Soil Water Measurement (eBook)

Author affiliation: DAVID COOPER graduated in Physics from Imperial College, London. He spent 23 years as a soil physicist with the UK Institute of Hydrology, later the Centre for Ecology & Hydrology (CEH), followed by 12 years as Head of the Hydrological Instruments Group at CEH. His work has focussed mainly on field measurement of soil water and solute fluxes and of soil hydraulic properties in a wide variety of lithologies and areas of the world, including at several sites in southern England, northern France, Kenya, Niger, Mauritius, India and China. He has contributed to advances in measurement of soil water content by neutron, capacitance and time domain reflectometry techniques, hydraulic properties measurement methods in situ in the field and soil water potential measurement using mercury manometer and pressure transducer tensiometers over extended periods at both shallow and deep depths, down to at least 60 m. He has six children and, at the time of writing, nine grandchildren.

Preface vi

Part I: Introduction 1

1 Soil Water in Context 3

2 How Does Water in Soil Interact with the Soil Matrix, Air, Roots, Gravity and Other Substances Present? 6

3 What Do We Need to Measure? 14

4 Spatial Variability 16

Part II: Water Content 21

5 Definitions 23

6 Gravimetric Method 26

7 Neutron Scattering 43

8 Dielectric METHODS 101

9 Dual-Probe Heat-Pulse Sensors 150

10 Electrical Resistivity Imaging 152

Part III: Water Potential 159

11 Water Potential Measurement 161

12 Tensiometers 164

13 Indirect Methods of Water Potential Measurement 203

14 Beyond .10 Metres Water Head 214

Part IV: Water Content - Potential Relations 223

15 Soil Water Characteristic Measurement 225

Part V: Hydraulic Conductivity 237

16 Hydraulic Conductivity Measurement and Prediction 239

17 Hydraulic Conductivity Measurement of Confined Soil Samples 241

18 Unconfined Measurements in the Field 257

Part VI: Solute Measurement 277

19 Principles and Pitfalls 279

20 Solution Sampling 283

21 Solute Concentra tion Estimation by Electrical Conductivity 292

Part VII: Water and Solute Movement 301

22 Water and Solute Transport Applications 303

23 Water and Solute Flux Measurement 306

24 Soil Water and Solute Balance Measurement and Estimation 312

Part VIII: Conclusion 333

25 Concluding Remarks 335

References 336

Index 353