ASSESSING ENVIRONMENTAL FLOW REQUIREMENTS FOR THE MARROMEU COMPLEX OF THE ZAMBEZI DELTA: APPLICATION OF THE DRIFT MODEL (DOWNSTREAM RESPONSE TO IMPOSED FLOW TRANSFORMATIONS) Compiled and edited by Dr. Richard Beilfuss Carr Foundation-USA and International Crane Foundation-USA Dr. Cate Brown Southern Water Ecological Research and Consulting-South Africa May 2006 Museum of Natural History - University of Eduardo Mondlane Maputo, Mozambique i Table of Contents TABLE OF CONTENTS ............................................................................................. II 1. INTRODUCTION..................................................................................................... 1 1.1 THE MARROMEU COMPLEX OF THE ZAMBEZI DELTA ........................................ 1 1.2 HISTORY OF WATER RESOURCES DEVELOPMENT IN THE ZAMBEZI DELTA.......... 2 1.3 INTEGRATING WATER RESOURCES MANAGEMENT WITH THE MARROMEU COMPLEX MANAGEMENT PLANNING PROCESS ................................................ 4 1.4 AIMS OF THE PROJECT.................................................................................... 5 1.5 THE USE OF EXPERT OPINION.......................................................................... 5 1.6 REPORT OVERVIEW ........................................................................................ 6 1.7 ACKNOWLEDGEMENTS ................................................................................... 6 2. THE PROCESS AND STUDY TEAM ..................................................................... 9 2.1 THE ENVIRONMENTAL FLOW PROCESS USED ................................................... 9 2.2 BASIC ASSUMPTIONS .................................................................................... 10 2.3 SCORING SYSTEM USED ............................................................................... 11 2.4 THE STUDY TEAM ......................................................................................... 11 2.5 THE TERMS OF REFERENCE FOR SPECIALISTS .............................................. 12 2.6 SCHEDULE OF ACTIVITIES ............................................................................. 14 3. BACKGROUND – HYDROLOGY AND HYDROPOWER .................................... 15 3.1 INTRODUCTION............................................................................................. 15 3.2 DESCRIPTION OF CHANGE LEVELS FOR DRY SEASON LOW FLOW..................... 15 3.3 DESCRIPTION OF CHANGE LEVELS FOR WET SEASON ANNUAL FLOWS ............. 17 3.4 DESCRIPTION OF CHANGE LEVELS FOR 1:5 FLOODING EVENT ......................... 23 3.5 MODELING TRADE-OFFS BETWEEN HYDROPOWER GENERATION AND ANNUAL FLOOD RELEASES FOR MEETING HYDROLOGICAL CHANGE LEVELS .................. 25 4. BACKGROUND - ZAMBEZI DELTA MASS TRANSFER MODEL...................... 34 4.1 INTRODUCTION............................................................................................. 34 4.2 TECHNICAL APPROACH................................................................................. 35 4.3 RESULTS ..................................................................................................... 39 4.4 CONCLUSIONS ............................................................................................. 53 5. SPECIALIST STUDY – AGRICULTURE.............................................................. 55 5.1 INTRODUCTION............................................................................................. 55 5.2 SELECTION OF KEY SUB-COMPONENTS.......................................................... 55 5.3 DESCRIPTION OF STATUS PRIOR TO RIVER REGULATION................................. 56 5.4 DESCRIPTION OF THE CURRENT TRAJECTORY IN CONDITION........................... 57 5.5 DESCRIPTION OF DESIRED TARGET CONDITION .............................................. 57 5.6 EVALUATION AND RANKING THE HYDROLOGICAL FLOW CATEGORIES............... 60 5.7 DRIFT CONSEQUENCES ............................................................................... 61 5.8 DISCUSSION................................................................................................. 61 6. SPECIALIST STUDY – ESTUARINE ECOLOGY AND COASTAL FISHERIES. 63 6.1 INTRODUCTION............................................................................................. 63 6.2 SELECTION OF KEY SUB-COMPONENTS.......................................................... 63 6.3 DESCRIPTION OF STATUS PRIOR TO RIVER REGULATION................................. 65 6.4 DESCRIPTION OF THE CURRENT TRAJECTORY IN CONDITION........................... 65 6.5 DESCRIPTION OF DESIRED TARGET CONDITION .............................................. 65 6.6 EVALUATION AND RANKING THE HYDROLOGICAL FLOW CATEGORIES............... 65 ii 6.7 DRIFT CONSEQUENCES ............................................................................... 