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September 1, 2009
Finally, some sense on the causes of a warmer south eastern Australia that has seen the annual inflow of one of Australia’s largest river basins drop nearly 80% in the seven years. The hotter drier conditions here have usually been put down to a big drought, with the implication that the drought will break and things will return to normal. 'Normal' in this context means the wetter conditions of the 1950s-1970s.
This is the position of most of the loud irrigator groups along the River Murray. They argue that the federal government needs to modernize the irrigation infrastructure, especially in Victoria (the Foodbowl Modernisation Project) since wetter times will return. The rains will comeback is the position of both the Coalition, who are opposed to the buy back of over-allocated water licences, and it, would appear, the Murray Darling Basin Authority.
Gary Sauer-Thompson, Clayton, Lake Alexandrina,South Australia, 2008
The South Eastern Australian Climate Initiative was set up in 2006 to find the causes for why south-east Australia had experienced a dramatic loss of rain. The crucial question is the why (drought or climate change?) and, secondly, how the drier conditions in the Murray-Darling Basin will affect stream and river flows in the Basin.
My understanding was that the loss of rain, and the weather patterns in southern Australia shifting to a dry phase was simply due to the rain-bearing storms shifting south off the continent. I had assumed that while the precise role of cyclical changes versus the impact of greenhouse gases remained unclear, changes in the basin are consistent with CSIRO computer modelling of the impacts of increased concentrations of greenhouse gas in the atmosphere.
Melissa Fyfe reports in The Age that scientists working on the research programme have discovered that the 13-year even of hotter drier conditions is not just a natural dry stretch--a drought--- but is a shift related to climate change.
They found that the rain has dropped away because the subtropical ridge - a band of high pressure systems that sits over the country's south - has strengthened over the past 13 years. These dry, high pressure systems have become stronger, bigger and more frequent and this intensification over the past century is closely linked to rising global temperatures.
The Wenthworth Group in their submission to the Senate Inquiry into the Coorong and Lower Lakes stated that we must reduce our extractions of water to:
(1) correct our over-allocation during a period of plenty, (2) to be more sustainable under climate cycles we have experienced in the past and (3) to adjust to declining water availability under climate change.....If we are to maintain healthy rivers and provide high quality water to produce food, our analysis suggests that the consumptive use of water across the Murray Darling Basin may have to be cut by between 42 and 53 percent below the current cap. This will require a re-design of our irrigation industries to bring the demand for water into alignment with the greatly reduced supply capacity from the rivers and groundwater.
If the likely future is one of reduced river flows, then the policy pathway for the Commonwealth is to acquire 300 to 400 GL of river flows into Lake Alexandrina and Lake Albert, to secure a sufficient reserve to maintain lake levels to avoid any significant release of acids this coming summer and autumn. I cannot see that happening myself.
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I am surprised by Fyfe's report that Rob Freeman, the Murray-Darling Basin Authority chief, told a water summit in Melbourne in August that he believed the extreme climate patterns that have dried out south-east Australia would not prove to be permanent:
Apparently, Freeman expressed confidence that wetter times would return.I am surprised because the Murray Darling Basin Authority helps to fund the research of the South Eastern Australian Climate Initiative (SEACI). So they would have access to the results of the on going research programme.
Freeman, in ignoring the science and calling it extreme, is an ideologist. he should know better since he was the chief executive of the South Australian Department of Water, Land and Biodiversity Conservation and the deputy president of the Murray-Darling Basin Commission.