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Feasibility of Fish Passage at Alameda Creek Diversion Dam

Feasibility of Fish Passage at Alameda Creek Diversion Dam

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4.0 Design Components and Preliminary Analysis4 DESIGN COMPONENTS AND PRELIMINARY ANALYSISThis section describes and evalu<strong>at</strong>es design components th<strong>at</strong> could potentially be used to providesteelhead passage <strong>at</strong> ACDD based on liter<strong>at</strong>ure review and experience with existing fish passageprojects. In conjunction with passage <strong>at</strong> ACDD, screening <strong>of</strong> the ACDT would also be required toprotect steelhead present <strong>at</strong> the diversion. <strong>Passage</strong> components are described and evalu<strong>at</strong>ed inSections 4.1 through 4.3; screening design components are described and evalu<strong>at</strong>ed in Section 4.4.Steelhead migr<strong>at</strong>ion consists <strong>of</strong> the following three primary elements:■■■adult immigr<strong>at</strong>ion;juvenile emigr<strong>at</strong>ion;post-spawn adult emigr<strong>at</strong>ion.Table 4-1 summarizes the steelhead life-stage time periods when each primary migr<strong>at</strong>ion elementoccurs. The time periods presented in the table are based upon the liter<strong>at</strong>ure review, survey d<strong>at</strong>acollected in the Upper <strong>Alameda</strong> <strong>Creek</strong> Sub-W<strong>at</strong>ershed, and personal communic<strong>at</strong>ions withindividuals familiar with the w<strong>at</strong>ershed.Table 4-1Steelhead <strong>Passage</strong> Element TimingMonth<strong>Passage</strong> Element Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug SepAdult Immigr<strong>at</strong>ion aJuvenile Emigr<strong>at</strong>ion bPost-spawn Adult Emigr<strong>at</strong>ion cSources:aGunther et al., 2000; Moyle, 2002bGunther et al., 2000; Brian Sak, pers. comm., 2009a; SFPUC, 2004cGunther et al., 2000Adult steelhead immigr<strong>at</strong>ion in the <strong>Alameda</strong> <strong>Creek</strong> W<strong>at</strong>ershed is expected to occur from Decemberthrough April, with the majority <strong>of</strong> immigr<strong>at</strong>ion occurring between December and March (Gunther et al.,2000). Juvenile steelhead emigr<strong>at</strong>ion n<strong>at</strong>urally occurs simultaneously with the smoltific<strong>at</strong>ion processwhen physiological changes occur th<strong>at</strong> adapt the juvenile fish to life in the ocean. In the <strong>Alameda</strong> <strong>Creek</strong>W<strong>at</strong>ershed, emigr<strong>at</strong>ing steelhead smolts are expected to migr<strong>at</strong>e downstream between March and June,with older fish (ages 2 and 3 years) generally migr<strong>at</strong>ing earlier (March and April) and younger fish (age1 year) migr<strong>at</strong>ing l<strong>at</strong>er (May and June) (Gunther et al., 2000). Juvenile steelhead may sometimes makesmall movements rel<strong>at</strong>ed to habit<strong>at</strong> choice (Kahler et al., 2001), and upstream movements fromspawning grounds into suitable summer rearing habit<strong>at</strong>s may sometimes occur (habit<strong>at</strong> in the studyarea is described in Section 6.1). Although most steelhead die after spawning, a significant number donot. As much as 20 to 30 percent <strong>of</strong> an annual steelhead run may be composed <strong>of</strong> repe<strong>at</strong> spawners(Shapovalov, 1953; Shapovalov and Taft, 1954). Steelhead th<strong>at</strong> survive spawning typically emigr<strong>at</strong>e tothe ocean before returning to spawn again. Migr<strong>at</strong>ions are typically expected to occur as described here,but are ultim<strong>at</strong>ely dependent upon the rainfall p<strong>at</strong>tern in a given year, which determines when flowssuitable for migr<strong>at</strong>ion are available. A flow dur<strong>at</strong>ion analysis and a storm peaking analysis would berecommended if further passage design for ACDD is requested; storm peaking analysis would furtherACDD <strong>Passage</strong> June 2009 Page 4-1

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