Fundamentals of Irrigation and On-farm Water Management: Volume 1 (eBook)

Fundamentals of Irrigation and On-farm Water Management: Volume 1 3
Foreword 5
Preface 7
Acknowledgements 9
Contents 11
Chapter 1: Introduction: Perspectives and General Concept of Irrigation 23
1.1 Availability of Water in the Earth 23
1.2 Variability of Water with Time and Space 24
1.3 General Concept of Irrigation 24
1.3.1 Irrigation Scheduling 24
1.3.2 Full Irrigation 25
1.3.3 Deficit Irrigation 25
1.4 Global Outlook: World Population and World Water Use 25
1.4.1 Trend of World Water Use 25
1.5 Challenges and Opportunities in Irrigation and Water Management 26
1.5.1 Challenging Factors 26
1.5.2 Opportunities 26
1.6 Physiographic and Economic Factors Affecting Irrigation and Water Management: Case Study, Bangladesh 27
1.6.1 National Economy and Agriculture 27
1.6.2 Basic Physical Factors in Agricultural Production 27
1.6.3 Challenges and Limiting Factors in Agriculture in Bangladesh 28
1.6.4 Physical Features of Bangladesh Influencing Water Resources Utilization 28
1.6.5 Climate and Cropping Pattern 29
1.6.6 Major Source of Irrigation Water in Bangladesh and Concern of Sustainability 31
1.6.7 Considerations in Current Water-Starved Situations 31
References 32
Chapter 2: Fundamentals of Irrigation Development and Planning 33
2.1 Factors Affecting Farm Production 33
2.1.1 Agro-Ecological Factor/Constraint 33
2.1.2 Soil Factor 34
2.1.3 Hydrological Factor 34
2.1.4 Crop Factor 34
2.1.5 Water Management 34
2.1.6 Fertility Management 34
2.1.7 Socio-Economic Factor/Constraint 34
2.1.8 Other Management Factors 35
2.2 Important Factors Affecting Irrigation Planning and Development 35
2.2.1 Soil 35
2.2.2 Climate 36
2.2.3 Topography 36
2.2.4 Water Source 36
2.2.5 Crop(s) to be Cultivated 37
2.2.6 Energy 37
2.2.7 Labor 37
2.2.8 Capital 37
2.2.9 Commodity/Product Market 37
2.2.10 Economic Factor 38
2.2.11 Environmental Aspect 38
2.2.12 National Policy and Priority 38
2.2.13 Socio-Cultural Aspects 39
2.2.14 Institutional Infrastructure 39
2.3 Irrigation Development in Asia and Pacific Region 39
2.3.1 Progressive Irrigation Development in Bangladesh 40
2.3.2 Irrigation Development in China 42
2.3.3 Irrigation Development in Iran 43
2.4 Impact of Irrigation on Environment and Ecosystem 44
2.4.1 Positive Impacts 45
2.4.1.1 Health 45
2.4.1.2 Socio-Economic 45
2.4.2 Negative Impacts 45
2.4.3 Degradation of Water Quality 46
2.4.3.1 Human Health Consequences 46
2.4.3.2 Ecosystem Consequences 46
2.4.3.3 Economic Consequences 46
2.4.4 Groundwater Abstraction 47
2.4.5 Water-Logging and Salinity 47
2.4.6 Health Risk 47
2.4.7 Simplification and Homogenization of the World´s Ecosystem 47
2.5 Land Classification for Irrigation 48
2.5.1 Concept of Land Classification 48
2.5.2 Importance of Land Classification 48
2.5.3 Standards of Land Classification 48
2.5.3.1 Basis and Methods 49
2.5.3.2 Land Assessment Criteria 49
2.5.4 Process of Land Classification 50
2.5.5 USBR Land Classification System 50
Relevant Journals 51
Relevant FAO Papers/Bulletins 51
Questions 51
References 52
Chapter 3: Weather: A Driving Force in Determining Irrigation Demand 53
3.1 Concept of Weather and Climate 53
3.2 Importance of Weather in Agriculture and Water Management 54
3.3 Basic Mechanisms of Weather Variability 55
3.3.1 Sun- Earth Geometry 55
3.3.2 Role of Monsoon Wind 56
3.3.3 Interaction Between Atmosphere, Ocean, and Land Surfaces 57
3.4 Weather Factors Determining/Influencing Crop Water Demand 57
3.4.1 Temperature 57
3.4.2 Humidity 58
3.4.3 Solar Radiation 58
3.4.4 Wind Speed 58
3.4.5 Sunshine Hour 58
3.5 Weather Elements Affecting Agriculture and Crop Production 58
3.5.1 Solar Radiation 59
3.5.2 Air Temperature 59
3.5.3 Rainfall 60
3.5.4 Air Humidity 60
3.5.5 Wind 60
3.5.6 Photoperiod or Day-Length 60
3.6 Definition, Measurement, and Analysis of Weather Variables 61
3.6.1 Rainfall 61
3.6.1.1 Formation of Rain 61
Orographic Barrier 62
Uneven Heating of the Earth Surface 62
3.6.1.2 Rainfall Pattern 62
Temporal Pattern 62
Spatial Pattern 63
3.6.1.3 Rainfall Analysis 63
Averaging Catchment Rainfall 63
Merits 63
Demerits 64
Merits 64
Demerits 64
Merits 65
Demerits 65
3.6.1.4 Rainfall Indices 65
Rainfall Distribution Coefficient 65
Rainfall Distribution Index (RDI) 66
Effective Rainfall 66
3.6.1.5 Rainfall Data Checking and Gap Filling 66
Data Checking for Error 66
Fill Up of Short Gaps in Daily Rainfall 66
Estimation of Missing Data Using Regression Technique 67
Extending Rainfall Data 67
3.6.1.6 Rain Gauge Networking 68
3.6.1.7 Examples on Rainfall Data Analysis 68
3.6.1.8 Probability Aspects of Rainfall 71
Concept of Probability 71
Some Related Terminologies 71
Exceedance Probability 71
Annual Exceedance Probability (AEP) 72
Risk 72
Probable Maximum Rainfall 72
Average Recurrence Interval (ARI) 72
Return Period 72
Dependable Rainfall 72
Rainfall in Wet, Normal, and Dry Years 72
Establishing Rainfall Probability Graph 73
Probable Seasonal Rainfall 73
Software Tools for Probability Analysis 74
Probability Under Different Perspectives 74
3.6.1.9 Peak Flow/Runoff Estimation from Rainfall Data 75
Rational Method 75
3.6.1.10 Flood Hydrograph and Unit Hydrograph 76
Unit Hydrograph 77
3.6.2 Solar Radiation 77
3.6.2.1 Basics of Solar Radiation and Its Classification 77
Emission of Radiation 77
Incidence of Solar Radiation to the Earth 78
Classification Solar Radiation on the Earth 78
3.6.2.2 Some Relevant Terminologies 79
Angle of Incidence 79
Albedo 79
Solar Constant 79
Solar Declination 80
Extraterrestrial Radiation 80
Terrestrial Radiation 81
Total Radiation or Global Radiation 81
Net Radiation 81
3.6.2.3 Solar Energy Balance 81
3.6.2.4 Measurement and Use of Solar Radiation 82
Measurement 82
Uses of Solar Radiation 83
3.6.2.5 Indirect Estimation of Solar Radiation 83
Richardson Model 84
Angstrom Model 84
Regression Model 84
3.6.2.6 Measurement of Bright Sunshine Period 86
3.6.2.7 Calculation of Day-Length or Photo Period 86
3.6.3 Air Temperature 88
