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situation, the salinity of the discharged water plays a major role in 

 determining the density difference between the ambient water and the 

 discharged water. As may be seen by examining the available data, this 

 can alter the applicability of the model to the situation existing in 

 New Haven Harbor. 



In December 1977, a hydrographic survey was conducted during 

 ebb tide. The stations for this survey are shown in Figure 3-1 and some 

 of the results in Table 3-3. If the water below 2 m at Station 4 is 

 fully mixed, the resulting temperature and salinity would be approxi- 

 mately 5.3 C and 22.4 ppt. We assume this mixing occurs in the gener- 

 ating station; thus, the discharged water would have a salinity of 22.4 

 ppt, a temperature of 13.6 C (5.3 C plus 8.3 C AT) and a corresponding 

 density of 16.6 o units. Table 3-3 shows the density at Station 8 at 

 1 m to be 10.5 a units and at 10 m to be 19.6 a units; thus, the 

 density of the discharge water is intermediate to that of the water at 

 1 m of depth and that at 10 m. This means that at Station 8 the plume 

 would not rise to the surface even though it is approximately 15 F (8.3 C) 

 waarmer than the surrounding water at discharge. The tendency for the 

 plume to stay submerged is further increased by the fact that, as the 

 water comes out of the discharge pipe, it is mixing with the deeper 

 waters near Station 8, lowering its temperature and increasing its 

 salinity and, thereby, its density. From this it is reasonable to 

 believe that the rise in temperature at Station 8 at 3 and 5 m below 

 the surface is due to a submerged plume; evidence of the plxime at 3 m 

 can be seen at Station 11 (Table 3-3) . A submerged plume that mixes 

 with the ambient water on all sides will have flow-away velocities that 

 are lower than those predicted by the physical model, where mixing 

 occurred only along the lower interface. The situation that leads to a 

 siibmerged plume occurs primarily during the winter when there is marked 

 salinity stratification. 



Most of the time, however, the salinity stratification is not 

 sufficient to result in a submerged plume. More normal conditions are 

 those that existed during the thermal surveys conducted by NAI during 



