Quality of a River - Water Quality
(pg 4 of 5)
Matters of SCALE
Changes that force a rise in temperature may
make a stream no longer able to sustain fish such
as trout. Changes can be small in scale and
relatively short-lived or large in scale and
relatively permanent. Beaver dams, for example,
slow current and cause water to spread out into
sunny ponds, raising temperatures in a small
segment of the stream.
However, human alterations to the watershed can
have even more dramatic effect. The types of dams
that humans construct tend to be massive and more
permanent. The impacts caused by these dams can
extend the entire length of the river.
Other types of alterations, though subtle, can
have far-reaching impacts. Clearing trees along a
stream corridor or paving large surfaces in the
watershed can permanently increase fluctuations in
both stream temperature and runoff.