 0.06 0.08 0.12 0.43

53 27 0.06 1.38 0.15 0.22 0.29 0.55 1.00

54 48 < 0.007 0.18 < 0.01 0.02 0.07 0.11 0.12

55 55 0.04 0.49 0.06 0.08 0.12 0.22 0.34

56 20 < 0.007 0.06 < 0.007 < 0.008 0.02 0.03 0.05

57 98 0.28 2.87 0.44 0.81 1.35 1.94 2.20

Appendix A-12. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

INORGANIC NITROGEN, milligrams per liter (mg/L) as nitrogen 

Site No.

No. of

obs.

Percentiles

Minimum Maximum

Appendix A-12
10 25 50 75 90

1 20 0.09 0.43 0.12 0.14 0.25 0.28 0.31

2 165 < 0.001 3.36 0.14 0.20 0.23 0.27 0.33

3 110 0.04 0.82 0.11 0.16 0.21 0.30 0.37

4 90 0.05 0.64 0.07 0.09 0.11 0.15 0.30

5 123 0.11 1.10 0.16 0.25 0.38 0.54 0.72

6 88 0.06 0.50 0.08 0.11 0.15 0.22 0.27

7 157 0.08 1.21 0.14 0.19 0.24 0.28 0.33

8 58 0.11 1.31 0.26 0.29 0.34 0.40 0.51

10 71 0.30 2.10 0.34 0.42 0.54 0.79 0.93

11 69 0.25 0.90 0.30 0.31 0.39 0.49 0.57

12 24 0.25 1.30 0.35 0.37 0.48 0.73 1.18

13 73 0.25 1.20 0.31 0.35 0.48 0.71 0.84

14 98 0.20 1.17 0.26 0.29 0.35 0.52 0.66

15 56 0.54 1.46 0.66 0.78 0.93 1.15 1.37

16 36 0.52 2.57 0.79 0.94 1.13 1.65 2.00

17 39 0.34 1.90 0.46 0.58 0.95 1.23 1.50

18 67 0.25 2.10 0.31 0.35 0.45 0.69 0.87

19 53 0.33 2.30 0.45 0.54 0.65 0.87 1.67

20 46 0.23 3.10 0.53 0.67 1.00 1.80 2.33

21 33 1.90 2.60 1.90 2.00 2.10 2.20 2.28

22 119 0.30 5.60 1.26 1.65 2.13 2.63 3.10

23 48 0.80 1.43 0.92 1.00 1.10 1.15 1.23

24 44 0.35 5.00 2.35 2.55 2.71 3.17 4.37

25 18 0.30 0.85 0.36 0.38 0.43 0.61 0.78

26 18 0.25 0.74 0.25 0.28 0.35 0.52 0.59

27 47 0.11 0.99 0.21 0.25 0.25 0.26 0.28

28 40 0.10 1.21 0.15 0.25 0.35 0.54 0.79

29 35 0.25 2.10 0.65 0.80 0.86 1.05 1.16

30 62 0.25 2.20 0.35 0.45 0.58 0.95 1.53

31 24 0.21 0.74 0.26 0.29 0.35 0.48 0.56

32 24 0.63 2.10 0.94 1.13 1.23 1.57 1.70

33 24 0.08 1.15 0.11 0.25 0.27 0.38 0.57

34 72 0.15 0.51 0.19 0.22 0.26 0.32 0.40

35 103 0.18 4.00 0.35 0.40 0.50 0.81 1.30

36 94 0.63 5.33 1.18 1.93 2.42 3.90 4.56

37 30 0.87 2.40 1.02 1.30 1.51 1.80 2.11

38 23 0.06 0.29 0.09 0.15 0.19 0.25 0.27

39 91 0.11 0.44 0.14 0.16 0.22 0.25 0.30

40 30 0.19 1.25 0.25 0.34 0.47 0.58 0.77

41 35 0.25 1.80 0.29 0.37 0.60 0.75 1.02

42 30 0.21 1.80 0.25 0.35 0.51 0.68 1.01

43 27 0.79 2.30 0.86 1.13 1.40 1.78 2.00

44 24 0.31 0.72 0.34 0.37 0.46 0.57 0.65

45 24 0.17 0.51 0.22 0.25 0.27 0.35 0.43

46 24 0.21 0.84 0.25 0.29 0.36 0.44 0.54

47 22 0.07 0.29 0.12 0.15 0.18 0.25 0.25

48 23 0.14 0.65 0.17 0.21 0.25 0.29 0.33

49 15 0.34 1.50 0.50 0.73 0.86 0.99 1.32

50 32 0.59 7.30 0.65 1.05 1.37 2.21 3.25

51 27 0.14 1.00 0.18 0.22 0.25 0.40 0.70

52 34 0.15 3.30 0.20 0.25 0.32 0.47 0.66

53 27 0.45 1.60 0.56 0.68 0.84 1.00 1.38

54 48 0.11 1.06 0.19 0.25 0.25 0.30 0.40

55 55 0.19 2.90 0.23 0.27 0.36 0.49 0.56

56 20 < 0.06 0.18 0.06 0.08 0.11 0.14 0.16

57 99 0.40 3.30 0.86 1.36 1.70 2.37 2.60

Appendix A-13. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

TOTAL NITROGEN, milligrams per liter (mg/L) as nitrogen

Site No.

