Study Links Food Production and Groundwater Levels

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Dwindling groundwater supplies from three heavily depleted aquifers, including one in California, are used to grow 18.5% of the nation's cereal grains, a new study says

Groundwater in America's major aquifers is being used up way faster than it's being replenished. But where does all that water go?

A lot of it is used in producing food for the nation’s city dwellers, a new study calculates.

Rather than try to figure out how much water farmers use in comparison with how much cities demand, the study's authors looked at the foods that groundwater is used to grow — and who gets to eat them.

“Cities and farms are linked,” said Megan Konar, a hydrologist in the Civil and Environmental Engineering Department at the University of Illinois at Urbana-Champaign and one of the authors of the study. “Rural areas produce the food that is consumed in urban areas. Sometimes we forget that.”

Konar and her colleagues wanted to know who eats the food produced with water from the most depleted aquifers in the United States. They looked at three of the most overdrawn groundwater systems in the country: the High Plains aquifer in the Midwest, the Mississippi Embayment aquifer in the Southeast and the Central Valley aquifer in California.

For each system, the researchers examined how much groundwater was withdrawn for agricultural irrigation, how many crops were produced using the groundwater, and how much water each type of crop consumed until it was ready for harvest. They also tracked where each crop was shipped.

They used publicly available data for their research: U.S. Geological Survey estimates of groundwater withdrawals for irrigation, U.S. Department of Agriculture estimates of crop production and the nonprofit Water Footprint Network estimates of how much water each type of crop needs to grow to maturity. The researchers used the U.S. Census Bureau’s Commodity Flow Survey and harbor-level export data to track where crops were distributed.

In doing so, they were able to calculate the amount of groundwater from each aquifer that was embodied in the crops and where those crops were eaten. They used figures from 2005 and 2007, as those were the most recent years that detailed data were available.

About 70% of the freshwater pumped up from America’s aquifers in 2005 was used for agriculture and livestock production, the Geological Survey reported.

Source: LA Times

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