The morning glory spillway is normally used in conjunction with a tunnel spillway when
the intake is a vertical shaft. Also, because of flow entry from the entire periphery, the
crest capacity is relatively high. Crest gates are not normally used because of access and
cost considerations as well as poor hydraulic conditions in the shaft with partially open
gates Exhibit 17.6 illustrates a morning glory spillway. Figures 17.16 and 17.17 show the
range of possible flow conditions in the crest area for a morning-glory spillway
(USBR,1987). The design procedure is as follows