<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:creator>Eve L. Kuniansky</dc:creator>
  <dc:date>1990</dc:date>
  <dc:description>&lt;p&gt;The potentiometric surface of the Edwards-Trinity aquifer system and contiguous hydraulically connected units (from December 1974 through February 1975) was mapped as part of the Edwards-Trinity Regional Aquifer-System Analysis (RASA) project. A major goal of the Edwards-Trinity RASA project is to understand and describe the regional flow system (Bush, 1986). The development of a digital ground-water flow model of the aquifer system is a key part of the project. This potentiometric map will be used in the calibration of the ground-water flow model and in understanding ground-water movement in the aquifer system.&lt;/p&gt;
&lt;p&gt;The map depicts the potentiometric surface of the major aquifers of the Edwards-Trinity aquifer system and contiguous units that form a continuous hydraulically connected regional aquifer within the study area in west-central Texas (fig. 1). The potentiometric surface of an aquifer is an imaginary surface defined by contouring locations of equal static head (the altitude to which water will rise in a well). The potentiometric surface map shows the direction of ground-water flow from higher to lower altitude.&lt;/p&gt;
&lt;p&gt;The study area extends beyond the aquifers of the Edwards-Trinity system to hydrologic divides, including the Colorado River and the Rio Grande (fig. 2).&lt;/p&gt;
&lt;p&gt;The data used to compile this map were obtained from the Texas Natural Resources Information System on magnetic tape and from Rees and Buckner (1980). The winter of 1974-75 (December 1974 through February 1975) was selected for mapping for two reasons: (1) More water-level data were available throughout the study area for this winter season than for other winter seasons, and (2) during winter there is almost no loss of ground water as a result of evaporation, irrigation withdrawals, and transpiration.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.3133/wri894208</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>U.S. Geological Survey</dc:publisher>
  <dc:title>Potentiometric surface of the Edwards-Trinity aquifer system and contiguous hydraulically connected units, west-central Texas, winter, 1974-75</dc:title>
  <dc:type>reports</dc:type>
</oai_dc:dc>