To address these needs, the Congress appropriated funds in 1991 for the USGS to begin the National Water-Quality Assessment (NAWQA) Program. The NAWQA Program builds upon an existing base of water-quality studies of the USGS, as well as those of other Federal, State, and local agencies. The objectives of the NAWQA Program are to:

Describe current water-quality conditions for a large part
    of the Nation's freshwater streams, rivers, and aquifers.
Describe how water quality is changing over time.
Improve understanding of the primary natural and human factors
    that affect water-quality conditions.

Assessing the quality of water in every location of the Nation would not be practical; therefore, NAWQA studies are conducted within areas called Study Units. These Study Units include more than 50 major river and aquifer systems that cover a diversity of hydrogeologic settings (Map).

National synthesis of data analysis, based on aggregation of comparable information obtained from the Study Units, is a major component of the program. This effort focuses on selected water-quality topics using nationally consistent information. Comparative studies will explain differences and similarities in observed water-quality conditions among study areas and will identify changes and trends and their causes. The first topics addressed by the national synthesis are pesticides, nutrients, volatile organic compounds, and aquatic biology. Discussions on these and other water-quality topics will be published in periodic summaries of the quality of the Nation's ground and surface water as the information becomes available.

The High Plains Regional Ground Water study began in 1998. Study planning and analysis of existing data will be done in the first 2 years of the study. After this 2-year period, ground-water data will be collected intensively for 6 years (high-intensity phase). Sampling will begin in the central High Plains and then progress to the southern High Plains and finally to the northern High Plains (Figure 1). A low-intensity phase will follow. The plan of activities to take place during the low-intensity phase are in the developmental stage. Results from the data collected in the high-intensity phase will help plan the type of activities that need to be conducted to examine long-term trends in the ground-water quality of this area. A series of technical and non-technical reports will describe and summarize results of data collection.