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<br /> <br />A/S FISH/WILDLIFE/PARK <br /> <br /> <br />. 05/0~/2003 16:10 FAX 2022084684 <br />. , <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />14100s <br /> <br />dramatic reductions in spawning habitat for both rainbow and brown trout and significantly <br />decrease total wetted surface area. <br /> <br />Stanford (1989) identifies 300 cfs as a minimum for fish under certain circumstances, while <br />Nehring (l988b) distinguishes between "minimum" and "optimum" flows. Both Nehring and <br />Stanford recognize the importance of base flows as well as periodic flushing flows to rejuvenate <br />and re-oxygenate habitats, remove accumulated organic debris, redistribute inorganic substratum, <br />and remove fine sediments that harbor tubifex worms, the host for the whirling disease organism. <br /> <br />Whirling disease is caused by a microscopic parasite and afflicts young salmonid fishes. This <br />disease is believed responsible for severe declines in rainbow trout populations throughout the <br />western United States (Zendt and Bergensen 2000). The whirling disease organism requires an <br />alternate host, a worm formally named Tubifex tubifex, to complete its life cycle. These Tubifex <br />worms inhabit fine, organically rich sediments of streams, lakes, and ponds. Brinkhurst (1996) <br />suggests that flushing flows sufficient to remove these fine substrates may be effective at <br />controlling whirling disease in streams and rivers. <br /> <br />To enhance native fish species, while at the same time assuring the continued presence of a self- <br />sustaining exotic trout sport fishery, requires base flows; annual peak and shoulder flows with <br />appropriate timing, mqgnitude, and duration; and occasional large peaks to create new biotic <br />habitats. Base flows of 300 eft arf! identified as a minimum flow. Appropriately timed annual <br />peaks between 2,500 and 10,000 eft remove fine sediment, accumulated organic debris, and <br />algae from the active channel without disrupting species life cycles. Rare, large peaks greater <br />than 10,000 eft redistribute inorganic substrate and create new biotic habitats. <br /> <br />Streamside Velletation: Flow regulation by upstream reservoirs is believed to be largely <br />responsible for the dramatic increase in riparian plants (both woody and herbaceous) throughout <br />the canyon (Lichvar, 1987; Auble et al., 1991). Reservoir operations have decreased the <br />magnitude and frequency of high flows and increased sununer and winter low flows, thus <br />essentially eliminating scouring flows and drought conditions that limited or restricted vegetation <br />establishment during the pre-impoundment period (Auble et aI., 1991). The elimination or <br />reduction of scouring flows has increased the occurrence and stability of depositional features <br />such as sediment bars and debris fans. These depositional features serve as ideal germination <br />and establishment sites for many woody riparian species. Once vegetation becomes established, <br />the shear stress associated with the reduced spring flows is insufficient to sCOut and UPI:oot newly <br />established vegetation. The lack of inundating flows (of sufficient depth or duration to submerge <br />individual plants and create anoxic soil conditions) has enhanced riparian plant survival. <br />Consequently, vegetation establishment is occuning in areas that in the past would not have <br />supported vegetation. This, in turn, reduces the amount of available macro-invertebrate and fish <br />habitat. <br /> <br />Friedman and Auble (1999) determined that mortality of woody riparian vegetation (for <br />example, trees such as Acer negundo, commonly termed box elder) occurs either by scour of <br />underlying rooted sediments or by inundation for more than 85 days during the May 1- October I <br />growing season. They further found that flow regulation by upstream reservoirs has reduced the <br /> <br />4 <br />