Queensland Premier Campbell Newman has warned some areas in the state's south east may run out of drinking water overnight if residents do not immediately cut back their water usage.
Queensland Urban Utilities (QUU) has asked residents of Brisbane, Ipswich, Logan, Redlands, Moreton Bay, Lockyer, Somerset and the Scenic Rim to conserve water until supplies are replenished.
The warning comes after the Mount Crosby water treatment facility went offline after becoming clogged with muddy floodwater.
QUU says the turbidity levels in the Brisbane River are four times what they were during the 2011 flood crisis.
The treatment plant is expected to be out of action for days.
Mr Newman urged Brisbane residents to haul in their water usage for the next 24 to 48 hours, saying the city could not sustain its usual level of water consumption - around 450 megalitres a day.
He said residents in Brisbane's southern suburbs would be affected by any water outage, but a group effort was needed to avoid supplies running dry.
Brisbane is currently drawing water from Gold Coast and Sunshine Coast reserves, and Mr Newman said people need to limit their water consumption to around 150 litres a day.
"The normal consumption of water across the greater Brisbane area is around 450 megalitres per day and right now - and this is the issue - we can only probably produce and supply around about half that," he said.
"We're drawing on water from the Gold Coast. We're drawing on water from the north and Sunshine Coast.
"We've ramped up the North Pine dam treatment plant to bring water in, but what we need people to do right now is conserve water.
"If people just used water at the normal rate in certain parts of Brisbane - and this is the worst case - if they just do this and we can't manage to sort of top up reservoirs and the like - and it is a technical thing - there are parts of Brisbane I'm advised that overnight could run dry."
Mr Newman urged people to hold off on non-essential water usage, but said restrictions did not apply to people cleaning up flood damage.
"We'd like you to please only use water for cooking, for drinking, for washing, showering and bathing and to completely cease using water for topping up pools, washing down driveways, cleaning boats and cars for the next couple of days or until further notice," he said.
"Those who have been hit by the floods and who need to use water to clean down their premises, that will be an exception.
"By all means do that, but please if you can use water-saving high-pressure hoses and Gerni gear, that would be very, very important."
Mr Newman says water may taste different but will comply with Australian drinking water guidelines.
Brisbane's Lord Mayor Graham Quirk says the water should only be used for living essentials, such as cooking and drinking.
He asked people to revert to the four-minute shower policy in place in south-east Queensland during the drought before the 2011 floods.
"As the Premier has indicated, [water] is probably the most critical issue," he said.
"We had a little rule in this city during the drought - it was a four-minute shower and we need to, over the next couple of nights, revert back to that policy.
"We don't want panic around this but we do want common sense, that's the critical thing."
Meanwhile, Brisbane City Council has put food waste bins in suburbs affected by power outages and a kerbside green-waste pick up will take place starting Monday.
"There was of course power outages in Brisbane for a significant period of time ... we've had provisions for 50 food waste bins in a range of about 36 suburbs impacted by significant power outages," said Mr Quirk.
© ABC 2013
18:16 EST Heavy rain has stranded about 40 people at William Creek in the South Australian outback due to flooded roads and low cloud has grounded aircraft.