Table Of ContentInvestigating Groundwater
INTERNATIONAL CONTRIBUTIONS TO HYDROGEOLOGY
29
Series Editor: Dr. Nick S. Robins
Editor-in-Chief IAH Book Series, British Geological Survey, Wallingford, UK
INTERNATIONAL CONTRIBUTIONS TO HYDROGEOLOGY
Investigating Groundwater
Ian Acworth
University of New South Wales, Australia
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Contents
Foreword ix
Acknowledgements xi
1 Groundwater environments 1
1.1 Early human movements based upon groundwater availability 1
1.2 Geological time span and types of rock 6
1.3 Groundwater in Australia 10
1.4 Groundwater in fractured rocks 20
1.5 Groundwater in basalt terrains 26
1.6 Groundwater in unconsolidated surficial deposits 34
1.7 Groundwater in limestone and chalk systems 36
1.8 Groundwater on oceanic islands 45
1.9 Groundwater terminology 47
2 Surface water and the atmosphere 51
2.1 Introduction 51
2.2 Properties of water 61
2.3 Radiation 63
2.4 Atmospheric and ocean circulations of water 72
2.5 Meteorological measurements 82
2.6 Rainfall 90
2.7 Streamflow measurement 99
2.8 Evaporation measurement 113
2.9 Estimates of evaporation from open water 115
2.10 Evapotranspiration estimates 117
3 Recharge, discharge and surface water groundwater
connectivity 129
3.1 Introduction 129
3.2 Groundwater recharge 130
3.3 Recharge estimates 133
3.4 Groundwater discharge 149
vi Contents vi
3.5 Connectivity of surface water and groundwater 151
3.6 Groundwater dependent ecosystems 158
4 Physical properties of soil and the hydraulic head 167
4.1 Physical properties of soil 167
4.2 Water content 170
4.3 Water potential 174
4.4 Hydraulic head 178
4.5 Signal analysis techniques 191
4.6 Sea water intrusion in coastal aquifers 193
5 Hydraulic conductivity and Darcy’s Law 197
5.1 Introduction to Darcy’s Law 197
5.2 Limitations of the Darcian approach 205
5.3 Flow in fractured rocks 207
5.4 Relationship between grain-size distribution and hydraulic conductivity 208
5.5 Laboratory measurement of hydraulic conductivity 213
5.6 Field measurement of hydraulic conductivity 215
6 Transport equations and steady-state flow 219
6.1 Transport equations 219
6.2 Groundwater transport 220
6.3 Steady-State Flow 225
6.4 Numerical solution to the steady-state flow equation 226
6.5 Analogies to groundwater flow 233
7 Aquifer storage and abstraction impacts 237
7.1 Water storage in the unsaturated zone 237
7.2 Confined aquifer storage 237
7.3 Effective stress in a saturated system 242
7.4 Undrained response to natural loading 250
7.5 Derivation of specific storage from records of hydraulic head
in confined aquifers 255
7.6 Derivation of specific storage – A linear poroelastic approach 260
8 Geophysical investigation techniques: seismic 263
8.1 Introduction to seismic methods 263
8.2 Cross-hole seismic method 276
8.3 Surface refraction methods 286
8.4 Seismic Refraction: Delay-time or plus-minus method 295
9 Geophysical investigation techniques: electrical 309
9.1 Electrical methods 309
9.2 Complex conductivity 314
vii Contents vii
9.3 Electrical potential theory 320
9.4 Continuous separation traversing (CST) 325
9.5 Vertical electrical sounding (VES) 327
9.6 Electrical conductivity imaging (ECI) 329
9.7 Induced potential (IP) measurements 333
9.8 Modelling of ECI data 335
9.9 Examples of ECI application: Black cotton soils 341
9.10 Coastal groundwater studies 346
9.11 ECI over fractured rock 351
9.12 IP Measurements 351
9.13 Electromagnetic profiling 352
10 Geophysical investigation techniques: gravity 361
10.1 Gravity Theory 361
10.2 Earth tides 368
10.3 General field procedures for a gravity survey of an area 368
10.4 Gravity corrections to g 371
obs
10.5 Modeling gravity data 374
10.6 Analysing gravity anomalies 374
10.7 Applications of the gravity method 375
11 Geophysical investigation techniques: heat 381
11.1 Introduction 381
11.2 Geothermal heat flow 381
11.3 Underground heat storage in the soil 384
11.4 Thermal imagery 384
11.5 Field measurement of temperature 388
11.6 Thermal properties 390
11.7 Fourier’s Law and differential equations for heat flow 391
11.8 Heat as a tracer 396
12 Drilling and sampling techniques 401
12.1 Cable-tool (percussion) drilling 401
12.2 Rotary Methods 402
