Many of Your Groceries Are Really Just Groundwater in Disguise
With its three long, narrow fingers spreading out into the Nevada desert, Lake Mead doesn’t look all that impressive on a map. The appearance belies its record-setting reality: The lake, fed by Colorado River water trapped by the Hoover Dam, is the largest surface reservoir in the United States.
According to a study published Monday in the Proceedings of the National Academy of Sciences, the amount of water sucked out of the U.S.’s three major aquifers in 2007 was equal to the reservoir's 22-cubic-mile capacity. That’s a massive amount of water by any measure—but even more so when it comes to groundwater, which is a resource that is very slow to replenish. It amounts to what the study's authors, led by Landon Marston at the University of Illinois, fairly call "overexploitation."
Marston and his colleagues looked at the ultimate end point of that water, whether it was pumped into municipal utility systems or into irrigation ditches, to give a stark sense of how groundwater moves around the country and, in some instances, around the globe. In terms of food, farms in the Central Valley, High Plains, and Mississippi Embayment aquifer regions accounted for one-fifth of the $300 billion ag economy.
In the year the study examined, 2007, much of California received between a third and a half of what constitutes a “normal” year’s rainfall. The past four years have seen even less precipitation, and with surface water deliveries at 60 percent of normal, the once gigantic Central Valley aquifer is the last resource for many of the state’s farmers. According to a NASA study, the aquifer is at an 11-trillion-gallon deficit. In 2012, drought parched vast stretches of Midwestern cropland, pushing farmers to rely on groundwater irrigation that tapped both the High Plains and the Mississippi Embayment, depending on their location. Then, last July, Lake Mead marked a record low.
All of which is to say that the situation since data was collected for this study, reportedly the first of its kind, has probably only gotten worse. The authors write that groundwater withdrawals “intensified” between 2000 and 2008, and the drilling rush in California would suggest that the trend has continued, at least in that part of the country.
Even so, the findings hold surprises. Despite all of the talk of exporting California water in the form of almonds and cattle feed, the authors found that 91 percent of “virtual groundwater transfers” stay in the U.S., with between 45 and 58 percent of the water ending up in states that don’t sit atop the aquifers. Taiwan and Japan are two of the chief importers of American groundwater, mainly in the form of grains, with 9.2 percent of Japanese cereals originated from U.S. farms. Of the 9 percent of virtual groundwater transfers that go overseas in the form of food or foodstuffs, half are destined for Asian markets.
With regard to California, where irrigated agriculture is far more diverse than that of the corn-and-soy-heavy Midwest, the study lends credence to the argument that meat, more than almonds, is the problem. Despite California supplying half of the country’s domestic fruits and vegetables, 38 percent of virtual groundwater transfers from the Central Valley aquifer are associated with meat products, while just 4 percent are tied up in fresh produce—a number that may be artificially low owing to the way some crops are categorized in the data source and one that has certainly gone up after four years of drought.
“There are always tradeoffs in our consumption decisions. For example, if city-dwellers in L.A. and San Francisco eat food grown with Central Valley groundwater, this would be applauded from an ‘eat local’ perspective,” Megan Konar, assistant professor of civil and environmental engineering at the University of Illinois and a coauthor of the study, said in an email. “However, from a water resources perspective, it may make sense to consume food grown with rainfall in other parts of the county.”
“These groundwater resources are finite and produce a lot of food for global markets,” she added. “Mining them now is essentially trading off future food security with current agricultural production. We should think of these aquifers as strategic national reserves.”
The U.S. keeps enough oil in reserve to keep the country running for a month or two in the event of a major supply disruption. Given the pressure on water resources in food-producing parts of the country, and the difficulty many cities are having meeting their needs, is it time to implement the Strategic Groundwater Reserve?