Wivenhoe Dam floodgates to open amid Queensland flooding fears

The plan to release 116,000 megalitres of water, to free up dam space, comes as Australia’s east coast faces another summer of flooding.

Wivenhoe Dam came close to overflowing in February. Picture: Liam Kidston

Floodgates at Queensland’s Wivenhoe Dam will be thrown open this weekend to free up space from an impending deluge as the east coast of Australia faces another summer of flooding.

Built to mitigate floods and supply drinking water to Brisbane, Wivenhoe Dam came dangerously close to overflowing in February when the Queensland capital received 80 per cent of its annual rainfall in six days.

Premier Annastacia Palas­zczuk said state-owned operator Seqwater would begin pre-­emptive releases on Saturday to reduce dam levels from 90 per cent to 80 per cent.

Dam engineers will be prohibited from making extra early releases, even when imminent Bureau of Meteorology forecasts warn rain will fall over Wivenhoe.

Instead, they will be forced to wait until rain is on the ground before controlled releases can be ordered to free up space in the flood storage compartment, Ms Palas­zczuk confirmed.

“No other changes,” she said. “We don’t know if the rain is going to fall over Wivenhoe so the minister has taken the expert advice.”

Ahead of the February flood, southeast Queensland was on the brink of drought with Wivenhoe rising from 60 per cent to 184 per cent in a few days.

Water reached just 39cm below the dam wall and had the rain not stopped, engineers would have been forced to take drastic action to urgently lower water levels to protect the dam’s structural integrity.

Water Minister Glen Butcher, who authorised the drawdown of Wivenhoe under special ministerial powers, said he was balancing risk of drought and flood.

“We are getting rid of 116,000 megalitres of southeast Queenslanders’ drinking water,” he said.

“Seqwater and dam experts are confident that at 80 per cent, with the forecast weather (for) this season, they will be able to manage that in whatever circumstance that happens in that dam.”

Mr Butcher said finding alternate drinking water options was “totally separate to flood ­mitigation”.

“Even if we have further drinking security, we are still going to have to manage flood mitigation dams,” he said.

Mr Butcher’s intervention came after calls in September from Brisbane lord mayor Adrian Schrinner to lower Wivenhoe before the third successive La Nina event took hold.

He believes Brisbane needs a new permanent water source ­before his city hosts the 2032 Olympics.

“I’m agnostic about whether that water source is another dam, desalination plant or recycled water,” he told The Australian.

“Another water source will help reduce the risk of residents facing harsh restrictions and the prospect of Brisbane running dry.

“Importantly, another water source will provide greater flexibility so state authorities can proactively reduce the level of Wivenhoe Dam whenever Brisbane faces a season of potentially severe weather.”

Ms Palaszczuk said bills would be cut by $55 to give southeast Queensland residents two weeks worth of free water.

“The discount will apply to water bills before December and will be fully rolled out by March.