Lare-scale Irrigation in some Midwestern states may be approaching their breaking points as unsustainable watering practices face diminishing water levels. In the next 25 years some parts of the country may go dry faster than expected.

The High Plains (or Ogallala) Aquifer spans 111 million acres totaling 173,000 square miles. It's a veritable underground ocean and is used to irrigate crops and support livestock in eight states from South Dakota to Texas.

The crops produced in the region are shipped everywhere throughout the world. It is one of the globe's major agricultural producing regions - and it's drying up.

Since the 1950s, when advancements in well technology and water pumping meant agriculturalists could extract record amounts of water, the aquifer has dropped roughly 274 million acre feet, the bulk of the decline happening since the mid-1980s.

Such a drop means water levels have dipped by more than 150 feet in parts of Texas' Panhandle and South West Kansas, according to a United States Geologic Survey 2011 report that compared water level declines in recent years with levels 60 years ago.

According to the study, 19 million acre-feet of water was extracted from the aquifer in 2005. That's a 375 percent increase from 1949.

Brownie Wilson, Kansas Geological Survey's water level database administrator, said out of 8.6 million acres of Ogallala-irrigated land in Kansas, 1.2 million acres of farm land will be at minimum threshold, or the level at which water can no longer be pumped from the ground for irrigation, within less than 25 years. That will add to the already 2.2 million acres of that state already at minimum threshold.

Some of the areas they got pumping, they are in trouble, said Virgina McGuire, a USGS hydrologist operating out Lincoln Nebraska.

McGuire said 97 percent of the water usage above the Ogallala Aquifer is for irrigation, and the pumping is unsustainable.

In 2009, 13 percent of the aquifer had sustained more than a 25 percent drop in its saturated thickness - or the depth of the aquifer. Another 5 percent sustained 50 percent drops, according to the report.

The problem, McGuire said, is that pumping from the aquifer exceeds its natural recharge, or the time it takes surface water to gradually trickle back down into the earth.

Something has got to give, and what is that - that's a good question, she said. It certainly seems like they have to do something.

Water recharging the aquifer flows West to East. Depending on how much rainfall the area receives, less than 2 millimeters at times flows back into the aquifer a year, McGuire said. That's less than one tenth of an inch.

Nebraska, for example, irrigated just under 6 million acres in 2002. That same state two years prior pumped just under 8 million acre-feet, the largest amount of water pumped out of the eight states withdrawing water from the aquifer, according to USGS data.

As of 2000, there was enough water in the aquifer to fill a flat bottomed container the size of Colorado to 45 feet. Another USGS report published in 2000, which detailed the amount of stored water in the aquifer, said 60 to 80 percent of of the water is readily available to commercial and municipal wells. And it is in those areas where water levels are dropping the most.

Kevin Dennehy, USGS' Director of Ground Water Resources, said agriculture as it is known today will have to change in the region to reflect diminishing water supplies.

He said, although the aquifer will never fully run dry, water will be too deep in the ground in areas for wells to effectively mine the water.

And in a region of the country where corn, a particularly thirsty crop, is grown in abundance, this spells trouble.

Emerson Nafziger, a professor of crop science at the University of Illinois, said no other crop other than corn is as water efficient relative to its yield, but that to grow 10 bushels, one would need roughly 27,000 gallons of water.

Nafziger said the evaporation rates on the high plains means crops in general require more irrigation.

From 1972 to 1997, the acreage dedicated to corn production has steadily grown over the aquifer. Numbers from the National Agricultural Statistics Service show corn is the leading crop in the high plains with more than 7 million irrigated acres.

But faced with high pumping costs and localized drought conditions, Nafziger said farmers in the area are having to change their production to less water dependent crops like grain sorghum.

I don't know if people can think they can do anything else than that, Nafziger said.

But economics is playing its own role. Drawn to high crop yields and attractive prices, farmers stuck with the delicate issue of balancing economic need with conservation in Southwest Kansas -- where water levels have taken a particularly large dip -- are not completely phasing out their thirsty crops and continue to tax the aquifer.

Troy Dumler, an agricultural economist with Kansas State University based outside Garden City, said he has seen farmers rotate crops types and practice less water-intensive tilling and irrigation practices in response to growing watering concerns - but they still have an economic incentive to pump large and unsustainable amounts of water from the ground.

The answer is really simple: you have to cut back on [your use of water], but how you do that is the complicated thing, Dumler said.

Complicating matters all the more is how certain parts of the state are drying up -- and some already have -- while others expect readily available water for decades to come.

Dumler said he suspects the state's hodgepodge watering issues makes it hard for large-scale farming reform in the area to gain traction. While he remains cautiously optimistic, he adds policies will have to eventually be drafted to help encourage even less water use.

I don't think we can just stick our head in the sand and say 'Oh everything will be fine,' Dumler said, who anticipates watering issues could prompt some movement within the agricultural industry away from the state.

For now, water in the state is a flowing resource but it remains to be seen for how much longer and how industry will respond to the area's looming water crunch.