Kalahari Desert and Seawater Desalination

[Chirios]

A strange quirk of Southern Africa, (Namiba, South Africa, Botswana, Zambia, Zimbabwe, Angola and Mozambique) is that the interior is actually lower down than the coastal regions; ignoring of course mountains and hills and such. Namibia recently built a desalination plant in Swakompund that can produce some 20 million m^3 of water. Domestic and industrial production for this plant is extremely close to the coast but I was wondering: would it be possible several, smaller versions of these plants and then divert water from the plants into the omarumba - dry river beds which start in central Namibia but flow into the Botswana - of the kalahari, to provide more water for this area?

[Zaune]

(Disclaimer: My understanding of geology is limited to what I've picked up from playing Dwarf Fortress.)

You could, but if it's below sea level then the water table ought to be close enough to the surface that it's equally or more economical to sink wells.

[Broomstick]

Of course, if you bring a whole lot more water to the area you're going to trigger some very significant changes in the ecosystem. Do you really want to do that?

[CaptHawkeye]

You're seriously trying to say bringing *more* water to an area bereft of it is a bad idea?

[Broomstick]

Depends on whether or not you value anything to how things currently are. Adding more water could cause the extinction of drought adapted species. Also, does anyone have any idea of how the drainage of the area would react? Adding more water might also mean problems with flooding. Adding too much water to poorly anchored soils will cause erosion and reduce the fertility of the land. Irrigation of desert regions with fresh water has led to various salts and minerals being leached from the soils, which can also destroy the fertility of the land (the Middle East has examples of this). Adding water in desert regions can also lead to an explosion of certain species, some of which might carry disease. This is believed to have been a cause of a hanta virus outbreak in the American Southwest called Four Corners Disease - a few years of higher than normal rainfall lead to a massive population increase in rodents which carry the disease. It wasn't trivial - hanta virus has a fatality rate of between 30% to 80%.

Right now there is a certain stability to the Kalahari. What is proposed here is a significant change in those conditions. While adding water to the environment would generate certain reactions we'd see as benefits it is hubris to think there might not be bad effects.

[Simon_Jester]

For Third World nations where much of their territory is one form or another of desert, the sheer grinding poverty imposed by hostile terrain may be considerably worse than he consequences of irrigating the desert.

It's one thing to preserve the deserts in a portion of your country, when you have the resources to build modern infrastructure to make life in the desert more comfortable. You sacrifice more to preserve the deserts when that's pretty much all your country's got- which is fairly close to the situation faced by Namibia.

[Broomstick]

Oh, the US doesn't do much to preserve its deserts - we're pretty aggressive at irrigating them for agriculture.

And we've had to deal with the consequences.

I understand that for third world countries the benefits may be seen to outweigh the negatives, but a short term gain in agriculture that leaves the soil permanently diminished, in a country too poor to apply artificial fertilizers, or that brings sufficient salts to the surface to sterilize the topsoil, are arguably not gains over the long term.

There is much to be learned from the mistakes of others. It's not that adding water can't be a net gain, but doing so without careful thought and planning may be trading one set of mistakes for another. If the US fucks up a big chunk of desert at least no one will starve in that nation. If Namibia does it mass starvation could be a distinct possibility. I'm wondering how much thought and knowledge of risks are going into this project?

[Sarevok]

The Kalahari desert is hardly "lifeless". Like every desert it has it's own life in it. I am not too fond of destroying one of the most unique desert ecosystems in the world for short term gain.

There are other ways of supplying Southern Africa with fresh water.

[aieeegrunt]

I'd be amazed if this didn't result in salt seeps making the area completely barren. Stuff like this has been tried in Australia and the Middle East and that is inevitably what happens.

[Chirios]

Oh, the US doesn't do much to preserve its deserts - we're pretty aggressive at irrigating them for agriculture.

And we've had to deal with the consequences.

