2o6 Journal of Agriculture. [8 April, 1907 



DRAINAGE AND IRRIGATION.* 



A. S. Kcuyon, C.E., Engineer for Agriculture. 



Cultivation without irrigation has been stated to be preferable to irri- 

 gation without cultivation, and there is no doubt that there is a great 

 deal of truth in such a statement. In our State, caireful and progressive 

 farmers have raised larger and better quality crops than others have 

 achieved with the same rainfall, and with the aid of irrigation water in 

 addition. Much of the improved result was, no doubt, due to better 

 cultivation methods ; but these improved methods also meant, to a slight 

 extent, drainage. The American teachers tell us that irrigation and drain- 

 age, or raither drainage and irrigation, are inseparable, drainage being the 

 more important. Our experience, now that we have had some years of 

 irrigation, is leading to the same conclusion. At Mildura, where irriga- 

 tion on a large scale and to an extent replacing rather than supplementing 

 the annual rainfall, was first put in operation, the early years did not 

 teach the lesson, owing to the fact that, with other mistakes apparently 

 unavoidable in the foundation of new occupations and hioustries, the 

 varieties and classes of trees planted were not generally suitable either 

 for the natural conditions or to give profitable returns. Seepage, of 

 course, both black and white, early made its appearance; trees died out 

 in the immediately affected parts, and general consternation ensued. 

 Blame was, however, imputed to the leakage from the channels only, and 

 not to the lack of drainage. Naturally, of cour.se, the first evidences of 

 over-saturation of the soil occurred near the channels, while the dying- 

 off of trees in soils not giving surface indications of seepage, was ascribed 

 to all sorts of other causes. Now^ that all the early inferior trees have 

 been got rid of, and the limits of direct seepage from the channels ascer- 

 tained, much more definite knowledge of the effects of over-watering is 

 a\ailable, and a considerable amount of attentioai is being paid to the 

 drainage problem. Shafts have been sunk through the surface sands, 

 loams, and clays into beds of drift, and drains of various kinds led into 

 them. These are only partially effective, and there is evinced a decided 

 tendency to instal complete systems of tile or agricultural pipe drains, 

 absolutely on the lines of old-world methods. The value of full-bearing, 

 well-selected orchards in Mildura now reaches to over ;^ioo per acre, so 

 that the comparatively heavy initial outlay is not so severelv felt. 



The spectacle, however, of a country like the Mallee frontage to the 

 Afurray River, at INlildura, requiring sub-soil pipe drainage is sufficiently 

 startling, and must inevitablv give much food for thought to those en- 

 gaged in either carrying on or advocating irrigation in our arid areas. 

 Mildura has, like all the Mallee areas, soils ranging from almost pure 

 sand to sandy clay, with beds comparatively near the surface of pure drift 

 sand. The sub-soil is frequently almost pure rubbly limestone (so-called) 

 — being generally the sulphate and rarelv the carbonate form of lime — 

 while in all case's lime in its various compounds is largely present. The 

 •'' water table," save in beds of lagoons or swamps — where water collects 

 in the rainv seasons — is generally at depths of 80 feet or over. The rain- 

 fall is on the average about 12 inches per annum only. The contra is 

 necessarily the volumes of water used in irrigating. These are large, 



* A paper read before the Adelaide Meeting of the Australasian Association for the Advancement of 

 Science, January, 1907. 



