Using Electrical Resistivity Imaging to Map Saline Groundwater and Subaqueous Spring Discharge: An Example From The Saline Wetlands of Eastern Nebraska

.............................................................................................................................. i ACKNOWLEDGEMENTS ..................................................................................................... iii DEDICATION ......................................................................................................................... ix LIST OF TABLES ..................................................................................................................viii LIST OF FIGURES ................................................................................................................viii LIST OF APPENDICES .........................................................................................................viii 1.0 INTRODUCTION ............................................................................................................... 1 1.1 Overview ................................................................................................................... 1 1.2 Purpose ..................................................................................................................... 4 2.0 BACKGROUND ................................................................................................................. 6 2.1 Saline Wetlands ........................................................................................................ 6 2.2 Geology ..................................................................................................................... 8 2.3 Previous Saline Wetlands Research ........................................................................ 11 2.4 ERI Background and Theory .................................................................................. 14 2.5 Data Inversion ........................................................................................................ 21 2.6 ERI Applications..................................................................................................... 21 3.0 METHODS ........................................................................................................................ 24 3.1 Data Acquisition ..................................................................................................... 24 3.1.1 Field Collection of Electrical Resistivity Data................................................... 24 3.1.2 Data Processing of Electrical Resistivity Data .................................................. 27 3.1.3 Establishing Survey Parameters ....................................................................... 28 3.1.4 Field Collection of Fluid EC Data .................................................................... 33 3.1.5 Field Collection of Fluid EC Data .................................................................... 34 3.1.6 Precipitation Data ............................................................................................ 36 3.2 Site Selection .......................................................................................................... 38 3.3 Site Characterization and Survey Set-up .............................................................. 40 4.0 RESULTS AND DISCUSSION ........................................................................................ 57 4.1 Fluid EC vs. Bulk Resistivity.................................................................................. 57 4.2 Raymond Road Site ................................................................................................. 59 4.3 Arbor Lake WMA ................................................................................................... 77 4.4 Whitehead Saline Wetland ...................................................................................... 85 4.5 Regional Synthesis .................................................................................................. 88 5.0 CONCLUSIONS ............................................................................................................... 93 6.0 RECOMMENDATIONS FOR FURTHER WORK ........................................................ 95 7.0 REFERENCES .................................................................................................................. 98 8.0 APPENDICES ................................................................................................................. 104 LIST OF TABLES Table 2.1: Electrical Resistivity Values for Common Earth Materials ........................................ 16 Table 3.1: Summary of Survey Parameters ................................................................................ 31 Table 3.2: Tables 3.2 a and 3.2 b displaying SuperSting R8 settings .......................................... 32 Table 4.1: Raymond Road; Fluid Electrical Conductivity Measurements ............................................................................ 60 Table 4.2: Arbor Lake Wildlife Management Area; Fluid Electrical Conductivity Measurements ............................................................................ 77 LIST OF FIGURES Figure 1.1: Saline Wetlands Map ............................................................................................... 3 Figure 2.1: Generalized Cross-section of Saline Wetland Geology ............................................ 10 Figure 2.2: Electrical Resistivity Theory; sub-surface current flow ........................................... 17 Figure 2.3: Electrical Resistivity Theory; sub-surface measurement distribution ....................... 18 Figure 2.4: Electrical Resistivity Theory; roll-along survey method .......................................... 20 Figure 3.1: SuperSting R8 field set-up ...................................................................................... 26 Figure 3.2: Map of HPRCC weather stations ............................................................................ 37 Figure 3.3: Hyetograph for HPRCC weather station Raymond 2NE .......................................... 38 Figure 3.4: Little Salt Creek WMA (Raymond Road); map of wetland extent ........................... 41 Figure 3.5: Little Salt Creek WMA (Raymond Road); wetland features .................................... 42 Figure 3.6: Little Salt Creek WMA (Raymond Road); survey locations .................................... 44 Figure 3.7: Arbor Lake WMA; map of wetland extent .............................................................. 47 Figure 3.8: Arbor Lake Wildlife Management Area; wetland features ....................................... 49 Figure 3.9: Arbor Lake Wildlife Management Area; in-stream spring features .......................... 50 Figure 3.10: Arbor Lake WMA; survey locations ..................................................................... 51 Figure 3.11: Whitehead Saline Wetland; map of wetland extent and survey locations ............... 54 Figure 3.12: Whitehead Saline Wetland Map; wetland features ................................................ 56 Figure 4.1: Fluid EC vs. Bulk Resistivity ................................................................................. 58 Figure 4.2: ERI Cross-section RRA_0203 ................................................................................. 61 Figure 4.3: ERI Cross-sections RRD_0102, RRC_0102, and RRB_0102 ................................... 65 Figure 4.4: ERI Cross-sections RRE_01, RRF_01, and RRG_01 ............................................... 70 Figure 4.5: ERI Cross-section RRH_01 ..................................................................................... 73 Figure 4.6: Figure 29: ERI Cross-sections RRA_01 and RRA_02 .............................................. 75 Figure 4.7: ERI Cross-sections AAA_01 and AAB_01 .............................................................. 78 Figure 4.8: ERI Cross-sections AAC_01, AAC_02, AAD_01, and AAE_01 .............................. 81 Figure 4.9: ERI Cross-section AAF_01 ..................................................................................... 84 Figure 4.10: Whitehead Saline Wetland; location map of fluid EC measurements ..................... 85 Figure 4.11: ERI Cross-sections WH[A]_01 and WHA_03 ....................................................... 87 Figure 4.12: Whitehead Saline Wetland ERI Cross-section; stream level .................................. 90 APPENDICES Appendix A: Drilling logs and location map for logs used in cross-section ............................. 104 Appendix B: Electrical Resistivity Arrays and Data Collection Expansion ............................... 119 Appendix C: GPS Data .......................................................................................................... 121 Appendix D: Fluid EC and Bulk Resistivity Data ................................................................... 150 DEDICATION This thesis is dedicated to my son, Augustus Rome Kelly-Selz. It was not until you came along that I truly found direction in my life. You have inspired me to learn more, do more, and achieve more as I watched you grow and experience life in this same manner. Your patience and understanding of my rigorous work schedule has been absolutely amazing, especially considering that I have been a student for most of your life. Your growing enthusiasm for geology and science has been a great motivation for me and your wonderment has become my own. I couldn’t have done it without you, Schmoopsie-poo; I love you.