Groundwater Availability of the Barton Springs Segment of the EdwardsAquifer, Texas: Numerical Simulations through 2050


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-year period (1979 through 1998) and pumpage values for 1989. Transient simulations were conducted using monthly recharge and pumping data for a 10-year 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 (root mean square error [RMS error, average of squared differences in measured and simulated discharges] 12 cfs), between measured and simulated water levels at different times, and between measured and simulated 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-year periods (2001 through 2050) and average recharge for a 3-year period and recharge from the 1950s drought for the remaining 7 years. 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 (less than or equal to 35 ft), whereas water-level declines under future drought conditions were much greater (greater than or equal to 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.


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