NATIONAL WATER-QUALITY ASSESSMENT PROGRAM

Water-Resources Investigations Report 02–4183

U.S. Department of the Interior

U.S. Geological Survey

Occurrence and Transport of Cadmium, Lead, and

Zinc in the Spokane River Basin, Idaho and

Washington, Water Years 1999–2001
Cover photos: Top left, mine tailings on the East Fork of Ninemile Creek; top right, Coeur d’Alene River near 

Cataldo during rain-on-snow event; center, discharge of metal-enriched sediment entering Coeur d’Alene Lake 

from the Coeur d’Alene River; bottom left, Spokane River near Spokane.
Occurrence and Transport of Cadmium, Lead, and 

Zinc in the Spokane River Basin, Idaho and 

Washington, Water Years 1999–2001

By Gregory M. Clark

Water-Resources Investigations Report 02–4183

Boise, Idaho

2003
U.S. DEPARTMENT OF THE INTERIOR

GAIL A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Any use of firm, trade, and brand names in this report is for

identification purposes only and does not constitute

endorsement by the U.S. Government.

Additional information can be obtained from:

District Chief

U.S. Geological Survey

230 Collins Road

Boise, ID 83702-4520

http://idaho.usgs.gov

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Acrobat Reader, at URL:

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Copies of this report can be purchased from:

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e-mail: infoservices@usgs.gov
Foreword iii

FOREWORD

Foreword

The U.S. Geological Survey (USGS) is committed to serve the Nation with accurate and timely scientific 

information that helps enhance and protect the overall quality of life, and facilitates effective management of water, 

biological, energy, and mineral resources (http://www.usgs.gov/). Information on the quality of the Nation’s water 

resources is of critical interest to the USGS because it is so integrally linked to the long-term availability of water 

that is clean and safe for drinking and recreation and that is suitable for industry, irrigation, and habitat for fish and 

wildlife. Escalating population growth and increasing demands for the multiple water uses make water availability, 

now measured in terms of quantity and quality, even more critical to the long-term sustainability of our communities and ecosystems.

The USGS implemented the National Water-Quality Assessment (NAWQA) Program to support national, 

regional, and local information needs and decisions related to water-quality management and policy 

(http://water.usgs.gov/nawqa/). Shaped by and coordinated with ongoing efforts of other Federal, State, and local 

agencies, the NAWQA Program is designed to answer: What is the condition of our Nation’s streams and ground 

water? How are the conditions changing over time? How do natural features and human activities affect the quality 

of streams and ground water, and where are those effects most pronounced? By combining information on water 

chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide sciencebased insights for current and emerging water issues and priorities. NAWQA results can contribute to informed 

decisions that result in practical and effective water-resource management and strategies that protect and restore 

water quality.

Since 1991, the NAWQA Program has implemented interdisciplinary assessments in more 

than 50 of the Nation’s most important river basins and aquifers, referred to as Study Units 

(http://water.usgs.gov/nawqa/nawqamap.html). Collectively, these Study Units account for more than 60 percent of the 

overall water use and population served by public water supply, and are representative of the Nation’s major hydrologic landscapes, priority ecological resources, and agricultural, urban, and natural sources of contamination. 

Each assessment is guided by a nationally consistent study design and methods of sampling and analysis. The 

assessments thereby build local knowledge about water-quality issues and trends in a particular stream or aquifer 

while providing an understanding of how and why water quality varies regionally and nationally. The consistent, 

multi-scale approach helps to determine if certain types of water-quality issues are isolated or pervasive, and 

allows direct comparisons of how human activities and natural processes affect water quality and ecological health 

in the Nation’s diverse geographic and environmental settings. Comprehensive assessments on pesticides, nutrients, volatile organic compounds, trace metals, and aquatic ecology are developed at the national scale through 

comparative analysis of the Study-Unit findings (http://water.usgs.gov/nawqa/natsyn.html). 

The USGS places high value on the communication and dissemination of credible, timely, and relevant science so that the most recent and available knowledge about water resources can be applied in management and policy decisions. We hope this NAWQA publication will provide you the needed insights and information to meet 

your needs, and thereby foster increased awareness and involvement in the protection and restoration of our 

Nation’s waters. 

The NAWQA Program recognizes that a national assessment by a single program cannot address all waterresource issues of interest. External coordination at all levels is critical for a fully integrated understanding of 

watersheds and for cost-effective management, regulation, and conservation of our Nation’s water resources. The 

Program, therefore, depends extensively on the advice, cooperation, and information from other Federal, State, 

interstate, Tribal, and local agencies, non-government organizations, industry, academia, and other stakeholder 

groups. The assistance and suggestions of all are greatly appreciated.

Robert M. Hirsch

Associate Director for Water
CONTENTS 

Foreword ................................................................................................................................................................ iii


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


Introduction ............................................................................................................................................................ 2


Data collection and analysis................................................................................................................................... 5


Stream discharge.............................................................................................................................................. 5


Trace metals..................................................................................................................................................... 5


Method for simulating trace-metal loads......................................................................................................... 8


Trace-metal occurrence and transport .................................................................................................................... 8


Measured trace-metal concentrations .............................................................................................................. 10


Simulation of trace-metal concentrations and loads........................................................................................ 10


Trace-metal transport....................................................................................................................................... 22


Trace-metal loading by reach .......................................................................................................................... 22


South Fork Coeur d’Alene River .............................................................................................................. 31


Main-stem Coeur d’Alene River............................................................................................................... 34


Coeur d’Alene Lake and Spokane River................................................................................................... 34


Conclusions ............................................................................................................................................................ 35


References cited ..................................................................................................................................................... 35


FIGURES 

1.	 Map showing locations of streamflow-gaging stations and the Spokane River Basin, Idaho 


and Washington ...................................................................................................................................... 3


2. Map showing locations of streamflow-gaging stations on and near the South Fork Coeur 

d’Alene River, Idaho .............................................................................................................................. 4


3–10. Graphs showing:


3.	 Stream discharge and sample collection dates at three streamflow-gaging stations in the 


Spokane River Basin, Idaho and Washington, water years 1999–2001 ....................................... 7


4.	 Relation between trace-metal concentrations and stream discharge at streamflow-gaging 


station 11 on the South Fork Coeur d’Alene River near Pinehurst, Idaho, water years 


1999–2001..................................................................................................................................... 9


5.	 Dissolved and total cadmium, lead, and zinc concentrations in water samples collected 


at main-stem and tributary streamflow-gaging stations in the Spokane River Basin, 


Idaho and Washington, water years 1999–2001 ........................................................................... 11


6.	 Stream discharge and measured and simulated concentrations of total lead and dissolved


zinc at streamflow-gaging station 11 on the South Fork Coeur d’Alene River near 


Pinehurst, Idaho, water years 1999 –2001..................................................................................... 18


7.	 Measured and simulated loads of total cadmium at four streamflow-gaging stations in 


the Spokane River Basin, Idaho and Washington, water years 1999–2001 ................................. 19


8.	 Measured and simulated loads of total lead at four streamflow-gaging stations in the


Spokane River Basin, Idaho and Washington, water years 1999–2001........................................ 20


9.	 Measured and simulated loads of total zinc at four streamflow-gaging stations in the


Spokane River Basin, Idaho and Washington, water years 1999–2001........................................ 21


10.	 Mean annual stream discharge and mean annual loads of total cadmium, lead, and zinc 


at main-stem and tributary streamflow-gaging stations in the Spokane River Basin, 


Idaho and Washington, water years 1999–2000 ........................................................................... 27


Contents v

11–13. Diagrams showing: 

11.	 Mean annual stream discharge, mean flow-weighted concentration, and mean annual 

load of total cadmium for main-stem and tributary streamflow-gaging stations in the 

Spokane River Basin, Idaho and Washington, water years 1999–2000 ....................................... 28 

12.	 Mean annual stream discharge, mean flow-weighted concentration, and mean annual 

load of total cadmium for main-stem and tributary streamflow-gaging stations in the 

Spokane River Basin, Idaho and Washington, water years 1999–2000 ....................................... 29 

13.	 Mean annual stream discharge, mean flow-weighted concentration, and mean annual 

load of total cadmium for main-stem and tributary streamflow-gaging stations in the 

Spokane River Basin, Idaho and Washington, water years 1999–2000 ....................................... 30 

TABLES 

1.	 Streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, where stream 

discharge and water-quality samples were collected to simulate concentrations and loads of 

cadmium, lead, and zinc, water years 1999–2001..................................................................................6 

2.	 Regression coefficients and coefficients of determination (r2

) for load models used to simulate 

dissolved and total cadmium, lead, and zinc loads at streamflow-gaging stations in the 

Spokane River Basin, Idaho and Washington, water years 1999–2001 ................................................. 12 

3.	 Simulated mean flow-weighted concentrations of cadmium, lead, and zinc at streamflowgaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2000 ............. 16 

4.	 Simulated annual loads of cadmium, lead, and zinc at streamflow-gaging stations in the 

Spokane River Basin, Idaho and Washington, water years 1999–2001................................................. 23 

5.	 Simulated mean annual loads of cadmium, lead, and zinc at streamflow-gaging stations in the 

Spokane River Basin, Idaho and Washington, water years 1999–2000................................................. 26 

6.	 Mean annual gains and (or) losses of stream discharge and cadmium, lead, and zinc loads in 

main-stem reaches of the South Fork Coeur d'Alene, Coeur d'Alene, and Spokane Rivers, 

Idaho and Washington, water years 1999–2000 .................................................................................... 32 

CONVERSION FACTORS AND ABBREVIATED WATER-QUALITY UNITS 

Multiply By To obtain 

cubic foot per second (ft3/s) 0.02832 cubic meter per second 

foot (ft) 0.3048 meter 

mile (mi) 1.609 kilometer 

pound per day (lb/d) 0.4536 kilogram per day 

pound per year (lb/yr) 0.4536 kilogram per year 

square mile (mi2) 2.590 square kilometer 

ton 0.9072 metric ton 

Abbreviated water-quality units: 

μg/L micrograms per liter 

μm micrometer 

mL milliliter 

vi Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington 
Abstract 1

Occurrence and Transport of Cadmium, Lead, and 

Zinc in the Spokane River Basin, Idaho and 

Washington, Water Years 1999–2001

By Gregory M. Clark

Abstract

Abstract

A water-quality investigation of the Clark 

Fork-Pend Oreille and Spokane River Basins began in 1997 as part of the U.S. Geological Survey 

National Water-Quality Assessment Program. As 

part of the investigation, selected streams in the 

Spokane River Basin were sampled for trace metals during water years 1999–2001. These data, 

combined with data collected as part of a U.S. 

Environmental Protection Agency Remedial Investigation/Feasibility Study, were used to assess the 

occurrence, loads, and transport of cadmium, lead, 

and zinc at 21 streamflow-gaging stations in the 

Spokane River Basin. 

Concentrations of dissolved and total cadmium, lead, and zinc varied widely both at and 

among stations. At most stations, dissolved cadmium and zinc composed most of the total concentrations; dissolved lead generally composed less 

than 10 percent of the total lead concentration. 

From the South Fork Coeur d’Alene River near 

Mullan downstream to the South Fork Coeur 

d’Alene River near Pinehurst, concentrations of 

trace metals increased 2 to 4 orders of magnitude. 

The mean flow-weighted concentrations of total 

cadmium, lead, and zinc near Pinehurst for water 

years 1999–2001 were 5.7, 80, and 810 micrograms per liter (μg/L), respectively. On the Coeur 

d’Alene River near Harrison, downstream from the 

confluence of the metal-enriched South Fork and 

the relatively dilute North Fork Coeur d’Alene 

River, the mean flow-weighted concentrations of 

total cadmium, lead, and zinc were 1.6, 88, and 

240 μg/L, respectively. Trace-metal concentrations 

were smaller in the Spokane River than in the 

Coeur d’Alene River because of dilution and 

retention in Coeur d’Alene Lake. The mean flowweighted concentrations of total cadmium, lead, 

and zinc in the Spokane River near Post Falls were 

0.32, 3.1, and 71 μg/L, respectively. 

Regression models relating the mass transport, or load, of trace metals to changes in stream 

discharge and time were successful in simulating 

the variability in trace-metal concentrations and 

loads. The median coefficient of determination for 

the load models for the 21 stations was largest for 

total lead (92 percent) and smallest for dissolved 

and total cadmium (82 percent). Whereas most of 

the cadmium and zinc loads in the Spokane River 

Basin were derived from the South Fork Coeur 

d’Alene River, most of the lead load was derived 

from the Coeur d’Alene River downstream from 

the confluence of the North and South Forks. Major 

tributary sources of trace metals to the South Fork 

Coeur d’Alene River were Canyon Creek, Ninemile Creek, and Government Gulch. These three 

tributaries contributed about 3,000 pounds of cadmium, 23,000 pounds of lead, and 310,000 pounds 

of zinc annually to the South Fork Coeur d’Alene 

River. Erosion and transport of sediment-bound 

lead in the Coeur d’Alene River was the primary 

source of total lead, accounting for almost 

400,000 pounds annually during water years 

1999–2000. Ground-water discharge in the area of 

the Bunker Hill Superfund site was a major source 

of zinc in the South Fork Coeur d’Alene River, 

contributing more than 250,000 pounds per year. 

During water years 1999–2000, the average 

annual loads of cadmium, lead, and zinc transported from the Coeur d’Alene, St. Joe, and St. 

Maries Rivers to Coeur d’Alene Lake were 8,900, 
2 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

500,000, and 1.4 million pounds, respectively. 

The Coeur d’Alene River accounted for more than 

99 percent of the total load of each of these three 

metals entering the lake. About 4,600 pounds of 

cadmium, 44,000 pounds of lead, and 980,000 

pounds of zinc were transported from Coeur 

d’Alene Lake into the Spokane River. Between the 

Spokane River near Post Falls, Idaho, and the Spokane River at Long Lake, Washington, there was 

an annual net loss of about 2,600, 20,000, and 

250,000 pounds of cadmium, lead, and zinc, 

respectively. About 2,000 pounds of cadmium, 

24,000 pounds of lead, and 730,000 pounds of 

zinc were transported annually downstream from 

Long Lake toward the Columbia River.

