Perth Basin

Brackish groundwater

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

• Brackish: Aquifers or their section within a Groundwater Management Area (GMA) where 100% of bores produce brackish groundwater.
• 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.

The Perth Basin contains significant brackish groundwater resources, estimated at around 490 GL across major aquifers like Superficial, Leederville–Parmelia and Yarragadee.

In the Perth Basin, the total unallocated groundwater classified as ‘brackish and mainly brackish’ is approximately 57.0 GL. Of the groundwater classified as ‘some brackish’, 116.2 GL remains unallocated, particularly in the North Perth Basin, offering potential for irrigated agriculture.

Desalination and brine management

The Superficial and Yarragadee aquifers present the most promising opportunities for brackish groundwater desalination. However, some groundwater may require pre-treatment due to high pH, elevated bicarbonate (HCO₃⁻) levels and other water quliaty parameters, before desalination.

When considering reverse osmosis (RO) for brackish water desalination, recovery rates are typically below 60%, especially with high concentrations of calcium (Ca), bicarbonate (HCO₃⁻), or sulfate . The implementation of pre-treatment technologies along with addition of antiscaling agents, can boost recovery rates to around 80%.

Additionally, the high magnesium (Mg) content in brine (exceeding 2,000 mg/L in some areas) offers potential for brine mining. Despite the advantages of brackish water desalination, challenges like water quality and brine management must be carefully addressed.

Aquifers in the Perth Basin can serve both as a storage solution for treated water and as a disposal option for brine. Permeate or brine reinjection into these aquifers could be part of a Managed Aquifer Recharge (MAR) scheme, though this would require extensive hydrogeological studies and regulatory approvals.

Renewable energy

The hybrid renewable energy cost for desalination of brackish groundwater is higher on average in the Perth Basin compared to the other analysed regions. However, the range in values across the Perth Basin is quite high. Taking a 90% reliability of energy supply level, the minimum energy cost is 76% lower than the maximum. Geographically, the cost is relatively lower along the coast, while increasing inland particularly in the southern regions of the basin.