Floodwaters moving down the river will increase daily flows to about 175 gigalitres a day by next week before rising again to 185 GL or possibly higher towards Christmas.
Authorities expect those flows to inundate up to 4000 properties, including shacks, homes and some businesses.
Of those about 455 are considered to be primary places of residence which will be flooded if flows go as high as 200 GL.
If flows push towards 250 GL then more than 1000 homes will be flooded.
Police Commissioner Grant Stevens said while the vast majority of those people at risk had put plans in place, officials would now contact each resident to ensure they were prepared.
However, Mr Stevens said forced evacuations were not being considered at this stage.
Premier Peter Malinauskas said those people who had already taken steps to deal with the rising water were to be commended.
But he said the government wanted to make sure everyone at risk was aware of what lay ahead.
"We've got to prepare for the worst and naturally hope for the best," he said.
"Ultimately the government can assume a lot of responsibility here but individuals in these circumstances do themselves and their families and the broader community a great service by thinking through their options and planning accordingly."
The flooding down the Murray is expected to be the worst since the 1970s. Areas most at risk include Renmark, near the Victorian border, and Mannum, east of Adelaide, where a levee is being built that will leave some businesses and homes unprotected.
The levee at Renmark has been upgraded to better protect the low-lying parts of the town, including the local hospital.
From Tuesday, flood-affected Riverland residents will be able to seek government support and assistance from a one-stop shop with the first Emergency Relief Centre to open in Berri.
The government last week announced a $51.6 million assistance package, including support for tourism and other businesses, and provide assistance to homeowners.
It includes $9.3 million for levee works, $4.8 million for sandbags and other defences, rental assistance for families, grants of up to $20,000 for businesses forced to close, and grants to buy generators for properties set to lose power.
Individuals will be able to apply for $400 personal hardships grants, with families to receive $1000.
As water levels rise, some properties have already been flooded while 65 roads across the Riverland have been closed, potentially isolating small communities.
About 700 properties have had their power cut with another 700 to suffer the same fate this week.
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