Wivenhoe Dam under full release during the recent flooding.
Wivenhoe Dam under full release during the recent flooding. Rob Williams

Lowering dam wouldn't change result

LOWERING the Wivenhoe Dam by 10 per cent before last month’s devastating floods would not have saved the Ipswich region from extensive damage, according to State Government officials.

Operators of the dam have been widely criticised for not releasing enough water on the weekend before Monday January 10, when the “inland tsunami” hit the Lockyer Valley region.

That Monday morning, the dam was at 148 per cent, meaning its flood mitigation compartment was already half full.

At the peak of the flooding disaster the dam was above 190 per cent full and dangerously close to tipping over.

Water experts said more water should have been released that weekend, but Natural Resources Minister Stephen Robertson yesterday defended the Wivenhoe Dam’s operators.

Ahead of the state Commission of Inquiry’s first hearing into the flooding disaster later this week, Mr Robertson said reducing the dam by 10 per cent would not have made a difference.

“Some of the work that’s already been done shows that if you reduce Wivenhoe Dam by certain amounts that, modelled against the flooding event that we saw last month, it wouldn’t have had a noticeable impact,” he said.

“That goes to the issue, which is the size of the event that we were talking about in January.

“There was so much water coming downstream, but also at the same time it was coming in lower from Wivenhoe through the Lockyer and the Bremer, which the Wivenhoe doesn’t control. So it was the combination.”

But he said the modelling was “only a very preliminary assessment”.

Andrew Dragun, an adjunct professor for Griffith University’s Australian Rivers Institute, said it was difficult to understand the lack of action on lowering the dam’s level.

He said the dam release takes about 36 hours to get to Brisbane and out to sea, meaning releases have to be taken days in advance of upcoming storms.

Seqwater is currently investigating whether it should lower the dam’s drinking-water supply below 100 per cent to give the dam a greater flood mitigation compartment considering the wet summer Queensland is experiencing.

Seqwater spokesman Mike Foster last week said different models were being considered to see if the dam’s flood mitigation function could be improved.

Mr Robertson said Seqwater was still awaiting information to complete its modelling, but hoped it would be finalised by the week’s end.

The commission into the flooding disaster will investigate the operation of Wivenhoe and Somerset dams and other issues.

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