Focusing on the highly developed Edwards aquifer, which supplies water for a large area of south-central Texas, this report presents a three-dimensional model of the porosity distribution in the aquifer, which quantifies the spatial distribution of water resources and provides information that can be used in ground-water flow and transport models. The study provides a detailed assessment of the amount of water in the Edwards aquifer as of 1996 on the basis of a large data set and a reproducible methodology.

This report summarizes results of a study based on outcrop and subsurface data that establishes a regional stratigraphic framework for assessments of the Ogallala and related aquifers. Results are broadly applicable to water resources investigations and efforts to remediate contaminated areas of the aquifer as well as to the understanding of depoisitonal environments, paleoclimate, and soil development during the late Tertiary and Quaternary.