Groundwater Hydrology

Contents Preface .....................................................................................................................xxi Acknowledgments ..................................................................................................xxv Authors .................................................................................................................xxvii Chapter 1 Introduction ..........................................................................................1 1.1 Introduction .................................................................................1 1.2 Water Availability ........................................................................2 1.2.1 Groundwater Availability ................................................4 1.3 Groundwater Systems .................................................................5 1.4 Science and Engineering of Groundwater ...................................6 1.5 Planning and Management of Groundwater ...............................8 1.5.1 Integrated Water Resources Management .....................10 1.5.2 Conflict Issues in Groundwater .....................................10 1.5.3 Economics of Water ......................................................11 1.5.4 Groundwater Sustainability ...........................................13 1.5.5 Supply and Demand Side Management ........................15 1.6 Tools and Techniques ................................................................17 1.7 People’s Perception: Public Awareness .....................................19 1.8 Groundwater Protection: Concerns and Acts ............................20 1.8.1 Clean Water Act.............................................................21 1.8.2 Groundwater Protection ................................................21 1.8.3 USEPA Groundwater Rule ............................................22 1.8.4 California’s Sustainable Groundwater Management Act ...........................................................23 1.9 Overall Organization of This Book ...........................................24 Problems .............................................................................................25 References ..........................................................................................25 Chapter 2 Groundwater Properties ......................................................................29 2.1 Introduction ...............................................................................29 2.2 Vertical Distribution of Subsurface Water .................................31 2.3 Aquifers, Aquitards, and Aquicludes ........................................33 2.4 Types of Aquifers ......................................................................33 2.4.1 Unconfined Aquifer .......................................................33 2.4.2 Confined Aquifers .........................................................34 2.4.3 Aquitard (Leaky) Aquifer ..............................................34 2.5 Groundwater Balance ................................................................35 2.5.1 Water Balance in Confined Aquifers .............................36 2.5.2 Water Balance in Unconfined Aquifers .........................37 2.5.3 Water Balance in Unsaturated Zone ..............................37 2.6 Compressibility and Effective Stress .......................................38 2.6.1 Compressibility of Water ...........................................38 2.6.2 Effective Stress ..........................................................38 2.6.3 Compressibility of a Porous Medium ........................40 2.6.4 Effective Stress in the Unsaturated Zone ..................42 2.7 Aquifer Compressibility ..........................................................42 2.8 Aquifer Characteristics ............................................................43 2.8.1 Porosity and Void Ratio .............................................44 2.8.2 Specific Yield in Unconfined Aquifers ......................46 2.8.3 Specific Retention......................................................47 2.8.4 Storage Coefficient and Specific Storage ..................48 2.8.5 Safe Yield of Aquifers ...............................................52 2.9 Storage in the Unsaturated Zone .............................................52 2.10 Water-Level Fluctuations .........................................................55 2.11 Groundwater in Karst ..............................................................55 2.11.1 Karst Aquifer .............................................................55 2.11.2 Types of Karst............................................................56 2.11.3 Fluctuation of Karst Aquifer ......................................56 2.11.4 Recharge of Karst Aquifer .........................................57 2.11.5 Groundwater Tracing in Karst ...................................58 2.11.6 Water Resources Problems in Karst ..........................58 Problems .............................................................................................59 References ..........................................................................................61 Chapter 3 Groundwater Hydrology .....................................................................63 3.1 Introduction .............................................................................63 3.2 Groundwater Movement ..........................................................63 3.2.1 