Groundwater is rapidly being depleted worldwide.

Groundwater is a crucial source Fresh water for agriculture, human consumption and industry in general. However, these aquifers are at risk from climate change, which is making them more inaccessible, and from their overexploitation, which poses a threat to economies and ecosystems.

Scientists from the University of California in Santa Barbara (USA) published in the journal Nature The largest measurement of groundwater levels in the world to date, covering nearly 1,700 aquifers. Although Satellite maps Provide information about storage trends and measure them on site By monitoring wells and analyzing them on a global scale, scientists and governments can gain a more comprehensive view of trends.

Their results show that the general trend is a global decline in water resources, with a decline of more than 0.5 meters per year in the 21st century, representing a reduction of 71% of the aquifer. However, they also offer examples of management successes and solutions.

This depletion can have a number of undesirable effects on human water supplies.

Debra Perrone (University of California)

“This depletion can have a number of undesirable effects on human water supplies. For example, it affects a well's ability to pump water to the surface, meaning it runs dry. Likewise, excessive pumping leads to seawater intrusion or deterioration in quality. And since groundwater and surface water resources are often interconnected, such over-extraction can impact the amount of water available in rivers,” he tells SINC. Debra PerroneAssociate Professor at American University in the Environmental Studies Program.

The research team published in 2021 Science another study that focused on constructed water wells. In this case the groundwater inflow was monitored. “Monitoring wells give us information about supply, while groundwater wells give us data about demand,” explains Perrone.

Greater impact in dry regions

The scientists collected data from national, subnational and various government registries. In total, it took three years, two of which were dedicated to cleaning and classifying this data. “That’s what it takes to make sense 300 million measurements the water level of 1.5 million wells over the last 100 years,” they say.

They then turned these numbers into real information about global trends, ultimately reviewing more than 1,200 publications and reconstructing the boundaries of aquifers in the research regions.

Groundwater is particularly important because it is a reliable, permanent source that can be used during periods of drought

Debra Perrone

By defining 1,693 aquifer systems around the world, they found that 36% of aquifers were declining by 0.1 meters per year, while 12% were declining rapidly at rates of more than 0.5 meters per year. Comparing these results with data on groundwater depletion from 1980 to 2000, the team found that 30% of the aquifers examined were experiencing a problem accelerated exhaustion in the 21st centuryespecially in dry regions.

Deepening of these waters occurs more frequently in these climate zones, with accelerated decline particularly common in dry and semi-arid cultivated areas. “An intuitive insight,” says the lead co-author Scott Jasechko, Professor at the Bren School of Environmental Sciences and Management of the same university.

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“But it’s one thing for something to be intuitive and quite another to show what happens with real data,” he adds.

Perrone emphasizes: “Water is a critical resource for human consumption, agricultural and industrial production. Groundwater is particularly important because it is a reliable, permanent source of water that can be used during droughts, when there is less rainfall and the flow of our rivers decreases. The Over-exploitation If there are shortages of these groundwater resources, they could hinder the adequate supply of important sectors.”

Reasons for moderate optimism

The researchers also found that 6% of the aquifers in the data were rising at a rate of 0.1 meters per year, while 1% were rising at a rate of 0.5 meters per year. This could be due to a decline in groundwater use, implementation of consumption policies, surface water transfers, or changes in land cover. and recharge projects managed. “This study shows that people can change things with conscious and concentrated effort,” emphasizes Jasechko.

Our data shows more than 100 aquifers where groundwater decline has slowed, stopped, or reversed

Scott Jasechko, University of California

One of the examples is in Tucson, Arizona. The allocated water from the Colorado River will be used to recharge the aquifer in the nearby Avra ​​Valley. The project saves this resource for future use. “Groundwater is often viewed as a bank account. “By systematically recharging the aquifers, we can store the water until it is needed,” says Jasechko. However, withdrawals have caused the mighty river to shrink at the surface. The Colorado rarely reaches its delta in the Gulf of California.

“Our work suggests we can be cautiously optimistic because our data shows more than 100 aquifers where groundwater decline has slowed.” slowed down, stopped or vice versa. “Cautious in the sense that the rates of decline in the level of these waters are much greater than the rates of rise of the groundwater level: it is easier to worsen the situation than to improve it,” says Perrone.

Stored groundwater can also benefit the region's ecology. In fact, when Perrone did a research report in 2014, he found that aquifer recharge can store six times more water per dollar than surface reservoirs. Another option they suggest is to focus on reducing demand.

The team is now focused on studying how groundwater levels change over time. in the context of climate change. Linking these rates of change to actual well depths allows for better predictions of where access is at risk.

Reference:

Debra Perrone et al. “Rapid groundwater decline in many aquifers worldwide.” Nature (2024)

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