202 IRRIGATION PRACTICE 



122. The border method. The border method of 

 irrigation is an open-field method. By this method the 

 field is divided by low flat ridges of earth into long narrow 

 strips, the lower ends of which are open. The ridges are 

 spaced about 50 feet apart and are frequently 800 feet 

 long. Water is guided over the land by field ditches. This 

 modification of the field-ditch method has for its purpose 

 the better control of the water. The ridges prevent the 

 water from spreading beyond the distance determined 



between the ridges. 

 This enables the 

 irrigator to watch the 

 water more closely. 

 When the .water 

 reaches the lower end 

 of the strip, it may be 



FIG. 41. Border method of irrigation. 



shut off and another 



strrp attacked. The advantages and disadvantages are, 

 practically, those explained for the field-ditch method, 

 except that the lateral ridges make the handling of the 

 water somewhat easier. In cultural operations the ridges 

 are in the way. (Figs. 40, 41.) 



123. The check method. This is the most important 

 of the closed -field variation of applying water by the 

 flooding method. The field is laid off into compartments 

 or checks wholly surrounded by levees. The water is 

 admitted at the upper end and completely fills the com- 

 partments until, hi many cases, it overflows at the lowest 

 point of the levee. This method of irrigation has been 

 practised from the earliest antiquity. The irrigated 

 countries of Europe, Asia and Africa employ this method 

 very largely. 



Evidently it is adapted only to comparatively level 



