Advanced Irrigation and Drainage Techniques

Advanced Irrigation and Drainage Techniques

Advanced Irrigation and Drainage Techniques

By

Sumitra Varman

Advanced Irrigation and Drainage Techniques

Sumitra Varman

ISBN - 9789361524394

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Preface

Welcome to the comprehensive exploration of Irrigation and Drainage Engineering tailored for undergraduate students in the United States. As burgeoning professionals in the field of civil and agricultural engineering, your journey through this book will delve into the intricacies of managing water resources with a focus on irrigation and drainage systems.

Irrigation and Drainage Engineering is a pivotal aspect of sustainable land use and agricultural productivity. This book has been meticulously crafted to provide you, the discerning undergraduate student, with a solid foundation in the principles, theories, and practical applications of water management. Our aim is to equip you with the technical prowess needed to address the challenges posed by an ever-changing climate and growing global population.

Throughout these pages, you will embark on an intellectual voyage exploring fundamental concepts such as soil-water-plant relationships, hydraulics of water conveyance, and the design of efficient irrigation and drainage systems. Real-world case studies and examples drawn from diverse agricultural landscapes will illustrate the relevance and impact of the principles elucidated in this book.

We understand the significance of preparing the next generation of engineers to address the complexities of water resource management. As you immerse yourself in the content presented, envision the role you will play in shaping sustainable practices that ensure food security and environmental stewardship.

I invite you to engage deeply with the material, apply theoretical knowledge to practical scenarios, and cultivate a holistic understanding of Irrigation and Drainage Engineering. Together, let us embark on a journey that not only enhances your technical expertise but also contributes to the collective endeavor of ensuring a resilient and sustainable future.

