A Parsimonious Model for Simulation of Flow
and Transport in a Karst Aquifer
By Michael E. Barrett, Ph.D, and Randall J. Charbeneau, Ph.D
ABSTRACT
A new type of lumped parameter model was developed to predict the
impacts of urban development on water quality and quantity in the Barton
Springs portion of the Edwards aquifer. The model differs from other
lumped parameter models by allowing vertical variation in model parameters
within cells. The aquifer was divided in five cells corresponding to
the watersheds of the creeks supplying recharge. Each cell was treated
as a completely mixed tank with a single well selected to represent
conditions in that portion of the aquifer. Simulations using historical
data from the period 1979 through 1995 showed that the model could accurately
reproduce measured water levels and average nitrogen concentrations
in the aquifer and at Barton Springs. The impact of urbanization was
simulated by estimating the changes in the hydrology of the creeks supplying
recharge. The modeling results suggest that an intense level of development
will reduce the average spring flow and significantly increase the average
nitrogen concentration in the aquifer.
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View the Whole Report...(3525
KB)
TABLE OF CONTENTS
FRONT MATTER...(25
KB)
Title Page
Acknowledgements
Abstract
Table Of Contents
List Of Tables
List Of Figures
1. INTRODUCTION...(400
KB)
1.1 Objectives
1.2 Significance of Work
1.3 Description of Study Area
2. LITERATURE
REVIEW...(10 KB)
3. HYDRAULIC
MODEL DEVELOPMENT...(922 KB) 3.1 Aquifer Recharge
3.2 Aquifer Discharge
3.3 Model Structure and Calibration
3.4 Sensitivity Analysis
3.5 Numerical Accuracy and Stability
3.6 Model Response to a Pulse Input
4. WATER QUALITY
MODEL...(386 KB)
4.1 Calculation of Input Mass to Aquifer
4.2 Calculation of Mass Output from Aquifer
4.3 Calculation of Mass Transfer Between Cells
4.4 Calculation of Cell Mass Balance
4.5 Transport Model Inputs
4.6 Simulation Results
4.7 Model Response to a Constituent Pulse Input
5. PREDICTING
THE EFFECTS OF URBANIZATION ON THE AQUIFER...(280 KB)
5.1 Model Inputs for Moderate Development Scenario
5.2 Model Inputs for Intense Development Scenario
5.3 Results of Simulation
5.4 Modeling other Constituents
6. CONCLUSIONS
AND RECOMMENDATIONS...(45 KB)
APPENDICES...(725
KB) Appendix A : FORTRAN Source Code and User's Manual
Appendix B : Comparison of Predicted with Observed Water Levels for
Aquifer Cells
Appendix C : Effect of Development on Aquifer Level and Water Quality
BIBLIOGRAPHY...(15
KB)
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