Could desalization be used to reverse deserticiation?

[Konig15]

I've read up on Desalinization techniques before, mostly on wiki, but also some others, but mostly they deal with present technologies and it's practical effect on Human needs.

I was thinking of something a little more abitious? Given the increasing rate of desertification, could pumping billions of gallons of water into the interiors of Africa and North America, stem, and them reverse the trend? Could Western North Africa be returned to it's classical period glory s the breadbasket of the Med? Could we theoretically, turn the Sahara back into the savana it supposedly was 10, 12 thousand years ago? We would certainly have a long way to go, but I thought I'd ask.

[Fingolfin_Noldor]

I do not think it to be that simple. The trouble is, the soil has long lost its ability to retain water, and it is very porous. All you will create is possibly a lot of mud.

I am not sure, but I think the key thing to do is somehow replace the top soil and somehow grow some trees there to stablise the top soil.

[Starglider]

You need to get a lot of organic material back into the topsoil. The simplest way to do that is let the really hardy grasses move in first, then let nature take its course. Eventually the place will turn into grassland. However to make it suitable for crops you'd probably have to let it go all the way to forest, then cut that down (and let it rot in place if you don't want to run into very-rapid-nutrient-depletion issues), /then/ plant crops, which will take centuries. Perhaps you could accelerate that by spraying/injecting organic fertiliser (liquified compost essentially) in huge quantities, I'm not sure.

[Admiral Valdemar]

You need to get a lot of organic material back into the topsoil. The simplest way to do that is let the really hardy grasses move in first, then let nature take its course. Eventually the place will turn into grassland. However to make it suitable for crops you'd probably have to let it go all the way to forest, then cut that down (and let it rot in place if you don't want to run into very-rapid-nutrient-depletion issues), /then/ plant crops, which will take centuries. Perhaps you could accelerate that by spraying/injecting organic fertiliser (liquified compost essentially) in huge quantities, I'm not sure.

This is a problem we'll have to contend with given climate shifts which seem to be making the poles more acceptable and the equator less hospitable. Most all our major agriculture is in areas today that are fast losing top soil and being affected by chaotic climate effects. But the north thawing and being habitable for agro-species isn't helpful when all the soil is totally inadequate for growing monocultures or much of anything we truly need.

Someone is going to really make a killing from fertiliser in the future.

[kinnison]

Short answer; no. The amounts of power needed are way beyond what can be devoted to the task.

However, there is another way. I believe that a fairly large proportion of the area of the Sahara is below sea level, if only slightly. One example, a small one, is the Qatarra Depression - which is no use to anyone at present, being a highly treacherous bog.

So; dig a BIG canal from somewhere (it doesn't really matter where, and it may well be several somewheres) on the ocean shore into the African interior, and let the sun do the desalinating for you. The area around the new inland sea will become much wetter; speed up the process by planting hardy grasses or some such and let Nature take its course.

This sounds to me like a damn good way of using some of the tens of thousands of nukes that are lying around. Nuclear charges for digging canals is an idea that started in the 1950s.

Some African countries would lose a fair bit of their area, and gain lots and lots and lots of tourist revenue.

[Sikon]

In some places such as some areas of Israel, Egypt, and elsewhere, there's been some work on desert reclamation, typically using natural sources of freshwater pumped from elsewhere. Using desalinated seawater to support vegetation is also possible in principle and has been done in some cases (especially some spots of high value land, such as resorts, a random example being this golf course in Dubai using a million gallons a day for its lawns).

It's not on the huge scale talked about in the opening post but with some similarities, applied to small, localized areas of deserts, creating the equivalent of an oasis in each spot.

It's possible to grow vegetation almost anywhere (excluding frozen regions), provided one goes to the trouble. A random example is hydroponic vegetable gardens set up on some Pacific islands in WWII:

Hydroponics is at least as ancient as the pyramids. A primitive form has been carried on in Kashmir for centuries.

[...] But as a farming tool, many believe it started in the ancient city of Babylon with it's famous hanging gardens, which are listed as one of the Seven Wonders of the Ancient World, and was probably one of the first successful attempts to grow plants hydroponically.