No. of

obs.

Percentiles

Minimum Maximum

Appendix A-13
10 25 50 75 90

1 20 0.004 0.23 0.005 0.006 < 0.01 < 0.01 0.05

2 165 < 0.001 0.06 0.003 0.01 < 0.01 0.01 0.02

3 110 < 0.001 0.09 0.006 < 0.01 0.011 0.02 0.03

4 90 0.002 0.19 0.003 0.004 0.008 0.01 0.02

5 123 0.007 0.17 0.01 0.02 0.03 0.05 0.08

6 88 < 0.001 0.05 0.003 0.004 0.007 < 0.01 0.01

7 157 < 0.001 0.06 0.005 0.008 0.01 0.02 0.03

8 58 < 0.01 0.40 < 0.01 < 0.01 0.02 0.03 0.06

10 71 < 0.01 0.12 < 0.01 < 0.01 0.02 0.03 0.04

11 69 < 0.01 0.17 < 0.01 0.02 0.03 0.04 0.05

12 24 0.01 0.06 0.01 0.02 0.04 0.05 0.06

13 73 < 0.01 0.43 0.01 0.03 0.04 0.06 0.12

14 98 < 0.01 0.11 0.01 0.02 0.03 0.04 0.05

15 56 < 0.01 0.27 0.02 0.03 0.04 0.06 0.11

16 36 0.02 0.22 0.03 0.04 0.06 0.13 0.16

17 39 < 0.01 0.28 0.02 0.03 0.06 0.11 0.14

18 67 < 0.01 0.14 < 0.01 0.02 0.04 0.07 0.08

19 53 0.03 0.43 0.04 0.05 0.07 0.11 0.21

20 46 0.02 0.39 0.04 0.05 0.07 0.10 0.16

21 28 < 0.01 0.04 < 0.01 < 0.01 0.01 0.02 0.02

22 119 < 0.01 0.41 0.04 0.06 0.08 0.12 0.15

23 44 < 0.01 0.17 < 0.01 < 0.01 0.014 0.02 0.05

24 42 < 0.01 0.25 0.02 0.03 0.05 0.08 0.10

25 18 0.01 0.11 0.02 0.03 0.05 0.07 0.07

26 18 < 0.01 0.10 0.02 0.03 0.04 0.05 0.08

27 47 0.008 0.25 < 0.01 < 0.01 0.01 0.03 0.05

28 40 0.003 0.57 < 0.01 < 0.01 < 0.01 0.05 0.10

29 35 < 0.01 0.05 < 0.01 < 0.01 < 0.01 0.02 0.05

30 62 < 0.01 0.33 0.03 0.05 0.07 0.10 0.12

31 24 0.008 0.12 < 0.01 0.01 0.02 0.04 0.07

32 24 0.02 0.11 0.04 0.05 0.06 0.08 0.08

33 23 0.007 0.23 0.008 < 0.01 < 0.01 0.02 0.10

34 72 0.01 0.09 < 0.01 0.01 0.03 0.05 0.06

35 103 0.02 1.3 0.04 0.06 0.10 0.18 0.30

36 94 0.08 0.63 0.17 0.26 0.32 0.43 0.49

37 30 0.06 0.35 0.07 0.08 0.10 0.12 0.16

38 23 0.003 0.07 0.004 < 0.01 < 0.01 0.01 0.03

39 91 0.001 < 0.05 0.003 0.004 0.005 0.009 < 0.01

40 30 < 0.01 0.07 < 0.01 0.02 0.04 0.05 0.05

41 35 0.02 0.25 0.03 0.04 0.05 0.07 0.09

42 30 < 0.01 0.64 0.02 0.05 0.10 0.15 0.22

43 27 0.02 0.18 0.06 0.08 0.11 0.15 0.16

44 24 < 0.01 0.08 0.02 0.03 0.03 0.05 0.07

45 24 < 0.01 0.12 < 0.01 < 0.01 0.03 0.04 0.08

46 24 0.02 0.15 0.02 0.03 0.05 0.06 0.06

47 23 0.004 < 0.05 0.005 0.009 < 0.01 0.01 0.02

48 23 < 0.01 0.05 < 0.01 < 0.01 0.02 0.03 0.04

49 15 0.02 0.23 0.02 0.04 0.05 0.07 0.14

50 32 0.06 1.12 0.08 0.09 0.10 0.13 0.15

51 27 < 0.01 0.10 < 0.01 0.01 0.02 0.04 0.07

52 34 0.03 0.19 0.04 0.04 0.05 0.08 0.13

53 27 < 0.01 0.20 0.02 0.04 0.05 0.10 0.12

54 48 0.007 0.15 < 0.01 0.01 0.02 0.02 0.04

55 55 < 0.01 0.06 0.02 0.02 0.03 0.04 0.04

56 20 0.003 0.02 0.003 0.004 0.007 0.008 0.008

57 99 0.02 0.31 0.06 0.08 0.11 0.13 0.17

Appendix A-14. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

TOTAL PHOSPHORUS, milligrams per liter (mg/L) as phosphorus

Site No.