3.6.3.1 Causes of Temperature Variation 88
Geographical Variation 89
Latitude 89
Atmospheric Reflectivity 89
Type and Characteristics of the Surface 89
Vegetation 89
Altitude 89
Temporal/Time-Dependent Variation 90
Seasonal Variation 90
Diurnal Variation 90
Earth Surface Reflectivity 90
3.6.3.2 Heat Conduction and Temperature Profile 91
3.6.3.3 Measuring Temperature 91
3.6.3.4 Expression and Interpretation of Temperature 91
Average Temperature 92
Normal Daily Temperature 92
Daily Temperature Range 92
3.6.4 Humidity 92
3.6.4.1 Concept and Expression 92
Absolute Humidity 92
Relative Humidity 92
Specific Humidity 93
Precipitable Water 93
3.6.4.2 Measurement of Humidity 93
Sources of Error in Measurement 93
3.6.4.3 Variability of Humidity 93
Temporal Variability 93
Spatial Variability 95
3.6.5 Air Pressure 95
3.6.5.1 Definition 95
3.6.5.2 Measurement and Expression 95
3.6.5.3 Implication of Air Pressure Value 95
3.6.6 Wind Speed 95
3.6.6.1 Concept and Expression 95
3.6.6.2 Measurement 96
3.6.6.3 Variation of Wind Speed 96
3.6.7 Evaporation 97
3.6.7.1 Concept and Factors Affecting Evaporation 97
Condensation 98
3.6.7.2 Latent Heats 98
Latent Heat of Vaporization 98
Latent Heat of Condensation 98
Latent Heat of Fusion 99
Latent Heat of Sublimation 99
3.6.8 Some Other Weather Phenomena 99
3.6.8.1 ENSO 99
3.6.8.2 Tropical Cyclone 100
3.6.8.3 Thunderstorm 100
3.7 Instrumentation for a Weather Station 101
3.8 Weather Forecasting and Agricultural Decision Making 101
3.8.1 Weather Forecasting 101
3.8.1.1 Meaning of Weather Forecast 101
3.8.1.2 Methods of Forecasting 102
3.8.1.3 Factors Affecting Choice of a Forecast Method 102
Description of Different Methods 102
Persistence Method (Method of Similarity) 102
Trend Method 103
Climatological Average Method 103
Analog Method 103
Statistical Method 103
Numerical Method 104
Discussion 104
3.8.2 Application of Weather Forecasting in Agricultural Decision Making 104
3.8.2.1 Application of Weather Forecast 105
3.8.3 Copying Strategy for Hazardous Weather Phenomena 105
3.8.3.1 Challenges 106
3.9 Agro-Climatic Indices 107
3.9.1 Use of Climatic Indices and Heat Units 107
3.9.2 Different Indices and Their Description 107
3.9.2.1 Degree-Days or Growing-Degree-Days (GDD) 107
3.9.2.2 Crop Heat Unit 108
3.9.2.3 Heliothermal Unit 108
3.9.2.4 Photo-Thermal Unit 109
3.9.2.5 Heat-Use Efficiency 109
3.9.3 Examples on Heat Unit Requirement of Crop 110
3.10 Climatic Potential Yield 111
3.10.1 Concept and Mathematical Formulation 111
3.10.2 Example on Calculation of Climatic Potential Yield 112
3.11 Agro-Climatic Classification for Crop Suitability 113
3.12 Greenhouse Effect and Its Consequences 114
3.12.1 Concept and Causes of Green House Effect 114
3.12.1.1 Green House Effect 114
3.12.1.2 Greenhouse Gases and Process of Their Development 115
3.12.1.3 Warming Potential of Green House Gases 117
3.12.1.4 Trends of the Greenhouse Gas Concentrations 117
3.12.1.5 Cyclic Variation of Greenhouse Gases 117
3.12.2 Possible Consequences of the Greenhouse Gases 117
3.12.3 Remediation/Abatement of Greenhouse Gas Generation 118
3.13 Climate Change and Crop Production 119
3.13.1 Meaning of Climate Change 119
3.13.2 Impact of Climate Change 120
3.13.2.1 General Impact on Society and Agriculture 120
3.13.2.2 Physical Impacts 120
3.13.2.3 Social Impacts 121
3.13.2.4 Agricultural Impact 121
3.13.2.5 Economic Impacts 121
3.13.2.6 Ecosystem 121
3.13.2.7 Impact on Crop Production 122
Carbon Dioxide 122
Temperature 122
Through Availability of Water 123
Effect of Higher Temperature on Crop Adaptability, Growth Acceleration, or Deceleration 123
Inhibition Through Low Temperature 123
Relevant Journals 123
FAO Papers 124
Exercise/Questions 124
References 126
Chapter 4: Soil: A Media for Plant Growth 128
4.1 Basics of Soil 128
4.1.1 Definition of Soil 128
4.1.2 Agricultural Soil 129
4.1.3 Components of Soil 129
4.1.4 Importance of Soil for Irrigation 130
4.2 Physical Properties of Soil 131
4.2.1 Qualitative Description of Soil Physical Properties 131
4.2.1.1 Color 132
4.2.1.2 Texture 132
4.2.1.3 Tilth 132
4.2.1.4 Slope 132
4.2.1.5 Depth 132
4.2.1.6 Water Holding Capacity and Drainability 133
4.2.1.7 Bulk Density 133
4.2.1.8 Specific Heat Capacity 133
4.2.2 Description and Measurement Techniques of Important Soil Physical Properties 133
4.2.2.1 Bulk Density 133
Understanding Soil Density 133
Definition of Soil Bulk Density 134
Factors Affecting Bulk Density 135
Typical Values of Bulk Density 136
Importance of Bulk Density 136
Determination of Bulk Density 136
Core Method 136
Clod Method 137
Excavation Method 139
Radiation Method 139
Regression Method (Indirect Estimation of Bulk Density) 140
Examples on Bulk Density and Moisture Determination 140
4.2.2.2 Particle Density 141
4.2.2.3 Soil Texture 141
Concept 141
Analysis of Particle Size 142
Hydrometer Method 143
Modifying Soil Texture 144
4.2.2.4 Soil Structure 144
Concept 144
Characterization 145
Significance 145
4.2.2.5 Porosity 145
Factors Affecting Porosity 145
Estimation of Porosity 146
Typical Values of Porosity 146
Relation Between Bulk Density, Particle Density, and Porosity 146
Relationship Between Porosity and Void Ratio 147
4.2.2.6 Mechanical Impedance 147
4.2.3 Infiltration 148
4.2.3.1 Concept 148
4.2.3.2 Infiltration Rate, Infiltration Capacity, and Other Relevant Terminologies 148
4.2.3.3 Significance of Infiltration 148
4.2.3.4 Factors Affecting Infiltration 149
Fluid Factor 149
Flow Condition 149
Management Practices 149
4.2.3.5 Typical Infiltration Curve 150
4.2.3.6 Infiltration Conditions 150
4.2.3.7 Mathematical Statement of Water Movement in Soil 151
Darcy´s Equation 151
Richards´ Equation 152
Other Forms of Richard´s Equation 154
Approximations/Assumptions in Richards´ Equation 154
Effect of Soil-Air 154
Soil Swelling 155
Non-Darcian Flow 155
Horizontal Infiltration (Absorption) of Water from Cracks 155
Vertical Infiltration of Rain or Irrigation Water 156
Flow of Water in a Heterogeneous Soil-Root System 156
