The vast grasslands of the High Plains in the central United States were settled by farmers and
ranchers in the 1880s. This region has a semiarid climate, and for 50 years after its settlement,
it supported a low-intensity agricultural economy of cattle ranching and wheat farming. In the
early twentieth century, however, it was discovered that much of the High Plains was underlain by
a huge aquifer. This aquifer was named the Ogallala aquifer after the Ogallala Sioux Indians, who
once inhabited the region.
The Ogallala aquifer is a sandstone formation that underlies some 583000 square kilometers of land
extending from northwestern Texas to southern South Dakota. Water from rains and melting snows has
been accumulating in the Ogallala for the past 30000 years. Estimates indicate that the aquifer
contains enough water to fill Lake Huron, but unfortunately, under the semiarid climatic conditions
that presently exist in the region, rates of addition to the aquifer are minimal, amounting to
about half a centimeter a year.
The first wells were drilled into the Ogallala during the drought years of the early 1930s. The
ensuing rapid expansion of irrigation agriculture, especially from the 1950s onward, transformed
the economy of the region. More than 100000 wells now tap the Ogallala, Modern irrigation devices,
each capable of spraying 4.5million liters of water a day, have produced a landscape dominated by
geometric patterns of circular green islands of crops. Ogallala water has enabled the High Plains
regions to supply significant amounts of the cotton, sorghum, wheat, and com grown in the United
States. In addition, 40 percent of American grain-fed beef cattle are fattened here.
This unprecedented development of a finite groundwater resource with an almost negligible
natural recharge rate-that is, virtually no natural water source to replenish the water supply
has cased water tables in the region to fall drastically. In the 1930s, wells encountered plentiful
water at a depth of about 15 meters; currently, they must be dug to depths of 45 to 60 meters or
more. In places,the water table is declining at a rate of a meter a year, necessitating the periodic
deepening of wells and the use of ever-more-powerful pumps. It is estimated that at current
withdrawal rates, much of the aquifer will run dry within 40 years. The situation is most critical
in Texas, where the climate is driest, the greatest amount of water is being pumped, and the
aquifer contains the least water. It is projected that the remaining Ogallala water will, by the
year 2030, support only 35 to 40 percent of the irrigated acreage in Texas that is supported
in 1980.
The reaction of farmers to the inevitable depletion of the Ogallala caries. Many have been
attempting to conserve water by irrigating less frequently or by switching to crops that require
less water. Others, however, have adopted the philosophy that it is best to use the water while
it is still economically profitable to do so and to concentrate on high-value crops such as cotton.
The incentive of the farmers who wish to conserve water is reduced by their knowledge that many
of their neighbours are profiting by using great amounts of water, and in the process are drawing
down the entire region's water supplies.
In the face of the upcoming water supply crisis, a number of grandiose schemes have been developed
to transport vast quantities of water by canal or pipeline from the Mississippi, or the Arkansas
rivers.
Unfortunately, the cost of water obtained through any of these schemes would increase pumping costs
at least tenfold, making the cost of irrigated agricultural products from the region uncompetitive
on the national and international markets. Somewhat more promising have been recent experiments
for releasing capillary water above the water table by injecting compressed air into the ground.
Even if this process proves successful, however, it would almost triple water costs. Genetic
engineering also may provide a partial solution, as new strains of drought-resistant crops continue
to be developed. Whatever the final answer to the water crisis may be, it is evident that within the
High Plains, irrigation water will never again be the abundant, inexpensive resource it was during
the agricultural boom years of the mid-twentieth century.