In situ, rapid determinations of effluent dispersion were made 

 utilizing the unusual temperature inversion associated with the 

 effluent stratum. Normally, temperature gradients decrease with 

 depth (Sverdrup et at 1942) and thermoclines generally have colder 

 water underlying warmer water. The hot, saline effluent, however, 

 formed the reverse situation with warmer water under cooler water. 

 This peculiarity enabled rapid identification of the effluent even 

 at some distance from the plant. It could be detected easily in 

 temperature casts with the electric thermometer and could also be 

 felt by SCUBA divers. The surface of the temperature inversion was 

 sufficiently well defined that a diver could swim above it and feel 

 the hot water with his hand. The rapid density change also caused 

 a visible, shimmering layer because of changes in the refractive 

 index of the water. 



On several occasions, effluent distribution throughout the harbor 

 was plotted by divers swimming along the top of the submerged 

 effluent stratum. In the first portion of this study, Rhodamine B 

 dye was added to the effluent and its distribution traced by divers 

 in the receiving water. This enabled analysis of the flow of effluent 

 into the system and showed a self-insulating mechanisms which is 

 described below. 



Thermal differences also enabled instantaneous analysis of the distri- 

 bution of the effluent by use of a Westinghouse thermister net. The 

 instrument consisted of fourteen cables deployed in the canal and 

 connected to a single control unit with a three-dimensional light 

 display. At the points indicated in Figure 5, the cables were connected 

 to five thermisters buoyed at five- foot intervals from the bottom up to 

 a depth of ten feet (3m). One strand (#5) continued to the surface to 

 give data above the ten-foot level. All the cables were connected to 

 a tie-down system so the array could be lowered to the bottom when not 

 in use. Although normal boat traffic carried less than ten feet (3m) 

 draft, occasional vessels drawing eighteen feet (5.5m) entered the 

 canal. In addition, tugs and fuel barges on occasion tied up to the 

 dock at the desalination plant which could have damaged the array. 



Each of the 72 thermisters was represented by a small light bulb in a 

 scale model of the canal. When the single control dial was set at a 

 particular temperature all of the lights representing thermisters above 

 that temperature lit up. By sequentially changing the dial setting, all 

 of the isotherms in the canal could be viewed three-dimensionally. With 

 the dial set at a particular temperature, an isotherm could be followed 

 over several hours or days. In this way, one could watch the hottest 

 portion of the effluent move through the canal as the plant began 

 operation or as tides or winds shifted. 



Initially, the cables were set in a rectangular grid pattern. This 

 pattern was changed to provide greater coverage of the canal, particu- 

 larly along the eastern portion, as this arrangement was more repre- 

 sentative of the general movement of the stratum under normal conditions. 

 The final arrangement, shown in Figure 5, provided readings along a 



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