INTRODUCTION

Introduction

Mining and ore-processing activities conducted 

since the late 1800s in the South Fork Coeur d’Alene 

River (SFCDR) Basin have altered the water quality, 

aquatic biological, and hydrologic conditions in the 

6,680-mi2 Spokane River Basin of northern Idaho and 

eastern Washington (fig. 1). Historical ore-processing 

activities resulted in large quantities of metal-rich tailings that were placed in and along streams (Long, 

1998). The tailings have produced, and continue to produce, trace-metal-contaminated water (Hartz, 1993; 

Woods, 2001a; Woods, 2001b) and extensive deposits 

of trace-metal-contaminated sediment throughout the 

SFCDR Basin, the channel and flood plain of the mainstem Coeur d’Alene River (CDR) (Spruill, 1993; 

Fousek, 1996; Bookstrom and others, 2001), and the 

lakebed of Coeur d’Alene Lake (Horowitz and others, 

1995; Woods and Beckwith, 1997). Annual snowmelt 

runoff, frequent rain-on-snow events, and occasional 

floods continue to transport and redistribute tracemetal-contaminated sediments throughout the CDR 

Basin, into the Spokane River of eastern Washington 

(Maret and Skinner, 2000; Grosbois and others, 2001), 

and as far downstream as the Columbia River (Bortleson and others, 1994). The National Sediment Inventory (U.S. Environmental Protection Agency [USEPA], 

1997) identified the Coeur d’Alene River and Lake as 

“areas of probable concern for sediment contamination,” the most severe contamination category in their 

assessment.

Considerable effort is underway to mitigate the 

adverse environmental effects of past mining in the 

basin, primarily in the SFCDR valley and its tributaries 

(Beckwith, 1998). The USEPA is directing cleanup of a 

21-mi2 Superfund site surrounding the defunct Bunker 

Hill Mine and ore-processing complex in Kellogg, 

Idaho (figs. 1 and 2). The State of Idaho, other Federal 

agencies, and the mining industry also are conducting 

site-specific sediment-removal, reclamation, and 

stream-channel rehabilitation projects. The USEPA is 

evaluating environmental contamination and remediation options in mining-affected areas outside the Superfund site in areas of the lower CDR, its flood plain and 

adjacent wetlands, and the lakebed of Coeur d’Alene 

Lake (Beckwith, 1998). In addition, the USEPA and 

the Idaho Department of Environmental Quality are 

currently under court order to develop Total Maximum 

Daily Loads for a number of water bodies that do not 

support one or more designated uses in the Spokane 

River Basin as a result of trace-metal contamination. 

In 1997, the U.S. Geological Survey (USGS) 

began a water-quality investigation of the Northern 

Rockies Intermontane Basins (NROK) encompassing 

the Clark Fork-Pend Oreille and Spokane River Basins 

of Montana, Idaho, and Washington (Tornes, 1997). 

The study was conducted as part of the USGS National 

Water-Quality Assessment (NAWQA) Program. One of 

the long-term goals of the program is to identify and 

describe current water-quality conditions and the factors that affect those conditions (Hirsch and others, 

1988). As part of the NROK NAWQA, selected streams 

in the Spokane River Basin, which includes the CDR, 

were sampled and analyzed for selected trace metals 

during water years (WYs) 1999–2001 (October 1, 1998, 

through September 30, 2001). 

The purpose of this report is to describe the occurrence and transport of cadmium, lead, and zinc in 

numerous stream reaches in the Spokane River Basin 

in Idaho and Washington. Stream discharge and tracemetal chemistry data were collected at 21 streamflowgaging stations in the basin during WYs 1999–2001 

and analyzed to quantify water and trace-metal concentrations and loads. The geographic and temporal distribution of data were sufficient to quantify the absolute 

and relative mass transport of water and trace metals 

during most of this time period from numerous tributaries, for most of the main stem of the SFCDR and 

CDR, into and out of Coeur d’Alene Lake, and for a 

large part of the Spokane River. 
Introduction 3

WASHING

EXPLANATION

Expanded area shown in figure 2Streamflow-gaging station and number (see table 1)

15

47°

48°

118° 117° 116°

Base compiled from U.S. Geological SurveyState base maps 1:1,000,000

00

1

10

Figure 1. Locations of streamflow-gaging stations and the Spokane River Basin, Idaho and Washington.

COEUR D'ALENE

INDIAN

RESERVATION

Pine

Creek

Hangman

Creek

River

North

Fork

Coeur

d'Alene

River

St Joe

River

Fork

Fork

North

St

Maries River

Spokane

River

Columbia

River

Spokane

Little

River

Spokane

South

Coeur

d'Alene

Lake

Long

Lake

Franklin D

Roosevelt

Lake

Kellogg

Harrison

Enaville

Cataldo

Pinehurst

Post

Falls

St Maries

Coeur

d'Alene

Plummer

Spokane

Santa

Calder

Smelterville Wallace

Mullan

BONNER

BENEWAH

KOOTENAI

LATAH

SHOSHONE

ADAMS WHITMAN

LINCOLN

SPOKANE

STEVENS

WASHINGTON

IDAHO

Bunker Hill

Superfund Site

19

18

17

16

15 8 6 11

12

1

14

20

21

Figure 1. Locations of streamflow-gaging stations and the Spokane River Basin, Idaho and Washington.
4 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington Cataldo Enaville Pinehurst Smelterville Kellogg Osburn Wallace Murray Prichard Mullan Government Gulch Moon Gulch Prichard Creek Canyon Creek Pine Creek Ninemile Creek

Placer

Creek

Big

Creek

South

Fork

Coeur d'A

North

Fork

Coeur d'Alene River 13

2

1

3

5

6 4

7

8

9

10

11

14

116° 15' 116° 07' 30" 116° 00' 115° 52' 30" 115° 

SHOSHONE

COUNTY

00

5

5

8 

EXPLANATION

Bunker Hill Superfund siteStreamflow-gaging station and number (see table 1)

Figure 2. Locations of streamflow-gaging stations on and near the South Fork Coeur d'Alene River, Idaho. Figure 2. Locations of streamflow-gaging stations on and near the South Fork Coeur d’Alene River, Idaho
Data Collection and Analysis 5

DATA COLLECTION AND ANALYSIS

Data Collection and Analysis

Stream Discharge

 Stream discharge at the 21 stations in the station 

network (figs. 1 and 2) was measured using standard 

USGS methods (Buchanan and Somers, 1968, 1969; 

Carter and Davidian, 1968). For 17 of the 21 stations, 

stream discharge was measured using a continuous 

record of water stage calibrated to periodic measurements. However, at 3 (stations 1, 5, and 6) of the 17 stations with stage recorders, collection of continuous 

record was discontinued on May 1, 2000, because of 

funding constraints. For these three stations, daily 

mean stream discharge measured from October 1, 

1998, through April 30, 2000, was correlated (indexed) 

to the daily mean stream discharge at a nearby station 

(or group of stations) with continuous record. The relation between the two stations then was used to generate 

the daily mean stream discharge for the discontinued 

station during the remaining time period for which 

loads were simulated (table 1). For example, the daily 

mean stream discharge at station 1 from October 1, 

1998, through April 30, 2000, was indexed to the daily 

mean stream discharge at station 8 minus the daily 

mean stream discharge at stations 7, 5, 4, and 3 (table 

1). The resultant relation was used to estimate the daily 

mean stream discharge for station 1 from May 1, 2000, 

through September 30, 2000. 

Stations 2, 7, and 9 were not instrumented with a 

continuous stage recorder. At these three stations, instantaneous stream discharge was measured over a 

wide range of water stages coinciding with the collection of water-quality samples. Hydrographs for WYs 

1999 and 2000 were generated for stations 2, 7, and 9 

by indexing the stream discharge measurements to 

nearby stations with continuous stream discharge 

record (table 1). Stream discharge for stations 1, 2, 5–7, 

and 9 was not estimated for WY 2001.

Station 16 is situated within the backwater created 

by Coeur d’Alene Lake and, therefore, does not have a 

valid stage-stream discharge relation. To estimate 

stream discharge at station 16, the USGS stream discharge model FourPt was used (Delong and others, 

1997). The model uses channel geometry and waterstage data at upstream and downstream stations within 

the stream reach being modeled. The model was calibrated using discharge measurements over a wide 

range of stream discharge and lake stage and was used 

to compute a daily mean stream discharge for station 

16 for WYs 1999–2001. 

Trace Metals

The trace-metal data used in this report were collected during WYs 1999–2001 as part of two overlapping studies conducted by the USGS. These studies 

were the NROK NAWQA study and the Remedial 

Investigation/Feasibility Study (RI/FS) of the Spokane 

River Basin (Woods, 2001b). Because these studies had 

somewhat different objectives, the number of samples 

collected at each station varied, ranging from a minimum of 16 samples collected at 6 stations to a maximum of 51 samples collected at station 11 (table 1). 

The sampling approach for both the NAWQA and 

RI/FS studies was to allocate samples over the full 

range of the station hydrograph to develop a robust 

relation between trace-metal concentration and stream 

discharge. In general, samples were collected on a 

fixed-interval frequency, and additional samples were 

collected during low or high stream discharge. Additional samples were collected as part of the RI/FS 

study during significant discharge events such as rain 

on snow, spring snowmelt runoff, and thunderstorms to 

characterize trace-metal transport during those time 

periods. Figure 3 shows the sampling frequency at stations 9, 11, and 16 during the period of study. The sampling frequency at station 9 (Government Gulch at 

Smelterville) is generally representative of the sampling frequency at 12 of the network stations (stations 

1, 2, 5–7, 9, 12, 13, 15, 17, 18, and 21). At these 12 stations, samples were collected routinely from October 

1998 through March 2000, when sampling was discontinued. Trace-metal loads were simulated only for WYs 

1999 and 2000 at these 12 stations. The sampling frequency at station 16 (CDR near Harrison) is representative of five stations in the station network (stations 3, 

4, 8, 10, and 16). At these five stations, samples were 

collected as just described; however, sampling was 

restarted in September 2000 and continued through the 

remainder of WY 2001 (fig. 3). At these five stations, 

trace-metal loads were simulated for WYs 1999–2001. 

The sampling frequency at station 11 generally represents the frequency at four stations in the network (stations 11, 14, 19, and 20) that were sampled routinely 

throughout WYs 1999–2001. Trace-metal loads at 

these four stations also were simulated for WYs 1999–

2001 (table 1). 
6 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

Samples at all stations were collected using nonmetallic samplers and cross-sectional, depth-integrated 

sampling procedures (Edwards and Glysson, 1988). 

Samples were composited and subsampled using a polyethylene churn or Teflon cone splitting device. Samples 

for whole-water recoverable (total) analyses were withdrawn directly from the splitting device. Samples for 

dissolved (smaller than 0.45-μm diameter) analyses 

were withdrawn directly from either the churn splitter 

or from a subsample of the cone splitter and passed 

through a pre-rinsed, 0.45-μm pore size, disposable 

Gelman capsule filter. All trace-metal samples were 

preserved with 2 mL of Ultrex nitric acid. Samples 

were shipped in plastic coolers to the USGS National 

Water Quality Laboratory (NWQL) in Denver, Colo. 

About 10 percent of the samples were submitted as 

blanks, field spikes, and duplicates for quality assurance purposes as described by Friedman and Erdmann 

(1982) and Mueller and others (1997).

 Samples at all stations were analyzed at the 

NWQL using similar analytical techniques. At the 

NWQL, samples were analyzed for total and dissolved 

concentrations of selected trace metals. Samples for 

total analysis were digested by heating with dilute 

hydrochloric acid and were filtered prior to analysis. 

Trace-metal concentrations were determined by atomic 

absorption spectrometry in conjunction with a graphite 

furnace and inductively coupled plasma-mass specTable 1. Streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, where stream discharge and water-quality samples 

were collected to simulate concentrations and loads of cadmium, lead, and zinc, water years 1999–2001

[Locations shown in figures 1 and 2; No., number; USGS, U.S. Geological Survey; SFCDR, South Fork Coeur d'Alene River; ID, Idaho; WA, Washington; C, 

continuous; I, indexed; M, modeled; —, station not indexed; NFCDR, North Fork Coeur d'Alene River; CDR, Coeur d'Alene River]

Station 

No.

USGS

station 

identificatio

n No. USGS station name

Type of 

stream 

discharge 

record

Stations used for 

stream discharge 

indexing

No. of tracemetal samples 

collected

Water years 

for which 

loads were 

simulated

1 12413040 SFCDR above Deadman Gulch near Mullan, ID C, I 8 - (7 + 5 + 4 + 3) 19 1999–2000

2 12413118 Canyon Creek near Burke, ID I 3 16 1999–2000

3 12413125 Canyon Creek above mouth at Wallace, ID C — 27 1999–2001

4 12413130 Ninemile Creek above mouth at Wallace, ID C — 28 1999–2001

5 12413140 Placer Creek at Wallace, ID C, I 4 17 1999–2000

6 12413150 SFCDR at Silverton, ID C, I 8 - 7 19 1999–2000

7 12413190 Moon Creek above mouth at Elk Creek, ID I 4 16 1999–2000

8 12413210 SFCDR at Elizabeth Park near Kellogg, ID C — 28 1999–2001

9 12413290 Government Gulch near mouth at Smelterville, ID I 10 16 1999–2000

10 12413445 Pine Creek below Amy Gulch near Pinehurst, ID C — 28 1999–2001

11 12413470 SFCDR near Pinehurst, ID C — 51 1999–2001

12 12411000 NFCDR above Shoshone Creek near Prichard, ID C — 17 1999–2000

13 12411935 Prichard Creek at mouth at Prichard, ID C — 18 1999–2000

14 12413000 NFCDR at Enaville, ID C — 48 1999–2001

15 12413500 CDR near Cataldo, ID C — 19 1999–2000

16 12413860 CDR near Harrison, ID M — 25 1999–2001

17 12414500 St. Joe River at Calder, ID C — 16 1999–2000

18 12414900 St. Maries River near Santa, ID C — 16 1999–2000

19 12419000 Spokane River near Post Falls, ID C — 47 1999–2001

20 12424500 Spokane River at 7-Mile Bridge, WA C — 24 1999–2001

21 12433000 Spokane River at Long Lake, WA C — 16 1999–2000
Data Collection and Analysis 7

STREAM DISCHARGE, IN CUBIC FEET PER SECOND

5,000

4,000

3,000

2,000

1,000

0

30,000

25,000

20,000

15,000

10,000

5,000

0

Dec.

