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

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.