Prepared in cooperation with Holloman Air Force Base and the City of Alamogordo Simulation of Ground-Water Flow in the Basin-Fill Aquifer of the Tularosa Basin, South-Central New Mexico, Predevelopment through 2040 Scientific Investigations Report 2004-5197 U.S. Department of the Interior U.S. Geological Survey Simulation of Ground-Water Flow in the Basin-Fill Aquifer of the Tularosa Basin, South-Central New Mexico, Predevelopment through 2040 By G.F. Huff Prepared in cooperation with Holloman Air Force Base and the City of Alamogordo Scientific Investigations Report 2004-5197 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey Charles G. Groat, Director U.S. Geological Survey, Reston, Virginia: 2005 For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225 For more information about the USGS and its products: Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov/ Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. iii Contents Abstract .......................................................................................................................................................... 1 Introduction ................................................................................................................................................... 1 Purpose and Scope ............................................................................................................................. 2 Study Area ............................................................................................................................................ 2 Acknowledgments ............................................................................................................................... 2 Geohydrology ................................................................................................................................................ 2 Geology .................................................................................................................................................. 2 Aquifer Properties ............................................................................................................................... 2 Ground- and Surface-Water Flows ................................................................................................... 4 Water Use ............................................................................................................................................. 7 Ground-Water Quality ......................................................................................................................... 8 Simulation of Ground-Water Flow .............................................................................................................. 8 Model Description ............................................................................................................................... 8 Mathematical Models ................................................................................................................ 8 Model Discretization .................................................................................................................. 8 Boundary Conditions .................................................................................................................. 8 Model Stresses ........................................................................................................................... 8 Mountain-Front Recharge ................................................................................................ 8 Ground-Water Withdrawal ............................................................................................... 9 Return Flow ......................................................................................................................... 9 Evapotranspiration .......................................................................................................... 23 Streams and Interbasin Ground-Water Flow .............................................................. 23 Simulated Hydrologic Properties ........................................................................................... 23 Model Calibration .............................................................................................................................. 23 Steady-State Calibration ......................................................................................................... 23 Transient Calibration ................................................................................................................ 25 Calibration Strategy and Results ............................................................................................ 26 Sensitivity Analysis ................................................................................................................... 29 Model Benchmarking and Potential Effects of Return Flow ...................................................... 29 Model Results ..................................................................................................................................... 30 Simulated Flows ........................................................................................................................ 30 Simulated Water Levels ........................................................................................................... 30 Declines in Simulated Water Levels ...................................................................................... 30 Generalized Simulated Directions of Ground-Water Flow ................................................. 33 Model Limitations .............................................................................................................................. 42 Summary ...................................................................................................................................................... 43 References Cited ........................................................................................................................................ 85 Appendix 1. Computation of Ground-Water-Flow Directions .............................................................. 89 iv Figures 1. Location of the Tularosa geologic basin and study area ...................................................... 3 2. Generalized section across the Tularosa Basin. Line of section shown in figure 1 ........ 5 3–11. Maps showing: 3. Location of subbasins on the margin of the Tularosa hydrologic basin (modified from Waltemeyer, 2001) ............................................................................................. 6 4. Location of ground-water flow-model grid ........................................................................... 18 5. Location of active ground-water flow-model layers ........................................................... 19 6. Location of cells in which recharge is implemented in the ground-water-flow model ........................................................................................................................................... 20 7. Areas of municipal ground-water withdrawals ................................................................... 21 8. Areas of agricultural ground-water withdrawals and agricultural surface-water diversions .................................................................................................................................... 22 9. Location of model cells representing steady-state and transient-model calibration points ....................................................................................................................... 24 10. Water-level contours representing measured 1911-12 water levels and simulated steady-state water levels in the uppermost active model cells ...................... 31 11. Zones of hydrologic properties ............................................................................................... 32 12–13. Graphs showing: 12. Test for nonnormality of steady-state residual errors ......................................................... 33 13. Values of steady-state residual errors, simulated steady-state water levels, and standard deviation and mean value of residual errors ....................................................... 34 14. Distribution of steady-state residual errors .......................................................................... 44 15–17. Graphs showing: 15A. Simulated and measured water levels from 1948 to 1995 at transient-model calibration points ....................................................................................................................... 45 15B. Simulated and measured water levels from 1948 to 1995 at transient-model calibration points ....................................................................................................................... 46 15C. Simulated and measured water levels from 1948 to 1995 at transient-model calibration points. ...................................................................................................................... 47 15D. Simulated