Darcian Flux or Flux Density and Flow Velocity 157
4.2.3.8 Solutions of the Richards´ Equation 157
4.2.3.9 Empirical Infiltration Equations 158
Horton´s Equation 159
Collis-George´s Equation 159
Green-Ampt Equation 159
Kostiakov Equation 160
Modified Kostiakov Equation 160
Branch Equation 161
4.2.3.10 Measurement of Infiltration 161
Single Ring Infiltrometer 161
Operational Technique 162
Double Ring Infiltrometer 162
Example on Infiltration Test Data Processing 163
4.2.4 Importance of Soil Physical Properties 164
4.2.4.1 Application of Principles of Soil Physical Properties to Field Problem 164
Case 1: A Layer of Finer Material Over a Coarser Material 164
Case 2: A Layer of Coarser Sand Over a Finer Material 165
4.2.4.2 Relation of Irrigation Scheduling and Drainage to Physical Properties of Soil 165
4.3 Chemical Properties of Soil 165
4.3.1 Soil pH 166
4.3.1.1 Definition and Expression of Soil pH 166
4.3.1.2 Causes for Acid Soils 166
4.3.1.3 Sources of H+ Ions in the Soil 166
4.3.1.4 Soil pH Determination 167
pH Determination Using pH Meter 167
4.3.2 Soil Cation Exchange 168
4.3.2.1 Concept 168
4.3.2.2 Factors Affecting Cation Exchange 168
4.3.2.3 Cation Exchange Capacity 168
4.3.2.4 Expression of Cation Exchange 168
4.3.2.5 Predicting CEC 169
4.4 Soil Hydraulic Properties 170
4.4.1 Importance of Soil Hydraulic Properties 170
4.4.2 Determination of Different Soil-Water Constants 170
4.4.2.1 Water Holding Capacity/Water Retention Capacity/Field Capacity 170
Determination of Water Holding Capacity 171
4.4.2.2 Saturation Capacity/Maximum Water Holding Capacity 173
4.4.2.3 Permanent Wilting Point Soil Moisture 173
4.4.3 Measurement of Soil Water 173
4.4.3.1 Concept, Factors Affecting Soil-Water and Measurement Approaches 173
Soil-Water Content 173
Factors Affecting Soil Water 173
Soil Texture 174
Soil Structure 174
Pore Space 174
Overburden Pressure or Compaction 174
Soil Water Measurement 174
4.4.3.2 Gravimetric Moisture Determination 175
Principle of the Method 175
General Considerations 175
Detail Systematic Working Method 176
Advantages of Gravimetric Method 177
Disadvantages 177
4.4.3.3 Radiological Method 178
Neutron Scattering Technique 178
Principle 178
Theory of Radiation 178
Radiological Terminologies 180
Working Procedure 181
Analyzing the Moisture Data 183
Philosophy of the First Method 183
Examples Explaining Moisture Calculation 184
Precautions and Protective Measures in Radiological Method 185
Gamma Attenuation Method 186
4.4.3.4 Electromagnetic Method 187
Concept 187
The TDR Instrument 187
Principle 187
Theoretical 187
TDR Options 189
TDR Sensors 189
Method 189
4.4.3.5 The Diviner 190
Description 190
Advantages Over Other Tools/Techniques 191
4.4.3.6 Electrical Resistance Block/Gypsum Block 191
Principle of the Method 192
4.4.3.7 Tensiometry Method 192
Principle of the Method 193
Drawbacks/Limitations of Tensiometer 193
Field of Use 194
Working Method 194
Preparing a Calibration Curve 194
Taking a Reading for Moisture Determination 195
4.4.3.8 Quick Draw Moisture Meter Method 196
4.4.3.9 Hand-Feel Method 197
4.4.3.10 Other Advance Methods 197
Psychrometer Method 197
Thermal Methods 197
Nuclear Magnetic Resonance Method 197
4.4.4 Soil-Water Potentials and Other Related Terminologies 198
4.4.4.1 Total Potential of Soil Water 198
Osmotic Potential 198
Capillary or Matric Potential 198
Gravitational Potential 199
4.4.4.2 Related Terminologies 199
Hydraulic Head 199
Differential Water Capacity 200
4.4.5 Determination of Soil Moisture Characteristics 200
4.4.5.1 Conceptualization of Soil Moisture Characteristics 200
Definition of Soil Moisture Characteristics 200
Importance of Soil Moisture Characteristics 201
Methods for Determining SMC Curve 201
4.4.5.2 Moisture Determination at Low Tension 201
Collection and Preparation of Core-Soil Sample 202
Porous Plate Method 202
Sand Table Method 202
Drainage Pipe at the Side 203
Drainage Pipe at the Bottom 204
4.4.5.3 Moisture Determination at High Tension 204
By Pressure Plate Apparatus 204
Principle of Pressure Plate Desorption Method 204
Description of Pressure Plate Apparatus 204
Materials and Methods 204
Example on Moisture Calculation from Pressure Plate Calculation 207
4.4.5.4 Indirect Estimation of Soil Moisture Characteristic 208
Statistical Approach 209
From Soil Physical Properties 209
4.4.5.5 Soil Moisture Characteristic Function 209
4.4.5.6 Hysteresis in Soil-Water Retention 211
Concept 211
Factors Affecting Hysteresis 212
4.4.5.7 Soil-Water Diffusivity 212
Definition, Importance/Significance, Measurement 212
Estimation of D from Intact Soil Core Evaporation 213
4.4.6 Hydraulic Conductivity 214
4.4.6.1 Water Movement Through Soil 214
Concept of Hydraulic Conductivity 214
Factors Affecting Hydraulic Conductivity 215
4.4.6.2 Measurement of Saturated Hydraulic Conductivity (Ksat) 215
Field Measurement of Ksat 215
Laboratory Measurement of Ksat 219
Core Method 219
Other Instruments/Methods 220
4.4.6.3 Measurement of Unsaturated Hydraulic Conductivity (Kunsat) 221
Instantaneous Profile Method 221
Internal Drainage Method 222
By Saturating Unsaturated Soil Core or Column 225
4.4.7 Swelling and Shrinkage Properties of Soil 226
4.4.7.1 Concept of Swelling and Shrinkage, and Extent of Cracking Clay Soil 226
4.4.7.2 General Properties and Behavior of Cracking Clay Soil 226
4.4.7.3 Shrinkage Curve 226
4.4.7.4 Problems with Cracking Clay Soil in Relation to Water Management 227
4.4.7.5 Problems of Applying General Approaches to Describe/Simulate Water Flow in Cracking Clay Soil 228
4.4.7.6 Determination of Shrinkage Characteristics 228
Balloon Method 229
Saran Resin Method 229
Principle of Saran Resin Method 229
4.4.7.7 Functional Form of Swelling and Shrinkage 230
Geometry of Shrinkage 230
Logistic Model of Shrinkage Characteristics 231
4.4.8 Biological Properties of Soil 231
4.4.8.1 Concept 231
4.4.8.2 Classification of Soil Organisms 232
4.4.8.3 Beneficial Effects of Soil Organisms 232
4.4.8.4 Factors Affecting Organism Populations 232
