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.
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.