How to harvest water from thin air
November 22nd, 2010It takes a moment to understand what the six-metre high net has been set up to capture: water. The Tshiavha Primary School’s water supply is pulled out of the fog that rises over this mountainous part of South Africa’s Limpopo Province.
The school’s fog net traps 2,500 litres of water per day, more than enough for the school’s pupils to drink.
The net consists of three six-metre-high wooden poles, set up nine metres apart. Steel cables stretch horizontally between the poles, over which a double layer of 30 percent shade cloth is draped. A gutter runs along the bottom of the shade cloth to channel the water into a storage tank.
Before the fog net was installed, villagers were forced to rely on inadequate water sources including pools fed by springs, often shared with livestock.
“We did not know that we can get water from fog. It is an amazing experience. Now we drink that water,” said Samson Malumedzha, the school’s principal.
Clean water from the net has quickly resulted in reduced incidence of waterborne diseases for the school’s children.
“We used to have a serious problem caused by lack of [clean] water; now that is the past,” he said. Besides the net, the community has also placed gutters on the school’s roof to trap more water.
“The project has helped us here at school and community. In our school, we have a school garden that is irrigated with fog-harvested water.”
Over a third of the more than 4,200 schools in Limpopo Province lack a reliable water source, affecting the health of some 54,000 children according to a University of Pretoria study that used geographic information systems data to find locations suitable for harvesting rainwater from fog. The necessary ingredients are regular fog with a high water content and sufficient wind to blow this moist air through the collecting net.
The study established a number of potential sites, including Tshiavha which is at a suitable elevation in the mountains facing the fog-bearing winds off the Indian Ocean several hundred kilometres away.
“There is no formal water supply in the area. They were still depending on water tankers to supply water to the community the project is a solution,” said Liesel Dyson from the University of Pretoria.
The net was set up by researchers Dyson’s university and the University of South Africa. She said the water harvested from the fog is entirely pure, and is obtained from a source that needs no fuel and has no moving parts that can break down.
The community is now being trained to look after the net and the government has pledged to support the initiative in other suitable sites. Villagers are already clamouring for help to install additional netting and trap more water.
“This is a very good initiative and we will support it to help others in the country,” said Deputy Minister of Water and Environmental Affairs Rejoice Mabudafhasi.
There are other fog nets in operation in South Africa including one at Tshanova, not far from Tshiavha, and another at Lepelsfontein on the far side of the country in the Western Cape Province.
By Chester Makana for IPS
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