9.14
mg/L
9.14
mg/L
87.5
%
1.14
mg/L
9.14
mg/L
9.14
mg/L
87.5
%
1.14
mg/L
The Dissolved Oxygen Saturation Calculator estimates the maximum concentration of dissolved oxygen that water can hold at a given temperature at standard atmospheric pressure. Dissolved oxygen (DO) is essential for aquatic life, and its saturation concentration decreases as water temperature increases.
This calculator uses a simplified polynomial approximation of the DO-temperature relationship for freshwater at sea level. It is widely used in aquaculture, water quality monitoring, wastewater treatment, and aquatic ecology to determine whether a water body is under- or super-saturated with oxygen.
DO saturation is estimated using the polynomial:
DOsat = 14.62 - 0.3898T + 0.006969T2 - 0.00005896T3
Where T is the water temperature in degrees Celsius. This approximation is valid for freshwater at standard atmospheric pressure (1 atm) for temperatures between 0 and 40 degrees Celsius. At higher elevations or in saline water, actual DO saturation is lower.
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At 20 degrees Celsius, freshwater at sea level can hold about 9.1 mg/L of dissolved oxygen at saturation.
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Cold water holds much more oxygen. At 5 degrees, DO saturation is nearly 12.8 mg/L, supporting cold-water fish like trout.
Gas solubility in water decreases as temperature increases because warmer water molecules have more kinetic energy, allowing dissolved gas molecules to escape more easily into the atmosphere. This is why cold mountain streams have more dissolved oxygen than warm lowland rivers.
At higher elevations, atmospheric pressure is lower, reducing the partial pressure of oxygen and thereby lowering DO saturation. As a rough guide, DO saturation decreases by about 3-4% for every 300 meters of elevation gain. This calculator assumes sea-level pressure.
Most fish require at least 5 mg/L of dissolved oxygen. Cold-water species like trout and salmon need 6-7 mg/L or more. Warm-water species like carp can tolerate levels as low as 3-4 mg/L. Below 2 mg/L (hypoxia), most aquatic organisms cannot survive, and below 0.5 mg/L is considered anoxic.
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