Water Allocation Models for the Incomati River Basin, Mozambique June 2016 Commissioned by Wetterskip Fryslân ARA-Sul Authors Froukje de Boer Peter Droogers Report FutureWater: 154 FutureWater Costerweg 1V 6702 AA Wageningen The Netherlands +31 (0)317 460050 [email protected] www.futurewater.nl Contents 1 Introduction 7 1.1 ARA-Sul 7 2 Incomati 8 2.1.1 Overview 8 2.1.2 Climate 9 2.1.3 Water Resources 9 2.1.4 Catchment Infrastructure 10 3 Water Allocation Models Development 12 3.1 WEAP backgound 12 3.2 WAM-Strategic 13 3.2.1 Introduction 13 3.2.2 Data 13 3.2.3 Factory Acceptance Test 20 3.2.4 Site Acceptance Test 27 3.2.5 Current situation 27 3.3 WAM-Operational 28 3.3.1 Introduction 28 3.3.2 Data 28 3.3.3 Factory Acceptance Test 36 3.3.4 Site Acceptance Test 45 4 Strategic Water Allocation using WAM-S 46 4.1 Scenario Development 46 4.2 Results 47 4.2.1 Water shortage 47 4.2.2 Reservoir volume 49 4.2.3 Outflow of Incomati into the Indian Ocean 49 4.2.4 Adaptation scenarios 51 4.2.5 Water quality 53 5 Water Licensing Scenarios using WAM-O 56 5.1 Scenario Development 56 5.2 Result 57 5.2.1 Water shortage 57 5.2.2 Reservoir volume 60 5.2.3 Outflow of Incomati into the Indian Ocean 61 2 6 Monitoring and Data Management 63 6.1 Data Needs 63 6.2 Data Availability 63 6.3 Recommendations on Monitoring and Data Management 64 7 Conclusions and Recommendations 66 7.1 Conclusions Current Project 66 7.2 Future Outlook 67 8 Selected References 68 APPENDIX I: WEAP Land Use Parameters 69 Appendix II: Climate change projection 71 APPENDIX III: Implementation of Scenarios 73 APPENDIX IV: Glossary 75 APPENDIX V: Errors in Water Balance Calculations 76 APPENDIX VI: Participants of Distance Training and Intensive Training Week 80 APPENDIX VII: Evaluation traineeship G. Macaringue 81 3 Tables Table 1. Some key data according to http://www.thewaterpage.com/WWW-domino2.PDF. ..... 10 Table 2. Number of agreed and realized nodes in WAM-S ........................................................ 21 Table 3. Flow gauging stations.................................................................................................... 21 Table 4. Factory Acceptance Test (FAT) for the flow at the Incomati entering Mozambique (1981-2010). ................................................................................................................... 23 Table 5. Factory Acceptance Test (FAT) for the inflow at Corumana (1989-2010). ................... 25 Table 6. Factory Acceptance Test (FAT) for the flow at Magude (1981-2010). .......................... 26 Table 7. Characteristics of the Corumana reservoir. ................................................................... 31 Table 8. Domestic water demand of cities included in WAM-O .................................................. 33 Table 9. Irrigation water demand included in WAM-O ................................................................ 33 Table 10. Daily water requirements (m3/s) of Xinavane and Maragra (source: ARA-Sul) .......... 34 Table 11. Monthly shares of water use for Xinavane and Maragra ............................................ 34 Table 12. Industrial water users included in WAM-O .................................................................. 35 Table 13. Number of agreed and realized nodes in WAM-O ...................................................... 36 Table 14. Factory Acceptance Test (FAT) for the Corumana reservoir volume (2005-2014). ... 38 Table 15. Factory Acceptance Test (FAT) for the outflow of the Corumana reservoir (2005- 2014). ............................................................................................................................. 39 Table 16. Summary of Corumana reservoir outflow in 2007 (source: ARA-Sul) ........................ 40 Table 17. Factory Acceptance Test (FAT) for the flow of Incomati at Magude (2005-2014). ..... 43 Table 18. Precipitation trend of 1975-2014 for the catchments in the Incomati River Basin ...... 47 Table 19. Exceedance probability of annual outflow of Incomati between 2011 and 2050 ........ 51 Table 20. Projected annual water shortage and percentage of days with water shortage in 2016 for different scenarios ..................................................................................................... 58 Table 21. Projected moment of the year the reservoir elevation will become lower than 95 m for different development scenarios .................................................................................... 60 Table 22. Projected moment of the year the reservoir elevation will become lower than 95 m for different inflow and water saving scenarios ................................................................... 