Monitoring efforts in the Clark Fork would be improved 

 if the mixing zones created when tributaries enter the river 

 were delineated. Otherwise, it is difficult to know if the 

 tributary water or the Clark Fork is actually being moni- 

 tored. 



The following actions are recommended to address these 

 issues. 



1. Monitor DO concentrations at key locations in the Clark 

 Fork. 



Initiate a special WQB monitoring program to measure 

 late summer, diel DO concentrations at key locations in 

 the basin. Twenty-four hour measurements could define 

 the duration as well as the magnitude of DO sags (the 

 length of the DO depletion might be as critical as the 

 minimum concentration) . The monitoring program should 

 provide a systematic evaluation of DO in the river to 

 determine if concentrations are affecting beneficial 

 uses. 



2. Monitor water temperature regimes in the Clark Fork. 



Initiate a program to characterize the water temperature 

 regimes in critical river reaches, particularly during 

 late summer. Temperature, like other water quality 

 parameters, is highly variable, and a long-term data 

 base is essential to interpret changes and to establish 

 long-term trends. Available temperature data should be 

 completed and analyzed to establish a historical data 

 base. 



3 . Document the extent of the mixing zone for Clark Fork 

 tributaries. 



Conduct a rhodamine dye study to determine the extent of 

 the mixing zone created when a tributary enters the 

 Clark Fork. Failure to consider the extent of mixing 

 could lead to erroneous interpretations regarding water 

 quality and its relationship to other uses. 



Monitoring 



Water quality monitoring is one of the essential tools 

 of water quality management. Scientifically valid data 

 collected over a long period are necessary to assess changes 

 in water quality. The need for water quality data on the 

 Clark Fork became most evident in 1983 when Champion Inter- 

 national, Inc., applied for a modification of its wastewater 



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