Fundamentals of Groundwater

Preface xv About the Companion Website xvii 1 Introduction to Groundwater 1 1.1 Why Study Groundwater? 1 1.2 Brief History of Groundwater 4 1.2.1 On Books 4 1.2.2 On the Early Evolution of Hydrogeological Knowledge 5 1.2.3 1960–2005 Computers and Contaminants 6 1.2.4 2005 and Onward: Research Diversified 8 References 9 2 Hydrologic Processes at the Earth’s Surface 12 2.1 Basin-Scale Hydrologic Cycle 12 2.2 Precipitation 15 2.2.1 Snowpack Distributions 20 2.3 Evaporation, Evapotranspiration, and Potential Evapotranspiration 20 2.4 Infiltration, Overland Flow, and Interflow 23 2.5 Simple Approaches to Runoff Estimation 25 2.6 Stream Flow and the Basin Hydrologic Cycle 30 2.6.1 Measuring Stream Discharge 30 2.6.2 Hydrograph Shape 32 2.6.3 Estimation of Baseflow 35 2.7 Flood Predictions 37 Exercises 38 References 40 3 Basic Principles of Groundwater Flow 42 3.1 Porosity of a Soil or Rock 42 3.2 Occurrence and Flow of Groundwater 45 3.3 Darcy’s Experimental Law 46 3.3.1 Darcy Column Experiments 47 3.3.2 Linear Groundwater Velocity or Pore Velocity 48 3.3.3 Hydraulic Head 49 3.3.4 Components of Hydraulic Head 50 3.4 Hydraulic Conductivity and Intrinsic Permeability 51 3.4.1 Intrinsic Permeability 52 3.4.2 Hydraulic Conductivity Estimated from Association with Rock Type 53 3.4.3 Empirical Approaches for Estimation 53 3.4.4 Laboratory Measurement of Hydraulic Conductivity 55 3.5 Darcy’s Equation for Anisotropic Material 56 3.6 Hydraulic Conductivity in Heterogeneous Media 57 3.7 Investigating Groundwater Flow 61 3.7.1 Water Wells, Piezometers, and Water Table Observation Wells 61 3.7.2 Potentiometric Surface Maps 62 3.7.3 Water-Level Hydrograph 63 3.7.4 Hydrogeological Cross Sections 65 References 67 4 Aquifers 69 4.1 Aquifers and Confining Beds 69 4.2 Transmissive and Storage Properties of Aquifers 70 4.2.1 Transmissivity 70 4.2.2 Storativity (or Coefficient of Storage) and Specific Storage 72 4.2.3 Storage in Confined Aquifers 73 4.2.4 Storage in Unconfined Aquifers 74 4.2.5 Specific Yield and Specific Retention 74 4.3 Principal Types of Aquifers 75 4.4 Aquifers in Unconsolidated Sediments 75 4.4.1 Alluvial Fans and Basin Fill Aquifers 75 4.4.2 Fluvial Aquifers 79 4.5 Examples Alluvial Aquifer Systems 80 4.5.1 Central Valley Alluvial Aquifer System 80 4.5.2 High Plains Aquifer System 81 4.5.3 Indo-Gangetic Basin Alluvial Aquifer System 82 4.5.4 Mississippi River Valley Alluvial Aquifer 83 4.5.5 Aquifers Associated with Glacial Meltwater 85 4.6 Aquifers in Semiconsolidated Sediments 87 4.7 Sandstone Aquifers 88 4.7.1 Dakota Sandstone 88 4.8 Carbonate-Rock Aquifers 89 4.8.1 Enhancement of Permeability and Porosity by Dissolution 90 4.8.2 Karst Landscapes 91 4.8.3 Floridan Aquifer System 93 4.8.4 Edwards-Trinity Aquifer System 94 4.8.5 Basin and Range Carbonate Aquifer 96 4.9 Basaltic and Other Volcanic-Rock Aquifers 97 4.10 Hydraulic Properties of Granular and Crystalline Media 99 4.10.1 Pore Structure and Permeability Development 99 4.11 Hydraulic Properties of Fractured Media 100 4.11.1 Factors Controlling Fracture Development 101 References 102 5 Theory of Groundwater Flow 106 5.1 Differential Equations of Groundwater Flow in Saturated Zones 106 5.1.1 Useful Knowledge About