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Quality of a River - Water Quality
Dissolved oxygen (pg 1 of 4)

Each natural stream has its characteristic regime of dissolved oxygen, related largely to temperature and the breakdown of organic material in the water.

In aquatic systems, oxygen is typically referred to as "dissolved oxygen" or O2, to distinguish it from "O" or oxygen in the H2O molecule. O2 is the available form of oxygen for aquatic organisms.

Just as water can hold a certain amount of dissolved sugar in suspension (its saturation point), water can also hold a given amount of dissolved oxygen. Unlike sugar, however, the saturation point of dissolved oxygen decreases as water warms.

Water temperature strongly influences the amount of dissolved oxygen in a stream because (1) the ability of water to hold dissolved oxygen decreases as temperature increases, and (2) warm temperatures increase the oxidation rates that remove dissolved oxygen from solution. For those reasons, warm streams often have much lower concentrations of dissolved oxygen than cold streams.


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Oxygen
Alkalinity
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