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01244 I November 19. 1993 . In August 1993. the 60-month study was repeated using more recent reservoir starting conditions. In some years. the latest 60-month result exceeded CRSM by as much as 8-14% or 480-800+ gWh per year. This difference was attribitable to (a) reservoir starting conditions. (b) Upper & Lower Basin depletion assumptions.. (c) inflow forecasts. and (d) inherent differences in the methods employed. . In November. special PRS studies were prepared which considered the incrementa 1 rate effects of 3 a lternat i ve short -term adjustment methods: (a) No adjustment. (b) 5-year linear adjustment. and (c) 60-month study projections. These PRS studies concluded that the these adjustment could affect the base rate (no adjustment) by as much as 0.32 mills. Sensitivities Since the initial application of the 5-year linear adjustment. Reclamation has updated their hydrology data base used in the CRSM modeling for power projections (CRSS Natural Flow Hydrologic Data Base. 12-91) to include the below-average inflow years. 1989 through 1990. A strlct interpretation of DOE RA 6120.2 might be that. with the most recent improvements to the input data. CRSM modeling would represent the best available "theoretical reservoir operation studies based on historical streamflow." The approach used in the development of the 60-month study by Reclamation. though possi b ly an improvement. can be characteri zed as an "expert system" which cannot be either duplicated or verified in detail by others since release decisions did not follow a strict algorithm or decision process. Reliance upon such an expert system approach would mean accepting the possibility of significant deviation in generation estimates from one year to the next should future studies be prepared by another. Due to the limited time available to study these most recent results and the significant change that would result in the forecasted generation. further analysis would seem prudent prior to consideration of such changes in methods for an initial rate repayment study. Alternatives/Options Option 1: CRSM Values without Adiustment. Continued Analysis of Short- term Methods. This option would suggest that middle-envelope smoothed average annual energy projections from CRSM be used wi thout short -term adjustment in the i ni ti a 1 rate propos a 1. Further analysis would be performed for future consideration. 60-Month Study. with Averaoe Inflow. This option would proposes that the results of the 1 atest 60-month study by Reclamation be used as an alternative to the linear interpolation methodology for short-term projections. In Option 2: