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# Sediment Transport in Irrigation Canals A New Approach

By

,

,

## Néstor Méndez V

ISBN 9781138026957
Published September 30, 2014 by CRC Press
312 Pages

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## Book Description

Sediment transport in irrigation canals influences to a great extent the sustainability of an irrigation system. Unwanted erosion or deposition will not only increase maintenance costs, but may also lead to unfair, unreliable and unequitable distribution of irrigation water to the end users. Proper knowledge of the characteristics, including behaviour and transport of sediment will help to design irrigation systems, plan effi cient and reliable water delivery schedules, to have a controlled deposition of sediments, to estimate and arrange maintenance activities, etc. The main aim of these lecture notes is to present a detailed analysis and physical and mathematical descriptions of sediment transport in irrigation canals and to describe the mathematical model SETRIC that predicts the sediment transport, deposition and entrainment rate as function of time and place for various flow conditions and sediment inputs. The model is typically suited for the simulation of sediment transport under the particular conditions of non-wide irrigation canals where the flow and sediment transport are strongly determined by the operation of the flow control structures. The lecture notes will contribute to an improved understanding of the behaviour of sediments in irrigation canals. They will also help to decide on the appropriate design of the system, the water delivery plans, to evaluate design alternatives and to achieve an adequate and reliable water supply to the farmers.

## Table of Contents

LIST OF FIGURES
LIST OF TABLES
PREFACE

1 INTRODUCTION

2 OPEN CHANNEL FLOW
2.1 Introduction
2.2 Flow types and characteristics
2.3 Geometry
2.4 Basic hydraulic principles
2.5 Velocity distribution
2.6 Uniform flow
2.7 Non-uniform steady flow
2.8 Some general aspects of unsteady flow
2.9 Basic differential equations for gradually varied unsteady flow
2.10 Solution of the de St. Venant equations
2.11 Rectangular channels and the method of characteristics

3 SEDIMENT PROPERTIES
3.1 Introduction
3.2 Density and porosity
3.3 Size and size distribution
3.4 Shape
3.5 Fall velocity
3.6 Characteristic dimensionless parameters

4 DESIGN CRITERIA FOR IRRIGATION CANALS
4.1 Introduction
4.2 Flow control systems
4.2.1 Upstream control
4.2.2 Downstream control
4.3 The role of sediment transport in the design of irrigation canals
4.3.1 Regime method
4.3.2 Tractive force method
4.3.3 Permissible velocity method
4.3.4 Rational method
4.3.5 Final comments
4.4 Appurtenant canal structures
4.4.1 Irrigation structures
4.4.2 Main hydraulic principles for irrigation structures
4.4.3 Hydraulics for some irrigation structures
4.4.4 General remarks

5 SEDIMENT TRANSPORT CONCEPTS
5.1 Introduction
5.2 Friction factor predictors
5.2.1 Introduction
5.2.2 Bed form development
5.2.3 Effects of grains and bed forms on the roughness of the bed
5.2.4 Roughness of the side slopes
5.2.5 Equivalent roughness for non-wide irrigation canals
5.2.6 Comparison of the equivalent roughness predictors in trapezoidal canals
5.2.7 Prediction of composite roughness in a rectangular canal
5.2.8 Effect of bed forms on the flow resistance
5.2.9 Determination of the friction factor
5.3 Governing equations for sediment transport
5.3.1 Introduction
5.3.2 Initiation of sediment movement
5.3.3 Sediment transport in non-wide canals
5.3.4 Effects of the canal geometry and flow characteristics on the sediment transport
5.3.5 Velocity distribution in a trapezoidal canal
5.3.6 Exponent of the velocity in the sediment transport predictors
5.3.7 Correction factor for the prediction of the total sediment transport
5.3.8 Predictability of the predictors with the correction factor
5.3.9 Sediment transport in non-equilibrium conditions
5.4 Morphological changes of the bottom level
5.4.1 The modified Lax method
5.4.2 Sediment movement
5.5 Conclusions

6 SETRIC, A MATHEMATICAL MODEL FOR SEDIMENT TRANSPORT IN IRRIGATION CANALS
6.1 Upstream controlled irrigation systems
6.1.1 Introduction
6.1.2 Water flow equations
6.1.3 Sediment transport equations
6.1.4 General description of the mathematical model
6.1.5 Input and output data
6.2 Downstream controlled irrigation systems
6.2.1 Background
6.2.2 Downstream control considerations
6.2.3 Aspects of the downstream control module
6.2.4 Input and output data
6.3 Conclusions

7 THE SEDIMENT TRANSPORT MODEL AND ITS APPLICATIONS
7.1 Introduction
7.2 Description of the hydraulic and sediment characteristics for the given examples
7.3 Case 1 Changes in the discharge at the headworks
7.4 Case 2 Changes in the incoming sediment load
7.5 Case 3 Controlled sediment deposition
7.6 Case 4 Flow control structures
7.7 Case 5 Maintenance activities
7.8 Case 6 Management activities
7.9 Case 7 Effect of the design of control structures on the hydraulic behaviour and sediment transport
7.10 Review

REFERENCES

SYMBOLS

APPENDIX A METHODS TO ESTIMATE THE TOTAL SEDIMENT TRANSPORT CAPACITY IN IRRIGATION CANALS
A.1 Introduction
A.2 Ackers and White method
A.3 Brownlie method
A.4 Engelund and Hansen method
A.5 Van Rijn method
A.6 Yang Method

APPENDIX B METHODS TO PREDICT THE FRICTION FACTOR
B.1 Van Rijn
B.2 Brownlie
B.3 White, Paris and Bettess
B.4 Engelund

APPENDIX C HYDRAULIC DESIGN OF IRRIGATION CANALS
C.1 Introduction
C.2 Alignment of an irrigation canal
C.3 Water levels
C.4 Earthwork
C.5 Design of irrigation canals
C.6 Boundary shear stresses
C.7 Sediment transport criteria
C.8 Transport of the bed material
C.9 Final remarks
C.10 Computer aided design of canals

APPENDIX D DESCRIPTION OF THE MAIN ASPECTS OF THE REGIME THEORY
D Some regime considerations
D.1 Sediments
D.2 Maturing of canals
D.3 Slope adjustments
D.4 Diversion of the sediment
D.5 Maintenance aspects
D.6 Flow capacity
D.7 Design considerations

APPENDIX E GLOSSARY RELATED TO SEDIMENT TRANSPORT

APPENDIX F FLOW DIAGRAMS

SUBJECT INDEX

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## Author(s)

### Biography

Herman Depeweg, his research topics at Delft Hydraulics were related to hydraulic structures and sediment transport. He joined IHE in 1986 to lecture in hydraulics, computer applications and irrigation with the focus on all engineering aspects of irrigation at main, tertiary and field level. At IHE he has guided several MSc and PhD researches in sediment transport and has given guest lectures for UNESCO-IHE around the world.

Krishna Paudel obtained in 2010 his PhD degree and his research topic has been the role of sediment in the design and management of irrigation canals. He has more than 24 years’ experience in the planning, design, construction, monitoring and management of irrigation projects. Currently, he is associated with Consolidate Management Services, Nepal and provides his professional expertise in water resource development projects.

Néstor Méndez obtained in 1998 his PhD degree and his research topic has been the transport of sediment in irrigation canals. He has been associate professor at the Universidad Centro Occidental ‘Lisandro Alvarado’ at Barquisimeto, Venezuela. Since 1999, he is also guest lecturer at UNESCO-IHE and at several universities in South America. At present, he is active as consultant in land and water development in Venezuela.