Central Queenslanders have expressed their anger over the perceived bungling of the construction of the Rookwood Weir, as state and federal governments argue over how to deal with a cost blowout on the water storage project.

Key points: Rookwood Weir was originally to supply water to local landowners

Rookwood Weir was originally to supply water to local landowners Reducing its size would leave virtually no water for farmers in the longer term

Reducing its size would leave virtually no water for farmers in the longer term The Queensland Government says the Prime Minister refused to commit more money to the weir

The weir is a $352 million water project led by the Queensland Government but funded equally by the Federal Government.

The original proposal was for the weir to hold 76,000 megalitres of water, for use by landowners and as a back-up water supply for the Rockhampton, Yeppoon and Gladstone regions.

Earlier this year, Queensland Natural Resources Minister Anthony Lynham announced the cost would exceed the initial budget, blaming the blowout on the rising price of concrete.

Last month, Mr Lynham said the weir could potentially be downsized to hold 54,000 instead of 76,000 megalitres to keep the project on budget.

Today farmers, graziers and politicians came together in protest of the changes calling for the "real Rookwood Weir" to be built.

Colin Dunne, a farmer and grazier west of Rockhampton at Duaringa, said he would have no access to water from the weir if it was built to the smaller scale.

"One minute you look as though you've got access to water, the next minute it's all gone, especially myself because I'm on the tail end of it so if the weir gets lowered I don't get any," he said.

"My time was wasted looking into it, money spent on it was wasted ... it's of no benefit to me anymore."

Federal LNP Member for Capricornia Michelle Landry organised the rally.

"We want Rookwood Weir built at full capacity at 76,000 megalitres. It's simply not good enough they don't know how much it's going to cost," she said.

Colin Dunne from Duaringa said he'll get no water if the weir's capacity is reduced. ( ABC News: Rachel McGhee )

'Nothing left for agriculture'

LNP Queensland senator Matt Canavan said around 30,000 megalitres of the weir's water would be reserved for the future growth of Gladstone, with about 20,000 megalitres reserved for future growth in Rockhampton and Yeppoon.

"You can do the numbers — if you take 20,000 megs off that 76,000, you're not left with any long-term necessarily for agriculture," Senator Canavan said.

He said the Federal Government would consider another budget proposal from the State Government if it outlined how the money was being spent.

"We don't write blank cheques. If they want us to consider an additional proposal in good faith, send us the details send all the information, give us access to your data."

State Labor Member for Rockhampton Barry Rourke said the weir would have "as much capacity as the budget allows".

Protesters called for the "real Rookwood Weir" to be built. ( ABC News: Rachel McGhee )

Mr Lynham said the Prime Minister had been approached for further funding, but he said no.

"We had a choice … the Premier asked for further funding, the Prime Minister categorically said no further funding would be available for this weir," Mr Lynham said.

"So we had a stark choice — either we build on budget, 352 [million dollars], or we walk away.

"We will not walk away.

"We're working with farmers to maximise the allocation and yield, so we're looking from 54 all the way up to 70,000 megalitres, depending on how this weir is built."

A spokesperson for the Prime Minister's office said they have received no request for additional funding.

Paradise Dam level falling

Meanwhile, it has been 10 days since SunWater began releasing 105,000 megalitres of water from Paradise Dam, near Bundaberg.

Campers along the Burnett River told the ABC the water level had dropped significantly, exposing the river bank and rotting weeds.

The falling level of Paradise Dam is revealing rotting vegetation along its banks. ( ABC News: Johanna Marie )

"There is a smell, a rotting vegetation type of smell," said Ileraine Nicholls, from Bundaberg.

"It just looks like the water is stagnating — it just doesn't look inviting."

North Burnett Mayor Rachel Chambers said the decision to release the equivalent of 32,000 Olympic-sized swimming pools of water from Paradise Dam would have a major tourism and economic impact on the region.

"We have to move pumps and there is infrastructure we have to look at, like the levels of our boat ramps," she said.

"We have two very popular camping areas being Paradise Dam and Mingo Crossing — we're working with SunWater to work out what these levels mean with the Christmas season coming up."