Water Quality in the Northern Rockies Intermontane Basins

Idaho, Montana, and Washington, 1999–2001


U.S. Geological Survey Circular 1235


By Gregory M. Clark, Rodney R. Caldwell, Terry R. Maret, Craig L. Bowers, DeAnn M. Dutton, and Michael A. Beckwith


This circular is available as a pdf.


This report contains the major findings of a 1999–2001 assessment of water quality in the Northern Rockies Intermontane Basins. It is one of a series of reports by the National Water-Quality Assessment (NAWQA) Program that present major findings in 51 major river basins and aquifer systems across the Nation.


In these reports, water quality is discussed in terms of local, State, and regional issues. Conditions in a particular basin or aquifer system are compared to conditions found elsewhere and to selected national benchmarks, such as those for drinking-water quality and the protection of aquatic organisms.


This report is intended for individuals working with water-resource issues in Federal, State, or local agencies, universities, public interest groups, or in the private sector. The information will be useful in addressing a number of current issues, such as the effects of agricultural and urban land use on water quality, human health, drinking water, source-water protection, hypoxia and excessive growth of algae and plants, pesticide registration, and monitoring and sampling strategies. This report is also for individuals who wish to know more about the quality of streams and ground water in areas near where they live, and how that water quality compares to the quality of water in other areas across the Nation.


The water-quality conditions in the Northern Rockies Intermontane Basins summarized in this report are discussed in detail in other reports that can be accessed from ( Detailed technical information, data and analyses, collection and analytical methodology, models, graphs, and maps that support the findings presented in this report in addition to reports in this series from other basins can be accessed from the national NAWQA Web site (


National Water-Quality Assessment Program

What kind of water-quality information does the NAWQA Program provide?

Introduction to this Report

Summary of Major Findings

Stream and River Highlights

Ground-Water Highlights

Introduction to the Northern Rockies Intermontane Basins

Major Findings

Historical mining activities have degraded water-quality conditions in numerous streams

Nutrient concentrations in streams generally are low

Fish in the Spokane River contain polychlorinated biphenyls (PCBs) at elevated concentrations

The Spokane River also contains low concentrations of pesticides and volatile organic compounds

Ground water in aquifers used for drinking-water supply in Spokane, Coeur d’Alene, and Missoula is generally of good quality

Study-Unit Design

Stream Chemistry and Ecology

Ground-Water Chemistry

References Cited



Points of Contact and Additional Information


The companion Web site for NAWQA summary reports:


Northern Rockies Intermontane Basins contact and web site:

USGS State Representative

U.S. Geological Survey

Water Resources Discipline

230 Collins Rd.

Boise, ID 83702



National NAWQA Program:

Chief, NAWQA Program
U.S. Geological Survey
Water Resources Discipline
12201 Sunrise Valley Drive, M.S. 413
Reston, VA 20192


For sale by


U.S. Geological Survey,

Information Services
Box 25286, Denver Federal Center
Denver, CO 80225


For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS
World Wide Web:


The text and graphics are presented here in pdf format (print quality). The full report is 15.7MB.


If you have Adobe® Acrobat® or Adobe® Acrobat® Reader® installed on your computer, you may view and print the PDF version of this report. Acrobat Reader, is a free download it from Adobe Systems, Inc.  Users with disabilities can view information concerning accessibility at


Return to Top


[an error occurred while processing this directive]
U.S. Department of the Interior, U.S. Geological Survey
Persistent URL:
Page Contact Information: Contact USGS
Last modified: Wednesday, November 23 2016, 12:23:41 PM
FirstGov button  Take Pride in America button