ARIZONA DEPARTMENT OF WATER RESOURCES REGIONAL GROUNDWATER FLOW MODEL OF THE TUCSON ACTIVE MANAGEMENT AREA, ARIZONA MODEL UPDATE AND CALIBRATION MODELING REPORT NO. 24 BY DALE MASON AND WESLEY HIPKE HYDROLOGY DIVISION PHOENIX, ARIZONA April, 2013 Table of Contents ABSTRACT ............................................................................................................................ V 1.0 INTRODUCTION......................................................................................................... 1 1.1 OBJECTIVE AND SCOPE ................................................................................................. 1 1.2 PROJECT SETTING ......................................................................................................... 1 1.3 PREVIOUS INVESTIGATIONS .......................................................................................... 3 1.4 ACKNOWLEDGEMENTS ................................................................................................. 3 2.0 REGIONAL GROUNDWATER FLOW SYSTEM .................................................. 4 2.1 HYDROGEOLOGIC FRAMEWORK........................................................................................ 6 2.1.1 Revised Basin Statigraphy ......................................................................................... 6 2.2 REGIONAL AQUIFER SYSTEM .......................................................................................... 10 2.3 GROUNDWATER BUDGET ................................................................................................ 11 2.3.1 Pre-development Water Budget .............................................................................. 11 2.3.2 Post-development Water Budget ............................................................................. 13 2.4 ESTIMATES OF GROUNDWATER IN STORAGE .................................................................. 21 3.0 SIMULATION OF GROUNDWATER FLOW ....................................................... 22 3.1 MODEL DESIGN .............................................................................................................. 22 3.1.1 MODFLOW Packages............................................................................................. 24 3.1.2 Model Boundaries ................................................................................................... 25 3.1.3 Model Layers ........................................................................................................... 27 3.1.4 Aquifer Parameters ................................................................................................. 28 3.2 SIMULATED INFLOWS AND OUTFLOWS ........................................................................... 30 3.2.1 Stream Flow Recharge ............................................................................................ 30 3.2.2 Incidental Recharge ................................................................................................ 42 3.2.3 Mountain Front Recharge ....................................................................................... 46 3.2.4 Groundwater Underflow ......................................................................................... 47 3.2.5 Groundwater Withdrawals ...................................................................................... 51 3.2.6 Evapotranspiration.................................................................................................. 52 4.0 MODEL CALIBRATION .......................................................................................... 55 4.1 CALIBRATION CRITERIA AND MODEL ERROR ................................................................. 55 4.2 CALIBRATION TARGETS .................................................................................................. 57 4.3 STEADY-STATE CALIBRATION ........................................................................................ 58 4.3.1 Steady-State Results ................................................................................................ 58 4.4 TRANSIENT CALIBRATION .............................................................................................. 64 4.4.1 Transient Calibration Results ................................................................................. 67 5.0 MODEL SUMMARY AND RECOMMENDATIONS............................................ 85 SELECTED REFERENCES ............................................................................................... 88 i Regional Groundwater Flow Model of the Tucson AMA List of Figures Figure 1. Tucson AMA model study area. ............................................................................... 2 Figure 2. Geopolitical boundaries within the Tucson AMA. ................................................... 5 Figure 3. Pre-development groundwater flow system, boundary conditions, and total saturated thickness map of the regional aquifer, Tucson model area. ............................... 7 Figure 4. Depth to bedrock map, Tucson model area. ............................................................. 9 Figure 5. Water level elevation in the fall of 2010, Tucson model area. ............................... 15 Figure 6. Stream gage locations, stream recharge segments, wastewater treatment plants, and precipitation stations, Tucson model area. 6A, AMA area; 6B inset area. ..................... 16 Figure 7. Underground Storage Facilities and Groundwater Storage Facilities recharge locations, Tucson model area. ......................................................................................... 20 Figure 8. Hydrograph of northern Avra Valley boundary well, Tucson Model area. ........... 21 Figure 9. Water storage calculation areas, Tucson model area. ............................................. 23 Figure 10. Extent of model layers, Tucson model area ......................................................... 29 Figure 11. Active extent and thickness of model layer 1, Tucson model area. ..................... 31 Figure 12. Active extent and thickness of model layer 2, Tucson model area. ..................... 32 Figure 13. Active extent and thickness of model layer 3, Tucson model area. ..................... 33 Figure 14. Hydraulic conductivity distribution of model layer 1, Tucson model area. ......... 35 Figure 15. Hydraulic conductivity distribution of model layer 2, Tucson model area. ......... 36 Figure 16. Hydraulic conductivity distribution of model layer 3, Tucson model area. ......... 37 Figure 17. Incidental recharge locations, Tucson model area. .............................................. 43 Figure 18. Annual effluent releases into the Santa Cruz River: 1950-2010. ......................... 45 Figure 19. CAP surface water deliveries to the Tucson AMA: 1990-2010. .......................... 46 Figure 20. Effluent recharge at USFs in the Tucson Model Area. ........................................ 47 Figure 21. Underflow, ET, and Natural Recharge Locations in the Tucson Model Area. .... 50 Figure 22. Estimated withdrawals in the Upper Santa Cruz and Avra Valley sub-basins. .... 52 Figure 23. Steady-State Pumping Distribution - Tucson Model Area ................................... 53 Figure 24. Pumping Distribution - 2010 in the Tucson Model area. ..................................... 54 Figure 25. 1940 Measured vs. Simulated Water Level Contours. ......................................... 60 Figure 26. Distribution of Simulated 1940 Head Residuals - Tucson Model. ....................... 61 Figure 27. 1940 Weighted Observed Heads vs. 1940 Weighted Simulated heads. ............... 63 Figure 28. 1940 Weighted Residuals vs. 1940 Unweighted Observed Heads ....................... 63 Figure 29. Simulated Groundwater withdrawals by Sector, Tucson AMA Model ............... 65 Figure 30. Simulated annual groundwater withdrawals - Tucson AMA Model.................... 66 Figure 31. 2010 Measured vs. Simulated Water Level Contours .......................................... 68 Figure 32. Distribution of simulated 2010 head residuals - Tucson Model. ......................... 70 Figure 33. 2010 Weighted Observed Heads vs. 2010 Weighted Simulated Heads ............... 71 Figure 34. 2010 weighted Residuals vs. 2010 Unweighted Observed Heads. ...................... 72 Figure 35. Maps showing well hydrograph locations, Tucson AMA model ......................... 76 ii Regional Groundwater Flow Model of the Tucson AMA List of Figures (cont.) Figure 36 Comparison of ADWR and USGS model simulated pumpage. ............................ 78 Figure 37. Simulated change in storage: Tucson AMA: 1940-2010. .................................... 82 Figure 38. Simulated change in storage: Avra Valley sub-basin: 1940-2010. ...................... 83 Figure 39. Simulated change in storage: Upper Santa Cruz sub-basin: 1940-2010 .............. 84 List of Tables Table 1. Conceptual steady-state groundwater budget, Tucson model area. ......................... 14 Table 2. USGS Stream Gages in the Tucson Model Area. .................................................... 18 Table 3. Estimated groundwater in storage, Tucson model area. .......................................... 22 Table 4. General Tucson model design components. ............................................................ 26 Table 5. Underground Storage Facilities in (USFs) the Tucson Model Study Area. ............ 48 Table 6. Groundwater Saving Facilities (GFSs) in the Tucson Model Study Area. .............. 48 Table 7. Mountain