Bauxite miner Alcoa will spend $15 million boosting research of the jarrah forest it mines, mostly in catchments vital to supplying water to Perth and WA’s south-west.

Last year, state-owned Water Corporation struggled to properly assess the risks to its dams from Alcoa’s forest clearing as it was hampered by “extensive knowledge gaps and multiple overlapping areas of uncertainty”, according to an August 2023 report obtained through a freedom of information request.

Alcoa’s funding will support a forest research centre for five years to look into caring for water as well as returning animals and diverse vegetation to mined areas, forest conservation beyond mining, and embracing Indigenous cultural values.

The US company will also boost its own team of environmental researchers from four to eleven.

In recent years, Alcoa’s mining has moved closer to Serpentine Dam, which supplies almost one-fifth of Perth’s water, and the extent of cleared areas has grown as mining outpaced revegetation.

Runoff of soil from these areas into the dam after heavy rainfall could make the water unusable either by contamination from oil or toxic forever chemical PFAS spilt by Alcoa, or by the soil making the water cloudy which renders existing water treatment plants ineffective.

The Water Corporation report noted that Alcoa’s mining has currently impacted nine of its 15 major water catchments.

“Treatment for all dams where mining activities have impacted drinking water catchments would likely be in the order of $2.6 billion, representing a 100 per cent increase in the cost of water to customers,” the report said.

Water Corporation’s concerns included a lack of data on groundwater and the cloudiness of the water before mining, untested methods used by Alcoa to reduce the risks, how rehabilitation affected water flow to the dam and how the replanted areas would change the behaviour of bushfires.