mark hughes
Corn irrigation using groundwater supply in Kabwe, Zambia.
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Billions of people in many parts of the world rely on water for drinking, irrigation and other uses, according to a new study that analyzes millions of groundwater measurements from 170,000 wells in more than 40 countries. It has become clear that underground water reserves are rapidly decreasing.
According to the researchers involved, this is the first study to summarize what is happening to groundwater levels on a global scale, and scientists believe that humans are overexploiting this precious underground resource and that it is not related to this. This will help us better understand the indirect effects of changes in rainfall. to climate change.
Groundwater, contained in cracks and pores in permeable rock known as aquifers, is a lifeline for people in parts of the world where rainfall and surface water are scarce, especially in northwestern India and the southwestern United States.
Decreased groundwater can make it difficult for people to access fresh water for drinking and irrigating crops, leading to land subsidence.
“This study was driven by curiosity. We wanted to better understand global groundwater conditions by analyzing millions of groundwater level measurements.” said co-lead author Debra Perrone, associate professor in the Environmental Studies Program at the University of California, Santa Barbara, in a news release about the study published in December 2015. Wednesday's journal “Nature”.
The authors found that 71% of the 1,693 aquifer systems studied will see groundwater levels decline between 2000 and 2022, with 617 aquifer systems, or 36%, experiencing groundwater levels of 0.1 meters per year. I found that it has decreased by more than that.
Data compiled by the researchers showed Spain's Ascoi-Sopramo aquifer experienced the fastest decline — with a median rate of 2.95 meters per year, said study co-author and University of California Bren School of Environmental Science and Management. Associate Professor Scott Jasechko said. Santa Barbara.
He added that some aquifer systems in Iran have one of the fastest rates of groundwater decline.
Although the research team was unable to collect data from large parts of Africa, South America and Southeast Asia due to lack of monitoring, Yasechko said the study included the countries with the most groundwater pumping worldwide. He said there was.
The study also highlights some success stories in Bangkok, Arizona and New Mexico, where water is being used to better regulate water use and replenish depleted aquifers. Groundwater is beginning to recover following interventions to redirect the water.
“Such 'good news' stories are very rare, but we are impressed by the smart strategies that have been implemented to address groundwater depletion in some locations,” Yasechko said in an email. Stated.
To understand whether the declines seen in the 21st century are accelerating, the researchers also accessed groundwater level data from 1980 to 2000 for the 542 aquifers studied.
They found that the decline in groundwater levels was accelerating 30% of the aquifer has increased in the first two decades of the 21st century, exceeding the decline recorded between 1980 and 2000.
“These cases of accelerated decline in groundwater levels are more than twice as prevalent as would be expected from random fluctuations in the absence of systematic trends over any period,” the study said. There is.
British Geological Survey hydrologist Donald John McAllister, who was not involved in the study, said that despite some gaps, this was a truly “impressive” data set.
“I think it's fair to say that, at least to my knowledge, this global compilation of groundwater data has certainly never been done on this scale,” he said.
“Groundwater is a very important resource, but one of the challenges…is that most people don't care about it because it's invisible. Our challenge is to educate policy makers about it. It’s about keeping the drum beat, insisting that we have resources that we must look after and that we can use them to build resilience and adapt to climate change.”
