Yesterday a Murrumbidgee food producer, Virginia Tropeano, had a letter printed in the local Murrumbidgee ‘Area News’ explaining that in an average rainfall year it take 5,000 gigalitres of water to keep the Lower Lakes artificially fresh.
Because of the sea dykes across the bottom of the Lower Lakes, they are totally dependent on water from upstream. In drought years this makes the Lower Lakes completely dependent on water in upstream storages. The only really large and reliable storages in drought years are in the upper Murray and Murrumbidgee catchments because they are the only snow fed catchments.
The Premier of South Australia, Jay Weatherill, wants 4,000 gigalitres more freshwater each year for South Australia as guaranteed supply. Because the Lower Lakes are Ramsar listed and because of the way the Water Act has been written, he is likely to get this water even if he has to take the Murray Darling Basin Authority to the High Court.
I think that in a good year, the most water that is ever allocated for food production in the Murrumbidgee is 2,500 gigalitres. Can someone verify this figure for me? Assuming I’m about right, Mr Weatherill wants all of this water and more.
If you have continued to read this far, and you are not an irrigator, you are probably getting bored with my use of these meaningless figures of thousands of gigalitres. So help me make this a more interesting story.
How much food can 2,500 gigalitres produce?
Farmers in the Murrumbidgee use about this volume of water to produce food.
What types of foods do they produce and how could the total volume, or caloric equivalent, be described in a meaningful way.
For example, can someone let me know for how many weeks or months the population of Australia could survive on food produced from 2,500 gigalitres of water?
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.