No. of

obs.

Percentiles

Minimum Maximum

Appendix A-14
10 25 50 75 90

1 4 < 1 < 1 < 1 < 1 < 1 < 1 < 1

2 33 < 0.02 2 < 0.02 < 0.02 < 0.04 < 1 1

3 9 < 1 1 < 1 < 1 < 1 < 1 1

4 79 < 0.02 2 < 0.04 < 0.04 < 1 < 1 1

5 96 1.48 18.2 2.6 4.4 7.1 9.2 12

6 22 < 1 < 1 < 1 < 1 < 1 < 1 < 1

7 78 < 1 2 < 1 < 1 < 1 < 1 1

8 15 < 1 < 1 < 1 < 1 < 1 < 1 < 1

10 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

11 11 < 1 2 < 1 < 1 < 1 < 1 < 1

12 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

13 24 < 1 1 < 1 < 1 < 1 < 1 < 1

14 11 < 1 < 1 < 1 < 1 < 1 < 1 < 1

15 0

16 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

17 12 < 1 1 < 1 < 1 < 1 < 1 1

18 11 < 1 < 1 < 1 < 1 < 1 < 1 < 1

19 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

20 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

21 10 < 1 2 < 1 < 1 < 1 < 1 1

22 0

23 12 < 1 2 < 1 < 1 < 1 < 1 1

24 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

25 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

26 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

27 0

28 11 < 1 < 1 < 1 < 1 < 1 < 1 < 1

29 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

30 8 < 1 1 < 1 < 1 < 1 < 1 1

31 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

32 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

33 9 < 1 1 < 1 < 1 < 1 < 1 1

34 8 < 1 1 < 1 < 1 < 1 < 1 1

35 23 < 1 < 1 < 1 < 1 < 1 < 1 < 1

36 15 < 1 2 < 1 < 1 < 1 < 1 1

37 8 < 1 1 < 1 < 1 < 1 < 1 1

38 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

39 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

40 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

41 11 < 1 < 1 < 1 < 1 < 1 < 1 < 1

42 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

43 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

44 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

45 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

46 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

47 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

48 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

49 6 < 1 < 1 < 1 < 1 < 1 < 1 < 1

50 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

51 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

52 7 < 1 < 1 < 1 < 1 < 1 < 1 < 1

53 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

54 18 < 1 2 < 1 < 1 < 1 < 1 1

55 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

56 13 < 0.02 < 1 0.04 0.04 < 1 < 1 < 1

57 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

Appendix A-15. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

DISSOLVED CADMIUM, micrograms per liter (μg/L)

Site No.

No. of

obs.

