Milking fog: the science of collecting drinking water

DPA

There is more to fog than you might think. Hundreds of litres of water, for example, and most of it of such a high quality that it can be drunk. It is possible to capture that water using nets and a group of experts in Germany have been discussing the concept of “milking fog” to supply drinking water in arid regions of the earth.

London once had a reputation as a foggy city but less well known is the mist of Iquique in northern Chile. However, this coastal city on the Pacific is a Mecca for fog scientists, according to Professor Otto Klemm. The climatologist’s eyes light up every time he mentions the place. “The fog is very dense there -- perfect for milking.” Klemm works at the Institute of Landscape Ecology at the University of Munster. By “milking” he means capturing fog for the purpose of scientific study. But the enormous nets Klemm and other scientists place in the landscape of South America and elsewhere are also used to collect drinking water.

The subject was discussed at the recent fifth International Conference on Fog, Fog Collection and Dew in Munster in northern Germany. Some 140 experts on fog from over 30 nations came together for the first time in Europe to discuss the topic.

Dry regions of the earth such as Iquique, which lies at the edge of the Atacama desert, have plenty of fog, a fact that could prove very useful to coming generations. Desert fog can supply water to areas where it is in short supply or where it may be scarce in future. “We’re not just talking about South America or Africa. Spain, for example, will probably experience a shortage of water in 50 to 100 years time.” Spain is already considering diverting rivers and building huge desalination plants.

A few regions in Spain, however, have plenty of fog. “There is a mountain chain on Spain’s eastern coast, for example, in the region around Valencia close to the sea. It has a similar geography to the Pacific coast of South America and Africa’s east. Clouds form over the sea, move over the land and fog is trapped by the mountains which can be milked,” says Klemm. But he also points out that milking fog cannot solve the problem of water shortage -- “at least not on a big scale.” But the German charity the Water Foundation is increasingly looking at fog as a source of water. “A few years ago we were laughed at. But we managed to achieve some success supplying water to small farmers and schools in Eritrea,” says Ernst Frost from the foundation. “In the foggy season it is possible to collect up to 170 litres of top quality water a day with a net. That’s enough for a really big family.” It has proven to be difficult, however, to train locals to maintain the nets. Frost says more education must be invested in that area. Because many Africans cannot afford to buy water from a tanker truck many women and children must walk miles to the next waterhole.

Klemm also highlights the low cost of collecting water with a net that costs about 13 dollars. The frame to support the net can be made of materials found at the site where it’s used. It is also not necessary to specially manufacture the nets. “The nets are made from woven synthetic fibres and are the same nets already used in many hot regions to provide shade from the sun,” he says.

The experts attending the conference also discussed ideas for using satellites to locate fog. Such information is already used by weather forecasters and by air traffic controllers. “But much of our work is basic research. We investigate what constitutes fog, how it develops, how polluted it is and what chemical reactions are taking place in the fog.” Klemm is conducting part of that research in a fog—rich forest in Taiwan. He has spent many nights there with local researchers trying to learn more of the secrets that are hidden in fog.