Water Corporation sourced 335,901 ML of water for the Perth metropolitan system in FY 2025-26. Net output from the hills dams was 33,164 ML, or 9.9% of the total. Groundwater provided 150,892 ML (44.9%) and the two seawater desalination plants 149,639 ML.
Two plants, one dominant
The Southern Seawater Desalination Plant produced 103,285 ML, 30.7% of the metropolitan total and more than its stated capacity of 100 billion liters a year. The Perth Seawater Desalination Plant added 46,354 ML. A third plant, the A$2.8 billion Alkimos Seawater Desalination Plant, is due to be fully operational by mid-2028 with 50 billion liters a year at Stage 1.
Dams at 40%
On June 30, 2026 the Perth hills dams held 228,903 ML of 566,688 ML capacity, 40%. South Dandalup, with 138,345 ML of capacity, was 16.5% full. The 2026 winter brought little relief: little more than 12.5 billion liters flowed into Perth's scheme dams in 2026 to early September, against a decade average of 75 billion liters a year.
Groundwater under limits
Groundwater is the largest single source but is being reduced to protect environmental values, including through the Gnangara allocation plan. Groundwater replenishment returns up to 28 billion liters of purified recycled water to aquifers each year. Water use per person in Perth was 124 kL in FY 2025-26.
Questions the report answers
How Water Corporation's source mix will change once Alkimos operates, who decides Perth's next source after 2028, and how network reliability and service delivery compare with the resource transition are covered in the full report. The full report, Water Systems Overview: Water Corporation, is available for USD 499. For a free overview, read the Water Corporation Utility Snapshot.