Environmental Engineering Reference
In-Depth Information
Figure 2.1
Glass of water.
(Kick a lettuce in the field and it will yell “Water!”)
destroying
(The Dutch
boy's finger remembered the view from Ararat) and
creating
(It has even
been said that human beings were invented by water as a device for
transporting itself from one place to another, but that's another story).
Always in motion, ever-flowing (whether at stream rate or glacier speed),
rhythmic, dynamic, ubiquitous, changing and working its changes, a
mathematics turned wrong side out, a philosophy in reverse, the ongo-
ing odyssey of water is irresistible.
Let's review a few basic facts about the water in that glass you are holding:
Water is liquid between 0°C and 100°C (32°F and 212°F), solid at or below 0°C
(32°F), and gaseous at or above 100°C (212°F). One gallon of water weighs 8.33
pounds (3.778 kilograms), and one gallon of water equals 3.785 liters. One
cubic foot of water equals 7.50 gallons (28.35 liters). One ton of water equals
240 gallons. One acre-foot of water equals 43,560 cubic feet (325,900 gallons).
Earth's rate of rainfall equals 340 cubic miles per day (16 million tons per
second).
As Robbins observed, water is always in motion. The one most essential
characteristic of water is that it is dynamic: Water constantly evaporates from
seas, lakes, and soil and transpires from foliage. It is transported through the
atmosphere and falls to Earth, where it runs across the land and filters down
to flow along rock strata into aquifers. Eventually, water finds its way to the
sea again—indeed, water never stops moving.
A thought that might not have occurred to most people looking at a glass
of water is, “Has someone tasted this same water before us?” Absolutely.
Remember, water is almost a finite entity. What we have now is what we have
had in the past. We are drinking the same water consumed by Cleopatra,
Aristotle, da Vinci, Napoleon, Joan of Arc (and several billion other folks
who preceded us)—because water is dynamic (never at rest) and because
water constantly cycles and recycles, as we discuss in the next section.
