fundamentals of irrigation and on-farm water management: volume 1 ||

Fundamentals of Irrigation and On-farm WaterManagement: Volume 1

M.H. Ali

Fundamentals of Irrigationand On-farm WaterManagement: Volume 1

M.H. AliAgricultural Engineering DivisionBangladesh Institute of Nuclear AgricultureBAU CampusMymensingh 2202Bangladesh

ISBN 978-1-4419-6334-5 e-ISBN 978-1-4419-6335-2DOI 10.1007/978-1-4419-6335-2Springer New York Heidelberg Dordrecht London

Library of Congress Control Number: 2010934381

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Foreword

Agriculture is one of the few industries that has been creating resources continu-

ously from nature. Sustainability of this industry is a crucial issue at now-a-days.

Agricultural technologies are important to feed the growing world population.

Agricultural engineering has been applying scientific principles for the optimal

use of natural resources in agricultural production for the benefit of humankind.

The role of agricultural engineering is increasing in the coming days at the

forthcoming challenges of producing more food with less water coupled with

climate uncertainty.

I am happy to know that a book entitled "Fundamentals of Irrigation andOn-farm Water Management", written by Engr. Dr. M. H. Ali, is going to be pub-

lished by Springer. The book is designed to cover the major fields of agricultural

and environmental engineering such as weather, plant, soil, water, and basics of

on-farm water management. The book will be quite useful for the students of

agricultural engineering. Students of other related branches of engineering sci-

ences, and engineers working in the field and at research institutes will also be

benifited. The book may serve as a text book for the students and as a practical

hand-book for the practitioners and researchers in the field of irrigation and on-farm

water management. Utilization of the recent literature in the area and citation of

relevant journals / reports have added a special value to this book. Considering the

topics covered, engineers, scientists, practitioners, and educators will find this book

as a valuable resource.

I hope this text-book will be used worldwide to promote agricultural production

and conservation of the most important natural resource, water.

Mymensingh, Bangladesh Dr. M. A. Salam

23 March, 2010 Director (Research)

Bangladesh Institute of Nuclear Agriculture

v

Preface

Water is the scarcest resource. Importance of judicious use of water in agricultural

sector for sustaining agricultural growth and to retard environmental degrada-

tion needs no elaboration. Judicious use of water for crop production requires

knowledge of weather, soil, crop, water quality, and drainage situation. Increasing

efficiency in conveyance and pumping systems also are of great concerns. Irrigation

management strategy practiced in normal soils may not appropriate in problematic

soils such as saline soils and drought prone areas. It is also utmost important to pay

attention to the economics in production system and all aspects of supply & demand

management of water. This book covers all of the above aspects. In addition, the

book covers some recent dimensions such as pollution from agricultural fields,

modeling in irrigation & water management, and application of geographical infor-

mation system (GIS) in irrigation & water management.

Sufficient workout problems are provided to explain the application of theory/

methodology in practice. Data sheets (with sample data) are provided for different

methods to understand the procedure easily.

This comprehensive and compact presentation of the book will serve as a text

book for undergraduate students in Agricultural Engineering, Biological Systems

Engineering, Bio-Science Engineering, Water Resource Engineering, and, Civil &

Environmental Engineering. It will also be helpful for the students of relevant fields

such as Agronomy, Biological Sciences, Meteorology, Ecology and Hydrology.

Although the target audience of the book is undergraduate students, post-graduate

students will also be benefited from the book. It will also serve as a reference

manual for field engineers, researchers and extension workers working in the above

mentioned fields.

It was tried to keep the language simple as possible to make understandable

to all category of readers having different language origins. Throughout the

book, the emphasis has been given on general description and principle of each

topic, and tried to cover experimental and technical details. However, the com-

prehensive journal references in each area (at the end of each chapter) should

enable the reader to pursue further study of special interest. In fact, the book

covers broad interdisciplinary subjects. The subject matter has been splitted into

vii

25 chapters in two volumes to clearly specify different topics so as to make

more understandable to the readers. This volume (volume 1) covers fundamental

aspects, and the second volume covers application aspects of irrigation and water

management.

