For decades, groundwater overexploitation has outpaced the data needed to quantify it at a global scale. A landmark new study published in Environmental Research Letters now closes much of that gap. Tracking 42,844 monitoring wells across 47 countries over 20 years, it delivers the most comprehensive in-situ assessment of groundwater level trends to date and confirms what many in the sector have long suspected, while also surfacing risks from rising water tables that remain poorly understood.
Nearly one third of groundwater level trends are declining, a clear sign of overexploitation
Researchers at the International Groundwater Resources Assessment Centre (IGRAC) in Delft analysed 20 years of monitoring data from 42,844 wells across 47 countries. Their conclusion: nearly one-third of groundwater level trends are declining, a clear sign of overexploitation. A further 18% are rising, which may sound reassuring, but the study shows that rising water tables carry their own serious risks.
A world of hotspots
The study devotes substantial attention to a problem that receives far less public discussion: the consequences of groundwater levels that rise too high
The global pattern is not uniform. In South America, where data was available for Brazil and Chile, 63% of wells showed declining trends. In Chile's Central and Norte Chico regions, water tables have dropped by an average of nine metres over the past two decades, with some wells recording falls exceeding half a metre per year. The situation has been described by researchers as approaching "day zero" for affected communities, with water increasingly delivered by tanker truck.
In the Middle East, depletion in some Jordanian aquifers approaches or exceeds one metre per year, contributing to the drying up of springs and the steady retreat of wetlands. India's Punjab, often called the country's breadbasket, has seen 63% of monitored wells decline, with average drops of around 20 metres over 20 years. The consequences ripple through farming communities, pushing up the cost of drilling and pumping, and threatening crop yields that underpin national food security.
Hotspots of decline are also well established in parts of Europe: southern Portugal and Spain, France's Aquitaine basin, southeastern Netherlands, Germany, Hungary and Bulgaria all feature in the study's global map of concern. In the United States, the Central High Plains aquifer, which supports roughly 20% of national corn, wheat and cotton production, saw 81% of monitored wells in decline, with an average drop of eight metres.
When rising water becomes a hazard
The study devotes substantial attention to a problem that receives far less public discussion: the consequences of groundwater levels that rise too high. In Thailand, groundwater management reforms introduced to reverse decades of over-abstraction in Bangkok have worked dramatically — 88% of Bangkok's monitored wells now show rising trends. Land subsidence, which had threatened the city at rates of tens of centimetres per year, has begun to stabilise. Bangkok stands out as a rare success story.
The study reviewed 29 case studies to document the real-world impacts of changing groundwater levels
Yet recovery is not without complications. Rising water tables have caused structural problems for deep foundations and increased liquefaction risk during earthquakes. In Taiwan, where similar bans on groundwater pumping were enacted in the 1970s, 54% of monitored wells in the Taipei basin are now rising, bringing seepage issues to infrastructure basements alongside the benefits.
In Denmark, groundwater emergence and flooding are a growing concern, particularly in urban areas where shallow aquifers are approaching the surface. Basement flooding, damage to road infrastructure, and infiltration into sewer systems are documented consequences. Across much of coastal Florida, sea-level rise is pushing water tables higher, creating conditions where heavy rainfall events push groundwater above ground level, a pattern that has contributed to some of the highest rates of flood insurance claims in the United States.
A cascade of consequences
The study reviewed 29 case studies to document the real-world impacts of changing groundwater levels. The range is striking. In Mexico City, decades of over-abstraction have reversed the natural upward pressure in confined aquifers, pulling surface pollutants downward into the city's main water supply. In West Bengal, excessive pumping has intensified naturally occurring arsenic contamination in shallow aquifers, with researchers warning that deeper aquifers, long considered safe, may lose their arsenic-free status within decades.
Ecosystems, too, bear the costs. In the Doñana wetlands of southern Spain, 71% of monitored wells are declining, and more than half the site's 3,000 ponds and lagoons have dried up in the past 40 years. Cork oak dieback and the replacement of endemic plant species by drought-tolerant varieties have been linked directly to falling water tables. In the Czech Republic, groundwater decline has weakened tree resistance to bark beetle infestation; between 2017 and 2022, the country's spruce growing stock fell by approximately 20%.
Not all impacts are negative. Where management has succeeded, the study documents genuine recovery. In parts of India's Gujarat and Andhra Pradesh, reduced irrigation subsidies and increased use of surface water have allowed groundwater storage to rebound.
The monitoring gap
Large portions of the world, North Africa, Sub-Saharan Africa, Central and East Asia, and parts of South America remain critically underrepresented in global groundwater monitoring networks
One of the study's clearest messages is that what cannot be measured cannot be managed. Large portions of the world, North Africa, Sub-Saharan Africa, Central and East Asia, and parts of South America remain critically underrepresented in global groundwater monitoring networks. The authors call for expanded investment in in-situ monitoring infrastructure and greater international data sharing.
New tools are available: low-cost sensors, satellite-based gravity measurements from the GRACE project, and machine learning approaches that can help fill spatial and temporal gaps. But the authors are emphatic that remote sensing cannot substitute for monitoring wells on the ground.
"Our findings underscore an urgent need for expanding monitoring programmes, protecting groundwater, and defining acceptable impacts to determine sustainable groundwater usage," the study concludes.
Groundwater moves slowly, responds to pressures over years or decades, and often shows no visible warning signs until a well runs dry or a sinkhole opens. The new study is a reminder that the resource underpinning much of the world's food and water supply is changing, and that the window to act remains open, but not indefinitely.
