UNIVERSITY OF NEWCASTLE UPON TYNE DEPARTMENT OF CIVIL ENGINEERING MULTICRITERION APPROACH TO THE EVALUATION OF IRRIGATION SYSTEMS PERFORMANCE Omer M.A. Elawad Thesis Submitted for the degree of Doctor of Philosophy April 1991 ACKNOWLEDGEMENTS I would like to express my sincere gratefulness to my two supervisors: Mr. J.W. Gowing of the Department of Agricultural and Environmental Sciences and Dr. J.A. Mawdsley of the Department of Civil Engineering, University of Newcastle Upon Tyne, United Kingdom. Their guidance and constructive comments were invaluable in completing this work. The Ministry of Irrigation, Sudan, granted me with a study leave in addition to full financial support during the time of this study. This is fully acknowledged. I am also indebted to many of my colleagues and friends for their help, particularly the staff of the Hydraulics Research Station of the Ministry of Irrigation, Wad Medani, Sudan, for their help in the data collection. Special thanks go to Dr. Ahmed Salih Hussain for his support and encouragement. Last and not least, I am deeply grateful to my parents and wife Sarnia for their patience and encouragements throughout the time of this study. This gratefulness is also extended to my sons Ehab and Harith. ABSTRACT Multicriterion Approach to the Evaluation of Irrigation Systems Performance In recent years the importance and the lack of comprehensive methodologies for measuring the performance of existing irrigation schemes has been widely expressed. The objective of this study is to develop a systematic procedure by which some use can be made of the large quantities of data, already routinely collected in irrigation schemes, for the purpose of their regular seasonal evaluation. Consideration is confined to the performance of the main irrigation system of small-holder, canal-fed irrigation schemes of the developing countries. A generalized conceptual framework has been developed for a methodology by which the performance criteria for any irrigation system can be identified and combined together into a single index which measures the overall performance of the system. Six criteria have been identified as adequate for characterizing the important features of the performance of any irrigation system. These are; adequacy, equity, water losses, water user convenience, cost and durability. New methods for characterizing each of adequacy, equity and water user convenience have been developed and tested using data from the Gezira scheme, Sudan. Characterization of adequacy, equity and water losses involves the development of a soil moisture simulation model and characterization of the water user convenience involves the use of the concept of the fuzzy set theory. Identification of the criteria to be used in evaluating any particular system(s) and evaluating the trade-offs between them requires the participation of the decision-maker in the system(s) to be evaluated. This is achieved through the use of the multi-attribute utility theory. It has been applied with a group of Sudanese officials in order to derive their utility functions. The utility function reflects the decision-maker's strength of preferences over different achievement levels of each objective and his trade-offs between different objectives. The derived utility functions are reported and their usefulness is discussed. The methodology developed provides a useful tool for measuring the performance of irrigation systems, comparing the performance of different systems and assessing improvement in performance resulting from rehabilitation investments. CONTENTS ACKNOWLEDGEMENTS ABSTRACT CONTENTS LIST OF FIGURES viii LIST OF TABLES xi LIST OF ABBREVIATIONS AND IMPORTANT SAMPLES xii 1. CHAPTER 1 - INTRODUCTION 1 1.1. Prelude 1 1.2. The Objective and Scope of the Study 4 1.3. Overview of the Thesis 7 2. CHAPTER 2 - LITERATURE REVIEW 10 2.1. Criteria for Irrigation Systems Performance Evaluation 10 2.1.1. Historical Background 10 2.1.2. Irrigation Efficiency 12 2.1.3. Equity 17 2.1.4. Consideration of Other Criteria 21 2.1.5. Productivity 26 2.1.6. Adequacy 27 2.2 Multicriteria Evaluation Techniques 30 2.2.1. Historical Background 30 2.2.2. Techniques Not Asking for Explicit Statement of Preferences 35 2.2.3. Techniques Requiring Explicit Statement of Preferences 38 3. CHAPTER 3 - CONCEPTUAL FRAMEWORK 45 3.1. General Approach for Evaluation 45 3.2. Nature of Irrigation Systems Objectives 48 3.2.1. Multiplicity and Conflicting Nature of the Objectives 49 3.2.2. Variability of Objectives and Trade-offs 50 3.3. Identification of the Performance Criteria 54 3.3.1. Desired Features of a Set of Attributes 54 