Mymensingh, Bangladesh Dr. M.H. Ali

viii Preface

Acknowledgements

I acknowledge the co-operation, suggestions and encouragement of the faculty

members of the Department of Irrigation & Water Management, Bangladesh

Agricultural University. I would like to thank Engr. Dr. M.A. Ghani, former

Director General of Bangladesh Agricultural Research Institute, and World Bank

Country Representative, Bangladesh, who critically reviewed the content and

structure of several chapters of the Book.

I am grateful to the authority of Soil Moisture Co., CPN Co., and Raj Instru-

mentations for supplying the pictures of their products and giving permission to use

the same in the book. I am also grateful to the authority of FAO and IRRI for giving

permission to reproduce their some material.

I am thankful to Dr. M.A. Salam, Director (Research), Bangladesh Institute of

Nuclear Agriculture, for going through the book and writing a few words about the

same in the form of ‘Foreword’.

My sincere thanks are also due to my affectionate wife Anjumanara Begham,

daughter Sanjida Afiate and son Irfan Sajid, for their support, understanding and

patience during preparation of the manuscript.

ix

Contents

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

1 Introduction: Perspectives and General Concept of Irrigation . . . . . . . . 1

1.1 Availability of Water in the Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Variability of Water with Time and Space . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.3 General Concept of Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.3.1 Irrigation Scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.3.2 Full Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3.3 Deficit Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.4 Global Outlook: World Population and World Water Use . . . . . . . . . . . 3

1.4.1 Trend of World Water Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.5 Challenges and Opportunities in Irrigation and Water Management . 4

1.5.1 Challenging Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.5.2 Opportunities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.6 Physiographic and Economic Factors Affecting Irrigation and Water

Management: Case Study, Bangladesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.6.1 National Economy and Agriculture . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.6.2 Basic Physical Factors in Agricultural Production . . . . . . . . . . . . . 5

1.6.3 Challenges and Limiting Factors in Agriculture

in Bangladesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.6.4 Physical Features of Bangladesh Influencing Water Resources

Utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.6.5 Climate and Cropping Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.6.6 Major Source of Irrigation Water in Bangladesh and Concern

of Sustainability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

xi

1.6.7 Considerations in Current Water-Starved Situations . . . . . . . . . . . 9

Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2 Fundamentals of Irrigation Development and Planning . . . . . . . . . . . . . . . 11

2.1 Factors Affecting Farm Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.1.1 Agro-Ecological Factor/Constraint . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.1.2 Soil Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.1.3 Hydrological Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.1.4 Crop Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.1.5 Water Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.1.6 Fertility Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.1.7 Socio-Economic Factor/Constraint . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.1.8 Other Management Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.2 Important Factors Affecting Irrigation Planning and Development . . 13

2.2.1 Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.2.2 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.2.3 Topography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.2.4 Water Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.2.5 Crop(s) to be Cultivated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2.6 Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2.7 Labor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2.8 Capital . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2.9 Commodity/Product Market . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2.10 Economic Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.2.11 Environmental Aspect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.2.12 National Policy and Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.2.13 Socio-Cultural Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.2.14 Institutional Infrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.3 Irrigation Development in Asia and Pacific Region . . . . . . . . . . . . . . . . . 17

2.3.1 Progressive Irrigation Development in Bangladesh . . . . . . . . . 18

2.3.2 Irrigation Development in China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2.3.3 Irrigation Development in Iran . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.4 Impact of Irrigation on Environment and Ecosystem . . . . . . . . . . . . . . . . 22

2.4.1 Positive Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.4.2 Negative Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.4.3 Degradation of Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.4.4 Groundwater Abstraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2.4.5 Water-Logging and Salinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2.4.6 Health Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2.4.7 Simplification and Homogenization of the World’s

Ecosystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2.5 Land Classification for Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.5.1 Concept of Land Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.5.2 Importance of Land Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

xii Contents

2.5.3 Standards of Land Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.5.4 Process of Land Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.5.5 USBR Land Classification System . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Relevant Journals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Relevant FAO Papers/Bulletins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3 Weather: A Driving Force in Determining Irrigation Demand . . . . . . . 31

3.1 Concept of Weather and Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.2 Importance of Weather in Agriculture and Water Management . . . . 32

