SUMMARY AND CONCLUSIONS 



Interest in the Denil-type fish ladder constructed at the Herting 

 power dam in Sweden led to the construction at Dryden Dam of one patterned 

 after the Swedish installation. Comparison of the Denil-type and pool- 

 type ladders was facilitated because it was possible to construct a Denil- 

 type ladder in one-half of the existing pool-type ladder at Dryden Dam. 



During the actual time that counting observations were conducted in 

 19li9 and 1951, the Denil-type was preferred by fish utilising the ladders. 

 In 110 hours ii5 minutes, 1,828 fish used the Denil-type ladder, and in 96 

 hours 55 minutes a total of 226 fish were counted through the pool-type 

 ladder. 



The Denil-type ladder at Dryden Dam occupies essentially the same 

 amount of space as the pool-type ladder. There is, therefore, some advan- 

 tage in the Denil construction in conservation of space, both from the 

 standpoint of its narrowness, and shorter length made possible by a steeper 

 slope. 



It was concluded, because of the baffles and higher flume wall con- 

 struction of the Denil-type ladder, that there is no substantial saving 

 in cost of construction over the standard pool-type ladder. 



'^th regard to flow requirements, Ihe data collected revealed that 

 the Denil-type ladder passed a greater number of fish per second-foot 

 of floxiT and required less attention. With only i^O percent more flow than 

 in the pool-type ladder, the Denil-tj'pe was utilized by 89 percent of the 

 fish counted through the ladders. 



Probably the most desirable feature of the Denil-tj'pe was the attrac- 

 tion flow it presented to fish. 



The study undertaken at Dryden Dam was somewhat limited in scope, and 

 it is hoped that the encouraging results may stimiilate further research 

 into the possibilities of the Denil-type ladder. One possibility for 

 adoption of the Denil-type which should be investigated is its installa- 

 tion at the downstream end of a pool-type ladder, since, on the basis of 

 observations at Drj'-den Dam, the Denil-type fish ladder is apparently 

 more effective in attracting fish than the small pool-type ladder common 

 to the Pacific Northwest. Additional studies also should be undertaken 

 to determine the height of dam that different species of fish can nego- 

 tiate by a continuo\is baffled channel without resting pools, and 

 investigations should be carried out to determine the practicability of 

 the Denil-type ladder at higher dams. 



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