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<br />Figure 8. Average minimum and maximum monthly cischarges during the pre-dam period (black. solid lines} and under the 'no action' (black
<br />dashed line,.;) and MLFF (grey dashed lines) operalir:z regimes. See Table III for a description of flow regime characteristics. Horizontal grid-
<br />lines show [he extent of overlap f)elween discharges rr..--..!elled in this study and daily discharge ranges. Note that the flow r;lJ1ges for lhe pre-dam
<br />period in May (1200-1300rn~;i) and June (l430-1S30m3Js) occur above the y.axis maximum
<br />
<br />Table vr. Persistent suitable habitat area (m2 x tOJ) atdaily discharge ranges t1J?i.ca\ Qftmeeh~stonca\ GCD operati.ng regimes.
<br />
<br /> Post-dam
<br />Reach Pre-dam
<br /> (2000 LSSF) (226 m'/s) No action (566--226m'/s) MLFF (566-425 m'/s)
<br />Shoreline (.:s:;; I I11. and .:s:;;O.2Smls)
<br />RI 6,1 0_0 0.2
<br />R2 0,9 0_0 0.4
<br />R3 0,7 0,0 0,1
<br />R4 8,1 0,0 0,1
<br />R5 l.8 0,0 0.4
<br />ALC 12,0 0,2 2.4
<br />PAL 18.4 0..5 16,8
<br />To'al (<;0,25 mls)
<br />RI 14,0 4-' 5.4
<br />R2 10,0 3.4 4.4
<br />R3 13.4 5_9 4,4
<br />R4 15,8 4,8 6,3
<br />R5 39,0 16,6 18_2
<br />ALC 18,7 2,0 5,6
<br />PAL 26,7 4,7 20,7
<br />
<br />the cross-stream direction towards the closest bank, had the highest retention rates_ The rheotactic behaviour was
<br />the next most effective, and the higher the sv.;mming speed. the higher the retention rate_ There was considerable
<br />reach-to-reach variation'on the effectiveness of swimming behaviour at maintaining high retention rates, At longer
<br />reaches (e,g, ALe, R I; Table I), particles starting near the centre of the channel with a bank-seeking behaviour had
<br />sufficient time to move into low-velocity water near the banks. and hence remain in the reach. In contrast. reaches
<br />that were relalively short had low retention rates even under the geotactic behaviour because the particles passed
<br />through the reach before entering low-velocity water near the banks.
<br />Retention rates under the passive behaviour were the least sensitive to discharge and very dependent on local
<br />morphology (Figure 10), Reaches R3 and R4 had considerably higher retention rates corripared to other sites at
<br />lower discharges. Large eddies take up a large proportion of the total wetted area of these reaches. and most par-
<br />ticles that were randomly assigned slarting positions in the eddies were retained. Retention rates were highest in
<br />reaches where eddies make up a large proportion of the wetted area_
<br />
<br />Copyright @ 2004 John Wiley &. Sons, Ltd.
<br />
<br />River Res. Applic. 20: 379-400 (2004)
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