EIS 305 Salinity in the Hunter River
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EIS 305 Salinity in the Hunter River: a report on the generation, treatment and disposal of saline minewater SALINITY IN THE HUNTER RIVER A REPORT ON THE GENERATION, TREATMENTAND DISPOSAL OF SALINE MINEWATER NEW SOUTH WALES COAL ASSOCIATION SALINITY IN THE HUNTER RIVER I. r A REPORT ON THE GENERATION, TREATMENT AND DISPOSAL OF SALINE MINEWATER I PREPARED FOR: PREPARED BY: NEW SOUTH WALES COAL ASSOCIATION CROFT & ASSOCIATES PTY. LIMITED • EAGLE HOUSE 125 BULLSTREET 25 WATT STREET P.O. BOX 5131B NEWCASTLE 2300 NEWCASTLE WEST 2302 049 26118 049261828 NATIONAL MUTUAL CENTRE LEVEL 2 IL 44 MARKET STREET SYDNEY 2000 02 297 202 DECEMBER 1983 91 if tiwtsiiiui'ti 1 TABLE OF CONTENTS Page SECTION 1: INTRODUCTION 1.1 STUDY BACKGROUND 1 1.2 STUDY OBJECTIVES 2 1.3 COMPANION STUDIES 3 1.4 ACKNOWLEDGEMENTS 3 SECTION 2: THE HUNTER REGION 2.1 GEOGRAPHY 4 2.2 GEOLOGY AND SOILS 4 2.3 METEOROLOGY 5 . 2.4 LAND USE 7 2.5 SURFACE WATERS 7 2.6 GROUNDWATER 8 SECTION 3: PROPOSED DEVELOPMENTS 3.1 REGIONAL DEVELOPMENT 9 3.2 COAL DEVELOPMENT 9 3.3 POWER GENERATION 11 3.4 COAL LIQUEFACTION 11 3.5 URBAN GROWTH 11 O 3.6 AGRICULTURE 12 3.7 FUTURE WATER REQUIREMENTS 12 SECTION 4 ORIGINS OF SALINITY 4.1 HISTORY OF SALINITY 14 4.2 HYDROLOGIC PROCESSES 14 4.3 TYPES OF LAND SALINISATION 15 4.4 DRY LAND SALINISATION 16 4.5 IRRIGATION SALINITY 16 SECTION 5 SALINITY MODEL FOR THE HUNTER RIVER 5.1 MODEL SPECIFICATION 18 5.2 DATA SOURCES 18 5.3 WATER RESOURCES COMMISSION MODEL 19 5.4 LOGIC NETWORK 19 5.5 METHODOLOGY 21 5.6 MODEL OUTPUT 24 SECTION 6: COLLIERY WATER BALANCES . L fl 6.1 THE CONCEPT OF WATER BALANCE 30 6.2 COLLIERY PROPRIETORS QUESTIONNAIRE 30 6.3 WATER MANAGEMENT STRATEGIES 31 6.4 WATER SUPPLY AND CONSUMPTION 31 6.5 COMPUTER SIMULATIONS 33 6.6 MODEL APPLICATION 35 6.7 WATER BALANCES FOR INDIVIDUAL MINES 36 SECTION 7 : CONSEQUENCES OF EXPANSION IN COAL MINING 7.1 INCREASES IN WATER DEMANDS 38 7.2 DISCHARGE REQUIREMENTS 38 7.3 CUMULATIVE IMPACTS OF MINEWATER DISCHARGES 39 SECTION 8 TREATMENT AND DISPOSAL OF SALINE WATER 8.1 OVERVIEW 42 8.2 DISPOSAL ALTERNATIVES 42 8.3 STAGED DISCHARGE 42 8.4 TRANSPORT BY PIPELINE TO SUITABLE RECEIVING WATERS 43 8.5 DEEP WELL INJECTIONS 44 8.6 EVAPORATION AND IN-PIT BURIAL 45 0 8.7 DESCRIPTION OF DESALINATION PROCESSES 46 8.7.1 Membrane Processes 46 8.7.2 Phase Change Processes by Distillation 49 8.7.3 Phase Change Processes by Freezing 52 8.7.4 Relative Economics of Desalination Processes 53 SECTION 9 : TOLERANCE OF IRRIGATED CROPS TO SALINITY 9.1 WATER FOR IRRIGATION 58 9.2 SALINITY EFFECTS ON CROP YIELDS 58 9.3 IRRIGATED CROPS GROWN ALONG THE HUNTER RIVER 59 0 9.4 SALINITY TOLERANCE OF CROPS 60 9.5 CHLORIDE TOXICITY 64 9.6 SODIUM HAZARD 66 9.7 ECONOMIC VALUE OF AGRICULTURAL OUTPUT 67 9.8 CONCLUSIONS 70 SECTION 10 : FINDINGS AND CONCLUSIONS 72 REFERENCES 75 0 APPENDIX 1 : N.S.W. COAL ASSOCIATION QUESTIONNAIRE OF COLLIERIES IN THE UPPER HUNTER REGION - SURVEY SHEET AND INSTRUCTIONS 78 0 APPENDIX 2 : SAMPLE OUTPUT FROM SALINITY MODEL 79 APPENDIX 3 : DETAILS OF TYPICAL MINES ADOPTED FOR WATER BALANCE MODELLING 92 APPENDIX 4 : SAMPLE OUTPUT FROM MINEWATER BALANCE MODEL 93 APPENDIX 5 SALINITY VALUES IN THE HUNTER RIVER WITH DIFFERENT LEVELS OF MINE DISCHARGES LIN im NTRODUCTON SECTION 1 1 1. INTRODUCTION 1.1 STUDY BACKGROUND The Hunter Valley has had a long history as an important centre of primary and secondary industry in New South Wales. The Upper Hunter provides a significant proportion of the State's milk and beef requirements, and since the beginning of the Nineteenth Century, has supplied coal for both domestic and overseas markets. In recent times, much of the State's capital investment has been directed to the Hunter region. Major power generation facilities have been established and preliminary planning has commenced for the manufacture of liquid synthetic fuels. Substantial water resource projects are being undertaken or are being planned with the construction of the Glennies Creek Dam, the Barnard River scheme and the enlargement of Glenbawn Darn. The coal industry is at the heart of current investment plans. Vast reserves of good quality steaming and coking coals are available in the valley, much of it at comparatively shallow depths. With the economies of scale introduced by modern earthmoving equipment, thirteen opencut mines are now producing coal. In the coming decade, expansion of these mines together with the establishment of a number of proposed new collieries will have the potential to substantially increase regional coal output. The Valley is comparatively well settled, with established communities and physical infrastructure. A wide diversity of land uses make various calls on the region's natural resources. The Hunter River and its major tributaries supply most of the water needed for agricultural and other purposes. The equitable allocation