Total dissolved gas concentrations frequently exceed standards downstream of Bonneville Dam during spring and summer months. It is a measurement of the amount of nitrogen gas, oxygen gas, argon gas and water vapor dissolved in water.
Water is saturated when it can hold no more dissolved gas under normal atmospheric conditions.
Like the air we breathe, water must have sufficient dissolved gas in the right proportions for aquatic life to survive and remain healthy. Washington and Oregon both have standards for the protection of aquatic life. Concentrations above this level are known to be harmful to fish, especially juvenile salmonids. Aquatic organisms exposed to supersaturation can develop gas bubble disease. It is frequently fatal in young salmonids.