The Owyhee Dam has a unique spillway known as "The Glory Hole" located partway up the dam that utilizes a 60-foot (18 m) in diameter tunnel to send excess water to the river below.  This spillway acts like a sink drain during high-water periods.

Check out the links below to watch some aerial videos of the spillway in action courtesy of The Idaho Statesman & The Bureau of Reclamation.

https://www.youtube.com/watch?v=DtHvG_5RWRA

https://www.idahostatesman.com/news/northwest/idaho/article142848289.html

Ring Gate during construction 1928-1932

Ring Gate during construction 1928-1932

High water period with water spilling through "Glory Hole"

Owyhee Dam "Glory Hole"

Visit the Bureau of Reclamation Site for more Project Details:

https://www.usbr.gov