40 BULLETIN 115, U. S. DEPARTMENT OF AGRICULTURE. 



be closed at will. Most of the locks on standard sheet-steel gates are 

 of this pattern. Other companies do not allow their consumers 

 either to open or close the delivery gates. For such a gate there 

 must be a positive lock which holds the gate shutter in the set posi- 

 tion as determined by the ditch tender. 



As stated before, water issuing under a gate shutter may be held 

 more nearly constant than that passing over a crest. On the other 

 hand, the amount of water delivered may be altered by the consumer 

 in spite of locks if the orifice is submerged. If the consumer has a 

 division box located close to the gate and the conditions of grade 

 and velocity of water in the various ditches leading from this divi- 

 sion box are such that the same amount of water in the head ditch 

 flows away more rapidly in one direction than in another, then the 

 back water against the delivery gate, and consequently the amount 

 of water passing the gate, may be altered by the consumer by shift- 

 ing the slides in his division box. This condition does not hold if 

 the water issues under a delivery gate shutter into the open air, as 

 there is no back water to be influenced by the consumer. An open- 

 air delivery is possible only where there is sufficient difference in 

 elevation between the canal and the head ditch to sacrifice some of 

 it so as to secure the result desired. 



DELIVERY GATE, CALIFORNIA DEVELOPMENT CO., CALIFORNIA. 



Figure 10 shows a good example of economical design for a rein- 

 forced concrete delivery box of the open-culvert form. Water is 

 diverted from a permanent canal where failure would cause much 

 damage, aside from the immediate cost of replacement so that the 

 upper wing walls extend farther into the bank than might be neces- 

 sary for most installations of this sort. It is to be noted that the 

 slots for the gate are placed slightly in front of the foot slab. The 

 reinforcement does not extend down into the cut-off wall, the latter 

 being used solely for the purpose of stopping seepage water. 



This gate was built in the fall of 1910. The 7.6 cubic yards of 

 concrete is a one to seven proportion of cement and gravel. A small 

 concrete pedestal is bolted in the four holes shown on the top of the 

 operating platform and to this pedestal is bolted the lever-lifting 

 device for the rack-and-pinion lift. The cast-iron rack is bolted to 

 the back of the gate stem. 



RADIAL DELIVERY GATE, TURLOCK IRRIGATION DISTRICT, CALIFORNIA. 



The deliveries to the consumers from the main laterals of the 

 Turlock irrigation district are now being made through simple con- 

 crete-box structures regulated with wooden radial gates. Plate VIII, 



