If you’re thinking of building and installing a single fog collector, these pages will help get you started.
Traditionally, fog collection projects have occurred in arid, rural, high altitude environments in developing countries that are populated by small villages or clusters of homes. Many of these small communities have water challenges as traditional water supplies become insufficient, polluted, or simply expire. Fog collection has proven to be a reliable water source for small communities when managed properly. NGO’s and/or relief organizations are traditional sponsors of fog collection projects. However, there is also growing interest in fog collection as a source of water for agriculture and irrigation.
A single fog collector, (SFC) – also referred to as a small fog collector – is generally used to evaluate the suitability of a specific area for a larger fog collection project. If the climatic conditions are conducive to fog collection and the collector is situated properly, the SFC will produce between 5-10 L of water a day. Some SFC’s have produced much larger amounts. If a SFC produces a consistent amount of water over a period of a year (allowing for seasonal variations) then a larger fog collector placed in the same location will reliably produce a proportionally greater amount of water on an ongoing basis.* One large fog collector, with a 40 m2 collecting surface, will typically produce an average of 200 L per day throughout the year. On some days no water is produced. On other days as much as 1000 L will be generated. The variability depends on the site. There are both day to day variations in fog-water production as well as seasonal variations, as is the case with rainfall.
The placement of the SFC must be carefully chosen and the volume of water it produces should be recorded on a daily basis over a period of several months. Ideally, a SFC that produces a sufficient volume of water should be left in place for a full year to record seasonable variations in collection rates. This will enable a community to plan in advance for dry periods, if they occur.
It must be pointed out that, when measuring fog using an SFC, it is vital to distinguish whether the collected water comes from fog, rain or drizzle. This is because for the purposes of collecting water from the atmosphere on a large scale, the way of collecting each size of water drop varies. Only in extremely arid regions, such as the north of Chile or coastal Peru, is the assumption of a negligible contribution by precipitation valid. In order to sort out the amount of precipitation that the SFC is collecting, rain should be measured with a rain gauge placed with its mouth at the ground surface.
Wind speed and direction should also be measured. Then, using the procedures outlined by Schemenauer and Cereceda (1994b), the partitioning of the water collected into fog and rain can be properly done. This helps guide the development of the project but it makes no difference to the user of water if it is a mixture of water and rain.
Many of the questions that arise when considering a fog collection project can be answered at our frequently asked questions page on our main web site. The information there is drawn from both more than 20 years experience and from published papers and reports. More information is available in the FogQuest Fog Collection Manual (2005), which can be purchased from FogQuest. Detailed scientific and technical information is available, in the form of many published papers, to our members in the Members’ Section of the FogQuest main web site.
SFC field guide 