A Place to Stand

the Qattara Depresssion is below sea level, with the lowest elevation being -133 meters. The eastern end of the depression is 210 km west of Cairo and 130 km southwest of Alexandria. Hughes and Hughes (1992) report the following charateristics for this region of northern Africa:


  For those interested in military history it played a signmificant paqrt in WW2. The Depression was essentially impassable and thus provided the one area in the western desert where a defencive line could not be outflanked. As such the shortest line connecting it to the sea, at a place called El Alamein was the ultimate allied defence line against the German armies under Rommel
  The proposal to flood it goes back some considerable time. According to Wikipedia

The Qattara Project is a large civil engineering project rivaling the Aswan High Dam intended to develop the Qattara Depression by flooding it. The depression is a region that lies below sea level and is currently a vast desert. By connecting the region and the Mediterranean Sea with tunnels and/or canals, water could be let into the area. The inflowing water would then evaporate quickly because of the desert climate. This way a continuous flow of water could be created if inflow and evaporation were balanced out. With this continuously flowing water hydroelectricity could be generated. Eventually this would result in a hyper-saline lake or a salt pan as the water evaporates and leaves the salt it contains behind.

All proposed routes for a tunnel and/or canal route from the Mediterranean Sea towards the Qattara DepressionThe proposals call for a large canal or tunnel being excavated of about 55 to 80 kilometres (34 to 50 mi) ...By balancing the inflow and evaporation the lake level can be held constant. Several proposed lake levels are -70m, -60m, -50m and -20m.

Plans to use the Qattara Depression for the generation of electricity date back to 1912 from Berlin geographer Professor Penck. In 1957 the American Central Intelligence Agency proposed to President Dwight Eisenhower that peace in the Middle East could be achieved by flooding the Qattara Depression. The resulting lagoon, according to the CIA, would have four benefits:
It would be "spectacular and peaceful."

It would "materially alter the climate in adjacent areas."

It would "provide work during construction and living areas after completion for the Palestinian Arabs."

It would get Egyptian president Gamel Abdel Nasser's "mind on other matters" because "he need[ed] some way to get off the Soviet Hook."

  So for political reasons it never happened. But it does look like it would be easy to do nowadays. 80 km, even assuming a canal cost as much as the tunnels the Norwegians build (£4m per km) would be about $320m (£200m) plus the cost of the turbines to make electricity. For something that can produce 2.8GW for the next 500 yearsw, till the sea fills up & becomes a salt pan, that is incredibly good value.

   Not so sure about it being a suitable home for the Palestinians - that does sound naive now but mainly because resettling the Palestinians has never been the Arab objective - their objective has ben to keep them as a moral stick to use against the Jews. Also if the land is going to be filled with salt water it will notbe so fertile. However salt water contains a number of elements that are valuable and which would be easier to extract from dry salt, or from more extreme concentrations of water, particularly if there was a cheap and reliable electricity supply.

   Most, like gold and uranium, are not currently extracted that way because it isn't cost effective but much of the world's magnesium is.

The process of extraction of Magnesium begins by mixing the seawater with its suspended salts, including magnesium hydroxide (Mg (OH) 2), with calcium oxide (CaO), also called ‘lime’, to make a slurry.


The slurry is permitted to rest for the solids to settle down at the bottom and the water rises to the top.

Then, the solids are removed, filtered, and washed to remove residual chlorides.

The end result is a loosely packed “cake” of material which is calcined in a kiln (a type of high temperature oven) to leave magnesium behind. Calcination is a thermal treatment process applied to ores and other solid materials in order to bring about a thermal decomposition, phase transition, or removal of a volatile fraction.

In the quantities available here it should be possible to do it permanently at very competitive prices. It might well also become possible to extract the other materials when these economies of scale work and when so m,uch of the work is already being done to get magnesium.

Variants;

 Dam off the southern portion letting the seawater reach there in 2 stages. Thus most of the area would remain at salt levels not far above those of normal seawater and could be inhabited, with the concomittant improvement of the climate and the collection of magnesium be restricted to the south.

Assuming it is possible, if the technological will (or an X-Prize) is there, to mass produce filters that could let through sea water without the impurities that stop it being fresh, through, then build a barrier of such at the mouth of the canal and turn Lake Qattara into a fresh water lake. I have suggested this in relation to the Dead Sea. A fresh water sea would certainly be able to support a bigger population than ever lived in Palestine.

Or fill it with fresh water taken from the Nile. But I can see those living alongside the Nile objecting.

This does tie in with a previous Big Engineering Project for taking water from Zaire to water the entire Sahara, which could have had one of the ultimate outlets have flowed into Qattara.  However looking at the 500 year timescale to fill the Qattara with seawater I suspect it would be at least centuries till all the other possible lakes had been filled and there was spare water to choose whether it shopuld go to qattara or the sea. Thus the 2 projects do not interfere with each other and since they both mean an enormous amount of water evaportating and mostly returning as rain, over the central Sahara, they complement each other.