Freshwater in the United States is really on the move. Much of the water pulled from underground reservoirs called aquifers gets incorporated into crops and other foodstuffs, which are then are shuttled around the country or transferred as far away as Israel and Japan, according to a new study. It shows how reliance on a finite supply of groundwater for agriculture threatens global food security. More than 18% of the U.S. supply of so-called cereal grains like corn, rice and wheat depends on a limited supply of groundwater found deep below the earth in aquifers, researchers found.
For the study, researchers evaluated data on virtual groundwater use to determine which areas rely most on overextended groundwater aquifers. Virtual groundwater refers to the transfer of water via products, agricultural and otherwise, rather than direct water use. The study included the Central Valley Aquifer in California, the High Plains Aquifer in the central U.S. and the Mississippi Embayment Aquifer in the area surrounding the Mississippi River.
Within the U.S., the metropolitan areas of San Francisco, Los Angeles, Dallas-Fort Worth and New Orleans topped the list of cities most reliant on groundwater aquifers. The implications of the study extend globally. Around 10% of cereal grains in Japan, Taiwan and Panama come from U.S. sources that rely on groundwater aquifers.
From the Arabian Peninsula to northern India to California’s Central Valley, nearly a third of the world’s 37 largest aquifers are being drained faster than they are being replenished, according to a recent study led by scientists at the University of California, Irvine. The aquifers are concentrated in food-producing regions that support up to two billion people.
With depletion of groundwater becoming a key concern across the world – yet again – the questions are many. For one, we do not precisely know how much groundwater exists in storage. Another open question is whether the governments and individuals who control groundwater can or will work to gain more knowledge about the extent of the resource and how much use is sustainable. Before these can be answered, we first need to gauge if our usage of water can be justified.
Read how the US’ water travels through the food chain here.