Environmental Engineering Reference
In-Depth Information
more water-rich countries. The United States exports huge amounts of
virtual water in its agricultural products and automobiles. The United
States and the European Union countries export to the Middle East and
North Africa as much water as fl ows down the Nile into Egypt for agri-
culture each year. The volume is more than 40 billion tons, embedded
in 40 million tons of grain.
How Do We Use It?
Water is used in three main areas: agriculture, industry, and homes.
Usage grew three times faster than America's population during the
twentieth century. The increase was due largely to the expansion of
agriculture, by far the biggest consumptive user of water in the United
States.
Agriculture
Farming drinks 34 percent of the nation's water, most of it from ground-
water. The profl igate use of groundwater is the reason a large part of
America's most productive cropland can be located in areas with rela-
tively low annual rainfall. Much of the midcontinental grain belt aver-
ages less than 25 inches of rain per year; the San Joaquin Valley in
California produces half of the nation's fruits and vegetables but receives
only 8 to 12 inches of rainfall in an average year. If farming were
restricted to areas of adequate rainfall, agricultural production in the
United States would be drastically reduced and would fl ourish only in
areas where rainfall was at least 30 inches annually, roughly the eastern
half of the country (fi gure 1.5).
Another reason agriculture is so widespread in the United States is
government water and crop subsidies. Water for farming from the federal
Bureau of Reclamation sells for $10.00 to $15.00 per acre-foot, and the
cheapest subsidized water sells for as little as $3.50 per acre-foot, even
though it may cost $100.00 to pump the water to the farmers. House-
holds in Palo Alto, California, pay $65.00 per acre-foot, and some urban
users in California pay as much as $230.00.
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In California's San Joaquin
Valley, 6,800 farms receive water from the federally funded Central
Valley Project, built in 1936 for $3.6 billion. The Environmental Working
Group reported in 2005 that in 2002, farms received $538 million in
combined water and crop subsidies, $416 million of which was for
water. In 2002, the average price for irrigation water from the Central
Valley Project was less than 2 percent of what residents of Los Angeles
