In parts of Chile's Atacama Desert it can go a century without meaningful rain, and the groundwater beneath its cities last refilled more than 10,000 years ago. Yet the same coastal air that starves the ground of rain carries something usable: fog. A new year-long field study concludes that "harvesting" that fog could become a practical water source not just for scattered farms but for the edges of a growing city.
Researchers tested the idea in Alto Hospicio, a fast-expanding municipality in northern Chile where roughly 10,000 people live in informal settlements. Only about 1.6 percent of those homes are connected to water networks; most residents rely on deliveries by truck. The findings appear in the journal Frontiers in Environmental Science.
Fog collectors are deliberately simple: a mesh strung between two posts intercepts wind-blown droplets, which trickle down into a gutter and on to storage tanks. The system is passive and needs no power. Across a 100-square-kilometre area around the city, the team measured yields of between 0.2 and 5 litres of water per square metre each day; at the seasonal peak, in August and September 2024, collection reached as much as 10 litres per square metre.
From rural fix to urban supply
"This research represents a notable shift in the perception of fog water use — from a rural, rather small-scale solution to a practical water resource for cities," said Virginia Carter Gamberini of Universidad Mayor, a lead author. On the study's figures, a net area of around 17,000 square metres could yield some 300,000 litres a week for the city's poorest neighbourhoods.
The approach has real limits. Fog is seasonal, running roughly May to October, the best collecting sites sit above and outside the city, and storing and distributing the water would require infrastructure that does not yet exist. Still, in a place where every litre is precious, the study reframes a modest, low-tech method as something a city could plan around rather than merely improvise.