Groundwater depletion is accelerating, but is not inevitable 

Groundwater, a crucial resource hidden beneath our feet, is declining across the globe. A comprehensive analysis from UC Santa Barbara indicates that groundwater depletion is not only a growing concern but is also accelerating. However, the experts report that proactive management can reverse these troubling trends.

Extensive research

Spanning nearly 1,700 aquifers and based on an analysis of 300 million water level measurements from 1.5 million wells over the past century, the research is unprecedented in scale. 

“This study was driven by curiosity. We wanted to better understand the state of global groundwater by wrangling millions of groundwater level measurements,” explained study lead author Professor Debra Perrone.

The process of data collection and analysis took three years, two of which were solely dedicated to cleaning and sorting the data.

Critical new insights 

The results revealed that groundwater levels are dropping in 71% of the studied aquifers, with this decline accelerating at an alarming rate. Groundwater depletion rates significantly sped up from 2000 to the present, particularly in arid and semi-arid regions under cultivation.

According to the researchers, the accelerating declines are occurring in nearly three times as many places as they would expect by chance.

Groundwater management 

Despite these grim revelations, the study also highlights examples of successful groundwater management. Notably, in 16% of the aquifer systems with historical data, declines observed in the 1980s and ’90s have reversed. 

Study co-lead author Scott Jasechko pointed out that human intervention can help. “This study shows that humans can turn things around with deliberate, concentrated efforts.”

An example of such success is Tucson, Arizona, where water from the Colorado River is used to replenish the nearby Avra Valley aquifer.

“Groundwater is often viewed as a bank account for water,” explained Jasechko. “Intentionally refilling aquifers allows us to store that water until a time of need.” 

Filling aquifers is a cost-effective and ecologically beneficial approach compared to above-ground water storage. However, such interventions aren’t without their trade-offs, as evidenced by the dwindling Colorado River.

Reducing demand 

The study suggests that reducing demand is as crucial as augmenting supply. Often this involves regulations, permitting and fees for groundwater use, noted Perrone, who is currently examining water law in the western U.S. to understand these diverse interventions. 

Regardless of whether it comes from supply or demand, aquifer recovery seems to require intervention, the researchers found. 

Complementary resources 

The team also leveraged data from the Gravity Recovery and Climate Experiment (GRACE) mission, which provides insights into groundwater conditions at a larger scale. This data offers a more comprehensive understanding of groundwater dynamics.

“The beauty of GRACE is that it allows us to explore groundwater conditions where we don’t have in-situ data,” said Perrone. “Our assessment complements GRACE. Where we do have in-situ data, we can explore groundwater conditions locally, a crucial level of resolution when you’re managing depletion.” 

In a previous paper published in 2021, the authors highlighted how withdrawing groundwater can affect nearby streams and surface water. Additionally, they are now exploring how groundwater levels vary over time in the context of climate change, aiming to predict where groundwater access is most at risk.

The study is published in the journal Nature. 

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