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SclentifIr Evaluation or Rlnlo &laal Opinlens on V.ndanpecd and Threatoned Ilishca in the Rlamnth River 1;uin! interim Rotiort (2002) <br />a1ry1i9HC ar z. uXn The NVOrIoL, neunemv g!kiano all nFhm mwzrvW <br />EVAL ybj10N OETHE B10L0G C,A1, ONNION ON KLANA -1H BASIN COW SALMON <br />111 <br />2500 <br />2000 <br />1500 <br />1000 V 9' 91911119. i i i I • t� <br />500 000 uo�bO 000aoo� il...1•000 <br />0000 00 0 <br />Spawning Run Smolt Migrat tan <br />Oct I Nov I Ike I Jan Feb Mar I Apr I May I Jun Jul I Aug Sep <br />• Dry Water Years, USBR proposed <br />o Critical Dry Water Years, USBR proposed <br />�— Mean, 5 Dry* Water Years, 1961 -1997 <br />r- Mean, 2 Critical Dry Water Years, 1961 -1997 <br />A NMFS Biological Opinion <br />Figure 6. Three flow regimes for the Klamath River below Iron Gate Dam: USBR <br />proposed (USBR 2001b: minima for dry and critical years), historical mean <br />minima for dry and critical dry years, and RPA minimum flows from NMFS <br />(2001). Hydrologic categories used by USBR in its proposals (dry years, <br />critical dry years) are explained in the text. <br />increased flow will be realized without special limitations. Year classes that have high <br />relative strength should have emerged from the wet years of the recent past flow regime <br />if flow is limiting. This does not appear to have been the case in the past decade, <br />however. Thus, factors other than dry -year low flows appear to be limiting to survival <br />and maintenance of coho, <br />Higher flows may work to the disadvantage of the coho population from July <br />through September if the source of augmentation for flow is warmer than the water to <br />which it is added. Flows in the main stem include not only water passing the Iron Gate <br />Darn, but also accruals from ungaged sources consisting of groundwater and small <br />tributaries. This accrual water is likely to be much cooler than the water coming from <br />upstream sources, which has been warmed by retention in lakes. Thus, the addition of <br />larger amounts of water from the sequence of reservoirs above Iron Gate Dam may be <br />disadvantageous to the fish. This issue apparently has not yet been studied in any <br />rigorous manner, yet it is critical to the evaluation of higher flows in the warmest months. <br />Increased flows also could have a detrimental effect on the availability of thermal <br />refugia. Thermal refugia created by groundwater seepage and small tributary flows may <br />be most accessible and most extensive at low flows. Increase in flows may reduce the <br />size of these refugia by causing more effective mixing of the small amounts of locally <br />19 <br />966-4 680/Z60'd 9EZ-1 899E998EOE S3 nOSU 1V IVN 100 -woad W11 ZOOZ- 80 -93d <br />