Percentiles

Minimum Maximum

Appendix A-15
10 25 50 75 90

14 2 3 2 2 2 2 3

2 33 0.2 38 0.2 0.2 0.7 3 8

3 9 < 1 5 < 1 < 1 1 3 3.4

4 29 < 0.2 4 < 1 < 1 < 1 1 3

5 47 < 1 11 < 1 < 1 1 2 4

66 1 5 1 1 2 2 4

7 36 < 1 11 < 1 < 1 < 1 2 5

8 15 < 1 13 1 2 3 3 5

10 8 < 1 2 < 1 < 1 2 2 2

11 11 < 1 2 < 1 < 1 1 2 2

12 8 1 5 1 1 2 3 5

13 24 < 1 3 < 1 < 1 < 1 1 1

14 11 < 1 2 < 1 < 1 1 2 2

15 0

16 13 < 1 3 < 1 < 1 1 2 3

17 11 < 1 5 < 1 < 1 1 3 5

18 11 < 1 5 < 1 < 1 1 2 2

19 12 < 1 7 < 1 1 1 2 4

20 12 < 1 5 < 1 < 1 2 2 3

21 10 < 1 3 < 1 < 1 1 1 2

22 0

23 12 < 1 4 < 1 < 1 < 1 < 1 2

24 12 < 1 2 < 1 < 1 < 1 2 2

25 8 < 1 5 < 1 < 1 < 1 2 4

26 8 < 1 1 < 1 < 1 < 1 1 1

27 0

28 11 < 1 1 < 1 < 1 < 1 < 1 1

29 8 < 1 40 < 1 < 1 < 1 1 13

30 8 < 1 4 < 1 < 1 1 2 4

31 8 < 1 2 < 1 < 1 < 1 < 1 1

32 8 < 1 2 < 1 < 1 1 1 2

33 17 < 1 2 < 1 < 1 < 1 1 1

34 8 < 1 1 < 1 < 1 1 1 1

35 23 < 1 3 < 1 < 1 1 1 2

36 15 < 1 6 < 1 1 1 2 3

37 8 < 1 5 < 1 < 1 1 2 3

38 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

39 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

40 12 < 1 1 < 1 < 1 < 1 1 1

41 11 < 1 2 < 1 < 1 1 2 2

42 8 < 1 4 1 1 1 2 3

43 8 < 1 4 < 1 < 1 3 3 3

44 8 < 1 3 < 1 < 1 < 1 1 2

45 8 < 1 3 < 1 < 1 2 2 2

46 8 < 1 2 < 1 < 1 < 1 1 1

47 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

48 8 < 1 1 < 1 < 1 < 1 1 1

49 18 1 4 1 1 2 2 3

50 8 < 1 2 < 1 < 1 2 2 2

51 8 1 2 1 1 2 2 2

52 7 1 10 2 3 3 4 6

53 8 < 1 11 < 1 < 1 <1 2 5

54 6 2 4 2 2 2 3 4

55 12 < 1 13 < 1 < 1 2 4 5

56 12 0.2 < 1 0.2 0.4 < 1 < 1 < 1

57 12 < 1 6 < 1 < 1 1 4 5

Appendix A-16. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

DISSOLVED COPPER, micrograms per liter (μg/L)

Site No.

No. of

obs.

PERCENTILES

Minimum Maximum

Appendix A-16
10 25 50 75 90

1 12 < 1 6 < 1 < 1 < 1 < 1 < 1

2 15 < 1 60 < 1 < 1 < 1 2 8

3 9 < 1 20 < 1 < 1 1 1 5

4 79 < 0.04 2 < 0.08 < 1 < 1 < 1 1

5 96 1 420 2 3 4 6 8

6 22 < 1 1 < 1 < 1 < 1 < 1 1

7 77 < 0.04 14 0.16 0.42 < 1 < 1 1

8 15 < 0.04 6 < 1 < 1 < 1 2 4

10 8 < 1 3 < 1 < 1 < 1 < 1 2

11 11 < 1 1 < 1 < 1 < 1 < 1 1

12 8 < 1 1 < 1 < 1 < 1 < 1 1

13 24 < 1 < 10 < 1 < 1 < 1 < 1 1

14 11 < 1 < 10 < 1 < 1 < 1 1 1

15 0

16 12 < 1 1 < 1 < 1 < 1 < 1 1

17 12 < 1 1 < 1 < 1 < 1 < 1 1

18 11 < 1 < 1 < 1 < 1 < 1 < 1 < 1

19 12 < 1 1 < 1 < 1 < 1 < 1 1

20 12 < 1 1 < 1 < 1 < 1 < 1 1

21 10 < 1 1 < 1 < 1 < 1 < 1 1

22 0

23 12 < 1 10 < 1 < 1 < 1 < 1 1

24 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

25 8 < 1 1 < 1 < 1 < 1 < 1 1

26 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

27 0

28 11 < 1 < 1 < 1 < 1 < 1 < 1 < 1

29 8 < 1 40 < 1 < 1 < 1 < 1 13

30 8 < 1 1 < 1 < 1 < 1 < 1 1

31 8 < 1 1 < 1 < 1 < 1 < 1 1

32 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

33 9 < 1 2 < 1 < 1 < 1 < 1 1

34 8 < 1 1 < 1 < 1 < 1 < 1 1

35 23 < 1 1 < 1 < 1 < 1 < 1 < 1

36 15 < 1 2 < 1 < 1 < 1 < 1 1

37 8 < 1 2 < 1 < 1 < 1 < 1 1

38 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

39 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

40 12 < 1 2 < 1 < 1 < 1 < 1 1

41 11 < 1 2 < 1 < 1 < 1 1 1

42 7 < 1 1 < 1 < 1 < 1 < 1 1

43 8 < 1 3 < 1 < 1 < 1 < 1 2

44 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

45 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

46 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

47 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

48 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

49 6 < 1 7 < 1 < 1 < 1 1 4

50 8 < 1 1 < 1 < 1 < 1 < 1 1

51 8 < 1 3 < 1 < 1 < 1 1 2

52 7 < 1 3 < 1 < 1 1 3 3

53 12 < 1 6 < 1 < 1 < 1 < 1 1

54 18 < 1 3 < 1 < 1 < 1 1 1

55 12 < 1 8 < 1 < 1 < 1 < 1 1

56 13 0.08 < 1 < 0.08 0.08 < 1 < 1 < 1

57 12 < 1 1 < 1 < 1 < 1 < 1 1

Appendix A-17. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

DISSOLVED LEAD, micrograms per liter (μg/L)

Site No.

No. of

obs.

