Authorities fear there is a chance the Paradise Dam in southern Queensland will become unsafe if there is a major flood, but will not reveal what structural or design issues could be at fault.

Key points: The Government has been criticised for a lack of consultation with graziers and farmers

The Government has been criticised for a lack of consultation with graziers and farmers Authorities met with irrigators last night behind closed doors

Authorities met with irrigators last night behind closed doors SunWater chair Leith Boully said the work had to begin immediately

The dam's capacity is being immediately reduced to 42 per cent and once the wet season is over, the spillway will be lowered by 5 metres, Natural Resources Minister Anthony Lynham said.

When asked if he was confident the dam could withstand a one-in-100-year flood, Dr Lynham said they had to be prepared for every situation.

"I've been advised that in extreme weather events there may be some difficulty," he said.

"We have to make sure that safety is a priority."

In 2013, water flowed over the spillway of Paradise Dam. ( ABC Local: Ross Kay - file photo )

Dr Lynham said it would be up to the dam's manager — SunWater — to decide if the technical report that led to Tuesday's sudden announcement will be released.

He announced on Wednesday an independent review into the dam and the community's readiness for another significant flood.

The dam, which was built by the Queensland government and opened in 2006, was damaged in the 2011 and 2013 floods and later repaired.

Bundaberg Mayor Jack Dempsey said council was told that SunWater made the decision to lower the dam's capacity based on recent core samples that examined the construction of the dam.

"It's not the effect of the two natural disasters, it's the actual structure and integrity of how the dam was built in the first place and where it was built," he said.

"This is the largest failure of a piece of infrastructure in Queensland's history.

Mr Dempsey (left) in 2013, when he was the police minister in the former Newman government. ( ABC Open: Lisa Clarke )

"This is the second most newest dam in Australia. There's a lot of questions."

Cr Dempsey wants the technical report released and a Senate inquiry into "how we got to this position in the first place".

Paradise Dam, about 100 kilometres south west of Bundaberg, is currently 75 per cent full and the equivalent of 32,000 Olympic swimming pools will be released.

Cr Dempsey said the region would now have to cope with a 20 per cent less water capacity, which would affect long-term investments.

Local businessman Geoff Augutis said any reduction in water security would have flow on impacts for business confidence. ( ABC News: Nicole Hegarty )

'Do your bloody jobs'

Stanthorpe and Granite Belt Chamber of Commerce president Graham Parker said a massive water release when his community was in the grip of drought highlighted the failure of successive governments in building vital water infrastructure.

He said it would be impractical and cost-prohibitive to truck the water 600 kilometres from Bundaberg to the Granite Belt, but believed a pipeline was needed to protect water security into the future.

"Do your bloody jobs and get a water grid built," Mr Parker said.

"We need a network to be able to distribute water through our state, from the places where they have more than they need, to the places where there is not enough.

"Yes, it's going to cost money — but we can spend a few billion dollars digging a tunnel somewhere to save people five or six minutes."

The Government has also been criticised for a lack of consultation with graziers and farmers along the Burnett River, who are battling a drought.

While graziers will be able to use the water for free when it is released over the next 10 weeks, some believe much of it will go to waste at sea.

"They were given notice as soon as possible," Dr Lynham said.

"I had to act swiftly on those recommendations.

"We have dam improvement programs all throughout Queensland, Paradise Dam's turn came up, they did their investigations and these were the recommendations passed on to me."

Authorities met with irrigators last night behind closed doors and another meeting was held in Bundaberg on Wednesday morning.

SunWater chair Leith Boully said the work had to begin immediately.

"Our intention is to make sure that the community stays safe," she said.

"We will be working with Building Queensland and the State Government, to look at what the options are post the completion of these works and we will be talking to community."

Avocado and macadamia farmer Joe Lyons says he was shocked to hear the dam wall will be lowered. ( ABC News: Nicole Hegarty )

'Why are we tipping water into the ocean?'

The Bundaberg irrigation scheme supplies water to farmlands and communities in the Burnett, Kolan and Isis Shire as well as Bundaberg city.

The scheme sources water from Fred Haigh Dam and Paradise Dam with more than 600 kilometres of channels and pipelines distributing water to about 1,000 properties.

Bundaberg avocado and macadamia farmer Joe Lyons was happy about getting free water in the short term, but was worried about water security with reduced ongoing capacity.

Map Paradise Dam is about 100 kilometres south west of Bundaberg.

"I'd love to say we could use all of that water but it's not going to happen," he said.

"We've had very good security of water in this region since Paradise Dam was built, however I do remember before Paradise — that we started one season on 3 per cent allocation.

"I've virtually got over the initial shock that they're going to lower a dam wall in this day and age but to SunWater's credit I think they've got a problem that they inherited."

Bundaberg resident and business owner Geoff Augutis said lowering the spillway could have negative impacts for the whole region.

"We've got a lot of people that are struggling with water at the moment," he said.

"My main concern was why are we tipping water into the ocean?

"Bundaberg is a town that is driven by agriculture.

"When farmers have good years the town has good years so it's definitely a concern from a business perspective."

Former Queensland premier Peter Beattie inspects Paradise Dam in 2006, the year it was opened. ( AAP: Lyndon Mechielsen )

Opposition Leader Deb Frecklington visited the dam today and met devastated farmers.

"They cannot utilise this amount of water in such a short period of time," she said, adding that 70 per cent of the state is in drought.

"Annastacia Palaszczuk has made a terrible decision and needs to reverse it.

"Towns are running out of water.

"We should always keep the community safe ... but it shouldn't be at the risk of losing this amount of water.

"If this is truly about the safety of Bundaberg people, then I want to see the document."