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Catch the cloud: Fog Harvesting-an alternative, clean, atmospheric water resource for the dry spell period

GHANASHYAM SINGH YUREMBAM (PI), ARPANA MANGER (JRF)

In the present scenario of climate change and an ever-increasing population, the availability of fresh and clean water is becoming a major problem worldwide. This water scarcity situation gets aggravated more during the dry spell season (winter); therefore exploring new water resources is the need of the hour. It is estimated that almost a third of the global population faces a scarcity of freshwater, due to water stress and shortages (Kummu et al. 2010). So, to preserve and sustain the global water supplies, alternative and sustainable technologies for the collection and distribution of freshwater must be explored. A plethora of options are available to improve the water use efficiencies, but these may not be sufficient to make the conventional water resources such as surface water in rivers and lakes, reservoirs, and aquifers meet human needs in many regions facing severe water shortages. Therefore, countries, regions, and communities facing water scarcity are increasingly looking at unconventional water resources to narrow down the gap between water supply and demand. Among the different sources of unconventional water, harvesting fog water is a promising, yet relatively unexplored and can be an important potential source of meeting the demands of water in areas of coastal, high-altitude, and forested regions. This green technology is reportedly most suitable for areas with high humidity and prone to fog formation.
Fog is a potential and alternative source of water that could be harvested using the innovative technology of fog collection systems. Fog can be defined as a cloud that touches the ground surface. Naturally, fog is formed through the cooling of air to below its dew point (producing advection and radiation fog) or by adding water vapour and thereby increasing the dew point (producing steam fog or frontal fog). In general, seven types of fog can be distinguished (LA Bruijnzeel et al., 2005) based on location and process of fog formation and the rest are based on geographical terms. Orographic fog is the type of geographical fog formed during uphill transport and adiabatic cooling of humid air masses. A combination of an ocean/waterbody with a near cost mountainous region is a favourable setting for collecting fog water (E Linacre, J Hobbs, 1987). Fog may represent a water input in cloud-immersed ecosystems, but may also be of practical use for human activities such as reforestation or agriculture in areas with low precipitation (Klemm et al., 2012). Harvesting of such moisture-laden fog from the air using simple low-cost water harvesting collection systems will have the potential to provide an alternative source of freshwater. Fog harvesting is the collection of water droplets from moisture-laden air by the installation of fog harvesting apparatus. Passive fog gauges generally consist of one or several screens of either vertical parallel filaments or a cross-linked open fabric where wind-driven fog water droplets first impact, condenses then droplets coalesce with one another to eventually increase their size and finally gets detached to drain into a collecting chamber. The shapes of the collector vary in different geometries from a rectangular mesh to cylindrical or polyhedral. Capturing water from the air and fog are often overlooked but hold great promise for a supply of clean water. Fog harvesting technology is particularly suitable for mountainous areas (400 to 1200 m) where communities often live in remote conditions, capital investment and other costs are generally found to be low in comparison with conventional sources of water supply (UNEP, 1997b). Around 3800 litres per day can be collected from a collecting surface area of about 70 m2 (Schemenauer et al, 2004).
The high potential areas for the implementation of this technology are coastal and hilly terrains where frequent fog events are common, especially in winter. Moreover, the climatic conditions of northeastern states of India especially Sikkim, Manipur, Arunachal Pradesh, Mizoram, and Nagaland are ideal for water augmentation during the dry spell season. Likewise, Sikkim, a northeastern state in the Eastern Himalayas, is known for its immense biodiversity and substantial water resources. However, due to growth in population, and industrialization, water scarcity is increasing especially during winter and is often a water-scarce period as compared to other seasons in Sikkim. Rainfall remains the principal mode of recharge of surface water, streams, springs and kholas in mountains. Due to its sloppy mountainous terrain, most of the rainfall drains very fast leading its way to the mighty Teesta and Rangeet. About 80% population of Sikkim across the region depends on springs, rivers, lake water (Sikkim First) and they further tapped water through pipelines and distribute it by the gravity method for their consumption, kitchen gardens, farms, cattle and poultry, etc. The changing pattern of rainfall, erratic rains and frequent droughts have resulted in the drying up of springs in many parts of the state, therefore increases the vulnerability of livelihoods for the people of Sikkim. Also as per a study conducted by International Mountain Development (Athar Parvaiz. 2017, The Wire), there is a major need for more research on the Himalayan precipitation process, as most studies have excluded the Himalayan watershed due to the regions extreme, complex topography and lack of adequate rain-gauge data. With such a numerous technology for water conservation such as rainwater harvesting, groundwater collection, desalinization and reclamation of wastewater etc., there's still a scarcity of water almost everywhere. To improve the quality and quantity of water in the region there is a need for an alternative approach. Fog harvesting is a new and green technology of water harvesting in which we can take from nature and implement for our purpose. Many researchers have quoted that the water harvested is even suitable for drinking as the fog gets purified naturally through sunlight. Besides this, fog harvesting is a very easy technique to maintain with no requirement of energy. This technology only utilizes the natural conditions surrounding and gravity flow. With this tune of potential solutions to the water scarcity solutions especially in the dry spell period, fog harvesting technology seems to be the need of the hour for a clean and safe quantum of water harvesting. As ongoing research, the College of Agricultural Engineering & Post Harvest Technology (CAEPHT, Ranipool, Sikkim, CAU-Imphal) is presently working on a Department of Science and Technology (DST) sponsored project on the development and feasibility of Fog Harvesting mechanism in Sikkim.
For further details, the PI of the project may be contacted at gyurembam@gmail.com
(Dr. Ghanashyam Singh Yurembam
Assistant Professor,
Soil & Water Conservation  Engg.
College of Agricultural Engineering & Post Harvest Technology (CAU-Imphal)
Ranipool, Gangtok – 737135 (Sikkim)


Sikkim at a Glance

  • Area: 7096 Sq Kms
  • Capital: Gangtok
  • Altitude: 5,840 ft
  • Population: 6.10 Lakhs
  • Topography: Hilly terrain elevation from 600 to over 28,509 ft above sea level
  • Climate:
  • Summer: Min- 13°C - Max 21°C
  • Winter: Min- 0.48°C - Max 13°C
  • Rainfall: 325 cms per annum
  • Language Spoken: Nepali, Bhutia, Lepcha, Tibetan, English, Hindi