PERCENTILES

Minimum Maximum

Appendix A-17
10 25 50 75 90

1 4 < 0.1 0.2 < 0.1 < 0.1 < 0.1 < 0.1 0.2

2 15 < 0.1 0.2 < 0.1 < 0.1 < 0.1 < 0.1 0.1

3 9 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

4 9 < 0.1 0.2 < 0.1 < 0.1 < 0.1 < 0.1 0.1

5 17 < 0.1 0.2 < 0.1 < 0.1 < 0.1 < 0.1 0.1

6 6 < 0.1 0.2 < 0.1 < 0.1 < 0.1 0.1 0.2

7 14 < 0.1 0.1 < 0.1 < 0.1 < 0.1 < 0.1 0.1

8 16 < 0.1 0.3 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

10 8 < 0.1 0.1 < 0.1 < 0.1 < 0.1 < 0.1 0.1

11 11 < 0.1 1 < 0.1 < 0.1 < 0.1 < 0.1 0.3

12 8 < 0.1 0.2 < 0.1 < 0.1 < 0.1 0.1 0.2

13 24 < 0.1 0.3 < 0.1 < 0.1 < 0.1 < 0.1 0.1

14 11 < 0.1 0.3 < 0.1 < 0.1 < 0.1 0.1 0.2

15 0

16 12 < 0.1 0.3 < 0.1 < 0.1 < 0.1 < 0.1 0.1

17 12 < 0.1 0.1 < 0.1 < 0.1 < 0.1 < 0.1 0.1

18 11 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

19 12 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

20 12 < 0.1 0.1 < 0.1 < 0.1 < 0.1 < 0.1 0.1

21 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

22 0

23 9 < 0.1 0.1 < 0.1 < 0.1 < 0.1 < 0.1 0.1

24 12 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

25 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

26 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

27 0

28 11 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

29 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

30 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

31 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

32 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

33 9 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

34 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

35 23 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

36 15 < 0.1 0.8 < 0.1 < 0.1 < 0.1 < 0.1 0.2

37 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

38 8 < 0.1 < 0.1 0.1 < 0.1 < 0.1 < 0.1 < 0.1

39 7 < 0.1 0.2 < 0.1 < 0.1 < 0.1 < 0.1 0.1

40 12 < 0.1 0.5 < 0.1 < 0.1 < 0.1 < 0.1 0.2

41 11 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

42 8 < 0.1 0.3 < 0.1 < 0.1 < 0.1 < 0.1 0.2

43 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

44 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

45 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

46 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

47 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

48 8 < 0.1 0.2 < 0.1 < 0.1 < 0.1 < 0.1 0.1

49 6 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

50 8 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

51 8 < 0.1 0.2 < 0.1 < 0.1 < 0.1 < 0.1 0.1

52 7 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

53 8 < 0.1 0.1 < 0.1 < 0.1 < 0.1 < 0.1 0.1

54 18 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

55 12 < 0.1 1.6 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1

56 0

57 12 < 0.1 0.1 < 0.1 < 0.1 < 0.1 < 0.1 0.1

Appendix A-18. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

DISSOLVED MERCURY, micrograms per liter (μg/L)

Site No.

No. of

obs.

PERCENTILES

Minimum Maximum

Appendix A-18
Minimum Maximum 10 25 50 75 90

1 4 < 1 < 1 < 1 < 1 < 1 < 1 < 1

2 15 < 1 < 1 < 1 < 1 < 1 < 1 < 1

3 9 < 1 < 1 < 1 < 1 < 1 < 1 < 1

4 22 < 0.7 < 2 < 1 < 1 < 1 < 1 < 2

5 40 < 0.7 < 2 < 0.7 < 1 < 1 < 1 < 2

6 6 < 1 < 1 < 1 < 1 < 1 < 1 < 1

7 29 < 0.7 < 2 < 0.7 < 0.7 < 1 < 1 < 1

8 24 < 1 < 1 < 1 < 1 < 1 < 1 < 1

10 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

11 11 < 1 < 1 < 1 < 1 < 1 < 1 < 1

12 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

13 24 < 1 1 < 1 < 1 < 1 < 1 1

14 11 < 1 < 1 < 1 < 1 < 1 < 1 < 1

15 0

16 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

17 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

18 11 < 1 < 1 < 1 < 1 < 1 < 1 < 1

19 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

20 12 < 1 1 < 1 < 1 < 1 < 1 1

21 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

22 0

23 9 < 1 < 1 < 1 < 1 < 1 < 1 < 1

24 12 < 1 1 < 1 < 1 < 1 1 1

25 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

26 8 < 1 1 < 1 < 1 < 1 < 1 1

27 0

28 11 < 1 1 < 1 < 1 < 1 1 1

29 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

30 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

31 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

32 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

33 9 < 1 < 1 < 1 < 1 < 1 < 1 < 1

34 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

35 23 < 1 < 1 < 1 < 1 < 1 < 1 < 1

36 26 < 1 < 1 < 1 < 1 < 1 < 1 < 1

37 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

38 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

39 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

40 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

41 11 < 1 < 1 < 1 < 1 < 1 < 1 < 1

42 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

43 8 < 1 1 < 1 < 1 < 1 < 1 1

44 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

45 8 < 1 < 2 < 1 < 1 < 1 < 1 < 2

46 8 < 1 1 < 1 < 1 < 1 1 1

47 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

48 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

49 6 < 1 < 1 < 1 < 1 < 1 < 1 < 1

50 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

51 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

52 7 < 1 < 1 < 1 < 1 < 1 < 1 < 1

53 8 < 1 < 1 < 1 < 1 < 1 < 1 < 1

54 23 < 1 < 1 < 1 < 1 < 1 < 1 < 1

55 12 < 1 < 1 < 1 < 1 < 1 < 1 < 1

56 7 < 0.7 < 2 < 0.7 < 0.7 < 0.7 < 2 < 2

57 12 < 1 < 2 < 1 < 1 < 1 < 1 1

Appendix A-19. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

DISSOLVED SELENIUM, micrograms per liter (μg/L)

Site No.

