Water Resources Modelling, Baseline Scenario, Yield Analysis, Stochastic Verification and Validation Integrated Water Resources Management Plan for the Orange-Senqu River Basin 2014 Report No. ORASECOM 014/2014 The Support to Phase 3 of the ORASECOM Basin-wide Integrated Water Resources Management Plan Study was commissioned by the Secretariat of the Orange-Senqu River Basin Commission (ORASECOM) with technical and financial support from the German Federal Ministry for Economic Cooperation and Development (BMZ) in delegated cooperation with the UK Department for International Development (DFID) and the Australian Department of Foreign Affairs and Trade (DFAT) implemented through Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ)°. Prepared by in association with Report No. ORASECOM 014/2014 l Support to Phase 3 of the ORASECOM Basin-wide integrated Water Resources Management Plan Water Resources Modelling, Baseline Scenario, Yield Analysis, Stochastic Verification and Validation Integrated Water Resource Management Plan for the Orange-Senqu River Basin Compiled by : Caryn Seago and Hermanus Maré WATER RESOURCES MODELLING, BASELINE SCENARIO, YIELD ANAYSIS, STOCHASTIC VERIFICATION AND VALIDATION Integrated Water Resources Management Plan for the Orange-Senqu River Basin – Phase 3 1. INTRODUCTION ..................................................................................... 1 1.1 Context and objectives of the Study 1 1.1.1 General Context 1 1.1.2 Water resources context 1 1.1.3 Phase 3 of the Basin-wide IWRM Plan 3 1.2 This Report 4 1.2.1 Rationale 4 1.2.2 Tasks undertaken under Work Package 4c 5 1.2.3 Objective of this report 6 1.2.4 Structure of the report 6 2. RESOURCE MODELLING AND SCENARIO SELECTION CONTEXT ........ 7 2.1 Current situation 7 2.1.1 Integrated Vaal System Operating rules 10 2.1.2 Orange Senqu system 14 2.1.3 Fish River Namibia 17 2.1.4 Molopo River catchment 17 2.2 Key water resource related Issues 18 2.3 National and Transboundary Priorities and Strategies 19 3. DEVELOPMENT AND MANAGEMENT OPTIONS ................................. 21 3.1 Process to define scenarios in support of the iwrmp 21 3.2 Baseline Scenario 28 3.2.1 Baseline Scenario Definition (Scenario 0) 28 Water resources modelling , Baseline scenario, yield anaysis, stochastic verification and validation / Integrated Water Resources Management Plan for the Orange - Senqu River Basin – Phase 3 3.3 Definition and selection of scenarios 31 4. WATER RESOURCE MODELING RESULTS ............................................. 39 4.1 Water Resource Planning Model Analysis 39 4.1.1 Baseline Scenario analyses and results 39 4.1.2 Results from Scenario 1.1 and 1.2 47 4.1.3 Results from Scenario 2.1 and 2.2 50 4.1.4 Analyse the impact of Updated EWRs (Scenario 3.1, 4.1 & 5.1) 57 4.1.5 Intervention options to increase the ORP system Yield - Scenario 4.2 & 4.3 61 4.2 Water Resource Yield Model Analysis 64 4.2.1 Orange River Project – Yield Impact due to Sedimentation 64 4.2.2 Caledon River – Impact due to Sedimentation 65 4.2.3 LHWP Storage and sedimentation 65 4.2.4 Vaal River System – Sedimentation Impacts 65 4.2.5 Neckartal Dam - Impact of sedimentation 65 4.3 Selected Core Scenario 66 4.3.1 Core Scenario Results - IVRS 66 4.3.2 Core Scenario Results – Greater Bloemfontein System 69 4.3.3 Core Scenario Results – Orange River Project (ORP) 73 4.3.4 Core Scenario Results – Other Important Water Supply Systems 80 5. EVALUATION CRITERIA ........................................................................ 87 6. PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS ............... 89 6.1 Baseline and updated baseline Scenarios 89 6.2 Scenario 2 – LHWP Phase ii impacts 90 6.3 Scenario 3 & 4 – EWR impacts 90 6.4 Core Scenario Results 92 6.4.1 Integrated Vaal River System 92 6.4.2 Orange River Project System (Gariep and Vanderkloof dams) 93 6.4.3 Greater Bloemfontein system 95 6.4.4 Recently completed Metolong Dam 95 6.4.5 Neckartal Dam currently under construction in Namibia 96 6.4.6 Botswana transfers 96 7. REFERENCES ......................................................................................... 97 ANNEXES ................................................................................................. 99 Annex 1. WRPM Schematic Diagrams 101 Annex 2. Demand Projections 105 Annex 3. Figures 123 Water resources modelling , Baseline scenario, yield anaysi s, stochastic verification and validation / Integrated Water Resources Management Plan for the Orange - Senqu River Basin – Phase 3 LIST OF FIGURES AND TABLES FIGURES Figure 1-1: Orange – Senqu River Basin ............................................................................................. 1 Figure 2-1: Location and size of reservoir storage in the Orange-Senqu Basin .......................... 