Differential Equations 107 5.1.2 More About Dimensionality 109 5.1.3 Deriving Groundwater Flow Equations 109 5.2 Boundary Conditions 113 5.3 Initial Conditions for Groundwater Problems 114 5.4 Flow-net Analysis 115 5.4.1 Flow Nets in Isotropic and Homogeneous Media 115 5.4.2 Flow Nets in Heterogeneous Media 118 5.4.3 Flow Nets in Anisotropic Media 119 5.5 Mathematical Analysis of Some Simple Flow Problems 120 5.5.1 Groundwater Flow in a Confined Aquifer 120 5.5.2 Groundwater Flow in an Unconfined Aquifer 121 5.5.3 Groundwater Flow in an Unconfined Aquifer with Recharge 123 References 125 6 Theory of Groundwater Flow in Unsaturated Zones and Fractured Media 126 6.1 Basic Concepts of Flow in Unsaturated Zones 126 6.1.1 Changes in Moisture Content During Infiltration 128 6.2 Characteristic Curves 128 6.2.1 Water Retention or θ(ψ) Curves 128 6.2.2 K(ψ) Curves 130 6.2.3 Moisture Capacity or C(ψ) Curves 132 6.3 Flow Equation in the Unsaturated Zone 133 6.4 Infiltration and Evapotranspiration 134 6.5 Examples of Unsaturated Flow 136 6.5.1 Infiltration and Drainage in a Large Caisson 136 6.5.2 Unsaturated Leakage from a Ditch 137 6.6 Groundwater Flow in Fractured Media 137 6.6.1 Cubic Law 137 6.6.2 Flow in a Set of Parallel Fractures 139 6.6.3 Equivalent-Continuum Approach 141 References 142 7 Geologic and Hydrogeologic Investigations 144 7.1 Key Drilling and Push Technologies 144 7.1.1 Auger Drilling 144 7.1.2 Mud/Air Rotary Drilling 145 7.1.3 Direct-Push Rigs 146 7.2 Piezometers and Water-Table Observation Wells 150 7.2.1 Basic Designs for Piezometers and Water-Table Observation Wells 150 7.3 Installing Piezometers and Water-Table Wells 152 7.3.1 Shallow Piezometer in Non-Caving Materials 152 7.3.2 Shallow Piezometer in Caving Materials 152 7.3.3 Deep Piezometers 153 7.4 Making Water-Level Measurements 154 7.5 Geophysics Applied to Site Investigations 155 7.5.1 Electric Resistivity Method 155 7.5.2 Capacitively Coupled Resistivity Profiling 158 7.5.3 Electromagnetic Methods 159 7.5.4 Large-Scale, Airborne Electromagnetic Surveys 160 7.5.5 Borehole Geophysical and Flow Meter Logging 162 7.5.6 Flowmeter Logging 164 7.6 Groundwater Investigations 166 7.6.1 Investigative Methods 167 References 168 8 Regional Groundwater Flow 170 8.1 Groundwater Basins 170 8.2 Mathematical Analysis of Regional Flow 171 8.2.1 Water-Table Controls on Regional Groundwater Flow 171 8.2.2 Effects of Basin Geology on Groundwater Flow 175 8.3 Recharge 179 8.3.1 Desert Environments 179 8.3.2 Semi-Arid Climate and Hummocky Terrain 180 8.3.3 Recharge in Structurally Controlled Settings 181 8.3.4 Distributed Recharge in Moist Climates 181 8.3.5 Approaches for Estimating Recharge 181 8.4 Discharge 183 8.4.1 Inflow to Wetlands, Lakes, and Rivers 183 8.4.2 Springs and Seeps 183 8.4.3 Evapotranspiration 185 8.5 Groundwater Surface-Water Interactions 186 8.6 Freshwater/Saltwater Interactions 189 8.6.1 Locating the Interface 190 8.6.2 Upconing of the Interface Caused by Pumping Wells 192 References 193 9 Response of Confined Aquifers to Pumping 195 9.1 Aquifers and Aquifer Tests 195 9.1.1 Units 196 9.2 Thiem’s Method for Steady-State Flow in a Confined Aquifer 197 9.2.1 Interpreting Aquifer Test Data 198 9.3 Theis Solution for Transient Flow in a Fully