Groundwater Pumping Reduces Global Aquifer Storage by 17 km3 per Year

Groundwater is a vital resource for many people around the world, especially in regions where surface water is scarce or unreliable.

However, excessive groundwater pumping can have serious consequences for the environment and the future availability of water.

A new study has revealed that global groundwater storage capacity is disappearing at an alarming rate, as the land above the aquifers sinks and collapses.

The global extent of land subsidence

(Photo : Mario Tama/Getty Images)

Land subsidence is the lowering of the ground surface due to the removal of fluids or solids from below. It can occur naturally or be induced by human activities, such as mining, oil and gas extraction, and groundwater pumping.

When groundwater is pumped out of an aquifer, the pore spaces between the soil and rock particles collapse, reducing the volume and storage capacity of the aquifer. This can cause the land above to sink, sometimes by several meters.

Land subsidence can have negative impacts on infrastructure, agriculture, ecosystems, and human health. It can damage buildings, roads, bridges, pipelines, and other structures, increasing the risk of flooding and erosion. It can also reduce crop yields, affect soil quality, and alter surface water and groundwater interactions.

Moreover, it can pose a threat to human safety, as it can trigger landslides, earthquakes, and sinkholes.

A new study, published in the journal Nature Communications, has mapped the loss of groundwater storage capacity around the world due to land subsidence.

The study, led by researchers from the Desert Research Institute, Colorado State University, and the Missouri University of Science and Technology, used a combination of publicly available data and computer modeling to estimate the extent and rate of land subsidence caused by groundwater pumping.

The study found that global aquifer storage capacity is disappearing at a rate of approximately 17 km3 per year, which is equivalent to the size of 7,000 Great Pyramids of Giza.

This loss of groundwater storage is permanent, and cannot be recovered even if the pumping stops.

The study also found that about 75% of the subsidence occurs over cropland and urban areas, highlighting the need for better groundwater management.

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The hotspots of groundwater-induced subsidence

The study identified the regions where land subsidence due to groundwater pumping is most severe and widespread.

The top three countries that account for most of the global groundwater storage loss are the United States, China, and Iran, with some regions experiencing more than 5 cm/year of land subsidence.

Some of the notable hotspots of groundwater-induced subsidence are:

•  California's Central Valley, where intensive agriculture relies heavily on groundwater irrigation.Previous research has shown that some parts of the valley have subsided by more than 2.5 meters since 1965, affecting infrastructure and water conveyance systems.

•  China's North China Plain, where groundwater is the main source of water for domestic, industrial, and agricultural use.The plain has experienced rapid urbanization and population growth, leading to increased groundwater demand and overexploitation. The study estimated that the plain has lost about 8.6 km3 of groundwater storage capacity per year, the highest among all regions in the world.

•  Iran's Tehran Basin, where groundwater is the primary source of drinking water for the capital city and its surrounding areas. The basin has faced severe water scarcity and drought in recent years, forcing the residents to pump more groundwater. The study found that the basin has subsided by more than 25 cm/year, causing damage to buildings and infrastructure.

The study also revealed that land subsidence due to groundwater pumping is not limited to these well-known cases, but is also occurring in many other regions around the world, such as India, Mexico, Indonesia, and Egypt.

The study used advanced machine learning techniques to predict the subsidence in regions where no data is available, based on factors such as land use and climate.

The study also used satellite data to validate the model's predictions and to monitor the changes in land elevation over time.

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