Climate Change Adaptation - Climate Resilient Agriculture for Ensuring Food Security - page 243

Fig. 12.11 Fog harvesting

12.3.4.2 Disadvantages
The initial cost of drip irrigation systems can be
higher than other systems. Final costs will depend
on terrain characteristics, soil structure, crops,
and water source. Higher costs are generally
associated with the costs of pumps, pipes, tubes,
emitters, and installation. Unexpected rainfall
can affect drip systems either by fl ooding emit-
ters, moving pipes, or affecting the fl ow of soil
salt content. Drip systems are also exposed to
damage by rodents or other animals. It can be dif-
fi cult to combine drip irrigation with mechanized
production as tractors and other farm machinery
can damage pipes, tubes, or emitters.

ern Africa (Angola, Namibia), South Africa,
Cape Verde, China, Eastern Yemen, Oman,
Mexico, Kenya, and Sri Lanka.
Fog harvesting technology consists of a single
or double layer mesh net supported by two posts
rising from the ground. Mesh panels can vary in
size. The ones used by the University of South
Africa in a fog harvesting research project mea-
sured 70 m 2 (UNISA 2008 ), whereas in Yemen, a
set of 26 small Standard Fog Collectors (SFC) of
1 m 2 were constructed. The material used for the
mesh is usually nylon, polyethylene, or polypro-
pylene netting (also known as “shade cloth”)
which can be produced to various densities capa-
ble of capturing different quantities of water from
the fog that passes through it (UNEP 1997 ). The
collectors are positioned on ridgelines perpen-
dicular to prevailing wind and capture and collect
water when fog sweeps through (Fig. 12.11 ). The
number and size of meshes chosen will depend
on the local topography, demand for water, and
availability of fi nancial resources and materials.
According to FogQuest, the optimal allocation is
single mesh units with spacing between them of
at least 5 m with additional fog collectors placed
upstream at a distance of at least ten times higher
than the other fog collector. In South Africa, the
university research project arranged several mesh
panels together in order to expand the water
catchment area and provide greater stability to
the structure in windy conditions (UNISA 2008 ).
The collector and conveyance system func-
tions due to gravity. Water droplets that collect on

12.3.5 Fog Harvesting

Fogs have the potential to provide an alternative
source of fresh water in dry regions and can be
harvested through the use of simple and low-cost
collection systems. Captured water can then be
used for agricultural irrigation and domestic use.
Research suggests that fog collectors work best
in locations with frequent fog periods, such as
coastal areas where water can be harvested as fog
moves inland driven by the wind. However, the
technology could also potentially supply water in
mountainous areas if the water is present in stra-
tocumulus clouds, at altitudes of approximately
400-1,200 m (UNEP 1997 ). In addition to Chile,
Peru, and Ecuador, the areas with the most poten-
tial to benefi t include the Atlantic coast of south-