Digital map of water-level changes in the High Plains Aquifer, 1980 to 1997

This data set was created to document the original map (McGuire, V.L. and
Fischer, B.C., 1999) produced by the High Plains Water-Level Monitoring Project
and to make available the data on this map for use with geographic information
systems.

This data set consists of digital water-level-change contours for the High
Plains aquifer in the central United States, 1980 to 1997. The High Plains
aquifer extends from south of 32 degrees to almost 44 degrees north latitude
and from 96 degrees 30 minutes to 104 degrees west longitude. The aquifer
underlies about 174,000 square miles in parts of Colorado, Kansas, Nebraska,
New Mexico, Oklahoma, South Dakota, Texas, and Wyoming.

This digital data set was created from 5,233 wells measured in both 1980 and
1997. The water-level-change contours were drawn manually on mylar at a scale
of 1:1,000,000. The contours then were converted to a digital map.

Introduction --

The information provided in this introduction is found in U.S. Geological
Survey Professional Paper 1400-B (Gutentag and others, 1984). This data set
consists of digital water-level-change contours for the High Plains aquifer in
the United States, 1980 to 1997. The High Plains aquifer, which underlies about
174,000 square miles in parts of eight states, is the principal water source in
one of the nation's major agricultural areas. In 1980, about 170,000 wells
pumped water from the aquifer to irrigate about 13 million acres.

The High Plains aquifer is a regional water-table aquifer consisting mostly of
near-surface sand-and-gravel deposits. In 1980, the maximum saturated thickness
of the aquifer was about 1,000 feet and averaged about 200 feet. Hydraulic
conductivity and specific yield of the aquifer depend on sediment types, which
vary significantly both horizontally and vertically. Hydraulic conductivity
ranged from less than 25 to greater than 300 feet per day and averaged 60 feet
per day. Specific yields ranged from less than 10 to 30 percent and averaged
about 15 percent.

The High Plains aquifer boundaries were determined by erosional extent of
associated geologic units and by hydraulic and physiographic boundaries where
the High Plains aquifer extends eastward from the Great Plains physiographic
province (Fenneman, 1931). In most of the area, the erosional extent of the
hydraulically connected Tertiary and Quaternary deposits were used as the
aquifer boundary. In eastern Nebraska, streams and physiographic boundaries
were used as the aquifer boundary.

Reviews Applied to Data --

This electronic report was subjected to the same review standards that apply to
all U.S. Geological Survey reports. Reviewers were asked to check the
topological consistency, tolerances, attribute frequencies and statistics,
projection, and geographic extent. Reviewers were given digital data sets for
checking against the source maps to verify the linework and attributes. The
reviewers checked the metadata files for completeness and accuracy.