Two decades of satellite data reveal global freshwater decline at unprecedented pace

Two decades of satellite data reveal a troubling global trend: vast areas of Earth’s continents are drying out at an unprecedented pace, a phenomenon the researchers call “mega-drying.” This process, driven by climate change, over-extraction of groundwater, and intensifying droughts, now contributes more to sea level rise than the melting of glaciers and ice sheets.

A team from Arizona State University, publishing their findings in Science Advances on August 9, highlights four massive drying zones spanning from North America across Eurasia to North Africa.

These zones threaten water supplies for billions of people and jeopardize food security, ecosystem health, and global stability, as reported on by SciTechDaily.

The study’s analysis draws on over 20 years of satellite observations from the US-German GRACE and GRACE-FO missions, which monitor terrestrial water storage—including surface water, soil moisture, groundwater, snow, and ice—since 2002. Their data show that dry areas are expanding by roughly twice the size of California every year. More importantly, dry regions are becoming drier faster than wet areas are becoming wetter, reversing long-held patterns in the global water cycle.

The article notes that this rapid drying poses a dire threat to freshwater availability. Currently, 75% of the world’s population lives in 101 countries experiencing significant freshwater loss over the past two decades. With global population expected to keep rising for the next 50 to 60 years, this growing water scarcity could spark widespread humanitarian crises.

A striking revelation of the study is that 68% of the water loss is from groundwater depletion alone. Groundwater, often called “ancient water,” is a hidden and non-renewable resource that communities have been tapping into unsustainably. The depletion of these deep reserves is accelerating sea level rise even more than the melting of glaciers and ice caps on land.

Jay Famiglietti, the study’s principal investigator and a Global Futures Professor at ASU, emphasized the urgency: “Continents are drying, freshwater availability is shrinking, and sea level rise is accelerating. The consequences of continued groundwater overuse could undermine food and water security for billions. This is an all-hands-on-deck moment — immediate action on global water security is critical.”

The publication cites lead author Hrishikesh A. Chandanpurkar, who explained that these groundwater reserves function like “ancient trust funds” meant for emergency use, such as during droughts. Instead, they are being depleted recklessly, without efforts to recharge them during wetter periods. This unsustainable usage edges the planet toward a potential “freshwater bankruptcy,” with severe consequences for agriculture, drinking water supplies, and natural ecosystems.

By Nazrin Sadigova