Table Of ContentMODELING WATER TABLE RESPONSE TO SUBIRRIGATION WITH A BURIED
MICROIRRIGATION LINE SOURCE FOR POTATO PRODUCTION
By
JADIR APARECIDO ROSA
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIALFULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OFFLORIDA
2000
to
Bruna and Lucas
?vf vi..\
ACKNOWLEDGMENTS
The author wishes to express his sincere appreciation to Dr. Kenneth L. Campbell
for his guidance, assistance and encouragement during the last part of my course of study.
Special gratitude is due to the late Prof. Allen G. Smajstria who was much more than an
adviser to me. He was a brilliant scientist and an esteemed friend. I would like to express
my deep admiration and respect for him in every possible way. He welcomed and helped
me in adjusting to living in a different country. Without his excellent advice, guidance,
patience and time, my work would not have been possible. It was a great pleasure and
precious experience working with him.
Special thanks are also due to the other members of my committee, Dr. D. Z.
Haman, Dr. F. S. Zazueta, Dr. S. J. Locascio, and Dr. L. H. Motz for their support.
The author is indebted to the Agricultural and Biological Engineering Department
for the use of its facilities. Appreciation is also expressed to other graduate students, and
faculty and staff members for their assistance, especially to Mr. Danny Burch for his
technical assistance.
Special gratitude goes to the taxpayers of Brazil, few of whom will ever read this
dissertation, but all of whom have contributed to it. Thanks to CAPES, my scholarship's
sponsor, and to IAPAR, my employer.
Finally, behind the scenes were my loving kids, Bruna and Lucas, who rejoiced
with me in good times and cheered me up in the bad.
in
TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS
in
LIST OF TABLES vii
LIST OF FIGURES viii
ABSTRACT x
CHAPTERS
INTRODUCTION
1 1
2 REVIEW OF LITERATURE 5
Variably Saturated WaterFlow 5
Flux Density Equation: Darcy’s Law 5
Conservation ofMass: Continuity Equation 6
General Unsaturated Flow Equation: Richards Equation 7
Solutions ofthe WaterFlow Equation 9
Soil Hydraulic Properties 12
Soil Water Characteristic Curve 13
Unsaturated Hydraulic Conductivity Curve 16
Soil Water Capacity 17
Hysteresis in Soil Hydraulic Properties 18
W
Root ater Uptake 20
WaterTable Management 22
Subsurface Drip Irrigation 27
MODEL DEVELOPMENT
3 30
Two-Dimensional Model Development 30
Initial Conditions 34
Boundary Conditions 34
Top Surface Boundary 34
Bottom Surface Boundary 35
Left Surface Boundary 36
Right Surface Boundary Condition 36
Seepage Surface Boundary 37
Surface Runoff 38
IV
Irrigation 40
Comer Nodes 41
Time Step Update 41
Grid Size 42
Estimation of Intemode Hydraulic Conductivity 43
Evaluation ofthe Soil Hydraulic Properties 44
Water Uptake by Plant Roots 45
Solution ofthe Two-Dimensional Model 46
Mass Balance Computation 47
4 MODEL TESTING 49
Infiltration in a Large Caisson 49
Water Movement in a Cropped Soil Profile 50
Transient, Two-Dimensional, Variably Saturated WaterTable Recharge 54
Transient, Two-Dimensional, Unconfined Drainage 55
5 EXPERIMENTAL PROCEDURE 58
Subirrigation System 58
RunoffMeasurement 61
Soil Hydraulic Characteristics 62
Soil Water Retention Curve 62
Saturated Hydraulic Conductivity 64
Climate Data 66
6 NUMERICAL SOLUTION: CALIBRATION 68
Soil Hydraulic Properties 68
Estimated Daily ET 71
Deep Percolation 75
WaterTable Levels 77
Runoff 79
Irrigation 82
Water Balance 87
7 MODEL VERIFICATION AND SENSITIVITY ANALYSIS 89
Model Verification 89
Estimated Daily ET 89
WaterTable Levels 91
Irrigation 91
Runoff 96
Deep Percolation 100
Water Balance 101
Sensitivity Analysis 102
v
8 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 106
Summary 106
Conclusions 107
Recommendations forFuture Research 108
APPENDICES
A MODEL ORGANIZATION 109
B NUMERICAL MODEL PROGRAM LISTING 115
LIST OF REFERENCES 153
BIOGRAPHICAL SKETCH 162
vi
LIST OF TABLES
4-
Table page
5-
4-1 Soil hydraulic parameters ofcrushed Bandelier Tuffused in the caisson flow
.
