Art. II. — Quantity of Water Consumed in Irrigation. 

 By W. W. Culcheth, M. Inst. C. E. 



[Kead 20th April, 1882.] 



I. — Introductory Remarks. 



1. In a country like Australia, where so little in the way of 

 irrigation has been accomplished, the experience of other 

 countries must be depended on. The author at first in- 

 tended giving the results of his own experience and obser- 

 vations (extending over a period of more than twenty 

 years) on irrigation generally in India, thinking the infor- 

 mation would be useful to many at the present time ; but 

 the limits prescribed for this paper would not permit of much 

 more than one branch of the subject — the quantity of water 

 required for irrigation — being treated in sufficient detail to 

 be really of any practical use. 



2. The quantity of water required for irrigation is a most 

 important point in connection with the probable success of 

 any proposed scheme; nevertheless, opinions of engineers 

 are much divided on the subject. Numerous experiments 

 and measurements of water actually consumed have been 

 made, often giving under various forms widely differing 

 results. In many cases, however, the differences are more 

 apparent than real, being in the conditions of the cases 

 rather than in the results themselves. Shortly before 

 leaving India, the author made several notes from the 

 official report (the latest he has seen) on the irrigation of 

 the North-western Provinces (India) for the year 1875-76. 

 At the time, the author had not arrived at the conclusions 

 about to be noticed, hence there will appear an incompleteness 

 of information on certain points, which cannot at present 

 be remedied. From these and other notes, some useful 

 results may be deduced, which the author will endeavour to 

 give in a convenient form for use in Australia. 



3. It is sometimes assumed that because a given supply 

 of water, has been made to irrigate so many acres, or, 

 expressed in the usual way, because a " duty " of so many 

 acres per cubic foot per second of canal discharge has been 



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