> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/theoretical-documentation/section-7-main-channel-processes/in-stream-nutrient-processes/oxygen/oxygen-saturation-concentration.md).

# Oxygen  Saturation Concentration

The amount of oxygen that can be dissolved in water is a function of temperature, concentration of dissolved solids, and atmospheric pressure. An equation developed by APHA (1985) is used to calculate the saturation concentration of dissolved oxygen:

$$Ox\_{sat}=exp\[-139.34410+\frac{1.575701*10^5}{T\_{wat,K}}-\frac{6.642308*10^7}{T\_{wat,K}^2}+\frac{1.243800*10^{10}}{T\_{wat,K}^3}-\frac{8.621949*10^{11}}{T\_{wat,K}^4}]$$    7:3.5.3

where $$Ox\_{sat}$$ is the equilibrium saturation oxygen concentration at 1.00 atm (mg O$$*2$$/L), and $$T*{wat,K}$$ is the water temperature in Kelvin (273.15+$$\degree$$C).


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