Third of Big Groundwater Basins in Distress
https://www.jpl.nasa.gov/news/study-third-of-big-groundwater-basins-in-distress
What You Need to Know About the World's Water Wars
Underground water is being pumped so aggressively around the globe that land is sinking, civil wars are being waged, and agriculture is being transformed.
https://www.nationalgeographic.com/science/article/world-aquifers-water-wars
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Third of Big Groundwater Basins in Distress
Groundwater storage trends for Earth's 37 largest aquifers from UCI-led study using NASA GRACE data (2003 - 2013). Of these, 21 have exceeded sustainability tipping points and are being depleted, with 13 considered significantly distressed, threatening regional water security and resilience. Credit: UC Irvine/NASA/JPL-Caltech
UC Irvine studies using NASA GRACE data find a third of Earth's largest groundwater basins are being rapidly depleted by human use, despite little data about how much water remains.
About one third of Earth's largest groundwater basins are being rapidly depleted by human consumption, despite having little accurate data about how much water remains in them, according to two new studies led by the University of California, Irvine (UCI), using data from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites.
This means that significant segments of Earth's population are consuming groundwater quickly without knowing when it might run out, the researchers conclude. The findings are published today in Water Resources Research.
"Available physical and chemical measurements are simply insufficient," said UCI professor and principal investigator Jay Famiglietti, who is also the senior water scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. "Given how quickly we are consuming the world's groundwater reserves, we need a coordinated global effort to determine how much is left."
The studies are the first to comprehensively characterize global groundwater losses with data from space, using readings generated by NASA's twin GRACE satellites. GRACE measures dips and bumps in Earth's gravity, which are affected by the mass of water. In the first paper, researchers found that 13 of the planet's 37 largest aquifers studied between 2003 and 2013 were being depleted while receiving little to no recharge.
Eight were classified as "overstressed," with nearly no natural replenishment to offset usage. Another five were found to be "extremely" or "highly" stressed, depending upon the level of replenishment in each. Those aquifers were still being depleted but had some water flowing back into them.
The most overburdened aquifers are in the world's driest areas, where populations draw heavily on underground water. Climate change and population growth are expected to intensify the problem.
"What happens when a highly stressed aquifer is located in a region with socioeconomic or political tensions that can't supplement declining water supplies fast enough?" asked Alexandra Richey, the lead author on both studies, who conducted the research as a UCI doctoral student. "We're trying to raise red flags now to pinpoint where active management today could protect future lives and livelihoods."
The research team -- which included co-authors from NASA, the National Center for Atmospheric Research, National Taiwan University and UC Santa Barbara -- found that the Arabian Aquifer System, an important water source for more than 60 million people, is the most overstressed in the world.
The Indus Basin aquifer of northwestern India and Pakistan is the second-most overstressed, and the Murzuk-Djado Basin in northern Africa is third. California's Central Valley, used heavily for agriculture and suffering rapid depletion, was slightly better off, but was still labeled highly stressed in the first study.
"As we're seeing in California right now, we rely much more heavily on groundwater during drought," said Famiglietti. "When examining the sustainability of a region's water resources, we absolutely must account for that dependence."
In a companion paper published today in the same journal, the scientists conclude that the total remaining volume of the world's usable groundwater is poorly known, with estimates that often vary widely. The total groundwater volume is likely far less than rudimentary estimates made decades ago. By comparing their satellite-derived groundwater loss rates to what little data exist on groundwater availability, the researchers found major discrepancies in projected "time to depletion." In the overstressed Northwest Sahara Aquifer System, for example, time to depletion estimates varied between 10 years and 21,000 years.
"We don't actually know how much is stored in each of these aquifers. Estimates of remaining storage might vary from decades to millennia," said Richey. "In a water-scarce society, we can no longer tolerate this level of uncertainty, especially since groundwater is disappearing so rapidly."
The study notes that the dearth of groundwater is already leading to significant ecological damage, including depleted rivers, declining water quality and subsiding land.
Groundwater aquifers are typically located in soils or deeper rock layers beneath Earth's surface. The depth and thickness of many large aquifers make it tough and costly to drill or otherwise reach bedrock and understand where the moisture bottoms out. But it has to be done, the authors say.
To read the technical papers, visit:
http://onlinelibrary.wiley.com/doi/10.1002/2015WR017349/abstract
and
http://onlinelibrary.wiley.com/doi/10.1002/2015WR017351/abstract
GRACE is a joint mission with the German Aerospace Center and the German Research Center for Geosciences, in partnership with the University of Texas at Austin. JPL developed the GRACE spacecraft and manages the mission for NASA's Science Mission Directorate, Washington.
For more information on GRACE, visit:
and
http://www.csr.utexas.edu/grace
NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.
For more information about NASA's Earth science activities, visit:
What You Need to Know About the World's Water Wars
Beijing is sinking.
In some neighborhoods, the ground is giving way at a rate of four inches a year as water in the giant aquifer below it is pumped.
