The central issue being discussed this week at the Commission of Inquiry into the Queensland floods is how to strike the right balance between flood mitigation and water security.

Wivenhoe Dam was built after the 1974 floods to protect the cities of Brisbane and Ipswich from another inundation.

In recent drought years it has been seen more as a drinking water reservoir and that compromised its value leading up to this summer's deluge.

Ipswich Mayor Paul Pisasale has no doubt why the dam was built.

"I think what's been happening over the last 15 years, everybody's been thinking about drought, drought, drought," he said.

"I think the most important thing is that people realise Wivenhoe Dam is there for flood mitigation, not water supply. I'd rather deal with a drought any day rather than a flood."

But Mr Pisasale's view is not a universal viewpoint, with Wivenhoe manager Seqwater putting water supply as its top priority.

In its submission to the flood inquiry on Wednesday, Seqwater lists its responsibilities as water supply, water quality and efficient and cost-effective operation of the water grid.

It made no mention of flood mitigation.

In October, Queensland Water Minister Stephen Robertson wrote to Seqwater and asked whether the dam level should be reduced in the light of forecasts of an intense and dangerous wet season.

The water authority responded, saying "releases may impact upon water supply security or damage property such as bridges downstream and impose a significant inconvenience and danger to residents downstream, with no benefits if rain doesn't fall in the catchment above the dam wall".

In the end, there was no time to lower the dam height before torrential rain in January created the more urgent problem of releasing water to protect the integrity of the dam itself.

No guarantee

On Wednesday at the inquiry, flood engineer Rob Ayre was asked by commissioner Justice Catherine Holmes whether there would be any practical benefit in temporarily lowering the full supply level of Wivenhoe when an extraordinary wet season was predicted.

Justice Holmes pointed out a reduction from 100 per cent to 75 per cent capacity would provide about 300,000 extra megalitres of flood buffer.

But Mr Ayre said dropping dam levels to 75 per cent would not necessarily help safeguard against a flood event as large as January's.

"I have a little bit of difficulty accepting the fact you would necessarily do it on a seasonal basis ... I don't necessarily think it would assist," he said.

While admitting reducing levels could help mitigate the effects of smaller floods, he warned doing so could impact Queensland's water security.

"It certainly would have an improvement on managing the smaller events," he said.

"I guess the other side of the coin then is what impact would it have on the water security aspects."

With the attention being given to the issue of water security versus flood mitigation at the inquiry, this is likely to be one of the key areas to be addressed when it makes interim recommendations before the next wet season.

Mr Pisasale says the inquiry should be allowed to take its course, but he did call for an end to the "blame game".

"We've got to ... really start working on solutions so this doesn't happen again. We can't change the past, but let's influence the future," he said.

But Mr Pisasale refused to be drawn on whether he thought dam levels should be lowered.

"I think what we've got to do is have a close look at Wivenhoe Dam in regards to flood mitigation and see whether we have to increase the height of it," he said.

"Things we have to do - let's start looking at exactly during the 2011 floods, and let's see what we can do now to minimise the effect on both Ipswich and Brisbane."