Weatherill says take water from the Nats

Responsibility for the Murray River must be kept out of the hands of the Nationals following the change in leadership, South Australian Premier Jay Weatherill says.

Mr Weatherill says the water portfolio should go to a South Australian and has suggested Liberal Senator Anne Ruston as a suitable candidate.

"It has to be a matter of urgent decision for the prime minister of this country to make sure the water portfolio is not handed to a National Party minister," the premier told reporters on Monday.

His comments came after Michael McCormack was named the new Nationals' leader following the move by Barnaby Joyce to stand down.

The premier Mr McCormack was already on record as opposing the Murray-Darling Basin Plan which was designed to return environmental flows to the river.

He said it was time to ensure the interests of downstream states were better protected.

"We need a South Australian in charge of the water portfolio so we can hold them to account for the delivery of the basin plan in full," Mr Weatherill said.

"The Nationals have shown time and time again they're acting in the interests of cotton farmers in NSW, putting the interests of South Australians who rely on the Murry-Darling Basin last."