350 



In effect, the critical assumptions require that a Snake River Reservoir drawdown would 

 have to operate flawlessly, with completely optimal conditions, in order for the drawdown 

 scenario to equal or exceed the salmon benefits obtained from the existing smolt 

 transportation program. This would necessitate that: 1 ) there would be no improvement 

 in smolt transportation benefit ratios over time; 2) there would exist high survival rates for 

 reservoir passage; 3) there would exist high fish guidance efficiency (FGE) levels for 

 project passage; 4) there would be no gas super-saturation or project passage problems; 

 5) there would be no adult return migration or passage problems; and 6) there would be 

 no latent smolt mortality below Bonneville Dam as a result of cumulative project passage 

 through the Snake-Columbia River system. 



The importance of relying on these critical assumptions, and the unlikely probability of 

 their collective occurrence, has been reviewed in detail by Olsen, Stevenson, and 

 Weitkamp (1992), using the Idaho Fish Manager model, calibrated to produce the same 

 results as life-cycle model analyses conducted by the Northwest Power Planning Council 

 staff (Passage Analysis Model). The Council staff reviewed the analysis conducted by 

 Olsen, Stevenson, ana Weitkamp (1992) and made the following observations (NPPC 

 1992): 



The [NPPC] analysis did not indicate that the four pool drawdown option can be 

 expected to provide the greatest benefit for Snake River spring Chinook. It did 

 indicate that the four pool drawdown option holds potential for increasing survival 

 in the average or better flow years if a number of uncertainties tum out favorably. 

 It also indicates that drawdown would actually lower survival relative to the baseline 

 in lower flow years, based on what we know about transportation...The analysis 

 also showed ttiat drawdown is extremely vulnerable to uncertainty in a number of 

 key factors such as predator control and fish guidance efficiency. The Olsen 

 report [Olsen. Stevenson, Weitkamp 1992] reiterates the conclusions of our 

 analysis regarding drawdown, only stating them much more strongly. 



The work by Anderson (1993b) further highlights the need for optimal critical 

 assumptions, in order for a Snake River Reservoir drawdown to be success. Anderson 

 (1993b) concludes that biological benefits from a drawdown are contingent on "there 

 being no adverse affect in drawdowns," and that the biological benefit estimates 

 calculated from a drawdown scenario are highly uncertain. 



An existing economic analysis of a John Day Pool drawdown from 262.5-263.5 

 (minimum irrigation pool) to 257 (minimum operation pooi) indicates that this 

 aitemative is among the least cost-effecUve measures available for salmon recovery 

 planning. 



The NMFS Economics Technical Committee has reviewed several key methodclogicaJ 

 factors inherent to an economic analysis of salmon recovery measures, under the 