4.4.9 Improvement of Soil Physical, Chemical, and Biological Properties 233
4.4.9.1 Soil or Land Degradation 233
4.4.9.2 Monitoring Indicators of Different Properties 233
4.4.9.3 Means of Improvement of Different Properties 234
Improvement of Soil Physical Properties 234
Improvement of Soil Chemical Properties 234
Improvement of Soil Biological Properties 235
4.4.9.4 Organic Farming 235
Relevant Journals 235
FAO Soil Bulletins 236
Questions 236
References 237
Chapter 5: Plant: A Machinery of Water Absorption 240
5.1 General Overview and Types of Plant 240
5.1.1 General Overview 240
5.1.2 Types of Plants 241
5.1.2.1 Terrestrial and Aquatic Plants 241
5.1.2.2 C3 and C4 Plants 242
5.1.2.3 CAM Plants 242
5.2 Development of Plants 242
5.2.1 Growth Stages of Field Crops 242
5.2.1.1 Numerical Measures of Growth and Development 243
5.2.1.2 Feekes Scale 243
5.2.1.3 Zadoks Scale 244
5.2.1.4 Haun Scale 246
5.2.1.5 Comparison Among Feekes, Zadoks, and Haun Scales 246
5.2.2 Growth and Development of Cereals: Example with Wheat Plant 246
5.2.2.1 Growth Stages of Wheat 246
Some Relevant Terminologies 248
Description of Growth Stages 249
Germination 249
Seedling Stage 250
Tillering and Head Differentiation 250
Stem and Head Growth 250
Head Emergence and Flowering 251
Milk Stage 251
Dough Development Stage 251
Ripening Stage 252
5.2.2.2 Critical Growth Stages of Wheat 252
5.2.2.3 Grain Yield Production 253
Sources of Photosynthates for Grain Yield 253
Expression of Wheat Yield 253
5.2.3 Thermal Time Requirement of Crop 253
5.3 Structure of Plant 254
5.3.1 General Structural Overview 254
5.3.2 Root Growth and Development 255
5.3.2.1 Root Growth 255
5.3.2.2 Structure of Root 256
5.3.2.3 Relation of Roots to Soil Moisture 257
5.3.2.4 Factors Affecting Root Development and Adaptation 257
5.3.2.5 Transport of Assimilates 258
Xylem Transport 258
5.4 Crop Growth Factors 258
5.4.1 Climatic Factors 259
5.4.1.1 Temperature 259
5.4.1.2 Solar Radiation 259
5.4.1.3 Carbon dioxide Levels 259
5.4.2 Water and Nutrient Supply 260
5.4.2.1 Water Supply 260
5.4.2.2 Nutrient Supply 260
5.5 Crop Growth Parameters 260
5.5.1 Leaf Area Index 260
5.5.1.1 Determination of LAI 261
5.5.2 Growth Rate and Relative Growth Rate 262
5.5.3 Root Study 263
5.5.3.1 Root Length Density 263
5.5.3.2 Method of Root Sampling 263
Auger Hole Method 263
Pit Sampling/Soil Monolith Sampling 264
Processing of the Sample and Preparing the Roots for Measurement 264
5.5.3.3 Measurement of Roots 265
Length Measurement 265
Taking Weight of Roots 265
Root to Shoot Weight Ratio 265
5.5.3.4 Increasing Available Water Supply for Plant Root 265
5.6 Dry-Matter Production in Plant and Its Partitioning 266
5.6.1 Determination of Total Biomass or Drymatter 266
5.6.2 Indices of Drymatter Partitioning 266
5.6.2.1 Root-Shoot ratio 266
5.6.2.2 Harvest Index 266
5.6.2.3 Harvest Ratio 267
5.6.3 Assimilate Partitioning/Remobilization of Prestored Carbon 267
5.6.4 Improving Assimilate Partitioning to Grain 268
5.7 Plant Water Relations 268
5.7.1 Theoretical Perspectives 268
5.7.2 Indices of Plant-Water Relations 269
5.7.3 Water Potential in Plant 270
5.7.3.1 Components of Water Potential 270
5.7.3.2 Osmotic Potential 270
5.7.3.3 Turgor Potential 270
5.7.3.4 Factors Affecting Plant Water Potential 270
5.7.3.5 Adjustment of Plant-Water Relations Components 271
5.7.4 Leaf Water Potential 271
5.7.4.1 Total Leaf Water Potential 271
Procedure for Estimation of Total Leaf Water Potential 272
5.7.4.2 Leaf Osmotic Potential 272
5.7.4.3 Turgor Pressure 273
5.7.5 Water Content/Water Retention 273
5.7.6 Relative Water Content/Relative Turgidity 273
5.7.6.1 Procedure for the Measurement of Relative Water Content 273
5.7.7 Relative Saturation Deficit 274
5.7.7.1 Determination of RSD 274
5.7.8 Relation Between Leaf Water Potential and Relative Water Content 274
5.7.8.1 Leaf Water Potential vs. Relative Water Content 275
5.8 Plant Biochemical and Physiological Aspects 275
5.8.1 Plant Biochemical Aspects 275
5.8.1.1 Photosynthesis 275
5.8.1.2 Leaf Chlorophyll and Sugar Content 276
5.8.2 Physiological Aspects 276
5.8.2.1 Transpiration Rate 276
Control of Transpiration 276
Measurement of Transpiration Rate 277
Transpiration Estimates by Gravimetric Method 277
5.8.2.2 Respiration 278
5.9 Water and Nutrient Uptake 278
5.9.1 Water Uptake Theory 278
5.9.1.1 Active Absorption 278
5.9.1.2 Passive Absorption 278
5.9.2 Nutrient Uptake 279
5.9.2.1 The Contact Exchange and Root Interception 280
5.9.2.2 Mass Flow or Convection 280
5.9.2.3 Diffusion 281
5.10 Critical Growth Stages of Plant and Water Demand for Whole Growth Period 281
5.10.1 Critical Growth Stages 281
5.10.2 Water Demand 282
5.11 Plant Adaptation to Stress/Drought: Stress Physiology 282
5.11.1 Mechanisms of Plant Survival 282
5.11.1.1 Drought Avoider 283
5.11.1.2 Drought Tolerator 283
5.11.1.3 Desiccation Tolerance 283
5.11.1.4 Dehydration Tolerance 284
5.11.2 Drought Tolerance Mechanism 284
5.11.2.1 Adaptive Response 284
5.11.2.2 Osmotic Adjustment 285
Chemicals in Osmotic Potential 286
Determination of Osmotic Adjustment 286
5.11.2.3 Other Reason/Mechanism for Plant Adaptation 286
Stress Preconditioning 286
5.11.3 Yield Estimation Under Drought Condition 286
5.12 Plant Production Models 287
5.12.1 APSIM 288
5.12.2 CropSyst 288
5.12.3 Oryza2000 288
5.12.4 SUCROS 288
Relevant Journals 289
Questions 289
References 290
Chapter 6: Water: An Element of Irrigation 292
6.1 Sources and Uses of Water 292
6.2 Special Characteristics of Water 293
6.3 The Hydrologic Cycle 293
6.3.1 Concept and Definition 293
6.3.2 Processes Involved in Hydrologic Cycle 294
6.3.3 Impact of Hydrologic Cycle 296
6.4 Water Quality Assessment 297
6.4.1 Meaning of Water Quality 297
6.4.2 Factors Affecting Quality of Water 297
6.4.3 Factors Affecting Suitability of Water for Irrigation 298
6.4.4 Water Quality Indicators/Parameters and Their Description 298
6.4.4.1 Color 299
6.4.4.2 Temperature 300
6.4.4.3 Electrical Conductivity 300
6.4.4.4 pH 300
6.4.4.5 Dissolved Oxygen 301
