Water from South Australia's desalination plant is going to be used to help drought-affected farmers around the country.
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.
"We are prepared to provide support, but we will not jeopardise our own water security or do anything that increases costs to South Australians.
"As part of this deal we have also secured a $10 million South Australian Drought Resilience Fund which will be available for our farmers."
The commitment is a one-off agreement with the ability to provide an extra 60GL in the next financial year if approved after review.
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."
South Australian Greens Senator Sarah Hanson-Young said the agreement did not deal with the chronic over-allocation of water, corporate greed or drought.
"Cutting SA's river water allocation in favour of turning on the desalination plant is short-term thinking and I worry SA will be left carrying the can, with less water flowing downstream, higher water prices for Adelaide, and no political will to tackle upstream greed and over-allocation.
"Minister Littleproud today failed to outline how the government will ensure the water cut from SA will even end up where it should.
"In the medium and longer term, the consequences of reducing flows by 100GL to the Lower Murray could be significant for the health of the River."