Freestone Streams - Part Two:

6/18/08

When the rain and snow falls from the sky it is pure and free from minerals and
is slightly acidic. It usually has a pH of approximately six. This can be affected by
acid rain. To avoid getting into a deep, involved discussion of acid rain, I will just
add this link:
http://www.epa.gov/acidrain/index.html  My purpose here is to show
that the pH changes from the headwaters to the slower moving water in the
foothills and how this affects the aquatic insect life.
As the water flows downhill, the pH will usually increase depending upon the
rocks, sand, gravel, and organic material (such as leaves and vegetation) the
water passes through. The pH of the headwater streams varies from region to
region depending on the composition of the soil and rocks but all in all in the
Smokies, varies only slightly. Rain forest type terrain, such as is found in the
Appalachian Mountains including of course, the Great Smoky Mountains
National Park, provides the water a different chemical composition than the more
barren slopes of the Rocky Mountains for example. If water passes through
volcanic rock, it is going to remain acidic much longer than water passing
through a forest. The pH of the water in the forest changes from the headwaters
to the foothills.
The different pH values of the water from its origin in the mountains too the
larger streams or river in the valleys
supports different groups of aquatic
insects
. The water temperature is generally higher in the lower sections of the
stream and this can
also be a factor that affects trout in that it changes
the insect population.
The speed of the water is also a big factor in determining which aquatic
insects exist.
Insects found in the fast flowing pocket water of the headwaters
may be quite different from those found in the slower moving water found at the
lower elevations.

Coming Up Next:
Freestone Streams - Part 3

Copyright 2008 James Marsh