The Work of Mr. Ted A. Small and Its Impact from Current Understanding of the Edwards Aquifer a Complex Karstic System

Allan K. Clark, Amy R. Clark, and George B. Ozuna
USGS, San Antonio, TX

The Edwards Aquifer of south-central Texas is a complex karstic system in which variations in lithologies, stratigraphy, structure, and conduit development have complicated the understanding of recharge and discharge. Mr. Theodore Allan Small had a career of over 50 years looking at the variations in the Edwards aquifer from far west Texas, Big Bend, Amistad Dam, eastward to Austin. Over the years Mr. Small helped refine our understanding of the Edwards aquifer by leading and/or participating in drilling programs, geophysical logging, development of hydrostratigraphic mapping from geophysical logs, mapping of subsurface structures, development of cross-sections of the Edwards Group and mapping the hydrostratigraphic units in the Edwards Aquifer recharge zone.

The initial efforts at refining the understanding to the Edwards aquifer began with a drilling program in the early 70’s in which cores were obtained from wells drilled through the Edwards Group and Edwards equivalent rocks extending from Uvalde County to Comal County. These cores were used to describe the lithologies and porosities of the various formations and members of the Edwards aquifer in the San Antonio Region of the Edwards Aquifer. During this drilling program pump test were carried out as well as hydrophysical surveys to obtain information on the transmissivities of the Edwards Aquifer. This program led to a hydrostratigraphic interpretation of the members of the Edwards aquifer by correlating with Dr. Pete Rose’s stratigraphic interpretation. After a better understanding subsurface hydrostratigraphy was established structural maps of the tops to the members were created as well as cross-sections across the San Antonio Region. Following completion of subsurface and borehole work various projects were conducted to map the surface expression of the various members and faulting.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas