Queensland Government plans to raise the Burdekin Falls Dam could have a drastic effect on the environment and threaten vital habitats, an oceanography expert has warned.

But a lack of replenishing sand reaching the Coral Sea from the nearby Burdekin River means erosion is threatening the bay’s long-term survival.

Adjunct Professor Eric Wolanski, an oceanography expert at James Cook University, said the Burdekin Falls Dam — the state’s largest — trapped 96 per cent of the sand entering the reservoir, leaving minor downstream rivers as the only source of necessary sand.

“That sand is needed to maintain Cape Bowling Green in the south-east wind season, [when] wind-waves and the current move sediment northward past Cape Bowling Green,” Dr Wolanski said.

“You need a supply of sand to come in and basically balance the loss of sand from waves and the current.”

Dr Wolanski said sand reaching the Burdekin River from tributaries downstream of the dam was not making its way out to sea due to insufficient water volumes, even during times of flood.

Kilometers of peninsula could be lost

“Unless a dam’s completely full at the start of the flood, the wall will always decrease the size of the flood, you need a big flood to move sand all the way to the sea,” he said.

“The bed of the river has risen one to two metres — there is still a lot of sand trapped in the river while Cape Bowling Green is being starved of sand.”

Sand levels have decreased so rapidly that a section of the peninsula that was 150 metres wide in 1980 had narrowed to just 24 metres in 2018, and was in danger of disappearing completely.

Research indicates a breach will occur within 10 years, leading to a loss of several kilometres of the peninsula.

Any breach and subsequent impact on the ecology of Bowling Green Bay is yet to be quantified, but additional wave pressure is likely to increase erosion at nearby coastlines.

Dr Wolanski said the proposal to raise the Burdekin Falls Dam and construct a dam at Urannah on the upper Broken River, a key tributary below the existing impoundment, could make the situation worse.

“That will be even worse. That’s one of the sources of the sand left now that reaches the sea — that would cut it and decrease the size of the floods,” he said.

A spokesperson from the Department of Environment and Science said the department would conduct an environmental assessment of the Burdekin Water Plan’s performance.

Replenishment of beaches along the Burdekin-Haughton floodplain and on Cape Bowling Green will be included in the study, which begins in April 2021.

Farming could suffer, says irrigator

Mario Barbagallo, who is chair of the Burdekin River Irrigation Area (BRIA) Irrigators’ group, said Queensland’s political parties were not listening to farmers about alternatives to raising the dam wall

“To raise that wall, it’s going to require a rate of return on the investment. We’re flat out paying for that water now, so how people are going to pay extra for that, I’m not sure,” he said.

“They need to work out what the cost would be and say: ‘At this price would you be interested in water and how much?’.”

The State Government has promised $16 million for a business case to investigate raising the dam’s wall by two to six metres, a project the Department of State Development estimates could cost between $358 million and $665 million.

But Mr Barbagallo said just $40 million could fund scheme upgrades to save water within the system’s 391 kilometres of pipelines and channels.

“We can do much better with what we’ve already got by modernising the Burdekin-Haughton water scheme, picking up a huge part of our loss allocation and converting it back,” Mr Barbagallo said.

Additional concerns have been raised about the ability of the river to recharge the aquifer for use by farmers in the delta region of the district, if the dam is raised.

Mr Barbagallo said some saw flows through the river as wasted water, however without it the lower delta and associated ecosystems could not survive.

BRIA Irrigators said projects including upgrading regulator gates could yield another 100,000 megalitres, enough to irrigate another 12,000 hectares of crops.

“It’s always been brushed aside, it’s not as sexy as saying we’re going to raise the dam,” he said.

“It should be — it should win the environmental vote and it makes sense, it would make water in the existing scheme more affordable because it’d be more efficient.”

A spokesman for Acting Minister for Water Steven Miles said the Government was working extensively with farmers and local stakeholders to fully understand the future demand of water in the region.

The detailed business case will be finished in late 2021. A separate environmental impact statement is also being completed.

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