Darcy’s Law ...............................................................63 3.2.1.1 Validity of Darcy’s Law..............................68 3.2.2 Hydraulic Head ..........................................................68 3.2.3 Hydraulic Conductivity .............................................69 3.2.3.1 Hydraulic Conductivity in Saturated Media ..........................................................69 3.2.3.2 Hydraulic Conductivity in Unsaturated Media ..........................................................70 3.2.3.3 Laboratory Measurement of Hydraulic Conductivity ...............................................72 3.2.3.4 Field Measurement of Hydraulic Conductivity ...............................................74 3.3 Homogeneous and Isotropic Systems ......................................75 3.3.1 Hydraulic Conductivity in Multilayer Structures ......76 3.4 Transmissivity .........................................................................80 3.5 Dupuit–Forchheimer Theory of Free-Surface Flow ................81 3.6 Groundwater Flow in Unsaturated Zone .................................83 3.7 Flownets .....................................................................................88 3.7.1 Isotropic and Homogeneous Media .............................88 3.7.2 Heterogeneous Media ..................................................92 3.7.3 Anisotropic Media .......................................................93 3.8 Statistical Methods in Groundwater Hydrology ........................95 3.8.1 Normal Distribution .....................................................95 3.8.2 Lognormal Distribution ...............................................97 3.8.3 t-Distribution ................................................................98 3.8.4 Chi-Square (χ2) Distribution ......................................100 3.8.5 Errors .........................................................................100 3.8.5.1 Sampling Error ..........................................100 3.8.5.2 Standard Errors .........................................100 3.8.6 Estimating Quantiles (Percentiles) ............................101 3.8.7 Probability/Frequency/Recurrence Interval ...............102 3.9 Time Series Analysis ...............................................................103 3.9.1 Nonstationary Hydrologic Variables ..........................103 3.9.2 Hydrologic Time Series Modeling .............................104 3.9.3 Data Preparation ........................................................105 3.9.4 Parameter Estimation .................................................108 3.9.4.1 Method of Moments .................................108 3.9.4.2 Method of L-Moments ..............................109 3.9.4.3 Method of Least Squares ..........................110 3.9.4.4 Method of Maximum Likelihood .............111 3.9.5 Goodness of Fit Tests .................................................113 3.9.5.1 Chi-Square Goodness of Fit Test ..............113 3.9.5.2 Tests of Normality ....................................115 3.9.6 Akaike’s Information Criterion ..................................117 3.9.7 Autoregressive Modeling ...........................................117 3.9.8 Moving Average Process ............................................121 3.9.9 Autoregressive Moving Average Modeling ...............122 3.9.9.1 Generation and Forecasting Using ARMA Models .........................................122 3.9.10 Autoregressive Integrated Moving Average Modeling ....................................................................123 3.9.10.1 Time Series Forecasting Using ARIMA Models ........................................124 Problems ...........................................................................................130 Appendix ..........................................................................................132 References ........................................................................................135 Chapter 4 Hydraulics of Groundwater ..............................................................139 4.1 Introduction ............................................................................. 139 4.2 Continuity Equation .................................................................139 4.3 Equation of Motion in Groundwater .......................................142 4.3.1 Groundwater Flow Equation ......................................144 4.4 Wells ........................................................................................153 4.4.1 Steady Flow into a Well ...............................................155 4.4.1.1 Confined Flow ...............................................155 4.4.1.2 Unconfined Flow ...........................................158 4.4.2 Unsteady State in a Confined Aquifer .........................161 4.4.2.1 Aquifer Test Application ...............................165 4.4.2.2 Theis Method of Solution .............................166 4.4.2.3 Cooper–Jacob Method of Solution ...............168 4.4.2.4 Variable Pumping Test ..................................172 4.4.3 Unsteady State for Unconfined Aquifer ......................175 4.5 Multiple-well Systems .............................................................181 4.6 Effective Conditions on Time-Drawdown Data ......................182 4.6.1 Recharge Boundary .....................................................182 4.6.2 Impermeable Boundary ...............................................184 4.6.3 Partially