Could we build a mammoth desalination plant on the Atlantic coast of Africa and irrigate the Sahel and Sahara?

Answer 1

It could be done, and if done on a large enough scale using advanced solar technology, could be cost effective.

Engineers are probably working on such a system now.

However, before this is done we should have some understanding of how irrigation will eventually change the environment. There's no point in doing this if the evapouration of water ends up concentrating salts at the surface, as has happened in several other regions over the past few thousand years. (Especially in the Indus valley.)

One of the problems in the Sahel is that people have been digging wells. While this seemed like a good idea 40 years ago, it turned out that nomadic farmers and wild animals stoped moving around from one place to the other.

The result of this was that there ultimately was a greater impact on the environment because there wasn't a rest period for the grasses and trees to allow them to recover, In the end the Sahel is more denuded than would otherwise have been the case.

The Sahel and large parts of the Sahara were once grasslands and even forested. The Romans and Carthaginians removed most of the forests, and since the region has been getting drier since the last ice age, nature took care of the rest.

In most of Africa, the soil is quite poor. The soil nutrients have been depleted. Adding water won't help much. Fertilizer would provide quicker results, and education in the techniques of permaculture would help rebuild those soils.
Learn to grow soil, and food will be a welcome byproduct.

It would be a good idea to study this a lot more. Just because we can think up a technological "fix" doesn't mean we should.

Answer 2

Sure, a desalination plant could be built..
But, the Sahara actually has a huge quantity of underground freshwater. In the '80s Libya tried different projects to utilize this deep groundwater.
Eventually, they came up with the Great Man-Made River Project, which was a huge underground aqueduct, pump stations, hydro power plants, and electrical transmission system to pump the fresh water from remote in the Sahara, over the mountains, to the coast, where it was needed by the people.

More recently, I know firsthand that freshwater is available in Algeria, at least in the Grand Erg Oriental (great eastern sand sea). We used it in the oilfields to replace the volume of produced oil with water, for proper oil reservoir management.

Answer 3

Since it's fantasy, why not build your plant on the north east coast, and let the prevailing winds carry the moisture across the whole top of the continent?
(The sahara used to be grasslands in moister times.)
To continue the fantasy, it would have to be a solar plant, and the cost would be huge, but it's not totally impossible.

Answer 4

yes, but what's the point of doing it?

its one of those "I can but is it worth it?" questions, something of that magnitude is definitely possible but costly, very very costly and there's no point in doing so

example: building a super nuke, super nukes are expensive over powered and just plain well, over doing it, and unneeded tech speaking any nuclear country could build a multi trillion mega ton nuke, but detonating just one would put the whole world into a nuclear winter regardless of where it was detonated

example 2: building an oil rig out in the middle of nowhere just to pump about 3 gallons of oil, was there some gain? yes, but was it worth the millions of dollars spent to build the rig? no

Answer 5

This would have to be solar powered to be efficient which I think could be done using partial vacuum technology. A bigger problem maybe trying to find topsoil to go on top of that silica. This type of project could more usefully employed to stop the encroachment of these deserts on fertile lands.

Answer 6

Its not nice to fool mother nature.

the Sahel and Sahara are there own ecosystems.

if it aint broke don't fix it.

Answer 7

Yes, and the energy required to do so would use up a good sized chunk of the oil left in the world.

Answer 8

Why would we want to. The world is like it's supposed to be. What would happen to all the life now there? It would die because you changed it's living conditions.

Answer 9

Too expensive

Answer 10

Um, what would you do with all of that salt?
I think the logistics of moving that much water over those distances would kill it.