Brackish Groundwater

Brackish groundwater in Westerrn Australia offers a promising source of water for desalination, which could help alleviate ongoing water availability issues in some parts of the state. This resource, defined here as salinity levels ranging from 1,000 to 15,000 mg/L of total dissolved solids (TDS), is gaining recognition as a viable option for deslination. Desalination of brackish groundwater in this range requires less ennergy, offers higher water recovery rates, and produces smaller brine (waste) volumes compared with seawater desalination.

This project evaluated brackish groundwater in Western Australia based on its occurance, quantity, and suitability for desalination. The analyses conducted were based on available groundwater information from various sources integrated with groundwater allocation and licensed entitlement data established by the state’s Department of Water and Environmental Regulation. These datasets contain inherent uncertainties; therefore, the project results should be considered as providing high-level overview at a state scale.

Groundwater resources in Western Australia

Western Australia’s groundwater resources are vital for supporting the state’s growing population, industries, and agriculture. The state has a variety of aquifer systems that vary in spatial extent, thickness and rock-composition and host acquifers of differing productivity and water quality.

These include:

  • regional-scale aquifers in the Perth Basin, Carnarvon Basin and Canning Basins, where multiple high-yield systems contain substantial brackish groundwater resources,
  • intermediate-scale aquifers hosted in palaeovalleys spread widely across the state, from the Canning Basin in the north to the southern coastline, providing variable but often moderate yields of brackish water, and
  • local-scale aquifers, typically found in fractured or weathered rocks and yielding smaller amounts of groundwater, which is often brackish to hypersaline.

Currently, it is estimated that about 4,000 GL of groundwater resources across Western Australia have been characterised, some of which is used for a variety of different purposes. As freshwater supplies become increasingly insufficient due to growing demand, the exploration and use of brackish groundwater for desalination is seen as a way to address water needs.

Summary of brackish groundwater resources in Western Australia

The project classified Western Australia’s brackish groundwater resources into different categories based on their salinity levels.

  • Brackish and mainly brackish: aquifers or their section within a groundwater management area (GMA) where over 50% of bores produce brackish groundwater.
  • Some brackish: aquifers or their section within GMA where 25% to 50% of the bores produce brackish groundwater.

Based on the analysis conducted, more than 50% of the aforementioned groundwater resources have been identified as brackish, while an additional 20%, although mostly fresh, still contains some brackish groundwater.

The Perth Basin contains abundant brackish groundwater resources hosted in the Superficial, Leederville–Parmelia, and Yarragadee aquifers. These aquifers host around 490 GL of brackish groundwater. Nearly 60 GL of groundwater, classified as ‘brackish’ and ‘mainly brackish’, is potentially available for allocation. Additionally, there are more than 110 GL of groundwater classified as ‘some brackish’ that remains potentially available, particularly in the North Perth Basin. These aquifers are well-suited for desalination, though some may require pre-treatment due to high pH levels and magnesium concentrations. Brine management options could include mining for magnesium due to its high concentrations in these aquifers.

The Canning Basin, also host an abundant of groundwater resources though large parts of the basin remain uncharacterised. Currently, its estimated that about 355 GL of groundwater resources have been characterised across the north and west of the basin, mots of which is fresh to marginal, though there is some brackish groundwater in places (only 3% of the basin’s characterised resources). The Broome Sandstone aquifer in the West Canning Groundwater Management Subarea and the Liveringa Group aquifers in the Canning-Kimberley Groundwater Management Subarea were identified as the most promising brackish groundwater resources. The Broome Sandstone aquifer is a high-yielding aquifer system suitable for a wide range of applications. The Liveringa Group aquifers are highly variable and often low-yielding, making them better suited for stock and domestic water supplies. However, they may be viable for community water supplies with appropriately designed and configured groundwater abstraction infrastructure. Currently, there is about 9.9 GL of groundwater hosted in the Broome Sandstone aquifer in the West Canning Groundwater Management Subarea that is partly brackish and potentially available for allocation. The Liveringa Group aquifers host about 9.3 GL of mainly brackish groundwater potentially available for allocation.

The Carnarvon Basin has limited data on groundwater quality and salinity, which complicates a comprehensive assessment. Currently, there is about 156 GL of characterised groundwater resources across the basin. Of these groundwater resources, about 97% have been identified to be ‘brackish or mainly brackish’. Based on the available data, the most promising opportunity for brackish groundwater development is from aquifers hosted in the the Keogh Formation and Ballythanna Sandstone in the south-east of the basin, primarily located in the Zuytdorp/Ningaloo and Talisker/Mia Mia Groundwater Management Sub-Areas (GMsAs). This represents about 24% of the basin’s currently characterised groundwater resources. Other parts of the basin may offer other opportunities, but some areas are data sparse, therefore aquifer attributions were not available for many individual groundwater bores to better characterise them.

Palaeovalley aquifers, which are moderately extensive and often host intermediate-scale groundwater systems found in ancient drainage lines, were identified as potentially promising brackish groundwater resources. These aquifers can exceed 1,000 GL in potential resources, although salinity tends to increase towards the south, particularly within the Yilgarn Block. Despite water quality concerns, over 300 GL of brackish groundwater has been allocated from these systems, with a further 250 GL in licensed entitlements.

In alluvial aquifers along the Pilbara coastline, from Onslow to the east of Port Hedland and along the Gascoyne River, there are brackish groundwater resources amounting to 54 GL, along with an additional 30 GL in entitlements. Approximately 41 GL remains potentially available for allocation, primarily in some coastal alluvial aquifers in the Pilbara and southern Groundwater Management Areas.

Fractured groundwater systems in mining regions are heavily exploited. Currently, there is nearly 220 GL of allocation limit and over 1,600 GL of licensed entitlements related to brackish groundwater. The latter is mainly linked to the mining regions of the Pilbara and Goldfields.

Data availability and quality

This project compiled a comprehensive database of over 117,000 bores for the assessment of groundwater quality and salinity across Western Australia. This database includes 44,000 bores with TDS data and 45,000 bores with inlet depths (depth that groundwater enters a bore) greater than 10 metres below the surface. However, data management challenges arose due to inconsistencies and variations in data standards across organisations. To address these issues, workflows were developed for data quality control and data standardisation, enabling more efficient integration, processing, and analysis of groundwater data. This data is available for download.

Conclusion

While brackish groundwater offers significant potential for desalination in Western Australia, several challenges must be addressed, including the variability in water quality and pre-treatment requirements before desalination, brine management regulations, and infrastructure costs. The desalination process itself can be complex and expensive, particularly in remote areas, and managing brine byproduct remains a key environmental concern. The infrastructure required for desalination plants, pipelines, and distribution systems also can be costly to establish and maintain.

Although challenges remain, with further technological advances and strategic investment, brackish groundwater could become a crucial resource to meet the state’s future water needs, supporting agriculture, industrial growth, and community water supplies in its more remote and arid regions. However, any future allocation of brackish groundwater resources is likely to depend on community and government acceptance of changes in groundwater resource availability and the approval of groundwater licences.