Inspired by beetles... a worldwide water harvesting proposal

More than 97% of the world’s water is salty but researchers are investigating using climate change itself along with a vertical water capture structure to harvest fresh water

Thu, 12 Jan, 2023 - 12:05

Richard Collins

Water water everywhere, nor any drop to drink

Namibia’s Skeleton Coast, where the Atlantic meets the desert, is ‘the graveyard of a thousand ships’. Rusting skeletal hulls, topped by perching seabirds, protrude from the sand.

Thick fogs roll in from the ocean, blinding pilots to danger; trapped inside great rolling waves, ships were doomed to disaster. Sailors who drowned were the lucky ones, those struggling ashore died of thirst and starvation; the Namib Desert gets less than 10mm of rainfall per year.

But wildlife thrives. Beetles face into the foggy morning wind atop the dunes, limbs spread-eagled to trap the airborne moisture. Desert-loving plants and lichens depend on the vapour. Thus begins a food-chain; black rhinos elephants and giraffes browse the surroundings of Etosha’s salt ‘pan’ inland. There are antelope cheetahs and lions.

Researchers at the University of Illinois, in a paper just published, propose harvesting water Namib beetle-style, worldwide.

According to UN Water, 2.3 billion people live in ‘ water stressed’ countries, with 733 million of them in ‘high and critically stressed’ regions. (Areas withdrawing a quarter or more of their renewable freshwater annually are deemed to be ‘stressed’.)

Roughly a sixth of the world’s population lives in ‘severely constrained agricultural areas’. About two-thirds of people experience ‘severe water scarcity’ during at least one month of the year. ‘Thank god we’re surrounded by water’, as the song says, but droughts occur even in Ireland.

Schematic illustration of Afeefa Rahman, Praveen Kumar, Francina Dominguez's proposed approach for capturing moisture above the ocean surface and transporting it to proximal land for improving water security

A study of African elephants at North Carolina Zoo showed that each uses an average of 325 litres of water per day. Demand can exceed 500 litres in hot weather. A horse sheds up to 40 litres of sweat a day. These are extreme examples, but all wild creatures need water and many have to cope with shortages.

Waste water recycling, sewage treatment and desalination, have a major part to play but these, the experts say, won’t be enough to meet future demands in many regions of the world. More than 97% of the world’s water is salty, but the oceans produce huge amounts of water vapour through evaporation.

This falls as rain, or is deposited as dew, over land. The problem, now, is to harvest the vapour. Cloud seeding techniques are not up to the job but the Illinois researchers suggest that an alternative ‘vapour harvesting technology’ could help address the problem.

"The atmosphere above the oceans proximal to the land can yield substantial sufficient fresh-water to support large centres of population," they claim.

Some species of Namib Desert Darkling beetle face into the foggy wind and stick their rear end up in the air (fog-basking behavior) which is thought to be just as important as body surface structure for harvesting water from the air

A vertical moisture capture structure 210m wide and 100m high, located offshore, "can provide a sufficient volume of extractable moisture to meet the daily potable needs of 500,000 people". Their calculations indicate that the approach would be effective in many drought-prone regions of the world.

Climate change is causing more droughts. Paradoxically, it also increases evaporation rates at sea and warmer air holds more moisture. These effects might render water harvesting more effective.

"An elegant feature of this proposed solution is that it works like the natural water cycle" according to the University website, a sentiment with which the Namib beetles would no doubt concur.