Global freshwater levels are falling, NASA-German satellites reveal

Earth’s freshwater reserves experienced a sudden decline starting in May 2014 and have remained persistently low, according to findings by an international team of scientists using NASA-German satellites. Observations from the Gravity Recovery and Climate Experiment (GRACE) mission revealed significant reductions in freshwater storage on land, including lakes, rivers and underground aquifers. The study, published in Surveys in Geophysics, suggests that this shift may indicate a transition to drier conditions on the continents.

Reduction of freshwater quantified

Between 2015 and 2023, freshwater levels on Earth were the same found are 180 cubic miles below the 2002 to 2014 average, according to Matthew Rodell, a hydrologist at NASA’s Goddard Space Flight Center. This amounts to more than twice the volume of Lake Erie. Contributing factors include droughts and increased reliance on groundwater for agricultural and urban needs, depleting reserves faster than they can be replenished. A 2024 United Nations report on water stress highlighted the societal risks of reduced water supplies, including famine, poverty and dependence on unsafe water sources.

Impact of global warming on water cycles

Research shows that rising global temperatures could worsen freshwater loss. Michael Bosilovich, a meteorologist at NASA Goddard, explained that warming intensifies evaporation and increases the atmosphere’s ability to retain moisture, leading to extreme rainfall. Although total annual precipitation remains stable, prolonged dry periods between these events reduce soil uptake, worsening drought conditions.

Persistent trends raise concerns

Satellite data showed that global freshwater did not recover after a major El Niño event between 2014 and 2016, which caused shifts in atmospheric patterns and widespread droughts. Rodell noted that 13 of the 30 most severe droughts since 2002 occurred after 2015. Although the link to climate change is not definitive, its co-occurrence with record high global temperatures has raised concerns about the future stability of freshwater supplies.

Hydrologist Susanna Werth of Virginia Tech, not affiliated with the study, highlighted the challenges in predicting long-term outcomes due to uncertainties in climate models. However, current trends are being closely watched for further implications.