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Scionrific LvaltIntinn of Biological Opinions on rndangored and Thrcatoncd Pl�hrs in the Klamath RIvcr Basin: intorh„ Rcporr (2l]02) <br />nccp:� meR•.naprli fmCcnti^^ cnl it rlufCUd I�b mvJ.ntml. a ^pv ^6'v rn� Zr�l l 1'M Part ^IISI AVLOkIlIY ^r Ik ICMw- 011 N6HV%kacrrvcd <br />SUMMARY <br />mortality (fish kills), for example, have not been associated with years of low water level. <br />Also, extremes of chemical conditions considered threatening to the welfare of the fish <br />have not coincided with years of low water level, and the highest recorded recruitment of <br />new individuals into the adult populations occurred through reproduction in a year of low <br />water level. Thus, the committee concludes that there is presently no sound scientific <br />basis for recommending an operating regime for the Klamath Project that seeks to ensure <br />lake levels higher on average than those occurring between 1990 and 2000. At the same <br />time, the committee concludes that there is no scientific basis for operating the lake at <br />mean minimum levels below the recent historical ones (1990 - 2000), as would be allowed <br />under the USBR proposal. Operations leading to lower lake levels would require <br />acceptance of undocumented risk to the suckers. <br />For the Klamath Basin coho, the NNVS RPA involves coordination of operations <br />as well as reduction of ramping rates for flows below the main -stern dams and increased <br />flows in the Klamath River main stem. Coordination and reduced ramping rates are well <br />justified. The pommittee, however, did not find clear scientific or technical support for <br />increased minimum flows in the Klamath River main stem. Although the proposed <br />higher flows a, intended to increase the amount of habitat in the main stem, the increase <br />in habitat spay that can occur through adjustments in water management in dry years is <br />small (a few p#rccnt) and possibly insignificant. Furthermore, tributary conditions <br />appear to be th 0 critical factor for this population; these conditions are not affected by <br />operations of to Klamath Project and therefore are not addressed in the RPA. Finally, <br />and most impf=tly, water added as necessary to sustain higher flows in the main stem <br />during dry yeVs would need to come from reservoirs, and this water could equal or <br />exceed the let4al temperatures for coho salmon during the warmest months. The main <br />stem already is excessively warm. Juvenile fish living there probably tolerate its <br />temperature only bccausc of the presence of groundwater seepage or small tributary flows <br />that provide packets of cool water. Addition of substantial amounts of warm water could <br />be detriment6to coho salmon by reducing the size of these thermal refuges. At the same <br />time. reduction in main -stem flows, as might occur if the USER proposal were <br />implemented, cannot be justified. Reduction of flows in the main stem would lead to <br />habitat conditions that are not documented, and thus present an unknown risk to the <br />population. <br />Conclusion <br />On the basis of its interim study, the committee concludes that there is no <br />substantial scientific foundation at this time for changing the operation of the Klamath <br />Project to maintain higher water levels in Upper Klamath Lake for the endangered sucker <br />populations or higber minimum flows in the Klamath River main stem for the threatened <br />coho population. The committee concludes that the USBR proposals also are unjustified, <br />however, because they would leave open the possibility that water levels in Upper <br />Klamath Lake and minimum flows in the Klamath River main stem could be lower than <br />those occurring over the past 10 years for specific kinds of climatic conditions. Thus, the <br />committee finds no substantial scientific evidence supporting changes in the operating <br />3 <br />966 -d BEO /910'd 9EZ -1 8998998EOE S30VOSM 1dbI M 10134081 W h ZOOZ- 80 -83d <br />