No water temperatures lethal to salmon have ever been recorded in 

 Deer Creek from its headwaters to the mouth of its canyon. But, in the 

 lower section of the stream from the canyon mouth to the Sacramento River, 

 lethal temperatures occur every summer. The onset of these conditions 

 varies with the weather, rainfall, and stream flow, but once these high 

 temperatures are reached, the lethal conditions are usually maintained 

 in the lower section of stream throughout the summer months. 



The monthly maximum and minimum and the average daily maximum and 

 minimum temperatures recorded for each month at Deer Creek Station are 

 shown in table 60 



Table 6. -™ Water temperatures at Deer Creek Station 



19 hi 



1 9 U 8 



Average Average Average Average 



daily Monthly daily Monthly daily Monthly daily Monthly 

 Month maximum maximum minimum maximum maximum raaximian minimum minimum 



Salmon in Deer Creek become lethargic and fail to migrate upstream 

 when stream flows decline and water temperatures increase. This lethargy 

 is overcome only when stream flows are increased and water temperatures 

 greatly reduced. Coincident with low stream flows and rising water tempera- 

 tures, gi'eat quantities of algae grow and are then separated from the 

 stream bottom and disintegrate as they move downstream. Water analyses 

 were londertaken in 19ii7 to learn if the disintegration of these algal 

 masses reduced the dissolved oxygen content of the water materially or 

 caused a marked change in the hydrogen-ion concentration. 



10 



