Study Suggests

Water is essential for life on Earth, but securing a reliable water supply is becoming one of the greatest challenges of our time. Traditional methods of assessing water security focus on where rain falls and how it is stored in rivers, lakes, and aquifers. However, new research suggests that this approach might be overlooking a critical factor: where the moisture that forms rain actually comes from.

A New Perspective on Water Security

Researchers from Stockholm University have developed an alternative method for quantifying global water scarcity risks by considering the environmental conditions and governability of the regions where moisture originates—before it even falls as rain. This upwind moisture, as the researchers call it, travels through the atmosphere before it eventually falls to the ground. The results of this study, published in Nature Water, reveal that when this factor is taken into account, the risks to global water security are significantly higher than previously thought.

“Water supply really originates beforehand, with moisture evaporated from land or in the ocean traveling in the atmosphere before falling as rain,” says Fernando Jaramillo, associate professor in physical geography at Stockholm University and lead author of the study. “This upwind moisture is commonly overlooked when assessing water availability.”

The Precipitationshed: A Global Connection

The study examined 379 hydrological basins worldwide, revealing that the risks to water security increase by nearly 50% when the origin of moisture is considered. The researchers found that many regions rely heavily on moisture that evaporates from distant locations, making them vulnerable to environmental changes far beyond their borders.

For instance, the Amazon basin in South America depends on moisture from the Andes mountains, while the Andes themselves rely on moisture from the Amazon rainforest. This interconnectedness means that deforestation or land-use changes in one region could have drastic effects on water availability in another.

Political and Environmental Implications

The study also highlights the role of political control in managing water resources. Land-use changes in upwind areas—such as deforestation or agricultural development—can significantly impact downwind water availability. Coastal countries like the Philippines, where most rainfall comes from the sea, face less risk from land-use changes. In contrast, inland countries like Niger, which depend on moisture from neighboring countries, are at much higher risk.

“For the Congo River basin, heavily reliant on moisture from neighboring countries with low environmental performance and governance, there are considerable risks due to potential deforestation and unregulated land use changes,” says Lan Wang-Erlandsson, co-author of the study and researcher at the Stockholm Resilience Centre.

A Call for International Cooperation

The findings underscore the need for international cooperation in managing water resources. Environmental regulations and governance in one country can have far-reaching effects on water security in another. As Jaramillo points out, “In the end, all water is connected, so we should not only mind how we manage our water resources within a region or country but also how our neighboring countries do.”

This study provides a new perspective on global water security, highlighting the importance of considering the origin of rain in assessments and policies. As the world faces increasing water challenges, understanding these complex interconnections will be crucial in developing effective strategies for managing this precious resource.