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Temperature 



Chinook salmon prefer temperatures between 7 and 14 degrees centigrade (45 to 

 58 degrees f ahrenheit ) ; salmon and trout show stress when temperatures exceed 

 18 degrees for more than a few hours or days (Bell 1984). Adult Nooksack 

 River spring chinook absolutely require temperatures below 23 degrees 

 centigrade (75 degrees fahrenheit) (Mike Barclay, Nooksack Indian Tribe, pers. 

 comm. ) . The Washington Administrative Code states that "Temperature shall not 

 exceed 18.0 *C due to human activities" (WAC 173-201-045 (2 ) (c) (iv) ) in waters 

 classified as axe the Chehalis streams. 



Present Condition . Throughout the mid-Chehalis, the temperature standard is 

 routinely exceeded from June to September, particularly near Centralia (Hiss 

 et al. 1983a; Aroner 1991; Pickett 1992). Clearly, these conditions are 

 unsuitable for holding adult salmon. If temperatures remain high enough 

 throughout the night, migration through the area could also be blocked. 



Efforts to reduce temperature have been very local; temperature controls have 

 been engineered into the Skookurachuck Dam, and are under study for the 

 Wynoochee Dam, but temperature problems in the Chehalis Basin have not been 

 studied in detail (Pickett 1992). 



Causes . Shade removal, resulting from logging (Newman, Weyerhaeuser Co., pers. 

 comm.), agriculture, and residential and industrial development (Barber, WDF, 

 pers. comm.), has contributed to seasonally recurring high temperatures 

 (Pickett 1992). Although current logging regulations sometimes require a 

 certain number of mature trees per length of stream bank to contribute to 

 instream woody debris, this arrangement guarantees only partial shading from a 

 thin row of large trees, rather than the potentially more complete shading and 

 cooling effect of a naturally dense growth of shrubs and trees of various 

 heights. Some farmers maintain pastures and crops directly adjacent to the 

 streambank and thus prevent shade trees and shrubs from establishing. Numerous 

 water withdrawals cumulatively reduce instream flow thereby raising 

 temperatures. 



Oxygen 



Salmonids require a concentration of at least five mg/1 dissolved oxygen in 

 the water for survival (Bell 1984) although six mg/1 is still considered 

 stressful. The WAC states that "freshwater dissolved oxygen shall exceed 8.0 

 mg/1" (WAC 173-201-045(2) (c) (ii) (A) ) , except that because of naturally low 

 water velocity in some reaches, the "Chehalis River from Scammon Creek (RM 

 65.8) to Newaukum River (RM 75.2) dissolved oxygen shall exceed 5.0 mg/1 from 

 June 1 to September 15." (WAC 173-201-080(8)). 



Present condition . The Chehalis-Centralia area between Miles 66 and 76 has 

 been the site of low dissolved oxygen in late summer and fall (Bernhardt 

 1974). Dissolved oxygen violations were also recorded at Centralia, Porter, 

 Montesano, and in the Satsop River (Hiss et ai. 1983a; Aroner 1991; Pickett 

 1992). 



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