Satellites reveal low freshwater levels worldwide

Remote monitoring from a (U.S.) NASA and German space collaboration shows a decrease in freshwater. Scientists report an abrupt drop started in May, 2014. They say that water levels have remained low.

Spacecraft known as the Gravity Recovery and Climate Experiment (GRACE) satellites have tracked gravitational variations from 2015 through 2023. When rivers, lakes and aquifers store more water, they exert slightly more powerful gravitational pull. Water level measurements are then calculated from the dataset. NASA hydrologist Matthew Rodell described the 2015-2023 decrease form 2002-2014 calculations as a loss “two and a half times the volume of Lake Erie.”

The study’s authors report that 13 of the world’s 30 most intense droughts observed by GRACE have occurred since January, 2015. They hypothesize that global warming is a factor of ongoing freshwater depletion. Under warming conditions, the atmosphere holds more water vapor. Lengthening time periods between intense rain or snowfall events dry out and harden soil. Then when the atmosphere is saturated and finally produces rain, soil conditions poorly absorb heavy downpours. The precipitation fails to recharge groundwater basins, and the stormwater runoff adds to flooding risk.

Michael Bosilovich, a NASA meteorologist said some runoff drains into fresh lakes and rivers. However, more runs into the ocean. Freshwater isn’t being replenished as it has been in the past.

Another six years of measurements are expected from the GRACE Follow-On satellites.