Table of Contents

Chapter-1

Introduction to Irrigation and Drainage Engineering 1

1.1 Importance of Irrigation 1

1.2 Types of Irrigation Systems 1

1.3 Crops and Water Requirements 4

1.4 Irrigation Efficiencies 4

1.5 Irrigation Management 5

1.6 Environmental Impacts of Irrigation 6

Conclusion 7

References 8

Chapter-2

Soil-Water Relationships 9

2.1 Soil Composition and Classification 9

2.2 Soil Water Potential 10

2.3 Infiltration and Percolation Rates 11

2.4 Soil Moisture Measurement 12

2.5 Solute Transport in Soils 12

Conclusion 13

References 14

Chapter-3

Water Resource Development 15

3.1 Hydrologic Cycle Processes 15

3.2 Precipitation Analysis 16

3.3 Streamflow and Runoff Estimation 17

3.4 Groundwater Occurrence and

Movement 18

3.5 Reservoir and Watershed

Management 18

3.6 Water Quality Evaluation 19

Conclusion 20

References 21

Chapter-4

Wells and Pumps 22

4.1 Types of Wells 22

4.2 Well Hydraulics 23

4.3 Pump Classification 24

4.4 Pump Performance Characteristics 25

4.5 Pump Selection Criteria 26

4.6 Pump System Design Considerations 28

Conclusion 28

References 29

Chapter-5

Surface Irrigation Methods 30

5.1 Border Irrigation 30

5.2 Basin Irrigation 31

5.3 Furrow Irrigation 32

5.4 Irrigation Scheduling 33

5.5 Surge Flow Irrigation 34

Conclusion 35

References 35

Chapter-6

Pressurized Irrigation Systems 36

6.1 Sprinkler Irrigation 36

6.2 Drip Irrigation 37

6.3 Hydraulic Design 38

6.4 Filtration and Maintenance 39

6.5 Precision Automation 40

6.6 Water Quality Protection 40

Conclusion 41

References 41

Chapter-7

Cross Drainage Works 42

7.1 Canal Falls 42

7.2 Canal Structures 43

7.3 Aqueducts and Super Passages 44

7.4 Drainage of Irrigated Lands 45

Conclusion 46

References 47

Chapter-8

Gated Diversion Headworks 48

8.1 River Diversion Systems 48

8.2 Canal Head Regulators 50

8.3 Cross Drainage and Communication Works 51

8.4 Sediment Transport and Exclusion 52

8.5 Intake Systems 54

Conclusion 54

References 55

Chapter-9

Gravity Dams 56

9.1 Forces on Gravity Dams 56

9.2 Stability Requirements 57

9.3 Material Properties 57

9.4 Stress Analysis 58

9.5 Excavation and Construction 58

9.5.1 Site Preparation and

Excavation 58

9.5.2 Construction of Gravity Dams 60

9.5.3 Environmental Considerations 63

9.5.5 Construction Scheduling and Project Management 65

9.5.6 Case Studies and Examples 66

9.5.7 Emerging Trends and Future Directions 69

Conclusion 71

References 71

Chapter-10

Storage Works and Penstock 72

10.1 Storage Principles 72

10.1.1 Purpose and Importance of

Storage Works 72

10.1.2 Types of Storage Works 72

10.1.3 Storage Capacity and Yield 73

10.1.4 Reservoir Sedimentation and Management 73

10.2 Small Earth Dams 74

10.2.1 Types and Components of

Small Earth Dams 74

10.2.2 Site Selection and

Investigation 75

10.2.3 Design Considerations 75

10.2.4 Construction Techniques 76

10.2.5 Operation and Maintenance 78

10.3 Penstocks and Outlet Works 79

10.3.1 Penstocks 79

10.3.2 Outlet Works 80

10.4 Reservoir Operation and

Management 81

10.4.1 Reservoir Operations 81

10.4.2 Reservoir Sedimentation Management 83

10.4.3 Water Quality Management 83

10.5 Spillways 84

10.5.1 Functions and Types of

Spillways 84

10.5.2 Spillway Design

Considerations 85

10.5.3 Ogee Crest Spillway Design 86

10.5.4 Chute Spillway Design 87

10.5.5 Shaft and Siphon Spillway

Design 88

10.5.6 Labyrinth Spillway Design 89

References 90

Chapter-11

Design of Main Canal 91

11.1 Alignment Considerations 91

11.2 Design Discharge 92

11.3 Canal Capacity 92

11.4 Canal Regulation 93

11.5 Canal Structures 94

11.6 Design of Distributary Network 94

11.7 Irrigation System Automation 95

Conclusion 95

References 96

Chapter-12

Irrigation Water Management 97

12.1 Measurement Methods 97

12.2 Soil-Water Relations 98

12.3 Scheduling Irrigation 98

12.4 Irrigation Methods 99

12.5 Irrigation Efficiencies 100

12.6 Drainage Requirements 100

12.7 Irrigation Water Quality 101

Conclusion 101

References 101

Chapter-13

Drainage Engineering 103

13.1 Benefits of Drainage 103

13.2 Surface and Subsurface Drainage 104

13.2.1 Surface Drainage 104

13.2.2 Subsurface Drainage 105

13.3 Drainage Investigation 106

13.4 Drainage System Design 106

13.5 Surface Drainage Design 107

13.6 Subsurface Drainage Design 107

13.7 Drainage of Land Development Sites 108

13.8 Drainage System Modeling 109

13.9 Construction Inspection 109

13.10 Operation and Maintenance 110

Conclusion 110

References 110

Chapter-14

Groundwater Hydrology 111

14.1 Aquifer Properties 111

14.2 Steady Flow Equations 112

