|....................... ......Fly Fishing Yellowstone National Park
A freestone stream is born at the top of mountains as drops of rainwater and
melting snow. 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. I In Yellowstone National
Park, many of the freestone streams start from small lakes. Usually, these small
lake have the tiny streams I mention above that flow into them, so in effect, they
still start as tiny trickles of water.
Often, 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.
That is not always the case, however. Many freestone streams in Yellowstone
start our in the plateau regions on relatively flat land with low gradient. These
are normally the meadow streams. At some point, these meadows streams
usually change to include fast water sections as they drop off the plateaus.
As these streams reach 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 such as smallmouth bass
will 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. In Yellowstone Country, it
is usually many miles from the headwaters before this occurs. Most often, it is
past the point where the rivers leave the high country mountains and high plains.
Copyright 2009 James Marsh