[...] Hydroponics is now defined as the science of growing plants without the use of soil, but by use of an inert medium, such as gravel, sand, peat, vermiculite, pubice or sawdust, to which is added a nutrient solution containing all the essential elements needed by the plant for its normal growth and development. Since many hydroponic methods employ some type of medium that contains organic material like peat or sawdust, it is often termed "soilless culture", while water culture alone would be true hydroponics.

[...] Dr. Gericke's application of hydroponics soon proved itself by providing food for troops stationed on non-arable islands in the Pacific in the early 1940s.

[...] The first triumph came when Pan American Airways decided to establish a hydroponicum on the distant and barren Wake Island in the middle of the Pacific Ocean in order to provide the passengers and crews of the airlines with regular supplies of fresh vegetables. Then the British Ministry of Agriculture began to take an active interest in hydroponics, especially since its potential importance in the Grow-More-Food Campaign during the 1939-1945 war was fully realized

[...] In wartime the shipping of fresh vegetables to overseas outposts was not practical, and a coral island is not a place to grow them, hydroponics solved the problem. During World War II, hydroponics, using the gravel method, was given its first real test as a viable source for fresh vegetables by the U. S. Armed Forces.

In 1945 the U. S. Air Force solved it's problem of providing it's personnel with fresh vegetables by practicing hydroponics on a large scale giving new impetus to the culture.

[...] One of the first of several large hydroponics farms was built on Ascension Island in the South Atlantic. Ascention was used as a rest and fuel stop by the United States Air Force, and the island was completely barren. Since it was necessary to keep a large force there to service planes, all food had to be flown or shipped in. There was a critical need for fresh vegetables, and for this reason the first of many such hydroponic installations established by our armed forces was built there. The plants were grown in a gravel medium with the solution pumped into the gravel on a preset cycle. The techniques developed on Ascension were used in later installations on various islands in the Pacific such as Iwo Jima and Okinawa.

On Wake Island, an atoll in the Pacific Ocean west of Hawaii, normally incapable of producing crops, the rocky nature of the terrain ruled out conventional farming. The U. S. Air Force constructed small hydroponic growing beds there that provided only 120 square feet of growing area. However, once the operation become productive, it's weekly yield consisted of 30 pounds of tomatoes, 20 pounds of string beans, 40 pounds of sweet corn and 20 heads of lettuce.

The U. S. Army also established hydroponic growing beds on the island of Iwo Jima that employed crushed volcanic rock as the growing medium, with comparable yields.

During this same period (1945), the Air Ministry in London took steps to commence soilless culture at the desert base of Habbaniya in Iraq, and at the arid island of Bahrein in the Persian Gulf, where important oil fields are situated. In the case of the Habbaniya, a vital link in Allied communications, all vegetables had had to be brought by air from Palestine to feed the troops stationed there, and expensive business.

[...] After World War II the military command continued to use hydroponics. For example, The United States Army has a special hydroponics branch, which grew over 8,000,000 lbs. of fresh produce during 1952, a peak year for military demand.

[...] For example, large hydroponic greenhouse complexes are now in operation in Tucson, Arizona (11 acres); Phoenix, Arizona (about 15 acres); and Abu Dhabi (over 25 acres), this installation uses desalted water from the Persian Gulf. Tomatoes and cucumbers have proven to be the most successful crops. Cabbages, radishes, and snap beans have also done very well.

Article

And there's a segment of this web page:

GETTING THE NUMBERS AND DOING THE ARITHMETIC

[...]
Many questions that concern people can be answered by getting some numbers and doing arithmetic with them. Usually just multiplication and division are involved.

The water supply problem for California provides a good example, because the relevant numbers are available. California is a drier than average part of the United States, but it is also the country's leading agricultural state in value of crops produced. There was a seven year period in the 1980s in which the rainfall was much less than average, and this directed a lot of public attention to water supply.

California uses about 35 million acre-feet of water per year and has a population of about 30 million people. That's a bit more than an acre-foot per person. For present purposes, an acre-foot per person is accurate enough, because some of the other numbers are more uncertain.
2002 note: Now it's 32 million people and 43 million acre-feet. The trouble with statistics is that they become obsolete.

