Could water vapor become a reliable source of fresh water?

Although a nearly limitless supply of fresh water exists in the form of water vapor above Earth’s oceans, it currently remains untapped. According to a new study led by the University of Illinois Urbana-Champaign, an investment in new infrastructure capable of harvesting oceanic water vapor could be a feasible and sustainable solution to limited supplies of fresh water in various locations around the globe.

The scientists evaluated 14 water-stressed locations across the world for the feasibility of a hypothetical structure that could capture water vapor from above the ocean and condense it into fresh water. 

“Water scarcity is a global problem and hits close to home here in the U.S. regarding the sinking water levels in the Colorado River basin, which affects the whole Western U.S.,” said study corresponding author Praveen Kumar, an expert in Civil and Environmental Engineering at the University of Illinois. “However, in subtropical regions, like the Western U.S., nearby oceans are continuously evaporating water because there is enough solar radiation due to the very little cloud coverage throughout the year.”

Previous wastewater recycling, cloud seeding, and desalination methods were only partly successful. For instance, desalination plants face sustainability issues due to the brine and heavy metal-laden wastewater produced. 

“Eventually, we will need to find a way to increase the supply of fresh water as conservation and recycled water from existing sources, albeit essential, will not be sufficient to meet human needs. We think our newly proposed method can do that at large scales,” Kumar said.

By performing atmospheric and economic analyses of the placement of hypothetical offshore structures 210 meters wide and 100 meters high, the researchers concluded that capturing moisture over ocean surfaces could be feasible for many water-stressed regions worldwide, and provide fresh water for large subtropical population centers. 

“The climate projections show that the oceanic vapor flux will only increase over time, providing even more fresh water supply,” said study lead author Afeefa Rahman, a PhD student at the University of Illinois. “So, the idea we are proposing will be feasible under climate change. This provides a much needed and effective approach for adaptation to climate change, particularly to vulnerable populations living in arid and semi-arid regions of the world.”

Interestingly, one of the most elegant features of this proposed technique is that it works in a similar way to the natural water cycle. “The difference is that we can guide where the evaporated water from the ocean goes,” concluded senior author Francina Dominguez, an atmospheric scientist at the same university.

The study is published in the journal Nature Scientific Reports.

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By Andrei Ionescu, Earth.com Staff Writer

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