California Water Science Center

What is NAWQA?

In 1991, the U.S. Geological Survey began a full-scale National Water-Quality Assessment (NAWQA) Program , to address the need for consistent and scientifically sound information for managing the Nation's water resources. This program is unique compared to other national water-quality assessment studies in that it integrates the monitoring of the quality of surface- and ground-waters with the study of aquatic ecosystems.

The goals of the NAWQA Program are to:
  1. Describe current water-quality conditions for a large part of the Nation's freshwater streams and aquifers (water-bearing sediments and rocks),
  2. Describe how water quality is changing over time, and
  3. Improve our understanding of the primary natural and human factors affecting water quality.

A major design feature of the NAWQA Program is the integration of water-quality information at a wide range of spatial scales, both within and among study units. Each assessment adheres to a nationally consistent study design which allows comparisons among river basins and comprehensive national evaluations.

National Synthesis Projects include:
Cycle I (1994 - 2004)

Assessing the quality of water in every location of the Nation would not be practical; therefore, NAWQA studies were conducted within areas called study units. These study units are composed of 59 major river and aquifer systems that represent the environmental diversity of the Nation (Map). The study units were divided into three groups, which were intensively studied on a rotational schedule. The first cycle of assessment for each group of study units consisted of 2 years of initial planning and retrospective analysis of existing data, 3 years of intensive data collection and analysis, and 6 years of report preparation and low-level assessment activity before the second cycle of intensive data collection and analysis begins.

In Cycle I, NAWQA focused primarily on the first goal of describing water-quality conditions. This was carried out with the Retrospective Analysis - a review and analysis of existing water-quality data, and the Occurrence and Distribution Assessment - intensive data collection to establish existing water-quality conditions of streams and major aquifers. Synoptic Studies of sources, transport, fate, and effect were limited in scope and emphasis during Cycle I.

A national summary of pesticides and nutrients can be found in Circular 1225 and Fact Sheet 116-99.

Cycle II (2004 - 2014)

In 2001, NAWQA began its second decade of intensive water-quality assessment on 42 of the Nation's most important river-basin and aquifer systems. The original 59 Cycle I study units were reduced to 42, either by elimination or combination, to accommodate budget reductions. In aggregate the 42 study units still account for more than 60 percent of the Nation's water use.

The three goals upon which the Program was initiated remain the foundation of the national assessment. Less emphasis will be placed on status assessment because of the substantial advances made in assessing the water-quality conditions during the first decade of investigations. However, the New Status Assessment will focus on sampling geographic gaps and analyzing for selected new constituents not studied in Cycle I.

More emphasis will be placed on describing long-term trends, and understanding human and natural factors that control water quality. Long-term trends will be studied by resampling stream and well sites established in Cycle I. These sites will be part of the Trend Networks for Streams and Ground Water. Reservoirs will be sampled for sediment cores as part of the Trend Network for Contaminants in Sediment. These cores provide a record of the depositional history because they contain sediment from past decades to present. Spatial Studies of Effects of Land-Use Change on Water Quality will address long-term trends by using spatial variability in land use to evaluate temporal changes. In addition, these studies will look more directly at effects of urbanization and a gricultural management practices on water quality. Factors that control water quality will be addressed with Topical Studies that not only focus on sources, transport processes, and effects, but will also address implications for water-quality management and the possibility of extrapolating to other unmonitored areas.

More information can be found in Fact Sheet 071-01 and Water Resources Impact (July 2002).

Document Accessibility: Part or all of these reports are presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view. Download the latest version of Adobe Reader, free of charge

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Page Last Modified: Thursday, 02-Jan-2014 17:16:39 EST