An expression of the variability of physical, chemical, and biological properties of a given ecosystem. A gradient of current speed is created in the river as it cascades down the mountain side. In this instance, daily fluctuations in water temperature, the amount of dissolved oxygen, pH, suspended particulates, macro invertebrate communities, fish species, and other characteristics of the freestone river are distributed along the gradient of gravity, insuring that no two stretches of the river behave the same.

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