Three-Dimensional Hydrogeologic Characterization of Fractured Carbonate Aquifers
Using Ground-Penetrating Radar

Georgios P. Tsoflias and John M. Sharp, Jr.
Department of Geological Sciences, The University of Texas at Austin,
Austin, TX 78712

For presentation at the 48th Annual Convention of the GCAGS in Corpus Christi, 10/98

ABSTRACT

    Three-dimensional characterization of subsurface hydrogeologic properties
is critical for understanding groundwater flow and has implications in water
resources development, and engineering / environmental studies. Major
cities rely on fractured anisotropic carbonate aquifers, such as the Edwards
aquifer in Texas. In order to predict flow in these aquifers, fracture
network and rock matrix hydraulic properties must be characterized accurately.
    Overlapping ground-penetrating radar surveys (one high-resolution
three-dimensional data volume, and four two-dimensional lines) were
collected over a fractured Silurian dolomite aquifer in Door County,
Wisconsin. 100 MHz and 200 MHz center frequency surveys provided a depth of
investigation of 20 and 12 meters, respectively, and vertical resolution in
the order of decimeters. The data successfully imaged varying carbonate
lithofacies, lithologic discontinuities, bedforms, and fractures in both the
unsaturated and saturated sections of the aquifer. Prominent flow conduits
had been identified previously by a dense network of monitoring wells, pump
tests and tracer tests. These conduits were clearly identifiable in the
ground-penetrating radar data volumes and delineated in three-dimensions by
distinct continuous reflections.

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