Fog Collection and its Variability in the Andean Mountain Range of Colombia: A Possible Source for Water Supply?

Hydrological droughts occur naturally in some regions of the Colombian Andean watersheds, some of them associated with large-scale climatic phenomena like El Nino. The associated water scarcity is aggravated by an advancing deforestation of the native highland forests. These events have negative consequences for the environment and for human development. Low water availability in arid/semiarid regions and water scarcity in surface sources in mountainous zones could be managed partially by means of water from fog collection. To date, fog collection variability and potential use of fog water as an alternative for water supply has not been evaluated in Colombia. This study evaluates the spatial and temporal fog collection variability and analyses the potential use of fog as an alternative source of water supply in an Andean rural region of southern Colombia, which is highly affected by droughts and low water availability. Fog collection experiments were carried out, and data collection covered both dry and rainy seasons in the period 2003 - 2005, with daily data registration of fog collection and drizzle/precipitation. Twelve Standard Fog Collectors (SFC), built from polypropylene mesh with a vertical collection surface of 1.0 m2, were installed in a mountainous zone with an area of approximately 500 ha, ranging from 1,680 to 1,850 m a.s.l. Chilean meshes with several shade coefficients were tested. In order to assess the spatial fog variability, isolines of fog-water collection rates were estimated using Kriging as the interpolation method. Our results suggest a high potential for the use of fog to supply domestic water requirements in rural areas. Also, the observed collection yields are consistent with some experimental results of fog harvesting from other countries in South America. Annual average collection rates amounted to 4.2 l/m2/day for precipitation + fog, and 3.3 l/m2/day for fog only. The temporal analysis indicates that the most important month for fog collection was June with 5.3 l/m2/day for rainfall + fog, and 5.0 l/m2/day for fog only in dry days. Finally, it was observed that the tested fog collectors can be also effective devices to collect rainwater, mainly in dry seasons.