Water Quality on the Island of Oahu

Hawaii, 1999–2001


U.S. Geological Survey Circular 1239


By Stephen S. Anthony, Charles D. Hunt, Jr., Anne M.D. Brasher, Lisa D. Miller, and Michael S. Tomlinson


This circular is available as a pdf.


This report contains the major findings of a 1999–2001 assessment of water quality on the island of Oahu, Hawaii. 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, 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 on Oahu 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 Highlights

Ground-Water Highlights

Introduction to the Oahu Study Unit

Land use is changing from agriculture to urban

Ground water provides public supplies, streams provide aquatic habitat and
irrigation water

Drinking-water aquifer is vulnerable to contamination

Below-normal rainfall may have affected water quality

Major Findings

Ground Water

Organic compounds were detected in most wells, but few concentrations
exceeded drinking-water standards

Nutrient concentrations were elevated in agricultural areas but did not exceed
drinking-water standards

Land use and aquifer vulnerability influence ground-water contamination

Mixtures of organic compounds were common in ground water

Ground-water contamination in central Oahu reflects decades-old releases and
former land use

Surface Water

Contaminants in stream water varied with land use, storms, and ground-water

Excess nutrients may adversely affect stream and coastal ecosystems

Streambed Sediment and Fish Tissue

Aquatic habitat is degraded by nonpoint-source pollution

Discontinued organochlorine pesticides persist in the environment

Human activities elevate trace elements in stream sediments

Stream Ecology

Urban alteration of stream habitat has adversely affected native aquatic species

Benthic invertebrates reflect degraded stream quality

Most identified invertebrates were nonnative

Study Unit Design

Ground-Water Chemistry

Stream Chemistry

Stream Ecology

References Cited


Appendix. Water Quality Data from the Island of Oahu, Hawaii, in a National Context

Points of Contact and Additional Information


The companion Web site for NAWQA summary reports:


Oahu Study Unit contact and Web site:

USGS State Representative

U.S. Geological Survey

677 Ala Moana Blvd. Suite 415

Honolulu, HI 96813



National NAWQA Program:

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


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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
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