67 6.8 DISCUSSION................................................................................................. 67 7. SPECIALIST STUDY – FRESHWATER FISHERIES .......................................... 68 7.1 INTRODUCTION............................................................................................. 68 7.2 SELECTION OF KEY SUB-COMPONENTS.......................................................... 69 7.3 DESCRIPTION OF STATUS PRIOR TO RIVER REGULATION................................. 70 7.4 DESCRIPTION OF THE CURRENT TRAJECTORY IN CONDITION........................... 72 7.5 DESCRIPTION OF DESIRED TARGET CONDITION .............................................. 73 7.6 EVALUATION AND RANKING OF THE HYDROLOGICAL FLOW CATEGORIES.......... 74 7.7 DRIFT CONSEQUENCES ............................................................................... 76 7.8 DISCUSSION................................................................................................. 76 8. SPECIALIST STUDY – LIVESTOCK ................................................................... 79 8.1 INTRODUCTION............................................................................................. 79 8.2 SELECTION OF KEY SUB-COMPONENTS.......................................................... 79 8.3 DESCRIPTION STATUS PRIOR TO RIVER REGULATION...................................... 79 8.4 DESCRIPTION OF THE CURRENT TRAJECTORY IN CONDITION........................... 80 8.5 DESCRIPTION OF DESIRED TARGET CONDITION .............................................. 80 8.6 EVALUATION AND RANKING THE HYDROLOGICAL FLOW CATEGORIES............... 80 8.7 DRIFT CONSEQUENCES ............................................................................... 80 8.8 DISCUSSION................................................................................................. 80 9. SPECIALIST STUDY – LARGE MAMMALS ....................................................... 82 9.1 INTRODUCTION............................................................................................. 82 9.2 SELECTION OF KEY SUB-COMPONENTS.......................................................... 86 9.3 DESCRIPTION OF STATUS PRIOR TO RIVER REGULATION................................. 87 9.4 DESCRIPTION OF THE CURRENT TRAJECTORY IN CONDITION........................... 88 9.5 DESCRIPTION OF DESIRED TARGET CONDITION .............................................. 89 9.6 EVALUATION AND RANKING THE HYDROLOGICAL FLOW CATEGORIES............... 89 9.7 DRIFT CONSEQUENCES ............................................................................... 89 9.8 DISCUSSION................................................................................................. 90 10. SPECIALIST STUDY – WATERBIRDS ............................................................. 91 10.1 INTRODUCTION............................................................................................. 91 10.2 SELECTION OF KEY SUB-COMPONENTS.......................................................... 91 10.3 DESCRIPTION OF STATUS PRIOR TO RIVER REGULATION................................. 93 10.4 DESCRIPTION OF THE CURRENT TRAJECTORY IN CONDITION........................... 93 10.5 DESCRIPTION OF DESIRED TARGET CONDITION .............................................. 94 10.6 EVALUATION AND RANKING THE HYDROLOGICAL FLOW CATEGORIES............... 94 10.7 DRIFT CONSEQUENCES ............................................................................... 95 10.8 DISCUSSION................................................................................................. 95 11. SPECIALIST STUDY – FLOODPLAIN VEGETATION ...................................... 96 11.1 INTRODUCTION............................................................................................. 96 11.2 SELECTION OF KEY SUB-COMPONENTS.......................................................... 97 11.3 DESCRIPTION OF STATUS PRIOR TO RIVER REGULATION................................. 99 11.4 DESCRIPTION OF THE CURRENT TRAJECTORY IN CONDITION......................... 100 11.5 DESCRIPTION OF DESIRED TARGET CONDITION ............................................ 100 11.6 EVALUATION AND RANKING THE HYDROLOGICAL FLOW CATEGORIES............. 100 11.7 DRIFT CONSEQUENCES ............................................................................. 102 11.8 DISCUSSION............................................................................................... 103 12. SPECIALIST STUDY – NATURAL RESOURCE UTILIZATION...................... 104 12.1 INTRODUCTION........................................................................................... 104 iii 12.2 SELECTION OF KEY SUB-COMPONENTS.......................................................