 | Schneider C. Well flows and root water uptake: impact of local hydraulic properties on larger scale subsurface water extraction: diss. … dr. rer. nat. / Helmholtz-Centre for Environmental Research, UFZ. - Leipzig: UFZ, 2009. - xxvi, 229 p.: ill., graph. - (PhD Dissertation; 13). - ISSN 1800-0387
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Zusammenfassung / Abstract ...................................... I
List of Symbols and Abbreviations ............................ XVII
1 Introduction ................................................. 1
1.1 Motivation .............................................. 1
1.2 Outline ................................................. 4
2 Theoretical background I: subsurface water flow and well
flows ....................................................... 11
2.1 Flow in porous media ................................... 11
2.1.1 Porous media .................................... 12
2.1.2 Transition to continuum scale ................... 12
2.1.3 Mass balance: continuity and diffusion
equation ........................................ 14
2.2 Subsurface ............................................. 17
2.3 Groundwater flow ....................................... 19
2.3.1 Well flows: radial groundwater flow ............. 20
2.3.2 Natural heterogeneity of hydraulic properties ... 23
2.3.3 Separation of scales ............................ 27
3 Large scale well flows in the saturated zone ................ 35
3.1 Introduction ........................................... 35
3.2 Model .................................................. 44
3.3 The concept of equivalent and coarse grained
conductivity ........................................... 45
3.4 Coarse Graining radially convergent flow toward
a well ................................................. 48
3.4.1 Uniform filtering ............................... 50
3.4.2 Nonuniform spatial filter for radially
convergent flow toward a well ................... 54
3.4.3 Numerical simulations ........................... 55
3.5 Interpreting an ensemble of pumping tests .............. 59
3.5.1 Results for coarse grained transmissivities ..... 63
3.5.2 Convergence of ensemble averaging ............... 65
3.6 Interpretation of single pumping tests ................. 68
3.7 Inverse modeling ....................................... 73
3.7.1 Estimating correlation length and geometric
mean ............................................ 74
3.7.2 Estimating the field Variance in ensemble
averaged drawdowns .............................. 76
3.8 Conclusion ............................................. 77
4 Interpreting small scale pumping tests ...................... 87
4.1 Introduction ........................................... 87
4.2 Model .................................................. 90
4.3 Coarse Graining for 3-dimensional short range well
flows .................................................. 91
4.4 Inversion of 3-D pumping test data by Firmani et al.
(2006) ................................................. 95
4.4.1 Numerical setup ................................. 96
4.4.2 Step I: estimation of horizontal integral
scale, geometric mean and variance .............. 98
4.4.3 Step II: additional estimation of anisotropy
ratio .......................................... 100
4.4.4 Limitations of the proposed procedure .......... 103
4.5 Summary and conclusion ................................ 103
4.6 Appendix .............................................. 105
5 Theoretical background II: unsaturated water flow and
root water uptake .......................................... 109
5.1 Soil water flow ....................................... 110
5.2 Root water uptake ..................................... 114
6 The split root modeling study in the unsaturated zone ...... 129
6.1 Introduction .......................................... 129
6.2 Background ............................................ 133
6.3 Methods ............................................... 136
6.3.1 Microscale Models Type I, Richards' equation
for flow towards a single root ................. 137
6.3.2 Microscale Model Type II: Simplifications for
flow towards a single root ..................... 140
6.3.3 Microscale Model Type III: Inclusion of root
radial resistance .............................. 140
6.3.4 Special case: root-water uptake for a split
root experiment in linear soil ................. 142
6.3.5 Macroscale Model ............................... 143
6.3.6 Model Scenarios and Input ...................... 143
6.4 Results ............................................... 145
6.4.1 Modeled macroscopic uptake considering only
soil resistance with a nonlinear Richards'
equation ....................................... 145
6.4.2 Comparison with simplified approaches .......... 150
6.4.3 Modulation of macroscopic water uptake by
plant factors: plant resistance ................ 153
6.5 Discussion ............................................ 156
6.6 Conclusion ............................................ 161
6.7 Appendix: Derivation of the Linear Split Root
Experiment ............................................ 164
7 Effects of root system on plants water uptake .............. 175
7.1 Introduction .......................................... 175
7.2 Models and methods .................................... 179
7.2.1 Bulk water flow in the unsaturated zone ........ 180
7.2.2 The hydraulic root water uptake model
"aRoot" ........................................ 182
7.2.3 The root architecture model .................... 191
7.2.4 The RLD model .................................. 193
7.2.5 Model input and scenarios ...................... 193
7.3 Results ............................................... 195
7.3.1 Influence of root architecture and hydraulic
root parameters on root water uptake
behavior ....................................... 195
7.3.2 Influence of root architecture on uptake
profiles ....................................... 197
7.3.3 Influence of root architecture on critical
point of water uptake limitation ............... 200
7.4 Discussion ............................................ 204
7.5 Summary and conclusions ............................... 207
8 Synthesis .................................................. 217
8.1 Summary and Conclusions ............................... 217
8.2 Outlook ............................................... 222
Acknowledgements/Danksagung ................................... 227
Curriculum Vitae .............................................. 231
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