Strategy, Development & Planning SEA Hydrology Ecohydrological Change Assessment Ecohydrological Change Assessment Statement of limitations This report has been prepared solely for the purposes of informing environmental impact assessment pursuant to the Environmental Protection Act 1986 (WA) and Environment Protection and Biodiversity Conservation Act 1999 (Cth) and is not intended for use for any other purpose. No representation or warranty is given that project development associated with any or all of the disturbance indicated in this report will actually proceed. As project development is dependent upon future events, the outcome of which is uncertain and cannot be assured, actual development may vary materially from this report. Ecohydrological Change Assessment i Ecohydrological Change Assessment Contents STATEMENT OF LIMITATIONS I CONTENTS II EXECUTIVE SUMMARY XIV PART I - INTRODUCTION 1 1. BACKGROUND 1 2. OBJECTIVES 2 3. REGIONAL MANAGEMENT STRATEGIES 4 3.1. Water Regional Management Strategy 4 3.2. Other Regional Management Strategies 4 4. ASSESSMENT METHODOLOGY 6 4.1. Knowledge status 7 4.2. Conceptualisation 8 4.3. Change Assessment 10 4.4. Management Response 12 4.5. Case Study - Ethel Gorge 12 PART II - EXISTING ENVIRONMENT 13 5. SETTING 13 5.1. Climate 13 5.2. Topography 14 5.3. Hydrology 14 5.4. Geology 17 5.5. Hydrogeology 20 5.6. Hydroclimatic variability 23 5.7. Ecology 26 Ecohydrological Change Assessment ii Ecohydrological Change Assessment 5.8. Regional Ecohydrology 28 5.9. Ecohydrological Sensitivity 33 6. ECOLOGICAL ASSETS AND ECOHYDROLOGICAL RECEPTORS 36 6.1. Coondewanna Flats – Coolibah and Lignum Flats 38 6.2. Ethel Gorge Stygobiont Community 41 6.3. Fortescue Marsh 44 6.4. Freshwater Claypans of the Fortescue Valley 48 6.5. Weeli Wolli Spring Community 50 7. OTHER ECOLOGICAL ASSETS 53 7.1. Tier 1 - Karijini National Park 53 7.2. Tier 1 - Mungaroona Range Nature Reserve 56 7.3. Tier 2 - Brockman Iron cracking clay communities of the Hamersley Range PEC 56 7.4. Tier 2 - Mt Bruce Coolibah-Lignum Flats 57 7.5. Tier 2 - Sand dune vegetation of the Hamersley Range/Fortescue Valley PEC 57 7.6. Tier 2 - West Angelas cracking clays communities PEC 58 7.7. Tier 2 - Wona Land System PEC - Four plant assemblages 58 7.8. Contingent ecological assets 59 8. CURRENT MINING OPERATIONS 60 8.1. BHP Billiton Iron Ore Operations 60 8.2. Third-Party Operations 60 PART III - CHANGE ASSESSMENT 62 9. STRESSORS 62 9.1. Strategic Proposal projects 62 9.2. Proposed Third-Party Operations 67 10. THREATENING PROCESSES 68 10.1. Groundwater drawdown 68 10.2. Reduced surface water availability 71 10.3. Surplus water management 75 Ecohydrological Change Assessment iii Ecohydrological Change Assessment 10.4. Acid and metalliferous drainage 78 10.5. Groundwater quality - saline intrusion 81 10.6. Surface water quality change 82 10.7. Pit lake impacts 83 11. REGIONAL CHANGE ASSESSMENT 86 11.1. Groundwater drawdown 87 11.2. Surface water availability 93 11.3. Surplus water 96 11.4. Acid and metalliferous drainage 97 11.5. Groundwater quality - saline intrusion 99 11.6. Surface water quality 99 11.7. Pit lakes 99 12. RECEPTOR CHANGE ASSESSMENT 100 12.1. Coondewanna Flats - Coolibah and Lignum Flats 100 12.2. Ethel Gorge Stygobiont Community 102 12.3. Fortescue Marsh 104 12.4. Freshwater Claypans of the Fortescue Valley 106 12.5. Weeli Wolli Spring Community 107 PART IV - MANAGEMENT 110 13. HIGH-LEVEL MANAGEMENT OBJECTIVES 110 14. REGIONAL LEVEL MANAGEMENT CONSIDERATIONS 111 15. RECEPTOR-LEVEL MANAGEMENT CONSIDERATIONS 113 15.1. Groundwater drawdown 113 15.2. Reduced surface water availability 114 15.3. Surplus water 114 15.4. AMD source potential 114 15.5. Groundwater quality - saline intrusion 115 15.6. Surface water quality 115 Ecohydrological Change Assessment iv Ecohydrological Change Assessment 15.7. Pit lakes 115 16. ETHEL GORGE CASE STUDY 120 16.1. Project domain and ecological assets 120 16.2. Change assessment – operational 121 16.3. Change assessment – closure 123 16.4. Monitoring, review and corrective actions 123 PART VI – REFERENCES 125 17. REFERENCES 125 Ecohydrological Change Assessment v Ecohydrological Change Assessment List of Figures Figure 1 Water Resource Management Strategy ............................................................................................... 5 Figure 2 Adaptive management within the Water RMS ....................................................................................... 5 Figure 3 Water management options in the Water RMS ..................................................................................... 6 Figure 4 Closure management options in the Closure and Rehabilitation RMS .................................................. 