Penetrating Wells...........................................186 4.7 Design of Wells ........................................................................188 4.8 Well Construction ....................................................................191 4.8.1 Cable-Tool Drilling ......................................................191 4.8.2 Rotary Drilling Method ...............................................191 4.8.2.1 Well Development ........................................192 Problems ...........................................................................................193 References ........................................................................................197 Chapter 5 Groundwater Quality ........................................................................199 5.1 Introduction .............................................................................199 5.2 Groundwater Constituents and Contaminants .........................199 5.2.1 Inorganic Contaminants ...............................................199 5.2.2 Organic Contaminants .................................................200 5.2.3 Dissolved Gasses .........................................................200 5.2.4 Particles .......................................................................202 5.3 Water Quality Standards ..........................................................203 5.4 Groundwater Solubility ...........................................................209 5.5 Disequilibrium and Saturation Index .......................................212 5.6 Sources of Groundwater Contamination .................................214 5.6.1 Disposal of Solid Wastes .............................................214 5.6.2 Underground Petroleum Tank Leakage .......................214 5.6.3 Disposal of Liquid Wastes ...........................................215 5.6.4 Sewage Disposal on Land ............................................215 5.6.5 Agricultural Activities .................................................216 5.6.6 Other Sources of Contamination .................................216 5.7 Mass Transport of Dissolved Contaminants ............................217 5.7.1 Diffusion ......................................................................218 5.7.2 Advection.....................................................................220 5.7.3 Mechanical Dispersion ................................................221 5.7.4 Hydrodynamic Dispersion ...........................................224 5.7.5 Derivation of the Advection–Dispersion Equation ......225 5.7.6 Solute Transport Equation ...........................................233 5.7.7 Capture-Zone Curves ...................................................234 5.8 Modeling Contaminant Release ..............................................240 5.8.1 Modeling Instantaneous Release of Contaminants ......240 5.8.1.1 Fourier Analysis in Solute Transport ............240 5.8.1.2 Point Spill Model ..........................................241 5.8.1.3 Vertically Mixed Spill Model .......................241 5.8.1.4 Vertical Mixing Region ................................242 5.8.2 Modeling Continuous Release of Contaminants .........244 5.8.2.1 Development of Contaminant Plume Models ..........................................................244 5.8.2.2 Simple Plume Model ....................................244 5.8.2.3 Point-Source Plume Model ...........................245 5.8.2.4 Gaussian-Source Plume Model .....................245 Problems ...........................................................................................248 References ........................................................................................250 Chapter 6 Groundwater Modeling ....................................................................251 6.1 Introduction .............................................................................251 6.2 Process of Modeling ................................................................251 6.3 Mathematical Modeling ...........................................................252 6.3.1 Analytical Modeling ....................................................253 6.3.2 Numerical Modeling ....................................................254 6.4 Finite-Difference Method ........................................................254 6.4.1 Forward Difference Equation ......................................257 6.4.2 Backward Difference Equation....................................261 6.4.3 Alternating Direction Implicit Method ........................262 6.4.4 Crank–Nicolson Difference Equation .........................281 6.5 Finite Element Method ............................................................284 6.5.1 Discretize the Problem Domain ...................................284 6.5.2 Derive the Approximating Equations ..........................290 6.5.3 Transient Saturated Flow Equation .............................303 6.5.4 Solute Transport Equation ...........................................311 6.6 Finite Volume Method .............................................................319 6.6.1 Steady-State One-Dimensional Flow Equation ...........319 6.6.2 Unsteady-State, One-Dimensional Flow Equation ......323 6.6.3 Two-Dimensional Flow Equation ................................324 6.6.4 Orthogonals Coordinate System ..................................333 6.7 Simulation of Groundwater Flow Using the Discrete Kernel Approach ......................................................................336 