There is a new study in Proceedings of the National Academy of Sciences that gives a visual graphic of just how serious the ground water depletion in California's Central Valley and the High Plains of the central United States. The water table system of the High Plains running through West Texas, through large portions of Oklahoma and Kansas, and in the majority of Nebraska at its Northern terminus. The Geographic boundary of the High Plains does not exactly match the water table boundaries (which are shifted somewhat to the east). I think I am typical of most American who associate the High Plains with cowboy western movies.
The High Plains are the least densely populated area within the continental United States.
The combined areas both extremely important to U.S. agriculture. They would not normally be thought of as “marginal” agricultural areas.Agriculture in the forms of cattle ranching and the growing of wheat, corn and sunflowers is the primary economic activity in the region. The aridity of the region necessitates either dryland farming methods or irrigation; much water for irrigation is drawn from the underlying Ogallala Aquifer, which makes it possible to grow water-intensive crops such as corn, which the region's aridity would otherwise not sustainable (Wikipedia).
|Texas High Plains and Central Valley California Droughts (from report)|
Groundwater Depletion in Semiarid Regions of Texas and California Threatens US Food Security
Science Daily, 28 May 2012 (via the University of Texas) (hat tip: NC)
California's Central Valley is sometimes called the nation's "fruit and vegetable basket." The High Plains, which run from northwest Texas to southern Wyoming and South Dakota, are 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...
"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 the study. "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."
Three results of the new study are particularly striking: First, during the most recent drought in California's Central Valley, from 2006 to 2009, farmers in the south depleted enough groundwater to fill the nation's largest human-made reservoir, Lake Mead near Las Vegas -- a level of groundwater depletion that is unsustainable at current recharge rates.
The report writers are skeptical of the various suggested solutions to the problem of ground water depletion.Second, a third of the groundwater depletion in the High Plains occurs in just 4% of the land area. And third, the researchers project that if current trends continue some parts of the southern High Plains that currently support irrigated agriculture, mostly in the Texas Panhandle and western Kansas, will be unable to do so within a few decades.
For various reasons, Scanlon and other experts don't think these or other engineering approaches will solve the problem in the High Plains. When groundwater levels drop too low to support irrigated farming in some areas, farmers there will be forced to switch from irrigated crops such as corn to non-irrigated crops such as sorghum, or to rangeland. The transition could be economically challenging because non-irrigated crops generate about half the yield of irrigated crops and are far more vulnerable to droughts.
"Basically irrigated agriculture in much of the southern High Plains is unsustainable," said Scanlon.