Table 1. — Surnnar;' of fishway capacity tests, 1956 



1/ Fishway ~ 6 pools, each 16 feet long, 6 feet wide and 6.3 feet deep yiith a 1 foot rise be- 

 tween pools. Head on weir — 0.8 foot. Flow^plunging unless otherwise noted. 



2/ Includes Jacks (arbitrarily all chinook 20" long end under), 



3/ Streaming flo-.vs developed at 1 or nore weirs in fishway, 



4/ Scrap fish present but not included in counts. 



Note is made here of the respective 

 sizes of the above experiments as a subse- 

 quent discussion will consider the possibil- 

 ity that capacity may have been achieved in 

 the September 7 trial while there was no 

 clear evidence that maximum passage was 

 reached in the July 13 trial. The inference 

 is, of course, that numbers alone are not a 

 valid measure of test magnitude. Size of 

 fish within the test must be considered if 

 each test is to be evaluated properly with 

 respect to gross content. 



Effect of Changing Hydraulics 

 on Fish Passage 



If there is to be a sound comparison 

 between tests, comparable physical condi- 

 tions must prevail. One of the major 

 difficulties encountered in our recent ex- 

 periments resulted from our inability to 

 control the established flow pattern in the 

 fishway. We have previously noted that the 

 established flow over weirs at the begin- 

 ning of each test was plunging. Some time 

 after fish had been introduced into the 

 fishway, their presence apparently disturbed 

 the flows sufficiently to change the pattern 

 from plunging (submerged motion) to stream- 



ing (surface motion). This phenomenon 

 usually commenced at the uppermost weir 

 (60) and was successively established at 

 succeeding downstream weirs. During several 

 trials streaming flows failed to develop. 

 Characteristically, once streaming flow was 

 established, it continued in effect for the 

 balance of thetest. 



Undoubtedly , 

 the beginning of 

 the upper limit at 

 be maintained. U 

 (7 1/2 inches wid 

 foot head was in 

 for the critical 

 Any disturbance o 

 have been produce 

 crest, could have 

 flow conditions. 



hydraulic conditions at 

 a test were approaching 



which plunging flows could 

 se of a broad crested weir 

 e) and the fact that 0.8- 

 effect on the weir attest 

 nature of the hydraulics, 

 f the flow, such as may 

 d by fish passing over the 



created the streaming 



Our concern with this development was 

 because of its effect on the movement of 

 fish. Figure 9 presents passage curves 

 obtained at two weirs in the capacity test 

 of July 5, 1956. Passage per unit time 

 over weir 54 produced a curve which was 

 essentially unimodal. Plunging flows ob- 

 tained at this weir during the entire 



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