About 190 gigalitres of water is predicted to flow through the river at Renmark in the next 48 to 72 hours, SA Premier Peter Malinauskas said on Saturday.
That peak is lower than the 220 gigalitres originally forecast.
"It means less homes being inundated. It means less people being displaced," Mr Malinauskas told reporters on Saturday.
"But it still does mean a substantial body of water at a level that we haven't seen in our state for a long, long time."
About 4000 properties along the Murray are still expected to be inundated in the coming weeks.
Some 3260 homes were disconnected from power on Saturday morning, while authorities have door-knocked close to 5000 properties as they encourage people to be prepared.
The premier said some affected residents have taken up emergency accommodation, with close to 25,000 beds available across the region.
"We have got a lot of capacity there for the worst-case scenario," Mr Malinauskas said.
The Murray is expected to peak at Mannum, about 200 kilometres southwest of Renmark, on January 7.
Meanwhile, ex-cyclone Ellie is bringing heavy rain to parts of the Northern Territory with the weather bureau issuing a warning for flash flooding.
The category one storm made landfall in the early hours of Friday and has since been downgraded to a tropical low.
But the Bureau of Meteorology is warning up to 250 millimetres of rain could still fall across the Carpentaria, Tanami and Barkly districts this weekend.
Up to 120mm could lash parts of the state within six-hour periods, while thunderstorms and heavy winds could also affect the towns of Tennant Creek, Wadeye, Nauiyu, Lajamanu, Elliott and Kalkarindji.
The bureau is advising NT residents to secure loose objects outside, seek shelter if conditions deteriorate, and avoid driving into water of unknown depths and currents.
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