The Review
How the lakes work
East and West Lake look like they’ve always been here. They haven’t. They’re perched above a regional groundwater system that stretches across inner Perth — and without active management, both would be dry. Here’s how they work.
Photo: Ian Stewart
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80 ha
Total reserve area
12.6 ha
Open water across both lakes
963 ML
Water added to the lakes in 2023–24
1990s
Levels restored within one year of pumping
Two lakes, one system
East and West Lake
Perry Lakes is really two connected wetlands, linked by a balance pipe beneath the causeway. Each has its own character — and its own role in the recovering ecosystem.
West Lake
West Lake
The larger, more exposed lake · ~9 ha open water
East Lake
East Lake
Quieter, sheltered, reed-fringed refuge
The groundwater story
Why the lakes need the water table
Perry Lakes are ‘perched’ wetlands — they sit in shallow depressions where the local water table is close to the surface. They’re not fed by rivers or streams. Their water comes from groundwater: specifically, from the superficial aquifer that underlies the Swan Coastal Plain.
That aquifer is recharged by rainfall. But since the 1970s, urban development across the Gnangara Mound — the regional groundwater dome that underlies inner Perth — has drawn the water table steadily down. Less native vegetation to capture rain. More hard surfaces. More bores extracting groundwater for irrigation.
The result: both Perry Lakes were completely dry in some summers through the 2000s and 2010s. The lakes hadn’t disappeared — the water table had just dropped below them.
Cross-section
Then — 2000s–2010s, water table below the lake
Now — since 2023, replenishment pipe added
The replenishment scheme
Bringing the water back
In 2023 the Town of Cambridge began diverting a share of the Herdsman Main Drain into West Lake. Within a single year, lake levels were back to where they were in the early 1990s.
Late 1990s – 2010s
Both lakes experience severe drying. Some summers completely dry.
2021
Town of Cambridge publishes the Perry Lakes Management Plan. Friends of Perry Lakes formed.
2022–23
Replenishment scheme designed and built. Herdsman Main Drain diverted to West Lake.
May 2023
Pumping begins. Water enters West Lake for the first time in years.
May 2024
963 ML delivered. Lake levels restored to early 1990s — within one year.
Ongoing
Average 2.6 ML/day pumped. 344 days pumping in the first year — 94% operating time.
963 ML
Water delivered, May 2023 – May 2024
26 ML/day
Average pump delivery rate
344 days
Days pumping — 94% operating time in year one
27 ML/day
Average total drain flow — only 10% diverted to the lakes
90 %
of the Herdsman Main Drain still reaches the ocean — the scheme takes only the share the lakes need.
The harder problem
The water is back. Keeping it healthy is the challenge.
Interactive StoryMap
Where does the water go?
Explore the full water story — from the Gnangara Mound aquifer to the drain at Floreat Beach. A scroll-driven guide to how Perry Lakes and the Swan Coastal Plain water system connect.