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<br />OOOli9 <br /> <br />Concerns Related to RIP Biology Committee Discussions <br />of Revised Gunnison River Flow Recommendations <br /> <br />The u.s. Fish and Wildlife Service's flow recommendations for the Gunnison and <br />Colorado Rivers have been subjected to considerable debate and modification based on <br />comments received by various members of the Recovery Program. Recently, in response to <br />concerns expressed in a Biology Committee minority report, the Service modified flow <br />recommendations to more closely meet recommendations made previously by Pitlick et aI. The <br />Pitlick recommendations were preferred by the minority because they were based on field <br />research in the Gunnison and Colorado rivers and therefore had the strongest scientific basis for <br />making recommendations. <br /> <br />, <br /> <br />Other members of the Biology Committee who had approved the previous set of flow <br />recommendations expressed concern that the revised recommendations did not specifY annual <br />instantaneous peaks and therefore did not provide enough guidance to dam operators and did not <br />represent a "natural hydrograph." Consequently, at the most recent Biology Committee meeting <br />(August 27 and 28, 2002), it was suggested that the recommendations be revised to include <br />specific instantaneous peak flow targets in each of the six hydrologic categories. We object to <br />this decision for a number of reasons that are detailed in this paper. <br /> <br />Peak flow recommendations for the Gunnison and Colorado Rivers are based on the <br />expressed need for channel maintenance. Pitlick's recommendations also target channel <br />maintenance. Without biological information on instantaneous peak flow requirements, the flow <br />recommendations should adhere to the Pitlick et al. (1999) recommendations for channel 1 <br />maintenance. <br /> <br />Pitlick's research on the Gunnison River indicates that since 1978 the channel has been in t <br />an equilibrium condition (i.e., the channel is being maintained with the flow regime that has been <br />in place since completion of the Aspinall Unit). Consequently, any departure from the historical <br />post-Aspinall flow regime should be based on scientific information related to a known <br />biological requirement or to specific channel-maintenance requirements. Peak flow targets <br />identified at the Biology Committee meeting for moderately wet, average wet, and average dry <br />years (60% of the years) represent significant increases above historical peak flows in these <br />hydrologic categories. <br /> <br />These peak flow targets appear to be based primarily on the professional judgment of , <br />several of the Biology Committee members. The only justification provided for an instantaneous <br />peak flow above the Pitlick thresholds is the significant motion threshold (16,000 cfs) at one of <br />Pitlick's transects near a suspected Colorado pikeminnow spawning habitat. This is insufficient <br />support for deviating from the specific Pitlick recommendations. No justification was provided <br />for any of the other peak flow targets. <br /> <br />We understand the desire to provide variation in annual peak flows and a "natural" <br />hydro graph. However we are concerned that the instantaneous peak flows recommended by the <br />Biology Committee have no scientific basis and are therefore subject to criticism. One of the <br />