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Klaus Bohne:

An Introduction into Applied Soil Hydrology

2005. 231 pages, 55 figures, 16 tables, Catena ISBN 978-3-923381-51-7, US-ISBN 978-1-59326-260-0, 17x24cm, 570 g
Language: English

(GeoEcology textbook)

ISBN 978-3-510-65390-4, paperback, price: 39.00 €

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Keywords

soilwaterenergygroundwaterhydraulicsolute transport

Contents

Synopsis top ↑

Historically speaking, soil science was associated with agriculture and was subdivided into several branches. One of them was soil physics, dealing with soil mechanics, soil and water relationships and solute transport through porous media. Today, we consider soil physics as part of environmental sciences. Soil hydrology, which comprises a large part of soil physics, may now be considered as part of hydrology and is closely related to geohydrology. This is the approach followed in this book.
Environmental issues frequently become critical and require taking effective measures to minimize disasters. Accordingly this book is written primarily from an engineering approach.
This book is addressing students, engineers and those working in the natural sciences to obtain a basic understanding of soil hydrology. Based on my university teaching over several decades, it is intended to help students with limited mathematical and physical background to fully appreciate selected basic concepts of soil hydrology. It will also appeal to readers who seek a concise introduction to soil hydrology. The reader will obtain an overall understanding of how processes in porous media may affect land use and the environment, and how to easily apply principles of soil hydrology to common problems.
There is an abundance of sophisticated equipment used to monitor, measure and analyze soil processes related to soil hydrology. The intention here is to help those readers who do not possess such equipment or expensive software. For those who cannot afford lengthy investigations, the information presented here can help in the development of measurement programs and suggest helpful ways to analyze field data. Throughout the book, simple applications of soil hydrological concepts are presented that yield effective, reasonable solutions to environmental management problems, farming technique problems, and issues in land reclamation and land improvement.
Attached you find a copy of the book on CD including an Appendix containing software to explain details, evaluate soil hydraulic parameters and perform simulations. The special file named “guide to files” outlines what each file does.

Table of Contents top ↑

Preface
1 Introduction: The soil as a reactor between the earth's
atmosphere and the subsurface 1