Q. Where did these numbers come from?

A. I remember the numbers, because I think about numbers quite a bit, but both numbers are available in The Statistical Abstract of the United States, a volume that is published every year by the Bureau of the Census. Actually the 1998 estimate of the population of California was 32,667,000, and the 1997 estimate of the population of the US was 267.2 million. If we ignore the discrepancy of years, we get that California has 12.2 percent of the US population.

Q. What if California became a total desert? Apparently this happened at least once in the last thousand years, judging from fossil sand dunes in the San Joaquin Valley. Would everyone die?

A. No. It would be quite a hit to the economy, but California could still maintain its agricultural production, although many products would be produced elsewhere. Here's where the arithmetic comes in.

During the seven year drought of the 1980s, the city of Santa Barbara constructed a plant for desalinating seawater. The cost of water from the plant would have been $2,000 per acre-foot [with some later desalination plants actually being substantially cheaper but with these figures good enough for their purpose]. If California had to get all its 35 million acre-feet of water by desalinating seawater, it would cost $70 billion per year. The gross domestic product of the US is given as $8 trillion. So we estimate the GDP of California at $980 billion. Spending $70 billion on water would be 7.1 percent of the GDP of the state. We'd notice it, but life would go on, not much changed. (Actually, California has slightly more than average per capita income for the US, so the percentage would be somewhat lower, but we don't need more accuracy than we already have.)

Assuming California lost all its water is an extreme case, but it is useful to do that computation, because it tells us that one particular doom won't happen. Without the arithmetic, we wouldn't know, and the rhetoric of The Cadillac Desert might win out.

It doesn't suggest that California build a large number of desalination plants just in case. We can expect to solve our water supply problems much more cheaply than by converting entirely to desalination.

Someone reminded me that desalination of seawater requires substantial energy. I don't have the numbers to say what that cost, but it is surely included in the Santa Barbara estimated cost. As became evident during the summer of 2000, the customary sources of California's electricity are under stress. Someday California may be faced with the choice between going without lawns and resuming the construction of nuclear power plants. I'll bet the voters will choose the latter.

Another example arose from a discussion in the newsgroup sci.environment. Someone argued that when oil became much more expensive, international grain trade would be infeasible and countries would have to raise their own food. It took a while to find the relevant fact, and I eventually telephoned a professor of ocean engineering at M.I.T. The relevant fact is that a large bulk carrier carrying grain uses one gallon of fuel for 1600 tonne-miles of transportation [one of the most efficient forms of transportation, only trains being comparable to ships]. Arithmetic tells us that even a 100 fold increase in oil prices wouldn't make international grain transportation infeasible, although it sure would damage the rest of the economy if there were no replacement for oil.

These examples are not important in themselves. They just illustrate the important point. Many questions can be settled by recourse to available statistics and arithmetic - arithmetic not higher mathematics, although higher mathematics is also useful. The converse is that failing to look up statistics and do the arithmetic is a recipe for ignorance.

The opening post also reminds me of nuplex proposals:

Within days of the cease-fire [after the 6-day war in 1967], former President Dwight D. Eisenhower presented President Johnson with a peace initiative under the laconic title of "A Proposal for Our Time." Drafted in cooperation with former Atomic Energy Commissioner Adm. Lewis L. Strauss, and Alvin Weinberg, director of the Oak Ridge National Laboratory, the proposal called for the construction of three dual-purpose nuclear desalination electric power stations, referred to as "atomic desalting" plants, one each to be built in Jordan, Israel, and Egypt. They would produce a combined output of 1,400 million cubic meters of water a year, equivalent to the entire flow of the Jordan river system!

Later, in June 1968, Eisenhower wrote an article about the initiative for Reader's Digest. The purpose of building large atomic desalting stations in the troubled region, Eisenhower wrote, "is not only to bring large arid regions into production and supply useful work for hundreds of thousands of people, but also, hopefully, to promote peace in a deeply troubled area of the world through a new cooperative venture among nations. I am optimistic enough to believe that the proposal, when implemented—as it is sure to be someday—may very well succeed in bringing stability to a region where endless political negotiations have failed...."

