When a well runs dry, people who rely on the water often have no warning. As the water table dips lower, the pump will begin to suck air and faucets will sputter as water stops flowing.
The consequences of years of gradual declines in groundwater suddenly become visible, leaving people struggling with the costs of drilling a deeper well or finding water from another source.
New research shows that in dozens of countries around the world, from the United States to India, wells are increasingly at risk. With even moderate declines in groundwater levels, researchers have found, millions of wells could run dry.
The researchers analyzed records for about 39 million wells in 40 countries or territories and found that between 6% and 20% of wells are no more than 5 meters (16 feet) deeper than the water table. If groundwater levels continue to decline just a bit more, many of those wells could be left high and dry.
“Up to one in five wells are not much deeper than their local groundwater level,” said Debra Perrone, an assistant professor of environmental studies at the University of California, Santa Barbara. “That's quite a lot of people that are vulnerable to having a well run dry.”
What the research found
Perrone and coauthor Scott Jasechko, an assistant professor of water resources at UCSB, compiled and analyzed millions of records of wells’ locations and depths and the dates they were drilled in countries across the world, from Canada to Argentina to Thailand.
They compared the depths of the wells to measured groundwater levels in countries that publish data, such as Mexico, France and Australia. They also used data from satellites that have tracked shifts in water resources globally and shown widespread declines in aquifers.
“Our work highlights the vulnerability of existing wells to groundwater depletion,” the researchers wrote in the study, which was published last week in the journal Science.
With water levels declining in many areas, newly drilled wells tend to be deeper than older wells. But the study also found, surprisingly, that newer wells aren’t being constructed deeper than older wells in some places where aquifers are falling, indicating that newer wells “are at least as likely to run dry as older wells if groundwater levels continue to decline.”
Chronic overpumping has been depleting groundwater in many parts of the western United States, from rural communities in Arizona to the farmlands of the southern High Plains in Kansas. As large farms with deep wells have pumped from the aquifers, water levels have dropped and some nearby homeowners have been left with dry wells.
A 2019 Arizona Republic investigation revealed how unchecked pumping by expanding farms has been draining groundwater while homeowners and rural towns have been left with mounting costs as wells run dry. The Republic’s analysis of state groundwater data showed water levels in nearly a fourth of the wells in the state’s monitoring program have dropped more than 100 feet since they were drilled, a loss that experts say is probably irrecoverable.
The investigation revealed that large corporate farms have been dramatically expanding their operations, that new well-drilling has been accelerating and that the largest declines in water levels have occurred in farming areas where there are no limits on pumping.
Heavy use of groundwater has dried up some desert streams and reduced the flow of other rivers in the Southwest. And in places, collapsing aquifers have led to sinking ground, leaving gaping fissures in the land and cracking roads and canals.
In California, water officials have recorded more than 2,800 reports of “household water supply shortages,” which generally involve dry wells, since 2013. Many of those wells dried up during the state’s last severe drought from 2012-16, and many of those cases occurred in the Central Valley, where agricultural pumping has been drawing down water levels for decades.
As the West’s water supplies are strained by deepening drought and the long-term effects of climate change, the latest research points to serious risks that many more wells could soon be in jeopardy as groundwater levels continue to sink lower.
A global crisis, from Africa to the Southwest
The new study is the first to compile and analyze well-drilling records showing locations and depths on a global scale, and the findings show how continuing groundwater depletion may threaten a large portion of existing wells in many countries.
In an accompanying article in Science, water scientists Jay Famiglietti and Grant Ferguson describe it as “the hidden crisis beneath our feet.”
“Jasechko and Perrone have helped make the invisible visible,” they wrote, saying the study delivers “a timely warning that universal access to groundwater is fundamentally at risk.”
Pumped Dry: The Global Crisis of Vanishing Groundwater
Famiglietti is a hydrologist and director of the Global Institute for Water Security at the University of Saskatchewan, where Ferguson is a professor focusing on hydrogeology.
“As groundwater levels decline around the world, only the relatively wealthy will be able to afford the cost of drilling deeper wells and paying for the additional power required to pump groundwater from greater depths,” Famiglietti and Ferguson wrote. They said low-income families, poorer communities and small farms “will experience progressively more limited access in the many regions around the world where groundwater levels are in decline.”
They pointed out that it’s already been happening in California’s Central Valley, where in many cases farmworkers and other low-income homeowners rely on the shallowest wells and have often been the ones left dealing with dry wells.
“Without intervention, the gap between the water ‘haves’ and ‘have nots’ will only widen further,” Famiglietti and Ferguson wrote.
Billions of people worldwide rely on groundwater pumped from wells for drinking water. Nearly half of the world’s irrigated agriculture depends on groundwater.
In previous research, Jasechko and Perrone analyzed nearly 12 million well-drilling records from across the United States and found that in many areas Americans have been drilling deeper for groundwater as levels decline.