2 Mechanical composition of mineral soils 2
2.1 Soil texture 2
2.1.1 Mechanical analysis 2
2.1.2 Grain size distribution 3
2.1.3 Textural classes 7 2.2 Soil structure 8
3 Basic parameters of bulk soil 9
3.1 Macroscopic approach 9
3.2 Soil as a three-phase system 9
3.3 Standard values of bulk density 14
4 Soil water balance in the field 16
4.1 Water balance equation 16
4.1.1 Precipitation 17
4.1.2 Surface runoff 19
4.1.3 Evapotranspiration 19
4.1.4 A first approximation to real évapotranspiration and groundwater recharge 23
4.1.5 Simplified approach to drainage and capillary rise 24
4.1.6 The soil water storage term 26
4.2 Measurement of soil water content in the field 27
4.3 Simulation of water storage in soil 29
4.3.1 Spreadsheet model of soil water storage (see Appendix, files “Simulations.xls” or “Simulations.sxc”) 30
4.3.2 Simple multi-layer soil water balance simulation model
(see Appendix, files “Swb”) 31
5 Energy status of water in soil 33
5.1 Total potential of soil water 33
5.2 Gravitational potential 35
5.3 Solute potential 36
5.4 Tensiometer pressure potential 38
5.4.1 Air pressure potential 38
5.4.2 Overburden potential 38
5.4.3 Hydrostatic pressure potential 39
5.4.4 Wetness and matrix potential 39
5.5 Soil water potential related to flow phenomena 40
5.6 Soil water potential and vapor pressure 43
5.7 Measurement of soil water potential 43
6 Water retention in soil 46
6.1 Capillary tubes 46
6.2 Soil water retention curve 48
6.2.1 Fundamentals 48
6.2.2 Differential water capacity, air entry point, and residual
water content 50
6.2.3 Pore size distribution 51
6.2.4 Effect of temperature on pressure head 52
6.2.5 Hysteresis 52 6.3 Mathematical functions representing the water retention curve 53
6.3.1 Introduction 53
6.3.2 The Brooks and Corey model 54
6.3.3 The van Genuchten model 56
6.3.4 Multi-porosity models 58
6.4 Obtaining soil water retention data 59
6.4.1 Field measurements 59
6.4.2 Laboratory methods 60
6.4.3 Estimation of soil water retention from non-hydraulic soil properties 63
7 Flow of water through saturated soil 64<(b>
7.0 Introduction 64
7.1 Flow through capillary tubes 64
7.2 Darcy's law 65
7.3 Steady-state flow of water in saturated soil 68
7.4 Saturated soil hydraulic conductivity 70
7.4.1 Specific permeability 70
7.4.2 Estimation of saturated hydraulic conductivity 71
7.4.2.1 Laboratory measurements 71
7.4.2.2 Field methods 73
7.4.2.3 Statistical data processing 74
7.4.2.4 Criticism and conclusions 74
7.4.2.5 Prediction of saturated soil hydraulic conductivity 75
7.4.2.6 Flow of water through saturated layered soil 76
8 Groundwater flow 80
8.1 Comment 80
8.2 Some basic terms of groundwater hydrology 80
8.3 Groundwater flow net 81
8.4 Aquifer 82
8.4.1 Hydraulic properties 82
8.4.2 Confined aquifer 84
8.5 Groundwater recharge and groundwater balance 85
8.6 Steady-state groundwater flow 87
8.6.1 One-dimensional flow 87
8.6.1.1 Introduction 87
8.6.1.2 Groundwater flow equation 89
8.6.2 Steady-state groundwater flow toward wells 92
8.7 Groundwater flow: The general case 93
8.8 Closing remarks 95
9 Flow through unsaturatd rigid soil 96
9.1 Fundamentals 96
9.2 Steady-state flow 97
9.3 Transient flow 99
9.4 Solutions to flow equations 102
10 Unsaturated soil hydraulic conductivity 105
10.1 Introduction 105
10.2 Models of unsaturated soil hydraulic conductivity 106
10.2.1 Gardner's equations 106
10.2.2 The Burdine and Brooks and Corey theory 107
10.2.3 The Mualem and van Genuchten theories 109
10.3 Measurement of unsaturated hydraulic conductivity 112
10.3.1 Overall view 112
10.3.2 Steady-state evaporation or seepage 112
10.3.3 Steady-state infiltration field methods: The disc infiltrometer 115
10.3.4 Non-steady laboratory methods 117
10.3.5 Non-steady field methods 118 10.4 Prediction of unsaturatd hydraulic conductivity 122
10.4.1 Predictions based on soil water retention 122
10.4.2 Pedotransfer functions 122
10.4.3 Databases 125
11 Elementary soil hydrologic processes 128
11.1 Introduction 128
11.2 Steady-state vertical flow: Capillary rise and constant
flux infiltration 129
11.3 Infiltration 134
11.3.1 Introduction 134
11.3.2 Vertical infiltration under pressure head boundary condition 135
11.3.2.1 Philip's infiltration formula 137
11.3.2.2 Haverkamp's equation 139
11.3.2.3 The Green and Ampt method 140
11.3.3 Vertical infiltration under flux boundary condition 143
11.3.4 Complicating phenomena occurring in field situations 143
11.3.4.1 Crust-topped and layered soils 143
11.3.4.2 Fingering and preferential flow 145
11.3.5 Redistribution 145
11.3.6 Infiltration-based methods to estimate soil hydraulic properties 146
11.3.7 Two-dimensional, flux boundary condition infiltration from
line and point sources 149
11.4 Internal drainage 151
11.4.1 Introduction 151
11.4.2 Internal drainage of groundwater-affected soils 152
11.4.3 Unit gradient drainage 155
11.4.4 The concept of field capacity 156
11.5 Drying of bare soil by evaporation 158
11.6 Soil hydrologic processes and Burgers' equation 159
12 Coupled heat and water flow in soil 161
12.1 Thermal properties of soil 161
12.2 Heat transport in soil 161
12.3 Non-isothermal flow of water through soil 162
12.4 Soil temperature changes in the field 164
13 Solute transport in soil 166
13.1 Introduction 166
13.2 Basic processes 166
13.2.1 Convection 166
13.2.2 Hydrodynamic dispersion 169
13.2.3 Diffusion 170
13.2.4 Total solute flux 172 13.3 Chemical reactions 173
13.3.1 Classification 173
13.3.2 Fast reactions (Classes I through III) 173
13.3.3 Slow reactions (Classes IV through VI) 176
13.4 Simplified approach to solute transport prediction 178
13.5 Convection-Dispersion Equation (CDE) 179
13.5.1 General problem 179
13.5.2 The simplified CDE and solutions 180
13.5.3 Breakthrough curves and solutions to the CDE 181
13.5.3.1 Experimental procedure and results 181
13.5.3.2 Analytical solutions to the CDE 183
13.5.4 Solute transport by groundwater flow 186
13.5.5 Non-equilibrium and the mobile-immobile concept 188
13.6 Parameter estimation 189
13.7 Stochastic descriptions of solute transport 190
14 Solute management: Soil salinization 191
14.1 Overview 191
14.2 Leaching requirement 193
14.3 Salt distribution in soil 194
14.3.1 Irrigation balances root water uptake 194
14.3.2 Irrigation on slowly permeable soils 196
14.4 The ultimate sink for soil salinity - the ocean 199
15 Soil water and crops 200
15.1 Soil moisture requirements 200
15.1.1 Optimal levels of plant available soil water 200
15.1.2 Deficit irrigation 202
15.2 Aeration 203
15.3 Soil mechanical properties 204
16 Closing remarks 205
16.1 Some general remarks on simulation models 205
16.2 Important issues not included in this book 206
References 208
Abbreviations 216
Glossary 218
Index 227