Penetrating, Confined Aquifer 199 9.4 Prediction of Drawdown and Pumping Rate Using the Theis Solution 201 9.5 Theis Type-Curve Method 201 9.6 Cooper–Jacob Straight-Line Method 204 9.7 Distance-Drawdown Method 206 9.8 Estimating T and S Using Recovery Data 208 References 214 10 Leaky Confined Aquifers and Partially-Penetrating Wells 216 10.1 Transient Solution for Flow Without Storage in the Confining Bed 216 10.1.1 Interpreting Aquifer-Test Data 218 10.2 Steady-State Solution 221 10.3 Transient Solutions for Flow with Storage in Confining Beds 223 10.4 Effects of Partially Penetrating Wells 229 References 235 11 Response of an Unconfined Aquifer to Pumping 236 11.1 Calculation of Drawdowns by Correcting Estimates for a Confined Aquifer 236 11.2 Determination of Hydraulic Parameters Using Distance/Drawdown Data 238 11.3 A General Solution for Drawdown 239 11.4 Type-Curve Method 241 11.5 Straight-Line Method 245 11.6 Aquifer Testing with a Partially-Penetrating Well 247 References 250 12 Slug, Step, and Intermittent Tests 251 12.1 Hvorslev Slug Test 251 12.2 Cooper–Bredehoeft–Papadopulos Test 255 12.3 Bower and Rice Slug Test 257 12.4 Step and Intermittent Drawdown Tests 259 12.4.1 Determination of Transmissivity and Storativity 260 12.4.2 Estimating Well Efficiency 263 References 268 13 Calculations and Interpretation of Hydraulic Head in Complex Settings 269 13.1 Multiple Wells and Superposition 269 13.2 Drawdown Superimposed on a Uniform Flow Field 271 13.3 Replacing a Geologic Boundary with an Image Well 272 13.3.1 Impermeable Boundary 272 13.3.2 Recharge Boundary 277 13.4 Multiple Boundaries 278 13.5 Calculation and Interpretation of Hydraulic Problems Using Computers 279 13.5.1 Numerical Models for Groundwater Simulations 279 13.5.2 Interpreting Aquifer Tests 281 References 282 14 Depletion of Groundwater Resources 283 14.1 Water-Level Declines from Overpumping 283 14.1.1 Challenges in the Investigation of Water-level Changes 285 14.2 Land Subsidence 285 14.2.1 Conceptual Model 286 14.2.2 Terzaghi Principle of Effective Stress 288 14.2.3 Subsidence in the San Joaquin Valley of California 289 14.2.4 Challenges in the Investigation of Subsidence 293 14.3 Connected Groundwaters and Surface Waters 294 14.3.1 Declines in Streamflow 294 14.3.2 Induced Infiltration of Streamflow 295 14.3.3 Capture Zone for a Well 298 14.3.4 Pumping of the High Plains Aquifer System and Streamflow Reduction 298 14.3.5 Streamflow Declines in Beaver-North Canadian River Basin 300 14.3.6 Challenges in the Investigation of Streamflow Loss 301 14.4 Destruction of Riparian Zones 301 14.5 Seawater Intrusion 303 14.5.1 Salinas River Groundwater Basin 304 14.6 Introduction to Groundwater Modeling 306 14.6.1 Conceptual Model 306 14.6.2 Model Design 308 14.6.3 Model Calibration and Verification 308 14.6.4 Predictions in Modeling 309 14.7 Application of Groundwater Modeling 309 References 312 15 Groundwater Management 315 15.1 The Case for Groundwater Sustainability 315 15.2 Groundwater Sustainability Defined 317 15.2.1 Sustainability Initiatives 317 15.2.2 Sustainability Indicators for the Sierra Vista Subwatershed in Arizona 318 15.2.3 Socioeconomic Policies and Instruments 320 15.3 Overview of Approaches for Sustainable Management 