South Australia will experience a second, higher River Murray flood peak with authorities saying they now expect 185 gigalitres to flow through per day in the second surge in late December.
The state government has said two peaks are expected, one in early December and another higher peak in late December around Christmas.
While 185 gigalitres is the high probability, there's a moderate chance of 200 gigalitres and a lower probability of 220 gigalitres during the second peak.
Premier Peter Malinauskas said a high probability of 175 gigalitres per day was still expected during the first peak in early December, with the low probability of 220 gigalitres per day, dropping down to 200 gigalitres a day.
"So while there is good news about what we expect at the beginning of December, we are certainly on high alert in respect to what will come across the border in late December," Premier Peter Malinauskas said.
Residents in Greater Adelaide consume about 200 gigalitres of water per year.
"We now face the prospect or that now coming across the border every single day in the River Murray," he said.
"It is a lot of water. It presents a lot of challenges."
Four kilometres of DefenCell flood barriers have been flown into Adelaide from Italy to be sent to the Riverland, and more than one million sandbags have been sourced.
Up to 4,000 properties will be flooded
The reinforcements are part of a $4.8 million flood protection package announced on Sunday.
However, Mr Malinauksas said up to 4,000 homes would still be inundated during the peak flows.
"The combination of a lot of DefenCell product and now over a million sandbags gives us a lot of confidence that where we can make a difference with these materials we do have the ability and the capacity to do so," Mr Malinauskas said.
"But the truth be told, of course, we can't protect every home.
"We can't have this much water come across the border and protect every single dwelling, which is why we are still working towards that 4,000 property number being inundated as a result of these additional flows."
Earlier this week the government declared a major emergency, which give Police Commissioner Grant Stevens additional powers to manage the flooding crisis.
SES chief executive Chris Beattie said residents needed to take action now and look at interactive maps available on the SES website to see whether their property would be inundated.
He said those affected needed to when they would be leaving their properties before it was too late.
"This may be driven by road closures in your area, by power disconnections, loss of sewerage or indeed when water inundates over the floorboard, but it is important that you determine early and in advance when you are going to leave," Mr Beattie said.
He said a levee being built to protect the Renmark Paringa District Hospital has been completed and there were number of other levees across the region currently under construction.
Wastewater to be cut from Riverland homes
SA Water's Nicola Murphy told ABC Radio Adelaide about 150 homes would be disconnected from wastewater services by December 9, with another 100 homes also facing disconnection.
Last week SA Power Networks warned about 2,000 properties would be disconnected from electricity in the coming weeks, with some homes and shacks already disconnected.
Ms Murphy said SA Water was working with affected residents to find suitable alternatives, including the use of portaloos and camp toilets.
"Anything we can do to help those residents we will, and that's something that we are working through with those people as they make their decisions at the moment whether to stay in their homes or perhaps relocate during the flood period," she said.
"What we need to think about is our network's total ability to cope with the additional volume of water getting into it and our pump stations being able to pump that through and we're trying to make sure that we maintain as many services as possible to the most number of customers for as long as possible.
"Thereby isolating one small part of the network we're looking to protect the rest of the network and keep those services going."
Ms Murphy said SA Water was also working to prevent any wastewater from entering floodwaters.
Access to health services will be 'hard'
Residents and visitors to the Riverland are also being urged to plan ahead for their health needs, with road closures imminent.
Australian Medical Association SA president Michelle Atchison said mosquito-borne viruses were also of concern.
"If you've got scripts that you need for the coming months, go and get them filled now, if you need a vaccination for your Japanese encephalitis virus, go and get it done now because in the coming weeks health services are going to be stretched because people are going to be using them, but also they are going to be hard to access," she said.
"There's lots of medicine that we can do by telehealth, but we can't give you a virus injection by telehealth so there are some things you need to start planning now."
She urged people to stock up on insect repellent before stocks began to run low.