Under the subtitle "A Power for Peace," Eisenhower wrote that the plants would be dual purpose, producing both water and electricity in order to enable development across 1,750 square miles (4,500 square kilometers) of barren land, which would form the centerpiece of a scheme to settle more than a million Palestinian refugees. As does LaRouche in his Oasis Plan, Eisenhower pointed to the regional scope of the project. The electricity produced, he said, "would be used in pumping water to areas as distant as Syria and Jordan, and perhaps under the Suez Canal to parts of Egypt. The rest would be utilized for the manufacture of needed fertilizer and other industrial purposes; a plentiful supply of electrical energy would bring to the Middle East vast new complexes of industry, just as it has to many other parts of the world."

Eisenhower estimated that the project would cost $1 billion and would be funded through a specially created international corporation supervised by the International Atomic Energy Agency.

[...] By the beginning of the 1960s, Oak Ridge National Laboratory had on its drawing boards proposals for the development of dual-purpose nuclear reactors for the generation of electricity and the desalination of water, and for the creation of nuclear agro-industrial complexes, or "nuplexes." One such proposed nuplex was the Bolsa Island plant, planned but never carried out, for Southern California.

Article

[The Duchess of Zeon]

FLOOD AL-QATTARAH!

God, I know what I'd be doing if I was the dictator of Egypt.

Seriously, that project would have a huge benefit, by bringing coastal temperatures deep into the desert and starting a rainfall cycle in the Sahara.

The best part is that it's not the only place it could be done in Northern Africa. Libya has two areas of major sub-oceanic depressions which could be flooded. Tunisia and Algeria share one such additional large basin. All of these (there are several more deeper in the interior, such as the Lake Tchad area, which would be rather more impractical to connect to the ocean, though it could be done with a monumental level of engineering achievement) would be easily flooded, though only one in Libya and al-Qattarah could also generate power; the others would simply become embayments with heavy evaporation which would bring rainfall to the idea and cool the surrounding area. There's another one, though, in the Horn of Africa, two major depressions, the Danikil depression, and a smaller but extremely deep one in Djibouti, which could be used for power generation and as well, being quite deep.

In the mid-east there's already a project, rare cooperation between Israel and Arabs (Jordan), to re-fill the Dead Sea with seawater from the ocean while generating electrical power, which is underway and points the way to other such projects.

For that matter, to deal with the problems of southern California, I have mused before on the eminently practical possibility of smashing an Aquaduct through the coastal ranges which could reflood much of the Imperial valley and bring the Salton Sea back up to its old levels, and simultaneously flood Death Valley and several surrounding valleys below sea level, while generating electricity. Thirsty Las Vegas and southern California could desperately use these projects. The electrical power generated could even be used to desalinate some of the water for drinking outright, in addition to the mediating effects on the climate and improved rainfall prospects.

This could also be done with Lake Eyre in Australia, and possibly some other basins, which desperately needs to do something of this sort, really.

[Starglider]

This could also be done with Lake Eyre in Australia, and possibly some other basins, which desperately needs to do something of this sort, really.

Of course Greenpeace would camp out in the basins, screaming about 'destroying desert ecosystems' or some such nonsense. Sadly I doubt the flooding would be fast or violent enough to drown any of them. All the more reason to use nukes to dig the canals actually, you might get some of them that way.

[CaptainChewbacca]

All this large-scale refacing of the globe reminds me of the atlantropa project, and the subsequent re-engineering of Africa proposed in the 1950's.

Get a load of Congo Lake and the Chad Sea.

Massive changes, but I think they'd do Africa some good in the long run.

[The Duchess of Zeon]

All this large-scale refacing of the globe reminds me of the atlantropa project, and the subsequent re-engineering of Africa proposed in the 1950's.

Get a load of Congo Lake and the Chad Sea.

Massive changes, but I think they'd do Africa some good in the long run.

