Environmental Engineering Reference
In-Depth Information
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All about W
ater: Basic Concepts
… During another visit to the New England Medical Center, three
months after Robbie's first complaints of bone pain, doctors noted that
his spleen was enlarged and that he had a decreased white-blood-cell
count with a high percentage of immature cells—blasts—in the periph-
eral blood. A bone marrow aspiration was performed. The bone mar-
row confirmed what the doctors had began to suspect: Robbie had acute
lymphatic leukemia.
—Jonathan Harr (1995)
Ea r t h's Blood
The watery environment in which single-cell organisms live provides them
food and removes their wastes, a function that the human circulatory system
similarly provides for the 60 to 100 trillion cells in a human body. The circu-
latory system brings each cell its daily supply of nutritive amino acids and
glucose and carries away waste carbon dioxide and ammonia, which will be
filtered out of our systems and flushed away through micturition and excre-
tory functions. The heart, the center of our circulatory system, keeps blood
moving on its predetermined circular path, a function so essential that if the
pump fails we quickly fail as well—and we die.
As single-celled organisms no longer, humans sometimes assume that
they no longer need a watery environment in which to live—but they aren't
paying close attention to the world around them. Actually, those of us who
live on Earth are as dependent upon the Earth's circulatory system as we are
on our own circulatory system. Just as the human heart pumps blood, circu-
lating it through a series of vessels, and just as our lives are dependent upon
that flow of blood, so life on Earth is dependent on the Earth's water cycle.
This cycle is so automatic that we generally ignore it until we are slapped
in the face by it. Just as we do not pay attention to the beating of our heart
unless it skips a beat or falters, until we are confronted by flood or drought or
until our plans are disrupted by rain, we ignore the water cycle, preferring to
believe that the water we drink comes out of the faucet, not from deep within
the belly of the Earth, placed there by a process we only dimly comprehend.
But, water is as essential to us and to the Earth as blood is in our bodies, and
the constant cycle water travels makes our lives possible.
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