For us, water is a precious and vital good. In a quarter of all regions of the world, however, there are too little clean fresh water all year round. This water shortage gets more than half of all people feel to feel worldwide, as a new study shows. For the first time, the researchers combined the drinking water reserves with the available water in the underground and water quality. From this holistic view of the global and regional water situation, a more differentiated picture of the problem can now be seen and local water management can be derived.
Our drinking water comes from lakes and rivers as well as groundwater, which is transported to the surface using pumps. However, if these sources or local water paths are polluted, the water must first be prepared and cleaned complex – and not all contaminants can be removed without residue. In addition, not all areas worldwide have the necessary technology for this. If the resources are too dirty, you have less fresh water to drink, wash, for animals and for industry. If the precious wet is also used to water dry soils for agriculture during drought times, the available amount of drinking water is also reduced.
Inventory of global water supplies
Researchers have now investigated Wenfeng Liu from the Chinese Agriculture University in Beijing how these factors affect global water shortages. To do this, they evaluated how much water is available on earth- divided into “blue” surface or groundwater and “green” rainwater in the form of soil moisture. In addition, they determined how the water quality developed from 2010 to 2019, depending on the annual requirement and availability of fresh water.
The analysis showed that at 22 to 26 percent of the global land area, water shortages had occurred all year round in at least one of the three dimensions examined – blue, green or clean water. This affected 58 to 64 percent of the world’s population, with the largest number of people of water shortages being exposed to in March. For at least one month between February and May, even 80 percent of people were temporarily affected by fresh water deficiency, mostly in Asia. In contrast, the most critical months were in the Mediterranean and the Middle East from July to September.
According to the evaluations, the most common lacks of rainwater and thus green water for agriculture. “In contrast, central Asia and large parts of Europe are mainly affected by blue water deficiency, especially between June and October,” reports the team. So there was too little drinking water for households and industry. In some areas such as California Central Valley and the Mediterranean, the green and blue water was scarce. In the northern lowlands of China, on the other hand, there were enough green rainwater for agriculture, but too little blue drinking water, the quality of which left a lot to be desired. In some areas, people were even affected in all three dimensions of water shortages, a total of around 0.53 billion people, especially in India, China and Pakistan.
Water shortage is larger than expected
This data show that more people worldwide are affected by water shortages than can be seen from previous studies. These had only considered the blue surface and groundwater supplies. However, since the green water and water quality also play a role, these factors must also be taken into account in order to determine the total available freshwater amounts, according to the team around Liu. “With the joint evaluation of these different forms of water shortage, our integrated rating fills an important gap by explicitly revealing so far overlooked water shortages.”
With the knowledge, water management could now be improved in the individual regions of the earth by using different measures as required. “For example, in regions with exclusively blue water deficiency, the focus should be on improving the water use efficiency in the private and industrial sector in order to reduce the demand for limited blue water resources,” said Liu and his colleagues. That would also apply to Germany. Regions that only suffer from poor water quality could lead their blue and green water into artificial wetlands and thus achieve natural water cleaning with the help of vegetation and microorganisms.
Areas in which there is too little rain, but there is enough blue water, in turn could significantly water their soils, the team said. Further options would be to grow less water -intensive food and cleaning and recycling of waste water and rainwater. Depending on the regional situation, the countries would have to combine these measures sensibly in order to counter their lack of water.
Source: Wenfeng Liu (Chinese agricultural university) et al.; Proceedings of the National Academy of Sciences, DOI: 10.1073/PNAS.2413541122
