• Eddie Mohoebi
Spokesperson, Dept of Rural
Development and Land Reform
+27 82 550 1445
Emily van Rijswijck
Every morning a small creature, the Stenocara gracilipes or Namib desert beetle, turns its back to the oncoming ocean fog and waits. Soon, water drops appear on its back – and then slide down special channels formed on its hardened shell, into the beetle’s waiting mouth.
The little beetle has successfully collected all the water it will need for the day.
And if a small beetle can do it, so can humans, as can be confirmed by at least three successful fog harvesting projects which are up and running around South Africa – in Lepelfontein in the Northern Cape, at Lusikisiki in the Eastern Cape and at the small rural Tshanova Primary School in the Southpansberg mountains in Limpopo.
The tender for a feasibility study has closed and a service provider will be appointed soon, confirmed departmental spokesperson Eddie Mohoebi.
The pilot project will get underway in 2012 with possible sites identified near Piet Retief, Donkerhoek, Madadeni, Shibange or Ntunda. The appointed contractor must also train community members to operate and maintain the system.
Part of the feasibility study will entail establishing the frequency of fog in the area.
“The outcome of the feasibility study will determine the area suitable for fog harvesting technology. At this point in time, it is difficult to determine where exactly the fog will be harvested,” says Mohoebi.
Excellent fog harvesting potential
The Mpumalanga escarpment has one of the highest precipitation levels in the country and offers excellent fog harvesting potential, according to Dr Anthony Turton, environmental advisor and water specialist.
Fog harvesting as a source of potable water in water scarce areas has been around for a long time, he says.
The first project of this nature in South Africa was conducted at Mariepskop in Mpumalanga in 1970. The harvesting yielded an astonishing 31 000 litres per month to the South African Air Force working at the radar station located there. It was then introduced as an interim water measure.
Prof Jana Olivier, a renowned climatologist, has been involved with fog harvesting research for many years. She believes the technique offers a viable option to communities, yet is largely ignored by water provision authorities.
In 2001 Olivier and her colleagues conducted a study on possible fog harvesting on South Africa’s west coast, which confirmed that this unconventional source of water has great potential, especially in water poor areas.
The study found that on average, yields of around 4.6 litres of water were collected per square metre of collecting surface per day. Maximum daily yields approached 4 000 litres. The findings were published in the Water Research Commission‘s Water SA journal in October 2002.
“The quality of the water was excellent. It appears that fog water collection may have considerable potential as an alternative water source at many other locations on the west coast of South Africa,” the study notes in the abstract.
Mahoebi says the department is similarly optimistic about the potential water yields of the new target areas, with the pilot project aiming to produce 5 000 to 15 000 litres of water per day.
“If the pilot project yields positive results, we will consider a large scale roll-out to feed into local water distribution networks,” adds Mohoebi.
A growing but dry country
According to the Department of Water Affairs only 35 % of South Africa’s surface area receives more than 500 mm of rain a year, with precipitation levels diminishing the further west one moves into the interior.
In South Africa, the highest fog frequencies are mostly located along the very dry west coast and in mountainous regions in the eastern and southern parts of the country, which experience an influx of moist air from the coast.
For fog collection to be effective, the site must be in an area where fog occurs frequently throughout the year, and lasts for a few hours at a time.
“Fog harvesting sites must be at least 1 000 metres above sea level and receive at least 90 days of fog precipitation per year for such a project to be viable,” confirms Mohoebi.
The water content of the fog should be high, and the fog must be accompanied by wind to ensure that a large enough volume of moist air is blown through the collecting screens.
The downside of such a project is that it yields relatively small amounts of water, which, depending on the area, may have to be treated as a result of contamination.
Simple equipment that’s easy to maintain
Yet the equipment needed is simple and requires little maintenance. A netting structure is erected between two poles and placed perpendicular to the prevailing wind.
Wind blows the low mist cloud into the nets where the water is intercepted. The water droplets aggregate, or gather together until they overcome gravity and slowly trickle into a gutter attached to the bottom of the net.
A simple sand filter removes solid impurities and the water is then channelled via pipes to water containers close by.
Before the Tshanova school got its fog harvesting apparatus, the 300 pupils had to bring their daily water supply with them as there was no infrastructure in place. Now, the fog harvester provides on average about 150 to 250 litres of water per day.
Turton himself is cautious about a project of this nature offering any long term or real solutions without making allowances for a more balanced approach to South Africa’s growing water shortages.
“You cannot fog harvest the volume of water we will need in this country,” he believes.
Instead Turton advocates for a complete behaviour change around water usage in general, with citizens changing from water consumers into water stewards.
“We should all become custodians of water,” says the 2010 South African Environmentalist of the Year.
Turton says the only solution is for South Africa to respect its wetlands which play a critical role in keeping river systems healthy. Greater emphasis should also be placed on educating children about water, he adds.