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Pool. As such, a John Day Pool drawdown would increase fre total percent smolt 

 survival below Bonneville Dam by less than 1 %. With the smolt transportation program 

 removed, and with fully optimal assumptions for smolt survival under a Snake River 

 drawdown scenario (a highly unlikely condition), a John Day Pool drawdown would 

 increase total smolt survival below Bonneville Dam by about 1%. But if existing fish 

 guidance efficiency (FGE) levels for the John Day Project decrease and smolt predator 

 concentrations increase within the reservoir (a likely condition), a John Day Pool 

 drawdown would either have no effect on smolt survival below Bonneville Dam or 

 increase survival by less than 1% (Anderson 1993a). The potential to decrease FGE and 

 increase predator concentrations under pool drawdown conditions has been identified 

 by Weitkamp and Sullivan (1993) and the Army Corps of Engineers (1992), as well. 



The modelling work developed by Anderson (1 993a). using CRISP 1 .4, is consistent with 

 the analysis prepared by the Northwest Irrigation Utilities (NIU), relying on the Idaho Fish 

 Manager spreadsheet model (Olsen 1992). In the modelling work prepared by NIU, a 

 John Day Pool drawdown was evaluated with: 1) the existing transportation program in 

 place; 2) a comprehensive set of recovery measures being implemented; and 3) optimal 

 smolt survival assumptions for a John Day Pool drawdown (reservoir smolt mortality 

 reduced by 10%). Under this set of fully optimized assumptions, the incremental effect 

 of a John Day Pool drawdown would amount to less than 1 00 Snake River adult salmon 

 returning to Idaho waters over one complete life-cycle (optimized life-cycle) . 



Biological benefit estimates derived from a John Day Pool drawdown-at best, about 

 a one percent increase in total smolt survival below Bonneville Dam-are fully 

 dependent on optimal critical assumptions for a Snake River Reservoir drawdown 



As indicated by Anderson (1993a), less than five percent of the initial Snake-Columbia 

 River smolt migration (spring Chinook) actually passes through the John Day Pool, with 

 the existing smolt transportation program in place. Consequently, even with optimal 

 assumptions for smolt survival within the John Day Pool-no decrease in fish guidance 

 efficiency at the John Day Project and no increase in smolt predator concentrations-a 

 pool drawdown results in less than a one percent increase in total smolt survival below 

 Bonneville Dam. 



If smolt transportation passage is removed, then any positive biological benefits derived 

 from a John Day Pool drawdown are fully dependent on the optimization of the critical 

 assumptions for a "workable" Snake River Reservoir drawdown scenario. The importance 

 of optimal or "best conditions" for the critical assumptions underlying a Snake River 

 drawdown scenario cannot be overstated, and the optimal conditions factor is a 

 fundamental component of the Snake River drawdown analyses conducted by Olsen, 

 Stevenson, and Weitkamp (1992) and by Anderson (1993b). 



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