FARMERS will today be told how much water they will lose to the environment.

Murray Darling Basin Authority boss Craig Knowles is due to brief irrigators and environmentalists on details of his Basin Community Committee's draft plan.

Rumours have circulated for weeks the MDBA will call on the basin's 2.2 million people to cut their diversions from the basin by an average 2800 gigalitres a year.

Federal Water Minister Tony Burke has already revealed details of the plan by declaring it must deliver an extra 2000 gigalitres to the Murray mouth in South Australia.

In a speech to the Sydney Institute last week, Mr Burke said the plan must ensure the Murray mouth remained open nine years in 10, which MDBA modelling shows can only be achieved with outflows of 2000GL a year.

Until now MDBA modelling has shown at least 3000GL would need to be diverted from irrigators to the environment to push 2000GL through the Murray mouth, with 1000GL needed to cover losses and to water other environmental sites.

Irrigation communities rejected the 3000GL claw-back when it was enshrined in the controversial guide to the proposed Murray Darling Basin plan released last October.

But industry sources have speculated Mr Burke's comments mean the MDBA has little choice other than to take back some of the 1000GL earmarked for other environmental assets within the basin and curb losses to cut the sustainable diversion limit to less then 3000 gigalitres.

Mr Knowles told The Weekly Times yesterday the draft plan was about "how you use the water, rather than just a volume".

It was a point highlighted by Mr Burke last week, when he said: "Smart and efficient use of environmental water including through environmental works and measures needs to allow these icon sites to go through a more normal wet and dry cycle".

It's expected Mr Knowles would reassure irrigators the Federal Government's $3.1 billion water buyout and $5.8 billion irrigation infrastructure programs were on track to deliver 2000 gigalitres by 2014, leaving 800 gigalitres or less to be recovered by 2019.

Mr Knowles said he "strongly agreed" with the Windsor Inquiry's recommendation on the potential for even more savings through reform across the basin.

Savings estimates have been as high as 500 gigalitres, but state water bureaucrats and irrigators warned reforms, such as introducing exchange rates on water trades and storage rules, could be difficult to implement.

Mr Knowles told The Weekly Times the timeline for implementing the plan by 2019 had to be able to adapt to works that boosted the efficiency of environmental watering.

National Irrigators Council chief executive Danny O'Brien said Mr Knowles had discussed reviewing the plan in 2015, to assess the effectiveness of environmental works and volumes.

Industry and government sources said Mr Knowles was selling the draft plan in two parts, with each state given "in valley" targets, while the Commonwealth worked on a basin-wide number delivering 2000 gigalitres to the Murray mouth.

Mr Knowles briefed state water ministers on their contribution to the draft plan.

Victorian Water Minister Peter Walsh said Mr Knowles had given him the numbers for the environmental assets in Victoria's valleys - the Ovens, Goulburn-Broken, Loddon, Campaspe and Kiewa.

He said Mr Knowles was keeping the Murray Valley target to himself, but farmers would soon work out the total.

Mr Burke stands ready to placate the states by handing over a large chunk of the $5.8 billion infrastructure fund in return for acceptance of the draft plan.

For Victoria, it means access to $953 million for the second stage of the Northern Victoria Irrigation Renewal Project.

In his speech last week, Mr Burke said he was negotiating a deal with the states that gave them more autonomy over federally funded water infrastructure projects in return for a guaranteed volume of water.

But while state governments and irrigators may begrudgingly accept the draft plan, green groups said they would reject less than 4000 gigalitres.

Australian Conservation Foundation healthy rivers campaigner Dr Arlene Harriss-Buchan said the basin needed an extra 4000 gigalitres.

One industry source said a key Green group was ready to mount legal action against the plan if it failed to meet the requirements of the Federal Water Act 2007 to give the environment "primacy" over social and economic issues.