In their latest study, they compiled and analyzed well completion records from 70 other databases. They gathered data from Brazil, Chile, Portugal, Spain, Namibia, South Africa and other countries, all representing about half of the groundwater that is pumped each year worldwide.
The analysis focused on countries for which data are readily available, including some that are among the biggest groundwater users, such as India (No. 1), the United States (No. 2) and Mexico, which is among the top seven nations. Other major groundwater users such as China, Pakistan and Iran weren’t included.
Groundwater crisis: How unchecked pumping is sucking aquifers dry in India
The researchers estimated that between 6% and 20% of wells aren’t much deeper than the water table — specifically, not more than 5 meters deeper — using two different global estimates of water tables from previous studies.
In six Southwestern states from California to New Mexico, the analysis showed the prevalence of wells with depths close to the water table was a little higher, with the lower estimate turning out to be 8% instead of 6%. And in Mexico, that lower estimate was even higher, at 12%.
The Southwest really “pops out” in the data because relatively deep wells are widespread, Jasechko said, and some areas have large numbers of very deep wells.
When Jasechko made a map of well depths in central and southern Arizona, wells deeper than 100 meters (328 feet) appeared as thick concentrations of red dots, like chili powder scattered across the map.
In some rural areas of Arizona, such as Willcox, large farming operations pump water from hundreds of feet underground, drawing on wells as deep as 2,500 feet. Nearby homeowners, many of whom have wells from 350 to 600 feet deep, are relatively vulnerable as pumping continues and water levels drop.
In these rural communities, the state has no rules limiting how much water is pumped, and recent proposals to establish some rules in unregulated areas have failed to move forward in the Legislature.
When wells run dry, homeowners often must pay tens of thousands of dollars to drill a deeper well or deepen the existing well. Others have turned to paying for water hauled by truck. While selling a property with a dry well could be appealing for some, it’s also tough to sell land without access to water.
“Deeper wells are expensive. And so this raises a number of equity and adaptation concerns over the long term,” Perrone said, “because the people who can drill deeper are the people with the money to do so.”
'A free-for-all': As groundwater declines in rural Arizona, oversight faces resistance
Declines in groundwater can result not only from overpumping but also from reductions in the amount of water that’s recharging aquifers, due to drought, climate change or a combination of factors.
The researchers said groundwater plays an especially vital role as the world gets hotter with climate change and as droughts grow more intense in the Western U.S. and other arid regions.
“I was surprised at how many places we found groundwater levels were declining, yet newer wells were not much deeper than older wells, implying new wells are at least as vulnerable,” Jasechko said.
He and other scientists often describe aquifers as underground “savings accounts” of water, finite resources that are naturally replenished very slowly and should be managed for long-term sustainability.
“I think this research has driven home how widespread reliance on groundwater is around the world, and just how important it is as a buffer against climate change and variability,” Jasechko said. “Excessive groundwater pumping can deplete groundwater reserves and cause wells to run dry. And that impacts people in terms of their access to clean and reliable tap water,” as well as access to water they depend on for their livelihoods.
Groundwater also is connected to rivers and streams and the ecosystems they support.
Some stretches of rivers receive inflows from groundwater, while in others, river water seeps down into aquifers. In a separate study this year, Jasechko, Perrone and other scientists found that two-thirds of streams lie above surrounding groundwater levels, showing many of these potentially “leaky” streams already may be losing flow as wells draw water close by.
Potential solutions
In their latest study, Jasechko and Perrone wrote that groundwater depletion is projected to continue in areas where it’s occurring and “expand to new areas.” Despite that, they said, some countries don’t have long-term groundwater monitoring programs. They suggested these countries start monitoring groundwater levels and making the data publicly available.
Perrone said there are a wide variety of solutions for managing groundwater and preventing undesirable outcomes, such as implementing science-based regulations, adopting water-saving technologies and using available water to recharge aquifers.
“The solutions are complex, but there are solutions that could get us to sustainable groundwater management,” Perrone said. For one thing, she said, having detailed local information about the water supply is fundamental.
At the global scale, Famiglietti and Ferguson said the findings show that “climate resilience is at considerable risk.”
They called for action to prevent widespread water shortages, saying the consequences of millions of wells running dry “would be severe and unparalleled,” posing major threats to food production and the health and livelihoods of millions.
“Disappearing groundwater resources may act as a trigger for violent conflicts and have the potential to generate waves of climate refugees,” they wrote. “Avoiding such a scenario is clearly paramount to human security.”
Ian James covers water, climate change and the environment for The Arizona Republic. Send him story tips, comments and questions at ian.james@arizonarepublic.com and follow him on Twitter at @ByIanJames.
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Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow The Republic environmental reporting team at environment.azcentral.com and @azcenvironment on Facebook, Twitter and Instagram.
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The Link LonkApril 29, 2021 at 01:32AM
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A 'hidden crisis': Millions of groundwater wells are at risk of running dry, scientists find - The Arizona Republic
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