Percent Saturation:

Percent Saturation: What does it Measure?

Dissolved oxygen levels may be viewed in terms of percent saturation or the percent of the potential capacity of the water to hold oxygen that is present.

The oxygen level of an aquatic system is not only dependent on production and consumption of oxygen. Oxygen is absorbed into the water from the atmosphere until levels at the surface equilibrate with levels in the atmosphere. At this point the system is said to be saturated.

Three factors affect the percent saturation (the highest DO level possible even in well aerated water):

1. Salinity: Fresh water can hold more oxygen that salt water.
2. Temperature: Cold water can hold more oxygen than warm water.
3. Atmospheric Pressure (Altitude): The greater the atmospheric pressure the more oxygen the water will hold.

Another way of looking at the amount of DO the water is capable of holding at saturation is when salinity, temperature, and altitude increase, oxygen at saturation decreases.

High percent saturation can occur even at low DO levels. Living organisms require specific minimum levels of dissolved oxygen to survive. Even though the water may have high % saturation, fish kills may occur. The temperature effect is compounded by the fact that living organisms increase their activity in warm water, requiring more oxygen to support their metabolism. Critically low oxygen levels often occur during the warm summer months when decreased capacity and increased oxygen demand, caused by respiring algae or decaying organic material, coincide.

Formula for Percent Saturation:

More information on Dissolved oxygen Measurement, click the link below to download the DO Meter (Code 1903) Manual.