6.4.4.6 Turbidity 301
6.4.4.7 Total Suspended Solid 302
6.4.4.8 Biochemical Oxygen Demand 302
6.4.4.9 Chemical Oxygen Demand 303
6.4.4.10 Micro-Organisms 303
6.4.4.11 Total Dissolved Solids 303
6.4.4.12 Nutrients Such as Phosphorus, Nitrogen, and Zinc 303
Phosphorus 303
Nitrogen 304
Zinc 304
6.4.4.13 Some Toxic Elements 304
Boron 304
Nitrate 304
Chloride 304
Iron 305
6.4.4.14 Dissolved Metals and Metalloids 305
Arsenic 305
Lead 305
Cadmium 306
Copper 306
6.4.4.15 Radioactive Elements 306
6.4.4.16 Pesticides, Herbicides, and Organics 306
6.4.4.17 Composite Indices 307
Sodium Absorption Ratio 307
Residual Sodium Carbonate 307
Kelley´s Ratio 307
Total Hardness 308
TDS 308
Salt Index 308
6.4.5 Water Quality Evaluation: Standards and Guidelines 309
6.4.5.1 Irrigation Water Quality 309
6.4.5.2 Assumptions in the Guideline 309
6.4.5.3 Drinking Water 311
Standard for Arsenic 311
6.4.6 Classification of Water for Its Quality Based on Different Parameters 313
6.5 Water Analysis: Measuring the Quality of Water 313
6.5.1 Analytical Methods 313
6.5.2 Some-Related Terminologies and Relationships 316
6.5.2.1 Milliequivalent Per Liter 316
6.5.2.2 Molar Solution 316
6.5.3 Workout Problems on Assessing Water Quality 317
6.5.4 Checking the Correctness of Water Analysis 319
6.5.4.1 Checking Methods 319
Anion-Cation Balance 319
Measured and Calculated TDS Balance 319
Measured and Calculated EC Balance 319
Calculated or Measured TDS to EC Ratio 320
6.5.4.2 Workout Problems on Checking Correctness of Water Analysis 320
Solution 320
Solution 321
6.6 Problems with Marginal/Poor Quality Irrigation Water for Crop Production 321
6.6.1 Major Issues and Considerations 321
6.6.2 Impact on Soil Physical Properties 322
6.6.3 Problem of Toxicity 322
6.6.4 Other Miscellaneous Problems 322
6.6.5 Yield Decrease Due to Poor Quality Water 323
6.7 Coping Strategies in Using Poor/Marginal Quality Irrigation Water for Crop Production 323
6.7.1 Management Strategies in Using Poor Quality Irrigation Water 323
6.7.1.1 Leaching 324
6.7.1.2 Neutralizing the Effect of Some Elements by Adding Ameliorants 324
6.7.1.3 Mixing of Different Quality Water 325
6.7.2 Workout Problems on Water Mixing and Leaching 325
6.8 Water Quality of River and Stream 327
6.9 Water Quality Models and Tools 327
6.9.1 Models 327
6.9.2 Tools 329
6.10 Contamination/Pollution of water 329
6.10.1 Major Sources of Water Contaminants 329
6.10.1.1 Agricultural Field and Rural Areas 330
6.10.1.2 Industrial Effluents 330
6.10.1.3 Urban Storm Water Runoffs 330
6.10.1.4 Residential and Municipal Sources 330
6.10.1.5 Radioactive Waste Disposal 330
6.10.1.6 Mining Operations 331
6.10.1.7 Processing of Wood 331
6.10.2 Arsenic Contamination: Causes, Consequences, and Mitigation/Remedial Measures 331
6.10.2.1 Extent of the Problem 331
6.10.2.2 Sources of Arsenic 332
Arsenic Containing Rocks 332
Industrial Effluents 333
Inorganic Arsenic 333
Agricultural Use of Herbicides, Pesticides 333
Other Sources 333
Properties of Arsenic 333
6.10.2.3 Forms of Arsenic 334
6.10.2.4 Toxic Effects of Arsenic 334
6.10.2.5 Causes/Theories of Arsenic Contamination 334
Oxy-Hydration/Reduction Theory 335
Oxidation Theory 335
6.10.2.6 Effects and Consequences of Arsenic Contamination/Poisoning 335
Health Effects 336
Effects on Crop Production 336
Social Effects 337
6.10.2.7 Mitigation/Remedial Measures of Arsenic Contamination 337
Strategic Measures 337
Removal Techniques of Arsenic from Water 338
Coagulation 338
Softening 338
Ion exchange 339
Reverse Osmosis 339
Oxidation and Filtration Process 339
Adsorption 339
Simple and Indigenous Approaches for Arsenic Removal 339
Decantation-Filtration Method 340
Pond sand filter 340
Three Pitchers Methods 340
6.10.2.8 Challenges and Needs 341
6.11 Protecting Water Quality 341
6.11.1 Protection Measures Against Potential Sources of Contamination 341
6.11.1.1 Controlling Commercial and Industrial Sources 342
6.11.1.2 Residential and Municipal Sources 342
6.11.1.3 Storm Water Runoff 342
6.11.1.4 Agricultural and Rural Sources 342
6.11.2 Management Measures 343
6.11.2.1 Regulatory Approach 343
6.11.2.2 Land-Use/Land Acquisition 343
6.11.2.3 Education 343
6.12 Treatment of Water 344
6.12.1 Different Methods of Treatment 344
6.12.2 Physical Treatment 344
6.12.2.1 Sedimentation 345
6.12.2.2 Filtration 345
6.12.2.3 Adsorption 345
6.12.2.4 Aeration 346
6.12.2.5 Distillation 346
6.12.2.6 Reverse Osmosis 346
6.12.3 Chemical Treatment 346
6.12.3.1 Flocculation/Coagulation 346
6.12.3.2 Ion Exchange 347
6.12.3.3 Softening 347
6.12.4 Biological Treatment 347
6.12.5 Water Purification in a Treatment Plant 347
Relevant Journals 348
Relevant FAO Irrigation and Drainage Papers 349
Questions 349
References 350
Chapter 7: Field Water Balance 351
7.1 Concepts, Sketch, and Mathematical Form of Field Water Balance 351
7.1.1 Concept of Field Water Balance 351
7.1.2 Mathematical Formulation 352
7.1.3 Limiting Conditions of the Water Balance Components 353
7.1.3.1 Upward Flux 353
7.1.3.2 Surface Runoff 353
7.1.3.3 Deep Percolation 354
7.2 Determination of Different Components of Water Balance 354
7.2.1 Evapotranspiration 354
7.2.1.1 Factors Influencing Evapotranspiration 355
Crop Factor 355
Crop Characteristics 355
Leaf Number and Leaf Area 355
Leaf Architecture 356
Leaf Rolling or Folding 356
Root Factor 356
Stomatal closure 356
Weather Factor 356
Soil Factor 356
Management Factor 357
7.2.1.2 Determination of ET 357
Direct Measurement 357
Field Measurement 357
Measurement by Lysimeter 358
7.2.1.3 Indirect Estimation of ET 360
Estimation of ET0 361
FAO Penman-Monteith Equation 361
FAO Temperature (Blaney-Criddle) Method 361
FAO Radiation Method 362
Hargreaves and Samani Method 363
Determination of Crop Coefficient (Kc) 363
Single Crop Coefficient 363
Dual Crop Coefficient 364
Factors Affecting Kc 364
Expression of Kc 365
Kc vs. Time 366
Kc vs. Percent Effective Cover 366
Kc vs. Heat Unit, Kc vs. LAI 366
Kc vs. Growth Stage 367
Other Empirical Formula for Estimating Evapotranspiration 367
