World Half Full
Fog nets bring water to arid Africa
For the past few years, during the Moroccan desert summertime drought, fog nets have been used to provide drinking water to thousands of people in remote mountain communities. Villagers are now able to irrigate their fields, turning desertified land back into green gardens, all thanks to a mathematician.
While Moroccan-born Aïssa Derhem was living in Canada and studying for a PhD in maths during the 1980s, he learned about how in the driest place on Earth — the Atacama Desert in Chile, where it has officially never rained — the locals use fog nets to catch what little moisture does enter the landscape.
The fog net is a multilayered mesh designed to attract and accumulate water particles where there’s ocean-born fog, but little or no rain. Derhem began to wonder if the same idea couldn’t help in his birthplace on the slopes of Mount Boutmezguida, in southwestern Morocco’s Lesser-Atlas range.
The people there are largely made up of Berber communities, notably women, children and the elderly; the men are often absent for months at a time, looking for work in the towns. In recent years, the region has been increasingly affected by drought; the desert has spread, and the water table is steadily sinking.
However, compared to the Atacama, winds there regularly top 115kph, too much for the fog net designs being used at the time. With his Moroccan NGO Dar Si Hmad, Derhem partnered with a German water charity Wasserstiftung to instal a new type of fog net known as Aqualonis that can withstand much higher wind speeds than earlier versions. Initially, just six fog nets were built covering an area of around 240 square metres along with nearly 1.6km of tubing and a fibreglass container to capture more than 1,000 litres of water daily.
With now more than 900 square meters of installed capacity, Dehrem’s is the largest fog collection site on Earth, and around 1,600 residents in this remote region now each have a water supply of 18 litres a day, exclusively from the fog collection nets.
Already families have returned to the villages around Mount Boutmezguida, the ultimate proof of Derhem’s success. The fog nets could easily provide three times as much water if placed closer to the coast at a lower elevation, meaning more families might be able to return.
TOP Fog nets in Morocco
ABOVE Aissa Derhem
PHOTO Fadel Senna