by Prof. Dr. Werner Müller
© Copyright by Werner Müller 2014
The Sahara constantly expands southward. This is not due to intervention of man into nature. Rather, the trade winds are responsible for that blow from the northeast permanently because of the Earth's rotation. They come from the Sahara, are very dry and escape the air in the Sahel by the moisture. For the vegetation thus lack the necessary water and the plant dries. Regardless of the reduction of greenhouse gases to global warming could be slowed down a little, when the growth of the desert could be stopped. A protected and / or emerging vegetation in the Sahel would then bind greenhouse gases.
It is important to look for ways to humidify the air in the Sahara, so that the Sahel not dry out or even condensed ideally moist air at night dew and the plants so new donates moisture.
While vacationing in Egypt, I have conducted two experiments. First, a 250 ml beaker was filled with water and placed on the balcony. It took two days, are evaporated to about 10% of the content. Then 250 ml. Of water were poured into a towel with a size of about 40 x 60 cm, which was thus moistened only medium strong. I ended up hanging over a chair and let it dry in the shade. It took about 3 hours.
Thus 347.222 ml of water would evaporate per hour on a towel m² - hanging on a clothesline in the sun probably even much more. Would on a clothesline 3 m² towels hung per m² and dried only 9 hours a day, so at least 3,125 liters of water per day would evaporate and m². In a country were the 3,125 km² m³ or a pool of 25 x 25 meters on each side and 5 m depth.
For cost reasons it can only salt water from the Mediterranean Sea to be pumped by pipeline in the desert, so that it can evaporate there. It must be ensured that no salt water enters the soil and could be the groundwater stocks from which oases are fed salty. In the next step residual salt would have to be recovered after evaporation and recycled.
For the evaporation plastic hoses are attached with a steel frame on a wire, are drilled into the small holes (such tubing has my father once connected to a water tank and used for more targeted watering strawberries). The cable is provided with hooks to the towels are appended. For metal grommets must be riveted into the towels, in which fit the hook. About the hoses seawater is continuously fed and so the towels are kept permanently moist.
Towels and hoses must be replaced at regular intervals and freed from salt residues. This must be done in time, so not particularly clog the holes in the hoses. It should be possible to lay hoses and towels in containers with fresh seawater, to loosen the salt deposits again. Probably the tubes must lie in water with low salt concentration (ie really fresh seawater), while the salt from the towels with more saline water (ie water in the tubes already have been cleaned) can be washed out. The brine (oversaturated salt water in which the salt is deposited already on the ground) should probably be moved to table salt in factories with tanker trucks for cleaning and processing. A pipeline would be quickly eaten up by salt. On the outward journey, the tankers would bring drinking water for the workers of the plant and transport the brine on the way back.
For the replacement of towels and hoses, the ropes would move slowly with an engine and bypasses at a central point. Here a worker takes the saline wipes off, dismantled another worker the old hose, a third worker mounted a cleaned hose and a fourth depends on the washed cloths. It has yet to be explored, at what intervals this work must be done.
The Mediterranean Sea has a salt content of 3.8% ( http://de.wikipedia.org/wiki/Mittelmeer# Salzgehalt ), is why with 38 liters of salt per cubic meter of water to be expected; at a throughput of 3,125 km² and a cubic meter of water the 118.75 m³ salt or 1,75 40-feet-container would be filled daily.
There are still many relationships are explored. The trade winds blow in the lower layers of the atmosphere continuously from the same direction. However, it is still exploring whether the humidified air remains in this air layer and which wind direction prevails in higher air layers. It would not make sense to let it evaporate with some effort in the Sahara water so that it then falls as rain again over the Mediterranean. At least the system may have to be switched off when south wind, as long as the water vapor would rise into the upper atmosphere.
The countries in which humidification would be, would not benefit. Which would result in the ideal case in countries of the Sahel region, but not be able to finance the investments. This is especially true when in front of an agricultural use only a few years plants have to be grown, which provide for soil improvement and bind CO2. One possible financing through international capital markets in which investors would initially buying in large scale land in the Sahel for cheapest prices in order to utilize it profitably for agriculture for a relaxation of the climate situation and an improvement of the soil can be extremely risky. It would be expected to political upheavals in those countries, according to which would be expropriated again the country. A sufficiently reliable for private investors political environment could be achieved only with a re-colonization of North Africa, the politically undesirable and would be politically well unenforceable as well.
Therefore, such a project, which may be useful in combating the effects of climate change is important, be organized only through public funds. In addition to means of official development assistance as from Germany and France would the EU and the World Bank into consideration. State financing is close also because climate change is a global challenge and private investors are not interested in combating it.
First of all a university with a department of Meteorology it to be contacted regarding technical issues (which amount of water has to evaporate, so that the following night forms of precipitation, how likely is it that the water vapor is not carried to the north, ...) to comple the agenda.
In continue my attempt would be repeated under laboratory conditions to determine with precise measurements of how much water evaporates in what time, and how much water it by as large holes must be conducted in the towels. This would require an expedition with a tanker sea water, towels and clothes horses ride into the desert.
With the data an application for research funding would formulated with the created a pilot plant and its operation is to be scientifically monitored. Of particular importance would be a satellite observation, with the formation of clouds and their resolution should be documented. The data obtained should be able to calculate seriously, how many such facilities are required for a halt to the desiccation of the Sahel region, and at which locations they would be useful. Only then could the cost be calculated reliably.