Environmental Engineering Reference
In-Depth Information
Water Use Levels Out
The good news is that growth in U.S. water usage from the 1980s
to today has remained relatively fl at or slowed despite population
growth. But, says USGS's Evenson, as the population continues to
grow, water use will increase, too. Unfortunately, growth doesn't
necessarily happen in places where water is abundant. “As our pop-
ulation grows, we tend to push into more and more areas where
our water supplies are more and more marginal,” Evenson says.
The number of gallons of water used per person per day actu-
ally declined between 1980 and 2000, according to Susan Hutson,
lead author of the U.S. Geological Survey's report entitled “Water
Use in the United States, 1950-2000” and contributing author to
the 2005 report.
25
(See Figure 1.3.) That's in part due to the Clean
Water Act, says Hutson. That statute limited water discharge for
industries and thermoelectric power plants. Because of those lim-
its, industries aggressively developed technology to recycle and
reuse water, thus minimizing their water withdrawals. In 1950, it
took an average 63 gallons of water to produce one kilowatt-hour
of energy. In 2005, it took just about a third of that. Also contribut-
ing to the decline in water-use numbers is the loss of some of the
nation's industrial base, which used to withdraw water directly from
rivers and lakes, or drill private wells. New industries today often
go to the public water supply instead, adds Hutson. Improvements
in land irrigation technology mean less water is needed, and they
make a difference in consumption numbers, too, she adds.
More highlights from that report:
26
Despite growing demands, the total amount of water with-
drawn per day for all uses in the United States (410 billion
gallons) is down from the peak withdrawal year of 1980.
Fresh surface water accounted for 78 percent of total with-
drawals in 1950, and only 66 percent in 2005. Saline surface
water (mainly for thermo-electric power generation) makes
up the rest.
California, Texas, Idaho, and Florida accounted for more
than one-fourth of all water withdrawals in 2005.
California had the largest surface-water withdrawals in 2005,
with irrigation as the primary use.
