Last updated: April 2026 | Author: Angus Hughson, Big Ditch Dam Building Company
A metal sludge-like layer is infecting two dams that provide water for showering and drinking in Sydney
The Cataract and Cordeaux dams have increased levels of iron, examinations have shown.
Tests show that inside this sludge there is also aluminium, manganese, lithium, strontium, barium, titanium, zinc and nickel.
The dams supply water to 600,000 people in the Macarthur region of Sydney
Records obtained under Freedom of Information reveal the dams have actually surpassed acceptable limits greater than 90 times in three years.
Water authorities claim the contamination is not an issue since various other sources of water are offered to “balance water quality”.
Yet they concede the dropping storages of Sydney’s dams are posing a significant challenge.
Tests show the contamination in the dam is getting worse.
Deepwater samples also showed levels of aluminium were uncommonly high in both dams.
The Macarthur area has no access to desalinated water from the Kurnell plant.
NSW Water Minister Melinda Pavey has not commented on the situation
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