Will the taps go dry? NASA satellites reveal sharp decline in global freshwater since 2014; linked to climate change

An international team of scientists, using data from NASA and German satellites, has found evidence that Earth’s total freshwater supply began to decline sharply in May 2014 and has stayed at lower levels ever since.  

In a study published in Surveys in Geophysics, the researchers suggested this shift could signal that Earth’s continents are entering a prolonged, drier period. 

From 2015 to 2023, satellite data revealed that the amount of freshwater stored on land — including lakes, rivers, and groundwater — was 290 cubic miles (1,200 cubic kilometers) lower than the average from 2002 to 2014. According to Matthew Rodell, a NASA hydrologist and study co-author, this is equivalent to losing two and a half times the volume of Lake Erie. 

The study notes that during droughts, especially with the expansion of irrigated agriculture, cities and farms increasingly rely on groundwater. This creates a cycle of depleting water supplies: freshwater reserves run low, rainfall and snow fail to replenish them, and more groundwater is extracted.

The resulting water shortages can put significant pressure on communities and agriculture, raising the risk of famine, conflict, poverty and disease, especially when people resort to contaminated water sources, as highlighted in a 2024 UN report on water stress. 

The researchers tracked the global drop in freshwater using data from the Gravity Recovery and Climate Experiment (GRACE) satellites, a joint mission between NASA and the German Aerospace Center.  

GRACE satellites monitor fluctuations in Earth’s gravity, revealing changes in the mass of water both on and beneath the surface. The first GRACE satellites operated from 2002 to 2017, while the GRACE–Follow On (GRACE–FO) satellites, launched in 2018, continue to monitor the planet’s water levels. 

The freshwater decline began with a severe drought in northern and central Brazil and was followed by significant droughts across Australasia, South America, North America, Europe and Africa. These droughts were linked to unusually warm ocean temperatures in the tropical Pacific, which contributed to a major El Niño event from late 2014 to 2016. This weather phenomenon disrupted rainfall patterns worldwide by shifting atmospheric jet streams. 

Despite the subsiding of the 2015-2016 El Niño, global freshwater levels did not recover. In fact, the study found that 13 of the 30 most intense droughts recorded by the GRACE satellites have occurred since 2015. Rodell and his colleagues suspect that climate change may be driving the ongoing depletion of freshwater. 

Global warming causes the atmosphere to hold more water vapour, which leads to more extreme weather events, including intense rainfall. However, NASA meteorologist Michael Bosilovich said that longer dry spells between heavy rainfalls prevent soil from absorbing as much water, making it harder for groundwater to be replenished. “When there’s extreme precipitation, the water tends to run off rather than soak into the ground,” Bosilovich added. This means less water is replenishing underground reservoirs, even as more moisture remains in the atmosphere. 

“Warming temperatures increase both the evaporation of water and the atmosphere's ability to hold moisture, amplifying drought conditions,” Bosilovich explained. 

While there are indications that global warming could be contributing to the decline in freshwater, it is challenging to draw a direct link, according to Susanna Werth, a hydrologist at Virginia Tech, who was not involved with the study. “There are uncertainties in climate models and measurements,” she explained. 

It remains uncertain whether global freshwater levels will recover to pre-2015 levels, stabilise, or continue to decrease. Given that the nine warmest years on record coincide with the onset of the freshwater decline, Rodell believes the trend may be linked to global warming. “We don’t think this is a coincidence, and it could be a sign of what’s to come,” he warned.