I understand that for third world countries the benefits may be seen to outweigh the negatives, but a short term gain in agriculture that leaves the soil permanently diminished, in a country too poor to apply artificial fertilizers, or that brings sufficient salts to the surface to sterilize the topsoil, are arguably not gains over the long term.

There is much to be learned from the mistakes of others. It's not that adding water can't be a net gain, but doing so without careful thought and planning may be trading one set of mistakes for another. If the US fucks up a big chunk of desert at least no one will starve in that nation. If Namibia does it mass starvation could be a distinct possibility. I'm wondering how much thought and knowledge of risks are going into this project?

Well, for Namibia, the bulk of the water will be used for Uranium extraction and processing, and the rest will be used for domestic consumption. None will be used for agricultural irrigation. My above statement was simply a "what if" type thing.

As for issues with changing the environment too quickly, anyway this could be limited?

[Broomstick]

Oh, lord - if you're using the water for uranium extraction, that is, mining you do not want to just flush it into the environment. It's not radiation that's a concern, as some might think, it's that mining waste is loaded with heavy metals and toxic chemicals. The US is struggling to clean up messes of that sort out west, it's terrible, just terrible stuff. Unless, of course, you purify the water before releasing it, but then you might as well turn around and pipe it back into the processing facility.

As for the changing the environment "too quickly" - it's not just that, but some processes such as salts leaching out of the ground will happen whether you change things slow or fast, and if it does happen it renders the soil sterile. The only way to avoid it is to use MUCH more water than strictly needed for agriculture, in which case you'll be dealing with run off problems, and with serious erosion as desert flora are not adapted to such quantities of water.

As pointed out, the Kalihari is far from lifeless. It's a desert, but it's fertile. The problem is that it can't support as many people per unit of area as some other regions on Earth, but the countries that share it are all suffering from overpopulation.

Here are some images of the Kalahari:


The vegetation is more spare than in non-desert areas, but there's still a visible amount of it, which varies seasonally. Think of the difference in visible foliage in a temperate climate between winter and summer. Types of vegetation also vary from very sparse scrub to actual trees (probably growing in seasonal stream beds or above subterranean water) But note also that the plants tend to widely separated. The soil between them is not held down. A sudden influx of water can wash that unsecured soil away, exposing plants roots, which then die, after which nothing is anchored and all the topsoil - and fertility - washes away.

Now, a gradual change in ground cover can, in theory, be achieved but only at the expense of wiping out most of the desert-adapted life. At which point your ground cover will require constant human intervention to maintain as the climate hasn't changed at all. If that maintenance fails the non-desert ground cover dies... and the desert life is gone so there is nothing to replace it. THEN you will have lifeless ground from horizon to horizon. At that point, you're looking a timescales longer than a human lifetime to recover. How much longer? Parts of the Middle East topsoil destroyed by damaging irrigation techniques have not yet recovered after thousands of years.

Don't get me wrong - I understand where your "what if?" came from. It is very tempting to make the desert bloom for our benefit. The problem is, experience has shown that it can (though does not always) end badly.

[Akhlut]

There's another problem we seem to be forgetting: when you desalinate water, you create a shitload of salt, either as a concentrated salt solution or as dry salt, depending on how you're desalinating your ocean water.

Now, what is Namibia going to do with thousands, if not eventually millions, of tons of salt/salt solution? If you dump it back into the ocean, then you're creating a dead zone in your own fishing grounds and making it that much more difficult on your equipment to desalinate your increasingly salty water. If just leave it laying around, then the eventual rainfall you do get is going to great a large sterile zone around your heaps of salt. If you bury it, then you have to do something with the enormous quantities of soil you dug up.

So, Namibia is going to have to spend money (or accept the losses in maintenance and fishing) to do something with a shitload of salt.

[Simon_Jester]

The Kalahari desert is hardly "lifeless". Like every desert it has it's own life in it. I am not too fond of destroying one of the most unique desert ecosystems in the world for short term gain.

There are other ways of supplying Southern Africa with fresh water.