No. of

obs.

PERCENTILES

Appendix A-19
10 25 50 75 90

1 4 7 77 7 8 10 10 57

2 27 1 28 1 3 6 13 22

3 9 < 3 40 < 3 4 13 17 24

4 79 < 3 66 < 3 4 5 13 20

5 87 227 2,100 376 576 1,060 1,400 1,695

6 22 < 1 26 < 1 < 1 8 < 20 20

7 78 29 140 38 48 63 78 91

8 15 4 40 5 9 10 15 20

10 8 < 3 28 3 4 7 10 16

11 11 < 3 12 < 3 < 3 6 9 9

12 8 3 23 4 7 10 12 18

13 24 < 3 21 < 3 < 3 < 3 6 11

14 11 < 3 320 < 3 < 3 4 13 16

15 0

16 12 < 3 140 < 3 4 11 15 101

17 12 < 3 15 < 3 5 7 10 13

18 11 < 3 11 < 3 < 3 6 8 9

19 12 < 3 9 < 3 < 3 4 6 7

20 12 < 3 8 < 3 3 5 6 7

21 10 < 3 11 < 3 4 5 8 9

22 0

23 12 < 3 20 < 3 < 3 5 9 14

24 12 < 3 22 < 3 < 3 5 8 10

25 8 < 3 100 3 4 6 25 59

26 8 < 3 10 < 3 < 3 < 3 7 8

27 0

28 11 < 3 10 3 4 5 8 10

29 8 < 3 17 < 3 4 7 13 14

30 8 < 3 12 < 3 < 3 6 10 11

31 8 < 3 7 < 3 4 5 5 6

32 8 < 3 12 < 3 < 3 < 3 7 9

33 9 < 3 8 < 3 < 3 < 3 7 7

34 8 < 3 7 < 3 < 3 4 6 6

35 23 < 3 7 < 3 < 3 5 6 6

36 15 < 3 25 < 3 4 7 10 16

37 8 < 3 8 < 3 < 3 4 6 7

38 8 < 3 13 < 3 < 3 < 3 < 3 6

39 9 < 3 6 < 3 < 3 < 3 4 4

40 11 < 3 24 < 3 < 3 4 8 10

41 11 < 3 21 < 3 < 3 6 8 9

42 8 < 3 9 < 3 4 6 8 8

43 8 < 3 5 < 3 < 3 < 3 4 4

44 8 < 3 4 < 3 < 3 < 3 4 4

45 8 < 3 16 < 3 < 3 4 12 13

46 8 < 3 210 < 3 < 3 5 6 67

47 8 < 3 20 < 3 < 3 < 3 5 10

48 8 < 3 7 < 3 < 3 < 3 < 3 4

49 6 < 3 7 3 5 6 7 7

50 8 < 3 4 < 3 < 3 < 3 4 4

51 8 < 3 5 < 3 < 3 3 4 4

52 7 9 21 9 11 12 15 16

53 8 < 3 170 4 6 7 53 97

54 18 < 3 24 < 3 < 3 5 10 10

55 12 < 3 19 < 3 < 3 6 9 10

56 13 < 1 4 < 1 < 1 < 1 2 4

57 12 < 3 80 < 3 < 3 5 13 14

Appendix A-20. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

DISSOLVED ZINC, micrograms per liter (μg/L)

Site No.

No. of

obs.

