DUTY AND DIVISION OF WATER 



337 



of highest profitableness or optimum duty. A beet field 

 is supplying beets to the factory at a contract price of 

 So a ton. The total cost of producing the beets, includ- 

 ing interest on the investment, may be assumed to be $60 

 an acre. The following table may then be constructed on 

 the basis of the crop yields in the Utah experiments on 

 the effect of varying quantities of water on the growth of 

 crops: 



Under the above conditions, the largest net income, 

 SI 00, was obtained when 30 acre-niches were spread over 

 3 acres. When spread over less or more land than this 

 the net income decreased. Similar results must be deter-* 

 mined for all of the standard crops, so that for any set of 

 conditions the most profitable depth of water may be 

 known. 



In different sections of the irrigated regions, 1 second- 

 foot of water serves from 25 to over 300 acres, with an 

 average near 75 to 100 acres. This great variation is 

 partly due to the differences in rainfall. Wherever the 

 rainfall is high, less irrigation water is required to mature 

 crops. This is not the main cause of the varying duty of 

 water, for the highest duty is usually found where the 

 rainfall is light, as in southern California. Differences 

 v 



