Arizona Spillway.

Overflow if needed.
The nominal elevation of this spillway is 1,221 feet above sea level, although movable control vanes could add another seven or eight feet to this.
Overflow has gone over this spillway only twice in the dam's history, in 1942 and again in 1982.
If the the water level were to again reach the lip of this overflow channel, the nominal depth of Lake Meade would be around 599 feet.
We say "nominal" because the lake has been gradually silting up since the day the dam was completed.