A kul tank, India.
Centre for Science and Environment, New Delhi
  Desert fog, Saudi Arabia.
X. Eichaker/Still Pictures
  A falaj in Oman.
Carole Hodgson
  A kund in the Thar desert.
Centre for Science and Environment, New Delhi
  Fog collectors, Chile.
Gil Moti/Still Pictures
 
         
 

There is no life without water. Yet people have made their homes in arid lands since ancient times, long before modern technology found ways of delivering water quickly and easily.

Ironically these modern methods often help cause desertification. Overpumping water from wells depletes aquifers, taking the water from them faster than rain - and time - can replenish it. Tapping prehistoric water from fossil aquifers - such as the massive Nubian Sandstone Aquifer System in Libya - is unsustainable because their waters, trapped underground for thousands of years, are not replaced. As the water fails, vegetation dies, and precious topsoil erodes away.

Similarly, overirrigating land causes salinization. As the water evaporates it causes a dangerous buildup of salts, making the soil infertile.

So perhaps it's time to revisit some of the ancient, well-tried - but often overlooked - ways of harvesting water. One of the oldest is named the qanat in Iran, the falaj in Oman, the foggara in Algeria and the madjirat in Andalusia. It originated some 3,000 years ago in ancient Persia, and is still employed throughout the Middle East and beyond.

Qanats bring underground water from hills and mountains down a gently sloping tunnel, often many kilometres long; frequent vertical shafts allow ventilation and maintenance.

The method spread east along the Silk Road to China and west to Spain - probably thanks to the Moors - and onwards to Mexico, Peru and northern Chile. It's a durable technology: a 2,700-year-old system still provides water to almost 40,000 people in the Iranian city of Gonabad. In all, the country retains over 160,000 kilometres of qanats.

Capturing and storing rainwater - often by households collecting it from their roofs - has also, of course, gone on for thousands of years. But people in the Thar desert in Rajasthan have been gathering it on a community level since the 1600s. Their groundwater supplies are too salty to drink, so they began collecting rainwater on special saucer-shaped catchments, measuring anything from 20 square metres to 2 hectares, built into the land. These are cleared of vegetation, graded into a gentle slope, and packed down with pond silt or gravel. Rain runs down the slope, through a mesh that filters out debris and into a kund, a covered, underground tank usually made of cement and covered with a dome-shaped lid.

 

Harvesting snow makes even cold deserts inhabitable. A centuries-old system in the Spiti valley, deep in the Indian Himalayas, uses diversion channels to tap glaciers up to
10 kilometres away. The water runs down the stone-lined channels, called kuls, to a circular tank in the village and is then used for irrigation. This allows the region to make its living from agriculture, even though the harsh climate supports little vegetation.

In the Spiti village of Poh, farmers are now also experimenting by filling a shaded reservoir with snow at the beginning of December. As spring arrives, the snow thaws at the ideal rate for irrigation. On a smaller scale, people in the Takhar province of Afghanistan get drinking water by collecting snow in pit reservoirs insulated with a layer of earth. Bamboo pipes channel out the water as the snow melts.

Regions with neither rain nor snow have long harvested fog and dew. People in South America's Atacama desert use piles of stones arranged to minimize evaporation. In parts of the Middle East, low walls built around vines ensure that the condensation falls right onto the plants. And Bedouins put out rugs and cloths to catch moisture from morning fog.

Water from dew is used to grow melons in China's arid Gansu province, where the cultivated area is covered by large pieces of gravel which capture condensation, deliver it to the soil and keep moisture from evaporating. And Professor Girija Sharan, a researcher designing greenhouses for the water-deprived village of Kothara, in Kutch, recently discovered that morning dew provided up to 9 litres a day from a 124-square-metre roof: he is now researching the best material for collecting the moisture, with the help of the World Bank.

Until 1987, the remote fishing village of Chungungo, in Chile, relied on trucked-in water. Then polypropylene nets were hung up to condense water as fog blows through them: the droplets run down into gutters and reservoirs, to be piped into homes. This has provided not just an independent and reliable drinking water source, but irrigation for crops. Its success has prompted similar schemes in Peru, Namibia and South Africa.

New technologies inspired by old ones can both solve immediate water crises and take the pressure off overstressed water sources. Importantly, they are sustainable - because they simply do not permit the use of more water than can be naturally replenished. So hope for the future may lie in the past.

 
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