This report includes a digital, three-dimensional (3-D) faulted hydrostratigraphic model we have constructed to represent the geologic framework of the Edwards aquifer system in the area of San Antonio, northern Bexar County, Texas. The model is based on mapped geologic relationships that reflect the complex structures of the Balcones fault zone, detailed lithologic descriptions and interpretations of about 40 principal wells (and qualified data from numerous other wells), and a conceptual model of the gross geometry of the Edwards Group units derived from prior interpretations of depositional environments and paleogeography.

The EarthVision 3-D software included in this publication is provided for use on four platforms: Windows 2000/XP, SGI, SUN, and Linux. Please see the Readme1.txt file for information about starting and using the software on each platform. The 3-D model and viewer software can be downloaded from this Web site, and they are also available on the CD-ROM version of this report, which is available as a sales item from Information Services, U.S. Geological Survey (1-888-ASK-USGS).

Earth Vision software is the intellectual property of Dynamic Graphics, Inc., and is used here with their permission. Other than those rights granted to the USGS and third parties to assist them in using this product (any venue), Dynamic Graphics, Inc., reserves all rights in their software. Any appearances of trade, product, or firm names, or private logos, in or on this product do not, and are not intended to, imply endorsement by the U.S. Government.