Groundwater Modeling of the Barton Springs
          Segment of the Edwards Aquifer, Texas             

Bridget Scanlon
Bureau of Economic Geology

Brian Smith
Barton Springs Edwards Aquifer Conservation District

ABSTRACT
A two-dimensional, numerical groundwater-flow model was developed for the Barton Springs segment of the Edwards aquifer to evaluate groundwater availability and predict water levels and spring flow in response to increased pumpage and droughts during the period 2001 through 2050. A steady-state model was developed on the basis of average recharge for a 20-yr period (1979 through 1998) and pumpage values for 1989. Transient simulations were conducted using monthly recharge and pumping data for a 10-yr period (1989 through 1998) that includes periods of low and high water levels. Values of hydraulic conductivity were estimated by calibrating the steady-state model using trial and error and automated inverse methods. Good agreement was found between measured and simulated flow at Barton Springs, potentiometric surfaces at different times, and time series of water levels in many of the monitoring wells. To assess the impact of future pumpage and potential future droughts on groundwater availability, transient simulations were conducted using extrapolated pumpage for 10-yr periods (2001 through 2050) and average recharge for a 3-yr period and recharge from the 1950's drought for the remaining 7 yr. Results of these simulations were compared with those using average recharge and future pumpage. Predicted water-level declines in response to future pumpage under average recharge conditions are small (£35 ft), whereas water-level declines under future drought conditions were much greater (£270 ft). Simulated spring discharge in response to future pumpage under average recharge decreased proportionally to future pumpage (2 cfs per decade), whereas spring discharge decreased to 0 cfs in response to future pumpage under drought-of-record conditions. Management of water resources under potential future drought conditions should consider enhanced recharge and conservation measures.

Scanlon, B. R., R. E. Mace, M. E. Barrett, and B. Smith. 2002. Can we simulate regional groundwater flow in a karst system using equivalent porous media models? Case study, Barton Springs Edwards Aquifer, USA. J. Hydrol. 276:137-158. [PDF]

Dr. Bridget Scanlon is a Senior Research Scientist at the Bureau of Economic Geology. She received her Ph.D. from the University of Kentucky in Lexington. Her research focused on karst hydrology in the Inner Bluegrass of Kentucky. She has worked at the Bureau of Economic Geology since 1987. Her research is mostly related to unsaturated zone hydrology and includes application of physical, chemical, and modeling studies for estimating recharge and contaminant transport.

Dr. Brian Smith is the Assessment Program Manager at the Barton Springs Edwards Aquifer Conservation District. He received his Ph.D. from the University of Texas at Austin. His work focuses on modeling and monitoring of groundwater flow in the Barton Springs aquifer.