This spillway consists of a vertical shaft and a horizontal conduit.
The top of the shaft is specially designe, through which water enters and then drops through a vertical shaft and finally gets carrie to the D/S side by a horizontal conduit.
This spillway is also sometimes know drop inlet or morning glory spillway.
The shaft spillway may be standard crest type or flat crest type.
Both types are shown in Fig. 14.10.
Small shaft spillway may be made from steel or concrete pipes, but large spillways are made from heavily reinforce pipes.
Diversion tunnels use for diverting the river water during the construction of the dam may be plugg and then use as shaft spillway by attaching vertical shafts to the horizontal tunnels.
Top flared inlet of the vertical shaft is know morning glory and is considered essential feature of the shaft spillway.