14.3 Groundwater Modeling Software 112

14.4 Aquifer Testing 113

14.5 Groundwater Models 113

14.6 Model Development Principles 114

14.7 Steady State Modeling 115

14.8 Transient Modeling 115

14.9 Model Calibration 116

14.10 Sensitivity Analysis 116

Conclusion 117

References 117

Chapter-15

Drainage Water Management 118

15.1 Controlled Drainage Concepts 118

15.2 System Design Considerations 119

15.3 Subsurface Drainage Control Design 119

15.4 Surface Drainage Control 120

15.5 Subirrigation Capability 121

15.6 Water Conservation Effects 121

15.7 Water Quality Benefits 122

15.8 System Management Approaches 122

15.9 Performance Evaluation 123

15.10 Design and Construction 123

15.11 Drainage Simulation Models 124

15.12 Agricultural Benefits 124

Conclusion 124

References 125

Chapter-16

Irrigation and Society 126

16.1 Agricultural Systems 126

16.2 Irrigation Development Scenarios 127

16.3 Policies and Regulations 127

16.4 Integrated Water Management 128

16.5 Irrigation and Rural Development 128

16.6 Societal Aspects of Irrigation Projects 129

16.7 Case Study: Aral Sea Basin Irrigation Impacts 129

16.8 International Development

Assistance 130

16.9 Case Study: Irrigation Impacts in

Pakistan 131

16.10 Management Transfer Programs 131

Conclusion 131

References 132

Glossary 133

Index 135

Chapter-1

Introduction to Irrigation and Drainage Engineering

1.1 Importance of Irrigation

Irrigation is the process of artificially supplying water to land and soil for agriculture. It is extremely important for crop cultivation for the following reasons:

1. Provides regular water supply: Many regions have erratic seasonal rainfalls insufficient for successful farming. Irrigation gives controlled water unaffected by erratic weather patterns.

2. Increases land productivity: Irrigated lands have higher yields than rain-fed lands, often doubling yields for most crops. Modern precision irrigation optimizes water application further enhancing productivity.

3. Allows multi-cropping: Some crops need water at different intervals which rainfall may not match. Irrigation allows sequential cropping of multiple crops annually through coordinated water supply.

4. Provides drought mitigation: Periodic droughts cause crop losses and famines. Irrigation buffers essential food production against meteorological droughts helping avoid related disasters and economic impacts.

5. Controls soil salinity: Natural land salinity hinders agricultural productivity over time. Irrigation flushing helps leach out accumulated salts from soil profile.

6. Enables ancillary activities: Beyond farming, irrigation enables ancillary industries like inland fisheries and animal husbandry giving livelihood opportunities and nutritional diversity.

Thus, artificial irrigation engineering is pivotal for intensified agriculture output meeting global food security needs as population expands while needing lesser land area under cultivation. Next, we examine main irrigation system categories and methods.

Fig. 1.1 Irrigation and Drainage System

https://images.app.goo.gl/6kP8YBvvSKHAyRuf8

1.2 Types of Irrigation Systems

Many types of irrigation systems supplying water to agricultural land have developed over centuries of practice. Broad classifications include:

1. Surface Irrigation: Water applied on land surface and allowed to flow over by gravity

2. Sprinkler Irrigation: Water sprayed on crops in form of simulated rainfall through pressured pipes network

3. Drip Irrigation: Water dripped to plant roots through network of valves, pipes, tubing

4. Manual Irrigation using water-lifting devices etc.

Surface Irrigation Methods

Land grading and field preparation helps achieve uniform distribution in surface irrigation for high efficiencies. Key surface irrigation types include:

1. Flood Irrigation: Flooding entire level basins or field borders through supply canals and dikes

2. Furrow Irrigation: Watering small furrows between planted rows under gravity flow

3. Border Strip Irrigation: Flooding strips of land bifurcated by small dikes

Water advances progressively wetting entire soil profile through infiltration and percolation while gravity drainage occurs once source cut-off. Earthen canals, pipes, gates, flumes, siphons help guide water flows based on field topography. Recirculation can optimize durations through sequenced plot watering. Excessive deep percolation causes water losses reduced by surge flow methods with intermittent supplies giving high overall efficiencies of 60-80% for surface irrigation with relatively uniform soils.

