CHAPTER III. PHYSICAL CHARACTERISTICS 



Physical characteristics of Sacramento River water were deter- 

 mined at the times of biological sampling. The results, which were gen- 

 erally consistent with those obtained during the water quality portion 

 of the investigation (Appendix B) , are summarized below. 



Temperatxires and Dissolved Oxygen 



Figures 1 through 8, inclusive, show air and water temperatures, 

 surface and bottom water dissolved oxygen concentrations, and dissolved 

 oxygen concentrations in interstitial waters of gravels. Fig\ires 9 and 

 10 show that the oxygen data are consistent with values obtained during 

 other phases of the investigation. 



Water teniperatures at Keswick (mile 305 '7) were generally about 

 50 *F. Downstream water teraperatiires approached equilibrium with air 

 temperatures at varying rates. 



Dissolved oxygen concentrations increased during the first 15 

 to 25 miles below Keswick and then generally decreased throiighout the 

 rest of the river (Figiires 9 and 10) . Surface and bottom dissolved oxygen 

 levels were generally about the same; of the 330 observations, signifi- 

 cantly lower concentrations at the bottom occurred only about two percent 

 of the time. 



Within the gravels in riffle areas, oxygen concentrations varied 



from about h to 12 ppm with average values about 2 ppm less than those 



in the overlying water (Fig\ire ll) . Wide variations were noted between 



closely spaced sampling points, with lower values generally associated 



with greater percentages of fines in the gravel. This may explain why 



successful salmon spawning occurs in very locelized areas within a general 



spawning reach. 



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