Environmental Engineering Reference
In-Depth Information
Figure 1.5
Average annual precipitation in the United States. (U.S. Water Resources council, 1968,
The Nation's Water Resources,
1968)
paid for drinking water, one-tenth the estimated cost of replacement
water supplies, and about one-eighth of what the public paid to buy its
own water back to restore the San Francisco Bay and delta.
19
Increased agricultural effi ciency in water use has contributed signifi -
cantly to water conservation efforts in the United States. Irrigation
methods have been improved by decreasing the use of fl ood irrigation
and up-into-the-air water sprinklers in favor of techniques such as having
drip tubes extending vertically from the sprinkler arm immediately above
the plants. Another effi cient method is drip irrigation, pioneered in Israel,
in which water is released in measured amounts from tubes on the
ground directly above the plant roots. Losses of water to evaporation
and runoff are nearly eliminated by these methods.
Industry
Nearly half (48 percent) of the 408 billion gallons used in the United
States goes to power plants, which have greatly reduced their water
requirements from the past. They have made the biggest reduction in
water use in recent decades, a result of water-saving technology driven
