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<br />1140
<br />
<br />T. C. GRAND ET ilL.
<br />
<br />250
<br />
<br />200
<br />150
<br />
<br />(a) Backwater 1
<br />'!:Y:v-., _,,~ Co ^,^ ,_,r"'" '___~, ---. 10%
<br />,',..::.::.,~~~':t:..~:,-:\ r
<br />- ,--.' j.",...-, "v' ......, 20%
<br />~_"':'-"'-'~~:~\rW .,... 30%
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<br />-0%
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<br />100
<br />
<br />50
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<br />Jul
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<br />Aug Sep Oct Nav Dec Jan
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<br />CI)
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<br />.5
<br />
<br />250 (c) Backwater 3
<br />200
<br />
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<br />:L\~~~J{,L~:,~~;:~;}~l ,
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<br />
<br />150
<br />100
<br />
<br />
<br />50
<br />
<br />o
<br />Jul
<br />
<br />Aug Sep Oct Nav Dec Jan
<br />
<br />250 (e) Backwater 5
<br />200
<br />
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<br />::;::::::~:::kt'--
<br />
<br />
<br />o
<br />Jul Aug Sep Oct Nav Dee Jan
<br />
<br />250 (b) Backwater 2
<br />200
<br />
<br />150
<br />100
<br />50
<br />
<br />::~r:;J\~\^
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<br />'~<".-~
<br />
<br />o
<br />Jul
<br />
<br />Aug Sep
<br />
<br />Oct Nav Dee Jan
<br />
<br />250 (d) Backwater 4
<br />
<br />200
<br />
<br />150
<br />
<br />100
<br />
<br />50
<br />
<br />o
<br />Jul Aug Sep Oct Nov Dec Jan
<br />
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<br />
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<br />250 (f) Backwater 6
<br />
<br />:: ~'~\
<br />
<br />
<br />50 ~
<br />o
<br />Jul Aug Sep Oct Nav Dee Jan
<br />
<br />Date
<br />
<br />Figure 11, Simulated invertebrate availability l# ' m -1) in backwaters 1 (a), 2 (b), 3 (c), 4 (d), 5 (e) ~U1d 6 (1) at 0, 10,20,30 and 40% within-day
<br />flow variation
<br />
<br />Although our model predicts that backwater temperature wilJ vary only slightly with the magnitude of within-day
<br />flow fluctuations, temperatures are predicted to decline with increasing flow variation, at least during the months
<br />when differences between mainstem and air temperature are greatest (j.e, summer). Mean daily temperature
<br />differences between the observed flow and 40% flow fluctuation scenarios were typically only 2 or 3GC, Although
<br />relatively small differences in temperature can contribute to variation in invertebrate production and fish
<br />bioenergetics (Elliott, 1982), the predicted temperature effect is within the error of our temperature model.
<br />One of the most interesting results to emerge fTOm these simulations is the variability observed among
<br />backwaters in their response to the magnitude of within-day flow fluctuations, In general, small, shallow
<br />backwaters were affected by flow fluctuations more dramatically than the larger, deeper backwaters typically
<br />inhabited by juvenile pikeminnow. Furthermore, backwaters differ in myriad ways other than size and depth,
<br />including their orientation to the mainstem and the substrates they contain (Day et aI" 1999), differences that may
<br />affect their responses to fluctuating flows. For example, backwaters containing cobble substrates may be less
<br />susceptible to invertebrate flushing than those with sand or gravel substrates. In contrast, backwaters whose
<br />
<br />Copyright t, 2006 John Wiley & Sons, Ltd,
<br />
<br />River Res, A.pplic, 22: 1125-1142 (2006)
<br />DOl: IO,l002/rra
<br />
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