48 



IRRIGATION FABMUT0. 



allowed. The location of the well or reservoir on or 

 near the highest point, fixes- the point of radiation of 

 the ditches, their lines being located according to the 

 grades secured and the lay of the land to be served. The 

 aim will always be to keep the water up as high as possi- 

 ble, for it is useless to sacrifice grade or make a ditch 

 run at a greater grade than is necessary. It is an easy 



FIG. 8. DROP AND REDUCTION 1'.<>\. 



tiling to 



matter to let the water down but a difficult 

 raise it. 



A method for dropping the grade of a ditch wlirn 

 the pitch becomes too great is shown in Figure 8. This 

 is a drop box for the fall and is often made a reduction 

 box as well. It is useful in places where the water .-uj- 

 ply is lessened by serving customers farther up the line, 

 or when the volume of water becomes less from any other 



