NASA satellites have picked up an abrupt drop in global fresh water that has showed no signs of recovery over the past decade.
A team of international scientists, reporting in Surveys in Geophysics, said the drop could indicate Earth’s continents have entered a persistently drier phase.
They said the abrupt drop in freshwater volume happened in 2014 and has remained low ever since.
The report said it was unclear whether water levels would rebound, hold steady, or resume their decline.
“Considering that the nine warmest years in the modern temperature record coincided with the abrupt freshwater decline, we don’t think this is a coincidence,” the report said.
“And it could be a harbinger of what’s to come.”
Satellite data from 2015 to 2023 showed that the average amount of freshwater stored on land in lakes, rivers and underground aquifers was 1200 cubic km lower than the average levels from 2002 to 2014.
“During times of drought, along with the modern expansion of irrigated agriculture, farms and cities must rely more heavily on groundwater,” the NASA report said.
“(This) 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.”
NASA Goddard meteorologist Michael Bosilovich said the freshwater reduction was likely also linked to global warming.
This warming led to the atmosphere holding more water vapor. This resulted in more extreme precipitation but longer periods for soil to dry and become more compact. This decreased the amount of water the ground could absorb.
“The problem when you have extreme precipitation is the water ends up running off instead of soaking in and replenishing groundwater stores,” Mr Bosilovich said.
“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.”
The full report is on the NASA website.