3.3 Basic Mechanisms of Weather Variability . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.3.1 Sun- Earth Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.3.2 Role of Monsoon Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.3.3 Interaction Between Atmosphere, Ocean,

and Land Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.4 Weather Factors Determining/Influencing Crop Water Demand . . . . 35

3.4.1 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.4.2 Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.4.3 Solar Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.4.4 Wind Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.4.5 Sunshine Hour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.5 Weather Elements Affecting Agriculture and Crop Production . . . . . 36

3.5.1 Solar Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.5.2 Air Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.5.3 Rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.5.4 Air Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.5.5 Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.5.6 Photoperiod or Day-Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.6 Definition, Measurement, and Analysis of Weather Variables . . . . . . 39

3.6.1 Rainfall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.6.2 Solar Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

3.6.3 Air Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

3.6.4 Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

3.6.5 Air Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

3.6.6 Wind Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

3.6.7 Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

3.6.8 Some Other Weather Phenomena . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

3.7 Instrumentation for a Weather Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

3.8 Weather Forecasting and Agricultural Decision Making . . . . . . . . . . . . 79

3.8.1 Weather Forecasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

3.8.2 Application of Weather Forecasting in Agricultural

Decision Making . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

3.8.3 Copying Strategy for Hazardous Weather Phenomena . . . . . . 83

Contents xiii

3.9 Agro-Climatic Indices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

3.9.1 Use of Climatic Indices and Heat Units . . . . . . . . . . . . . . . . . . . . . 85

3.9.2 Different Indices and Their Description . . . . . . . . . . . . . . . . . . . . . 85

3.9.3 Examples on Heat Unit Requirement of Crop . . . . . . . . . . . . . . . 88

3.10 Climatic Potential Yield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

3.10.1 Concept and Mathematical Formulation . . . . . . . . . . . . . . . . . . . . 89

3.10.2 Example on Calculation of Climatic Potential Yield . . . . . . . . 90

3.11 Agro-Climatic Classification for Crop Suitability . . . . . . . . . . . . . . . . . . . 91

3.12 Greenhouse Effect and Its Consequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

3.12.1 Concept and Causes of Green House Effect . . . . . . . . . . . . . . . . . 92

3.12.2 Possible Consequences of the Green House Gases . . . . . . . . . . 95

3.12.3 Remediation/Abatement of Greenhouse Gas Generation . . . . 96

3.13 Climate Change and Crop Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

3.13.1 Meaning of Climate Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

3.13.2 Impact of Climate Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Relevant Journals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

FAO Papers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Exercise/Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

