The dry bores appear to be aggregated in certain areas. These areas now form a break in the continuity of the aquifer.
The aquifers have been penetrated by a very large number of waterbores, which complicates the task of long term protection of the resource. Some 4700 artesian bores have been drilled, and 3100 of these remain flowing.
There is a wide body of historical evidence showing the continued decline of the available yield from the aquifer.
In a paper in 1969, the declining yield in the NSW section of the Basin, up until that time, was reported. The data is transcribed in the table below.
Peak Aggregate Flow From Bores in NSW
||Output in million gallons per day
||Total number of bores
||Number of flowing bores |
From Journal IEAust.,March, 1969, page 37.
The table shows the way the annual output decreased markedly from 1910 while the number of bores increased. It is of interest to note the comments that accompanied the presentation of the above data in that 1969 paper. "The reduction of flows quoted above should not be construed, as it was in the early1900's, as indicating a limited life to this resource. It is largely a function of the hydraulics of bores in confined aquifers, the theory of which was not adequate until 1935."
With such reassurance, based on a fundamental misconception of the characteristics of the aquifers, and similar reassurances over the years, the disastrous waste of water has continued to this day.
It is stated in the web page, "Great Artesian Basin Facts", that the estimated total water storage is 8,700 million megalitres. I am not aware how that figure was assessed, but it is clearly in error. It is equivalent to a uniform depth of water of 5 metres in thickness over the entire area of the Basin. It may be an estimate of all of the captive water in all of the saturated sandstones, which is something radically different to the potentially recoverable water in the joints and fissures in the aquifers.
The total volume of water taken from the Basin in the past 100 years is about 50 million megalitres. That is equivalent to 100 times the volume of Sydney Harbour (0.5 million megalitres). With waste of water at 80 percent and more, the waste of water to date has been equal to more than 80 times the volume of Sydney Harbour.
In the light of the evidence of declining pressures and declining yields, it is quite likely that the remaining volume of accessible water may be substantially less than the yield to date, certainly less than half, say 20 million megalitres or much lower.
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