Federal Water Minister Penny Wong appears to have rejected a second rescue option for the Murray River's ailing lower lakes.
Her department has told a parliamentary inquiry there is enough water in the southern storages of the Murray-Darling Basin to save the lower lakes from acidification in the medium-term.
But buying that water and sending it downstream would cost up to $1 billion in lost production, and put at risk $5 billion in permanent plantings, it said.
"We really do have to ensure we retain permanent plantings in areas such as the Riverland for example," Senator Wong told ABC Radio today.
"But what we will do is continue to purchase permanent allocations from willing sellers that give these communities, these irrigators, time to adjust."
Buying out permanent licences - the rights to a share of future water - is a different concept to buying out water which actually exists and has already been allocated.
Senator Wong has rejected another rescue option canvassed by the department - buying water from the Menindee Lakes on the Darling River in western NSW.
"It would be irresponsible to release that water," she said.
But she has left open a third option - flooding the lower lakes with seawater - a proposal opposed by conservationists.
"No one wants to have to make that decision," she said.
The department says the lower lakes have until at least February next year before urgent action must be taken to save them.
"At the moment we are in a holding pattern," Senator Wong said.
"There are no easy options when it comes to the Murray-Darling Basin, there are only hard choices."
