NASA satellites reveal abrupt drop in global freshwater levels

An international team of scientists using observations from NASA-German satellites has found evidence that Earth’s total amount of freshwater dropped abruptly starting in May 2014 and has remained low ever since.

The researchers identified the decrease in freshwater using observations from the Gravity Recovery and Climate Experiment (GRACE) satellites. Reporting in Surveys in Geophysics, the researchers suggested the shift could indicate Earth’s continents have entered a persistently drier phase.

From 2015 through 2023, satellite measurements showed that the average amount of freshwater stored on land — that includes liquid 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 Matthew Rodell, one of the 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.”

The map shows the years that terrestrial water storage hit a 22-year minimum (i.e., the land was driest)

at each location, based on data from the GRACE and GRACE/FO satellites.

A significantly large portion of the global land surface reached this minimum in the nine years since 2015, which happen to be the nine warmest years in the modern temperature record.

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 is putting 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 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 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 have occurred since January 2015. Rodell and colleagues suspect that global warming might be contributing to the enduring freshwater depletion.

The researchers say 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, Rodell said:

“We don’t think this is a coincidence, and it could be a harbinger of what’s to come.”