DIGITAL DATA SETS THAT DESCRIBE AQUIFER CHARACTERISTICS OF THE HIGH PLAINS AQUIFER IN WESTERN OKLAHOMA

By Carol J. Becker, Donna Runkle, and Alan Rea

U.S. Geological Survey Open-File Report 96-451

Prepared in cooperation with the
State of Oklahoma, Office of the Secretary of Environment

Oklahoma City, Oklahoma
1997

TABLE OF CONTENTS

INTRODUCTION

This diskette contains digitized aquifer boundaries and maps of hydraulic conductivity, recharge, and ground-water level elevation contours for the High Plains aquifer in western Oklahoma. This area encompasses the panhandle counties of Cimarron, Texas, and Beaver, and the western counties of Harper, Ellis, Woodward, Dewey, and Roger Mills. The High Plains aquifer underlies approximately 7,000 square miles of Oklahoma and is used extensively for irrigation. The High Plains aquifer is a water-table aquifer and consists predominately of the Tertiary-age Ogallala Formation and overlying Quaternary-age alluvial and terrace deposits. In some areas the aquifer is absent and the underlying Triassic, Jurassic, or Cretaceous-age rocks are exposed at the surface. These rocks are hydraulically connected with the aquifer in some areas (Havens and Christenson, 1984).

The High Plains aquifer is composed of interbedded sand, siltstone, clay, gravel, thin limestones, and caliche. The proportion of various lithological materials changes rapidly from place to place, but poorly sorted sand and gravel predominate. The rocks are poorly to moderately well cemented by calcium carbonate (Havens and Christenson, 1984).

The hydraulic conductivity, recharge, and aquifer boundaries were constructed by extracting lines from published digital surficial geology data sets (Cederstrand 1996a, 1996b, 1996c, 1996d, 1996e) based on a scale of 1:125,000 for the panhandle counties and 1:250,000 for the western counties. Some of the lines were digitized from boundaries in the U.S. Geological Survey publication, "Altitude and configuration of the 1980 water table in the High Plains regional aquifer, northwestern Oklahoma," by Havens (1982) and were used by Havens and Christenson (1984) in a ground-water flow model in the U.S. Geological Survey publication, "Numerical simulation of the High Plains regional aquifer, northwestern Oklahoma." The hydraulic conductivity and recharge information are from pages 17 and 18 of the report by Havens and Christenson (1984). The water-level elevation contours are from sheets 1 and 2 of the report by Havens (1982).

Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. The hydraulic conductivity and recharge are closely interrelated. As long as these two model inputs are in balance the model has a small mean residual; it represents the natural system numerically. If the hydraulic conductivity is accurately known, the model can be used to accurately determine recharge. Likewise, if the hydraulic conductivity is poorly known, then the recharge will be poorly determined. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

In most aquifers, hydraulic conductivity measurements made in wells or in cores will range over several orders of magnitude, even over short horizontal and vertical distances. Hydraulic conductivity values derived from ground-water flow models represent areal generalizations and do not reflect the large local variance in well or core measurements. Recharge probably varies considerably over the local area, and model recharge is at best an average over an area at least as large as the model grid (and probably much larger than a single cell).

Compilation of the data sets was funded under a cooperative Joint Funding Agreement between the U.S. Geological Survey and the State of Oklahoma, Office of the Secretary of Environment.

PURPOSE

These data sets were created for a project to develop data sets to support ground-water vulnerability analysis. The objective was to create and document digital geospatial data sets from published reports or maps, or existing digital geospatial data sets that could be used in ground-water vulnerability analysis.

FILE FORMATS

The data sets provided in this report are available in nonproprietary and ARC/INFO export file formats. (See NOTES section.) Files, except those with ".GIF" or ".GZ" extensions, are ASCII format files.

The data sets stored in the generic, public-domain Digital Line Graph (DLG-3) Version 3, Optional format have file extensions of ".DLG". Designed for data interchange, the DLG-3 format allows the simple creation of a vector polygon or line data structure. The topological linkages are explicitly encoded for node, area, and line elements. The files are composed of 8-bit ASCII characters organized into fixed logical records of 80 bytes. A detailed description of the DLG-3 Optional format may be found in the data users guide 3, Digital Line Graphs from 1:2,000,000-scale maps (U.S. Geological Survey, 1990).

