Sydneysiders are being reassured the water supply is safe to drink despite a canal linked to Warragamba Dam being shut down.
Low levels of cryptosporidium have been detected, with authorities now treating the water in the canal.
New South Wales deputy chief health officer Kerry Chant says there is no health risk.
“We think this is a good idea, in terms of closing down the upper canal to try and identify a source,” she said.
“It seems like a good idea to do.”