Flooding along the Murray in South Australia has been declared a major emergency as the state braces for two distinct peaks in water flows.
Premier Peter Malinauskas says the latest information suggests flows will rise to about 175 gigalitres a day by early December and could then go higher towards the end of the month and into early January.
The second peak has been influenced by the most recent rains interstate in critical catchment areas and the release of water from the Hume Dam.
"This is a moving feast that is technically complicated and very much dependent on multiple sources of data," Mr Malinauskas said on Monday.
"These forecasts, every time we receive them, they tend to go up.
"We now have the prospect of a second peak, which could potentially be even higher than the first."
Officials said the water flow forecasts for the second peak should be available later this week.
The declaration of a major emergency gives Police Commissioner Grant Stevens wider powers to respond to the situation and better co-ordinate relief efforts.
Mr Stevens said the state's emergency centre had been activated and, given the latest information, the declaration was prudent to best mitigate the impact of rising water levels.
It gives him the power to direct resources and infrastructure, evacuate locations and direct that utilities are cut off.
It also ensures all the economic, social and environmental impacts are properly considered.
"Essentially anything that's necessary to support the response to the flood event," the commissioner said.
The flooding down the Murray is set to flood thousands of shacks, homes and businesses in SA, with at least 4000 properties likely to be inundated.
That number could go much higher if forecasts for water flows continue to rise.
Renmark is considered the town most at risk and work has been underway for several weeks to shore up the town's levees which were designed to withstand river flows of 210GL a day.
But concerns are rising for Mannum, east of Adelaide, where work will be done to strengthen its levees amid fears parts of the town could be flooded.
Mr Malinauskas and his cabinet will travel to the Riverland on Tuesday to announce a support package for flood-affected locals.
The flood along the Murray will be the worst since the 1970s.
Some roads in the Riverland are set to be closed, although most ferry services will continue to operate.
Almost all houseboat operators on the river have shut down, with the faster-flowing water too dangerous.
