120 



| HO 



C "00 



3 



S 90 



§ 80 



iu 70 

 o 

 BE 

 Ul 



o. 60 



Sj 50 

 o 



g 40 



Q 



uj 30 



3 



o 



(/> 20 



10 









r 



i 





! 



I 



I 



^ 1954-55 

 D 1967-68 



^ 



! 



i 





I 



I 



Figure 15. — Average concentration of dissolved oxygen in 

 the lower Columbia River during 1967-68 compared 

 with levels given by Sylvester (1958) for 1954-55. 



MAR. MAY JUN. JUL. AUG. SEP. NOV. DEC. 



Table 11. — Comparison of limnological data collected in 1960 (Sylvester and Carlson, 1961), 



1967, and 1968 



ACKNOWLEDGMENTS 



Lawrence Davis, William Parente, and 

 Maurice Laird assisted with the field work for 

 this study. 



LITERATURE CITED 



EVANS ELECTROSELENIUM LIMITED. 



(n.d.) Atomic absorption analytical methods. 



Vol. I. Evans Electroselenium Limited, 



Halstead, England. Various pagination. 



GRIFFIN, W. C„ F. A. WATKINS, JR., and 



H. A. SWENSON. 



1956. Water resources of the Portland, 



Oregon, and Vancouver, Washington, 



area. U.S. Dep. Int., Geol. Surv. Circ. 



372, 45 pp. 



HACH CHEMICAL COMPANY. 



1967. Water and wastewater analysis proce- 

 dures. Its Catalog 10, Ames, Iowa, 104 pp. 



SCAROLA, JOHN F. 



1968. Cladocera and copepoda in McNary 

 Reservoir, 1965-66. Northwest Sci. 

 42: 112-114. 



STRICKLAND, J. D. H., and T. R. PARSONS. 

 1965. A manual of sea water analysis. 2d 

 ed., rev. Fish. Res. Bd. Can., Bull. 125, 

 203 pp. 

 SYLVESTER, R. O. 



1958. Water quality studies in the Columbia 

 River Basin. U.S. Fish Wildl. Serv., 

 Spec. Sci. Rep. Fish. 239, 134 pp. 

 SYLVESTER, R. O., and D. A. CARLSON. 



1961. A report on lower Columbia River 

 basic quality data analysis for the year 



13 



