Sydney Harbour turns brown as authorities warn against swimming after floods

Heavy rainfall can cause untreated sewage containing viruses and bacteria to flow into waterways posing health risks to swimmers

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Pollution washed into Sydney's beaches and waterways could linger for days, with state authorities urging swimmers to exercise caution after the flood disaster.

Sydney Harbour turned brown as a result of storm water carrying soil and debris, and algal blooms have appeared on the usually pristine sands of Hyams beach in the Jervis Bay region.