Why is water scarcity one of the greatest threats of our time?
The images of dried-up riverbeds and cracked earth, which in recent years have been coming more and more often from Spain, Portugal and Italy, bear witness to a problem that was long considered a concern of other continents. In 2022 the river Po experienced its worst drought in seventy years, while the reservoirs on the Iberian Peninsula at times had worryingly low levels. Climatologists explain that higher temperatures not only accelerate evaporation, but also change the distribution of rainfall, so that heavy downpours are increasingly followed by long dry periods. Droughts, however, are not an exclusively European phenomenon: from East Africa and the Middle East to large parts of India, millions of people struggle with a chronically insecure water supply.
The largest consumer of fresh water is not households, as is often wrongly assumed, but agriculture. According to estimates by the Food and Agriculture Organization, irrigation accounts for about 70 per cent of the water that humans draw from rivers, lakes and underground reserves. Particularly problematic is that water-intensive crops such as rice, cotton or avocados are often grown precisely in dry regions where every litre is precious. In southern Spain, for example, huge areas of greenhouses are irrigated with water from wells, a large proportion of which, according to environmental organisations, were dug without a permit.
When surface waters dry up, farmers turn to groundwater, which, unlike rivers, renews itself extremely slowly, in some cases over centuries or even millennia. Satellite measurements, which register the smallest changes in the Earth's gravitational field, show that underground reserves are shrinking in numerous regions, from northern India to California. The consequences are visible even to the naked eye: in Mexico City, built on a former lake bed, the ground is sinking in places by more than 20 centimetres a year.
Given these trends, more and more states are relying on desalination, that is on turning seawater into drinking water. The Gulf states, such as Saudi Arabia and the United Arab Emirates, but also Israel, already cover a significant part of their drinking water needs in this way. The technology, however, has its price: the plants consume enormous amounts of energy, which in the region is still mainly obtained from fossil fuels. In addition, the process produces highly concentrated brine, which, if it is discharged into the sea without proper treatment, can harm marine ecosystems.
Water scarcity is also a geopolitical issue, especially in places where several states share the same river basin. The best-known example is the Nile: Ethiopia built a huge hydroelectric plant on the Blue Nile, while Egypt, which depends almost entirely on this river, fears that it will receive less and less water. Similar tensions exist around the Tigris and Euphrates, whose waters are shared by Turkey, Syria and Iraq, as well as around the Indus between India and Pakistan. Although open wars over water have so far been rare, experts believe that climate change could intensify such disputes if international cooperation is not strengthened.
However, responsibility does not lie only with governments and with large consumers. A household that regularly showers briefly instead of taking a bath, fixes leaking taps and runs the washing machine only when it is full can save hundreds of litres a week. An even greater influence is exerted by so-called virtual water, that is the amount of water that is embedded in the production of food and clothing. For one kilogram of beef, for example, several thousand litres of water are needed, which is many times more than for the same amount of grain. That is why more moderate meat consumption and less wasted food are among the most effective ways in which individuals can reduce their own water footprint.