Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized i Report No: 148630 – AFR Leveraging the Landscape Case Study of Erosion Control through Land Management in the Lake Victoria Basin May 2020 Environment, Natural Resource and Blue Economy Global Practice The World Bank © 2020 The World Bank 1818 H Street NW, Washington DC 20433 Telephone: 202-473-1000; Internet: www.worldbank.org Some rights reserved This work is a product of the staff of The World Bank. The findings, interpretations, and conclusions expressed in this work do not necessarily reflect the views of the Executive Directors of The World Bank or the governments they represent. The World Bank does not guarantee the accuracy of the data included in this work. 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Table of Contents ABBREVIATIONS AND ACRONYMS .................................................................................. iv ACKNOWLEDGMENTS ......................................................................................................... vi EXECUTIVE SUMMARY ...................................................................................................... vii CHAPTER 1. INTRODUCTION .............................................................................................. 1 CHAPTER 2. OVERVIEW OF LAND DEGRADATION AND SLWM PRACTICES IN LVB ........................................................................................................................................... 4 2.1 Land Degradation Problems in the LVB ........................................................................... 4 2.2 SLWM practices in LVB .................................................................................................... 5 CHAPTER 3. INTRODUCTION TO CASE STUDY AREA AND METHODOLOGY ........ 8 3.1 Description of the case study area .................................................................................. 8 3.2 Methodology used in the case study ............................................................................ 11 CHAPTER 4. LAND DEGRADATION AND EFFECTIVENESS OF SLWM–CASE STUDY FINDINGS ................................................................................................................ 17 4.1 Characterization of land degradation in the Simiyu River Catchment .......................... 17 4.2 Geo-spatial information of the selected hotspot micro-catchments ............................ 24 Spatio-temporal pattern of vegetation degradation in the micro-catchments .................. 29 4.3 Effectiveness of the identified SLWM options .............................................................. 34 4.4 Projected effectiveness of the selected SLWM under the near future climate change scenarios .............................................................................................................................. 38 4.5 Summary of the case study’s analytical findings ........................................................... 40 4.6 Beyond technical solutions ............................................................................................ 41 CHAPTER 5. MONITORING INDICATORS AND MEASURES OF SOIL EROSION REDUCTION .......................................................................................................................... 44 5.1 Overview of M&E approaches ....................................................................................... 44 5.2 M&E Indicators .............................................................................................................. 46 5.3 Methods for M&E of soil erosion and sediment ........................................................... 50 CHAPTER 6. RECOMMENDATIONS AND CONCLUSIONS ........................................... 54 6.1 Enhancing SLWM ........................................................................................................... 54 6.2 Developing an M&E system for SLWM .......................................................................... 55 6.3 Concluding remarks ....................................................................................................... 56 REFERENCES ........................................................................................................................ 57 i List of Tables Table 1. Classification of soil erosion risk. ............................................................................. 13 Table 2. Data used in the SWAT model, sources and their resolutions ................................. 13 Table 3. Model parameters used to represent pre-SLWM and Post SLWM conditions ......... 16 Table 4. Land use/cover change in the Simiyu catchment (1986-2016) ................................. 17 Table 5. Calibration and validation statistics........................................................................... 20 Table 6. Simulated flow, sediment yield, sediment and nutrient loads at the outlet of Simiyu catchment (1980-2009) ........................................................................................................ 21 Table 7. Kabondo micro-catchment land use/cover change (1986-2016) .............................. 24 Table 8. Nyamatembe micro-catchment land use/cover change (1986-2016) ........................ 25 Table 9. Gully length and density in Kabondo and Nyamatembe micro-catchments ............. 32 Table 10. Annual average flow, sediment and nutrient loads in Kabondo micro-catchment from 1980 to 2009 ................................................................................................................ 34 Table 11. Annual average flow, sediment and nutrient loads in Nyamatembe micro-catchment from 1980 to 2009 ................................................................................................................ 34 Table 12. SLWM interventions found in the pilot micro-catchments of the Simiyu catchment .............................................................................................................................................. 34 Table 13. Effectiveness of selected SLWM in sediment and nutrient reduction in Nyamatembe micro-catchment in 1980-2009 ...................................................................... 37 Table 14. Effectiveness of selected SLWM in sediment and nutrient reduction in Kabondo micro-catchment in1980-2009 ............................................................................................. 37 Table 15. Effectiveness of selected SLWM in sediment and nutrient reduction in Simiyu catchment in 1980-2009 ....................................................................................................... 38 Table 16. Projected change in average annual temperature and annual rainfall in the near future scenario (2010-2039). ................................................................................................ 38 Table 17. Projected flow, sediment load and concentration, and nutrient loads in Simiyu catchment, Kabondo and Nyamatembe micro-catchments in the near future (2010-2039) without SLWM..................................................................................................................... 39 Table 18. Relative change in water quality and quantity parameters in Simiyu catchment induced by the selected SLWM in the near future (2010-2039) under RCP 8.5.................. 40 Table 19. Relative change in water quality and quantity parameters in Kabondo micro- catchment induced by the selected SLWM in the near future (2010-2039) under RCP 8.5 40 Table 20. Relative change in water quality and quantity parameters in Nyamatembe micro- catchment induced by the selected SLWM in 2010-2039 under RCP 8.5 ........................... 40 Table 21. Farm level SLWM indicators proposed by SLWM specialists in Uganda and Tanzania ............................................................................................................................... 49 ii List of Figures Figure 1. Topography map of the Simiyu River Catchment, Tanzania ..................................... 8 Figure 2. Soil Map of the Simiyu River Catchment, Tanzania ................................................. 9 Figure 3. Land use/cover of Simiyu River Catchment ............................................................ 10 Figure 4. Variation of average monthly rainfall, potential evapotranspiration, and discharge at the outlet of the Simiyu River (1999–2004) ......................................................................... 10 Figure 5. Land use/cover in Simiyu River Catchment (2016) ................................................