During overfall flow conditions with 1.2 feet 

 of head, the fish often moved about the pool 

 considerably before passing to the next pool. 



Steelhead .--The performance of steelhead 

 under various flow conditions (table 8) was 

 similar to that evidenced in tests with chinook 

 salmon. The increase in head on the weir 

 induced faster ascents when orifices were 

 open and slower ascents when orifices were 

 closed. The fastest ascent occurred when only 

 orifice flows were present, and the slowest 

 ascents occurred during the overfall-only 

 condition. 



Observations from the viewing area revealed 

 that steelhead actively explored the lower half 

 of the pool when orifices were closed. During 

 test condition 2C (orifices closed and high 

 flow), steelhead nearly always rested on tb 

 bottonn of the pool. Characteristic behavic 

 during orifice flow as direct passage throug 

 the pool in line with the orifices. 



Weir Overfall vs. Orifice Passage 



Observations were made at weir 60 to deter- 

 mine if various species preferred the weir 

 overfall or the orifice during ascent. Tests 

 were made on individual chinook, steelhead, 

 and sockeye, and on two group releases of all 

 species available. 



The percentage of individual chinook, steel- 

 head, and sockeye using weir overfalls and 

 orifices was calculated for May through Sep- 

 tember (table 9). Chinook and steelhead showed 

 a seasonal difference in behavior. During May 

 and June most chinook preferred the orifice, 

 but during July, August, and Septennber they 

 preferred the weir overfalls. Steelhead, how- 

 ever, preferred weir overfalls early in the 

 season and orifices later on. Sockeye con- 

 sistently preferred the weir overfalls. 



Two group releases, comprised of both 

 salmonids and other fish, provided additional 

 information on the preference of various 

 species for either the overfall or the orifice 

 during passage (table 10). Salmon and steel- 

 head responses were comparable to those in 

 the tests with individual fish. Squawfish 

 ( Ptychocheilus oregonensis ), suckers (Catos- 

 tomus sp.), and carp (Cyprinus carpio) de- 

 cidedly preferred orifice passage while shad 

 ( Alosa sapidissima ) predominantly preferred 

 the overfall. 



are shown as a cumulative percentage of all 

 fish completing an ascent of six pools in 60 

 minutes or less. Data for the 1-on- 16-slope 

 fishway apply to a structure 11.5 feet wide, 

 whereas the 1-on- 10 material is based on 

 tests conducted in fishways both 8 and 16 feet 

 wide. While seasonal distribution of fish in the 

 respective comparisons differed, the major 

 portion of the chinook, steelhead, and sockeye 

 runs in each year Avas covered fairly well. 



These comparisons show that the three 

 species made faster ascents in the 1-on- 10- 

 slope fishway than in the 1-on- 16-slope fish- 

 way. The difference in performance of chinook 

 and sockeye salmon in the t'wo fishways was 

 less than that of steelhead, but a trend of 

 somewhat faster ascent in the 1-on- 10 slope 

 was still apparent. 



The performance of fish in the two fishway 

 slopes may be further compared by examining 

 results of capacity tests in the respective 

 fishways. Tests in a 1-on- 16-slope fishway on 

 June 25, 1957, (Elling, 1960) can be compared 

 with the tests of June 20 and 27, 1960, in this 

 report. Mostly chinook salmon were used in 

 the 1957 and 1960 tests. Respective median 

 elapsed times for the 1957 tests were 9.2, 10.0, 

 and 13.1 minutes, whereas in the I960 tests, 

 passage times for a similar ascent of six 

 pools were 7.1 and 7.9 nninutes. Again, these 

 data appear to parallel results of the compari- 

 son with individual fish; that is, a somewhat 

 faster ascent occurred in the 1-on- 10-slope 

 fishway than in the 1-on- 16-slope fishway. 



The foregoing analysis must, of course, be 

 considered with some reservation because 

 conditions for passage were not comparable 

 in the two fishways; that is, orifices were 

 present in the 1-on- 10 slope and lacking in the 

 1-on- 16 slope. Without knowing how orifices 

 would have affected passage in the 1-on- 16- 

 slope fishway, we must await comparisons of 

 both fishway designs with orifices under pro- 

 totype conditions before we can make the final 

 analysis. Nevertheless, results of the current 

 work appear to be sufficiently encouraging to 

 warrant a judgment that a 1 -on- 10-slope fish- 

 way of the design tested should be as suitable 

 for passage of fish as the conventional 1-on- 

 16- slope fishways now used on the Columbia 

 River. 



SUMMARY AND CONCLUSIONS 



COMPARISON OF PERFORMANCE IN 

 1-ON-lO- AND 1-ON-16-SLOPE FISHWAYS 



A preliminary evaluation of the test fishway 

 may be made by comparing passage times of 

 fish in the six-pool Ice Harbor design to simi- 

 lar data from previous tests in a six-pool 

 section of a 1 -on- 16-slope fishway without 

 orifices. Passage tinnes by species (fig. 18) 



A full-scale, six-pool section of the pro- 

 posed 1-on- 10-slope Ice Harbor fishway de- 

 sign was tested in the Fisheries-Engineering 

 Research Laboratory at Bonneville Dam be- 

 fore constructing the prototype. Pools were 

 16 feet wide by 10 feet long (weir center to 

 weir center). The key feature of this fishway 

 is the special weir design consisting of a 

 center baffle and vertical flow stabilizers, 

 with 5-foot wide overfall sections on each side 



17 



