This report contains digital data sets describing water use, toxic chemical
releases, metropolitan areas, and population density of the conterminous United
States. The data source for the water-use data is from the U.S. Geological
Survey (USGS) (U.S. Geological Survey, 1990, 1998b; Lanfear, 1984). The toxic
chemical release information is from the U.S. Environmental Protection Agency
(1997, 1998), ... and the metropolitan area and population density data sets were
derived from data provided by the U.S. Bureau of the Census (1995) and the
Consortium for International Earth Science Information Network (1995). Because
most of the source materials do not cover Alaska and Hawaii, only the
conterminous 48 states are included in these data sets.
Compilation of the data sets was supported by the National Water-Quality
Assessment (NAWQA) Program of the U.S. Geological Survey. The objectives of the
NAWQA Program are to: (1) describe current water-quality conditions for a large
part of the Nation's freshwater streams, rivers, and aquifers, (2) describe how
water quality is changing over time, and (3) improve the understanding of the
primary natural and anthropogenic factors that affect water-quality conditions.
National analysis of data, based on aggregation of comparable information
obtained from across the United States, is a major component of the NAWQA
Program. The data sets included in this report were created for NAWQA national
data analysis activities.