PROBLEM OF THE GREAT AUSTRALIAN ARTESIAN BASIN. 20 £ 



G. N. Griffiths — at the first-named in great numbers — must 

 be correlated with a reduction of potential in the south- 

 west. This could have been due either to too great a leak- 

 age, or perhaps to a diminution of effective area brought 

 about by the headward erosion and to the lowering of the 

 water-shed, as discussed earlier, or probably with much 

 greater likelihood to the lesser rainfall following upon the 

 period of Pleistocene glaciation, or all these causes may 

 have acted in combination. 



If this be correct, then the conclusion seems inevitable 

 that the Basinlhas passed maturity and is noiu in decline. 



Some support is also afforded by the observation that the 

 Einasleigh Hot Springs near'Ohillagoe appear to be drying 

 up, as many of the basins are empty and much of the cal- 

 careous sinter is crumbling away. 



In view of the great drain being made by the existing 

 bores, estimated at between 600 and 700 million gallons 

 per day, it remains to be seen whether there will come 

 about a corresponding reduction in the output of the mound 

 springs; that some of them have already been affected is 

 indeed indicated by the reported diminution in flow of those 

 at Saxby Downs in Queensland (II, § 2801). 



When to this is added the disquieting fact that the yield 

 of the bores, is as a whole, falling off at the rate of perhaps 

 as much as 6 or 7% annually, the fear arises lest the 

 reduction in flow be due not merely to the temporary 

 readjustment towards equilibrium, but to an actual over- 

 draft upon the existing resources of the Basin. One can 

 hardly accept Jack's opinion that in view of the vast sub- 

 marine leakage, the withdrawal by bores is infinitesimal in 

 comparison, with the inference that no control or restriction 

 would be necessary. 



There is great need therefore, until such time as sufficient 

 evidence be forthcoming to decide this question, to legislate 



