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Here's an idea I posted back in 2010 on SF writer Charlie Stross' blog:
[Cut interesting stuff about mass desalination, uses for brine in solar-thermal storage, direct wind-electricity conversion, increasing evaporation and rainfall with passive boundary layer disruptors.]
Which brings up another thought - the outflow of the major rivers into the Mediterranean and east Atlantic is mostly wasted. Perhaps the smart solution to greening the Sahara is just to build bloody big pipes to move the fresh water. Neutral to slightly positive buoyancy, guyed to the seafloor, deep enough to be mostly out of harms way but shallow enough for divers to repair. The sea salinity would be preserved by leaving most of the rivers' waters to go out to sea, and by the fact that the water will only be temporarily held by the new Saharan ecosystem, in the long run raining back into the sea (and providing more cloud cover on the southern Mediterranean shore which could make the waters cooler and thus more fertile.) A pressurized system would be desirable to move the water and keep the seawater out, so the pipes could be made from tensile materials, such as flexible plastics which would also prevent corrosion and allow integrated safe anti-fouling compounds (silver ions, not too expensive because of the low amounts needed). Using flexible sheet materials, and looking at the cube-square law for very big pipes (hoses, really), the mass of the system apart from the gravel in the anchors would be less than 1/10,000 the water in the system and on the order of 1/100,000,000 of the water delivered in a year. So even if a ton of water is worth a penny and a ton of hose costs $100,000, it would still have a gross payoff of 10:1 in a year, more than enough to pay for the rest of what would be needed. It's hard to find that kind of economy in a desalination scheme.