Potential Evapotranspiration 368
7.2.2 Evaporation 368
7.2.2.1 Concept and Importance of Evaporation 368
7.2.2.2 Evaporation Process 369
Evaporation from Free Water Surface 369
Evaporation from Soil Surface 369
7.2.2.3 Factors Influencing Evaporation 369
Evaporation from Free Water Body 369
Available Energy 370
Humidity (Actual and Relative) of Adjacent Air 370
Temperature of the Air 370
Flow of Air Above the Water Surface 370
Impurities of Water 370
Pressure over the Surface 370
Evaporation from Soil Surface/Crop Field 370
Amount of Soil Water 371
Type of Soil 371
Percent Shading/Bare Surface 371
Rate of Drying 371
Tillage or Mulching 372
7.2.2.4 Measurement/Estimation of Evaporation from Free Water Surface 372
Direct Measurement 372
Estimation of Evaporation by Empirical Equations 372
Dalton Equation 372
Penman Equation 373
Mayer Formula 373
Rohwer Formula 373
Measurement of Evaporation by Evaporation Pan 374
Description and Operation of USWB Class-A Pan Evaporimeter 374
Measurement of Evaporation in USWB Pan 375
Pan Coefficient 375
Relation Between Evapotranspiration and Pan Evaporation 375
7.2.2.5 Evaporation from Bare Soil and Crop Field 376
Bare Soil 376
Cropped Soil 376
7.2.2.6 Effect of Salinity on Evaporation 376
7.2.3 Surface Runoff 377
7.2.4 Deep Percolation or Deep Drainage 377
7.2.4.1 Concept 377
7.2.4.2 Factors Affecting Deep Percolation 378
7.2.4.3 Determination of Deep Percolation 378
From Field-Plot Water Balance 379
By Drainage Lysimeter 379
By Darcian Flux Calculation 380
Chloride Mass Balance in Soil 380
Water Table Rise 381
7.2.4.4 Typical Deep Percolation Rates 381
7.2.5 Upward Flux/Capillary Rise from Water-Table 382
7.2.5.1 Concept and Its Importance 382
7.2.5.2 Factors Affecting Upward Flow/Ground-Water Table Contribution 382
7.2.5.3 Estimation of Upward Flux 383
In the Absence of a Zero Flux Plane 383
In Presence of a Zero Flux Plane 384
Empirical Equations for Estimating Water-Table Contribution 384
7.2.5.4 Magnitude of Contribution of Upward Flow 385
7.2.6 Determination of Change in Soil-Water storage 385
7.2.7 Workout Problems 386
Relevant Journals 391
FAO Papers 391
Questions/Exercises 391
References 392
Chapter 8: Soil-Water-Plant-Atmosphere Relationship 393
8.1 Concept of Soil-Plant-Atmospheric Continuum 393
8.1.1 Some-Related Concepts/Terminologies 394
8.1.1.1 Water Potential 394
8.2 Soil-Water-Plant-Atmosphere Interrelations 395
8.2.1 Different Soil-Water Coefficients 395
8.2.1.1 Field Capacity 395
8.2.1.2 Permanent Wilting Point 395
8.2.1.3 Saturation Capacity 395
8.2.1.4 Water Holding Capacity or Water Retention Capacity 395
8.2.1.5 Effect of Load on Water Retention 396
8.2.1.6 Maximum Available Moisture or Maximum Plant Available Moisture 396
8.2.1.7 Maximum Readily Available Moisture 397
8.2.1.8 Presently Available Soil Moisture 397
8.2.1.9 Depletion of Available Soil Water 398
8.2.1.10 Air Entry Suction or Air Entry Potential 398
8.2.2 Plant-Water Relations 398
8.2.3 Soil Wetness and Evaporation Relationship 399
8.2.3.1 Empirical Equation of Evaporation from Soil 400
8.2.4 Root Water Uptake in Relation to Soil-Moisture 400
8.2.4.1 Flow of Water to Plant Roots 401
8.2.5 Hydraulic Conductance in Soil-Leaf Pathway 402
8.2.6 Plants Response to Soil Moisture Deficit 403
8.2.6.1 Factors Affecting Plant Response to Water Stress 403
The Frequency of ``Deficit or Drought´´ and Wet Periods 404
Degree and Duration of Drought 404
The Speed of Onset of Drought 404
The Pattern of Soil-Water Deficit 404
The Sequence of Deficit 404
The History of Deficit 405
The Cultivar or Species 405
Growth Stage of the Crop 405
8.2.6.2 Effects of Water Stress on Plant System 405
Germination 406
Plant Stand 407
Tillering 407
Lai 407
Nutrient Uptake 407
Yield Reduction 408
Assimilate Partitioning/Harvest Ratio 408
Radiation Use Efficiency and Dry Matter Production 408
8.2.7 Water Flow Through Soil-Plant-Atmospheric Continuum 408
8.2.7.1 Flow from Soil Through Root to the Vascular System 409
8.2.7.2 Longitudinal Flow in the Xylem 410
8.2.7.3 From the Xylem to the Sub-Stomatal Cavities in the Leaf 410
8.2.7.4 Stomatal Control of Transpiration 410
8.2.8 ET Under Depleting Moisture 411
8.2.8.1 Woodhead´s Equation 411
8.2.8.2 Jensen Model 412
8.2.8.3 Modified Jensen Model 412
8.2.9 Workout Problems 413
References 417
Chapter 9: Crop Water Requirement and Irrigation Scheduling 418
9.1 Crop Water Requirement 418
9.1.1 Definition 418
9.1.2 Factors Affecting Crop Water Requirement 419
9.1.2.1 Crop Factor 419
9.1.3 Calculation/Estimation of Crop Water Requirement 420
9.1.4 Difference Between Crop Water Requirement and Irrigation Water Requirement 420
9.1.5 Water Requirement of Major Field Crops 421
9.2 Irrigation Water Requirement 421
9.2.1 Factors Affecting Irrigation Requirement 422
9.2.1.1 Soil Factor 422
9.2.2 Components of Total Water Requirement for Irrigation 422
9.2.2.1 Water Requirement for Land Soaking 422
9.2.2.2 Water Requirement for Land Preparation 423
9.2.2.3 Water for Leaching 423
9.2.2.4 Net Irrigation Water Requirement for Normal Growth Period (Wnci) 424
9.2.3 Total Irrigation Water Requirement 424
9.2.3.1 Total Net Irrigation Water Requirement 424
9.2.3.2 Gross Irrigation Water Requirement (Wgross) 425
9.2.4 Sample Examples on Calculation of Irrigation Water Requirement 426
9.3 Basics of Irrigation Scheduling 427
9.3.1 Concept of Scheduling 427
9.3.2 Indicators of Irrigation Need Assessment 428
9.3.3 Factors Affecting Irrigation Scheduling 428
9.3.3.1 Goal/Strategy of Irrigation 429
9.3.3.2 Soil Factor 430
9.3.3.3 Weather Factor 431
9.3.3.4 Water-Table Depth 431
9.3.3.5 Design of the Existing Irrigation System 431
9.3.3.6 Volume of Soil to Be Irrigated 431
9.3.3.7 Cultural Management 431
9.3.3.8 Economic Factor 432
9.3.4 Common Irrigation Scheduling Methods Used by the Farmers 432
9.3.5 Advanced Irrigation Scheduling Approaches 432
9.3.6 Factors Influencing Choice of Irrigation Scheduling Method 433
9.4 Description of Different Irrigation Scheduling Methods or Approaches 433
