Groundwater is a very important source of fresh water for agriculture, human consumption and industry in general. But these groundwater they are in danger With climate change making them more inaccessible and overexploitation threatening economies and ecosystems.
Scientists from the University of California in Santa Barbara (USA) published in the journal Nature Largest assessment of groundwater levels worldwide to date it has covered approximately 1,700 aquifers. Although satellite maps provide information on storage trends, measuring monitoring wells in situ and analyzing them on a global scale gives scientists and governments a broader view of trends.
The results show that the general trend is a global decrease in water resources. Fall of more than 0.5 meters per year in the 21st centuryso one Decrease in 71% of aquifers. But they also provide examples of management success and ways to address it.
The general trend is a global reduction in water resources; There is a decrease of more than 0.5 meters per year in the 21st century.
“This depletion can have a number of undesirable effects on human water resources. For example, it affects a well’s ability to pump water to the surface, meaning it dries out. Additionally, excessive pumping also causes seawater intrusion or quality degradation. “Given that groundwater and surface water sources are often interconnected, such excessive extraction could impact the amount of water available in rivers,” Debra Perrone, an associate professor in the American university’s Environmental Studies Program, tells SINC.
The research team has already published it in 2021. Science Another study focused on constructed water wells. In this case, groundwater flow monitoring was carried out. “Monitoring wells give us information about supply, while groundwater wells give us data about demand,” Perrone explains.
Greater impact in dry areas
Scientists collected data from national, local, and different institutional registries. It took three years in total; Two years of this were devoted to cleaning and classifying this data. “That’s what it takes to be meaningful 300 million water level measurements from 1.5 million wells in the last 100 years”, they assure.
They then turned these figures into factual information about global trends, eventually examining more than 1,200 publications and reconstructing the boundaries of aquifers in their study areas.
Identifying 1,693 aquifer systems planetwide, they found: 36% of aquifers are decreasing at a rate of 0.1 meter per year, while 12% are rapidly decreasing at rates exceeding 0.5 meter per year.. Comparing these findings with groundwater depletion data from 1980 to 2000, the team found that 30% of the aquifers studied face rapid depletion in the 21st century, especially in dry regions.
The deepening of these waters is more common in these climates, and the acceleration of the decrease is especially common in arid and semi-arid agricultural areas. It’s an “intuitive finding,” according to co-senior author Scott Jasechko, a professor at the same university’s Bren School of Environmental Science and Management.
“But it’s one thing for something to be intuitive, it’s another to show what’s happening with real-world 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 and perennial water source that can be used during drought, When there is less rainfall and the flow of our rivers decreases. “Overexploitation of these groundwater resources could result in the denial of adequate supply to key sectors during shortages.”
Reasons for moderate optimism
Researchers also found: 6% of aquifers increased by 0.1 meter per year, while 1% increased by 0.5 meter per year. This may be the result of reductions in groundwater depletion, implementation of depletion policies, surface water transfers, or changes in land cover and managed recharge projects. “This study shows that people can change things with deliberate and concentrated efforts,” Jasechko emphasizes.
One example is in Tucson, Arizona. Water allocated from the Colorado River is used to replenish the aquifer in the nearby Avra Valley. The project stores this resource for future use. “Groundwater is often viewed as a bank account. Intentionally recharging aquifers allows us to store this water until it is needed.” says Jasechko. But the retreats have caused the mighty river to diminish at the surface. The Colorado rarely reaches its delta in the Gulf of California.
“Our study suggests that we can be cautiously optimistic about what our data suggest More than 100 aquifers where groundwater decline has slowed, stopped or reversed. It’s cautious in the sense that the rates of decline in these water levels are much higher than the rates of rise in groundwater levels: It’s easier to make things worse than to make them better,” Perrone says.
Stored groundwater can also benefit the ecology of the region. In fact, while preparing a research report in 2014, Perrone discovered: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 focusing on examining how groundwater levels change over time in the context of climate change. Linking these rates of change to actual well depths will provide better estimates of where access is at risk.
Reference work: https://www.nature.com/articles/s41586-023-06879-8
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