20-Week Public Consultation Period for Murray-Darling Proposal Ends Today. (April 16, 2012)

14% of the nation's land mass is contained within the Murray Darling Bain and it contributes just under 40% of Australia's agricultural income. In 2009 water usage in the Basin amounted to just over 13,600 gigalitres, which is just about the equivalent of 25 Sydney Harbours full.

The tentative proposal put forward for consultation by  the Murray-Darling Basin Authority is for a reduction to 10,873 gigalitres per annum by 2019.

Perhaps unsurprisingly this has met with disapproval by both environmentalists (the reduction is too little) and the regions agriculturalists (it's too much).

Dated March 28 2012 CSIRO issued Assessment of the ecological and economic benefits of environmental water in the Murray–Darling Basin: The final report to the Murray–Darling Basin Authority from the CSIRO Multiple Benefits of the Basin Plan Project; its 250 page evaluation was produced by a committee chaired by geographer Ian Prossor, CSIRO Science Director, Water for a Healthy Country Flagship.

Dr Prosser together with specialists which included economics, hydrology, environmental studies came to the conclusion that direct economic benefits derived from the plan would total somewhere between $3 billion to $8 billion.

However, Dr Prosser noted in talking with Nature's Stephen Pincock that "the real value is certain to be significantly higher, because not all environmental benefits could be given a monetary value".

He also said that he felt that to date unfortunately the information about "benefits would be to the environment" was little discussed. In his view "It was lopsided [in fact] "We found that there would be substantial ecological benefits... [Nevertheless] We found that [a reduction of] 2,800 gigalitres a year does not meet all environmental targets".

Taking issue with the report Tom Chesson, Australia's National Irrigators Council’s chief executive, told Australia’s ABC News: "Basically the authors themselves have admitted that the methodology and actually coming up with a figure for cost–benefit of the environment is next to impossible."

Which brought a sharp rejoinder from Ian Prosser that although putting a monetary value on the benefits was a complex job it was possible and in fact: "We made sure it was a dispassionate analysis, so we have probably underestimated the benefits. There are equal uncertainties in the costs."

As Mr Pincock reports: "The draft plan will now be submitted to the Australian government's legislative forum on the Murray–Darling Basin, which is made up of federal and state ministers. Subject to their response, it will go to the federal environment minister for approval. Only when he is satisfied will the plan be presented to Parliament. The plan is scheduled for full implementation in 2019.

Below is the report's summary of the "Major Conclusion: economic benefits of flow".