Ogallala Aquifer
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The Ogallala Aquifer is located beneath the Great Plains in the United States. It is an aquifer (concentration of groundwater) that dates back to the last ice age, over 10,000 years ago. The Ogallala has become depleted due to extraction for irrigation purposes.

The original article can be found at: http://en.wikipedia.org/wiki/Ogallala_Aquifer.
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