Climate Change Adaptation - Climate Resilient Agriculture for Ensuring Food Security - page 244

Table 12.5 Water collection rates from f og collectors

12.3.5.1 Advantages
Atmospheric water is generally clean, does not
contain harmful microorganisms, and is immedi-
ately suitable for irrigation purposes. In a number
of cases, water collected with fog harvesting tech-
nology has been shown to meet World Health
Organization standards (UNISA 2008 ). The envi-
ronmental impact of installing and maintaining
the technology is minimal. Once the component
parts and technical supervision have been secured,
construction of fog harvesting technology is rela-
tively straightforward and can be undertaken on
site. The construction process is not labor inten-
sive, only basic skills are required, and, once
installed, the system does not require any energy
for operation. Given that fog harvesting is particu-
larly suitable for mountainous areas where com-
munities often live in remote condition, capital
investment and other costs are generally found to
be low in comparison with conventional sources
of water supply (UNEP 1997 ).

Total collecting
surface (m 2 )

Water collected
(liters/day) Project

University of South
Africa

70 3,800

Yemen 40 4,500
Cape Verde 200 4,000
Dominican Republic 40 4,000
Eritrea 1,600 12,000
Sources: UNISA ( 2008 ), Schemenauer et al . ( 2004 ), Wash
technology, FogQuest

the mesh run downwards and drip into a gutter at
the bottom of the net from where they are chan-
neled via pipes to a storage tank or cistern.
Typical water production rates from a fog collec-
tor range from 200 to 1,000 l per day, with vari-
ability occurring on a daily and seasonal basis
(FogQuest). Effi ciency of collection improves
with larger fog droplets, higher wind speeds, and
narrower collection fi bers/mesh width. In addi-
tion, the mesh should have good drainage
characteristics. Water collection rates from fog
collectors are shown in Table 12.5 .
The dimensions of the conveyance system and
storage device will depend on the scale of the
scheme. Storage facilities should be provided for
at least 50 % of the expected maximum daily vol-
ume of water consumed. For agricultural pur-
poses, water is collected in a regulating tank,
transferred to a reservoir, and then fi nally into an
irrigation system that farmers can use to water
their crops (UNEP 1997 ).
Drought caused by climate change is leading to
reductions in the availability of fresh water supplies
in some regions. This is having an impact on agri-
cultural production by limiting opportunities for
planting and irrigation. Fog harvesting provides a
way of capturing vital water supplies to support
farming in these areas. Furthermore, when used for
irrigation to increase forested areas or vegetation
coverage, water supplies from fog harvesting can
help to counteract the desertifi cation process. If the
higher hills in the area are planted with trees, they
too will collect fog water and contribute to the
aquifers. The forests can then sustain themselves
and contribute water to the ecosystem, helping to
build resilience against drier conditions.

12.3.5.2 Disadvantages
Fog harvesting technologies depend on a water
source that is not always reliable, because the
occurrence of fogs is uncertain. However, certain
areas do have a propensity for fog development,
particularly, mountainous coastal areas on the
western continental margin of South America.
Further, calculation of even an approximate quan-
tity of water that can be obtained at a particular
location is diffi cult (Schemenauer and Cereceda
1994 ). This technology might represent an invest-
ment risk unless a pilot project is fi rst carried out
to quantify the potential water rate yield that can
be anticipated in the area under consideration.

12.3.6 Interventions

12.3.6.1 Research and Development

￿ Development of crop variants with high water-

use effi ciency levels such as those capable of
regulating stomata closure and opening, etc.

￿ Exploring structural and technological

measures to enhance water-use effi ciency with
reference to various types of crops, soils,
agroclimatic zones, etc.