The ARC/INFO export files are ASCII files that utilize a proprietary format. The "NONE" compression option was used with the ARC/INFO EXPORT command. The ARC/INFO export files have file extensions of ".E00".

The data set files have ".GZ" extensions and were compressed for distribution. These files need to be uncompressed to access the digital data. The GUNZIP utility is an MS-DOS executable program that will uncompress the data files. To uncompress a file, type at the MS-DOS prompt:

GUNZIP -aN AQBOUND.GZ

This command will uncompress the file and restore its original name. For example: "AQBOUND.DLG" or "AQBOUND.E00" .

A documentation file (known as metadata) is provided for each data set. The documentation files comply with the Federal Geographic Data Committee (FGDC) Content Standards for Digital Geospatial Metadata (Federal Geographic Data Committee, 1994). The FGDC-compliant metadata files contain detailed descriptions of the data sets, and include narrative sections that describe the procedures used to produce the data sets in digital form.

A graphic image also is provided in a Graphics Interchange Format (GIF) file. GIF files are easily displayed on a variety of computer systems that use readily available display software including Internet browser software. This image provides a simplified view of the data sets, and may be used for browsing purposes. The GIF file portrays significantly less spatial resolution and information content than the actual data sets.

No software is provided with these data sets. Users will need GIS software to use the data sets. The U.S. Geological Survey does not recommend or endorse any particular software package for use with these data sets. For some links to more information on GIS software and capabilities, see:  The GIS FAQ (Frequently Asked Questions), GIS Companies on the WWW, USGS GIS Information.

DATA ORGANIZATION

A_NOTICE.TXT

Liability disclaimer

BROWSE.GIF

Browse image of the data sets in Graphics Interchange Format (GIF)

AQBOUND

Complete documentation of the data sources and procedures used to create the aquifer boundary data set and links for retrieval of the data set.

COND

Complete documentation of the data sources and procedures used to create the hydraulic conductivity data set and links for retrieval of the data set.

RECHARG

Complete documentation of the data sources and procedures used to create the recharge data set and links for retrieval of the data set.

WLELEV

Complete documentation of the data sources and procedures used to create the ground-water level elevation contour data set and links for retrieval of the data set.

GEOMETRIC REGISTRATION

The Albers Equal Area map projection (Snyder, 1987) was chosen for the data sets. This projection is appropriate for maps of the conterminous United States because of the visual presentation and equal-area characteristics, which facilitates areal analysis. The projection is cast on the North American Datum of 1983. This projection slightly distorts shapes and distances (scale) in order to maintain equal-area properties. Scale is true along the standard parallels, which are to the north and south of Oklahoma. Scale distortion in Oklahoma reaches a maximum of slightly less than one percent at the northern border of the state. The following table provides map projection information.

Albers Equal Area projection parameters
[GRS1980, Geodetic Reference System 1980; NAD83, North American Datum 1983]

Projection parameters:
Spheroid	GRS1980
Datum	NAD83
First standard parallel	29 30 00 North
Second standard parallel	45 30 00 North
Central meridian	96 00 00 West
Latitude of projection origin	23 00 00 North
Coordinate system parameters:
False easting	0
False northing	0
Planimetric units of measure	meters

NOTES

Use of trade names is for descriptive purposes only, and does not imply endorsement by the U.S. Government.

ARC/INFO software was used in the development of the data sets. The data sets were processed using the ARC/INFO Revision 7.0.3 software package, running on a Data General AViiON workstation. Further processing was done using ARC/INFO Revisions 7.0.4 and 7.1.1 on a SUN Enterpise 4000 running Solaris Version 2.5.1. File names in this document are enclosed in quotation marks and type set in upper case.

REFERENCES CITED

Cederstrand, J.R., 1996a, Digital geologic map of Beaver County, Oklahoma: U.S. Geological Survey Open-File Report 96-371, based on a scale of 1:125,000, 1 diskette. (Available in nonproprietary and ARC/INFO formats.)