Running Waters - Mathematics and Statistics for the Environment - page 557

19 Running Waters
In terms of practical usefulness the waste assimilation capacity of streams as a water resource has its
basis in the complex phenomenon termed stream self-purification. . This is a dynamic phenomenon
reflecting hydrologic and biologic variations, and the interrelations are not yet fully understood in pre-
cise terms. However, this does not preclude applying what is known. Sufficient knowledge is available
to permit quantitative definition of resultant stream conditions under expected ranges of variation to
serve as practical guides in decisions dealing with water resource use, development, and management.
— Velz (1970)
Running water is hypnotic, like fire watching, wave watching, or dust-mote watching.
19.1 BALANCING THE AQUARIUM
An outdoor excursion to the local stream can be a relaxing and enjoyable undertaking. However,
when the wayfarer arrives at the local stream, spreads a blanket on its bank, and then looks out upon
its flowing mass and discovers a parade of waste and discarded rubble bobbing along cluttering the
adjacent shoreline and downstream areas, he quickly loses any feeling of relaxation or enjoyment.
The sickening sensation only increases as our observer closely scrutinizes the putrid flow. He rec-
ognizes the rainbow-colored shimmer of an oil slick, interrupted here and there by dead fish and
floating refuse, and the slimy fungal growth that prevails. At the same time, the observer's sense
of smell is also alerted to the noxious conditions. Along with the fouled water and the stench of
rot-filled air, the observer notices the ultimate insult and tragedy: a sign warning, ”DANGER—NO
SWIMMING or FISHING.” The observer soon realizes that the stream before him is not a stream at
all; it is little more than an unsightly drainage ditch. He has discovered what ecologists have known
and warned about for years—that is, contrary to popular belief, rivers and streams do not have an
infinite capacity for taking care of pollution (Spellman, 1996).
Before the early 1970s, occurrences such as the one just described were common along the
rivers and streams near main metropolitan areas throughout most of the United States. Many
aquatic habitats were fouled during the past because of industrialization, but our streams and riv-
ers were not always in such deplorable condition. Before the Industrial Revolution of the 1800s,
metropolitan areas were small and sparsely populated. Thus, river and stream systems within or
next to early communities received insignificant quantities of discarded waste. Early on, these
river and stream systems were able to compensate for the small amount of wastes they received;
when wounded by pollution, nature has a way of fighting back. In the case of rivers and streams,
nature provides their flowing waters with the ability to restore themselves through their own
self-purification process. It was only when humans gathered in great numbers to form great cities
that the stream systems were not always able to recover from having received great quantities of
refuse and other wastes.
What exactly is it that human populations do to rivers and streams? Halsam (1990) pointed
out that man's actions are determined by his expediency. Add to this the fact that most people do
not realize that we have the same amount of water as we did millions of years ago. Through the
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