USE OF CONCRETE PIPE IX IRRIGATION. 



43 



the water in the lateral is divided in proportion to the separate 

 acreages to be served. The Covina Water Co. has installed diver- 

 sion boxes that are fitted with galvanized sheet-iron gates. The 

 gates are all set at the same elevation in the box and water may 

 spill over into the orchard pipe lines on every side of the box. The 

 gates are usually made with rectangular orifices that have several 

 sizes of openings. As the head is the same on each gate, the correct 

 proportion of water will be delivered to each unit, independently 

 of the head over the 

 orifice. 



Pipe can be used 

 to advantage for 

 constructing diver- 

 sion boxes as shown 

 in figures 21 and 22. 

 TVhere there is con- 

 siderable pressure to 

 contend with at the 

 point of diversion, 

 pipe structures can 

 be built up in a sin- 

 gle length to the re- 

 quired height and 

 gates operated from 

 the top of the 

 stands. Overflow 

 stands (fig. 23) can 

 be made by building 

 spillways and thus 

 keeping a constant 

 head on the mains 



or laterals. Overflow stands may operate automatically, requiring 

 no gates, or gates may be made from ordinary orchard valves that 

 can be manipulated from the outside of the stand. 



TVhere pressure is excessive or there is an objection to high stands. 

 diversion boxes are sometimes built that extend only a few feet 

 above the ground surface, and a top is provided over the stand that 

 will withstand the pressure as shown in figure 24. Alfalfa valves are 

 commonly used to close the top of the stand. Lateral gates may 

 either be of the common, sliding type, or may be orchard valves that 

 are loosened by turning on a threaded bolt. 



A diversion box has been designed that will relieve high pres- 

 sures without the use of high relief or overflow stands. This box 

 makes use of an automatically controlled valve that will open the 

 gate in the main when pressures tend to become high at the point of 



Fig. 22. 



-A diversion box formed wholly of concrete pipf 

 having small air vents. 



