Climate change is accelerating groundwater depletion

Key messages

• The pace of global groundwater depletion is accelerating, relative to the 1980-2000 period, driven by compounding climate pressures and rising socioeconomic demands.
• Groundwater is a dynamic, climate-sensitive component of the global water cycle, and climate change is increasingly disrupting hydrological regimes by destabilising groundwater recharge. At the same time, global groundwater withdrawal rates have rapidly outpaced population growth, with future demands, especially from food production, expected to exacerbate this challenge.
• Groundwater is a critical buffer against climate change impacts on agriculture. However, increased groundwater withdrawal for irrigation to counteract warming temperatures is not a sustainable adaptation strategy.
• Beyond water scarcity, groundwater depletion carries major environmental and socioeconomic costs. These include land subsidence that damages agricultural and urban areas, and in coastal areas, saltwater intrusion can be further exacerbated as aquifers are depleted.

After polar ice, groundwater is our second largest freshwater source – supporting nearly half of humanity. It anchors water and food security for hundreds of millions, particularly in places with erratic rainfall patterns. In the early 20th century, global groundwater withdrawal increased roughly proportional to population, but since around 1960, rates have tripled from approximately 312 km³/yr to over 1,000 km³/yr, while global population has only increased by a factor of 2.6; factors beyond population growth, therefore, are at play. Most pumped groundwater is used for irrigation, and the United Nations’ Food and Agriculture Organization (FAO) estimates there will be a 30% increase in irrigated agriculture in the coming decades, especially in developing countries, to feed a population of 10 billion by 2050. With drier summers predicted and less evenly distributed rainfall in many areas across the world, our reliance on groundwater as a stable resource will become even more important. And while climate change plays a significant role in altering irrigation needs, socio-economic drivers such as the intensification of agriculture and changes in dietary preferences are at least equally important in driving long-term groundwater depletion trends. Consequently, groundwater availability will be a major challenge for Earth’s growing and increasingly prosperous population in the 21st century.

Groundwater is a critical buffer against the impacts of climate change on agriculture, as it enables the cultivation of water-demanding crops with multiple harvests per year, such as alfalfa or avocados, in arid regions like Arizona and Chile. But using groundwater as an adaptation strategy to counteract warming temperatures may lead to increased irrigation withdrawals, thereby accelerating depletion rates in already stressed groundwater zones like in India. The launch of the Gravity Recovery and Climate Experiment (GRACE) satellite mission in 2002 marked a turning point in global groundwater observations, enabling the visualisation of Groundwater Storage anomalies based on changes in Earth’s gravitational pull. Until then, our understanding had been derived from drilled wells and inspection of geological records. GRACE revealed, with a monthly resolution, significant declines across key agricultural zones worldwide. It observed groundwater reductions of 0.26 cm/yr and 1 cm/yr between 2003 and 2024, in the Central Valley and the Southern High Plains of the USA, respectively. During the same period, notable declines of 0.66 cm/yr and 0.44 cm/yr were observed in Northwestern India and the North China Plain.

More recently, GRACE’s limitations have been highlighted, including its coarse spatial resolution, the relatively short time period of 2002–2024 of collected data, and the difficulty distinguishing different water storage components (i.e., groundwater, soil moisture, and snow water storages). Bridging the gap between traditional local groundwater measurements and remote-sensing observations is crucial for actionable management, especially in vulnerable regions with limited well observations, like sub-Saharan Africa. There, groundwater supplies 75% of drinking water and faces climate-driven depletion. The International Groundwater Resources Assessment Centre was founded in 2003 by UNESCO and the World Meteorological Organization, to consolidate global information on groundwater. Two decades on, national data-sharing policies and varying data formats have made compiling a global well database challenging.

A global compilation of more than 170,000 groundwater-level time series from 40 countries, encompassing nearly 300 million observations, provides a dataset spanning four decades and enabling comparison of trends in 1,693 aquifers worldwide between 1980–2000 and 2000–2022. Beyond confirming that groundwater decline is indeed widespread, the analysis observed that in almost half of the declining aquifer systems worldwide, the pace at which groundwater levels drop accelerated in the most recent two decades. Over 80% of all aquifers experiencing accelerated declines are located in cultivated drylands where precipitation has declined and agricultural land use has intensified.

A recent study showed that groundwater is a dynamic, climate-sensitive component of the global water cycle. Under anthropogenic pressures, its behaviour has shifted in critical ways; global groundwater recharge, in which water moves downward from surface water to groundwater, is increasingly destabilised by climate change. Groundwater recharge dynamics are disrupted, particularly in snowmelt-dependent basins, where the earlier peak-flows that result from climate change, reduce infiltration, and exacerbate storage losses. Simultaneously, droughts diminish recharge rates, and intense rainfall often fails to percolate due to soil compaction or rapid runoff. Many arid regions are likely to experience significant declines in recharge due to decreased precipitation and higher evapotranspiration (Figure 5A).

Groundwater decline also leaves behind empty pore space (Figure 5E), into which the land above subsides, posing an imminent threat to agricultural land and urban communities in megacities such as Bangkok, Shanghai, Jakarta, or Manila. While this is by far the largest socio-economic threat associated with groundwater decline, coastal regions are additionally threatened by seawater intrusion into aquifers (Figure 5D). Small islands are particularly vulnerable, as freshwater floating above seawater can easily become salinised due to over-pumping, reduced recharge, and storm surges – all of which may intensify with climate change. Once an aquifer is contaminated, it can take decades to replenish it with clean freshwater.

Declining groundwater levels can often result from water wastage and unsustainable groundwater withdrawal, which can be mitigated through improved irrigation methods and better water management. Policies that address transboundary governance and Managed Aquifer Recharge, which currently offset less than 10% of global extraction, are also important. This approach acknowledges the interdependence of groundwater, surface water, and the ecosystems that rely on them. It will be crucial for mitigating cascading impacts on biodiversity and human water security in an era of accelerating climate change. Policies that operate across boundaries and involve stakeholders at all levels are considered more effective because of flexibility, adaptability, and ability to engage, at the same time they account for complex social-ecological systems interactions (Box 2).

In an increasingly water-stressed world, sustainable groundwater futures demand urgent action that balances human needs with ecosystem health. Successful sustainable groundwater management requires long-term monitoring and meaningful stakeholder involvement in planning and policy decisions. An analysis of 108 plans under California’s Sustainable Groundwater Management Act revealed that most failed to comprehensively include stakeholders, leaving many unprotected from groundwater depletion. When stakeholders were engaged, their needs were better addressed, underscoring the importance of resource monitoring, inclusive policymaking, and the integration of diverse stakeholders for the long-term sustainability of groundwater.