Great Artesian Basin
GREAT ARTESIAN BASIN RECHARGE ASSUMPTIONS UNDER CHALLENGE
A series of papers from Emeritus professor Lance Endersbee has begun a debate on the model of the great artesian basin.
For many years landholders who live near and on the supposed recharge area of the Great Artesian Basin have questioned the accuracy of government department claims that the area mapped as such could really provide the recharge of the Great Artesian Basin. The supposed "recharge area" is a narrow strip of sandyish soil which has mainly yellow jack trees and associated vegetation on it. It runs up the eastern side of the G.A.B. There are older Government maps which have the recharge area drawn in other areas, so it has always been a theoretical idea.
There is a lot of evidence that would refute the "yellow jack country" of the Desert Uplands as being the recharge area of the G.A.B. It`s an issue that concerns a number of people because Sub-ordinate legislation (Water Management Plan for the Cooper Creek catchment) was quietly passed on 10/2/2000 by the Qld Govt (without the Longreach DNR or the public knowing about it for a month).The sub-ordinate legislation declared that a strip of country (the Yellow Jack area) is the recharge of the G.A.B. There was even a map put into the plan that defined the area concerned. The plan decided (against local opinion) there would be no guarantee that bores even for stock and domestic purposes would be approved in future - no reasons were given. Plenty of people wrote objections to the plan but all were ignored. (the standard consultation process it seems)
However there have always been some reasons that local landholders and bore drillers believe recharge is not occurring in the Desert Uplands.
These are some that I am aware of.
(1) In the Desert Uplands, the rock strata lays horizontal, not vertical as the government model suggests it should .
(2) There is only a little water above the first layer of rock which would indicate only minimal rainfall infiltration occurs in the sandy "Yellow Jack Country" anyway.
(3) The "supposed recharge" sandy soil has several hard rock and associated tight clay layers in it below the first rock layer and above the "best" water bearing aquifer.
(4) There are several water bearing aquifers above the "best" and main aquifer. (sometimes they have internal pressure, sometimes not)
(5) The water often rises 10 metres or more when the "best" aquifer is hit. (It`s a confined aquifer with pressure in it so how does rain water get in? The pressure can not be caused by water pressure because of points (6) and (7) below).
(6) There are large differences in the altitude levels of the standing level of the water in the "supposed recharge area" bores. i.e. ranging from approx 550 to 950 feet above sea level (altitude of the land, less the depth of the bore to water) For example. If the land altitude is 950 feet above sea level, and the bore water is at 400 feet depth, the bore water altitude is at 550 feet above sea level.
(7) The top of several flowing bores north of the supposed recharge area, are higher in altitude (Approx 1100 feet above sea level) compared with the standing bore water in the supposed recharge area. (Approx 550 - 950 feet above sea level)
(8) Several years ago, an Oil drilling company drilled a test bore down to 1000 metres in the recharge area and water flowed out . In that location water level in all the windmill bores are 150 - 170 metres below the surface.
So to summarise, the Queensland government has legislated that in the narrow strip of "yellow jack country" in the Desert Uplands, the rain infiltration goes though several layers of rock and associated clay and then under a sealed layer so that it builds up substantial pressure to cause 3000 bores to flow hundreds of kilometres away and sometimes higher in altitude to where water supposedly enters the aquifer.
Emeritus Professor Lance Endersbee (Melbourne) gives several technical explanations of why he believes there is no apparent recharge areas and that the G.A.B. is probably a limited resource. (Click here to go to research and articles and read Prof. Endersbee's papers).
Comments by Leon Ashby (whose property "Barcoorah" is a few kms from the "supposed recharge" area)