Feb.

Apr.

June

Aug.

Oct.

Dec.

Feb.

Apr.

June

Aug.

Oct.

Dec.

Feb.

Apr.

June

A

Oct.

ug.

WATER YEAR 1999 WATER YEAR 2000 WATER YEAR 2001

Station 16 – Coeur d'Alene River near Harrison, Idaho

Station 11 – South Fork Coeur d'Alene River near Pinehurst, Idaho

Station 9 – Government Gulch at Smelterville, Idaho

Continuous stream discharge

unavailable for water year 2001

50

40

30

20

10

0

Stream discharge

Sample collected at indicated

 stream discharge

Figure 3. Stream discharge and sample collection dates at three streamflow-gaging stations in the Spokane River Basin, Idaho and

Washington, water years 1999–2001. (Locations shown in figures 1 and 2)

Figure 3. Stream discharge and sample collection dates at three streamflow-gaging stations in the Spokane River Basin, Idaho and 

Washington, water years 1999–2001. (Locations shown in figures 1 and 2)
8 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

trometry (Fishman, 1993). Quality assurance/quality 

control procedures used at the NWQL were documented 

by Pritt and Raese (1995).

Method for Simulating Trace-Metal Loads

Trace-metal concentrations generally vary in relation to stream discharge. For example, in samples collected during WYs 1999–2001 from the SFCDR near 

Pinehurst, concentrations of total cadmium and total 

zinc decreased and concentrations of total lead increased with increasing stream discharge (fig. 4). The 

relation between concentration and stream discharge 

noted at Pinehurst typifies many of the mining-affected 

streams in the CDR Basin (Woods, 2001a). Because of 

the variability in trace-metal concentration, summary 

statistics such as a mean station concentration used to 

characterize a stream might be biased because of variations in sampling frequency and the timing of sampling 

during the period of data collection. For this analysis, 

the annual trace-metal load and mean flow-weighted 

concentrations were simulated for each station. The 

model used for this analysis is based on the ratingcurve method (Cohn and others, 1989, 1992; Crawford, 

1991), which uses regression to estimate constituent 

loads in relation to stream discharge and time. Similar 

models have been used to estimate concentration for 

days when no samples were collected (Gilroy and 

others, 1990), to estimate the basin flux of nutrients 

(Goolsby and others, 1999), and to determine trends in 

water-quality data (Smith and others, 1987). A common form of this type of regression model is:

lnL = I + a(lnQ) + b(lnQ2

) + c(T) 

+ d[sin(2πT)] +e[cos(2πT)] + ε

where

L is the constituent load;

I is the regression intercept;

Q is stream discharge;

T is decimal time in years from the 

beginning of the calibration period;

a, b, c, d, and e are regression coefficients that remain 

constant over time; and

ε is unaccounted error associated with 

the regression model. 

This regression captures the dependence of concentration on discharge, season (the sine and cosine 

terms), and any long-term trend. For the load simulations in this report, the T term is equal to 0.0, 1.0, or 

2.0, for October 1, 1999, 2000, and 2001, respectively. 

Because the trace-metal concentrations included censored values (values less than the analytical reporting 

limit), model coefficients were estimated by the maximum-likelihood method (Dempster and others, 1977; 

Wolynetz, 1979). In the absence of censored values, the 

maximum-likelihood method is equivalent to ordinary 

least-squares regression. 

Separate regression models were calibrated for 

each constituent for each station using some or all of 

the predictor variables in the regression equation. The 

best model for each constituent/station combination 

was selected on the basis of Aikaike Information Criteria (Aikaike, 1981; Judge and others, 1985). The criteria are designed to achieve a good compromise between using as many predictor variables as possible to 

explain the variance in load while minimizing the standard error of the resulting estimates. Estimates of the 

logarithms of daily constituent loads for each station 

were computed using the selected model and daily 

mean stream discharge. Bias introduced by conversion 

of the logarithm of load into estimates of load was corrected using the Bradu-Mundlak method (Bradu and 

Mundlak, 1970; Cohn and others, 1989; Crawford, 

1991). 

Annual loads were simulated as the sum of the 

daily loads (computed using the station regression 

models) for each year. For stations 3, 4, 8, 10, 11, 14, 

16, 19, and 20, annual loads were simulated for WYs 

1999–2001; for all other stations, annual loads were 

simulated for WYs 1999–2000. A mean flow-weighted 

concentration for WYs 1999–2000 was simulated as 

the total station load during 1999–2000 divided by the 

total stream discharge at the station during the same 

time period. 

TRACE-METAL OCCURRENCE AND TRANSPORT 

Trace-Metal Occurrence and Transport 

The occurrence and transport of trace metals in 

the Spokane River Basin are controlled primarily by 

the metal source and input rate, the tendency of metals 

to adhere to sediment, and the transport of water and 

sediment through the basin. Primary sources of trace 

metals to the SFCDR, CDR, and Spokane Rivers 
Trace-Metal Occurrence and Transport 9

TRACE-METAL CONCENTRATION, IN MICROGRAMS PER LITER

STREAM DISCHARGE, IN CUBIC FEET PER SECOND

Total Cadmium

10

30

8

4

20

2

6

3

Total Zinc

3,000

1,000

2,000

800

600

400

300

50 60 100 300 600 1,000 3,000 6,000 10,000

1,000

Total Lead

600

300

100

60

30

10

Figure 4. Relation between trace-metal concentrations and stream discharge at streamflow-gaging station 11 on the South Fork 

Coeur d’Alene River near Pinehurst, Idaho, water years 1999–2001. (Location shown in figures 1 and 2)
10 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

include headwater streams, tributary inflows, groundwater inflow, overland runoff from flood plains, and 

erosion of streambank and streambed materials. Once 

trace metals are mobilized in an aquatic system, they 

can be redistributed within streams and rivers, especially during periods of high stream discharge when 

transport is at a maximum. 

Measured Trace-Metal Concentrations

Boxplots are useful in illustrating the range and 

relative concentrations of trace metals in the main-stem 

and tributary stations in the Spokane River Basin (fig. 5). 

However, when comparing station concentrations, it is 

important that boxplots for each station represent similar hydrologic conditions. Although the number of 

samples collected at each station during WYs 1999–

2001 was variable (table 1), the relative distribution of 

samples collected at various stream discharges is similar, and the general patterns in concentrations shown in 

figure 5 are assumed to represent the actual variability. 

Concentrations of dissolved and total cadmium, 

lead, and zinc in samples collected during WYs 1999–

2001 varied widely, both at and among stations (fig. 5). 

At most of the stations, dissolved cadmium and zinc 

composed most of the total concentrations. In contrast, 

dissolved lead generally composed only a small part of 

the total concentration, often less than 10 percent. A 

large amount of variability at individual stations was 

particularly evident in the concentrations of total lead, 

primarily as a response to changes in stream discharge. 

Concentrations of cadmium, lead, and zinc also varied 

widely along the main stem of the SFCDR, the CDR, 

and the Spokane River. From station 1 on the SFCDR 

near Mullan downstream to station 6 on the SFCDR at 

Silverton, concentrations of cadmium, lead, and zinc 

increased dramatically (fig. 5). At station 6, the concentrations of cadmium, lead, and zinc were generally 1 to 

3 orders of magnitude larger than at station 1. Primary 

sources of trace-metal loading to the 9.3-mi reach 

between stations 1 and 6 are Canyon and Ninemile 

Creeks (stations 3 and 4, respectively). Water discharging from these two tributaries contained some of the 

largest cadmium, lead, and zinc concentrations in the 

station network (fig. 5). From station 6 downstream to 

station 11 on the SFCDR near Pinehurst, trace-metal 

concentrations remained elevated (fig. 5). Sources of 

trace metals to the SFCDR in the 16-mi reach between 

stations 6 and 11 include Moon Creek, Government 

Gulch, Pine Creek, and ground-water discharge from 

the shallow alluvial aquifer adjacent to the SFCDR. 

Median concentrations of total cadmium (190 μg/L) 

and total zinc (6,300 μg/L) at Government Gulch (station 9) were the largest in the station network. The 

median concentrations of total cadmium, lead, and zinc 

at station 11 were 6.7, 19, and 1,100 μg/L, respectively 

(fig. 5).

From station 11 downstream to station 15 on the 

CDR near Cataldo, the concentrations of cadmium, 

lead, and zinc decreased as water from the relatively 

dilute North Fork Coeur d’Alene River (NFCDR) 

mixed with the metal-enriched water of the SFCDR 

(fig. 5). From station 15 downstream 32 mi on the CDR 

to station 16 near Harrison, the median concentrations 

of dissolved and total cadmium and zinc remained relatively constant, whereas the median concentrations of 

dissolved and total lead more than doubled (fig. 5). The 

median concentrations of total cadmium, lead, and zinc 

at station 16 were 1.7, 23, and 290 μg/L, respectively.

The large decrease in the concentrations of cadmium, lead, and zinc between station 16 and station 19 

on the Spokane River near Post Falls (fig. 1) indicates 

dilution and the effectiveness of Coeur d’Alene Lake in 

trapping trace metals. The median concentrations of 

total cadmium, lead, and zinc at station 19 were 0.23, 

1.4, and 64 μg/L, respectively (fig. 5). The median concentrations at station 19 represent a decrease from the 

median concentrations at station 16 of about 86, 94, 

and 78 percent, respectively. From station 19, 66 mi 

downstream to station 21 on the Spokane River at Long 

Lake, the concentrations of dissolved and total cadmium, lead, and zinc generally declined to concentrations similar in magnitude to those in the SFCDR at 

station 1 (fig. 5). Concentrations of total lead increased 

slightly between stations 19 and 20 and subsequently 

decreased between stations 20 and 21. At station 21 

(the most downstream station in the station network), 

the median concentrations of total cadmium, lead, and 

zinc were 0.085, 0.79, and 35 μg/L, respectively. 

Simulation of Trace-Metal Concentrations and 

Loads

Regression coefficients and coefficients of determination (R2) for the best-fit regression model for 

loads of dissolved and total cadmium, lead, and zinc 

are presented in table 2. Mean flow-weighted concentrations simulated from the models are presented in 
Trace-Metal Occurrence and Transport 11

CONCENTRATION, IN MICROGRAMS PER LITER 100,000

10,000

30,000

1 8 6

STREAMFLOW-GAGING STATION NUMBER

Zinc

Lead

Cadmium

11 16 15 19 21 20 2 4 359

MAIN STEM TRIBUTARY

7 10 13 12 14 18 17

60,000

1,000

3,000

6,000

100

300

600

10

30

60

1

3

6

0.1

0.3

0.6

10,000

1,000

3,000

6,000

100

300

600

10

30

60

1

3

6

0.1

0.3

0.6

0.01

0.03

0.06

1,000

100

300

600

10

30

60

1

3

6

0.1

0.3

0.6

0.001

0.003

0.006

0.01

0.03

0.06

Largest value

75th percentile

Median

25th percentile

Smallest value

Total concentration

Dissolved concen-

 tration

Figure 5. Dissolved and total cadmium, lead, and zinc concentrations in water samples collected at main-stem and tributary streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2001. (Locations shown in figures 1 and 2) 

Figure 5. Dissolved and total cadmium, lead, and zinc concentrations in water samples collected at main-stem and tributary streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2001. (Locations shown in figures 1 and 2)
12 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

Table 2. Regression coefficients and coefficients of determination (R2

) for load models used to simulate dissolved and total cadmium, lead, 

and zinc loads at streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2001

[The regression equation is lnL = I + a(lnQ) + b(lnQ2) + c(T) + d[sin(2πT)] + e[cos(2πT) + ε: where L is the constituent load; I is the regression intercept; 

Q is stream discharge; T is time in decimal years from the beginning of the calibration period; a, b, c, d, and e are regression coefficients; and ε is the unaccounted error in the model; No., number; USGS, U.S. Geological Survey; R2

 represents the amount of variance explained by the model; station locations 

shown in figures 1 and 2; —, coefficient for indicated term not used in the model; SFCDR, South Fork Coeur d'Alene River; NFCDR, North Fork Coeur 

d'Alene River; CDR, Coeur d'Alene River; ID, Idaho; WA, Washington] 

Regression coefficient

Station 

No. USGS station name I abcde

 R2

(percent) 

