Professional opinion 2008/05
Prepared by Geoscience Australia for the Australian Government Department of the Environment, Water, Heritage and the Arts
Chapters of the report
- Chapter 1 Introduction (PDF - 690 KB) | (RTF - 929 KB)
- Chapter 2 Regional Overview (PDF - 313 KB) | (RTF - 334 KB)
- Chapter 3 Overview of Groundwater Resources in the Broken Hill Region (PDF - 652 KB) | (RTF - 769 KB)
- Chapter 4 Groundwater in the Murray Geological Basin (PDF - 2,597 KB) | (RTF - 1,498 KB)
- Chapter 5 Groundwater in Near-Surface Sediment Aquifers (PDF - 1,108 KB) | (RTF - 1,251 KB)
- Chapter 6 Groundwater in the Great Artesian Basin (PDF - 527 KB) | (RTF - 571 KB)
- Chapter 7 Groundwater in the Darling Geological Basin (PDF - 659 KB) | (RTF - 616 KB)
- Chapter 8 Groundwater in Fractured Rock Aquifers (PDF - 726 KB) | (RTF - 690 KB)
- Chapter 9 - Groundwater Options for Broken Hill (PDF - 1,506 KB) | (RTF - 844 KB)
- Chapter 10 Recommended Future Workplan (PDF - 60 KB) | (RTF - 115 KB)
- Appendix 1 References (PDF - 56 KB) | (RTF - 88 KB)
- Appendix 2 Glossary (PDF - 35 KB) | (RTF - 56 KB)
- Appendix 3 Salinity Descriptions (PDF - 16 KB) | (RTF - 18 KB)
- Appendix 4 Darling Geological Basin Stratigraphic Profiles (PDF - 87 KB) | (RTF - 157 KB)
- Appendix 5 River Murray Corridor Groundwater Investigation (PDF - 563 KB) | (RTF - 4,124 KB)
Groundwater resources within 150 kilometres of Broken Hill are generally of moderate to poor quality (brackish to saline) and variable yield (mostly low). There are no readily accessible, potable groundwater resources of sufficient capacity or sustainability to provide a single reliable urban supply option for Broken Hills long-term water requirements. However, although there is no one alternative to Broken Hills reliance on the Menindee Lakes, a combination of groundwater extraction and aquifer storage options could contribute towards the citys future water supply strategy.
Our preliminary assessment suggests that conjunctive surface water groundwater operations based around the existing urban water infrastructure are technically feasible, and could contribute significant water savings to the broader Darling River system by reducing the severity and scale of current evaporative and transmission losses from the Menindee Lakes.
In the Broken Hill region, groundwater flow systems of varying scale and complexity operate in each of the major hydrogeological systems, these being:
- Sedimentary sequences of the Murray Geological Basin, situated south and south-east of Broken Hill. These deposits are up to several hundred metres thick and include permeable sand-rich aquifers which underlie the Menindee Lakes;
- Near-surface sediments, deposited mainly by rivers. These include shallow channel and floodplain deposits associated with the Darling River and parts of its former course, sub-surface palaeochannels formed by ancient drainage systems, and fan-like systems of alluvial and colluvial sediment developed around the margins of basement uplands;
- Aquifers of the Great Artesian Basin, located over 100 km away to the north of Broken Hill;
- Thick sedimentary formations of the Darling Geological Basin, partially buried by younger sediments of the Murray Geological Basin; and
- Fractured rock aquifers of generally low groundwater quality and yield which occur in outcropping geological basement rocks.
Groundwater resource options
Detailed assessment of existing data and information for each hydrogeological system indicates that development of future groundwater resource options for Broken Hill are most viably focussed on the sediments of the Murray Geological Basin, and associated near-surface alluvial deposits. Of specific interest are the multiple aquifer systems at different sub-surface depths in the vicinity of Menindee LakesDarling River Floodplain, and at other locations along the existing MenindeeBroken Hill pipeline. Considerable scope exists to develop an integrated water supply strategy for Broken Hill, enhancing the existing surface water operations at Menindee and the Stephens Creek and Umberumberka Reservoirs by:
- Developing Managed Aquifer Recharge (MAR) in suitable geological formations underlying the Menindee Lakes, and at other locations along the existing pipeline corridor, e.g., Yancowinna Creek and Stephens Creek. Prospective targets for Aquifer Storage and Recovery (ASR) include the Pliocene Sands and the Renmark Group, whereas enhanced recharge for the near-surface Coonambidgal and Shepparton Formations on the Darling Floodplain could involve bank infiltration;
- Extracting fresh to saline quality groundwater for contingency purposes from prospective aquifers, including shallow alluvial aquifers near the Darling River (similar to Wilcannias groundwater supply system), and intermediate-level aquifers of the Murray Geological Basin (e.g., the Pliocene Sands and Renmark Group). These groundwater resources would probably require treatment using the existing (or upgraded) desalination facilities;
- Evaluating the groundwater potential of deeper sedimentary porous rock aquifers to provide fresh to brackish quality groundwater, especially favourable sandstone horizons within Late Devonian to Cretaceous age formations in the Menindee Trough; and
- Investigating the groundwater resource potential of alluvial fan deposits along the Mundi Mundi Fault Escarpment, in combination with possible capture of seepage from the nearby Umberumberka Reservoir.
These options are not seen to be mutually exclusive or separated from surface water management in the region. A conjunctive management approach is recommended, where a combination of surface water and groundwater supply and storage methods are implemented. This provides enhanced and more flexible storage capacity, the ability to mix supply options (depending on current and forecasted climate conditions) and greater strategic reserves in an environment of episodic surface water flows and high evaporative losses. Preliminary estimates of aquifer storage volumes suggest that MAR schemes with a combined underground storage capacity of 3050 GL/yr would represent a reasonable target.
Our assessment suggests that considerable potential exists for groundwater resources to become part of Broken Hills future urban water supply system. The development of Managed Aquifer Recharge (MAR) operations in the vicinity of existing water supply infrastructure warrants particular consideration. However, the level of detailed hydrogeological information for the preferred target areas is currently insufficient to underpin further development. At Menindee in particular, there is a need to characterise and better understand the entire geological profile of surface materials and landforms, shallow alluvial deposits, intermediate Murray Geological Basin sediments and deeper sedimentary formations of the Menindee Trough. To this end, a phased future workplan involving (i) baseline data acquisition and interpretation, (ii) detailed feasibility assessment and (iii) pilot trials, is recommended. In this way, the risks associated with fully implementing a conjunctive management approach incorporating groundwater storage and supply can be identified and reduced.