DUTY AND DIVISION OF WATER 345 



duties were calculated from the measurements taken at 

 the heads of the laterals and are smaller than would be 

 the case were measurements made at the farms them- 

 selves. During these years of increasing duty, crop- 

 yields were equally good, and crop quality was improved. 

 The increasing duty of water under this system is still 

 going on, with the result that farming conditions are 

 being greatly improved. This is the history of all the 

 larger canals in America that have received competent 

 and constant supervision. The duty of water is steadily 

 increasing throughout the whole of western America. 



207. Idaho results. A series of recent investigations 

 in Idaho further brings out the present duty of water in 

 w r estern America. Bark measured the quantities of water 

 used by 168 Idaho farmers. Most of these farmers had 

 been farming only a few years, and since the duty of 

 water is always lowest at the beginning of irrigation prac- 

 tice, the measurements represent maximum use. The 

 irrigation season for grain varied from thirty-six to forty- 

 six days, and for alfalfa from ninety-six to one hundred 

 and twenty-two days. It was found that the crops re- 

 ceived on an average practically 2 feet, or 24 inches of 

 water, which, for an irrigation season of four months, would 

 be equivalent to about 120 acres to the second-foot of water. 

 Where water was plentiful, much was used; where water 

 was scarce, little was used. Moreover, it was found that 

 the entire need for water fell on the four months, May to 

 August inclusive. It is likely that for all ordinary crops 

 the irrigation season seldom exceeds four months and in 

 many cases is covered by two months. 



208. Miscellaneous results. H. M. Wilson, a high 

 authority on irrigation matters, presents the following as 

 the duty of water for 1 second-foot of water: In western 



