longer apparent. The trend of increase shown 

 in figure 8 would have been even better de- 

 fined except for vertical as well as horizontal 

 variation. Vertical gradations of water tem- 

 perature and dissolved oxygen were well 

 defined near the bank, but were not nearly 

 as pronounced as near the center of the stream 

 (table 9). 



Interchange of Flowing Stream 

 Water with Water in the Gravel of 

 the Streambed 



Studies of interchange of flowing stream 

 water with water in the gravel of the stream- 

 bed were started as soon as it became apparent 

 that ground water was usually low in dissolved 

 oxygen content and that dissolved oxygen levels 

 decreased with depth in the streambed. The 

 extent and method of interchange in salmon 

 spawning riffles had not been thoroughly 

 demonstrated. 



Wickett (1954) suggested that intragravel 

 water containing a large amount of dissolved 

 oxygen comes from the stream through per- 

 colation. Cooper (1959) reported that inter- 

 change is greatly increased by placing a few 

 large rocks on the surface of the streambed. 

 Interchange was indicated by the work of 

 Fisheries Research Institute personnel (un- 

 published) and of Skud (1954) on changing 



temperatures and salinities in the gravel of 

 intertidal zones through the tidal cycle. 



Interchange of water between stream and 

 streambed was first demonstrated in the 

 Indian Creek spawning riffle in 1958. At that 

 time upwelling of intragravel water was shown 

 by inserting fluorescein dye into standpipes 

 placed at various depths in the gravel and 

 mapping the subsequent appearance of dye- 

 marked water at the surface of the streambed. 

 Descent of surface water was demonstrated 

 by marking flowing stream water masses with 

 dye and capturing dye-marked water in stand- 

 pipes placed at different depths in the gravel 

 downstream from the point of insertion. 



The mechanics of interchange in the Indian 

 Creek riffle were qualitatively studied in 

 more detail in 1959; results of this work 

 appear in a report by Vaux and Sheridan 

 (1960). 



Water in Gravel of Streambanks 

 and Gravel Bar 



Temperatures of water in the gravel of the 

 main stream channel closely approximated 

 temperatures of the flowing stream (except 

 in areas under ground-water influence dis- 

 cussed previously). Because of interchange, 

 dissolved oxygen levels of water in the gravel 



Table 9. — Comparison of dissolved oxygen and temperature 

 gradations at two locations in Indian Creek study riffle, 



September 1959 



Depth 



in 

 gravel 



Near the bank 



(ground-water seepage) 



Near center of stream 

 (no ground-water 

 seepage — interchange) 



Dissolved 

 oxygen 



Tempera- 

 ture 



Dissolved 

 oxygen 



Tempera- 

 ture 



Inches 



ifc-A - 



F. 



*fe./l . 



F. 



7.0 



51.0 



10.1 



51.0 



10 



4.4 



50.5 



9.9 



50.8 



15 

 20 



1.4 



0.5 



48.0 



45.5 



9.7 



51.0 



15 



