DUTY AND DIVISION OF WATER 



335 



a term which cannot, under present conditions, be fixed. 

 As time goes on, and irrigation practices are improved, 

 there will be an increasingly high duty of water obtained 

 in the irrigated section. 



The absolute duty of water means the sum of the water 

 applied to the plant in irrigation and the water supplied 

 from the soil moisture and by rains during the growing 

 season. This duty is usually expressed as the depth in 



FIG. 93. Lateral outtake from large canal. 



inches over the land. For instance, in a certain experi- 

 ment, 6.4 inches of water were taken from the soil; 15.3 

 inches were added by irrigation, making a total of 21.7 

 inches, the absolute duty. 



The net duty of water means the area of land covered 

 by the water received by the farmer at the farm head- 

 gate. It is practically identical with the absolute duty, 

 except that the water stored in the soil and the rains during 

 the summer are not taken into account. 



The gross duty of water means the area of land served 

 by the water at the intake of the canal, or occasionally 