 Dissolved cadmium 

1 SFCDR above Deadman Gulch near Mullan, ID -5.022 2.084 — -0.876 -0.934 1.257 42

2 Canyon Creek near Burke, ID - 6.015 1.081 — — -0.399 0.476 64

3 Canyon Creek above mouth at Wallace, ID 0.905 0.926 -0.152 — 0.145 0.378 78

4 Ninemile Creek above mouth at Wallace, ID -0.091 0.742 — — 0.028 0.241 87

5 Placer Creek at Wallace, ID - 3.724 1.033 -0.398 -1.016 — — 17

6 SFCDR at Silverton, ID 2.379 0.570 -0.130 -0.439 0.346 0.215 88

7 Moon Creek above mouth at Elk Creek, ID - 4.241 1.246 -0.103 -0.141 -0.677 -0.031 24

8 SFCDR at Elizabeth Park near Kellogg, ID 1.842 0.685 -0.090 — -0.013 0.097 93

9 Government Gulch near mouth at Smelterville, ID 0.998 0.684 — — -0.111 0.824 68

10 Pine Creek below Amy Gulch near Pinehurst, ID -1.816 0.956 -0.087 — 0.010 0.282 82

11 SFCDR near Pinehurst, ID 2.843 0.609 -0.108 -0.084 0.117 0.196 92

12 NFCDR above Shoshone Creek near Prichard, ID - 0.435 0.147 — -1.144 — — 13

13 Prichard Creek at mouth at Prichard, ID - 2.822 0.830 0.164 — —— 89

14 NFCDR at Enaville, ID - 2.047 0.967 —— —— 55

15 CDR near Cataldo, ID 2.988 0.421 — -0.165 0.240 0.144 92

16 CDR near Harrison, ID 2.932 0.913 -0.142 -0.140 -0.215 0.174 94

17 St. Joe River at Calder, ID - 0.768 1.572 — -1.510 0.824 1.575 51

18 St. Maries River near Santa, ID -3.610 1.406 — — 0.205 1.186 42

19 Spokane River near Post Falls, ID 1.758 1.109 — -0.094 0.235 0.116 95

20 Spokane River at 7-Mile Bridge, WA 1.001 1.529 — — —— 98

21 Spokane River at Long Lake, WA 0.935 1.565 — — 0.665 -0.085 90

Total cadmium 

1 SFCDR above Deadman Gulch near Mullan, ID -5.207 1.106 —— —— 76 

2 Canyon Creek near Burke, ID -6.206 0.771 0.223 — —— 66

3 Canyon Creek above mouth at Wallace, ID 0.856 0.941 -0.115 — 0.164 0.363 67

4 Ninemile Creek above mouth at Wallace, ID 0.081 0.808 — — 0.019 0.244 87

5 Placer Creek at Wallace, ID -3.255 0.924 — -1.726 — — 7

6 SFCDR at Silverton, ID 2.113 0.605 — -0.308 0.282 0.256 82

7 Moon Creek above mouth at Elk Creek, ID -4.552 1.290 — — -0.793 -0.039 20

8 SFCDR at Elizabeth Park near Kellogg, ID 1.955 0.682 — -0.070 — — 83
Trace-Metal Occurrence and Transport 13

Regression coefficient

Station 

No. USGS station name I abcde

 R2

(percent) 

Total cadmium —Continued

9 Government Gulch near mouth at Smelterville, ID 1.012 0.712 — — -0.133 0.797 67

10 Pine Creek below Amy Gulch near Pinehurst, ID -1.738 0.833 — -0.130 0.159 0.275 72

11 SFCDR near Pinehurst, ID 2.851 0.690 — -0.110 0.087 0.168 82

12 NFCDR above Shoshone Creek near Prichard, ID -0.881 -0.981 0.652 -2.256 2.385 1.078 99

13 Prichard Creek at mouth at Prichard, ID -2.360 1.035 0.081 -0.131 — — 99

14 NFCDR at Enaville, ID -1.910 1.323 — — —— 81

15 CDR near Cataldo, ID 2.760 0.809 0.130 — -0.080 0.241 96

16 CDR near Harrison, ID 2.965 0.843 — -0.208 — — 89

17 St. Joe River at Calder, ID -0.773 0.495 — -1.261 1.063 0.844 52

18 St. Maries River near Santa, ID -4.625 0.875 — — —— 39

19 Spokane River near Post Falls, ID 2.007 1.140 — -0.105 0.211 0.112 96

20 Spokane River at 7-Mile Bridge, WA 1.305 1.393 0.174 — — — 96 

21 Spokane River at Long Lake, WA 1.215 1.047 -0.373 — 0.982 -0.200 96 

 Dissolved lead 

1 SFCDR above Deadman Gulch near Mullan, ID -3.648 1.714 — — -0.618 1.285 74

2 Canyon Creek near Burke, ID -3.660 1.079 — — —— 50

3 Canyon Creek above mouth at Wallace, ID 1.673 0.873 — -0.234 — — 88

4 Ninemile Creek above mouth at Wallace, ID 0.789 1.002 -0.101 -0.163 — — 89

5 Placer Creek at Wallace, ID -2.625 0.501 -0.190 — — — 29

6 SFCDR at Silverton, ID 2.001 0.630 — — -0.011 -0.249 93

7 Moon Creek above mouth at Elk Creek, ID -3.118 -0.075 — -1.135 1.656 0.652 73

8 SFCDR at Elizabeth Park near Kellogg, ID 1.850 0.787 — -0.177 -0.022 -0.254 98

9 Government Gulch near mouth at Smelterville, ID -2.013 1.114 -0.467 — 0.437 0.427 60

10 Pine Creek below Amy Gulch near Pinehurst, ID -2.319 1.083 0.096 — — — 90

11 SFCDR near Pinehurst, ID 2.429 0.644 0.063 -0.151 0.108 -0.383 94

12 NFCDR above Shoshone Creek near Prichard, ID -2.443 0.996 — — —— 8

13 Prichard Creek at mouth at Prichard, ID -0.490 1.276 — -0.919 — — 97

14 NFCDR at Enaville, ID -1.444 1.048 0.164 — — — 93

15 CDR near Cataldo, ID 3.063 0.425 0.170 -0.435 0.689 -0.796 94

16 CDR near Harrison, ID 3.606 1.217 — — —— 87

17 St. Joe River at Calder, ID 0.596 -0.131 0.289 -1.373 1.230 0.143 74 

18 St. Maries River near Santa, ID -2.796 1.494 — — —— 73

Table 2. Regression coefficients and coefficients of determination (R2) for load models used to simulate dissolved and total cadmium, lead, 

and zinc loads at streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2001—Continued
14 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

Regression coefficient

Station 

No. USGS station name I abcde

 R2

(percent) 

 Dissolved lead —Continued

19 Spokane River near Post Falls, ID 1.354 1.506 0.242 — — — 82

20 Spokane River at 7-Mile Bridge, WA 1.000 1.661 0.470 — — — 98

21 Spokane River at Long Lake, WA 3.181 2.772 — -0.864 — — 67

Total lead 

1 SFCDR above Deadman Gulch near Mullan, ID -1.241 1.672 — — 0.070 1.065 85

2 Canyon Creek near Burke, ID -4.720 0.899 0.297 0.668 — — 93

3 Canyon Creek above mouth at Wallace, ID 2.290 1.172 0.258 -0.279 — — 61

4 Ninemile Creek above mouth at Wallace, ID 1.072 1.429 0.219 — — — 92

5 Placer Creek at Wallace, ID -3.581 0.990 0.276 0.617 — — 94

6 SFCDR at Silverton, ID 2.617 1.065 0.483 — — — 91

7 Moon Creek above mouth at Elk Creek, ID -3.883 1.782 0.348 — -1.177 0.539 31

8 SFCDR at Elizabeth Park near Kellogg, ID 2.745 1.375 0.358 -0.230 — — 92

9 Government Gulch near mouth at Smelterville, ID -1.272 1.530 — — 0.128 0.404 75

10 Pine Creek below Amy Gulch near Pinehurst, ID -1.878 1.387 0.244 — — — 89

11 SFCDR near Pinehurst, ID 4.260 1.321 0.426 -0.352 — — 98

12 NFCDR above Shoshone Creek near Prichard, ID -2.226 1.164 0.312 — — — 92

13 Prichard Creek at mouth at Prichard, ID -1.346 1.661 0.349 — — — 89

14 NFCDR at Enaville, ID 0.131 1.333 0.564 -0.391 — — 98

15 CDR near Cataldo, ID 4.217 2.050 0.250 — -0.782 -0.194 98

16 CDR near Harrison, ID 4.985 1.346 0.303 — — — 93

17 St. Joe River at Calder, ID 0.981 1.080 — -1.491 0.311 0.386 75

18 St. Maries River near Santa, ID -1.171 3.023 -0.519 — -2.287 0.600 84

19 Spokane River near Post Falls, ID 3.292 1.686 0.215 — -0.237 -0.354 93

20 Spokane River at 7-Mile Bridge, WA 3.092 1.702 0.573 — — — 99

21 Spokane River at Long Lake, WA 3.457 2.146 — — — — 90

Dissolved zinc

1 SFCDR above Deadman Gulch near Mullan, ID 0.890 0.939 — -0.570 -0.082 0.809 75

2 Canyon Creek near Burke, ID -0.140 1.262 -0.118 -0.346 0.114 0.582 73

3 Canyon Creek above mouth at Wallace, ID 5.854 0.915 -0.170 — 0.217 0.414 81

4 Ninemile Creek above mouth at Wallace, ID 4.976 0.746 — — 0.031 0.300 84

5 Placer Creek at Wallace, ID -1.665 0.801 — — — — 58

6 SFCDR at Silverton, ID 7.444 0.478 -0.129 -0.311 0.340 0.292 83

7 Moon Creek above mouth at Elk Creek, ID 1.271 1.271 -0.112 -0.254 -0.727 0.103 26

8 SFCDR at Elizabeth Park near Kellogg, ID 6.824 0.685 -0.102 — 0.054 0.124 87

Table 2. Regression coefficients and coefficients of determination (R2) for load models used to simulate dissolved and total cadmium, lead, 

and zinc loads at streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2001—Continued
Trace-Metal Occurrence and Transport 15

Regression coefficient

Station 

No. USGS station name I abcde

 R2

(percent) 

Dissolved zinc —Continued

9 Government Gulch near mouth at Smelterville, ID 4.495 0.679 — — -0.107 0.829 69

10 Pine Creek below Amy Gulch near Pinehurst, ID 3.929 0.731 — -0.152 0.325 0.275 77

11 SFCDR near Pinehurst, ID 7.783 0.562 -0.075 -0.061 0.043 0.175 92

12 NFCDR above Shoshone Creek near Prichard, ID 1.099 1.460 -0.274 — — — 54 

13 Prichard Creek at mouth at Prichard, ID 3.063 0.822 0.083 -0.173 0.235 0.066 98

14 NFCDR at Enaville, ID 3.095 1.241 -0.078 — — — 95

15 CDR near Cataldo, ID 8.055 0.376 — -0.180 0.193 0.096 95

16 CDR near Harrison, ID 8.092 0.657 -0.120 -0.130 0.078 0.225 97

17 St. Joe River at Calder, ID 1.604 1.174 — — — — 75

18 St. Maries River near Santa, ID -0.003 1.548 — — — — 77

19 Spokane River near Post Falls, ID 7.383 1.047 — -0.083 0.271 0.247 98

20 Spokane River at 7-Mile Bridge, WA 6.927 1.515 -0.115 — 0.023 0.276 97

21 Spokane River at Long Lake, WA 6.702 1.195 — — 0.943 0.169 92

Total zinc 

1 SFCDR above Deadman Gulch near Mullan, ID 1.269 1.118 — -0.584 0.338 0.808 82

2 Canyon Creek near Burke, ID 0.058 1.033 — -0.510 0.299 0.387 93

3 Canyon Creek above mouth at Wallace, ID 5.852 0.916 -0.163 — 0.218 0.422 82

4 Ninemile Creek above mouth at Wallace, ID 5.107 0.800 — — 0.030 0.331 88

5 Placer Creek at Wallace, ID -1.574 0.978 0.294 — — — 95

6 SFCDR at Silverton, ID 7.421 0.476 -0.121 -0.299 0.350 0.289 85

7 Moon Creek above mouth at Elk Creek, ID 1.194 1.078 — -0.279 -0.433 0.160 37

8 SFCDR at Elizabeth Park near Kellogg, ID 6.714 0.741 — — 0.057 0.150 83

9 Government Gulch near mouth at Smelterville, ID 4.516 0.694 — — -0.123 0.791 66

10 Pine Creek below Amy Gulch near Pinehurst, ID 3.578 0.866 — — 0.198 0.269 80

11 SFCDR near Pinehurst, ID 7.848 0.642 — -0.092 0.012 0.179 81

12 NFCDR above Shoshone Creek near Prichard, ID 0.923 0.702 — — 1.307 0.019 79

13 Prichard Creek at mouth at Prichard, ID 3.172 0.853 0.123 -0.241 0.325 0.056 99

14 NFCDR at Enaville, ID 3.220 1.473 — — — — 89

15 CDR near Cataldo, ID 7.970 0.591 0.127 -0.154 0.080 0.154 96

16 CDR near Harrison, ID 7.953 0.776 — -0.139 -0.005 0.208 88

17 St. Joe River at Calder, ID 1.604 1.178 — — — — 76

18 St. Maries River near Santa, ID 0.294 1.339 — — — — 37

19 Spokane River near Post Falls, ID 7.300 1.101 — — 0.249 0.195 98

20 Spokane River at 7-Mile Bridge, WA 7.039 1.382 — — — — 92

21 Spokane River at Long Lake, WA 6.926 1.287 — — 0.875 0.188 94

Table 2. Regression coefficients and coefficients of determination (R2) for load models used to simulate dissolved and total cadmium, lead, 

and zinc loads at streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2001—Continued
16 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

table 3. For the 21 stations in table 3, the median ratios 

of the dissolved to total concentrations of cadmium, 

lead, and zinc were 87, 14, and 92 percent, respectively. 