PERCENTILES

Minimum Maximum

Appendix A-20
10 25 50 75 90

1 21 < 1 250 < 1 1 5 13 67

2 59 < 1 39 < 1 < 1 1 3 7

3 34 1 117 2 4 11 20 31

4 41 < 1 80 1 1 3 8 14

5 70 < 1 216 1 1 4 10 24

6 41 < 1 34 < 1 1 3 5 10

7 63 < 1 57 2 3 7 16 28

8 49 < 1 46 < 1 1 4 12 17

10 29 < 1 98 < 1 3 11 33 53

11 42 < 1 240 2 21 45 66 112

12 24 < 1 8 < 1 < 1 < 1 3 6

13 72 1 4770 7 28 79 242 404

14 56 < 1 184 4 8 26 54 111

15 21 8 580 12 69 120 188 330

16 36 20 1980 56 79 162 304 570

17 39 2 1280 35 87 171 262 458

18 39 < 1 66 2 4 6 19 35

19 35 < 1 53 < 1 1 7 11 40

20 33 < 1 390 2 4 11 20 37

21 16 < 1 5 < 1 < 1 < 1 1 3

22 6 100 697 188 288 335 387 549

23 27 < 1 25 1 2 2 4 10

24 42 < 1 660 19 66 125 181 235

25 18 < 1 1770 3 9 69 191 442

26 18 < 1 1260 < 1 17 39 63 539

27 13 2 110 2 4 21 26 68

28 38 < 1 130 1 4 18 54 75

29 35 1 267 2 6 32 57 91

30 31 5 1060 8 49 85 129 197

31 23 4 420 13 17 40 58 97

32 23 4 180 7 11 22 35 86

33 24 < 1 220 1 3 4 10 14

34 70 < 1 560 < 1 < 1 1 2 4

35 101 2 1030 9 22 42 76 190

36 92 35 3600 81 183 402 647 1078

37 30 2 480 22 64 100 239 305

38 22 < 1 34 < 1 < 1 2 5 15

39 24 < 1 28 < 1 < 1 4 8 12

40 27 < 1 28 < 1 < 1 1 2 7

41 35 7 2680 36 100 280 415 496

42 30 < 1 920 11 47 160 295 499

43 26 13 740 42 90 120 204 351

44 24 2 1440 41 58 96 161 537

45 24 4 332 9 27 41 66 164

46 24 3 1220 7 18 74 165 291

47 23 < 1 22 < 1 1 3 11 19

48 24 8 142 8 14 24 57 82

49 14 1 90 1 2 6 14 43

50 32 20 2600 46 87 231 523 1010

51 28 3 360 7 12 25 53 146

52 33 < 1 720 9 40 83 140 191

53 27 1 1400 8 21 81 193 485

54 47 1 144 3 7 10 22 40

55 41 < 1 400 2 10 39 76 116

56 8 < 1 22 < 1 < 1 2 6 18

57 49 < 1 234 4 8 37 63 111

Appendix A-21. Selected water-quality data collected at sites in the Idaho statewide surface-water-quality 

monitoring network, 1989 – 2002

FECAL COLIFORM BACTERIA,colonies per 100 milliliters 

Site No.

PERCENTILES

Minimum Maxinum

No. of

obs.

Appendix A-21
Site No. Date

Cadmium, 

biota, tissue, 

recoverable 

dry weight 

(μg/g)

 Copper, 

biota, tissue, 

recoverable 

dry weight 

(μg/g)

 Lead, 

biota, tissue, 

recoverable 

dry weight 

(μg/g)

Mercury 

biota, tissue 

recoverable 

dry weight 

(μg/g)

Selenium, 

biota, tissue, 

recoverable 

dry weight 

(μg/g)

 Zinc, 

biota, tissue, 

recoverable 

dry weight 

(μg/g)

3 09/10/98 1.0 42 0.3 0.2 3.2 110

4 06/16/98 8.2 13 2.9 0.6 7.6 96

09/14/00 16 120 6.2 0.1 2 450

06/17/98 10 150 12 0.3 4.8 290

08/17/99 17 210 13 0.3 5.6 600

6 07/08/98 3.8 85 3.4 0.4 3.9 160

7 07/12/99 3.5 35 2.3 0.1 4.4 150

07/29/96 0.4 14 0.5 0.3 5.1 67

07/22/97 <.3 320 <.3 0.1 9.7 120

33 09/04/97 1.8 79 1.1 0.4 2.8 160

37 08/06/97 0.6 38 <.2 0.2 4.4 96

54 08/14/97 1.9 100 0.4 0.4 5.5 190

09/13/00 <.2 10 <.2 0.1 2.2 95

09/01/99 0.5 17 <.2 0.3 5.6 87

4 06/16/98 <.1 1.5 0.7 0.1 0.8 20

06/17/98 0.6 1.8 1.7 0.1 1.1 36

08/17/99 0.2 1.8 2.1 0.1 1.4 45

6 07/08/98 <.2 1.5 <.2 0.2 1 16

37 08/06/97 <.2 1.3 <.2 0.9 1 25

11 08/06/96 0.5 50 <.2 0.3 3.3 100

14 09/10/96 1.6 87 <.2 1 5.3 170

17 09/09/96 1.2 88 <.3 0.2 5.4 240

36 12/11/96 0.3 27 <.1 <.1 1.7 110

57 07/23/96 0.4 31 <.2 0.2 5.1 100

Appendix B. Concentrations of selected trace elements in tissue of fish collected at selected sites in the Idaho 

statewide surface-water-quality monitoring network, 1996-2000

[Site locations shown in figure 1; No., number; μg/g, micrograms per gram; <, less than]

Whole-body fish

Fish liver

Fish fillet

5

22

5

56

Appendix B-1
Site 

No. Date

Aldrin, 

biota, 

whole 

organism, 

wet weight, 

(μg/kg)

alpha-HCH, 

biota, 

whole 

organism, 

wet weight, 

(μg/kg)

beta-HCH, 

biota, 

whole 

organism, 

wet weight, 

(μg/kg)

cisChlordane 

biota, 

whole 

organism, 

wet weight, 

(μg/kg)

cisNonachlor, 

biota, whole 

organism, 

wet weight, 

(μg/kg)

DCPA, 

biota, 

whole 

organism, 

wet 

weight, 

(μg/kg)

delta-HCH, 

biota, 

whole 

organism, 

wet 

weight, 

(μg/kg)

Dieldrin, 

biota, 

whole 

organism, 

wet 

weight, 

(μg/kg)

