September 3 () –
Humanity faces greater risks to water supplies than expected given environmental conditions and the possibilities of use where rain occurs.
The common idea of global water supply is rain that falls on the earth’s surface and is then stored in aquifers, lakes and rivers. This idea is generally used to assess water security and the risk of water scarcity. However, A new study published in Nature Water It shows how water risks depend on the governance and environmental conditions present in the windward zones, that is, the areas from which the moisture for rainfall comes.
“The water supply actually originates up front, with evaporated moisture from land or ocean traveling into the atmosphere before falling as rain. This windward moisture is often overlooked when assessing water availability,” he says. in a statement Fernando Jaramillo, associate professor of physical geography at Stockholm University and head of the study.
When a lake or river is shared between different countries or authorities, assessments and regulations primarily apply an upstream perspective, considering conditions in the upstream direction from the water body. In contrast, an upwind perspective considers the area where evaporated water is transported before ending up as rainfall. The area is known as a precipitation basin and can cover large areas of the Earth’s surface.
“For example, in tropical South America, most of the Amazon basin is downstream of the Andes mountain range, while large areas of the Andes are themselves downwind of and dependent on the Amazon rainforest, making these two regions dependent on each other for water supplies,” says Fernando Jaramillo.
The study examined 379 hydrological basins around the world.revealing that water security risks are significantly greater when considering the upwind origin of water.
“With this approach, we see that 32,900 km3/year of water needs worldwide face a very high risk, an increase of almost 50 percentcompared to 20,500 km3/year resulting from the more traditional upstream approach,” says José Posada, a former PhD student at Stockholm University and lead author of the study.
Since a large amount of water evaporates from plants, changes in land use can affect water availability downwind. If deforestation and agricultural development are predominant in windward areas, the amount of moisture provided by vegetation may decrease, reducing downwind rainfall and increasing the risk to water security.
“In coastal countries like the Philippines, most of the rainfall comes from the sea, meaning that changes in land use pose very few risks to water security. In contrast, in inland countries like Niger, rainfall comes mainly from moisture evaporating in neighbouring countries like Nigeria and Ghana. This puts many landlocked countries at risk of water shortages. in a high-risk situation regarding water security that is affected by changes in land use“, says Fernando Jaramillo.
In other words, political factors such as environmental management and regulations in areas where moisture evaporates first can affect water security in completely different areas.
“For example, the Congo River basin, which is highly dependent on moisture from neighbouring countries with poor environmental performance and poor governance according to global indicators, faces considerable risks due to potential deforestation and unregulated land use changes in neighbouring areas“says Lan Wang-Erlandsson, a researcher at the Stockholm Resilience Centre at Stockholm University and co-author of the study.
Add Comment