4 Soil: A Media for Plant Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

4.1 Basics of Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

4.1.1 Definition of Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

4.1.2 Agricultural Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

4.1.3 Components of Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

4.1.4 Importance of Soil for Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

4.2 Physical Properties of Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

4.2.1 Qualitative Description of Soil Physical Properties . . . . . . . . . . 110

4.2.2 Description and Measurement Techniques of Important

Soil Physical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

4.2.3 Infiltration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

4.2.4 Importance of Soil Physical Properties . . . . . . . . . . . . . . . . . . . . . . . 143

4.3 Chemical Properties of Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

4.3.1 Soil pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

4.3.2 Soil Cation Exchange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

4.4 Soil Hydraulic Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

4.4.1 Importance of Soil Hydraulic Properties . . . . . . . . . . . . . . . . . . . . . 149

4.4.2 Determination of Different Soil-Water Constants . . . . . . . . . . . 149

4.4.3 Measurement of Soil Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

4.4.4 Soil-Water Potentials and Other Related Terminologies . . . . 177

4.4.5 Determination of Soil Moisture Characteristics . . . . . . . . . . . . . . 179

4.4.6 Hydraulic Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

4.4.7 Swelling and Shrinkage Properties of Soil . . . . . . . . . . . . . . . . . . . 205

4.4.8 Biological Properties of Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

xiv Contents

4.4.9 Improvement of Soil Physical, Chemical, and Biological

Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212


FAO Soil Bulletins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

5 Plant: A Machinery of Water Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

5.1 General Overview and Types of Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

5.1.1 General Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

5.1.2 Types of Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

5.2 Development of Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

5.2.1 Growth Stages of Field Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

5.2.2 Growth and Development of Cereals: Example with

Wheat Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

5.2.3 Thermal Time Requirement of Crop . . . . . . . . . . . . . . . . . . . . . . . . 232

5.3 Structure of Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

5.3.1 General Structural Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

5.3.2 Root Growth and Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

5.4 Crop Growth Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

5.4.1 Climatic Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

5.4.2 Water and Nutrient Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

5.5 Crop Growth Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

5.5.1 Leaf Area Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

5.5.2 Growth Rate and Relative Growth Rate . . . . . . . . . . . . . . . . . . . . 241

5.5.3 Root Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

5.6 Dry-Matter Production in Plant and Its Partitioning . . . . . . . . . . . . . . . . 245

5.6.1 Determination of Total Biomass or Drymatter . . . . . . . . . . . . . 245

5.6.2 Indices of Drymatter Partitioning . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

5.6.3 Assimilate Partitioning/Remobilization of Prestored

Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

5.6.4 Improving Assimilate Partitioning to Grain . . . . . . . . . . . . . . . . 247

5.7 Plant Water Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

5.7.1 Theoretical Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

5.7.2 Indices of Plant–Water Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

5.7.3 Water Potential in Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

5.7.4 Leaf Water Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

5.7.5 Water Content/Water Retention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

5.7.6 Relative Water Content/Relative Turgidity . . . . . . . . . . . . . . . . . 252

5.7.7 Relative Saturation Deficit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

5.7.8 Relation Between Leaf Water Potential and Relative

Water Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

5.8 Plant Biochemical and Physiological Aspects . . . . . . . . . . . . . . . . . . . . . . 254

5.8.1 Plant Biochemical Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254

5.8.2 Physiological Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

Contents xv

5.9 Water and Nutrient Uptake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

5.9.1 Water Uptake Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

5.9.2 Nutrient Uptake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

5.10 Critical Growth Stages of Plant and Water Demand for Whole

Growth Period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260

5.10.1 Critical Growth Stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260

5.10.2 Water Demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

5.11 Plant Adaptation to Stress/Drought: Stress Physiology . . . . . . . . . . . . . 261

5.11.1 Mechanisms of Plant Survival . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

5.11.2 Drought Tolerance Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

5.11.3 Yield Estimation Under Drought Condition . . . . . . . . . . . . . . . . 265

5.12 Plant Production Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

5.12.1 APSIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

5.12.2 CropSyst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

5.12.3 Oryza2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

5.12.4 SUCROS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267


Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

6 Water: An Element of Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

6.1 Sources and Uses of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

6.2 Special Characteristics of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

6.3 The Hydrologic Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

6.3.1 Concept and Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

6.3.2 Processes Involved in Hydrologic Cycle . . . . . . . . . . . . . . . . . . . . 273

6.3.3 Impact of Hydrologic Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275

6.4 Water Quality Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

6.4.1 Meaning of Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

6.4.2 Factors Affecting Quality of Water . . . . . . . . . . . . . . . . . . . . . . . . . 276

6.4.3 Factors Affecting Suitability of Water for Irrigation . . . . . . . 277

6.4.4 Water Quality Indicators/Parameters and Their Description 277

6.4.5 Water Quality Evaluation: Standards and Guidelines . . . . . . 288

6.4.6 Classification of Water for Its Quality Based on Different

Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

6.5 Water Analysis: Measuring the Quality of Water . . . . . . . . . . . . . . . . . . 292

6.5.1 Analytical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

6.5.2 Some-Related Terminologies and Relationships . . . . . . . . . . . 295

6.5.3 Workout Problems on Assessing Water Quality . . . . . . . . . . . . 296

6.5.4 Checking the Correctness of Water Analysis . . . . . . . . . . . . . . . 298

6.6 Problems with Marginal/Poor Quality Irrigation Water for Crop

Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

6.6.1 Major Issues and Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

6.6.2 Impact on Soil Physical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . 301

6.6.3 Problem of Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

xvi Contents

6.6.4 Other Miscellaneous Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

6.6.5 Yield Decrease Due to Poor Quality Water . . . . . . . . . . . . . . . . . 302

6.7 Coping Strategies in Using Poor/Marginal Quality Irrigation

Water for Crop Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

6.7.1 Management Strategies in Using Poor Quality

Irrigation Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

6.7.2 Workout Problems on Water Mixing and Leaching . . . . . . . . 304

6.8 Water Quality of River and Stream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

6.9 Water Quality Models and Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

6.9.1 Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

6.9.2 Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308

6.10 Contamination/Pollution of water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308

6.10.1 Major Sources of Water Contaminants . . . . . . . . . . . . . . . . . . . . . 308

6.10.2 Arsenic Contamination: Causes, Consequences,

and Mitigation/Remedial Measures . . . . . . . . . . . . . . . . . . . . . . . . . 310