Fig. 1.2 Surface Irrigation

https://images.app.goo.gl/bzWdoyfCzakiQGvb7

Sprinkler Irrigation Systems

Sprinkler systems simulate natural rainfall through pressurized pipes equipped with nozzles spraying water droplets upwards or sideways covering entire soil surface. Main components comprise:

1. Pump or pressurized water source to create required sprinkler operating heads

2. Network layout of mainline and sub main pipes of varying diameters (50-200 mm)

3. Laterals with distributed sprinkler heads spaced optimally between 8-15 m ranges

Water is propelled upwards by pump pressure creating a spray pattern from nozzles covering crop area with application depth 10-50 mm per hour. Rotating sprinklers cover circular areas while linear move laterals irrigate rectangular lands. Sprinklers are positioned 3-12 m above ground optimizing uniformity and wind drift resisting capabilities for 70-85% efficiency. High initial investment is offset by 20+ year life spans with low labor costs aided by automation. However wind distortions of spray patterns can constrain operations occasionally. Low flow sprinklers help enhance water application precision.

Fig. 1.3 Sprinkler Irrigation

https://images.app.goo.gl/bf2h37z87uEosLmp7

Drip Irrigation Techniques

Drip irrigation comprises a network of valves, pipes, tubing that enable water to drip slowly at root zones of plants at same rates as soil permeability. This high efficiency, targeted irrigation technique prevents wastages via surface evaporation or deep drainage while optimizing crop water needs. Key components are:

1. Filtration units and water source

2. Valves, controllers and pressure regulators

3. Mainlines and submains of larger diameter pipes

4. Laterals having emission devices like drippers and micro-sprinklers

Emitters release water slowly at rates between 2-20 liters per hour directly at plant vicinity either above or below surface. Emitter spacing of 30 cm to 1 m governs wetting patterns with 1-2 liters per plant daily being adequate. Inline drippers have separable components while online drippers are fixed integrally during manufacturing. Careful control of pressure compensating emitters enables 85-95% high application efficiency even in undulating terrain. Fertigation injecting fertilizer chemicals into irrigation water saves costs enhancing productivity vastly. However, drip systems need intensive maintenance of filters. Initial investments also remain higher but longevity can exceed 10 years through durability.

Fig. 1.4 Drip Irrigation

https://images.app.goo.gl/kjqDqqnfH8LH7eJP6

Manual Irrigation Devices

Before piped conveyance systems became widespread, manual irrigation lifting devices drew water from rivers, lakes and wells for land application. Many traditional water lifting mechanisms remain relevant today including:

1. Shadoof: Lever balanced long pole to lift waterskin buckets (Mesopotamia)

2. Persian Wheel: Animal or human powered rotary wheel with pots transporting water

3. Archimedes Screw: Inclined rotating screw inside pipe raising water (Egypt)

4. Chain Pump: Endless chain with fitted disks for lifting (China)

5. Rope and Bucket: Pulling rope and leather buckets from open wells (India)

These manual techniques are still used by smallholder farmers in developing regions lacking electricity access and piped irrigation infrastructure. Simple, decentralized devices provide low cost, sustainable irrigation with little operational skill answering small scale watering needs. But labor requirements are high, and volumes supplied modest limiting scalability. Hence automated pumped schemes are expanding for larger irrigated commands. We examine common water lifting devices and distribution systems next.

Water Lifting Devices

River diversion and canal flows utilize gravity adequately but lifting water from subsurface sources to fields requires energy input for irrigation pumps. Key pump types include:

1. Centrifugal Pumps: Impellers rotating inside casing transmit kinetic energy to water particles pushing flow – most common pump with higher flow rates rather than pressure head.

2. Submersible Pumps: Immersed pump and motor units placed directly inside water bodies like bore wells saving space while extracting from lower depths – extensive usage for agricultural groundwater pumping but require priming.

3. Mixed Flow Pumps: Combining radial and axial flow components of centrifugal pumps to optimize performance – used where medium heads and discharges needed.

4. Positive Displacement Pumps: Mechanical motion of gears, pistons or diaphragms displace fixed cavity volumes of fluid per rotation cycle generating high pressure – have lower capacities but useful for high heads demanding lower flows like drip systems.

Fuel, solar or electric motors provide drive power matching flow discharge needs up to a few thousand liters per minute with total heads from 10 up to 150 meters which piping distribution system sizing