Rain Producing Influences in South Australia. 98 



Ihat these factors are operating in connection with the lakes of 

 -South AustraUa. 



Mr. W. E. Abbott, of Wingen, New South Wales, in various 

 papers read before the Royal Society of New South Wales, has 

 given many emphatic proofs of the effects of ring-barking in 

 increasing the flow from springs, and making permanent the 

 flow of streams previously only intermittent. 



The Willochra Creek. 



The chief source of water supply for Lake Torrens seems to 

 be the Willochra Creek, which drains a belt of country extending 

 south as far as Booleroo, and north as far as Hawker, two 

 stations about 70 miles apart. The area of this can hardly be 

 less than 2000 square miles. It is, of course, rather a dry area, 

 the average annual rainfall ranging from 12 inches at Hawker, 

 to 16 inches about Booleroo, but is liable to have quite a wet 

 •climate for months at a time. For instance, at Booleroo periods 

 of six months' duration in 1916 and 191 7 gave ly^ and 15 

 inches respectively; 5 months gave 12 inches in 1920, and 13 

 inches in 1921 ; 4 months in 1909 gave 13 inches ; 3 months gave, 

 in 1889, 12^ inches; in 1893, 11.6 inches; in 1908, 10 inches, 

 and so on. Hawker has similar records : 14 inches in 3 months 

 in 1889; 13 inches in 4 months in 1892; 15.2 inches in 5 months 

 in 1916; 13.3 inches in 4 months in 191 7; 20.4 inches in 6 

 months in 1920; and 14 inches in the first 5 months of 1921. 

 These are quite sufficient to turn the creek into a very con- 

 siderable river during these periods. 



"Run-off" Rains. 



Failing actual data, 1 ventured on an estimate of the variations 

 in the water supply of Lake Torrens, based upon the probable 

 run-off from the Willochra Creek basin, using the rain stations 

 Booleroo, Quorn and Hawker. This required some assumptions 

 of a very general character. The basin being well drained, I 

 adopted as "run-off" falls in winter, anything over 2 inches for 

 the first month, and irj for each consecutive month following, 

 and in summer 3 inches for the first month, and 2 inches for 

 each following month. This probably errs on the side of 

 moderation, for falls of 2 or 3 inches are not uncommon in one 

 day, but at all events it provides a fairly definite scale by which 

 to compare the periods. The first really wet period was from 



