Groundwater around the planet is rapidly depleting

Groundwater levels are falling, but the good news is that this can be reversed. Success stories with proactive management policies show that this trend can be improved.

Groundwater is an important source of fresh water for agriculture, human consumption and industry in general. However, aquifers are threatened by climate change, meaning they are no longer as available and if overused, threaten economies and ecosystems.

Scientists from the University of California in Santa Barbara (USA) have just published in the journal Nature the largest ever assessment of groundwater levels in the world, covering nearly 1.700 aquifers. While satellite maps provide information on storage trends, measuring in situ monitoring wells and analyzing them on a global scale helps scientists and governments get a broader picture of reserve trends.

Their results show a general trend of global decline in water resources, with a decrease of more than 0,5 meters per year in the 71st century, corresponding to a XNUMX% reduction in aquifers. However, they also provide successful examples and management solutions.

"This depletion can have a series of undesirable effects on the human water supply. For example, it affects a well's ability to pump water to the surface, meaning it runs dry. Likewise, excessive pumping also causes seawater intrusion or quality degradation. And, since groundwater and surface water resources are often interconnected, such over-extraction can affect the amount of water available in rivers."said Debra Perrone, assistant professor in the Environmental Studies Program at American University.

The team published in the magazine Science another study of wells built in 2021. In this case, groundwater flow was monitored. “Monitoring wells give us information about supply, while groundwater wells give us data about demand,” explains Perrone.

underground water

The impact is greater in arid regions

The researchers collected data from national, subnational and different agency registries. It took three years in total, two of which were spent cleaning and classifying the data. "That's what it takes to make sense of 300 million water level measurements from 1,5 million wells over the last 100 years.", they say.

They then turned these numbers into real trends by reviewing more than 1200 publications and reconstructing the boundaries of the aquifers in the areas they studied. By identifying 1.693 aquifer systems around the planet, they found that 36% of aquifers are declining by 0,1 meters per year, and 12% are declining rapidly at a rate greater than 0,5 meters per year.

Comparing these results with groundwater depletion data from 1980 to 2000, the team found that 30% of the aquifers studied have experienced rapid decline in the XNUMXst century, especially in arid regions.

In this climate, deepening of these water bodies is more common and rapid decline occurs especially in arid and semi-arid agricultural lands. "An intuitive discovery"said co-author Scott Jaseczko, a professor at the Bren School of Environmental Science and Management at the same university. “But it is one thing for something to be intuitive and quite another to show what is happening with real-world data."He added.

Perrone emphasized: “Water is a critical resource for human consumption and agricultural and industrial production. Groundwater is especially important because it is a reliable, perennial source of water that can be used during drought, when there is less rainfall and the flow of our rivers decreases. Overexploitation of these underground water resources could hinder adequate supply to key sectors during shortages.".

Reasons for moderate optimism about groundwater

The researchers also found that 6% of the aquifers included in the data were rising at a rate of 0,1 meters per year and 1% at a rate of 0,5 meters per year. This may be due to reductions in groundwater use, implementation of consumption policies, surface water diversions or changes in land cover and managed recharge projects. "This research shows that people can make a difference with specific, focused efforts"Jasechko emphasized.

An example is Tucson, Arizona. Water drawn from the Colorado River is used to recharge the aquifer in the nearby Avra ​​Valley. The project preserves this resource for future use. “Groundwater is often thought of as a bank account. Intentional recharging of aquifers allows us to store this water until we need it”Jasechko said.
However, the diversion of water flow has caused the Colorado River to decline in flow, which now rarely reaches the Gulf of California delta.

"Our work shows that we can be cautiously optimistic because our data shows that more than 100 aquifers have slowed, stopped or reversed groundwater decline. Care must be taken in the sense that the rate at which the water level falls is much greater than the rate at which the water table rises: it is easier to make the situation worse than to improve it”Perrone said.

The collected groundwater can also benefit the area's ecosystem. In fact, when Perrone prepared his investigative report in 2014, he discovered that the resources Aquifers They could hold six times more water per dollar than surface reservoirs. Another option they suggest is to focus on reducing demand.

Currently, the research team is focused on studying changes in groundwater levels over time in the context of climate change. Comparing this rate of change to actual drilling depth will allow for better prediction of when access to water is at risk.

With information of:


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