The Edwards aquifer of South Texas has a complex and highly heterogeneous flow system. Integration of multiple data sets has the best chance of providing an adequate glimpse of the nature of the heterogeneities and their impact on aquifer performance. Karst has developed in this carbonate aquifer in response to the interaction of structure and gradient. Karst capture, favored by fractures of the Balcones Fault Zone, has diverted surface-water flow from toward the Gulf of Mexico into the subsurface and caused it to flow eastward and discharge at Comal and San Marcos Springs. We mapped large troughs in the potentiometric surface by grouping the large volume of historic-water-level data according to aquifer stage. Cave orientations confirm a history of karst capture at a smaller scale.

We are examining the implications of these karst trends for interpreting natural chemistry and introduced-contaminant distribution, as well as high-frequency water-level records.