The Edwards Aquifer: A Resource in Conflict

John M. Sharp
Jay L. Banner

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The Edwards aquifer of central Texas is an extensive, karstified flow system developed in rocks deposited on a Cretaceous limestone platform. Development of the aquifer was controlled by changes in sea level, large-scale hydrodynamic and tectonic processes in the Gulf of Mexico, and local climatic and geomorphic processes. The aquifer is a vital water resource and provides a diverse set of habitats, including those for several endangered species that live in its major spring systems. Because of its unique stratigraphic, hydraulic, and hydrochemical properties, the Edwards aquifer is a natural laboratory that is well suited for hydrogeologic studies. Because of numerous economic, social, and political interests in the use of the water and because of the rapid rate of population growth (and urbanization) of its watersheds, the aquifer is also a source of political conflict. Competing interests for its waters have stimulated an ongoing debate over how the aquifer would best be utilized. Historical water-balance analysis demonstrates that major water shortages will develop with the recurrence of historic decadal droughts. Future decisions regarding the aquifer’s use will therefore have significant socioeconomic and environmental ramifications. These decisions should be based upon accurate hydrogeological data. The general nature of how the aquifer functions is understood, but more detailed interpretations are needed. Application of ground-water flow models based on field data and natural geochemical tracers have the potential to reduce uncertainties in the details of how the aquifer functions now and will function in response to potential future developments.