9.4.1 Climatic Approach/Evapotranspiration Basis 433
9.4.1.1 Shortcomings 434
9.4.2 Pan Evaporation 434
9.4.2.1 Shortcoming 435
9.4.3 Crop Growth Stage Basis 435
9.4.3.1 Advantage 436
9.4.3.2 Shortcomings 436
9.4.4 Soil Moisture Basis 436
9.4.4.1 Irrigation Scheduling Using Neutron Probe 436
9.4.4.2 Advantage 437
9.4.4.3 Shortcoming 437
9.4.5 Deficit Irrigation 437
9.4.5.1 Background 437
9.4.5.2 Concept and Definition 438
9.4.5.3 Need of Deficit Irrigation 438
9.4.5.4 Modes of Deficit Irrigation 439
9.4.5.5 Procedure for Adopting Deficit Irrigation 439
9.4.5.6 Risk/Uncertainty, Advantage, and Constraint of Deficit Irrigation 439
Risk 439
Advantages 440
Constraints 440
9.4.5.7 Reasons/Mechanisms for Increased Water Productivity Under Deficit Irrigation 440
9.4.5.8 Deficit Irrigation and Wheat Yield Relationship 441
9.4.5.9 Deficit Irrigation and Rice Yield Relationship 441
9.4.5.10 Yield and Water Productivity Relationship Under Deficit Irrigation 441
9.4.6 Soil Water Potential 442
9.4.7 Leaf Water Potential 442
9.4.7.1 Shortcomings 444
9.4.8 Stress Day Index 444
9.4.8.1 Stress Day Factor 444
9.4.8.2 Crop Susceptibility Factor 445
9.4.8.3 Advantage of SDI Method 445
9.4.8.4 Shortcoming 446
9.4.9 Irrigation Calendar 446
9.4.9.1 Shortcomings 446
9.4.10 Soil-Moisture Balance Approach or Check-Book Approach 447
9.4.10.1 Concept and Methodology 447
9.4.10.2 Disadvantages 447
9.4.11 Modeling Approach for Irrigation Management 447
9.4.11.1 Limitations/Shortcomings 449
9.4.12 Real-Time Irrigation Scheduling System 449
9.4.12.1 Shortcoming of Real-Time Irrigation Scheduling 450
9.4.13 Irrigation Scheduling Under Limited/Variable Water Supply, Variable Rainfall, and Saline Condition 450
9.4.13.1 Challenges 451
9.4.14 Sample Workout Problems on Irrigation Scheduling 451
9.5 Irrigation Command Area Designing 456
9.5.1 Concept of Command Area 456
9.5.2 Relevant Terminologies 456
9.5.2.1 Gross Command Area 456
9.5.2.2 Culturable or Cultivable Command Area 456
9.5.2.3 Intensity of Irrigation 457
9.5.2.4 Peak Irrigation Demand 457
9.5.2.5 Kor Period and kor Depth 457
9.5.3 Duty, Delta, and Base Period 457
9.5.3.1 Duty 457
9.5.3.2 Delta 458
9.5.3.3 Base Period 458
9.5.3.4 Relationship Among Duty, Delta, and Base Period 458
9.5.4 Factors Affecting Peak Irrigation Demand 459
9.5.5 Identification of Problem in the Command Area 459
9.5.5.1 Checklist of Physical Problems 459
9.5.5.2 Land Development Works 460
9.5.5.3 Financial Aspects 460
9.5.6 Command Area Development 460
9.5.7 Designing Command Area 461
9.5.7.1 Single Crop 461
9.5.7.2 Multiple Crops 461
9.5.8 Sample Layout of a Command Area 462
9.5.9 Sample Examples on Duty-Delta and Command Area 463
Relevant Journals 468
FAO Papers/Reports 468
Questions/Exercises 469
References 470
Chapter 10: Measurement of Irrigation Water 472
10.1 Basics of Water Measurement 472
10.1.1 Purpose of Water Measurement 472
10.1.2 Types of Flow Measuring Devices 473
10.1.2.1 Volumetric Flow Measuring Devices 473
10.1.2.2 Velocity Measuring Devices 474
10.1.2.3 Water Height Measuring Devices 474
10.1.3 Selection of a Water Measuring Device 474
10.1.4 Basic Terminologies and Hydraulic Principles of Flow Measurement 475
10.1.4.1 Flow Rate or Discharge 475
10.1.4.2 Head of the Fluid 475
10.1.4.3 Velocity of Approach 475
10.1.4.4 Continuity Equation 475
10.1.4.5 Fluid Pressure: Pascal´s Law 475
10.1.4.6 Steady and Unsteady Flow 476
10.1.4.7 Bernoulli´s Equation 476
10.1.4.8 Specific Energy 476
10.1.4.9 Critical Depth, Critical Velocity, and Critical Flow 476
10.1.4.10 Flow Through Pitot Tube 477
10.1.4.11 Empirical Equation of Discharge Over Rectangular Weir 478
10.1.4.12 Empirical Equation of Flow Over V-Notch 479
10.1.5 Permanent Flow Measuring Structure 480
10.1.5.1 Characteristics of Flow Measuring Structure 480
10.1.5.2 General Rules for Setting a Flow Measuring Structure 480
10.1.5.3 Setting Permanent Structure/Flume in the Canal 480
Selection of Location 481
Canal Characteristics 481
Formulation of Design Criteria 481
Minimum Freeboard 481
Shape of the Control Section 482
Design 482
10.2 Measurement of Flow in Small Irrigation Channel 482
10.2.1 Area-Velocity Method 482
10.2.1.1 Advantage 483
10.2.1.2 Disadvantage 483
10.2.2 Stream Gauging: Stage-Discharge Relationship 484
10.2.3 By Flume 484
10.2.3.1 Theoretical Aspects 484
10.2.3.2 Types of Flume 485
10.2.3.3 Parshall Flume 485
10.2.3.4 Cut-Throat Flume 486
10.2.4 By Portable Weir 487
10.2.5 By V-Notch 487
10.2.6 Tracer Method 488
10.2.6.1 Concept and Principle 488
10.2.6.2 Criteria of Tracer 488
10.2.6.3 Constant Injection Method 489
Merits 490
Demerits 490
10.2.6.4 Slug Injection Method 490
Merit 490
Demerit 491
10.2.7 Automated Instrumentation 491
10.3 Measurement of Velocity, Area, and Water Depth (or Head) 491
10.3.1 Measurement of Velocity 491
10.3.1.1 Pitot Tube 492
10.3.1.2 Surface Float Method 493
10.3.1.3 Current Meter 493
10.3.1.4 Electromagnetic Gages 493
10.3.2 Measurement of Water Depth 494
10.3.2.1 Ultrasonic Water Depth Meter (or Ultrasonic Level Transmitter) 494
10.3.3 Measurement of Channel Cross-Sectional Area 494
10.3.3.1 Average Ordinate Rule 494
10.3.3.2 Trapezoidal Rule 495
10.3.3.3 Simpson´s Rule 495
10.4 Measurement of Pipe Flow/Pump Discharge 496
10.4.1 Direct Measurement 496
10.4.2 Co-ordinate Method 496
10.4.3 By Orifice meter 498
10.4.3.1 Theory 498
10.4.3.2 Working Principle 498
10.4.4 By Venturimeter 499
10.4.5 By Flume or V-Notch 500
10.5 Sample Workout Problems on Water Flow Rate Measurement 500
Relevant Journals 504
FAO Papers 504
Questions/Exercise 504
References 506
Chapter 11: Water Conservation and Harvesting 507
11.1 Concept and Definition of Water Conservation 507
11.2 Means or Methods of Water Conservation 508
11.2.1 Reducing Evaporation 508
11.2.1.1 From Water Surfaces 508
11.2.1.2 From Crop Field 509
11.2.1.3 Water Harvesting and Runoff Farming 509
11.2.2 Reducing Evapotranspiration 510
11.2.2.1 Improving Irrigation Efficiency 510
