Senate committee felt that the uncertainties were such that no further production approvals should be given pending the completion of the Queensland Water Commission’s Surat Basin groundwater model and the CSIRO and Geoscience Australia basin scale investigations of water resources (Recommendation 3, para 2.58). However, a serious question has been raised as to whether risk can in fact be reduced to acceptable levels at a farm level.... Let’s have a closer look at this “wicked” problem. We are perhaps all familiar with the cutaway images such as the one on the ABC CSG site of neat sedimentary layers like a sponge cake, which clearly distinguish, for example, the coal seams and the aquifers of the Great Artesian Basin (GAB). Hydrogeologist John Polglase here and here tells us that these diagrams are drawn to show simple concepts, and are not a reflection of the reality beneath our feet. What we have today is the result of physical and chemical processes over many millions of years, with much lifting, folding, faulting and interpenetration of major geological systems. Interestingly, the Senate report (para 2.11) tells us that the GAB was formed from sediments deposited 65 million to 250 million years ago. This site tells us that the Surat Basin coal deposits were formed through six sedimentary cycles over the Jurassic/Cretaceous periods, roughly the same time frame. What we have is a complex dynamic rock/fluid/gas system which is always changing. Polglase describes it thus: Below ground, water and gas are constantly moving through fractures and fissures in the sedimentary rocks, at various rates under varying pressures. The rocks are also moving—continuously or abruptly—as nature balances and rebalances the stresses and strains according to the laws of physics.
Posted on: Sun, 07 Jul 2013 01:34:30 +0000
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