Committee on Resources - Hornady-Marshall Auditorium College Park

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sciondflervaluntion of Biologleal Opinions on EndangercO and Threatencd plebes in the Klamath River Basin: Tntorim Report 12602) nnp:� �,�aC• NnwnWruunxva, m�nlrlk.him.cnrp+iph}71MU.21011 TboNallfird., nc3ftInV 4S klarlcm 311VONttcrvea - ' - - . - . � .. _ .- _ "'------ — — . V% «. -,. 'tf .erg habitat suitability is diffic , It and subject to considerable uncertainty. Numerical methods are now being applied to r ie estimation of habitat area in relation to flow UNSE 1999). Those methods are Comm ly used in evaluating habitat, but in final form they require extensive field measurem;ts that are not yet available. Initial modeling suggests that, while greater amounts of habitat for salmonids accompany higher flows, the percentage increase of habitat space corresponding to increases in flow that are possible during dry years is relatively small (a few percent: lNSE 1999, NUTS 2001). Water tempera is a major concern for the welfare of the Klamath Basin coho salmon. Summer temperatures appear to be especially critical. In the nearby Matolle River, which contains Cobb that are part of the SONCC ESU, the juvenile coho reside almost entirely in tribut es but do not persist where summer daily maximum temperatures exceed 18° for more than a week (Welsh at al. 2001). Summer temperatures in the Klam th River main stem are suboptimal or even lethal to juveniles (NMFS 2001). Hight erstures are the result of reduced flow in the main stem and in tributaries as a result of cUversions, warming of water in lakes prior to its flow to the main stem, and loss of shading., Climate variability, although probably responsible for some interannual thermal varlaom-4 is unlikely to be an important factor by comparison with changes in flow and logs �friparian vegetation. Juvenile coho probably are able to use the main -stern habitat only through behaviorally- mediated thermal regulation involving selection of areas of groundwater entry ( "cold pools ") or small tributary flows that have cooler water than most of the main stem. Modeling has sho" that higher releases of water to the main stem can reduce water temperature slightly (Deal and Orlob 1999), provided that manipulation of flow itself does not raise the base temperature (see below). It is unlikely, however, that the small degree of cooling that could be accomplished in this way would affect survival of coho salmon because temperatures would continue to be suboptimal. Further modeling is in progress. The biological opinion issued by the National Marine Fisheries Service for the Klamath Basin coho salmon states that the Klamath Project harms coho in the Klamath main stem (NMFS 2001). The NMFS presents an RPA with three components: (1) higher monthly minimum flows for the main steal of the Klamath River for April through November as a means of maximizing habitat space in the main stem and suppressing maximum water temperatures, (2) suppression of ramping rates below Iron Cate Dam, and (3) coordination involving other agencies. Figure 6 shows the minimum flows that are given by NMFS as part of its RPA, and shows minimum flows proposed by USBR as part of its biological assessment as well as historical low flows in dry and critical dry years (note that in selected months flows can be higher in critical dry years than in dry years because of water management practices). The RPA- proposed low flows ate well above historical operating conditions, which in turn are above the minima proposed by USBR. The proposed low -flow limits on the Klamath River may not be of significant benefit to the coho population. While the provision of additional flow seems intuitively to be a prudent measure for expanding habitat, the total habitat expansion that is possible given the limited atnount of water that is available in dry years is not demonstrably of much importance to maintenance of the population. In wet years, any benefits from 18 966-4 660 /IEO'd 9EZ -1 899899880E snnosm 1VaI m 100 -woad W11 ZOOZ- 80 -83d