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The Ogallala Aquifer and Its Role as a Threatened American Resource

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This page was developed from a paper written by a delegate to the 2008 APEC Youth Camp held in Puno, Peru.  The purpose of the Youth Camp was to learn about sustainable development especially as it pertains to water-based economies as well as to investigate the culture and economy of the Lake Titicaca region in Peru.


Contents



Abstract

The Ogallala geological formation of the American Midwest is home one of the most vital water sources for American agriculture—the High Plains aquifer.  Commonly referred to as the Ogallala aquifer, it covers an area of 174,000 square miles across eight states and holds over 978 trillion gallons of fresh water.  The aquifer currently supplies approximately 30% of the nation’s irrigation water, whereby it sustains 15% of the domestic corn and wheat crops as well as 25% of the cotton crop.  Since groundwater mining of the aquifer accelerated in the last century, the water table has dropped 10-50 feet in depth in most regions, with several recorded drops of over 100 feet.  The impervious geological formation of the Ogallala and the naturally arid climate of the Midwest both inhibit groundwater recharge of the aquifer.  What recharge is accomplished has brought arsenic, chloroform, pesticides, and other compounds into the aquifer.  Today the water of the Ogallala aquifer is severely degraded in terms of quantity and quality, which has large-scale implications for America’s economic productivity.  Without governmental and educational programs highlighting efficient irrigation practices, and a significant mobilization to utilize recycled water sources, the High Plains region may face an unprecedented threat to its economic security.

Full Text

The Ogallala formation is home to the High Plains aquifer in the Midwestern United States.  The High Plains aquifer, often referred to as the Ogallala aquifer because it is located in the saturated portion of the formation, is one of the most agriculturally important water sources in America.  The sediments of the Ogallala formation date largely to the Pliocene and Miocene when the Great Plains were an inland sea and the Rocky Mountains were tectonically active, producing what became the Ogallala sediment.  Sand, silt, coarse gravel, and clay were deposited up to 900 feet deep in some areas, filling in valleys that had been eroded in Permian, Triassic, Jurassic, and Cretaceous rock. Today the water is anywhere from zero to 400 feet deep, averaging about 100 feet, and it covers an area of 174,000 square miles across eight states—shown as the shaded region in the figure to the right.   The aquifer holds over 978 trillion gallons of water , but quality and depth of the Ogallala groundwater is rapidly declining as water is being pumped from its reservoirs far faster than fresh water can replace it.


The Ogallala aquifer was virtually untouched until the 1910s, but the post-depression wartime government of the 1940s readily subsidized irrigation projects drawing from the aquifer as drilling technology improved.  The dry grassland states of the central United States were quickly developed into major crop producing regions.  As of 1980, “20% of the irrigated land in the United States overlay the Ogallala, 30% of the irrigation ground water in the United States was being pumped from it, and 40% of the grain-fed beef cattle slaughtered in the United States were being fattened in the six states of the High Plains.”   The aquifer’s use for irrigation supports significant fractions of the nation’s economy, 15% of the domestic corn and wheat as well as 25% of the cotton crop are raised on Ogallala water.   This extreme reliance on the Ogallala aquifer has taken a dramatic toll on the ground water supply, both quantitatively and qualitatively.


The Ogallala lies under one of the driest portions of the United States.  The plains states cannot support profitable agriculture without irrigation because dry farming there would be economically unfeasible.  Today the aquifer is being drained at such an alarming rate that an alternative source will have to be found in the next fifteen years at most.  In most areas covering the Ogallala the water table has dropped 10-50 feet since groundwater mining began, with drops of over 100 feet recorded in several agricultural regions.  Two main factors are contributing largely to this observed drop in the water table.


The first main cause for the Ogallala’s drying up is that the Midwest has a naturally dry climate.  The native plant species in the region are dry grasses and the plains states receive little rainfall most years, so profitable agriculture is only possible with intense irrigation.  Water is being pumped out and recharged to the aquifer at different annual rates across each region covering it.  One of the most critical sites is in the Texas High Plains, where roughly ten times as much water is being pumped out of the aquifer as is being replaced by rainfall.  Second, the composition of the aquitards also hinders refilling of the aquifer.  “Lacustrine deposits, consisting primarily of clay and silt, line the bottom of the many playa lakes on the High Plains. The sediments are virtually impermeable, thus restricting natural recharge to the underlying formation.”  Although the Ogallala Formation is home to many of these playa lakes that collect rainwater and runoff during rainy periods, the calcium carbonate and caliche upper aquitard hinders that water from seeping down to the water table.


The water deficit in the hardest hit portions of the aquifer can be visualized as one teacup of water being replaced for every gallon being removed because of this imbalance , which is clearly not sustainable.  Educational programs have been successfully implemented in some regions to reduce peak daytime irrigation in favor of irrigating when the sun in lowest in the sky.  Irrigating at high noon can lead to a greater than 30% loss of water to evaporation, essentially throwing away this dwindling resource.  Irrigating a similar field in the early morning and evening instead leads to about 15% in losses, which is a notable improvement.  The most efficient method to continue growing crops in this dry environment would be to switch to drip irrigation.  Drip irrigation reduces evaporation losses to around 5% by distributing water directly at the soil surface, but it is not currently used in large-scale agricultural operations.   Government subsidies may encourage that technology to be refined and scaled-up, which would significantly reduce strain on the Ogallala aquifer.  Educational and subsidy programs may save the government money in the long run by helping farmers adopt sustainable practices to avoid water shortages.


The omnipresent state of agriculture in the region is also causing the waning groundwater supply to become contaminated by runoff.  A recent study performed by the USGS in the High Plains region of the Ogallala showed that the groundwater contained numerous contaminants including arsenic, radon, chloroform and pesticides to name a few.   These chemicals are all specifically outlined in the Safe Drinking Water Act as having adverse health effects, and they are all present in the aquifer at rates that exceed EPA guidelines.   Even if drastic measures are taken to preserve the Ogallala in its already heavily damaged state, the numerous Midwestern communities drawing their municipal water supply from the aquifer will face extremely high costs of purifying the water or, in the probable case, they will continue to consume poisoned water instead.


The Ogallala aquifer is being used today to supply residential and agricultural communities across eight Midwestern states.  For nearly 80 years the nation’s breadbasket has been irrigated from Ogallala groundwater—a practice so unsustainable it severely threatens an aquifer that had flourished for over a million years.  Farmlands are already shrinking on some portions of the Ogallala that have been mined of water.  As the water table continues to plummet the High Plains will have to take drastic measures, whether communities import costly water or abandon the most profitable farming in the nation.  Either way the decision has to be made soon because the aquifer that once held enough water to cover the entire United States under 1.5 feet of water is rapidly running out.


References

Image of the Ogallala Aquifer <http://www.geology.iastate.edu/gccourse/issues/society/ogallala/1.gif>.

 
Asia-Pacific Economic Cooperation (APEC)