Plans to continue tapping the Murray River for significant amounts of Adelaide's water supply were revealed in SA's new 40-year water security plan, which follows calls for upstream states such as Victoria to return more water to the ailing river.

The plan was seized on by the Victorian Government, whose relationship with Labor colleagues in South Australia has been strained by threats of High Court action over Murray River politics.

More than 90 per cent of Adelaide's drinking water was sourced from the Murray in recent years, and the new plan aims to diversify Adelaide's water-supply options.

But the fine print shows that new options such as desalination will not reduce Adelaide's drain on the Murray, but will merely account for an expected increase in demand for water.

"Although Adelaide will reduce reliance on the River Murray through additional diverse supplies, the state will still need its entitlement for River Murray water," the plan says.

The document also suggests that cost will determine which of Adelaide's water sources are drawn on most in the future — raising the likelihood that river water will remain a staple, given it is a cheaper option than desalination.

"In practice, the unit cost of water from each source would determine the actual supply mix," the plan says.

Victoria's acting Water Minister, Gavin Jennings, said South Australia could do more to improve the environmental health of the Murray.

"The Murray River supplies almost all of Adelaide's drinking water yet (SA Premier) Mike Rann cries crocodile tears for the state of the Lower Lakes," he said. "Rather than pointing at Victoria, South Australia should take responsibility for its own water woes."

South Australia's Commissioner for Water Security, Robyn McLeod, said the state was planning significant growth, so it could not reduce Adelaide's Murray River water use.