Irrigation Water Management: Training Manual No. 1 - Introduction to Irrigation

Table of Contents

Provisional edition

FAO - FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS

a manual prepared jointly
by
C. Brouwer
International Institute for Land Reclamation and Improvement
and
A. Goffeau
M. Heibloem
FAO Land and Water
Development Division

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying or otherwise, without the prior permission of the copyright owner. Applications for such permission, with a statement of the purpose and extent of the reproduction, should be addressed to the Director, Publications Division, Food and Agriculture Organization of the United Nations, Via delle Terme di Caracalla, 00100 Rome, Italy.

� FAO 1985

This electronic document has been scanned using optical character recognition (OCR) software and careful manual recorrection. Even if the quality of digitalisation is high, the FAO declines all responsibility for any discrepancies that may exist between the present document and its original printed version.

Table of Contents

PREFACE

CHAPTER 1 - BASIC TERMS AND CALCULATIONS

1.1 Introduction to surface area

1.1.1 Triangles
1.1.2 Squares and Rectangles
1.1.3 Rhombuses and Parallelograms
1.1.4 Trapeziums
1.1.5 Circles
1.1.6 Metric Conversions

1.2 Surface areas of canal cross-sections and farms

1.2.1 Determination of the surface areas of canal cross-sections
1.2.2 Determination of the surface area of a farm

1.3 Introduction to volume

1.3.1 Units of volume
1.3.2 Volume of water on a field

1.4 Introduction to flow-rate

1.4.1 Definition
1.4.2 Calculation and Units

1.5 Introduction to percentage and per mil

1.5.1 Percentage
1.5.2 Per mil

1.6 Introduction to graphs

1.6.1 Example 1
1.6.2 Example 2

1.7 Test your knowledge

1.7.1 Questions
1.7.2 Answers

CHAPTER 2 - SOIL AND WATER

2.1 The soil

2.1.1 Soil composition
2.1.2 Soil profile
2.1.3 Soil texture
2.1.4 Soil structure

2.2 Entry of water into the soil

2.2.1 The infiltration process
2.2.2 Infiltration rate
2.2.3 Factors influencing the infiltration rate

2.3 Soil moisture conditions

2.3.1 Soil moisture content
2.3.2 Saturation
2.3.3 Field capacity
2.3.4 Permanent wilting point

2.4 Available water content
2.5 Groundwater table

2.5.1 Depth of the groundwater table
2.5.2 Perched groundwater table
2.5.3 Capillary rise

2.6 Soil erosion by water

2.6.1 Sheet erosion
2.6.2 Gully erosion

CHAPTER 3 - ELEMENTS OF TOPOGRAPHY

3.1 Slopes

3.1.1 Definition
3.1.2 Method of expressing slopes
3.1.3 Cross slopes

3.2 Elevation of a point

3.2.1 Definition
3.2.2 Bench mark and mean sea level

3.3 Contour lines
3.4 Maps

3.4.1 Description of a map
3.4.2 Interpretation of contour lines on a map
3.4.3 Mistakes in the contour lines
3.4.4 Scale of a map

CHAPTER 4 - RAINFALL AND EVAPOTRANSPIRATION

4.1 Rainfall

4.1.1 Amount of rainfall
4.1.2 Rainfall intensity
4.1.3 Rainfall Distribution
4.1.4 Effective Rainfall

4.2 Evapotranspiration

4.2.1 Evaporation
4.2.2 Transpiration
4.2.3 Evapotranspiration
4.2.4 Factors influencing crop evapotranspiration

CHAPTER 5 - IRRIGATION SYSTEM

5.1 Main intake structure and pumping station

5.1.1 Main intake structure
5.1.2 Pumping station

5.2 Conveyance and distribution system

5.2.1 Open canals
5.2.2 Canal structures

5.3 Field application systems

5.3.1 Surface irrigation
5.3.2 Sprinkler irrigation
5.3.3 Drip irrigation

5.4 Drainage system

CHAPTER 6 - DRAINAGE

6.1 Need for drainage
6.2 Different types of drainage

6.2.1 Surface drainage
6.2.2 Subsurface drainage

CHAPTER 7 - SALTY SOILS

7.1 Salinization
7.2 Salinity

7.2.1 Water salinity
7.2.2 Soil salinity

7.3 Crops and saline soils
7.4 Sodicity
7.5 Improvement of saline and sodic soils

7.5.1 Improvement of saline soils
7.5.2 Improvement of sodic soils

7.6 Prevention of salinization

7.6.1 Irrigation water quality
7.6.2 Irrigation management and drainage