6.11 Protecting Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

6.11.1 Protection Measures Against Potential Sources

of Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

6.11.2 Management Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322

6.12 Treatment of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323

6.12.1 Different Methods of Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323

6.12.2 Physical Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323

6.12.3 Chemical Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325

6.12.4 Biological Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326

6.12.5 Water Purification in a Treatment Plant . . . . . . . . . . . . . . . . . . . . 326


Relevant FAO Irrigation and Drainage Papers . . . . . . . . . . . . . . . . . . . . . . . . . . . 328

Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

7 Field Water Balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

7.1 Concepts, Sketch, and Mathematical Form of Field Water Balance 331

7.1.1 Concept of Field Water Balance . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

7.1.2 Mathematical Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

7.1.3 Limiting Conditions of the Water Balance Components . . 333

7.2 Determination of Different Components of Water Balance . . . . . . . . 334

7.2.1 Evapotranspiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

7.2.2 Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

7.2.3 Surface Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357

7.2.4 Deep Percolation or Deep Drainage . . . . . . . . . . . . . . . . . . . . . . . 357

7.2.5 Upward Flux/Capillary Rise from Water-Table . . . . . . . . . . . 362

7.2.6 Determination of Change in Soil-Water storage . . . . . . . . . . 365

7.2.7 Workout Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366


FAO Papers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

Contents xvii

Questions/Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

8 Soil–Water–Plant–Atmosphere Relationship . . . . . . . . . . . . . . . . . . . . . . . . . . 373

8.1 Concept of Soil–Plant–Atmospheric Continuum . . . . . . . . . . . . . . . . . . . 373

8.1.1 Some-Related Concepts/Terminologies . . . . . . . . . . . . . . . . . . . . . . 374

8.2 Soil–Water–Plant–Atmosphere Interrelations . . . . . . . . . . . . . . . . . . . . . . 375

8.2.1 Different Soil–Water Coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375

8.2.2 Plant–Water Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378

8.2.3 Soil Wetness and Evaporation Relationship . . . . . . . . . . . . . . . . . 379

8.2.4 Root Water Uptake in Relation to Soil-Moisture . . . . . . . . . . . . 380

8.2.5 Hydraulic Conductance in Soil–Leaf Pathway . . . . . . . . . . . . . . . 382

8.2.6 Plants Response to Soil Moisture Deficit . . . . . . . . . . . . . . . . . . . . 383

8.2.7 Water Flow Through Soil–Plant–Atmospheric Continuum . . 388

8.2.8 ET Under Depleting Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391

8.2.9 Workout Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393


Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397

9 Crop Water Requirement and Irrigation Scheduling . . . . . . . . . . . . . . . . . 399

9.1 Crop Water Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399

9.1.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399

9.1.2 Factors Affecting Crop Water Requirement . . . . . . . . . . . . . . . . . 400

9.1.3 Calculation/Estimation of Crop Water Requirement . . . . . . . . . 401

9.1.4 Difference Between Crop Water Requirement and Irrigation

Water Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401

9.1.5 Water Requirement of Major Field Crops . . . . . . . . . . . . . . . . . . . . 402

9.2 Irrigation Water Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402

9.2.1 Factors Affecting Irrigation Requirement . . . . . . . . . . . . . . . . . . . . 403

9.2.2 Components of Total Water Requirement for Irrigation . . . . . 403

9.2.3 Total Irrigation Water Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . 405

9.2.4 Sample Examples on Calculation of Irrigation

Water Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407

9.3 Basics of Irrigation Scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408

9.3.1 Concept of Scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408

9.3.2 Indicators of Irrigation Need Assessment . . . . . . . . . . . . . . . . . . . . 409

9.3.3 Factors Affecting Irrigation Scheduling . . . . . . . . . . . . . . . . . . . . . . 409

9.3.4 Common Irrigation Scheduling Methods Used

by the Farmers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413

9.3.5 Advanced Irrigation Scheduling Approaches . . . . . . . . . . . . . . . . 413

9.3.6 Factors Influencing Choice of Irrigation Scheduling Method . 414

9.4 Description of Different Irrigation Scheduling Methods

or Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414

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9.4.1 Climatic Approach/Evapotranspiration Basis . . . . . . . . . . . . . . . 414