The groundwater has been so depleted that China’s capital city, home to more than 20 million people, could face serious disruptions in its rail system, roadways, and building foundations, an international team of scientists concluded earlier this year. Beijing, despite tapping into the gigantic North China Plain aquifer, is the world’s fifth most water-stressed city and its water problems are likely to get even worse.
Beijing isn’t the only place experiencing subsidence, or sinking, as soil collapses into space created as groundwater is depleted. Parts of Shanghai, Mexico City, and other cities are sinking, too. Sections of California’s Central Valley have dropped by a foot, and in some localized areas, by as much as 28 feet.
Around the world, alarms are being sounded about the depletion of underground water supplies. The United Nations predicts a global shortfall in water by 2030. About 30 percent of the planet’s available freshwater is in the aquifers that underlie every continent.
More than two-thirds of the groundwater consumed around the world irrigates agriculture, while the rest supplies drinking water to cities. These aquifers long have served as a backup to carry regions and countries through droughts and warm winters lacking enough snowmelt to replenish rivers and streams. Now, the world’s largest underground water reserves in Africa, Eurasia, and the Americas are under stress. Many of them are being drawn down at unsustainable rates. Nearly two billion people rely on groundwater that is considered under threat.
Richard Damania, a lead economist at the World Bank, predicts that without adequate water supplies, economic growth in the most stressed parts of the world could decline by six percent of GDP. His findings conclude that the most severe impacts of climate change will deplete water supplies.
“If you are in a dry area, you are going to get a lot less rainfall. Run-off is declining,” he says. “People are turning to groundwater in a very, very big way.”
But few things are more difficult to control than groundwater pumping, Damania says. In the United States, farmers are withdrawing water at unsustainable rates from the High Plains, or Ogallala Aquifer, even though they have been aware of the threat for six decades.
“What you have in developing countries is a large number of small farmers pumping. Given that these guys are earning so little, there is very little you can do to control it,” Damania says. “And you are, literally, in a race to the bottom.”
As regions and nations run short of water, Damania says, economic growth will decline and food prices will spike, raising the risk of violent conflict and waves of large migrations. Unrest in Yemen, which heavily taps into groundwater and which experienced water riots in 2009, is rooted in a water crisis. Experts say water scarcity also helped destabilize Syria and launch its civil war. Jordan, which relies on aquifers as its only source of water, is even more water-stressed now that more than a half-million Syrian refugees arrived.
Jay Famiglietti, lead scientist on a 2015 study using NASA satellites to record changes in the world’s 37 largest aquifers, says that the ones under the greatest threat are in the most heavily populated areas.
"Without sustainable groundwater reserves, global security is at far greater risk,” he says. “As the dry parts are getting drier, we will rely on groundwater even more heavily. The implications are just staggering and really need to be discussed at the international level.”
Below are answers to your key questions.
Where is groundwater the most threatened?
The most over-stressed is the Arabian Aquifer System, which supplies water to 60 million people in Saudi Arabia and Yemen. The Indus Basin aquifer in northwest India and Pakistan is the second-most threatened, and the Murzuk-Djado Basin in northern Africa the third.
How did these giant basins become so depleted?
Drought, bad management of pumping, leaky pipes in big-city municipal water systems, aging infrastructure, inadequate technology, population growth, and the demand for more food production all put increasing demand on pumping more groundwater. Flood irrigation, which is inefficient, remains the dominant irrigation method worldwide. In India, the world’s largest consumer of groundwater, the government subsidizes electricity – an incentive to farmers to keep pumping.
How has irrigation changed farming?
Irrigation has enabled water-intensive crops to be grown in dry places, which in turn created local economies that are now difficult to undo. These include sugar cane and rice in India, winter wheat in China, and corn in the southern High Plains of North America. Aquaculture has boomed in the land-locked Ararat Basin, which lies along the border between Armenia and Turkey. Groundwater is cold enough to raise cold-water fish, such as trout and sturgeon. In less than two decades, the aquifer there has been drawn down so severely for fish ponds that municipal water supplies in more than two dozen communities are now threatened.
How much water remains?
More is known about oil reserves than water. Calculating what remains in aquifers is extraordinarily difficult. In 2015, scientists at the University of Victoria in British Columbia, Canada concluded that less than six percent of groundwater above one-and-a-half miles (two kilometers) in the Earth’s landmass is renewable within a human lifetime. But other hydrologists caution that measurements of stores can mislead. More important is how the water is distributed throughout the aquifer. When water levels drop below to 50 feet or less, it is often not economically practical to pump water to the surface, and much of that water is brackish or contains so many minerals that it is unusable.
Is there any good news?
Depleted groundwater is a slow-speed crisis, scientists say, so there's time to develop new technologies and water efficiencies. In Western Australia, desalinated water has been injected to recharge the large aquifer that Perth, Australia's driest city, taps for drinking water. China is working to regulate pumping. In west Texas, the city of Abernathy is drilling into a deeper aquifer that lies beneath the High Plains aquifer and mixing the two to supplement the municipal water supply.
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