The State and Federal governments have agreed to use the Adelaide desal plant to produce around 40GL this financial year, which means water which is normally taken from the Murray River will be available for use by farmers.

The Federal Government will take care of the extra costs needed to produce the water as well as provide the extra water to farmers at less than market rates.

Premier Steven Marshall said the state was proud to lend its support.

"South Australia survived some of the most extreme effects of the Millennium Drought and fully understand the terrible impacts that drought has on farmers, families, regional communities and the nation," Mr Marshall said.

"As part of this deal we have also secured a $10 million South Australian Drought Resilience Fund which will be available for our farmers."

State Minister for Environment and Water David Speirs it was the "right thing to do".

"There are farmers across the country crying out for help to keep livestock alive and ultimately feed Australian families," Mr Speirs said.

"Given our desalination plant sits virtually unused, it's time to increase its production so water is made available to drought-affected farmers across the nation.

"This is right thing to do at a time of national urgency, and our agreement protects our water security, the cost of water in South Australia and helps drought-affected farmers who are doing it very tough."

The commitment is a one-off agreement with the ability to provide an extra 60GL in the next financial year if approved after review.