Artificial rain in the United Arab Emirates
In the United Arab Emirates, clouds are precious. Despite being one of the driest regions in the world, they also compete every year for the per capita world record for water usage per person. According to estimates, groundwater in the Emirates may already be used up by 2023. Now hopes are pinned on new technologies: since the 1990s, experiments have been carried out with so-called cloud seeding. Small propeller planes fly right into the middle of clouds that would otherwise likely move on without any rain falling from them. Tiny salt particles are sprayed into the cloud from nozzles on the aeroplane. If everything goes as planned, the water held in the cloud concentrates around the salt and falls to the ground as rain. This technique, however, is disputed: according to the World Meteorological Organisation of the United Nations (WMO) more than fifty states carry out this so-called weather modification – but there are no precise numbers about the results, costs and the possible dangers of these interventions, such as extreme precipitation or floods.
Harvesting fog in Chile
In 2006, the Chilean village Peña Blanca faced the threat of desertification. The entire region 300 kilometres north of the Chilean capital Santiago, which is characterised by agriculture, had extreme water scarcity. But there was plenty of fog in the coastal region along the foothills of the Andes. Salvation came in the form of big nets: “catching fog” as it is often called, was developed by the Chilean physicist Carles Espinosa as early as 1956. Drinking water is obtained from fog by stretching very fine-meshed nets across regions in the hills. Tiny droplets of mist gather and, once heavy enough, they drip into collecting basins. There, the water is filtered and, thanks to gravity, flows straight down into the village of Peña Blanca. In 28 nets with a total area of 252 square metres, up to 1,500 litres of fog water are harvested per day. It’s used for irrigation – and for a few years now it has even been used to brew beers, which has boosted tourism in the region. This technology, which is comparatively low in cost and maintenance, is now also being used in numerous other arid regions of the world, such as in Peru, Eritrea and Morocco.
Using seawater to ease the Australian water crisis
Across the continents, it only rains less than in Australia in Antarctica. Some towns in the inland of the subcontinent have to make do with less than 200 millimetres of precipitation per year. Up until the end of the 1990s, the Australian water demand could be met using dams and cisterns. But now there is a drought nearly every summer as well as a risk of forest fires. The technique that hopes to bring relief is called seawater desalination by reverse osmosis. In desalination plants, the water is pressed through a membrane that holds back the salt contained in the water. What comes out is drinking water. But the technique has a drawback: it uses enormous amounts of energy. A desalination plant uses two to four kilowatt hours of electricity per cubic metre of drinking water — which is why some Australians sarcastically call water gained through this technique “bottled energy.” Modern units, powered by renewable energies, give scope for hope. The first big desalination plant was set up 2006 in the port of Perth and used wind power to gain its electricity. Until today, thirty plants are in operation across the country. More and more of them are using nearby wind or wave powered plants to produce the required electricity.
In remote communities and on small islands they are even building solar powered desalination plants. This technique is on the rise worldwide: in 2022 desalination plants are already supplying half a billion people with drinking water — around 22,000 plants in 170 countries produce 130 billion litres of freshwater a day.
Ancient water reservoirs in Iran
As early as 1400 BC, the people living in what is now Iran were faced with the challenge of ensuring the water supply of dry regions. They showed themselves to be resourceful engineers and their irrigation systems are still used today. Usingunderground tunnels water was carried for many kilometres from ground water reservoirs at higher altitudes. This irrigation system made it possible to populate dryer regions of Iran as well as parts of the Persian plateau in the northeast regions of the country. About 37,000 of these so-called “Qanat” pipe systems are still in operation in the plateau regions of Yazd, Chorasan and Kerman, supplying the rural areas with drinking water. Qanats, therefore, are among the oldest irrigation systems used today worldwide. They are made up of a horizontal tunnel that taps into an underground water source. A tunnel with a slight incline enables the maintenance of the system. One of the oldest, still preserved qanats, built 2,700 years ago, is located in the town of Gonabad. Running across some 30 kilometres, it transports water for 40,000 people. Eleven Iranian qanats were declared UNESCO world heritage sites in 2016.
Compiled by Gundula Haage
With additional reporting by Justus Tamm