The primary water source for countless homes, farms, and cities is under threat. Unsustainable groundwater withdrawals are resulting in groundwater declines that threaten ecosystems and economies alike. New research published today in Nature reveals an acceleration in rates of groundwater depletion, emphasizing the need for comprehensive strategies to safeguard groundwater resources.

In this new study—led by researchers at the University of California, Santa Barbara, ETH Zurich, Rutgers University, King Abdulaziz University, and University College London—scientists compiled a global database of groundwater-level measurements to assess trends in 1,693 aquifers from over 170,000 wells. Their analysis shows that groundwater declines are not only widespread, but that rates of decline have accelerated over the past four decades in many aquifers.

Groundwater depletion poses a threat to agricultural production and domestic water access. Nearly half of all water withdrawals for global irrigation are supplied by groundwater, meaning groundwater depletion can jeopardize crop yields. For example, recent research has suggested that falling groundwater levels in parts of India could reduce agricultural production by as much as 68% (source: Jain et al., 2021).

Beyond food production, billions of people rely on groundwater wells to meet their needs, underscoring the magnitude of this threat.

Groundwater Level Declines Accelerate

The analysis of 300 million groundwater level observations spanning forty years (1980 to 2022) found that, in 30 percent of these aquifer systems, the rate of groundwater level decline was faster in the early 21st century relative to the 1980s and 1990s. This finding demonstrates an acceleration in the rates of groundwater decline.

Changes in global precipitation patterns help to explain some of these accelerated declines. Reductions in precipitation can cause groundwater levels to fall by decreasing aquifer recharge rates (a direct impact of climate on groundwater) or by elevating demand for groundwater during droughts (an indirect impact of climate on groundwater; source: Taylor et al. 2013).

This analysis shows that over 80% of aquifers experiencing accelerated declines are located in areas where precipitation declined over the past 40 years, highlighting potential links between changes in climate trends, and groundwater use and replenishment.

Accelerated depletion of aquifers has consequences for communities across the globe.

In Iran’s Western Qazvin Plain Aquifer, an acceleration in the rate of groundwater level decline is driven by population growth, increased agricultural production, and abstraction of groundwater (source: Yazdi et al. 2021). From 1939 to 2009, the total amount of annual groundwater extraction increased from 1 million to 30 million cubic meters per year (source: Babaee et al., 2019). As a result, land subsidence has intensified and increased the risk of damage to buildings and other infrastructure.

In southeastern Spain, accelerated declines in groundwater levels have caused seawater to contaminate coastal aquifers (source: Giménez & Morell, 1997). This salinization of groundwater can render groundwater unfit for use, and jeopardize agricultural production and domestic access to water supplies as wells are abandoned.

The acceleration of groundwater depletion is evidence that current groundwater uses are unsustainable in some places, suggesting a need for interventions to protect agricultural production and domestic water access.

The second finding of this recent research highlights specific areas that have turned things around via interventions that have slowed, stopped, or even reversed groundwater depletion.

Cases of Hope

Specifically, this research also identifies cases where the groundwater depletion of the 1980s and 90s was halted, allowing aquifers to refill. These cases highlight potential solutions that have addressed the needs of specific aquifers and reversed groundwater declines.