West Pilbara water source planning

The Department of Water and Environmental Regulation (DWER) is responsible for all water and environmental regulation. They determine how much water can be taken from groundwater and surface water resources, while safeguarding the sustainability of the resource and protecting the water dependent environment. 

Water Corporation is the principal supplier of water, wastewater, drainage and some bulk irrigation services to homes, businesses and farms in Western Australia. DWER and the Department of Health are our regulators, and the Economic Regulatory Authority is responsible for setting Water Corporation's license to operate and supply services.

Water Corporation are licensed to take up to 15 gigalitres (15 billion litres) per annum from Harding Dam, but this relies on this source being recharged regularly through cyclones or heavy prolonged rainfall events. 

We are licensed to take nine gigalitres (9 billion litres) from the Millstream aquifer per annum. This will be reduced to 6 gigalitres (6 billion litres) per annum in five years’ time under the direction of Department of Water and Environmental Regulation (DWER). 

Current scheme demand is 8.3 gigalitres, supplied through the conjunctive use of Harding Dam and Millstream. This is currently sitting at 82% of the reliable water (based on recharge from heavy rainfall events) available from these two sources. This excludes Rio Tinto Iron Ore’s component of scheme demand as this demand is met from their Bungaroo Borefield.  

The following options have been considered and ruled out: 

• Groundwater - No unallocated, high yielding, sustainable groundwater source was identified. Sites considered included Kumina Creek, Lower Fortescue River, Sholl Shear Zone, KT Area and Harding Alluvials.
• Managed aquifer recharge – As Harding Dam has high evaporation rates it was considered whether water could be stored in an aquifer. Due to limited unsaturated thickness in the Harding alluvials this was ruled out as there would be no yield benefit.
• Third party supplier – Water Corporation is considering third party opportunities however it’s not expected that this option would provide full demand requirements.

• Seawater intake location - an intake that captures good quality clean seawater is important in reducing the complexity of the treatment process, the size of the plant site, its environmental footprint and ensuring the reliability of water supply. This can be achieved by either an open seawater intake or subsurface water intake.
• Location of plant - locating the seawater desalination plant close to a water source will result in the most efficient design, and will minimise capital and operational requirements, as well as environmental impacts. An area of up to six hectares may be required for the plant, this is dependent on earthworks required for the selected site and the design of the treatment process.
• Location of brine outfall - the salty water that is left at the end of the desalination process is known as brine and is returned to the ocean via an ocean outfall pipeline with diffusers at the end. A suitable outfall location needs to consider ocean movement and mixing of brine to minimise environmental impact.
• Power supply - with the aim to utilise renewable power to align with Water Corporation's objective to be net zero by 2035.
• Transfer infrastructure (pipes and pumps) - to connect the treated drinking water to the scheme.

Before we determine the location of a preferred water source, we consider the following factors at a minimum:

• Water quality
• Drying climate patterns and rainfall/streamflow data
• Impacts on local ecosystems and flora and fauna habitats
• Aboriginal Heritage and Native Title rights
• Community feedback and impact on private landowners
• Water treatment requirements and amount of water needed
• Cost of supplying water to our customers, including building the required infrastructure