Endrin, 

biota, 

whole 

organism, 

wet 

weight, 

(μg/kg)

Heptachlor, 

epoxide, 

biota, whole 

organism, 

wet weight, 

(μg/kg)

Heptachlor, 

biota, whole 

organism, 

wet weight, 

(μg/kg)

Hexac

benz

biota, 

organ

wet w

(μg/

3 09/10/98 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <4 06/16/98 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <

06/17/98 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <08/17/99 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <

6 07/08/98 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <

07/07/98 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <09/01/99 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <

7 07/12/99 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <

11 08/06/96 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <14 09/10/96 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <17 09/09/96 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <

07/29/96 <5 <5     <28    

07/22/97 <5 <5 <5 <5 <5 <5 <5 E5 <5 <5 <5 <

57 07/23/96 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <33 09/04/97 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <36 12/11/96 <5 <7 <5 <10 <10 <5 <8 <14 <16 <10 <5 <37 08/06/97 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <54 08/14/97 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <2256

5

Appendix C. Concentrations of organochlorine compounds and lipids in whole-body fish collected at selected sites in the Idaho statewide surface-water-q

1996-1999[Site locations shown in figure 1; μg/kg, micrograms per kilogram; <, less than; E, estimate; , no data]
Site 

No. Date

Mirex, 

biota, 

whole 

organism, 

wet weight 

(μg/kg) 

o,p'-DDE, 

biota, 

whole 

organism, 

wet weight 

(μg/kg)

o,p'-DDE, 

biota, 

whole 

organism, 

wet weight 

(μg/kg)

o,p'-DDT, 

biota, 

whole 

organism, 

wet weight 

(μg/kg)

o,p'-

Methoxy 

chlor, biota, 

whole 

organism, 

wet weight 

(μg/kg)

Oxychlordane, biota, 

whole 

organism, 

wet weight 

(μg/kg)

p,p'-DDD, 

biota, 

whole 

organism, 

wet weight 

(μg/kg)

p,p'-DDE, 

biota, 

whole 

organism, 

wet weight 

(μg/kg)

p,p'-DDT, 

biota, 

whole 

organism, 

wet weight 

(μg/kg)

p,p'- 

Methoxy 

chlor, biota, 

whole 

organism, 

wet weight 

(μg/kg)

 PCBs, 

biota, whole 

organism, 

wet weight 

(μg/kg)

Pentachloroanisole, 

biota, 

whole 

organism, 

wet weight 

(μg/kg)

3 09/10/98 <5 <5 <5 <5 <5 <5 <5 11 <5 <5 60 <5 4 06/16/98 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 150 <5 5 06/17/98 <5 <5 <5 <5 <5 <5 <5 14 <5 <5 310 <5 

08/17/99 <5 <5 <5 <5 <5 <5 <5 9 <5 <5 200 <5 

6 07/08/98 <5 <5 <5 <5 <5 <5 <5 10 <5 <5 <50 <5 

56 07/07/98 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <50 <5 

09/01/99 <5 <5 <5 <5 <5 <5 <5 5 <5 <5 <50 <5 

7 07/12/99 <5 <5 <5 <5 <5 <5 <5 11 <5 <5 270 <5 

11 08/06/96 <5 <5 <5 <5 <5 <5 E16 290 17 <5 50 <5 14 09/10/96 <5 <5 <5 <5 <5 <5 E17 250 13 <5 60 <5 17 09/09/96 <5 <5 <5 <5 <5 <5 <5 47 E13 <5 240 <5 22 07/29/96  <8   E16 650 38 <7 50  

07/22/97 <5 <5 <5 <5 <5 <5 8 68 6 <5 60 <5 

57 07/23/96 <5 <5 <5 <5 <5 <5 E17 470 E11 <5 <50 <5 33 09/04/97 <5 <5 <5 <5 <5 <5 5 79 14 <5 <50 <5 36 12/11/96 <5 <5 <5 <5 <5 <5 52 770 E60 <10 100 <5 37 08/06/97 <5 <5 <5 <5 <5 <5 24 810 50 <5 <50 <5 54 08/14/97 <5 <5 <5 <5 <5 <5 <5 33 6 <5 <50 <5 

Appendix C. Concentrations of organochlorine compounds and lipids in whole-body fish collected at selected sites in the Idaho statewide surface-water-qualitnetwork, 1996-1999--Continued
Manuscript approved for publication, February 13, 2005.

Manuscript released on World Wide Web, June 2005, , 

at http://id.water.usgs.gov

Prepared by U.S. Geological Survey Publishing staff, 

Idaho District, Boise, Idaho:

Launa H. Allen

Linda G. Buckmaster

Linda K. Channel

Richard L. Helton

Barbara N. Kemp

For more information concerning the research in this report, contact:

Idaho District Chief

U.S. Geological Survey, Idaho Water Science Center

230 Collins Road

Boise, Idaho 83702-4520
1989 – 2002 — SIR 2005 – 5033

Hardy, M.A., Parliman, D.J., and O’Dell, Ivalou — Status of and changes in water quality monitored for the Idaho statewide surface-water-quality network,