SPILLWAYS FOR RESERVOIRS AND CANALS. 



31 



the effects of this departure and verify or correct the theory of the 

 parting water column in siphons under relatively high heads would 

 be of benefit, and the tests taken on the Yuma installation, where 

 the design is identical 

 except for the converg- 

 ing outlet, could be con- 

 trasted. 



As a method of auto- 

 matically safeguarding 

 the freeboard of a canal 

 at isolated points, the 

 small siphon shown in 

 figure 2, Plate XI, and 

 in text-figure 11 is a 

 good example. These 

 figures illustrate the 

 siphon at the head of the 

 East Park Feed Canal of 

 the Orland project. It is 

 designed to operate when the water stands 

 0.2 foot' above the top of the waste weir 

 at the place of diversion, and thus fur- 

 nish a close regulation of the water sur- 

 face. The estimated capacity is 99 sec- 

 ond-feet, with 0.50 taken as the discharge 

 coefficient. This was one of the first in- 

 stallations in the United States and followed the 

 European custom of inclined draft tube, the slope 

 of the ground at the site being particularly 

 adapted to the design. 



EUROPEAN PRACTICE. 



The Italian engineer Luigi Luiggi describes 

 numerous siphon spillways which have applied to 

 dams and to many power and irrigation canals. 1 

 prevailing type is a square tube built of reinforced con- 

 crete and capable of discharging from 1 to 525 second- 

 feet, varying, of course, according to section and the head 

 under which they operate, which ranges up to 34 feet. 

 To produce larger discharges where head was limited, siphons are 

 placed in batteries. A typical example of clever control by the siphon 

 spillway is shown in the case of the Logalunga Reservoir, near Genoa, 



1 Transactions of the International Engineering Congress, 1915, Waterways and Irriga- 

 tion Section. 



