# The Suez Canal: Alleged difference in levels between the Red Sea and the Mediterranean **URL:** \ **Category:** Factual Questions\ **Created:** [August 20, 2020, 2:30pm UTC](https://boards.straightdope.com/t/the-suez-canal-alleged-difference-in-levels-between-the-red-sea-and-the-mediterranean/918590 "2020-08-20T14:30:29Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [August 20, 2020, 2:30pm UTC](https://boards.straightdope.com/t/the-suez-canal-alleged-difference-in-levels-between-the-red-sea-and-the-mediterranean/918590/1 "2020-08-20T14:30:29Z")
I have repeatedly read the claim that an objection that was raised in the 19th century against proposals to construct a Suez Canal was that the sea level of the Red Sea was considerably higher than that of the Mediterranean. A canal would therefore causes masses of water to flow downhill and cause destrcution along the way. For an example for these claims, see item 2 [here](https://www.history.com/news/9-fascinating-facts-about-the-suez-canal). I find it hard to believe that such ideas were widely held among serious experts as late as the 19th century, a time when the overall geography of the world was quite thoroughly explored and natural sciences were well established. The Mediterranean and Red seas are both part of the interconnected world ocean, so how could there be differences in altitude between them? Was this really an idea that was seriously believed in? ---
**Author:** ![ASL\_v2.0](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asl_v2.0/32/3525_2.png) [@ASL\_v2.0](https://boards.straightdope.com/u/ASL_v2.0)\ **Post date:** [August 20, 2020, 3:01pm UTC](https://boards.straightdope.com/t/the-suez-canal-alleged-difference-in-levels-between-the-red-sea-and-the-mediterranean/918590/2 "2020-08-20T15:01:00Z")
Blame it on Napoleon: > [@](#): > > After accompanying the expedition to the remains of the [Canal of the Pharaohs](https://en.m.wikipedia.org/wiki/Canal_of_the_Pharaohs), built by [Necho II](https://en.m.wikipedia.org/wiki/Necho_II) between the [River Nile](https://en.m.wikipedia.org/wiki/River_Nile) and [Suez Gulf](https://en.m.wikipedia.org/wiki/Suez_Gulf) and improved by [Ptolemy II](https://en.m.wikipedia.org/wiki/Ptolemy_II), he was commissioned by Bonaparte to edit an account of the Canal. He was made a member of the [Institut d’Égypte](https://en.m.wikipedia.org/wiki/Institut_d%27%C3%89gypte) on 22 August 1798, in the mathematics section. > > With his brother [Gratien](https://en.m.wikipedia.org/wiki/Gratien_Le_P%C3%A8re) and other engineers working alongside them, he carried out three building programmes (from 19 January to 5 February 1799, in September 1799, and finally in November to December 1799) to [measure the levels](https://en.m.wikipedia.org/wiki/Levelling) of the isthmus, in difficult conditions due to Bedouin attacks and the lack of water. In the rain, he concluded that there was a 9 m difference between the levels of the [Mediterranean](https://en.m.wikipedia.org/wiki/Mediterranean) and [Red Sea](https://en.m.wikipedia.org/wiki/Red_Sea), an error which persisted until the measurements carried out by [Paul-Adrien Bourdaloue](https://en.m.wikipedia.org/wiki/Paul-Adrien_Bourdaloue) in 1847. > **[Jacques-Marie Le Père](https://en.wikipedia.org/wiki/Jacques-Marie_Le_P%C3%A8re)** > > Jacques-Marie Le Père (Paris, 25 April 1763 – Granville, 15 June 1841) was a French civil engineer. > He accompanied the French Campaign in Egypt and Syria, was director of 'Ponts et Chaussées' (bridges and roads) in Egypt. After accompanying the expedition to the remains of the Canal of the Pharaohs, built by Necho II between the River Nile and the Gulf of Suez and improved by Ptolemy II, he was commissioned by Bonaparte to edit an account of the Canal. He was made a member of the Institut d'Égyp... ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [August 20, 2020, 3:08pm UTC](https://boards.straightdope.com/t/the-suez-canal-alleged-difference-in-levels-between-the-red-sea-and-the-mediterranean/918590/3 "2020-08-20T15:08:16Z")
Due to currents, tides, salinity, temperature, etc, the average level of the world ocean can be different than the sea level at a particular location. For example, we shouldn’t be surprised if for any semi-isolated body, like the Red Sea, that the mean level will be different between summer and winter for the same body of water at a particular spot on the shore. In this case, the Med and Red Sea should not have such a large difference. I would be surprised if they did, though I would not be shocked if it were found to be a tenth of that (20 cm) on any given day just due to local conditions, especially if we’re just looking at the points on either end of the canal. This is, after all, the case on either end of the Panama Canal, which due to local conditions, sees the Pacific side a bit higher than the Atlantic side on average. On average, the Pacific and Atlantic have the same mean level but not at the points they hit Panama. And the level of the tides is very different on either side of the isthmus. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [August 20, 2020, 3:38pm UTC](https://boards.straightdope.com/t/the-suez-canal-alleged-difference-in-levels-between-the-red-sea-and-the-mediterranean/918590/4 "2020-08-20T15:38:36Z")
