Seasonal variation was apparent in most 

 types of data. Figures 6 to 10 show the 

 average values in the lower river for 



24 



each type of data (by sampling date) and 

 disclose the following information on seasonal 

 variation. 



22 - 



20 



18 r 

 16 



g l4 



12 

 10 

 8 - 

 6 - 

 4 - 

 2 

 



TEMPERATURE 



32 - 

 28 

 - 24 



^ 20 

 H 16 



tr 



o 



TURBIDITY 



JUL ' AUG. 1 SEP. ' OCT. ' NOV. 1 DEC. 1 JAN.' FEB. 1 MAR. 1 APR. 1 MAY ' JUN. ' JUL. ' AUG.' SEP. 'OCT. ' NOV.' DEC 

 1967 1968 



Figure 6. — Average water temperature (a) and turbidity (b) in the lower Columbia River, July 1967 through December 1968. 



