A new study has found that more than one-third of US states in the southern Great Plains could run out of groundwater within the next 30 years. Of course, running out of groundwater is never good, but this could be especially bad news for human populations and especially the US since this is a key agricultural region of the country.
The new study, published this week in the Proceedings of the National Academy of Sciences, finds that the two most important aquifers in the US, one under the High Plains of the central US and the other under California’s Central Valley, are actually being unsustainably drained from these agricultural uses.
“The nation’s food supply may be vulnerable to rapid groundwater depletion from irrigated agriculture,” the University of Texas writes.
"Groundwater depletion has been most severe in the purple areas indicated on these maps of (A) the High Plains and (B) California's Central Valley. These heavily affected areas are concentrated in parts of the Texas Panhandle, western Kansas, and the Tulare Basin in California's Central Valley. Changes in groundwater levels in (A) are adapted from a 2009 report by the U.S. Geological Survey and in (B) from a 1989 report by the USGS."
The researchers hope that this information will lead to more sustainable use of water in these regions, but they also conclude that any irrigated agriculture is now unsustainable in some places.
The researchers say that some societal changes are already underway in response to this issue.
“We’re seeing decreases in rural populations in the High Plains,” said Bridget Scanlon, senior research scientist at The University of Texas at Austin’s Bureau of Economic Geology and lead author of the study. ”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.”
To put the scale of this issue into perspective a bit, consider this fact: “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 man-made reservoir, Lake Mead near Las Vegas.”
Another shocking piece of information from the study is that about 33% of the High Plains groundwater depletion comes from activities on just 4% of the region’s land. Again, it’s the water-intensive and water-inefficient agriculture production of the region that is most responsible for the depletion.
“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.”
Again, as the title above notes, perhaps the most concerning overall finding of the study is that, without a change in practices, some areas of these regions will be unable to support irrigated agriculture within the next 30 years.
Here’s more from the University of Texas on potential solutions:
“Scanlon and her colleagues suggested several ways to make irrigated agriculture in the Central Valley more sustainable: Replace flood irrigation systems (used on about half of crops) with more efficient sprinkle and drip systems and expand the practice of groundwater banking—storing excess surface water in times of plenty in the same natural aquifers that supply groundwater for irrigation. Groundwater banks currently store 2 to 3 cubic kilometers of water in California, similar to or greater than storage capacities of many of the large surface water reservoirs in the state. Groundwater banks provide a valuable approach for evening out water supplies during climate extremes ranging from droughts to floods.
“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.”
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