> [@Great\_Antibob](#): > > This is, after all, the case on either end of the Panama Canal, which due to local conditions, sees the Pacific side a bit higher than the Atlantic side on average. On average, the Pacific and Atlantic have the same mean level but not at the points they hit Panama. And the level of the tides is very different on either side of the isthmus. Yes. Due to the configuration of the Bay of Panama, the tidal range on the Pacific side is 20 ft, while that on the Atlantic side is about 2 ft. If a sea level canal were ever built (which is a bad idea for other reasons) it would still need locks due to the tidal variation. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 20, 2020, 8:34pm UTC](https://boards.straightdope.com/t/the-suez-canal-alleged-difference-in-levels-between-the-red-sea-and-the-mediterranean/918590/5 "2020-08-20T20:34:59Z")
Of course, canal locks have been in existence for a long time, anyway. If the canal you’re building needs locks, well then, build locks. ---
**Author:** ![Iggy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/iggy/32/3364_2.png) [@Iggy](https://boards.straightdope.com/u/Iggy)\ **Post date:** [August 20, 2020, 10:54pm UTC](https://boards.straightdope.com/t/the-suez-canal-alleged-difference-in-levels-between-the-red-sea-and-the-mediterranean/918590/6 "2020-08-20T22:54:25Z")
Even the winds can have an effect. Sustained southerly winds might be expected to raise the sea level on the Red Sea end of the Suez canal by just a bit by pushing water up into the Red Sea. And similarly winds would tend to blow water away from shore on the Med side of the canal, lowering the sea level at that point by a small amount. Switch to a northerly wind and the effect would be reversed. Such NNW winds are common in the northern Red Sea during the Indian monsoon and correlate with a lower sea level at Port Suez. This pattern was noted in [Wind induced sea level variability in the Red Sea](https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000GL012442) (pdf at link). " There is a very good agreement between the model and observations, indicating that the basic mechanism responsible for the variability of the sea surface height inside the Red Sea on seasonal time scales is the wind pattern. " The net effect of the NNW winds is that the sea level in Port Suez in the northern Red Sea is 30cm lower, on average, that the sea level in the mid Red Sea at Port Sudan. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [August 21, 2020, 2:06pm UTC](https://boards.straightdope.com/t/the-suez-canal-alleged-difference-in-levels-between-the-red-sea-and-the-mediterranean/918590/7 "2020-08-21T14:06:09Z")
An interesting sidelight on this is that Ptolemy’s observation of slightly different levels between the mediterranean and the Red Sea may be responsible for the way he mapped the world. Science writer (anf sf/fantasy author) L. Sprague de Camp once suggested that the reason that Ptolemy drew the Indian Ocean and the Mediterranean as physically isolated bodies of water (as in this map – [Ptolemy's world map - Wikipedia](https://en.wikipedia.org/wiki/Ptolemy%27s_world_map) or [British Library](https://www.bl.uk/collection-items/ptolemy-world-map) ) may be because he reasoned the same way the OP has done. If the bodies were connected, then the principle of water “finding its own level” would result in the sea levels in the Mediterranean and the Red Sea (connected to the Indian Ocean) having to be the same if they were connected. Since the levels differed, the bodies of water could not be connected, so he drew the Indian Ocean as a land-locked feature. (DeCamp’s article first appeared in the June 1969 issue of The Magazine of Fantasy and Science Fiction, p. 34 – [Fantasy & Science Fiction v036n06 (1969 06) (PDF) : Free Download, Borrow, and Streaming : Internet Archive](https://archive.org/details/Fantasy_Science_Fiction_v036n06_1969-06_PDF/page/n31/mode/2up?q=Indian) Others believe that the “land-locked Indian Ocean” was a medieval conceit imposed on Ptolemy’s map – [Ptolemy's Geographia - Bell Library: Maps and Mapmakers](https://apps.lib.umn.edu/bell/map/PTO/GEO/indian.html) )