Many countries suffer low levels of rainfall. Areas such as Saudi Arabia have managed to make a lot of land arable by using centre-pivot irrigation schemes:
but they have done so mainly by using water from aquafers that is not being replenished. Fossil water supplies such as these would eventually run out. By contrast, the UAE has considered capturing clouds from the Indian Ocean and somehow dragging them to the UAE where they could be seeded to irrigate land. There are many current and near future water capture and desalination schemes, and new techniques are developed every month that might help to make these better and cheaper options, but most of these are intended to provide water for families, not for massive scale irrigation. Cloud capture would seem somewhat problematic – how could a cloud be encased, and given the enormous weight of water involved if it is to be useful, how could it be transported? Huge plastic bags towed by airships? Surely not!
Perhaps not plastic, but how about graphene? Being extremely thin makes a a graphene membrane very lightweight, and though graphene is porous to water, only a small fraction of a cloud would go missing on the way. We can’t make large graphene sheets yet, let alone anything big enough to encase a cloud, but we’re looking at the far future here, and by 2040-2050, surely that would be perfectly feasible. One of my own ideas, folded graphene, would allow the membrane to change its shape dynamically as needed so once in the air, suspended from an airship, it could encase a cloud. See:
One of the slides in the article shows the principle of 3D shape change membrane for encasement. Excuse the poor graphics. The other applications discussed are mostly not relevant directly to cloud capture, but development of any of them would create a market mechanism to accelerate development of folded graphene generally, so the many military applications for example could help yield this useful humanitarian spinoff.
So it should be feasibly to encase a cloud. Clouds normally blow with the wind, and if their natural route was over the UAE, it would not suffer low rainfall, so the cloud must be dragged or otherwise directed. If it were dragged, by an airship for example, the overall forces needed to make progress against the wind could easily tear such a fragile membrane apart. However, physics might help.
Folded graphene would be able to change its shape enormously and quickly. This would allow a cloud to be reshaped. It could be shaped to maximise or minimise its heating by the sun, thus altering its altitude to make use of wind current differences. An encased cloud could also take the shape of a dynamic aerodynamic container with a large keel and sails dynamically protruding at various places, pointing in various directions. By making use of the different wind speeds at its range of altitudes and across its breadth, its shape could be manipulated dynamically to use the winds just like a yacht, to make progress in whatever direction is required.
The folded graphene blog also illustrates the concept of a ‘jellyfish’. Shaping the cloud in such a way and using jellyfish-style movements could propel it gently towards its destination.
Alternatively, simply making it highly aerodynamic might greatly reduce the forces needed to drag it, so an airship might then be useful.
I’m not suggesting any of these approaches could be done soon, but in 2 or 3 decades, I don’t see why it should not be feasible. By then, other approaches to obtaining fresh water via harvesting or desalination might make it irrelevant, but maybe they won’t. Maybe we could see funny shaped clouds moving the wrong direction in the sky, to drop their contents on UAE fields. Or indeed on any country suffering low rainfall.
A typical cumulus cloud is about a cubic kilometer in volume, and has about 500 tons of water. Larger clouds can be much, much heavier. A big storm-cloud could have over a million tons of water. Encasing a 1 cu km cloud needs at least 6 sq km of graphene, which at 0.763mg/sq m = 4.5kg, less than 0.001% of the total mass. Plenty of scope for using multiple layers if need be.