How long has it been since water in the deepest part of the Ogallala Aquifer percolated into the ground from the surface?

The Ogallala Aquifer is a large underground aquifer that spans eight states in the Great Plains region of the United States. It is estimated that the water in the deepest part of the Ogallala Aquifer has been percolating into the ground from the surface for approximately 10,000 to 12,000 years.