Flooding the Qattara Depression?

It appears that the Qattara Depression (which is actually in Egypt) would hold about one ten-millionth of the water in the oceans. Just a drop in the ocean, really, and unlikely to make a noticeable difference. In any case, the plan involves letting water flow in at a rate where it will be balance by high levels of evaporation in that very hot climate, so that they could keep generating electricity, and not have to stop once the depression was full.

The average sea level has only increased about one centimeter, the last 100 years and may only increase one more millimeter in the next 20 years, so assuming we put a million times a million cubic meters = 1000 cubic kilometers of sea water in the Quattara Depression, that would lower the world ocean by one millimeter if we have 10^15 square meters = one billion square kilometers square meters of world ocean area. The actual area is somewhat less, and that amount of water is somewhat less than the capacity of Lake Ontario which likely has greater average depth. So yes, it might offset the ocean rise between now and 2042. Projecting farther into the future is likely just guessing, so I will leave you to refine the numbers.

Some added complications are: Perhaps half of the added water will soak into the lake bottom for a salty aquifer for several (perhaps many) kilometers near the lake and this is a location with low humidity, so a million times a million cubic kilometers may evaporate each 20 years, making Lake Quattara very salty after a few centuries. Some of the evaporated water will fall as rain and return to the ocean, long term. It will be very costly to pump the water into the lake as a siphon is not practical with a high point more than about 7 meters above the average Red Sea high tide water height which would require a tunnel 100 plus kilometers long.

Some compromise numbers: Siphon aided pumping to a high point of 20 meters above sealevel, would allow shorter tunnels and maximum lake depth of 150 meters, before reverse flow without pumping occurred. Another 20 meters would likely mean the lake holds about 20% more water. We need to pump for about 20 years to fill the lake at 100,000 times a million cubic meters per year. Less than half full = about 75 meters we could use water turbines near the lake surface to recover perhaps half of the pumping energy. Local humidity would increase, and rainfall increase with the lake nearly full so perhaps we could complete filling on schedule even if a few of the many pumps were beyond economical repair.

Yes the long tunnel would not require pumping (except to start the siphon and could generate some electricity until the lake was about 125 meters deep, but the tunnel would have to be huge to move 75 feet plus evaporation and soaking in, in 20 years, but that is good if generating electricity is the primary object. If we get new ice age with the Red Sea near empty, partially emptying the lake into the Red Sea could also generate electricity but lakeside home owners would feel betrayed if the lake was even partially emptied. Neil

Puh-lease! Are you for real? The oceans currently cover about 75% of Earth's surface. Do you seriously think that a depression that covers less than 1% of the dry land, with an average depth of much, much less than 130 meters could even possibly come close to holding all of the water from the glaciers that cover Antarctica and Greenland that are up to a mile thick?

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Firstly, Qattara Depression is in our country , Egypt , and i don't know when it was in Libya :/ !!!!!!!!!!!!!!!!

Secondly, Qattara Depression isn't wide enough to offset the expected rise in sea levels, but i can say when all Depressions in the whole world will be flooded, that's would be more effective.