Figure 15. — Operational view of the Ice Harbor fishway with McNary crests on right 

 and The Dalles crests on left. Note reduced turbulence In flow pattern on right. 

 Corners on downstream face of the weir baffles on left are chamfered and those on 

 right squared. Eventual design of prototype was modified to conform with structure 

 on right. 



also improved over that under The Dalles -type 

 condition. Generally, faster ascents occurred 

 when the McNary crest was used (table 6). 



The plane-surface-ogee-type crest also 

 effectively reduced the air space beneath the 

 weir nappe. Performances of fish under this 

 condition compared favorably with those under 

 the McNary crest condition for the same gen- 

 eral period. 



The generally improved hydraulic condition 

 and favorable performance of fish under the 

 modified weir crest conditions led to a rec- 

 ommendation that McNary-type crests be used 

 in the prototype. 



Weir Baffle Design 



During some of the tests the downstream 

 face of the weir baffles were chamfered and 

 on others they were squared (fig. 15). With a 

 chamfered face on the weir baffles, overfall 

 flows flared toward the center of the pool 

 (fig. 13). Squaring the face of the weir baffles 

 appeared to improve the weir overfall condi- 

 tion by confining the spill to a direct in-line 

 flow. 



Effect of Flow Conditions 



The proposed Ice Harbor fishway was de- 

 signed to operate with an overfall and orifice 



flow with about 1 foot of head on the weirs. 

 During evaluation tests, various flow condi- 

 tions (figs. 16 and 17) were examined to assess 

 their effect on passage of individual chinook 

 salmon and steelhead trout. These included 

 (1) overfall and orifice flows with 0.95-foot 

 and 1.20-feet of head on the weirs, (2) overfall 

 flows with 0.95-foot and 1.20-feet head on the 

 weirs and with the orifices closed, and (3) ori- 

 fice flows with no overfall. McNary-type 

 crests were installed during these tests. 



Chinook .- -Results of tests with individual 

 chinook salmon (table 7) showed that certain 

 flow conditions materially affected their move- 

 ment in the fishway. Under the overfall and 

 orifice flow condition, the median passage 

 time was significantly less when the head on 

 the weirs was 1.20 feet than when it was 0.95 

 foot. When only overfall flows prevailed and 

 the head on the weir was 1.20 feet, the median 

 passage time was significantly greater than 

 that under the overfall flow condition with 

 0.95-foot head on the weirs. 



Performance under orifice flows only (with- 

 out overfall) compared favorably with that 

 under the overfall-flow-only condition with 

 0.95-foot head on the weirs. When only orifice 

 flows prevailed, chinook salmon responded 

 quite readily to this hydraulic condition and 

 spent little time in roaming about the pool. 



14 



