New Drinking Water Source: Fog

In 1987, on the mountains a few kilometers inland, a joint Chilean-Canadian project began to investigate the science and technology associated with fog collection. In March 1992 a pipeline was completed and the fog water, from 75 collectors began to flow down the mountain to the village.

The 340 villagers now each receive 30 liters of water daily, enabling them to broaden their diets and change their lives in many ways. The villagers now have their own water authority, charge for the water consumed and maintain the water system.

"Fog collection is a resource that should be evaluated in areas where other traditional sources of water, for example, surface water, wells or rainwater collection, cannot meet the needs of the people and where a water pipeline or desalination plants are impractical or too costly, " says Robert Schemenauer, an Emeritus Research Scientist with the Department of the Environment in Canada.

"The project costs are small, the technology simple, the water of very good quality and the source sustainable for periods of hundreds or thousands of years."

He emphasizes that there is a growing need for fresh water in both developing and developed countries because of increasing populations and the contamination of existing supplies. In situations where the conditions are suitable, fog could be the answer.

"As clouds move over hills and mountains, the hilltops and ridges are enveloped in fogs. Just as the leaves and needles of trees can collect some of the water in these fogs, large artificial collectors can produce a flow of potable water," he explains.

A fog collector is simply a vertical frame that supports a section of mesh. It is typically made of two supporting posts, and cables on which the mesh is suspended.

In addition, there is a network of guy wires to support the posts, a plastic trough to collect the water, and pipes to move water from the troughs to a reservoir or cistern. Large collectors are usually 12 meters long and 6 meters high.

The mesh covers the upper 4 meters of the collector. This gives a collecting surface of 48 square meters and typical water production rates from one collector of from 150-750 liters a day depending on the site. In most projects to date a double layer of polypropylene mesh has been used.

The mesh is ultraviolet-protected and has a lifetime of about 10 years. It costs 25 cents per square meter in Chile and is available in other countries, from other suppliers, at a somewhat higher cost.

The first intensive assessment of the fog collection potential took place in 1990, and subsequently there have been a number of both private sector and institutional projects.

For the last several years the Commission of European Communities has sponsored a scientific project in the southern coastal desert.

The project uses fog water for irrigation of a plot of thousands of native and introduced tree seedlings and shrubs on the coastal hills as part of a reforestation scheme.

A new project has just been completed at Pachamama Grande, an indigenous community in the south of Ecuador at an elevation of 3,700 meters.

"The local people are participating in the project and are delighted at the prospects of having a clean water supply," says Schemenauer. This is the first project where private sector donations have played a major role in funding the fog water supply for a village.

"In the complexity of a project it is sometimes easy to lose sight of the simplicity of the water source and how basic water is to the needs of the people. But there are moments when the villagers themselves bring one back to reality," says Schemenauer.

"For example, when they call the spinning cups of the anemometers 'butterflies' or when they tell you that even the animals got sick from drinking from the previous water source, a little canal by the village."

In 1989 and 1990 a major evaluation was undertaken in the Sultanate of Oman on the Arabian Peninsula. Very high fog collection rates were measured during the period June to September during the south west Monsoon.

There are also several evaluation projects under way in Mexico and a project with two sites in Nepal. The focus of these later projects is on domestic water supplies for rural areas.

"Fog collection will not be the total answer to the world's water shortages," Schemenauer says. "However, it is an example of how we can work with what nature gives us and of how developing and developed countries can pool their skills to initiate low- technology, sustainable water projects."