Streams have always had to carry and digest wastes that enter them
through drainage from the land. It is one of their functions in the
scheme of things, and so well have they performed it through the
millennia that human beings have been able to take it for granted.
Within limits that might be considered normal, the ability of running
water to handle loads of waste is phenomenal, and in earlier times those
normal limits were seldom exceeded, for even in populated areas the
general lack of sanitary sewer systems kept the loads from being
concentrated.
In civilized parts of the modern world, however, there are now so many
people generating so many wastes of one kind and another, which often
enter the streams at concentrated points, that the streams can no longer
digest them without help. Too often, in the face of uncontrolled human
increase and expansion, that help has either been denied them or has
been weak and perfunctory. The result is plain enough now in the sorry
mess of sick or dead or dying waters that we Americans have on our
hands, the heritage of having kept on taking them for granted long after
we had bred ourselves out of the right to do so.
As civilized rivers go, the Potomac is rather lucky. It is polluted, but
many parts of it are not nearly as dirty as people are sometimes led
into believing by a look at the summertime estuary at Washington. The
fabled and scenic German Rhine, for instance, is much more degraded in
its main flowing reaches than is the Potomac, and so are a majority of
the other rivers in the northeastern United States and many elsewhere in
the country. Industrialization on the Potomac and its tributaries has
been spotty so far, and there are no really big clusters of population
in the upper parts of the Basin. Furthermore, pollution here has already
been given quite a lot of dedicated and expert attention and some
rectification. Thus anyone who travels up and down the river and its
tributaries finds many miles of pleasant flowing streams capable of
sustaining fish and the other things that are supposed to live in and
around water, and fit to soothe frayed nerves.
He will find a lot of grubby and unsoothing stretches too, extensive in
places, and even in the pleasant streams troubles exist that are
invisible to the eye. There is little to be complacent about, for
threats are multiplying rather than fading, and some parts of the
Potomac river system already need more than help; they need
resurrection.
[Illustration]
The Basin has several standard sorts of pollution, often found in one
combination or another. Chemical contamination occurs along the North
Branch, in areas where pesticides and other economic poisons get into
the stream system, and in spots and stretches where specific industrial
wastes create local problems. There is much and widespread pollution
through organic wastes--often sewage solids, but not always--whose
breakdown by natural processes may demand so much oxygen that a stream
has little or none left over to maintain aquatic life and "stay alive."
Sometimes associated with organic wastes and sometimes entering the
river system otherwise are dangerous bacteria, and also the so-called
"nutrients"--dissolved fertilizing agents that can stimulate excessive
growth of algae or weeds in the water to the detriment of other forms of
life, often to such a degree that these plants' death and decay sets off
a whole new cycle of oxygen demand. And there is sediment washed off the
land, which clouds the water and settles out into a smothering cloak on
the bottom, building up in quiet stretches into ugly and damaging mud
banks and shoals.