Water Turbidity 



Summer studies of the trans- 

 parency of water adjacent to the tower 

 have been made using a hydrophotometer. 

 The studies record light-transmission 

 values ranging from 20 to 80 percent, 

 based on a distilled water standard of 

 100 percent. Throughout the winter 

 months the clearer water readings 

 approach 100 percent. 



Water turbidity is caused by in- 

 organic, dissolved matter and various 

 forms of biological material. However, 

 most turbidity in the water column is 

 related to the phytoplankton population. 

 During summer, plankton blooms fre- 

 quently develop just below the surface, 

 with a low transparency reading (less 

 than 20 percent) . Patchiness is caused 

 in part by vertical circulation which 

 brings clearer water upward, creating 

 zones of high transparency within the 

 general turbid region. Following the 

 heavy surface blooms, the lower levels 

 of the water column become more turbid 

 and the upper level clears. 



The area of maximum turbidity 

 frequently coincides with the maximum 

 vertical thermal gradient. Because the 

 thermocline oscillates vertically with 

 internal waves, the associated turbid 

 layer also oscillates. In some cases, 

 water visibility changes with the tide, 

 with periods of high waves, and with 

 vertical or horizontal water mass 

 boundaries. As irregular turbid zones 

 move past the tower, changes in light 

 transmission as great as 50 percent may 

 occur in 2 minutes. 



TEMPERATUfc 

 SENSOR 



Water transparency is determined by a hydropho- 

 tometer (alpha meter). The device measures light 

 scattering and absorption by particles in the water 

 at varying levels. Temperature and biological speci- 

 mens are taken concurrently and at the same level. 



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