Floodwaters peak in more South Australian towns but emergency far from over

Floodwaters are peaking in parts of South Australia along the River Murray but authorities warn the emergency is far from over.

Premier Peter Malinauskas said floodwaters have peaked at Renmark, 254km northeast of Adelaide, and are moving downstream in the weeks ahead.

"The speed it is occurring is faster than what was originally anticipated, not by a significant margin," he said.

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"In a way that is good news, the sooner the peak passes through the system the better it is."

It comes as a car with three people inside entered an area that was flooded in Renmark and had to be rescued.

"They lost control of the vehicle and they were safely recovered and brought to safety by a swift water rescue team," police commissioner Grant Stevens said.

"The people were on the roof, there would have been a fair bit of water inside the car."

Malinauskas said on the other side of the peak where townships have already flooded the river is receding rapidly.

He said by mid-January the volume of water is expected to decrease to 150 gigalitres.

It currently sits at 180 gigalitres.

"Ordinarily, this time of year the average volume of water we see in the river is 15 to 18 gigalitres, obviously 180 gigalitres is a lot more than that," he said.

"We have a long way to go before we get down to the average we see during the course of summer."

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Overnight, stormwater infrastructure failed at Mannum causing a "significant amount" of river water to inundate Mary Ann reserve.

SES Chris Beattie said emergency services had to issue an evacuation order for 12 homes in the area at 2am due to the flooding.

Three homes chose to evacuate while two others sheltered in place.

He said the infrastructure failure would not impact the broader networks of levees but warned it was not out of the question that other stormwater pipes could burst.

"Stormwater systems present operational challenges when we have levees fully engaged," he said.

"It occurs when we have too much water pressure build up through the pipes."

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The flood emergency has been slow-moving through the state but Beattie said peaks will begin to occur over the next seven days.

"We will see the peak flows through the Riverland townships by the end of the next seven days," he said.

"Over the following week we will see the mid Murray townships will have the peak transverse that stretch of the river."

There are 10 flood warnings in place for South Australia currently.

Restrictions are in place for activities on the River Murray and Malinauskas said the government is looking to lift them as quickly as possible.