12.3 Sampling methods 416
13 Geophysical logging 425
13.1 Introduction 425
13.2 Caliper logs 428
13.3 Verticality logs 430
13.4 Fluid property logs 432
13.5 Fundamentals of nuclear geophysics 436
13.6 Neutron logs 442
13.7 Resistivity and electromagnetic logging 446
13.8 Logging via pushed or hammered sondes 451
13.9 Log interpretation 456
viii Contents viii
14 Hydrochemistry and groundwater isotopes 459
14.1 Introduction 459
14.2 Basic aquatic chemistry 461
14.3 Origin of solutes 468
14.4 Geochemical modelling 471
14.5 Example of hydrochemical analysis 472
14.6 Isotopes 475
14.7 Example: Use of radioactive and stable isotopes in a sand aquifer
at Hat Head, NSW 482
14.8 Example: The use of stable isotopes of water from the Maules
Creek Catchment in northern NSW 487
14.9 Carbon isotopes 495
14.10 Chlorine-36 499
15 Well hydraulics, radial flow modelling and single well tests 501
15.1 Introduction 501
15.2 Review of definitions 501
15.3 Groundwater flow equations 507
15.4 Analytical solution methods to the radial flow equation 508
15.5 Numerical Solutions to the Radial Flow Equation 517
15.6 Radial Flow Model Results 532
15.7 Non-Darcy flow close to an abstraction well 534
15.8 Specific capacity 548
15.9 Interpretation of step-test data 551
A The international system of units – SI 561
Bibliography 565
Index 581
SERIES IAH International Contributions to Hydrogeology (ICH) 585
Foreword
Hydrogeology covers many different aspects of science and engineering and has been
taught internationally in both Geology Schools and Engineering Schools, each perhaps
withanappropriatebias.Soilscientists,biologists,microbiologists,geophysicists,chemists,
organic chemists, botanists and water engineers are all concerned to some degree with the
movement of water through semi-pervious membranes, and a wide and diverse literature
has developed which is all, to some degree, relevant to the study of hydrogeology. Fully
understanding hydrogeology requires that the reader is aware of all the different branches
of science and engineering and sufficiently skilled that they can understand the way in
which some of the important concepts have been defined in parallel using completely dif-
ferentconceptsanddefinitions.Comprehensionisfurthercomplicatedbythewidelydiffer-
enteducationsthatareaderbringstothetext.Forthisreasonalargenumberofimagesand
figures are included in this book in the firm belief that a picture really is worth a thousand
words!
Thesubjectareaislargeandnoonebookcanhopetocoverallaspectsofthisfield.Some
rationalebehindthechoiceforwhattoincludeandwhathasbeenleftoutisthereforeappro-
priate.ThematerialhasbeendevelopedinAustraliawiththeuseofmanyAustralianexam-
ples.Althoughthemethodsandapplicationshaveageneralapplicability,someappreciation
of the Australian environment is useful, and this is presented in the first chapter. It is now
appreciated that many groundwater resources are of considerable age; however, there is
little understanding of theprevailing climate that occurred in Australia at thetime ground-
waterwasrecharged.AustraliaisunlikeEuropeanandNorthAmericanenvironmentswhere
soil and water were very significantly changed and reset during the last ice age. A brief
review of climate change is therefore also presented in the first chapter. There can be
littleappreciationofthedifferentaquifertypesinwhichgroundwateroccurs,sotheremain-
derofthechapterpresentsareviewoftheoccurrenceofgroundwaterindifferentgeological
environments.
Chapter2isconcernedwithsurfacewaterprocesses.Itisincludedasthehydrogeologist,
particularlyfromageologicalbackground,isfrequentlyunawareoftheimportantprocesses
andmeasuringtechniquesrequiredtoestimaterainfall,evaporation,evapotranspirationand
runoff.Thesearethemajorfluxesofwaterthatoccuratthesurfaceoftheearthandground-
water recharge is difficult (or impossible) to predict without the ability to quantify these
fluxes. Chapter 3 reviews the interconnectivity of surface water and groundwater which
leads to a discussion on groundwater recharge processes and calculations.
Chapters 4 to 7 cover basic hydrogeological concepts, while Chapters 8 to 11 provide
detail of appropriate geophysical techniques. The narrative then moves to subsurface
