River Murray irrigators will share an extra 50 gigalitres of water in dry years under a new management plan for the waterway.
In years when irrigators receive less than 100 per cent of their water entitlements, the allocation used for Adelaide's drinking water will be cut to 100GL, and the extra water made available to primary producers.
Adelaide's population will rely on the desalination plant at Port Stanvac for water if required.
The other major change for irrigators will be the terminology around their water licenses.
The previous water classes have been given new names and reorganised within an "all-purpose consumptive pool".
There was "no risk" of household water restrictions even if SA Water's take was reduced, state government ministers Ian Hunter and Leon Bignell said in a joint statement.
"We have systems in place ready to deal with a lack of water," Mr Bignell, the Agriculture Minister, said.
"Every drop of water is vital when it comes to keeping permanent plantings alive and helping growers with their annual crop."
Mr Hunter, the Minister for Water and the River Murray, said the management plan would provide security for both water users and the environment.
He said ensuring even flow during dry years would keep the Murray Mouth open, flushing salt from the system and sustaining wetlands and floodplains.
Liberal Member for Chaffey Tim Whetstone welcomed the policy change, which he said had been wanted by river communities and Opposition MPs for years.
“Riverland irrigators are a key economic driver for South Australia and it is critical they are given greater water security, particularly during dry years,” he said.
“Ensuring irrigators have greater access to water provides greater security for regional jobs.”
However, he called for more information about when the desalination plant would be used.
The new plan came into effect on October 3 and was announced by Mr Hunter on a visit to Murray Bridge this morning.
South Australia is normally entitled to 1850GL of water per year, of which 1154GL is set aside for consumptive purposes such as households, farming and industry.
The last dry year for irrigators was 2016-17, when a 36 per cent opening allocation was confirmed only days before it came into effect.
Allocations were then increased back to 100pc within two months, leaving business owners fuming at the uncertainty they had been made to deal with.
The government now announces opening allocations on April 30 of each year.
Minister accused of leaving Coorong high and dry
The plan's release was a timely distraction for Mr Hunter, who had been criticised earlier in the week for allegedly witholding 45GL of South Australian environmental water from the Coorong and Lower Lakes for household use in Adelaide, but accepting 150GL of environmental water from interstate at the same time.
New South Wales Irrigators Council chief executive officer Mark McKenzie said the allegations, reported in The Australian, showed South Australia was undermining the Murray-Darling Basin Plan.
“Minister Hunter has been constantly harping at the upstream states about abiding by the basin plan and how the Lower Lakes, Coorong and Murray Mouth need more water," he said.
"Whatever SA Water states about the legality of its water take practices, it is a very low act by the SA government."
He called for a federal inquiry.
National Irrigators Council chairman Steve Whan was more measured in his response, saying South Australia's actions were legal under the terms of the basin plan, just like irrigators' use of water in the Barwon Valley.
"These issues are not as black and white as ... those wishing to score political points would have us believe," he said in a newsletter.
"Those tasked with making the plan work, including state governments, need to show a bit of willingness to work with each other if they want to see the plan succeed."