The thermal structure (fig. 31) on 23 July was 

 characterized by a steep gradient and a pronounced vertical 

 oscillation between the hours of 1056 and 1600. The oscil- 

 lation produced a 15-foot upward displacement of the thermo- 

 cline. Areas of least transparency (60 percent and less) 

 are centered directly above the oscillation. 



Figure 33 gives light transmission data for 24 July 

 from 0030 to 1300. Transparency, measured at 0030 and 

 0515, was 75 percent or above throughout the water column. 

 At 0905 turbid water appeared at 10 and 20 feet (53 and 58 

 percent, respectively), and at 1030 transparency between 

 those depths (at 15 feet) had decreased to 45 percent. Sur- 

 face transparency at 1030 was 70 percent. The first red 

 water apparent at the surface appeared at the tower site 

 at 1035. The hydrophotometer was operated at 1042 in the 

 center of a large red-water mass. At this time, trans- 

 mission ranged from 31 percent at the surface to more than 

 90 percent near the bottom. Light transmission increased 

 from 47 percent at 20 feet to more than 90 percent at 30 

 feet. The red water persisted around the tower until after 

 1200. Extreme variation in transparency was measured 

 during these operations. During the period from 0030 to 

 1300, transmission at the surface ranged from 31 to 87 

 percent. Surface to near-bottom values ranged from 31 

 to 99 percent. 



In contrast to the situation on 23 July, temperature 

 (fig. 34) between the hours of 0023 and 1133 on 24 July 

 showed no major oscillations. The steepest gradient of 

 the thermocline was between the surface and 40 feet with 

 a range from 70°F at the surface to 54°F at 40 feet. 



54 



