Evacuation of Sediments from Reservoirs

Contents

Illustrations XV

1. Executive summary 1

1.1. Introduction, 3

1.2. Summary of conclusions, 4

1.2.1. Review of sedimentation in reservoirs, 4

1.2.2. Research into factors which influence sediment flushing, 7

1.2.3. Worldwide experience of sediment flushing, 9

1.2.4. Geographical areas suited to flushing, 11

1.2.5. Site-specific investigations and design considerations, 13

2. Review of sedimentation in reservoirs 15

2.1. Summary, 17

2.2. World total reservoir storage, 17

2.2.1. ICOLD World register of dams, 17

2.2.2. Other sources, 18

2.2.3. Conclusion, 18

2.3. Worldwide distribution of existing storage, 18

2.3.1. Global water resources, 18

2.3.2. Geographical distribution, 19

2.4. World demand for more storage, 19

2.4.1. Population, 19

2.4.2. Irrigation, 21

2.4.3. Hydropower, 21

2.4.4. Conclusion, 23

2.5. Distribution of demand for more storage, 23

2.5.1. Europe, 23

2.5.2. North America, 24

2.5.3. South and Central America, 25

2.5.4. Africa, 26

2.5.5. Asia and Oceania, 27

2.5.6. Summary, 28

2.6. Rate and distribution of construction of new reservoirs, 28

2.6.1. Worldwide, 28

2.6.2. Distribution of construction of storage, 30

2.6.3. Comparison of storage construction with demand, 30

2.7. Rate and distribution of loss of storage, 31

2.7.1. Rate of loss of storage, 31

2.7.2. Distribution of loss of storage, 32

2.8. Trends in the rate of loss of storage, 34

2.9. Reservoir size and rate of loss of storage, 35

2.10. Requirements for new storage, 36

3. Research into factors which influence flushing 37

3.1. Introduction, 39

3.2. The mechanism of flushing, 40

3.3. The development of criteria for successful flushing, 42

3.3.1. Sediment balance, 42

3.3.2. Sustainable reservoir capacity, 47

3.3.3. Evaluation of flushing criteria, 50

3.3.4. Practical criteria for successful flushing, 50

3.4. Summary of the requirements for effective flushing, 58

3.4.1. Hydraulic conditions required for efficient flushing, 58

3.4.2. Quantity of water available for flushing, 59

3.4.3. Mobility of reservoir sediments, 59

3.4.4. Site-specific factors, 60

3.4.5. Constraints on the ultimate capacity achievable by sediment flushing, 60

3.4.6. Economic assessment, 60

3.4.7. Summary, 60

3.5. Numerical models, 61

4. Worldwide experience of sediment flushing 63

4.1. Introduction, 65

4.2. Flushing, 66

4.3. Worldwide experience of flushing, 67

4.3.1. Overview, 67

4.3.2. Flushing techniques, 67

4.3.3. Sediments flushed, 70

4.4. Case studies of reservoir flushing, 71

4.4.1. Summary, 71

4.4.2. Findings, 81

4.4.3. Summary of findings, 88

5. Geographical areas suited to flushing 91

5.1. Worldwide variation in erosion rates, 93

5.1.1. Factors that affect erosion, 93

5.1.2. Estimates of global sediment yield, 93

5.1.3. Maps of global variation in sediment yields, 100

5.2. Climatic zones of the world, 101

5.2.1. Introduction, 101

5.2.2. Precipitation regimes and their seasonal variation, 101

5.2.3. Koppen classification, 108

5.2.4. Relationship between climate zone and erosion rates, 115

5.3. Geographical areas suitable for flushing, 120

5.3.1. Introduction, 120

5.3.2. Factors affecting erosion rates, 120

5.3.3. Sediment delivery ratio, 122

5.3.4. Hydrological characteristics, 123

5.3.5. Areas of the world which are best suited to reservoir flushing, 123

6. Site-specific investigations and design considerations 125

7. References 131

8. Bibliography 141

Appendices 149

Appendix 1. Reservoir data, 151

Appendix 2. Numerical model case study, 163

Appendix 3. Flushing case studies, 171

Appendix 4. Erosion, 211

Index 251