Riverland communities are now being warned to expect higher River Murray flows "well into January" and the potential flooding of "hundreds of shacks", as heavy rain and dam releases interstate make it harder to predict the impact.
SA Water Minister Susan Close said daily flows across the border were expected to reach 135 gigalitres in December, but there was now a "moderate possibility" that that figure could reach 150 gigalitres.
"What has changed is that we're expecting that water to last for longer," Ms Close said.
"The 135 gigalitres [a day] is likely to last through December and into January so the Riverland and lower Murray need to be prepared for higher water lasting for a significant period of time."
More than 330,000 sandbags are expected to be deployed across the region, and authorities have advised about 10 to 20 should suffice for most "average-sized homes".
"With 135 gigalitres of water, there will be hundreds of shacks and also homes that are outside of shack areas where there's flood inundation above the floor," State Emergency Service chief executive Chris Beattie said.
"It's important that those households and businesses that are going to be impacted take action."
Holiday revellers have been warned to be "extra cautious", with the SES saying that while tourists should not be discouraged from visiting the Riverland over summer, they should be aware of various increased risks posed by the higher flows.
"Be cognisant of the extra vegetation that creates risks, particularly if you're in the water or in kayaks and the like," he said.
"Certainly, for those that would contemplate water skiing or using powerboats, you need to be aware that there's a lot of debris in the water and it can create a significant risk of injury."
Levees repaired as dam releases create uncertainty
Urgent repairs to more than a dozen levees have either been undertaken or will begin in coming days, after concerns were raised about the capacity of infrastructure in Renmark and the potential impact on the local hospital.
"We were … particularly concerned about the levees in the Renmark-Paringa area and of the 22 levees there, 15 have already been looked at, four have had site works commence and two [have been] completed," Ms Close said.
"The rest of them have either been inspected and are going to have works undertaken from next week."
Interstate at the Hume Dam, east of Albury-Wodonga, the Murray-Darling Basin Authority has increased releases from 50 gigalitres a day to 75 gigalitres a day in response to further downpours.
"Whilst those dam releases out of the Hume Dam in particular will increase flows, we're not expecting that to contribute to an increased peak, but more so the duration of the peak flows," Mr Beattie said.
The minister also said it was "increasingly likely" that blackwater events would cause fish to die in large numbers, especially as the weather gets warmer and the mercury climbs into the mid-30s next week.
"Oxygen is removed from the water because there's a lot of organic material washed in, and that can cause fish die-offs," Ms Close said.
"We expect this to be more likely in the next week or so because temperatures are going to start rising."
The SES said there had already been an "escalation of operational activity" in SA because of the passing of weather fronts across the state in the past week.
A community meeting was held in Renmark last night to update locals on the situation, and the SES said it was working with the Department of Environment and Water and SA Water engineers to assess local infrastructure.
