The Hells Canyon Case 146 



contains many dissimilar estimates of power output which arise 

 out of differences in assumptions governing the determining vari- 

 ables. In order to achieve comparability among plans of develop- 

 ment, we have attempted to obtain estimates based on common 

 assumptions which reflect a consensus of expert witnesses as to rea- 

 sonableness of technical assumptions, appropriateness of measures 

 used, etc.^^ 



Several measures of power output are available. In the Pacific 

 Northwest, served basically by hydroelectricity, estimates of prime 

 power appear to be the most relevant.^^ The amount of prime 

 power from the Hells Canyon development will change over time, 

 however, and different basic assumptions will alter the estimated 

 total power output for both plans of development. Several methods 

 are available. First, we could use an estimated average length of 

 critical period and estimated depletion, generally accepted as rea- 

 sonable by the expert witnesses. Or we could use an estimated 

 average annual prime power output, based on changes in critical 

 period during the time span. Finally, we could move to a some- 

 what different method by comparing time streams of estimated 

 input and output. For our purpose, we have employed the first 

 method — largely because this enables us to cull from the record 

 the maximum relevant data, which are both consistent among plans 

 of development, and useful in illustrating some of the significant 

 aspects of the total problem. ^^ 



At the site of development, annual benefits would be accounted 

 for by 647,000 kilowatts of prime power generated at the High 

 Dam and 585,000 kilowatts at the three dams, as well as a certain 

 amount of navigation service provided on the reservoirs them- 

 selves. Downstream benefits would accrue from increased prime 

 power at eight installations (314,000 kilowatts resulting from the 



" Even so, our results should be regarded as useful only in illustrating some 

 of the basic factors underlying efficient multiple purpose development, rather 

 than a definitive determination of the most efficient plan of development for 

 Hells Canyon. 



'« FPC, Decision, op. cit., p. 45. 



" In general, while different assumptions or approaches in analysis will yield 

 different estimates for total power output, this is of little consequence if the 

 differences between plans remain relatively unchanged. To the extent that this 

 is not the case, we will provide results obtained by alternative methods for com- 

 parative purposes. 



