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Roots Revealed Blog




It's Water Over the Bridge

Posted: 12/25/2013
Posted By: Doug Kusak - Cultural History Interpreter


Aqueduct

For those who’ve ever wondered what an aqueduct is, we’d like to provide you with an earworm clue. Ready? Sing: “Like a bridge over troubled water . . .”

Okay. Sorry ‘bout that. But the song may help you to remember that an aqueduct is most closely associated with a bridge that conveys water over a lower-lying area. In the case of the Ohio & Erie Canal, that often means an aqueduct conveys the metered, calm flow of canal water over other natural and potentially more turbulent waterways: rivers, streams, creeks, and the like.

The name “aqueduct” comes from Latin: “aqua” (water) and “ducere” (to lead). So “aqueduct” really refers to the entire system of water conveyance: pipes, ditches, canals, tunnels, bridges, and everything else that’s channeling the water. But because the Roman Empire built aqueducts that included massive stone arched bridges, some of which are still in use today, we tend to associate the word “aqueduct” with only the bridge carrying the water.

Water runs downhill. We are in an area with a lot of water and a lot of downhill runs that go every direction (except, of course, up). The water takes the path of least resistance – the path we’d equate with being easiest. That’s why creeks, streams, and rivers flow where they flow – they’re following the path of least resistance (provided their course hasn’t been re-engineered by humans or beavers).

When constructing a canal, engineers are more interested in conveying the water along the path they contrived, rather than simply letting the water run where physics will lead it. The canal designers choose a route based on physics (water runs downhill!), but also apply engineering and economics to their plans (simply put, they want the shortest route they can afford). If there’s a depression (valley, etc.) along the canal route, a means of conveying the canal’s water across the depression becomes necessary so that the canal water stays in the canal instead of running downhill and out of the canal.

Just as a bridge can convey trains, autos, pedestrians, etc. over a depression, a bridge can be made to convey water. There are some different considerations – keeping the water on the bridge vs. making sure water runs off the bridge; making the bridge strong enough to support the weight of flowing water; having a downhill slope to keep the water moving; etc. – but spanning the depression is the key.

The aqueducts along the Ohio & Erie Canal are no longer the canal’s originals – wear and tear, erosion, flooding, freeze/thaw cycles have all taken their toll – but in areas where the flow of canal water is maintained, such as the Mill Creek Aqueduct in the Ohio & Erie Canal Reservation, you can still see where the original aqueducts were, how an aqueduct works, and how canal engineers can overcome depression.


Doug Kusak
Cultural History Interpreter
CanalWay Center


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