I completely agree. Let's hire the engineers for the Three Gorges Dam and get started immediately. We will, of course, also have to hire some outfit like Executive Outcomes to eliminate the local governments, but that will be worth the positive result at the end of the day. The less water that is flowing into the ocean, the slower ocean level rise will take place. The larger we make the ocean on our own by blasting out canals to areas with high evaporation rates in the desert that won't otherwise be flooded.. Ahh.

The biggest, boldest, and perhaps most plausible project, however, is blasting a canal from the Black Sea to the Caspian directly across southern Russia. By flooding the Caspian basin we could theoretically reduce world ocean levels by a whole foot, and the potential electrical power generation would be immense.

The Russians and Kazakhs are already working on a precursor project, turning around several of their rivers which push to the Arctic and diverting much of their water into the Aral Sea basin, or at least, the project has been authorized in a country flush with oil revenues. We'll see if it comes to fruition. It was originally planned back in the Soviet Days, along with the diversion of part of the Volga. Contrary to popular belief they were fully aware of the problems of drying out the Aral basin, and that was their solution. They just didn't last long enough or have enough money to implement it.

[Mayabird]

It's Lake Assal, the small but very deep depression in Djibouti, for the benefit of everyone here. It's only about ten miles (16 kilometers) from the sea.

And as a historical note, al-Qattarah/Qattarah Depression was going to be flooded for hydrosolar (water flows in, water evaporates, more water flows in) power and surveying was about to begin...and then World War II broke out. The Battle of El Alamein was fought over one of the more promising routes for the canal that would carry water to the depression.

Desalination is very energy-intensive so if it's going to be used large-scale, massive nuclear-powered desalination plants would be the way to go. Nuplex...I like it!

The thing about desertification is that the evapo-transpiration cycle needs to be set up. The Amazon basin makes half of its own rain. Water comes in from the sea in clouds, but as it evaporates and plants release water, it gets back into the atmosphere and comes raining back down. Part of the problem with deforestation IS the breaking of that cycle, where water can evaporate more quickly from deforested land and escape, and transpiration doesn't occur at the same rate on grassy land than densely forested land. It could be done (the Sahara was once a savanna, after all) but it would be a lot of work.

One step I would recommend for starting would be the growing of mangrove forests on sea beaches bordering desert land. Mangroves are currently limited in the places they can grow because your average beach lacks certain nutrients that they need (mostly iron and available nitrogen) but they can grow in salt water. By planting them in steel cans with the bottoms knocked out (protection for the seedlings, and an iron infusion) with a small bag of nitrogen fertilizer, they can be made to grow in places where they did not before. They can be irrigated by sea water, and has been demonstrated to work a hundred meters inland. Once the mangroves start growing, they attract fish and other sea life that like using mangrove roots as shelters, and their leaves and seed pods can be used as food for goats and camels (but not sheep, for some reason). Start a transpiration cycle, give the locals something for their own support (seafood and fodder for their animals), AND mangrove forests are great for shielding shelters on the interior from tsunamis and storms. So at the end of your mangrove forest canal-system-thingy, you could have a big nuplex for fresh water to irrigate the desert beyond.

Mangroves are very productive, and the projects can be started at low cost and with very little skilled labor or technology. Heck, one of the most successful projects is in Eritrea. And they'll be there for shielding if you ever get the money and supplies together for a nuplex or something else.

A couple links on my whole mangrove spiel:
http://mangrove.org/
http://www.mangroveactionproject.org/

[Konig15]

Mangroves, huh?

Fascinating! I was going to also suggest nuclear powered desalinization, but I thought that might muddy up the waters a bit. I'm still hoping for Fusion power later in the century, but whether it will be here no one can say. My uncle who works in Livermore said essentialy about Fusion power, 'who knows who cares?' Still, I think with all the damage we've done to the planet, we can clean up our mess a little.

[Sea Skimmer]

Holy hell, a California environmentalist writer who supports river diversion to save the Aral Sea and can actually supply some numbers on what it will take! He seems to support it partly to reduce sea level rise in the Caspian, but that’s reasonable since its level is already rising fast enough to wipe out a number of towns, and a massive expansion of its size is a far more radical and time consuming plan.
Link

The canal routes

[CaptainChewbacca]

All this large-scale refacing of the globe reminds me of the atlantropa project, and the subsequent re-engineering of Africa proposed in the 1950's.