The relatively large R2 values for the models 

(table 2) indicate that, at most of the stations, the models successfully simulated the variability in trace-metal 

Table 3. Simulated mean flow-weighted concentrations of cadmium, lead, and zinc at streamflow-gaging stations in the Spokane River Basin, 

Idaho and Washington, water years 1999–2000

[Station locations shown in figures 1 and 2; No., number; USGS, U.S. Geological Survey; SFCDR, South Fork Coeur d'Alene River; CDR, Coeur d'Alene 

River; ID, Idaho; NFCDR, North Fork Coeur d'Alene River; WA, Washington]

Simulated mean flow-weighted concentration

(micrograms per liter)

Station 

No. USGS station name

Dissolved 

cadmium

Total 

cadmium

Dissolved 

lead

Total 

lead

Dissolved 

zinc

Total 

zinc

Main-stem stations

1 SFCDR above Deadman Gulch near Mullan, ID 0.03 0.06 0.33 4.7 7.1 13

6 SFCDR at Silverton, ID 4.3 4.7 7.2 64 640 650

8 SFCDR at Elizabeth Park near Kellogg, ID 3.9 4.5 3.9 58 570 620

11 SFCDR near Pinehurst, ID 4.9 5.7 4.0 80 700 810

15 CDR near Cataldo, ID 1.1 1.6 1.5 37 160 210

16 CDR near Harrison, ID 1.2 1.6 6.2 88 200 240

19 Spokane River near Post Falls, ID 0.25 0.32 0.43 3.1 68 71

20 Spokane River at 7-Mile Bridge, WA 0.17 0.24 0.41 4.0 52 60

21 Spokane River at Long Lake, WA 0.12 0.11 0.41 1.3 34 42

Tributary stations

2 Canyon Creek near Burke, ID 0.04 0.07 0.59 1.7 6.8 7.4

3 Canyon Creek above mouth at Wallace, ID 12 13 23 165 1,700 1,700

4 Ninemile Creek above mouth at Wallace, ID 14 14 26 140 2,200 2,300

5 Placer Creek at Wallace, ID 0.03 0.03 0.35 1.2 1.4 3.0

7 Moon Creek above mouth at Elk Creek, ID 0.35 0.41 0.31 2.9 69 69

9 Government Gulch near mouth at Smelterville, ID 150 150 6.8 26 4,900 5,000

10 Pine Creek below Amy Gulch near Pinehurst, ID 0.34 0.34 0.51 3.3 89 93

12 NFCDR above Shoshone Creek near Prichard, ID 0.04 0.02 0.07 0.25 1.5 2.4

13 Prichard Creek at mouth at Prichard, ID 0.13 0.15 0.29 5.6 28 32

14 NFCDR at Enaville, ID 0.04 0.05 0.09 2.0 5.1 11

17 St. Joe River at Calder, ID 0.03 0.02 0.03 0.05 1.3 1.3

18 St. Maries River near Santa, ID 0.07 0.01 0.22 0.49 2.7 2.5
Trace-Metal Occurrence and Transport 17

loads. The median R2 of the load models for all 21 stations was largest for total lead (92 percent), and smallest for dissolved and total cadmium (82 percent). In 16 

of the load models for total lead, the lnQ2 term was significant with a positive coefficient (table 2), indicative 

of concentrations that increase dramatically with 

increased stream discharge. In contrast, in 10 of the 

load models for dissolved zinc, the lnQ2 term was significant with a negative coefficient indicative of concentrations that decrease dramatically with increased 

stream discharge. The influence of stream discharge on 

the concentrations of total lead and dissolved zinc at 

station 11 is illustrated in figure 6. The measured concentrations in figure 6 represent samples collected 

onsite; the simulated concentrations represent values 

from the load models in table 2. During all 3 years of 

sampling, the measured and simulated annual peak 

concentrations of total lead coincided with the annual 

peak stream discharge (fig. 6). During 1999–2001, the 

peaks occurred during the spring snowmelt runoff. 

Conversely, the measured and simulated concentrations 

of dissolved zinc were smallest during the annual peak 

stream discharge. 

In general, the load models for stations where 

trace-metal concentrations were relatively large were 

better at simulating the actual loads than were models 

for stations where concentrations were near the analytical reporting limit. At the eight stations where flowweighted concentrations of trace metals were largest 

(stations 3, 4, 6, 8, 9, 11, 15, and 16), the median R2

values of the load models were 90, 82, 91, 92, 86, and 

84 percent for dissolved and total cadmium, lead, and 

zinc, respectively. At the seven stations where flowweighted concentrations were smallest (stations 1, 2, 5, 

12, 14, 17, and 18), the median R2 values were 47, 59, 

62, 93, 74, and 84 percent for dissolved and total cadmium, lead, and zinc, respectively. The lower R2 values 

at these seven stations probably were attributable to a 

larger number of censored data values and, thus, less 

confidence in the analytical results. 

Relations between measured and simulated loads 

of total cadmium, lead, and zinc at four stations are 

shown in figures 7, 8, and 9, respectively. Although the 

measured and simulated loads of total cadmium, lead, 

and zinc compare favorably during most of the 3 years 

of sampling, a hysteresis effect on trace-metal loads is 

evident during snowmelt runoff. Hysteresis is a result 

of differences in trace-metal concentrations for a given 

stream discharge over the ascending and descending 

limbs of the stream hydrograph. As stream discharge is 

rising, materials stored within the stream channel or in 

terrestrial zones become mobile as they are subjected 

to increased stream velocities. Samples collected during the ascending limb and near the peak of the stream 

hydrograph typically contain larger concentrations of 

sediment and sediment-associated trace metals than 

samples collected during the descending limb. The 

magnitude of the hysteresis effect can be affected by 

antecedent conditions and by the magnitude of the 

stream discharge generating hysteresis. Clark and 

Woods (2001) and Woods (2001a) documented the 

hysteresis effect on sediment and trace-metal concentrations at numerous stations in the SFCDR. Measured 

sediment and sediment-associated trace-metal concentrations were between 1.5 and 3.6 times larger on the 

ascending limb of the snowmelt runoff hydrograph 

than on the descending limb at nearly equal discharge. 

In contrast, dissolved trace-metal concentrations 

showed minimal effect from hysteresis (Woods, 

2001a). 

Because the load models developed in this study 

do not account for hysteresis, errors in the load simulations may occur during short time periods (daily or 

weekly) when the stream discharge is changing rapidly. 

Hysteresis is particularly evident at station 11 on the 

SFCDR near Pinehurst (figs. 7, 8, and 9). On April 14, 

2000, the mean stream discharge at station 11 peaked 

at 4,630 ft3/s and the measured loads of total cadmium, 

lead, and zinc on that day were 150, 17,000, and 

19,000 lb, respectively. The simulated loads of total 

cadmium, lead, and zinc on April 14 were 81, 13,000, 

and 10,000 lb, respectively, or underestimates of the 

measured loads by 46, 24, and 47 percent, respectively. 

Three days later on April 17, the daily mean stream discharge at station 11 had decreased to 2,380 ft3/s and the 

measured loads of total cadmium, lead, and zinc were 

45, 930, and 5,400 lb, respectively. The simulated loads 

on April 17 of total cadmium, lead, and zinc were 51, 

1,600, and 6,600 lb, respectively, or overestimates of 

the measured loads by 13, 72, and 22 percent, respectively. Thus, during short periods of time, significant 

errors in the load simulations may result from hysteresis. However, over periods of longer duration (monthly 

or annually), the errors associated with hysteresis 

would probably balance out and the overall resultant 

error in the estimates of total loads would be minimized. 
18 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington TRACE-METAL CONCENTRATION, IN MICROGRAMS PER LITER

1,000

600

Station 11 – South Fork Coeur d'Alene River near Pinehurst, Idaho 3,000

STREAM DISCHARGE, IN CUBIC FEET PER SECOND

10,000

9,000

8,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

300

100

60

30

10

6

3

1

Oct.

Dec.

Feb.

Apr.

June

Aug.

Oct.

Dec.

Feb.

Apr.

June

Aug.

Oct.

Dec.

Feb.

Apr.

June

Aug.

WATER YEAR 1999 WATER YEAR 2000 WATER YEAR 2001

Measured

dissolved zinc

Stream discharge

Measured

total lead

Simulated total lead

Simulated dissolved zinc

Figure 6. Stream discharge and measured and simulated concentrations of total lead and dissolved zinc at streamflow-gaging

station 11 on the South Fork Coeur d'Alene River near Pinehurst, Idaho, water years 1999–2001. (Location shown in figure 2)

Figure 6. Stream discharge and measured and simulated concentrations of total lead and dissolved zinc at streamflow-gaging 

station 11 on the South Fork Coeur d’Alene River near Pinehurst, Idaho, water years 1999 –2001. (Location shown in figure 2)
Trace-Metal Occurrence and Transport 19

TOTAL CADMIUM LOAD, IN POUNDS PER DAY

500

10

5

300

Dec.

Feb.

Apr.

June

Aug.

Oct.

Dec.

Feb.

Apr.

June

Aug.

Oct.

Dec.

Feb.

Apr.

June

A

Oct.

ug.

WATER YEAR 1999 WATER YEAR 2000 WATER YEAR 2001

Station 19 – Spokane River near Post Falls, Idaho

Station 3 – Canyon Creek at Wallace, Idaho 50

30

3

5

1

0.5

10

1,000

30

Station 16 – Coeur d'Alene River near Harrison, Idaho

300 Station 11 – South Fork Coeur d'Alene River near Pinehurst, Idaho

100

50

10

3

5

3

1

100

50

30

50

1

0.5

30

100

0.3

0.1

10

5

3

Measured load

Simulated load

Figure 7. Measured and simulated loads of total cadmium at four streamflow-gaging stations in the Spokane River Basin,

Idaho and Washington, water years 1999–2001. (Locations shown in figures 1 and 2)

Figure 7. Measured and simulated loads of total cadmium at four streamflow-gaging stations in the Spokane River Basin, Idaho and 

Washington, water years 1999–2001. (Locations shown in figures 1 and 2)
20 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington TOTAL LEAD LOAD, IN POUNDS PER DAY 100,000

1,000

500

50,000

30,000

Oct.

Dec.

Feb.

Apr.

June

Aug.

Oct.

Dec.

Feb.

Apr.

June

Aug.

Oct.

Dec.

Feb.

Apr.

June

Aug.

WATER YEAR 1999 WATER YEAR 2000 WATER YEAR 2001

Station 19 – Spokane River near Post Falls, Idaho

Station 3 – Canyon Creek at Wallace, Idaho 10,000

5,000

3,000

50

100

10

1

500

200,000

3,000

Station 16 – Coeur d'Alene River near Harrison, Idaho

50,000

30,000

Station 11 – South Fork Coeur d'Alene River near Pinehurst, Idaho

10,000

5,000

1,000

300

500

100

30

10

50

300

100

50

30

10,000

5,000

3,000

500

10

5

300

2,000

3

1

100

50

30

1,000

300

30

5

3

5

20

1,000

Measured load

Simulated load

Figure 8. Measured and simulated loads of total lead at four streamflow-gaging stations in the Spokane River Basin,

Idaho and Washington, water years 1999–2001. (Locations shown in figures 1 and 2)

Figure 8. Measured and simulated loads of total lead at four streamflow-gaging stations in the Spokane River Basin, Idaho and 

Washington, water years 1999–2001. (Locations shown in figures 1 and 2)
Trace-Metal Occurrence and Transport 21

TOTAL ZINC LOAD, IN POUNDS PER DAY

1,000

500

Oct.

Dec.

Feb.

Apr.

June

Aug.

Oct.

Dec.

Feb.

Apr.

June

Aug.

Oct.

Dec.

Feb.

Apr.

June

Aug.

WATER YEAR 1999 WATER YEAR 2000 WATER YEAR 2001

Station 19 – Spokane River near Post Falls, Idaho

Station 3 – Canyon Creek at Wallace, Idaho 5,000

3,000

100

500

30,000

3,000

Station 16 – Coeur d'Alene River near Harrison, Idaho

50,000

30,000

Station 11 – South Fork Coeur d'Alene River near Pinehurst, Idaho

10,000

5,000

1,000

10,000

5,000

3,000

1,000

300

500

300

5,000

100

50

3,000

20,000

30

20

500

300

10,000

Measured load

Simulated load

Figure 9. Measured and simulated loads of total zinc at four streamflow-gaging stations in the Spokane River Basin,

Idaho and Washington, water years 1999–2001. (Locations shown in figures 1 and 2)

Figure 9. Measured and simulated loads of total zinc at four streamflow-gaging stations in the Spokane River Basin, Idaho and 

Washington, water years 1999–2001. (Locations shown in figures 1 and 2)
22 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

Trace-Metal Transport

Annual loads of dissolved and total cadmium, 

lead, and zinc were simulated using the load models 

from table 2 and daily mean stream discharge for each 

station (table 4). Loads for WYs 1999 and 2000 were 

simulated for each of the 21 stations in the station network; data were sufficient to simulate loads for WY 

2001 at only 9 stations. The mean daily stream discharge at the 21 stations decreased by an average of 12 

percent from WY 1999 to WY 2000, and at the 9 stations with available data, decreased by an average of 58 

percent from WY 2000 to WY 2001. At station 15 on 

the CDR near Cataldo, the annual mean discharge for 

WYs 1999–2001 represented about 126, 107, and 43 

percent, respectively, of the historical (WYs 1911–

2001) annual mean of 2,540 ft3/s (Brennan and others, 

2002). At station 19 on the Spokane River at Post Falls, 

the annual mean discharge for WYs 1999–2001 represented about 121, 110, and 43 percent, respectively, of 

the historical (WYs 1913–2001) annual mean of 6,240 

ft3/s (Brennan and others, 2002). Because stream discharge is a primary factor controlling trace-metal transport, changes in the annual mean discharge over the 3 

years of sampling resulted in some large differences in 

annual trace-metal loads. At station 16 on the CDR 

near Harrison, the WY 1999 loads of total cadmium, 

lead, and zinc were 10,000, 470,000, and 1.5 million 

lb, respectively. In WY 2001, the loads at station 16 

were only 2,800, 88,000, and 480,000 lb, respectively, 

or a decrease of 72, 81, and 68 percent from the WY 

1999 loads. In comparison, samples collected on February 10, 1996, during flooding in the CDR Basin 

(Beckwith, 1996) indicate 1-day loads of total cadmium, lead, and zinc at the station near Harrison of 

2,400, 1.4 million, and 350,000 lb, respectively. These 

1-day loads represented about 27 percent of the average 

annual cadmium load for WYs 1999–2000 (table 5), 

about 2.8 times the average annual lead load, and about 

25 percent of the average annual zinc load near Harrison. 

