National Water-Quality Assessment (NAWQA) Program

U.S. Geological Survey
Open-File Report 94-70

Overview of the National Water-Quality Assessment Program

By P.P. Leahy and T.H.Thompson



The Nation's water resources are the basis for life and our economic vitality. These resources support a complex web of human activities and fishery and wildlife needs that depend upon clean water. Demands for good-quality water for drinking, recreation, farming, and industry are rising, and as a result, the American public is concerned about the condition and sustainability of our water resources. The American public is asking: Is it safe to swim in and drink water from our rivers or lakes? Can we eat the fish that come from them? Is our ground water polluted? Is water quality degrading with time, and if so, why? Has all the money we've spent to clean up our waters, done any good? The U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program was designed to provide information that will help answer these questions.

NAWQA is designed to assess historical, current, and future water-quality conditions in representative river basins and aquifers nationwide. One of the primary objectives of the program is to describe relations between natural factors, human activities, and water-quality conditions and to define those factors that most affect water quality in different parts of the Nation. The linkage of water quality to environmental processes is of fundamental importance to water-resource managers, planners, and policy makers. It provides a strong and unbiased basis for better decisionmaking by those responsible for making decisions that affect our water resources, including the United States Congress, Federal, State, and local agencies, environmental groups, and industry. Information from the NAWQA Program also will be useful for guiding research, monitoring, and regulatory activities in cost effective ways.


The NAWQA Program's unique design provides consistent and comparable information on water resources in 60 important river basins and aquifers across the Nation. Together, these areas account for 60 to 70 percent of the Nation's water use and population served by public water supplies and cover about one-half of the land area of the Nation. Investigations of these 60 areas, referred to as "study units," are the principal building blocks of the NAWQA Program.

The similar design of each investigation and use of standard methods make comparisons among the study unit's results possible. Regional and national assessments can be made. These regional and national assessments, referred to as "National Synthesis," focus on priority national issues, including non-point source pollution, sedimentation, and acidification. Each issue is unique and manifests itself differently among the Nation's diverse geographic, geologic, hydrologic, and climatic settings. The challenge and goal for NAWQA is, therefore to identify the common environmental characteristics associated with the occurrence of key water-quality constituents and to explain their differences throughout the Nation.


In 1991, NAWQA began the transition from a pilot program to a full-scale program with the start of 20 study-unit investigations, along with synthesis activities on a national scale. In October, 1993 an additional 20 study-unit investigations started. When fully implemented in 1997, the program will include hydrologic investigations of 60 study areas that are distributed throughout the Nation. Timetable
To make the program cost effective and manageable, intensive assessment activities in each of the study units are being conducted on a rotational rather than a continuous basis, with one-third of the study units being studied intensively at any given time For each study unit, 3- to 5-year periods of intensive data collection and analysis will be alternated with 5- to 6-year periods of less intensive study and monitoring.

(NAWQA map) Locations of the 60 NAWQA study units and their proposed implementation dates (25K GIF)

Coinciding with the study-unit investigations are the national synthesis assessments. The large geographic extent and large variability in environmental factors throughout the Nation, and limited resources make it necessary to focus on a limited set of high priority water-quality issues. Generally, two to four national synthesis topics will be studied at a given time. Two issues of national priority--the occurrence of nutrients and pesticides in rivers and ground water--were selected as the first issues investigated by national synthesis. These topics were ranked among the highest in importance because of widespread environmental and public health concerns and because information necessary for a national assessment of these contaminants was incomplete.

The next topic for national synthesis is the occurrence and distribution of volatile organic compounds (VOCs). Many VOCs are toxic and are a major focus of a number of Federal regulations related to water quality. Major work elements planned for the study of VOCs in 1994 and 1995 are to (1) identify regulated and non-regulated VOCs; (2) determine the amounts of VOCs released to water, land, and air, and (3) evaluate strategies to characterize the use and releases of VOCs to the environment, including ground water.

The first two years of both study-unit investigations and national synthesis studies involve compilation and analysis of existing information. In addition to USGS data, information and methods developed by other Federal agencies, as well as by State and local agencies, universities, and volunteer organizations are reviewed and integrated as appropriate. This preliminary information on water-quality conditions, trends, and functions forms the basis of a three-year period of intensive data collection and analysis to fill identified gaps in subsequent years.

Perennial data collection and sequential assessments in the study units and regional and national synthesis are key attributes of the program, not only to define changes and trends, but also to build an evolving understanding of water quality in each of the study units and across the Nation. This understanding will be achieved through careful analysis and interpretation of long-term data sets on the physical, chemical, and biological characteristics of the water resource. The data sets will be related to carefully compiled information on hydrology and geology and changes in land-use activities and management practices. The long-term commitment of the NAWQA Program to water-quality monitoring at local, regional, and national scales is designed to answer critical questions about the status and trends in the quality of our Nation's water.


The NAWQA Program is producing many useful findings about our local, regional, and national water resources.

Highlights of NAWQA Study Unit Findings

Selected early results from the National Synthesis on Pesticides and Nitrates include the following:

Results from the NAWQA Program are being released to the public through a variety of publications as elements of the studies are completed.


Communication and coordination between U.S. Geological Survey personnel and other interested scientists and water-management organizations are critical components of the NAWQA program. Early in the program, the National Academy of Sciences reviewed the proposed activities and issued a report supporting the program. Since 1991, the NAWQA Advisory Council, a panel of Federal scientists, has met to ensure use of the best and most current scientific methods and to ensure national relevance of the program's findings. In 1993, representatives from National, State, and regional organizations; Native American groups; professional and technical societies; public interest groups; private industry; and the academic community were invited to join the Council. At the study-unit level, each investigation now underway has a local liaison committee consisting of representatives with water-resources responsibilities or interests from Federal, State, and local agencies, universities, and the private sector. Specific activities of each liaison committee include (1) the exchange of information about water-quality issues of regional and local interest, (2) the identification of sources of data and information, (3) assistance in the design and scope of project products, and (4) the review of project planning documents and reports.

For further information about this report, contact the National Water-Quality Assessment Program office.

U.S. Department of the Interior, U.S. Geological Survey
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