Posted by Big Gav in coal seam gas
Larvatus prodeo has a look at the impact of the coal seam gas boom in Queensland on farmers and aquifer levels - Coal seam gas prospects: economic bonanza or future industrial wasteland?.
Coal Seam Gas (CSG) (together with open cut coal mining) is “the single biggest environmental issue in Queensland’s history”. Mining threatens to turn the Darling Downs, one of Australia’s prime food bowls, into an “industrial wasteland”.
Thus spake Drew Hutton, a senior figure in The Greens in Queensland, who grew up in Chinchilla and who is resigning all his positions with The Greens to devote himself to working with some 20 groups in the area on the Downs and in the Surat Basin that are fighting mining projects. He has just completed a 1000km study tour of the region which extends from Toowoomba to west of Roma.
Some of the statistics are mind boggling.
Hutton told Steve Austin on local ABC radio that the area of concern was from Toowoomba to west of Roma. That’s about 400km, the distance from Sydney to Cooma, or half the distance between Melbourne and Adelaide. In this area there is going to be about $100 billion worth of mining investment in coming years. A minimum of 40,000 gas wells will be drilled in the area. But the number could be 100,000 or “almost anything”.
CSG extraction (image and even simpler explanation here) involves bringing water to the surface. Hutton says that miners expect to extract 10 million megalitres of water from the coal seams, much of which is salty and will be left to evaporate in ponds constructed on the plains.
Correct me if I’m wrong, but I think that’s 10,000 gigalitres, or if you like 20 Sydharbs, a Sydharb being 500 gigalitres or 400,000 acre-feet or the volume of water in Sydney Harbour.
From what I can make out there are two types of aquifer – alluvial and sandstone. The Landline program Pipe Dreams (video there now, transcript here) said the the coal seams were mostly 300-600 metres down. The alluvial aquifers would be shallower, but so also should be the sandstone aquifers of the Great Artesian Basin, since the sandstone was laid down more recently than the Carboniferous period (see here and the cutaway profile in Fgure 6.1 here).
In any case experience has already shown that the act of drilling can reduce or drain the levels of the aquifers accessed by farms. Obviously the process of production will do so even more. Presumably Part 2 of the Landline program will make all this clear.
The importance of underground water cannot be overstressed. Many farms rely entirely on underground water. It is said that 22 of 23 towns in the area use the aquifers for town water supply. This reference gives the allocations at 96,720 Ml/yr as against a sustainable yield of 71,960 Ml/yr (water allocations are being revised downwards). The figure going around is that CSG operators plan to extract up to 350,000 megalitres a year.
Obviously there are grounds to worry about the impact of CSG extraction not just on individual farms but on the viability of the whole aquifer system as a resource.