Western Australia Tap Water Quality

Water Sources

Western Australia has undergone a dramatic shift in its water supply strategy over the past two decades. Perth, once dependent on dam catchments in the Darling Range, now sources the majority of its drinking water from desalination and groundwater. The Perth Seawater Desalination Plant at Kwinana and the Southern Seawater Desalination Plant near Binningup together supply roughly half of Perth’s water.

The Gnangara and Jandakot groundwater mounds provide a significant share of the remaining supply. Surface water from dams such as Mundaring Weir and Canning Dam now contributes a smaller fraction due to declining inflows caused by reduced rainfall since the 1970s.

Regional WA is served by an extraordinary pipeline network. The Goldfields and Agricultural Water Supply Scheme, originating at Mundaring Weir, delivers water over 600 kilometres to Kalgoorlie-Boulder and surrounding communities.

Treatment Approach

The Water Corporation operates treatment plants across the state. Desalinated water undergoes reverse osmosis, followed by remineralisation and disinfection. Dam and groundwater sources receive conventional treatment including filtration and chlorination or chloramination.

Fluoride is added to Perth’s water supply and many regional centres. Some remote communities in the Kimberley and Pilbara receive minimally treated groundwater.

Key Challenges

Declining Rainfall

Perth has experienced a roughly 20 percent decline in average annual rainfall since the mid-1970s. Stream flows into dams have dropped by over 80 percent compared to long-term averages, making desalination essential for supply security.

Vast Distances

WA covers 2.5 million square kilometres — roughly one-third of the continent. Delivering water to mining towns, pastoral stations, and remote Aboriginal communities across this area is logistically demanding and expensive.

Groundwater Sustainability

Increasing extraction from the Gnangara Mound has lowered water table levels, affecting wetland ecosystems. Balancing water supply needs with environmental protection remains an ongoing policy challenge.

Regulatory Framework

The Department of Health regulates drinking water quality in WA. The Water Corporation is the principal water utility, operating under oversight from the Economic Regulation Authority. Water quality is monitored against the ADWG, with results reported annually.

Infrastructure Highlights

WA’s Integrated Water Supply Scheme connects dams, desalination plants, groundwater sources, and over 30 treatment facilities through thousands of kilometres of pipeline. The Goldfields pipeline, completed in 1903 and still operational, is a heritage-listed engineering achievement.