Dissolved Oxygen

Rainfall is assumed to be saturated with oxygen. To determine the dissolved oxygen concentration of surface runoff, the oxygen uptake by the oxygen demanding substance in runoff is subtracted from the saturation oxygen concentration.

Oxsurf=Oxsatκ1cbodsurqtov24Ox_{surf}=Ox_{sat}-\kappa_1*cbod_{surq}*\frac{t_{ov}}{24} 4:5.3.1

where OxsurfOx_{surf} is the dissolved oxygen concentration in surface runoff (mg O2O_2/L), OxsatOx_{sat} is the saturation oxygen concentration (mg O2O_2/L), κ1\kappa_1 is the CBOD deoxygenation rate (day1^{-1}), cbodsurqcbod_{surq} is the CBOD concentration in surface runoff (mg CBOD/L), and tovt_{ov} is the time of concentration for overland flow (hr). For loadings from HRUs, SWAT+ assumes κ1\kappa_1 = 1.047 day1^{-1}.

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