NASA Satellites Reveal Abrupt Drop in Global Freshwater Levels

From a NASA news release:

The Gravity Recovery and Climate Experiment (GRACE) satellites, operated by the German Aerospace Center, German Research Centre for Geosciences, and NASA. GRACE satellites measure fluctuations in Earth’s gravity on monthly scales that reveal changes in the mass of water on and under the ground. Dr. Matthew Rodell was part of the team that determined how to measure the change in water mass.

From 2015 through 2023, satellite measurements showed that the average amount of freshwater stored on land — that includes surface water like lakes and rivers, plus water in aquifers underground — was 290 cubic miles (1,200 cubic km) lower than the average levels from 2002 through 2014, said Dr. Rodell, one of the current study authors and a hydrologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s two and a half times the volume of Lake Erie lost.”

During times of drought, along with the modern expansion of irrigated agriculture, farms and cities must rely more heavily on groundwater, which can lead to a cycle of declining underground water supplies: freshwater supplies become depleted, rain and snow fail to replenish them, and more groundwater is pumped. The reduction in available water puts a strain on farmers and communities, potentially leading to famine, conflicts, poverty, and an increased risk of disease when people turn to contaminated water sources, according to a UN report on water stress published in 2024.

The NASA team identified this abrupt, global decrease in freshwater using observations from the GRACE satellites. The original GRACE satellites flew from March 2002 to October 2017. The successor GRACE–Follow On (GRACE–FO) satellites  launched in May 2018. GRACE data has provided a global picture of water storage trends for over two decades now and could be an invaluable tool for understanding water resource availability. The data from the GRACE missions measured a gradual global depletion of terrestrial water storage from 2005 to 2015 of approximately 1287 gigatonnes (Gt) of water. The data from GRAACE and GRACE-FO from 2016 – 2023 has found no recovery in water land water storage.  Since water on earth is neither created nor destroyed the loss of terrestrial water is found in the seas. Seo et al found that the water loss from the land was equivalent to about 3.52 mm of global mean sea level (GMSL) rise.

The decline in global freshwater reported in the current study began with a massive drought in northern and central Brazil, and was followed shortly by a series of major droughts in Australasia, South America, North America, Europe, and Africa. Warmer ocean temperatures in the tropical Pacific from late 2014 into 2016, culminating in one of the most significant El Niño events since 1950, led to shifts in atmospheric jet streams that altered weather and rainfall patterns around the world. However, even after El Niño subsided, global freshwater failed to rebound.  In fact, Rodell and team report that 13 of the world’s 30 most intense droughts observed by GRACE occurred since January 2015. Rodell and colleagues suspect that global warming might be contributing to the enduring freshwater depletion.

Global warming leads the atmosphere to hold more water vapor, which results in more extreme precipitation, said NASA Goddard meteorologist Michael Bosilovich. While total annual rain and snowfall levels may not change dramatically, long periods between intense precipitation events allow the soil to dry and become more compact. That decreases the amount of water the ground can absorb when it does rain. 

“The problem when you have extreme precipitation,” Bosilovich said, “is the water ends up running off,” instead of soaking in and replenishing groundwater stores. Globally, freshwater levels have stayed consistently low since the 2014-2016 El Niño, while more water remains trapped in the atmosphere as water vapor. “Warming temperatures increase both the evaporation of water from the surface to the atmosphere, and the water-holding capacity of the atmosphere, increasing the frequency and intensity of drought conditions,” he noted.

It is not yet certain that the terrestrial water storage loss is linked to decadal climate variations or to longer-term changes associated with a warming climate. The certain data from the GRACE missions is not long enough the data has only been available since 2002. Since the late 1990s, there have been reports of considerable declines in evapotranspiration associated with decreasing soil moisture and increasing atmospheric vapor pressure declines. Further study is necessary to determine the cause of this observed water loss. It remains to be seen whether global freshwater will rebound to pre-2015 values, hold steady, or resume its decline. Considering that the nine warmest years in the modern temperature record coincided with the abrupt freshwater decline, Dr. Rodell said, “We don’t think this is a coincidence, and it could be a harbinger of what’s to come.”

from Rodell et al.- see citing below

Nonlinearity in the trend of GRACE time series: improving understanding of global total water storage changes over two decades | Environmental Earth Sciences

Rodell, M., Barnoud, A., Robertson, F.R. et al. An Abrupt Decline in Global Terrestrial Water Storage and Its Relationship with Sea Level Change. Surv Geophys 45, 1875–1902 (2024). https://doi.org/10.1007/s10712-024-09860-w

An Abrupt Decline in Global Terrestrial Water Storage and Its Relationship with Sea Level Change | Surveys in Geophysics

NASA Satellites Reveal Abrupt Drop in Global Freshwater Levels - NASA Science

Ki-Weon Seo et al. , Abrupt sea level rise and Earth’s gradual pole shift reveal permanent hydrological regime changes in the 21st century.Science387,1408-1413(2025).DOI:10.1126/science.adq6529

Article was updated after Ki-Weon Seo et al research was actually published.