The Kalahari isn't lifeless, but it isn't exactly the Nile Delta, either. The desert's low economic productivity is a very serious problem for Namibia, a country which suffers from the usual problems of sub-Saharan Africa to a great extent and has few exports save the products of its mines.

If they want to irrigate certain portions of their desert, I really don't think that's unreasonable. Not when people place such high value on the preservation of the country's deserts but doesn't choose to make up for the costs imposed on the people who have to live in a desert.

Broomstick is totally right that if this is screwed up it may leave Namibia much worse off in the long run, and that the project should be undertaken very cautiously, if it is to be undertaken at all. But I can't blame the Namibians for wanting it done.

Oh, lord - if you're using the water for uranium extraction, that is, mining you do not want to just flush it into the environment. It's not radiation that's a concern, as some might think, it's that mining waste is loaded with heavy metals and toxic chemicals. The US is struggling to clean up messes of that sort out west, it's terrible, just terrible stuff. Unless, of course, you purify the water before releasing it, but then you might as well turn around and pipe it back into the processing facility.

Ah, yes. Absolutely right.

God, that is not what you want washing around your backcountry. And I have a horrible suspicion that the Namibians (because of aforesaid grinding poverty) aren't worrying about that issue as much as they should...

[Zaune]

Now, what is Namibia going to do with thousands, if not eventually millions, of tons of salt/salt solution?

Filter out the impurities, bag it up and sell it if they've got any sense; salt is quite a valuable commodity.

[Chirios]

Oh, lord - if you're using the water for uranium extraction, that is, mining you do not want to just flush it into the environment. It's not radiation that's a concern, as some might think, it's that mining waste is loaded with heavy metals and toxic chemicals. The US is struggling to clean up messes of that sort out west, it's terrible, just terrible stuff. Unless, of course, you purify the water before releasing it, but then you might as well turn around and pipe it back into the processing facility.

Uranium extraction, and processing.

As for the changing the environment "too quickly" - it's not just that, but some processes such as salts leaching out of the ground will happen whether you change things slow or fast, and if it does happen it renders the soil sterile. The only way to avoid it is to use MUCH more water than strictly needed for agriculture, in which case you'll be dealing with run off problems, and with serious erosion as desert flora are not adapted to such quantities of water.

So you'd have to introduce plantlife better suited to that environment.

As pointed out, the Kalihari is far from lifeless. It's a desert, but it's fertile. The problem is that it can't support as many people per unit of area as some other regions on Earth, but the countries that share it are all suffering from overpopulation.

Well, Botswana doesn't, it has a population of 1.6 million. But the problem here is largely economic. The desert cannot be used for large scale farming and it can't be used for manufacturing, which means that the people in Namibia and Botswana are relegated to a very, very poor lifestyle, unless the water problems can be solved.

Now, a gradual change in ground cover can, in theory, be achieved but only at the expense of wiping out most of the desert-adapted life. At which point your ground cover will require constant human intervention to maintain as the climate hasn't changed at all. If that maintenance fails the non-desert ground cover dies... and the desert life is gone so there is nothing to replace it. THEN you will have lifeless ground from horizon to horizon. At that point, you're looking a timescales longer than a human lifetime to recover. How much longer? Parts of the Middle East topsoil destroyed by damaging irrigation techniques have not yet recovered after thousands of years.
Don't get me wrong - I understand where your "what if?" came from. It is very tempting to make the desert bloom for our benefit. The problem is, experience has shown that it can (though does not always) end badly.

tbf, wasn't that due to the mongols coming along and f*cking their dams and canals up? .

[Broomstick]

What lead to vast swaths of territory around the Mediterranean (not just the Middle East but also parts of Greece and North Africa and such) becoming so degraded are a number of factors. Yes, invaders played a role, but they didn't cause the soil salt content of all those areas to rise (deliberate salting aside, those were very localized incidents). They didn't cause the massive erosion which, because the eroded landscape is now so familiar to us, we don't even recognize as diminished. They didn't cut down all the fabled cedars of Lebanon. Many of the peoples who did that damage honestly did so because they didn't know any better. We do.