61 Table 23. Projected percentage of the year 2016 during which the outflow of Incomati to the Indian Ocean will be lower than 5 m3/s for different development scenarios................. 62 Table 24. Projected percentage of the year 2016 during which the outflow of Incomati to the Indian Ocean will be lower than 5 m3/s for different inflow and water saving scenarios 62 Table 25. Participants of the distance training ............................................................................ 80 Table 26. Final participants for intensive training week in Mozambique: .................................... 80 Figures Figure 1. Overview of the Incomati Basin. .................................................................................... 8 Figure 2. Subbasins in the Incomati River Basin. ......................................................................... 9 Figure 3: Relation between spatial scale and physical detail in water allocation tools. The green ellipses show the key strength of some well-known models. (Source: Droogers and Bouma, 2014) ................................................................................................................. 12 Figure 4: Elevation (in meters) based on HydroSHEDS ............................................................. 14 Figure 5: Watersheds delineation based on DEM and country borders. .................................... 15 Figure 6: Schematization of Catchments in WAM-S as implemented in WEAP. ........................ 15 Figure 7: Population density in cap / km2 (Source: www.worldpop.org.uk). ................................ 17 Figure 8: Total population for each of the 24 sub-basins. ........................................................... 18 4 Figure 9. Relationship between population per catchment and industrial units and irrigation area (top) and resulting water demand (bottom). ................................................................... 19 Figure 10. Flow gauging stations in Mozambique. ...................................................................... 22 Figure 11. Observed and simulated flow for the Incomati entering Mozambique. ...................... 23 Figure 12. Observed and simulated flow for the inflow into Corumana. ..................................... 24 Figure 13. Location of streamflow gauging stations 43 and 44. .................................................. 25 Figure 14. Observed and simulated flow for the flow at Magude. ............................................... 26 Figure 15. Annual water balance for the entire Incomati Basin. ................................................. 27 Figure 16. Annual water balance for the entire Incomati Basin, showing only water in the river (Runoff, Return Flows) and abstractions from the river (Outflow, Abstractions) and reservoirs (ReservoirE, Δ Storage). ............................................................................... 28 Figure 17. Flow gauging stations in South-Africa and Mozambique (only E23 and E43). .......... 29 Figure 18. Schematization of WAM-O. ........................................................................................ 30 Figure 19. Monthly shares of annual water use for Xinavane and Maragra ............................... 35 Figure 20. The sluices of Corumana reservoir (http://www.panoramio.com/photo/96326009) .. 36 Figure 21. Observed and simulated daily reservoir volumes of the Corumana reservoir. .......... 37 Figure 22. Observed and simulated averaged monthly outflows of the Corumana Reservoir between 2005 and 2014. ................................................................................................ 38 Figure 23. Observed and simulated monthly averaged outflows of the Corumana reservoir over 2005-2014. ..................................................................................................................... 39 Figure 24. Daily observed outflow (red line) and simulated outflow (blue line) of Corumana Reservoir in 2007. .......................................................................................................... 40 Figure 25. Hydropower turbine outflow versus reservoir elevation (upper panel) and versus reservoir inflow (lower panel). ........................................................................................ 41 Figure 26. Observed and simulated averaged monthly flows at Magude between 2005 and 2014. ............................................................................................................................... 42 Figure 27. Observed and simulated monthly averaged outflows of the Corumana reservoir over 2005-2014. ..................................................................................................................... 43 Figure 28. Observed streamflow of Incomati at Ressano Garcia (red line), at Magude (green line) and simulated streamflow