Farm Irrigation (Practical Farming)

165 Pages·1997·27.99 MB·English

by  Neil Southorn

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NEIL SOUTHORN
INKATA PRESS
INKATA PRESS
A division of Butterworth-HeinemannA ustralia
AUStralia
Butterworth-Heinemann, 18 Salmon Street, Port Melbourne, 3207
singapo=
Butterworth-Heinemann Asia
United Kingdom
Butterworth-Heinemann Ltd, Oxford
USA
Butterworth-Heinemann, Newton
National Library of Australia Cataloguing-in-Publhtioatione ntry
Southorn,N eil.
Irrigation and drainage.
Includes index.
ISBN 0 7506 8937 4.
1. Irrigation farming. 2. Drainage. I. Title. (Series :
Practical farming).
631.587
01997 Neil Southorn
Published b Reed International Books Australia. Under the Copght
(Jth),
Act 1968 no part of this publication may be reproduced y any
process, qlectronic or otherwise, without the spedic written permission of
the coppght owner.
Enquines should be addressed to the publishers.
Typeset by Ian MacArthur, Hornsby Heights, NSW.
Printed in Singapore by Chung Printing.
Contents
Acknowledgments 7
Introduction 9
CHAPTER 1: Imgationplanning 14
Water supply 14
soil 22
24
Topography
Stormwater management and
tailwater recirculation 25
Sys tem design capacity 26
Application efficiency 27
Uniformity of application 29
Watertables and salinity 30
Selection of irrigation method 31
Project management 32
CHAPTER 2: Soil water 33
Soil texture 33
Soil structure 36
Water in the soil matrix 36
Measurement of soil water content
or soil suction 38
The root zone 43
Assessing requirements 45
Infiltration and water application rates 47
Water movement through the profile 49
CHAPTER 3: Evapotmnspiration 50
The transpiration process 50
Estimating evapotranspiration 53
Peak irrigation demand 58
Irrigation planning in a variable climate (box) 61
5
COntenh
CHAPTER 4: Irrigation scheduling 62
Water budget 62
Allowance for rainfall 65
Gross irrigation application 66
Deficit irrigation 67
CHAPTER 5: Surjhce irrigation 68
Surface irrigation methods 68
Characteristics of surface irrigation 71
Reticulation of water 73
Management 74
Summary of design procedures 77
CHAPTER 6: way im*ption 80
Suitability of spray irrigation 80
Types of spray systems 82
Sprinkler design and performance 92
Application rates 96
Uniformity of distribution 97
Summary of design procedures 98
Maintenance 99
CHAPTER 7: Microirrigation systems 100
Types of emitter 101
Water quality and filtration 105
Fertigation and chemical injection 109
Automation 111
Summary of design procedures 112
Maintenance 113
CHAPTER 8: Reticulation 115
Pump stations 115
Pipelines 126
Jointing procedures for PVC pipes (box) 132
Channels 143
CHAPTER 9: Drainuge 147
Benefits 148
Types of drains 150
Subsurface drainage materials and installation 153
Drainage systems 155
Drain design 156
R e f m s 160
*I
161
6
Acknowledgments
Special thanks to Joanne for assisting with the manuscript,
and the following organisations:
Netafkn Australia Pty Ltd
Central Highlands Management
NSW Agriculture
Irricrop Technologies Pty Ltd
Sentek Pty Ltd
Electronic Irrigation Systems
James Hardie Irrigation Pty Ltd
Viidex Tubemakers Pty Ltd
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I
rrigation makes a major contribution to agricultural
production by making a whole range of crops viable in an
otherwise unreliable climate, and helping insure against
drought. However irrigation does not automatically guarantee
profit and acclaim. It is a high cost exercise, using water from
increasingly limited supplies, and raises environmental
concerns in the community. Many of the pressures facing
some irrigators have been caused by a lack of understanding
in the past of the best practices necessary for design,
installation and management. This book attempts to
summarise the key factors and processes in successful
irrigation.
Chapters 5,6 and 7 describe different irrigation methods.
Existing irrigators may be looking to convert to a different
method, or to mo% their existing system to use less water
or reduce labour costs. New entrants to the industry will need
to decide the best method of irrigation for their situation.
The book covers irrigation methods for larger scale agricul-
tural and horticultural crops, and does not cover landscape
irrigation or hydroponics.
The technology associated with the detailed design of
irrigation systems is quite specialised and best left to experts.
Irrigation systems work to relatively tight specifications. It
would be unusual for landowners to design and install their
own equipment or earthworks. Consequently, this book
provides only an introduction to irrigation methods, to enable
consideration of the best watering method for specific
situations, sufficient for feasibility planning.
Sometimes, that choice is pre-determined. For example,
irrigation of orchard or plantation rows in undulating to steep
country can only be effectively achieved by microirrigation.
Where the site is relatively flat, soil types suitable, and
environmental hazards minimal, the choice of irrigation
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