The vast grasslandsof the High Plains in the central United States were settled by farmers andranchers in the 1880s. This region has a semiarid climate, and for 50 yearsafter its settlement, it supported a low-intensity agricultural economy ofcattle ranching and wheat farming. In the early twentieth century, however, itwas discovered that much of the High Plains was underlain by a huge aquifer (arock layer containing large quantities of groundwater). This aquifer was namedthe Ogallala aquifer after the Ogallala Sioux Indians, who once inhabited theregion.
The Ogallalaaquifer is a sandstone formation that underlies some 583,000 square kilometersof land extending from northwestern Texas to southern South Dakota. Water fromrains and melting snows has been accumulating in the Ogallala for the past30,000 years.Estimates indicate that the aquifer contains enough water tofill Lake Huron, but unfortunately, under the semiarid climatic conditions thatpresently exist in the region, rates of addition to the aquifer are minimal,amounting to about half a centimeter a year.
The first wellswere drilled into the Ogallala during the drought years of the early 1930s. Theensuingrapid expansion of irrigation agriculture, especially from the1950s onward, transformed the economy of the region. More than 100,000 wellsnow tap the Ogallala. Modern irrigation devices, each capable of spraying 4.5million liters of water a day, have produced a landscape dominated by geometricpatterns of circular green islands of crops. Ogallala water has enabled theHigh Plains region to supply significant amounts of the cotton, sorghum, wheat,and corn grown in the United States. In addition, 40 percent of Americangrain-fed beef cattle are fattened here.
This unprecedented development of a finite groundwater resource with an almost negligible naturalrecharge rate—that is,virtually no natural water source to replenish the water supply—hascaused water tables in the region to fall drastically. In the 1930s, wellsencountered plentiful water at a depth of about 15 meters; currently, they mustbe dug to depths of 45 to 60 meters or more. In places, the water table isdeclining at a rate of a meter a year, necessitating the periodic deepening ofwells and the use of ever-more-powerful pumps. It is estimated that at currentwithdrawal rates, much of the aquifer will run dry within 40 years. Thesituation is most critical in Texas, where the climate is driest, the greatestamount of water is being pumped, and the aquifer contains the least water. Itis projected that the remaining Ogallala water will, by the year 2030, supportonly 35 to 40 percent of the irrigated acreage in Texas that is supported in1980.
The reaction offarmers to the inevitabledepletion of the Ogallala varies. Many havebeen attempting to conserve water by irrigating less frequently or by switchingto crops that require less water. Others, however, have adopted the philosophythat it is best to use the water while it is still economically profitable todo so and to concentrate on high-value crops such as cotton. The incentive ofthe farmers who wish to conserve water is reduced by their knowledge that manyof their neighbors are profiting by using great amounts of water, and in theprocess are drawing down the entire region’s water supplies.
In the face of theupcoming water supply crisis, a number of grandiose schemes have been developedto transport vast quantities of water by canal or pipeline from theMississippi, the Missouri, or the Arkansas rivers. Unfortunately, the cost ofwater obtained through any of these schemes would increase pumping costs atleast tenfold, making the cost of irrigated agricultural products from theregion uncompetitive on the national and international markets. Somewhat morepromising have been recent experiments for releasing capillary water (water inthe soil) above the water table by injecting compressed air into the ground.Even if this process proves successful, however, it would almost triple watercosts. Genetic engineering also may provide a partial solution, as new strainsof drought-resistant crops continue to be developed. Whatever the final answerto the water crisis may be, it is evident that within the High Plains,irrigation water will never again be the abundant, inexpensive resource it wasduring the agricultural boom years of the mid-twentieth century.
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