42 BULLETIN 115, TJ. S. DEPARTMENT OF AGRICULTURE. 



TYPICAL TUBE DELIVERY WITH IRON GATES. 



In the extensively irrigated region around Greeley and Fort Col- 

 lins, and in the Arkansas Valley, in Colorado, a particular type of 

 delivery gate has been used for a number of years and its use is 

 spreading gradually to other States of the West. This is essentially 

 a tube through the bank, with a cast-iron or sheet-iron gate at the 

 canal end. Figure 11 shows this type of gate as used by one of the 

 companies in northern Colorado. After a careful study of a great 

 many installations of this type it is believed that the gate set at 

 an angle of 75° with the pipe line gives the best results. This 



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Pig. 11. — Tube delivery used by North Poudre Irrigation Co., Colorado. 



slope will agree quite closely with the slope assumed by the banks of 

 canals which have been in service for years, becoming overhung with 

 grass and weeds. This slope allows a light concrete or masonry face 

 to rest against the bank, more as a lining around the pipe opening 

 than as a retaining wall, which it would be if the face were made 

 vertical. 



If the centers of the gates delivering water from above the same 

 check all are set at the same elevation, and the grade of the pipe 

 outlets is made the same, then all the deliveries will vary in ap- 

 proximately the same proportion when the head changes. 



If it is not desirable to use check gates and hold the water against 

 the delivery gates, then the latter should be set so that the bottoms 

 of the tubes are approximately level with the bottom of the canal. 

 Various grades are used for the laying of the pipes, but if the topog- 



