Fog-water harvesting along the West Coast of South Africa: a feasibility study

Abstract

Many parts of the West Coast of South Africa experience severe water shortages throughout the year. Despite the meager rainfall, however, the region is subject to a high incidence of fog which might provide water for water-poor communities. This paper investigates the fog water potential of the area. Since fog water collection rates are to some extent dependent upon the spatial and temporal characteristics of fog, these aspects were investigated. Pilot fog collectors were erected at six West Coast sites and the water collection rates measured over a three to four year period. It was found that the incidence of fog is mostly confined to the coastal zone below the 200 m contour line with fog frequency decreasing with latitude within this zone. The highest water collection rates were recorded at Cape Columbine where volumes in excess of 2.5 l/m2 of collecting surface can be expected to be collected per day. Of this, approximately 90% is due to fog deposition alone, while rainfall contributes to the remaining 10%. The quality of the water is good and fit for human consumption. WaterSA Vol.28(4) 2002: 349-360