11.2.2.2 Irrigation Scheduling 510
11.2.2.3 Alternate Furrow Irrigation 511
11.2.2.4 Changing Crops 511
11.2.2.5 Antitranspirants 511
11.2.2.6 Natural Vegetation and Phreatophytes 511
11.2.3 Seepage Control 512
11.2.4 Reducing Quality Degradation 512
11.2.5 Cloud Seeding 512
11.2.6 Surface Storage and Groundwater Recharge 513
11.2.7 Treating and Reusing Sewage or Other Contaminated Water 513
11.2.8 Using Super-Absorbents 513
11.2.8.1 Factors Affecting Absorbency 514
11.2.8.2 Applications of Super-Absorbents 514
11.3 Water Harvesting 515
11.3.1 Definition 515
11.3.2 Background/The Need of Water Harvesting 515
11.3.3 Historical Overview: Old Practices of Rainwater Harvest 515
11.3.4 Prerequisite of Rainwater Harvesting 516
11.3.5 The Need and Prospects of Water Harvesting: Case Study, Bangladesh 516
11.3.5.1 The Need of Water Harvesting 516
11.3.5.2 Prospects of Water Harvesting 517
11.3.6 Techniques of Rain-Water Harvesting 517
11.3.6.1 Rain-Water Harvest from External Catchment 517
11.3.6.2 In Situ Rain-Water Harvest 518
11.3.6.3 Harvesting in Farm-Pond 518
11.3.6.4 Rain-Water Harvesting with Storage 518
11.3.7 Sample Examples on Rainwater Harvesting 519
11.4 Groundwater Recharge 519
11.4.1 Extent and Magnitude of the Problem 519
11.4.2 Methods of Groundwater Recharge 520
11.4.2.1 Recharge from Natural Water Bodies 520
11.4.2.2 Artificial Recharge 520
11.4.2.3 Recharge from Crop Lands by Making Ridge 521
11.4.2.4 Recharge Through Canal Water Supply During Off-Irrigation Season 521
11.4.2.5 Recharge Through Land-Overflow/Infiltration Basin 521
11.4.2.6 Recharge by Making Dam/Sluice Gates 521
11.4.2.7 Recharge by Making Large Reservoir 522
11.4.2.8 Recharge Through Tube-Well (Recharge Well) 522
11.5 Rubber Dam: A New Prospect of Surface Water Storage/Harnessing 522
11.5.1 Definition and Types of Rubber Dam 522
11.5.2 Different Parts of a Rubber Dam 524
11.5.3 Site Selection for a Dam 525
Relevant Journals 526
Relevant FAO Papers/Water Reports 526
Questions 526
References 527
Chapter 12: Economics in Irrigation Management and Project Evaluation 528
12.1 Economic Aspects in Irrigation Management and Crop Production 528
12.1.1 Water as an Economic Good 529
12.1.2 Typical Criteria of a Technology 529
12.1.3 Significance of Economic Analysis 530
12.2 Basics of Economic Theories and Concepts 531
12.2.1 Demand and Supply 531
12.2.2 Cost and Revenue Curve 532
12.2.2.1 Cost Curve 532
12.2.2.2 Components of Cost of Production 532
12.2.2.3 Revenue or Benefit Curve 533
12.2.2.4 Features of Cost Curve 534
12.2.2.5 Considerations in Calculating Benefit-Cost Ratio 535
Benefit Stream 535
Cost Stream 535
12.2.2.6 Marginal Cost 535
12.2.2.7 Marginal Benefit 536
12.2.2.8 Cost and Revenue Function 537
12.3 Economic Considerations in Irrigation and Crop Production 537
12.3.1 Economic Consequences of Low Irrigation Efficiency 537
12.3.2 Economic Efficiency vs. Irrigation Efficiency 538
12.3.3 Optimal Levels of Water Use 538
12.3.3.1 Land-Limiting Condition 539
12.3.3.2 Water-Limiting Condition 539
12.3.4 Opportunity Cost of Water 540
12.3.5 Farm-Level Profit Maximization 540
12.3.6 Maximizing Social Benefit 540
12.4 Mathematical Formulation for Minimum Cost or Maximum Profit 541
12.4.1 Minimizing Cost 541
12.4.2 Maximizing Net Benefit 541
12.5 Different Water Productivity Indices in Irrigation Management 542
12.5.1 Water Productivity (EET) 542
12.5.2 Productivity of Irrigation Water (Eir) 542
12.5.3 Marginal Productivity of Irrigation Water 542
12.6 Economic Analysis Under Different Resource Constraints and Different Budget Considerations 543
12.6.1 Analysis Under Different Budget Consideration 543
12.6.1.1 Partial Budget Analysis 543
12.6.1.2 Full Budget Analysis 543
12.6.2 Analysis Under Different Resource Constraints 543
12.6.2.1 Land-Limiting Condition 543
Considerations and Procedures of Economic Analysis for Land-Limiting Condition 543
Land Use Cost 544
Operation Cost 544
Interest on Operating Capital 544
Gross Return Calculation 545
Net Return Calculation 545
12.6.2.2 Water-Limiting Condition 545
12.6.3 Example on Economic Analysis for Different Irrigation Management Strategies 545
12.7 Economic and Financial Analysis of Development Projects 548
12.7.1 Different Economic and Financial Indices and Related Terminologies 549
12.7.1.1 Present and Future Values 549
12.7.1.2 Benefit-Cost Ratio 549
12.7.1.3 Least-Cost Analysis 549
12.7.1.4 Cost Effectiveness 549
12.7.1.5 Opportunity Cost 550
12.7.1.6 Initial Investment 550
12.7.1.7 Salvage Value 550
12.7.1.8 Nominal and Real Values (Cost, Benefit, and Interest Rate) 550
12.7.1.9 Income Stream or Cash Flow 551
12.7.1.10 Internal Rate of Return 551
12.7.1.11 Discounting 552
12.7.1.12 Discount Rate 552
12.7.1.13 Compounding 552
12.7.1.14 Discounted Cash Flow 552
12.7.2 Expression of Cost and Benefit 553
12.7.3 Analysis of NPV 555
12.7.3.1 Step 1: Forecasting the Benefits and Costs 555
Cost Forecasting 555
12.7.3.2 Step 2: Determination of Discount Rate 556
Impact of Discount Rate on NPV Estimates 556
12.7.3.3 Step 3: Calculation of NPV 557
12.7.3.4 Step 4: Compare the NPVs of the Alternatives 557
12.7.4 The NPV Curve 557
12.7.5 Discounting/Compounding Formula Under Different Perspectives 558
12.7.5.1 Single Installment/Cash Flow of Money 558
Single Installment Compounding 559
Annual Compounding Rate for Multiple Payments 559
Single Installment Discounting 560
12.7.5.2 Uniform Annual Cash Flow 560
Accumulated Future Value: Compounding 560
Annual Compounding Rate for Multiple Payments 561
Accumulated Present Value - Discounting 561
12.7.5.3 Discrete Non-uniform Annual Cash Flow 561
12.7.6 Project Selection Among Alternatives 562
12.7.6.1 Indicators 562
12.7.6.2 Comparative Merits and Demerits of Each Indicator 562
12.7.6.3 Selection Criteria 563
Mutually Independent Projects 563
Mutually Exclusive Projects 563
12.7.7 Examples on Financial Analysis and Project Selection 563
12.7.7.1 Suggesting the Best Project 568
Relevant Journals 570
Questions 571
References 573
Index 574