TURBIDITY- -TEMPERATURE 



To show the relation of the thermal structure to the 

 turbidity structure of the water, isotherms were super- 

 imposed on the lines of equal transparency of the preceding 

 three figures. Figures 10, 11, and 12 are similar to figures 

 1 , 8, and 9, but have isotherms drawn in to show the temper- 

 ature structure. These illustrations show considerable 

 correlation between turbidity and temperature, particularly 

 with regard to long-period changes in the level of the turbidity 

 isolines. However, there were several short-period fluctu- 

 ations that cannot be correlated with the thermocline. It 

 should be noticed that, in some cases, the clearer water 

 was near the surface and in others near the bottom. In 

 either case the long-period lowering of the isoline is associated 

 with the lowering of the thermocline and vice versa. 



By comparing figures 10 and 7, it can be seen that, on 

 a large scale, the isotherms followed the same general cycles 

 and levels as the lines of equal transparency. In both sets 

 of isolines there appears to be a vertical oscillation having 

 a period about equal to that of a tidal cycle. From the close 

 correlation of the large features, it appears that on this 

 day the clear water was a warm water mass and the more 

 turbid water was a colder one. Small-scale fluctuations, 

 however, do not always correlate. 



Figure 10. Time-depth plot of water transparency at the 

 USNEL tower on 19-2 July 1960 and the corresponding 

 temperature structure of the water (heavy lines) in degrees 

 Fahrenheit. Transparency less than 60 per cent is shaded. 



15 



