In what has been described as a world first, a troubled $1.2 billion Queensland dam will have to be rebuilt after experts discovered its wall could not be repaired.
Paradise Dam north of Brisbane was assessed after it was lowered almost six metres in 2020 because of safety concerns.
There had been fears the dam could collapse after it was so badly damaged during ex-tropical cyclone Oswald in 2013 that the water level had to be lowered 5.8m to prevent a disaster.
Work on restoring the dam wall began last year, with the state and federal governments each committing $600 million.
But Water Minister Glenn Butcher on Thursday said experts had discovered the dam wall was "not secure enough to do that work".
He said the "only option" was to build a new wall 70m downstream.
"This is a world first," he told reporters.
"There are not too many dams in the world that have these issues with the concrete that we are seeing at Paradise Dam.
"The last thing we want to do is ... risk the people of Bundaberg with an asset that potentially won't last a very severe weather event.
"We want to make sure we deliver a 100-year asset for this community."
Operator Sunwater said the dam had been a "complex and challenging asset" for a long time.
"The quality of concrete that sits within the dam structure itself doesn't allow us to continue to reinforce and build on that structure," Sunwater CEO Glenn Stockton said.
"We have confidence that the dam is safe today but the issue for us is ... rebuilding the dam is not a viable alternative."
Sunwater said the dam's current operations were safe because of its lower supply level.
Bundaberg state Labor MP Tom Smith backed the construction of a new dam.
"Sunwater have highlighted that there are 60,000 people downstream of Paradise Dam who would be potentially in life-threatening danger should a failure occur," he said.
No time-frame has been given for the new dam's construction but it is expected to take years.
Sunwater said in the meantime the dam would be maintained at its existing level and would continue to be a reliable water source for local farmers.
Mr Butcher said the $1.2 billion state-federal funding was "still there" for the project.
"We want to make sure that the people of the Bundaberg region know that we are here to make sure that this new dam wall is delivered," he said.
Paradise Dam was built in 2005 on the Burnett River with a capacity of 300,000 megalitres.
It is the main water storage supply for the region which produces more than $1 billion worth of agricultural produce a year.
"There are so many questions that need to be answered, like why has it taken four years for the government and Sunwater to discover this problem," Mark Mammino from peak body Canegrowers said.
The Bundaberg Chamber of Commerce said it had hoped the dam would be rebuilt.
"We're now looking out to at least 10, maybe 15 years before we see anything happen," a spokesman said.
Opposition Leader David Crisafulli called the dam rebuild decision a "kick in the guts" for the region.
