Background Information
Percent Saturation is the amount of oxygen dissolved in the water sample compared to the maximum amount that could be present at the same temperature. For example, water is said to be 100% saturated if it contains the maximum amount of oxygen at that temperature. A water sample that is 50% saturated only has half the amount of oxygen that it could potentially hold at that temperature. Sometimes water can become supersaturated with oxygen because of rapidly tumbling water. This usually lasts for a short period of time but can be harmful to fish and other aquatic organisms. DO Percent Saturation values of 80-120% are considered to be excellent and values less than 60% or over 125% are considered to be poor.

The Percent Saturation of Dissolved Oxygen depends on the temperature of the water and elevation of the water testing site.  Determine the altitude (elevation) or atmospheric pressure and use the table below to determine the correction factor.  Multiply the Dissolved Oxygen level (in ppm) by the correction factor.

Use the chart below to convert the corrected Dissolved Oxygen level in ppm to a Percent Saturation of Dissolved Oxygen (ppm is equivalent to mg/L). To do this, follow these instructions:

1. Mark the corrected Dissolved Oxygen value on the lower line of the Level of oxygen saturation chart below.
2. Then, mark the water temperature on the upper line on the chart.
3. Draw a straight line from oxygen in mg/L mark to the water temperature mark.
4. The converted Percent Saturation value is where the drawn straight line passes through the % saturation line.
   NOTE: Percent Saturation values of 80 - 120% are considered to be excellent, and values less than 60% or over 125% are considered to be poor.

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