SPILLWAYS FOR EESEBVOIES AND CANALS. 
17 
above to water surface below the dam. Flow through a siphon is 
produced by the difference in the elevation of the water surface at 
the inlet of the siphon and the elevation of the water surface at the 
SECTION A-A 
SECTION B-B 
I if;* 
PLAN of SIPHON 
SECTION F-F 
Fig. 5. — Cross-section and section plan of siphon spillway. South San Joaquin irriga- 
tion district, Ilipon, Calif. 
outlet end ; or in case the latter is not submerged to seal the siphon, 
and the water has a free discharge, it is measured to the center of 
the outlet opening. In such cases the flow is treated as if it were 
through a short tube with various forms of inlet, and further limited 
149907°— 20 2 
