GATE STRUCTURES FOR IRRIGATION CANALS. 51 



regardless of moderate fluctuations in the supplying stream, the inlet 

 pipe is set below the headgate and the outlet carried to a lower level. 

 This is possible only where a diversion dam of some sort is used and 

 the outlet pipe discharges into the stream below the diversion dam, 

 and where this water is lower than the proposed water in the canal 

 below the gate. Only one lever is used, connected to the gate at one 

 end and the counterweighted tank at the other. When more water 

 than is desired enters the canal it fills the well through the inlet pipe, 

 raises the tank, and lowers the gate until equilibrium is established. 

 If the supply falls then the water in the well gradually passes out 

 through the outlet pipe, the tank falls, raising the gate, and thus 

 allowing more water to enter. 



The operation of these gates in the Turlock district is practically 

 instantaneous and allows the canals to be run with larger heads of 

 water than would otherwise be safe. 



Where the level of the water, and consequently the volume, in a 

 side lateral or consumer's delivery is to be held constant the inlet pipe 

 is placed at the desired level in the lateral, but the double system of 

 levers operates on the check gate as before. This system could be 

 used to insure uniform deliveries to consumers and would protect 

 the banks above the check also, because the rising water above the 

 check would increase the delivery to the side lateral, flow into the 

 well, raise the tank, lower the counterweight, and lift the check gate 

 sufficiently for the excess water to pass on down the canal. 



The particular structure shown in figure 14 combines both an au- 

 tomatic check and a drop located on lateral No. 7, which carries 

 about 200 second-feet of water. The height of the open ends of both 

 inlet and outlet pipes may be adjusted, as they can be swung about 

 on the threads of the elbows. About two-thirds of the way up these 

 two pipes the gage rods are attached. The slots in the rods are 

 slipped over staples set in the concrete walls near the top and pad- 

 locks through the staples over the bars lock the device. 



The bucket or tank hanging in the well is made of No. 16 gal- 

 vanized iron, 44 inches in diameter and 3 feet high, the top lapping 

 over a |-inch round pipe stiffener and riveted thereto. Two straps 

 of \ by 1^ inch iron pass completely around the bucket at right 

 angles to each other and are brought together 2 feet above the rim. 



The concrete counterweight hung below the intersection of the 

 lines of the two levers is of convenient shape and weighs about 300 

 pounds more than that portion of the gate to be lifted by it. 



The automatic radial gate is built up of double 1-inch Oregon pine. 

 Before being set in the concrete the ends of the pipe axle are bored 

 and 12-inch pins thrust through them, which prevent the axle turn- 

 ing in the concrete. 



