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002555 ." . ..1 .., ' .' .,., tYIng tt~ese ';::llUeS :0 Dorn ms(onc .3pU 5 CiJnCItlOnS ancpowerplant re~ease c:rpac!ry G.unng tne January through July period. ylonthIy volumes of 1,2 and 1,5 MAF were evaluated as possible triggers for implementing a BHBF prior to the release of monthly volumes greater than these values. This approach was proposed by several members of the Transition Work Group earlier in 1997 as Reclamation was forced to release water at rates of 27.000 cfs as the result of very high runoff forecasts (greater than 150 percent of normal), The use of the runoff forecast as a percent of normal was also investigated. recognizing that risk ofspilIs is closely tied to high runoff volumes, A "percent of normal" forecast could be established as a trigger. Variables in this approach include the timing of such a determination and the magnitude of the forecast percentage, Recommended Trigger Conditions for a Purposeful BHBF The subgroup has thoroughly discussed and analyzed this issue of risk ofspilIs, We have found that an answer to the question of a triggering risk level to be very subjective, However with some concerns as described below, we recommend the following process for determining the appropriateness ofa BHBF: I _ We conclude that the current January 1 target storage content of21.5 MAF is appropriate. unless and until operating experience or modeling shows otherwise. 2 _ We conclude that the current July 31 target storage content of23,8 MAF (0,5 MAF storage buffer) is appropriate, 3 _ We conclude that the aggressiveness of high winter releases should be moderated to some extent. by (I) seeking to maintain a more uniform level of monthly releases resulting from forecast changes. and (2) by limiting January monthly releases to 1.2 MAF unless driven to higher levels by large forecasted spring runoff that would require higher releases to safely pass the spring runoff. discussed in item number 4 below. This conclusion recognizes that high powerplant releases have significant effects on downstream resources. not limited to just sediment transport. Attempting to limit the January release volume to 1.2 MAf reduces the likelihood that high winter releases in excess of25.000 cfs would occur without being preceded by a BHBF and moves the timing of the BHBF detennination closer to the March/April target time frame, 4 _ We recommend that a BHBF in excess ofpowerplant capacity could be released upon meeting the following conditions. subject to the environmental appropriateness of such a flow: ,"'~ .... .,' a ;:When the J~lllIf)' or February forecast for the January - July spring runoff exceeds 13 MAF (about 140 percent of normal) and would likely precipitate extremely large monthly 6