130 E. T. Quayle: 



(5) Improved Rainfall of last Ten Years only marked 



in connection with Irrigation Districts and Mallee 



Improvements. 



The foregoing considerations suggested another test. The de- 

 cade (1910-9) being one of considerable progress in clearing and 

 cropping of the Mallee, and especially in irrigation and water stor- 

 age in the Kerang-Swan Hill areas, the districts immediately in 

 lee of these should show some improvement in their annual rain- 

 fall. To show this it was obviously necessary to base all rainfall 

 comparisons upon a common period. The best seemed to be the 

 30-year period, beginning with 1885. This, for Victoria, gave 

 me a little more than 200 stations, for each of which I compared 

 the average annual rainfall of the last ten years with that for 

 the standard 30-year period. The percentage departures from 

 this normal were plotted on a map. The results were very 

 striking. For almost all south of the Divide, the whole of the 

 Wimmera, except the river drainages, and for the two Mallee 

 .stations east of Lake Tyrrell, the last ten years were slightly 

 ■drier than the normal, and the same was the case with a few 

 scactered stations in the Central North. Over the north-east 

 and northern slopes generally there was an appreciable rise, 

 averaging about 4 per cent. But there was one area showing a 

 very marked rise. From Swan Hill, along the Murray to Cohuna, 

 the plus departures ranged from 12 to 15 per cent., and thence 

 southwards to Korong Vale they exceeded 10 per cent. The 

 area showing these increases exceeds 2000 square miles. But this 

 is not all. It is continued westwards in a narrow strip hugging 

 the southern fringe of the newer Mallee clearings as far ap- 

 parently as Lake Hindmarsh. The increase over this area ap- 

 proximates to 10 per cent. The larger increase may be assumed 

 due to the combined effect of irrigation and Mallee improve- 

 ments — the smaller to the latter only. It would, therefore, appear 

 that the complete development of Mallee occupation will bring 

 in a rainfall approximating to that of the lower Goulburn valley, 

 and that irrigation will further increase this result. 



On the accompanying map, kindly drawn by Mr. Curtin, the 

 data just referred to are plotted. The numbers indicate per- 

 centage departures of the mean of the last ten years' rainfall 

 (1910-1919), from that of the 30-year period, 1885-1914. The 

 areas where the plus departures exceed 5 or 10 per cent, are 



