Dissolved oxygen dynamics model and its application in estuary subject to turbidity variability

To determine the effect of turbidity variation on dissolved oxygen in estuarine areas, a system dynamics model of dissolved oxygen has been developed. It offers us a closer insight to the effect of turbidity on underwater light climate, sequentially the photosynthetic yield. The one-dimension model comprises five parts: re-aeration, biochemical oxygen demand, nitrogenous oxygen demand, photosynthesis and respiration of the phytoplankton. According to the comparison, it is revealed that the model including logarithmic relationship between light attenuation coefficient and turbidity is the best one. The diel dissolved oxygen dynamics show that fluctuation changes with single peak-valley type. Turbidity is an important factor which controls the DO dynamics in the estuary and varies inversely with DO. There are significant differences in the responses of DO to turbidity disturbances at each season. Temperature is the most sensitive parameter followed by wind speed and BOD decay rate coefficient.