.......................  ......Fly Fishing Yellowstone National Park

08/30/09

Freestone Streams

Some anglers just getting started fly fishing don't really understand what is
meant by the name "freestone stream". Some anglers that have been trout
fishing for a long time have really never stopped to think about what it means.
All the streams in Yellowstone National Park are freestone streams. Some of the
come from small lakes but there are usually some small feeder freestone
streams that fill the lake. Those streams are still called freestone streams. In the
park, as well as anywhere else a freestone stream exist, the freestone streams
are purely a product of Mother Nature.

A freestone stream is born at the top of mountains as drops of rainwater and
melting snowflakes. As gravity forces these droplets 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 that you can step across. The tiny streams eventually join
other tiny steams to form larger ones.

These tiny streams are made larger along the way by many other trickles of
water and eventually become streams that are large enough to be named and
shown on maps. These streams are usually the headwaters of what will become
a large freestone stream or river.

Generally, water in the headwater streams is fast moving pocket water. Most
headwaters fall through steep gradients and rapidly flow downhill. As the stream
reaches the lower elevations of the foothills the gradients become less and less
and the flow of the water decreases accordingly. As more and more water
collects the streams become wider. The water in the larger streams slows as it
moves through the valley.

As the stream reaches the lower elevations of the valley and the flows
decrease, the temperature increases. Eventually the water will become too warm
to support trout and other warm water species of fish become more prevalent.
The slower moving water will not hold as much dissolved oxygen as the faster
moving headwaters. This also becomes an important factor in the stream’s
ability to support trout.

Continued tomorrow....

Copyright 2009 James Marsh