Whereas stream discharge increased incrementally at each successive station on the main stem from 

station 1 on the SFCDR downstream to station 21 on 

the Spokane River, the loads of total trace metals did 

not follow the same pattern (fig. 10). From station 1 

near Mullan to station 16 on the CDR near Harrison, 

the trace-metal loads increased continuously as tributaries and other sources contributed stream discharge 

and trace metals to the SFCDR and the CDR. Primary 

tributary sources of trace-metal loads between station 1 

on the SFCDR and station 16 on the CDR are Canyon 

Creek (station 3), Ninemile Creek (station 4), Government Gulch (station 9), Pine Creek (station 10), and the 

NFCDR (station 14). Although the combined stream 

discharge from Canyon Creek, Ninemile Creek, and 

Government Gulch was, on average, only 78 ft3/s during WYs 1999 and 2000, these three tributaries contributed an average of about 3,000 lb/yr of cadmium, 

23,000 lb/yr of lead, and 310,000 lb/yr of zinc to the 

SFCDR (figs. 11–13). Pine Creek and the NFCDR contributed an average of 2,320 ft3/s of stream discharge 

and about 340 lb/yr of cadmium, 9,400 lb/yr of lead, 

and 79,000 lb/yr of zinc to the SFCDR. 

Trace-metal loads decreased significantly between 

station 16 on the CDR near Harrison, through Coeur 

d’Alene Lake, and downstream to station 19 on the 

Spokane River near Post Falls (figs. 10–13). During 

WYs 1999 and 2000, the average loads at station 19 

were about 4,600 lb/yr of cadmium, 44,000 lb/yr of 

lead, and 980,000 lb/yr of zinc. Between station 19 and 

station 21 at Long Lake, Washington, the trace-metal 

loads decreased further; average loads of total cadmium, lead, and zinc at station 21 were about 2,000, 

24,000, and 730,000 lb/yr, respectively.

Trace-Metal Loading by Reach

The source area contributing trace-metal loads 

measured at a station in the station network is the entire 

watershed upstream from that station. The network in 

the Spokane River Basin divides the basin into smaller 

subareas so that the load of metals contributed from 

specific areas can be determined. Thus, the relative 

importance of each subarea to the overall loading of 

trace metals to the Spokane River Basin can be estimated. Measurements at stations near the mouths of 

tributaries provide an estimate of integrated loads from 

the entire tributary watershed, and measurements at 

main-stem stations provide an estimate of incremental 

metal loading in a downstream manner. The station network also allows an approximation of the total load of 

trace metals discharged to Coeur d’Alene Lake, the 

load trapped within the lake, and the load moving 

through the lake and into the Spokane River. 

The average annual incremental gains and (or) 

losses of stream discharge and trace-metal loads 

between main-stem stations on the SFCDR, CDR, and 

Spokane River from unmeasured sources were esti-
Trace-Metal Occurrence and Transport 23

Water year 1999 simulat

Station 

No. USGS station name

Mean daily 

stream discharge 

(ft3/s)

Dissolved 

cadmium

 Total 

cadmium 

Dissolved 

lead

Main-stem stations

1 SFCDR above Deadman Gulch near Mullan, ID 46 3 6 29 6 SFCDR at Silverton, ID 268 2,500 2,600 3,700 8 SFCDR at Elizabeth Park near Kellogg, ID 418 3,000 3,700 3,500 

11 SFCDR near Pinehurst, ID 687 6,600 7,900 5,800 115 CDR near Cataldo, ID 3,040 7,000 9,600 11,000 216 CDR near Harrison, ID 3,050 7,700 10,000 38,000 419 Spokane River near Post Falls, ID 7,530 3,900 5,000 6,100 20 Spokane River at 7-Mile Bridge, WA 7,910 2,500 3,700 5,500 21 Spokane River at Long Lake, WA 9,240 2,100 2,100 10,000 

Tributary stations

2 Canyon Creek near Burke, ID 40 3 6 47 3 Canyon Creek above mouth at Wallace, ID 60 1,300 1,400 2,900 4 Ninemile Creek above mouth at Wallace, ID 19 490 520 1,000 5 Placer Creek at Wallace, ID 45 4 4 28 7 Moon Creek above mouth at Elk Creek, ID 9 7 8 8 9 Government Gulch near mouth at Smelterville, ID 4 1,100 1,100 49 

10 Pine Creek below Amy Gulch near Pinehurst, ID 197 130 140 200 12 NFCDR above Shoshone Creek near Prichard, ID 836 85 52 120 13 Prichard Creek at mouth at Prichard, ID 225 55 71 180 14 NFCDR at Enaville, ID 2,240 160 230 390 17 St. Joe River at Calder, ID 2,560 230 120 260 18 St. Maries River near Santa, ID 435 60 9 190 

Table 4. Simulated annual loads of cadmium, lead, and zinc at streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water year[Loads were simulated using the equations from table 2; station locations shown in figures 1 and 2; No., number; USGS, U.S. Geological Survey; ft3/s, cubic feet per secon

CDR, Coeur d'Alene River; NFCDR, North Fork Coeur d'Alene River; ID, Idaho; WA, Washington]
24 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington Station No. USGS station name Mean daily stream discharge (ft3/s) Dissolved cadmium Total cadmium Dissolved lead Total lead 

Main-stem stations 1 SFCDR above Deadman Gulch near Mullan, ID 33 1 4 22 310 

6 SFCDR at Silverton, ID 216 1,600 1,800 3,200 21,000 8 SFCDR at Elizabeth Park near Kellogg, ID 362 2,900 3,200 2,500 32,000 

11 SFCDR near Pinehurst, ID 584 5,700 6,400 4,300 74,000 15 CDR near Cataldo, ID 2,710 5,600 8,900 6,200 210,000 16 CDR near Harrison, ID 2,730 6,200 7,700 34,000 530,000 19 Spokane River near Post Falls, ID 6,850 3,300 4,200 6,000 42,000 20 Spokane River at 7-Mile Bridge, WA 7,360 2,400 3,700 6,800 70,000 21 Spokane River at Long Lake, WA 8,440 2,100 1,900 4,100 23,000 

Tributary stations

2 Canyon Creek near Burke, ID 35 2 4 41 140 3 Canyon Creek above mouth at Wallace, ID 52 1,300 1,400 2,100 12,000 4 Ninemile Creek above mouth at Wallace, ID 18 480 510 840 4,700 5 Placer Creek at Wallace, ID 36 1 1 28 110 7 Moon Creek above mouth at Elk Creek, ID 9 5 7 3 47 9 Government Gulch near mouth at Smelterville, ID 3 1,000 1,000 46 160 

10 Pine Creek below Amy Gulch near Pinehurst, ID 164 110 110 160 1,100 12 NFCDR above Shoshone Creek near Prichard, ID 756 25 6 110 390 13 Prichard Creek at mouth at Prichard, ID 210 52 59 69 2,900 14 NFCDR at Enaville, ID 2,030 140 210 380 10,000 17 St. Joe River at Calder, ID 2,380 55 34 66 100 18 St. Maries River near Santa, ID 391 60 8 170 340 

Water year 1999 simulated load

Table 4. Simulated annual loads of cadmium, lead, and zinc at streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water year

2000
Trace-Metal Occurrence and Transport 25

Station 

No. Station name

Mean daily 

stream discharge 

(ft3/s)

Dissolved 

cadmium

 Total 

cadmium 

Dissolved 

lead

Total 

lead

Main-stem stations

8 SFCDR at Elizabeth Park near Kellogg, ID 138 1,500 1,500 1,000 3,400 

11 SFCDR near Pinehurst, ID 232 2,900 2,900 2,100 8,500 16 CDR near Harrison, ID 1,060 2,200 2,800 11,000 88,000 19 Spokane River near Post Falls, ID 2,690 1,000 1,200 1,300 8,800 20 Spokane River at 7-Mile Bridge, WA 3,150 660 980 1,000 9,000 

Tributary stations

3 Canyon Creek above mouth at Wallace, ID 32 830 850 1,100 4,600 4 Ninemile Creek above mouth at Wallace, ID 8 260 260 360 1,100 

10 Pine Creek below Amy Gulch near Pinehurst, ID 55 39 33 43 140 14 NFCDR at Enaville, ID 763 56 62 110 360 

Water year 1999 simulated load, in p

Table 4. Simulated annual loads of cadmium, lead, and zinc at streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 19

2001
26 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington Table 5. Simulated mean annual loads of cadmium, lead, and zinc at streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, wate

[Station locations shown in figures 1 and 2; No., number; USGS, U.S. Geological Survey; ft3/s, cubic feet per second; SFCDR, South Fork Coeur d'Alene River; CDR, Co

North Fork Coeur d'Alene River; ID, Idaho; WA, Washington] Simulated mean annual load, in pou

Station No. USGS station name Mean annual stream discharge (ft3/s) Dissolved cadmium Total cadmium Dissolved lead Total lead 

Main-stem stations 1 SFCDR above Deadman Gulch near Mullan, ID 40 2 5 25 360 

6 SFCDR at Silverton, ID 242 2,000 2,200 3,400 30,000 8 SFCDR at Elizabeth Park near Kellogg, ID 390 3,000 3,400 3,000 44,000 

11 SFCDR near Pinehurst, ID 636 6,200 7,200 5,000 100,000 15 CDR near Cataldo, ID 2,880 6,300 9,200 8,600 200,000 16 CDR near Harrison, ID 2,890 7,000 8,800 36,000 500,000 19 Spokane River near Post Falls, ID 7,190 3,600 4,600 6,000 44,000 20 Spokane River at 7-Mile Bridge, WA 7,640 2,400 3,700 6,200 61,000 21 Spokane River at Long Lake, WA 8,840 2,100 2,000 7,000 24,000 

Tributary stations

2 Canyon Creek near Burke, ID 38 3 5 44 130 3 Canyon Creek above mouth at Wallace, ID 56 1,300 1,400 2,500 18,000 4 Ninemile Creek above mouth at Wallace, ID 18 480 520 920 5,000 5 Placer Creek at Wallace, ID 40 2 2 28 100 7 Moon Creek above mouth at Elk Creek, ID 9 6 7 5 51 9 Government Gulch near mouth at Smelterville, ID 4 1,000 1,000 48 180 

10 Pine Creek below Amy Gulch near Pinehurst, ID 180 120 120 180 1,200 12 NFCDR above Shoshone Creek near Prichard, ID 796 55 29 120 390 13 Prichard Creek at mouth at Prichard, ID 217 54 65 120 2,400 14 NFCDR at Enaville, ID 2,140 150 220 380 8,200 17 St. Joe River at Calder, ID 2,470 140 77 160 260 18 St. Maries River near Santa, ID 413 60 9 180 400 
Trace-Metal Occurrence and Transport 27

MEAN ANNUAL TRACE-METAL LOAD, IN POUNDS PER YEAR 10,000,000

1,000,000

3,000,000

1 8 6

STREAMFLOW-GAGING STATION NUMBER

Total zinc

Total lead

Total cadmium

11 16 15 19 21 20 2 4 359

TRIBUTARY

7 10 13 12 14 18 17

6,000,000

100,000

300,000

600,000

10,000

30,000

60,000

1,000

3,000

6,000

100

300

600

1.000,000

100,000

300,000

600,000

10,000

30,000

60,000

1,000

3,000

6,000

100

300

600

10

30

60

100,000

10,000

30,000

60,000

1,000

3,000

6,000

100

300

600

10

30

60

1

3

6

MEAN ANNUAL STREAM DISCHARGE, IN CUBIC FEET PER SECOND

100,000

10,000

30,000

60,000

1,000

3,000

6,000

100

300

600

10

30

60

1

3

6

100,000

10,000

30,000

60,000

1,000

3,000

6,000

100

300

600

10

30

60

1

3

6

100,000

10,000

30,000

60,000

1,000

3,000

6,000

100

300

600

10

30

60

1

3

6

Trace-metal load

Stream discharge

MAIN STEM

Figure 10. Mean annual stream discharge and mean annual loads of total cadmium, lead, and zinc at main-stem and tributary streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water year 1999–2000. (Locations shown in figures 1 and 2)

Figure 10. Mean annual stream discharge and mean annual loads of total cadmium, lead, and zinc at main-stem and tributary 

streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2000. (Locations shown in figures 

1 and 2)
28 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

Figure 11. Mean annual stream discharge, mean flow-weighted concentration, and mean annual load of total cadmium for mainstem and tributary streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2000.

(Locations shown in figures 1 and 2; ft3/s, cubic feet per second; ∝g/L, micrograms per liter; lb/yr, pounds per year)

38 ft3/s, 0.07 ∝g/L

5 lb/yr

Station 2

Canyon Creek

near Burke

40 ft3/s, 0.06 ∝g/L

5 lb/yr

Station 1

South Fork Coeur d'Alene

River near Mullan

242 ft3/s, 4.7 ∝g/L

2,200 lb/yr

Station 6

South Fork Coeur d'Alene

River at Silverton

56 ft3/s, 13 ∝g/L

1,400 lb/yr

Station 3

Canyon Creek

at Wallace

796 ft3/s, 0.02 ∝g/L

29 lb/yr

Station 12

North Fork Coeur d'Alene

River near Prichard

2,140 ft3/s, 0.05 ∝g/L

220 lb/yr

Station 14

North Fork Coeur d'Alene

River at Enaville

18 ft3/s, 14 ∝g/L

520 lb/yr

Station 4

Ninemile Creek

9 ft3/s, 0.41 ∝g/L

7 lb/yr

Station 7

Moon Gulch

40 ft3/s, 0.03 ∝g/L

2 lb/yr

Station 5

Placer Creek

4 ft3/s, 150.0 ∝g/L

1,000 lb/yr

Station 9

Government Gulch

180 ft3/s, 0.34 ∝g/L

120 lb/yr

Station 10

Pine Creek

390 ft3/s, 4.5 ∝g/L

3,400 lb/yr

Station 8

South Fork Coeur d'Alene

River at Elizabeth Park

636 ft3/s, 5.7 ∝g/L

7,200 lb/yr

Station 11

South Fork Coeur d'Alene

River near Pinehurst

217 ft3/s, 0.15 ∝g/L

65 lb/yr

Station 13

Prichard Creek

at Prichard

2,880 ft3/s, 1.6 ∝g/L

9,200 lb/yr

Station 15

Coeur d'Alene River

near Cataldo

2,890 ft3/s, 1.6 ∝g/L

8,800 lb/yr

Station 16

Coeur d'Alene River

near Harrison

2,470 ft3/s, 0.02 ∝g/L

77 lb/yr

Station 17

St. Joe River

413 ft3/s, 0.01 ∝g/L

9 lb/yr

Station 18

St. Maries River

7,190 ft3/s, 0.32 ∝g/L

4,600 lb/yr

Station 19

Spokane River

near Post Falls

7,640 ft3/s, 0.24 ∝g/L

3,700 lb/yr

Station 20

Spokane River

at 7-Mile Bridge

8,840 ft3/s, 0.11 ∝g/L

2,000 lb/yr

Station 21

Spokane River

at Long Lake

Coeur d'Alene

Lake

Figure 11. Mean annual stream discharge, mean flow-weighted concentration, and mean annual load of total cadmium for mainstem and tributary streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2000. 