6 Figure 5 Stepwise methodology used in the ecohydrological change assessment ............................................. 9 Figure 6 Schematic figure showing regional aquifer / groundwater system and likely connectivities ................ 22 Figure 7 Generic mine types for Marra Mamba and Brockman deposits ........................................................... 22 Figure 8 SILO database yearly rainfall at Ethel Gorge ...................................................................................... 24 Figure 9 Derived long-term streamflow at Fortescue River (DOW 708011) ...................................................... 25 Figure 10 Long term groundwater level changes at the Ophthalmia borefield and Yandi operations .............. 26 Figure 11 Landscape arrangement of ecohydrological units (EHUs) ............................................................... 30 Figure 12 Coondewanna Flats ecohydrological conceptualisation .................................................................. 40 Figure 13 Ethel Gorge ecohydrological conceptualisation ............................................................................... 43 Figure 14 Fortescue Marsh ecohydrological conceptualisation ....................................................................... 47 Figure 15 Freshwater claypans ecohydrological conceptualisation ................................................................. 49 Figure 16 Weeli Wolli Spring ecohydrological conceptualisation ..................................................................... 52 Figure 17 Karijini National Park landscape context .......................................................................................... 55 Figure 18 Ecohydrological change potential matrix – groundwater drawdown ............................................... 70 Figure 19 Ecohydrological change potential matrix – surface water availability.............................................. 75 Figure 20 AMD source potential matrix ........................................................................................................... 81 Figure 21 EHUs subject to groundwater drawdown - BHP Billiton Iron Ore only ............................................. 89 Figure 22 EHUs subject to groundwater drawdown - cumulative .................................................................... 89 Figure 23 Change in groundwater resource in the study area ......................................................................... 91 Figure 24 Proportion of EHUs subject to reduced surface water availability - BHP Billiton Iron Ore ................ 95 Figure 25 Proportion of EHUs subject to reduced surface water availability - cumulative ............................... 95 Figure 26 Indicative water balance for BHP Billiton Iron Ore and third-party mining areas .............................. 98 Figure 27 Water management focus based on EHU conceptualisation ......................................................... 112 Ecohydrological Change Assessment vi Ecohydrological Change Assessment List of Tables Table 1 Main surface water catchments in the study area ............................................................................... 15 Table 2 Prominent hydrological features .......................................................................................................... 17 Table 3 Regional stratigraphy .......................................................................................................................... 19 Table 4 Generic mine types considered in the ecohydrological change assessment ....................................... 21 Table 5 General attributes of landscape ecohydrological units (EHUs) ........................................................... 31 Table 6 Landscape-scale ecohydrological sensitivity to change in groundwater regimes ................................ 34 Table 7 Landscape-scale ecohydrological sensitivity to change in surface water regimes .............................. 35 Table 8 Tier 1 and Tier 2 ecological assets considered in the ecohydrological change assessment ............... 37 Table 9 Active BHP Billiton Iron Ore and third-party mining operations ........................................................... 61 Table 10 Proposed operations in Central Pilbara region ................................................................................ 63 Table 11 Proposed operations in Eastern Pilbara region ............................................................................... 64 Table 12 Proposed BHP Billiton Iron Ore and third-party operations in the Fortescue Marsh region ............. 65 Table 13 Proposed BHP Billiton Iron Ore and third-party operations in the Marillana Creek region ............... 66 Table 14 Potential environmental impacts associated with