3.3.2. Hierarchy of Objectives 55 3.4. Durability 62 3.5. Operation and Maintenance Cost 64 3.5.1. What Costs are to be Included in the Evaluation 64 4. CHAPTER 4 - CHARACTERIZATION OF THE CASE STUDY 66 4.1. Irrigation Systems in Sudan 66 4.1.1. Historical Background 66 4.1.2. Distribution of Existing Irrigation Developments 67 4.1.3. Soil Type and Salinity 70 4.1.4. Water Availability 71 4.1.5. Management Structure 73 4.1.6. Methods of Irrigation 75 4.2. Gezira Irrigation Scheme 76 4.2.1. Climate 76 4.2.2. Scheme Lay Out 78 4.2.3. Management Organization 82 4.2.4. Method of Water Management 83 4.2.5. Allowance for Transmission Losses 86 4.3. Data Routinely Collected in Irrigation Systems in Sudan 87 4.3.1. Meteorological Data 88 4.3.2. Agricultural Data 89 4.3.3. Soil and Crop Characteristics 90 4.3.4. Cost Elements 90 4.3.5. Water Supply Data 92 5. CHAPTER 5 - WATER SUPPLY ADEQUACY, EQUITY AND WATER LOSSES 97 5.1 Adequacy of Irrigation Supply 97 5.2. Soil/Water Reservoir System 99 5.3. Actual Evapotranspiration 102 iv 5.3.1. Climate 103 5.3.2. Crop Characteristics 103 5.3.3. Soil Moisture Availability 104 5.4. Soil Moisture Simulation Model 106 5.4.1. Description of the Model 106 5.4.2. Validation of the Simulation Model 108 5.4.3. Model Example Output 111 5.5. Characterization of Water Stress Condition 113 5.6. Characterization of the Water Supply Adequacy 115 5.6.1. The Stress Intensity-Duration Curve 116 5.6.2. The Irrigation Adequacy Index (IAI) 120 5.7. Characterization of Equity 127 5.8. Characterization of Water Losses 129 5.9. Analysis of Water Supply to the Gezira Scheme 131 5.9.1. Supplies at the Dam Headwork 132 5.9.2. Supplies at the Minor Canals Off-takes Level 134 5.9.3. Supplies at the Field Outlet Level 139 5.10. Discussion of Results 142 6. CHAPTER 6 - WATER USERS CONVENIENCE 147 6.1. Introduction 147 6.2. features of a convenient Water supply schedule 148 6.2.1. Predictability 149 6.2.2. Timing of the Water Supply 150 6.2.3. Flow Rate and Duration of Supply 152 6.3. An Approach for Evaluation 153 6.4. Fuzzy sets 155 6.5. Operation rule for Fuzzy Sets 158 6.5.1. Union and Intersection 159 6.5.2. Hedges 160 6.5.3. Convexity 161 6.5.4. Normalization 163 6.5.5. Linguistic Approximation 164 6.6. Aggregation of Opinions 165 6.7. Evaluation of the Irrigator Convenience 168 V 6.8. Utility Measure 172 6.9. Computerization of the Analysis 174 6.10. Sensitivity Analysis 175 6.11. Application in the Gezira Scheme, Sudan 177 6.12. Concluding Remarks 181 7. CHAPTER 7 - OVERALL PERFORMANCE INDEX 183 7.1. Motivation for MAUT 184 7.2. Derivation of the Overall utility Function 186 7.2.1. Preparation for the Assessment 187 7.2.2. Verification of the Necessary Independence Conditions 188 7.2.3. Assessing Individual Attribute Utility Functions 194 7.2.4. Determination of the Scaling Constants 196 7.3. Application to the Irrigation Systems in Sudan 197 7.4. Overall Performance Index 212 7.5. Application in the Gezira scheme, Sudan 214 7.6. Concluding Remarks 219 8. CHAPTER 8 - SUMMARY, CONCLUSION AND RECOMMENDATIONS 223 8.1. Summary 223 8.2. Conclusions and contributions of the Study 226 8.2.1. General Conclusions 226 8.2.2. Conclusions related to the Case Study 229 8.2.3. Contributions of the Study 231 8.3. Appraisal of the Study 231 8.4. Recommendations for other Studies 234 REFERENCES 236 APPENDICES 245 APPENDIX A - SOIL MOISTURE VARIATION GRAPHS 245 APPENDIX B - AN INTERVIEW WITH A DECISION-MAKER 258 vi APPENDIX C.1 - SOIL MOISTURE SIMULATION MODEL 266 APPENDIX C.2 - MODEL FOR CALCULATING IRRIGATION ADEQUACY INDEX (IAI) 275 vii LIST OF FIGURES 2.1 Graphical solution of a multiobjective problem with two objective. 33 3.1 Adopted hierarchy of objectives and criteria of irrigation systems. 59 4.1 Distribution of the main existing and proposed irrigation developments in Sudan. 68 4.2 The Gezira irrigation scheme (source: Wallach (1988)). .0.4 77 4.3 Typical lay out of the field irrigation system in the Gezira scheme. 80 5.1 Contributions of different subareas to the total soil moisture reservoir volume. 100 5.2 Variation of ETa with the soil moisture level. 105 5.3 Variation of the crop factor (k c ) for the crops grown in the Gezira scheme (derived from Farbrother (1977)). 0.04 110 5.4 Assumed root development pattern for the crops grown in the Gezira scheme. 110 5.5 Measured and predicted soil moisture variation: GARS farm, Wad Medani, Sudan. 111 5.6 Irrigation, rainfall and ETo. Number 18, Hamza minor. 112 5.7 Average soil moisture, Number 18, Hamza minor, 1986/87 season. 112 5.8 Soil moisture variation curve and different stress, levels, Number 18, Hamza minor, 1986/87 season.