Modifying Climate. 123" 



to south-east and south from these should show some benefit from 

 them, at all events during the chief growing season. 



In dealing with the effects of sheets of water upon our own 

 climate I have already shown the benefits derived by parts of 

 South Australia from the Spencer Gulf, even as far north as 

 Port Augusta, and especially around Germein Bay, from a sheet 

 of water twenty miles across. Not many of our storages would 

 compare in area even with this body of water, but it has to be 

 remembered that the surface of the reservoir is multiplied many 

 times by any effective scheme of irrigation. For example, the 

 Burrinjuck reservoir has an area of only 20 square miles, but 

 will hold at any one moment water enough to irrigate to a depth 

 of one foot 771,000 acres, or 1200 square miles. If such an 

 area as that could be irrigated, the evaporation resulting would 

 be such as to have a most important effect not only upon the 

 rainfall of the adjacent areas, but upon the precipitation over 

 the area feeding the reservoir itself. 



So far, only some 40,000 acres are occupied for the purpose 

 for which this storage was made, but in Victoria in 1916 a total 

 of 288,000 acres were under irrigated culture. When the 

 1,000,000 acre foot storages on the Upper Murray and the Sugar 

 Loaf scheme on the Goulburn are added to the Burrinjuck, 

 and the various other storages completed or projected, the area 

 can be vastly increased. 



Data from stations bordering on or within the irrigation areas 

 give some indications of rainfall effects, but these are necessarily 

 indefinite. The uncertainties as to the distribution of the areas, 

 under irrigation, the crops irrigated, whether of grass, wheat,, 

 lucerne, etc., and the variation in effect owing to differences in 

 the character of the seasons, etc., make only very approximate 

 estimates possible. Before 1891, when the Goulburn Weir was. 

 constructed the area of land irrigated must have been infinitesi- 

 mal, and up till 1895, owing to abundant rains, there was little- 

 need for irrigation. The county of Rodney was the most fav- 

 ourably situated to make use of the Goulburn supplies, but this 

 was not completely reticulated till 1904, by which time the War- 

 anga basin was under construction. In 1904-5 the total area 

 irrigated was 166,000 acres. Of this Rodney had 40,000, Tra- 

 gowel 29,000; Cohuna 29,000, Macorna 11,000, Swan Hill 10,000,. 

 Wardilla 9000, etc. This rapid development was owing to the 

 series of drought years which culminated in 1902. By 1906-7 the 

 area was less, rose to 232,000 in 1907-8, another drought year, 