6.8 Saturated-Unsaturated Transport (SUTRA) Code ...................346 6.9 MODFLOW .............................................................................347 Problems ...........................................................................................364 References ........................................................................................366 Chapter 7 Groundwater Planning and Management .........................................369 7.1 Introduction .............................................................................369 7.2 Data Collection ........................................................................370 7.3 Simulation Techniques ............................................................371 7.3.1 Model Calibration .......................................................372 7.3.2 Model Verification .......................................................372 7.3.3 Model Predictions .......................................................373 7.3.3.1 Artificial Neural Networks ...........................374 7.3.3.2 Fuzzy Sets and Parameter Imprecision ........389 7.3.3.3 System Dynamics .........................................395 7.3.3.4 Agent-Based Modeling .................................405 7.4 Optimization Models for Groundwater Management .............409 7.4.1 Optimization Model for Groundwater Operation ........410 7.4.2 Optimization Model for Capacity Expansion ..............413 7.4.3 Optimization Model for Water Allocation ...................417 7.4.4 Optimization Model for Conjunctive Water Use .........420 7.4.5 Optimal Groundwater Quality Management Model ...421 7.4.6 Optimization Model for Parameters of Groundwater Model ....................................................422 7.5 Optimization Techniques .........................................................423 7.5.1 Single-Criterion Optimization .....................................424 7.5.2 Multi-criteria Optimization .........................................426 7.5.2.1 Sequential Optimization ...............................427 7.5.2.2 The ε-Constraint Method ..............................427 7.5.2.3 The Weighting Method .................................428 7.5.2.4 Interactive Fuzzy Approach ..........................430 7.5.3 Special Methods for Groundwater Optimization ........432 7.5.3.1 Dynamic Programming ................................432 7.5.3.2 Genetic Algorithm ........................................434 7.5.3.3 Simulation Annealing ...................................438 7.6 Conflict Resolution ..................................................................440 7.6.1 Stakeholder Involvement .............................................446 7.6.1.1 Effective Meeting Facilitation ......................447 7.6.1.2 Conflict Handling .........................................447 7.6.1.3 Quantifying Meeting Outcomes ...................448 7.6.2 Application of Game Theory in Multi-objective Groundwater Management ..........................................449 7.6.2.1 Non-cooperative Stability Definitions ..........452 7.7 Groundwater Systems Economics ...........................................452 7.7.1 Economic Analysis of Multiple Alternatives ...............457 7.7.2 Economic Evaluation of Projects Using Benefit–Cost Ratio Method .........................................459 7.8 Case Studies ............................................................................460 7.8.1 Case 1: Development of a System Dynamics Model for Water Transfer ............................................460 7.8.1.1 Area Characteristics .....................................461 7.8.1.2 Conflict Resolution Model for Land Resources Allocation in Each Zone..............461 7.8.1.3 Results of the Conflict Resolution Model ....463 7.8.1.4 Optimal Groundwater Withdrawal in Each Zone .....................................................464 7.8.1.5 Sizing Channel Capacity ..............................464 7.8.1.6 Conclusion—Making Technologies Work ...465 7.8.2 Case 2: Conflict Resolution in Water Pollution Control for an Aquifer .................................................466 7.8.2.1 Water Resources Characteristics in the Study Area ..........................................466 7.8.2.2 Conflict Resolution Model ...........................468 7.8.2.3 Results and Discussion .................................471 7.8.3 Case 3: An Agent-Based Modeling Application in Groundwater ............................................................472 7.8.3.1 Case Study Characteristics ...........................472 7.8.3.2 Model Characteristics ...................................473 7.8.3.3 Model Calibration and Verification ..............475 7.8.3.4 Results of Agent-Based Modeling ................475 7.8.4 Case 4: Development of a Noncooperative Game in Groundwater Management ......................................476 7.8.4.1 Area Characteristics .....................................476 7.8.4.2 Simulation-Multi-objective Optimization Model ...........................................................477 Problems ...........................................................................................482 References ........................................................................................486 Chapter 8 Surface Water and Groundwater Interaction ....................................491 8.1 Introduction .............................................................................491 8.2 