SIMULATION OF GROUNDWATER CONDITIONS IN THE COLORADO RIVER DELTA, MEXICO by Eden Jael Feirstein1 Francisco Zamora2 Leticia Beatriz Vionnet3 Thomas Maddock III1 May 2008 1Department of Hydrology and Water Resources University of Arizona Tucson, Arizona 85721 2 Sonoran Institute Tucson, AZ 85710 3 Facultad de Ingeniería y Ciencias Hídricas (FICH) - Universidad Nacional del Litoral (UNL) - CC 217 - 3000 Santa Fe, Argentina Table of Contents Table of Contents................................................................................................................ 1 List of Figures..................................................................................................................... 3 List of Tables ...................................................................................................................... 7 Acknowledgements............................................................................................................. 8 Abstract............................................................................................................................... 9 CHAPTER 1: Overview ................................................................................................... 10 1.1 Introduction............................................................................................................. 10 1.2 The Modern CRD ................................................................................................... 12 1.3 Purpose and Goals of Model………………………………………………………12 1.4 Previous Investigation/Models................................................................................ 13 CHAPTER 2: Description of Study Area ......................................................................... 17 2.1 Location and Physiography..................................................................................... 17 2.2 Geology................................................................................................................... 21 2.3 Climate.................................................................................................................... 23 2.3.1 Climate- Temperature ...................................................................................... 23 2.3.2 Climate- Rainfall.............................................................................................. 24 2.4 Vegetation and Wildlife.......................................................................................... 26 2.5 Pre Development..................................................................................................... 27 2.5.1 Pre Development- Natural History .................................................................. 27 2.5.2 Pre Development- Land Use............................................................................ 27 2.6 Post Development Land Use and History............................................................... 28 CHAPTER 3: Hydrogeology and Hydrology................................................................... 31 3.1 Regional Hydrologic Units ..................................................................................... 31 3.1.1 Wedge Zone and Coarse Gravel Zone............................................................. 32 3.1.2 Upper Fine-Grained Zone................................................................................ 33 3.2 Groundwater Hydrology ......................................................................................... 36 3.3 Surface Water.......................................................................................................... 37 3.3.1 Streamflow....................................................................................................... 38 CHAPTER 4: Conceptual Model...................................................................................... 44 4.1 Modeling Method.................................................................................................... 44 4.2 Water-Year Concept ............................................................................................... 45 4.3 Model Domain ............................................................................................................ 45 4.4 Geologic Boundaries............................................................................................... 46 4.5.1 Model Layers- 1............................................................................................... 46 4.5.2 Model Layers- 2............................................................................................... 47 4.6 Precipitation Related Recharge............................................................................... 48 4.7 Net Agricultural Recharge ...................................................................................... 48 4.8 Well Pumping ......................................................................................................... 53 4.9 Riparian Evapotranspiration ................................................................................... 58 4.10 Rivers, Drains, Canals........................................................................................... 60 CHAPTER 5: Numerical Model....................................................................................... 64 1 5.1 Modeling Method.................................................................................................... 64 5.2 Flow Model............................................................................................................. 65 5.3 MODFLOW............................................................................................................ 66 5.4 Spatial and Temporial Discretization............................................................................. 66 5.5 Net Agricultural Recharge ...................................................................................... 68 5.6 Well Pumping ......................................................................................................... 69 5.7 Riparian Evapotranspiration ................................................................................... 69 5.8 Stream-Aquifer Interaction ..................................................................................... 70 5.9 Boundary Conditions .............................................................................................. 72 CHAPTER 6: Calibration and Sensitivity ........................................................................ 76 6.1 Calibration............................................................................................................... 76 6.2 Groundwater Observation Data .............................................................................. 76 6.3 Water Level Measurements .................................................................................... 78 6.4 Initial Condition...................................................................................................... 78 6.5 Transient ................................................................................................................. 83 6.6 Sensitivity Analysis ................................................................................................ 86 6.7 Streambed Conductance.......................................................................................... 87 6.8 Agricultural Recharge............................................................................................. 88 CHAPTER 7: Results and Analysis .................................................................................. 91 7.1 Capture.................................................................................................................... 91 7.2 Drawdown............................................................................................................... 95 7.3 Stream-Aquifer Interaction ..................................................................................... 98 7.4 Stream Stage ......................................................................................................... 103 7.5 Water Budget ........................................................................................................ 104 7.6 Conclusions........................................................................................................... 108 7.4 Closing Comments................................................................................................ 110 Chapter 8: References..................................................................................................... 112 APPENDIX A: Contour Maps of Observation Data ...................................................... 117 APPENDIX B: Capture Calculations ............................................................................. 128 2 List of Figures Figure 1.1, Location map of the United States-Mexico border region. ............................ 10 Figure 2.1, Regional view of the Colorado River delta in the context of the Salton Trough. The Colorado River enters the delta from the northeast and makes up part of the international boundary between the United States and Mexico............................ 18 Figure 2.2, Quickbird satellite image of the Colorado River delta superimposed with the MCRD groundwater model domain (highlighted in red) and the Colorado River (represented in blue). .................................................................................................. 19 Figure 2.3, Area of the Andrade Mesa wetlands