IL 

 J 



3 



in 



o 



o 

 u 



K 

 3 



U 



3 

 O 

 Z 

 O 



o 



CO 



JAN 



FEB 



MAR APR MAY JUN 



AUG SEP OCT NOV 



DEC 



COLUMBIA RIVER AT ROCK ISLAND 



Average Monthly Water Quality 

 1954 - 1957 



FIG. 24 



5:5 



