This map shows the years in which terrestrial water storage reached a 22-year low (i.e., the land was driest) in each location, based on data from the GRACE and GRACE/FO satellites. - NASA EARTH OBSERVATORY/WANMEI LIANG
MADRID, 15 Nov. (EUROPA PRESS) –
The total amount of fresh water on Earth has decreased dramatically since May 2014. and it has remained low ever since.
In a report based on satellite data published in Investigations in Geophysicsan international team of scientists suggests that the change could indicate that the Earth’s continents they have entered a persistently drier phase.
From 2015 to 2023, satellite measurements showed that the average amount of fresh water stored on Earth (which includes liquid surface water such as lakes and rivers, plus water in underground aquifers) was 290 cubic miles (1,200 kilometers cubic) lower than average levels from 2002 to 2023. 2014, he said in a statement Matthew Rodell, one of the study’s authors and a hydrologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s two and a half times the lost volume of Lake Erie.”
In times of drought, coupled with the modern expansion of irrigated agriculture, farms and cities must rely more on groundwater, which can lead to a cycle of dwindling groundwater reserves: freshwater reserves become depleted, rain and snow fail to replenish them, more groundwater is pumped. Reducing available water puts pressure on farmers and communities, which can lead to famine, conflict, poverty and increased risk of disease when people turn to contaminated water sources. according to a United Nations report on water stress published in 2024.
The team of researchers identified this sharp global decline in freshwater using observations from the GRACE (Gravity Recovery and Climate Experiment) satellites, operated by the German Aerospace Center, the German Research Center for Geosciences and NASA. GRACE satellites measure fluctuations in Earth’s gravity on monthly scales that reveal changes in the mass of water above and below the ground. Subsequent GRACE-Follow On (GRACE-FO) satellites were launched in May 2018.
The decline in global freshwater reported in the study began with a massive drought in northern and central Brazil, and was followed shortly by a series of severe droughts in Australasia, South America, North America, Europe and Africa. Warmer ocean temperatures in the tropical Pacific from late 2014 to 2016, culminating in one of the most significant El Niño events since 1950, caused changes in atmospheric jet streams which have altered weather and precipitation patterns around the world.
However, even after El Niño subsided, global freshwater did not recover. In fact, Rodell and his team report that 13 of the 30 most intense droughts observed by GRACE have occurred since January 2015. Rodell and his colleagues suspect that global warming could be contributing to persistent freshwater depletion.
Global warming causes the atmosphere to hold more water vapor, resulting in more extreme precipitation, said meteorologist Michael Bosilovich of NASA’s Goddard Center. While total annual precipitation and snowfall levels may not change dramatically, extended periods between heavy precipitation events allow the ground to dry and become more compact. This decreases the amount of water the soil can absorb when it rains.
“The problem when you have extreme rainfall,” Bosilovich said, “is that the water ends up running off,” rather than being absorbed and replenishing groundwater reserves. Globally, freshwater levels they have remained consistently low since the 2014-2016 El Niñowhile a greater amount of water remains trapped in the atmosphere in the form of water vapor. “Rising temperatures increase both the evaporation of water from the surface to the atmosphere and the water-holding capacity of the atmosphere, which increases the frequency and intensity of drought conditions,” he underlined.
While there is reason to suspect that the sharp decline in freshwater is largely due to global warming, it may be difficult to definitively link the two factors, said Susanna Werth, a hydrologist and remote sensing scientist at Virginia Tech, who was not affiliated with the project. study. “There are uncertainties in climate predictions,” Werth said. “Measurements and models always contain errors.”
It remains to be seen whether global freshwater will return to pre-2015 values, remain stable, or resume its decline. Noting that the nine warmest years in the modern temperature record coincided with the sharp decline in freshwater, Rodell said: “We do not believe this is a coincidence and could be a harbinger of things to come.”
How can communities and governments effectively manage water resources to combat the freshwater crisis?
Interview Between Time.news Editor and Hydrologist Matthew Rodell
Editor: Good afternoon, Matthew. Thank you for joining us to discuss this critical issue regarding the decline of global freshwater levels. Your recent report presents a stark picture of our planet’s water resources. Could you start by explaining how the decline has been measured and the significance of these findings?
Matthew Rodell: Thank you for having me. We’re utilizing satellite data from the GRACE and GRACE-Follow On satellites to measure fluctuations in Earth’s gravity, which directly relates to changes in water mass both on the surface and underground. Our findings indicate that since May 2014, the total amount of freshwater has decreased sharply and has remained low since then. Specifically, the average freshwater storage from 2015 to 2023 was about 290 cubic miles lower than the average levels from 2002 to 2014. To put that into perspective, that’s two and a half times the lost volume of Lake Erie!
Editor: That’s a staggering amount. What are the primary factors contributing to this decline?
Matthew Rodell: The major factor appears to be a cycle of drought exacerbated by climate change. It started around 2014 with significant droughts in Brazil and has since spread globally, affecting places like Australasia, North America, Europe, and Africa. The El Niño phenomenon also played a role by altering weather and precipitation patterns, but even after it subsided, freshwater levels did not bounce back. This indicates a shift toward a persistently drier phase on Earth.
Editor: It sounds like a concerning trend. You referenced a cycle where increased irrigation leads to more groundwater pumping, which further depletes freshwater reserves. Could you elaborate on the implications of this cycle for agriculture and communities?
Matthew Rodell: Absolutely. In times of water scarcity, farmers and urban areas increasingly rely on groundwater, which may already be under stress. When groundwater levels drop, it’s difficult to replenish those sources. The consequences can be severe: as freshwater availability decreases, it puts pressure on agriculture, leading to food shortages, increased poverty, and potential conflict. The 2024 United Nations report on water stress warns about the heightened risk of diseases as communities may turn to contaminated water sources in desperate times.
Editor: This paints a sobering picture. What role does global warming play in these changes to our freshwater resources?
Matthew Rodell: Global warming is likely a significant contributing factor. Warmer temperatures cause the atmosphere to hold more water vapor, leading to extreme precipitation events. However, while total annual precipitation may seem stable, the longer intervals between these events allow the ground to dry out significantly. Consequently, even if we receive heavy rainfall, it may not be enough to offset groundwater depletion caused by prolonged dry spells.
Editor: With such alarming data, what steps do you think governments and communities should take to address this freshwater crisis?
Matthew Rodell: Immediate action is crucial. Countries need to adopt better water management practices, such as investing in sustainable irrigation techniques, enhancing water conservation strategies, and educating communities about responsible water use. Global cooperation is also necessary to tackle the underlying issues of climate change, which is fundamentally driving many of these water crises. Sustainable practices and policies could help us transition toward a more resilient water future.
Editor: Thank you, Matthew, for your insightful analysis and for bringing attention to this pressing global issue. It’s clear that we need to take collective responsibility to protect our freshwater resources before it’s too late.
Matthew Rodell: Thank you for having me. The future of our planet’s water resources depends on the actions we take today.