Water Dynamics
By Dick Babine
Go With The Flow
You probably never thought that you would have to learn very much about the water that you will be fishing but the truth of the matter is that you will never consistently find fish without a clear understanding of the dynamics of a liquid in motion. I don't mean to go scientific on you, but fish will find particular places in the water column in order to be comfortable, nesting areas, feeding lanes, resting and safety points. These places are created by the waters effect on the surface of the land over which it flows.
No two bodies of water are the same, but they all have similarities. The amount of water and the chemical makeup greatly influence the size and numbers in a particular area. This chemical formula determines the waters ability to support a healthy environment for aquatic creatures and plants. This chemical formula results in the amount of food generated and in turn will determine the amount of fish that a particular area will support.
We all know that water will seek its own level and this is called a water gradient. In any water gradient there is a variation in current speed due to the friction of the water against itself and the lands surface over which it flows. This is why all waters will try to find the lowest point by flowing towards sea level. Although the water may come up against many obstacles during its journey, it will twist, turn, and even in some cases flow up a small grade in order to accomplish its goal of seeking the land over which it flows lowest point.
These ribbons of water will flow into each other, end up flowing into a pond or lake and even reach the ultimate low point, the ocean. During the waters journey, there are four primary sources of resistance that attempt to stop, alter or redirect its force. The first obstacle is the land over which it flows. The surface of the land creates a force called friction and attempts to slow the water down by pulling against it as the water flows across its surface. The second force applied against the water is the air above the surface and although this seems trivial the fact remains that it does have an effect on the water by creating a much less negative resistance than the bottom of the water column where the greatest resistance is created.
These two negative forces will cause the water to roll in a downstream direction. The third type of force is an immovable object, which is so much stronger than the force of the flowing water that the water is forced to flow in another direction. These obstacles are not only solid rock faces or heavy graveled embankments but also can be objects that are in the water itself such as fallen trees, smaller rocks and even aquatic vegetation. The fourth source of frictional resistance is the water itself. This friction is less on the surface because the air under which it flows creates much less friction then at the bottom of the water, where the water is forced over a very rough surface. This phenomenon occurs in all parts of the water column.
Streams and rivers flowing downhill move at a rate, rhythm, and pattern that are determined by the topography of the surface of the land over which it flows. All streams and rivers will develop these same characteristics regardless of their size. The degree of gradient and the level of bottom resistance will determine the size and frequency of these physical characteristics. These variations are the most important factors you can learn because they hold the key to how most aquatic life forms live and survive.
The physical characteristics described are commonly called: Riffles, Runs and Pools and these same characteristics are all formed naturally in that same order. Each section of the river or stream will have its own distinctive aquatic creature living in that particular area, as a result of their ability to adapt to that particular type of environment. The riffle areas will have both clinging and crawling nymphs. The soft silt, muddy bottoms and flat areas of a pool will have the borrowing nymphal forms present. In the graveled areas of the tail of the pool, you may find the cased and free- swimming caddis. Areas that have weed beds and other aquatic vegetation will encourage the survival of both crawling and free-swimming types of nymphs.
