Rain Producing Influences in South Australia. 99* 



been partly due to the filling of the rarely filled lake system along 

 the Darling. 



1 895- 1904. Drought was predominant during this decade,, 

 and tropical influences on the whole ineffective. The very severe 

 three years' drought which began in July, 1895, ^lust have dried 

 up the moisture in the lake beds, and there was no appreciable 

 run-off to renew it until 1903. This being so, we should look 

 for the area partially dependent upon the lakes for its rainfall 

 to show the greatest deficiencies during this period. This is 

 shown very well, the minus isopleths for this decade showing 

 much the same contouring as the plus for 1910-1919. This 

 reversal is even shown along the southern and south-eastern 

 borders of the Mallee, which is at it ought to be, the Mallee still 

 being largely wilderness or unimproved. 



1905-1914. This being a transition period, both for agricul- 

 tural development and lake storage, its isopleths do not stand 

 out as those for 1910-1919, but similar tendencies are strikingly 

 shown. The agricultural progress of Eyre Peninsula is 

 apparently reflected in rising rainfall to south-east of the areas, 

 that is, on the foot of Yorke Peninsula and the eastern end of 

 Kangaroo Island ; the Western Wimmera is gaining by the clear-^ 

 ing and cultivation of the South Australian Mallee across the 

 border ; and the rainfall from Wentworth to Lake Torrens is 

 distinctly on the up grade. 



It supplies, moreover, another exceedingly neat proof of the 

 effectiveness of the floodings from the Murray River system in: 

 increasing the rainfall on the river flats, the rainfall isopleths over 

 the Riverina and northern Victoria, which were minus, giving an 

 almost exact copy of those for the wet decade, 1885-1894, which 

 of course were plus. 



All three decades thus bring their evidence to support in 

 various ways the theory that the rainfall is largely affected by 

 local influences. The coincidences in areas affected are very 

 striking. 



Another point made clear is that the decennial rainfall oscilla- 

 tions are far greater east from the South AustraHan lake system 

 than west of it, which is itself fairly strong evidence that the 

 variation in the lake supplies is a large disturbing factor. The 

 figures also suggest for inland New South Wales a rainfall 

 dependence upon previous downpours in Queensland, and 

 especially those tending to fill Lake Eyre. 



