THE Murray-Darling Basin Plan can’t deliver anything tangible and meaningful for communities, industry or the environment while its water sharing plans are based on averages.
Averages are a meaningless concept in the real world given the highly variable nature of Australian rainfall. The draft plan identifies 10,873 gigalitres as the maximum amount of water on water that can be “sustainably” extracted from the Basin on average each year.
But this number is a product of politics, not science, and has no real meaning in terms of river health.
The draft plan acknowledges the highly variable nature of the system – Schedule 1 explains annual inflows to the Basin in the past 114 years have ranged from a high of 117,907GL in 1956 to only 6740 GL in 2006 – and notes this natural variability of flows is important to Basin ecology.
Yet this variability is then ignored in arriving at one number: the sustainable diversion limit of 10,873GL based on a calculated average inflow to the entire Murray Darling Basin of 31,599GL.
The draft plan gives the impression there has been gross over-allocation of this average inflow by claiming on average only about 12,000GL reaches the Murray Mouth – hinting that much more water should flow out the Murray ‘s Mouth to the sea.
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Jennifer Marohasy BSc PhD has worked in industry and government. She is currently researching a novel technique for long-range weather forecasting funded by the B. Macfie Family Foundation.