9.4.2 Pan Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415

9.4.3 Crop Growth Stage Basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416

9.4.4 Soil Moisture Basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

9.4.5 Deficit Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418

9.4.6 Soil Water Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423

9.4.7 Leaf Water Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423

9.4.8 Stress Day Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425

9.4.9 Irrigation Calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

9.4.10 Soil-Moisture Balance Approach or Check-Book Approach . 428

9.4.11 Modeling Approach for Irrigation Management . . . . . . . . . . . . 428

9.4.12 Real-Time Irrigation Scheduling System . . . . . . . . . . . . . . . . . . . 430

9.4.13 Irrigation Scheduling Under Limited/Variable Water

Supply, Variable Rainfall, and Saline Condition . . . . . . . . . . . 431

9.4.14 Sample Workout Problems on Irrigation Scheduling . . . . . . . 432

9.5 Irrigation Command Area Designing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437

9.5.1 Concept of Command Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437

9.5.2 Relevant Terminologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437

9.5.3 Duty, Delta, and Base Period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438

9.5.4 Factors Affecting Peak Irrigation Demand . . . . . . . . . . . . . . . . . 440

9.5.5 Identification of Problem in the Command Area . . . . . . . . . . . 440

9.5.6 Command Area Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441

9.5.7 Designing Command Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442

9.5.8 Sample Layout of a Command Area . . . . . . . . . . . . . . . . . . . . . . . . 443

9.5.9 Sample Examples on Duty-Delta and Command Area . . . . . 444


FAO Papers/Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449

Questions/Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451

10 Measurement of Irrigation Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453

10.1 Basics of Water Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453

10.1.1 Purpose of Water Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . 453

10.1.2 Types of Flow Measuring Devices . . . . . . . . . . . . . . . . . . . . . . . 454

10.1.3 Selection of a Water Measuring Device . . . . . . . . . . . . . . . . . 455

10.1.4 Basic Terminologies and Hydraulic Principles of Flow

Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456

10.1.5 Permanent Flow Measuring Structure . . . . . . . . . . . . . . . . . . . . 461

10.2 Measurement of Flow in Small Irrigation Channel . . . . . . . . . . . . . 463

10.2.1 Area–Velocity Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463

10.2.2 Stream Gauging: Stage–Discharge Relationship . . . . . . . . 465

10.2.3 By Flume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465

10.2.4 By Portable Weir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468

10.2.5 By V-Notch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468

Contents xix

10.2.6 Tracer Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469

10.2.7 Automated Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472

10.3 Measurement of Velocity, Area, and Water Depth (or Head) . . 472

10.3.1 Measurement of Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472

10.3.2 Measurement of Water Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475

10.3.3 Measurement of Channel Cross-Sectional Area . . . . . . . . . 475

10.4 Measurement of Pipe Flow/Pump Discharge . . . . . . . . . . . . . . . . . . . . 477

10.4.1 Direct Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477

10.4.2 Co-ordinate Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477

10.4.3 By Orifice meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479

10.4.4 By Venturimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480

10.4.5 By Flume or V-Notch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481

10.5 Sample Workout Problems on Water Flow Rate Measurement . 481

Relevant Journals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485

FAO Papers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485

Questions/Exercise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487

11 Water Conservation and Harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489

11.1 Concept and Definition of Water Conservation . . . . . . . . . . . . . . . . . 489

11.2 Means or Methods of Water Conservation . . . . . . . . . . . . . . . . . . . . . . 490

11.2.1 Reducing Evaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490

11.2.2 Reducing Evapotranspiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492

11.2.3 Seepage Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

11.2.4 Reducing Quality Degradation . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

11.2.5 Cloud Seeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

11.2.6 Surface Storage and Groundwater Recharge . . . . . . . . . . . . . 495