Interaction between Surface and Groundwater .......................491 8.2.1 Infiltration ....................................................................492 8.2.2 Concepts of Interaction between Surface Water and Groundwater ................................................................492 8.2.3 Bank Storage and Baseflow Recession .......................495 8.2.3.1 Master-Depletion Curve Method ..................496 8.2.3.2 Seasonal Recession Method (Meyboom Method) ........................................................497 8.2.3.3 Constant-Discharge Baseflow Separation ....498 8.2.3.4 Constant-Slope Baseflow Separation ...........498 8.2.3.5 Concave-Baseflow Separation ......................499 8.2.4 Groundwater and Lakes ...............................................500 8.3 Conjunctive Use of Surface and Groundwater ........................502 8.3.1 Advantages of Conjunctive Use ..................................503 8.3.2 Impediments of Conjunctive Use ................................504 8.3.3 Case Study 1: Conjunctive Use of Surface and Groundwater in Lakhaoti Canal Uttar Pradesh, India ..............................................................504 8.3.4 Surface and Groundwater Conjunctive Use Modeling .....................................................................507 8.3.5 Multi-objective Conjunctive Use Optimization ..........515 8.3.5.1 Groundwater Resource Sustainability Limits ...........................................................516 8.3.6 Case Study 2: Application of Genetic Algorithms and Artificial Neural Networks in Conjunctive Use of Surface and Groundwater Resources ......................517 8.3.6.1 Simulation Model .........................................517 8.3.6.2 Optimization Model Framework ..................521 8.3.6.3 Results and Discussion .................................523 8.3.7 Case Study 3: Water Allocation from the Aquifer-River System Using a Conflict Resolution Model ........................................................524 8.3.7.1 Optimization Model Framework ..................528 8.3.7.2 Results and Discussion .................................530 8.3.8 Case Study 4: Conjunctive Use and Crop Pattern Management ................................................................532 8.3.8.1 Optimization Model Structure ......................534 8.3.8.2 Results and Discussion .................................537 8.4 Operation of Groundwater Resources in Semiarid Region .....538 Problems ...........................................................................................540 References ........................................................................................541 Chapter 9 Aquifer Restoration and Monitoring ................................................543 9.1 Introduction .............................................................................543 9.2 Partitioning Process .................................................................544 9.3 Retardation ..............................................................................546 9.4 Natural Losses of Contaminants..............................................547 9.4.1 Volatilization ...............................................................548 9.4.2 Biological Degradation ...............................................548 9.4.3 Plant Uptake ................................................................549 9.5 Groundwater Pollution Control ...............................................550 9.5.1 Institutional Tools ........................................................550 9.5.1.1 Regional Groundwater Management ...........550 9.5.1.2 Land Zoning .................................................550 9.5.1.3 Effluent Charges/Credits ..............................550 9.5.1.4 Guidelines ....................................................551 9.5.1.5 Aquifer Standards and Criteria .....................551 9.5.2 Source Control Strategies ............................................551 9.5.3 Stabilization/Solidification Strategies .........................552 9.5.4 Well Systems ...............................................................554 9.5.5 Interceptor Systems .....................................................554 9.5.6 Surface Water Control, Capping, and Liners ...............555 9.5.7 Sheet Piling .................................................................556 9.5.8 Grouting ......................................................................557 9.5.9 Slurry Walls .................................................................557 9.6 Treatment of Groundwater ......................................................559 9.6.1 Air Sparging ................................................................559 9.6.2 Carbon Adsorption ......................................................560 9.6.3 Adding Chemicals and In Situ Chemical Oxidation ...561 9.6.4 Thermal Technologies .................................................562 9.6.5 Bioremediation Techniques .........................................563 9.6.6 Dissolved Phase (Plume) Remediation .......................564 9.6.6.1 Pump and Treat ............................................564 9.6.6.2 Permeable Reactive Barriers ........................564 9.7 Aquifer Restoration—Overdraft Issues ...................................566 9.7.1 Case Study: The National Restoration and Remediation of Groundwater Resources in Iran .........567 9.7.1.1 General Purpose ...........................................567 9.7.1.2 Projects .........................................................567 9.7.1.3 Operational Program (Action Plans) ............568 9.7.1.4 Time Table ....................................................569 9.8 Monitoring Subsurface Water ..................................................569 9.8.1 Vadose-Zone Monitoring.............................................570 9.8.2 Groundwater Monitoring .............................................571 9.8.3 Water Quality Variable Selection ................................572 9.8.4 Geostatistical Tools for Water Quality-Monitoring Networks .....................................................................573 9.8.4.1 Kriging .........................................................574 9.8.5 Location of Water Quality Monitoring Stations ..........577 9.8.5.1 Definition and Discretization of the Model Domain .............................................578 9.8.5.2 Calculation of Weights for Candidate Monitoring Sites ...........................................579 9.8.5.3 Optimal Configuration of a Monitoring Well Network ...............................................580 9.8.5.4 Kriging Method in Designing an Optimal Monitoring Well Network ............................581 9.8.5.5 Genetic Algorithms in Designing an Optimal Monitoring Well Network ..............582 9.8.6 Sampling Frequency ....................................................584 9.8.6.1 Methods of Selecting Sampling Frequencies ....584 9.8.6.2 Single Station and Single Water Quality Variable ........................................................585 9.8.6.3 Single Station and Multiple Water Quality Variables ....................................586 9.8.6.4 Multiple Stations and a Single Water Quality Variable ......................................587 9.8.6.5 Multiple Stations and Multiple Water Quality Variables ....................................588 9.8.7 Entropy Theory in a Water Quality-Monitoring Network ...................................................................588 9.8.7.1 Entropy Theory .......................................589 9.9 Managed Aquifer Recharge ...................................................591 9.9.1 Principal Consideration ...........................................591 9.9.1.1 Sources of Recharge Water and Its Quality Considerations ...........................593 9.9.1.2 Hydrogeological Settings and Controls on Recharge .............................594 9.9.1.3 MAR Methods ........................................595 9.9.2 MAR in Support of Groundwater Sustainability .....600 9.9.2.1 MAR in Urban Settings ..........................600 9.9.2.2 MAR in Agricultural Settings .................602 9.9.2.3 MAR in Coastal Areas ............................606 9.9.3 The United Nations MAR Portal .............................607 9.10 Summary ...............................................................................607 Problems ...........................................................................................607 References ........................................................................................609 Chapter 10 Groundwater Risk and Disaster Management ..................................615 10.1 Introduction ...........................................................................615 10.2 Groundwater Risk Assessment ..............................................616 10.2.1 Elements of Risk Assessment ..................................616 10.2.2 Assessment of Dose-Response ................................618 10.2.3 Risk Assessment Methods and Tools .......................619 10.2.3.1 Potency Factor for Cancer-Causing Substances ..............................................620 10.2.4 Environmental Risk Analysis ..................................624 10.3 Groundwater Risk Management ............................................625 10.3.1 Groundwater Risk Mitigation ..................................626 10.4 Groundwater Disaster ............................................................627 10.4.1 Requirements for Institutional and Technical Capacities ................................................................627 10.4.2 Prevention and Mitigation of Natural and Man-Induced Disasters ............................................628 10.4.3 Disaster Management Phases ..................................629 10.5 Disaster Indices .....................................................................630 10.5.1 Reliability ................................................................630 10.5.2 Resiliency ................................................................636 10.5.3 Vulnerability ............................................................636 10.6 Groundwater Vulnerability ....................................................637 10.6.1 Drought ....................................................................638 10.6.1.1 Drought Indicators ..................................641 10.6.1.2 Drought Triggers .....................................641 10.6.1.3 Drought Management Strategy Plan .......643 10.6.1.4 Drought Vulnerability Maps ...................643 10.6.1.5 Drought Early Warning Systems ............644 10.6.1.6 Case Study ..............................................644 10.6.1.7 Qanats .....................................................645 10.6.2 Flood ........................................................................647 10.6.2.1 Maps of Groundwater Flood Hazard ......648 10.6.3 Land Subsidence ......................................................650 