The Edwards Aquifer Authority relies heavily on groundwater flow models to characterize groundwater flow conditions in the San Antonio segment of the Edwards Aquifer and to serve as the basis for predicting impacts of water-resource management scenarios. Currently, the Edwards Aquifer Authority uses a MODFLOW finite-difference model developed in 2004 by the U.S. Geological Survey to perform these water-resource management analyses. There are recognized limitations and shortcomings in the 2004 MODFLOW model, including questions about the conceptual model on which the numerical model is based.
The Edwards Aquifer Authority undertook two initiatives to reduce uncertainty in models used to perform water-resource management analyses. One initiative was undertaken to advance the 2004 MODFLOW model through a series of recalibration exercises. The second initiative was to develop a second groundwater-flow model that is conceptually independent of the 2004 MODFLOW model. The objective of a second model is not to replace the 2004 MODFLOW model; but to provide an independent numerical tool against which to compare the 2004 MODFLOW model predictions. This report documents the development of the alternative numerical groundwater model of the Edwards Aquifer for the Edwards Aquifer Authority.