The Australian Greens have called on the Rann Labor Government to come clean about the details of the prospective water deal done with upstream states before this weekend's state election, according to Green Senator Sarah Hanson-Young.

Senator Hanson-Young, Greens spokesperson on the Murray Darling Basin, says she welcomes the prospect of more water coming down the river, but says that the government must release the details.

"It's always good to see more water for the river, but one has to question the timing of this announcement - luckily for Mr Rann it happens in the last week of a tight election campaign,'' Senator Hanson-Young said.

"What we need to know is what is the breakdown of this water figure. How much of the 400GL will go towards the neediest part of the river - 90 per cent? 50 per cent? 10 per cent?

"There are many different needs competing for precious water allocations, but it is critical that as much water as possible is allowed to reach the bottom end of the river and the Lower Lakes, to protect the system for future generations.''

The Greens have argued consistently that the Murray Darling Basin needs immediate action, rather than the delayed action promised by the Federal Government and Coalition.

"South Australia should not have to go cap in hand to upstream states whenever we get a flood-year in order, just to guarantee a viable water allocation.

"The only way to have long-term, sustainable management of the system is to have an independent, national authority with the power to make decisions without worrying about bickering politicians.

"The system needs to be managed across state borders, and there must be specific water allocation for the environment. We can't afford more delays, we need action now to fast-track the Basin plan, and to empower an authority to take the hard decisions on water.''