EFFECTS OF URBANIZATION ON THE EDWARDS AQUIFER: BARTON SPRINGS SEGMENT

The karstic Edwards Aquifer underlies a rapidly growing, urbanizing region. The management of the aquifer is complicated by environmental, political, and legal issues and, in the past few decades, our conceptual models of the aquifer have changed significantly and partly because of urbanization. As urban sprawl extended over the aquifer’s recharge zone, discharge from Barton Springs has become higher relative to precipitation. Some of this is due to increased recharge from urbanization (leaky water mains, sewers, and storm drains and irrigation return flow) that, in times of drought, are highly significant. Although recharge is primarily from losing streams, leakage from adjacent units, revised estimates of direct recharge, and shifting groundwater divides must also be considered. Dye tracing studies document previously unknown discharge sites and unexpected flow directions. Finally, urban construction has altered the permeability field and epikarst and has rerouted some streams, such as Little Zilker Creek, that formerly recharged and probably still recharge the aquifer. This has creates problems for urban planning as areas contributing to Barton Springs have different criteria than zones that do not. These alterations, coupled with the presence of anthropogenic contaminants, present challenges for the preservation of the springs with their endangered species and for aquifer management.