Up to 180 gigalitres a day is already flowing into the River Murray with people in the Riverland being told to expect between 190 and 220 gigalitres a day by the end of the year.
Authorities had initially warned of a peak in Renmark about December 14, and another peak later in the month because of flows coming from the Victorian catchments and Hume releases.
"As they've travelled through the system they've sort of merged, so they haven't built on top of each other, they've effectively merged together and because the peak at the end of the month will be higher it's effectively a continuum of the same now," Ben Bruce from the Department for Environment and Water said.
Emergency Services Minister Joe Szakacs said the community was well prepared to deal with the flows.
"When we have our river communities faced with very significant impacts there is never good news," he said.
"But we are comforted that the assuredness of flows in that 190 gigalitre to 200 gigalitre range are materialising, that we know that those flows will peak at late December 2022, and that the preparations that we are undertaking and that the preparations that are continuing are well within range to support our community when they need it."
SES chief executive Chris Beattie said authorities had already doorknocked more than 5,000 dwellings — more than 1,000 of those had already experienced some level of inundation.
"SES expects that the number of properties that are inundated will increase over December in line with the forecasts and that by the end of December somewhere around 4,000 properties will be inundated," he said.
"Currently there's a bit over 2,000 disconnections in terms of power to customers and SES expects this number to increase too over December such that by the peak flows of 190 to 220 gigalitres by the end of December there will be around 4,000 customers that have been disconnected."
The opposition is calling on the state government to expand its financial assistance for flood-affected communities to help businesses stay open.
Opposition Leader David Speirs has spent the past few days visiting communities along the river and said many people were already falling through the cracks when it came to support.
He said a JobKeeper-type payment was needed for businesses to stay afloat if the flooding lasts for several months.
"We are seeing too many businesses having to make a perverse decision to either close if they want to access grant funding and support or stay open and get by and continue to employ people but perhaps make no profit or make a loss," he said.
Work has continued on a levee along Renmark's riverfront and in Mannum, where the local football club used sandbagging as a pre-season exercise.
About 40 players filled 440 sandbags last night.
Berri property becomes island
The high water level has turned Damien Hunt's property near Berri into an island.
Mr Hunt is from Martin's Bend — east of the town — and, while his house is above the water, his driveway is not; it is currently covered in knee-deep water.
"We are definitely the only house in Berri that has been cut off, as an island as it stands today," Mr Hunt said.
"It probably really became serious with our access probably four or five days ago. Prior that we could enter and go on [with] life as normal, so it's come up really, really quick.
"It's day-by-day at the moment, depending on water levels over the next seven days —[they] will be really, really crucial."
He said he did not want to rely on family and friends for accommodation, but expected to because of a shortage of places to book commercially.
"With the house cut off, it's pretty tricky at the moment, trying to get the kids in and out," he said.
"I work in Loxton, so it's probably about an hour drive at the moment, so it's hard to get to work and back, get the family in and out every day. It is a bit of a challenge."
Watch out for snakes and kangaroos
Deb Kelly, a vet and the former animal welfare manager for the Department for Environment and Water, said snakes and kangaroos were good swimmers and should be avoided during flooding.
"A lot of people get hurt because they try and rescue a kangaroo they think is drowning," he said.
"And in many cases the kangaroo is swimming to higher ground, but they will climb on anything they can find.
"So, therefore, if you try and rescue one, there is a good chance that a kangaroo that weighs nearly as much as you do is going to try and climb on you and can drown you as well."
Concern about blackwater events
Department of Primary Industries and Regions (PIRSA) Riverland and Murraylands coordinator Barb Cowey said she was confident there would be fish kills as River Murray levels rise and the threat of blackwater increases.
Hypoxic blackwater events have occurred during floods interstate, but authorities say it has not been detected in South Australia at this stage.
Ms Cowey told a community meeting in Loxton that there had been some Murray cod deaths and blackwater detected near the border this week.
"We have in place a whole lot of processes and people ready to be activated if there is any major fish kills," she said.
"Unfortunately, we're pretty confident that will happen at some stage and we really need to ask the community to be our eyes."
Joshua Zugajev from SA Water said the taste and smell of drinking water could change if there was a black water event in South Australia but it would still be safe and clean to drink.
"It just makes that water from the river more challenging for the treatment plants to process," he said.
"Now, they're designed to cope with that, but as that quality deteriorates further they might not be able to fully remove all the taste and odour."
Many people in the Riverland drink rainwater from tanks rather than piped river water.
