Oxygen Sag Curve with Thermal Overload

A deterministic model is developed for the oxygen sag curve for a variable temperature condition under thermal overload. With the help of this model, optimal locations of thermal and organic outlets with respect to each other can be determined for a predetermined minimum dissolved oxygen concentration in the river. In the presence of the thermal overload, the critical oxygen concentration (lowest) is much lower than that under constant temperature conditions of the stream, and it occurs earlier, the recovery of DO could be faster, and indeed the DO level downstream may be higher than under the constant temperature condition. The critical DO concentration and the critical oxygen deficit do not necessarily occur at the same point in the presence of the thermal overload. The mathematical models presented herein could be used in place of the constant temperature models.