A new study led by NASA researchers suggests that Earth’s freshwater supply has undergone a series of major changes, likely driven by man-made factors, primarily climate change, and water management strategies.
In a paper published in Thursday’s issue of the journal, Nature, researchers based their findings on various sources, including 14 years of observations from NASA’s Gravity Recovery and Climate Experiment (GRACE) mission, and satellite precipitation data from the Global Precipitation Climate Project. The study covered freshwater sources from 34 different regions around the world, and suggested that a lot of the world’s wettest land areas were getting wetter, with the driest areas conversely drying up further.
According to study lead author Matt Rodell, head of the NASA Goddard Space Flight Center’s Hydrological Sciences Laboratory, the study marks the first time global freshwater availability has been tracked by means of satellite observations.
“A key goal was to distinguish shifts in terrestrial water storage caused by natural variability — wet periods and dry periods associated with El Niño and La Niña, for example — from trends related to climate change or human impacts, like pumping groundwater out of an aquifer faster than it is replenished.”
Aside from the aforementioned data sources, Rodell and his colleagues derived their data from NASA and the U.S. Geological Survey’s Landsat imagery, and existing reports of agricultural, mining, and reservoir operations-related human activities that could influence the supply of global freshwater. It was through the analysis of the blended data from various sources that the researchers were able to get a clear picture of how freshwater supplies had changed from the 14-year period starting in 2002 and ending in 2016.
As explained in a NASA news release, freshwater can be found in various places, including rivers, lakes, snow, ice, groundwater, and soil, and is generally used for drinking and for agricultural purposes when found on land. Freshwater could also play a role in sea level rise as climate change continues to melt our planet’s polar ice sheets. And as far as the world’s supplies are concerned, the researchers noted that there were increases and decreases in some regions adding up to some “major hydrologic change,” despite supplies remaining stable in other parts of the world.
In a statement, NASA Jet Propulsion Lab scientist and study co-author Jay Famiglietti said that the high latitudes and tropics, which are among Earth’s top wet land areas, are getting wetter in what appears to be a “distinctive pattern.” In between those areas are dry areas that are getting progressively drier, while the dry areas now have “multiple hotspots” that appeared due to a lack of groundwater, he added.
While the study suggested that human factors were mainly responsible for the aforementioned phenomenon, with man-made global warming causing ice sheets and glaciers to melt, Famiglietti added that more time and more research — a “much longer dataset,” as he described it — might be needed to determine what drives the rest of the global freshwater changes, and if climate change is indeed the main culprit for such patterns in the GRACE mission’s data.