6- example 49
4-2. Soil hydraulic parameters for the second example 51
3. Soil hydraulic parameters used in the third example 54
6-
7-1. Parameters used in van Genuchten's equation to describe the soil hydraulic
properties ofPlacid Fine Sand 62
1. Parameters in van Genuchten's equation determined using original and
calibrated soil water retention curves for Placid Fine Sand 69
6-2. Lengths ofthe stages and crop coefficients for potato used in this work 74
6-3. Measured and simulated runoffvolumes for three storm events in 1996 82
4. Water Balance for the 1996-simulation period 87
1. Water Balance for the 1997-simulation period 102
7-2. Sensitivity analysis ofselected parameters for the 1997 simulation period 105
A-l Input files and type ofinformation read 110
.
A-2. Output files and type ofdata printed 112
A-3. List ofsignificant variables ofthe two-dimensional model 113
Vll
2- LIST OF FIGURES
3-
Figure page
3-
4-
1. Schematic ofthe plant water stress response, a(h), as used by Feddes
et al. (1978) 21
1. Grid system for finite difference two-dimensional model after discretizing
equation (2.9). Nodes are located at the centroid ofthe cells 31
2 Finite difference grid for the field problem 39
1 Predicted water pressure head during transient infiltration in Bandelier
Tuff 50
4-
4-2. Simulated pressure heads at the surface for the second example, as
5-
simulated with HYDRUS and this work 52
HYDRUS
45--3. Simulated water content at selected times (days) with
(symbols) and this work (lines) for the second example 52
6-
4-4. Precipitation and location ofthe water table level for the second example,
as simulated with the HYDRUS and this work computer program 53
4-5. Simulation oftransient water table mounding, comparing results from
this work and experimental data collected by Vauclin et al. (1979) 55
6. Simulation oftransient drainage, comparing results from this work and
experimental data collected by Vauclin et al. (1975) 57
1. Layout ofthe field research experiment 59
5-2. Soil moisture curve for Placid Fine Sand 63
3. Fitted and observed soil moisture retention curves for one equivalent layer
ofPlacid Fine Sand 63
1. Fitted soil moisture retention curves with original and calibrated
parameters 70
6-2. Predicted hydraulic conductivity with original and calibrated parameters 71
vm
6-3. Simulated distribution ofthe daily ET over a 24-hr cycle 73
%
6-4. Crop coefficient curve for potato used in this study 74
6-5. Daily values ofpotential evapotranspiration (Penman) and crop ET for
the 1996 simulated period 76
6-6. Relationship between flux and hydraulic head at the bottom ofthe soil
6-
profile 78
7-
6-7. Observed and simulated water table in the 1996 growing season 80
6-8. Cumulative observed and simulated irrigation in the 1996 growing season 86
9. Simulated and observed water tables during a period ofirrigation late in
the 1996 growing season 88
1. Daily values ofpotential evapotranspiration (Penman) and crop ET for
the 1997 simulated period 90
7-2. Observed and simulated water table in the 1997 growing season 92
7-3. Scattergram ofobserved and simulated water table depth (taken positive
downward) in the 1997 simulation 93
7-4. Cumulative observed and simulated irrigation in the 1997 growing season 94
7-5. Water table profile during irrigation in the early and mid seasons 97
7-6. Water table profile during irrigation in the early and mid hours ofthe day 97
7-7. Cumulative observed and simulated runoffin the 1997 growing season 98
7-8. Measured rainfall versus simulated and observed runoffduring the 1997
simulation period 101
IX
Abstract ofDissertation Presented to the Graduate School
ofthe University ofFlorida in Partial Fulfillment ofthe
Requirements for the Degree ofDoctor ofPhilosophy
MODELING WATER TABLE RESPONSE TO SUBIRRIGATION WITH A BURIED
MICROIRRIGATION LINE SOURCE FOR POTATO PRODUCTION
By
Jadir Aparecido Rosa
May 2000
Chairman: Kenneth L. Campbell
Major Department: Agricultural and Biological Engineering
In northeast Florida, the greatest use of fresh water resources is for supplemental
irrigation of agricultural crops, including potato, one of the major crops in this area.
Potatoes are grown on beds in soils that require irrigation even though if they are subject
to naturally occurring high water tables. Most potato fields are irrigated using
conventional semi-closed seepage systems that are not as efficient as most other irrigation
methods. Research has shown the technical feasibility of subirrigation with a buried
microirrigation system for vegetable crops in Florida, with a reduction in runoffrates and
irrigation requirements as compared to the conventional semi-closed seepage irrigation
system.
The contribution of high water tables to soil water extracted by agricultural crops
in combination with subsurface drip irrigation had not been studied accurately. Field
plots were installed at the University of Florida Hastings Agricultural Research Center
Yelvington Farm, and potatoes were produced during three spring growing seasons to
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