11.2.7 Treating and Reusing Sewage or Other

Contaminated Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495

11.2.8 Using Super-Absorbents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495

11.3 Water Harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497

11.3.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497

11.3.2 Background/The Need of Water Harvesting . . . . . . . . . . . . . 497

11.3.3 Historical Overview: Old Practices of Rainwater Harvest 497

11.3.4 Prerequisite of Rainwater Harvesting . . . . . . . . . . . . . . . . . . . . 498

11.3.5 The Need and Prospects of Water Harvesting:

Case Study, Bangladesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498

11.3.6 Techniques of Rain-Water Harvesting . . . . . . . . . . . . . . . . . . . 499

11.3.7 Sample Examples on Rainwater Harvesting . . . . . . . . . . . . . 501

11.4 Groundwater Recharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 501

11.4.1 Extent and Magnitude of the Problem . . . . . . . . . . . . . . . . . . . 501

11.4.2 Methods of Groundwater Recharge . . . . . . . . . . . . . . . . . . . . . . 502

11.5 Rubber Dam: A New Prospect of Surface Water

Storage/Harnessing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504

11.5.1 Definition and Types of Rubber Dam . . . . . . . . . . . . . . . . . . . . 504

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11.5.2 Different Parts of a Rubber Dam . . . . . . . . . . . . . . . . . . . . . . . . . 506

11.5.3 Site Selection for a Dam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507


Relevant FAO Papers/Water Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508

Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509

12 Economics in Irrigation Management and Project Evaluation . . . . . 511

12.1 Economic Aspects in Irrigation Management and Crop

Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511

12.1.1 Water as an Economic Good . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512

12.1.2 Typical Criteria of a Technology . . . . . . . . . . . . . . . . . . . . . . . . 512

12.1.3 Significance of Economic Analysis . . . . . . . . . . . . . . . . . . . . . . 513

12.2 Basics of Economic Theories and Concepts . . . . . . . . . . . . . . . . . . . . . 514

12.2.1 Demand and Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514

12.2.2 Cost and Revenue Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515

12.3 Economic Considerations in Irrigation and Crop Production . . . 520

12.3.1 Economic Consequences of Low Irrigation Efficiency . . 520

12.3.2 Economic Efficiency vs. Irrigation Efficiency . . . . . . . . . . . 521

12.3.3 Optimal Levels of Water Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521

12.3.4 Opportunity Cost of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523

12.3.5 Farm-Level Profit Maximization . . . . . . . . . . . . . . . . . . . . . . . . . 523

12.3.6 Maximizing Social Benefit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523

12.4 Mathematical Formulation for Minimum Cost or Maximum

Profit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524

12.4.1 Minimizing Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524

12.4.2 Maximizing Net Benefit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524

12.5 Different Water Productivity Indices in Irrigation Management 525

12.5.1 Water Productivity (EET) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525

12.5.2 Productivity of Irrigation Water (Eir) . . . . . . . . . . . . . . . . . . . . 525

12.5.3 Marginal Productivity of Irrigation Water . . . . . . . . . . . . . . . 525

12.6 Economic Analysis Under Different Resource Constraints and

Different Budget Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526

12.6.1 Analysis Under Different Budget Consideration . . . . . . . . 526

12.6.2 Analysis Under Different Resource Constraints . . . . . . . . . 526

12.6.3 Example on Economic Analysis for Different Irrigation

Management Strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528

12.7 Economic and Financial Analysis of Development Projects . . 531

12.7.1 Different Economic and Financial Indices and Related

Terminologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532

12.7.2 Expression of Cost and Benefit . . . . . . . . . . . . . . . . . . . . . . . . . . 536

12.7.3 Analysis of NPV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538

12.7.4 The NPV Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540

Contents xxi

12.7.5 Discounting/Compounding Formula Under Different

Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541

12.7.6 Project Selection Among Alternatives . . . . . . . . . . . . . . . . . . . 545

12.7.7 Examples on Financial Analysis and Project

Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 546


Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557

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fundamentals of irrigation and on-farm water management: volume 1 ||

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