WATR SECURITYGlobal Groundwater Depletion Is Accelerating, but Is Not Inevitable
Groundwater is rapidly declining across the globe, often at accelerating rates. Researchers raise the alarm over declining water resources, but offer instructive examples of where things are going well, and how groundwater depletion can be solved.
Groundwater is rapidly declining across the globe, often at accelerating rates.Writing in the journal Nature, UC Santa Barbara researchers present the largest assessment of groundwater levels around the world, spanning nearly 1,700 aquifers. In addition to raising the alarm over declining water resources, the work offers instructive examples of where things are going well, and how groundwater depletion can be solved. The study is a boon for scientists, policy makers and resource managers working to understand global groundwater dynamics.
“This study was driven by curiosity. We wanted to better understand the state of global groundwater by wrangling millions of groundwater level measurements,” said co-author Debra Perrone, an associate professor in UC Santa Barbara’s Environmental Studies Program.
The team compiled data from national and subnational records and the work of other agencies. The study took three years, two of which were spent just cleaning and sorting data. That’s what it takes to make sense of 300 million water level measurements from 1.5 million wells over the past 100 years.
Next came the task of translating the deluge of data into actual insights about global groundwater trends. The researchers then scoured over 1,200 publications to reconstruct aquifer boundaries in the regions of inquiry and evaluate groundwater level trends in 1,693 aquifers.
Their findings provide the most comprehensive analysis of global groundwater levels to date, and demonstrate the prevalence of groundwater depletion. The work revealed that groundwater is dropping in 71% of the aquifers. And this depletion is accelerating in many places: the rates of groundwater decline in the 1980s and ’90s sped up from 2000 to the present, highlighting how a bad problem became even worse. The accelerating declines are occurring in nearly three times as many places as they would expect by chance.
Groundwater deepening is more common in drier climates, with accelerated decline especially prevalent in arid and semi-arid lands under cultivation — “an intuitive finding,” said lead author Scott Jasechko, an associate professor in the university’s Bren School of Environmental Science & Management. “But it’s one thing for something to be intuitive. It’s quite another to show that it’s happening with real-world data.”
On the other hand, there are places where levels have stabilized or recovered. Groundwater declines of the 1980s and ’90s reversed in 16% of the aquifer systems the authors had historical data for. However, these cases are only half as common as would be expected by chance.
