South Australia’s Liberal Opposition has accused the Government of wasting millions of dollars worth of water.

Liberal Member for Chaffey Tim says almost 12 gigalitres of water was pumped from the River Murray into the Mount Bold reservoir in recent months, but it has all now flushed away in heavy rainfall.

“What we've seen now is the lack of planning and I think it's really the lack of gumption by the Minister to understand that when we do have fall projections of high rainfall, that needs to be put into the mixing pot when we're going to ... continue to pump the River Murray at the expense of South Australian water users,” Mr Whetstone said.

“We have to understand that that water that is spilled has a potential value of about $34 million if that was to be put on the water market, plus the cost of pumping that water.”

Mr Whetstone said SA Water knew enough in April to decide not to pump the water in the first place.

“I have met with the Minister on a number of occasions with the forward projection scenario not just for pumping River Murray water into Mount Bold, but it's also the forward projections in announcing irrigators' allocations.

“He was less than interested and that's why I've raised the concern that we continue to pump water from the Murray at high cost to the cost of every South Australian, as we watch a large amount of water at that huge value, flow out to sea.”

But Water and River Murray Minister Ian Hunter says SA Water worked with experts at the BoM to plan water allocation.

“They do a very critical analysis to balance all of those things, the cost of pumping, what the likely infall's going to be through rain throughout the year, and come up with a solution,” he said.

“And it works pretty well for us, but of course when it does to the significant level it has done in recent weeks, they do have to release water for the safety of the community and to keep that dam safe.”

SA Water has issued a statement say it is in regular contact with the weather bureau, but could not say what reservoir inflows would be each month.

“Reservoir inflows are highly variable. For example, more water flowed into Mount Lofty Ranges reservoirs in July 2016 than during the entire 2015-16 financial year,” the statement said.

“When a reservoir reaches near or at capacity, we perform a controlled release of water downstream to mitigate flooding and safety risks.”