199 



by the courtesy of the Commonwealth Meteorologist (Mr. H. 

 A. Hunt), and further efforts have been made to discover 

 the exact relationship that exists between the rainfall and 

 the variation in the lake levels. The rainfall records of 

 County Lowan (Vict.) are specially considered, because that 

 area has been shown (by A. S. Kenyon, loc. cit.J to be the 

 main gathering ground for the underground supplies of this 

 portion of the Murray Gulf sub-artesian basin. 



It has been pointed out by the Government Geologist 

 (Mr. L. Keith Ward), in his Annual Report for 1915, that the 

 underground water in south-eastern South Australia, although 

 generally accepted as forming portion of the "Murray Gulf 

 sub-artesian basin," is really of a dual character: — 



(a) Sub-artesian water which is under greater pressure 



than that of the atmosphere, and which has 

 travelled for some distance through the porous 

 beds in which it is contained. 



(b) Ground water derived from the downward percol- 



ation of the rainfall, occupying the pores, joints, 

 etc., in the limestones, and being under atmos- 

 pheric pressure only. 



Observations made by the writer confirm the belief that 

 the water underlying the Mount Gambier region mainly par- 

 takes of the nature of ground water, but is influenced by the 

 annual increment of water received under pressure from the 

 regions to the north and north-east. 



For the purpose of discovering, if possible, the relation- 

 ship between the rainfall and the variation in lake levels, 

 consideration must be given to the following figures, which 

 cover the last 26 years : — 



A. The annual December levels of the Blue Lake, 



measured from a datum line selected by the 

 Hydraulic Engineer's Department. 



B. The annual rainfall of the south-eastern counties of 



South Australia, as published in the Statistical 

 Register of that State. 



C. The rainfall of County Lowan, in Victoria, as sup- 



plied by the Commonwealth Meteorologist. 



A. B. C. 



Ft. In. In. In. 



1895 



... 25 



10 



22-03 



• 17-47 



1896 



... 25 



11 



18-74 



1527 



1897 



... 24 



H 



1755 



13-85 



1898 



... 22 



n 



21-29 



1803 



1899 



... 21 



n 



1982 



16-27 



