valve system, which prevents the lower end 

 of the standpipe from becoming filled with 

 silt. 



Another adaptation developed at Mill 

 Creek allows the use of the conductivity 

 bridge for measuring dilution and apparent 

 velocity in the gravel. The bridge combined 

 with the opening and closing feature of the 

 standpipe makes possible precisely timed 

 and accurate determination of displacement 

 of water in the standpipe by resistance 

 measurements of a dilution of salt solution. 

 Laboratory comparisons between displacement 

 and measured velocity appear consistent and 

 reliable. 



Migration of particles of silt is 

 known to cause blockage of pores in the 

 gravel and thus cause inadequate seepage. 

 The result is a low level of dissolved oxy- 

 gen, poor delivery of oyxgen, cind inadequate 

 cleansing of wastes all of which lead to 

 mortality of spawn. 



Assessment of the above limitations 

 will be better defined by a greater number 

 of tests. 



LITERATURE CITED 



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BURMISTER, DONALD M. 



1954. Principles of permeability testing 

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CHRISTIANSEN, J. E. 



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FANCHER, G. H. , AND J. A. LEWIS 



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FISHEL, V. C. 



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salmon in Mill Creek, a tributary of 

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GIRARD, JAMIN M. 



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HAZEN, ALLEN 



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JONES, CHESTER W. 



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KING, HORACE WILLIAMS, AND ERNEST F. BRATER 



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