Question

The siphons installed within a gravity dam to spill the surplus reservoir water are known as ______________________

(a) hooded type siphon spillway

(b) tilted outlet type siphon spillway

(c) both hooded and titled type siphon spillway

(d) shaft spillway

This question was addressed to me in a job interview.

This question is from Shaft Spillway topic in division Spillways, Energy Dissipators and Spillway Gates of Irrigation Engineering

Answer 1

Right choice is (b) tilted outlet type siphon spillway

To elaborate: The siphon pipe is installed within the body of the dam and an air vent may be connected with it. The outlet is submerged to avoid the entry of the air in the siphon from the d/s end. When the air enters the siphon through the vent, siphoning action cannot take place and the flow will stop.