Hey Ray! Explaining The Line In The Confluence Of The Three Rivers

Meteorologist Ray Petelin is back with another home science lesson!

Video Transcript


- Hey, Ray!

- That's so cool.

RAY PETELIN: Scientifically, some mixtures mix well, others don't, and some mixtures just take time.

ELIZABETH PETELIN: Please tell me we're going to mix up something delicious.

RAY PETELIN: Well, let's see if we can turn a viewer question into something delicious.

ELIZABETH PETELIN: So what's the question?

RAY PETELIN: The question is, why is there a line at the point where the Monongahela and Allegheny Rivers meet to form the Ohio River? It's something you may have noticed if you watch the rivers.

ELIZABETH PETELIN: There is no way I'm drinking Mon water.

RAY PETELIN: I don't think you need to drink Mon water this time. But we are going to find out a different way, what that line is. And for that, we're going to talk to Fred McMullen. He is a coordination meteorologist at the National Weather Service office in Pittsburgh, and they work closely with the US Army Corps of Engineers and the United States Geological Society to maintain and monitor the riverways around our area.

So Fred, what is that line?

FRED MCMULLEN: So the line is really a function of what we call rock bottom. And it's a thing where the two rivers, the Allegheny and the Mon, have different river composits. So the Mon has a silty or sandstone bottom, with finer sand, which, when we get the heavier rain, it gets stirred up more easily. And that's why you get a darker appearance of the Mon River versus the Allegheny, bigger gravel, coarser sand, and the river doesn't get stirred up as much. And therefore, it kind of maintains the same color through the duration of an event versus the Mon, which changes color.

ELIZABETH PETELIN: So does it take time for these ingredients to mix into the Ohio River?

FRED MCMULLEN: Yeah, and you have different components on the river tops. So again so it's kind of like oil and vinegar, right? You mix oil and vinegar, you get a kind of a separation in the bottle. And then, same thing that we have at the point, where we have different colors coming together because different sediments have been mixed up. And then therefore, you know, again, they differentiate, they separate. And then eventually, at some point down the Ohio River, they merge and they get diluted. And therefore, the river becomes one color again.

RAY PETELIN: Sometimes it's lighter, sometimes it's darker. So what's the setup that makes it more noticeable?

FRED MCMULLEN: Northern West Virginia, southwestern Pennsylvania gets heavy rainfall, maybe northwest didn't get any rainfall. And so you'll definitely see that really stark contrast on those situations versus if we had a widespread rainfall across western Pennsylvania and northern West Virginia where the Mon begins. You can see a little bit of coloration in the Allegheny, but more pronounced in the Monongahela River.

RAY PETELIN: That's awesome. Thanks, Fred.


RAY PETELIN: All right, now let's make our own line at the point. You get to be the Monongahela River with this chocolate syrup. I'm going to be the Allegheny with this milk. And, mix them up.


And there you have it, science.

ELIZABETH PETELIN: On second thoughts, I will drink Mon water.

RAY PETELIN: Reporting from home--

ELIZABETH PETELIN: I'm Elizabeth Petelin.

RAY PETELIN: --and I'm meteorologist, Ray Petelin.

Save some for me.