What if Atlantropa was built?

According to Wikipedia, the net outflow from the Black Sea is twice the inflow, so a dam would only cause it to rise until it overflows and washes Istanbul away.

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Sorry, but I am having difficulty following your logic.

If you reduce inflow by 1/3, water levels should drop.
And lower water levels mean less outflow because out flowing water has difficulty topping the Dardenelles. The Black Sea would shrink from a Sea to a brackish lake, to salt marsh and might dry up completely like Death Valley or the aural Sea.

As for a dam bursting and flooding Istanbul ..... I thought one of the goals was to generate hydro-electric power, which requires carefully controlled outflow gates directing water to generator turbines???????
 
According to Wikipedia, the net outflow from the Black Sea is twice the inflow, so a dam would only cause it to rise until it overflows and washes Istanbul away.
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Sorry, but I am having difficulty following your logical.

If you stop 1/3 of inflow, Black Sea levels will drop until outflow can longer top the Dardenelles. Then the Black Sea becomes an endhoric lake with no outflow.
Over the years it will become progressively more salt and shallow. Unfortunately the lowest of the newly dry land will be too salty for farming. Salt marshes at the bottom might never dry out. It all depends how much water still flows down the Danube, Don, etc. Rivers.
The Black Sea might eventually dry up like the Aral Sea or Death Valley (USA).
 
I doubt the plan is to block it off but rather allow the same outflow while harnessing that for electricity. Even maintaining the same sea levels there would produce a huge amount of power.
Yes, and that is precisely why the black sea would become fresher: as the water flows out, the salt is not replaced since the the only inflow is now freshwater.
 
Isn't the amount of concrete required to build the Atlantropa dams several times the annual world production? And doing it back in the 30s?

That's actually the point.

Atlantropa was intended to bring world peace by, quite literally, bankrupting anyone who would have the capacity to launch a largescale war and diverting all the resources for such a project into a massive boondoggle.

Of course, the basic problem is that all the countries required to get it started would also find themselves with the compete destruction of their economies due to the total loss of the coasts (can't construct a canal to every fishing village on the Italian coast after all).
 
Basic math: the strait is 13km wide and 600m average deep. Rubble pile closing the strait would be thus about 8 cubic kilometers, meaning 20 billion tons of rubble. With typical cost $200 per ton, the total price would be 4 trillion $. Roughly US GDP for 3 months. Realistically, will need about 20 years for rough fill and then 10 years for cementing. As about sabotage, it will shrug off everything smaller than nuclear bomb.
Build a double track railway bridge across the Straits. (This could be based on a pontoon bridge concept, with piers sunk in the bedrock, or a massive suspension bridge). Now. Run freight trains across at 100 km/h each way, spaced as closely as possible. It should be 'easy' to get 90 cars each holding 100 tonnes to go each way about 2 minutes apart (so, a new train enters every minute, half going north, half south). Obviously, some of these trains will hold actual goods, but most can carry your rubble, which they dump off over the edge of the bridge as they travel. On average, then, you have something like 90 cars dumping per minute, or 1.5/s. Each car is 100 tonnes.
So. 1.5E2 tonnes/s
Total volume, you say, is 20 billion tonnes. So, 2E10 tonnes. That can be dumped in ~1.5E8 s. Now, a year is 3.1E7 seconds so approximately 5 years
 
It would allow easy passage between Africa and Europe without requiring ships.
The existing port infrastructure already suffices to handle European/North African trade. Easy passage for people between Africa and Europe is of questionable benefit considering the costs of building the bridge and something that many in Europe would actively want to oppose. Think of the political consequences for someone funding an extremely expensive project to make it easier for Muslims to come to Europe.
 

