World running out of fresh water: NASA data
“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 the lead author on both studies, Alexandra Richey, 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 sixty 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, utilized heavily for agriculture and suffering rapid depletion, was slightly better off but 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,” Famiglietti said. “When examining the sustainability of a region’s water resources, we absolutely must account for that dependence.”
In a companion paper published yesterday in the same journal, the scientists conclude that the total remaining volume of the world’s usable groundwater is poorly known, with often widely varying estimates, but is likely far less than rudimentary estimates made decades ago.
By comparing their satellite-derived groundwater loss rates to what little data exists on groundwater availability, they found major discrepancies in projected “time to depletion.” In the overstressed Northwest Sahara Aquifer System, for example, this fluctuated between 10 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,” Richey said. “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 soil or deeper rock layers beneath Earth’s surface. The depth and thickness of many make it tough and costly to drill to or otherwise reach bedrock and learn where the moisture bottoms out. But it has to be done, according to the authors.
“I believe we need to explore the world’s aquifers as if they had the same value as oil reserves,” Famiglietti said. “We need to drill for water the same way that we drill for other resources.”
— Read more in Alexandra S. Richey et at el., “Quantifying renewable groundwater stress with GRACE,” Water Resources Research (16 June 2015) (DOI: 10.1002/2015WR017349); and Alexandra S. Richey et al., “Uncertainty in global groundwater storage estimates in a total groundwater stress framework,” Water Resources Research (16 June 2015) (DOI: 10.1002/2015WR017351)
