Guidelines for designing and evaluating surface irrigation systems

Table of Contents


by W.R. Walker
Professor and Head
Department of Agricultural and Irrigation Engineering
Utah State University
Logan, Utah, USA
(Consultant to FAO)

Rome, 1989

The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

ISBN 92-5-102879-6

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© FAO 1989

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Table of Contents



1. The practice of irrigation

1.1 The perspective and objectives of irrigation
1.2 Irrigation methods and their selection

1.2.1 Compatibility
1.2.2 Economics
1.2.3 Topographical characteristics
1.2.4 Soils
1.2.5 Water supply
1.2.6 Crops
1.2.7 Social influences
1.2.8 External influences
1.2.9 Summary

1.3 Advantages and disadvantages of surface irrigation

1.3.1 Advantages
1.3.2 Disadvantages

2. Surface irrigation systems

2.1 Introduction to surface irrigation

2.1.1 Definition
2.1.2 Scope of the guide
2.1.3 Evolution of the practice

2.2 Surface irrigation methods

2.2.1 Basin irrigation
2.2.2 Border irrigation
2.2.3 Furrow irrigation
2.2.4 Uncontrolled flooding

2.3 Requirements for optimal performance

2.3.1 Inlet discharge control
2.3.2 Wastewater recovery and reuse

2.4 Surface irrigation structures

2.4.1 Diversion structures
2.4.2 Conveyance, distribution and management structures
2.4.3 Field distribution systems

3. Field measurements

3.1 Field topography and configuration
3.2 Determining water requirements

3.2.1 Evapotranspiration and drainage requirements
3.2.2 Soil moisture principles
3.2.3 Soil moisture measurements
3.2.4 An example problem on soil moisture

3.3 Infiltration

3.3.1 Infiltration functions
3.3.2 Typical infiltration relationships
3.3.3 Measuring infiltration
3.3.4 An example infiltrometer test

3.4 Flow measurement

3.4.1 Cutthroat flumes
3.4.2 Example of cutthroat flume calibration
3.4.3 Rectangular thin-plate weirs
3.4.4 Example of rectangular sharp crested weir analysis
3.4.5 V-notch weirs

3.5 Field evaluation

3.5.1 Advance phase
3.5.2 Ponding phase or wetting
3.5.3 Depletion phase
3.5.4 Recession phase

4. Evaluation of field data

4.1 Objectives of evaluation

4.1.1 Field data

4.2 Performance measures

4.2.1 Application uniformity
4.2.2 Application efficiency
4.2.3 Water requirement efficiency
4.2.4 Deep percolation ratio
4.2.5 Tailwater ratio
4.2.6 Integration measures of performance

4.3 Intermediate analysis of field data

4.3.1 Inflow-outflow
4.3.2 Advance and recession
4.3.3 Flow geometry
4.3.4 Field infiltration

4.4 System evaluation

4.4.1 Furrow irrigation evaluation procedure
4.4.2 Border irrigation evaluation
4.4.3 Basin irrigation evaluation

4.5 General alternatives for improvement
4.6 An example furrow irrigation evaluation

4.6.1 Field infiltration characteristics
4.6.2 Evaluation of system performance
4.6.3 Measures to improve performance

5. Surface irrigation design

5.1 Objective and scope of design
5.2 The basic design process

5.2.1 Preliminary design
5.2.2 Detailed design

5.3 Computation of advance and intake opportunity time

5.3.1 Common design computations

5.4 Furrow irrigation flow rates, cutoff times, and field layouts

5.4.1 Furrow design procedure for systems without cutback or reuse
5.4.2 Design procedure for furrow cutback systems
5.4.3 Design of furrow systems with tailwater reuse
5.4.4 Furrow irrigation design examples

5.5 Border irrigation design

5.5.1 Design of open-end border systems
5.5.2 Design of blocked-end borders
5.5.3 An open-end border design example
5.5.4 A blocked-end border design example

5.6 Basin irrigation design

5.6.1 An example of basin design

5.7 Summary

6. Land levelling

6.1 The importance of land preparations
6.2 Small-scale land levelling
6.3 Traditional engineering approach

6.3.1 Initial considerations
6.3.2 Engineering phase
6.3.3 Adjusting for the cut/fill ratio
6.3.4 Some practical problems
6.3.5 An example problem

6.4 Laser land levelling

7. Future developments

7.1 Background
7.2 Surge flow

7.2.1 Effects of surging on infiltration
7.2.2 Effects of surging on surface flow hydraulics
7.2.3 Surge flow systems

7.3 Cablegation
7.4 Adaptive control systems
7.5 Water supply management


Appendix I - Fortran 77 surface irrigation design program

FAO irrigation and drainage papers