321 15.3.1 Indicator Tracking 321 15.3.2 Water Balance Analyses 322 15.3.3 Model-Based Analyses of Sustainability 326 15.4 Strategies for Groundwater Sustainability 327 15.4.1 Increasing Inflows 327 15.4.1.1 Managed Aquifer Recharge (MAR) 327 15.4.1.2 Traditional MAR Approaches 329 15.4.1.3 “Sponge City” and Opportunities for Unmanaged Aquifer Recharge 330 15.4.2 Reducing Outflows 331 15.4.2.1 Replacing Groundwater with Surface Water 331 15.4.2.2 Reduction in Water Used for Irrigation 331 15.4.3 Scaling Issues with Sustainability 331 15.5 Global Warming Vulnerabilities 332 15.6 Chemical Impacts to Sustainability 334 15.6.1 Salinization 334 15.6.2 Geogenic and Aenthropogenic Contamination 335 15.6.3 Salinity and Contamination—Indo-Gangetic Basin (IGB) Alluvial Aquifer 336 15.6.4 Seawater Intrusion 339 References 342 16 Water Quality Assessment 345 16.1 Dissolved Constituents in Groundwater 346 16.1.1 Concentration Scales 346 16.2 Constituents of Interest in Groundwater 348 16.2.1 Gases and Particles 348 16.2.2 Routine Water Analyses 350 16.2.3 Contamination: Expanding the Scope of Chemical Characterization 351 16.2.3.1 Contaminated Sites 351 16.2.4 Comprehensive Surveys of Water Quality 352 16.3 Water Quality Standards 353 16.3.1 Health-Based Screening Levels—USGS 353 16.3.2 Secondary Standards for Drinking Water 354 16.3.3 Standards for Irrigation Water 355 16.4 Working with Chemical Data 356 16.4.1 Relative Concentration and Health-Based Screening 356 16.4.2 Scatter Diagrams and Contour Maps 358 16.4.3 Contour Maps 359 16.4.4 Piper Diagrams 360 16.5 Groundwater Sampling 362 16.5.1 Selecting Water Supply Wells for Sampling 362 16.6 Procedures for Water Sampling 363 16.6.1 Well Inspection and Measurements 363 16.6.2 Well Purging 363 16.6.3 Sample Collection, Filtration, and Preservation 364 References 364 17 Key Chemical Processes 366 17.1 Overview of Equilibrium and Kinetic Reactions 366 17.1.1 Law of Mass Action and Chemical Equilibrium 367 17.1.2 Complexities of Actual Groundwater 368 17.1.3 Deviations from Equilibrium 369 17.1.4 Kinetic Reactions 371 17.2 Acid–Base Reactions 372 17.3 Mineral Dissolution/Precipitation 374 17.3.1 Organic Compounds in Water 375 17.4 Surface Reactions 375 17.4.1 Sorption Isotherms 376 17.4.2 Sorption of Organic Compounds 377 17.4.3 Ion Exchange 379 17.4.4 Clay Minerals in Geologic Materials 380 17.4.5 Sorption to Oxide and Oxyhydroxide Surfaces 381 17.5 Oxidation–Reduction Reactions 382 17.5.1 Kinetics and Dominant Couples 384 17.5.2 Biotransformation of Organic Compounds 385 17.5.3 pe-pH and E H -pH Diagrams 385 17.5.4 Quantifying Redox Conditions in Field Settings 386 17.5.5 Redox Zonation 388 17.6 Microorganisms in Groundwater 389 17.6.1 Quantifying Microbial Abundances 390 17.6.2 Microbial Ecology of the Subsurface 390 References 392 18 Isotopes and Applications 395 18.1 Stable and Radiogenic Isotopes 395 18.2 18 O and Deuterium in the Hydrologic Cycle 397 18.2.1 Behavior of D and 18 O in Rain 400 18.3 Variability in 18 O and Deuterium in Groundwater 401 18.3.1 Spatial and/or Temporal Variability of δ 18 O and δD Compositions in Aquifers 401 18.3.2 Connate Water in Units with Low Hydraulic Conductivity 402 18.4 Evaporation and the Meteoric Water Line 403 18.4.1 Other