(Locations shown in figures 1 and 2; ft3

/s, cubic feet per second; μg/L, micrograms per liter; lb/yr, pounds per year)
Trace-Metal Occurrence and Transport 29

Figure 12. Mean annual stream discharge, mean flow-weighted concentration, and mean annual load of total lead for mainstem and tributary streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2000.

(Locations shown in figures 1 and 2; ft3/s, cubic feet per second; ∝g/L, micrograms per liter; lb/yr, pounds per year)

38 ft3/s, 1.7 ∝g/L

130 lb/yr

Station 2

Canyon Creek

near Burke

40 ft3/s, 4.7 ∝g/L

360 lb/yr

Station 1

South Fork Coeur d'Alene

River near Mullan

242 ft3/s, 64 ∝g/L

30,000 lb/yr

Station 6

South Fork Coeur d'Alene

River at Silverton

56 ft3/s, 165 ∝g/L

18,000 lb/yr

Station 3

Canyon Creek

at Wallace

796 ft3/s, 0.25 ∝g/L

390 lb/yr

Station 12

North Fork Coeur d'Alene

River near Prichard

2,140 ft3/s, 2 ∝g/L

8,200 lb/yr

Station 14

North Fork Coeur d'Alene

River at Enaville

18 ft3/s, 140 ∝g/L

5,000 lb/yr

Station 4

Ninemile Creek

9 ft3/s, 2.9 ∝g/L

51 lb/yr

Station 7

Moon Gulch

40 ft3/s, 1.2 ∝g/L

100 lb/yr

Station 5

Placer Creek

4 ft3/s, 26 ∝g/L

180 lb/yr

Station 9

Government Gulch

180 ft3/s, 3.3 ∝g/L

1,200 lb/yr

Station 10

Pine Creek

390 ft3/s, 58 ∝g/L

44,000 lb/yr

Station 8

South Fork Coeur d'Alene

River at Elizabeth Park

636 ft3/s, 80 ∝g/L

100,000 lb/yr

Station 11

South Fork Coeur d'Alene

River near Pinehurst

217 ft3/s, 5.6 ∝g/L

2,400 lb/yr

Station 13

Prichard Creek

at Prichard

2,880 ft3/s, 37 ∝g/L

200,000 lb/yr

Station 15

Coeur d'Alene River

near Cataldo

2,890 ft3/s, 88 ∝g/L

500,000 lb/yr

Station 16

Coeur d'Alene River

near Harrison

2,470 ft3/s, 0.05 ∝g/L

260 lb/yr

Station 17

St. Joe River

413 ft3/s, 0.49 ∝g/L

400 lb/yr

Station 18

St. Maries River

7,190 ft3/s, 3.1 ∝g/L

44,000 lb/yr

Station 19

Spokane River

near Post Falls

7,640 ft3/s, 4 ∝g/L

61,000 lb/yr

Station 20

Spokane River

at 7-Mile Bridge

8,840 ft3/s, 1.3 ∝g/L

24,000 lb/yr

Station 21

Spokane River

at Long Lake

Coeur d'Alene

Lake

Figure 12. Mean annual stream discharge, mean flow-weighted concentration, and mean annual load of total lead for main-stem 

and tributary streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2000. (Locations 

shown in figures 1 and 2; ft3

/s, cubic feet per second; μg/L, micrograms per liter; lb/yr, pounds per year)
30 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

Figure 13. Mean annual stream discharge, mean flow-weighted concentration, and mean annual load of total zinc for mainstem and tributary streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2000.

(Locations shown in figures 1 and 2; ft3/s, cubic feet per second; ∝g/L, micrograms per liter; lb/yr, pounds per year)

38 ft3/s, 7.4 ∝g/L

560 lb/yr

Station 2

Canyon Creek

near Burke

40 ft3/s, 13 ∝g/L

1,000 lb/yr

Station 1

South Fork Coeur d'Alene

River near Mullan

242 ft3/s, 650 ∝g/L

310,000 lb/yr

Station 6

South Fork Coeur d'Alene

River at Silverton

56 ft3/s, 1,700 ∝g/L

190,000 lb/yr

Station 3

Canyon Creek

at Wallace

796 ft3/s, 2.4 ∝g/L

3,800 lb/yr

Station 12

North Fork Coeur d'Alene

River near Prichard

2,140 ft3/s, 11 ∝g/L

46,000 lb/yr

Station 14

North Fork Coeur d'Alene

River at Enaville

18 ft3/s, 2,300 ∝g/L

84,000 lb/yr

Station 4

Ninemile Creek

9 ft3/s, 69 ∝g/L

1,200 lb/yr

Station 7

Moon Gulch

40 ft3/s, 3 ∝g/L

240 lb/yr

Station 5

Placer Creek

4 ft3/s, 5,000 ∝g/L

35,000 lb/yr

Station 9

Government Gulch

180 ft3/s, 93 ∝g/L

33,000 lb/yr

Station 10

Pine Creek

390 ft3/s, 620 ∝g/L

480,000 lb/yr

Station 8

South Fork Coeur d'Alene

River at Elizabeth Park

636 ft3/s, 810 ∝g/L

1,000,000 lb/yr

Station 11

South Fork Coeur d'Alene

River near Pinehurst

217 ft3/s, 32 ∝g/L

14,000 lb/yr

Station 13

Prichard Creek

at Prichard

2,880 ft3/s, 210 ∝g/L

1,200,000 lb/yr

Station 15

Coeur d'Alene River

near Cataldo

2,890 ft3/s, 240 ∝g/L

1,400,000 lb/yr

Station 16

Coeur d'Alene River

near Harrison

2,470 ft3/s, 1.3 ∝g/L

6,400 lb/yr

Station 17

St. Joe River

413 ft3/s, 2.5 ∝g/L

2,100 lb/yr

Station 18

St. Maries River

7,190 ft3/s, 71 ∝g/L

980,000 lb/yr

Station 19

Spokane River

near Post Falls

7,640 ft3/s, 60 ∝g/L

900,000 lb/yr

Station 20

Spokane River

at 7-Mile Bridge

8,840 ft3/s, 42 ∝g/L

730,000 lb/yr

Station 21

Spokane River

at Long Lake

Coeur d'Alene

Lake

Figure 13. Mean annual stream discharge, mean flow-weighted concentration, and mean annual load of total zinc for main-stem 

and tributary streamflow-gaging stations in the Spokane River Basin, Idaho and Washington, water years 1999–2000. (Locations 

shown in figures 1 and 2; ft3

/s, cubic feet per second; μg/L, micrograms per liter; lb/yr, pounds per year)
Trace-Metal Occurrence and Transport 31

mated for WYs 1999 and 2000 (table 6). The estimates 

were based on the differences in loads between mainstem stations and measured tributaries in the reach 

(figs. 11–13). The gains and (or) losses in stream discharge and loads that were unaccounted for by the station network are termed “unmeasured” in table 6. In 

main-stem reaches with both unmeasured stream discharge and unmeasured positive loads, the trace-metal 

concentration in the unmeasured stream discharge was 

estimated as the unmeasured load divided by the 

unmeasured stream discharge and appropriate conversion factors. Primary sources of unmeasured stream 

discharge and trace-metal loads in the Spokane River 

Basin are ungaged tributaries, ground-water discharge, 

overland flow, and dissolution and erosion of material 

in stream channels.

 Stream discharge increased in all of the mainstem reaches; unmeasured sources accounted for at 

least part of the increase. Unmeasured stream discharge ranged from less than 1 percent in reach 5 

between stations 15 and 16 to 36 percent in reaches 1 

and 2 between stations 1 and 8 (table 6). Trace-metal 

loading (including the unmeasured loads) to main-stem 

reaches occurred primarily upstream from Coeur 

d’Alene Lake. 

SOUTH FORK COEUR D’ALENE RIVER

Reach 1 includes the measured contributions from 

Canyon Creek and Ninemile Creek. Although these 

two tributaries contributed about 31 percent of the 

stream discharge measured at the downstream end of 

reach 1 (station 6), they accounted for about 87 percent 

of the cadmium, 77 percent of the lead, and 88 percent 

of the zinc loads at station 6. About 36 percent of the 

stream discharge in reach 1, and 14, 23, and 10 percent 

of the total cadmium, lead, and zinc loads, respectively, 

were from unmeasured sources. The relative percentages of unmeasured stream discharge and trace-metal 

loads in reach 1 indicate that, overall, unmeasured 

sources in reach 1 had smaller concentrations of total 

cadmium (1.7 μg/L), total lead (40 μg/L), and total 

zinc (170 μg/L) than did the measured sources draining 

mining-affected areas. 

Unmeasured sources contributed an average of 

139 ft3/s (36 percent) of stream discharge to reach 2, 

about 1,200 lb/yr (35 percent) of cadmium, 14,000 

lb/yr (32 percent) of lead, and 170,000 lb/yr (35 percent) of zinc. Estimated concentrations of total cadmium, lead, and zinc in the unmeasured sources were 

4.4, 51, and 620 μg/L, respectively. On the basis of the 

percent contributions of stream discharge and tracemetal loads in reach 2, the trace-metal concentrations 

in the unmeasured sources were similar to those in the 

SFCDR in reach 2. A ground-water seepage study conducted along the SFCDR during low stream discharge 

in the summer and fall of 1999 documented that, in 

parts of reach 2, ground water contributed about 1 and 

220 lb/d of cadmium and zinc, respectively, to the 

SFCDR (Barton, 2002). This ground-water contribution, if extrapolated over the 2-year period of study, 

would account for about 30 percent of the cadmium 

load and about 48 percent of the zinc load from unmeasured sources to reach 2. Although there was a net gain 

of 14,000 lb/yr of lead from unmeasured sources to 

reach 2, there was a loss of 400 lb/yr of dissolved lead. 

The ground-water seepage study documented a loss of 

dissolved lead of about 1.4 lb/d in reach 2 (Barton, 

2002), similar in magnitude to the loss of 400 lb/yr (1.1 

lb/d) shown in table 6. Woods (2001b) suggested that 

losses of dissolved lead in the SFCDR are attributable 

to formation of a lead/iron complex and subsequent 

conversion to a particulate or colloidal form. During 

low stream discharge, this complex would be retained 

in the stream channel and subsequently transported 

downstream during increased stream discharge, thus 

accounting for at least part of the gain in the total load 

of lead in reach 2.

Reach 3 of the SFCDR between station 8 at Elizabeth Park near Kellogg and station 11 near Pinehurst 

includes the Bunker Hill Superfund site (fig. 2). During 

1999–2000, the loads of cadmium, lead, and zinc 

approximately doubled in the 8-mi length of the reach 

(table 6 and figs. 11–13). Government Gulch (station 9) 

and Pine Creek (station 10) contributed about 1,100 

lb/yr (15 percent) of cadmium, 1,400 lb/yr (1 percent) 

of lead, and 68,000 lb/yr (7 percent) of zinc to reach 3. 

