Capturing water from fog - on a large scale - could provide some of the driest cities in the world with drinking water.
This is what researchers in Chile have concluded after studying the potential of fog harvesting in the desert city of Alto Hospicio in the north of the country, where the average rainfall is less than 0.19in (5mm) per year. However, clouds of fog that regularly gather over the mountain city are an untapped source, researchers say.
Capturing fog water is remarkably simple - a mesh is hung between poles, and when the moisture-laden clouds pass through that fine mesh, droplets form. The water is then channelled into pipes and storage tanks. Lead researcher Dr Virginia Carter Gamberini, from Universidad Mayor, calculates that on an annual average water collection rate, one square metre of mesh - through which the moisture-laden clouds pass - can capture of 2.5 litres per day.
This fog capturing system has been used at a small scale for several decades, mainly in rural South and Central America, but also in Morocco, on the edge of the Sahara Desert. Dr Carter says a "new era" of much larger-scale fog harvesting could provide a more secure and sustainable supply of water in urban environments where it is most needed.
The researchers calculate that 17,000 square metres of mesh could produce enough water to meet the weekly water demand of 300,000 litres that is currently delivered by truck to urban slums in Alto Hospicio.
Dr Gamberini says that Chile is "very special" for its sea fog, "because we have the ocean along the whole country and we have the mountains" and her team is currently working on a "fog harvesting map" of the whole country. "Water from the clouds", as Dr Carter describes it, could, "enhance our cities' resilience to climate change, while improving access to clean water."