- Abstract:
- This dataset contains the sampling sites and data for the U.S. Geological Survey National
Water-Quality Assessment (NAWQA) Program Study-Unit investigations of Surface Water
Nutrients for the conterminous United States, excluding the High Plains Regional
Ground-Water Study.
- Purpose:
- The National Water-Quality Assessment Program is designed to describe the status and trends in the quality of the Nation's ground- and surface-water resources and to provide a sound understanding of the natural and human factors that affect the quality of these resources (Leahy and others, 1990). A "Study Unit" is a major hydrologic system in which NAWQA studies are focused. Study Units are geographically defined by a combination of ground- and surface-water features (Gilliom and others, 1995).
As part of the NAWQA program, Study-Unit investigations were planned for 60 areas throughout the Nation to provide a framework for national and regional water-quality assessments (Leahy and others, 1990). The 60 planned Study-Units were divided into three groups of 20. Each group would be intensively studied on a rotational basis with 20 studies beginning in fiscal year 1991 (FY 1991 runs from October 1990-September 1991), 20 more studies beginning in fiscal year 1994 (October 1993-September 1994), and the final 20 studies beginning in fiscal year 1997 (October 1996-September 1997). Each study cycle would span 10 years. In 1996, the number of Study-Units was scaled back to 59 when two of the original 60 Study Units combined. Also, because of budgetary restraints, some of the original planned Study Units have been scheduled to start later than originally planned and others have not even been scheduled to start yet.
This coverage contains the boundaries for the 57 Study Units within the conterminous United States, excluding the High Plains Regional Ground Water-Study, which was conceived in late 1997. The coverage also includes the name, starting date, and NAWQA standard abbreviation of each Study Unit plus various codes to help display the data.
This data set is used primarily to display the location of NAWQA Study Units and for analysis of data at the national scale. It is not recommended for either local or regional analysis due to the small scale of most of the features.
- Supplemental_Information:
- Point