Unmeasured sources in reach 3 contributed about 62 

ft3/s (10 percent) of stream discharge and about 2,700 

lb/yr (38 percent) of cadmium, 55,000 lb/yr (55 percent) of lead, and 450,000 lb/yr (45 percent) of zinc to 

the SFCDR (table 6). On the basis of the 1999 seepage 

study described previously (Barton, 2002), groundwater recharge to reach 3 contributed about 2 lb/d of 

dissolved cadmium and 730 lb/d of dissolved zinc, primarily in a 2- to 4-mi reach of the SFCDR centered 

around Smelterville (fig. 2). Extrapolated to annual 

loads, the ground-water contributions of total cadmium 
32 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

]

Mean annual 

stream discharge 

(ft3/s)

 Mean annual load, in pounds per year

Dissolved 

cadmium

Total 

cadmium 

Dissolved 

lead Total lead

Dissolved 

zinc Total zinc

Reach 1: Station 1 to Station 6

Sum of stations 1, 3, 4, and 5

Station 6

154

242

1,800

2,000

1,900

2,200

3,500

3,400

23,000

30,000

270,000

300,000

280,000

310,000

Unmeasured stream discharge or load 88 200 300 -100 7,000 30,000 30,000

Amount unmeasured or lost in reach 36% 10% 14% 3% 23% 10% 10%

Concentration of unmeasured stream 

discharge (μg/L) NA 1.2 1.7 — 40 170 170

Reach 2: Station 6 to Station 8

Sum of stations 6 and 7

Station 8

251

390

2,000

3,000

2,200

3,400

3,400

3,000

30,000

44,000

300,000

440,000

310,000

480,000

Unmeasured stream discharge or load 139 1,000 1,200 -400 14,000 140,000 170,000

Amount unmeasured or lost in reach 36% 33% 35% 12% 32% 32% 35%

Concentration of unmeasured stream 

discharge (μg/L) NA 3.7 4.4 — 51 510 620

Reach 3: Station 8 to Station 11

Sum of stations 8, 9, and 10

Station 11

574

636

4,100

6,200

4,500

7,200

3,200

5,000

45,000

100,000

510,000

880,000

550,000

1,000,000

Unmeasured stream discharge or load 62 2,100 2,700 1,800 55,000 370,000 450,000

Amount unmeasured or lost in reach 10% 34% 38% 36% 55% 42% 45%

Concentration of unmeasured stream 

discharge (μg/L) NA 17 22 15 450 3,000 3,700

Reach 4: Station 11 to Station 15

Sum of stations 11 and 14 2,776 6,400 7,400 5,400 110,000 900,000 1,000,000

Station 15 2,880 6,300 9,200 8,600 200,000 920,000 1,200,000

Unmeasured stream discharge or load 104 -100 1,800 3,200 90,000 20,000 200,000

Amount unmeasured or lost in reach 4% 2% 20% 37% 45% 2% 17%

Concentration of unmeasured stream 

discharge (μg/L) NA — 8.8 16 440 97 970

Table 6. Mean annual gains and (or) losses of stream discharge and cadmium, lead, and zinc loads in main-stem reaches of the South Fork

Coeur d'Alene, Coeur d'Alene, and Spokane Rivers, Idaho and Washington, water years 1999–2000

[Station locations shown in figures 1 and 2; negative stream discharge or load (number in bold) represents reach losses; ft3/s, cubic feet per second; μg/L, 

micrograms per liter; NA, not applicable; —, no increase in stream discharge and (or) trace-metal load
Trace-Metal Occurrence and Transport 33

Reach 5: Station 15 to Station 16

Station 15 2,880 6,300 9,200 8,600 200,000 920,000 1,200,000

Station 16 2,890 7,000 8,800 36,000 500,000 1,100,000 1,400,000

Unmeasured stream discharge or load 10 700 -400 27,400 300,000 180,000 200,000

Amount unmeasured or lost in reach <1% 10% 4% 76% 60% 16% 14%

Concentration of unmeasured stream 

discharge (μg/L) NA — — — — — —

Reach 6: Station 16 to Station 19

Sum of stations 16, 17, and 18 5,773 7,200 8,900 36,000 500,000 1,100,000 1,400,000

Station 19 7,190 3,600 4,600 6,000 44,000 940,000 980,000

Unmeasured stream discharge or load 1,417 -3,600 -4,300 -30,000 -456,000 -160,000 -420,000

Amount unmeasured or lost in reach 20% 50% 48% 83% 91% 15% 30%

Concentration of unmeasured stream 

discharge (μg/L) NA — — — — — —

Reach 7: Station 19 to Station 20

Station 19 7,190 3,600 4,600 6,000 44,000 940,000 980,000

Station 20 7,640 2,400 3,700 6,200 61,000 780,000 900,000

Unmeasured stream discharge or load 450 -1,200 -900 200 17,000 -160,000 -80,000

Amount unmeasured or lost in reach 6% 33% 20% 3% 28% 17% 8%

Concentration of unmeasured stream 

discharge (μg/L) NA — — 0.2 19 — —

Reach 8: Station 20 to Station 21

Station 20 7,640 2,400 3,700 6,200 61,000 780,000 900,000

Station 21 8,840 2,100 2,000 7,000 24,000 590,000 730,000

Unmeasured stream discharge or load 1,200 -300 -1,700 800 -37,000 -190,000 -170,000

Amount unmeasured or lost in reach 14% 13% 46% 11% 61% 24% 19%

Concentration of unmeasured stream 

discharge (μg/L) NA — — 0.3 — — —

Mean annual 

stream discharge 

(ft3

/s)

 Mean annual load, in pounds per year

Dissolved 

cadmium

Total 

cadmium 

Dissolved 

lead Total lead

Dissolved 

zinc Total zinc

Table 6. Mean annual gains and (or) losses of stream discharge and cadmium, lead, and zinc loads in main-stem reaches of the South Fork

Coeur d'Alene, Coeur d'Alene, and Spokane Rivers, Idaho and Washington, water years 1999–2000—Continued
34 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

and zinc to reach 3 would be 730 and 266,000 lb/yr, 

respectively, or 27 and 59 percent of the unmeasured 

loads. 

MAIN-STEM COEUR D’ALENE RIVER

Combined, the NFCDR and SFCDR discharged 

about 7,400, 110,000, and 1 million lb/yr of total cadmium, lead, and zinc, respectively, during 1999–2000 

(table 6 and figs. 11–13). Of these totals, the SFCDR 

accounted for about 97, 92, and 96 percent of the cadmium, lead, and zinc loads, respectively. The NFCDR 

and SFCDR contributed 96 percent of the stream discharge and 84, 22, and 75 percent, respectively, of the 

total cadmium, lead, and zinc loads measured 32 mi 

downstream at station 16 on the CDR near Harrison 

(table 6). Unmeasured sources contributed about 

390,000 lb/yr of lead (78 percent) and 400,000 lb/yr of 

zinc (29 percent) to reaches 4 and 5 (table 6). The 

hydrologic processes that appear to account for most of 

the lead entering reaches 4 and 5 are erosion and transport of sediment-bound lead contained in the river 

channel and banks. Lead-rich sediments containing at 

least 1,000 parts per million, or more than 30 times 

background concentrations, cover almost 75 percent of 

the CDR flood plain from the confluence of its North 

and South Forks to its mouth at Coeur d’Alene Lake 

(Bookstrom and others, 2001). The increase in zinc 

load in reaches 4 and 5 also may be derived from sediment or other particulate sources, or it may be contributed from ground-water discharge. The relatively small 

increase in stream discharge from unmeasured sources 

in reach 5 indicates that ground water is not a major 

source of stream discharge between stations 15 and 16. 

However, if the river is losing water to and regaining 

water from the alluvial aquifer, dissolution of aquifer 

material may provide zinc to the CDR in reach 5. Further investigation would be necessary to determine 

whether this process provides the large increase in the 

zinc load in the lower reaches of the CDR. 

COEUR D’ALENE LAKE AND SPOKANE RIVER

On the basis of annual loads in the CDR near Harrison (station 16), the St. Joe River at Calder (station 

17), and the St. Maries River near Santa (station 18), 

Coeur d’Alene Lake received about 8,900 lb/yr of cadmium, 500,000 lb/yr of lead, and 1.4 million lb/yr of 

zinc during WYs 1999–2000. Although the CDR, as 

measured at station 16, contributed about half of the 

measured stream discharge to the lake, it contributed 

more than 99 percent of the cadmium, lead, and zinc 

loads, and the St. Maries and St. Joe Rivers combined 

contributed less than 1 percent. The loads transported 

from Coeur d’Alene Lake, as measured in the Spokane 

River near Post Falls (station 19) indicate that the lake 

retains a large part of the trace-metal loads that it 

receives. Horowitz and others (1995) estimated that 

about 82.5 million tons of trace-metal-enriched sediments have been deposited on or in the lakebed. The 

lake is especially efficient in trapping total lead, which 

is generally associated with sediment particles. Bookstrom and others (2001) estimated that about 300,000 

tons of lead is present in the sediments on the lake bottom. Of the half million lb/yr of lead entering the lake 

during 1999–2000, only about 44,000 lb/yr, or less 

than 10 percent, was transported from the lake into the 

Spokane River (fig. 12). Coeur d’Alene Lake is less 

efficient trapping cadmium and zinc than trapping lead. 

About 4,600 lb/yr of cadmium and 980,000 lb/yr of 

zinc, or about 52 and 70 percent of the loads entering 

the lake, respectively, were transported from the lake 

into the Spokane River (figs. 11 and 13). 

In reach 7 between stations 19 and 20 on the Spokane River, there was a loss of 900 and 80,000 lb/yr of 

cadmium and zinc, respectively, and a gain of 17,000 

lb/yr of lead (table 6 and figs. 11–13). In the upstream 

part of reach 7, depending on the streamflow conditions, the Spokane River may lose more than 500 ft3/s 

of stream discharge to the underlying Spokane Valley/Rathdrum Prairie alluvial aquifer (Bolke and Vaccaro, 1981; Gearhart and Buchanan, 2000). This discharge from the Spokane River to the aquifer transports 

dissolved trace metals, primarily cadmium and zinc, as 

far as 200 ft from the river margin (Marti and Garrigues, 2001). The cadmium and zinc transported to the 

aquifer probably account for most of the decrease in 

the loads between stations 19 and 20. In the downstream part of reach 7, the Spokane River becomes primarily a gaining reach as a result of the reversal in the 

stream/aquifer gradient, and the Spokane River 

receives recharge from the aquifer. Overall, annual 

mean stream discharge in reach 7 increased by 450 

ft3/s. However, cadmium and zinc were retained in the 

reach, possibly by sorption or precipitation processes 

within the aquifer (Rod Caldwell, U.S. Geological Survey, written commun., 2002). The increase in the lead 

load in reach 7 is probably attributable to mobilization 

and transport of sediment-bound lead deposited within 
References Cited 35

the channel of the Spokane River. Concentrations of 

lead exceeding 1,000 parts per million in samples collected from the Spokane River near Post Falls (station 

19) have been documented (Grosbois and others, 

2001). Lead in the bed sediment of the Spokane River 

probably can be attributed to extreme floods in the 

CDR Basin. These floods transport large quantities of 

sediment-bound lead through Coeur d’Alene Lake and 

into the Spokane River (Grosbois and others, 2001; 

URS-Greiner, Inc. and CH2M-Hill, Inc, 2001). 

Whereas stream discharge increased in reach 8 of 

the Spokane River by an average of 1,200 ft3/s (14 percent) during 1999–2000, the loads of trace metals 

decreased. The loads of cadmium, lead, and zinc at station 21, located at the outlet of Long Lake (fig. 1), indicate that a large part of the trace-metal loads entering 

the lake are retained. Similar to Coeur d’Alene Lake, 

Long Lake appears especially efficient at trapping lead, 

which was reduced in reach 8 by about 37,000 lb/yr (61 

percent) during WYs 1999–2000. About 2,000 lb/yr of 

cadmium, 24,000 lb/yr of lead, and 730,000 lb/yr of 

zinc were transported downstream from reach 8 toward 

the Columbia River (figs. 11–13). Overall, between the 

CDR near Harrison (station 16) and the Spokane River 

at Long Lake (station 21), about 6,800, 476,000, and 

670,000 lb/yr of cadmium, lead, and zinc, respectively, 

were lost to Coeur d’Alene Lake, the Spokane River, 

and Long Lake. These losses represent about 76 percent of the cadmium load, 95 percent of the lead load, 

and 48 percent of the zinc load delivered to Coeur 

d’Alene Lake during WYs 1999–2000. 

CONCLUSIONS

The results of this study confirm findings from 

previous investigations that have identified mining 

activities in mineralized areas of the South Fork Coeur 

d’Alene River (SFCDR) as the primary source of tracemetal-contaminated water and sediment in the SFCDR, 

Coeur d’Alene River (CDR), Coeur d’Alene Lake, and 

Spokane River. The transport of three trace metals of 

environmental concern (cadmium, lead, and zinc) 

was evaluated for water years 1999–2001 using an 

approach that quantified their concentrations and loads 

at 21 stations in the Spokane River Basin. The results 

demonstrate that during the 3 years of study, cadmium 

and zinc entering Coeur d’Alene Lake and transported 

downstream in the Spokane River were derived largely 

from the SFCDR Basin, primarily from miningaffected tributaries and the shallow alluvial aquifer 

adjacent to the SFCDR. Cadmium and zinc were transported in streams predominantly in the dissolved (less 

than 0.45 micrometer) form and, at most stations, concentrations were inversely correlated with stream discharge. In contrast to cadmium and zinc, lead was 

transported in streams primarily in the particulate form, 

and total lead concentration at all stations was positively correlated with stream discharge. Transport of 

lead occurs primarily during elevated stream discharge 

when lead-rich sediments stored in stream channels 

and the flood plain of the CDR are eroded and transported downstream. 

The load models presented in this report are a 

valuable tool for assessing trace-metal transport in the 

Spokane River Basin. As additional data are collected, 

they can be integrated with existing data to modify the 

models and improve understanding of the relation between trace-metal concentrations and stream discharge. 

Future data collection activities targeted at extreme 

flow conditions (either high or low stream discharge) 

would provide essential data for understanding the 

mechanisms of trace-metal transport and estimating 

annual loads in the Spokane River Basin. In addition, 

continued sampling at stations such as the SFCDR near 

Pinehurst, the CDR near Harrison, and the Spokane 

River near Post Falls would provide data for evaluating 

trends and assessing the efficacy of remediation activities designed to reduce trace-metal loading to streams 

in the Spokane River Basin. 

REFERENCES CITED

References Cited

Aikaike, H., 1981, Likelihood of a model and information criterion: Journal of Econometrics, v. 16, 

p. 3–14.

Barton, G.J., 2002, Dissolved cadmium, zinc, and lead 

loads from ground-water seepage into the South 

Fork Coeur d’Alene River system, Northern 

Idaho, 1999: U.S. Geological Survey WaterResources Investigations Report 01–4274, 130 p.

Beckwith, M.A., 1996, Water-quality data collected 

during floods in the Coeur d’Alene River, Northern Idaho, February 1996: U.S. Geological Survey Fact Sheet FS–219–96, 4 p.

——— 1998, Concepts for monitoring water quality in 

the Spokane River Basin, Northern Idaho and 

Eastern Washington: U.S. Geological Survey 

Open-File Report 98–534, 25 p.
36 Cadmium, Lead, and Zinc in the Spokane River Basin, Idaho and Washington

Bolke, E.L., and Vaccaro, J.J., 1981, Digital-model 

simulation of the hydrologic flow system, with 

emphasis on ground water, in the Spokane Valley, 

Washington and Idaho: U.S. Geological Survey 

Open-File Report 80–1300, 43 p. 

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