downdraft, and (2) introducing dye through a 

 standpipe 6 or more Inches below the gravel 

 surface and tracing its movement by detection 

 in standpipes at greater depths. 



3. Upward interchange from gravel to 

 stream was followed by introducing dye below 

 the gravel surface and tracing its direction of 

 flow through appearances in pipes at lesser 

 depths and at the gravel surface. 



Direction of interchange depends on stream 

 surface profile and bed surface configura- 

 tion: 



1. Direction of interchange in that part of a 

 riffle with a concave surface (stream gradient 

 decreases in direction of flow) was upwards — 

 intragravel to stream. 



2. Direction of interchange in that part of a 

 riffle with a convex surface (stream gradient 

 increases in direction of flow) was down- 

 wards — stream to intragravel. 



3. Direction of interchange under the 

 troughs of standing waves created by irregu- 

 larities in the streambed was upwards; intra- 

 gravel to stream. Direction of interchange 

 under crests of waves was downwards— 

 stream to intragravel. 



ACKNO W LEDGMENTS 



The writer wishes to acknowledge the guid- 

 ance of William L. Sheridan and William J. 

 McNeil in the field studies. He is also in- 

 debted to William F. Royce, Robert L. 

 Burgner, and Charles O. Junge, Jr. of the 

 Fisheries Research Institute and to Eugene P. 

 Richey of the Department of Civil Engineering 

 of the University of Washington for helpful 

 suggestions and criticism in the preparation 

 of this paper. 



LITERATURE CITED 



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COOPER, A. C. 



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HOBBS, DERISLEY F. 



1937. Natural reproduction of Quinnat sal- 

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McNEIL, WILLIAM J. 



1962. Variations in the dissolved oxygen 

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O'CONNOR, DONALD J., and WILLIAM E. 



DOBBINS. 



1956. The mechanism of reaeration in 

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POLLARD, R. A. 



1955. Measuring seepage through salmon 

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