Eli5: Panama canal and water locks

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Im sure people have come across the videos where ships passing through said canal or similar ones go through one or more “water lock”. Water levels between connected water bodies should be the same right? Why do they need to raise or lower the passing ships?

In: Planetary Science

5 Answers

Anonymous 0 Comments

Your question hits on the answer: the reason locks are needed are for canal systems where the water level is **not** the same throughout.

In the case of the Panama Canal, it does end up on the ocean on both sides, but in the middle, the canal itself is not actually at sea level. The canal is about 50 miles long, and in between the lock systems, the water level is actually higher than sea level. There’s a lake in the middle, Gatun Lake, that is about 80 feet higher than sea level, and the water in the canal is at Gatun Lake level. They dammed a river to make this artificial lake rather than having to physically dig out a channel all the way along.

Anonymous 0 Comments

They need to raise or lower the ships because the height of the water level between different sections of the canal – which don’t share a direct connection – isn’t the same. It was built this way because if all the water level was the same, you would need to dig the entire canal to sea level across the whole of panama, which wasn’t feasible. Instead some parts of the canal are at higher elevations and locks are used to access them

Anonymous 0 Comments

the panama canal is a bit different from other canals because of the varying elevations of the terrain. They either would have had to dig extremely (and unfeasibly) deep, or they could build it in a way to allow ships to traverse the elevation changes of the terrain. As it is, they already had a hard time removing enough earth for the current canal; the United States even proposed using buried/detonated [nuclear bombs](https://en.wikipedia.org/wiki/Project_Plowshare) for widening the canal in the 50’s.

The Pacific is also ~20cm* higher than the Atlantic, so if it were just open there would be a constant current of water, not to mention the tides are different as well. The Pacific side level changes about 6x* more than the Atlantic side with the tides.

**source: [https://core.ac.uk/download/pdf/268174985.pdf](https://core.ac.uk/download/pdf/268174985.pdf)

Anonymous 0 Comments

> Water levels between connected water bodies should be the same right?

They don’t have to be, and often aren’t.

The Suez Canal in Egypt is a rare example of a canal where the water on both sides *do* happen to be more or less the same. That canal has no locks because, indeed, it does not need them.

The Panama canal is an entirely different beast. Even *if* the bodies of water on the two sides were at the same height (and, surprise surprise, they aren’t), the main thing that particular canal is actually doing is *lifting the ships across the land*, moreso than just making up the height difference.

The Americas have one long mountainous backbone running all the way from tip to tip. Draw a horizontal line across either continent and you will cross mountains somewhere. Panama is no exception. If you want to get from one ocean to the other, you need to go up and over these. No way around that. (Or, well, there is away around that, but avoiding that way was *the whole point*.)

I suppose in theory you could carve straight through them, or even tunnel beneath them. But that’s a ridiculously monumental proposition. The canal in its current form was already an engineering marvel that took a lot of time, a lot of money, and frankly, a lot of lost lives to complete. They were not going to be moving any more earth than they already had to to get that done.

Perhaps the only thing that made the Panama canal project viable at all is the fact that, by pure happenstance, there’s a large natural lake midway through the crossing, nestled in the mountains. The water level of that lake is high above the oceans on either side, but if you can somehow lift ships up to that level, the lake can be a shortcut, reducing the amount of work cutting channels. So that’s what the canal does: you come in from one side, locks raise you up to the lake, you cross the lake, and more locks lower you back down.

Anonymous 0 Comments

>Water levels between connected water bodies should be the same right?

What, No? Rivers flow downhill. Even though a lake at the top is “connected” to the ocean through a river, it doesn’t means all that water volume instantly equalizes. Rivers only exist BECAUSE they’re not at the same level.