As previously mentioned, mixing in the near-field occurs during the plume rise over the outfall diffuser. The observations indicate that some of this initial mixing occurs between 15 and 11 m depth. Two ambient TS - points from those two depths were then considered to account for variability in background conditions.
Fig. 10 shows temperature and salinity measured at Section 1 plotted in a TS - diagram. TS - points measured at the same depth were plotted with the same color: red, blue and black correspond respectively to 12, 10 and 8~m depth. The isopycnals (lines of constant density) are labelled in sigma units.
Simultaneously, initial mixing lines are drawn between the effluent TS - point (not shown) Te = 35° and S e = 2 psu, and the two ambient TS - points (Ta and Sa) at 15 and 11 m depth. TS - points of these two mixing lines with equal dilutions delimit intervals of initial dilutions. TS - points (Tm and Sm ) for dilution factors of 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 100, 120, 150, 200, 300 and 400 are indicated.
Dilution can be estimated empirically based on the fact that TS - points in the plume are single end-members of the mixing between the effluent and the receiving waters. The TS - points in the plume with the lowest dilution falling into an initial dilution zone establish the minimum initial dilution.
Was this article helpful?