trurle

Banned
Build a double track railway bridge across the Straits. (This could be based on a pontoon bridge concept, with piers sunk in the bedrock, or a massive suspension bridge). Now. Run freight trains across at 100 km/h each way, spaced as closely as possible. It should be 'easy' to get 90 cars each holding 100 tonnes to go each way about 2 minutes apart (so, a new train enters every minute, half going north, half south). Obviously, some of these trains will hold actual goods, but most can carry your rubble, which they dump off over the edge of the bridge as they travel. On average, then, you have something like 90 cars dumping per minute, or 1.5/s. Each car is 100 tonnes.
So. 1.5E2 tonnes/s
Total volume, you say, is 20 billion tonnes. So, 2E10 tonnes. That can be dumped in ~1.5E8 s. Now, a year is 3.1E7 seconds so approximately 5 years
The bottleneck section is actually loading rubble to transports rather than dumping rubble to water. Imagine the hordes of heavy-duty excavators and loaders throwing the rubble to cars or barges, and take into account needed de-centralization to avoid supply roads congestion. I actually estimated initial fill to be done by hopper barges rather than by railway cars. It is much more cost-efficient and avoids extreme pipelining (and therefore, crowding) of your one-dimensional railway supply line. Remember, the cheapest way to build island is to dredge sand from sea bottom and to move it to another locations before just reversing dredger machinery. Reducing the number of loading/unloading operations is of the paramount importance. Unfortunately, sand is not very good material for this project due steep bottom gradients and strong sea currents, therefore more expensive (and difficult to procure&load) stone rubble may be necessary. Also, i must point out what 13km suspension bridge is technical impossibility. Pylons of Messina had just 3.7km span, and suspension bridges are limited to 2km with the current materials tech.

P.S. By the way, with realistic evaporation-driven flow of 50kt/s and step height 200m, the power generation by Atlantropa would be around 100 GW. For comparison: entire Earth civilization currently produce just around 2500 GW (up from ~800 GW in 1965 when Atlantropa could be launched). Therefore, Atlantrope electrical power would be important but not critical.
 
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It would allow easy passage between Africa and Europe without requiring ships.
Ships carry move than trucks going down a salty, sandy, desert hot pit. Besides, so what if you can get to Europe to Africa? That means you get to North Africa, with the Sahara behind it. Sahara Sea or not, it is going to be a miserable place without trade opportunities.
 
Don't forget that the sea level of the Mediterranean was to be lowered only very slowly. There would have been plenty of time to cultivate the newly gained and secure it before desertification can start.
 
Don't forget that the sea level of the Mediterranean was to be lowered only very slowly. There would have been plenty of time to cultivate the newly gained and secure it before desertification can start.
That is something not usually brought up, I will admit. But what would they cultivate? Still lots of rocks and sand. And the rest of the sea... Well, look at the Aral Sea. The salt and pollution all increases in concentration. Fish die. Shellfish go extinct in many areas. And the Greek Islands are screwed, as now many islands become mountains. Also, where would they get the dirt for all of this cultivation? And I cannot really think of a single country who would like this. Sure, most of the states left in an Axis victory would want to expand. But that meant outwards or overseas. To gain territory, not to eat into their maritime zones. It would be an object of horror if people learned the very shape of their countries were going to change beyond comprehension, or if they were going to suddenly become landlocked. Italy would never accept such a thing unless the Nazis showed themselves willing to utterly level a few regions. And if it ever came to that (as in relationships dipping so much, not necessarily trying to wipe out entire regions) the Germans would annex northeast, and croon about their Mediterranean Coast, to lose that... Yes, I know people suggested canals allowing Venice to still have water. It wouldn't be the same.
 
Ah. Well, that map looks far, FAR too green to be realistic. I'd anticipate desertification and environmental destruction on a par to (or even worse than, given the far greater area and even greater population density of the regions which would be directly afflicted by the repercussions of Atlantropa) the Soviet 'Great Plan for the Transformation of Nature' which turned the Aral Sea into the Aralkum Desert. In such a scenario, you'd likely see the Tabernas Desert, miniscule at the present time IOTL, expanding to encompass the entirety of the Levante region- the entire eastern region of the Iberian Peninsula, along with the expanded Balearic Islands and much of South-West France, would become desert, and effectively become an extension of the Sahara. Much of the merged island of Sardinia-Corsica would go the same way, as wouldmuch of the expanded island of Sicily. And practically all the land on the bottom and the right hand side of that map there would be either sandy desert or white salt flats. The result? Total desolation and near-total depopulation of the entire Mediterranean (and Black Sea) basins, all in the name of generating hydroelectric power to be provided to a population base which would no longer exist. I mean, it's not like there'd have been any way to export hydroelectric power cost-effectively, least of all over the kind of distances you'd need to reach any nations (or regions, rather- no telling what the political map of Europe would look like by the time the map looked like that) who wouldn't have been desolated by the cataclysmic ecological collapses which the project would have brought about...

Surely if they see desertification occur they'll let more water through the dam...

Seems kind of absurd to suggest people would out their feet up for fifty years
 
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