Science Natural Science What Is Fossil Water? Geology and Renewability Can these non-renewable water sources keep up with demand in the 21st century? By Gia Mora Gia Mora Facebook Twitter Writer and Quality Team Editor University of Colorado University of Pisa Gia is a writer, performer, and producer who has written extensively about veganism, food waste, and sustainable living. Learn about our editorial process Updated October 25, 2022 Fact checked by Olivia Young Fact checked by Olivia Young Twitter Ohio University Olivia Young is a writer, fact checker, and green living expert passionate about tiny living, climate advocacy, and all things nature. She holds a degree in Journalism from Ohio University. Learn about our fact checking process Share Twitter Pinterest Email Science Space Natural Science Technology Agriculture Energy In This Article Expand Geography and Geology Sustainability Outlook Frequently Asked Questions Fossil water refers to underground reservoirs formed during the last glacial ice age. Also known as petrowater or paleowater, fossil water borrows its name from paleontology. Like a traditional fossil, fossil water is trapped in rock—sometimes for millennia. These aged aquifers acquired their water from melting ice and prehistoric lakes that pooled into subterranean layers of water-porous rocks, silt, and sand. Over time, those layers were covered with more sediment, effectively sealing off the water from Earth’s surface for tens of thousands of years. Just 70 years ago, farmers began drilling into fossil aquifers, pumping water to previously dry climates worldwide. Today, billions of people rely on fossil aquifers for their drinking water and as irrigation to grow staple food crops. Geography and Geology Fossil water appears all over the globe in humid, semi-arid, and arid regions as well as areas of permafrost. Lake Vostok, for example, is one of more than 70 subglacial lakes trapped beneath Antarctica's ice sheet. The Nubian Sandstone Aquifer System is the biggest fossil aquifer in the world and runs beneath the four northeast African nations. The Arabian peninsula, eastern Australia, the Parisian basin in France, the Great Plains of the U.S., and parts of Mexico and California all rely on paleowater for agriculture, sanitation, and consumption. Regardless of the current climate of these places, sometime before the Holocene epoch (the geologic age in which we now live), the planet was much wetter. These more humid climate conditions allowed aquifers—water-bearing layers of semi-porous rock and other materials—to form. Fossil aquifers are frequently contained by layers of impermeable rocks and clay, preventing the aquifer from absorbing any precipitation. Some petrowater not encased in a hard outer layer is so far beneath the ground that it's often only detectable by airborne electromagnetic surveys. Understandably, these aquifers are nearly impossible to replenish. Other fossil water sits beneath deserts where there’s not enough annual precipitation to refill the aquifers. Today, billions of people in some of the world’s most arid regions—such as in North America, Iran, India, and Africa—rely almost entirely on petrowater. Research published in 2017 found that fossil water accounts for up to 85% of all groundwater in the top meter of the Earth’s crust. Most well water drawn from sources 250 meters (820 feet) and lower also comes from fossil aquifers. Sustainability If left untouched by human activities, paleowater would remain in equilibrium. But as the need to grow crops (often to feed livestock) expanded around the world in the last half of the 20th century, many farmers turned to fossil aquifers. These free water sources provided enormous advantages for communities in dry climates, turning previously inhospitable areas into lush farming zones. Unfortunately, once fossil water has been pumped to the surface, it can take thousands of years to replenish. Experts estimate, for example, that once the Ogallala aquifer in the High Plains has been fully mined, it would take over 6,000 years to restore it to its original levels. As an aquifer is depleted, pumping water becomes more difficult and more expensive. The water brought to the surface can become brackish, requiring desalination, especially if it’s used as drinking water. Deplete an aquifer too quickly and it can collapse on itself, further trapping existing supplies. The Future of Fossil Water Because fossil water is non-renewable, aquifers around the world risk soon being mined dry: The Ogallala aquifer, which supplies nearly one-third of the groundwater used for irrigation in the U.S., may have only 30 to 50 years of remaining productivity. NASA satellite studies confirm irreparable aquifer declines in India. Experts have spent the last decade warning that Yemen is running out of water. In Africa, the non-renewable Nubian aquifer will have to support an estimated 731 million people by 2050. Experts already predict that more than 60% of people in the world will experience water scarcity by 2025, and thanks to global warming, increasing temperatures will only make matters worse. These stark realities understandably spark fear in the hearts of people in arid climates who depend on fossil water to cultivate resource-intensive crops like wheat and rice. In order to support a more sustainable future, farmers in fossil water-dependent regions must use less water, grow alternative drought-friendly crops, and rely on imports for staple foods that previously underpinned the agricultural economy. Frequently Asked Questions Why is fossil water important? Some of the world’s biggest bodies of fossil water are the primary water sources for huge swaths of the global population. That poses a problem for arid and semi-arid climates that don’t receive enough precipitation to replenish fossil aquifers, leading to fears of water scarcity, decreased staple crop production, and higher food costs. How old is fossil water? Fossil water is at least 11,000 years old, dating back to the end of the last glacial ice age. Some fossil water, like the aquifer in Libya, has been carbon dated to 40,000 years ago. Is fossil water a renewable source? Yes. Like fossil fuels, fossil water formed over an extended period of time during a previous geological era. Once a fossil aquifer has been depleted, it may take thousands of years to replenish it—if it can be replenished at all, given projected expectations for rising global temperatures and the demand for water to serve a growing population. View Article Sources Siegert, M., Ellis-Evans, J., Tranter, M. et al. Physical, chemical and biological processes in Lake Vostok and other Antarctic subglacial lakes. Nature 414, 603–609 (2001). doi:10.1038/414603a "Nubian Sandstone Aquifer, Egypt." NASA Jet Propulsion Laboratory. "The Ogallala Aquifer." The Kerr Center for Sustainable Agriculture. 2014. "Arid Arabian Peninsula Is Tapping into Vast Groundwater Reserves." American Geophysical Union. 2019. Mir, R., et al. “Fossil Water: Last Resort to Resolve Long-Standing Water Scarcity?” Agricultural Water Management, vol. 261, 2022, p. 107358. doi:10.1016/j.agwat.2021.107358 De Jong, Menso, et al. “Identifying Paleowater in California Drinking Water Wells.” Quaternary International, vol. 547, 2020, pp. 197–207. doi:10.1016/j.quaint.2019.04.008 Jasechko, S., et al. "Global aquifers dominated by fossil groundwaters but wells vulnerable to modern contamination." Nature Geosci 10, 425–429 (2017). doi:10.1038/ngeo2943 "NIFA Impacts: Saving the Ogallala Aquifer, Supporting Farmers." United States Department of Agriculture. 2021. "Groundwater Facts." National Ground Water Association. "Fossil Water." Bureau of Economic Geology EarthDate. Glass, Nicole. "The Water Crisis in Yemen: Causes, Consequences and Solutions." Global Majority E-Journal, vol. 1, no. 1, June 2010, pp. 17-30. Sherif, M.I., and N.C. Sturchio. "Elevated radium levels in Nubian Aquifer groundwater of Northeastern Africa." Sci Rep 11, 78 (2021). doi:10.1038/s41598-020-80160-0 "Water Scarcity." World Wildlife Fund. "'Fossil Water' in Libya." NASA Earth Observatory.