Abstract

Recognition of eight hydrostratigraphic subdivisions of the carbonate rocks composing the Edwards aquifer in the eastern part of the San Antonio, Texas, area has provided a basis for determining the permeability and storage capacity of the aquifer.

The field studies that provided data for subdividing the aquifer included the drilling of eight test holes that were cored through the entire thickness of the aquifer, geophysical logging of the test holes and all available noncored water wells, packer tests, and salt-dilution tests. Samples of the test-hole cores were analyzed in the laboratory to determine porosity, permeability, and mineralogy.

The authors’ concept of the hydrogeologic framework of the aquifer is that of a multilayered unit in which ground-water circulation is mainly through highly permeable hydrostratigraphic subdivisions and hydraulically interconnected fault zones.