of water to different geographic areas and amongst various user groups requires the application of a rational and wide reaching resource management strategy. Substantial demands are already being placed on water from the river, and these demands will increase with expansions in irrigation, mining and power generation. In addition to volumetric requirements, the maintenance of satisfactory water quality will become an increasingly important objective. Runoff from some parts of the river catchment is moderately to highly saline under natural conditions, particularly during low flow regimes. There can be quantifiable costs, both economic and environmental, in permitting river salinity to increase. Whilst there is a well developed legislative 0 framework for the protection of water quality in rivers, the setting of appropriate and achievable control standards is a pre-requisite for successful environmental protection. To encourage research and informed discussion on aspects of consumption and water quality in the Hunter, the New South Wales Coal Association commissioned Croft & Associates Pty. Limited to undertake a study of river salinity. The present report details the approaches, findings and conclusions of the study team. • 0 1.2 STUDY OBJECTIVES The objectives of the salinity study were as follows: * to investigate the causes and effects of salinity in the Hunter River * to quantify under what circumstances coal mines may need to discharge saline waters * to determine by superimposing the findings of the above enquiries, what effects an expansion of mining could have on the Hunter River * to establish what measures are feasible to reduce these impacts The study team responded to a steering group consisting of the Environmental Committee of the New South Wales Coal Association. Interim findings and study directions were discussed at progress meetings, and beneficial feed-back was obtained from colliery operators with mines throughout the study area. The present report commences with a brief account of the general characteristics of the Hunter Region, and outlines some of the developments proposed in the coming 10 to 20 years. It then describes the origins of land and river salinisation. Details of a computer based mathematical model are presented to quantify river flows and salt loads under a variety of meteorological conditions. Further models are then described to evaluate water balances in operating mines. The outputs of these models are combined to investigate short and long term impacts from existing and proposed collieries. Options for the treatment and disposal of excess saline waters are reviewed, and the tolerance of irrigated crops to varying salinity levels is explored. A final section presents the findings and conclusions of the study. Background information, detailed technical matters and descriptions of the various computer simulations are included as appendices. 1.3 COMPANION STUDIES The present salinity study is one of a number of initiatives supported by the New South Wales Coal Association. Companion studies have been commissioned into several research areas associated with the mining and beneficiation of coal. Two other projects are of particular relevance. The first, being conducted by Australian Groundwater Consultants Pty. Ltd. is examining the quality and availability of groundwater throughout the Hunter Valley. A second project being undertaken by the N.S.W. Soil Conservation Service is researching rehabilitation techniques in opencut coal mines. 3 1.4 ACKNOWLEDGEMENTS The study team would like to formally acknowledge the support, assistance and guidance provided by the Environmental Committee of the New South Wales Coal Association under the chairmanship of Mr. B. Howe. Committee members were drawn from most of the operating mines in the Upper Hunter, and they were able to provide a wealth of detailed information on aspects of colliery planning, water conservation and pollution control. The permanent staff of the Association were able to provide a valuable overview of issues relevant to all producers. Special thanks must be given to Mr. J. Hannan, Executive Officer, Technical and Mr. K.C. Wallin, Secretary, N.S.W. Environmental Committee for their encouragement and co- ordination. Finally, we would like to acknowledge the help of the Water Resources Commission in providing river gauging and monitoring data and in discussions held at the beginning of our research programme. S . 0 THE HUNTER REGION SECTION 2 4 2. THE HUNTER REGION 2.1 GEOGRAPHY The Hunter Valley is a drainage basin on the central coast of New South Wales. It is located about 140 kilometres north of Sydney, and occupies a total area of about 22,000 square kilometres. Of the total area, about 16,449 square kilometres are upstream of the township of Singleton. A locality plan is given in Figure 1. The Valley is bounded by rugged hills with deeply dissected gullies.