Follow Highway 70 through central Kansas on a hot summer's day and you'll invariably see this: a flat sea of cornstalks, stretching from horizon to horizon as far as the eye can see.
It was not always so. The High Plains region of the United States -- a subregion of the Great Plains stretching from the Midwest to the Rockies -- encompasses some of the most productive agricultural land in the country, but 200 years ago it was arid grassland. Its transformation was accomplished through innovations in technology and relied on a finite resource -- water.
Farmers withstood the High Plains' frequent droughts and dry spells by pumping groundwater from the region's aquifers, a trend that accelerated sharply with the electrification of rural America in the early 20th century. Since then, the levels of those aquifers have been dropping at an accelerating pace.
The recent drought that has gripped much of the Southwest for almost three years has thrown the issue into stark relief. A number of states and the U.S. Geological Survey have issued reports in recent weeks highlighting sharp drops in regional water levels due to increased groundwater pumping.
"The past year, we've had just about the biggest drop in groundwater levels I can remember," said Janie Hopkins, manager of the groundwater division of the Texas Water Development Board.
A recent study by the board found that water levels declined a median total of 4.8 feet between 2010 and 2011, nearly three times higher than the median decline of 2009 to 2010. Considering that the drought is ongoing in many of the districts, water managers fear the findings for 2012 and perhaps even 2013 will be similarly severe.
An accelerating rate of decline
The nation's largest aquifer is the Ogallala, underlying more than 170,000 square miles of the High Plains region and stretching across eight states, from Nebraska to Texas. A major source of both irrigation and domestic consumption, it is also one of the fastest-declining groundwater reserves in the country.
A recent study by USGS found that its rate of depletion accelerated sharply over the past decade with declines from 2001 to 2008 accounting for 32 percent of the cumulative depletion over the course of the entire 20th century. In places, water table levels have fallen 160 feet since the mid-20th century.
"During the 1940s and 1950s, the growth of populations and the expansion of industry meant many more farmers were drilling wells, particularly in the High Plains," said Leonard Konikow, a research hydrologist with USGS. "This was land that had never been irrigated before -- land that ordinarily wouldn't have supported these kinds of crops."
While aquifers do recharge over time -- the nation's water tables kept to a relatively constant level during the historically wet, cool years of the 1960s and 1970s -- that rate of recharge can't make up for water use in the West.