How Do Spillways Work?

We normally build a dam to hold water back and store it for use in water supply, irrigation, hydropower, or flood control. But sometimes we have to let some water go. Whether we need it downstream or the impounded water behind the dam is simply too full to store any more, nearly every dam needs a spillway to safely discharge water. The spillway is a critical part of any dam and often the most complex component. So how does it work?

Writing/Editing/Production: Grady Hillhouse
Thumbnail Photo: Doug Letterman (CC BY 2.0)

Tonic and Energy by Elexive is licensed under a Creative Commons Attribution License

This video is sponsored by Skillshare.

[danielwiegert]

One thing I think you should include, "Then things go wrong" show example on failed structures and lessons learned by them.

[ElectricGears]

One important advantage to note about controlled spillways is that they allow the dam to lower the level of the reservoir significantly below normal in anticipation of a large inflow. This allows them to absorb far more volume while maintaining the same outflow during the storm (or less to assist downstream dams that are picking up extra flow from the watershed between them).

[ThePhosee]

I have unexplainable terrifying fear of these round spillways even looking at them on the screen.

[notsure]

Me: It's 12:57 AM, I'm gonna sleep now.
Youtube: Hey, do you wanna watch a video about spillways?
Will watch 10/10

[jamesjanisko]

I really love it when you cover new material that incorporates previous videos. That building of knowledge makes me very happy. When you talked about weirs and I didn’t have to go back to those videos because I’ve already watched them and knew what you were talking about...made me feel a bit educated on hydraulics. Can’t thank you enough for putting out such quality content.

[Prosper_NA]

I'm a civil engineering major at Boise State and I just wanted to say that I watch your videos to supplement my coursework all the time. You make it fun and interesting to learn about what most people would consider mundane. So thanks.

[ArthurSavage]

I worked on the control system for a spillway at a hydroelectric dam in BC, Canada. A key component was to maintain minimum flow to keep fish alive in the river. We used redundant PLCs and three instruments from two manufacturers for every measurement required (level etc).

[Niekel]

Horror holes! Imagine falling into on of these

[spkrman]

Congratulations on 1 million subscribers. Love your videos. So educational and informative. Keep it up.

[JoshuaOtusanya]

I learn more on YouTube than I ever learned in school.

-Josh Otusanya

[ihavevisionfearme]

I always shit myself when I see these things to be honest, at least when I was young. They look terrifying.

[Dominic_LaSalle]

This channel was one of the main reasons I chose civil engineering as my major. I can't thank you enough for the excellent, high quality videos.


Congrats on 1 million!

[FlymanMS]

Wendover = Planes and trains

Practical Engineering = Concrete and water

[pieguy]

Jan: chill
Feb: chill
Mar: chill
Apr: chill
May: chill
Jun: chill
Jul: chill
Aug:
Sep: chill
Oct: chill
Nov: chill
Dec: chill

[simonrancourt]

In Québec, LG-2's spillway is called "The Giants' Stairway" : 10 steps 10 metres (32 ft) high and 122 metres (400 ft) wide, each step is larger than 2 football fields

[erictaylor]

4:18 This particular spillway scared me as a kid, as it was on the lake near where I grew up. As a kid, I was scared that it might swallow me, even if I was miles away on the other side of the lake.

[SpaceDave-onuv]

"Water can cause major damage" just use FLEX TAPE

[helgebrekke]

4:11 It can change as the bell mouth chokes, but how does it change?
As a non-engineer guessing, I'm expecting it gets an additional "pull" from the speed the water picks up as it chokes, that ups the capacity of the spillway, but it would be really interesting to hear more about that.

[marycombs]

You should do a few videos on some of the famous dams around the world, talk about how they work and the main reasons why they were built, and wether they still serve that purpose.

[crx_doubletrouble]

Have you made a video about diffrent kind of fish ladders, elevators and steps? Lots of dams yes, but it affects how fish reach their breeding grounds. There is a lot of various solutions to the problem, would like to see your take on that. I would watch :)