It's not that you couldn't safely and sustainably irrigate part of the Kalahari region to the benefit of those who live there. You could. The problem is that it can be easy to screw this sort of thing up. If it's done I'd want to see it done right.

Oh, by the way - the salt produced by desalinization can be sold. Salt is still worth money. In addition to using it in food salt is used in a lot of chemical processes.

[PainRack]

What lead to vast swaths of territory around the Mediterranean (not just the Middle East but also parts of Greece and North Africa and such) becoming so degraded are a number of factors. Yes, invaders played a role, but they didn't cause the soil salt content of all those areas to rise (deliberate salting aside, those were very localized incidents). They didn't cause the massive erosion which, because the eroded landscape is now so familiar to us, we don't even recognize as diminished. They didn't cut down all the fabled cedars of Lebanon. Many of the peoples who did that damage honestly did so because they didn't know any better. We do.

It's not that you couldn't safely and sustainably irrigate part of the Kalahari region to the benefit of those who live there. You could. The problem is that it can be easy to screw this sort of thing up. If it's done I'd want to see it done right.

Oh, by the way - the salt produced by desalinization can be sold. Salt is still worth money. In addition to using it in food salt is used in a lot of chemical processes.

I was under the impression that the salt produced by desalinisation itself is not fit for commercial consumption without further processing...

[Broomstick]

Sea salt isn't pure sodium chloride, there are other chemicals in it as well. How much further you need to refine it depends on what you are using it for. But really, ANY source of salt is likely to require further refining prior to many uses.

[Psychic_Sandwich]

I was under the impression that the salt produced by desalinisation itself is not fit for commercial consumption without further processing...

So build a plant to do the processing. That sort of thing is exactly what sub-Saharan Africa needs; salt is extremely useful in many industrial processes. For example, if they're desalinating seawater, they're going to get some potassium salts, which can be used to make fertiliser, on top of the usual sodium chloride. They'll also get magnesium and calcium salts in about the same quantity as potassium, but I don't know what those can be used for.

[Broomstick]

Magnesium salts can be used in tofu production as a coagulant. It can be used as a de-icer in place of sodium chloride and is supposedly less toxic to roadside plant life and less corrosive to the road (probably more expensive, though). Since it tends to absorb water it can also be used for dust control, even around livestock if you don't go too crazy with it. Probably has other uses I'm not aware of, particularly in the chemical industry.

Calcium salts I'm less familiar with, but a quick search show uses from desiccants to medicinal uses to use in cement formulas and no doubt other things.

Basically, sea salt, with its variety of chemicals, is a definite source of all sorts of useful things as long as an economic means of extraction can be found. It can be sold for the shaker on the dinner table or as a raw material for the chemical industry or, as mentioned, you could build a factory to refine it next to your desalination plant.

Again, this assumes a method at all reasonable. Apparently most currently running desalinization plants do not try to sell off the brine/salt.

[Master of Cards]

(Disclaimer: My understanding of geology is limited to what I've picked up from playing Dwarf Fortress.)

You could, but if it's below sea level then the water table ought to be close enough to the surface that it's equally or more economical to sink wells.

That actually won't help at all. Water Tables and Aquifers require an aquitard to contain the groundwater. That aquatard could be anything from a bed of shale or beds of clay.

[muthukumaran]

Water is a source of life but the world has a total of 1.65 billion km3 of Water. However, only 0.3% of this total quantity is theoretically usable as a fresh water, and only 10% of that i.e. 0.03% of the world’s water is capable of economical utilization.

In the environment report ‘Global 2000’ the following comments occur:
“The notion that water is a freely available resource will no longer be encountered anywhere in the world in 20 years time".

Worldwide sea water desalination has been a very effective and economical way of producing potable water for drinking and industries. It is a myth that, sea water desalination is so exorbitantly expensive that it is unaffordable.


http://canadianclear.com/desalination.html

http://canadianclear.blogspot.com/