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The local inhabitants came to realize the area was at the time well suited for farming , due in part to the fact that large portions of the region sit atop one of the world 's largest groundwater reservoirs , the Ogallala Aquifer .
 Ogallala Aquifer
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Ogallala Aquifer