Science Advances: Groundwater Mining Has Produced Greater SLR Impacts Than Melting Of Greenland's Ice Sheet [View all]

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Although climate change is a contributing factor, with elevated temperatures sapping moisture out of the ground, the main culprit is overpumping of groundwater. After that water is put to human use, it escapes into the ocean where, the study found, it has contributed more to sea level rise than the melting of the Greenland ice sheet. Total water storage losses on land, of which groundwater is the largest component, account for 44 percent of global mean sea level rise, compared to about 37 percent from Greenland and roughly 19 percent from melting in Antarctica. The fact that “human management of water resources has such a significant effect on sea level rise, I think that has not been seen before,” said Martin Stute, a hydrologist at Barnard College who did not contribute to the study. He pointed out that even the National Oceanic and Atmospheric Administration is still characterizing the transfer of groundwater to the ocean as a fairly minor addition to sea level rise.

Unless stringent water management policies are implemented on a global scale, the Science Advances study’s principal investigator, Jay Famiglietti, warns that the consequences could trigger extreme political instability, given that 75 percent of the world’s population resides in countries affected by this extreme drying. “What this study makes clear is that the world is looking at incredible sea level rise,” he said. “I think threats to food security and food production [aren’t] receiving enough attention.”

Such policies may not be forthcoming anytime soon. The United States, which sources half of its drinking water from groundwater, has no unifying water management plan, instead relying on a piecemeal local network of regulations. California passed the Sustainable Groundwater Management Act, which aims to regulate water withdrawals and prevent aquifer exhaustion, in 2014, but the state isn’t expected to reach sustainable water use patterns until the early 2040s. Other states like Louisiana and Maine grant landowners “absolute dominion” over groundwater under their property — meaning any landowner can draw endlessly from their well, even at the expense of their neighbor, even as aquifers are depleted and threatened by saltwater intrusion.

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Other research shows that groundwater depletion is only part of the story: What’s left of that water, another recent study in the peer-reviewed journal Nature Geoscience shows, is heating up. Study author Susanne Benz explained that the effects of global warming have started to penetrate underground, 40 or 50 meters deep in some areas. Warming could degrade groundwater quality by increasing microbial production, and warmer water makes it easier for dangerous chemical elements usually locked safely away in rock, such as arsenic, to dissolve into drinking water. It could also upend freshwater habitats in lakes, ponds, and rivers — allowing more harmful algae blooms and killing off aquatic life.

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https://grist.org/science/groundwater-depletion-study-sea-level-rise/