Copyright 2018 James Marsh
Fly Fishing Freestone Trout Streams - Part One
Generally, trout streams are classified as freestone trout streams, taiilwaters and spring creeks. Of course, there
are streams that have various combinations of spring creek water, tailwaters and freestone stream water, In this
case, we are only covering freestone streams.
A freestone trout stream is born at the top of a mountain as drops of rainwater and a melting snow pack or
snowflakes. As gravity forces these droplets of water to seep through the crevices of rocks, soil and organic
matter, they combine into small trickles of water. These trickles eventually collide and become larger and larger.
They form tiny streams. These tiny streams eventually join other tiny steams to form larger ones. These little
streams are made larger along the way by many other trickles of water and eventually become large enough to
have a name and be shown on a map. Often, these small streams are the headwaters of what will become a large
freestone stream or river.
Generally, water in the headwater streams is at a higher elevation than the main stream. At some point, if not its
entire length, most headwaters fall through steep gradients and rapidly flow downhill. As the stream reaches the
lower elevations the gradients become less and the flow of the water decreases accordingly. As more and more
water collects, the stream become wider and wider. The water in the larger streams slows down as it moves
through the flatter terrain of the valley.
As it reaches the low elevations of the valley and the flows decrease due to the increased volume of water, the
temperature increases. Eventually the water will become too warm to support trout and other warm water species
of fish such as smallmouth bass start showing up The slower, moving water will not hold as much dissolved oxygen
as the fast moving headwaters. This too becomes an important factor in the stream’s ability to support trout.
Depending upon the rocks, sand, gravel, and organic material (such as leaves and vegetation) the
water passes through as it flows downhill, the pH will usually increase. The pH of the headwater streams varies
from region to region, depending on the composition of the soil and rocks. Rain forest type terrain, such as is
found in the Appalachian Mountains and the Pacific, provides the water a different chemical composition than the
more barren slopes of the Rocky Mountains, for example. The pH of the water also changes from the headwaters
to the foothills.
The different pH values of the water, from its origin in the mountains to 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.
Because the water is usually fast moving pocket water, mayflies found in the headwaters are usually clingers.
Caddisflies are not very plentiful in these waters because of the acidic level of the water and consequent low
Many species of stoneflies are in their prime habitat in the highly oxygenated water. This water, which is usually
slightly acidic, will not support plant life such as algae. The aquatic insects must rely on other source of food.
When the stream becomes the "run, pool, riffle" type of stream, normally found in lower elevation trout streams,
the pH is generally higher and the water begins to support more species of aquatic insects that eat algae.
The stream’s volume of water and rate of flow is strictly dependant upon Mother Nature. The amount of water in
the stream can vary drastically with the seasons of the year. Heavy rainfall that usually occurs in the spring
months makes the freestone streams large and turbulent and sometimes flood beyond their normal banks. In the
late summer and fall months of the year, most freestone streams reach their lowest levels. Sometimes the flow
can become so slow and the dissolved oxygen levels so low that it become tough for trout to survive. This is
especially true in the lower sections of the streams in the foothills.
Continued in our next article "Fly Fishing Freestone Trout Streams - Part Two".
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