Some scientists think agriculture that relies on irrigation from groundwater in some areas of California’s Central Valley and the High Plains of the U.S. is unsustainable over the long haul because of water being needed for consumer needs other than food production.

 "We're already seeing changes in both areas," said Bridget Scanlon, senior research scientist at The University of Texas at Austin's Bureau of Economic Geology and lead author of a study published in the Proceedings of the National Academy of Sciences. "We're seeing decreases in rural populations in the High Plains. Increasing urbanization is replacing farms in the Central Valley. And during droughts some farmers are forced to fallow their land. These trends will only accelerate as water scarcity issues become more severe," Scanlon is quoted as saying in a ScienceDaily article.

Periods of drought show extreme depletion of groundwater that cannot be recharged quickly, and agricultural production, as being practiced today, uses too much water to justify continuing in the same manner as in the recent past.

The researchers note how California's Central Valley is sometimes called the nation's "fruit and vegetable basket," and the High Plains is sometimes called the country's "grain basket."

“Combined, these two regions produced agricultural products worth $56 billion in 2007, accounting for much of the nation's food production. They also account for half of all groundwater depletion in the U.S., mainly as a result of irrigating crops,” the ScienceDaily article notes.

Scanlon, U.S. Geological Survey scientists and Université de Rennes of France scientists used water level records from thousands of wells, data from NASA's GRACE satellites, and computer models to study groundwater depletion.

The study suggests some ways to alleviate the groundwater depletion in the Central Valley but has no answers for the High Plains other than eliminating agricultural production using irrigation. "Basically irrigated agriculture in much of the southern High Plains is unsustainable," lead author Scanlon is quoted as saying.

Read the ScienceDaily article here.