7 Figure 2-2: Location of transfers in the Orange-Senqu Basin ......................................................... 8 Figure 4-1: IVRS Curtailment Plot Baseline Scenario ...................................................................... 42 Figure 4-2: ORP Curtailment Plot Baseline Scenario ...................................................................... 43 Figure 4-3: Greater Bloemfontein Curtailment Plot Baseline Scenario ....................................... 44 Figure 4-4: Bloemhof Dam storage projection for Baseline Scenario......................................... 45 Figure 4-5: Water quality (TDS) in the Vaal River just downstream of Vaal Barrage ................ 46 Figure 4-6: Water quality (TDS) in the Vaal River just downstream of Vaal Barrage ................ 47 Figure 4-7: Water quality (TDS) in the Vaal River just upstream of Douglas Weir...................... 47 Figure 4-8: Water quality (TDS) in the Orange River at the River Mouth .................................... 48 Figure 4-9: Bloemhof Dam storage projection for Scenario 1.1 .................................................. 49 Figure 4-10: Gauteng water supply area North/South catchment divide and sewage drainage areas ............................................................................................................. 50 Figure 4-11: Duel support requirements from LHWP Polihali Dam ............................................... 51 Figure 4-12: LHWP transfer to the Vaal Scenario 2.1 versus 2.2 .................................................. 52 Figure 4-13: Simulated Polihali Dam support to the IVRS and to the ORP ................................. 52 Figure 4-14: Polihali Dam Storage Projection Scenario 2.2........................................................... 53 Figure 4-15: Vaal Dam storage Projection Scenario 2.1 versus 2.2 ............................................. 53 Figure 4-16: Bloemhof Dam Storage Projection Scenario 2.1 versus 2.2 .................................... 54 Figure 4-17: Gariep Dam Storage Projection Scenario 2.1 versus 2.2 ........................................ 55 Figure 4-18: Namakwa urban and mining water supply Scenario 2.1 & 2.2 ............................. 55 Figure 4-19: Namakwa urban and mining water supply Scenario 3.1 & 2.2 ............................. 57 Figure 4-20: Gariep Dam storage projections for Scenario 4.1 & 2.2 ......................................... 58 Figure 4-21: Namakwa urban and mining water supply Scenario 4.1 & 2.2 ............................. 58 Figure 4-22: Gariep Dam Storage projection for Scenario 4.1 & 5.1 .......................................... 59 Figure 4-23: Namakwa urban and mining water supply Scenario 4.1 & 5.1 ............................. 59 Figure 4-24: Combined Gariep and Vanderkloof Storage projection for Scenario 4.1 & 4.2 62 Figure 4-25: Namakwa urban and mining water supply Scenario 4.1 & 4.2 ............................. 62 Figure 4-26: Combined Gariep and Vanderkloof Storage projection for Scenario 4.2 & 4.3 62 Figure 4-27: Namakwa urban and mining water supply Scenario 4.2 & 4.3 ............................. 63 Figure 4-28: Vaal Dam Storage projection for Scenario 2.2 & 4.3 .............................................. 63 Figure 4-29: Vaal Dam and Vaal System Storage projection for Scenario 4.3 ......................... 63 Figure 4-30: Vaal System Storage projection for Scenario 7.1 & 7.2 ........................................... 66 Figure 4-31: The Integrated Vaal system Water balance using high demand projection with WC/WDM, the removal of unlawful irrigation and desalination of the AMD water. ............................................................................................................................. 67 Water resources modelling , Baseline scenario, yield anaysis, stochastic verification and validation / Integrated Water Resources Management Plan for the Orange - Senqu River Basin – Phase 3 Figure 4-32: Vaal System Curtailment Plot for Scenario 7.1 & 7.2 ............................................... 68 Figure 4-33: Polihali Dam and LHWP Storage projections for Scenarios 7.1 & 7.2 .................... 68 Figure 4-34: Greater Bloemfontein Water Supply System ............................................................ 70 Figure 4-35: Greater Bloemfontein System Water balance ......................................................... 70 Figure 4-36: Greater Bloemfontein System Storage projection for Scenario 7.1 & 7.2 ............ 71 Figure 4-37: Greater Bloemfontein System supply for Scenario 7.1 & 7.2 .................................. 72 Figure 4-38: Orange River project water supply system ............................................................... 73 Figure 4-39: Orange River Project