Digital map of the saturated thickness of the High Plains Aquifer, 1996-97

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

This digital data set consists of saturated thickness contours for the High
Plains aquifer in Central United States, 1996-97. 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 data set was based on 10,085 water-level measurements, 49 stream
elevations, (March 1997) and 10,036 water-level elevations from wells (1,370
from 1996 and 8,666 from 1997) and the base of aquifer value for each
measurement location. The saturated thickness at each measurement location was
determined by subtracting the water-level elevation from the base of aquifer at
that location.

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 saturated thickness contours for the High Plains aquifer in Central
United States, 1996-97 (modified from Weeks and Gutentag, 1981; Cederstrand and
Becker, 1999). 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 standard that applies
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.