10.6.3.1 Subsidence Calculation ...........................651 10.6.3.2 Monitoring Land Subsidence ..................652 10.6.3.3 Reducing Future Subsidence ..................652 10.6.3.4 Examples of Subsidence .........................653 10.6.4 Widespread Contamination .....................................653 10.6.4.1 Vulnerability Assessment in Groundwater Pollution ............................657 10.6.4.2 DRASTIC Method ..................................659 10.6.5 Case Study: Development of Vulnerability Maps for a Drought ...........................................................664 10.6.5.1 Summary .................................................668 Problems ...........................................................................................669 References ........................................................................................671 Chapter 11 Climate Change Impacts on Groundwater .......................................675 11.1 Introduction ...........................................................................675 11.2 Climate Change .....................................................................676 11.3 Climate Change Impacts on Hydrological Cycle ..................677 11.3.1 Floods and Droughts ................................................678 11.3.2 Agricultural Droughts ..............................................679 11.3.3 Water Use ................................................................679 11.3.4 Water Quality ...........................................................680 11.3.5 Habitat .....................................................................680 11.3.6 Hydroelectric Power ................................................680 11.3.7 Snowpack .................................................................681 11.3.8 River Flow ...............................................................681 11.4 General Climate Change Impacts on Groundwater ...............681 11.4.1 Hydrological Components Affecting the Groundwater ............................................................683 11.4.1.1 Temperature and Evaporation .................683 11.4.1.2 Precipitation ............................................683 11.4.1.3 Soil Moisture ..........................................685 11.4.2 Direct Impacts of Climate Change on Groundwater ............................................................686 11.4.2.1 Groundwater Recharge ...........................687 11.4.2.2 Recharge Estimation Methods ................688 11.4.2.3 Aquifers Recharging ...............................689 11.4.2.4 Hydraulic Conductivity ...........................689 11.4.3 Indirect Impacts of Climate Change on Groundwater ............................................................690 11.4.3.1 Sea-Level Rise ........................................690 11.4.3.2 Saltwater Intrusion in Coastal Aquifers ..................................................691 11.4.3.3 Storm Surge and Saltwater Intrusion ......693 11.4.3.4 Ghyben–Herzberg Relation between Freshwater and Saline Waters .................694 11.4.3.5 Island Freshwater Lens ...........................695 11.4.3.6 Land Use and Land Cover ......................698 11.5 Groundwater Quantity and Quality Concerns .......................698 11.5.1 Depletion of Groundwater Table .............................698 11.5.2 Deterioration of Groundwater Quality ....................699 11.5.2.1 Increasing Groundwater Contamination ....699 11.5.2.2 Salinization of Groundwater by Sea-Level Rise ........................................699 11.6 Adaptation to Climate Change ..............................................700 11.6.1 Artificial Recharge ...................................................701 11.6.2 Modification of Groundwater Extraction Pattern ....701 11.6.3 Injection Barrier .......................................................702 11.6.4 Subsurface Barrier ...................................................702 11.6.5 Tidal Regulators .......................................................702 11.7 IPCC Assessment Report .......................................................702 11.8 Climate Change Simulation ...................................................704 11.8.1 Spatial Variability ....................................................705 11.8.1.1 Recent Communities’ Scenarios Development ...........................................705 11.8.1.2 Downscaling ...........................................707 11.8.1.3 Regional Models .....................................708 11.8.2 Statistical Downscaling ...........................................709 11.9 Downscaling Models .............................................................712 11.9.1 Statistical Downscaling Model ................................712 11.9.2 LARS-WG Model ...................................................715 11.10 New Insights—Risks and Vulnerabilities ............................724 11.11 Climate Change Impacts on Water Availability in an Aquifer .................................................................................725 11.12 Conclusion ...........................................................................732 Problems ...........................................................................................732 References ........................................................................................734 Index ...................................................................................................................... 739