Get a load of Congo Lake and the Chad Sea.

Massive changes, but I think they'd do Africa some good in the long run.

I completely agree. Let's hire the engineers for the Three Gorges Dam and get started immediately. We will, of course, also have to hire some outfit like Executive Outcomes to eliminate the local governments, but that will be worth the positive result at the end of the day. The less water that is flowing into the ocean, the slower ocean level rise will take place. The larger we make the ocean on our own by blasting out canals to areas with high evaporation rates in the desert that won't otherwise be flooded.. Ahh.

The biggest, boldest, and perhaps most plausible project, however, is blasting a canal from the Black Sea to the Caspian directly across southern Russia. By flooding the Caspian basin we could theoretically reduce world ocean levels by a whole foot, and the potential electrical power generation would be immense.

The Russians and Kazakhs are already working on a precursor project, turning around several of their rivers which push to the Arctic and diverting much of their water into the Aral Sea basin, or at least, the project has been authorized in a country flush with oil revenues. We'll see if it comes to fruition. It was originally planned back in the Soviet Days, along with the diversion of part of the Volga. Contrary to popular belief they were fully aware of the problems of drying out the Aral basin, and that was their solution. They just didn't last long enough or have enough money to implement it.

I hadn't heard about that notion, but I am skeptical if only because such a canal would require about 9 locks on each end and it would be 700 miles long. If they can get it done, though, more power to them. I would be glad to see the Caspian and the Aral finally become more fully integrated into the world economy. The Volga-Don canal just can't handle it all.

[The Duchess of Zeon]

All this large-scale refacing of the globe reminds me of the atlantropa project, and the subsequent re-engineering of Africa proposed in the 1950's.

Get a load of Congo Lake and the Chad Sea.

Massive changes, but I think they'd do Africa some good in the long run.

I completely agree. Let's hire the engineers for the Three Gorges Dam and get started immediately. We will, of course, also have to hire some outfit like Executive Outcomes to eliminate the local governments, but that will be worth the positive result at the end of the day. The less water that is flowing into the ocean, the slower ocean level rise will take place. The larger we make the ocean on our own by blasting out canals to areas with high evaporation rates in the desert that won't otherwise be flooded.. Ahh.

The biggest, boldest, and perhaps most plausible project, however, is blasting a canal from the Black Sea to the Caspian directly across southern Russia. By flooding the Caspian basin we could theoretically reduce world ocean levels by a whole foot, and the potential electrical power generation would be immense.

The Russians and Kazakhs are already working on a precursor project, turning around several of their rivers which push to the Arctic and diverting much of their water into the Aral Sea basin, or at least, the project has been authorized in a country flush with oil revenues. We'll see if it comes to fruition. It was originally planned back in the Soviet Days, along with the diversion of part of the Volga. Contrary to popular belief they were fully aware of the problems of drying out the Aral basin, and that was their solution. They just didn't last long enough or have enough money to implement it.

I hadn't heard about that notion, but I am skeptical if only because such a canal would require about 9 locks on each end and it would be 700 miles long. If they can get it done, though, more power to them. I would be glad to see the Caspian and the Aral finally become more fully integrated into the world economy. The Volga-Don canal just can't handle it all.

No, just one end, the Caspian end. The Black Sea side would have to be at sea-level to gain the advantage of electrical generation from sending the water downhill on the Caspian side. It would require a massive amount of blasting, granted, but it's well within the capability of modern equipment developed for super-strip-mining operations, but the locks would only have to deal with, say, 30 meters of fall there, at the point of a super-massive earth-fill dam which would lock off the end of the canal on that side. We could completely divert the Volga to the Aral, with the artificial canal maximized for power generation and navigation alike, to make the Aral Sea even larger than it traditionally was, leaving just enough Volga water flowing to the Caspian to keep the navigation channel open. The rest of the water into the Caspian basin would come from the Black Sea.