Terrestrial water storage is the total amount of water stored on land, including ice, surface water, groundwater and soil moisture. Although short-term droughts are not unusual, recent studies observed long-term changes in the global terrestrial water storage.
A new study based on data gathered between 2002 and 2024 by NASA’s GRACE and GRACE-FO missions found that these changes are here to stay – and accelerating at an alarming rate.
The research, published in July concluded that regions that are subject to drying are growing by twice the size of California every year. In the Northern Hemisphere, this is giving rise to what researchers call “mega-drying regions” – interconnected hot spots of drought on a continental scale. Although there are also areas that are getting wetter, the balance is tipping firmly towards mass drying.
Driving this shift is large-scale groundwater depletion, the long-term reduction of water storage in underground aquifers due to its widespread pumping, mainly for uses in agriculture. This phenomenon accounts for 68% of observed changes in terrestrial water storage. Other causes include water losses in high-latitude areas such as Canada and Russia, where ice and permafrost are melting due to increasing temperatures, as well as extreme droughts in Central America and Europe.
The impacts of this trend are profound, according to the authors, and can be felt on a global scale. At the beginning of the study’s measurements in 2020, around 6 billion people, or 75% of the world population, lived in areas with decreasing freshwater availability. A terrestrial decrease in water availability translates into more sea water, eventually accelerating sea level rise. The study warns that this process is now a bigger contributor to the rising sea levels than the melting ice sheets.
The research followed the release of a report by the UN Convention to Combat Desertification (UNCCD), which found that some of the most severe drought events ever recorded have taken place since 2023. Tens of millions of people, especially in southern and eastern Africa, are driven to food insecurity, malnutrition, and forced migration due to the compound impacts of water mismanagement, El Niño, and climate change. In Somalia, for example, an estimated 43,000 excess deaths may have been caused by drought in 2022 alone, according to the report.
The report identifies drought hotspots all over the world, from the Mediterranean to Central and South America and Southeast Asia. In Spain, for example, 60% of the agricultural land was facing drought in April 2023, while 88% of the Turkish territory is currently at risk of desertification.
“Drought is no longer a distant threat. It is here, escalating, and demands urgent global cooperation,”.
To meet these new challenges, the report recommends “immediate action that involves systemic, cross-sectoral solutions and international cooperation,” looking especially at strengthening ecosystems and improving water management while ensuring that access to resources remains equitable.
Some quick fixes to mitigate the problem are available, according to the report.
In some parts of the world, for example, up to 80% of the available water is lost to leaks in aging or inefficient water infrastructure. Repairing and maintaining this infrastructure could significantly increase freshwater availability for some communities.
On its own, however, this is not enough. Decisive action to mitigate climate change by decreasing greenhouse gas emissions remains crucial. Likewise, shifting to more sustainable agricultural practices is critical, given that the sector is by far the largest consumer of freshwater in the world.
A Guest Editorial