Dissolved Oxygen

It is calculated by measuring the amount of gaseous oxygen dissolved in an aqueous solution.  Total dissolved gas concentrations in water should not exceed 110 percent. Concentrations above this level can be harmful to aquatic life. Fish in waters containing excessive dissolved gases may suffer from "gas bubble disease"; however, this is a very rare occurrence. The bubbles or emboli block the flow of blood through blood vessels causing death. External bubbles (emphysema) can also occur and be seen on fins, on skin and on other tissue. Aquatic invertebrates are also affected by gas bubble disease but at levels higher than those lethal to fish.

Adequate dissolved oxygen is necessary for good water quality. Oxygen is a necessary element to all forms of life. Natural stream purification processes require adequate oxygen levels in order to provide for aerobic life forms. As dissolved oxygen levels in water drop below 5.0 mg/l, aquatic life is put under stress. The lower the concentration, the greater the stress. Oxygen levels that remain below 1-2 mg/l for a few hours can result in large fish kills.


Chicago River

7.3 +/- 0.4 (6.3-7.9) mg/L

Clear Creek/ (Chamber Creek)

(Clear Creek)
Mean of dissolved oxygen: 9.9
Standard: 4.4
Ranges: 4-22

(Chamber Creek)
Mean of dissolved oxygen: 11.2
Standard: 6.1
Ranges: 4.5-32

Sava River

Mean of dissolved oxygen for trial 1: 6.86 mg/L
Mean of dissolved oxygen for trial 2: 7.9 mg/L
Mean of dissolved oxygen for trial 3: 6.84 mg/L

Ohio River

Mean of dissolved oxygen: 6.674 mg/L