196 



IRRIGATION PRACTICE 



of growth is retarded. Much work yet needs to be done 



on this subject. 



/ The various modifications of the flooding method 

 / may be grouped into (1) flooding open fields, and (2) flood- 

 / ing closed fields. Open fields are those not surrounded by 



levees. Closed fields are those completely surrounded by 



levees, making a compartment into which water is 



admitted. 



120. Permanent ditches. A permanent system of 



ditches, having in view immediate and probably future 



FIG. 34. A permanent ditch in an orange grove (Redlands). 



needs, should be constructed on every farm, to connect 

 the canal with the field to be irrigated. The ditches should 

 be placed so as to interfere as little as possible with regu- 

 lar agricultural operations, and they should conform 

 either to the contour of the land, or to some well defined 

 plan for dividing the farm into fields. The laying out and 



