West Australian water authorities are cutting future water allocations across the Murray groundwater area by 40 per cent. 

WA Water Minister Simone McGurk says that a 23 per cent drop in rainfall requires sweeping changes to licensed water in the Murray region, in the state's south-west.

New allocations for the Murray groundwater area, located an hour south of Perth, cut the region's access to future available water by 40 per cent, and line up ongoing reviews to look at further reductions. 

Areas such as Pinjarra and Nambeelup will have no groundwater and shallow aquifer water left to allocate.

The update includes a staged reduction of Alcoa's water licence for the Cattamarra Coal Measures aquifer in Pinjarra - the site of a water-intensive bauxite refinery.

Reductions will begin in 2026 and equate to a cut of 2.5 billion litres. The company says it is “investigating alternative water sources for our operational needs at Pinjarra Alumina Refinery”. 

WA’s Department of Water and Environmental Regulation (DWER) says the current level of licensed water is unsustainable. 

“We are working with Alcoa to reduce the impacts of their abstraction, which is contributing to declining trends not only in the Pinjarra but also the Nambeelup sub-area,” a spokesperson said.

“These risks and impacts can be appropriately managed through reducing groundwater abstraction.

“The department will provide assistance to Alcoa for the investigation of water use efficiency.”

DWER says the declining water levels are having an impact on environmentally sensitive waterways.

“Allowing more abstraction in sub-areas where groundwater levels are declining would threaten the resource’s capacity to supply the required quantity and quality of groundwater into the future,” a department statement said.