The Ogallala Aquifer

Here is a link to the Wikipedia article. Summarizing, this is one of the world's largest aquifers overlying 174,000 square miles in the Great Plains. It supplies 82% of the drinking water of those living within it's boundaries. "Today about 27% of the irrigated land in the entire United States lies over the aquifer, which yields about 30% of the ground water used for irrigation in the United States." And finally, the aquifer has a recharge rate of 6000 years. In other words it would take that long to refill it.

History

"Early settlers of the semiarid High Plains were plagued by crop failures due to cycles of drought, culminating in the disastrous Dust Bowl of the 1930s. Only after World War II, when center-pivot irrigation became available, was the land mass of the High Plains aquifer system transformed into one of the most agriculturally productive regions in the world."

At places the water table is decreasing at a rate of 5 feet per year. This requires deepening of wells minimally. In places in Texas, the Oklahoma Panhandle and Southwest Kansas, the aquifer has been completely drained.

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