DUTY AND DIVISION OF WATER 343 



special districts. It is not likely that any unusually high 

 duty of water prevails in South America. 



204. Duty of water in Australia. Irrigation on a large 

 scale is just beginning to be developed in Australia. The 

 methods there adopted are based upon the best practices 

 of the world, notably upon those of the United States. 

 The duty of water, as it is developed in Australia, does 

 not differ materially from that of North America. Many 

 of the projects are comparatively new and the duty is 

 low, but will become higher as more complete irrigation 

 practices are adopted. 



205. Duty of water in North America. The chief 

 irrigated section of North America covers western Canada 

 and the western United States. These two districts are 

 so similar in climatic and soil conditions that whatever 

 is true of one is generally true of the other. Some excellent 

 duty of water experiments have been made for this section, 

 by the United States Department of Agriculture under 

 the direction first of Elwood Mead and later of Samuel 

 Fortier. The gross duty of water was determined for 

 a number of representative canals in all of the western 

 states. As a general result, Teele declares that "It appears 

 that 3^ to 4 acre-feet are required at the heads of unlined 

 earth canals. This can be taken safely as a basis for 

 computation." This means that the duty of water for 

 1 second-foot, flowing for 60 days, varies from 34 to 

 27 acres; flowing for 120 days, from 68 to 54 acres, 

 and flowing for 180 days, from 102 to 80 acres. This gross 

 duty for western North America does not represent, even 

 approximately, the net duty of water, for the irrigation 

 investigations of the United States Department of Agri- 

 culture have shown for a series of representative canals 

 that nearly 60 per cent of the water is lost between the 



