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Austin Geological Society
The Barton Springs/Edwards Aquifer Conservation District, in cooperation with the City of Austin, injected non-toxic organic dyes into two caves within the Barton Springs segment of the Edwards aquifer to trace groundwater flow paths and determine groundwater-flow velocities. Antioch and Cripple Crawfish Caves are located about 14.0 and 17.5 miles south, respectively, of Barton Springs, the primary discharge point from the aquifer. Twenty-five pounds of sodium fluorescein were injected into Antioch Cave on August 2, 2002 and arrived at Barton Springs between 7 to 8 days after the injection. Thirty-five pounds of eosine were injected into Cripple Crawfish Cave on August 6, 2002 and arrived at Barton Springs in less than 3.5 days after the injection. Under high spring flow conditions, groundwater-flow velocities from Antioch Cave and Cripple Crawfish Cave to Barton Springs are estimated to be 2.0 and 5.0 miles per day, respectively. Detections of dye at water-supply wells indicate a karst system composed of multiple diverging flow paths from these caves that, while recharging surface water, create mounds in the potentiometric surface. Groundwater flow then re-converges as it flows northeast, before discharging at Barton Springs. Interpreted flow paths generally coincide with troughs in the potentiometric surface in the hydraulically unconfined zone and ridges in the potentiometric surface in the hydraulically confined zone of the aquifer. Most interpreted flow paths are oriented normal to potentiometric surface contours. However, some interpreted flow paths are oriented parallel to potentiometric surface contours, indicating a highly anisotropic flow system. Groundwater flow was traced in wells along paths that are parallel to the N40E (dominant) and N45W (secondary) fault and fracture trends presented on geologic maps. Rapid groundwater flow velocities to springs and detections at wells indicate that conduits are an important component of flow, and the bimodal structural grain has influenced the development of conduits in the Edwards aquifer. Open Access - Permission by Author(s) See Extended description for more information.
Barton Springs (Austin, Texas, United States), Geology
1 online resource
Hunt, Brian B., "Dye tracing recharge features under high-flow conditions, Onion Creek, Barton Springs Segment of the Edwards aquifer, Hays County, Texas" (2005). KIP Data Sets and Technical Reports. 65.