Water levels in Wivenhoe Dam have more than trebled in just three days as a result of a "rain bomb" hovering over Queensland's south-east, conjuring up fears of a repeat of the disastrous 2011 floods.
But authorities say the latest flood event, expected to inundate thousands of houses "above the floorboards", bears no resemblance to the 2011 event which destroyed around 28,000 homes.
Wivenhoe water levels have increased from about 684,000 megalitres on Thursday to 2.137 million megalitres at 6:20am on Monday.
The dam was sitting at 182.9 per cent capacity as of 8am Monday morning.
But Seqwater spokesman Mike Foster said the dam's storage could take millions of litres more water before reaching the capacity seen during the 2011 catastrophe.
Releases from Wivenhoe Dam in 2011 were blamed for contributing to the floods that inundated large swathes of south-east Queensland, including Brisbane.
Wivenhoe was built in the 1980s to provide flood protection to south-east Queensland after the devastating 1974 floods which saw 14 people lose their lives and thousands of homes inundated.
"I keep reminding people we got two 1974 flood events 30 hours apart [in 2011]," Mr Foster said.
"We had to make decisions from a dam safety perspective, which was all gates open and getting water out as quickly as you possibly can."
The 2011 extreme weather event occurred at a time of high ground saturation levels after a wet autumn and winter.
That's in contrast to 2022 with Wivenhoe’s capacity last Thursday sitting at just 58.7 per cent.
Using manuals rewritten after the 2011 floods, Mr Foster said controlled releases of water from Wivenhoe Dam had begun and would continue for at least the next four to five days.
"At the moment there is more water coming in than what we're putting out," he said.
"The reason we do that is that we don't want to exacerbate what's already happening.
Controlled water releases
Water released from Wivenhoe Dam typically takes 16 to 24 hours to reach Brisbane, according to Seqwater.
Dam operators released the first volume of water for an hour on Friday night, and another release started at 4am on Sunday.
"The first lot of that water won't actually hit the Brisbane system until the early hours of tomorrow morning," Mr Foster said.
He said the Friday release did not coincide with Brisbane's high tide early Sunday morning.
"The releases are nothing to do with what's occurred, unfortunately, around Brisbane late yesterday into today," he said.
Wivenhoe's "flood compartment" can take more than two million megalitres of water on top of the 1.165 million megalitres the dam holds for drinking water.
At 4pm on Sunday, more than half of Wivenhoe's flood storage capacity was still available.
Reacting to criticism that water releases from Wivenhoe Dam should have started earlier, Premier Annastacia Palaszczuk said she could not control nature.
"No-one expected this rain bomb to be sitting over the south-east of our state for such a long period of time," she said.
"This is like an unpredictable cyclone.
As heavy rain continues over Brisbane, Ms Palaszczuk has asked south-east Queenslanders to conserve water until problems at the Mt Crosby Water Treatment Plant can be rectified.
"I know this might sound a bid odd, but until we can get the treatment system back online, please conserve your drinking water," she said.
