online_do:   Dissolved oxygen (DO) sag curve

Ss = f(T)           L = Lr/n

O0 = [Qs/(Qs + Qe)] Os

Oj+1 = Oj + L (ko/v) (Ss - Oj) - L (kd/v) Du e-(kd/v)xj+1

Differential equation for DO sag               Streeter-Phelps equation


Deoxygenation constant kd              Oxygenation constant ko

INPUT DATA:

Select:   

[Choose SI or U.S. Customary units].   [Default: SI units; program resets to default units].


Stream (optional):     

Stream discharge Qs (m3/s) [ft3/s]:     

Water temperature T (oC) [oF]:     

[Saturation dissolved oxygen is at zero salinity and mean sea level].

Dissolved oxygen (upstream) Os (mg/L):     

Effluent discharge Qe (L/s) [ft3/s]:     

Effluent biochemical oxygen demand De (mg/L):     

Stream velocity v [m/s] [ft/s]:     

Deoxygenation constant kd (day-1):     

Oxygenation constant ko (day-1):     

Total reach length Lr (km) [mi]:     

Number of space steps n:     
(nmax = 200)
[ Leave blank to choose default n = 10 ]

OUTPUT:

Space
interval
j		Distance
(km)		DO
(this model)
(mg/L)		DO
(Streeter-Phelps)
(mg/L)		DO
difference
(mg/L)
     

            

  Your request was processed at  06:34:56 pm on October 30th, 2025

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