Deviations from GMWL 404 18.4.2 Illustrative Applications with Deuterium and Oxygen- 18 404 18.4.2.1 Role of Wetland in Streamflow 404 18.4.2.2 Integrated Study of Recharge Dynamics in a Desert Setting 405 18.5 Radiogenic Age Dating of Groundwater 406 18.5.1 Exploring Old and New Concepts of Age for Groundwater 408 18.5.2 Carbon- 14 409 18.5.3 Chlorine-36 and Helium-4: Very Old Groundwater 411 18.5.4 Tritium 412 18.5.5 Categorial Assessments Using Tritium Ages 414 18.6 Indirect Approaches to Age Dating 416 18.6.1 Isotopically Light Glacial Recharge 417 18.6.2 Chlorofluorocarbons and Sulfur Hexafluoride 417 References 420 19 Mass Transport: Principles and Examples 423 19.1 Subsurface Pathways 423 19.2 Advection 425 19.3 Dispersion 427 19.3.1 Tracer Tests 427 19.3.2 Dispersion at Small and Large Scales 429 19.4 Processes Creating Dispersion 429 19.5 Statistical Patterns of Mass Spreading 431 19.6 Measuring, Estimating, and Using Dispersivity Values 433 19.6.1 Sources with a Continuous Release 433 19.6.2 Available Dispersivity Values 434 19.7 Dispersion in Fractured Media 435 19.8 Chemical Processes and Their Impact on Water Chemistry 437 19.8.1 Gas Dissolution and Redistribution 437 19.8.2 Mineral Dissolution/Precipitation 438 19.8.3 Cation Exchange Reactions 439 19.8.4 Dissolution/Utilization of Organic Compounds 439 19.8.5 Redox Reactions 439 19.9 Examples of Reactions Affecting Water Chemistry 441 19.9.1 Chemical Evolution of Groundwater in Carbonate Terrains 441 19.9.2 Shallow Brines in Western Oklahoma 441 19.9.3 Chemistry of Groundwater in an Igneous Terrain 442 19.9.4 Evolution of Shallow Groundwater in an Arid Prairie Setting 443 19.10 A Case Study Highlighting Redox Processes 444 19.10.1 Iron and Manganese 444 19.10.2 Arsenic 445 19.10.3 Nitrate 446 19.10.4 Machine Learning for Mapping Redox Conditions 447 References 450 20 Introduction to Contaminant Hydrogeology 452 20.1 Point and Nonpoint Contamination Problems 452 20.2 Families of Contaminants 455 20.2.1 Minor/Trace Elements 455 20.2.2 Nutrients 455 20.2.3 Other Inorganic Species 456 20.2.4 Organic Contaminants 456 20.2.4.1 Petroleum Hydrocarbons 456 20.2.4.2 Halogenated Aliphatic Compounds 457 20.2.4.3 Halogenated Aromatic Compounds 457 20.2.4.4 Polychlorinated Biphenyls 458 20.2.4.5 Health Effects 458 20.2.5 Biological Contaminants 458 20.2.6 Radionuclides 458 20.3 Presence or Absence of Nonaqueous Phase Liquids (NAPLs) 459 20.4 Roles of Source Loading and Dispersion in Shaping Plumes 460 20.4.1 Source Loading 460 20.5 How Chemical Reactions Influence Plumes 461 20.5.1 Biodegradation of Organic Contaminants 462 20.5.2 Degradation of Common Contaminants 462 20.5.3 Reactions Influencing Plume Development 463 20.6 Nonaqueous Phase Liquids in the Subsurface 464 20.6.1 Features of NAPL Spreading 464 20.6.2 Occurrence of DNAPLs in the Saturated Zone 466 20.6.3 Secondary Contamination Due to NAPLs 466 20.7 Approaches for the Investigation of Contaminated Sites 466 20.7.1 Preliminary Studies 467 20.7.2 Reconnaissance Geophysics 467 20.7.3 Soil Gas Characterization 467 20.7.4 Distribution of Dissolved Contaminants 468 20.7.5 Plume Maps 470 20.7.6 Mapping the Distribution of NAPLs 471 20.8 Field Example of an LNAPL Problem 473 References 478 Index 481