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Publication Date
January 2004
Abstract
CONTENTS PREFACE...................................................................................xi EXECUTIVE SUMMARY...............................................................xiii 1.0 INTRODUCTION...........................................................................1 1.1 Purpose and Approach............................................................2 1.2 Concepts and Definitions of Sustainable Yield.................................3 2.0 SETTING.....................................................................................4 2.1 Study Area...........................................................................4 2.2 Previous Aquifer Studies..........................................................4 2.3 Geology..............................................................................6 2.4 Hydrogeology.......................................................................7 2.4.1 Aquifer Boundaries..............................................7 2.4.2 Recharge...........................................................8 2.4.2.1 Surface Recharge........................................8 2.4.2.2 Subsurface Recharge....................................8 2.4.3 Discharge..........................................................9 2.4.3.1 Spring Flow...............................................9 2.4.3.2 Pumpage.................................................10 2.4.4 Groundwater Storage and Flow...............................11 2.4.5 1950's Drought..................................................12 2.4.6 Trinity Aquifer...................................................12 3.0 NUMERICAL GROUNDWATER MODELING.....................................13 3.1 Purpose and Approach of Modeling.............................................13 3.2 Previous Work: 2001 GAM......................................................14 3.2.1 2001 GAM Simulations.................................................16 3.3 Transient-Model Recalibration..................................................16 3.3.1 Water Levels..............................................................17 3.3.2 Spring flow................................................................18 3.3.3 Sensitivity Analyses......................................................19 3.4 Predictions..........................................................................19 3.4.1 Pumping...................................................................19 3.4.2 Impacts to Spring Flow and Water Levels............................20 3.5 Qualifications and Data Needs................................................21 3.6 Major Findings.....................................................................24 4.0 IMPACTS TO WATER LEVELS AND WATER-SUPPLY WELLS FROM 1950'S DROUGHT CONDITIONS AND PUMPING...............................25 4.1 Methods.............................................................................25 4.1.1 Data Sets..................................................................26 4.1.1.1 Structure-Contour Maps........................................26 4.1.1.2 Potentiometric Maps............................................27 4.1.1.3 Simulated Drawdown..........................................28 4.1.1.4 Well Data.........................................................28 4.1.2 Saturated Aquifer Thickness Analysis.................................29 4.1.3 Saturated Borehole Thickness Analysis...............................30 4.2 Results..............................................................................31 4.3 Discussion..........................................................................32 4.4 Major Findings.....................................................................35 5.0 CONCLUSIONS...........................................................................36 5.1 Acknowledgments.................................................................36 6.0 REFERENCES.............................................................................38 7.0 GLOSSARY OF HYDROGEOLOGIC TERMS......................................44 TABLES 3-1. Comparison of measured and simulated water-level values and residuals from the 2001 GAM and recalibrated model 3-2. Comparison of hydraulic conductivity for the 2001 GAM and recalibrated GAM 4-1. Composite potentiometric data 4-2. Simulated drawdown in wells under 1950's drought conditions and various pumping scenarios 4-3. Saturated aquifer thickness analysis under 1950's drought conditions and various rates of pumping 4-4. Saturated borehole analysis under 1950's drought conditions and various rates of pumping 4-5. Total impact to wells under 1950's drought conditions and various rates of pumping FIGURES 2-1. Location map of study area 2-2. Cross section of Barton Springs and Trinity Aquifers in Hays County 2-3. Histogram of permitted and actual pumping 3-1. Hydrograph of simulated and measured spring flow from 1950's drought 3-2. Map of zonal distribution of hydraulic conductivity in the recalibrated GAM 3-3. Scatter plot of simulated results from 2001 GAM and recalibrated GAM plotted against measured low-flow 1950's water levels 3-4. Comparison of simulated and measured water-level elevation hydrographs of the study area 3-5. Scatter plot of spring-flow simulations from the 2001 GAM and recalibrated GAM and mean of measured spring-flow values for all flow conditions and low-flow conditions 3-6. Sensitivity of transient simulated spring discharge to recharge, specific yield, and specific storage 3-7. Sensitivity of transient calibration water levels to specific storage 3-8. Sensitivity of transient calibration water levels to specific yield 3-9. Sensitivity of transient calibration water levels to recharge 3-10. Hydrograph of simulated spring flow under 1950's drought conditions and 0.66, 10, and 15 cfs pumping rates 3-11. Simulated potentiometric surface contour map under average conditions and 19 cfs of pumping and drought conditions with 19 cfs pumping 4-1. Structure contour of the elevation of the bottom of the Edwards Aquifer 4-2. Isopach map of the Edwards Aquifer 4-3. Potentiometric map of the Edwards Aquifer under 1950's drought conditions 4-4. Simulated drawdown from pumping 10 cfs at the end of the 10-yr simulation 4-5. Potentiometric map of 1950's drought conditions and 10 cfs pumping 4-6. Histogram of specific-capacity values from the unconfined portion of the Edwards Aquifer and distribution and classed values of specific-capacity data 4-7. Saturated-thickness contour map of the Edwards Aquifer under 1950's drought conditions with minimal pumping 4-8. Composite of 100-ft saturated aquifer thickness contour lines under 1950's drought conditions with 0.66, 5, 10, 15, and 19 cfs of pumping 4-9. Chart summarizing number of wells impacted under 1950's drought conditions and various pumping rates APPENDICES A. Groundwater Availability of the Barton Springs Segment of the Edwards Aquifer, Texas: Numerical Simulations through 2050 B. Sensitivity Analysis of Southern Groundwater Divide C. List of participants and affiliations at sustainable yield meetings at the BSEACD: September 10, 2003 and March 24, 2004. Open Access - Permission by Publisher See Extended description for more information.
Keywords
Barton Springs (Austin, Texas, United States), United States, Geology
Type
Text
Language
English
Publisher
Barton Springs / Edwards Aquifer Conservation District
Identifier
K26-01374
Recommended Citation
Hunt, Brian B. and Smith, Brian A., "Evaluation of sustainable yield of the Barton Springs segment of the Edwards Aquifer, Hays and Travis counties, central Texas" (2004). KIP Data Sets and Technical Reports. 73.
https://digitalcommons.usf.edu/kip_data/73
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