Foggy Notions for a Thirsty World

April 26, 2011 5:40:09 AM

Tim Wall

Tim's 072

Collecting fog with mesh panels is becoming a popular technique for developing communities to pull water out of low-hanging clouds.

Shreerang Chhatre, an engineer at the Massachusetts Institute of Technology, has now developed a mesh that mimics the way a desert beetle gets a drink.

800px-Namib_desert_beetleThe Namib beetle‘s (Stenocara gracilipes) shell collects moisture from the air and channels it to the beetle’s mouth. The shell harvests the life-giving liquid using bumps on the beetle’s back that attract water. But channels between the bumps repel it, causing a tiny current of water to trickle into the beetle’s parched mouth.

Chhatre’s mesh uses a similar collection of water-attracting and water-repelling surfaces to pull water out of the air.

Similar mesh collecting devices in Peru have already proven that trapping fog works to alleviate thirst in small communities.

A pilot program of 36 of Chhatre’s mesh nets is now supplying water for 150 people in Tojquia, Guatemala.

Wide Angle: Tech Saving Water

Mesh “You have to get the local community to participate from the beginning,” said Melissa Rosato, project manager for FogQuest, a Canadian charitable organization, in an MIT press release. “They’re the ones who are going to be managing and maintaining the equipment.”

Women are especially important for the success of the project, as they are often the ones responsible for collecting water. “If women are not involved, chances of a long-term sustainable project are slim,” said Rosato.

One major problem with setting up these water collectors is that the people most in need also lack money to buy the mesh.

BLOG: Water from Fog

In the hills around perpetually cloudy800px-Fog_desert_Lima_and_Trujillo,_Peru Lima, Peru, slum dwellers lack access to clean running water, but they have plenty of fog.

The hills have been deforested for about 500 years, since the Spanish chopped them down to build the ciudad that Francisco Pizarro founded.

Residents of Bellavista, an impoverished squatter community on the outskirts of Lima, started using mesh panels to collect water in 2007 with the assistance of German aid organization Alimón.

The run-off collects in troughs that run to swimming-pool-sized tanks. Four nets, each 8 meters by 4 meters, can collect 480 liters of water in a 24 hour period. The residents now get enough extra water to also irrigate small gardens.

“These fog nets have improved our quality of life. We can grow vegetables for our families and use all this moisture in the fog, which would otherwise be wasted, rather than having to buy water,” said resident Noe Neira Tocto in an interview with the BBC.

Tim's 038The vegetables and fruit trees the residents grow then provide a source of income, which helps the communities pay for the nets.

Some of the run-off is also used to irrigate trees. As the trees grow, they in turn trap more fog. The run-off from the trees may eventually refill aquifers that have been dry for centuries.

“Without being irrigated, it would take 400 years for a tara tree to grow to full height in this desert, but with 4-years-worth of watering, it will fruit,” said Luis Marquez Cano, a forestry engineer at the National Agrarian University and an adviser on the project.

Lima, Peru is the second largest desert city, after Cairo, Egypt. But unlike Cairo which has the mighty Nile River nearby, Lima gets it’s water from a the tiny Rimac River. The Rimac is fed by water melting off glaciers high in the Andes. The glaciers melt in the summer and re-form in the winter, but lately they have been doing a lot more melting that re-forming.

BLOG: Shedding Light on a Fast-Melting Glacier

As the glaciers disappear, Lima and other cities around the world which depend on glacial melt water, are running dry.

Fog capture in this regard is a temporary fix to an otherwise growing problem: meeting the high water demands of the middle and upper class.

Tim's 041“For small rural villages and isolated communities, it can be a lifeline,” said FogQuest’s Bob Shemenauer in an interview with freelance reporter Gaia Vince.

“But, once a community gets large enough to support businesses, such as cafes, swimming pools, and so on, the per capita water use goes up from 40-50 liters per person, to hundreds. Then, governments need to invest in piped water supply.”

“We understand that democracy means access to basic services,” said Guillermo Leon, director of Lima’s water board, in an interview with the BBC.

“But we have to appeal for the solidarity of the people who already have water to reduce their consumption – there’s no point in laying new water pipes just to deliver a trickle,” Leon said.

IMAGE 1: Peru’s coastal fog (Tim Wall).

IMAGE 2: The Namib Beetle (Wikimedia Commons).

IMAGE 3: Mesh being tested for use on fog-harvesting devices by Shreerang Chhatre and colleagues at MIT. (Patrick Gillooly).

IMAGE 4: An abandoned restaurant in the middle of the desert between Lima and Trujillo, Peru. The Andes Mountains are in the background (mostly obscured by fog). (Wikimedia Commons).

IMAGE 5: A glacier melting in Peru’s Huascarán National Park (Tim Wall).

IMAGE 6: A pool of melted glacial water in the Peruvian Andes. A decade ago, this area was underneath a glacier. (Tim Wall).